Search

Selective inversion recovery (SIR) is a quantitative magnetization transfer (qMT) method that provides estimates of parameters related to myelin content in white matter, namely the macromolecular pool-size-ratio (PSR) and the spin-lattice relaxation rate of the free pool (R 1f ), without the need for independent estimates of ∆B 0 , B 1 + , and T 1 . Although the feasibility of performing SIR in the human brain has been demonstrated, the scan times reported previously were too long for whole-brain applications. In this work, we combined optimized, short-TR acquisitions, SENSE/partial-Fourier accelerations, and efficient 3D readouts (turbo spin-echo, SIR-TSE; echo-planar imaging, SIR-EPI; and turbo field echo, SIR-TFE) to obtain whole-brain data in 18, 10, and 7 min for SIR-TSE, SIR-EPI, SIR-TFE, respectively. Based on numerical simulations, all schemes provided accurate parameter estimates in large, homogenous regions; however, the shorter SIR-TFE scans underestimated focal changes in smaller lesions due to blurring. Experimental studies in healthy subjects (n = 8) yielded parameters that were consistent with literature values and repeatable across scans (coefficient of variation: PSR = 2.2-6.4%, R 1f  = 0.6-1.4%) for all readouts. Overall, SIR-TFE parameters exhibited the lowest variability, while SIR-EPI parameters were adversely affected by susceptibility-related image distortions. In patients with relapsing remitting multiple sclerosis (n = 2), focal changes in SIR parameters were observed in lesions using all three readouts; however, contrast was reduced in smaller lesions for SIR-TFE, which was consistent with the numerical simulations. Together, these findings demonstrate that efficient, accurate, and repeatable whole-brain SIR can be performed using 3D TFE, EPI, or TSE readouts; however, the appropriate readout should be tailored to the application., (Copyright © 2020 Elsevier Inc. All rights reserved.)

The locus coeruleus (LC) is the major origin of norepinephrine in the central nervous system, and is subject to age-related and neurodegenerative changes, especially in disorders such as Parkinson's disease and Alzheimer's disease. Previous studies have shown that neuromelanin (NM)-sensitive MRI can be used to visualize the LC, and it is hypothesized that magnetization transfer (MT) effects are the primary source of LC contrast. The aim of this study was to characterize the MT effects in LC imaging by applying high spatial resolution quantitative MT (qMT) imaging to create parametric maps of the macromolecular content of the LC and surrounding tissues. Healthy volunteers (n = 26; sex = 17 F/9M; age = 41.0 ± 19.1 years) underwent brain MRI on a 3.0 T scanner. qMT data were acquired using a 3D MT-prepared spoiled gradient echo sequence. A traditional NM scan consisting of a T 1 -weighted turbo spin echo sequence with MT preparation was also acquired. The pool-size ratio (PSR) was estimated for each voxel using a single-point qMT approach. The LC was semi-automatically segmented on the MT-weighted images. The MT-weighted images provided higher contrast-ratio between the LC and surrounding pontine tegmentum (PT) (0.215 ± 0.031) than the reference images without MT-preparation (-0.005 ± 0.026) and the traditional NM images (0.138 ± 0.044). The PSR maps showed significant differences between the LC (0.090 ± 0.009) and PT (0.188 ± 0.025). The largest difference between the PSR values in the LC and PT was observed in the central slices, which also correspond to those with the highest contrast-ratio. These results highlight the role of MT in generating NM-related contrast in the LC, and should serve as a foundation for future studies aiming to quantify pathological changes in the LC and surrounding structures in vivo., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Background: Quantitative susceptibility mapping (QSM) offers a consistent hemorrhage volume measurement independent of imaging parameters., Purpose: To investigate the magnetic susceptibility of intracerebral hemorrhage (ICH) as a quantitative measurement for monitoring treatment in hematoma patients., Study Type: Prospective., Population: Twenty-six patients with acute ICH were recruited and enrolled in treatment including surgery or medication (mannitol) for 1 week., Field Strength/sequence: A 3D gradient echo sequence at 3.0T., Assessment: The hematoma volumes on computed tomography (CT) and QSM were calculated and used for correlation analysis. Magnetic susceptibility changes from pre- to posttreatment were calculated and compared to the National Institutes of Health stroke scale (NIHSS) measure of neurological deficit for each patient., Statistical Tests: Mean susceptibility values were calculated over each region of interest (ROI). A one-sample t-test was used to assess the changes of total volumes and mean magnetic susceptibility of ICH identified between pre- and posttreatment images (P < 0.05 was considered significant) and the Bland-Altman analysis with 95% limits of agreement (average difference, ±1.96 SD of the difference). Regression of volume measurements on QSM vs. CT and fitted linear regression of mean susceptibility vs. CT signal intensity for hematoma regions were conducted in all patients., Results: Good correlation was found between hemorrhage volumes calculated from CT and QSM (CT volume = 0.94*QSM volume, r = 0.98). Comparison of QSM pre- and posttreatment showed that the mean ICH volume was reduced by a statistically insignificant amount from 5.74 cm 3 to 5.45 cm 3 (P = 0.21), while mean magnetic susceptibility was reduced significantly from 0.48 ppm to 0.38 ppm (P = 0.004). A significant positive association was found between changes in magnetic susceptibility values and NIHSS following hematoma treatment (P < 0.01)., Data Conclusions: QSM in hematoma assessment, as compared with CT, offers a comparably accurate volume measurement; however, susceptibility measurements may enable improved monitoring of ICH treatment compared to volume measurements alone., Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:907-915., (© 2018 International Society for Magnetic Resonance in Medicine.)

The data presented in this article accompany the research article entitled "Longitudinal Atlas for Normative Human Brain Development and Aging over the Lifespan using Quantitative Susceptibility Mapping" (Zhang et al., 2018) [1]. The longitudinal evolution of magnetic susceptibility in human brain indicates critical characteristics of normal brain development and aging. In the corresponding research article, we build longitudinal QSM atlases over various age intervals using 166 healthy subjects (83F/69M) with an age range of 1-83 years old. Based on the newly built atlases, we investigate the regional evolutions of magnetic susceptibility in the brain. In this article, we report anatomical evolutions of the age-specific QSM atlases in deep gray matter nuclei and in two selected white matter fiber bundles. In addition to iron-rich brain nuclei, the evolution patterns of the magnetic susceptibility in the amygdala and hippocampus are also presented.

Longitudinal brain atlases play an important role in the study of human brain development and cognition. Existing atlases are mainly based on anatomical features derived from T1-and T2-weighted MRI. A 4D developmental quantitative susceptibility mapping (QSM) atlas may facilitate the estimation of age-related iron changes in deep gray matter nuclei and myelin changes in white matter. To this end, group-wise co-registered QSM templates were generated over various age intervals from age 1-83 years old. Registration was achieved by combining both T1-weighted and QSM images. Based on the proposed template, we created an accurate deep gray matter nuclei parcellation map (DGM map). Notably, we segmented thalamus into 5 sub-regions, i.e. the anterior nuclei, the median nuclei, the lateral nuclei, the pulvinar and the internal medullary lamina. Furthermore, we built a "whole brain QSM parcellation map" by combining existing cortical parcellation and white-matter atlases with the proposed DGM map. Based on the proposed QSM atlas, the segmentation accuracy of iron-rich nuclei using QSM is significantly improved, especially for children and adolescent subjects. The age-related progression of magnetic susceptibility in each of the deep gray matter nuclei, the hippocampus, and the amygdala was estimated. Our automated atlas-based analysis provided a systematic confirmation of previous findings on susceptibility progression with age resulting from manual ROI drawings in deep gray matter nuclei. The susceptibility development in the hippocampus and the amygdala follow an iron accumulation model; while in the thalamus sub-regions, the susceptibility development exhibits a variety of trends. It is envisioned that the newly developed 4D QSM atlas will serve as a template for studying brain iron deposition and myelination/demyelination in both normal aging and various brain diseases., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Magnetic susceptibility is an important source of contrast in magnetic resonance imaging (MRI), with spatial variations in the susceptibility of tissue affecting both the magnitude and phase of the measured signals. This contrast has generally been interpreted by assuming that tissues have isotropic magnetic susceptibility, but recent work has shown that the anisotropic magnetic susceptibility of ordered biological tissues, such as myelinated nerves and cardiac muscle fibers, gives rise to unexpected image contrast. This behavior occurs because the pattern of field variation generated by microstructural elements formed from material of anisotropic susceptibility can be very different from that predicted by modelling the effects in terms of isotropic susceptibility. In MR images of tissue, such elements are manifested at a sub-voxel length-scale, so the patterns of field variation that they generate cannot be directly visualized. Here, we used pyrolytic graphite sheet which has a large magnetic susceptibility anisotropy to form structures of known geometry with sizes large enough that the pattern of field variation could be mapped directly using MRI. This allowed direct validation of theoretical expressions describing the pattern of field variation from anisotropic structures with biologically relevant shapes (slabs, spherical shells and cylindrical shells).

Quantitative susceptibility mapping (QSM) is increasingly used to measure variation in tissue composition both in the brain and in other areas of the body in a range of disease pathologies. Although QSM measurements were originally believed to be independent of the echo time (TE) used in the gradient-recalled echo (GRE) acquisition from which they are derived; recent literature (Sood et al., 2016) has shown that these measurements can be highly TE-dependent in a number of brain regions. In this work we systematically investigate possible causes of this effect through analysis of apparent frequency and QSM measurements derived from data acquired at multiple TEs in vivo in healthy brain regions and in cerebral microbleeds (CMBs); QSM data acquired in a gadolinium-doped phantom; and in QSM data derived from idealized simulated phase data. Apparent frequency measurements in the optic radiations (OR) and central corpus callosum (CC) were compared to those predicted by a 3-pool white matter model, however the model failed to fully explain contrasting frequency profiles measured in the OR and CC. Our results show that TE-dependent QSM measurements can be caused by a failure of phase unwrapping algorithms in and around strong susceptibility sources such as CMBs; however, in healthy brain regions this behavior appears to result from intrinsic non-linear phase evolution in the MR signal. From these results we conclude that care must be taken when deriving frequency and QSM measurements in strong susceptibility sources due to the inherent limitations in phase unwrapping; and that while signal compartmentalization due to tissue microstructure and content is a plausible cause of TE-dependent frequency and QSM measurements in healthy brain regions, better sampling of the MR signal and more complex models of tissue are needed to fully exploit this relationship., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Functional magnetic resonance imaging (fMRI) studies of the auditory region of the temporal lobe would benefit from the availability of image contrast that allowed direct identification of the primary auditory cortex, as this region cannot be accurately located using gyral landmarks alone. Previous work has suggested that the primary area can be identified in magnetic resonance (MR) images because of its relatively high myelin content. However, MR images are also affected by the iron content of the tissue and in this study we sought to confirm that different MR image contrasts did correlate with the myelin content in the gray matter and were not primarily affected by iron content as is the case in the primary visual and somatosensory areas. By imaging blocks of fixed post-mortem cortex in a 7 T scanner and then sectioning them for histological staining we sought to assess the relative contribution of myelin and iron to the gray matter contrast in the auditory region. Evaluating the image contrast in [Formula: see text]-weighted images and quantitative [Formula: see text] maps showed a reasonably high correlation between the myelin density of the gray matter and the intensity of the MR images. The correlation with T 1 -weighted phase sensitive inversion recovery (PSIR) images was better than with the previous two image types, and there were clearly differentiated borders between adjacent cortical areas in these images. A significant amount of iron was present in the auditory region, but did not seem to contribute to the laminar pattern of the cortical gray matter in MR images. Similar levels of iron were present in the gray and white matter and although iron was present in fibers within the gray matter, these fibers were fairly uniformly distributed across the cortex. Thus, we conclude that T 1 - and [Formula: see text]-weighted imaging sequences do demonstrate the relatively high myelin levels that are characteristic of the deep layers in primary auditory cortex and allow it and some of the surrounding areas to be reliably distinguished.

Objective: The aim of this study was to compare the use of high-resolution phase and QSM images acquired at ultra-high field in the investigation of multiple sclerosis (MS) lesions with peripheral rings, and to discuss their usefulness for drawing inferences about underlying tissue composition., Materials and Methods: Thirty-nine Subjects were scanned at 7 T, using 3D T 2*-weighted and T 1-weighted sequences. Phase images were then unwrapped and filtered, and quantitative susceptibility maps were generated using a thresholded k-space division method. Lesions were compared visually and using a 1D profiling algorithm., Results: Lesions displaying peripheral rings in the phase images were identified in 10 of the 39 subjects. Dipolar projections were apparent in the phase images outside of the extent of several of these lesions; however, QSM images showed peripheral rings without such projections. These projections appeared ring-like in a small number of phase images where no ring was observed in QSM. 1D profiles of six well-isolated example lesions showed that QSM contrast corresponds more closely to the magnitude images than phase contrast., Conclusions: Phase images contain dipolar projections, which confounds their use in the investigation of tissue composition in MS lesions. Quantitative susceptibility maps correct these projections, providing insight into the composition of MS lesions showing peripheral rings.

The aim of this study was to investigate the efficacy of vibration warm-up to enhance sprint performance. 12 males involved in representative team sports performed 4 warm-up conditions in a randomised order performed at least 24 h apart; VbX warm-up (VbX-WU); Neural activation warm-up (Neu-WU); Dynamic warm-up (Dyn-WU) and Control (No VbX). Participants completed 5 m sprint at 30 s, 2:30 min and 5 min post warm-up where sprint time, kinetics, and temporal components were recorded. There was no significant (p>0.05) main effect or interaction effect between the split sprint times of 1 m, 2.5 m, and 5 m. There was a condition effect where vertical mean force was significantly higher (p<0.05) in Dyn-WU and Control compared to Neu-WU. No other significant (p>0.05) main and interaction effects in sprint kinetic and temporal parameters existed. Overall, all 4 warm-up conditions produced comparable results for sprint performance, and there was no detrimental effect on short-duration sprint performance using VbX-WU. Therefore, VbX could be useful for adding variety to the training warm-up or be included into the main warm-up routine as a supplementary modality., (© Georg Thieme Verlag KG Stuttgart · New York.)

Objective: A systematic review of randomised controlled trials reporting the efficacy of antibiotics compared with placebo in the treatment of acute rhinosinusitis in children., Design: Systematic review and meta-analysis., Data Sources: Cochrane Register of Controlled Trials, Medline, Embase and references obtained from retrieved articles., Results: Four studies fitted the selection criteria for inclusion. Risks for internal bias were thought to be small for each study, but external bias is potentially significant. The pooled OR for symptom improvement at 10-14 days favouring the use of antibiotics was 2.0 (95% CI 1.16 to 3.47; I(2)=14.8%)., Conclusions: While the meta-analysis provides evidence to support the use of antibiotics for acute rhinosinusitis in children, it is the assessment of this review that such efficacy has not been adequately demonstrated. There remains a clear methodological challenge in the examination of this important clinical question; this challenge relates to difficulties in the application of appropriate diagnostic and inclusion criteria which are also consistent between studies.

Objective: This randomised, examiner-blind parallel group study was designed to evaluate the safety and efficacy of a rechargeable oscillating/pulsating toothbrush (Oral-B ProfessionalCare 7000, Oral-B Laboratories; PC 7000) and a battery-operated toothbrush (Crest SpinBrush Pro, Procter & Gamble Company; SBP) in the reduction of gingivitis, bleeding and plaque over a 3-month period., Methods: After 12-18 hours of no oral hygiene, subjects had oral tissue examinations, and gingival and plaque assessments to determine eligibility in the study. Subjects were stratified and randomised into treatment groups based on initial whole mouth mean plaque (Turesky modification of Quigley Hein Plaque Index) and gingivitis (Löe & Silness Gingival Index) scores and gender. Subjects were instructed to brush twice daily with their assigned toothpaste and toothbrush. Clinical parameters were assessed at baseline, and after 1 and 3 months of use. Within treatment comparisons from baseline were analysed using t-test; between treatment comparisons were analysed using ANOVA., Results: Data were obtained from 92 subjects (PC 7000 n=45; SBP n=47). No significant differences were found in baseline plaque, gingivitis and bleeding between groups. Both treatment groups had significant reductions from baseline in plaque, gingivitis and bleeding scores. PC 7000 demonstrated significantly greater reductions compared to SBP in whole mouth plaque at 1 month: 0.39 +/- 0.43 vs. 0.16 +/- 0.42 and 3 months: 0.32 +/- 0.48 vs. 0.04 +/- 0.41. PC 7000 also demonstrated significant reductions compared to SBP in gingivitis at 3 months for whole mouth: 0.14 +/- 0.09 vs. 0.10 +/- 0.10 and approximal areas: 0.11 +/- 0.08 vs. 0.08 +/- 0.09. There were no significant differences between toothbrushes in bleeding at either time point: Safety examinations revealed no apparent difference in soft and hard tissue abnormalities between groups., Conclusion: The PC 7000 toothbrush demonstrated significantly greater reductions in plaque and gingivitis compared to the SPB over a 3-month period.

Tooth whitening is one of the most widely accepted esthetic procedures in dentistry. Various treatment options include in-office and prescribed at-home bleaching procedures, over-the-counter bleaching kits, and whitening dentifrices. This study evaluated and compared a 6% hydrogen peroxide tooth bleaching gel delivered on polyethylene film (HP) with an 18% carbamide peroxide brush-applied liquid gel (CP). A total of 59 subjects completed this 2-week, examiner blind, randomized, parallel group study. Both treatments were applied twice daily for 2 weeks according to the manufacturer's instructions. Evaluations for oral safety and Vita tooth shade were conducted by a dental examiner at baseline and 2 weeks after product use. In addition, the ShadeVision System was used to determine changes in Vita shade and L*a*b* values. Based on both the examiner and ShadeVision System assessments, both treatments significantly improved tooth shade. Improvements in Vita tooth shade based on the adjusted mean for HP were 2.64 (P < 0.001) and 2.33 (P < 0.001) for the examiner and ShadeVision System assessments, respectively, compared with improvements of 1.04 (P = .004) and 0.42 (P = 0.029) for CP users, respectively. The difference between treatments was found to be significant for both the examiner (P = .005) and ShadeVision (P = .001) assessments. Findings from the L*a*b* data derived from the ShadeVision System were in agreement with Vita assessments, with significant differences for changes in L*, a*, and b* in favor of HP users (P = .001). In this study, the ShadeVision method of color analysis was relatively easy to use and demonstrated significant differences between 2 OTC whitening products using both Vitapan and L*a*b* means of assessment.

Objective: To compare the safety and efficacy of a novel battery-operated interdental cleaning device (Oral-B Hummingbird) [ID], fitted with either a flossette or pick attachment, versus hand-held dental floss in the reduction of plaque and gingivitis when combined with manual tooth brushing over a 30-day period., Methodology: This randomized, examiner blind, parallel group study assessed three treatment groups: ID/flossette (ID/F), ID/pick (ID/P), and unwaxed manual dental floss. All groups used the same soft manual toothbrush and toothpaste. The 84 subjects were stratified to treatment groups based on initial whole mouth mean plaque scores, gingivitis scores, and gender. Subjects were instructed to brush twice daily and use their assigned interdental method once daily in the evening before brushing. Gingivitis, gingival bleeding, and plaque were evaluated at baseline and Day 30., Results: A total of 78 subjects completed all aspects of the study and were included in the analyses. There was no significant difference between treatment groups in baseline plaque, gingivitis, and bleeding scores. After 30 days, statistically significant reductions from baseline gingivitis and bleeding scores were found for all groups (p < 0.0001), but there were no significant statistical differences among groups. Whole mouth and approximal plaque scores were significantly reduced from baseline in the manual floss and ID/F groups after 30 days of product use, with no significant difference between groups. Plaque reduction for both the manual floss and ID/F groups was significantly greater than the ID/P group. All interdental cleaning methods were safe as used in the study, with no evidence of oral hard or soft tissue trauma., Conclusion: The Oral-B Hummingbird was safe and effective in reducing approximal plaque and gingival inflammation, and provides a useful alternative device for interdental cleaning.

Purpose: To compare the safety and efficacy of two recently introduced modern power toothbrushes with different characteristics., Materials and Methods: This was a single-blind, randomized, crossover study which compared the ability of two power toothbrushes to remove plaque during a 2-minute brushing period. The two brushes were the Braun Oral-B 3D Excel (D17), a rechargeable toothbrush with an oscillating/rotating/pulsating action and the Colgate Actibrush, a battery-operated device with an oscillating/rotating action. Seventy-four healthy subjects from a general population who met the inclusion/exclusion criteria used the two brushes on alternate days for a period of familiarization before returning to the test facility. At this visit, subjects with a whole mouth mean Proximal/Marginal Plaque Index of > or = 2.20 after 23-25 hours of no oral hygiene were randomly assigned to one of two treatment sequences, D17/Actibrush and Actibrush/D17, balanced for age and gender. Subjects brushed with their assigned toothbrush after which post-brushing plaque scores were recorded. After a 2-week washout phase subjects returned to the test facility and brushed with the alternate toothbrush as described. Data from the two visits were pooled, after which plaque removal efficacies were compared. Change from prebrushing treatment means were compared using ANOVA with models appropriate for the crossover design., Results: Both toothbrushes were found to be safe and both significantly reduced plaque levels (P < or = 0.0001), but the D17 was significantly more effective than the Actibrush for the whole mouth and for approximal sites. Plaque reductions for the D17 were 46.5%, 55.2% and 42.9% for whole mouth, marginal and approximal sites, respectively while reductions for the Actibrush for the whole mouth, marginal, and approximal sites, were 41.5%, 52.5% and 36.8% respectively. It is concluded that the Braun Oral-B D17 may offer advantages in terms of plaque removal over the battery-powered Actibrush, particularly at hard to reach approximal sites.

Purpose: To compare the safety and efficacy of a manual toothbrush and a battery-operated power toothbrush in two separate studies, one utilizing a single-use design and the other a 3-month parallel-group design., Materials and Methods: The toothbrushes compared in the two studies were the Oral-B CrossAction manual toothbrush and the Colgate Actibrush battery-operated power toothbrush. The single-use study, which used a single-blind, cross-over design, involved 71 healthy subjects, who were instructed to abstain from oral hygiene for 23-25 hours prior to brushing with each of the two toothbrushes. Plaque was measured using the Proximal Marginal Index (PMI) pre- and post-brushing. The 3-month parallel-group study involved a total of 113 subjects who had plaque (PMI), gingivitis and bleeding (Loe and Silness) scored at baseline and after 1 and 3 months of product use., Results: In both studies, the two toothbrushes were found to be safe. In the single-use study, significantly greater amounts of plaque were removed by the CrossAction manual toothbrush than by the Actibrush for the whole mouth as well as for marginal and approximal sites (P < 0.001). In the 3-month study, significantly greater plaque reduction was achieved with the CrossAction brush, the advantage being significant at 1 month for all sites except lingual sites (P < 0.05). At 3 months, there were consistent numerical advantages in favor of the CrossAction at all sites except lingual sites. Reductions in gingivitis were found to be similar with both toothbrushes.

Purpose: To compare the safety and plaque removal efficacy of two angled-bristled toothbrushes., Materials and Methods: The brushes were compared using a single-use, cross-over designed study, where healthy subjects from a normal population brushed their teeth with their assigned toothbrush for a timed 60 seconds. Pre- and post-brushing plaque levels were evaluated after disclosing, using the Proximal/Marginal Plaque Index. At the first visit, 100 subjects with a plaque index of > or = 2.20 after 23-25 hours of no oral hygiene were enrolled in the study. At the end of the study, data from 91 subjects were suitable for analysis. The two treatment sequence groups, X-Aktiv/CrossAction and CrossAction/X-Aktiv, were balanced for age and gender and, at each visit, pre-brushing plaque scores did not differ significantly between the two groups. Data from the two visits were pooled, after which plaque removal efficacies were compared., Results: Both toothbrushes were found to be safe and both significantly reduced plaque levels (P< or = 0.0001), but the CrossAction was significantly more effective than the X-Aktiv for whole mouth and marginal sites, as well as the difficult-to-access approximal areas (P< or = 0.0008). For the whole mouth, the CrossAction was 11.8% more effective; for marginal sites the difference was 12.6%, and for approximal sites the difference was 11.4%. It is concluded that the Oral-B CrossAction toothbrush is significantly more effective with respect to plaque removal than the Dr. Best X-Aktiv.

Background: The authors undertook a controlled clinical study to determine the efficacy of a tartar-control antiseptic mouthrinse in inhibiting the development of supragingival dental calculus., Methods: After undergoing a dental prophylaxis, 334 subjects with a moderate rate of calculus formation were stratified and randomly assigned to one of three groups: positive control (using a tartar-control toothpaste and an antiseptic rinse), negative control (using a regular toothpaste and an antiseptic mouthrinse) or experimental (using a regular dentifrice and a tartar-control mouthrinse). Subjects brushed and rinsed twice daily, unsupervised, for four months. The researchers assessed subjects' calculus levels using the Volpe-Manhold Index, or VMI, after 16 weeks., Results: Using analysis of covariance, the authors found that both the experimental group (which used a tartar-control rinse containing zinc chloride) and the positive control group (which used a tartar-control dentifrice containing pyrophosphate) demonstrated statistically significantly lower VMI scores (P = .001) than the negative control group (which used a regular dentifrice and an antiseptic rinse). Both anticalculus agents provided a clinically relevant 21 percent reduction in calculus formation., Conclusion: An antiseptic mouthrinse containing 0.09 percent zinc chloride as the anticalculus agent provides a clinically relevant reduction in calculus formation in people with a moderate rate of such formation., Clinical Implications: A tartar-control mouthrinse with zinc chloride as the tartar-control ingredient is clinically effective in reducing the formation of calculus.

Purpose: To investigate the safety and efficacy of a new toothbrush with a novel brush head design (Oral-B CrossAction) in comparison with seven leading manual brushes., Materials and Methods: Seven independent clinical studies, each involving approximately 100 healthy subjects from a general population, were carried out using a crossover design. In each study, the Oral-B CrossAction toothbrush was compared with an alternative brush for plaque removal efficacy. Plaque was evaluated before and after brushing for 60 s using the Proximal/Marginal Plaque Index. Subjects were randomly assigned to the two brushes in each study and after brushing at visit 1 they returned after a further 2 weeks to repeat the procedure with the second brush., Results: All toothbrushes in the seven studies significantly reduced levels of plaque from their pre-brushing values and were found to be safe with no evidence of oral soft tissue trauma. In each of the studies, the CrossAction was found to be significantly (P < 0.05) more effective than the comparison brush for whole mouth plaque scores, as well as for plaque scores at the gingival margin and proximal surfaces. Advantages in favor of the CrossAction ranged from 9.8% to 23.2% for whole mouth plaque, from 5.3% to 20.6% for the gingival margin and from 12.8% to 24.5% for proximal surfaces. It was concluded that the novel brush head design of the CrossAction toothbrush provides enhanced plaque removal, especially from proximal surfaces, and that this toothbrush is significantly more effective than all seven toothbrushes tested.

Mice (Ins.Dd1) with hypoinsulinemic diabetes were created by increased expression of syngeneic major histocompatibility complex (MHC) class I protein in pancreatic beta-cells. The diabetic state was characterized in these mice by high glucose concentrations and islet pathology. To determine whether a neuropathy would develop, motor and sensory conduction velocities (CV) were determined in the sciatic nerves of 2-, 4-, and 7-month-old control and diabetic littermate male mice. Recording bipolar electrodes were placed in the plantar muscles of the hind foot of anesthetized (ketamine/xylazine) mice. Bipolar stimulating electrodes were positioned near the sciatic nerve at the sciatic notch or near the tibial nerve at the ankle. Motor CV from alpha-motor fibers and sensory CV from proprioceptive Aalpha nerves were measured and expressed as meters per second (m/s). Group data are reported as mean +/- SE and compared by analysis of variance. The CVs from nondiabetic mice (controls) were not different across the three ages and averaged 41.3 +/- 1.7 m/s for motor and 38.7 +/- 1.7 m/s for sensory. The motor CVs from diabetic mice at 2 and 4 months were similar to controls. Sensory CVs were unchanged at 2 months but were lower at 4 months (18.9 +/- 2.4 m/s). Both sensory (23.9 +/- 2.1 m/s) and motor (18.9 +/- 1.8 m/s) CVs were significantly reduced at 7 months, which is indicative of a polyneuropathy. NGF has well-known trophic effects on sympathetic and small sensory neurons. To determine whether NGF could influence this neuropathy, 6-month-old control and diabetic mice were divided into the following groups: 1) control + vehicle, 2) diabetic + vehicle, and 3) diabetic + NGF (1 mg/kg, 3x week, s.c.). After 1 month of treatment, motor and sensory CVs were determined. In some mice, the branches of the sciatic nerve were exposed and in situ recordings from the sural nerve were performed to determine compound C-fiber CV, integral, and amplitude. Sensory CV, determined via Hoffmann's reflex (H-reflex) (A-fiber), was decreased in diabetic compared with control animals as expected (P < 0.05), and NGF did not alter this parameter. Continuing diabetes reduced the amplitude (0.9 +/- 0.2 vs. 3.2 +/- 0.7 mV x 10(-2); P < 0.05) and integral (6.9 +/- 1.9 mV/ms vs. 18.8 +/- 4.4 mV/ms; P < 0.05) of the C-fiber response versus control, suggesting fiber loss. NGF treatment normalized C-fiber amplitude (2.9 +/- 0.8 mV x 10(-2)) and integral (21.2 +/- 6.5 mV/ms) in animals with established diabetes, with no effect on blood glucose. The C-fiber CV was similar in all groups, indicating that the animals had some normally conducting small fiber sensory nerves. These studies characterized a motor and sensory polyneuropathy in transgenic diabetic mice and are the first to demonstrate directly that NGF treatment can protect or restore abnormal sensory C-fiber function.

We hypothesized that the increased glomerular permeability to serum proteins in the nephrotic syndrome might lead to alterations of the somatotropic hormone axis, thereby contributing to growth failure and catabolism in the nephrotic state. The insulin-like growth factors (IGF)-I and -II and the IGF binding proteins (IGFBP)-1, -2 and -3 were analyzed in serum and urine of 21 children with the nephrotic syndrome and normal glomerular filtration rate. Mean age-related serum IGF-I levels by RIA (-0.53 +/- 0.34 SD) were slightly, but significantly (P < 0.05) decreased compared with the reference population, whereas mean age-related serum IGF-II levels (0.68 +/- 0.21 SD) were slightly, but significantly (P < 0.005) increased. The urinary excretion rate of both peptides was enhanced fivefold. By RIA, mean age-related serum IGFBP-1 (2.05 +/- 0.19 SD) and, even more pronounced, IGFBP-2 (5.97 +/- 0.65 SD) were clearly elevated despite a 12-fold and 2-fold increase of the respective urinary excretion rate. There was a tight and specific correlation between age-related serum IGFBP-2 levels and the degree of the nephrotic syndrome, as estimated by serum albumin levels (r = -0.78, P < 0.0001). Serum immunoreactive IGFBP-3 levels were also elevated (1.79 +/- 0.33 SD) in nephrotic serum, due to an increase of low-molecular weight IGFBP-3 fragments. By FPLC analysis, there was a decrease of the 150 kDa IGFBP ternary complex in nephrotic serum, which in the presence of normal concentrations of the acid-labile subunit by RIA appears to be due to a reduction of intact IGFBP-3. Serum levels of the high-affinity GH binding protein that presumably reflects GH receptor status in tissues were normal. In summary, total serum IGFs in children with the nephrotic syndrome are normal, but the binding of IGFs to IGFBPs in the circulation is altered with a shift from the 150 kDa IGFBP complex to an excess of low molecular weight IGFBPs. Because increased unsaturated high-affinity IGFBPs in nephrotic serum have the ability to inhibit IGF action on target tissues by competing with the type 1 IGF receptor for IGF binding, this alteration is likely to contribute to growth failure and tissue catabolism in the nephrotic state.

The first efforts to produce recombinant human growth hormone (GH) for clinical use were begun by scientists at Genentech, Inc., almost a generation ago, late in 1979. The very small market for GH that was predicted at the time led to this manufacturing effort being done as a demonstration project. Among the early issues was whether the Escherichia coli host cell could be routinely produced in a stable manner and be inactivated after the GH production run (as required by Federal guidelines) without the GH being permanently denatured. A 10 L E. coli process was developed, and phase I testing began in early 1981. The approval of this recombinant GH product by the FDA in 1985 paved the way for many improvements and a sustained production effort in the next decade. The more than 1990 fermentation runs have produced tons of E. coli and more than 130 pounds of GH for both clinical research and the treatment of severely short children.

Growth retardation in children with chronic renal failure (CRF) despite normal or elevated GH levels indicates a peripheral insensitivity to the action of GH. One possible molecular mechanism is a reduced density of GH receptors in GH target organs. In humans, the circulating high affinity GH binding protein (GHBP) is thought to reflect GH receptor expression, because it is derived from the extra-cellular domain of the GH receptor by proteolytic cleavage. We, therefore, analyzed serum GHBP levels by ligand-mediated immunofunctional assay in 126 children with CRF compared to reference values obtained by analysis of 773 healthy children. In 77% of CRF patients, serum GHBP concentrations were below the mean for age- and gender-matched controls. The decrease in serum GHBP levels was related to the degree of renal dysfunction. In advanced CRF (glomerular filtration rate, < 35 mL/min.1.73 m2), mean age- and gender-adjusted GHBP levels were -1.40 +/- 0.18 SD score; 36% of patients had GHBP levels below the normal range (< -2 SD score). Children with end-stage renal disease (n = 26) had the lowest GHBP levels (-2.25 +/- 0.22 SD score). Multiple linear regression analysis revealed that body mass index, rather than glomerular filtration rate, is the prevailing determinant of serum GHBP levels in CRF. GHBP levels correlated with both the spontaneous growth rate ( r = 0.44; P < 0.0001) and the growth response to GH therapy (r = 0.48; P < 0.005), indicating decreased sensitivity to both endogenous and exogenous GH. Subcutaneous GH therapy did not consistently affect serum GHBP levels after 3 months of treatment. It is suggested that low GHBP levels in children with CRF represent a quantitative tissue GH receptor deficiency as one of the molecular mechanisms of GH insensitivity.

Recent studies in children suggest that there are age-related differences in the insulin-like growth factor I (IGF-I) response to malnutrition. To extend this observation, immature 4-wk-old male rats were fasted for 3 days, fed ad libitum (control), or fed 60 or 40% of control calories (restricted) and compared with 8-wk-old young adults. Over the 3-wk study period, serum total IGF-I levels of the older rats were stable despite reduced insulin levels, whereas IGF-I increased 2.2-fold in the younger controls. With the 40% diet, younger and older rats changed body weight +1 and -1 body wt/day, respectively (P < 0.0001). The restricted younger animals reduced serum IGF-I IGF binding protein-3, acid-labile subunit, and growth hormone binding protein levels significantly more than the restricted older animals. Fasting decreased most of these parameters by 40%, serum insulin by approximately 80%, and body weight by 9%, regardless of age. We conclude that the suppression of the IGF-I system in response to chronic undernutrition, but not acute fasting, is greater in maturing than young adult rats.

Reexamination of the hexapeptide GH-releasing peptide (GHRP-6) structure/function has lead to the development of four novel classes of compound that stimulate GH release. Each class is represented as follows: a pentapeptide, G-7039; a tetrapeptide, G-7134; a pseudotripeptide, G-7502; and a rigid cyclic heptapeptide, G-7203. The EC50 values for these compounds, determined by GH dose-response curves using primary cultures of rat pituitary cells, were 0.18, 0.34, 10.6, and 0.43 nM, respectively. To demonstrate that these compounds were acting at the putative GHRP receptor, challenges were made using combinations that included GHRP-6 and GH-releasing hormone (GHRH). All four new classes further increased GH release in combination with GHRH, but not with GHRP-6. Homologous desensitization occurred after 45 min of exposure to the new compounds while the cells remained sensitive to GHRH. Somatostatin inhibited all of these compounds. Additionally, G-7039 elevated free calcium, as occurs with GHRP-6. All four classes elicited a robust GH release, a small increase in PRL, and no change in LH, FSH, ACTH, or TSH. We conclude that these novel compounds are potent and direct stimulators of pituitary GH release, with in vitro attributes that suggest mediation via a specific GHRP-like mechanism.

The hierarchy of diet components (e.g., protein, carbohydrate, vitamins, and minerals) influencing growth hormone (GH), insulin-like growth factor-I (IGF-I), and their binding proteins (BP) is not well defined. Young adult rats were fed diets for 1 mo that included low protein or 60% and 40% of carbohydrate calories. We hypothesized that levels of both hormones, their dominant BPs and liver IGF-I mRNA would fall, and that part of the mechanism for decreasing serum IGF-I would be enhanced IGFBP-3 protease activity. By day 30, caloric deprivation to 40% lowered serum GH, GHBP, IGF-I and IGFBP-3, and liver IGF-I mRNA. This was the only condition resulting in body weight loss (-15%) vs 39% gain in controls. Restriction to 60% calories had no impact on BP levels, slightly lowered IGF-I (-12%) in the face of a 95% inhibition of GH levels, while allowing a modest 9% body weight gain. Protein deprivation lowered serum GH, IGF-I and IGFBP-3, and liver IGF-I mRNA, while GHBP levels were normal. The reduced total IGF-I under these dietary conditions could not be explained by an increase in IGFBP-3 protease activity, or a decrease in the association of IGF-I with IGFBP-3 and the acid labile subunit.

Relaxin (Rlx) is best understood as a protein hormone of pregnancy that can influence pelvic and cervical connective tissue as well as uterine smooth muscle activity. Thus, it was unexpected that dense Rlx binding sites would be found in the rat cardiac atrium. To functionally characterize this finding, isolated rat atria were challenged with Rlx (0.3 to 30 ng/ml), and they responded with an increased rate (+36%) and force (+38%) of contraction Further studies in conscious normotensive and spontaneously hypertensive rats established by minipump circulating Rlx levels of about 0.5 and 5 ng/ml over 1 to 2 wks. There were significant increases in heart rate of 10-15%, with no consistent changes in blood or urine volume, water or food intake, and mean arterial pressure. We conclude that Rlx can directly stimulate rat cardiac atrial activity in vitro and cause chronotropy in vivo.

Relaxin is a member of the insulin family of polypeptides that is best known as a reproductive hormone. In an effort to elucidate the mechanism of action of relaxin we previously localized the specific binding sites of a 32P-labeled relaxin in the rat uterus and brain. These studies suggested that, in addition to its classical role in pregnancy, relaxin might have other physiological functions. In the present paper we describe the specific and high-affinity binding of relaxin to the cardiac atrium of both male and female rats. The relaxin binding could not be displaced by peptides belonging to the same family [insulin, insulin-like growth factor I (IGF-I)] or by peptides that were identified in the atrium or were known to have cardiovascular functions (atrial natriuretic peptide, angiotensin II). The dissociation constant for relaxin in the atrium was estimated to be 1.4 nM, which was similar to that found in the uterus (1.3 nM) and the brain (1.4 nM). In view of the close association of relaxin with reproduction, an experiment was also performed to compare the relaxin binding in the uterus and heart after gonadectomy and sex steroid treatment. It was found that the relaxin binding in the rat uterus was diminished by 53% overall following ovariectomy but was restored to 90% of normal levels when treated with estrogen (but not with testosterone). In contrast, the relaxin binding in the rat heart was not affected by castration or sex steroid treatment. We conclude that specific and high-affinity relaxin receptors exist in the atrium of both the male and female rat heart and that these are regulated differently than the relaxin receptors in the uterus.

Recombinant human growth hormone (HuGH) and human prolactin (HuPRL), but not GH of bovine or porcine origin, prime human neutrophils for enhanced superoxide anion (O2-) secretion. Since HuGH, but not GH of other species, effectively binds to the HuPRL receptor (HuPRL-R), we used a group of HuGH variants created by site-directed mutagenesis to identify the receptor on human neutrophils responsible for HuGH priming. A monoclonal antibody (MAb) directed against the HuPRL-R completely abrogated O2- secretion by neutrophils incubated with either HuGH or HuPRL, whereas a MAb to the HuGH-R had no effect. The HuGH variant K172A/F176A, which has reduced affinity for both the HuGH-binding protein (BP) and the HuPRL-BP, was unable to prime human neutrophils. This indicates that priming is initiated by a ligand-receptor interaction, the affinity of which is near that defined for receptors for PRL and GH. Another HuGH variant, K168A/E174A, which has relatively low affinity for the HuPRL-BP but slightly increased affinity for the HuGH-BP, had much reduced ability to prime neutrophils. In contrast, HuGH variant E56D/R64M, which has a similar affinity as wild-type HuGH for the HuPRL-BP but a lower affinity for the HuGH-BP, primed neutrophils as effectively as the wild-type HuGH. Finally, binding of HuGH to the HuPRL-BP but not to the HuGH-BP has been shown to be zinc dependent, and priming of neutrophils by HuGH was also responsive to zinc. Collectively, these data directly couple the binding of HuGH to the HuPRL-R with one aspect of functional activation of human target cells.

Growth hormone administration effects a positive nitrogen balance in part by recycling glutamine nitrogen as glutamate at the expense of ureagenesis. The study presented here focuses on the response of the isolated perfused hypophysectomized rat kidney to acute growth hormone administration during infusions of either glutamine or glutamate. Growth hormone at 50 nM acutely decreases the renal utilization of both glutamine and glutamate while enhancing reabsorption of the latter. During glutamine infusions of either 1,000 or 500 nmol/min, growth hormone markedly reduced net glutamine utilization by 55% at the high loads and reversed utilization to release at the lower load; associated with decreased glutamine utilization was reduced ammonium production and increased glutamate release. Although glutamine reabsorption was unchanged, glutamate reabsorption increased and NH4+ excretion decreased. During glutamate infusion of 180 nmol/min, growth hormone reduced glutamate utilization 66%, the residual utilization matching increased glutamate reabsorption was associated with enhanced bicarbonate reabsorption and a redistribution of NH4+ release into the urine; all three responses were eliminated by amiloride. These responses to growth hormone are consonant with reduced glutamate oxidation underlying decreased glutamine utilization and accelerated luminal Na+-H+ exchange mediating luminal transport, events that are conceivably interrelated.

Measurements of arterial pressure, heart rate, and plasma vasopressin were obtained in unanesthetized late-pregnant rats after administration of human relaxin (hRlx) alone or in conjunction with hemorrhage. Forty-two timed-pregnant rats were prepared with chronic femoral cannulas on the 17th day of pregnancy for measurements on the 19th day. In three separate sets of experiments, mean arterial pressure and heart rate were measured for 10 min before administration of 2 mg/kg hRlx, 100 micrograms/kg hRlx, or vehicle and for 20 h thereafter; plasma vasopressin was determined 20 min before and 3 min after administration of hRlx or vehicle and 20 min after performing a 15-ml/kg 3-min hemorrhage. Neither mean arterial pressure nor heart rate was significantly different among rats administered 2 mg/kg hRlx, 100 micrograms/kg hRlx, or vehicle. Plasma vasopressin was not significantly different among rats administered 2 mg/kg hRlx, 100 micrograms/kg hRlx, or vehicle. The decreases and subsequent compensatory changes in mean arterial pressure and heart rate after hemorrhage and the increases in plasma vasopressin were not significantly different among rats administered vehicle or hRlx.

The effect of growth hormone on tubular H+ secretion by the hypophysectomized and intact rat was studied in the isolated functioning kidney. Net acid secretion was estimated as the sum of HCO3- absorption plus NH+4 excretion. Kidneys from either intact or hypophysectomized rats were isolated and perfused over a 90-min time course during which either recombinant human growth hormone (GH), insulin-like growth factor-1 (IGF-1), porcine insulin, or vehicle was added; hormone response was then compared with the time controls. Compared with kidneys from intact rats, hypophysectomized rat kidneys exhibited a marked acidification defect, net H+ secretion, 13,530 +/- 600 vs. 17,860 +/- 810 (SE) nmol/ml of glomerular filtrate (GF). Administering GH (50 nM) increased net H+ secretion within 15 min in both hypophysectomized and intact groups to a maximum of 17,950 +/- 910 and 20,960 +/- 1,100 nmol/ml GF, respectively; neither insulin nor IGF-1 (50 nM) was able to mimic GH's effect. Addition of 1 mM amiloride completely abolished the GH-accelerated acid secretion and greater than 70% of the basal net acid secretion rate. Furthermore, GH-enhanced volume absorption was also abolished by amiloride, although neither NaCl nor glutamine absorption was affected. GH-accelerated acid secretion and coupled volume absorption could be observed at concentrations as low as 3.5 nM with half-maximal effect at 12 nM, which is within the range of GH concentration achieved during episodic GH surges. Finally administering GH in vivo to hypophysectomized rats enhanced net acid secretion and urinary acidification, consistent with accelerated tubular H+ secretion as one physiological expression of GH action.

Maitotoxin is a potent marine poison that mobilizes calcium in most vertebrate cell types and accelerates secretion from anterior pituitary cells. It is not known whether voltage-sensitive calcium channels or other mechanisms initiate the effects of maitotoxin on anterior pituitary cells. Changes in intracellular Ca2+ levels may also be achieved by releasing internal calcium stores via inositol trisphosphate (InsP3). Indeed, maitotoxin rapidly increased inositol phosphate accumulation in a concentration-dependent manner. Calcium channel antagonists such as nifedipine and verapamil did not block this response nor did calcium-mobilizing agents (BAYk8644, A23187) mimic this effect. These data suggest that the mechanism by which maitotoxin acts at the pituitary may include the activation of an enzyme that produces the calcium-mobilizing signal InsP3.

Prolactin binds to lymphocytes and monocytes and can modulate immune cell function. It was postulated that proteins released from activated macrophages and lymphocytes could directly influence prolactin release and thus form an endocrine control loop during infection, tumor invasion, or inflammation. This hypothesis was tested by exposing cultured rat anterior pituitary cells to murine tumor necrosis factor-alpha (TNF-alpha) and/or interferon-gamma (IFN-gamma) for 24 h before a 4-h test of cell function. Overall prolactin accumulation during this first 24 h was inhibited by TNF-alpha and markedly reduced by TNF-alpha plus IFN-gamma. In contrast, thyroid-stimulating hormone levels were unchanged in these same media. During the subsequent 4-h challenge, both cytokines reduced thyrotropin-releasing hormone-stimulated prolactin release but had no effect on inhibited prolactin release mediated by dopamine and somatostatin receptors. Cellular viability (assessed by trypan blue and chromium release assays) and prolactin cell content were unchanged after TNF-alpha or IFN-gamma treatment. We conclude that both TNF-alpha and IFN-gamma have the potential to act directly on anterior pituitary cells to slow the rate of prolactin release.

The transmembrane signaling events of GH were investigated in the liver, a major target organ of GH action. Recombinant human GH when added to freshly isolated rat hepatocytes rapidly stimulated the production of sn-1,2-diacylglycerol (DAG). The generation of DAG was biphasic with the first transient peak observed at 2 min and the second peak at 15 min (1.2-fold and 1.4-fold over control, respectively). Levels of DAG continued to be elevated above those in control cells at 30 min. The response was dose-dependent with an EC50 of 0.15 nM. Both bovine GH and rat GH, which bind to the rat GH receptor but not to the PRL receptor, also stimulated DAG production. Similarly, human PRL, which binds to the PRL but not GH receptor, stimulated DAG formation to a comparable extent. These results suggest that production of DAG may be an early signaling event mediated by hormone stimulation of both the GH and PRL receptors.

Relaxin is a member of the insulin family of polypeptide hormones and is known to exert its biological effects on various parts of the mammalian reproductive system. Biologically active human relaxin has been chemically synthesized based on the nucleotide sequence obtained from an ovarian cDNA clone. In the present study synthetic human relaxin was radiolabled by phosphorylation with cAMP-dependent protein kinase and [gamma-32P]ATP to a specific activity of 5000 Ci/mmol. The phosphorylated relaxin was purified on cation exchange high performance liquid chromatography and was shown to co-migrate with relaxin on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Mass spectrometry revealed a single phosphorylated site on the B chain of relaxin. The 32P-relaxin was able to bind to a goat anti-relaxin antibody, and this binding could be displaced by unlabeled relaxin in a concentration-dependent manner. A comparison of the concentration responses of cellular cAMP production stimulated by relaxin and phosphorylated relaxin in a primary human uterine cell line showed that phosphorylation did not affect the in vitro biological efficacy of relaxin. This made it suitable for in situ autoradiographic localization of relaxin binding sites in rat uterine, cervical, and brain tissue sections. Displacement of the binding of 100 pM 32P-relaxin by 100, 10, and 3 nM unlabeled relaxin, but not by 100 nM insulin, insulin-like growth factor-I, and an insulin-like growth factor-I analog, demonstrated the high affinity and specificity of such binding. We conclude that 32P-labeled human relaxin is biologically and immunologically active and that this novel probe binds reversibly and with high affinity to classical (e.g. uterus) and unpredicted (e.g. brain) tissues.

Prolactin cells were isolated from male rat pituitaries and studied individually with the reverse hemolytic plaque assay. Plaque area, linearly correlated with radioimmunoassayable prolactin in the culture medium, and percent lactotrophs were measured. A 20-h incubation period markedly enhanced the potency and efficacy of dopamine to inhibit prolactin release compared with an assay conducted on the day of enzymatic dispersion. Frequency histograms of plaque areas showed unimodal distributions after angiotensin II (ANG II)-stimulated prolactin release, with the mode shifting to the right. In contrast, the addition of dopamine to either basal or ANG II-stimulated lactotrophs shifted the mode to the left and decreased the overall range of plaque areas. No clear evidence for discrete subpopulations was generated with this approach; rather, an extensive range of secretory behavior was defined as a continuum, indicating a diverse repertoire of secretory potential in different lactotrophs. Furthermore, comparing lactotrophs from the lateral wings with the central region of the pituitary suggested that lateral cells were less inhibited by dopamine treatment. We conclude that this improved assay allows more precise assessment of the contribution that single lactotrophs make to the population response to dopamine and ANG II.