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Background: Parallel imaging is widely adopted to accelerate functional MRI (fMRI) data acquisition, through various strategies that involve multi-channel receiver coils. However, the non-uniform spatial sensitivity of multi-channel receiver coils may introduce unwanted artifacts when head motion occurs during the few-minute long fMRI scans. Although prospective correction provides a promising solution for alleviating the head motion artifacts in fMRI, the relative position of the fixed multi-channel receiver coils moves in the moving reference frame, potentially resulting in artifactual signal., New Method: We used numerical simulations to investigate this effect on fMRI using two parallel imaging schemes: sensitivity encoding (SENSE) and generalized autocalibrating partially parallel acquisitions (GRAPPA) with acceleration factors 2 and 4, towards characterizing the regime over which parallel-imaging fMRI with prospective motion correction will benefit from updating coil sensitivities to reflect relative positional change between the head and the receiver coil. Moreover, six subjects were scanned with acceleration factors 2 and 4 while performing a simple finger-tapping task with and without overt head motion., Results: Updating coil sensitivities showed significant positive impact on standard deviation and activation maps in presence of overt head motion compared to that obtained with no overt head motion., Comparison With Existing Methods: The parallel imaging fMRI with updated coil sensitivity maps were compared to that with the coil sensitivity maps acquired at the reference position., Conclusions: Head motion in relation to a fixed multi-channel coil can adversely affect the quality of parallel imaging fMRI data; and updating coil sensitivity map can mitigate this effect., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Background and Purpose: Our goal was to develop a novel technique for measuring a small number of localized spectra simultaneously and in a time-efficient manner., Materials and Methods: Using appropriate radiofrequency pulses, the magnetization from multiple voxels is excited simultaneously and then separated (reconstructed) by using the individual coil-sensitivity profiles from a multichannel receiver coil. Because no gradients are used for k-space encoding, constrained source space MR spectroscopy provides a time advantage over conventional spectroscopic imaging and an improved signal-to-noise ratio per square root of unit time over single-voxel spectroscopy applied at each successive location. In the present work, we considered prototype application of constrained source space MR spectroscopy for 2 voxels., Results: Experimental data from healthy volunteers and simulation results showed that constrained source space MR spectroscopy is effective at extracting 2 independent spectra even in the challenging scenario of the voxels being closely spaced. Also, from 6 patients with various types of brain cancer we obtained 2-voxel constrained source space MR spectroscopy data, which showed spectra of clinical quality in half the time required to perform successive single-voxel MR spectroscopy., Conclusions: Constrained source space MR spectroscopy provides clinical quality spectra and could be used to probe multiple voxels simultaneously in combination with Hadamard encoding for further scan-time reductions., (© 2015 by American Journal of Neuroradiology.)

The percutaneous absorption of tritiated water ((3)H(2)O) through sulfur mustard (SM) exposed abdominal pig skin was measured using in vitro Franz-type static diffusion cells. The barrier function to water permeation following exposure to liquid SM for 8 min and excision 3h later did not change significantly. A small, but statistically significant difference (P<0.05) in steady state penetration (Jss), permeability coefficient (Kp) and lag time (t(L)) of (3)H(2)O was observed between fresh skin and skin stored frozen (-20 °C) for up to two weeks. Steady-state penetration and Kp values were significantly higher (P < 0.05) in skin stored frozen compared with fresh skin. Fresh naïve skin had an average Kp of 1.65 × 10(-3) cm h(-1), whereas frozen naïve skin was 2.04 × 10(-3) cm h(-1). Fresh SM exposed skin had a mean Kp of 1.72 × 10(-3) cm h(-1), whereas frozen SM exposed skin was 2.31 × 10(-3) cm h(-1). Lag times were also shorter (P<0.05) in skin that had been stored frozen. Frozen, SM-exposed porcine abdominal skin may be used for in vitro penetration studies, but effects of treatment and storage on the barrier layer should be taken into account., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

To better understand the contributions of effort on cortical activation associated with motor tasks, healthy participants with varying capacities for isolating the control of individual finger movements performed tasks consisting of a single concurrent abduction of all digits (Easy) and paired finger abduction with digits 2 and 3 abducted together concurrently with digits 4 and 5 (Hard). Brain activity was inferred from measurement using functional magnetic resonance imaging. Effort was measured physiologically using electrodermal responses (EDR) and subjectively using the Borg scale. On average, the Borg score for the Hard task was significantly higher (p=0.007) than for the Easy task (2.9+/-1.1 vs. 1.4+/-0.7, respectively). Similarly, the average normalized peak-to-peak amplitude of the EDR was significantly higher (p=0.002) for the Hard task than for the Easy task (20.4+/-6.5% vs. 12.1+/-4.9%, respectively). The Hard task produced increases in sensorimotor network activation, including supplementary motor area, premotor, sensorimotor and parietal cortices, cerebellum and thalamus. When the imaging data were subdivided based on Borg score, there was an increase in activation and involvement of additional areas, including extrastriate and prefrontal cortices. Subdividing the data based on EDR amplitude produced greater effects including activation of the premotor and parietal cortices. These results show that the effort required for task performance influences the interpretation of fMRI data. This work establishes understanding and methodology for advancing future studies of the link between effort and motor control, and may be clinically relevant to sensorimotor recovery from neurologic injury.

Echo-planar imaging (EPI) -based diffusion tensor imaging (DTI) is particularly prone to spike noise. However, existing spike noise correction methods are impractical for corrupted DTI data because the methods correct the complex MRI signal, which is not usually stored on clinical MRI systems. The present work describes a novel Outlier Detection De-spiking technique (ODD) that consists of three steps: detection, localization, and correction. Using automated outlier detection schemes, ODD exploits the data redundancy available in DTI data sets that are acquired with a minimum of six different diffusion-weighted images (DWIs) with similar signal and noise properties. A mathematical formulation, describing the effects of spike noise on magnitude images, yields appropriate measures for an outlier detection scheme used for spike detection while a normalization-dependent outlier detection scheme is used for spike localization. ODD performs accurately on diverse DTI data sets corrupted by spike noise and can be used for automated control of DTI data quality. ODD can also be extended to other MRI applications with data redundancy, such as dynamic imaging and functional MRI., ((c) 2009 Wiley-Liss, Inc.)

If the ureter becomes blocked, the resultant increased pressure may be relieved by inserting a double-J stent (a polymer tube, usually punctuated with holes). A major clinical problem associated with stent use is reflux (retrograde flow of urine from the bladder to the kidney), which may result in infections, scarring, and even renal failure. We develop a mathematical model, treating the ureter as an elastic tube and the stent as a permeable rigid tube within it. We investigate how the number of holes in the stent wall affects the total amount of reflux that occurs when bladder pressure rises, by considering the limits of a highly-permeable stent, and an impermeable stent. We find that, in the scenarios we consider, the highly-permeable stent gives rise to less total reflux than the impermeable one.

* The working group was set up by the Veterinary Products Committee in response to current concern in both the public domain and in the scientific community about possible health risks related to the routine vaccination of cats and dogs. The working group concluded that vaccination plays a very valuable role in the prevention and control of the major infectious diseases in cats and dogs. Although adverse reactions to vaccination, including lack of efficacy, occasionally occur, the working group concluded that the overall risk/benefit analysis strongly supports their continued use. * Although for some diseases there is evidence of a longer duration of immunity following vaccination than the one year which is typically recommended on the product literature, there is currently insufficient information to propose revaccination intervals other than those proposed by the manufacturer and approved by the regulatory process. * Notwithstanding this, in view of the occasional occurrence of adverse reactions, the working group recommends that the product literature indicates that the regime for booster vaccinations is based on a minimum duration of immunity rather than a maximum. The working group further recommends that the product literature should state that a risk/benefit assessment should be made for each individual animal by the veterinary surgeon in consultation with the owner with respect to the necessity for each vaccine and the frequency of its use. * The evidence suggests that cats appear to be susceptible to the occasional development of sarcomas at sites of injection and there is some further evidence to suggest that, although other products may be involved, this may be more associated with the use of vaccines containing aluminium-based adjuvants. The working group therefore recommends that a generic warning to this effect should appear on the product literature for all feline vaccines administered by injection. The working group also highlighted the need for professional and educational bodies in the UK to bring to the attention of veterinary practitioners appropriate methods for prevention, diagnosis and treatment of this serious condition. * The working group considered in depth the monitoring of adverse reactions, including the advantages and disadvantages of surveillance schemes. A range of options for carrying out further epidemiological (analytical) studies was also considered. However, the working group emphasised that surveillance schemes, and the UK Veterinary Medicines Directorate (VMD) Suspected Adverse Reaction (SAR) Surveillance Scheme in particular, provided a very valuable resource. The large database within the VMD scheme (collected since 1985) was analysed as part of this report. Figures were derived in terms of incidence (reporting rate) of certain clinical signs per 10,000 doses, and risk factors as identified by statistical analysis. However, due to a number of constraints, the analysis was not fully comprehensive and the interaction of possible risk factors was not determined. * Product-related control charts were developed in order to detect changes in incidence rates of adverse reactions (per 10,000 doses sold) both within and between different vaccines. Such charts provide a powerful way to detect changing trends in incidence and, when used in conjunction with product characteristics, they may identify possible causes. In general, the data showed that the incidence of adverse reactions to cat and dog vaccines per 10,000 doses of product sold was relatively low. Although under-reporting is a feature of such surveillance schemes, it does appear that, overall, vaccination of cats and dogs should be considered safe and effective. * Finally, the working group was conscious, while preparing this report, of the extensive media coverage that has been given to the issue of the safety of human vaccines, in particular the mumps, measles and rubella (MMR) vaccine. The working group emphasises that the conclusions and recommendations included in this report relate only to the vaccines used in cats and dogs. The issues identified are specific to the diseases and species examined and no attempt should be made to draw analogous conclusions in relation to vaccines administered to humans.

A new class of devices are described for improving investigation of somatosensory neuronal activation using fMRI. Dubbed magnetomechanical vibrotactile devices (MVDs), the principle of operation involves driving wire coils with small oscillatory currents in the large static magnetic field inherent to MRI scanners. The resulting Lorentz forces can be oriented to generate large vibrations that are easily converted to translational motions as large as several centimeters. Representative data demonstrate the flexibility of MVDs to generate different well-controlled vibratory and tactile stimuli to activate special proprioceptive and cutaneous somatosensory afferent pathways. The implications of these data are discussed with respect to the literature on existing devices for producing sensorimotor activation, as well as expanding the scope of current fMRI investigations., (Copyright 2001 Wiley-Liss, Inc.)

In functional magnetic resonance imaging (fMRI) studies, long experiment times and small intensity changes associated with brain activation frequently lead to image artifacts due to head motion. Methods to minimize and correct for head motion by restraint, fast imaging, and retrospective image registration are typically combined but do not completely solve the problem, particularly for specific patient populations. As an initial step toward optimizing future designs of head restraints and improving motion correction techniques, the head motion characteristics of groups of stroke subjects, age-matched controls, and young adults were investigated with the aid of an MR simulator and a highly accurate position tracking system. Position measurements were recorded during motor tasks involving either the hand or the foot. Head motion was strongly dependent on the subject group and less upon the task conditions based on ANOVA calculations (P < 0.05). The stroke subjects exhibited approximately twice the head motion compared to that of age-matched controls, and the latter's head motion was about twice that of young adults. Moreover, the range of head motion in stroke subjects over all tasks was approximately 2 +/- 1 mm, with the motion occurring predominantly as translation in the superior-inferior direction and pitch rotation (nodding). These results lead to several recommendations on the design of fMRI motor experiments and suggest that improved motion correction strategies are required to examine such patient populations comprehensively., (Copyright 2001 Academic Press.)

Objective: To estimate the prevalence of Huntington disease (HD) in New South Wales on Australian Census Day (6 August) 1996., Design: Survey of records of the Huntington Disease Service and major hospitals, and of neurologists, psychiatrists, clinical geneticists and genetic counsellors., Subjects and Setting: All patients in NSW who, on Census Day 1996, either had a definite diagnosis of HD (motor signs of chorea or ataxia and family history of HD or positive DNA test result) or would have had signs and later received a definite diagnosis (assessed 1 April 1997 to 1 July 1999)., Main Outcome Measures: Prevalence (HD patients per 100,000 population); patient characteristics; year and basis of diagnosis., Results: 380 patients with definite HD were identified, giving a prevalence of HD in NSW in 1996 of 6.29 per 100,000 population (95% CI, 5.68-6.96). A third of HD patients were aged 60 years or older. Diagnosis was confirmed by DNA testing for 171 patients (45%), including 30 (8%) with no recorded family history. Average numbers of new diagnoses per year were 11.8 (1984-1988), 21.8 (1989-1993) and 28.6 (1994-1998). Estimated number of people with a 50% risk of inheriting the HD mutation was 25.2 per 100,000 population. Estimated incidence of HD in 1996 was 0.65 per 100,000 population., Conclusions: Prevalence of HD in NSW is similar to estimated prevalence in other Australian and Western populations. Increasing numbers of cases are being diagnosed, and the 18 chronic care beds currently designated for HD patients in NSW are unlikely to be sufficient.

To characterize changes in the MR parameters of tissues due to thermal coagulation, a series of T(1), T(2), diffusion, and magnetization transfer measurements were performed on a variety of ex vivo tissues: murine slow twitch skeletal muscle, murine cardiac muscle, murine cerebral hemisphere, bovine white matter, murine liver tissue, bovine retroperitoneal adipose tissue, hen egg white, human prostate and human blood. Standardized heat treatments were performed for each tissue type, over the temperature range from 37 degrees C to 90 degrees C. For all tissues, changes in each MR measurement resulting from thermal coagulation were observed above a threshold temperature of approximately 60 degrees C. These changes are explained based on biophysical knowledge of thermal damage mechanisms and the MR properties of normal tissues, and are particularly relevant for interpreting the changes in image contrast that are observed when MRI is used to guide and monitor thermal coagulation therapy procedures. Magn Reson Med 42:1061-1071, 1999., (Copyright 1999 Wiley-Liss, Inc.)

With use of an established physical model, numeric simulations were performed to evaluate current imaging protocols for the two primary applications of magnetization transfer: cerebral magnetic resonance angiography and neuroimaging of white matter disease. The authors found that the current technique is appropriate in the former but suboptimal in the latter. Further clinical investigations could potentially improve magnetization protocols for neuroimaging.

Focused ultrasound heating of ex vivo bovine kidney and liver was monitored using magnetic resonance imaging (MRI) to investigate the quantitative relationship between time-dependent temperature elevations and altered contrast in MR images due to thermal coagulation. Proton resonance frequency shift MR thermometry was performed during heating at 10 sec intervals (single-slice fast spoiled GRASS [FSPGR], theta/TE/TR 30 degrees/11/39 msec, field of view 8 cm, 256 x 256, 3 mm slice thickness, 1 NEX); post-heating MR images were T1-weighted (3D-FSPGR, theta/TE/TR 60 degrees/25/200 msec, 1 mm slice thickness, 3 NEX). Analysis of the resulting temperature versus time data using the Arrhenius relationship and a simple binary discrimination model showed that thermal coagulation occurred with heating at approximately 54 degrees C for 10 sec in both tissues and could be predicted with approximately 625 microm spatial resolution. These results suggest that quantitative MR guidance of thermal coagulation therapy is feasible, and they provide information useful for designing future investigations in vivo.

Detailed measurements of the T1-weighted, T2-weighted, and MT-weighted signal were performed for ex vivo muscle samples heated to various temperatures for different times. Consistent, monotonic increases in signal intensity were observed with progressive thermal coagulation, corresponding to an increase in T2 relaxation time and an increase in MT-weighted signal for temperatures above 60 degrees C. The relationship for T1 relaxation was more complex, showing a decrease in T1 relaxation from 40 to 60 degrees C and an increase above 60 degrees C. These techniques provide a more direct measure of tissue thermal coagulation than that provided by MR thermometry and suggest MR imaging strategies for the optimization and monitoring of thermal coagulation therapy protocols that create thermal damage in target tissues.

The magnetic resonance absorption spectrum, T1 and T2 relaxation time distributions, and magnetization transfer properties of ex vivo breast tissue have been characterized at 1.5 T and 37 degrees C. The fraction of fibroglandular tissue within individual tissue samples (n = 31) was inferred from the tissue volumetric water content obtained by integration of resolvable broad-line fat and water resonances. The spectroscopically estimated water content was strongly correlated with that extracted enzymatically (Pearson correlation coefficient 0.98, P < < 0.01), which enabled the assignment of principal relaxation components for fibroglandular tissue (T2=0.04+/-0.01, T1=1.33+/-0.24 s), and for adipose tissue (T2=0.13+/-0.01, T1=0.23+/-0.01 s, and T2=0.38+/-0.03, T1=0.62+/-0.16 s). Th e relaxation components for fibroglandular tissue exhibited strong magnetization transfer, whereas those for adipose tissue showed little magnetization transfer effect. These results ultimately have applicability to the optimization of clinical magnetic resonance imaging and research investigations of the breast.

To summarize and compare magnetization transfer data from biological tissues, a method was developed to extract the average absorption lineshape of the semi-solid pool directly from magnetization transfer experimental data along with the four other parameters that characterize the two-pool model of exchange. Magnetization transfer data for several biological tissues were analyzed using this method and the resulting "flexible" lineshapes were compared with super-Lorentzian and "Kubo-Tomita" lineshapes. The use of flexible lineshapes noticeably improves the fit of the two-pool model to the data. The derived flexible lineshapes of all the tissues analyzed are physically realistic and show remarkably consistent behavior.

MR techniques providing accurate measurement of relative volumetric water content and multicomponent T2 relaxation times from a large volume of interest, have been implemented for characterization of breast tissue in vivo. In a sequence of 20-s breath-holds, data are obtained from much of the breast volume while suppressing signal from the chest wall and torso. Relative water content of each breast is calculated from one-dimensional fat and water profiles obtained using a hybrid two-point Dixon method (TE/TR = 17/5000 ms). Multicomponent T2 relaxation measurements are calculated from T2 decay curves obtained using a CPMG train of rectangular pulses (TE/TR = 8/5000 ms, 140 echoes) preceded by saturation pulses to localize longitudinal magnetization spatially. These techniques, validated in phantoms and human volunteers, are suitable for quantitative study of breast tissue in vivo, and in particular to investigate the potential role of MR for assessment of breast cancer risk.

Monte Carlo simulations were performed to determine whether the multicomponent T2 distribution of tissue can be estimated accurately from T2 decay data acquired in vivo. Simulated data were generated for white matter, fast twitch muscle, and breast tissue. The signal-to-noise ratio, number of data samples, and minimum echo time were varied from the experimental conditions currently achievable with MRI to those achievable for in vitro experiments. Data were fitted by a distribution of T2 values using the T2NNLS algorithm, and statistics characterizing the estimated T2 components were determined. Current MRI techniques were found to provide conditions insufficient for accurate multicomponent T2 analysis on a pixel-by-pixel basis. However, volume localization methods that measure T2 decay from a large volume of interest have potential for this analysis. These results illustrate a general framework for development of new techniques to measure T2 decay accurately in vivo.

The duration of effect of levodopa has been reported by some authors to be shorter in fluctuating parkinsonian patients with long standing disease than in stable patients. Other authors report no difference in the two groups of patients. We assessed motor fluctuations and response duration in 15 Parkinson's disease patients. Three patterns of response were observed: deterioration within one day on placebo and marked fluctuations on levodopa; deterioration after one day on placebo and moderate fluctuations on levodopa; no deterioration during 3 days of placebo and no fluctuations on levodopa. One patient who did not deteriorate or fluctuate did both when restudied 12 years later. This study confirms that, in addition to the short duration response to a single dose of levodopa, there is a long duration response to levodopa which is lost as the disease progresses. Loss of this long duration response to levodopa may be a key factor in the emergence of fluctuations in Parkinson's disease.

An autopsy was performed on a 72-y-old Caucasian female who had received a carotid artery injection of thorium dioxide in 1953. The body was dissected in such a manner as to provide for radiobiological evaluation as well as to determine histologically the distribution of Thorotrast in the tissues and its complications. Thorotrast was identified within the liver, spleen, lymph nodes, bone marrow, and surrounding the right carotid artery (the injection site). The cause of death was gastric hemorrhage complicating pancytopenia secondary to refractory anemia with excess of blasts (myelodysplastic syndrome).

Thirty subjects complaining of a decrease in soft contact lens wearing time secondary to dry eye discomfort were selected for our study. All subjects were between the ages of 25 and 40 and selected on the basis of subjective dry eye complaints alone. Five of these subjects had punctum that were too small to facilitate plug placement and were therefore eliminated from further study. Removable silicone punctal plugs were monocularly placed in the lower puncta of the remaining 25 subjects. In an attempt to minimize the placebo effect, both puncta were manipulated equally prior to plug insertion and the patient was not told which eye had been treated. Three weeks following plug placement, blind data assessment showed that 18 of the 25 subjects reported, on average, a 34.6 percent increase in comfortable contact lens wearing time in the treated eye. Three subjects reported no subjective increase in comfortable wearing time and four subjects were unable to tolerate the punctal plugs for more than a week due to plug-related discomfort. Problematic epiphora was not reported in any of the treated eyes. Reversible inferior punctal occlusion, when tolerated, can significantly increase comfortable contact lens wearing time while still allowing enough drainage from the upper puncta to prevent epiphora.

Objective: To compare the effects of single doses of oral levodopa, subcutaneous apomorphine and sublingual apomorphine., Design: Single-blind placebo-controlled comparative study., Setting: Subjects were admitted as day patients to the neurology ward., Patients: Five patients with idiopathic Parkinson's disease and "end of dose deterioration" entered and completed the study., Interventions: Patients were given domperidone (20 mg by mouth three times a day) to prevent nausea and apomorphine (1-3 mg by subcutaneous injection), apomorphine in glycerol (10-30 mg sublingually) or their usual levodopa regimen., Main Outcome Measures: Efficacy, time to onset of effect and duration of effect of oral levodopa, subcutaneous apomorphine and sublingual apomorphine. Tremor amplitude and timed pegboard and gait tasks were used as objective indices of clinical state., Results: Maximal efficacy of the three treatments was comparable (P = 0.28-0.99). Mean latency to onset of effect of both formulations of apomorphine was less than that of levodopa (P = 0.022-0.048) but so was the duration of effect (P = 0.044-0.049)., Conclusions: Sublingual apomorphine may be a convenient means of rapidly terminating "off" periods associated with long term levodopa therapy.

A 58-year-old man had a left jugulodigastric mass, which was found to be cystic by computed tomography, and no evidence of other lesions. Grossly and histologically, the surgical specimen consisted of a thin-walled, fluid-filled cyst lined by squamous epithelium that varied in appearance from benign to invasive squamous cell carcinoma. The findings supported a differential diagnosis of branchial cleft carcinoma (BCCA) versus cystic growth of a lymph node metastasis from an occult malignancy. On this basis, guided biopsies of the upper aerodigestive tract were performed, with strong suspicion of a tonsillar bed lesion. Microscopic examination revealed the primary tumor within tissue excised from the left tonsillar fossa. Comparison of the current case with cases of BCCA and cystic tonsillar metastases from the literature illustrated the potential pitfalls in rendering a diagnosis of BCCA. Recognition of this lesion as a distinctive clinical variant of oropharyngeal carcinoma is warranted.

A modification of the USP HPLC method [ United States Pharmacopeia XXII, pp. 1444-1446] for the assay of the purity of verapamil hydrochloride has been evaluated for the determination of the drug content and related compounds in drug raw material. The method enables the resolution of 16 related compounds from the parent drug and, in most cases, from each other. The minimum quantifiable amount for most related compounds is less than 0.05%. Six drug raw material samples are analysed and the total impurities found to be 0.3% or less. All drug assay values were within the USP recommended limits of 99.0-100.5%.

A high-performance liquid chromatographic (HPLC) method has been developed for the determination of famotidine and related compounds in drug raw materials and formulations. The minimum detectable amount of the available related compounds is less than 0.02% and the minimum quantifiable amount is less than 0.1%. Famotidine impurity levels were between 0.5 and 2.5% in raw materials. 0.44% in one tablet sample and about 3% in an IV solution, allowing for stabilizers.

Ten percent of North American blacks have one of four forms of sickle cell disease. Eight to nine percent have sickle cell trait (AS disease); One-half to one percent have SThal disease; Four-tenths percent have SS disease; One-tenth to three-tenths percent have SC disease. The SC and SThal forms present with the most frequent and severe ocular manifestations, including proliferative and non-proliferative retinopathies. Approximately 1% of the black population is at risk for serious ocular complications. The purpose of this paper is to familiarize the reader with the retinal signs, transmissibility, and pathophysiology of a high incidence disease. Early recognition and referral results in prolonged visual function if proper therapy is undertaken. A brief overview of ocular therapies is included.

Senile macular choroidal degeneration (SMCD) is responsible for the majority of cases of new central vision loss in the over-fifty population. It is also the single largest cause of legal blindness in the United States. Choroidal neovascular membranes are frequently associated with SMCD and initiate a disciform process that may lead to profound central vision loss. Clinically, it is very difficult to visualize actual new vessel membranes without the aid of rapid sequence fluorescein angiography; various clinical signs, however, are indicative of their presence. Recognition of choroidal neovascular membranes is important; certain membranes lend themselves to photocoagulation by the retinal specialist. This treatment may be successful in preventing further severe and permanent visual loss in some individuals. The purpose of this paper is to discuss the mechanisms of disciform macular degeneration, as well as the clinical signs important to the recognition of choroidal neovascular membranes.

Two freshwater chlorophytes, Chlorella vulgaris and Scenedesmus obliquus, were grown in inorganic carbon-limited continuous cultures in which HCO(3) was the sole source of inorganic carbon. The response of the steady-state growth rate to the external total inorganic carbon concentration was reasonably well described by the Monod equation; however, the response to the internal nutrient concentration was only moderately well represented by the Droop equation when the internal carbon concentration was defined on a cellular basis. The Droop equation was totally inapplicable when total biomass (dry weight) was used to define internal carbon because the ratio of carbon to dry weight did not vary over the entire growth rate spectrum. In batch cultures, maximum growth rates were achieved at the CO(2) levels present in atmospheric air and at HCO(3) concentrations of 3 mM. No growth was observed at 100% CO(2). Both nitrogen uptake and chlorophyll synthesis were tightly coupled to carbon assimilation, as indicated by the constant C/N and C/chlorophyll ratios found at all growth rates. The main influence of inorganic carbon limitation appears to be not on the chemical structure of the biomass, but rather on cell size; higher steady-state growth rates lead to bigger cells.