Search

A fluorescent derivative of GDP was prepared by the reaction of 2'-amino-2'-deoxy-GDP with fluorescamine. This derivative binds tightly (KD approximately 4.5 X 10(-8) M) to elongation factor Tu (EF-Tu) from Escherichia coli. The emission properties, including spectra, polarizations, and lifetimes, for fluorescamine-GDP free in solution and bound to EF-Tu are presented. Emission data on the fluorescamine-ethylamine conjugate are also given. A multifrequency phase and modulation lifetime study (using nine modulation frequencies over the range of 2-80 MHz) indicated that the emissions of these three systems were well characterized by single exponential decays corresponding to 1.45 ns for the fluorescamine-ethylamine derivative in buffer and to 7.74 and 11.03 ns for the fluorescamine-GDP derivative free in buffer and bound to EF-Tu, respectively. Multifrequency differential polarized phase fluorometry results indicated a rotational relaxation time of the protein-probe complex of approximately 88 ns; these data also indicated the lack of significant local motion for the probe. Addition of excess GDP to the EF-Tu-probe complex led to displacement of the fluorescamine-GDP derivative as evidenced by the change in both the steady-state and dynamic polarization values. The observed increase in fluorescence intensity upon displacement allowed us to follow the kinetics of the dissociation reaction; a dissociation rate constant of 5.0 X 10(-3) S-1 was determined. These results demonstrate the utility of this 2'-amino-2'-deoxy-GDP analogue as a probe of guanosine nucleotide dependent systems.

The intrinsic fluorescence properties of elongation factor Tu (EF-Tu) in its complexes with GDP and elongation factor Ts (EF-Ts) have been investigated. The emission spectra for both complexes are dominated by the tyrosine contribution upon excitation at 280 nm whereas excitation at 300 nm leads to exclusive emission from the single tryptophan residue (Trp-184) of EF-Tu. The fluorescence lifetime of this tryptophan residue in both complexes was investigated by using a multifrequency phase fluorometer which achieves a broad range of modulation frequencies utilizing the harmonic content of a mode-locked laser. These results indicated a heterogeneous emission with major components near 4.8 ns for both complexes. Quenching experiments on both complexes indicated limited accessibility of the tryptophan residue to acrylamide and virtually no accessibility to iodide ion. The quenching patterns exhibited by EF-Tu-GDP and EF-Tu X EF-Ts were, however, different; both quenchers were more efficient at quenching the emission from the EF-Tu x EF-Ts complex. Steady-state and dynamic polarization measurements revealed limited local mobility for the tryptophan in the EF-Tu x GDP complex whereas formation of the EF-Tu x EF-Ts complex led to a dramatic increase in this local mobility.

In response to recent papers describing traditional Micronesian and Polynesian methods of navigating at night-time in the Pacific Ocean, a simple device is offered for determining time at night in the Southern Hemisphere to within a quarter of an hour or so - assuming that one knows the approximate date and that the Southern Cross is not obscured by cloud! The device is a type of volvelle, and is based on the 'nocturnal', an instrument invented in Europe in the sixteenth century. [ABSTRACT FROM AUTHOR]

Dorsal root ganglia and sciatic nerve of the peripheral nervous sytem (PNS) were studied to examine the expression of platelet-derived growth factor (PDGF) and and PDGF alpha- and beta-receptors. High level expression of PDGF were detected in neonatal rat dorsal root ganglia and sciatic nerve. The receptors, on the other hand, were highly expressed in neonatal rat PNS. The findings indicate that PDGF play a role in the development of the PNS and in maintenance of peripheral neurons.

Background: National cardiac registries are increasingly used for informing health policy, improving the quality and cost-effectiveness of patient care, clinical research, and monitoring the safety of novel treatments. However, the quality of registries is variable. We aimed to assess the characteristics and quality of national cardiac registries across all subspecialties of cardiac care.Methods: Publications relating to national cardiac registries across six cardiac subspecialty domains were identified by searching MEDLINE and the Google advanced search function with 26 438 citations and 4812 full-text articles reviewed.Results: A total of 155 registries, representing 49 countries, were included in the study. Of these, 45 related to coronary disease or percutaneous coronary intervention, 28 related to devices, arrhythmia, and electrophysiology, 24 related to heart failure, transplant, and mechanical support, 21 related to structural heart disease, 21 related to congenital heart disease, and 16 related to cardiac surgery. Enrollment was procedure-based in 60% and disease-based in 40%. A total of 73.10 million patients were estimated to have been enrolled in cardiac registries. Quality scoring was performed using a validated registry grading system, with registries performing best in the use of explicit variable definitions and worst in assessment of data reliability. Higher quality scores were associated with government funding, mandated enrollment, linkage to other registries, and outcome risk adjustment. Quality scores and number of registries within a country were positively correlated with each other and with measures of national economic output, health expenditure, and urbanization.Conclusions: There has been remarkable growth in the uptake of national cardiac registries across the last few decades. However, the quality of processes used to ensure data completeness and accuracy remain variable and few countries have integrated registries covering multiple subspecialty domains. Clinicians, funders, and health policymakers should be encouraged to focus on the range, quality, and integration of these registries. Registration: URL: https://www.crd.york.ac.uk/prospero; Unique identifier: CRD42020204224. [ABSTRACT FROM AUTHOR]

Introduction: Amlodipine overdoses have significant cardiac toxicity and are difficult to treat. Methylene blue has potential as a treatment for overdoses.Methods: A randomized controlled study of methylene blue as a treatment for amlodipine toxicity was conducted in C57Bl/6 mice. A baseline echocardiography was followed by gavage administration of amlodipine (90 mg/kg). Five minutes after gavage, animals received either vehicle solution (controls) or methylene blue (20 mg/kg) by intra-peritoneal injection. Animals were continuously monitored, and cardiac parameters were acquired every 15 min up to two hours.Results: Only 50% of control animals survived to the two-hour endpoint compared to 83% that received methylene blue. Amlodipine delivery induced significant reduction in left ventricular ejection fraction (EF), fractional shortening (FS), stroke volume (SV), and cardiac output (CO) in the vehicle treated animals relative to animals in the treatment group (p < 0.05 vehicle versus Methylene blue for EF, FS, SV, CO, and HR).Discussion: The amlodipine dose induced cardiotoxicity that were effects were more pronounced in the untreated group. 50% vehicle controls quickly progressed into heart failure (within 90 min of exposure) and did not survive the two h observation endpoint. Distinctly, only one animal from the Methylene blue treatment group did not survive (83% survival) the study. Additionally, the surviving animals from the Methylene blue group displayed significantly higher ejection fraction, fractional shortening, stroke volume, and cardiac output compared to vehicle group, indicating that methylene blue preserved cardiac function.Conclusion: In this mouse model of amlodipine overdose, methylene blue decreased cardiac toxicity. [ABSTRACT FROM AUTHOR]

Introduction Increased risk of opportunistic infection—e.g., varicella zoster infection—secondary to therapies is a cause of morbidity in inflammatory bowel disease [IBD] patients. The UK vaccination schedule does not include varicella immunisation. We aimed to evaluate the varicella screening and immunisation programme in a paediatric IBD population. Methods Data regarding IBD diagnosis, varicella status, and consequent immunisations/treatment interventions were collected retrospectively from the records of patients diagnosed with IBD over a 10-year period [2009–2018]. Results In all, 520 IBD patients were diagnosed; 505/520 [97%] had varicella testing; 46/505 [9%] were naïve. Of 501 patients, 391[78%] were tested before or within 7 days of diagnosis; this increased in the second 5-year period compared with the first (229/268 [85%] versus 162/233 [70%]; p  <0.00001). Median diagnosis age of naïve patients was lower [8.3 years versus 12.8 years; p  <0.00001]. Where vaccination was feasible, 21/31 [68%] had two and 7/31 [23%] one immunisation. Prednisolone induction led to lower rates of vaccination (5/13 [39%] versus 23/33 [70%] for other induction therapies; p  =0.02). Of 28 vaccinated patients, 5 [18%] had suspected breakthrough varicella; and 6/18 [33%] unimmunised patients required post-exposure prophylaxis or treatment for varicella. Immunisation was associated with a decrease in patients requiring post-exposure prophylaxis (0/28 [0%] versus 5/18 [28%]; p  =0.0006) and varicella-related hospital admission (1/28 [4%] versus 4/18 [22%]; p  =0.01). Conclusions High rates of varicella screening and immunisation within a PIBD population are possible, resulting in a reduction in hospital admissions for varicella treatment. Varicella immunisation may be of increasing importance within the PIBD population with the emergence of novel therapeutic strategies. [ABSTRACT FROM AUTHOR]