To bud or not to bud: the RET perspective in CAKUT

Congenital anomalies of the kidneys or lower urinary tract (CAKUT) encompass a spectrum of anomalies that result from aberrations in spatio-temporal regulation of genetic, epigenetic, environmental, and molecular signals at key stages of urinary tract development. The Rearranged in Transfection (RET) tyrosine kinase signaling system is a major pathway required for normal development of the kidneys, ureters, peripheral and enteric nervous systems. In the kidneys, RET is activated by interaction with the ligand glial cell line-derived neurotrophic factor (GDNF) and coreceptor GFRα1. This activated complex regulates a number of downstream signaling cascades (PLCγ, MAPK, and PI3K) that control proliferation, migration, renewal, and apoptosis. Disruption of these events is thought to underlie diseases arising from aberrant RET signaling. RET mutations are found in 5–30 % of CAKUT patients and a number of Ret mouse mutants show a spectrum of kidney and lower urinary tract defects reminiscent of CAKUT in humans. The remarkable similarities between mouse and human kidney development and in defects due to RET mutations has led to using RET signaling as a paradigm for determining the fundamental principles in patterning of the upper and lower urinary tract and for understanding CAKUT pathogenesis. In this review, we provide an overview of studies in vivo that delineate expression and the functional importance of RET signaling complex during different stages of development of the upper and lower urinary tracts. We discuss how RET signaling balances activating and inhibitory signals emanating from its docking tyrosines and its interaction with upstream and downstream regulators to precisely modulate different aspects of Wolffian duct patterning and branching morphogenesis. We outline the diversity of cellular mechanisms regulated by RET, disruption of which causes malformations ranging from renal agenesis to multicystic dysplastic kidneys in the upper tract and vesicoureteral reflux or ureteropelvic junction obstruction in the lower tract.     

Experimental Keratitis Due to Pseudomonas aeruginosa: Model for Evaluation of Antimicrobial Drugs

An improved method for experimental keratitis due to Pseudomonas aeruginosa is described. Essential features of the method are use of inbred guinea pigs, intracorneal injection of bacteria, subconjunctival injection of antibiotics, “blind” evaluation of results, and statistical analysis of data. Untreated ocular infections were most severe 5 to 7 days after infection. Sterilized bacterial suspensions caused no abnormalities on day 5. Tobramycin and polymyxin B were more active than gentamicin against two strains of Pseudomonas. This model is suitable for many types of quantitative studies on experimental keratitis.     

Chronic benzodiazepine administration potentiates high voltage-activated calcium currents in hippocampal CA1 neurons

Signs of physical dependence as a consequence of long-term drug use and a moderate abuse liability limit benzodiazepine clinical usefulness. Growing evidence suggests a role for voltage-gated calcium channel (VGCC) regulation in mediating a range of chronic drug effects from drug withdrawal phenomena to dependence on a variety of drugs of abuse. High voltage-activated (HVA) calcium currents were measured in whole-cell recordings from acutely isolated hippocampal CA1 neurons after a 1-week flurazepam (FZP) treatment that results in withdrawal-anxiety. An approximately 1.8-fold increase in Ca(2+) current density was detected immediately after and up to 2 days but not 3 or 4 days after drug withdrawal. Current density was unchanged after acute desalkyl-FZP treatment. A significant negative shift of the half-maximal potential of activation of HVA currents was also observed but steady-state inactivation remained unchanged. FZP and diazepam showed use- and concentration-dependent inhibition of Ca(2+) currents in hippocampal cultured cells following depolarizing trains (FZP, IC(50) = 1.8 microM; diazepam, IC(50) = 36 microM), pointing to an additional mechanism by which benzodiazepines modulate HVA Ca(2+) channels. Systemic preinjection of nimodipine (10 mg/kg), an L-type (L)-VGCC antagonist, prevented the benzodiazepine-induced increase in alpha-amino-3-hydroxy-5-methylisoxasole-4-propionic acid receptor (AMPAR)-mediated miniature excitatory postsynaptic current in CA1 neurons 2 days after FZP withdrawal, suggesting that AMPAR potentiation, previously linked to withdrawal-anxiety may require enhanced L-VGCC-mediated Ca(2+) influx. Taken together with prior work, these findings suggest that enhanced Ca(2+) entry through HVA Ca(2+) channels may contribute to hippocampal AMPAR plasticity and serve as a potential mechanism underlying benzodiazepine physical dependence.     

In vitro antimicrobial activity of some cyclic hydroxamic acids and related lactams.

Against Enterobacter aerogenes 13048, Serratia marcescens 13880, Klebsiella pneumoniae 10031, Pseudomonas aeruginosa 10145, Escherichia coli 9723, Lactobacillus casei 7469, Lactobacillus plantarum 8014, Leuconostoc dextranicum 8086, and Streptococcus faecalis 8043, the mean minimal inhibitory concentrations of three cyclic hydroxamic acids, 3-amino-3,4-dihydro-1-hydroxycarbostyril, the 6-chloro analog, and the 7-chloro analog, were 0.6, 0.6, and 0.2 micrograms/ml, and those of the corresponding lactams, 3-amino-3,4-dihydrocarbostyril, the 6-chloro analog, and the 7-chloro analog, were 60, 60, and 6 micrograms/ml, respectively. Under the same assay conditions the mean minimal inhibitory concentrations of chloramphenicol and kanamycin were both 2 micrograms/ml. In addition, the cyclic hydroxamic acids but not the lactams inhibited the growth of Candida albicans at minimal inhibitory concentrations ranging from 20 to 200 micrograms/ml, at pH 7, as compared with that of amphotericin B, at 2 micrograms/ml.     

Nurse-based evaluation of point-of-care assays for glycated haemoglobin

BACKGROUND: Various devices are now available to measure glycated haemoglobin (HbA1c) outside of the laboratory. The aim of this study was to assess the performance of these point-of-care instruments in the hands of non-laboratory trained personnel. METHODS: Two nursing staff tested samples from patients attending a diabetes research clinic using the following point-of-care devices for HbA1c-Metrica A1C Now, Bayer DCA 2000, Cholestech GDX and Axis-Shield Nycocard HbA1c. In addition they performed regular analysis of quality control samples. The effects on analytical performance of multiple operators as well as laboratory-trained staff, were also assessed. All measurements were compared to a boronate-affinity HPLC method in the central laboratory. RESULTS: The mean HbA1c difference of the point-of-care devices compared to the laboratory reference method ranged from -0.31% to +0.39%. Only the DCA device had a between batch imprecision of less than 5%. The analytical performance obtained by laboratory staff was similar to nursing staff for 3 devices and better for the Nycocard device. CONCLUSIONS: On the basis of the results obtained by nursing staff, only the DCA of the devices tested, can be recommended for measurement of HbA1c outside of the laboratory.     

Activity of gentamicin, tobramycin, polymyxin B, and colistimethate in mouse protection tests with Pseudomonas aeruginosa.

Mouse protection tests were carried out with four antibiotics and six strains of Pseudomonas aeruginosa. All strains were susceptible to all four antibiotics by an in vitro test. A heavier bacterial inoculum increased the mean effective dose of gentamicin and tobramycin, but not polymyxin B. Second and third doses of gentamicin in the mouse protection test made little change in the mean effective dose. In the mouse protection tests, tobramycin was the most active antibiotic if the results were analyzed in terms of the therapeutic index or ratio of toxicity to efficacy. Colistimethate was poorly inactive in vivo. Polymyxin B was most active on an absolute basis but also was the most toxic. One strain of Pseudomonas was classified as resistant to gentamicin in vivo although it was susceptible in vitro. Strains of Pseudomonas that were uniformly susceptible to antibiotics in vitro were not uniformly susceptible in the mouse protection test to low doses of antibiotic.     

Effects of temperature on heat pain adaptation and habituation in men and women

We recently reported that women report greater pain adaptation and habituation to moderately painful heat stimuli than men (Hashmi and Davis [16]); but slightly lower temperatures were needed to evoke moderate pain in the women. Hardy et al (1962) and LaMotte (1979) suggested that pain adaptation is most prominent at modest noxious heat temperatures and may occur at temperatures close to pain thresholds. Thus, as a follow-up to our previous study, we examined the role of absolute temperature in pain adaptation and habituation in men and women and assessed whether pain threshold impacts these findings. We hypothesised that pain adaptation and habituation would be more prominent at low and moderate temperatures, and that higher temperatures would induce pain adaptation and habituation in women but not in men. We further hypothesized that pain adaptation would not be correlated with pain thresholds. To test this, we obtained continuous ratings of pain evoked by 44.5-47.5°C stimuli applied to the dorsal foot of men and women. Each run consisted of three 30 s stimuli at the same temperature with a 60 s inter-stimulus interval. Women showed within-stimulus adaptation of total pain at all temperatures, but men showed significant adaptation to temperatures less than 47 °C. There were no sex differences in inter-stimulus habituation and both men and women reported habituation to temperatures less than 46 °C. Pain thresholds did not correlate with pain adaptation. These data highlight the temperature-sensitivity and sex differences of pain adaptation and habituation.