Effects of initial conditions on the Hoffman reflex

The Hoffmann reflex is a monosynaptic reflex elicited by electrical stimulation of afferent nerve fibres. The amplitude of the reflex response may be measured both by EMG recording from the muscle and by sensing the muscle twitch. These two effects are dependent, not only on the amplitude of the stimulus, but on the state of excitability of the afferent-efferent synaptic pools and on the mechanical state of the muscle. Voluntary control of the stimulated muscle influences these conditions but the effects on the EMG are quite different from those on the twitch. This paper discusses these effects under isometric conditions.     

Modulation of postural reflexes by voluntary movement: 1. Modulation of the active limb

Experiments were performed involving isometric activation/relaxation of the agonist-antagonist muscle groups about the ankle joint. It is shown that phasic changes of foot torque in the dorsal direction are associated with a transient inhibition of the soleus H-reflex which is independent of anterior tibial contraction. During phasic changes in foot torque in the plantar direction, facilitation, as opposed to disinhibition of the soleus H-reflex, is graded by soleus contraction. These results support the hypothesis that the sensitivity of the monosynaptic reflex arc is one of the controlled variables of the motor system. The stretch reflex of a shortening muscle is generally facilitated, while that of a lengthening muscle is inhibited. These hypotheses are in keeping with our present knowledge of the linkage between skeletomotor and fusimotor neurones for the organization of voluntary movements.     

The effect of finasteride on the expression of vascular endothelial growth factor and microvessel density: a possible mechanism for decreased prostatic bleeding in treated patients

PURPOSE: Several studies have confirmed the benefit of finasteride in limiting hematuria from benign prostatic hyperplasia. Vascular endothelial growth factor (VEGF), a potent stimulator of angiogenesis, and microvessel density have been independently evaluated in the mechanism of decreased bleeding observed in patients treated with finasteride. We evaluated the expression of VEGF and suburethral prostatic microvessel density in patients with benign prostatic hyperplasia treated with finasteride. MATERIALS AND METHODS: The study included 24 patients undergoing prostatic surgery for benign disease, of whom 12 were given finasteride for a minimum of 6 weeks before surgery and the remaining 12 served as controls. Sections from the prostatic urothelium and hyperplastic prostate were individually stained for CD34 specific for nascent blood vessels and VEGF. Analysis of each specimen was performed in a blinded fashion. Microvessel density was calculated by counting the number of positively stained blood vessels on 10 consecutive, nonoverlapping, high power fields within the suburethral and hyperplastic prostate compartments. VEGF expression was examined by immunohistochemistry. Statistical analysis of the results was performed using Student's t test. RESULTS: Prostatic suburethral VEGF expression and microvessel density were significantly lower in the finasteride group compared to controls (p <0.05). Differences in VEGF expression and microvessel density at the level of the hyperplastic prostate were not found to be significantly different between the 2 groups.CONCLUSIONS Decreased expression of VEGF by finasteride inhibits angiogenesis and significantly decreases microvessel density in prostatic suburethral tissue. This sequential relationship provides histochemical insight into the mechanism by which finasteride reduces prostatic urethral bleeding.     

Robust multi-tissue gene panel for cancer detection

Background  

We have identified a set of genes whose relative mRNA expression levels in various solid tumors can be used to robustly distinguish cancer from matching normal tissue. Our current feature set consists of 113 gene probes for 104 unique genes, originally identified as differentially expressed in solid primary tumors in microarray data on Affymetrix HG-U133A platform in five tissue types: breast, colon, lung, prostate and ovary. For each dataset, we first identified a set of genes significantly differentially expressed in tumor vs. normal tissue at p-value = 0.05 using an experimentally derived error model. Our common cancer gene panel is the intersection of these sets of significantly dysregulated genes and can distinguish tumors from normal tissue on all these five tissue types.     

Vitamin A supplements are well tolerated with the pentavalent vaccine

The Expanded Programme on Immunisation provides an opportunity to deliver vitamin A supplements to young infants in order to improve their vitamin A status. However, concerns have been raised about the safety of administering high dose vitamin A supplements to infants less than 6 months of age in developing countries. A randomized controlled trial was carried out by the Kintampo Health Research Centre to assess the safety and immunogenicity of administering 15 mg retinol equivalent (RE)1 vitamin A alongside the pentavalent "diphtheria-polio-tetanus-Haemophilus influenzae b-hepatitis B vaccine" at 6, 10 and 14 weeks of age. All mothers received a post-partum supplement of 120 mg RE vitamin A as per national policy. Mothers of infants who had been vaccinated were visited 24 h after vaccination to assess the side effects of the vaccine. They were also interviewed about adverse events which may have occurred in the past 4 weeks since the child was vaccinated. There were significantly fewer reports of illnesses and fever in infants who had been given vitamin A compared to infants in the control group. The pentavalent vaccine was found to be tolerable when administered with vitamin A according to the WHO/EPI schedule for infant immunisation at 6, 10 and 14 weeks. There were few complaints made by the mothers of the children which were not thought to be related to giving vitamin A with the vaccines. There were six deaths in the trial, five in the intervention group and one in the control RR 4.65 (0.55-39.5), p = 0.12. Due to the high point estimate of 4.65, we wish to urge caution in administering high doses of vitamin A to young infants with the pentavalent vaccine at 6, 10 and 14 weeks of age.