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Biomedical subjects

K Iyer

Publications and source records attributed to K Iyer.

23 records · Page 2Linked to original sources
PubMed1986

Interaction between gabaergic and opioid pathways in the regulation of gonadotropin secretion in males.

The effects of naloxone infusion given together with an infusion of LRH on gonadotropin secretion, were studied in 6 normal male volunteers before and after pretreatment with the GABA-transaminase inhibitor, valproic acid. In concordance with previous studies, naloxone infusion augmented the LRH-stimulated secretion of LH. Baseline serum LH concentrations were not significantly different after valproic acid pretreatment compared to control values. Similarly, valproic acid pretreatment failed to blunt the naloxone-augmented LRH-stimulated secretion of LH. Our data suggest that the previously reported animal studies on the central suppressive effect of GABA on endogenous LRH release is less prominent than the suppressive effect of opioidergic regulatory mechanisms in the human male.

Adult↗
PubMed1986

Beta-endorphin/beta-lipotropin release and gonadotropin secretion after acute exercise in normal males.

The plasma beta-endorphin (beta-EP) and beta-lipotropin (beta-LPH) response to acute exercise and the relationship of these opioid peptides to basal and luteinizing hormone-releasing hormone (LRH)-stimulated luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretion was studied in eight normal male volunteers. Acute exercise resulted in a rise in plasma beta-LPH levels that returned to base line when measured 60 min after exercise. Plasma beta-EP levels did not demonstrate any rise when measured immediately after 20 min of exercise or at 60 min after exercise. Serum LH concentrations in individual volunteers declined to nadir values 60-180 min after exercise after which they showed a rebound to levels higher than the preexercise values in three of five volunteers in whom nadir LH levels were attained before the final (180 min) measurement. Serum FSH concentrations were unaltered by exercise. Acute exercise similarly did not alter the LH/FSH response to exogenous LRH stimulation. Pretreatment of the volunteers with the narcotic antagonist, naloxone, failed to alter the postexercise or LRH-stimulated LH and FSH release. The data suggest that beta-EP does not exert a suppressive effect on LH secretion after acute exercise in normal human males. Whether the suppression of LH secretion after acute exercise in unconditioned males is due to factor(s) cosecreted with beta-LPH, an increase in brain beta-EP or to alternate mechanisms such as alteration in central dopaminergic or GABAergic tone remains to be established.

Adult↗
PubMed1981

Progressive sensory loss in familial dysautonomia.

Clinical variability in sensory impairment was demonstrated among 75 patients with familial dysautonomia. Older patients had a greater tendency toward increased dysfunction in pain sensation, joint position and Romberg's sign, and vibratory sense. Significant worsening with increased age was supported by retesting of 53 patients after a five-year interval. Sensory and motor axon loss were indicated by electrodiagnostic testing of peripheral nerves and abnormal cortical somatosensory evoked potentials. Familial dysautonomia is a hereditary disease with variable penetrance which involves both failure of intrauterine development of neurons and their postnatal maintenance.

Adolescent↗
PubMed1976

Mercury poisoning in a dentist.

We examined a dentist with chronic elemental mercury poisoning electrophysiologically. Motor conduction in the upper and lower limbs was normal. Sensory nerve action potentials in the ulnar and median nerves were normal, but could not be elicited in the superfical peroneal nerves. Conduction velocity of the sural nerves was normal, but the action potential amplitude was abnormal. Following treatment with penicillamine, sensory conductions in the lower limbs returned to normal.

Dentistry↗