PubMed Health⌕ Search

Biomedical subjects

J N Singh

Publications and source records attributed to J N Singh.

At least 19 recordsLinked to original sources
PubMed2003

Ptychodiscus brevis toxin enhances the frequency-dependent depression of the monosynaptic reflex in neonatal rat spinal cord in vitro.

The involvement of frequency-dependent depression (FDD) of synaptic transmission for the depressant action of the Ptychodiscus brevis toxin (PbTx) was investigated in neonatal rat spinal cord in vitro. The stimulation of a dorsal root by train of pulses (five stimuli) at different frequencies evoked potentials in the ventral root (monosynaptic reflex, MSR). Amplitude of the fifth response as percent of first response at 0.1, 0.2, 0.5, 1.0 and 2.0 Hz were 90, 80, 75, 70 and 50%, respectively. In Mg2+-free medium, PbTx depressed the MSR and also enhanced the FDD in a concentration-dependent manner. Further, the PbTx-induced depression can well be correlated with the enhancement of FDD (r=0.98). In the presence of Mg2+ (1.3 mM), the FDD was greater than that in the absence of Mg2+. But in the presence of Mg2+ PbTx did not alter FDD, even though there was 25% depression at 28 microM (significantly lesser than in Mg2+-free medium). The results indicate that the Mg2+-sensitive component of PbTx-induced depression of MSR is mediated via the neuronal systems involving FDD.

Action Potentials↗
PubMed2002

Relative potency of synthetic analogs of Ptychodiscus brevis toxin in depressing synaptic transmission evoked in neonatal rat spinal cord in vitro.

Effects of Ptychodiscus brevis toxin (PbTx) analogs on the spinal synaptic transmission in neonatal rats in vitro were evaluated. PbTx1/PbTx2 had aromatic groups and PbTx3/PbTx4 had aliphatic groups. All the analogs depressed monosynaptic reflex (MSR) and polysynaptic reflex (PSR) in a concentration-dependent manner. The maximal depression of MSR (75% from initial) and PSR (96%) was at 84 microM for PbTx1. Concentration to produce 25% inhibition from initial (IC25) by PbTx1 for MSR and PSR was < or =2.8 microM. The maximal depression of MSR (80%) was at 96 microM and PSR (100%) was at 32 microM by PbTx2. IC25 for MSR and PSR were 5.5 microM and <3.2 microM, respectively. PbTx3 decreased MSR by 25% maximally (=IC25) at 36 microM. The depression of PSR fluctuated and was maximal (75%) at 108 microM and IC25 was 6.2 microM. PbTx4 depressed MSR and PSR at the maximum of 35% at 32 microM and IC25 for MSR was 8.3 microM and for PSR was 35 microM. Rank order of potency of toxins for depressing MSR was PbTx1>PbTx2>>PbTx4>PbTx3; and for PSR it was PbTx2>PbTx1>PbTx3>>PbTx4. Results indicate that the toxins having aromatic groups exhibited greater neurotoxicity.

Animals↗
PubMed2002

Involvement of N-methyl-D-aspartate receptors for the Ptychodiscus brevis toxin-induced depression of monosynaptic and polysynaptic reflexes in neonatal rat spinal cord in vitro.

The effects of Ptychodiscus brevis toxin (PbTx) on the Ia-alpha motoneuron synaptic transmission in neonatal rat spinal cord in vitro was examined. The stimulation of a dorsal root evoked monosynaptic (MSR) and polysynaptic reflex (PSR) potentials in the segmental ventral root in Mg2+-free medium. Superfusion with PbTx (2.8-84 microM) depressed the MSR and the PSR in a concentration-dependent manner. At 2.8 microM of PbTx, the depression of MSR and PSR was 24+/-8.3% and 37+/-9.7%, respectively. The maximal depression was seen at 84 microM of the toxin (78% for MSR and 96% for PSR). The concentration of toxin required to produce 50% depression was 28.3+/-6.4 microM for MSR and 5.5+/-1.1 microM for PSR. The PbTx (28 microM) did not alter the magnitude of the dorsal root or the ventral root potentials. Addition of MgSO4 (1.3 mM) or DL-2-amino-5-phosphonovaleric acid (APV; 10 microM) to the physiological solution abolished the PSR totally and decreased the MSR by about 30%. In both the conditions, the PbTx-induced depression of the MSR was attenuated significantly. The PbTx-induced depression was blocked completely in the presence of APV+6-cyano-7-nitroquinoxaline-2,3-dione (0.1 microM). NMDA (1 microM) by itself did not alter the magnitude of MSR or PSR but enhanced the PbTx-induced depression (28 microM) of PSR significantly. 7-Chlorokynurenic acid (3 microM; glycine(B) antagonist) did not block the PbTx-induced depression of MSR. D-serine (glycine(B) agonist) did not reverse the PbTx-induced depression of reflexes although it reversed the 7-chlorokynurenic acid-induced depression of PSR. The results indicate that the PbTx depressed the spinal reflexes without altering the magnitude of dorsal root or ventral root activity. The depression of the PSR involved NMDA receptors while that of the MSR involved NMDA and non-NMDA receptors. The PbTx actions did not involve the glycine(B) site of the NMDA receptor.

Action Potentials↗
PubMed1993

Human uterine protein in relation to infertility.

The concentration of electrophoretic protein in the uterine fluid of infertile women is significantly higher at all the phases of the menstrual cycle, except at phase I where it is significantly (p < 0.01) lower than parous women. At phase III (ovulatory phase) the concentration of electrophoretic protein (2812.00 micrograms/ml) is maximum in infertiles, and shows a highly significant (p < 0.001) increase over that of parous women (954.85 micrograms/ml). The highest level of electrophoretic protein at phase III in infertile women is due to maximum increase in anodic (electronegative) protein at this stage. This suggests that significant (p < 0.001) increase in concentration of anodic protein in the uterine fluid of infertile women at the ovulatory phase adds negative charge on sperm membrane that may possibly affect the capacitation of spermatozoa, thus causing infertility in women.

Adult↗
PubMed1993

LDH-x in azoospermia: a new diagnostic alternative to vasography and testicular biopsy.

Activities of different isozymes of lactate dehydrogenase were studied in semen samples from fertile, and different groups of infertile men. No isozyme except the sperm specific LDH-x or C4 showed any difference in activity with changes in sperm density. Activity of LDH-x exhibited a trend positive to changes in sperm density and became absent in obstructive and vasectomized azoospermia. Among other types of azoospermia, the activity became very high in maturation arrest but very low in patients with testicular biopsy showing germ cell aplasia, such as in SCOS and ghostlike tubules. Diagnostic usefulness of the estimation of LDH-x activity in semen is discussed.

Biopsy↗
PubMed1993

Modifications in the seminal protein pattern and concentration among infertile men.

Lower concentrations of protein observed in semen of infertile men were mostly due to absence of vesicular proteins with higher isoelectric pH above pH 8.3. Two to four proteins with lower isoelectric pH showing electrophoretic mobility and originating both from seminal vesicle and prostate were absent in infertile semen samples. Concentrations of such proteins among oligozoospermic and azoospermic samples with complete maturation arrest and Sertoli cell only syndrome decreased mainly towards cathode, whereas, in vasectomized azoospermia the number of protein bands decreased both towards cathode and anode, though the concentration decreased mainly in the anodic proteins.

Electrophoresis↗
PubMed1992

Effect of insulin and thyroxine on catalase, glutathione-s-transferase, GSH and GSSG in alloxan diabetic rat red cells.

The levels of catalase (CAT), glutathione-s-transferase (GST), reduced glutathione (GSH) and oxidised glutathione (GSSG) were measured in red blood cells from control (C) and diabetic rats (D). Diabetes was induced by alloxan administration and diabetic rats were treated with insulin (D+I) and thyroxine (D+T4). On the third day of insulin withdrawal the CAT activity increased significantly. The GST activity showed an increase in D and D+I for one week, thyroxine treatment to D rats resulted in maintaining the GST activity at control levels. The levels of GSH and GSSG increased in D red cells after one week of insulin withdrawal but later, the GSH level was below the control level while the GSSG was at its control level. Insulin treatment to D rats did not reverse GSH level to control initially but controlled it at a later stage. Thyroxine, though, reversed GSH levels but enhanced GSSG in D rat red cells.

Animals↗
PubMed1990

Antifertility effects of leaf extracts of some plants in male rats.

Ethanolic leaf extracts of different local folklore plants (Azadirachta indica, Beaumontia grandiflora, Chordia dichotoma, Casiarea tomentosa, Diospyros embryopteris, Milletia auriculata and Melia azedarach) were investigated for antifertility effects on male rats in oral doses of 100 mg/kg daily for 21 days. Though, none of these extracts interfered with spermatogenesis, anti-implantational and abortifacient effects were observed in females mated by the males fed with leaf extracts of A. indica and C. dichotoma. Leaf extract of B. grandiflora besides having anti-implantational and abortifacient effects, had luteolytic effects. Abolition of libido in 100% males by leaf extracts of D. embryopteris and M. azedarach and in 60% of males by extract of C. tomentosa preclude these plants for antifertility use.

Animals↗
PubMed1989

Blood bioamines, cortisol and aminoacid levels in leukemic patients.

In patients of chronic myeloid leukemia blood adrenaline, noradrenaline, dopamine and glutamate level were significantly elevated. The GABA levels were decreased along with no significant alterations in aspartate levels in these patients. In cases of acute myeloid leukemia only adrenaline and glutamate levels were enhanced with decreased GABA levels. However, plasma cortisol levels were significantly enhanced in both chronic and acute myeloid leukemia patients. These observations suggest that the circulating bioamines, cortisol and certain aminoacids level are considerably altered in chronic and acute myeloid leukemia. All these changes may possibly be attributed to the stress induced by the disease.

Adolescent↗
PubMed1984

Sarcolemmal alterations during the development of genetically determined cardiomyopathy.

The purpose of this study was to identify alterations in specific enzyme and Ca2+ binding activities in cardiac sarcolemmal fractions from UM-X7.1 myopathic Syrian hamsters during the development of cardiomyopathy. Experimental and healthy control animals were examined from 25 to 200 days of age. Sarcolemmal Na+, K+-ATPase activity was depressed in the myopathic hamsters throughout the time course of this study. Sarcolemmal ATP-independent Ca2+ binding was found to be depressed in experimental animals as early as 55 days of age. Ca2+ -stimulated, Mg2+ -dependent ATPase activity was depressed in the experimental animals by 90 days of age and this decrease in enzyme activity was accompanied by a decrease in ATP-dependent Ca2+ binding capacity of the sarcolemmal membranes. Mg2+ -ATPase and Ca2+ -ATPase activities were only affected in the latter stages of the disease (155 to 200 days old). NaF, epinephrine and Gpp(NH)p stimulation of the sarcolemmal adenylate cyclase activity was also observed to be attenuated during the latter stages of the disease. These defects in adenylate cyclase system of the sarcolemmal fraction appeared specific since basal adenylate cyclase activity was not altered at any age studied. The results demonstrate that the earliest lesions in sarcolemmal activity in myopathic hamster heart occur in Na+, K+-ATPase and ATP-independent Ca2+ binding capacity. These defects correspond temporally to the initial stages of cardiac necrotic development in this strain of myopathic hamster.

Adenosine Triphosphatases↗
PubMed1983

Energy production and utilization in contractile failure due to intracellular calcium overload.

Intracellular calcium overload was produced by perfusing the Ca2+- deprived rat hearts for 5 or 10 min with normal medium containing 1.25 mM Ca2+ for 10 min and changes in the myofibrillar and membrane ATPase, sarcolemmal adenylate cyclase, mitochondrial oxidative phosphorylation and high energy phosphate stores in failing hearts were examined. Myocardial creatine phosphate and ATP were decreased by the intracellular calcium overload whereas the myofibrillar, mitochondrial and microsomal ATPase activities were not altered. The intracellular calcium overload markedly depressed the mitochondrial oxidative phosphorylation as well as sarcolemmal Ca2+ ATPase, Mg2+ ATPase, Na+ - K+ ATPase and adenylate cyclase. These results suggest that abnormalities in the process of energy production rather than energy utilization may primarily account for the depressed energy state of hearts failing due to an intracellular calcium overload.

Adenosine Diphosphate↗