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PubMed1985

Effects of pup sucking behaviour on inhibition of sexual behaviour and ovulatory secretion of LH in lactating rats.

The time-interval between parturition and the display of sexual receptivity varied between 13.5 +/- 0.7 and 35.9 +/- 2.5 days in rats with litters of between 1 and 24 pups. Body weight gain decreased and the avidity of pup sucking behaviour, measured by the latency before the pups, placed on the ventrum of an anaesthetized mother, attached to a nipple of the mother, increased as litter size increased. Litter-shifting procedures, which introduced asynchrony between the lactational age of the mother and the age of the pups, produced deficiencies in sucking behaviour and did not prolong the time-interval between parturition and the display of sexual receptivity by the mother. By keeping the lactational age of the mother in synchrony with the age of the pups and depriving the pups of maternal contact and nutrition every alternate day, the time-interval between parturition and the display of sexual receptivity by the mother was prolonged by 17 days, the avidity of pup sucking behaviour markedly enhanced and the body weight gain of the pups retarded in comparison with mothers and pups continuously living together. The results show that the display of the first postlactational behavioural oestrus and surge of pituitary LH secretion can be greatly delayed by an increase in the avidity of pup sucking behaviour.

Animals↗
PubMed1983

Quantitative estimation of anaerobic and oxidative energy metabolism and contraction characteristics in intact human skeletal muscle in response to electrical stimulation.

A set up for electrical stimulation of the human quadriceps femoris muscle and registration of tension is described. Normal values for the frequency-tension relations and relaxation time are presented. There was no relationship between contraction characteristics and fibre type distribution. Muscle tissue was sampled after electrical stimulation by percutaneous biopsy technique. Phosphocreatine (PCr) decreased during a 75 s isometric contraction from 76 mmol per kg dry muscle down to a mean value of 9 mmol. Lactate increased during the same time period from 5 mmol per kg dry muscle to 100 mmol. At end of contraction there was a rapid resynthesis of PCr with a half time of about 20 s while the lactate content decreased slowly. The relaxation time of the muscle was prolonged from 38 ms, in non-fatigued muscle, to 128 ms after 75 s of isometric contraction. The relaxation time was normalized after the contraction at the same rate as the resynthesis of PCr. It is proposed that the relationship between PCr and lactate of contracting muscle can be used as an index of glycolytic capacity and that the rate of resynthesis of PCr after contraction is a measure of oxidative capacity. Relaxation time measurements alone may be used as a non-invasive estimation of the oxidative capacity.

Adenosine Diphosphate↗
PubMed1996

Changes in the electrical properties of supraoptic nucleus oxytocin and vasopressin neurons during lactation.

Magnocellular oxytocin (OT) and vasopressin (VP) neurons adopt different firing patterns in response to relevant physiological stimuli. OT neurons selectively display short (2-4 sec), high-frequency bursts of action potentials that are highly synchronized and correlated with OT release during lactation. The present experiments were done to determine whether the electrophysiological properties of OT neurons differ from those of VP neurons, and whether these properties are modulated during lactation to support short bursting activity. Intracellular recordings in vitro were obtained from immunochemically identified supraoptic neurons of diestrous or lactating female rats. Resting membrane potential, input resistance, membrane time constant, and the depolarizing afterpotential did not differ among groups. However, near spike threshold, OT, but not VP, neurons expressed a sustained outward rectification that was removed by small hyperpolarizing pulses and a rebound depolarization that occurred at the offset of these hyperpolarizing pulses. The rebound depolarization was short ( < 2 sec), supported brief bursts of action potentials, and was significantly larger during lactation. Neurons expressing the outward rectification also exhibited strong spike frequency adaptation during prolonged (1-4 sec) depolarization. Spike width, the Ca(2+)- dependent afterhyperpolarization, and the degree of spike broadening of OT, but not VP, neurons were also larger during lactation, suggesting an increase in Ca2+ influx per spike. The results indicate that OT neurons possess properties favoring the expression of short spike trains, and that some of these properties are enhanced during lactation. In addition, spikes in OT neurons may promote more Ca2+ influx in this state.

Action Potentials↗
PubMed2004

Glycogen reduction in non-exercising muscle depends on blood lactate concentration.

The purpose of this study was to determine for the first time by repeated non-invasive 13C-NMR spectrometry whether blood lactate concentration affects glycogen reduction in non-exercising muscle during prolonged (6 h) physical exercise in healthy adult males. Such an effect would indirectly show that glycogenolysis independent of nervous activation occurs in non-exercising muscle. After an overnight fast, 12 subjects performed alternating one-leg cycle exercise and arm cranking exercise at an average work load of 106 (SD 26) W [63 (9)% maximum oxygen consumption for one-leg exercise] and 69 (13) W [61 (10)% maximum oxygen consumption for arm cranking exercise], respectively. During the 6-h exercise test, glycogen concentration of the non-exercising calf muscle decreased by 17 (7)% while the glycogen concentration in the exercising calf muscle decreased by 45 (8)%. In a resting control group (n=6), the glycogen concentration did not decrease significantly. The higher the exercise intensity and therefore blood lactate concentration, the smaller was the glycogen reduction in the non-exercising calf muscles. We conclude that during prolonged physical exercise glycogenolysis in non-exercising human muscles decreases as exercise intensity increase contrary to exercising muscles. This observation might be an indirect evidence for a non-exercise induced glycogenolysis in inactive muscles.

Adult↗
PubMed1985

Cardiac dysfunction during status epilepticus in the neonatal pig.

Cardiovascular complications frequently occur during status epilepticus. To determine the changes in systemic and pulmonary arterial pressure, cardi output, and left ventricular contractility during seizures, 1-week-old pigs were intubated, paralyzed, mechanicall entilated, and catheterized with a Swan-Ganz catheter. Seizures were induced with intravenous bicuculline. Early changes consisted of significant systemic and pulmonary arterial hypertension. After 2 hours of seizures, the animals developed progressive systemic hypotension and decreased cardiac output. M-mode echocardiography disclosed a decrease in left ventricular contractility. Cardiac tissue frozen in situ showed a significant increase in lactate and reductions in glucose, triglyceride, and adenosine triphosphate levels. Prolonged seizures in the neonatal pig result in cardiac dysfunction, which may play a role in the development of epileptic brain damage.

Acid-Base Equilibrium↗
PubMed1985

Study of a time lag in the assay of Escherichia coli membrane-bound dehydrogenases based on tetrazolium salt reduction.

The Escherichia coli membrane-bound D-lactate dehydrogenase and succinate dehydrogenase were assayed on the basis of the phenazine methosulfate- (PMS-) mediated reduction of the tetrazolium salt, MTT. An initial slower phase (lag) in the time-course of the reaction was observed and analyzed. The results were as follows. (1) The time lag in the assay of the D-lactate dehydrogenase was eliminated by preincubating the membranes with PMS plus D-lactate, with PMS plus succinate, or with PMS plus NADH (conditions which implicated PMS reduction). (2) When the D-lactate dehydrogenase was assayed by another method based on the measurement of the pyruvate formed, neither was a time lag observed nor was the enzyme activity affected by membrane preincubation with PMS plus D-lactate. (3) Although the superoxide radical was involved in MTT reduction, this radical seemed not to participate in the generation of the time lag. (4) Membranes whose D-lactate dehydrogenase activity had previously been destroyed by heating at 80 degrees C for 1 min, were able to prolong the time lag in MTT reduction when added to the assay medium for the D-lactate dehydrogenase from untreated membranes, whereas membranes previously heated at 100 degrees C instead of 80 degrees C did not have this effect. It was concluded that the E. coli membranes interfered in the dehydrogenase assay based on the PMS-mediated reduction of MTT. The time lag was interpreted as a period during which the interfering substance reacted with reduced PMS inhibiting the reduction of MTT.

Escherichia coli↗
PubMed1986

Aerobic performance capacity in paraplegic subjects.

To determine adaptation to prolonged exercise in paraplegics, maximal O2 uptake (VO2max) and lactate threshold (LT) were evaluated during an arm cranking exercise in nine patients (P) and nine able-bodied (AB) subjects. Mean VO2max averaged 25.1 and 31.6 ml X min-1 X kg-1 in P and AB groups respectively. VO2max in P was found to be directly related to the level of spinal injury: the higher the lesion the lower the uptake. Lactate threshold expressed as a percentage of VO2max was higher in P (59%) than in AB (43%), and close to that observed in arm-trained athletes. Since training has less effect on VO2max in paraplegics than in able-bodied subjects, attributable to a deficiency in the circulatory adaptation of paraplegics to exercise, the observed differences between AB and P in lactate threshold and submaximal exercise indicate that the possible effect of training in paraplegics is located at the level of intracellular chemistry, with a diminution in glycogenolysis (higher LT) and a higher rate of lipid utilization (lower RQ).

Adult↗
PubMed2001

Neuroendocrine changes and fertility in breast-feeding women.

Breast-feeding through the suckling stimulus suppresses fertility for a variable time after birth. Initially there is a period of pituitary gonadotroph recovery from the suppressive effects of the high steroid levels of pregnancy, followed by a period of suppressed ovarian activity associated with limited follicle growth. During this period of breast-feeding-induced amenorrhea, the pulsatile secretion of luteinizing hormone (LH), which reflects hypothalamic gonadotropin-releasing hormone (GnRH) release, is erratic and much slower than the one pulse per hour required in the normal follicular phase of the menstrual cycle to drive follicle growth. At some time the suckling stimulus drops below a threshold resulting in a resumption of reasonably organized pulsatile LH secretion, which is associated with development of follicles and some steroid secretion. However, positive feedback of estradiol which triggers the preovulatory LH surge and ovulation appears to be blocked by continued suckling, until suckling is reduced further and positive feedback and ovulation resumes. Often while women continue to breast-feed the first few ovulations and menses are associated with inadequate corpus luteum function, which would probably not support a pregnancy. Eventually normal menstrual cycles resume when suckling declines further. The duration of amenorrhea and subsequent period of inadequate luteal function varies greatly between mother-baby combinations, and in different societies. Exactly how the suckling stimulus reduces pulsatile secretion of GnRH/LH is not clear, although clinical studies do not support a role for opioids or dopamine. The role of prolactin remains uncertain since suckling releases both prolactin and suppresses GnRH release. Regardless of the precise mechanism, it is clear that breast-feeding in women can suppress fertility for prolonged periods, and women may proceed from pregnancy through lactation to another pregnancy and lactation with no menstrual period for several years.

Breast Feeding↗
PubMed1989

Effect of nutritional status on insulin sensitivity in vivo and tissue enzyme activities in the rat.

The hyperinsulinaemic-glucose-clamp technique, in combination with measurement of glucose turnover in conscious unrestrained rats, was used to assess the effects of nutritional status on insulin sensitivity in vivo and glucose metabolism. Liver, heart and quadriceps skeletal-muscle glycogen content and activities of pyruvate dehydrogenase (PDH) and glycogen synthase were measured both basally and at the end of a 2.5 h glucose clamp (insulin 85 munits/h) in rats 6, 24 and 48 h after food withdrawal. Clamp glucose requirement and glucose turnover were unchanged by fasting. Activation of glycogen synthase and glycogen deposition in liver and skeletal muscle during the clamps were also not impaired in rats after a prolonged fast. By contrast with skeletal muscle, activation of cardiac-muscle glycogen synthase and glycogen deposition during the clamps were markedly impaired by 24 h of fasting and were undetectable at 48 h. Skeletal-muscle PDH activity fell with more prolonged fasting (6 h, 15.3 +/- 3.4%; 24 h, 4.7 +/- 0.7%; 48 h, 4.3 +/- 0.6% active; P less than 0.005), but at 24 and 48 h was stimulated by the clamp to values unchanged by the duration of fasting. Stimulation of cardiac PDH activity by the clamp was, however, impaired in rats fasted for 24 or 48 h. Basal hepatic PDH did not change significantly with fasting (6 h, 5.3 +/- 1.1%; 24 h, 4.6 +/- 0.7%; 48 h, 3.9 +/- 0.5%), and, although it could be partly restored at 24 h, very little stimulation occurred at 48 h. Hepatic pyruvate kinase and acetyl-CoA carboxylase activity were both stimulated by the clamps, and this was not impaired with more prolonged fasting. During the glucose clamps, blood concentrations of lactate, pyruvate and alanine were increased to a greater extent in rats fasted for 24 and 48 h than in rats studied 6 h after food withdrawal. The findings suggest that, although sensitivity to insulin of whole-body glucose disposal is unchanged with fasting, there may be qualitative differences in the metabolism of glucose.

Animals↗
PubMed2003

Lacticacidosis after short-term infusion of propofol for anaesthesia in a child with osteogenesis imperfecta.

We describe the case of a 7-year-old boy with osteogenesis imperfecta, who underwent anaesthesia with propofol-fentanyl-nitrous oxide-suxamethonium for orthopaedic surgery of a distal femur fracture. He developed lacticacidosis after short-term propofol infusion (150 min, mean infusion rate 13.5 mg.kg-1.h-1) associated with a prolonged recovery time without serious haemodynamic changes. The highest lactate concentration was 9.2 mmol.l-1 at 160 min after discontinuation of propofol. There was no significant increase in body temperature. The boy fully recovered.

Acidosis, Lactic↗
PubMed1980

Alterations in plasma corticosteroids, insulin and selected metabolites in horses used in endurance rides.

The effects of prolonged exercise on plasma concentrations of corticosteroids, insulin, glucose, lactate and beta-hydroxybutrate were studied in a group of horses competing in a 160 km endurance ride. Of the 53 horses included in the study at the outset, 23 completed the course. Plasma corticosteroids increased while glucose and insulin decreased during exercise. Little change occurred in plasma lactate or beta-hydroxybutyrate. The parameters studied did not result in the finding of any consistent significant differences beteeen individuals that completed and those that did not complete the course.

Adrenal Cortex Hormones↗
PubMed1994

SWIMMING METABOLISM OF WILD-TYPE AND CLONED ZEBRAFISH BRACHYDANIO RERIO

The availability of a gynogenetic isogenic homozygous diploid clonal strain (C) of the zebrafish (Brachydanio rerio), combined with the small adult body size of the species, made possible a study of the following two questions. (1) Is the genetic uniformity of a group of fish reflected in decreased variability of features of organismic performance physiology? (2) Is the metabolic cost of subcarangiform swimming significantly different in small fishes compared with large ones? Wild-type (WT) and C strain zebrafish maintained at 28 &deg;C can all swim very rapidly [up to relative swimming speeds of 13 body lengths s-1 (BL s-1)] for extended periods (at least 2 h) without visibly tiring. Oxygen consumption rates were measured for both types at swimming speeds of 1.5&shy;13 BL s-1. Whole-body lactate concentrations were also measured during routine activity and after prolonged exercise for both fish types. The slopes of the linear regressions between the logarithm of mass-specific oxygen consumption rates and relative swimming speeds for WT zebrafish were low (0.010&shy;0.024) and were not significantly different from zero. Regression slopes were also low (0.009&shy;0.026), but different from zero, for C zebrafish. Standard metabolic rates were 0.60&shy;1.54 and 0.40&shy;0.85 ml O2 g-1 h-1 for WT and C zebrafish respectively. Variances of slopes were significantly larger for WT than for C fish. Whole-body lactate concentrations and their variances were not significantly different between types and between rested and exercised fishes. The results demonstrate unusual swimming performance capacities, a remarkably low cost of swimming and some reductions in variability of C fish. Several possible explanations for the results are discussed.

Journal Article↗
PubMed1991

[A case of Kearns-Sayre-Shy syndrome with abnormal signal intensity on MRI in cerebral white matter and brainstem].

A 42-year-old woman was admitted for complaining of gait disturbance lasting for 2 years. She had a past history of hearing loss and bilateral ocular ptosis since her age of 21 years. Neurological examinations revealed severe external ophthalmoplegia, ptosis and muscular weakness of neck and extremities, but no dementia. Laboratory examinations showed high level of serum CK and slight elevations of CSF protein, lactate and pyruvate. The QT interval on ECG was prolonged. The EEG finding was slightly abnormal. The neurogenic pattern on EMG was noted. Muscle biopsy was performed at the quadriceps muscle. Its specimens demonstrated mixed changes of muscular atrophy and ragged red fibers. From these findings, Kearns-Sayre-Shy syndrome was diagnosed. It was noted in this case that brain MRI (T2-weighted image) revealed bilateral diffuse high signal intensity areas on cerebral white matter and brainstem. It seems that the lesions of central nervous system may progress subclinically for many years in cases of KSS, as our case shows.

Adult↗
PubMed1987

Protein carboxyl methyltransferase facilitates conversion of atypical L-isoaspartyl peptides to normal L-aspartyl peptides.

Prolonged incubation of L-isoaspartate-containing forms of lactate dehydrogenase (231-242), sperm activating peptide, and adrenocorticotropin (22-27) at 37 degrees C, pH 7.4, with S-adenosyl-L-methionine and protein carboxyl methyltransferase from bovine brain leads to extensive conversion of the atypical isopeptide bond to a normal peptide bond. For the lactate dehydrogenase-related peptide, conversion was 80% complete after 24 h. For the other two peptides, conversion reached a level of approximately 65% after 48 h. The mechanism of conversion involves (i) rapid enzymatic methylation of the alpha-carboxyl of the L-iso-Asp residue; (ii) nonenzymatic demethylation resulting in formation of an L-aspartyl cyclic imide; and (iii) a slow, nonenzymatic hydrolysis of the cyclic imide to form a mixture of 15-25% normal L-Asp peptide and 75-85% L-iso-Asp peptide. The regenerated L-iso-Asp peptide is remethylated and the cycle is repeated. The extent of conversion is limited by a competing side reaction wherein the L-imide slowly racemizes, leading to the formation of mainly D-iso-Asp peptide, which is not a substrate for the methyltransferase. The ability of protein carboxyl methyltransferase to initiate conversion of L-iso-Asp residues to normal L-Asp suggests a possible role for this enzyme in facilitating the repair or degradation of deamidated proteins in vivo.

Amino Acid Sequence↗
PubMed1995

Influence of recombinant human erythropoietin on hematological and hemostatic parameters with special reference to microhemolysis.

Twenty chronic hemodialysis patients with renal anemia (hematocrit < 25%) received recombinant human erythropoietin (40 IU/kg body weight 3 x weekly) intravenously after each dialysis. Prior to and at 4, 8 and 12 weeks after commencement of erythropoietin therapy, hematocrit together with hemostasis and microhemolysis parameters were determined. There were significant increases in hematocrit, platelet count and platelet retention, but a significant fall in the initial clearly prolonged bleeding time. Free plasma hemoglobin likewise increased. Conversely, lactate dehydrogenase, prothrombin time, fibrinogen, antithrombin III activity, protein C activity and protein S concentration were all unaltered. The positive effect on bleeding time and platelet retention is most probably caused by an increase in adenosine diphosphate due to the hematocrit-dependent rise in the blood shear stress via physiologic microhemolysis (raised free plasma hemoglobin).

Adult↗
PubMedDate not supplied

Infant feeding practices in a rural community of west Bengal.

A study on breast feeding and weaning practices was carried out in a sample of 57 lactating mothers of rural community. Although early start and prolonged breast feeding was an universal practise, but timely weaning was neglected and offered to 54.5% of infants only. On the contrary, introduction of artificial milk to young infants was a culturally accepted baby feeding.

Age Factors↗
PubMed1985

Effects of detraining on responses to submaximal exercise.

Seven endurance-trained subjects were studied 12, 21, 56, and 84 days after cessation of training. Heart rate, ventilation, respiratory exchange ratio, and blood lactate concentration during submaximal exercise of the same absolute intensity increased (P less than 0.05) progressively during the first 56 days of detraining, after which a stabilization occurred. These changes paralleled a 40% decline (P less than 0.001) in mitochondrial enzyme activity levels and a 21% increase in total lactate dehydrogenase (LDH) activity (P less than 0.05) in trained skeletal muscle. After 84 days of detraining, the experimental subjects' muscle mitochondrial enzyme levels were still 50% above, and LDH activity was 22% below, sedentary control levels. The blood lactate threshold of the detrained subjects occurred at higher absolute and relative (i.e., 75 +/- 2% vs. 62 +/- 3% of maximal O2 uptake) exercise intensities in the subjects after 84 days of detraining than in untrained controls (P less than 0.05). Thus it appears that a portion of the adaptation to prolonged and intense endurance training that is responsible for the higher lactate threshold in the trained state persists for a long time (greater than 85 days) after training is stopped.

Blood Glucose↗