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Biomedical subjects

L L Levitsky

Publications and source records attributed to L L Levitsky.

45 records · Page 3Linked to original sources
PubMed1979

Effect of androgen on growth hormone secretion and growth in boys with short stature.

The response of plasma growth hormone (GH) to insulin-induced hypoglycaemia (IIH) and arginine infusion (AI) was studied in 22 young males (ages 8 to 17 years) with short atature and absent or delayed sexual maturation, before and after androgen administration. During initial evaluation, 5 patients had blunted GH response to IIH, 12 responded subnormally to AI and 4 failed to respond normally to either stimulus. These same studies were repeated in each patient following androgen administration. The source of androgen was as follows: a) 5 days of testosterone propionate (25 mg intramuscularly daily) in 20 patients. b) Methyltestosterone, 10 mg t.i.d. orally for four days in the other 2 subjects. In almost every case, androgen administration resulted in raising the levels of fasting GH and enhancement of the GH responses to IIH and AI was observed. Patients manifesting subnormal GH responses to these stimuli before androgen consistently demonstrated a normal response when challenged with identical stimuli during androgen administration. Growth velocities during the year following these studies were significantly increased in most instances and the growth spurts correlated well with the progression of sexual maturation. Sustained improvement in the GH responses to IIH and AI were uniformly observed in 3 patients when repetitive studies were performed 8 to 12 months later during spontaneous advancing sexual development. The results indicate that brief androgen administration can be helpful in delineating the cause of growth retardation in boys with short stature and delayed sexual maturation, particularly when the diagnosis of isolated growth hormone deficiency is suspected. They also offer prognostic value in determining growth potential in this same group of young males.

Administration, Oral↗
PubMed1978

Glucagon response to arginine in growth hormone deficient children before and after treatment with growth hormone and in children with non-endocrine short stature.

In order to assess the role of growth hormone in the modulation of alpha cell function, the plasma pancreatic glucagon response to intravenous arginine (0.5 g/kg) was determined in thirty-two children with non-endocrine short stature and in eighteen growth hormone deficient children. 60 min after arginine infusion, the growth hormone deficient children had significantly higher (P less than 0.05) plasma glucagon values than the children with non-endocrine short stature. Following short-term growth hormone therapy (2 iu qd or bid for 5 days) in eleven of these growth hormone deficient children, plasma pancreatic glucagon response to arginine was diminished, and there was a significantly (P less than 0.02) more rapid return to basal values than in the untreated group. The same trends persisted after long-term growth hormone therapy (2 iu three times per week for 12-30 months) in ten children but were not statistically significant. We conclude that growth hormone may play a role in modulating plasma pancreatic glucagon response. The persistent glucagon response to arginine noted in growth hormone deficient children might reflect a greater gluconeogenic stress imposed upon these children during fasting or decreased catabolism of glucagon in the growth hormone deficient state.

Adolescent↗
PubMed1977

Metabolic response to fasting in experimental intrauterine growth retardation induced by surgical and nonsurgical maternal stress.

Experimental intrauterine growth retardation was produced by two groups of neonatal rats by maternal sham surgery or by maternal obligatory exercise during the last 5 days of gestation (forced swim). Both experimental groups of neonates had lower plasma glucose and higher plasma insulin levels than controls after a 4-hour fast. Fetal stunting may be produced by a variety of maternal stresses in the rat and may be associated with alterations in the hormonal and glycemic response to fasting. Studies of the metabolic effects of experimental intrauterine growth retardation must be interpreted with caution if control animals have been subjected to intrauterine stress.

Animals↗
PubMed1977

Fasting plasma levels of glucose, acetoacetate, D-beta-hydroxybutyrate, glycerol, and lactate in the baboon infant: correlation with cerebral uptake of substrates and oxygen.

The energy-rich substrates available to the fasting stressed baboon neonate and infant are quantitatively similar to the metabolic fuels presented to the stressed low birth weight human newborn. Within a few hours after birth, fasting arterial plasma glucose levels in the baboon neonate approximate those of 4-6-week-old baboon infants after a 20-hr fast. Lactate levels are high and comparable for both age groups. In contrast, beta-hydroxybutyrate is quite low in the immediate neonatal period, but rises to significantly higher levels (P less than 0.001) after a fast at 4-6 weeks. In addition, glycerol levels are higher (P less than 0.02) in the fasted older infant compared with the fasting neonate. Computation of mean cerebral blood arteriovenous differences and oxygen equivalents for animals studied in the first 50 hr of life demonstrates that glucose uptake can account for 50% or less of cerebral oxygen consumption in the newborn period. In confirmation, the respiratory quotient in these animals is 0.52 +/- 0.06. Cerebral oxygen consumption in the immediate neonate is greater than can be explained by utilization of glucose and the small quantities of acetoacetate and beta-hydroxybutyrate available at this time. At birth, cerebral uptake of lactate is noted, but this phenomenon is not observed at 6 and 12 weeks of age.

Acetoacetates↗
PubMed1976

Stimulation of DNA synthesis in isolated chondrocytes by somatomedin. II. Validation of the assay for clinical use and comparison with stimulation of protein synthesis.

The effects of GH on cartilage may be mediated by a variety of serum factors (somatomedins; SM). We have reported (Endocrinology 90: 1086, 1972) stimulation of thymidine incorporation in isolated chicken embryo chondrocytes by normal human serum. This was greater than that caused by serum from patients with hypopituitarism. We have now compared the stimulatory activity estimated by [3H]thymidine incorporation (SMT) with that estimated by [3H]leucine incorporation in 46 sera from children with GH deficiency; with short stature, but normal GH responsiveness; or with normal stature and normal GH responsiveness. These activities were also measured in sera from 9 normal adults and 12 acromegalics. Sera from GH deficient children had reduced SMT activity (.54 +/- .04; (mean +/- SE) P less than .01) compared to normal children (.83 +/- .08) whereas the sera from children with short stature and normal GH responsiveness had higher levels than normal (1.19 +/- .10: P less than .02). Acromegalic adults averaged higher SMT activity than normal adults (1.62 +/- .15 vs. 1.17 +/- .11; P less than .05). In sharp contrast, the leucine incorporation was essentially the same in the different groups of children. These studies have validated the use of the incorporation of thymidine into isolated chicken embryo chondrocytes as an adjunct in the evaluation of children with short stature (82.6% of the samples from children gave results that were consistent with their status as determined by provocative tests for GH). The disparity between the results with thymidine incorporation and those with leucine incorporation is as yet unexplained.

Adolescent↗
PubMedDate not supplied

Abnormal cardiac function after exercise in insulin-dependent diabetic children and adolescents.

We evaluated the cardiac response to dynamic exercise in a group of otherwise healthy insulin-dependent older children and adolescents and in a nondiabetic control group by postexercise echocardiography. Both groups had similar left ventricular function at rest. After exercise we found abnormalities in the indicators of systolic function, fractional shortening (0.37 vs. 0.43) and rate-corrected velocity of circumferential fiber shortening (2.80 vs. 3.35 circumferences/s). In addition, we found an association of flattened interventricular septal motion with finger contractures in the diabetic subjects. Echocardiographic abnormalities in asymptomatic young diabetic adolescents can be elucidated by postexercise echocardiography. Postexercise echocardiography is a noninvasive procedure that can easily be done in the adolescent population and is useful for evaluating subclinical cardiomyopathy.

Adolescent↗