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Biomedical subjects

A D Rogol

Publications and source records attributed to A D Rogol.

At least 73 records · Page 4Linked to original sources
PubMed1994

Growth at puberty: interaction of androgens and growth hormone.

Puberty is characterized by the onset and continued development of secondary sexual characteristics and an abrupt onset of linear growth. Growth in boys occurs due to the rising levels of androgens and also indirectly mediated by growth hormone (GH) and the insulin-like growth factors. Data are presented to show marked androgen-dependence of GH increases at puberty. The mode of this increase is through an augmentation in the amplitude of the pulses rather than in their frequency. Shortly after the maximal rate of growth, the pattern of GH release reverts toward that of the prepubertal child. To investigate the neuroendocrine mechanism through which androgens increase the mean circulating GH level, deconvolutional analysis has been applied. At mid-puberty the maximal rate of GH release per secretory burst and the total amount released per burst were increased. There were no significant alterations in the duration or frequency of the GH secretory burst or in the serum half-life reflecting the metabolic clearance of the hormone. Thus, the pubertal growth spurt in boys is likely subserved by the altered neurosecretory dynamics for GH. These altered hormone levels likely produce the equally profound changes in body composition, regional fat distribution, and muscular strength that occur during puberty in boys.

Adolescent↗
PubMed1994

Hypopituitarism.

Explore the source record for details and available documents.

Adrenocorticotropic Hormone↗
PubMed1993

Alterations in the neuroendocrine control of growth hormone secretion in the uremic rat.

Chronic renal insufficiency (CRI) is associated with growth failure in children and laboratory rats and is considered to be due, in part, to co-existent malnutrition. Alterations in hypothalamic control of growth hormone (GH) secretion have been suggested in uremic patients. We sought to determine whether factors unique to CRI play a role in this disturbance of GH regulation. Using in situ hybridization histochemistry, we compared messenger RNA (mRNA) levels for the hypothalamic neurohormones GH-releasing hormone (GHRH) and somatostatin (SRIH) in three groups: rats with CRI induced by 5/6 nephrectomy (NPX, N = 4); sham-operated, ad libitum fed rats (SAL, N = 5); and sham-operated, pair-fed rats (SPF, N = 5). We also measured plasma GH at 10 minute intervals for a six hour period via intra-atrial cannulae. The NPX group had significantly lower hypothalamic GHRH mRNA concentrations than both other groups; in addition, these levels were significantly lower in the SPF than in the SAL group. Concentrations of hypothalamic SRIH mRNA did not differ significantly among the three experimental groups. Six-hour mean plasma GH concentrations were significantly lower in the SPF (18.3 +/- 1.8 micrograms/liter) than in either the SAL (27.0 +/- 3.3 micrograms/liter) or the NPX groups (36.8 +/- 7.2 micrograms/liter); the difference in the mean plasma GH levels in the NPX vs. the SAL group did not attain statistical significance. This study provides evidence for an effect of CRI on the neuroendocrine control of GH secretion not related to caloric intake.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Cholinergic and opioid involvement in release of growth hormone during exercise and recovery.

Cholinergic and opioid pathways have been implicated as mediators of the increased growth hormone (GH) release observed during exercise. This study compared the GH responses induced by a moderate-intensity exercise bout during treatment with placebo (Plac), the opioid receptor antagonist naltrexone (Nalt), the indirect cholinergic agonist pyridostigmine (PD), or a combination of the two drugs (P + N). Ten active males served as subjects (age, 25.1 +/- 0.6 yr; wt, 79.7 +/- 2.5 kg; % body fat, 14.9 +/- 1.4; peak oxygen consumption, 46.2 +/- 2.7 ml.kg-1 x min-1). Blood samples were drawn at 5-min intervals during the 4.5-h testing period to determine the GH concentration. The testing period was divided as follows: 0600-700 h = baseline, 0700-0800 h = preexercise, 0800-0830 h = exercise, and 0830-1030 h = recovery. Drugs were administered 1 h before exercise (at 0700 h). Exercise consisted of 30 min of cycling at an individualized work load previously found to elicit a blood lactate concentration of 2.5 mM. Heart rate, oxygen consumption, blood lactate, and blood glucose were measured throughout the exercise period. Results indicated that neither the resting GH concentration nor the metabolic parameters during exercise were altered by the treatments. Peak serum GH concentration was not significantly altered by the treatments (range 7.3 +/- 2.0 to 12.6 +/- 4.4 micrograms/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Altered growth hormone secretory dynamics in prepubertal males with constitutional delay of growth.

We have used the technique of deconvolution analysis to determine if abnormalities in growth hormone (GH) secretion or metabolic clearance underlie the observed alterations in circulating hormone concentrations in a group of seven prepubertal males with constitutional delay of growth (SHORT-DBA). The results were compared with data obtained from 13 healthy, short prepubertal males (SHORT) and 11 healthy prepubertal male subjects of normal stature (NORMAL). Although the mean 12-h overnight GH production rates were invariant among the groups (8.0 +/- 1.0 versus 7.3 +/- 0.7 versus 6.7 +/- 1.2 micrograms/L, NORMAL versus SHORT versus SHORT-DBA for all comparisons), different secretory mechanisms were operative. The secretory burst half-duration (time interval of the secretory event at half-maximal amplitude) of the SHORT-DBA subjects (26 +/- 1 min) was greater (p = 0.02) than that of the SHORT group (20 +/- 1 min); values for both the SHORT and SHORT-DBA subjects were indistinguishable from that of NORMAL controls (22 +/- 2). Both the mass of GH released per secretory episode and the maximal rate of hormone secretion were less (p < or = 0.02 and the p < 0.01, respectively) for the SHORT-DBA subjects [16 +/- 2 micrograms/unit of body distribution volume (Lv) and 0.6 +/- 0.1 microgram/Lv/min, respectively] compared with those of the NORMAL (26 +/- 2 micrograms/L, and 1.1 +/- 0.1 micrograms/Lv/min, respectively) and SHORT (28 +/- 4 micrograms/Lv and 1.3 +/- 0.2 micrograms/Lv/min, respectively) groups; values for the latter two groups were indistinguishable.(ABSTRACT TRUNCATED AT 250 WORDS)

Body Height↗
PubMed1993

Estimation of daily cortisol production and clearance rates in normal pubertal males by deconvolution analysis.

To investigate daily cortisol production and clearance rates in a group (n = 18) of normal unstressed pubertal males, we applied deconvolution analysis to serum cortisol concentrations obtained every 20 min for 24 h. Subject-specific characterization of adrenocortical secretory episodes, cortisol production rate, and serum hormone half-life for nine early pubertal (Tanner I or II; early) and nine late pubertal (Tanner IV or V; late) subjects was undertaken to assess potential roles of sexual maturation and changing gonadal steroid hormone concentrations on glucocorticoid physiology. The estimated cortisol production rate for the early group [16.8 +/- 1.3 mumol/m2 x day (6.1 +/- 0.4 mg/m2 x day)] was indistinguishable from that of the late subjects [14.8 +/- 1.4 mumol/m2 x day (5.3 +/- 0.5 mg/m2 x day)]. No differences were observed between the two pubertal groups in the secretory burst frequency and half-duration, mass of cortisol released per secretory episode, average maximal rate of hormone secretion, and serum cortisol half-life. A significant diurnal pattern of cortisol secretion was observed for all subjects manifest by nyctohemeral variations in the frequency of adrenocortical secretory bursts, the amplitude (maximal rate of cortisol secretion) and the mass of cortisol released per secretory episode. Maximum serum hormone concentrations occurred between 0706 and 1114 h. We conclude that in normal pubertal males: 1) cortisol production rates as estimated by deconvolution analysis are in agreement with other recent independent isotopic estimates, but are lower than many previous estimates; 2) the rise in serum gonadal steroid hormone levels is unassociated with alterations in the production rate or metabolic clearance of cortisol; and 3) increased secretory burst frequency, increased amplitude (maximal rate of cortisol secretion attained within each secretory event), and increased mass of cortisol released per adrenocortical secretory episode give rise to the normal diurnal rhythm of circulating cortisol.

17-Hydroxycorticosteroids↗
PubMed1993

A longitudinal assessment of hormonal and physical alterations during normal puberty in boys. I. Serum growth hormone-binding protein.

Previous studies have provided compelling evidence that GH secretion increases transiently during midpuberty in normally growing children. Although it is likely that the increase in GH production serves a primary role in generating the pubertal growth spurt, such a conclusion necessarily assumes that other essential "down-stream" components of the GH axis responsible for mediating the effects of GH remain unchanged. To investigate this concept, we assessed longitudinally another important component of the endogenous GH axis, the serum GH-binding protein (GHBP)/receptor system, in a cohort of 11 normal boys as they matured through normal puberty. At 4-month intervals over 4.0-5.1 yr, 24-h serum GH concentration profiles and serum GHBP activity were evaluated. Serum GHBP levels varied over a more than 12-fold range (40-504 pmol/L) among all subjects. However, the values for individual subjects consistently varied within more narrow limits. The coefficient of variation for values from all subjects was 51% compared to the mean intrasubject coefficient of variation of only 30% (P < 0.05). Although the highest GHBP level (all subjects) was 12.6-fold greater than the lowest, the mean intrasubject range was only 3.1 +/- 0.5-fold (P < 0.05). The overall mean serum GHBP level correlated directly with the overall mean body mass index (r = 0.69; P = 0.018), but correlated inversely with the mean 24-h GH concentration (r = -0.61; P < 0.05). There was no significant increase in the GHBP level during puberty. However, because mean 24-h GH concentrations did increase during midpuberty, the data suggest that an increase in the relative amounts of free vs. bound GH develops during the period of the pubertal growth spurt. These data indicate that serum GHBP levels are regulated in individual children within much more narrow limits than those present in the larger population and do not undergo the dramatic changes during puberty typical of GH secretion and linear growth velocity. As a consequence, alterations may develop in the relative amounts of free vs. bound GH present in serum during the midpubertal years compared to those present during either the prepubertal or postpubertal periods. The majority of the known age-related increase in serum GHBP levels probably occurs before the period of active pubertal development. These findings strengthen further the concept that the midpubertal changes in GH secretion serve a primary role in generating the growth spurt.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Determination by Skeleton↗
PubMed1993

Characterization of pulsatile secretion and clearance of plasma cortisol in premature and term neonates using deconvolution analysis.

Pulsatile secretion of cortisol (F) has not been documented in the newborn infant. Using repeated blood sampling and deconvolution analysis, we investigated F secretion and elimination dynamics in a group of five premature (gestational age, 24-34 weeks) and five term neonates. These infants had required placement of an umbilical arterial cannula for monitoring respiratory status, but were otherwise clinically stable. Blood samples were obtained at 15-min intervals for a 6-h period. All plasma F determinations were 58 nmol/L (2.1 micrograms/dL) or more, and pulsatile F secretion was observed in all infants. No significant differences were noted between the two groups with regard to 6-h mean plasma F concentration [350 +/- 129 (premature) vs. 277 +/- 54 nmol/L (term)], plasma corticosteroid-binding globulin (14 +/- 0 vs. 13 +/- 1 mg/L), F secretory burst frequency (4 +/- 0 vs. 5 +/- 1 bursts/6 h), mass of F secreted per burst [760 +/- 480 vs. 310 +/- 100 nmol/Lv [Lv, liter of F distribution volume)], F production rate (FPR; 2.7 +/- 1.4 vs. 1.1 +/- 0.2 mumol/Lv.6 h), or plasma F half-life (45 +/- 6 vs. 56 +/- 4 min). However, the premature infants had a significantly longer F secretory burst half-duration (63 +/- 18 vs. 6.7 +/- 4.0 min; P < 0.01) and a significantly lower maximal F secretory rate (9.4 +/- 3.4 vs. 100 +/- 26 nmol/Lv.min; P < 0.02) than the term infants. Body surface area and body weight were inversely correlated with F secretory burst half-duration (r = -0.74 and -0.75, respectively); both were also positively correlated with the maximal F secretory rate (r = 0.66 and 0.72). The two most premature infants had significantly greater mean plasma F and FPR than the other three premature and all of the term infants. Extrapolating to 24 h and correcting for the distribution volume of F and body surface area, we estimate FPR to be approximately 17-24 mumol/m2.24 h (6.6-8.8 mg/m2.24 h) for newborn infants of 34 weeks or more gestational age. These values are consistent with newer estimates of FPR in older children and adults determined using either deconvolution analysis or stable isotope dilution methods.

Adrenal Cortex↗
PubMed1993

Alterations in growth hormone secretion and clearance in adolescent boys with insulin-dependent diabetes mellitus.

At puberty, elevated circulating GH concentrations are found, with a parallel increase in the levels of insulin-like growth factor-I (IGF-I). However, these hormonal changes are less well understood in children with insulin-dependent diabetes mellitus (IDDM) during the peripubertal years. Since the metabolic derangement is often associated with elevated circulating GH and diminished serum IGF-I levels, we sought to determine whether similar alterations occur in boys with IDDM. A multiple parameter deconvolution analysis was applied to serum GH concentrations measured at 20-min intervals for 24 h in 25 boys with IDDM. Subjects were divided into 3 pubertal groups, pre (n = 9), early (n = 8), and late (n = 11), according to Tanner stage. Glycosylated hemoglobin and body mass index-SD scores were indistinguishable among groups. Forty nondiabetic peripubertal boys served as controls. Similar to those in the normal boys, circulating GH concentrations and serum IGF-I levels increased during puberty in the boys with IDDM. The augmented circulating GH concentrations occur due to an increase in GH secretion, as determined by calculated daily GH production rates (760 +/- 119 vs. 1025 +/- 121 vs. 1821 +/- 266 micrograms/day, respectively for the 3 groups). IGF-I levels were decreased in prepuberty in the boys with IDDM and were overcome with increasing pubertal development (0.68 +/- 0.13 vs. 0.78 +/- 0.11 vs. 1.53 +/- 0.20 U/mL; P < 0.05). There was an increase in the maximal rate of GH secretion per burst (amplitude) during prepuberty (0.54 +/- 0.05 vs. 0.88 +/- 0.17 microgram/L.min, control vs. IDDM; P = 0.03) and early puberty (0.64 +/- 0.10 vs. 0.88 +/- 0.10 microgram/L.min; p = 0.04). The differences in amplitude between the controls and the boys with IDDM were absent once puberty was well established (1.00 +/- 0.10 vs. 1.02 +/- 0.14 microgram/L.min; P > 0.05). The metabolic clearance of GH was increased in the late pubertal boys with IDDM compared to that in their controls (GH half-life, 24.0 +/- 1.0 in control vs. 19.8 +/- 0.5 min in diabetics; P = 0.006). We conclude that comparable increments in GH secretion and serum IGF-I levels in boys with IDDM in moderate glycemic control and controls are presumably related to increased levels of testosterone in both groups. However, differences exist with respect to GH secretory burst amplitude (augmented) and serum IGF-I concentrations (decreased) before puberty is reached. These alterations disappear with the establishment of puberty.

Adolescent↗
PubMed1993

Altered growth hormone (GH) secretion in vivo and in vitro in the diabetes-prone BB/Worcester rat.

Diminished concentrations of growth hormone (GH) have been observed in the male BB/Wor rat with diabetes mellitus (DM). The precise mechanism(s) responsible for the altered GH levels is not entirely understood. We have therefore employed independent techniques to investigate potential alterations in: 1) the peripheral metabolism of the hormone; 2) GH release by somatotropes; and 3) hypothalamic regulation of GH secretion. An extra group of insulin-untreated animals was included for the studies of acute DM. The results demonstrate diminished circulating mean concentrations of GH (35 +/- 4 vs. 16 +/- 4 micrograms/l; mean +/- SEM; control vs. animal with DM; P = 0.006) due to impaired GH secretion. In particular, there was a decrease in the mass of GH secreted per burst (230 +/- 22 vs. 136 +/- 34 micrograms/l; P = 0.04) and in the GH secretory rate (24 +/- 4 vs. 9 +/- 3 micrograms/l/min; P < 0.01). No differences in the secretory burst frequency, (5.3 +/- 0.3 vs. 5.2 +/- 0.5 #/8-h; P = 0.68), secretory half-duration (10 +/- 2 vs. 17 +/- 2 min; P = 0.09), or serum GH half-life (8 +/- 1 vs. 6 +/- 1 min; P = 0.13) were observed. In vitro studies of acutely dispersed somatotropes obtained from rats with DM demonstrated increased sensitivity to GHRH (1 nM), as detected by a greater mean hemolytic plaque area following exposure to an EC50 dose of the secretagogue (14.3 +/- 3.3 vs. 17.4 +/- 3.5 microns 2 x 10(3); P = 0.049), and diminished sensitivity to SRIH (1 nM) inhibition of GH release following exposure to an EC50 dose of the secretagogue (10.0 +/- 1.2 vs. 14.9 +/- 2.3 microns2 x 10(3); P = 0.026). The number of the pituitary cells (18.0 +/- 2.8 vs. 15.3 +/- 1.0 x 10(5) cells; P = 0.38) as well as the number of somatotropes (7.3 +/- 1.4 vs. 7.6 +/- 0.9 x 10(5) cells; P = 0.87) were indistinguishable between experimental groups. Hypothalamic gene transcript levels for GH-releasing hormone (GHRH) and somatotropin release-inhibiting hormone (SRIH) were evaluated by in situ hybridization histochemistry to assess cellular synthetic activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Age Factors↗
PubMed1992

Exercise training at and above the lactate threshold in previously untrained women.

We examined the effects of training at and above the lactate threshold in previously untrained women. Twenty-four untrained eumenorrheic women (age = 31.3 +/- 4.0 yrs, wt = 66.2 +/- 7.6 kg, ht = 166.4 +/- 5.8 cm) were assessed at baseline [during days 1-3 of the menstrual cycle (MC)] and every 4 MC after that (for 1 year) for VO2 and velocity (V) at LT, fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM, and Max. Subjects were assigned to control (C, n = 7), at LT/LT, trained 6 days/week at the velocity associated with LT, (n = 9) or above LT (greater than LT, trained 3 days/week at the velocity midway between V LT and V Max and 3 days/week at V LT, n = 8) groups. Exercise prescriptions were adjusted after each assessment and each group progressed similarly in weekly mileage. No between group differences were observed before training. After training the greater than LT group had significantly higher values than the C and /LT groups for LT (p less than 0.05). For FBLC of 2.0, 2.5, and 4.0 mM and Max, the greater than LT group values were greater than the C group (p less than 0.05). No differences were observed after training between the /LT and C groups. Although the greater than LT group had higher VO2 and V Max values than the /LT group after training, these differences were not statistically significant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

The effect of training intensity on ratings of perceived exertion.

We examined the effects of intensity of training on ratings of perceived exertion (RPE) at the lactate threshold (LT), fixed blood lactate concentrations (FBLC) of 2.0, 2.5 and 4.0 mM and peak in 25 untrained eumenorrheic women (mean +/- SD: age = 30.9 +/- 4.1 yrs; height = 165.7 +/- 5.9 cm; weight = 65.5 +/- 7.6 kg) who completed one year of run training. Subjects were recruited as sedentary controls or were randomly assigned to one of two training groups: 1) at the lactate threshold (at LT) or 2) above the lactate threshold (greater than LT). The at LT group trained at velocity LT and the greater than LT group trained at the velocity midway between velocity LT and peak velocity. Training subjects were reevaluated every fourth menstrual cycle and training intensity was adjusted. The control group was reassessed at menstrual cycle 12. Before training no among group differences were observed for VO2 or velocity at LT, FBLC and peak. Both training groups increased VO2 at LT, FBLC and peak as a result of training (p less than 0.05), with the greater than LT group exhibiting greater improvement than the at LT group (VO2 at LT, FBLC of 2.0, 2.5 and 4.0 mM and peak increased by 6.4, 5.3, 5.1, 4.0 and 4.7 ml/kg.min-1 for at LT and by 10.4, 9.2, 8.6, 5.1 and 5.9 ml/kg.min-1 for greater than LT; p less than 0.05). Similar findings were observed for the velocity associated with these lactate concentrations. No pre/post differences were observed in VO2 or velocity for the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Dietary patterns, eating behaviors, and bone mineral density in women runners.

Although reduced gonadal steroid hormone concentrations appear to play a major role in lower trabecular bone mineral density (BMD) in women with athletic amenorrhea, dietary deficiencies and eating behaviors may also affect BMD in women runners. To investigate this possibility, dietary patterns (7-d records), eating-disorders inventory (EDI), and BMD were examined in nine nonrunning eumenorrheic control (Contl) and 32 women runners classified as eumenorrheic (n = 19, Eumen) and oligo/amenorrheic (a group in which some were oligomenorrheic and some were amenorrheic; Ol/Am, n = 13). Runner groups had similar cardiorespiratory fitness, body composition, and training characteristics. Lumbar spine BMD was lower in the Ol/Am runners (-12%, P less than 0.05) but proximal femur BMD did not differ. Dietary intake and EDI subscale scores were similar among the groups. However, there was an inverse trend between EDI subscale scores for bulimia and ineffectiveness and femoral BMD in the Ol/Am runners (r = -0.62 to -0.71, P less than 0.05). These results suggest that self-reported dietary intake and/or eating behaviors do not predict reproductive-function alterations in women runners, but eating behaviors may be associated with lower BMD in Ol/Am runners.

Adolescent↗
PubMed1992

Durability of the reproductive axis in eumenorrheic women during 1 yr of endurance training.

Menstrual cycle (MC) alterations occur in some endurance-training women. We hypothesized that a prospective running program would evoke alterations in MC phase lengths and in the physiological frequency of pulses of luteinizing hormone (LH) and/or diminish 24-h integrated serum LH concentrations in some women. In addition, we postulated that women who train more intensively (above the lactate threshold) would show alterations in gonadotropin release earlier in the training program or to a greater degree. To test these hypotheses, we examined the effects of different exercise intensities on physiological and endocrine responses. Twenty-three healthy eumenorrheic gynecologically mature (postmenarchal age 17.8 +/- 0.9 yr) untrained women undertook a 1-yr training program at one of two exercise intensities, one at a velocity corresponding to the lactate threshold (LT) and the other halfway between that of LT and peak running velocity, or served as controls. Training distance was the same in each exercise group. Physiological measurements were repeated every four MC to track changes in fitness and readjust training velocities. The lengths of the MC and the follicular and luteal phases were determined from hormonal concentrations. Body composition, nutritional intake, and pulsatile release of LH were determined. The women ran approximately 790 miles. Each group improved physiologically, with the greater than LT group improving to a greater degree. A less than 2-day decrease in the luteal phase length was observed only in the greater than LT group. No significant changes for any parameter of pulsatile LH release were noted between exercise groups. No significant changes in nutritional intake and only small changes in body composition were noted in either exercise group despite the added energy expenditure of exercise. We conclude that a progressive exercise program of moderate distance and intensity does not adversely affect the robust reproductive system of gynecologically mature eumenorrheic women.

Adult↗
PubMed1992

Reproductive hormones and bone mineral density in women runners.

We examined the relationships among reproductive hormone concentrations and bone mineral density (BMD) in 43 women runners classified as eumenorrheic (n = 24), oligomenorrheic (n = 8), or amenorrheic (n = 11). Results were compared with a eumenorrheic nonrunner control group (n = 11). Serum 17 beta-estradiol, progesterone, and dehydroepiandrosterone sulfate concentrations were determined in daily blood samples for 21 days, and integrated concentrations (areas under the curve) were calculated. BMD was assessed at the lumbar spine and proximal femur by dual-photon absorptiometry. As expected, 17 beta-estradiol, progesterone, and lumbar spine BMD were higher in the control and eumenorrheic runner groups than in the oligomenorrheic and amenorrheic runner groups (P less than 0.05). Progesterone concentration was significantly correlated with lumbar spine BMD in the eumenorrheic runners (r = 0.61). None of the steroid hormones was significantly related to BMD in the oligomenorrheic/amenorrheic group. The present data suggest that circulating levels of gonadal steroid hormones affect axial BMD in eumenorrheic runners.

Adolescent↗
PubMed1992

Endurance training amplifies the pulsatile release of growth hormone: effects of training intensity.

The effects of intensity of run training on the pulsatile release of growth hormone (GH) were investigated in 21 eumenorrheic untrained women. The O2 consumption (VO2) at the lactate threshold (LT); fixed blood lactate concentrations (FBLC) of 2.0, 2.5, and 4.0 mM; peak VO2; maximal VO2; body composition; and pulsatile release of GH were measured. Subjects in both the at-lactate threshold (/LT, n = 9) and above-lactate threshold (greater than LT, n = 7) training groups increased VO2 at LT and FBLC of 2.0, 2.5, and 4.0 mM and VO2max after 1 yr of run training. However, the increase observed in the greater than LT group was greater than that in the /LT group (P less than 0.05). No change was observed for the control group (n = 5). No among- or within-group differences were observed for body weight, although trends for reductions in percent body fat (P less than 0.06) and fat weight (P less than 0.15) were observed in the greater than LT group, and both training groups significantly increased fat-free weight (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Exogenous androgen does not alter hypothalamic proopiomelanocortin gene transcript levels in the sexually immature male rat.

To investigate possible mechanisms whereby the augmentation of hypothalamic proopiomelanocortin (POMC) messenger ribonucleic acid (mRNA) levels occurs with pubertal development, we employed the techniques of testosterone administration and in situ hybridization histochemistry in sexually immature male rats. Six animals from each of the following groups were studied: (1) untreated controls (CTRL); (2) empty capsule (SHAM); (3) testosterone capsule (TEST), and (4) untreated adults (ADLT). Capsules were implanted at 21 days of age. Groups 1-3 were sacrificed at 35 days of life; group 4 at 55 days. Ventral prostate and seminal vesicle weights were obtained to assess the biologic effect of testosterone. Hybridizations were performed on coronal brain slices through the region of the arcuate nucleus using a 35S-labeled oligonucleotide probe complementary to a 30-base sequence within POMC mRNA. Anatomically matched tissue sections (11 per animal, from the retrochiasmatic region rostrally to the premammillary nucleus caudally) were exposed to x-ray film, followed by densitometric analysis. The mean serum testosterone concentration of the TEST group was significantly greater than that of the ADLT animals; values for the CTRL and SHAM rats were undetectable. The accessory sex organ weights of the ADLT animals were greater than those of the TEST rats; both values were greater than those of the CTRL and SHAM groups which were indistinguishable. Increased levels of hypothalamic POMC mRNA were observed in the male rat after pubertal development.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗