Daily rhythm of plasma insulin in Japanese quail (Coturnix c. japonica) fed ad libitum

1. Plasma levels of immuno-reactive insulin (IRI) of 6 groups of 5-week-old quail, held on a 16L:8D photoregime, were measured every 4 hr, for 24 hr. 2. Concentrations of plasma IRI varied during the 24 hr period (Anova, P < 0.003). Insulin levels were high (mean = 857 pg/ml) from 6 a.m. (light onset) until 6 p.m. (4 hr before light offset) and low (mean = 185 pg/ml) at 10 p.m. and 2 a.m. 3. IRI concentrations at 6 a.m., 10 a.m., 2 p.m. and 6 p.m. were significantly different from values at 2 a.m. and 10 p.m. by Waller grouping. 4. Low IRI levels at light offset (10 p.m.--when the birds had full crops and were in an absorptive state) and high levels at light onset (6 a.m.--before feeding resumed) indicate that feeding does not fully account for the IRI rhythm.

Freerunning circasemilunar spawning rhythm of Fundulus grandis and its temperature compensation

Gulf killifish, Fundulus grandis, exhibit rhythmic reproductive activities that are synchronized with semilunar tidal fluctuations in their Gulf coast habitat. These cyclic activities, monitored through daily egg collections, persist in the laboratory for as long as four months with periods near the tidal period of 13.7 days. In nature, a specific semilunar spawning phase is maintained with respect to tidal cycles. However, in the laboratory, the phase may gradually advance or delay. These phase changes occur as a result of small differences between the periods of the spawning cycle and concurrent tidal cycle. Changes in the phase of the spawning cycle can be produced after several cycles by exposing fish to different temperatures (21 and 27°C). However, the period of the spawning cycle changes only slightly with temperature. Q10 calculations produce a value not significantly different from 1.0, indicating nearly complete temperature compensation. These results provide evidence for an endogenous circasemilunar cycle that is temperature-compensated and freeruns in the laboratory.

Timed bromocriptine administration reduces body fat stores in obese subjects and hyperglycemia in type II diabetics

Obese postmenopausal female volunteers were given timed daily oral dosages of bromocriptine, and tested for reduction of body fat stores. This dopamine agonist has been shown to reset circadian rhythms that are altered in obese animals and to reduce body fat levels in several animal models. The participants were instructed not to alter their existing exercise and eating behavior during treatment. Skinfold measurements were taken on 33 subjects as indices of body fat. The measurements (e.g., suprailiac) were reduced after six weeks by about 25%, which represents a reduction of 11.7% of the total body fat. These dramatic decreases in body fat, which are equivalent to that produced by severe caloric restriction, were accompanied by more modest reductions of body weight (2.5%), indicating a possible conservation of protein that is usually lost as a consequence of such caloric restriction. The effects of bromocriptine treatment on body fat and hyperglycemia were also examined in non-insulin dependent diabetics being treated with oral hypoglycemics (7 subjects) or insulin (7 subjects). Total body fat was reduced by 10.7% and 5.1% in diabetics on oral hypoglycemics and insulin, respectively, without any significant reductions in body weight. Hyperglycemia was reduced in most of the 15 diabetic subjects treated leading to euglycemia and even cessation of hypoglycemic drugs in 3 of the 7 subjects during 4-8 weeks of bromocriptine treatment. These findings support the hypothesis that obesity and type II diabetes may be treated effectively with bromocriptine when administered at the proper times and dosages.

Transurethral radiofrequency heating or thermotherapy for benign prostatic hypertrophy: a prospective trial on 65 consecutive cases

65 consecutive cases with symptomatic benign prostate hypertrophy were treated with transurethral radiowave thermotherapy (TURF) using the Thermex-II at a temperature of 44.5 degrees C. We report uroflowmetry and symptom scores after a follow-up of 6 months. The mean age was 63 years, the mean maximal flow (Qmax) was 8.3 ml/s, mean voided volume was 195.6 ml, mean residual urine was 60.7 ml and the mean Madsen symptom score 9.7. Values at baseline and at 1, 3 and 6 months after TURF are discussed. The mean subjective symptom score dropped to 6.3 (p < 0.01). In the entire group, the objective measure scores (OMS) did not change significantly. However the OMS improved significantly in a subgroup with a Qmax < 10.0 ml/s. The Madsen symptom score improved in 70% of the cases after 6 months.

Bromocriptine inhibits the seasonally occurring obesity, hyperinsulinemia, insulin resistance, and impaired glucose tolerance in the Syrian hamster, Mesocricetus auratus

Seasonally obese-hyperinsulinemic female Syrian hamsters were injected daily with bromocriptine or saline for a period of 34 days to test for effects of bromocriptine on body fat store levels, hepatic triglyceride secretion, glucose tolerance, and plasma insulin and glucose concentrations. The effects of bromocriptine on body fat store levels, as well as on plasma insulin and glucose concentrations, in seasonally obese hamsters were compared with the levels of body fat, plasma insulin, and plasma glucose observed in seasonally lean hamsters. Bromocriptine treatment substantially improved glucose intolerance and reduced the total and stimulated areas under the glucose tolerance curve by 33% after 14 days of treatment. After 34 days of treatment, bromocriptine reduced body fat store levels by 36% and hepatic triglyceride secretion by 40% without any concurrent change in food consumption. Furthermore, bromocriptine reduced the plasma insulin level by 70%, while slightly reducing plasma glucose concentration (ie, 68% reduction in the insulin to glucose ratio). The reductions of body fat, plasma insulin, and plasma insulin to glucose ratio produced by bromocriptine in seasonally obese hamsters are equivalent to those observed in seasonally lean hamsters. Shifts in phase relationships of circadian neuroendocrine rhythms have been demonstrated to regulate annual cycles of metabolism in vertebrates, including the Syrian hamster. The effects of bromocriptine can also be explained as an alteration of such a circadian mechanism.

Effect of 12 hr temporal relation of serotonin and dopamine precursor drugs (5-HTP and L-DOPA) on photosexual responses of immature Japanese quail

To study the interaction of photoperiod and circadian neurotransmitter activity, L-DOPA L-dihydroxyphenylalanine, dopamine precursor) was administered daily, 12 hr after 5-HTP (5-hydroxy tryptophan, serotonin precursor) in sexually immature Japanese quail, raised under short photoperiod (LD8:16) since hatching. The 12 hr treatment of 5-HTP and L-DOPA was given under continuous condition of light for 11 days. After treatment the quail were transferred to intermediate day length (LD 13.5:10.5). The cloacal gland size of drug treated group increased significantly in comparison to control. The quail were then transferred to short photoperiod (LD 8:16). The cloacal gland size of both the groups started decreasing gradually but the rate was significantly low in drug treated quail in comparison to control. The results indicate that the endogenous mechanism controlling seasonality may be reset by drugs that influence serotonergic and dopaminergic activity. The 12 hr relation between the two drugs is stimulatory for gonadal growth under intermediate day length and retards the rate of regression when transferred to short days.

Hepatic vagotomy abolishes the circadian rhythm of lipogenic responsiveness to insulin and reduces fat stores in hamsters

The effects of hepatic vagotomy upon the circadian rhythm of lipogenesis and body fat store levels were tested in seasonally obese Syrian hamsters. Lipogenesis was studied 8 weeks after surgery by measuring the incorporation of label into epididymal and retroperitoneal fat pad lipid in animals killed 30 min after intraperitoneal [3H]-glucose injection and 2 h after bovine insulin injections. A marked circadian variation in insulin-stimulated lipogenesis was present in sham-operated controls. The peak of lipogenic activity occurred at light onset and was 3-fold greater than during the middle of the photophase. The peak in the circadian variation of plasma insulin coincided with the peak of lipogenic responsiveness to insulin in these animals. Hepatic vagotomy completely abolished the circadian variation in insulin-stimulated lipogenesis and reduced the magnitude of the daily lipogenic peak at light onset by 65%, but only slightly altered the phase of the circadian variation in plasma insulin by 4 h. Hepatic vagotomy did not influence plasma glucose levels, which did not vary as a function of time of day in either group. Body fat stores were severely reduced (40%) by hepatic vagotomy when examined 8 weeks after surgery. The present study demonstrates important roles for interactions of the circadian rhythms of insulin and tissue lipogenic responses to insulin in the regulation of body fat stores. Furthermore, this study demonstrates that hepatic vagal activity regulates the daily interval of lipogenic responsiveness to insulin and thereby directly influences body fat stores in the Syrian hamster.

Bromocriptine-induced reduction of body fat in pigs

An experiment was conducted with 36 crossbred finishing pigs (18 male castrates and 18 females) to evaluate the effect of bromocriptine implants on growth, feed intake, feed efficiency, plasma urea nitrogen (PUN) and carcass characteristics. Three levels of bromocriptine (0, 5 and 10 mg/[pig.d]) were administered, via implants at the base of the ear, to six (two replicates of three) male castrates or to six (two replicates of three) intact female pigs (2 x 3 factorial arrangement of treatments). Average initial weight of pigs at the time of implantation was 89.7 kg, and the implants remained in the pigs for 28 (replicate 1) or 30 (replicate 2) d prior to slaughter. Gain, feed intake and efficiency of feed utilization were not affected (P greater than .10) by bromocriptine. Plasma urea nitrogen was lower in female pigs administered 10 mg bromocriptine; bromocriptine did not affect PUN of male pigs (gender x bromocriptine, P less than .08). Tenth rib fat thickness and average backfat thickness were lower (P less than .06) and percentage of muscling was higher (P less than .06) in pigs implanted with bromocriptine. Female pigs had less 10th rib fat but larger loin eye areas and a greater percentage of muscling than male pigs.

Properly timed injections of cortisol and prolactin produce long-term reductions in obesity, hyperinsulinaemia and insulin resistance in the Syrian hamster (Mesocricetus auratus)

Naturally obese female Syrian hamsters were injected daily with prolactin at 0 or 12 h after cortisol injections for 10 days while held in constant light. Controls were similarly injected with saline. Animals were then held on short daylengths (10 h light:14 h darkness) for 10 weeks. They were allowed free access to food and water from birth to time of death. Ten weeks after treatment, retroperitoneal fat stores, plasma concentrations of insulin and glucose, and hypoglycaemic responsiveness to exogenous insulin were determined. The control groups as well as the 12-h hormone treatment group were obese, hyperinsulinaemic and insulin resistant. However, the 0-h treatment dramatically reduced retroperitoneal fat stores (41-55%), plasma insulin concentration (60-70%) and the insulin to glucose ratio (63-68%) compared with controls. Values for these parameters in the 0-h treatment groups were similar to those of their lean litter-mates. Furthermore, the 0-h group but not the 12-h group was more sensitive than control animals to the hypoglycaemic effects of exogenous insulin at doses 0.2 and 2.0 U/kg body weight. These results demonstrate that timed daily injections of cortisol and prolactin in specific temporal relationships can produce marked reductions in obesity, hyperinsulinaemia and insulin resistance in the Syrian hamster that persist long after the termination of treatment. This study also suggests an important role for the interactions of circadian neuroendocrine systems in the regulation of these metabolic states.

Melatonin mediates alternation of seasonality in Syrian hamsters

The annual cycle of reproductive activity in the Syrian hamster, Mesocricetus auratus, is the result of interaction between seasonal changes in daylength (photoperiodism) and seasonal changes in responsiveness to daylength (seasonality). The present experiment was designed to investigate the role of the pineal gland and its hormone, melatonin, in the alternation of seasonality (scotosensitivity and scotorefractoriness). Male hamsters were maintained on short daylengths (10L:14D) to establish scotorefractoriness, and then they were transferred to long daylengths (14L:10D) for conversion to scotosensitivity (sensitive to short daylengths). Before transfer to long daylengths, some of the hamsters were pinealectomized and others were sham-operated or unoperated. Some of the pinealectomized hamsters received single daily melatonin or saline injections while on long daylengths. After 14 wk on long daylengths, the hamsters were transferred to short daylengths for 10 wk to test for conversion to scotosensitivity. Pinealectomized hamsters were given three daily melatonin injections while on short daylengths. Such treatment is known to promote gonadal regression in scotosensitive but not in scotorefractory hamsters. Examination of testes after the short daylength interval revealed that exposure of nonpinealectomized hamsters to long daylengths had reestablished scotosensitivity (regressed testes). Pinealectomized hamsters that received no melatonin replacement while on long daylengths remained scotorefractory (enlarged testes), whereas those that received single daily injections of melatonin during long daylengths were found to be scotosensitive. These results indicate that a daily pulse of melatonin during expsoure to long daylengths has an important role in reestablishing responsiveness (scotosensitivity) to short daylengths.

Prolactin influences the circadian rhythm of lipogenesis in primary cultured hepatocytes

Hepatocytes from male Syrian hamsters were cultured in the presence of insulin and assayed for lipogenesis by following (14C)acetate incorporation into total cell lipid at 4 hourly intervals over a 48-h period. Circadian rhythms of lipogenic activity were observed on days 2 and 3 of culture. Although the phases of the rhythms were similar, the amplitude of the peak levels of lipogenesis declined from day 2 to 3. Addition of prolactin to the culture reversed this decline when introduced at specific times relative to the lipogenic peaks. Prolactin more than doubled lipogenesis only at the daily peaks of lipogenic activity and only when added to culture 20 h before the times of peak lipogenesis. The results are the first to demonstrate important roles for circadian rhythms and a direct prolactin stimulation in the regulation of lipogenesis in primary hepatocyte culture.

Reductions of body fat stores and total plasma cholesterol and triglyceride concentrations in several species by bromocriptine treatment

Administrations (injections and in feed) of bromocriptine, a dopamine agonist that inhibits prolactin secretion, reduced body fat stores and plasma total cholesterol and triglyceride concentrations in several rodent species (Syrian hamsters, Djungarian hamsters, Swiss Webster mice and obese Zucker rats). Body fat indices were reduced by at least 50% in the hamsters and mice within 10-15 days of treatment and by 29% in 8 weeks in the rats. Bromocriptine reduced total plasma cholesterol concentration by 17% in Syrian hamsters, 41% in mice and 30% in rats fasted before blood sampling. In nonfasted obese rats, bromocriptine dramatically reduced both cholesterol (from 440 to 130 mg/dl) and triglyceride (from 1570 to 540 mg/dl) levels compared with controls. These findings offer further evidence for a primary role of prolactin in lipid metabolism and indicate that bromocriptine may be useful for treating obesity and lipid-based cardiovascular disorders.

Resetting the annual cycle with timed daily injections of 5-hydroxytryptophan and L-dihydroxyphenylalanine in Syrian hamsters

Daily injections of dihydroxyphenylalanine (DOPA), a precursor for dopamine synthesis, given 12 hr after daily injections of 5-hydroxytryptophan (5-HTP), a serotonin precursor, induced uterine growth and increased serum thyroxine and luteinizing hormone (LH) concentrations in scotosensitive female hamsters maintained on short daylengths. On the other hand, daily injections of DOPA given at the same time as daily injections of 5-HTP reduced uterine weights and serum concentrations of thyroxine and LH in scotorefractory female hamsters. These results indicate that the endogenous mechanism controlling seasonality (scotosensitivity and scotorefractoriness) in the Syrian hamster may be reset by drugs that influence serotonergic and catecholaminergic activity. This seasonal mechanism might involve two circadian systems that undergo seasonal changes in their phase relations.

Bromocriptine alters hormone rhythms and lipid metabolism in swine

Hormones, metabolites and activities involved in lipid synthesis were assayed in pigs made leaner by bromocriptine treatment. Market size female swine were allowed free access to food under natural lighting conditions and implanted with bromocriptine pellets designed to release 10 mg/pig/day for 28 days in an effort to inhibit prolactin secretion. Between the 2nd and 3rd week of treatment, plasma samples were obtained from each group at 4-hour intervals throughout the day for assays of prolactin, cortisol, insulin, triglyceride, cholesterol and glucose concentrations. Twenty-eight or thirty days after the implantations, all animals were sacrificed for determinations of backfat thickness and insulin binding in the liver. At sacrifice, bromocriptine treatment reduced backfat thickness by 14% and insulin binding to partially purified hepatic membranes by 39% compared with control values. At 14 days following implantations, there were dramatic daily variations in plasma cortisol and prolactin levels in the control pigs and these rhythms were markedly altered in phase and amplitude in the bromocriptine-treated pigs. Bromocriptine reduced by 45, 20 and 13% the high levels of triglyceride, glucose, and cholesterol, respectively, that were found in control pigs near sunset. Plasma insulin concentrations did not vary during the day in control pigs and bromocriptine did not influence the insulin levels. The findings support important roles for a temporal synergism of cortisol and prolactin rhythms in maintaining hepatic lipogenic responsiveness to insulin. Bromocriptine treatment alters these hormonal relations and reduces lipid synthesis.

Reduction of body fat stores by inhibition of prolactin secretion

Reductions of prolactin secretion by bromocriptine treatment for 24 days reduced fat stores (abdominal and epididymal fat depots) in hamsters by 25-49% compared with control animals. However, body weights and food consumption were not affected. These results further substantiate an important role for prolactin in regulation of fat metabolism and indicate that bromocriptine might be used to decrease fat stores.

Circadian and seasonal variations of plasma insulin and cortisol concentrations in the Syrian hamster, Mesocricetus auratus

Circadian rhythms of plasma insulin, cortisol, and glucose concentrations were examined in scotosensitive (reproductively sensitive to inhibitory effects of short daylengths) and scotorefractory male and female Syrian hamsters (Mesocricetus auratus) maintained on short (LD 10:14) and long (LD 14:10) daylengths. The baseline concentration (mean of all values obtained every 4 hr six times of day) of insulin was much greater in female than in male scotosensitive hamsters kept on short daylengths. These differences in insulin concentration may account for the observed heavy fat stores in female and low fat stores in male scotosensitive hamsters kept on short daylengths. The baseline concentrations of cortisol were approximately equal in both scotosensitive and scotorefractory males held on short and long daylengths, but were relatively low in females held on short daylengths and especially high in scotorefractory females held on long daylengths. The plasma concentrations of both cortisol and insulin varied throughout the day in many of the groups tested. However, the variations were not equivalent. The circadian variations of cortisol were similar irrespective of sex, seasonal condition and daylength. Peak concentrations generally occurred about 12 hr after light onset. In contrast, the circadian variations of insulin differed markedly. For example in male hamsters, robust daily variations were found in scotosensitive hamsters held on short daylengths but not on long daylengths and in scotorefractory hamsters held on long daylengths but not on short daylengths. Furthermore, the daily peak occurred during the light in the scotosensitive hamsters and during the dark in the scotorefractory animals. Neither the daily feeding pattern (about 60% consumed during dark) nor the daily variations of glucose concentration varied appreciably with seasonal condition or daylength. They do not appear to determine nor directly reflect the variations in cortisol and glucose concentrations. It is postulated that the daily rhythms of cortisol and insulin are regulated by different neural pacemaker systems and that changes in the phase relations of circadian systems account in part for seasonal changes in body fat stores.

Fattening responses to daily intervals of heat exposure in the Syrian hamster

Warm ambient temperature (38 degrees C) provided daily for one hr induced time-dependent changes in body weight and fat stores in the Syrian hamster. In animals held on 10-hr daily photoperiods and room temperature (23 degrees C), daily one-hour thermopulses at 8 and 20 hr after light onset stimulated increases in body weights and indices of body fat storage. Abdominal fat pad weights of these groups were twice those of untreated controls after 17 and 28 days of thermoperiodic treatments. On the other hand, daily thermopulses were completely ineffective at 0 and 16 hr after light onset. These results demonstrate that body fat stores may be influenced by a temporal interaction of environmental stimuli and implicate underlying circadian mechanisms in the regulation of body fat.

Prolactin permits the expression of a circadian variation in insulin receptor profile in hepatocytes of the golden hamster (Mesocricetus auratus)

Insulin receptor profile was determined in freshly isolated hamster hepatocytes at two times (07.00 and 16.00 h) during a 14-h daily photoperiod (08.00-22.00 h). The hamsters were pretreated for 5 days with bromocriptine (to inhibit prolactin release), bromocriptine and prolactin replacement, or control saline injections. The insulin receptor profile was determined by Scatchard plot analysis. The insulin receptor number (high and low affinity) was three times greater at 07.00 than at 16.00 h among saline-injected controls. However, their affinities did not differ. Bromocriptine pretreatment reduced (70%) both the high and low affinity receptor numbers and increased the affinity of the high affinity receptor at 07.00 h. Prolactin replacement in bromocriptine-treated hamsters restored the receptor profile at 07.00 h to control values. These data indicate that prolactin facilitates the expression of a circadian variation in insulin receptor profile.

Prolactin permits the expression of a circadian variation in lipogenic responsiveness to insulin in hepatocytes of the golden hamster (Mesocricetus auratus)

Lipogenesis was determined at two times (07.00 and 16.00 h) during a 14-h daily photoperiod (08.00-22.00 h) in freshly prepared hamster hepatocytes with or without addition of insulin. The hamsters were pretreated for 5 days with bromocriptine (to inhibit prolactin secretion), bromocriptine and prolactin replacement, or control saline injections. Lipogenesis was determined by incorporation of [14C]acetate into total cell lipids over a 30-min interval. Lipogenesis was three times greater at 07.00 than at 16.00 h and insulin was effective in stimulating further lipogenesis only at 07.00 h. Bromocriptine pretreatment severely reduced incorporation of radiolabel at 07.00 h to levels comparable with controls at 16.00 h and completely inhibited the stimulatory effect of insulin at 07.00 h. Prolactin replacement in bromocriptine-treated hamsters reversed the inhibitory effect of bromocriptine on hepatocyte lipogenesis and promoted dramatic lipogenic responses to insulin at 07.00 h. These results indicate that insulin stimulates hepatic lipogenesis only during some portion of a day and that prolactin facilitates the lipogenic response.

Circadian and seasonal variations of lipogenesis in the Gulf killifish, Fundulus grandis

Lipogenesis was measured in male Gulf killifish at three seasons under different environmental conditions. Cold temperature is stimulatory for lipogenesis in the fall and spring, but warm temperature is more stimulatory during the summer. The highest rate of lipogenesis occurs during the spring. However, total body fat content is relatively low at that time, which suggests that lipids are being actively mobilized as well. A high rate of lipogenesis also occurs at a cold temperature (20 degrees C) during the fall, and more lipids are stored at that time of year, as evidenced by higher liver and body fat stores. Both lipogenesis and total body fat content are at a minimum during the summer. These results indicate that high levels of lipid synthesis do not necessarily result in higher body fat content, as the latter is the product of both lipid synthesis and lipid mobilization. This study is also in agreement with previous studies which had indicated a changing responsiveness to temperature during the annual cycle of the Gulf killfish.

Circadian rhythms of lipogenic and hypoglycaemic responses to insulin in the golden hamster (Mesocricetus auratus)

Lipogenesis and blood glucose concentrations were determined at 4-hourly intervals in control and insulin-treated golden hamsters maintained on 14-h daily photoperiods (08.00-22.00 h). Lipogenesis was studied by measuring the incorporation of label into liver and fat pad lipids in animals killed 30 min after i.p. [3H]acetate injection and 2 h after insulin or saline (control) injections. Circadian rhythms of lipogenesis and plasma glucose concentration were present in both control and insulin-treated hamsters. In control animals most lipogenic activity occurred during the dark period and early during the daily photoperiod (14 h light: 10 h darkness). There were dramatic differences in the lipogenic (fat pad) and hypoglycaemic responses to insulin which varied as a function of the time of day at which insulin was injected. Insulin stimulated fivefold increases in lipid deposition (fat pad incorporation) when injected late during the dark period but had little or no effect 4-8 h after the onset of light. Daily injections for 8 days also produced variable cumulative effects on body fat stores as a function of the time of day. Insulin injected late during the dark period stimulated a 40% increase in abdominal fat weight over controls, whereas insulin injected at 4 and 12 h after the onset of light had no effect on abdominal fat weight. Insulin decreased plasma glucose concentrations markedly at 8 and 20-24 h after the onset of light but had no apparent hypoglycaemic activity (120 min after its injection) at 4 h after the onset of light.(ABSTRACT TRUNCATED AT 250 WORDS)

Tryptophan feeding adversely influences pregnancy

Additional tryptophan during pregnancy reduces embryo and neonate survival in the golden hamster, Mesocricetus auratus. Relatively small doses of exogenous serotonin have been reported to cause abortions in several vertebrate species (1, 2, 3, 4, 5). Smaller doses reduce litter sizes, increase still births and neonate abnormalities, and otherwise influence pregnancy adversely. These effects are produced by serotonin throughout pregnancy, beginning at implantation (6). The availability of tryptophan is probably the most important rate limiting factor in serotonin synthesis (7). Inasmuch as tryptophan is an essential amino acid and is not synthesized by the body, the diet is the sole source; studies have shown that increases (8) or decreases (9) in dietary tryptophan lead to concomitant changes in serotonin content. Because tryptophan is employed in humans to promote sleep (10, 11, 12) and to decrease appetite (13) we felt it might be important to test whether increased amounts of diet tryptophan can adversely influence pregnancy.

Tryptophan feeding induces sensitivity to short daylengths in photorefractory hamsters

The annual cycle of reproduction in the golden hamster (Mesocricetus auratus) is characterized by gonadal regression in response to decreasing daylengths in fall. However, hamsters become refractory to the inhibitory effects of short daylengths in late winter when gonadal recrudescense occurs. Our results show that addition of tryptophan to the diet of photorefractory hamsters causes them to respond to short daylengths in a manner similar to photosensitive hamsters in winter. Similar tryptophan treatment did not influence testes weights and fat stores of hamsters maintained on long daylengths.

Adrenal innervation may be an extrapituitary mechanism able to regulate adrenocortical rhythmicity in rats

The daily rhythm of plasma corticosteroid concentration was studied in nonhypophysectomized rats and in hypophysectomized rats implanted with beeswax pellets containing ACTH and T4. In the first experiment, male hypophysectomized rats were placed on a 12-h light, 12-h dark cycle (onset of light, 0600 h) with food and water available ad libitum. Beeswax pellets containing 1.5 mg ACTH and 150 micrograms T4 were implanted sc in these rats. Beginning 4 days after the implantation of ACTH and T4, daily rhythms of plasma corticosteroid concentration were detected in these rats on 3 successive days. The injection of sodium pentobarbital (40 mg/kg BW) or atropine sulfate (10 mg/kg BW) ip at 1200 h blocked the expected rise in plasma corticosteroid concentration at 1800 h in both these rats and a group of intact rats. In the second experiment, adrenal innervation was disrupted by spinal cord transection at the T-7 level. L-1-transected rats served as operated controls, and a third group was maintained as unoperated controls. One week after surgery, daily rhythms of plasma corticosteroid concentration were present in both unoperated and L-1 controls (P less than 0.01) but not in the T-7-transected rats. Inasmuch as an extrapituitary mechanism was capable of maintaining adrenocortical rhythmicity in hypophysectomized rats and disruption of adrenal innervation suppressed adrenocortical rhythmicity, it was hypothesized that adrenal innervation may be an extrapituitary mechanism which has a role in adrenocortical rhythmicity.