Daily rhythms of insulin and glucose levels in the plasma of sea bass Dicentrarchus labrax after experimental feeding

Significant and inverse circadian rhythms are demonstrated in glucose and plasma insulin in fish fed a natural diet. The highest glucose levels are found during the light period, around feeding time, and the insulin level peaks during the dark period. As a possible cause for the insulin rhythmicity, the daily variations in several plasma amino acids are considered. The feeding times could be a training factor for metabolic rhythms, which are maintained even during a fast of 7 days. The differences in the compositions of the diets could be responsible for the lack of circadian rhythms in fish fed on a commercial diet.     

Adrenergic regulation of insulin secretion from the chicken pancreas in vitro

Adrenergic regulation of insulin secretion in the chicken was studied using a perifused pancreas fragment preparation. Beta-adrenergic stimulation by 50 μM isoproterenol potentiated theophylline-stimulated insulin secretion. Glucose at 19.5 mM did not stimulate insulin secretion, a finding consistent with previous reports of chicken pancreas sensitivity in vitro. Pretreatment with 50 μM isoproterenol did not alter this glucose insensitivity. Alpha-adrenergic stimulation by 50 μM epinephrine in the presence of beta blockade by sotalol or by 50 μM phenylephrine did not alter insulin secretion. Inhibition of insulin secretion by somatostatin could be demonstrated, however. Epinephrine, 50 and 0.164 μM, potentiated theophylline-stimulated insulin release and at 50 μM stimulated insulin secretion as an off-response even in the absence of theophylline. It is concluded that adrenergic regulation of insulin secretion in the chicken is primarily mediated through beta-adrenergic receptors, resulting in stimulation of insulin secretion.     

Effects of pinealectomy and melatonin treatment on liver and plasma metabolites in the goldfish, Carassius auratus

The effects of pineal removal on daily variations and levels of some liver and plasma metabolites were examined in the goldfish, Carassius auratus. Pinealectomy abolishes the liver glycogen daily variation and decreases hepatic glycogen levels in goldfish maintained on specific photoperiod regimes during spring and summer. Neither the daily variation nor the levels of hepatic glycogen are affected by pinealectomy during the fall. Pinealectomy alters the plasma glucose daily variation and increases the levels of this metabolite in fishes maintained on long photoperiods during the summer. During the fall the daily variation of plasma glucose is abolished by pinealectomy and blood sugar levels are decreased. The diurnal fluctuation of plasma lipid is altered by pinealectomy during the summer. Plasma lipid levels are elevated in pinealectomized fishes during winter, spring, and summer. The daily variation of liver lipid levels is altered by pinealectomy during the autumn. Melatonin treatment increases liver glycogen reserves in goldfish maintained on a long, but not a short, photoperiod during the spring. Plasma glucose levels are also elevated by melatonin treatment. Therefore, the pineal organ participates in regulating levels and daily variations of some metabolites. The influence of the pineal on metabolites varies with season and day length.     

Changes in the pituitary and plasma LH,plasma and follicular progesterone and estradiol,and plasma testosterone and estrone concentrations during the ovulatory cycle of the quail (Coturnix coturnix japonica)

Luteinizing hormone (LH) and sex steroid hormones in the pituitary, plasma, and hierarchical follicles of the quail maintained under 14L:10D condition were measured during the ovulatory cycle at 2-hr intervals using radioimmunoassay. Pituitary levels of LH during the ovulatory cycle showed two peaks which occurred 16 and 10 hr before ovulation. A significant decrease in LH concentration was observed from 10 to 6 hr before ovulation, shortly after the onset of light (dawn). Plasma LH started to increase from 10 hr before ovulation, and reached a peak 6 hr before ovulation. Plasma progesterone also started to increase shortly after dawn and reached a peak 4 hr before ovulation. A single peak of plasma testosterone was observed 6 hr before ovulation. Two peaks of plasma estradiol concentration were observed at 22 and 6 hr before ovulation. A similar tendency of the change in plasma concentration of estrone to that of estradiol was observed during the ovulatory cycle. In the largest follicle, the progesterone content started to increase from 10 hr before ovulation, reached a peak 2 hr before ovulation and decreased abruptly after the ovulation. The contents of the second to fourth largest follicles were low. These findings strongly suggest that progesterone in the largest follicle is a main cause of ovulation by producing enzymes which act to break the follicle membrane. The estradiol contents of the third and fourth largest follicles were high, and showed the peak at 18 hr before ovulation in the third largest one and at 8 hr before ovulation in the fourth largest one. The contents of the largest, ruptured, and the second largest follicles were low compared with the third or fourth largest one. These results suggest that the onset of light may be a signal for the increases of plasma LH and progesterone and follicular progesterone which are responsible for the induction of ovulation in the quail.     

Cortisol and its effects on plasma thyroid hormone and electrolyte concentrations in fresh water and during seawater acclimation in yearling coho salmon,Oncorhynchus kisutch

Plasma cortisol, thyroxine (T₄), and triiodothyronine (T₃) concentrations increased during seawater (SW) acclimation in yearling coho salmon, Oncorhynchus kisutch. Maximal concentrations of cortisol (220 ng/ml) occurred within 1.5 hr after the ambient water was changed from fresh water (FW) to SW; after 21 days in SW, cortisol levels were still slightly elevated (23 ng/ml) compared to those in FW fish (8 ng/ml). Plasma T₄ concentrations peaked (14 ng/ml) at 12 and 72 hr after exposure to SW, and they were higher than those in FW fish (4 ng/ml) at all sample times. Maximal concentrations of T₃ (8 ng/ml) occurred within 12 hr after exposure to SW, followed by a return to FW control levels (4 ng/ml) within 24 hr. Chronic treatment with cortisol significantly lowered plasma T₃ concentrations in FW and during SW exposure, but it had no significant effect on T₄ concentrations. Cortisol treatment lowered gill NaK-ATPase activity in FW fish, but it did not affect plasma osmolarity, Na, K, Ca, or Mg in fish in FW or during SW acclimation.     

Annual changes in plasma and liver in relation to vitellogenesis in the female rainbow trout, Salmo gairdneri

As part of a study on the physiological participation of ovarian steroids in the regulation of the synthesis of vitellogenin in the liver of the rainbow trout, Salmo gairdneri, an inventory was made of some relevant variables throughout the annual cycle. The annual reproductive cycle can be divided into four physiological periods: a previtellogenic period (March–April), a period of endogenous vitellogenesis (May–July), a period of exogenous vitellogenesis (August–December), and a period of ovulation and spawning (January–February). Quantitative studies have been carried out of the hepatosomatic and gonadosomatic indices, of the concentrations of total proteins, vitellogenin, free phosphates, and vitellogenin-bound phosphates in the plasma, and of the concentration of total proteins and vitellogenin in the liver. The plasma vitellogenin concentration increased from 0.1 mg/ml in May to 12.9 mg/ml in November, the vitellogenin-bound phosphates were hardly detectable in May, but had increased to 6.1 μmol/ml in December, the hepatosomatic index increased from 12 in March to 30 in December, and the gonadosomatic index increased from 6 in June to 222 in December. The free plasma phosphates varied considerably in the different specimens. The total plasma protein levels had a constant value of about 100 mg/ml throughout the annual cycle, except during previtellogenesis, when the levels had decreased to 60 mg/ml. The total liver protein levels per gram liver gradually decreased from 234 mg in July to 136 mg in January, and increased rapidly again in the following months. Vitellogenin of the type as detected in the plasma, was not found in the liver. During exogenous vitellogenesis, plasma vitellogenins with different degrees of phosphorylation appeared to be present. The ultrastructural examination of the liver indicated large amounts of rough endoplasmic reticulum and a large Golgi system from October to December, whereas glycogen and lipid droplets were found in June and July.     

Structure-activity relationships of mammalian, chicken, and salmon gonadotropin releasing hormones in vivo in goldfish

Mammalian, chicken, and salmon gonadotropin releasing hormones (GnRHs), and anlogs of each peptide, were injected either alone or in combination with pimozide into goldfish, and the changes in serum gonadotropin (GtH) levels determined. The native peptides had similar potencies in terms of magnitude and duration of the GtH response. Analogs of LHRH that are superactive in mammals are also superactive in goldfish; although [(imBzl)-D-His6, Pro9-NEt]-LHRH is very highly superactive in mammals it has activity similar to [D-Ala6, Pro9-NEt]-LHRH in goldfish. D-Ala6 or (imBzl)-D-His6 substitutions of [Trp7, Leu8, Pro9-NEt]-LHRH are not superactive in goldfish, whereas the D-Arg6 substitution is highly superactive, indicating that there are differences in the factors that make salmon and mammalian GnRH superactive. These results also indicate that the structural modifications that determine superactivity of GnRHs in goldfish differ from what is known for mammals.     

Isolation and characterization of reptilian insulin, glucagon, and pancreatic polypeptide: complete amino acid sequence of alligator (Alligator mississippiensis) insulin and pancreatic polypeptide

The insulin, glucagon, pancreatic polypeptide, and somatostatin contents of acid-alcohol extracts of alligator pancreas have been estimated by heterologous radioimmunoassay, and the insulin, glucagon, and pancreatic polypeptide have been isolated. The amino acid sequences of the insulin and pancreatic polypeptide were determined. The sequence of the insulin A chain is identical to that of chicken insulin A chain, while the B chain exhibits three conservative substitutions when compared to that of the chicken. Pancreatic polypeptide from the alligator is similar in sequence to that of chicken PP, but contains seven substitutions, most of which are conservative and preserve characteristics essential for conformation. The amino acid composition of alligator glucagon is identical to that of duck glucagon.     

Egg-laying hormone: direct action on the ovotestis of Aplysia

The bag cells are a group of neuroendocrine cells located in the abdominal ganglion of Aplysia californica. These cells induce egg laying in the animal through the release of neurohormone(s). Previous experiments established that an extract of bag cells releases eggs from isolated ovotestis fragments in a dose-dependent manner. (F. E. Dudek and S. S. Tobe, 1978, Gen. Comp. Endocrinol. 36, 618-627.) Experiments presented here were conducted to purify and identify the component(s) of bag cell extract with the egg-releasing activity. Bag cell extracts were fractionated by means of gel-filtration chromatography followed by cation-exchange chromatography. Column eluates were assayed for egg-release activity on isolated ovotestis fragments by the method of Dudek and Tobe (1978). Only one component purified from the crude extract had egg-releasing activity. This component was identified as egg-laying hormone (ELH) based on its purification characteristics, effects on neuronal activity, and migration on thin-layer chromatography. In dose-response studies egg release increased with the concentration of ELH and had a threshold of 8 X 10(-10) M or less. ELH had the same dose-response relationship in egg release assays when present in purified form or as a component of bag cell extract. These data show that ELH acts directly on the ovotestis and that ELH is the only component of bag cell extract with egg-release activity. Taken with the results of other studies (W. D. Branton, S. Arch, T. Smock, and E. Mayeri, 1978. Proc. Nat. Acad. Sci. USA 75, 5732-5736. B. S. Rothman, P. Brownell, and E. Mayeri, 1979. Soc. Neurosci. Abstr. 5, 260. E. Mayeri and B. S. Rothman, 1982.(ABSTRACT TRUNCATED AT 250 WORDS)     

Spontaneous pituitary tumorigenesis and plasma oestradiol in ageing female C57BL/6J mice

Macroscopic pituitary tumours occur with increasing frequency in ageing female C57BL/6J mice. Tumour incidence rises steadily between 14 and 30 months from 6 to 61%. Two stepwise increments in pituitary weight, indicative of hyperplasia, occur prior to the appearance of tumours. The first, at 5 months, coincides with the onset of regular estrous cyclicity, and hence maximal exposure to plasma oestradiol (E₂). Average plasma E₂ concentration in cycling mice is 15.4 pg/ml ± 1.73 SE. The second increment, at 14 months, coincides with the first appearance of tumours and with the onset of cycle irregularity, which is characterized by persistent vaginal cornification and a 50% reduction in exposure to E₂. Although exogenous E₂ can induce pituitary tumours, its reduced concentration during the initial phase of tumorigenesis suggests that altered sensitivity or other factors are involved.     

Hepatic estrogen receptors and plasma estrogen-binding activity in the Atlantic salmon

Livers of male and female immature Atlantic Salmon (Salmo salar) contain specific high-affinity [3H]estradiol binding sites in cytosol (Kd 2-4 nM, concentration about 0.6 pmol/g liver). Low levels of high-affinity binding are detectable in salt extracts of nuclei of untreated fish, but injections of estradiol result in transient depletion of the cytosol binder and in accumulation of high levels of binding sites in nuclear salt extracts (Kd 5-6 nM; concentration about 6 pmol/g liver). Both the cytosol and nuclear binding sites are temperature sensitive and are optimally assayed by incubation at 2 degrees. Both are specific for estradiol and diethylstilbestrol (DES) and no significant competition by dihydrotestosterone (DHT), progesterone, or hydrocortisone is seen. The triphenylethylene nonsteroidal antiestrogen, 4-hydroxytamoxifen, exhibits an affinity comparable to that of estradiol. The nuclear binding activity sediments with a coefficient of 3.6 S in salt-containing sucrose density gradients, and is stable on storage at -20 degrees for several months. The cytosol binder on the other hand is not stable on sucrose density gradients or on prolonged storage. Salmon plasma contains two [3H]estradiol binding components, one with a relatively high affinity for [3H]estradiol (kd 13 nM) and the other having a much lower affinity but present in high concentrations. The high-affinity plasma binder exhibits distinctive specificity with no affinity for DES or 4-hydroxytamoxifen but some affinity for DHT and progesterone. These properties serve to distinguish the plasma activity from the intrahepatic estrogen binders. The salmon liver estrogen receptor system has many features in common with typical estradiol receptors from other vertebrates. Immature salmon liver appears to be the richest source of hepatic estrogen receptor so far found for any vitellogenic species.     

The effects of light reception on circulating estrogen levels in female goldfish, Carassius auratus: importance of retinal pathways versus the pineal.

The effects of pinealectomy, optic tract section, or exposure to continuous darkness on serum estradiol-17β levels in the goldfish were examined during the spring and fall. Pineal removal had no effect on serum estrogen levels or GSI in either fall or spring. Optic tract section decreased serum estrogen levels in both spring and fall experiments. Ovarian regression was initiated in fish exposed to continuous darkness and optic tract-sectioned fish during the spring, but fish maintained in darkness exhibited no change in serum estrogen levels. Our data imply that it is primarily retinal pathways which mediate the effects of increasing daylength on goldfish ovarian development during the spring.     

Controlled trial of nutritional supplementation, with and without branched chain amino acid enrichment, in treatment of acute alcoholic hepatitis

Sixty-four patients admitted with acute alcoholic hepatitis, with or without underlying cirrhosis, were randomized regardless of encephalopathy to receive a controlled diet either alone, or supplemented orally, nasogastrically, or intravenously as necessary, with 2000 kCal and 10 g nitrogen daily. Whether this came from a conventional protein source or a branched chain amino acid enriched formulation was also randomly determined. In the absence of renal failure, nitrogen intakes of 10 g or more daily were invariably associated with positive nitrogen balance, but complications of liver dysfunction prevented the attainment of significantly more positive balance in the supplemented groups than in controls. Neither in the series as a whole, nor in any identifiable subgroup of patients, was mortality affected by treatment. Changes in prothrombin time and in measured nutritional parameters during the study did not differ between supplemented and control groups, and the observed changes in midarm muscle circumference appeared to reflect changes in degree of fluid retention. Neither enteral nor parenteral branched chain amino acids showed any consistent effect upon encephalopathy.     

Effects of catecholaminergic agonists and antagonists on serum gonadotropin concentrations and ovulation in goldfish: evidence for specificity of dopamine inhibition of gonadotropin secretion

The elevated serum gonadotropin (GtH) levels in goldfish receiving two injections of des Gly10, [D-Ala6] LH-RH ethylamide (LH-RH-A), given 12-hr apart, were reduced by apomorphine, a dopamine agonist, injected at either the first or the second LH-RH-A injection. Serum GtH concentrations in goldfish given two injections of LH-RH-A at a 3-hr interval were also depressed by bromocriptine, a specific D-2 dopamine receptor agonist, administered simultaneously with both LH-RH-A injections. Injections of dopamine antagonists, pimozide or metoclopramide (a specific D-2 antagonist) caused increased serum GtH concentrations in normal goldfish, but no changes were found following injections of the alpha-adrenergic antagonist phentolamine, the beta-adrenergic antagonist propranolol, or the sympathomimetic agent octopamine. Injection of pimozide or metoclopramide at the time of the second of two LH-RH-A injections given at an interval of 12 hr potentiated the LH-RH-A-induced increase in serum GtH concentrations; injections of phentolamine, propranolol, or octopamine did not alter the response to LH-RH-A. Injections of pimozide or metoclopramide also increased the frequency of ovulation in LH-RH-A-injected gravid female goldfish. These results suggest that stimulation of dopamine receptors can block the potentiating effect of multiple injections of GtH-releasing hormone, as well as ongoing LH-RH-A-stimulated release. The results also indicate that the dopamine inhibition of GtH secretion is specific and may be mediated by receptors resembling the D-2 type receptors in mammals.     

The effect of altering the external calcium concentration and a calcium channel blocker, verapamil, on microvascular leaky sites and dextran clearance in the hamster cheek pouch

The role of calcium in contractile mechanisms has been well documented. Since the formation of intraendothelial gaps may be due to a contractile process, these studies were initiated to describe the effects of altering the external calcium concentration and a calcium blocker, verapamil, on the development of leaky sites and clearance of dextran in the hamster cheek pouch under normal and histamine-stimulated conditions. Adult Syrian hamsters were anesthetized and tracheostomized, and the femoral vein was cannulated for injecting the FITC-Dextran-70K. In all hamsters, a removable plastic chamber was placed in the cheek pouch to observe and collect suffusate from the microvasculature. In one series of experiments, suffusion was begun with either "normal" calcium (1.5 mM) or a calcium-free, Ringer's bicarbonate (pH 7.4, 36 degrees) buffer. After a 30-min period, fluorescein-labeled dextran (FITC-Dextran-70K) was given intravenously and the number of leaky sites and dextran clearance determined for 30-45 min. Two 5-min periods of stimulation with histamine (10(-7) and 10(-6) M) followed by a 30-min equilibration were completed while the above measurements were repeated. Then, the suffusate was switched to the opposite calcium buffer and the same sequence repeated. A similar protocol was followed using either the "normal" buffer or a high (4.5 mM)-calcium buffer. In another series of experiments, similar measurements were completed with and without verapamil (10(-4) M) using a "normal" calcium buffer and histamine-stimulated conditions. In the control, nonstimulated state, there was a significant increase in the leaky sites while suffusing with low-calcium buffer; however, there were no changes in leaky sites while suffusing with the high-calcium buffer. In the histamine-stimulated state, the increase in the number of leaky sites and dextran clearance was attenuated with the low-calcium buffer and potentiated with the high-calcium buffer. While suffusing with the verapamil buffer, there was an increase in the control number of leaky sites and in the histamine-stimulated state there was an attenuation of the histamine-stimulated response. These results indicate that external calcium influences and modulates microvascular leaky sites in normal and stimulated states and that the formation of leaky sites and dextran clearance after histamine stimulation require the transmembrane flux of calcium. Also, the formation of leaky sites was coupled directly to the clearance of dextran.     

The luteotrophic effect of homoplastic pituitary pars distalis homogenate,PMSG, and HCG on the corpora lutea of the hypophysectomized frog, Rana cyanophlyctis (SCHN)

The effect of homoplastic pituitary pars distalis homogenate (PDH), PMSG, and HCG on the postovulatory follicles/corpora lutea (CL) of the frog Rana cyanophlyctis was studied to elucidate the factors regulating the life span of the luteal cells. Ovulation and spawning was induced in hypophysectomized frogs using PDH. Starting from Day 1 of spawning $\text{1}\text{2}$ PDH, 50 IU PMSG, or 50 IU HCG was injected daily for 3 days. In the saline-injected control frogs, the granulosa lutein cells regressed markedly on Day 2 with a steady progressive increase in the pycnosis of their nuclei. The sudanophilic lipid droplets of the luteal cells were fine on Day 1 but became coarser and reduced in number on subsequent days. Histochemically, the luteal cell 3β-HSDH and G-6-PDH also decreased drastically by Day 2. In PDH-treated frogs the granulosa lutein cells were healthy on all 4 days of the experiment. The nuclear diameter of the luteal cells increased progressively due to PDH. The pycnosis of the luteal cells was limited to 7.6% on Day 4 due to PDH as opposed to 68% seen in the controls. Histochemically, 3β-HSDH and G-6-PDH activities remained much higher than in the controls with abundant sudanophilic lipids (both fine and coarse) in the luteal cells of PDH treated frogs even on Day 4. PMSG treatment also maintained the granulosa lutein cells beyond their normal life span but the luteotrophic effect was less than that of PDH. HCG was least effective. The present studies suggest that the structural integrity of CL in the frog can be extended beyond the normal life span by injecting PDH or PMSG.     

Aging changes in the kidneys of two poeciliid fishes,the guppy Poecilia reticulatus and the Amazon molly P. formosa

Histological surveys of the kidneys of two poeciliid fishes, the Amazon molly Poecilia formosa and the guppy P. reticulatus, throughout their lifespans showed no regular aging trends. Few kidney lesions were found in the Amazon molly until very late in life, 60 months or more, when obsolescent glomeruli and dilated renal tubules occurred. Guppies showed involutional changes of the renal system earlier, and the lesions became more severe with age, particularly in male fish. Hemopoietic tissue was reduced in amount in older fish of both species. Guppies of a year and older had marked accumulation of melanin in the melanomacrophage centers of the kidney, and the amount present increased with age. By contrast, there was little melanin deposition in mollies until almost the end of the lifespan. Hyaline droplets were consistently seen in the renal tubules of the mollies, but were rare in guppies. The degenerative changes in the kidneys of these two teleosts are similar to those seen in the kidneys of aging mammals. Despite the loss of normal structure in older fish, it seemed unlikely that degeneration of the kidney was directly involved in aging and death.     

The distribution of fetal mortality in ageing C57BL/6J mice: A statistical analysis

Fetal death in 11–12-month-old C57BL/6J mice is first recognized on day 10 post-coitum and it increases in incidence over the subsequent three days until more than a third of all fetuses are affected. Thereafter, there is little change in the incidence of resorption sites which apparently persist until term. Analysis of 104 pregnancies between days 13–19 suggested that the loss of individual fetuses is due to local factors operating at random along the uterine wall whereas whole litter resorption results from a systemic factor, though this is not progesterone deficiency.