Spirulina maxima prevents fatty liver formation in CD-1 male and female mice with experimental diabetes

The dietary administration of 5% Spirulina maxima (SM) during four weeks to diabetic mice, starting one week after a single dose of alloxan, 250 mg/Kg body weight, prevented fatty liver production in male and female animals. The main action of SM was on triacylglycerol levels in serum and liver. There was also a moderate hypoglycemia in male mice. The thiobarbituric acid reactive substances also decreased in serum and liver after SM administration. There was also a decrease in the percentage of HDL in diabetic mice that was reverted by the SM administration. The sum of LDL + VLDL percentages was also partially normalized in diabetic animals by the SM administration. An additional observation was the lower incidence of adherences between the liver and the intestine loops in the diabetic mice treated with SM compared with diabetic mice without SM. Male and female mice showed differences to diabetes susceptibility and response to SM, the female being more resistant to diabetes induction by alloxan and more responsive to the beneficial effects of SM. It is worth future work of SM on humans looking for better quality of life and longer survival of diabetic patients.     

Prolactin control of growth and prolactin autoregulation in cultured human pituitary cells

A human pituitary cell line (18-54,SF) grows in serum-free medium and secretes prolactin (PRL). Autoregulation of pituitary cell growth and PRL production by exogenously supplied ovine PRL (oPRL) was investigated. Human PRL (hPRL) and oPRL stimulated pituitary cell growth up to 92% and 85%, respectively, at hPRL and oPRL additions of 100-1,000 ng/ml. Short-term (1 h) incubation of the cells with oPRL decreased hPRL secretion from the cells by 72% at 10 ng/ml addition. Intracellular hPRL was stimulated under the same conditions by 50-275% at oPRL concentrations of 10-1,000 ng/ml. Long-term (10 days) incubation of the cells with oPRL had no significant effect on extracellular or intracellular hPRL production. These data suggest that the pituitary gland can serve as a primary feedback site and that PRL can autoregulate its own production as well as affect the growth of pituitary cells.     

Induction of lactogenic receptors. I. In the liver of hypophysectomized female rats.

To identify the hormones which affect lactogenic receptors in the liver of chronically hypophysectomized female rats, hormones were injected s.c. for 7 days. Specific binding (%, SB) of labelled ovine prolactin (PRL) in liver membrane preparations (1000,000 X g pellet) of controls was 1%. Estradiol (E2), cortisone (Con), ACTH or bovine growth hormone (bGH) treatment did not induce hepatic binding sites for PRL. Human GH and a single dose of 2mg PRL (but not lower doses) increased SB of PRL. Treatment with oPRL plus ACTH was less effective than hGH plus ACTH (13 vs 28%); combinations of oPRL plus Con as well as administration of oPRL plus ACTH to hypophysectomized and adrenalectomized female rats did not induce SB for PRL. Therapy with oPRL plus hGH (26%) was more potent than oPRL plus bGH (2%). These studies suggest that PRL, GH, and ACTH induce and in concert with sex steroids, modulate the lactogenic receptors in the female rat liver. The effect of ACTH is not due to increased adrenal corticoid secretion.     

Sex-specific effects of prolactin on food intake by rats

While prolactin (PRL) has been reported to increase food intake by virgin female rats, its effects on food intake by male rats are relatively unexplored. The present studies examined the possibility that PRL has sex-specific effects on food intake by rats. In the first study, intact female and male rats were given subcutaneous injections of saline vehicle or ovine (o) PRL (1.0 mg/kg) twice daily at 08:00 and 20:00 h for 10 days. Food intake, body weight, and water intake were measured daily. Results indicate that oPRL administration increased food intake by an average of 4.5 g per day in female subjects, but did not significantly alter body weight or water intake. Male rats treated with oPRL did not significantly alter their food intake, even after an additional five days of treatment. In the second study, a wide range of oPRL doses (vehicle, 0.02, 0.2, 2.0, and 20.0 mg/kg/day) were tested in gonadectomized female and male rats. The results indicate that female rats responded to increasingly larger doses of oPRL with greater increases in food intake, with a maximum increase of approximately 6. 1 g per day at a dose of 20.0 mg/kg. In contrast, male rats maintained baseline levels of intake across all oPRL doses tested. These data suggest that PRL has sex-specific effects on food intake.     

Effects of prolactin on aldosterone secretion in rat zona glomerulosa cells

Acute effects and action mechanisms of prolactin (PRL) on aldosterone secretion in zona glomerulosa (ZG) cells were investigated in ovariectomized rats. Administration of ovine PRL (oPRL) increased aldosterone secretion in a dose-dependent manner. Incubation of [3H]-pregnenolone combined with oPRL increased the production of [3H]-aldosterone and [3H]-deoxycorticosterone but decreased the accumulation of [3H]-corticosterone. Administration of oPRL produced a marked increase of adenosine 3',5'-cyclic monophosphate (cAMP) accumulation in ZG cells. The stimulatory effect of oPRL on aldosterone secretion was attenuated by the administration of angiotensin II (Ang II) and high potassium. The Ca2+ chelator, ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA, 10(-2) M), inhibited the basal release of aldosterone and completely suppressed the stimulatory effects of oPRL on aldosterone secretion. The stimulatory effects of oPRL on aldosterone secretion were attenuated by the administration of nifedipine (L-type Ca2+ channel blocker) and tetrandrine (T-type Ca2+ channel blocker). These data suggest that the increase of aldosterone secretion by oPRL is in part due to (1) the increase of cAMP production, (2) the activation of both L- and T-type Ca2+ channels, and (3) the activation of 21-hydroxylase and aldosterone synthase in rat ZG cells.     

Polyhormonal regulation of avian and mammalian corticosteroidogenesis in vitro

1. The combined actions of ACTH, corticosterone and prolactin (PRL) in the acute regulation of corticosteroidogenesis were investigated using isolated adrenocortical cells from intact and hypophysectomized (hypox) rats (Rattus norvegicus) and from intact male domestic fowl (Gallus gallus domesticus). 2. Exogenous corticosterone suppressed to about 50% ACTH-induced corticosterone production of cells from either species. This suppression, in part, was due to corticosterone degradation. 3. oPRL, in the presence or absence of ACTH, raised corticosterone production of hypox rat cells, but not intact rat and domestic fowl cells. 4. In addition, oPRL counteracted the corticosterone-induced suppression of net ACTH-stimulated corticosterone production of hypox rat and intact domestic fowl cells, but not intact rat cells. 5. The potency of oPRL with domestic fowl cells was 4 times that with hypox rat cells. 6. Furthermore, in domestic fowl cells, the effect of oPRL was Ca2+-dependent.     

Growth response, endocrine profiles and reproductive performance of fine-wool ewe lambs treated with ovine prolactin before breeding

Twenty-four 6-mo-old ewe lambs received one of two ovine prolactin (oPRL) treatments 28 d before fall breeding. Beginning on the first day of treatment (Day 0), 12 lambs received a subcutaneous injection (12 ml) of a carrier vehicle (0 mg oPRL) on alternate days for 28 d while 12 lambs received injections containing 5 mg oPRL. On Days 0 and 28, jugular blood was collected from six lambs in each group before treatment and at 30-min intervals for 6 h thereafter. Neither feed intake, efficiency of gain nor animal weights differed (P > 0.20) between groups. One hour after treatment on Day 0, ewe lambs receiving 5 mg oPRL had greater (P < 0.10) serum PRL levels than did controls (121.9 and 61.5 +/- 24.7 ng/ml, respectively). Differences in serum PRL persisted throughout remaining sampling intervals on both Days 0 and 28. Serum samples obtained on alternate days during the 28-d treatment period revealed no differences (P > 0.20) in PRL concentrations between control (48.3 +/- 5.3 ng/ml) and oPRL-treated (55.7 +/- 5.3 ng/ml) ewes. Neither serum insulin nor growth hormone responded (P > 0.05) to exogenous oPRL on either Day 0 or 28. No difference (P > 0.30) in percentage of ewe lambs cycling during treatment or breeding was detected between groups. Subsequent lambing percentages were similar (P > 0.30), with 36.4% of control and 25.0% of oPRL-treated ewes producing offspring. Administering 5 mg oPRL on alternate days for 28 d before breeding did not enhance growth and(or) reproductive performance in virgin ewe lambs.     

Effect of prolactin on blood pressure and cardiovascular responsiveness in the rat

The effects of chronic ovine PRL (oPRL) infusion on resting systolic blood pressure (BP), heart rate, and pressor responsiveness to acute administration of norepinephrine and angiotensin were studied in adult male Sprague-Dawley rats. oPRL was administered over 7 days, via osmotic pump implanted ip on Day 1, at rates of 0, 0.15, 0.30, 0.60, 1.20, and 4.80 micrograms/hr. Resting BP and heart rate were indirectly determined in conscious rats by tail cuff technique on Days 1, 4, and 7 following pump implantation. In addition, acute pressor responses to ia norepinephrine (4.3 micrograms) and angiotensin (1.25 micrograms) were directly measured via arterial cannula in halothane-anesthetized rats on Day 7 of oPRL administration. oPRL infusion did not alter resting BP or heart rate over the 7 days. However, oPRL increased the BP response to norepinephrine at infusion rates of 0.60 and 4.80 micrograms/hr (P less than 0.01 vs controls). Body weight increases during the study were also greater in groups receiving 0.15, 0.30, 0.60, and 4.80 micrograms oPRL/hr (P less than 0.05) than those in control animals. oPRL decreased pressor responses to angiotensin at infusion rates of 0.30 and 1.20 micrograms/hr (P less than 0.01). These data suggest that, although the vascular effects of oPRL may not be evident under resting conditions, oPRL enhances vascular reactivity to norepinephrine infusion and depresses vascular reactivity to angiotensin infusion. Furthermore, at oPRL infusion rates which affect pressor responses to norepinephrine, oPRL increases body weight gain. These findings support a role for PRL in cardiovascular regulation during conditions of altered sympathetic activity.     

Sexual conflict over mating in a spider: increased fecundity does not compensate for the costs of polyandry

Female multiple mating (polyandry) is a widespread but costly behavior that remains poorly understood. Polyandry may arise when whatever benefits females accrue from multiple mating outweigh the costs, or males manipulate females against the females' best interests. In a polyandrous spider Stegodyphus lineatus females may mate with up to five males, but behave aggressively toward additional males after the first mating. Female aggressiveness may act to select for better quality males. Alternatively, females may try to avoid superfluous matings. To test these alternatives, we allocated females into single-mating (SM) and double-mating treatments. Double-mated females either accepted (DM) or rejected (RE) the second male. DM females laid more eggs, but did not produce more offspring than SM and RE females. Offspring of DM females were smaller at dispersal than offspring of SM and RE females. Also, nest failure was significantly more common in DM females. Paternal variables did not influence female reproductive success, whereas maternal body condition explained much of the variation. We show that polyandry is costly for females despite the production of larger clutches and suggest that multiple mating results from male manipulation of female remating behavior.     

Changes in somatomedin activity in anorexia nervosa

Somatomedin (SM) activity, GH, T3 and T4 were investigated in 6 girls with anorexia nervosa during hospitalization and at outpatient clinic. On admission, serum T3 (27-62 ng/dl) and SM activity (0.24-0.55 U/ml) were low in all cases, while basal GH was extremely high in 2 cases. A significant negative correlation was found between SM activity and basal GH during the course of treatment (r = -0.61, p less than 0.02). The change in SM activity was related to that of the serum T3 level and a significant positive correlation was found between SM activity and serum T3 (r = 0.80, p less than 0.001). These data suggest that decreased SM activity may suppress the inhibitory effect of SM on GH release and may raise the basal GH level. SM activity is one of the indicators of the nutritional condition in anorexia nervosa as well as the serum T3 concentration.     

Lactogenic response of mouse mammary explants from different days of pregnancy to placental lactogen and pituitary prolactin

The lactogenic response of mouse mammary gland explants to human placental lactogen (hPL) and ovine pituitary prolactin (oPRL) was examined on days 10 to 18 of pregnancy by measuring 3H-amino acid incorporation into calcium-rennin precipitable casein. To determine the lactogenic response of the explants, the mean slopes of dose-response curves were calculated for each hormone treatment. Slope means of dose-response curves for oPRL and hPL did not differ from each other on any day of pregnancy examined. A triphasic pattern of response was suggested when slope means of dose-response curves for both hormones were plotted as a function of day of gestation. Peak responses were observed on days 10, 13 and 17-18. Combinations of oPRL and hPL, in ratios of oPRL:hPL = 2:1 and oPRL:hPL = 1:2, also produced a triphasic pattern of sensitivity very similar to that produced by either hormone alone. These results suggest that mouse mammary explants may be more sensitive to oPRL and hPL on days 10, 13 and 17-18 of pregnancy.     

Down-regulation of prolactin receptors in the liver, mammary gland and kidney of female virgin rat, infused with ovine prolactin or human growth hormone

Down regulation of prolactin (PRL) receptors resulting from i.v. infusion of oPRL or human growth hormone (hGH) into female virgin rats was demonstrated. A decrease of over 85% in the number of free receptors was achieved within 15 - 30 min using infusion of oPRL or hGH at 25 micrograms/h and remained at this level until the end of infusion. Ovine growth hormone or recombinant bovine growth hormone at ten-fold higher concentration had no effect at all. The decrease in the specific binding resulted from a lower number of binding sites and not from change in the dissociation constants. The decrease in the total receptors in the liver was more gradual and leveled off at 40 - 50% of the initial value. Our results suggest that a change in blood PRL or hGH level may lead to a new steady state in the number, occupancy and distribution of prolactin receptors.     

Prolactin induces yawning and the stretch-yawning syndrome in young adult male rats

Herein we report that subcutaneous injection of low doses of ovine prolactin (oPRL) induce yawning in young adult male rats. The most effective dose of oPRL in evoking yawning was 0.25 microgram/kg body weight (5.2 yawns/60 min at 1000 hr vs 0.3 in control animals). Doses of 0.025, 0.05, 2.5, 25, and 250 micrograms/kg were less effective. Interestingly, yawning in response to oPRL changes over the course of one circadian cycle with highest frequency at 1600 hr (11 yawns/80 min vs 2 yawns/80 min in animals injected with boiled oPRL). The onset of yawning in most oPRL-treated rats began approximately 40 min after oPRL injection, whereas with apomorphine the latency to the response was about 10 min. These results indicate that oPRL in addition to other hypophysial peptides such as ACTH and MSH can stimulate yawning. It is proposed that PRL after initial activation of the nigrostriatal dopamine system secondarily induces yawning by inhibition of this system via an autoreceptor-mediated negative feedback mechanism. This may explain the long latency to the response.     

Effect of serum and serum lipoproteins on testosterone production by adult rat Leydig cells in vitro.

The effect of serum factors other than luteinizing hormone on Leydig cell testosterone secretion was examined using an in vitro bioassay system based on the stimulation of purified adult rat Leydig cells during a 20 h incubation in the presence of a maximal dose of human chorionic gonadotrophin (hCG). Charcoal-extracted serum and testicular interstitial fluid (IF) from normal adult male rats were separated into lipoprotein and lipoprotein-deficient fractions by density ultracentrifugation. Stimulatory bioactivity was found in the lipoprotein fraction of both serum and IF, although the levels of lipoprotein and corresponding bioactivity recovered from IF were significantly lower (25%) than those of serum. There was no difference between the effects of serum lipoproteins on Leydig cell testosterone production stimulated by either hCG or dibutyryl cAMP. In time-course studies, the serum lipoprotein fraction had no effect on hCG-stimulated testosterone production in vitro at 3.0 or 6.0 h, but partially prevented the normal decline in hCG-stimulated testosterone production after 6.0 h. In contrast, unfractionated serum was stimulatory at all time-points. In the absence of hCG, the lipoprotein fraction was stimulatory at both 6.0 and 20 h, although not at 3.0 h. The lipoprotein-deficient protein fraction of serum had no effect on hCG-stimulated testosterone production alone, but significantly enhanced the bioactivity of the lipoprotein fraction, and caused a dose-dependent stimulation of testosterone production in the presence of a constant concentration of serum lipoproteins. Both a stimulatory peak of activity (apparent MW 40-80 kDa), and a large MW (> 100 kDa) inhibitor of testosterone production were identified in serum after fractionation by gel filtration (Sephadex G-100). The data indicate that (i) the stimulatory effect of serum on short-term hCG-stimulated Leydig cell testosterone production in vitro is predominantly due to the serum lipoprotein fraction, possibly by providing additional precursors for testosterone synthesis, (ii) the biological activity of the lipoproteins is influenced by both stimulatory and inhibitory serum proteins in addition to luteinizing hormone, and (iii) that serum lipoproteins may be involved in supporting Leydig cell steroidogenesis in vivo.     

Modulation of testicular receptors for LH, FSH and prolactin by the administration of ovine prolactin in mature rat

To elucidate the role of prolactin on testicular function, we treated mature rats with ovine prolactin (oPRL) and investigated the dose and time-dependent changes in testicular LH, FSH and prolactin receptors as well as in serum gonadotropin and steroid levels. Twelve week-old rats were injected sc with a single dose of various amounts of oPRL (0.2, 1 and 5 IU) and killed on the first, second and third days after the treatment. Testicular LH receptor decreased to 59% of the control level as a function of time while prolactin receptor increased to 244% maximally of the control level on the second day. In contrast, FSH receptor changed in a different fashion. Smaller amounts of oPRL (0.2 and 1 IU) raised the receptor level to 193% of the control level on the first day whereas a larger amount (5 IU) did not change the receptor, which tended to remain in a low level throughout the experimental period. The serum FSH level significantly increased in every group on the second day, then returned to the control range by the third day. On the other hand, the serum testosterone level changed in a characteristic manner, decreased significantly in every group on the first day though not in a dose-dependent fashion, returned to normal on the second day and significantly increased in the 0.2 IU group on the third day (p less than 0.01). Similarly, the serum estradiol level decreased in the oPRL-treated groups on the first day and was restored on the second day.(ABSTRACT TRUNCATED AT 250 WORDS)     

Direct biphasic modulation of gonadotropin-stimulated testicular androgen biosynthesis by prolactin

Prolactin (PRL) exerts both stimulatory and inhibitory effects upon testicular steroidogenesis in vivo. The direct effects of PRL on biosynthesis of testicular androgen were studied in primary cultures of testicular cells obtained from adult, hypophysectomized or neonatal, intact rats. In cells from adult animals, treatment with human chorionic gonadotropin (hCG) (10 ng/ml) significantly increased testosterone and progesterone production relative to their respective controls. In contrast, neither steroid was increased by treatment with rat PRL (rPRL) or ovine PRL (oPRL) alone. Upon addition of 0.1-3 ng/ml of either rPRL or oPRL to the hCG-treated cultures, testosterone production was progressively increased up to a maximum of 70% greater than with hCG alone. However, when PRL exceeded 3 ng/ml, the testosterone response began to decline and was 39 or 24% less than from cells treated with hCG alone at 300 ng/ml of rPRL or oPRL, respectively. A similar biphasic response pattern was observed in cells from neonatal animals. In contrast to the biphasic effect of PRL on production of androgen, PRL treatment enhanced hCG-stimulated production of progesterone in a dose-related manner without exerting an inhibitory effect. At 3 and 300 ng/ml, rPRL augmented hCG action by 2.5- and 8-fold, respectively. Similarly, in the presence of inhibitors of pregnenolone metabolism, rPRL also enhanced hCG-stimulated production of pregnenolone. Quantitation of steroid intermediates in the testosterone biosynthetic pathway revealed that the stimulatory effect of 3 ng/ml rPRL on testosterone production was associated with 1.3- and 2.8-fold increases in accumulation of androstenedione and 17 alpha-hydroxyprogesterone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Lactogenic response of mouse mammary explants from different days of pregnancy to placental lactogen and pituitary prolactin

Summary The lactogenic response of mouse mammary gland explants to human placental lactogen (hPL) and ovine pituitary prolactin (oPRL) was examined on days 10 to 18 of pregnancy by measuring³H-amino acid incorporation into calcium-rennin precipitable casein. To determine the lactogenic response of the explants, the mean slopes of dose-response curves were calculated for each hormone treatment. Slope means of dose-response curves for oPRL and hPL did not differ from each other on any day of pregnancy examined. A triphasic pattern of response was suggested when slope means of dose-response curves for both hormones were plotted as a function of day of gestation. Peak responses were observed on days 10, 13 and 17–18. Combinations of oPRL and hPL, in ratios of oPRL:hPL=2∶1 and oPRL:hPL=1∶2, also produced a triphasic pattern of sensitivity very similar to that produced by either hormone alone. These results suggest that mouse mammary explants may be more sensitive to oPRL and hPL on days 10, 13 and 17–18 of pregnancy. This work was supported by grants from the National Science Foundation (76-01928) and the National Institutes of Health (5 S06RR08132-0251) to F. Talamantes.     

Ovine placental lactogen stimulation of ornithine decarboxylase activity in brain and liver of neonatal rats

Ovine placental lactogen (oPL), growth hormone (oGH), prolactin (oPRL) and human placental lactogen (hPL) were administered intracisternally (ic) or intraperitoneally (ip) to 17 day old rats and brain and liver ODC activities determined four hours later. When given ic, oPL, oGH and oPRL caused significant increases in brain ODC activity, while hPL had no significant effect. After ip administration, oPL and oGH also caused a significant increase in brain as well as liver ODC activity but oPRL and hPL were without significant effect. The stimulation of polyamine metabolism by oPL together with earlier reports of its potent somatotropic effects and its high concentration in the fetus supports the hypothesis that oPL may be important in the regulation of fetal growth.     

Bioconversion of waste office paper to gluconic acid in a turbine blade reactor by the filamentous fungus Aspergillus niger

Gluconic acid production was investigated using an enzymatic hydrolysate of waste office automation paper in a culture of Aspergillus niger. In repeated batch cultures using flasks, saccharified solution medium (SM) did not show any inhibitory effects on gluconic acid production compared to glucose medium (GM). The average gluconic acid yields were 92% (SM) and 80% (GM). In repeated batch cultures using SM in a turbine blade reactor (TBR), the gluconic acid yields were 60% (SM) and 67% (GM) with 80-100 g/l of gluconic acid. When pure oxygen was supplied the production rate increased to four times higher than when supplying air. Remarkable differences in the morphology of A. niger and dry cell weight between SM and GM were observed. The difference in morphology may have caused a reduction of oxygen transfer, resulting in a decrease in gluconic acid production rate in SM.     

Serum sphingomyelin levels are related to the clearance of postprandial remnant-like particles

It is known that sphingomyelin (SM) content is higher in apolipoprotein B-containing particles (BLps) than in high density lipoproteins and that BLp levels, including chylomicrons and their remnant particles, are positively related to atherosclerosis. To evaluate the relationship between serum SM and postprandial remnant particle levels, we determined SM, triglyceride (TG), and cholesterol levels in serum and in remnant-like particles (RLPs) before and 3, 5, 7, and 10 h after a high-fat meal in 31 healthy subjects. We found that serum SM, like serum TG, was increased to its maximum 3 h after fat loading and then gradually decreased to basal levels after 10 h. More important, we determined that SM and TG levels in RLPs were parallel. Serum SM was positively correlated with serum TG (P <0.001), RLP SM (P <0.001), RLP TG (P <0.001), and RLP cholesterol (P <0.001) levels. It is our conclusion that serum SM is a marker for the clearance of RLPs.