Photoperiod and ovulatory menstrual cycles in female macaque monkeys

Macaques (Macaca mulatta and M. assamensis) which had been maintained on a 12L :12D light cycle for the previous 4 years and had 25-35-day menstrual cycles were randomly assigned to two groups. Those in Group 1 were kept in 12L :12D for 13 months. Those in Group 2 were subjected to three successive 5-month periods of 20L :4D, 4L :20D and 20L :4D. There were no significant differences between the two groups in the frequency, duration and percentage of ovulatory menstrual cycles, suggesting that photoperiod is not the sole regulator of seasonal breeding in these animals.     

Enhanced luteinizing hormone release by luteinizing hormone-releasing hormone in incubating female turkeys (Meleagris gallopavo)

To determine what role pituitary responsiveness plays in the suppression of gonadotropin level during incubation in the turkey, the ability of the pituitary to release luteinizing hormone (LH) in response to luteinizing hormone-releasing hormone (LHRH) was compared in incubating, laying, and photorefractory birds. In all three groups, the i.m. injection of LHRH (4 micrograms/kg) increased serum LH levels; however, the LH response was markedly enhanced in the incubating turkeys as compared with the laying (6.6-fold increase over preinjection levels vs. 1.9-fold; p less than 0.05) or the photorefractory birds (9.7-fold vs. 3.1-fold; p less than 0.05). The LHRH-induced LH release was also determined in turkeys as they shifted from the laying to the incubating phase of the reproductive cycle. This response increased (p less than 0.05) in magnitude as the birds started to incubate. The high prolactin level of incubating turkeys does not have a depressing effect on LHRH-stimulated LH release; thus, impaired LH response to LHRH is not a mechanism involved in the diminished gonadotropin secretion of incubating turkeys.     

Double ovulatory cycles in some captive turbot, Scophthalmus maximus L.

The hypothesis that the paired ovaries of turbot, Scophthalmus maximus , ovulate alternately was tested and rejected as a possible explanation for the double ovulatory cycles found in some captive turbot. It is suggested that these double cycles are caused by variation patterns in the hormone-release cycles of individual females.     

Prevention of lithocholate--induced cholestasis by cycloheximide, an inhibitor of protein synthesis

Our previous investigations have shown that lithocholic acid (LCA)-induced cholestasis is associated with an increased synthesis of microsomal cholesterol which is transported with LCA and incorporated in the bile canalicular membrane. As the significance of these changes remains unknown the effect of interference with microsomal protein synthesis and/or with the cellular transport of cholesterol was studied. Male Wistar rats were injected i.p. with cycloheximide at the dose of 15 micrograms/100 g BW 3 times over a 24-hour period. After cannulating the common bile duct and collecting bile for one hour, the animals were either injected i.v. with 12 mumoles C14-LCA/100 g BW or with a 7.5% albumin solution and bile was collected for another hour. LCA injection in untreated animals reduced bile flow by more than 90% of control values. In contrast, bile flow in the group treated with cycloheximide and LCA was normal and did not differ from that of animals given cycloheximide alone. Bile salt secretion rate was increased in the cycloheximide-LCA group over the control groups. This was mainly due to the secretion of more than 80% of the injected LCA and was confirmed by the distribution of the radioactivity. By electron microscopy, the liver in the cycloheximide-LCA group did not show any of the well defined changes associated with LCA-induced cholestasis. These data suggest that microsomes play an important role in the pathogenesis of LCA cholestasis and that inhibition of microsomal protein synthesis can prevent its development.     

Sex steroids in cervical mucus of spontaneous or induced ovulatory cycles

Evaluation of sex steroids in cervical mucus was performed at different phases of spontaneous or clomiphene-citrate-induced ovulatory cycles. To this end, 11 women with normal ovulatory cycles and 9 subjects with polycystic ovary syndrome of comparable age and body mass index were investigated. Serum and cervical mucus samplings were assessed for 17beta-estradiol (E2), progesterone, testosterone, and sex hormone binding globulin levels at the pre-, peri-ovulatory, and mid-luteal phases of the cycle. The cervical mucus maturation index also was estimated in all women. Measurable amounts of E2 were found in most mucus samples with a cyclic variation in all cases. The highest E2 and mucus maturation index values coincided, but both lagged by 24 h behind the serum mid-cycle peak of this steroid. Detectable amounts of progesterone were found in the luteal phase, testosterone was present at low levels throughout the cycle, but sex hormone binding globulin was undetectable in all cervical mucus samples. Differences between spontaneous or drug-induced ovulatory cycles were not found. It is concluded that sex steroids are present in human cervical mucus, showing variations similar to those in peripheral blood. The significance of these findings is not clear at present, but it is probably related to the cyclic changes of cervical epithelium and gland secretion. An important implication of the absence of measurable sex hormone binding globulin amounts in cervical mucus is that the free fraction of sex steroids present in that fluid are presumably higher, and therefore, expected to exert greater biologic activity than in peripheral blood.     

Reversal of endotoxin-mediated shock by NG-methyl-L-arginine, an inhibitor of nitric oxide synthesis

Septic shock is a life-threatening condition that results from exposure to bacterial endotoxin. It is manifested by cardiovascular collapse and mediated by the release of cytokines such as tumor necrosis factor. Some of these cytokines cause the release of vasoactive substances. In the present study, administration of 40 microgram/kg of bacterial endotoxin to dogs caused a 33% decrease in peripheral vascular resistance and a 54% fall in mean arterial blood pressure within 30 to 90 minutes. Vascular resistance and systemic arterial pressure returned to normal within 1.5 minutes after intravenous administration of NG-methyl-L-arginine (20 mg/kg), a potent and selective inhibitor of nitric oxide synthesis. L-Arginine reversed the effect of L-NMA and restored the endotoxin-induced hypotension. Although NG-methyl-L-arginine injection increased blood pressure in control dogs, the hypertensive effect was much greater in endotoxemic dogs (24.8 +/- 2.7 mmHg vs 47.8 +/- 6.8 mmHg, p = 0.01, n = 4). NG-Methyl-L-arginine caused only a modest increase in blood pressure in dogs made hypotensive by continuous intravenous infusion of nitroglycerin (17.1 +/- 5.0 mm Hg, n = 3). These findings suggest that nitric oxide overproduction is an important contributor to endotoxic shock. Moreover, our findings demonstrate for the first time, the utility of nitric oxide synthesis inhibitors in endotoxic shock and suggest that such inhibitors may be of therapeutic value in the treatment of septic shock.     

Reinitiation of DNA synthesis in quiescent mouse keratinocytes; Regulation by polypeptide hormones,cholera toxin,dexamethasone, and retinoic acid

Summary Cloned mouse keratinocytes (MK-1 cells) display density-dependent growth arrest when reaching confluency in a serum-free medium with a calcium concentration <0.1 mM, supplemented only with insulin and transferrin. In this quiescent state, greater than 95% of the cell population is in the G_0/1 phase of the cell cycle. Treatment of quiescent MK-1 cells with 1 to 10 ng/ml epidermal growth factor (EGF) resulted in a sharp burst of DNA synthetic activity. Both insulin and cholera toxin potentiated the mitogenic effect of EGF, but neither agent was necessary or sufficient to induce thymidine incorporation into DNA. Dexamethasone abolished the effect of insulin, but not the mitogenic effect of EGF alone. In contrast, retinoic acid (RA) did not possess any mitogenic effect for quiescent MK-1 cells, nor did it modulate the actions of EGF or dexamethasone. A number of commercially available crude extracts of bovine brain and pituitary were also capable of initiating DNA synthesis in resting MK-1 cells. Finally, transforming growth factor type beta (TGFβ) proved to be a potent inhibitor of the mitogen-induced DNA synthesis in MK-1 cells (IC₅₀∶10pM). This defined culture system is eminently suited to study the regulation of DNA synthesis of epidermal cells. In addition, it can be used as a sensitive bioassay for the detection of epidermal mitogens, as well as inhibitors of DNA synthesis such as TGFβ. Supported by PHS Award CA-41556 from the National Cancer Institute, Bethesda, MD.     

Reinitiation of deoxyribonucleic acid synthesis by deoxyribonucleic acid initiation mutants of Escherichia coli: role of ribonucleic acid synthesis, protein synthesis, and cell division.

The dnaA and dnaC genes are thought to code for two proteins required for the initiation of chromosomal deoxyribonucleic acid replication in Escherichia coli. When a strain carrying a mutation in either of these genes is shifted from a permissive to a restrictive temperature, chromosome replication ceases after a period of residual synthesis. When the strains are reincubated at the permissive temperature, replication again resumes after a short lag. This reinitiation does not require either protein synthesis (as measured by resistance to chloramphenicol) or ribonucleic acid synthesis (as measured by resistance to rifampin). Thus, if there is a requirement for the synthesis of a specific ribonucleic acid to initiate deoxyribonucleic acid replication, this ribonucleic acid can be synthesized prior to the time of initiation and is relatively stable. Furthermore, the synthesis of this hypothetical ribonucleic acid does not require either the dnaA of dnaC gene products. The buildup at the restrictive temperature of the potential to reinitiate deoxyribonucleic acid synthesis at the permissive temperature shows rather complex kinetics the buildup roughly parallels the rate of mass increase of the culture for at least the first mass doubling at the restrictive temperature. At later times there appears to be a gradual loss of initiation potential despite a continued increase in mass. Under optimal conditions the increase in initiation potential can equal, but not exceed, the increase in cell division at the restrictive temperature. These results are most easily interpreted according to models that postulate a relationship between the initiation of deoxyribonucleic acid synthesis and the processes leading to cell division.     

Reinitiation of host DNA synthesis in senescent human diploid cells by infection with simian virus 40

Human diploid fibroblasts, TIG-1, cease to proliferate at about 60-62 population doubling level. In their senescent state used in this study, the percentage of nuclei labeled by [3H]thymidine for 48 h was around 1-2% in fresh medium containing 5-40% fetal bovine serum. The percentage of labelled nuclei increased up to 10-fold after infection with SV40. This increase reflects stimulation of cell DNA synthesis because: 1. The increase also occurred when ts A900 was used for infection at the non-permissive temperature, under these conditions viral DNA synthesis is inhibited; 2, the increase paralleled the stimulation of [3H]thymidine incorporation into DNA in a Hirt-precipitate fraction from SV40-infected cells. UV-irradiated SV40 had reduced ability to induce DNA synthesis. A viable deletion mutant of SV40, d1940, had almost the same activity to induce cell DNA synthesis as did wild-type SV40. Equilibrium density gradient centrifugation analysis of DNA labelled with 5-bromodeoxyuridine (BrdU) supported semiconservative replication rather than repair synthesis. We conclude that a considerable fraction of human diploid cells in a senescent population initiate host DNA replication by infection with SV40, although these cells cannot be stimulated with fetal bovine serum.     

New data on ovulatory action of estrogens during 5 day cycles in rats

A peculiar laboratory strain W1 of Wistar rats has 5 day cycles and can be made precociously receptive to a male by an injection of estradiol 10 mcg sc at 1500 of Cycle Day 2 (Diestrus III). In the course of repeating previous work the authors noted that receptivity increased from 25 to 63%, and they investigated the mechanism by checking ovaries of estrogen treated females histologically for ovulation, in comparison with ovaries of females exposed to males during the night of Diestrus III. In this experiment 56% of estrogen treated rats ovulated. 41 out of 60 (68%) of the paired rats accepted a male (verified by sperm in vaginal smear), and 93% of these ovulated. Of the 19 who were unreceptive, 1 (5.3%) ovulated (p.001). Thus estrogen treatment is much more effective than previously observed; 5 day cycling rats have a related precocity of sexual receptivity and capacity to ovulate under this stimulus.     

Stress-induced heat-shock protein synthesis in peripheral leukocytes of turkeys,Meleagris gallopavo

• 1.1. Thermal stress, in vitro and in vivo, induced the synthesis of heat-shock proteins, HSP90, HSP70, and HSP23 in turkey leukocytes.
• 2.2. HSP induction was both temperature- and time-dependent.
• 3.3. Salinity-specific stress proteins were expressed with elevated osmolality in culture medium.