Photoperiod and temperature interact to affect the GnRH neuronal system of male prairie voles (Microtus ochrogaster).

Individuals of numerous species limit energy expenditure during winter by inhibiting reproduction and other nonessential functions. To time these adaptations appropriately with the annual cycle, animals rely on environmental cues that predict, well in advance, the onset of winter. The most commonly studied environmental factor that animals use to time reproduction is photoperiod. Rodents housed in short photoperiods in the laboratory or in naturally declining day lengths exhibit pronounced alterations in reproductive function concomitant with alterations in the hypothalamic gonadotropin-releasing hormone neuronal system. Because animals in their natural environment use factors in addition to photoperiod to time reproduction, the present study sought to determine the independent effects of photoperiod and temperature, as well as the interaction between these factors, on reproductive parameters and the GnRH neuronal system. Male prairie voles were housed in either long (LD 16:8) or short (LD 8:16) day lengths for 10 weeks. Animals in each photoperiod were further subdivided into groups housed in either mild (i.e., 20 degrees C) or low (i.e., 8 degrees C) temperatures. As shown with immunohistochemistry, voles that underwent gonadal regression in response to short photoperiods and long-day voles housed in low temperatures (and maintained large gonads) exhibit higher GnRH-immunoreactive (GnRH-ir) neuron numbers in the preoptic area/anterior hypothalamus (POA/AH) relative to all other groups. In addition, voles that underwent gonadal regression in response to both short days and low temperatures did not exhibit an increase in GnRH-ir neuron numbers compared to long-day, mild-temperature controls. These data suggest that photoperiod and temperature interact to influence reproductive function potentially by alterations of the GnRH neuronal system.

Retinoic acid receptor beta expression and growth inhibition of gynecologic cancer cells by the synthetic retinoid N-(4-hydroxyphenyl) retinamide.

BACKGROUND: The synthetic retinoid N-(4-hydroxyphenyl) retinamide (4HPR) can inhibit the growth of tumor cells. Preliminary results from a clinical trial suggest that 4HPR may reduce ovarian cancer incidence. We examined the growth-inhibitory effects of 4HPR on gynecologic cancer cell lines in vitro and the role of retinoid receptors in modulating this effect. METHODS: Twelve human gynecologic cancer cell lines (the ovarian cell lines--A224, AD10, UCI 101, UCI 107, SKOV3, 222, CP70, ML3B, and ML5; the cervical cell lines--HT3 and ME180; and the endometrial cell line--Hec 1A were tested for sensitivity to 4HPR (by assaying cell proliferation rates). Gel electrophoretic analysis of DNA fragmentation was used to measure programmed cell death (apoptosis). Specific retinoid receptor (retinoic acid receptor [RAR] and retinoid X receptor) messenger RNA (mRNA) levels were measured by northern blot hybridization. AD10 cells were stably transfected with human RARbeta complementary DNA, and the effect of 4HPR on cell proliferation was examined. RESULTS: 4HPR inhibited the growth of all 12 cell lines, but to varying degrees; IC50 values (i.e., concentrations that inhibit proliferation by 50%) ranged from 0.3 to 9 microM. Following 4HPR treatment, ovarian cancer cells that were sensitive to 4HPR (222, CP70, and UCI 101; IC50 <3 microM) contained higher levels of RARbeta transcripts than more resistant cells (AD10, ME180, Hec 1A, and A224; IC50 > or =3 microM) (2.8-fold; two-sided P = .006). Anchorage-independent growth of transfected AD10 cells expressing high levels of RARbeta was totally abolished, even in the absence of 4HPR; transfectants expressing low levels of RARbeta exhibited lower levels of anchorage-independent growth and grew more slowly in the presence of 4HPR than control untransfected AD10 cells. CONCLUSION: 4HPR inhibited the proliferation of ovarian cancer cells in vitro; RARbeta expression appeared to be associated with this effect.

The association between alcohol and breast cancer: popular press coverage of research.

OBJECTIVES: This study was undertaken to examine popular press reports of the association between alcohol and breast cancer. METHODS: Articles from scientific journals and stories from newspapers and magazines published from January 1, 1985, to July 1, 1992, were retrieved from six on-line databases. Lay press stories were analyzed to determine which medical articles were publicized and what information was reported. RESULTS: Fifty-eight scientific articles on the relationship of alcohol and breast cancer were found, and 64 newspaper and 23 magazine stories were retrieved. The press cited 11 studies, 19% of those published during the study period. Three studies were featured in 77% of popular press stories. No scientific review articles were reported. Behavioral recommendations were given to the public in 63% of stories. CONCLUSIONS: The vast majority of scientific studies on alcohol and breast cancer were ignored in press reports. We encourage researchers and the popular press to give the public a broader understanding of public health issues.

A competitive enzyme-linked immunosorbent assay (ELISA) to detect retronecine and monocrotaline in vitro.

Antibodies to the nonesterified pyrrolizidine nucleus, retronecine (155 mol.wt), were produced in rabbits and detected using an avidin-biotin antibody ELISA. A competitive ELISA for the detection of retronecine and the cyclic diester monocrotaline was also developed using the antiserum produced against the hapten conjugate, retronecine-bovine serum albumin. Retronecine was obtained by hydrolysis of monocrotaline, succinylated and directly coupled to bovine serum albumin or ovalbumin. Antibodies to the pyrrolizidine nucleus, retronecine, can be detected within 5 min after the addition of substrate using the avidin-biotin ELISA. Competitive inhibition of antibodies to retronecine is obtained by the addition of known amounts (0-11.42 micrograms/microliters) of either the homologous antigen, retronecine, or the heterologous antigen, monocrotaline, however, retronecine acts as the better competitor.

Rapid decline in blood antimyotoxin levels in the presence of myotoxin A from prairie rattlesnake (Crotalus viridis viridis) venom.

The disappearance of antibodies to myotoxin a from the bloodstream in mice was measured with a specific ELISA over a ninety-six hour period in the presence and absence of myotoxin a. A gradual disappearance of antibodies to myotoxin in the absence of toxin was observed during the 96 hr sampling period, although antibodies were still detectable at 96 hrs. However, in the presence of myotoxin a very rapid decrease of antimyotoxin occurred. When antiserum injection was followed by myotoxin injection (5 min. later) the decline in antibodies was immediate and no antibodies could be detected 30 min. after the antiserum injection. When antiserum was injected either immediately or 30 min. after toxin, antibody levels declined sharply and were non-detectable 1 hr. after antiserum injection. These results have clinical significance since they indicate that antimyotoxin can still bind the toxin, even when administration of the antiserum is delayed for 30 min. after injection of the toxin. Multiple injections of antiserum may be required to maintain a neutralizing level of antiserum.

Detection of myotoxin alpha-like proteins in various snake venoms.

Ninety-five venom samples from eight snake genera (Agkistrodon, Bitis, Bothrops, Calloselasma, Crotalus, Sistrurus, Naja and Vipera) including venoms of Crotalus species of different geographical origin were assayed using immunodiffusion or an ELISA for the presence of the small basic protein, myotoxin alpha, known to cause muscle necrosis. Of the eight genera investigated, only Crotalus and Sistrurus venoms contained detectable amounts of myotoxin alpha-like proteins. The venoms of 13 out of 17 rattlesnake species investigated contained proteins immunologically similar to myotoxin alpha, including 12 Crotalus species and one Sistrurus species. The highest amounts were detected in venoms of C. exsul, C. viridis oreganus and C. v. viridis. Qualitative differences in the presence or absence of myotoxin alpha-like proteins were observed in the venoms of C. cerastes, C. horridus, C. lepidus, C. mitchelli, C. scutulatus, C. viridis and S. catenatus specimens of different geographic origin. The toxin was not detected in the venoms obtained from C. adamanteus, C. atrox, C. enyo or C. vegrandis specimens. The toxin appears to be widely distributed among rattlesnake species in the new world, but may vary qualitatively by geographical region in several species and subspecies.

Use of affinity-purified antibodies to measure the in vivo disappearance of antibodies to myotoxin a.

Antiserum against myotoxin a was purified using affinity chromatography. Myotoxin a was conjugated to an Affi-Gel agarose gel bead support and crude antiserum applied to the column. Antibody was eluted with distilled water, acetic acid and phosphate-buffered saline, and the protein concentration in the effluent was estimated by the absorbance at 280 nm. Antibody eluted with distilled water was used to develop an ELISA to detect antibodies to myotoxin in the bloodstream. Mice were injected with either 0.10, 0.15 or 0.20 ml of crude antiserum, and blood samples were taken during a four-week period. Samples were assayed for antimyotoxin using the antibody detection ELISA. Blood levels of antimyotoxin decreased significantly (P less than 0.05) within 1 hr after mice received 0.10 ml of crude antiserum (i.v.). Levels of antimyotoxin in mice given 0.15 and 0.20 ml of antiserum decreased significantly at 3 hr after the injection. Mice given 0.20 ml antiserum had significantly (P less than 0.05) higher amounts of antimyotoxin than mice receiving 0.10 ml antiserum during the 24-hr period after injection. However, after 24 hr all three treatment groups had less than 100 ng antimyotoxin/ml and did not differ significantly from one another. Measurement of antivenom in the bloodstream of snakebite patients might help determine if and when additional antivenom should be administered.

Prolactin and its involvement in fluid regulation in the bovine.

Plasma prolactin (PRL) concentrations, osmolality, water consumption, feed intake, urine excretion, and fecal water output were determined in twelve steers of 3 breeds exposed to 5 feed and water regimes. Breed differences were found in water intake and plasma PRL concentrations when feed and water were ad lib., however, during any of the other 4 treatments, responses were similar between breeds. During dehydration and feed restriction, water intake, urine, fecal water, and plasma prolactin decreased; however, during hydration and refeeding such changes were not as clearly related. No consistent relationships between plasma prolactin and osmolality were found. Data suggests that PRL's role in fluid regulation in the bovine is most likely associated with alterations in renal hemodynamics rather than by changes in plasma osmolality.