Instrument for precision long-term ß-decay rate measurements.

We describe an experimental setup for making precision measurements of relative ß-decay rates of (22)Na, (36)Cl, (54)Mn, (60)Co, (90)Sr, (133)Ba, (137)Cs, (152)Eu, and (154)Eu. The radioactive samples are mounted in two automated sample changers that sequentially position the samples with high spatial precision in front of sets of detectors. The set of detectors for one sample changer consists of four Geiger-Müller (GM) tubes and the other set of detectors consists of two NaI scintillators. The statistical uncertainty in the count rate is few times 0.01% per day for the GM detectors and about 0.01% per hour on the NaI detectors. The sample changers, detectors, and associated electronics are housed in a sealed chamber held at constant absolute pressure, humidity, and temperature to isolate the experiment from environmental variations. The apparatus is designed to accumulate statistics over many years in a regulated environment to test recent claims of small annual variations in the decay rates. We demonstrate that absent this environmental regulation, uncontrolled natural atmospheric pressure variations at our location would imprint an annual signal of 0.1% on the Geiger-Müller count rate. However, neither natural pressure variations nor plausible indoor room temperature variations cause a discernible influence on our NaI scintillator detector count rate.

Highly improved precision of the hypophysectomized female rat body weight gain bioassay for growth hormone by increased frequency of injections, avoidance of antibody formation, and other simple modifications.

Mediocre precision has been a frustrating feature of the hypophysectomized female rat body weight gain bioassay for GH, especially human GH (hGH), in the original procedural format of injections once daily, ip, for 10-14 days. Consequently, the principal conditions that influence the bioassay's precision were identified and appropriately modified, by detailed systematic analysis of the daily body weight gain response to treatment with bovine GH (bGH) and hGH. Under identical conditions, the slope and precision of dose-response curves for hGH were markedly inferior to those for bGH. This prompted revision of the injection frequency for hGH to four times daily, sc. Dramatic improvement in slope and precision for hGH resulted, nearly equal to the excellent slope and precision attained for bGH with twice daily injections, sc. In addition, direct and indirect assessment of GH antibody formation pinpointed day 8 as the time of onset of growth-neutralizing antibodies, which are deleterious to precision and accuracy. Accordingly, the injection period was limited to 7 days. A warm environment of 31-32 C to sustain optimal animal health and responsiveness and objective specifications for selection of animals were also used. These modifications, incorporated into standardized procedures (four times daily injections, sc, 7 consecutive days, for hGH; twice daily injections, sc, 7 consecutive days, for bGH) produced a lambda, the index of precision, which hovered on the highly respectable bioassay value of 0.2 consistently and reliably. The demonstration of differing performance characteristics and differing immunogenicities of bGH and hGH in the rat invalidates the use of one as the reference standard for the bioassay of the other, and beclouds the quantitative meaning of all prior data derived in that way.

Stimulation of supranormal growth in prepubertal, adult plateaued, and hypophysectomized female rats by large doses of rat growth hormone: physiological effects and adverse consequences.

A supranormal rate of growth in intact, prepubertal, 26-day-old female rats was evoked by administration of large doses of highly purified rat GH (rGH). In response to daily doses of 1 and 5 mg/rat (13.6 mg/kg BW and 68 mg/kg BW), sc, for 20 days, body weight (BW) gain increased 51% and 73%, and skeletal growth increased 27% and 40%, respectively. Serum rGH in treated rats rose as much as 69-fold greater than that of controls. Feed efficiency, the ratio of weight gained to feed consumed, increased from 19.8% to 32.0%. This rGH treatment depleted pituitary GH content as much as 58% and caused hepatomegaly. These effects, as well as the accelerated growth rate, reverted to normal after cessation of rGH treatment. Onset of puberty in rGH-treated rats was delayed an average of 2.7 days. A similar stimulatory effect on BW gain, but not skeletal growth, as well as depletion of pituitary GH content, and hepatomegaly, was elicited by rGH treatment in adult, plateaued female rats. These effects in plateaued rats reverted to normal after cessation of GH treatment, and 50% of the body weight gain was rapidly lost. The largest dose of rGH used, 5 mg/day, was apparently toxic, resulting in a 20% higher mortality rate in treated prepubertal and plateaued female rats. Antibody formation was not the cause of the toxicity, since antibodies against rGH were undetectable at the lowest dilutions of serum tested. Serum rat insulin-like growth factor I (RIA), 3.5 U/ml in untreated intact prepubertal rats, increased to 4.7 and 5.0 U/ml, respectively, after 20 days of rGH treatment. In hypophysectomized rats, serum rat insulin-like growth factor I (RIA), undetectable in controls, was increased to 1.63 U/ml after 14 days treatment with 1 mg rGH/day. This study demonstrates that greater than normal growth can be stimulated in normal female rats by administration of large doses of homologous GH, but at the risk of serious adverse effects. Possible implications for the administration of GH to non-GH-deficient children, to promote taller stature, are clear.

Pineal gland - pituitary (alpha-MSH) interrelationships in fur priming and reproductive cycles in mink (Mustela vison).

Our investigations show that blindness, either natural or surgically induced results in a lack of fur priming and sexual development. Definite genetic color phase differences were observed in the sensitivities of the biological clocks for initiating fur priming, testicular development and time of breeding and whelping. Finely-bred dark mink molted and their pelts primed later in the fall than did either pastel or opaline mink. Testicular development was earlier and more extensive for the opaline, but was intermediate for the pastels and slower and least extensive for the finely-bred dark mink. The dark mink, however, bred earlier than did either the pastel and opaline strains. Hedlund (deaf, white) mink pelted about the same time as the pastels and opalines, but they bred and whelped later than the above three strains of mink. Plasma alpha-MSH levels were inversely related to testosterone levels and testicular development. It was high in all three strains (darks, pastels and opalines) during both the spring and autumnal molts, but was low during testicular development and breeding.

Contractility of seminiferous tubules as related to sperm transport in the male.

The mammalian testes have several mechanisms to propel the nonmotile spermatozoa in the seminiferous tubules through the rete testis into the epididymis. These include (a) contractions of the testicular capsule and the seminiferous tubules and (b) fluid flow through the excurrent ducts resulting from active transport of fluids and electrolyte into the seminiferous tubules from the extracellular space. The efflux of fluids and sperm from the testis appears to closely parallel spermiation. An increased output of fluid may result from prostaglandins (PGF2 alpha) and possibly oxytocin (not all species respond to oxytocin) as a result of capsular contractions compressing and expelling the fluid from the tubules. Seminiferous tubular contractions do not result from nervous stimulation but are linked to PGs and cyclic nucleotide generation. They are regulated to some extent by androgens and the lesser response of the tubules to 5 alpha-dihydrotestosterone compared to testosterone can be explained by their interaction with androgen binding protein and their action on phospholipase A2 activity for PG synthesis.