Readiness: observations and comments from a medical team deployment.

The evolving strategy of the United States in dealing with the changing world order calls for a force structure capable of fighting and winning two nearly simultaneous major regional conflicts and conducting a range of other military operations. Readiness is a key factor in this new strategy. Consequently, major paradigm shifts are occurring within the Air Force Medical Service. Maintaining current and accurate medical records on personnel to meet deployment requirements is a significant challenge. Historically, time and resources are consumed determining the deployability of troops prior to a deployment. This adds to the cost of doing business and increases the time required to clear the deploying team, even though there is an established process to avoid these very problems. The experience of a recent medical team deployment to Bosnia is discussed. Future directions given the implementation of TRI-CARE, the Preventive Health Assessment Program, and the Strategic Health Resourcing Plan are also considered.

Hormonal basis of variation in oestrous cyclicity in selected strains of mice.

Reproductive hormone secretion and ovarian LH receptor content were studied during the oestrous cycle of mice that differed in fertility after genetic selection. Strain variation in the secretory pattern of progesterone was observed along with differences in the timing and magnitude of prolactin release. Scatchard analysis showed similar affinities of the LH receptor for hCG in strains with increased or decreased reproductive performance, with a single order of binding sites during both pro-oestrus and dioestrus. The number of unoccupied LH receptors during pro-oestrus was greatest in mice with increased reproductive performance. These results provide evidence that trait selection can change gonadotrophin receptor concentration and the dynamics of hormone secretion during the oestrous cycle of the mouse.

Influence of embryonic and maternal genotype on gestational events in the mouse.

Mice with high and low prenatal survival were used to study the influence of maternal and embryonic genotype on the timing of implantation, conceptus growth and gestation length. Mice selected for large litter size (Line S1) or rapid post-weaning weight gain (Line G) showed implantation was delayed and gestation prolonged in mice with low prenatal survival (Line G). Reciprocal transfer of Line-S1 and -G embryos to pseudopregnant recipients indicated that conceptus growth was influenced by maternal as well as embryonic genes, at least until mid-pregnancy. In contrast, fetal genotype had a major effect on the length of gestation.

Male and female genotype mediate pheromonal regulation of the mouse estrous cycle.

Estrous cyclicity was studied to examine the possibility that strain differences in the regularity of the mouse estrous cycle are the result of different olfactory signals produced by the male. Females with regular estrous cycles (lines E and S1) were housed in the olfactory presence of males from a line with irregular cycles (line CN-) or in the presence of males of their own line (used as a control). Females with irregular cycles (line CN-) were housed in the presence of males from a line with regular cycles (line E) or were exposed to males of their own line. The regularity of the estrous cycle decreased in line E females (regular cycles) when exposed to line CN- males (irregular cycles). The decreased regularity of line E cyclicity resulted from an increased period of diestrus, i.e., lengthening of the cycle. In contrast, line S1 females (regular cycles) did not show any change in estrous cyclicity when exposed to line CN- males. The period of diestrus increased in line CN- females when they were exposed to line E males. These results provide evidence that 1) the genotype of the male can influence the regularity of the estrous cycle, and 2) the genotype of the female regulates her responsiveness to environmental factors (e.g., male odor).

Equol: a contributor to enigmatic immunoassay measurements of estrogen.

The efficacy of radioimmunoassay (RIA) for the measurement of estradiol-17 beta (E2) in murine plasma was investigated. When Sephadex LH-20 or celite column chromatography was used to separate E2 from estrone (E1) and other cross-reacting compounds, the results were erratic if small volumes of mouse plasma were resolved. Assay of a diethyl ether extract of plasma (500 microL) was the most practical method for estimating the concentration of estradiol-17 beta in mice. This method was used to determine the pattern of estrogen secretion during the estrous cycle, on the day of implantation and during pregnancy. No convincing change in estrogen secretion was observed in the diestrous/proestrous mouse. By comparison, estrogen levels were elevated during pregnancy. Taken together, these results implied that cross-reactive components in plasma masked low levels of endogenous estrogen. Further evaluation of mouse plasma and urine using a co-chromatography technique to examine estrogen elution from a reverse-phase HPLC system followed by GC/MS analysis indicated the presence of equol [7-hydroxy-3-(4-hydroxyphenyl)chroman], a phytoestrogen metabolite with a ring structure similar to estradiol-17 beta. Equol and possibly other cross-reactive components of plasma may account for the apparent lack of increased estrogen secretion during the mouse estrous cycle and on the day of implantation as determined by the radioimmunoassay of ether extracts of plasma.

HPLC separation of anti-estrogen and estrogen receptor binding components of mouse plasma.

Proestrous mouse plasma and urine were subjected to diethyl ether extraction, enzyme hydrolysis and HPLC separation of estrogen components. Radioimmunoassay of the treated proestrous samples with a broad spectrum anti-estrogen serum failed to detect estradiol-17 beta, estrone or estriol. HPLC chromatograms contained two peaks of immunoreactive and estrogen receptor binding material with polarities between those of estriol and estradiol-17 beta. Similar peaks were detected in HPLC chromatograms of urinary extracts from ovariectomized and ovariectomized-adrenalectomized mice. The least polar of the two peaks produced a mass spectrum identical to that of authentic equol [7-hydroxy-3-(4'-hydroxyphenyl)chroman], a phytoestrogen metabolite. The presence of significant quantities of circulating equol in all strains studied, combined with apparently low plasma levels of endogenous classical estrogens during proestrus, confound attempts to study estrogen secretion in the mouse.

Inhibition of prolactin secretion by moderate and high doses of testosterone.

The effects of different doses of testosterone on basal and stimulated secretion of prolactin (PRL) were investigated. Intact female mice of the S/W strain were injected sc with 0, 1, 10, 20, 50, 250, 500, 1000, 2500, or 5000 micrograms of testosterone propionate (TP) once daily for 4 weeks. Serum testosterone concentrations of TP injected mice rose 2- to 5-fold above those of controls at 1- to 50-micrograms doses, and 25- to 600-fold over controls in mice given higher doses of the steroid. Administration of 1 microgram of TP, the lowest dose tested, had no significant effects on basal serum PRL concentrations and only slightly inhibited the release of PRL induced by perphenazine, but the weight and PRL concentration of the pituitary gland were significantly depressed. However, at doses of 10, 20, and 50 micrograms TP, perphenazine-induced PRL release, pituitary PRL concentration, and pituitary gland weight were all reduced in a dose-related manner. The basal serum PRL concentrations decreased by the time the dose of TP reached 50 micrograms. In contrast, higher doses of TP (250 micrograms and above) reversed the suppression of these parameters: pituitary gland weight and basal serum PRL levels were restored to control levels, whereas pituitary PRL concentrations and perphenazine-induced PRL release were partially restored. These results suggest that administration of moderate and large doses of testosterone may suppress natural episodic and acute releases of PRL.

Estrogen and thymic hormone interactions in the female mouse.

This study showed that there are relationships between thymic and adrenal/ovarian endocrine actions. A 4 mg/kg dose of thymosin fraction 5 (TSN5) advanced vaginal opening and elevated estrogen levels. Single estradiol benzoate (EB) injections decreased thymus weight and caused a transient reduction in circulating plasma levels of thymosine alpha 1 (TSN alpha 1), a peptide component of TSN5. Circulating estrogen levels were elevated when TSN alpha 1 levels were undetectable. Also, TSN alpha 1 levels decreased with age and after a prolonged athymic state. The thymus was shown to involute after a single TSN5 injection, suggesting the existence of a negative hormonal feedback on the thymus. Additionally thymectomy at 3 days of age was shown to delay vaginal opening while thymectomy at 30 days of age failed to produce any significant effect on reproductive maturation. Although much research is still needed, our results provide additional evidence of a relationship between the endocrine thymus and ovary.

Prolactin status of hereditary dwarf mice.

Snell (dw/dw) and Ames (df/df) dwarf mice of both sexes were evaluated for immunoassayable PRL in plasma and for the presence of PRL-containing cells in the hypophysis. Regardless of the method of blood collection (decapitation or cardiac or orbital puncture), minimal concentrations of PRL were detected in the plasma of hereditary dwarf mice. PRL secretion was not augmented in Snell or Ames female dwarfs after treatment with perphenazine or estradiol benzoate, stimuli which greatly increased PRL release in normal female littermates. Comparison of PRL levels in dwarf animals (dw/dw or df/df) using two different homologous RIAs substantiated the observation that male and female dwarfs are PRL deficient. Mammotropes, readily detectable in the pituitary glands of all normal siblings of Snell and Ames mice, were absent from the dwarf mouse hypophysis, which was markedly reduced in size. The lack of PRL-containing cells in the dwarf mouse pituitary may explain why peripheral PRL levels in this animal are below those measured in hypophysectomized mice.

Regulation of progesterone secretion by LH and prolactin during the first half of pregnancy in the mouse.

Pregnant mice were treated with antiserum to LH or bromocriptine to inhibit the activity of LH and prolactin, respectively. Luteal function was monitored by the radioimmunoassay of plasma progesterone. Bromocriptine treatment on Days 2 or 5 of pregnancy produced a rapid decrease in progesterone secretion, but had no effect on luteal function when given on Days 6, 7 or 8 of gestation. Treatment with LH antiserum before implantation did not inhibit progesterone secretion, but luteal function was severely impaired when the antiserum was given on Days 5--9 of pregnancy. These results demonstrate the dynamic nature of luteal dependency on prolactin and LH, and indicate that LH is an essential component of the luetotrophic complex of the mouse.

Concentrations of luteinizing hormone in the serum of male mice after short-term aggressive interaction.

Adult male mice were castrated and implanted with silicone elastomer capsules containing either testosterone or sesame oil. Brief exposure to a strange male opponent depressed levels of LH in castrated animals treated with oil, but did not add to the suppressive effects of testosterone on the concentration of LH in serum. Accessory organ weights were not affected by brief aggressive encounters, nor were levels of testosterone in serum altered in response to repeated encounters with a submissive (olfactory bulbectomized) male opponent. The observation that exposure to a strange male conspecific suppressed secretion of gonadotrophin in the absence of gonadal androgen(s) suggests that stress-responsibe, antigonadotrophic factors can inhibit pituitary-gonadal function. A mechanism whereby gonadotrophin secretion may be suppressed in the androgen-deprived state is discussed.

Serum prolactin in the male mouse from birth to maturity.

The pattern of prolactin secretion was determined throughout the development of the male mouse. Levels of prolactin were at their lowest from birth to 20 days of age. A dramatic increase in serum prolactin occurred during pubertal maturation coincident with rapid growth of the accessory organ system. These events preceded the pubertal rise in the level of serum testosterone that is characteristics of this species.

Plasma testosterone during pregnancy in the mouse.

Levels of plasma testosterone (T) were studied throughout pregnancy and on the day of parturition in selected strains of mice. A dramatic midpregnancy increase in androgen occurred in both strains examined (peak on day 9). A second increase in plasma T was found during the latter half of gestation (days 14-17), at which time plasma estradiol levels were elevated.