Fatal sibling aggression, precocial development, and androgens in neonatal spotted hyenas.

Fatal neonatal sibling aggression is common in predatory birds but has not been previously reported in wild mammals. Spotted hyena females are strongly masculinized, both anatomically and behaviorally, apparently by high levels of androgens during ontogeny. Neonates display elevated androgen levels, precocial motor development, and fully erupted front teeth. Litters are usually twins, and siblings fight violently at birth, apparently leading to the death of one sibling in same-sex litters, whereas in mixed-sex litters both siblings usually survive.

A mechanism for virilization of female spotted hyenas in utero.

Female spotted hyenas exhibit male-like genitalia and dominance over males. Hyena ovarian tissues incubated in vitro produced large quantities of the steroid hormone precursor androstenedione. The activity of aromatase, which converts androstenedione to estrogen, was one-twentieth as great in hyena versus human placental homogenates. In comparison, the activity of 17 beta-hydroxysteroid dehydrogenase, which converts androstenedione to testosterone, was equal in the two homogenates. The limited aromatase activity may allow the hyena placenta to convert high circulating concentrations of androstenedione to testosterone, which results in virilization of the fetal external genitalia and possibly destruction of fetal ovarian follicles. Androstenedione production by residual ovarian stromal cells during reproductive life accounts for the epigenetic transmission of virilization in female spotted hyenas.

Placental expression and molecular characterization of aromatase cytochrome P450 in the spotted hyena (Crocuta crocuta).

At birth, the external genitalia of female spotted hyenas (Crocuta crocuta) are the most masculinized of any known mammal, but are still sexually differentiated. Placental aromatase cytochrome P450 (P450arom) is an important route of androgen metabolism protecting human female fetuses from virilization in utero. Therefore, placental P450arom expression was examined in spotted hyenas to determine levels during genital differentiation, and to compare molecular characteristics between the hyena and human placental enzymes. Hyena placental P450arom activity was determined at gestational days (GD) 31, 35, 45, 65 and 95 (term, 110), and the relative sensitivity of hyena and human placental enzyme to inhibition by the specific inhibitor, Letrozole, was also examined. Expression of hyena P450arom in placenta was localized by immuno-histochemistry, and a full-length cDNA was cloned for phylogenetic analysis. Aromatase activity increased from GD31 to a peak at 45 and 65, apparently decreasing later in gestation. This activity was more sensitive to inhibition by Letrozole than was human placental aromatase activity. Expression of P450arom was localized to syncytiotrophoblast and giant cells of mid-gestation placentas. The coding sequence of hyena P450arom was 94% and 86% identical to the canine and human enzymes respectively, as reflected by phylogenetic analyses. These data demonstrate for the first time that hyena placental aromatase activity is comparable to that of human placentas when genital differentiation is in progress. This suggests that even in female spotted hyenas clitoral differentiation is likely protected from virilization by placental androgen metabolism. Decreased placental aromatase activity in late gestation may be equally important in allowing androgen to program behaviors at birth. Although hyena P450arom is closely related to the canine enzyme, both placental anatomy and P450arom expression differ. Other hyaenids and carnivores must be investigated to determine the morphological and functional ancestral state of their placentas, as it relates to evolutionary relationships among species in this important taxonomic group.

A continuing survey of drug-resistant tuberculosis, New York City, April 1994.

BACKGROUND: A 1991 survey showed high levels of drug resistance among tuberculosis patients in New York, NY. As a result, the tuberculosis control program was strengthened, including expanded use of directly observed therapy and improved infection control. METHODS: We collected isolates from every patient in New York City with a positive culture for Mycobacterium tuberculosis during April 1994; results were compared with those in the April 1991 survey. RESULTS: From 1991 to 1994, the number of patients decreased from 466 to 332 patients. The percentage with isolates resistant to 1 or more antituberculosis drugs decreased from 33% to 24% (P < .01); with isolates resistant to at least isoniazid decreased from 26% to 18% (P < .05); and with isolates resistant to both isoniazid and rifampin decreased from 19% to 13% (P < .05). The number of patients with isolates resistant to both isoniazid and rifampin decreased by more than 50%. Among never previously treated patients, the percentage with resistance to 1 or more drugs decreased from 22% in 1991 to 13% in 1994 (P < .05). The number of patients with consistently positive culture results for more than 4 months decreased from 130 to 44. A history of antituberculosis treatment was the strongest predictor of drug resistance (odds ratio = 3.1; P < .001). Human immunodeficiency virus infection was associated with drug resistance among patients who never had been treated for tuberculosis. CONCLUSIONS: Drug-resistant tuberculosis declined significantly in New York City from 1991 to 1994. Measures to control and prevent tuberculosis were associated with a 29% decrease in the proportion of drug resistance and a 52% decrease in the number of patients with multidrug-resistant tuberculosis.

Sexual dimorphism of perineal muscles and motoneurons in spotted hyenas.

Female spotted hyenas are known for their male-like genitalia, high levels of aggression, and dominance over males, characteristics which are attributed to exposure to elevated levels of testosterone in utero. Although the nervous system of spotted hyenas has not previously been examined, one might predict that neural systems which are sexually dimorphic in other mammals would be monomorphic in this species. Spinal motoneurons which innervate muscles associated with the phallus are located in Onuf's nucleus and are more numerous in males than in females in a wide array of mammals. Onuf's nucleus was examined in adult and neonatal spotted hyenas and, contrary to expectation, was found to be sexually dimorphic in the typical mammalian pattern: Males have significantly more motoneurons in Onuf's nucleus than do females. This dimorphism was correlated with a previously undescribed dimorphism in the relevant target musculature. Specifically, the morphology of the bulbocavernosus muscle is distinctly different in male and female spotted hyenas. Pregnant hyenas were treated with anti-androgen in an attempt to interfere with the actions of androgen during fetal development. Motoneuron number in Onuf's nucleus and the morphology of the bulbocavernosus muscle were feminized in males exposed to anti-androgen in utero.

Identification of a novel oxazolidinone (U-100480) with potent antimycobacterial activity.

During the course of our investigations in the oxazolidinone antibacterial agent area, we have identified a subclass with especially potent in vitro activity against mycobacteria. The salient structural feature of these oxazolidinone analogues, 6 (U-100480), 7 (U-101603), and 8 (U-101244), is their appended thiomorpholine moiety. The rational design, synthesis, and evaluation of the in vitro antimycobacterial activity of these analogues is described. Potent activity against a screening strain of Mycobacterium tuberculosis was demonstrated by 6 and 7 (minimum inhibitory concentrations or MIC's < or = 0.125 micrograms/mL). Oxazolidinones 6 and 8 exhibit MIC90 values of 0.50 micrograms/mL or less against a panel of organisms consisting of five drug-sensitive and five multidrug-resistant strains of M. tuberculosis, with 6 being the most active congener. Potent in vitro activity against other mycobacterial species was also demonstrated by 6. For example, 6 exhibited excellent in vitro activity against multiple clinical isolates of Mycobacterium avium complex (MIC's = 0.5-4 micrograms/mL). Orally administered 6 displays in vivo efficacy against M. tuberculosis and M. avium similar to that of clinical comparators isoniazid and azithromycin, respectively. Consideration of these factors, along with a favorable pharmaco-kinetic and chronic toxicity profile in rats, suggests that 6 (U-100480) is a promising antimycobacterial agent.

Exposure to naturally circulating androgens during foetal life incurs direct reproductive costs in female spotted hyenas, but is prerequisite for male mating.

Among all extant mammals, only the female spotted hyena (Crocuta crocuta) mates and gives birth through the tip of a peniform clitoris. Clitoral morphology is modulated by foetal exposure to endogenous, maternal androgens. First births through this organ are prolonged and remarkably difficult, often causing death in neonates. Additionally, mating poses a mechanical challenge for males, as they must reach an anterior position on the female's abdomen and then achieve entry at the site of the retracted clitoris. Here, we report that interfering with the actions of androgens prenatally permanently modifies hyena urogenital anatomy, facilitating subsequent parturition in nulliparous females who, thereby, produce live cubs. By contrast, comparable, permanent anatomical changes in males probably preclude reproduction, as exposure to prenatal anti-androgens produces a penis that is too short and has the wrong shape necessary for insertion during copulation. These data demonstrate that the reproductive costs of clitoral delivery result from exposure of the female foetus to naturally circulating androgens. Moreover, the same androgens that render an extremely unusual and laborious process even more reproductively costly in the female are apparently essential to the male's physical ability to reproduce with a normally masculinized female.

Virilization of the female spotted hyena cannot be explained by alterations in the amino acid sequence of the androgen receptor (AR).

The external genitalia of the female spotted hyena are male in character, consistent with virilization by androgens during embryogenesis that results in the fusion of the vaginal labia to form a pseudo scrotum and enlargement of the clitoris to form a phallus. Explanations advanced to account for these anatomic differences have centered on the production or metabolism of androgens in utero or on abnormalities of the androgen receptor (such as a constitutively active AR). The structure of the spotted hyena AR was examined at the level of genomic DNA and cDNA. Southern analysis detected two Eco RI endonuclease cleavage fragments (4.4 and 4.7 kb) that encode the bulk of the AR hormone-binding domain. Isolation of the smaller fragment from a size fractionated genomic library revealed that it contained exons 6, 7 and 8. The remaining portions of the coding sequence were cloned by RT-PCR and RACE analyses. The spotted hyena cDNA sequence predicts protein 912 amino acids in length, which is most closely related to the sequence of the dog AR. Although a number of differences in the predicted amino acid sequence are identified, particularly within the amino terminus, only single amino acid substitutions are present in the DNA- and ligand-binding domains compared to the human AR. In transfection assays, the spotted hyena AR does not exhibit constitutive activity and responds normally to a range of androgenic and non-androgenic ligands. These findings suggest that the structural changes in the AR do not account for the abnormal virilization in the female spotted hyena. These results serve to focus attention on processes proximal (an abnormality of hormone formation in situ) or distal (activation by other mechanisms of processes normally regulated by androgen) to the AR as the cause of the virilization.

Scent marking (pasting) in a colony of immature spotted hyenas (Crocuta crocuta): a developmental study.

Pasting, a stereotypic form of anal gland scent marking, was studied in 2 cohorts (N = 20) of captive spotted hyenas (Crocuta crocuta). A significant increment in the frequency of pasting occurred in both cohorts as the animals approached sexual maturity; however, gonadectomy during the early juvenile age period had no significant effects on subsequent pasting frequency. Dominant hyenas in both cohorts tended to scent-mark more frequently than subordinates during the late subadult period. Pasting was facilitated by the immediately preceding pasting activities of other hyenas, as has been reported to occur in nature, and olfactory investigation was the most common behavior preceding pasting.

Medical considerations and planning for short distance road races.

Short distance road races are popular in most communities, and athletic trainers are often asked to coordinate the medical coverage for such events. The medical support needed to successfully cover marathons, triathlons, and other endurance events has been well documented. However, little information has been presented regarding medical considerations for shorter distance races. Heat illness is often seen in short distance races, especially when the environmental conditions are extreme. Successful coverage of races of any length includes thorough planning and preparation, adequate supplies, and competent personnel. Medical coverage includes organizing the medical tent at the finish line, selecting appropriate protocols for treatment, and identifying a physician who will act as the race's medical director. It may also be necessary to provide medical coverage on the race course, at other areas, and at the finish line. The purpose of this paper is to inform the medical community, and athletic trainers in particular, of some of the details that should be considered when planning race coverage. The information detailed within may also be applied to other sports-related medical coverage provided by athletic trainers.