'Double-head' antlers in red deer Cervus elaphus ssp. in which the antler cores survived the death of the cortex.

An unusual case of spike antlers in male red deer is described in which the antler core apparently survived the partial mineralization of the cortex in the first rut and then in the next year supported a new, "antleroma-like" growth. On one side of the antler beam a "separation gap" developed between the living core and the dead cortex. On the opposite side a new growth of antler tissue was observed; this was made of spongious bone which in some areas partially resembled peruke-like growth and in others resembled antler "pearls". This new tissue, which developed probably in the second antler cycle, grew in the right antler from the base to the apex but in the left antler it was limited to the lower portion of the beam. This new tissue might still have been covered with velvet when the deer was shot. It is speculated that hypoandrogenism or partial lack of testosterone receptors was responsible for the survival of the antler core and the subsequent proliferation of new antler tissue in the following year.

Seasonal variations in hair pigmentation of white-tailed deer and their relationship to sexual activity and plasma testosterone.

Intensity of hair pigmentation of dorsal scrotum, nose, cheek and forehead areas of seven mature, male white-tailed deer were determined from close-up colour slides taken once a month during a 2-year period. Blood samples and skin biopsies from forehead areas were taken at the same time as the photographs. Plasma testosterone (T) levels were measured by radioimmunoassay and T in the skin was investigated by immunohistology. Seasonal variations of hair pigmentation are most pronounced in the forehead region followed by the cheek, scrotum, and nose area. Peak blood levels of T (15.4 ng/ml) were detected in November. The highest correlation between T levels and pigmentation of the forehead area (R = 93%; R2 = 0.87), was established when pigmentation values were shifted two months ahead. Immunohistologically detectable T was localized in hair follicles, hair sheets and apocrine glands but not in the sebaceous glands. It is hypothesized that pigmentation of head regions might serve as a visual cue indicating the sexual status of an individual.

Circadian and circannual rhythms of LH, FSH, testosterone (T), prolactin, cortisol, T3 and T4 in plasma of mature, male white-tailed deer.

Circadian and circannual rhythm of plasma LH, FSH, testosterone (T), prolactin, cortisol, triiodothyronine (T3) and thyroxine (T4) were investigated in two mature male white-tailed deer. No circadian rhythms were detected. Seasonal levels of LH and FSH were reached in September and October; troughs occur in May and June. Maximal T values were detected in November and December (the time of the rut); minimal levels occur between February and July. Prolactin peaked in May and June; minimal levels were detected between October and February. T3 exhibited two maxima; the first in the May-June period, the second in the September-October period. T4 showed no recognizable circannual rhythm. Cortisol levels were found to be much higher during cold months (December-April) than during the rest of the year. The least variable circadian levels were that of FSH and prolactin, with LH, T4, T3, cortisol and testosterone following in descending order. Cannulation stress might have some effect on the levels of testosterone, LH and cortisol. Correlation between LH and testosterone levels were detected mainly during sexually active periods.

The effect of neurogenic stimulation on the development and growth of bony tissues.

In order to elucidate the mechanisms of neurogenic control of bone development and growth, the effects of traumatic and electric stimulation on the development, size, and shape of antler bone tissue were investigated. Unilateral growth of antler in a female deer was initiated after traumatic stimulation of the frontal bone. Electrical stimulation of antler nerves or antler periosteum resulted in an increase in more than 70% in antler length and over 40% in weight. Stimulation of antler nerves also resulted in abnormal shape of antlers. The role of periosteal nerves and the participation of the central nervous system in the responses to stimulation is discussed.

Thyroxine levels in male and female white-tailed deer (Odocoileus virginianus).

Four major findings are described: (1) The episodic secretion of thyroxine in mature male white-tailed deer is most pronounced in the warmer months (June and September) and least demonstrated during the coldest months (November and January); (2) no clear annual rhythm of thyroxine was demonstrated in juvenile or mature male or mature barren female white-tailed deer. The monthly mean levels in mature males and females oscillate between 11 and 14 microgram/100 ml throughout the year; (3) the seasonal levels of thyroxine in mature males are almost identical with the thyroxine levels of adult barren females; (4) the seasonal thyroxine levels of juvenile males are constantly higher than levels found in mature males. However, when these deer reach the age of 3 years, their thyroxine levels decrease to those of the adult. The collected data could serve as a tool of evaluation of population structure for wildlife management purposes.

The role of sex hormones in the growth of antler bone tissue. I: Endocrine and metabolic effects of antiandrogen therapy.

Cyproterone acetate (CA), an antiandrogenic compound, was used in order to investigate the role of testosterone in bone growth processes. The formation of Haversian systems in the growing antlers of white-tailed deer (Odocoileus virginianus) were substantially affected by only 3.5 mg of CA kg/wk. The mineralization processes of the bone matrix were almost completely blocked and the antlers persisted in growing throughout the whole year. Plasma levels of thyroxine, alkaline phosphatase and GH were higher while cortisol and testosterone levels were lower than in controls. No differences were registered in plasma levels of Ca, P or urea nitrogen. Despite hypertrophy of interstitial tissue, spermatogenesis was almost completely blocked. The sexual behaviour and the body appearance of experimental animals was typical for castrates.

Growth hormone and cortisol levels in the annual cycle of white-tailed deer (Odocoileus virginianus).

The annual cycles of growth hormone and cortisol levels in white-tailed deer were followed. No significant difference was found in the average cortisol levels in a large group of animals during the year. In contrast to cortisol, growth hormone (GH) investigated by heterologous bovine GH radioimmunoassay, seems to have a distinct annual rhythm. High levels of GH in plasma were found between casting and the first week of antler growth with the peak of 23.1 ng/ml (estimated in bovine GH equivalents) in the middle of April. From the middle of June until the middle of November a plateau averaging 3 ng/ml was found. The relationships between very rapid growth of a bone tissue and the influence of GH and sex hormones are discussed.