Testosterone production by the fetal testes of silver foxes selected for their domesticated behavior]

Testosterone content was determined by radioimmune assay in the testes of silver foxes between the 31st and 50th days of gestation. Small quantities of testosterone were found in the testes already at the 31st day of prenatal life, gradually increasing up to a maximum value at the 50th day. No significant difference in testosterone content was found between domesticated and undomesticated silver foxes during prenatal life. It is suggested that selection for domesticated behaviour affects rather central control of endocrine functions than steroid biosynthesis in the testes.     

Change in testosterone content in the testes and peripheral blood in male rats during postnatal development]

Changes in testosterone content have been studied in the testes and peripheral blood in male rats from the 1st till the 42nd day after birth. The correlation was established between the level of luteinizing hormones in the blood and that of testosterone in the testes during the first 5 days after birth.     

Intracranial allometry and craniologic changes during domestication of silver foxes]

Skull proportions and pattern of intracranial allometry in farm foxes of bred domesticated populations are compared. Changes in skull measurements and bivariate allometry are observed in domesticated males, which in this respect become closer to domesticated females. The changes in the allometry pattern in the domesticated population points to deep modifications of regulatory ontogenetic processes which underlie the allometric growth. However, morphological changes in domesticated foxes cannot be only accounted for by allometry.     

Role of corticosteroids in the ontogenetic development of behavior in silver foxes

In domesticated at the age from 30-th to 60-th days foxes an intensification of orienting-investigating behaviour takes place in unknown situation. Cortisol level is not changed. In foxes, selected for aggressive behaviour towards man, at 30 days age the orienting-investigating behaviour is also observed, and hormone concentration does not differ from that in domesticated fox-cubs. In aggressive cubs of 45 days a defensive behaviour develops and cortisol content in blood significantly increases. Participation is discussed of adrenal cortex hormones in manifestation of defensive reactions and mechanisms of restriction of sensitive period of socialization.     

Trade-off between floor level and floor material in farmed silver foxes

Farmed silver foxes (Vulpes vulpes) were allowed to balance their known preference for an elevated floor against their presumed preference for a sand floor. In Experiment 1, foxes had to choose between two identical cages, connected with an opening. One cage had a wire floor and the other had a sand floor, but the cages either were on the same (low or elevated) or on different levels (one cage 40 cm higher than the other). In Experiment 2, the cage pairs were connected with a 1.2 m long wire-mesh tunnel, one cage was always on a higher level (50 cm) than the other. In Experiment 1, foxes always preferred the sand floor during their active time. They also preferred the sand floor for resting, if it was on the same level as wire floor, but did not show any genuine preference if the floors were on different levels. In Experiment 2, foxes never preferred the lower floor. They preferred the elevated sand floor for activity and the elevated wire floor for lying. When two floors were identical they preferred the elevated one. Their rest consisted of 11-22 bouts, a major part of these being spent in the preferred cage. They also preferred a previous lying site to a new one, often exclusively and independently of floor material. In Experiment 1 foxes preferred the sand floor whereas in Experiment 2 they preferred the elevated floor indicating that the ability of a trade-off situation to rank resources depends on the method it is inflicted.     

Lymphocyte subpopulation state of the human lung during prenatal development]

Distribution of surface lymphocyte markers was assessed in foetus lung by cytofluorimetry using monoclonal antibodies produced by "Ortho Diagnostic systems" and "Becton Dickinson". Seven lymphocyte subpopulations were detected in developing lungs even at the pseudoglandular stage (8-15 weeks). There was a significant increase in these lymphocyte subpopulations in canalicular stage. Quantity of T3+ cells increased 8-fold and B-cells 10-fold. There was a tendency to increased number of cortical thymocytes (T6+), and to decreased ratio T6+/T3+ lymphocytes. The ratio of immunoregulatory lymphocyte subpopulations (T4+/T8+) resembled that of these subpopulations in adult human lung rather than in cord blood. In canalicular stage the share of lung lymphoid cells in S-phase was decreased.     

Phenogenetic analysis of various changes in the color of fur in silver foxes originated during domestication

Quantitative and qualitative analysis of pigmentation in "singne"-type fur color mutation arising in silver foxes during domestication, was made. It was shown that the decrease in quantity of eumelanine in hair and uneven distribution of pigment granules lengthwise the hair were the reason for formation of "singnes".     

Seasonal changes in the testes of the silver fox

In 14 mature male silver foxes in spring and autumn by means of counting dots and transsections, relative and absolute summational volumes and areas of the seminiferous tubule surfaces, interstitial glandulocytes (Leydig's cells) and stroma have been calculated. Average diameter and total length of the tubules have been determined. Increased mass of the testes in spring is the result of a proportional enlargement of the total volume of the seminiferous tubules and stroma, while the total volume of the endocrinic part in the organ changes insignificantly. The increase of the total volume of the seminiferous tubules occurs at the expense of the increasing diameter, though their total length remains the same.     

The gradual vocal responses to human-provoked discomfort in farmed silver foxes

Vocal indicators of welfare have proven their use for many farmed and zoo animals and may be applied to farmed silver foxes as these animals display high vocal activity toward humans. Farmed silver foxes were selected mainly for fur, size, and litter sizes, but not for attitudes to people, so they are fearful of humans and have short-term welfare problems in their proximity. With a human approach test, we designed here the steady increase and decrease of fox–human distance and registered vocal responses of 25 farmed silver foxes. We analyzed the features of vocalizations produced by the foxes at different fox–human distances, assuming that changes in vocal responses reflect the degrees of human-related discomfort. For revealing the discomfort-related vocal traits in farmed silver foxes, we proposed and tested the algorithm of “joint calls,” equally applicable for analysis of all calls independently on their structure, either tonal or noisy. We discuss that the increase in proportion of time spent vocalizing and the shift of call energy toward higher frequencies may be integral vocal characteristics of short-term welfare problems in farmed silver foxes and probably in other captive mammals.     

Brain tyrosine hydroxylase activity in behavior-selected silver foxes

In two groups of silver foxes--i.e. selected by the domestic type of behaviour and aggressive ones--studies have been made on the activity of the key enzyme in biosynthesis of catecholamines--i.e. tyrosine hydroxylase from the brain. Domesticated animals exhibited higher enzymic activity in the locus coeruleus, hypothalamus and cortex. Animals from both groups did not differ with respect to the level of tyrosine hydroxylase activity in the corpus striatum. The enzymic reactions of homogenates from locus coeruleus region of the brain in both groups of animals, as well as homogenates from the corpus striatum of the brain of aggressive animals exhibited low and approximately equal values of Michaelis constant for tyrosine. The value of KM was 3 times higher in the hypothalamus in both groups of foxes and in the corpus striatum of tame animals. Presumably, selection of silver foxes for the domestic type of behaviour resulted in the increase of biosynthesis of catecholamines in the brain due to the increase in the number of enzyme molecules. The increase in the activity of tyrosine hydroxylase in noradrenaline system of the brain may be associated with changes in the behavioural pattern of animals resulting from selection.     

Morphology of hair pigmentation in wild red foxes,silver foxes,and their hybrids

The effects of dominant allele Ar of locus Agouti on the morphology of hair pigmentation were described in foxes. The Ar allele was shown to determine the type of melanin and its content in hair with no effect on the morphology of pigment granules and their distribution throughout a hair. Using the method of electron spin resonance (ESR), the types of melanin (eumelanin and pheomelanin) and their content in the hair of red (ArArEE) and silver (aaEE) foxes and their hybrids (AraEE) were determined. In silver foxes, only one type of melanin (eumelanin) was found. In red foxes and their hybrids (which are phenotypically similar but darker than red foxes), both types of melanin (eu- and pheomelanin) were found. The highest melanin content was detected in the coat of silver foxes. In the hybrids, the total melanin content was lower than in silver foxes, but significantly higher than in red foxes. In red foxes, the contribution of pheomelanin to the total hair melanin content was twice as large as in the hybrids.     

Adenosine accumulation causes metabolic disorders in testes and associates with lower testosterone level in obese mice

Overweight and obese men face numerous health problems, including type 2 diabetes, subfertility, and even infertility. However, few studies have focused on the effects of nutritional status and obesity‐related regulatory signals on fertility deficiency. Our previous observations have shown that the elevation of plasma 5'‐adenosine monophosphate (5'‐AMP) and the accumulation of adenosine in liver and muscle of obese diabetic db/db mice are related to insulin resistance. Here, we found that adenosine accumulation in testis is a common marker of both genetic obesity and high‐fat‐diet induced obese mice. An messenger RNA sequencing analysis indicated that 78 upregulated genes and 155 downregulated genes in the testis of 5'‐AMP‐treated mice overlapped with the same genes in the testis of ob/ob mice, and these genes belonged to the clusters of steroid metabolic process and regulation of hormone levels, respectively. Serum testosterone was reduced in ob/ob and 5'‐AMP‐treated mice. Metabolomic analysis based on ¹H nuclear magnetic resonance showed that the testicular metabolic profiles of ob/ob mice were similar to those of 5'‐AMP treated mice. Exogenous 5'‐AMP inhibited the phosphorylation of AKT and mammalian target of rapamycin signal transduction and reduced the proliferating cell nuclear antigen expressions in testes. Our results suggest that the accumulation of adenosine causes metabolic disorders in testes and associates lower testosterone level in obese mice.     

Effect of prenatal stress on the pituitary-adrenal axis in blue foxes

Handling is a source of stress for farm bred blue foxes. The influence of handling during the late gestation period on the pituitary--adrenal axis was studied in 10-day old male and female blue foxes. Cortisol and progesterone were measured by radioimmunoassay in the plasma, adrenal homogenates, and in vitro incubates from animals of both sexes. Adrenals were incubated in vitro in the absence or presence of ACTH. In addition, the adrenal weight and plasma concentration of ACTH were assessed. In cubs of both sexes, the adrenal weight was decreased after prenatal stress. The plasma concentration of progesterone and the adrenal cortisol in vitro production were elevated in the prenatally stressed female cubs, as compared to the control, along with the adrenal progesterone in vitro production in prenatally stressed male cubs. The adrenal cortisol and progesterone content and plasma ACTH and cortisol concentrations were not affected by prenatal stress. In conclusion, the results of this study suggest that the prenatal stress induced by handling pregnant vixens can affect the pituitary--adrenal axis in neonatal offspring, this effect being more pronounced in female cubs.     

The effects of malnutrition on the prenatal development of rat brain]

Female rats were submitted to caloric and protein restriction 8 days before fecondation and during pregnancy. A reduction of the number of brain cells in the fetuses was evident only after the 20th day of pregnancy. This reduction appeared to be limited to glial cells, and not to affect neurons contrarily to what had previously been stated by some authors.     

Testosterone production in fetal testes of the silver fox

Testosterone content was studied in fetal serum and testes of silver foxes during different periods of prenatal life. The first sign of testosterone synthesis in the testes could be detected starting from the 31st day of gestation by radioimmunoassay. Subsequently its content sharply increased and showed maximum value on the 50th day. Detectable serum testosterone level in male silver fox fetus was noted from the 40th day, its serum concentration increased in prenatal life, but only insignificantly. Testicular production of testosterone was stimulated by hCG at the stages studied from Day 40 on. It is supposed that silver fox testes were able to respond to gonadotrophin not earlier than by Day 40 of prenatal life, but the establishment of pituitary-testicular interrelationship was clearly demonstrated at the end of embryogenesis (Day 50).