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.     

Domestication in the silver fox (Vulpes fulvus Desm): Changes in physiological boundaries of the sensitive period of primary socialization

The physiological boundaries of the sensitive period of primary socialization were studied in the silver fox (Vulpes fulvus Desm). A total of 273 farm-bred foxes from 59 litters were observed from 1976 to 1978; pups were produced by vixens from two populations, one selected for domesticated behaviour and the other unselected. Results indicate that the age when the eyes are fully open, when the response to sound first appears and when exploratory behaviour is first shown in strange surroundings is 3 weeks, on average. The age when the socialization period starts appears to be 20–25 days old. The optimum period of the formation of primary social bonds appears to be 30–35 days, when maximum exploration in a novel situation is shown. The 40–45 days period appears to be the upper boundary of primary socialization in unselected foxes because pups show fear in response to novel stimuli, which prevents exploration. In pups from the population of domesticated foxes, the sensitive period of socialization is prolonged to over 60–65 days old.     

Observation of marking-like behavior, marking behavior, and growth of the scent gland in young Mongolian gerbils (Meriones unguiculatus) of an inbred strain.

A marking-like behavior (defined by authors), a marking behavior, and growth of the scent glands were observed in young Mongolian gerbils of an inbred strain. In males and females, a marking-like behavior, in which animals rub their abdominal scent glands on the floor, began to be seen at the age of 19 days and could be seen in almost all the gerbils at 22 days of age during the suckling period. The frequency of this behavior was highest at 60 days of age (males: 17.9/10 min, females: 15.4/10 min) and there was no sex difference. Marking behavior, in which animals rub their abdominal scent glands on small protruding objects, began to be seen at the age of 40 days in males and 50 days in females. The frequency of this behavior tended to increase until 90 days of age in males (13.7/10 min), but the levels were low (2.5-5.0/10 min) in females. The values in the male group therefore tended to be higher than that in the female group. Macroscopic scent gland pads were clearly observed at the age of 30 days in males, but not until 45 days of age in females. At the age of 45-90 days, the length of the scent gland pad in males and females was 2.1-2.8 and 1.6-1.7 cm, respectively and the width was 0.3-0.5 in males and 0.2-0.3 cm in females. During this period, the length and depth of the pads in males were significantly greater than those in females (p < 0.05). Histological examination of the structure of the scent glands after the age of 45 days showed that the development of clusters of acinar cells in females occurred much later than that in males, but the basic structure of these glands was similar in both sexes. These results suggest that the marking-like behavior was manifested although during the period when the scent glands had not yet developed, whereas true marking behavior first occurred when the glands were moderately well developed.     

Changes in Leydig cell function during sexual maturation in the mouse

Changes in androgen production by isolated Leydig cells were evaluated from 20 through 60 days of age in the mouse. Leydig cells were obtained by mechanical dissociation of testes, purified by centrifugation in metrizamide gradients, and incubated with increasing concentrations of human chorionic gonadotropin (hCG). Testosterone and 5 alpha-androstane-3 alpha, 17 beta-diol (androstanediol) were measured by radioimmunoassay in samples of cells plus medium. Sensitivity of mouse Leydig cells, evaluated as the concentration of hCG that elicited half-maximum androgen responses, was essentially the same at all ages. Maximum testosterone production increased by about 20-fold from 20 to 45 days of age but was no greater at 60 days than at 45 days. Maximum androstanediol production increased by about 3- to 4-fold from 20 to 25 days and declined after 30 days of age. Androstanediol predominated over testosterone by about 2-fold at 20 days; this relationship was reversed by 30 days, and at later ages testosterone greatly predominated over androstanediol (by at least 4- and 6-fold at 45 and 60 days of age, respectively). Maximum total androgen production, estimated from the sum of the values for testosterone and androstanediol, increased by about 7-fold from 20 to 30 days of age and remained essentially constant thereafter. These results are compared with those from previous studies of the rat.     

Modification of modulatory sites of NMDA receptor in the fetal guinea pig brain during development

Ontogeny of the NMDA receptor and modification of its modulatory sites in the developing fetus brain was determined. MK-801 binding characteristics in the presence of glycine, glutamate, Mg²⁺ and spermine were determined and used as an index of NMDA receptor modification. Experiments were performed on guinea pig fetuses at 30, 45, 50, 55, and 60 days (term=63 days) of gestation. The Bmax value increased approximately three-fold from 30 days to 60 days of gestation. The Kd value decreased during the 45–50 day period and then increased toward the end of gestation. The Bmax value reached its maximum level by 55 days of gestation, indicating the presence of a maximum number of NMDA receptors by this age, while the apparent affinity of the receptor showed its peak at 45–50 days of gestation, indicating a potential role for NMDA receptor during the proliferation period of brain development in the guinea pig fetus. The activation of NMDA receptor in the presence of glutamate (10 M) and glycine (10 M), as measured by MK-801 binding, was absent at 30 days gestation, with the earliest observation occurring at 35 days gestation. The spermine dependent activation decreased with gestational age. Mg²⁺ ions increased MK-801 binding in the range of 1–20 M concentration. Sensitivity to Mg²⁺ dependent activation increased with the gestational age (from 10 M Mg²⁺ at 45 days to 2.5 M at 55 and 60 days). These results indicate that an increase in number and activation of the NMDA receptor by glutamate and glycine during brain development might increase the susceptibility of the fetal brain to NMDA receptor mediated excitotoxicity as gestation approaches term.     

草原兔尾鼠的生长发育

在人工饲养条件下，对初生至１００日龄的草原兔尾鼠进行逐日观察，并测量其个体的体重、体长、尾长、、后足长、记录其生长发育特征。幼鼠睁眼期为１０－１２日龄；自由采食期为１５－１８日龄；断奶期为１９－２０日龄；性成熟期为４５－６０日龄。生长发育大致分为四个阶段；乳鼠阶段，初生至１５日龄，体长７０毫米以下；幼鼠阶段，１６－３０日龄，体长７０－８４毫米；亚成体阶段，３０－６０龄，体长８５－９２毫米；成体阶段     

Effect of Dietary Vanadium on the Ileac T Cells and Contents of Cytokines in Broilers

The purpose of this 42-day study was to examine the effect of dietary vanadium on the ileac T cells and contents of cytokines including interleukin-2 (IL-2), interleukin-6 (IL-6), and interferon-gamma (IFN-γ) in broilers by flow cytometry and enzyme-linked immunosorbent assay. A total of 420 one-day-old avian broilers were divided into six groups (seven replicates in each group and ten broilers in each replicate) and fed on control diet or the same diet supplemented with 5, 15, 30, 45, and 60 mg/kg vanadium in the form of ammonium metavanadate. The results showed that the percentages of CD3(+), CD3(+)CD4(+), and CD3(+)CD8(+) T cells in both ileac lamina propria lymphocytes (LPLs) and intraepithelial lymphocytes (IELs) were significantly lower (P < 0.05 or P < 0.01) in the 45- and 60-mg/kg groups than in the control group from 14 to 42 days of age. The CD4(+)/CD8(+) ratio was increased in ileac LPLs in the 60-mg/kg group at 28 days of age, and in ileac IELs in the 60-mg/kg group at 28 days of age and in the 45-mg/kg group at 42 days of age. Meanwhile, the ileac IL-2, IL-6 contents were decreased (P < 0.05 or P < 0.01) in the 60-mg/kg group from 14 to 42 days of age and in the 45-mg/kg group from 28 to 42 days of age in comparison with those of the control group. It was concluded that dietary vanadium in excess of 30 mg/kg reduced the ileac T cell population and percentages of T cell subsets, and IL-2, IL-6, and IFN-γ contents, implying that the immune function of local intestinal mucosa in broilers could be affected by the dietary vanadium.     

Increase in testicular androgen receptor during sexual maturation in the rat

Androgen receptor concentration was measured by exchange with 3H-dimethylnortestosterone (DMNT) in cytosol and nuclear extracts from testes of rats 15-90 days of age. Dissociation kinetics verified the necessity of an extended incubation (86 h) for maximum exchange at 4 degrees C. Nuclear androgen receptor concentration per mg DNA decreased between 15 and 25 days of age, from 375 to 146 fmol per mg DNA, then increased to 584 fmol per mg DNA at 90 days. Testicular receptor content also increased between 25 and 90 days of age. Cytosol receptor concentration patterns were similar to nuclear androgen receptor patterns. The affinity of the receptor for the ligand did not change with age (mean Kd = 0.88 nM). No significant difference in androgen receptor concentration per cell was detected between cultured peritubular cells from animals 25 and 45 days of age. Androgen receptor concentrations in freshly isolated peritubular cells could not be determined. There also was no difference in receptor concentration per cell in a Leydig cell-enriched fraction from animals between 25 and 45 days of age. Although androgen receptor concentrations per Sertoli cell increased between 15 and 35 days of age, the increase in Leydig cell number over the same period probably accounted for approximately 75% of the increase in receptor per testis between 25 and 45 days of age.     

Development of pancreatic hydrolases in inbred mice

Pancreatic content of lipase, amylase, trypsinogen, chymotrypsinogen and protein was studied in suckling and weaned mice at different ages. Protein content in pancreatic tissue was low at 15 days when compared with 30, 45 and 60 days of age. Specific activities of lipase and chymotrypsinogen were higher at 15 days of age, but chymotrypsinogen was not different at the studied ages post weaning. Amylase exhibited the highest value at 15 days and a marked depression at 30 days, and trypsinogen specific activity was not different between the studied groups. The present study demonstrates an age dependent enzyme pattern in mouse pancreas and reflects an active biosynthetic mechanism in suckling mice.     

Exaltation phenomenon during the teaching of an instrumental defense reflex to animals of various ages

Dogs of 1.5 and 7 months and rats of 15, 20, 30, 45, 60, 80, and 100 days of age were given acquisition training in an escape task. The previous observations suggested that difficulties in defensive conditioning typically found in young animals were connected with their generalized perception of Igarning conditions. To facilitate the discrimination of the environmental factors a conditioned signal was not applied and the home cage was used as a "safe" compartment. The intertrial intervals were increased up to 2 hours for dogs and 24 hours for rats. Under such conditions an acquisition of escape reaction was most rapid in animals of early age. The period of effective learning (exaltation) in rats began from 20 and lasted to 60 days of age, the maximal efficiency being observed at 20 days. Pups of 1.5 months had learned more quickly than those of 7 months of age. Variations of learning efficiency in ontogeny of rats were positively correlated with changes of correct escape reaction search activity. Phenomenon of learning exaltation in ontogeny was supposed to be connected with the high level of activity of perception and association cerebral mechanisms being the result of immaturity of inhibitory structures.     

Functional Validation of the Gallus Chick's Response to the Maternal Food Call1

The term functional validation has been used to describe situations in which fully developed behaviours require appropriate environmental support during an early sensitive period if the initial level of responsiveness is to be maintained. The primary objective of the present study was to determine if an age-related decline in responsiveness to the maternal feeding call occurred in Gallus chicks and, if so, whether or not brief exposure to the call during an early responsive period would maintain responsiveness beyond that period. A decline in responsiveness to the call was observed beyond three days of age in dark-reared chicks. Exposure to the call for 7.5 min before three days of age was adequate to maintain responsiveness at five days of age.     

Changes in the renal corpuscles during early postnatal ontogeny of the rat (stereologic analysis)

Kidneys of 60 white rats at the age of 1-45 days of postnatal life have been investigated. Increase in size of the renal corpuscles during the developmental process is accompanied with certain changes in the form and variability of volumes in the structures studied. During early postnatal period, against the background of linear increase in the size of the renal corpuscles, the parameters of variability in volumes, form and in the total number of the renal corpuscles in the organ change non-linear. Stabilization moment of the total number (11-14 days) on the 8th-10th day outgoes that for the parameters of the form and variability of the renal corpuscle volumes.     

Effect of temperature and the role of testicular descent on post-natal testicular androgen production in the mouse.

Testes from mice aged 3, 15, 25, 30 or 60 days were incubated under basal conditions or in the presence of hCG. One testis from each animal was incubated at 37 degrees C while the contralateral testis was incubated at 32 or 34 degrees C. During development total androgen production in response to hCG (at 32 degrees C) showed a marked increase between 15 and 30 days. The major androgens secreted at this time were testosterone and 5 alpha-androstane-3 alpha,17 beta-diol. There was little change in total androgen production between 30 and 60 days but by 60 days testosterone was the dominant androgen. Both basal and hCG-stimulated androgen production were temperature sensitive. These effects were most pronounced at 30 and 60 days with androgen production significantly inhibited at 37 degrees C. To examine the role of testicular descent in regulating steroidogenesis animals were rendered unilaterally cryptorchid at 19 days of age. At 25 days, when descent is normally completed in the mouse, there was no significant difference in steroidogenesis between scrotal and abdominal testes. By 30 days, however, the steroidogenic potential of the abdominal testis was significantly lower than that of the scrotal testis. These results show that testicular steroidogenesis is sensitive to temperature changes around the time of testicular descent, although descent itself is not required to achieve an adult level of steroidogenesis. The results also show, however, that testicular descent is required to maintain the adult level of steroidogenesis.     

Developmental staging and thalidomide teratogenicity in the green monkey (Cercopithecus aethiops).

The developmental stages of 11 Cercopithecus aethiops embryos, 24 to 45 days post-mating, are described. The onset of organogenesis in this species is approximately five to seven days later than that reported for macaques and baboons. This temporal difference in the embryonic period is an important factor in the analysis of the subsequent teratogenic study. Oral administration of thalidomide in single or multiple (3-day) treatment periods to pregnant green monkeys between days 28 and 33 resulted in defects of the limbs which resemble those observed in macaques and baboons. However, the sensitive period occurs approximately four days later than that reported for another nonhuman primates. These results indicate that the sensitive period of the limbs to thalidomide coincides with their earliest development.     

Testicular binding of 125I-HCG in developing estrogenized and androgenized rats.

The present work describes changes seen in the binding of 125I-HCG by testis homogenates of rats injected at the age of three days with 400 microgram estradiol-17beta-dipropionate, or 250 microgram testosterone propionate. Estrogenized and androgenized male rats showed a marked decrease of gonadotropin binding in testis at the 30th, 45th and 60th postnatal day. These results show that delayed sexual maturation of male rats treated with estrogen and androgen in the neonatal period is also related to pubertal decrease of testicular gonadotropin receptors.     

Effect of Dietary Vanadium on Cecal Tonsil T Cell Subsets and IL-2 Contents in Broilers

The purpose of this 42-day study was to investigate the effects of dietary excess vanadium on intestinal immune function by histopathological observation of cecal tonsil and changes of the cecal tonsil T cell subsets by method of flow cytometry. Four hundred twenty 1-day-old avian broilers were divided into six groups and fed on a corn-soybean basal diet as control diet or the same diet amended to contain 5, 15, 30, 45, and 60 mg/kg vanadium supplied as ammonium metavanadate. In comparison with those of control group, lymphocytes in the lymphatic nodule of cecal tonsil were apparently decreased in 45 and 60 mg/kg groups. The percentage of CD(3)(+) T cells was decreased (p?相似文献   

Performance of Holstein calves receiving equal quantities of milk at fixed or variable amounts per day during milk-feeding period

Two experiments were conducted to determine the effects of feeding equal quantities of milk during the pre-weaning period through different milk-feeding regimes on calf growth, starter intake and selected blood metabolites. In experiment 1, 44 female Holstein calves (3 days of age and 39.2±4.3 kg of BW) were distributed randomly to one of two milk-feeding programs (1 calf per pen; 22 pens per treatment group): (1) consistent (CONS; 6 l/day of milk from days 3 to 60 and 3 l/day from days 61 to 65 of age) or (2) step-up/step-down (SUSD; 5 l/day of milk from days 3 to 15, 8 l/day from days 16 to 40, 6 l/day from days 41 to 50, 3 l/day from days 51 to 60 and then 2 l/day from days 61 to 65 of age). No difference between treatments was observed in starter consumption, feed efficiency, hip width and heart girth. However, pre-weaning average daily gain (ADG) tended to be greater in CONS than in SUSD calves (0.78 v. 0.70 kg/day; P=0.07). Blood β-hydroxybutyrate at day 45 (pre-weaning) was lower in SUSD than in CONS calves (0.14 v. 0.21±0.013 mmol/l). In experiment 2, 26 male Holstein calves (3 days of age and 39.4±4.1 kg of BW) were assigned at random to one of two milk-feeding protocols (1 calf per pen; 13 pens per treatment group): (1) consistent (CONS; (7 l/day of milk from days 3 to 40 and 2 l/day from days 41 to 45 of age) or (2) step-down (STD; 8 l/day of milk from days 3 to 30, 4 l/day from days 31 to 40 and 2 l/day from days 41 to 45 of age). The milk-feeding program had no effect on the performance measurements, with the exception that ADG (days 15 to 30), starter intake (days 30 to 45) and heart girth (day 45) were greater in STD than in CONS calves. In conclusion, it appears that if the total amount of milk intake is held constant over the course of milk-feeding period, the method of milk feeding would have negligible effects on calf performance.     

Ontogeny of T Cells in the Pig Fetus

Mononuclear cells isolated from thymus, spleen and cord blood of pig fetuses ranging in age from 48 to 112 days were examined for the presence of sheep red blood cell rosette-forming cells (SRBC-RFC). After an initial increase from 77 % (mean) at 48 days of gestation to 88 % at 60 days, the proportion of SRBC-RFC in thymus remained constant throughout the gestational period. In spleen and cord blood, the proportion of SRBC-RFC increased with age, from occasional rosette-forming cells at 48 days of gestation to 21 % and 30 %, respectively, at 112 days. The demonstrated development of SRBC-RFC in the thymus, spleen and cord blood is considered to reflect the ontogeny of T cells in these fetal pig tissues.     

Early Diagnosis of Extrahepatic Biliary Atresia in an Open-Access Medical System

Introduction

Biliary atresia (BA) is the most common cause of cholestatic jaundice in infancy. Early diagnosis and surgical management, ideally before 60 days of age, result in improved outcomes. We aimed to determine the age at diagnosis of BA in the Military Health System (MHS) and to compare the age at diagnosis by access to care models. We hypothesized that children with BA receiving primary care in military facilities have an earlier age at diagnosis due to decreased economic and access barriers.

Methods

Data for all Tricare enrollees born in fiscal years 2004–2008 with a diagnosis of BA were extracted from MHS databases. Non-parametric tests, Kaplan-Meier curves and log rank tests compared differences in age at diagnosis by type of primary care facility, gender, prematurity and presence of additional anomalies.

Results

64 subjects were identified within the five year period. Median age at diagnosis was 40 days [range 1–189], with 67% diagnosed by 60 days and 80% by 90 days. 45 (70%) received civilian primary care within the MHS. There was no difference in the median age at diagnosis between subjects in the MHS with civilian primary care vs. military primary care (37 days [1–188] vs. 46 days [1–189]; p = 0.58).

Conclusion

In the MHS, two-thirds of infants with biliary atresia are diagnosed prior to 60 days of life. Gender, prematurity or presence of additional anomalies do not affect the timing of diagnosis. Civilian and military primary care models within the MHS make timely diagnoses of biliary atresia at equivalent rates.     

Intraovarian adrenergic nerves in the guinea-pig: Development from fetal life to sexual maturity

Summary The development of the intraovarian adrenergic nervous system was investigated in the guinea-pig by use of chemical determination of catecholamines with high performance liquid chromatography (HPLC) and with the formaldehyde-induced fluorescence method for visualization of adrenergic nerves (Falck-Hillarp technique). Ovaries from fetuses (39–40, 45–50, 55–57, 60–63 days of gestation) and young animals (1, 2, 3, 7, 14, 30, 40–45 days of age) were included in the study. The noradrenaline concentration was low in the ovaries from the youngest fetuses but increased with age, reaching a maximum level at 2 days post partum. A marked decrease in noradrenaline concentration from the second to the third day of life was found as a consequence of the rapid increase in the ovarian weight during this time. A similar decrease in ovarian noradrenaline concentration after a period of rapid ovarian growth was noted at 30 days of age. Measurable amounts of adrenaline were found in the ovary only in the fetal stages; the highest concentration (0.73 g) was detected at 55–57 days of gestation.