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Biomedical subjects

N Snapir

Publications and source records attributed to N Snapir.

At least 37 records · Page 2Linked to original sources
PubMed1991

Sexual differentiation of copulatory behaviour in the male chick requires gonadal steroids.

1. Embryonic injections of 0.3 mg/egg of tamoxifen (TAM), 0.2 mg/egg CI-628 (both antioestrogens), 0.5 mg/egg (ATD (aromatisation inhibitor), or antibodies to oestradiol (E), all suppressed male copulatory activity (MCA) in young male chicks. 2. Embryonic injections with either flutamide (F, androgen antagonist) or high dose of antibodies to testosterone (T) only slightly suppressed MCA. 3. TAM had no effect on embryonic plasma LH levels, 24 and 48 h after injection. 4. It seems that at the embryonic stage oestradiol is required for the normal differentiation of MCA.

Animals↗
PubMed1990

The response of broilers' adiposity to testosterone after embryonic exposure to androgen and tamoxifen.

1. The effects of early exposure of heavy breed (HB) chicks to an anti-oestrogen (tamoxifen--TAM) and to an androgen which cannot be aromatised (5 alpha-dihydrotestosterone--DHT) on subsequent adiposity and its response to testosterone were studied. 2. Embryonic TAM administration reduced adiposity in females but not in males at 8 weeks of age. Embryonic DHT produced similar responses but to a lesser extent. 3. Testosterone propionate (TP) administration during growth had no effect on adiposity in any of the treated groups but TP reduced adiposity in males which had been exposed to DHT at the embryonic stage.

Adipose Tissue↗
PubMed1990

The effect of tamoxifen on sexual puberty of turkey toms and Muscovy drakes.

The effects of Tamoxifen (TAM) on reproductive traits in young turkey toms and Muscovy drakes were studied. At 6 wk of age, five toms were injected every other day with 1 mg TAM/kg BW, while six others were treated with corn oil (controls). In the toms, using TAM advanced semen production by 4 wk (13.5 versus 17.5 wk of age) and increased the size of the snood and testes. Similarly, in the Muscovy drake, using TAM enhanced penis growth and advanced semen production by 5 wk.

Animals↗
PubMed1990

The effect of tamoxifen on semen fertilization capacity in White Leghorn male chicks.

Tamoxifen (TAM) is an antiestrogen that advances sexual puberty in cockerels, turkey toms, and Muscovy drakes. The effect of TAM on semen-fertilization capacity in White Leghorn (WL) male chicks was assayed in the present study. Sixty, 2-wk-old, male chicks were divided into two equal groups. The chicks from one group were injected im with 1 mg of TAM per kg of BW every other day; those from the second group were vehicle-treated (with corn oil) and served as controls. Each chick was paired with a virgin, WL laying hen. When semen was produced, the paired female was inseminated twice a week. The results revealed that TAM administration caused the early production of fertile semen, which resulted in the first normal descendants as early as 8 wk of age and brought about 100% of parenthood by the age of 88 days.

Animals↗
PubMed1990

The role of plasma thyroid hormones in the regulation of body weight of single comb White Leghorn and broiler embryos.

Studies were conducted to determine if sex differences in embryo weights existed in a light-weight breed of chickens (the Single Comb White Leghorn, SCWL) and in a heavy broiler strain of chickens. Plasma thyroid hormone concentration was measured to determine its relationship to embryo weight. Male SCWL embryos were heavier than females at 15 and 17 days of incubation, but not at 13 days. Male broiler embryos were heavier than females at 13 and 15 days of incubation, but not at 17 days. There was no sex difference in the levels of plasma triiodothyronine (T3) or of tetraiodothyronine (T4) of SCWL embryos at those respective ages. The plasma T4 in male broiler embryos was significantly lower than that in the females at 15 and 17 days of incubation, but not at 13 days. There was no relationship between plasma T3, and the weight of SCWL embryos. There were significant linear regressions of embryo weight on the plasma T4 levels for SCWL males at 13 and 15 days of incubation and for SCWL females at 13 and 17 days of incubation, respectively. A significant regression of embryo weight on plasma T4 was found in female broiler embryos at 13 days of age, but not in females at other ages or in males at any of the ages studied.

Age Factors↗
PubMed1989

Embryonic sex steroids affect mating behavior and plasma LH in adult chickens.

Chicken embryos of both sexes were treated with either antiestrogen (tamoxifen = T), antiandrogen (flutamide = F), aromatization inhibitor (ATD = A), estradiol (E), or oil (control = C). Before puberty, some males of each group were castrated. At puberty, birds were tested under the following regimes: castrated males injected daily with testosterone propionate (CAS + TP) or estradiol benzoate (CAS + EB), intact males (M-INT), intact females (F-INT), and females injected daily with TP (F-TP). In the M-INT and CAS + TP males, E treatment suppressed masculine mating behavior. The embryonic treatments with T, F, and A demasculinized only the frequency of copulations. None of the antihormone treatments caused any masculinization of the sexual activity in the F-TP birds. Untreated males had higher plasma LH than females. The embryonic treatment with E reduced (feminized) the LH levels in CAS + EB birds. This effect was less pronounced in M-INT birds. The results suggest that in chickens, estradiol plays a role in the masculinization of copulatory behavior potential in the developing male embryo. High embryonic estradiol reduces the potential for displaying male sexual behavior at puberty. Feminization of LH secretion requires a high level of estradiol in both embryonic and adult life.

Androstatrienes↗
PubMed1989

The effect of tamoxifen on the reproductive traits in White Leghorn cockerels.

Fifty White Leghorn male chicks were divided into five equal groups of ten chicks each. Beginning at two weeks of age they were injected on each alternate day as follows: corn oil as a vehicle control or 0.5, 1.0, 5.0, or 10.0 mg tamoxifen/kg/b.wt. The whole experimental period lasted until twelve weeks of age. The two lowest doses of tamoxifen (TAM) enhanced comb growth, while the highest dose suppressed it. The two lowest doses of TAM also caused an earlier increase in sexual activity of the chicks, and precocious production of semen. At nine weeks of age the 0.5 and 1.0 mg doses of TAM increased plasma testosterone to a level three times higher than in the controls. This effect was not observed with the highest dose of TAM. At 12 weeks of age the chicks treated with 1 mg TAM had larger testes than the controls and produced three times more sperm per ejaculation. At this stage chicks treated with the highest dose of tamoxifen produced less sperm than the control and had smaller testes and adenohypophyses.

Aging↗
PubMed1989

Effect of embryonic and neonatal administration of tamoxifen on adiposity in the broiler chicken.

1. The effect of early exposure of heavy breed (HB) chicks to an anti-oestrogen (tamoxifen--TAM) on later adiposity was studied. 2. TAM administration at the embryonic stage, but not at the day of hatching, reduced adiposity in females but not in males, at 8 to 9 weeks of age. This reduction in adiposity in females minimised or even alleviated the excess of fat in females compared to males.

Adipose Tissue↗
PubMed1989

Recovery of ova and their re-insertion into the hen's oviduct through a fistula.

1. The first loop of the domestic hen's magnum was fistulated. A cannula mounted with a collecting tube served to trap the passing ova about 2.5 h following ovulation. 2. Nine out of 10 fistulated hens resumed ovulation about 2 to 5 weeks following surgery. A total of 63 magnal ova were collected. 3. Five of the magnal ova were successfully returned to the oviduct through the fistula and resulted in 5 normal soft-shelled eggs. The success of ova reimplantation was affected by prolapse of the posterior part of the oviduct and the timing of ova return.

Animals↗
PubMed1989

Role of the basomedial hypothalamus in regulation of adiposity, food intake, and reproductive traits in the domestic fowl.

Bilateral basomedial hypothalamic (BMH) electrolytic lesions in White Leghorn cockerels produced six main physiological categories characterized by typical sets of symptoms: 1) functional castration (FC); hyperphagia, obesity, occasional diabetes insipidus, involuted adenohypophysis, dwarfism, atrophied comb and testes, reduced hematocrit, reduced plasma testosterone and thyroid activity, involuted thymus and adrenal cortex and elevated liver fat and plasma triglycerides and free fatty acids. The FC birds demonstrated defective immune response for the first 12 to 16 wk post-surgery. 2) functional castration with large comb (FCLC); hyperphagia, obesity, transient diabetes insipidus, slight diminution of adenohypophy-seal weight with marked reduction in basophilic cell population, fully atrophied testes but only slight reduction in comb size and hematocrit, plasma testosterone levels between those found in the first category and the control. 3) obese with normal testes (ONT); hyperphagia, obesity, high level of plasma lipids, normal histological organization of the adenohypophysis, normal testes, semen production and comb size. The next three categories exhibited physiological syndromes identical to the former three categories except for food intake, which operationally could be defined as normal. A marked difference among the BMH-lesioned birds was found in sexual behavior when the FC birds completely lost their libido. None of the replacement therapy regimens caused complete rehabilitation from adiposity or restoration of reproductive traits. Lipoprotein lipase activity increased at an early stage postlesioning and preceeded the development of hyperphagia. Placement of BMH lesions in newly hatched chicks resulted in marked dwarfism and obesity without hyperphagia. The BMH-lesioned heavy breed White Rock cockerels exhibited a lesser degree of adiposity than the light White Leghorn birds. Removal of the olfactory bulbs and destruction of the septal area resulted in increased thyroid activity, with secondary hyperphagia without obesity. In a short-term study, administration of sodium pentobarbital to the BMH area resulted in increased feeding. Conversely, glucose administration to the same area suppressed feeding in satiated but not in food-deprived chickens.

Adipose Tissue↗
PubMed1988

The effect of electrolytic lesions in the baso-medial-hypothalamus on the immune response of the chicken.

Electrolytic lesions of the baso-medial-hypothalamus (BMH) cause numerous dysfunctions of the endocrine system, many of which have been implicated in regulating immune responses. The objective of this report was to evaluate the direct effects of electrolytic lesions in the BMH on the immune response of the chicken. Our results indicate that temporary immune response impairment, as evaluated by both T and B lymphocyte related responses, occurred only in birds that expressed both brain damage and endocrine dysfunction, whereas birds expressing brain damage alone had normal immune responses. The possible regulation of immune responses by the BMH via the endocrine system is discussed.

Animals↗
PubMed1988

Fertile semen from 9-week-old chicks treated with tamoxifen.

White Leghorn male chicks were injected with 1 mg/kg BW of tamoxifen (an anti-estrogen) on alternating days between 2 and 9 wk of age. This treatment increased testes weight and induced semen production in response to the abdominal massage procedure. Insemination of laying hens with this semen resulted in hatching of live chicks from their eggs.

Animals↗
PubMed1987

Testosterone and adiposity in the chicken: the effect of breed and sex.

The leaning role, previously suggested for testosterone in chickens, was tested in males and females of fatty and lean breeds. The breeds used were the White Leghorn (WL), of which the male is very lean, and the White Giant (WG) and the White Cornish X White Rock (WCWR), in which both sexes accumulate fat. Castration of WL males induced adiposity and replacement therapy with testosterone propionate (TP) reduced the fat to normal. However, in males of the fatty breeds, neither castration nor TP administration had any effect on adiposity. Similarly, long-term supplementation of a high dose of TP had no effect on the level of adiposity in females of both the heavy and the light breeds. Thus, the leaning effect found for testosterone in the WL male is not a general phenomenon in chickens but rather a specific response of the WL male.

Adipose Tissue↗
PubMed1987

Food intake and biogenic amine concentrations in brain regions of chicks following intracerebroventricular injection of six-hydroxydopamine.

The effect of catecholamine depletion within three brain regions on subsequent food intake and body weight gain were investigated in two week-old chicks. Two levels of pargyline (P; 50 mg/kg and 100 mg/kg intraperitoneally) and three levels of six-hydroxydopamine (6-OHDA; 0, 200 micrograms (136 free base) and 300 micrograms (204 free base) intracerebroventricularly) were administered to 36 chicks (n = 6 per treatment). The greatest reduction in food intake and body weight gain occurred in the group given 100 mg/kg P, 300 micrograms 6-OHDA. These chicks displayed an average aphagic response of 4.5 days. Chicks given the higher drug doses were hyperactive when handled and displayed difficulty in orienting their bills when attempting to consume pellets. Biogenic amines were determined in three brain regions (striatum, hypothalamus and brainstem) using high pressure liquid chromatography with electrochemical detection. Dopamine (DA) was reduced (p less than 0.05) in the striatum of all groups treated with 6-OHDA when compared to their respective controls. Significant depletions of norepinephrine (NE) occurred in all three brain regions in all groups treated with 6-OHDA when compared with their respective control groups (p less than 0.05). In contrast, striatal epinephrine levels were elevated in chicks given 100 mg P plus 6-OHDA. It is proposed that depletions of both DA and NE contribute to the aphagic or anorexic response of chicks following administration of the neurotoxin 6-OHDA.

Animals↗
PubMed1987

Application of the filial imprinting phenomenon to broiler chicks at a commercial farm.

Ten thousand broiler chicks on commercial farms in Israel were imprinted to blue and red plastic boxes (20 x 20 x 40 cm) containing loud speakers (8 omega, 12 W) equipped with a tape recorder, in which a classical music cassette had been placed. Upon reaching 3 wk of age, an attempt was made to move these chicks from the training area (A) to a new area (B) using the imprinting objects. This experiment was repeated four times: May, August and November of 1985, and in January 1986. During the warm months of May and August 30 to 60% of the experimental chicks followed the imprinting objects toward Area B. During the cold months and in all four repetitions with the controls, less than 5% of the flocks moved from Area A to Area B. Winter chicks may have been imprinted on brooder heaters. In all repetitions, most of the imprinted chicks distributed themselves equally over Area B 1 h after the doors between Areas B and A were closed. Controls, however, crowded around the door between Areas A and B resulting in the death of many chicks by asphyxiation. This study has shown that thousands of heavy strain chicks can be easily attached to an imprinting stimulus and it may be possible to apply this phenomenon for commercial purposes.

Acoustic Stimulation↗
PubMed1986

The gonadotropic-axis involvement in the course of the filial following response in the domestic fowl chick.

The detachment process of the domestic chick from its mother, or any other imprinting object occurs between the sixth and tenth week after hatching. The present study (Experiment I), examines whether the detachment process parallels endocrine events that precede prepuberty. Immediately upon hatching, groups of heavy strain chicks were imprinted to a colored foam rubber ball for 72 hours. The bond between these chicks and the imprinting object was then tested, and plasma LH and testosterone were assayed once a week until the chicks were 10 weeks of age; the sexual development of chicks of the same strain was studied at the same time. At the outset of the detachment period (5-7 weeks) an increase in plasma testosterone and a decrease in plasma LH was found. In addition, the comb and testes showed a definite weight increase while the bursa of Fabricius showed a significant decline in weight. In Experiment II, the beginning of the detachment process was induced by injecting 3 to 4 week old chicks with testosterone-propionate, estradiol-benzoate and 5 alpha-dihydrotestosterone. Our evidence therefore appears to demonstrate that testosterone and its metabolites induce the detachment process by the same mechanism used to stimulate sexual behavior in juvenile chicks.

Animals↗
PubMed1986

Induction of precocious development of reproductive function in cockerels by tamoxifen administration.

To examine the effects of tamoxifen, a known estrogen antagonist in the chicken, two groups of cockerels were injected every other day from hatching until 7 weeks of age with 1 and 10 mg tamoxifen/kg body weight (BW), respectively. A third group was injected with 1 mg tamoxifen/kg BW every 3 days from 5 to 10 weeks of age. All groups treated with tamoxifen had increased testes weight, but BW and pituitary weights did not differ from controls. In contrast to controls, seminiferous epithelium of testes from treated cockerels showed spermatogenesis up to the spermatid elongation stage. We suggest that the antiestrogen effect of tamoxifen increased circulating LH, which stimulated testes growth and precocious spermatogenesis.

Animals↗