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Biomedical subjects

J N Petitte

Publications and source records attributed to J N Petitte.

35 records · Page 2Linked to original sources
PubMed1994

Profiles of chicken macrophage effector functions.

In contrast to the mammalian system, avian species lack the so-called "resident" or "harvestable" macrophage population in the abdominal exudate. However, macrophages can be recruited into the chicken's abdominal cavity (presumably from the blood monocyte pool) if an inflammatory agent such as Sephadex is injected. The kinetics of inflammatory cell recruitment in terms of time, cell type, and state of activation to perform a particular effector function is currently an active area of research. This report will provide information on several chicken macrophage effector functions, including in vivo chemotaxis, phagocytosis, bacterial uptake and killing, biosynthesis of nitric oxide and various enzymes, and monokines such as interleukin-1 and granulocyte colony-stimulating factor.

Acid Phosphatase↗
PubMed1993

Early development of the chick embryo.

The ultrastructure of the early chick embryo was investigated, using scanning (SEM) and transmission electron microscopy (TEM). Eggs were obtained from the shell gland by injecting hens intravenously with a synthetic prostaglandin or arginine vasopressin. Embryos were examined during late cleavage (stages IV-VI, Eyal-Giladi and Kochav, '76), formation of the area pellucida (stages VII-XI), and formation of the hypoblast (stages X-XIV). SEM highlighted the reduction in cell number at the underside of the embryo during formation of the area pellucida although it became apparent that the thickness of the embryo is not reduced to a single layer of cells at stage X. In addition, blastomeres at the perimeter of embryos (stages V-VI) project filopodial extensions onto a smooth membrane that separates the sub-embryonic cavity from the yolk. During hypoblast formation, epiblast cells generate stellate projections at their basal aspect, thus providing a meshwork for the advancing secondary hypoblast cells. By stage XII the epiblast was one cell thick and reminiscent of a columnar epithelium when viewed transversely. Cells of the deep portion of the posterior marginal zone were distinguished morphologically in the stage XII embryo by their many cell surface projections and ruffled appearance. Blastomeres at the perimeter of stage V-VI embryos projected filopodial extensions onto a smooth membrane which separates the sub-embryonic cavity from the yolk. This membrane is presumed to be confluent with the cytolemma. Evidence is presented demonstrating the presence of intracellular membrane-bound droplets which are hypothesised to contain sub-embryonic fluid.

Animals↗
PubMed1993

Brain content of cGnRH I and II during embryonic development in chickens.

We used specific radioimmunoassays to measure chicken gonadotropin-releasing hormones I and II (cGnRH I and II) in extracts of chicken brain as a first step in determining whether these peptides may function identically during embryonic development in birds. In three experiments chicken embryo brains were removed at various times between Day 6 of incubation and hatching. In Experiment 3, the sex of embryos was identified by means of polymerase chain reaction amplification of a W chromosome-specific DNA sequence. Brain concentrations of cGnRH I increased sharply from Day 6 of incubation to Day 8, then decreased until Day 10 to Day 12, followed by an increase beginning on approximately Day 17 and continuing until hatch. In contrast, cGnRH II concentration remained low until about Day 14 of incubation, then increased progressively until, at hatch, brain content of cGnRH II was approximately 9 to 11 times that of cGnRH I. The difference in development pattern and total content of these peptides supports the view that any physiologic function they may have might be differentiated as early as Day 7 of incubation.

Animals↗
PubMed1993

Avian macrophages: contribution to cellular microenvironment and changes in effector functions following activation.

The capacity of macrophages to generate metabolites and monokines having effector and regulatory functions can result in a major impact on their cellular microenvironment. Macrophage products synthesized in response to bacterial lipopolysaccharide stimulation include reactive oxygen and nitrogen intermediates as well as tumor necrosis factor (TNF). These secreted products of macrophages exhibit bioactivity either locally or systemically. Although the mechanism of action of avian monokines such as TNF-like factor may be similar to their mammalian counterparts, chicken TNF seems to lyse cells of chicken origin and not of mammalian origin. Furthermore, the generation and activity of products such as TNF is directly influenced by environmental stressors such as heat and toxins.

Animals↗
PubMed1991

Efficient transfection of chicken cells by lipofection, and introduction of transfected blastodermal cells into the embryo.

Chicken blastodermal cells (CBCs) and primary chicken fibroblasts (PCFs) have been lipofected with a variety of lacZ constructs encoding Escherichia coli beta-galactosidase (beta-gal). A reporter construct (phspPTlacZpA) containing a mouse heat-shock protein 68 gene (hsp 68) promoter was used to establish conditions for efficient lipofection. The construct, in circular or linear plasmid form or as reporter sequences alone, was transferred efficiently by incubating the cells for 3.5 h in a mixture of 6.2 micrograms Lipofectin (a cationic liposome preparation from Bethesda Research Laboratories) and 1.55-3.1 micrograms DNA per mL DMEM. These lipofection conditions were used to transfer a reporter construct (pCBcMtlacZ) containing a Zn(2+)-inducible chicken metallothionein (cMt) promoter, and constructs showing constitutive expression due to Rous sarcoma virus plus chicken beta-actin (pmiwZ) or cytomegalovirus (pMaori3) promoters. Endogenous chicken beta-gal and transferred bacterial beta-gal activity could be distinguished clearly by incubating the cells with the substrate, Xgal, at pH 4.3 or 7.4, respectively. Expression of phspPTlacZpA in chicken cells did not appear to require specific induction of the mouse hsp68 promoter, whereas expression of pCBcMtlacZ required treatment of the cells for 6-12 h with 150 microM ZnCl2. Bacterial beta-gal activity was observed following lipofection of CBCs that were cultured in suspension or plated. The efficiency of lipofection was at least 1 in 25 for CBCs, judging by the proportion of cells shown to have beta-gal activity 16-24 h after lipofection treatment began; these events could represent transient or stable incorporation of the construct.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Daily infusion of corticosterone and reproductive function in the domestic hen (Gallus domesticus).

The purpose of this study was to examine the effect of the daily infusion of corticosterone on reproductive function in the laying hen and to determine the relationship between the cyclic pattern of plasma concentrations of corticosterone on the open-period for the preovulatory release of LH. An exogenous rhythm of plasma levels of corticosterone was generated using an osmotic pump. Corticosterone was infused subcutaneously into laying hens at rates of 5, 10, 15 or 30 micrograms/hr for a duration of 10 hr beginning with the onset of darkness or at 15 micrograms/hr for 4 hr, or continuously at 30 micrograms/hr. Daily infusions greater than 15 micrograms/hr and the continuous infusion resulted in cessation of ovulation, ovarian and oviductal regression, hyperphagia, and elevated levels of plasma corticosterone compared to that observed in control hens. The hens which were infused with 5 or 10 micrograms/hr of corticosterone maintained normal reproductive function with plasma concentrations of corticosterone that were approximately the same as those in the control hens. The effect of infusing 10 micrograms/hr of corticosterone on the open-period for the preovulatory release of LH was determined under constant light. No significant changes were observed in the frequency distribution of the times of oviposition when hens were infused with 10 micrograms/hr of corticosterone for 12 hr from 9:00 to 21:00 hr or 21:00 to 9:00 hr each day.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of metyrapone on the timing of oviposition and ovarian steroidogenesis in the laying hen.

1. The purpose of this study was to observe the effects of metyrapone on the time of oviposition and LH-stimulated steroidogenesis by granulosa cells and small yellow follicles. 2. In experiment 1, White Leghorn hens were injected for 11 d with 240 mg metyrapone 5 h before 'lights off'. Control hens were injected with 1 ml of vehicle (PEG-400). Metyrapone treatment resulted in a 28% decrease in the rate of lay and the modal frequency of the time of oviposition was phase-shifted by 15 h. 3. In experiment 2, hens were injected with 240 mg metyrapone 5 h before 'lights off' or at 'lights on'. While metyrapone treatment reduced the rate of lay, a clear phase-shift in the distribution of oviposition was not observed. Basal and LH-stimulated progesterone synthesis by the granulosa cells of the largest follicle and oestradiol synthesis by small yellow follicles was significantly reduced. 4. Metyrapone treatment significantly reduced basal, but not LH-stimulated output of androstenedione by whole small yellow follicles compared to that observed in control hens. 5. The addition of metyrapone in vitro to isolated granulosa cells from the three largest preovulatory follicles inhibited LH-stimulated progesterone production in a dose-specific manner. 6. The results of this study suggest that the ability of metyrapone to perturb the open-period is a pharmacological effect mediated through inhibition of ovarian and adrenal steroidogenesis.

Androstenedione↗
PubMed1991

Assessment of functional gametes in chickens after transfer of primordial germ cells.

The ability of primordial germ cells (PGCs) transferred from donor to recipient embryos to form functional gametes was assessed using feather colour as a phenotypic marker. Donor primordial germ cells were obtained in blood samples taken from Dwarf White Leghorn embryos, homozygous for the dominant allele at the locus for 'dominant white' plumage (I), which had been incubated for 52 h. Blood samples containing PGCs were transferred by intravascular injection to Barred Plymouth Rock embryos (ii) incubated for 53, 72 and 96 h. Of the embryos which hatched, 28 were male and 31 were female. All chicks were raised to sexual maturity and test mated with Barred Plymouth Rock fowl. All of the 3117 offspring exhibited the typical Barred Plymouth Rock phenotype; no Barred Plymouth Rock x Dwarf White Leghorn chicks were obtained. The results of this study suggest that the frequency of transmission of the donor line genotype after PGC transfer must be improved for this technique to be useful for the routine development of transgenic poultry.

Animals↗
PubMed1991

Variability in preincubation embryo development in domestic fowl. 1. Effects of nest holding time and method of egg storage.

Embryos of eggs from Single Comb White Leghorn hens were analyzed to determine whether nest holding time and method of storage had a significant effect on postoviposition embryonic growth prior to incubation. Eggs were collected from 38- to 42-wk-old hens naturally inseminated and housed in floor pens. The experiment had a 2 x 2 factorial arrangement of treatments with two nest holding times and two storage methods. Eggs were collected within 1 h of oviposition, placed on cardboard egg flats, and stored unpacked (Treatment 1), or put on flats, and packed in 30-dozen egg cases (Treatment 2). Eggs in Treatments 3 and 4 were marked within 1 h of oviposition, but remained in the nest for 6 to 7 h. These eggs were separated into unpacked (Treatment 3), and packed (Treatment 4) groups. All eggs were stored at 13.8 C for 4 days. A total of 250 embryos were staged after storage for development using the Eyal-Giladi and Kochav classification. Least square means (LSM) for stage of development were: Treatment 1, 10.76; Treatment 2, 11.52; Treatment 3, 12.41; and Treatment 4, 12.36. For the main effects, nest holding time significantly affected stage of development (P = .0001), but storage method (P = .1140) and nest holding time by storage method interaction (P = .0730) did not. Comparison of LSM of Treatment 1 versus 3 (P = .0001), 2 versus 4 (P = .0152), and 1 versus 2 (P = .0214) were significant, but Treatment 3 versus 4 (P = .8595) was not.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Reptilian and avian follicular hierarchies: models for the study of ovarian development.

The presence of an ovarian follicular hierarchy is a characteristic feature of reptiles and birds. The hierarchy contains follicles at all stages of maturation and therefore, varying degrees of sensitivity to the ovulation-inducing effects of the gonadotropins. In the hen, ovulability is gained as the ability of the follicle to produce androgens and estrogens declines and the ability to produce progesterone increases. In the mature follicle, the granulosa cells are the site of progesterone production whereas the theca cells produce androgens and estrogens. Small follicles that have not yet been (and may never be) recruited into the yolk-filled hierarchy are the major producers of androgens and estrogens within the ovary. In reptiles the ovarian follicular hierarchy includes non-vitellogenic follicles and in some species includes follicles destined to become atretic. These two features distinguish the reptiles from the birds and provide experimental biologists with a unique model to investigate the physiological events that regulate the most common fate of ovarian follicles, atresia.

Animals↗
PubMed1990

Production of somatic and germline chimeras in the chicken by transfer of early blastodermal cells.

Cells were isolated from stage X embryos of a line of Barred Plymouth Rock chickens (that have black pigment in their feathers due to the recessive allele at the I locus) and injected into the subgerminal cavity of embryos from an inbred line of Dwarf White Leghorns (that have white feathers due to the dominant allele at the I locus). Of 53 Dwarf White Leghorn embryos that were injected with Barred Plymouth Rock blastodermal cells, 6 (11.3%) were phenotypically chimeric with respect to feather colour and one (a male) survived to hatching. The distribution of black feathers in the recipients was variable and not limited to a particular region although, in all but one case, the donor cell lineage was evident in the head. The male somatic chimera was mated to several Barred Plymouth Rock hens to determine the extent to which donor cells had been incorporated into his testes. Of 719 chicks hatched from these matings, 2 were phenotypically Barred Plymouth Rocks demonstrating that cells capable of incorporation into the germline had been transferred. Fingerprints of the blood and sperm DNA from the germline chimera indicated that both of these tissues were different from those of the inbred line of Dwarf White Leghorns. Bands that were present in fingerprints of blood DNA from the chimera and not present in those of the Dwarf White Leghorns were observed in those of the Barred Plymouth Rocks.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

The effect of corticosterone on the response of the ovary to pregnant mare's serum gonadotrophin in sexually immature pullets.

Several studies have suggested that a functional relationship exists between the adrenal gland and the ovary. The purpose of this study was to determine the effect of corticosterone on the sensitivity of the ovary to exogenous gonadotrophin. Sexually immature White Leghorn pullets, 18 weeks of age, were infused with 30 micrograms/hr of corticosterone for 14 days. After 7 days of infusion, the pullets were injected with 3, 15, 75, or 375 IU pregnant mare's serum gonadotrophin (PMSG) for 7 days. Controls consisted of noninfused pullets injected according to the same doses of PMSG. Blood samples were obtained on Days 3, 6, 8, 10, and 12 of infusion and were assayed for plasma concentrations of luteinizing hormone (LH), estradiol, and corticosterone by radioimmunoassay. The daily injections of 75 or 375 IU PMSG in noninfused pullets resulted in an increase in ovarian and oviductal weight and the formation of a hierarchy of yolk-filled follicles. This was accompanied by an increase in the plasma concentrations of estradiol and a decrease in the plasma concentrations of LH. The infusion of corticosterone significantly increased the plasma concentrations of this steroid over that observed in the control pullets and was not related to the dose of PMSG. This increase in plasma levels of corticosterone was associated with a significant decline in the plasma concentrations of LH and estradiol before the injection of PMSG. After 6 days of PMSG treatment, the plasma concentrations of estradiol increased to that observed in control pullets and was dependent upon the dose of PMSG injected.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The effect of corticosterone on the photoperiodic response of immature hens.

White Leghorn pullets, 18 weeks of age, were infused with 30 micrograms/hr of corticosterone for 14 days. After 7 days of continuous infusion, the pullets were photostimulated by transfer from 8L:16D to 16L:8D. Noninfused controls were either photostimulated on Day 7 or remained on an 8L:16D photoschedule. Blood samples were obtained on 3, 6, 8, 10, and 12 days of infusion and were assayed for plasma concentrations of LH, estradiol, and corticosterone by radioimmunoassay. On Day 14 all birds were weighed and sacrificed, and the ovarian and oviductal weights were recorded. Photostimulation had no effect on plasma concentrations of corticosterone. The infusion of corticosterone significantly raised the plasma concentration to 5.2 ng/ml, suppressed the photo-induced rise in plasma concentrations of LH, and resulted in significantly lower plasma concentrations of estradiol. After 7 days of photostimulation either with or without corticosterone infusion, there were no significant differences in mean ovarian weight. The oviducal weight of hens infused with corticosterone was, however, significantly lowered. It is suggested that one of the mechanisms associated with the antigonadal effect of corticosterone involves an inhibition of Gn-RH release by the hypothalamus.

Animals↗
PubMed1984

Interrelationships between the hypothalamus, pituitary gland, ovary, adrenal gland, and the open period for LH release in the hen (Gallus domesticus).

The asynchronous ovulatory cycle of the hen is believed to be the consequence of two interacting systems, one of which is circadian and regulates the timing of the preovulatory LH surge. In support of this proposition, the open period for LH release was shown to oscillate with the same periodicity as the photoschedule when the hens were exposed to 14 L:7 D, 14 L:10 D, and 14 L:14 D. In addition, it was demonstrated that follicular maturation is not affected by or synchronized with the photoperiod. The physiological system that transduces the light/dark cycle into an open period for LH release has not been identified although circumstantial evidence supports the idea that the adrenal gland plays a role in this function. This evidence includes the anatomical juxtaposition of the left ovary and adrenal gland, innervation of steroid-producing cells within the follicle by nerve tracts passing through the adrenal glands, the ability of injections of metyrapone to alter the timing of preovulatory LH release, the ability of injections of corticosterone to induce ovulation when a mature follicle is present in the ovary, and the ability of dexamethasone or infusions of corticosterone to block ovulation. Recently we have also shown that infusions of corticosterone will block the gonadotropic effect of PMSG, will inhibit the photoperiodic response, and do not affect the release of LH in response to injections of GnRH. The addition of corticosterone to incubations of dispersed granulosa cells does not affect their response to LH. These data suggest that corticosterone may modulate the responsiveness of the hypothalamus to tropic stimuli and demonstrate that exposure to corticosterone can alter the responsiveness of some ovarian tissues to gonadotropins.

Adrenal Glands↗
PubMed1983

The influence of cage versus floor pen management of broiler breeder hens on subsequent performance of cage reared broilers.

Chicks from breeder hens maintained in cages or floor pens were reared in Lohman battery cages in three separate trials. The ages of the breeder flock at the time of egg collection were 29, 36, and 54 weeks, respectively. The fertility of the artificially inseminated caged hens was significantly (P less than .05) lower than that of the naturally mated hens. The source of hatching eggs had no effect on early embryonic mortality, feed conversion, or growing period mortality in any broiler trials. Hatchability of all eggs set was significantly (P less than .05) lower for caged breeders in Trials 2 and 3. In all trials, eggs from caged hens produced significantly (P less than .05) larger day-old chicks than their floor-housed counterparts; however, these chicks were significantly (P less than .05) heavier at slaughter only in Trial 2. Carcass evaluations for breast blisters, keel malformations, and leg abnormalities revealed that the severity of each condition was associated with the sex of the broiler and that, within sexes, maternal housing management had no effect.

Animal Husbandry↗
PubMed1982

The influence of flock uniformity on the reproductive performance of broiler breeder hens housed in cages and floor pens.

Two flocks of broiler breeder hens, differing in uniformity of body weight, were evaluated under cage and floor management systems over a 28-week period. Hens were housed singly in cages (N = 280) or in litter floor pens (N = 304). Caged hens were artificially inseminated with .05 ml of pooled semen once weekly. Floor birds were mated naturally. During the first 10 weeks of production, the more uniform flock exhibited significantly higher egg production than the less uniform flock. Uniformity did not influence cumulative egg production, egg weight, fertility, or mortality. Initial egg production was similar for caged and floor housed hens, but the caged birds attained significantly higher egg production during peak production. Caged females showed higher egg weights and body weights than did the floor females throughout the study. Naturally mated birds attained significantly higher fertility than artificially inseminated birds (94.9 vs. 90.6). Correlation coefficients for the weights of caged hens at 20 and 24 weeks with 24, 32, 40, and 50 week weights, total eggs per bird, and age at first egg indicated that body weight at 24 weeks was a better indicator of subsequent flock performance than was body weight at 20 weeks.

Animals↗