Hr Postoviposition Research Articles

Relaxin: An Ovarian Hormone in an Avian Species (Gallus domesticus)

The objective of this study was to characterize the biochemical, immunological, and biological activity of avian relaxin and to immunolocalize relaxin-like peptides in the ovary of the hen (Gallus domesticus). A relaxin-like peptide was partially purified from ovaries of actively laying hens by size-exclusion chromatography and further purified by ion-exchange chromatography on CM-cellulose. Those fractions containing relaxin immunoreactivity were identified with the use of a homologous porcine relaxin radioimmunoassay on selected column effluent and pooled, and a sample was subjected to SDS–gel electrophoresis. The SDS–gel-separated proteins were electrotransferred onto a nitrocellulose membrane and immunostained with an antiserum to porcine relaxin which showed the presence of a single band of ≈6000 daltons. The dose–response curve generated by avian relaxin-like peptide in the homologous porcine relaxin radioimmunoassay was parallel to that produced by the porcine relaxin standard. Like porcine relaxin, avian relaxin-like peptide eluted from the Sephadex G-50 in an elution volume for a molecule of ≈6000 daltons, was retained on CM-cellulose, and was bioactive inin vitroinhibition of spontaneous contractions of estrogen-primed mouse uterus (a relaxin bioassay). Using an antiserum specific to porcine relaxin, avian relaxin-like peptide was immunolocalized to the granulosa cells of postovulatory follicle from ovary of a hen less than 24 hr postoviposition. No immunostaining was detected in the cells of the largest preovulatory follicles or when the antiserum was preabsorbed with porcine relaxin prior to staining. The finding of this study indicates that the avian postovulatory follicle, like the corpus luteum of other vertebrate species (sharks and mammals), contains a relaxin-like peptide.

A scanning electron microscope study of the developing embryo of Manduca sexta (L.) (Lepidoptera : Sphingidae)

Scanning electron microscopy of the developing Manduca sexta (Lepidoptera : Sphingidae) embryo reveals that the body wall of the insect undergoes considerable morphogenesis beginning at 20 hr post-oviposition. The elongated 19 hr embryo contracts in length, which gives rise to the formation of rudimentary segments. By 33 hr, many of the appendage anlagen are visible, the presumptive spiracles appear as bifurcate pits and the proctodeum begins invagination. During this same period, prior to katatrepsis, the body walls become established, and the segments and appendages develop. Between 50 and 60 hr post-oviposition, involution of the oral cavity and reorientation of the associated gnathal appendages occurs. During this same period, katatrepsis and provisional dorsal closure take place. Developmental polarity is evident as a distinctive wave of specialization proceeding posterior to anterior in the thorax/abdomen, and anterior to posterior in the head. Configuration of the oral cavity is strikingly prognathous until just prior to eclosion. Two embryonic molts are apparent, as determined by the remnants of ecdysed “embryonic cuticles”.

Preovulatory concentrations of progesterone and estradiol in plasma and their relationships with eggshell quality in the laying hen.

Laying hens were divided into high and low shell quality groups on the basis of egg specific gravity during the 5th, 7th, and 9th months of egg production. Concentrations of progesterone and estradiol-17 beta in the plasma were determined by radioimmunoassay in blood samples taken by cardiac puncture from hens at either 18, 21, or 24 hr postoviposition. Egg production and egg weight were not significantly different between shell quality groups; however, hens in the low shell quality group were heavier (P less than .05), had longer clutches (P less than .05), and lower egg specific gravity (P less than .0001) than hens in the high shell quality group. Egg production and clutch size declined (P less than .01) in both groups with increased age. Plasma estradiol and progesterone concentrations were not different between shell quality groups or among periods of production, though progesterone and estradiol concentrations were greater (P less than .005) at 21 hr postoviposition than at 18 or 24 hr. The correlation coefficient between plasma concentrations of estradiol and progesterone was significant. There was no significant association between the plasma concentrations of these hormones and egg shell quality. These data suggest that concentrations of estradiol and progesterone in plasma, during the 6 hr before ovulation, are not highly related to shell quality in the laying hen.

Arterial Blood Gas, pH, and Bicarbonate Values in Laying Hens Selected for Thick or Thin Eggshell Production

Bicarbonate, pH, carbon dioxide partial pressure (pCO2), and oxygen partial pressure (pO2) were measured in blood samples collected anaerobically from the brachial arteries of domestic fowl from lines selected for thick (TK) or thin (TN) eggshell production. The blood values of TK and TN hens were compared 6 hr prior to oviposition and continued at 2-hr intervals until 10 hrs postoviposition. Percent shell values were measured for eggs laid 2 days prior to and during blood sampling. Hens with TK shells had significantly (P<.001) higher percent shell values than hens with TN shells. The measured blood parameters (bicarbonate. pH, pCO2, and pO2) did not differ significantly (P>.05) when TK and TN hens were compared at the time of oviposition. However, between 2 and 6 hr postoviposition, TN hens had significantly lower blood pH, pO2, and bicarbonate than did TK hens. Arterial pCO2 tended to be higher in TN hens than in TK hens, but this difference was significant only at 6 hr preoviposition. These results show that TN hens develop metabolic acidosis relative to TK hens during the first 6 hr postoviposition.

Concentrations of Selected Cations in Turkey Serum and Oviductal Mucosae

Concentrations of selected cations in serum and oviductal mucosae were determined in samples taken immediately after laying and at 8 to 12 hr and 18 to 22 hr postoviposition in turkey hens at 2 and 17 weeks of egg production. Serum zinc (Zn) and magnesium (Mg) at 2 weeks of egg production and copper (Cu) and sodium (Na) at 17 weeks of egg production were influenced by time postoviposition. In general, serum Cu declined and Zn, Ca, and Mg concentrations increased between the 2nd and 17th week of egg production. Cation concentrations varied between the infundibular, uterine, uterovaginal junction (UVJ), and vaginal mucosae but showed less variation within individual segments over the postoviposition times examined. Pooled mean concentrations of cations within each segment revealed that the UVJ mucosa, when compared to the remaining segments, was higher in Zn, Cu, Fe, and Na in hens 2 weeks after egg production and in Zn after 17 weeks of egg production. The relatively high concentration of Zn in the UVJ mucosa may be related to the sperm storage capacity of this region.

The meiotic process and aneuploidy.

Normal females developing at 25 degrees C produce their first population of oocytes at 132 +/- 2 hr post oviposition. Entrance of the oocytes into premeiotic interphase signals initiation of DNA replication which continues for 30 hr. Coincidentally, extensive SCs appear, averaging 50 microns (132 hr), peaking at 75 microns (144 hr), and continuing into early vitellarial stages. Recombinational response to heat, evidenced by enhancement or induction of exchange, is limited to the S-phase with a peak at 144 hr coinciding with maximal extension of the SC. Coincidence of synapsis and recombination response with S at premeiotic interphase is contrary to their conventional localization at meiotic prophase. The interrelationship between exchange and nondisjunction has been clarified by the Distributive Pairing Model of meiosis. Originally revealed through high frequencies of nonrandom assortment of nonhomologous chromosomes, distributive pairing has been shown to follow and to be noncompetitive with exchange, to be based on size-recognition, not homology, and as a raison d'etre, to provide a segregational mechanism for noncrossover homologs. Rearrangements, recombination mutants, and aneuploids may contribute noncrossover chromosomes to the distributive pool and so promote the nonhomologous associations responsible for nondisjunction of homologs and regular segregation of nonhomologs. Further information concerning early meiotic events and their relation to segregation has been revealed by studies of the ts rec-1(26) mutant. Application of the restrictive temperature (31 degrees C) at sequential times during development shows wild-type activity to be drastically reduced beginning at 126/132 hr, terminating at 162 hr, and so coinciding with S and the heat-sensitive period of the normal genome. EMs of serially sectioned oocyte nuclei maintained at the restrictive or control temperature reveal SCs to be indistinguishable, and implicate recombination rather than synapsis as the target of the mutant. Activity of rec-1(26) in the range 17 degrees to 31 degrees C reveals a sharp decline between 28+ degrees and 31 degrees C, typical of a denaturation curve. If denaturation of the rec protein by the restrictive temperature marks its active phase, it follows that recombination terminates at the end of S when the restrictive temperature becomes ineffective. The notion that synapsis ensures regular segregation (35) is invalidated by rec-1(26) whose normal synapsis at the restrictive temperature is followed by a 200-fold increase in nondisjunction at segregation, as compared to the control.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma Phosphorus at 0, 6, and 21 Hours Postoviposition in Hens Laying in the Morning or Afternoon

Two experiments were conducted using White Leghorn hens. Blood samples were collected immediately following oviposition (0 hr) or 6 or 21 hr postoviposition from hens laying in the morning or afternoon. Plasma phosphorus was determined at each time period. In Experiment 1, plasma phosphorus at oviposition was essentially the same for hens laying in the morning or afternoon (3.95 and 4.10 mg/dl, respectively). At 6 hr postoviposition plasma phosphorus was lower than that observed at 0 hr (3.22 and 3.15 mg/dl, respectively). When comparing plasma phosphorus levels at 21 hr postoviposition of hens laying in the morning or afternoon a higher (P≤.05) phosphorus level was observed for hens that laid in the morning (5.90 vs. 4.91, respectively). In Experiment 2, plasma phosphorus levels at 0 and 6 hr postoviposition were 3.32 vs. 3.18 and 2.81 vs. 2.74 mg/dl for hens laying in the morning and afternoon, respectively. At 21 hr postoviposition, phosphorus values of 5.30 vs. 3.65 mg/dl were reported for hens laying in the morning and afternoon, respectively.Data also indicated that on the day a hen does not lay an egg, plasma phosphorus does not rise. An hypothesis is offered to explain the difference in egg shell quality between eggs laid in the morning or afternoon.

Cyclic Changes in Plasma Phosphorus of Laying Turkeys

Plasma phosphorus of laying turkeys measured at 0, 6, 18, and 24 hr after oviposition showed a cyclic pattern similar to that reported for laying chickens. Plasma phosphorus was lowest at oviposition and remained relatively low until 6 hr postoviposition; values at 18 and 24 hr postoviposition were higher. Plasma phosphorus was higher (P<.05) 24 hr postoviposition than 0 or 6 hr postoviposition. The changes were assumed to be associated with egg shell calcification and bone resorption. Plasma phosphorus values of turkey toms measured during a 24-hr period remained constant and were not significantly (P<.05) different from each other.

Turkey Sperm Oxygen Consumption, Motility, and Percentage Dead After Incubation in Tissue Homogenates

Turkey oviductal segments and the most recent postovulatory follicle were removed from hens killed .25, 8 to 12, and 18 to 22 hr postoviposition (PO), homogenized, and centrifuged. Supernatant and precipitate fractions were lyophilized, and known quantities were incubated with washed spermatozoa for 90 min at 40 to 41 C. All supernatants and precipitates significantly increased sperm O2 consumption within the PO intervals, but no differences were observed within a segment between the PO intervals. Generally, both fractions decreased postincubation sperm motility and increased the percentage of dead spermatozoa within the PO intervals, but no differences were observed within a segment between the PO intervals. Magnal supernatants stimulated the least amount of O2 consumption while maintaining postincubation sperm motility and percentage dead levels comparable to control values. Sperm motility and percentage dead after incubation in infundibular supernatants were comparable to control levels yet stimulated O2 consumption about fourfold over that of controls. Uterine and uterovaginal junction supernatants stimulated sperm O2 consumption about fivefold over that of controls in spite of lowered postincubation sperm motility and higher percentage dead.

Ecdysone levels and distribution of acid phosphatase, acidic glycosidases, and cytochrome [formula omitted] oxidase during the third-instar stage of Stomoxys calcitrans (L.)

The activities, subcellular distributions, and relative specific activities (RSA) are reported for seven acidic glycosidases, acid phosphatase, and cytochrome c oxidase in third-instar larvae of Stomoxys calcitrans (L.). At ca. 120 hr post oviposition, the RSA of five of the glycosidases and acid phosphatase began to increase in the mitochondrial-lysosomal fraction. A peak of 20-hydroxyecdysone occurred at ca. 120 hr post oviposition; which was followed by a gradual increase until the white prepupal stage was reached. No ecdysone was found, an indication of its rapid metabolism to 20-hydroxyecdysone.

Chicken and Turkey Oviductal pH at Known Times Postoviposition

Broiler-type chickens and turkeys were killed 2 to 10 min, 8 to 12 hr, and 18 to 22 hr postoviposition (PO), and pH values were determined in each oviductal segment. In the broiler-type chicken, significant pH differences were observed in the fimbria (from 7.28 at 2 to 10 min PO to 7.41 at 8 to 12 hr PO), distal infundibulum (from 7.02 at 2 to 10 min PO to 7.21 at 8 to 12 hr PO), uterovaginal junction (UVJ) (from 6.92 at 18 to 22 hr PO to 7.18 at 8 to 12 hr PO), and midvagina (from 7.15 at 2 to 10 min PO to 7.51 at 8 to 12 hr PO). In the turkey, significant pH differences were observed in the isthmus (from 6.01 at 2 to 10 min PO to 6.81 at 18 to 22 hr PO), uterus (from 6.77 at 2 to 10 min PO to 7.03 at 8 to 12 hr PO), UVJ (from 6.93 at 2 to 10 min PO to 7.24 at 8 to 12 hr PO) and everted vagina (from 6.95 at 8 to 12 hr and 18 to 22 hr PO to 7.30 at 2 to 10 min PO). It is not known at this time if the small range in pH found between the same oviductal segments at different times PO influence oviductal sperm metabolism, motility, or fertilizing capacity.

The ovaries, ring gland, and neurosecretion during the second gonotrophic cycle in the housefly, Musca domestica

Houseflies ( Musca domestica) at 12 to 32 hr postoviposition showed a 19% decrease in the amount of stainable material in the median neurosecretory cells (MNC), but insects ovariectomized after oviposition had a 48% decrease in stained material by 2 hr postoviposition, which persisted. This decrease in neurosecretory material (NSM) from the neurosecretory cells after oviposition and ovariectomy was followed by a 45% increase in the synthesis of NSM. Implanting ovaries into flies after oviposition and ovariectomy lessened the decrease in the amount of stained NSM from the MNC by 20 to 40%. Insects that had their ring glands removed (-RG) during the late vitellogenic phase in the first gonotrophic cycle developed mature eggs in the first cycle, but when these eggs were oviposited, the second cycle of eggs was not activated and did not develop past stage 4 or 5, and the amount of stained material in the MNC decreased 45%. However, the -RG flies allowed to retain mature eggs in the first cycle did not show a decrease in stained NSM. Thus, storage and release of NSM is independent of the ring gland but dependent upon activated ovaries. The data suggest that the oöstatic hormone is produced by NSM-activated ovaries which prevent the further release of NSM. Thus, when oviposition removes the source of oöstatic hormone, NSM is released, which activates the next gonotrophic cycle to develop and to produce oöstatic hormone. This interaction of NSM release with oöstatic hormone production maintains the cyclicity of egg development in houseflies.