The relationship between eggshell porosity and air space gas tensions measured before and during the parafoetal period and their effects on the hatching process in the domestic fowl.

The partial pressure of gases in the air space were measured before and during the parafoetal period for domestic fowl eggs of the same initial weight but varying in eggshell conductance. Embryos developed and hatched normally from eggs with a wide range of shell conductance and resultant air space gas partial pressures. Air space PO2 levels measured just before pipping ranged from 55 to 65 mm Hg in low and high conductance eggs, respectively, whilst PCO2 levels ranged from 75 to 55 mm Hg. With increasing shell conductance embryos membrane-penetrated and pipped the shell later, but hatch time was unaffected. Membrane penetration and external pipping appeared to occur in response to the partial pressures of gas in the air space but not in response to one particular level of air space PO2 or PCO2. During the parafoetal stage air space PO2 decreased at about 3.8 mm Hg/h and air space PCO2 increased at about 1.8 mm Hg/h and these rates of change were unaffected by eggshell conductance.

Haematology and morphological changes in young broiler chicks with experimentally induced hypoxia.

The haematology, histology and ultrastructure of day-old broiler chicks subject to experimentally induced hypoxia during incubation were examined. Some birds were allowed to reach five weeks old before examination. All the red blood cell parameters, namely, haemoglobin, packed cell volume and red cell counts were raised significantly in hypoxic birds compared with control material and the results closely resembled the haematological profile of young broilers with an ascitic syndrome. By week 5 these parameters had returned to normal. Morphological changes were seen in all the organs examined from day-old hypoxic chicks. The lungs showed much congestion and large numbers of granulocytes were present in hearts, and testes. In the livers, hepatocytes contained enlarged mitochondria together with a reduction in glycogen content. Congested lungs were seen at five weeks old but recovery to normal morphology was observed in all other organs.

Effect of two gas mixtures on growth of the domestic fowl embryo from days 14 through 17 of incubation.

Eggs weighing 62.5 +/- 0.5 gm when fresh were incubated in air in a forced-draft incubator for 13 days during which time their shell conductance to water vapor (GH2O) was determined. Eggs whose shells represented the entire range of GH2O values present in the population were then incubated for a further 4 days in either air or an experimental gas mixture. Embryo dry weights were determined after a total of 408 hr of incubation to assess the affect of the experimental gas mixture on embryonic development. Embryo growth was found to be stimulated for all eggshell conductances by 4 days incubation in a 50% oxygen/50% nitrogen mixture. This suggests that the decrease in oxygen within the egg that occurs during development normally limits embryonic growth. Growth of the embryo was unaffected by 4 days incubation in a mixture of 17% oxygen/83% helium. This mixture reduced the carbon dioxide tension in the airspace but did not affect the oxygen tension relative to eggs incubated in air. It is suggested, therefore, that the carbon dioxide that builds up within eggs during incubation does not limit embryo growth.

A note on eggshell porosity, nest humidity and the effects of DDE in the grey heron (Ardea cinerea).

Water vapour conductance (GH2O) was determined for 25 grey heron Ardea cinerea eggs in the laboratory, and in nests during natural incubation at two Scottish colonies. The mean GH2O of eggs measured in the nest which successfully hatched was 9.0 mgH2O/mmHg/day and the mean water vapour pressure gradient between egg and nest (delta PH2O), measured using "calibrated" duck eggs, averaged at 31 mmHg (4.13 kPa). Based on eggshell porosity results, from the eggs which hatched, such a gradient would result in a loss of water from the eggs during incubation equivalent to 11% of their fresh weight. Shell thickness, the number of pores/cm2 of eggshell and DDE content were also determined for the 25 eggs measured in the laboratory. Eggs containing high levels of DDE had thinner shells, more pores in the eggshell and a higher overall eggshell porosity. The main problem posed by a high level of DDE would appear, however, not to be an excessive water loss from the egg during incubation, but rather eggshell thinning leading to a loss of the egg due to breakage in the nest.

The effects of eggshell porosity on blood-gas and acid-base status of domestic fowl embryos within eggs of the same weight.

Eggshell porosity affects the metabolism and growth of the developing embryo and is likely, therefore, to influence blood-gas and acid-base status. PO2 in the airspace and in blood from the allantoic vein, PCO2 in the airspace and in blood from the allantoic artery and allantoic vein, and pH of blood from the allantoic artery and vein are all affected by shell porosity. Low porosity eggshells result in an increased retention of carbon dioxide within the egg, in partial compensation for which an increase in the level of bicarbonate in the blood is predicted. It is concluded that some of the wide variation in blood physiology data between eggs at the same stage of incubation, which has been recorded in the scientific literature, is the result of variation in shell porosity between eggs.

Effects of d-norgestrel-releasing intracervical devices in the nonhuman primate, Erythrocebus patas.

Primates (Erythrocebus patas) were implanted with intracervical devices which slowly released d-norgestrel at either of two rates: 38 +/- 12 microgram/day (high dose, 4 animals) or 14 +/- 10 microgram/day (low dose, 3 animals). An additional 8 animals received placebo devices or were untreated controls. All animals were studied for 3 months of exposure, at which time they were necropsied and evaluated. The uterus in all of the high dose primates had endometrial stromal and epithelial hyperplasia and, in two primates, suppurative endometritis. Similar, but less severe, uterine changes were present in animals of the low dose group. Systemic effects included evidence of diminished menstrual cycling and an absence of corpora lutea at both dose levels. Our results indicate that local application of these levels of d-norgestrel for contraception produces effects similar to those from systemically administered d-norgestrel.

Low-level, progestogen-releasing vaginal contraceptive devices.

Silicone rubber vaginal contraceptive devices of four different formulations, which release predetermined, controlled doses of three progestogens at four distinct levels, were designed and fabricated, and tested in 90-day clinical trials. Data obtained with 70 of the devices indicated that in vivo release rates (microgram/day +/- S.D.) for the formulations were: progesterone, 1400 +/- 30; norethindrone (two levels), 49.4 +/- 2.4, 196 +/- 21; d-norgestrel, 21.6 +/- 1.4. Clinical studies with these devices indicate that the women usually ovulate (with the exception of the high-dose norethindrone-releasing devices) while sperm penetration of the cervix was inhibited by all four fromulations, most consistently by the norgestrel-releasing devices.

PIP: 4 different formulations, which released predetermined, controlled doses of 3 progestogens at 4 distinct levels, were incorporated into newly designed and fabricated silicone rubber vaginal contraceptive devices. 90-day clinical trails tested in vivo release rates of 70 devices; the rates were: progesterone, 1400+ or -30 mcg/day; norethindrone (2 levels), 49.4+ or -2.4 and 196+ or -21 mcg/day; and d-norgestrel, 21.6+ or -1.4 mcg/day. Clinical studies with these devices indicated that the women usually ovulated (with the exception of the high-dose norethindrone-releasing device), whereas sperm penetration of the cervix was inhibited by all 4 formulations, most consistently by the norgestrel-releasing device. Data from a shelf-life study indicated that there were no significant differences between the amount of progestogen in freshly fabricated devices and that in devices stored at room temperature for 2 years.

Fabrication and testing of vaginal contraceptive devices designed for release of prespecified dose levels of steroids.

PIP: Polydimethylsiloxane (Silastic) intravaginal devices of 3 different designs were tested both in vivo and in vitro as delivery systems for d-norgestrel, norethindrone, and progesterone. The devices were toroids measuring 55.6 mm in diameter and 9.5 mm in cross-section. In vitro release rates were determined by placing the devices in a stirred stream of isotonic saline for 30-60 days, and certain others were tested following in vivo use. 78 devices used in clinical trials for an average 92.5 days formed the basis for in vivo data. In vitro relase rates at 10 days did not differ significantly from those at the end of testing, and they accorded closely with the in vivo release rates. 1 design problem encountered was the reduction in release rate once a certain portion of the dose had been expended.^ieng