Various Stages Of Incubation Research Articles

Preliminary characterization of a chlamydial agent isolated from embryonated snow goose eggs in northern Canada.

Chlamydiae-like, streptomycin-resistant parasites have been isolated from a high percentage of embryonated snow goose eggs collected at various stages of incubation; the agents stained specifically by immunofluorescence with antiserum against psittacosis and multiplied intensively in the yolk sacs of chicken embryos and induced in mice the production of antibodies that reacted in complement-fixing (CF) tests with a psittacosis group antigen. The isolates showed a high infectivity, but a low pathogenicity for chick embryos and mice. High doses of the isolate produced no cytopathic effect (CPE) in cultured mouse peritoneal macrophages and L cells. Release of lysosomal acid phosphatase did not occur in the inoculated macrophages throughout the time of observation.

Early Lesions in Chicken and Turkey Embryos Inoculated with Mycoplasma gallisepticum Strain S6 at Various Stages of Incubation

Much of the variability reported in earlier studies of the lesions induced in chick embryos by mycoplasma is probably referrable to the use of poorly characterized organisms. Another important discrepancy results from the use of dead and chilled embryos, which would also tend to cloud the histopathologic results. This study sought only to define the early lesions of Mycoplasma gallisepticum (Strain S6) infections in chicken and turkey embryos at various stages of incubation. The only previous embryo work with this strain of Mycoplasma is that of Casorso (1), who reported the failure of this organism to produce lesions in 7-day-old chicken embryos. No histopathologic studies seem to have been made of this infection in turkey embryos. The S6 strain of M. gallisepticum is a neurotropic strain isolated from a turkey brain which readily produces a severe cerebral arteritis when inoculated intravenously in poults aged 2 to 7 weeks (4,5,6). By this route it is much less pathogenic to chicks. Thomas et al. (6) found only a single case of very mild arteritis among 8 inoculated 3-day-old hatched chicks. However, they demonstrated that this organism produced a toxin that was probably responsible for the vascular changes. This strain, in addition to its neurotropic tendencies, will incite severe respiratory disease in turkeys and chickens, depending on the route of inoculation (9).

Fatty Acid Composition of Chick Embryo and Egg Yolk at Various Stages of Incubation

Adipose tissue fatty acid composition of the chick embryo is similar to egg fatty acids but does not resemble the composition of non-adipose or structural lipids (Feldman et al., 1962; and Baker, 1961). This suggests that the fatty acid composition of chick embryo may be at maximal variance with egg fat during the early stages of incubation when adipose tissue formation is minimal and that the variance may decrease during the latter stages of incubation when adipose tissue formation is maximal.To test this hypothesis, the fatty acid composition of chick embryos and yolk contents at various ages was determined and compared to that of a six-day-old chick brain. Eggs from White Leghorn hens fed a corn-soya diet were incubated. Random samples of four eggs each were withdrawn from the incubator for analysis after 0, 8, 12, 16, and 20 days of incubation. Each egg was analyzed separately. The yolk…

Lipid transport in the laying hen and the incubating egg

Tracer doses of tripalmitin, C 14 -labeled in both the glycerol and fatty acid moieties, were fed to laying hens over a 3-week period. The radioactivities of triglyceride and phospholipid glycerol and their fatty acids, as well as of the unsaponifiable matter, were determined in various organs and tissues. Similar determinations were carried out on the lipids of eggs from those hens at various stages of incubation. Only 1.3% of the dietary tripalmitin glycerol, but 13.4% of its fatty acids, were transferred to the eggs. Triglyceride transport through the intestinal mucosa and ovary was accompanied by replacement of an appreciable fraction of its glycerol. Phospholipids passed from ovary to eggs without change. The relatively high isotope concentration in the glycerol of carcass glycerides indicates that considerable accumulation of dietary glycerol occurs in adipose tissue. New evidence is presented for the ability of the hen's ovary to synthesize sterols. During incubation, triglycerides were transported from yolk to embryo without change in activity, while phospholipids underwent hydrolysis with loss of glycerol activity. Evidence is presented indicating synthesis of fatty acids and sterols in the embryo.

Properties of dextrans isolated from whole cultures at various stages of incubation

1. 1. The decrease in viscosity which dextran from Leuc. mesenteroides NRRL B-512 exhibits when left in the culture fluid after synthesis is complete was shown to result from partial degradation to smaller macromolecular size. 2. 2. Other dextrans representing a diversity of structures from three species were shown to remain unchanged in cultures as long as 49 days. 3. 3. Length of incubation appeared not to influence the presence in cultures of two strains studied of polysaccharide products separable from the dextran component on the basis of solubility. 4. 4. Leuc. dextranicum NRRL B-1146 produces a dextran closely comparable in structure to that from the B-512 strain, but which is not degraded in the culture fluid. The only polysaccharide produced by this strain is dextran; in contrast to the B-512 strain, it produces no 50–65% ethanol-insolubles. 5. 5. Dextrans isolated prior to and at the time of complete fermentation showed differences so small as to be of questionable structural significance.

A Simple Field Candler for Waterfowl Eggs

In nesting studies of waterfowl and other game birds it is often desirable to determine the stages of incubation of clutches of eggs. This information makes it possible to determine when incubation began and to calculate the date of hatching. In some studies, the stage of incubation has been determined by breaking an egg of each clutch. This is an unnecessary waste, and for species which lay parasitically in other birds' nests, such as the redhead and ruddy duck, the breaking of one egg has little value because eggs in a single nest may be in many stages of incubation. Westerskov (1950) discussed the need for age determination of embryos and presented several methods which he used in the laboratory in working with pheasant and European partridge eggs. These methods were weighing, floating, and candling of eggs. The use of egg weights in the field necessitates carrying a delicate balance and making calculations from the weights in order to determine the stage of incubation. In the second method, eggs are floated in water; their buoyancy and position are related to the stage of incubation. While this method is satisfactory for use in the laboratory or for species which nest over water, it is inconvenient for land nesters. This technique permits rapid age determination in the early stages of incubation but becomes less accurate as incubation progresses. By the use of a laboratory candler, Westerskov found that the size of the air cell and the early development of the embryo were good criteria for determining the stage of incubation of pheasant eggs. The increased density of the yolk mass plus the opacity of the shell reduced visibility so that the embryo could not be seen properly after the first week of incubation; but the size of the air cell proved an excellent criterion throughout. The use of the air cell in candling chicken eggs has been reported by many workers, including Banner (1920), and Lamon (1921). Candling has been little used in the field because of the lack of simple and efficient equipment. Evans (1951) used a cardboard mailing tube for candling duck eggs in the field; from the comparative size of the air cell, he determined when the eggs were near hatching. Hanson (1954a) developed a battery-operated field candler which provided excellent visibility of many details of the egg. He presented a list of criteria and photographs of eggs at various stages of incubation (1954b). In order to develop criteria by which the stage of incubation of duck eggs could be determined in the field with the simple mailing tube suggested by Evans, the present study was initiated in the spring of 1952. Twenty-six redhead, ten canvasback, five pintail, and five mallard eggs were candled when brought into the hatchery, found to be fresh, and were placed in an incubator. The development of these eggs was followed with the mailing tube candler.

Tolerance of Incubating Pheasant Eggs to Exposure

Michigan's ring-necked pheasant (Phasianus colchicus) population, in common with pheasant populations across the rest of the continent, underwent a decline in the mid-1940's. The decline was characterized by a lessened production of young, as evidenced by lower fall age ratios, and by a decreased proportion of hens observed with broods in summer. The average number of chicks in each brood, however, did not change significantly in Michigan during the years of decline and subsequent recovery. This suggests that the factors operating to limit reproduction prevented entire clutches from being laid or from hatching, or destroyed entire broods, rather than operating by destruction of eggs or chicks one by one. During the early years of the decline there appeared to be some correlation of lowered production of young with lowered mean temperatures and excessive precipitation in spring months. Allen (1946) reported this in Michigan, and Ginn (1948) found an apparent inverse correlation between amount of spring precipitation and fall kill. Kimball (1948) stated that 11 of 12 pheasant workers listed weather as a likely cause of the pheasant depression. In later years of the pheasant and during subsequent recovery, this apparent correlation has not always followed; it is now obvious that there is no simple relationship between spring weather and fall populations. Nevertheless, since climatological factors are influential in determining range of a species, and since there still was the suspicion that annual climatological conditions affect yearly population fluctuations of the shorter-lived species, experimentation to determine climatic toleration of pheasant eggs seemed worthwhile. A series of experiments was devised in which eggs in various stages of incubation were exposed to lowered temperatures or simulated rainfall for varying periods of time. Work was done at the Michigan Department of Conservations's game farm at Mason, Michigan, as part of Pittman-Robertson Project W-38-R, Survey of the Ringnecked Pheasant in Michigan. Examination of the literature reveals references to limited experiments with (1) exposure of unincubated pheasant eggs to lowered temperatures, (2) exposure of incubating pheasant eggs to higher than normal temperatures, (3) exposure of incubating and unincubated chicken eggs to lowered temperatures. But no references to the effects of lowered temperature on incubating pheasant eggs could be found. English (1941) found that unincubated pheasant eggs could be exposed to temperatures as low as 100 F. for a total of 5? hours in three 1ior 2-hour periods on alternate days without appreciable loss of viability. Romanoff et al (1938) reported on the effects of incubation temperatures varying between 950

Studies on host-virus interactions in the chick embryo-influenza virus system. IV. The role of inhibitors of hemagglutination in the evaluation of viral multiplication.

The role of inhibitors of hemagglutination in the evaluation of host-virus interactions in the chick embryo-influenza virus system has been analyzed. Comparisons were made between materials (allantoic fluids and membrane suspensions) derived from in vivo (growth curve) experiments at hourly intervals after inoculation, and from in vitro tests in which normal allantoic fluids and membrane suspensions were incubated with virus at 37 degrees C. for various periods of time. In both instances large amounts of virus were added to the systems, resulting in comparable concentrations of the agent. The seeds employed were either fully active or irradiated by ultraviolet light to the extent that the virus lost its capacity to increase but kept its interfering and hemagglutinating properties. The various materials were assayed for (a) the hemagglutinating titers of the virus present in the systems before and after heating to 56 degrees C.; (b) the concentration of inhibitor in the materials at various stages of incubation after heating to 70 degrees C. for 30 minutes as measured by the hemagglutination-inhibition reaction with native or heated test virus (30 minutes 56 degrees C.); and (c) the degree of adsorption of the hemagglutinins present in the materials onto chicken red cells at 0 degrees C. and their subsequent elution at 37 degrees C. The effects of receptor-destroying enzyme (RDE), treatment with sodium periodate, or high speed centrifugation on the inhibitory activities were studied in some of the tests. The essential results which indicate certain sources of error in the evaluation of host-virus interactions as well as means for studying virus activity at the early stages of the infectious process, were as follows: 1. Though some inhibitory effects on hemagglutination were noticeable in the allantoic fluid during the 1st hour after inoculation they were, as a rule, no longer apparent after this interval, and treatment with RDE did not increase the hemagglutinin titers. Thus, the interpretation of growth curve data concerning allantoic fluids hardly seems to be affected by inhibitor. On the other hand, striking effects were noted with the membrane suspensions of growth curve experiments in that RDE shortened the latent period to 2 hours and the titers in the first few positive samples (4 to 5 hours) increased) whereas in later harvests no such effect was noted. Under these conditions complement-fixation antigens and hemagglutinins made their appearance in the tissues simultaneously and not as previously reported the former prior to the latter. However, the infectivity showed increments only several hours after these two activities had become measurable. Thus the hypothesis of the stagewise development of influenza virus is still supported by these data. 2. Using the inhibition of hemagglutination technic it was found that the inhibitor in allantoic fluid rapidly decreased as a result of the action of active and irradiated virus, but destruction was never complete. In the membranes of the in vivo series only active seed led to loss of inhibitor, again without complete destruction, beginning at the time complement-fixing antigen and hemagglutinins became measurable. Irradiated seed was without effect in vivo whereas, in the in vitro tests it equalled the activity of the active virus. The implications of this difference in the effectiveness of active and irradiated seed in vivo with regard to the understanding of the mode of viral multiplication are discussed. 3. Although many factors may influence the shape of adsorption-elution curves it is felt that at 0 degrees C. the extent of adsorption is directly related to the amount of inhibitor present in the systems. In the early hours after inoculation the degree of adsorption was relatively small but it increased gradually with the time of incubation. The inhibitor of adsorption was destroyed by RDE and NaIO(4) and was only partially sedimentable by high speed centrifugation. In every respect studied its properties corresponded with the findings obtained with inhibitors in the hemagglutination-inhibition technic. Although the difference in the rapidity of inhibitor destruction as measured by the various technics might suggest a multiplicity of inhibitors it is felt that it rather denotes a greater sensitivity of the adsorption technic as compared to the others.

Chorio-Allantoic Grafts of Entire and Fragmented Blastoderms of the Chick

ABSTRACT The most important work which has yet been done in the experimental embryology of early stages of the chick is that of Hoadley, whose principal contributions are contained in four papers (1926 a, b, c, d). Three of these describe chorio-allantoic grafts of transverse one-fifths of blastoderms at various stages of incubation, while the fourth (1926 d) deals with experiments in which the blastoderm was cut into two pieces while remaining in situ on the yolk, the operation again being performed at several different stages.