Showing papers on "Incubation published in 1980"
TL;DR: Water loss during incubation is mandatory if the relative water content of an egg at the end of incubation was to remain essentially the same as at the beginning, and the 11% difference between the altricial and precocial categories is statistically significant.
Abstract: Synopsis. The loss of mass in eggs during incubation was examined and evidence is presented to show that this is essentially due to loss of water. The mean fraction of water lost by diffusion throughout incubation is 0.150 ? 0.025 S.D. per gram of egg and 0.162 ? 0.026 S.D. per gram of egg content for 81 species. The water fraction of fresh eggs and of hatching eggs was examined in 32 species divided according to maturity at hatching, and found to be very similar, within each category (83% in altricial; 83% in semi-altricial; 78% in semi-precocial; 72% in precocial eggs). The 11% difference between the altricial and precocial categories is statistically significant. During incubation, dry matter is metabolized, in? creasing the water fraction which is further increased by metabolic water production. Hence, water loss during incubation is mandatory if the relative water content of an egg at the end of incubation is to remain essentially the same as at the beginning. Equations are de? veloped which allow one to estimate the difference between diffusive water loss and the total water loss in altricial and precocial eggs, caused by additional water loss during pipping and hatching.
292 citations
TL;DR: Differences in growth patterns account for the observed differences in metabolic rates and total energy costs of development in precocial birds and in species that have unusually long incubation periods.
Abstract: Metabolic rates of embryos of precocial birds increase rapidly until about 80% through incubation, then increase slowly remain constant or even decline. In altricial species, embryo metabolic rates increase continuously and at an accelerating rate through out incubation. Total energy cost of development is higher in precocial than in altricial species. Growth patterns of altricial and precocial embryos differ in the same way as does metabolic rate. Embryo growth rates decline late in incubation in precocial species, but increase continuously in altricial species. Embryo metabolic rate in cal/hr (P) is related to embryo mass in grams (M) and growth rate in grams/day (GR) by the equation P = 12.17GR + 1.66M + 1.81. The energy cost of growth in avian embryos is 292 cal/g. The energy cost of maintenance is 1.66 cal/g hr and appeals to be independent of embryo mass. Differences in growth patterns account for the observed differences in metabolic rates and total energy costs of development. High energy costs of maintenance account for high total developmental costs in piecocial species and in species that have unusually long incubation periods.
210 citations
198 citations
TL;DR: A new enzyme-kinetic method based on radioimmunoassay of angiotensin I generated during incubation of plasma and excess sheep or ox renin substrate that does not require prior extraction of renin, is technically simple, and is sufficiently sensitive to measure subnormal renin levels.
145 citations
TL;DR: Results indicate that both water and low dissolved oxygen concentration are necessary for hatching to occur and are likely to exist in the field when stranded eggs are immersed in water.
Abstract: Salinity, pH, dissolved oxygen, hydration, and temperature were examined as possible environmental cues that might intiate hatching in Fundulus heterolitus. Incubation in or transfer to water adjusted to ranges of salinity, pH, and temperature within the physiological range of the species had no direct effect on hatching. Eggs incubated in water with dissolved oxygen concentrations greater than 6 ml O2/L or solutions of Carbowax PEG 4000 producing an osomotic flux of water out of the eggs delayed hatching indefinitely. Incubation of eggs in air delayed hatching, regardless of the pO2. Eggs delayed for periods of up to 1 mo by incubation in air or in highly oxygenated water hatched normally when placed in water of 4 ml O2/L or less. Additionally, eggs that were partially dehydrated by incubation in air did not hatch when placed in a pressurized container of mineral oil. These results indicate that both water and low dissolved oxygen concentration are necessary for hatching to occur. Both of these conditions are likely to exist in the field when stranded eggs are immersed in water.
127 citations
TL;DR: The data support the prediction that in smaller individuals, environmental factors increasingly affect anatid incubation rhythms, and factors affecting the incubation rhythm are examined in order to evaluate the prediction.
Abstract: -Nesting behavior of wild Northern Shovelers (Anas clypeata) was studied in 1974 and 1975 near Delta, Manitoba, Canada. Laying and incubation rhythms are described and adaptive aspects of the incubation rhythm discussed. Factors affecting total time spent off the nest per day, recess frequency, and recess duration are investigated with simple correlation and multiple regression analysis. The data support my prediction that in smaller individuals, environmental factors increasingly affect anatid incubation rhythms. Small size and concomitant critical dependence on food resources during incubation have apparently been important in the evolution of the Northern Shoveler's incubation behavior. The relationship of fasting endurance to body size has probably been of fundamental importance in the evolution of avian incubation behavior. Avian incubation behavior has probably evolved in relation to at least three major factors: (1) physical requirements of the embryos for development; (2) metabolic requirements of the parent(s); and (3) predation on eggs and the parent(s). The requirements of the embryos must be met through incubation behavior that compensates for fluctuating environmental conditions, allow the parent(s) to maintain and/or acquire sufficient energy to support body metabolism, and reduce the probability of predation. Environmental variables have little or no effect on incubation rhythms of Canada Geese (Branta canadensis) or Trumpeter Swans (Cygnus buccinator) (Cooper 1978, 1979). These large waterfowl fast during incubation (MacInnes et al. 1974, Cooper 1978, 1979, Raveling 1979) and their large eggs cool relatively slowly; hence, these birds are able to incubate unaffected by brief environmental fluctuations. Fasting endurance, or the period of time an individual can survive on stored energy, decreases with body size (Calder 1974). Small species are probably unable to subsist exclusively on body reserves during incubation and therefore, must rely more on environmental food resources (Skutch 1962, White and Kinney 1974, Afton 1978, 1979a). Thus, I predict that in smaller anatids as compared with larger, environmental factors should have more effect on incubation rhythms. This paper describes laying and incubation rhythms of the Northern Shoveler (Anas clypeata). Factors affecting the incubation rhythm are examined in order to evaluate my prediction. METHODS The 777-ha study area was located 12 km east of Delta, Manitoba, Canada and has been described in detail by Caldwell (1976). Nesting behavior of wild Northern Shovelers was studied in 1974 and 1975 by direct observation and with strip chart, thermistor-event recorders (Rustrak 2133) that synchronously recorded hen attentiveness and incubation temperatures. The h 's presence at the nest was detected with an infrared photoelectric relay (Microswitch MLS-3). Detailed descriptions of the nest monitoring system and its operation are given in Cooper and Afton (in press). Nests were found by watching females fly to their nests or by flushing hens from cover with a dog or a chain drag device (Higgins et al. 1969). Clutch size and relative amounts of nest down were recorded upon discovery and subsequent visits. In nests found with complete clutches, incubation stage was estimated by opening one egg to determine the age of the embryo. Embryos were aged by comparison with known-age photos as in Caldwell and Snart (1974). Air temperature was continuously recorded on the area with a thermograph (Marshalltown 1000A)+housed 1.2 m above ground in a standard meteorological shelter. Records of daily sunshine duration were obtained from the University of Manitoba Delta Marsh Field Station, 18.5 km west of the study area. Additional weather data were provided by the Canadian Forces Base at Portage la Prairie, 21 km to the south. Although incubation actually begins before the clutch is completed (Afton 1979b), "day 1 of incubation" is defined as the day of clutch completion in order to allow comparisons with previously published information. Periods spent on the nest by the hen are termed "sessions," while periods off the nest are "recesses." "Incubation constancy" is the average percent of time spent on the nest per day (Skutch 1962). Multiple regression analysis was used to investigate factors affecting the incubation rhythm. Data were analyzed using the backward elimination procedure (Draper and Smith 1966:167) with the MULTREG statistical program (Weisberg 1977). A regression model which included all independent variables was calculated as the first step of this procedure. Then, the least important variables, as judged by the reduction of sum of squares unexplained by regression, were individually excluded in subsequent models until all remain-
101 citations
TL;DR: Observations support the view that prolactin is associated with incubation in birds, though the data do not permit a conclusion as to whether an increase in Prolactin secretion causes incubation behaviour or is stimulated by it.
Abstract: The concentrations of prolactin and LH were measured in the plasma of male and female mallards (Anas platyrhynchos) during the breeding season. The concentration of prolactin in the female birds was low before and during egg-laying, increased threefold (P less than 0.001) during incubation and returned to basal levels immediately after the young were hatched. The drakes, which do not participate in incubation in this species, had fairly low prolactin levels throughout the breeding period; levels being slightly higher during the incubation phase than at other times but still much lower (P less than 0.001) than in the incubating females. Concentrations of LH in the females were high during egg-laying but declined at the onset of incubation. In the drakes levels of LH remained high for much longer and did not appear to decline at a fixed time relative to the reproductive cycle of the female birds. These observations support the view that prolactin is associated with incubation in birds, though the data do not permit a conclusion as to whether an increase in prolactin secretion causes incubation behaviour or is stimulated by it.
96 citations
TL;DR: Data are presented for oxygen consumption water loss during incubation water vapor conductance of the shell and pore number of avian eggs and the way in which these values relate not only to egg mass but also to incubation time and it is proposed that all functions are proportional to the product of egg mass and rate of development.
Abstract: Data are presented for oxygen consumption water loss during incubation water vapor conductance of the shell and pore number of avian eggs and the way in which these values relate not only to egg mass but also to incubation time It is proposed that all these functions are proportional to the product of egg mass and rate of development where the latter is defined as the inverse of incubation time These interrelationships account at the end of incubation for similar O2 and CO2 tensions in the air space of eggs utilization of calories (05 kcal g−1) and water loss (15 g g−1)
84 citations
TL;DR: Data suggest that receptor-linked internalization of a polypeptide hormone provides a mechanism that couples degradation of the ligand with loss of the cell surface receptor.
Abstract: 125I-human growth hormone (125I-hGH) binds specifically to receptors on cultures human lymphocytes (IM-9). When this process is studied by use of quantitative EM radioautography, under conditions of incubation at 15 degrees C for 5 min, the ligand is localized to the plasma membrane of the cell. At 30 degrees and 37 degrees C, however, 125I-hGH is progressively internalized by the cell as a function of time. The internalized ligand is found predominantly in the Golgi region of the cells, with a five-fold preferential localization to membrane-bounded structures with the morphological and cytochemical characteristics of lysosomes. Up to 59% of these lysosome-like structures are positive for the acid phosphatase reaction under the conditions of incubation at 37 degrees C for 120 min. When the cell associated radioactivity after 15-120 min of incubation at 37 degrees C is extracted in 1 M acetic acid and filtered on a Sephadex G-100 column, 58-73% of the material elutes as intact hGH. When cells are incubated with 125I-hGH at 37 degrees C for 15-120 min, separated from the incubation medium, and washed and diluted 100-fold, the percent 125I-hGH dissociable decreases as a function of increasing time of incubation. When cells are incubated with 125I-hGH for 15 min at 37 degrees C and the radioactivity that dissociates from the cells during 15-90 min is studied, the labeled material appearing in the incubation medium is progressively degraded as a function of time of incubation. When the dissociation process is studied radioautographically, grains are found both in plasma membrane and intracelluar compartments after 30 min of association, but after 30 and 120 min of dissociation a higher proportion of grains are in the intracellular compartment. After 120 min of association, there is less dissociation from either compartment and a preferential increase of grains in the intracellular compartment. These data suggest that receptor-linked internalization of a polypeptide hormone provides a mechanism that couples degradation of the ligand with loss of the cell surface receptor.
75 citations
TL;DR: Much of the dissolved alanine (800 nm) was biologically unavailable and a more realistic free dissolved pool would be ∼10 nM.
Abstract: The turnover rate constants (k) of alanine in coastal marine sediments were measured using 3H-and 14C-alanine in tracer amounts (less than in situ concentrations of alanine in the porewater). After incubation 14C-label was recovered in free dissolved alanine, adsorbed alanine, volatile fatty acids and carbon dioxide pools. Alanine left the free dissolved pool by two processes: 1) adsorption (k=0.06 min-1) and 2) biological uptake (k=0.16 min-1). Adsorption of alanine was deduced from the persistence of 14C-alanine, which was slowly metabolized after an initial rapid rate of degradation. Adsorption was confirmed in biologically inactivated sediments. The adsorbed 14C-alanine was only partially exchanged by the addition of excess non-labelled alanine, indicating the existence of at least 2 different adsorbed pools. The rates of adsorption and desorption were equal, but the k-values were different, indicating that the adsorbed pool was 2500 fold greater than the free pool. From the biological turnover rate constant (0.16 min-1), the mineralization percentage (80%) and the concentration of alanine (800 nmol l-1 of porewater) a mineralization rate in the sediment of 75 nmol cm-3 d-1 was determined. This was in excess of the measured total NH4+production. It is concluded that much of the dissolved alanine (800 nm) was biologically unavailable and a more realistic free dissolved pool would be ∼10 nM.
69 citations
TL;DR: Tolerance of a broad range of temperatures during development and a slow rate of development represent a suite of physiological adaptations which facilitate breeding success of a species with patterns of parental behavior that impose unusual physiological demands on the developmental process.
Abstract: Embryos of the fork-tailed storm petrel survived exposure to 26, 30, and 34 C. However, during artificial incubation at 26 C, metabolic rate did not increase, and presumably development did not progress. When incubated at 30 and 34 C, eggs showed a gradual increase in metabolism commensurate with development, but success of pipping and hatching was much greater at 34 C than at 30 C. The reduction of metabolic Q10 to 1.55 at temperatures above 34 C suggests that the optimum incubation temperature is near 34 C. Embryos tolerated periodic chilling-24-h exposure to 10 C every fourth day, which simulates environmental conditions when parents neglect the egg during foraging trips. During chilling to 10 C, metabolic rate was only 5% of that at 34 C, and development was presumably arrested. The energy expended by embryos during absence of the parents should thus be negligible. However, the total incubation period is increased, and development is slow even when the egg is warm. Low conductance of the eggshell to w...
TL;DR: Nematodes' tendency to migrate toward warmer temperatures, when placed below incubation temperature, decreased during 6–7 days incubation at 20 or 25 C and the nematodes reversed direction: incubating at 2–5 C inhibited this reversal.
TL;DR: The results suggest that the input CMV genome persists in most initially infected cells, survives PFA incubation, and is active again after PFA release, which differs from abortive CMV infections.
Abstract: Cytomegalovirus (CMV Ad. 169)-induced late antigens are specifically inhibited by phosphonoformate (PFA). Four fresh isolates of CMV were also inhibited by PFA to varying degrees. The kinetics of CMV immediate early antigens (IEA) and early nuclear antigens (EA) produced in the presence of PFA were compared to the early phase of the replicative infection. After anticomplement immunofluorescence with anti-IEA and anti-EA, microimmunofluorometry of individual CMV-infected nuclei was performed. CMV-induced antigens had a two-wave appearance, with maxima at 6 and 24 h postinfection. The same was seen in the presence of PFA. CMV EA-containing cells persisted for more than 5 weeks in the presence of PFA, but decreased in frequency and antigen content. The inhibition of virus replication was reversible after all incubation periods assayed. After PFA release, IEA and EA appeared again in many cells, and the kinetics were similar to that of initial infection. The results suggest that the input CMV genome persists in most initially infected cells, survives PFA incubation, and is active again after PFA release. This differs from abortive CMV infections.
TL;DR: Three experiments on a high-broody strains of chickens that had not been selected for egg production for 50 generations and one experiment on a commercial strain of turkeys were conducted to test the effectiveness of mammalian prolactin (NIH-S10) in inducing regression of the ovary and incubation behavior.
TL;DR: The eggs of sea birds with long incubation times are large in relation to the size of the adult bird in the two species that have been studied, and the high energy content of the egg is paralleled by the greater total amount of oxygen consumed during incubation, so that prolonged incubation probably entails a comparatively high allocation of energy resources to maintenance requirements.
Abstract: Sea birds with long incubation periods are identified, together with the features of their incubation physiology which distinguish them from birds in general. Most sea birds with prolonged incubation are members of the order Procellariformes. The majority of Pelecaniformes and Charadniformes with long incubation periods are tropical species. The total amount of water lost from the egg during incubation is a similar fraction of the initial egg weight in sea birds with prolonged incubation as in other birds. The oxygen consumption of the newly hatched chick is similarly related to the chick weight, regardless of the duration of incubation. Within the constraints imposed by these similarities, sea birds with prolonged incubation display a number of adaptations. The daily rate of water loss from the egg, the water vapor conductance of the egg shell, and the total functional pore area of the egg are all relatively low in sea birds with prolonged incubation. The eggs of sea birds with long incubation times are large in relation to the size of the adult bird in the two species that have been studied, the high energy content of the egg is paralleled by the greater total amount of oxygen consumed during incubation. However, the growth of the embryo is relatively slow in at least one sea bird with a long incubation time so that prolonged incubation probably entails a comparatively high allocation of energy resources to maintenance requirements. In some species with prolonged incubation, the interval between pipping and hatching is also long and it appears to be a period of great physiological importance. Ecologically prolonged incubation is associated with either pelagic feeding habits or a tropical environment, both factors may be related to food supply.
TL;DR: The follicle preparations had the ability to concentrate iodide, synthesize thyroglobulin, and respond to TSH exposition by increased cyclic AMP production and were well preserved after incubation for 5 hr.
TL;DR: It is concluded that (a) the short circulatory t 1/1 ofGTN following clinical administration is explained, at least in part, by rapid metabolism in blood and (b) it is necessary to rapidly centrifuge blood from GTN-treated patients and to freeze the plasma in order to prevent the breakdown of GTN prior to analysis.
Abstract: Nitroglycerin (GTN) (at a concentration of 50 ng/mL) was incubated aerobically at 37 °C with whole blood, resuspended cells, and plasma from five normal volunteers. At several time periods following the initiation of the incubation (0, 1.5, 3, 5, 10, and 20 min for blood and resuspended cells, and 0, 30, 45, 60, 120, and 180 min for plasma) the samples were assayed for GTN in the incubation medium. Linear regression analyses were performed between the logarithm of the percentage GTN remaining and incubation time in order to determine the rate of disappearance of GTN from each system. A short t1/2 for GTN was found in blood (6.2 min) and resuspended red cells (6.6 min) whereas a longer t1/2 of 53.4 min was determined in plasma. These data indicate that the metabolism of GTN in human blood is rapid and predominantly localized in the cellular compartment of the blood. It is concluded that (a) the short circulatory t1/2 of GTN following clinical administration is explained, at least in part, by rapid metaboli...
TL;DR: It is suggested that although voltage‐sensitive channels exist on juxtaglomerular cells, angiotensin II activates an independent pathway for Ca mobilization, which plays an inhibitory coupling role in the control of renin secretion from the ju X‐ray diffraction apparatus.
Abstract: 1. Renin was secreted by rat renal cortical slices incubated at 37 degrees C in a physiological saline solution. 2. Secretion was nearly abolished by incubation in a medium containing 60 mM-K. Secretion could be restored to the control level by the addition of 5 X 10(-7) M-D-600 (methoxy verapamil) to 60 mM-K medium. 3. Angiotensin II inhibited renin secretion in a concentration-dependent manner. Concentrations of D-600 ranging from 1 to 3 X 10(-6) M (two to sixfold higher than required to block the inhibitory effect of high K) failed to antagonize the inhibitory effect of angiotensin II. 4. Ca is required for the inhibitory effect of angiotensin II, however, as Ca-depletion (incubation of slices in a medium with Na2EGTA and no added CaCl2)( progressively decreased and finally abolished any inhibitory effect. 5. These results confirm and extend previous observations suggesting that Ca plays an inhibitory coupling role in the control of renin secretion from the juxtaglomerular apparatus. Moreover, they suggest that although voltage-sensitive channels exist on juxtaglomerular cells, angiotensin II activates an independent pathway for Ca mobilization.
TL;DR: The female enhances while the young (eggs or squab) suppress LH in male ring doves, resulting in an increase in LH following removal of eggs that is more prolonged in late incubation than in early incubation.
Journal Article•
TL;DR: The feces of some normal humans were previously shown to be mutagenic by the Salmonella mutagenicity assay with strain TA100, but this appears to be due to a single type of compound which may be produced by anaerobic bacteria.
Abstract: The feces of some normal humans were previously shown to be mutagenic by the Salmonella mutagenicity assay with strain TA100. In the present study, the mutagenicity of feces of certain donors can be increased by anaerobic incubation for 96 h. The increase in mutagenicity did not occur upon incubation in the cold or in air, in the presence of antimicrobial agents or it the feces were sterilized by heat. On thin-layer chromotographs, the relative mobility of fecal mutagen from all donors after incubation was the same in any one of 4 different solvent systems. The major mutagenicity appears to be due to a single type of compound which may be produced by anaerobic bacteria.
TL;DR: Results indicate that atrazine is not degraded by bacteria but bound, thus simulating biodegradation, and evidence is presented that physicochemical decomposition of the herbicide is more significant than microbial degradation.
Abstract: Degradation of14C-ring labeled atrazine (2-choloro-4-(ethylamino)-6-(isopropylamino)-s-triazine) by bacterial populations from soil, waters and activated sludges was investigated and compared with non-biological decomposition in sterile solutions. Within two weeks, 0.6% Cl-deethyl- and 0.1% Cl-deisopropylatrazine had been formed in sterile 0.02 M phosphate buffer, pH 7.2. In biodegradation studies, bacterial populations were enriched and incubated in media containing atrazine and high or low levels of nutrients. Nutrient supply had a strong effect on the fate of atrazine in bacterial cultures, whereas the origin of bacteria was of minor importance. In 31 of 33 mixed populations investigated, the herbicide was largely converted to unidentified compounds. Incubation with high levels of nutrients resulted in 17% to 57% of these compounds being constant after one and two weeks of incubation. In parallel experiments with low nutrient supply, the compounds were present in amounts of 7% to 57% after one week. The proportions of the unidentified compounds dropped within the second week of incubation, while atrazine reappeared correspondingly. The amounts of dealkylated metabolites generally did not exceed those of sterile solutions. The results indicate that atrazine is not degraded by bacteria but bound, thus simulating biodegradation. Evidence is presented that physicochemical decomposition of the herbicide is more significant than microbial degradation.
TL;DR: The differentiation of retinal ganglion cells was investigated in chick embryos, with special attention to accurate incubation times from stage 20 to after hatching, and the morphological differentiation of these cells comprised four main events.
Abstract: The differentiation of retinal ganglion cells was investigated in chick embryos, with special attention to accurate incubation times from stage 20 (about 3 days of incubation) to after hatching (after 20 days of incubation). The morphological differentiation of these cells comprised four main events:
1.
Shortening of the bipolar processes attached to the inner and outer limiting membranes and the sprouting of an axon from part of the cell body. These were recognized at stage 25 (about 4.5 days of incubation) by Golgi impregnation methods.
2.
Beginning of differentiation of the dedrites, which was recognized at stage 29 to 31 (about 6 or 7 days of incubation).
3.
The rapid development of the dendrites. This occurred at stage 34 (about 8 days of incubation).
4.
The essential completion of the retinal ganglion cells, which was recognized at stage 39 (about 13 days of incubation).
TL;DR: Of the enzymes tested, (1 leads to 3)-beta-D-glucanases are the most effective and their action is markedly enhanced by the addition during incubation of chitinase, trypsin or lipase.
Abstract: SUMMARY: The resistance of Candida albicans to amphotericin B methyl ester increases rapidly as cultures enter the stationary phase of growth; organisms harvested after several days in the stationary phase may have a resistance two or three orders of magnitude greater than that of exponentially growing organisms. This resistance is decreased by incubation of the organisms with enzymes which attack components of the cell wall. Of the enzymes tested, (1 → 3)-β-d-glucanases are the most effective; incubation of 7 d batch cultures with exo-(1 → 3)-β-d-glucanase at a concentration of 10 μg enzyme protein (mg dry wt organisms)-1 for 24 h at 37 °C and pH 6·5 reduces the resistance of the organisms to a value approximating to that of exponentially growing organisms. Resistance is also decreased by treatment with chitinase, lipase, trypsin, α-mannosidase and (1 → 6)-β-d-glucanases but, on a specific activity basis, none of these enzymes is as effective as (1 → 3)-β-d-glucanase. The action of (1 → 3)-β-d-glucanase is markedly enhanced by the addition during incubation of chitinase, trypsin or lipase.
TL;DR: It was concluded that the availability of acetyl-CoA had a decisive influence on both the rate of synthesis ofacetylcholine and its steady-state concentration, and accord with the view that, at the ultimate level, the synthesis of acetycholine is controlled by the Law of Mass Action.
Abstract: Slices of rat caudate nuclei were incubated in vitro in media containing, among other constituents, three different concentrations of glucose (0.5, 2 and 10 mM), 0.2 mM-choline, paraoxon as an inhibitor of cholinesterase, and 5 mM- or 30 mM-K+. After 30 and 60 min of incubation, the concentrations of acetyl-CoA, acetylcholine and choline in the tissue and of acetylcholine in the incubation medium were measured. The content of acetyl-CoA in the sliced varied in direct relation to the concentration of glucose in the incubation medium. The content of acetylcholine in the slices and, in experiments with high K+, also the amount of acetylcholine released into the incubation medium varied in direct relation to the concentration of glucose in the incubation medium and to the concentration of acetyl-CoA in the slices; the relation between the concentrations of acetyl-CoA and of acetylcholine in the slices was linear. It was concluded that the availability of acetyl-CoA had a decisive influence on both the rate of synthesis of acetylcholine and its steady-state concentration. The observations accord with the view that, at the ultimate level, the synthesis of acetylcholine is controlled by the Law of Mass Action.
TL;DR: In quails, H-Y antigen is induced by oestrogens in the gonads of the originally H-y negative homogametic sex but not in non-gonadal tissues, consistent with the view that oestrogen act via H- Y antigen in the organization of the avian gonad.
TL;DR: Several sites on commercial beef, pork and lamb carcasses were sampled at the end of the slaughterline and empirical sampling plans are proposed to detect the highest count on a carcass by bulking samples from known dirty sites.
Abstract: Several sites on commercial beef, pork and lamb carcasses were sampled at the end of the slaughterline. Total viable counts (TVC) of bacteria were assessed by incubation at 37, 20 and 1 degree C in addition to presumptive coliforms (PC), Enterobacteriaceae (ENT) and faecal streptococci (FS). Statistical analyses showed consistently dirty sites within an abattoir but these sites varied from one abattoir to another. Inter-site differences were unaffected by the incubation temperature of the TVC. Numbers of PC, ENT and FS did not mimic TVC. Empirical sampling plans are proposed to detect the highest count on a carcass by bulking samples from known dirty sites. At the end of the slaughterline TVC 37 degrees C is the most useful bacteriological index.
Journal Article•
TL;DR: The results show that the high plasma concentrations of Prl found during incubation are not initiated or maintained only by the stimulus of nesting, and suggest that the decline in Prl levels at the end of incubation could be related to the pipping and hatching of eggs, and the consequent shift to maternal behavior.
TL;DR: Analysis of induction of chromosomal aberration after incubation of V79-379A cells with 10 mM metronidazole in aerobic and hypoxic conditions has shown that, in concordance with cytotoxic effect, this drug exhibits a significant clastogenic action i hypoxic, but not in oxic cells.
Abstract: The analysis of induction of chromosomal aberration after incubation of V79-379A cells with 10 mM metronidazole in aerobic and hypoxic conditions has shown that, in concordance with cytotoxic effect, this drug exhibits a significant clastogenic action in hypoxic, but not in oxic cells. The duration of the post-incubation period after incubation with drug is important for expression of chromosomal damage. It is probable that other nitroaromatic drugs showing enhanced cytotoxicity in hypoxia, which are widely used in medicine, could also belong to such specific class of mutagens.
TL;DR: It is suggested that in vitro incubation with high concentrations of beta-agonists induces a desensitization of the beta-receptor of human myometrium.
Abstract: Isoprenaline and terbutaline relaxed myometrial strips from pregnant women and increased their content of cAMP. The highest measured cAMP concentration, about twice the control level, was determined after a 3-min incubation. Subsequently, the cAMP level declined and approached the basal level after about 60 min. The spontaneous contractions of the myometrial strips were abolished for about 20 min, but reappeared gradually after that time, although the beta-agonists were present in the incubation medium all the time. The decrease of the beta-adrenoceptor responses was not due to an inactivation of the drug tested, or dependent on any diffusible inhibitor substance, since the incubation medium containing the beta-agonist from the 60-min incubation elicited a normal response when added to a fresh myometrial preparation. We suggest that in vitro incubation with high concentrations of beta-agonists induces a desensitization of the beta-receptor of human myometrium.