Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

Factors Affecting Incubation Rhythms of Northern Shovelers

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-

C3e: an acidic fragment of human C3 with leukocytosis-inducing activity.

Abstract: We have isolated a leukocytosis-inducing peptide of degraded human C3 that has the electrophoretic behavior of prealbumin and a m.w. of 10,000 to 12,000. The peptide has been designated C3e. It was generated by two methods: Incubation of isolated C3 with 2% (w/w) trypsin for 120 min at 37°C, or incubation of serum at 37°C for 5 days under sterile conditions. C3e preparations obtained by the two methods were virtually indistinguishable with respect to molecular size, amino acid composition, and immunochemical properties. The electrophoretic mobility of C3e at pH 8.6 is -7.5 × 10 -5 cm 2 V -1 sec -1 . Anti-C3e reacts with C3e, C3, C3b, and C3c, but not with C3a or C3d. Since the β-chain of C3 is not affected by the liberation of C3e, it is concluded that C3e arises from cleavage of the portion of the α-chain that is part of the C3c fragment. Purified C3e was found to mobilize leukocytes from bone marrow upon perfusion of isolated rat femur. Intravenous injection of C3e into rabbits caused a 2- to 3-fold increase in the number of circulating leukocytes after 60 min which lasted 2 hr. Leukocytosis was preceded by mild leukopenia. Leukocytosis-inducing activity was abrogated by treating C3e preparations with solid phase anti-C3. Incubation of heparinized rabbit blood with radioiodinated C3e resulted in preferential binding of C3e to polymorphonuclear leukocytes. Intradermal injection of C3e into rabbits evoked increased vascular permeability after 15 to 30 min. The evidence indicates that C3e is a fragment of C3 with biologic activity distinct from that of other C3 fragments.

Effects of aflatoxin B1 on the development of the bursa of Fabricius and blood lymphocyte acid phosphatase of the chicken.

Abstract: 1. In this study, embryotoxicity and effects of in ovo administration of aflatoxin B1 (AFB1) on the embryonic development of the bursa of Fabricius were determined in fertilised chicken eggs by histological methods and histochemical demonstration of acid phosphatase (ACP-ase) enzyme. Peripheral blood lymphocyte percentages were also estimated. 2. Embryonic stages were determined according to the Hamburger-Hamilton (H-H) scale. Mortality rates increased in AFB1-injected groups in a dose-dependent manner. Embryonic deaths were concentrated at H-H 31 in the 5 ng AFB1/egg group while the deaths were highest at H-H 25 in the 10 and 20 ng AFB1/egg groups. In the 40 ng AFB1/egg group, embryonic deaths mostly occurred during the first 70 to 72 h of incubation (H-H 20). 3. Bursal development was quite similar at d 7 of incubation in control and all experimental groups although development had been substantially impaired and retarded at d 10 of incubation in 10, 20 and 40 ng AFB1/egg groups. A gradual decrease of A...

Co-incubation of human spermatozoa with Chlamydia trachomatis serovar E causes premature sperm death

Abstract: The aim of this work was to investigate the effect of elementary bodies (EB) of Chlamydia trachomatis serovars E and LGV on sperm motility, viability and acrosomal status. Highly motile preparations of spermatozoa from normozoospermic patients were co-incubated for 6 h with 0.54x10(6) EB per ml. At 1, 3 and 6 h of incubation, sperm motility was determined by computer-assisted semen analysis (CASA) and the proportion of dead cells determined by the hypo-osmotic swelling (HOS) test. Acrosomal status was also examined using a standard monoclonal antibody assay. In the absence of EB, the percentage of motile spermatozoa remained >69% over the 6h incubation and the proportion of dead spermatozoa at <12%. However, during the incubation with EB of serovar E there was a significant decline in the percentage of motile spermatozoa (P < 0.05), and a corresponding increase in the proportion of dead spermatozoa (P < 0.05) at all time-points. However, following incubation with serovar LGV, only the percentage of dead spermatozoa after 6 h incubation was significantly different from the control (P < 0.05). The amount of acrosome-reacted spermatozoa remained unchanged (<16%) in all incubations at all time-points. Dose-response experiments indicated that increasing the concentration of EB to 2.5x10(6) per ml did not significantly alter the results. Furthermore, co-incubation of spermatozoa with dead EB (killed by heat treatment) abolished the chlamydia-mediated response, indicating that the effect is a result of the live organism and not soluble components or membrane elements. These data suggest that a detrimental effect on sperm function by some serovars may be an as yet unrecognized component of infertility problems.

Rapid formation of hydrogen-producing granules in an anaerobic continuous stirred tank reactor induced by acid incubation.

Abstract: A novel approach to rapidly initiate granulation of hydrogen-producing sludge was developed in an anaerobic continuous stirred tank reactor at 37 degrees C. To induce microbial granulation, the acclimated culture was subject to an acid incubation for 24 h by shifting the culture pH from 5.5 to 2.0. The culture was resumed to pH 5.5 after the incubation and the reactor was operated at hydraulic retention times (HRTs) of 12, 6, 2, 1, and 0.5 h in sequence. Microbial aggregation took place immediately with the initiation of acid incubation and granules were developed at 114 h. No granule was observed in the absence of acid incubation in the control test. Changing the culture pH resulted in improvement in surface physicochemical properties of the culture favoring microbial granulation. The zeta potential increased from -11.6 to -3.5 mV, hydrophobicity in terms of contact angle improved from 31 degrees to 43 degrees and extracellular proteins/polysaccharides ratio increased from 0.2 to 0.5-0.8. Formation of granular sludge facilitated biomass retention of up to 32.2 g-VSS/L and enhanced hydrogen production. The hydrogen production rate and hydrogen yield increased with the reduction in HRT at an influent glucose concentration of 10 g/L once steady granular sludge layer was formed, achieving the respective peaks of 3.20 L/L x h and 1.81 mol-H(2)/mol-glucose at 0.5 h HRT. The experimental results suggested that acid incubation was able to initiate the rapid formation of hydrogen-producing granules by regulating the surface characteristics of microbial aggregates in a well-mixed reactor, which enhanced the hydrogen production.