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PubMed2000

Protein tyrosine phosphorylation during prolonged in vitro incubation of ejaculated bovine spermatozoa is regulated by the oxidative state of the medium.

Protein tyrosine phosphorylation plays a regulatory role in a multitude of physiological processes in sperm. Changes in protein tyrosine phosphorylation, viability, and motility were studied as a function of extended incubation of bovine sperm in vitro at ambient temperature (18-20 degrees C). Fresh ejaculates were incubated after dilution for 8 days. On Days 0, 2, 5, and 8, an aliquot of sperm was incubated with or without theophylline at 37 degrees C for 30 min prior to assessing sperm viability, motility, and tyrosine phosphorylation of soluble and whole-cell proteins. There was a time-dependent decline in sperm motility, which was to some extent reversed by incubation with theophylline. The sum of the phosphotyrosine signal from two soluble proteins (M(r) 67 000 and 36 000) declined with incubation time in both theophylline-treated and untreated sperm. There were major differences in the pattern of tyrosine phosphorylation during incubation between ejaculates from different bulls. Tyrosine phosphorylation of a number of proteins from whole-cell extracts increased in a time-dependent manner during in vitro incubation and was unaffected by the presence of theophylline in the medium. The oxygenation state of the incubation medium had profound effects on sperm motility, viability, and tyrosine phosphorylation of proteins from whole-cell extracts. Sperm motility and viability declined more rapidly under aerobic compared with anaerobic conditions. Tyrosine phosphorylation of proteins from whole-cell extracts increased considerably during anaerobic incubation, while there was no significant change during aerobic incubation. This increase in phosphorylation due to anaerobic incubation was reversed when sperm were transferred from an anaerobic to an aerobic environment, indicating that the oxygenation state of the medium regulates both protein tyrosine kinases and phosphatases. In addition, sperm incubated under aerobic conditions for 5 days retained the ability to phosphorylate proteins when transferred to an anaerobic environment. The increase in protein tyrosine phosphorylation during in vitro incubation took place in a medium that did not contain capacitating substances such as heparin, sodium bicarbonate, or BSA. It transpired over a time scale of days and was not augmented by an increase in intracellular cAMP concentration through phosphodiesterase inhibition. Protein tyrosine phosphorylation during extended in vitro incubation at ambient temperature was significantly inhibited by the presence of oxygen in the medium.

Aerobiosis↗
PubMed1988

Concerning the assays for autonomic nerve receptors. Effects of incubation temperature and time on alterations in the number of receptors.

Alterations in autonomic nerve receptors play an important role in various pathological conditions, including bronchial asthma. Nevertheless, receptor assay conditions such as incubation temperature and incubation time are not consistent among various investigators. This study was designed to clarify the effects of incubation temperature and time on alterations in the number of autonomic nerve receptors. Guinea pig lung membranes were divided into five groups which were incubated under different incubation temperatures and over different incubation times. After incubation, the following experiments were performed. Beta-, alpha-1-adrenergic, and muscarinic acetylcholine receptor assays were performed by direct binding technique using L-3H-dihydroalprenolol, 3H-bunazosin, and L-3H-quinuclidinyl benzilate, respectively. Elevation of incubation temperature and prolongation of incubation time caused a significant decrease in the number of beta-adrenergic receptors and an increase in the number of alpha-1-adrenergic receptors. The number of muscarinic acetylcholine receptors did not change significantly in spite of changes in incubation temperature and time. Adenylate cyclase activity was measured by following the synthesis of cyclic adenosine monophosphate from nonradioactive adenosine triphosphate. Isoproterenol-stimulated adenylate cyclase activity decreased significantly in correspondence with the elevation of incubation temperature and prolongation of the incubation time. Contents of free fatty acids in lung membranes were measured by high-performance liquid chromatography. Free fatty acid contents increased significantly in accordance with elevation of incubation temperature and prolongation of incubation time which reflected on the degradation of membrane phospholipids.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenylyl Cyclases↗
PubMed2006

Embryonic developmental plasticity of the chick: increased CO(2) during early stages of incubation changes the developmental trajectories during prenatal and postnatal growth.

This study investigated the effect of non-ventilation of the incubator during the first 10 days of incubation on carbon dioxide (CO(2)) concentrations in the incubator and its effects on the embryonic and post-hatch development of the chicken (Gallus gallus). Two different incubation conditions were created, one incubator was kept at standard conditions, with adequate ventilation (V) and a second incubator was non-ventilated (NV) during the first ten days of incubation, allowing the CO(2) to rise. After the first 10 days, both incubations were continued under standard conditions. The experiment was repeated twice with different ages of the breeders (45 and 60 wks) which resulted in different CO(2) levels at ED10 (1.5 and 1%). The CO(2) concentration in the V incubators remained below 0.1% in these first 10 days. The eggs of the NV incubation showed higher pCO(2) levels in the air cell from ED10 until ED14 compared to the eggs of the V group. The NV embryos had significantly higher absolute and relative (to egg weight) body weights from ED10 until ED18, pointing to an accelerated embryonic growth. At internal pipping, the NV chick embryos had higher plasma corticosterone and T(3) levels and higher pCO(2) in the air cell. Chicks incubated under NV conditions hatched 10 h earlier in the first and 15 h earlier in the second experiment and the spread of hatch was narrower. During the post-hatch period, the NV chickens had a higher body weight compared to the V chickens. From these results, it is clear that higher levels of CO(2) during the first ten days of incubation have persistent (epigenetic) effects during the incubation and early post-hatch period.

Animals↗
PubMed2005

Effect of eggshell temperature during incubation on embryo development, hatchability, and posthatch development.

An experiment was conducted to study the effects of different eggshell temperature (EST) profiles during incubation on embryo mortality, hatchability, and embryo development. Furthermore, chicks from different EST profiles were reared under low and high housing temperatures to investigate subsequent posthatch growth and rectal temperature. Two batches of eggs were used in this experiment. Hatching eggs were subjected to 36.7 or 37.8 degrees C EST during the first week, to 37.8 degrees C EST during the second week, and to 37.8 or 38.9 degrees C EST during the third week of incubation. Posthatch housing temperature decreased from 35 degrees C at d 1 to 30 degrees C at d 7 (high) or decreased from 30 degrees C at d 1 to 25 degrees C at d 7 (low). The difference between machine temperature and EST (DT) was used to illustrate the effect of EST on heat production during incubation. DT differed per batch, and was smallest when eggs were incubated at 36.7 degrees C instead of 37.8 degrees C during wk 1. High EST during wk 3 of incubation (38.9 degrees C instead of 37.8 degrees C) reduced DT only in batch 2. Embryo development was most retarded in eggs incubated at 36.7 degrees C EST compared with at 37.8 degrees C during the first week of incubation. However, highest hatchability and embryo development were always found when EST was maintained at 37.8 degrees C constantly throughout incubation. Chicks that hatched from eggs incubated at low EST during wk 1 of incubation had lower rectal temperature after hatching, especially under low housing temperatures, and this effect lasted until 7 d posthatch in batch 1. The highest rectal temperatures were always found in chicks incubated at 37.8 degrees C EST constantly throughout incubation. Eggs and chicks from different batches require different environmental conditions for optimal embryo development, hatchability, and posthatch growth. Rearing temperature and incubation conditions affect the ability of young chicks to maintain their rectal temperature during the first week posthatch.

Animals↗
PubMed2000

Influence of selection for increased body weight, egg production, and shank width on the length of the incubation period of turkeys.

An experiment was designed to study the influence of selection for increased 16-wk BW (F line), egg production (E line), and shank width (FL line) in turkeys on length of the incubation period and to estimate the influence of adult BW (BW50) and egg weight on the incubation period. The base populations for the F, FL, and E lines were randombred control (RBC)2, F, and RBC1, respectively. An additional RBC (RBC3) was also included in the study. The experimental turkey lines differed in length of the incubation period in all trials, indicating genetic differences exist. The E line, in general, had a longer incubation period than the RBC1 line, due to an increase in the time required for external pipping. The FL line had a longer period of incubation than the F line. Differences in the length of the incubation period between the F and RBC2 lines were inconsistent. The F line had a shorter incubation period than the RBC2 line in Trial 1, whereas there was no difference between lines in Trial 2. In Trial 3, the comparison of the F and RBC2 lines was influenced by treatment of the eggs prior to setting. When the eggs were held at room temperature for 29 h prior to setting, the F line had a longer incubation period than the RBC2 line, whereas when the eggs were set directly from the egg cooler, there was no line difference. The line differences in length of the incubation period could not be explained by line differences in egg weight based on a comparison of line means for these traits. Within lines, the regression of length of the incubation period on egg weight was positive and significantly different from zero in three of the six lines. Overall regression of hatching time on egg weight and BW50 was positive for egg weight and negative for BW50. However, only 4% of the variation in the length of the incubation period could be explained by variation in egg weight and BW50. Within lines, the regression coefficient of length of the incubation period on BW50 was not significantly different from zero in any line but the sign was negative in five of six lines.

Animals↗
PubMedDate not supplied

The influence of incubator wall on the irradiation intensity of phototherapy.

A clear dose-response relationship has been demonstrated between the irradiance and the effectiveness of phototherapy. This study is designed to detect if there is any difference in irradiance between the inside and outside of different types of incubators. Forty-four incubators of two different types and with ages up to 18 years were included. In comparison with the measurement taken outside an incubator, the mean spectral irradiance detected within a single-walled incubator was significantly decreased (p < 0.001) while that detected within a double-walled incubator was slightly increased (p = 0.014). The reduction of spectral irradiance within an incubator correlated with the degree of incubator wall damage with a maximal loss of 15%. However, the irradiance did not correlate with the age of the incubator. In conclusion, the spectral irradiance received within an incubator was influenced by the type of incubator and the wall damage. Measuring the irradiance within an incubator prior to phototherapy should be emphasized, especially for those incubators with severely damaged walls.

Dose-Response Relationship, Radiation↗
PubMed2004

Incubation temperature for ostrich (Struthio camelus) eggs.

The impact of incubation temperature on egg weight loss, embryonic mortality, incubation period, hatchability, and chick weight in 394 ostrich (Struthio camelus) eggs was studied. Eggs were obtained from 3 farms in Texas. Three incubation temperatures (36.5, 37.0, or 37.5 degrees C) with relative humidity ranging from 20 to 30% were used. Results showed that incubation of fertile eggs at 36.5 degrees C increased hatchability and incubation period in comparison with other treatments. The incidence of dead in shell and total dead embryos was increased at 37.5 degrees C when compared with 36.5 degrees C. No differences in hatchability, incubation period, dead-in-shell embryos, and total dead embryos were observed between eggs incubated at 37.0 or 37.5 degrees C. Neither chick weight nor egg weight loss at 7, 14, 28, or 38 d of incubation was affected by incubation temperature, but egg weight loss at 21 d was lower for eggs incubated at 37.5 degrees C than for the other treatments. Results show that the most effective incubation temperature for the ostrich is lower than the most effective incubation temperature for most bird species.

Animals↗
PubMed1990

Analysis of linkage between scrapie incubation period and the prion protein gene in mice.

A single gene is known to have a predominant influence on scrapie incubation period in mice. In crosses between strains that give a short incubation period, such as NZW mice, and those which give a long incubation period, such as I/LnJ mice, long incubation period was dominant using a Chandler scrapie agent isolate. Recently a close linkage was found between the incubation period gene and the prion protein (PrP) structural gene in I/LnJ mice crossed to NZW mice. Because this linkage suggested an important role for PrP in the pathogenesis of scrapie we sought to verify the linkage between these genes and extended the analysis to three additional mouse strains. All four of the mouse strains that we evaluated, I/LnJ, P/J, MA/MyJ, and RIIIS/J, had incubation periods longer than those of the NZW mice to which they were crossed. In addition, all four strains shared an XbaI restriction enzyme polymorphism, which suggested that all four strains might also exhibit linkage between the incubation period and the PrP structural gene. Very strong linkage between PrP and incubation period was found in I/LnJ and P/J mice crossed to NZW mice, whereas less obvious linkage was demonstrated for MA/MyJ mice crossed to NZW mice. In MA/MyJ mice genes other than PrP also had an obvious influence on incubation period. In RIIIS/J mice no linkage was shown. Although linkage between PrP and incubation period was very significant in I/LnJ and P/J mice, a few animals were identified in both crosses that represented potential recombinants in which PrP and incubation period did not segregate together. Therefore, although these phenotypes are certainly linked in I/LnJ and P/J mice, it is possible that PrP and incubation period are controlled by separate genes.

Animals↗
PubMed1983

Effect of atmosphere and duration of incubation on primary isolation of group A streptococci from throat cultures.

The optimal incubation conditions for isolation of group A streptococci from throat cultures are controversial. Therefore, we compared the effects of aerobic and anaerobic incubations after 24 and 48 h on the recovery of group A streptococci. Throat swabs submitted to the clinical laboratory were inoculated onto duplicate 5% sheep blood agar plates, incubated aerobically or anaerobically (GasPak jar) at 35 degrees C, and examined semiquantitatively after 24 and 48 h. Group A streptococci were identified by the fluorescent-antibody technique. Of 1,040 specimens, 506 (48.6%) grew beta-hemolytic streptococci, including 200 (19.2%) group A streptococci. Group A streptococci were recovered significantly more often with anaerobic incubation than with aerobic incubation after 24 h (182 versus 138; P less than 0.001) and after 48 h (193 versus 174; P less than 0.05). Non-group A beta-hemolytic streptococci also were recovered significantly more often with anaerobic incubation after 24 and 48 h (P less than 0.001). Colony counts were not affected by the incubation atmosphere. We conclude that incubation of throat cultures in an anaerobic atmosphere is superior to incubation in air for detection of group A streptococci. The greater sensitivity of anaerobic incubation, however, may not justify the extra laboratory effort and cost required to differentiate group A streptococci from the non-group A streptococci detected as a result of anaerobic incubation. Throat cultures should be examined after 24 and 48 h, especially if plates are incubated aerobically.

Adult↗
PubMed1986

Factors affecting prolactin secretion during the breeding cycle of the ring dove (Streptopelia risoria) and its possible role in incubation.

Plasma prolactin began to increase significantly about 5 days after the onset of incubation in both sexes of the dove to reach a peak at the time of hatch. At this time, the concentration of prolactin in the plasma of the female was significantly higher than in the male. In the middle of the incubation period prolactin levels measured over a 24-h period remained constant in both sexes, although the male sits during the middle of the day and the female for the rest of the time. Nest deprivation resulted in a sharp, significant decline in the concentration of prolactin in both sexes. Newly hatched squabs stimulated the release of prolactin only in those doves which had been incubating eggs for several days. A distinct sex difference was observed in the expression of nest defence behaviour of the ring dove during the breeding cycle. At the time of laying, the female was significantly more aggressive than the male and her aggression increased only slightly up to the time of hatching. In contrast, male aggression increased gradually from a low level at laying to reach a peak at the time of hatching. The levels of plasma progesterone in the female showed a significant increase around the time of lay. No significant changes occurred in the plasma concentration of either progesterone or 17 alpha-hydroxyprogesterone in the male. Administration of prolactin increased the length of time of incubation of infertile eggs. Nest manipulations which had the effect of inducing the doves to begin incubation 4 days before laying showed that (1) the length of time of incubation of infertile eggs is fixed and independent of events which occur at courtship or oviposition, (2) the initiation of the increase in plasma prolactin concentration during incubation is independent of events which occur at courtship and oviposition and (3) the termination of incubation is always preceded by a fall in the concentration of plasma prolactin. It is concluded that the length of time of incubation is dependent upon sustained raised levels of plasma prolactin. The concentration of plasma prolactin increases several days after the onset of incubation in response to the tactile stimulation of sitting. High levels, if maintained by visual stimulation from the nest, maintain incubation for a fixed period. After this, if the eggs fail to hatch, prolactin levels fall and the doves cease incubation and begin a new cycle.

Animals↗
PubMed2000

Effect of short periods of high incubation temperature on hatchability and incidence of embryo pathology of turkey eggs.

1. Turkey eggs were incubated at 38.0 degrees and 38.5 degrees C at different stages of embryo development and for periods of 3 to 25 d. Results were compared with control eggs incubated at 37.5 degrees C. The age of mortality, the incidence of malpositions and the incidence of morphological abnormalities were recorded from all unhatched eggs. 2. Eggs incubated at 38.5 degrees C for 5 or more days hatched significantly less well than eggs incubated at 37.5 degrees C. Eggs incubated at 38.5 degrees C for 3 d hatched worse than controls but not significantly so. Eggs incubated between 0 and 25 d and 7 and 12 d but not between 0 and 6, 13 and 18 and 19 and 25 d, at 38.0 degrees C had significantly lower hatchabilities than eggs incubated at 37.5 degrees C. 3. Lowest hatchabilities were obtained when the eggs were incubated at high temperatures between 7 to 12 d and 6 to 10 d, indicating that embryos at this stage of development are more likely to succumb to high temperature than at other ages. 4. Increases in embryo mortality due to overheating were seen in weeks 3 and 4 of incubation and at the pipping stage. This was observed even when the period of overheating occurred in weeks 1 and 2 of incubation. 5. Embryos malpositioned with their head in the small end of the egg were seen at a higher incidence when overheating in the 2nd or 3rd quarter of the incubation period.

Animals↗
PubMed1999

The effect of clutch cooling rate on starling, Sturnus vulgaris, incubation strategy.

In avian species where only one parent incubates, that parent must divide its time between the mutually exclusive activities of incubation and foraging in such a way as to maintain both body condition and clutch temperature within certain limits. In a uniparental incubator, the starling, we experimentally reduced the rate at which unattended clutches of eggs cooled down and monitored the resulting changes in the parent's incubation strategy. Opposite to the predictions of standard models of time allocation during incubation, parents spent a much greater percentage of each 24-h period incubating when the rate of clutch cooling was reduced. Incubation bouts lasted significantly longer on experimental nests than on control nests, both during the daytime and overnight. Mean foraging bout duration did not differ between the two groups of nests. These results are consistent with the hypotheses that parental foraging success cues the end of a foraging bout, and that parental energy level cues the end of an incubation bout. However, most previous studies suggest that parents spend less time incubating when the rate of clutch cooling is slow. If parental energy level cues departure, these results can be explained only if the amount of time available for incubation is constrained in these cases by the time a parent must spend foraging in order to maintain body condition. Such parents should take more time away from incubation when the unattended clutch cools slowly, as this is when the cost of being absent is minimized. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2005

The effect of gamete co-incubation time during in vitro fertilization with frozen-thawed unsorted and sex-sorted ram spermatozoa on the development of in vitro matured adult and prepubertal ewe oocytes.

In vitro matured adult (Experiment 1) and prepubertal (Experiment 2) ewe oocytes were co-incubated with unsorted or sex-sorted frozen-thawed spermatozoa for 2 to 3 h (short) or 18 to 20 h (long) to determine the effects of reducing the gamete co-incubation time during IVF on subsequent embryonic development in vitro. For oocytes derived from adult ewes, there were no differences in oocyte fertilization and cleavage at 24 h post insemination (hpi) between types of spermatozoa or co-incubation times (P > 0.05). By 48 hpi, oocyte cleavage was higher after a short (390/602, 64.8%) compared with a long (381/617, 61.7%) co-incubation (P < 0.05), and was not significantly different for unsorted (266/372, 71.5%) and sex-sorted (505/849, 59.9%) spermatozoa. Blastocyst formation from cleaved oocytes was similar for unsorted (150/266, 56.4%) and sex-sorted (295/505, 58.4%) spermatozoa, but was higher after a short (240/390, 61.5%) than long (205/381, 53.8%) co-incubation (P < 0.05). Oocyte development to the blastocyst stage was not different for unsorted (150/372; 40.3%) and sex-sorted (295/847; 34.8%) spermatozoa but was significantly increased by a short (240/602, 39.9%) compared with a long (205/617, 33.2%) co-incubation. Fertilization of oocytes from prepubertal ewes was similar for types of spermatozoa and for duration of co-incubation. Oocyte cleavage (48 hpi) was similar for a short (241/377, 63.9%) and long (226/349, 64.8%) co-incubation with unsorted spermatozoa, but was increased (P < 0.05) by a long co-incubation (286/500, 57.2% versus 163/517, 31.5%) with sex-sorted spermatozoa. Blastocyst formation from cleaved oocytes was similar for unsorted (230/467, 49.3%) and sex-sorted (186/449, 41.4%) spermatozoa, and a short (200/404, 49.5%) or long (216/512, 42.1%) co-incubation. However, oocyte development to the blastocyst stage was higher (P < 0.05) after IVF with unsorted (230/726, 37.1%) than sex-sorted (186/1017, 18.3%) spermatozoa. Reducing the duration of gamete co-incubation did not deleteriously affect the in vitro development of adult and prepubertal ewe derived oocytes after IVF with unsorted and sex-sorted spermatozoa. In general, sex-sorting had no substantial influence on fertilization and embryo development rates.

Animals↗
PubMed2002

Effect of preculture freezing and incubation on bacteriological isolation from subclinical mastitis samples.

In this study the sensitivity of three methods of isolation of udder pathogens from milk samples from subclinical mastitis cases was compared. For analysis 1827 quarter milk samples were selected. Milk was cultured using a standard culture technique (0.01 ml of fresh milk streaked on a sheep blood agar plate and on Edward's medium). In addition, an inoculum of 0.01 ml of the original milk sample was incubated for 24h at 37 degrees C in broth, followed by culture using the standard culture technique. In the third method, the whole milk sample was frozen for 24h, and then incubated for 24h at 37 degrees C, followed by culture using standard culture technique. The isolation percentage of Staphylococcus aureus was 4.7% for standard culture technique, 14.2% for incubation in broth, and 21.5% for the combination of freezing plus incubation. Isolation percentage of Streptococcus dysgalactiae and Streptococcus agalactiae was highest using the standard culture technique, while isolation rate of Streptococcus uberis was not different among the three methods used. With increasing somatic cell count, the likelihood of S. aureus, S. dysgalactiae and S. uberis isolation increased. Based on the relative sensitivity, defined as the isolation rate using a single technique compared to the isolation rate of the three techniques together, a combination of standard culture technique and freezing plus incubation was most attractive for achieving a high isolation rate of S. agalactiae and S. dysgalactiae. Relative sensitivity of S. uberis isolation was highest using the standard culture technique and incubation in broth, while S. aureus was most often isolated using a combination of incubation in broth and freezing plus incubation. A combination of the three methods increased the isolation rate for S. dysgalactiae, S. uberis and S. aureus. The standard culture technique, together with the combination of freezing plus incubation, can be recommended for isolating major udder pathogens. If S. aureus is the pathogen of main interest, using incubation in broth together with the combination of freezing plus incubation performed best.

Animals↗
PubMed2005

Effect of intensity of eggshell pigment and illuminated incubation on hatchability of brown eggs.

The effects of intensity of brown eggshell pigment (light (LBP), medium (MBP) and dark (DBP)) and light intensity during incubation (low and high, 900 to 1380 and 1430 to 2080 lux, respectively) on eggshell characteristics, embryonic growth, hatchability traits, chick hatching weight and hatching time were investigated using eggs from a meat-type breeder (Hybro) flock at 32, 36 and 41 weeks of age in three trials. With eggs of similar weights the intensity of brown pigment was not associated with eggshell weight and thickness, and did not influence embryo weight and egg weight loss during incubation. The shade of brown pigment of eggs laid by young hens influenced the percentage hatchability (HP) of eggs incubated under light. Illuminated incubation improved HP of LBP eggs (compared with MBP and DBP eggs) from 32- and 36-week-old hens, but had no significant effect on HP of eggs from 41-week-old hens. Light intensity during incubation did not influence egg weight loss. High intensity of light during incubation reduced HP and increased early death percentage (EDP) in the LBP and MBP groups, and did not influence HP and EDP in the DBP group. Brown eggshell pigment and intensity of light during incubation did not influence hatching time. It is concluded that the shade of brown pigment, intensity of light during incubation and age of the breeder hens influenced the hatchability performance of embryos from brown eggs. Light during incubation improved the hatchability of embryos in light brown eggs laid by young hens and the shade of brown pigment of eggs laid by older hens did not influence hatchability under illuminated incubation. High intensity of light during incubation reduced hatchability of light and medium brown eggs, but not the dark brown eggs.

Animals↗
PubMed1989

Host genetic control of incubation periods of Creutzfeldt-Jakob disease in mice.

Host genetic control of the incubation period of Creutzfeldt-Jakob disease (CJD) was studied using various inbred strains of mice, including B10 congenic strains. Various incubation periods were found in mice injected either intracerebrally or intraperitoneally with the Fukuoka 1 strain of the CJD agent; NZW/Sea and A/JJms had the shortest, and B10.AKM/Ola and C57BL/6J the longest, incubation periods. Length of the CJD incubation period did not correlate with the genetic markers tested, i.e. the murine major histocompatibility (H-2) complex (which has previously been reported to be linked to a gene influencing CJD incubation period in mice), coat colour or sex genes. In NZW/Sea x C57BL/6J F1 hybrid mice the CJD incubation periods were similar to that of the parent with the longest incubation period. Incubation periods of the backcross progeny from F1 and NZW/Sea were intermediate between those of the parental mice and had a unimodal distribution pattern. A similar observation was made on the progeny of the A/JJms x C57BL/6J mating. On the other hand, the length of incubation period for the NZW/Sea x B10.AKM/Ola F1 hybrid fell between those for the two parents and the NZW/Sea x A/JJms F1 hybrid had a significantly longer incubation period than those of the two parents. These results suggest that polygenes probably control the length of the CJD incubation period in mice.

Alleles↗
PubMed2000

Evolution of passerine incubation behavior: influence of food, temperature, and nest predation.

Incubation behavior is one component of reproductive effort and thus influences the evolution of life-history strategies. We examined the relative importance of body mass, frequency of mate feeding, food, nest predation, and ambient temperature to explain interspecific variation in incubation behavior (nest attentiveness, on- and off-bout durations, and nest trips per hour) using comparative analyses for North American passerines in which only females incubate. Body mass and frequency of mate feeding explained little variation in incubation behavior. We were also unable to detect any influence of foot; diet and foraging strategy explained little interspecific variation in incubation behavior. However, the typical temperature encountered during reproduction explained significant variation in incubation behavior: Species breeding in colder environments take shorter bouts off the nest, which prevents eggs from cooling to temperatures below the physiological zero temperature. These species must compensate for shorter off-bouts by taking more of them (thus shorter on-bouts) to obtain needed energy for incubation. Nest predation also explains significant variation in incubation behavior among passerines: Species that endure high nest predation have evolved an incubation strategy (long on- and off-bouts) that minimizes activity that could attract predators. Nest substrate explained additional variation in incubation behavior (cavity-nesting birds have shorter on-bouts and make more frequent nest trips), presumably because nest predation and/or temperature varies among nest substrates. Thus, nest predation can influence reproductive effort in a way previously not demonstrated--by placing a constraint on parental activity at the nest. Incubating birds face an ecological cost associated with reproductive effort (predation of entire brood) that should be considered in future attempts to explain avian life-history evolution.

Animal Feed↗
PubMed1972

Effect of several components of anaerobic incubation on antibiotic susceptibility test results.

The factors influencing the in vitro activity of antibiotics during anaerobic incubation were studied by the disc method with a facultative organism, Escherichia coli. We observed the effects of incubation aerobically, anaerobically (Torbal jars), in a CO(2) incubator, and aerobically and anaerobically with all CO(2) removed. We also monitored pH changes during incubation and observed the effect of two different initial agar pH values (7.4 and 8.3). With aminoglycosides, zones were larger at pH 8.3 and, in each agar pH group, zones were decreased by incubation with increased CO(2) (anaerobically and CO(2) incubator). A fall in agar pH took place during the first 5 to 7 hr of incubation when increased CO(2) was present. Decreased aminoglycoside zones in the presence of increased CO(2) were due to fall in agar pH. Erythromycin showed the same zone size changes as the aminoglycosides. Chloramphenicol zones were somewhat smaller at the lower medium pH. Zones around tetracycline discs were largest after incubation anaerobically. Further aerobic (or CO(2)) incubation of plates after anaerobic incubation resulted in large "zones of relative inhibition" around the aminoglycoside discs. This suggests that these antibiotics had become more active after exposure to aerobic conditions. Our studies indicate that antibiotic susceptibility test results can be significantly altered by several components of anaerobic incubation including changes in agar pH and CO(2) concentration as well as anaerobiosis per se.

Anaerobiosis↗