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PubMed1995

Effects of Incubation Time and Temperature on In Vitro Selective Delignification of Silver Leaf Oak by Ganoderma colossum.

The effects of incubation time and temperature on the ability of isolates of the chlamydosporic and thermophilic fungus Ganoderma colossum (Fr.) C. F. Baker to cause selective delignification of Quercus hypoleucoides A. Camus were evaluated by standard in vitro agar block tests. Chemical and scanning electron microscopy studies of decayed wood were used to determine the extent of selective delignification or simultaneous decay caused by each fungal isolate. At 35 deg C, the percent weight loss increased from 6.1% after 4 weeks to a maximum of 32.5 to 33.0% after 16 and 20 weeks of incubation. The average percent Klason lignin-chlorite holocellulose ratios (PKL/CHC) decreased from 0.35 in the control wood block to 0.22 in wood blocks incubated for 12 weeks; this indicated selective delignification. The average PKL/CHC increased for the 16- and 20-week incubation periods, indicating greater removal of polysaccharides during longer incubation periods. In temperature studies, the percent weight loss after 12 weeks was 26 to 27% between 30 and 40 deg C and less than 16% for the 25 and 45 deg C treatments. The average PKL/CHC ranged from 0.18 to 0.16 between 35 and 40 deg C, whereas they were 0.23 and 0.31 for the 25 and 45 deg C treatments, respectively. Scanning electron microscopy confirmed an optimum temperature range near 35 to 40 deg C and incubation times of 8 to 12 weeks for selective delignification. Under these conditions, ray parenchyma, fiber tracheids, and vessels were devoid of middle lamella; pit regions of cells were visible with significantly enlarged apertures; and individual cells were separated and clearly delimited. Extensive delignification of wood occurred throughout the wood blocks evaluated. Incubation times longer than 12 weeks resulted in greater degradation of wood cell walls and thus in greater removal of the polysaccharide component of the wood. For incubation times of 4 weeks or a temperature of 25 deg C, limited to no degradation of cells was observed. At 45 deg C, walls of fiber tracheids were eroded and ray parenchymal cells were extensively degraded, indicating that simultaneous degradation of cell walls occurred. Thus, the incubation temperature influenced the type of decay by G. colossum observed on oak wood blocks: extensive selective delignification at 35 to 40 deg C after more than 8 weeks of incubation or simultaneous decay at 45 deg C with 14% weight loss after 12 weeks of incubation. Isolates of G. colossum may prove useful in studies on mechanisms of delignification and biotechnological applications (e.g., biopulping) of lignin-degrading fungi.

Journal Article↗
PubMed2003

Effect of incubation temperature on isolation of Campylobacter jejuni genotypes from foodstuffs enriched in Preston broth.

Preston broth and agar incubated at either 37 or 42 degrees C have been widely used to isolate campylobacters from foodstuffs. The consequences of using either incubation temperature were investigated. Retail packs of raw chicken (n = 24) and raw lamb liver (n = 30) were purchased. Samples were incubated in Preston broth at 37 and 42 degrees C and then streaked onto Preston agar and incubated as before. Two Campylobacter isolates per treatment were characterized. Poultry isolates were genotyped by random amplification of polymorphic DNA (RAPD), pulsed-field gel electrophoresis (PFGE), and flagellin PCR-restriction fragment length polymorphism, and lamb isolates were genotyped by RAPD only. In total, 96% of the poultry and 73% of the lamb samples yielded campylobacters. The lamb isolates were all Campylobacter jejuni, as were 96% of the poultry isolates, with the remainder being Campylobacter lari. The incubation temperature had no significant effect on the number of positive samples or on the species isolated. However, genotyping of the C. jejuni isolates revealed profound differences in the types obtained. Overall (from poultry and lamb), the use of a single incubation temperature, 37 degrees C, gave 56% of the total number of RAPD C. jejuni genotypes, and hence, 44% remained undetected. The effect was especially marked in the poultry samples, where incubation at 37 degrees C gave 47% of the PFGE genotypes but 53% were exclusively recovered after incubation at 42 degrees C. Thus, the incubation temperature of Preston media selects for certain genotypes of C. jejuni, and to detect the widest range, samples should be incubated at both 37 and 42 degrees C. Conversely, genotyping results arising from the use of a single incubation temperature should be interpreted with caution.

Animals↗
PubMedDate not supplied

Glucose consumption and lactate production of human placental tissue under different conditions of in vitro incubation.

OBJECTIVE: To assess the glycolytic activity of human placental tissue in the third trimester as measured by glucose consumption and lactate production under different conditions of in vitro incubation. METHOD: An incubation technique was used to study the metabolic activity of the human placenta by comparing large blocks (0.3 cm3, T1) and small fragments (explants, 0.03 cm3, T2). Placentas were obtained from premature (28-33 weeks) and term (39-41 weeks) deliveries. In addition, different experimental conditions were used to investigate the influence of incubation medium (Earle's buffer and cell culture medium NCTC = 135), medium oxygen pressure (PO2) (400 and 30 mmHg), and regional sampling of placental tissue (central, intermediate, and peripheral). All media contained glucose (1 g/L). The tissue (2-3 g/25 mL medium, pH 7.2-7.4) was incubated for 3 hours at 37C. 3H-inulin was used for the determination of the extracellular space. RESULTS: Incubation of both tissue forms yielded a higher metabolic activity as measured by glucose consumption and lactate production when incubated with Earle's buffer compared with incubations with NCTC medium. In general, the metabolic activity was consistently higher for small fragments compared with the large blocks. Extracellular space values found for large fragments (25-31%) were significantly lower than for small pieces (39-46%), indicating that an equilibration of the medium with the extracellular space is inadequate with large fragments. Incubation with small fragments showed that 1) there is a tendency for higher metabolic activity during incubation with lower PO2, 2) the metabolically most active part of the placenta is the intermediate tissue region, and 3) placental metabolic activity was significantly higher at 28-33 weeks (n = 5) than at term (n = 6). These differences were not seen with large fragment incubations. CONCLUSION: The smaller tissue fragments are preferable for the in vitro incubation study of placental glucose metabolism. Apparently, there are differences in the metabolic activity with regard to the placental tissue region and gestational age.

Culture Media↗
PubMedDate not supplied

Comparative mold and yeast recovery analysis (the effect of differing incubation temperature ranges and growth media).

Environmental monitoring methodology for recovering fungal organisms often dictates the use of a selective medium incubated at ambient temperatures (20-25 degrees C) for as many as seven days incubation to ensure reliable recovery. However, these methods (which must remain standardized for identification purposes) are not the only avenue environmental monitoring programs may follow. This study comparatively analyzed recovery rates of fungal organisms cultured on both a general purpose bacteriological nutrient medium (Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80), and on a medium selective for the growth of yeasts and molds (Sabouraud Dextrose Agar). The bacteriologic medium was incubated at elevated temperatures (30-35 degrees C) for 70-72 hours then transferred to ambient temperatures for another 70-72 hours incubation. The control case selective medium was incubated solely at 20-25 degrees C for 110-130 hours. Additionally, in a separate test the selective medium was incubated at the same temperature and time specifications as the bacteriologic medium to analyze recovery capabilities. Equivalent or better recovery was obtained for all test panel organisms of yeasts and molds using Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80 incubated at 30-35 degrees C. Equivalent or better recovery was obtained for eight of the nine test panel organisms of yeasts and molds incubated at elevated temperatures on Sabouraud Dextrose Agar versus recovery on Agar versus recovery on Sabouraud Dextrose Agar incubated solely at 20-25 degrees C. No inhibition of growth was observed at the elevated temperature range of 30-35 degrees C. Three days incubation at elevated temperatures was a sufficient incubation period to detect the test organisms cultured on Tryptic Soy Agar supplemented with Lecithin and Polysorbate 80.

Culture Media↗
PubMed2001

Improvement of the culture conditions for in vitro production of cattle embryos in a portable CO2 incubator.

The effects of different concentrations of growth hormone (GH) on in vitro maturation (IVM), fertilization (IVF) and culture (IVC) of bovine oocyte/embryos in CR1aa or CR2aa media using a simple CO2 incubator were investigated. The IVM/IVF/IVC of oocytes were carried out in the presence of 0, 50, 100 and 200 ng/ml GH in the medium. The proportion of metaphase II oocytes was significantly higher (p < 0.05) in 200 ng/ml compared with 0 ng/ml GH in CR1aa medium (59 versus 85%, respectively), but this effect was not observed under CR2aa. Higher concentrations of GH yielded lower rates of unfertilized ova and thus superior cleavage rates (36.5 +/- 0.2 and 63.5 +/- 2.0% versus 17.5 +/- 0.2 and 82.5 +/- 1.5% or 40.4 +/- 0.6 and 59.6 +/- 1.4% versus 16.6 +/- 1.2 and 83.4 +/- 6.2% for 0 and 200 ng/ml GH in portable or ordinary incubator, respectively) in CR1aa. This dose-dependent effect was also observed in the percentages of transferable embryos, although not statistically different (17.2 +/- 1.7 versus 27.3 +/- 1.8% and 16.6 +/- 3.1 versus 26.0 +/- 1.4%, for 0 versus 200 ng/ml GH in portable and ordinary incubator, respectively). In contrast to the CR1aa, different concentrations of GH in CR2aa medium did not increase either fertilization or cleavage rates. In fact, higher concentrations of GH in this medium negatively affected the rate of transferable embryos. Hence, percentages of transferable embryos obtained in the portable incubator under 0 or 50 ng/ml GH were higher (p < 0.05) compared with those obtained in 100 or 200 ng/ml GH (35.4 +/- 5.7 or 40.5 +/- 5.4% versus 22.4 +/- 2.4 or 15.5 +/- 2.1%, respectively). There was however, no significant difference in the rate of transferable embryos in an ordinary incubator employing CR2aa medium, but the trend was more or less similar to that observed in the portable incubator. Despite the fact that relatively fewer oocytes were employed for the culture in the ordinary incubator, overall results observed employing the simple portable CO2 incubator were within the range of those obtained in an ordinary incubator: implying that the simple portable incubator can effectively be employed for the in vitro production of bovine embryos under field conditions.

Animals↗
PubMed2000

Influence of incubation temperature on morphology, locomotor performance, and early growth of hatchling wall lizards (Podarcis muralis).

Eggs of wall lizards (Podarcis muralis) were incubated at three temperatures approaching the upper limit of viability for embryonic development in this species (26, 29, and 32 degrees C) to assess the influence of temperature on various aspects of hatchling phenotype likely affecting fitness. The thermal environment affected size and several morphometric characteristics of hatchling lizards. Hatchlings from eggs incubated at 32 degrees C were smaller (snout-vent length, SVL) than those from 26 and 29 degrees C and had smaller mass residuals (from the regression on SVL) as well as shorter tail, head, and femur relative to SVL. Variation in the level of fluctuating asymmetry in meristic and morphometric traits associated with incubation temperatures was quite high but not clearly consistent with the prediction that environmental stress associated with the highest incubation temperatures might produce the highest level of asymmetry. When tested for locomotor capacity in trials developed at body temperatures of 32 and 35 degrees C, hatchlings from the 32 degrees C incubation treatment exhibited the worst performance in any aspect considered (burst speed, maximal length, and number of stops in the complete run). Repeated measures ANCOVAs (with initial egg mass as covariate) of snout-vent length and mass of lizards at days 0 and 20 revealed significant effects of incubation temperature only for mass, being again the hatchlings from eggs incubated at 32 degrees C those exhibiting the smallest final size. All together, our results evidenced a pervasive effect of thermal regime during incubation (and hence of nest site selection) on hatchling phenotypes. However, incubation temperature does not affect hatchling phenotypes in a continuous way; for most of the analysed traits a critical threshold seems to exist between 29 and 32 degrees C, so that hatchlings incubated at 32 degrees C exhibited major detrimental effects. J. Exp. Zool. 286:422-433, 2000.

Adaptation, Physiological↗
PubMed1998

Effects of incubation temperature on the energetics of embryonic development and hatchling morphology in the Brisbane river turtle Emydura signata.

Incubation temperature and the amount of water taken up by eggs from the substrate during incubation affects hatchling size and morphology in many oviparous reptiles. The Brisbane river turtle Emydura signata lays hard-shelled eggs and hatchling mass was unaffected by the amount of water gained or lost during incubation. Constant temperature incubation of eggs at 24 degrees C, 26 degrees C, 28 degrees C and 31 degrees C had no effect on hatchling mass, yolk-free hatchling mass, residual yolk mass, carapace length, carapace width, plastron length or plastron width. However, hatchlings incubated at 26 degrees C and 28 degrees C had wider heads than hatchlings incubated at 24 degrees C and 31 degrees C. Incubation period varied inversely with incubation temperature, while the rate of increase in oxygen consumption during the first part of incubation and the peak rate of oxygen consumption varied directly with incubation temperature. The total amount of oxygen consumed during development and hatchling production cost was significantly greater at 24 degrees C than at 26 degrees C, 28 degrees C and 31 degrees C. Hatchling mass and dimensions and total embryonic energy expenditure was directly proportional to initial egg mass.

Animals↗
PubMed2006

Incubation temperature and phenotypic traits of Sceloporus undulatus: implications for the northern limits of distribution.

Cold environmental temperature is detrimental to reproduction by oviparous squamate reptiles by prolonging incubation period, negatively affecting embryonic developmental processes, and by killing embryos in eggs directly. Because low soil temperature may prevent successful development of embryos in eggs in nests, the geographic distributions of oviparous species may be influenced by the thermal requirements of embryos. In the present study, we tested the hypothesis that low incubation temperature determines the northern distributional limit of the oviparous lizard Sceloporus undulatus. To compare the effects of incubation temperature on incubation length, egg and hatchling survival, and hatchling phenotypic traits, we incubated eggs of S. undulatus under temperature treatments that simulated the thermal environment that eggs would experience if located in nests within their geographic range at 37 degrees N and north of the species' present geographic range at latitudes of 44 and 42 degrees N. After hatching, snout-vent length (SVL), mass, tail length, body condition (SVL relative to mass), locomotor performance, and growth rate were measured for each hatchling. Hatchlings were released at a field site to evaluate growth and survival under natural conditions. Incubation at temperatures simulating those of nests at 44 degrees N prolonged incubation and resulted in hatchlings with shorter SVL relative to mass, shorter tails, shorter hind limb span, slower growth, and lower survival than hatchlings from eggs incubated at temperatures simulating those of nests at 37 and 42 degrees N. We also evaluated the association between environmental temperature and the northern distribution of S. undulatus. We predicted that the northernmost distributional limit of S. undulatus would be associated with locations that provide the minimum heat sum (approximately 495 degree-days) required to complete embryonic development. Based on air and soil temperatures, the predicted northern latitudinal limit of S. undulatus would lie at approximately 40.5-41.5 degrees N. Our predicted value closely corresponds to the observed latitudinal limit in the eastern United States of approximately 40 degrees N. Our results suggest that soil temperatures at northern latitudes are not warm enough for a sufficient length of time to permit successful incubation of S. undulatus embryos. These results are consistent with the hypothesis that incubation temperature is an important factor limiting the geographic distributions of oviparous reptile species at high latitudes and elevations.

Analysis of Variance↗
PubMed1988

Increased lead uptake and inhibition of ALAD-activity in isolated rat hepatocytes incubated with lead-diethyldithiocarbamate complex.

Dithiocarbamates can form lipid soluble complexes with lead and are known to markedly increase tissue uptake of lead and potentiate toxic effects of lead in rats. Cellular effects of the interactions between lead and diethyldithiocarbamate were studied in primary cultures of rat hepatocytes. The cells were incubated with lead acetate (PbAc) or lead-diethyldithiocarbamate complex (Pb(DTC)2), labelled with 203Pb. The lipid soluble Pb(DTC)2 was rapidly taken up in the cells and after 30 min incubation the cellular levels of lead were approximately 40 times higher in cells incubated with Pb(DTC)2 than in cells incubated with a similar concentration of PbAc. The maximal cellular uptake of lead was reached after 4 h incubation with Pb(DTC)2, while incubation with PbAc caused a slow continuously increasing uptake of lead during the 20 h incubation. The enzyme delta-aminolevulinic acid dehydratase (ALAD) was inhibited to a much higher extent by Pb(DTC)2 compared to PbAc after incubations with similar concentrations of lead. Maximal inhibition of ALAD activity was reached at a cellular concentration of 0.5-1 nmol Pb/mg protein, irrespective of which form of lead was used in the incubation. Pb(DTC)2 was shown to inhibit ALAD activity also in vitro when incubated with purified ALAD enzyme. The rapid and high intracellular uptake and cellular response of Pb(DTC)2, shown in the present study, may explain the drastic effects of dithiocarbamates on lead distribution and toxicity previously shown in vivo.

Animals↗
PubMed1990

Immunocytochemistry on free-floating sections of rat brain using microwave irradiation during the incubation in the primary antiserum: light and electron microscopy.

We studied the effects of microwave irradiation during the incubation of free-floating brain sections with primary antibodies against gamma-aminobutyric acid (GABA), enkephalin and vasopressin. Vibratome sections of perfusion-fixed rat brain were incubated: (a) overnight at room temperature (20-22 degrees C), (b) during various periods of time under microwave irradiation, such that the induced temperatures did not exceed 10 degrees C, (c) same as (b) but with induced temperatures not exceeding 40 degrees C, (d) without microwave irradiation, at 4-10 degrees C (temperature control for (b)), (e) same as (d) but at 40 degrees C (temperature control for (c)). During the incubation-irradiation we continuously monitored the temperature and controlled it by cooling and by manipulating the energy output of the magnetron. The peroxidase immunocytochemical procedure was completed using for all sections the same incubation parameters. Selected GABA-immunoreacted sections were examined in the electron microscope. Incubation at 10 degrees C in the primary antiserum as short as 30 min, with or without microwave irradiation, already results in (weak) binding of the antibodies to immunoreactive structures. One or 2 h of incubation in the primary antiserum in the microwave oven at 40 degrees C or at the same temperature outside the microwave oven results in excellent staining of GABA-immunoreactive structures and of good staining of enkephalin- or vasopressin-immunoreactive structures. The ultrastructural details were much better preserved in incubated-irradiated sections than in sections incubated overnight and only slightly less preserved than in the other control sections. There is no improved penetration of the antibodies into the sections. We conclude that by using microwave technology or by raising the temperature of the incubation medium, the time of incubation, at least in these antisera, can be shortened drastically, whereas the ultrastructural details remain well preserved.

Animals↗
PubMed2004

Effect of post-thaw incubation on sperm kinematics and acrosomal integrity of ram spermatozoa cryopreserved in medium-sized French straws.

The objectives were to assess the effect of post-thaw in vitro incubation on motion characteristics and acrosomal integrity of ram spermatozoa of native Malpura and Bharat Merino breeds maintained under a semi-arid tropical environment. Good quality semen samples of both breeds were diluted, packaged in medium-sized straws, and frozen under controlled conditions. Straws were thawed at 60 degrees C for 10s and thawed samples were incubated at 37 degrees C for 4h. Post-thaw motion characteristics and acrosomal integrity of incubated spermatozoa were assessed (by computer-aided semen analysis and Giemsa staining, respectively) just prior to incubation and at hourly intervals thereafter. There was a significant effect of incubation time on motility characteristics and the proportion of spermatozoa with normal acrosomes; 81.4% (arcsin transformed value, 65.2) of spermatozoa were motile at the start of incubation, with 47.9% (arcsin transformed value, 44.4) motile after 4h. At the corresponding times, there were normal acrosomes in 65.8 (arcsin transformed value, 54.8) and 55.7% (arcsin transformed value, 48.9) of spermatozoa, respectively. The percentage straightness of spermatozoa varied during incubation (P < 0.01). However, there was no significant change in percentage linearity, curvilinear velocity, average path velocity, straight line velocity, lateral head displacement, and beat cross frequency of spermatozoa during incubation. There were no breed variations in any motility parameters during incubation, except percentage straightness (P < 0.05), lateral head displacement (P < 0.05) and beat cross frequency (P < 0.01). That sperm motility and acrosomal morphology were very acceptable immediately post-thaw and after 4h of incubation indicated the efficacy of cryopreserving ram spermatozoa under controlled conditions in medium-sized straws.

Acrosome↗
PubMed2006

A short sperm-oocyte incubation time ZBA in the dog.

The fertilising capacity of a semen sample can be predicted by evaluation of spermatozoa with in vitro tests. The zona pellucida binding assay (ZBA) accounts for several parameters and interprets the interaction between the spermatozoa and the oocyte. The present study was made in two parts. The aim of the first experiment was to evaluate whether the sperm binding capacity of oocytes varies between different oocyte pools. Each zona binding was made with oocytes from different bitches, using pooled frozen-thawed semen from the same two dogs. The sperm-oocyte complexes were incubated for 1h. There was a significant difference between the six replicates in the number of sperm bound to the zona pellucida (ZP), which indicates that the sperm binding capacity of the ZP differs between oocyte pools. The aims of the second experiment were to evaluate the effects of five different treatments of the spermatozoa on the ZBA, and to evaluate two different incubation times of the sperm-oocyte complexes. ZBAs were made with: fresh semen; semen kept chilled for 1 or 2 days prior to the ZBA; and with semen that had been frozen with or without Equex. The oocytes and spermatozoa were incubated for 1 or 4h. For fresh semen and for semen frozen without Equex, incubation for 1h resulted in a higher number of bound spermatozoa per oocyte than incubation for 4h (P<0.0001). When the effect of the different sperm treatments on the number of spermatozoa bound to the ZP was evaluated, it was found that this number was higher for fresh spermatozoa than for chilled or frozen-thawed spermatozoa both after 1 and 4h of co-incubation (P<0.0001). After 1-h incubation of the sperm-oocyte complexes, spermatozoa chilled for 1 day showed better zona binding capacity than spermatozoa chilled for 2 days, and spermatozoa frozen without Equex had a better zona binding capacity than spermatozoa frozen with Equex. Sperm motility and sperm plasma membrane integrity were higher in fresh than in chilled and frozen-thawed semen. The acrosome integrity was high in all groups of treated semen. In conclusion, 1-h incubation of the sperm-oocyte complexes seems to be sufficient for fresh and chilled semen. Further studies are required to establish the optimal incubation time for sperm-oocyte complexes when frozen-thawed semen is evaluated, as a comparison between semen frozen with Equex and semen frozen without Equex gave different results depending on whether the incubation time was 1 or 4h (in the present study), or 6h [Ström Holst B, Larsson B, Linde-Forsberg C, Rodriguez-Martinez H. Evaluating chilled and frozen-thawed dog spermatozoa using a zona pellucida binding assay.

Animals↗
PubMed1966

Effects of prolonged incubation of isolated fat cells on their response to hormones stimulating lipolysis and glucose metabolism.

1. The metabolism of isolated fat cells from parametrial adipose tissue of starved normal rats was studied during 8hr. incubation. 2. There was a three- to eight-fold increase in conversion of glucose into carbon dioxide, fatty acids and glycerol during the fourth to eighth hours of incubation in 4% albumin buffer over that seen during the first 4hr. of incubation. 3. The addition of growth hormone and dexamethasone to fat cells at the start of the incubation period accelerated lipolysis during the first 4hr. of incubation but no further effect was seen during the fourth to eighth hours of incubation. Addition of growth hormone and dexamethasone to fat cells that had been incubated for 4hr. did not accelerate lipolysis during the next 4hr. whether fat cells were incubated with or without glucose. 4. Fat cells incubated for prolonged periods also displayed a reduced sensitivity to the lipolytic action of adrenocorticotrophic hormone. 5. During prolonged incubation there was no damage to the cells as judged by the retention of two soluble cytoplasmic enzymes, lactate dehydrogenase and malate dehydrogenase, within the cells.

Adipose Tissue↗
PubMed1980

Mechanisms of loss of latency of lysosomal enzymes. Effects of incubation on the properties of lysosomal membranes.

1. The effects of sucrose and KCl on the loss of latency of lysosomal enzymes caused by incubation at 37 degrees C, pH 7.4, were examined by using Triton-filled lysosomes from rat liver and two fractions from livers of rats not injected with Triton. 2. After incubation, the percentage free activity of lysosomal enzymes was measured before and after cooling to 0 degrees C in order to determine the amount of latency lost at 37 degrees C without cooling and the additional amount lost on cooling the incubated lysosomes to 0 degrees C. 3. The latency that is lost without cooling is first decreased and then increased by increasing the osmotic strength of the incubation medium with KCl, or with sucrose in the presence of KCl. However, if the osmotic strength is increased with sucrose alone, loss of latency is decreased up to 0.25M-sucrose, but is increased only slightly at higher sucrose concentrations. Apparently the lysosome is permeated by hyperosmolar KCl but not by sucrose during incubation. 4. If the osmotic strength of the assay medium is increased with KCl, the loss of latency caused by incubation for 60 min in hyperosmolar KCl is repressed. Thus it appears that a KCl-permeated lysosome can be obtained which is relatively stable until exposure to lower osmolarities. 5. The loss of latency caused by cooling incubated lysosomes to 0 degrees C is largely eliminated if the osmotic strength of the medium in which the lysosomes are cooled is raised sufficiently with either sucrose or KCl. 6. Osmotic-fragility curves were obtained after incubation for 1 and 60 min at iso-osmoticity (0.2M-KCl or 0.25 M-sucrose). Although little loss of latency occurs at iso-osmoticity, lysosomes incubated for 60 min display greatly increased fragility on exposure to hypo-osmolar KCl, hypo-osmolar sucrose or hyperosmolar KCl. 7. It is suggested that permeability to KCl at 37 degrees C and the increase in fragility on exposure to hypo-osmolar conditions are both consequences of injury, probably from enzymic action, sustained by the lysosomal membrane during incubation at 37 degrees C.

Animals↗
PubMedDate not supplied

Cytogenetic consequences of microwave irradiation on mammalian cells incubated in vitro.

A 2450 MHz microwave oven was converted into a microwave incubator. Rat kangaroo RH5 and RH16 cells were incubated in the incubator and were subcultured every 5 to 7 days. The temperature of the cell cultures in the incubator was maintained at 37 degrees C. The cells were incubated with direct microwave irradiation continuously for 50 passages and then returned to a conventional incubator and allowed to grow for another 30 passages. Cell growth rate was significantly reduced after 7 or 15 subculture passages under irradiation. Chromosome aberrations emerged after the cells had been microwave-incubated for about 20 passages. The long-term irradiation caused 0.84 chromosome breaks per cell in RH5 cell cultures and 0.10 breaks per cell in RH16 cell cultures. After the cell cultures had been returned to the conventional incubator and maintained for 30 passages, the number of chromosomes breaks was greatly reduced in both cell cultures. The number of polyploid cells was increased to 35 percent and 31 percent during the irradiation, and was significantly reduced in the conventional incubator. Many RH5 cells lost one chromosome and became 10-chromosome cells. The number of 10-chromosome cells increased during irradiation and continued to increase after being returned to the conventional incubator.

Animals↗
PubMed1998

Breeding biology of Muscovy duck Cairina moschata in natural incubation: the effect of nesting behavior on hatchability.

A breeding biology study of a genetically unselected variety of Muscovy duck Cairina moschata was conducted in an experimental duck unit in Maputo, Mozambique (25 degrees 58' S, 32 degrees 35' E), to gain insight into factors affecting hatchability during natural incubation. Nesting and incubation behaviors were recorded by daily nest visits. Of 1,338 nests investigated, 70% were incubated until hatching. In 23% of the incubated nests, eggs were laid by more than one duck in the same nest, indicated as dump nests. Artificial dump nests (15% of the incubated nests) were created by adding eggs (690 eggs) from nests abandoned by the duck before incubation had started. A total of 37% of the incubated nests contained eggs that were laid after the onset of incubation (nonterm eggs). Similar hatching rate was found between ducks raised in parks with or without access to swimming water. No significant difference was found in hatchability between normal (0.76) and dump nests (0.77). Artificial dump nests showed higher hatching rates than nests containing nonterm eggs. Dump nesting appears to be a reproductive strategy used by the Muscovy duck to enhance duckling production. Hatching rate was strongly influenced by the length of laying period (period between the ovoposition of the first egg until the onset of incubation) and reproduction cycle (laying period and incubation period). Hatchability was higher for clutches with a shorter reproduction cycle. It is concluded that nesting behavior of the domesticated Muscovy duck is similar to that of its wild ancestor.

Animals↗
PubMed1990

Desensitization of beta-adrenoceptor-mediated functional responses of guinea pig atria by in vitro incubation with isoprenaline.

Positive inotropic and chronotropic responses to (-)-isoprenaline were recorded in guinea pig isolated paced left and spontaneously beating right atria. Concentration-response curves were determined before and after incubation with 10(-6) M (-)-isoprenaline for various times from 0.5 to 8 h. Before construction of the postincubation curve, isoprenaline was washed from the tissue for either 0.5 or 1 h. Preincubation curves were corrected from controls for time-dependent changes in sensitivity. After a 2-h incubation with 10(-6) M isoprenaline and a 0.5-h washout, there was a significant rightward shift of the right atrial rate curve [concentration ratio (CR) 10.6 +/- 2.1]. This was reversed by extending the washout to 1 h. After a 4-h incubation, however, a poorly reversible desensitization occurred, the curve still being significantly shifted after a 1-h washout (CR, 17.4 +/- 6.2). A higher incubation concentration, 10(-5) M, appeared to produce greater desensitization as a depression of the maximum response, however, this was an artifact caused by the failure to wash the isoprenaline from the tissue. When left atria were paced throughout the incubation period, a substantial nonspecific depression of the maximum response to 73.7 +/- 7.6% occurred. When pacing was stopped during incubation, only a rightward shift of the curve was produced by incubation with isoprenaline (10(-6) M), with no change of maximum (96.5 +/- 6.3%). There was no cross-desensitization of histamine in either the left (unpaced while incubating) or right atria after a 4-h incubation period with isoprenaline (10(-6) M). The desensitization was therefore beta-adrenoceptor specific and of the homologous type. After an 8-h incubation, there was an additional depression of the postincubation maximum which was greater in the left (68.9 +/- 2.3%) than right atria (85.2 +/- 5.4%). This true reduction of the maxima indicates that desensitization had effectively removed a proportion of the beta adrenoceptors.

Animals↗
PubMed1991

Prolonged incubation of skeletal muscle in vitro: prevention of increases in glucose transport.

During experiments involving prolonged incubation of skeletal muscle, we observed large increases in glucose transport activity. The basal rate of 3-O-methylglucose (3-MG) transport increased two- to fourfold in rat epitrochlearis muscles incubated for 9 h without insulin in Krebs-Henseleit buffer supplemented with 8 mM glucose. The stimulatory effect of a low concentration of insulin (30 microU/ml, added during the final 30 or 60 min of incubation) on glucose transport activity was enhanced 2.5-fold after 6 h and approximately 5-fold after 9 h of incubation. Exposure of muscles to 100 microU/ml of insulin for the first 8 h inhibited slightly but significantly the increase in insulin-stimulated 3-MG transport over a 9-h incubation period. Incubation of muscles in minimal essential medium (MEM) for 9 h inhibited the time-dependent rise in basal and insulin-stimulated transport by approximately 45%. The effect of MEM was reproduced with MEM essential, but not nonessential, amino acids. Incubation of muscles with MEM plus 100 microU/ml of insulin for the first 8 h prevented the increases in 3-MG transport activity measured after a 9-h incubation period. Muscles incubated for 9 h maintained ATP and phosphocreatine concentrations, and changes in glycogen concentrations were small. Thus we have defined conditions for long-term incubation of skeletal muscle under which a progressive increase in glucose transport is prevented.

Amino Acids↗