Showing papers on "Incubation published in 1972"

Nitrogen Mineralization Potentials of Soils

Abstract: Net mineralization of N in 39 widely differing soils was determined over a 30-week period at 35C, using incubation intervals of 2, 2, 4, 4, 4, 6, and 8 weeks. Mineral N was leached from the soils before the first incubation and following each of seven incubations by means of 0.01M CaCl₂ and a minus-N nutrient solution. Soil water contents were adjusted by applying suction (60 cm Hg), and losses of water during incubation under aerobic conditions were negligible. With most soils, cumulative net N mineralized was linearly related to the square root of time, t½. The pH of soils changed very little in the course of 30 weeks' incubation. Because of the generally consistent results, the data were employed in calculating the N mineralization potential, Nₒ, of each soil, based on the hypothesis that rate of N mineralization was proportional to the quantity of N comprising the mineralizable substrate. Values of Nₒ ranged from about 20 to over 300 ppm of air-dry soil. The fraction of total N comprising Nₒ varied widely (5 to 40%) among soils. Mineralization rate constants did not differ significantly among most of the soils. The most reliable estimate of the rate constant, k was .054 ± .009 week⁻¹. The time required to mineralize one-half of Nₒ, t½, was estimated to be 12.8 ± 2.2 weeks. Results suggest that the forms of organic N contributing to Nₒ were similar for most of the soils.

Prostaglandin E1 Effects on Adenosine 3′:5′-Cyclic Monophosphate Concentration and Phosphodiesterase Activity in Fibroblasts

Abstract: Incubation of L-929 and L-2071 fibroblasts with prostaglandin E1 (PGE1) caused a rapid increase in the cyclic AMP content of these cells. A maximal effect was produced with 0.2 μg PGE1 per ml. At a concentration of 4 μg/ml, PGE2 was almost equally effective, but PGF2α and PGA2 were much less so. 2.6 μM epinephrine, 0.4 mM serotonin, and 0.2% ethanol were without effect. In L-929 cells, cyclic AMP concentrations remained elevated for 2-5 hr, and then declined, although even after a 24-hr incubation the medium contained PGE1 in a concentration sufficient to increase maximally the cyclic AMP content of cells not previously exposed to this compound. A second addition of PGE1 after 5 or 24 hr did not produce another increase in the concentration of cyclic AMP. After incubation with PGE1 for 24 hr, cyclic AMP phosphodiesterase activity, assayed with 0.56 μM substrate, was increased 30-100%; the activity rose further between 24 and 48 hr. It is suggested that the increase in phosphodiesterase activity that appears to be a consequence of prolonged elevation of cyclic AMP concentration may account at least in part for the apparent “refractoriness” to PGE1 that develops after incubation for several hours with this compound.

The demonstration of acid phosphatase in in vitro cultured tissue cells. Studies on the significance of fixation, tonicity and permeability.

Abstract: 1. Methods for the fine structural demonstration of acid phosphatase were studied in monolayers of in vitro cultured cells after fixation with glutaraldehyde. 2. Inactivation of enzyme activity occurred rapidly during the initial phase of glutaraldehyde fixation. 3. Fixation for more than 5 min did not cause further marked inactivation of enzyme activity. 4. Stabilization of the cells for cytochemical incubations required a fixation for at least 30 min in glutaraldehyde. 5. The total osmolality of the fixative was of minor importance, in contrast to the major importance of effective osmolality, for obtaining optimum cytochemical and ultra-structural results. 6. Following proper fixation, the osmotic strength of the washing and incubation solutions was not critical. 7. With short fixation times, the composition of the washing and incubation solutions was of major importance. 8. Dimethyl sulphoxide in washing and incubation media was effective in shortening incubation times (thereby preventing the occurrence of unspecific precipitates and derangement of fine structure).

Competition between different scrapie agents in mice.

Abstract: STRAINS of scrapie agent differ in a number of their biological properties, one of which is average incubation period1,2. Incubation period is inversely proportional to dose for all known strains of scrapie and some differ so markedly that there is no overlap in their dose-incubation period curves. A large dose of one agent takes longer to produce the disease than the LD50 dose of another agent3. Two such scrapie agents are 22A and 22C when compared by intracerebral injection of VM mice. Agent 22A has a much shorter incubation period than 22C in VM mice because they carry the p7 allele of the sine gene that controls scrapie incubation. It should therefore be possible to produce mixed infections in VM mice, but to ensure that the clinical disease is produced by the 22A agent. It can be checked that 22A causes the disease, rather than 22C, by examining the distribution of brain lesions2. Interaction during pathogenesis between the two agents—competition or synergism—would be seen as a difference in the incubation period of 22A. We achieved mixed infection by injecting 22C first and 22A on a later occasion.

Incubation Schedules of Four Species of Calidridine Sandpipers at Barrow, Alaska

Abstract: eggs are laid before daily minimum temperatures exceed freezing (Brown 1968; MacLean 1969) and subfreezing temperatures may occur on occasional "nights" (18:00-06:00) throughout the nesting season. Incubation under these conditions might be expected to assume one of two forms. Shorebirds might either incubate virtually 100% of the time or might show a fluctuating incubation constancy which reflects the prevailing danger of cold-exposure to unattended eggs. A study of nest attendance between clutch completion and the start of hatching should reveal whether 24-hr periodicities and noncyclic fluctuations of incubation constancy occur, and if so, whether these correspond to fluctuations in environmental factors.

A model in mice for the pathogenesis and treatment of rabies.

Abstract: to the incubation periods seen in man. Amputation of the inoculated feet within 18 days after inoculation was a life-saving procedure, indicating that the virus stays at or near the site of introduction for most of the long incubation period. Equine antiserum to rabies administered 24 hr after inoculation of virus failed to reduce mortality but resulted in singularly prolonged incubation periods. A significant reduction in mortality was noted in only two groups, one given equine antiserum to rabies and daily doses of duck-embryo vaccine (23% vs. 51% in the controls), and the other given one dose of a highly potent tissue-culture vaccine (3% vs. 51%). In rabies studies over the years, attempts have been made to establish animal models that simulate the incubation periods in man in order to study the pathogenesis of the disease and to evaluate treatment. Most experiments were done with some type of fixed virus or "street" virus isolate, with relatively short periods of incubation between inoculation of virus and onset of disease [1-6], and were often terminated within a few months after initiation. In the majority of the experiments, no protection was found with any kind of postexposure treatment. Incubation periods in man are rarely as short as those observed in experimental animals; the median for 22 persons who died of rabies in the United States between 1946 and 1965

Potassium: Effect on DNA Synthesis and Multiplication of Baby-Hamster Kidney Cells

Abstract: The relations between DNA synthesis, cell multiplication, and external potassium concentration have been investigated in cultured baby-hamster kidney cells. When the potassium concentration was raised from 8 mM to 114 mM by equimolar replacement of sodium, DNA synthesis and cell multiplication were almost completely inhibited. This inhibition was reversible even after 72 hr of incubation in medium with a high concentration of potassium. There is a consistent difference between the cultured cells and polyoma virus-transformed cells in response to high-potassium medium, a higher-potassium concentration being required to inhibit multiplication of polyoma virus-transformed cells to the same extent as that of the nontransformed cells.

Bacterial Flora in the Digestive Tracts of Marine Fish-III

Abstract: The response of some representative strains of the indigenous and the other bacterial groups isolated from the digestive tracts of marine fish to the environmental conditions to be encountered in the stomach, i.e. low pH value and gastric juice, was examined. The results obtained are summarized as follows: (1) In the cases of the indigenous bacterial groups (I-a1 and I-a11) and IV group, viability was not much influenced by 5 hour's incubation at pH 4.0; however, remarkable loss in viability was observed in the other groups under the same conditions. The turbidity of cell suspensions, in general, did not decrease markedly on incubation at pH 4.0. (2) When gastric juice prepared from red sea bream was added to the pH 4.0 suspension, the viability of the strains of I-d and VI-b groups was significantly decreased after 5 hours' incubation. A marked decrease in turbidity was also observed with the strains of III, VI-b and VII groups, in the presence of gastric juice at pH 4.0. Pepsin, lysozyme and gastric juice from gizzard shad did not decrease the viability. (3) The strains of the indigenous bacterial and VI-b groups grew well at pH 5.0, while the others did not grow under this condition. These facts suggest that the indigenous bacterial groups (I-a1 and I-a11) are uniquely resistant or adapted to the environmental conditions in the stomach of marine fish.

Uptake and release of glutamate in cerebral-cortex slices from the rat

Abstract: 1. Cerebral-cortex slices from rat brain, loaded with labelled l-glutamate as a result of aerobic incubation with labelled glucose, lost less than 15% of this glutamate on subsequent incubation in the presence of unlabelled glucose and l-glutamate. This indicates that very little exchange occurs between extracellular l-glutamate and glutamate accumulated in the neurons as a result of glucose metabolism. 2. Slices, loaded with labelled l-glutamate as a result of aerobic incubation in a medium containing unlabelled glucose and labelled l-glutamate, lost more than half of this glutamate on subsequent incubation in the presence of unlabelled l-glutamate. This indicates that exchange occurs between extracellular glutamate and glutamate accumulated in brain slices as a result of its uptake from the incubation medium. 3. Evidence was obtained suggesting that only a part of the glutamate, accumulated in brain slices as a result of its uptake from an incubation medium containing both glucose and l-glutamate, entered the neurons; apparently almost all the rest entered the glia. 4. It is concluded that the slices contain a pool of glutamate, derived from glucose and located in the neurons, which is poorly exchangeable with extracellular glutamate, and another pool of glutamate, derived from extracellular glutamate and located in the glia, which is freely exchangeable with extracellular glutamate.

Effect of Several Components of Anaerobic Incubation on Antibiotic Susceptibility Test Results

Abstract: 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.

Seasonal changes in the reproductive system of the female white-crowned sparrow, Zonotrichia leucophrys gambelii, in captivity and in the field. 2. The incubation patch.

Abstract: The ventral apterium of free-living female White-crowned Sparrows (Zonotrichia leucophrys gambelii) becomes an incubation patch during the breeding season. At this time, it loses its feathers, increases in wet and defatted dry weight, and undergoes marked histological alterations. At times of year other than the breeding season, the apterium consists of a low squamous epidermis and a thin, poorly vascularized dermis of dense connective tissue. The dermis is separated from subcutaneous tissue by an internal elastic lamina. During the breeding season, the epidermis is a proliferative, stratified squamous eptihelium with well-defined basal, intermediate, transitional, and cornified layers; and the dermis consists of a superficial layer of collagen and a deep layer of highly vascular areolar connective tissue, noticeably edematous and mildly inflamed. Blood vessels are frequently in large groups in the center of the dermis. Edema and hypervascularity are most pronounced during incubation, but the epidermis is best developed during egg-laying. The apterium reverts to its basal state after the incubation period. Captive females, which do not breed, do not develop incubation patches.

In vitro activation of cellular immune response to gross virus-induced lymphoma

Abstract: Spleen cells from W/Fu rats 40 days or more after immunization with a syngeneic Gross virus-induced leukemia were unreactive in direct cytotoxic assays Incubation of these immune cells at 37°C for 12 hr or longer, in the absence of antigen, resulted in the appearance of specific cytotoxic reactivity Other lymphoid cells from the immune rats also were activated upon in vitro incubation, but to a lesser extent Experiments were performed to define the necessary conditions and the mechanism for the in vitro incubation Activation was temperature dependent, occurring at 37°C but not at 4°C Immune serum suppressed the activation, but normal rat serum also had some inhibitory activity Passage of immune cells through a nylon column, before preincubation, prevented activation In contrast, exposure to nylon after preincubation did not remove cytotoxic reactivity These findings demonstrate the reversal of a central inhibition of immune cell activity The explanations offered for this phenomenon included change in surface characteristics of the immune cells during in vitro incubation, and the possible need for an adherent helper cell

The formation of cholest-5-ene-3β,26-diol as an intermediate in the conversion of cholesterol into bile acids by liver mitochondria

Abstract: 1. When [(14)C]cholesterol was incubated with rat liver mitochondria, radioactive 26-hydroxycholesterol, 3beta-hydroxychol-5-enoic acid and other bile acids were isolated from the incubation mixture. 2. In the absence of added 26-hydroxycholesterol, the specific radioactivity of the 26-hydroxycholesterol formed from [(14)C]cholesterol during the incubation was higher than that of the 3beta-hydroxychol-5-enoic acid. Addition of increasing amounts of 26-hydroxycholesterol led to a progressive fall in the specific radioactivity, and to a progressive increase in the mass, of the 3beta-hydroxychol-5-enoic acid recovered at the end of the incubation. 3. It is concluded that 26-hydroxycholesterol is an intermediate in the formation of 3beta-hydroxychol-5-enoic acid from cholesterol. 4. Comparison of the specific radioactivity of the 26-hydroxycholesterol formed in the incubation mixture with that of the added [(14)C]cholesterol indicates that endogenous cholesterol in mitochondria is accessible to cholesterol 26-hydroxylase.

Effects of d-Glucosamine, d-Mannosamine, and 2-Deoxy-d-glucose on the Ultrastructure of Ascites Tumor Cells in Vitro

Abstract: Ehrlich ascites carcinoma and Sarcoma 180 ascites tumor cells were treated in vitro with amino sugars, and the resulting changes were studied by light and electron microscopy. Addition of d-glucosamine or d-mannosamine to the incubation medium provoked striking cytoplasmic and nuclear changes. The earliest changes, seen after incubation for 15 min, included vacuolization of the cytoplasm and separation of the electron-lucent filamentous parts of the nucleolonema and nucleolar vacuole at the periphery of the nucleolus. As the time of incubation increased, vacuolization of the cytoplasm increased gradually, accompanied by retraction of the cytoplasm around the nucleus. After complete extrusion of its electron-lucent components, the nucleolus became condensed. At the end of 3 hr of incubation, 95% of the tumor cells had pycnotic, polymorphic, or disintegrating nuclei, and the nucleoli in nearly all the cells examined consisted almost exclusively of the compacted, granular, electron-dense nucleolonema. After 4 hr, most tumor cells exhibited various degrees of disintegration. Incubation of these tumor cell lines for 4 hr with 2-deoxyglucose resulted in no significant structural alteration in the ascites tumor cells.

The Effects of Arabinosylcytosine on Cultured Human Lymphoma Cells

Abstract: Summary Asynchronous human lymphoma cells incubated with various concentrations of 1-β-d-arabinofuranosylcytosine (ara-C) for 1 hr did not exhibit loss of viability. A similar situation existed when ara-C was presented for 1 hr to synchronized cells at various points of the cell cycle. However, when treatment was extended for 48 hr in asynchronous populations, a decrease in survivors to about 2% was elicited. Synchronized S-phase cells exposed to ara-C for 14 hr also showed a decrease in survival to 4%. Incubation with ara-C inhibited triatiated thymidine uptake irreversibly for at least 8 hr after the drug was removed from the external environment. The fact that the lymphoma cells possess low levels of ara-C kinase may explain the ineffectiveness of the drug with short exposures. After 24 hr incubation, about 30% of the total intracellular ara-C had been incorporated into nucleic acids.

Lysosomal enzymes in aquatic species. II. Distribution and particle properties of thermally acclimated muscle lysosomes of rainbow trout, Salmo gairdneri.

Abstract: 1. 1. Subcellular particles demonstrated structure-linked latent activity and single peak optimum activity in the acid pH range. 2. 2. Maximum activity of each acid hydrolase at different incubation temperatures varied from one enzyme to another. 3. 3. At 28°C incubation temperature there was greatest stability of all the acid hydrolases. 4. 4. The specific activity of cytochrome oxidase was significantly higher at cold thermal regimens. 5. 5. After differential centrifugation the highest relative specific activity of the enzymes was always found in the light mitochondrial fraction regardless of acclimation temperature.

Role of amino acid metabolites in the formation of soil organic matter

Abstract: Carbon-14 labelled cellulose or glucose were added to a medium loam and two sandy soils. The soils were incubated at 20°C for about 6 yr under laboratory conditions. Six to 12 per cent of the labelled carbon added to the soils was transformed into metabolites hydrolysable to amino acids during the first 10–30 days of the incubation period. The newly-formed metabolites decayed slowly as incubation continued. During the first 100–300 days of the incubation, losses of labelled amino acid carbon from soil were curvilinear when plotted on a semi-logarithmic scale. After this time the decay curves became linear, indicating half lives of 6–7 yr for the labelled carbon in amino acids. However, the labelled amino acid metabolites decayed at a faster rate than the native amino acid compounds of the soil, since they constituted a gradually decreasing percentage of total soil amino acid carbon as incubation proceeded. Twenty-six to 30 per cent of the total labelled carbon remaining in the soils after 6 yr of incubation was located in amino acids when the labelled carbon was added as cellulose, compared to 43 per cent when the labelled carbon was added as glucose. The amounts of amino acid metabolites extracted by sodium hydroxide or by the chelating ion-exchange resin Dowex A-1 decreased during the period of incubation. The unlabelled soil carbon as a whole was more extractable by the resin treatment than the labelled. Sixteen protein amino acids and two amino sugars were detected in hydrolysates of soils that had been incubated with either labelled cellulose or glucose for 6 yr. Each of these compounds was isolated and found to contain labelled carbon.

Changes in mood during incubation of acute febrile disease and the effects of pre-exposure psychologic status.

Abstract: &NA; Psychologic measures of mood, distress and psychologic vulnerability were obtained from young male volunteers participating in experimental tularemia studies before exposure, during incubation of disease and during the acute and convalescent illness periods. Daily temperature and fever records were maintained. It was found that the onset of negative mood feelings was prodromal to fever in the majority of subjects. Psychologically vulnerable subjects tended to react to a greater degree and to show more severe illness as measured by the duration of fever than did the nonvulnerable subjects.

The Induction of Amylase Synthesis in Barley Aleurone Layers by Gibberellic Acid I. RESPONSE TO TEMPERATURE

Abstract: The lag phase between application of gibberellic acid to barley aleurone layers and the beginning of amylase synthesis is at a minimum at 30 °C. This temperature is also the optimum for enzyme synthesis. Incubation temperature has little effect on the background activity found in the absence of gibberellic acid, or on the concentration of enzyme retained in the tissue in the presence of hormone. When aleurone layers spend only 2 h of the lag period at 30 °C, and the remainder of the incubation at 25 or 15 °C, the lag period is considerably reduced. Short-term incubation at 30 °C is most effective in reducing the lag period at 25 °C when given for the first 2 h after gibberellic-acid addition. Under these conditions ('tempera ture stepdown incubation') the lag period is reduced to that with the whole incubation at 30 °C. The temperature stepdown incubation has a sharp pH optimum of 5-00-5-05 and its effectiveness is increased by the presence of iron in the medium. There are thus two rate limiting reactions during the lag period, the first highly temperature sensitive, the second relatively temperature insensitive.

Tumor thromboplastin activity In vitro

Abstract: The thromboplastin activity of tissue culture media, before and after incubation with T-241 Lewis sarcoma cells of mouse origin, or with embryonic mouse epithelial or muscle fibroblasts, was measured by means of a calcium reconstitution assay. Incubation of the embryonic epithelial or muscle fibroblasts increased the thromboplastin activity of the tissue culture media more than did incubation with tumor cells, even though analysis of protein showed that there were more tumor cells than normal cells present at the time of incubation. It is concluded that there is no evidence for a unique “Cancer Coagulative Factor” at least in this system. In vitro studies of the effect of trauma in increasing the release of thromboplastin activity from both normal and tumor tissues, suggest that the mutual destruction of both tissues could account for the elevated levels observed in some patients with cancer.

The Effect of Exogenous IAA and Kinetin on Nitrate Reductase, Nitrite Reductase and Glutamate Dehydrogenase Activities in Excised Pea Roots

Abstract: Nitrate reductase (NO3R) activity, nitrite reductase (NO2R) activity and NADH2 dependent glutamate dehydrogenase (GDH) activity were followed in extracts from excised pea roots incubated under aseptic conditions for 9 and 24 h in nitrate containing nutrient medium to which IAA was added in concentrations promoting lateral root formation (1 × 10−5; 3 × 10−5; 5 × 10−5 M) and kinetin in concentrations which reduce lateral root formation (0.1; 1; 5 mg 1−1, that is 4.65 × 10−7;4.65 × 10−6 and 2.3 × 10−5 M). NO3R activity was not influenced by IAA, NO2R activity was slightly depressed by IAA after 24 h incubation and GDH activity was slightly increased after 24 h incubation in the presence of IAA. Kinetin decreased NO3R activity significantly both after 9 h and 24 h incubation, slightly increased NO2R activity after 9 h incubation but slightly decreased it after 24 h incubation, and did not affect GDH activity after 24 h incubation. However, when applied together with IAA, kinetin abolished the promoting effect of IAA on GDH activity. IAA neither reversed nor accentuated the effect of kinetin on NO2R activity. Nevertheless the depressing effect of kinetin on NO3R activity was emphasized by the presence of IAA after 9 h incubation. The results obtained indicate that reduced nitrate assimilation due to the depression of nitrate reductase activity caused by kinetin probably contributes to the negative growth effect of kinetin in pea root segments grown in nitrate medium.

The tissue dynamics of heart morphogenesis. I. The phenomena of cell death. B. Topography.

Abstract: Zones of cell death in the chick embryo heart were demonstrated by a study of cardiac morphogenesis on the light microscopical level. Between the 2nd and 20th day of incubation 31 foci of cell degeneration were found. The greatest number of dying cells occured on the 4th day of incubation and was located in the heart bulbus and bulbar cushions. The largest number of different degenerative foci were present on the 6th incubation day. Starting on the 10th day of incubation, both the number of degeneration zones and their population of dying cells decreased.