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Showing papers on "Incubation published in 1975"


Book ChapterDOI
01 Jan 1975

186 citations


Journal ArticleDOI
TL;DR: The studies indicate that the incubation step is best carried out in undiluted plasma at the pH optimum for renin (pH 5.7) in the presence of EDTA, neomycin, and DFP or PMSF, and by using these conditions, incubation of low-renin samples can be prolonged for up to 18 hr, because angiotensinases and converting enzyme are completely inhibited.

163 citations


Journal ArticleDOI
01 Oct 1975-The Auk
TL;DR: The present study was undertaken to describe more adequately the natural incubation environment of Mallard eggs and the hen behavior that produces this environment.
Abstract: THE natural incubation environment of wild Mallards (Anas platyrhynchos) has received little deterministic study. Prince et al. (1969a) considered the general effect of temperature and humidity under artificial conditions upon Mallard embryos. Batt and Cornwell (1972) intensively investigated the effect of cold on Mallard embryos, while Snart (1970) studied the upper thermal limits of Mallard embryos. They found Mallard embryos much more tolerant of cold than of heat. The above research employed artificial incubation and environmental chamber treatments. The present study was undertaken to describe more adequately the natural incubation environment of Mallard eggs and the hen behavior that produces this environment. Incubation behavior has been more thoroughly studied in avian species other than waterfowl. The incubation period is divided into attentive and inattentive periods which are related to species and clutch size (Skutch 1962). Incubation behavior and attentiveness are also affected by external stimuli (Kossack 1950, Kropivniui 1968, Barry 1962). Kendeigh (1952) reviewed the general daily rhythm of attentiveness to the nest by Anatids. Semenov-Tyan-Shanski and Bragin (1969) studying incubation behavior of Green-winged Teal (Anas crecca) and Common Goldeneye (Bucephala clangula) found the duck spent 1/7 to 1/8 of the incubation period off the nest. Cooper (1976) in an intensive study of Canada Goose (Branta canadensis) breeding behavior, found the female spent 98.5% of the incubation period on the nest. Kossack (1950) reported egg wetting in Canada Geese but the function of such behavior is unclear. McKinney (1952) described Mallard behavior patterns resulting in egg movements. Drent (1970) found Herring Gull (Larus argentatus) eggs maintained relatively constant orientation to gravitational forces, but they were frequently moved by the adult. Egg turning by the Wood Duck (Aix sponsa), a cavity nester, occurred about once a day (Stewart 1971). Temperatures of naturally incubated bird eggs and nests have been investigated frequently, but little work has been done with waterfowl species. Egg temperatures were recorded for the Canada Goose (Kossack 1947, Cooper 1976) and Wood Duck (Breckenridge 1956).

133 citations


Journal ArticleDOI
TL;DR: In this paper, the effect of incubation time on most probable number estimates of autotrophic nitrifying bacteria was investigated by using waters, rooted aquatic plants, sediments, and slimes as inoculum sources.
Abstract: The effect of incubation time on most-probable-number estimates of autotrophic nitrifying bacteria was investigated by using waters, rooted aquatic plants, sediments, and slimes as inoculum sources. Maximum most probable numbers of the NH4+-oxidizing group were attained in 20 to 55 days (median, 25). Estimates of NO2- oxidizers were highest at termination (103 to 113) days.

128 citations


Journal ArticleDOI
TL;DR: Endogenous progesterone was measured in ovaries of the frog Xenopus laevis following the administration of gonadotropins that induce meiotic maturation and ovulation of large oocytes and in vivo treatment with HCG or FPH resulted in an eight- or eleven-fold increase as compared to tissue that was not pretreated in vivo.
Abstract: Endogenous progesterone was measured in ovaries of the frog Xenopus laevis following the administration of gonadotropins that induce meiotic maturation and ovulation of large oocytes. Ovarian pieces were incubated for 0, 1, 3, 5, or 10 h in Gurdon’s solution in the presence or absence of human chorionic gonadotropin (HCG; 20 lU/mI) or a frog pituitary homogenate (FPH; 0.04 pituitary/mI). Each incubation sample was scored for ovulation and maturation at the end of its incubation period, homogenized in the medium, and extracted for progesterone with petroleum ether. Following purification on Sephadex LH-20, extracts were assayed for progesterone by a radioimmunoassay that was validated for use with frog ovarian tissue. In 13 experiments, mean (! SEM) progesterone concentration in untreated ovarian tissue was 3.7 ± 0.5 ng/gm at time zero and progesterone levels did not change significantly during 10 h of incubation. HCG-treated tissue (n = 6) exhibited a linear, two-fold increase in progesterone for the first 3 h of incubation and maintained that level for the remainder of the incubation. FPH treatment (n = 10) produced a linear six-fold increase in progesterone over the course of 10 h. Mean progesterone content across time was significantly greater (P<0.005) in FPH-treated tissue than in HCG-treated tissue. Both differed significantly (P<0.05) from untreated controls. In tissue treated with HCG the percent oocyte maturation was correlated (P<0.10) with both mean progesterone concentration across time and progesterone concentration at 10 h of incubation; ovulation did not occur. In FPH-treated tissue progesterone concentration was not correlated with percent maturation but was correlated (P<0.05) with the number of ovulations/gm. Treatment of ovarian pieces with the gonadotropins following a 10 h incubation in Gurdon’s solution produced effects similar to those following treatment at time zero. In vivo treatment with HCG prior to in vitro incubation of ovarian tissue with HCG or FPH resulted in an eight- or eleven-fold increase, respectively, in peak progesterone concentration as compared to tissue that was not pretreated in vivo. In two experiments large, preovulatory follicles contained sufficiently more (P<0.05) progesterone following FPH treatment than did smaller follicles. Both large and small FPH-treated follicles had significantly higher levels of progesterone than untreated control tissue.

88 citations


Journal Article
TL;DR: The properties and inducibility of aryl hydrocarbon hydroxylase (AHH) in cultured human lymphocytes were studied, and a sensitive method of analysis has been developed.
Abstract: The properties and inducibility of aryl hydrocarbon hydroxylase (AHH) in cultured human lymphocytes were studied, and a sensitive method of analysis has been developed. In agreement with other reports, peripheral blood lymphocytes per se had no activity and required pretreatment in culture with a mitogen for conversion to lymphoblasts to possess AHH activity. This activity had an absolute requirement for reduced nicotinamide adenine dinucleotide phosphate. Under our conditions of incubation, reduced nicotinamide adenine dinucleotide (1.3 mM) or ethylenediaminetetraacetic acid disodium salt (1 mM), when added to reduced nicotinamide adenine dinucleotide phosphate-fortified incubation mixture, caused about 30% increase in activity and MnCl2 caused an appreciable inhibition. The reaction was linear with the number of cells, with up to 16.8 X 10-6 cells contained in the incubation mixture, and had a pH optimum of 8.5. The enzyme was fairly stable at -70 degrees and retained about 90% of the original activity for 15 days. The enzyme activity in the mitogen-stimulated lymphocyte cultures appeared slowly and reached a maximum at 48 to 72 hr of incubation at 37 degrees, after which it considerably decayed with time. Viability of the cells in culture also decayed considerably after 72 hr and reached about 50% level at 120 hr. The enzyme was inducible with 3-methylcholanthrene and dibenz(a,h)anthracene. Dibenz(a,h)anthracene was a much more potent inducer than 3-methylcholanthrene and evoked a response in cells that would be considered noninducible with 3-methylcholanthrene. By using purified lymphocytes and Roswell Park Memorial Institute Medium 1640, providing larger surface area during culture, harvesting the cells at the time of minimum cell death and maximum AHH activity, and assaying AHH at its pH optimum of 8.5 instead of 7.6, it was possible to enhance the sensitivity of the assay an average of 17-fold.

83 citations


Journal ArticleDOI
13 Feb 1975-Nature
TL;DR: This work established that competition occurred between different scrapie agents intracerebrally injected into mice, indicated by an increase in the incubation period of the lethal scrapie agent when a different scraie agent had also been injected to impede its pathogenesis.
Abstract: MANY strains of scrapie agent have been isolated which differ in their biological properties, such as incubation period and type of brain lesion1. We have shown previously that competition occurred between different scrapie agents intracerebrally injected into mice2, indicated by an increase in the incubation period of the lethal scrapie agent when a different scrapie agent had also been injected to impede its pathogenesis. We did not establish whether the increased incubation resulted from replication of the lethal agent being hindered throughout or at particular stages of pathogenesis, or whether the increased incubation period resulted from some loss of effective titre.

73 citations


Journal ArticleDOI
TL;DR: Eggs of lake whitefish (Coregonus clupeaformis) were incubated in a constant-flow incubator at constant temperatures of 0.5 C, and equations were derived for predicting development time to 20 successive stages, and to hatching, at constant incubation temperatures and at fluctuating daily mean temperatures.
Abstract: Eggs of lake whitefish (Coregonus clupeaformis) were incubated in a constant-flow incubator at constant temperatures of 0.5, 2.0, 4.0, 5.9, 7.8, and 10.0 C. The time from fertilization to median hatch was inversely related to temperature, and ranged from 41.7 days at 10.0 C to 182 days at 0.5 C. The percentage hatch was highest (70.9-73.3%) at 4.0, 5.9, and 7.8 C, and was greatly reduced (6.0-28.4%) at 0.5, 2.0, and 10.0 C. The mortality of embryos was greatest during the early stages of development. Abnormally developed fry were most frequent (85.9% of the hatch) at 10.0 C, and least frequent (2.8%) at 4.0 C. Mean lengths of fry at hatching were shorter at 7.8 and 10.0 C (12.4 and 8.8 mm, respectively) than at lower temperatures (13.1 to 13.5 mm). The optimum temperature range for incubation of lake whitefish eggs was 3.2 to 8.1 C. Equations were derived for predicting development time to 20 successive stages, and to hatching, at constant incubation temperatures and at fluctuating daily mean wat...

58 citations


Journal ArticleDOI
TL;DR: The data are interpreted to suggest that the ‘loading' of proteins onto the transport system is inhibited during Ca2+‐free incubation and that the apparent transport of radioactive proteins during Ca1+‐ free incubation conditions might reflect proximo‐distal movement of either microtubular protein or some other protein components of the Transport system.
Abstract: —The effects of Ca2+-free incubation medium on in vitro axoplasmic transport of proteins were studied in the central and peripheral branches of primary afferent spinal neurons of frog. Following exposure of dorsal root ganglia to [3H]leucine, the amount of radioactive protein transported along the axons during a subsequent 19 h period was decreased by approximately 60 per cent in preparations incubated in Ca2+-free, 1 mm-EGTA medium compared to those in normal medium. In similar Ca2+-free conditions the endogenous calcium levels were decreased to one-fourth the levels found following incubation in normal medium. Neither raising EGTA concentrations to 10 mm nor incubation in Ca2+-free medium prior to the [3H]leucine pulse were found to decrease the amount of transported protein in Ca2+-free medium by more than 70 per cent. The decrement in the amount of transported proteins did not appear to be due to an effect of Ca2+-free medium upon either the uptake of [3H]leucine into ganglion cells or upon the incorporation of radioactive amino acid into protein. The data are interpreted to suggest (i) that‘loading' of proteins onto the transport system is inhibited during Ca2+-free incubation and (ii) that the apparent transport of radioactive proteins during Ca2+-free incubation conditions might reflect proximo-distal movement of either microtubular protein or some other protein components of the transport system. It is proposed that calcium ions might function as reversible bonds between the transport system and‘transported' proteins.

44 citations


Journal ArticleDOI
TL;DR: Characteristics of the clearing-factor lipase response of isolated fat-cells differ in several respects from those observed earlier with intact adipose tissue from 24h-starved rats, due to changes in the relative amounts of two different molecular forms of the enzyme that occur during the isolation of theFat-cells.
Abstract: 1. When fat-cells are isolated from the epididymal adipose tissue of 24h-starved rats and incubated at 25 degrees C in the presence of dialysed serum, glucose, insulin, amino acids and heparin, the total clearing-factor lipase acitivity of the incubation system increases progressively over a period of several hours. 2. All of the increase in activity is accounted for by the appearance of enzyme in the appearance of enzyme in the incubation medium and the fat-cell activity does not change significantly. Cycloheximids, at a concentration that prevents protein synthesis, does not affect the appearance of enzyme in the incubation medium, but the fat-cell enzyme activity is decreased in its presence. 3. The magnitude of the increase in total clearing factor lipase activity is unaffected by the omission of heparin from the medium. However, less enzyme is extracted in tis absence and the fat-cell activity increases. Cycloheximide again only affects the rise in cell activity and does not alter the activity in the incubation medium. 4. When serum in the incubation medium is replaced by casein, the distribution of enzyme between the cells and the medium is changed, but the magnitudes of the increases in total enzyme activity are similar. 5. These characteristics of the clearing-factor lipase response of isolated fat-cells differ in several respects from those observed earlier with intact adipose tissue from 24h-starved rats (Robinson & Wing, 1971; Cryer et al., 1973). The differences could be due, in part, to changes in the relative amounts of two different molecular forms of the enzyme that occur during the isolation of the fat-cells.

38 citations


Journal Article
TL;DR: This membrane binding of globin during incubation provides a model for the study of Heinz body formation in clinical disorders and reveals a new protein band that was identical to globin monomers.

Journal ArticleDOI
TL;DR: It is discussed that embryonic responsiveness to temperature changes in the environment during natural incubation may play some role in later behavioral capabilities.
Abstract: In 3 experiments we have attempted to determine the extent to which the chick embryo is behaviorally and physiologically responsive to short term changes (.5-2 hr) in the normal ambient incubation temperature. Embryos ranging in age from 6-20 days of incubation have been examined after exposure to temperatures ranging from 30.5 degrees to 44.4 degrees C (normal incubator and nesting temperatures are 37-38 degrees C). At 6,9 and 12 days of age the heart rate and the duration of amnion contractions were significantly altered by exposure to temperature either higher or lower than normal although overt neuromuscular activity (motality) remains unchanged. At 15 and 20 days, however, (hatching occurs on Day 21) the rate of neuromusclar activity is altered at both low and high temperatures. At 20 days, beak-clapping, vocalization, and respiration rates also change reliably upon short-term exposure to both high and low temperatures. The possibility is discussed that embryonic responsiveness to temperature changes in the environment during natural incubation may play some role in later behavioral capabilities.

Journal ArticleDOI
TL;DR: The accumulation of alpha-aminoisobutyric acid by placental slices is increased dramatically upon prior incubation of the slices in amino acid-free, buffered saline, suggesting that a reduced availability of amino acids may initiate compensatory changes in the synthesis of cellular transport proteins.


Journal ArticleDOI
TL;DR: In this article, a comparison of four extractants on four soils in an incubation study indicated that sulfate extracted by 0.15% calcium chloride was most closely correlated with CO2 evolution and nitrogen mineralization through a 14-week incubation period.
Abstract: The comparison of four extractants on four soils in an incubation study indicated that sulfate extracted by 0.15% calcium chloride was most closely correlated with CO2 evolution and nitrogen mineralization through a 14-wk incubation period. Air-drying the incubated samples was found to introduce sulfur transformations, which were unrelated to microbiological activity as measured by CO2 evolution. Accordingly, drying incubated samples prior to analysis is not recommended for sulfur mineralization studies. Soil:extractant ratios (using CaCl2) influenced levels of sulfate extracted from incubated samples, particularly those containing adsorbed sulfate. A comparison of a simple closed incubation system with an open system indicated that under the conditions employed, the closed system remained aerobic, and accordingly was suitable for sulfur mineralization studies.

Journal ArticleDOI
TL;DR: Results prove that the anti-m#{252}llerian hormone is a macromolecule and suggest that it is probably a protein, and that part of the activity is due to hormone newly synthesized during the incubation.
Abstract: Mullerium-inhibiting activity was detected in incubation media of calf fetal testicular tissue. Dialysis of the medium did not modify its biological activity, but testosterone content of dialyzed medium was diminished by 92 percent. Four-fold concentration of incubation medium greatly enhanced its biological activity, which was destroyed by heat and blockage of sulphydryl groups by 0.5 M iodoacetic acid. Addition of cycloheximide to the medium during incubation decreased its biological activity, indicating that part of the activity is due to hormone newly synthesized during the incubation. These results prove that the anti-m#{252}llerian hormone is a macromolecule and suggest that it is probably a protein.

Journal ArticleDOI
TL;DR: Salbutamol had an effect similar to isoprenaline, i.e. it induced the release of renin into the medium without affecting production, and was about a third as potent as isperenaline.
Abstract: 1 Isolated renal cortical cells of the cat have been demonstrated to produce renin on incubation in vitro. After 2 h of incubation, without added agonist, the total amount of renin in the flask increased by a mean of 27.2 percent. The increase in renin content of the incubation flask was found to be present in the medium. 2 Noradrenaline (1.18 times 10-minus 4M) and adrenaline (1.09 times 10-minus 4M) added to the incubation medium stimulated renin production by 45 and 34% respectively, compared with the incubated controls. Most of the increase in renin production was present in the incubation medium. 3 Isoprenaline did not stimulate renin production. However, when added to the incubation medium at a concentration of 0.72 times 10-minus 4M there was a significant decrease in the cellular content and a significant increase in the medium content of renin. This increase was at least as great as that observed with adrenaline and noradrenaline. 4 Salbutamol had an effect similar to isoprenaline, i.e. it induced the release of renin into the medium without affecting production. In this respect it was about a third as potent as isoprenaline.

Journal ArticleDOI
TL;DR: The results indicate that the development of alpha-amylase activity in de-embryonated maize kernels is independent of an embryo or an exogenous source of gibberellic acid and suggest that this process involved protein synthesis.
Abstract: The development of amylase activity in extracts from de-embryonated and GA 3 -treated de-embryonated maize kernels ( Zea mays L.) was determined during a 10-day incubation period. The increase in activity was compared with activity extracted from endosperms dissected from germinating whole kernels. Chromatographic analysis of reaction products as well as physicochemical characterization demonstrated that the activities from GA 3 -treated and nontreated tissue were comparable and that part of the activity was attributable to α-amylase. Concomitant with the increase in activity was the appearance of a number of starch-degrading bands, as evidenced by polyacrylamide gel electrophoresis. Actinomycin-D (20 μg/ml) and cycloheximide (5 μg/ml), when present in the incubation medium at early periods of incubation, were capable of inhibiting the development of amylase activity and of preventing the appearance of the starch-degrading bands. The results indicate that the development of α-amylase activity in de-embryonated maize kernels is independent of an embryo or an exogenous source of gibberellic acid and suggest that this process involved protein synthesis.

Journal ArticleDOI
TL;DR: Altered alterations in the flow of carbon into cellular constituents when cells are treated with cinnamic and ferulic acids explain, at least in part, why these compounds in scopoletin.
Abstract: and scopoletin. All test compounds except chlorogenic acid were completely inhibitory at a 10-M concentration, resulting in death of the cells prior to completion of the growth cycle. To assess the cellular effects of two commonly named plant inhibitors, ferulic and cinnamic acids, these compounds were provided to cultures during incubation of cells with glucose-UL"4C. Incubation of cells with glucose-UL-'4C in the presence of 10-4M ferulic acid resulted in increased incorporation of 14C into the soluble lipid fraction along with decreased incorporation of "4C into protein, organic acids, and soluble amino acids. Treatment of the cells with 10-5M cinnamic acid during the incubation period resulted in a significant decrease in incorporation of I4C into protein. These alterations in the flow of carbon into cellular constituents when cells are treated with cinnamic and ferulic acids explain, at least in part, why these compounds in

Journal ArticleDOI
TL;DR: Differences between the duration of interaction of TSH and PGE1 with thyroid may be dependent or a more gradual dissociation to tissue bound TSH, a more rapid inactivation of bound-PGE1, or both.
Abstract: Differences exist in the rates at which hormones are inactivated by, or dissociate from, their target tissues. The present studies examined the binding of biologically active TSH to thyroid slices and compared its characteristics to those of PGE1. Canine thyroid slices were initially incubated with 5 mU/ml of bovine TSH (TSH-Initial) for 15 min, washed and incubated in media free of hormone for 3 hr. At the conclusion of this second incubation period, all slices were again washed. Some were then transferred to media containing 10-2M theophylline for a final 10 min incubation and subsequent measurement of cAMP and protein kinase, while others were transferred to media containing [l-l4C]glucose without theophylline fora final 45 min incubation to assess glucose oxidation. Identically treated slices never exposed to TSH served as controls, while others were exposed to TSH only during the final 10 or 45 min incubation periods (TSH-Final). cAMP content determined after the final 10 min incubation in theophylli...

Journal ArticleDOI
TL;DR: A system has been developed for long-term incubation of rat thymus cells in sus pension in a chemically defined medium consisting of medium 199 and methylcellulsoe to study quantitatively the full time-course of glucocorticoid actions, from the early inhibitory effects on glucose uptake to the slow cytolytic effects.
Abstract: A system has been developed for longterm incubation of rat thymus cells in suspension in a chemically defined medium consisting of Medium 199 and methylcellulose. With this system it is possible to study quantitatively the full time-course of glucocorticoid actions, from the early inhibitory effects on glucose uptake to the slow cytolytic effects. Cells incubated under these conditions preserve their sensitivity to the inhibitory effects of cortisol on glucose uptake for at least 12 h. Glucocorticoids at physiological concentrations lead to cytolysis (measured by reduction in viable cell counts determined by a modification of the pronase-cetrimide method) by 12 h incubation time. The cytolytic effect exhibits well-defined dose-response relationships and specificity for glucocorticoids. By 24 h, cortisol at 10-6M consistently reduces the total cell count by about 15‰, and the viable cell count by about 40‰. Cortisol is active down to 10-7M. Dexamethasone is roughly 10 times as active as cortisol, and corti...

Journal ArticleDOI
TL;DR: 5-Hydroxytryptamine, prostaglandin E1 and dopamine do not significantly enhance cyclic AMP formation in guinea-pig brain slices in either the presence in, or the absence of calcium ions from the incubation medium, but in calcium-free Krebs-Ringer solution a pronounced effect of noradrenaline on cyclicAMP levels is observed.
Abstract: In guinea-pig cerebral cortical slices cyclic AMP concentrations increase during incubation with histamine+noradrenaline. After 10 min of incubation the levels of cyclic AMP start to decline. When calcium ions are omitted from the incubation medium, cyclic AMP levels do increase to a greater extent under the same conditions and do not drop during 30 min incubation. In the presence of calcium ions cyclic AMP synthesis can not be elicited by noradrenaline alone. In calcium-free Krebs-Ringer solution a pronounced effect of noradrenaline on cyclic AMP levels is observed. This effect of noradrenaline is shown to be mediated by a classical α-type receptor. 5-Hydroxytryptamine, prostaglandin E 1 and dopamine do not significantly enhance cyclic AMP formation in guinea-pig brain slices in either the presence in, or the absence of calcium ions from the incubation medium. Under depolarizing conditions of incubation the stimulatory effect of ouabain or 125 mM K+ is blocked in a calcium-free medium, while with the depolarizing agent veratridine no significant reduction of cyclic AMP formed during incubation in a calcium-free medium is obtained.

Journal ArticleDOI
TL;DR: It is proposed that the analog nucleosides are first split by purine nucleoside phosphorylase (PNPasc), liberating the corresponding free base, which then reacts with 5-phosphoribosyl-1-pyrophosphate (PRPP) and the salvage enzyme, hypoxanthine-guanine phosphorIBosyltransferase (HGPRTase) to form analog monophosphate nucleotides.

Journal ArticleDOI
TL;DR: No significant difference was observed between whey collected from locally immunised mammary glands and that from non-immunised glands within each group, but the numbers of viable bacteria were greatly reduced when blood serum or whey were incorporated in incubation mixtures.

Journal ArticleDOI
TL;DR: It is suggested that the hormonal and situational cues are not only important contributory factors but also complement one another in the induction of incubation behaviour.
Abstract: Male ring doves (Streptopelia risoria) were treated with either progesterone or dexamethasone (a powerful ACTH inhibitor) and tested for incubation behaviour. Progesterone treatments shortened the latency of incubation response by facilitating nest-related pre-incubation behaviour patterns in the nest bowl and components of incubation behaviour. The accumulated rather than the daily dose level of progesterone injections appeared to be the determinant factor in mediating behavioural effects. Dexamethasone treatment at the dosage of 100 mug/day for 7 days inhibited the overall expression of male courtship behaviour. None of the dexamethasone-treated ring doves "sat" in 2 weeks. It is suggested that the hormonal and situational (non-hormonal) cues are not only important contributory factors but also complement one another in the induction of incubation behaviour.


Journal ArticleDOI
TL;DR: No active transport mechanism could be demonstrated for uric acid, hypoxanthine, or xanthine in rat or hamster jejunum in rat and hamster everted jejunal sacs.
Abstract: The in vitro transport of [2-14C]uric acid, [8-14C]hypoxanthine, and [8-14C]xanthine, each dissolved in Krebs–Ringer bicarbonate buffer, was studied with everted jejunal sacs from rat and hamster. No evidence could be obtained for the development of a concentration gradient between the intracellular fluid and the incubation medium or between the sac contents and the incubation medium, for any of the three oxypurines. Inhibitors of active transport, such as anaerobiosis or dinitrophenol, had no significant effect on the rate of transport. A large percentage of hypoxanthine and xanthine was oxidized to uric acid in the sac-wall homogenate, sac contents, and incubation medium during the course of the incubation. This oxidation could be prevented by addition of allopurinol (3 mM) to the incubation medium, but concentration gradients were still not obtained. No active transport mechanism could be demonstrated for uric acid, hypoxanthine, or xanthine in rat or hamster jejunum.

Journal ArticleDOI
TL;DR: Ungerminated microconidia of Fusarium oxysporum have a mean cell DNA content of 0-134 times 10--12 g/cell with a guanine-plus-cytosine composition of 50-75%.
Abstract: SUMMARY: Ungerminated microconidia of Fusarium oxysporum have a mean cell DNA content of 0.134 X 10-12 g/cell with a guanine-plus-cytosine composition (% GC) of 50–75%. During germination, the first dry weight increase of the spore population was detected after 3 h incubation and the first germ tube appeared after 4 h. The total DNA of the culture sharply increased after 5 h, followed by a pause at 6 h. At this time the DNA content per nucleus was maximal and the first nuclear divisions were detected. Pauses in the rise of total DNA of the culture and in the [14C]adenine incorporation pattern suggest that there is partial synchrony in DNA synthesis at the beginning of incubation. This is also supported by the fact that until 8 h, only hyphae with 1, 2 and 4 nuclei were observed. [14C]adenine incorporation into DNA averaged 2.68% of the total taken up in 10 h incubation.

Journal ArticleDOI
TL;DR: It is suggested that castration stimulates the release and synthesis of hypothalamic LH-RF in male rats, and in control hypothalami the content was significantly higher in control than in castrated rats.
Abstract: The effect of castration upon hypothalamic LH-RF synthesis and content was determined in mature male rats. In each single experiment 20 hypothalami from both normal and 60-day-castrated rats were bisected into symmetrical portions. For the determination of LH-RF synthesis 20 hypothalamic halves were incubated for 120 min. After incubation the tissue was homogenized in medium containing 1 N acetic acid, and centrifuged; 1.0 ml of the supernatant was used to test LH-RF activity. In the other 20 halves, hypothalamic LH-RF content was determined: the samples were homogenized without incubation in 1 N acetic acid, centrifuged, and LH-RF activity was tested in 1.0 ml of the supernatant. LH-RF activity was determined in vivo in ovariectomized rats pre-treated with estrogen-progesterone by measuring, by radioimmunoassay, the LH modifications in serum after the i.v. administration of the extracts. Hypothalamic LH-RF content was significantly higher in control than in castrated rats (p is less than 0.001). After incubation there were no changes in the LH-releasing potency of control hypothalami compared with non-incubated tissue, whereas a significant increase (616%) was found after the incubation of hypothalami from castrated rats. On the other hand, after incubation LH-RF activity was higher (p is less than 0.02) in castrated than in control hypothalami. These results suggest that castration stimulates the release and synthesis of hypothalamic LH-RF in male rats.

Journal ArticleDOI
TL;DR: Compartmentation of the ATP precursor pool for cyclic AMP is suggested by the difference in ATP/cyclicAMP ratios for endogenous and labelled compounds, and by the ineffectiveness of antimycin A 1 in decreasing the conversion rate of labelled adenine nucleotides to [ 14 C]cyclic AMp.