Showing papers on "Incubation published in 1978"
TL;DR: Data indicate that a species of Prolactin which is identical to pituitary prolactin by the criteria of immunoprecipitation and gel chromatography is synthesized by human decidual tissue in vitro.
154 citations
TL;DR: The results indicate that transformation may play an important role in the adaptation of the Bacilli to their natural habitat.
Abstract: Genetically labelled strains of Bacillus subtilis have been shown to exchange blocks of linked genes while growing together in soil. After eight days of incubation, 79% of unselected colony-forming units exhibited a phenotype containing markers from both parents; the parental strains were not detected after the first day of incubation. High frequencies of trans-formation were also obtained by adding genetically labelled deoxyribonucleic acid to single-strain soil cultures. Observed linkage of genetic markers was greater in soil transformation than in standard laboratory procedures. The results indicate that transformation may play an important role in the adaptation of the Bacilli to their natural habitat.
144 citations
Journal Article•
TL;DR: Thermotolerance induced in Chinese hamster ovary (CHO) cells by a 45° heat treatment and developed at 37° resulted in an increased D 0 but a reduced extrapolation number, n, of a subsequent 45°Heat survival curve, which was dependent upon the conditioning hyperthermia treatment.
Abstract: Thermotolerance induced in Chinese hamster ovary (CHO) cells by a 45° heat treatment and developed at 37° resulted in an increased D 0 but a reduced extrapolation number, n , of a subsequent 45° heat survival curve. The time course and magnitude of thermotolerance development were dependent upon the conditioning hyperthermia treatment. Within 2 hr after a 10-min exposure to 45°, the n of the subsequent 45° hyperthermia survival curve increased approximately 5-fold with little change in the D 0 . Thereafter, n returned to control values, whereas the D 0 increased by a factor of 5 by 8 hr and then only slowly disappeared at a rate of 0.1 min at 45° per hr of incubation at 37°. A conditioning dose of 5 min at 45° increased the D 0 of the subsequent 45° heat survival curve by a factor of 3.3 within 2 hr, but then the D 0 returned to control values at the same rate as after a conditioning treatment of 10 min at 45°. CHO cells incubated at 40° grew normally without any evidence of cell killing for more than 2 generations, and incubation at 40° for 0 to 7 hr prior to acute heating at 45° did not induce thermotolerance in terms of an increased D 0 . However, the D q of the 45° heat survival curve was increased approximately 3-fold by 40° preincubation for 7 hr. Increasing the incubation temperature from 37 to 39–41° between 45° heat treatments did not alter the thermotolerant D 0 of the subsequent 45° heat survival curve but did reduce n to 1.0. In addition, the survival curves following 45° conditioning and incubation at 39, 40, or 41° were displaced downward by factors of 5.3, 47, and 360, respectively. The enhanced cell killing resulting from post-45° hyperthermia incubation at 39–41° may be due to the conversion of sublethal damage to lethal damage independently of the induction of thermotolerance.
122 citations
TL;DR: One of the species of human interferon produced by incubation of leukocytes with Newcastle disease virus was purified to homogeneity and exhibited one peak of activity coinciding with a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
Abstract: One of the species of human interferon produced by incubation of leukocytes with Newcastle disease virus was purified to homogeneity. It exhibited one peak of activity coinciding with a single protein band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis.
121 citations
TL;DR: Lymphocytes from normal untransfused individuals and 3 untransFused AA patients enhanced significantly CFU-C growth from both HLA-matched and -mismatched marrows.
103 citations
TL;DR: In this article, cultures of six fungi and two bacteria were added to samples of aggregates in which either 14C-labeled glucose or starch was thoroughly distributed in macro-and micropores or in control samples where the labelled substrates were added in preformed aggregates and considered to be mainly in macropores.
Abstract: Cultures of six fungi and two bacteria were added to samples of aggregates in which either 14C-labelled glucose or starch was thoroughly distributed in macro- and micropores or in control samples where the labelled substrates were added to the preformed aggregates and considered to be mainly in macropores. The release of 14CO2 was monitored over a 24-day incubation.
In the control samples with substrates mainly in macropores, the bacteria were as active as fungi in releasing 14CO2 from both soils. When the substrates were distributed in macro- and micropores in aggregates made from a fine sandy loam, the fungi were more efficient than bacteria in releasing 14CO2. This was not the case in a self-mulching clay.
The initial flush of 14CO2 released during incubation of the amended fine sandy loam was due mainly to fungi, which were followed by a secondary bacterial population. The change in populations occurred simultaneously with a step in the cumulative 14CO2 release curve thought to be due to the utilization of all the labelled substrate added, followed by renewed respiration as the secondary population flourished. The results presented fit well with an efficiency of C assimilation by micro-organism in soil of about 60%.
98 citations
86 citations
TL;DR: In the first comparative consideration of the metabolism of avian embryos, Rahn et al. (1974) predicted that, for eggs of different species but of the same mass, “plateau” metabolic rate is inversely related to the length of the incubation period and can be predicted most accurately from the equation.
Abstract: In the first comparative consideration of the metabolism of avian embryos, Rahn et al. (1974) made several important assumptions and offered a number of interesting predictions. One of their assumptions was that the relation between metabolic rate and incubation age (days incubated) is the same in all avian species as it is in the chicken (Gallus gallus). A second important assumption was that the partial pressures of oxygen and carbon dioxide in the air cell during the plateau phase are essentially the same in all species, regardless of egg mass and incubation period. This assumption led Rahn et al. to predict that, for eggs of different species but of the same mass ( W), “plateau” metabolic rate (I&,) * is inversely related to the length of the incubation period (I) and can be predicted most accurately from the equation:
80 citations
TL;DR: The female Goldcrest incubates alone and is not regularly fed by her mate, and may be fully developed before the clutch is completed, on average being shortest during the midday hours.
Abstract: The female Goldcrest incubates alone and is not regularly fed by her mate. Incubation starts gradually already during the egg-laying period, and may be fully developed before the clutch is completed. From that time onward the hourly mean egg temperature remains remarkably constant, largely independent of time of day and weather conditions. The overall mean egg temperature, recorded during the continuous incubation period, was 36.54?C. The female regulated the temperature of the eggs by adjusting her attentive time. This is achieved by (1) varying the duration of the periods-off, which is inversely correlated with air temperature, and (2) varying the duration of the periods-on, which is less influenced by the weather conditions, but is significantly correlated with the time of day (light intensity), on average being shortest during the midday hours.
74 citations
TL;DR: The various data suggest that 1) monodeiodination of T3 and rT3 to T2 is enzymic in nature; 2) liver and kidney may be the major sites of metabolic transformations of T1 and T2, and 3) propylthiouracil and iodoacetic acid inhibited conversion of both T3and rT2 in an uncompetititve and a non-competitive manner.
Abstract: To study conversion of 3,5,3′-triiodothyroinine (T3) and 3,3′,5′-triiodothyronine (rT3) to 3,3 - diiodothyronine (T2) in vitro, T3 or rT3 was incubated at pH 7.35 with homogenates of several rat tissues (liver, kidney, muscle, heart, lung, spleen, intestines, and brain) for 15 min at 37 C. The T2 generated during incubation was measured in an ethanol extract of the incubation mixture by a specific RIA of T2; T4, T3, and rT3 crossreacted in the T2 RIA only to an extent of 0.006, 0.2, and 0.04%, respectively. T2 was produced regularly when T3 or rT3 was incubated with liver or kidney homogenates; other tissues generated little or no T2 under similar conditions. Studies with liver homogenates revealed that production of T2 from both T3 and rT3 was influenced significantly by tissue and substrate concentrations, temperature, pH and duration of incubation. T3- as well as rT3-monodeiodinating activities were unaffected by large doses (≥3 μM) of sodium iodide, diiodotyrosine, and methimazole, but were inhibited ...
69 citations
01 Jan 1978
TL;DR: Eggs of the common snapping turtle, Chelydra serpentina, were incubated at constant temperatures of 20-35?C and the rate of development during the final weeks of incubation appeared to be independent of temperature.
Abstract: Eggs of the common snapping turtle, Chelydra serpentina, were incubated at constant temperatures of 20-35?C. Incubation was successful at temperatures of 22-30?C. Duration of incubation was inversely related to temperature. The rate of development during the final weeks of incubation appeared to be independent of temperature.
TL;DR: Stria vascularis from guinea pig cochleae was incubated in vitro to determine its metabolic response to variations in substrate and ion composition of the incubation medium, and glucose appears to be an adequate substrate for stria in vitro since glutamate, pyruvate, and fumarate did not increase the respiratory rate.
Abstract: Stria vascularis from guinea pig cochleae was incubated in vitro to determine its metabolic response to variations in substrate and ion composition of the incubation medium. The respiratory rate at 37 degrees C in a medium containing glucose and pyruvate as substrate was 17.3 +/- 1.33 (SEM, n = 51) microliter O2/mg dry weight-hour. The stria could not maintain constant respiration by relying solely upon endogenous fuel stores. With substrate supplied, the ATP level could be maintained at about 73% of that existing in vivo. Glucose appears to be an adequate substrate for stria in vitro since glutamate, pyruvate, and fumarate did not increase the respiratory rate. Succinate increased respiration markedly but did not increase the ATP level. Ouabain (10(-4) M) caused a 48% decrease in the respiratory rate. Incubation in Na+-free and K"-free medium, each resulted in irreversible decrease of respiratory rate comparable to (or greater than) that caused by ouabain. These data are in accord with the high activity of Na+-K+-ATPase in the stria and the pronounced sensitivity of the endolymphatic potential to ouabain.
TL;DR: In this paper, an isotope-recovery experiment demonstrated that 13.7% of added l−14C−hexadecane was converted to 14C−cell carbon and 14CO2 after 375 h incubation.
Abstract: Reducing sediments of Lake Mendota were challenged to demonstrate evidence of anaerobic conversion of l‐14C‐hexadecane to 14CO2. Low levels of 14CO2 were detected above formaldehyde controls in anoxic sediment and bottom waters and in surface water sparged with nitrogen. Aerobic incubation of the same sediment and water demonstrated extensive conversion of l‐14C‐hexade‐cane to 14CO2. The low levels of 14CO2 detected in anaerobic incubation were not increased by addition of nitrate or in a pre‐reduced medium containing nitrate and sulfate. An isotope‐recovery experiment demonstrated that 13.7% of added l‐14C‐hexadecane was converted to 14C‐cell carbon and 14CO2 after 375 h incubation.
TL;DR: Artificially incubated mallard eggs were treated externally with No. 2 fuel oil or Southern Louisiana crude oil at various times during the incubation period, and few external malformations of any kind were observed among survivors of the oil exposure.
Abstract: Artificially incubated mallard eggs were treated externally with 5 microliter of No. 2 fuel oil or 5 microliter of Southern Louisiana crude oil at various times during the incubation period. Embryos were most sensitive to petroleum during the first 10 days of incubation. Southern Louisiana crude oil was more toxic to mallard embryos than No. 2 fuel oil. Hatching weights of ducklings from treated eggs were usually not different from hatching weights of control ducklings. Petroleum may cause bill abnormalities among embryos exposed to a lethal amount of oil early in incubation, but few external malformations of any kind were observed among survivors of the oil exposure. The breeding effort of colonial aquatic birds would be in the greatest danger from oil contamination when a large portion of the birds are in the early stages of incubation.
Journal Article•
TL;DR: The results give an indication of the repairability of benzo( a )pyrene-induced DNA damage in human lung cells that are related to the target tissues of polycyclic aromatic hydrocarbon carcinogenesis in humans.
Abstract: Repair of DNA damage induced by the proximate benzo( a )pyrene metabolites (±)-7β,8α-dihydroxy-9α,10α-or 9β,10β-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene was studied in the human alveolar tumor line A549. The fragmentation and subsequent reconstitution of DNA parent strands upon treatment of A549 cells with the proximate metabolites (±)-7β,8α-dihydroxy-9α,10α- or 9β,10β-epoxy7,8,9,10-tetrahydrobenzo( a )pyrene was followed by the alkaline elution procedure. In the same experiments the effect of the benzo( a )pyrene diol-epoxide treatment on the lengths of the newly synthesized daughter strands and the total amounts of DNA synthesized was determined as a function of posttreatment incubation. Parental DNA strands were fragmented within the first 3 hr following drug treatment and then slowly elongated to the length of untreated control samples during 30 hr of incubation. Benzo( a )pyrene diol-epoxide treatment also caused the formation of increased fractions of short daughter strands within the first 3 hr of incubation. The fraction of short daughter strands returned to control levels after 15 hr of incubation. (±)-7β,8α-dihydroxy-9α,10α- or 9β,10β-epoxy-7,8,9,10-tetrahydrobenzo( a )pyrene exerted similar effects on the integrity of parental DNA and on daughter strand synthesis. The total amount of DNA synthesized within a 30-min period decreased to 10 to 25% of untreated control cultures during 30 hr of incubation.
Our results give an indication of the repairability of benzo( a )pyrene-induced DNA damage in human lung cells that are related to the target tissues of polycyclic aromatic hydrocarbon carcinogenesis in humans.
TL;DR: The present investigation was undertaken in order to establish an optimal tissue pretreatment and an optimal incubation medium for the histochemical demonstration of succinate dehydrogenase and yielded blameless morphological integrity and enzyme localization as well as optimal SDH-activity.
Abstract: The present investigation was undertaken in order to establish an optimal tissue pretreatment and an optimal incubation medium for the histochemical demonstration of succinate dehydrogenase (E.C. 1.3.99.1). The investigations were performed on steroid producing (testicle, adrenal gland) and steroid dependent (Fallopian tube) tissues. We studied the influences of formalin fixation, acetone, magnesium ions, cyanides, electron carriers (phenazine methosulfate, menadione, coenzyme Q10), osmolarity, substrate concentration and inhibitors (oxalacetate, oxalate, malonate, 4-chloromercuribenzoic acid). The following procedure yields blameless morphological integrity and enzyme localization as well as optimal SDH-activity: Freezing of tissue cubes (diameter less than 5 mm) in propane cooled with liquid nitrogen or in melting freon. Incubation of 5 μm cryostat sections in narrow jars in the following medium (38.5 ml):
The incubation medium has an osmolarity of 440 mosm. The incubation is carried out for 10 min at 37° C in darkness. To avoid non specific formazan deposits in lipid containing tissues a preincubation of the cryostat sections in 100% acetone at −22° C or −40° C for 7–10 min and an incubation time of 20–30 min is recommended. Control incubations adduced proof at the specificity of the SDH demonstration. Parallel incubation without PMS in order to determine indirectly the content of endogenous CoQ10 is further recommended.
TL;DR: Demonstration of synergism between trimethoprim and sulfamethoxazole against 10 Nocardia isolates was found to be critically dependent upon the isolate, the duration of incubation, and the trimETHoprim-sulfameth oxazole ratio.
Abstract: Demonstration of synergism between trimethoprim and sulfamethoxazole against 10 Nocardia isolates was found to be critically dependent upon the isolate, the duration of incubation, and the trimethoprim-sulfamethoxazole ratio Inoculum effect was not significant The trimethoprim-sulfamethoxazole ratio in the commercial, fixed-dose combination was found to contain too little trimethoprim to be optimal for Nocardia
TL;DR: 5-HT may be a growth promoting or regulating factor for embyronal brain and the optimal doses have been determined.
TL;DR: Prolonged incubation of fetal rat calvaria with sCT, PGE1, and PGE2 caused a significant increase in concentration of cAMP at 15 min, followed by a decrease thereafter.
Abstract: Incubation of fetal rat calvaria with parathyroid hormone (PTH, 2 U/ml) causes an initial rise in cAMP concentration in the tissue at 15 min, followed by a decrease upon further incubation, but concentrations remain above control levels for at least 120 min. The decrease in cAMP levels could not be explained by hormone inactivation or by secretion into the medium of a hormone inhibitor. Calvaria incubated for 60 min with PTH did not respond to the addition of new PTH, but addition of salmon calcitonin (sCT, 100 mU/ml) or prostaglandin E1 (PGE1, 2.5 μg/ml) at this point clearly resulted in a further increase in cAMP concentration. Prolonged incubation of calvaria with sCT, PGE1, and PGE2 also caused a significant increase in concentration of cAMP at 15 min, followed by a decrease thereafter. Tissue incubated with sCT for 60 min did not respond to the addition of new sCT, but responded to newly added PTH. Similarly, tissue incubated for 60 min with PGE1, did not respond to addition of new PGE1, but responde...
TL;DR: The results suggest that reversible glycosylation with N-acetyl-D-glucosamine residues may serve as a regulatory signal for the conversion of the active factor to its inactive form under favorable nutritional status.
Abstract: A cell surface component from quiescent BALB/c 3T3 mouse cells that inhibits DNA synthesis and cell division when added to a culture of growing 3T3 cells has been detected. The inhibition of DNA synthesis by this factor was dependent on concentration and time of incubation; a transient exposure of cells to the factor followed by incubation in its absence for 20 hr was sufficient to elicit its inhibitory effect. The active component appears to be protein in nature, as judged by heat inactivation and trypsin sensitivity. Extracts obtained in an identical manner from quiescent 3T3 cells that had been preincubated in situ with uridine diphosphate N-acetyl-D-glucosamine (UDP-GlcNAc) did not inhibit DNA synthesis. The effect was specific for UDP-GlcNAc: incubation with three other nucleotide sugars yielded active component. Incubation of the inactive component from UDP-GlcNAc-treated cells with purified N-acetyl-β-D-glucosaminidase in vitro restored its inhibitory property. Extracts from growing cells failed to inhibit DNA synthesis. These results suggest that reversible glycosylation with N-acetyl-D-glucosamine residues may serve as a regulatory signal for the conversion of the active factor to its inactive form. We propose that the onset of quiescence of 3T3 cells is due to a casual relationship between depletion of growth factors in the culture medium and the presence of the active regulatory factor on the cell surface that inhibits DNA synthesis; conversion of the regulatory factor to its inactive form under favorable nutritional status may be viewed as a switch that allows DNA synthesis to resume.
TL;DR: The prostaglandin synthetase activity in fish and marine invertebrates was measured by the incubation of 14C-labeled dihomo-γ-linolenic acid with a tissue homogenate with moderate activity, whereas the activity was very low in gonad.
Abstract: The prostaglandin synthetase activity in fish and marine invertebrates was measured by the incubation of 14C-labeled dihomo-γ-linolenic acid with a tissue homogenate. The tissues of sea-squirt, crab, bivalves and carp have a synthetic activity of prostaglandins from dihomo-γ-linolenic acid, but the yields of prostaglandins were generally low (<10% conversion) compared with those of the renal medulla of rabbit (about 20%). Of the tissues, the moderate activity was observed in gill and mantle, whereas the activity was very low in gonad. Some unidentified products from the incubation mixture were detected by autoradiography.
TL;DR: The adaptive radiation of parental care in waterfowl, p. 357-392, is a model for social behaviour in birds and mammals and helps clarify the mechanisms behind family integration in ducks.
Abstract: BERGMAN, R. D., AND D. V. DERKSEN. 1977. Observations on Arctic and Red-throated Loons at Storkersen Point, Alaska. Arctic 30:41-51. COLLIAS, N. E., A~TII E. C. COLLIAS. 1956. Some mechanisms of family integration in ducks. Auk 73 : 378-400. GOTTLIED, G. 1965. Imprinting in relation to parental and species identification by avian neonates. J. Comp. Physiol. Psychol. 59:345-356. H~~HN, E. 0. 1972. Arctic Loon breeding in Alberta. Can. Field-Nat. 86:372. JOHNSGARD, P. A., AND J. KEAR. 1968. A review of parental carrying of young by waterfowl. Living Bird 7:89-102. KEAR, J. 1970. The adaptive radiation of parental care in waterfowl, p. 357-392. In J. H. Crook Led.], Social behaviour in birds and mammals __I. Academic Press, London. KLOPFER. P. H. 1959. The develonment of sotmAsignal preferences in ducks. ALU
TL;DR: For Homarus gammarus in the North Irish Sea, a notional spawning date of 15 August was selected on the basis of substantial commercial catch data, and can be used to calculate the temperature regime required to cause hatching at a preselected time.
Abstract: For Homarus gammarus in the North Irish Sea, a notional spawning date of 15 August was selected on the basis of substantial commercial catch data. Berried females were exposed to fluctuating temperature regimes, with average temperatures between 10.0° and 18.3°C. Incubation periods ranged between 3.6 and 9.5 months. The relationship between incubation period and the sum of monthly average temperatures was approximately linear, and can be used to calculate the temperature regime required to cause hatching at a preselected time. At 10.4°C (the local annual average temperature), the estimated incubation period is 11 months. This is compared with data for H. americanus, which indicate an incubation period of 11.4 months at a local annual average temperature of about 8.1°C. The implications of this are discussed.
TL;DR: The human polymorphonuclear leukocyte possesses the ability to generate T( 3) and rT(3) from substrate T(4) and in cord blood leukocytes, the putative enzymes catalyzing T(3%) and r(3)-generating activities appear to be functionally intact under the experimental conditions employed.
Abstract: Extrathyroidal monodeiodination of l-thyroxine (T4) is the principal source of l-triiodothyronine (T3) and l-reverse-triiodothyronine (rT3) production. To define some of the cellular factors involved, we examined T3 and rT3 generation from added nonradioactive T4 in human polymorphonuclear leukocytes, using radioimmunoassays to quantify the T3 and rT3 generated. Under optimum incubation conditions which included a pH of 6.5 in sucrose-acetate buffer, the presence of dithiothreitol as a sulfhydryl-group protector, and incubation in an hypoxic atmosphere, significant net generation of T3 and rT3 was observed. Of the several subcellular fractions studied, the particulate fraction obtained by centrifugation at 27,000 g was found to possess the highest T3- and rT3-generating activities per unit quantity of protein. With respect to T3 generation from substrate T4, the Km was 5 μM and the Vmax was 7.2 pmol/min per mg protein. Propylthiouracil, methimazole, and prior induction of phagocytosis inhibited both T3 and rT3 generation, but T3 generation was inhibited to a greater extent. rT3, in a concentration equimolar to that of substrate T4, did not alter T3 generation, but inhibited T3 generation when the molar ratio of rT3 to T4 approached 10:1. Under the incubation conditions employed, particulate fractions of leukocytes obtained from five cord blood samples displayed an essentially normal relationship between T3- and rT3-generating activities, despite the distinctly divergent serum T3 and rT3 concentrations in these samples. From our findings, we draw the following conclusions: (a) the human polymorphonuclear leukocyte possesses the ability to generate T3 and rT3 from substrate T4; (b) the T3- and rT3-generating activities are associated principally with the 27,000 g particulate fraction and display enzymic characteristics with a sulfhydryl-group requirement; (c) T3-generating activity appears to be more susceptible to inhibitory influences than rT3-generating activity; and (d) in cord blood leukocytes, the putative enzymes catalyzing T3 and rT3 generation appear to be functionally intact under the experimental conditions employed.
Journal Article•
TL;DR: During repeated administration, plateau levels of immunoassayable digoxin progressively fall, suggesting that digoxin stimulates its own clearance, which is greater than that determined from total serum radioactivity.
Abstract: The pharmacokinetics of digoxin were studied in three groups of rabbits. In the first two groups, radioimmunoassay was used as the analytic technique. After single i.v. doses of 0.8 mg (0.239 mg/kg) of digoxin, disappearance of digoxin from serum had three exponential phases. The mean (±S.E.) apparent elimination half-life for radioimmunoassayable digoxin was 14.8 ± 3.2 hours. With daily 0.8-mg injections of digoxin to eight female rabbits, mean (±S.E.) serum concentrations at 12 and 24 hours after the first dose were 0.62 ± 0.06 and 0.21 ± 0.03 ng/ml, respectively. After the seventh dose, these values fell to 0.23 ± 0.09 and 0.09 ± 0.04 ng/ml, respectively, significantly lower than the predicted concentrations (P< .01). The third group of animals received 0.2 mg/kg of digoxin daily for 13 days. The first and 13th doses included 216 µCi of [3H]digoxin, labeled in the C12 position. Disappearance of total serum radioactivity had three exponential phases after both doses, and kinetic parameters as determined from 3H-counts were not significantly different. The apparent elimination half-life of serum radioactivity was 33.9 ± 1.8 hours. Recovery of radioactivity was 15% in urine and 75% in the feces over 96 hours after both doses. The amount of chloroform-extractable radioactivity in serum and urine tended to be higher after the first dose, but the differences generally did not reach significance. After incubation of urine with hydrochloric acid and with glucuronidase-sulfatase, chloroform-extractable radioactivity more than doubled after both doses. Thus, digoxin is extensively metabolized by the rabbit. Digoxin clearance measured by the more specific radioimmunoassay is greater than that determined from total serum radioactivity. During repeated administration, plateau levels of immunoassayable digoxin progressively fall, suggesting that digoxin stimulates its own clearance. This change in clearance is not reflected by the pharmacokinetics of total radioactivity.
TL;DR: The in vitro responsiveness of diaphragms from 18-day-old fasted normal rats to bovine growth hormone (bGH) with time was studied by determining the accumulation of a-aminoisobutyric acid and 3–0 methylglucose and the incorporation of phenylalanine into diaphagm proteins.
Abstract: The in vitro responsiveness of diaphragms from 18-day-old fasted normal rats to bovine growth hormone (bGH) with time was studied by determining the accumulation of a-aminoisobutyric acid (AIB) and 3–0 methylglucose (3-OMG) and by determining the incorporation of phenylalanine into diaphragm proteins. An estimate of the time course of the effect of GH was obtained by adding the different labeled substances to the incubation medium at different time periods after the start of the incubation. bGH (5 μg/ml) stimulated the uptake of AIB and 3-OMG and the incorporation of phenylalanine between 0–60 min after the start of the incubation. This period was then followed by a period of 60–120 min during which no further stimulation occurred in spite of the continuous presence of the hormone, i.e. the diaphragm was “refractory” to GH. When the incubation period was extended beyond the “refractory phase,” the uptake of AIB and the incorporation of phenylalanine once again increased in diaphragms exposed to bGH. The p...
TL;DR: The results suggest (1) glucose utilization by skeletal muscle in tissue culture is limited by phosphorylation, not transport; (2) as much as 50% of glucose‐derived pyruvate enters mitochondrial pathways; and (3) glutamine carbon may be utilized simultaneously with glucose consumption and this process accounts for high rates of ammoniagenesis.
Abstract: The suitability of an established myogenic line (L6) for the study of skeletal muscle intermediary metabolism was investigated. Myoblasts were grown in tissue culture for ten days at which time they had differentiated into multinucleated myotubes. Myotube preparations were then incubated for up to 96 hours in 10 ml of Dulbecco's modified Eagle medium containing 10% fetal calf serum. Glucose was utilized at a nearly linear rate, 3.0 nmol/min/mg protein. Intracellular glucose was detectable throughout the incubation, even when medium glucose was as low as 16 mg%. During the initial 28 hours of incubation, when net lactate production was observed, only 35% of the glucose utilized was converted to lactate. Alanine was produced in parallel to lactate at an average rate of 0.6 nmol/min/mg protein. In concert with active glutamine utilization, high rates of ammoniagenesis were observed as medium glutamine decreased from 3.3 mM to 0.49 mM and medium ammonia increased from 2.3 mM to 6.2 mM, between zero time and 96 hours of incubation, respectively. The cells maintained stable ATP and citrate levels, and physiologic intracellular lactate/pyruvate ratios (10–24) throughout 96 hours of incubation. These results suggest (1) glucose utilization by skeletal muscle in tissue culture is limited by phosphorylation, not transport; (2) as much as 50% of glucose-derived pyruvate enters mitochondrial pathways; (3) glutamine carbon may be utilized simultaneously with glucose consumption and this process accounts for high rates of ammoniagenesis.
TL;DR: It is suggested that for some period of time after internalization of CF label on cell surface the plasma membrane is devoid of any detectable negative charge.
TL;DR: Data indicate that both gonadotrophins activate the adenylate cyclase system of the isolated granulosa cells while FSH in addition stimulates the phosphodiesterase activity, and cAMP levels remained high or increased until the time of ovulation.
Abstract: A technique for the mechanical isolation of granulosa cells from the rat ovary is described. Cyclic AMP formation by the isolated granulosa cells of the follicles in various stages of development was studied in response to the administration in vitro of gonadotrophins. In granulosa cells from small to medium-sized follicles FSH but no LH stimulated cAMP formation, while in cells from pre-ovulatory follicles both gonadotrophins had a stimulatory effect. The effects of both gonadotrophins were transient with a maximal response after 15 to 60 min of incubation. In the presence of the phosphodiesterase inhibitor, 3-isobutyl-methylxanthine, the action of FSH was potentiated and prolonged while the response to LH was unaffected. These data indicate that both gonadotrophins activate the adenylate cyclase system of the isolated granulosa cells while FSH in addition stimulates the phosphodiesterase activity. Consecutive determinations of cAMP during and after the pre-ovulatory LH-FSH surge, demonstrated a rise of cAMP levels in granulosa cells from the pre-ovulatory follicles following endogenous gonadotrophin release. cAMP levels remained high or increased until the time of ovulation.
TL;DR: It is concluded that NA and 5HT enter the cells by facilitated diffusion and the entry of NA and5HT displayed countertransport, an additional feature of facilitated diffusion.
Abstract: 1. Accumulation of noradrenaline (NA), 5-hydroxytryptamine (5HT) and tyramine by rabbit erythrocytes was measured at 37 degrees C in vitro. 2. Of the amines used only NA was broken down during incubation. This was a result of intracellular catechol-O-methyl transferase activity. 3. NA and 5HT entered the red cells by similar processes which were temperature-sensitive (cooling to 0 degrees C inhibited accumulation) and had saturation kinetics. The entry of NA was partially stereospecific; the (-)-isomer accumulated twice as fast as did (+)-NA. 5HT and NA competed for entry. Tyramine entry was unaffected by cooling, was not saturable and did not affect the entry of either NA or 5HT. NA and 5HT entered the erythrocytes at rates which were proportional to their lipid solubilities. 4. Metabolic inhibitors had no effect on amine transport. Inhibitors of amine transport in other tissues produced only small non-specific reductions of NA accumulation in the red cells. 5. Amine accumulation was a symmetrical process (no amine was retained by the red cells if the concentration gradient was reversed). It is concluded that NA and 5HT enter the cells by facilitated diffusion. The entry of NA and 5HT displayed countertransport, an additional feature of facilitated diffusion. 6. The relationship between the physical properties of the amines and the routes by which they entered the erythrocytes is discussed.