Showing papers on "Incubation published in 1968"

An incubation method for estimating the carbon content of phytoplankton in natural samples1

Abstract: In this method, the phytoplankton standing stock as carbon was calculated from carbon assimilation rates, measured at 24 and 48 hr, during incubation of seawater samples on shipboard. The method requires exponential growth at constant specific growth rate of the phytoplankton in the sample during incubation and relies on the fact that the rate of synthesis of cell substance is proportional to the quantity of cell substance present. Growth was so extensive that nutrients had to be added to the samples before the 48-hr incubations to maintain exponential growth. Light intensity during incubation affected results, and matching the incubation intensity to that in situ seemed best. Carbon: chlorophyll a ratios found in phytoplankton off La Jolla, California, averaged about 90 in nutrient-depleted surface layers and about 30 in deeper, nutrient-rich water. Photosynthetic rates per unit chlorophyll a, calculated from 24-hr incubations, were high due to chlorophyll a synthesis during incubation.

Rapid Starch Synthesis Associated With Increased Respiration in Germinating Lily Pollen

Abstract: In vitro studies of germinating Lilium longiflorum pollen showed that starch increased more rapidly during the first 30 minutes of incubation than during the next several hours. The period of rapid starch formation coincided with the first period of high respiration. An estimate was made of the extra ATP utilized to form extra starch during the first 30 minutes, and this estimate indicates that starch synthesis accounts for a significant portion of the initial high rate of respiration. This pattern of respiration and starch synthesis was not altered when pollen germinated in a pentaerythritol medium that could not be metabolized instead of the standard sucrose medium.Sucrose was the predominant sugar in mature lily pollen. This sugar decreased 50% during several hours incubation in pentaerythritol culture medium. Reducing sugars remained low during incubation which may indicate that sucrose breakdown is regulated by the rate of utilization of hexose units.

Studies on the Metabolism of C19‐Steroids in Rat Liver

Abstract: The formation of polar, saturated C19steroids with a 3-keto-5α-configuration after incubation of 17β-hydroxyandrost-4-en-3-one (testosterone) with 105,000 ×g microsomes of adult male rat liver was investigated. The metabolites were isolated by thin-layer chromatography and were identified as 2β-,6β-(tentatively), 7α-, and 16α-hydroxy-5α-dihydrotestosterone by means of gas chromatography-mass spectrometry. The same compounds were also isolated after incubation with 2β-,6β-,7α-, and 16α-hydroxytestosterone, respectively. Incubation with 5α-dihydrotestosterone, however, resulted in the formation of 2β-,7α-, and 16α-hydroxy-5α-dihydrotestosterone whereas no 6β-hydroxy-5α-dihydrotestosterone could be found.

Detection of limiting or surplus nitrogen in algae and aquatic weeds(1).

Abstract: The rate of NH4 +-N absorption by algae and aquatic weeds in the dark has been shown to be 4-5 times greater for plants which are N-limited as compared to plants with sufficient available N. Eight species of green algae, 2 blue-green algae, 2 diatoms, and 3 aquatic weeds were used to demonstrate the usefulness of the test in determining if available N was in surplus or limited supply in a particular environment. The test was shown not to differentiate between blue-green algae capable of fixing N (4 species) from media with NO3 -N or without combined nitrogen. The factors influencing the results of NH4(+) -N absorption tests have been investigated. In order to differentiate between plants with sufficient available N and those which are N limited, the rate of NH4 (+) -N absorption (0.1 mg N) over 1-hr incubation in the dark by 10-20 mg of algae or aquatic weed tissues is measured. The relatively simple analysis for NH4 (+) -N in the samples makes it very easy to follow the changing N nutrition of plants in cultures with a limited N supply or in the presence of possible N sources.

Release of Free Fatty Acids and Loss of Hill Activity by Aging Spinach Chloroplasts

Abstract: The free fatty acid content of spinach chloroplasts, isolated at pH 5.8 to 8.0, has been found to vary between 3.1 and 5.5% of the total chloroplast fatty acids. When chloroplasts were incubated at room temperature for 2 hours, the free fatty acids increased by 42% and the Hill activity decreased by 70%. After 2 hours of incubation at 37°, the free fatty acids increased about 3-fold and the Hill activity decreased to almost 0. The addition of crystalline bovine serum albumin largely prevented the loss of Hill activity at room temperature and at 5°, but had little effect during incubation at 37°. Both the release of free fatty acids and the loss of Hill activity were pH dependent. The losses were the least during incubation at pH 5.8 and the greatest during incubation at pH 8.0. The major free fatty acids released at pH 5.8 were saturated, while those released at pH 7.0 or 8.0 were mainly the unsaturated acids, α-linolenic acid and hexadecatrienoic acid.

Incubation of eggs of three species of Chelid tortoises, and notes on their embryological development

Abstract: Incubation periods and nest contents of three species of chelid tortoises in northern Victoria were recorded. Mean incubation period for eggs of Emydura macquari (Cuvier) was 75 days and average number of eggs per nest was 15.7; for Chelodina longicollis (Shaw), 138 days and 10.7 eggs per nest; for Chelodina expansa Gray, normally exceeding 324 days and 15.4 eggs per nest. In abnormal seasons C. expansa hatchlings may emerge from the nest in less than 193 days or more than 522 days after eggs were deposited. Eggs artificially incubated at 30°C consistently develop more quickly than those at lower temperatures under natural conditions. In the field nest temperatures closely approximate the mean daily air temperature. Embryos of C. expansa are tolerant to nest temperatures ranging from 4.9°C minimum to 29.6°C maximum. The other species are subject to variations of about 15 degC with up to 8.5 degC variation being recorded in 1 day. Development of early embryos approximated that recorded for cryptodire tortoises. However, there are large individual differences in the period of incubation needed for specific stages to be reached, especially between embryos of the short-necked and long-necked species of these pleurodire tortoises. It is suggested that differences in the anatomy of their eggs are the main factors in the different incubation periods between short-necked and long-necked species.

Brood-protection in a Deep-sea Holothurian, Oneirophanta mutabills Théel

Abstract: BROOD-PROTECTION is known to occur in thirty species of holothurians belonging to the orders Dendrochirota and Apoda. All are littoral–sublittoral and most are inhabitants of cold seas, especially the Antarctic. The brood-protecting Dendrochirota usually carry their young on the body-surface or in pockets invaginated from the body-surface. Some Dendrochirota and most of the brood-protecting Apoda have a coelomic incubation, the juveniles passing through a free-swimming stage in the body-fluid of the mother. The Antarctic synaptid Taeniogyrus contortus (Ludwig) breeds the young within the ovaries, which they leave at a length of 3 mm (the adult specimens measure 20–45 mm) (ref. 1).

Changes in Erythrocyte Membrane and Autohaemolysis during in Vitro Incubation

Abstract: Summary. Spontaneous autohaemolysis occurs as sterile defibrinated blood is incubated at 37°C. This study was undertaken to identify the membrane changes which occurred during autohaemolysis and the effect upon these of supplementary glucose. After 24 hours of incubation the earliest membrane change recognized was the loss of small amounts of cholesterol; this occurred equally in incubations with and without added glucose. Spherocytes were prominent in incubations without added glucose but were infrequent when supplementary glucose was provided. During the second 24 hours of incubation cholesterol loss increased and phospholipids eluted from the cell surface. In this period of incubation cholesterol and phospholipid loss was less in incubations provided with supplementary glucose. The major individual phosphatides lecithin, sphingomyelin, phosphatidylethanolamine and phosphatidylserine were lost in proportion to their original concentration in the membrane. Membrane protein did not decrease as cell lipid loss occurred.

A temperature-sensitive event in interferon production.

Abstract: Summary The production of interferon by chick embryo cells infected with Semliki Forest virus and incubated at 42° is dependent on a period of incubation at 36°. During incubation at 36° virus-directed RNA synthesis occurs and it is suggested that the temperature-sensitive event in interferon production is an early stage in virus multiplication rather than a process controlled by the cell genome.

Salmonella penetration of fertile and infertile chicken eggs at progressive stages of incubation.

Abstract: The shell and shell membrane systems of fertile chicken eggs undergo marked changes during incubation and embryonic development. Tyler and Simkiss (2) described these changes and confirmed that the membranes separate from the shell of fertile eggs (except for that portion over the air cell) by about the 15th or 16th day of incubation. The outer membrane does not come away cleanly from the shell but carries with it the ends of the mammillary knobs, including the mammillary cores. In earlier studies (4) of the penetration patterns of salmonella organisms through the outer structures of chicken eggs, the incubation periods used most frequently have been short periods up to 24 hrs at 990F, or eggs have been exposed to salmonella and stored for extended periods before examination. The work reported herein was undertaken as a systematic investigation of salmonella penetration into fertile hatching eggs at various stages of embryonic development, in comparison with penetration of infertile eggs maintained under identical conditions of incubation.

Some observations on the oxidation of glucose by enzymes in soil in the presence of toluene

Abstract: Changes in glucose concentrations were slight on incubation in a system of fresh soils, buffer, and toluene at 37°C and were not significantly detectable by a titrimetric method. Such changes would be too small to affect the accuracy of assays of enzymes hydrolysing carbohydrates in soil where activities are measured by glucose production. Oxygen uptake was slight but increased significantly when glucose was added to four undried soils incubated with toluene; uptake was greater at 37°C than at 24°C. Numbers of viable bacteria declined during incubation. Oxidation of glucose was negligible in a similar system with air-dried soils. Gluconic acid and 2-ketogluconic acid were identified as metabolic products from glucose incubated with soils and toluene. There was an approximate equivalence of oxygen uptake and acid production after incubation for 24 hours but not after longer periods. In the absence of toluene, both gluconic and 2-ketogluconic acids were readily metabolised by soils on incubation at 37°C. Results suggest that glucose oxidase and gluconate dehydrogenase are present in soils but that only a small proportion of glucose would be metabolised by oxidase activity in soils under natural conditions. Other oxidoreductase enzymes would also be active in soils.

Some characteristics and optimum incubation conditions of in vitro progesterone synthesis by bovine corpora lutea.

Abstract: In view of the widespread use of in vitro incubations of corpus luteum slices for a variety of purposes, experiments were conducted to establish optimum incubation conditions and to determine some of the sources of error variation observed in this system. A 2-hr incubation period was sufficient to detect an LH (luteinizing hormone) induced stimulation of progesterone synthesis; longer incubation times yielded higher levels of synthesis but did not increase the precision of the assay. The pH optimum for the incubation system was between 7.15 and 7.55. Addition of 1 μmole NADPH2 resulted in a consistent stimulation of progesterone synthesis, even in those groups already maximally stimulated with LH, suggesting that 2 different mechanisms are operative for the 2 stimulating agents. NADPH2 did not change the regression coefficient or the precision of the assay. Addition of nicotinamide (30 HIM) resulted in higher rates of progesterone synthesis, presumably by maintaining the integrity of the pyridine nucleoti...

Selective enhancement of glycolytic activity by incubation of yeast cells in sugars and polyols

Abstract: Incubation of yeast cells for 21 hours in solutions of certain sugars and polyols produces cells capable of forming CO2 from glucose at a high rate and without an initial lag as compared to cells s...

Biosynthesis of progesterone and 20-alpha-hydroxypregn-4-en-3-one by the rat ovary during the estrous cycle and early pregnancy.

Abstract: Rat ovaries were removed for incubation during the middle of the light cycle each day: prior to the hypophyseal release of LH on the day of proestrus. Significant in vitro synthesis of progesterone and 20α-hydroxypregn-4-en-3-one (20α-OH-P) was found to occur from endogenous precursors in ovarian slices obtained from rats at each of 4 stages of the estrous cycle. The synthesis of 20α-OH-P was twice the synthesis of progesterone with no significant differences in synthesis of either compound among days of the estrous cycle. Luteinizing hormone caused a significant increase in both steroids when added to the incubation medium and was similarly effective at all stages of the cycle. In early diestrus, the corpora lutea were shown to be responsible for most of the progestin synthesis as determined by incubation of the isolated structures. The incorporation of radioactivity from acetate-1-14C was unrelated to total biosynthesis; the specific activities of both progesterone and 20α-OH-P were lowest at estrus and...

The metabolism of phytohaemagglutinin during incubation with human peripheral lymphocytes.

Abstract: The mechanism of action of PHA in in vitro leucocyte cultures was investigated with respect to the fate of the mitogen during the 3-day blastogenic response. It was demonstrated that incubation of the leucocytes with PHA for only 5 minutes followed by incubation for 72 hours in medium devoid of PHA was sufficient to initiate mitosis and blastogenesis. However, the minimum incubation time with PHA required to induce maximum blastogenesis was 6 hours. Furthermore, it was demonstrated that the mitogen is bound to cells in culture but the experimental findings suggest that this cell-bound mitogen is not degraded during the 3-day incubation period.

Distribution and fate of 2-C14-glucose in the liver fluke, Fasciola hepatica L., after short in vitro incubation.

Abstract: Adult stages of Fasciola hepatica L. were incubated in 2-C14-glucose for 10 minutes. The distribution and fate of C14 was followed by microautoradiography and paper electrophoresis and paper chromatography in combination with autoradiography. It was found that C14 accumulated predominately in the parenchyme and in the suckers. Within the fluke C14 was found in high molecular weight compounds like glycogen and in acids belonging to the citric acid cycle. These acids were not observed in the incubation medium. Labelled compounds behaving like amino acids were found both in the fluke and in the incubation medium.