PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “physiological characteristics”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 163 records · Page 9Linked to original sources
PubMedDate not supplied

[Effect of cyclic changes in culture conditions on the growth kinetics and physiological characteristics of yeasts].

Candida utilis, Saccharomyces cerevisiae and Candida scottii were used to study the effect of cyclic changes in the pH and pO2 within a range of 1 to 60 min on their growth kinetics and physiological properties. These changes were shown to increase the specific growth rate from 0.33 to 0.5-0.6 h-1 without decreasing the economic coefficient and the quantity of budding cells during 2-3 generations of the exponentially growing batch culture of C. utilis. Optimal conditions of cyclic changes in the pO2 (minutes) were found to increase the specific growth rate of C. scottii and S. cerevisiae. The authors discuss a hypothesis for the formation of intermediate products in the substrate oxidation in the course of pulse aeration by the yeasts during the aerobic stage and the utilization of the products at the anaerobic stage of cyclic regimes. The paper describes a mathematical model for the yeast growth under the nonsteady-state conditions of pH and pO2, which accounts for the formation and utilization of possible intermediate biosynthetic products within the studied time intervals.

Candida↗
PubMed1987

Anatomical and physiological characteristics of vestibular neurons mediating the vertical vestibulo-ocular reflexes of the squirrel monkey.

The morphology of 35 vestibular neurons whose firing rate was related to vertical eye movements was studied by injection of horseradish peroxidase intracellularly into physiologically identified vestibular axons in alert squirrel monkeys. The intracellularly injected cells were readily classified into four main groups. One group of cells, down position-vestibular-pause neurons (down PVPs; N = 12), increased their firing rate during downward eye positions, paused during saccades, and were located in the medial vestibular nucleus (MV) and the adjacent ventrolateral vestibular nucleus (VLV). They had axons that crossed the midline and ascended in the medial longitudinal fasciculus (MLF) to terminate in the trochlear nucleus, the lateral aspect of the caudal oculomotor nucleus, and the dorsal aspect of the rostral oculomotor nucleus. A second group of cells (N = 15) were also located in the MV and VLV, but increased their firing rate during upward eye positions, and paused during saccades. These cells had axons that crossed the midline and ascended in the contralateral MLF to terminate in the medial aspect of the oculomotor nucleus. A third group of cells (N = 4) were located in the superior vestibular nucleus, generated bursts of spikes during upward saccades, and increased their tonic firing rate during upward eye positions. These cells had axons that ascended laterally to the ipsilateral MLF to terminate in regions of the trochlear and oculomotor nuclei similar to those in which down PVPs terminated. A fourth group of cells (N = 4), located in the VLV, had axons that projected to the spinal cord, although they had firing rates that were significantly correlated with vertical eye position. Electrical stimulation of the vestibular nerve evoked spikes at monosynaptic latencies in each of the above classes of cells, six of which were injected with horseradish peroxidase. Each group of cells had collateral projections to other areas of the brainstem. Some of the neurons that projected to the contralateral trochlear and oculomotor nuclei had collaterals that crossed the midline to terminate in the oculomotor nucleus ipsilateral to the soma, and some gave rise to small collaterals that terminated in the abducens nucleus. Other areas of the brainstem that received collateral inputs from neurons projecting to oculomotor and trochlear nuclei included the interstitial nucleus of Cajal, the caudal part of the dorsal raphe nucleus, the nucleus raphe obscurus, Roller's nucleus, the intermediate and caudal interstitial nuclei of the MLF, and the nucleus prepositus.

Animals↗
PubMed2002

The human fetal venous system: normal embryologic, anatomic, and physiologic characteristics and developmental abnormalities.

OBJECTIVE: The introduction of high-resolution ultrasonography combined with color-coded Doppler imaging offered a breakthrough in the evaluation of the human fetal venous system, considerably enhancing our understanding of fetal venous circulation in normal physiologic conditions, as well as providing us the ability to study circulatory changes in abnormal circumstances. The purpose of this study was to describe the normal anatomic development and complex of anomalies of the human fetal venous system and to review recently published series of these anomalies. METHODS: Normal embryologic and anatomic development is described. An English language literature search of recent MEDLINE listings was performed to glean data from recently published series reporting prenatal diagnosis of the various anomalies and their associated malformations. RESULTS: Anomalies of the human fetal venous system occur sporadically, often associated with cardiac or other malformations. The pathophysiologic mechanisms leading to abnormal in utero development of the human venous system remain largely undetermined. On the basis of the type of vein involved, embryologic precursor, and etiologic correlation (primary or secondary), classification into 4 major groups is described. CONCLUSIONS: Prenatal evaluation of fetuses found to have anomalies of the venous system should include a careful search for cardiac anomalies, including pulmonary venous drainage, and a detailed anatomic survey of the umbilical, portal, hepatic, and ductal systems to determine aberrant communication and, if possible, to discover clues to systemic diseases or thromboembolic phenomena.

Ductus Arteriosus↗
PubMed2002

Physiological characteristics of the biocontrol yeast Pichia anomala J121.

The yeast Pichia anomala J121 prevents mold spoilage and enhances preservation of moist grain in malfunctioning storage systems. Development of P. anomala J121 as a biocontrol agent requires in-depth knowledge about its physiology. P. anomala J121 grew under strictly anaerobic conditions, at temperatures between 3 degrees C and 37 degrees C, at pH values between 2.0 and 12.4, and at a water activity of 0.92 (NaCl) and 0.85 (glycerol). It could assimilate a wide range of C- and N-sources and produce killer toxin. A selective medium containing starch, nitrate, acetic acid, and chloramphenicol was developed for P. anomala. P. anomala was equally sensitive as Candida albicans to common antifungal compounds. Growth ability at a range of environmental conditions contributes to the competitive ability of the biocontrol yeast P. anomala J121.

Anaerobiosis↗
PubMed1988

Physiological characteristics of Culex pipiens populations in the Middle East.

We determined whether exposure to a short day-light regime of 14 h 15 min induces ovarian diapause in Culex pipiens L. mosquitoes from Israel and whether differences occur in certain morphological, physiological and behavioural traits. Samples from nineteen localities in Israel, from 33 degrees 05' N to 29 degrees 35' N latitude, conformed to the morphological criteria of Cx pipiens, sensu stricto (i.e. wider spread of dorsal than of ventral arms of the aedeagus) as determined by negative DV/D ratios of the male. Autogenous females occurred at frequencies of 4-55% in all areas of Israel throughout the breeding season. No mating barriers were detected between individuals of autogenous and anautogenous genotypes. Autogenous females were no more prevalent from polluted or enclosed breeding sites than from others with various degrees of openness. In general, Cx pipiens females fed equally well on human (35% engorgement) and avian (22% engorgement) hosts (P less than 0.01). Although females from the southern part of the study region appeared to be incapable of ovarian diapause, at least some of those from the north experienced diel-mediated diapause. We conclude that, in the Middle East, the 33rd parallel provides a southern limit to the range of Cx pipiens with capability for diel-mediated ovarian diapause, but that non-diapausing Cx pipiens s.l. are present at least as far south as Elat (20 degrees 25' N) on the coast of the Gulf of Aquaba.

Animals↗
PubMed1973

Some Physiological Characteristics of the Ethylene-requiring Tomato Mutant Diageotropica.

The diageotropica mutant of tomato (Lycopersicon esculentum Mill.) is shown to require exogenous ethylene for normal growth and development. This single gene mutant is characterized by unsupported horizontal growth of shoots and roots, dark green hyponastic leaf segments, thin rigid stems, and primary and adventitious roots which lack lateral roots. Experiments with growth regulators indicate that the mutant does not produce normal amounts of ethylene in response to auxin treatment. Tests with ethylene-producing compounds or ethylene precursors demonstrate that the mutant requires ethylene for normality. Ethylene concentrations as low as 0.005 microliters per liter are capable of completely normalizing mutant characteristics. This mutant with its isogenic parent variety, cv. VFN8, should be a suitable tool for investigating auxin-stimulated ethylene production and their interrelationship in the control of plant morphology and physiology.

Journal Article↗
PubMed1975

Immunological and physiological characteristics of the rapid immune hemolysis of neuraminidase-treated sheep red cells produced by fresh guinea pig serum.

The rapid hemolysis by fresh guinea pig serum known to occur with neuraminidase-treated sheep red cells has been investigated with respect to the immunological and physiological properties of the lytic process. The following observations were made: (a) The susceptibility to hemolysis is directly proportional to the amounts of neuraminic acid enzymatically released from the cell surface. Complement lysis is mediated through binding of an IgM antibody protein to membranes of neuraminidase-treated cells. (b) Hemolysis is relatively temperature-independent above about 28 degrees C but below which a decrease in the hemolysis rate occurs. Arrhenius activation energies above and below the transition temperature were therefore found to be different. (c) Colloid osmotic swelling of neuraminidase-treated high potassium sheep red cells with a chloride ion concentration ratio near unity suspended in high potassium medium could not be prevented by sucrose. Hence, colloid osmotic swelling before lysis must be due to the entrance of sucrose and water since sucrose was the only external solute not at equilibrium. (d) From the rate of swelling and the apparent flux of sucrose under nonsteady state conditions an experimental permeability coefficient (P) for sucrose of 3-10(-8) cm-s-1 was computed. Comparison with a theoretical P of 4-10(-6) cm-s-1 for sucrose freely permeating through a single, hypothetical membrane lesion per cell of 60 A effective diameter indicates a membrane lesion which permits the passage of solutes larger than cations, but clearly constrains the free diffusion of sucrose.

Animals↗