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At least 19 recordsLinked to original sources
PubMed1975

[Estrus synchronization in cattle by means of chlormadinone acetate ("Bovisynchron" Jenapharm) in the tropics. II. First results of the estrus synchronization of cattle with "Bovisynchron" at the Republic of Mali].

The first experiments are reported on oestrus synchronization in cattle in the Republic of Mali. The animals recieved Bovisynchron twice a day orally over a period of 15 days. The synchronization effect was marked; insemination was performed on the 5th and 6th day p.s. The intensity of the oestrus and especially the results of pregnancy are in close relationship to the breeding conditions and the general status of the animals. The oestrus synchronization is considered a favourable biotechnical method for regulating the reproduction provided that the animals are kept stationary or temporarily stationary.

Animals↗
PubMed1978

A new analytical method for determining duration of phases, rate of DNA synthesis and degree of synchronization from flow-cytometric data on synchronized cell populations.

L-cells synchronized by mitotic selection were investigated by flow-cytometry and the fractions of cells in the various cell cycle compartments were determined as a function of time. A new analytical evaluation procedure was developed, by which the mean transit-times of cells through various cell cycle phases can be calculated from these data. Three examples for application of the method are presented: (1) determination of the duration of G1, S, G2 + M and of the whole cell cycle; (2) calculation of the rate of DNA synthesis in several subcompartments of the S-phase; and (3) evaluation of the degree of synchronization at different stages of the cell cycle.

Cell Cycle↗
PubMed1975

Adenine nucleotide metabolism in heat-synchronized Tetrahymena.

The metabolism of acid soluble adenine nucleotides in heat-synchronized Tetrahymena pyriformis GL has been studied. In addition, the effect of the synchronizing temperature (34 degrees C) on adenine nucleotide metabolism in heat-synchronized cells has been determined. In cells induced to divide synchronously through heat treatment (cyclic pulses of 34 degrees C for 30 min alternating with a 30 min recovery period at 28 degrees C) variations occurred in the levels of adenine nucleotides when samples of cells were analysed at the end of the last thermal period and at various time preceding the first synchronous cell division. The specific activities of the adenine nucleotides were found to be significantly higher during a pulse label period performed at the end of the last thermal period than at any time during the subsequent synchronous division cycle. The synchronizing temperature was found to partially deplete the intracellular stores at ATP in heat synchronized cells. This decrease was reversible with ATP levels recovering after 15 min of incubation at 28 degrees C. Fluctuations in the levels and specific activities of the adenine nucleotides are discussed in their relation to macromolecular synthesis and the cell cycle in Tetrahymena.

Adenine Nucleotides↗
PubMed1979

[Chemotherapy in solid transplantation tumors following synchronization (author's transl)].

In order to examine whether the effects due to cytostatics might be improved by synchronization, cytosin-arabinoside, hydroxyurea or Vincristin were administered to rats bearing solid transplantation tumors, at different intervals following synchronization. The three substances, interfering with the S-phase of the cells, show significantly improved therapeutic results with quickly proliferating Walker-carcinosarcoma after a synchronization by hydroxyurea. Cyclophosphamide on the other hand, being effective through several phases of the cell cycle, furnishes no evidence of any essential therapeutic result. Analogous therapeutic experimentation using slowly growing neurosarcomas yielded no better results after synchronization. The concept of synchronization treatment may be approved, therefore, with certain limitations: firstly, synchronization with hydroxyurea can be maintained for a short time only, and the cancerous cells pass throught the first phases of the cell cycle following synchronization for the most part together with normal cells; secondly, only tumors with an important growth fraction and only cytostatics that do not affect several phases of the cell cycle are appropriate for synchronization therapy.

Animals↗
PubMed1979

The effect of high mesencephalic transection (cerveau isolé) and pentobarbital on basal forebrain mechanisms of EEG synchronization.

A study was made of the effects of high mesencephalic transection (cerveau isolé) and low doses of pentobarbital on the cortical synchronizations elicited in acute immobilized cats by (a) low frequency stimulation of the lateral hypothalamus (HL) and nucleus ventralis anterior thalami (VA) and (b) by low and high frequency stimulation of the laterobasal preoptic region (RPO) and olfactory tubercle (TbOf). The results obtained were as follows: (1) The synchronizations induced by basal forebrain stimulations were found to survive in acute cerveau isolé cats, moreover, even a facilitation of the synchronizing effect were observed. (2) A gradual facilitation was observed upon TbOf and RPO stimulation, while in the case of VA and HL stimulations, the facilitation appeared immediately after the transection. (3) Low doses of pentobarbital depressed the cortical effects of TbOf stimulation, while an increase of the synchronizing effect of low frequency VA and HL stimulation was found. The observations suggested that (i) the synchronizing mechanism in the ventral part of the basal forebrain (RPO and TbOf) differs from that of the thalamus and HL; (ii) the basal forebrain synchronizing mechanism is effective without the contribution of the brain stem; (iii) the mechanism responsible for the synchronizing effect of low frequency HL stimulation is similar as that described for the thalamus.

Animals↗
PubMed1976

[Hydroxyurea synchronization of cellular proliferation in the esophageal epithelium of mice with tumors].

The synchronizing effect of hydroxyurea on the passage of the esophagus epithelia cells through the stage of the DNA synthesis and mitosis was investigated in albino mice bearing sarcoma. Dinrnal variations in the number of epithelial cells at these stages of the mitotic cycle were taken into consideration. Two mutually complementary indices for the measurement of the shifts in the cell population and the rate of the synchronization are used. Two cell groups which passed the S-phase and mitosis synchronously were found in artificial synchronization in the esophageal epithelium. The synchronization indices characterizing the first group were lower than control. In the second group the cell count during the DNA synthesis was double as compared with the number of cells synthesizing DNA in natural synchronization; however, the rate of the changes in the synchronism was the same in the experimental and control groups.

Animals↗
PubMed1976

Electroencephalographic synchronization induced by stimulation of small intestine and splanchnic nerve in cats.

1. In freely moving cats, the cortical desynchronization elicited by painless rhythmic distension, or by low voltage electric stimulation, of the small intestine in drowsiness and slow wave sleep is extinguished following a few repetitions. After extinction of the arousal reaction, similar intestinal stimulation was systematically followed by the appearance of synchronized activity, or an increase of spontaneous synchronization, in the explored cortical areas (parieto-occipital). 2. Intestinal or splanchnic stimulation at an intensity below threshold for cortical desynchronization immediately induced synchronized activity without any need of previous repetitions of stimulation. 3. Stimuli which were followed by synchronization excited only the large (Abeta) splanchnic afferents. The authors conclude that intestinal receptors may be one of the sources of synchronizing influence which can contribute to the regulation of the sleep-wakefulness cycle and that the large splanchnic afferents may play a role in the induction of synchronization.

Afferent Pathways↗
PubMed1977

Cell cycle characteristics of synchronized and asynchronous populations of human cells and effect of cooling of selected mitotic cells.

The method of synchronizing cells by means of mitotic selection has been adapted to the human line NHIK 3025. Increase in cell number as a function of time in asynchronous and synchronous populations was studied as well as mitotic index as a function of time after selection of synchronized populations. Phase durations of the cell cycle of synchronous populations were determined by 3H-thymidine incorporation and scintillation counting. The relative phase durations of exponentially growing asynchronous populations were determined by mathematical analysis of DNA-histograms recorded by flow cytofluorimetry. Both the generation time and the various phase durations of the cell cycle were found to be the same in asynchronous and synchronous populations. It was found that NHIK 3025 cells are damaged by cooling to 4 and 0 degrees C so that cooling of selected cells in order to increase the yield would reduce the quality of the synchronized populations.

Cell Count↗
PubMed1975

Synchronization of human motor units: possible roles of exercise and supraspinal reflexes.

Some normal human subjects show definite synchronization of the motor units in hand muscles (i.e., the impulses from two or more motor units coincide in time more frequently than expected for independent random processes). Subjects who show synchronization tend to use their hands to exert large, brief forces, either in their work (e.g., manual laborers) or recreational activities (e.g., weightlifters). In this study all seven weightlifters examined showed a significant degree of synchronization. Furthermore, after 6 weeks of using the first dorsal interosseus muscle of the hand to exert maximal, voluntary contractions, the level of synchronization increased substantially in four control subjects, and the average level became significantly different from zero. Weightlifters also showed greater late reflex responses than control subjects, but no significant difference in earlier spinal reflexes. Two late reflex waves are described which probably involve fast pathways to and from motor cortes. We suggest that supraspinal connections from motor cortex directly to spinal motoneurons may be enhanced as a result of training to the point where they produce a significant synchronization of motor units during steady, voluntary contractions.

Electric Stimulation↗
PubMed1978

Morphological and functional correlates of synchronous beating between embryonic heart cell aggregates and layers.

We have examined correlations between morphological and functional evidence of cell coupling between aggregates of beating embryonic heart cells and underlying layers. Synchronously beating aggregate-layer pairs were compared with asynchronous pairs. Intracellular microelectrode studies demonstrated that asynchronously beating aggregate-layers could not be induced to beat synchronously by electrical stimulation of the aggregate, whereas 86% of synchronous instances showed propagation of stimulating current pulses from aggregate to layer. By freeze fracture we have found significant differences both in the number and in the total area of gap junctions between the aggregate-layer interfaces of synchronous and asynchronous preparations. The data suggest that synchronous beating is a reliable functional indication of effective ionic coupling, and requires a certain area and number of gap junction/cell.

Action Potentials↗
PubMed1977

The influence of growth substrate and capacity for oxidative phosphorylation on respiratory oscillations in synchronous cultures of Escherichia coli K12.

Fluctuations in cell volume during exponential growth of Escherichia coli K12 changed the effectiveness of the continuous-flow centrifugation method for preparing synchronous cultures. Rates of oxygen uptake in synchronous cultures were measured using an electrode system open to the atmosphere. In synchronous cultures of both the parental strain and an adenosine triphosphatase-deficient mutant, which was incapable of oxidative phosphorylation, respiration rates doubled during the cell cycle but oscillated with a periodicity of approximately half a cycle. Synchronous cultures of the parental strain growing on glycerol and Casamino acids showed a stepwise pattern of oxygen consumption. Continuous flow centrifugation did not markedly affect the increases in the numbers and respiration rates of cells in syndhronous cultures. Respiratory oscillations also occurred on inoculation of a late-stationary phase culture into fresh medium, although synchronous division was not observed. The possible mechanisms underlying respiratory fluctuations under different growth conditions are discussed.

Amino Acids↗
PubMed1978

Cellular autolytic activity in synchronized populations of Streptococcus faecium.

The autolytic capacity of Streptococcus faecium (S. faecalis ATCC 9790) varied during synchronous cell division. This phenomenon was initially observed in rapidly dividing populations (TD=30 to 33 min) synchronized by a combination of induction and size selection techniques. To minimize the problems inherent in studies of cells containing overlapping chromosome cycles and possible artifacts generated by induction techniques, the autolytic capacities of slowly dividing populations (TD=60 to 110 min) synchronized by selection only were examined. Although the overall level of cellular autolytic capacity was observed to decline with decreasing growth rate, sharp, periodic fluctuations in cellular autolytic capacity were seen during synchronous growth at all growth rates examined. On the basis of similar patterns of cyclic fluctuations in autolytic capacity of cultures synchronized by (i) selection, (ii) amino acid starvation followed by size selection, and (iii) amino acid starvation followed by inhibition of DNA synthesis, a link of such fluctuations with the cell division cycle has been postulated.

Amino Acids↗