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Biomedical subjects

I Müller

Publications and source records attributed to I Müller.

At least 163 records · Page 9Linked to original sources
PubMed1981

Xenograft rejection in marine sponges. Isolation and purification of an inhibitory aggregation factor from Geodia cydonium.

In sponges there exists a graft rejection mechanism in which an inhibitory aggregation factor is involved. The inhibitory aggregation factor has been isolated from a culture medium containing dissociated cells of the sponge Geodia cydonium. Using ion-exchange and gel fractionation the factor was purified and shown to be electrophoretically pure. The factor has a molecular weight of 27000 and was characterized as a glycoprotein. The activity of the inhibitory aggregation factor was not affected by heat treatment, but treatment with trichloroacetic acid resulted in the irreversible loss of activity. The inhibitory aggregation factor affects the aggregation-factor-mediated reaggregation of dissociated sponge cells by extension of the lag phase preceding the aggregation process; the endpoint of the reaggregation process is not changed. The inhibitory aggregation factor competes with the aggregation receptor for the binding site on the aggregation factor. The inhibitory aggregation factor is not synthesized if homologous aggregation factor is added to the dissociated cells. The results indicate that the inhibitory aggregation factor is synthesized in xenografts of the system Geodia cydonium--Geodia rovinjensis after a grafting period of at least 3 days. Following the synthesis of the factor, the concentration of the extractable aggregation factor decreases.

Animals↗
PubMed1981

Lectin, a possible basis for symbiosis between bacteria and sponges.

From the marine sponge Halichondria panicea a lectin was isolated and characterized. The homogeneous lectin (composed of protein to 80.7% and of neutral carbohydrates to 14.1%) had a molecular weight of 78,000 (determined by gel filtration) and consisted of four subunits with a molecular weight of 21,000 each (determined by gel electrophoresis in the presence of sodium dodecyl sulfate). The hemagglutinating activity was only slightly dependent upon ionic strength and incubation temperature and did not require divalent cations, but it was inhibited by reagents for thiol groups. The Halichondria lectin was completely inhibited in hemagglutination competition experiments in the presence of fetuin, D-galacturonic acid, D-glucuronic acid, polygalacturonic acid, or L-fucose. The purified Halichondria lectin did not cause reaggregation of dissociated H. panicea cells. From the same sponge species bacteria were isolated and identified as Pseudomonas insolita. These bacteria were cultivated in marine broth 2216. Under these culture conditions the bacteria grew only in the presence of the homologous lectin; the lectin-caused effect was not abolished by D-glucuronic acid or D-galacturonic acid. However, after addition of a polysaccharide-containing fraction isolated from P. insolita, the lectin-caused, growth-promoting effect was abolished. Other lectins were found to exhibit no growth-promoting effect. On the basis of colony counts, P. insolita was the predominant bacterial species in the sponge extract; 1.9 X 10(6) Pseudomonas colonies were measured in extracts isolated from 1 g of sponge. The assumption of an interrelationship between the sponge and the bacterium is supported by the results indicating that the Halichondria lectin has no effect on the growth of such bacteria isolated from six other marine sponge species. Evidence is presented which indicates that the Halichondria lectin is not utilized during growth of the Pseudomonas species. Lectin activity was detected on the surface of mucoid cells from H. panicea. From the data obtained the possibility is discussed that the Halichondria lectin is a basis for a symbiotic relationship between the sponge and the bacterium.

Animals↗
PubMed1981

[Insulin and cortisol levels in blood plasma and adrenal gland mass in swine during the perinatal period].

The level of immunoreactive insulin activity and glucose in blood plasma of the umbilical vein was found to be lower than that in maternal venous blood plasma, in the last third of intra-uterine development, that is between the 80th and 112th day. No age-dependent differences were recordable regarding immunoreactive insulin activity in foetal blood plasma. Concentrations of glucose and immunoreactive insulin in venous blood plasma of piglets were found to rise, within 24 hours from birth, due to milk intake. Such rises were statistically significant but differed by individuals. None of the above parameters increased in fasting piglets. Cortisol in foetal blood plasma was found to be low, usually less than 5 ng/ml, on the 80th, 100th, and 106th day of intra-uterine life, but it went up between the 106th and 112th day. The highest concentrations were recorded from the oldest foetuses, 114 day of intra-uterine development. The cortisol levels in the blood plasma of the mothers of the above mentioned foetuses varied between 5 ng/ml and 70 ng/ml. Relative adrenal gland weight in animals aged 112 and 114 days was found to be significantly higher than that in foetuses aged 80, 100, and 106 days. No significant postnatal change in relative adrenal gland weight was recorded from piglets in the first nine days of life.

Adrenal Glands↗
PubMed1981

Cell aggregation of the marine sponge Geodia cydonium. Identification of lectin-producing cells.

A D-galactose-specific lectin, purified from the marine sponge Geodia cydonium, is present on the cell surface of mucoid cells, free choanocytes and choanocyte clusters, as revealed first, by the adhesion assay which is based on the formation of "rosettes" with erythrocytes, and second, by immunofluorescence studies. Using the same techniques no lectin could be identified on the surface of archaeocytes. Rosette formation was inhibited in the presence of 20 mM D-lactose as well as after preincubation of erythrocytes with purified lectin. Titration experiments in a hemagglutination assay showed that the highest level of extractable lectin (5% of the total protein) is found in mucoid cells, lower concentrations are determined in choanocyte clusters (0.07%), free choanocytes (0.05%) and archaeocytes (0.01%). Only the mucoid cells were found to synthesize lectin which is secreted and subsequently transferred to the cell surface of other cell types. As one consequence of the binding of the lectin to the cell surface of aggregation-deficient choanocytes or archaeocytes, the conversion of these cells to aggregation-susceptible ones is observed. These results support previous evidence that the lectin is involved in the reaggregation process of single cells in the homologous biological system.

Animals↗
PubMed1980

Sponge cell aggregation.

Dissociated sponge cell system has proved to be a useful model to study the process of cell aggregation both on cellular and subcellular level. The purpose of this review is to discuss recent results obtained from experiments with the marine sponge Geodia cydonium. Dissociated cells form functional aggregates during a process which can be sub-divided into three phases: first, formation of small primary aggregates in the presence of Ca2+; second, formation of secondary aggregates in the presence of an aggregation factor and third, reconstitution of a functional system of water-containing channels by rearrangement in the secondary aggregates. On subcellular level a series of macromolecules are known which are involved in the control of aggregation and separation of sponge cells: Aggregation factor, aggregation receptor, anti-aggregation receptor, beta-glucuronidase, beta-glucuronosyltransferase, beta-galactosyltransferase, beta-galactosidase and a lectin. These components might be linked in the following sequence: (a) Activation of the aggregation receptor by its enzymic glucuronylation; (b) Adhesive recognition of the cells, mediated by the aggregation factor and the glucuronylated aggregation receptor; (c) Inactivation of the aggregation receptor by its deglucuronylation with the membrane-associated beta-glucuronidase; (d) Cell separation due to either the loss of the recognition site (glucuronic acid) of the aggregation receptor for the aggregation factor or to an inactivation of the aggregation factor by the anti-aggregation receptor. The activity of the anti-aggregation receptor is most likely controlled by the Geodia lectin. The events leading to cell-cell recognition cause a change in the following metabolic events: Increase of oxygen uptake, decrease of cyclic AMP level, increase of cyclic GMP level and stimulation of programmed syntheses.

Animals↗
PubMed1980

Calendar life span versus budding life span of Saccharomyces cerevisiae.

This investigation is concerned with the internal factors governing the life span of individual yeast cells. The life span may be limited either by the number of buds a cell can produce or by internal measurement of metabolic time. The natural relationship between the number of cells a single cell can produce and the passage of time was modified by three different kinds of treatment: (1) by cooling the cells for several hours each day; (2) by preculturing the cells in media which inhibit cell division before allowing logarithmic growth; and (3) by culturing the cells in a medium which reduces the rate of budding. All these methods led to a prolongation of chronological life span, but the life span measured by the number of buddings remained remarkably constant. We therefore conclude that there is some kind of factor involved in the budding process which determines life span.

Cell Division↗
PubMed1980

[Effect of the intravenous administration of a sorbitol solution on the blood plasma content of sorbitol, fructose, glucose, insulin and free fatty acids as well as on the sorbitol half-life in calves, young and adult cattle].

Average sorbite half-life values were 11.8 minutes in two fasting calves, 18.7 minutes in three calves after drinking, 16.4 minutes in five heads of young cattle, and 16.6 minutes in two heads of adult cattle, following intravenous injection of 0.5 g/kg live weight of sorbite solution. Sorbite conversion thus proved adequate and better than glucose conversion. Fructose levels in the blood plasma of fasting calves as well as of young and adult cattle underwent statistically significant rises, following sorbite infusion, the steepest rise being recorded from adult cattle. Significant glucose and insulin increases following sorbite infusion were recordable only from blood plasma of adult cattle. Concentrations of free fatty acids in blood plasma were quite irregular.

Animals↗