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Biomedical subjects

M Schmitz

Publications and source records attributed to M Schmitz.

At least 127 records · Page 7Linked to original sources
PubMed1985

The influence of different cryopreparations on the distribution of ions in bullfrog myocard cells.

Bullfrog heart muscle trabecula are shock-frozen in liquid propane cooled by liquid nitrogen and then processed for X-ray microanalysis in two different ways: 1. Freeze-drying followed by vacuum embedding. 2. Cryoultramicrotomy and freeze-drying. Stained sections of freeze-dried, embedded tissue exhibit detailed ultrastructure, but are useless for X-ray microanalysis. Unstained, dry cut plastic-sections are suitable for X-ray microanalysis, but the ultrastructure appears faint. Higher electron optical contrast and peak-to-background ratio of X-ray spectra are generally obtained in freeze-dried cryosections. Both preparation methods show that the X-ray spectra are influenced by the quality of cryofixation. The phosphorus/potassium ratio in nuclei increases with increasing ice crystal size.

Animals↗
PubMed1985

X-ray microanalysis in cryosections of natively frozen Paramecium caudatum with regard to ion distribution in ciliates.

Cells of Paramecium caudatum were shock-frozen without pretreatment for cryoultramicrotomy and freeze-dried for subsequent X-ray microanalysis. Na, Mg, P, S, Cl, K, and Ca were detected in different amounts in several subcellular compartments. In particular, calcium was localized below the cell surface (pellicle). Trichocysts were found to contain significant amounts of Na in their base but not in the tip. Na, Mg, P, S, Cl, K, Ca were found in electron dense deposits within the lumen of the contractile vacuole. A small K concentration was found in the cytoplasm and in the mitochondria. X-ray microanalysis of the element distribution in different subcellular compartments provides information for the understanding of cellular functions such as exocytosis, locomotion, and ion regulation.

Animals↗
PubMed1983

[New nutritional index for preoperative evaluation of malnutrition as a risk factor in surgery].

In a retrospective trial preoperative anthropometric and biochemical dates of 72 cancer patients were measured. All patients underwent a major surgical resection. Discriminant analysis and a computer-based stepwise regression procedure were used to identify the most important variables. It was able to compute a linear predictive model of 7 variables, called Nutritional Index, relating risk of operative mortality to preoperative nutritional status. In a prospective control trial it was possible to confirm the predictive value of the Nutritional Index by nutritional assessment of 204 surgical patients undergoing a major surgical procedure. This Nutritional Index provides a quantitative classification in surgical patients at high, low and without increased risk of nutritionally based complications.

Female↗
PubMed1981

[Effect of anaerobiosis in 6 blood-culture media on the recovery rate of aerobic microorganisms (author's transl)].

Commercially manufactured blood-culture bottles with 6 different culture media have been considered in this study. The bottles were respectively supplemented with 10% fresh human blood and inoculated with obligate aerobic and facultative anaerobic microorganisms known to cause bacteremia and fungemia. The inoculum size ranged from less than 10 to 10(2) CFU per blood-culture bottle. The study was carried out by alternately incubating one set of bottles anaerobically for two days before being vented, while the other set was vented immediately after inoculation. The effect of anaerobic and aerobic atmospheres on growth intensity, recovery rate and survival durability of the 11 microbial strains has been studied. The maintenance of anaerobic atmosphere for 2 days before venting the blood-culture bottles caused: a) 2 to 4 days delay in detecting nonfastidious bacteria and fungi; b) rapid death of acid-sensitive bacteria in poorly buffered culture media; c) inability of fastidious bacteria to grow in any of the 6 culture media. On the other hand venting the blood-culture bottles immediately after inoculation enabled: a) rapid detection of bacteria by an early subculture after 8 hours of incubation; b) diagnostic advantage of at least 2 days with rapidly growing bacteria which make more than 50% of the whole microbial spectrum; c) good growth of fastidious bacteria. Collectively, brain heart dipeptone broth proved to be the most effective culture medium for detection of obligate aerobic microorganisms responsible for bacteremia.

Acinetobacter↗
PubMed1980

[Biochemical demonstration of HCO3--und Cl--dependent ATPase activities in the rectum of larval dragonflies and inhibition of rectal chloride uptake by thiocyanate (author's transl)].

Hydrogencarbonate and chloride activated, ouabain-insensitive ATPase activities are demonstrated in the salt-absorbing rectum of larval dragonflies. Maximal activation is achieved at approx. 30 mM HCO3- and 20 mM Cl-, respectively. The stimulation of each anion obeys Michaelis-Menten kinetics Km values are 4.65 mM for HCO3-- and 10.25 mM for Cl--activation. The activating anion of one type of ATPase simultaneously exerts an inhibitory effect on the other. Cl--activation is also reduced by Mg.ATP in concentrations above 0.5 mM and by Tris-Hepes buffer exceeding 2.5 mM. Both anion-dependent ATPase activities are found enriched in subcellular membraneous fractions of the rectum. Thiocyanate inhibits both activities and causes a significant decrease in rectal uptake of radioactive chloride from hypo-osmotic external solution. In the case of HCO3- dependent ATPase a competitive inhibition as SCN- was found with an inhibitor constant of Ki=0.5 mM.

Adenosine Triphosphatases↗
PubMed1979

Secretory granules and progesterone secretion by ovine corpora lutea in vitro.

To study the relationship between formation and release of Golgi-derived secretory granules and progesterone secretion, slices of ovine luteal tissue were incubated in the presence of LH and/or calcium ionophore A23187. Increases in progesterone secretion in response to LH and/or ionophore were accompanied by a concomitant release of secretory granules. In contrast, in the presence of colchicine, LH-stimulated progesterone secretion was significantly reduced (P less than 0.01), granule formation appeared to be blocked, and there was little evidence of exocytosis. In addition, unusual pleomorphic membrane-bounded saccules containing an electron-dense material were abundant throughout the centrospheric region of cells treated with colchicine. Because of the close parallelism between formation and release of Golgi-derived secretory granules and progesterone secretion, it appears that progesterone secretion may be coupled to exocytosis of secretory granules. Although the exact content and function of the secretory granules described remains to be elucidated, the data obtained are compatible with the notion that they may contain a progesterone carrier protein.

Animals↗
PubMed1979

The clinical nurse specialist: implementing the role in a hospital setting.

The introduction of a clinical nurse specialist into a functioning patient care setting represents a major institutional change, and implementation of the role should involve all affected staff members. The authors describe how one nurse unilaterally negotiated her role using an exchange theory approach. They make recommendations to help nursing service administrators aid in role negotiation.

Female↗
PubMedDate not supplied

Pulse experiments as a prerequisite for the quantification of in vivo enzyme kinetics in aromatic amino acid pathway of Escherichia coli.

Glucose pulse experiments were performed to elucidate their effects on the carbon flux into the aromatic amino acid pathway in different Escherichia coli strains. Using a 3-deoxy-D-arabino-heptulosonate 7-phosphate (DAHP, aroB(-))-producing strain, a fed-batch fermentation strategy specialized for glucose pulse experiments was developed and further applied for 3-dehydroshikimate (DHS, aroE(-))- and shikimate 3-phosphate (S3P, aroA(-))-producing E. coli strains. The strains overexpress a feedback-resistant DAHP synthase and additional enzymes to prevent rate-limiting steps in the aromatic amino acid pathway. Changes of carbon flux into the aromatic amino acid pathway were determined via extracellular metabolite accumulations using (1)H NMR and HPLC measurements. As an important result, a close relationship between pulse intensity and aromatic metabolite formation rates was identified. The more downstream an aromatic pathway intermediate was located, the stronger the glucose pulse intensity had to be in order to detect significant changes in product formation. However, with the experimental conditions chosen, changes after pulse were detected even for shikimate 3-phosphate, the most downstream accumulating metabolite of this experimental series. Hence glucose pulse experiments are assumed to be a promising tool even for the analysis of final pathway products such as, for example, L-phenylalanine.

3-Deoxy-7-Phosphoheptulonate Synthase↗
PubMedDate not supplied

Localization of Ca2+ at the plasma membrane of bullfrog myocardial cells.

Cellular distribution and localization of Ca2+ in bullfrog myocardial cells was investigated on the light and electron microscopical level using different preparation procedures. Fixation and dehydration in glutaraldehyde and ethanol solutions containing increased amounts of Ca2+ (5-25 mM) cause the formation of numerous electron-dense deposits at the external face of the sarcolemma. X-ray microanalysis demonstrates that the deposits are mainly composed of calcium. Similar results were obtained in cryopreparations by quick-freezing of fresh myocardial tissue. Granules with a diameter of 16.6 nm, which clearly exceed all other cell constituents in contrast, are found at the entire myocardial cell surface. Besides an increased amount of calcium the granules contain potassium and phosphorus. Fluorescence microscopy on single cells obtained from bullfrog atrium by treatment with digestive enzymes and stained with chlorotetracycline (CTC) as a fluorescent probe for membrane-bound Ca2+ clearly support the observations made on the fine structural level. A strong fluorescence signal depending on the CTC- and Ca2+-concentration of the incubation medium is observed at the sarcolemma and can be inhibited by addition of La3+. The results of the present investigation suggest that the surface coat of the sarcolemma of myocardial cells represents an important compartment for accumulation and release of external Ca2+. The external lamina which partly covers the surface of myocardial cells seems not to be involved in the Ca2+ exchange.

Animals↗
PubMedDate not supplied

Histochemical demonstration of an ATP-dependent Ca2+-pump in bullfrog myocardial cells.

In the present investigation different finestructural and histochemical procedures were employed to demonstrate normal morphology and Ca2+-transport mechanism in bullfrog atrial myocardium. For normal morphology specimens were fixed in 1% OsO4, 2.5% glutaraldehyde or liquid propane at -185 degrees C before they were prepared for conventional embedding and freeze-etching, respectively. Special interest was focussed on the caveolae system, which is composed of single, spherical membrane invaginations (diameter, 85 nm), randomly distributed at the entire cell periphery. The caveolae enlarge the cell surface by 24.5% and occupy 8.5% of the cellular volume. The caveolae membrane contains a few intramembraneous particles with a diameter of 8.4 nm comparable to the size of ATPases as found in other cells. For histochemistry the specimens were first stabilized by treatment with 50% glycerol, 0.025% glutaraldehyde or 0.15% formaldehyde and then incubated in a medium containing 4 mM CaCl2, 4 mM EGTA, 5 mM MgCl2, 5 mM K2C2O4, 5 mM ATP and 20 mM histidine at pH 7.0. This incubation always succeeded in the formation of electron-dense deposits with elliptical shape, measuring 100-200 nm in length and 10-30 nm in diameter. According to X-ray spectra they deliver a characteristic calcium-peak and can be found within two different cellular compartments: in small invaginations of the sarcolemma, i.e. the caveolae-system, and in the intrafibrillar sarcoplasmic reticulum. The elliptical deposits can be clearly distinguished from round electron-dense granules measuring 16 nm in diameter, which are located within randomly distributed small vesicles and composed of potassium and phosphate. Contrary to the elliptical deposits the round granules are also present in controls and seem to be identical with the so-called atrial granules. In comparison to observations obtained with the same method in other muscular systems and derived from various control experiments the results of this study favour the existence of an ATP-dependent Ca2+-pumping mechanism in frog atrial muscle bound to both, the sarcoplasmic reticulum and the caveolae system.

Adenosine Triphosphate↗
PubMedDate not supplied

A psychosocial model of health behavior: implications for nutrition education, research and policy.

The paper presents a multidimensional psychological model of determinants of health behavior, tested empirically in three countries to ascertain its validity. The model postulates that given that ethnic, socioeconomic, and biological statuses (exogenous variables) are homogeneous, a health risk-taking behavior in a population is a function of direct, additive, and interaction effects of five categories of independent variables both internal to the persons and external in the action environment. Although the model is tested on contraceptive behavior, it is argued that the determinants and basic processes of this risk-taking behavior are similar to those involved in other health risk behaviors and that the five basic factors identified affect nutritional behaviors as well. The paper presents several broad implications on the model for nutrition education and research; but holds that specific implications could be best derived by the specialists in nutrition field.

Contraception↗
PubMedDate not supplied

A novel human malignant fibrous histiocytoma cell line of the heart (MFH-H) with secretion of hematopoietic growth factors.

Primary malignant fibrous histiocytoma (MFH) exhibits an extremely adverse prognosis. Investigations into the principles determining the biological aggressiveness of this cardiac tumor would be facilitated by an appropriate in vitro model. Therefore, we report on the first permanent cell line (MFH-H), derived from a human cardiac MFH. The original tumor had shown coexpression of cytoskeletal filaments typical of mesenchymal (vimentin), epithelial (cytokeratins) and neurogenic (neurofilaments) differentiation. This potential for multidirectional differentiation was observed in the MFH-H cell line as well and indicated marked plasticity of gene activation acquired during the process of neoplastic transformation. Pronounced genetic alterations also became evident from cytogenetic analysis, which revealed a highly variant karyotype with multiple numeric and structural chromosomal aberrations. Secretion of G-CSF, GM-CSF and M-CSF was shown to be another feature of deregulated gene expression in MFH-H cells. Direct autocrine effects of their hematopoietic growth factors, however, were precluded by the lack of the corresponding receptors. In conclusion, the cell line MFH-H will provide an appropriate in vitro model to analyze the biological properties of this cardiac malignancy in more detail, especially with regard to a possible immunomodulating capacity of MFH-derived hematopoietic growth factors.

Adult↗