Biomedical subjects
Publications and source records attributed to H Maier.
Subpopulations of different proliferative status are determined during cell-density dependent proliferation of 3T3 cells. From these data the probability of conversion of proliferative to quiescent cells is derived and found to correlate well with published data on binding of growth-inhibiting factors secreted from growth-inhibited cells.
Calcium injection in the pig elicits a fast transient response which reinstates the calcium concentration to within normal limits between 30 and 40 min after injection. Although the fate of the calcium that disappeared is not known, the present experiments eliminate the kidneys and the bone remodeling cells as the main short-term regulators. The fast response is independent of parathyroid hormone but is greatly dependent of calcitonin. Further experiments are being performed to discover the nature and site of the regulating mechanisms.
In the present investigation the electrolyte excretion pattern in pilocarpine and citric acid-stimulated human parotid and submandibular saliva was studied dependent upon the flow. In parotid saliva, stimulated by a subcutaneous injection of pilocarpine, significantly higher concentrations of total calcium, ionized calcium, inorganic phosphate and sodium were registered, while the concentration of potassium was significantly lower in comparison to the results obtained after citric acid stimulation. This behaviour was explained as a consequence of a sympathetic-like action of pilocarpine.
The methodology for continuous ionography (monitoring of electrolytic composition) of the pancreatic secretion using a multianalyser is described. The system employs special electrodes which make use of sensing elements constructed of carrier-membrane discs. The procedure has been applied successfully in investigations on animals and is presently being tested in the clinical diagnostic laboratory. The apparatus can also be used for discontinuous measurements, in which case it has the advantage of needing only extremely small quantities of fluid which can be analyzed successively for the different ions, as the electrodes are connected in series.
The effect of Verapamil on ionized calcium transport in the parotid gland and duct system was investigated in eight male volunteers. Transepithelial Ca++-transport was inhibited, as shown by markedly enhanced excretion of calcium in parotid saliva.
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The control of ionized calcium (Ca++), total calcium, and citrate levels in serum were determined in dogs during autotransfusion (AT) of blood stabilized with heparin, ACD (formula B) and CPD. Blood samples were taken according to the changes of aortic pressure (AOP), which was continuously monitored. Taking the values during the stable phase of AOP preceding the AT as baseline, Ca++ dropped by 27% with ACD and by 34% with CPD at the maximum decrease of AOP immediately after the AT. The corresponding increase of citrate was 174% with ACD and 521% with CPD, while total calcium remained stable. Thus cardiac depression after AT of citrated blood seems to be mainly caused by the drop of Ca++, which is significantly more pronounced with CPD, corresponding to the higher content of citrate.
The influence of different sexual hormone levels during menstrual cycle on the composition of human parotid saliva was investigated. During mid-cycle there were significantly enhanced concentrations of ionized calcium, total calcium, inorganic phosphate and sodium in parotid saliva. The changes in chloride concentrations were parallel to that of sodium and the excretion of postassium was inverse to that of sodium. The maximal out-put of total protein and alpha-amylase was found during midcycle and menstruation.
A simplified method for the anaerobic measurement of ionized calcium in serum of venous blood by use of ion-selective electrodes--the monovette-technique--is described. For estimation of Ca++ a new electrode type--the disk-electrode (11, 12, 13, 14)--charged with a synthetic, electrically neutral Ca++-carrier of the octandioic acid-type (1), is tested.
Anaerobically prepared serum samples from healthy subjects were simultaneously analysed for Ca++ in a flow-through-system of three ion selective disc-electrodes (electrochemical multimeasurementsystem). Two of the sensors contained electrically charged ligands, the third contained a neutral carrier. With neutral carriers an improvement of performance was noted in that there was a large increase in selectivity toward H+- and NH+4-ions and a distinct enhancement of reproducibility.
By the development of a disc-electrode and of an electrically neutral calcium carrier a precise determination of calcium ions in the parotid saliva has become available. With this new and simple method an exponential flow rate dependance of the concentration of calcium ions was found in normal persons. A steady state was observed in higher flow rates than 0.5 ml/min. The ionized/total calcium ratio was 54% in the average and was not influenced significantly by the flow rate. The values of both the ionized and total calcium concentrations were slightly lower in females than in men. The salivary ionized calcium concentration was significantly reduced in patients with arterial hypertension, and was not influenced by the flow rate. Its percentage against total calcium was 42% and was reduced to 39% by increased flow rates.
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The regional localization of CMP-N-acetylneuramic acid hydrolase at the hepatocyte surface was studied by using plasma membranes and hepatocytes isolated from rat liver. 1. By homogenization of the rat liver plasma membrane preparations and subsequent discontinuous sucrose gradient centrifugation, one light and two heavy membrane fractions were obtained. The origin of these three subfractions is discussed based on the specific activities in the three fractions of 5'-nucleotidase, alakaline phosphatase and Mg2+-ATPase and on electron microscopic examination of the fractions. Evidence is given suggesting that the light fraction is derived from the bile canalicular surface of the plasma membrane, and that the heavy fractions are derived predominantly from the sinusoidal and lateral surfaces of the liver cell membrane. CMP-AcNeu hydrolase was present at highest specific activity in one of the heavy subfractions. Therefore it is concluded that CMP-AcNeu hdyrolase is located preferentially in the sinusoidal and/or lateral plasma membrane parts of the liver cell. 2. Experiments with intact and disintegrated hepatocytes isolated from rat liver indicated that CMP-AcNeu hydrolase is located at the surface of the cell membrane, with its functional group directed to the outside.
The properties and subcellular distribution of CMP-N-acetylneuraminic acid (CMP-NAcNeu) hydrolase were studied in the cortex of calf kidney. The pH optimum was 9.0 in both Tris - HCl and glycine/NaOH buffer. The apparent Km was 0.47 mM and the apparent V 15.3 mumol/h/g wet wt of calf kidney cortex. A stimulation by divalent metal ions (Ca2+ and Mg2+) was demonstrated for the hydrolase. In the presence of Triton X-100 an increase in enzyme activity was observed. CMP-NAcNeu hydrolase was inhibited by EDTA, beta-mercaptoethanol, nucleoside phosphates and nucleotide-sugars. The inhibition was more pronounced when a sub-optimal CMP-NAcNeu concentration was used. The enzyme appeared to be localized in the plasma membranes. In the plasma membrane preparation of calf kidney cortex, which was derived mainly from the proximal tubule cells, the yield of CMP-NAcNeu hydrolase (13%) and its increase in specific activity (9-fold) was as high as for the plasma membrane marker enzymes. From subcellular distribution studies it appeared that the enzyme was localized mainly at the bursh border side of the plasma membrane of the proximal tubule cell.
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We carried out two case-control studies on the relative risk of head and neck cancer in association with tobacco and alcohol consumption. The first study carried out at the ENT Department of the University hospitals of Heidelberg and Giessen (FRG) comprised 200 male patients with squamous cell cancer of the head and neck and 800 control subjects matched for sex, age, and residential area (1:4 matching design). Of the tumour patients, 4.5% had never smoked, in contrast to 29.5% of the control group. The average tobacco and alcohol consumption of the patients was approximately twice as high as in the control subjects. The highest alcohol and tobacco consumption was observed in patients suffering from oropharyngeal cancer. Tobacco and alcohol increased the risk of head and neck cancer in a dose-dependent fashion and acted as independent risk factors. In heavy smokers (greater than 60 pack-years) a relative risk of 23.4 (alcohol adjusted) was calculated. Combined alcohol and tobacco consumption showed a synergistic effect. The risk ratio increased more in a multiplicative than in an additive manner. Oral and laryngeal cancer were associated with the highest tobacco-associated risk values. The highest ethanol-associated risk values were associated with oropharyngeal and laryngeal cancer. The second study was carried out at the ENT Department of the University of Heidelberg on 164 males with squamous cell carcinoma of the larynx and 656 control subjects matched for sex, age and residential area (1:4 matching design). Of the cases, 4.2% had never smoked, compared with 28.5% of the control subjects.(ABSTRACT TRUNCATED AT 250 WORDS)