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Biomedical subjects

G Maier

Publications and source records attributed to G Maier.

At least 55 records · Page 3Linked to original sources
PubMed1987

[Are there differences in prodromal illnesses, symptoms and prognosis for various forms of mesenteric infarct?].

Comparing 105 patients with mesenteric infarction, the typical attributes of the underlying diseases, arterial embolization (aE) (n = 26), arterial thrombosis (aT) (n = 40), venous thrombosis (vT) (n = 32) and combined arterio-venous occlusion (n = 7) could be demonstrated. Present heart disease, diabetes and arterial hypertonia, rapid onset of symptoms, severe abdominal pain and signs of peritonitis, extended gangrene of bowel and a high mortality of about 90% is the typical combination for aE. Over 70 years old patients with higher incidence of arteriosclerosis, more digitalis intake, longer duration of symptoms and with bowel problems in the past have a higher incidence of aT and a slightly better prognosis. Risk of thrombosis, long-standing symptoms and a clearly better prognosis are typical for the vT.

Aged↗
PubMed1987

[Measures for reducing exposure to scattered radiation in urologic roentgen diagnosis].

A simple device to reduce the urologic examiner's exposure to radiation is presented. The doses the examiner and his assistant staff are exposed to performing various methods of urologic radiodiagnosis were measured and the following exposure to radiation determined with and without radioprotective device. The measurements demonstrate, that already by simple measures considerable reduction of the exposure to radiation can be obtained for examiner and assistant personnel. The frequently neglected importance of scattered radiation resulting from urologic radiography is discussed.

Humans↗
PubMed1986

Molecular characterization of a karyophilic, histone-binding protein: cDNA cloning, amino acid sequence and expression of nuclear protein N1/N2 of Xenopus laevis.

In the amphibian oocyte, most of the non-chromatin-bound histones are not free but form complexes with specific karyophilic proteins, the most prominent being nucleoplasmin and 'protein N1/N2'. Using antibodies against polypeptide N1 and N2 (Mr approximately 105,000 and approximately 110,000) we have isolated, from a Xenopus laevis ovary lambda gt11 expression library, several full length cDNA clones encoding one of the two closely related polypeptides N1 and N2 (these could not be distinguished by hybridization techniques). The amino acid sequence deduced from one of these clones (N1/N2, lambda 106.2) defines a polypeptide of mol. wt 64,774. The remarkably high difference between the value of Mr approximately 110,000 estimated from SDS-PAGE mobility and the true mol. wt has been found for (i) the cell protein, (ii) the polypeptide synthesized in vitro by transcription and translation and (iii) the fusion protein with beta-galactosidase expressed in Escherichia coli, indicating that the protein runs anomalously on SDS-PAGE. The amino and carboxy termini of the purified protein N1/N2 have been confirmed by direct amino acid sequencing of CNBr fragments. The amino acid sequence displays two glutamic acid-rich domains, which are probably involved in the interaction with the histones, and a putative nuclear targeting signal with high homology to that of the SV40 large T-antigen which is located near the carboxy terminus.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1986

Rising multiple-dose pharmacokinetics of labetalol in hypertensive patients.

Labetalol, a drug possessing both alpha- and beta-adrenergic blocking activities, is used in the treatment of hypertension. The current study was undertaken to elucidate the steady-state pharmacokinetics of labetalol following a rising oral multiple-dosage regimen. Twelve patients received oral labetalol every 12 hours for 18 days. An initial dose of 100 mg was increased at three-day intervals to 200, 300, 400, and 600 mg q12h. Selected blood samples were taken at various times following drug administration at each dose level and analyzed for labetalol levels by a specific high-performance liquid chromography assay. The pharmacokinetics of labetalol are best described by a two-compartment open model with first-order absorption. The half-lives of the absorption, distribution, and elimination phases are 0.6, 1.3, and 8.3 hours, respectively. The steady-state plasma drug concentrations are predictable from the pharmacokinetic data and are in good agreement with the observed values. Steady-state levels are reached by the third day at each dose level studied and increase proportionally with dose.

Adult↗
PubMed1986

[Results of conservative treatment of distal radius fractures].

The results of conservative treatment of fractures of the distal radius in 303 patients over a period of two years are demonstrated. 226 patients could be followed-up. The healing of the fracture was satisfactory in 78%, while the results regarding the various age groups showed considerable differences. Along with the demonstration of the functional and anatomical results in relation to age, sex, and localization the technique of fracture treatment as well as follow-up treatment are discussed.

Adolescent↗
PubMed1986

Cytokeratin expression in simple epithelia. I. Identification of mRNA coding for human cytokeratin no. 18 by a cDNA clone.

To study the regulation of the expression of cytokeratins characteristic of simple epithelia, i.e., human cytokeratins nos. 7, 8, 18, and 19, we prepared several cDNA clones coding for these proteins and their bovine counterparts. In the present study, we describe a cDNA clone of the mRNA coding for human cytokeratin no. 18, which was isolated from an expression library using the monoclonal antibody, KG 8.13. This clone (756 nucleotides, excluding the polyA portion), encodes approximately one-half of the mRNA (approximately 1.4 kb), identifies one mRNA band in Northern-hybridization blots, and specifically selects one mRNA species coding for cytokeratin no. 18, as demonstrated by translation in vitro. Comparison of the deduced amino acid sequence--confirmed by direct amino-acid-sequence analyses of some polypeptide fragments produced by cleavage with cyanogen bromide--indicated that cytokeratin no. 18 is a member of the acidic (type I) subfamily of cytokeratins. It has only limited sequence homologies in common with other intermediate-sized filament proteins, and these are essentially restricted to certain domains of the alpha-helical rod portion. The carboxyterminal tail sequence does not contain glycine-rich elements, thus distinguishing this cytokeratin from those acidic (type I) cytokeratins that are characterized by this feature. The similarities and differences between cytokeratin no. 18 and previously described epidermal cytokeratins are discussed in relation to the differences in the stability of the complexes which this cytokeratin forms with basic (type II) cytokeratins, as well as in relation to possible functional differences of cytokeratins in simple and stratified epithelia.

Amino Acid Sequence↗
PubMed1985

DNA intercalators induce specific release of HMG 14, HMG 17 and other DNA-binding proteins from chicken erythrocyte chromatin.

Chicken erythrocyte nuclei were incubated with DNA intercalating agents in order to isolate from chromatin specific DNA-binding proteins whose binding specificity may be determined by DNA secondary and/or tertiary structure. The intercalating agents ethidium bromide (EtBr) and propidium iodide induce the specific release of high mobility group proteins HMG 14 and HMG 17 under low ionic strength conditions. Chloroquine (CQ) intercalation also results in the selective liberation of HMG 14 and HMG 17, but, in addition, selectively releases other nuclear proteins (including histone H1A) in a pH- and ionic strength-dependent fashion. The use of this new 'elutive intercalation' technique for the isolation and purification of 'sequence-specific' and 'helix-specific' DNA-binding proteins is suggested.

Animals↗
PubMed1985

Cumulative causation and selectivity in labour market oriented migration caused by imperfect information.

This paper is concerned with the implications of job search models for migration. In contrast to earlier models, the model described here does not assume perfect information about the wage offer distribution. "In this model information about the wage offer distribution is imperfect and accumulated through the search process. When based on this search model, the migration model is largely enriched and also more realistic. Strategies, which are suboptimal or even absurd with perfect information about the wage offer distribution, such as purchase of information, can be preferable in a migration model, when imperfect information is assumed." The author suggests that the model can explain many phenomena utilized in the argumentation of polarization theory. Consideration is also given to selectivity with respect to age, educational status, and risk preference, as well as the cumulative effects caused by past migration flows and the size of regions. (summary in FRE, GER)

Age Factors↗
PubMed1984

Effect of sleep on quazepam kinetics.

The effect of sleep on quazepam kinetics was studied in 12 normal adult men. In a randomized two-way crossover design, each subject received one 15-mg quazepam tablet either at night just before sleep or in the morning after a night's sleep. Blood samples were drawn before and at specified times (to 120 hr) after dosing. To assure that blood collection did not interfere with sleep, blood was drawn by an indwelling catheter from a large arm vein. Plasma concentrations of quazepam and its two major plasma metabolites (which are also active) 2-oxoquazepam and N-desalkyl-2-oxoquazepam (N-desalkylflurazepam) were determined by specific GLC methods. Kinetic analysis was by a two-compartment open model with first-order absorption/formation kinetics. Quazepam was rapidly absorbed with both administration times; absorption t 1/2 was 0.7 to 0.9 hr. Absorption lag time was slightly longer after the nighttime dose (1.0 and 0.6 hr). Maximum concentration and AUC of quazepam and 2-oxoquazepam and AUC of N-desalkyl-2-oxoquazepam were somewhat higher after nighttime dosing, most likely a result of decreased apparent volume of distribution of the central compartment after the nighttime dose (5.0 l/kg for nighttime dosing and 8.6 l/kg for morning dosing). The elimination t 1/2s of quazepam, 2-oxoquazepam, and N-desalkyl-2-oxoquazepam after the morning dose were 25, 28, and 79 hr, which did not differ from those values after the nighttime dose. In general, time of dosing had no appreciable effect on quazepam kinetics or those of its major active plasma metabolites. The small differences between the two dose times are not expected to have clinical significance.

Absorption↗
PubMed1983

HLA antigens in White and Black South African diabetics.

The HLA A and B specificities in 72 Whites with type 1 or juvenile-onset diabetes mellitus (JOD), 53 Blacks with type 1 diabetes or JOD and 52 Blacks with type II or maturity-onset diabetes (MOD) were determined and compared with those in 278 Whites and 311 Blacks who were not diabetic. In Whites with JOD, frequencies of HLA A1 and B8 antigens were significantly increased, whereas those of the A3 and B17 antigens were reduced. Blacks with JOD had an increased frequency of HLA B8. By contrast, in Blacks with MOD the antigen frequencies were not significantly altered. The D-locus antigens Dw3 (DRw3) and Dw4 (DRw4), which bear the strongest associations with JOD in Whites, need to be examined in Black South African diabetics.

Adult↗
PubMed1982

Is transferrin normal in idiopathic haemochromatosis?

Family studies were done to ascertain whether there is linkage between the transferrin locus and the HLA loci on chromosome 6. The findings in four families in which there was variation at the transferrin locus did not demonstrate any linkage, with 17 of the 30 offspring of heterozygous parents being recombinants and 13 non-recombinants. These results indicate that the HLA linked defect responsible for increased iron absorption in idiopathic haemochromatosis is not a consequence of any abnormality in the primary structure of transferrin.

Female↗
PubMed1982

The effects of airway pressure on cardiac function in intact dogs and man.

Ventilation with positive end-expiratory pressure (PEEP) is associated with reduced cardiac output, but the mechanisms involved are controversial. Possible explanations include increased intrathoracic pressure, reflex changes in myocardial inotropism, pulmonary vascular obstruction and abnormal ventricular interaction. Three types of conscious canine preparations were developed to examine simultaneously each of these factors during ventilation with PEEP. In addition, similar measurements were obtained in patients after cardiac surgical procedures and compared with the results of animal experiments. The primary cause of reduced cardiac output during PEEP appeared to be a diminished end-diastolic volume of the left ventricle, and this appeared to be the result of elevated intrathoracic pressure and increased impedance to blood flow through the lungs. Abnormal interventricular septal shifting and reflex autonomic alterations did not appear to be significant in the normal cardiovascular system. These data provide insight into the cardiac effects of PEEP and emphasize the importance of simultaneous quantification of biventricular performance when assessing cardiopulmonary function.

Animals↗
PubMed1981

Cell density dependent DNA replication in Ehrlich ascites tumour cells.

DNA replication of Ehrlich ascites tumour cells was investigated in suspensions with different cell densities by incorporation in vitro of tritiated thymidine and alkaline sucrose gradient analysis of the newly formed DNA. It is demonstrated that the incorporation of [3H]thymidine and chain growth of newly made DNA decreases with increasing cell density. The inhibition of DNA synthesis observed at high cell densities can be prevented if diffusible substances are removed by incubating the cells in dialysis tubes. This indicates that the changes in DNA synthesis are caused by diffusible inhibitors released from the tumour cells.

Animals↗
PubMed1981

Dependency of proximal tubular fluid transport on the load of glomerular filtrate.

In hydropenic rats, the reabsorption of glomerular filtrate by the proximal convoluted tubules was measured before and after reduction of its intratubular flow rate. Three different protocols were used. (1) In 26 tubules (14 rats), nephron glomerular filtration rate (SNGFR) was varied from 37.2 +/- 7.3 to 20.4 +/- 7.1 nl/min by microperfusing their loops of Henle at 0 to 5 nl/min and 40 nl/min, respectively. This 43% reduction of SNGFR was followed by a 36.0 +/- 23.3% reduction of volume reabsorption rate (P less than 0.001). Between both parameters a linear regression line can be calculated, which is given by y = 0.92 chi + 0.0017. (2) In 17 tubules (14 rats), SNGFR was altered again by feedback from 46.0 +/- 9.7 to 28.8 +/- 9.3 nl/min. The volume resorption from the first half of the proximal convoluted tubule was compared with the reabsorption in its late proximal segments, which were microperfused with proximal tubular fluid at a rate of 20 nl/min. The 36.8% reduction of SNGFR was followed by only a 28.2% reduction of volume reabsorption rate in the first half of the tubule. In the microperfused segments, however, reabsorption remained unaltered. (3) In 29 tubules (21 rats), at the midpoint of proximal convolutions, some of the tubule fluid was removed by a suction pump, and volume reabsorption rate in the late segments was compared with that in the early parts of this tubule, when SNGFR remained stable. The reduction of intratubular flow from 27.7 +/- 8.5 to 14.7 +/- 5.8 nl/min, which is 53% of control, were followed by a reduction of volume reabsorption rate in the late segment to 60.6% control. Between both parameters a regression line was calculated, which is given by y = 0.76 chi +/- 0.01. We conclude that the rate of volume reabsorption by the proximal tubule depends on its intratubular load of glomerular filtrate and, further, that this dependency accounts predominantly for the maintenance of glomerular tubular balance under conditions of hydropenia.

Absorption↗
PubMed1980

A spin labeling study of the effects of inorganic ions and pH on the conformation of spectrin.

The structure of spectrin from human erythrocytes has been investigated by the EPR technique measuring the mobility of the protein spin label, 4-maleimido-2,2,6,6-tetramethylpiperidinooxyl. Conformational changes in the protein induced by variation of the concentrations of NaCl, Na2SO4, KCl, CaCl2 and MgCl2 and of pH have been studied. It could be demonstrated that both Ca2+ and Mg2+ give rise to structural changes by binding to specific sites, whereas the monovalent cations (K+, Na+) seem to act via ionic strength. A model is used to correlate the spin label mobility with the radius of the protein. In the Ca2+- and Mg2+-binding experiments, the decrease in the spin label mobility has been interpreted on the basis of the theory of multiple chemical equilibria. These experiments have been compared with EPR spectra measured at different pH values. The results support the model in that binding of H+, Ca2+ or Mg2+ reduces the charges located on the protein surface: the 'discharging' reduces the repulsive forces on the surface of the molecule and consequently, the protein contracts in discrete steps.

Calcium↗