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Biomedical subjects

W Hofmann

Publications and source records attributed to W Hofmann.

At least 181 records · Page 10Linked to original sources
PubMed1990

Cryo-electron microscopic studies of relaxed striated muscle thick filaments.

Electron micrograph images of rapidly frozen suspensions of thick filaments from four different muscle types are presented. Their optical and computer transforms are compared with images and diffraction patterns of negatively stained filaments and with X-ray data from the same muscles. We conclude that myosin head arrangement can be preserved on rapid freezing and that the images produced can be analysed by image processing techniques to give new information on thick filament structure.

Actin Cytoskeleton↗
PubMed1990

The popliteal artery entrapment syndrome: presentation, morphology and surgical treatment of 13 cases.

The morphology, clinical parameters and treatment of the popliteal artery entrapment syndrome (PAES) are presented on the basis of 13 of our own cases and from the literature. PAES is based on a segmental vascular compression due to an anatomical anomaly of the popliteal region and a new classification is presented distinguishing three variants according to the different anatomical conditions. PAES is mostly found in young sportsmen with well-developed muscles. Clinical symptoms are acute or chronic, and the diagnosis is made by physical examination, angiography and Doppler ultrasound, both in neutral position and in plantar flexion. Although thromboendarterectomy in some cases leads to good results, the preferred surgical therapy is decompression of the entrapped artery and reconstruction of the arterial pathway by vein graft interposition. The results were excellent in nine of 13 cases. In two patients, a recurrent thrombosis necessitated a femoro-crural bypass and in two others the entrapment was only diagnosed during reoperation for aneurysms of the venous graft.

Adult↗
PubMed1990

A generalized state-vector model for radiation-induced cellular transformation.

A mathematical model is developed, detailing the manner in which radiation brings about the transformation of cells to a state of uncontrolled growth. The model is based on the concepts of initiation and promotion, with the irradiation acting both to damage intracellular structures and to change the state of cells surrounding a damaged (initiated) cell. The complete model requires that the radiation produce two forms of damage within a cell, with at least one of the forms requiring an interaction which is a function of time since irradiation. Some form of contact inhibition must be removed, with this step being a function of the probability that a cell in an initiated state will be surrounded by n dead cells. The cell then must divide, with the probability of moving the cell to the final transformed state being a function of the number of cellular divisions. Prior to irradiation, it is assumed that cells may be characterized by an initial state vector describing the probability that any given cell is in one of the states specified by the model. The resulting model then is used to explain data concerning in vitro irradiation of cells by acute doses of X-rays, alpha particles and neutrons. Limited tests of the theory under conditions of fractionated irradiation are also provided. A controlling factor in such studies is the number of cells already in intermediate states prior to the irradiation.

Alpha Particles↗
PubMed1990

Lung dosimetry of thorotrast patients.

Deposits of intravascularly injected Thorotrast in the reticulo-endothelial system of Thorotrast patients are a continuous source of 220Rn. In this study, we modeled the transport of 220Rn from these deposits through the body into the lungs, exhalation of 220Rn from the lungs, production of 220Rn progeny in the lungs and their exhalation, and mucociliary clearance of 220Rn progeny deposited on airway surfaces. The injection of 1 mL Thorotrast produces annual doses of 0.48 mGy y-1 to the bronchial epithelium and 0.95 mGy y-1 to pulmonary tissue. Based on a mean injected volume of about 25 mL and an average exposure time of 30 y, German Thorotrast patients received a mean bronchial lifetime dose of 357 mGy. Despite these relatively high doses, comparable to exposure in uranium miners, no excess lung cancers could be observed in the epidemiologic follow-up study. This apparent discrepancy between predicted and observed bronchial tumors may have important implications for lung dosimetry and risk assessment of inhaled 222Rn progeny.

Bismuth↗
PubMed1990

[Ambulatory cardiologic care: comparison between patients from a referral hospital and from community health centers].

PURPOSE--Comparison between patients from a cardiology referral center and those from community health facility. PATIENTS AND METHODS--564 (5.3%) of 10667 patients from the referral center--Instituto do Coração (InCor) and 105 (58.6%) of 169 from community health facility--Centro de de Santo Amaro (CSSA), São Paulo. RESULTS--217 (35.8%) patients in InCor and 27 (25.5%) in CSSA were younger than 40 years of age. Female patients were more frequent: 316 (56%) in InCor and 70 (66.7%) in CSSA. In InCor, 317 (56.2%) patients lived in São Paulo City and in CSSA all the patients live in the surroundings. Forty-three percent of the patients sought for medical attention in InCor by themselves, without medical referral. The diagnosis of heart disease was established in 81% of the patients in InCor and in 92.5% of the patients in CSSA. Other tests (besides electrocardiogram and chest roentgenogram) were considered to be indicated in 35% of the patients from InCor. The diagnoses were: a) coronary heart disease in 92 (20.1%) cases (InCor) and in 8 (8.2%) cases (CSSA); b) valvular heart disease in 46 (10.1%) cases (InCor) and in 9 (9.2%) cases (CSSA); c) mitral valve prolapse in 31 (6.8%) cases (InCor) and in 7 (7.1%) cases (CSSA); d) congenital heart disease in 10 (2.2%) cases (InCor) and in 1 (1%) case (CSSA); e) systemic arterial hypertension in 161 (35.2%) cases (InCor) and in 55 (56.1%) cases (CSSA); f) Chagas' infection or Chagas' heart disease in 44 (9.6%) cases (InCor) and in 8 (8.2%) cases (CSSA); g) cardiac rhythm disorders in 38 (8.3%) cases (InCor) and in 8 (8.2% cases (CSSA); h) other diseases in 33 (7.2%) cases (InCor) and in 1 (1%) (CSSA); i) diseases of the aorta in 2 (0.4%) cases (InCor) and in 1 (1%) (CSSA). Medical treatment was recommended to 71.5% of the patients from the InCor and to 92.5% of the patients from CSSA. CONCLUSION--Our data suggest a degree of similarity between the groups of patients cared for in a cardiology referral center in our city in relation to a community health facility. These data may be useful in planning optimal use of referral hospitals facilities in our city.

Adult↗
PubMed1990

[Prognosis and therapy of primary epithelial liver tumors. Evaluating a personal patient sample].

Prognostically relevant factors and treatment were analysed in 103 patients suffering from primary epithelial liver tumors (88 HCC, 15 CCC). Ninety of them underwent operations: 14 liver transplantations, 32 resections, 44 explorative laparotomies. The resection rate was 38%, the 30-day mortality in transplantation 14%, in resection 22%. The 5-year survival after resection was about 25%. Liver transplantation resulted in 50% 1-year and 40% 2-year survival. Long-term prognosis was positively influenced by cirrhosis and formation of a tumor capsule. Indications for operative management depend only on extension of tumor growth and concomiting liver cirrhosis as biology of epithelial liver tumors is poorly understood.

Adenoma, Bile Duct↗
PubMed1990

[Urosepsis and uroseptic shock].

The currently high letality rate of uroseptic shock may be reduced by early recognition of symptoms and adequate therapy with elimination of causes. Decisive for the septic shock are initial disturbances of the microcirculation in the presence of hyperdynamic circulatory regulation with following disorders of the coagulation system, tissue metabolism, acid-base-balance and heart contractility. In the therapeutic armament the important role of vasoactive substances is stressed. In an analysis of 59 patients suffering from urosepsis the intrinsic and iatrogenic causes, the bacterial spectrum and the emergency operative interventions are evaluated, whereas a letality rate of nearly 12% and an injury grade of 34% are estimated.

Bacterial Infections↗
PubMed1990

[Important virus infections of the respiratory tract in cattle from the clinical point of view].

The etiological participation of different viruses in the pneumonia complex of cattle is undisputed. The significance of the individual viruses in the genesis of disease symptoms is still mostly unclear. Since the pneumonia complex of cattle is a multifactorial syndrome, vaccination programs as the only measure of prophylaxis in most cases do not show the desired effect. Against those viral agents causing self-standing diseases of the respiratory tract, specific vaccinations are applicable with success. Prerequisite for their effectiveness, however, is the exact etiological clarification of the cause of disease or of the existing infections respectively in the herd. The frequency of possible viral agents in infections of the respiratory tract in cattle from herds of the province of Schleswig-Holstein found in routine diagnostic work during the last four years is presented in addition.

Animals↗
PubMed1990

[Diagnostic value of radioisotope clearance in patients with a single kidney].

In a group of patients with solitar kidney a radioisotope clearance was performed to determine exactly the renal functional status and to reduce the blind area of standard diagnostical parameters. In 41 percent of these patients a restriction of the glomerular or tubular value was found. In the same way the function-diminishing effect of hypertension on renal plasma flow and tubular-secretory function was determine. In the present study of dynamic radioisotope investigations in patients with solitar kidney could be verified.

Glomerular Filtration Rate↗
PubMed1989

Preparative isolation of glycoproteins from plasma membranes of different rat organs.

By a combination of high-performance affinity chromatographic (HPAC) methods, several membrane proteins from liver, Morris hepatoma and kidney were isolated. The use of a tandem system, consisting of a concanavalin A (ConA) and a wheat germ agglutinin (WGA) high-performance liquid chromatographic (HPLC) column, as a first purification step allowed the isolation of proteins directly from organ homogenates. In a subsequent step, the membrane proteins can be isolated by simply using a combination of immunoaffinity HPLC and preparative sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). However, with these methods most proteins lose their biological activity. If native proteins are required, a combination of different HPAC methods has to be applied. Several membrane proteins were isolated in milligram amounts under non-denaturing conditions using either HPAC columns or Mem Sep membranes with immobilized lectins, collagen, amino acids, crown ethers or heparin.

Animals↗
PubMed1989

[Recent treatment results in feeding-related calf diarrhea with special reference to diet and Diaproof K].

Appearance of diarrhea was studied in 758 calves over a period of 6 years in the "Klinik für Klauentierkrankheiten". The incidence of the disease varied each year between 19% and 48% with a mortality rate up to 3%. Different methods of feeding were chosen and proved. Good results were obtained giving sour colostrum twice in the first day, followed by five days feeding sour milk replacer continued afterwards with sour milk. In this case the diarrhea rate was 22%; in comparison to 41% caused by normal milk products. A shortened duration of unspecific diarrhea in calves (1-2 days) was seen when Diaproof K from Atarost, a dietetic powder, was administered. Diarrhea disease with bad health conditions need a specific treatment.

Animal Feed↗
PubMed1989

Expression of native rabbit light meromyosin in Escherichia coli. Observation of a powerful internal translation initiation site.

The cDNA-sequence coding for rabbit skeletal muscle light meromyosin (LMM) was placed under the control of the lambda promoter (PL) of an Escherichia coli expression vector. The resulting plasmid pEXLMM74 expressed non-fused rabbit skeletal muscle LMM with yields ranging from 1 to 5% of the total proteins of E. coli. This LMM was specifically recognized by polyclonal antibodies raised against chicken pectoralis muscle myosin. It could be highly enriched from E. coli extracts by using two cycles of high and low ionic strength buffer. The partially purified protein contained a major side-product, with a calculated molecular mass of 59 kilodaltons, that is produced by translation initiation from a site in the coding region of LMM. After deletion of the translation initiation site derived from the expression plasmid, only the 59 kilodalton protein is expressed in E. coli from the resulting plasmid pEXLMM59. Both the 74 and 59 kilodalton proteins were shown to form paracrystals. They were studied by electron microscopy using negative staining and were found to show characteristic striations with an axial periodicity of about 43 nm. By circular dichroism measurement we showed that the purified 59 kilodalton protein is folded mostly as an alpha-helix.

Animals↗
PubMed1989

Structural differences between human and rat lungs: implications for Monte Carlo modeling of aerosol deposition.

The geometrical structure of the lung is one of the main factors governing inhaled particle deposition; structural differences among different species are, therefore, of great importance for extrapolation modeling. A statistical analysis of morphometric data for the human and rat tracheobronchial tree reveals significant interspecies differences in airway branching patterns: compared to the relatively dichotomous and symmetric structure of the human lung, the rat lung displays a more monopodial airway branching pattern. Thus, for the rat lung, we recommend characterizing the properties of a given airway, i.e., its size, physiologic function, and distance from the trachea, by its diameter rather than by a theoretically assigned generation number. A Monte Carlo method is used to construct an airway geometry along each inhaled particle's path by randomly selecting airway parameters from their frequency distributions and the correlations among them. While the airway geometry is selected randomly, particle deposition in individual airways is calculated analytically. These stochastic deposition calculations allow for structural differences between the human and rat lung, and the variability of the airway system within each species.

Aerosols↗
PubMed1989

Human subject age and activity level: factors addressed in a biomathematical deposition program for extrapolation modeling.

A deterministic aerosol deposition model, previously validated by data from adult inhalation exposure experiments, is used to study particle deposition within the developing human lung. Here, two age-dependent lung morphologies are presented, in which the number of tracheobronchial (TB) generations is complete at birth but airway dimensions vary with age; the number of pulmonary (P) generations, however, changes with age, as do the alveolated airway dimensions. Deposition patterns within the two morphologies are compared. For the light and heavy respiratory-activity levels considered, regional TB and P, and total (TB + P) lung deposition fractions are calculated. For all particle sizes (0.2-9.0 microns diameters) tested, total deposition in both morphologies was minimal for the 30-y-old adult and maximal for either of the youngest subjects (7 and 22 mo old). A breakdown of total deposition into lung compartments was specifically addressed for one morphological model. Age-dependent deposition models are intended to aid in future extrapolation efforts to assess the threat to human health from airborne contaminants.

Adult↗
PubMed1989

A diagnostic programme for quantitative analysis of proteinuria.

A spectrum of quantitative methods was adapted to the Kone Specific Analyser for the purpose of recognizing, quantifying and differentiating various forms of proteinuria. Total protein, IgG, albumin and alpha 1-microglobulin (measured by turbidimetry), N-acetyl-beta-D-glucosaminidase activity and creatinine (measured photometrically), were measured in undiluted urine; in addition alpha 1-microglobulin was measured in serum. Within and between run precision, accuracy and linearity of the turbidimetric methods were in good agreement with nephelometric procedures. All turbidimetric methods exhibited a correlation coefficient r greater than 0.98 when compared with the radial immunodiffusion procedure as reference method. Total protein measured turbidimetrically with the Kone Specific Analyser was in good agreement with the manual biuret procedure. The low detection limits and linearities allowed quantification of urine analytes from the lower range of normals up to ten times the upper limit of normals. The measured analytes exhibited stability in urine at pH 4-8 over at least seven days at 4-6 degrees C and -20 degrees C. Only IgG showed a significant loss (up to 30 percent), when measured after storage at -20 degrees C. Quantities per mol creatinine showed significantly lower intra-individual and inter-individual variability than quantities per liter. In 31 normal persons, the intraindividual variation was lowest for N-acetyl-beta-D-glucosaminidase activity (13%) and highest for total protein (33%), when measured in the second morning urine on 5 consecutive days. When related to creatinine, results obtained in the second morning urine showed no significant differences from those in 24 h urine, except for alpha 1-microglobulin which gave lower values in 24 h urines. The upper normal limits, calculated as the 95% ranges, were determined from 154 urines of 31 individuals. Nearly all analytes showed an asymmetric distribution. Because of a wide tailing of the upper limit, preliminary upper normal limits were set above this range: (table; see text) Application of the newly adapted programme to unselected urines sent for urine analysis revealed a threefold increase in the proportion of results outside the normal ranges, compared with the routinely used protein test strip procedure. All additional positive urines exhibited either signs of glomerular or tubular proteinuria. Determination of albumin or N-acetyl-beta-D-glucosaminidase excretion was sufficient to detect these additional cases.

Diagnosis, Differential↗
PubMed1989

[Urinary proteins in patients with diabetes mellitus].

In the second morning urine of 51 patients with diabetes mellitus (type I/II) albumin, N-acetyl-beta-D-glucosaminidase (NAG), alpha 1-microglobulin (alpha 1-M/U), creatinine (reference parameter) as well as serum alpha 1-microglobulin and creatine were determined. Following an international expert recommendation, three groups were formed depending on albumin excretion: group 1: albumin less than 24 mg/g creatinine (normal range) group 2: albumin greater than 24 mg/g creatinine and less than 200 mg/g creatinine (so called microalbuminuria) group 3: albumin greater than 200 mg/g creatinine (manifest proteinuria) The urinary tubular parameters NAG and alpha 1-microglobulin were above normal range in 17 and 21% respectively in group 1. For group 2 the results were abnormal in 94 and 69% and for group 3 in 100% of patients. Albuminuria correlated with NAG activity, but not with alpha 1-microglobulin excretion. These results indicate, that measuring NAG and alpha 1-microglobulin as markers for tubular dysfunction can give additional diagnostic informations about type and degree of diabetic nephropathy.

Acetylglucosaminidase↗