Biomedical subjects
M Kern
Publications and source records attributed to M Kern.
[Optimizing the bond between metal and bonding agent in bonded restorations using a simplified silicoating procedure].
The tensile bond strengths of five different resinbonding-systems to a Co-Cr-alloy (Dentitan) are tested. The samples were stored in artificial saliva (37 degrees C) up to 150 days and thermocycled (5 degrees-55 degrees C, 18,750 cycles). In contrast to micromechanical bonding-systems, mechanical-chemical ones showed no significant changes in tensile bonding strength during this observation period. The tribochemical silicoating procedure (Rocatec) seems to be suitable for Co-Cr-alloys used in resin-bonded restorations.
Acute anemia results in an increased glucose dependence during sustained exercise.
We evaluated whether acute anemia results in altered blood glucose utilization during sustained exercise at 26.8 m/min on 0% grade, which elicited approximately 60-70% maximal O2 consumption. Acute anemia was induced in female Sprague-Dawley rats by isovolumic plasma exchange transfusion. Hemoglobin and hematocrit were reduced 33% by exchange transfusion to 8.6 +/- 0.4 g/dl and 26.5 +/- 1%, respectively. Glucose kinetics were determined by primed continuous infusion of [6-3H]glucose. Rates of O2 consumption were similar during rest (pooled means 25.1 +/- 1.8 ml.kg-1.min-1) and exercise (pooled means 46.8 +/- 3.0 ml.kg-1.min-1). Resting blood glucose and lactate concentrations were not different in anemic animals (pooled means 5.1 +/- 0.2 and 0.9 +/- 0.02 mM, respectively). Exercise resulted in significantly decreased blood glucose (4.0 +/- 0.2 vs. 4.6 +/- 0.1 mM) and elevated lactate (6.1 +/- 0.4 vs. 2.3 +/- 0.5 mM) concentrations in anemic animals. Glucose turnover rates (Rt) were not different between anemic and control animals at rest and averaged 58.8 +/- 3.6 mumol.kg-1.min-1. Exercise resulted in a 30% greater increase in Rt in anemic (141.7 +/- 3.2 mumol.kg-1.min-1) than in control animals (111.2 +/- 5.2 mumol.kg-1.min-1). Metabolic clearance rates (MCR = Rt/[glucose]) were not different at rest (11.6 +/- 7.4) but were significantly greater in anemic (55.2 +/- 5.7 ml.kg-1.min-1) than in control animals (24.3 +/- 1.4 ml.kg-1.min-1) during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)
Influence of age and exercise training on lipid metabolism in Fischer-344 rats.
The influence of training on fatty acid and glyceride synthesis by liver and adipose tissue homogenates of young and old Fischer-344 rats was examined. Four groups of rats (10 animals/group) were studied: young untrained, young trained, old untrained, and old trained. Training of each group was for 10 wk at 75% maximal O2 uptake. Young rats were killed at 6 mo of age and old rats were killed at 27 mo of age. Fatty acid synthesis was assessed by measuring the activities of acetyl-CoA carboxylase, fatty acid synthase, ATP citrate-lyase, "malic" enzyme, and glucose-6-phosphate dehydrogenase. Glyceride synthesis was evaluated by determining the rate of incorporation of [14C]glycerol 3-phosphate into lipids. In addition, lipoprotein lipase activity was measured in acetone-ether powders of adipose tissue from the four groups of rats. In liver, training had no effect on fatty acid or glyceride synthesis in either group. However, aging caused a significant decrease in the activities of four of the lipogenic enzymes but had no effect on glyceride synthesis. Training caused an increase in fatty acid synthase and glyceride synthesis in adipose tissue, and aging decreased lipoprotein lipase activity. It was concluded that training enhances the synthetic capacity of lipids by adipose tissue but that aging had a more profound effect in that the activities of the enzymes involved in these processes were lower in the old rats. Furthermore, the decreased activity of lipoprotein lipase in the older rats may explain the higher plasma triglyceride levels that were observed in these animals.
[Qualitative assessment of the marginal areas of bonded bridges followed up for 60 months].
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[Testing of periodontal response to abutment teeth with tapered crowns or cast clasps using the Periotest instrument].
62 patients were examined on average 5.3 months after the insertion of removable partial dentures concerning changes of the periotest values of the abutment and control teeth. With help of the periotest procedure little parodontal reactions of the abutment teeth could be shown, which would not been recognized with normal clinical examination.
[Prosthetic concerns of partially edentulous jaw--treatment concept of the 90s].
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Effects of training on blood glucose kinetics during glucose challenge in rats.
We hypothesized that endurance training would alter blood glucose kinetics in rats given an exogenous glucose challenge. Primed-continuous infusion of H14CO3- and [3-3H]glucose were given to fasted rats during an intravenous glucose load of approximately 150% of the normal endogenous appearance rate for 3 h. In all rats blood glucose concentrations increased with loading, but in trained animals glucose stabilized at significantly lower levels. Trained animals had lower blood glucose turnover rates than the controls (75 +/- 2.3 vs. 120 +/- 6.3 mumoles/kg x min, respectively). Glucose metabolic clearance rates in trained rats (11.5 +/- 1.7) were not different from those in controls (11.6 +/- 1.2 ml/kg x min). Gluconeogenic rates estimated from incorporation of 14C into blood glucose did not differ between trained and untrained groups. However, the rate of hepatic glucose release estimated from the difference between tracer measured and exogenous appearance rate was lower in the trained group. These findings support the concept that when resting trained animals are challenged with an exogenous load, more glucose is diverted to anabolic processes as opposed to increased turnover.
[Age-related changes in the intercellular substance of human hyalin and collagen-fiber cartilage tissue].
The articular cartilage of the hip joint and the intervertebral disks (LIV and LV), obtained from 42 corpses without any signs of pathology in these tissues, have been investigated. Six age groups have been distinguished: 21-30, 31-40, 41-50, 51-60, 61-70, 71 years of age and older. After the topo-optic reactions have been get, double refraction of glycosamineglycans (GAG) and collagen is studied in the structure and orientational regularity is estimated in these macromolecules in the matrix. The peculiarities on distribution of the collagenous fiber fasciculi in the intercellular substance in the hyalin and collagen-fibrillar cartilaginous tissue are demonstrated at the areas and depending on the age. Correlations in qualitative and quantitative changes of the GAG and collagen with age are analysed; this gives certain possibilities to reveal signs of similarity and difference in morphogenesis of hyalin and collagen-fibrillar cartilage tissue. Basing on the comparative analysis performed concerning the GAG and collagen state in the age aspect, as well as taking into account the data of previously performed investigations, the collagenous carcass can be characterized as the most stable component of the intercellular substance of cartilages, possessing a great reserve of strength. Homokinesis of the cartilaginous tissue is performed at the expense of the GAG; this ensures a high ability of the cartilaginous tissue to adaptation. A hypothesis on the GAG role in realization of adaptive rearrangements of the cartilaginous matrix at the macromolecular level is put forward.
[Caries occurrence and periodontal condition in 100 dental students in their clinical semester. A clinical study].
The purpose of this study was to examine the prevalence of caries and periodontal condition of 100 randomly selected clinical dental students (73 males, 27 females) in the age range of 22-37 years (means = 26.1 +/- 3.3 years). The statistical analysis revealed the following results: DMF-T Index (Klein & Palmer 1940) = 12.61 +/- 5.41 Plaque Index (Silness & Löe 1964) = 0.37 +/- 0.23 Gingiva Index (Löe & Silness 1963) = 0.39 +/- 0.20 Periodontal pocket depth = 1.65 +/- 0.27 mm. In relation to the results of other studies, clinical dental students had a decreased DMF-T Index and were in a better state of oral health and restaurations as compared to other groups of the same age. Female students had significantly less carious teeth, plaque and gingival disease than the male students. Increasing age had a highly significant correlation to DMF-T Index. Gingiva Index and pocket depth, whereas Plaque Index was correlated to a lesser degree. Plaque was confirmed as the essential factor of gingival disease.
[Pheochromocytoma with anuria, heart failure and malignant arrhythmias].
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Intracellular signalling of initiation of DNA synthesis: effect of cell-free extracts from anti-receptor-stimulated B lymphocytes on spleen cell nuclei.
To study the relatively late intracellular signals involved in the proliferative response of B lymphocytes to antibodies specific for surface membrane immunoglobulins, extracts from antibody activated cells were mixed with Xenopus laevis splenic nuclei, and the incorporation of thymidine 5'-triphosphate into DNA was assessed. The slight incorporation observed with either nuclei or extract alone was markedly enhanced upon mixing the two entities when the extract was derived from cells cultured with but not without anti-receptor antibody. The appearance of active extract correlated well with the culture requirements necessary for the induction of B lymphocyte proliferation and, as revealed by time course studies, the active component arises relatively late in the activation process. Moreover, the appearance of active extracts is independent of DNA synthesis but is dependent on protein synthesis as judged from studies with metabolic inhibitors. Appropriate homogenization of activated cells yielded nuclei and cytoplasm with 85% of the activity confined to nuclei. In addition, purified active extracts exhibited DNA binding although the active component was readily distinguishable from polymerase alpha by chromatographic techniques. It is tentatively concluded that the active component represents either some replication protein other than polymerase or some earlier signal necessary to induce the formation or utilization of replicating proteins.
Evaluation of left ventricular systolic and diastolic dysfunction during transient myocardial ischemia produced by angioplasty.
Acute myocardial ischemia is known to cause impairment of both left ventricular systolic and diastolic function. To further investigate these changes as well as their relation to common clinical variables (electrocardiographic [ECG] changes and chest pain), 32 patients were evaluated with Doppler echocardiography during coronary angioplasty. Doppler indexes of left ventricular diastolic function included the ratios of peak early to late and peak early to mean diastolic velocities as well as the ratios of early to late and first third to total velocity integral (one-third filling fraction). All diastolic indexes showed significant impairment by 15 seconds after coronary occlusion (ratio peak early to late filling velocity: 1.11 versus 0.96, p less than 0.01; ratio peak early to mean filling velocity: 1.9 versus 1.7, p less than 0.01; ratio early to late velocity integral: 1.58 versus 1.25, p less than 0.01; one-third filling fraction: 41.2 versus 37.7, p less than 0.01). Left ventricular systolic function was evaluated during coronary occlusion both qualitatively, as assessed by the appearance of a new wall motion abnormality on two-dimensional echocardiography (mean 28.8 seconds), and quantitatively by measurement of systolic percent area change on the two-dimensional short-axis view as well as the Doppler echocardiographic stroke integral index. Systolic indexes did not show significant change until 30 seconds after balloon inflation (percent area change: 42.8 versus 29.2, p less than 0.01; stroke integral index: 11.04 versus 9.36, p less than 0.01). ECGs were performed at 15 second intervals.(ABSTRACT TRUNCATED AT 250 WORDS)
Ascorbic acid requirement and assessment of ascorbate status in the common marmoset (Callithrix jacchus).
Marmosets can tolerate an ascorbic acid (AA) deficiency for several weeks without clinical symptoms. After being fed an AA-free diet for 3 months, nonspecific deficiency symptoms became obvious. Different dietary levels of AA resulted in corresponding serum ascorbate levels. The kidney threshold of AA in marmosets is comparable to that in humans. When the minimal AA requirement is defined as the amount that is necessary to maintain a serum AA level above the kidney threshold, then about 20 mg AA/kg body weight is needed. This intake was achieved in our trial with a diet containing 500 ppm AA. Thus, the AA requirement of marmosets is severalfold higher than the AA requirement of humans.
Morphological studies on the articular cartilage of old rats.
Age-dependent morphological alterations of the tibial articular cartilage were studied in 26-month-old Wistar rats of both sexes. Young and adult rats (6 and 10 months of age, respectively) served as a basis for comparison. Light microscopic histology, polarization optical analysis (toluidine-blue staining with or without the addition of 0.2, 0.4 or 0.8 M MgCl2, as well as after phenol reaction) as well as transmission electron microscopy were applied. The main observations are: (1) According to the histological findings, the proportion of the zones changes with age; the subchondral bone layer becomes wider and separated to a certain extent, while the fibres become demasked. (2) Polarization microscopy revealed a disorientation of both the proteoglycane (PG) and collagen molecules; considering the available biochemical data, this phenomenon involves both quantitative and structural changes, as well as differences in the localization of the PG and collagen molecules. (3) Electron microscopy also supports the structural alterations of the collagen (thin and thick, as well as non-striated, fragmented fibres). Cellular alterations are also observed parallel with the changes of the matrix (cell organelles occur less frequently, signs of degeneration and disintegration, rupture of the plasma membrane, as well as accumulation of lipid-bodies can be seen. On the basis of the findings, one can consider the articular cartilage in the old rats as a tissue which is still in equilibrium, however, aged chondrocytes with decreased function become predominant in it. This state can be modified into a pathological one by various mechanical, endocrinological, iatrogenic, post-traumatic, etc., influences through the alterations of the cell-matrix interactions.
Esophageal peristaltic dysfunction in peptic esophagitis.
Esophageal exposure to acid is a major determinant in the pathogenesis of reflux esophagitis. In this study, we analyzed the esophageal peristaltic function of 177 patients and asymptomatic volunteers for abnormalities that could lead to prolonged esophageal acid clearance. The subjects were divided into five groups: normal volunteers, patient controls, patients with noninflammatory gastroesophageal reflux disease, patients with mild esophagitis, and ones with severe esophagitis. Manometric data were analyzed for the occurrence of failed primary peristalsis, for the occurrence of feeble peristalsis in the distal esophagus, and for hypotensive lower esophageal sphincter pressure. From an analysis of the data on control patients, peristaltic dysfunction was defined as the occurrence of either failed primary peristalsis or hypotensive peristalsis in the distal esophagus for over half of the test swallows. Peristaltic dysfunction was increasingly prevalent with increasing severity of peptic esophagitis, occurring in 25% of patients with mild esophagitis and 48% of patients with severe esophagitis. A correlation did not exist between the occurrence of peristaltic dysfunction and hypotensive lower esophageal sphincter pressure (less than or equal to 10 mmHg). We conclude that peristaltic dysfunction occurs in a substantial minority of patients with peptic esophagitis and could contribute to increased esophageal exposure to refluxed acid material.
[Use of hyperbaric oxygen therapy in patients with tobacco-alcohol amblyopia].
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Differential response of lymphocytes to free and sepharose-linked anti-immunoglobulin during different phases of the cell cycle.
During proliferation induced by anti-immunoglobulins, B lymphocytes undergo cell volume increases prior to onset of DNA synthesis. Although both Sepharose-linked and free anti-immunoglobulin evoked essentially identical increases in cell volume, the Sepharose-linked antibody induced a significantly greater DNA synthesis than free antibody as judged from [3H]thymidine incorporation studies using mass cell culture technique, as well as by using autoradiographic analysis of individual cells. These findings are considered in terms of possible differences in triggering cell volume increases and DNA synthesis by free and linked anti-immunoglobulin and/or the possible existence of B cell subpopulations responding differentially to free and to linked antibody.