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Biomedical subjects

F Maier

Publications and source records attributed to F Maier.

At least 19 recordsLinked to original sources
PubMed2001

Hydroxyapatite induction and secondary aggregation of calcium oxalate, two important processes in calcium stone formation.

Stone formation has often been ascribed to crystal aggregation and fixed particle growth on kidney calcifications. In this paper, the influence of hydroxyapatite (HAP) and of preformed calcium oxalate (CaOx) aggregates on CaOx crystallization was studied in freshly voided urine. Crystallization was induced by different oxalate loads and precipitates were analyzed by the spectrophotometric measurement of sedimentation time (ST), which decreases with increasing particle size. The fact that the ST of aggregates (STA) is significantly lower than the ST of other particles demonstrates that STA is a useful indicator for aggregation. At relatively low oxalate loads the addition of HAP to urine increased STA by a factor of 4.3 (P < 0.001). After a second oxalate load, STA decreased by 56% (P < 0.001), indicating secondary growth of the preexisting aggregates. HAP induced and primary CaOx aggregation occurred at low pH at which a high ionic calcium concentration (Ca2+) was measured. In urine, crystals are coated by macromolecules creating a negative surface potential with a consecutive accumulation of cations such as Ca2+. This Ca2+ accumulation could be responsible for the enhancement of aggregation by preexisting particles, which seems to be important for stone formation and which can otherwise hardly be explained in the presence of coated crystals.

Calcium↗
PubMed2000

Origin of surface conductivity in diamond

Hydrogen-terminated diamond exhibits a high surface conductivity (SC) that is commonly attributed to the direct action of hydrogen-related acceptors. We give experimental evidence that hydrogen is only a necessary requirement for SC; exposure to air is also essential. We propose a mechanism in which a redox reaction in an adsorbed water layer provides the electron sink for the subsurface hole accumulation layer. The model explains the experimental findings including the fact that hydrogenated diamond is unique among all semiconductors in this respect.

Journal Article↗
PubMed2000

Nucleation and aggregation of calcium oxalate in whole urine; spectrophotometric sedimentation analysis: a new approach to study the aggregation of calcium oxalate dihydrate.

Spectrophotometric and scanning electron microscopic (SEM) studies of oxalate-induced crystallization have been performed in whole urine with and without continuous magnetic stirring and before and after millipore filtration of urine. With continuous stirring, preferential nucleation was observed and this followed second order kinetics. Important crystal aggregation only occurred after an oxalate load above 1 mmol/l and without stirring. Under these conditions and at an ionic calcium concentration of 2 mmol/l, single crystals and aggregates of calcium oxalate dihydrate and monohydrate of well defined sizes were produced. Single dehydrates, their aggregates and the other particles could be distinguished by their significantly different sedimentation rates. From sedimentation curves an aggregation ratio for calcium oxalate dihydrate (aggregated/total dihydrate particles) was extrapolated. Millipore filtration removing important urinary macromolecules increased this aggregation ratio as well as the size of the aggregates on SEM pictures.

Calcium Oxalate↗
PubMed2000

Ethics in home care agencies.

Ethics committees offer the opportunity to air ethical differences in a nonadversarial manner, enabling those involved to discuss and understand their differences. Establishing processes for an ethics committee involves reflection on basic ethical principles of conduct governing an individual or group. Agencies can learn from the process of ethical decisionmaking in home care organizations that have achieved accreditation either through CHAP or through JCAHO.

Accreditation↗
PubMed1999

Comparison of the muscle fiber diameter and satellite cell frequency in human muscle biopsies.

Satellite cells are responsible for the formation of postnatal muscle fibers. The number, mitotic activity, and differentiation potential of satellite cells and the muscle fiber diameter are tightly regulated events in normal muscle. The signal that induces satellite cells to stop proliferation once the determined muscle fiber size has been reached in normal growth is not known. The aim of the present study was to determine whether a correlation exists between satellite cell frequency and muscle fiber diameter in human muscle disease. Muscle biopsies from 7 cases of Duchenne muscular dystrophy (DMD), 8 other muscular dystrophies, 23 cases of inflammatory myopathy, and 22 cases of neurogenic atrophy were examined. The satellite cell number was elevated in DMD and neurogenic atrophy but not in other muscular dystrophies or inflammatory myopathies. Nevertheless, in all the diseased muscles, but not in normal controls, there was a significantly higher relative frequency of satellite cells with increasing fiber diameter. It has been shown before that satellite cells show ultrastructural and autoradiographic signs of activation and proliferation in myopathic and neurogenic conditions. We assume that we are dealing with activated, not quiescent, satellite cells in diseased muscle and that under these conditions the fiber diameter does not represent a stop signal for satellite cells to proliferate. The data suggest that not only the number of satellite cells matters in diseased muscle, as has been shown before, but that it is their behavior that influences, at least in part, progress and severity of muscle diseases.

Adolescent↗
PubMed1999

Satellite cells as players and targets in normal and diseased muscle.

Satellite cells (SC), also termed adult myoblasts, are mononuclear cells of myogenic lineage. They are attached to the muscle fiber plasma membrane and surrounded by a common basement membrane. The characteristic localization differentiates them from embryonic and fetal myoblasts. SC are able to leave the G0 phase in which they usually reside in normal adult muscle, enter the mitotic cycle, and differentiate to express muscle-specific proteins. The activation of SC into the mitotic compartment and their progression to the differentiative compartment are processes which are tightly regulated by myogenic regulatory factors of the MyoD family and the cyclin-dependent kinases and their inhibitors. Those factors are in turn regulated by growth factors and innervation. SC are key features in muscle fiber growth, regeneration, and hypertrophy. Furthermore, they are targets in denervation atrophy, which results in SC loss in the long run. There is evidence from experimental work that SC age, and that they are a heterogeneous cell population in terms of mitotic cycle duration and have the ability to differentiate. Little is known of SC in human diseased muscle beyond their number. SC heterogeneity must be taken into account if future therapy strategies for muscular dystrophies are designed.

Adult↗
PubMed1994

Antagonistic effects of fluconazole and 5-fluorocytosine on candidacidal action of amphotericin B in human serum.

This study addressed the effects of fluconazole and 5-fluorocytosine on the candidacidal activity of amphotericin B in the presence of human serum. A Candida albicans isolate that was susceptible to all three agents according to standard testing procedures was employed. Fungicidal activity was estimated by using a flow cytometric procedure that exploited the fact that yeast cells killed by amphotericin B diminish in size and take up propidium iodide. The following findings were made. (i) Fluconazole and 5-fluorocytosine each failed to inhibit pseudohyphal formation and cell aggregation even when applied at 10 and 50 micrograms/ml, respectively, for up to 10 h. Hence, these agents were not fungistatic when tested in the presence of serum. (ii) Simultaneous application of 5-fluorocytosine had neither enhancing nor inhibitory effects on the fungicidal activity of amphotericin B. However, yeasts that were preincubated for 20 h with 5-fluorocytosine became less susceptible to killing by amphotericin B. (iii) Fluconazole exerted a frank antagonistic effect on the fungicidal activity of amphotericin B. Thus, under our in vitro conditions, both fluconazole and 5-fluorocytosine can overtly antagonize the candidacidal action of amphotericin B.

Amphotericin B↗
PubMed1991

Electrophysiologic effects of the calcium antagonist isradipine, a double-blind placebo-controlled study.

The electrophysiologic effects of the calcium channel antagonist isradipine in comparison to placebo were evaluated in a double-blind study with 9 patients in each group. The two patient groups were not different with respect to their cardiac disease, baseline electrophysiologic parameters, or blood pressure. Isradipine significantly decreased the systolic (P less than 0.01) and diastolic (P less than 0.05) blood pressure, whereas sinus cycle length was significantly (P less than 0.05) decreased in the placebo group and the isradipine group with no difference between the groups. The influence of isradipine and placebo on sinus node recovery time, effective refractory period of the atrioventricular node, intranodal conduction time (AH interval) and PR interval were not significant. In conclusion, isradipine significantly decreased systolic and diastolic blood pressure. The decrease in sinus cycle length after intravenous isradipine was not significantly different from the decrease seen in the placebo group. Atrioventricular conduction was not significantly affected.

Blood Pressure↗
PubMed1989

[Nicolai Guleke--the founder and pioneer of neurosurgery in Thuringia].

After the representation of the biographical data and stages of development in the life of Prof. Nikolai Guleke (25th April 1878 to 4th April 1958) it is shown on the basis of his services as a director of the Surgical University Clinic in Jena how he deserved particularly well of the development of neurosurgery. Besides his skills in the surgical-technical field his close co-operation with the then director of the Neurological Clinic of the Jena University, Hans Berger, is appreciated as well as his scientific work, summarised in Volume III/1 of the ten volumes comprising surgical teachings by Kirschner "Interventions in the Cranium, Brain, at the Vertebral Column, the Spinal cord and the Branches of the N. trigeminus". Nikolai Guleke is considered to be an outstanding personality in the history of surgery of our country.

Germany↗
PubMed1987

[Thrombocyte transfusion: increase in platelets in relation to clinical and immunologic prerequisites].

We determined in 35 patients with severe thrombocytopenia (AML n = 10; ALL n = 4; CML = 1; idiopathic myelofibrosis n = 1, aplastic anemia n = 1; undergoing bone-marrow transplantation n = 17) factors influencing the corrected count increment (CCI) after platelet transfusions. Out of 195 transfusions 86 (44%) failed to increased platelet counts (CCI less than 5 X 10(9) platelets/l). A significant percentage of transfusion failures occurred in patients with splenomegaly and/or fever (54% vs. 29%; p less than 0.002). Antibodies directed against donor platelets were found only twice. No correlation between reactivities demonstrable by the lymphocytotoxic test (n = 144) or the radioimmune antiglobulin test (n = 67) and the CCI was obvious. HLA antigen identity was also not predictive. Thus, transfusion failures in patients with low alloimmunization will not be predicted by in vitro antibody screenings. The patients' clinical condition has the most important influence on posttransfusion increment.

Anemia, Aplastic↗
PubMed1986

[Neurosurgical aspects of arachnoid cysts].

After an analysis of the patients treated in the last five years, a report is given on 9 cases of arachnoid cysts as a rare form of intracranial space occupation. The etiology of the arachnoid cysts has not been fully cleared up yet, but the semipermeability of the cyst membrane appears to be an important pathogenetic factor. Today, the diagnosis of the disease is verified by CT techniques. In case of the occurrence of clinical symptoms the treatment should always be carried out in the form of an operation.

Adolescent↗
PubMed1983

Results of treatment with tamoxifen in oligozoospermic men.

15 men, aged 32-42, with normo- and hypogonadotropic oligozoospermia were treated with the non-steroidal compound tamoxifen. The therapeutic period lasted for 6 month and tamoxifen was administered orally in a daily dose of 2 X 10 mg. The seminal and hormonal parameters were evaluated. A significant increase in sperm density was only found in responders. The compound showed no effect in men having a hypergonadotropic stage. The changes in endocrine parameters as levels of plasma testosterone, estradiol and gonadotropins were similarly affected in "responders" and "non-responders". Treatment with tamoxifen revealed no side effects regarding sexual behaviour, development of gynecomastia or nipple pains.

Adult↗
PubMed1982

[Iodine deficiency in Salzburg in spite of iodized table salt prophylaxis].

Urinary iodine excretion was determined in 293 medical technical and nursing students in hospitals of the province Salzburg. The average urinary iodine excretion amounted to 46.6 +/- 18 micrograms iodine per gram creatinine. 67.6% of the students showed a deficiency of iodine II, whilst 98.3% had a deficiency of iodine I according to WHO criteria. Urinary iodine levels and natriuria are closely correlated, indicating that iodized table salt probably constitutes the most important source of iodine. 73 of the students had a palpable giotre, 10 of these being nodular. Our investigations, together with those of Innsbruck, Graz and Vienna, demonstrate the existence of generalized iodine deficiency in spite of iodized salt prophylaxis, which has been legally enforced in all of Austria since 1963. Iodized table salt prophylaxis has, thus, led to a drastic decrease in goitres in children, but is not sufficient to eliminate iodine deficiency in adults. An increased level of iodization of table salt, as has been put into force in Switzerland, must be called for in Austria, too.

Adolescent↗