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Biomedical subjects

B Wendt

Publications and source records attributed to B Wendt.

18 recordsLinked to original sources
PubMed2000

The impact of diets with different magnesium contents on magnesium and calcium in serum and tissues of the rat.

The impact of three different magnesium diets (70, 1,000 and 9,000 ppm) on total, ionized and bound magnesium as well as ionized calcium in serum and total calcium and magnesium in femoral bone, skeletal muscle, heart and liver of male Sprague-Dawley rats was investigated. The percentage of ionized serum magnesium was unproportionally high in rats fed a low magnesium (70 ppm) diet. Femoral magnesium was correlated with ionized and total serum magnesium. In contrast, there was generally no correlation between total serum magnesium and the magnesium fractions in skeletal muscle, heart and liver. In rats fed the magnesium deficient diet, total cardiac concentration of magnesium was even significantly increased along with total calcium content, while there were no effects on total muscle and liver magnesium. Within the single groups, ionized serum calcium was never proportional to dietary magnesium, but in all three magnesium diet groups together, it was inversely correlated with dietary magnesium. Moreover, ionized serum calcium was inversely correlated with both ionized and total serum magnesium. In all 3 groups together, the concentrations of total calcium and magnesium in heart and skeletal muscle were correlated, within the single groups correlation existed only in the 1000 ppm group. Magnesium influx via calcium channels during low magnesium intake has been seen in non cardiac tissues [35,36], but nothing similar is known about non selective channels for divalent cations in the heart [33]. Thus, magnesium uptake by cardiac cells along with calcium seems to be possible, especially at low intracellular magnesium concentrations, but is still poorly investigated. We suggest that the calcium-antagonistic effect of magnesium is related to the turnover rate of magnesium rather than to its tissue concentrations.

Animals↗
PubMed1998

Structural and functional comparison of agents interfering with dihydroorotate, succinate and NADH oxidation of rat liver mitochondria.

Mitochondrially bound dihydroorotate dehydrogenase (EC 1.3.99.11) catalyses the fourth sequential step in the de novo synthesis of uridine monophosphate; this enzyme uses ubiquinone as the proximal and cytochrome oxidase as is the ultimate electron transfer system. Here, seven compounds with proven antiproliferative activity and in vitro antipyrimidine effects were investigated with isolated functional mitochondria of rat tissues in order to differentiate their anti-dihydroorotate dehydrogenase potency versus putative effects on the respiratory chain enzymes. Ten microM of brequinar sodium, the leflunomide derivatives A77-1726, [2-cyano-3-cyclopropyl-3-hydroxy-enoic acid (4-trifluoromethylphenyl)-amide], MNA 279, (2-cyano-N-(4-cyanophenyl)-3-cyclopropyl-3-oxo-propanamide), MNA715 (2-cyano-3-hydroxy-N-(4-(trifluoromethyl)-phenyl-6-heptanamide), HR325 (2-cyano-3-cyclopropyl-3-hydroxy-N-[3'-methyl-4'-(trifluoromethyl)phenyl ]-propenamide), and the diazine toltrazuril completely inhibited the dihydroorotate-induced oxygen consumption of liver mitochondria. Succinate and NADH oxidation were found to be influenced only at elevated drug concentration (100 microM), with the exception of HR325, 10 microM of which caused a 70% inhibition of NADH and 50% inhibition of succinate oxidation. This was comparable to the effects of toltrazuril, which caused an approximate 75% inhibition of NADH oxidation. Ciprofloxacin was shown here to have only marginal effects on the redox activities of the inner mitochondrial membrane. This differentiation of drug effects on mitochondrial functions will contribute to a better understanding of the in vivo pharmacological activity of these drugs, which are presently in clinical trials because of their immunosuppressive, cytostatic or anti-parasitic activity. A comparison of the influence of A77-1726, HR325, brequinar and 2,4-dinitrophenol on energetically coupled rat liver mitochondria revealed only a weak uncoupling potential of A77-1726 and brequinar. In addition, a modeling study was raised to search for common spatial arrangements of functional groups essential for binding of inhibitors to dihydroorotate dehydrogenase. From the structural comparison of different metabolites and inhibitors of pyrimidine metabolism, a 6-point model was obtained by conformational analysis for the drugs tested on mitochondrial functions, pharmacophoric perception and mapping. We propose our model in combination with kinetic data for a rational design of highly specific inhibitors of dihydroorotate dehydrogenase.

Aniline Compounds↗
PubMed1996

[Diagnosis of osteoporosis with ultrasound densitometry of the calcaneus].

PURPOSE: We evaluated the speed of sound (SOS) and broadband ultrasound attenuation (BUA) at the os calcis as an indicator of osteoporosis and observed the age-related changes in ultrasound values in normal women. MATERIALS AND METHODS: BUA and SOS were measured in 236 women using the "Achilles" densitometer (Lunar, Madison, Ohio). From the BUA and SOS values the BUA/SOS Index ("Stiffness" Index) is calculated. We investigated 55 female patients with osteoporosis (aged 43-85 years) and 181 healthy women (aged 20-80 years). RESULTS: Ultrasound values for women with osteoporosis were significantly lower than those for the normal control group. The Z-score compared with young normals was higher for the BUA/SOS Index (-3.1) than for BUA (-2.5) and SOS (-3.0). At a BUA/SOS Index of 68 the sensitivity was 85 %, and the specificity was 77 % for patients with osteoporotic fractures. We found a significant decline with age in SOS (r = -0.55), BUA (r = -0.50) and BUA/SOS Index (r = -0.57). CONCLUSION: Ultrasound bone densitometry at the os calcis can be used as a screening test in the diagnosis of osteoporosis.

Adult↗
PubMed1992

Immunocytochemistry of dopamine in the brain of the locust Schistocerca gregaria.

Catecholamine-induced histofluorescence studies have suggested a rich innervation of the locust brain by dopamine-containing neurons. To provide a basis for future studies on dopamine action in this insect, the location and morphology of neurons reacting with antisera against dopamine were investigated in the supraoesophageal ganglion of the locust, Schistocerca gregaria. In each brain hemisphere, about 100 interneurons in the midbrain and approximately 3,000 cells in the optic lobe show dopamine-like immunoreactivity. All major areas of the brain except the calyces of the mushroom body, the antennal lobe, large parts of the lobula, and some areas in the inferior lateral protocerebrum contain immunoreactive neuronal processes. The arborization patterns of most dopamine-immunoreactive cell types could be identified through detailed reconstructions. The central body exhibits the most intense immunostaining. It is innervated by at least 40 pairs of dopamine-immunoreactive neurons belonging to three different cell types. Additional arborizations of these neurons are in the superior protocerebrum and in the lateral accessory lobes. A group of 4 immunoreactive neurons with ramifications in the antennal mechanosensory and motor center gives rise to a dense meshwork of varicose fibers in the pedunculus and parts of the alpha- and beta-lobes of the mushroom body. Other cell types innervate the ventrolateral protocerebrum, the inferior protocerebrum and the posterior optic tubercles. Three descending neurons originating in the tritocerebrum exhibit dopamine-like immunoreactivity. In the optic lobe, about 3,000 columnar intrinsic neurons of the medulla and a group of centrifugal tangential cells with arborizations in the medulla and lamina are dopamine-immunoreactive.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

[Non-tropical pyomyositis in Germany].

Haematogenous primary pyomyositis predominantly caused by staphylococcus aureus is a well-known entity in tropical regions. It is sporadicly observed in non-tropical areas. Lack of clinical familiarity not seldom contributes to delayed recognition of pyomyositis in the suppurative or complicated state. Initially, healing usually can be achieved by antibiotic treatment adjusted by antibiotic treatment adjusted to pyogenic staphylococci. Late stages require concomitant surgical or transcutaneous drainages of pus. In addition, treatment for osteomyelitis or bacterial carditis as typical complications may be necessary. The review of pyomyositis is illustrated by three case-reports from Germany.

Adult↗
PubMed1990

[Emergencies and management by the family practitioner].

4.6% of all consultations realized by family doctors (including consultations in the doctor's practice, visits to the patients' homes, medical on-call service) can be characterized as emergency consultations. In the provision of health care by family doctors those circumstances that require medical intervention without delay are to be characterized as emergency situations (even if life is not immediately threatened). 11.6% of all emergency calls are made because of a cold (in particular, in the case of small children) or a hurt (open wound, contusion, or fracture). According to physicians, 54.5% of the emergency consultations were based on urgent circumstances. In those cases where only life-threatening circumstances were registered as emergency cases, 15.2% of the above percentage of emergency consultations were underestimated by the patients as to their urgency.

Adolescent↗
PubMed1988

Effect of amino acid substitutions and deletions on the thermal stability, the pH stability and unfolding by urea of bovine calbindin D9k.

The influence of amino acid substitutions and deletions on the stability of bovine calbindin D9k, the smallest protein known with a pair of EF-hand calcium-binding sites, has been studied using circular dichroism and ultraviolet absorption spectroscopy. The five modifications are confined to one of the two Ca2+ -binding sites. The Ca2+-loaded forms of the wild-type and mutant calbindins are too stable to be significantly denatured by heating at 90 degrees C or by adding 8 M urea. For the Ca2+-free (apo) forms thermal unfolding appears to be only half complete at 90 degrees C, while denaturation is complete in 7-8 M urea. Four of the mutant proteins show reduced resistance towards unfolding by urea, but one of the modified proteins (Glu-17----Gln) shows an increased stability, presumably because of a reduced electrostatic repulsion in the native state. According to X-ray crystallographic data the OH group of the single tyrosine of calbindin (Tyr-13) is hydrogen-bonded to the carboxyl group of Glu-35, thus linking the two alpha helices flanking the N-terminal Ca2+ site. The pK of ionization of the Tyr-13 hydroxyl group was over 13 for calcium forms of the wild-type protein, between 12.3 and 12.8 for the calcium form of three mutants and between 11.5 and 11.7 for the apoproteins. Significant differences in pH stability between wild type and mutants were observed in the calcium forms, but were not apparent in the apo forms.

Amino Acids↗
PubMed1987

The effect of mercuric salts on the electro-rotation of yeast cells and comparison with a theoretical model.

The rotational spectrum of yeast cells changed after pre-treatment of the cells with HgCl2 or Hg(NO3)2 and became indistinguishable from that of ultrasonically produced cell walls. The spectrum of the affected cells contained a peak which could only be explained by attributing a conductivity to the cell walls that was higher than that of the medium. Theoretical models of the rotational response are fully in accord with the experimental spectra. It is shown that the rotation method is capable of measuring even the low cell wall conductivity of yeast cells (which was found to be 33 microS/cm at 10 microS/cm medium conductivity). Knowledge of the spectra allowed a field frequency to be selected at which untreated cells showed no rotation, but at which cells affected by treatment with Hg(II) identified themselves by rotating in the same direction as the field. Calculation of the percentage of cells showing this co-field rotation gave an index (termed the co-field rotation value) of the proportion of the cells that were affected. Using this technique, effects of 25 nmol/l Hg(II) could be demonstrated. In media of low conductivity (10 microS/cm) the change in the rotational spectrum was usually 'all-or-none', whereas at 200 microS/cm a graded Hg(II)-mediated change became apparent. The co-field rotation method showed that the action of small quantities of Hg(II) was still increasing after 3 h of incubation and paralleled the Hg(II)-induced K+ release. A rapid reduction of the effects of Hg(II) was seen when 3-30 mM K+ (or Na+) or when 1 mM Ca2+ were present in the incubation medium, or as the pH was increased. At high incubation cell concentrations the toxic effect of Hg(II) was reduced, apparently due to binding by the cells.

Calcium↗
PubMedDate not supplied

Rotation of cells and ion exchange beads in the MHz-frequency range.

Whereas human red blood cells and protoplasts of leaves of Avena sativa show rotation only at discrete frequencies in the kHz-range of a linear alternating electric field, rotation of these cells is observed at practically every frequency in the MHz range (15 to 200 MHz). The cell rotation in the MHz-range can be explained in terms of field induced polarisation and orientation of permanent dipoles within the membrane and the cell. This interpretation is supported by the finding that Chelex beads (polystyrene cross-linked with divinylbenzene and coupled to iminodiacetic acid) do exhibit rotation in the MHz-range, but not in the kHz-range. It is most interesting that the Cu2+- and Ca2+-forms of the Chelex beads show a shift in the rotation frequency spectrum in addition to an increase in the magnitude of the rotation speed with respect to the Na+-form. At frequencies in the MHz-range at which rotation of the Chelex beads is not observed, formation of chains of beads from the electrodes occurs instead. This is due to positive polarisation of the beads leading to positive dielectrophoresis. The results support the view that rotation needs negative polarisability which is determined by the functional groups.

Edible Grain↗