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Biomedical subjects

H Wiesinger

Publications and source records attributed to H Wiesinger.

At least 55 records · Page 3Linked to original sources
PubMed1989

Purification and characterization of sorbitol dehydrogenase from bovine brain.

Sorbitol dehydrogenase (EC 1.1.1.14) was isolated from bovine brain and purified 3,000-fold to apparent homogeneity, as judged by polyacrylamide gel electrophoresis. The purified enzyme had a specific activity of 36 units/mg of protein; a molecular weight of 39,000 for each of the four identical subunits and 155,000 for the intact enzyme were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel exclusion chromatography, respectively. The presence of one Zn2+ per subunit was confirmed by atom absorption spectroscopy; inactivation of the enzyme by metal-chelating agents points to the essential role that Zn2+ plays in the catalytically competent enzyme. The enzyme is also inactivated by thiol-blocking reagents; with respect to inactivation by sodium pyrophosphate, sorbitol dehydrogenase is different from closely related alcohol dehydrogenase.

Aldehyde Reductase↗
PubMed1989

Characteristics of sorbitol uptake in rat glial primary cultures.

Uptake of [U-14C]sorbitol was studied in astrogliarich rat primary cultures. Initial rate of sorbitol uptake is proportional to sorbitol concentration between 20 microM and 400 mM. Sorbitol transport is not inhibited by glucose, fructose, and a variety of structurally related polyols, or by cytochalasin B, an inhibitor of glucose transport. Phloretin, phlorizin, filipin, and n-hexanol, all compounds that alter the properties of biological membranes, and the sulfhydryl reagent p-chloromercuribenzoate inhibit sorbitol uptake to various degrees. Variation in the concentrations of extracellular Na+ and K+ does not affect transfer of sorbitol across the cell membrane. It is concluded that sorbitol is taken up into glial cells by a diffusion process, not involving a carrier and probably not through the lipid bilayer, but through a proteinaceous channel-like structure.

Animals↗
PubMed1989

Short photoperiod and cold activate brown fat lipoprotein lipase in the Djungarian hamster.

Activation of lipoprotein lipase (LPL) in brown fat of the Djungarian hamster ensures substrate supply for nonshivering thermogenesis. Cold acclimation [5 degrees C ambient temperature (Ta)] in long photoperiod [light-dark (LD) 16:8] increased brown fat LPL activity from 4.7 to 22.7 nmol oleate.mg-1.min-1 within 1 day. Slight reduction of this high LPL activity was observed during prolonged cold exposure for up to 4 wk. Deacclimation (transfer from 5 to 23 degrees C Ta) caused total inactivation of brown fat LPL within 4 days. Short photoperiod (LD 8:16) also stimulates brown fat LPL activity. Its effect can be summarized by three different observations. At thermoneutrality short photoperiod elevated LPL activity to 7.1 instead of 4.7 nmol.mg-1.min-1 observed in long photoperiod. Second, at low ambient temperature short photoperiod reinforces the effect of cold acclimation. Maximum LPL activity of cold-exposed Djungarian hamsters averaged 23.7 nmol.mg-1.min-1 in long photoperiod and was elevated to 35.5 nmol.mg-1.min-1 in short photoperiod. Third, inactivation of LPL during deacclimation was delayed in short photoperiod. These results demonstrate that photoperiod as well as ambient temperature may be cooperatively used as environmental cues for seasonal acclimation of brown fat substrate supply for nonshivering thermogenesis.

Acclimatization↗
PubMed1989

Photoperiod and thermoregulation in vertebrates: body temperature rhythms and thermogenic acclimation.

Evidence has recently begun to accumulate that photoperiodic responses of mammals and birds may affect the control of energy balance and thermoregulation. Exposure to short photoperiod can lower the set point for body temperature regulation in birds and mammals, as well as the voluntarily selected body temperature in ectothermic lizards. This decrease is accompanied by a reorganization of circadian or ultradian rhythms of body temperature, particularly an increase in periods spent at rest with minimum body temperatures. Short photoperiod is also used as an environmental cue for induction of seasonal torpor or facilitation of hibernation. During winter, cold tolerance of small mammals is improved by an increase of nonshivering thermogenesis in brown fat. Thermogenic capacity of brown fat (respiratory enzymes, mitochondria, uncoupling protein) is enhanced in response to short photoperiod. This response is mediated via an increase in the activity of sympathetic innervation in brown fat. Moreover, an exposure to short photoperiod prior to low temperatures may act in preparing brown fat for facilitated thermogenesis during acclimation to cold. This shows that photoperiodic control not only affects energy balance indirectly via the control of reproduction or body mass, but may directly interact with central control of thermoregulation and may influence the process of acclimatization.

Activity Cycles↗
PubMed1988

[Spontaneous course of Wegener's granulomatosis].

Two cases of Wegener's granulomatosis are reported. During the 5 and 9 years course of the disease complete remissions and the disappearance of pulmonary opacities were found without specific treatment. Since 1970 cytotoxic drugs, e.g. cyclophosphamide, are frequently used for the treatment of Wegener's granulomatosis. The evaluation of the follow-up showed in these patients that in most cases the side-effects of the therapy, and not the primary disease, limited the life-expectancy. This especially applies for patients with mild forms of Wegener's granulomatosis, in which the initiation of a cytotoxic therapy should carefully be evaluated.

Aged↗
PubMed1987

[Pathology of proximal tubal occlusion--morphologic evaluation. Results following microsurgical anastomosis].

Even today, the etiology of proximal tubal occlusion is still a controversial subject. The introduction of microsurgery in gynecology has provided a method of eliminating the main symptom of proximal tubal occlusion, i.e., sterility. Pregnancy rates of 25-30% can be achieved in overall patient collectives. Accurate histologic analyses of the specimens are essential for clinicopathological classification in three prognosis groups. For stage I patients, pregnancy rates of up to 50% (patient-related) can be achieved. Postoperative counseling can thus be differentiated on the basis of the histological results. For stage III patients the pregnancy rate is unlikely to be acceptable, even after waiting for a prolonged period of time. It has not been established whether reconstructive tubal surgery or alternative therapeutic procedures (I.V.F. and E.T.) have better chances of success in stage II. Accurate histologic analysis of the surgical specimens is an essential prerequisite for individualized sterility counseling and therapy.

Constriction, Pathologic↗
PubMed1987

C1-esterase inhibitor in early septicemia.

In bacteremic pigs, both administered human C1INH and endogenous C1INH lost inhibitory activity. In septic pigs which received human C1INH a difference between immunologically determined concentration and inhibitory activity of C1INH became apparent. In animals which survived at least 24 hrs the C1INH activity showed an acute phase response. In a model of E. coli bacteremia in weaned pigs administration of human C1INH showed protective effects on lung capillary permeability as well as less leucocytosis.

Animals↗
PubMed1986

Quantification of fatty acid activation of the uncoupling protein in brown adipocytes and mitochondria from the guinea-pig.

Brown adipocytes from cold-adapted guinea-pigs (C-cells) are more sensitive to uncoupling by exogenous palmitate than are cells from warm-adapted animals (W-cells) with much less uncoupling protein. Half-maximal respiratory stimulation of C-cells requires 80 nM free palmitate. Noradrenaline-stimulated lipolysis is not rate-limiting for the respiration of either C-cells or W-cells. Half-maximal stimulation of fatty acid oxidation by mitochondria from warm-adapted guinea-pigs (W-mitochondria) and cold-adapted guinea-pigs (C-mitochondria) both require 12 nM free palmitate. Palmitate uncouples C-mitochondria much more readily than M-mitochondria, paralleling its action on the adipocytes. The uncoupling is partially saturable, about 100 nM free palmitate being required for half-maximal response of C-mitochondria. W- and C-mitochondria show identical binding characteristics for palmitate. The respiratory increase of mitochondria is calculated as a function of bound palmitate. After correcting for the residual uncoupling protein present in W-mitochondria, palmitate is estimated to be almost ineffective as an uncoupler of brown fat mitochondria in the absence of the protein. It is concluded that fatty acids display characteristics required of a necessary and sufficient physiological activator of the uncoupling protein.

Adaptation, Physiological↗
PubMed1986

[Unusual location of a granular cell myoblastoma (Abrikosov tumor)].

A case of an unusual location of a granular cell myoblastoma is reported. This tumour is considered to be of neurogenic origin and has been found in different areas of the head and neck. A profound description of the histologic features is provided as well as a remark on the differential diagnosis and a review of the appropriate literature.

Connective Tissue↗
PubMed1985

Thermodynamics of the reactions catalyzed by the multifunctional enzyme complex tryptophan synthase.

The intrinsic enthalpy changes (corrected for hydration of D-glyceraldehyde 3-phosphate) for the reactions catalyzed by the alpha and beta 2 subunits of tryptophan synthase from Escherichia coli have been determined calorimetrically. Cleavage of indoleglycerol phosphate (alpha reaction) was found to be associated with a delta H value of 54.0 +/- 2.5 kJ mol-1, while condensation of indole with L-serine (beta reaction) involved -80.3 +/- 4.6 kJ mol-1'. By direct determination of the enthalpy concomitant with the overall synthesis of tryptophan from indoleglycerol phosphate and L-serine an enthalpy value of -13.4 +/- 5.6 kJ mol-1 was observed. In view of the uncertainties of the literature data used for calculation of the hydration contribution, the agreement between the directly measured delta H value of the overall reaction and the sum of the enthalpies of the alpha and beta reactions is fair. Deamination of L-serine, a side reaction catalyzed preferentially by the isolated beta 2 pyridoxal 5'-phosphate2 subunit, was shown to be associated with an enthalpy change of -7.3 +/- 0.4 kJ mol-1.

Buffers↗
PubMed1985

[Invasive aspergillosis of the head and neck].

Aspergillosis of the paranasal sinuses after invasion of the neighbouring orbit and/or the sella turcica may simulate a malignant tumour. Exploratory excisions usually lead to the diagnosis of a chronic sinusitis. With the aid of special staining methods as well as cultural and serological tests the diagnosis of an aspergilloma can be established.

Adult↗
PubMed1984

Kinetic and thermodynamic parameters for Schiff base formation of vitamin B6 derivatives with amino acids.

Thermodynamic and kinetic parameters for Schiff base formation of pyridoxal 5'-phosphate and pyridoxal with epsilon-aminocaproic acid as well as of pyridoxal 5'-phosphate with L-serine were obtained in 0.1 M sodium pyrophosphate buffer as a function of temperature. Changes in enthalpy, which were determined by direct microcalorimetry, were small at 25 degrees C, but varied strongly with pH for the reaction of pyridoxal 5'-phosphate with the amino acids. In contrast to the fast Schiff base formation of pyridoxal 5'-phosphate, a very slow reaction was found for pyridoxal and epsilon-aminocaproic acid concomitant with a larger change in enthalpy. By preventing hemiacetal formation the phosphate moiety plays a crucial role.

Amino Acids↗
PubMed1984

Linkage of subunit interactions, structural changes, and energetics of coenzyme binding in tryptophan synthase.

The energetics of binding of the coenzyme pyridoxal 5'-phosphate (PLP) to both the apo beta 2 subunit and the apo alpha 2 beta 2 complex of tryptophan synthase from Escherichia coli has been investigated as a function of pH and temperature by direct microcalorimetric methods. At 25 degrees C, pH 7.5, the binding process proceeds in the time range of minutes and shows a biphasic heat output which permits resolution of the overall reaction into different reaction steps. Binding studies on the coenzyme analogues pyridoxal (PAL), pyridoxine 5'-phosphate (PNP), and pyridoxine (POL) to the protein as well as a comparison of these results with data from studies on PLP binding to epsilon-aminocaproic acid have led to a deconvolution of the complex heat vs. time curves into fast endothermic contributions from electrostatic interaction and Schiff base formation and slow exothermic contributions from the interactions between PLP and the binding domain. The pH-independent, large negative change in heat capacity of about -9.1 kJ/(mol of beta 2 X K) when binding PLP to beta 2 is indicative of major structural changes resulting from complex formation. The much smaller value of delta Cp = -1.7 kJ/(mol of beta 2 X K) for binding of PLP to alpha 2 beta 2 clearly demonstrates the energetic linkage of protein-protein and protein-ligand interactions. Calorimetric titrations of the apo beta 2 subunit with PLP at 35 degrees C have shown that also at this temperature positive cooperativity between the two binding sites occurs. On the basis of these measurements a complete set of site-specific thermodynamic parameters has been established.(ABSTRACT TRUNCATED AT 250 WORDS)

Calorimetry↗
PubMed1984

Energetic adaptation of ligand binding to subunit structure of tryptophan synthase from Escherichia coli.

The binding of indole and L-serine to the isolated alpha and beta 2 subunits and the native alpha 2 beta 2 complex of tryptophan synthase from Escherichia coli was investigated by direct microcalorimetry to reveal the energetic adaptation of ligand binding to the subunit structure of a multienzyme complex. In contrast to the general finding that negative heat capacity changes are associated with ligand binding to proteins, complex formation of indole and the alpha subunit involves a small positive change in heat capacity. This unusual result was considered as being indicative of a loosening of the protein structure. Such an interpretation is in good agreement with results of chemical accessibility studies (Freedberg & Hardman, 1971). Whereas the thermodynamic parameters of indole binding are not influenced by the subunit interaction, the large negative change in heat capacity of -6.5 kJ/(K X mol of beta 2) measured for the binding of L-serine to the isolated beta 2 subunit disappears completely when serine interacts with the tetrameric complex. These data demonstrate that the energy transduction pattern and therefore the functional roles of the substrates indole and L-serine vary strongly with the subunit structure of tryptophan synthase.

Escherichia coli↗