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Biomedical subjects

J Winkler

Publications and source records attributed to J Winkler.

At least 19 recordsLinked to original sources
PubMed1998

Biosynthesis of the 3-acetyl and 13(1)-oxo groups of bacteriochlorophyll a in the facultative aerobic bacterium, Rhodovulum sulfidophilum--the presence of both oxygenase and hydratase pathways for isocyclic ring formation.

Using (18)O-labelling and mass spectrometry, we have examined bacteriochlorophyll a formation in Rhodovulum sulfidophilum, formerly known as Rhodobacter sulfidophilus, which forms large amounts of BCh1 a both aerobically in the dark and anaerobically in the light. R. sulfidophilum, growing under strict anaerobiosis in the light, possesses hydratases which incorporate (18)O label from H2(18)O into both the 13(1)-oxo and 3-acetyl oxygens; in addition, the four carboxyl oxygens at C13(3) and C17(3) were labelled by H2(18)O. Under aerobic conditions in the dark, the labelling of the 13(1)-oxo group by H2(18)O was reduced indicating that (16)O was being incorporated into this group from air. R. sulfidophilum, grown in the dark under an atmosphere initially containing 50% (18)O2 in Ar, possessed an oxygenase which incorporated (18)O label from (18)O2 specifically into the 13(1)-oxo group; under these conditions the acetyl and carboxyl groups remained unlabelled. Thus, both an oxygenase and hydratase operate in R. sulfidophilum to form the 13(1)-oxo group of ring E of BCh1 a; the 3-acetyl group oxygen, however, arises only from water via a hydratase.

Bacteriochlorophylls↗
PubMed1998

Short-term and complete reversal of NGF effects in rats with lesions of the nucleus basalis magnocellularis.

Rats received bilateral quisqualic acid lesions of the nucleus basalis magnocellularis. Three weeks after lesioning, osmotic minipumps were implanted that released recombinant human nerve growth factor or cytochrome c at a dosage of 5.0 microg rat-1 day-1 through intracerebroventricular cannulas for 7 weeks. One quarter of the rats were sacrificed at the end of the treatment, while the rest of the animals were sacrificed 2, 8, and 12 weeks after termination of NGF/cc treatment. ICV administration of nerve growth factor (NGF) transiently reduced weight gain. NGF maximally increased choline acetyltransferase activity in all cortical regions, the olfactory bulb and the hippocampus between 20% and 56% at the end of the treatment. This increase linearly declined and completely regressed during the 12-week withdrawal period both in regions affected and unaffected by the lesion. Administration of NGF induced a short-lasting hypertrophy of low affinity NGF receptor immunoreactive neurons within the nucleus basalis magnocellularis (NBM), the horizontal limb of the diagonal band of Broca, and the medial septum. In contrast, QUIS-induced NBM lesions permanently reduced ChAT activity most pronounced in the frontal and parietal cortex up to 45%. Furthermore, QUIS induced a permanent loss of p75NGFr-immunoreactive neurons within the NBM and the DB without affecting the MS. These findings suggest that degenerating cholinergic neurons of the NBM and HDB do not spontaneously recover after lesioning and may require continuous neurotrophic support by NGF to ameliorate cholinergic hypofunctioning.

Animals↗
PubMed1998

Cholinergic strategies for Alzheimer's disease.

Alzheimer's disease is a devastating degenerative disorder of the central nervous system that results in gradual deterioration of cognitive function and severe alteration of personality. Degeneration of neurons in the nucleus basalis Meynert, the origin of the major cholinergic projections to the neocortex, occurs early in the course of the disease, and is correlated with the cognitive decline. This link between cholinergic dysfunction in the basal-cortical system and cognitive deficits has focused scientific efforts on developing tools to elucidate the neurobiological role of the cholinergic system in cognition and to develop therapeutic interventions in the disorder. An important step in understanding the mechanisms underlying cognitive dysfunction has been the development of in vivo rodent models that mimic some of the features of Alzheimer's disease. Acute excitotoxic or immunotoxic lesions of the nucleus basalis in rodents have revealed a role of the basal-cortical system in attention, learning and memory. More recent advances in developing mouse gene technology offer newer models to systematically examine the underlying neuropathological cascade leading to dysfunctions in mnemonic processing. Using in vivo rodent models, several cholinergic enhancement strategies have been tested and proven to be effective in alleviating lesion-induced cognitive deficits, including neuropharmacological approaches (acetylcholinesterase inhibitors), neurotrophic factor administration (nerve growth factor), and transplantation of cholinergic-enriched fetal grafts. Successful results have also been obtained using ex vivo gene transfer to deliver nerve growth factor or acetylcholine to compromised regions of the basal-cortical system. Gene therapy may be of particular interest for clinical applications, because this approach provides a method for topographically restricted and selective delivery of therapeutic genes and their products to afflicted areas of the brain. Advanced techniques in molecular biology (e.g., exogenous regulatable gene transfer) and newly developed tools of modern neuroscience (e.g., neural precursor cells) will be important contributions for deciphering the biological bases of neuronal degeneration and for refining therapeutic strategies for Alzheimer's disease.

Acetylcholine↗
PubMed1998

[New nerve cells for the adult brain. Adult neurogenesis and stem cell concepts in neurologic research].

A growing branch of neuroscience is investigating conditions that permit neurogenesis in the adult brain. Partially, this aims at using the neuroectodermal stem or precursor cells that persist in the adult brain to induce neuroregenerative processes in the treatment for neurologic disorders. In ex vivo approaches, isolated precursor cells are implanted into the host brain, while in vivo concepts favor a stimulation of precursor cells in situ.

Adult↗
PubMed1998

An alpha-actinin-profilin chimaera with two alternatively operating actin-binding sites.

Studying the mode of interaction between actin and actin-binding proteins, we constructed a chimaeric protein consisting of the sequence for bovine profilin I (P), to which the sequence for the actin-binding domain of Dictyostelium discoideum alpha-actinin (alphaA1-2) was fused N-terminally. The resulting hybrid clone was expressed in Escherichia coli, and the chimaeric protein, alphaA1-2P, purified by affinity chromatography on poly-(L-proline) (PLP) columns and identified using specific antibodies. High resolution electron microscopy demonstrated that this protein consists of two discrete subdomains. In biochemical, viscometric and electron microscopic analyses, we showed that both modules in this molecule are biologically active. The chimaera binds to poly-(L-proline) and inhibits the polymerization of G-actin in KCl, which is consistent with the assumption that the profilin part is intact. Inhibition of actin polymerization in KCl was stronger than that of the parental profilin, and the Kd value of its interaction with rabbit skeletal muscle actin, as determined by falling ball viscometry, was smaller (mean value 0.5 x 10(-6) M, as compared to 1.9 x 10(-6) M for bovine profilin). In 2mM MgCl2, the actin polymerized rapidly, consistent with the interpretation that under these conditions the chimaera, like profilin, is less efficient as an actin-sequestering agent. In the presence of alphaA1-2P, the resulting filaments were decorated with particles projecting from the filament axis. We conclude that under these conditions the alphaA1-2 domain of alphaA1-2P is preferentially active, attaching the chimaeric particles laterally to the filaments. Hence, the parental modules combined in alphaA1-2P permit this molecule to switch from a G-actin- to an F-actin-binding form.

Actinin↗
PubMed1998

Rhinocerebral zygomycosis following bone marrow transplantation in chronic myelogenous leukaemia. Report of a case and review of the literature.

We report on a man suffering from chronic myelogenous leukaemia treated by allogeneic bone marrow transplantation who, in the late post-transplantation phase, developed a hyperacute fatal invasive rhinocerebral zygomycosis. The origin of the ascending infection was the sinus sphenoidalis from which fungal hyphae spread to the central nervous system via the skull and the dura mater. The first symptoms of this severe infection were cerebral convulsions and a bilateral total amaurosis. The isolation of the pathogen from post mortem tissue was not successful. The present case is compared with previous reports of zygomycoses after bone marrow transplantation.

Adult↗
PubMed1998

Analysis of breast milk to assess exposure to chlorinated contaminants in Kazakstan: high levels of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) in agricultural villages of southern Kazakstan.

To assess levels of chlorinated contaminants in breast milk, we measured organochlorine pesticides, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins (PCDDs), and polychlorinated dibenzofurans (PCDFs) in breast milk samples collected in 1994 according to the World Health Organization protocol from 92 donors that were representative of regional populations in southern Kazakstan. High levels (10-120 pg/g fat) of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD), the most toxic of the PCDD/PCDF congeners, were found in breast milk samples from an agricultural region. TCDD was the major contributor (75%) to the international toxicity equivalents of these samples. The same distinctive PCDD/PCDF congener pattern was found in 15 breast milk samples and 4 serum samples collected in 1996 in a follow-up study, and has now been confirmed by three analytical laboratories.

Adolescent↗
PubMed1998

[Successful therapy of pulmonary aspergillosis in a patient with non-Hodgkin lymphoma].

UNLABELLED: ANAMNESIS AND CLINICAL PICTURE: A 65-year old male with non-Hodgkin lymphoma developed severe invasive pulmonary aspergillosis during a state of leucopenia after chemotherapy. INVESTIGATION: The initial manifestation was an infiltration in the right upper lobe of the lung, identified by lung scintigraphy as a peripheral wedge-shaped loss of perfusion. Both serum and bronchoalveolar lavage extreme high titre of Aspergillus antigen were seen as a laboratory indication of an invasive aspergillosis. The mould Aspergillus fumigatus was repeatedly isolated from bronchoalveolar lavage and bronchial secretion. THERAPY AND CLINICAL COURSE: Treatment was started with amphotericin B plus 5-flucytosine together with repeatedly bronchoscopic instillation of miconazole followed by thoracosurgical intervention with resection of the right upper lobe of the lung. Despite prophylaxis by itraconazole, a relapse of invasive aspergillosis occurred three months later probably due to persistence of aspergillus fungal elements in the left lung. The aspergillosis relapse was treated at first with liposomal amphotericin B. After eighteen days of treatment this was changed to a combination of 5-flucytosine with oral application of itraconazole, and cure was achieved.

Aged↗
PubMed1997

A Study of the Mechanism of Bleaching Cotton Using Peracids and Hydrogen Peroxide as Model Systems

The mechanism of bleaching cotton dyed with the reactive dye 5-(4,6-dichlorotriazinyl)aminofluorescein has been investigated using hydrogen peroxide as a model system. A general strategy for the study of the mechanism and kinetics of bleaching is presented followed by the relevant theory to enable a discriminatory assessment of the experimental data obtained. A brief extension to the industrially relevant class of peracid bleaches is given. Copyright 1997 Academic Press. Copyright 1997Academic Press

Journal Article↗
PubMed1997

Flexibility and fine structure of smooth-muscle alpha-actinin.

The microfilament protein alpha-actinin exists as a dimer. The N-terminal regions of both polypeptides, arranged in antiparallel orientation, comprise the actin-binding regions, while the C-terminal, larger parts consist of four spectrin-like repeats that interact to form a rod-like structure. To elucidate the fine structure of smooth-muscle alpha-actinin, we used energy-filtered transmission electron microscopy in conjunction with negative staining. Survey pictures of the protein purified from chicken gizzard revealed discrete, elongated particles whose length and width varied with the ionic strength of the buffer. It was determined to to 29.3 nm x 4.8 nm in 0.05 M KCl and 32.6 nm x 4.4 nm in 0.15 M KCl. Both ends of the molecule displayed hook-like structures consisting of globular domains, which were highly variable in their orientation with respect to the long axis of the molecule. Their location at the ends of the molecule, and the finding that these hooks were missing from particles obtained by thermolysin digestion indicated that they probably correspond to the N-terminal actin-binding regions. The rod-like center of the molecule revealed discrete globular masses which probably comprise the spectrin-like repeats. Their arrangement was compatible with the interpretation that three spectrin repeats of each polypeptide chain can form pairs with the respective sequences of the other chain. The rod-like 53-kDa fragment obtained after thermolysin digestion largely retained this structural organization but appeared wider (22.5 nm x 5.9 nm). Our results help to clarify previous discrepancies on the quatenary organization of alpha-actinin and suggest that effective actin-binding and cross-linking of alpha-actinin is based on the high flexibility of the terminal hooks.

Actinin↗
PubMed1997

Epidermal growth factor and fibroblast growth factor-2 have different effects on neural progenitors in the adult rat brain.

Neurons and glia are generated throughout adulthood from proliferating cells in two regions of the rat brain, the subventricular zone (SVZ) and the hippocampus. This study shows that exogenous basic fibroblast growth factor (FGF-2) and epidermal growth factor (EGF) have differential and site-specific effects on progenitor cells in vivo. Both growth factors expanded the SVZ progenitor population after 2 weeks of intracerebroventricular administration, but only FGF-2 induced an increase in the number of newborn cells, most prominently neurons, in the olfactory bulb, the normal destination for neuronal progenitors migrating from the SVZ. EGF, on the other hand, reduced the total number of newborn neurons reaching the olfactory bulb and substantially enhanced the generation of astrocytes in the olfactory bulb. Moreover, EGF increased the number of newborn cells in the striatum either by migration of SVZ cells or by stimulation of local progenitor cells. No evidence of neuronal differentiation of newborn striatal cells was found by three-dimensional confocal analysis, although many of these newborn cells were associated closely with striatal neurons. The proliferation of hippocampal progenitors was not affected by either growth factor. However, EGF increased the number of newborn glia and reduced the number of newborn neurons, similar to the effects seen in the olfactory bulb. These findings may be useful for elucidating the in vivo role of growth factors in neurogenesis in the adult CNS and may aid development of neuronal replacement strategies after brain damage.

Animals↗
PubMed1997

Energy-filtered electron microscopy reveals that talin is a highly flexible protein composed of a series of globular domains.

Talin is a multidomain cytoskeletal protein containing discrete binding sites for acidic phospholipids, beta-integrin, actin and vinculin. Hence, it is thought to link microfilaments to the cytoplasmic membrane in cell-matrix adhesion sites, and this should critically depend on talin structure. To obtain more information on the latter, we used energy-filtered transmission electron microscopy of negatively stained talin purified from chicken smooth muscle. We show that in buffers of physiological ionic strength, talin adopts an elongated shape (56 +/- 7 nm in length), consisting of a series of globular masses. While these compact elements, arranged like beads on a string, were of rather uniform dimensions (3.8 nm in diameter), their center-to-center spacings varied, indicating the flexibility of the connecting strands. The ends of the elongated molecules frequently formed loops. The images obtained are consistent with the assumption that, under the conditions used, the majority of the talin molecules are monomeric. A minor fraction appeared as dimers, composed of two chains only partially intertwined, thus giving rise to Y-shaped particles. Electron micrographs revealed that the biochemically defined 50-kDa N-terminal talin head domain is composed of two globular subunits, while chemical cross-linking provided evidence that the C-terminal 220-kDa fragment is solely responsible for dimerization. These results imply that in the dimeric molecules, the polypeptide chains are arranged in parallel, in contrast to what has been described for human-platelet talin. In buffers of low ionic strength (0.02 M instead of 0.15 M KCl), the molecules collapsed into a compact shape. By showing the high flexibility and versatility of its morphology, our data favour the concept of talin as an important resilient link in microfilament-plasma-membrane attachment.

Animals↗
PubMed1997

Reversible Schwann cell hyperplasia and sprouting of sensory and sympathetic neurites after intraventricular administration of nerve growth factor.

Substantial dysfunction and loss of cholinergic neurons occur in Alzheimer's disease (AD). Nerve growth factor (NGF) is a potent neurotrophic factor for cholinergic basal forebrain neurons, and the use of NGF to stimulate residual dysfunctional cells in AD is being considered. To define the effects of NGF on other cell populations in the brain, NGF was continuously infused into the lateral ventricle of rats for 7 weeks. At the end of treatment, Schwann cell hyperplasia and abundant sensory and sympathetic neurite sprouting were observed in the subpial region of the medulla oblongata and the spinal cord. Following withdrawal of NGF, the Schwann cell hyperplasia and sprouting of sensory and sympathetic neurites disappeared completely. These findings suggest that better temporal and spatial delivery systems for NGF must be explored to limit potential undesirable side effects while maintaining the survival and function of diseased basal forebrain cholinergic neurons.

Animals↗