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Biomedical subjects

A Hofer

Publications and source records attributed to A Hofer.

At least 73 records · Page 4Linked to original sources
PubMed1997

Cloning and characterization of the R1 and R2 subunits of ribonucleotide reductase from Trypanosoma brucei.

Ribonucleotide reductase (RNR) catalyzes the rate limiting step in the de novo synthesis of deoxyribonucleotides by directly reducing ribonucleotides to the corresponding deoxyribonucleotides. To keep balanced pools of deoxyribonucleotides, all nonviral RNRs studied so far are allosterically regulated. Most eukaryotes contain a class I RNR, which is a heterodimer of two nonidentical subunits called proteins R1 and R2. We have isolated cDNAs encoding the R1 and R2 proteins from Trypanosoma brucei. The amino acid sequence identities with the mouse R1 and R2 subunits are 58% and 63%, respectively. Recombinant active trypanosome R1 and R2 proteins were expressed in Escherichia coli and purified. The R2 protein contains an iron-tyrosyl free radical center verified by EPR spectroscopy and iron analyses. Measurement of cytidine 5'-diphosphate reduction by the trypanosome RNR in the presence of various allosteric effectors showed that the activity is highest with dTTP, dGTP, or dATP and considerably lower with ATP. The effect of dGTP is either activating (alone) or inhibitory (in the presence of ATP). Filter binding studies indicated that there are two classes of allosteric effector binding sites that bind ATP or dATP (low-affinity dATP site) and ATP, dATP, dGTP, or dTTP (high-affinity dATP site), respectively. Therefore, the structural organization of the allosteric sites is very similar to the mammalian RNRs, whereas the allosteric regulation of cytidine 5'-diphosphate reduction is unique. Hopefully, this difference can be used to target the trypanosome RNR for therapeutic purposes.

Amino Acid Sequence↗
PubMed1997

Immunohistochemical detection of human skin nerve fibers.

The autonomic nervous system is involved in different functions such as transduction of afferent sensory inputs, trophic actions, modulation of immunologic events and thermoregulation. In the present investigation, we studied the pattern of human autonomic skin innervation with special reference to its relation to blood vessels, hair follicles, sweat glands and sensory receptors. For the first time, two clinically important areas have been compared: the skin of the forearm and of the face. Using indirect immunohistochemistry, we analyzed the distribution of calretinin (CR), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY), substance P (SP), neurokinin A (NKA), vasoactive intestinal peptide (VIP), nitric oxide synthase (NOS), tyrosine hydroxylase (TH), histamine, serotonin, enkephalin, and, enzyme histochemically, NADPH-diaphorase (NADPH-d). In the epidermis, we found nerve fibers containing SP, NKA and CGRP. In the dermis, SP-, CR-, VIP-, CGRP- and NKA-positive nerve fibers were detected. Particularly the large nerve fibers contained CR. VIP-positive fibers occurred especially around hair follicles and sweat glands. CGRP-positive nerve fibers were located close to the epidermal basal membrane, in the wall of blood vessels, and to a lesser extent around hair follicles. Immunoreactivity for SP and NKA in the dermis was observed predominantly in the papillary layer near the epidermal basal membrane. All neuropeptides tested in this study were also detected in the nerve fibers of the subcutis. Most of them were CGRP- and VIP-positive. They occurred in association with sweat glands and large arteries. NPY-positive nerve fibers are predominant in the wall of arteries, arterioles and veins. Nerve fibers containing NKA and SP were less common and identified only in the walls of large arteries in deeper dermal layers. In double-staining experiments, the NADPH-d reaction and reactivity to tubulin revealed a partial co-localization in nerve fibers, blood vessel walls, around glands and ganglionic cells. VIP-positive fibers were more common in the face skin than in the forearm. However, in forearm we detected more NPY-, CGRP-, NKA- and SP-positive nerve fibers than in face skin. These findings are important for future studies on skin disorders, such as sensory neuropathies, inflammatory reactions or allergic responses of human skin.

Blood Vessels↗
PubMed1997

Primary clinical response and long-term follow-up of solar keratoses treated with topically applied 5-aminolevulinic acid and irradiation by different wave bands of light.

Photodynamic therapy with 5-aminolevulinic acid (ALA-PDT) is based on photosensitization by endogenous synthesis of protoporphyrin IX and its transient accumulation especially in malignant epithelially derived tissues. Recent studies have indicated that ALA-PDT is effective for the treatment of solar keratoses (SK), but there has been a lack of long-term clinical follow-up. The goal of the present study was to investigate the immediate and long-term effect of ALA-PDT on SK. Twenty-eight patients with a total of 251 SK were enrolled in the study. Standard treatment involved the topical application of 20% ALA, under occlusive and light-shielding dressing for 4 hours before exposure to UVA and/or different wave bands or wave band combinations of polychromatic visible light (full-spectrum visible light, and/or different wave bands of filtered visible light > 515, > 530, > 570, or > 610 nm) in one or two treatment sessions. The primary complete response rate of SK to ALA-PDT was 64% after one treatment, but 85% when the responses to a second treatment were included. Taken all treatments together, the complete response rate for lesions on face, scalp and neck was 93% for full-spectrum visible light, 96% for the combination of full-spectrum visible light and filtered light, 91% for different wave bands of filtered visible light, and 100% for the combination of long wave UVA and full-spectrum visible light, respectively. The complete response rate for lesions on forearms and hands was 51% for full-spectrum visible light and 33% for the combination of full-spectrum visible light and filtered light. The greater response rate for SK on the face, scalp, and neck was associated with a higher surface fluorescence and immediate response rate after ALA photosensitization at these sites (chi 2; p = 0.0001). However, due to the treatment protocol the mean light dose applied to lesions on the face, scalp and neck (50 J cm-2) was substantially higher than that for lesions on forearms and hands (35 J cm-2). In the long term follow-up of SK on face scalp and neck, the projected disease-free rate at 36 months after therapy was 71% for lesions treated with full-spectrum visible light versus 23% for lesions treated with different wave bands of filtered light (Log rank-Mantel Cox; p = 0.0001). These results indicate that treatment with full-spectrum visible light at higher light doses may be the most effective and promising form of light exposure in ALA-PDT of SK.

Administration, Topical↗
PubMed1996

Regulation of connexin-43, GFAP, and FGF-2 is not accompanied by changes in astroglial coupling in MPTP-lesioned, FGF-2-treated parkinsonian mice.

Basic fibroblast growth factor (bFGF; FGF-2) has potent trophic effects on developing and toxically impaired midbrain dopaminergic (DAergic) neurons which are crucially affected in Parkinson's disease. The trophic effects of FGF-2 are largely indirect, both in vitro and in vivo, and possibly involve intermediate actions of astrocytes and other glial cells. To further investigate the cellular and molecular mechanisms underlying the restorative actions of FGF-2, and to analyse in more detail the changes within astroglial cells in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine)-lesioned striatum, we have studied striatal expression and regulation of connexin-43 (cx43), the principal gap junction protein of astroglial cells, along with the expression of glial fibrillary acidic protein (GFAP), FGF-2, and functional coupling. Our results show an immediate, yet transient increase in cx43 mRNA, and a sustained increase in FGF-2 mRNA, GFAP-positive cells, and cx43-immunoreactive punctata following the MPTP lesion, without any induction of functional coupling between astrocytes and other glial cells as revealed by dye coupling of patched cells. Unilateral administration of FGF-2 in a piece of gelfoam caused a further increase in cx43-positive punctata immediately adjacent to the implant, which was more pronounced than after application of a gelfoam containing the nontrophic control protein cytochrome C. These changes were parallelled by a small increase in cx43 protein determined by Western blot, but not by alterations in the coupling state of cells in the vicinity of the gelfoam implant. Although our data indicate that MPTP and exogenous FGF-2 may alter expression and protein levels of cx43, they do not support the notion that increases in cellular coupling may underly the trophic and widespread actions of FGF-2 in the MPTP-model of Parkinson's disease.

Animals↗
PubMed1996

C-erbB2/neu transfection induces gap junctional communication incompetence in glial cells.

Astrocytes form functional networks that participate in active signaling in which external stimuli are generated and amplified in many of the same ways as in neurons. Gap junctions between astrocytes offer the structural avenue by which the electrical and metabolic signals are propagated from one cell to another. Little is known about the trafficking, assembly, and degradation mechanisms of the major astrocytic gap junction protein connexin43. We have studied a glial cell line transfected with the C-erbB2/neu oncogene (neu+), finding severe interruption of gap junctional communication after stable transfection. Evidence from Western blotting and phosphorylation studies showed that the processing of connexin43 to its higher phosphorylated isoforms is disturbed. Confocal laser imaging indicates that the major deficit in the neu+ cells is attributable to a lack in plaque assembly of connexin43. Because the neu+ cells also lack N-CAM proteins and because work from others has indicated a close relationship between communication competence and constitutive CAM expression, our data suggest that expression of C-erbB2/neu oncogene alters cell-cell association via CAM proteins, which thereby affects gap junction plaque assembly and appropriate phosphorylation of connexin43.

Animals↗
PubMed1996

Lack of association of bovine MHC class I alleles with carcass and reproductive traits.

The present study was carried out to examine whether a relationship between bovine major histocompatibility complex (BoLA) class I alleles and carcass traits or reproductive performance exists in Braunvieh and Fleckvieh AI (artificial insemination) bulls. The influence of BoLA class I (BoLA-A) alleles on deregressed breeding values for net growth rate, carcass index and thigh volume was assessed in Braunvieh crosses and Fleckvieh bulls with a gene substitution model. The reproductive traits: non-return rate and interval between first and last insemination of daughters (female fertility), as well as non-return rate of inseminated cows (male fertility), were only investigated in Fleckvieh animals. No influence of the BoLA-A region on the traits evaluated could be demonstrated. An improper, i.e. less restrictive analysis would have led to spurious results.

Alleles↗
PubMed1994

Cloning and in situ localization of a brain-derived porin that constitutes a large-conductance anion channel in astrocytic plasma membranes.

We have cloned a protein from bovine brain, brain-derived voltage-dependent anion channel 1 (BR1-VDAC), that is identical to a recently sequenced plasmalemmal-bound porin from human lymphocytes. mRNA hybridization indicates that BR1-VDAC is widely distributed throughout nervous and nonnervous tissues. In situ localization substantiated that the BR1-VDAC is associated with the plasmalemma of astrocytes. A monoclonal antibody that recognizes the N terminus of the BR1-VDAC protein completely blocks an astrocytic high-conductance anion channel that has electrophysiological similarities with the mitochondrial VDAC. Since the high-conductance anion channel in astrocytes has been shown to respond to hypoosmotic solutions, its molecular identification provides the basis for a better understanding of volume regulation in brain tissue.

Animals↗
PubMed1994

Astrocytes as rapid sensors of peripheral axotomy in the facial nucleus of rats.

Facial nerve transection leads to functional and structural reactions in lesioned motor neurones and surrounding glial cells. Data from this study provide evidence that the most rapid reaction described so far consists of an increase in immunoreactivity of connexin-43 (cx-43), the predominant gap junction protein in astrocytes. The ipsilateral facial nucleus is selectively marked as early as 0.75 to 1.5 hours after axotomy, while the unlesioned side as well as the unoperated controls remain faintly stained. Thus, enhanced coupling capacity of astrocytes by gap junctions appears to be a sensitive indicator of modified neuronal-glial interaction in the CNS.

Animals↗
PubMed1993

Facial nerve lesions lead to increased immunostaining of the astrocytic gap junction protein (connexin 43) in the corresponding facial nucleus of rats.

After peripheral transection of the facial nerve, immunostaining of astrocytic gap junction protein changed in the corresponding brainstem nucleus of the rat. Enhanced connexin-43 immunoreactivity was restricted to the ipsilateral facial nucleus and to astrocytes surrounding lesioned motoneurons. This reaction is focally distinct, and marks only a part of the astrocytic network indicating a local plasticity of intercellular coupling. These results suggest that astrocytes work as sensors of signals which either depend on the integrity of neighboring neurons or inform about neuronal disorders.

Animals↗
PubMed1992

Fibrinogen Milano IV, another case of congenital dysfibrinogenemia with an abnormal fibrinopeptide A release (A alpha 16 Arg----His).

An abnormal fibrinogen, denoted as 'fibrinogen Milano IV', has been found in a 36-year-old woman without any bleeding manifestations or thrombotic tendency. Routine coagulation studies revealed prolonged thrombin and reptilase clotting times, very low plasma fibrinogen concentration determined by the functional assay but a normal fibrinogen concentration measured by the immunologic assay. Turbidity curves, measured following addition of thrombin to purified fibrinogen Milano IV, both in presence of calcium or EDTA, were markedly delayed. Release of fibrinopeptide B by thrombin was normal, whereas only half the normal amount of fibrinopeptide A was cleaved. The fibrinopeptide A peak of fibrinogen was preceded by an abnormal fibrinopeptide A*. Both peaks were collected for amino acid analysis which showed an exchange of arginine by histidine in position 16 of the A alpha chain of the fibrinopeptide A*.

Abortion, Spontaneous↗
PubMed1991

[Year-round antibody profile of groups of horses of a herd kept in isolation after differently terminating use of an experimental viral combination vaccine].

The commercial vaccine "Resequin F Konz." devised against viral respiratory infections of horses contains the abortigenic Equine Herpesvirus-1 (EHV-1). Therefore we had used it in our protection project of the Austrian Lipizzaners+ primarily to prevent abortions. Taking into account the recent perception that for young horses the respiratory-pathogenic EHV-4 type is essential Behringwerke Marburg added this particular virus to their market product to produce a multicomponent experimental vaccine. We examined this vaccine for its antibody induction as well as their persistence against each of its viral components. On groups of foals we did this regarding its prophylactic effect against respiratory infections. Furthermore, we investigated its immunogenicity in adult horses, hoping for a potentiating effect of EHV-4 against EHV-1, mediating enhanced protection against abortion caused by the latter virus. This experimental vaccine proved excellently tolerable, its immunogenicity against either equine herpesvirus type was considerable, was very good against both equine influenza subtypes, was low, however, against retroviruses types 1 and 3. Recommendations are made for seasonal optimal spacing of vaccinations, taking into account the prevalent dissemination phases of the viruses involved, the different age groups of horses and their respective use.

Abortion, Veterinary↗
PubMed1990

Fibrinogen Milano. VI: A heterozygous dysfibrinogenemia (A alpha 16 Arg----His) with bleeding tendency.

Congenital heterozygous dysfibrinogenemia was diagnosed in a young woman with bleeding tendency. 3 other asymptomatic members of her family (mother and the 2 sisters) had abnormal fibrinogen. The proposita's plasma exhibited prolonged thrombin and reptilase times. Plasma fibrinogen concentration determined by functional assay was 0.3 g/l, whereas immunologic assay revealed normal fibrinogen levels. Turbidity curves, representing the rate of thrombin-induced fibrin formation, were markedly delayed both in the presence and absence of Ca2+. Isoelectric focusing and SDS electrophoresis of reduced fibrinogen showed normal charge and size of the subunit chains. Release of fibrinopeptide B by thrombin was normal, whereas HPLC elution diagrams of fibrinopeptide A showed an abnormal peak A* with a slightly shorter retention time than the normal fibrinopeptide A. The amino acid analysis showed that the arginine in peak A* is replaced by histidine (A alpha 16 Arg----His).

Adolescent↗
PubMed1990

Fibrinogen Geneva, a new case of A alpha 16 Arg----Cys dysfibrinogenaemia.

A new congenital variant of fibrinogen, from which only half the normal amount of fibrinopeptide A can be released by thrombin, was found in three members of a family having no major bleeding or thrombotic tendency. Following carboxamidomethylation of the reduced fibrinogen chains, an abnormal peptide was cleaved by thrombin from the amino terminus of the A alpha-chain (A* alpha 1-19) and isolated by reversed phase high-performance liquid chromatography. Amino acid analysis indicated the presence of carboxymethyl cysteine in this A alpha-chain fragment which in normal fibrinogen is devoid of cysteine. We conclude that fibrinogen Geneva is another fibrinogen variant with the substitution A alpha 16 Arg----Cys.

Blood Coagulation Tests↗
PubMed1989

[Catecholamine and cortisol concentrations in plasma from cattle at parturition].

Cows with spontaneous parturition (n = 8) and cows with flumethasone (n = 3) or prostaglandin (n = 3) induced parturition were used in this study. Catecholamine concentrations from cows in the periparturient period were measured in order to evaluate the stress of birth on the dam and the calf. The plasma content of both norepinephrine and epinephrine in late pregnancy was not different from control values in the 3rd to 6th month of pregnancy (norepinephrine 3.27 +/- 0.99 nmol/l plasma and epinephrine 0.98 +/- 0.45 nmol/l plasma), though both parameters appear elevated in the pregnant group. Norepinephrine concentrations rose to a value of 4.50 nmol/l immediately after birth, whereas epinephrine levels did not show an increase post partum. In two neonates norepinephrine and epinephrine values were 2-3 times higher than in the dams and decreased to the values of the dams within 48 hours. Synthetic glucocorticoids can mimic the increase of cortisol, which leads to birth. Cortisol concentrations in the cows remained unaffected by induction of parturition by prostaglandins. Newborn calves showed values of about 330 nmol/l, which also declined within 48 hours to values similar to those measured in the dam (9-28 nmol/l). As stress and exogenous glucocorticoids may affect antibody production, the IgG-content of the colostrum was examined. Prostaglandin induction of birth did not alter the IgG-content of colostrum, but flumethasone produced a decrease of about 14.5%. It is therefore concluded that pre-term birth induction does not produce negative effects on the supply of IgG.

Animals↗