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Biomedical subjects

E Hofer

Publications and source records attributed to E Hofer.

At least 55 records · Page 3Linked to original sources
PubMed1994

Measuring activation patterns of the heart at a microscopic size scale with thin-film sensors.

To study the spread of excitation in ventricular heart preparations we have designed a fast, high-resolution recording and mapping system. Papillary muscles were dissected from the isolated guinea pig hearts. The preparation was fixed in a tissue bath and superfused with Tyrode solution. Linear and two-dimensional arrays of Ag/AgCl electrodes were made on glass with a thin-film technique. The transparent sensors with up to 24 electrodes (spaced 50, 90, or 180 microns apart) were positioned close to the surface of the preparation with a custom-designed three-dimensional micromanipulator. Extracellular signals were simultaneously recorded by a 24-channel data acquisition system with a 200 kHz per channel sample rate, with 12-bit amplitude resolution and a maximum data length of up to 3 MB. Digitized video images of the electrode array and the underlaying preparation were used to identify the locations of the recording sites. A UNIX-based computer system with a custom-designed data acquisition and database program was used to control the instruments and to manage the experimental data. This technique gave signals with excellent signal-to-noise ratios (up to 65 dB) and permitted accurate evaluation of the time and the site of the local activation with high resolution (to within 5 microseconds, 50 microns). We describe the spread of excitation within the area of a few cells and found a substantial dispersion of conduction velocities. Beat-to-beat comparison of activation patterns showed relatively small variations in the spread of excitation (a few microseconds).

Action Potentials↗
PubMed1994

[Nuclear magnetic resonance tomography findings in obsessive-compulsive disorder].

Eighteen patients with a DSM-III-R diagnosis of obsessive-compulsive disorder (OCD) were imaged by MR and compared to a control group of 18 patients with clinically diagnosed unspecific headaches. Weighted spin-echo sequences were carried out with a 1.5T unit in both axial and coronal planes T1 (TR 700/TE 15 ms) and T2 (TR 2500/TE 15.70). The ferritin distributions in the basal ganglia and in the midbrain were evaluated; in addition, the width of the pars compacta in the midbrain on the basis of the criteria of Braffmann et al. 1988, the widths of the inner subarachnoid spaces on the basis of the ventricular index quotient VIQ (TerBrugge, 1986), and the widths of the outer subarachnoid spaces were conducted. The latter was undertaken by three independent investigators whose results were in agreement with one another. In 12 of the OCD patients (n = 18) there was a total of 25 pathological MRI findings; in the control group there were 6 pathological MRI findings in only 6 of the patients (n = 18). In conclusion pathological changes were found at different locations, but a connection between a specific neuroanatomic system and obsessive-compulsive disorder could not be demonstrated.

Adult↗
PubMed1993

Cytokine-inducible expression in endothelial cells of an I kappa B alpha-like gene is regulated by NF kappa B.

The transient expression of many different genes is mediated by the inducible transcription factor p50-p65 NF kappa B, which in turn is regulated by complex formation with its inhibitor I kappa B alpha. We describe here that in porcine aortic endothelial cells, either IL-1 alpha, TNF alpha or LPS upregulates an inhibitor of NF kappa B which we refer to as ECI-6. ECI-6 is by structural and functional criteria an I kappa B alpha protein, the porcine homologue of MAD-3, pp40 and RL/IF-1. We have studied the promoter of the ECI-6/I kappa B alpha gene and provide three lines of evidence that its expression is directly regulated by NF kappa B. First, the 5' regulatory region of ECI-6/I kappa B alpha contains two sites that bind NF kappa B in electrophoretic mobility shift assays. Second, expression following transfection of an ECI-6/I kappa B alpha promoter-luciferase reporter construct is dependent on a co-transfected NF kappa B-p65 subunit. Third, pretreatment of endothelial cells with antioxidants, agents that inhibit activation of NF kappa B, inhibit the expression of ECI-6/I kappa B alpha. We conclude that the regulated expression of ECI-6/I kappa B alpha could represent a novel feedback mechanism by which NF kappa B downregulates its own activity after transient activation of target genes has been achieved.

Amino Acid Sequence↗
PubMed1993

Analysis of some factors involved in the virulence mechanism of Vibrio cholerae non-01.

A study was carried out to evaluate the potential intestinal toxicity of 188 samples of Vibrio cholerae non-01 isolated from seawater found along the beaches of Rio de Janeiro city. Three different assays were carried out involving: (a) detection of vascular permeability factor (PF) in guinea pigs (together with assessment of two culture media for production of the toxin); (b) intestinal fluid accumulation (FA) in suckling mice; and (c) detection of haemolysin. The results demonstrated that both culture media gave a similar level of performance. In the animal assays, 43% of the samples induced PF in guinea pigs, 28.7% caused intestinal fluid accumulation in suckling mice, and 63.28% contained haemolysin. Only 4.25% of the samples gave positive results in all three tests.

Animals↗
PubMed1993

[Abortions in a lower Austrian sheep facility caused by Coxiella burnetii].

In a flock of sheep the causal connection between abortions and the infection with Coxiella burnetii is demonstrated serologically, bacteriologically and by pathological examination. In order to identify C. burnetii as causing agent in case of abortions the submission of placental parts in addition to the fetus, in combination with a serological control of the flock, is recommended. To check the seroprevalence of C. burnetii in the region concerned random blood samples of 12 flocks were taken and analysed by CFT. At least 10 samples per herd, taken from animals more than 1 year old, were examined. Positive titers were found in 5.6% of the checked animals which originated from 6 different flocks. Health risks of different groups of the human population are being discussed.

Abortion, Veterinary↗
PubMed1992

Candidate natural killer cell receptors.

Among the high points of immunological discovery has been the identification of antigen-recognizing receptors on B and T cells. Of the lymphocyte populations, only the NK cell receptor remains unknown. Consequently, any newly-recognized, cell-surface molecules expressed selectively on NK cells, especially ones that can transmit a signal to the cell upon appropriate ligand interaction, are possible candidates. This article describes such candidates.

Animals↗
PubMed1992

Analysis of some virulence factors of Vibrio vulnificus isolated from Rio de Janeiro, Brazil.

Twenty strains of V. vulnificus isolated from the environment were investigated for characteristics related to their infectivity such as colonial morphology, enzymatic activity and animal assays. The presence of DNase, chitinase, amylase, lecithinase and gelatinase was observed in 100% of the strains, haemolytic activity was absent, and variable results were obtained in elastase, collagenase and chondroitinase. In the animal assays, 70% of the strains were lethal to adult mice, while 45% caused fluid accumulation in suckling mice. Although all strains had opaque colonies, only 3 of the 20 had the three enzymes elastase, collagenase and gelatinase, and only one of these was virulent in animal assays.

Animals↗
PubMed1992

Cellular Vmax reflects both membrane properties and the load presented by adjoining cells.

This study was designed to test the hypothesis that the electrical load seen at a microelectrode impalement site is sensitive to the direction of propagation of the approaching wavefront as a reflection of an altered spatial relationship between the impalement site and the surrounding microscopic electrical boundaries located up- and downstream. These boundaries correspond to the different sizes and shapes of the impaled and surrounding cells as well as to the distribution of the associated electrical connections between the cells. The effects of changes in these geometric relationships on maximum rate of rise of transmembrane potential (Vmax) were investigated in canine ventricular muscle by measuring Vmax in different cells while the direction of propagation was changed from along the longitudinal axis to the transverse axis of the fibers or the direction of conduction was reversed along either of these axes. Comparison of the Vmax values for longitudinal propagation (LP) and transverse propagation (TP), each in one direction, showed that TP Vmax was significantly greater than LP Vmax (P < 0.001). However, the values of Vmax were different from cell to cell during LP (93-139 V/s) and TP (110-181 V/s). The absolute values of LP Vmax and TP Vmax at the same site varied independently of each other, e.g., some of the lowest LP Vmax values occurred at the same site as the highest TP Vmax values. Furthermore, at the same site, Vmax changed considerably when propagation was maintained along the longitudinal axis but the direction of conduction was reversed. Similar prominent changes in Vmax occurred when the direction was reversed along the transverse axis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

A new superfamily of lymphoid and melanoma cell proteins with extensive homology to Schistosoma mansoni antigen Sm23.

A novel cDNA clone termed R2 was isolated by subtractive hybridization of a cDNA library of phytohemagglutinin (PHA)/phorbol myristate acetate-stimulated Jurkat cells and by rescreening a cDNA library of PHA-stimulated peripheral blood lymphocytes. It hybridizes to a single mRNA species of about 2.2 kb, which is inducible in lymphoid cells and codes for a protein of 267 amino acids which contains four potential transmembrane domains. A computer-aided comparison showed strong homology to four other membrane proteins, the pan B cell marker CD37, the pan leukocyte marker CD53, the melanoma antigen ME491 and, surprisingly, the Schistosoma mansoni antigen Sm23. The four human proteins share a number of additional similarities in their overall structure. These include identical spacing of the transmembrane domains, similar hydrophobicity plots, possible N-linked glycosylation sites of similar number and position as well as similar distribution of the cysteine residues. The majority of these characteristics are still conserved in the evolutionary most distant member of this family, the Schistosoma mansoni antigen Sm23. Here we introduce this new protein superfamily and characterize the inducible, lymphoid-specific member R2.

Amino Acid Sequence↗
PubMed1990

Characterization of the human cyclophilin gene and of related processed pseudogenes.

The human cyclophilin gene was isolated from a genomic library derived from leucocyte DNA and sequenced. The gene contains five exons and four introns. The amino acid sequence deduced from the exons matches perfectly the one previously determined from the T-cell cyclophilin cDNA. A TATA box is visible in the promoter region and putative Sp1 binding sites are also found there as well as in the first intron. Six members of the middle repetitive Alu gene family are present in one or other orientation in the non-coding regions of the cyclophilin gene. Hybridisation of genomic DNA to probes derived from the promoter region or the first intron indicates that the cyclophilin gene is present as a single copy in the human haploid genome. Seven other cyclophilin-related DNA clones isolated from the same library were also characterized. They show a high degree of similarity to the cyclophilin cDNA and are colinear to it. However, multiple genetic lesions, often including deletion and/or insertion events which modify the reading frame, are found in these clones which are therefore likely to represent processed pseudogenes.

Amino Acid Sequence↗
PubMed1990

Transcription and expression of transforming growth factor type beta in the skin of progressive systemic sclerosis: a mediator of fibrosis?

Progressive systemic sclerosis is characterized by extensive generalized fibrotic destruction associated with increased accumulation of collagen and other extracellular macromolecules in the skin and other involved organs. It has been suggested that mediators released from mononuclear or endothelial cells play a critical role in the initial activation of connective tissue metabolism. Transforming growth factors beta(TGF-beta 1, TGF-beta 2) mediate the inhibition of epithelial cell proliferation and the induction of fibronectin and collagen gene expression. Therefore, we investigated the distribution of both TGF-beta 1 and TGF-beta 2 mRNA and the final proteins in PSS skin in comparison with other inflammatory dermatoses and healthy controls by means of in situ hybridization and immunohistochemistry. Our studies revealed TGF-beta 1 and -beta 2 mRNA in dermal and subcutaneous infiltrating cells in both acute and chronic PSS, but also in the other inflammatory skin disorders. In the vicinity of this infiltrate single TGF-beta positive fibroblasts could be found in acute PSS. The cytoplasm of epithelial cells of all skin adnexa showed TGF-beta transcripts and no apparent differences were seen in the distribution and number of autoradiographic grains between diseased and healthy skin samples. Especially, we could demonstrate abundant expression of TGF-beta 1/2 in epithelial hair follicle cells of the outer root sheath. Generally, the expression of TGF-beta 2 was less abundant than TGF-beta 1. Immunohistochemical studies revealed the same distribution pattern of the final proteins. Our data indicate that TGF-beta expression in infiltrating cells is not a specific feature of fibrotic disease, but seems to be associated with highly proliferating cells in general, perhaps functioning as common mediator in regulation of cellular physiology with special importance for negative control of cell growth.

Adult↗
PubMed1989

Transforming growth factor-beta inhibits the generation of cytotoxic T cells in virus-infected mice.

The immunoregulatory effects of human recombinant transforming growth factor (rTGF) beta 1 and human recombinant glioblastoma-derived T cell suppressor factor (rG-TsF)/TGF beta 2 was investigated in mice infected with lymphocytic choriomeningitis virus (LCMV) or vaccinia virus. Starting on the day of infection, i.p. injections of 1 microgram/day or rTGF-beta 1 or rG-TsF/TGF-beta 2 suppressed the generation of virus specific CTL. The effect of TGF-beta on CTL (day 8) was less pronounced when TGF-beta treatment was delayed for 3 days after LCMV infection. rG-TsF/TGF-beta 2 also has an inhibiting effect on CTL-mediated disease in LCMV-infected mice: it prolonged the survival time of mice infected with LCMV and reduced the local swelling reaction after infection into the footpad. These results indicate that rTGF-beta 1 and rG-TsF/TGF-beta 2 influence T cell immune reactivity in vivo.

Animals↗
PubMed1989

Antimicrobial resistance among Salmonella serovars isolated from different sources in Brazil during 1978-1983.

A total of 748 Salmonella strains (97 serovars) isolated from human (291), animal (119), environmental (141), food (102) and animal feed (95) sources were examined for resistance to 9 antimicrobial agents. Most of the human isolates were from hospitalized patients (282). An overall resistance rate of 98.8% was determined with 100% for human and environmental isolates. Resistance to sulfadiazine (87.7%) was most common, followed by streptomycin (61.2%), ampicillin (39%) and trimethoprim-sulphamethoxazole (37.9%). Fifty one different resistance patterns were identified with Su (164 strains), Su-Sm (122) and Su-Sm-Tc-Cm-Km-Ap-Nx-Gm-Tm (95) predominating, the latter occurring only in human isolates. Multiple resistance was most frequently found among human isolates, particularly in S. derby and S. typhimurium strains. The relationship between antibiotic resistance, serovar and source of isolation of the Salmonella strains is discussed.

Animals↗
PubMed1988

The glioblastoma-derived T cell suppressor factor/transforming growth factor-beta 2 inhibits T cell growth without affecting the interaction of interleukin 2 with its receptor.

Human glioblastoma cells secrete a peptide termed glioblastoma-derived T cell suppressor factor (G-TsF) which inhibits T cell activation. Recently, purification and cloning of G-TsF revealed that G-TsF is identical to transforming growth factor-beta 2. As shown here, G-TsF suppresses the growth of an ovalbumin-specific mouse T helper cell clone (OVA-7T) independently of the stimulus used being either (a) antigen in the presence of antigen-presenting cells, or (b) interleukin 2 (IL2) or (c) phorbol ester and calcium ionophore. Furthermore, in the presence of antibodies against IL2 receptors, G-TsF was able to suppress the residual proliferation still observed when OVA-7T were stimulated with phorbol ester/ionophore. G-TsF failed to inhibit the release of IL3 from OVA-7T activated with IL2. Taken together, the data provide evidence that G-TsF does not directly interfere with interactions of IL2 with its receptor but rather inhibits T cell activation by interfering with an as yet unidentified pathway used by both IL2 and phorbol ester/ionophore. When analyzing different monokines and lymphokines for its effect on G-TsF-induced suppression of T cell growth the only factor found to partially neutralize the effect of G-TsF was tumor necrosis factor-alpha.

Animals↗
PubMed1987

The structure of procalcitonin of the salmon as deduced from its cDNA sequence.

Oligonucleotide probes based on the known amino acid sequence of salmon calcitonin were used to screen a cDNA library obtained from ultimobranchial glands of salmon for clones encoding salmon calcitonin. From the cDNA sequence of strongly hybridizing clones the complete primary structure of the calcitonin precursor could be deduced. Its overall structure is identical with the structures of procalcitonins from other vertebrates and has the highest homology with the chicken precursor.

Amino Acid Sequence↗