Search PubMed⌕ Search

Biomedical subjects

R Thoma

Publications and source records attributed to R Thoma.

At least 37 records · Page 2Linked to original sources
PubMed1999

Efficient expression, purification and crystallisation of two hyperthermostable enzymes of histidine biosynthesis.

Enzymes from hyperthermophiles can be efficiently purified after expression in mesophilic hosts and are well-suited for crystallisation attempts. Two enzymes of histidine biosynthesis from Thermotoga maritima, N'-((5'-phosphoribosyl)-formimino)-5-aminoimidazol-4-carb oxamid ribonucleotide isomerase and the cyclase moiety of imidazoleglycerol phosphate synthase, were overexpressed in Escherichia coli, both in their native and seleno-methionine-labelled forms, purified by heat precipitation of host proteins and crystallised. N'-((5'-phosphoribosyl)-formimino)-5-aminoimidazol-4-carb oxamid ribonucleotide isomerase crystallised in four different forms, all suitable for X-ray structure solution, and the cyclase moiety of imidazoleglycerol phosphate synthase yielded one crystal form that diffracted to atomic resolution. The obtained crystals will enable the determination of the first three-dimensional structures of enzymes from the histidine biosynthetic pathway.

Aldose-Ketose Isomerases↗
PubMed1999

[Chlamydia abortion in sheep: possibilities for serological diagnosis using a competitive ELISA and insight into the epidemiologic situation in Switzerland].

466 sheep sera out of 19 flocks in Switzerland were examined by a competitive enzyme linked immunosorbent assay (cELISA) for antibodies against Chlamydia psittaci "serotype 1" ("ovine enzootic abortion"). Since numerous positive reactors were found in flocks without abortion history, 30 fecal samples out of two of these flocks were examined by PCR for evidence of chlamydial DNA. One of these samples turned out to contain DNA of Chlamydia psittaci "serotype 1". These results suggest, that in Switzerland "serotype 1" of Chlamydia psittaci is widespread not only as cause of chlamydial abortion but also as latent intestinal infection in sheep. The resulting difficulties for serological diagnosis of chlamydial abortion and possible solutions based on the cELISA are discussed. The complement fixation test (CFT), still considered as standard method for serological examination for Chlamydiae, has additionally been applied.

Abortion, Veterinary↗
PubMed1998

A histidine gene cluster of the hyperthermophile Thermotoga maritima: sequence analysis and evolutionary significance.

The sequences of histidine operon genes in hyperthermophiles are informative for understanding high protein thermostability and the evolution of metabolic pathways. Therefore, a cluster of eight his genes from the hyperthermophilic and phylogenetically early bacterium Thermotoga maritima was cloned and sequenced. The cluster has the gene order hisDCBdHAFI-E, lacking only hisG and hisBp, and does not contain intercistronic regions. This compact organization of his genes resembles the his operon of enterobacteria. Sequence analysis downstream of the stop codon of hisI-E identifies a region with a significantly higher cytosine over guanosine content, which is indicative of a rho-dependent termination of transcription of the his operon. Multiple sequence alignments of N1-((5'-phosphoribosyl)-formimino)-5-aminoimidazole-4-carboxyam ide ribonucleotide isomerase (HisA) and of the cycloligase moiety of imidazoleglycerol phosphate synthase (HisF) support the previous assignment of the (beta alpha)8-barrel fold to these proteins. The alignments also reveal a second phosphate-binding motif located in the first halves of both enzymes and thereby support the hypothesis that HisA and HisF have evolved by a sequence of two gene duplication events. Comparison of the amino acid compositions of HisA and HisF from mesophiles and thermophiles shows that the thermostable variants of both enzymes contain a significantly increased number of charged amino acid residues and may therefore be stabilized by additional salt bridges.

Aldose-Ketose Isomerases↗
PubMed1997

Mixed infections with porcine Chlamydia trachomatis/pecorum and infections with ruminant Chlamydia psittaci serovar 1 associated with abortions in swine.

In a previous immunohistological study, chlamydiae were detected in 5 out of 139 cases of swine abortion, and a possible implication of C. psittaci serovar 1 was suggested. The present study sought to classify the chlamydiae found in the fetal organs of these abortions. DNA extracted from 15 paraffin-embedded tissue specimens (10 livers and 5 lungs, obtained from 10 fetuses from 9 cases of abortion) was amplified in a nested PCR with Chlamydia omp1 genus-specific primers. Chlamydia DNA was amplified in 9 liver and 2 lung specimens. Eight of the amplification products were cloned, and 5 clones of each amplification were sequenced. Sequence analysis demonstrated in 7 specimens the simultaneous presence of porcine C. trachomatis S45 and C. pecorum 1710S omp1 genotypes. All DNA fragments of 1 amplification were identical to the ruminant C. psittaci B577 omp1 genotype (serovar 1). The results suggest that mixed infections with porcine C. trachomatis and C. pecorum dominate chlamydial infections associated with abortion in swine, but ruminant abortigenic C. psittaci are also found.

Abortion, Veterinary↗
PubMed1997

Effects of lithium and carbamazepine on thyroid hormone metabolism in rat brain.

The effects of lithium (LI) and carbamazepine (CBM) on thyroid hormone metabolism were investigated in 11 regions of the brain and three peripheral tissues in rats decapitated at three different times of day (4:00 A.M., 1:00 P.M., and 8:00 P.M.). Interest was focused on the changes in the two enzymes that catalyze: (1) the 5'deiodination of T4 to the biologically active T3, i.e., type II 5'deiodinase (5'D-II) and (2) the 5 (or inner-ring) deiodination of T3 to the biologically inactive 3'3-T2, i.e., type III 5 deiodinase (5D-III). A 14-day treatment with both LI and CBM induced significant reductions in 5D-III activity. However, 5'D-II activity was elevated by CBM and reduced by LI, both administered in concentrations leading to serum levels comparable with those seen in the prophylactic treatment of affective disorders. The effects were dose dependent, varied according to the region of the brain under investigation, and strongly depended on the time of death within the 24-hour rhythm. The consequences of these complex effects of LI and CBM on deiodinase activities for thyroid hormone function in the CNS and also their possible involvement in the mechanisms underlying the mood-stabilizing effects of both LI and CBM remain to be investigated.

Animals↗
PubMed1997

Developmental instability and cerebral lateralization.

On the basis of prior studies of handedness, it was predicted that variations from modal asymmetry scores on cognitive tasks, in either direction from the mean, would be associated with an elevated incidence of classic markers of developmental instability (minor physical anomalies and fluctuating anatomic asymmetries). University students (N = 146) were administered 4 tasks that typically reveal functional asymmetries: the fused rhymed words dichotic listening task, the line bisection task, the chimeric faces task, and the cartoon faces task. A composite measure of developmental instability was computed from minor physical anomalies and fluctuating asymmetries. Participants with greater evidence of developmental instability had more atypical lateralization scores, deviating more from the sample mean, in either direction. Directional asymmetries were unrelated to developmental instability. These results suggest that developmental instability influences variation in the lateralization of cognitive skills as well as handedness.

Adolescent↗
PubMed1997

Chlamydiae in porcine abortion.

Formalin-fixed, paraffin-embedded fetal livers and lungs from 139 cases of swine abortion were investigated retrospectively for chlamydiae by means of immunohistochemistry. Using a genus-specific antibody, chlamydial antigen was found in eight livers obtained from five (3.6%) abortion cases from different herds. All lung sections were negative. Chlamydiae were also labeled in five of the eight positive livers using a monoclonal antibody against immunotype 1 of Chlamydia psittaci; the remaining three livers were negative. No reactivity was seen using an antibody specific for C. trachomatis. Chlamydiae should be considered a cause of abortion in sows in Switzerland. Porcine abortigenic strains identified in this study differed immunologically from intestinal strains (known to be mainly C. trachomatis) but shared similarities with abortigenic chlamydiae of ruminants.

Abortion, Septic↗
PubMed1997

Elevated 3,5-diiodothyronine concentrations in the sera of patients with nonthyroidal illnesses and brain tumors.

This study reports the development of a highly sensitive and reproducible RIA for the measurement of 3,5-diiodothyronine (3,5-T2) in human serum and tissue. The RIA employs 3-bromo-5-[125I]iodo-L-thyronine (3-Br-5-[125I]T1) as tracer, which was synthesized carrier free by an interhalogen exchange from 3,5-dibromo-L-thyronine (3,5-Br2T0). The detection limits were 1.0 fmol/g and 0.8 pmol/L in human brain tissue and serum, respectively. T3, diiodothyroacetic acid, and 3-monoiodothyronine cross-reacted with a 3,5-T2 antibody to the extent of 0.06%, 0.13%, and 0.65%, respectively. Serum concentrations of 3,5-T2 were measured in 62 healthy controls and 4 groups of patients with nonthyroidal illness, i.e. patients with sepsis (n = 24), liver diseases (n = 23), head and/or brain injury n = 15), and brain tumors (n = 21). The mean serum level of 3,5-T2 in the healthy subjects was 16.2 +/- 6.4 pmol/L. Concentrations of 3,5-T2 were significantly elevated in patients with sepsis (46.7 +/- 48.8 pmol/L; P < 0.01), liver diseases (24.8 +/- 14.9 pmol/L; P < 0.01), head and/or brain injury (24.1 +/- 11.3 pmol/L; P < 0.05), and brain tumors (21.6 +/- 4.8 pmol/L; P < 0.01). In all 4 patient groups, serum levels of T3 were significantly reduced, confirming the existence of a low T3 syndrome in these diseases. Serum concentrations of 3,5-T2 were significantly elevated in patients with hyperthyroidism (n = 9) and were reduced in patients with hypothyroidism (n = 8). The levels of T4, T3, and 3,5-T2 were measured in normal human tissue samples from the pituitary gland and various brain regions and in brain tumors. In normal brain tissue, the concentrations of 3,5-T2 ranged between 70-150 fmol/g, and the ratio of T3 to 3,5-T2 was approximately 20:1. In brain tumors, however, T3 levels were markedly lower, resulting in a ratio of T3 to 3,5-T2 of approximately 1:1. Recent findings suggest a physiological, thyromimetic role of 3,5-T2, possibly stimulating mitochondrial respiratory chain activity. Should this prove to be correct, then the increased availability of 3,5-T2 in nonthyroidal illness may be one factor involved in maintaining clinical euthyroidism in patients with reduced serum levels of T3 during nonthyroidal illness.

Astrocytoma↗
PubMed1997

[A case of acute disseminated Mucor encephalitis in a heifer].

The case of a 2 1/2 year old Swiss Braunvieh heifer suffering from an acute disseminated mycotic encephalitis caused by a Mucorales spp. infection is presented. Clinical signs and analysis of cerebrospinal fluid (increased protein concentration and pleocytosis) were typical for an acute encephalitis, probably due to a listeriosis. The histological examination of the brain revealed an acute disseminated thrombo-embolic encephalomyelitis due to a fungi infection, morphologically consistent with Mucorales spp. The occurrence of bovine cerebral mucormycosis is rare and therefore the veterinarian should become aware of a case which was clinically not distinguishable from a listeriosis.

Animals↗
PubMed1996

[Isolation of Corynebacterium diphtheriae subsp. belfanti from a cow with chronic active dermatitis].

Diphtheria is an acute communicable disease of man caused by C. diphtheriae. Pharyngeal and cutaneous forms are described, where from both toxigenic and nontoxigenic strains can be isolated. The occurrence of C. diphtheriae in dairy cattle has already been reported in the past. The pathogens were isolated from ulcerated teats and from the milk of cows with mastitis as well. These animals were considered to play a role in the transmission of the disease to man. This paper describes the isolation and characterization of C. diphtheriae in a 4 years old cow with generalized, partly ulcerative and purulent skin lesions. Bacteriological examination revealed the presence of very numerous corynebacterium-like organisms, which were characterized as C. diphtheriae subsp. belfanti, a nontoxigenic subspecies of C. diphtheriae. The significance of C. diphtheriae in veterinary medicine and the possible role of cattle as a reservoir of these organisms are discussed.

Animals↗
PubMed1995

Activation of ZAP-70 kinase activity by phosphorylation of tyrosine 493 is required for lymphocyte antigen receptor function.

ZAP-70 is a protein tyrosine kinase (PTK) required for T-cell development and T-cell antigen receptor (TCR) function. ZAP-70 is associated with the phosphorylated antigen receptor and undergoes tyrosine phosphorylation following receptor activation. We demonstrate here that tyrosine phosphorylation of ZAP-70 results in an increase in its catalytic activity and that this activation is mediated by the phosphorylation of tyrosine residue 493 by the src family of PTKs. The activity of baculoviral expressed ZAP-70 was up-regulated 10-fold when ZAP-70 was co-infected and phosphorylated by the src family PTK, lck. Mutation of Y493 alone abrogated the ability of ZAP-70 to be activated by lck. Moreover, we demonstrate that phosphorylation of Y493 and activation of ZAP-70 is required for antigen receptor-mediated induction of interleukin-2 (IL-2) secretion in lymphocytes.

Amino Acid Sequence↗
PubMed1994

Activation and inactivation of thyroid hormone by type I iodothyronine deiodinase.

The prohormone thyroxine (T4) is activated by outer ring deiodination (ORD) to 3,3',5-triiodothyronine (T3) and both hormones are degraded by inner ring deiodination (IRD) to 3,3',5'-triiodothyronine (rT3) and 3,3'-diiodothyronine, respectively. Indirect evidence suggests that the type I iodothyronine deiodinase (ID-I) in liver has both ORD and IRD activities, with preference for rT3 and sulfated iodothyronines as substrates. To establish this, we have compared the ORD of rT3 and IRD of T3 and T3 sulfate by homogenates of cells transfected with rat ID-I cDNA and by rat liver microsomes. In both preparations rT3 is the preferred substrate, while deiodination of T3 is markedly accelerated by its sulfation. Kinetic analysis provided similar Km and Vmax values in cell homogenates and liver microsomes. These data demonstrate unequivocally that ID-I is capable of both activating and inactivating thyroid hormone by ORD and IRD, respectively.

Animals↗
PubMed1994

In vitro binding of 3,5-di-iodo-L-thyronine to rat liver mitochondria.

In this study we have demonstrated that specific binding sites for 3,5-di-iodo-L-thyronine (3,5-T2) can be detected in rat liver mitochondria. After incubation with the homogenate, liver mitochondria bound only a small portion of [3,5-125I]T2. The addition of a 100-fold excess of unlabelled 3,5-T2 caused the displacement of on average 50-60% of the [3,5-125I]T2 bound. Specific binding of 3,5-T2 to rat liver mitochondria occurred rapidly; a maximum was achieved after 5 min. Maximal binding was obtained at 37 degrees C, while at 0 degrees C and 20 degrees C the values were only slightly lower. Binding was maximal at pH 7.0; mean (+/- S.E.M.) values for the apparent association constant and the binding capacity (calculated at pH 7.0, 0 degrees C and after 30 min of incubation) were 0.5 +/- 0.04 x 10(8) M-1 and 0.4 +/- 0.04 pmol/mg mitochondrial protein respectively. The specificity of binding, examined in competition studies, followed the order: 3,5-T2 > 3,3'-di-iodo-L-thyronine > 3',3,5-tri-iodo-L-thyronine > thyroxine. Other iodothyronines (3',5'-di-iodo-L-thyronine, 3,5-di-iodo-D-thyronine, 3,3',5'-tri-iodo-L-thyronine, 3-iodo-L-thyronine and 3,5-di-iodothyroacetic acid) showed little or no competition. This suggests that the specific 3,5-T2 binding sites could be of biological relevance with respect to the understanding of the mechanism of physiological action of thyroid hormones at the cellular level.

Adenosine Triphosphate↗
PubMed1989

[Fulminant sepsis following posttraumatic splenectomy--OPSI (overwhelming postsplenectomy infection) syndrome].

We report a case of fulminant sepsis 10 years after posttraumatic splenectomy. The low-cardiac-output stage of the septic shock with disseminated intravascular coagulation (DIC), which was already marked on admission to the intensive care unit, could not be overcome despite appropriate shock treatment. The pathogenetic spectrum includes more than 70% pneumococci, but any pathogen can trigger an overwhelming postsplenectomy infection (OPSI) syndrome. Pathogenetically, the OPSI syndrome is primarily due to distinctly reduced bacterial clearance from loss of the reticuloendothelial tissue in the spleen. Appropriate treatment of the septic shock is of prime therapeutic importance. In summary, the following recommendations can be made: 1. Nonspecific symptoms of infection in splenectomized patients, such as fever, call for immediate clarification with respect to the onset of a septic process. Immediate admission to a hospital, close monitoring, including blood cultures, and immediate antibiotic therapy are unavoidable. 2. The aim of treatment is to prevent DIC by aggressive therapy of the septic shock with prevention of the low-output stage. 3. Splenectomized patients must be informed of the possibility of a serious, potentially fatal infection and its premonitory symptoms. An emergency passport is appropriate. 4. In view of the few side effects of the vaccine, all splenectomized patients should be immunized against pneumococci. Children under 2 years of age should furthermore receive prophylactic oral penicillin up to the age of 5.

Adult↗
PubMed1980

[Problem in indication and artificial ventilation during segmental resection of the trachea (author's transl)].

Based on clinical experience and lung function data (bronchial resistance and inspiratory and expiratory FEV1) obtained in experiments with stenosis in the front of the mouth, bronchial resistance and inspiratory and expiratory FEV1 should first be determined. Resection of tracheal stenosis is indicated at a bronchial resistance of more than 5 cm H2O/1/s. This corresponds to a stenosis diameter of less than 8 mm. In the case of carinal resection, one lung can be ventilated by artifical respiration for a short time only. The data obtained during resection confirm the well-known requirement of clamping the opposite pulmonary artery.

Airway Resistance↗
PubMed1979

[Nitroglycerine in chronic obstructive pulmonary disease (author's transl)].

The effect of 0.8 mg nitroglycerine on haemodynamics and pulmonary functions was examined in 12 patients with chronic obstructive pulmonary disease. Resting heart rate was increased from 72 to 82/min by nitroglycerine, but at rest and on exercise there was only a slight reduction in systolic blood pressure, the diastolic level remaining essentially unchanged. There was a decrease in cardiac index of 16 and 15% at rest and on exercise, respectively. A highly insignificant reduction in mean pulmonary artery pressure occurred both at rest and on exercise. Respiratory variations of pulmonary artery pressure markedly decreased after nitroglycerine and correlated well with airway resistance, which fell by 28%. Pulmonary vascular resistance fell from 188 to 149 dyn.s.cm-5. Vital capacity increased after nitroglycerine as a sign of reduction of pulmonary emphysema. Partial pressure of arterial oxygen and carbon dioxide showed no definite changes at unchanged respiratory rates. Thus nitroglycerine produces a marked improvement in haemodynamics and pulmonary function without any increase in ventilatory distribution abnormalities. These results support the use of nitroglycerine as one of several means of treating chronic obstructive pulmonary disease.

Adult↗