Search PubMed⌕ Search

Biomedical subjects

J Koch

Publications and source records attributed to J Koch.

At least 145 records · Page 8Linked to original sources
PubMed1994

The heterodisulfide reductase from Methanobacterium thermoautotrophicum contains sequence motifs characteristic of pyridine-nucleotide-dependent thioredoxin reductases.

The genes hdrA, hdrB and hdrC, encoding the three subunits of the iron-sulfur flavoprotein heterodisulfide reductase, have been cloned and sequenced. HdrA (72.19 kDa) was found to contain a region of amino acid sequence highly similar to the FAD-binding domain of pyridine-nucleotide-dependent disulfide oxidoreductases. Additionally, 110 amino acids C-terminal to the FAD-binding consensus, a short polypeptide stretch (VX2CATID) was detected which shows similarity to the region of thioredoxine reductase that contains the active-site cysteine residues (VX2CATCD). These findings suggest that HdrA harbors the site of heterodisulfide reduction and that the catalytic mechanism of the enzyme is similar to that of pyridine-nucleotide-dependent thioredoxin reductase. HdrA was additionally found to contain four copies of the sequence motif CX2CX2CX3C(P), indicating the presence of four [4Fe-4S] clusters. Two such sequence motifs were also present in HdrC (21.76 kDa), the N-terminal amino acid sequence of which showed sequence similarity to the gamma-subunit of the anaerobic glycerol-3-phosphate dehydrogenase of Escherichia coli. HdrC is therefore considered to be an electron carrier protein that contains two [4Fe-4S] clusters. HdrB (33.46 kDa) did not show sequence similarity to other known proteins, but appears to possess a C-terminal hydrophobic alpha-helix that might function as a membrane anchor. Although hdrB and hdrC are juxtaposed, these genes are not near hdrA.

Amino Acid Sequence↗
PubMed1994

Functional analysis of human alpha 1(I) procollagen gene promoter. Differential activity in collagen-producing and -nonproducing cells and response to transforming growth factor beta 1.

To gain a further understanding of the regulation of human type I collagen gene expression under physiologic and pathologic conditions, we characterized 5.3 kilobase pairs (kb) of the human alpha 1(I) procollagen gene promoter. A series of deletion constructs containing portions of the alpha 1(I) procollagen 5'-flanking region (with end points from -5.3 kb to -84 base pairs (bp)) ligated to the chloramphenicol acetyltransferase (CAT) reporter gene were transiently transfected into NIH/3T3 cells. Maximal CAT activity was observed with constructs having 5' end points from -804 to -174 bp. A further 5' deletion to -84 bp caused a marked reduction in CAT activity. Cells transfected with plasmids containing longer 5'-flanking fragments of the alpha 1(I) procollagen gene (-2.3 or -5.3 kb) showed reduced CAT activity compared with the -804 bp construct. The activity of the alpha 1(I) procollagen promoter was much lower in cells that do not normally express type I collagen (HeLa cells) compared with collagen-producing NIH/3T3 cells. The CAT activity of deletion constructs containing longer 5' regions than -84 bp was increased by approximately 2-fold in NIH/3T3 cells treated with transforming growth factor beta 1 (TGF beta 1). Electrophoretic mobility shift assays indicated that protein-DNA complex formation with a probe corresponding to the -170 to -80 bp fragment of the alpha 1(I) procollagen promoter was markedly enhanced in nuclear extracts prepared from TGF beta 1-treated fibroblasts as compared with untreated fibroblasts. The DNA binding activity stimulated by TGF beta 1 was specific for an Sp1-like sequence at positions -164 to -142 bp in the promoter. These results demonstrate that 1) there are both positive and negative cis-acting regulatory elements in the human alpha 1(I) procollagen promoter, 2) these regulatory regions function differently in collagen-producing and -nonproducing cells, 3) the alpha 1(I) procollagen promoter contains TGF beta 1-responsive sequences located between -174 and -84 bp from the transcription start site, and 4) TGF beta 1 caused marked stimulation of the DNA binding activity of a nuclear factor interacting with an Sp1-like binding site located within a region encompassing -164 to -142 bp of the alpha 1(I) procollagen promoter.

3T3 Cells↗
PubMed1994

[The primary treatment of velar, palatal and vomer malformations as a prerequisite for normal speech development].

In this article the embryology, morphology, pathophysiology, and treatment of the cleft malformation of the hard, the soft palate, and the vomer are described. A therapy is suggested, which minimizes the risk that these children are suffering from an impaired development of speech. Therefore, it is necessary: 1. to recognize the full extent of the malformation, 2. to close the cleft before the development of hearing and speech is finished as these 2 abilities are fundamental milestones of a normal psychosocial development. 3. Nearly normal anatomical and functional structures are to be achieved with the surgical treatment. Therefore the construction of 2 nasal floors, the correct adaptation of the vomer to the palatal plates, and the intravelar veloplasty with the preparation of the aponeurosis are most important determinants. This treatment can avoid secondary operations to improve the results of hearing and speech.

Child, Preschool↗
PubMed1994

Comparison of results of haematological and clinical chemical analyses of blood samples obtained from the cephalic and external jugular veins in dogs.

The study was performed to investigate the difference in the concentration of several haematological and clinical chemical blood components in blood obtained from the cephalic and external jugular veins in 23 dogs. A total of 17 laboratory tests were analysed and, except for two clinical chemical blood components, there was no decisive difference in the test results obtained in blood samples collected from the cephalic and external jugular vein in dogs. For creatinine and potassium, however, there was a significant difference in the test results between the two veins, the highest results in general being measured in jugular venous blood. These findings indicate that it may be advisable to establish standardised procedures when collecting blood samples and make adjustments for the difference in test results when interpreting them.

Analysis of Variance↗
PubMed1994

[Unilateral caudal cranial nerve paralysis in extracranial carotid dissection].

Focal cerebral ischemic symptoms, Horner's syndrome and mostly ipsilateral headache are the characteristic clinical triad of extracranial carotid artery dissection. Lower cranial nerve palsies seem to be uncommon and rare. By means of two cases with identical clinical symptoms and of a literature review we make clear, that ipsilateral lower cranial nerve palsies, especially a hypoglossal nerve palsy, are not uncommon. Without focal cerebral ischemic symptoms they can be the only sign of extracranial carotid artery dissection. Computed tomography of the skull base with regard to the high cervical internal carotid artery is as an usually quickly available examination an alternative to magnetic resonance imaging.

Aortic Dissection↗
PubMed1994

Mucosal infection of neonatal rhesus monkeys with cell-free SIV.

Although the mechanisms for maternal transmission are unknown, approximately half of the infants congenitally infected with the human immunodeficiency virus type 1 (HIV-1) seem to become infected late in gestation or during delivery. Previously, we have developed a rhesus monkey model for congenital infection by injecting cell-free simian immunodeficiency virus (SIV) directly into amniotic fluid. Our results suggested that fetal infection may have occurred via skin or mucous membrane exposure. Mucosal surfaces have also been implicated as a portal of virus entry by a study in which the presence of serosanguinous fluid in neonatal gastric aspirates correlated with an increased rate of HIV-1 transmission. To test whether cell-free virus could transverse intact neonatal mucosal surfaces, we administered SIVmac251 orally to four rhesus monkey neonates within 1 hr following cesarean section delivery. All four neonates developed viremia and were positive by cocultivation and PCR. Seroconversion occurred in three of the four neonates. The SIV dose given was within physiological range as shown by end-point dilution of virus stock and viremic plasma samples of juvenile rhesus monkeys. This primate model for mucosal transmission of cell-free virus features a high infection rate, thus making studies of mucosal immunity and the development of strategies to prevent intrapartum virus transmission possible.

Animals↗
PubMed1994

Short term effects of acute inhibition of the angiotensin-converting enzyme on the renin-angiotensin system and plasma atrial natriuretic peptide in healthy dogs fed a low-sodium diet versus a normal-sodium diet.

The purpose of the present study was to quantify some of the short term responses of the renin-angiotensin system (RAS) to a recommended dosage of the angiotensin-converting enzyme inhibitor enalapril in clinically healthy dogs fed a normal-sodium and a low-sodium diet. A single dose of enalapril (0.5 mg/kg PO) was given to eight clinically healthy male Beagle dogs after a period where the dogs were fed a normal-sodium diet and low-sodium diet, respectively. Serum angiotensin-converting enzyme activity (ACE), plasma renin activity (PRA), plasma aldosterone concentration (PAC), and plasma atrial natriuretic peptide (ANP) concentration were measured during the following twenty-four hour period. The data indicate that enalapril induced a potent blockade of the renin-angiotensin system (RAS) for at least twenty-four hour. Specifically, enalapril during low-sodium diet elicited an exaggerated increase in PRA and a diminished decrease in ACE and ANP when compared to the results of the drug during normal-sodium diet. Long term controlled studies of enalapril in dogs with congestive heart failure (CHF) are warranted in order to determine the duration of action and optimal dose of enalapril.

Aldosterone↗
PubMed1994

Effects of a low sodium diet with a high potassium content on plasma endothelin-1, atrial natriuretic peptide and arginine vasopressin in normal dogs.

Eight clinically healthy male beagle dogs received a low sodium diet for 5 weeks. Before and after this period the dogs received a control diet for 3 weeks. Both diets provided the dogs with approximately 6.8 mmol K+/kg/day. Neither introducing nor withdrawing the low sodium diet changed the plasma concentrations of endothelin-1 (ET-1), atrial natriuretic peptide (ANP) and arginine vasopressin (AVP). Pooled data from the control periods were not different from the low sodium period for either ET-1 (2.31 pg/ml and 2.09 pg/ml, P = 0.21), ANP (42.51 pg/ml and 38.99 pg/ml, P = 0.44) or AVP (4.14 pg/ml and 4.16 pg/ml, P = 0.91). It was concluded that ET-1, ANP and AVP in normal dogs are unaffected by a 6-fold change in sodium intake in the presence of a high potassium intake.

Animals↗
PubMed1994

Estimates of components of variance of the rectal temperature in clinically healthy dogs in a hospital environment.

The rectal temperature is frequently measured in the morning on a daily basis in hospitalized dogs. Besides comparing the measured temperature to a population-based reference interval, it may also be of interest to evaluate the differences between consecutive measurements in order to follow the health status of a particular dog. In veterinary clinical chemistry, a parameter referred to as the critical difference, which can be used to judge if the difference between two consecutive measurements may be safely ascribed to random variation or not, has recently been introduced. The purpose of the present study was to obtain an estimate of the critical difference of the rectal temperature based on measurements of the rectal temperature in clinically healthy dogs in a hospital environment. The rectal temperature was measured in a standardized manner on 6 different days in 7 dogs. The total variance was estimated as 0.1015. The inter-individual variance was 0.0428, and the intra-analytical variance including the analytical variance was 0.0587. From these components of variance, the critical difference was calculated as 0.69 degrees C. Thus, the rectal temperature measured in the morning in hospitalized dogs can be expected to fluctuate about 0.7 degrees C from day to day due to random variation alone.

Analysis of Variance↗
PubMed1994

Fast, sensitive multicolor detection of nucleic acids in situ by PRimed IN Situ labeling (PRINS).

PRimed IN Situ labeling (PRINS) has become an alternative to traditional fluorescence in situ hybridization (FISH) methods for detection of nucleic acids in situ. PRINS is based on sequence-specific annealing in situ of an unlabeled DNA probe. The probe serves as a primer for chain elongation in situ, catalyzed by a suitable DNA polymerase that uses labeled nucleotides as substrate. The fact that the probe is unlabeled means that high probe concentrations can be utilized, making the hybridization very fast. We describe here a fast method for detection of three different target sequences visualized in different colors with PRINS. An advantage, relative to FISH, is that even probes with different melting temperatures can be detected in the same metaphase with optimal stringency for each probe.

DNA Probes↗
PubMed1994

Limitation of shock-wave-induced renal tubular dysfunction by nifedipine.

In a prospective randomized study, the effects of the calcium entry blocker nifedipine on shock-wave-induced tubular impairment were studied. 24 patients with renal pelvic or calyceal stones undergoing anesthesia-free extra-corporeal shock wave lithotripsy (ESWL) without ancillary measures were randomly assigned to the nifedipine group (n = 12) or the control group (n = 12). Four doses of nifedipine (10 mg t.i.d.) were given orally, starting the night before ESWL. Controls received no medication. To assess renal tubular function, the urinary excretion of alpha 1-microglobulin (A1M), N-acetyl-beta-glucosaminidase (NAG) and Tamm-Horsfall protein (THP) were measured before, immediately, 12 and 24 h after ESWL. After lithotripsy, there was a rise in urinary A1M and NAG which was significantly higher in the control than in the nifedipine group. THP, a glycoprotein synthesized by distal tubular cells, fell significantly less in the nifedipine group compared to the controls. Our results indicate that nifedipine exhibits a protective effect on shock-wave-induced tubular damage similar to verapamil. The underlying mechanisms are not clarified yet, direct actions on tubular cells and interference with renal hemodynamics have to be discussed.

Acetylglucosaminidase↗
PubMed1994

Some effects of a low sodium diet high in potassium on the renin-angiotensin system and plasma electrolyte concentrations in normal dogs.

Eight normal male Beagle dogs received 0.7 mmol Na+/kg/day for 5 weeks and 4.0 mmol Na+/kg/day in one 3 week control period preceding and another similar period following the low sodium period. The dogs received 6.8 mmol K+/kg/day throughout the study. The median plasma renin activity (PRA) and plasma aldosterone concentration (PAC) were higher in the low sodium period than in the following control period (0.67 versus 0.28 ng/ml/h, p < 0.0001) and (204 versus 31 pg/ml, p < 0.0001). PRA and PAC quickly stabilized on a new steady level in response to altered intake of sodium chloride. The angiotensin-converting enzyme (ACE) activity was not changed by the altered intake of sodium chloride. The plasma concentrations of sodium and chloride were increased during the low sodium period. This could be due to an indirect effect of the high potassium intake of the dogs. Potassium leads to an increased secretion of aldosterone and thereby to an increased retention of sodium and chloride in the kidney. The possible implications of a high potassium content in a low sodium diet are discussed.

Aldosterone↗
PubMed1993

Products of enzymatic reduction of benzoyl-CoA, a key reaction in anaerobic aromatic metabolism.

Benzoyl-coenzyme A is the most common central intermediate of anaerobic aromatic metabolism. Studies with whole cells of different bacteria and in vitro had shown that benzoyl-CoA is reduced to alicyclic compounds, possibly via cyclohexadiene intermediates. This reaction is considered a 'biological Birch reduction'. We have elucidated by NMR techniques the structures of six products of [ring-13C6]benzoate reduction. The reaction is catalyzed by extracts from cells of a denitrifying Pseudomonas strain K172 anaerobically grown with benzoate and nitrate as sole carbon and energy sources. The assay mixture contained [ring-13C6]benzoate plus traces of [U-14C]benzoate, Mg2+, ATP, coenzyme A (CoA), and Ti(III) as reductant. The use of the multiply 13C-labelled precursor increases the sensitivity of NMR detection and allows the analysis of crude product mixtures by two-dimensional coherence transfer procedures such as total correlation 13C-NMR spectroscopy and 13C-filtered 1H-NMR spectroscopy. The time course of product formation is consistent with the following order of events. Benzoyl-CoA is formed from benzoate via benzoate-CoA ligase. The first ring reduction product observed is cyclohex-1,5-diene-1-carboxyl-CoA. The next intermediate is 6-hydroxycyclohex-1-ene-1-carboxyl-CoA which is derived from the diene by addition of water. Part of the diene seems to be reduced to cyclohex-1-ene-1-carboxyl-CoA which becomes hydrated to trans-2-hydroxycyclohexane-1-carboxyl-CoA; these two intermediates may be side products in vitro. The first non-cyclic intermediate formed by beta-oxidation is 3-hydroxypimelyl-CoA. This aliphatic C7 dicarboxylic acid is proposed to be oxidized via glutaryl-CoA and crotonyl-CoA to three molecules of acetyl-CoA and one molecule of CO2. A similar product pattern was observed in the benzoate-degrading phototrophic bacterium Rhodopseudomonas palustris. This indicates that the enzymatic reduction of benzoyl-CoA may be mechanistically similar in different anaerobes.

Acyl Coenzyme A↗
PubMed1993

Long-term results of sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens.

In an attempt to minimize postoperative astigmatism while retaining the advantages of implanting intraocular lenses with large optics, sutureless phacoemulsification with implantation of a 7-mm polymethyl methacrylate intraocular lens was performed through a modified scleral tunnel in 100 consecutive patients. Visual and keratometric results, as well as complications, were recorded during a follow-up period of 12 months. Average uncorrected visual acuity improved from 20/153 before surgery to 20/66 as early as 1 week after surgery. Average best corrected visual acuity improved from 20/86 before surgery to 20/39 as early as 1 week after surgery. No significant changes in visual acuity were recorded thereafter. The absolute value of keratometric astigmatism was not increased significantly at any postoperative examination time. The induced cylinder shifted from 1.26 diopters x 74.40 degrees at 1 week to 1.22 D x 1.50 degrees at 1 month after surgery, without further relevant changes thereafter. Mean (+/- SD) endothelial cell loss was 7.2% +/- 6.1% at 1 month and 12.2% +/- 5.4% at 6 months after surgery. Corneal thickness was not increased significantly at any postoperative examination time. Implantation of intraocular lenses with large optics through a scleral tunnel allows quick visual rehabilitation as well as early stability of refraction.

Adult↗