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Biomedical subjects

H Schwarz

Publications and source records attributed to H Schwarz.

At least 145 records · Page 8Linked to original sources
PubMed1989

[Inflammatory aneurysm of the abdominal aorta and ureteral obstruction].

The incidence of inflammatory abdominal aortic aneurysm (IAAA) is reported in between 5 and 15% of all cases of abdominal aortic aneurysms (AAA). As a diagnostic hint the CT- or MRI-scan shows the ureters typically displaced medially, caused by a simultaneously visible retroperitoneal perianeurysmal fibrosis. In IAAA, one has to expect about 25% ureteral congestion, uni- or bilateral. Since the probability of rupture of IAAA--in the natural course between 15 and 25% of the cases--does not apparently differ much from the arteriosclerotic AAA, the operative aorto-iliac reconstruction with bypass grafting is the only solution and procedure of choice. Postoperatively, renal insufficiency caused by congestion normalizes: long-term follow-up by CT-scanning demonstrates the regression of both retroperitoneal fibrotic process and ureteral entrapment. Therefore, the dangerous ureterolysis results to be unnecessary. Hydronephrosis due to ureteral obstruction following aorto-iliac bypass grafting, if progressive or symptomatic, should be treated first non-operatively by ureteral splint.

Aorta, Abdominal↗
PubMed1989

Labeling properties of sucrose-infiltrated cryosections.

Plastic transverse sections of labeled semithick and ultrathin cryosections prepared by the Tokuyasu procedure demonstrate that section surfaces can be smooth or rough, sometimes showing fracture-like structures. These surface irregularities can arise from specimen properties, sectioning/fracturing and compression during sectioning, loss of cytoplasmic material during labeling, and from the final drying step. Nevertheless, small and sensitive marker molecules like 4 nm gold-protein A, ferritin-IgG and 1 nm gold-IgG bind predominantly to the cryosection surface of even mildly fixed specimens as long as the section is well preserved. In our experiments, marker penetration is enhanced by section damage. Marker incubation of ultrathin cryosections obtained by cryo transverse sectioning of IgG-labeled semithick cryosections shows also that penetration of uncoupled antibodies into cytoplasm and nuclei of chicken erythrocytes is limited.

Animals↗
PubMed1989

Influence of fixatives and embedding media on immunolabelling of freeze-substituted cells.

Fixatives and embedding media are known to alter antigen epitopes and reduce antibody recognition unpredictably. Every antigen-antibody interaction may be influenced differently. In this study we concentrate on the influence of fixatives, commonly used in immuno-electron microscopy, the dehydration process, and the embedding media Lowicryl HM20 and K4M. The results obtained with our model system show that: the lesser chemical fixation, the more intense the labelling, and that dehydration by freeze-substitution preserves the antigenicity better than dehydration by progressive lowering of temperature, PLT, and finally that there is no obvious difference in labelling between the apolar Lowicryl HM20 and the polar Lowicryl K4M.

Animals↗
PubMed1989

[Wood dust concentrations in wood processing industries].

68 mean values of airborne shift concentration of total dust were measured at 9 factories of woodworking industries. The values varied from 0.18 to 59.3 mg/m3 for area sampling. But at 63% of the woodworking machines with exhaustion the area sampling shift concentration of total dust reached fewer values than 5 mg/m3. This is a significant decrease of dust concentration in the last ten years.

Air Pollutants, Occupational↗
PubMed1988

Dihydrofolate reductase (mouse) and beta-galactosidase (Escherichia coli) can be translocated across the plasma membrane of E. coli.

Hybrid genes were constructed. One, ompA153-dfr, encoded the precursor of the 325 residue Escherichia coli outer membrane protein OmpA up to residue 153 which was fused to the complete 186-residue dihydrofolate reductase of the mouse. The other, ompA219-lacZ, coded for the same precursor up to residue 219 which was fused to 1017 COOH-terminal residues of the 1023-residue subunit of the beta-galactosidase of E. coli. Full expression of the ompA153-dfr gene caused accumulation of its precursor and of that of the chromosomally encoded OmpA protein. When the amount of product was reduced, no pro-OmpA and very little pro-hybrid protein accumulated. The precursor was processed and the mature protein was fully accessible to trypsin in permeabilized cells. Expression of the ompA219-lacZ gene led to the presence of the hybrid protein at only 20-30% of the amount expected. About 20% of it appeared to be incorporated in the outer membrane. All of the hybrid was quantitatively accessible to trypsin in permeabilized cells. When the hybrid gene was overexpressed, the protein was found associated with the plasma membrane in the cytosol. It is concluded that both beta-galactosidase and dihydrofolate reductase could quantitatively traverse the plasma membrane, provided the amounts synthesized were sufficiently small.

Animals↗
PubMed1988

Internal deletions in the gene for an Escherichia coli outer membrane protein define an area possibly important for recognition of the outer membrane by this polypeptide.

A series of overlapping deletions has been constructed in the ompA gene which encodes the 325-residue Escherichia coli outer membrane protein OmpA. Immunoelectron microscopy showed that the OmpA fragments were either located in the periplasmic space or were associated with the outer membrane. Apparently an area between residues 154 and 180 is required for this association; all proteins missing this area were found to be periplasmic. The nature of this association remained unknown; no membrane-protected tryptic fragments could be identified for any of these polypeptides. Hybrid genes were constructed encoding parts of the periplasmic maltose binding protein and an area of the ompA gene coding for residues 154-274. The corresponding proteins were not localized to the outer membrane but remained attached to the outer face of the plasma membrane, possibly because the normal mechanism of release from this membrane was impaired. In the OmpA protein the conspicuous sequence Ala180-Pro-Ala-Pro-Ala-Pro-Ala-Pro187 exists. Frameshift mutants were constructed to eliminate this sequence. There was no effect on the incorporation of the mutant proteins into the outer membrane. Thus, this "hinge" region is not involved in sorting. A proposal suggesting the existence of a sorting signal common to several outer membrane proteins (Benson, S. A., Bremer, E., and Silhavy, T. J. (1984) Proc. Natl. Acad. Sci. U. S. A. 81, 3830-3834) was subsequently rejected (Bosch, D., Leunissen, J., Verbakel, J., de Jong, M., van Erp, H., and Tommassen, J. (1986) J. Mol. Biol. 189, 449-455; Freudl, R., Schwarz, H., Klose, M., Movva, N. R., and Henning, U. (1985) EMBO J. 4, 3593-3598). Although it is not known whether or not the outer membrane association observed represents a step in the normal sorting mechanism, it is concluded that it remains an open question whether or not a sorting signal, as proposed originally, exists in outer membrane proteins.

Amino Acid Sequence↗
PubMed1988

The influence of amino substitutions within the mature part of an Escherichia coli outer membrane protein (OmpA) on assembly of the polypeptide into its membrane.

The membrane part of the 325-residue outer membrane protein OmpA of Escherichia coli encompasses residues 1-177. This part is thought to cross the membrane eight times in antiparallel beta-strands, forming four loops of an amphipathic beta-barrel. With the aim of gaining some insight into the mechanism of sorting, i.e. the way the protein recognizes and assembles into its membrane, a set of point mutants in the ompA gene has been generated. Selection for toxicity of ompA expression following mutagenesis with sodium bisulfite yielded genes with multiple base pair substitutions, the majority of which resulted in amino acid substitutions in the membrane moiety of the protein. None of the altered proteins was blocked in membrane incorporation. A proline residue exists at or near each of the presumed turns at the inner side of the outer membrane. Using oligonucleotide-directed mutagenesis, each of them was replaced by a leucine residue which is thought to be a turn blocking residue. None of these proteins had lost the ability to be incorporated into the membrane. Apparently, leucine residues are tolerated at turns in this protein. To interfere with the formation of antiparallel beta-strands, four double mutants were prepared: ompA-ON3 (Ala11----Pro, Leu13----Pro), -ON4 (Ala11----Asp, Leu13----Pro), -ON5 (Gly160----Val, Leu162----Arg), and -ON6 (Leu164----Pro, Val166----Asp). The former three proteins and even quadruple mutants consisting of a combination of ompA-ON2 or -ON4 with -ON5 were not defective in membrane assembly. In contrast, the OmpA-ON6 protein was translocated across the plasma membrane but could not be incorporated into the outer membrane. It is concluded that at least one rather small area of the polypeptide is of crucial importance for the assembly of OmpA into the outer membrane.

Amino Acid Sequence↗
PubMed1987

Study of hereditary fructose intolerance by use of 31P magnetic resonance spectroscopy.

The effect of fructose on liver metabolism in patients with hereditary fructose intolerance (HFI) and in heterozygotes for HFI was studied by 31P magnetic resonance spectroscopy (31P-MRS). In patients with HFI (n = 5) ingestion of small amounts of fructose was followed by an increase in sugar phosphates and decrease in inorganic phosphate (Pi) in the liver that could be detected by 31P-MRS. 31P-MRS could be used to diagnose fructose intolerance and to monitor the patients' compliance with a fructose-restricted diet. In heterozygotes (n = 8) 50 g fructose given orally led to accumulation of sugar phosphates and depletion of Pi in the liver. Fructose also induced a larger increase in plasma urate in heterozygotes than in control subjects. The effect of fructose on liver Pi and plasma urate was most pronounced in heterozygotes with gout (n = 3). Heterozygosity for HFI may predispose to hyperuricaemia.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1987

A nonstructural polypeptide encoded by immediate-early transcription unit 1 of murine cytomegalovirus is recognized by cytolytic T lymphocytes.

We have constructed target cells by cotransfection of the MHC gene Ld and fragments of murine cytomegalovirus (MCMV) DNA coding for nonstructural immediate-early (IE) proteins. Transfectants were tested by using CTL clone IE1 with specificity for an IE epitope presented in association with Ld. Data show that clone IE1 recognizes a product of the ie1 transcription unit of MCMV, and that its specificity is shared by approximately 25% of polyclonal IE-specific CTL. The results provide the first definite evidence that expression of a herpes virus IE gene encoding a regulatory protein gives rise to antigen expression detectable by specific CTL.

Animals↗
PubMed1987

Stability studies on derivatives of the bovine pancreatic trypsin inhibitor.

Gibbs energy, enthalpy, and entropy data were determined for two selectively modified analogues of bovine pancreatic trypsin inhibitor (BPTI) to provide a model free set of thermodynamic parameters that characterize (a) the energetic and entropic contributions of the 14-38 disulfide bridge and (b) the variation of the overall stability resulting from the introduction of two negative charges into the positions 14 and 38. The two BPTI analogues studied were BPTI having Cys-14 and Cys-38 carboxymethylated (BPTI-RCOM) and BPTI having Cys-14 and Cys-38 carboxamidomethylated (BPTI-RCAM). They were obtained from native BPTI by reduction, followed by modification of the sulfhydryl groups with iodoacetic acid or iodoacetamide, respectively. The temperature dependence of all thermodynamic parameters of BPTI is drastically altered in the absence of the third disulfide bridge. Even the apparently minute difference of two dissociable carboxyl groups instead of uncharged amide groups in positions 14 and 38 has surprisingly large effects on the temperature dependence of the stabilization enthalpy. The Gibbs energy of BPTI at pH 2, 25 degrees C, decreases by approximately 70% when the 14-38 disulfide bond is cleaved. BPTI-RCOM is more stable than BPTI-RCAM in the whole pH range studied. The difference of -4 kJ/mol at pH 2, 25 degrees C, is reduced to -2.7 kJ/mol at pH 5, 25 degrees C. This finding demonstrates that the presence of two negative charges reduces the higher stability of BPTI-RCOM slightly; however, the overall effect of the two charges is still a stabilization.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1987

Predicted structure of tail-fiber proteins of T-even type phages.

The sequences of the tail fiber protein 36 of the phages T4, T2, K3, and Ox2 were analyzed for homologies and for folding patterns using structure prediction methods. No repeating motif was found. A model for the fiber structure is proposed in which beta-strands of about 6 amino acids are separated by turns. In the beta-strand, hydrophobic amino acids are found alternating with hydrophilic ones. Such amphipathic beta-strands can be stabilized by dimer formation. The dimerization occurs in a parallel fashion so that both N-termini are at one end of the dimer. This structure represents a rigid fiber. Our model is consistent with electron microscopic data and electron diffraction patterns for the T4 tail fiber. The observation that all fiber components are found as dimers supports our model. Sequences of the receptor recognition proteins 38 of T-even type phages reveal an architecture different from the architecture of the fiber proteins 36 and 37 of these phages.

Amino Acid Sequence↗
PubMed1987

T-even-type bacteriophages use an adhesin for recognition of cellular receptors.

Protein 38 of the Escherichia coli phage T4 is thought to be required catalytically for the assembly of the long tail fibers of this phage. It is shown that this protein of phage T2 and the T-even-type phage K3 and Ox2 act differently. It was found that NH2-terminal fragments of the protein, expressed from cloned fragments of gene 38 of phage K3, bind to gene 38 amber mutants of phage T2. Such phage or T2 gene 38 amber mutants, grown on a non-permissive host, possess a complete set of six tail fibers but are non-infectious. Both types of non-infectious phage could be repaired by incubation with an extract of cells harboring a cloned gene 38 of a host range mutant of phage K3, K3hx. The repaired phages had the host range of K3hx and not of T2. Immuno-electron microscopy showed that protein 38 is located at the free ends of the long tail fibers of phages T2, K3 and Ox2. The protein serves the recognition of the cellular receptor, i.e. it acts as an adhesin.

Amino Acid Sequence↗
PubMed1987

Role of antibodies to murine leukemia virus p15E transmembrane protein in immunotherapy against AKR leukemia: a model for studies in human acquired immunodeficiency syndrome.

Previous studies have demonstrated that the onset of AKR leukemia could be dramatically delayed and the overall incidence significantly reduced following treatment with high-titered heterologous antibodies directed against the gp71 major glycoprotein of the virus. However, to be maximally successful, the treatment had to be initiated during the postnatal period of the AKR mouse, encompassing a narrow window representing approximately the first 3 days of life. In the present study we sought to extend this barrier by including antibodies directed against a second envelope component of the virion, the transmembrane protein, p15E. We demonstrate that although neither antibodies to gp71 nor antibodies to p15E could influence the course of leukemia development when applied individually later in life, a combination of the two antibodies was effective even if given as late as 5 months after birth. The significance of these studies is discussed in relation to human retrovirus-associated diseases.

Acquired Immunodeficiency Syndrome↗
PubMed1987

Release of soluble pilin antigen coupled with gene conversion in Neisseria gonorrhoeae.

Gene conversion appears to be the frequent mechanism in Neisseria gonorrhoeae that leads to an altered expression of pilin, the subunit component of the pili. In this process segments of variable sequence information, the minicassettes, are transferred from silent storage loci into an expression locus. As a putative consequence of the rearrangement in the pilE gene, gonococci can enter a different phase of pilin production. Although the removal of a 7-amino acid leader peptide results in the production of typical P+ pilin used to form pili, the loss of an additional 39 amino acids yields S-pilin, a soluble form of pilin that is efficiently secreted into the extracellular environment. Both pilin types can coexist in an apparently homogeneous culture. Ps cells usually are piliated, although less extensively with regard to the length and the number of the pili when compared with P+ cells. Ps cells form T3/T4-type colonies also typical of nonpiliated cells (P-). The observations further suggest that the classical nonsecretory P- phenotype is not generated as a rule by precise gene conversion but rather by genetic changes that cause the production of an over-length pilin (L-pilin).

Amino Acid Sequence↗
PubMed1987

The signal sequence suffices to direct export of outer membrane protein OmpA of Escherichia coli K-12.

We studied whether information required for export is present within the mature form of the Escherichia coli 325-residue outer membrane protein OmpA. We had previously analyzed overlapping internal deletions in the ompA gene, and the results allowed us to conclude that if such information exists it must be present repeatedly within the membrane part of the protein encompassing amino acid residues 1 to 177 (R. Freudl, H. Schwarz, M. Klose, N. R. Movva, and U. Henning, EMBO J. 4:3593-3598, 1985). A deletion which removed the codons for amino acid residues 1 to 229 of the OmpA protein was constructed. In this construct the signal sequence was fused to the periplasmic part of the protein. The resulting protein, designated Pro-OmpA delta 1-229, was processed, and the mature 95-residue protein accumulated in the periplasm. Hence, information required for export does not exist within the OmpA protein.

Amino Acid Sequence↗