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Biomedical subjects

M Kowalski

Publications and source records attributed to M Kowalski.

At least 73 records · Page 4Linked to original sources
PubMed1992

[Plasma extravasation in the tracheo-bronchial airways. Mechanisms and physiopathological consequences in asthma].

Plasma extravasation (EP) is an important phenomenon during the course of inflammation. In asthmatic subjects, EP is produced not only in the walls of the airways, but also in the lumen. This has consequences for the bronchial calibre and the qualitative and quantitative characteristics of the secretions. Numerous experimental methods have been developed in animals in order to study EP induced in the airways by different stimuli. For the most part these are inapplicable in man where EP is generally validated in an indirect fashion by measuring the quantity of certain plasma proteins, such as albumin in the secretions or the bronchoalveolar lavage. EP is linked to an increase in the permeability of the vessels, notably this is situated in the subepithelial zone. It is influenced by the appearance of disruption between the endothelial cells and possibly amplified by an increased blood flow linked to vasodilatation. It is the association of these phenomena of epithelial hyperpermeability which favours the appearance of EP in the lumen. In experimental systems the greater part of the mediators implicated in the pathophysiology of asthma are capable of inducing EP in the airways. The perfecting of reliable and non-invasive methods of study is, however, necessary to achieve a perfect understanding of the role of EP in the pathophysiology of asthma or other inflammatory diseases of the bronchi and to assess the efficacy of this parameter of different therapeutic techniques.

Animals↗
PubMed1991

[Orthotopic liver transplantation--indications and results].

Indications for and results of orthotopic liver transplantation (OLT) were modified over the past ten years by new immunosuppressive agents, earlier timing of transplantation and better knowledge of potential complications. In 1990, OLT appears justified in the treatment of all liver disease threatening life, in the absence of contraindications and other possible treatments. Between July 1987 and December 1990, 21 patients were transplanted at the Geneva University Hospital. Three children received part of an adult liver (two or three segments), using the reduced-size liver transplantation technique. Four OLTs had to be performed in an emergency situation. Two patients died within six months of transplantation, one after 7.5 months, and the last patient died after one year from cancer recurrence. 17 patients are presently alive (81%) at 4 to 39 months (median 14 months) following OLT. More than the mere survival, however, the quality of life regained after transplantation prompts us to consider transplantation early in the progress of the disease.

Adolescent↗
PubMed1991

Internal fixation with a self-compressing plate and lag screw: improvements of the plate hole and screw design. 1. Mechanical investigation.

For a number of years, self-compressing plates, with oval holes and using special drill guides, have been in use. Recently, the advantages offered by lag screw interfragmentary compression inserted through the plate have gained prominence. Often such screws are inserted in an inclined position toward the fracture plane for better efficiency. It has also become evident that inclined screws placed into oval holes undergo a displacement toward the fracture. Efforts to improve the effect of this technique have led to a new plate and screw interaction that is described herein. The result is versatility and efficiency of the fracture fixation.

Biomechanical Phenomena↗
PubMed1991

Internal fixation with a self-compressing plate and lag screw: improvements of the plate hole and screw design. 2. In vivo investigations.

A mechanically improved design of bone plate and screw was compared in vivo with conventional plate fixation. This method was investigated biologically in a standardized osteotomy model on sheep tibiae. It was found that maintenance of reduction of an osteotomy was facilitated and there was no adverse effect of this fracture fixation system on bone remodeling. The modified implant permits the reduced surgical approach to the bone through one plane and optimal fixation of the fracture or osteotomy.

Animals↗
PubMed1991

Attenuation of human immunodeficiency virus type 1 cytopathic effect by a mutation affecting the transmembrane envelope glycoprotein.

The cytopathic effects of human immunodeficiency virus type 1 (HIV-1) infection are specific for cells that express the CD4 viral receptor and consist of syncytium formation and single-cell lysis. Here we report that a mutation (517A) affecting the amino terminus of the HIV-1 gp41 transmembrane envelope glycoprotein resulted in a virus that was markedly less cytopathic than was wild-type HIV-1. In systems in which cell-to-cell transmission of HIV-1 occurred, the replication ability of the 517A virus was comparable with that of the wild-type virus. Even though the levels of viral protein expression, virion production, and interaction of the envelope glycoproteins with CD4 were similar for the 517A and wild-type viruses, both syncytium formation and single-cell lysis were attenuated for the 517A mutant virus. These results demonstrate that an envelope glycoprotein region important for mediating post-receptor binding events in cell membrane fusion is important for the induction of cytopathic effects by HIV-1. These results also indicate that levels of HIV-1 viral proteins or viral particles produced in infected cells are in themselves not sufficient to induce cytopathic effects.

Amino Acid Sequence↗
PubMed1990

Free-flow electrophoresis under microgravity: evidence for enhanced resolution of cell separation.

A mixture of fixed rabbit, guinea pig and rat erythrocytes, suspended in a relatively conductive solution, was separated by means of continuous free flow electrophoresis (CFFE) under 1 g- and microgram- conditions using a specially designed electrophoretic module. Short duration microgram conditions were realized on board a sounding rocket. Due to the energy input and the associated thermal convection a separation of the three differently charged cell types in distinct peaks was not possible under 1 g-conditions as shown by reference experiments on the ground before launch. In contrast to the poor resolution under 1 g-conditions, clear separation of the cell mixture could be recorded after lift-off of the rocket under microgram-conditions. Repeated measurements demonstrated that the separation profile was completely stable during the entire microgram-phase of about 6 min. Since the CFFE experiment in space was an exact replica of the ground reference experiments, the results demonstrated unambiguously the potential of CFFE for cell separation under microgram-conditions in media of high ionic strength.

Animals↗
PubMed1990

Rapid complementation assays measuring replicative potential of human immunodeficiency virus type 1 envelope glycoprotein mutants.

Rapid assays which measure the ability of mutant human immunodeficiency virus type 1 envelope glycoproteins to mediate cell-free and/or cell-to-cell transmission of virus are described. By using these assays, envelope glycoprotein mutants with varying degrees of syncytium-forming ability were tested for ability to complement viral replication in trans. As expected, mutants that dramatically affect association of the gp120-gp41 envelope subunits, CD4 binding, or membrane fusion were unable to form syncytia or to support cell-free or cell-to-cell transmission. Surprisingly, some membrane fusion-defective mutants significantly attenuated in syncytium-forming ability were able to complement viral replication. Conversely, mutations in the carboxyl terminus of gp41 transmembrane glycoprotein, although not affecting syncytium-forming ability, significantly attenuated both forms of virus transmission. These results indicate that syncytium formation is not sufficient for cell-to-cell transmission of human immunodeficiency virus type 1. Furthermore, virus transmission appears to be less sensitive to inhibition of membrane fusion than is syncytium formation.

Animals↗
PubMed1990

Electrofused mammalian cells analyzed by free-flow electrophoresis.

Somatic cell fusion is a powerful and widely used technique. In recent years, electrofusion has become increasingly popular because it is a gentle process that can be optically controlled and carefully monitored using appropriate fusion chambers and because it permits the efficient fusion of smaller cell numbers. However, damage of the cell membrane and cell lysis occurs during application of the electrical field and is accompanied by changes in surface charge which can be detected by free-flow electrophoresis. In this study, we evaluated free-flow electrophoresis to detect changes in cell viability after application of electric-field conditions employed in mammalian cell electrofusion and to separate dead cells and cell debris from intact unfused or fused cells.

Animals↗
PubMed1990

Effects on CD4 binding of anti-peptide sera to the fourth and fifth conserved domains of HIV-1 gp120.

Antisera to peptides that represent regions within the fourth and fifth conserved domains of the human immunodeficiency virus type 1 (HIV-1) gp120 were tested for recognition of the gp120 glycoprotein and for the ability to interfere with gp120 binding to the CD4 receptor molecule. Antisera to both peptides contained equivalent antibody titers, showed equivalent reactions with denatured gp120 on Western blot, and had group-specific reactivity. Preincubation of gp120 with either anti-peptide sera prebound to a solid phase substantially blocked soluble CD4 binding to gp120. Similarly, preincubation of gp120 with CD4-positive cells substantially diminished recognition of gp120 by both anti-peptide antisera. These results provide serologic evidence that regions near or within the fourth and fifth conserved domains of gp120 are involved in CD4 binding. However, neither anti-peptide sera could block soluble gp120 from binding to CD4-positive cells nor inhibited HIV-1 envelope-mediated syncytium formation or virus infection. These results demonstrate that antisera to regions proximal to the CD4 binding site of gp120 may compete poorly with CD4 for gp120 binding.

Animals↗
PubMed1989

Antibodies to CD4 in individuals infected with human immunodeficiency virus type 1.

The attachment of human immunodeficiency virus type 1 (HIV-1) to target cells is mediated by a specific interaction between the viral envelope glycoprotein (gp120) and the CD4 receptor. Here we report that approximately 10% of HIV-1-infected individuals produce antibodies that recognize the extracellular portion of the CD4 molecule. Carboxyl-terminal deletions of CD4 that do not affect HIV-1 gp120 binding eliminate recognition of CD4 by patient antisera. In contrast, mutations in the amino-terminal domain of CD4 that attenuate HIV-1 gp120 binding do not diminish CD4 recognition by patient antisera. These results suggest that HIV-1 infection can generate antibodies directed against a region of the viral receptor distinct from the virus-binding domain.

Acquired Immunodeficiency Syndrome↗
PubMed1988

A soluble CD4 protein selectively inhibits HIV replication and syncytium formation.

The CD4 (T4) molecule is expressed on a subset of T lymphocytes involved in class II MHC recognition, and is probably the physiological receptor for one or more monomorphic regions of class II MHC (refs 1-3). CD4 also functions as a receptor for the human immunodeficiency virus (HIV) exterior envelope glycoprotein (gp120) (refs 4-9), being essential for virus entry into the host cell and for membrane fusion, which contributes to cell-to-cell transmission of the virus and to its cytopathic effects. We have used a baculovirus expression system to generate mg quantities of a hydrophilic extracellular segment of CD4. Concentrations of soluble CD4 in the nanomolar range, like certain anti-CD4 monoclonal antibodies, inhibit syncytium formation and HIV infection by binding gp120-expressing cells. Perhaps more importantly, class II specific T-cell interactions are uninhibited by soluble CD4 protein, whereas they are virtually abrogated by equivalent amounts of anti-T4 antibody. This may reflect substantial differences in CD4 affinity for gp120 and class II MHC.

Animals↗
PubMed1988

Cis-acting sequences responsive to the rev gene product of the human immunodeficiency virus.

Expression of high levels of the structural proteins of the human immunodeficiency virus type 1 (HIV-1) requires the presence of two regulatory genes, the trans-activator (tat), and the regulator of virion protein expression (rev. previously called art or trs). The experiments described here show that expression of virion proteins is dependent upon a small region located in the envelope gene called the cis-acting antirepression sequence (CAR). The CAR region of the envelope sequence is both necessary and sufficient for rev-dependent capsid protein expression. The experiments also show that a defect in either rev or CAR results in a dramatic decrease in the accumulation of the genomic and envelope mRNAs and an overproduction of more extensively spliced viral mRNA species.

Base Sequence↗
PubMed1987

Functional regions of the envelope glycoprotein of human immunodeficiency virus type 1.

The envelope of the human immunodeficiency virus type 1 (HIV-1) plays a central role in the process of virus entry into the host cell and in the cytopathicity of the virus for lymphocytes bearing the CD4 molecule. Mutations that affect the ability of the envelope glycoprotein to form syncytia in CD4+ cells can be divided into five groups: those that decrease the binding of the envelope protein to the CD4 molecule, those that prevent a post-binding fusion reaction, those that disrupt the anchorage of the envelope glycoprotein in the membrane, those that affect the association of the two subunits of the envelope glycoprotein, and those that affect post-translational proteolytic processing of the envelope precursor protein. These findings provide a functional model of the HIV envelope glycoprotein.

Amino Acid Sequence↗
PubMed1987

Inhibition of human immunodeficiency virus syncytium formation and virus replication by castanospermine.

Castanospermine (1,6,7,8-tetrahydroxyoctahydroindolizine) is a plant alkaloid that modifies glycosylation by inhibiting alpha-glucosidase I. Castanospermine is shown to inhibit syncytium formation induced by the envelope glycoprotein of the human immunodeficiency virus and to inhibit viral replication. The decrease in syncytium formation in the presence of castanospermine can be attributed to inhibition of processing of the envelope precursor protein gp160, with resultant decreased cell surface expression of the mature envelope glycoprotein gp120. In addition, castanospermine may cause defects in steps involved in membrane fusion after binding of CD4 antigen. The antiviral effects of castanospermine may be due to modifications of the envelope glycoprotein that affect the ability of the virus to enter cells after attachment to the CD4 cell receptor.

Alkaloids↗