PubMed Health⌕ Search

Biomedical subjects

T Ksiazek

Publications and source records attributed to T Ksiazek.

At least 19 recordsLinked to original sources
PubMed1995

Cross-neutralization of hantaviruses with immune sera from experimentally infected animals and from hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome patients.

Plaque-reduction neutralization tests were done with eight of nine known representative hantaviruses and immune sera from experimentally infected animals and from patients with hemorrhagic fever with renal syndrome (HFRS) or hantavirus pulmonary syndrome (HPS). Results obtained with animal sera demonstrated each virus to be antigenically unique. Neutralization with the HPS patient sera was highest with Sin Nombre (SN) virus and to a lesser extent with Black Creek Canal (BCC) virus. Sera from Korean HFRS patients reacted best with Hantaan virus, but cross-reactivity with all other viruses except Thottapalayam (TPM) virus was also observed. Sera from Swedish HFRS patients reacted best with Puumala virus but cross-reacted with Prospect Hill, SN, and BCC viruses and to a lesser extent with all of the other viruses except TPM virus.

Animals↗
PubMed1994

Enzyme-linked immunosorbent assay using a recombinant baculovirus-expressed Bacillus anthracis protective antigen (PA): measurement of human anti-PA antibodies.

We developed an antigen capture enzyme-linked immunosorbent assay (ELISA) which does not require purified protective antigen (PA) for detection of human antibodies to Bacillus anthracis PA. Lysates of Spodoptera frugiperda (Sf-9) cells infected with recombinant baculovirus containing the PA gene were used as the source of PA to develop the ELISA. Recombinant PA from crude Sf-9 cell lysates or PA purified from B. anthracis Sterne strain was captured by an anti-PA monoclonal antibody coated onto microtiter plates. We demonstrated that human serum antibody titers to PA were identical in the ELISA whether we used crude Sf-9 cell lysates containing recombinant baculovirus-expressed PA or purified Sterne PA. Finally, false-positive results observed in a direct ELISA were eliminated with this antigen capture ELISA. Thus, the antigen capture ELISA with crude preparations of baculovirus-expressed PA is reliable, safe, and inexpensive for determining anti-PA antibody levels in human sera.

Animals↗
PubMed1990

[Epidemic of Rift Valley fever in the Islamic republic of Mauritania. Geographic and ecological data].

During and after the Rift Valley Fever epidemic in southern mauritania, we conducted epidemiological inquiries in order to determine epidemic and epizootic areas. The epidemic area was divided into two different zones. The first was located along the right bank of the Senegal River, around the town of Rosso. The second was located near the town of Kaedi. This epidemic area was included within the epizootic area, which stretched to the south, between Rosso and Saint-Louis. Several ecological changes had occurred in the recent past including erection of dams on the Senegal River for irrigation, and heavier rainfall than during previous years.

Animals↗
PubMed1990

[Evaluation of indicators of health in the area of Trarza during the epidemic of Rift Valley fever in 1987].

Randomized epidemiological studies conducted inside the Rift Valley fever epidemic area permitted an estimate of the different epidemiological rates. For the town of Rosso, the total number of infected persons was estimated at 9,320, the total number of symptomatic diseases at 1,013 and the number of deaths at 47. The minimal number of deaths for the area which had access to the hospital was 232. The immunity rate in the town was 34.89% after the epidemic. The ELISA test was used to test human and animal IgG and IgM antibodies. Human samples were collected using the "confetti" technique. After the epizootic the incidence was 36.9% and the immunity was 70.06% for animals sampled in the town.

Animals↗
PubMed1983

Application of optical diffractometry in studies of cell fine structure. Comparison of arterial smooth muscle cells in contractile and synthetic state.

Arterial smooth muscle cells in contractile and synthetic state were analyzed by optical diffractometry. Cell sections (80-90 nm) were photographed in an electron microscope and diffraction patterns of the plates (negatives) were produced using a helium-neon laser. Radial and angular distributions of light intensity in the diffractograms were measured and digitized using an electronic detector plate consisting of ring- and wedge-shaped photosensitive elements; radial distributions provide information about size of structures and distances between them and angular distributions about spatial orientation of structures in the images. Micrographs of nuclei and cytoplasm were analyzed separately (40-50 plates in each group). Computerized statistical analysis of radial distributions of light intensity showed that the nuclear chromatin pattern differed between cells in contractile and synthetic state. The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 96.5% of the cases. Analysis of radial distributions of light intensity similarly showed marked differences in cytoplasmic structure between cells in contractile state (dominated by bundles of myofilaments) and synthetic state (dominated by cisternae of rough endoplasmic reticulum). The probability that the observed difference could have arisen purely by chance was less than 10(-5). Computer-aided classification to the a priori known cell group was correct in 92.0% of the cases. In contrast, analysis of angular distributions of light intensity did not indicate any statistically significant differences between contractile and synthetic state cells. A likely reason is that both myofilaments and cisternae of rough endoplasmic reticulum were arranged in parallel. The results demonstrate that optical diffractometry is a useful method for image analysis in studies of cell fine structure. It provides information about size and orientation of structures with poorly defined shape and is particularly well suited for studies on cell differentiation and effects of pharmacological and other experimental treatments on cell fine structure. It represents an alternative and a complement to stereology for quantitative and objective evaluation of morphological data.

Animals↗
PubMed1983

Demonstration of stimulatory effects of platelet-derived growth factor on cultivated rat arterial smooth muscle cells. Differences between cells from young and adult animals.

The effects of platelet-derived growth factor (PDGF) on DNA synthesis and proliferation in cultures of arterial smooth muscle cells obtained from young and adult rats, respectively, were measured. Addition of 10-20 ng/ml of PDGF to medium MCDB 104 induced DNA synthesis in quiescent cultures of cells from young animals to a similar extent as 10-20% whole blood serum (WBS). PDGF further stimulated proliferation of the cells in medium MCDB 104, although less markedly than 10% WBS. Antibodies against PDGF partially inhibited the growth response after stimulation with serum. This shows that PDGF is a major growth factor in serum for these cells and that PDGF can promote entrance into and passage through S phase and mitosis independent o plasma factors. Cells from adult animals were also found to respond to PDGF, although a higher concentration (25 ng/ml) was required to obtain a maximum effect. These cells, however, responded better than cells from young animals to stimulation with serum. Further, antibodies against PDGF did not inhibit the growth-stimulatory effect of serum to any appreciable extent. Thus, serum contains growth factors other than PDGF that stimulate preferentiaLly the proliferation of smooth muscle cells from adult animals.

Aging↗
PubMed1983

Endocytosis of cationic and anionic proteins in cultivated arterial smooth muscle cells.

Confluent secondary cultures of rat arterial smooth muscle cells were exposed to cationic and anionic derivatives of ferritin and horseradish peroxidase and studied electron microscopically in order to clarify the influence of molecular net charge on surface binding and endocytosis of proteins. The cationic markers bound uniformly to the plasma membrane. They were then ingested by membrane invagination and via small vesicles transported to lysosomes and the Golgi complex. These organelles were both labelled already after 30 min of incubation. With longer exposure times (2-4 h), an increasing accumulation within the lysosomes was observed, whereas the labelling of the Golgi complex decreased. In spite of continued interiorization of plasma membrane carrying the cationic markers, the cells retained their ability to bind the latter to the surface. The anionic markers did not bind to the cell surface, were taken up in the fluid phase, and later observed only in lysosomes. If assuming that the cationic and anionic proteins serve as markers for the plasma membrane and fluid phase, respectively, but do not affect the intracellular path of interiorized membrane, these results indicate that the endocytic vesicles fuse with and empty their content into lysosomes and that part of the incoming membrane subsequently is transferred to the Golgi complex for possible recirculation back to the cell surface. If, on the other hand, the net charge of the exogenous marker influences the path of the vesicles, there may exist more than one recovery route for membrane interiorized by endocytosis.

Animals↗
PubMed1983

Leu 7+ (HNK-1+) cells. I. Selective compartmentalization of Leu 7+ cells with different immunophenotypes in lymphatic tissues and blood.

In the present immunohistochemical studies, Leu 7+ (HNK-1+, human natural killer and killer) cells were found to occupy preferentially germinal centres of follicles in lymph nodes and tonsils. Leu 7+ cells were also present in germinal-like zones of spleen follicles and in mantle zones of hyperplastic thymus follicles and varied in localization in lymph nodes involved in different types of follicular centre cell-derived malignant lymphomas. Most of the Leu 7+ cells in the follicles expressed the Leu 3 (helper/inducer) marker. Double staining studies of tonsil sheep erythrocyte-rosetting and peripheral blood mononuclear cell suspensions showed that two main, mutually complementary, subpopulations of Leu 7+ cells could be distinguished in both cases, namely Leu 7+/Leu 4+ (subdivided into Leu 2+ (suppressor/cytotoxic) and Leu 3+) and Leu 7+/Leu 4-, including mostly cells with OKM 1 (myelomonocytic) characteristics. Thus, in the tonsil cell suspension the cells with Leu 7+ Leu 3+/OKM 1- immunophenotype strongly predominated, whereas among peripheral blood mononuclear cells Leu 7+Leu 2+/OKM 1- and Leu 7+/OKM 1+ immunophenotypes were mostly observed.

Antibodies, Monoclonal↗
PubMed1983

Leu 7+ (HNK-1+) cells. II. Characterization of blood Leu 7+ cells with respect to immunophenotype and cell density.

In the present study, combined methods (indirect immunofluorescence with monoclonal antibodies, Percoll density fractionation, FACS analysis, and the cytotoxicity test) were used for further characterization of peripheral blood Leu 7+ cells (human NK and K cells). The Leu 7+ cell content was found to be relatively higher in the low-density cell fraction in which cells of large granular lymphocyte morphology predominated. However, Leu 7+ cells were also present in intermediate and high-density fractions. Low-density Leu 7+ cells were characterized by both Leu 2 (T suppressor/cytotoxic) and OKM1 (myelomonocytic) markers, whereas among high-density Leu 7+ cells the Leu 2 phenotype strictly predominated. Depletion of OKT3+ cells from the non-adherent cell population caused a decrease of cells with T helper and T suppressor phenotypes but did not have this effect on Leu 7+ and OKM1+ cells. After depletion of Leu 7+ cells from the OKT3- population the content of both T suppressor and OKM1+ cells decreased. Both the present results and previous reports enable us to conclude that two main Leu 7+ cell subpopulations are present in blood, namely Leu 7+Leu 2+/Leu 4+ and Leu 7+/OKM1+ cells. The presence of small and large Leu 7+ cells was also shown by FACS analysis.

Cell Separation↗
PubMed1983

Phenotype modulation in primary cultures of arterial smooth muscle cells. On the role of platelet-derived growth factor.

Smooth muscle cells were isolated from adult rat aorta by collagenase digestion, grown in primary culture in the presence of 10% whole blood serum (WBS), and studied by quantitative electron microscopy and thymidine autoradiography in order to correlate cellular fine structure and proliferation. On day 2-4, the cells passed through a structural transition from contractile to synthetic state. In the former they were characterized by predominance of cytoplasmic microfilament bundles and in the latter by an extensive rough endoplasmic reticulum (RER) and a large Golgi complex. The disappearance of the microfilament bundles was accompanied by a transient increase in lysosomal volume density but no signs of bulk autophagy. This suggests that microfilaments were disassembled into subunit proteins and that lysosomes were engaged in adjusting the pool of free subunits into a new equilibrium. RER cisternae grew out from the nuclear envelope and successively spread throughout the cytoplasm. Stacks of Golgi cisternae were organized in a circumscribed juxtanuclear region. The structural modulation occurred also in medium containing 10% plasma-derived serum (PDS). Its onset was delayed by addition of antibodies (50 micrograms/ml) against platelet-derived growth factor (PDGF) to 10% WBS-medium and speeded up by addition of purified PDGF (25 ng/ml) to 10% PDS-medium. Otherwise, the kinetics of the structural modulation was the same in all experimental groups. The observations could not be explained by overgrowth of contaminating fibroblasts since (1) successive steps in the process were clearly evident, (2) the cells surrounded themselves by an incomplete basement membrane, a characteristic feature of smooth muscle, and (3) mitomycin C blocked cell growth but not conversion from contractile to synthetic state. After 3-4 days of culture in 10% WBS-medium, active DNA synthesis and cellular proliferation were initiated as determined autoradiographically and by cell counting. Electron microscopic autoradiography showed that all cells were morphologically in the synthetic state at the time of entrance into S-phase. Initially, the cells grew at a lower rate in the presence of PDGF antibodies but after 5-6 days of culture attained a rate similar to that in the controls. No distinct proliferation was obtained in 10% PDS-medium unless purified PDGF (10 ng/ml) was added during the first days of culture. The results suggest that the structural modulation of the smooth muscle is an absolute but not sufficient prerequisite for cellular proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1983

Cell surface components and growth regulation in cultivated arterial smooth muscle cells.

The surface of rat arterial smooth muscle cells was characterized with respect to some of its chemical and functional properties. The effects of selective enzymic degradations (hyaluronidase, chondroitinases, heparitinase or neuraminidase) on [35S]sulphate-prelabelled cells and on binding sites for cationized ferritin (CF) were examined to assess the presence and relative importance of individual species of macromolecules on the cell surface. The results indicate that about half of the strongly anionic sites on the cell surface (binding CF at pH 2.0) could be ascribed to sulphate groups of glycosaminoglycans and about half to carboxyl groups of sialic acid residues in glycoproteins and/or glycolipids. Weaker anionic sites (binding CF at pH 7.0) largely originated from carboxyl groups of glycosaminoglycans. Chondroitin sulphate and heparan sulphate were the main glycosaminoglycans. The surface of cells from young animals showed a higher glycosaminoglycan and a lower sialic acid content than that of cells from adult animals. Continuous treatment of the cultures with neuraminidase stimulated serum-induced initiation of DNA synthesis, while treatment with hyaluronidase or heparitinase inhibited it. Addition of hyaluronic acid, heparin or heparan sulphate to the culture medium inhibited initiation of DNA synthesis as well as cell proliferation. The effect was more marked in cultures of cells from young animals than from adults, although the latter cells were found to grow at a higher rate and to higher densities. These results suggest a role for cell-surface and pericellular glycoconjugates in growth regulation. A possible mechanism of action is that these molecules, due to their anionic charge or by steric exclusion, interfere with the binding of platelet-derived growth factor, a highly cationic polypeptide, to its cell-surface receptor.

Animals↗