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Biomedical subjects

A Lazar

Publications and source records attributed to A Lazar.

At least 55 records · Page 3Linked to original sources
PubMed1991

Immobilization of animal cells in fixed bed bioreactors.

Immobilization of animal cells has become a highly popular means of achieving high-density animal cell cultures. The advantages of immobilization are that it stabilizes cells in culture and enables long-term culture periods to be achieved. Immobilization increases cell productivity by increasing the usable substrate surface area for anchorage-dependent cells, or by facilitating perfusion of anchorage-independent cells. A method for production of secreted biological products from anchorage-dependent and independent cells is described. The method is based on immobilization of animal cells within the polymeric matrix of polyurethane foam, packed in a fixed bed bioreactor.

Journal Article↗
PubMed1991

Long term variceal sclerotherapy: is endoscopic sclerosis a unique therapeutic approach and a true alternative to surgery?

Endoscopic sclerotherapy has been used to control acute variceal haemorrhage which persists despite conservative therapy, prevent recurrent variceal haemorrhage in patients with a history of oesophageal haemorrhage, and to prevent a haemorrhage in patients with oesophageal varices who never bled. In this short paper I will cover our personal experience with more than 2000 patients receiving particularly paravariceal endoscopic sclerotherapy of bleeding esophageal varices, and especially present the results of our prospective and controlled randomized trials (Table 1) and underline the thesis that endoscopic sclerotherapy and surgical procedures for patients with portal hypertension are complementary supporting measures or options.

Acute Disease↗
PubMed1991

[Elective-selective Warren splenorenal shunt operation. Prognosis of liver function and esophageal varices hemorrhage after repeat sclerotherapy in liver cirrhosis].

From March 1st, 1982 to March 1st 1990 399 patients were admitted to the Heinz-Kalk-Hospital with recurrent bleeding from esophageal varices. Therapy of first choice was acute or elective endoscopic sclerotherapy. Early recurrences and uncontrollable hemorrhage were treated by Linton-Nachlas tube or if unsuccessful by devascularisation procedure. Two early or late bleeding recurrences were defined as sclerotherapy failures and choosen after passing a selection analysis (liver volume 1000 to 2500 ml, portal perfusion more than 30%, liver biopsy without activity or progression, exclusion of stenosis in the arterial supply of the liver and Child-Pugh classification A and B) for a selective-elective splenorenal Warren shunt (SRS). In 10 of 44 selected patients (11%) with an underlying disease of intrahepatic block in 95%, mostly alcoholic origin (65%) intraoperatively the performance of an SRS was technically problematic or impossible. Therefore, a mesocaval interposition shunt was carried out. Early mortality of 34 SRS was 5.9% (2 patients) and late mortality 17.6% (6 patients). No encephalopathy and shunt thrombosis were recorded. Postoperative angio- and sequential scintigraphies proved that portal perfusion was preserved during the first two years, but diminished. Liver function remained stable, too. One case of early rebleeding could be successfully managed by emergency endoscopic sclerotherapy. Five- and eight-years survival rate, according to the method of Kaplan-Meier is about 70%. We conclude that the SRS is the treatment of choice for elective management of recurrent bleeding of esophageal varices refractory to sclerotherapy. Its performance should be not enforced; in case of technical difficulties narrow-lumen mesocaval interposition shunt is an excellent alternative.

Adolescent↗
PubMed1991

The development of the subconcepts of death in young children: a short-term longitudinal study.

A short-term longitudinal design and the probabilistic latent class method of analysis were used to study the development of young children's understanding of death. 99 first and second graders were interviewed individually in the fall and spring. The results support the notion that the subconcepts of death--irreversibility, cessation, causality, and inevitability--need to be studied separately and in relation to one another. Children first understand the subconcepts of irreversibility and inevitability. Development of these subconcepts does not seem to be conditional on each other. However, at least one of these subconcepts must be understood before the child understands the subconcepts of cessation or causality. The pattern of development of these subconcepts is different when the referent object is human versus animal. The overall methodology offers promise in understanding the development of these concepts in young children.

Attitude to Death↗
PubMed1990

[Surgical measures in recurrent hemorrhage from esophageal and gastric varices after sclerotherapy--a prospective study].

From Jan 1, 1982 to Jan 1, 1990 692 patients were admitted because of acute or recurrent hemorrhage from esophagogastric varices. Initial management was endoscopic sclerotherapy. 14 pat. were excluded. In 26 of 311 Child-Pugh C-patients a gastroesophageal disconnection and in 5 because of a portal pressure over 30 mmHg a narrow-lumen mesocaval interposition shunt (NLMCS) were performed because of uncontrollable hemorrhage. Hospital mortality was 31%. 182 pat. belonged to Child-Pugh class A and 185 to B. In 194 long-term injection sclerotherapy was successful; 173 were sclerotherapy failures and selected for shunt operation at the end of the selection analysis. 85 refused shunt operation or did not fulfill selection criteria. Thus, 88 pat. were shunted mainly by NLMCS and distal splenorenal shunt. Sclerotherapy and shunt group were comparable. Hospital mortality showed no difference. Five year life-expectancy was significantly higher in shunted patients. Thus, in sclerotherapy failures early a shunt-indication should be discussed.

Esophageal and Gastric Varices↗
PubMed1987

Microcarriers as a culturing system of insect cells and insect viruses.

There is an increasing interest in culturing of insect cells, which are host for arthropod-born (Arbo) viruses. The potential applications of Arbo viruses are in the following two main fields: 1. Medical applications (e.g. preparation of viral vaccines and viral antigens for diagnostic purposes). 2. As bioinsecticides in pest control in horticulture, agriculture and forestry. One of the potential cell substrates for these applications is an anchorage-dependent-mosquito cell line established from embryonic tissues of Aedes aegypti (AA). The following areas were investigated in the reported research with the AA cell line: The AA cells were successfully propagated in microcarrier (MC)-culturing-systems. Of the tested MC's the cellulose-based microgranular MC (DE-53 of Whatman, having an exchange capacity of 2 meq/g) was found to be the best MC. Cells grew in MCs-cells aggregates in submerged spinner culture. The AA-MC's culture was successfully scaled-up to 8 litre culture volume. "Trypsinization" of the AA cells from the MC surface is successfully done by RDB, a dispersion agent from a plant origin (produced and marketed at the author's Institute). Other known dispersion agents (trypsin, collagenase, pronase) failed to disperse the AA cells from the MC. A serum-free medium was developed for culturing the AA cells on the DE-53 MC's. Bovine serum albumin was the main serum substituant in the developed medium. Arboviruses, from the Toga group, were grown in the AA-MC culture. Sindbis virus (from alpha-group) and West Nile virus (from the Flavi group), chronically infected the AA cells, which continuously produce and liberate these two viruses.(ABSTRACT TRUNCATED AT 250 WORDS)

Aedes↗
PubMed1987

Production of carcinoembryonic antigen from a human colon adenocarcinoma cell line. II. Use of monoclonal antibodies to carcinoembryonic antigen for antigen purification and characterization.

Monoclonal antibodies (McAbs) were prepared against carcinoembryonic antigen (CEA), derived from human metastases to the liver of primary colon adenocarcinoma. A stable clone, secreting monoclonal anti-CEA antibody (Ab), was selected. The hybridoma cells were grown in BALB/C mice, forming ascites fluids containing 2-5 mg/ml of the relevant McAbs. Ascites fluids were purified using a DEAE-Sephacel column. The purified immunoglobulin fraction was characterized as IgG2b, having a dissociation constant of 2 X 10(-9)M. The potential use of these McAbs for CEA diagnosis and purification was evaluated: the IgG2b fraction, when bound to Sepharose 4B, facilitated the purification of CEA from spent media of a human colon adenocarcinoma cell line, resulting in iodination grade CEA; the anti-CEA McAbs demonstrated differential histochemical staining of various sections, both fresh and fixed; the McAbs were also found to be suitable as tagging Abs in a CEA RIA.

Adenocarcinoma↗
PubMed1987

Production of carcinoembryonic antigen from a human colon adenocarcinoma cell line. I. Large-scale cultivation of carcinoembryonic antigen-producing cells on cylindric cellulose-based microcarriers.

A continuous cell line from a human colon carcinoma, designated HuCC1-14, was successfully grown on cyclindrical cellulose microcarriers (MC) charged by DEAE. The cells grow on these carriers as large cell-MC aggregates and maintain high cell densities in submerged conditions for extended periods. HuCC1-14 cells secrete into the culture medium significant amounts of carcinoembryonic antigen (CEA). Maximum efficiency in CEA secretion occurred after the cells switched from logarithmic growth to stationary phase. At this state, high CEA levels could be obtained with low-serum medium which greatly facilitates subsequent product purification. The described method provides a system which can be scaled-up and produce this tumor-associated antigen in essentially unlimited amounts and reproducible quality for detection and monitoring of cancer patients.

Adenocarcinoma↗
PubMed1986

Interpersonal influences in adolescent drug use--the role of older siblings, parents, and peers.

Drawing data from the first year of a longitudinal study of 508 families with focal adolescents aged 11 to 13 years and their older siblings (14 to 18 years), the investigators examined the influence of older siblings' drug-using attitudes and behaviors, in comparison with parental and peer drug-using attitudes and behaviors, on focal adolescents' nonuse and use of substances. Older siblings are frequently a source of drugs and use substances with their young siblings, though peers remain the primary source and the most frequent coursers. For most substances, frequency of use was predicted by older sibling and peer substance use, each after controlling for the other. Parental drug use was found to be minimal in comparison to older siblings and peers. Findings relative to the potentially important role of older siblings in influencing their younger siblings' drug-using behavior are discussed.

Adolescent↗
PubMed1985

Studies on cell binding and internalization of human lymphoblastoid (Namalva) interferon.

The binding of iodinated human lymphoblastoid Namalva interferon to Namalva cells, to a human fibroblast cell strain (FS11), and to a bovine kidney cell line (MDBK) was characterized. Scatchard analysis of the binding data indicated the presence of about 1000-2000 receptors per cell and dissociation constants of the order of 0.1 to 0.01 nM. Two subspecies of Namalva interferon (16 K and 20 K), which differ in their antiviral activity toward bovine and human cells, were found to bind with the same affinity toward bovine MDBK cells but to differ in their affinity to human cells. Experimental results indicated that at 37 degrees C the bound interferon is internalized within 15 min after binding to Namalva cells, and then degraded in the lysosomes. Exposure of Namalva cells to interferon resulted in a 40% reduction of the number of cell surface receptors (down-regulation).

Animals↗
PubMed1985

Agarose-polyacrolein microsphere beads: a new microcarrier culturing system.

A new microcarrier (MC) culturing system for anchorage-dependent cells is described. The system is based on polyacrylein microspheres encapsulated in agarose and derivatized by various amino ligands. In practice, any protein or ligand with primary amino groups may be covalently bound to the microspheres through their aldehyde groups. The ease with which the beads may be derivatized enables the preparation of MC with desired surface properties for growing a variety of cells. In this model system the beads were derivatized by 2-(diethylamino)ethylamine (DEAE), diaminohexane (DAH), poly-L-lysine (PL), gelatin and collagen. The derivatized beads supported the growth of primary cells, diploid cell strains and established cell lines for biological studies as well as for production of various cell products.

Acrolein↗
PubMed1985

RDB--a new product of plant origin for cell culture dispersion.

RDB is a crude preparation extracted from a plant source. It is a very potent agent for dispersion of monolayer cell cultures as well as for the preparation of primary cell suspensions. It was found to be most effective in dispersing a wide range of animal and mosquito cells and dissociating neuronal and muscular tissue for primary cell cultures. RDB was also found to be useful for preparation of primary culture for chick embryo fibroblasts. After treatment with RDB cell viability was found to be 98% as compared to 85% in trypsin treated monolayer cultures. Routine dispersion of monolayer cultures with RDB does not have any negative effect on confluency of the newly split cultures. RDB was found to have no adverse effects on viral replication and plating efficiency of Rift Valley Fever Virus, Sindbis Virus and West Nile Virus.

Animals↗
PubMed1984

Purification and properties of the alpha-interferon receptor of human lymphoblastoid (Namalva) cells.

The interferon receptor was solubilized from human lymphoblastoid (Namalva) cell membranes with Triton X-100. It was purified by chromatography on wheat-germ lectin-Sepharose and hydroxyapatite and by affinity chromatography on interferon-hexanoyl-Sepharose. The partially purified receptor was analyzed by gel filtration on Sepharose 6B and by sucrose gradient sedimentation in the presence of 0.1% Triton X-100. Gel filtration analysis yielded a Stokes radius of 74 A for the receptor-Triton X-100 complex. Sedimentation in sucrose gradients revealed an heterogeneous pattern of distribution with a plateau of activity between 4 and 10 S. Removal of suspected lipid material and Triton X-100 by extraction with isoamyl alcohol resulted in an accelerated rate of receptor sedimentation in a sodium dodecyl sulfate-containing sucrose gradient. Under these conditions it manifested an apparent sedimentation coefficient of 13.6 S. The dissociation constants Kd derived from Scatchard analysis of binding data with the purified receptor were in the range of 0.2-0.5 nM.

Cell Line↗