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Biomedical subjects

J Litwin

Publications and source records attributed to J Litwin.

At least 19 recordsLinked to original sources
PubMed1997

Intensive venous sampling of adrenocorticotropic hormone in rats with sham or paraventricular nucleus lesions.

Adrenocorticotropic hormone (ACTH) secretion from the anterior pituitary is predominantly regulated by corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) synthesized in neurons of the paraventricular nucleus (PVN) of the hypothalamus. Secretion of ACTH occurs in pulsatile bursts. To explore the relationship between hypothalamic control and the pulsatile pattern of ACTH secretion, we measured ACTH in 2 min blood samples over 4 h in rats with intact and lesioned PVN during hypovolemic-stress or control conditions and also measured median eminence (ME) levels of CRH, AVP, and oxytocin (OT). Mean plasma ACTH was highest in the sham lesioned-hypovolemic group, lowest in the sham lesioned-control group and intermediate in the two PVN-lesioned groups. CRH in the ME was negligible in the lesioned animals and correlated with OT and AVP. Pulsatile secretion was observed despite PVN ablation. Visual inspection of composite time series suggested different temporal patterns of ACTH secretion. Principal components analysis of the individual ACTH time series revealed three significant eigenvectors which correlated differentially with the three treatment groups. Neither lesioned group had the steep rise over 10 min seen in plasma ACTH in the non-lesioned groups. Delayed ACTH rise after 30-60 min occurred in all but the sham control group. Our data suggest that CRH is responsible for immediate secretion of ACTH in response to hypovolemic stress and that regulators from non-PVN sites may be responsible for more delayed secretion of ACTH in this setting. The persistence of ME AVP and OT levels in the face of > 90% reduction in ME CRH levels leaves open the question of a role for one or both of these peptides in the delayed ACTH response following stress onset and in the generation of pulsatile ACTH secretory bursts.

Adrenocorticotropic Hormone↗
PubMed1992

The growth of Vero cells in suspension as cell-aggregates in serum-free media.

Vero cell lines, usually considered anchorage-dependent, could be grown as cell-aggregates in suspension culture with serum-free media. Several different combinations of base media gave growth results above 10(6) cells/ml (NCTC 135:SFRE 199-1; NCTC 135:Waymouth MB 752/1; NCTC 135:RPMI 1640). Insulin was not essential for growth and Bovine Serum Albumin could be diluted out of the media if linoleic acid was present. The size and density of the aggregates formed varied depending on the media used.

Animals↗
PubMed1991

Serum-free medium for fermentor cultures of hybridomas.

Hybridomas lend themselves particularly well to large scale cultivation techniques since they grow as single cells in suspension without requiring attachment to a substrate. Furthermore, many cell strains have been adapted to grow in serum-free (SF) media to a similar cell density and antibody production as in serum containing media. This review will concern itself mainly with the cultivation of hybridomas in SF-media in bioreactors of various types with the ultimate goal of producing large quantities of monoclonal antibodies (mAb).

Animals↗
PubMed1987

The growth of polio virus in human diploid fibroblasts grown with cellulose microcarriers in suspension cultures.

Human diploid fibroblasts have been successfully grown with cellulose fiber microcarriers in suspension giving values of between 1 to 2 X 10(6) cells/ml. When infected with polio virus type 1 titers were obtained which were at least as good or better than those obtained with monkey kidney cells and similar to that obtained with Vero cells. Good results were also obtained using conventional microcarriers such as Cytodex, Biosilon and Gelibeads. Our results suggest that many of the technical difficulties in growing human diploid fibroblasts on microcarriers can be overcome allowing these cells to be a favourable alternative to heteroploid cells as a substrate for viral vaccine production.

Biotechnology↗
PubMed1985

The growth of human diploid fibroblasts as aggregates with cellulose fibres in suspension.

Human diploid fibroblasts can grow as small cell masses in aggregation with cellulose fibres in suspension but not as conventional monolayers on the surface of the fibres. Using Eagle's MEM with 10% calf serum and various anionic cellulose exchangers in suspension, added human fibroblasts build aggregates of cells with the cellulose fibres enmeshed within these clumps. A concentration of 3 mg cellulose per ml inoculated with between 1 X 10(5) to 1.3 X 10(5) cells per mg cellulose gave an estimated yield of at least 1.5 X 10(6) cells per ml after 7 to 8 days incubation. Cell growth was measured as an increase in protein by a modification of Lowry's method.

Cell Aggregation↗
PubMed1985

Further studies on a tryptose based serum-free medium for human diploid fibroblasts.

A serum-free medium containing Eagle's MEM, transferrin, tryptose and dexamethasone as active ingredients was able to support the growth of human diploid fibroblast cells for over 20 population divisions. However, the cells stopped growing at an earlier age and the growth rate was half that of cells grown in Eagle's MEM + 10% calf serum. The results of efforts to improve this medium show that: the addition of insulin to the medium is not required, but dexamethasone is absolutely essential; there is an antagonism between adenosine and cytidine which is inhibitory for growth; the addition of extra amino acids such as arginine, lysine, methionine, tryptophane, phenylalanine, isoleucine, cystine, serine or hydroxyproline is inhibitory for growth.

Amino Acids↗
PubMed1983

Deficiency of short-lived suppressor cells controlling T-lymphocyte colony formation in acute lymphoblastic leukemia.

Short-lived suppressor cell (SLSC) activity controlling T-lymphocyte colony formation in vitro was evaluated in patients with acute lymphoblastic leukemia (ALL). No SLSC activity was found in patients in acute phase of the disease. On the other hand, patients in remission frequently had higher SLSC activity than controls. No correlation between colony count and thymidine incorporation as well as T-cell numbers was found in ALL patients.

Adolescent↗
PubMed1980

Preliminary results on the use of human diploid fibroblasts for inactivated polio virus vaccine production.

Human diploid fibroblast strains WI-38 and MRC 5 can be routinely grown in Eagles medium to densities between 2x10(5) and 1x10(5) cells/cm2. Polio virus type 1 grew to higher titers in WI-38 than MRC 5; types 2 and 3 grew equally well in both strains. After inactivation with 5 mM formaldehyde at 30 degrees C immunogenicity values were obtained which compared favourably with those obtained from monkey kidney preparations.

Antibodies, Viral↗
PubMed1979

Clonal proliferation of lymphoid and myeloid progenitor cells in patients with hematological abnormalities.

Myeloid and lymphoid stem cell colony formation (GM-CFU) and L-CFU) was studied in patients with lymphoproliferative diseases, aplastic anemia and other hematological abnormalities. Most patients with acute lymphatic leukemia had low number of L-CFU with decreased or normal GM-CFU, while in Hodgkin's disease and chronic lymphatic leukemia L-CFU growth was very poor with only minor abnormalities of GM-CFU formation. Aplastic anemia was characterized by a decreased GM-CFU and normal L-CFU. Coculture studies suggested that a diminished colony formation may be linked to circulating lymphocytes that inhibit L-CFU as well as the reduction in number of precursor cells.

Adult↗
PubMed1979

Necessary amino acids and vitamins for the growth of human diploid fibroblasts.

Only 2 amino acids and one vitamin were found to be essential for the growth of human embryonic diploid lung fibroblasts when 10% undialysed calf serum was used as a medium supplement. These amino acids were either glutamine + cysteine or serine + homocysteine. Replacing cysteine or homocysteine with cystine or homocystine, respectively, reduced growth. The growth rate in the glutamine + cysteine medium was slightly less than that in Eagle's medium, but the in vitro life time was similar. Folic acid was the only vitamin needed to support cell growth in vitro. The addition of other vitamins had no stimulatory effect with the possible exception of nicotinamide. When other amino acids were added to glutamine + cysteine none showed stimulatory effects but tryptophan was either toxic or inhibitory for the 3 human diploid strains examined. Serine was inhibitory for WI-38 but not for MRC5 cells. Subtle nutritional differences appear to exist between fibroblasts of the same type obtained from different embryos.

Amino Acids↗