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C Walker

Publications and source records attributed to C Walker.

At least 397 records · Page 22Linked to original sources
PubMed1982

Technical aspects of low 3H-thymidine incorporation by mitogen stimulated canine peripheral blood lymphocytes in vitro.

The value of [3H]-thymidine incorporation as a measurement for mitogen induced proliferation of dog peripheral blood lymphocytes (PBL) has been examined. The cells were cultured in RPMI 1640, enriched with 10% autologous plasma for 48 hours at 37 degrees C, 5% CO2 and 95% relative humidity. Under these conditions a great variability in [3H]-thymidine incorporation was observed. By analysis of CPM and number of activated cells (G1), it was found that comparable number of G1 cells were generated in human and dog PBL. Also, the membrane transport of thymidine was very similar for lymphocytes of the two species. Nevertheless, a low [3H]-thymidine incorporation by dog PBL was frequently seen, and this phenomenon could be related to a release of soluble substance(s) within the cultures. When the cultured cells were washed and resuspended in fresh medium immediately before pulsing, the expected CPM per G1 cell could be obtained. Since it has been described in the literature that macrophages can produce cold thymidine in macrophage enriched lymphocyte cultures, the in vitro response of non-adherent dog PBL was analyzed. Mitogen stimulation of such non-adherent cells resulted in CPM per G1 cells very similar to those obtained with washed cells. Based on these data, it is suggested that the production of cold thymidine might be one of the technical problems related to cultures of lectin stimulated dog PBL in vitro and it should be taken into consideration, if [3H]-thymidine incorporation is used as the only measure of lymphocyte proliferation.

Adult↗
PubMed1982

Human lymphocyte proliferation. I. Correlation between activated and proliferating T-lymphocytes.

The response of human peripheral blood lymphocytes to Con A and PHA has been analyzed by [3H]thymidine incorporation and cytofluorometry. Using the latter method, it is possible to quantitate the number of cells in the G0 phase (normal RNA and DNA content) and in the G1 phase (elevated RNA, but normal DNA content). A very high correlation is found between numbers of Con A or PHA-induced G1 cells and [3H]thymidine incorporation in healthy donors. This high correlation is found when culture medium is enriched with 10% autologous plasma or 10% AB-serum. The use of a recently developed defined serum-free medium (RPMI 1640 with albumin, alanine, transferrin, sodium selenite and zinc chloride), however, suggest that donors can be divided into two groups according to different medium requirements for PHA-stimulated lymphocytes. Because several immunoregulatory mechanisms at the level of T-lymphocytes take place in the G1 phase, it can therefore be expected that cytofluorometric analyses of lymphocytes in the various cell cycle phases may improve the interpretation of altered lymphocyte response to lectins and antigens.

Cell Cycle↗
PubMed1982

Evaluation of murine thymocyte stimulation using a defined culture medium.

The ability of RPMI 1640 enriched with FCS or AATSZ (L-alanine, BSA, human transferrin, zinc chloride, and sodium selenite) to support mitogen-induced activation (G0-G1 shift) and proliferation (G1-S shift) of thymocytes has been investigated. The two culture media were found to be equally supportive. In terms of viability, differences were detected in the number of recovered viable cells, but this could be related to alterations in adherent properties, rather than viability of the cells. For the examination of a PHA-induced proliferation, IL-1-containing suppernatants, deriving from normal or induced peritoneal macrophages, were prepared. The supportive capacity of these preparations showed no significant difference between AATSZ and FCS. Despite the excellent supportive capacity for the mitogen-stimulated thymocyte cultures, the AATSZ medium was not able to support all established cell lines tested. A T cell (MOLT 4F) and a macrophage cell line (SK 1) grew equally well in AATSZ- and FCS-enriched medium, but a B cell (U 266) and a null-cell line (Reh) did not proliferate at all. When cells from the latter two lines were cultured in AATSZ medium, they did not complete the RNA-synthesis required for DNA-synthesis, as judged by cytofluorography. From the experiments presented it is concluded that the AATSZ medium offers several advantages, such as easy standardization of culture conditions, and no essential disadvantages for studying mitogen-stimulated thymocytes in vitro. On the other hand, some lymphoid cell lines do require culture conditions that the AATSZ medium cannot provide.

Animals↗
PubMed1982

Sugar intake and weight and height of pupils of 16 years in South Africa ethnic groups.

In South African ethnic groups--Blacks. Indians, European-African-Malay, and whites--measurements were made on a total of 2037 pupils, aged 16 yr, of sugar intake, weight, and height. In the various subgroups there was no clear-cut trend for high sugar-consuming pupils (upper thirds), compared with low sugar-consuming pupils (lower thirds), to have greater mean weights and heights. presumably, high consumers of sugar eat less of nonsugar foods, and vice versa. In approximate gradings for habitual physical activity, a slight trend was apparent for those in upper thirds to have higher mean sugar intakes.

Adolescent↗
PubMed1982

Development of a serum-free defined culture medium for lymphoblast transformation tests of mouse spleen and thymus cells.

By analysis of thymidine uptake during the first 4 h of incubation and by examining the responsiveness of unfractionated mouse spleen cells upon mitogenic or allogeneic stimulation, some serum factors of major importance for in vitro cultivation of lymphocytes have been examined. Albumin and l-alanine are essential for the maximal preservation of the in vivo-initiated lymphocyte activity during the first hours of incubation in vitro. Transferrin plays a major role in the lymphocyte proliferation, induced by mitogens in vitro, and, finally, zinc and selenium exert a clear enhancing effect on the response to an allogeneic stimulation. The AATSZ medium (RPMI 1640 enriched with l-alanine, albumin, transferrin, zinc chloride, and sodium selenite) enables a proliferation of the same magnitude as or higher than FCS medium. The kinetics are the same, and the cell viability is comparable, but standardization is much simpler with AATSZ. This is primarily because FCS binds some mitogens and contains inhibitors. Consequently, the standardization of such a culture system is dependent on variations from serum batch to serum batch. On the other hand, the current composition of the AATSZ medium promotes the sticking capacity of T lymphocytes and does not support growth of all lymphoid cell lines. Consequently, this defined medium, although not yet suitable as optimal medium for all lymphocyte functions, can advantageously be used for short-term studies of most murine lymphocyte functional and cooperation studies in vitro.

Alanine↗
PubMed1982

L-serine degradation in Escherichia coli K-12: directly isolated ssd mutants and their intragenic revertants.

Two methods for the direct isolation of spontaneous ssd mutants of Escherichia coli K-12 strains are described; (i) by growth with L-serine as the carbon source, and (ii) by low-level kanamycin resistance. A newly isolated mutant had the same phenotype as the mutant described previously, including inefficient use of the glucose, inability to growth with succinate, altered transport characteristics, and altered resistance to certain growth effectors. Succinate-utilizing derivatives which appear to be intragenic are characterized in detail. The relation between the mutants isolated here and mutants which are thought to have impairment in a system of coupling respiratory energy to active transport (ecfB mutants) is discussed.

Biological Transport, Active↗
PubMed1982

L-serine degradation in Escherichia coli K-12: a combination of L-serine, glycine, and leucine used as a source of carbon.

Escherichia coli K-12 strain CU1008 cannot use L-serine as the sole carbon source, but it could use L-serine as an auxiliary carbon source with glucose, L-alanine, or pyruvate and could derive energy from L-serine to support oxygen uptake. CU1008 grew with L-serine if it was also provided with glycine and leucine. These may act by increasing the available activity of L-serine deaminase; other explanations are also explored.

Energy Metabolism↗
PubMed1982

L-Serine deaminase activity is induced by exposure of Escherichia coli K-12 to DNA-damaging agents.

The synthesis of L-serine deaminase in Escherichia coli K-12 was induced after exposure of cells to a variety of DNA-damaging agents, including UV irradiation, nalidixic acid, and mitomycin C. Synthesis was also induced during growth at high temperature. A mutant constitutive for SOS functions showed an elevated level of L-serine deaminase activity. The response to DNA-damaging agents thus may be mediated via the SOS system.

Antibiotics, Antineoplastic↗
PubMed1981

Time course of chronic haloperidol and clozapine upon operant rate and duration.

Operant response rate and average response duration were recorded for two groups of six rats each responding under a FR 10 schedule of food reinforcement. Using a chronic dosing regime, the effects of haloperidol (0.5 mg/kg) on operant performance were evaluated in one group 2.5, 5.0, 7.5 and 10.0 h after drug treatment. The other group received clozapine (5.0 mg/kg) 1.0, 2.0, 3.0 and 4.0 h before data collection. For both drugs time since injection produced significant effects on both rate and duration: rate increased and duration decreased as a function of time after injection. Haloperidol tended to have a greater lengthening effect upon response duration than did clozapine. In addition, changes in behavior as a function of time after haloperidol injection were observed to approximate previously published pharmacokinetic data for haloperidol administered according to dosing regimens similar to those used here.

Animals↗
PubMed1981

Value of serial carcinoembryonic antigen determinations for early detection of recurrent cancer.

Carcinoembryonic antigen (CEA) has been monitored at intervals of approximately three months in patients who had undergone potentially curative surgery for breast cancer, head and neck cancer, lung cancer, and colorectal cancer, but who were considered to be at high risk of recurrence. Monitoring of CEA in patients' serum was of no value for the early detection of tumour recurrence in either breast or head and neck cancer patients. It was of value for the early detection of lung cancer recurrence, but these patients were always beyond the scope of cure. In colorectal cancer patients, two-thirds of recurrences were heralded by a rising CEA, but only one of 15 patients had disease confined to local tissues which could be totally excised, although a further three patients had liver metastases which were apparently localized to one lobe of the liver. For colorectal cancer patients, serial CEA estimations are an effective method for the early diagnosis of recurrence, although this seldom translates into improved patient benefit.

Breast Neoplasms↗
PubMed1981

A mutation affecting L-serine and energy metabolism in E. coli K12.

The effects of a pleiotropic mutation ssd are described. This mutation results in decreased efficiency in the use of glucose and fructose as carbon source, inability to use succinate or to grow anaerobically, an alteration in the activity of enzymes responsible for the synthesis and degradation of L-serine, increased resistance to certain antibiotics, and a deficiency in proline transport. This mutation resembles various previously described mutations thought to affect' energy coupling factor' and is located in the same region of the chromosome. While the gene product affected by this mutation is still unidentified, it is clear that L-serine metabolism cannot be understood merely in terms of providing L-serine and its derivatives.

Anaerobiosis↗
PubMed1981

Serum glycoproteins in diagnosis and monitoring of patients with large-bowel cancer.

The profile of serum glycoproteins is altered in malignancy with a relative increase in acute phase reactant proteins. A prospective study has been performed to investigate three sugar moieties (hexose, hexosamine and sialic acid) of these glycoproteins in the serum of large-bowel cancer patients as a possible guide to recurrence, and to compare these three variables with carcinoembryonic antigen (CEA). The three variables indicated the presence of colorectal cancer in over 65 per cent of 107 cancer-bearing subjects. Furthermore, the appearance of metastatic disease was associated with abnormalities in these variables in 10 of 11 patients, and appears more accurately reflected than with CEA. However, the three variables and CEA are cumulative in their value for predicting recurrent cancer. Monitoring of acute phase reactant proteins may therefore be of potential clinical benefit for monitoring of colorectal cancer patients at high risk of recurrence.

Carcinoembryonic Antigen↗
PubMed1980

Amnionitis with intact amniotic membranes involving Streptobacillus moniliformis.

A 23-year-old black woman was admitted to the hospital in premature labor with intact amniotic membranes. The patient was afebrile and did not have any obvious signs of infection. Gram stain of the amniotic fluid, obtained via transabdominal amniocentesis, revealed the presence of gram-negative rods. The bacterium was identified as Streptobacillus moniliformis, the agent of rat-bite fever.

Adult↗
PubMed1980

Introduction to cells in culture as studied by SEM.

The use of SEM to study cell surface topography though useful in many instances is a much stronger research resource when correlated with other techniques. This introduction to the symposium on cells in culture as studied by SEM will illustrate various experiments correlating high voltage electron microscopy with SEM and immunofluorescence microscopy with SEM. In addition, experiments will be discussed on the motile behavior and topography of cells on modified substrates, and the morphology of cellular outgrowth from tissue explants.

Animals↗