Search PubMed⌕ Search

Biomedical subjects

C Young

Publications and source records attributed to C Young.

At least 217 records · Page 12Linked to original sources
PubMed1989

The Agrobacterium tumefaciens virC1 gene product binds to overdrive, a T-DNA transfer enhancer.

In Agrobacterium tumefaciens, a cis-active 24-base-pair sequence adjacent to the right border of the T-DNA, called overdrive, stimulates tumor formation by increasing the level of T-DNA processing. Recent results from our laboratory have suggested that the virC operon which enhances T-DNA processing probably does so because the VirC1 protein interacts with overdrive (N. Toro, A. Datta, M. Yanofsky, and E. W. Nester, Proc. Natl. Acad. Sci. USA 85:8558-8562, 1988). We report here the purification of the VirC1 protein from cells of Escherichia coli harboring a plasmid containing the coding sequences of the virC locus of the octopine Ti plasmid. By gel mobility shift and DNase I footprinting assays, we showed that this purified virC1 gene product binds to overdrive but not to the right border of T-DNA.

Bacterial Proteins↗
PubMed1989

Australia's population: a long-term view.

Some general issues concerning current and future population trends in Australia are considered. The author argues against the need for continued high levels of population growth. She concludes that "the least disruptive path to eventual equilibrium is to maintain fertility near replacement level and to reduce the migrant intake to about one-third of the current level, i.e. to a net intake of about 50,000 per year."

Australia↗
PubMed1988

A comparative investigation of three methods of separation of CD4 and CD8 cells from human peripheral blood cells.

A comparison was made of the phenotypic purities and functional efficiencies of CD4 and CD8 cell subsets, separated by three methods. CD4 and CD8 monoclonal antibodies were used for positive and negative selection of T cells by (a) panning, (b) red cell rosetting, and (c) complement mediated killing techniques. The viability of the CD4 and CD8 cell subsets, separated by any of the three methods and assessed by the dye exclusion method, was greater than 95%. An inverse relationship was found between the yields and purities of the CD4 and CD8 cell subset. The most efficient separation of the T cells was achieved by positive selection using the rosetting method; 95.3 +/- 1.8% of the CD4 subset reacted with antibodies to CD4 and 1.4 +/- 0.5% with antibodies to CD8 antigens. The separated CD8 subset showed 90.7 +/- 0.4% reacting with CD8 and 3.5 +/- 1.3% with CD4 antibodies. This separation was slightly better than that achieved by the panning method. However, the positive methods of selection gave lower yields than the negative selection methods. The five CD4 and five CD8 cell subsets were assessed functionally by stimulating with a mitogen (phytohaemagglutinin), a bacterial antigen (purified protein derivative) and a viral antigen (herpes simplex virus). The results suggest that the uptake of [3H]thymidine is generally most efficient with the positively selected rosetting CD4 and CD8 cell subset.

Antibodies, Monoclonal↗
PubMed1988

Understanding the central processing limit in consistent-mapping visual search tasks.

Effects of load (i.e., the number of stimuli in the display) have been observed in multiple-frame studies using a consistent mapping of stimuli to responses (e.g., Fisher, 1982, 1984). In a series of four experiments, it is shown that these effects are not the consequence of differences across the high- and low-load conditions in either decision noise or peripheral masking. Additionally, it is shown that of two modes of limited capacity (a limited-channel and divided-capacity model) considered as possible explanations of load effects in tasks where subjects are required to locate a target, only one--the limited-channel model--is consistent with the results from all three location tasks. Finally, it is argued that the limited-channel model predicts not only the behavior observed in the four consistent-mapping experiments reported in this article but also the behavior observed in several related consistent-mapping tasks (Kleiss & Lane, 1986; Shiffrin & Gardner, 1972).

Attention↗
PubMed1988

Association of the virD2 protein with the 5' end of T strands in Agrobacterium tumefaciens.

The soil bacterium Agrobacterium tumefaciens can incite tumors in many dicotyledonous plants by transferring a portion (T-DNA) of its Ti plasmid into susceptible plant cells. The T-DNA is flanked by border sequences that serve as recognition sites for specific cleavage by an endonuclease that comprises two virD-encoded proteins (VirD1 and VirD2). After cleavage, both double-stranded, nicked T-DNA molecules and single-stranded T-DNA molecules (T strands) were present. We have determined that a protein is tightly associated with, and probably covalently attached to, the 5' end of the T strands. Analysis of deletion derivatives in Escherichia coli, immunoprecipitation, and a procedure combining immunoblot and nucleic acid hybridization data identified this protein as the gene product of virD2.

Bacterial Proteins↗
PubMed1988

CD4 and CD8 cell responses to herpes simplex virus in Behçet's disease.

The finding of part of the Herpes simplex virus type 1 (HSV1) genome in peripheral blood leucocytes of some patients with Behcet's disease (BD) led to investigations of T cell responses to HSV1 in this disease. A significantly impaired uptake of 3H-thymidine by CD4 cells was found in BD, as compared with healthy HSV1 sero-positive subjects. The impaired cellular response appeared to be specific to HSV1, as neither cytomegalovirus nor varicella-zoster virus showed depressed CD4 cell responses in BD. A similar impairment of CD4 cell responses to HSV1 was found in patients with recurrent herpetic infections, known to be caused by latent HSV1 infections. However, in rheumatoid arthritis which was selected as an unrelated autoimmune disease. 3H-thymidine uptake by CD4 cells stimulated with HSV1 was enhanced. CD8 cells showed generally rather a low uptake of 3H-thymidine, nevertheless, the values in BD and recurrent herpetic infection were again lower than those in sero-positive controls or rheumatoid arthritis. The results are consistent with the hypothesis that HSV1 might be involved in the immunopathogenesis of BD.

Adult↗
PubMed1987

Differential early rearing affects response to overfeeding in B6D2F2 mice.

Male and female B6D2F2 mice, reared in small (Sm = 4), medium (Md = 8) and large (Lg = 12) litters, were maintained on high-fat, high-carbohydrate (EXP) or chow (CH) diets beginning at 14 weeks. EXP mice consumed more calories and gained more weight than CH mice; these effects were greatest in the Sm animals. Each sex responded similarly. Caloric efficiency was highest in the Sm EXP and male animals. Total body fat in males showed that Sm greater than Md greater than Lg and EXP greater than CH. The thermogenic capacity was measured by total oxygen consumption and body temperature response during acute cold stress, and protein content and cytochrome c oxidase activity in interscapular brown adipose tissue (1BAT). Sm mice had a smaller decrease in temperature and consumed less oxygen per gram body weight than Lg, suggestive of a contributing role of increased insulation. When oxygen consumption was expressed as a function of body weight0.75, EXP greater than CH, but there were no other significant dietary effects. Neither litter size nor diet appeared to affect protein content or cytochrome c oxidase activity in 1BAT. These results show that early rearing experience effects both behavioural and physiological variables associated with the maintenance of adult body weight in mice, but these effects do not appear to be mediated through 1BAT.

Animals↗
PubMed1987

Control of the kilA gene of the broad-host-range plasmid RK2: involvement of korA, korB, and a new gene, korE.

Broad-host-range plasmid RK2 encodes several different kil genes which are potentially lethal to an Escherichia coli host. The kil genes and the essential RK2 replication gene trfA are regulated by the products of kor genes. We have shown previously that kilA can be controlled by a constitutively expressed korA gene. In this study, we have found that the wild-type, autoregulated korA gene is insufficient for control of kilA cloned on high-copy-number plasmids. One of two other genes must also be present with korA. One gene is korB, originally discovered by its ability to control the determinants in the kilB region and later found to affect expression of both trfA and korA. The other is a new gene, korE, which has been cloned from the 2.2' to 4.1' region located between korC and kilA. Studies with a kilA-cat fusion suggest that korA, korB, and korE all participate in the control of kilA gene expression.

Chromosome Mapping↗
PubMed1987

Initial clinical studies of piritrexim.

Piritrexim (PTX) is a second-generation, lipid-soluble inhibitor of dihydrofolate reductase (DHFR). Metabolic inhibition occurs within seconds after rapid diffusion into human cancer cells. We describe the initial phase I studies with iv and oral forms of this drug given on a daily basis for 5 days to patients with cancer. The dose-limiting toxicity is primarily hematologic (leukopenia, granulocytopenia, thrombocytopenia), but phlebitis is also encountered with iv administration and gastrointestinal problems (nausea, vomiting) with oral administration. Oral toxicity can be reduced by giving the daily dose in 2 divided doses. The maximum tolerated dose (MTD) for the iv route is 170 mg/m2 per day for 5 days; for the oral route it is 480 mg/m2 per day for 5 days. Unlike an earlier lipid-soluble folate antagonist, piritrexim did not cause neurologic or histamine-like disorders.

Administration, Oral↗
PubMed1986

The virD operon of Agrobacterium tumefaciens encodes a site-specific endonuclease.

Tumor formation by Agrobacterium tumefaciens involves the transfer and integration of a defined segment (T-DNA) of tumor-inducing (Ti) plasmid DNA into the plant nuclear genome. A set of plasmid genes outside the T-DNA, the vir genes, are thought to mediate the transfer process. We report here that the virD operon encodes a site-specific endonuclease that cleaves at a unique site within each of the 24 bp direct repeats that flank the T-DNA. The endonuclease function was further localized to the 5' end of this operon by demonstrating that cleavage does not occur in virD mutant strains of Agrobacterium and that the 5' end of the virD operon is sufficient to direct cleavage in E. coli. Analysis of nucleotide sequence and protein data indicate that two proteins of 16.2 and 47.4 kd are involved.

Amino Acid Sequence↗
PubMed1986

Modulation of cellular immunity in malnutrition: effect of interleukin 1 on suppressor T cell activity.

T-lymphocyte mitogenesis is impaired in protein-energy malnutrition. The effect of interleukin 1 (IL-1) on the augmentation of suppressor cell activity during concanavalin A-induced lymphocyte proliferation was measured using IL-1 and lymphocytes from protein malnourished and control rabbits. Addition of IL-1 to lymphocyte cultures from control donors enhanced the suppression of fresh lymphocytes to phytohaemagglutinin (PHA). Addition of IL-1 to lymphocyte cultures from malnourished donors abrograted the suppressor cell activity. Isoelectric focusing showed the presence of a protein band with a pI of about 7.0 in the IL-1 supernatants from protein malnourished and control donors. The results suggest that severe protein malnutrition alters the ability of T-lymphocytes to respond appropriately to IL-1 rather than simply affecting synthesis of this monokine.

Animals↗
PubMed1986

Total parenteral nutrition during pregnancy.

Parenteral hyperalimentation or total parenteral nutrition has become an established therapy for patients with a wide variety of conditions that preclude oral feeding. Because pregnancy is an infrequent event in poorly nourished women with acute or chronic illness, total parenteral nutrition has not been widely used for pregnant patients. Some obstetricians believe that total parenteral nutrition entails risks in excess of its potential benefit to pregnancy and demands skills and knowledge that are either not available or are in limited supply. Sufficient favorable clinical experience has accumulated over the past 15 years so that total parenteral nutrition can be recommended in the management of malnutrition during pregnancy. The purpose of this report is to review the authors' experience and the literature about total parenteral nutrition during pregnancy.

Adult↗
PubMed1986

Chronic exercise stress in mice depresses splenic T lymphocyte mitogenesis in vitro.

This study investigated changes in functional response to splenic T lymphocytes of mitogens following acute and chronic exposure to endurance exercise. Splenic T cell response in vitro to concanavalin A (Con A) and the total number of lymphocytes per spleen were compared between mice assigned to the following treatment conditions: (a) exercise training (EX) by treadmill running (28 m/min, 8 degrees slope for 30 min, 5 times per week for 4 weeks preceded by 2 weeks of endurance build-up), (b) exercise training as above followed by a single, acute bout of exercise to exhaustion (EX + AC) (35 m/min, 8 degrees slope, 30 min to 2 h duration) (c) exposure to the novel environment for 6 weeks without exercise (control), and exposure to the novel environment as in (c) followed by a single, acute bout of exercise to exhaustion. Treadmill running for 6 weeks significantly enhanced succinate dehydrogenase activity in skeletal muscle compared to the sedentary, control condition, and was broadly interpreted as indicative of a training effect. EX mice had significantly reduced splenic lymphocyte proliferative responses to optimal and supraoptimal concentrations of Con A compared with control animals. Incorporation of [3H]thymidine into splenic lymphocytes from EX + AC mice was the most markedly depressed. Total number of lymphocytes per spleen was significantly lower in EX compared with control mice. These results suggests that chronic exercise challenge in mice is associated with T lymphocyte hyporesponsiveness in the secondary lymphoid organs, such as the spleen.

Animals↗