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Biomedical subjects

T Roberts

Publications and source records attributed to T Roberts.

At least 19 recordsLinked to original sources
PubMed1992

Asymmetric mitotic segregation of the yeast spindle pole body.

The yeast KAR1 gene is required for spindle pole body (SPB) duplication and nuclear fusion. We determine here that KAR1-beta-galactosidase hybrid proteins localize to the outer face of the SPB. Remarkably, after SPB duplication, the hybrid protein was found associated with only one of the two SPBs, usually the one that enters the bud. Using an ndc1 mutant, which forms a defective SPB at the nonpermissive temperature, we found that the hybrid was exclusively associated with the "new" SPB. Two regions of KAR1 contribute to its localization; an internal 70 residue region was necessary and sufficient to localize hybrids to the SPB, and the hydrophobic carboxyl terminus localized proteins to the nuclear envelope. The localization domains correspond to two functional domains required for SPB duplication. We suggest that KAR1 is anchored to the nuclear envelope and interacts with at least one other SPB component during the cell cycle.

Cell Compartmentation↗
PubMed1992

Tyrosine phosphorylation of rasGAP and associated proteins in chronic myelogenous leukemia cell lines.

The Philadelphia chromosome (Ph1), detected in virtually all cases of chronic myelogenous leukemia, is formed by a reciprocal translocation between chromosomes 9 and 22 that fuses BCR encoded sequences upstream of exon 2 of c-ABL. This oncogene produces a fusion protein (p210BCR/ABL) in which the ABL tyrosine kinase activity is elevated. This elevated kinase activity is essential for transformation, but the mechanisms involved are unknown. We report here that p21ras GTPase activating protein (rasGAP) or rasGAP-associated proteins p190 and p62 are phosphorylated on tyrosine in Ph1 (+) cell lines. Further, rasGAP coimmunoprecipitates with p210BCR/ABL in these cell lines. These results suggest that rasGAP or associated proteins are potential substrates for p210BCR/ABL kinase and thus directly link p210BCR/ABL with a signal transduction pathway known to be activated by hematopoietic growth factors (p21ras).

Fusion Proteins, bcr-abl↗
PubMed1992

Soluble CD23 levels are elevated in the serum of patients with primary Sjögren's syndrome and systemic lupus erythematosus.

The low affinity IgE receptor Fc epsilon RII (CD23) is important in several aspects of T and B cell function. In this study serum levels of soluble CD23 (sCD23) were measured in three groups: 26 female patients with systemic lupus erythematosus (SLE), 21 females with primary Sjögren's syndrome (pSS) and 25 normal healthy females. The concentration of sCD23 was determined using an enhanced chemiluminescent sandwich ELISA developed in this laboratory. Increased levels of sCD23 were observed in pSS and in SLE patients compared with controls (median 23.0 versus 8.6, P less than 0.0002 and 18.1 versus 8.6, P less than 0.002 respectively). While the median level of sCD23 was found to be higher in pSS than in SLE the difference was not statistically significant. Patients with SLE and pSS on glucocorticoid treatment had significantly lower levels of sCD23 than patients not on this treatment (median 28.9 versus 14.4, P less than 0.05). Amongst the control patients sCD23 was inexplicably lower in the female members relative to the males (median 8.5 versus 12.3, P less than 0.05). Although serum IgG and IgA levels were significantly elevated in pSS and SLE patients relative to controls there was no direct correlation between sCD23 and the serum levels of these immunoglobulins. We conclude that B cell hyperactivity which occurs in both pSS and SLE is associated with raised levels of sCD23.

Adult↗
PubMed1991

The role of diet in the development of breast cancer: a case-control study of patients with breast cancer, benign epithelial hyperplasia and fibrocystic disease of the breast.

A case-control study was undertaken to investigate the role of diet in women with breast cancer, and in two groups of women with benign breast disease: epithelial hyperplasia, and fibrocystic disease without hyperplasia. The study provides data which suggest that the consumption of red meat, savoury meals (pizza, pies, stew, etc.) and of starches is disadvantageous, while the consumption of chicken and fish, and of fruit, appears to be beneficial. These patterns were present for both the breast cancer patients and the patients with benign epithelial hyperplasia. One-third of breast cancer patients had changed their diet after their diagnosis, compared to only around 12% in controls and patients with benign breast disease. Overall, the women studied had changed their diet to reduce their intake of sugars, dairy products and meat, and increased their intake of poultry, fish, fruit and vegetables over the past decade; but the breast cancer group was less likely to have made this change.

Adult↗
PubMed1990

Treatment of functional menorrhagia by radiofrequency-induced thermal endometrial ablation.

42 patients were enrolled in a trial of radiofrequency-induced thermal endometrial ablation for the treatment of functional menorrhagia. The radiofrequency electromagnetic energy was delivered via a probe placed within the endometrial cavity. 10 patients received 330 kJ of energy, 10 received 445 kJ, and the other 22 received 660 kJ. 19 (87%) of those receiving the highest dose became amenorrheic or had a considerable reduction in menstrual flow. The procedure is simple and the heat induced in the endometrium does not penetrate much beyond the inner layers of the myometrium. There is no need for distension of the uterine cavity with flushing media.

Adult↗
PubMed1990

Experimental and clinical studies with radiofrequency-induced thermal endometrial ablation for functional menorrhagia.

A method of ablating the endometrium has been introduced into clinical practice that uses radiofrequency electromagnetic energy to heat the endometrium, using a probe inserted through the cervix. Preliminary studies suggest that over 80% of patients treated will develop either amenorrhea or a significant reduction in flow. The advantages of radiofrequency endometrial ablation over laser ablation or resection are the avoidance of intravascular fluid absorption, simplicity (no special operative hysteroscopic skills are required), speed of operation, and reduced cost compared with the Nd:YAG laser. In this paper, we describe the experimental studies performed during development of this new technique.

Adult↗
PubMed1990

A cytologic study of the effect of Kolanut on the keratinization of the palatal mucosal of Nigerian smokers.

An exfoliative cytologic study of the palatal mucosa was undertaken in 96 Nigerian male volunteers aged between 17 and 65 years. The volunteers were categorised into the following four groups: Group 1--Smokers, kolanut chewers; Group 2--Smokers; Group 3--Kolanut chewers; and Group 4--Non-smokers, non-kolanut chewers, Variation in the degree of palatal keratinization was evaluated using karyopyknotic indices. Statistical analysis based on one way analysis of variance showed that smoking and kolanut chewing had a statistically significant influence (P less than 0.05) on the variation of palatal keratinization among the volunteers. Distribution of karyopyknotic indices among groups was such that Group 1 greater than Group 2 greater than Group 3 greater than Group 4. Observation from this study suggests a potentiation of the cigarette smoking-induced palatal keratinization by kolanut.

Adolescent↗
PubMed1989

The colony stimulating factor-1 receptor associates with and activates phosphatidylinositol-3 kinase.

Colony stimulating factor-1 (CSF-1) is a lineage-specific growth factor required for proliferation and survival of mononuclear phagocytes and their precursors. The CSF-1 receptor belongs to a family of ligand-activated protein-tyrosine kinases. Activation of the platelet-derived growth factor receptor, but not the CSF-1 receptor, leads to an increase in phospholipase C activity and a subsequent elevation in intracellular calcium. Recent studies have shown that a novel phosphoinositol (PtdIns) kinase, termed PtdIns-3 kinase, is stimulated by the platelet-derived growth factor receptor and certain oncogenes in the protein-tyrosine kinase family. PtdIns-3 kinase phosphorylates the D-3 hydroxyl position of the inositol ring of PtdIns, and its products do not participate in the generation of the second messenger inositol 1,4,5-trisphosphate (Ins(1,4,5)P3). Here we report that addition of CSF-1 is followed by activation of PtdIns-3 kinase in a macrophage cell line (P388 D1), which contains CSF-1 receptors, and in BALB/c fibroblasts made to express the human CSF-1 receptor. Furthermore, we show that activation of the CSF-1 receptor results in the accumulation in intact cells of polyphosphoinositides phosphorylated at the D-3 position of the inositol ring. Thus activation of the CSF-1 receptor stimulates PtdIns-3 kinase activity, indicating a novel pathway for CSF-1 receptor-mediated signal transduction.

Animals↗
PubMed1989

Repetition priming of face recognition in a serial choice reaction-time task.

Marshall & Walker (1987) found that pictorial stimuli yield visual priming that is disrupted by an unpredictable visual event in the response-stimulus interval. They argue that visual stimuli are represented in memory in the form of distinct visual and object codes. Bruce & Young (1986) propose similar pictorial, structural and semantic codes which mediate the recognition of faces, yet repetition priming results obtained with faces as stimuli (Bruce & Valentine, 1985), and with objects (Warren & Morton, 1982) are quite different from those of Marshall & Walker (1987), in the sense that recognition is facilitated by pictures presented 20 minutes earlier. The experiment reported here used different views of familiar and unfamiliar faces as stimuli in a serial choice reaction-time task and found that, with identical pictures, repetition priming survives and intervening item requiring a response, with both familiar and unfamiliar faces. Furthermore, with familiar faces such priming was present even when the view of the prime was different from the target. The theoretical implications of these results are discussed.

Choice Behavior↗
PubMed1988

Isozymes of alpha-amylase in the porcine pancreas: population distribution.

1. Three isozymes of pancreatic alpha-amylase, PPA 1, PPA 2, and PPA 3, were observed in a porcine population of 50 animals. 2. Isozyme PPA 2 was common to each pancreas. 3. Three phenotypic patterns were described as: (A) consisting of PPA 2 alone (20%); (B) consisting of PPA 1 and PPA 2 (78%); and (C) consisting of all three forms (2%). 4. Amylase isozymes were separated by anion exchange chromatography using DE53. 5. Individual isozymes corresponded to one of the three isozymes found in pancreatin. 6. Individual isozymes were inhibited equally by an amylase inhibitor from wheat. 7. Differences in amylase isozymes were attributed to genetically controlled mechanisms and not to artifacts of isolation.

Animals↗