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J Easton

Publications and source records attributed to J Easton.

At least 19 recordsLinked to original sources
PubMed1991

Beta 1-4-galactosyltransferase gene expression is regulated during entry into the cell cycle and during the cell cycle.

Mammalian glycosyltransferases have been implicated in a wide variety of functions besides N-linked glycosylation, including developmental processes. For this reason, we studied the effects of cell cycle and entry into the cell cycle on beta 1-4-galactosyltransferase gene expression. In this study we report that beta 1-4-galactosyltransferase (GalTase) gene expression is, indeed, regulated during the normal cell cycle, peaking during late G1-, S, and early G2 phase of the cell cycle. In addition, GalTase gene expression is regulated in a manner that resembles other "early response" genes such as jun and fos upon reentry into the cell cycle from quiescence. Finally, we show that the GalTase gene is differentially expressed during murine embryogenesis and in terminally differentiated adult tissues. It is most abundant in testis, followed by skeletal muscle and spleen. The reasons for this pattern of differential expression in adult tissues are unknown. These studies should provide important new information regarding GalTase gene expression, its regulation, and its potential link to other developmental functions.

Animals↗
PubMed1991

The role of passive stretch and repetitive electrical stimulation in preventing skeletal muscle atrophy while reprogramming gene expression to improve fatigue resistance.

The effects of mechanical stimuli on preserving muscle mass while transforming them into slow, fatigue resistant muscles have been studied in the rabbit. When combined, stretching and electrical stimulation (10 Hz) induce rapid and marked growth of muscles. This procedure also more rapidly activates the transformation process(es) than when either stretching or electrical stimulation (10 Hz) are used alone. Stretch by itself is also anabolic causing useful lengthening of muscles and preventing collagen accumulation. In contrast, muscle inactivity leads to rapid atrophy, fiber shortening and reduced muscle compliance. We believe these findings have important implications to cardiomyoplasty.

Animals↗
PubMed1991

Regulated expression of a cell division control-related protein kinase during development.

Protein kinases are important signaling molecules that are known constituents of cellular pathways critical for normal cellular growth and development. We have recently identified a new protein kinase, p58, which contains a large domain that is highly homologous to the cell division control p34cdc2 protein kinase. This new cell division control-related protein kinase was originally identified as a component of semipurified galactosyltransferase; thus, it has been denoted galactosyltransferase-associated protein kinase. In vitro, this protein kinase has been shown to phosphorylate a number of substrates, including histone H1, casein, and galactosyltransferase. In vivo, we have found that this protein kinase affects galactosyltransferase enzyme activity and that it is apparently involved in some aspect of normal cell cycle regulation. In this report, we find that the p58 gene is evolutionarily well conserved and expressed ubiquitously, but to varying extents, in adult tissues. In developmentally staged embryos, p58 expression was elevated early in embryogenesis and then decreased dramatically. In the murine submandibular gland, p58 expression was elevated between day 14 and day 16 post coitus. Expression in the submandibular gland appeared to parallel the proliferation and differentiation of specific cell types as judged by in situ hybridization. These studies indicate that the p58 protein kinase may have a critical function during normal embryonic development and that this protein kinase continues to be expressed in differentiated adult tissues.

Amino Acid Sequence↗
PubMed1990

Brain death and organ donation in a neurosurgical unit: audit of recent practice.

OBJECTIVE: To assess the potential for increasing the yield of donors by comparing the current pattern of brain death and organ donation in a neurosurgical unit with that reported in 1981 and with a recent national audit. DESIGN: Retrospective review of all deaths for 1986, 1987, and 1988 and prospective data for 1989. SETTING: A regional neurosurgical unit serving 2.7 million population. RESULTS: Of 553 deaths, 35% (191) patients died while on a ventilator and 17% (92) after discontinuation of ventilation. Medical contraindications to donation were found in 23% (32) of 141 patients tested for brain death, in 38% (19) of 50 patients who died while being ventilated who were not tested, and in 12% (11) of 92 patients no longer being ventilated. Consent for donation was sought in 88% (96) of 109 medically suitable brain dead patients and granted in 70% (67) of these. Half those with permission for multiorgan donation had only the kidneys removed. CONCLUSIONS: More organs may be lost owing to transplant team logistics than by failure to seek consent from relatives of brain dead patients. The estimated size of the pool of potential donors depends on what types of patients might be considered. Ensuring that all who die while being ventilated are tested for brain death and considering the potential for donation before withdrawing ventilation could yield more donors. Ventilating more patients who are hopelessly brain damaged to secure more donors raises ethical and economic issues.

Brain Death↗
PubMed1989

Superoxide generation and its modulation by adenosine in the neutrophils of subjects with asthma.

Airway inflammation with neutrophil infiltration may play a role in airway hyperreactivity. Neutrophils may exert their effects through the generation of superoxide O2- anion and other oxygen-derived free radicals. O2- generation by neutrophils has been demonstrated to be modulated by adenosine at physiologic concentrations. Therefore, we have investigated the function of peripheral blood neutrophils with respect to O2- anion generation and its regulation by adenosine in both subjects with asthma and normal subjects and also the relationship between O2- anion generation and airway hyperresponsiveness in subjects with asthma. Purified neutrophils were obtained from eight subjects with stable asthma and seven normal control subjects not taking chronic medications. O2- anion generation in subjects with asthma was significantly higher compared with that of normal subjects after stimulation with either N-formyl-methionyl-leucyl-phenylalanine (mean, 14.8 nmol/10(6) cells for subjects with asthma versus mean, 9.6 nmol/10(6) cells for normal subjects; p less than 0.01) or phorbol myristate acetate (mean, 13.6 nmol/10(6) cells versus mean, 8.1 nmol/10(6) cells; p less than 0.05). Adenosine inhibited N-formyl-methionyl-leucyl-phenylalanine-stimulated O2- anion generation in a dose-related fashion in subjects with asthma and normal subjects to a similar degree. Adenosine had no effect on O2- anion generation after phorbol myristate acetate stimulation. These results indicate that neutrophils from subjects with asthma produce more O2- anion when they are stimulated than do neutrophils from normal subjects and that this difference is not due to adenosine modulation. In subjects with asthma, O2- anion generation correlated with the degree of airway hyperresponsiveness to inhaled methacholine.

Adenosine↗
PubMed1989

Secretion of antidiuretic hormone in neurosurgical patients: appropriate or inappropriate?

In neurosurgical patients with hyponatraemia (plasma sodium less than 130 mmol/l) and natriuresis, increased antidiuretic hormone (ADH) secretion may be appropriate rather than inappropriate. Ten such patients were studied prospectively to assess circulating ADH concentration and body fluid volumes. Compared with a control group, the mean plasma ADH level was significantly elevated (0.9 pmol/l (s.e.m. = 0.2) versus 0.2 pmol/l (s.e.m. = 0.1], the total body water was normal (101% (s.e.m. = 3) versus 100% (s.e.m. = 6], while the blood volume was significantly reduced (89% (s.e.m. = 3) versus 104% (s.e.m. = 5]. The elevated ADH level was therefore appropriate to a reduced blood volume. This suggests that, in neurosurgical patients with hyponatraemia, fluid restriction could be dangerous. Serial observations in this small group of patients showed that salt replacement and normal fluid intake resulted in a fall in the elevated ADH levels.

Acute Disease↗
PubMed1988

A method for the preparation of mononuclear cells devoid of platelet contamination and its application to the evaluation of putative alpha-receptors in normal and asthmatic subjects.

Receptor studies of human mononuclear leukocytes (MNLs) are complicated by the presence of contaminating platelets which have common receptors. A method was devised to produce MNLs free of platelets (less than 1%) and consists of sequential Ficoll-Hypaque gradients, a BSA gradient and a washing step. Lack of platelet contamination was confirmed by the following criteria: (a) microscopic evaluation using fluorescent dyes showed less than 1% platelets; (b) PGE1 stimulation of the leukocyte membrane adenylate cyclase required addition of exogenous GTP while the platelet cyclase did not; (c) immunoblots of the cells and membranes using antibodies strongly reactive against platelet membranes showed no reactivity against MNL membranes; (d) [3H]yohimbine showed no binding in MNL membranes under conditions where substantial binding to platelets was detected. MNLs were viable as judged by dye exclusion. PHA stimulation of lymphocytes was unimpaired. Plasma membranes of MNLs were prepared by brief sonication and fractionation on a sucrose step gradient. Binding studies using 3H-DHE, an alpha-receptor ligand, revealed no binding in MNLs from normal subjects (n = 6). By contrast, studies on cells from subjects with mild asthma with medication appropriately withheld (n = 8) showed low levels of binding (60-300 fmol/10(6) cells). The subtype and functionality of the putative alpha-receptors are being further evaluated.

Adenylyl Cyclases↗
PubMed1988

Communication aids.

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Communication Devices for People with Disabilities↗
PubMed1988

Macroglossia and posterior fossa disease.

We describe five cases of macroglossia in patients with posterior fossa disease and suggest that the primary mechanism is neurogenically determined rather than one of vascular obstruction or local trauma.

Adult↗
PubMed1988

Epstein-Barr virus serology in the control of nasopharyngeal carcinoma.

Epstein-Barr virus (EBV) is suspected as being etiologically related to nasopharyngeal carcinoma (NPC). Antibodies to EBV antigens have been used in the early detection of NPC and serologic assays are being utilized in the mass screening of high risk populations. While areas of potential application to disease control, such as therapy, are still in the developmental phase, EBV serology has been reported to be of value in the detection of early relapse. Since the data from a series of studies provide conflicting results, however, in this report we review the current information regarding detection of early relapse and describe specific areas that require particular attention if the role of EBV serology in this aspect of NPC control is to be well defined.

Antigens, Viral↗
PubMed1978

Experimental infection of Callithrix Jacchus marmosets with Herpesvirus ateles, Herpesvirus saimiri, and Epstein Barr virus.

We inoculated common marmosets (Callithrix Jacchus) with Herpesvirus ateles (HVA), Herpesvirus saimiri (HVS), and Epstein-Barr virus (EBV). HVA-induced tumors contained several cell types, including giant cells reminiscent of the Sternberg-Reed cells observed in human Hodgkin's disease. HVS and EBV did not induce tumors, although HVS was present in lymphocytes and elicited a strong antibody response. EBV elicited only a variable antibody response. We feel that more common marmosets should be used to determine if the pathologic and immunologic lesions caused by HVA would be a suitable animal model for Hodgkin's disease and/or other malignant lymphomas of man. Inconsistency in the induction of tumors by EBV and HVS in common marmosets suggets that this species may be a different type of model for human cancer research than the cottontop marmoset, which is the most susceptible animal host for EBV and HVS oncogenesis.

Animals↗
PubMed1978

Clinical evaluation of EBV serology in American patients with nasopharyngeal carcinoma.

There is now extensive immunological, biological and biochemical evidence to support a possible etiological relationship between EBV and NPC in patients from different geographical locations. Besides providing information on the question of etiology, the results from immunological investigations suggest that antibodies to some of the EBV-associated antigens might also be of clinical importance in the diagnosis and prognosis of NPC. To determine the possible clinical application of EBV serology to American NPC, sera from patients seen at the Mayo Clinic and the National Institutes of Health were examined for antibodies to EBV-associated antigens in an effort to identify those parameters which most reliably distinguish NPC from other types of cancer. The results show that high antibody titres to EBV-induced EA and the presence of antibody to EBV antigens in the IgA immunoglobulin fraction were the two most specific discriminating parameters, although neither was infallible. These findings are discussed in relation to future studies that are needed in order to determine the potential clinical value of EBV serology to the diagnosis and prognosis of NPC.

Antibodies, Viral↗
PubMed1977

Enhanced oncogenic behavior of human and mouse cells after cellular hybridization with Burkitt tumor cells.

Studies were made of the expression of the Epstein-Barr virus (EBV) in somatic hybrids of Burkitt tumor cells and human or mouse cells to determine whether EBV genetic information associated with the capacity to transform leukocytes of human and non-human primates could be maintained and expressed in nonlymphoblastoid cells. Data obtained thus far suggest that at least one characteristic associated with cellular transformation (loss of contact inhibition) is expressed only in nonlymphoblastoid cells in which the EBV genome is maintained. In addition, we have demonstrated that human epithelial/Burkitt hybrid cells (D98/HR-1 and D98/Raji) are more oncogenic in nude (athymic) mice than are cells of the human epithelial parental line, D98, or one of the Burkitt lymphoblastoid parent cell lines (Raji); the HR-1 Burkitt parent cell line was as oncogenic as the hybrid cell lines but the time required to induce tumors was much longer. Thus, human epithelial cells show alteration of growth properties in vitro and in vivo after cellular hybridization with Burkitt tumor cells.

Animals↗