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J Easton

Publications and source records attributed to J Easton.

At least 19 recordsLinked to original sources
PubMed2001

Rasburicase.

Rasburicase (recombinant urate oxidase) is a uricolytic agent which has been developed for the prevention and treatment of chemotherapy-induced hyperuricaemia at a dosage of 0.15 or 0.2 mg/kg/day in patients with haematological malignancies. Significant reductions from baseline in plasma uric acid levels were seen in 3 noncomparative and 1 randomised comparative trial of rasburicase in patients with, or at high risk of, hyperuricaemia. A multicentre, nonblind, randomised trial found that patients who received intravenous rasburicase 0.2 mg/kg/day experienced an average 2.6-fold less exposure to uric acid than those who received oral allopurinol 10 mg/kg/day. There was no evidence of renal insufficiency in 3 noncomparative trials which monitored creatinine levels to assess renal function during chemotherapy and rasburicase treatment. Rasburicase was generally well tolerated in clinical trials, with skin rashes reported in approximately equals 2% of patients. Bronchospasm, nausea and vomiting, and haemolysis occurred less frequently. In all cases the patients had also received chemotherapy prior to the adverse event.

Adolescent↗
PubMed2001

CD63 associates with the alphaIIb beta3 integrin-CD9 complex on the surface of activated platelets.

The tetraspanins are integral membrane proteins expressed on cell surface and granular membranes of hematopoietic cells and have been identified in multi-molecular complexes with specific integrins. In resting platelets, CD63, a member of the tetraspanin superfamily, is present in dense granule and lysosomal membranes and, following platelet activation, translocates to the plasma membrane. In the present study, platelet activation by thrombin leads to incorporation of CD63 into the Triton-insoluble actin cytoskeletal fraction. This incorporation was inhibited by preincubation of platelets with RGDS or EGTA and did not occur in platelets from a patient with Glanzmann's thrombasthenia, suggesting that it was dependent upon alphaIIbbeta3. In activated platelets, the anti-CD63 MoAb, D545, co-immunoprecipitated CD63 with other surface-labeled proteins, including alphaIIbbeta3 and another tetraspanin, CD9. The association of CD63 with CD9 and alphaIIbbeta3, was not inhibited by preincubation of platelets with RGDS or EGTA. D545 did not inhibit the adhesion of activated platelets to purified extracellular matrix proteins, but significantly decreased adhesion of thrombin-activated platelets to neutrophils in a rosetting assay. D545 also caused disaggregation of platelets stimulated by ADP, but had no effect on aggregation induced by other agonists. These results are consistent with the proposal that CD63 becomes part of an alphaIIbbeta3-CD9-CD63 integrin-tetraspanin complex in activated platelets--an association that may modulate the function of alphaIIbbeta3-dependent interaction with other cells such as neutrophils.

Adult↗
PubMed1999

Abnormalities in the p34cdc2-related PITSLRE protein kinase gene complex (CDC2L) on chromosome band 1p36 in melanoma.

The two genes encoding the PITSLRE protein kinase isoforms, CDC2L1 and CDC2L2, are localized to human chromosome band 1p36. The PITSLRE protein kinases are a part of the p34cdc2 supergene family. Several protein products of the CDC2L locus may be effector(s) in apoptotic signaling. The larger PITSLRE p110 isoforms appear to regulate some aspect of RNA splicing/transcription during the cell cycle. One or more of these genes may function as tumor suppressor genes in melanoma. Using fluorescence in situ hybridization, one allele of the CDC2L gene complex on chromosome 1 was either deleted or translocated in 8 of 14 different melanoma cell lines. We also observed mutations in the 5' promoter region of the CDC2L1 gene in four different cell lines relative to normal melanocytes using PCR-SSCP analysis and direct DNA sequencing. Western blot analysis revealed decreased level of PITSLRE protein expression in several cell lines, as well as in four surgical malignant melanoma specimens relative to normal melanocytes. Thus, the decreased PITSLRE protein expression appears to result from deletion of the CDC2L alleles and possibly by mutations within the 5' promoter region. We propose that aberrations in the CDC2L genes may contribute to the pathogenesis or progression of melanoma.

Base Sequence↗
PubMed1999

Multiple DNA repair mechanisms and alkylator resistance in the human medulloblastoma cell line D-283 Med (4-HCR).

PURPOSE: We have previously reported preferential repair of DNA interstrand crosslinks in the 4-hydroperoxycyclophosphamide-resistant human medulloblastoma cell line D-283 Med (4-HCR). We now report further studies that explored the potential mechanisms underlying this repair. METHODS: Limiting dilution assays and Western, Southern, and Northern blots were used to compare specific differences between D-283 Med (4-HCR) and its parental line D-283 Med. RESULTS: D-283 Med (4-HCR) was cross-resistant to melphalan and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), with O6-alkylguanine-DNA alkyltransferase (AGT) levels of 466+/-164 fmol/mg protein; AGT levels in the parental line, D-283 Med, were 76+/-96 fmol/mg. The increase in AGT activity was not a result of gene amplification. Depleting AGT with O6-benzylguanine partially restored sensitivity to BCNU. Both cell lines were deficient in the human mismatch protein MutLalpha. ERCC4 mRNA and poly(ADP-ribose) polymerase levels were similar in both cell lines, and ERCC1 mRNA levels were 2- to 2.5-fold lower in D-283 Med (4-HCR). Topoisomerase I levels were 2- to 2.5-fold higher in D-283 Med compared with D-283 Med (4-HCR). CONCLUSION: These results, while illustrating the multiple differences between D-283 Med and D-283 Med (4-HCR), do not explain the enhanced DNA interstrand crosslink repair seen in D-283 Med (4-HCR).

Antineoplastic Agents, Alkylating↗
PubMed1998

Disruption of the cyclin D/cyclin-dependent kinase/INK4/retinoblastoma protein regulatory pathway in human neuroblastoma.

The p16INK4a (MTS1) and pl8INK4c gene products are normal, and highly expressed, in human neuroblastoma cell lines. The retinoblastoma protein (pRb) was, nonetheless, phosphorylated and functional in these cells. Such high levels of p16INK4a/p18INK4c should normally inhibit cyclin-dependent kinase (CDK) 4 and 6 activities in cells containing functional pRb, delaying cell cycle progression and growth. These neuroblastoma cell lines express both CDK4 and CDK6 mRNA and protein, but only significant CDK6 protein kinase activity was detected in this study. In addition, CDK6 was not present in p16INK4a immune complexes in cells with significant kinase activity, although p16INK4a levels were high. Others have shown that a specific mutation in the NH2-terminal region of the CDK4 gene product can disrupt p16INK4a binding, thereby bypassing its inhibitory activity. To determine whether mutation of the CDK6 gene, or some other mechanism, is responsible for the CDK6 kinase activity in these cell lines, several complementary analyses were performed. The CDK6 gene from each cell line was examined for mutations that might affect p16INK4a binding, whereas p16INKa add-back experiments were performed with CDK6 immune complexes to assess p16INK4a function. A bona fide CDK6 mutation that disrupts p16INK4a binding and prevents inhibition of CDK6 protein kinase activity was identified in 1 of 17 neuroblastoma cell lines. The mechanism(s) responsible for disruption of p16INK4a inhibitory activity in the remaining cell lines is unknown, but these results suggest that neuroblastoma cells may bypass the cell cycle block imposed by constitutive expression of wild-type p16INK4a in novel ways.

Carrier Proteins↗
PubMed1998

Duplication of a genomic region containing the Cdc2L1-2 and MMP21-22 genes on human chromosome 1p36.3 and their linkage to D1Z2.

Cdc2L1 and Cdc2L2 span approximately 140 kb on human chromosome 1p36.3. The products of the Cdc2L genes encode almost identical protein kinases, the PITSLRE kinases, which have functions that may be relevant to the regulation of transcription/splicing and apoptotic signaling. These genes are deleted/translocated in neuroblastomas with MYCN gene amplification, a subset of malignant melanomas, and in a newly delineated deletion syndrome. Here we report that the p36.3 region of human chromosome 1 consists of two identical genomic regions, each of which contain a Cdc2L gene linked to a metalloprotease (MMP) gene in a tail-to-tail configuration. This duplicated genomic region is also linked tightly to D1Z2, a genetic marker containing a highly polymorphic VNTR (variable number tandem repeat) consisting of an unusual 40-bp reiterated sequence. Thus, these genes and the polymorphic marker D1Z2 are organized as follows: telomere-D1Z2-5'-MMP22-3'-3'-Cdc2L2-5'-5'-Cdc2L1 -3'- 3'-MMP21-5'-centromere. Remarkably, the introns and exons of Cdc2L1 and Cdc2L2, as well as their flanking regions, are essentially identical. A total of 15 amino acid differences, 12 nonconservative and 3 conservative, can be found in the 773-786 amino acids specified by the various products of the Cdc2L genes. Two separate promoter/5' untranslated (UT) regions, CpG1 and CpG2, are identical to a reported previously methylated genomic CpG sequence and are used to express >20 different Cdc2L transcripts from the two genes. The expression of CpG2 transcripts from Cdc2L1 and Cdc2L2 is tissue/cell-line specific. CpG1 transcripts are expressed ubiquitously from both genes, with perhaps some bias towards the expression of CpG1 Cdc2L1 mRNAs in certain hematopoietic cells.

5' Untranslated Regions↗
PubMed1997

Massive delayed hemolysis following peripheral blood stem cell transplantation with minor ABO incompatibility.

After hematopoietic stem cell transplantation, delayed immune hemolysis may occur when donor-derived B lymphocytes carried with the graft produce immune antibodies against the recipient's incompatible red cells. We report the occurrence of this syndrome in the context of minor blood group incompatibility between donor and recipient after peripheral blood stem cell (PBSC) transplantation. On day 12 post-transplant there was abrupt onset of hemolysis necessitating supportive treatment with hydration and transfusions. Because, as compared to bone marrow, PBSC grafts are enriched with lymphocytes, more frequent and intense delayed immune hemolysis may be anticipated when using PBSC. This complication is described most often when cyclosporine alone is used for immunosuppression following the graft. The addition of methotrexate, which with CyA forms the classic regimen for the prevention of graft-vs-host disease, may diminish the frequence and severity of this adverse reaction.

ABO Blood-Group System↗
PubMed1994

Analysis of the 5' flanking sequences from the human protein kinase p58 (PITSLRE beta 1)-encoding gene.

The p58 (PITSLRE beta 1) protein kinase (PK) is a member of a large supergene family related to the master mitotic protein kinase, p34cdc2. This PK is also a member of a sub-family itself, with at least six additional related PITSLRE PK isoforms expressed by alternative splicing and promoter utilization from three duplicated genes. Minimal overproduction of the PITSLRE beta 1 PK in Chinese hamster ovary cells results in a late mitotic delay, suggesting that this PK's function may be related to the cell cycle [Bunnell et al., Proc. Natl. Acad. Sci. USA 87 (1990) 7467-7471]. Further studies using structural and functional mutants have shown that PITSLRE PKs are involved in signaling apoptosis. The gene encoding the PITSLRE beta 1 PK has previously been isolated and structurally characterized [Eipers et al., Genomics 13 (1992) 613-621]. Here we characterize the minimal essential promoter for this gene. Analysis of a 1.18-kb stretch of DNA located upstream from the PITSLRE beta 1 start codon demonstrates that significant cat gene expression can be driven by a construct containing this sequence. Deletion studies of this DNA fragment have defined a minimal promoter that extends 144 bp 5' of the previously mapped transcription start point (tsp), and 521 bp 5' of the start codon. This region of PITSLRE beta 1 DNA does not contain canonical TATA-box sequences or G + C-rich sequences associated with many promoters, yet it has approximately 20% of the promoting activity when compared to the SV40 early promoter. This suggests that this DNA sequence is a relatively strong basal promoter of a previously uncharacterized type.

Base Sequence↗
PubMed1994

Molecular cloning and expression of alternatively spliced PITSLRE protein kinase isoforms.

Minimal ectopic expression of the p58GTA protein kinase results in a provocative phenotype involving cell cycle delay, mitotic catastrophe, and decreased cell viability. In addition, this kinase is well conserved evolutionarily, ubiquitously expressed, and its genes map to a position on human chromosome 1 frequently deleted in the late stages of tumorigenesis. Here we report that the p58GTA protein kinase is a member of a larger subfamily of proteins. The mRNAs encoding these proteins are generated by alternative splicing from multiple duplicated genes. These isoforms range in size from 50 to 110 kDa. Divergence between the alternatively spliced isoforms is localized to the amino-terminal region of the molecule. The entire p58GTA open reading frame is conserved in most of these p58GTA isoforms. The predicted sequences of the larger isoforms encode bipartite nuclear localization signal sequences and extensive polyglutamic acid domains. Antibodies to the p58GTA isoform were used to confirm the presence of the alternatively spliced isoforms in different cell types as well as identify two additional isoforms that appear to arise from a separate gene(s). Cellular fractionation studies indicate that one of the isoforms is found only in the nucleus, and the remainder are found in both the cytoplasm and the nucleus. Expression and localization of some p58GTA isoforms suggest that they may have specialized cellular functions. Because of the large number of isoforms generated from multiple genes we propose naming these kinases PITSLRE alpha 1, alpha 2-1, alpha 2-2, alpha 2-3 alpha 2-4, beta 1, beta 2-1, and beta 2-2 based on the conserved sequence of the PSTAIRE box unique to p34cdc2 kinases and the gene from which they are transcribed.

Alternative Splicing↗
PubMed1994

[Prevention of viral recurrence following liver transplantation for post-hepatitis B and B-delta cirrhosis].

The incidence of recurrence of hepatitis B virus (HBV) following orthotopic liver transplantation (OLT) is as high as 80% when no attempt at prevention has been considered. HBV reinfection is associated with the reappearance of hepatitis B surface antigen (HBsAg) and HBV DNA in serum and, in most cases, with rapid severe graft damage. Immunoprophylaxis using polyclonal anti-HBs immunoglobulins reduces the risk of recurrence but this long-term therapy remains highly expensive. In this report, we use fresh frozen plasma (FFP) with high titers of anti-HBs immunoglobulins in an attempt to reduce HBV recurrence. From July 1987 to September 1993, 11 patients underwent OLT for HBV-related liver disease (18% of our OLT patients). FFP were administered to 6 patients continually for 7 to 46 months. Only one patient, under long-term immunosuppressive treatment before OLT, was reinfected 7 months after OLT. Rapid development of graft failure was observed with histologic manifestations of a fibrosing cholestatic hepatitis, leading to patient death after 12.5 months with concomitant bacterial infection. In this protocol, the rate of reappearance of HBsAg was 17%, a figure which can be favorably compared with other reports. All patients were subsequently tested for HCV and HIV and remained negative. In conclusion, FFP with high titers of anti-HBs immunoglobulins is at least as effective as polyclonal anti-HBs immunoglobulins in reducing the rate of HBV recurrence following OLT. The estimated cost of this new immunoprophylaxis method is less than 10% of the classical prophylaxis based on purified human polyclonal anti-HBs immunoglobulins.

Graft Rejection↗
PubMed1994

Thyroid-induced changes in the growth of the liver, kidney, and diaphragm of neonatal rats.

Eu-, hypo- and hyper-thyroid rats were studied 12 days postpartum. Hypothyroidism was induced by administering propylthiouracil (PTU) via the mother's drinking water between late gestation and throughout lactation. This procedure effectively blocked the normal early postnatal surge of T3 and T4. In contrast, hyperthyroidism was induced in the young pups by daily injections of T4 from day 3 postpartum. The effects of these experimental manipulations of thyroid status on the rates of protein turnover and growth of the liver, kidney, and diaphragm were studied and compared with measurements made on appropriate euthyroid control tissues. Tissue rates of protein synthesis were decreased in response to hypothyroidism with consequent growth retardation of all three tissues and the whole animal. In contrast, the three body tissues responded very differently to the induction of hyperthyroidism. Hepatic rates of protein synthesis and growth were completely unaffected by thyroid excess. The response of the diaphragm was essentially the reverse of that seen with hypothyroidism, i.e., the enhanced rates of protein synthesis and protein degradation leading to muscle hypertrophy. The rates of protein turnover in the kidney were also increased, but unlike the diaphragm the net result was renal atrophy. Clearly, thyroid hormones influence the normal rapid growth of the neonate and its individual tissues. However, beyond a certain concentration the threshold of responsiveness to these hormones seems to vary between individual tissues.

Animals↗
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↗