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Biomedical subjects

D Fisher

Publications and source records attributed to D Fisher.

At least 73 records · Page 4Linked to original sources
PubMed1998

MAP kinase inactivation is required only for G2-M phase transition in early embryogenesis cell cycles of the starfishes Marthasterias glacialis and Astropecten aranciacus.

Downregulation of MAP kinase is a universal consequence of fertilization in the animal kingdom. Here we show that oocytes of the starfishes Astropecten aranciacus and Marthasterias glacialis complete meiotic maturation and form a pronucleus when treated with 1-methyladenine and then complete DNA replication and arrest at G2 if not fertilized. Release of G2 by fertilization or a variety of parthenogenetic treatments is associated with inactivation of MAP kinase. Prevention of MAP kinase inactivation by microinjection of Ste11-DeltaN, a constitutively active budding yeast MAP kinase kinase kinase, arrests fertilized eggs at G2 in either the first or the second mitotic cell cycle, in a dose-dependent manner. G1 arrest is never observed. Conversely, inactivation of MAP kinase by microinjection of the MAP kinase-specific phosphatase Pyst-1 releases mature starfish oocytes from G2 arrest. The role of MAP kinase in arresting cell cycle at various stages in oocytes of different animal species is discussed.

Adenine↗
PubMed1998

Age-related neurodegeneration and oxidative stress: putative nutritional intervention.

This review describes age-related changes that occur in neuronal function and cites evidence to show that these alterations may be the result of increased sensitivity to oxidative stress (OS). Evidence is presented to show that the abilities to mitigate the OS effects and to repair the damage from OS show decline as a function of age. Results from age- and OS-sensitive tests are given; these results indicate that one of the major sites of action of OS is the membranes, especially if compromised by high amounts of sphingomyelin, and one of the major effects of OS is to further alter the calcium disregulation in aging. It is suggested that attempts to increase antioxidant protection through diets comprised of fruits and vegetables identified as being high in total antioxidant activity might prevent or reverse the deleterious OS effects on neuronal aging.

Aging↗
PubMed1998

PEGylation of cytokines and other therapeutic proteins and peptides: the importance of biological optimisation of coupling techniques.

Polyethylene glycol (PEG) modification, PEGylation, is a well established technique which has the capacity to solve or ameliorate many of the problems of protein and peptide pharmaceuticals. It is one of the most important of the molecule altering structural chemistry (MASC) techniques and in many settings is enabling technology. The use of PEG as a linker molecule is also beginning to make a contribution to the production of exciting new products. We have previously reviewed the marked differences between methods of PEGylation and the surprising and dramatic impact of different coupling techniques (using different activated PEGs) on factors such as retention of bioactivity, stability and immunogenicity of the resulting PEGylated proteins and peptides. Numerous factors play a part in this variation: the presence or absence of linkers between the PEG and the target molecule; the nature and stability of the bond(s) between the PEG, linker and target; the impact of PEG attachment on surface charge; the coupling conditions; and the relative toxicity of the activated polymer and/or coproduct(s). These are not, however, the only sources of qualitative differences in PEGylated products. Our own experience whilst developing a linkerless PEGylation technique (i.e. one attaching only PEG to the target molecule), which we devised to overcome all the major problems of pre-existing PEGylation techniques, was that considerable modification of the prototype method and a process of 'biological optimisation' was required to achieve good results in terms of conservation of bioactivity. Biological optimisation has not, as far as we are aware, been systematically applied by other groups working in PEGylation. It is the term we use to describe an iterative process for examining and refining all the steps in the PEGylation process, including manufacturing the activated polymer, in order to achieve the best possible conservation of bioactivity and other beneficial features of the method. The application of this biologically optimised PEGylation technique, using tresyl monomethoxy PEG (TMPEG), to a variety of target proteins reveals, as outlined in this review, an exceptional ability to conserve biological activity of the target. This, and the benefit of adding nothing other than PEG itself (which has an excellent safety record), to the protein, as well as other manufacturing and practical advantages, makes the method ideal for the modification of cytokines and other therapeutic proteins.

Animals↗
PubMed1998

A randomized trial of recombinant human interleukin-11 following autologous bone marrow transplantation with peripheral blood progenitor cell support in patients with breast cancer.

This study assessed the safety and efficacy of recombinant human interleukin (rhIL)-11 in decreasing platelet transfusion requirements in patients with breast cancer who were undergoing autologous bone marrow transplantation (ABMT) with peripheral blood progenitor cell (PBPC) support. After high-dose therapy with cyclophosphamide, cisplatin, and carmustine, 80 patients were randomized to one of three treatment groups: placebo (26), 25 microg/kg of rhIL-11 (28), and 50 microg/kg of rhIL-11 (26). Of those randomized, 75 (94%) received at least one dose of the masked study drug and the remaining 5 (6%) withdrew consent before study drug administration. In the placebo group, each patient received an average 12.4 (+/-10.2) platelet transfusions vs. 9.2 (+/-5.0) in the 25-microg/kg rhIL-11 group (p = 0.17) and 9.9 (+/-3.5) in the 50-microg/kg rhIL-11 group (p = 0.34). There was no statistically significant difference between the rhIL-11 groups and the placebo group in the median number of days to platelet recovery. Neutrophil and red blood cell recovery were similar for all treatment groups. The imbalance in the number of patients already alloimmunized at study entry in the rhIL-11 groups (12) and in the placebo group (1) may have confounded the primary efficacy assessment. Most adverse events were related to the high-dose chemotherapy. Generally mild edema and minor conjunctival bleeding (grades 1 or 2) were statistically associated with rhIL-11 administration (p < 0.04). There was no association between rhIL-11 and the occurrence of atrial arrhythmias, although there was a suggestion of an association with rhIL-11, 5 of 50 cases vs. 1 of 25 in the placebo group. Two cardiovascular events, tachycardia and hypotension (grade 1 or 2), occurred in the 50-microg/kg rhIL-11 group. The number of patients who discontinued study drug dosing because of an adverse event was distributed across all treatment groups. In summary, rhIL-11 was safe and well tolerated in this study. The results did not demonstrate that rhIL-11 treatment significantly decreased platelet transfusion requirements after high-dose chemotherapy with ABMT and PBPC support.

Adult↗
PubMed1998

The Polo-like kinase Plx1 is a component of the MPF amplification loop at the G2/M-phase transition of the cell cycle in Xenopus eggs.

We have investigated whether Plx1, a kinase recently shown to phosphorylate cdc25c in vitro, is required for activation of cdc25c at the G2/M-phase transition of the cell cycle in Xenopus. Using immunodepletion or the mere addition of an antibody against the C terminus of Plx1, which suppressed its activation (not its activity) at G2/M, we show that Plx1 activity is required for activation of cyclin B-cdc2 kinase in both interphase egg extracts receiving recombinant cyclin B, and cycling extracts that spontaneously oscillate between interphase and mitosis. Furthermore, a positive feedback loop allows cyclin B-cdc2 kinase to activate Plx1 at the G2/M-phase transition. In contrast, activation of cyclin A-cdc2 kinase does not require Plx1 activity, and cyclin A-cdc2 kinase fails to activate Plx1 and its consequence, cdc25c activation in cycling extracts.

Animals↗
PubMed1998

Germinal vesicle material is dispensable for oscillations in cdc2 and MAP kinase activities, cyclin B degradation and synthesis during meiosis in Xenopus oocytes.

We have investigated at a molecular level the requirements for germinal vesicle (nuclear) material during the course of meiosis in Xenopus oocytes. We present the localization of some cell cycle proteins in stage VI oocytes; most of those analyzed are cytoplasmic, although some (MAD, 26S proteasome) are distributed between the cytoplasm and the germinal vesicle. By analyzing changes in individual oocytes, we find that the unphosphorylated form of cyclin B2 disappears and the phosphorylated form is then degraded in both nucleated and enucleated oocytes. Enucleated oocytes are also capable of resynthesizing both cyclin B1 and cyclin B2 after the initial degradation and of reactivating cdc2 kinase. Synthesis of mos protein and activation of MAP kinase concomitant with cdc2-cyclin B reactivation are also unaffected by prior removal of the germinal vesicle.

Animals↗
PubMed1997

MAPK inactivation is required for the G2 to M-phase transition of the first mitotic cell cycle.

Down-regulation of MAP kinase (MAPK) is a universal consequence of fertilization in the animal kingdom, although its role is not known. Here we show that MAPK inactivation is essential for embryos, both vertebrate and invertebrate, to enter first mitosis. Suppressing down-regulation of MAPK at fertilization, for example by constitutively activating the upstream MAPK cascade, specifically suppresses cyclin B-cdc2 kinase activation and its consequence, entry into first mitosis. It thus appears that MAPK functions in meiotic maturation by preventing unfertilized eggs from proceeding into parthenogenetic development. The most general effect of artificially maintaining MAPK activity after fertilization is prevention of the G2 to M-phase transition in the first mitotic cell cycle, even though inappropriate reactivation of MAPK after fertilization may lead to metaphase arrest in vertebrates. Advancing the time of MAPK inactivation in fertilized eggs does not, however, speed up their entry into first mitosis. Thus, sustained activity of MAPK during part of the first mitotic cell cycle is not responsible for late entry of fertilized eggs into first mitosis.

Animals↗
PubMed1997

CD6-depleted allogeneic bone marrow transplantation for acute leukemia in first complete remission.

The appropriate timing of bone marrow transplantation (BMT) for adults with acute myelogenous leukemia (AML) and acute lymphoblastic leukemia (ALL) is controversial. Although allogeneic transplantation results in a lower risk of disease recurrence than intensive chemotherapy alone, overall outcome following BMT may not be improved due to the higher incidence of therapy-related fatal complications, frequently as a result of the development of graft-versus-host disease (GVHD). Selective T-cell depletion of donor marrow can reduce the incidence of GVHD and thereby limit transplant-related toxicity. Herein we report the risk of GVHD, incidence of transplant related mortality (TRM), likelihood of disease relapse, and overall survival in adult patients undergoing BMT with CD6 depleted allogeneic marrow for acute leukemia in first remission. Forty-one consecutive allogeneic transplants were performed on patients with acute leukemia and high-risk features (28 AML, 13 ALL) using T12 monoclonal antibody and complement to remove CD6+ T cells from donor marrow. No pre- or posttransplant immune suppressive medications for GVHD prophylaxis were administered. The actuarial estimated risk of grade 2 to 4 acute GVHD was 15% in patients receiving HLA identical grafts. Chronic GVHD developed in five patients. The estimated risk of TRM for patients in first complete remission was 5% at Day +100 and 16% at 2 years. Fatalities attributable to infection with cytomegalovirus or Epstein-Barr virus occurred in only three patients. Estimated probabilities of relapse, overall survival, and event-free survival at 4 years were 25%, 71%, and 63%, respectively. No significant differences in GVHD, TRM, relapse rate, or survival was observed for patients with AML compared with those with ALL. Allogeneic transplantation with CD6 depleted bone marrow is effective in consolidating remissions of high-risk patients with acute leukemia in first remission without excessive toxicity.

Acute Disease↗
PubMed1997

Aggressive bone destruction in acute megakaryocytic leukemia: a rare presentation.

Acute megakaryocytic leukemia (AMKL) is a rare subtype of acute myeloid leukemia which is more common in children. Although the bone changes in leukemia are well documented, there are only a few reports of the AMKL subtype. We present an exceptional case of a young girl with very aggressive AMKL, who demonstrated symmetrical destructive lesions of the long bones characteristic of this disease. Lytic lesions of the skull and jaws were also present, and these have not been previously described in AMKL.

Bone and Bones↗
PubMed1997

Oxidant injury in PC12 cells--a possible model of calcium "dysregulation" in aging: I. Selectivity of protection against oxidative stress.

Previous research has suggested that the initial effects of cellular free radical neurotoxic insult involve large increases in intracellular Ca2+. However, the exact role of oxidative stress on the various parameters involved in these increases has not been specified. The present experiments were performed to examine these parameters in PC12 cells exposed to 5, 25, or 300 microM H2O2 for 30 min in growth medium alone or containing either nifedipine (L-type Ca2+ antagonist), conotoxin (N-type antagonist), Trolox (vitamin E analogue), or alpha-phenyl-n-tert-butylnitrone (nitrone trapping agent; PBN). The concentrations of H2O2 were chosen by examining the degree of cell killing induced by exposure to graded concentrations of H2O2. The 5 and 25 microM concentrations of H2O2 produced no significant cell killing at either 30 min or 24 h after treatment, whereas the 300 microM concentration produced a moderate degree of cell killing that did not increase between the two times. Fluorescent imaging was used to visualize intracellular Ca2+ changes in fura-2-loaded cells. Baseline (pre-30 mM KCl) Ca2+ levels were increased significantly by H2O2 treatment (e.g., 300 microM, 200%), but the rise in the level of free intracellular Ca2+ after KCl stimulation (i.e., peak) was decreased (e.g., 300 microM, 50%) and the cell's ability to sequester or extrude the excess Ca2+ (i.e., Ca2+ recovery time) after depolarization was decreased significantly. All compounds prevented baseline Ca2+ increases and, with the exception of conotoxin, antagonized the peak decreases in Ca2+. It is interesting that after 300 microM H2O2 exposure, only Trolox was partially effective in preventing these deficits in recovery. Conotoxin increased the decrement recovery in the absence of H2O2. However, in cells exposed to 5 or 25 microM H2O2, conotoxin as well as the other agents were effective in preventing the deficits in recovery.

Aging↗
PubMed1997

Unusual misplacement sites of percutaneous central venous lines in the very low birth weight neonate.

Percutaneously placed central venous lines have become an intricate part of the medical management of the very low birth weight infant. It is critically important that health care providers involved with the placement of these catheters be familiar with the possible subtle sites for catheter misplacement. We present two case reports of inadvertent ascending lumbar vein catheterization with a percutaneously placed Silastic catheter where the saphenous vein was used for venous access. The literature is reviewed with regard to the history of use, indications, placement, and associated complications of these catheters.

Catheterization, Central Venous↗
PubMed1997

Recombinant human hemoglobin does not affect renal function in humans: analysis of safety and pharmacokinetics.

BACKGROUND: Recombinant human hemoglobin (OptroD; rHb1.1) is a genetically engineered protein produced in Escherichia coli. The two alpha-globin polypeptides are genetically joined, resulting in a stable tetramer that does not dissociate into dimers or monomers. Historically, infusion in humans of acellular hemoglobin preparations has resulted in renal toxicity. This study was performed to evaluate the safety and pharmacokinetics of rHb1.1 when infused in humans. METHODS: After giving informed consent, 48 healthy male volunteers were randomly assigned to receive either 0.015-0.32 g/kg 5% rHb1.1 (n = 34) or an equivalent amount of 5% human serum albumin (HSA; n = 14) infused intravenously over 0.8-1.9 h. Serum creatinine, creatinine clearance, urine N-acetyl-beta-glucosaminidase, and serum rHb1.1 concentrations were measured before and at timed intervals after infusion. RESULTS: Postinfusion urine N-acetyl-beta-glucosaminidase activity did not exceed preinfusion values at any interval in either group. Serum creatinine did not differ from preinfusion values at 1 day, 2-3 days, or 7 days after infusion for either group. Creatinine clearance increased significantly for the HSA group 12 h after infusion (138 +/- 16 ml/min, means +/- SE) and in the rHb1.1 group 1 day after infusion (112 +/- 5 ml/min; P < 0.05). Values for creatinine clearance did not differ from preinfusion values for either group at any other postinfusion interval; serum creatinine and creatinine clearance did not differ between groups at any time. The amount of hemoglobin excreted in the urine did not exceed approximately 0.04% of the administered rHb1.1 dose in any volunteer. Plasma clearance of rHb1.1 decreased and half-life increased as a function of increasing plasma concentration (e.g., the half-life was 2.8 h at a plasma concentration of 0.5 mg/ml and 12 h at 5 mg/ml). The incidence of gastrointestinal symptoms, fever, and chills was greater after infusion of rHb1.1 than after HSA (P < 0.05). CONCLUSIONS: No evidence for rHb1.1-mediated nephrotoxicity was observed in volunteers given doses of rHb1.1 as large as 0.32 g/kg. Because the clearance of rHb1.1 varies inversely with its concentration, additional studies with larger doses are necessary to determine the half-life expected in clinical use. Administration of rHb1.1 to conscious humans is associated with some side effects, such as gastrointestinal upset, fever, chills, headache, and backache.

Adolescent↗
PubMed1997

Inhibition of human neutrophil beta2-integrin-dependent adherence by hyperbaric O2.

Animal and clinical investigations have reported that exposure to hyperbaric O(2) improved the outcome of some reperfusion injuries. Animal studies have suggested that this may be due to an inhibition of leukocyte adherence to injured endothelium. This investigation tested the hypothesis that exposure to hyperbaric O(2) would inhibit beta2-integrin-dependent adherence of human neutrophils. Subjects were exposed to O(2) at partial pressures of up to 3 atmospheres absolute (ATA; 1 ATA = 0.1 MPa) for 45 min, and neutrophil binding to nylon columns and to fibrinogen-coated surfaces was measured. Exposure to O(2) at 2.8 or 3.0 ATA inhibited beta2-integrin-dependent neutrophil adherence but had no effect on the cell-surface expression of beta2-integrins, respiratory burst in response to phorbol ester, or non-beta2-integrin-dependent adherence to plastic plates coated with a fibronectin-like protein. beta2-Integrin adherence was restored by incubating blood with 8-bromoguanosine 3',5'-cyclic monophosphate (cGMP) and hyperbaric O(2) inhibited synthesis of cGMP by neutrophils stimulated with N-formyl-Met-Leu-Phe (FMLP). In studies of cell fractions, the activity of membrane guanylate cyclase was found to be increased by incubation with FMLP as well as by atrial natriuretic peptide (ANP) plus ATP. Hyperbaric O(2) had no effect on the basal activity of soluble or membrane-bound guanylate cyclase. However, hyperbaric O(2) inhibited the function of both the extracellular binding domain of membrane guanylate cyclase as well as intracellular catalytic activity. There are approximately 7,300 membrane guanylate cyclase molecules per cell, based on binding studies with ANP, with a dissociation constant of approximately 450 pM. Hyperbaric O(2) inhibits the function of human neutrophil beta2-integrins by a process linked to impaired synthesis of cGMP.

Adult↗
PubMed1997

Release of glutathione from erythrocytes and other markers of oxidative stress in carbon monoxide poisoning.

Rats exposed to CO in a manner known to cause oxidative stress in brain exhibited a twofold increase in plasma levels of oxidized proteins, thiobarbituric acid-reactive substances (TBARS), oxidized glutathione (GSSG), and reduced glutathione (GSH). Changes were neither directly related to hypoxic stress from carboxyhemoglobin nor significantly influenced by circulating platelets or neutrophils. Treatment with the nitric oxide synthase inhibitor N omega-nitro-L-arginine methyl ester inhibited elevations in GSH and GSSG but not changes in oxidized proteins or TBARS, suggesting that two oxidative mechanisms may be operating in this model and that GSH and GSSG elevations involved nitric oxide-derived oxidants. Elevations of blood GSH and GSSG occurred at different anatomic sites, indicating that no single organ was the source of the increased peptides. Animals that underwent exchange transfusion with a hemoglobin-containing saline solution did not exhibit elevations in GSH and GSSG, suggesting that blood-borne cells released these peptides in response to oxidative stress. In in vitro studies, erythrocytes, but not platelets and leukocytes, responded to oxidative stress from peroxynitrite by releasing GSH, whereas no release was observed in response to nitric oxide or superoxide. Glucose, maltose, and cytochalasin B, agents that protect extracellular components of the hexose transport protein complex from oxidative stress, prevented GSH release. The data indicate that nitric oxide-derived oxidants are involved in CO-mediated oxidative stress within the vascular compartment and that elevations of several compounds may be useful for identifying exposures to CO likely to precipitate brain injury.

Animals↗
PubMed1997

Changing jobs: an essential part of career development.

Supported employment, by definition, assumes the need for ongoing support. Despite this, assumptions inherent within regulations and policies of federal and state rehabilitation systems appear to be at variance with this definition: Job placement is viewed as final and support is temporary. Consequently, retraining and replacement services following the termination of a job are an afterthought, job change is equated with failure, and retraining is a reaction to this failure. In contrast, models of career development for the general population assume that changing jobs is an integral part of career development. In this paper we have applied this more normative view of career development to the rehabilitation system and the provision of supported employment.

Career Choice↗