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Biomedical subjects

K Hewitt

Publications and source records attributed to K Hewitt.

At least 19 recordsLinked to original sources
PubMed2000

Transient NMDA receptor inactivation provides long-term protection to cultured cortical neurons from a variety of death signals.

NMDA receptor antagonists, such as (+)-5-methyl-10, 11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate (MK-801), potently block glutamate-induced neuronal death in myriad in vitro cell models and effectively attenuate ischemic damage in vivo. In this report, a novel role for MK-801 and other NMDA receptor antagonists in preconditioning neurons to withstand a wide range of subsequent lethal insults is described. A brief 30 min exposure to 0.1 microM MK-801, applied up to 96 hr before a "lethal" insult, protected primary cortical neurons from a diverse group of neurotoxic agents, including NMDA, beta-amyloid, staurosporine, etoposide, and oxygen-glucose deprivation. This neuroprotective preconditioning by MK-801 arose from transient NMDA receptor inactivation, because the noncompetitive NMDA receptor antagonists memantine and nylindin and the competitive antagonist AP-5 gave similar effects. MK-801 protection was dependent on new protein synthesis during the first 2 hr, but not from 2 to 5 hr, after MK-801 exposure. The MK-801 transient did not alter the ability of NMDA to trigger normally lethal [Ca(2+)](i) influx 48 hr later, but it did block early downstream signaling events coupled to NMDA neurotoxicity, including PKC inactivation and the activation of calpain. Moreover, MK-801 protected neurons from staurosporine-induced apoptosis, although caspase activation in these cells was unimpeded. It is likely that the stress associated with transient inactivation of NMDA receptors triggered a rapid compensatory survival response that provided long-term protection from a spectrum of insults, inducing apoptotic and nonapoptotic death. The possibility that MK-801 preconditioning blocks an event common to seemingly diverse death mechanisms suggests it will be an important tool for obtaining a clearer understanding of the salient molecular events at work in neuronal death and survival pathways.

Adrenergic beta-Agonists↗
PubMed2000

Evaluation of glutathione-sensitive fluorescent dyes in cortical culture.

The sensitivity of six fluorophores to glutathione (GSH) was evaluated in living rat cortical neuronal/glial mixed cultures during the first 23 days in vitro (DIV). Four of the dyes require glutathione-S-transferase (GST) to form a fluorescent conjugate, potentially conferring specificity for GSH: these included t-butoxycarbonyl-Leu-Met-7-amino-4-chloromethylcoumarin (CMAC), 7-amino-4-chloromethylcoumarin (CMAC-blue), monochlorobimane (MCB), and 5-chloromethylfluorescein diacetate (CMFDA). The final two dyes examined, 2,3-naphthalenedicarboxaldehyde (NDA) and o-phthaldehyde (OPD), do not require GST for adduct formation with GSH. To examine the specificity of the dyes for GSH, cultures grown less than 6 DIV were pretreated with diethyl maleate or DL-buthionine-(S, R)-sulfoximine to deplete endogenous GSH. This resulted in a substantial loss of staining by CMAC, CMAC-blue, and MCB and partial loss of staining by OPD, indicating specificity for GSH, while staining by CMFDA or NDA was not altered, indicating a lack of specificity for GSH. Neurons experienced a dramatic decline in GSH levels relative to astrocytes between 5-6 DIV, as shown by a loss of neuronal staining with CMAC, CMAC-blue and MCB. This decrease in staining was not due to a decrease in GST activity, as neurons stained with the GST-insensitive OPD also exhibited a decline in GSH-sensitive staining. Immunolabeling experiments demonstrated that CMAC staining co-localized with GFAP-positive astrocytes, but not with MAP-2-positive neurons, in 18 DIV cultures. Finally, CMAC was exploited as a specific morphological marker of astrocytes in cultures aged >5 DIV. CMAC staining was employed to monitor astrocyte proliferation and to resolve astrocytes in living mixed cultures co-loaded with the Ca(2+)-sensitive dye, calcium green 5N-AM. GLIA 30:329-341, 2000. Published 2000 Wiley-Liss, Inc.

Animals↗
PubMed1999

Evidence that brain-derived neurotrophic factor neuroprotection is linked to its ability to reverse the NMDA-induced inactivation of protein kinase C in cortical neurons.

Several lines of evidence indicate that a rapid loss of neuronal protein kinase C (PKC) activity is a characteristic feature of cerebral ischemia and is a necessary step in the NMDA-induced death of cultured neurons. Exposing embryonic day 18 primary rat cortical neurons to 50 microM NMDA or 50 microM glutamate for 10 min caused approximately 80% cell death over the next 24 h, but excitotoxic death was largely averted, i.e., by 70-80%, in cells pretreated with brain-derived neurotrophic factor (BDNF). An 8-h preexposure to BDNF (50-100 ng/ml) maximally protected cortical cells from the effects of NMDA and glutamate, although the transient application of BDNF between 8 and 4 h before NMDA was equally protective. These effects of BDNF were abolished at supralethal, i.e., >100 microM, NMDA concentrations. It is significant that BDNF pretreatment prevented the inactivation of PKC in cortical cells normally seen 30 min to 2 h following lethal NMDA or glutamate exposure. This BDNF effect did not arise from changes in NMDA channel activity because neither whole-cell NMDA current amplitudes nor increases in intracellular free Ca2+ concentration were altered by the 8-h BDNF pretreatment. Furthermore, BDNF offered no neuroprotection to cells treated with the PKC inhibitors staurosporine (10-20 nM), calphostin C (1-2.5 microM), or GF-109203X (100 nM) at the time of NMDA addition. These results underscore the importance of PKC inactivation in glutamate-induced neuronal death. They also suggest that BDNF neuroprotection arises, at least in part, via its ability to block the mechanism by which pathophysiological Ca2+ influx through the NMDA receptor causes membrane PKC inactivation.

Animals↗
PubMed1999

Stem cell function and engraftment is not affected by "in vivo purging" with rituximab for autologous stem cell treatment for patients with low-grade non-Hodgkin's lymphoma.

The chimeric anti-CD20 monoclonal antibody rituximab (Rituxan; IDEC Pharmaceuticals, San Diego, CA, and Genentech, Inc, San Francisco, CA) has recently been approved by the US Food and Drug Administration as single-agent treatment of relapsed/refractory low-grade or follicular non-Hodgkin's lymphoma. Initial results from the pivotal clinical trial revealed that response rates to rituximab were higher in patients who previously had high-dose therapy and autologous stem cell transplantation. We have initiated a clinical trial that combines the use of rituximab with high-dose chemotherapy followed by autologous stem cell transplantation for patients with chemosensitive relapsed follicular small cleaved or mantle cell lymphoma. A unique feature of this study is that in addition to eight maintenance infusions of rituximab after autologous stem cell transplantation, patients also received rituximab 375 mg/m2 2 days before a granulocyte colony-stimulating factor-mobilized stem cell collection as "in vivo purge." We report on preliminary results demonstrating the safety and efficacy of the in vivo purge on 10 patients undergoing stem cell mobilization, nine of whom have already undergone transplantation. The peripheral blood CD34+ counts were 14.92 and 20 x 10(6)/L on day 4 and day 5, respectively, of the stem cell mobilization with granulocyte colony-stimulating factor. This compares with 11.7 and 11.8 x 10(6)/L, respectively, for the control population. The median CD34 stem cell yield in the graft collection was 3.7 x 10(6)/kg in patients receiving rituximab in vivo purge compared with 3.1 x 10(6)/kg in the control population. The target stem cell collection was successfully collected in six of 10 patients in a 1-day single large-volume leukapheresis collection, while two patients required 2 days and the last two patients required 3 days. Functional assays revealed the stem cell colony-forming unit-granulocyte monocyte and burst-forming unit-erythrocyte to be 55 and 44 colonies per plate, respectively, for the patients receiving the in vivo rituximab purge. This compares favorably with 37 and 38.5 colonies per plate, respectively, for the control population. Neutrophil engraftment took a median of 11 days for both cohorts; platelet independence was achieved in 8 days compared with 10 days for the control population. The median number of platelet transfusions was two for patients receiving rituximab and 2.5 for the control group. Assessment of serum cytokines immediately before the rituximab infusion during the stem cell mobilization and immediately after revealed a twofold to sevenfold increase in interleukin-1beta, tumor necrosis factor-alpha, and interleukin-6. The polymerase chain reaction analysis for minimal residual disease in stem cell collections and in peripheral blood and bone marrow samples of these patients will help to determine the efficacy of rituximab in vivo purge on disease progression.

Adult↗
PubMed1998

Neurobehavioral effects of chronic ingestion of Great Lakes chinook salmon.

Cross-generational chronic feeding of either a 5 or a 20% lyophilized Lake Huron (LH) or Lake Ontario (LO) chinook salmon diet to rats caused no observable effects on many behavioral dimensions including activity, exploration, sensorimotor function, and stereotypy. As assessed by the Morris water maze and the radial arm maze, there was no diet-induced impairment of spatial learning or long-term memory. There was no evidence that the fish diets caused an exaggerated response to food reward reduction as had been observed previously for rats fed Oswego area Lake Ontario salmon. Effects of the fish diets with the exception of one statistically significant but probably meaningless effect on the Morris water maze for females were found only for male rats and only for males who ate the 20% diet. F1 male rats were reluctant to traverse a runway for a single pellet reward. Performance of the reference/working memory version of the radial arm maze was affected for the F1 LO-20 rats and for the F2 LH-20 rats. Until further research is conducted it would be unwise to ignore indications that male rats may show some effect of chronic consumption of the highest concentration of these diets, particularly on tasks that require intact frontocortical dopamine function.

Analysis of Variance↗
PubMed1997

Advanced therapeutics program.

It has been a very exciting year for the advanced therapeutics team. We have seen our program become a reality, having successfully transplanted our first patients early this spring. The clinical and laboratory parts of our team work well together, never losing sight of our common goal-providing a state-of-the-art program for our patient population. The role of primary nurse coordinator remains a challenging one as the technological advancements in science and medicine continually provide us with the knowledge to make changes and improvements in our care.

Humans↗
PubMed1996

Immunosuppressive toxicity of CAMPATH1H monoclonal antibody in the treatment of patients with recurrent low grade lymphoma.

We have studied, as part of a group of international multicenter phase II clinical trials, the toxicity and effectiveness of CAMPATH1H administered intravenously three times a week in an outpatient setting to patients with recurrent or progressive low grade lymphoma. We report here on the toxicity and therapeutic results of the first seven patients treated before the study was closed prematurely because of unacceptable toxicity. Classical complete or partial responses of treatment were seen in three of seven patients. One complete response lasted 8.5 months and the other complete response is ongoing at 1 year. Responses occurred in nodal sites as well as in skin and peripheral blood. The first three or four antibody infusions in each patient was associated with grade 1 or 2 side-effects including rigor, fever, facial flushing, nausea, vomiting, hives, wheezes, hypotension, and/or diarrhea but these subsequently decreased or disappeared. The most significant toxicity was profound lymphopenia and associated infection, usually viral. Six of seven patients had culture or serologically documented infections and four patients had two or more such episodes. All infections responded to temporary discontinuation of antibody therapy and appropriate antiviral or antibiotic agents. We conclude that CAMPATH1H monoclonal antibody has therapeutic activity against low grade non-Hodgkin's lymphoma but that this activity is limited by marked lymphopenia and an unacceptably high frequency of serious infection at the dose and schedule used in this trial.

Adult↗
PubMed1992

Combined treatment with MK-801 and nicardipine reduces global ischemic damage in the gerbil.

BACKGROUND AND PURPOSE: Excessive activation of the N-methyl-D-aspartate receptor by glutamate produces an influx of Ca2+, which in turn is thought to lead to ischemic cell death. In this study we evaluated the combined treatment of the N-methyl-D-aspartate antagonist dizocilpine (MK-801) and the dihydropyridine Ca2+ channel blocker nicardipine for the reduction of hippocampal CA1 neuronal loss. METHODS: Global ischemia was induced by bilateral carotid artery occlusion in the gerbil. Body temperature was maintained between 36.5 degrees C and 37.5 degrees C during surgery. MK-801 (5.0 mg/kg) was injected 15 minutes after occlusion whereas nicardipine was given by injection and via a micro-osmotic pump (1.0 mg/kg/day) for 3 days. RESULTS: Postischemic treatment with MK-801 reduced CA1 cell loss by 27.0%, whereas nicardipine reduced CA1 cell loss by 13.3%. Combined postischemic treatment with these drugs yielded an additive, protective effect (44.5% reduction of CA1 loss) that did not appear to result from postischemic hypothermia as assessed by skull and rectal temperature recordings. CONCLUSIONS: Our results demonstrate that MK-801 plus nicardipine significantly attenuates CA1 cell death after forebrain ischemia in the gerbil. Excitatory amino acid antagonists in combination with Ca2+ channel antagonists may be an effective therapy in patients exposed to global ischemic insult.

Animals↗
PubMed1991

Parent education in preventing behaviour problems.

The 'parent education package' (PEP) uses a combination of leaflets and health visitor intervention to help parents prevent the development of behaviour problems in their children. In evaluating PEP Kevin Hewitt et al found that, though popular with parents, the programme produced no actual behaviour change in their children. The results suggest that a successful prevention programme should perhaps focus on encouraging parents to think more positively about their children.

Child Behavior Disorders↗
PubMed1989

Sleep problems in pre-school children.

Records were kept by one health visitor on the progress of nine children with sleeping difficulties. All the children were from socially disadvantaged families. The results reveal that the individual constructional treatment programmes which were applied by the health visitor were effective within a brief period and were not costly. Implications for health visiting practice are discussed and further issues about behavioural treatment and service delivery raised.

Child, Preschool↗
PubMed1987

Sequential chemotherapy and radiation for nasopharyngeal cancer: absence of long-term benefit despite a high rate of tumor response to chemotherapy.

Between April 1981 and December 1983, patients with locoregional carcinoma of the nasopharynx were treated with two courses of chemotherapy administered before radiation therapy. Chemotherapy consisted of methotrexate, bleomycin, and cisplatin, which were administered at 3-week intervals, and radiation therapy was scheduled to commence 3 weeks after the start of the second course. Forty-nine of 51 consecutive patients were treated; only one patient progressed on chemotherapy, and of 36 patients with measurable neck nodes, eight had complete and 19 had partial clearance (greater than 50% decrease in cross-sectional area) of these nodes when assessed before initiation of radiotherapy. Despite the high rate of tumor response (75%; 95% confidence limits, 59% to 91%), the actuarial survival and disease-free survival curves were almost identical to those recorded for a consecutive group of 140 historical controls of similar stage distribution treated with radiation alone. This chemotherapy provided a high rate of tumor remission, but did not appear to convey long-term benefit to patients when used before radiation therapy.

Actuarial Analysis↗
PubMed1980

Diagnosed mental disorder in children and use of health services in four organized health care settings.

The authors present comparative data on the extent, nature, and impact of diagnosed mental disorder among children under 18 years of age seen during 1975 in four organized health care settings. Between 3.3% and 10.1% of the children seen were diagnosed as having a mental disorder in the study year, representing an annual prevalence of between 2.2% and 8.2% of the "covered" child populations. Transient situational disturbances, behavior disorders, and special symptoms were the most common diagnoses; the more severe disorders (organic brain disease, schizophrenia, and affective and other psychoses) accounted for less than 4% of all diagnosed mental disorder. Patients with diagnosed mental disorder used non-mental-health services (except those of pediatricians) appreciably more often than did patients without such a diagnosis.

Adolescent↗