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Biomedical subjects

C J Long

Publications and source records attributed to C J Long.

At least 37 records · Page 2Linked to original sources
PubMed1993

Effects of enhancer mutations on the expression of human immunodeficiency virus 1-regulated luciferase and diphtheria toxin A chain genes in transfected cells.

This study explores human immunodeficiency virus 1 (HIV-1)-regulated diphtheria toxin A (DT-A) gene expression as a means of eradicating HIV-infected cells. Previously, we constructed luciferase and DT-A plasmids, containing cis-acting Tat and Rev responsive elements, which showed low basal expression and required both Tat and Rev for maximal expression. Cell lines which had stably integrated the DT-A constructs were resistant to HIV production. To reduce toxicity due to basal expression, this study investigates the effect of mutations in the HIV enhancer on expression of luciferase and DT-A plasmids. Some mutations were found to substantially reduce basal expression while still allowing for trans-activation. Such mutations, in combination with attenuated versions of DT-A, may make regulated toxin gene expression feasible as a therapy for AIDS.

Diphtheria Toxin↗
PubMed1993

Encapsidation of a recombinant LuIII parvovirus genome by H1 virus and the fibrotropic or lymphotropic strains of minute virus of mice.

We previously constructed a recombinant LuIII parvovirus genome lacking viral coding sequences and used it to generate luciferase-transducing virions, by cotransfection of cells with a helper plasmid expressing LuIII viral proteins. Here, we describe similar cotransfections using alternative, replication-defective helpers encoding the non-structural and capsid proteins of parvovirus H1, or of either the fibrotropic or lymphotropic parvovirus strain of minute virus of mice [MVM(p) or MVM(i)]. Each cotransfection generated transducing virus which directed luciferase expression after infection of HeLa cells. The transducing activity of virus produced using either LuIII or H1 helper plasmids could be specifically neutralized by antiserum raised against the corresponding infectious virus. When the recombinant LuIII parvovirus was pseudotyped with MVM(p) or MVM(i), the resulting virions efficiently expressed luciferase after infection in human or murine cells known to be permissive for both MVM strains. The MVM(p) pseudotyped virus also expressed this reporter efficiently when infected into the murine A9 fibroblast line. In contrast, the recombinant virus generated with an MVM(i) helper gave luciferase expression that was barely detectable after infection of A9 cells which are highly restrictive for MVM(i) productive infection. These results support the notion that the allotropic determinant of these MVM strains functions through their capsid proteins. Pseudotyping of recombinant parvovirus genomes should be useful in controlling their host range as vectors, and in studying mechanisms influencing the permissiveness of parvovirus infections.

Capsid↗
PubMed1992

Effects of severe closed-head injury on three stages of information processing.

The present study investigated the loci of the information-processing delay that characteristically follows severe closed-head injury (CHI). Sternberg's additive-factors logic was used to determine the effects of severe CHI on the central information-processing stages of stimulus encoding, memory comparison, and decision-making/response-selection. The task variables used to define the stages operationally were stimulus quality, memory set size, and stimulus-response compatibility. Twenty subjects who had sustained a severe CHI more than 18 months earlier and 20 matched control subjects completed a stimulus encoding by response selection task in Experiment 1, and a Sternberg high-speed memory scanning task in Experiment 2. The CHI group performed the stimulus encoding and decision-making/response-selection stages of processing significantly slower than did the control group. However, no significant group differences were found on the memory comparison stage, suggesting that memory comparison processes may be relatively intact in long-term patients with severe head trauma. The results are discussed in relation to a global and a late-specificity hypothesis of central processing deficits following severe CHI. The possibility that cognitive processes demanding less attention may be more resilient to injury is also considered.

Adult↗
PubMed1992

Inhibition of HIV production in cells containing an integrated, HIV-regulated diphtheria toxin A chain gene.

Construction of a DNA plasmid that expresses a diphtheria toxin A chain (DT-A) gene under control of human immunodeficiency virus (HIV-1) proteins Tat and Rev has been described. Here the generation of HeLa cell clones containing integrated, HIV-regulated DT-A sequences is reported. Five such clones were identified by their decreased expression of a luciferase reporter gene transiently cotransfected with Tat- and Rev-encoding plasmids. The decreased luciferase expression most probably was due to activation of the integrated DT-A gene because higher luciferase activity could be restored by introducing either DT antitoxin or a gene encoding a mutant, DT-resistant elongation factor 2 (the intracellular target for DT-A). Analysis by polymerase chain reaction (PCR) indicated that all clones expressed DT-A encoding RNA. The clones were then transfected with an HIV proviral clone and were tested for HIV production; all five clones demonstrated substantially impaired HIV production compared with parental HeLa cells, as shown by p24 assays of culture supernatants. Our success in generating these cell lines indicates that extremely low basal expression has been achieved in view of the high cellular lethality of DT-A. HIV-regulated expression of DT-A may be applicable as a gene therapy approach for the acquired immune deficiency syndrome (AIDS), to bring about selective suicide of HIV-infected cells before production of viral progeny.

Cloning, Molecular↗
PubMed1992

Inhibition of human immunodeficiency virus-1 production resulting from transduction with a retrovirus containing an HIV-regulated diphtheria toxin A chain gene.

Expression of a gene encoding the diphtheria toxin A (DT-A) chain, under the control of human immunodeficiency virus-1 (HIV-1) proteins Tat and Rev, has previously been shown to confer on cells an impaired ability to produce HIV. That work was done in HeLa cell lines that had stably integrated the regulated DT-A gene in a plasmid context. To increase the efficiency with which the HIV-regulated DT-A gene could be introduced into cells, we studied a recombinant, amphotropic murine leukemia virus containing the HIV-regulated DT-A transcription unit. Here we demonstrate that such recombinant retroviruses can be packaged, for both wild-type DT-A and an attenuated version, tox 176. In transient transfection assays, the proviral constructs exhibited similar basal and trans-activated levels of DT-A expression to the parental plasmids. Transduced H9 cells expressed the integrated DT-A gene upon transfection with plasmids encoding Tat and Rev, as assayed by decreased expression of a cotransfected luciferase reporter gene. Furthermore, the transduced H9 cells were substantially impaired in their ability to produce HIV, as demonstrated by p24 assays of culture supernatants following either transfection with an HIV proviral clone or infection with HIV-IIIB. These data demonstrate that basal expression of the regulated DT-A gene has been reduced to a tolerable level, both in packaging cells and transduced H9 cells. The use of HIV-regulated retroviruses encoding the highly lethal DT-A product may eventually be applicable as a gene therapy approach for the acquired immunodeficiency syndrome (AIDS).

Cell Line↗
PubMed1991

Activation of a diphtheria toxin A gene by expression of human immunodeficiency virus-1 Tat and Rev proteins in transfected cells.

Expression of a gene encoding the diphtheria toxin A (DT-A) fragment, controlled by tissue specific regulatory elements, has previously been used to kill selected cell populations. Here, we have examined the feasibility of controlling DT-A expression using regulatory systems from the human immunodeficiency virus (HIV-1) genome. Plasmids were constructed which express either DT-A or, as a model system, the luciferase (luc) reporter gene, under control of HIV-1 long terminal repeat (LTR) sequences (-167 to +80). While trans-activation by expression of the viral protein Tat was demonstrated, significant basal expression was observed. To reduce basal expression, cis-acting negative regulatory elements from the env region of the HIV-1 genome were inserted in the 3' untranslated region of both the luc and DT-A constructs. This dramatically reduced basal expression from the HIV LTR, and now both viral regulatory proteins Tat and Rev were required for maximal trans-activation. Such regulation of DT-A expression might be therapeutically applied to selectively kill HIV-infected cells in acquired immunodeficiency syndrome (AIDS) and AIDS-related complex (ARC).

Diphtheria Toxin↗
PubMed1991

Decision strategies for cerebral dysfunction IV: determination of cerebral dysfunction.

The present study examined the contribution of tests that compose the Impairment Index with regard to their ability to predict brain impairment. The investigation further examines the ability of various other tests, chosen because of their observed usefulness in detecting brain impairment. Subjects composing the brain damaged group (n = 298) were found to be impaired on both CT and EEG examinations. The pseudo-neurological control group (n = 193) consisted of patients referred for testing yet all non-neuropsychological tests were normal. Discriminant analyses were conducted to determine the weightings of each test as well as to determine the overall prediction accuracies of three groupings of tests. These analyses demonstrate that tests, not comprising the Impairment Index, are of predictive value in determining dysfunction: Thurstone Word Fluency and a 60 minute delayed recall from the WMS. Overall prediction accuracies of the various test groupings ranged from 73.52% to 78.02%. No statistically significant reduction of accuracy resulted with cross validation. All tests of statistically predictive value and all prediction results with their corresponding discriminant formulas are reported as well as a discussion of the application of these findings.

Journal Article↗
PubMed1990

Decision strategies in neuropsychology II: determination of age effects on neuropsychological performance.

The relationship of age to neuropsychological test performance was explored on the subtests comprising the Halstead-Reitan Battery and allied tests. Performance of 192 pseudo-neurologic control patients across 10-year age intervals from 16 to 65 was analyzed. The findings indicate a strong age-performance effect on spatial and more complex integrative tests with peak performance between 25 to 35 years of age and a decline thereafter. A lack of significant decline was noted on sensory, motor, and language tasks. The findings reveal that there is a curvilinear change in performance as a function of age and were discussed with regard to the obvious need to modify decision strategies to account for the age of the patient.

Journal Article↗
PubMed1990

Decision strategies in neuropsychology III: the relationship among lateralized dysfunction, etiology and depression.

The present study examines depression as a function of lateralized dysfunction and etiology. The proposed hypothesis is: patients with left hemisphere lesions would be depressed, whereas patients with right hemisphere lesions would not. A total of 61 patients (26 right hemisphere, 35 left hemisphere) having either a stroke, tumor, or penetrating head wound, completed the MMPI and were given a neuropsychological evaluation. Lesion localization was based on electroencephalography and neuroradiological procedures. A regression formula derived from the MMPI assessed depression. Two analyses were performed between: (i) right and left lesioned groups of mixed etiology and a control group, and (ii) right and left cerebrovascular lesioned groups and a control group. Potentially confounding factors, such as, diagnosis, demographic factors, degree of neuropsychological impairment, presence or absence of aphasia, and lesion localization were examined. Regardless of etiology, left and right lesioned patients did not significantly differ in their depression score, nor was either group considered depressed based on the criteria used in this study to measure depression.

Journal Article↗
PubMed1990

Decision strategies in neuropsychology I: determination of lateralized cerebral dysfunction.

This study addressed the issue concerning neuropsychological assessment and the determination of hemispheric lateralization. Based upon the different processing strategies employed by each hemisphere, several neuropsychological tests were hypothesized to discriminate between left hemisphere and right hemisphere damage. Lesion localization was determined by neurological examination, electroencephalography, and/or neuroradiological procedures for the 111 patients (47 right hemisphere, 64 left hemisphere) who were given a neuropsychological evaluation. Two strategies are presented for lateralizing cerebral impairment, a discriminant analysis and a decision process using one standard deviation as a cut-off point. These two strategies are compared with The Key Approach of Russell, Neuringer, and Goldstein (1970) and Simpson and Vega's WAIS Sign Test. The efficacy of decision strategies used to predict lateralization is discussed.

Journal Article↗
PubMed1989

What is the relationship between the endothelium derived relaxant factor and nitric oxide?

Nitric oxide gas in solution (NO) relaxes blood vessels with similar actions and pharmacodynamics as the endothelium derived relaxant factor (EDRF) and has been proposed to be a component of the materials released from stimulated endothelial cells. Certain data however suggest that EDRF and NO may not be identical. In some non-vascular smooth muscles, NO and EDRF exhibit markedly different pharmacologic profiles. Furthermore the interaction of EDRF and NO with anion exchange resins differ. The hypothesis that EDRF is identical to nitric oxide gas in solution or a nitrogen oxide containing compound is discussed.

Animals↗
PubMed1989

Models of aging and neuropsychological test performance decline with aging.

While some researchers have claimed that normal aging need not be accompanied by significant neuropsychological deficits ("preserved function" models), others have asserted that aging is associated with significant deficits in either specific or general cognitive functioning ("specific" vs "general" decline models). Among the significant decline models, there is disagreement regarding which functions are affected and to what degree, and at what point in the normal life span such a decline becomes significant. This study examined the neuropsychological test performance of 86 adults with no objective evidence of brain dysfunction. Significant decline, beginning as early as the 30s or 40s, was seen on all measures except the simple motor task of finger tapping. These results are viewed as supporting a model of differential decline of specific functions nested within a general decline model.

Adolescent↗
PubMed1988

Comparative pharmacology of endothelium-derived relaxing factor and nitric oxide.

The present study was designed to characterize endothelium-derived relaxing factor (EDRF) and nitric oxide (NO) by employing both biological and chemical methods. EDRF was released by the calcium ionophore A23187 from cultured bovine pulmonary artery endothelium (BPAE) grown on microcarrier beads and then superfused in a cell column. The maximum relaxations induced by EDRF (83%) or NO (79%) on phenylephrine (PE)-contracted rabbit aorta were similar. In contrast, EDRF was only half as potent as NO in relaxing the KCl-contracted rabbit aorta. EDRF induced a concentration-dependent relaxation of both PE-contracted rabbit aorta and histamine-contracted guinea pig aorta that was accompanied by a marked elevation in cyclic GMP levels. However, EDRF was vascular selective and did not relax or increase cyclic GMP levels of the histamine-contracted taenia coli of either species. NO was not vascular selective and relaxed both aorta and taenia coli and also markedly increased cyclic GMP levels in each. NO also relaxed dog femoral artery and gastrointestinal smooth muscle preparation of the lower esophageal sphincter, whereas EDRF only relaxed the femoral artery. Experiments were also performed describing the actions of a series of different resins: anion exchange resins (NH2/NH, AG-1), cation exchange resin (-COOH), reversed phase resin (C18) and hemoglobin-agarose on EDRF- or NO-induced relaxation. NH2/NH, AG-1 and hemoglobin-agarose resins inhibited EDRF-induced relaxation, but -COOH and C18 did not. The inhibition was dependent on the amount of resin employed. NO-induced relaxation was blocked only by hemoglobin-agarose but by none of the other resins.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

The inhibition of release of endothelium-derived relaxant factor by manoalide, a potent inhibitor of phospholipase A2.

1 The inhibitory action of manoalide on vascular relaxation was characterized. Manoalide was a potent inhibitor of endothelium-dependent relaxations in the isolated aorta of the rabbit. Responses to acetylcholine (ACh), A23187 and substance P were reduced by manoalide in a dose-dependent manner whilst those to nitroglycerin were unaffected. 2 Repeated washing of manoalide-treated tissues did not restore the relaxant response to ACh, indicating an irreversible action of manoalide. Scanning electron microscopic studies revealed that the endothelium remained intact on manoalide-treated tissues. 3 Rabbit aortae from which the endothelium had been removed relaxed in response to perfusion with ACh when delivered via an upstream endothelium-bearing tissue, indicating release of an endothelium-derived relaxant factor (EDRF). Incubation of the tissue without endothelium with manoalide (100 nM; 30 min) or inclusion of manoalide in the superfusate at a point just distal to the endothelium bearing tissue did not reduce the relaxant potency of EDRF. 4 Contractile responses of the guinea-pig isolated ileum to ACh were not affected by manoalide and, furthermore, binding of [3H]-quinuclidinyl benzilate to striatal membranes was not reduced by manoalide except at very high concentrations. 5 Manoalide therefore appears to inhibit vascular relaxation with a selectivity directed towards that mediated by EDRF. A direct antagonism of neither cholinoceptors nor EDRF receptors occurs and it is suggested that manoalide acts at a site within the endothelium to inhibit the synthesis and/or release of EDRF. Based upon these and previous data the possibility that EDRF is lipid-like or controlled by an arachidonic acid metabolite must continue to be considered.

Animals↗
PubMed1987

Adenosine reduces agonist-induced production of inositol phosphates in rat aorta.

In rat aortic strips rendered permeable with digitonin, inositol trisphosphate induced an efflux of 45Ca from the tissue. This release was not affected by adenosine. In tissues not treated with digitonin the contents of inositol trisphosphate (IP3) and its metabolite inositol 1-phosphate (IP1) were significantly enhanced by noradrenaline in the lithium-treated rat aorta. Adenosine was without effect on levels of IP1 or IP3 in tissues which had not been pretreated with noradrenaline, however, the noradrenaline-enhanced tissue content of IP1 was reduced by adenosine in a dose-dependent manner. The reduction in IP1 content by adenosine was enhanced by the uptake blocker dipyridamole (10 microM) and was blocked by the adenosine receptor antagonist 8-phenyltheophylline (10 microM). Adenosine may therefore lower production of inositol phosphates and thus reduce the stimulated release of calcium from intracellular stores. It is proposed that a reduction in phosphatidylinositol turnover may play a role in adenosine-mediated relaxation of blood vessels.

Adenosine↗
PubMed1986

The effects of adenosine on receptor sensitivity in the rat vas deferens.

In the guinea-pig isolated vas deferens adenosine augments the contractile response to noradrenaline (NA). Adenosine also augments the contractile response to NA and phenylephrine in the prostatic portion of the transversely bisected rat vas deferens. However, adenosine appeared to neither augment nor diminish the responses to carbachol, 5HT or high K+. Repetitive exposure of the vas to various agonists induced a desensitisation specific to the particular agonist used. The rate of return of responsiveness (the rate of resensitization) was investigated and, in particular, the effect of adenosine on that rate. In the rat vas deferens the rate of resensitization of responses to NA was retarded by adenosine and this effect was abolished by 8-phenyltheophylline and by yohimbine, but not by atropine or propranolol. Neither 8-phenyltheophylline, yohimbine, propranolol nor atropine by themselves affected the rate of resensitization of the rat alpha-adrenoceptor. Adenosine had no effect on the rate of resensitization of responses to phenylephrine, 5HT, carbachol or high K+. It is considered that the potentiation of catecholamine responses by adenosine involves solely alpha 1-receptors but that the retardation of resensitization may involve alpha 2-receptors which do not contribute directly to contraction.

Adenosine↗
PubMed1986

Postconcussion symptoms after head trauma: interpretation and treatment.

Postconcussion symptoms frequently present significant barriers to recovery after head injury. For most patients, emphasis on either organic or functional factors as the sole basis for such symptoms is unwarranted. In addition to the psychologic and behavioral impact of such deficits, recognition of cognitive deficits arising from head injury is an important means of comprehending postconcussion symptoms. We recommend structured recovery programs involving the matching of cognitive capabilities to stress level in treating postconcussion symptoms.

Acute Disease↗