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Biomedical subjects

B Levine

Publications and source records attributed to B Levine.

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

Oral antiplatelet efficacy of the platelet GPIIb/IIIa antagonist, DMP754 in non-human primates.

Binding kinetic studies with XV459, the active form of DMP754, demonstrated comparable binding kinetics (Kd and Koff) with platelets obtained from either human or baboons which were different from that with platelets obtained from dogs. Therefore, the present study was undertaken to evaluate the antiplatelet efficacy of DMP754 following oral administration in baboons. The dose levels evaluated were 0.1 and 1.0 mg/kg, IV and 0.1, 0.3, 1.0, and 3.0 mg/kg, oral of DMP754. Oral doses of DMP754 resulted in dose- and time-related inhibition of platelet aggregation along with a modest effect on bleeding time prolongation. DMP754 at similar oral doses had 24 hours of antiplatelet effects in baboon as compared to 8-12 hours duration of antiplatelet efficacy in dogs. At maximal antiplatelet doses DMP754 demonstrated no significant effects on platelet count, clinical chemistry or hemodynamic profiles in baboons. These data suggest that DMP754 is a potent orally active antiplatelet agent with extended duration after once a day oral administration in non-human primate.

Administration, Oral↗
PubMed1998

Conduction aphasia in a 3-year-old with a left posterior cortical/subcortical abscess.

A 3-year-old, right-handed girl developed a conduction-type aphasia following a second generalized seizure in the setting of a developing abscess involving left subcortical and cortical angular gyrus and arcuate fasciculus, and the posterior corpus callosum. The language disorder was fluent, characterized by age appropriate mean length of utterance and syntax, but with markedly reduced spontaneity of output, rapid rate of speech and mild dysarthria. Comprehension was relatively, but not completely spared. Naming, repetition, and reading (letters) were initially markedly impaired. Improvements in naming and repetition were associated with both literal and semantic paraphasias. Writing skills in the form of drawing were spared, but a mild apraxia to verbal command and imitation was initially present. Despite her young age, this child's fluent conduction aphasia and lesion localization were adult-like. Multimodal memory difficulties appeared to underlie what is best described as conduction aphasia.

Abscess↗
PubMed1998

Quantitative fluorescence resonance energy transfer measurements using fluorescence microscopy.

Fluorescence resonance energy transfer (FRET) is a technique used for quantifying the distance between two molecules conjugated to different fluorophores. By combining optical microscopy with FRET it is possible to obtain quantitative temporal and spatial information about the binding and interaction of proteins, lipids, enzymes, DNA, and RNA in vivo. In conjunction with the recent development of a variety of mutant green fluorescent proteins (mtGFPs), FRET microscopy provides the potential to measure the interaction of intracellular molecular species in intact living cells where the donor and acceptor fluorophores are actually part of the molecules themselves. However, steady-state FRET microscopy measurements can suffer from several sources of distortion, which need to be corrected. These include direct excitation of the acceptor at the donor excitation wavelengths and the dependence of FRET on the concentration of acceptor. We present a simple method for the analysis of FRET data obtained with standard filter sets in a fluorescence microscope. This method is corrected for cross talk (any detection of donor fluorescence with the acceptor emission filter and any detection of acceptor fluorescence with the donor emission filter), and for the dependence of FRET on the concentrations of the donor and acceptor. Measurements of the interaction of the proteins Bcl-2 and Beclin (a recently identified Bcl-2 interacting protein located on chromosome 17q21), are shown to document the accuracy of this approach for correction of donor and acceptor concentrations, and cross talk between the different filter units.

Animals↗
PubMed1998

Relationship of plasma buprenorphine and norbuprenorphine to withdrawal symptoms during dose induction, maintenance and withdrawal from sublingual buprenorphine.

AIMS: Examine the relationship between buprenorphine and norbuprenorphine plasma concentrations with subject-reported withdrawal symptomatology during buprenorphine dose induction, maintenance treatments (daily and alternate-day dosing) and withdrawal. DESIGN: Two groups of randomly assigned subjects inducted onto buprenorphine and maintained on 8 mg daily by the sublingual route for 18 days. Group 1 continued to receive daily buprenorphine to day 36. Group 2 subjects received alternate-day dosing of buprenorphine and placebo on days 19 to 36. Both groups received placebo on days 37 to 52. SETTING: Inpatient facilities at the Addiction Research Center, Intramural Research Center, NIDA, Baltimore, MD. PARTICIPANTS: Eleven male, heroin-dependent volunteers participating in a research study. INTERVENTION: Medications for treatment of withdrawal symptoms were prescribed as needed after day 39 (72 hours after the last dose of buprenorphine). MEASUREMENTS: Plasma concentrations of buprenorphine and norbuprenorphine, withdrawal symptomatology and pupil diameter. FINDINGS: The mean steady-state buprenorphine plasma concentration (24 hours) after daily administrations of sublingual buprenorphine for study days 21-35 was 0.80 ng/ml, and the mean alternate day steady-state buprenorphine plasma concentration (24 hours) was 0.77 ng/ml. Daily and alternate day steady-state norbuprenorphine plasma concentrations were 1.10 and 0.90 ng/ml, respectively. Predicted alternate day steady-state buprenorphine and norbuprenorphine plasma concentrations at 48 hours were 0.49 ng/ml and 0.57 ng/ml, respectively. Withdrawal scores varied inversely with plasma concentration. There were no significant differences between Groups 1 and 2 during steady-state (days 21-35) with regard to withdrawal scale scores or pupillary diameter. The overall, mean terminal elimination half-lives for buprenorphine and norbuprenorphine were 42 and 57 hours, respectively. CONCLUSIONS: during daily buprenorphine maintenance, plasma concentrations greater than 0.7 ng/ml of buprenorphine and norbuprenorphine were associated with minimal withdrawal symptoms. The long elimination half-life of buprenorphine suggested that increasing the buprenorphine dose with alternate-day administration may provide an effective, flexible therapy regimen for the treatment of opioid dependence.

Administration, Sublingual↗
PubMed1998

Episodic memory and the self in a case of isolated retrograde amnesia.

Isolated retrograde amnesia is defined as impaired recollection of experiences pre-dating brain injury with relatively preserved anterograde learning and memory. We present findings from a patient (M.L.) with isolated retrograde amnesia following severe traumatic brain injury (TBI) that address hypotheses of the interrelationships of focal neuropathology, episodic memory and the self. M.L. is densely amnesic for experiences predating his injury, but shows normal anterograde memory performance on a variety of standard tests of recall and recognition. The cognitive processes underlying this performance were examined with the remember/know technique, which permits separation of episodic from non-episodic contributions to memory tests by quantifying subjects' reports of re-experiencing aspects of the encoding episode. The results demonstrated that M.L. does not episodically re-experience post-injury events to the same extent as control subjects, although he can use familiarity or other non-episodic processes to distinguish events he has experienced from those he has not experienced. M.L.'s MRI showed damage to the right ventral frontal cortex and underlying white matter, including the uncinate fasciculus, a frontotemporal band of fibres previously hypothesized to mediate retrieval of specific events from one's personal past. Recent functional neuroimaging evidence of an association between right frontal lobe functioning and episodic retrieval demands suggest that M.L.'s memory deficits are related to this focal injury. This hypothesis was supported by right frontal polar hypoactivation in M.L. in response to episodic retrieval demands when he was examined with a cognitive activation H2(15)O PET paradigm that reliably activated this frontal region in both healthy controls and patients with TBI carefully matched to M.L. (but without isolated retrograde amnesia). He also showed increased left inferomedial temporal activation relative to control subjects, suggesting that his spared anterograde memory is mediated through increased reliance on medial temporal lobe structures. Re-experiencing events as part of one's past is based on autonoetic awareness, i.e. awareness of oneself as a continuous entity across time. This form of awareness also supports the formulation of future goals and the implementation of a behavioural guidance system to achieve them. The findings from this study converge to suggest that M.L. has impaired autonoetic awareness attributable to right ventral frontal lobe injury, including right frontal-temporal disconnection. Reorganized brain systems mediate certain preserved cognitive operations in M.L., but without the normal complement of information concerning the self with respect to both past and future events.

Adult↗
PubMed1998

Diabetes and decomposition: a case of diabetic ketoacidosis with advanced postmortem change.

The case is presented of a 34-year-old man, an insulin-dependent diabetic, who was found decomposed in his apartment. The victim had been recently discharged from a mental hospital and was to be monitored by the community's mental health personnel. While the autopsy revealed little in the way of disease, toxicological studies yielded a blood acetone level of 0.070 g/dl and a urine acetone level of 0.086 g/dl. The medical examiner ruled the cause of death diabetic ketoacidosis. To support this conclusion in the absence of a vitreous humor glucose concentration, 18 well-documented cases of diabetic ketoacidosis were reviewed, and acetone concentrations were compared with the acetone concentrations found in the presented case.

Acetone↗
PubMed1998

Structural interactions between actin, tropomyosin, caldesmon and calcium binding protein and the regulation of smooth muscle thin filaments.

The basic structure and functional properties of smooth muscle thin filaments were established about 10 years ago. Since then we and others have been working on the details of how tropomyosin, caldesmon and the Ca(2+)-binding protein regulate actin interaction with myosin. Our work has tended to emphasize the similarities between caldesmon and troponin function whilst others have been more concerned with the differences. The need to resolve the resulting differences has stimulated us to find new and more direct ways of investigating the mechanism of thin filament regulation. In recent years an apparent divergence has opened up between functional measurements, which indicate an allosteric-cooperative regulatory mechanism in which caldesmon and Ca(2+)-binding protein control actin-tropomyosin state in the same way as troponin, and structural measurements which show thin filament structures unlike striated muscle thin filaments. The challenge is to interpret function in terms of structure. We have combined functional studies with expression and mutagenesis of caldesmon and with structural methods including X-ray crystalography of tropomyosin-caldesmon crystals, electron microscopy and helical reconstruction of actin-tropomyosin-caldesmon complexes and high resolution nuclear magnetic resonance spectroscopy of the C-terminus of caldesmon in interaction with actin and calmodulin. We have used this information to propose a structural mechanism for caldesmon regulation of the smooth muscle thin filament.

Actins↗
PubMed1998

Sindbis virus induces apoptosis through a caspase-dependent, CrmA-sensitive pathway.

Sindbis virus infection of cultured cells and of neurons in mouse brains leads to programmed cell death exhibiting the classical characteristics of apoptosis. Although the mechanism by which Sindbis virus activates the cell suicide program is not known, we demonstrate here that Sindbis virus activates caspases, a family of death-inducing proteases, resulting in cleavage of several cellular substrates. To study the role of caspases in virus-induced apoptosis, we determined the effects of specific caspase inhibitors on Sindbis virus-induced cell death. CrmA (a serpin from cowpox virus) and zVAD-FMK (N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone) inhibited Sindbis virus-induced cell death, suggesting that cellular caspases facilitate apoptosis induced by Sindbis virus. Furthermore, CrmA significantly increased the rate of survival of infected mice. These inhibitors appear to protect cells by inhibiting the cellular death pathway rather than impairing virus replication or by inhibiting the nsP2 and capsid viral proteases. The specificity of CrmA indicates that the Sindbis virus-induced death pathway is similar to that induced by Fas or tumor necrosis factor alpha rather than being like the death pathway induced by DNA damage. Taken together, these data suggest a central role for caspases in Sindbis virus-induced apoptosis.

Alphavirus Infections↗
PubMed1998

Protection against fatal Sindbis virus encephalitis by beclin, a novel Bcl-2-interacting protein.

bcl-2, the prototypic cellular antiapoptotic gene, decreases Sindbis virus replication and Sindbis virus-induced apoptosis in mouse brains, resulting in protection against lethal encephalitis. To investigate potential mechanisms by which Bcl-2 protects against central nervous system Sindbis virus infection, we performed a yeast two-hybrid screen to identify Bcl-2-interacting gene products in an adult mouse brain library. We identified a novel 60-kDa coiled-coil protein, Beclin, which we confirmed interacts with Bcl-2 in mammalian cells, using fluorescence resonance energy transfer microscopy. To examine the role of Beclin in Sindbis virus pathogenesis, we constructed recombinant Sindbis virus chimeras that express full-length human Beclin (SIN/beclin), Beclin lacking the putative Bcl-2-binding domain (SIN/beclinDeltaBcl-2BD), or Beclin containing a premature stop codon near the 5' terminus (SIN/beclinstop). The survival of mice infected with SIN/beclin was significantly higher (71%) than the survival of mice infected with SIN/beclinDeltaBcl-2BD (9%) or SIN/beclinstop (7%) (P < 0.001). The brains of mice infected with SIN/beclin had fewer Sindbis virus RNA-positive cells, fewer apoptotic cells, and lower viral titers than the brains of mice infected with SIN/beclinDeltaBcl-2BD or SIN/beclinstop. These findings demonstrate that Beclin is a novel Bcl-2-interacting cellular protein that may play a role in antiviral host defense.

Alphavirus Infections↗
PubMed1998

The transmembrane domains of Sindbis virus envelope glycoproteins induce cell death.

Sindbis virus, the prototype alphavirus, kills cells by inducing apoptosis. To investigate potential mechanisms by which Sindbis virus induces apoptosis, we examined whether specific viral gene products were able to induce cell death. Genes encoding the three structural proteins--capsid, the precursor E1 (6K plus E1), and the precursor E2 (P62 or E3 plus E2)--were cotransfected with a beta-galactosidase reporter plasmid in transient-transfection assays in rat prostate adenocarcinoma AT3 cells. Cell death, as determined by measuring the loss of blue cells, was observed in AT3 cells transfected with 6K plus E1 and with P62 but not in cells transfected with capsid. Deletion mutagenesis of P62 indicated that large regions of the cytoplasmic domain and extracellular domain were not essential for the induction of cell death. However, constructs containing the minimal E3 signal sequence fused to the E2 transmembrane domain and the minimal E3 signal sequence fused to the E1 transmembrane domain induced death as efficiently as full-length P62 and 6K plus E1, whereas no cell death was observed after transfection with a control construct containing the E3 signal sequence linked to the transmembrane domain of murine CD4. These data demonstrate that intracellular expression of the transmembrane domains of the Sindbis virus envelope glycoproteins can kill AT3 cells.

Amino Acid Sequence↗
PubMed1998

Considerations in the interpretation of urine analyses in suspected opiate intoxications.

Over the years, it has been observed that in many suspected opiate intoxications, a urine screen using the standard 300 ng/mL cutoff has produced negative results. Subsequent analysis of the blood in many of these cases, in fact, were positive for morphine. To identify the frequency of this occurrence and to determine a more appropriate urine screening cutoff, paired blood and urine specimens were tested for opiates at the above cutoffs. Over the 6 months period of this study, 102 cases were identified where the blood morphine concentration by Roche Abuscreen was greater than 100 ng/mL of "morphine equivalents." All positive cases were confirmed as morphine by gas chromatography-mass spectrometry. Seventy nine of these cases, or 77%, had urine concentrations by Abuscreen exceeding 300 ng/mL of "morphine equivalents." The remaining 23 cases had urine morphine concentrations less than 300 ng/mL by Abuscreen. Urine specimens were then reanalyzed by Abuscreen using dilutions of the 300 ng/mL calibrator: 50, 75, and 150 ng/mL. Even with the use of a 50 ng/mL cutoff, 9 of these 23 specimens tested negative by Abuscreen. Moreover, 23 of the 67 cases or 34% in which the cause of death was narcotic intoxication had urine opiate concentrations by Abuscreen less than the recommended 300 ng/mL cutoff. These results indicate the critical importance in cases of suspected narcotic intoxication of screening the blood in addition to urine.

Data Interpretation, Statistical↗
PubMed1998

The effects of focal and diffuse brain damage on strategy application: evidence from focal lesions, traumatic brain injury and normal aging.

A new test of strategy application was designed to be relatively free of the constraints that limit the standard neuropsychological assessment of supervisory abilities. The validity of the test was assessed in 3 samples of participants with varying degrees of supervisory deficits and frontal systems dysfunction: focal frontal lesions, traumatic brain injury (TBI), and normal aging. Inefficient strategy application varied systematically across the 3 groups and was not due to extraneous factors such as forgetting the test instructions. Previous case studies have emphasized strategy application deficits in the face of normal neuropsychological test performance. In this study, it was shown that strategically impaired participants from a consecutive series can include those both with and without deficient neuropsychological test performance. When neuropsychological impairment was present, it was greatest on executive functioning tasks. Among participants with nonstrategic performance, there was evidence for a dissociation of knowledge from action. This finding was not specific to focal frontal lesions. A number of supervisory processes contributing to strategy application were identified. Exploratory analyses indicated differential effects of lesion location on these processes, especially inferior medial frontal and right hemisphere lesions. Overall, the results supported the use of unstructured tasks in the assessment of supervisory abilities.

Adolescent↗
PubMed1998

The effects of focal anterior and posterior brain lesions on verbal fluency.

Seventy-four patients with focal brain lesions were compared to a neurologically normal control group on tasks of letter-based and category-based list generation. When patients were divided only by right frontal, left frontal, or nonfrontal lesion sites, the pattern of fluency impairments confirmed prior claims. When more precise lesion sites within the frontal lobes were compared between groups classified based on their fluency performance, much more specific brain-behavior relations were uncovered. Damage to the right dorsolateral cortical or connecting striatal regions, the right posterior area, or the medial inferior frontal lobe of either hemisphere did not significantly affect letter-based fluency performance. Superior medial frontal damage, right or left, resulted in moderate impairment. Patients with left dorsolateral and/or striatal lesions were most impaired. Left parietal damage led to performance relatively equivalent to the superior medial and left dorsolateral groups. The same lesion sites produced impairments in category based fluency, but so did lesions of right dorsolateral and inferior medial regions. Task analysis and correlations with other measures revealed that different cognitive processes related to different brain regions underlie performance on verbal fluency tests.

Adult↗
PubMed1998

Vitamin B2 interference with TDx drugs-of-abuse assays.

Migraine is a headache condition found in significant frequency in the general population. One recent study has shown that riboflavin, Vitamin B2, is an effective prophylactic treatment for this headache condition. One subject in a recent study conducted by the Division of Forensic Toxicology, Armed Forces Institute of Pathology (AFIP) was taking 200 mg of riboflavin twice daily for the prevention of migraine headaches. When that subject's urine was tested using Abbott TDx drugs-of-abuse assays a number of tests resulted in a MX BKG error and all samples had BLK I values greater than those observed with normal urine specimens. The MX BKG error occurs when the BLK I value is greater than the upper limit determined by the manufacturer for a particular assay. High BLK I values may result if the specimen being analyzed contains a fluorophore that will compete with the fluorescein-labeled antibody used in the assay. This error serves as a notification that an interfering substance may be present and the assay is not performing according to manufacturer-specifications. Upon termination of riboflavin therapy the subject's BLK I values began to decrease within 60 h of the last 200 mg dose. A second subject began chronic riboflavin use to confirm this interferent effect. Elevated BLK I values resulted within 3 h of a single 200 mg dose and MX BKG errors occurred 1 h after a second 400 mg dose. No false negative results were noted with either subject (both subjects used butalbital and the first subject also used hydrocodone and diazepam during the study), suggesting that riboflavin is not an adulterant. Riboflavin use, however, does interfere with the TDx DAU assays and may result in quantitative values being determined which are of questionable validity in the face of an elevated BLK I value or may result in only an MX BKG error and no quantitative value reported. It is unclear if the interfering fluorophore is simply riboflavin itself or a combination of riboflavin and its metabolic products. Results obtained on urine samples collected from individuals using prophylactic riboflavin for migraine prevention and analyzed by TDx may be of questionable validity. Such samples may require analysis utilizing another immunoassay technique that does not employ a fluorescein-labeled antibody.

Fluorescence Polarization Immunoassay↗
PubMed1997

Cyclin dependent kinase inhibitors and dominant negative cyclin dependent kinase 4 and 6 promote survival of NGF-deprived sympathetic neurons.

Neuronal apoptosis plays a critical role in both normal development and disease. However, the precise molecular events controlling neuronal apoptosis are not well understood. Previously, we hypothesized that cell cycle regulatory molecules function in controlling the apoptotic pathways of trophic factor-deprived neurons. To test this hypothesis, we used the RNA alphavirus Sindbis to express three known cyclin dependent kinase inhibitors (CKIs), p16(ink4), p21(waf/cip), and p27(kip1), and dominant negative mutant forms of four known G1 cyclin dependent kinases (CDKs), Cdk2, Cdk3, Cdk4, and Cdk6, in primary cultured rat superior cervical ganglion sympathetic neurons. We demonstrate that expression of each of the CKIs protects the postmitotic cultured neurons from apoptotic death evoked by withdrawal of NGF. In addition, we show that expression of dominant negative forms of Cdk4 or Cdk6, but not Cdk2 or Cdk3, protects NGF-deprived sympathetic neurons from death. Such findings suggest the participation of several CDKs and their cognate cyclins in a neuronal apoptotic pathway.

Animals↗
PubMed1997

Tramadol distribution in four postmortem cases.

Four postmortem cases are reported in which the analgesic drug tramadol was identified. Tramadol is an alkaline extractable drug and elutes from a HP-5 column without the need for derivatization. Two metabolites of tramadol, N-desmethyl and O-desmethyl tramadol were also identified. Heart blood concentrations of tramadol in the four cases ranged from 0.17 to 4.4 mg/l. Tissue distribution of tramadol in the four cases failed to identify a sequestration site. None of the deaths reported were attributed to tramadol intoxication.

Adult↗
PubMed1997

Effects of aging on conditional associative learning: process analyses and comparison with focal frontal lesions.

Conditional associative learning (CAL), a measure validated in studies of frontal lesions, was used to evaluate the hypothesis that age-related cognitive decline is related to frontal dysfunction. Older adults and focal frontal participants showed impaired CAL performance, but the deficit was greater in the latter group, where it was specific to participants with dorsolateral prefrontal cortical (DLPFC) lesions. The deficits were attributable to strategic rather than basic associative processes. Error scores described ways in which past information failed to guide behavior, and they were related to lesion location. Congruence between older adults and DLPFC participants on a measure of defective inhibition suggests that age-related decline in inhibitory processes is due to DLPFC dysfunction.

Adolescent↗