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Biomedical subjects

A M Smith

Publications and source records attributed to A M Smith.

At least 253 records · Page 14Linked to original sources
PubMed1993

Evaluation of response perseveration of rats in the radial arm maze following reinforcing and nonreinforcing drugs.

The behavioral effects of three drugs with high abuse potential (amphetamine, heroin, and nicotine) and two substances with low abuse potential (haloperidol and scopolamine) were evaluated in an eight-arm radial maze. Rats were trained to explore the maze for the food reward. Unlike most radial arm maze paradigms, a food pellet was made available every time the rat entered an arm; thus, no external restrictions were placed upon rats' exploratory pattern. Following 3 days of drug-free training, rats were injected prior to testing with one of the five drugs. Analysis of the sequences of arm entries demonstrated that the variability of the search strategy was significantly decreased by amphetamine, heroin, and nicotine. In contrast, scopolamine and haloperidol either decreased or had no effect on preservation. These data, along with previous data on ethanol and diazepam, lead to the speculation that drugs of abuse may share the common property of reducing behavioral variability.

Amphetamine↗
PubMed1993

Purification of a cathepsin L-like proteinase secreted by adult Fasciola hepatica.

A cysteine proteinase released in vitro by Fasciola hepatica was purified to homogeneity by Sephacryl S-200 gel filtration chromatography followed by QAE-Sephadex chromatography. The purified enzyme resolves as a single band with an apparent molecular size of 27 kDa on reducing SDS-polyacrylamide gel electrophoresis; however, under non-reducing conditions it migrates as multiple bands, each with enzymatic activity, in the apparent molecular size range 60-90 kDa. The sequence of the first 20 N-terminal amino acids of the enzyme shows considerable homology with cathepsin L-like proteinases. Immunolocalisation studies revealed that the cathepsin L-like proteinase is concentrated within vesicles in the gut epithelial cells of liver fluke.

Amino Acid Sequence↗
PubMed1993

Cathepsin L proteinase secreted by Fasciola hepatica in vitro prevents antibody-mediated eosinophil attachment to newly excysted juveniles.

Cathepsin L-like activity was demonstrated in the excretory/secretory (E/S) products of Fasciola hepatica newly excysted juveniles (NEJ), 3-week-old, 5-week-old and mature flukes using the fluorogenic substituted 7-amino-4-methylcoumarin substrates Z-phe-arg-AMC, Z-arg-arg-AMC and Z-arg-AMC. Gelatin-substrate polyacrylamide gel analysis revealed that the E/S from each of these stages contained multiple proteolytic enzymes; however, the pattern of proteinases obtained for NEJ E/S differed markedly from that of all other stages examined. The four NEJ proteinases identified were inhibited by leupeptin and Z-phe-ala-diazomethyl ketone indicating that each had cathepsin L-like activity. The E/S products of all four developmental stages contain an enzyme capable of cleaving immunoglobulin at the hinge region, the activity of which is also inhibited by Z-phe-ala-diazomethyl ketone. Using in vitro cell attachment assays we show that the cathepsin L-like proteinase purified from the E/S products of adult F. hepatica can prevent the antibody-mediated attachment of eosinophil to NEJ. These experiments indicate that this proteinase has an important biological function in immune evasion.

Animals↗
PubMed1993

Competitive athletes: preinjury and postinjury mood state and self-esteem.

In a prospective study, we determined whether preinjury and postinjury differences existed in the mood state and self-esteem of competitive athletes. The influence of severity of injury, gender, level of participation in sports, and type of sport on these dependent variables was also measured. Among 238 male and 38 female athletes from hockey, basketball, baseball, and volleyball teams, 36 sustained 43 injuries. Significant postinjury increases were noted for depression (P < 0.0001) and anger (P = 0.0012), whereas vigor (P < 0.0001) was significantly less after injury. When the 36 injuries were classified, 27 were minor or moderate (nonparticipation in sports for only one or two weekly assessments), and 9 were severe (nonparticipation for three or more weekly assessments). When a stepwise multiple regression equation was used to predict the scores for postinjury depression, the only significant predictor was the severity of injury (F = 8.48 [1, 34]; R2 = 0.30; P = 0.0063). Of the following physical and psychosocial variables--level of participation, type of sport, age, previous injury, preinjury stress, gender, mood state scales, and self-esteem--only level of participation (P < 0.0001) and type of sport (P = 0.0004) were predictors of injury. The significant preinjury and postinjury differences in mood state suggest that postinjury mood disturbances reported in previous studies are likely attributable to the occurrence of injury, are related to the severity of injury, and do not merely reflect a disturbed preinjury mood.

Affect↗
PubMed1993

Soluble isoforms of starch synthase and starch-branching enzyme also occur within starch granules in developing pea embryos.

Developing wild-type pea embryos contain two major isoforms of starch synthase and two isoforms of starch-branching enzyme. One of the starch synthases and both starch-branching enzymes occur both in the soluble fraction and tightly bound to starch granules. The other starch synthase, which is very similar to the waxy proteins of other species, is exclusively granule-bound., It is inactive when solubilized in a native form from starch granules, but activity is recovered when the SDS-denatured protein is reconstituted from polyacrylamide gels. Evidence is presented which indicates that all of these proteins become incorporated within the structure of the granule as it grows. It is proposed that the granule-bound waxy protein is active in vivo at the granule surface, whereas the remaining proteins are active in the soluble fraction of the amyloplast. The proteins become trapped within the granule matrix as the polymers they synthesize crystallize around them, and they probably play no further part in polymer synthesis.

1,4-alpha-Glucan Branching Enzyme↗
PubMed1993

Nutritional concerns of women with breast cancer.

Health professionals should assess the nutrition information needs of women with breast cancer in order to provide appropriate services. Questionnaires were mailed to 143 Reach to Recovery volunteers who had had surgery for breast cancer, and 72% responded. The subjects were mostly concerned about and wanted information on diets for cancer prevention, low-fat diets, weight reduction, and vitamin supplements. Findings also showed the potential for excessive vitamin/mineral use among one-third of respondents and a tendency toward weight gain regardless of whether or not chemotherapy was received. The results provide direction for development of nutrition educational materials and programs for women with breast cancer.

Adult↗
PubMed1993

Genetic diversity of penicillin-binding protein 2B and 2X genes from Streptococcus pneumoniae in South Africa.

Streptococcus pneumoniae (the pneumococcus) is believed to have developed resistance to penicillin by the production of altered forms of penicillin-binding proteins (PBPs) that have decreased affinity for penicillin. Sixty-eight clinical isolates of serogroup 6 and 19 pneumococci (MICs, < 0.015 to 8 micrograms/ml) were randomly selected from hospitals across South Africa which are at substantial geographic distance from each other. The polymerase chain reaction was used to isolate the penicillin-binding domain of PBPs 2B and 2X from the chromosomal DNAs of the bacteria; the purified PBP DNA was digested with restriction enzymes, the fragments were end-labelled and separated on polyacrylamide gels, and the DNA fingerprints were visualized following autoradiography. Fingerprint analysis revealed that at least 19 PBP 2B gene variants occur in the serogroup 6 and 19 pneumococci. The PBP 2B gene revealed a uniform profile among penicillin-susceptible isolates, with variation from this profile occurring only in isolates for which MICs were > or = 0.06 micrograms/ml. Analysis of the PBP 2X gene revealed a greater diversity in the population with 26 variant genes, including some diversity among susceptible isolates. Discrete profiles of both genes were found only within narrow bands of the penicillin MIC, so that the gene pattern predicted the MIC. PBP 2X gene variation and the lack of variability among PBP 2B genes in pneumococci inhibited at low MICs confirm that PBP 2X alteration may be responsible for low-level penicillin resistance, while alterations in both PBP 2B and PBP 2X are required for high-level resistance. The extensive diversity of PBP genes in South African serogroup 6 and 19 strains suggests that altered PBP genes have arisen frequently in this population.

Bacterial Proteins↗
PubMed1993

Comparison of cerebellar and motor cortex activity during reaching: directional tuning and response variability.

1. The responses of 262 motor cortex cells and 223 cerebellar neurons were recorded during whole-arm reaching movements toward targets lights in eight evenly distributed directions radiating from a common central starting position. The reaching movements were followed by a 2-s target hold period where a fixed arm posture was actively maintained to stabilize the hand over the target light. 2. Cerebellar neurons had a higher mean tonic discharge rate while holding over the starting position (22.9 imp/s) than did motor cortex cells (12.5 imp/s). The mean population response curve describing the changes in activities with movement direction was likewise shifted toward higher frequencies in the cerebellum compared with the motor cortex, but the amplitude of the two curves was about equal. Therefore, the baseline discharges of cerebellar neurons were higher, but their changes in activity during movement were similar to those of motor cortical cells. 3. Motor cortex neurons were more strongly related to active maintenance of different arm postures than were cerebellar units. This was shown by a larger posture-related population response curve in the motor cortex (half-wave amplitude of cosine function was 11.2 imp/s, compared with 7.0 imp/s for cerebellar neurons), which represented the average response curve calculated from all the cells of the population. Furthermore, the motor cortex population had a higher percentage of single cells with tonic responses while the hand was held over different targets (tonic and phasic-tonic cells composed 57% of motor cortex population, compared with 38% of cerebellar population). Proportionately more cerebellar cells were phasically related to the movements. 4. The majority of motor cortex cells (58%) showed reciprocal changes relative to the center-hold time activity where the activity increased for movements in the preferred direction and decreased for movements in the opposite direction. Most of the remaining cells (40%) showed graded changes where the activity increased gradually as reaching was directed closer to the preferred direction. In contrast, the most common cerebellar response pattern was graded (38%). Only 26% were reciprocal and 18% were non-directional. The remaining 2% of motor cortical cells and 18% of cerebellar neurons could not be readily assigned to any of these three response classes. 5. Sector widths were calculated to measure the dispersion of individual cerebellar and motor cortical cell activities about the eight movement directions. Sector widths calculated from the absolute activities were always broader for cerebellar neurons (i.e., the cells were more broadly tuned).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1993

High-dose etoposide and melphalan, and autologous bone marrow transplantation for patients with advanced Hodgkin's disease: importance of disease status at transplant.

PURPOSE: To evaluate an intensive therapy regimen of high-dose etoposide and melphalan and autologous bone marrow transplantation (ABMT) in advanced Hodgkin's disease; and to determine possible prognostic factors that predict for long-term disease-free survival (DFS). PATIENTS AND METHODS: Seventy-three patients with advanced Hodgkin's disease who had failed to achieve remission with front-line chemotherapy (n = 16) or who had relapsed (n = 57) were treated with high-dose etoposide 60 mg/kg and melphalan 160 mg/m2 and ABMT. Previous therapy included mechlorethamine, vincristine, procarbazine, and prednisone (MOPP) alternating with doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD), or hybrid MOPP/ABV. All patients received pretransplant cytoreduction with conventional-dose salvage chemotherapy and 40 also received pretransplant extended-field radiation to areas of bulky nodal disease (> 5 cm). RESULTS: Response to high-dose etoposide and melphalan was determined at 3 months post-ABMT. The complete response (CR) rate was 75% (95% confidence interval [CI], 64% to 84%), including 35 of 50 patients with measurable disease before ABMT (70%; 95% CI, 60% to 86%). There were three early deaths (septicemia) and four late deaths (three interstitial pneumonitis, one intracerebral hemorrhage). Actuarial DFS is 38.6% at 4 years. Multivariate regression analysis showed that disease status at the time of ABMT (no evidence of disease [NED], nonbulky residual disease [NBRD], or bulky disease) was the most important factor determining DFS: 68% of those transplanted with NED versus 26% for patients with NBRD and 0% for bulky disease (P = .0002, log-rank test). Relapse in a previous radiation field was the only other significant prognostic factor. CONCLUSION: Etoposide and melphalan is an effective and well-tolerated intensive therapy regimen in advanced Hodgkin's disease. Patients in complete remission after conventional-dose salvage therapy transplanted with this regimen enjoy superior long-term DFS.

Adolescent↗
PubMed1993

Dominant and nondominant negative C-erbA beta 1 receptors associated with thyroid hormone resistance syndromes augment 12-O-tetradecanoyl-phorbol-13-acetate induction of the collagenase promoter and exhibit defective 3,5,3'-triiodothyronine-mediated repression.

C-erbA receptors and v-erbA have been shown to functionally interact with 12-O-tetradecanoyl-phorbol-13-acetate (TPA)-inducible gene expression. These proteins enhance trans-activation by c-jun, and the c-erbA receptors in the presence of thyroid hormone repress TPA and c-jun induction of transcription. Also, v-erbA can abrogate T3-mediated repression. We have examined how dominant negative (S and CL) and nondominant negative (G-H) receptors cloned from various patients with thyroid hormone resistance syndromes affect expression of the collagenase promoter induced with TPA. The CL receptor (ARG315HIS mutation) has a 2-fold reduction in T3-binding affinity compared with human c-erbA beta 1 wild-type (WT) receptor, whereas the G-H receptor (ARG311HIS) and S receptor (deletion, THR codon 332) have T3-binding affinities reduced by 100-fold and greater than 100-fold, respectively. These mutant receptors were cotransfected with a collagenase promoter (-1200 to +63 base pairs) chloramphenicol acetyltransferase reporter gene (Col-CAT) into COS-7 cells. Levels of CAT reporter gene expression after transient transfection were determined in the presence or absence of 3-10 nM T3 and the presence or absence of 100 nM TPA. Unoccupied CL receptor and G-H and S receptors stimulated TPA-induced Col-CAT expression 1.5- to 9-fold. The CL receptor with thyroid hormone totally repressed TPA induction of the collagenase receptor. In the presence of thyroid hormone, the enhancing effects by S and G-H receptors on TPA-induced Col-CAT expression were unaffected and minimally diminished, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

[Babinski and movement synergism].

Babinski's hypothesis that the cerebellum plays an important role in controlling movement synergies is re-interpreted in the light of more recent neurophysiological data. Originally Babinski derived the concept of synergy from the study of movement kinematics, but today, synergy implies an underlying combination of simultaneous muscular activities. It is suggested that the fundamental unit of muscular synergy is the reciprocal inhibition or the co-contraction of antagonist muscles. Various experimental data suggest that an increase in Purkinje cell discharge decreases muscular activity and relaxes antagonist muscles. Inversely, a decrease of cerebellar cortical efferent activity increases nuclear excitability and as a result the long descending motor pathways. Consequently the cerebellum, by controlling joint stiffness through the level of co-contraction in antagonist muscles, would have a significant action in directing multi-joint movement and postural adjustments.

Cerebellum↗
PubMed1993

The nursing research internship program: providing research training in the clinical setting.

Today's changing health care delivery system with its emphasis on restructuring patient care services requires of nursing greater accountability for patient care services and a more careful and systematic examination of patient outcomes. Nursing research can help the profession meet these challenges. The New York City Health & Hospitals Corporation's Nursing Research Internship Program gives nurses an opportunity to become involved in research and serve as research resources to their colleagues. This program offers instruction in research methods, development and conduct of a research project, and participation in ongoing research activities.

Clinical Nursing Research↗
PubMed1993

Comparing cerebellar and motor cortical activity in reaching and grasping.

The activity of single cells in the cerebellar and motor cortex of awake monkeys was recorded during separate studies of whole-arm reaching movements and during the application of force-pulse perturbations to hand-held objects. Two general observations about the contribution of the cerebellum to the control of movement emerge from the data. The first, derived from the study of whole arm reaching, suggests that although both the motor cortex and cerebellum generate a signal related to movement direction, the cerebellar signal is less precise and varies from trial to trial even when the movement kinematics remain unchanged. The second observation, derived from the study of predictable perturbations of a hand-held object, indicates that cerebellar cortical neurons better reflect preparatory motor strategies formed from the anticipation of cutaneous and proprioceptive stimuli acquired by previous experience. In spite of strong relations to grip force and receptive fields stimulated by preparatory grip forces increase, the neurons of the percentral motor cortex showed very little anticipatory activity compared with either the premotor areas or the cerebellum.

Animals↗
PubMed1992

Synthesis and evaluation of 2-pyridinone derivatives as HIV-1-specific reverse transcriptase inhibitors. 2. Analogues of 3-aminopyridin-2(1H)-one.

A series of nonnucleoside 3-aminopyridin-2(1H)-one derivatives was synthesized and evaluated for HIV-1 RT inhibitory properties. Several analogs proved to be potent and highly selective antagonists with in vitro IC50 values as low as 19 nM in the enzyme assay using rC.dG as template-primer. Two compounds from this series, 3-[[(4,7-dimethylbenzoxazol-2-yl)methyl]-amino]-5-ethyl-6-methy lpyridin-2(1H)-one (34, L-697,639) and the corresponding 4,7-dichloro analogue (37, L-697,661) inhibited the spread of HIV-1 IIIb infection by 95% in MT4 cell culture at concentrations of 25-50 nM and were selected for clinical trials as antiviral agents.

Aminopyridines↗