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Biomedical subjects

A M Smith

Publications and source records attributed to A M Smith.

At least 307 records · Page 17Linked to original sources
PubMed1990

Seasonality of mania in New Zealand.

This paper examines the seasonal variation in manic admissions over a five year period in New Zealand. There is a significant monthly variation in admission rates with a spring/summer peak. Breakdown by sex, age and admission status suggested that there is no particular subgroup responsible, but that young first admissions and older female readmissions do not follow this trend. Examination of the monthly admission rates revealed that this peak is not constant from year to year. Possible mechanisms, which link fluctuating environmental variables with an irregular spring/summer peak for manic admissions, are discussed.

Adult↗
PubMed1990

Measurement of renal blood flow by 131I-labelled sodium iodohippurate imaging in a rat model of herpes encephalitis.

Renal blood flow was assessed qualitatively over a 30 min period in a rat model of herpes encephalitis by extra-renal scintigraphic imaging following the injection of 131I-labelled sodium iodohippurate. No significant differences were observed for renal blood flow in either kidney between (or within) infected and control groups. Our data suggest that kidney function is not compromised in this animal model of encephalitis. The results are discussed in the context of the development of a non-invasive protocol for the in vivo diagnosis of herpes encephalitis.

Animals↗
PubMed1989

HM-PAO-imaging and herpes encephalitis.

Selective uptake of the cerebral blood-flow imaging agent 99mTc-hexamethylpropyleneamine oxime (HM-PAO) by Human Herpesvirus 1 (HSV-1) infected cells was investigated in vivo and in vitro. No specific uptake of HM-PAO was observed either in encephalitic rats (by brain scintigraphic imaging or by immunoperoxidase staining/autoradiography of brain sections) or in HSV-1 infected Vero cells.

Animals↗
PubMed1989

Interference by phosphatases in the spectrophotometric assay for phosphoenolpyruvate carboxylase.

The aim of this work was to discover the extent of interference by phosphoenolpyruvate (PEP) phosphatase in spectrophotometric assays of PEP carboxylase (EC 4.1.1.31) in crude extracts of plant organs. The presence of PEP phosphatase and lactate dehydrogenase (EC 1.1.1.27) in extracts leads to PEP-dependent NADH oxidation that is independent of PEP carboxylase activity, and hence to overestimation of PEP carboxylase activity. In extracts of three organs of pea (Pisum sativum L.: leaves, developing embryos, and Rhizobium nodules), two organs of wheat (Triticum aestivum L.: developing grain and endosperm), and leaves of Moricandia arvensis (L.) D.C., lactate dehydrogenase activity was at most only 16% of that of PEP carboxylase at the pH optimum for PEP carboxylase activity. Endogenous PEP phosphatase and lactate dehydrogenase are thus unlikely to interfere seriously with the assay for PEP carboxylase at its optimum pH. Addition of lactate dehydrogenase to PEP carboxylase assays- a proposed means of correcting for nonenzymic decarboxylation of oxaloacetate to pyruvate-resulted in increases in PEP-dependent NADH oxidation from zero (Rhizobium nodules) to 131% (wheat grains). There was no obvious relationship between the magnitude of this increase and conditions in the assay that might promote oxaloacetate decarboxylation. However, the magnitude of the increase was highly positively correlated with the activity of PEP phosphatase in the extract. Addition of lactate dehydrogenase to PEP carboxylase assays can thus result in very large overestimations of PEP carboxylase activity, and should only be used as a means of correction for oxaloacetate decarboxylation for extracts with negligible PEP phosphatase activity.

Journal Article↗
PubMed1989

Evidence that the rb Locus Alters the Starch Content of Developing Pea Embryos through an Effect on ADP Glucose Pyrophosphorylase.

The aim of this work was to discover whether the rb locus of peas (Pisum sativum L.) affects seed starch content through action on an enzyme of starch synthesis in the developing embryo. The phenotypic effects of this locus are like those of the better characterised, unlinked r locus, which affects seed starch content through action on starch-branching enzyme. Embryos recessive at one or both of these loci (RRrbrb, rrRbRb, rrrbrb) have lower starch contents from an early stage of development than embryos dominant at these loci (RRRbRb). Maximum catalytic activities of enzymes of the pathway from sucrose to starch (sucrose synthase EC 2.4.1.13, UDP glucose pyrophosphorylase EC 2.7.7.9, ADP glucose pyrophosphorylase EC 2.7.7.27, ADP glucose-starch synthase EC 2.4.1.21, starch-branching enzyme EC 2.4.1.18) were compared in developing embryos of three lines of rbrb peas and four lines of RbRb peas. The only consistent difference between the two sorts of embryo was in the activity of ADP glucose pyrophosphorylase, which was at least tenfold lower in rbrb than in RbRb embryos. The activity in rbrb embryos was in most cases less than the estimated rate of starch synthesis of RRRbRb embryos. We conclude that the effect of the rb locus on the starch content of pea seeds is mediated through an alteration in the activity of ADP glucose pyrophosphorylase in the developing embryo.

Journal Article↗
PubMed1989

Cerebellar neuronal activity related to whole-arm reaching movements in the monkey.

1. Three monkeys were trained to make whole-arm reaching movements from a common central starting position toward eight radially arranged targets disposed at 45 degrees intervals. A sample of 312 cerebellar neurons with proximal-arm receptive fields or discharge related to shoulder or elbow movements was studied in the task. The sample included 69 Purkinje cells, 115 unidentified cortical cells, 65 interpositus neurons, and 63 dentate units. 2. The reaching task was divided into three movement-related epochs: a reaction time, a movement time, and holding over the target. All neurons demonstrated significant changes in discharge during one or more of these three epochs. Almost all of the cells (95%) showed a significant change in activity during the movement, whereas 68-69% of the cells showed significant changes from premovement activity during the reaction time and holding periods. 3. During the combined reaction time-movement period, 231/312 cells were strongly active in the task. Of these, 151 cells (65.4%) demonstrated unimodal directional responses. Sixty-three had a reciprocal relation to movement direction, whereas 88 showed only graded increases or decreases in activity. A further 37 cells (16.0%) were nondirectional, with statistically uniform changes in discharge in all eight directions. The remaining 43 cells (18.6%) showed significant differences in activity for different directions of movement, but their response patterns were not readily classifiable. 4. The proportion of directional versus nondirectional cells was consistent across the four cell populations. However, graded response patterns were more common and reciprocal responses less common among Purkinje and dentate neurons than among unidentified cortical cells and interpositus neurons. 5. The distribution of preferred directions of the population of cerebellar neurons covered all possible movement directions away from the common central starting position in the horizontal plane. When the preferred direction of each cell in the sample population was aligned, the mean direction-related activity of the cerebellar population formed a bell-shaped tuning curve for the activity recorded during both the reaction time and the movement, as well as during the time the arm maintained a fixed posture over the targets. A vector representation also showed that the overall activity of the cerebellar population during normal reaching arm movements generated a signal that varied with movement direction. 6. These results demonstrate that the cerebellum generates a signal that varies with the direction of movement of the proximal arm during normal aimed reaching movements and is consistent with a role in the control of the activity of muscles or muscle groups generating these movements.

Animals↗
PubMed1989

Transbronchial needle aspiration in clinical practice. A five-year experience.

We conducted a five-year review of our use of TBNA during bronchoscopy in our clinical practice. Out of 1,630 bronchoscopic procedures, 633 patients (39 percent) had TBNA performed as part of the initial examination. Mediastinal nodes were sampled in 86 percent of the patients who had TBNA performed, and 127 (23 percent) of 547 of these aspirates were positive. Other areas of mucosal abnormality of the tracheobronchial tree were also sampled by TBNA under direct vision and showed malignant cells in 44 (25 percent) of 176 aspirates. Of 363 patients first diagnosed as having carcinoma of the lung who had TBNA of N2 nodes, 41 (59 percent) of 70 with small-cell tumors were positive, as were 83 (28 percent) of 293 with non-small-cell malignant neoplasms. Comparison of cytologic results obtained by TBNA with histologic material in 109 cases showed an excellent correlation. In 31 cases (4 percent of all TBNA), the aspirate provided the sole means of establishing the diagnosis of cancer. Two patients were thought to have false-positive aspirates. No complications of therapeutic significance were encountered. We believe that TBNA is a safe and effective way to assess mediastinal lymphatic involvement in the staging of lung cancer and that TBNA can be safely performed as part of the initial bronchoscopic examination in patients suspected of having malignant neoplasms of the chest.

Adenocarcinoma↗
PubMed1988

Does the mutant mouse lurcher have deficits in spatially oriented behaviours?

Lurcher mutant mice, in comparison to normal mice, had directional deficits in the Morris milk tank test and in a water-maze spatial alternation task. The lurcher mutants also showed an initial lack of spontaneous alternation and did not alternate in one behavioral condition when the inter-trial interval was lengthened. Lurcher mice were slower to learn a simple left/right position response to escape a T-maze by swimming although their motor coordination was good. Paradoxically, no deficit was observed in learning to select a left or right position for food in the same T-maze although the goal-directed locomotion was very ataxic. Overall, the lurcher mutants have difficulty in guiding themselves in the water toward a visible goal.

Animals↗
PubMed1988

At least three different RNA polymerase holoenzymes direct transcription of the agarase gene (dagA) of Streptomyces coelicolor A3(2).

Using a combination of gel filtration and anion exchange FPLC, three different RNA polymerase holoenzymes from Streptomyces coelicolor A3(2) have been separated. Each holoenzyme transcribes from only one of the four promoters of the S. coelicolor A3(2) dagA gene. Holoenzyme reconstitution experiments identified the sigma factors responsible for recognition of two of the promoters. The previously identified E sigma 49 transcribes from the dagA p3 promoter, whereas a novel species, E sigma 28, recognizes the dagA p2 promoter. Circumstantial evidence suggests that the third holoenzyme, which transcribes from the dagA p4 promoter, is the previously identified E sigma 35. This level of transcriptional complexity supports the idea that RNA polymerase heterogeneity may play a central role in the regulation and coordination of gene expression in this biochemically and morphologically complex bacterium.

Base Sequence↗
PubMed1988

HIV surveillance by testing saliva.

Saliva specimens were tested for HIV antibody (anti-HIV) by an immunoglobulin G (IgG) antibody capture radioimmunoassay (GACRIA) and three sensitive commercial assays. In tests on 460 seronegative subjects and 196 seropositive subjects GACRIA was 99.8% specific and 100% sensitive. The Wellcome HIV monoclonal and Abbott recombinant DNA enzyme-linked immunosorbent assays (ELISAs) were also highly specific (99.8%, 100%) but they were less sensitive (90.9%, 82.0%). The Fujirebio particle agglutination assay was sensitive (97.8%) but its specificity was poor (84.1%). In testing saliva specimens from populations with an anti-HIV prevalence greater than 0.5%, sampling by GACRIA alone could provide a good estimate of the true prevalence. For true prevalences less than 0.5% good estimates could only be obtained if positive GACRIA reactions were confirmed by another independent salivary assay. Salivary testing for anti HIV is a convenient and potentially an accurate epidemiological tool.

Acquired Immunodeficiency Syndrome↗