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Biomedical subjects

G Smith

Publications and source records attributed to G Smith.

At least 19 recordsLinked to original sources
PubMed1992

Production of cytochrome P450 reductase yeast-rat hybrid proteins in Saccharomyces cerevisiae.

We present a novel strategy for increasing the level of functional mammalian cytochrome P450 (Cyt.P450) and NADPH:cytochrome P450 reductase enzymes produced in yeast. A cDNA encoding the rat P450 reductase was modified by the addition of a sequence coding for the N-terminal region of P450 reductase from Saccharomyces cerevisiae. The addition of this hydrophobic tail greatly increased the apparent stability of the reductase protein produced in S. cerevisiae, as compared to the unmodified rat P450 reductase. When the rat hybrid reductase was produced simultaneously with one of two mammalian Cyt.P450s, the rat CYP2B1 or the human CYP2A6, there was a significant increase in the specific activity of each of the Cyt.P450s. The optimization of this approach and its extrapolation to other organisms should lead to a marked improvement in our ability to study and exploit the P450 system.

Amino Acid Sequence↗
PubMed1992

High frequency of malaria-specific T cells in non-exposed humans.

A major goal of current candidate malaria vaccines is to stimulate the expansion of clones of malaria-specific lymphocytes. We have examined the in vitro T cell responses of a group of malaria exposed and non-exposed adult Caucasian donors to recombinant circumsporozoite (CS) proteins, one of which is undergoing clinical trials, to blood-stage parasites, and to synthetic peptides copying the CS protein and defined blood-stage proteins. In nearly all individuals tested, CD4 T cell proliferation or lymphokine production occurred in response to whole parasite or CS protein stimulation, and T cells from many individuals responded to synthetic peptides. T cell responses were major histocompatibility complex-restricted, and stimulation of T cells with malaria parasites or CS protein did not appear to expand a population of T cell receptor gamma/delta cells. Malaria-specific responses were independent of prior malaria exposure, and in some cases exceeded the magnitude of response to tetanus toxoid. Specific T cells are present in high frequency in the peripheral blood of many donors who have never been exposed to malaria. Although malaria-specific CD4 T cells play an important role in immunity, these data question whether vaccines need to stimulate such cells, and focus attention on other aspects of malaria immunity which may be more critical to a successful vaccine.

Amino Acid Sequence↗
PubMed1992

Enzymatic activity and immunoreactivity of extracellular phospholipase A2 in inflammatory synovial fluids.

Synovial fluid PLA2 concentration was measured by an ELISA technique using monoclonal antibodies raised against human recombinant "synovial-type" group II phospholipase A2. This ELISA was specific for synovial-type PLA2 and did not detect pancreatic (group I) PLA2. In all synovial fluids examined, including rheumatoid, osteoarthritic, psoriatic, and gouty fluids, synovial fluid PLA2 enzyme activity significantly correlated with PLA2 immunoreactivity (P < 0.001). Within the limits of the ELISA technique, there was no evidence for the presence of specific or nonspecific modulation of PLA2 activity by either putative PLA2 activating or inhibitory proteins.

Arthritis↗
PubMed1992

The role of blood microfilters in clinical practice.

Blood filters have been available since the 1930s. In this review we evaluate the role of microaggregate filters (MF) in certain transfusion complications, namely non-haemolytic febrile transfusion reactions (NHFTR), pulmonary injury, thrombocytopenia, fibronectin depletion and histamine release. We review the latest generation of leucocyte depleting filters and discuss their role in preventing alloimmunisation, immunosuppression and CMV transmission. Finally, we provide a rationale for the role of blood microfiltration in the present day practice of intensive care medicine.

Blood Transfusion↗
PubMed1992

The development and mortality of the free-living stages of Haemonchus contortus in laboratory culture.

Haemonchus contortus eggs were cultured in intact fecal pellets at various temperatures (5-35 degrees C) for 22 days. Temperature and relative humidity were kept constant throughout the incubation period. Nl larval development occurred at 5 degrees C; peak third-stage larval recovery occurred at 20 degrees C. Egg mortality was an age-dependent phenomenon, whereas larval mortality remained constant irrespective of larval age. Development was characterized by a minimum development time followed by a transition to the next stage which occurred at a constant rate. All rates were temperature dependent. The minimum development times reported here are much less than those previously reported. Based on these results a mathematical model was used to describe the demography of the free-living stages of H. contortus at various temperatures.

Animals↗
PubMed1992

Serum phospholipase A2 enzyme activity and immunoreactivity in a prospective analysis of patients with septic shock.

Massive elevations of serum phospholipase A2 activity have been documented in patients with septic shock. Serum PLA2 activity correlated to the degree and duration of circulatory collapse, while purified native PLA2 reproduced hypotension in experimental animals. In a prospective study of patients with septic shock, we have determined the relationship of PLA2 enzyme activity to PLA2 immunoreactivity using radiolabelled E. coli phospholipid substrate and an ELISA specific for group II human nonpancreatic PLA2. In all patients, there was a clear concordance of the two assays. Maximal PLA2 concentration was increased a mean of 554-fold over normal levels. We found no evidence to support the presence of activating or inhibitory proteins. These data confirm that the observed increase in serum PLA2 activity in septic shock is due to intravascular release of group II nonpancreatic PLA2.

Antibodies, Monoclonal↗
PubMed1992

Safety and immunogenicity in volunteers of a recombinant Plasmodium falciparum circumsporozoite protein malaria vaccine produced in Lepidopteran cells.

A recombinant Plasmodium falciparum circumsporozoite (CS) antigen (rPfCSA) was produced in insect cells using a baculovirus expression vector containing the entire CS gene. This near full-length CS antigen was adsorbed onto aluminium phosphate for use as a malaria vaccine. In a study of safety and immunogenicity, 20 volunteers were divided into four groups of five each and inoculated intramuscularly with 10, 100, 500 or 1000 micrograms of vaccine. Primary vaccinations were followed by two booster immunizations at 2 and 6 months. Three volunteers developed prominent local reactions manifested as tenderness, redness and swelling at the injection site following the second or third vaccination. All symptoms resolved spontaneously within 72 h. Postimmunization sera from six of 20 volunteers showed seroconversions as measured by Western blot, using rPfCSA as antigen. However, specific anti-CS protein antibody could not be detected by indirect immunoflourescence against intact sporozoites or by ELISA using rPfCSA or peptide to the repeat region. In addition, 18 of 20 volunteers developed antibody to baculovirus proteins as determined by ELISA and/or Western blot. Antigen-driven replication studies using peripheral blood mononuclear cells from vaccinees failed to detect proliferative responses specific to CS protein. This recombinant CS protein vaccine, as formulated, was minimally immunogenic in humans.

Adult↗
PubMed1992

The mortality and fecundity of Haemonchus contortus in parasite-naive and parasite-exposed sheep following single experimental infections.

Parasite-exposed lambs and their parasite-naive controls were experimentally infected once only with 30,000 H. contortus larvae at 3, 9, 12, and 20 weeks following termination of a moderate immunizing infection of 30,000 H. contortus larvae. Previously exposed lambs, challenged at 3 weeks, had a significant reduction in the total H. contortus worm burden as compared to parasite-naive controls. No difference in the total H. contortus worm burden was found between parasite-exposed or parasite-naive lambs challenged at 9 weeks or thereafter. Female worms were found to be significantly smaller in lambs previously exposed to the parasite as compared to those found in parasite-naive lambs. The average parasite fecundity was 4700 eggs per female worm per day. Previous exposure of the lambs to the parasite had no effect on parasite fecundity. Various mathematical models were used to examine parasite fecundity. Parasite fecundity was found to increase in the initial post-challenge period reaching a constant value approximately 58 days after challenge infection. No density-dependent constraints on fecundity were observed.

Animals↗
PubMed1992

Optical performance of the super-reversed intraocular lens.

We compared the aniseikonia, Seidel aberrations, spot diagrams, and peripheral refractive power errors of a schematic eye with a super-reversed intraocular lens (IOL) and with conventional IOLs. The results did not indicate that the super-reversed IOL performs better optically than the other IOLs, primarily because of its poorer on-axis image performance. However, this disadvantage can be overcome by aspherizing the super-reversed IOL.

Aniseikonia↗
PubMed1992

Relationship between facial expressiveness and sympathetic activation in emotion: a critical review, with emphasis on modeling underlying mechanisms and individual differences.

Two important questions bearing on personality processes and individual differences are how do facial expressiveness and sympathetic activation vary as a function of the intensity of an emotional stimulus, and what is the functional mechanism underlying facial expressiveness and sympathetic activation in emotion? A formulation is proposed that is based on 2 propositions: (a) All strong emotions result in some degree of activation of the organism (i.e., principle of stimulus dynamism) and (b) there are individual differences in the gain (amplification) operating on the facial expressive and sympathetic response channels (i.e., principle of individual response uniqueness). This formulation organizes much of the existing data on internalizers and externalizers and yields novel predictions regarding the subpopulation labeled as generalizers.

Arousal↗
PubMed1992

Movements of the vocal cords on induction of anaesthesia with thiopentone or propofol.

Using a fibreoptic laryngoscope, we have recorded on video tape the movements of the vocal cords after induction of anaesthesia with either propofol or thiopentone. The angle formed by the vocal cords decreased after induction of anaesthesia in both groups. This reduction in angle was significantly greater in the thiopentone group. The vocal cords closed completely in four patients in the thiopentone group and one patient in the propofol group. This difference may be explained by greater depression of laryngeal reflexes by propofol and this may account for the lower incidence of laryngospasm after induction of anaesthesia with propofol in comparison with thiopentone.

Adult↗
PubMed1992

Studies of antibody-dependent enhancement of human immunodeficiency virus (HIV) type 1 infection mediated by Fc receptors using sera from recipients of a recombinant gp160 experimental HIV-1 vaccine.

Subneutralizing concentrations of sera from human immunodeficiency virus (HIV)-1-infected patients augment HIV infection mediated by Fc receptor uptake by human monocytes and the monocytic cell line U937. Antibody-dependent enhancement (ADE) and neutralization activity were studied in the sera of HIV-1 antibody-negative volunteers who had been immunized with three 40-micrograms doses of a recombinant gp160 (rgp160) candidate HIV vaccine. Volunteers were vaccinated with rgp160 or a hepatitis B vaccine as a control on days 0, 30, and 180. Sera were obtained before and after three doses of vaccine and were tested for ADE and neutralization activity. Serum samples collected before vaccination showed neither neutralization nor ADE activity. Thirteen sera from volunteers who received gp160 and four from placebo recipients failed to show ADE. Three sera showed low levels of neutralization of strain IIIB of HIV. Vaccination with this dose of rgp160 produced neutralizing antibodies in some subjects but did not induce detectable enhancing antibodies.

AIDS Vaccines↗
PubMed1992

Colposcopic and histologic findings and human papillomavirus (HPV) DNA test variability in young women positive for HPV DNA.

The purpose of this study was to determine the prevalence of human papillomavirus (HPV)-related disease in women positive for HPV DNA by using a commercially available DNA detection kit and to compare these results to HPV DNA variability observed in repeated sampling. Young women attending family planning clinics who were positive for HPV DNA on routine screening were asked to return for a repeat HPV DNA test, cytology, colposcopy, and biopsy if indicated. Of the 78 women examined, 35% had biopsy-verified low-grade dysplasia of the cervix, and 64% had evidence of HPV-related disease somewhere in the anogenital area. Fifty percent of the women had a negative test on repeat sampling, but there was no association between DNA persistence at the second visit and colposcopic/histologic findings. In conclusion, the minority of women positive for HPV DNA have latent infection. In addition, variability in detection is common and unrelated to the presence of HPV-related disease.

Adolescent↗