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Biomedical subjects

S McPherson

Publications and source records attributed to S McPherson.

At least 19 recordsLinked to original sources
PubMed1995

Immune responses induced by administration of encapsidated poliovirus replicons which express HIV-1 gag and envelope proteins.

Several viruses have been exploited for the development of recombinant vaccine vectors in which to express foreign proteins. Recently, we have described a system utilizing the RNA virus, poliovirus. We have constructed poliovirus genomes in which regions of the capsid have been substituted with gene fragments of the HIV gag and env genes. A complementation system has been designed to encapsidate defective genomes by providing the capsid protein in trans from a recombinant vaccinia virus (VV-P1). Serial passage in the presence of VV-P1 resulted in the generation of stocks of these encapsidated replicons. Infection of cells with these encapsidated replicons resulted in the expression of the recombinant protein as a fusion protein with the poliovirus capsid proteins VP4 and VP1. In this study, we have utilized encapsidated replicons which express the HIV-1-gag capsid protein (p24) as well as 1.5 kb of the HIV-1 env gene. Stocks of these encapsidated replicons were obtained by 20 serial passages in the presence of VV-P1. In addition, passage of the encapsidated replicons in the presence of poliovirus type 2 Lansing resulted in the encapsidation of the replicons by the capsid proteins provided by poliovirus. The administration of the type 2 Lansing/encapsidated replicons expressing HIV-1 gag in BALB/c mice by intramuscular, intrarectal, or intragastric routes resulted in the generation of antibodies in the serum and secretions against both poliovirus and HIV-1 gag. To prove that the replicons alone are immunogenic, we administered replicons expressing either HIV-1 gag or env to transgenic mice which expressed the receptor for poliovirus type 1. Immunization of these mice by the intramuscular route resulted in the generation of serum antibodies specific for poliovirus as well as for HIV-1 antigens. The results obtained led us to the conclusion that the replicons are immunogenic when given alone or in the presence of poliovirus. These results are important for the use of the poliovirus replicons as a recombinant vaccine vector.

AIDS Vaccines↗
PubMed1995

An aspartic acid at amino acid 108 is required to rescue infectious virus after transfection of a poliovirus cDNA containing a CGDD but not SGDD amino acid motif in 3Dpol.

The poliovirus RNA-dependent RNA polymerase (3Dpol) contains a region of homology centered around the amino acid motif YGDD (amino acids 326 to 329), which has been postulated to be involved in the catalytic activity of the enzyme. Previous studies from this laboratory have used oligonucleotide site-directed mutagenesis to substitute the tyrosine amino acid at this motif with other amino acids (S. A. Jablonski and C. D. Morrow, J. Virol. 67:373-381, 1993). The viruses recovered with 3Dpol genes with a methionine mutation also contained a second mutation at amino acid 108 resulting in a glutamic acid-to-aspartic acid change (3D-E-108 to 3D-D-108) in the poliovirus RNA polymerase. On the basis of these results, we suggested that the amino acid at position 108 might interact with the YGDD region of the poliovirus polymerase. To further investigate this possibility, we have constructed a series of constructs in which the poliovirus RNA polymerases contained a mutation at amino acid 108 (3D-E-108 to 3D-D-108) as well as a mutation in which the tyrosine amino acid (3D-Y-326) was substituted with cysteine (3D-C-326) or serine (3D-S-326). The mutant 3Dpol polymerases were expressed in Escherichia coli, and in vitro enzyme activity was analyzed. Enzymes containing the 3D-D-108 mutation with the wild-type amino acid (3D-Y-326) demonstrated in vitro enzyme activity similar to that of the wild-type enzyme containing 3D-E-108. In contrast, enzymes with the 3D-C-326 or 3D-S-326 mutation had less in vitro activity than the wild type. The inclusion of the second mutation at amino acid 3D-D-108 did not significantly affect the in vitro activity of the polymerases containing 3D-C-326 or 3D-S-326 mutation. Transfections of poliovirus cDNAs containing the substitution at amino acid 326 with or without the second mutation at amino acid 108 were performed. Consistent with previous findings, we found that transfection of poliovirus cDNAs containing the 3D-C-326 or 3D-S-326 mutation in 3Dpol did not result in the production of virus. Surprisingly, transfection of the poliovirus cDNAs containing the 3D-D-108/C-326 double mutation, but not the 3D-D-108/S-326 mutation, resulted in the production of virus. The virus obtained from transfection of polio-virus cDNAs containing 3D-D-108/C-326 mutation replicated with kinetics similar to that of the wild-type virus. RNA sequence analysis of the region of the 3Dpol containing the 3D-C-326 mutation revealed that the codon for cysteine (UGC) reverted to the codon for tyrosine (UAC). The results of these studies establish that under the appropriate conditions, poliovirus has the capacity to revert mutations within the YGDD amino acid motif of the poliovirus 3Dpol gene and further strengthen the idea that interaction between amino acid 108 and the YGDD region of 3Dpol is required for viral replication.

Amino Acid Sequence↗
PubMed1995

'Good prognosis tumours' in breast cancer screening.

The Forrest Report led to the introduction of the breast screening programme with the aim of reducing mortality from breast cancer. In 1989 a breast screening programme was introduced to the South Bucks District and now two cycles have been completed. The findings are of a high yield of good prognosis tumours 71% and 72%, respectively. These encouraging figures are reflected in a high response rate and with a fall in the incidence of non-screen-detected tumours.

Aged↗
PubMed1994

Characterization of poliovirus replicons encoding carcinoembryonic antigen.

Recombinant vaccines hold great promise for the prevention and therapy of infections diseases and cancer. We have explored the use of poliovirus as a recombinant vector to deliver genes into cells for the purpose of vaccination. For our studies, we have chosen to express the gene-encoding carcinoembryonic antigen (CEA) using a novel poliovirus vector. We have constructed a recombinant CEA-poliovirus replicon in which the CEA gene was substituted for the poliovirus capsid gene. Following in vitro transcription, the RNA was transfected into cells to demonstrate CEA expression. We found that a genome in which the region encoding the signal sequence of the CEA protein (amino acids 1-34) was removed was replication competent (i.e., referred to as a replicon). We encapsidated the CEA-poliovirus replicon by transfecting this RNA into cells previously infected with a recombinant vaccinia virus (VV-P1) which expresses the poliovirus capsid protein (P1). Serial passage in the presence of VV-P1 resulted in the generation of stocks of these encapsidated replicons. Infection of cells with the encapsidated replicon containing the CEA-poliovirus genome resulted in expression of the CEA protein. To test immunogenicity, mice susceptible to poliovirus were given three doses of the encapsidated replicons via the i.m. route. By the third administration, a CEA-specific antibody response was detected. Potential future use of the poliovirus replicon system as both a parenteral and oral vaccine vector is discussed.

Amino Acid Sequence↗
PubMed1994

Cytokines and HIV envelope glycoprotein gp120 stimulate Na+/H+ exchange in astrocytes.

The pathogenesis of the human immunodeficiency virus (HIV)-associated cognitive/motor complex, or acquired immunodeficiency syndrome (AIDS) dementia complex, is unknown, but it afflicts over 50% of all patients infected with HIV-1. Because neurons are not directly infected with HIV-1, the causes of neuronal dysfunction are undoubtedly indirect. We investigated the role of the astrocyte in the development of AIDS dementia complex, focusing on cytokine and HIV-1 gp120 stimulation of Na+/H+ exchange (NHE) activity of primary rat astrocytes. Our results show that the cytokines tumor necrosis factor-alpha, interferon (IFN)-gamma, and interleukin (IL)-1 beta (all found to be elevated in the central nervous system of AIDS patients), can stimulate Na+/H+ exchange, but that transforming growth factor-beta, IL-2, and IL-6 do not. IFN-gamma and gp120-induced activation of Na+/H+ exchange appears to be mediated through activation of tyrosine kinase (TK), because TK inhibitors block the action of IFN-gamma and gp120. Additionally, gp120 induces tyrosine phosphorylation of two proteins (approximately 90 and 130 kDa), which is also inhibited by TK inhibitors. The predominant NHE isoform present in rat astrocytes is NHE-1; however, other isoforms are also present. We conclude that Na+/H+ exchange of rat astrocytes can be differentially stimulated by cytokines and HIV-1 gp120. We hypothesize that the resultant increase in intracellular pH with its concomitant changes in astrocyte membrane permeability properties produces an imbalance in the K+ and glutamate microenvironment of the neurons, leading to a rise in intraneuronal Ca2+ and eventual neuronal dysfunction and/or demise.

Amiloride↗
PubMed1994

Estimating the variations and autocorrelations in dietary intakes on weekdays and weekends.

The high incidence of breast cancer in the U.S. and the possible link with dietary fat has led to the development of educational programmes for reducing women's fat intakes by agencies such as the National Cancer Institute and the U.S. Department of Agriculture. In this paper, we analyse the effects of an intervention on the intakes of 12 nutrients by 37 women in the Houston area. We estimate a dynamic random effects model by maximum likelihood to estimate the between and the within variations and the autocorrelations using 7 consecutive food records before and after the intervention programme. The main findings are that the pattern of within variations differs during weekdays and weekends. Secondly, the mean intakes of nutrients such as beta-carotene and ascorbic acid tend to be lower on weekends. Lastly, the intervention programme reduced the overall fat intakes and also increased the variation in the consumption of foods high in fats during weekdays. We discuss the implications of the results for the design of further studies.

Adult↗
PubMed1994

Human immunodeficiency virus-1 reverse transcriptase heterodimer stability.

Structural and biochemical evidence strongly supports a heterodimeric (p66p51) active form for human immunodeficiency virus-1 reverse transcriptase (RT). Heterodimer stability was examined by sedimentation analysis as a function of temperature and ionic strength. Using NONLIN regression software, monomer-dimer-trimer and monomer-dimer-tetramer association models gave the best fit to the analytical ultracentrifuge sedimentation equilibrium data. The heterodimer is the predominant form of RT at 5 degrees C, with a dimerization Ka value of 5.2 x 10(5) M-1 for both models. Ka values of 2.1 x 10(5) and 3.8 x 10(5) M-1 were obtained for the respective association models at 20 degrees C. RT in 50 and 100 mM Tris, pH 7.0, completely dissociates at 37 degrees C and behaves as an ideal monomeric species. The dissociation of RT as a function of increasing temperature was also observed by measuring the decrease in sedimentation velocity (sw,20). If the stabilization of the heterodimer was due primarily to hydrophobic interactions we would anticipate an increase in the association from 21 degrees C to 37 degrees C. The opposite temperature dependence for the association of RT suggests that electrostatic and hydrogen bond interactions play an important role in stabilizing heterodimers. To examine the effect of ionic strength on p66p51 association we determined the changes in sw,20 as a function of NaCl concentration. There is a sharp decrease in sw,20 between 0.10 and 0.5 M NaCl, leading to apparent complete dissociation. The above results support a major role for electrostatic interactions in the stabilization of the RT heterodimer.

Cold Temperature↗
PubMed1994

Inhibition of human immunodeficiency virus type 1 reverse transcriptase by the 5'-triphosphate beta enantiomers of cytidine analogs.

(-)-beta-L-2',3'-Dideoxycytidine (L-ddC) and (-)-beta-L-2',3'-dideoxy-5-fluorocytidine (L-FddC) have been reported to be potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) and type 2 (HIV-2) in vitro. In the present study, the 5'-triphosphates of L-ddC (L-ddCTP) and L-FddC (L-FddCTP) were demonstrated to competitively inhibit HIV-1 reverse transcriptase (RT), with inhibition constants (KiS) of 2 and 1.6 microM, respectively, when a poly(rI).oligo(dC)10-15 template primer was used; in comparison Ki values for beta-D-2',3'-dideoxycytidine 5'-triphosphate (D-ddCTP) and beta-D-2',3'-dideoxy-5-fluorocytidine 5'-triphosphate (D-FddCTP) were 1.1 and 1.4 microM, respectively. Use of the mutant RT at position 184 (substitution of methionine to valine [M184V]), which is associated with resistance to beta-L-2',3'-dideoxy-3'-thiacytidine (3TC) and beta-L-2',3'-dideoxy-5-fluoro-3'-thiacytidine (FTC), resulted in significant increases (50- to 60-fold) in Ki values for L-ddCTP and L-FddCTP, whereas the elevation in Ki values for D-ddCTP and D-FddCTP was moderate (2-fold). L-ddCTP and L-FddCTP did not inhibit human DNA polymerases alpha and beta up to 100 microM. In contrast, D-ddCTP and D-FddCTP inhibited human DNA polymerase beta, with Ki values of 0.5 and 2.5 microM, respectively. By using sequencing analysis, L-ddCTP and L-FddCTP exhibited DNA chain-terminating activities toward the parental HIV-1 RT, whereas they were not a substrate for the mutant M184V HIV-1 RT.L-ddC and L-FddC did not inhibit the mitochondrial DNA content of human cells up to a concentration of 10 microM, whereas D-ddC and D-FddC decreased the mitochondrial DNA content by 90% at concentrations of 1 and 10 microM, respectively. All of these results suggest that further development of L-ddC, and L-FddC in particular, is warranted as a possible anti-HIV candidate.

Antiviral Agents↗
PubMed1994

The incidence of gestational diabetes mellitus in the Illawarra area of New South Wales.

The incidence of gestational diabetes in the Illawarra area is 7.2% (95% CI: 6.0-8.4). This was determined by data collected by 2 prenatal clinics and 3 private practitioners during 1993. The incidence rate varied between 5.1% at one hospital to 11.3% with a private practitioner. This variation was mainly due to differences in age and ethnic background. The highest incidence rate of 11.9% was found in women of Asian background.

Adult↗
PubMed1992

Cognitive performance in relatives of patients with probable Alzheimer disease: an age at onset effect?

Cognitive performance of 32 siblings and children of patients with probable Alzheimer disease was assessed longitudinally over an interval averaging 4 years. Mean scores were within normal limits for age on all measures at both test times. However, relatives of patients with early-onset dementia (less than or equal to 67 years) were more likely to show a decline in performance from the first to second testing than relatives of patients with late-onset dementia. Additional follow-up will be needed to determine the reliability of performance trajectories and to assess whether mild cognitive changes are related to future dementia. However, findings suggest that it may be important to consider family history of dementia in studies of normal cognitive aging.

Aged↗
PubMed1991

Sensitization of low-dose-rate irradiation by nonlethal hyperthermia.

To assess whether hyperthermia could radiosensitize cells irradiated at a low dose rate, Chinese hamster V79 cells were simultaneously heated and irradiated at 0.86 Gy/h. The data showed that heat treatments at 39 and 40 degrees C, which did not induce heat killing alone or high-dose-rate radiosensitization, resulted in enhanced cell killing with low-dose-rate irradiation. The dose-modification factor (ratio of the slopes of the curves for low dose rate and high dose rate) was reduced to 1.8 at 39 degrees C and 1.4 at 40 degrees C, compared to a value of 2.1 at 37 degrees C. These data indicate that nonlethal heat treatments can cause enhanced radiosensitization under low-dose-rate conditions. The implications of these results for interstitial thermoradiotherapy are discussed.

Animals↗
PubMed1990

Anomalous origin of bronchial arteries: potential pitfall of embolotherapy for hemoptysis.

Bronchial artery embolization was performed in two patients with anomalous origins of the bronchial artery. In one patient, the anomalous bronchial artery originated from the convex surface of the aortic arch between the origins of the brachiocephalic and left carotid arteries, while in the other, it originated from the internal mammary artery. Anomalous bronchial arteries represent a potential pitfall during bronchial artery embolization. Radiologists involved in embolotherapy for hemoptysis should therefore be alerted to the possible presence of anomalous bronchial arteries, especially when significant bronchial artery supply to areas of abnormal pulmonary parenchyma is not demonstrated at a catheter search or aortography of the descending aorta. In these instances, arch aortography should be performed to identify anomalous origins of the bronchial arteries or other nonbronchial systemic collateral vessels.

Adult↗
PubMed1990

Surgery for achalasia cardiae: the Dor operation.

This review describes our use of the Dor operation in the management of 22 patients with achalasia of the cardia over the period 1970 to 1989. There was a male to female ratio of 1.8:1. All presented with dysphagia of varying degree, with regurgitation (86%), weight loss (73%), pain (59%) and chest infections (14%) being associated symptoms. Two patients had undergone previous balloon dilatation, with temporary benefit. The morbidity was low and follow-up results were good in 94% of cases. None of the patients had symptoms of gastro-oesophageal reflux in the postoperative period. In our experience, the Dor modification of the Heller operation has yielded gratifying results.

Adolescent↗