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Biomedical subjects

A J Hay

Publications and source records attributed to A J Hay.

At least 37 records · Page 2Linked to original sources
PubMed1994

Tonsil surface and core cultures in recurrent tonsillitis: prevalence of anaerobes and beta-lactamase producing organisms.

The bacterial flora of the tonsil surface and core was compared in patients suffering from recurrent tonsillitis. Surface swabs and tonsil core tissues were received as paired samples from 50 patients admitted for elective tonsillectomy. Analysis of paired samples from individual patients revealed differences in the bacterial flora of the tonsil core and the tonsil surface. Of 366 aerobic isolates, 30% grew from the surface alone, 26% from the core only and 44% from both sites. Of 290 anaerobic isolates, 35% grew from the surface alone, 33% from the core only and 31% from both sites. The total number of isolates from surface and core samples was similar (average 9.2 and 8.8, respectively). The range of species isolated was also similar for both surface and core samples, as was the proportion of organisms producing beta-lactamase from each site (10.7% and 9.5%, respectively). Eighty-two percent of patients carried beta-lactamase-producing organisms on either the tonsil surface or in the core tissue. A surface swab does not reliably reflect the types of organisms present in the tonsil core in individual patients. Anaerobes are a major component of tonsil surface and core bacterial flora in patients with recurrent tonsillitis. The high carriage rate of beta-lactamase-producing organisms in the tonsils should be considered when selecting antimicrobial therapy for persistent or recurrent tonsillitis.

Adolescent↗
PubMed1994

Synthesis and anti-HIV activity of some novel diaryl phosphate derivatives of AZT.

Novel diaryl phosphate triester derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridate chemistry. These materials were designed to act as membrane-soluble pro-drugs of the bio-active free nucleotides. In particular, novel parasubstituted diaryl phosphate derivatives were prepared. In vitro evaluation revealed the compounds to have a pronounced and selective antiviral effect, the magnitude of which varied considerably with the nature of the aryl substituent. In particular, strongly electron-withdrawing aryl substituents correlate with high anti-HIV potency in C8166 cells. Along with AZT, the compounds are poorly effective in JM cells, which appear to lack thymidine kinase, indicating the phosphates to act as pro-drugs of the nucleoside rather than of the free phosphate.

Animals↗
PubMed1994

Functional reconstitution in lipid vesicles of influenza virus M2 protein expressed by baculovirus: evidence for proton transfer activity.

The influenza virus M2 protein was expressed from a recombinant baculovirus in Spodoptera frugiperda Sf9 cells, purified and reconstituted into artificial membrane vesicles. The specific inhibitor amantadine overcame the toxic activity of the protein and boosted the rate of M2 synthesis by a factor of 10, allowing yields of about 1 mg of purified M2 protein per g of Sf9 cells. M2 protein expressed in this system was phosphorylated and palmitoylated and displayed properties similar to the authentic virus protein. Purified wild-type M2 protein and an amantadine-resistant mutant M2 (M2 delta) with a deletion in the trans-membrane domain (amino acids 28 to 31) were incorporated into lipid vesicles, which were loaded with the fluorescent pH indicator pyranine. On imposition of an ionic gradient, M2 caused a decrease in intravesicular pH, which was susceptible to inhibition by 0.1 to 1 microM-rimantadine or N-ethyl-rimantadine. M2 delta behaved similarly but exhibited the expected drug resistance. These experiments indicate that isolated M2 functions as an ion channel and demonstrates in vitro M2-mediated proton translocation.

Amantadine↗
PubMed1994

Role of virion M2 protein in influenza virus uncoating: specific reduction in the rate of membrane fusion between virus and liposomes by amantadine.

The anti-influenza virus drug amantadine was shown to reduce the rate of fusion of liposomes with influenza A viruses whose replication is inhibited by this drug. The fusion with amantadine-resistant viruses was unaffected. Experiments with reassortant and mutant viruses showed that this effect was linked to the M2 protein and not to the haemagglutinin of the virus. The proton ionophore monensin, on the other hand, substantially increased the rate of fusion of the viruses tested. These results indicate that the kinetics of virus-liposome fusion can be modulated by the virus M2 protein, the target of amantadine action, and it is postulated that the M2 ion channel functions by transporting protons into the virion interior and facilitating virus uncoating.

Amantadine↗
PubMed1994

Toxic inhibition of smooth muscle contractility by plant-derived sesquiterpenes caused by their chemically reactive alpha-methylenebutyrolactone functions.

1. Previous studies have shown that extracts of feverfew (Tanacetum parthenium) and parthenolide, a sesquiterpene alpha-methylenebutyrolactone obtained from it, inhibit smooth muscle contractility in a time-dependent, non-specific and irreversible manner. 2. The hypothesis that this toxic effect is due specifically to the presence in the sesquiterpene lactone of the potentially reactive alpha-methylene function was tested on rabbit isolated aortic ring preparations. This was done (a) by comparing the effects of two plant-derived sesquiterpene lactones purified from yellow star thistle (Centaurea solstitialis): cynaropicrin (an alpha-methylenebutyrolactone) and solstitialin 13-acetate (lacking the alpha-methylene function), and (b) by chemically inactivating the alpha-methylene functions in cynaropicrin and parthenolide by reaction with cysteine. 3. The results show that the characteristic smooth muscle inhibitory profile is demonstrated by the two alpha-methylenebutyrolactones (parthenolide and cynaropicrin), but not by the compound lacking this functional group (solstitialin 13-acetate), or by those previously active compounds in which it has been inactivated with cysteine. 4. Thus the alpha-methylene function is critical for this aspect of the toxic pharmacological profile of the sesquiterpene butyrolactones, which are natural products widely distributed in the Compositae family of flowering plants.

Animals↗
PubMed1994

Polymerase chain reaction for screening clinical isolates of corynebacteria for the production of diphtheria toxin.

AIMS: To assess the performance of the polymerase chain reaction (PCR) when used to screen rapidly large numbers of corynebacteria for toxin production; and to determine the incidence of false positive PCR results with non-toxigenic Corynebacterium diphtheriae isolates. METHODS: Eighty seven recent British isolates of corynebacteria were assayed by PCR. All isolates were assayed from both blood and tellurite agar within a five day period. Thirty three non-toxigenic isolates of C diphtheriae from six countries were also tested by PCR and by the Elek immunodiffusion assay. RESULTS: There was complete concordance between the results of PCR and traditional methods on the recent British isolates, with one exception: an Elek positive "C ulcerans" isolate, which was PCR positive from tellurite but not from blood agar. One of the thirty three (3%) non-toxigenic isolates of C diphtheriae was PCR positive. CONCLUSIONS: These results suggest that PCR compares favourably with traditional methods for the detection of toxigenic corynebacteria and that it represents a powerful new tool in the diagnosis of an old disease.

Base Sequence↗
PubMed1993

Inhibition of HIV infection by flavanoids.

Of a variety of flavanoids, the flavans were generally more effective than flavones and flavanones in selective inhibition of HIV-1, HIV-2 or SIV infection. Studies of their effects on the binding of sCD4 and antibody to gp120 indicated that the effective compounds interact irreversibly with gp120 to inactive virus infectivity and block infection.

CD4 Antigens↗
PubMed1992

Diarrhoea.

Explore the source record for details and available documents.

Diarrhea↗
PubMed1992

Bacteriology of anal fistulae.

Anal fistulae are said to arise from cryptoglandular infection of the anal glands, which lie within the intersphincteric space. The type and virulence of the micro-organism responsible may determine whether an anal fistula develops. The microbiology of chronic anal fistulae has not been reported previously. Twenty-five consecutive anal fistulae were studied prospectively (eight intersphincteric fistulae, 12 trans-sphincteric fistulae, two suprasphincteric fistulae, one extrasphincteric fistula, one superficial fistula, one anovaginal fistula). There were 18 men and seven women, with a median age of 42 (range 22-71) years. Patients with Crohn's disease or acute anorectal suppuration were excluded. In 18 patients, 0.1 ml granulation tissue from the track of the fistula was obtained and processed within 4 h using standard microbiological techniques. Sixty-nine isolates representing at least 17 species were obtained. The predominant organisms were Escherichia coli (22 per cent), Enterococcus spp. (16 per cent) and Bacteroides fragilis (20 per cent). The majority of the growths were obtained only from enrichment. Bacteria from only one patient grew at a dilution of 10(3). Granulation tissue from 25 patients was processed for mycobacterial culture, and Mycobacterium tuberculosis was grown from one patient. No other mycobacterium was isolated. The chronic inflammation in anal fistulae does not seem to be maintained by either excessive numbers of organisms or organisms of an unusual type.

Adult↗
PubMed1992

Emergence and transmission of influenza A viruses resistant to amantadine and rimantadine.

Amantadine- and rimantadine-resistant viruses have been recovered from approximately 30% of patients treated for acute H3N2 subtype influenza and less often from their close contacts receiving drug prophylaxis. The limited data suggest that resistant viruses can emerge rapidly during drug therapy, as early as 2-3 days into treatment. These viruses retain their resistance phenotype during multiple passages in the laboratory and appear to be genetically stable in this regard. Studies in families and in nursing homes indicate that resistant isolates appear to be transmissible from treated patients and cause typical influenza in contacts receiving drug prophylaxis. It is unknown whether resistant human viruses are capable of competing with wild-type ones during multiple cycles of infection in the absence of the drug. These viruses appear to be pathogenic, and no evidence indicates that they differ from wild-type strains. Thus, these viruses clearly possess the biologic properties that are associated with clinically important drug resistance. However, limited information is available to assess their actual impact. It is unknown what degree of selective drug pressure would be required to cause substantial transmission of resistant viruses during community outbreaks. Natural selection of antigenic variants and disappearance of previous variants may prevent the emergence of viruses that have been altered in the genes coding both for the surface glycoproteins and for the M2 protein. However, the emergence of drug-resistant influenza viruses appears to pose potential clinical problems in certain epidemiologic situations involving close contact with treated patients.

Amantadine↗
PubMed1992

Influence of amantadine resistance mutations on the pH regulatory function of the M2 protein of influenza A viruses.

Mutations in the influenza M2 membrane protein which confer resistance to the antiviral drug amantadine are exclusively located within the transmembrane region of the molecule. The influence of specific amino acid substitutions on the activity of the M2 protein in influenza A virus-infected cells is assessed in this report by their effects upon haemagglutinin (HA) stability and virus growth. A number of amino acid substitutions, e.g., L26H, A30T, S31N and G34E reduced the activity of the M2 protein of A/chicken/Germany/34 (Rostock) and caused a substantial increase in expression of the low-pH form of HA. The adverse effects of the mutations on virus replication were evident from changes selected during subsequent passage of the mutant viruses in the presence or absence of amantadine: reversion to wt, the acquisition of a second suppressor mutation in M2, or the appearance of a complementary mutation in HA which increased its pH stability. In contrast, 127T and 127S, mutations which were most readily selected following passage of the wt virus in the presence of drug, caused an increase in M2 activity. Furthermore, in double mutants the 127T mutation suppressed the attenuating effects of the A30T and S31N mutations on M2 activity. The influence of primary structure on the consequences of particular amino acid changes was further emphasized by the contrasting effects of the G34E mutation on the activities of two closely related proteins, causing an increase in the activity of the M2 of A/chicken/Germany/27 (Weybridge) as opposed to the decrease in activity of the Rostock protein. Estimates of differences in trans Golgi pH based on the degree of conversion of HA to the low-pH form, or complementation of differences in pH stability of mutant HAs, indicate that changes in M2 may influence pH within the transport pathway by as much as 0.6. The results thus provide further evidence that M2 regulates transmembrane pH gradients in the trans Golgi. Incompatibility between particular HA and M2 components and the selection of M2 mutants with suboptimal activity stresses the essential relationship between the structures and functions of these two virus proteins.

Amantadine↗
PubMed1992

Evidence that the amantadine-induced, M2-mediated conversion of influenza A virus hemagglutinin to the low pH conformation occurs in an acidic trans Golgi compartment.

Amantadine treatment of cells infected with H7 strains of influenza A viruses causes an M2 protein-mediated conversion of hemagglutinin (HA) from its native to its low pH conformation. Immunofluorescence and electron microscopic observations showed that the structural alteration and hence drug action occur shortly after HA exits from the Golgi complex during its passage through the strans Golgi region. Using the DAMP/anti-DNP pH probe it is evident that virus infection causes increased acidity of the trans Golgi region and that vesicles containing low pH HA in amantadine-treated virus-infected cells are particularly acidic. These results indicate therefore that the alteration in HA is the direct consequence of exposure to an adverse low pH and provide further support for the conclusion that the M2 protein, the target of amantadine action, is involved in regulating vesicular pH, a function important for the correct maturation of the HA glycoprotein.

Amantadine↗
PubMed1992

Maturation of influenza A virus hemagglutinin--estimates of the pH encountered during transport and its regulation by the M2 protein.

The susceptibility of H7 influenza A viruses to the M2-mediated alteration in HA resulting from treatment with amantadine or rimantadine depends both on the pH stability of HA and the pH encountered during transport to the plasma membrane of the particular virus-infected cell. pH stabilities of a range of virus mutant HAs exhibited an inverse correlation with drug sensitivity and the proportion of low-pH HA expressed on the surface of infected cells in the absence of drug. The lowest pH encountered during transport was thus estimated from the proportion of HA expressed in its native conformation and its pH stability profile. Lower drug sensitivity and improved HA maturation of MDCK cells compared to that in CEF reflect the higher pH within the appropriate compartment of the former. Differences in apparent pH resulting from infection with two closely related virus strains, Rostock or Weybridge, e.g., approximately 6.0 and 5.4, respectively, in CEF, were abrogated by rimantadine treatment (pH approximately 5.2 in CEF) and were attributable to intrinsic properties of their respective M2 proteins. The greater activity of the Rostock M2, which was estimated to be capable of increasing vesicular pH by as much as 0.8 pH units, correlates with the lower pH stability of the HA. This emphasizes the essential relationship between the characteristics of the two virus proteins as well as the subtle role of M2 in regulating the pH of the transport pathway to protect the structural integrity of the hemagglutinin glycoprotein.

Amantadine↗
PubMed1992

Aryl phosphate derivatives of AZT retain activity against HIV1 in cell lines which are resistant to the action of AZT.

Novel aryl phosphate derivatives of the anti-HIV nucleoside analogue AZT have been prepared by phosphorochloridate chemistry. These materials are designed to act as membrane-soluble pro-drugs of the bio-active free nucleotides. In vitro evaluation revealed the compounds to have a pronounced, selective antiviral activity, which, in one case, was more potent than the parent nucleoside AZT. The magnitude of the biological effect varied considerably with the nature of the phosphate-blocking group. Moreover, one of the compounds, a phosphoramidate, is particularly active in a cell line restrictive to the activity of AZT, due to poor phosphorylation therein. These data support the suggestion that the phosphate derivatives exert their biological effects via intracellular release of the nucleotide forms.

Antiviral Agents↗
PubMed1992

Regulation of pH by the M2 protein of influenza A viruses.

Inhibition of the function of the M2 protein by amantadine can cause a conformational change in the haemagglutinin (HA) of H7 influenza A viruses and the consequent expression of the low pH form of the glycoprotein on the surface of virus-infected cells. Immunofluorescence studies showed that this conversion occurs shortly after HA exists from the Golgi complex apparently during its transport through the trans Golgi network and using the pH probe, DAMP/anti-DNP, that it is the direct result of reduced vesicular pH. The lowest pHs encountered were estimated using mutant HAs differing in pH stability to be approximately 5.2 and 5.6 in virus-infected CEF or MDCK cells, respectively, in the absence of functional M2. Depending on the particular M2, this protein was responsible for increases in vesicular pH of up to 0.8 units. The influence of mutations in both HA and M2 on the maturation of native HA illustrates the important relationship between the structural and functional properties of these two proteins. Using the fluorescent probe SNARF-1 the M2 protein was also shown to be largely responsible for the 0.3-0.4 unit reduction in intracellular pH of virus-infected cells. The data thus provide further evidence for the pH regulatory function of M2 and its importance for the maturation of the HA glycoprotein.

Amantadine↗
PubMed1992

The occurrence of bacteraemia associated with the use of oral and nasopharyngeal airways.

In order to determine whether placement of oral or nasopharyngeal airways during anaesthesia induces a significant bacteraemia, 36 ASA grade 1 or 2 patients undergoing body surface surgery, in whom it was anticipated that spontaneous respiration would be maintained, were randomly allocated to one of two groups. One group was given oral airways and the other, nasopharyngeal. A series of blood samples, which were taken before and after airway insertion, were cultured aerobically and anaerobically. Nasal and oral swabs were taken at the same time. Single isolates of Corynebacterium species and Acinetobacter species, together with two isolates of Staphylococcus epidermidis were grown from one culture bottle from 4 of the 36 patients studied. None of the oral or nasal swabs, or any of the subsequent or previous blood samples produced positive cultures for these organisms in these four patients. We believe that these results represent skin commensal contamination rather than bacteraemia in these four patients, and that bacteriological considerations should not influence decisions about the type of airway used during anaesthesia. However, prophylactic antibiotic therapy should still be provided for all high risk cases.

Adult↗
PubMed1991

Amantadine selection of a mutant influenza virus containing an acid-stable hemagglutinin glycoprotein: evidence for virus-specific regulation of the pH of glycoprotein transport vesicles.

Mutants of influenza Rostock virus (H7N1 subtype) were selected for resistance to amantadine hydrochloride at concentrations of the antiviral drug known to affect the function of the virus M2 transmembrane protein. Sequence analysis revealed that three mutants had no changes in M2 but contained a lysine to isoleucine substitution in the hemagglutinin (HA) membrane glycoprotein at position 58 of HA2. The mutant viruses were found to fuse membranes at a pH value 0.7 lower than wild type and to exhibit changes in the conformation of their HAs specifically at the lower pH. The homologous lysine to isoleucine substitution was introduced by site-specific mutagenesis into the HA of X-31 influenza virus (H3 subtype), which was expressed by using vaccinia virus recombinants. The expressed HA also mediated membrane fusion and changed in conformation at a pH value 0.7 lower than wild type. These results indicate that increased acid stability of the HA obviates the consequences of the inhibition of M2 function by amantadine and provide further evidence for the role of M2 in regulating the pH of vesicles involved in glycoprotein transport to the cell surface.

Amantadine↗