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Biomedical subjects

D Perry

Publications and source records attributed to D Perry.

At least 73 records · Page 4Linked to original sources
PubMed1989

High-performance liquid chromatographic determination of delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine in complex media by precolumn derivatisation with dansylaziridine.

A novel method is described for the trace level quantitation of the tripeptide delta-(L-alpha-aminoadipyl)-L-cysteinyl-D-valine (ACV) in complex fermentation media, using a high-performance liquid chromatographic, pre-column derivatisation technique. The procedure is based upon the reaction of the ACV monomer with 5-dimethylaminonaphthalene-1-sulphonylaziridine (dansylaziridine) and produces a highly fluorescent product. Reaction conditions between the reagent and tripeptide were investigated and optimal conditions established. Linear calibration graphs were obtained over the ranges 227-0.56 micrograms/ml and 227-5.6 ng/ml. The extracellular ACV levels produced in fermentation broths of several different fungal strains and species were determined using this technique. The method was compared using ACV standards in buffer solutions for ease of use, sensitivity and selectivity with two other pre-column derivatisation procedures, using dithionitrobenzoic acid and monobromobimane, which also exploit the reaction with the sulphydryl group of the ACV monomer.

Acremonium↗
PubMed1989

Monocyte killing of human squamous epithelial cells: role for thrombospondin.

Human peripheral blood monocytes maintained in culture for 18 h were examined for killing of normal human keratinocytes and squamous carcinoma cells. Keratinocytes grown under conditions which maintain the undifferentiated state were highly sensitive to killing but these cells became resistant to killing after induction of differentiation. A line of squamous carcinoma cells obtained from an undifferentiated tumor (designated as UM-SCC-11B) was sensitive to killing while a second line obtained from a more well-differentiated tumor (designated as UM-SCC-22B) was resistant. Several observations suggested that interaction of monocytes with the squamous epithelial cells was mediated, in part, through thrombospondin (TSP). Monocytes synthesized TSP and were positive by immunofluorescence for surface TSP. The normal and malignant squamous epithelial cells also expressed surface TSP as well as unoccupied TSP receptors and our previous studies have shown that both TSP and its receptor are much more prominently displayed on the undifferentiated cells than on the differentiated cells. A series of anti-TSP monoclonal antibodies inhibited killing. These included an antibody directed against the Mr 25,000 NH2-terminal region of the molecule which has heparin-binding activity and three antibodies the epitopes of which lie within the Mr 140,000 non-heparin-binding fragment of TSP. High concentrations of exogenously added TSP as well as the recombinant form of the heparin-binding domain from the TSP molecule also partially inhibited killing while laminin and fibronectin were ineffective. Taken together, these data suggest that TSP and TSP receptors on monocytes and squamous epithelial cells play a role in monocyte-mediated killing of the squamous epithelial cells.

Antibodies, Monoclonal↗
PubMed1989

Genetic linkage among cloned genes of Streptococcus mutans.

Mapping vectors containing antibiotic resistance markers inserted adjacent to or within different cloned genes from Streptococcus mutans were used to determine the relative positions of these genes on the chromosome. The gtfA, ftf, and scrB genes were inserted into streptococcal mapping vector pVA891 adjacent to an Emr gene, whereas the Emr marker was inserted directly into the gtfB gene. These chimeric plasmids were transformed into S. mutans GS-5, selecting for Emr transformants. To determine the positions of the cloned genes relative to each other, it was necessary to construct plasmids labeled with a different antibiotic resistance marker. Thus, a Tetr gene was inserted adjacent to gtfB in the appropriate mapping vector and within the ftf and scrB genes with a mini-Mu transposon (Mu dT). The chimeric plasmids were transformed into the appropriate Emr recipients, and the DNA from the resulting Emr Tetr transformants was used in linkage studies. Based on the cotransfer data, gtfB was not closely linked to gtfA, ftf, or scrB. However, gtfA cotransferred with ftf and scrB at frequencies of approximately 96 and 80%, respectively. The percent cotransfer of ftf and scrB was approximately 92. These data indicate that the three genes are clustered on the GS-5 chromosome, with ftf located between gtfA and scrB. Little, if any, linkage was observed between these genes and a variety of other random markers.

Cloning, Molecular↗
PubMed1989

Algoneurodystrophy following herpes zoster.

Algoneurodystrophy frequently follows an identifiable triggering event. It is not widely recognized that herpes zoster can precipitate algoneurodystrophy and three such cases are described here. In one, the affected dermatome did not correspond to the limb involved by the algoneurodystrophy.

Aged↗
PubMed1988

Factors affecting the isopenicillin N synthetase reaction.

1. Isopenicillin N synthetase (IPNS) from Cephalosporium acremonium, which requires Fe2+ and O2 for activity, was highly purified for studies of factors affecting its conversion of delta-(L-alpha-aminoadipoyl)-L-cysteinyl-D-valine (LLD-ACV) into isopenicillin N (IPN). EDTA was used to quench the reaction by removal of Fe2+. 2. IPNS was inactivated during the course of the conversion of LLD-ACV into IPN, although it was relatively stable in the absence of LLD-ACV under otherwise similar conditions. In the presence of GSH and ascorbate each IPNS molecule carried out about 200 catalytic events before inactivation, but the turnover number was decreased 5-fold in the absence of ascorbate. 3. After trace metal ions had been removed from IPNS and other components of the reaction mixture by Chelex-100 resin, only about 10 microM-Fe2+ was required for maximum stimulation. Several other transition-metal ions were inhibitors of the enzyme. 4. Both dithiothreitol (DTT) and GSH stimulated IPNS activity, but GSH, unlike DTT, was not rapidly oxidized in the presence of O2 and Fe2+. 5. IPNS was rapidly inhibited by the thiol-blocking reagents N-ethylmaleimide and 2,2'- and 4,4'-dipyridyl disulphide, but not by 5,5'-dithiobis-(2-nitrobenzoic acid) in the same concentration. Inhibition by 2,2'-dipyridyl disulphide could be reversed by DTT.

Acremonium↗
PubMed1985

Mapping of a cloned glucosyltransferase gene in Streptococcus mutans.

A cloned glucosyltransferase (gtfA) fragment, inserted adjacent to an erythromycin resistance (Eryr) marker in plasmid pVA891, was used in transformation experiments to determine the genetic location of gftA on the Streptococcus mutans chromosome. Eryr (gftA) cotransformed with a methionine (Met+) marker at a frequency of approximately 23%, whereas cotransfer with a number of other markers was not observed. The number of Met+ transformants was approximately 50-fold greater than the number of Eryr transformants. Furthermore, over 20% of the Eryr transformants were always Met+, whereas less than 1% of the Met+ transformants were Eryr, indicating the extreme asymmetrical cotransfer of these markers. The results indicate that S. mutans genes can be mapped by this procedure.

Chromosome Mapping↗
PubMed1985

Asbestosis. Bronchoalveolar lavage fluid proteins and their relationship to pulmonary epithelial permeability.

We measured levels of albumin and immunoglobulins in serum and bronchoalveolar lavage (BAL) fluid in 28 men with asbestosis and 11 control subjects. The half-time clearance of inhaled diethylene triamine pentacetate labelled with technetium-99m (99mTc-DTPA) from the lungs (t1/2LB) was measured in 26 patients with asbestosis and in 31 normal nonsmoking controls. In those individuals in whom immunoglobulins were detected in BAL fluid, the mean IgG:albumin ratio in BAL fluid was 0.30 (range, 0.11 to 0.97), significantly less than the ratio of 0.43 (0.28 to 0.66) in control subjects (p less than 0.05). There was no significant difference in IgA:albumin ratios between patients and control subjects. The mean BAL:serum albumin ratio in patients with asbestosis was 2.3 X 10(-3) (range, 0.2 to 9.5 X 10(-3), significantly greater than the ratio of 1.2 X 10(-3) (0.5 to 2.0 X 10(-3] in control subjects (p less than 0.02). The t1/2LB was significantly shorter in both smokers and nonsmokers with asbestosis, compared with 31 normal nonsmoking controls, but there were no relationships between t1/2LB and BAL:serum albumin ratio or any other BAL protein levels in either smokers or nonsmokers with asbestosis.

Adult↗
PubMed1984

Spectrophotometric determination of affinities of peptides for their transport systems in Escherichia coli.

The use of novel synthetic peptides to measure peptide transport by spectrophotometric means is described. These peptides contain glycine residues alpha-substituted with thiophenol and are recognized as substrates by both peptide transport systems and intracellular peptidases of Escherichia coli (Kingsbury et al., Gilvarg, C., Proc. Natl. Acad. Sci. U.S.A. 81:4573-4576, 1984). Transport and peptidase cleavage results in the intracellular release of thiophenol, which exits rapidly from the cell. The release of thiophenol from these peptides by cell suspensions can be measured with Ellman sulfhydryl reagent [5,5'-dithiobis(2-nitrobenzoic acid)] and provides a direct determination of the rate of peptide transport. The reductions in thiophenol release from these peptides resulting from the addition of peptide competitors enable the affinities of the competitors for their transport systems to be determined. By this method, it is shown that the dipeptide transport system is more restrictive with respect to changes in the amino acid sidechains of its substrates than those of the oligopeptide transport system.

Biological Transport↗
PubMed1984

Increased serum IgE concentrations during infection and graft versus host disease after bone marrow transplantation.

Serum IgE concentrations estimated in 25 bone marrow transplant recipients during episodes of infection or graft versus host disease, or both, were raised not only in some patients with acute graft versus host disease but also in many patients with infection. Raised values were not seen in chronic graft versus host disease. The routine estimation of serum IgE in bone marrow transplant recipients had minimal value because of the lack of specificity of the IgE response.

Acute Disease↗
PubMed1983

The use of cysteinyl peptides to effect portage transport of sulfhydryl-containing compounds in Escherichia coli.

We describe a method by which sulfhydryl compounds may be transported into Escherichia coli as the mixed disulfides with a cysteine residue of a di- or tripeptide. Transport occurs through the di- or oligopeptide transport systems, and it is suggested that subsequent release of the sulfhydryl compound occurs as a result of a disulfide exchange reaction with components of the sulfhydryl-rich cytoplasm. The free sulfhydryl compounds used here (2-mercaptopyridine and 4-[N-(2-mercaptoethyl)]aminopyridine-2,6-dicarboxylic acid) show weak growth-inhibitory properties in their own right, but disulfide linkage to a cysteinyl peptide results in a considerable enhancement (up to 2 orders of magnitude). This is the first example of the use of the peptide transport systems of E. coli to effect portage transport of a poorly permeant molecule by using attachment to the side chain of one of the amino acid residues of a peptide; all previous examples have involved the incorporation of amino acid analogues into the peptide backbone. The synthesis of cysteinyl peptides containing disulfide-linked 2-mercaptopyridine is described. Displacement of the 2-mercaptopyridine by sulfhydryl compounds of interest proceeds rapidly and quantitatively in aqueous alkaline solution to provide the required peptide disulfides.

Aminopyridines↗
PubMed1983

Metabolism of alanylalanyl-S-[N-(2-thioethyl)]aminopyridine-2, 6-dicarboxylic acid]cysteine by suspensions of Escherichia coli.

The attachment of 4-[N-2-(mercaptoethyl)]aminopyridine-2,6-dicarboxylic acid (MEPDA) to AlaAlaCys through a disulfide bond to the cysteine residue has been described (Boehm, J. C., Kingsbury, W. D., Perry, D., and Gilvarg, C. (1983) J. Biol. Chem. 258, 14850-14855). The peptide disulfide showed enhanced growth inhibitory properties in Escherichia coli compared to the free sulfhydryl compound. Genetic evidence was presented to show that this side chain-modified peptide utilizes the oligopeptide transport system to gain entry to the cell. Following transport of the peptide, MEPDA is liberated by disulfide exchange reactions with sulfhydryl-containing components of the cell pool. In this paper, we examine in more detail the metabolism of this peptide. Using gel filtration chromatography to examine filtrates from cell suspensions incubated with the peptide, it was shown that loss of the peptide from the medium is accompanied by a corresponding increase in a component having the properties of MEPDA. The release of sulfhydryl groups from the peptide by cell suspensions could be monitored by Ellman's reagent and was found to be dependent upon peptide transport. Following cleavage of the disulfide bond, MEPDA is able to cross the cytoplasmic membrane and exit from the cell as a relatively lipophilic uncharged metal chelate.

Biological Transport, Active↗
PubMed1983

Ambulatory ventricular tachycardia: characteristics of the initiating beat.

One hundred ten 24-hour Holter ECG recordings from 82 ambulatory patients with 341 episodes of ventricular tachycardia (VT) were analyzed. Most VT was precipitated by ventricular premature beats (VPBs) with prematurity indices (coupling interval/QT) between 1.0 and 2.0. However, a disproportionate number of VPBs initiating VT occurred early and late in the cardiac cycle compared with isolated VPBs. VT rate was not related to preceding heart rate, but faster basic rates appeared to protect against VT of extended duration. Approximately 80% of episodes of VT were initiated by VPB forms also seen in isolation. Of the 20% of VT initiated by a VPB of new morphology, one third occurred late in the cardiac cycle; almost none were early cycle.

Adult↗
PubMed1983

Genetic transformation of putative cariogenic properties in Streptococcus mutans.

Rough colonial morphology and bacteriocin production, two properties which may be associated with the cariogenicity of Streptococcus mutans, were transformed into several strain GS-5 mutants defective in each respective property. Transformation was determined by observing the frequency of cotransfer of these properties with different reference markers. The rough colonial transformants were identical to the parental GS-5 strain with respect to ability to synthesize water-insoluble glucans and undergo in vitro sucrose-dependent colonization of glass surfaces. Alterations in the growth medium and the concentration of the initial cell inoculum resulted in an approximate 10-fold increase in the frequency of transformation of strain GS-5 compared to previous observations.

Bacteriocins↗
PubMed1981

Human and animal togavirus antibodies in congenitally deformed infants.

The cord bloods of 30 congenitally malformed infants, born consecutively at the Worcester Royal Infirmary, were screened for serological evidence of infection with Border disease and bovine virus diarrhoea viruses as well as for the presence of rubella-, cytomegalovirus-, and measles-specific IgM. Despite Border disease and bovine virus diarrhoea being endemic among sheep and cattle in counties bordering Wales, none of the cord blood samples contained antibodies to Border disease or bovine virus diarrhoea viruses. No rubella-, measles-, or cytomegalovirus-specific IgM was detected. When the total immunoglobulins were estimated, 15 of the malformed infants and elevated levels, but in a control group of 35 infants born in the same unit, none showed significantly elevated immunoglobulin levels.

Antibodies, Viral↗
PubMed1981

Peptide transport in Staphylococcus aureus.

Using the agar diffusion test of Zähner et al. (1960), it was demonstrated that bacilysin and a variety of di- and tri-L-peptides compete with each other for uptake into Staphylococcus aureus. Several di- and tripeptides containing L-phenylalanine produced transient growth inhibition of S. aureus NCTC 6571, but not of bacilysin-resistant mutants. The results confirm that the major peptide transport system in S. aureus recognizes both di- and tripeptides as substrates.

Agar↗