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Biomedical subjects

I R Smith

Publications and source records attributed to I R Smith.

At least 19 recordsLinked to original sources
PubMed1997

Comprehensive physical map of the Cydia pomonella granulovirus genome and sequence analysis of the granulin gene region.

A cloned strain of Cydia pomonella granulovirus, CpGV-M1, was obtained using successive rounds of an in vivo limiting dilution method. A detailed physical map of the genome was constructed using 11 restriction enzymes. The region containing the granulin gene and an open reading frame immediately upstream of the granulin gene was sequenced. This region showed a high degree of homology to the equivalent region from Cryptophlebia leucotreta granulovirus with 98% amino acid identity for the granulins and 68% identity for the putative polypeptides encoded by the upstream ORFs. These latter polypeptides contained two zinc finger-like motifs and showed a low degree of homology to ME53 from Autographa californica nucleopolyhedrovirus (AcMNPV). Evidence is presented for a similar upstream ORF in Artogeia rapae GV also. Hybridization studies showed that the CpGV genome had a similar overall organization to the Artogeia rapae GV genome. Hybridization between CpGV and AcMNPV was limited to fragments spanning about 15% of each genome suggesting that very few genes are highly conserved between GVs and NPVs.

Amino Acid Sequence↗
PubMed1996

A proposed model to monitor heparin therapy using the concentrated thrombin time which allows standardisation of reagents and improved estimation of heparin concentrations.

The concentrated thrombin time (CTT), a thrombin time performed with a high concentration of thrombin, was evaluated as an alternative to the activated partial thromboplastin time (APTT) for monitoring of heparin therapy. Forty-nine plasmas from patients receiving unfractionated heparin therapy were tested. It was first demonstrated that CTTs using three commercial reagents could be standardised against CTTs performed with a reference reagent, MRC reagent 66/305. For comparison, APTTs were performed on the plasmas. As a benchmark of the degree of heparinisation, the heparin concentration of the plasmas was determined by chromogenic anti-IIa heparin assays, therapeutic range being 0.2-0.4 units/ml. The optimal relationships of the CTTs and APTT with the heparin concentration were established. These were used to predict the heparin concentrations of the plasmas from the results of the APTT, CTT performed with the reference reagent, and transformed CTT performed with each of the three commercial reagents. In predicting the assayed plasma heparin concentrations, the accuracy of the APTT was only 53%, while the CTT was from 78 to 82%. The CTT can be standardised and, subject to results of clinical trials, could provide an improved method of monitoring heparin therapy.

Afibrinogenemia↗
PubMed1993

Characterization of new baculovirus genotypes arising from inoculation of Pieris brassicae with granulosis viruses.

Previous studies have shown that of 15 Artogeia (Pieris) rapae granulosis virus isolates (ArGV1 to ArGV15) only two, ArGV1 and ArGV2, gave a normal dose-mortality response in larvae from an established colony of Pieris brassicae. We report here that at extremely high doses, approaching 10000 times the LD50 for ArGV1 and ArGV2, three other ArGV isolates caused low and irregular levels of mortality in P. brassicae. At similar doses Agrotis segetum GV caused 43% mortality in one infection, but no deaths ensued from other inoculations with this virus. Restriction endonuclease analysis of viral DNA recovered from individual larval cadavers revealed that, in most cases, progeny virus differed from the inoculum and consisted either of ArGV1 or of novel genotypes explicable as recombinants between genomes of the inoculum and of ArGV1. Field-collected P. brassicae inoculated with ArGV8 yielded a similar range of progeny genotypes. Physical maps were constructed for two such recombinants, based on comparative restriction analysis with reference to the published map of ArGV1 and to those of ArGV5 and ArGV8, which are presented. Replication of the inoculum genotype was observed in only two infections. The origin of ArGV1 DNA appearing among progeny from these infections and the relevance of our results to identifying ArGV DNA sequences that modulate pathogenicity for P. brassicae are discussed.

Animals↗
PubMed1993

Cost-conservative dentistry: appropriate dentistry at lower cost.

Dental practitioners in both private and public dentistry are faced with patients who for reasons of public or private finance are not able to be treated with the most sophisticated available dentistry. A concept of appropriate dentistry is provided whereby, with reference to available literature, it is shown that cost-conservative treatment can be provided that is likely to be satisfactory to both the client and the practitioner.

Cost Control↗
PubMed1991

Loss of glutathione S-transferases in pollution-associated liver neoplasms in white suckers (Catostomus commersoni) from Lake Ontario.

White suckers (Catostomus commersoni) are one of two species of bottom-feeding fish in which various liver neoplasms are more prevalent in urban/industrial sites in western Lake Ontario than in less polluted sites in the Great Lakes. Previous studies indicate that white suckers excrete metabolites of various polycyclic aromatic hydrocarbons (PAHs) in bile, and that glutathione transferase (GST)-mediated conjugation is a major detoxification pathway for the PAH benzo[alpha]pyrene. To determine whether hepatocarcinogenesis in these wild fish is associated with induced GST-dependent resistance to carcinogens, we examined the expression of immunoreactive GSTs in liver neoplasms and putatively preneoplastic altered hepatocellular foci from white suckers collected from several polluted sites in western Lake Ontario. Histological sections of liver with altered hepatocellular foci, hepatocellular adenomas, hepatocellular carcinomas, bile duct adenomas and bile duct carcinomas were examined for GST immunoreactivity by the peroxidase-antiperoxidase (PAP) technique with polyclonal antiserum specific for all major GST isoenzyme subunits found in normal liver of white suckers. All bile duct adenomas, bile duct carcinomas and hepatocellular carcinomas were markedly or completely deficient in immunoreactive GST in comparison with surrounding normal hepatocytes. The majority of the hepatocellular adenomas were also deficient. Most altered hepatocellular foci had normal GST staining, but several GST-deficient altered hepatocellular foci were observed. However, none of the preneoplastic or advanced liver neoplasms expressed induced GST, suggesting that carcinogenesis is not associated with selection for GST-dependent resistance. Loss of hepatocellular GSTs may be incidental to neoplastic progression in these fish, or might be important in increasing susceptibility of some preneoplastic populations of hepatocytes to further DNA damage by environmental or endogenous chemicals that are normally detoxified by GSTs.

Animals↗
PubMed1990

The dependence of the International Sensitivity Index on the coagulometer used to perform the prothrombin time.

This study was designed to detect any effect that different types of coagulation instrument may have on the International Sensitivity Index (ISI) of a thromboplastin. Manufacturers of commercial thromboplastins now calibrate their reagents against the World Health Organization international reference preparation to assign them an ISI. This enables the prothrombin time (PT) estimated with that reagent to be expressed as an International Normalised Ratio (INR). One batch of Thromborel S was calibrated against the Australasian Reference Thromboplastin (ART). The Thromborel S was used on three photo-optical instruments, the Automated Coagulation Laboratory (ACL) (Instrumentation Laboratory), the Cobas Fibro (Roche), and the Coag-a-Pet (General Diagnostics). PTs using ART were performed manually using the reference method. The ISIs calibrated in our laboratory when the ACL and Cobas Fibro were used were not significantly different at the 95% level, being 1.102 +/- 0.018 and 1.134 +/- 0.022 respectively. The ISI with the Coag-a-Pet of 1.223 +/- 0.023 was significantly different to that of the ACL and the Cobas Fibro at the 95% level. The flowcharts for a computer program to perform the necessary calculations are provided. The program allows for the entry and editing of data from the calibration procedure, and provides a mean normal PT and normal range, the ISI and 95% confidence limits of the calibration, and a chart for the conversion of the test PTs to INRs. The authors have made available an IBM compatible program for the calibration of thromboplastins.

Blood Coagulation Tests↗
PubMed1990

Pathogenesis of skin and liver neoplasms in white suckers from industrially polluted areas in Lake Ontario.

Increased prevalences of epidermal and hepatobiliary neoplasms in white suckers (Catostomu commersoni) and brown bullheads (Ictalurus nebulosus) in the Western region of Lake Ontario have been associated with industrial pollution, but the identity and causative role of environmental carcinogens have not yet been established. Most epidermal tumors of lip and body skin are benign focal proliferations that occur in fish from the polluted Hamilton region, and also in fish from less polluted sites in the Great Lakes. These skin tumors in white suckers do not have consistent alterations in cellular glutathione S-transferases (GST), suggesting that growth of skin tumors is not promoted by chemicals normally detoxified by GST. However, elevated levels of glutathione peroxidase (GPO) and glutathione reductase (GR) in skin papillomas are indicative of promotional peroxidative tissue injury, either caused directly by xenobiotics or indirectly by chemical-induced inflammation. Liver tumors in white suckers from Lake Ontario include preneoplastic, benign, and malignant populations of hepatocellular and biliary cells, all of which are more prevalent in fish from polluted sites. These liver tumors are consistently associated with chronic cholangiohepatitis and segmental cholangiofibrosis, but these conditions also occur in white suckers in non-industrial locations. Thus, the natural occurrence of biliary disease, not attributable to industrial pollution, may have some influence on the development of liver tumors. Some preneoplastic lesions and the majority of neoplastic hepatocellular and biliary lesions in white suckers have low levels of total GST, indicating that these liver neoplasms are not promoted by xenobiotics normally detoxified by hepatic GSTs.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

The role of glutathione S-transferases in the hepatic metabolism of benzo[a]pyrene in white suckers (Catostomus commersoni) from polluted and reference sites in the Great Lakes.

1. Orally administered 3H-benzo[a]pyrene (3H-BaP) was excreted in the bile of White Suckers predominantly as water soluble metabolites some of which were hydrolyzed by arylsulfatase or beta-glucuronidase. 2. Non-hydrolysible polar metabolites comprised a substantial proportion of biliary metabolites. 3. HPLC analysis revealed fluorescent and 3H-labelled peaks which co-eluted with standards of the glucuronide and sulfate conjugates of BaP. 4. The most polar peak co-chromatographed with a double-radiolabelled metabolite produced in vitro with 3H-BaP and 35S-glutathione. 5. Inhibition of epoxide hydrolase in vitro reduced all water soluble metabolites except the glutathione conjugate of BaP. 6. Glutathione conjugation represents a major hepatic detoxication pathway of BaP in White Suckers.

Animals↗
PubMed1988

Physical map and polyhedrin gene sequence of Lymantria dispar nuclear polyhedrosis virus.

Restriction maps of the 166.6-kb genome of Lymantria dispar multiply-enveloped nuclear polyhedrosis virus (LdMNPV clone g) were constructed for BamHI, BglII, EcoRI, EcoRV, HindIII and KpnI, using cosmid pVK102 and pBluescript vectors. Southern hybridizations indicated that the LdMNPV genome contains five dispersed regions of intragenomic sequence homology. The polyhedrin gene of LdMNPV was located within BglII-E and the sequence of the 735-nucleotide (nt) coding region and 678 nt of flanking DNA was determined. A conserved 14-nt sequence, associated with transcriptional start points in other polyhedrins, was identified at 44 to 57 nt upstream from the start codon. The deduced polyhedrin amino acid (aa) sequence showed a high degree of homology with a previously determined protein sequence for LdMNPV polyhedrin (89%) and with deduced amino acid sequences for three other MNPV polyhedrins (74%). Optimal alignment of the four sequences indicated that LdMNPV polyhedrin possesses a single aa insertion at residue 4 and a single aa deletion at residue 164.

Amino Acid Sequence↗
PubMed1988

In vivo isolation of baculovirus genotypes.

Restriction endonuclease profiles of a wild-type granulosis virus from Artogeia rapae (ArGV3) and a nuclear polyhedrosis virus from Lymantria dispar (LdMNPV) indicated that the preparations were genotypically heterogeneous. Eight constituent genotypes were isolated from ArGV3 by low mortality dose infections of late instar A. rapae and analysis of progeny viral DNA recovered from individual cadavers. Three distinct genotypes were isolated from LdMNPV by the same approach, using L. dispar larvae. These results show that larval mortality can occur as a consequence of productive infection by a single virus particle. Comparative physical mapping of the eight ArGV3 genotypes suggested that their diversity may be partly attributable to recombination during natural coinfection.

DNA Restriction Enzymes↗
PubMed1988

Development of a new physicochemical model for brain penetration and its application to the design of centrally acting H2 receptor histamine antagonists.

A rational approach to the design of centrally acting agents is presented, based initially upon a comparison of the physicochemical properties of three typical histamine H2 receptor antagonists which do not readily cross the blood-brain barrier with those of the three brain-penetrating drugs clonidine (6), mepyramine (7) and imipramine (8). A good correlation was found between the logarithms of the equilibrium brain/blood concentration ratios in the rat and the partition parameter, delta log P, defined as log P (1-octanol/water)-log P (cyclohexane/water), which suggests that brain penetration might be improved by reducing overall hydrogen-bonding ability. This model has been employed as a guide in the design of novel brain-penetrating H2 antagonists by the systematic structural modification of representatives of different structural types of H2 antagonists. Although marked increases in brain penetration amongst congeners of cimetidine (1), ranitidine (9), and tiotidine (10) were achieved, no compound was found with an acceptable combination of H2 antagonist activity (-log KB in the guinea pig atrium greater than 7.0) and brain penetration (steady-state brain/blood concentration ratio greater than 1.0). Conversely, structural modification of N-[[(piperidinyl-methyl)phenoxy]propy]acetamide (30) led to several potent, novel compounds which readily cross the blood-brain barrier. One of these, zolantidine (SK&F 95282, 41), whose -log KB is 7.46 and steady-state brain/blood ratio is 1.4, has been identified for use in studying histaminergic H2 receptor mechanisms in brain. Comparison of delta log P values with the logarithms of the brain/blood ratios for 20 structurally diverse compounds for which data became available confirms a highly significant correlation and supports the general validity of this model.

Algorithms↗
PubMed1988

Zolantidine (SK&F 95282) is a potent selective brain-penetrating histamine H2-receptor antagonist.

1. The novel benzthiazole derivative zolantidine (SK&F 95282) is a potent antagonist of histamine at H2-receptors in guinea-pig atrium and rat uterus. Only apparent pA2 values of 7.46 and 7.26 respectively could be calculated since the slopes of the Schild plots were significantly less than unity. 2. Zolantidine is equally potent as an antagonist at histamine H2-receptors in guinea-pig brain. The compound inhibited histamine stimulated adenylate cyclase (pKi 7.3) and dimaprit stimulated adenosine 3':5'-cyclic monophosphate (cyclic AMP) accumulation (approx pA2 7.63), and competed with [3H]-tiotidine binding (pKi 7.17). 3. Zolantidine is at least 30 fold more potent at H2-receptors than at other peripheral and central receptors investigated. 4. Infusion of zolantidine into rats produces a brain concentration greater than the plateau blood concentration (brain/blood ratio 1.45). 5. Zolantidine is thus characterized as a potent selective brain-penetrating H2-receptor antagonist, and will be a valuable pharmacological tool for investigating possible physiological and pathological roles for histamine in the central nervous system.

Animals↗
PubMed1987

Evidence for low brain penetration by the H1-receptor antagonist temelastine (SK&F 93944).

Competition by the potent selective H1-receptor antagonist temelastine (SK & F 93944) with [3H]mepyramine binding to mouse cortex H1-receptors has been measured in vitro and vivo. The data were compared with that obtained using the classical H1-receptor antagonists mepyramine and promethazine and indicated that temelastine has relatively low ability to penetrate the blood-brain barrier compared with the latter two compounds. These studies also revealed that temelastine has relatively low affinity for mouse cortex H1-receptors compared with its affinity for H1-receptors in guinea-pig ileum and cortex, suggesting that it may be a useful compound with which to investigate potential H1-receptor tissue and species-related differences.

Animals↗
PubMed1986

3H-tiotidine binding to guinea-pig cortical and striatal membranes.

3H-Tiotidine has been identified as a suitable radioligand for the H2-receptor. We have confirmed and extended structure-binding affinity studies in the guinea-pig cortex, and established a structure-binding affinity relationship consistent with the H2-receptor in guinea-pig striatum. Cimetidine-displaceable 3H-tiotidine binding was observed also in the nucleus accumbens.

Animals↗
PubMed1986

N-Methyldimaprit (SK&F92054). A chemical control for the histamine H2-receptor agonist dimaprit.

Dimaprit analogues having alkyl substituents on the isothiourea group have no detectable H2-agonist activity on the guinea-pig atrium. N-Methyldimaprit [S-[3-(N,N-dimethylamino)propyl]-N'-methylisothiourea] (SK&F92054) is identified as a compound which may serve as a suitable chemical control when studying the actions of dimaprit at putative H2-histamine receptors. Concentrations of N-methyl-dimaprit (up to 3 X 10(-3) M) had no agonist activity in vitro on the guinea-pig atrium (less than 0.005% of the activity of histamine), rat uterus (up to 2 X 10(-3) M,) or as a stimulant of guinea-pig ventricular adenylate cyclase (up to 10(-3) M). N-Methyldimaprit at 10(-3) M also did not significantly stimulate acid secretion in the rat isolated stomach preparation; it was a very weak stimulant of gastric acid secretion (less than 0.2% of the activity of histamine) in vivo in the lumen-perfused stomach of the anaesthetised rat but exhibited marked tachyphylaxis on repeated administration. N-Methyldimaprit has two basic centres, macroscopic pKa values 8.31 and 9.58 at 40 degrees C.

Adenylyl Cyclases↗
PubMed1985

A study of cryosurgery and the CO2 laser in treatment of carcinoma in situ (CIN III) of the uterine cervix.

The results of laser and cryosurgical treatment in 106 patients with histologically proven carcinoma in situ of the uterine cervix (CIN III) are presented. Seventy-one patients were treated with the laser and in 63 of these further follow-up with colposcopy and cytology failed to show any abnormality. This represents an initial success rate of 89%. In 8 patients (11%) initial treatment was considered to have failed because of persistent dyskaryotic smears and histological evidence of cervical intraepithelial neoplasia (CIN II-III). Six of these patients were treated successfully with a further laser application and two patients had conization. The overall success rate for the laser was 97%. Thirty-five patients were treated with cryosurgery and subsequent follow-up was negative in 29 of these patients (83%). The 6 treatment failures (17%) were subsequently successfully treated with local destructive therapy (4 with cryosurgery, 1 with laser, and 1 with needle diathermy). The overall success rate for cryofreezing was 94.2%. In cases of CIN III the laser is more likely to achieve eradication of the lesion with a single application than cryofreezing.

Adolescent↗
PubMed1984

A coupled assay for histidine decarboxylase: in vivo turnover of this enzyme in mouse brain.

A sensitive coupled assay for histidine decarboxylase has been developed. This method involved conversion of [3H]histidine into [3H]histamine by the enzyme sample, with methylation of this product in situ, catalysed by the enzyme histamine N-methyltransferase, to yield [3H]N-tele-methylhistamine. The radioactive product was separated from the substrate by (i) extraction into chloroform, (ii) ion-exchange chromatography and (iii) liquid cation-exchange extraction. The "no tissue" assay blank comprised 0.0007% of the substrate radioactivity. Sample material with a histidine decarboxylase activity of as little as 0.14 fmol/min/ml (measured at 1 microM histidine) gave double the blank value. More than 50 assays could be performed in one day. This assay was used to determine the in vivo changes in mouse brain histidine decarboxylase activity following irreversible inhibition with (+) alpha-fluoromethylhistidine (alpha-FMH). From the time course of recovery of enzyme activity the half-life of histidine decarboxylase in vivo was calculated to be 53 h.

Animals↗