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Biomedical subjects

A Paterson

Publications and source records attributed to A Paterson.

At least 37 records · Page 2Linked to original sources
PubMed2000

The streptococcal superantigen SMEZ exhibits wide allelic variation, mosaic structure, and significant antigenic variation.

The frequencies of the newly identified streptococcal superantigen genes smez, spe-g, and spe-h were determined in a panel of 103 clinical isolates collected between 1976 and 1998 at various locations throughout New Zealand. smez and spe-g were found in every group A Streptococcus (GAS) isolate, suggesting a chromosomal location. The spe-h gene was found in only 24% of the GAS isolates and is probably located on a mobile DNA element. The smez gene displays extensive allelic variation and appears to be in linkage equilibrium with the M/emm type. 22 novel smez alleles were identified from 21 different M/emm types in addition to the already reported alleles smez and smez-2 with sequence identities between 94. 5 and 99.9%. Three alleles are nonfunctional due to a single base pair deletion. The remaining 21 alleles encode distinct SMEZ variants. The mosaic structure of the smez gene suggests that this polymorphism has arisen from homologous recombination events rather than random point mutation. The recently resolved SMEZ-2 crystal structure shows that the polymorphic residues are mainly surface exposed and scattered over the entire protein. The allelic variation did not affect either Vbeta specificity or potency, but did result in significant antigenic differences. Neutralizing antibody responses of individual human sera against different SMEZ variants varied significantly. 98% of sera completely neutralized SMEZ-1, but only 85% neutralized SMEZ-2, a very potent variant that has not yet been found in any New Zealand isolate. SMEZ-specific Vbeta8 activity was found in culture supernatants of 66% of the GAS isolates, indicating a potential base for the development of a SMEZ targeting vaccine.

Alleles↗
PubMed2000

Barriers to community support for the dementia carer: a qualitative study.

OBJECTIVES: To understand how carers of dementia sufferers gain access to community support and to determine potential barriers for carers. DESIGN: Qualitative study using semi-structured interviews of carers after an Aged Care Assessment Team intervention. SETTING: Australian metropolitan Aged Care Assessment Team. SUBJECTS: 24 live-in carers of dementia sufferers. MAIN OUTCOME MEASURES: Carers' subjective experience of sources of stress in their care of the dementia sufferer focusing on interactions with the general practitioner and formal community support agencies. RESULTS: Most carers suffered high levels of stress, mainly due to behaviour disturbances and care needs of the dementia sufferers. Problems with health care agencies were also reported by a majority of the carers to be contributors to their distress. General practitioners were perceived to have referred dementia sufferers late for community care, despite the carer having experienced difficulties for a considerable time period. Carers also complained that too little information was provided about the diagnosis of dementia, how to deal with problem behaviours and how to access support services before and after the assessment procedure. CONCLUSIONS: Problems with the interaction between the carer and the general practitioner appear to be important in delaying access to appropriate support and information. Earlier recognition of carers' problems, the provision of better education and earlier access to support services may lessen the degree of stress experienced by carers.

Adult↗
PubMed2000

Expression of progastrin-derived peptides and somatostatin in fundus and antrum of nonulcer dyspepsia subjects with and without Helicobacter pylori infection.

The hypergastrinemia and hyperacidity associated with Helicobacter pylori infection has been explained by either a primary excess of gastrin or a lack of inhibitory influence by somatostatin (SOM). The objective of the present study was to compare the concentrations of fundic and antral SOM- and antral progastrin-derived peptides in nonulcer dyspepsia (NUD) subjects with and without H. pylori infection. Antral and fundic mucosal biopsies were extracted and assayed for SOM and gastrin amide, glycine-extended gastrin (gastrin gly), progastrin, and total gastrin. There was a significant sixfold reduction in antral SOM but no change in fundic SOM content in H. pylori-infected subjects compared to uninfected subjects. Antral gastrin amide concentrations were significantly higher in infected subjects. However, the concentrations of the nonamidated gastrin forms (progastrin and glycine-extended gastrin) were significantly lower in the infected subjects, indicating an increased conversion of the precursor forms of gastrin to amidated gastrin, the type known to stimulate gastric acidity. The present study demonstrates that the elevated gastrin concentrations associated with H. pylori infection may be due to a reduction in the paracrine inhibitory effect of SOM on antral gastrin release. In addition, the posttranslational processing of gastrin to the amidated forms is increased in infected subjects, explaining why the elevation in antral gastrin is confined to the amidated form.

Adult↗
PubMed2000

Abnormal modelling of the humeral head in the tricho-rhino-phalangeal syndrome: a new radiological observation.

The case of a 27-year-old female patient with tricho-rhino-phalangeal (TRP) type I syndrome is reported. The patient demonstrated the classical features of slowly growing hair, a bulbous nose and brachydactyly with swelling at the interphalangeal joints, but in addition showed some of the less common manifestations such as supernumerary teeth and prognathism. To the authors' knowledge this is the first reported case in which modelling abnormalities of the proximal humerus mirror those seen in the femoral head. This adds weight to the argument that the skeletal abnormalities in TRP are part of a generalized bone dysplasia.

Adult↗
PubMed2000

Elevated renal rind.

We describe the findings from a group of five infants ranging in age from 3 weeks to 13 months who had shock of differing causes. In each case, sonographic evaluation of the abdomen revealed bilateral perirenal hyperechoic bands several millimeters thick, surrounding a thin, hypoechoic rim of fluid. The findings were identified during the acute phase of each child's illness and persisted after the patient's condition had clinically improved, eventually resolving in the three surviving children. We have dubbed this sign the "elevated renal rind." We believe that the changes are likely secondary to systemic inflammatory mediators and do not reflect localized intraabdominal disease.

Acute Disease↗
PubMed1999

Development of an assay for phospholipase C using column-reconstituted, extruded phospholipid vesicles.

The reconstitution of heterotrimeric G proteins into phospholipid vesicles has been widely used for the measurement of PLC-beta activity in vitro. We have developed an improved and sensitive method for the assay of PLC-beta activity. This approach involves reconstitution of purified betagamma dimers into extruded phospholipid vesicles containing phosphatidylinositol 4, 5-bisphosphate and using a gel-filtration technique to separate the reconstituted vesicles from monodispersed betagamma dimers and the detergent used to solubilize G proteins. The method provides physical information about the partitioning of betagamma dimers into phospholipid vesicles and was used to examine the effect of different prenyl groups on the gamma subunits in the activation of PLC-beta. The beta1gamma1 dimer (containing the farnesyl group) and the beta1gamma2 dimer (containing the geranylgeranyl group) were purified from baculovirus-infected Sf9 insect cells and were found to partition equally into phospholipid vesicles. The beta1gamma2 dimer is more potent and effective in stimulating PLC-beta activity than the beta1gamma1 dimer. The EC50 values of betagamma dimers for the activation of PLC-beta determined with this method were lower than those determined by previous methodology, showing that betagamma subunits have a subnanomolar affinity for PLC-beta.

Animals↗
PubMed1999

PDK1 acquires PDK2 activity in the presence of a synthetic peptide derived from the carboxyl terminus of PRK2.

BACKGROUND: Protein kinase B (PKB) is activated by phosphorylation of Thr308 and of Ser473. Thr308 is phosphorylated by the 3-phosphoinositide-dependent protein kinase-1 (PDK1) but the identity of the kinase that phosphorylates Ser473 (provisionally termed PDK2) is unknown. RESULTS: The kinase domain of PDK1 interacts with a region of protein kinase C-related kinase-2 (PRK2), termed the PDK1-interacting fragment (PIF). PIF is situated carboxy-terminal to the kinase domain of PRK2, and contains a consensus motif for phosphorylation by PDK2 similar to that found in PKBalpha, except that the residue equivalent to Ser473 is aspartic acid. Mutation of any of the conserved residues in the PDK2 motif of PIF prevented interaction of PIF with PDK1. Remarkably, interaction of PDK1 with PIF, or with a synthetic peptide encompassing the PDK2 consensus sequence of PIF, converted PDK1 from an enzyme that could phosphorylate only Thr308 of PKBalpha to one that phosphorylates both Thr308 and Ser473 of PKBalpha in a manner dependent on phosphatidylinositol (3,4,5) trisphosphate (PtdIns(3,4,5)P3). Furthermore, the interaction of PIF with PDK1 converted the PDK1 from a form that is not directly activated by PtdIns(3,4,5)P3 to a form that is activated threefold by PtdIns(3,4,5)P3. We have partially purified a kinase from brain extract that phosphorylates Ser473 of PKBalpha in a PtdIns(3,4,5)P3-dependent manner and that is immunoprecipitated with PDK1 antibodies. CONCLUSIONS: PDK1 and PDK2 might be the same enzyme, the substrate specificity and activity of PDK1 being regulated through its interaction with another protein(s). PRK2 is a probable substrate for PDK1.

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1999

Phosphorylation by protein kinase C decreases catalytic activity of avian phospholipase C-beta.

The potential role of protein kinase C (PKC)-promoted phosphorylation has been examined in the G-protein-regulated inositol lipid signalling pathway. Incubation of [32P]Pi-labelled turkey erythrocytes with either the P2Y1 receptor agonist 2-methylthioadenosine triphosphate (2MeSATP) or with PMA resulted in a marked increase in incorporation of 32P into the G-protein-activated phospholipase C PLC-betaT. Purified PLC-betaT also was phosphorylated by PKC in vitro to a stoichiometry (mean+/-S. E.M.) of 1.06+/-0.2 mol of phosphate/mol of PLC-betaT. Phosphorylation by PKC was isoenzyme-specific because, under identical conditions, mammalian PLC-beta2 also was phosphorylated to a stoichiometry near unity, whereas mammalian PLC-beta1 was not phosphorylated by PKC. The effects of PKC-promoted phosphorylation on enzyme activity were assessed by reconstituting purified PLC-betaT with turkey erythrocyte membranes devoid of endogenous PLC activity. Phosphorylation resulted in a decrease in basal activity, AlF4(-)-stimulated activity, and activity stimulated by 2MeSATP plus guanosine 5'-[gamma-thio]triphosphate in the reconstituted membranes. The decreases in enzyme activities were proportional to the extent of PKC-promoted phosphorylation. Catalytic activity assessed by using mixed detergent/phospholipid micelles also was decreased by up to 60% by phosphorylation. The effect of phosphorylation on Gqalpha-stimulated PLC-betaT in reconstitution experiments with purified proteins was not greater than that observed on basal activity alone. Taken together, these results illustrate that PKC phosphorylates PLC-betaT in vivo and to a physiologically relevant stoichiometry in vitro. Phosphorylation is accompanied by a concomitant loss of enzyme activity, reflected as a decrease in overall catalytic activity rather than as a specific modification of G-protein-regulated activity.

Animals↗
PubMed1998

Evidence for an Alzheimer disease susceptibility locus on chromosome 12 and for further locus heterogeneity.

CONTEXT: Alzheimer disease (AD) susceptibility genes have been identified on chromosomes 1, 14, 19, and 21, and a recent study has suggested a locus on chromosome 12. OBJECTIVE: To confirm or refute the existence of a familial AD susceptibility locus on chromosome 12 in an independent sample of familial AD cases. DESIGN: Retrospective cohort study. DNA data for 6 chromosome 12 genetic markers were evaluated using parametric lod score and nonparametric linkage methods and linkage heterogeneity tests. The latter include the admixture test of homogeneity in the total group of families and the predivided sample test in families stratified by the presence or absence of an apolipoprotein E (APOE) epsilon4 allele among affected members. Parametric analyses were repeated assuming autosomal dominant inheritance of AD and either age- and sex-dependent penetrance or zero penetrance for the analysis of unaffected relatives. SETTING: Clinical populations in the continental United States, Canada, Argentina, and Italy. PATIENTS: Fifty-three white families composed of multiple members affected with AD, from whom DNA samples were obtained from 173 patients with AD whose conditions were diagnosed using established criteria and from 146 nondemented relatives. MAIN OUTCOME MEASURE: Presence of an APOE epsilon4 allele among affected family members. RESULTS: Using parametric methods, no evidence for linkage to the region spanned by the chromosome 12 markers could be detected if familial AD is assumed to arise from the same genetic locus in all 53 families. However, significant evidence for linkage was detected in the presence of locus heterogeneity using the admixture test (odds ratio, 15, 135:1). The estimated proportion of linked families within the 53 families examined varied between 0.40 and 0.65, depending on the genetic model assumed and APOE status. The precise location of the AD gene could not be determined, but includes the entire region suggested previously. Nonparametric linkage analysis confirmed linkage to chromosome 12 with the strongest evidence at D12S96 (P<.001). CONCLUSIONS: Our data provide independent confirmation of the existence of an AD susceptibility locus on chromosome 12 and suggest the existence of AD susceptibility genes on other chromosomes. Screening a larger set of families with additional chromosome markers will be necessary for identifying the chromosome 12 AD gene.

Adult↗
PubMed1998

Activation of protein kinase B beta and gamma isoforms by insulin in vivo and by 3-phosphoinositide-dependent protein kinase-1 in vitro: comparison with protein kinase B alpha.

The regulatory and catalytic properties of the three mammalian isoforms of protein kinase B (PKB) have been compared. All three isoforms (PKBalpha, PKBbeta and PKBgamma) were phosphorylated at similar rates and activated to similar extents by 3-phosphoinositide-dependent protein kinase-1 (PDK1). Phosphorylation and activation of each enzyme required the presence of PtdIns(3,4,5)P3 or PtdIns(3,4)P2, as well as PDK1. The activation of PKBbeta and PKBgamma by PDK1 was accompanied by the phosphorylation of the residues equivalent to Thr308 in PKBalpha, namely Thr309 (PKBbeta) and Thr305 (PKBgamma). PKBgamma which had been activated by PDK1 possessed a substrate specificity identical with that of PKBalpha and PKBbeta towards a range of peptides. The activation of PKBgamma and its phosphorylation at Thr305 was triggered by insulin-like growth factor-1 in 293 cells. Stimulation of rat adipocytes or rat hepatocytes with insulin induced the activation of PKBalpha and PKBbeta with similar kinetics. After stimulation of adipocytes, the activity of PKBbeta was twice that of PKBalpha, but in hepatocytes PKBalpha activity was four-fold higher than PKBbeta. Insulin induced the activation of PKBalpha in rat skeletal muscle in vivo, with little activation of PKBbeta. Insulin did not induce PKBgamma activity in adipocytes, hepatocytes or skeletal muscle, but PKBgamma was the major isoform activated by insulin in rat L6 myotubes (a skeletal-muscle cell line).

3-Phosphoinositide-Dependent Protein Kinases↗
PubMed1998

An evaluation of how MRI is used as a pre-operative screening investigation in patients with temporal lobe epilepsy.

AIMS: A retrospective analysis was carried out of how magnetic resonance imaging (MRI) is used as a pre-operative screening investigation in patients with a clinical diagnosis of medically intractable temporal lobe epilepsy (TLE). Up to 65% of such patients are said to have hippocampal sclerosis (HS). MATERIALS AND METHODS: Forty-six patients in a 26-month period underwent MR examination on a 1.5 T scanner according to a routine protocol. Each patient had coronal T1-weighted and oblique coronal T2-weighted scans performed. Hippocampal volume was calculated from the T1-weighted images, the T2-weighted images being assessed for relative hippocampal signal intensity. Each individual patient's medical records were audited. RESULTS: Thirty per cent of patients in our study had a diagnosis of HS made on their MR scan. No patient had a diagnosis of HS made without prior clinical evidence of seizure lateralization. Sixty-eight per cent of patients with clinical evidence of a unilateral seizure focus had HS diagnosed by MR scanning. Forty-three per cent of patients did not have clinical evidence of an unilateral seizure focus. It was found that over 25% of patients referred to the unit did not fit the criteria of having medically intractable TLE. Nine per cent of patients had previously stated that they did not want epilepsy surgery. CONCLUSION: The lower than expected diagnostic rate of HS in this patient population reflects the broad criteria used in referring patients for imaging studies. This is likely to mirror the initial investigation of these patients outside specialist units where more extensive investigation prior to MRI is available. However, when MRI is used as an initial screening investigation, this study indicates that implementation of simple clinical criteria should significantly reduce the number of unnecessary scans.

Adolescent↗
PubMed1998

Analysis of the butyrylcholinesterase gene and nearby chromosome 3 markers in Alzheimer disease.

The K-variant of butyrylcholinesterase (BCHE-K) recently has been reported to be associated with Alzheimer disease (AD) in carriers of the epsilon4 allele of the apolipoprotein E (APOE) gene. We have re-examined the frequency of the BCHE-K allele in a large data set of both sporadic and familial cases of AD disease, and we have also examined the segregation of three genetic markers on chromosome 3 near BCHE . Our data neither support an association of BCHE-K with sporadic or familial AD, nor do they suggest the existence of another gene nearby on chromosome 3 as a common cause of familial AD.

Aged↗