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S Slater

Publications and source records attributed to S Slater.

At least 37 records · Page 2Linked to original sources
PubMed1998

Effects of purified SeqA protein on oriC-dependent DNA replication in vitro.

In vivo studies suggest that the Escherichia coli SeqA protein modulates replication initiation in two ways: by delaying initiation and by sequestering newly replicated origins from undergoing re-replication. As a first approach towards understanding the biochemical bases for these effects, we have examined the effects of purified SeqA protein on replication reactions performed in vitro on an oriC plasmid. Our results demonstrate that SeqA directly affects the biochemical events occurring at oriC. First, SeqA inhibits formation of the pre-priming complex. Secondly, SeqA can inhibit replication from an established pre-priming complex, without disrupting the complex. Thirdly, SeqA alters the dependence of the replication system on DnaA protein concentration, stimulating replication at low concentrations of DnaA. Our data suggest that SeqA participates in the assembly of initiation-competent complexes at oriC and, at a later stage, influences the behaviour of these complexes.

Bacterial Outer Membrane Proteins↗
PubMed1998

Lithium and clozapine-induced neutropenia/agranulocytosis.

Lithium administration was used in a patient with a clozapine-induced neutropenia and in another with complete agranulocytosis to assess whether lithium could stimulate neutrophil production. In both cases, following lithium administration, the neutrophil count was increased to the normal range within 6 days. In the patient who had presented a neutropenia, clozapine treatment was then reinstated in the presence of lithium and continued without the neutrophil count dropping into the yellow-alert range thereafter.

Adult↗
PubMed1998

Multiple beta-ketothiolases mediate poly(beta-hydroxyalkanoate) copolymer synthesis in Ralstonia eutropha.

Polyhydroxyalkanoates (PHAs) are a class of carbon and energy storage polymers produced by numerous bacteria in response to environmental limitation. The type of polymer produced depends on the carbon sources available, the flexibility of the organism's intermediary metabolism, and the substrate specificity of the PHA biosynthetic enzymes. Ralstonia eutropha produces both the homopolymer poly-beta-hydroxybutyrate (PHB) and, when provided with the appropriate substrate, the copolymer poly(beta-hydroxybutyrate-co-beta-hydroxyvalerate) (PHBV). A required step in production of the hydroxyvalerate moiety of PHBV is the condensation of acetyl coenzyme A (acetyl-CoA) and propionyl-CoA to form beta-ketovaleryl-CoA. This activity has generally been attributed to the beta-ketothiolase encoded by R. eutropha phbA. However, we have determined that PhbA does not significantly contribute to catalyzing this condensation reaction. Here we report the cloning and genetic analysis of bktB, which encodes a beta-ketothiolase from R. eutropha that is capable of forming beta-ketovaleryl-CoA. Genetic analyses determined that BktB is the primary condensation enzyme leading to production of beta-hydroxyvalerate derived from propionyl-CoA. We also report an additional beta-ketothiolase, designated BktC, that probably serves as a secondary route toward beta-hydroxyvalerate production.

Acetyl-CoA C-Acyltransferase↗
PubMed1997

CD45 regulates Src family member kinase activity associated with macrophage integrin-mediated adhesion.

BACKGROUND: Adhesion of leukocytes to the extracellular matrix and to other cells is mediated by members of the integrin family of adhesion molecules. Src family kinases are activated upon integrin-mediated adhesion. In lymphocytes, CD45 is a leukocyte-specific transmembrane protein tyrosine phosphatase that activates Src family kinases associated with B-cell and T-cell antigen receptor signaling by constitutive dephosphorylation of the inhibitory carboxy-terminal tyrosine phosphorylation site. Here, we show that CD45 is also important in downregulating the kinase activity of Src family members during integrin-mediated adhesion in macrophages. RESULTS: We found that CD45 colocalized with beta2 integrin and the Src family kinase p53/56(lyn) to adhesion sites in bone marrow-derived macrophages. Macrophages from CD45(-/-) mice were unable to maintain integrin-mediated adhesion. In adherent macrophages, absence of CD45 led to the hyperphosphorylation and hyperactivation of p56/59(hck) and p53/56(lyn), but not of p58(c-fgr). CD45 directly inactivated p59(hck) but not p56(lck) in transient transfection assays. Furthermore, coexpression of CD45 with p59(hck) or p56(lyn) containing a tyrosine to phenylalanine mutation at the carboxy-terminal negative regulatory site resulted in decreased tyrosine phosphorylation of the Src family member kinases due to dephosphorylation of the potentiating tyrosine phosphorylation site within the kinase domain. CONCLUSIONS: Using primary bone marrow macrophages, these studies demonstrate that CD45 regulates Src family kinases and is required to maintain macrophage adhesion. CD45 decreases Src family kinase activity by dephosphorylating the tyrosine residue located within the kinase domain.

Animals↗
PubMed1997

Expression of heat shock proteins in chronic pancreatitis: protective or pathogenic roles?

The tissue-distributions of heat shock proteins (HSP) identified by monoclonal antibodies ML-30, TB-78, CA-Str7-1, and MAB 72/73 have been examined in formalin-fixed and paraffin wax-embedded tissues from 10 normal pancreatic specimens and 92 cases of chronic pancreatitis. The chronic pancreatitis cases were divided by probable etiology into alcohol-related, postacute pancreatitis, or idiopathic. The HSP identified by ML-30 and CA-Str7-1 were constitutively expressed, with a regional distribution, by duct and ductular epithelial cells in all normal pancreatic tissues. The HSP detected by ML-30 were expressed uniformly throughout the cytoplasm of the majority of ductular epithelial cells in all cases of chronic pancreatitis, irrespective of suspected etiology, and in the ducts of all but two cases of alcohol-associated chronic pancreatitis. The HSP defined by CA-Str7-1 were identified in the majority of duct or ductular epithelial cells in most of the cases of chronic pancreatitis, although possible differential expression was observed with respect to etiology (ie, there seemed to be less HSP in cases of postalcohol pancreatitis). The HSP identified by TB-78 were not constitutively expressed by normal pancreatic tissues but were found in a few scattered epithelial cells in two of these cases. However, significant expression of these HSP were observed in most epithelial cells in a population of cases regarded as either alcohol-associated (0.05 > p > 0.02) or postacute chronic pancreatitis (0.01 > p > 0.001). The HSP identified by monoclonal antibody MAB 72/73 were either not demonstrable or were expressed at very low levels in both the normal and inflamed pancreatic tissues. Expression of the four groups of HSP molecules appeared to be differentially regulated both in normal pancreatic and in chronic pancreatitis tissues. These differences in expression may indicate different functions in normal tissues, with either a protective or a pathogenic role for these proteins in the diseased state. Our current findings support the hypothesis that expression of certain HSP, particularly those identified by TB-78, may be involved in the pathogenesis of distinct subtypes of chronic pancreatitis. Our data do not suggest that HSP are the primary targets of immune-mediated cytotoxic activity; nevertheless, enhanced expression of these molecules by pancreatic ductular epithelial cells does provide an environment in which increased amounts of endogenous intracellular peptides may be transported to the cell surface, thereby becoming potential targets of immune-surveillance and cell-mediated cytotoxicity. Conversely, HSP may play a protective role in such a manner that selected groups of pancreatic ductular epithelial cells withstand cytotoxic damage of chemical, metabolic, or immune origin, and for significantly increased periods of time than they would otherwise; HSP thereby conserve a population of "reserve" epithelial cells from which pancreatic regeneration might occur. Identification of distinct pathogenic groups, defined according to precise immunohistochemical criteria, might provide the basis of a functional assessment and hence allow development of biologically appropriate strategies for managing individual patients with chronic pancreatitis.

Adult↗
PubMed1996

Suspected intussusception: is ultrasound a reliable diagnostic aid?

BACKGROUND: Infantile intussusception often presents with symptoms more common to less dangerous conditions, and diagnosis must be established as early as possible. Clinical diagnosis is often wrong and contrast enema is invasive. Sonography is painless and harmless and if it provides a reliable method of diagnosis or exclusion of intussusception, diagnostic delay will be avoided. METHODS: In the John Hunter Hospital, Newcastle, between 1993 and 1994, the names of all children referred for abdominal sonography with a degree of suspicion of intussusception were recorded, and the histories were subsequently reviewed. RESULTS: Fifty patients were studied. Forty-one patients had no sonographic evidence of intussusception and nine patients had positive findings. None of the 41 patients who had negative sonograms proved to have intussusception. The nine patients who had positive findings were subjected to air enema. In two patients the sonographic diagnosis was proved wrong. In the other seven patients it was confirmed. Thus there were two false positives and no false negatives. CONCLUSION: Sonography is a reliable aid to the clinical diagnosis of intussusception.

Child↗
PubMed1995

E. coli SeqA protein binds oriC in two different methyl-modulated reactions appropriate to its roles in DNA replication initiation and origin sequestration.

The seqA gene negatively modulates replication initiation at the E. coli origin, oriC. seqA is also essential for sequestration, which acts at oriC and the dnaA promoter to ensure that replication initiation occurs exactly once per chromosome per cell cycle. Initiation is promoted by full methylation of GATC sites clustered in oriC; sequestration is specific to the hemimethylated forms generated by replication. SeqA protein purification and DNA binding are described. SeqA interacts with fully methylated oriC strongly and specifically. This reaction requires multiple molecules of SeqA and determinants throughout oriC, including segments involved in open complex formation. SeqA interacts more strongly with hemimethylated DNA; in this case, oriC and non-oriC sequences are bound similarly. Also, binding of hemimethylated oriC by membrane fractions is due to SeqA. Direct interaction of SeqA protein with the replication origin is likely to be involved in both replication initiation and sequestration.

Bacterial Outer Membrane Proteins↗
PubMed1993

Palpation of the thyroid gland.

The initial clinical clue to the existence of a disorder of the thyroid gland often is the detection of a physical abnormality of the gland. Adequate palpation of the gland is an essential component of the evaluation of a suspected disorder of the thyroid gland. Provided herein are guidelines that others have found useful in improving their skill in this aspect of physical diagnosis.

Humans↗
PubMed1992

Immortalization of murine primary spleen cells by v-myc, v-ras, and v-raf.

Growth factor-independent cell lines, including four lines characterized as macrophages, were isolated by infection of BALB/c mouse primary spleen cells with combinations of three retroviruses encoding v-myc, v-ras, and v-myc/v-raf. Proliferating cell lines were isolated only rarely, and after long crisis periods, following the introduction of myc and raf by infection with J2 virus, or of myc and ras by coinfection with myc309 and raszip6 viruses. However, sequential infections with all three viruses--myc plus ras cells reinfected with J2, or J2 followed by myc plus ras coinfection--resulted in rapid outgrowth of cell lines which grew at high growth rates to high densities. When cells were treated with anti-IgG F(ab')2/IL-4/IL-5 to specifically stimulate B cells, cell lines were isolated readily by infection with myc plus ras alone, J2 alone, or all three viruses. These cell lines arose after shorter crisis times and all grew at high growth rates and to high densities. Analysis of cell surface markers and immunoglobulin gene arrangement revealed no lymphoid characteristics in any of the lines. Four cell lines express all three macrophage markers analyzed (F4/80, Mac1, FcR), and many others are Mac1+ and/or FcR+. Out of 20 immortalized cell lines tested, 13 show clonal growth in soft agar, and 3/6 of these produced tumors in BALB/c mice, indicating that fully transformed cells may be isolated by these procedures. In at least one of the cell lines, integration of all three infecting viruses has occurred.

Animals↗
PubMed1992

Mutant p53 expression in solar keratosis: an immunohistochemical study.

Thirty-eight solar keratoses from 32 patients were studied for expression of mutant p53 protein by an immunohistochemical technique. Twenty-eight of the 38 solar keratoses (73.7%) showed positive and variable nuclear labelling, whereas 10 specimens were immunonegative. The nuclear immunopositivity which was seen in all variants was mostly diffuse in distribution. The adjacent "normal" epidermis of 8 keratoses showed positive mutant p53 labelling. Eight of the keratoses were associated with invasive squamous cell carcinoma of which only two were immunopositive. Cytoplasmic labelling was never a feature. The study demonstrates that mutant p53 protein is commonly expressed in all variants of solar keratosis and that its expression correlates with atypical keratinocyte proliferation. It is proposed that the demonstration of mutant p53 in the adjacent normal epidermis may be a potential marker of early neoplastic transformation.

Aged↗
PubMed1992

Production of poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) in a recombinant Escherichia coli strain.

An Escherichia coli strain has been constructed that produces the copolymer poly-(3-hydroxybutyrate-co-3-hydroxyvalerate) P(HB-co-HV). This has been accomplished by placing the PHB biosynthetic genes from Alcaligenes eutrophus into an E. coli fadR atoC(Con) mutant and culturing the strain in M9 minimal medium containing glucose and propionate. 3-Hydroxyvalerate incorporation is absolutely dependent on the presence of both glucose and propionate, and 3-hydroxybutyrate-3-hydroxyvalerate ratios in the copolymer can be manipulated by altering the propionate concentration and/or the glucose concentration in the culture. P(HB-co-HV) production can be accomplished by using a wide variety of feeding regimens, but the most efficient is to allow the culture to grow to late log phase in minimal medium containing acetate and then add glucose and propionate to initiate copolymer production. A broad range of propionate concentrations can be used in the culture to stimulate 3-hydroxyvalerate incorporation; however, the most efficient utilization of propionate occurs at concentrations below 10 mM. 3-Hydroxyvalerate molar percentages in the copolymer are relatively constant over the course of growth. The copolymer has been purified and confirmed to be P(HB-co-HV) by gas chromatography/mass spectrometry and differential scanning calorimetry.

Alcaligenes↗
PubMed1991

The lesbian family life cycle: a contextual approach.

A recent broadening of family life cycle theory to include the various family norms deriving from ethnic differences, single parenting, divorce, and remarriage has not extended to the lesbian family experience. The need to articulate a lesbian family life cycle is underscored here with particular attention to the specific challenges and coping mechanisms of this particular family experience.

Family↗
PubMed1991

Role of cattle in the epidemiology of tick-bite fever in Zimbabwe.

Almost 100% of 52 cattle tested from the southern areas of Zimbabwe were found to have antibodies reactive with Rickettsia conorii compared with less than 30% of 120 cattle from the north. Steers artificially infected with R. conorii isolated from Amblyomma hebraeum were found to show no hematological or biochemical signs of disease but did seroconvert. Clinical signs of infection were restricted to regional lymphadenopathy and dermal erythema, edema, and tenderness at the inoculation site. Rickettsemia was detectable for at least 32 days postinfection. Our findings indicate that cattle could be involved in the transmission of rickettsias by A. hebraeum and may serve as a reservoir of human tick-bite fever in southern Africa.

Animals↗