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C A Smith

Publications and source records attributed to C A Smith.

At least 199 records · Page 11Linked to original sources
PubMed1996

Mutation spectra of M13 vectors containing site-specific Cis-Syn, Trans-Syn-I, (6-4), and Dewar pyrimidone photoproducts of thymidylyl-(3'-->5')-thymidine in Escherichia coli under SOS conditions.

The mutations spectra of cis-syn, trans-syn-I, (6-4), and Dewar pyrimidone photoproducts of the TT site of AATTAA and TATTAT in the (-) strand of a heteroduplex M13 vector were obtained in an excision and photoreversal repair deficient Escherichia coli host under SOS conditions. Oligonucleotides containing site-specific photoproducts were annealed to a complementary uracil-containing (+) strand that contained one or more unique pairs of nucleotide mismatches and used to prime (-) strand synthesis with a DNA polymerase and dNTPs. Following DNA synthesis, the reaction mixtures were incubated with T4 DNA ligase and ATP and then used to transfect SOS-induced competent CSRO6F' cells (uvrA6 and phr-1). The transfectants were plated, gridded, and probed by oligonucleotides specific for progeny of the (-) and (+) strands. Individual progeny of the photoproduct-containing (-) strands were plaque purified and sequenced by the dideoxy method. The cis-syn and trans-syn-I dimers were found not to be very mutagenic (<9%), the Dewar product more so (<33%), and the (6-4) product the most mutagenic (<73%). The mutation spectra were similar to those previously reported for the same photoproducts of the TT site of AGTTGG in the (+) strand of an M13 vector [Lawrence, C. W., et al. (1990) Mol. Gen Genet. 222, 166-168; LeClerc, J. E., et al. (1991) Proc. Natl. Acad. Sci. U.S.A. 88, 9685-9689] except that -1 deletion mutations were not observed for the trans-syn-I photoproducts, and a lower frequency of 3'-T-->C mutations was observed for the (6-4) photoproduct. Evidence that a small percentage of (+) strand repair of a double mismatch to the 3'-side of the photoproduct. Evidence that a small percentage of (+) strand repair of a double mismatch to the 3'-side was obtained from transfection experiments in which a second double mismatch was introduced opposite or flanking the photoproduct. Analysis of the minor tandem mutations induced by the (6-4) and Dewar products suggests that the SOS polymerase complex is able to elongate what amounts to double mismatches opposite these photoproducts and is consistent with the action of a highly processive polymerase that lacks proofreading ability.

Bacteriophage M13↗
PubMed1996

Polymorphism in serotonin transporter gene associated with susceptibility to major depression.

UNLABELLED: BACKGROUND; The serotonin transporter of the brain provides the primary target for the action of selective antidepressant drugs. We set out to identify polymorphisms of the serotonin transporter gene and to find out whether there was a relation between any such polymorphisms and the occurrence of affective disorder. METHODS: A comparison of a polymorphic region of the human serotonin transporter gene was carried out between two groups. The study group comprised 83 patients (39 unipolar depressive disorder, 44 bipolar disorder) with major affective disorder. The control group comprised 122 anonymous blood donors, and 71 volunteers who had been screened for psychiatric disorders. FINDINGS: We detected three novel alleles of the variable-number-tandem-repeat (VNTR) region (STin2.9, STin2.10) and Stin2.12) containing nine, ten and 12 copies of the VNTR element, respectively. The frequencies of the different forms of the allele in the control group were compared with those in the affective disorder group. There was a significant difference between the control and affective disorder groups, largely explained by the excess of the STin2.9 allele in the unipolar group (chi2=10.05, p<0.004 [Bonferroni corrected]). The presence of the allele with nine copies of the repeat was significantly associated with risk of unipolar disorder (odds ratio=6.95 [95% CI 1.8-27.2]). INTERPRETATION: This association, for an obvious candidate gene, may provide a critical starting point for an understanding of the likely polygenic contributions towards susceptibility to affective disorder.

Alleles↗
PubMed1996

Apoptosis: molecular regulation of cell death.

The field of apoptosis is unusual in several respects. Firstly, its general importance has been widely recognised only in the past few years and its surprising significance is still being evaluated in a number of areas of biology. Secondly, although apoptosis is now accepted as a critical element in the repertoire of potential cellular responses, the picture of the intra-cellular processes involved is probably still incomplete, not just in its details, but also in the basic outline of the process as a whole. It is therefore a very interesting and active area at present and is likely to progress rapidly in the next two or three years. This review emphasises recent work on the molecular mechanisms of apoptosis and, in particular, on the intracellular interactions which control this process. This latter area is of crucial importance since dysfunction of the normal control machinery is likely to have serious pathological consequences, probably including oncogenesis, autoimmunity and degenerative disease. The genetic analysis of programmed cell death during the development of the nematode Caenorhabditis elegans has proved very useful in identifying important events in the cell death programme. Recently defined genetic connections between C. elegans cell death and mammalian apoptosis have emphasised the value of this system as a model for cell death in mammalian cells, which, inevitably, is more complex. The signals inducing apoptosis are very varied and the same signals can induce differentiation and proliferation in other situations. However, some pathways appear to be of particular significance in the control of cell death; recent analysis of the apoptosis induced through the cell-surface Fas receptor has been especially important for immunology. Two gene families are dealt with in particular detail because of their likely importance in apoptosis control. These are, first, the genes encoding the interleukin-1 beta-converting enzyme family of cysteine proteases and, second, those related to the proto-oncogene bcl-2. Both of these families are homologous to cell death genes in C. elegans. In mammalian cells the number of members of both families which have been identified is growing rapidly and considerable effort is being directed towards establishing the roles played by each member and the ways in which they interact to regulate apoptosis. Other genes with established roles in the regulation of proliferation and differentiation are also important in controlling apoptosis. Several of these are known proto-oncogenes, e.g. c-myc, or tumour suppressors, e.g. p53, an observation which is consistent with the importance of defective apoptosis in the development of cancer. Viral manipulation of the apoptosis of host cells frequently involves interactions with these cellular proteins. Finally, the biochemistry of the closely controlled cellular self-destruction which ensues when the apoptosis programme has been engaged is also very important. The biochemical changes involved in inducing phagocytosis of the apoptotic cell, for example, allow the process to be neatly integrated within the tissues, under physiological conditions. Molecular defects in this area too may have important pathological consequences.

Amino Acid Sequence↗
PubMed1996

Gender and psychological well-being of persons with rheumatoid arthritis.

OBJECTIVE: This study examined the relationship of gender and psychological well-being (PWB) in community-dwelling persons with rheumatoid arthritis (RA). METHOD: Data from the first wave of two longitudinal panel studies of persons with RA were examined (93 men and 276 women in panel 1; 60 men and 147 women in panel 2). Subjects completed self-report questionnaires on behavioral aspects of RA. Psychological well-being was assessed in both panels by the Center for Epidemiologic Studies-Depression Scale, using its 4 subcomponents, including positive and negative affect. Panel 2 had additional measures of PWB, namely the Positive and Negative Affect Schedule and the Satisfaction With Life Scale. Potential explanatory variables were then examined in an attempt to account for the observed gender differences. RESULTS: Gender differences were found for negative indicators of PWB, while positive indicators of PWB showed no significant differences by gender. As with other community samples, women reported higher levels of depressive symptoms and negative mood than men. Quality of emotional support, passive pain coping, and physical functional impairment could only partially explain the observed gender differences in this study. CONCLUSION: The relationship of gender to negative indicators of PWB cannot easily be diminished or dismissed. The mechanisms by which gender differentially affects PWB need to be further explored in order to intervene appropriately to help men and women with RA achieve an optimal quality of life.

Adult↗
PubMed1996

Cloning and characterization of the chlorophyll biosynthesis gene chlM from Synechocystis PCC 6803 by complementation of a bacteriochlorophyll biosynthesis mutant of Rhodobacter capsulatus.

A bacteriochlorophyll a biosynthesis mutant of the purple photosynthetic bacterium Rhodobacter capsulatus was functionally complemented with a cosmid genomic library from Synechocystis sp. PCC 6803. The complemented R. capsulatus strain contains a defined mutation in the bchM gene that codes for Mg-protoporphyrin IX methyltransferase, the enzyme which converts Mg-protoporphyrin IX to Mg-protoporphyrin IX methylester using S-adenosyl-L-methionine as a cofactor. Since chlorophyll biosynthesis also requires the same methylation reaction, the Synechocystis genome should similarly code for a Mg-protoporphyrin IX methyltransferase. Sequence analysis of the complementing Synechocystis cosmid indicates that it contains an open reading frame exhibiting 29% sequence identity to BchM. In addition, expression of the Synechocystis gene in the R. capsulatus bchM mutant via the strong R. capsulatus puc promoter was shown to support nearly wild-type levels of bacteriochlorophyll a synthesis. To our knowledge, the Synechocystis sequence thus represents the first chlorophyll biosynthesis gene homolog of bchM. The complementing Synechocystis cosmid was also shown to code for a gene product that is a member of a highly conserved family of RNA binding proteins, the function of which in cyanobacteria remains undetermined.

Amino Acid Sequence↗
PubMed1996

Ion microscopic imaging of calcium during 1,25-dihydroxyvitamin D-mediated intestinal absorption.

A combination of ion microscopic and conventional radionuclide techniques was employed to investigate the temporal-spatial dynamics of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3]-stimulated intestinal calcium (Ca) absorption. At varying times following the administration of a single intravenous dose of 1,25(OH)2D3 to vitamin D-deficient chicks, transepithelial transport and tissue retention of Ca were quantitated in vivo, using the ligated duodenal loop technique and 47Ca as the tracer. The localization of Ca in the intestinal tissue during absorption was monitored by ion microscopy, using the stable Ca isotope, 44Ca, as the absorbed species. There was little transepithelial absorption of Ca in the vitamin D-deficient animals despite a substantial tissue accumulation of luminally derived Ca, the latter localizing predominantly in the brush border region of the enterocyte, as shown by the 44Ca-ion microscopic images. The early (30 min-1 h) response to 1,25(OH)2D3 was an increased tissue uptake of luminal 47Ca, which also primarily associated with the brush border region, again as shown by ion microscopy. At 2-4 h after the 1,25(OH)2D3 dose, there was a progressive redistribution of Ca from the brush border region throughout the cytoplasm and into the lamina propria. At 8-16 h, 47Ca absorption was maximal and 44Ca was sparsely distributed in the intestinal tissue. 47Ca absorption gradually declined and reached pre-dose levels by 72 h. At this time, tissue 44Ca was again largely limited to the brush border region. These results provide support for the multiple actions of 1,25(OH)2D3 on the intestinal Ca absorption process. The ion microscopic images provided unique information on the specific time-dependent changes in the tissue localization of Ca during the process of its intestinal absorption as affected by 1,25(OH)2D3.

Animals↗
PubMed1996

Insulin inhibits changes in the phospholipid profiles in sciatic nerves from streptozocin-induced diabetic rats: a phosphorus-31 magnetic resonance study.

Sciatic nerve phospholipids obtained from insulin-treated streptozocin-induced diabetic, non-treated streptozocin-induced diabetic, and healthy, control male Sprague-Dawley rats after eighteen weeks of diabetes were studied by 31P NMR spectrometry. Eleven phospholipids resonances were identified as follows: Phosphatidic acid (Chemical shift, 0.30 ppm), dihydrosphingomyelin (0.13 ppm), ethanolamine plasmalogen (0.07 ppm), phosphatidylethanolamine (0.03 ppm), phosphatidylserine (-0.05 ppm), sphingomyelin (-0.09 ppm), lysophosphatidylcholine (-0.28 ppm), phosphatidylinositol (-0.30 ppm), alkylacylglycerophosphorylcholine (-0.78 ppm), choline plasmalogen (-0.80 ppm), and phosphatidylcholine (-0.84 ppm). Diabetic rats showed that phosphatidylcholine was significantly elevated (p < 0.05), and ethanolamine plasmalogen and choline plasmalogen were significantly lower when compared with both control and insulin treated rats. The choline ratio (choline-containing phospholipids over noncholine phospholipids) was significantly elevated in the diabetic group, when compared with both control and insulin-treated groups. The ethanolamine ratio (ethanolamine-containing phospholipids over nonethanolamine phospholipids) and the ratio of the ethanolamine ratio over the choline ratio, was significantly elevated in the control and the insulin-treated groups when compared with the diabetic group. The presence of phosphatidic acid and the significance in phosphatidylcholine and ethanolamine plasmalogen, suggested that insulin had a role in the phosphatidylcholine metabolism in the rat nerve.

Animals↗
PubMed1996

Active site comparisons highlight structural similarities between myosin and other P-loop proteins.

The phosphate binding loop (P-loop) is a common feature of a large number of enzymes that bind nucleotide whose consensus sequence is often used as a fingerprint for identifying new members of this group. We review here the binding sites of nine purine nucleotide binding proteins, with a focus on their relationship to the active site of myosin. This demonstrates that there is considerable conversation in the distribution and nature of the ligands that coordinate the triphosphate moiety. This comparison further suggests that at least myosin and the G-proteins utilize a similar mechanism for nucleotide hydrolysis.

Amino Acid Sequence↗
PubMed1996

Long-term restoration of immunity against Epstein-Barr virus infection by adoptive transfer of gene-modified virus-specific T lymphocytes.

Adoptive transfer of antigen-specific cytotoxic T lymphocytes (CTLs) offers safe and effective therapy for certain viral infections and could prove useful in the eradication of tumor cells. Whether or not the infused T cells persist for extended periods, retaining their ability to expand in response to antigenic stimulation, is not known. We now report long-term detection of gene-marked Epstein-Barr virus (EBV)-specific CTLs in immunocompromised patients at risk for the development of EBV lymphoproliferative disease. Infusions of CTLs not only restored cellular immune responses against EBV, but also established populations of CTL precursors that could respond to in vivo or ex vivo challenge with the virus for as long as 18 months. Our findings support wider use of antigen-specific CTLs in adoptive immunotherapy.

Bone Marrow Transplantation↗
PubMed1996

Multiple cutaneous basal cell carcinomas: glutathione S-transferase (GSTM1, GSTT1) and cytochrome P450 (CYP2D6, CYP1A1) polymorphisms influence tumour numbers and accrual.

The genetic factors that mediate the pathogenesis of multiple primary cutaneous basal cell carcinomas (BCC) are largely unclear. Thus, some patients suffer many BCC (>30) and/or rapid accrual (number of tumours/year from first presentation) of further lesions. We have studied, in 827 English Caucasians, the influence of polymorphism in carcinogen-metabolizing enzymes on susceptibility to this cancer. Accordingly, we describe, first, a cross-sectional analysis of the influence of GSTM1, GSTT1, CYP2D6 and CYP1A1 genotypes on tumour numbers, and secondly, a longitudinal analysis, in 169 of these cases, of the effect of these genes on tumour accrual. We have confirmed the expected importance of age and number of lesions at presentation, and male gender and skin type as risk factors. Furthermore, the cross-sectional analysis showed CYP1A1 m1m1 (P = 0.004; rate ratio 1.242) and CYP2D6 EM (P < 0.001, rate ratio 1.266) are associated with increased numbers of BCC. The longitudinal study showed, after adjustment for age and tumour number at presentation, that GSTT1 null (P < 0.001, rate ratio 2.677) and CYP2D6 EM (P < 0.001, rate ratio 2.154) were significant determinants of accrual while CYP1A1 Ile/Ile was associated with slower accrual than the Ile/Val and Val/Val genotypes (P = 0.008, rate ratio 0.690). We believe these are the first genetic factors to be associated with tumour accrual. No significant interactions between genotypes were identified, though the combinations GSTM1 null/skin type 1 (P < 0.001, rate ratio 2.702), CYP2D6 EM/male gender (P = 0.049, rate ratio 1.279) and CYP2D6 EM/blue+green eyes (P = 0.046, rate ratio 1.388) influenced tumour numbers. Previous studies indicate the importance of effective repair of UV-damaged DNA in the pathogenesis of multiple BCC; indeed the influence of GSTM1 may result from its ability to utilize 5'-hydroxymethyluracil. However, the finding that CYP2D6 and CYP1A1 influence tumour numbers and accrual indicates detoxification of unknown molecules is important and supports the view that factors other than UV are important in the pathogenesis BCC.

Adult↗
PubMed1996

Activation-induced peripheral blood T cell apoptosis is Fas independent in HIV-infected individuals.

T cell apoptosis has been proposed as an important contributor to the functional defects and depletion of T cells in HIV-infected individuals. However, the mechanisms involved in this apoptosis have not been elucidated. We recently showed that peripheral blood T cells from HIV-infected individuals are especially susceptible to Fas antigen-induced apoptosis. In this study we examine the role of Fas, CTLA-4, tumor necrosis factor (TNF) receptors (TNFR) and CD30, receptors known to be involved in T cell activation-induced cell death (AICD), in the spontaneous and activation (anti-CD3)-induced apoptosis of peripheral blood T cells from asymptomatic HIV-infected individuals. We report here that spontaneous and activation-induced T cell apoptosis cannot be inhibited by reagents that block interactions of Fas, CTLA-4, p55 and p75 TNFR and CD30 with their respective ligands. We also show that IL-12, IFN-gamma, IL-4 and IL-10 cannot modify spontaneous, activation- and anti-Fas-induced apoptosis. Anti-Fas preferentially induced CD4+ T cell apoptosis whereas AICD induced apoptosis equally in CD4+ and CD8+ T cells. We conclude that T cell AICD in HIV infection is not mediated by Fas, thus indicating that Fas-induced and activation-induced T cell apoptosis are independent mechanisms of apoptosis which may play different roles in the pathogenesis of HIV infection.

Abatacept↗
PubMed1996

Apnea prolongation via short-term inhibition.

Central apneas during sleep are frequently of longer duration than predicted and persist despite high levels of chemical stimuli. We provide evidence that suggests that this apnea prolongation represents a central inertia in the control system mediated by reciprocal inhibition of inspiration.

Animals↗
PubMed1996

Structure of a variable number tandem repeat of the serotonin transporter gene and association with affective disorder.

We have recently reported an association between a polymorphism of a variable number tandem repeat (VNTR) region of the serotonin transporter gene and susceptibility to major depressive disorder. We identified three alleles containing respectively 9 (STin2.9), 10 (STin2.10) and 12 (STin2.12) copies of a repetitive element. We report here the sequences of the three alleles. The repetitive element conformed to the consensus sequence, GGCTGYGACCY(R)GRRTG, where Y = T/C, R = G/A, with loss of the 12th base pair in one of the repeating elements. We have also extended the numbers of cases and controls in the study. The frequencies of the three alleles in 119 individuals with single or recurrent major depressive episodes, 128 individuals with bipolar disorder and a group of 346 controls were compared. There was a significant difference between patients with affective disorder and controls in the proportion of individuals carrying the STin2.9 allele. For the risk of unipolar disorder given a single STin2.9 allele, the odds ratio was 4.44 (95% Cl, 1.65-11.95) and for bipolar disorder 3.22 (95% Cl, 1.15-9.09). The findings support the hypothesis that allelic variation in the serotonin transporter gene may contribute to susceptibility for both major depression and bipolar disorder.

Alleles↗
PubMed1996

New developments in the management of violent children and adolescents.

Paediatricians are often asked to see children and adolescents with behavioural disorders which include an element of violence directed at peers, family members or teachers. Inevitably this group of children poses a considerable management challenge, irrespective of the multiple aetiological contributions to the behaviours. This paper renews some of the evidence for a neurophysiological contribution to violent behaviour, provides a rationale for pharmacological treatment, and outlines a suggested management plan based on extensive clinical experience. The results of this regimen have been highly successful. This regimen is inexpensive, successful and empowers both patients and family through the development of positive interpersonal interactions.

Adolescent↗
PubMed1996

Estimating linkage heterogeneity.

The admixture model for linkage heterogeneity is modified to take account of the difference in recombination fractions in the two sexes. The data used may concern a single (marker) locus on one chromosome, which is suspected of being sometimes near a (disease) locus for a particular condition of interest, or there may be data on more than one locus on this chromosome. There may be data on a locus or loci on a second chromosome, which is also suspected of sometimes carrying an allele for the condition in question. The general principle for the analysis is the same in all such cases, though details may differ. The object is to estimate the relevant recombination fractions, and the proportions of cases in which the allele for the condition falls on each chromosome.

Chromosomes, Human, Pair 16↗
PubMed1996

Adenovirus-pulsed dendritic cells stimulate human virus-specific T-cell responses in vitro.

Adenovirus infections cause significant morbidity and mortality in immunocompromised patients, yet little is known about the immune response to adenovirus infections. We established a system for the generation of a cytotoxic immune response to adenovirus in vitro. Cytotoxic T cells (CTLs) were derived from normal donors by using peripheral blood dendritic cells as antigen-presenting cells. The CTLs were found to contain a mixture of effector cells that recognized virus peptides in the context of both class I and class II antigens. Endogenous viral gene expression was not required to sensitize cells to lysis by adenovirus-specific CTLs. CTLs raised against subgroup C adenovirus type 5 can lyse cells infected with subgroup B adenovirus type 11, indicating that viruses of different subgroups have epitopes in common. This system holds promise for defining the human immune response to adenovirus, including characterization of the viral protein(s) against which the response is generated, and the identity of the effector cells. Such studies are in progress.

Adenoviridae↗
PubMed1996

Negative pressure-induced deformation of the upper airway causes central apnea in awake and sleeping dogs.

We investigated the effects of negative pressure (NP) in the isolated upper airway (UA) in three unanesthetized dogs. The UA was isolated, and the dogs breathed through an endotracheal tube while wearing a fitted fiberglass snout mask. NP (-2 to -32 cmH2O) was applied in a square wave below the larynx or at the snout at end expiration and was held until inspiratory effort during wakefulness, non-rapid-eye-movement (NREM) sleep, and rapid-eye-movement (REM) sleep. During all states of consciousness, NP applied to the UA prolonged expiratory time (TE) 1) below a threshold of -8 to -10 cmH2O, which coincided with closure of the oro- and/or velopharynx; and 2) in a progressive fashion at more negative pressures than threshold, up to a mean apneic length of 324% of the control value (or 13.9 s) at -30 cmH2O. TE prolongation was less during REM sleep at a given NP (P < 0.05). Augmented tonic genioglossal electromyographic activity also occurred with the applied NP during wakefulness and NREM sleep but not with REM sleep. NP (-20 to -32 cmH2O) applied as a brief pulse (300-500 ms) during NREM sleep caused transient airway occlusion, terminated the breath during inspiration, and prolonged TE when applied at end expiration. Central apneas always persisted beyond the termination of the UA closure. TE prolongation in response to NP persisted in the presence of a topical anesthetic nebulized through the UA sufficient to abolish the laryngeal gag reflexes. We conclude that UA closure and deformation will cause significant TE prolongation during all states of consciousness and activation of the genioglossus muscle during wakefulness and NREM sleep but not during REM sleep.

Animals↗