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Biomedical subjects

A Wilson

Publications and source records attributed to A Wilson.

At least 127 records · Page 7Linked to original sources
PubMed1999

Unexpectedly late expression of intracellular CD3epsilon and TCR gammadelta proteins during adult thymus development.

During adult thymus development immature CD4(-)CD8(-) [double-negative (DN)] precursor cells pass through four phenotypically distinct stages defined by expression of CD44 and CD25: CD44(hi)CD25(-) (DN1), CD44(hi)CD25(+) (DN2), CD44(lo)CD25(+) (DN3) and CD44(lo)CD25(-) (DN4). Although it is well established that the TCR beta, gamma and delta genes are rearranged and expressed in association with the CD3 components in DN thymocytes, the precise timing of expression of the TCR and CD3 proteins has not been determined. In this report we have utilized a sensitive intracellular (ic) staining technique to analyze the expression of ic CD3epsilon, TCR beta and TCR gammadelta proteins in immature DN subsets. As expected from previous studies of TCR beta rearrangement and mRNA expression, icTCR beta(+) cells were first detected in the DN3 subset and their proportion increased thereafter. Surprisingly, however, both icCD3epsilon(+) and icTCR gammadelta(+) cells were detected at later stages of development than was predicted by molecular studies. In particular icCD3epsilon protein expression coincided with the transition from the DN2 to DN3 stage of development, whereas icTCR gammadelta protein expression was only detected in a minor subset of DN4 cells. The implications of these findings for alphabeta lineage divergence will be discussed.

Age Factors↗
PubMed1999

Flanking regulatory sequences of the Tetrahymena R deletion element determine the boundaries of DNA rearrangement.

In the ciliate Tetrahymena thermophila, thousands of DNA segments of variable size are eliminated from the developing somatic macronucleus by specific DNA rearrangements. It is unclear whether rearrangement of the many different DNA elements occurs via a single mechanism or via multiple rearrangement systems. In this study, we characterized in vivo cis-acting sequences required for the rearrangement of the 1.1-kbp R deletion element. We found that rearrangement requires specific sequences flanking each side of the deletion element. The required sequences on the left side appear to span roughly a 70-bp region that is located at least 30 bp from the rearrangement boundary. When we moved the location of the left cis-acting sequences closer to the eliminated region, we observed a rightward shift of the rearrangement boundary such that the newly formed deletion junction retained its original distance from this flanking region. Likewise, when we moved the flanking region as much as 500 bp away from the deletion element, the rearrangement boundary shifted to remain in relative juxtaposition. Clusters of base substitutions made throughout this critical flanking region did not affect rearrangement efficiency or accuracy, which suggests a complex nature for this regulatory sequence. We also found that the right flanking region effectively replaced the essential sequences identified on the left side, and thus, the two flanking regions contain sequences of analogous function despite the lack of obvious sequence identity. These data taken together indicate that the R-element flanking regions contain sequences that position the rearrangement boundaries from a short distance away. Previously, a 10-bp polypurine tract flanking the M-deletion element was demonstrated to act from a distance to determine its rearrangement boundaries. No apparent sequence similarity exists between the M and R elements. The functional similarity between these different cis-acting sequences of the two elements is firm support for a common mechanism controlling Tetrahymena rearrangement.

Animals↗
PubMed1999

An illustrative example of infant and child death review in South Dakota: "the 1998 annual report of the Regional Infant and Child Mortality Review Committee".

Local, regional, or state infant and child death review teams provide an excellent mechanism for identifying risk factors for infant and childhood deaths along with establishing a conduit for effecting preventive measures to reduce the number of deaths in these particularly vulnerable age groups. In 1997, a predecessor of the current Regional Infant and Child Mortality Review Committee was established in Minnehaha County as South Dakota's first non-Indian review committee for infant and childhood deaths. The 1998 Review Committee's annual report to the public is presented in this paper as an illustration of what can be expected from such a committee along with the specific public health concerns identified and their potential remedies. Especially noted in the committee's 1998 report is an alarming increase in Sudden Infant Death Syndrome (SIDS) death in the region and the educational role the Back to Sleep Campaign can play in the prevention of SIDS. The annual report serves as an example to illustrate how local review mechanisms can identify community strategies that may promote the health and well being of infants and children in their review areas.

Adolescent↗
PubMed1999

Factors associated with the provision of anti-smoking advice by general practitioners.

The acceptability of advice about smoking in the consultation has recently been questioned. We report a study that explored patients' attitudes to general practitioners' (GPs) anti-smoking advice and the characteristics of patients with whom GPs chose to discuss smoking. Patients who recalled the advice were generally positive about stopping smoking. This could be explained by the observation that GPs were more likely to advise smokers who perceived their problems to be smoking-related and were more motivated to stop smoking. The implications of this finding are discussed.

Adult↗
PubMed1998

A limited role for beta-selection during gamma delta T cell development.

T cells belong to two distinct lineages expressing either alpha beta or gamma delta TCR. During alpha beta T cell development, it is clearly established that productive rearrangement at the TCR beta locus in immature precursor cells leads to the expression of a pre-TCR complex. Signaling through the pre-TCR results in the selective proliferation and maturation of TCR beta+ cells, a process that is known as beta-selection. However, the potential role of beta-selection during gamma delta T cell development is controversial. Whereas PCR-RFLP and sequencing techniques have provided evidence for a bias toward in-frame VDJ beta rearrangements in gamma delta cells (consistent with beta-selection), gamma delta cells apparently develop normally in mice that are unable to assemble a pre-TCR complex due to a deficiency in TCR beta or pT alpha genes. In this report, we have directly addressed the physiologic significance of beta-selection during gamma delta cell development in normal mice by quantitating intracellular TCR beta protein in gamma delta cells and correlating its presence with cell cycle status. Our results indicate that beta-selection plays a significant (although limited) role in gamma delta cell development by selectively amplifying a minor subset of gamma delta precursor cells with productively rearranged TCR beta genes.

Animals↗
PubMed1998

Critical involvement of Tcf-1 in expansion of thymocytes.

T cell maturation in Tcf-1(-/-) mice deteriorates progressively and halts completely around 6 mo of age. During fetal development thymocyte subpopulations seem normal, although total cell numbers are lower. By 4 to 6 wk of age, obvious blockades in the differentiation of CD4- 8- thymocytes are observed at two distinct stages (CD44+ 25+ and CD44- 25-), both of which are normally characterized by extensive proliferation. This lack of thymocyte expansion and/or differentiation was also observed when Tcf-1(-/-) progenitor cells from the aorta-gonad-mesonephros region (embryonic day 11.5), fetal liver (embryonic day 12.5/14.5), and fetal bone marrow (embryonic day 18.5) were allowed to differentiate in normal thymic lobes (fetal thymic organ cultures) or were injected intrathymically into normal recipients. Despite these apparent defects in thymocyte differentiation and expansion, adult Tcf-1(-/-) mice are immunocompetent, as they generate virus neutralizing Abs at normal titers. Furthermore, their peripheral T cells have an activated phenotype (increased CD44 and decreased CD62L expression) and proliferate normally in response to Ag or mitogen, suggesting that these cells may have arisen from the early wave of development during embryogenesis and are either long lived or have subsequently been maintained by peripheral expansion. As Tcf-1 is a critical component in the Wnt/beta-catenin signaling pathway, these data suggest that Wnt-like factors play a role in the expansion of double-negative thymocytes.

Animals↗
PubMed1998

Cloning and mapping of a cDNA for methionine synthase reductase, a flavoprotein defective in patients with homocystinuria.

Methionine synthase catalyzes the remethylation of homocysteine to methionine via a reaction in which methylcobalamin serves as an intermediate methyl carrier. Over time, the cob(I)alamin cofactor of methionine synthase becomes oxidized to cob(II)alamin rendering the enzyme inactive. Regeneration of functional enzyme requires reductive methylation via a reaction in which S-adenosylmethionine is utilized as a methyl donor. Patients of the cblE complementation group of disorders of folate/cobalamin metabolism who are defective in reductive activation of methionine synthase exhibit megaloblastic anemia, developmental delay, hyperhomocysteinemia, and hypomethioninemia. Using consensus sequences to predicted binding sites for FMN, FAD, and NADPH, we have cloned a cDNA corresponding to the "methionine synthase reductase" reducing system required for maintenance of the methionine synthase in a functional state. The gene MTRR has been localized to chromosome 5p15.2-15.3. A predominant mRNA of 3.6 kb is detected by Northern blot analysis. The deduced protein is a novel member of the FNR family of electron transferases, containing 698 amino acids with a predicted molecular mass of 77,700. It shares 38% identity with human cytochrome P450 reductase and 43% with the C. elegans putative methionine synthase reductase. The authenticity of the cDNA sequence was confirmed by identification of mutations in cblE patients, including a 4-bp frameshift in two affected siblings and a 3-bp deletion in a third patient. The cloning of the cDNA will permit the diagnostic characterization of cblE patients and investigation of the potential role of polymorphisms of this enzyme as a risk factor in hyperhomocysteinemia-linked vascular disease.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1998

Melanosomal defects in melanocytes from mice lacking expression of the pink-eyed dilution gene: correction by culture in the presence of excess tyrosine.

Mutations in the murine pink-eyed dilution (p) gene, or its human homologue P, result in oculocutaneous albinism. Melanocytes cultured from mice lacking p gene expression exhibit defective melanogenesis, but following culture in the presence of high concentrations of L-tyrosine, increased melanin deposition is observed. Electron microscopy and image analysis demonstrated that untreated p mutant melanocytes exhibited small melanosomes, largely of stages I-II. Following tyrosine treatment, increased proportions of stage III-IV melanosomes, almost normal in size, were observed. Levels of tyrosinase protein and to a lesser extent of tyrosinase-related protein-1 (TRP-1) were subnormal but rose dramatically following stimulation by tyrosine. Levels of TRP-2 and Pmel17/silver gene product were not altered, nor were the levels of mRNA for tyrosinase, TRP-1, TRP-2, or the Pmel17/silver gene product. As expected, the 110-kDa product of the p gene was absent from both stimulated and unstimulated p mutant cells. In a melanoblast line derived from the same mice, excess tyrosine failed to stimulate visible melanogenesis or increase the low levels of tyrosinase. The melanosomes in these cells were smaller still than those in the mutant melanocytes even when cultured in the presence of excess tyrosine. Thus, absence of the p gene product affects melanosomal structure and protein composition at the posttranscriptional level. These defects are correctable at least in part by supplementation with L-tyrosine.

Albinism, Oculocutaneous↗
PubMed1998

High expression of the HMG box factor sox-13 in arterial walls during embryonic development.

Members of the Sox gene family of transcription factors are defined by the presence of an 80 amino acid homology domain, the High Mobility Group (HMG) box. Here we report the cloning and initial analysis of murine Sox-13 . The 984 amino acids Sox-13 protein contains a single HMG box, a leucine zipper motif and a glutamine-rich stretch. These characteristics are shared with another member of the Sox gene family, Sox-6. High level embryonic expression of Sox-13 occurs uniquely in the arterial walls of 13.5 days post coitum (dpc) mice and later. Low level expression was observed in the inner ear of 13.5 dpc mice and in a limited number of cells in the thymus of 16.5 dpc mice, from which Sox-13 was originally cloned. At 18.5 dpc, Sox-13 is expressed in the tracheal epithelium below the vocal cord and in the hair follicles. The Sox-13 protein binds to the consensus HMG box motif, AACAAAG, but does not transactivate transcription through a concatamer of this motif. Sox-13, like other members of the Sox family likely plays an important role in development.

Amino Acid Sequence↗
PubMed1998

Evidence of stage-specific element for germ-line transcription of the TCR alpha gene located upstream of J alpha49 locus.

T cell receptor (TCR) genes are rearranged and expressed in an ordered manner during T cell development. The basic mechanism regulating this stepwise DNA alteration is poorly understood. To address this issue, we explored the presence of a stage-specific element for germ-line transcription of the TCR alpha gene which is closely associated with gene rearrangement. First, germ-line transcription of the TCR alpha gene including the first segment of the J alpha locus, J alpha49, was delayed compared to that of the TCR beta gene in both normal and TCR-transgenic (Tg) mice. Furthermore, expression of this transcript could be induced by CD3epsilon-mediated signals in recombination-activating gene (RAG)-2-deficient mice. In TCR-Tg mice, the endogenous J alpha49 germ-line transcript could not yet be observed at the CD25+ double-negative (DN) stage when the TCR alpha transgene was expressed. Of immature T cell hybridomas derived from either scid thymocytes (CD25+ DN) or immature CD8-single positive (ISP) thymocytes, only the latter hybridoma expressed the J alpha49 germ-line transcript. These data indicate that the J alpha49 germ-line transcription occurs only at a specific developmental stage. Second, to determine which elements may be regulating stage specificity, we performed transient transfection analysis with a reporter gene and demonstrated that the upstream region of the J alpha49 locus possesses promoter activity in correlation with germ-line transcription in ISP-derived but not in SCID-derived hybridomas. These results indicate that the expression of TCR alpha germ-line transcripts is regulated in a stage-specific manner by a cis-element located within the J alpha locus.

Animals↗
PubMed1998

Experimental mucosal induction of uveitis with the 60-kDa heat shock protein-derived peptide 336-351.

Subcutaneous (s.c.) immunization of rats with the human 60-kDa heat shock protein (HSP)-derived peptide 336-351 induced clinical and/or histological uveitis in 80 % of rats. Subsequent experiments to prevent the development of uveitis by oral or nasal administration of the peptide have failed. Instead, uveitis was induced in 74.6 % of rats given the peptide orally (5 times), in 75 % given the peptide nasally (5 times) or 91.7 % of those administered the peptide by both routes (10 times). Histological examination showed that any one route of administration of the peptide elicited iridocyclitis in 42.2 % but loss of photoreceptors only in 4.9 % of rats. In contrast, sequential administrations of the peptide by a combined mucosal-s.c. route resulted in iridocyclitis in only 25 % but loss of photoreceptors in 40 % of animals. Examination of mRNA from CD4-enriched splenic cells by reverse transcription-PCR failed to yield significant differences in Th1 or Th2 cytokines. Treatment with monoclonal antibody (mAb) to CD4 yielded a dose-dependent decrease in uveitis from 82 % to 25 %. Similarly, treatment with IL-4 significantly decreased the development of uveitis from 68 % to 30.4 %. Conversely, treatment of the rats with mAb to CD8 greatly enhanced the onset of uveitis (from about 22 days in the controls to 11 days) and all the rats developed uveitis by day 24. Thus, CD4+ cells mediate, whereas CD8+ cells suppress the development of uveitis. We suggest that this novel experimental mucosal model of induction of uveitis by the human 60-kDa HSP-derived peptide 336-351, which is specific in stimulating T cell responses in Behcet's disease, is consistent with the oro-genital onset of this disease and the development of uveitis.

Administration, Intranasal↗
PubMed1998

Aneurysms of the pancreaticoduodenal arteries: a change in management.

Since the first report of an aneurysm involving the pancreaticoduodenal arteries a century ago, only 83 cases have been reported in our collective review of the English literature. Their presentation varies from indistinct abdominal pain to hemorrhagic shock, often making the diagnosis onerous. The mortality rate in this patient group has been significant, and in cases reported since 1980, the mortality rate remains at 17% (7 deaths/42 reported cases). Surgery has been, and continues to be, the cornerstone of therapy, with an incumbent mortality rate of 19% (5 deaths/26 patients treated surgically since 1980). This case report and 100-year review of the literature describes the causes, natural history, and historic management of pancreaticoduodenal artery aneurysms. Most importantly, it demonstrates the use of angiographic embolization in the definitive management of these aneurysms with no mortality.

Aneurysm↗
PubMed1998

Effects of regular exercise in management of chronic idiopathic constipation.

Regular physical exercise has long been considered in the management of chronic constipation. This recommendation is probably based on the assumption that exercise shortens the transit time through the gastrointestinal tract. However, on the basis of previous studies, the effect of exercise on the transit remains controversial at best. Therefore, it was the goal of the present study to assess the influence of regular physical exercise, what average people may consider routine exercise, in the management of chronic idiopathic constipation. The study population consisted of eight patients, seven women and a man, with chronic idiopathic constipation. They were studied for six weeks, including two weeks of rest and four weeks of regular exercise. Patients had a submaximal exercise test, before and after the exercise period, to determine their rate of perceived exertion (RPE), the target heart rate, and the intensity of exercise they can perform. In addition to their routine daily activities, they exercised 1 hr a day, five days a week according to their performance at the initial exercise tolerance test. They kept a daily activity log and maintained their normal dietary intake during this period. The patients overall physical activity was assessed by a pedometer. They also maintained a diary of the number and consistency of their bowel movements and the amount of straining required for defecation. The impact of exercise on constipation was assessed by utilizing an index that took into consideration all three parameters of bowel function. Results of the study revealed that patients covered 1.8+/-0.33 and 3.24+/-0.28 miles/day in the rest period and during the exercise period, respectively (P = 0.007). The intensity of exercise may have improved the level of training as reflected on the mean maximum time before and after exercise period (P = 0.039). This level of exercise did not improve their constipation indices, which were 9.11+/-0.65 and 8.57+/-1.08 in the rest and exercise periods, respectively (P = 0.68). In conclusion, physical activity, to the extent that people consider "regular exercise," does not play a role in the management of chronic idiopathic constipation.

Adult↗