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S D Smith

Publications and source records attributed to S D Smith.

At least 199 records · Page 11Linked to original sources
PubMed1990

Characterization of the breakpoint of a t(14;14)(q11.2;q32) from the leukemic cells of a patient with T-cell acute lymphoblastic leukemia.

The leukemic cells and derivative cell line from a 74-year-old male with T-cell acute lymphoblastic leukemia showed chromosomal abnormalities including a t(14;14)(q11.2;q32). This translocation is characteristic of a variety of T-cell malignancies, particularly T-cell prolymphocytic leukemia and the clonal proliferations of peripheral T cells in patients with ataxia-telangiectasia. Using DNA probes that spanned the T-cell receptor alpha chain (TCRA) joining (J) locus, the DNA rearrangement caused by the translocation was identified, cloned, and sequenced. The breakpoint shows site-specific juxtaposition of a TCRA joining segment and DNA from a region of 14q32 centromeric to the immunoglobulin heavy chain locus. Comparison of restriction map and nucleotide sequence from this translocation with other related chromosomal breakpoints suggests a dispersion of breakpoints throughout the 14q32 region.

Amino Acid Sequence↗
PubMed1990

Familial dyslexia: use of genetic linkage data to define subtypes.

Specific reading disability is an example of a complex behavioral disorder which is clinically heterogeneous. It is probably also heterogeneous at the levels of etiology and process (pathogenesis), but there may not be a 1:1:1 mapping of etiology to process to clinical outcome. Thus, classification of cases by clinical features may not lead to discovery of the underlying processes or etiologies, and it may be profitable to define subgroups by etiology. There is evidence for genetic etiology in some cases, but there is genetic heterogeneity as well. Possible genetic models for specific reading disability include polygenic, oligogenic, and single gene inheritance, and there are several types of genetic analysis that can be used to determine which of these modes of inheritance may be present. Identification of individual genes is possible in single gene and oligogenic disorders. Clinical studies and molecular analysis can then be used to determine gene function.

Adult↗
PubMed1990

Sigmoid volvulus in childhood.

Although it is common in the adult population, sigmoid volvulus is unusual in childhood. We report the cases of four children treated for sigmoid volvulus, and we review an additional 44 cases. The mean age of occurrence was 8 years. Predisposing factors were present in 33%. Abdominal pain (66%), vomiting (31%), and obstipation (10%) were the most common symptoms. Abdominal findings included distention (69%), tenderness (41%), and a mass (10%). The classic roentgenographic omega sign of volvulus was present on plain films in only 29% of the cases. Barium enema examination was diagnostic in 61% of the cases in which it was used. Nonoperative treatment by barium enema or proctoscopy was successful in all 17 cases in which it was attempted. The recurrence rate after nonoperative treatment was 31%. Thirty children had operation. The mortality in the group of patients having "derotation" alone was 29%. Immediate resection was associated with a 25% mortality; none of the patients who had elective resection died. Sigmoid resection is the definitive treatment for children as well as adults, but nonoperative decompression to allow for elective resection should be attempted in patients who have no evidence of peritonitis.

Adult↗
PubMed1990

Characterization of factors that direct transcription of rat ribosomal DNA.

The protein components that direct and activate accurate transcription by rat RNA polymerase I were studied in extracts of Novikoff hepatoma ascites cells. A minimum of at least two components, besides RNA polymerase I, that are necessary for efficient utilization of templates were identified. The first factor, rat SL-1, is required for species-specific recognition of the rat RNA polymerase I promoter and may be sufficient to direct transcription by pure RNA polymerase I. Rat SL-1 directed the transcription of templates deleted to -31, the 5' boundary of the core promoter element (+1 being the transcription initiation site). The second factor, rUBF, increased the efficiency of template utilization. Transcription of deletion mutants indicated that the 5' boundary of the domain required for rUBF lay between -137 and -127. Experiments using block substitution mutants confirmed and extended these observations. Transcription experiments using those mutants demonstrated that two regions within the upstream promoter element were required for optimal levels of transcription in vitro. The first region was centered on nucleotides -129 and -124. The 5' boundary of the second domain mapped to between nucleotides -106 and -101. DNase footprint experiments using highly purified rUBF indicated that rUBF bound between -130 and -50. However, mutation of nucleotides -129 and -124 did not affect the rUBF footprint. These results indicate that basal levels of transcription by RNA polymerase I may require only SL-1 and the core promoter element. However, higher transcription levels are mediated by additional interactions of rUBF, and possibly SL-1, bound to distal promoter elements.

Animals↗
PubMed1990

rUBF, an RNA polymerase I transcription factor from rats, produces DNase I footprints identical to those produced by xUBF, its homolog from frogs.

Rat cells contain a DNA-binding polymerase I transcription factor, rUBF, with properties similar to UBF homologs that have been purified from both human (hUBF) and frog (xUBF) cells. In this note we report the affinity purification of rUBF to apparent homogeneity and show that UBFs from both rat and frog have identical footprinting characteristics on templates from either species. Furthermore, xUBF was able to stimulate transcription from rat RNA polymerase I promoters in a partially fractionated rat extract that was UBF dependent. These results strengthen the conclusion that all vertebrate cells contain a UBF homolog whose DNA-binding specificity and function have been strongly conserved.

Animals↗
PubMed1990

Phonological processing skills and deficits in adult dyslexics.

This article presents 4 experiments aimed at defining the primary underlying phonological processing deficit(s) in adult dyslexia. 5 phonological processes, all involving spoken language, were studied: phoneme perception, phoneme awareness, lexical retrieval of phonology, articulatory speed, and phonetic coding in verbal short-term memory. 2 differently ascertained adult dyslexic groups, familial dyslexics (n = 15) and clinic dyslexics (n = 15), were the subjects in each experiment. These dyslexic groups were chosen because deficits that persist until adulthood and that are found in differently ascertained dyslexic groups are more likely to be primary. Each dyslexic group was compared to 2 control groups, chronological age (CA) controls who were similar in age and sex, and younger reading age (RA) controls who were similar in reading age and sex. The main finding was a clear deficit in phoneme awareness in both dyslexic groups, with each dyslexic group performing significantly worse than both CA and RA controls. Moreover, performance on the 2 phoneme awareness tasks together uniquely accounted for substantial variance in nonword reading. The clinic but not the familial dyslexics appeared to have an additional deficit in verbal short-term memory. No clear deficits were found in either dyslexic group in phoneme perception, lexical retrieval, or articulatory speed.

Adult↗
PubMed1990

Testicular temperatures measured by thermistor probe and contact thermography.

The results of this study indicate that contact scrotal thermography provides a means for detecting relative differences in temperatures within the testes, but absolute temperatures, as determined by thermistor probes, are about 5% lower. The data do not indicate that this difference is constant, and a simple correction factor cannot be used to equilibrate the two methods of determining the intratesticular temperature. The data also indicate that elevated intratesticular temperatures are associated with surgically induced varicoceles in monkeys.

Animals↗
PubMed1989

Accelerated rates of ribosomal RNA synthesis during growth of contracting heart cells in culture.

Contractile activity of neonatal cardiac myocytes stimulated hypertrophic growth as compared with nonbeating cells that were depolarized with 50 mM KCl. Growth of contracting myocytes was associated with an increased rRNA content as measured by the total RNA/DNA ratio. The fractional rates of rRNA synthesis (K8) and rRNA degradation were determined in contracting and nonbeating myocytes to assess their relative contributions in increasing rRNA content during growth. The values for K8 were calculated from the specific radioactivity of 3'-[3H]UMP in 18 and 28 S rRNA after purification by hybridization to cloned rDNA. The cellular [3H]UTP pool served as the precursor for rRNA synthesis in myocytes that were labeled with 50 microM [3H]uridine. K8 values for 18 and 28 S rRNA in contracting myocytes were accelerated by 59 and 53%, respectively, after 3 days as compared with nonbeating myocytes. Calculations of the rate of cellular rRNA synthesis, which took into account the increased content of myocyte rRNA, revealed that synthesis of both 18 and 28 S rRNA was accelerated 2-fold after 2 days of contraction. The derived values for degradation of 18 and 28 S rRNA were increased marginally in contracting myocytes, but cellular rRNA degradation rates averaged 57% higher. The difference between cellular rates of rRNA synthesis and degradation in contracting myocytes accounted for the 30% increase in rRNA content. These data demonstrated that increased rRNA content in contracting myocytes resulted from acceleration of the fractional rate of rRNA synthesis.

Animals↗
PubMed1989

The gene for enhancer binding proteins E12/E47 lies at the t(1;19) breakpoint in acute leukemias.

The gene (E2A) that codes for proteins with the properties of immunoglobulin enhancer binding factors E12/E47 was mapped to chromosome region 19p13.2-p13.3, a site associated with nonrandom translocations in acute lymphoblastic leukemias. The majority of t(1;19)(q23;p13)-carrying leukemias and cell lines studied contained rearrangements of E2A as determined by DNA blot analyses. The rearrangements altered the E2A transcriptional unit, resulting in the synthesis of a transcript larger than the normal-sized E2A mRNAs in one of the cell lines with this translocation. These observations indicate that the gene for a transcription factor is located at the breakpoint of a consistently recurring chromosomal translocation in many acute leukemias and suggest a direct role for alteration of such factors in the pathogenesis of some malignancies.

Child↗
PubMed1989

lyl-1, a novel gene altered by chromosomal translocation in T cell leukemia, codes for a protein with a helix-loop-helix DNA binding motif.

We have characterized a transcription unit at chromosome band 19p13 that lies at the site of a chromosomal translocation breakpoint in T cell acute lymphoblastic leukemia. The lyl-1 gene is structurally altered following a t(7;19) translocation, resulting in its head-to-head juxtaposition with the T cell receptor C beta gene and truncation of lyl-1 RNA. The predicted protein product of the lyl-1 gene contains a potential helix-loop-helix DNA binding motif also found in several proteins involved in the control of cellular proliferation and differentiation: all members of the Myc family, MyoD1, myogenin, the Drosophila achaete-scute, twist, and daughterless proteins, and two recently described immunoglobulin enhancer binding proteins. The implication of lyl-1 in cellular transformation suggests that other proteins containing similar DNA binding motifs may also be involved with neoplastic transformation in various cellular lineages.

Amino Acid Sequence↗
PubMed1989

Cytotoxic T lymphocytes specific for self tumor immunoglobulin express T cell receptor delta chain.

CTL are thought to play a role in the elimination of transformed cells in vivo. The effectiveness of such CTL is in part dependent on recognition of tumor specific antigens. Among the best characterized tumor-specific antigens are the unique or idiotypic determinants on the Ig of B cell lymphomas. Here we describe the generation and properties of human CTL specific for the idiotype on autologous B cell tumors. These cells are CD3+,CD4-,CD8- and express the delta chain of the TCR. Such cells may prove useful in tumor-specific adoptive therapy.

Adolescent↗
PubMed1989

Consistent breakage between consensus recombinase heptamers of chromosome 9 DNA in a recurrent chromosomal translocation of human T cell leukemia.

Chromosomal translocations in lymphoid tumors frequently result from recombination between a normally rearranging antigen receptor gene and a normally non-rearranging second locus. The possibility that the lymphocyte recombinase apparatus plays a role in determining the position of breakage at the second locus has been a matter of controversy because of the inconsistent presence of heptamer-like recognition sequences adjoining breakpoints at this site. To further investigate this issue, sites of DNA recombination were analyzed in both the der(9) and der(7) products of t(7;9)(q34;q32), a recurrent translocation of human acute lymphoblastic leukemias (T-ALL). In each of three separate cases, the translocation has divided the TCR-beta locus, juxtaposing chromosome 9 DNA 5' to a J-region in the der(9) product and 3' to a D-region in the der(7) product, with variably sized N-insertions and small deletions detectable at the junctions. All three cases contain breakpoints in chromosome 9 DNA tightly clustered between two closely spaced, and oppositely oriented heptamer sequences, CAC(A/T)GTG, which perfectly match the consensus heptamer sequence recognized by the lymphocyte recombinase apparatus in normal antigen receptor gene rearrangement. In no case was there evidence of directly duplicated sequences in the two reciprocal products, as is often associated with recombination involving random staggered breakage of DNA. Taken together, these results support a mechanism for this particular translocation proceeding by recombinase-mediated breakage of both participating chromosomes.

Base Sequence↗
PubMed1989

In vivo transmural potential difference: an early monitor of rejection in small bowel transplantation.

To determine if serial measurements of transmural potential difference (TMPD) can serve as an early monitor of rejection in small bowel transplantation, three groups of rats were studied. The groups are defined as follows: (1) group 1, isolated loop (N = 5): 20 cm of distal jejunum was defunctionalized (Thiry-Vella loop); (2) group 2, isotransplant (N = 5): 20 cm of distal jejunum was isotransplanted between inbred Lewis rats, as a Thiry-Vella loop; the native bowel remained in continuity; (3) group 3, allotransplant (N = 8): allotransplantation as in group 2 but between outbred Sprague-Dawley rats. Using luminal and peritoneal electrodes, TMPD was measured serially every third day. Biopsies of the stoma were taken on the same days for histologic examination of rejection. Group 1 animals (isolated loop) did not show a significant decrease in TMPD from day 1 to day 20. Group 2 (isotransplant animals) had a significant decrease in TMPD as compared with group 1 on day 5 (P less than .01), but by day 8, TMPD returned to baseline. Biopsies in groups 1 and 2 showed no signs of rejection. Group 3 (allotransplant animals) showed a significant decrease in TMPD as compared with group 1 on day 5 (P less than .01). The severity of the histologic signs of rejection parallelled the TMPD decrease throughout the remainder of the study. Monitoring TMPD is a sensitive method of detecting early rejection in small intestine transplantation.

Animals↗