Biomedical subjects

L D Thompson

Publications and source records attributed to L D Thompson.

87 records · Page 5Linked to original sources

PubMed1989

Transfer RNA intron processing in the halophilic archaebacteria.

An in vitro assay system has been developed for the Halobacterium volcanii tRNA intron endonuclease using in vitro generated precursor RNAs. A partially purified enzyme preparation is capable of precise and accurate excision of the intron from the halobacterial tRNA(Trp) precursor. The cleavage reaction produces products having 5' hydroxyl and 2',3' cyclic phosphate termini. Processing of precursor molecules containing deletions within the exon regions indicates that the halobacterial endonuclease does not require intact mature tRNA structure in the substrate; this is in contrast to the eukaryotic endonuclease enzyme that has an absolute requirement for these structures. The large halobacterial tRNA(Trp) intron does not appear to be a primary site for recognition by the endonuclease, however, its removal affects cleavage efficiency. Through a comparison of the structural and sequence features of the halobacterial substrates and the precursors of other archaebacterial intron-containing precursors, a common element is proposed for the recognition of substrates by intron endonuclease.

Base Sequence↗

PubMed1989

AIDS awareness.

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Acquired Immunodeficiency Syndrome↗

PubMed1988

A tRNA(Trp) intron endonuclease from Halobacterium volcanii. Unique substrate recognition properties.

We report on the properties of a partially purified tRNA intron endonuclease from the archaebacterium Halobacterium volcanii. This enzyme is capable of precise excision of the 104-nucleotide intron from halo-bacterial pre-tRNA(Trp) substrates generated in vitro by T7 RNA polymerase transcription. The reaction requires divalent cations (Mg2+ or Ca2+) or spermidine, is inhibited by monovalent cations, and produces 5'-hydroxyl and 2',3'-cyclic phosphate termini. Unlike the universal substrate recognition properties characteristic of the eukaryotic tRNA intron endonucleases, this enzyme is specific for halophilic tRNA(Trp) substrates. The partially purified enzyme is not capable of removing the intron from a yeast pre-tRNA(Phe) substrate. Analysis of the enzyme's ability to cleave tRNA(Trp) substrates lacking exon sequences demonstrated that the mature tRNA-like structure is not required in the substrate. A substrate retaining the intact intron and only the anticodon stem and loop exon regions was efficiently cleaved. Deletions within the intron indicated that the intron was not a primary site for recognition by the endonuclease; however, its presence affects the efficiency of the cleavage reaction. The possible relationship of this enzyme to other RNA endonucleases is discussed.

Base Sequence↗

PubMed1987

Fatty acid profiles and sensory and carcass traits of tissues from steers and swine fed an elevated monounsaturated fat diet.

Twelve Angus X Hereford steers were assigned to either a control high-energy diet or a test diet consisting of 20% rapeseed at the expense of 20% corn. Twelve pigs were allotted to a control diet and two test diets containing either 10 or 20% canola oil (CO). Both CO and oil in the rapeseed contained 60 to 64% oleic acid. Cattle fed rapeseed exhibited little effect from the diet due to apparent indigestibility of the rapeseed. Total saturated fatty acids decreased from 40% in adipose tissue of the control pigs to 15% in the 20% CO-fed pigs. The ratio of monounsaturated to saturated fatty acids (M/S) increased from 1.19 in adipose tissue from control pigs to 3.63 with the addition of 20% CO to the diet. In muscle, the M/S ratio increased from 1.21 in control pigs to 2.46 in the 20% CO treatment group. The percentage of the saturated fatty acids in muscle decreased from 42% in the control to 23% in the 20% CO treatment. Significant increases in "oiliness" and decreases in fat firmness were observed when increasing levels of canola oil were fed. Sensory traits, cooking loss and shear-force values of pork chops were similar among treatment groups. In conclusion, monounsaturated fatty acid content can be elevated substantially in pork without adversely influencing the quality of the meat, thus producing a product perceived to be more healthful by the consumer.

Adipose Tissue↗

PubMed1986

Fusion of pro region of subtilisin to staphylococcal protein A and its secretion by Bacillus subtilis.

Subtilisin is synthesized as a preproenzyme in Bacillus subtilis. We fused that region of the subtilisin gene, (apr[BamP]), which encodes the signal sequence and pro region, to the mature gene sequence (spa) for a heterologous protein (staphylococcal protein A). B. subtilis cells harboring this gene fusion synthesized a fusion protein consisting of the signal and pro sequence of subtilisin fused to the protein A; the signal sequence was processed and a fusion protein (pro + protein A) was secreted into the growth medium.

Amino Acid Sequence↗

PubMed1986

Secretion of a heterologous protein from Bacillus subtilis with the aid of protease signal sequences.

Secretion vectors based on the genes from Bacillus amyloliquefaciens P for alkaline protease (aprBamP) and neutral protease (nprBamP) were constructed. With both aprBamP and nprBamP, a unique restriction site was introduced 3' of the predicted signal coding region by using the technique of oligonucleotide-directed mutagenesis. The new sites enabled us to fuse a heterologous gene to the expression and secretion elements. We used the protein A gene (spa) from Staphylococcus aureus as a heterologous gene. Bacillus subtilis cells carrying the resulting apr-spa or npr-spa gene fusions synthesized the fusion protein. B. subtilis cells were also capable of removing the signal peptide from the fusion protein, as indicated by the appearance of processed protein A into the growth medium. In addition, these gene fusions allowed us to identify the signal processing site of both the APR-SPA and NPR-SPA proteins.

Bacillus↗

PubMed1985

Perturbation of fibrinolysis inhibitors in progressive systemic sclerosis.

Significance of fibrinolysis in pathophysiology of progressive systemic sclerosis (PSS) has been the subject of much speculation. Renal disease in PSS was associated with significant depression of an inhibitor of fibrinolysis, antithrombin III (ATIII), independent of general disease activity. Association of ATIII depression with plasminogen consumption supports an active role for plasmin or another ATIII-inhibitable enzyme in the pathophysiology of renal disease in PSS, and may explain the thrombotic tendency and propensity for fibrin deposition.

Antithrombin III↗

PubMed1985

Perturbation of protease inhibitors and substrates in inflammatory arthritis.

Defective systemic fibrinolysis and articular persistence of fibrinlike material are well recognized in RA. Perturbation of the major plasma protease inhibitors, A1AT, A2MG, and AT III, was explored in RA, psoriatic arthritis, and Reiter's syndrome. Experimental evidence is presented and assessed with respect to the potential role of serine esterases and their inhibitors in the pathophysiology of inflammatory arthritis.

Adult↗

PubMed1984

Use of chromosomal integration in the establishment and expression of blaZ, a Staphylococcus aureus beta-lactamase gene, in Bacillus subtilis.

With several different vectors, attempts were made to establish blaZ, a Staphylococcus aureus beta-lactamase gene, in Bacillus subtilis. Stable establishment of blaZ in B. subtilis was achieved by use of a vector that allowed the integration of a single copy of the gene into the chromosome of that host. blaZ was expressed in the heterologous host since B. subtilis strains carrying integrated blaZ produced beta-lactamase and were more resistant to ampicillin than was wild-type B. subtilis. blaZ was stably inherited in such strains, as no loss of the ability to produce beta-lactamase was observed after growth in nonselective liquid medium or on solid medium. In contrast, a blaZ-containing restriction fragment could not be established in B. subtilis with either pUB110- or pC194-based vectors. Similarly, a pC194-based shuttle vector (pGX318) containing the 5' end of blaZ (including the promoter and the coding region for the signal sequence and the first few amino acids of the mature protein) was unable to transform B. subtilis. Two derivatives of pGX318 that could be stably established in B. subtilis were isolated. The structures of these derivatives suggested that inactivation of the blaZ promoter was associated with the acquisition of the ability to be established.

Ampicillin↗

PubMed1984

Genes for alkaline protease and neutral protease from Bacillus amyloliquefaciens contain a large open reading frame between the regions coding for signal sequence and mature protein.

The genes for alkaline protease (apr[BamP]) and neutral protease (npr[BamP]) from Bacillus amyloliquefaciens have been isolated and expressed in Bacillus subtilis. The DNA sequences of apr[BamP] and npr[BamP] revealed, in each case, the presence of a large open reading frame. The inferred amino acid sequence of either gene contained a signal sequence and an additional polypeptide sequence ('pro' sequence) preceding the mature protein. Based on DNA sequence, the start point of translation has been identified as amino acid residue - 107 for apr[BamP] and -221 for npr[BamP]. To demonstrate that the start point of translation of apr[BamP] in vivo is probably at codon -107, codon -103 (AAA) was changed to an ochre (TAA) by site-directed mutagenesis. Alkaline protease was produced from this ochre mutant derivative of apr[BamP] only when the host strain was Su+. The presence of a pro sequence may be common to all of the secreted proteases from bacilli.

Amino Acid Sequence↗

PubMed1984

Cystic lesion of the thymus. An occasionally malignant cervical and/or anterior mediastinal mass.

Between 1965 and 1982, we treated 46 patients with cystic lesions of the thymus. Thirty patients had anterior mediastinal cysts, nine had cysts which were large enough to be both cervical and mediastinal, and seven had cervical cysts. The majority (40/46) presented with asymptomatic masses. Six patients presented with distinct complaints: dysphagia (four patients), hoarseness owing to vocal cord paralysis (one patient), and cervical pain (one patient). All six had benign thymic cysts. The diagnosis of a cystic mass was established prior to operation by ultrasonography and computed axial tomography in our last three patients. These two techniques delineated the capsule and the central fluid in those three cases. All 46 patients had the mass resected without mortality or significant morbidity, except for resection of the phrenic nerve in one patient with malignant cystic thymoma. Cervical cysts were excised through cervical incisions. Cysts located in the anterior mediastinum and cervical-mediastinal cysts required median sternotomy or right thoracotomy for successful resection. Pathological examination showed that 39 patients had benign thymic cysts, three had benign cystic thymoma, two had malignant thymoma, one had a seminoma arising in the thymus, and one had a lymphoblastoma. We believe that a cystic thymic mass which can be detected by ultrasonography and computed tomography, although usually benign, does not eliminate the possibility of malignancy, and resection, therefore, is indicated.

Adolescent↗

PubMed1983

Relationship of clinical findings in systemic lupus erythematosus to seroreactivity.

We have characterized 52 consecutive patients fulfilling 4 or more of the American Rheumatism Association criteria for systemic lupus erythematosus in order to provide, for the first time, a homogeneous sample for statistical comparison of antinuclear antibody (ANA)-positive and ANA-negative groups. Ten patients (19%) were seronegative. There was no significant difference in age, disease activity, organ system involvement, erythrocyte sedimentation rate, immune complex levels, or C3 levels. The ANA-negative group showed a higher incidence of involvement for whites and men. Leukopenia, lower levels of antibody to DNA, and higher C4 levels were also characteristic of the ANA-negative group.

Adult↗

PubMed1983

Distribution of restriction enzyme sites in the bovine parvovirus genome and comparison to other autonomous parvoviruses.

A physical map has been constructed for bovine parvovirus (BPV) replicative form (RF) DNA synthesized in vitro. Analysis of restriction enzyme digestion products for 12 enzymes by neutral gel electrophoresis allowed the mapping of 26 cleavage sites between the 3' and 5' termini of the in vitro RF DNA. Cleavage sites for these enzymes were not detected within the 3'-terminal hairpin. HindIII, SalI, SmaI, SstII and XorII did not cleave BPV DNA, while 12 other enzymes cleaved the genome at one to four sites. Eleven additional enzymes were shown to cleave the genome at 8 to 20 sites. Comparison of the restriction site locations for BPV with those of other autonomous parvoviruses suggests that there may be conservation within the genome of certain restriction sites.

Animals↗

PubMedDate not supplied

From the Archives of the AFIP. Mucinous cystic neoplasms of the pancreas: radiologic-pathologic correlation.

Mucinous cystic neoplasms of the pancreas are rare primary tumors. They have pathologic and clinical similarities to biliary cystadenomas of the liver and mucinous cystic tumors of the ovary. Mucinous cystic neoplasms of the pancreas typically affect middle-aged women and arise in the tail of the pancreas. Gross pathologic and imaging features usually are those of a large, multilocular cystic mass. There is, however, a spectrum of radiologic findings that overlaps with those of other entities including pancreatic pseudocyst, other primary epithelial and nonepithelial tumors of the pancreas, and metastases. In most cases, ultrasound and computed tomography are the mainstays for radiologic evaluation, with magnetic resonance imaging having a complementary role. All mucinous cystic neoplasms should be considered as mucinous cystadenocarcinomas of low-grade malignant potential. Complete surgical excision alone results in an excellent clinical outcome and disease-free survival, irrespective of histologic or radiologic parameters in over 90% of cases studied.

Adult↗

PubMedDate not supplied

Telecytologic diagnosis of breast fine needle aspiration biopsies. Intraobserver concordance.

OBJECTIVE: To determine the intraobserver concordance between telecytologic and glass slide diagnosis of breast fine needle aspirates. STUDY DESIGN: Twenty-five cases, originally received in consultation, were each examined by three cytopathologists. An average of seven compressed digital images per case were presented, together with a brief clinical history, using the http protocol and an internet browser. RESULTS: Agreement between the telecytologic and glass slide diagnosis ranged from 80% to 96%. Nevertheless, two cases that had been unequivocally diagnosed as malignant based upon video images were considered to be benign by the same pathologist when reviewing the glass slides. Both diagnostic confidence and self-concordance were higher for one pathologist having significant previous video microscopy experience. CONCLUSION: Although intraobserver concordance between telecytologic and glass slide diagnoses of breast fine needle aspirates is high, refinement of existing criteria for diagnosis of malignancy, taking account of the particular limitations associated with telecytologic diagnosis, may be prudent prior to widespread use of telecytology for fine needle aspiration evaluation.

Adult↗