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Biomedical subjects

J W Brown

Publications and source records attributed to J W Brown.

At least 19 recordsLinked to original sources
PubMed1992

Characterization and expression of U1snRNA genes from potato.

U1 small nuclear RNAs (U1snRNAs) occur in the nucleus of plants and animals where, complexed with several proteins in the form of U1 small nuclear ribonucleoprotein particles (U1snRNPs), they play an important role in precursor messenger RNA (pre-mRNA) splicing. Ten potato U1snRNA genes have been isolated on two genomic clones illustrating the clustering of this multigene family on the potato genome. Based on both the sequence of their coding regions and upstream regulatory elements, seven of the genes are potentially functional. The other three genes were pseudogenes with defective promoter or coding region sequences. Analysis of expression of individual cloned U1snRNA genes in transfected tobacco protoplasts was impossible due to the similarity of U1snRNA sequences in tobacco. However, by marking the coding regions with oligonucleotides or constructing chimaeric genes consisting of a potato U1snRNA promoter region and maize U5snRNA coding region, three of the U1 promoter regions were shown to be transcriptionally active.

Base Sequence↗
PubMed1992

The use of bronchotomy and retrograde dilatation to repair acquired obliterative bronchial obstruction.

A case is presented of acquired obliterative mainstem bronchial obstruction with total ipsilateral lung atelectasis and contralateral lung hyperexpansion. The condition failed to improve after a suitable trial of positive airway pressure and medical management. Penetration of the obstructing lesion bia bronchotomy and a distal retrograde approach successfully opened the airway and the patient has been symptom-free for more than 9 months. This unique approach may be useful in other selected patients with similar acquired lesions.

Airway Obstruction↗
PubMed1992

Phrenological studies of aphasia before Broca: Broca's aphasia or Gall's aphasia?

The history of aphasia is usually taken to begin with Broca's (1861a,b) discovery of the correlation of aphemia with damage to the posterior inferior portion of the frontal lobes and the subsequent relation to left hemisphere. That there were prior, even biblical, references to aphasia is not in dispute, nor that, according to Benton and Joynt (1960), almost all the clinical forms of aphasia had been described prior to 1800. The significance of Broca's case studies, therefore, lies in the association of motor aphasia with focal pathology in the frontal lobe. This paper examines the status of aphasia localization prior to Broca, and, specifically, the extent to which Broca's discovery may have been anticipated by the phrenologists.

Aphasia, Broca↗
PubMed1992

The varieties of ribonuclease P.

Ribonuclease P is a ribozyme involved in tRNA processing that is present in all cells and organelles that synthesize tRNA. Most of our understanding of ribonuclease P derives from studies of the bacterial enzyme. This enzyme has been characterized biochemically and a secondary structure for the RNA subunit has been proposed. Isolation and characterization of ribonuclease P from diverse Archaea and Eukarya are now modifying and adding to our model of this unusual enzyme. The latter instances of RNase P differ from the bacterial version, but similarities are emerging.

Animals↗
PubMed1992

Operative intervention in active endocarditis in children: report of a series of cases and review.

We describe in detail 14 children (age, less than or equal to 19 years) who underwent operative intervention during active infection of the heart and/or great vessels. The series included five children less than 6 years old, who constitute 10% of all such cases reported in this age group to date. We also review the 132 published reports in which children underwent operative intervention during active endocarditis. We found the following: (1) The survival rate for all cases was 77%. (2) Persistent infection, embolic phenomena, and increasing congestive heart failure were the most frequent indications for operative intervention. (3) Survival rates were independent of the duration of preoperative antibiotic treatment. (4) Survival rates were independent of positive results of cultures of blood or tissue obtained at operation. (5) The perioperative mortality in our series was 14%. (6) Only 67% of patients had conditions thought to predispose to endocarditis. (7) Except for removal of catheter-associated cardiac masses from neonates, operative intervention in active endocarditis was uncommon among children less than 4 years old. (8) Staphylococcus aureus and viridans streptococci were the etiologic agents in the majority of cases of endocarditis requiring operation during active infection in children.

Adolescent↗
PubMed1992

Surgery for atrioventricular node reentry tachycardia. Results with surgical skeletonization of the atrioventricular node and discrete perinodal cryosurgery.

Surgical treatment options for interruption of atrioventricular node reentrant tachycardia include (1) skeletonization of the atrioventricular node by dissecting it from most of its atrial inputs and (2) discrete cryosurgery of the perinodal tissues by applying a series of sequential cryolesions to the atrial tissues immediately adjacent to the atrioventricular node. Both these techniques attempt to interrupt one of the dual atrioventricular node conduction pathways while preserving the other. This report describes 17 consecutive patients who underwent surgical treatment, 10 patients with skeletonization of the atrioventricular node and seven patients with discrete perinodal cryosurgery. There were 10 female and seven male patients and their ages ranged from 28 to 56 years (mean 38). Two of the 17 patients had Wolff-Parkinson-White syndrome and their accessory pathways were interrupted before the atrioventricular nodal reentrant tachycardia was ablated. All the procedures were performed in a normothermic beating heart while atrioventricular conduction was monitored closely. In the skeletonization technique, the right atrial septum was mobilized and the atrioventricular node exposed anterior to the tendon of the Todaro. The perinodal cryosurgical procedure was also performed through a right atriotomy and a series of sequential 3 mm cryolesions were placed around the borders of the triangle of Koch on the inferior right atrial septum. There were no operative deaths. Two patients who underwent the skeletonization operation had heart block necessitating pacemaker therapy. At postoperative electrophysiologic study, no echoes or atrioventricular nodal reentrant tachycardia were inducible in any of the 17 patients. All patients have remained free of arrhythmia recurrence and have required no antiarrhythmic therapy after a follow-up of 5 to 28 months (mean 14). In conclusion, both atrioventricular node skeletonization and perinodal cryosurgery successfully ablate atrioventricular nodal reentrant tachycardia; however, perinodal cryosurgery appears to be safer in avoiding heart block, is more easily performed, and is our procedure of choice for the management of medically refractory atrioventricular nodal reentrant tachycardia.

Adolescent↗
PubMed1992

Anterior wall left ventricular aneurysm repair. A comparison of linear versus circular closure.

To determine the efficacy of ventricular closure techniques, we reviewed our experience with 62 patients who survived the repair of aneurysms of the anterior wall of the left ventricular from 1984 through 1989. Forty of these patients underwent aneurysm repair by standard linear closure and 22 by a circular closure technique. After a mean follow-up interval of 3 years, there were no demonstrable differences in angina class, New York Heart Association functional classification, or survival. In 41 surviving patients, postoperative left ventricular dimensions and function were satisfactorily evaluated by standard echocardiographic measurements. No significant differences were found in postoperative long-axis left ventricular systolic diameter or in short-axis systolic or diastolic areas. There was a significantly larger long-axis diastolic diameter in the circular closure group; however, there was no difference in this parameter when the ratios of postoperative to preoperative lengths were compared. Further intragroup comparisons demonstrated an increase in short-axis areas postoperatively within the circular closure group in contrast to a decrease in patients in the linear closure group; these changes were not statistically significant. There was no significant difference in postoperative ejection fraction between the two closure groups, although minor reductions were found in the circular closure group. These data demonstrate no significant difference between the linear and circular closure techniques with respect to standard echocardiographic parameters, functional classification, and survival.

Actuarial Analysis↗
PubMed1991

Cloning and characterisation of a U6 small nuclear RNA gene from potato.

Using a mixed U6 snRNA gene probe and a low stringency hybridization procedure we have isolated a U6 snRNA containing clone from a potato genomic library in lambda EMBL 3. This clone contains a single U6 snRNA gene which has been subcloned and sequenced. Southern blotting experiments using this gene and the heterologous U6 genes as probes indicate that the potato U6 gene family consists of more than 20 members. The potato U6 gene sequence shows high identity to previously characterised plant U6 snRNA gene sequences and possesses correctly positioned and spaced transcription control elements suggesting that it is an active gene.

Base Sequence↗
PubMed1991

Sequence variation and linkage of potato U2snRNA-encoding genes established by PCR.

Plant uridylate-rich small nuclear RNA (UsnRNA)-encoding genes (UsnRNA) are present as multigene families exhibiting greater sequence variation than has been described in animal UsnRNA families. The potato U2snRNA multigene family has 25 to 40 potential gene members. Four gene variants have been analysed to date, two of which are linked. In order to investigate U2snRNA expression in potato in terms of the function of such sequence variation in development, the degree of sequence variation in both the coding region and flanking regions in this gene family must be assessed. On the assumption that at least some U2snRNA genes are linked, a polymerase chain reaction (PCR) approach, using primers designed to amplify intergenic nucleotide sequences including coding and 5' flanking regions, has been devised. Six new U2snRNA gene variant sequences and one U2snRNA pseudogene sequence have been generated. In addition, six new flanking region sequences have been produced which, in contrast to other plant UsnRNA gene families, show considerable variation in the important upstream sequence element. This PCR approach may be applicable to the analysis of genomic organisation and sequence variation of other multigene families.

Base Sequence↗
PubMed1991

Long-range structure in ribonuclease P RNA.

Phylogenetic-comparative and mutational analyses were used to elucidate the structure of the catalytically active RNA component of eubacterial ribonuclease P (RNase P). In addition to the refinement and extension of known structural elements, the analyses revealed a long-range interaction that results in a second pseudoknot in the RNA. This feature strongly constrains the three-dimensional structure of RNase P RNA near the active site. Some RNase P RNAs lack this structure but contain a unique, possibly compensating, structural domain. This suggests that different RNA structures located at different positions in the sequence may have equivalent architectural functions in RNase P RNA.

Bacillus subtilis↗
PubMed1991

Evolutionary conservation of the spliceosomal protein, U2B''.

U1 and U2snRNPs play key roles in pre-mRNA splicing. The interactions between the U1 and U2snRNP-specific proteins, U1A, U2A' and U2B'' and their respective UsnRNAs are of interest both to elucidate their roles in splicing, and as models to study RNA-protein interactions. We have cloned a full-length cDNA, encoding U2B'', from potato. This is the first report of a sequence for a plant UsnRNP protein. The plant U2B'' sequence exhibits extensive similarity with the human U2B'' protein at both the DNA and amino acid levels. The evolutionary conservation at the protein level, particularly in sequences implicated in determining specific binding to U2snRNA, suggests conservation of U2B'' function from plants to man. The significance of amino acid substitutions in the RNP-80 motif with respect to U2snRNA binding in plants is discussed.

Amino Acid Sequence↗
PubMed1991

Sequence and expression of potato U2 snRNA genes.

Plant UsnRNA multigene families show a high degree of sequence variation among individual gene members. The potato U2snRNA gene family consists of between twenty-five and forty genes. Four potato U2snRNA gene variants have been isolated. Despite the sequence variation in coding and flanking regions, all maintain the conserved U2snRNA secondary structure and all contain the plant UsnRNA promoter elements: the upstream sequence element (USE) and TATA-like box in the -70 and -30 regions respectively. In RNase A/T1 protection analyses, one of the genes, PotU2-22, protected high levels of full length U2snRNA transcripts in potato leaf, stem, root and tuber RNA. Thus, PotU2-22 or genes with identical coding regions, are highly expressed in these potato organs and therefore represent a major subset of functional U2snRNA genes. Similar expression levels of the PotU2-22 sequence variant were also found in four genetically different potato cultivars and also in tobacco, a species closely related to potato, suggesting conservation of the coding regions of expressed U2snRNA genes. A second gene, PotU2-4, protected very low levels of full length transcripts while a third gene, PotU2-11, was not expressed in the potato organs analysed. The relative expression levels of the gene variants may reflect individual gene differences in, for example, the USE and TATA regulatory elements, or variations in gene copy number.

Animals↗
PubMed1991

Radiopacity of direct ceramic inlay restoratives.

The radiopacity of two new ceramic restorative materials (Dicor MGC and Cerec Vita Blocks) manufactured for use in producing direct inlays with the 'Cerec CAD-CAM' system was determined. Dicor MGC had a radiopacity significantly greater than that of enamel, while Cerec Vita Blocks had a radiopacity significantly less than that of dentine. It is concluded that Dicor MGC has a radiopacity suitable for its use as an intracoronal restorative for posterior teeth. The low radiopacity of Cerec Vita Blocks means that the use of radiopaque luting cement is essential to permit detection of secondary caries around restorations of this material. Furthermore, marginal overhangs around restorations made from Cerec Vita Blocks will be difficult to detect radiographically.

Analysis of Variance↗