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Biomedical subjects

G D Pearson

Publications and source records attributed to G D Pearson.

At least 19 recordsLinked to original sources

Traumatic thoracic aortic rupture in the pediatric patient.

BACKGROUND: Traumatic thoracic aortic rupture is a rare injury in the pediatric patient. Experiences with thoracic aortic rupture in patients less than 17 years of age are needed to help identify factors that can influence injury occurrence, diagnosis, management, and outcome. METHODS: Between July 1989 and December 1995, 6 children were treated operatively for thoracic aortic rupture from blunt trauma at a level I pediatric trauma center. The average age was 13.2 years (range, 8 to 16 years). There were 4 females and 2 males. There were 5 motor vehicle accidents and 1 bicycle accident. Aortic injury was suspected based on the mechanism of injury and abnormal chest roentgenogram results, and was confirmed by aortography (3 cases) or chest computed tomography (2) and transesophageal echocardiography (3). Life-threatening central nervous system or gastrointestinal injuries were evaluated or treated first. Operative repair of the thoracic aorta was performed by cardiopulmonary bypass (2 patients) and clamp and sew technique (4). RESULTS: Aortic ruptures were complete transections at the ligamentum arteriosum in 5 of 6 (83%); the other case was a cervical arch pseudoaneurysm. Associated injuries included pulmonary contusion (100%), pelvic/long bone fractures (50%), visceral laceration/perforation (50%), central nervous system (33%), paraplegia (17%), and myocardial contusion (17%). There were no rib fractures. Four of 5 patients (80%) were not wearing seat belts, and 2 of these were ejected. The average time from injury to the operating room was 17.6 hours (range, 5 to 48 hours); the time from diagnosis to the operating room exceeded 5 hours with aortography and was less than 3 hours with chest computed tomography and transesophageal echocardiography. Each diagnostic modality accurately identified an aortic injury. The average time for cardiopulmonary bypass and for clamp and sew was 52 minutes (range, 49 to 55 minutes) and 34 minutes (range, 16 to 45 minutes), respectively. One patient with preoperative paraplegia regained partial function; there were no other patients with paraplegia. There were no deaths. All patients are alive 2 months to 7 years after repair. CONCLUSIONS: The multiply injured child with severe blunt trauma and an abnormal chest roentgenogram requires a search for aortic injury. We believe the most effective algorithm to follow for the diagnosis of traumatic thoracic aortic rupture in the child involves selective performance of chest computed tomography and transesophageal echocardiography. Our experience suggests that the mechanism of injury, the duration to diagnosis of an aortic injury, and failure to use seat belts may contribute to morbidity. A high index of suspicion and a systematic approach to the diagnosis and to the management strategy for injuries to the thoracic aorta can contribute to a good outcome in those few children who survive the injury.

Adolescent

Small (< or = 3 cm) hyperechoic renal masses: comparison of helical and convention CT for diagnosing angiomyolipoma.

OBJECTIVE: Because hyperechoic renal masses may represent angiomyolipomas or small renal cancers, CT is often used to reveal the fatty component, which allows diagnosis of angiomyolipoma in most cases. Because conventional CT can fail to reveal fat in angiomyolipomas 3 cm or smaller, we conducted a study to determine whether helical CT would improve our detection of fat and allow more of these masses to be diagnosed as angiomyolipomas. SUBJECTS AND METHODS: We used helical and conventional CT to examine 20 masses (5-29 mm in diameter) in 17 patients who had a small hyperechoic mass detected sonographically. Densitometry was performed by three readers and the mean attenuation values were compared. RESULTS: Of the 20 masses, we diagnosed angiomyolipoma in 16 masses using helical CT and in 14 masses using conventional CT. In 11 masses, we found the measured attenuation values to be more negative on helical CT scans than on conventional CT scans. In five masses, we found the opposite to be true. In the remaining four masses, we were unable to diagnose angiomyolipoma. Of the masses that we diagnosed as angiomyolipoma, the mean attenuation value when examined with helical CT (-44 H) was more negative than with conventional CT (-35 H) but not significantly so (p = .058). However, in the subset of patients with masses that were 2 cm or less in diameter (n = 14), the mean attenuation values on helical CT were significantly lower than on conventional CT (-40 H versus -30 H, p < .05). Likewise, for masses with attenuation values that differed by more than 6 H (n = 8), when imaged by the two techniques we again found that mean attenuation values on helical CT were significantly lower (-43 H versus -24 H, p < .05). CONCLUSION: Helical CT revealed angiomyolipoma across all cases as well as conventional CT did. Also, helical CT was more sensitive in revealing fat in masses less than 2 cm in diameter and in masses in which the attenuations of the two CT techniques differed by a significant amount. We preferred helical CT over conventional CT when examining hyperechoic masses for the purpose of diagnosing angiomyolipoma.

Adult

CTX genetic element encodes a site-specific recombination system and an intestinal colonization factor.

In Vibrio cholerae, the genes encoding cholera toxin (ctxAB) are located on a segment of DNA (termed the "core" region) that is flanked by two or more copies of a repeated sequence called RS1. Together these DNA units comprise the CTX genetic element. Evidence presented here suggests that RS1 sequences encode a site-specific recombination system, which allows integration of a suicide plasmid carrying RS1 into an 18-base-pair sequence (attRS1) located on the chromosome of nontoxigenic V. cholerae strains. Strains of V. cholerae with large deletions removing attRS1 and the entire CTX genetic element no longer undergo site-specific recombination with the RS1 sequence. Additionally, these deletion strains show a defect in intestinal colonization. Recombination experiments localize the gene responsible for enhancing colonization to a portion of the core region of the CTX element. The identified gene encodes a peptide that is highly similar in amino acid sequence to the flexible pilin of Aeromonas hydrophila. These results have important implications in the construction of stable, live attenuated cholera vaccines.

Amino Acid Sequence

Sequence conversion during postreplicative adenovirus overlap recombination.

Sequence conversion efficiently transfers genetic information in high yield during postreplicative adenovirus overlap recombination. This process is intrinsically nonreciprocal, depends on adenovirus-specific strand-displacement replication by both partner molecules, and requires that complementary sequences on displaced strands must exceed a minimal length to form a heteroduplex intermediate.

Adenoviridae

Symmetrical adenovirus minichromosomes have hairpin replication intermediates.

A special class of panhandles (hairpin or foldback structures) arising from the replication of symmetrical adenovirus (Ad) minichromosome dimers and oligomers have been identified by two-dimensional gel electrophoresis. Hairpins provide evidence for replicative intermediates in the pathway for Ad complementary-strand synthesis. Furthermore, larger inverted sequences give Ad minichromosomes a replicative advantage.

Adenoviridae

Determinants of outcome in hospitalized infants with congenital heart disease.

To identify determinants of adverse outcome in this era of early, definitive treatment, retrospective data were analyzed for 1988 on infants aged less than 1 year with congenital cardiac disease hospitalized at The Johns Hopkins Hospital. In this cohort of 108 infants, 34% (37 of 108) had complex cardiac disease, 33% (36 of 108) had major extracardiac anomalies, 88 patients (81%) underwent 116 surgical procedures, 37% (40 of 108) were hospitalized for greater than 28 days and 29% (31 of 108) died during the first year. Univariate analysis showed that complex disease (i.e., severe ventricular hypoplasia, ventricular septal malalignment or outflow atresia), extracardiac anomalies, early initial presentation, and prolonged stay in the intensive care unit were significantly associated with infant death, whereas surgery was associated with a significantly increased rate of survival. The findings for complex disease and surgery persisted in multiple logistic regression analysis. It is concluded that outcome in most infants with congenital cardiac defects is now extremely favorable, and that major research and preventive efforts should focus on complex congenital cardiac defects.

Female

Strands hybridize in postreplicative adenovirus overlap recombination.

We describe a postreplicative mechanism for adenovirus overlap recombination. An adenovirus minichromosome system was used to study overlap recombination driven by adenovirus DNA replication. Crossing-over appeared to occur equally at, but not within, the borders of the overlap between partner molecules. We propose that recombination in the minichromosome system proceeds through an intermediate formed by direct hybridization of complementary sequences on displaced strands generated by adenovirus-specific DNA replication. Some, but not all, heterologous regions in the intermediate are susceptible to mismatch correction. This pathway is intrinsically nonreciprocal and differs significantly from other adenovirus recombinational mechanisms that have been described previously.

Adenoviruses, Human

Cardiac care for infants. Determinants of hospital charges for acute care.

We analyzed hospital use and inpatient charges retrospectively for infants hospitalized at a tertiary referral center in the first year of life for cardiac disease. For 93 infants hospitalized between August 1987 and June 1989, there were 1.8 admissions per patient, with a median stay of 14 days; 24.7% required more than 28 days of acute inpatient care. Total hospital charges (excluding professional fees) in the first year of life were $3,417,612, which represents $36,749 per infant and $35,386 per survivor. Reimbursement totaled 93.2% of charges. Multivariate analysis revealed that complex disease, surgery, and length of stay in the intensive care unit were significantly associated with increased charges, while extracardiac anomalies, birth weight, outcome, and type of insurance were not. The economic benefits of averting infant death outweigh the associated costs by as much as 5.4 to 1. We conclude that current treatment of most infants with cardiac disease is both effective and economically beneficial.

Baltimore

Inverted repeats direct repair of adenovirus minichromosome ends.

Adenovirus DNA initiates strand-displacement replication from origins located in identical inverted terminal repetitions (ITRs). Panhandle structures, formed by base pairing between ITRs on the displaced strands, have been proposed as replication intermediates for complementary strand synthesis. We have used a model system, which separates adenovirus replication origin sequences from those involved in panhandle formation, to study the length and sequence integrity of panhandles. By making a series of unidirectional deletion in the panhandle sequence, we show that 31 bp are necessary for panhandle formation. Removal of long stretches of 3'-unpaired nucleotides distal to the panhandle is extremely efficient. Our results argue for the formation of panhandles during adenovirus DNA replication and provide a mechanism for maintaining sequence identity between distantly located inverted repetitions. The size constraint may explain why the adenovirus ITRs are larger than the viral DNA replication origins.

Adenoviridae

Crosslinking of DNA by dehydroretronecine, a metabolite of pyrrolizidine alkaloids.

Dehydroretronecine (DHR), a major metabolite of the pyrrolizidine alkaloids, has been shown to bind and crosslink pBR322 plasmid DNA and M13 viral DNA, as monitored by electron microscopy and agarose gel electrophoresis. The crosslinking was alkali-stable and varied with time, temperature, pH and reactant ratios. Although the binding of DHR to single-stranded M13 DNA was 3-fold higher than to double-stranded M13 DNA, only the double-stranded DNA was crosslinked. Intra- and inter-molecular crosslinking occurred with both linear and circular forms of double-stranded DNA. Electron microscopy showed that incubations with low DHR/DNA ratios yielded mostly DNA monomers and dimers while higher ratios produced larger aggregations, some of which were equivalent in size to dozens of individual DNA molecules. The average number of intermolecular crosslinks per molecule estimated by Poisson statistics was essentially the same using data from electron microscopy or DHR-binding. DHR generated single strand scissions equally well in both single- and double-stranded molecules.

Alkylation

Criteria for extracorporeal membrane oxygenation in a population of infants with persistent pulmonary hypertension of the newborn.

Extracorporeal membrane oxygenation (ECMO) has been available since 1975 as a therapy of last resort to provide adequate oxygenation for term infants with acute lung disorders that do not respond to maximal medical therapy. Virtually all term infants with serious lung disease have persistent pulmonary hypertension of the newborn (PPHN) characterized by significant right-to-left shunting of blood and severe diffusion defects manifested as increased alveolar-arterial oxygen gradients (AaDO2). Criteria for initiation of ECMO therapy have been developed in several institutions but at the present time there are no universal criteria applicable to all infants with PPHN. We have attempted to establish entry criteria that may be used for different populations of infants with PPHN. Based on a retrospective review of 30 infants with PPHN in our institution, we have defined standards of maximal medical therapy. An alveolar-arterial oxygen difference (AaDO2) of greater than or equal to 610 for 8 hours has been shown to be associated with 79% mortality in this population. This AaDO2/time interval is established as a major criterion for institution of extracorporeal membrane oxygenation.

Carbon Dioxide

Molecular characterization and phylogenetic studies of a wound-inducible proteinase inhibitor I gene in Lycopersicon species.

A gene coding for proteinase inhibitor I, whose expression is induced in tomato leaves (Lycopersicon esculentum L. var. Bonny Best) in response to wounding or insect attacks, was isolated from a genomic library and characterized. The nucleotide sequence revealed that the gene is complete and encodes the sequence of an inhibitor I cDNA that was previously isolated from a cDNA library prepared from wound-induced mRNA from tomato leaves. This gene is located 13.1 kilobase pairs (kbp) upstream from an inhibitor II gene. The wound-inducible gene is interrupted by two intervening sequences of 445 and 404 bp, situated within the codons of amino acids 17 and 47, respectively, of the open reading frame. In addition to the presence of putative regulatory sequences, TATAAA and CCACT, two copies of an imperfect direct repeat approximately 100 bp long were identified in the 5'-flanking region. Phylogenetic comparisons of wound-inducible inhibitor I genes within the genomes of various Lycopersicon species revealed that the repeat is found in seven ancestral species of tomato.

Amino Acid Sequence

Characterization of the bovine prothrombin gene.

The bovine prothrombin gene was characterized by Southern blot analysis of bovine genomic DNA using bovine prothrombin cDNA fragments as hybridization probes. These analyses suggested that the bovine genome contains a single prothrombin gene that is at least 10 kilobase pairs (kbp) in size. To characterize the gene more thoroughly, two bovine genomic phage libraries were screened by using prothrombin cDNAs as hybridization probes. Heteroduplex analysis of the cloned genomic DNA and cDNA showed that the prothrombin gene is 14.9 kbp in size and contains at least 14 exons interrupted by 13 introns. The exons vary in size from 28 to 317 base pairs (bp), while the introns vary in size from less than 100 to 6940 bp. Regions of self-complementarity were observed within some of the introns, suggesting the presence of inverted repeat sequences. The bovine prothrombin gene shows similarities in structure to both the human prothrombin gene and the human factor IX gene.

Amino Acid Sequence

Adenovirus sequences required for replication in vivo.

We have studied the in vivo replication properties of plasmids carrying deletion mutations within cloned adenovirus terminal sequences. Deletion mapping located the adenovirus DNA replication origin entirely within the first 67 bp of the adenovirus inverted terminal repeat. This region could be further subdivided into two functional domains: a minimal replication origin and an adjacent auxillary region which boosted the efficiency of replication by more than 100-fold. The minimal origin occupies the first 18 to 21 bp and includes sequences conserved between all adenovirus serotypes. The adjacent auxillary region extends past nucleotide 36 but not past nucleotide 67 and contains the binding site for nuclear factor I.

Adenoviridae

DNA homologies between the rainbow trout, chum salmon and coho salmon.

The thermal stabilities of hybrid duplexes between the DNAs from three salmonid fish species were monitored as measures of DNA homology. The chum salmon, Oncorhynchus keta, and coho salmon, Oncorhynchus kisutch, had more DNA homology with each other than either had with the rainbow trout, Salmo gairdnerii. Morphological, ecological and protein similarities between the coho salmon and the rainbow trout may be due to parallel or convergent evolution.

Animals

Adenovirus infection elevates levels of cellular topoisomerase I.

We have developed a specific, sensitive, and quantitative assay for topoisomerase I, which is based on the formation of a covalent enzyme-DNA intermediate. Our assay measures the quantitative transfer of 32P radioactivity from 32P-labeled DNA to topoisomerase I. Since 32P-labeled topoisomerase molecules are resolved by NaDodSO4/PAGE, HeLa topoisomerase I (100 kDa) and calf thymus topoisomerase I (82 kDa) can be quantitatively assayed in the same reaction mixture. The assay can detect at least 0.3 ng (3 fmol) of topoisomerase I. We have used our assay to measure the levels of topoisomerase I activity in crude extracts of nuclei prepared from uninfected, adenovirus-infected, and adenovirus-transformed human cells. The evidence suggests that an adenovirus early gene product, presumably a protein encoded in early region 1A (E1A), increases cellular topoisomerase I activity at least 10-fold. Immunoblotting analysis with antiserum against calf thymus topoisomerase I shows that the increase in activity is due to an increase in the amount of enzyme.

Adenoviridae

Molecular cloning of the six mRNA species of infectious hematopoietic necrosis virus, a fish rhabdovirus, and gene order determination by R-loop mapping.

Plasmids carrying cDNA sequences to the mRNA species of infectious hematopoietic necrosis virus were constructed and cloned into Escherichia coli. Characterization of 21 cloned plasmids by hybridization to mRNA blots identified sets of plasmids with homology to each of the six viral mRNA species. R-loop mapping with these cDNA plasmids determined that the gene order on the infectious hematopoietic necrosis virus genome is (3')N-M1-M2-G-NV-L(5').

Animals

Site-specific nicking within the adenovirus inverted terminal repetition.

Site-specific nicking occurs on the l-strand, but not on the r-strand, of the adenovirus left inverted terminal repeat. Nicks are presumably introduced into double- or single-stranded DNA by a cellular endonuclease in an ATP-independent reaction. The consensus nick site has the sequence: (sequence in text).

Adenoviridae