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Biomedical subjects

K A Brown

Publications and source records attributed to K A Brown.

At least 37 records · Page 2Linked to original sources
PubMed2001

The use of hepatitis C viral RNA levels in liver tissue to distinguish rejection from recurrent hepatitis C.

Persistence of hepatitis C virus (HCV) after orthotopic liver transplantation is almost universal in HCV-infected patients. Histological examination of liver biopsy specimens can be variable in distinguishing between recurrent hepatitis C and acute cellular rejection. The purpose of this study is to determine whether hepatic HCV RNA levels can be used to distinguish rejection from recurrent HCV by determining whether hepatic HCV RNA levels correlate with histological characteristics and clinical course. Seventy-two biopsy specimens were evaluated from 36 liver transplant recipients with HCV and elevated liver-related enzyme levels. Based on histological findings and clinical response to therapy, patients were defined as belonging to 1 of 5 groups: (1) definite rejection, (2) probable rejection, (3) indeterminate findings, (4) probable HCV, and (5) definite HCV. Hepatic HCV RNA was quantified using the Amplicor Monitor assay (Roche Diagnostic Systems Inc, Branchburg, NJ). There was a difference across groups in HCV RNA levels (P =.046). The median HCV RNA level was 10,695 copies/mg of tissue DNA in the definite-HCV group compared with 1,024 copies/mg of tissue DNA in the definite-rejection group. Using pairwise comparisons, significant differences were found between definite HCV and definite rejection, probable HCV and definite rejection, probable HCV and probable rejection, and probable HCV and indeterminate. Our findings support the following conclusions. (1) In liver transplant recipients, hepatic HCV RNA levels are statistically greater in patients with recurrent HCV than rejection, although there is considerable overlap between groups. (2) Patients with low HCV RNA levels were unlikely to have recurrent HCV. (3) Patients with minimal and indeterminate findings on biopsy (group 3) had low HCV RNA levels.

Adult↗
PubMed2001

Liver transplantation.

Continued discussion over organ allocation and distribution remained a focal point in the field of liver transplantation in the year 2000. Despite the ongoing debate, no significant changes were implemented in the current allocation system. By far, the most widely discussed topic in liver transplantation this year was live donor adult-to-adult liver transplantation. Several authors reported on their initial experience, with both recipient and donor outcomes appearing excellent. As the number of transplant centers performing this procedure increases we look forward to further studies regarding the safety and long-term outcome of this innovative procedure. Studies on viral hepatitis after liver transplantation again focused on the problem of recurrent hepatitis B and hepatitis C. Several small studies found benefit in patients with hepatitis B treated with intramuscular hepatitis B immunoglobulin and lamivudine after transplantation. Although breakthrough replication remains a problem in some patients, these studies offer hope that combination therapy for hepatitis B may provide improved long-term graft survival in these patients. In patients with hepatitis C, several studies focused on identifying risk factors to predict graft recurrence of the virus after liver transplantation. Both cellular rejection and level of viral replication may be important predictors of recurrent hepatitis C virus in the graft. Early treatment reports using interferon and ribavirin suggest that some patients may have a viral response during therapy; however, it is short lived, and tolerance of medication is difficult. Certainly, we look forward to further studies looking at means of prevention and treatment of viral hepatitis in patients undergoing liver transplantation.

Journal Article↗
PubMed2001

Failure of single-toxin assays to detect clostridium difficile infection in pediatric inflammatory bowel disease.

OBJECTIVES: The aims of this retrospective study were 1) to determine the ability of single-toxin assays for Clostridium difficile to detect infection among pediatric patients with inflammatory bowel disease (IBD) and 2) to determine the toxin assays routinely used by pediatric tertiary care hospitals in the United States. METHODS: Stool specimens from patients with IBD (submitted from January, 1996, to August, 1999) were evaluated for the presence of C. difficile toxin A and toxin B. Toxin profile (toxin A alone, toxin B alone, toxin A and B together) was compared in positive specimens. A phone interview was conducted with representatives from laboratories in 22 pediatric hospitals to investigate which toxin assays were routinely used. RESULTS: A total of 697 specimens were submitted from 284 IBD patients. In all, 81 IBD patients (28.5%) had at least one documented infection. Toxin A assay failed to identify 41.5% of C. difficile infections. Toxin B assay failed to detect 34.9% of C. difficile infections. Toxin profile changed in 55% of patients with multiple infections. Of the hospitals surveyed, 59% did not test for both toxins. CONCLUSIONS: Single-toxin assays for C. difficile fail to detect a significant percentage of infections. The toxins identified during one infection are not predictive of the toxins identified in subsequent infections. Despite this, many pediatric hospitals do not routinely use both toxin assays to diagnose C. difficile infection. When infection is suspected, assays for C. difficile toxin A and toxin B should be requested.

Adolescent↗
PubMed2001

The effects of leucodepletion in patients who develop the systemic inflammatory response syndrome following cardiopulmonary bypass.

The development of the systemic inflammatory response syndrome (SIRS) is associated with increased morbidity and mortality. Numerous anticytokine trials have failed to demonstrate any outcome benefit and there has been little evidence of improvement in the prognosis of this condition over the past 20 years. This study examines the effect of using a white cell filter designed to remove polymorphonuclear cells (PMNs) in patients who developed SIRS 36 h after cardiopulmonary bypass (CPB). Twenty-four patients were randomized to receive either leucofiltration (LF) or control therapy (CT). The two groups were well matched at study entry in terms of age, severity of illness and length of time on CPB. LF patients received 60 min filtration periods using a venovenous extracorporeal circuit at a flow rate of 200 ml/min with the cycle repeated every 12 h while SIRS and other entry criteria were met. CT patients received standard therapy. LF patients received an average of 4.2 cycles (range 1-8) and, after 15 min filtration, the total leucocyte count had fallen from 16.2 +/- 5.3 to 10.4 +/- 3.3 x 10(9)/l and PMN from 14.4 +/- 5.2 to 8.3 +/- 4.2 x 10(9)/l. The mean platelet count changed from 127 +/- 87 to 117 +/- 82 x 10(9)/l. No adverse effects related to leucodepletion were observed. There was no difference between the groups in either mortality or length of stay at the intensive care unit or at hospital discharge. Organ function was assessed regularly during the study period and significant changes occurred only in respiratory and renal function. In the LF patients, respiratory function assessed by change in hypoxaemia index from baseline and renal function assessed by serum creatinine showed significant treatment effects compared to CT patients (p < 0.01, < 0.01 respectively); three CT patients, but no LF patients, received haemofiltration during the study period. Leucofiltration safely and effectively removes circulating PMNs from patients with SIRS following CPB. This may result in improved pulmonary and renal function in these patients. Further studies are required of the kinetics and phenotypic characteristics of PMN removal by leucofiltration and a larger multicentre study will be necessary to determine whether this novel therapy has a significant outcome benefit in critically ill patients with SIRS.

Aged↗
PubMed2001

Leucodepletion and the interaction of polymorphonuclear cells with endothelium in systemic inflammatory response syndrome.

The abnormal interaction of polymorphonuclear cells (PMNs) with blood vessel walls is considered to underlie the multiple organ failure of systemic inflammatory response syndrome (SIRS). This consideration is supported by the present finding that PMNs from patients with SIRS are activated, as assessed by an increased distribution of cells bearing CD64, enhanced expression of CD11b and decreased expression of CD62L, and are highly adhesive to endothelial monolayers. Passage of SIRS blood through leucodepletion filters in a laboratory-designed extracorporeal circuit resulted in a marked depletion of PMNs. Of the PMNs that remained in the blood, far fewer cells bound to cultured endothelial cells in comparison with PMNs prior to leucofiltration. We propose that leucofiltration of SIRS blood will limit the number of PMNs available for binding to blood vessel walls and, hence, reduce the pathological manifestations associated with this disorder.

Case-Control Studies↗
PubMed2001

Identification from a bitemark in a wad of chewing gum.

A wad of used chewing gum recovered from the scene of a burglary contained impressions of human teeth. Casts of these impressions displayed unique morphological characteristics which were found to show concordance with corresponding features present on casts of the posterior teeth of a suspect.

Adolescent↗
PubMed2000

Circulating rotavirus-specific antibody-secreting cells (ASCs) predict the presence of rotavirus-specific ASCs in the human small intestinal lamina propria.

Rotaviruses are the most important cause of infectious diarrhea in children throughout the world. Protection is most likely mediated by small-intestinal virus-specific IgA. However, neither fecal nor serum virus-specific IgA clearly correlates with protection against challenge. The capacity of rotavirus-specific antibodies and rotavirus-specific antibody-secreting cells (ASCs) in the circulation to predict the presence of ASCs in the intestines of children was evaluated. Mononuclear cells from intestinal biopsy samples and blood from 21 children were enriched for CD38, a marker of terminally differentiated B cells, and evaluated for the presence of virus-specific and total IgA- and IgG-secreting cells, by ELISPOT assay. Serum virus-specific IgA and IgG levels were determined by ELISA. The ratio of virus-specific to total IgA-secreting cells in the blood correlated with that found in the small, but not large, intestine. In contrast, serum rotavirus-specific IgA correlated less well with the presence of virus-specific ASCs in the small intestine.

ADP-ribosyl Cyclase↗
PubMed2000

Flow cytometric analysis of different adhesion molecules expression on circulating CD14- and CD64- human dendritic cell precursors.

Blood dendritic cell precursors (DCps) are identified as mononuclear leukocytes expressing HLA-DR but lacking the characteristic antigens associated with T cells (CD3), NK cells (CD16 and CD56) and B cells (CD 19). Dendritic cell precursors are distinguished from monocytes by their lack of expression of CD64 rather than of CD14. This study investigated whether CD14- DCps differed from CD64-DCps, which were predominantly CD14+, in their expression of five well-characterised adhesion molecules. There were significantly fewer cells expressing CD11b, CD18 and CD29 in the CD64-DCp population compared with CD14- DCps, and this CD64- DCp subpopulation also had a lower expression of CD11b and CD18. Our results suggest that the two DC precursor subpopulations may differ from one another in their binding characteristics to blood vessel walls and to other leukocytes.

Antigens, CD↗
PubMed2000

Purification, characterization, cDNA cloning and expression of a novel ketoreductase from Zygosaccharomyces rouxii.

A novel ketoreductase isolated from Zygosaccharomyces rouxii catalyzes the asymmetric reduction of selected ketone substrates of commercial importance. The 37.8-kDa ketoreductase was purified more than 300-fold to > 95% homogeneity from whole cells with a 30% activity yield. The ketoreductase functions as a monomer with an apparent Km for 3,4-methylenedioxyphenyl acetone of 2.9 mM and a Km for NADPH of 23.5 microM. The enzyme is able to effectively reduce alpha-ketolactones, alpha-ketolactams, and diketones. Inhibition is observed in the presence of diethyl pyrocarbonate, suggesting that a histidine is crucial for catalysis. The 1.0-kb ketoreductase gene was cloned and sequenced from a Z. rouxii cDNA library using a degenerate primer to the N-terminal sequence of the purified protein. Furthermore, it was expressed in both Escherichia coli and Pichia pastoris and shown to be active. Substrate specificity, lack of a catalytic metal, and extent of protein sequence identity to known reductases suggests that the enzyme falls into the carbonyl reductase enzyme class.

Alcohol Oxidoreductases↗
PubMed2000

Chemical and physiological characterization of fluo-4 Ca(2+)-indicator dyes.

We have developed fluo-4, a new fluorescent dye for quantifying cellular Ca2+ concentrations in the 100 nM to 1 microM range. Fluo-4 is similar in structure and spectral properties to the widely used fluorescent Ca(2+)-indicator dye, fluo-3, but it has certain advantages over fluo-3. Due to its greater absorption near 488 nm, fluo-4 offers substantially brighter fluorescence emission when used with excitation by argon-ion laser or other sources in conjunction with the standard fluorescein filter set. In vitro, fluo-4 exhibited high fluorescence emission, a high rate of cell permeation, and a large dynamic range for reporting [Ca2+] around a Kd(Ca2+) of 345 nM. We have also developed several Ca(2+)-indicators related to fluo-4 having lower affinities for Ca2+ that are useful in cellular studies requiring quantification of higher [Ca2+]. In a variety of physiological studies of live cells, fluo-4 labeled cells more brightly than did fluo-3, when challenged with procedures designed to elevate calcium levels. Fluo-4 is well suited for photometric and imaging applications that make use of confocal laser scanning microscopy, flow cytometry, or spectrofluorometry, or in fluorometric high-throughput microplate screening assays. Because of its higher fluorescence emission intensity, fluo-4 can be used at lower intracellular concentrations, making its use a less invasive practice.

3T3 Cells↗
PubMed2000

Sequencing of the Francisella tularensis strain Schu 4 genome reveals the shikimate and purine metabolic pathways, targets for the construction of a rationally attenuated auxotrophic vaccine.

Francisella tularensis is the etiological agent of tularemia, a serious disease in several Northern hemisphere countries. The organism has fastidious growth requirements and is very poorly understood at the genetic and molecular levels. Given the lack of data on this organism, we undertook the sample sequencing of its genome. A random library of DNA fragments from a highly virulent strain (Schu 4) of F. tularensis was constructed and the nucleotide sequences of 13,904 cloned fragments were determined and assembled into 353 contigs. A total of 1.83 Mb of nucleotide sequence was obtained that had a G+C content of 33.2%. Genes located on plasmids pOM1 and pNFL10, which had been previously isolated from low virulence strains of F. tularensis, were absent but all of the other known F. tularensis genes were represented in the assembled data. F. tularensis Schu4 was able to grow in the absence of aromatic amino acids and orthologues of genes which could encode enzymes in the shikimate pathway in other bacteria were identified in the assembled data. Genes that could encode all of the enzymes in the purine biosynthetic and most of the en- zymes in the purine salvage pathways were also identified. This data will be used to develop defined rationally attenuated mutants of F. tularensis, which could be used as replacements for the existing genetically undefined live vaccine strain.

Bacterial Vaccines↗
PubMed2000

Liver transplantation.

Survival after liver transplantation has steadily improved, in part because of newer immunosuppression, which may offer decreased long-term side effects. Reduction of steroids early in the course of transplant continues to be a goal, with satisfactory results in terms of both risk of rejection and reduction of side effects. Dominating the literature and the press in 1999 was the controversy surrounding the way in which livers are allocated. Regulation by the federal government was proposed to change the way the United Network of Organ Sharing distributes and allocates livers. Prompted by the shortage of organs, living-donor liver transplantation has blossomed. Continued experience in pediatric patients has shown excellent survival rate and quality of life. In adults, further experience is being gained with respect to the use of right lobes for transplantation. Early data suggest that this is a potential alternative to cadaveric transplantation in adults, with acceptable risk to the donor. Despite advances made in improving the technical aspects of transplantation, recurrent disease remains a significant issue. Lamivudine appears to be a potent inhibitor of hepatitis B virus DNA replication after liver transplantation, although resistance remains a significant problem. Further review of transplantation for hepatitis C virus is encouraging, with excellent five-year survival rate. However, studies evaluating the evolution of fibrosis in these patients throw caution on those results, showing increased progression to cirrhosis over time. Further follow-up of these patients is needed to more accurately assess long-term impact of hepatitis C on morbidity and mortality rates after liver transplantation.

Journal Article↗
PubMed2000

Evaluating the effects of functional communication training in the presence and absence of establishing operations.

We conducted functional analyses of aberrant behavior with 4 children with developmental disabilities. We then implemented functional communication training (FCT) by using different mands across two contexts, one in which the establishing operation (EO) that was relevant to the function of aberrant behavior was present and one in which the EO that was relevant to the function of aberrant behavior was absent. The mand used in the EO-present context served the same function as aberrant behavior, and the mand used in the EO-absent context served a different function than the one identified via the functional analysis. In addition, a free-play (control) condition was conducted for all children. Increases in relevant manding were observed in the EO-present context for 3 of the 4 participants. Decreases in aberrant behavior were achieved by the end of the treatment analysis for all 4 participants. Irrelevant mands were rarely observed in the EO-absent context for 3 of the 4 participants. Evaluating the effectiveness of FCT across different contexts allowed a further analysis of manding when the establishing operations were present or absent. The contributions of this study to the understanding of functional equivalence are also discussed.

Adolescent↗
PubMed2000

Correlations among p53, Her-2/neu, and ras overexpression and aneuploidy by multiparameter flow cytometry in human breast cancer: evidence for a common phenotypic evolutionary pattern in infiltrating ductal carcinomas.

Human solid tumors develop multiple genetic abnormalities that accumulate progressively in individual cells during the course of tumor evolution. We sought to determine whether there are specific sequences of occurrence of these progressive evolutionary changes in human breast cancers by performing correlated cell-by-cell measurements of cell DNA content, p53 protein, Her-2/neu protein, and ras protein by multiparameter flow cytometry in 56 primary tumor samples obtained at surgery. In addition, p53 allelic loss and Her-2/neu gene amplification were determined by fluorescence in situ hybridization in cells from the same samples. We reasoned that if there is a specific order in which genetic changes occur, the same early changes would be found consistently in the cells with the fewest abnormalities. We reasoned further that late-developing abnormalities would not occur alone in individual cells but would almost always be found together with the early changes inherited by the same cells. By these criteria, abnormalities involving p53 generally occurred early in the course of development of invasive breast cancers, whereas ras protein overexpression was found to be a late-occurring phenomenon. Within individual tumors, cellular p53 overexpression was often observed alone in individual cells, whereas ras protein overexpression was rarely observed in the absence of p53 overexpression and/or Her-2/neu overexpression in the same cells. Furthermore, the intracellular level of each abnormally expressed protein was found to increase progressively as new abnormalities were acquired. Infiltrating ductal carcinomas exhibited characteristic phenotypic patterns in which p53 allelic loss and/or p53 protein overexpression, Her-2/neu amplification and/or overexpression, aneuploidy, and ras overexpression accumulated within individual cells. However, this pattern was not a prominent feature of lobular breast cancers. All six lobular breast cancers studied were diploid. p53 allelic loss and/or early p53 overexpression, and late ras cooverexpression in the same cells were less common in lobular breast cancers than in infiltrating ductal carcinomas. Although Her-21neu overexpression was a common finding in lobular breast cancers, Her-2/neu amplification was not observed in these tumors.

Aneuploidy↗
PubMed2000

Bitemarks in chocolate: a case report.

Police investigating a theft from a chocolate factory recovered three pieces of chocolate with irregular fractured surfaces displaying a pattern of marks made by human teeth. A highly accuracy dental impression material was used to prepare casts of these marks which were examined and photomicrographed, confirming that they had in fact been produced by human teeth. Casts and photomicrographs of the suspect's teeth were made in order to record the fine details of the casts of the dentition. Unique characteristics evident on these casts included a small notch on the incisal edge of the upper right lateral incisor, wear facets on the incisal edges of the upper central incisors and on the lower right lateral incisor and a space of approximately 1.5 mm between the upper left central incisor and lateral incisor which was rotated about 20 degrees distally. Both direct and photomicrographic comparisons between the casts of the chocolates and of the suspect's dentition revealed correspondence between their unique characteristics.

Bites, Human↗
PubMed1999

Early dipyridamole (99m)Tc-sestamibi single photon emission computed tomographic imaging 2 to 4 days after acute myocardial infarction predicts in-hospital and postdischarge cardiac events: comparison with submaximal exercise imaging.

BACKGROUND: Because of its brief hemodynamic effects and minor effect on determinants of myocardial oxygen demand, vasodilator stress myocardial perfusion imaging (MPI) can be applied very early after acute myocardial infarction (AMI) for risk stratification, allowing management decisions to be made earlier and thus potentially shortening hospitalization stays, reducing costs, and preventing early cardiac events. This multicenter randomized trial compared the prognostic value of early dipyridamole MPI and standard predischarge submaximal exercise MPI in patients who presented with AMI. METHODS AND RESULTS: Patients who presented with their first AMI (n=451) were randomized in a 3:1 ratio to undergo either both an early (day 2 to 4) dipyridamole (99m)Tc-sestamibi MPI study and a predischarge (day 6 to 12) submaximal exercise (99m)Tc-sestamibi MPI study or only the predischarge study. Multivariate predictors of in-hospital cardiac events included nuclear imaging summed stress and summed reversibility scores and peak creatine kinase. For postdischarge cardiac events, multivariate predictors in patients undergoing dipyridamole MPI included only the summed stress, reversibility, and rest imaging scores and anterior MI. For a given summed stress score, the interaction of reversibility score further improved the predictive value. Dipyridamole MPI showed better risk stratification than submaximal exercise MPI. CONCLUSIONS: Dipyridamole MPI very early after MI predicts early and late cardiac events, with superior prognostic value compared with submaximal exercise imaging. The extent and severity of the stress defect and reversibility of the defect were the most important predictors of cardiac death and recurrent MI. This technique can allow management decisions to be made earlier with regard to AMI patients and could have important economic impact if applied widely.

Dipyridamole↗