PubMed Health⌕ Search

Biomedical subjects

E A Brown

Publications and source records attributed to E A Brown.

At least 19 recordsLinked to original sources
PubMed1992

Why do human hepatitis viruses replicate so poorly in cell cultures?

The five viruses which classically cause hepatitis in man represent diverse families of viruses and share in common only a striking hepatotropism and substantial restrictions to replication in conventional cell cultures. Hepatitis A virus is unique among these viruses in that it is amenable to propagation in cell culture, but replication of this virus is much slower and less efficient than replication of other picornaviruses. This probably reflects less efficient cap-independent viral translation, as well as restrictions at other points in the replication cycle. We speculate that the significantly restricted replication of hepatitis viruses in cell culture reflects evolutionary forces controlling their transmission and propagation through human populations.

Base Sequence↗
PubMed1992

Secondary structure of the 5' nontranslated regions of hepatitis C virus and pestivirus genomic RNAs.

The RNA genomes of human hepatitis C virus (HCV) and the animal pestiviruses responsible for bovine viral diarrhea (BVDV) and hog cholera (HChV) have relatively lengthy 5' nontranslated regions (5'NTRs) sharing short segments of conserved primary nucleotide sequence. The functions of these 5'NTRs are poorly understood. By comparative sequence analysis and thermodynamic modeling of the 5'NTRs of multiple BVDV and HChV strains, we developed models of the secondary structures of these RNAs. These pestiviral 5'NTRs are highly conserved structurally, despite substantial differences in their primary nucleotide sequences. The assignment of similar structures to conserved segments of primary nucleotide sequence present in the 5'NTR of HCV resulted in a model of the secondary structure of the HCV 5'NTR which was refined by determining sites at which synthetic HCV RNA was cleaved by double- and single-strand specific RNases. These studies indicate the existence of a large conserved stem-loop structure within the 3' 200 bases of the 5'NTRs of both HCV and pestiviruses which corresponds to the ribosomal landing pad (internal ribosomal entry site) of HCV. This structure shows little relatedness to the ribosomal landing pad of hepatitis A virus, suggesting that these functionally similar structures may have evolved independently.

Animals↗
PubMed1992

Genetic, antigenic and biological differences between strains of hepatitis A virus.

Recent studies have documented a considerable degree of genetic divergence among wild-type hepatitis A virus (HAV) strains recovered from different geographical locations. Human HAV strains can be grouped into four genotypes (I, II, III and VII) and unique simian strains belong to three additional genotypes (IV, V and VI). Between each of these genotypes, the nucleotide sequence varies at 15-25% of base positions in the P1 region. Despite this, there is good evidence that most, if not all, human strains of HAV are closely related antigenically. In contrast, although simian strains recovered from Old World monkeys are cross-reactive in immunoassays employing polyclonal antibodies, these strains have significant antigenic differences from human HAV strains. Nonetheless, because biological differences in the host range of these strains apparently preclude significant human infection, this is unlikely to pose a problem in controlling HAV infections with active immunization. Inactivated and attenuated vaccines produced from genotype I human strains (HM175 or CR326) are likely to provide protection against all relevant human HAV strains.

Animals↗
PubMed1992

Prevalence of antibodies to hepatitis C in dialysis patients and transplant recipients with possible routes of transmission.

The prevalence of hepatitis C infection and possible predisposing factors was assessed in a renal unit. Of 343 patients at our renal dialysis centre, 37 (10.8%) were anti-HCV positive by a 1st-generation assay (ELISA, Ortho/Chiron) and confirmed positive in 35 (10.2%) with a 2nd-generation test (UBI, New York). Anti-HCV positivity was significantly associated with: duration of renal replacement therapy (P < 0.0001); quantity of blood transfused (P < 0.002); duration of hospital haemodialysis (P = 0.0001); duration with a functional renal transplant (P = 0.039); and aspartate aminotransferase (P < 0.0001). Logistic regression determined the following variables to be independent risk factors: duration of renal replacement therapy with a relative risk of 34.3 for 5-9 years and 87.4 when the duration was in excess of 10 years; renal transplant for less than 1 year (relative risk of 5.0); transfusion in excess of 50 units of blood (relative risk of 11.6). Clinical assessment of anti-HCV-positive patients revealed peripheral signs of chronic liver disease in 40%, hepatomegaly in 34%, and splenomegaly in 9%. This prevalence of hepatitis C infection is similar to other European and North American centres, but contrasts with low prevalence rates reported from dialysis populations in the UK. It adds further support for routine screening of blood and possibly organ donors and implementation of further infection control measures in dialysis centres.

Adult↗
PubMed1992

Lipid and lipoprotein (a) concentrations in renal transplant patients.

Lipid and lipoprotein concentrations, including lipoprotein (a), were measured in 67 clinically stable renal allograft recipients and compared with age- and sex-matched controls. Median lipoprotein (a) concentrations were significantly elevated in the transplant group (P = 0.048), with the distribution of apoprotein (a) isoforms being similar between the two groups. The transplant group also demonstrated significant elevations in cholesterol (P less than 0.0001), triglycerides (P = 0.0007) and low-density lipoprotein cholesterol (P less than 0.0001). There was no significant difference in high-density lipoprotein cholesterol concentrations between the groups although there was the expected tendency for higher values in females. Lipoprotein abnormalities are common following renal transplantation and these patients also demonstrate elevated lipoprotein (a) values. This unique lipoprotein is known to be atherogenic and may contribute to the development of vascular disease, which is a common mode of death in these patients.

Adolescent↗
PubMed1992

Quantification of the degradation products of sevoflurane in two CO2 absorbants during low-flow anesthesia in surgical patients.

Sevoflurane, a new inhalational anesthetic agent has been shown to produce degradation products upon interaction with CO2 absorbants. Quantification of these sevoflurane degradation products during low-flow or closed circuit anesthesia in patients has not been well evaluated. The production of sevoflurane degradation products was evaluated using a low-flow anesthetic technique in patients receiving sevoflurane anesthesia in excess of 3 h. Sevoflurane anesthesia was administered to 16 patients using a circle absorption system with O2 flow of 500 ml/min and average N2O flow of 273 ml/min. Preoperative and postoperative hepatic and renal function studies were performed. Gas samples were obtained from the inhalation and exhalation limbs of the anesthetic circuit for degradation product analysis and analyzed by gas chromatography/mass spectrometry for four degradation products. The first eight patients received sevoflurane anesthesia using soda lime, and the following eight patients received anesthesia using baralyme as the CO2 absorbant. CO2 absorbant temperatures were measured during anesthesia. Of the degradation products analyzed, only one compound [fluoromethyl-2, 2-difluoro-1-(trifluoromethyl) vinyl ether], designated compound A, was detectable. Concentrations of compound A increased during the first 4 h of anesthesia with soda lime and baralyme and declined between 4 and 5 h when baralyme was used. Mean maximum inhalation concentration of compound A using baralyme was 20.28 +/- 8.6 ppm (mean +/- SEM) compared to 8.16 +/- 2.67 ppm obtained with soda lime, a difference that did not reach statistical significance. A single patient achieved a maximal concentration of 60.78 ppm during low-flow anesthesia with baralyme. Exhalation concentrations of compound A were less than inhalation concentrations, suggesting patient uptake.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1992

Mutations within the 5' nontranslated region of hepatitis A virus RNA which enhance replication in BS-C-1 cells.

Passage of human hepatitis A virus (HAV) in cell culture results in attenuation of the virus as well as progressive increases in the efficiency of virus replication in cell culture. Because the presence of identical mutations within the 5' nontranslated regions (5'NTRs) of several independently isolated cell culture-adapted HAV variants suggests that the 5'NTR may play a role in determining this change in virus host range, we constructed chimeric infectious cDNA clones in which portions of the 5'NTR of cell culture-adapted HM175/p35 virus were replaced with cDNA from either wild-type virus (HM175/wt) or a second independently isolated, but closely related cell culture-adapted virus (HM175/p16). Substitution of the complete 5'NTR of HM175/p35 with the 5'NTR of HM175/wt resulted in virus with very small replication foci in continuous African green monkey kidney (BS-C-1) cells, indicating that 5'NTR mutations in HM175/p35 virus are required for optimal growth in these cells. A chimera with the 5'NTR sequence of HM175/p16 retained the large foci of HM175/p35 virus, while the growth properties of other viruses having chimeric 5'NTR sequences indicated that mutations at bases 152 and/or 203 to 207 enhance replication in BS-C-1 cells. These findings were confirmed in one-step growth experiments, which also indicated that radioimmunofocus size is a valid measure of virus replication competence in cell culture. An additional mutation at base 687 of HM175/p16 had only a minor role in enhancing growth. In contrast to their effect in BS-C-1 cells, these 5'NTR mutations did not enhance replication in continuous fetal rhesus monkey kidney (FRhK-4) cells. Thus, mutations at bases 152 and/or 203 to 207 enhance the replication of HAV in a highly host cell-specific fashion.

Animals↗
PubMed1992

Pharmacokinetics of ciprofloxacin and vancomycin in patients with acute renal failure treated by continuous haemodialysis.

To determine appropriate doses of ciprofloxacin and vancomycin for septic patients with acute renal failure (ARF) treated by continuous arteriovenous and venovenous haemodialysis, (CAVHD/CVVHD), we performed pharmacokinetic studies in patients receiving these antibiotics. All patients were treated by CAVHD/CVVHD using Hospal AN69S 0.43 m2 filters and Fresenius 1.5% peritoneal dialysis fluid at dialysate flow rates (Qd) of 1 and 2 l/h. Patients received ciprofloxacin 200 mg i.v. 12-hourly (n = 6) or 8-hourly (n = 5); vancomycin 1 g i.v. was administered to 10 patients approximately every 48 h to maintain therapeutic plasma levels. For ciprofloxacin, volume of distribution (Vdarea) was 136.5 +/- 9.81, terminal elimination half-life (t1/2) 6.4 +/- 0.8 h, and total body clearance (TBC) 264.3 +/- 22.9 ml/min (mean +/- SEM). Mean sieving coefficient (S/C) was 0.76 +/- 0.05 and filter clearances at Qd 1 and 2 l/h were 16.2 +/- 1.9 and 19.9 +/- 1.1 ml/min respectively. For vancomycin, Vdarea was 60.7 +/- 5.11, t1/2 24.7 +/- 2.6 h and TBC 31.0 +/- 4.6 ml/min. Mean S/C was 0.66 +/- 0.08 and filter clearances at Qd 1 and 2 l/h 12.1 +/- 2.0 and 16.6 +/- 2.0 ml/min. These data suggest that patients with ARF treated by CAVHD/CVVHD should be given ciprofloxacin 200 mg i.v. 8-12-hourly and vancomycin every 48 h.

Acute Kidney Injury↗
PubMed1991

Genetic variability within the 5' nontranslated region of hepatitis A virus RNA. Implications for secondary structure and function.

The RNA genome of hepatitis A virus (HAV) contains a lengthy and relatively well conserved 5' nontranslated region (5'NTR). In other picornaviruses, the 5'NTR has been shown to have important functions related to the initiation of viral translation and replication of viral RNA, functions which are critically dependent on both primary and secondary RNA structure. We have utilized a phylogenetic approach to construct a model of the secondary structure of the HAV 5'NTR. By comparing the nucleotide sequences of genetically divergent simian and human HAV strains, we identified a series of covariant nucleotide substitutions which are predictive of conserved, double-stranded helical structures within the 5'NTR, and which thus permitted improved thermodynamic modeling of the secondary structure. The model was further refined based on the observed sites of cleavage of synthetic RNA by single- and double-strand specific RNAses. The results of these studies suggest that the 5'NTR of HAV has a general organization similar to that of other picornaviruses, and shares certain structural features and perhaps specific functions with the 5'NTRs of the cardioviruses and aphthoviruses.

Base Composition↗
PubMed1991

A multistate outbreak of Norwalk virus gastroenteritis associated with consumption of commercial ice.

Between 19 and 27 September 1987, a cluster of outbreaks of gastrointestinal illness occurred among persons who had attended a museum fund-raiser in Wilmington, Delaware and an intercollegiate football game in Philadelphia. A survey of four groups attending these events showed that 31% (191/614) became ill. Altogether, those who consumed ice were 12 times more likely to experience either vomiting or diarrhea than those who did not (attack rate, 55% vs. 4%, P less than .001). Ice consumed at the events was traced to a manufacturer in southeastern Pennsylvania whose wells had been contaminated when flooded by a nearby creek after a torrential rainfall on 8 September. Of 19 affected persons tested within 1 week of exposure, 13 (68%) had at least a fourfold rise in antibody titer to the Norwalk virus. This report, the first to document an association of contaminated commercial ice with Norwalk gastroenteritis should prompt reassessment of government regulation of the production and distribution of ice.

Antibodies, Viral↗
PubMed1991

Pharmacokinetics of cefuroxime and ceftazidime in patients with acute renal failure treated by continuous arteriovenous haemodialysis.

To determine appropriate doses of cefuroxime and ceftazidime for septic patients with acute renal failure (ARF) treated by continuous arteriovenous haemodialysis (CAVHD), we performed pharmacokinetic studies in patients receiving these antibiotics. All patients were treated by CAVHD using Hospal AN69S 0.43 m2 filters and Fresenius 1.5% peritoneal dialysis fluid at dialysate flow rates (Qd) of 1 and 2 l/h. Patients received cefuroxime 500 mg (n = 11) or 750 mg (n = 1), or ceftazidime 500 mg (n = 9) i.v. 12-hourly and all studies were done at steady-state. For cefuroxime, volume of distribution (Vdarea) was 22.8 +/- 3.5 l, terminal elimination half-life (t1/2) 12.6 +/- 2.2 h and total body clearance (TBC) 22.3 +/- 3.0 ml/min (mean +/- SEM). Mean sieving coefficient (SC) was 0.90 +/- 0.12 and filter clearances at Qd 1 and 2 l/h were 14.0 +/- 2.3 and 16.2 +/- 3.4 ml/min respectively. For ceftazidime, Vdarea was 31.1 +/- 6.5 l, t1/2 14.7 +/- 3.3 h, and TBC 24.8 +/- 0.8 ml/min. Mean SC was 0.86 +/- 0.03, and filter clearances at Qd 1 and 2 l/h 13.1 +/- 1.2 and 15.2 +/- 1.5 ml/min. Satisfactory plasma concentrations of both antibiotics were maintained in all patients during treatment. These data suggest that cefuroxime 500-750 mg and ceftazidime 500 mg 12-hourly are suitable doses for patients with ARF treated by CAVHD.

Acute Kidney Injury↗
PubMed1991

Amino acid clearances and daily losses in patients with acute renal failure treated by continuous arteriovenous hemodialysis.

OBJECTIVE: To determine daily amino acid and total protein losses in patients with acute renal failure receiving total parenteral nutrition (TPN) during treatment by continuous arteriovenous hemofiltration with hemodialysis (CAVHD). DESIGN: Prospective, nonrandomized study. SETTING: Patients in the ICU of a regional nephrology referral center. PATIENTS: Eight clearance studies of individual amino acids were performed in six patients with acute renal failure receiving TPN. Daily nitrogen intake was 9 g (one patient), 14 g (two patients), and 18 g (three patients). The clearances of individual amino acids were measured at two dialysis flow rates to calculate daily amino acid and total proten losses. RESULTS: Amino acid clearance rates ranged from 7.8 +/- 2.2 (glutamic acid) to 25.2 +/- 4.8 mL/min (3-methylhistidine) at a dialysate flow rate of 1 L/hr and from 13.6 +/- 1.7 (tryptophan) to 33.7 +/- 4.3 mL/min (3-methylhistidine) at a dialysate flow rate of 2 L/hr. These results represent daily amino acid losses of 1.5 +/- 0.4% (glutamic acid) to 111.6 +/- 16.6% (tyrosine) of the nutritional input at a dialysate flow rate of 1 L/hr and 2.1 +/- 0.6% (glutamic acid) to 145.8 +/- 17.8% (tyrosine) at a dialysate flow rate of 2 L/hr. Total losses would represent 8.9 +/- 1.2% and 12.1 +/- 2.2%, respectively, of the daily protein input. CONCLUSIONS: These studies confirm that amino acid clearances are relatively high during CAVHD and daily losses should therefore be considered.

Acute Kidney Injury↗
PubMed1991

The 5' nontranslated region of hepatitis A virus RNA: secondary structure and elements required for translation in vitro.

Although the lengthy 5' nontranslated regions (5'NTRs) of other picornaviral RNAs form highly ordered structures with important functions in viral translation, little is known about the 5'NTR of hepatitis A virus (HAV). We determined the nearly complete 5'NTR nucleotide sequences of two genetically divergent HAV strains (PA21 and CF53) and included these data in a comparative phylogenetic analysis of the HAV 5'NTR. We identified covariant nucleotide substitutions predictive of conserved secondary structures and used this information to develop a model of the 5'NTR secondary structure, which was further refined by thermodynamic predictions and nuclease digestion experiments. According to this model, the 5'NTR comprises six major structural domains. Domains I and II (bases 1 to 95) contain a 5'-terminal hairpin and two stem-loops followed by a single-stranded and highly variable pyrimidine-rich tract (bases 96 to 154). The remainder of the 5'NTR (domains III to VI, bases 155 to 734) contains several complex stem-loops, one of which may form a pseudoknot, and terminates in a highly conserved region containing an oligopyrimidine tract preceding the putative start codon by 13 bases. To determine which structural elements might function as an internal ribosome entry site, RNA transcripts representing the HAV 5'NTR with progressive 5' deletions were translated in rabbit reticulocyte lysates. The translation product was truncated, unprocessed P1 polyprotein. Removal of the 5'-terminal 354 bases of the 5'NTR had little effect on translation. However, deletion to base 447 slightly decreased translation, while deletion to base 533 almost completely abolished it. These data indicate that sequences 3' of base 355 play an important role in the translation mechanism utilized by genomic-length HAV RNA. Significantly, this region shares several conserved structural features with the internal ribosome entry site element of murine encephalomyocarditis virus.

Animals↗
PubMed1990

Dialysis arthropathy: a clinical, biochemical, radiological and histological study of 36 patients.

Out of a population of 97 haemodialysis patients, 36 patients with dialysis arthropathy were identified. Dialysis arthropathy is a chronic symmetrical polyarthritis which affected 97 per cent of the patients who had been undergoing cuprophane haemodialysis for more than 10 years. It commonly affected the shoulders, hips, hands, knees and wrists, worsening with time and extending to other joints. Fifty-eight per cent of the patients complained of morning stiffness and 47 per cent complained of exacerbation of shoulder pain during or after haemodialysis. Half of the patients also suffered from carpal tunnel syndrome, which recurred and was associated with a long-lasting disability. The most common radiological abnormality was periarticular bone cysts, followed by articular erosions and a destructive spondyloarthropathy, but clinical symptoms were more common than radiological signs. Patients with dialysis arthropathy had a higher C-reactive protein level than patients without arthropathy (18.6 mg/l versus 11.4 mg/l), indicative of an inflammatory process. Some of the clinical manifestations of the disease correlated with levels of C-reactive protein and ferritin. Serum ferritin levels correlated strongly with the units of blood transfused in the past five years (RS = 0.83), and the logarithm of ferritin level correlated weakly with C-reactive protein (r = 0.32). Haemarthroses were documented in 19 per cent of patients. Mean serum beta 2-microglobulin was elevated in the patients with (57.3 mg/l) and without arthropathy (50.7 mg/l), and there was no difference in the parathormone or aluminium levels between these groups. Articular tissue was obtained in 25 patients; beta 2-microglobulin amyloid was present in 24. Larger deposits were present in the capsular tissue, and these appeared to replace collagen bundles in eight cases. Amyloid deposits replaced the lining layer in six cases. It is likely therefore that amyloid disrupts normal joint function by replacing normal joint tissue. Mild chronic synovitis with haemosiderin deposition were found in approximately 60 per cent of cases. These findings suggest that amyloid derived from beta 2-microglobulin has a primary role in the pathogenesis of dialysis arthropathy, but there was also evidence of inflammatory processes. It is suggested that iron overload or haemarthroses might contribute to the inflammation, but other factors, such as dialysis-related bioincompatibility reactions, may also have a role.

Adult↗
PubMed1990

A relationship between L-serine degradation and methionine biosynthesis in Escherichia coli K12.

While wild-type Escherichia coli K12 cannot grow with L-serine as carbon source, two types of mutants with altered methionine metabolism can. The first type, metJ mutants, in which the methionine biosynthetic enzymes are expressed constitutively, are able to grow with L-serine as carbon source. Furthermore, a plasmid carrying the metC gene confers ability to grow on L-serine. These observations suggest that in these mutants, L-serine deamination may be a result of a side-reaction of the metC gene product, cystathionine beta-lyase. The second type is exemplified by two newly isolated strains carrying mutations mapping between 89.6 and 90 min. These mutants use L-serine as carbon source, and also require methionine for growth with glucose at 37 degrees C and above. The phenotypes of the new mutants resemble those of both met and his constitutive mutants in some respects, but have been differentiated from both of them.

Chromosome Mapping↗