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D J Brown

Publications and source records attributed to D J Brown.

At least 55 records · Page 3Linked to original sources
PubMed2000

Class 1 integron-borne, multiple-antibiotic resistance encoded by a 150-kilobase conjugative plasmid in epidemic vibrio cholerae O1 strains isolated in Guinea-Bissau.

In the 1996-1997 cholera epidemic in Guinea-Bissau, surveillance for antimicrobial resistance showed the emergence of a multidrug-resistant strain of Vibrio cholerae O1 during the course of the epidemic. The strain was resistant to ampicillin, erythromycin, tetracycline, furazolidone, aminoglycosides, trimethoprim, and sulfamethoxazole. Concomitant with the emergence of this strain, we observed a resurgence in the number of registered cholera cases as well as an increase in the case fatality rate from 1.0% before the emergence of the multiple-drug-resistant strain to 5.3% after the emergence of the strain. Our study shows that the strain contained a 150-kb conjugative multiple-antibiotic resistance plasmid with class 1 integron-borne gene cassettes encoding resistance to trimethoprim (dhfrXII) and aminoglycosides [ant(3")-1a]). The finding of transferable resistance to almost all of the antibiotics commonly used to treat cholera is of great public health concern. Studies should be carried out to determine to what extent the strain or its resistance genes have been spread to other areas where cholera is endemic.

Anti-Bacterial Agents↗
PubMed2000

Everett Kinsey lecture. The elusive causes of keratoconus: a working hypothesis.

PURPOSE: Keratoconus is a diseasethat has been recognized clinically for many years. However, it is only more recently that a better understanding has been achieved in the area of keratoconus pathogenesis. The purpose of this paper is to summarize the completed research, review ongoing studies, and present a hypothesis for keratoconus pathology. METHODS: We used immunochemistry and molecular techniques to characterize keratoconus corneas. RESULTS AND CONCLUSIONS: Our hypothesis attempts to incorporate many of the recognized biochemical and molecular abnormalities found in the keratoconus corneas. Our hypothesis states: 1) there is abnormal processing of the free radicals and superoxides within the keratoconus corneas; 2) there is a build-up of destructive aldehydes or peroxynitrites within the corneas; 3) the cells that are damaged irreversibly undergo the process of apoptosis; and 4) the cells that are damaged reversibly undergo wound healing or repair. As part of the wound healing process, various degradative enzymes and wound healing factors are upregulated, which leads to focal areas of corneal thinning and fibrosis. Future studies will be directed to testthis working hypothesis and determine if these theories are valid.

Apoptosis↗
PubMed1999

A phase II safety and efficacy study of amprenavir in combination with zidovudine and lamivudine in HIV-infected patients with limited antiretroviral experience. Amprenavir PROAB2002 Study Team.

OBJECTIVE: To determine the safety and efficacy of amprenavir (APV) in combination with lamivudine (3TC) and zidovudine (ZDV). DESIGN: Multicenter, randomized, partially blinded trial. SETTING: Nine study sites in the United States and Europe. PATIENTS: A group of 84 HIV-infected subjects with no prior 3TC or protease inhibitor therapy experience, CD4 cell count > or = 150 x 10(6) cells/l, and plasma HIV RNA > 10000 copies/ml. INTERVENTIONS: 3TC/ZDV with one of three doses of APV (900, 1050, or 1200 mg) versus 3TC/ZDV with 1050 mg placebo. All medications were dosed twice daily. The 1050 mg placebo and the APV 1050 mg dose were administered blinded. After 12 weeks, APV 1050 mg was substituted for 1050 mg placebo in the control group and the blind was maintained. MAIN OUTCOME MEASURES: Reduction in plasma HIV RNA from baseline; proportion of subjects with plasma HIV RNA < 400 copies/ml; and an increase in CD4 cell count from baseline. RESULTS: During the initial 12-week study period, APV/3TC/ZDV-treated subjects had greater viral suppression than the group receiving two nucleosides. By 48 weeks, 89% of subjects in the group taking the highest APV dose (1200 mg) had plasma HIV RNA < 400 copies/ml while 42% of the 900 mg group and 60% of the 3TC/ZDV group (1050 mg APV added at week 12) had plasma HIV RNA < 400 copies/ml using an as-treated analysis. By 60 weeks, 86% of subjects in the APV 1200 mg group had plasma HIV RNA < 400 copies/ml in the as-treated analysis, while 25% (900 mg), 43% (1050 mg), and 20% (1200 mg) of subjects had viral load <400 copies/ml in a strict intent-to-treat analysis owing to treatment discontinuations. Median CD4 cell count increases at week 60 were highest for the three treatment groups who received APV throughout the study, by intent-to-treat and as-treated analyses. The most common adverse events considered to be possibly drug related were nausea, rash, oral paresthesia, diarrhea, and fatigue. CONCLUSIONS: Treatment with APV, dosed at 1200 mg twice daily in combination with 3TC/ZDV, resulted in sustained viral suppression. This combination represents a potent alternative initial antiretroviral regimen for protease inhibitor-naive individuals.

Adult↗
PubMed1999

Nematode transmission of tobacco rattle virus serves as a bottleneck to clear the virus population from defective interfering RNAs.

DI7 is a defective interfering RNA derived from RNA 2 of tobacco rattle tobravirus (TRV) isolate PpK20. Tobacco was transformed with DI7 cDNA fused to the CaMV 35S promoter. Upon infection of the transgenic plants with TRV isolate PpK20 or the serologically unrelated isolate PaY4, the transgenic DI7 RNA started to accumulate at high levels and strongly interfered with accumulation of wild-type (wt) RNA 2. When DI7 transgenic plants infected with isolate PpK20 were used as source plants in nematode-transmission experiments, the vector Paratrichodorus pachydermus efficiently transmitted virus to healthy bait plants. However, the nematodes transmitted only the wt virus present in the transgenic source plants, whereas virus particles containing the abundant, accumulated DI7 RNA were excluded from transmission. Evidence is presented that wt RNA 2 and DI7 RNA are encapsidated in cis by their encoded CPs, which are known to be functional and nonfunctional in transmission, respectively. This mechanism would result in defective interfering RNAs, which rapidly arise after mechanical transmission of the virus in the laboratory, being eliminated from tobraviruses under natural field conditions. Also this mechanism which acts with nematode transmitted virus isolates contrasts with that of vector-transmission of defective potyviruses and luteoviruses by wt helper viruses.

Animals↗
PubMed1999

Assessment of degree of oxidative stress and antioxidant concentrations in dogs with idiopathic dilated cardiomyopathy.

OBJECTIVE: To assess degree of oxidative stress and antioxidant concentrations in dogs with idiopathic dilated cardiomyopathy (IDCM). DESIGN: Prospective study. ANIMALS: 18 dogs with IDCM and 16 healthy control dogs. PROCEDURE: Concentrations of malondialdehyde (an indicator of oxidative stress); vitamins A, C, and E; glutathione peroxidase; and superoxide dismutase were measured. RESULTS: Glutathione peroxidase concentration was significantly increased in dogs with IDCM, compared with control dogs. Vitamin A and superoxide dismutase concentrations were not significantly different between groups. A negative correlation was found between disease severity and plasma vitamin E concentration. Disease severity was not correlated with concentrations of other antioxidants. Medications did not significantly affect oxidant or antioxidant concentrations. CONCLUSIONS AND CLINICAL RELEVANCE: The change in glutathione peroxidase concentration and the correlation between vitamin E concentration and disease severity suggest that the oxidant-antioxidant system may play a role in development of IDCM.

Animals↗
PubMed1999

Enhanced expression of a transmembrane phosphotyrosine phosphatase (LAR) in keratoconus cultures and corneas.

The purpose of the study was to identify genes that are differentially expressed in normal versus keratoconus corneas. Total RNA isolated from corneal stromal cell cultures was reverse-transcribed and then amplified by the polymerase chain reaction (PCR) using defined, arbitrary primers. The products were displayed on polyacrylamide gels and bands that were differentially expressed were excised, re-amplified and subcloned. The resulting clones were sequenced and utilized as probes for Northern blots with cultured cell RNA or Southern blots of corneal cDNA. One of the products that appeared to be more highly expressed in keratoconus cultures and corneas displayed 100% homology with leukocyte common antigen related protein (LAR), a transmembrane phosphotyrosine phosphatase. Western analyses and immunohistochemistry with monoclonal and/or polyclonal antibodies to LAR were used to examine keratocyte cultures and fresh frozen normal, keratoconus and pseudophakic bullous corneas. We identified a gene product with 100% homology to LAR that is expressed at the RNA level in keratoconus corneas and cell cultures but is found only at low or undetectable levels in normal cultures and normal and pseudophakic bullous keratopathy (PBK) corneas. By Western blotting and immunofluorescence with specific LAR antibodies, the protein was identified in keratoconus stromal cell cultures but not in normal cultures. When fresh frozen tissue was examined, LAR protein was localized to numerous stromal cells throughout central keratoconus corneas, while no central staining was seen in normal or bullous keratopathy corneas. LAR, a transmembrane phosphotyrosine phosphatase, is more highly expressed in keratoconus corneas and stromal cell cultures as demonstrated by differential display, Northern analyses, immunohistochemistry and Western blotting.

Adolescent↗
PubMed1999

In vivo development of Theileria annulata: major changes in efferent lymph following infection with sporozoites or allogeneic schizont-infected mononuclear cells.

The object of these experiments was to study the pathogenesis and kinetics of Theileria annulata infection in the efferent lymph of the draining lymph nodes of calves. Efferent lymphatics of calves were cannulated prior to infection with T. annulata sporozoite or an allogeneic schizont cell line. Potentially lethal sporozoite challenge induced cell shut-down from days 4-6 and then a massive increase in output of blasting cells (both infected and non-infected) in the efferent lymph. The rate of lymph flow and total cell output increased to 5 to 10-fold from day 6 onwards. Sporozoites were never isolated from the efferent lymph. However, large numbers of parasite-infected cells were seen in efferent lymph from the sixth day of infection. The animals inoculated with an allogeneic T. annulata-infected cell line exhibited only a small increase in flow rate and cell output. Parasite-infected cells of recipient origin were seen in efferent lymph from day 11 onwards. However, cells of donor origin were never isolated either from efferent lymph or peripheral blood. Thus the parasite transferred from the inoculated donor cell line to the cells of the recipient before schizonts appeared in efferent lymph.

Animals↗
PubMed1999

Phage type conversion in Salmonella enterica serotype Enteritidis caused by the introduction of a resistance plasmid of incompatibility group X (IncX).

The plasmid pOG670, a 54 kb, conjugative plasmid that specifies resistance to ampicillin and kanamycin and belonging to the incompatibility group X (IncX), was transferred into 10 isolates of Salmonella enterica serotype Enteritidis belonging to 10 different phage types (PT1, 2, 3, 4, 8, 9, 9b, 10, 11 and 13). Acquisition of the plasmid by these strains did not result in the loss of any resident plasmids but resulted in phage type conversion in 8 of the 10 strains (PT1, 2, 4, 8, 9, 9b, 10 and 11). The observed changes in phage type were found to result from the loss of sensitivity to 3 of the 10 typing phages used (phages 3, 5 and 7). Where the conversion resulted in a change to a defined phage type, both the new and original PTs belonged to the same, previously described, evolutionary lines. Enteritidis PTs 1, 4 and 8, commonly associated with poultry world-wide, were converted to PTs 21, 6 and 13a respectively. The results indicate a different route for phage type conversion Enteritidis from others reported in the literature and, although IncX plasmids are not normally present in PT8 or PT13a, may suggest a possible mechanism/link connecting these phage types.

Animals↗
PubMed1999

Levels of virulence are not determined by genomic lineage of Salmonella enterica serotype Enteritidis strains.

Mouse virulence and the ability to adhere to, and invade cultured MDCK cells were investigated in 38 phage type reference strains of Salmonella enterica serotype Enteritidis and correlated with genomic lineage. The genomic lineage of 11 of the strains was determined in the present study; one IS200 and one ribotype pattern that had not been reported previously were observed. Log c.f.u. in the spleen 10 days post intraperitoneal (i.p.) infection with 3x10(3) bacteria (logVC10) varied between 2.9 and 8.7. The reference strains of PT7 and PT23 were found to be semi-rough and were of low virulence. All other strains possessed smooth LPS. Within each of the two major clonal lines, as well as among phage types outside these, both highly virulent and moderate to low virulent strains were present. While all strains of PT1, PT2 and PT8 were highly virulent, low virulent strains were detected in PT4 and PT13. The ability to adhere to, and invade MDCK cells varied between phage types (adherence between 13 and 61% of the inocula and invasion between 4 and 151% of the adherent cells). The results of the cell culture experiments did not correlate with the results of mouse virulence tests. No correlation between clonal lineage and virulence was found within S. Enteritidis. It seems most likely that some strains have lost some of the essential factors enabling this serotype to cause successful systemic infection.

Animals↗
PubMed1999

Similarities in the genome organization of tobacco rattle virus and pea early-browning virus isolates that are transmitted by the same vector nematode.

Although sequence data have been obtained for several tobravirus isolates, only two of these isolates are nematode-transmissible. Tobacco rattle virus (TRV) PpK20 is transmitted by Paratrichodorus pachydermus, whereas pea early-browning virus (PEBV) TpA56 is transmitted by Trichodorus primitivus. To clarify whether differences in the genome structure of these isolates are relevant to the specificity of interactions with particular vector nematodes, or merely reflect a taxonomic difference between TRV and PEBV, we have sequenced RNA2 of a new isolate of TRV (TpO1) that is transmitted by the same vector nematode as PEBV TpA56 but is not transmitted by the nematode vector of TRV PpK20. TRV TpO1 RNA2 encodes, in 5' to 3' order, a coat protein (CP), a 9K protein, a 2b (29K) protein and a 2c (18K) protein. Amino acid sequence comparison shows that both the CP and 2b proteins of TRV TpO1 resemble more closely the analogous proteins from PEBV TpA56 than those from TRV PpK20. Also, the TRV TpO1 9K protein has similarities with the PEBV 9K protein whereas this protein is lacking in TRV PpK20.

Amino Acid Sequence↗
PubMed1999

Analysis of gene expression in human bullous keratopathy corneas containing limiting amounts of RNA.

PURPOSE: To validate the use of polymerase chain reaction (PCR)-amplified full-length cDNA as a substitute for mRNA in nucleic acid array and gene expression analysis. METHODS: Total RNA was isolated from age-matched normal autopsy corneas and pseudophakic bullous keratopathy (PBK) corneas. Full-length cDNA was generated and PCR amplified using the Smart cDNA synthesis technology. Southern blot analysis of this cDNA was compared with Northern blot analysis of the RNA. Amplified cDNA was used to probe a commercial gene array. By immunohistochemistry, the expression pattern of several adhesion molecules represented on the array was assessed. RESULTS: The cDNA produced by the Smart cDNA system gave results very similar to those of northern blot analysis when examined for beta2-microglobulin, Rab geranylgeranyl transferase, and tenascin-C. This cDNA obtained from normal or PBK corneas was labeled and used to probe a 588 gene array (Clontech). Among other differences, beta6 integrin was detected only with the PBK probe, beta-catenin was markedly elevated in PBK, and beta4 integrin appeared to be reduced in PBK. Immunohistochemical patterns of these proteins were consistent with the hybridization signals on the gene array. CONCLUSIONS: Smart cDNA synthesis and nucleic acid arrays were combined and validated for the first time to identify differential gene expression in normal and diseased corneas. These techniques require very little RNA such as that equivalent to a half of a single cornea, which is useful when the amount of tissue is limiting. Altered expression of adhesive proteins beta6 integrin and beta-catenin may be related to the formation of epithelial bullae and microcystic changes in PBK patients.

Antigens, CD↗
PubMed1998

A stage-specific, parasite-induced, "window" of in vivo interferon-gamma production is associated with pathogenesis in Theileria annulata infection.

The tick-borne protozoan parasite Theileria annulata causes tropical theileriosis, a severe leukoproliferative disease of cattle, which naive susceptible animals fail to control. The parasite infects and transforms macrophages, developing in the local draining lymph node. IFN gamma has been shown to block parasite development in newly infected cells, and inhibits the growth of fully differentiated macroschizont stage-infected cells in vitro. However, the parasite has been found to specifically induce IFN gamma production by T cells and appears to flourish in the face of this T cell-derived response in vivo. Here we show that the production of IFN gamma in vivo is tightly controlled by the parasite. Induction of cytokine production by T cells is not initiated until the parasite has developed beyond the IFN gamma sensitive trophozoite stage. Cytokine production is kept high as infected macrophages develop, and IFN gamma appears to play an active role in maintaining the growth of these cells. Once the infection is fully established, IFN gamma is down regulated, avoiding potential inhibitory effects. Thus by controlling T cell IFN gamma production, the parasite induces a "window" of cytokine expression which promotes its own growth, but avoids potential inhibitory effects of the cytokine.

Animals↗
PubMed1998

Phytotherapeutic approaches to common dermatologic conditions.

In this review, we discuss some common herbal preparations historically used for dermatologic conditions and recent studies that support their use. The traditional practice of topically treating dermatologic conditions with plant-derived medicines predates the cultures of ancient Egypt and remains vital today in the industrialized cultures of both the United States and Europe. Recent scientific studies lend support to some of the claims of herbal practitioners for the safety and efficacy of many herbs. The studies also elucidate, in some cases, the mechanisms by which these herbs act. With the growing interest in alternative and complementary therapies, practitioners need more information. Clinical studies and collected observations will help define specific indications for choice of herbal treatment based on both the skin disorder and the unique characteristics of the patient involved.

Humans↗
PubMed1998

Theileria annulata: the expression of two novel macroschizont antigens on the surface of infected mononuclear cells differs during in vitro attenuation of a virulent cell line.

The first part of this study of the biological mechanisms underlying attenuation of virulent Theileria annulata macroschizont-infected cell lines screened four pairs of T. annulata (Hisar) in vivo- and in vitro-derived macroschizont-infected cell lines (lines) and identified a single in vivo-derived line, which induced lethal tropical theileriosis. The other seven lines were relatively avirulent. Analysis of the clinical, hematological, and parasitological responses of cattle immunized with different passages of the virulent line after in vitro culture showed that it was partly attenuated by passage (p) 50 and avirulent by p130. Clones representing the three glucose phosphate isomerase (GPI) isotypes, which constituted the newly isolated virulent culture, were obtained from p3 by limiting dilution; p50 and p130 consisted of one isotype. The second part of the study raised monoclonal antibodies (MAbs) against macroschizont-infected cells, as reagents for detecting antigenic differences between virulent and avirulent parasites, and identified two MAbs that recognized the surface of infected cells as well as macroschizonts. MAb EU1 recognized an antigen expressed by all the lines tested, whether in vitro- or in vivo-derived, whether uncloned or cloned, and irrespective of extent of subpassage in culture. MAb EU106 recognized an antigen whose expression by the virulent line and its clones disappeared on passage in culture. This antigen was not expressed at all by the avirulent in vitro-derived line prepared with cells from the same calf. Both antigens were expressed by lines infected with other stocks of T. annulata, including two lines known to induce lethal disease. The different profiles of expression of the two novel antigens, recognized by MAbs EU1 and EU106, by the line undergoing attenuation suggest (1) that the two antigens interact differently with the bovine immune system; and (2) that there are two, very different, potential roles for these antibodies in the development of vaccines against T. annulata infections.

Animals↗
PubMed1998

A new cytochrome P450 (CYP30) family identified in the clam, Mercenaria mercenaria.

A full-length clone with sequence similarity to genes in the cytochrome P450 superfamily was isolated from a cDNA library prepared from female Mercenaria mercenaria gonadal tissue. This clone was isolated while screening an expression library with an antibody prepared against a peptide sequence within the ligand-binding region of the murine Ah receptor. Comparison of the predicted amino acid sequence of this clone to those of other cytochrome P450 genes indicated that the closest overall sequence similarity (38%) was to proteins predicted from genes in the CYP3 family. Northern blots indicated the presence of a transcript of the appropriate size (3.0 kb) with homology to the clam cytochrome P450. In vitro translation of the cDNA clone produced a 50.7-kDa protein as determined by SDS-polyacrylamide gel electrophoresis. The in vitro translated protein was not recognized on Western blots by two polyclonal antibodies specific for members of the CYP3 family. Since the degree of similarity to existing cytochrome P450 families was below the 40% level required for membership, and the expressed protein was not recognized by CYP3-specific antibodies, this clam cytochrome P450 cDNA has been placed in a new family, cytochrome P450 30 (CYP30).

Amino Acid Sequence↗
PubMed1998

Localization of TIMP-1, TIMP-2, TIMP-3, gelatinase A and gelatinase B in pathological human corneas.

PURPOSE: Determine the tissue distribution patterns for tissue inhibitors of metalloproteinases (TIMP-1, TIMP-2, TIMP-3), gelatinase A and gelatinase B in normal and pathologic corneas. METHODS: Corneas were examined by immunohistochemistry, using antibodies to TIMP-1, TIMP-2, TIMP-3, gelatinase A or gelatinase B. RESULTS: In normal corneas, TIMP-1 antibody stained the epithelium and endothelium. TIMP-2 and TIMP-3 stained the epithelium, keratocytes and endothelium. Gelatinase A staining was weak and restricted to the epithelial cells. Radial keratotomy scars showed increased staining for TIMP-1 and TIMP-2 around the epithelial cell plug and along the incision. Bullous keratopathy corneas showed TIMP staining patterns similar to normal corneas and increased gelatinase A staining in regions of subepithelial fibrosis. Stromal scars of keratoconus corneas also had increased staining with TIMP-1 and TIMP-2 antibodies. In many keratoconus corneas, the TIMP-3 staining pattern was similar to normal corneas. However, in some keratoconus corneas, when Bowman's layer was missing, the stroma beneath was completely devoid of TIMP-3 antibody staining. No gelatinase B was seen in either the normal or diseased corneas. CONCLUSION: These data suggest that TIMP-1 and TIMP-2 are important for scar formation and corneal remodeling, since they were found in increased amounts at radial keratotomy incision sites and keratoconus scars. The significance of the focal stromal defects in TIMP-3 staining, associated with absence of Bowman's layer on keratoconus corneas, needs to be elucidated. At the stages of disease examined in this study, gelatinase B may not play a significant role in these pathological processes, since it was not seen in any of the corneas examined.

Base Sequence↗