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Biomedical subjects

D Gilbert

Publications and source records attributed to D Gilbert.

At least 55 records · Page 3Linked to original sources
PubMed1999

IgM anti-myeloperoxidase antibody-secreting lymphocytes are present in the peripheral repertoire of lupus mice but rarely differentiate into IgG-producing cells.

Two IgM, kappa anti-myeloperoxidase (MPO) monoclonal antibodies, 6D6 and 9B5, bound to MPO in a solid-phase enzyme-linked immunosorbent assay were derived from the splenocytes of (NZB x NZW) F1 and MRL/lpr-lpr mice, respectively. 6D6 gave a characteristic perinuclear immunofluorescence staining pattern on ethanol-fixed human neutrophils, bound to the native form of MPO by immunoblotting and had a high constant affinity for MPO as demonstrated by real-time specific interaction. 9B5 produced a cytoplasmic immunofluorescence staining pattern, reacted with the heavy chain of MPO and had a low constant affinity for MPO. The heavy-and light-chain variable region genes of monoclonal antibodies (mAb) 6D6 and 9B5 were sequenced and found to be highly homologous to germline genes and to contain negatively charged amino acids in the complementarity determining regions. IgM MPO-binding activity was observed in most BW and MRL/lpr-lpr mouse sera, which may correspond to polyclonal activation of B cells, whereas IgG anti-MPO antibodies could be rarely detected. Thus, this study indicates that (i) BW and MRL/lpr-lpr mice do not delete IgM anti-MPO secreting B cells, do not maintain these B cells in a state of anergy, but most individuals are not able to spontaneously induce the class-switching of this autoantibody population; (ii) IgM anti-MPO antibodies can recognize different epitopes on MPO and produce different immunofluorescence staining pattern on ethanol-fixed human neutrophils, as demonstrated by the immunochemical properties of the two lupus-mouse derived mAb.

Amino Acid Sequence↗
PubMed1999

Motif-based searching in TOPS protein topology databases.

MOTIVATION: TOPS cartoons are a schematic ion of protein three-dimensional structures in two dimensions, and are used for understanding and manual comparison of protein folds. Recently, an algorithm that produces the cartoons automatically from protein structures has been devised and cartoons have been generated to represent all the structures in the structural databank. There is now a need to be able to define target topological patterns and to search the database for matching domains. RESULTS: We have devised a formal language for describing TOPS diagrams and patterns, and have designed an efficient algorithm to match a pattern to a set of diagrams. A pattern-matching system has been implemented, and tested on a database derived from all the current entries in the Protein Data Bank (15,000 domains). Users can search on patterns selected from a library of motifs or, alternatively, they can define their own search patterns. AVAILABILITY: The system is accessible over the Web at http://tops.ebi.ac.uk/tops

Algorithms↗
PubMed1998

Early anti-nucleosome autoantibodies from a single MRL+/+ mouse: fine specificity, V gene structure and pathogenicity.

In systemic lupus erythematosus, the nucleosome assumes a central role in the autoimmune response to self antigens. To gain insight into the etiology and pathogenesis of anti-nucleosome antibodies (Ab), we analyzed a panel of six IgG-secreting hybridomas derived from a single young MRL +/+ mouse at the onset of the autoimmune response. All monoclonal antibodies (mAb) bound exclusively the native nucleosome, and represented five different clonotypes that recognized diverse nucleosomal epitopes, typical of a polyclonal response. The VH-complementarity-determining region (CDR)3 regions exhibited unique stretches of charged amino acids with different polarity that may be important for the interaction with the nucleosome. These early anti-nucleosome mAb displayed striking structural differences with not only anti-DNA, but also with anti-nucleosome Ab, that appear later in disease. Two of the mAb deposited in kidney glomeruli after in vivo administration to RAG-1-deficient mice, suggesting that diverse B cell clones, possibly selected by the nucleosome itself, may play a role in the initiation of kidney damage.

Amino Acid Sequence↗
PubMed1998

Genotyping of forensic short tandem repeat (STR) systems based on sizing precision in a capillary electrophoresis instrument.

Automated fluorescence analysis of polymerase chain reaction (PCR)-amplified short tandem repeat (STR) systems by capillary electrophoresis (CE) is becoming an established tool both in forensic casework and in the implementation of both state and national convicted offender DNA databases. A new capillary electrophoresis instrument, the ABI Prism 310 Genetic Analyzer, along with the Performance Optimized Polymer 4 (POP-4) provides an automated and precise method for simultaneously analyzing ten fluorescently labeled STR loci from a single PCR amplification kit, which provides a power of discrimination of approximately one in five billion from a single PCR amplification. Data are presented on sizing precision, sizing accuracy, and resolution for the STR loci in the AmpFlSTR Profiler kit. Sizing accuracy is highly dependent on the electrophoresis system, and therefore the reporting of alleles based on the nucleotide size obtained from an electrophoresis system is not recommended for forensic work. The precision of the 310 capillary electrophoresis system, coupled with software developed for automated genotyping of alleles based on the use of an allelic ladder, allows for accurate genotyping of STR loci. Sizing precision of < or = 0.16 nucleotide standard deviation was obtained with this system, thus allowing for accurate genotyping of length variants that differ in length by a single nucleotide.

Alleles↗
PubMed1998

Lichenoid erythrodermic bullous pemphigoid of the African patient.

BACKGROUND: Lichen planus (LP) pemphigoides is defined by the concurrence of bullous pemphigoid (BP) and LP lesions. However, other autoimmune bullous skin diseases such as paraneoplastic pemphigus or bullous lupus erythematosus may also be associated with lichenoid eruptions. OBJECTIVE: Our purpose was to describe 3 African patients with a similar form of lichenoid erythrodermic BP. METHODS: Medical records of the 3 patients were reviewed for clinical, histologic, and biologic data. The ultrastructural localization of autoantibody deposits was studied by direct and indirect immunoelectron microscopy. The antigenic specificities recognized by the patients' sera were analyzed by immunoblotting on human epidermal extracts. RESULTS: Three black African men had a severe lichenoid erythroderma associated with BP lesions involving the skin and mucosa. Histologic and direct immunofluorescence examination of skin and mucosal lesions were consistent with the diagnosis of BP associated with a lichenoid dermatitis. Immunoblot analysis of sera detected anti-BPAG1 and anti-BPAG2 antibodies and immunoelectron microscopy showed IgG deposits localized in the lamina lucida and the hemidesmosomes. The 3 patients were natives of an area near the Senegal River and had the common HLA-DR10 haplotype. CONCLUSION: The clinical and histologic features of these 3 patients were distinct from classic LP pemphigoides. Their common geographic origin and the presence of the HLA-DR10 haplotype suggest that these cases represent a particular type of lichenoid erythrodermic BP, which is probably determined by genetic factors.

Adult↗
PubMed1998

Lamellar granule biogenesis: a role for ceramide glucosyltransferase, lysosomal enzyme transport, and the Golgi.

Although lamellar granules are critical to the formation of the epidermal permeability barrier and are a known marker of late keratinocyte differentiation, very little is known about the physiologic regulators of lamellar granule assembly and extrusion. Ceramide glucosyltransferase (CGT), the enzyme responsible for the synthesis of lamellar granule glucosylceramides (GlcCer; the precursors of the stratum corneum ceramides), is localized to the Golgi apparatus in other cell types. We have found that CGT is induced during keratinocyte culture differentiation coincident with increased GlcCer content and the appearance of lamellar granules. In this study we show that the differentiation-related CGT induction is likely mediated at the transcriptional level. In addition, all-trans retinoic acid, a well-known inhibitor of keratinocyte differentiation, prevents the appearance of lamellar granules and decreases culture CGT activity and GlcCer content without affecting sphingomyelin or total lipid content, indicating a specific inhibition of this enzymatic pathway. These data show a direct relationship between CGT activity and epidermal differentiation, suggesting that regulation of CGT expression is a critical part of epidermal barrier generation. The differentiation dependence of CGT activity, the key role of this Golgi-localized enzyme in epidermal GlcCer synthesis, and our previous finding that ceramides are converted to GlcCer in the Golgi apparatus in keratinocyte cultures, strongly suggest a Golgi origin for lamellar granules. In contrast to CGT, the activity of the lysosomal enzymes acid lipase and glucocerebrosidase is less clearly related to epidermal differentiation and the appearance of lamellar granules, although both enzymes show striking colocalization and enrichment in a subcellular lamellar granule fraction derived from pig epidermis. Acid lipase activity in the lamellar granule fraction was found to contain primarily a small lysosomal form of the enzyme, whereas total acid lipase secreted by keratinocyte cultures was found to contain a mannose-6-phosphorylated large prelysosomal form as well as a small lysosomal form. That secreted acid lipase activity is derived from both prelysosomal and lysosomal compartments suggests there may be multiple pathways by which lysosomal enzymes are secreted from keratinocytes. The combined secretion of lipid and lysosomal enzymes from lamellar granules places these organelles in the category of "dual-function" specialized secretory vesicles described in certain other cell types. Electron microscopic images of lamellar granules show shapes consistent with cross-sections of tubules or buds from tubules in addition to vesicles. These images provide evidence for the involvement of trans-Golgi network tubules and/or buds in lamellar granule synthesis and secretion.

Animals↗
PubMed1998

Perspectives on switching oral acyclovir from prescription to over-the-counter status: report of a consensus panel.

The proposed switching of oral acyclovir from prescription to over-the-counter (OTC) status for the 5-day episodic treatment of genital herpes was considered by a consensus panel. It was concluded that self-diagnosis/misdiagnosis, misuse, and adverse drug effects were potential problems with the OTC use of acyclovir. While acyclovir reduces asymptomatic shedding of herpes simplex virus type 2, the reduction in transmission of virus potentially resulting from increased acyclovir use was felt to be of unknown extent but likely to be of benefit overall. The availability of acyclovir would likely be improved. There were differences in opinion as to whether widespread availability of acyclovir (prescription or OTC) may speed the development of viral resistance. However, all panel members felt that granting OTC status may set an undesirable precedent for the switch from prescription to OTC use of other systemically administered antiinfective agents. The effect of this precedent, in terms of accelerating development of multidrug-resistant bacteria, was a major concern of all panel members. The consensus was that the switch of acyclovir to OTC status could not be supported.

Acyclovir↗
PubMed1998

Ceftriaxone once daily for four weeks compared with ceftriaxone plus gentamicin once daily for two weeks for treatment of endocarditis due to penicillin-susceptible streptococci. Endocarditis Treatment Consortium Group.

This randomized, multicenter, open-label study compared the efficacy and safety of monotherapy with 2 g of intravenous ceftriaxone once daily for 4 weeks with those of combination therapy with 2 g of intravenous ceftriaxone and 3 mg of intravenous gentamicin/kg once daily for 2 weeks as therapy for endocarditis due to penicillin-susceptible streptococci. Sixty-one patients were enrolled in the study. Clinical cure was observed for 51 evaluable patients both at termination of therapy and at the 3-month follow-up: 25 (96.2%) of 26 monotherapy recipients and 24 (96%) of 25 combination therapy recipients. Of the 23 patients in each treatment group who were microbiologically evaluable, 22 (95.7%) in each group were considered cured. No patient had evidence of relapse. Fourteen patients (27.5%) required cardiac surgery after initiation of treatment, including five monotherapy recipients and nine combination therapy recipients. Adverse effects were minimal in both treatment groups. We conclude that 2 g of ceftriaxone once daily for 4 weeks and 2 g of ceftriaxone in combination with 3 mg of gentamicin/kg once daily for 2 weeks are both effective and safe for the treatment of streptococcal endocarditis.

Adolescent↗
PubMed1998

Approaches to the automatic discovery of patterns in biosequences.

This paper surveys approaches to the discovery of patterns in biosequences and places these approaches within a formal framework that systematises the types of patterns and the discovery algorithms. Patterns with expressive power in the class of regular languages are considered, and a classification of pattern languages in this class is developed, covering the patterns that are the most frequently used in molecular bioinformatics. A formulation is given of the problem of the automatic discovery of such patterns from a set of sequences, and an analysis is presented of the ways in which an assessment can be made of the significance of the discovered patterns. It is shown that the problem is related to problems studied in the field of machine learning. The major part of this paper comprises a review of a number of existing methods developed to solve the problem and how these relate to each other, focusing on the algorithms underlying the approaches. A comparison is given of the algorithms, and examples are given of patterns that have been discovered using the different methods.

Algorithms↗
PubMed1998

Activity of trovafloxacin (with or without ampicillin-sulbactam) against enterococci in an in vitro dynamic model of infection.

Antibiotic-resistant enterococci are being increasingly identified as causal agents of infection. Trovafloxacin is a new fluoronaphthyridone with enhanced activity against gram-positive cocci and variable activity reported against Enterococcus spp. Twenty-one strains of vancomycin-resistant Enterococcus faecium and two strains of Enterococcus faecalis (one vancomycin resistant) were studied at an initial inoculum of 10(6) CFU/ml in time-kill assays with trovafloxacin (3 mg/liter), ampicillin-sulbactam (100/50 mg/liter), and the combination. Six strains of E. faecium (five vancomycin resistant) also were studied in an in vitro two-compartment dynamic model that mimics human pharmacokinetics with trovafloxacin simulated at 300 mg every 12 h (q12h), ampicillin-sulbactam at 2/1 g q6h, and the combination. Peripheral compartments were sampled q2h for 30 h for bacterial counts. Trovafloxacin MICs ranged from 0.5 to 32 mg/liter, and the nine strains of vancomycin-resistant E. faecium for which MICs were < or =2 mg/liter were more likely to show a reduction of 2 log units or more in viable counts in time-kill assays than were strains for which MICs were higher. Synergism with ampicillin-sulbactam was found for only one strain (trovafloxacin MIC, 16 mg/liter). Similar results were obtained in the pharmacokinetic model, with 2- to 4-log-unit reductions in viable bacteria for trovafloxacin-susceptible strains. Although no convincing evidence of synergism was found, ampicillin-sulbactam in combination minimized late bacterial regrowth of two trovafloxacin-susceptible strains. These data suggest that this high dose of trovafloxacin (with or without ampicillin-sulbactam) might be useful against strains of vancomycin-resistant E. faecium for which MICs were < or =2 mg/liter.

Ampicillin↗
PubMed1997

FlyBase: a Drosophila database. The FlyBase consortium.

FlyBase is a database of genetic and molecular data concerning Drosophila. FlyBase is maintained as a relational database (in Sybase) and is made available as html documents and flat files. The scope of FlyBase includes: genes, alleles (and phenotypes), aberrations, transposons, pointers to sequence data, clones, stock lists, Drosophila workers and bibliographic references. The Encyclopedia of Drosophila is a joint effort between FlyBase and the Berkeley Drosophila Genome Project which integrates FlyBase data with those from the BDGP.

Animals↗
PubMed1997

A complementarity-determining region peptide of an anti-desmosome autoantibody may interact with the desmosomal plaque through molecular mimicry with a cytoplasmic desmoglein 1 sequence.

The sera of patients with pemphigus, a group of autoimmune blistering skin diseases, contain autoantibodies directed against components of adhering junctions termed desmosomes. F12, a human monoclonal antibody derived from a pemphigus patient, recognizes an unknown polypeptide of the desmosomal and hemidesmosomal plaques. The third complementarity-determining region of the F12 heavy chain (VH-CDR3) was shown to share a four-amino-acid sequence (GSSG) with the intracellular domains of desmoglein 1 and bullous pemphigoid antigen 2 which interact with components of, respectively, the desmosomal and hemidesmosomal plaques. Computer modeling of F12 showed that the GSSG sequence protudes inside the antigen-combining site and thus might be involved in antigen interactions. The GSSG sequence is essential to F12 function, since a peptide containing the VH-CDR3 inhibited its binding to target antigens while VH-CDR3 peptides with specific modifications of the GSSG sequence did not. These data allow us to hypothesize that certain autoantibodies produced during the course of an autoimmune disease can behave as adhesion molecules, through the molecular mimicry of the motif involved in protein/protein adhesion, and to propose a new self-antigen binding mechanism for some autoantibodies.

Amino Acid Sequence↗
PubMed1997

Idiotypic analysis of anti-nucleosome monoclonal antibodies derived from lupus mice.

3F6 and 2E1 are anti-(H2A-H2B) monoclonal antibodies derived from a 12-month-old (NZBxNZW)F1 mouse that diverged from the same clonal precursor by somatic mutations. Rabbit anti-idiotypic antisera were prepared against these two monoclonal antibodies and used as probes to analyse the properties and expression of 3F6 and 2E1 idiotypes. Both idiotypes were conformational, distant from the antigen binding site and did not correlate with a VH- or VL-chain usage. 3F6 was preferentially bound by anti-3F6 idiotype but was weakly recognized by anti-2E1 idiotype suggesting, since 3F6 derives from 2E1, that 3F6 bore idiotypic determinants generated by somatic mutations. While none of the murine anti-DNA monoclonal antibodies tested expressed 2E1 or 3F6 idiotypes, 3F6 idiotype could be detected on approximately one-third of anti-(H2A-H2B) monoclonal antibodies derived from other lupus strains of mice, demonstrating the presence of cross-reactive idiotypes on autoantibodies directed against a nucleosome that could result from somatic mutations.

Animals↗