Biomedical subjects

R M Brown

Publications and source records attributed to R M Brown.

At least 19 recordsLinked to original sources

PubMed2004

Diagnostic difficulties with common SURF1 mutations in patients with cytochrome oxidase-deficient Leigh syndrome.

In three unrelated patients with systemic cytochrome oxidase deficiency resulting from mutations in the SURF1 gene, the same mutation in the splice donor site of intron 3 was identified. All three patients were compound heterozygotes, two for the common insertion/deletion mutation in exon 4. In all three cases, complete definition of the causative mutations was only resolved by combined analysis of cDNA and genomic DNA. Several factors were identified that contributed to the diagnostic difficulties: preferential amplification of deleted cDNA, significant formation of heteroduplexes in cDNA PCR amplification and unequal representation of heterozygous peaks in genomic DNA sequences. These patients emphasize the need to perform mutation analysis on both cDNA and genomic DNA wherever possible.

Alternative Splicing↗

PubMed2003

A pathogenic glutamate-to-aspartate substitution (D296E) in the pyruvate dehydrogenase E1 subunit gene PDHA1.

In a patient with fatal neonatal lactic acidosis due to pyruvate dehydrogenase deficiency, the only potential mutation detected was c.888C>G in PDHA1, the gene for the E1alpha subunit of the complex. This would result in a substitution of glutamate for aspartate (D296E). Pathogenicity of this minor alteration in amino acid sequence was demonstrated by expression studies. By comparing the mutant sequence with the known structures of the E1 components of pyruvate dehydrogenase and the closely related branched chain alpha-ketoacid dehydrogenase, an explanation for the profound consequences of the mutation can be proposed.

Amino Acid Substitution↗

PubMed2002

A primary tumour of the oesophagus with both melanocytic and schwannian differentiation. Melanocytic schwannoma or malignant melanoma?

A 76 year old white woman presented with a four month history of dysphagia and weight loss. Clinical, radiological, and endoscopic examination revealed a pigmented mass in the lower third of the oesophagus. The preoperative diagnosis, including biopsy examination, was that of malignant melanoma. Following oesophageal resection, the mass was found to be a localised, relatively superficial tumour with light, electron microscopic, and immunohistochemical features common to both Schwann cells and melanocytes. The patient survived 46 months after surgery and died of a stroke, with no evidence of tumour recurrence. The tumour is presented as a case of melanocytic schwannoma, with unique features when compared with oesophageal melanotic schwannomas and malignant melanomas described in the literature. The differential diagnosis is discussed and an origin from a common precursor cell of neural crest origin is postulated.

Aged↗

PubMed2001

Correlation of immunohistochemical molecular staging of bladder biopsies and radical cystectomy specimens.

PURPOSE: To determine the relationship of p53, retinoblastoma (RB), and p16 expression between precystectomy transurethral resection bladder (TURB) biopsy and matched cystectomy specimens; and to determine the value of p53 immunoreactivity for predicting progression and survival in patients undergoing radical cystectomy. METHODS AND MATERIALS: We performed p53 immunohistochemical staining on matched archival TURB and cystectomy specimens taken from 40 patients. Twenty-seven and 26 of these patients were also evaluated for RB and p16 expression, respectively. RESULTS: Twenty-eight (70%) of the TURB and 22 (55%) of the cystectomy specimens stained positive for p53. RB and p16 protein expression were altered in 19 (70%) and 19 (73%) of the TURB specimens, respectively, and 19 (70%) and 19 (73%) of the cystectomy specimens, respectively. There was a strong correlation between p53, RB, and p16 expression and TURB and cystectomy specimens (all p < 0.001). In preoperative and postoperative multivariate analyses, biopsy p53 and cystectomy p53 were independently associated with disease progression (p = 0.049 and p = 0.034, respectively) and bladder cancer-related death (p = 0.044 and p = 0.037, respectively). CONCLUSION: p53, RB, and p16 expression patterns on TURB specimens correlate with cystectomy specimens. p53 immunoreactivity is an independent predictor of disease progression and bladder cancer survival. These data support the potential of prognostic staging using immunohistochemical analysis on bladder biopsy specimens prior to neoadjuvant or definitive therapy.

Adult↗

PubMed2001

The synthesis of megatubes: new dimensions in carbon materials.

Extremely large carbon tubes, some exceeding 5 microm in diameter, were produced with both laser and electric arc techniques using graphite, a transition metal catalyst, and a reactive third-body gas. We have named these structures carbon megatubes. They are the first carbonaceous tubes large enough to observe using optical microscopy. We also report the synthesis of what we believe to be the first self-assembled branched nanotubes. In addition to their extreme diameters and unique morphologies, X-ray photoelectron spectroscopy has shown that these tubes also contain a significant amount of nitrogen atom incorporation into the graphite lattice. Subsequently, these nitrogen functionalities were shown to interact with rhenium pentacarbonyl bromide and serve as anchor points to tether molecules to the surface of the tubules.

Journal Article↗

PubMed2001

A SURF1 gene mutation presenting as isolated leukodystrophy.

Mitochondrial respiratory chain defects are increasingly recognized in patients with leukodystrophy. We report the first case of leukodystrophy with systemic cytochrome oxidase deficiency caused by a loss of function mutation in the SURF1 gene in a 2-year-old girl presenting with failure to thrive, global neurodevelopmental regression, and lactic acidosis. Although all previously reported mutations in the SURF1 gene have been found in patients with cytochrome oxidase (COX)-deficient Leigh syndrome, the phenotype associated with SURF1 protein deficiency should be extended to include leukodystrophy.

Acidosis, Lactic↗

PubMed2001

A putative plant homolog of the yeast beta-1,3-glucan synthase subunit FKS1 from cotton (Gossypium hirsutum L.) fibers.

A novel plant gene CFL1 was cloned from cotton (Gossypium hirsutum L.) fibers by expressed sequence tag (EST) database searching and 5'-RACE (rapid amplification of cDNA ends). This gene shows sequence homology with FKS1 which has been identified as the putative catalytic subunit of the yeast beta-1,3-glucan synthase. It encodes a protein (CFL1p) of 219 kDa with 13 deduced transmembrane helices and 2 large hydrophilic domains, one of which is at the N-terminus and the other in the internal region of the polypeptide. CFL1 displays 21% identity and 41% similarity to FKS1 at the amino acid level over its entire length, with 31% identity and 52% similarity for the hydrophilic central domain. Using RNA and protein blot analysis, CFL1 was found to be expressed at higher levels in cotton fibers during primary wall development. CFL1 also had a strong expression in young roots. Using a calmodulin (CaM)-gel overlay assay, the hydrophilic N-terminal domain of CFL1p was shown to bind to CaM, while the hydrophilic central domain did not. A putative CaM-binding domain, 16 amino acids long, was predicted in the hydrophilic N-terminal domain. Moreover, a product-entrapment assay demonstrated that a protein associated with an in vitro-synthesized callose pellet could be labeled by anti-CFL1 antibodies. Our finding suggests that CFL1 is a putative plant homolog of the yeast beta-1,3-glucan synthase subunit FKS1 and could be involved in callose synthesis.

Calmodulin-Binding Proteins↗

PubMed2001

5 a day fruit and vegetable intervention improves consumption in a low income population.

OBJECTIVE: This study evaluated the Michigan Farmers' Market Nutrition Program in one Michigan county to determine its effect on fruit and vegetable consumption behavior. SUBJECTS/SETTING: Subjects were selected from WIC and Community Action Agency populations: 564 low income women completed the pretest; 455 completed the posttest. Attrition rate was 19.3%. INTERVENTION: Subjects were assigned to one of 4 interventions: education about the use, storage and nutritional value of fruits and vegetables, distribution of farmers' market coupons, both education and coupons, or no intervention. DESIGN: Education-only and coupon and education groups were randomly assigned; clinic appointment timing determined assignment to no-intervention and coupon-only groups. MAIN OUTCOME MEASURES: A self-administered questionnaire before and after intervention measured attitudes about fruit and vegetable consumption and intake of fruits and vegetables. WIC records documented redemption of coupons. STATISTICAL ANALYSES: Data analysis included 2-way multivariate analysis of covariance, univariate analysis of covariance, logistic regression, and covariance structure modeling. RESULTS: Both the education interventions and the coupon interventions had positive effects. Coupons had a direct effect on increasing fruit and vegetable consumption behavior but no effect on attitudes. Education had a direct effect on attitudes and seemed to exert an effect on consumption behavior through attitudes. The maximum impact of the intervention was achieved through a combination of education and coupons. APPLICATIONS: This study demonstrated that a low-income population may be more likely to increase its fruit and vegetable consumption behavior when incentives such as coupons improve affordability.

Analysis of Variance↗

PubMed2001

Structure--function characterization of cellulose synthase: relationship to other glycosyltransferases.

A combined structural and functional model of the catalytic region of cellulose synthase is presented as a prototype for the action of processive beta-glycosyltransferases and other glycosyltransferases. A 285 amino acid segment of the Acetobacter xylinum cellulose synthase containing all the conserved residues in the globular region was subjected to protein modeling using the genetic algorithm. This region folds into a single large domain with a topology exhibiting a mixed alpha/beta structure. The predicted structure serves as a topological outline for the structure of this processive beta-glycosyltransferase. By incorporating new site-directed mutagenesis data and comparative analysis of the conserved aspartic acid residues and the QXXRW motif we deduce a number of functional implications based on the structure. This includes location of the UDP--glucose substrate-binding cavity, suggestions for the catalytic processing including positions of conserved and catalytic residues, secondary structure arrangement and domain organization. Comparisons to cellulose synthases from higher plants (genetic algorithm based model for cotton CelA1), data from neural network predictions (PHD), and to the recently experimentally determined structures of the non-processive SpsA and beta 4-galactosyltransferase retest and further validate our structure-function description of this glycosyltransferase.

Amino Acid Sequence↗

PubMed2001

E-cadherin expression predicts clinical outcome in carcinoma in situ of the urinary bladder.

OBJECTIVES: The clinical course of carcinoma in situ (CIS) of the bladder is highly variable. Our objective in this study was to describe E-cadherin expression patterns in CIS with and without papillary disease and to determine whether altered E-cadherin expression is associated with disease progression and survival in patients with CIS of the bladder. METHODS: Tumor specimens from 53 patients who had CIS in the absence of muscle-invasive carcinoma on bladder biopsy were identified. Formalin-fixed paraffin sections were processed using a hot citric acid antigen retrieval method, followed by immunostaining with anti-E-cadherin monoclonal antibody. Expression patterns were evaluated in a blinded fashion and scored as normal and abnormal, which included absent and various degrees of heterogeneous immunostaining. Outcomes analyzed were recurrence, progression, and survival. RESULTS: Loss of normal membrane E-cadherin immunoreactivity was found in 17 patients (32%). At a median follow-up of 131 months, abnormal E-cadherin expression was significantly associated with disease recurrence (P = 0.0087), disease progression (P = 0.0003), and bladder cancer-specific survival (P = 0.0285). In multivariate analyses, E-cadherin expression was independently associated with disease recurrence (P = 0.019, 95% confidence interval [CI] 1.342 to 5.940), disease progression (P = 0.002, 95% CI 2.049 to 17.989), and bladder cancer-specific survival (P = 0.025, 95% CI 1.179 to 10.432). CONCLUSIONS: Loss of E-cadherin expression in patients CIS with and without papillary disease of the bladder predicts disease recurrence, disease progression, and bladder cancer-specific death. CIS with and without papillary disease associated with abnormal E-cadherin expression may represent a biologically more aggressive cancer, requiring early definitive therapy. This hypothesis should be evaluated in larger studies and prospective clinical trials.

Adult↗

PubMed2001

"Nematic ordered cellulose": a concept of glucan chain association.

Native cellulose consists of a set of parallel chains composed of glucose. Most of the time, these chains are highly ordered and form a structure that is known as a microfibril. On the other hand, highly crystalline forms of cellulose are more difficult to process and often are unpredictable in their behavior. If an ordered but noncrystalline form of cellulose could be produced, this would greatly extend the possibilities of usage of cellulose to new areas. In this paper, we have produced such a new supermolecular structure of cellulose, called nematic ordered cellulose. The unique characteristics of this supermolecular structure of cellulose have been clarified using various kinds of physicochemical analyses. Using a high-resolution transmission electron microscopic approach, we have also imaged the single glucan chains, demonstrating the close but nonprecise association usually found in crystalline biopolymers.

Carbohydrate Conformation↗

PubMed2001

Localization of c-di-GMP-binding protein with the linear terminal complexes of Acetobacter xylinum.

Specific labeling of a single row of cellulose-synthesizing complexes (terminal complexes, TC subunits, TCs, or TC arrays) in Acetobacter xylinum by antibodies raised against a 93-kDa protein (the cyclic dignanylic acid-binding protein) has been demonstrated by using the sodium dodecyl sulfate (SDS)-freeze-fracture labeling (FRL) technique. The antibodies to the 93-kDa protein specifically recognized the TC subunits on the protoplasmic fracture (PF) face of the outer membrane in A. xylinum; however, nonlabeled TCs were also observed. Two types of TC subunits (particles or pits) are observed on the PF face of the outer membrane: (i) immunogold-labeled TCs showing a line of depressions (pits) with an indistinct particle array and (ii) nonlabeled TC subunits with a distinct single row of particle arrays. The evidence indicates that the labeling patterns differ with respect to the presence or absence of certain TC subunits remaining attached to the replica after SDS treatment. This suggests the presence of at least two TC components, one in the outer membrane and the other in the cytoplasmic membrane. If the TC component in the outer membrane is preferentially fractured and remains attached to the ectoplasmic fracture face (or outer leaflet) of the outer membrane, subsequent replica formation reveals a pit or depression with positive antibody labeling on the PF face of the outer membrane. If the TC component in the outer membrane remains with the PF face (or inner leaflet) of the outer membrane, the innermost TC component is removed during SDS treatment and labeling does not occur. SDS-FRL of TCs in A. xylinum has enabled us to provide the first topological molecular analysis of component proteins in a cellulose-synthesizing TC structure in a prokaryotic organism.

Bacterial Proteins↗

PubMed2001

Cellulose in cyanobacteria. Origin of vascular plant cellulose synthase?

Although cellulose biosynthesis among the cyanobacteria has been suggested previously, we present the first conclusive evidence, to our knowledge, of the presence of cellulose in these organisms. Based on the results of x-ray diffraction, electron microscopy of microfibrils, and cellobiohydrolase I-gold labeling, we report the occurrence of cellulose biosynthesis in nine species representing three of the five sections of cyanobacteria. Sequence analysis of the genomes of four cyanobacteria revealed the presence of multiple amino acid sequences bearing the DDD35QXXRW motif conserved in all cellulose synthases. Pairwise alignments demonstrated that CesAs from plants were more similar to putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and Nostoc punctiforme American Type Culture Collection 29133 than any other cellulose synthases in the database. Multiple alignments of putative cellulose synthases from Anabaena sp. Pasteur Culture Collection 7120 and N. punctiforme American Type Culture Collection 29133 with the cellulose synthases of other prokaryotes, Arabidopsis, Gossypium hirsutum, Populus alba x Populus tremula, corn (Zea mays), and Dictyostelium discoideum showed that cyanobacteria share an insertion between conserved regions U1 and U2 found previously only in eukaryotic sequences. Furthermore, phylogenetic analysis indicates that the cyanobacterial cellulose synthases share a common branch with CesAs of vascular plants in a manner similar to the relationship observed with cyanobacterial and chloroplast 16s rRNAs, implying endosymbiotic transfer of CesA from cyanobacteria to plants and an ancient origin for cellulose synthase in eukaryotes.

Amino Acid Sequence↗

PubMed2000

Mutations in the X-linked pyruvate dehydrogenase (E1) alpha subunit gene (PDHA1) in patients with a pyruvate dehydrogenase complex deficiency.

Defects in the pyruvate dehydrogenase (PDH) complex are an important cause of primary lactic acidosis, a frequent manifestation of metabolic disease in children. Clinical symptoms can vary considerably in patients with PDH complex deficiencies, and almost equal numbers of affected males and females have been identified, suggesting an autosomal recessive mode of inheritance of the disease. However, the great majority of PDH complex deficiencies result from mutations in the X-linked pyruvate dehydrogenase (E1) alpha subunit gene (PDHA1). The major factors that contribute to the clinical variation in E1alpha deficiency and its resemblance to a recessive disease are developmental lethality in some males with severe mutations and the pattern of X-inactivation in females. To date, 37 different missense/nonsense and 39 different insertion/deletion mutations have been identified in the E1alpha subunit gene of 130 patients (61 females and 69 males) from 123 unrelated families. Insertion/deletion mutations occur preferentially in exons 10 and 11, while missense/nonsense mutations are found in all exons. In males, the majority of missense/nonsense mutations are found in exons 3, 7, 8 and 11, and three recurrent mutations at codons R72, R263 and R378 account for half of these patients with missense/nonsense mutations (25 of 50). A significantly lower number of females is found with missense/nonsense mutations (25). However, 36 females out of 55 affected patients have insertion/deletion mutations. The total number of female and male patients is thus almost the same, although a difference in the distribution of the type of mutations is evident between both sexes. In many families, the parents of the affected patients were studied for the presence of the PDHA1 mutation. The mutation was never present in the somatic cells of the father; in 63 mothers studied, 16 were carriers (25%). In four families, the origin of the new mutation was determined to be twice paternal and twice maternal.

Amino Acid Sequence↗

PubMed2000

A comparison of physostigmine and benzodiazepines for the treatment of anticholinergic poisoning.

STUDY OBJECTIVE: To compare the efficacy and safety of physostigmine with benzodiazepines for the treatment of agitation and delirium associated with anticholinergic poisoning. METHODS: We conducted a retrospective study of 52 consecutive patients referred to a university hospital toxicology consultation service who were treated with physostigmine, benzo-diazepines, or both for anticholinergic agitation and delirium. Patients treated with physostigmine were compared with those treated with benzodiazepines with respect to demographics, severity of poisoning, response to treatment, side effects of treatment, and complications. RESULTS: Physostigmine controlled agitation and reversed delirium in 96% and 87% of patients, respectively. Benzodiazepines controlled agitation in 24% of patients but were ineffective in reversing delirium. Initial treatment with physostigmine (n=30) resulted in a significant decrease in the incidence of agitation (P <.001) and level of central nervous system stimulation (P <.001), whereas initial treatment with benzodiazepines (n=22) did not (P =.03 and P =.05, respectively). Patients treated initially with physostigmine had a significantly lower incidence of complications (7% versus 46%; P <. 002) and a shorter time to recovery (median, 12 versus 24 hours; P =. 004) than those treated initially with benzodiazepines. There were no significant differences between these groups in the incidence of side effects (7% versus 14%; P =0.6) and length of stay (median, 32 versus 39 hours; P =.15). CONCLUSION: Results suggest that physostigmine is more effective and safer than benzodiazepines for the treatment of anticholinergic agitation and delirium. A prospective controlled study is necessary to confirm such findings.

Administration, Oral↗

PubMed2000

Cellulose synthases and related enzymes.

The discovery of a large number of genes encoding cellulose synthases and related glycosyltransferases in plants has led to a renewed interest in the biosynthesis of cell-wall polysaccharides. A number of approaches, including virus-induced gene silencing have proven useful in the functional analysis of these genes. X-ray analysis of the structures of a few glycosyltransferases has led to the identification and confirmation of the role of conserved residues within this group of enzymes. Analysis of related enzymes has provided useful information on the possible domain organization of cellulose synthases and the requirement for at least two separate glycosyltransferase activities in the processive synthesis of sugar chains.

Cellulose↗

PubMed2000

Mucosal bacille calmette-Guérin vaccination of humans inhibits delayed-type hypersensitivity to purified protein derivative but induces mycobacteria-specific interferon-gamma responses.

We conducted a placebo-controlled, double-dose-escalation trial of oral bacille Calmette-Guérin (BCG) vaccination in 48 healthy volunteers. Seven of 32 BCG recipients became purified protein derivative (PPD)-positive after dose 1, and only 1 remained positive after dose 2, which suggests that oral BCG has inhibitory effects on delayed-type hypersensitivity (DTH) responses. Ten of the original placebo recipients and 11 oral BCG recipients were recruited to return for an intradermal BCG booster vaccination. Five of 10 original placebo recipients developed PPD responses >/=10 mm, but none of 11 oral BCG recipients developed PPD induration after they received an intradermal BCG booster (P<.05; Fisher's exact test). These results document persistent inhibitory effects of oral BCG vaccination on mycobacteria-specific DTH responses. Despite inhibition of DTH, oral BCG induced significant increases in mycobacteria-specific interferon (IFN)-gamma responses in peripheral blood mononuclear cells. More detailed studies of cytokine and homing molecule expression indicated that differential mucosal versus cutaneous trafficking may explain the dissociation between IFN-gamma and DTH responses.

Adolescent↗

PubMed1999

GTPase activity and biochemical characterization of a recombinant cotton fiber annexin.

A cDNA encoding annexin was isolated from a cotton (Gossypium hirsutum) fiber cDNA library. The cDNA was expressed in Escherichia coli, and the resultant recombinant protein was purified. We then investigated some biochemical properties of the recombinant annexin based on the current understanding of plant annexins. An "add-back experiment" was performed to study the effect of the recombinant annexin on beta-glucan synthase activity, but no effect was found. However, it was found that the recombinant annexin could display ATPase/GTPase activities. The recombinant annexin showed much higher GTPase than ATPase activity. Mg2+ was essential for these activities, whereas a high concentration of Ca2+ was inhibitory. A photolabeling assay showed that this annexin could bind GTP more specifically than ATP. The GTP-binding site on the annexin was mapped into the carboxyl-terminal fourth repeat of annexin from the photolabeling experiment using domain-deletion mutants of this annexin. Northern-blot analysis showed that the annexin gene was highly expressed in the elongation stages of cotton fiber differentiation, suggesting a role of this annexin in cell elongation.

Adenosine Triphosphatases↗