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Biomedical subjects

R J Smith

Publications and source records attributed to R J Smith.

At least 91 records · Page 5Linked to original sources
PubMed2000

2E4/Kaptin (KPTN)--a candidate gene for the hearing loss locus, DFNA4.

Stereocilia of the inner ear play an integral role in the mechanotransduction of sound. Their structural support is derived from actin filaments and actin-binding proteins. We have identified a novel actin-binding protein, 2E4-kaptin (KPTN), which appears to be involved in this structural network. Using double label immunofluorescence, we now show that KPTN extends beyond the barbed ends of actin filaments at the tips of stereocilia, and using cloned human cDNA, we mapped KPTN to chromosome 19q13.4. A combination of FISH, radiation hybrid mapping and YAC screening localized KPTN between markers D19S412 and NIB1805, making this gene an excellent functional and positional candidate for DFNA4, a form of autosomal dominant non-syndromic hearing loss. We identified a second family with inherited deafness that also maps to the DFNA4 region. To screen KPTN for deafness-causing mutations, we first determined its genomic structure and then completed a mutational analysis by direct sequencing and SSCP in affected family members. Although no deafness-causing mutations were identified in the coding region, KPTN remains an excellent candidate gene for hearing loss; by synteny, its murine orthologue also remains a candidate gene for the Nijmegan waltzer (nv) mouse mutant, which has vestibular defects and a variable sensorineural hearing loss.

Adult↗
PubMed2000

Effects of simulated solar disinfection of water on infectivity of Salmonella typhimurium.

To determine whether cells of Salmonella typhimurium rendered nonculturable by simulated solar disinfection retain infectivity for mice. Bacteria suspended in water were exposed to UVA irradiation for up to 8 h. Culturability, determined by colony forming unit and Most Probable Number counts, fell by six log10 units, while cellular activity determined by the Kogure cell elongation test was retained by approximately 5% of the cells present after 8 h. Intraperitoneal doses of nonculturable cells and active but nonculturable (ABNC) cells exceeding the LD50 of the test organism and BALB/c mouse host, respectively, by 4 and 3 orders of magnitude failed to produce detectable infections. Culturable cells that had been irradiated for 1.5 h were less infective (virulent) than their nonirradiated counterparts. Nonculturable and ABNC cells of Salm. typhimurium produced by UVA irradiation do not retain infectivity for mice. Although ABNC cells could be produced by low cost solar disinfection systems, they do not appear to pose a potential infection hazard.

Animals↗
PubMed2000

The M34T allele variant of connexin 26.

GJB2 encodes the protein Connexin 26, one of the building blocks of gap junctions. Each Connexin 26 molecule can oligomerize with five other connexins to form a connexon; two connexons, in turn, can form a gap junction. Because mutations in GJB2 are the most common cause of congenital severe-to-profound autosomal recessive nonsyndromic hearing loss, the effect of the Connexin 26 allele variants on this dynamic 'construction' process and the function of any gap junctions that do form is particularly germane. One of the more controversial allele variants, M34T, has been hypothesized to cause autosomal dominant nonsyndromic hearing loss. In this paper, we present clinical and genotypic data that refutes this hypothesis and suggests that the effect of the M34T allele variant may be dependent on the mutations segregating in the opposing allele.

Alleles↗
PubMed2000

Temporal bone histopathology in connexin 26-related hearing loss.

OBJECTIVE: Mutations in GJB2, a gene that encodes a gap junction protein, Connexin 26 (Cx26), are responsible for approximately one third of sporadic severe-to-profound or profound congenital deafness and half of severe-to-profound or profound autosomal recessive nonsyndromic hearing loss (ARNSHL). Mouse mutants homozygous for knockouts of this gene are nonviable, precluding histopathologic studies of the associated inner ear pathology in this animal model. Therefore, we studied archival temporal bone sections to identify temporal bone donors with Cx26-related deafness. STUDY DESIGN: Temporal bone donors with a history of congenital severe-to-profound or profound deafness were identified in the registry of the Temporal Bone Library at the University of Iowa. Histological findings were interpreted in a blinded fashion. DNA extracted from two celloidin-embedded mid-modiolar sections from each temporal bone was screened for the 35delG Cx26 mutation. The entire coding region of Cx26 was screened for other deafness-causing mutations if the 35delG mutation was detected. RESULTS: Of five temporal bone donors with congenital severe-to-profound deafness, one donor was found to have Cx26-related deafness. This individual was a Cx26 compound heterozygote, carrying the 35delG mutation and a noncomplementary Cx26 missense mutation on the opposing allele. Microscopic evaluation of this temporal bone showed no neural degeneration, a good population of spiral ganglion cells, near-total degeneration of hair cells in the organ of Corti, a detached and rolled-up tectorial membrane, agenesis of the stria vascularis, and a large cyst in the scala media in the region of the stria vascularis. CONCLUSION: This study is the first to report the temporal bone histopathology associated with Cx26-related deafness. Preservation of neurons in the spiral ganglion suggests that long-term successful habilitation with cochlear implants may be possible in persons with severe-to-profound or profound Cx26-related deafness.

Adult↗
PubMed2000

Age-related mitochondrial DNA mutations in the human larynx.

OBJECTIVE: To determine whether age-related mitochondrial DNA mutations occur in the human larynx. STUDY DESIGN: Genetic study of cadaveric larynx specimens. METHODS: Vocal fold mucosa, thyroarytenoid muscle, and cricoarytenoidjoint tissue were harvested from 13 fresh postmortem larynges (age range, 2 d-82 y). DNA was extracted from each sample, and the polymerase chain reaction (PCR) was used to amplify a target DNA sequence resulting from the common age-associated, 4977-base-pair (bp) mitochondrial DNA deletion. PCR products were visualized by agarose gel electrophoresis. Automated sequencing determined the sequence of identified PCR products. SUBJECTS: Thirteen cadaveric larynges were obtained through the University of Kentucky Medical Center (Lexington, KY). Specimens from patients with a history of head and neck cancer, previous laryngeal trauma, or surgery were excluded. RESULTS: Strongly positive bands were identified in samples from three individuals. Weaker bands were seen in samples from four other samples. No band was noted from the two pediatric larynges. Different band patterns were seen among the three different tissue sites in the larynges with positive PCR products, but no consistent pattern was seen. Sequencing of the identified PCR products from selected samples confirmed that they were products of the age-associated, 4977-bp mitochondrial DNA deletion. CONCLUSIONS: An age-associated mitochondrial DNA deletion was detected in several post-mortem human larynges. Its presence seemed to increase in appearance with age. In the larynges in which the deletion occurred, there were individual regional differences in the occurrence of the deletion, but no consistent pattern was noted across all individuals who carried the deletion.

Adult↗
PubMed2000

Localization of fungal fimbriae by immunocytochemistry in pathogenic and nonpathogenic isolates of Venturia inaequalis.

Pathogenic and nonpathogenic isolates of Venturia inaequalis were grown in liquid culture. Hyphae were treated with two types of fimbrial antiserum (AU- and AV-1) and examined by immunofluorescent microscopy, in order to establish the distribution of fimbrial epitopes in whole cell mounts. The AV-1 antiserum was specific for the glycoprotein subunits while the AU-antiserum was specific for the protein moieties present on the fimbriae of Mycobotryum violaceum. The use of fimbrial antiserum with immunocytochemistry and transmission electron microscopy demonstrated a clear distinction between pathogenic and nonpathogenic isolates of V. inaequalis, based on the appearance of the fungal cell wall and the distribution of fimbrial epitopes labeled with AV-1 antiserum and immunogold complex. In actively growing hyphae of the pathogenic isolate, characterized by distinct cellular organelles, small vacuoles, and lipid bodies, fimbrial epitopes were concentrated in the fungal cell wall and were present minimally on the outer surface. In contrast, actively growing hyphae of the nonpathogenic isolate of V. inaequalis had extensive fine hair-like protrusions in the fungal cell wall which labeled with the AV-1 antiserum and immunogold. The distribution of fimbrial epitopes in V. inaequalis was highly dependent on the developmental growth stage of the fungal mycelium. Aging mycelia in both the pathogenic and nonpathogenic isolates of V. inaequalis were characterized by a large central vacuole and no label. In the pathogenic and nonpathogenic isolates of V. inaequalis grown in vitro, the distribution of fimbrial glycoprotein epitopes provided a more complex profile than that seen in M. violaceum.

Antibodies↗
PubMed2000

DFNA 2, 5, 8, 12.

Explore the source record for details and available documents.

Carrier Proteins↗
PubMed2000

Value of pH probe testing in pediatric patients with extraesophageal manifestations of gastroesophageal reflux disease: a retrospective review.

Extended pH probe testing is often performed in patients believed to have extraesophageal symptoms of gastroesophageal reflux disease (GERD), although for this indication its diagnostic value is not well established. A retrospective review of all patients who underwent pH probe testing between 1994 and 1998 was conducted to determine the outcome of antireflux therapy in the subgroup with probable extraesophageal symptoms of GERD. Sixty-eight patients underwent antireflux therapy and had adequate follow-up after pH probe testing to be included in the study. Fifty-eight patients (85%) responded to antireflux therapy (improved, 44%; cured, 41%). The positive predictive value of distal pH probe testing was greater than 90%, but the negative predictive value was less than 50%. The reproducibility of pH probe testing on different study days was poor, but pH probe testing was helpful in assessing the adequacy of antireflux therapy. The presence of gastrointestinal symptoms did not correlate with the response of extraesophageal symptoms to antireflux therapy. Thirteen patients underwent double-probe pH studies. The mean percent time the pH was less than 4 in the upper esophagus was 2.6% (range, 1% to 9.6%). Twelve of these patients were improved or cured with antireflux therapy. Distal pH probe testing is of limited benefit in predicting whether patients with extraesophageal symptoms of GERD will respond to antireflux therapy. If extraesophageal symptoms of GERD are suspected, patients should undergo an empiric trial of antireflux therapy. Distal pH probe testing should be reserved for assessing the adequacy of antireflux therapy if symptoms persist. A prospective, randomized, controlled study will aid in determining the predictive value of double-probe pH studies in pediatric patients with probable extraesophageal symptoms of GERD.

Adolescent↗
PubMed2000

Studies of the variability of the genes encoding the insulin-like growth factor I receptor and its ligand in relation to type 2 diabetes mellitus.

Insulin-like growth factor I (IGF-I) is an important regulator of many aspects of growth, differentiation, and development, and as low birth weight has been associated with impaired glucose tolerance and overt type 2 diabetes in adult life, we considered the genes encoding the IGF-I and the IGF-I receptor (IGF-IR) as candidates for low birth weight, insulin resistance, and type 2 diabetes. Here we report the mutational analysis of the coding regions of the IGF-I and IGF-IR performed on genomic DNA from probands of 82 Danish type 2 diabetic families. No mutations predicting changes in the amino acid sequences of the IGF-I or IGF-IR genes were detected, but several silent and intronic polymorphisms were found. The impact of the most prevalent polymorphism, GAG1013GAA of the IGF-IR, was evaluated in a population-based sample of 349 young healthy subjects, where the variant had an allele frequency of 0.44 (95% confidence interval, 0.40-0.48). No significant relationships between this variant and birth weight, birth length, or insulin sensitivity index were detected. In addition, we did not observe any significant differences in allelic frequencies of the codon 1013 variant between 395 type 2 diabetic patients (allele frequency, 0.52; 95% confidence interval, 0.49-0.55) and 238 matched glucose-tolerant control subjects (allelic frequency, 0.47; 95% confidence interval, 0.43-0.50). In conclusion, variability in the coding regions of IGF-I and the IGF-IR does not associate with reduced birth weight, insulin sensitivity index, or type 2 diabetes in the Danish population.

Adult↗
PubMed2000

Human cancer risk and exposure to 1,3-butadiene--a tale of mice and men.

OBJECTIVES: The purpose of this study was to evaluate empirically the relevance of animal-bioassay-based models for predicting human risks from exposure to 1,3-butadiene (BD) using epidemiologic data. METHODS: Relative-risk results obtained with a regression model in a recent epidemiologic study were used to estimate leukemia risk for occupational and environmental exposures to BD and to compare these estimates with those previously derived from an analysis of animal bioassay data. RESULTS: The estimates of risk were found to be highly dependent on the model used when low levels of exposure were evaluated that are of environmental concern, but not at the levels of occupational concern. For example, at the level (1 part per million) of the recently revised standard of the Occupational Safety and Health Administration in the United States the estimates of lifetime excess risk ranged from 1 to 8 per 1000 workers. The range of the risk estimates derived from the epidemiologic models was remarkably similar to the range of risk estimates for occupational exposures (1 to 9 per thousand) previously developed by Dankovic et al in 1993 from an analysis of a mouse bioassay study for lymphocytic lymphoma. CONCLUSIONS: Results for BD seem to provide another example of a high degree of concordance between the risk predictions from models of toxicologic and epidemiologic data, particularly at occupational levels of exposure.

Adult↗
PubMed2000

Clinical PET imaging with the C-PET camera.

OBJECTIVE: Clinical PET studies require a high-performance and user-friendly PET camera. The C-PET camera uses a simple design and a large field of view for these purposes. METHODS: We describe the camera features, daily quality control, and routine clinical study preparation, performance, processing and presentation from the technologist's perspective. RESULTS: The C-PET camera is used for whole-body cancer, cardiac and brain imaging. It operates clinically near its peak performance. The 25.6-cm axial field of view (FOV), lack of interplane septa and singles transmission capability allow 70 cm of the body to be surveyed in less than 1 h with good image quality. Quality control procedures take 30 min per day. Clinical scans and image processing are menu driven, allowing the technologist to perform several tasks simultaneously. Fully corrected images typically are available for physician review within 1 h of acquisition. The current procedures are outlined. CONCLUSION: The C-PET camera uses a clinically oriented design for rapid acquisition and presentation of high-quality PET images. Operation is straightforward and user-friendly.

Female↗
PubMed2000

Saving the diabetic foot.

This article reviews the pathophysiology, anatomy, and proper care of foot infections in the diabetic patient. Several case studies are presented.

Combined Modality Therapy↗
PubMed1999

The mitochondrial TIM22 preprotein translocase is highly conserved throughout the eukaryotic kingdom.

The Mohr-Tranebjaerg syndrome (MTS), a neurodegenerative syndrome characterized by progressive sensorineural hearing loss, dystonia, mental retardation and blindness, is a mitochondrial disease caused by mutations in the deafness/dystonia peptide 1 (DDP1) gene. DDP1 shows similarity to the yeast proteins Tim9, Tim10 and Tim12, components of the mitochondrial import machinery for carrier proteins. Here, we show that DDP1 belongs to a large family of evolutionarily conserved proteins. We report the identification, chromosomal localization and expressional analysis of six human family members which represent further candidate genes for neurodegenerative diseases.

Amino Acid Sequence↗