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Biomedical subjects

R W Taylor

Publications and source records attributed to R W Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1999

Peptide nucleic acid delivery to human mitochondria.

Peptide nucleic acids (PNAs) are synthetic polynucleobase molecules, which bind to DNA and RNA with high affinity and specificity. Although PNAs have enormous potential as anti-sense agents, the success of PNA-mediated gene therapy will require efficient cellular uptake and sub-cellular trafficking. At present these mechanisms are poorly understood. To address this, we have studied the uptake of biotinylated PNAs into cultured cell lines using fluorescence confocal microscopy. In human myoblasts, initial punctate staining was followed by the release of PNAs into the cytosol and subsequent localisation and concentration in the nucleus. To determine whether PNAs could also be used as therapeutic agents for mtDNA disease, we attempted to localise PNAs to the mitochondrial matrix. When attached to the presequence peptide of the nuclear-encoded human cytochrome c oxidase (COX) subunit VIII, the biotinylated PNA was successfully imported into isolated organelles in vitro. Furthermore, delivery of the biotinylated peptide-PNA to mitochondria in intact cells was confirmed by confocal microscopy. These studies demonstrate that biotinylated PNAs can be directed across cell membranes and to a specific sub-cellular compartment within human cells - highlighting the importance of these novel molecules for human gene therapy.

Animals↗
PubMed1999

An mtDNA mutation in the initiation codon of the cytochrome C oxidase subunit II gene results in lower levels of the protein and a mitochondrial encephalomyopathy.

A novel heteroplasmic 7587T-->C mutation in the mitochondrial genome which changes the initiation codon of the gene encoding cytochrome c oxidase subunit II (COX II), was found in a family with mitochondrial disease. This T-->C transition is predicted to change the initiating methionine to threonine. The mutation load was present at 67% in muscle from the index case and at 91% in muscle from the patient's clinically affected son. Muscle biopsy samples revealed isolated COX deficiency and mitochondrial proliferation. Single-muscle-fiber analysis revealed that the 7587C copy was at much higher load in COX-negative fibers than in COX-positive fibers. After microphotometric enzyme analysis, the mutation was shown to cause a decrease in COX activity when the mutant load was >55%-65%. In fibroblasts from one family member, which contained >95% mutated mtDNA, there was no detectable synthesis or any steady-state level of COX II. This new mutation constitutes a new mechanism by which mtDNA mutations can cause disease-defective initiation of translation.

Adult↗
PubMed1999

Lactose malabsorption and rate of bone loss in older women.

OBJECTIVES: to study the prevalence of lactose malabsorption with increasing age and to determine whether lactose malabsorbers consume less dietary calcium, have lower bone mineral density or display faster bone loss than lactose absorbers. DESIGN: 80 healthy Caucasian women aged 40-79 years (20 per decade) were studied for 1 year. METHODS: breath hydrogen exhalation was measured for 3 after a 50 g oral lactose challenge. Bone density was assessed in the radius, femoral neck, lumbar spine and total body by dual energy x-ray absorptiometry and dietary calcium intake was estimated by 4-day diet records and food-frequency questionnaires. RESULTS: lactose malabsorption rose with age (15% in those aged 40-59 years versus 50% in those aged 60-79; P < 0.01). Malabsorbers aged 70-79 years consumed significantly less calcium than lactose absorbers of this age (P < 0.05). Baseline total body calcium values were lower in lactose malabsorbers (n=26) than in lactose absorbers (n=54) but age-adjustment eliminated this difference. Bone change (% per year) was correlated with dietary calcium intake at the femoral neck and trochanter (P < 0.05) but was not statistically greater in malabsorbers than in absorbers. CONCLUSIONS: the ability to absorb lactose declines in the 7th decade. This may contribute to decreased dietary intakes of milk products and calcium in elderly women. However, lactose malabsorption without reduction in calcium intake has little effect on bone mineral density or the rate of bone loss.

Adult↗
PubMed1998

Diagnosis of mitochondrial disease: assessment of mitochondrial DNA heteroplasmy in blood.

Mitochondrial DNA (mtDNA) mutations are an important cause of neurological disease. The identification of causative mtDNA mutations may be particularly troublesome in blood where there are often low levels of mutant mtDNA. This is evident from a recent study in which heteroplasmic mtDNA mutations in cytochrome c oxidase genes were incorrectly thought to be linked to Alzheimer's disease. We wished to explore whether analysis of blood mtDNA, prepared by a number of DNA extraction procedures, influenced the diagnosis of mtDNA disease. DNA was extracted by different procedures from 4 patients with heteroplasmic mtDNA mutations, and the level of heteroplasmy investigated by radioactive PCR-RFLP analysis. Whilst there was no consistent decrease in the level of mtDNA heteroplasmy, we observed the coamplification of a novel mtDNA pseudogene from DNA samples extracted by a simple 'boiling' procedure using primers designed to screen for the tRNALeu(UUR) A3243G mutation. This pseudogene was readily amplified from DNA extracted from rho degrees (mtDNA-less) cells, confirming its nuclear location. We believe that mtDNA pseudogenes may therefore present significant difficulties in the accurate identification of pathogenic heteroplasmic mtDNA mutations in blood.

DNA, Mitochondrial↗
PubMed1998

A novel mitochondrial DNA point mutation in the tRNA(Ile) gene: studies in a patient presenting with chronic progressive external ophthalmoplegia and multiple sclerosis.

We report a new mutation, a G to A transition at nucleotide position 4298 within the mitochondrial tRNA(Ile) gene in a patient with chronic progressive external ophthalmoplegia and multiple sclerosis. The mutation, which alters an evolutionary conserved nucleotide within the anticodon stem, was heteroplasmic in skeletal muscle but was not present in the patient's blood. Single fibre PCR analysis revealed significantly higher levels of the G4298A mutation in cytochrome c oxidase (COX) negative fibres than in COX-positive fibres. This mutation represents the seventh pathogenic nucleotide substitution to be found in this gene and as such confirms the tRNA(Ile) gene as a susceptible "hot spot" for mitochondrial DNA point mutations. Of particular interest is that this patient has the clinical features of both multiple sclerosis and a mitochondrial DNA disorder.

Animals↗
PubMed1998

Plasma leptin values in relation to bone mass and density and to dynamic biochemical markers of bone resorption and formation in postmenopausal women.

After the menopause it has been noted that heavier women conserve bone better than those with lower body weight. The protective effect of obesity on bone mass has been ascribed to a high body fat content. The present study of 54 postmenopausal women was undertaken to determine whether circulating plasma levels of leptin, the newly described hormone produced in adipocytes, were correlated with age-adjusted total body bone mineral content (BMC) or bone mineral density (BMD), or with dynamic biochemical markers of bone resorption or of bone formation. Leptin values were strongly correlated with all measures of adiposity (P < 0.001). Age-adjusted values for BMC and BMD, respectively, were also positively correlated (P < 0.001) with body weight (r = 0.643, r = 0.502), total fat mass (r = 0.557, r = 0.510) and with plasma leptin concentrations (r = 0.480, r = 0.551), confirming a positive relationship between fat mass and bone mass. By contrast, no significant correlations were observed between plasma leptin and dynamic markers of bone resorption (urinary deoxypyridinoline/creatinine r = -0.105, hydroxyproline/creatinine r = -0.193) or formation (plasma osteocalcin r = 0.103). Because there was no evidence for an association between ciculating plasma levels of leptin and biochemical markers of either osteoclastic or osteoblastic activity we conclude it is unlikely that circulating leptin plays any significant direct role in controlling bone cell activity. Our results do not support the hypothesis that leptin mediates the bone-sparing effects of obesity.

Aged↗
PubMed1998

Mechanism and specificity of lanthanide series cation transport by ionophores A23187, 4-BrA23187, and ionomycin.

A23187, 4-BrA23187, and ionomycin transport several lanthanide series trivalent cations at efficiencies similar to Ca2+, when compared at cation concentrations of approximately 10(-5) M, ionophore concentrations of approximately 10(-6) M, and a pH of 7.00. Selectivity sequences and the range of relative rates are as follows: A23187, Nd3+ > La3+ > Eu3+ > Gd3+ > Er3+ > Yb3+ > Lu3+ (approximately 34-fold); 4-BrA23187, Nd3+ > Eu3+ > Gd3+ > La3+ > Er3+ > Yb3+ > Lu3+ (approximately 34-fold); ionomycin, La3+ > Yb3+ > Nd3+ > Lu3+ > Er3+ > Eu3+ > Gd3+ (approximately 4-fold). At concentrations between 9 and 250 microM, La3+ is transported by an electroneutral mechanism, predominately through mixed complexes of the type (ionophore)2La-OH (A23187 and 4-BrA23187) or (ionophore)La-OH (ionomycin), when no membrane potential is present. For all three ionophores, an induced potential of approximately 160 mV accelerates transport by approximately 50-100%. However, measured values of H+/La3+ exchange indicate that only 4-BrA23187 displays a significant electrogenic activity under these conditions. At a La3+ concentration of 17 mM, transport by all three ionophores is electroneutral and apparently occurs through complexes of type (ionophore)3La (A23187 and 4-BrA23187) or (ionophore)La-OH (ionomycin). Analysis of these patterns in a context of comproportionation equilibria involving the transporting species and free La3+ indicates that the species containing three ionophore molecules are formed on the membrane when aqueous phase solution conditions would strongly favor a 1:1 complex, based upon previous studies in solution. The implications of this and other findings are discussed.

Aminoquinolines↗
PubMed1998

Eruptive abnormalities in orthodontic treatment.

In the course of orthodontic practice, it is inevitable that one will encounter what is termed here eruptive abnormalities. These abnormalities include teeth that are impacted, ectopically erupting, or transposed. Hyperdontia and hypodontia are also included for consideration. The treatment plans developed to address these anomalies must take into account the space needs of the patient and how one can best gain, maintain, or redistribute that space. Also, soft tissue reactions to the movements also should be considered.

Anodontia↗
PubMed1998

Validation of a short food frequency questionnaire to assess calcium intake in children aged 3 to 6 years.

OBJECTIVE: To assess the validity of a short calcium food frequency questionnaire (FFQ) for use in young children. DESIGN: Calcium intake from an estimated 4 d diet record (4DDR) was compared with the calcium intake from a 35 item FFQ specifically designed to assess habitual calcium intake and previously validated for adult women. SUBJECTS: Forty-one girls and 26 boys aged 3-6 y recruited by advertisement for studies of nutrition and bone health. RESULTS: Mean (s.d.) calcium intakes were 798 mg (271) and 942 mg (419) for the 4DDR and FFQ respectively, (r = 0.52). Mean difference (s.d. of difference) in calcium intake between the two methods was 144 mg (355), showing that the FFQ may estimate calcium intakes 565 mg below to 854 mg above diet record values. 84% of subjects when classified by the 4DDR fell into the same or adjacent quartiles when classified by the FFQ. Only two subjects were classified in extreme quartiles for the two methods. The FFQ correctly identified 68% of children with recorded intakes less than 800 mg. CONCLUSIONS: The short calcium FFQ tended to overestimate actual calcium intakes in young children, and would not be appropriate for determining calcium intake of individuals. However, the FFQ demonstrated good ability to classify subjects into extremes of calcium intake. Moreover, the predictive value of the FFQ in identifying children with intakes below the current recommended intake of 800 mg was reasonably high (79%).

Adult↗
PubMed1998

Determining cephalometric norms for Caucasians and African Americans in Birmingham.

The purpose of this study was to establish age- and sex-specific normative data for Caucasians and African Americans in Birmingham, Ala. Subjects (136) between 6 and 18 years old were included in the study. Chang's method (AF-BF) and 12 other measurements were used as determinates of the skeletal sagittal jaw relationship. All subjects had acceptable facial profiles and Class I occlusion. Subjects were divided into eight subgroups based on race, gender, and age. Differences of mean cephalometric values were tested using parametric and nonparametric statistical tests. Compared with Caucasians, African Americans had greater mean values for all measurements except AFB and AF-BF. More negative values were found for the African Americans in the Wits appraisal. Most measurements were found to decrease with age. These findings support our hypothesis that cephalometric norms should be based on racial, sex, and age differences.

Adolescent↗
PubMed1998

Mesh diagram cephalometric norms for Americans of African descent.

The aim of this study was to establish cephalometric norms for African-American males and females, to compare these measurements with the findings of Alexander's "Alabama analysis," and to construct mesh templates for various age groups. The sample we evaluated included 71 African-Americans, divided into four groups: girls (8 to 12 years), boys (8 to 12 years), adolescent females (13 to 20 years), and adolescent males (13 to 20 years). The subjects met the following criteria: (1) normal Class I dental and skeletal relationship with minimal crowding, (2) balanced facial profile, and (3) no history of orthodontic treatment. The cephalometric radiographs were traced by hand, and linear and angular measurements were averaged to establish a mean with which to locate the anatomic landmarks used in the mesh diagram. In this study the African-Americans differed significantly from white Americans with regard to dental, skeletal, and soft tissue parameters. On average, the African-American subjects displayed larger SNA and ANB angles, more proclined lower incisors, and a more acute interincisal angle than did the white sample. Measurements between our African-American group and that of Alexander's African-American group in the "Alabama analysis" were consistent.

Adolescent↗
PubMed1998

Body mass index, waist girth, and waist-to-hip ratio as indexes of total and regional adiposity in women: evaluation using receiver operating characteristic curves.

Receiver operating characteristic (ROC) curves were constructed to assess the value of body mass index (BMI) as a screening measure for total adiposity and to examine waist-to-hip ratio (WHR) and waist circumference as measures of central fat distribution. Body fat reference measurements were determined by dual-energy X-ray absorptiometry (DXA). The study population comprised 96 healthy white women aged 16-80 y. A positive reference test was defined as a result at or above the 75th percentile for our study population for all DXA measurements. Sensitivity and specificity were calculated at several percentile cutoffs for BMI, WHR, and waist girth. The areas under the ROC curves were calculated to compare the relative ability of each anthropometric technique to correctly classify subjects according to the reference measurement for that technique. BMI (our 75th percentile = 27.3) performed well as a screening measure of total adiposity, correctly identifying 83% of subjects with a high body fat mass while misclassifying only eight subjects [four false-negatives (subjects with high fat mass who were in the low BMI category) and four false-positives (subjects with a low fat mass who were in the high BMI category)]. The screening performance of WHR (our 75th percentile = 0.81) was lower, accurately categorizing 58% of subjects while misclassifying 28 subjects. By contrast, waist circumference (our 75th percentile = 86.9 cm) was significantly better than WHR at screening for regional fat distribution, accurately classifying 83% of subjects and misclassifying eight subjects (P < 0.05). We conclude that BMI and waist circumference provide simple yet sensitive methods for the estimation of total and central adiposity in groups of adult women.

Absorptiometry, Photon↗
PubMed1998

Effects of inhaled nitric oxide in patients with acute respiratory distress syndrome: results of a randomized phase II trial. Inhaled Nitric Oxide in ARDS Study Group.

OBJECTIVES: To evaluate the safety and physiologic response of inhaled nitric oxide (NO) in patients with acute respiratory distress syndrome (ARDS). In addition, the effect of various doses of inhaled NO on clinical outcome parameters was assessed. DESIGN: Prospective, multicenter, randomized, double-blind, placebo-controlled study. SETTING: Intensive care units of 30 academic, teaching, and community hospitals in the United States. PATIENTS: Patients with ARDS, as defined by the American-European Consensus Conference, were enrolled into the study if the onset of disease was within 72 hrs of randomization. INTERVENTIONS: Patients were randomized to receive placebo (nitrogen gas) or inhaled NO at concentrations of 1.25, 5, 20, 40, or 80 ppm. MEASUREMENTS AND MAIN RESULTS: Acute increases in PaO2, decreases in mean pulmonary arterial pressure, intensity of mechanical ventilation, and oxygenation index were examined. Clinical outcomes examined were the dose effects of inhaled NO on mortality, the number of days alive and off mechanical ventilation, and the number of days alive after meeting oxygenation criteria for extubation. A total of 177 patients were enrolled over a 14-month period. An acute response to treatment gas, defined as a PaO2 increase > or =20%, was seen in 60% of the patients receiving inhaled NO with no significant differences between dose groups. Twenty-four percent of placebo patients also had an acute response to treatment gas during the first 4 hrs. The initial increase in oxygenation translated into a reduction in the FIO2 over the first day and in the intensity of mechanical ventilation over the first 4 days of treatment, as measured by the oxygenation index. There were no differences among the pooled inhaled NO groups and placebo with respect to mortality rate, the number of days alive and off mechanical ventilation, or the number of days alive after meeting oxygenation criteria for extubation. However, patients receiving 5 ppm inhaled NO showed an improvement in these parameters. In this dose group, the percentage of patients alive and off mechanical ventilation at day 28 (a post hoc analysis) was higher (62% vs. 44%) than the placebo group. There was no apparent difference in the number or type of adverse events reported among those patients receiving inhaled NO compared with placebo. Four patients had methemoglobin concentrations >5%. The mean inspired nitrogen dioxide concentration in inhaled NO patients was 1.5 ppm. CONCLUSIONS: From this placebo-controlled study, inhaled NO appears to be well tolerated in the population of ARDS patients studied. With mechanical ventilation held constant, inhaled NO is associated with a significant improvement in oxygenation compared with placebo over the first 4 hrs of treatment. An improvement in oxygenation index was observed over the first 4 days. Larger phase III studies are needed to ascertain if these acute physiologic improvements can lead to altered clinical outcome.

Acute Disease↗
PubMed1998

Plasma leptin in relation to regional body fat in older New Zealand women.

BACKGROUND: Leptin is the protein product of the obesity (ob) gene and is produced in adipose tissue. Plasma leptin values are highly correlated with total body fat mass but less is known concerning relationships of leptin with regional adiposity. AIM: To investigate associations between leptin and dual energy X-ray absorptiometry (DEXA) measures of regional body fat deposition in older New Zealand women. METHODS: Body composition was measured in 80 women aged 40 to 79 years (20 in each decade) using DEXA. Height and weight were measured by conventional anthropometry. Plasma leptin concentrations were assayed by radioimmunoassay. RESULTS: Leptin was strongly correlated (p < 0.001) with weight (r = 0.751), body mass index (r = 0.782), total fat mass (r = 0.854) and % fat mass (r = 0.813). A statistical model with trunk fat (kg) and leg fat (kg) as the independent variables showed that trunk fat accounted for 72.1% of the variance in plasma leptin with leg fat explaining only a further 1.6% of the variance. No relationships were found between leptin and age, height, lean tissue mass or menopausal status (p > 0.05). CONCLUSIONS: We conclude that trunk fat explains more of the variance in circulating leptin concentrations than leg fat, suggesting that the propensity to leptin resistance may be increased in women with higher central adiposity.

Absorptiometry, Photon↗
PubMed1998

Bone mineral density in girls with forearm fractures.

In childhood, the most common site of fracture is the distal forearm. To determine whether young girls with these fractures have low bone density more commonly than fracture-free controls, we measured bone density at the radius, spine, hip, and whole body and total body bone mineral content, lean tissue mass, and fat mass by dual-energy X-ray absorptiometry in 100 Caucasian girls aged 3-15 years with recent distal forearm fractures and 100 age- and gender-matched controls. Bone density (age-adjusted ratios of all cases:controls with 95% confidence intervals) was lower in cases at the ultradistal radius 0.963 (0.930-0.996), 33% radius 0.972 (0.945-0.999), lumbar spine 0.945 (0.911-0.980), hip trochanter 0.952 (0.918-0.988), and total body 0.978 (0.961-0.995). Moreover, osteopenia (defined as Z score below -1), was more common in cases than controls (p < 0.05) in the forearm, spine, and hip, with one third of fracture cases having low spinal density. Odds ratios (95% confidence intervals) for low bone density were: ultradistal radius, 2.2 (1.1-4.6); lumbar spine, L2-L4, 2.6 (1.3-4.9); and femur trochanter, 2.0 (1.0-3.9). Fracture patients aged 8-10 years weighed more (mean +/- SD) than age-matched controls (37.2+/-8.0 kg vs. 32.5+/-6.6 kg, p < 0.01) while older patients reported lower current and past calcium intakes than matched controls (p < 0.05). We conclude that low bone density is more common throughout the skeleton in girls with forearm fractures than in those who have never broken a bone, supporting the view that low bone density may contribute to fracture risk in childhood.

Adolescent↗