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Biomedical subjects

D Dyer

Publications and source records attributed to D Dyer.

At least 19 recordsLinked to original sources
PubMed2001

Abrasion and stain removal by different manual toothbrushes and brush actions: studies in vitro.

BACKGROUND AND AIMS: A limited amount of data using flat trim multitufted toothbrushes shows that abrasion of substrate surfaces by a standard toothpaste varies dependent on filament stiffness and configuration; soft brushes producing the most abrasion. The aims of these studies in vitro were to assess toothpaste abrasion of acrylic and stain removal by 5 proprietary medium toothbrushes with different head filament arrangements, and a prototype brush with rectangular filaments. The prototype brush had a medium texture in the long axis and soft texture at right angles to the long axis. MATERIAL AND METHOD: Optically clear acrylic was used as the substrate for abrasion by a standard toothpaste. Loss of substrate was determined by profilometry after 5000, 10000, 15000 and 20000 linear or rotary brushing actions. Stain removal was determined spectrophotometrically from optically clear acrylic specimens stained by chlorhexidine tea soaking sequences. Stained specimens were brushed with water using linear or rotary actions and measurements taken every 10 s to 60 s. RESULTS: Abrasion was progressive with increasing strokes and the pattern for each brush and brush action was to a first approximation linear. Overall, abrasion was significantly greater with linear compared to rotary action. Also overall brushes differed in the abrasion produced with both actions and particularly at greater exposure times. Within brush differences for the two motions were all significant by 20000 strokes except for the prototype brush. Stain removal was progressive over time with each brush but the pattern was non-linear. For the proprietary brushes the rotary motion removed less stain. For the prototype brush more stain was removed with the rotary action. Overall brushes differed significantly in stain removal within each motion and for each motion most differences between the proprietary and prototype brushes reached significance. CONCLUSIONS: The differences between brushes for both abrasion and stain removal must in large part relate to the filament contact area with the substrate surface. Whilst the model may not be predictive of clinical differences, it could find use to establish minimum criteria for toothbrush action.

Acrylic Resins↗
PubMed2001

Mode of reproduction and amplified fragment length polymorphism variation in purple needlegrass (Nassella pulchra): utilization of natural germplasm sources.

A dominant plant of the California grasslands, purple needlegrass [Nassella pulchra (Hitchc.) Barkworth] is an important revegetation species in its native range. The amplified fragment length polymorphism (AFLP) method was used to elucidate mode of reproduction and nucleotide variation among 11 natural populations and three selected natural germplasm releases of N. pulchra. A total of 12 co-dominant AFLPs, informative within eight populations, failed to reveal any heterozygous individuals, indicating very high selfing rates (S(H)=1). Estimates of nucleotide diversity within populations ranged from 0 to 0.00069 (0.00035 average), whereas the total nucleotide divergence among populations ranged from 0.00107 to 0.00382 (0.00247 average). Measures of population differentiation (GS) in terms of Shannon-Weaver diversity values and estimated nucleotide substitutions were 0.90 and 0.86, respectively. Although some of the sample populations contained a mixture of true breeding genotypes, most populations could be distinguished unambiguously. Moreover, geographical distance between the natural source populations was significantly correlated with genetic distance (r = 0.60) among the corresponding sample populations. Results indicate that inbreeding, combined with founder effects and/or selection, has contributed to the differentiation of N. pulchra populations. Foundation seed populations of the selected natural germplasm releases were genetically well defined and most similar to natural seed collected near the corresponding source populations. Thus, these commercial germplasm sources will be made practically available and useful for conservation plantings within the intended areas of utilization.

California↗
PubMed2000

Studies in vitro of abrasion by different manual toothbrush heads and a standard toothpaste.

BACKGROUND: Loss of dentine at the buccal cervical region of teeth has a multifactorial aetiology. However, a considerable amount of circumstantial evidence, supported by laboratory experiments, implicates toothbrushing with toothpaste as a consistent factor. Most interest has centred around the abrasivity of toothpastes, particularly since a toothbrush alone has negligible effects on dentine. The influence of filament stiffness on toothpaste abrasion was the subject of some studies, mostly at least 2 decades ago, and produced conflicting conclusions. Numerous changes to toothbrush design and construction have taken place in recent years. AIMS: The aim of this study was to measure the abrasion of a standard substrate, acrylic, by a standard toothpaste carried on modern brands of toothbrushes classified by manufacturers as hard (3 brands), medium (3 brands) and soft (6 brands). METHOD: The substrate was brushed for 20,000 strokes with at least 6 heads from each brand. Measurements of substrate loss were made at 5000 stroke increments by profilometry. RESULTS: Substrate loss for all brushes showed a pattern of abrasion which was to a first approximation linear. Overall, hard brushes caused least abrasion and soft brushes the most, with differences between groups being significant. Within-group differences between brands reached significance for soft and medium brushes but not hard brushes. CONCLUSIONS: The results could be explained by increased retention of toothpaste by smaller diameter filaments and denser tufts on soft brushes and the greater flexion of filaments increasing the area of contact with the surface. Calculations on the clinical outcome of these data in vitro indicate that toothbrushing with toothpaste alone would produce minimal damage to dentine even over many years. Differences between brushes therefore are probably of little clinical significance. Certainly, the data do not support the use of hard brushes, particularly in view of the potential detrimental effects to gingival tissues.

Hardness↗
PubMed1999

Germination responses and boron accumulation in germplasm from Chile and the United States grown with boron-enriched water.

Boron (B) is toxic to most plant species when accumulated in high concentrations. Differences in a plant's ability to adapt to high concentrations of B may depend on the origin of the germplasm. Chilean and domestic (U.S.) germplasm, corn (Zea mays L.), carrots (Daucus carotas), tomato (Lycopersicum esculentum L.), and alfalfa (Medicago sativa L.) were evaluated for germination, emergence of cotyledonary leaves, and tissue B accumulation under high-B conditions in both an environmental growth chamber and a greenhouse. Increasing B levels (20-40 mg B liter-1) inhibited the percentage germination for both the Chilean and domestic germplasm. Chilean germplasm exhibited generally a greater percentage of healthy cotyledonary leaves at the 20 mg B liter-1 treatment than the domestic germplasm. Comparing B concentrations between both germplasm grown and irrigated with B-enriched water (10-20 mg B liter-1) under greenhouse conditions, leaves from domestic germplasm contained more B. Moreover, B troxicity symptoms were more severe for the tested plant species from the domestic germplasm. Apparent B tolerance by germplasm of different origin should be further tested under field conditions.

Boron↗
PubMed1999

Correlation of CT findings with clinical evaluations in 261 patients with symptomatic bronchiectasis.

OBJECTIVE: In a multicenter study, we evaluated the relationships between the extent and severity of bronchiectasis on CT and clinical symptoms, spirometric abnormality, and sputum characteristics. SUBJECTS AND METHODS: The study population included 261 patients with symptomatic, physiologically significant bronchiectasis, who were enrolled in another study evaluating the clinical efficacy of deoxyribonudease in treatment of bronchiectasis. Patients with cystic fibrosis, allergic bronchopulmonary aspergillosis, and fungal or mycobacterial infection were excluded. In addition to high-resolution CT scanning, all patients underwent clinical evaluation, spirometry, and sputum culture. CT features scored by consensus of two observers included the extent of bronchiectasis, type of bronchiectasis (cylindric, varicose, or cystic), extent of mucoid impaction, and degree of bronchial wall thickening. RESULTS: Scores for the severity and extent of bronchiectasis correlated with the forced expiratory volume in 1 sec (FEV1) (r = -.362, p < .0001) and with the forced vital capacity (FVC) (r = -.362, p < .0001). Scores for bronchial wall thickening correlated with the FEV1 (r = -.367, p < .0001) and FVC (r = -.239, p < .001). Patients with cystic bronchiectasis were significantly more likely to grow Pseudomonas from their sputa and to have purulent sputa than were patients with cylindric or varicose bronchiectasis. Patients with cystic bronchiectasis had significantly lower FEV1 and FVC values than did patients with cylindric or varicose bronchiectasis. CONCLUSION: In this patient population, we found weak but significant correlations between the degree of morphologic abnormality on CT and the extent of physiologic impairment. Cystic bronchiectasis was associated with sputum purulence and with the growth of Pseudomonas. CT classification of the type of bronchiectasis may be useful as an index of severity of disease.

Bronchi↗
PubMed1999

Risk factors for infection with Toxoplasma gondii for residents and workers on swine farms in Illinois.

Risk factors for Toxoplasma gondii infection in workers and residents of swine farms were studied on 43 farms in Illinois. Blood samples were collected from 174 adults in 1993. The T. gondii seroprevalence was 31%. An interview was conducted with each participant, obtaining information on demographic characteristics and behaviors suspected to affect the risk of T. gondii infection. Factors associated with increased risk of T. gondii seropositivity were a higher number of seropositive cats trapped on the farm, male sex, rearing pigs on pasture, and gardening. Factors associated with a decreased risk were handling of pig feed and presence of cats inside the pig facilities. Thus, infection of cats with T. gondii increased the risk of human infection, and contact with soil was a likely mechanism for transmission. The increased risk of seropositivity in males is attributed to less attention paid to cleanliness in food preparation and eating.

Adult↗
PubMed1998

Biotin uptake by human colonic epithelial NCM460 cells: a carrier-mediated process shared with pantothenic acid.

Previous studies showed that the normal microflora of the large intestine synthesizes biotin and that the colon is capable of absorbing intraluminally introduced free biotin. Nothing, however, is known about the mechanism of biotin absorption in the large intestine and its regulation. To address these issues, we used the human-derived, nontransformed colonic epithelial cell line NCM460. The initial rate of biotin uptake was found to be 1) temperature and energy dependent, 2) Na+ dependent (coupling ratio of 1:1), 3) saturable as a function of concentration [apparent Michaelis constant (Km) of 19.7 microM], 4) inhibited by structural analogs with a free carboxyl group at the valeric acid moiety, and 5) competitively inhibited by the vitamin pantothenic acid (inhibition constant of 14.4 microM). Pretreatment with the protein kinase C (PKC) activators phorbol 12-myristate 13-acetate (PMA) and 1, 2-dioctanoyl-sn-glycerol significantly inhibited biotin uptake. In contrast, pretreatment with the PKC inhibitors staurosporine and chelerythrine led to a slight, but significant, increase in biotin uptake. The effect of PMA was mediated via a marked decrease in maximal uptake velocity and a slight increase in apparent Km. Pretreatment of cells with modulators of the protein kinase A-mediated pathway, on the other hand, showed no significant effect on biotin uptake. These results demonstrate, for the first time, the functional existence of a Na+-dependent, specialized carrier-mediated system for biotin uptake in colonic epithelial cells. This system is shared with pantothenic acid and appears to be under the regulation of an intracellular PKC-mediated pathway.

Alkaloids↗
PubMed1996

Chest physiotherapy and post-extubation atelectasis in infants.

We investigated the role of chest physiotherapy (CPT) in preventing post-extubation atelectasis (PEA) in infants. Sixty-three infants who were admitted to the neonatal intensive care unit and intubated for more than 24 hours and who showed no evidence of atelectasis by chest x-ray prior to extubation were enrolled in the study. Infants were randomly assigned to 2-hourly CPT, 4-hourly CPT, or a no CPT group. Chest physiotherapy began immediately after extubation and consisted of postural drainage, bilateral chest vibration, and suctioning. A second chest x-ray was obtained on all infants 24 hours following extubation. The three groups were comparable in birth weight, gestational age, and duration of intubation. In the 24-hour period following extubation, the incidence of PEA was not statistically significant in the three groups (P = 0.33). Two infants in the 2-hourly CPT group were placed on nasal continuous positive airway pressure; two in each of the 2-hourly and the no CPT groups required re-intubation and intermittent positive pressure ventilation to treat symptomatic atelectasis. We conclude that post extubation chest physiotherapy as used in this study did not prevent atelectasis in extubated infants.

Drainage, Postural↗
PubMed1996

The use of phosphodiesterase inhibitor (dipyridamole) to wean from inhaled nitric oxide.

A full-term, male neonate developed persistent pulmonary hypertension, and responded to high-frequency oscillatory ventilation and inhaled nitric oxide (INO). Discontinuation of INO was attempted three times and was followed by severe desaturations due to right-to-left shunt through the patent ductus arteriosus and patent foramen ovale. As a result of this rebound pulmonary hypertension, the neonate was maintained on INO therapy for 6 days. Successful discontinuation was achieved by using the phosphodiesterase inhibitor, dipyridamole. We speculate that during exogenous INO therapy, endogenous nitric oxide was inhibited, thus cyclic guanosine 3',5'-monophophate, the smooth muscle relaxant, was rapidly hydrolyzed. By inhibiting phosphodiesterase, smooth muscle relaxation occurred, and consequently weaning from INO was achieved.

Administration, Inhalation↗
PubMed1994

Selective bronchial occlusion for treatment of bullous interstitial emphysema and bronchopleural fistula.

A preterm infant, ventilated for hyaline membrane disease, had severe right-sided pulmonary interstitial emphysema, left-sided compression atelectasis, and bronchopleural fistula. Several modalities of treatment were tried and were unsuccessful. Selective bronchial occlusion with a balloon catheter resulted in dramatic improvement in the patient's clinical and radiographic condition.

Bronchi↗
PubMed1993

Multidisciplinary rehabilitation of chronic work-related upper extremity disorders. Long-term effects.

The prevalence of work-related upper extremity disorders has significantly increased in the past decade. Persistent pain, loss of function, and associated work disability in patients with work-related upper extremity disorders appears to be affected by multiple factors including physical capabilities in relation to work demands, ergonomic risk factors on the job, and psychological factors related to worker traits, psychological readiness to return to work, and ability to manage symptoms. The complex nature of these disorders suggests the utility of a multidisciplinary program targeted at these factors. The present study is an investigation of the long-term vocational outcome of a multicomponent rehabilitation program that includes physical conditioning, work conditioning, work-related pain and stress management, ergonomic consultation, and vocational counseling/placement. Two groups equivalent on measures of duration of work disability, pain severity, fear of reinjury, psychological distress, perceived work environment, age, and education level were exposed to either the comprehensive work rehabilitation intervention (n = 19) or usual care (n = 15). Return-to-work status was determined at an average of 17 months posttreatment (range, 3 to 35 months) for the treatment group and an average of 18 months postevaluation (range, 5 to 30 months) for the usual care group. Findings indicated that 74% of the treatment group returned to work or were involved in state-supported vocational training in contrast to 40% of the control group (P < .05). For those who returned to work, 91% of the treatment group were working full-time in contrast to 50% of the control group (P < .05). Although the treatment group demonstrated a higher return-to-work rate than controls, the work reentry rate was not as high as similar approaches with work-related low back pain (80% to 88% return-to-work rate). These findings suggest the need to modify treatment components to facilitate an increased return-to-work rate. Areas that may prove useful include a greater emphasis ergonomic modifications at the workplace to reduce the risks of repetitiveness, force, awkward posture, and insufficient work/rest cycles, as well as efforts to modify work style directly in order to reduce the impact of ergonomic stressors on the ability to perform essential job tasks. In combination with traditional work hardening efforts directed at improving strength and flexibility of the upper extremities and work-related pain and stress management training, these ergonomic and work-style modification efforts may contribute to increases in the percentage of work disabled cases who successfully return to competitive work.

Arm Injuries↗
PubMed1992

The effect of active serum albumin on PC12 cells: I. Neurite retraction and activation of the phosphoinositide second messenger system.

Vertebrate blood sera contain a factor that triggers oscillatory chloride currents in Xenopus oocytes through activation of the phosphoinositide/Ca2+ second system. The active serum component consists of lipids bound to an isoform of serum albumin that we have named active serum albumin (ASA). In undifferentiated PC12 cells, micromolar concentrations of ASA inhibit the early morphological changes induced by NGF, whereas in differentiated PC12 cells ASA caused a rapid withdrawal of neurites, which was reversible and dependent upon culture age. In contrast to normal serum, plasma and thrombin did not cause neurite retraction. Preincubation of ASA with monospecific antibodies to serum albumin suppressed its ability to induce neurite retraction in a dose dependent fashion. As in the oocyte, ASA activated the phosphatidylinositol second messenger system of PC12 cells, causing a several fold increase in Ins1,4,5P3 levels within minutes of application. The Ins1,4,5P3 increase was also blocked, in a titratable fashion, when ASA was preincubated with monospecific antibodies to serum albumin. This suggests that ASA-induced neurite retraction in PC12 cells may depend, at least in part, on activation of the phosphatidylinositol second messenger system. Results involving albumin-depleted sera show that ASA is the main factor responsible for serum vulnerability of neurites in PC12 cells. These findings point to some limitations in the use of serum in culture media, and raise the possibility that the serum factor may impair neuronal plasticity in disorders that are accompanied by the activation of blood coagulation together with a breakdown of the blood-brain barrier.

Animals↗
PubMed1992

The effect of active serum albumin on PC12 cells: II. Intracellular Ca2+ transients and their role in neurite retraction.

In the preceding paper it was shown that an isoform of serum albumin (ASA; active serum albumin) causes a rapid retraction of neurites and increases intracellular content of Ins1,4,5P3 in PC12 cells. Here we examined whether ASA's effects in nerve growth factor-differentiated PC12 cells were mediated through the Ins1,4,5P3/Ca2+ second messenger pathway by monitoring intracellular Ca2+ (Ca2+i) with Fura2. It was found that ASA caused a dose-dependent increase in Ca2+i. In Ca(2+)-free medium, the increase in Ca2+i elicited by ASA was smaller, but the rise in Ins1,4,5P3 content was not appreciably changed. The small Ca2+i increase seen in Ca(2+)-free medium was probably due to the release of Ca2+ from Ins1,4,5P3-sensitive intracellular stores. In Ca(2+)-containing medium the Ca2+ transient induced by ASA was not affected by organic Ca2+ channel blockers, but decreased when Co2+, Mn2+ or Zn2+ were present in the extracellular medium. The effect of other ligands, such as carbachol and bradykinin, whose receptors are coupled to the phosphoinositide system was also investigated. Carbachol at concentrations from 2 to 200 microM, and bradykinin at a concentration of 2 microM did not cause neurite retraction, whereas 200 microM bradykinin caused an approximately 40% decrease in neurite length. Thapsigargin, a Ca(2+)-ATPase inhibitor, caused a sustained elevation of Ca2+i and retraction of neurites, whereas depolarization of the cells by high K+ gave only a transient elevation of Ca2+i, and no neurite retraction. Therefore, a sustained elevation in Ca2+i might be a sufficient trigger to induce neurite retraction in differentiated PC12 cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

A serum factor that activates the phosphatidylinositol phosphate signaling system in Xenopus oocytes.

Blood sera from many vertebrate species elicit large oscillatory chloride currents in oocytes from the frog Xenopus laevis. Rabbit serum was active at dilutions as great as one part in 10 million. Intracellularly applied serum was ineffective, and externally applied serum failed to trigger oscillatory currents when the intracellular level of ionized calcium was prevented from rising by loading the oocyte with EGTA. The serum also caused an increase of inositol 1,4,5-trisphosphate in the oocyte. We conclude that serum contains a factor which activates a membrane receptor that is coupled to the phosphatidylinositol second messenger system. The active factor is a protein with an apparent molecular mass of 60-70 kDa in gel permeation chromatography. Although the normal function of the serum factor is still unknown, it may have far-reaching implications, because it acts on the multifunctional phosphatidylinositol phosphate signaling system. Also, because of its great potency the serum factor and Xenopus oocytes are very useful for probing the operation of the phosphatidylinositol system.

Animals↗
PubMed1989

Amino terminus is essential to the structural integrity of recombinant human interferon-gamma.

Species lacking either 8 or 10 residues at the amino terminus of recombinant human interferon-gamma (Hu-IFN-gamma) were generated by limited digestion with Staphylococcus aureus V8 protease. A crude digest, consisting predominantly of these species, were completely inactive in inducing antiviral activity and the expression of HLA-DR antigens on HL-60 cells. The NH2-terminal deletion fragments were separated from residual intact IFN-gamma and from smaller polypeptides by reverse phase high performance liquid chromatography (HPLC) at pH 2.2. Intact IFN-gamma, purified by HPLC and subsequently refolded by dilution in 0.1 M sodium phosphate buffer (pH 7.5, 0.1% bovine serum albumin) was similar to untreated IFN-gamma in terms of binding to its cell surface receptor and in inducing antiviral activity and the expression of HLA-DR molecules. Conversely, biological activity was not detected in purified fragments 8-139 and 10-139. Examination of fragments 8-139 and 10-139 by far-UV circular dichroism revealed that cleavage of 8-10 residues at the amino terminus accompanied a dramatic change in secondary structure (6% alpha-helical and 36% beta-sheet content) as compared to untreated or HPLC-purified IFN-gamma (66% alpha-helix and 0% beta-sheet content). In summary, these results indicate that the amino terminus contributes to the structural integrity of the IFN-gamma molecule.

Amino Acid Sequence↗
PubMed1986

Recombination near the antibiotic resistance locus penB results in antigenic variation of gonococcal outer membrane protein I.

In gonococci, the nonspecific antimicrobial resistance locus penB is known to be closely linked to loci designated nmp that alter the Mr and antigenicity of the outer membrane porin protein I (P.I). We report that after selection for the linked donor penB locus, occasional recombinants expressed P.I with some epitopes from each parent. These hybrid P.I antigens were stable on subculture and were transformed at a locus closely linked to penB. The hybrid P.I antigens were detected with monoclonal antibodies in both coagglutination and Western blot assays. The alterations of P.I antigenicity may have resulted from recombination between structural genes for P.I that are closely linked to penB.

Antigens, Bacterial↗