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Biomedical subjects

C Robinson

Publications and source records attributed to C Robinson.

At least 253 records · Page 14Linked to original sources
PubMed1992

Excessive production of reactive oxygen metabolites by inflamed colon: analysis by chemiluminescence probe.

Reactive oxygen metabolites (ROMs) are involved in inflammatory diseases and are postulated to contribute to tissue injury in colitis. To determine whether excessive ROMs are generated by inflamed colonic mucosa and to identify possible sources and type of ROMs, mucosal ROMs were estimated in rats and humans using a chemiluminescence probe. Colitis was induced in rats by intracolonic injection of acetic acid or intraperitoneal injection of mitomycin C. Intact, inflamed colon in rats produced more ultraweak chemiluminescence than normal colon. Inflamed mucosal scrapings from both rat models produced significantly more luminol-enhanced chemiluminescence. Addition of catalase, an H2O2 scavenger, or azide, a myeloperoxidase inhibitor, into the media significantly decreased chemiluminescence from inflamed mucosal scrapings. Indomethacin, an antioxidant cyclo-oxygenase inhibitor, also decreased chemiluminescence, but MK-866, a 5-lipoxygenase inhibitor, had no effect. Colonic biopsy specimens obtained during colonoscopy from patients with ulcerative colitis also produced more catalase-inhibitable chemiluminescence than normal colonic mucosa. These data indicate that excessive ROMs are produced by inflamed colonic mucosa in both humans and rats, which may contribute to tissue injury.

Adult↗
PubMed1992

Thermal analysis of commercial Gutta-percha using differential scanning calorimeter and dynamic mechanical thermal analysis.

Gutta-percha is the most widespread root canal filling material and knowledge of its chemical and thermomechanical properties is of a great interest to its use in clinical dentistry. In the present investigation, the results from differential scanning calorimeter were compared with those obtained by dynamic mechanical thermal analysis. A significant correlation was established between these results and the chemical composition of six different commercial samples of gutta-percha.

Calorimetry, Differential Scanning↗
PubMed1992

Effect of moisture and aging on gutta-percha.

The purpose of this article was to study the plasticizing effect of controlled levels of different humidities on native and commercial gutta-percha samples. It was expected that the results might provide the practicing endodontist with invaluable insight into the mechanical properties of commercial gutta-percha cones (i.e. retrievability, malleability, flexibility, torsional, and bending ability). The "conditioning" of the gutta-percha samples depended greatly on the percentage of compatible and incompatible substances. Mixtures of native gutta-percha with compatible substances (e.g. wax) showed greater elongation, tensile strength, and number of rotations but lower deformation angle than mixtures of native gutta-percha with incompatible substances (e.g. salts, metal oxides). The observed lower values for tensile strength and torsional strain and higher value for elongation and number of rotations for wet samples compared with the dry ones were attributed to the plasticizing effect on gutta-percha of the insertions of water molecules in the polymer chains.

Drug Storage↗
PubMed1992

Impact of a shielded safety syringe on needlestick injuries among healthcare workers.

OBJECTIVES: Evaluate the impact of a shielded 3 cc safety syringe on needlestick injuries among healthcare workers. DESIGN: Surveillance study. SETTING: Three medical centers. RESULTS: The total number of needlesticks from all sources rose from 134 during the baseline period to 140 during the study phase. However, the overall rate of needlesticks involving 3 cc syringes decreased from 14/100,000 inventory units to 2/100,000, and the frequency declined substantially at each of the participating medical centers. CONCLUSIONS: These results suggest that shielded syringes and related technology may offer potential for reducing the risk of needlestick injuries among hospital and other healthcare employees. This study should be viewed as a preliminary effort to assess the potential of shielded-syringe technology for reducing the risk of needlestick injuries among healthcare workers. The results are encouraging, but more clinical experience with this new device and longer follow up are essential to provide the data necessary for a definitive assessment of efficacy.

Humans↗
PubMed1992

Perceptions of pediatricians' helpfulness: a national study of mothers of young disabled children.

A national sample of 503 mothers of young children (up to six years of age) with developmental disabilities was surveyed to determine the extent to which their family pediatricians are helpful in providing information and support. The respondents ranged from lower-middle to upper class, with the mean SES reflective of middle socio-economic status. Their children had a variety of disabilities that qualified them to receive early intervention services. The majority of the mothers found their pediatricians helpful about issues related directly to their child's medical condition. However, few found them helpful with issues relating to the effect of the disability on their child's development, or to their own personal or family needs.

Child↗
PubMed1992

Enamel ultrastructure in pigmented hypomaturation amelogenesis imperfecta.

Hypomaturation amelogenesis imperfecta (AI) is a hereditary condition of enamel that is presumed to result from defects during the maturation stage of enamel development. This study characterized the enamel ultrastructure and enamel crystallite morphology, as well as the distribution of organic material in enamel affected with pigmented hypomaturation AI. Enamel exhibiting autosomal recessive pigmented hypomaturation AI was sectioned or fractured and examined using light microscopy, scanning electron microscopy and transmission electron microscopy. Enamel samples were treated with 30% NaOCl or 8 M urea to remove organic components and determine the effect of deproteinization on crystallite morphology. These were compared with untreated normal enamel samples. The enamel crystallites in hypomaturation AI exhibited considerable variability in size and morphology. Examination of deproteinized tissue indicated that the AI crystallites had a thick coating, presumably of organic or partially mineralized material, which was not visible in normal enamel. The results of this investigation provide further evidence that hypomaturation AI is associated with the retention of organic material that is most probably enamel protein. Enamel protein retention is likely to be involved in the inhibition of normal crystallite growth resulting in the morphological crystallite abnormalities associated with this disorder.

Amelogenesis Imperfecta↗
PubMed1992

A flexible and rapid pH cycling procedure for investigations into the remineralisation and demineralisation behaviour of human enamel.

A rapid and flexible model system has been developed to study human enamel behaviour under conditions of oscillating pH similar to those experienced in the mouth. The model uses realistic time intervals and operates at in vivo temperatures (35-37 degrees C). Mineral loss or gain is measured quantitatively on a volume basis. Results indicate that for single 1-day periods with three 20-min exposures to acid, 1% v/v of enamel mineral was lost. These results, together with the histological appearance of the tissue, are in close agreement with previous studies of enamel caries.

Calcium↗
PubMed1992

Influence of occlusion on the fluoride distribution in rat molar cementum.

This study was undertaken to examine the influence of occlusion on the fluoride distribution in cementum following an experiment in which the occlusion in rats was locally altered by extracting the upper left molar. These and control rats with normal occlusion were given water containing 0 or 100 ppm fluoride for 12 weeks. The fluoride distributions in cementum from both first lower molars of the same animal were compared. The fluoride concentrations had increased throughout the tissue as a result of increased fluoride administration, irrespective of any changes in occlusion. They were, as usual, generally highest at or near the cementum surface and decrease towards the interior of the tissue. Where there had been a change in occlusion, the thickness of cementum was less than that of the contralateral tooth, but, despite this, the fluoride profiles in contralateral teeth were similar in both experimental and control rats. In the experimental rats, on the other hand, the total fluoride tended to be lower, and the mean fluoride tended to be higher in left molars without antagonists. These findings were never seen in the control rats. It was concluded that the alteration in occlusion influenced the fluoride distribution in the cementum through its effect on the rate of cementum formation.

Animals↗
PubMed1992

Determination of volumes of fluid in the mouth by fluoride dilution.

A dilution technique, with fluoride as a marker, has been developed to measure the volume of saliva and other fluids in the mouth. Immediately after swallowing, a small amount of fluoride solution is placed in the mouth, mixed with the oral fluids, and expelled from the mouth. The fluoride concentration of the expelled oral fluid is measured and the volume of fluid in the mouth at the time of spitting calculated from the fluoride dilution. Mean values of 0.75 +/- (SD) 0.28 ml for males and 0.72 +/- (SD) 0.16 ml for females were recorded. The accuracy of the volume determination is about +/- 0.10 ml in vivo. This technique has provided a convenient and rapid means of determining saliva volumes. It could also be used to determine rates of secretion and may prove useful in the clinic for assessing a patient's salivary competence.

Adult↗
PubMed1992

The role of albumin in developing rodent dental enamel: a possible explanation for white spot hypoplasia.

The uptake of serum albumin by maturation-stage rodent enamel and the resulting effects on the growth of enamel crystallites were investigated in vitro. Albumin uptake was demonstrated by means of gel electrophoresis and confirmed by Western blotting with use of monoclonal antibodies. Measurement of crystal size was carried out by direct TEM measurement of enamel crystallite outlines after incubations in metastable solutions of calcium phosphate. The ability of endogenous enamel enzymes to degrade albumin was investigated by substrate-specific zymography. The results showed that albumin could be taken up by maturation-stage enamel and produce inhibition of crystallite growth. There was no detectable proteolytic activity in the enamel against albumin substrate, which suggests that albumin entering enamel by extravasation in vivo may produce incomplete tissue maturation, resulting in a white, opaque appearance on eruption.

Animals↗
PubMed1992

A case management system for infants with chronic illnesses and developmental disabilities.

Continuity of care has been identified as a priority goal for infants with developmental disabilities or chronic illnesses who are faced with long-term or frequent hospitalizations. This goal was accomplished by Project Continuity, a family-centered intervention and care coordination system in which the family plays an integral role in the planning and implementation of the care plan. Procedures borrowed from diverse traditions including job analysis from industrial psychology and quality assurance from health care were used to describe, monitor, and assess the complex professional behaviors and outcomes of care coordination.

Child Health Services↗
PubMed1992

Improving documentation of aggressive behavior in nursing home residents.

1. Although 66% of the 1.3 million elderly nursing home residents in the US exhibit aggressive tendencies, research indicates that caregivers underdocument aggressive incidents. As a result, the extent of aggression is unknown. 2. This study found that LPNs reported the largest percentage (41%) of the 51 documented aggressive incidents, which reportedly occurred most frequently in the bathroom (49% of the time) between 5 AM and noon (86% of the time). Most aggressive residents (55.1%) never had visitors. 3. This study concludes that nursing practice would benefit from a consistent definition of aggression, an easy-to-use clinical instrument to collect data on aggression, and caregiver education programs on assessing aggression.

Aged↗
PubMed1992

Immune responsiveness and risk of illness in U.S. Air Force Academy cadets during basic cadet training.

It has been proposed, but not confirmed, that environmental stressors alter immune function and increase the risk of viral infection among healthy individuals. We evaluated this hypothesis, examining the relationship among stress, immune function, and illness in 96 first-year U.S. Air Force Academy cadets during orientation and 4 weeks later during the stressful environment of Basic Cadet Training (BCT). Perceived stress and well-being levels of cadets were assessed via questionnaire. Immune responsiveness was analyzed by PHA-stimulated thymidine uptake in mononuclear leucocytes and by serologic evidence of reactivation of the Epstein-Barr virus (EBV). We documented significant declines in in vitro PHA-induced lymphocyte transformation (-35%; p less than 0.05) and subjective well-being (-19%; p less than 0.05) from orientation to BCT with corresponding, significant increases in perceived stress (+32%; p less than 0.05). Despite significantly altered in vitro immune responsiveness, there was no serologic evidence of EBV reactivation nor was there an association between these measures and risk of illness as determined by medical chart review and self-reported symptoms. These results suggest that reduced in vitro immune responsiveness during a moderate stressor may not necessarily lead to an increased risk of infection and/or reactivation of EBV in normal individuals.

Aerospace Medicine↗
PubMed1992

Characterization and cell cycle-regulated expression of mouse B-myb.

We have isolated a full-length mouse B-myb cDNA clone and used this to examine cell cycle-regulated expression of this gene. Mouse B-Myb was predicted to comprise 704 amino acids and to be 84% homologous with human B-Myb. There were three regions of extensive amino acid homology which may indicate functional domains: the first corresponded to the c-Myb DNA-binding domain, while the second had no counterpart in c-Myb but was instead homologous to a short segment of the related A-myb protein. The third region of homology is partially conserved in both c-Myb and A-Myb and may correspond to the c-Myb negative regulatory domain. Stimulation of quiescent 3T3 fibroblasts with serum was found to result in induction of B-myb expression in late G1 and to lead to high levels of gene transcripts that persisted through S phase. Similarly, maximum B-myb mRNA levels were reached in G2/M synchronized cells prior to entry into S phase. These results are consistent with a role in G1/S transition as has been suggested for c-myb.

Amino Acid Sequence↗
PubMed1992

Cobalt cardiomyopathy. A report of two cases from mineral assay laboratories and a review of the literature.

Two young men employed in the mineral assay industry developed non-inflammatory cardiomyopathy. By review of clinical findings, elicitation of occupational and environmental histories, work-site evaluations, and ascertainment of tissue cobalt levels, Nevada Public Health authorities confirmed these cases to be due to occupational cobalt exposure. Hair and heart cobalt levels were elevated for the cases, but control samples had no detectable cobalt. Excess ischemic heart disease mortality among cobalt-exposed workers may reflect misdiagnosis of cardiomyopathy.

Adult↗