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Biomedical subjects

C Robinson

Publications and source records attributed to C Robinson.

At least 343 records · Page 19Linked to original sources
PubMed1988

The dissolution rate of enamel in acid in developing rat incisors.

This study was undertaken to determine the changes in this dissolution rate at different developmental stages after different fluoride dietary regimes. Four groups of Wistar rats received water with 0, 25, 50 and 100 parts/10(6) fluoride respectively for 10 weeks. Six exposed windows of 2 mm2 were prepared on the enamel surface of the upper incisors, corresponding to six different developmental stages. The acid-dissolution rates were determined at each window by using 1.4 M sodium acetate-hydrochloric acid buffer (pH 2.3). The rate of enamel dissolution was highest in the matrix-formation stage and dropped sharply in a step-wise fashion towards the stages of secondary mineralization and iron deposition. The dissolution rate in the maturation stage decreased significantly with increasing intake of fluoride. However, in the pigmented enamel, the opposite occurred. The iron pigmentation or the porosity in this region of fluorosed enamel might be responsible for the change in the dissolution rate of the pigmented enamel.

Animals↗
PubMed1988

Fluoride distribution and histological structure of human cementum.

Thirty-one teeth taken post-mortem from 10 subjects aged from 40 to 66 years were studied. A close relationship was found between fluoride (F) distribution and histological structure. Although, as in all mineralized tissues, F concentrations tended to be highest towards the external surface, individual patterns of F distribution also seemed to reflect the histological pattern, especially the distribution of cellular or acellular cementum. In general, F concentrations were high in acellular and low in cellular cementum.

Adult↗
PubMed1988

Decreased plasma membrane fluidity in the development of atherosclerosis in cholesterol-fed rabbits.

Rabbits were fed a diet supplemented with 3% peanut oil or 3% peanut oil plus 0.5% cholesterol. Aortas from rabbits fed the cholesterol supplemented diet for 2 weeks were free of grossly visible lesions; however, aortas from rabbits fed this diet for 10 weeks exhibited extensive lesion development. Lesions were not observed in aortas of rabbits fed the high-fat supplemented diet. The fluorescence anisotropy of DPH was significantly (P = 0.0001) increased in plasma membranes isolated from aortas of rabbits fed the high-fat plus cholesterol vs. high-fat supplemented diet; the increase in fluorescence anisotropy observed after only 2 weeks on diet (0.201 +/- 0.002 vs. 0.144 +/- 0.002) was similar to that observed after 10 weeks on diet (0.244 +/- 0.002 vs. 0.193 +/- 0.001). The data support the hypothesis that plasma membrane fluidity [is decreased in atherosclerosis and indicate the decrease in membrane fluidity] occurs early in the development of the disease.

5'-Nucleotidase↗
PubMed1988

The beta-chains of DP4 molecules from different haplotypes are encoded by the same gene.

The nucleotide sequence of a complete cDNA gene from a DP4-positive HLA-homozygous cell line, PGF, has been determined. This sequence is identical to the exon sequences in a genomic clone derived from another DP4-positive cell line, Priess. In contrast, our DP cDNA sequence shares only limited homology with partial cDNA sequences obtained from clones of three DP4-negative cell lines. On the basis of these results, we conclude that the phenotypic variation of DP alleles is directly attributable to the nucleotide sequence heterogeneity of DP-beta genes. That is, each phenotypic allelic form of DP antigen corresponds to a distinctly different DP-beta gene. Furthermore, this correspondence is found to be unaffected by the markers present at the DQ and DR loci, since the haplotypes of the PGF and Priess cell lines are, respectively, DR2,DQw1,DP4 and DR4,DQw3,DP4.

Amino Acid Sequence↗
PubMed1988

Effects of 1-epinephrine on hemodynamics and cardiac function in coronary disease: dose-response studies.

To assess the effects of elevated epinephrine levels on cardiovascular performance in patients with coronary artery disease (CAD), epinephrine was infused intravenously into eight patients with normal coronary anatomy and 22 patients with CAD at dose rates of 0.06, 0.12, 0.18, and 0.24 micrograms/kg/min. Hemodynamic responses to epinephrine were not significantly different between the two groups. However, contractility increased significantly more (P less than 0.05) and end-systolic volume decreased significantly more (P less than 0.025) in normal subjects than in those with CAD. Plasma norepinephrine concentrations increased significantly (P less than 0.05) at 0.24 micrograms/kg/min epinephrine, indicating activation of sympathetic nervous system. Epinephrine ischemic thresholds ranged from 652 to 3362 pg/ml. Patients with CAD compared with normal subjects had more frequent ventricular arrhythmias (55% vs. 25%), chest pain (50% vs. 13%), and ischemic ECG changes (73% vs. 13%). These results indicate that although epinephrine induced myocardial ischemia in CAD, hemodynamics and ventricular pump function were maintained.

Adult↗
PubMed1988

The immunoglobulin E- and calcium-dependent release of histamine and eicosanoids from human dispersed mastocytosis spleen cells.

The clinical features of systemic mastocytosis have been ascribed to mast cell-dependent mediators, but there have been no studies of their release from isolated cells. We have investigated the release of histamine and eicosanoids from isolated spleen cells obtained from tissue of a mastocytosis patient undergoing therapeutic splenectomy. Dispersed cell preparations contained lymphocytes 65.9%, monocytes/macrophages 22.3%, neutrophils 9.9%, mast cells 1.1%, and eosinophils 0.8%; upon challenge with 0.1-3.0 microM A23187 they released histamine much greater than PGD2 greater than TXB2 greater than LTB4 greater than LTC4 approximately equal to LTD4 greater than LTE4. With immunological activation of passively sensitized cells, histamine and PGD2 release had similar dose-response characteristics, but TXB2, LTC4, LTD4, and LTE4 release differed in reaching maximum at 50 micrograms/ml and declining at 125 micrograms/ml anti-human IgE. Percoll centrifugation separated most of the histamine-containing cells to the middle of the gradient, but they were refractory to release with 0.3 microM A23187 or 50 micrograms/ml anti-IgE. Spontaneous release of histamine from these cells was not abnormally high (1.3%-4.5%). Electron microscopy of tissue sections revealed large numbers of mast cells with empty granules. It is possible that the refractory cells observed are such mast cells where intracellular histamine is no longer granule-associated. Most net histamine and PGD2 release was confined to cells at the bottom of the gradients (1.078-1.09 g/ml), although some release of PGD2 occurred near the top (1.05-1.058 g/ml). There was a significant correlation between the net release of histamine and PGD2 with both immunological (r = 0.92; n = 16) and A23187 (r = 0.97, n = 14) activation. These studies provide evidence for a link between PGD2 and histamine release in mastocytosis spleen cells.

Adult↗
PubMed1988

Comparative vascular effects of histamine, prostaglandin (PG) D2 and its metabolite 9 alpha,11 beta-PGF2 in human skin.

In this double-blind study we have investigated the vascular effects of prostaglandin, (PG) D2, in normal skin and compared these effects with histamine and the initial PGD2 metabolite 9 alpha, 11 beta-PGF2. In eight healthy subjects the vascular response to intradermal injections of histamine, PGD2, a combination of histamine and PGD2, and 9 alpha,11 beta-PGF2, was assessed by measurement of the weal and flare area. Histamine caused dose-related increases in weal area (P less than 0.01). The weal response due to PGD2 was greater than saline control only at a dose of 71.0 and 710 nmol (P less than 0.05). Because of the small size of the weal produced by PGD2 when compared with histamine, it was not possible to determine their relative potencies. Histamine and PGD2 caused dose-related increases in flare area (P less than 0.05), and when compared at a response level of 10 cm2 and 15 cm2, histamine was 45 and 251 (P less than 0.01) times more potent than PGD2 in molar terms. Weal and flare responses due to 9 alpha,11 beta-PGF2 were similar to those observed with the equimolar concentration of PGD2. The weal and flare responses when PGD2 and histamine when combined were not significantly different from that predicted by a purely additive effect. We conclude that histamine is likely to be an important mediator contributing towards increased vascular permeability and vasodilatation following immunological activation of skin mast cells in vivo, while PGD2 and its metabolite 9 alpha, 11 beta-PGF2 play only a minor role.

Dinoprost↗
PubMed1988

Leukotriene C4 and histamine in early allergic reaction in the nose.

We have examined the measurements of LTC4 and histamine in nasal lavage fluids and blown secretions as a possible model of the early mediator events during nasal allergy. A nasal challenge with grass pollen extract was undertaken on two separate occasions in 20 patients with a history of seasonal rhinitis and a positive immediate skin test to grass pollen. A 2 ml nasal lavage was performed before allergen challenge, and blown secretion collected separately 15 min after the provocation, followed by a final 2 ml nasal lavage. The dilution of nasal secretion by the lavage fluid was determined using 99mTc-labelled albumin as an exogenous marker added to the fluid. The amounts of admixture in the nasal lavages did not correlate to the concentrations of LTC4 and histamine, indicating that the variable amounts of nasal secretion in nasal lavage do not constitute a confounding variable for measurements of LTC4 and histamine. In the pre-challenge lavages, the median concentrations, of LTC4 and histamine were 1.7 and 52 nmol/l respectively. Following allergen challenge neither LTC4 nor histamine measured in nasal lavage showed any significant change from pre-challenge baseline values. However, measurements of both mediators in the blown secretion showed a significantly higher concentration than in the pre- or post-challenge lavage samples, compatible with transitory release during the acute allergic reaction. However, it seems doubtful whether measurements of LTC4 or histamine can be compared between blown secretion and nasal lavage fluid, even if the dilution factor is disregarded.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Anti-smoking advice for young diabetic smokers: is it a waste of breath?

The effect of health counselling on the smoking habits of 60 diabetic patients (aged less than 40 years) was assessed. Measurement of breath carbon monoxide (CO) and urinary cotinine, a metabolite of nicotine, were used as objective markers of smoking. All patients wished to cease smoking and the impact of health counselling was reviewed in a 'Stop Smoking' clinic. In addition to routine advice on the health hazards of smoking, half the patients and their families also received further counselling during a home visit by a health visitor. After 6 months many of the 60 patients claimed to have reduced their cigarette consumption. However, the urinary cotinine concentrations did not confirm this. Only one patient actually stopped smoking and he had sustained a myocardial infarction during the study. There was a small but significant reduction of breath CO in the patients seen at home by the health visitor but the urinary cotinine concentrations were unchanged. This suggests that these patients abstained from smoking for only a few hours before attending the 'Stop Smoking' clinic.

Adult↗
PubMed1988

Bronchoconstrictor and antibronchoconstrictor properties of inhaled prostacyclin in asthma.

Prostacyclin (PGI2) is generated in appreciable amounts during allergic reactions in human lung tissue. To define its activity on human airways we have studied the effects of doubling concentrations of inhaled PGI2 and its hydrolysis product 6-oxoprostaglandin F1 alpha (6-oxo-PGF1 alpha) on specific airway conductance (sGaw), maximum expiratory flow at 30% vital capacity (Vmax30), forced expiratory volume in 1 s (FEV1), and static lung volumes in subjects with mild allergic asthma. In a second study the effect of inhaled PGI2 on bronchoconstriction provoked by increasing concentrations of inhaled prostaglandin (PG) D2 and methacholine was observed. Inhalation of PGI2 up to a concentration of 500 micrograms/ml had no significant effect on sGaw but produced a concentration-related decrease in FEV1 and Vmax30 in all subjects. In two of four subjects inhalation of PGI2 also increased residual volume and decreased vital capacity but had no effect on total lung capacity. PGI2, but not 6-oxo-PGF1 alpha, protected against bronchoconstriction provoked by either PGD2 or methacholine whether airway caliber was measured as sGaw, FEV1, or Vmax30. The apparent disparity between the bronchoconstrictor and antibronchoconstrictor effects of PGI2 might be explained by its potent vasodilator effect in causing airway narrowing through mucosal engorgement and reducing the spasmogenic effects of other inhaled mediators by increasing their clearance from the airways.

6-Ketoprostaglandin F1 alpha↗
PubMed1988

Availability of fluoride at different sites in the buccal sulcus.

After rinsing with a fluoride solution, the amounts of fluoride taken up by small pieces of dentine placed strategically about the mouth varied considerably from site to site in the oral cavity. The pattern of fluoride availability in this subject's mouth was in line with previous findings about fluoride distribution in his labial sulcus. The present results therefore suggest by analogy that considerable variations in fluoride clearance and concentration must exist throughout the oral cavity. These previous studies of fluoride clearance from the labial sulcus also showed that there are marked differences between individuals. The present findings, emerging from a study of 1 subject, therefore imply a need for more information about the variations in the availability, concentration and clearance of fluoride and, by extrapolation, of other substances throughout the mouths of different individuals.

Absorption↗
PubMed1988

Mineral and protein concentrations in enamel of the developing permanent porcine dentition.

Calcium, phosphorus and protein analyses have been performed on developing permanent enamel from the mandibular dentition of the domestic pig. The pattern of mineralization and protein loss was similar from tooth to tooth and similar to teeth from other species. Comparison of different teeth at the same developmental stages (secretion--stage 1, transition--stage 2 and maturation - stage 3) revealed remarkably similar concentrations of calcium, phosphorus, and protein regardless of tooth type. These data were similar to those from other deciduous dentitions, except that maturing/mature tissue in the pig seemed less well mineralized.

Age Factors↗
PubMed1988

Maturation in developing permanent porcine enamel.

Mineral content per tissue volume was investigated in developing permanent porcine enamel and contrasted with weight-related data. Levels of mineralization were correlated directly with the histological appearance of the overlying enamel organ. Magnesium concentrations were measured at different stages of enamel development. Mineral levels rose from approximately 30% per volume of tissue during the secretory stage to approximately 60% in mature tissue. This is much lower than final mineral levels in enamel of other species. Enamel containing low mineral levels was adjacent to tall secretory ameloblasts which had reduced in height by approximately 50% at a point corresponding to the beginning of the maturation stage. Magnesium concentrations remained relatively constant throughout the secretory stage, at 0.2% Mg by weight. These rose by 3-4 times in the enamel of the maturation stage. The low levels of mineralization in the mature porcine enamel did not appear to be due to enamel pathology, and the possibility of porcine teeth erupting in an immature, partially porous condition is discussed.

Ameloblasts↗
PubMed1988

Diagnosis and treatment of monosymptomatic hypochondriacal psychosis in chronic renal failure.

The authors describe a case of a patient who presents with a delusional interpretation of a somatic symptom, uremic pruritus. The literature on the diagnosis and treatment of monosymptomatic hypochondriacal psychosis (MHP) is reviewed and discussed. There is an effective treatment available for this disabling condition--a neuroleptic agent called pimozide, which appears to have a selective ability to block central dopaminergic receptors.

Adult↗
PubMed1988

Antibodies to Epstein-Barr virus-specific DNase and DNA polymerase in the chronic fatigue syndrome.

In an attempt to examine further the association between active Epstein-Barr virus (EBV) infection and the chronic fatigue syndrome (chronic EBV syndrome, or chronic or atypical mononucleosis), antibodies acting against EBV-specific DNase and DNA polymerase, which are expressed only during virus replication, were assayed. Serum samples from 25 healthy EBV-seropositive individuals neutralized 3.5 +/- 5.1 U (mean +/- SD) of DNase activity and 14.7 +/- 8.5 U of DNA polymerase activity. From these values were selected upper limits of anti-EBV enzyme activity of 17.9 and 31.3 U neutralized in normal individuals, respectively (representing the 95% confidence limit). Serum samples from six groups of subjects representing a variety of EBV-related illnesses were then studied. Only patients with notably elevated anti-EBV antibody titers to viral capsid antigen (VCA) (greater than 10,000) had elevated levels of anti-EBV DNase (38 to 56 U neutralized) and anti-EBV DNA polymerase (72 to 106 U neutralized). Three additional patients and two geriatric controls with average anti-EBV early antigen/VCA titers had slightly elevated levels of antibody to EBV DNA polymerase. IgA anti-VCA, anti-early antigen antibodies, or both, were also detected in the same patients who had high EBV DNase and polymerase antibody levels. These antibody profiles are similar to those in patients with nasopharyngeal carcinoma. Since three of the six patients with elevated anti-EBV enzyme antibody levels developed fatal lymphomas, patients with chronic EBV and this antibody profile might be in another illness category at risk for malignant disease.

Aged↗
PubMed1988

Heliox treatment for spinal decompression sickness following air dives.

Enforced delay in treatment of spinal decompression sickness following scuba diving can result in paraplegia. Poor response from initial recompression to 18 m presents the clinician with a difficult management problem. Theoretical objections have been raised to the use of He-O2 as treatment regimen. We report 3 cases that show He-O2 to be an excellent method of treatment in spinal decompression sickness after air diving.

Adult↗