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Biomedical subjects

C Robinson

Publications and source records attributed to C Robinson.

At least 433 records · Page 24Linked to original sources
PubMed1982

Inactivation of prostaglandins in the perfused rat lung.

Inactivation in the isolated perfused rat lung of prostaglandins (PG) D2, E1, F2 alpha, I2 and the metabolites 6-keto PGF1 alpha (=6KF1 alpha) and 13, 14-dihydro-15-keto PGF2 alpha (= KH2F2 alpha) was studied using 5 min perfusion of 7-10 ng/ml PG in Krebs' solution containing 0.02 microCi/ml tritiated PG and 4.5% bovine serum albumin (BSA). The parameters measured were (a) extent of inactivation (F2 alpha greater than E1 greater than D2 greater than 6KF1 alpha greater than I2; KH2F2 alpha unchanged), (b) the accumulation of PG within the lung measured as tissue to medium ratio (F2 alpha = D2 greater than E1 greater than 6KF1 alpha greater than I1 - KH2F2 alpha) and (c) rate of equilibration of PG within the lung measured as "wash-in t 1/2" (D2 greater than F2 alpha greater than E1 greater than I2 = 6KF1 alpha = KH2F2 alpha). Removal of sodium ions produced a small decrease in PGD2 and PGE1 breakdown but not of PGF2 alpha whereas breakdown of all PGs was markedly inhibited at 5 degrees. Removal of BSA enhanced PGE1 and PGI2 breakdown but not that of PGF2 alpha. Addition of 10% BSA inhibited PGE1 breakdown but not that of PGF2 alpha. Binding of PGs to 4.5% BSA was PGE1 = KH2F2 alpha greater than D2 greater than F2 alpha, and increased at 10% BSA or after removal of sodium ions. These data support the view that PGs must be taken up into pulmonary cells by a transmembrane carrier process as a prerequisite for enzymatic breakdown. The metabolites are then released back into the pulmonary circulation.

Animals↗
PubMed1981

Effect of surfactant on tetracycline absorption across everted rat intestine.

Absorption of tetracycline hydrochloride (500 micrograms/ml) from oxygenated modified Krebs buffer in randomized everted rat jejunal segments was determined alone and in the presence of calcium, polysorbate 80, and calcium plus polysorbate 80. Surfactant increased absorption of tetracycline in the presence and absence of calcium, with 0.01% (w/v) polysorbate 80 increasing transfer to the greatest extent of the concentrations examined(0.005, 0.01, 0.05, 0.1, and 1%); tetracycline hydrochloride + 12.5 mM CaCl2, 143 +/- 45 micrograms/ml; tetracycline hydrochloride + polysorbate 80, 389 +/- 18 micrograms/ml; tetracycline hydrochloride + 12.5 mM CaCl2 + polysorbate 80, 255 +/- 31 micrograms/ml. On the premise that the effective surfactant concentration is similar to the critical micelle concentration, an absorption mechanism based on micellar solubilization is postulated.

Animals↗
PubMed1981

Histology of enamel organ and chemical composition of adjacent enamel in rat incisors.

By avoiding chemical fixation and using a freeze-drying technique, it proved possible to examine the enamel organ of rat mandibular incisors histologically while retaining the adjacent enamel of the same tooth for chemical analysis. The dramatic alterations which occur in enamel organ histology, such as ameloblast shortening and the development of hte papillary layer, could then be compared directly with mineral uptake and mineral content of the adjacent enamel. Both enamel and adjacent enamel organ were sampled as a continuous series of pieces, 0.5 mm in width, from youngest (apical) to oldest (incisal) tissue. Short ameloblasts were associated directly with the beginning of a rapid uptake of phosphate ions during the maturation phase and also coincided with the beginning of a steep rise in mineral content. By implication, some loss of matrix may also occur at this point. Development of the highly vascular papillary layer preceded ameloblast shortening and may be associated with changes in the organic matrix prior to its disappearance from the tissue. Further development of this layer was associated with ameloblast shortening. This may also therefore be associated with mineral uptake during maturation.

Animals↗
PubMed1981

Chemical changes during formation and maturation of human deciduous enamel.

The appearance and chemical composition of a number of developing human deciduous incisors indicated that the enamel passes through the following four developmental stages: 1. Partially mineralized matrix is secreted and some extracellular breakdown occurs. 2. Selective replacement of matrix proteins by tissue fluid begins. 3. Almost all of the matrix protein is replaced by tissue fluid and an influx of calcium phosphate occurs. 4. The enamel becomes almost fully mineralized, mature and hard. These stages of development are similar to those described in rat and bovine tissue. the number of stages simultaneously present in a single tooth differed from rat and bovine enamel, however, as did the rate of change in amino acid composition from developing to mature tissue.

Amino Acids↗
PubMed1981

Fixation of spinal reflexes in rats by central and peripheral sensory input.

Two methods were used to demonstrate retention of postural asymmetries after spinal cord section in adult rats. In the first preparation, postural asymmetries of the hindlimbs were induced by placing electrolytic lesions in the anterior cerebellum. Asymmetry was found to consistently outlast a spinal cord section if 45 min were allowed between brain lesion and cord section. A certain percentage of rats allowed 35 or 40 min also demonstrated the retention. In the second preparation, postural asymmetries induced by 45 min of direct hindlimb stimulation were also retained after spinal section. Rhizotomy prior to stimulation resulted in a lack of appreciable asymmetry upon termination of the stimulation. Finally, retention of a hindlimb-stimulation-induced asymmetry was observed in animals that underwent a spinal section prior to the stimulation. The present series of studies demonstrates that the "spinal fixation" phenomenon can be obtained by induction of postural alterations from central (cerebellar lesion) and peripheral (hindlimb stimulation) sources. In addition, results obtained from spinal animals indicate that retention of peripherally induced asymmetry is not crucially dependent on higher brain center activity but rather seems to be more dependent on long-term alterations that occur directly in the spinal reflex system.

Animals↗
PubMed1981

Stability of prostacyclin in human plasma and whole blood: studies on the protective effect of albumin.

The biological half-life of prostacyclin in Krebs solution, human cell-free plasma or whole blood was measured by bracket assay on ADP-induced platelet aggregation. At 37 degrees C, pH 7.4, plasma and blood reduced the rate of loss of antiaggregatory activity compared with Krebs solution. The protective effect of plasma was greater than that of whole blood. This effect could be partially mimicked by the addition of human or bovine serum albumin to the Krebs solution. The stabilisation afforded by human serum albumin was dependent on the fatty acid content of the albumin, although this was less important for bovine serum albumin.

Adult↗
PubMed1980

Evidence for functionally distinct pools of phospholipase responsible for prostaglandin release from the perfused guinea-pig lung.

The release of prostaglandin- and thromboxane-like material from the isolated perfused guinea-pig lung was elicited by challenge with arachidonic acid, bradykinin, histamine and ovalbumin (in ovalbumin-sensitised animals), and detected by superfusion cascade bioassay. Mepacrine inhibited release to all agents except arachidonic acid. Dexamethasone and fludrocortisone inhibited release induced by histamine and anaphylactic challenge but not by bradykinin or arachidonic acid. These results suggest two functionally distinct pools of phospholipase responsible for initiating prostaglandin biosynthesis in the guinea-pig lung.

Animals↗
PubMed1980

Pattern and model makers, proportionate mortality 1972-1978.

A proportionate mortality study of deceased white male workers in the pattern and model making trades was conducted. Death certificates were obtained for 1257 death benefit-eligible members of the Pattern Makers' League of North America who had died in the years 1972-1978, and age-adjusted proportionate mortality was calculated using 1975 United States white male death rates. For the entire nationwide union, statistically significant excess proportions of deaths were observed due to colon cancer (proportionate mortality ratio, PMR = 167) and to brain tumors (PMR = 211). A statistically significant excess proportion of deaths due to colon cancer (PMR = 163) and to leukemia (PMR = 200) were observed among the members of the predominantly wood shop locals. Nonsignificant excess proportions of cancer deaths occurred at a number of other anatomical sites. Predominant occupational exposures included wood and plastic dusts and epoxy resins in wood shops and cutting oil mists and solvent vapors in the metal shops. These results suggest the need for better work practices in this industry while more definitive studies are completed.

Brain Neoplasms↗
PubMed1980

Electroencephalographic analysis: a methodology for evaluating psychotherapeutic process.

The relationship between individual differences in listening style and clinical sensitivity was studied. Listening style is conceptualized as extending from a critical, analytic, focused attitude to a holistic, intuitive, free-floating attitude. We studied the listening styles of psychiatric residents while they listened to a tape recording, a 17-minute fragment of a psychotherapy that had been rated by a panel of experts as containing 22 cues reflecting the patient's concern with termination of treatment. The ability of clinicians to identify these cues is our experimental measure of clinical sensitivity. Our measures of listening style include eyeblink rate, memory for high-imagery words, and electroencephalogram recorded from electrodes over the right and left temporal areas, all measured while psychiatric residents listened to the tape. Results suggested that an abundance of alpha indicates a readiness on the part of the listener to process clinically relevant information. In addition, a listening style with engagement of the right hemisphere predicted clinical sensitivity. These findings suggest ways to study how the skilled clinician "tunes" himself empathically to his patient.

Alpha Rhythm↗