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Biomedical subjects

M F Collins

Publications and source records attributed to M F Collins.

31 records · Page 2Linked to original sources
PubMed1984

The effects of low-level lead exposure in developing rats: changes in circadian locomotor activity and hippocampal noradrenaline turnover.

The circadian spontaneous locomotor activity of rats exposed to 0.1 mg lead/kg, po from 3 days until 4 and 6 weeks of age was similar to that of controls. However, hyperactivity during initial hours of recording was observed in rats that were treated with lead (Pb) until 8 weeks of age. When treatment was discontinued for 2 weeks, previously Pb-exposed rats had a tendency to be hypoactive. The elevated locomotor activity in 8-week-old lead-treated rats was not accompanied by any significant changes of noradrenaline levels in the cerebral cortex or hippocampus. Alterations in noradrenaline content of the hippocampus were, however, observed in rats that had been treated with Pb for 4 and 6 weeks. The turnover rate of noradrenaline in the hippocampus was also found to be significantly reduced following treatment for 6 weeks. Regional distribution of Pb in the brains of lead-exposed rats showed a large accumulation of the metal in the hippocampus. The alterations of the noradrenergic function in the hippocampus may be associated with the preferential storage of lead in this region.

Aging↗
PubMed1983

Adhesion of human platelets to purified solid-phase von Willebrand factor: studies of normal and Bernard-Soulier platelets.

Human Factor VIII associated von Willebrand factor (VIII:vWF) binds to human platelets in vitro only in the presence of a mediator such as ristocetin, thrombin or ADP. Studies reported here were designed to determine if human platelets will adhere to solid-phase VIII:vWF. Human VIII:vWF was purified from a phosphate precipitate of A1(OH)3 absorbed plasma using 4% agarose and DEAE cellulose. Purified VIII:vWF (90 units of VIII:vWF activity/mg) was coated on dialysis membranes using ultrafiltration (final concentration of 0.4 units/cm2). Membranes (0.5 cm2) were held stationary in human citrated PRP suspension or washed platelet suspensions and stirred continuously for 5 minutes at 37 degrees C. The membranes were then rinsed in phosphate buffered saline, fixed, stained, and examined by light and scanning electron microscopy. Abundant normal platelets adhered to VIII:vWF-coated membranes, while minimal adhesion was seen on uncoated membranes and membranes coated with albumin. Adhesion occurred without ristocetin, thrombin, ADP or other agonist and in the presence of Ca+2/Mg+2 ions. Preincubation of the VIII:vWF coated membranes with monospecific rabbit anti-VIII:vWF inhibited the adhesion reaction. However, preincubation of VIII:vWF coated membranes with naturally occurring human anti-FVIIIc antibodies failed to interfere with platelet adhesion. Platelets from a patient with Bernard-Soulier Syndrome (BSS) which did not bind human VIII:vWF in the presence of ristocetin or aggregate with bovine cryoprecipitate also did not adhere to VIII:vWF-coated membranes.

Blood Coagulation Factors↗
PubMed1979

Factors involved in enzyme-linked immunoassay of viruses and evaluation of the method for identification of enteroviruses.

A quantitative enzyme-linked immunosorbent assay was used for identification of selected enteroviruses: poliovirus type 1, echovirus type 6, coxsackievirus A type 9, and coxsackievirus B types 1 through 6. Partially purified viral antigens or virus-specific antibodies were adsorbed to polystyrene spectrophotometer cuvettes, which permitted the assays to be reported and compared in terms of enzyme units specifically reacting. Both the adsorbed antigen and the adsorbed antibody methods were approximately equal in terms of sensitivity and specificity of reaction. By use [14C]leucine-labeled enteroviruses, the amount of virus that bound to the plastics used was shown to be dependent on the purity of the virus preparation used, but it was higher than the amount that was bound by plastics coated with viral antibody. Diluents which contained 0.15% (vol/vol) Tween 20 and 2.0% (wt/vol) bovine serum albumin in phosphate-buffered saline, pH 7.2, were found to be the most effective in inhibiting nonspecific adsorption of immunoreagents. However, the presence of these inhibitors in phosphate-buffered saline solutions also caused desorption of virus or viral antibody during immunoassays; the amount of virus desorption varied with the type of preparation used, and antibody desorption was dependent on the concentration of antibody initially used for adsorption. For specific identification of a given enterovirus type by the enzyme-linked immunosorbent assay method used, approximately 10(5) plaque-forming units of virus per assay tube were required.

Echovirus 6, Human↗
PubMed1976

Quantitation of immunoglobulin adsorption to plastics.

Adsorption of 125I-labelled rabbit IgG to plastics (cellulose nitrate, polyallomer, polystyrene, polyvinyl) was primarily dependent on initial antibody concentration and, to a lesser extent, on time allowed for adsorption. The highest concentration tested (100 mug/ml) gave the highest quantities adsorbed after 18 h at room temperature. This concentration, however, gave the lowest percent adsorption (6.5 to 12.0%) of the initial amount. IgG concentration of 10 mug/ml resulted in 25.0 to 65.1% adsorption over the same time period; at 1 mug/ml, 47.0 to 96.6% of the initial amount was adsorbed. All of the plastics tested adsorbed IgG to approximately the same degree, with the exception of cellulose nitrate. This plastic adsorbed 32 to 49% less than the others, under maximal adsorption conditions.

Adsorption↗
PubMed1974

Comparison of techniques and immunoreagents used for indirect immunofluorescence and immunoperoxidase identification of enteroviruses.

Peroxidase-conjugated antibodies were found to be as sensitive as those conjugated to fluorescein-isothiocyanate (FITC) for identification of selected enterovirus types by the indirect technique. Peroxidase conjugates, however, were found to give fewer nonspecific reactions. The reasons for the higher specificity of the immunoperoxidase technique appear to be related to the relative size, charge, and uniformity of the preparations. Monomers of peroxidase-conjugated globulin are larger than those of FITC conjugates, but the latter readily form aggregates. This was shown by chromatography on Sepharose 6B columns: various FITC-conjugated globulins eluted before those conjugated to peroxidase and before (125)I-labeled immunoglobulin G. The net charge of the conjugates was determined by adsorption to ion-exchange columns. FITC-labeled globulins had a negative net charge, eluting at pH 5.1 from diethylamino-ethyl-Sephadex A-50 columns. Peroxidase conjugates were not retained by either cationic or anionic exchangers at pH values ranging from 4.0 to 10.5. Further, the fluorescein/protein ratios of FITC conjugates from different commercial sources and of those prepared in the laboratory were found to be variable; higher fluorescein/protein ratios (>2:1) give a higher degree of nonspecific reactions, whereas the peroxidase/protein ratio does not appear to affect specificity. These characteristics of peroxidase conjugates make the immunoperoxidase technique easier to standardize and more reliable for enterovirus identification than the immunofluorescence technique.

Animals↗