Search PubMed⌕ Search

Biomedical subjects

M C Williams

Publications and source records attributed to M C Williams.

At least 163 records · Page 9Linked to original sources
PubMed1980

Hemolytic properties of special materials exposed to a shear flow, and plasma changes with shear.

Three types of materials of special interest to the NIH Biomaterials Program were evaluated for their tendency to induce hemolysis when exposed to a laminar blood flow between rotating parallel disks. The three types were: (1) TDMAC-heparinized surfaces of polycarbonate (Lexan), silicone rubber, and polyvinylchloride; (2) polyacrylamide hydrogels (PAH) prepared by three different chemical processes; and (3) fluorinated ethylcellulose (FEC). All were compared to a polyethylene (PE) standard, to normalize data for variations in blood quality. Multiple tests, showing good reproducibility, demonstrated: FEC is a very low hemolyzer, about 60% of the PE; PAH surfaces are poorer than PE, giving 120-220% of PE hemolysis depending on fabrication and shipment history; and TDMAC-heparinized surfaces are highly hemolytic, in the range 160-440% of PE depending on substrate. Plastics used as substrates for the coating cited above were also evaluated: Delrin, Lexan, Nylon 6, propylene, and a polyether urethane. Tentative explanations are advanced for hemolytic variations, in terms of surface chemistry and material interactions with the blood.

Acrylic Resins↗
PubMed1980

Unilamellar liposomes made with the French pressure cell: a simple preparative and semiquantitative technique.

A simple, rapid, and almost quantitative technique is described for the preparation of 1-40 ml of homogeneous unilamellar liposomes from dilute or concentrated aqueous suspensions of egg phosphatidylcholine. Aqueous suspensions of lipid are placed with the chamber of a French pressure cell at room temperature and rapidly extruded at 20,000 psi through the small orifice. A single pass transforms more than 70% of the extruded lipid into a homogeneous population of single-wall bilayer vesicles; more than 90% is transformed by recycling the lipid through the French pressure cell. About 95% of these liposomes range between 150-300 A in diameter (mean 200 A). The liposomes are stable for days to months when stored under nitrogen at 0.4 degrees C and can be prepared at 0 degrees, 25 degrees, or 37 degrees C. The liposomes appeared unaltered by repeated passages through the French pressure cell and no degradation of the phospholipid was detected after ten consecutive cycles at 20,000 psi in the absence of a nitrogen atmosphere. The method is especially useful for trapping small molecular weight substances because the concentration of both lipid and solute can be made quite high. Cholesterol up to 45 mole % can be incorporated into larger liposomes of egg phosphatidylcholine (mean diameter 315 A). Other phospholipids and different lipid mixtures can also be transformed into unilamellar vesicles with this method which has the advantage that additional steps of ultracentrifugation, column chromatography, dialysis, and concentrating procedures are usually unnecessary. Multilayered liposomes of small size (980 A mean diameter; > 95% between 500-1,500 A) are produced at lower pressure (3,000 psi). The latter are separated by gel permeation chromatography from a second population of homogeneous vesicles of even smaller size (580 A mean diameter; > 95% between 300-900 A) that contain two bilayer shells.

Biochemistry↗
PubMed1980

Field and experimental studies in cattle and sheep poisoned by nitro-bearing Astragalus or their toxins.

Various species of nitro-containing Astragalus, and the toxic principle of these plants, 3-nitropropionic acid or 3-nitro-1-propanol, were fed to sheep and cattle at doses which produced chronic or acute intoxication. The signs of intoxication produced were similar to those observed in poisoning that occurs under field conditions. The signs of intoxication were emphysema and difficulty in locomotion. Primary microscopic lesions were observed in the lungs and CNS. The lungs had varying degrees of alveolar emphysema and there were varying degrees of wallerian degeneration of the spinal cord.

1-Propanol↗
PubMed1979

Isolation of alveolar type II cells by centrifugal elutriation.

Centrifugal elutriation (counterflow centrifugation) was used to develop a reproducible method for obtaining a nearly pure population of isolated alveolar type II cells. Lung was dissociated into individual cells with recrystallized trypsin, and the type II cells were partially purified by centrifugation on a discontinuous density gradient. The alveolar type II cells were finally purified by centrifugal elutriation. Cells were collected from the elutriator rotor by stepwise increases in flow rates. Cells obtained at flow rates of 7 and 14 ml per min were lymphocytes, other small cells, a few type II cells and cell debris; cells collected at flow rates of 18 and 22 ml per min were mainly type II cells; and cells collected at flow rates of 28, 34 and 43 ml per min were macrophages, some type II cells, other lung cells and cell aggregates. At flow rates of 18 and 22 ml per min, 1.9 +/- 1.0 x 10(6) cells per rat lung (mean +/- S.D., n=30) were recovered of which 86 +/- 6% were type II cells. At these flow rates, 94% of the cells excluded the vital dye erythrosin B from their cytoplasm. They consumed oxygen at a rate of 101 +/- 21 nmol per hr . 10(6) cells (mean +/- S.D., n=4), and their oxygen consumption increased only 10% after 10 mM sodium succinate was added. The cells incorporated [14C]leucine into protein and lipid for 4 hr. Electron micrographs of the cells collected at flow rates of 18 and 22 ml per min show a high percentage of morphologically intact alveolar type II cells. We conclude that centrifugral elutriation is a reproducible method for obtaining nearly pure, metabolically active alveolar type II cells.

Animals↗
PubMed1979

Dengue in the Caribbean: virus isolation in a mosquito (Aedes pseudoscutellaris) cell line.

During outbreaks of dengue fever in the Caribbean in 1977 and 1978 a continuous cell line derived from Aedes pseudoscutellaris was successfully used for the isolation of dengue virus strains from acute human sera. 238 strains were isolated and culture fluid was successfully used as antigen for the identification of several strains. The isolates all produced a marked syncytial cytopathic effect often visible as early as four days after inoculation. The method was successfully employed in the field where, because of their low optimal incubation temperature, the cells suffered no ill effects under ambient conditions. The isolation method was found to be much more sensitive than conventional mouse inoculation.

Aedes↗
PubMed1979

The ultrastructure of bronchial macrophages and lymphocytes in sarcoidosis.

A physical interaction between macrophages and lymphocytes was observed more frequently in bronchial lavage fluid obtained from patients with sarcoidosis than from normal volunteers, irrespective of their history of smoking. In this spontaneous interaction more than two lymphocytes were commonly seen adhering to a macrophage without evidence of cytoplasmic bridging or membrane fusion. To a greater extent than in normal volunteers, macrophages from patients with sarcoidosis were characterized by the appearance of a more highly irregular cell surface, more membrane bound inclusions, however, was positively correlated with the smoking history of the individual, and the number of surface projections (microvilli) of macrophages from smokers appeared to be reduced. Significant differences were not apparent in the nuclear or cellular diameters of macrophages from sarcoid and normal individuals.

Bronchi↗
PubMed1979

Hemolysis with red cell covered surfaces.

Polypropylene (PP) disks activated by exposure to ammonia glow discharge were used as substrates for red cells deposited from saline suspensions. In some cases these cell-coated disks were further treated by glutaraldehyde to bind the cells more strongly. Each disk was used in a rotational blood-shearing device to induce hemolysis, which was compared with that induced by virgin PP. When the cell coating was uniform and dense from a single settling of cells, the glutaraldehyde-fixed surfaces were about 10% less hemolytic than PP. Non-fixed cells detached from outer regions of the disk and apparently contributed additional hemolysis in the process. Secondary layers of settled cells, both fixed and non-fixed, also proved to be more hemolytic than PP. Coatings of gamma-globulin reduced hemolysis relative to uncoated cell surfaces. The best performance was that of activated surfaces without cells, with hemolysis about 20% less than PP. Tests of cells hemolyzing during detachment in a saline medium suggested that hemolysis of whole blood involves a series of brief attachment/detachment events at the solid surface.

Ammonia↗
PubMed1979

Bonding erythrocytes to plastic substrates by glow-discharge activation.

A procedure was developed for attaching erythrocytes to various plastics. Plastic disks were exposed to ammonia glow discharge (AGD) and found thereafter to form weak bonds with red cells settling from a dilute saline suspension poured over the disks. When the disks were used to produce a rotating shear flow, complete cell detachment was observed for stresses exceeding 34 dynes/cm2. Far stronger bonding was achieved by treating AGD-bonded cells with glutaraldehyde, and subsequent shearing failed to detach any cells (maximum stress 58 dynes/cm2). The proposed chemical mechanism involves attachment of -NH2 groups on the plastic during AGD, and formation also of carbonyl oxygen later, to provide sites for hydrogen bonding with the cell membrane. Subsequent glutaraldehyde exposure produces crosslinking between disk and cell, as well as fixing the cell in the normal way. Thus, the initial step succeeds in attaching erythrocytes in a deformable condition but rather weakly, while the second step produces rigid cells which are also bonded more strongly.

Ammonia↗
PubMed1979

Material effects in shear-induced hemolysis.

A rotating-disk apparatus for shearing blood was employed to compare 22 materials for their tendency to cause hemolysis during standardized low-stress (130 dynes/cm2 maximum) laminar flow conditions. Rigid plastics, hydrogels, and carbons were among the materials tested. Time-independent ranking of the materials was possible for 75% of the data; these rankings correlated linearly (for polymers) with the critical surface tension gammac over the range 20--46 dyne/cm, with low gammac being associated with low hemolysis. Surface morphology was also found to influence hemolysis. Roughness in the 1--15 micron range had a distinct effect on hemolysis kinetics for polyethylene surfaces. This suggest that failure to find time-independence in 25% of the material rankings can be attributed to inadequate control of the roughness variable. It also emphasizes the importance of surface morphology, as well as surface chemistry, as a biocompatibility parameter.

Acrylamides↗
PubMed1979

Observations on shear-induced hemolysis.

New data are reported on chemical and mechanical factors affecting the hemolysis of blood in a rotating-parallel-disk apparatus used in biomaterials studies described elsewhere. The hemolytic potential for a blood is found to correlate with plasma components LDH and total triglycerides existing prior to shear. Antibiotics are shown to suppress hemolysis, unrelated to bacterial action. The kinetics of measured hemoglobin release are analyzed in terms of a red cell population having a distribution of fragilities, sample storage age, and possible hemoglobin adsorption. Blood/gas interfacial effects are examined by varying the gas and the extent of interface, and found to be minimal under normal testing conditions. Several geometric and dynamic parameters are varied to illustrate the complexities of engineering design and scale-up.

Biocompatible Materials↗
PubMed1979

Tetramethylbenzidine--a substitute for benzidine in hemoglobin analysis.

Plasma hemoglobin is routinely measured by some modification of the benzidine-hydrogen peroxide method, particularly at low concentrations. Because benzidine is carcinogenic, and thus impractical for clinical use under current restrictions, the identification of a noncarcinogenic benzidine derivative has become important. 3,3',5,5'-tetramethylbenzidine fulfills this criterion, and consequently a method is described in this paper which uses it for hemoglobin determinations in the range of 1 to 100 mg/dl. Absorption spectra show this method to be far less influenced by plasma proteins and other substances than the benzidine method, and moreover the sensitivity of TMB is at least seven times that of benzidine under comparable conditions.

Benzidines↗
PubMed1979

Emory milkvetch (Astragalus emoryanus var emoryanus) poisoning in chicks, sheep, and cattle.

A severe outbreak of Emory milkvetch poisoning in cattle and sheep occurred near Roswell, New Mexico, in the spring of 1975. Mortality averaged 2% to 3% and morbidity averaged 15% to 20%. Emory milkvetch collected from the infested area contained miserotoxin measured as 5 to 9 mg of NO2/g of plant (dry weight). Chicks fed extracts of Emory milkvetch showed toxic signs when fed one dose as 300 mg of NO2/kg of body weight, and died within 5 to 8 hours when fed milkvetch as 400 mg of NO2/kg. A sheep fed Emory milkvetch for 7 days in the form of 38 mg of NO2/kg/day developed signs of nitro poisoning on the 7th day. Cattle were poisoned or died when fed Emory milkvetch as 12 to 20 mg of NO2/ig for several days. The toxic signs observed in the field and under experimental conditions were similar.

Animals↗
PubMed1979

Serological evidence of dengue virus activity in children on the Northern Leeward Islands (Netherlands Antilles).

An arbovirus serologic survey of school children on the Northern Leeward Islands (Saba, St. Eustatius and St. Maarten) using haemagglutination inhibition (HI) detected a high proportion of reactors to dengue types 1,2, and 3. Analysis in relation to age showed an increasing proportion to be positive with increasing age. The results of an all-age survey on St. Eustatius 1970 led to the hypothesis of possible dengue serotype 1 activity on St. Eustatius around 1900, whilst it is thought that dengue type 2 was endemic at other times. In view of the continuous high endemic dengue activity the (re)-appearance of dengue serotype 1 next to type 2 and 3 may be the prelude to the occurrence of the dengue shock syndrome.

Adolescent↗
PubMed1979

Parvovirus as a cause of enteritis and myocarditis in puppies.

A gastro-enteritis syndrome mimicking feline panleukopaenia was diagnosed in young dogs in the Republic of South Africa. Parvovirus was demonstrated by electron microscopy in the faeces of these animals. In addition an acutely fatal, acute to sub-acute non-purulent interstitial myocarditis occurred in pups in the same area. Histopathologically large basophilic intranuclear inclusion bodies were seen in the myocardium of these cases. The two syndromes generally occurred separately, but in two cases were found in the same individuals. The literature on the subject is briefly reviewed and the clinical and pathological findings in these outbreaks are reported.

Animals↗
PubMed1979

Disseminated intravascular coagulation: a complication of Babesia canis infection in the dog.

Disseminated intravascular coagulation is described as a complication of Babesia canis infection in the dog. B. canis infection in the dog is characterized as a mild (uncomplicated) or severe (complicated) disease. The clinical, coagulation and haematological, pathological and histopathological findings of the severe disease are described. Thrombocytopenia is reported as occurring in both the mild and severe forms of B. canis infection in the dog.

Animals↗