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M D Morris

Publications and source records attributed to M D Morris.

At least 91 records · Page 5Linked to original sources
PubMed1988

Optical errors in a liquid chromatography absorbance cell.

The shadowgraph method is used to visualize mobile phase flow through a liquid chromatography absorbance cell with "Z" flow geometry. It is shown that mixing is incomplete in the cell. Composition gradients persist throughout the elution of any sample. The gradients systematically change as the sample flows through the cell. Additionally, window wedge angles are measured in several cells. The implications for low noise absorbance detectors are discussed.

Azo Compounds↗
PubMed1988

A comparison of dose-response models for death from hematological depression in different species.

Many radiation-induced lethality experiments have been published for various mammalian species. From those studies a subset of studies reflecting useful biological and physical variables has been compiled into a database suitable to study interspecific variability of radiosensitivity, dose-rate dependence of sensitivity, dose-response behavior within each experiment, etc. The data compiled were restricted to continuous and nearly continuous exposures to photon radiations having source energies above 100 keV. Photon source energy, exposure geometry, and body weight considerations were used to select studies where the dose to hematopoietic tissue was approximately uniform. The database reflects 13 mammalian species ranging in size from mouse to cattle. Some 211 studies were compiled, but only 105 were documented in adequate detail to be useful in development and evaluation of dose-response models of interest to practical human exposures. Of the 105 studies, 70 were for various rodent species, and 35 were for non-rodent groups ranging from standard laboratory primates (body weight approximately 5 kg) to cattle (body weight approximately 375 kg). This paper considers seven different dose-response models which are tested for validity against those 105 studies. The dose-response models include: right-skewed extreme value, left-skewed extreme value, log-logistic, log-probit, logistic, probit, and Weibull models. In general, the log transformation models did not improve model performance and the extreme value models did not seem consistent with the preponderance of the data. Overall, the probit and the logistic models seemed preferable over the Weibull model.

Animals↗
PubMed1988

Rapid scanning thermal lens/laser transmission densitometer.

An automated densitometer based on the thermal lens principle is described. The apparatus also operates as a conventional laser transmission densitometer. Comparison of the performance in both modes shows that thermal lens densitometry provides lower detection limits, but that transmission densitometry is more satisfactory at high optical densities. The instrument is characterized with proteins separated by SDS-PAGE and stained with Coomassie Brilliant Blue G250.

Densitometry↗
PubMed1988

Small-sample confidence limits for parameters under inequality constraints with application to quantal bioassay.

A family of methods is presented for constructing confidence limits for the parameters of a collection of distributions when a simple ordering is assumed among the parameters. The methods are shown to yield confidence limits that are exact or conservative for finite samples. For discrete distributions, one of the methods produces confidence limits that are at least as tight as the limits produced by a commonly used single-sample procedure. Confidence limits are demonstrated for a binomial quantal bioassay problem assuming a nondecreasing dose-response function. Results of a simulation study show that competing asymptotic methods can produce serious discrepancies between nominal and actual coverage probabilities for binomial samples of sizes up to 30, and demonstrate that the new approach can be competitive with the asymptotic methods when the latter maintain their nominal error rates.

Animals↗
PubMed1986

Improved graft patency associated with altered platelet function induced by marine fatty acids in dogs.

Female mongrel dogs fed a marine fish diet rich in long-chain polyenoic fatty acids had improved patency of small-diameter arterial prosthetic grafts as compared to controls. Also, in vivo platelet function as measured by bleeding times was significantly prolonged. Eicosapentaenoic acid, not found in the serum of control animals, was present in relatively high concentrations in both the serum and a platelet-rich fraction of the marine oil-fed group. Eicosapentaenoic acid, unlike arachidonic acid, does not induce platelet aggregation and this phenomonon may account for the altered platelet function demonstrated in our animals and hence the improved graft patency. These data lend further support to the role of platelets in determining the patency of vascular grafts.

Animals↗
PubMed1986

Inhibition of murine interferon production following in vivo administration of benzo[a]pyrene.

To investigate whether alteration in interferon (IFN) production might serve as a biomarker for certain toxic chemical exposures, an in vivo mouse model system was studied. Female C3H mice were injected intraperitoneally with varying doses of benzo[a]pyrene (BP), and at various times subsequent to this treatment, serum IFN levels, following Sendai virus induction, were determined by a cytopathic effect inhibition assay. Doses of 4.6 mg/mouse (180 mg/kg body weight) caused a significant depression in IFN production at 12, 48, and 120 h after BP administration. Doses of 0.46 mg also produced significant decreases at 48 h following exposure. At 48 h post-BP treatment, the reduction in serum IFN titers in treated animals relative to controls was: 62% for the 0.46-mg dose, and 94% for the 4.6-mg dose. These results indicate that systemic administration of BP can significantly depress the whole-animal IFN response to viral stimulation, and that such depression can persist for a rather extended period at certain dose levels.

Analysis of Variance↗
PubMed1986

Thyroid cancer risk in the population around the Nevada Test Site.

Potential thyroid cancer risk in Utah populations due to weapons testing fallout has been examined in two ways. Thyroid cancer incidence rates for Utah for the years 1973-77 were compared to those of the reporting areas of the Surveillance, Epidemiology and End Results Registry. In addition, numbers of lifetime thyroid cancer cases and distribution of probability of causation values for those cases have been estimated for a population of about 23,000 who were in the fallout area of three major shots at the Nevada Test Site during the 1950s. A computer program designed to estimate numbers of expected and excess cases occurring in the remaining lifetime after exposure was used to make the estimates. The estimates of internal dose distribution within various age at exposure groups were made using dose estimates developed by the Off-Site Radiation Exposure Review Project. The potential human risk from 131I at low doses is far from certain. The upper bound risk must be considered to be near that for low doses of acutely delivered external radiation to the thyroid. A practical upper limit for risk from low-dose 131I was taken to be one per million per rad-yr for males and four per million per rad-yr for females (although absolute upper limits would need to be higher). The upper bound estimate of excess cases in the lifetime of the population is about 13, compared to an estimate of about 58 cases expected to occur in the population on the basis of ordinary incidence. If excess risk is assumed to increase linearly with dose, and not to change with age, 12 of 13 excess cases fall into the group aged 18 and below at the time the dose occurred, and 11 of 13 excess cases fall into the group exposed to 10 rad or more.

Adolescent↗
PubMed1984

The distribution of serum high density lipoprotein subfractions in non-human primates.

The ultracentrifugal flotation patterns in 1.2 g/ml solvent and ultracentrifugal gradient distribution of high density lipoproteins (HDL) from the primates--human, apes and monkeys--were determined, with emphasis on the gorilla species of apes and rhesus monkeys. Diets for non-human primates were commercial chow, which is low in cholesterol. Molecular weights and protein, cholesterol, phospholipid and triglyceride compositions of various density fractions were determined on human, gorilla and rhesus HDL. The HDL2/HDL3 ratio was determined from the two peaks observed upon flotation in high salt in the analytical ultracentrifuge. The HDL2 of all three species of apes--gorillas (Gorilla gorilla), chimpanzees (Pan troglodytes) and orangutans (Pongo pygmaeus)--was always greater than HDL3, while that of all six species of Old World monkeys--Rhesus (Macaca mulatta), sooty mangabeys (Cercocebus atys), cynomolgus (Macaca fascicularis), stumptails, (Macaca arctoides) patas (Erythrocebus patas) and African greens (Cercopithecus aethiops)--was less. In addition, the HDL3 concentration in five gorillas was about 15 mg/dl as cholesterol while the HDL2 concentration was 92 mg/dl, much lower and higher, respectively, than humans. HDL2 of gorillas was similar in density and molecular weight to that of humans. The distribution of densities in gorilla HDL was predominantly in HDL2, while rhesus HDL usually, but not always, was unimodal, having a density distribution similar in heterogeneity to human HDL3, but somewhat less dense (peaking at 1.109 vs. 1.129 g/ml). The molecular weight of rhesus HDL was about the same as human HDL3 in all three density subfractions and at the peak density.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗