Showing papers by "University of Nevada, Reno published in 1979"

Seasonal and year-to-year differences in food selection by beavers.

Abstract: Selection of trees for food by a colony of beavers in central Massachusetts was studied from September 1972 through April 1974. The beavers exhibited both seasonal and year-to-year differences in preference for certain genera. Pine was selected against during fall but not spring, and there was a switch in preference from birch during fall 1972 to oak and witch hazel in fall 1973. These differences may partly reflect greater seasonal stability in concentrations of stored nutrients in coniferous tree bark than in deciduous tree bark, and greater year-to-year stability in bark concentrations of stored nutrients in non-mast-seeding species than in mast-seeding species (1972 was a mast year for oaks in central Massachusetts).

A Model for Orographic Precipitation in the North-Central Great Basin

Abstract: The orographic effect, measured as the ratio of mountain to valley precipitation at 72 pairs of stations in the north-central Great Basin, was tested against 29 relief, location and synoptic parameters. Parameters found significant were then subjected to stepwise multiple regression to develop equations explaining the spatial variation of precipitation for each calendar month, two synoptic seasons and the year. The monthly and seasonal equations explained 52–83% of spatial variance and the annual equation 65%. They showed that the ratio increased with station elevation difference and in winter with proximity to the Pacific Ocean; significant relationships also occurred with station pair orientation, and in summer with ocean direction and Pacific storm rainfall. Best results were obtained either for pairs with long-term records or those with both stations topographically close together. An equation using mean monthly Great Basin wind speed and Pacific storm rainfall explained 88% of the annual var...

Myrmekite as a marker between preaqueous and postaqueous phase saturation in granitic systems

Abstract: A nonreplacive, nonexsolution model of myrmekite growth is based on textural relationships in the Sand Springs porphyritic granodiorite, west-central Nevada. A sequence of crystallization is divided into (1) a preaqueous-phase saturation stage, characterized by major growth of plagioclase (zoned)., quartz, and K-feldspar (phenocrysts), and (2) a postaqueous-phase saturation stage characterized by myrmekite, final euhedral growth of plagioclase and quartz, and final growth of K-feldspar phenocrysts and most K-feldspar of the matrix, including some crystals with adularia-habit characteristics. Myrmekite results from micropressure quenching during the separation of an aqueous phase as crystallization progresses. The occurrence of myrmekite as lobate units on plagioclase, extending into K-feldspar, results from precipitation of oligoclase (the basic ingredient of myrmekite) as local continuations of plagioclase growth from a melt that simultaneously expels an aqueous-rich fluid enriched in K-feldspar component. Late K-feldspar crystallizes from the aqueous-rich fluid, filling in around the myrmekite. Quartz in myrmekite represents the inability of silica to diffuse from the quenched melt and occurs as vermicules chiefly in accord with the principles of binary eutectic crystallization. The Sand Springs myrmekite model is tested by evaluating its occurrences in aplite-pegmatite systems, in granitic gneisses, and in the hydrothermal secondary K-feldspar environment. Myrmekite commonly occurs in all but the hydrothermal environment, which is postmyrmekite, and a fundamentally magmatic origin can be reasoned for the other rock types if the tectonic environment during crystallization is also considered.

Review of bite mark evidence

Abstract: Exactness and precision of detail characterize the techniques and methodologies by which bite mark evidence has been analyzed. Admissibility of scientific evidence into the courts requires that it be based on accepted procedures within the area of that discipline. Admission of bite mark evidence is traced from 1923; methods by which the evidence has been analyzed and those techniques currently being developed are reviewed.

Comment on Barkow

Abstract: The "Noble Savage" who heeds Barkow's (1978) advice to invest his time in his sister's children when parental certainty drops to 1/3 would be doing himself, and his genes, a disfavor. While Barkow correctly computes the probability of common genes between father and child at 1/6, the native's relatedness to his sister would not be 1/4 plus (1/4) (1/3) as Barkow asserts. If parental certainty is 1/3, then the likelihood that an individual and his sister

Mutagenic effects of some anticancer antibiotics.

Abstract: Considering the strong correlation observed between carcinogenic and mutagenic properties of chemicals, a study of the genetic effects of antineoplastic agents is warranted in as much as these agents may ‘cure’ certain types of cancers but may initiate some other types; in addition, an understanding of the effects of these antibiotics on possible transmissible alterations in the genetic material would be beneficial. The genetic effects of some antibiotic anticancer agents, viz., daunomycin (daunorubicin), adriamycin, bleomycin, actinomycin D, and mitomycin C are reviewed. Even though these are structurally unrelated (except for adriamycin and daunomycin), all these chemicals interfere with DNA synthesis through intercalation (daynomycin, adriamycin, and actinomycin), removal of basis from DNA (bleomycin), or co-valent bonding with DNA (mitomycin C) and strand breakage. In some case a parallelism is found between these chemicals and radiation (e.g., mitomycin C vs UV and bleomycin vs X-rays). All these chemicals have a reversible effect on the cell cycle only when applied at low concentrations. The G 0 stage is the most resistant and the S phase, the most sensitive to these chemicals, bleomycin having a general non-phase-specific effect. Actinomycin binds to chromatin differentially along the length of chromosome, and about 90% of this binding is with the DNA. Andriamycin, daunomycin and bleomycin also bind to chromatin, but not enough is known about differential binding. Phenomena such as enzymatic reduction, e.g., in the case of anthracyclines, seem to confer tissue specificity. The ability of actinomycin D to induce point mutations has been challeged, and most mutation-like effects appear to be epigenetic. The anthracyclines do not appear to be mutagenic either. Mitomycin C is mutagenic, however, perhaps because of its alkylating properties, as shown by studies with several species of micro-organisms, Drosophila, Habrobracon, mice, and human HLA system. Bleomycin has recently been shown to be a locus-specific mutagen in yeast. The study of chromosomes from lymphocytes and bone marrow of individuals receiving chemotherapy, and also in vitro studies, have revealed aberrations, an effect common to all other chemicals. However, the major effect is found when the treatment affects the S phase, except with bleomycin, which also happens to be the only chemical with an effect on prophase chromosomes. Mitomycin and bleomycin alos appear to effect the G 0 chromatin in mammals. The major effect of mitomycin C is the production of quadriradials by way of involving homologous chromosomes at corresponding, and preferentially heterochromatic, areas. No other chemical with such great specificity, has been found. Aberrations produced by mitomycin and actinomycin are exclusively of chromatid type, whereas others produce both chromatidand chromosome-type aberrations — both fragments and exchanges. The aberrations are localized in a nonrandom fashion along the length of the genome except with bleomycin, which does not show ‘hot sports’ as convincingly as other chemicals do. Mitomycin C, daunomycin, and adriamycin are very potent inducers of sister chromatid exchanges (SCEs), whereas bleomycin is a poor inducer of this phenomenon. There appears to be a cell-type specificity for induction of both chromosome aberrations and sister chromatid exchanges, though it is not the same at the two end points. The study of somatic crossing-over and meiotic effects has been confined primarily to plants, except for the study of meiotic phenomena in mice and Hebrobracon and Drosophila. Again mitomycin C turns out to be the most effective chemical in these regards. From these and other data on synergistic effects observed in a variety of organisms, there is an urgent need to draw conclusions on the effects of these chemicals on human genetic material in relation to transmissible changes, origin of neoplasia, and the control of cell growth as affected by genetic alterations brought about by these chemicals.

Hyperthermic enhancement of chromosome damage and lack of effect on sister-chromatid exchanges induced by bleomycin in Chinese hamster cells in vitro.

Abstract: Chinese hamster cells M-3, were treated with BLM (1–4 μg/ml) for 30 min to 1 h at 37° or 43°C. After treatment, the cells were reincubated at 37° until recovery. The material treated at 43° showed increased damage expressed as chromosome and chromatid-type breaks and exchanges. Since the amount of BLM entering the cell at 37° is supposedly similar to that which enters the cell at 43°, the enhanced damage is the result of true synergism, and not the facilitation of the drug's entry into the cell.

Conformational Analysis of (+)- (3R)-Methylcyclohexanone from Temperature-dependent Circular Dichroism Measurements

Abstract: Conformational analysis of 3-methylcyclohexanone assumed a special importance some time ago in connection with the so-named "3-alkylketone effect." Klyne and Robins and Walker noted that in the axial conformation of 3-methylcyclohexanone one of the 1,3-diaxial H:CH3 interactions of methylcyclohexane was missing and concluded that the conformational energy difference between axial and equatorial methyl forms should be lowered from the value of 7.11 kJ/mol (for methylcyclohexane) to one-half the value, or 3.55 kJ/mol. The difference (3.55 kJ/mol) between methyl A-values in methylcyclohexane and 3-methylcyclohexanone is called the 3-alkylketone effect. In order to generate an experimental value, thermochemical equilibration studies of cis-3,5-dimethylcyclohexanone on Pd(C) were carried out by Allinger and Freiberg to yield a conformational energy of ΔH° = 5.69 kJ/mol for the trans to cis epimerization. The authors concluded in favor of a greatly reduced 3-alkylketone effect of ca. 1.7 kJ/mol. The value of ΔH° differs from that of Rickborn (7.5 kJ/mol) derived from isomenthone and menthone equilibrations, but falls near to the data derived by Cotterill and Robinson in their base-catalyzed equilibration studies of 2,5-dimethylcyclohexanone [ΔH(e → a) = +5.4 kJ/mol and ΔS(e → a) = -0.2 eu] and 2-t-butyl-5-methylcyclohexanone [ΔH(e → a) = 6.4 kJ/mol and ΔS(e → a) = -0.5 eu]. Subsequently, Allinger et al. indicated conformational energies associated with the equatorial (E), axial (A) and twist (T) conformers (Fig. 1) of 3-methylcyclohexanone as 0, 5.9, and 13.8 kJ/mol, respectively, with a room temperature conformational mixture of 94, 5, and 1%, respectively. More recently Nakamura and I'Haya calculated rotational strengths using CNDO/2 and INDO methods for various probable conformers of 3-methyl-cyclohexanone and suggested a mixture of 83% E, 9% A, 7% T and 1% twist chair at 300°K, and 100% E at 81°K. Surprisingly, there has been no experimentally derived conformational analysis of 3-methylcyclohexanone itself; so, we report herein our conformational analysis of (+)-(3R)-methylcyclohexanone using variable temperature circular dichroism (CD) spectroscopy.

Effects of ion implantation on deep levels in GaAs

Abstract: We have studied the effects of ion implantation in GaAs using the techniques of deep-level transient spectroscopy. Samples included an unimplanted epitaxial buffer layer, a sample implanted directly into that buffer layer and then capped with Si3N4, a sample implanted into that buffer layer through a similar cap, and a sample implanted directly into a semi-insulating substrate and then capped. All implants were with Si29 and both types of implant were annealed at 860°C for fifteen minutes. We find that the total density of deep levels is not changed significantly by direct implantation, capping and annealing but that implantation through a cap greatly in creases the total deep-level concentration. Deep levels found in implanted layers after capping and annealing are primarily characteristic of the substrate or buffer layer into which the implantation is made, unless the implant is through a cap in which case contaminants from the capping process may be evident at high densities.

Catalytic Addition of Electrophiles to β-Dicarbonyls

Abstract: Substitutionally inert metal β-diketonates undergo typical aromatic electrophilic substitution reactions1, though it has recently been convincingly argued2 that these systems possess little aromatic character. The relatively acidic methine hydrogens on the chelate rings are stoichiometrically replaced in a stepwise manner to yield mixtures of mono-, di- and tri-substituted products as schematically illustrated in reaction (1).

Light and electron microscopic observations of the acute sublethal hepatotoxic effects of Mirex in the rat.

Abstract: The fire-ant poison, Mirex, was administered via stomach tube (dosage 200 mg/kg) to 50 adult Mai-Wistar male rats and the resultant histopathologic lesions produced in their livers after six days post-intubation are described. Light (LM) and electron microscopic (EM) technques revealed cellular and subcellular alterations in response to this sublethal dosage. Pathologic lipid accumulations occurred in Mirex-exposed rats and this fat appeared in a distinctive periportal zonation pattern. Additional lesions were detected in centrolobular zones with the EM and included severe glycogen depletion, altered regularity in the architecture of rough or granular endoplasmic reticulum (GER), dilated GER cisternae, free ribosomes, and proliferation of smooth endoplasmic reticulum. Periportal hepatocytes exhibited apparent reduction in numbers of cytoplasmic organelles and development of many, large lipid-containing vacuoles. Myelin figures were sometimes associated with developing lipid (liposomes), suggesting a contribution of myelin membranes to the developing lipid droplets or vice versa. Biochemical studies revealed that glycogen levels dropped markedly, lipid content greatly increased, and protein/DNA and RNA/DNA values decreased.

Alterations of Nucleic Acid and Protein Syntheses in Vivo in the Chick Embryo Mediated by Captan

Abstract: 1. The objective of this investigation was to measure the effects of captan on DNA, RNA and protein biosyntheses in limbs of developing chick embryo, in vivo. 2. Captan (12p.p.m.) was injected into the egg on day 4 of incubation and macromolecular syntheses were measured on days 8--14. 3. Total DNA content was unaffected by captan, but incorporation of [3H]thymidine was inhibited over the entire time range; the period of peak specific activity (day 11) was inhibited in treated samples to 67% of control. 4. Total RNA content was reduced in the earlier days but returned to normal by day 14, whereas incorporation of [3H]uridine was lowered throughout the period. The timing of peak specific activity for RNA synthesis was delayed by 2 days in treated eggs and was inhibited by 32% when peak days were compared. 5. Total protein concentration was slightly lowered by captan treatment in the mid-range of the days measured and the incorporation of [3H]valine was retarded in the early days; peak periods of synthesis were similar in magnitude but were shifted from days 9--10 in control to day 11 in treated embryos.