Immunoglobulin absorption in calf neonates with special considerations of stress

The concept that hyperadrenalemia resulting from stress may suppress colostral immunoglobulin absorption or terminate intestinal permeability in the bovine neonate has not been substantiated by objective research. Experiments with exogenous corticosteroids or induction of endogenous secretion of the adrenals have not demonstrated the same effect as in rodents where precocious maturation of intestinal epithelium terminates macromolecular protein absorption. Evidence is given that certain prepartum stressors on the dam may influence colostral immunoglobulin absorption in the calf. High environmental temperature influences colostral immunoglobulin absorption.     

Colostral immunoglobulin transfer in calves II. The rate of absorption

The rate and pattern of colostral immunoglobulin absorption, based upon increase in concentration of immunoglobulin in serum in calves, has been determined from the interaction of three factors: starting age of colostral feeding, amount of colostrum fed, and time after feeding. All immunoglobulin classes show common characteristics of absorption following a rapid transfer during the first 4 h after feeding. An analysis of three-dimensional response surface for each of the three immunoglobulin classes indicated positive linear trend in the amount fed up to 2 liters. Rates of absorption in succeeding time periods following the initial feeding had decreasing linear trends. That is, age at first feeding had an inverse effect on rate of absorption. A linear-by-linear interaction between amount fed and starting age as shown for all three classes. Only immunoglobulin IgM had a significant quadratic response for amount fed. Concentration of immunoglobulin in the pooled colostrums fed had no influence on rate of absorption. Evidence is that 2 liters of colostrum fed to Holstein calves may be optimum in the range studied for maximum pinocytotic activation of absorptive cells and maximum rate of absorption.     

The tensile straining of oxidized Fe-Cr-Al-Y alloys

The apparent tensile fracture strains, at which cracking of α-Al₂O₃ scales formed on Fe-Cr-Al-Y alloys during oxidation in 1 atm oxygen at 1200 °C occur, have been determined by two methods at room temperature. The values are reproducible and depend on the oxidation time but are within the range 1.4% to 2.3%. These are significantly higher than other published values for thermally formed oxides. It has also been observed that an intermediate thermal cycle to room temperature during the oxidation period does not affect significantly the subsequently measured fracture strain. These relatively high values are discussed in terms of two tentative hypotheses, one relating to flaws in the oxide, the other to possible loss of cohesion of oxide which is too fine to be detected by the methods used.     

Genetic diversity of lake whitefish in lakes Michigan and Huron; sampling,standardization, and research priorities

We combined data from two laboratories to increase the spatial extent of a genetic data set for lake whitefish Coregonus clupeaformis from lakes Huron and Michigan and saw that genetic diversity was greatest between lakes, but that there was also structuring within lakes. Low diversity among stocks may be a reflection of relatively recent colonization of the Great Lakes, but other factors such as recent population fluctuation and localized stresses such as lamprey predation or heavy exploitation may also have a homogenizing effect. Our data suggested that there is asymmetrical movement of lake whitefish between Lake Huron and Lake Michigan; more genotypes associated with Lake Michigan were observed in Lake Huron. Adding additional collections to the calibrated set will allow further examination of diversity in other Great Lakes, answer questions regarding movement among lakes, and estimate contributions of stocks to commercial yields. As the picture of genetic diversity and population structure of lake whitefish in the Great Lakes region emerges, we need to develop methods to combine data types to help identify important areas for biodiversity and thus conservation. Adding genetic data to existing models will increase the precision of predictions of the impacts of new stresses and changes in existing pressures on an ecologically and commercially important species.     

Effect of stress on blood leucocyte and milk somatic cell counts in dairy cows.

Blood and milk samples from Holstein cows were examined for total blood leucocyte count, differential blood leucocyte count, milk quality test, and somatic cell count in milk while the cows were stressed by corticotropin injection, confinement in a heat-humidity chamber, or environmental-heat stress by exposure during the hot summer months of June through November in southern Arizona. All three stressing conditions resulted in a moderate blood leucocytosis. Modest increases in somatic cell counts of milk were associated with corticotropin injection and environmental-heat stress. Positive correlations were recorded between blood leucocytes and somatic cell counts of milk in mastitis-free cows injected with corticotropin and between percent blood neutrophils and somatic cell counts of milk in environmental-heat stressed cows with no evidence of current mastitis.     

The effects of load and substrate hardness on the development and maintenance of wear-protective layers during sliding at elevated temperatures

Transitions to low wear rates often occur during sliding between contacting metal surfaces, due to the establishment of high-resistance load-bearing layers. Such layers are developed from compaction of wear debris particles, with adhesion between the particles being an important factor in determining whether the layers are maintained, leading to wear protection, or break down, leading to abrasive wear. They are formed more easily and retained more effectively at higher temperatures, due to increased sintering and adhesion between the debris particles and to enhanced oxidation of these particles. This paper presents the results of a study of the reciprocating sliding wear and friction of dissimilar combinations of pin and disc steel specimens (high-speed steel and high-chrome steel pins and carbon steel discs) at temperatures of 500–600°C, with emphasis on the influence of load and substrate hardness on the development and maintenance of such wear-protective particulate layers. Complex relationships occur between the effects of increased load in producing larger debris particles, in decreasing the critical particle size for establishing the layers and in decreasing the separation between the sliding surfaces, and the effects of hardness of the substrates on the sizes and amounts of wear particles and on the topographies of the wear scars. The relationships are complicated further by oxidation and sintering of debris particles, leading to development of oxide or oxide-containing ‘glaze’ surfaces, and subsequent breakdown of the layers during sliding.     

The early stages of oxidation of ion-implanted nickel at high temperature

The early stages of oxidation of nickel implanted with nickel, chromium, or lithium ions in oxygen at 1100°C have been studied using various electron-optical techniques. The unimplanted metal develops initially a fine-grained, convoluted scale having a ridged, cellular structure. Subsequently, the oxide grains increase in size significantly and oxidation becomes predominantly controlled by diffusion of Ni ²⁺ ions across a compact, columnar scale. Implantation of the surface with nickel ions has no significant effect on the initial oxidation behavior. However, after implantation with chromium or lithium ions, the development of the NiO scale is, in the early stages of oxidation, suppressed by formation of NiCr ₂O₄ or LiO₂ nodules, respectively. Subsequently, the implanted species are incorporated into the steady-state NiO scale where they dope the oxide and thus influence the diffusion rate of Ni ²⁺ ions through it. As would be predicted, the steady-state oxidation rate of chromium-implanted nickel is increased while that of lithium-implanted nickel is decreased compared with that of the unimplanted metal.     

The Effects of Elevated Ambient Temperatures on the Friction and Wear Behavior of Some Commercial Nickel Base Alloys

Measurements of friction and wear during sliding of specimens of Nimonic 75, C263, Nimonic 108 and Incoloy 901 on like specimens in air at temperatures from 20 to 800 C are presented. Under the sliding conditions used, all the alloys show a transition temperature, above which low wear and a low coefficient of friction during sliding are observed after a time and below which these parameters remain relatively high throughout. These temperatures are about 150 C for N75, about 200 C for C263 and N108 and between 200 and 300 for Incoloy 901. At given temperatures above the transition temperatures, the coefficient of friction-time loci show sharp, generally very reproducible, changes from relatively high to low coefficients of friction. The times at which these occur decrease with increasing temperature for a given alloy. Such changes can be closely correlated to the formation of a stable, adherent, thermally softened, oxide layer or glaze on the load-bearing areas during sliding. Once the glaze is established, very little further wear takes place. These tribological properties of the glaze are associated with its low shear strength and the high strength of the underlying alloy substrate. They depend more on its physical properties than on its precise chemical composition. It is concluded that high strength, relatively rapid transient oxidation rates, and appropriate physical properties of the resulting oxide films are important qualities in alloys employed under sliding conditions in air at elevated temperatures.