On the distribution of tree growth stresses

Summary A plane strain pure bending elastic model is used to predict stress states in a cylindrically orthotropic cylinder due to asymmetric strain distributions continously induced at the periphery. A general solution for the stress states related to each component of the strain distribution expanded in a Fourier series is given. Details of solutions for eleven representative tree species are given. Also the change of curvature of a stem caused by a measured peripheral strain distribution is computed for a given period of growth.     

Residual stresses caused by growth stresses within a stem with radially varying spiral grain angle – two numerical solution approaches: 1) finite element method and 2) transfer matrix method

Two numerical methods, the Finite Element (FE) method and the Transfer Matrix (TM) method, have been applied to derive a solution for residual stresses in a stem. The source of stress is the maturation strains in new wood cells, which give rise to growth stresses. The methods are generally applicable to the case of spiral grain with a grain angle varying with radius, which often is the case in trees. Also, the methods allow for the elastic constants to vary with the radius, which is important to model, for example, juvenile wood. The numerical solutions are checked against an analytical solution in the case of a constant grain angle, and are found to coincide. In addition, the two methods are shown to independently produce the same stress distribution for one pattern of grain angle variation. This shows that the methods are reliable, and they will be used for obtaining a wider range of solutions in a subsequent paper. Received: 13 January 1998     

An extension of Jacobs' method for measuring residual growth strains in logs

Summary Previous methods for measuring residual longitudinal growth strain distributions in logs are reviewed. An extension is given of Jacobs' method for measuring growth strains which yields residual strain information at many points in the cross section other than along the diametrical plank. Some of the longitudinal growth strain distributions measured using the new method are presented.This work was supported in part by NSF Grant ENG-74-02428     

Oral Cyclosporine Treatment in Dogs: A Review of the Literature

Cyclosporine is an immunomodulatory drug used to treat an increasing spectrum of diseases in dogs. Cyclosporine is a calcineurin inhibitor, ultimately exerting its inhibitory effects on T‐lymphocytes by decreasing production of cytokines, such as interleukin‐2. Although, in the United States, oral cyclosporine is approved in dogs only for treatment of atopic dermatitis, there are many other indications for its use. Cyclosporine is available in 2 oral formulations: the original oil‐based formulation and the more commonly used ultramicronized emulsion that facilitates oral absorption. Ultramicronized cyclosporine is available as an approved animal product, and human proprietary and generic preparations are also available. Bioavailability of the different formulations in dogs is likely to vary among the preparations. Cyclosporine is associated with a large number of drug interactions that can also influence blood cyclosporine concentrations. Therapeutic drug monitoring (TDM) can be used to assist in attaining consistent plasma cyclosporine concentrations despite the effects of varying bioavailability and drug interactions. TDM can facilitate therapeutic success by guiding dose adjustments on an individualized basis, and is recommended in cases that do not respond to initial oral dosing, or during treatment of severe, life‐threatening diseases for which a trial‐and‐error approach to dose adjustment is too risky. Pharmacodynamic assays that evaluate individual patient immune responses to cyclosporine can be used to augment information provided by TDM.     

Effects of melatonin,p-chlorophenylalanine,and α-methylparatyrosine on plasma gonadotropin level and ovarian activity in the catfish,Heteropneustes fossilis: A study correlating changes in hypothalamic monoamines

The effects of (ip, 10 injections over 20 days) of melatonin (75 g 100 g^–1 BW), the serotonin (5-HT)-synthesis blocker, para-cholorophenylalanine (p-CPA, 10 mg 100g^{–1 BW}) and the catecholamine-synthesis blocker, -methylparatyrosine (-MPT, 10 mg 100 g^–1 BW) on gonadotropin (GTH) secretion and ovarian activity were studied in ^{Heteropneustes fossilis} during late preparatory to early prespawning (April–May). The treatments resulted in significant reductions of plasma GTH and estradiol-17 levels, the gonadosomatic index, frequency distribution of vitellogenic and postvitellogenic oocytes, and ovarian and serum ³²p-labelled alkali-labile phosphoprotein (a marker of vitellogenic activity). Most of the oocytes were nonvitellogenic or had undergone atretic changes. The hepatic ³²-phosphoprotein content increased significantly over the saline control value. The effects were similar and pronounced in the p-CPA and melatonin-treated groups but were moderate in the -MPT-treated group. Hypothalamic 5-HT content and turnover were significantly inhibited in the p-CPA and melatonin-treated groups but the content and turnover of catecholamines were not. The -MPT treatment decreased significantly the content and turnover of dopamine (DA), noradrenaline (NA), and adrenaline (A) but did not influence the 5-HT content or turnover. These results suggest that 5-HT, NA and A are stimulatory to GTH secretion and that melatonin may act on the serotonergic system to inhibit the pituitary-gonadal axis.to whom correspondence should be addressed.A part of the results was presented at the International Workshop on Pineal gland: Its molecular signals and published as an abstract in Neuroendocrinol. Lett. 14: 399 pp., 1992.     

Effect of sub-lethal nitrite on selected haematological parameters in fingerling Catla catla (Hamilton)

A sub‐lethal nitrite toxicity trial was conducted using static conditions for a period of 96 h with fingerlings of Catla catla (21.4±3.6 g). Fingerlings were exposed to five concentrations of nitrite, that is, 1, 2, 4, 8 and 10.4 mg L^?1 and a nitrite‐free control to study changes in haematological parameters. Nitrite caused an increase in immature erythrocyte population (7–24%) in lower concentrations (0–4 mg L^?1) at 6 h while they were absent in higher concentrations. The total erythrocyte count was reduced at 6 h followed by an increase at 12 h with further reduction up to 96 h in all concentrations of nitrite. The 96‐h exposure resulted in 21.2–31.8% reduction in erythrocyte population in 1–10.4 mg L^?1 nitrite. The haemoglobin content decreased progressively with increasing nitrite concentrations as well as exposure periods. Total leukocyte count decreased initially at 6 h in all treatments followed by an increase after 12 h, signifying development of a protective response of the body to nitrite stress. Blood glucose decreased initially up to 24 h followed by an increase through 96 h. Serum protein level decreased continuously with increasing exposure period. The study revealed that exposure to nitrite caused changes in almost all the haematological parameters in the fingerlings depending on the concentration as well as exposure period. Nitrite being one of the important inorganic nutrients often recorded at higher levels in intensively cultured ponds, the present study highlights its adverse impact on fish and stressed the need for the management of this nutrient in culture ponds.     

Effect of the seaweed Ascophyllum nodosum on lambs during forced walking and transport

The objective of this study was to determine the effect of feeding Ascophyllum nodosum (ANOD) to lambs at 0 (control), 0.5, 1, or 2% of DMI/d for 2 wk on lamb physiology in response to forced walking and transport during hot weather. Forty-four lambs (26 kg +/- 4.3) were used, and each lamb swallowed 3 gelatin capsules filled with ANOD or their normal 16% CP, pelleted grain ration twice daily, with the amount of ANOD dependent on the treatment. The amount of ANOD did not affect ear canal temperature or cortisol concentrations during 60 min of forced walking. The range between the minimum and maximum ear canal temperature for each lamb during 12 h of transport was narrower in lambs receiving the 2% ANOD than the control group (P = 0.05), and the 2% ANOD group also had lower (P = 0.05) ear canal temperatures than the control group during hot periods of transport. After 4 (P = 0.09) and 8 h (P = 0.05) of transport, the control group tended to have greater cortisol concentrations than the 2% ANOD group. Many differences among treatments were found in plasma protein, albumin, calcium, phosphorus, glucose, blood urea nitrogen, aspartate aminotransferase, magnesium, sodium, potassium, and chloride concentrations posttransport; mainly, the control and 0.5% ANOD groups had greater (P < 0.05) concentrations than the other 2 treatments. Aldosterone concentrations were greater in the control and 0.5% ANOD group than in the 1 and 2% ANOD groups before transport, whereas the concentrations were not different after transport, suggesting pretransport concentrations were lowered by supplementation. The 1 and 2% ANOD groups lost more BW than the control group as a result of transport (P = 0.04). After transport, no differences were observed in the latency for lambs to drink, eat, or lay. There was a suppression of the IgG and IgM antibody responses at 4 and 7 d after administration of ovalbumin, with greater ANOD supplementation rates suppressing antibody response the greatest. Although ANOD decreased ear canal temperature in hot periods of transport, stabilized electrolyte concentrations, and decreased cortisol throughout transport, it also suppressed the antibody response indicating that the effect of ANOD on immune function merits further investigation.     

Effect of fluoride on axenic cultures of diatoms

Algal bioassay studies on the effect of F concentrations on diatoms Nitzschia palea (freshwater) and Amphora coffeaeformis (brackishwater) were conducted in the laboratory. Significant enhancement of growth occurred in N. palea at F concentrations between 10 and 110 mg L^?1. In A. coffeaeformis statistically significant stimulation occurred at 70 mg L^?1 F and above 90 mg L^?1 F the growth declined. The results indicate that the diatom N. palea and A. coffeaeformis can tolerate high F concentration.     

Fire intensity effects on seed germination of native and invasive Eastern deciduous forest understory plants

Low-intensity fires were important for maintaining the structure of Eastern deciduous forests (EDFs) for thousands of years before European settlement of North America, though fire suppression became a standard management practice in the 1930s. More recently, prescribed fires have been reintroduced to EDF habitats to aid in the restoration of native plant diversity, but invasions of non-native species such as Microstegium vimineum (Japanese stiltgrass) may increase prescribed fire intensity and suppress colonization of native species. As fire becomes a more common management tool in these habitats, it is vital to predict fire temperature effects on the native and non-native species present in the system. In this study, we found that prescribed fires in areas invaded by Microstegium can be 250-300 °C hotter than fires in nearby native-dominated areas. We then compared the effects of fire on germination rates of six native and three non-native EDF understory species representing the range of functional groups common in this habitat. We manipulated both fire intensity (temperature and length of exposure) and type of fire effect (direct flame and indirect furnace heat) to generate germination curves and make predictions about potential prescribed fire effects on populations of these species. There were very different responses among species to both direct (flame) and indirect (furnace) heating. Germination of three native species, Lycopus americana (American water horehound), Verbesina alternifolia (wingstem), and Vernonia gigantea (tall ironweed), showed signs of being stimulated by heating at low temperatures, while germination of all non-native species (M. vimineum, Elaeagnus umbellata, and Schedonorus phoenix) were inhibited at these lower intensities. High fire intensity (temperatures above 300 °C) effectively killed most species, though one native species, Senna hebacarpa (American senna) and one non-native species, E. umbellata (autumn olive), were capable of tolerating 500 °C temperatures. We conclude that high-intensity prescribed fires in habitats invaded by Microstegium may reduce seed germination of some non-native species, but may also inhibit the regeneration of native understory species.     

Environmental nitroso compounds: reaction of nitrite with creatine and creatinine

Creatine reacts with nitrite under acid conditions to produce first sarcosine and then N-nitrososarcosine, which is a weak carcinogen in the rat. Creatinine reacts with acidified nitrite to produce either creatinine-5-oxime or 1-methylhydantoin-5-oxime, depending on reaction conditions. The toxicity and environmental significance of these compounds is not yet known.