Effect of grazing pasture with a low selenium content on the concentrations of triiodothyronine and thyroxine in serum,and GSH-Px activity in erythrocytes in cows in Chile

AIM: To determine the effect of grazing pasture that had a low selenium (Se) concentration on serum concentrations of tri iodothyronine (T₃) and thyroxine (T₄), and erythrocyte glutathione peroxidase (GSH-Px) activity in dairy cows.

METHODS: Forty pregnant Friesian cows were grazed on pasture that contained 0.03–0.04 ppm Se on a dry matter (DM) basis. Two months before parturition, 20 cows were randomly selected and treated with 1 mg Se/kg bodyweight subcutaneously, as barium selenate (Group Se-S). The other group (Se-D) was not supplemented. Blood samples were taken before supplementation (-60 days) and 30, 60, 90, 180 and 270 days after parturition, for determination of concentrations of T₃ and T₄ in serum, and GSH-Px activity in erythrocytes.

RESULTS: Erythrocyte GSH-Px activity in the Se-D group was >60 U/g haemoglobin (Hb) throughout the experiment. Supplementation increased (p>0.05) activities to >130 U/g Hb throughout lactation. Mean serum concentrations of T₄ in Se-D and Se-S cows increased from 23.7 (SEM 0.7) and 23.4 (SEM 0.8) nmol/L, respectively, in the prepartum period to 69.6 (SEM 0.1) and 67.6 (SEM 0.2) nmol/L, respectively, at 180 days of lactation (p>0.01), and no effect of Se supplementation was evident. Serum concentrations of T₃ in Se-D cows decreased (p>0.05) from 1.6 (SEM 0.1) nmol/L prepartum to 1.0 (SEM 0.2) nmol/L at the beginning of lactation, and remained lower (p>0.05) than those in the Se-S cows which did not decrease after calving and ranged from 1.9 (SEM 0.1) to 2.4 (SEM 0.2) nmol/L throughout lactation.

CONCLUSIONS: Serum T₃ concentrations decreased during early lactation in unsupplemented cows grazing pastures low in Se (0.03–0.04 ppm) and both serum T₃ and erythrocyte GSH-Px activities were consistently lower throughout lactation compared with Se-supplemented cows. Se supplementation had no effect on serum T₄ concentrations.     

建设农民的精神家园——浅议推进“农家书屋”的科学可持续发展

从＂农家书屋＂的现状分析,探究＂农家书屋＂建设中所存在的问题,并提出进一步推进＂农家书屋＂科学可持续发展,从而在农村文化建设中发挥更大作用的对策。     

The Eucalyptus shoot and leaf pathogen Teratosphaeria destructans recorded in South Africa

Species of Teratosphaeria include some of the most important fungal pathogens of plantation-grown eucalypt trees. During routine disease surveys, symptoms and signs of leaf spot and blight were observed on the foliage of one-year-old E. grandis × E. urophylla hybrids in the Zululand region of KwaZulu-Natal, South Africa. These were distinct from those caused by the well-known and leaf-infecting fungus Teratosphaeria suttonii, which is not considered an important pathogen in the country. Culture and morphological characteristics as well as DNA sequences for three gene regions were used to compare the fungus isolated from the newly emerging symptoms with those for known Teratosphaeria species. DNA sequences were the same as those for T. destructans and this was consistent with the distinctive morphology of the asexual spores and the symptoms on leaves. Teratosphaeria destructans is an aggressive pathogen and actions will be needed to ensure that it does not impart serious losses to the local forestry industry.     

The helminth fauna of indigenous white storks (Ciconia ciconia)

120 carcasses of white storks originating from the federal countries Saxonia-Anhalt and Brandenburg where examined between 1994 and 2000 for internal parasites. The established parasite spectrum consisted of 8 trematode (Tylodelphis excavata, Chaunocephalus ferox, Cathemasia hians, Echinostoma revolutum, Echinoparyphium sp., Monilifer spinulosus, Ignavia ciconiae and Brachylaimus sp.), 4 cestode (Anomotaenia discoidea and 3 Hymenolepidae species) and at least 3 nematode species (Capillaria spp., Syngamus palustris and Contracaecum microcephalum). 5 of the helminths are considered to be stork specific. Considering host age groups the highest percentage of infected birds was found in adults.     

Malignant Mixed Sex Cord-stromal Tumour in a Stallion

A 30-year-old Standardbred stallion was examined for unilateral scrotal swelling. Physical and ultrasound examinations revealed a painless enlarged left testis with a non-homogeneous echogenicity, when compared with the controlateral testis. The stallion underwent left unilateral orchiectomy. Grossly, the excised testis was irregularly enlarged (12 x 9 x 9 cm; weight: 530 g) and firm. The sections showed that testicular parenchyma was replaced by a lobulated, greyish-white mass, which involved the epididymal head. At microscopy, a dual Leydig and Sertoli cell tumour component could be seen. Neoplastic Sertoli cells were prevalent and presented pleomorphic cells, mitotic figures and occasional vascular invasion. Tumour patterns showed tubular and solid areas, cord-like or diffuse in appearance, among which newly formed Leydig cell nests and low-density fibrillar bundles were interposed. Immunohistochemically, a weak to moderate immunostaining for vimentin, AE(1)/AE(3) cytokeratin, alpha-1-antitrypsin and CD99 antigens was found in the growing Sertoli cells, whose nuclear MIB-1 labelling index scored 13 +/- 2%. The Leydig tumour cells, on the other hand, displayed a moderate to strong positivity for alpha-inhibin, vimentin, AE(1)/AE(3) cytokeratin, neurone-specific enolase and CD99. On the basis of these findings, a diagnosis of malignant mixed sex cord-stromal tumour was made.     

A comparative review of the mammalian toxicity of Bacillus thuringiensis-based pesticides

The extensive mammalian toxicity studies performed to support the safety of Bacillus thuringiensis-containing pesticides clearly demonstrate that the tested isolates are not toxic or pathogenic. Toxicity studies submitted to the US Environmental Protection Agency to support the registration of B. thuringiensis subspecies have failed to show any significant adverse effects in body weight gain, clinical observations, or upon necropsy. Infectivity/pathogenicity studies have shown that the intact rodent immune system responds as expected to eliminate B. thuringiensis gradually from the body after oral, pulmonary or intravenous challenge. Similar clearance patterns were observed with B. subtilis and B. sphaericus, which also were non-toxic to test animals. The results also indicate that the currently used protocols for toxicity/pathogenicity evaluations of micro-organisms in laboratory animals have provided useful and necessary information for risk assessment. The study results raise the issue, however, of whether some reduced set of toxicily/pathogenicity studies could be required for new B. thuringiensis isolates of already registered subspecies, and whether this reduced data set would also apply to subspecies not yet registered as pesticidal active ingredients.     

Carbon dioxide exchange of developing avocado (Persea americana Mill.) fruit

Net efflux of CO(2) from attached avocado (Persea americana Mill.) fruit was measured periodically from three weeks after anthesis to fruit maturity. Net CO(2) exchange was determined in daylight (light respiration, R(l)) at a photosynthetic photon flux (PPF) greater than 600 micromol m(-1) s(-1), and in the dark (dark respiration, R(d)). Dark respiration and R(l) were highest during the early cell division stage of fruit growth (about 25 and 22 nmol CO(2) g(dw) (-1) s(-1), respectively) and decreased gradually until fruit maturity to about 1 and 0.5 nmol CO(2) nmol CO(2) g(dw) (-1) s(-1), respectively. Fruit photosynthesis, calculated from the difference between R(d) and R(l), ranged from 0.5 to 3.1 nmol CO(2) g(dw) (-1) s(-1). Net rate of CO(2) assimilation on a fruit dry weight basis was highest during the early stages of fruit growth and reached the lowest rate at fruit maturity. Net rate of CO(2) assimilation of fruit exposed to light was 0.4 to 2.5% of that for fully expanded leaves. Although the relative amount of carbon assimilated by the fruit was small compared with the total amount of carbon assimilated by the leaves, the data indicate that avocado fruit contribute to their own carbon requirement by means of CO(2) assimilated in the light.     

Flooding, root temperature, physiology and growth of two Annona species

The effects of root zone temperature (RZT) and flooding on physiology and growth of Annona glabra L. (pond apple) and A. muricata L. (soursop) were investigated. Trees planted in containers were exposed to RZTs of 5, 10, 20, 25 or 35 degrees C in controlled root temperature chambers. Trees at each RZT were either non-flooded (control) or continuously flooded. There were four replications over time for each treatment combination. Pond apple was more flood-tolerant than soursop. A combination of flooding and RZTs of 5 and 10 degrees C resulted in tree mortality of both species by Week 4. Only trees that appeared to develop morphological adaptations survived continuous flooding. In both species, net CO2 assimilation (A) decreased to nearly zero within 1 week following exposure to RZTs of 5 or 10 degrees C and became consistently negative over the remaining experimental period. Flooding reduced leaf chlorophyll index (measured with a SPAD meter), A and plant growth, and increased root electrolyte leakage from soursop. Optimum growth occurred at RZTs of 25 to 35 degrees C for non-flooded pond apple trees and at 20 to 25 degrees C for flooded trees. Soursop exhibited maximum growth at RZTs of 35 degrees C under non-flooded conditions and at 25 degrees C under flooded conditions.