Antioxidant activity of Paraguayan plant extracts

The antioxidant properties of six medical herbs used in the traditional Paraguayan medicine were studied using free radical-generating systems. The methanol extracts from Aristolochia giberti, Cecropia pachystachya, Eugenia uniflora, Piper fulvescens, Schinus weinmannifolia and Schinus terebinthifolia protected against enzymatic and non-enzymatic lipid peroxidation in microsomal membranes of rat. C. pachystachya, E. uniflora, S. weinmannifolia and S. terebinthifolia showed the highest scavenging activity on the superoxide and DPPH radicals.     

Physiological implications of seasonal variation in membrane-associated calcium in red spruce mesophyll cells

We examined the pattern of seasonal variation in total foliar calcium (Ca) pools and plasma membrane-associated Ca (mCa) in mesophyll cells of current-year and 1-year-old needles of red spruce (Picea rubens Sarg.) and the relationship between mCa and total foliar Ca on an individual plant and seasonal basis. Foliar samples were collected from seedlings and analyzed on 16 dated at 2- to 3-week intervals between June 1994 and March 1995. Concentrations of mCa in current-year needles were more seasonally dynamic and responsive to temporal environmental changes than either mCa concentrations of 1-year-old needles, which were largely stable, or total foliar Ca concentrations in both tissues. In current-year needles, mCa was barely evident in early summer, increased steadily through summer, and then increased dramatically in early fall and surpassed the concentration in 1-year-old needles. Coincident with the first severe frost, mCa concentrations in current-year needles declined significantly and subsequently maintained concentrations comparable to those of 1-year-old needles. Following an extended January thaw, which included 5 days of minimum temperatures > 5 degrees C, mCa concentrations of current-year needles temporarily, but significantly, declined. However, there was no change in mCa concentrations of 1-year-old needles or total Ca concentrations of either tissue. Total Ca concentrations were stable through midsummer in both tissues, doubled in late summer, and then were stable in both tissues throughout fall and winter. Total Ca concentrations were consistently higher in 1-year-old than in current-year needles. Correlations between concentrations of mCa and total foliar Ca were consistently low and mostly nonsignificant. Thus, the dominant, but insoluble, extracellular Ca pool reflected in commonly measured total foliar Ca concentrations is not a meaningful surrogate for the physiologically important and labile pool associated with the plasma membrane-cell wall compartment of red spruce mesophyll cells. It is likely that shifts in the critical mCa compartment would not be detected by analysis of total foliar Ca pools. Seasonal changes in mCa concentration seemed to parallel seasonal changes in membrane structure, and possibly the important role of extracellular Ca in transducing messages associated with environmental signals.     

Physiological changes in red spruce seedlings during a simulated winter thaw

We evaluated net photosynthesis, respiration, leaf conductance, xylem pressure potential (XPP) and cold hardiness in red spruce (Picea rubens Sarg.) seedlings exposed to either a continuous thaw (CT) or a daytime thaw with freezing nights (FN) for 8 days during mid-winter. Physiological differences between CT and FN seedlings were evident for all measured parameters. However, the temporal expression of treatment differences varied among parameters. When compared to FN seedlings, CT seedlings had higher rates of respiration following 24 h of treatment, and a higher net photosynthetic rate, leaf conductance and XPP after 48 h of treatment. The CT seedlings were significantly less cold tolerant than the FN seedlings following 4 days of thaw, whereas FN seedlings did not deharden over the 8 days of treatment. Examination of temporal trends among thaw-associated changes in physiology suggested that, although greater carbon exchange occurred as stomatal conductance increased, the transition from negative to positive net photosynthesis was not the result of increases in conductance, but may have been associated with thaw-induced increases in XPP. Because thaw-associated changes in gas exchange and cold hardiness were offset in time, we conclude that, if changes in these processes are physiologically linked, the linkage is indirect.     

Antimicrobial activity and cytotoxicity of Aerva lanata

Aerva lanata whole plant showed interesting antimicrobial activities (ethyl acetate and methanol extracts) and significant cytotoxic properties (petroleum ether, ethyl acetate and methanol extracts).     

In situ experimental freezing produces symptoms of winter injury in red spruce foliage

Two mechanisms have been proposed to explain winter injury to needles of red spruce (Picea rubens Sarg.): (1) desiccation, which is characterized by net loss of foliar water from the needle to the environment, with cell injury resulting from dehydration; and (2) freezing, which is characterized by direct injury to cells resulting from intracellular or extracellular ice formation during exposure to low temperature. To compare the separate and combined effects of freezing and desiccation, branches of a mature red spruce at 1160 m were (a) experimentally frozen in situ to -50 degrees C; (b) cut and tied in their original orientation and allowed to desiccate passively; or (c) both frozen in situ and cut and tied in their original orientation. Needle water content, electrolyte leakage (an index of cell injury), and needle color were monitored for 60 days after treatment. Freezing resulted in immediate increases in electrolyte leakage, rapid water loss, and reddening necrosis of needles similar to that of naturally injured needles. Cutting resulted in more gradual water loss, no significant changes in electrolyte loss until severe desiccation had occurred, and a change in the color of the needles to a dull green. Because freezing produced reddening necrosis, a key symptom of winter injury, whereas desiccation did not, we conclude that freezing is probably the primary cause of winter injury in red spruce, and that desiccation is a secondary effect.     

Transport,storage and mobilization of nitrogen by trees and shrubs in the wet/dry tropics of northern Australia

Xylem sap from woody species in the wet/dry tropics of northern Australia was analyzed for N compounds. At the peak of the dry season, arginine was the main N compound in sap of most species of woodlands and deciduous monsoon forest. In the wet season, a marked change occurred with amides becoming the main sap N constituents of most species. Species from an evergreen monsoon forest, with a permanent water source, transported amides in the dry season. In the dry season, nitrate accounted for 7 and 12% of total xylem sap N in species of deciduous and evergreen monsoon forests, respectively. In the wet season, the proportion of N present as nitrate increased to 22% in deciduous monsoon forest species. These results suggest that N is taken up and assimilated mainly in the wet season and that this newly assimilated N is mostly transported as amide-N (woodland species, monsoon forest species) and nitrate (monsoon forest species). Arginine is the form in which stored N is remobilized and transported by woodland and deciduous monsoon forest species in the dry season. Several proteins, which may represent bark storage proteins, were detected in inner bark tissue from a range of trees in the dry season, indicating that, although N uptake appears to be limited in the dry season, the many tree and shrub species that produce flowers, fruit or leaves in the dry season use stored N to support growth. Nitrogen characteristics of the studied species are discussed in relation to the tropical environment.     

Induction of tibial dyschondroplasia by carbamate and thiocarbamate pesticides

Tibial dyschondroplasia (TD) is a major poultry leg problem, the natural etiology of which is unknown. Certain dithiocarbamate pesticides such as tetramethyl thiuram disulfide (thiram) have been shown to induce the disease in chickens. Because many different carbamate and thiocarbamate chemicals are used in a number of agricultural, industrial, and household applications, the objective of this study was to determine whether all chemicals of these categories induce TD and whether there is a concentration-dependent relationship between the ingestion of these chemicals and the incidences and the severity of the disease. Week-old broiler chicks were fed diets containing thiram or other assorted carbamate and thiocarbamate pesticides mixed in feed for 24-48 hr between ages 8 and 10 days. The birds were killed on day 15 and the proximal tibial and tarsometatarsal growth plates were evaluated for the presence and severity of TD lesions. TD was distinguished by broadening of growth plates; upon histologic exam chondrocytes appeared to be shrunken and dead. When compared by including equimolar concentrations of these chemicals in the feed, the dithiocarbamates with more than two sulfide groups, such as disulfiram, ferbam, thiram, and ziram were potent inducers of TD, whereas those with two sulfides to no sulfide group appeared ineffective at inducing TD. Both thiram and ferbam also reduced the bird's body weights. Thiram increased the incidence and the severity of the disease, denoted by TD index, in a dose-dependent manner. These results suggest that inadvertent contamination of feed or litter with some of these or similar chemicals may cause leg problems in poultry.     

Heparan sulfate is a selective attachment factor for the avian coronavirus infectious bronchitis virus Beaudette

The avian coronavirus infectious bronchitis virus (IBV) strain Beaudette is an embryo-adapted virus that has extended species tropism in cell culture. In order to understand the acquired tropism of the Beaudette strain, we compared the S protein sequences of several IBV strains. The Beaudette strain was found to contain a putative heparan sulfate (HS)-binding site, indicating that the Beaudette virus may use HS as a selective receptor. To ascertain the requirements of cell-surface HS for Beaudette infectivity, we assayed for infectivity in the presence of soluble heparin as a competitor and determined infectivity in mutant cell lines with no HS or glycosaminoglycan expression. Our results indicate that HS plays a role as an attachment factor for IBV, working in concert with other factors like sialic acid to mediate virus binding to cells, and may explain in part the extended tropism of IBV Beaudette.     

Comparison of two doses of ropivacaine for lumbosacral epidural analgesia in buffalo calves (Bubalus bubalis)

Six male buffalo calves aged from six to eight months and weighing 100 to 120 kg were used to evaluate the efficacy and safety of caudal epidural analgesia produced by doses of 37.5 mg (5 ml) and 75 mg (10 ml) ropivacaine (0.75 per cent). The study was completed in two phases. In phase 1, all the animals were used twice to evaluate the analgesic and clinical effects of two doses of ropivacaine. In phase 2, the animals were divided into two groups of three to evaluate the effects of two doses of ropivacaine on some haemodynamic and acid-base parameters. Signs of analgesia, as evidenced by a loss of response to pinprick stimulation, were recorded only at the tail, perineum and hindlimbs of the animals given 5 ml ropivacaine, but they extended from the tail to the thorax (T9) in the animals given 10 ml ropivacaine. The duration of analgesia was five to six hours in the animals given 5 ml ropivacaine and seven to eight hours in the animals given 10 ml ropivacaine. Animals of both groups became recumbent, but the score for ataxia was higher in the animals given 10 ml ropivacaine. The respiratory rate decreased significantly (P<0.05) below the baseline in the animals given 10 ml ropivacaine, but the rectal temperature, heart rate, mean arterial pressure, central venous pressure and acid-base and electrolyte parameters did not change significantly in either group.     

Three-colour flow cytometric detection of PrP in ovine leukocytes

PrP(c) (cellular prion protein, CD230) expression by subpopulations of lymphoid cells has been widely investigated in a variety of species, possibly because of the possible link between transmissible spongiform encephalopathies (TSE) transmission and blood transfusion. However, the role of the immune cells in the transmission of the disease is still unclear. Here we describe the optimisation and standardisation of a three-colour staining procedure to detect PrP in association with phenotypic and activation markers in ovine immune cells. We demonstrate a reproducible, flexible and sensitive method and that the combination of isotype-specific antibodies and Fab fragments is feasible. To our knowledge, this is the first report of such labelling of ovine cells. Using this method, we were able to detect differences in levels of PrP expression between blood and lymph node cells of the same animal, and considerable variability between animals. Moreover, we were able to explore possible associations between PrP expression and cellular activation and to identify cell subsets with different labelling patterns. We are currently employing this approach to evaluate variations in immunological parameters during experimental infection in sheep.