Growth and Physiological Responses of Triticum aestivum and Deschampsia caespitosa Exposed to Petroleum Coke

Methylibium petroleiphilum PM1, which is capable of degrading of methyl tert-butyl ether (MTBE), was immobilized in calcium alginate gel beads. Various applications were explored to increase the mechanical strength of these gel beads. The introduction of 0.3 mol/L calcium chloride into the crosslinking solution, 0.002 mol/L calcium chloride into the growth medium, and 0.2% polyethyleneimine (PEI) as chemical crosslinking agent increased the stability of the Ca-alginate gel beads under the operation conditions of the bioreactor. The degradation rates of MTBE by the immobilized cells in the bioreactor system operated in batch and continuous mode , respectively, were compared. A MTBE biodegradation rate of 5.79 mg/L·h was reached for over 400 h (50 batches), and the immobilized cells in the bioreactor removed >96% MTBE during 50 days of operation. Molecular analysis of the PM1 cells revealed that microbial growth occurred predominantly as microcolonies in the outer area of the beads during the first 20 days of operation. The results of this study show that a continuous-mode, fixed-bed bioreactor reactor coupled with PM1-immobilized cells is a promising technology for remediating MTBE-contaminated groundwater.     

Survey of potato spindle tuber viroid in seed potato growing areas of the United States

Fourteen United States (U.S.) seed potato certification agencies surveyed all U.S. seed potato growing areas for presence of the potato spindle tuber viroid (PSTVd). The survey included general surveillance, which involved searching for the occurrence of PSTVd in state seed potato certification records from 1990 through 2000, and a field survey, which involved testing selected crops for PSTVd infection by nucleic acid dot blot hybridization during 1999 through 2001. No PSTVd incident was documented in any of the state certification records, nor was PSTVd detected in the field surveys. All U.S. seed-growing areas were determined to be free of PSTVd. It is concluded that PSTVd has been eradicated and freedom from potato spindle tuber viroid has been successfully maintained in all of the seed potato growing areas in the United States.     

Height-diameter models with random coefficients and site variables for tree species of Central Maine

Height-diameter models were developed for nine tree species common to the northeastern United States: Abies balsamea, Acer rubrum, Betula papyrifera, B. populifolia, Picea rubens, P. mariana, Pinus strobus, Populus tremuloides, and Tsuga canadensis. Stem heights and diameters were collected from 6 146 trees (between 136 and 2615 trees per species) on 50 plots within 10 structurally diverse stands that are part of a long-term silvicultural experiment in central Maine. The models were developed using both generalized nonlinear least squares (GNLS) and multi-level, mixed-effects approaches. Mixed-effects approaches were superior to GNLS, with inclusion of site covariates (tree density and basal area) accounting for some of the variability explained by the random coefficients in the full mixed-effect models. Analysis of plot-level parameter estimates suggested that differences in stand structure (even-aged vs. uneven-aged silvicultural practices) had a significant influence on the height-diameter relationships.     

重视猪群健康状态,加强养猪生产的最薄弱环节

影响猪生产性能的三个重要元素(遗传、健康和营养)之间的无法解脱的联系决定了养猪生产的成功或失败.一个永恒的三角关系(图1)将它们连在一起,并且在此关系中每一个元素会持续地影响其它二个中的每一个.健康是这三者中最难以定量的一个,往往也是此三角关系中最为薄弱的环节.能够改善此薄弱环节的计划和重视猪群健康的打算将会提高猪的总体生产性能.     

Habitat overlap of juvenile and adult lake trout of Great Bear Lake: Evidence for lack of a predation gradient?

A range of organisms, from plankton to fish, commonly shift their habitat distributions horizontally or vertically due to predation risk. Juvenile lake trout, Salvelinus namaycush, are generally viewed as occupying deep areas of lakes to decrease predation pressure from adults. In contrast, we found that juvenile lake trout from Great Bear Lake, NT, Canada, occupied a variety of habitats and from shallow to deep depths (0–150 m), overlapping with adult lake trout. No evidence occurred for a length depth‐based segregation (e.g., ontogenetic shift). Genetic variation was also similar among juveniles in the different depth zones. However, isotopic niches and C:N ratios among juveniles showed some variability in niche widths and positions for individuals caught from the 51–150 m zone compared to juvenile individuals caught from 0–20 m and 21–50 m zones. The uniformly distributed adult lake trout in Great Bear Lake may evenly distribute predation pressure (including cannibalism) across shallow‐ and deep‐water habitats more than in other lakes. As a result, juveniles may respond to differences in foraging opportunities rather than predation risks. Juvenile lake trout did not appear to conform to the general pattern of juveniles seeking a deep‐water refuge to reduce predation risks. In contrast, juvenile lake trout of Great Bear Lake displayed broad resource use across all depths and habitats.     

Golden Shiner Notemigonus crysoleucas× Rudd Scardinius erythrophthalmus Hybrids: Gonad Histology and Spawning Trials

Hybrid fish were produced in ponds by crossing golden shiners × rudd ( Notemigonus crysoleucas × Scardinius erythrophthalmus ) and rudd × golden shiners. Histologically, testes from the hybrids contained spermatocytes that resembled those of the parental species, but no sperm were observed. Lack of sperm in hybrids could have been a seasonal effect. The ovaries of both types of hybrids contained variable numbers of morphologically normal, vitellogenic oocytes and numerous abnormal oocytes in the chromatin nucleolar stage. Abnormal oocytes were necrotic or had irregularly shaped nuclei and clumped chromatin. Many oocyte nests contained infiltrating macrophnges. Spawning trials with F₁ hybrids did not result in spawning behavior or production of F₂ generation fish. Colden shiner × rudd hybrids are of reduced fecundity, but sterility was not conclusively demonstrated.     

Effects of oestradiol benzoate injections, exposure to the boar and age on the attainment of puberty in the gilt

Thirty large white cross Landrace prepubertal gilts from five litters were allocated at random within litters to one of six treatment. All the gilts were given three daily intramuscular injections of 6 micrograms/kg liveweight of oestradiol benzoate but the first injection was given at either 100 days, 120 days, 140 days, 160 days, 180 days or 200 days old. From the time the first oestrogen injection was given, until the end of the experiment, the gilts were allowed daily contact with a boar for 20 minutes. The gilts were mated with a mature boar at the appearance of the second oestrus and they were slaughtered 20 days later. The numbers of gilts ovulating in the treatment groups were determined from plasma progesterone concentrations measured twice weekly throughout the experiment. The numbers of gilts ovulating within 10 days of the oestradiol benzoate injections were 3 of 5, 1 of 5, 0, 0, 3 of 5 and 1 of 5, respectively, in the groups first treated at 100 days, 120 days, 140 days, 160 days, 180 days and 200 days old. For those gilts which were successfully mated, no significant differences were observed between the treatment groups in the number of viable embryos per gilt.     

FEASIBILITY FOR ULTRASOUND‐GUIDED INJECTION OF THE COLLATERAL LIGAMENTS OF THE DISTAL INTERPHALANGEAL JOINT IN HORSES

Desmitis of the collateral ligament of the distal interphalangeal joint is a cause of lameness in performance horses. The objective of this prospective, experimental, ex vivo feasibility study was to evaluate the success of ultrasound‐guided injection of the collateral ligaments of the distal interphalangeal joint in the equine forelimb. Seventy‐six ultrasound‐guided dye injections of the collateral ligament of the distal interphalangeal joint were performed on horses’ cadaver limbs. The hooves were sectioned transversely to verify the location of the dye relative to the collateral ligaments and surrounding structures. Evaluations of transverse sections were performed independently by two experienced observers. A scoring system was used to assess injection of the collateral ligament of the distal interphalangeal joint at the proximal, middle, and distal aspect over the length of the ligament. The collateral ligament was injected at any point in 97.4% of cases. The ligament was injected over the entire scored length in 43.2% of cases (32/74), over two scored length areas in 45.9% of cases (34/74), and in one area in 10.8% of cases (8/74). The distal interphalangeal joint and the common digital extensor tendon were also injected in 81.6% (62/76) and 43.4% (33/76) of the cases, respectively. Use of the ultrasound had a positive and negative predictive value of 98% and 9%, respectively. In this study, ultrasound guidance was useful for confirming injection of the collateral ligament of the distal interphalangeal joint but did not prevent injecting the distal interphalangeal joint and the common digital extensor tendon.