Fine scale variability in soil extracellular enzyme activity is insensitive to rain events and temperature in a mesic system

While soil extracellular enzyme assays (EEAs) are frequently used to infer soil microbial function, the data typically reflect a small number of sampling points across a season, and it is unclear to what extent soil EEA may vary on the time scale of days to weeks. Rain events, in particular, may cause rapid shifts in EEA, and fine scale temporal data are needed to properly assess the generality of EEA data collected at coarser time scales. We examined soil EEA 2-3 times per week in the field from June to November in the context of natural rain events and temperature fluctuations, and explored how long-term water addition altered EEA responses. We also tested the short-term effects of water addition on the distribution of EEA in intact soil mesocoms and leachate. There was little temporal variation in EEA for the hydrolases phosphatase, N-acetyl-glucosaminidase and β-glucosidase, despite the occurrence of multiple large rain events and large soil temperature fluctuations. Phenol oxidase activity correlated significantly with seasonal trends in temperature and soil moisture, but was highly variable at short time scales, and the latter did not correlate significantly with short-term changes in soil microclimate. EEA generally increased in response to long-term water addition, and in soil mesocosms water addition did not significantly redistribute EEA among the upper and lower soil layers, and leachate EEA was three orders of magnitude lower than soil EEA. Overall, our results reveal relatively minor short-term variation in EEA for hydrolase enzymes, and no discernable response to temperature fluctuations or precipitation over the short term. However, high short-term variation in phenol oxidase activity suggests that it may be difficult to infer temporal trends in EEA for this enzyme from a limited number of sampling points.     

Inheritance and physiological basis for 2,4-D resistance in prickly lettuce (Lactuca serriola L.)

Experiments were conducted to determine the inheritance and physiological basis for resistance to the synthetic auxinic herbicide (2,4-dichlorophenoxy)acetic acid (2,4-D) in a prickly lettuce biotype. Inheritance of 2,4-D resistance in prickly lettuce is governed by a single codominant gene. Absorption and translocation were conducted using (14)C-2,4-D applied to 2,4-D-resistant and -susceptible biotypes. At 96 h after treatment (HAT), the resistant biotype absorbed less applied 2,4-D and retained more 2,4-D in the treated portion of the leaf compared to the susceptible biotype. The resistant biotype translocated less applied 2,4-D to leaves above the treated leaf and crown at 96 HAT compared to the susceptible biotype. No difference in the rate of metabolism of 2,4-D was observed between the two biotypes. Resistance to 2,4-D appears to originate from a reduced growth deregulatory and overstimulation response compared to the susceptible biotype, resulting in lower translocation of 2,4-D in the resistant prickly lettuce biotype.     

H3N2亚型犬流感病毒HA1基因的原核表达及抗原性分析

为原核表达H3N2亚型犬流感病毒(CIV)HA1蛋白,本研究利用特异性引物扩增CIV H3分离株的HA1基因,将其克隆到pMD18-T载体后进行序列测定。再将其亚克隆于pET-32a(+)中构建重组表达质粒pET-HA1。将该质粒转化于大肠杆菌BL21(DE3)中,经IPTG诱导,SDS-PAGE电泳分析,表达的重组蛋白约为58 ku。纯化的HA1蛋白经western blot和Dot-ELISA鉴定表明,表达的重组HA1蛋白可以与H3N2亚型CIV阳性血清发生特异性反应。     

Alternative therapeutic options for medical management of epilepsy in apes

Phenobarbital has been the primary antiepileptic drug used in primates, but the dosage required for seizure control is frequently associated with significant side effects. Newer antiepileptic drugs and adjunctive therapies currently being used in human medicine provide additional options for treatment of nonhuman primates. This report describes different drug regimes used for control of epileptic seizures in apes at the Milwaukee County Zoo (Milwaukee, Wisconsin, U.S.A.), including the addition of acetazolamide to phenobarbital, levetiracetam, carbamazepine, and the use of extended cycle oral contraceptives to assist seizure control in female apes with catamenial epilepsy.     

Invertase storage stability and sucrose hydrolysis in solids as affected by water activity and glass transition

Research continues to differentiate the impact of water activity (a(W)) and the glass transition temperature (T(g)) on chemical reactions. Invertase with and without sucrose was incorporated into low and high molecular weight poly(vinylpyrrolidone) model systems (PVP-LMW and PVP-K30, respectively). Invertase activity and sucrose hydrolysis were monitored during storage at a(W) = 0.32-0.75 and 30 degrees C. Pseudo-first-order rate constants for activity loss in PVP-K30 were not different, regardless of the system being glassy or rubbery. In PVP-LMW, invertase stability decreased with increasing a(W). An a(W) > 0.62 was required for sucrose hydrolysis to occur in PVP-LMW. PVP molecular weight appeared to affect invertase stability and reactivity. No dramatic change around T(g) was found in either invertase stability or sucrose hydrolysis, suggesting that T(g)-dictated mobility has a minimal effect on these reactions in amorphous solids.     

Low reproductive success of leatherback turtles, Dermochelys coriacea, is due to high embryonic mortality

We examined the mechanism responsible for low reproductive success in leatherback turtles (Dermochelys coriacea) at Playa Grande, Costa Rica: low egg fertilization versus high rates of embryonic death. Leatherbacks at this beach had a high rate of fertility (=93.3%±2.5%, n=819). We incubated 10 eggs from every clutch encountered of 19 females during 3 months of the 1998-1999 nesting season. Fertility rate of some females decreased during the nesting season, but overall was high. Detection of fertility was difficult using standard methods because fertility rates cannot be determined accurately from nests excavated after hatching because of egg decomposition. Removal and incubation of eggs from nests provided a better estimate. Embryonic death, particularly in the beginning of incubation before embryos are visible to the unaided eye, was the cause of low hatching success in this population. Hatching success increased with increasing fertility and differed between females, with some mothers having 71-81% success and others 23-32%. Embryonic death and not low egg fertility drives poor recruitment at Playa Grande. Improved conservation of this species at Playa Grande will require a better understanding of the mechanism behind embryonic death.     

Cloning and expression of desoxyhemigossypol-6-O-methyltransferase from cotton (Gossypium barbadense)

Terpenoids play an important role in defense against insects and pathogens in cotton. These terpenoids contain phenolic groups. Metabolites in which the phenolic group has been converted to a methoxy group are less toxic to most insects and pathogens and thus may alter resistance. Here is reported the cloning of a gene from Gossypium barbadense that encodes the enzyme that methylates the phenolic group of desoxyhemigossypol (dHG) exclusively at the 6-position, dHG-6-O-methyltransferase (dHG-6-OMT). Partial peptide sequences from digests of purified dHG-6-OMT were used to design primers for RT-PCR amplification of cDNA fragments from poly(A) mRNA. Fragments were extended to full length using 5' and 3' RACE. The resulting cDNA codes for a 365-residue polypeptide with a calculated molecular weight of 40.6 kDa, in agreement with the molecular mass of purified dHG-6-OMT. When expressed in Escherichia coli, the bacterial lysates showed a high specificity for the methylation of desoxyhemigossypol, differentiating the cloned gene from other pathogen-induced methyltransferases.