Simultaneous detection of Aeromonas salmonicida,Flavobacterium psychrophilum,and Yersinia ruckeri,three major fish pathogens,by multiplex PCR

A multiplex PCR assay based on the 16S rRNA genes was developed for the simultaneous detection of three major fish pathogens, Aeromonas salmonicida, Flavobacterium psychrophilum, and Yersinia ruckeri. The assay proved to be specific and as sensitive as each single PCR assay, with detection limits in the range of 6, 0.6, and 27 CFU for A. salmonicida, F. psychrophilum, and Y. ruckeri, respectively. The assay was useful for the detection of the bacteria in artificially infected fish as well as in fish farm outbreaks. Results revealed that this multiplex PCR system permits a specific, sensitive, reproducible, and rapid method for the routine laboratory diagnosis of infections produced by these three bacteria.     

Inhibition of HhaI DNA (Cytosine-C5) methyltransferase by oligodeoxyribonucleotides containing 5-aza-2'-deoxycytidine: examination of the intertwined roles of co-factor,target, transition state structure and enzyme conformation

The presence of 5-azacytosine (ZCyt) residues in DNA leads to potent inhibition of DNA (cytosine-C5) methyltranferases (C5-MTases) in vivo and in vitro. Enzymatic methylation of cytosine in mammalian DNA is an epigenetic modification that can alter gene activity and chromosomal stability, influencing both differentiation and tumorigenesis. Thus, it is important to understand the critical mechanistic determinants of ZCyt's inhibitory action. Although several DNA C5-MTases have been reported to undergo essentially irreversible binding to ZCyt in DNA, there is little agreement as to the role of AdoMet and/or methyl transfer in stabilizing enzyme interactions with ZCyt. Our results demonstrate that formation of stable complexes between HhaI methyltransferase (M.HhaI) and oligodeoxyribonucleotides containing ZCyt at the target position for methylation (ZCyt-ODNs) occurs in both the absence and presence of co-factors, AdoMet and AdoHcy. Both binary and ternary complexes survive SDS-PAGE under reducing conditions and take on a compact conformation that increases their electrophoretic mobility in comparison to free M.HhaI. Since methyl transfer can occur only in the presence of AdoMet, these results suggest (1) that the inhibitory capacity of ZCyt in DNA is based on its ability to induce a stable, tightly closed conformation of M.HhaI that prevents DNA and co-factor release and (2) that methylation of ZCyt in DNA is not required for inhibition of M.HhaI.     

Pancreatic hepatocytes in hamsters (Mesocricetus auratus) infected with Trypanosoma cruzi

Hepatocytic metaplasia may be induced in hamsters by carcinogens, and associated with aging, diabetes or chronic pancreatitis. By means of histopathologic and immunohistochemic studies, we observed pancreatic hepatocytes in hamsters infected and reinfected with Trypanosoma cruzi. The change was seen in 18 (19%) out of 94 infected animals, and was not found among 53 controls, Normal islet cells were immunoreactive for neuron-specific enolase and not reactive for NCL-HAS. Metaplastic cells were immunoreactive for NCL-HAS and not reactive for islet hormones and enolase. No relationship was observed between number of inoculations and metaplasia; however, the intensity of the inflammatory process and sequels seems to favor the development of metaplastic cells. Hamsters infected with T. cruzi may be useful to study hepatocytic metaplasia, and contribute to clarify aspects of Chagas' disease and pancreatic changes. Our data indicate that aging, in addition to inflammation and atrophy, plays a role in this change.     

A reversible abnormal form of myelin: an X-ray scattering study of human sural and rat sciatic nerves

A sural nerve dissected from a recently dead patient displayed an unusual X-ray diffraction pattern, suggesting that in situ and at the time of the patient's death the myelin sheaths were in a swollen state. Diffraction patterns of the swollen type were also recorded from: (1) a sural nerve from the corpse of a neurologically healthy person after soaking the nerve with Ringer solution at pH 5.5; (2) sciatic nerves dissected from rat cadavers at increasing time after death. In all the cases the swollen patterns reversed to the native type upon superfusion with Ringer solution at pH 7.3. The postmortem effect is to decrease the pH of the fluids surrounding the nerves in the cadavers. Our experiments show that the early postmortem processes have the effect of acidifying PNS nerves and that as a consequence of acidification the myelin sheaths swell.     

Screening and characterization of Bacillus thuringiensis isolates from Brazil for the presence of coleoptera-specific cry genes

Forty-three Bacillus thuringiensis isolates from Brazil and 3 from Argentina were screened, using the polymerase chain reaction (PCR), for various coleoptera-specific cry genes. Seven isolates produced specific and/or nonspecific DNA fragments in a PCR reaction with primers specific for two coleopteran cry genes and 4 of these produced DNA fragments with primers specific for 7 known coleopteran cry genes. These isolates showed, by electron microscopy, the presence of spherical crystals. They also showed proteins of around 70 kDa which were immunologically similar to the Cry3Aa protein from B. thuringiensis subsp. tenebrionis. The 3 isolates from Argentina were toxic to T. molitor, and although no isolate from Brazil showed toxicity, they might show toxicity to another insect species.     

Adenosine deaminase prefers a distinct sugar ring conformation for binding and catalysis: kinetic and structural studies

Several recent X-ray crystal structures of adenosine deaminase (ADA) in complex with various adenosine surrogates have illustrated the preferred mode of substrate binding for this enzyme. To define more specific structural details of substrate preferences for binding and catalysis, we have studied the ADA binding efficiencies and deamination kinetics of several synthetic adenosine analogues in which the furanosyl ring is biased toward a particular conformation. NMR solution studies and pseudorotational analyses were used to ascertain the preferred furanose ring puckers (P, nu(MAX)) and rotamer distributions (chi and gamma) of the nucleoside analogues. It was shown that derivatives which are biased toward a "Northern" (3'-endo, N) sugar ring pucker were deaminated up to 65-fold faster and bound more tightly to the enzyme than those that preferred a "Southern" (2'-endo, S) conformation. This behavior, however, could be modulated by other structural factors. Similarly, purine riboside inhibitors of ADA that prefer the N hemisphere were more potent inhibitors than S analogues. These binding propensities were corroborated by detailed molecular modeling studies. Docking of both N- and S-type analogues into the ADA crystal structure coordinates showed that N-type substrates formed a stable complex with ADA, whereas for S-type substrates, it was necessary for the sugar pucker to adjust to a 3'-endo (N-type) conformation to remain in the ADA substrate binding site. These data outline the intricate structural details for optimum binding in the catalytic cleft of ADA.     

The lipophilicity of phorbol esters as a critical factor in determining the pattern of translocation of protein kinase C delta fused to green fluorescent protein

Our previous study showed differential subcellular localization of protein kinase C (PKC) delta by phorbol esters and related ligands, using a green fluorescent protein-tagged construct in living cells. Here we compared the abilities of a series of symmetrically substituted phorbol 12,13-diesters to translocate PKC delta. In vitro, the derivatives bound to PKC with similar potencies but differed in rate of equilibration. In vivo, the phorbol diesters with short, intermediate, and long chain fatty acids induced distinct patterns of translocation. Phorbol 12,13-dioctanoate and phorbol 12,13-nonanoate, the intermediate derivatives and most potent tumor promoters, showed patterns of translocation typical of phorbol 12-myristate 13-acetate, with plasma membrane and subsequent nuclear membrane translocation. The more hydrophilic compounds (phorbol 12,13-dibutyrate and phorbol 12,13-dihexanoate) induced a patchy distribution in the cytoplasm, more prominent nuclear membrane translocation, and little plasma membrane localization at all concentrations examined (100 nM to 10 microM). The highly lipophilic derivatives, phorbol 12,13-didecanoate and phorbol 12, 13-diundecanoate, at 1 microM caused either plasma membrane translocation only or no translocation at incubation times up to 60 min. Our results indicate that lipophilicity of phorbol esters is a critical factor contributing to differential PKC delta localization and thereby potentially to their different biological activities.     

Comparison of NK-1 Receptor Antagonist (Maropitant) to Morphine as a Pre-Anaesthetic Agent for Canine Ovariohysterectomy

Objective

To compare the NK-1 receptor antagonist maropitant to morphine during and after surgery in dogs undergoing ovariohysterectomy (OHE).

Methods

30 healthy female dogs were randomly divided to receive either a pre-anaesthetic dose of morphine (0.5 mg/kg SQ) or maropitant (1 mg/kg, SQ) prior to OHE. Anaesthesia was induced with propofol and maintained with isoflurane. Expired isoflurane concentration, heart rate (HR), systolic arterial pressure (SAP) and respiratory rate were measured. Post-operative pain scores and appetite were evaluated during the recovery period. Rescue analgesia (morphine 0.1 mg/kg IV) was administered as needed post-operatively based on blinded pain score assessments.

Results

Although clinically comparable; during surgical stimulation, the maropitant group had lower HR (108±18 vs 115±24 bpm; p = 0.04), lower SAP (114±23 vs 125±23 mmHg; p = 0.003) and required slightly lower percent of isoflurane anaesthetic (1.35±0.2 vs 1.51±0.4%; p = 0.005), when compared to the morphine group. In the recovery period, the maropitant group had lower pain scores at extubation (1.7±0.7 vs 3.4±2.3; p = 0.0001) and were more likely to eat within 3 hours after extubation (64.7 vs 15.3%). However, post-operative rescue analgesia requirements were similar between groups. All other measured parameters were similar between groups. The overall difference observed between groups was small and all monitored and measured parameters were within the expected range for anesthetized dogs.

Clinical Significance

No major differences in cardiorespiratory parameters or anaesthetic requirements were observed between maropitant and morphine when used as a pre-anesthetic agent for OHE. Further studies are necessary to fully elucidate the benefits of maropitant as a pre-anaesthetic agent for canine OHE.     

Use of Drosophila deoxynucleoside kinase to study mechanism of toxicity and mutagenicity of deoxycytidine analogs in Escherichia coli

Most bacteria, including Escherichia coli, lack an enzyme that can phosphorylate deoxycytidine and its analogs. Consequently, most studies of toxicity and mutagenicity of cytosine analogs use ribonucleosides such as 5-azacytidine (AzaC) and zebularine (Zeb) instead of their deoxynucleoside forms, 5-aza-2′-deoxycytidine (AzadC) and 2′-deoxy-zebularine (dZeb). The former analogs are incorporated into both RNA and DNA creating complex physiological responses in cells. To circumvent this problem, we introduced into E. coli the Drosophila deoxynucleoside kinase (Dm-dNK), which has a relaxed substrate specificity, and tested these cells for sensitivity to AzadC and dZeb. We find that Dm-dNK expression increases substantially sensitivity of cells to these analogs and dZeb is very mutagenic in cells expressing the kinase. Furthermore, toxicity of dZeb in these cells requires DNA mismatch correction system suggesting a mechanism for its toxicity and mutagenicity. The fluorescence properties of dZeb were used to quantify the amount of this analog incorporated into cellular DNA of mismatch repair-deficient cells expressing Dm-dNK and the results showed that in a mismatch correction-defective strain a high percentage of DNA bases may be replaced with the analog without long term toxic effects. This study demonstrates that the mechanism by which Zeb and dZeb cause cell death is fundamentally different than the mechanism of toxicity of AzaC and AzadC. It also opens up a new way to study the mechanism of action of deoxycytidine analogs that are used in anticancer chemotherapy.