ABC transporters in the protozoan parasite Leishmania

ATP-binding cassette (ABC) transporters constitute one of the biggest and most conserved protein families in the evolutionary scale. Many of them are of enormous clinical relevance, due to their relationship with genetic diseases and drug resistance during the treatment of cancer and infectious diseases. Leishmaniasis is a major and globally widespread group of parasitic diseases, whose treatment has been complicated by the expansion of resistance to conventional drugs. Here, we review the current knowledge about ABC transporters in Leishmania spp, with special attention to their relationship with the drug-resistance phenotype.

The acrosomic reaction in stallion spermatozoa: inductive effect of the mare preovulatory follicular fluid

In the female genital tract, spermatozoa must undergo capacitation and acrosome reaction prior to fertilization. A number of factors may induce physiological acrosome reaction assayed in vitro. The aims of this study are to determine the inductive effect of the preovulatory follicular fluid on the sperm acrosomal status in the equine, once some characteristics of the follicular fluid during folliculogenesis had been evaluated. The spermatozoa were obtained from cauda epididymes of adult stallion. Follicular fluid was taken from mare ovarian follicles classified according to their diameter. In these fluids, total protein, progesterone, estradiol and osmolarity were determined. Afterwards, the effect of preovulatory follicular fluid (50%) upon induction of the acrosomic reaction in stallion capacitated spermatozoa was assayed. Results show that during folliculogenesis the ratio progesterone/estrogen is below 1. In large preovulatory follicles, there is a sharp increase of progesterone, reaching a ratio progesterone/estrogen close to 4. Protein concentration and osmolarity increase together with follicular development, being osmolarity very high at the preovulatory stage. Follicular fluid--in vitro--increases the percentage of spermatozoa with acrosome reaction, maintaining high rates of vitality and motility. The characteristics of follicular fluid undergo dynamic changes during the folliculogenesis, such as steroid level, protein concentration and osmolarity. These events may play a role in the reproductive process in vivo, considering that in vitro the follicular fluid is a very effective inductor of the acrosome reaction, with optimum levels of vitality and motility.

Part III. Direct enzymatic esterification of lactic acid with fatty acids

Lipase catalyzed esterification reactions between lactic acid and several fatty acids have been studied. Difficulties arise in esterifying lactic acid because of the potential for this substance to act both as an acyl donor and as a nucleophile. These difficulties were minimized via strategies which greatly increased the yield of the desired ester. Use of the companion fatty acid in excess with respect to lactic acid in an apolar solvent (n-hexane) in which the lactic is not completely dissolved has been employed to minimize the potential for lactic acid to act as an acyl donor in a self-polymerization reaction.Beneficial and sinergistic effects of both silica gel and molecular sieves on conversion to the desired product are described. However, careful control of the amount of molecular sieves used is required. This fact is a consequence of two opposing effects of this material: i.e. adsorption of both lactic acid and water from the reaction mixture. For reaction between caprylic and lactic acids, use of an excessive amount of enzyme reduces the extent of conversion to 2-O-caproyl-lactic acid.A very pure ester of the L-enantiomer (optical rotation of [alpha]D(25) = -23.5) can be prepared in n-hexane using a four fold excess of caprylic acid and Candida antarctica lipase. Optimum reaction conditions lead to 35% yield of 2-O-caproyl-lactic acid, a result which is close to the maximum yield that can be enantioselectively obtained from commercial grade lactic acid (68 mole per cent monomer).

Potency analysis of inactivated vaccines for Aujeszky's disease virus (ADV), strain RC/79: lymphocyte stimulation in immunized pigs

Mitogenic and antigenic lymphocyte stimulation was examined in pigs that had been immunized with 2 inactivated vaccines which had been prepared with Aujesky's disease virus (ADV), strain RC/79. One vaccine was partially purified by ultra-centrifugation (Vaccine A) the other one was not (Vaccine B). A second dose of vaccine had no influence over the blastogenic response when the lymphocytes were stimulated with phytohemoagglutinin (PHA). Lymphocyte response to the ADV antigen in the immunized pigs was significantly higher at day 30 post inoculation than at day 0 indicating that it was highly specific. Cellular antigens contained in the viral cultures produced a slight non-specific response as shown by a low increase in the levels of lymphocyte blastic transformation (LBT) in the control group at day 30 p.i., this group only received a non infected Vero cell suspension. This was the case in pigs that received vaccine A as well as in those that were vaccinated with vaccine B. Vaccine B contains a greater quantity of contaminating cellular antigens, since it is an impure vaccine. Such antigens could act as non-specific immunomodulators, potentiating cell-mediated immunity (CMI). This assay demonstrated that inactivated vaccines produced with VPR-RC/79, partially purified and unpurified are capable of inducing a humoral immune response. The blastogenic reaction of the peripheral blood lymphocytes to antigens of ADV strain RC/79, indicated that the employed immunogens also induced the CMI. Results indicate that the analyzed immunogens could be considered for the possible implementation of epidemiological measures, which imply the use of vaccines to prevent pseudo-rabies in Argentina.

Streptogramin resistance and shared pulsed-field gel electrophoresis patterns in vanA-containing Enterococcus faecium and Enterococcus hirae isolated from humans and animals in Spain

The present study was performed to determine if any of the 45 vanA-containing Enterococcus faecium or 18 vanA-containing E. hirae strains were shared by chickens (32 E. faecium/l7 E. hirae) and humans (13 E. faecium/1 E. hirae) using pulsed field gel electrophoresis (PFGE) and to study quinupristin-dalfopristin (Q-D) resistance. Seven of the 45 E. faecium isolates (from 2 outpatients and from 5 poultry products) were resistant to Q-D (MIC > or = 16 microg/ml); one strain was shown to have satA by PCR and sequencing and, in the other six isolates, the recently described satG gene was demonstrated. Six different PFGE patterns were detected among the 7 Q-D E. faecium-resistant isolates. None of the E. hirae isolates showed Q-D resistance. Among the 45 vanA -containing E. faecium strains, 25 unrelated clones were found by PFGE with highly diverse patterns and an indistinguishable PFGE pattern was observed in vanA-containing E. faecium strains from two humans and two poultry products. A single PFGE pattern was detected in 17 of 18 vanA-containing E. hirae isolates, obtained from one human and 16 chicken samples. Based on the presence of indistinguishable PFGE patterns among VR E. faecium and E. hirae from humans and chickens, we conclude that horizontal transfer of these strains could occur between both groups.

Bacteriophage lambda and plasmid pUR288 transgenic fish models for detecting in vivo mutations

We adapted transgenic rodent mutation assays based on fish carrying bacteriophage lambda and plasmid pUR288 vectors to address the needs for improved methods to assess health risks from exposure to environmental mutagens and also to establish new animal models to study in vivo mutagenesis. The approach entails separating the vectors from fish genomic DNA and then shuttling them into specialized strains of E. coli bacteria to analyze spontaneous and induced mutations in either lacI and cII or lacZ mutational targets. Fish exhibited low frequencies of spontaneous mutants comparable to the sensitivity of transgenic rodent models. Mutations detected after treating fish with chemical mutagens showed concentration-dependent, tissue-specific, and time-dependent relationships. Spontaneous and induced mutational spectra also were consistent with the specificity of known mutagens, further supporting the utility of transgenic fish for studies of in vivo mutagenesis.

Bacteriocin production in vancomycin-resistant and vancomycin-susceptible Enterococcus isolates of different origins

Bacteriocin production was determined for 218 Enterococcus isolates (Enterococcus faecalis [93] and E. faecium [125]) obtained from different origins (human clinical samples [87], human fecal samples [78], sewage [28], and chicken samples [25]) and showing different vancomycin susceptibility patterns (vancomycin resistant, all of them vanA positive [56], and vancomycin susceptible [162]). All enterococcal isolates were randomly selected except for the vancomycin-resistant ones. A total of 33 isolates of eight different bacterial genera were used as indicators for bacteriocin production. Forty-seven percent of the analyzed enterococcal isolates were bacteriocin producers (80.6% of E. faecalis and 21.6% of E. faecium isolates). The percentage of bacteriocin producers was higher among human clinical isolates (63.2%, 81.8% of vancomycin-resistant isolates and 60.5% of vancomycin-susceptible ones) than among isolates from the other origins (28 to 39.3%). Only one out of the 15 vancomycin-resistant isolates from human fecal samples was a bacteriocin producer, while 44.4% of fecal vancomycin-susceptible isolates were. The bacteriocin produced by the vanA-containing E. faecium strain RC714, named bacteriocin RC714, was further characterized. This bacteriocin activity was cotransferred together with the vanA genetic determinant to E. faecalis strain JH2-2. Bacteriocin RC714 was purified to homogeneity and its primary structure was determined by amino acid sequencing, showing an identity of 88% and a similarity of 92% with the previously described bacteriocin 31 from E. faecalis YI717. The presence of five different amino acids in bacteriocin RC714 suggest that this could be a new bacteriocin. The results obtained suggest that the epidemiology of vancomycin resistance may be influenced by different factors, including bacteriocin production.

The role of peritoneal dialysis catheter configuration in preventing catheter tip migration

Migration of the peritoneal dialysis (PD) catheter from the pelvis to the upper abdomen frequently results in peritoneal dialysis failure and removal of the catheter. Previous studies compared PD catheter survival in various catheter configurations. These studies included single-cuff and double-cuff, straight-end and curled-end catheters, and showed an incidence of catheter migration ranging from 5%-35% depending on the catheter type. Recent studies demonstrated that the double-cuff, Swan-neck, curled-end configuration is associated with a considerably lower incidence of migration. Most of these studies, however, had a small patient sample or no control group, or they compared nonequivalent catheters (for example, Swan-neck, curled-end versus straight, non-curled-end). Over a six-year period, we examined two similar double-cuff, curled-end catheters: Group I catheters had a straight segment between the two cuffs, and Group II catheters had a 60 degrees Swan-neck bend between the two cuffs (Quinton Instrument Co., Bothell, WA, U.S.A.). The two catheters were identical, except for the presence or absence of the Swan-neck bend. All catheters were placed by the closed laparoscopic technique. In the two groups of patients in whom the catheters were implanted, no statistically significant difference was observed in primary disease, age, sex, race, weight, prior abdominal surgery, or duration of dialysis before catheter migration. In group I, 33 of the 219 patients developed catheter migration (15%); in group II, 2 patients of 243 patients developed catheter migration (less than 1%, p = 0.002). In conclusion, the Swan-neck configuration presents an independent factor in preventing PD catheter migration. Review of previous studies and the data from our study, show that double-cuff, curled-end, Swan-neck PD catheters are superior to other catheters in regard to prevention of catheter migration and should be the catheter of choice in PD patients.

Preoperative vancomycin prophylaxis for newly placed peritoneal dialysis catheters prevents postoperative peritonitis

The role of vancomycin and other antibiotics in treatment of acute peritonitis in peritoneal dialysis patients is well established. However, the role of preoperative vancomycin or cephalosporins in preventing early infection in newly placed peritoneal dialysis catheters remains controversial. We performed a prospective randomized study to examine the role of vancomycin or cefazolin prophylaxis in decreasing the incidence of postoperative peritonitis. Over 8-year period, 265 patients undergoing 305 permanent peritoneal catheter placement procedures were randomized into three groups. Group I (103 procedures) received a single intravenous (i.v.) dose of 1000 mg vancomycin 12 hours before the peritoneal catheter placement procedure. Group II (102 procedures) received a single i.v. dose of 1000 mg of Ancef (cefazolin) 3 hours before the procedure. Group III (100 procedures) received no antibiotics preoperatively for a least one week before the procedure. Patients were monitored for peritonitis during the following 14 days. Peritonitis developed in 1 patient (1%) in Group I (vancomycin group) compared to 12 patients (12%) in Group III (control group), p = 0.002, and in 9 patients (9%) in Group II (cefazolin group) compared to Group III, p = 0.68. We conclude that the use of preoperative single-dose i.v. vancomycin prophylaxis for permanent peritoneal dialysis catheter placement reduces the risk of postoperative peritonitis. Cefazolin did not achieve a statistically significant difference from the control group and may not provide adequate prophylaxis.

Pulse oral versus pulse intraperitoneal calcitriol: a comparison of efficacy in the treatment of hyperparathyroidism and renal osteodystrophy in peritoneal dialysis patients

Controversy exists among various studies in regard to the efficacy of oral (p.o.) versus parenteral calcitriol. Some studies suggest that intravenous (i.v.) calcitriol is superior to p.o. calcitriol for treating renal osteodystrophy in hemodialysis patients; others suggest that these routes of administration are equivalent. To our knowledge, no large, prospective, randomized study compares intraperitoneal (i.p.) to p.o. calcitriol in adult peritoneal dialysis patients. We conducted a prospective randomized study in 76 patients (38 on i.p. calcitriol and 38 on p.o. calcitriol), whom we followed for 48 months. Of the 76 patients, 34 (18 in the i.p. group and 16 in the p.o. group) completed the 48-month study period. Calcitriol dosing was similar in both groups (3-6 micrograms per week in three divided doses). Dose adjustments were made depending on levels of parathyroid hormone (PTH), serum calcium, phosphorus, and calcitriol. No significant difference was seen between the groups in regard to age, sex, race, body mass index, dialysis duration, or cause of ESRD. Neither was any difference in the incidence of peritonitis seen between the groups. In the first 3-6 months, PTH decreased equivalently in both groups. The PTH level remained suppressed in the i.p. group throughout the remainder of the study, but, in the p.o. group, PTH returned to its pretreatment level after 3-6 months. Mean serum calcium was not different in the two groups. In the p.o. group, a considerably higher mean follow-up phosphorus level (6.8 +/- 2.3 mg/dL versus 4.7 +/- 1.4 mg/dL, p = 0.008), PTH level (384 +/- 146 pg/mL versus 162 +/- 64 pg/mL; p = 0.005), and alkaline phosphatase level (178 +/- 37 IU/L versus 72 +/- 21 IU/L, p = 0.02) were seen as compared to the i.p. group. In the i.p. group, resolution of osteodystrophy occurred in all patients at the end of the study; in the p.o. group, 5 patients maintained or developed osteodystrophy by the end of the study (p = 0.016). We conclude that i.p. calcitriol is more effective than pulse p.o. calcitriol in lowering PTH and alkaline phosphatase levels and in resolving renal osteodystrophy, and that i.p. calcitriol is associated with a lower incidence of hyperphosphatemia and elevated Ca x PO4 byproduct.

Effect of Staphylococcus toxins isolated from dairy cow milk on Vero cell monolayers

The effect produced on Vero cell monolayers by toxins derived from Staphylococcus strains was characterized. 210 milk samples taken from dairy cows suffering from sub-clinical mastitis were analyzed. Strains belonging to the Staphylococcus genus were isolated from 73 of these milk samples. The production of toxins was then stimulated from these strains when they were cultured in Dolman's medium. The study of cell cultures showed that 53 toxin samples induced marked and irreversible cellular changes. This is compared to 42 samples (57.5%) which were strongly cytotoxic. The remaining 11 samples were shown to be slowly cytotoxic. 16% of the total toxins did not induce cell damage and 11% of the toxins produced cellular damage that was reversible in less than 24 hrs, and were designated as cytotonic. Haemolytic actively in vitro, using sheep red blood cells, was assessed using toxins that caused alteration in the monolayers. The results indicate that 46.51% of the toxins showed beta haemolytic activity, 2.32% alpha haemolytic activity, and 51.16% showed neither alpha nor beta haemolytic activity. The later type of activity did however cause damage to cultured cells, which suggests that the causative agent could be delta toxin. This study reveals a strong predominance of beta haemolytic strains in the dairy farm studied. These strains induced in vitro cell damage, and it is possible to speculate that mammary gland tissue damage is similarly produced, which may be attributed to both beta and/or delta haemolytic toxins.

Detection of mutations in transgenic fish carrying a bacteriophage lambda cII transgene target

To address the dual needs for improved methods to assess potential health risks associated with chemical exposure in aquatic environments and for new models for in vivo mutagenesis studies, we developed transgenic fish that carry multiple copies of a bacteriophage lambda vector that harbors the cII gene as a mutational target. We adapted a forward mutation assay, originally developed for lambda transgenic rodents, to recover cII mutants efficiently from fish genomic DNA by lambda in vitro packaging. After infecting and plating phage on a hfl- bacterial host, cII mutants were detected under selective conditions. We demonstrated that many fundamental features of mutation analyses based on lambda transgenic rodents are shared by transgenic fish. Spontaneous mutant frequencies, ranging from 4.3 x 10(-5) in liver, 2.9 x 10(-5) in whole fish, to 1.8 x 10(-5) in testes, were comparable to ranges in lambda transgenic rodents. Treatment with ethylnitrosourea resulted in concentration-dependent, tissue-specific, and time-dependent mutation inductions consistent with known mechanisms of action. Frequencies of mutants in liver increased insignificantly 5 days after ethylnitrosourea exposure, but increased 3.5-, 5.7- and 6. 7-fold above background at 15, 20, and 30 days, respectively. Mutants were induced 5-fold in testes at 5 days, attaining a peak 10-fold induction 15 days after treatment. Spontaneous and induced mutational spectra in the fish were also consistent with those of lambda transgenic rodent models. Our results demonstrate the feasibility of in vivo mutation analyses using transgenic fish and illustrate the potential value of fish as important comparative animal models.

Effects of auditory stimuli correlated with different probabilities of water delivery in a limited-hold temporal schedule

Four rats were exposed to two different tone frequencies, each tone being correlated with independent probabilities of water delivery in a temporally defined schedule. The schedule consisted of a 60-s T cycle, with 30-s t(D) and t(Delta) succesive subcycles. t(D) and t(Delta) were assigned complementary probabilities of water delivery (1.0-0, 0.75-0.25, 0.5-0.5 and 1.0-0) in succesive phases. Each of the first three experimental phases was followed by five consecutive probe sessions using the same probability values, and in which water was delivered independently of responding at the end of each subcycle. Three additional rats were exposed to the same conditions, except that only one tone was used in t(D) and t(Delta). The highest frequencies of responding were observed in two of the rats exposed to differential tone frequencies, an effect that was correlated with lower percentages of lost water deliveries, shorter response latencies, and less variability in the intervals between successive water presentations. In the last phase in which probabilities of water delivery in t(D) and t(Delta) were 1.0 and 0, respectively, response frequency was always higher in t(Delta). These results suggest that the number of water deliveries obtained in the early cycles of every session were responsible for the total number of responses and its correlated effects.

Modulation of the ERK pathway of signal transduction by cysteine proteinase inhibitors

Cell proliferation requires the coordinate synthesis and degradation of many proteins. In addition to the well-characterized involvement of the proteasome in the degradation of several cell cycle-regulated proteins, it has been established that cysteine proteinases are also involved in the control of cell proliferation, but their role is currently not understood. By using both synthetic cysteine proteinase inhibitors and overexpression of T-kininogen (T-KG), a physiologically relevant cysteine proteinase inhibitor, we show that inhibition of cysteine proteinases results in a severe inhibition of the ERK pathway of signal transduction. Mechanistically, this effect appears to be the result of stabilization of the ERK phosphatase MKP-1, which leads to an enhanced dephosphorylation (and hence inactivation) of ERK molecules. These results are specific to cysteine proteinase inhibitors and are not observed when either serine proteinases or the proteasome are inhibited. We hypothesize that inhibition of cysteine proteinases in vivo leads to a dysregulation of the ERK pathway, which results in an inability of the cell to transmit to the nucleus the signals generated by the presence of growth factors, thus resulting in loss of cell proliferation.

High-level amikacin resistance in Pseudomonas aeruginosa associated with a 3'-phosphotransferase with high affinity for amikacin

This work describes the characterization of the phosphotransferase enzymatic activity responsible for amikacin resistance in two clinical Pseudomona aeruginosa strains, isolated from a hospital that used amikacin as first-line aminoglycoside. Amikacin-resistant P. aeruginosa PA40 and PA43 (MIC: 128 mg/l) were shown to have APH activity with a substrate profile similar to that of APH(3')-VI. The enzyme from P. aeruginosa PA40 was purified to > 70% homogeneity. The Km of amikacin for this enzyme was 1.4 microM, the Vmax/Km ratio for amikacin was higher than for the other aminoglycosides tested and PCR and DNA sequencing ruled out the presence of aph(3')-IIps. Amikacin resistance in this strain was, therefore, associated with APH(3')-VI and the high affinity of this enzyme for amikacin could explain the high-level resistance that we observed.

Aminoglycoside-modifying enzymes in high-level streptomycin and gentamicin resistant Enterococcus spp. in Spain

Aminoglycoside resistance was evaluated in 690 enterococcus strains isolated from different clinical sources originating from patients at the University Clinic Hospital of Zaragoza (Spain). The enterococci obtained from clinically significant samples (blood, urine, or exudates) showed more high-level resistance to gentamicin and streptomycin (65 and 42%, respectively) than those isolated from faecal samples (49 and 23%, respectively). Aminoglycoside-modifying enzymes (AME) from 119 of these high-level gentamicin and streptomycin resistant enterococcus strains were studied. The most frequent AMEs found were APH(3') and AAC(6')-APH(2"). More than one enzyme was detected in 71% of the strains (four different enzymes in 5% of the strains). Three Enterococcus faecalis strains had ANT(4')(4") enzymatic activity. Different enzymatic expressions of the bifunctional enzyme AAC(6')-APH(2") were demonstrated in strains in which the complete aac(6')-aph(2") gene was detected by PCR and hybridization: (i) AAC(6') + APH(2") activity; (ii) AAC(6') only; (iii) APH(2") only; and (iv) no activity of AAC(6') or APH(2").