Free radicals derived from γ-radiolysis of water and AAPH thermolysis mediate oxidative crosslinking of eGFP involving Tyr-Tyr and Tyr-Cys bonds: the fluorescence of the protein is conserved only towards peroxyl radicals

The enhanced green fluorescent protein (eGFP) is one of the most employed variants of fluorescent proteins. Nonetheless little is known about the oxidative modifications that this protein can undergo in the cellular milieu. The present work explored the consequences of the exposure of eGFP to free radicals derived from γ-radiolysis of water, and AAPH thermolysis. Results demonstrated that protein crosslinking was the major pathway of modification of eGFP towards these oxidants. As evidenced by HPLC-FLD and UPLC-MS, eGFP crosslinking would occur as consequence of a mixture of pathways including the recombination of two protein radicals, as well as secondary reactions between nucleophilic residues (e.g. lysine, Lys) with protein carbonyls. The first mechanism was supported by detection of dityrosine and cysteine-tyrosine bonds, whilst evidence of formation of protein carbonyls, along with Lys consumption, would suggest the formation and participation of Schiff bases in the crosslinking process. Despite of the degree of oxidative modifications elicited by peroxyl radicals (ROO^•) generated from the thermolysis of AAPH, and free radicals generated from γ-radiolysis of water, that were evidenced at amino acidic level, only the highest dose of γ-irradiation (10 kGy) triggered significant changes in the secondary structure of eGFP. These results were accompanied by the complete loss of fluorescence arising from the chromophore unit of eGFP in γ-irradiation-treated samples, whereas it was conserved in ROO^•-treated samples. These data have potential biological significance, as this fluorescent protein is widely employed to study interactions between cytosolic proteins; consequently, the formation of fluorescent eGFP dimers could act as artifacts in such experiments.

The N-terminal Part of Arabidopsis thaliana Starch Synthase 4 Determines the Localization and Activity of the Enzyme

Starch synthase 4 (SS4) plays a specific role in starch synthesis because it controls the number of starch granules synthesized in the chloroplast and is involved in the initiation of the starch granule. We showed previously that SS4 interacts with fibrillins 1 and is associated with plastoglobules, suborganelle compartments physically attached to the thylakoid membrane in chloroplasts. Both SS4 localization and its interaction with fibrillins 1 were mediated by the N-terminal part of SS4. Here we show that the coiled-coil region within the N-terminal portion of SS4 is involved in both processes. Elimination of this region prevents SS4 from binding to fibrillins 1 and alters SS4 localization in the chloroplast. We also show that SS4 forms dimers, which depends on a region located between the coiled-coil region and the glycosyltransferase domain of SS4. This region is highly conserved between all SS4 enzymes sequenced to date. We show that the dimerization seems to be necessary for the activity of the enzyme. Both dimerization and the functionality of the coiled-coil region are conserved among SS4 proteins from phylogenetically distant species, such as Arabidopsis and Brachypodium This finding suggests that the mechanism of action of SS4 is conserved among different plant species.

[Multidisciplinary management of retinoblastoma: Experience in 37 eyes]

OBJECTIVE

To report the results of the multidisciplinary management of patients with retinoblastoma, including survival, enucleation rate, and systemic chemoreduction success.

METHODS

A retrospective study was conducted on 27 patients (37 eyes) diagnosed with retinoblastoma, and treated by a multidisciplinary team in San Juan de Dios Hospital. Demographic information, clinical characterization, survival, local and systemic treatments were included in the analysis. Patients treated with intra-arterial chemotherapy (IAC) were also reviewed.

RESULTS

The study included14 male patients (52%). The median of age at presentation was 8 months (0.16-90). The median follow-up time was 33 ± 21 months. The diagnosis was made in 10 (37%) cases after 15 months old, with a median of 35 months (24-90). 17 (63%) patients had unilateral retinoblastoma, and 10 (37%) bilateral retinoblastoma. Leukocoria, isolated or associated with other signs, was the most frequent reason for referral (63%). Global enucleation rate was 57% (n=21), being the primary treatment in 15 (55%) patients. Enucleation rate in unilateral retinoblastoma was 76.5%, and for bilateral retinoblastoma, it was 60% for one eye and 10% for both. Systemic chemotherapy was prescribed in 17 (63%) patients, with a mean number of cycles of 5.3 ± 2.1. The overall success of chemoreduction and focal therapy in order to avoid external radiotherapy and/or enucleation was 68%. Three patients were treated with IAC as a salvage therapy, controlling the tumor in 2 patients at 6 months of follow-up. These are the first cases reported in Chile. Survival rate was 100%.

CONCLUSION

Multidisciplinary management of retinoblastoma led to a survival rate and morbidity comparable with international reports.

Geographical structuring of Trypanosoma cruzi populations from Chilean Triatoma infestans triatomines and their genetic relationship with other Latino American counterparts

In order to obtain more information about the population structure of Chilean Trypanosoma cruzi, and their genetic relationship with other Latino American counterparts, we performed the study of T. cruzi samples detected in the midgut content of Triatoma infestans insects from three endemic regions of Chile. The genetic characteristics of these samples were analysed using microsatellite markers and PCR conditions that allow the detection of predominant T. cruzi clones directly in triatomine midgut content. Population genetic analyses using the Fisher's exact method, analysis of molecular variance (AMOVA) and the determination of F(ST) showed that the northern T. cruzi population sample was genetically differentiated from the two southern population counterparts. Further analysis showed that the cause of this genetic differentiation was the asymmetrical distribution of TcIII T. cruzi predominant clones. Considering all triatomines from the three regions, the most frequent predominant lineages were TcIII (38%), followed by TcI (34%) and hybrid (8%). No TcII lineage was observed along the predominant T. cruzi clones. The best phylogenetic reconstruction using the shared allelic genetic distance was concordant with the population genetic analysis and tree topology previously described studying foreign samples. The correlation studies showed that the lineage TcIII from the III region was genetically differentiated from the other two, and this differentiation was correlated with geographical distance including Chilean and mainly Brazilian samples. It will be interesting to investigate whether this geographical structure may be related with different clinical manifestation of Chagas disease.

[Evaluation of the technique of immunomagnetic separation for recovery of Escherichia coli O157:H7 in milk creams]

The utility of immunomagnetic separation (IMS) for the recovery of Escherichia coli O157:H7 in milk creams was evaluated. The efficiency of different pre-enrichments broths previous to ISM was determined and different agars were analyzed (differential and/or selective) for plating of the inmunobeads. Portions of 25 g from milk creams were inoculated with pathogen low levels (50, 10 and 1 cell/g) and then, were enriched in buffered peptone water with vancomycin (BPW-V), buffered peptone water with vancomycin and cefixime (BPW-VC) and triptone soya broth with vancomycin, cefixime and tellurite (TSB-VCT) being incubated 35 degrees C/18 hours. Then, IMS was applied and immunobeads were plated onto sorbitol MacConkey agar (SMA), sorbitol MacConkey agar with cefixime and tellurite (SMA-CT) and chromogenic agar with tellurite and cefixime (CRGA-TC). It was observed significant differences (p < 0.05) in the recovery percentages according to the pre-enrichment broth used, being obtained the biggest recovery rates with the use of TSB-VCT for the three inocula levels. The recovery rates did not vary significantly (p < 0.05) among the utilized agars, while the number of inoculated cells impacts the recovery percentages, being bigger as it increases the inocula. In conclusion, IMS is a sensitive method for the recovery of Escherichia coli O157:H7 in milk creams, recommending for isolation of this pathogen, the enrichment in TSB-VCT, application of IMS, and plating of immunobeads onto nonselective agar (SMA) and selective agar (SMA-TC or CRGA-TC).

[Prevalence of calorie protein malnutrition among patients in chronic hemodialysis]

BACKGROUND

Malnutrition has been strongly associated with morbidity and mortality in hemodialysis patients. In the other hand, dialysis allows a nutritional improvement in patients with more than 12 months in dialysis.

AIM

To study the prevalence of malnutrition among patients in hemodialysis.

PATIENTS AND METHODS

We measured clinical, anthropometric and biochemical parameters of nutritional status in chronic hemodialysed patients. Results were related to individual time in dialysis. Patients with more and less than 12 months in dialysis were compared.

RESULTS

Twenty nine patients (18 male) aged 14 to 65 years old, were studied. Mean caloric intake was 23.8 Cal/Kg and protein intake was 0.7 g/Kg. Mean body mass index was 21.7 +/- 3.7 kg/m2 Thirty eight percent of patients had a body mass index of less than 20 kg/m2. Mean serum albumin was 4.1 +/- 0.7 g/L; mean prealbumin was 33.5 +/- 7.9 mg% and creatinine was 9.6 +/- 2.8 mg%. Serum cholesterol was 182 mg% and triacylglycerol 129 mg%. PCR was 42.2 +/- 18.8 and Kt/V was 1.45 +/- 0.3. We did not find a correlation between nutritional markers and time in dialysis or a difference in nutritional parameters between patients with less or more than 12 months in dialysis.

CONCLUSIONS

These patients in chronic dialysis have a high prevalence of caloric malnutrition, which may be due to a poor caloric intake. Protein malnutrition parameters were normal in most patients. The absence of abnormal lipid levels, common in chronic renal failure, is noticeable.

[Aschersonia basicystis on scale insects (Homoptera: Coccidae) in Venezuela]

The fungus Aschersonia basicystison scale insects (Homoptera: Coccidae) is described and illustrated on the basis of the examination of Venezuelan collections, using transmitted light and differential interference contrast optical microscopy.

[Endometrial interference of synthetic estrogens in fertility regulation.Is it necessary to interfere with the antiovulatory mechanism at the central nervous system level in order to obtain contraception?]

For some time the anti-ovulatory activity of certain estrogen/progestagen preparations was the main approach in fertility control. Up to date a drastic dosage reduction of both steroid hormones has been accomplished ameliorating the side effects on the one hand, and being active compounds as contraceptives, in the other. Currently, there are a wide variety of oral contraceptives available with a variety of estrogen doses combined with different progestagens. The estrogen content is a high as 80 micrograms and as low as 20 micrograms, moreover, such formulations are prescribed beginning the 1st or the 5th day of the menstrual cycle. By studying plasma and endometrial samples simultaneously obtained from chronic oral contraceptive users taking either 30 micrograms or 50 in such pills; a 17-beta-estradiol pattern was attained as that seen during follicular maturation in the ovulatory cycle only women under the lower dose of synthetic estrogen. However, in the endometrium such a cyclicity did not take place; in parallel circulating progesterone in both groups never reach levels greater than 5.0 ng/ml. Results offer to find a local critical period during the ovulatory menstrual cycle to achieve with much lower hormonal dosages a different approach in future methods of contraception.

Psychological considerations in colonoscopy

In summary, psychological issues around the colonoscopy procedure have not yet been fully studied or even formulated. The framework taken here is to consider psychological preconditions to disease, psychological barriers to screening, and ways to maximize the psychological strength of patients when presenting serious diagnoses. Two common themes are present in this review. First, the idea of hopelessness and loss of personal control is present throughout the research in terms of personality predispositions, decisions to seek care, and outcome of disease when present. Physicians need to address the question, what can I do to maximize the hopefulness of this person before, during, and after screening? Are we encouraging an optimistic perspective in the lives of others? The second theme is closely related and that is the critical nature of the patient/physician relationship in all stages of health/illness behavior. It is often the positive, empathic strength of this relationship that affects patient behavior and ultimately the patient's medical outcome. Future research as well as physician self-examination and increased knowledge in this area are truly important. It is in this way that the procedure of colonoscopy truly becomes part of the total patient care.

Sinefungin as treatment for American Leishmania in sensitive BALB/c and resistant C57BL/6 mice

Using inbred BALB/c and C57BL/6 mice as animal models for American cutaneous leishmaniasis, we evaluated the inhibitory effect of sinefungin on foot-pad infection produced by 5 different Leishmania isolates. When treatment was initiated a few days, or even 2 weeks, after infection, an obvious leishmanicidal effect was detected on mice infected with Leishmania mexicana or L. braziliensis isolates, which lasted at least 50 weeks for all isolates studied. The optimal dose schedule was 4 mg/kg body weight/day, injected ip for 10 consecutive days; lower doses produced only a short leishmanistatic effect. The optimal dose found was 50-fold lower than the LD50. In vitro studies using Leishmania-infected murine peritoneal macrophages showed sinefungin as a powerful inhibitory drug, mean ED50 for the several Leishmania isolates studied being 50 ng/ml. No correlation was found between in vitro sensitivity of culture promastigotes and in vivo sensitivity to sinefungin of an American Leishmania isolate.

American Leishmania spp: formycin B treatment of cutaneous leishmaniasis in mice

Using foot-pad infection of female C57BL/6, DBA/2J and NMRI-IVIC mice as an animal model for American cutaneous leishmaniasis (ACL), we evaluated the inhibitory effect of Formycin B (FoB) on the infection produced by 7 different Leishmania isolates. When treatment was initiated some days, or even some weeks, after infection a significant leishmanistatic effect was detected on mice infected with all Leishmania isolates, which reached 30-55 weeks for some isolates. The optimal dose schedule was 1.25 mg/kg body weight/day, injected intraperitoneally for 20 consecutive days. Significant differences in the sensitivity of various Leishmania spp. to FoB were found, either in vivo, or in vitro where a high [3H]FoB incorporation rate was found only for certain Leishmania isolates. The low toxicity of this drug and the sensitivity of the 7 Leishmania isolates tested suggest that FoB could be useful in the treatment of ACL.

Biological activity of analogs of guanine and guanosine against American Trypanosoma and Leishmania spp

The growth inhibitory effects of six guanine and guanosine analogs, 3-deazaguanine (compound 1); 3-deazaguanosine (compound 2); 6-aminoallopurinol (compound 3); 9-beta-xylofuranosyl guanine (compound 4); a ribosylated derivative of compound 3, 6-aminopyrazolo(3,4-d)pyrimidin-4-one (compound 5); and 5-aminoformycin B (compound 6), were tested against some pathogenic members of the family of American Trypanosomatidae. Compounds 1 and 2 were highly active against Trypanosoma cruzi, Trypanosoma rangeli, and American Leishmania spp. in in vitro culture forms. Both compounds also showed antiprotozoal activity in T. cruzi-infected mice, with the optimal dose being about 30 mg/kg of body weight per day given as 10 consecutive doses. Compound 3 was the most active compound in vitro, inhibiting all of the American Trypanosomatidae culture forms tested. It was also highly inhibitory in mice that were acutely infected with T. cruzi, with the optimal dose being about 10 mg/kg of body weight per day. Ribosylation of compound 3 resulted in a derivative that showed decreased inhibitory activity on Trypanosomatidae multiplication. Compound 6 was highly inhibitory of in vitro multiplication of American Leishmania and T. rangeli but had no effect on T. cruzi epimastigotes and on mice that were acutely infected with T. cruzi. Compound 4 showed only a slight effect on T. cruzi epimastigotes.