Processing of Snake Venom Metalloproteinases: Generation of Toxin Diversity and Enzyme Inactivation

Snake venom metalloproteinases (SVMPs) are abundant in the venoms of vipers and rattlesnakes, playing important roles for the snake adaptation to different environments, and are related to most of the pathological effects of these venoms in human victims. The effectiveness of SVMPs is greatly due to their functional diversity, targeting important physiological proteins or receptors in different tissues and in the coagulation system. Functional diversity is often related to the genetic diversification of the snake venom. In this review, we discuss some published evidence that posit that processing and post-translational modifications are great contributors for the generation of functional diversity and for maintaining latency or inactivation of enzymes belonging to this relevant family of venom toxins.

Vitamin E supplementation reduces oxidative stress in beta thalassaemia intermedia

OBJECTIVE

The aim of this investigation was to study the effect of vitamin E treatment in oxidative stress of red and white cells of beta-thalassaemia intermedia patients.

METHODS

Nine patients undergoing occasional transfusions (5 females/4 males), median age 39 years (range 15-74), were recruited for oral daily administration of 400 IU vitamin E for 3 months. Twenty-seven milliliters of peripheral blood was obtained before and after 3 months of treatment, and 3 months after treatment completion. In the case of transfused patients (n = 4), blood was obtained at least 30 days after transfusion. Reactive oxygen species (ROS) was measured by flow cytometry; red blood cell (RBC) reduced glutathione (GSH) was measured by dinitrothiocyanobenzene reduction, serum malondialdehyde was measured in terms of thiobarbituric acid-reactive substances (TBARS), and alpha-haemoglobin-stabilizing protein (AHSP) mRNA expression was measured by real-time polymerase chain reaction of reticulocyte RNA extracts.

RESULTS

beta-Thalassaemia patients presented basal levels of RBC ROS, GSH and serum TBARS statistically different compared with healthy controls. However, after vitamin E administration, patients presented a significant reduction in erythrocyte RBC ROS and serum TBARS levels. In parallel, red cell GSH was significantly increased after treatment. Peripheral mononuclear cells and T lymphocytes also demonstrated a reduction in ROS production. Therefore, after treatment, no significant differences were detected comparing patients and normal controls. Three months after treatment completion, all measurements showed a tendency of returning to basal values. A significant reduction in reticulocyte number was observed after vitamin E treatment. Vitamin E treatment did not modify levels of haemoglobin or AHSP mRNA expression.

CONCLUSION

Although vitamin E is not capable of reducing anaemia in these patients, it could be useful for reducing oxidative damage in other target organs of beta-thalassaemic patients. Finally, this is the first study to analyse the effects of vitamin E on ROS production in red and white blood cells and AHSP mRNA expression.

Simultaneous occurrence of advanced neuroblastoma and acute myeloid leukemia

The authors report the case of a 4-year-old boy with a diagnosis of stage IV neuroblastoma (NB), who had been treated with 6 cycles of cyclophosphamide, doxorubicin, cisplatin, and etoposide for 12 months. The patient reached partial remission and presented a diagnosis of acute myelomonocytic leukemia (M4 AML), confirmed by immunophenotyping. After 2 months of therapy for leukemia, the child died with both malignancies in activity. A necropsy histologically confirmed the simultaneity of the two diseases. The authors review the possibilities of this association. The review leads to the conclusion that AML can occur as a secondary malignancy after the onset of the neuroblastoma, or be suggested by a misdiagnosis. The simultaneous occurrence of both as described here is not, however, found in the literature, to the best of the authors' knowledge.

Disseminated Langerhans' cell histiocytosis and massive protein-losing enteropathy

Symptomatic involvement of the gastrointestinal (GI) tract as a prominent symptom in Langerhans' cell histiocytosis (LCH) is uncommon, occurring in less than 1 to 5% of all cases, even when the disease is in its disseminated form. Up to now, there have been reports of 18 cases of LCH with GI manifestations, including our 2 cases, with diarrhea (77.7%), protein-losing enteropathy (33.3%) and bloody stool being the most frequent findings. The authors present two patients with severe diarrhea and refractory hypoalbuminemia, and with the protein-losing enteropathy documented by Cr51-labeled albumin studies. A review of the literature indicated that the presence of GI symptoms is often associated with systemic disease as well as with poor prognosis, mainly under 2 years of age. Radioisotopes are useful for documenting protein loss in several diseases with high specificity and sensitivity, and their utilization in the cases reviewed here permitted diagnoses in 6 children, as well as improved therapeutic management.

[Enteropathogens associated with acute diarrheal disease in children]

OBJECTIVE: Aiming a better understanding of the distribution of enteropathogens in Brazil, we have investigated the prevalence of enteropathogens in acute infantile diarrhea in children of low economic level from São José do Rio Preto, SP.METHODS: A prospective study with 196 children under age five, all with diarrhea, and 33 control subjects was conducted at Hospital de Base de São José do Rio Preto during 1995. This Hospital is associated to a Medicine School and offers free assistance to patients of low economic level who live in the area. RESULTS: Enteropathogens were identified in 48% of the cases and 27% of the controls. Shigella species were isolated in 21% of the cases, EPEC in 10.7%, Salmonella species in 5.6%. The other enteropathogens studied represented 12 % of the isolate pathogens from case children. In the controls 18.2% of atypical EPEC were isolated. Isolation of Shigella species increased with increasing age of cases and peaked in spring, whereas EPEC was common in early infancy and peaked in spring and winter.CONCLUSIONS: Among São José do Rio Preto children, Shigella species and diarrheiogenic E. coli strains (EPEC, ETEC, EAggEC, EIEC) were isolated throughout the year as a cause of diarrhea bringing children to a medical attention. Most of the pathogens were isolated in spring (mainly Shigella and Salmonella), so the temperature and humidity of the environment must be very important.

Evidence that synaptobrevin is involved in fusion between synaptic vesicles and synaptic plasma membrane vesicles

We have developed a model system, consisting of rat brain synaptic vesicles and rat brain synaptic plasma membrane vesicles, to study the fusion process associated with the exocytotic release of neurotransmitters. Our results show a significant increase in the extent of fusion when the reaction takes place in cytosol compared to that obtained when fusion is carried out in buffer. This effect is mediated by cytosolic proteins, although N-ethylmaleimide-sensitive factor does not play a role in fusion. We also registered an almost complete inhibition of fusion when synaptic vesicles were pre-incubated with botulinum toxin B, indicating that synaptobrevin plays an important role in the coalescence of membrane lipids of the interacting membranes.

Measles antibody prevalence after mass immunization campaign in Niterói, state of Rio de Janeiro, Brazil

Three months after a mass vaccination campaign (coverage: 100%) against measles a random seroepidemiological survey was carried out in students aged 1 to 19 years old in the Municipality of Niterói, State of Rio de Janeiro. Blood samples were tested for measles antibodies by enzyme immunosorbent assay (EIA) and negative cases were tested again using hemagglutination inhibition (HI) and plaque reduction neutralization (PRN). Of the 798 samples tested by EIA, 718 (90.2%) were positive for measles antibodies. PRN test was more sensitive than EIA and HI in detecting measles specific antibodies. The total antibody prevalence increased from 90.2% to 93.2% when HI was employed in EIA negative specimens and to 98.9% when PRN was used. After the mass vaccination campaign a marked decrease in measles incidence was observed in the municipality studied, showing the effectiveness of the strategy used for measles control in developing countries.

A t(9;11) translocation in childhood acute mixed leukemia

We present the case of a child with acute lymphoid leukemia (ALL) who was morphologically classified as FAB L1 (PAS and peroxidase were negative). Remission was achieved with an ALL-type protocol (GBTLI). Five months after the discontinuation of therapy, the patient presented mixed leukemia (CD10, CD19, CD13 and CD33 were positive) with t (9;11) (p21;q23) translocation. Unfortunately, as cytogenetic and immunophenotype studies were not performed at diagnosis, two possibilities could be considered for the relapse; secondary mixed leukemia with clonal chromosome changes, or mixed leukemia from the beginning.

Serological findings during a measles outbreak occurring in a population with high vaccine coverage

From March 1991 to April 1992, serum samples for IgM detection were collected from 112 clinical measles cases reported to the Health Department of Niterói, State of Rio de Janeiro. The positivity exceeded 90% for specimens collected from the 5th to the 29th day after the onset of the disease. After day 30 a decline in IgM detection was observed, although positivity has been detected up to 90 days after the onset of the symptoms. Forty-four patients (48.9%) with an IgM response had a history of prior measles vaccination. In 5 of the 22 measles-IgM negative cases the infection was due to other agents (rubella: 4 cases, dengue: 1 case). These results show that sensitivity of the test employed for confirming suspected measles cases is high, even in vaccinated patients.

Parameters affecting fusion between liposomes and synaptosomes. Role of proteins, lipid peroxidation, pH and temperature

We investigated the effect of several parameters, such as temperature, pH and proteins, on the fusion between synaptosomes, freshly isolated from rat brain cortex, and large unilamellar phosphatidylserine liposomes. These studies were carried out in both peroxidized and nonperoxidized synaptosomes. Mixing of membrane lipids was monitored using a fluorescence resonance energy transfer assay. Ascorbate (0.8 mM)/Fe2+ (2.5 microM)-induced peroxidation of synaptosomes enhanced the fusion process (twofold) which may reflect an increase in synaptosomal protein hydrophobicity and hence a facilitation of intermembrane aggregation. The fusion process was shown to be temperature sensitive, a reduction in the extent being observed (twofold) as the temperature was lowered from 37 to 25 degrees C. This effect may be due to changes in membrane fluidity. The fusion process is pH dependent, an increase in both kinetics and extent being observed when the pH was lowered from 7.4 to 5.5. A significant inhibition (92% at pH 7.4; 35% at pH 5.5) of the interaction between synaptosomes and liposomes by trypsin pretreatment of synaptosomes was found, thus indicating that the fusion reaction is a protein-mediated process. The inhibitory effect of trypsin at pH 5.5 is not so strong as that at physiological pH. These results suggest that, in addition to the involvement of proteins, nonspecific interactions between the synaptosomal and liposomal membranes under acidic conditions may also play a role in the fusion process. The investigation of binding of synaptosomes to liposomes under several experimental conditions provided evidence for the participation of proteins in membrane aggregation, as well as for the role of electrostatic forces in this process, at mild acidic pH.

Teniposide plus cytarabine as intensification therapy and in continuation therapy for advanced nonlymphoblastic lymphomas of childhood

PURPOSE AND METHODS

Thirty-nine consecutive children (age, 2 to 11 years) with nonlymphoblastic (NL) lymphomas were treated uniformly with chemotherapy based on the LNH-II-85 protocol. The protocol consisted of a remission-induction phase that lasted 30 days and started with cyclophosphamide (CTX) 1.2 g/m2 on day 1, followed by vincristine (VCR) 1.5 mg/m2 on days 3, 10, 17, and 24, daunomycin (DAUNO) 60 mg/m2 on days 12 and 13, and prednisone 40 mg/m2/d for 30 days. If a complete remission was achieved, an intensification regimen was given that consisted of eight courses of teniposide (VM-26) 165 mg/m2 plus cytarabine (ARA-C) 300 mg/m2 every 4 days according to bone marrow tolerance. A continuation phase was subsequently started, with alternating courses of thioguanine (6-TG) 300 mg/m2/d for 4 days plus CTX 1.2 g/m2 on day 5; hydroxyurea 2.5 g/m2/d for 4 days plus DAUNO 45 mg/m2 on day 5; VCR 1.5 mg/m2 plus methotrexate (MTX) 120 mg/m2 (24 hours apart); mercaptopurine (6-MP) 500 mg/m2/d for 4 days plus MTX 40 mg/m2; and VM-26 plus ARA-C for 3 courses (4 days apart), by the end of 48 weeks. CNS prophylaxis consisted of intrathecal administration of MTX, ARA-C, and dexamethasone according to age, administered three times during remission induction and every 6 weeks afterwards.

RESULTS

By the end of the analysis in July 1991, 38 of 39 patients had attained a complete remission and 36 were event-free survivors. Two failures that occurred after completion of therapy were second malignancies (acute lymphocytic leukemia and acute nonlymphocytic leukemia).

CONCLUSION

These results are significantly better than those obtained with less intensive former regimens performed in our institution before the availability of VM-26. The favorable impact of an intense consolidation phase with VM-26 is remarkably exemplified by three additional patients not included in this study whose families withdrew them from therapy after the intensification phase, all three of whom have been in remission.

Toxocariasis simulating hepatic recurrence in a patient with Wilms' tumor

We report the case of a 3-year-old girl with stage I Wilms' tumor of favorable histology. During the course of chemotherapy 5 months post-diagnosis, an abdominal ultrasonogram revealed hypoechoic areas consistent with hepatic tumor recurrence. A liver biopsy performed to rule out recurrence of the malignancy was suggestive of toxocariasis and the diagnosis was confirmed by serologic testing. Although the patient had few classic signs of visceral larva migrans, her eosinophilia and family social history should have suggested this possibility. This case demonstrates that hepatic toxocariasis should be considered in evaluating hepatic hypoechoic lesions in a child, even when features typical of the disease are absent.

[Non-Hodgkin's lymphomas in childhood: results of treatment in patients in stage III]

From January 1980 to December 1984, 22 children with non-Hodgkin's lymphoma were admitted to the "Instituto da Criança-HCFMUPS" and according to the LNH-I-80 Protocol including a remission induction phase (Cyclofosfamide day 1, Vincristine days 3, 10, 17, 24, Daunomycin days 12 and 13, Prednisone for 30 days), followed by a continuation phase (Cyclofosfamide x 7 days + Adriamycin day 8 ARA-C x 4 days + Vincristine day 5, Mercaptopurine x 4 days + Methotrexate day 5) alternating three pairs of drugs during 72 weeks. Mercaptopurine and Methotrexate given during additional 48 weeks completes therapy. Twenty-one out of 22 patients attained complete remission. One patient died after widespread infection. Six relapses occurred, five of them in Burkitt's lymphoma patients. Although highly effective in the non-Burkitt's patients, the LNH-I-80 Protocol failed in keeping Burkitt's patients in event free survival.