[Impact of secondary irradiation on operators during coronary arteriography]

BACKGROUND

The activity over cellular genetic pattern of ionizing radiation can produce stochastic and unspecific damages. Interventional cardiology operators have increasing exposure times to ionizing radiation and there is no information about the real protection conferred by simple radiological protection devices.

AIM

To assess the magnitude of secondary ionizing radiation exposure of operators during conventional coronary arteriography, evaluating the radiation exposure during different beam projections and the usefulness of leaded aprons.

MATERIAL AND METHODS

Ionizing radiation received by operators during coronary arteriography was measured using a Geiger-Müller Victoreen model 490 counter. The device was placed in the ventral region, covered by the leaded apron and in the unprotected dorsal region. Radiation was measured in right and left projections during fluoroscopy and shooting.

RESULTS

In right projection, the intensity of ionizing radiation in ventral and dorsal regions was 1.24 +/- 1.1 and 2.9 +/- 4 mR/h respectively (p = 0.08). In left projection, the figures were 2.95 +/- 3 and 7.86 +/- 7.2 mR/h respectively (p = 0.001). During shooting in left projection the radiation exposure in ventral and dorsal regions was 9.66 +/- 6.7 and 32.8 +/- 27 mR/h respectively (p < 0.001). During shooting in right projection that figures were 10.1 +/- 16 and 20.7 +/- 39.8 mR/h respectively (p = 0.09). No correlation between radiation exposure and patients surface area was observed.

CONCLUSIONS

Secondary radiation received by operators is higher during shooting and in left projections. Leaded apron confers a partial protection for ventral region, and great fluctuations in the magnitude of radiation exposure were recorded. Unprotected dorsal region receives a greater amount of radiation in left projections.

Mice lacking the gamma interferon receptor have an impaired granulomatous reaction to Schistosoma mansoni infection

The egg-induced granulomatous reaction in Schistosoma mansoni-infected individuals develops within the portal system of the liver and is the major pathological finding in schistosomiasis. We have infected mice lacking the gamma interferon (IFN-gamma) receptor with S. mansoni larvae and studied the development of hepatic granulomas in these mutant mice in comparison to that in control wild-type mice. In the absence of IFN-gamma activity, a dramatic reduction in the size and architecture of the granuloma was observed. Granulomas from mutant mice were smaller than those from the control group and showed a significant reduction in the number of infiltrating inflammatory cells. Moreover, they appear to prematurely progress to the chronic phase of the reaction at a time when the control group still has acute inflammation. Our data suggests a pivotal role for IFN-gamma in the early events of the granulomatous reaction in vivo.

Agreement between premortem and postmortem diagnoses in patients with acquired immunodeficiency syndrome observed at a Brazilian teaching hospital

Acquired immunodeficiency syndrome (AIDS) is one of the main causes of death in adults worldwide. More commonly than in the general population, in patients with AIDS there is substantial disagreement between causes of death which are clinically suspected and those established by postmortem examination. The findings of 52 postmortem examinations were compared to the premortem (clinical) diagnoses, and there was 46% agreement between them. Fifty two percent of the patients had more than one postmortem diagnosis, and 48% had at least one AIDS-related disease not suspected clinically. Cytomegalovirus infection was the commonest (30.7%) autopsy finding, but not a single case had been suspected premortem. Bacterial infection, tuberculosis, and histoplasmosis were also common, sometimes not previously suspected, postmortem findings. This study shows that multiple infections occur simultaneously in AIDS patients, and that many among them are never suspected before the postmortem examination. These findings suggest that an aggressive investigation of infections and cancers should be done in patients with AIDS, particularly in those who do not respond to therapy of an already recognized condition.

Free radical production by azomethine H: effects on pancreatic and hepatic tissues

The antimalarial properties of azomethine H represent the basis for its use as a chemotherapeutic agent. This work was carried out in order to verify the biological side effects of azomethine H and to clarify the contribution of reactive oxygen species (ROS) in this process. It was shown that azomethine H increased serum activities of amylase, alanine transaminase (ALT) and the TBARS concentrations, in rats. No changes were observed in glutathione peroxidase and catalase activities. The drug-induced tissue damage might be due to superoxide radicals (O2.-), since Cu-Zn superoxide dismutase activities were increased by azomethine H treatment. This study allows tentative conclusions to be drawn regarding which reactive oxygen metabolites play a role in azomethine H activity. We concluded that (O2.-) maybe produced as a mediator of azomethine H action.

Real time electrochemical detection of 5-HT/insulin secretion from single pancreatic islets: effect of glucose and K+ depolarization

We report a highly sensitive electrochemical approach suitable for the real time measurement of insulin release from single islets of Langerhans, the functional endocrine units in the pancreas. The method is based on the detection of the insulin surrogate 5-hydroxytryptamine (5-HT) by carbon fibre microelectrodes implanted in the islets. Based on the combination of this novel approach with the simultaneous microfluorometric recording of cytosolic free Ca2+ concentration ([Ca2+]i), we demonstrate that glucose-stimulated islets secrete 5-HT/insulin in a pulsatile fashion under physiological conditions, and that this activity is encoded by synchronous [Ca2+]i oscillations. The sensitivity to detect variations in minute amounts of secreted materials is partially conferred by the fact that the tracer is released into a relatively confined space (the intraislet interstitial space).

Structure and inhibition of plasmepsin II, a hemoglobin-degrading enzyme from Plasmodium falciparum

Plasmodium falciparum is the major causative agent of malaria, a disease of worldwide importance. Resistance to current drugs such as chloroquine and mefloquine is spreading at an alarming rate, and our antimalarial armamentarium is almost depleted. The malarial parasite encodes two homologous aspartic proteases, plasmepsins I and II, which are essential components of its hemoglobin-degradation pathway and are novel targets for antimalarial drug development. We have determined the crystal structure of recombinant plasmepsin II complexed with pepstatin A. This represents the first reported crystal structure of a protein from P. falciparum. The crystals contain molecules in two different conformations, revealing a remarkable degree of interdomain flexibility of the enzyme. The structure was used to design a series of selective low molecular weight compounds that inhibit both plasmepsin II and the growth of P. falciparum in culture.

Structure-based design of achiral, nonpeptidic hydroxybenzamide as a novel P2/P2' replacement for the symmetry-based HIV protease inhibitors

A combination of structure-activity studies, kinetic analysis, X-ray crystallographic analysis, and modeling were employed in the design of a novel series of HIV-1 protease (HIV PR) inhibitors. The crystal structure of a complex of HIV PR with SRSS-2,5-bis[N-(tert-butyloxycarbonyl)amino]-3,4-dihydroxy-1, 6-diphenylhexane (1) delineated a crucial water-mediated hydrogen bond between the tert-butyloxy group of the inhibitor and the amide hydrogen of Asp29 of the enzyme. Achiral, nonpeptidic 2-hydroxyphenylacetamide and 3-hydroxybenzamide groups were modeled as novel P2/P2' ligands to replace the crystallographic water molecules and to provide direct interactions with the NH groups of the Asp29/129 residues. Indeed, the symmetry-based inhibitors 7 and 19, possessing 3-hydroxy and 3-aminobenzamide, respectively, as a P2/P2' ligand, were potent inhibitors of HIV PR. The benzamides were superior in potency to the phenylacetamides and have four fewer rotatable bonds. An X-ray crystal structure of the HIV PR/7 complex at 2.1 A resolution revealed an asymmetric mode of binding, in which the 3-hydroxy group of the benzamide ring makes the predicted interaction with the backbone NH of Asp29 on one side of the active site only. An unexpected hydrogen bond with the Gly148 carbonyl group, resulting from rotation of the aromatic ring out of the amide plane, was observed on the other side. The inhibitory potencies of the benzamide compounds were found to be sensitive to the nature and position of substituents on the benzamide ring, and can be rationalized on the basis of the structure of the HIV PR/7 complex. These results partly confirm our initial hypothesis and suggest that optimal inhibitor designs should satisfy a requirement for providing polar interactions with Asp29 NH, and should minimize the conformational entropy loss on binding by reducing the number of freely rotatable bonds in inhibitors.

Multiphasic action of glucose and alpha-ketoisocaproic acid on the cytosolic pH of pancreatic beta-cells. Evidence for an acidification pathway linked to the stimulation of Ca2+ influx

Glucose stimulation raises the pHi of pancreatic beta-cells, but the underlying mechanisms are not well understood. We have now investigated the acute effects of metabolizable (glucose and the mitochondrial substrate alpha-ketoisocaproic acid, KIC) and nonmetabolizable (high K+ and the K-ATP channel blocker tolbutamide) insulin secretagogues on the pHi of pancreatic beta-cells isolated from normal mice, as assessed by BCECF fluorescence from single cells or islets in the presence of external bicarbonate. The typical acute effect of glucose (22-30 mM) on the pHi was a fast alkalinization of approximately 0.11 unit, followed by a slower acidification. The relative expression of the alkalinizing and acidifying components was variable, with some cells and islets displaying a predominant alkalinization, others a predominant acidification, and others yet a mixed combination of the two. The initial alkalinization preceded the [Ca2+]i rise associated with the activation of voltage-sensitive Ca2+ channels. There was a significant overlap between the glucose-evoked [Ca2+]i rise and the development of the secondary acidification. Depolarization with 30 mM K+ and tolbutamide evoked pronounced [Ca2+]i rises and concomitant cytosolic acidifications. Blocking glucose-induced Ca2+ influx (with 0 Ca2+, nifedipine, or the K-ATP channel agonist diazoxide) suppressed the secondary acidification while having variable effects (potentiation or slight attenuation) on the initial alkalinization. KIC exerted glucose-like effects on the pHi and [Ca2+]i, but the amplitude of the initial alkalinization was about twice as large for KIC relative to glucose. It is concluded that the acute effect of glucose on the pHi of pancreatic beta-cells is biphasic. While the initial cytosolic alkalinization is an immediate consequence of the activation of H+-consuming metabolic steps in the mitochondria, the secondary acidification appears to originate from enhanced Ca2+ turnover in the cytoplasm. The degree of coupling between glucose metabolism and Ca2+ influx as well as the relative efficacies of these processes determines whether the acute pHi response of a beta-cell (or of a tightly coupled multicellular system such as an islet of Langerhans) is predominantly an alkalinization, an acidification, or a mixed proportion of the two.

Inhibition and catalytic mechanism of HIV-1 aspartic protease

The structure of the HIV-1 protease in complex with a pseudo-C2 symmetric inhibitor, which contains a central difluoroketone motif, has been determined with X-ray diffraction data extending to 1.7 A resolution. The electron density map clearly indicates that the inhibitor is bound in a symmetric fashion as the hydrated, or gemdiol, form of the difluoroketone. Refinement of the complex reveals a unique, and almost symmetric, set of interactions between the geminal hydroxyl groups, the geminal fluorine atoms, and the active-site aspartate residues. Several hydrogen bonding patterns are consistent with that conformation. The lowest energy hydrogen disposition, as determined by semiempirical energy calculations, shows only one active site aspartate protonated. A comparison between the corresponding dihedral angles of the difluorodiol core and those of a hydrated peptide bond analog, calculated ab-initio, shows that the inhibitor core is a mimic of a hydrated peptide bond in a gauche conformation. The feasibility of an anti-gauche transition for a peptide bond after hydration is verified by extensive molecular dynamics simulations. The simulations suggest that rotation about the C-N scissile bond would readily occur after hydration and would be driven by the optimization of the interactions of peptide side-chains with the enzyme. These results, together with the characterization of a transition state leading to bond breakage via a concerted exchange of two protons, suggest a proteolysis mechanism whereby only one active site aspartate is initially protonated. The steps of this mechanism are: asymmetric binding of the substrate; hydration of the peptidic carbonyl by an active site water; proton translocation between the active site aspartate residues simultaneously with carbonyl hydration; optimization of the binding of the entire substrate facilitated by the flexible structure of the hydrated peptide bond, which, in turn, forces the hydrated peptide bond to assume a gauche conformation; simultaneous proton exchange whereby one hydroxyl donates a proton to the charged aspartate, and, at the same time, the nitrogen lone pair accepts a proton from the other aspartate; and, bond breakage and regeneration of the initial protonation state of the aspartate residues.

The complete sequence of a 9000 bp fragment of the right arm of Saccharomyces cerevisiae chromosome VII contains four previously unknown open reading frames

We report the sequence of a 9000 bp fragment from the right arm of Saccharomyces cerevisiae chromosome VII. Analysis of the sequence revealed four complete previously unknown open reading frames, which were named G7587, G7589, G7591 and G7594 following standard rules for provisional nomenclature. Outstanding features of some of these proteins were the homology of the putative protein coded by G7589 with proteins involved in transcription regulation and the transmembrane domains predicted in the putative protein coded by G7591.

Reactive oxygen generation by azomethine H: a new antimalarial drug

Superoxide radical (O2-) is a free radical that may be involved in various toxic processes. Cu-Zn superoxide dismutase catalyzes the dismutation of the superoxide free radical and protects cells from oxidative damage. A rat bioassay validated for the identification of the toxic effects of azomethine H revealed increased serum activities of amylase, alanine transaminase, and alkaline phosphatase. The lipoperoxide and bilirubin concentrations were also increased in animals that received azomethine H (1 g/kg) from ascorbic or hydrochloric acid solutions. Azomethine H increased Cu-Zn superoxide dismutase activity. This elevation of Cu-Zn superoxide dismutase activity was highest on the 7th day and was at levels comparable with those of control rats from day 60 onwards. Superoxide is an important intermediate in the action and toxicity of azomethine H.

The relaxant action of jatrophone in rat portal vein. A comparison with protein kinase C inhibitors

Jatrophone, staurosporine and H-7, caused graded inhibition of rat portal vein contractions induced by phorbol 12-myristate 13-acetate (PMA), noradrenaline, endothelin-1 or KCl, with IC50s of 86 nM, 13 microM, 11 microM and 9 microM, respectively. Jatrophone was equipotent to H-7, but 100 to 500 fold less potent than staurosporine. Jatrophone, H-7 and staurosporine, also dose-dependently inhibited rhythmic contractions of the rat portal-mesenteric vein with IC50s of 15 microM, 9 microM and 75 nM, respectively. Jatrophone, H-7 and staurosporine caused graded relaxations of preparations contracted with endothelin-1 or PMA with IC50s of 12 and > 1000 microM, 8 and 13 microM and 7 and 12 nM, respectively. All three compounds caused graded inhibition of caffeine-induced contractions in Ca(2+)-free solution containing EGTA. The similarity between the vasorelaxant actions of jatrophone, staurosporine and H-7 in rat portal vein suggests that jatrophone acts, at least in part, through inhibition of PKC-dependent mechanisms. Moreover, like the PKC inhibitors, its vasorelaxant action may also involve other mechanisms unrelated to protein kinase C inhibition.

[Occurrence of cysticercosis in autopsies performed in Uberlandia, Minas Gerais, Brazil]

3937 autopsies were performed between 1971 and 1993 in the Serviço de Anatomia Patológica of the Hospital de Clínicas of the Fundação de Assistência, Estudo e Pesquisa de Uberlândia, Universidade Federal de Uberlândia, in Minas Gerais, Brazil. At this Service of Pathology are realized all the autopsies of the municipal district of Uberlândia. The analysis of 2862 concluded autopsy reports, of death above the age of one year, disclosed 39 cases (1.4%) of cysticercosis. The age range was 16 to 83 years and 66.6% were males; 82.1% of the patients were from Minas Gerais State, 15.4% were from Goiás State, and in one case (2.5%) the origin was not registered. From these 39 cases, 35 (89.7%) showed central nervous system involvement, isolated or in association to other clinical forms of the disease; in 9 occurred the isolated or associated cardiac form; in 4 the muscular form, isolated or associated, was found; 4 presented the isolated or associated visceral form. In only 7 (17.9%) cases, the cysticercosis was assumed to be the direct cause of the death.

Mechanisms of bradykinin-induced contraction of the guinea-pig gallbladder in vitro

1. The mechanisms underlying bradykinin (BK)-mediated contractions in strips of guinea-pig gallbladder (GPG) were examined by use of selective bradykinin (BK) receptor agonists and antagonists. 2. Addition of BK and related kinins (0.1 pM-10 microM) after 2 h of equilibration of the preparation caused graded contractions characterized by two distinct phases: high affinity (0.1 pM-1 nM) and low affinity (3 nM-10 microM). The rank order of potency for the first phase (mean EC50, pM) was: BK (1.36) = Hyp3-BK (1.44) = Lys-BK (1.54) > Tyr8-BK (2.72) > Met-Lys-BK (4.30). The rank order of potency for the second phase (mean EC50, nM, at concentration producing 50% of the contraction caused by 80 mM KCl) was: Hyp3-BK (8.95) > Met-Lys-BK (12.78) > Tyr8-BK (33.75) > Lys-BK caused by 80 mM KCl) was: Hyp3-BK (8.95) > Met-Lys-BK (12.78) > Tyr8-BK (33.75) > Lys-BK (60.92) > BK (77.35). The contractile responses (g of tension) to 3 microM of BK (the highest concentration tested) were: Hyp3-BK, 1.76 +/- 0.09; BK, 1.65 +/- 0.12; Lys-BK, 1.45 +/- 0.13; Tyr8-BK, 1.36 +/- 0.15 and Met-Lys-BK, 1.36 +/- 0.15. The selective B1 agonist, des-Arg9-BK, caused only a weak contraction with maximal response (0.21 +/- 0.05 g), which corresponded to approximately 10% of that induced by BK. 3. BK-induced contraction in GPG was inhibited by indomethacin (3 microM) or ibuprofen (30 microM), and was partially reduced by phenidone (30 microM), but was not affected by atropine (1 JM), nicardipine (1 gM),Ca2+-free medium plus EGTA, dazoxiben (30 nM), L-655,240 (10 nM, a selective receptor antagonist ofthromboxane A2), MK-571 (0.1 microM, a selective leukotriene D4 receptor antagonist), tetrodotoxin(0.3microM), CP 96,345 (0.3 microM, a NK1 receptor antagonist), mepyramine (1 microM), glibenclamide (1 microM), H-7(3 microM), staurosporine (100 nM), or phorbol 12-myristate 13-acetate (1 microM). However, BK-induced contractions in GPG maintained in Ca2+-free medium were markedly attenuated by ryanodine (10microM).4. Prostaglandin E2, prostaglandin F2alpha or U46619 (0.1 nM to 100microM), caused concentration-dependent contractions in GPG with mean EC50s of 3.1 microM; 1.7 microM and 0.47 nM and maximal responses of1.36 +/-0.15; 1.32 +/- 0.20 and 0.96 +/- 0.09 g, respectively.5. The selective B2 receptor antagonists, Hoe 140, NPC 17731 and NPC 17761 (0.01 -1 microM), caused concentration-dependent displacements to the right of the contractile concentration-response curve for BK. The selective B1 receptor antagonist, des-Arg9-[Leu8]-BK (1 microM), did not affect BK-induced GPG contraction.6. These data suggest that both high and low affinity BK responses in GPG are mediated by activation of B2 receptors, and that BK-mediated contraction in GPG depends on the release of intracellular Ca2+sources sensitive to ryanodine. In addition, BK-induced contraction in GPG is mediated by release of proinflammatory eicosanoid(s) derived from the cyclo-oxygenase pathway from arachidonic acid metabolism unrelated to thromboxane A2, and seems not to be coupled to activation of a protein kinase C-dependent mechanism.

Intracerebroventricular administration of cholecystokinin reduces stereotypy in dopamine-supersensitive rats

Cholecystokinin (CCK-8) coexists with dopamine in some neurons and modulates dopaminergic neurotransmission. In the present study we determined the effect of CCK-8 on stereotyped behavior in supersensitive dopaminergic system. Adult male Wistar rats, weighing 200-250 g, were used. Dopaminergic supersensitivity was induced by long-term haloperidol (HAL) treatment (30 days: 1.0 mg/kg twice a day). Seventy-two hours after HAL withdrawal animals received CCK-8 (14.5 nmol/5 microliters) or saline intracerebroventricularly (icv) before being tested for apomorphine (APO, 0.6 mg/kg, sc)-induced stereotyped behavior. Experimental groups were: long-term HAL-treated rats that received saline (HSAL, N = 9) or CCK-8 (HCCK, N = 11) icv and long-term saline-treated rats that received CCK-8 (SCCK, N = 9) or saline (SSAL, N = 8) icv. As expected, HSAL rats showed statistically significant higher stereotypy scores than SSAL rats (42 +/- 1.7 vs 31 +/- 1.6; P < 0.05) and CCK-8 significantly reduced stereotyped behavior in supersensitive rats (42 +/- 1.7 vs 37 +/- 1.5; P < 0.05). These results show that CCK-8 icv reduces stereotypy in dopaminergic-supersensitive rats, and suggest that the dopamine supersensitivity phenomenon can be modulated by CCK-8.

Frequency of cholelithiasis in alcoholics

In order to determine the frequency of biliary lithiasis in alcoholic patients without signs of hepatic cirrhosis, we submitted 106 male alcoholics (mean age, 42.2 +/- 11.2 years) to ultrasound examination of the biliary system. Cholelithiasis was present in 6 (5.6%). We did not observe any association between the quantity of ethanol consumed and/or the time of consumption and the presence of cholelithiasis. There was no significant difference between the frequency of cholelithiasis in these patients and that found in autopsies carried out on 716 male patients (6%) at the Hospital de Clínicas, Universidade Federal de Uberlândia, during the period 1982 to 1993. Thus, we conclude that in the cases we examined, alcoholism did not represent a risk factor for biliary lithogenesis.

Haemodynamic effects of pressure-controlled ventilation versus volume-controlled ventilation in patients submitted to cardiac surgery

OBJECTIVE

To compare the haemodynamic effects of pressure-controlled ventilation (PCV) with volume-controlled ventilation (VCV) in patients after cardiac surgery.

DESIGN

Prospective clinical study.

SETTING

Post-operative cardiac surgical ICU.

SUBJECTS

Twenty sequential elective adult patients with no previous chronic lung disease and aged less than 70 years old.

INTERVENTIONS

One hour after ICU admission and receiving mechanical ventilation utilising sinusoidal flow, patients were divided into two groups according to cardiac index (CI): group I: CI > 2.5 l/min/M2 and group II: CI < 2.5 l/min/M2. They were submitted randomly to 15 minutes' PC or VC mode, a 30-minute wash-out period of mechanical ventilation with a sinusoidal flow pattern, and then alternate PC or VC mode for 15 more minutes. Data were statistically compared using analysis of variance (ANOVA) with a significance level of 5%. Sedatives and muscle relaxants were given as necessary.

ENDPOINTS

Data were obtained at the end of 15 minutes under each ventilatory mode, observing a 30-minute interval between each.

MEASUREMENTS

Standard cardiorespiratory parameters were measured or calculated using conventional monitoring (including cardiac output), Qs/Qt, A-aDO2 alveolar-arterial oxygen difference, peak inspiratory pressure, mean airway pressure and dynamic compliance (C).

RESULTS

No significant differences between PCV and VCV modes, or between groups, were seen in MPAP, MAP, PCWP, RAP, heart rate, O2ER, VO2I, Paw, C, A-aDO2 and Qs/Qt. However, DO2I (p = 0.0063), LVSWI, (p = 0.0001) and RVSWI (p = 0.0053) showed a statistically significant difference between groups I and II. No influence of VCV or PCV on these parameters was seen. There was a slight significant difference between groups for PVR (p = 0.0205). In contrast, CI (p = 0.0001) and SVR (p = 0.0062) showed significant differences among groups, but also a significantly favourable effect of PCV over VCV (p = 0.0239 and p = 0.0318 respectively). Finally, a significant reduction (p = 0.0001) in peak inspiratory pressure with PCV was observed.

CONCLUSION

PC and VC ventilatory modes had comparable effects on patients with preserved or depressed cardiac output. Patients ventilated with PCV showed significantly higher values for cardiac index, a decreased SVR, as well as significantly lower values for inspiratory pressure when compared with VCV patients.

[Prevalence of biliary lithiasis in cirrhotics: necropsy evaluation]

In order to investigate a possible association between hepatic cirrhosis and biliary lithiasis, an analysis on 3,332 necropsy report diagnosis was carried out. Gallstones were present in 19.5% of 123 cirrhotics and in 4.9% of 3,209 non-cirrhotics patients. We concluded that lithiasis is significantly more frequent in cirrhotics than in non-cirrhotics. Chronic hemolysis, slow emptying of the gallbladder, and defective bile acidification by the gallbladder would explain such association. The male-to-female ratio of lithiasis occurrence was 2.08:1 in the cirrhotic group and 2.4:1 among the non-cirrhotics. This difference was not significant. Pigmentary gallstones were commoner among cirrhotics and significantly more frequent in cirrhotics than in non-cirrhotics. This would be explained by chronic hemolysis and by bilirubin conjugation defects. Lithiasis was more frequent in secondary biliary cirrhosis, followed by postnecrotic cirrhosis of viral etiology.

Background Ca2+ influx mediated by a dihydropyridine- and voltage-insensitive channel in pancreatic beta-cells. Modulation by Ni2+, diphenylamine-2-carboxylate, and glucose metabolism

A stepwise increase in extracellular Ca2+ concentration ([Ca2+]o) can evoke insulin release from pancreatic islets in the absence of secretagogues. We have investigated the ionic mechanism underlying this secretory response by recording intracellular free Ca2+ concentration ([Ca2+]i) from single mouse islets of Langerhans using ratiometric fura-2 microfluorometry. In the presence of 11 mM glucose, the [Ca2+]i undergoes fast oscillations associated with bursting electrical activity. Nifedipine (10 microM) suppressed these oscillations and markedly lowered the [Ca2+]i. Raising the [Ca2+]o from 2.56 to 12.8 mM in the continued presence of 11 mM glucose and nifedipine evoked pronounced [Ca2+]i rises of variable amplitude and time course. This effect was dose-dependent (EC50 = 3.6 mM) and remained essentially unchanged in the absence of glucose or in the presence of 3 mM glucose and nifedipine, conditions where beta-cells are hyperpolarized by approximately -25 mV. Depleting the acetylcholine-mobilizable internal Ca2+ pools by repetitively challenging the islets with acetylcholine in the absence of Ca2+ actually potentiated the standard high Ca2+ responses. The latter were strongly reduced by millimolar concentrations of Ni2+ (70% reduction at 3 mM) and by diphenylamine-2-carboxylate (DPC; IC50 = 145 microM), a blocker of nonselective cation channels. The standard high Ca2+ responses were relatively insensitive to the glycolytic inhibitor mannoheptulose. It is proposed that the high Ca(2+)-evoked [Ca2+]i responses are primarily accounted for by Ca2+ influx through dihydropyridine- and voltage-insensitive, nonselective cation channels. These channels do not appear to be under the control of glucose metabolism. Although their function is unknown, they may be essential to supplying the beta-cells with Ca2+ in the absence of stimulatory levels of fuel secretagogues.

[Can the Mantoux test be used in BCG vaccinated children?]

This prospective trial was realized in 371 children previously vaccinated with BCG in the first month of life in whom the Mantoux tuberculin test was done and read 48-72 hours afterwards. Among 371 BCG-vaccinated children, 106 (28.57%) were Mantoux reactive, 10 of whom with clinical tuberculosis. There was no statistically significant difference in the tuberculin test between the control group (59 non-BCG-vaccinated children) and 180 vaccinated children, considering those under 6 years old. When we compared by age, we verified that just 36.36% of the children at the age 2 reacted positively to PPD.

The effect of dithiothreitol on the activity of tityustoxin from the scorpion Tityus serrulatus venom

The acetylcholine (ACh) liberating effect on rat brain slices of tityustoxin, an alpha toxin from the scorpion Tityus serrulatus venom, was measured in the absence and presence of dithiothreitol (DTT). The rate of net ACh liberation by toxin concentrations of 2 nmol in 5 ml of organ bath, was 7.5 +/- 0.09 nmol g-1 min-1. If DTT at a final concentration of 1 mM was added after a 10-min incubation period with toxin alone, inhibition of tityustoxin activity was 94%. With DTT 0.1 or 0.01 mmolar inhibition was 74% and 57%, respectively. The intense secretagogue effect, both in salivary and pancreatic glands of adult rats, induced by sublethal doses of tityustoxin was not affected by i.v. injection 10 min later of DTT 1 mumol g-1 of rat weight. When tityustoxin was injected i.p. at a dose 3 times the LD50 in mice, death ensued in 40 to 60 min. If toxin inoculation in mice was followed 10 min later by DTT 1 mumol g-1 of mouse weight, injected i.p. or i.v., deaths were delayed to 90 to 110 min, but no survival was observed. At necropsy, none of the mice treated with DTT showed any signs of pulmonary edema.

[Mechanical reperfusion in acute myocardial infarction after failure of thrombolysis with intravenous streptokinase]

AIM

to report the clinical evolution of four patients with acute myocardial infarction that were subjected to immediate coronary angioplasty due to the failure of reperfusion with streptokinase.

BACKGROUND

the limitations for the use of thrombolytic agents, an accepted treatment of acute myocardial infarction, or their uncertain results in selected groups of patients has prompted the search for mechanical revascularization infarction subjected to thrombolytic therapy with streptokinase (1.500.000 U i.v.) after administration of hydrocortisone (100 mg i.v.) and acetyl salicylic acid (500 mg od). After 60 min thrombolytic therapy and due to hemodynamic depression with requirement of inotropic agents or the absence of clinical signs of reperfusion, the patients were subjected to coronary angiography. In view of a total occlusion or severe stenosis of the artery responsible for the infarction, an immediate transluminal angiography was performed to improve coronary flow.

RESULTS

transluminal coronary angioplasty revascularized arteries with total occlusion or increased the lumen of those with severe residual stenosis. This was accompanied by reduction in pain and hemodynamic improvement. In one patient with complete AV block, conduction was improved and sinus rhythm was recovered. Echocardiographic controls showed preservation of ventricular function with persistence of segmental motility alterations.

CONCLUSIONS

transluminal coronary angioplasty can be a revascularization alternative in patients with acute myocardial infarction and failure of reperfusion with systemic streptokinase.

Bursting electrical activity in pancreatic beta-cells: evidence that the channel underlying the burst is sensitive to Ca2+ influx through L-type Ca2+ channels

In glucose-stimulated pancreatic beta-cells, the membrane potential alternates between a hyperpolarized silent phase and a depolarized phase with Ca2+ action potentials. The molecular and ionic mechanisms underlying these bursts of electrical activity remain unknown. We have observed that 10.2-12.8 mM Ca2+, 1 microM Bay K 8644 and 2 mM tetraethylammonium (TEA) trigger bursts of electrical activity and oscillations of intracellular free Ca2+ concentration ([Ca2+]i) in the presence of 100 microM tolbutamide. The [Ca2+]i was monitored from single islets of Langerhans using fura-2 microfluorescence techniques. Both the high-Ca(2+)- and Bay-K-8644-evoked [Ca2+]i oscillations overshot the [Ca2+]i recorded in tolbutamide. Nifedipine (10-20 microM) caused an immediate membrane hyperpolarization, which was followed by a slow depolarization to a level close to the burst active phase potential. The latter depolarization was accompanied by suppression of spiking activity. Exposure to high Ca2+ in the presence of nifedipine caused a steady depolarization of approximately 8 mV. Ionomycin (10 microM) caused membrane hyperpolarization in the presence of 7.7 mM Ca2+, which was not abolished by nifedipine. Charybdotoxin (CTX, 40-80 nM), TEA (2 mM) and quinine (200 microM) did not suppress the high-Ca(2+)-evoked bursts. It is concluded that: (1) the channel underlying the burst is sensitive to [Ca2+]i rises mediated by Ca2+ influx through L-type Ca2+ channels, (2) both the ATP-dependent K+ channel and the CTX- and TEA-sensitive Ca(2+)-dependent K+ channel are highly unlikely to provide the pacemaker current underlying the burst.(ABSTRACT TRUNCATED AT 250 WORDS)

Crystal structures of native and inhibited forms of human cathepsin D: implications for lysosomal targeting and drug design

Cathepsin D (EC 3.4.23.5) is a lysosomal protease suspected to play important roles in protein catabolism, antigen processing, degenerative diseases, and breast cancer progression. Determination of the crystal structures of cathepsin D and a complex with pepstatin at 2.5 A resolution provides insights into inhibitor binding and lysosomal targeting for this two-chain, N-glycosylated aspartic protease. Comparison with the structures of a complex of pepstatin bound to rhizopuspepsin and with a human renin-inhibitor complex revealed differences in subsite structures and inhibitor-enzyme interactions that are consistent with affinity differences and structure-activity relationships and suggest strategies for fine-tuning the specificity of cathepsin D inhibitors. Mutagenesis studies have identified a phosphotransferase recognition region that is required for oligosaccharide phosphorylation but is 32 A distant from the N-domain glycosylation site at Asn-70. Electron density for the crystal structure of cathepsin D indicated the presence of an N-linked oligosaccharide that extends from Asn-70 toward Lys-203, which is a key component of the phosphotransferase recognition region, and thus provides a structural explanation for how the phosphotransferase can recognize apparently distant sites on the protein surface.

Trypanosoma cruzi meningoencephalitis and myocarditis in a patient with acquired immunodeficiency syndrome

We report the case of a 52-year-old male heterosexual patient with acquired immunodeficiency syndrome (AIDS) and reactivation of Chagas' disease manifested by meningoencephalitis and myocarditis, diagnosed post-mortem. Unexplained reactivation of Chagas' disease should be included among the diagnostic criteria of AIDS in human immunodeficiency virus positive patients. On the other hand, AIDS should be considered in the differential diagnosis of patients with unexplained reactivation of Chagas' disease.

[Percutaneous transluminal angioplasty in stenosis of Blalock-Taussig pulmonary systemic shunt in an adult patient]

AIM

The report of a female patient with tricuspid atresia and severe stenosis of the pulmonary artery, stenosis of the left pulmonary-systemic shunt and occlusion of the right systemic-pulmonary shunt.

BACKGROUND

The use of transluminal angioplasty has been extended to the treatment of several congenital cardiopathies and, in some of them, it is the therapeutic procedure of choice.

METHODS

Dilatation of the distal stenosis of the pulmonary-systemic shunt with a coaxial system composed initially by an 8 French right Judkins carrier catheter with a soft tip through which a 0.014" (0.036 cm) coronary angioplasty guidewire and 3 and 4 mm balloon catheters were advanced successively. Subsequently a 0.028" interchange Rosen guide was advanced, gradually introducing balloon catheters up to 8 mm of diameter.

RESULTS

The dilatation with balloon catheter systems of increasing diameter allowed to amplify the stenosis zone, improving arterial oxygen partial pressure and saturation without evidences of left lung hyperflux. Considering the anatomic characteristics of the pulmonary systemic shunt, the use of carrier catheters facilitates the penetration of balloon catheters to the stenosis zone.

CONCLUSION

Percutaneous transluminal angioplasty may be used with success in patients with stenosis of Blalock-Taussig shunts, independent of the anastomosis curvature and even if the magnitude of the stenosis is significant.

Ion channels in icosahedral virus: a comparative analysis of the structures and binding sites at their fivefold axes

An analysis of the crystallographically determined structures of the icosahedral protein coats of Tomato Bushy Stunt Virus, Southern Bean Mosaic Virus, Satellite Tobacco Necrosis Virus, Human Rhinovirus 14 and Mengovirus around their fivefold axes is presented. Accessibilities surfaces, electrostatic energy profile calculations, ion-protein interaction energy calculations, free energy perturbation methods and comparisons with structures of chelating agents are used in this study. It is concluded that the structures built around the viral fivefold axes would be adequate for ion binding and transport. Relative ion preferences are derived for the binding sites, using free energy perturbation methods, which are consistent with the experimental data when available. In the cases where crystallographic studies determined the existence of ions on the fivefold axes, our results indicate that they would correspond to ions in crystallization or purification buffers. The environment of the fivefold axes are rich in polar residues in all icosahedral viral structures whose atomic coordinates are available, including some that are not being analyzed in detail in this work. The fivefold channel-like structures have most of the basic properties expected for real ion channels including a funnel at the entrance, a polar internal environment with frequent alternation of acidic and basic residues, ion binding sites, the capability to induce ion dehydration and ion transit from the external viral surface to the binding sites.

High external Ca2+ levels trigger membrane potential oscillations in mouse pancreatic beta-cells during blockade of K(ATP) channels

Glucose depolarizes the pancreatic beta-cell and induces membrane potential oscillations, but the nature of the underlying oscillatory conductance remains unknown. We have now investigated the effects of the Ca2+ ionophore ionomycin and high external Ca2+ concentration ([Ca2+]o) on glucose-induced electrical activity and whole islet intracellular free Ca2+ concentration ([Ca2+]i), under conditions where the K(ATP) channel was blocked (100 microM tolbutamide or 4 microM glibenclamide). Raising [Ca2+]o to 10.2 or 12.8 mM, but not to 5.1 or 7.7 mM, turned continuous electrical activity into bursting activity. High [Ca2+]o (12.8 mM) regenerated a pattern of fast [Ca2+]i oscillations overshooting the levels recorded in tolbutamide. Ionomycin (10 microM) raised the [Ca2+]i and synergized with 5.1 mM Ca2+ to hyperpolarize the beta-cell membrane. The data indicate that a [Ca2+]i-sensitive and sulphonylurea-insensitive oscillatory conductance underlies the beta-cell bursting activity.

[Angiographic findings in non-Q wave infarction and their relation to ST-T changes]

Non q wave myocardial infarction has been attributed to occlusion of a vessel with no ECG representation, early reperfusion of the occluded artery or occlusion of a vessel with generous collateral flow. The coronary arteriography of 84 patients with non Q wave myocardial infarction performed at 16 + 17 (SD) days after infarction was analyzed. Main left lesion was found in 6 (17%), single vessel disease in 30 (36%), two vessel disease in 18 (24%) and 3 vessel disease in 16 (19%). The "culprit" vessel had a critical residual lesion in 38 patients (45%): 22 affected the left anterior descending artery, 10 the circumflex, and 5 the right coronary artery. No residual lesion was found in 10 patients (12%). An occluded artery was found in 32 patients (38%): circumflex in 20, right coronary artery in 9 and left anterior descending in 3 (p < 0.01). Significant collateral flow to the occluded vessel was present in 41% of cases. The ST segment was analyzed in 82 patients. Depression of ST was found in 29 (35%), elevation in 22 (27%), negative T waves in 17 (21%) and minimal alterations in 17%. There was no correlation between ST levels and coronary occlusion of the culprit artery. Depression of ST was more commonly (p < 0.01) associated with severe coronary artery disease (main left or 3 vessel disease), which may be related to the poorer prognosis in these cases.

Acute fatal Trypanosoma cruzi meningoencephalitis in a human immunodeficiency virus-positive hemophiliac patient

A 37-year-old hemophiliac patient with known, asymptomatic human immunodeficiency virus infection and chronic Chagas' disease was admitted to the hospital complaining of fever and headache. A computed tomographic scan revealed multiple ring-enhancing lesions in both cerebral hemispheres. No antibodies to Trypanosoma cruzi were found in the cerebrospinal fluid. Treatment for toxoplasmosis of the central nervous system, which was considered the most likely diagnosis, was instituted, but the patient died after progressive neurologic deterioration. An autopsy revealed severe meningoencephalitis caused by T. cruzi.

SISCOPE: a multiuser information system for gastrointestinal endoscopy

SISCOPE is an integrated data management system for use in gastrointestinal endoscopy units which operates in the multiuser mode on UNIX minicomputers or MS-DOS personal computers and can be used for patient bookings, endoscopic data entry and retrieval, and automatic report generation in upper gastrointestinal endoscopy, proctologic examinations, colonoscopy and peritoneoscopy. The description of endoscopic findings is remarkably detailed and data entry very rapid due to an advanced design of input screens that incorporates several recent concepts, including windows, menu bars and pull-down menus; typing is eliminated as data is entered with a mouse by pointing at options within menus. Endoscopic findings can be described under eight headings: morphology, topography, qualifiers, modifiers, signs of bleeding, endoscopic diagnosis, pathological diagnosis and etiology. Terminology is based strictly 3on the OMED system. SISCOPE also allows recording of details on endoscopic procedures, indications for the examination, preparation, premedication, complications and late entry of pathology reports. After entering all data, a report in natural language is produced automatically, the entire process taking one minute on average. Data retrieval programs give on-line access to previous examinations of a given patient and automatically generate activity reports. A formal language allows direct queries to the database and transfer of data for statistical analysis or other data processing. The system is simple to learn and use because operation is intuitive and all endoscopic techniques share the same basic menu structure and screen design.

[Myocardial ischemia in patients older than 70 years of age. Clinical and angiographic aspects]

We studied 77 patients with clinical suspicion of ischemic heart disease whose age ranged from 70 to 84 years. Patients with atypical angina had mostly normal coronary arteries, while those with unstable angina usually had three vessel disease or main left disease. According to the left ventricular function, surgery was considered safe in 66% of patients with unstable angina and 33% of those with stable angina. One patient developed a pseudoaneurysm at the arterial puncture site and hematomas were present in 3 other patients. Currently we try to avoid coronary arteriography in older patients with atypical angina due to its low yield.

Vitamins B1 and B6 tubular electrodes as FIA detectors; their use in the analysis of pharmaceutical products

Ion-selective electrodes without an inner reference solution and tubular potentiometric detectors for the determination of vitamins B1 and B6 in pharmaceutical preparations by flow injection analysis (FIA) are reported. The membranes were prepared with the vitamin tetra(2-chlorophenyl)borate (TCPB) dissolved in o-nitrophenyloctyl ether (o-NPOE) and immobilized on PVC. Intrinsic behaviour of the tubular detectors was assessed using a low-dispersion single-channel FIA manifold and was compared with conventionally-shaped electrodes using the same membrane. Data obtained in the determination of vitamins B1 and B6 in pharmaceutical preparations with a double channel flow injection manifold incorporating the tubular detectors are presented and compared with those obtained by the U.S. Pharmacopeia method and by direct potentiometry with conventionally-shaped electrodes.

[Structuring a clinical information system for hospital services: BASELINE]

Clinical database systems have been in use since 1972, but they still fail to meet most of the requirements they were aimed at. This includes not only the management of administrative tasks, but particularly the support of medical activities. Our study presents an experimental model of a clinical database system for general hospitals, mainly dedicated to the support of some basic, fundamental clinical activities, namely the management of baseline patient data. This model is based on a modular concept, and its core is represented by a Minimal Data Base Set designed to meet the specific requirements of each Department and of each distinct area within a Department. The system does not interfere with routine clinical work and tries to offer a high level of services to users. A number of utilitary programs simplify user interaction with the system, such as a menu-driven data-entry program, a semi-automatic codification program that follows the OMS/ICD-9-CM coding system, and a menu-driven program for data retrieval. Basically, this system can be helpful for the automatic edition of clinical reports and the retrieval of patient records meeting conditions specified by the clinician.

IgG subclasses responsible for immune clearance in mice infected with Trypanosoma cruzi

To examine the role of different immunoglobulin subclasses in the immune clearance of Trypanosoma cruzi, mice containing bloodstream trypomastigotes were injected intravenously with immune serum, IgG-depleted serum, or with the IgG1 or IgG2 fractions and the rate of removal of the parasites from circulation was determined. Using IgG concentrations similar to those found in the immune serum, the rate of clearance mediated by IgG2 was six-fold higher than that obtained with IgG1. This difference did not appear to be due to differences in antibody specificity, as Western blotting showed that each isotype recognized a similar set of antigens extracted from the parasite. However, the T. cruzi specific antibody content of the IgG2 was approximately five-fold higher than IgG1. When the dose of IgG was adjusted to equalize the antibody content, the clearance ability of the IgG1 and IgG2 was very similar. It is concluded that the two subclasses have a similar clearance ability.

Multiple sclerosis with early childhood onset. A case report

A 2 year old boy was admitted owing to a subacute episode of ataxic gait and hearing deficit. Computerized tomography (CT) was normal and cerebrospinal fluid (CSF) analysis revealed gamma globulins level of 15.4% (normal 7 to 14%). There was spontaneous remission after 7 months. At 5 years of age the boy incurred a second episode with predominantly right appendicular ataxia and tonic gaze deviation to the right side. CT showed a low-density lesion in the white matter adjacent to the right frontal horn. Visual and auditory evoked potentials were abnormal. CSF revealed a mild increase in gamma globulins level of 14.5% with an abnormal T lymphocyte subsets study. The combination of visual, cerebellar, brain stem and paraventricular lesions with clear remissions and exacerbations, supported by CT, CSF and evoked potentials findings suggests the diagnosis of multiple sclerosis even at this early age.

Refined structure of southern bean mosaic virus at 2.9 A resolution

The T = 3 capsid of southern bean mosaic virus is analyzed in detail. The beta-sheets of the beta-barrel folding motif that form the subunits show a high degree of twist, generated by several beta-bulges. Only 34 water molecules were identified in association with the three quasi-equivalent subunits, most of them on the external viral surface. Subunit contacts related by quasi-3-fold axes are similar, are dominated by polar interactions and have almost identical calcium binding sites. There is no metal ion on the quasi-3-fold axis, as previously reported. Subunits related by quasi-2-fold and icosahedral 2-fold axes have different contacts but nevertheless display almost identical interactions between the antiparallel helices alpha A. A dipole-dipole type interaction between these helices may produce an energetically stable hinge that allows two types of dimers in a T = 3 assembly. The temperature factor distribution, the hydrogen-bonding pattern, and the contacts across the icosahedral 2-fold axes suggest that one of the dimer types is present in the intact virion and probably also in solution; the other is produced only during capsid assembly. Interactions along the 5-fold axes are mainly polar and possibly form an ion channel. The beta-sheet structures of the three subunits can be superimposed with considerable precision. Significant relative distortions between quasi-equivalent subunits occur mainly in helices and loops. The two dimeric forms and the subunit distortions are the consequence of the non-equivalent subunit environments in the capsid.

Changes in the pattern of protein synthesis during zoospore germination in Blastocladiella emersonii

Using two-dimensional gel electrophoresis, we analyzed the pattern of proteins synthesized during Blastocladiella emersonii zoospore germination in an inorganic solution, in both the presence and absence of actinomycin D. During the transition from zoospore to round cells (the first 25 min), essentially no qualitative differences were noticeable, indicating that the earliest stages of germination are entirely preprogrammed with stored RNA. Later in germination (after 25 min), however, changes in the pattern of protein synthesis were found. Some of these proteins (a total of 6 polypeptides) correspond possibly to a selective translation of stored messages, whereas the majority of the changed proteins (22 polypeptides) corresponds to newly synthesized mRNA. Thus, multiple levels of protein synthesis regulation seem to occur during zoospore germination, involving both transcriptional and translational controls. We also analyzed the pattern of protein synthesis during germination in a nutrient medium; synthesis of specific polypeptides occurred during late germination. During early germination posttranslational control was also observed, several labeled proteins from zoospores being specifically degraded or charge modified.

Acquisition of thermotolerance during development of Blastocladiella emersonii

In the fungus Blastocladiella emersonii the synthesis of heat-shock proteins is developmentally regulated; particular subsets of heat-shock proteins are induced by heat shock during sporulation, germination and growth and some heat shock-related proteins are spontaneously expressed during sporulation (Bonato et al., 1987, Eur. J. Biochem., in press). Nevertheless, acquisition of thermotolerance can be induced at any stage of the life cycle. The development of thermotolerance is correlated with the enhanced synthesis of some heat-shock proteins: hsp 82a, hsp 82b, hsp 76, hsp 70, hsp 60, hsp 25, hsp 17b. Other hsps are not specifically involved in thermotolerance.

Differential expression of heat-shock proteins and spontaneous synthesis of HSP70 during the life cycle of Blastocladiella emersonii

The heat-shock response in Blastocladiella emersonii is dependent on the developmental stage. Cells exposed to elevated temperatures at different stages of the life cycle (sporulation, germination or growth) show a differential synthesis of heat-shock proteins (hsps). Of a total of 22 polypeptides induced, particular subsets of hsps appear in each phase, demonstrating a non-coordinate heat-shock gene expression. In contrast, heat-shock-related proteins (hsp76, hsp70, hsp39a) are spontaneously expressed at a high level during sporulation. By the criteria of two-dimensional gel electrophoresis and partial proteolysis mapping, the 70,000-Da protein, whose synthesis is induced spontaneously during sporulation, is indistinguishable from the heat-inducible hsp70. The techniques of in vitro translation, and Northern analysis using a Drosophila hsp70 probe, demonstrated that enhanced synthesis of hsp70, which occurs during heat-shock treatment and spontaneously during sporulation, is associated with an accumulation of hsp70 mRNA. These observations suggest that hsp70 gene expression is induced during sporulation.

Heat shock protein synthesis during development in Caulobacter crescentus

Caulobacter crescentus cells respond to a sudden increase in temperature by transiently inducing the synthesis of several polypeptides. Two of the proteins induced, Hsp62 and Hsp70, were shown to be analogous to the heat shock proteins of Escherichia coli, GroEL and DnaK, respectively, by immunological cross-reactivity with antibodies raised against the E. coli proteins. Two-dimensional gel electrophoretic resolution of extracts of cells labeled with [35S]methionine during heat shock led to the identification of 20 distinct Hsps in C. crescentus which are coordinately expressed, in response to heat, at the various stages of the cell division cycle. Thus, a developmental control does not seem to be superimposed on the transient activation of the heat shock genes. Nonetheless, under normal temperature conditions, four Hsps (Hsp70, Hsp62, Hsp24b, and Hsp23a) were shown to be synthesized, and their synthesis was cell cycle regulated.

The structure of a T = 1 icosahedral empty particle from southern bean mosaic virus

The structure of a T = 1 icosahedral particle (where T is the triangulation number), assembled from southern bean mosaic virus coat protein fragments that lacked the amino-terminal arm, was solved by means of model building procedures with the use of 6-angstrom resolution x-ray diffraction data. The icosahedral five-, three-, and twofold contacts were found to be similar, at this resolution, to the analogous contacts (icosahedral five-, quasi-three-, and quasi-twofolds) found in the parent T = 3 southern bean mosaic virus. However, the icosahedral fivefold contacts of the T = 3 structure are the most conserved in the T = 1 capsid. These results are consistent with a mechanism in which pentameric caps of dimers are the building blocks for the assembly of T = 1 and T = 3 icosahedral viruses.

[Occurrence of human and wild strains of Schistosoma mansoni in pre-Amazonia. I. Study of mollusks]

Foram isoladas na região da Baixada Maranhense (Brasil), linhagens humana (H) e silvestre(S) de Schistosoma mansoni a partir de miracídios eclodidos de ovos encontrados em fezes de doentes humanos autóctones da Região e de fígados de roedores silvestres naturalmente infectados. Biomphalaria glabrata, descentes de caramujos coletados no campo, foram expostos, isoladamente, aos miracídios H e S, mantidos isolados em moluscário e observados durante 100 dias. Moluscos normais foram mantidos nas mesmas condições de ambiente em que foram submetidos os infectados e tomados como controle da experiência. Foram anotados os indices de infecção dos moluscos, as datas da eliminação de cercárias, quantidade de larvas eliminadas e mortalidade dos moluscos. Os dados sugeriram melhor adaptação do esquistossomo da linhagem H à B. glabrata. A linhagem S, por sua vez, foi três vezes mais virulenta do que a linhagem H. Estes dados foram comparados com os encontrados na literatura especializada e verificado diversidades nos comportamentos parasitológicos das linhagens em estudo, quando comparados com os encontrados nas linhagens H e S oriundas do Vale do Rio Paraíba do Sul, no Estado de São Paulo (Brasil).