Biaxial mechanical/structural effects of equibiaxial strain during crosslinking of bovine pericardial xenograft materials

We have investigated the effect of biaxial constraint during glutaraldehyde crosslinking on the equibiaxial mechanical properties of bovine pericardium. Crosslinking of cruciate samples was carried out with: (i) no applied load, (ii) an initial 25 g ( approximately 30 kPa) equibiaxial load, or (iii) an initial 200 g (approximately 250 kPa) equibiaxial load. All loading during crosslinking was done under a defined initial equibiaxial load and subsequently fixed biaxial strain. Load changes during crosslinking were monitored. Mechanical testing and constraint during crosslinking were carried out in a custom-built biaxial servo-hydraulic testing system incorporating four actuators with phase-controlled waveform synthesis, high frame-rate video dimension analysis, and computer-interfaced data acquisition. The paired biaxial stress strain responses under equibiaxial loading at 1 Hz (before and after treatment) were evaluated for changes in anisotropic extensibility by calculation of an anisotropy index. Scanning electron microscopy (SEM) was performed on freeze-fractured samples to relate collagen crimp morphology to constraint during crosslinking. Fresh tissue was markedly anisotropic with the base-to-apex direction of the pericardium being less extensible and stiffer than the circumferential direction. After unconstrained crosslinking, the extensibility in the circumferential direction, the stiffness in the base-to-apex direction, and the tissue's anisotropy were all reduced. Anisotropy was preserved in the tissue treated with an applied 25 g load; however, tissue treated with an applied 200 g load became extremely stiff and nearly isotropic. SEM micrographs correlated well with observed extensibility in that the collagen fibre morphology changed from very crimped (unconstrained crosslinking), to straight (200 g applied load). Biaxial stress-fixation may allow engineering of bioprosthetic materials for specific medical applications.

[Mechanical study of stiffness in LIM-41 external fixator assemblages submitted to torsion strain]

The mechanical stiffness of LIM-41 external fixator assemlages submitted to torsional strain was studied. A condition of unstable fracture was reproduced. The authors evaluated the effect of of Schanz pin configurations, defined as "distal", "standard" and "proximal", and of the distance, 20 mm, 40 mm or 60 mm between the external fixator and the element employed to simulate bone. The authors conclude that stiffer LIM-41 assemblages are obtained if the "standard" or "proximal" configurations are employed, on which some pins are placed near the fracture simulation site, and if the external fixator body is fitted closer to the bone simulating element, having the former variable greater influence over the stiffness coefficient.

Failure of protection induced by a Brazilian vaccine against Brazilian wild rabies viruses

This report shows that the SMB vaccine currently used in Brazil for human immunisation provides different degrees of protection in mice, depending on the rabies virus strain used as challenge. Using the NIH and Habel potency tests to evaluate the protective activity of rabies vaccine, we observed that vaccinated mice showed a higher resistance to a challenge with a fixed rabies virus (CVS-Challenge Virus Strain). The vaccine potency using the Habel or NIH tests was respectively > 6.4 (log 10) and 1.0 (Relative Potency-RP) when the fixed rabies virus was used for challenge, and from 2.9 to 4.3 (log 10) or 0.13 to 0.8 (RP) when different wild rabies viruses were used for challenge. The presence of virus neutralising antibodies (VNA) could not explain the differences of susceptibility after vaccination, since sera of vaccinated animals had similar VNA levels against both fixed and wild strains before virus challenge (respectively, 5.6 +/- 0.24 and 5.0 +/- 0.25 IU/ml of VNA against the fixed rabies virus and the 566-M strain of wild rabies virus in sera of mice vaccinated with 0.2 units of vaccine). Only cell-mediated immunity parameters correlated with the protection induced by vaccination. The IFN gamma titers found in sera and brain tissues of animals challenged with CVS strain were higher (from 36.7 +/- 5.7 to 293.3 +/- 46.2 IU/ml) than those found in mice challenged with 566-M virus strain (from 16.7 +/- 5.8 to 36.7 +/- 5.8). The proliferation index of spleen cells obtained with CVS stimulation reached a maximal value of 15.1 +/- 0.7 while spleen cells from vaccinated mice stimulated with 566-M virus failed to proliferate. The implications of these data in human protection by vaccination are discussed.

Bovine papillomavirus transmission and chromosomal aberrations: an experimental model

Enzootic haematuria and urinary bladder cancer in cattle are associated with feeding on bracken fern and bovine papillomavirus (BPV) infection. An increased rate of chromosomal aberrations in peripheral blood lymphocytes from chronically affected haematuric cows raised in bracken fern pastures has been reported, suggesting the presence of BPV in the peripheral blood of afflicted animals. The purpose of the present investigation was to examine the role of peripheral blood as a potential BPV-transmitting agent and search for clastogenic effects in experimentally infected animals kept on a bracken fern-free diet. Healthy cows were inoculated with blood samples of haematuric animals every two weeks for 18 months. Recipient cows, their offspring, donor animals and a control group were kept on a bracken fern-free diet throughout the experiment. Clinical and molecular analyses for detection of BPV infection were carried out periodically in all groups. Short-term lymphocyte cultures were performed to assess chromosomal aberration levels. The donor cows, the recipient cows and their offspring presented increased levels of chromosomal aberrations. BPV-2 DNA was identified by Southern blotting, PCR and cycle-sequencing of PCR products in peripheral blood of donor and recipient animals and in the progeny of recipient animals. Data support both the concept that BPV can be transmitted through blood and the hypothesis that infection with the virus causes the clastogenic alterations observed in the present experimental model. The presence of BPV-2 DNA and chromosomal alterations in peripheral blood of offspring at the moment of birth is evidence for vertical transmission of BPV.

Genetic damage in exfoliated cells of the uterine cervix. Association and interaction between cigarette smoking and progression to malignant transformation?

OBJECTIVE

To determine, through the micronucleus (MN) test, the cytogenetic effects of cigarette smoking on exfoliated cells from the uterine cervix in women with normal smears and women with inflammatory atypia, squamous intraepithelial lesion (SIL) (cervical intraepithelial neoplasia [CIN] 1-3) and cervical cancer.

STUDY DESIGN

The study group consisted of 200 women divided into three subgroups: group 1 (n = 116), women periodically undergoing cervical cytology and residents of Salvador-Bahia; group II (n = 57), women residing in São Paulo and previously selected because of a possible cytopathologic test positive for such conditions as human papillomavirus infections or malignant or premalignant cervical lesions (CIN 1-3); group III (n = 27), inmates of the Tatuapé Penal Institution, São Paulo. All the women underwent cytologic and colposcopic examination, and biopsies were performed on 68 of them.

RESULTS

Considering the samples as a whole and using the chi(2) test for rare events, the number of MNs in smokers was significantly greater than in nonsmokers. It was also greater in women with larger exposure to smoking. The occurrence of MN was significantly lower in women with normal smears (smokers and nonsmokers) than in those showing any kind of pathologic alteration. In nonsmokers the occurrence of MN was similar between those with inflammatory atypia (IA) or low grade (L) SIL (CIN 1) and significantly higher in women with more severe lesions or high grade (H) SIL (CIN 2 and 3). Smokers with LSIL (CIN 1) showed a higher number of MNs than nonsmokers with a comparable diagnosis and smokers with IA. No differences were observed when compared with smokers with HSIL (CIN 2 and 3). MN occurrence was not associated with other risk factors for SIL or cancer development, such as age at first coitus, number of sexual partners, multiparity and use of hormonal contraceptives.

CONCLUSION

These results suggest that the mutagenic effect of cigarette smoking occurs in cervical cells and that the progression of SIL is associated with increased frequency of chromosomal damage. Moreover, the data suggest that cigarette smoking introduces an additional risk to the progression of low grade LSIL (CIN 1). MN testing would be helpful in monitoring smokers with this kind of lesion.

Thermomechanical analysis of collagen crosslinking in the developing lamb pericardium

In a developing lamb model, we have used hydrothermal isometric tension (HIT) techniques to assess collagen crosslink stability and its contribution to the mechanical properties of the pericardium. Strip samples of tissue were either: (i) heated to a 90 degrees C isotherm or (ii) heated in 5 degrees C increments between 60-90 degrees C and then 93 and 97 degrees C isotherms. The half-life of stress relaxation associated with peptide bond hydrolysis (t1/2) was calculated at each isotherm. The activation energy, Eact, for the hydrolysis-associated relaxation process was also calculated using the data from the stepwise HIT tests--a technical improvement which significantly reduces the experimental time required to develop statistically valid measurements. Crosslinking in the pericardium increased during development and was demonstrated both by thermoelasticity and by resistance to enzymatic solubilization. We observed greater conversation to thermally stable crosslinks upon maturation, the ratio of the NaBH4-stabilized/unstabilized half-lives peaking at 21 days postnatal. Whereas tissue from lambs (119 day fetal, and 3 day and 21 day postpartum) showed an early maximum and rapid decay of force, NaBH4 stabilization significantly increased thermal stability and yielded profiles similar to those in adult tissue.

[Bacteremia after endoscopic retrograde cholangiopancreatography with and without therapeutic procedure: frequency, associated factors and clinical significance]

PURPOSE

To determine the frequency, associate factors and clinical features of bacteremia in patients undergoing endoscopic retrograde cholangiopancreatography (ERCP), with or without therapeutic procedures.

METHODS

Prospectively, 42 consecutives patients undergoing 46 endoscopic retrograde cholangiopancreatographies (ERCPs) from August to December 1994 were analyzed. The search for bacteremia was done by drawing 6 blood samples for cultures from peripheral blood. Two blood samples were collected before the ERCP and 4 of them after. The bottles used for cultures were Bactec bottles. The bottles were incubated in the Bactec 9240 system, and eventual bacteria detect were identificated by the manual routine of the laboratory and also with the autoScan/Microscan system.

RESULTS

All blood cultures obtained before the ERCPs were negatives. Bacteremia were detected after 7 endoscopic procedures. In two episodes of bacteremia, the microorganism identified (Staphylococcus epidermidis) was considered to be a contaminant. The other 5 episodes of bacteremia were considered true bacteremia (frequency- 10.9%), and the microorganisms identified were: Streptococcus viridans, Corynebacterium sp., Enterobacter cloacae, Klebsiello oxytoca and Enterobacter aerogenes. This episodes were more frequent in the blood cultures obtained immediately after the ERCPs (p < 0.05), and occurred exclusively in the patients who were not receiving antibiotics (p = 0.0192). Clinical manifestation of the episodes of bacteremia were not detected.

CONCLUSION

The episodes of bacteremia occurred exclusively in the patients who were not receiving antibiotics, were transient and completely no symptomatic.

Liver of the brown trout, Salmo trutta (Teleostei, Salmonidae): a stereological study at light and electron microscopic levels

BACKGROUND

A quantitative study was undertaken for the first time on the normal liver of male and female 2-year-old brown trout, Salmo trutta.

METHODS

Liver was fixed by controlled perfusion. Organ-level morphometry provided weight and volume. A two-stage stereological approach was performed at light and electron microscopy levels. Systematic sampling and point-counting morphometry were used for estimating the relative volumes of the structural compartments. Total absolute volumes of these components were obtained by multiplying each volume density by the volume of its reference space.

RESULTS

Liver volume was 3,423.6 mm3 for males and 3,657.4 mm3 for females. Parenchyma accounted for 95% of hepatic volume. Veins and bile ducts occupied, respectively, 76% and 17% of the stroma, whereas arteries, connective tissue, and melanomacrophages together composed only 6%. Hepatocytes occupied 88% of the parenchyma. Nonhepatocytic cells (endothelium, biliary epithelial cells, Ito cells, and macrophages) composed 4% of the parenchyma, the capillary lumen 6%, and other spaces (Disse space, canaliculi, and lumina of preductules and ductules) composed 2%. Significant sexual differences were found: (1) Females showed a greater parenchymal volume density (0.85% vs. 0.35%) and absolute volume (29.5 mm2 vs. 11.7 mm3) of Ito cells; (2) macrophages of females also presented a greater parenchymal volume density (0.94% vs. 0.46%), but not absolute volume.

CONCLUSIONS

The need to analyze both relative and absolute stereological data was stressed. Similarities and differences were detected between brown trout and other species (fishes and mammals); the findings suggest that, despite architectural differences, some quantitative parameters of liver microanatomy were retained during phylogeny. Factors mediating sexual differences in Ito cells and macrophages were discussed and the need for further studies was highlighted.

Anti-MHV3 state induced by IFN gamma in macrophages is not related to arginine metabolism

In contrast to BALB/c mouse macrophages, the A/J macrophages after activation by interferon gamma (IFN gamma) develop an anti-MHV3 effect which correlates with the resistance to virus infection. To understand the cellular basis of this antiviral effect, we studied the possible involvement of arginine metabolism through nitric oxide (NO) and arginase induction, since these metabolic pathways have been described as implicated in antiviral activities of macrophages. The studies were performed by activating macrophages with inducers of NO (IFN gamma) and arginase (IL4 IL10). NO synthase (iNOS) and arginase inhibitors (N-methyl-arginine, NMA, and hydroxyarginine, OH-ARG) were used. The results show that in both macrophage populations, no spontaneous synthesis of NO occurred and the MHV3 enhanced the NO release induced by IFN gamma. After activation with IFN gamma, BALB/c macrophages released higher amounts of NO than the A/J macrophages. The inhibition of IFN gamma-induced NO-synthesis with NMA or with arginine free medium did not affect the virus replication. In BALB/c macrophages, IL4 or IL10, induced higher amounts of arginase than in A/J macrophages. In both macrophage populations the MHV3 infection had no influence on the arginase synthesized, and the inhibition of the arginase with OH-ARG had no influence on the virus growth. The level of MHV3 replication or inhibition was also not influenced when we used macrophages from knockout mice for the iNOS gene, and as a consequence were unable of synthesizing NO. These data indicate that NO and arginase do not participate in the anti-MHV3 state induced by IFN gamma in macrophages.

Radiosensitivity of blood lymphocytes from basocellular carcinoma patients, as detected by the micronucleus assay

Cytogenetic techniques, the micronucleus (MN) assay, in particular, have been widely used in population monitoring, biological dosimetry and early detection of groups susceptible to cancer. Individuals respond differently to several environmental agents. The efficiency of the cellular repair mechanisms would be responsible, at least to some extent, for individual differences in sensitivity to neoplasia. In order to determine the sensitivity of cancer patients to ionizing radiation, blood cultures from untreated individuals with basocellular carcinoma, young healthy subjects and older healthy subjects, were irradiated in vitro with 60Co at doses ranging from 0 to 500 cGy and submitted to the cyto-B micronucleus assay; the frequency of cells and distribution of MN and dose-response relationships were analyzed. Results showed that cancer patients had a lower frequency of cells with spontaneous MN than older healthy subjects. The frequency of micronucleated cells was not different in patients and healthy subjects, but not the distribution of MN per radiation dose: for the carcinoma group, while the proportion of cells with one MN decreases drastically, the proportion of the cells with two or more MN increases with the same intensity. Our results show that the proportion of damaged cells is similar in patients with basocellular carcinoma and healthy subjects, but the magnitude of radiation-induced lesion is greater in the cancer patients.

Effect of applied uniaxial stress on rate and mechanical effects of cross-linking in tissue-derived biomaterials

Conformational changes in collagen fibrils, and indeed the triple helix, can be produced by application of mechanical stress or strain. We have demonstrated that the rate of cross-linking in glutaraldehyde and epoxide homobifunctional reagents can be modulated by uniaxial stress (strain). Two poly(glycidyl ether) epoxides were used: Denacol EX-810 (a small bifunctional reagent), and Denacol EX-512 (a large polyfunctional reagent). To prevent any possible effect from being masked by saturation of cross-linking sites, bovine pericardium was cross-linked to such an extent that the increase in collagen denaturation temperature, Td, was one-half of the maximal rise achievable with each reagent. Uniaxial tensile stress of 0, 15, 124 or 233 kPa was applied during cross-linking. Cross-linking rate (as observed by increase in Td) increased with increasing stress to a maximum at 124 kPa in glutaraldehyde at pH 7 but decreased in EX-810 at pH 7. In each case, the effect was small but statistically significant. No effect was observed with the larger EX-512. Cross-linking under increasing stress also showed systematic effects on mechanical properties: decreasing extensibility and plastic strain while increasing tensile strength. In each case, the effects of the epoxides were slightly different from those of glutaraldehyde. In preparation for the above experiments, studies of the effect of pH, temperature, and exposure time were carried out for each epoxide and (to a lesser extent) for glutaraldehyde. Again, systematic changes in mechanical properties were observed with increasing Td. Conformational changes in collagen produced by mechanical stress (strain) modulate the rate of cross-linking and the resulting mechanical properties; however, the effects are sensitive to the reagent employed.

Solvent environment modulates effects of glutaraldehyde crosslinking on tissue-derived biomaterials

Bioprosthetic materials utilized in the construction of heart valves and vascular grafts possess limited performance and viability in vivo. This is due (in part) to the failure of these materials to mimic the mechanical properties of the host tissue they replace. If bioprosthetic materials could be engineered to meet the mechanical performance required in vivo, the functional lifetime of implants would be increased. In this study, glutaraldehyde/solvent solutions of decreasing dielectric constant (polarity) were utilized to modify the properties of crosslinked collagen in whole bovine pericardial tissue. Solvents included phosphate buffer, methanol, 95% (w/w) ethanol, n-propanol, and n-butanol. Exogenous crosslinking was verified in collagen by thermal denaturation tests and amino acid analyses. Tensile mechanical behavior of collagenous pericardial samples was found to depend upon the dielectric constant (polarity) of the glutaraldehyde/solvent solutions employed; however, treatment in the solvents alone had little, if any, effect. As the dielectric constant of the solvents decreased, three mechanical properties were systematically altered: plastic strain fell from a mean of 8.9 +/- 1.5% (buffer) to 1.6 +/- 0.4% (n-butanol); strain at fracture increased from 32.2 +/- 2.6% (buffer) to 55.6 +/- 4.6% (n-butanol); and percent stress remaining after 1000-s stress relaxation from an 80-g initial load fell from 86.3 +/- 1.1% (buffer) to 76.9 +/- 1.0% (n-butanol). Crosslinking using a glutaraldehyde/n-butanol solution produced materials with tensile mechanical behavior that was very close to that of fresh tissue; however, the flexural properties of the treated tissue were different from those of fresh tissue. This decoupling of the flexural and tensile mechanical behaviors of crosslinked bioprosthetic materials is unique to this form of treatment. The observed phenomena may be the results of conformational changes in collagen facilitated by polar/nonpolar interactions with the solvent that are "locked in" by the action of glutaraldehyde. This technique may aid in the "customized" design of mechanical properties in tissue-derived biomaterials.

Evaluation of the genotoxic potential of flumethrin in mouse bone marrow by chromosomal analysis and micronucleus test

The genotoxic potential of the pyrethroid flumethrin was evaluated by using the combined protocol of metaphase analysis and micronucleus test in vivo in mouse bone marrow. The dermal route was tested in a single treatment and the intraperitoneal (i.p.) route in a single and a multiple treatment. Flumethrin showed a cytotoxic effect on both myelopoiesis and erythropoiesis, as evidenced by a reduction in the mitotic index and in polychromatic erythrocyte values. An increase in the frequency of gaps after the dermal exposure and of breaks only at the highest dose tested in the i.p. treatment indicates a weak clastogenic potential of the compound. A significant increase in the frequency of micronucleated polychromatic erythrocytes was observed after single and multiple i.p. treatments. In the latter, the induction of micronuclei was highly significant but not accompanied by an increase in breaks. This may indicate that the clastogenic effect might not account by itself for the induction of micronuclei, which could also have arisen from an aneugenic potential of flumethrin.

Biomechanical and ultrastructural comparison of cryopreservation and a novel cellular extraction of porcine aortic valve leaflets

Heart valve substitutes of biological origin often fail by degenerative mechanisms. Many authors have hypothesized that mechanical fatigue and structural degradation are instrumental to in vivo failure. Since the properties of the structural matrix at implantation may predetermine failure, we have examined the ultrastructure, fracture, mechanics, and uniaxial high-strain-rate viscoelastic properties of: (1) fresh, (2) cryopreserved, and (3) cellular extracted porcine aortic valve leaflets. The cellular extraction process is being developed in order to reduce immunological attack and calcification. Cryopreservation causes cellular disruption and necrotic changes throughout the tissue, whereas extraction removes all cells and lipid membranes. Both processes leave an intact collagen and elastin structural matrix and preserve the high-strain-rate viscoelastic characteristics of the fresh leaflets. Extraction does cause a 20% reduction in the fracture tension and increases tissue extensibility, with the percent strain at fracture rising to 45.3 +/- 4 (mean +/- SEM) from 31.5 +/- 3 for fresh leaflets. However, extraction does preserve matrix structure and mechanics over the physiological loading range. Glutaraldehyde fixation produces increased extensibility, increased elastic behavior, and, when applied to extracted leaflets, it causes a marked drop in fracture tension, to 50% of that for fresh leaflets. The combination of extraction and fixation may lead to early degenerative failure. The cellular extraction technique alone may be a useful alternative to glutaraldehyde fixation in preparing bioprosthetic heart valves.

Outcome and quality of life of patients with severe chronic limb ischaemia: a cohort study on the influence of diabetes

OBJECTIVE

To determine the influence of diabetes on the use of arterial reconstruction, the rate of amputation and death, and the quality of life of patients with severe limb ischaemia.

DESIGN

A prospective study of patients with the first episode of ischaemia.

SETTING

University tertiary referral centre.

METHODS

Thirty-seven patients with diabetes and 50 without diabetes, were studied over a 12 month period with complete follow-up.

MAIN OUTCOME MEASURES

The proportion of patients undergoing an arterial reconstruction, amputation rate, death rate, and quality-of-life scores.

RESULTS

Patients with diabetes underwent an arterial reconstruction less often than patients without diabetes (7/37 vs. 18/50). The odds of patients with diabetes having a higher incidence of adverse outcome was 1666:1 for minor amputation, 26:1 for major amputation, and 4.7:1 for death. There was a tendency towards a lower quality of life for patients with diabetes at 3 (OR 1.94, p = 0.036), 6 (OR 1.58, p = 0.117), and 12 (OR 1.47, p = 0.185) months.

CONCLUSIONS

In patients with diabetes, (1) the opportunity of undergoing an arterial reconstruction is lower, (2) morbidity and mortality are higher, and (3) the quality of life tends to be worse.

[Analysis of the program of control of the use of antimicrobials at the Hospital São Paulo--Escola Paulista de Medicina]

BACKGROUND AND OBJECTIVE

Antimicrobial agents represent a group of drugs that are frequently used in hospitals. Approximately, 50% of hospitalized patients receive at least one antimicrobial drug during the hospitalization period. However, half of these drugs are prescribed incorrectly. The objective of this paper was to analyse the antimicrobial control program that has been used at Escola Paulista de Medicina since 1989.

CASUISTIC & METHODS

The prescription of eleven controlled antibiotics should be done in a special form. Any requisition of a controlled antibiotic was evaluated, within 24 hours, by an infection diseases specialist who was hired exclusively for this function.

RESULTS

During 1989, 5,573 controlled antimicrobials were requested by the hospital staff, and 17.6% of them were considered inadequate and were refused. Such a percentage was high considering that our institution is a university hospital where the antibiotic usage should be more precise and adequate. We also should take into account that the indication of only 11 antimicrobial drugs were evaluated.

CONCLUSION

The results allow us to conclude that each hospital should have not only a policy on antimicrobial usage but also an effective program of control of these drugs.

[Medicine and statistics]

Doctors as researchers often resort to hypothesis testing and confidence intervals in the statistical analysis of study results. On the one hand, the use of statistical software has made this task easier. On the other hand, this has not contributed to neither a better understanding of statistical concepts nor to a seminal cooperation between doctors and statisticians. This note shows that the classical statistical theory, also called frequentist or Fisherian, offers probability statements that are very indirect ones. Bayesian statistics, on the other hand, gives a probability statement which is a more direct answer to the research question. Of course, this latter approach would hardly be considered without a close cooperation with an statistician. An improvement in the meaning of the probability statements may be seen as a gain in quality. An effective cooperation with statisticians, an issue that is more ethical than methodological, is directed to achieving a research of a better quality, so avoiding the scandal of poor medical research.

Mouse hepatitis virus type 3 infection provokes a decrease in the number of sinusoidal endothelial cell fenestrae both in vivo and in vitro

Fenestrations of hepatic endothelial cells play an active role as a sieving barrier allowing extensive exchange between the blood and liver parenchyma. Alteration of these structures may be induced in the course of various pathological events and provoke important perturbations of liver function. We demonstrate here that sinusoidal endothelial cells are permissive for mouse hepatitis virus 3 (MHV3) in vivo and in vitro and that this infection leads to a striking decrease in the number of fenestrae. The disappearance of these structures observed under scanning electron microscopy or in cryofracture preparations in vivo and in vitro cannot be reversed by the action of cytochalasin B on the microfilament network. The decrease in the porosity seems to be related directly to the productive infection of the endothelial cells, because it was not observed in A/J mice resistant to the virus and in susceptible BALB/c mice immunized with a thermosensitive mutant in which no viral replication occurs. In conclusion, a viral infection of liver endothelial cells may cause extensive loss of the fenestrations and thus lead to important functional pertubations.

Specific T-cell response correlates with resistance of genetic heterogeneous mouse populations to mouse hepatitis virus 3 infection

In a recently published study [Vassão RC, Mello IGC, Pereira CA (1994) Arch Virol 137: 277-288] we have shown that the genetically selected high antibody responder mice (HIII) are susceptible and the low antibody responder counterparts (LIII) are resistant to death induced by experimental infection with mouse hepatitis virus 3 (MHV3). This report shows that the MHV3 titers in the peritoneal exudate (PE) of HIII mice, 3 days after infection, were more than 2 log greater than in the resistant LIII mice, the interferon gamma (IFN gamma) titers in the PE of both mouse populations being not significantly different. The treatment with monoclonal antibodies (mAb) against CD4+ or CD8+ T cells induced susceptibility among LIII mice. The depletion of CD4+ T-cell subset in LIII mice was evidenced by, and led to a significant reduction in, the IFN gamma synthesis in their PEs with a 100 fold increase in MHV3 titers. When lymph node cells (LNC) were harvested from MHV3-infected mice and stimulated "in vitro" with MHV3 inactivated by ultraviolet radiation (uv-MHV3), only LNC from LIII mice were capable of proliferating and synthesizing significant amounts of interleukin 2 (IL-2). The LNC proliferation and IL-2 synthesis were inhibited by treatment with mAbs against CD4 or CD8 molecules. The MHV3 infection induced in both lines of mice a profound depression of the mitogenic response of LNC to phytohemaglutinin (PHA). A correlation between the specific T-cell response and the resistance to MHV3 infection is discussed.

Neutralization of the effect of Crotalus durissus terrificus venom by gangliosides

We determined the ability of a mixture of gangliosides (16% GD1b, 19% GT1b, 21% GM1, 40% GD1a) to neutralize the effect of Crotalus durissus terrificus (Cdt) venom in vitro and in vivo. Protection was indicated by the absence of muscular contractions, hind limb paralysis or death of BALB/c mice (16-18 g) after receiving Cdt venom (1 microgram Cdt venom containing 0.6 microgram protein) at the doses indicated. A dose of Cdt venom above 0.9 microgram (ip) or 1 microgram (im) induced muscular contraction and above 1.2 micrograms (ip) or 5.5 micrograms (im) the venom induced muscular contraction and hind limb paralysis. Cdt venom above 2.5 micrograms (ip) or 9 micrograms (im) induced all these symptoms and 95 to 100% death in experimental animals. The lethal dose 50% of the Cdt venom used was 8 micrograms (im) and 1.5 micrograms (ip). In in vitro studies, 4 mg gangliosides neutralized the effect of up to 1.5 micrograms Cdt venom. Quantities as low as 0.2 mg gangliosides were capable of neutralizing 0.9 microgram of Cdt venom in vitro. Intramuscular treatment with 1 mg gangliosides performed 60 min after the intramuscular injection of 5 micrograms Cdt venom protected 100% of the animals. In contrast, no protection was achieved with intraperitoneal treatment with gangliosides. The data show that gangliosides were effective in neutralizing the toxic effects induced by Crotalus durissus terrificus venom both in vitro and in vivo and that post-exposure intramuscular treatment with gangliosides could protect animals experimentally inoculated with the venom.

A multi-sample denaturation temperature tester for collagenous biomaterials

The temperature at which collagen denatures from a triple helix to a random coil structure is a useful measure of the degree of crosslinking. A new multi-sample denaturation temperature tester (DTT) has been constructed for rapid determination of the collagen denaturation temperature of natural tissues and collagenous biomaterials. To validate the system, the denaturation temperatures measured for the DTT are compared with results from differential scanning calorimetry (DSC). Data are presented for bovine pericardium in three states with denaturation temperatures ranging from 68 to 85 degrees C: fresh, or crosslinked with glutaraldehyde or the epoxide reagent Denacol EX-512 poly (glycidyl ether). Denaturation temperatures measured by DTT were not significantly different from those measured by differential scanning calorimetry (DSC); however, DSC onset systematically occurred at a slightly lower temperature than that measured by DTT. This result, seen only for fresh tissue is in agreement with earlier experiments using hydrothermal isometric tension (HIT) testing. By contrast, DTT and DSC onset were identical for the exogenously crosslinked materials. Since the measured transition temperature was independent of initial load, this variable may be chosen to yield sharper force-temperature transitions with a given sample geometry. This instrument allows accurate assessment of collagen denaturation temperatures for multiple samples in a fraction of the time required by other methods.

Interferon-gamma levels during the course of Trypanosoma cruzi infection of Calomys callosus (Rodentia-Cricetidae) and Swiss mice

Serum levels of interferon-gamma (IFN-gamma) were evaluated in Calomys callosus and Swiss mice during the course of infection by four strains of Trypanosoma cruzi. All strains stimulated the production of this interleukine; however, the timing of its onset and permanence varied among strains and between the two animal models. When chronically infected animals with no detectable serum IFN-gamma were challenged with the homologous strain, they produced quantities comparable with those obtained during the acute phase of infection. In C. callosus there was a correlation between H2O2 liberation by peritoneal macrophages and serum IFN-gamma levels, whereas no such correlation was found in mice. C. callosus had a higher capacity to heal histopathological lesions, whereas lesions in mice were progressive. The results obtained suggest that C. callosus develops well-adapted immune mechanisms that may be important for its role as a reservoir of T. cruzi.

Prediction of relapse in patients with breast cancer by DNA cytometry

Nuclear DNA content was quantified for 193 ductal invasive breast carcinomas in a prospective study. The results were correlated with various clinical parameters. Of these tumours 66.2% were non-diploid and the incidence of non-diploid tumours is significantly higher in later stages of the disease. The median DNA values distribution tend to be bimodal, although in stage III a large number of cases showed DNA values between 2C and 4C. No association was observed between ploidy and menopause, lymph node status or incidence of recurrence. The mean times of relapse were 22.4 and 18.8 months in diploid and non-diploid groups, respectively. The present data suggest association between non-diploidy and tumour aggressiveness. Using Bayesian statistical analysis, the probability of the mean time of relapse in diploid group to be longer than in non-diploid group, given the data, is 0.875.