Electron microscopic aspects of membrane alterations during bacterial cell lysis.
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Bacillus cereus↗
Biomedical subjects
M T Silva
Publications and source records attributed to M T Silva.
Electron microscopic study on the effect of the oxidation of ultrathin sections of Bacillus cereus and Bacillus megaterium.
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Acetates↗
Chronic morphine consumption decreases wheel running and wheel running-reinforced behavior in rats.
The purpose of this experiment was to evaluate the effects of morphine self-administration on wheel running and wheel running-reinforced lever pressing in rats. The home cage was equipped with a bottle that contained either water, a saccharin-flavored 0.5-mg/ml morphine solution, or saccharin (0.25%). The bottle was available for either 1 or 3 h. The bottle was then removed, and 20-22 h after removal, the rats were moved to an operant chamber in which lever presses earned 15 s access to a running wheel (according to a variable interval (VI) 40-s schedule). The morphine condition was in effect for 69 days, and consumption gradually increased to a level of 67 mg/kg/day. During the morphine condition, wheel running and lever pressing decreased. Following the removal of morphine, (so that the home-cage bottles provided a 0.25% saccharin solution), the two instrumental behaviors increased to the pre-morphine (water) levels. However, the increases were not immediate, and in the first post-morphine session, lever pressing and wheel turning remained at the depressed morphine level. The post-morphine increase in lever pressing was substantially larger than the increase in wheel running. The results support the hypothesis that chronic opiate consumption reduces the frequency of some nondrug-related behaviors, and that this, in turn, increases preference for the opiate.
Animals↗
Tamoxifen induces ultrastructural alterations in membranes of Bacillus Stearothermophilus.
Tamoxifen (TAM), a non-steroid antiestrogen, is the mostly used drug for chemotherapy and chemoprevention of breast cancer. However, the mechanisms by which TAM inhibits cell proliferation in breast cancer are not fully understood. TAM strongly incorporates in biomembranes and a variety of effects have been assigned to biophysical and biochemical interactions with membranes. Therefore, a better understanding of the physicochemical basis of interaction of TAM with biomembranes is essential to elucidate the molecular mechanisms of action. A strain of Bacillus stearothermophilus has been used as a model to clarify the interaction of TAM with the cell membrane. TAM effects on the ultrastructure of membranes of this bacterium were evaluated by electron microscopy. Important ultrastructural alterations were observed in B. stearothermophilus treated with TAM, namely change in the geometry of the membrane profile from asymmetric to symmetric, disaggregation of ribosomes, coagulation of the cytoplasmic matrix, occurrence of mesossomes, appearance of fractures in membranes and the alteration of the ultrastructure of cell wall. These ultrastructural alterations confirm that TAM is a membrane-active drug and that membrane damage may be involved in molecular mechanisms of cell death induced by this drug.
Dose-Response Relationship, Drug↗
[Serum immunoglobulins in children perinatally exposed to human immunodeficiency virus]
OBJECTIVE: Hypergammaglobulinemia is an early manifestation of perinatal HIV infection. Our objective was to analyze the differences in serum immunoglobulin levels between infected and seroreverter children and their association with clinical outcome. METHODS: We carried out a historical prospective study with 107 infected and 90 seroreverter children. We compared the IgA, IgG, and IgM levels between infected and seroreverters in the first 18 months of life; IgA, IgG, and IgM as surrogate markers of infection; and IgA, IgG, and IgM levels in the first 5 years in infected children, according to clinical outcome. The Mann-Whitney test was used for comparison between groups. Surrogate markers were assessed according to sensitivity, specificity, positive and negative predictive values, and J index. RESULTS: Infected children, when compared to seroreverters, showed significantly higher levels of: IgM from the 1st to the 5th trimester; IgA and IgG from the 2nd to the 6th trimester (P </= 0.05). Levels of IgA >/= 90 mg/dl in the 2nd trimester and IgG >/= 1,700 mg/ dl or 1,200 mg/dl in the 2nd and 3rd trimesters were associated with HIV infection with J indexes of 0.97, 0.92, and 0.93, respectively. Infected children in the B and C categories, compared to those in the N and A, showed higher levels of IgM from the 2nd to the 4th year, and IgA from the 3rd to the 5th year (P </= 0.05). CONCLUSIONS: The temporal progression of IgA, IgG, and IgM levels showed an early and intense stimulation to the synthesis of immunoglobulin in infected children. Clinical and epidemiological indicators showed that such levels may be surrogate markers of infection. Higher IgM and IgA levels from the 2nd to the 5th year in more severely infected children suggest a dysfunction in immune regulation secondary to persistent antigenic stimulation.
Journal Article↗
[Evolution of hematological parameters in a group of children with human immunodeficiency virus infection - HIV 1]
OBJECTIVE: To analyze the evolution of clinical and hematological aspects of the children infected with HIV 1. METHODS: Using the CDC criteria, 1994, 37 children with HIV infection were selected, followed up at the Immunodeficiency Clinic at UNICAMP. The study is longitudinal descriptive. Complete blood count, ferritin, serum iron, TIBC and direct Coombs were carried out. RESULTS: The clinical category that predominated wasB(45.94%) and categories A and C were equal (27.03%). All of them were having antiretroviral therapy. Hypochromic and microcytic anemia were seen in 100% of patients up to 12 months of age. There was association between anemia and the progression of the disease, both clinical (p=0.031) and immunological (p=0.0027) and with lymphopenia too (p=0.033). Thrombocytopenia occurred in 10 to 25% of the patients. Low serical ferritin was seen in 2.7% of the cases and low serum iron in 11.1%. All the 15 patients analyzed had negative Coombs test. There was weight and height reduction in 23.5 to 45% of the children and 70.3% had clinical manifestations up to 9 months of age. During the follow up 13.2% of the patients died. CONCLUSIONS: There was association between anemia and lymphopenia with the progression of the disease. In relation to the aetiology of the anemia, about 10% can be considered anemia of chronic disease. Probably the hematological abnormalities seen in peripheral blood are the consequences of loss of control of cellular death mechanism and hematopoiesis in individuals infected by HIV 1.
Journal Article↗
[Kaposiform hemangioendothelioma associated with Kasabach-Merritt syndrome]
OBJECTIVE: To describe a case of kaposiform hemangioendothelioma, the only malignant tumor of vascular origin specific of childhood.METHODS: We report a case of a 40-days-old girl who presented with a giant hemangioma of the face. Rapid enlargement of the tumor lead to laryngeal compression with severe respiratory distress. She had also a consumptive thrombocytopenic coagulopathy (Kasabach-Merritt syndrome).RESULTS: She was admitted to the pediatric intensive care unit of the Hospital das Clínicas da Universidade Estadual de Campinas and mechanical ventilation was introduced. A ten day course of dexamethasone was only partially effective. We then started alpha-2a interferon at a dose of 1.8 million units/m(2)/day by subcutaneous route, but she died four days after the onset of this therapy. The microscopic features showed a kaposiform hemangioendothelioma.CONCLUSION: We discuss this unusual fatal evolution of a rapidly growing hemangioma and its hematological complications.
Journal Article↗
Case for the panel. Helicobacter pylori, III: ultrastructural detection of outer multicircular membranes of unknown origin and function.
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Cell Membrane↗
Pleiotropic control mutations affecting the sporulation of Bacillus subtilis.
Mutations affecting quantitatively the production of the sporulation-associated extracellular alkaline protease were isolated and characterized. They fall into at least five genes, three of which, ScoA, B and C, were mapped in the argC-metC region. The pleiotropic effects of these mutations concern several or all of the following: rate and timing of protease production, synthesis of alkaline phosphatase, time-course of spore formation. Electron microscopic evidence indicates delayed switch from one morphological stage to another. The nature of the Sco mutations and the genetic regulation of sporulation are discussed.
Alkaline Phosphatase↗
Correlation viability/morphology in Mycobacterium leprae.
The present study regards the correlation between the percent of viable M. leprae (as determined by the mouse foot pad technique) and the quantitative ultrastructural analysis of M. leprae cells in 6 armadillo's samples and 1 nude mouse foot pad. The quantitative ultrastructural study of 3 LL patients and 1 M. leprae-infected nude mouse was correlated to the Morphological Index. The results show that most M. leprae cells with continuous undeformed cell walls, continuous symmetric membranes, ribosomes and fibrilar nucleoids are viable bacilli. Some cells with the above ultrastructural pattern may be dead bacilli that did not yet enter the macrophage-induced degradative process that results in the disposal of the bacteria. Our results also show that degenerating M. leprae cells largely predominate in most samples studied. This means that, even in the absence of anti-leprosy treatment, dead M. leprae cells accumulate in the host's tissues. This point has to be taken into account in the calculation of the generation time of M. leprae in vivo, the dynamics of the leprosy bacillus in susceptible hosts being influenced by the simultaneous occurrence of growth, death and degradation. Since known facts in regards to the physiology of bacterial membranes make it difficult to accept the PAS-symmetric membrane of viable M. leprae as the membrane of growing bacilli, a search of M. leprae cells with asymmetric membranes was undertaken in appropriate samples from nude mice. Several M. leprae cells with normal ultrastructure and Thiéry-asymmetric membranes were found in the foot pads of one mouse. Although this observation must be confirmed in another sample, it suggests that M. leprae would not be an exception to the general concept that the membranes of all growing Gram-positive bacteria have PAS-positive components located only in the outer layer. The M. leprae cells that have normal ultrastructure and symmetric membranes and that are viable would represent some sort of resting cells, that is, living but not growing bacteria. All the, 11, 263 individual bacillary profiles scored in the ultrastructural study included in the present study exhibited the micromorphological characteristics of acid-fast bacteria.
Animals↗
Ultrastructure of Mycobacterium leprae and other acid-fast bacteria as influenced by fixation conditions.
A procedure using aldehydes, OsO4, Ca++ and uranyl acetate was selected for study of the fixation of Mycobacterium leprae in skin biopsies of leprosy patients. The ultrastructural pattern of recognized normal M. leprae cells fixed by the above procedure was characterized, and was found to be similar to that of other acid-fast bacteria fixed by the same procedure, except for the geometry of the membrane profile. Under such fixation conditions, this profile is always asymmetric in in vitro-cultured normal Nocardia asteroides, M. aurum and M. tuberculosis, whereas in skin biopsies no M. leprae cells with asymmetric membranes have been found so far. The implications of this observation for the interpretation of the ultrastructure of damaged M. leprae cells found in skin biopsies are discussed.
Calcium↗
Ultrastructural alterations of mycobacterium leprae in skin biopsies of untreated and treated lepromatous patients.
1. -- Mycobacterium leprae cells under a process of progressive disaggregation are present in the skin of both treated and untreated patients. 2. -- The ultrastructural alterations observed during the degenerative process seem to be qualitatively similar in treated and untreated patients. 3. -- The proportion of altered M. leprae cells increases during the treatment, mainly with rifampicin and rifampicin + clofazimine + diaminodiphenyl sulfone. 4. -- The cell wall of M. leprae is the last bacterial structure to disappear during the degenerative process.
Cell Membrane↗