Ultrastructural and biochemical aspects of liver mitochondria during recovery from ethanol-induced alterations. Experimental evidence of mitochondrial division.

To study the morphologic and biochemical changes occuring in liver mitochondria during recovery from ethanol-induced injury, rats fed a 6-month high-alcohol regimen plus a nutritionally adequate diet which did not induce fatty liver were compared with isocalorically fed controls. After this period the alcohol-fed animals displayed striking ultrastructural changes of liver mitochondria and a decreased respiratory activity with succinate or malate-glutamate as substrate. On the contrary, the respiratory rate with I-glycerophosphate was 50% increased. Regression changes were studied after alcohol was withdrawn from the diet. Enlarged mitochondria rapidly disappeared (in 24 hours), although a few megamitochondria were still present after 8 days of abstinence. A similar recovery was observed for the functional alterations. At the end of the experimental period, only a slight decrease of the maximal respiratory rate using malate-glutamate as a substrate was noted. The ultrastructural findings and the morphometric data suggest that the way in which mitochondrial normalization takes place is based on partition of these organelles.     

Modulation of immune responses in mice by oral administration of niflumic acid

The in vivo effects of non-steroidal anti-inflammatory drugs (NSAIDs) on the host immune system are still poorly understood. However, through inhibition of prostaglandin synthesis, NSAIDs may exhibit immunomodulating properties. The present work was aimed at evaluating the influence of niflumic acid on immune responses when administered orally for 7 consecutive days to 8-week-old inbred mice. Immunological tests were performed 24 h after the arrest of the treatment. At a dosage of 50 mg/kg/day, niflumic acid exerted noticeable immunostimulating effects, as shown by an increase in plaque-forming cell numbers after in vivo immunization with sheep red blood cells, an augmentation of spleen cell proliferation responses to stimulation with T- or B-cell mitogens and of T-cell cytotoxic response to allogenic cells. Phagocytosis-induced chemiluminescence of peritoneal macrophages was also enhanced whereas interleukin-1 production by these cells was depressed, but without concomitant modification in interleukin-2 production by T-cells. Increasing the niflumic acid dosage to 75 mg/kg resulted in the disappearance of the immunostimulatory effects on lymphocytes responses. Macrophage activities were affected similarly in mice receiving 50 mg/kg. These results demonstrate that niflumic acid is able to stimulate in vivo several immunological functions and, consequently, to maintain host immune defenses. Interestingly, it depressed interleukin-1 production, known to play a major role in the inflammatory process.     

Studies of the solubility of different calcium phosphate ceramic particles in vitro

In vitro solubility tests of hydroxyapatite, tetracalcium phosphate or tricalcium phosphate particles were performed in lactate, citrate, Gomoris or Michaelis buffer with pH 6.2 or 7.2 and in aqua destillata. The results showed that in general the solubility decreased in the order tetracalcium phosphate greater than tricalcium phosphate greater than hydroxyapatite, except for lactate or citrate buffer where the solubility order was tetracalcium phosphate = tricalcium phosphate greater than hydroxyapatite. The influence of the specific buffer used is much larger than either pH or specific calcium phosphate salt tested. The pH stability of lactate buffer and aqua destillata is very low, the other buffer solvents had a rather stable pH value.     

A crude extract of Artocarpus integrifolia contains two lectins with distinct biological activities.

The crude extract derived from seeds of Artocarpus integrifolia (jack fruit) contains two fractions with different biological activities for lymphocytes. One fraction is the D-galactose-binding lectin, jacalin, obtained by affinity purification on a D-galactose agarose column. The other, which is a component of the flow-through fraction (FT), is responsible for the mitogenic activity observed with human PBMC and murine spleen cells. In contrast, jacalin inhibits FT- and ConA-induced proliferative activity of human PMBC and murine spleen cells. This inhibition is not due to toxicity, because: (1) jacalin induces significant levels of IL-3/GM-CSF but not of IL-2 and/or IL-4 in murine spleen cells; (2) jacalin does not affect the capacity of these cells to secrete IL-2 or IL-4 as supernatants obtained from spleen cells sequentially stimulated with jacalin and ConA contain IL-2 and/or IL-4 as well as IL-3/GM-CSF. The ligand for the mitogen contained in the FT fraction is D-mannose as determined by sugar inhibition studies.     

A “Stopper” mutant of Neurospora crassa containing two populations of aberrant mitochondrial DNA

Summary [E35], an extranuclear mutant of Neurospora crassa has all the phenotypic characteristics of the stopper mutants (De Vries et al. 1980). In the present work, the mitochondrial DNA as well as the mitochondrial translation products are characterized further. The primary mutational event appears to have been the deletion of about 4 kbp from the wild-type genome. Moreover, after prolonged vegetative growth the mutant accumulates an 8-m circular mtDNA, which was demonstrated both by electronmicroscopy and by restriction enzyme analysis. Hence, the mutant contains two populations of aberrant mitochondrial DNA, the smaller of which is an amplification of the rRNA-tRNA part of the larger. We propose that the primary deletion has generated a signal in the larger DNA which can cause premature termination of replication at the deletion site, and subsequent circularization of the unfinished daughter molecule. Finally, the deleted part may contain a determinant for synthesis of a protein of 11 kDal. The function of this protein, which is not a subunit of the F₀ ATPase, is not yet known.Abbreviations (k)bp (kilo)basepairs - kDal kilodalton - mt mitochondrial     

Gastroenteropancreatic hormonal changes during exercise

Peripheral plasma concentrations of gastroenteropancreatic peptides were measured during a 3-h period of bicycle exercise at 40% of maximal oxygen uptake in six normal men. Marked increases (P < 0.02) were found in vasoactive intestinal polypeptide (VIP) [1.8 +/- 0.7 (rest) vs. 22.3 +/- 5.4 pmol x l-1 (mean +/- SE) (3 h)], secretin (0.5 +/- 0.5 vs. 11.1 +/- 2.7 pmol x l-1), pancreatic polypeptide (PP) (4.0 +/- 1.5 vs. 46.3 +/- 11.5 pmol x l-1), somatostatin (SRIF) (12.8 +/- 1.2 vs. 17.7 +/- 0.6 pmol x l-1), whereas no changes occurred in gastric inhibitory polypeptide (37.3 +/- 5.9 vs. 39.2 +/- 9.8 pmol x l-1). Immunoreactive insulin and C-peptide decreased from 0.08 +/- 0.004 and 0.39 +/- 0.03 pmol x l-1, respectively, to 0.04 +/- 0.003 (P < 0.005) and 0.13 +/- 0.02 (P < 0.001). The significant decrease in C-peptide and in the C-peptide-to-insulin molar ratio indicate decreased insulin secretion and clearance, respectively, during exercise. Plasma glucose decreased [5.0 +/- 0.1 (rest) vs. 4.2 +/- 0.3 mmol.l-1 (3 h)] (P < 0.01). During 3 h of rest, none of the measured parameters had changed. The marked exercise-induced changes in plasma concentrations of PP, secretin, VIP, and SRIF are provocative. We know in detail neither the stimuli for the release of these peptides nor their physiological role during exercise.     

Phenotypic study of peripheral blood leucocytes in HTLV-I-infected individuals from Minas Gerais,Brazil

The human T-cell lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) associated with the HTLV-I is a well-defined clinical-pathological entity in which the virus and host immune responses contribute to the pathological mechanism. In this study, flow cytometric analysis of whole peripheral blood leucocytes (PBL) was performed to evaluate the immunological status of HTLV-I-infected individuals in an effort to better understand the role of the immune system in the development of HAM/TSP. We have evaluated three groups of infected patients including asymptomatic (AS = 18), ambulatory/oligosymptomatic (AM = 14) and hospitalized HAM/TSP individuals (HO = 42). Noninfected healthy blood donors were used for the control group (NI = 32). Our results demonstrated that the HO group presents an increased percentage of circulating T cells and a decreased percentage of B and natural killer (NK) cells, leading to the highest T/B-cell ratio in comparison with the other groups. Interestingly, while an increased percentage of activated CD4+HLA-DR+ T lymphocytes was observed in both AM and HO, only HO presented higher percentage of activated CD8+HLA-DR+ in combination with the highest CD18 surface expression. This was true for all cell populations analysed, including T lymphocytes, monocytes and neutrophils. Moreover, the HO group was distinguished by a dramatic decrease in the percentage of CD8+CD28+ lymphocytes. Taken together, these findings demonstrate a potent cellular immune activation response involving primarily CD8+ T cells that is concomitant with disease progression in HAM/TSP. We also show that an upregulation of CD18 expression, a hallmark for increased cell migratory potential, might play a critical role in the development/maintenance of HAM/TSP.     

The heat stable antigen (CD24) is not required for the generation of CD4+ effector and memory T cells by dendritic cells in vivo

Previous work has established that CD24 is a costimulatory molecule for T-cell clonal expansion. Studies using CD24 -/- mice demonstrated that CD24 plays a critical role in the CD28-independent immune response against virus and soluble antigens. The role of CD24 on dendritic cells (DCs) has not been reported. Here, we compare the CD24(+/+) and CD24(-/-) DCs in the induction of initial clonal expansion and elicitation of memory CD4(+) T cells in vivo. Our results demonstrate that the CD24 expressed on DCs is essential neither for the induction of initial T-cell clonal expansion nor for elicitation of memory activity of primed T cells in vivo.     

Acute Trypanosoma cruzi infection differentially affects CD3 and Thy-1 mediated T cell activation.

Monoclonal antibodies directed against the Thy-1 molecule or the CD3 complex were used to analyze the activation of T cells from mice acutely infected with Trypanosoma cruzi. When stimulated with G7, a mitogenic anti-Thy-1 monoclonal antibody, spleen cells from infected mice showed a markedly reduced or absent response that could not be restored by varying the culture time or the antibody concentration. However, cells from acutely infected animals proliferated to 145-2C11, an anti-CD3 monoclonal antibody. Flow cytometric analysis showed that the impaired response to G7 could not be attributed to a lack of expression of Thy-1 or CD3. Indeed, G7 seemed to deliver a positive signal to the cells since the proliferative response was completely restored by the addition of PMA. Moreover, purified T cells from infected mice responded to G7 in the presence of accessory cells from uninfected animals. These results suggest that a defective co-stimulatory cell function could be involved in the immunosuppression. In addition, our data present evidence against a generalized T cell anergy in the acute phase of the disease, since CD3-mediated activation was normal.     

The glycemic index of some foods common in Mexico

To investigate the increase of glycemia due to the ingestion of usual food in Mexico, portions with 50 g of carbohydrate form white corn tortilla, yellow corn tortilla, spaghetti, rice, potatoes, beans brown and black, nopal (prickle pear cactus) and peanuts, compared with white bread, were given to 21 healthy and 27 non-insulin-dependent diabetic subjects. Serum glucose and insulin were measured every 30 min for 180 min long. Glycemic index was obtained as: (area under curve of glucose with test food/area under curve of glucose with white bread) X 100. A corrected index was calculated subtracting the area corresponding to initial values. Insulin index was obtained similarly. Each sample was studied 14-18 times. Glycemic and insulin indexes of white and yellow corn tortilla, spaghetti, rice and potatoes were not different from bread (P greater than 0.05). Corrected glycemic indexes of brown beans (54 +/- 15, +/- SE) and black beans (43 +/- 17) were low (p less than 0.05), as well as corrected insulin indexes (69 +/- 11 and 64 +/- 10 respectively, (P less than 0.02). Peanuts had low glycemic (33 +/- 17, P less than 0.01), but normal insulin index. Nopal had very low glycemic and insulin indexes (10 +/- 17 and 10 +/- 16, P less than 0.0001). These data might be useful in prescribing diets for diabetic subjects.