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Biomedical subjects

M Costa

Publications and source records attributed to M Costa.

At least 325 records · Page 18Linked to original sources
PubMed1991

Protective effect of vitamin E against chromosomal aberrations and mutation induced by sodium chromate in Chinese hamster V79 cells.

The effect of vitamin E on chromosomal aberrations and mutation caused by Na2CrO4 was investigated in Chinese hamster V79 cells. Pretreatment with 25 microM alpha-tocopherol succinate (vitamin E) for 24 h prior to chromate exposure (2.5-5 microM) resulted in a decrease of metal-induced chromosomal aberrations. Na2CrO4 (2.5-7.5 microM) induced mutations at the HGPRT locus, but only within a very limited concentration range. This mutagenic response could also be suppressed by pretreatment with vitamin E. These results suggest that vitamin E can protect cells from the clastogenic and mutagenic action of chromate compounds, possibly through its ability to scavenge chromium(V) and/or free radicals.

Animals↗
PubMed1991

Cardiotoxicity and cytotoxicity of the anthracycline analog 4'-deoxy-4'-iodo-doxorubicin.

The cardiotoxicity and cytotoxicity of the novel doxorubicin (DXR) derivative 4'-deoxy-4'-iodo-DXR were evaluated and compared to DXR. A single dose of DXR 10 mg/kg i.v. in anesthetized rats induced a significant widening of S alpha T segment of the electrocardiogram, an increase in both mean arterial blood pressure and heart rate and a fall in systemic arterial dP/dtmax, while 4'-deoxy-4'-iodo-DXR 4 mg/kg i.v. induced a significant widening of S alpha T segment and an increase in mean arterial blood pressure. A chronic cardiomyopathy was induced over a 6-week period by three injections of DXR 3 mg/kg per week i.v. and was characterized by a progressive enlargement of S alpha T segment, a flattening of T wave, the occurrence of arrhythmias and histological alterations of myocardium. The contractile responses to adrenaline of isolated hearts from DXR-treated animals were significantly reduced compared to controls. 4'-Deoxy-4'-iodo-DXR (1.2 mg/kg per week three times) induced minor ECG alterations and sporadic episodes of arrhythmias. The contractile responses of isolated hearts were not significantly different from those of controls and microscopic examination of hearts revealed only minor changes. Cytotoxicity in vitro was evaluated by the colony formation assay; based on IC50, 4'-deoxy-4'-iodo-DXR was up to six times more cytotoxic than DXR on four human cancer cell lines. These results suggest that 4'-deoxy-4'-iodo-DXR is significantly less cardiotoxic and more cytotoxic than DXR.

Animals↗
PubMed1991

Identification and immunohistochemistry of cholinergic and non-cholinergic circular muscle motor neurons in the guinea-pig small intestine.

Motor neurons which innervate the circular muscle layer of the guinea-pig small intestine were retrogradely labelled, in vitro, with the carbocyanine dye, DiI, applied to the deep muscular plexus. By combining retrograde tracing and immunohistochemistry, the chemical coding of motor neurons was investigated. Five classes of neuron could be distinguished on the basis of the co-localization of immunoreactivity for the different antigens; the five classes were also characterized by different lengths and polarities of their axonal projections and by their cell body shapes. Two classes with local or orally directed axons were immunoreactive for choline acetyltransferase and substance P and are likely to be cholinergic excitatory motor neurons. Two other classes had anally directed axons; they were immunoreactive for vasoactive intestinal polypeptide and are likely to be inhibitory motor neurons. A small proportion of neurons with short projections to the circular muscle were immunoreactive for neither substance P nor for vasoactive intestinal polypeptide, but are likely to be cholinergic. The morphological and histochemical identification of excitatory and inhibitory motor neurons provides a neuroanatomical basis for the final motor pathways involved in the polarized reflex motor activity of the gut.

Animals↗
PubMed1991

Immunohistochemical identification of cholinergic neurons in the myenteric plexus of guinea-pig small intestine.

It is well established that acetylcholine is a neurotransmitter at several distinct sites in the mammalian enteric nervous system. However, identification of the cholinergic neurons has not been possible due to an inability to selectively label enteric cholinergic neurons. In the present study an immunohistochemical method has been developed to localize choline acetyltransferase, the synthetic enzyme for acetylcholine, in order that cholinergic neurons can be visualized. The morphology, neurochemical coding and projections of cholinergic neurons in the guinea-pig small intestine were determined using double-labelling immunohistochemistry. These experiments have revealed that many myenteric neurons are cholinergic and that they can be distinguished by their specific combinations of immunoreactivity for neurochemicals such as calretinin, neurofilament protein triplet, substance P, enkephalin, somatostatin, 5-hydroxytryptamine, vasoactive intestinal peptide and calbindin. On the basis of their previously described projections, functional roles could be attributed to each of these populations. The identified cholinergic neurons are: motorneurons to the longitudinal muscle (choline acetyltransferase/calretinin); motorneurons to the circular muscle (choline acetyltransferase/neurofilament triplet protein/substance P, choline acetyltransferase/substance P and choline acetyltransferase alone); orally directed interneurons in the myenteric plexus (choline acetyltransferase/calretinin/enkephalin); anally directed interneurons in the myenteric plexus (choline acetyltransferase/somatostatin, choline acetyltransferase/5-hydroxytryptamine, choline acetyltransferase/vasoactive intestinal peptide); secretomotor neurons to the mucosa (choline acetyltransferase/somatostatin); and sensory neurons mediating myenteric reflexes (choline acetyltransferase/calbindin). This information provides a unique opportunity to identify functionally distinct populations of cholinergic neurons and will be of value in the interpretation of physiological and pharmacological studies of enteric neuronal circuitry.

Animals↗
PubMed1991

Protein phosphorylation in guinea-pig myenteric ganglia and brain: presence of calmodulin kinase II. protein kinase C and cyclic AMP kinase and characterization of major phosphoproteins.

The aim of this study was to demonstrate the presence of calmodulin-stimulated protein kinase II, protein kinase C, and cyclic AMP-stimulated protein kinase in isolated myenteric ganglia and to characterize the major ganglia phosphoproteins using biochemical and immunochemical techniques. Ganglia from the small intestine of guinea-pigs were isolated, disrupted by sonication in Triton X-100, and phosphorylated. The phosphoprotein patterns obtained were compared with those of synaptosomes from guinea-pig and rat cerebral cortex. Myenteric ganglia were as rich in protein kinase C and cyclic AMP-stimulated protein kinase as brain tissue, but the level of calmodulin-stimulated protein kinase II was relatively lower. The alpha subunit of calmodulin-stimulated protein kinase II was detected by immunoblotting and the beta subunit by autophosphorylation. The ratio of beta to alpha subunit was considerably higher in ganglia than in brain and ganglia beta subunit had a lower apparent molecular weight than the brain enzyme. A number of neuronal phosphoproteins were found in ganglia including the 87,000 mol. wt phosphoprotein, synapsins 1a and 1b, and proteins IIIa and IIIb. A phosphoprotein of 48,000 mol. wt had many of the characteristics of the B-50 protein but was not the same. In addition, a number of other phosphoproteins not previously identified in neurons were found in ganglia including those with apparent molecular weights of 60,000 and 58,000 that were the major calmodulin kinase substrates. The guinea-pig enteric nervous system has been extensively studied but, unlike other parts of the mammalian nervous system, little is known about the intracellular mechanisms underlying its functions. A technique for isolating myenteric ganglia is now available and we have used this preparation to characterize the major protein kinase and phosphoproteins present in this tissue. The results obtained will allow the phosphorylation of the various proteins to be investigated after physiological or pharmacological manipulation of myenteric ganglia in situ and in vivo.

Animals↗
PubMed1991

Complexing of actin and other nuclear proteins to DNA by cis-diamminedichloroplatinum(II) and chromium compounds.

Actin was found to be the major protein crosslinked to the DNA of intact Chinese hamster ovary cells that were treated with either potassium chromate (hexavalent) or cis-diamminedichloroplatinum(II) (cis-platinum). This protein was identified as actin by its mol. wt (45 kd), its isoelectric point (pI = 5.4), positive reactivity with an actin antibody, and by protease mapping. Additionally, a purified actin standard migrated to the same location in a two-dimensional gel system as p45. Actin comprised approximately 20% of the protein component in chromate-induced DNA-protein crosslinks. In addition, to actin, several other major proteins (e.g. 53 kd, pI = 5.2, 50 kd, pI = 9) were crosslinked to DNA following exposure to cis-platinum or chromate. These proteins were abundant in the nuclear matrix fraction. Hexavalent chromate is the toxicologically active form because it is readily taken up into cells by an anion transport system. In contrast, trivalent chromium is considerably less toxic because it cannot enter the cell; however, most of the hexavalent form is eventually reduced to the trivalent form inside the cell. Previous studies have suggested that the trivalent form of chromium participates in complexing DNA with proteins. DNA-protein crosslinks were formed in isolated nuclei or in mixtures of purified DNA and protein incubated with trivalent chromium. However, the formation of these complexes required at least 16 h of incubation to exchange the parent compound ligands. Hexavalent chromate did not form these complexes in vitro under similar conditions. Incubation of trivalent chromium with purified actin and DNA resulted in DNA-actin crosslinks as detected by an electrophoretic mobility different from that of either free actin or DNA when the complex was transferred from a gel to nitrocellulose and stained for protein. These studies describe a new technique for detecting DNA-protein complexes and demonstrate that actin-DNA structures in intact cells create sites that selectively react with metal DNA-protein crosslinking agents.

Actins↗
PubMed1991

Alteration in restriction enzyme digestion patterns detects DNA--protein complexes induced by chromate.

DNA--protein complexes isolated from CHO cells treated with at least 10-30 microM potassium chromate exhibited an alteration in the degradation of the DNA by restriction enzymes compared to DNA--protein complexes isolated from untreated cells. This alteration in restriction enzyme digestion of DNA--protein complexes induced by chromate was shown to depend upon the binding of trivalent chromium to the DNA and upon the protein associated with the DNA, since both EDTA pretreatment and protease K reversed the inhibition of restriction enzyme degradation of the DNA. The inhibition of restriction enzyme degradation of DNA--protein complexes may be utilized as an indirect way to detect DNA--protein complexing induced by chromate and perhaps other agents.

Animals↗
PubMed1991

Alveolar gas composition and exchange during deep breath-hold diving and dry breath holds in elite divers.

End tidal O2 and CO2 (PETCO2) pressures, expired volume, blood lactate concentration ([Lab]), and arterial blood O2 saturation [dry breath holds (BHs) only] were assessed in three elite breath-hold divers (ED) before and after deep dives and BH and in nine control subjects (C; BH only). After the dives (depth 40-70 m, duration 88-151 s), end-tidal O2 pressure decreased from approximately 140 Torr to a minimum of 30.6 Torr, PETCO2 increased from approximately 25 Torr to a maximum of 47.0 Torr, and expired volume (BTPS) ranged from 1.32 to 2.86 liters. Pulmonary O2 exchange was 455-1,006 ml. CO2 output approached zero. [Lab] increased from approximately 1.2 mM to at most 6.46 mM. Estimated power output during dives was 513-929 ml O2/min, i.e. approximately 20-30% of maximal O2 consumption. During BH, alveolar PO2 decreased from approximately 130 to less than 30 Torr in ED and from 125 to 45 Torr in C. PETCO2 increased from approximately 30 to approximately 50 Torr in both ED and C. Contrary to C, pulmonary O2 exchange in ED was less than resting O2 consumption, whereas CO2 output approached zero in both groups. [Lab] was unchanged. Arterial blood O2 saturation decreased more in ED than in C. ED are characterized by increased anaerobic metabolism likely due to the existence of a diving reflex.

Adult↗
PubMed1991

Gastrulation in Drosophila: the formation of the ventral furrow and posterior midgut invaginations.

The ventral furrow and posterior midgut invaginations bring mesodermal and endodermal precursor cells into the interior of the Drosophila embryo during gastrulation. Both invaginations proceed through a similar sequence of rapid cell shape changes, which include apical flattening, constriction of the apical diameter, cell elongation and subsequent shortening. Based on the time course of apical constriction in the ventral furrow and posterior midgut, we identify two phases in this process: first, a slow stochastic phase in which some individual cells begin to constrict and, second, a rapid phase in which the remaining unconstricted cells constrict. Mutations in the concertina or folded gastrulation genes appear to block the transition to the second phase in both the ventral furrow and the posterior midgut invaginations.

Animals↗
PubMed1991

DNA-protein complexes induced by chromate and other carcinogens.

DNA-protein complexes induced in intact Chinese hamster ovary cells by chromate have been isolated, analyzed, and compared with those induced by cis-platinum, ultraviolet light, and formaldehyde. Actin has been identified as one of the major proteins complexed to DNA by chromate based upon its molecular weight, isoelectric point, positive reaction with an actin polyclonal antibody, and proteolytic mapping. Chromate and cis-platinum both complex proteins of similar molecular weight and isoelectric points, and these complexes can be disrupted by chelating agents and sulfhydryl reducing agents, suggesting that the metal itself is participating in binding rather than having a catalytic or indirect role (i.e., oxygen radicals). In contrast, formaldehyde complexed histones to the DNA, and these complexes were not disrupted by chelating or reducing agents. An antiserum raised to chromate-induced DNA-protein complexes reacted primarily with 97,000 kDa protein that did not silver stain. Slot blots, as well as Western blots, were used to detect formation of p97 DNA crosslinks. This protein was complexed to the DNA by all four agents studied.

Animals↗
PubMed1991

Langerhans' cell histiocytosis: a case report.

The authors describe the morphologic features of Langerhans' cell histiocytosis and discuss the main prognostic factors which divide patients into two groups requiring different treatment. They then describe a case of multifocal Langerhans' cell histiocytosis due to pelvic osteolysis and early diabetes insipidus, emphasizing the effectiveness of the combination of surgery and chemotherapy and the rapid reparative new bone formation.

Child↗
PubMed1991

Electrocardiogram during deep breath-hold dives by elite divers.

A portable ECG recorder was used during breath-hold dives at sea by 3 elite divers to 65 and 45 m. ECG was also recorded during nonimmersed maximal breath holds in the divers and 8 control subjects. Heart rate in the dives decreased rapidly to 20-24 beats.min(-1). During the surface experiments in the divers, bradycardia was much slower in onset, reaching 28-36 beats.min(-1) at the end of the breath holds. The divers showed a more consistent bradycardial response than the controls. The difference in temporal pattern of bradycardia, in the dives and in the breath holds by the divers, may have been due to face immersion in cold water, chest compression, and/or redistribution of blood into the chest with concomitant stimulation of cardiac and other mechanoreceptors. Arrhythmias, mostly supraventricular and ventricular premature complexes, were observed coincidently with the lowest heart rates, presumably reflecting a high vagal tone. In addition, cardiac distention at depth might have made the heart more prone to arrhythmias, while in the surface breath holds hypoxia might have accounted for a similar effect.

Adult↗
PubMed1990

Identification of enteric motor neurones which innervate the circular muscle of the guinea pig small intestine.

Retrograde transport of the carbocyanine dye DiI from the deep muscular plexus of guinea pig small intestine was carried out in organotypic culture to identify circular muscle motor neurones. Seventy-four % of DiI labelled neurones were located within 4 rows of myenteric ganglia oral or anal to the application site. Some motor neurones had axons extending up to 37 rows of myenteric ganglia in the anal direction, or long axons travelling up to 18 rows of ganglia in the oral direction. Ninety four percent of the filled cells had Dogiel type I soma morphology; of these, neurones oral to the application site consistently had lamellar dendrites and were readily distinguishable from those located anally which had short filamentous dendrites. The methods described in this study make it possible to distinguish circular muscle motor neurones from other cell types in the myenteric plexus for the first time.

Animals↗
PubMed1990

Cytology of pseudomyxoma peritonei: report of two cases arising from appendiceal cystadenomas.

Pseudomyxoma peritonei is the clinical term for the diffuse deposition of mucus within the peritoneal cavity secondary to a mucinous tumor of the ovary or appendix. This gelatinous ascites, or "jelly-belly," may result in death from loss of intestinal function and intestinal obstruction caused by peritoneal implants rather than visceral invasion. Microscopic evaluation of peritoneal fluid is frequently an initial diagnostic test; however, in a search of the recent literature we were surprised to find only one case report of the cytologic features. This prompted us to report the cytologic findings in the peritoneal fluid of two cases of pseudomyxoma peritonei arising from appendiceal mucinous cystadenomas.

Adult↗
PubMed1990

Analysis of DNA-protein complexes induced by chemical carcinogens.

DNA-protein complexes induced in intact cells by chromate have been isolated and compared with those formed by other agents such as cis-platinum. Actin has been identified as one of the major proteins that is complexed to the DNA by chromate based upon a number of criteria including, a molecular weight and isoelectric point identical to actin, positive reaction with actin polyclonal antibody, and proteolytic mapping. Chromate and cis-platinum both complex proteins of very similar molecular weight and isoelectric points and these complexes can be disrupted by exposure to chelating or reducing agents. These results suggest that the metal itself is participating in rather than catalyzing the formation of a DNA-protein complex. An antiserum which was raised to chromate-induced DNA-protein complexes reacted primarily with a 97,000 protein that could not be detected by silver staining. Western blots and slot blots were utilized to detect p97 DNA-protein complexes formed by cis-platinum, UV, formaldehyde, and chromate. Other work in this area, involving studying whether DNA-protein complexes are formed in actively transcribed DNA compared with genetically inactive DNA, is discussed. Methods to detect DNA-protein complexes, the stability and repair of these lesions, and characterization of DNA-protein complexes are reviewed. Nuclear matrix proteins have been identified as a major substrate for the formation of DNA-protein complexes and these findings are also reviewed.

Actins↗
PubMed1990

Inhibitory prejunctional muscarinic receptors at sympathetic nerves do not operate through a cyclic AMP dependent pathway.

In mouse atria previously incubated with [3H]-noradrenaline, carbachol (1.0 mumo1/l) significantly inhibited the fractional stimulation-induced (S-I) outflow of radioactivity. The inhibitory effect of carbachol was greater in the presence of the alpha-adrenoceptor antagonist phentolamine (1.0 mumol/l), which by itself significantly increased the S-I outflow of radioactivity. In both cases the inhibitory effect of carbachol was blocked by atropine (0.3 mumol/l), suggesting that the effect was mediated through muscarinic receptors. 8-Bromo cyclic AMP (270 mumol/l) in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX, 100 mumol/l), was used to maximally enhance the S-I outflow of radioactivity through the cyclic AMP mechanism. The inhibitory effect of carbachol either in the presence or in the absence of phentolamine, was not reduced in the presence of 8-bromo cyclic AMP and IBMX. Similar results with carbachol in the presence of 8-bromo cyclic AMP and IBMX were also found in rat right atrial strips which had been incubated with [3H]-noradrenaline. These results suggest that the effects through inhibitory prejunctional muscarinic receptors are not mediated by cyclic AMP. The protein kinase inhibitor, staurosporine (0.1 mumol/l), significantly blocked the enhancing effects of 8-bromo cyclic AMP (270 mumol/l) plus IBMX (100 mumol/l) on the S-I outflow of radioactivity from rat atrial strips. The inhibitory effect of carbachol (1.0 mumol/l) however, was not reduced in the presence of staurosporine, suggesting that protein kinases affected by staurosporine (protein kinase A, protein kinase C) are not involved in the post-receptor mechanism for inhibitory prejunctional muscarinic receptors. This finding further rules out the involvement of cyclic AMP in muscarinic inhibition. The inhibitory effect of carbachol either by itself or in the presence of phentolamine, was not reduced in atria from mice that had been pretreated with pertussis toxin (1.5 or 3.0 micrograms). Furthermore, in rat atrial strips, the inhibitory effect of carbachol either in the presence or in the absence of phentolamine, was also not altered by pretreating the rats with pertussis toxin (8.4 micrograms). The results suggest that in both tissues the major mechanism for inhibition of noradrenaline release through muscarinic receptors does not involve a pertussis toxin sensitive G protein.

1-Methyl-3-isobutylxanthine↗
PubMed1990

A blotting method for monitoring the formation of chemically induced DNA-protein complexes.

The formation and identification of DNA-protein crosslinks are usually detected by filter binding assays such as alkaline elution. We describe a modified blotting method to selectively identify DNA-protein complexes (DPCs) formed in vitro by either Cr3+ ion or formaldehyde. This protocol allows DPC formation in vitro to be assayed with various chemical agents, requires minimal usage of radioactivity, and is performed in a shorter time frame than that commonly used to resolve DPCs from free proteins and unbound DNA.

Actins↗