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Biomedical subjects

M Costa

Publications and source records attributed to M Costa.

At least 523 records · Page 29Linked to original sources
PubMed1981

Substance P immunoreactive sensory nerves supply the rat iris and cornea.

The presence, distribution and origin of substance P immunoreactive axons in the rat iris and cornea were investigated in whole mount preparations. A dense network of substance P immunoreactive axons was found throughout the iris but not in the ciliary body. In the cornea, substance P immunoreactive axons were found in the substantia propria, in the subepithelial layer and in the corneal epithelium. Following electrocoagulation of the ophthalmic nerve, most of the substance P immunoreactive axons in the iris and cornea disappeared. No changes in the substance P immunoreactive axons occurred after removal of the superior cervical ganglion. It is concluded that the iris and the cornea are supplied by sensory nerves containing substance P immunoreactivity.

Animals↗
PubMed1981

Phosphorylation of nuclear and DNA-binding proteins in proliferating and quiescent mammalian cells.

The dependence of cell proliferation on nuclear protein phosphorylation was studied with exponential-phase and stationary-phase cultures of Chinese-hamster ovary cells. Nuclear proteins were fractionated, according to their DNA-binding affinities, by using sequential extractions of isolated nuclei with increasing concentrations of NaCl. When viable whole cells were labelled with H332PO4, phosphorylation of nuclear proteins was found to be lower in quiescent cells than in proliferating cells. Phosphorylation of nuclear proteins soluble in 0.30M-NaCl (less than 50% of these proteins bind to DNA) was greater than for those proteins soluble in higher salt concentrations (80-100% of these proteins bind to DNA). Cyclic AMP enhanced the phosphorylation of nuclear proteins soluble in 0.3 m-NaCl by 40-50%, and this stimulation was independent of cell growth. Cyclic AMP also increased the phosphorylation of nuclear proteins soluble in 0.6M-NaCl and 2.0M-NaCl by 40-50% in exponential-phase cultures, but not in stationary-phase cultures. Several examples of specific phosphorylation in response to cyclic AMP were observed, including a 35000-mol.wt. protein in the 0.30 M-NaCl-soluble fraction and several proteins larger than 100000 molecular weight within this fraction. A major peptide of molecular weight approx. 31000 extracted with 0.6M-NaCl was also phosphorylated. Its phosphorylation was independent of cyclic AMP in exponential-phase cultures, and it was not phosphorylated in plateau-phase cells. These changes in cell-growth-dependent phosphorylation occurred in the absence of any apparent qualitative changes in the nuclear protein molecular-weight distributions. These data demonstrate that (1) phosphorylation of nuclear proteins is dependent on the culture's proliferative status, (2) both cyclic AMP-dependent and cyclic AMP-independent specific phosphorylation occurs, and (3) the cyclic AMP-dependent growth-independent phosphorylation that occurs does not appear to be a modification of DNA-binding proteins, whereas the cyclic AMP-dependent growth-dependent phosphorylation does involve modification of DNA binding proteins.

Animals↗
PubMed1981

Projection of ventrolateral medullary (A1) catecholamine neurons toward nucleus tractus solitarii.

The distribution and interconnections of brainstem catecholamine cell groups thought to be important in cardiovascular control were studied using histochemical and ultrastructural techniques in the rabbit. Lesions and microinjections of horseradish peroxidase (HRP) were made in the nucleus tractus solitarii in the dorsomedial medulla, and in the ventrolateral medulla. After lesions of the dorsomedial medulla the fluorescence intensity of the A1-group of catecholamine neurons was increased, and swollen axons could be seen coursing from the ventrolateral medulla toward the lesions on the same side, but not the opposite side. Most of these axons ran in a band about 2 mm in width, centered at the level of the obex. Electron microscopically, specific cells, identified as A1-catecholamine neurons, showed evidence of chromatolysis after the dorsomedial lesions. Following injection of HRP into the nucleus tractus solitarii. A1-catecholamine cells in the ventrolateral medulla on the same side contained the reaction product. Lesions of the ventrolateral medulla did not produce evidence of a reciprocal projection of A2-catecholamine neurons toward the ventrolateral medulla. Thus axons of the A1-group of catecholamine neurons in the ventrolateral medulla project toward the ipsilateral nucleus tractus solitarii in a relatively compact band at the level of the obex. On the other hand, the A2-group of catecholamine neurons in the dorsomedial medulla does not appear to send projections toward the A1-group.

Animals↗
PubMed1981

The fine structure of the submucous plexus of the guinea-pig ileum. I. The ganglia, neurons, Schwann cells and neuropil.

A fine structural study was made of the ganglia, neurons, Schwann cells and neuropil of the submucous plexus of the guinea-pig ileum. The arrangement of the plexus as seen by light microscopy is briefly described. Submucous ganglia are small, containing an average of eight neurons per ganglion (compared with 43 in myenteric ganglia) and are connected with each other by fine nerve strands. The cell bodies of neurons and Schwann cells and a neuropil consisting of neuronal and Schwann cell processes from the ganglia. No other cell types or blood vessels are found within the ganglia. Ganglia are surrounded by a continuous basal lamina but lack a well-defined connective tissue investment. The glial investment of neurons is incomplete: many neurons lie directly beneath the basal lamina with no intervening Schwann cell processes, and the plasma membranes of adjacent neurons are often directly apposed over large areas. Other areas of apposition occur between the cell bodies and processes of neurons and Schwann cells. Desmosome-like membrane specializations may be seen between neurons and other neurons or Schwann cells. Submucous neurons could not be categorized according to size, shape, organelle content or types of processes. Processes emerging from nerve-cell bodies were placed into four broad categories on the basis of shape and microtubule content. Many bundles of closely apposed small nerve profiles lacking intervening Schwann processes are found in the neuropil in addition to a large number of vesiculated varicosities, some of which are directly apposed to the plasma membranes of nerve-cell bodies. A small proportion of vesiculated profiles from synapses with nerve cell bodies, their processes and profiles in the neuropil. From their structure, submucous neurons appear to form a more homogeneous population than myenteric neurons. Because of their incomplete investment they are more likely to be freely exposed to substances diffusing in the extraganglionic tissue than are neurons of sympathetic ganglia.

Animals↗
PubMed1981

The fine structure of the submucous plexus of the guinea-pig ileum. II. Description and analysis of vesiculated nerve profiles.

A fine structural study has been made of the vesiculated nerve profiles of the submucous plexus of both normally innervated and extrinsically denervated segments of guinea-pig ileum. Two types of nerve profiles could be readily distinguished by their vesicular content after conventional fixation. The first type, comprising 5% of all intrinsic profiles, consisted of predominantly small vesicles containing electron dense material which usually formed a ring around the inner face of the vesicular membrane but sometimes partially or completely filled the vesicle. These profiles, termed ring-vesicle-containing profiles, remained after extrinsic denervation, and their vesicular content did not change following injection of reserpine or 5-hydroxydopamine. Thus ring-vesicle-containing profiles are not adrenergic. Profiles which were positive for the uranaffin method were similar in morphology and frequency of occurrence to ring-vesicle-containing profiles, although it is not possible to say that they are the same. The second type of profile, comprising 95% of all intrinsic profiles, contained varying proportions of large granular and small clear vesicles. These heterogeneous profiles were present in both normally innervated and extrinsically denervated tissue. Their vesicular content did not change following injection of reserpine, however, some profiles of this type in normally innervated, but not in extrinsically denervated, intestine contained electron dense deposits after injection of 5-hydroxydopamine. This means that noradrenergic profiles are a subpopulation of the heterogeneous profiles in normally innervated tissue. Analysis of intrinsic heterogeneous profiles showed that the proportion and packing density of large granular vesicles formed continuous distributions which did not provide any basis for further subdivision of this type of profile. Ring-vesicle-containing and heterogeneous profiles often formed synapses with neuronal cell bodies and processes. Two rarer types of profiles were also seen. The first type contained mainly small flattened vesicles which took up 5-hydroxydopamine and was not present in extrinsically denervated tissue. This type, like the group described above, is considered to be noradrenergic. The second rare type contained large numbers of lysosome-like dense bodies and vesicles of different sizes and content and was seen in both normally innervated and denervated tissue. This type probably represents spontaneously degenerating nerve profiles.

Animals↗
PubMed1981

Branching patterns and projections of enteric neurons containing different putative transmitters.

Methods have been developed for the microsurgical interruption of nerve pathways in the wall of the intestine and for the immunohistochemical localization of antigens in whole mounts. These methods have made it possible to determine accurately the distributions and projections of neurons containing different putative transmitters. In this week neurons with substance P, somatostatin and 5-hydroxytryptamine-like immunoreactivity are described. Projections of noradrenergic neurons are also demonstrated. Each substance is associated with a unique set of neurons having precise projections within the intestine.

Animals↗
PubMed1981

Independence of REM density from other REM sleep parameters before and after REM deprivation.

The aim of our work was to investigate the interrelationships among rapid eye movement (REM) percent, latency, and density and their variations during different nights in an adequate REM-deprivation study. Twenty male subjects slept for 7 consecutive nights in the laboratory: 2 adaptation, 1 base line, 2 deprivation, and 2 recovery. Wilcoxon's test showed a significant increase in REM percent and a decrease in REM latency from base line to recovery nights. REM density on the contrary showed a decrease, possibly due to dilution caused by increased time spent in stage REM. Eye movement activity appears to remain stable after REM deprivation. Furthermore, REM density showed no correlation with other REM sleep measures, while its highly significant correlations across nights make it a reliable and stable descriptor of an individual's sleep pattern. The independence of eye movement activity with respect to other parameters of REM sleep is suggested.

Adolescent↗
PubMed1981

Multiple forms of bovine liver rhodanese.

The heterogeneity of crystalline rhodanese from bovine liver has been studied. The enzyme was separated by preparative disc electrophoresis into four stable forms designated I(3.5%), II(17.0%), III(62.0%) and IV(17.5%). All these components have the same molecular weight of about 35,000 both in native and denaturing conditions. No differences in the primary structure have been detected in amino acid composition and by peptide mapping. Although the isolated forms show similar values of specific activity, except form I, their content of transferable sulfur is different. The enzyme-sulfur complexes of the four components have slightly different circular dichroism spectra in the near ultraviolet, though their spectra in the sulfur-free state are identical. We conclude that these forms are conformational isomers originated from form IV which is predominant in the mitochondrial extract of liver cells.

Animals↗
PubMed1981

Residual catecholamines in extrinsically denervated guinea-pig ileum.

1. Concentrations of noradrenaline, adrenaline and dopamine were measured in the submucosa and myenteric plexus of innervated and extrinsically denervated guinea-pig ileum using a sensitive radioisotope enzymatic assay for catecholamines. 2. Subcellular fractionation studies indicated that the microsomal fraction obtained from both layers of the normal ileum was greatly enriched with noradrenaline compared to the total homogenate. Low levels of adrenaline and dopamine were also detected in both layers of the ileum. 3. After extrinsic denervation or pretreatment with reserpine, noradrenaline was reduced to less than 3% and could no longer be visualized histochemically. Small proportions of the adrenaline and dopamine also disappeared after extrinsic denervation. 4. The residual amounts of noradrenaline, adrenaline and dopamine present after extrinsic denervation were not sensitive to reserpine and were not concentrated in microsomal fractions suggesting that these amines are not stored as neurotransmitters in intrinsic neurons of the intestine.

Animals↗
PubMed1981

Importance of new catecholamine pathways in control of blood pressure.

The first comprehensive maps of central catecholamine pathways referred to both noradrenaline and dopamine neurons. They described the catecholamine neurons as having their cell bodies in the brainstem with spinal axons descending mainly from two medullary cell groups (A1 and A2) and with ascending axons arising mainly from more rostral groups (A3-A13). More recent work utilising immunohistochemistry has established the presence of adrenaline neurons in the brain, in two medullary cell groups (C1 and C2). While these were originally thought to lie within the rostral part of the A1 and A2 cell groups, work from this laboratory has now established that the adrenaline neurons are topographically distinct from the A1 and A2 cells, do not fluoresce with standard methods, and are collected into three groups, the third group (C3) lying in the midline of the rostral medulla. Work in this laboratory using a combination of histochemical fluorescence and retrograde transport of horseradish peroxidase has demonstrated that existence of a descending dopaminergic projection from the hypothalamus to the spinal cord, indicating that descending pathways can arise well above the medulla. Recent studies on the A1 neurons have established the presence of projections from the A1 cells to the median eminence of the hypothalamus and towards the nucleus tractus solitarius in the medulla. Other experiments have demonstrated that most of the descending catecholamine axons do not arise from the A1 and A2 cell groups in the caudal medulla, but higher up in the brainstem especially from the A5 and A7 cell groups. These new descriptions of central catecholamine neurons will necessarily modify the interpretation of many experiments on the central regulation of arterial pressure.

Animals↗
PubMed1981

Evidence for and significance of the projection of VIP neurons from the myenteric plexus to the taenia coli in the guinea pig.

Immunohistochemical studies of the distribution of vasoactive intestinal polypeptide were made in the cecum from normal guinea pigs and from guinea pigs after lesions of the cecal wall had been made. These experiments were designed to determine the origin of the vasoactive intestinal polypeptide axons which supply the taenia of the cecum in order to ascertain whether the projections of the vasoactive intestinal polypeptide neurons were consistent with VIP being contained in enteric inhibitory neurons. Vasoactive intestinal peptide was found in nerve cell bodies of both the myenteric and submucous taenia and the myenteric plexus the vasoactive intestinal polypeptide fibers in the taenia disappeared, but there was no effect on these fibers if the taenia was separated from the submucous plexus or surrounding muscle while leaving connections with the myenteric plexus intact. Retrograde degenerative signs were seen in VIP fibers and nerve cell bodies of the myenteric plexus after removal of the taenia. In conclusion, VIP is contained in neurons that have the same projections as the enteric inhibitory neurons from the myenteric plexus to the taenia of the cecum.

Animals↗
PubMed1981

Phagocytosis, cellular distribution, and carcinogenic activity of particulate nickel compounds in tissue culture.

The uptake, toxicity, and morphological transformation efficacy of various water-insoluble nickel compounds were examined in tissue culture. Particles (2.2 to 4.8 micrometers) of crystalline Ni3S2, crystalline NiS, and crystalline Ni3Se2 were actively phagocytized by cultured cells as determined by light and electron microscopy. However, particles of similar size consisting of amorphous NiS and metallic nickel were not significantly phagocytized despite long exposure periods to high concentrations. X-ray fluorescence spectrometry measurements of metal levels in subcellular fractions isolated from cells treated with crystalline Ni3S2, crystalline NiS, or amorphous NiS confirmed that amorphous NiS did not significantly enter the cells, either as a phagocytized particle or in a solubilized form, while the other two crystalline nickel compounds were actively taken up. Cells treated with amorphous NiS contained nickel levels generally less than 10% of the nickel levels in whole cells and in cytoplasmic fractions, or nuclear fractions of cells treated with either crystalline NiS or crystalline Ni3S2. The phagocytized nickel particles were always observed in the cytoplasm with light and electron microscopy, but substantial nickel levels were measured in the nuclear fraction. These and other results suggest that the nickel particles were broken down in the cytoplasm to a size range no longer detectable with the electron microscope and then subsequently entered the nucleus. Control experiments suggest that at least 20% of the nickel measured in the nucleus isolated from cells treated with Ni3S2 is no longer part of a sedimentable particle with the same particle size and/or solubility properties of the parent compound. A substantial portion of the nickel associated with the nuclear fraction coprecipitated with trichloroacetic acid-insoluble material, suggesting that nickel binds strongly to cellular macromolecules. The phagocytized particulate nickel compounds were more cytotoxic as determined by reduction of cell-plating efficiency and induced more morphological transformations in the Syrian hamster embryo cell transformation assay than did the particulate nickel compounds which were not phagocytized. Manganese dust inhibited the morphological transformation induced by Ni3S2 and also reduced the phagocytosis of Ni3S2 particles.

Animals↗