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Biomedical subjects

A Villa

Publications and source records attributed to A Villa.

At least 253 records · Page 14Linked to original sources
PubMed1991

Heterogeneity of microsomal Ca2+ stores in chicken Purkinje neurons.

Chicken cerebellum microsomes were subfractionated on isopycnic, linear sucrose (15-50%) density gradients. The distribution of four markers of intracellular, rapidly-exchanging Ca2+ stores, i.e. the Ca2+ pump, the receptors for inositol 1,4,5-trisphosphate (IP3) and ryanodine (Ry), and calsequestrin (CS, an intralumenal, high capacity Ca2+ binding protein) was investigated biochemically and immunologically. In the cerebellum, high levels of these markers are expressed by one of the cell types, the Purkinje neuron. Heavy subfractions were enriched in both CS and Ry receptor, intermediate subfractions in the IP3 receptor, while the Ca2+ pump was present in both intermediate and heavy subfractions. Intact cells and pelleted subfractions were examined by conventional and immuno-electron microscopy (immunogold labeling of ultrathin cryosections with anti-CS and anti-IP3 receptor antibodies). Of the strongly CS-labeled, moderately dense-cored vacuoles (calciosomes) recently described in chicken Purkinje neurons only partly exhibited labeling for the IP3 receptor as well, and the rest appeared negative. The latter were enriched in a heavy subfraction of the gradient where Ry receptors were also concentrated, whereas the CS-rich vacuoles in an intermediate subfraction were almost always IP3 receptor-positive. The population of CS-rich calciosomes of chicken Purkinje neurons appears therefore to be molecularly heterogeneous, with a part responsive to IP3 and the rest possibly sensitive to Ry.

Animals↗
PubMed1991

Intracellular Ca2+ stores in chicken Purkinje neurons: differential distribution of the low affinity-high capacity Ca2+ binding protein, calsequestrin, of Ca2+ ATPase and of the ER lumenal protein, Bip.

To identify intracellular Ca2+ stores, we have mapped (by cryosection immunofluorescence and immunogold labeling) the distribution in the chicken cerebellar cortex of an essential component, the main low affinity-high capacity Ca2+ binding protein which in this tissue has been recently shown undistinguishable from muscle calsequestrin (Volpe, P., B. H. Alderson-Lang, L. Madeddu, E. Damiani, J. H. Collins, and A. Margreth. 1990. Neuron. 5:713-721). Appreciable levels of the protein were found exclusively within Purkinje neurons, distributed to the cell body, the axon, and the elaborate dendritic tree, with little labeling, however, of dendritic spines. At the EM level the protein displayed a dual localization: within the ER (rough- and smooth-surfaced cisternae, including the cisternal stacks recently shown [in the rat] to be highly enriched in receptors for inositol 1,4,5-triphosphate) and, over 10-fold more concentrated, within a population of moderately dense, membrane-bound small vacuoles and tubules, identified as calciosomes. These latter structures were widely distributed both in the cell body (approximately 1% of the cross-sectional area, particularly concentrated near the Golgi complex) and in the dendrites, up to the entrance of the spines. The distribution of calsequestrin was compared to those of another putative component of the Ca2+ stores, the membrane pump Ca2+ ATPase, and of the ER resident lumenal protein, Bip. Ca2+ ATPase was expressed by both calciosomes and regular ER cisternae, but excluded from cisternal stacks; Bip was abundant within the ER lumena (cisternae and stacks) and very low within calciosomes (average calsequestrin/Bip immunolabeling ratios were approximately 0.5 and 36.5 in the two types of structure, respectively). These results suggest that ER cisternal stacks do not represent independent Ca2+ stores, but operate coordinately with the adjacent, lumenally continuous ER cisternae. The ER and calciosomes could serve as rapidly exchanging Ca2+ stores, characterized however by different properties, in particular, by the greater Ca2+ accumulation potential of calciosomes. Hypotheses of calciosome biogenesis (directly from the ER or via the Golgi complex) are discussed.

Animals↗
PubMed1991

Natural anticoagulants in systemic lupus erythematosus. Deficiency of protein S bound to C4bp associates with recent history of venous thromboses, antiphospholipid antibodies, and the antiphospholipid syndrome.

The association of thrombosis with antiphospholipid antibodies (aPL) in patients with systemic lupus erythematosus (SLE) could be due to their interference with natural phospholipid dependent anticoagulant mechanisms. We studied antigenic protein C (APC), functional protein C (FPC), free protein S (FPS), protein S bound to C4 binding protein (C4bp-S), antithrombin III (ATIII), as well as IgG and IgM anticardiolipin antibodies (aCL) in 38 patients with SLE with a history of thromboses and 70 patients with SLE without such history. We found a high frequency of deficiencies of natural anticoagulants in both groups of patients with SLE but, because of patient selection, we could not determine the actual prevalence of these defects. Patients having had a venous thrombosis in the previous year had low C4bp-S more frequently than patients with older or no thromboses. When we divided our patients with SLE into those who had a definite, probable, questionable or no antiphospholipid syndrome (aPS) we found the frequency of C4bp-S deficiency to be significantly higher in those with definite aPS than in those without aPS. Intermediate proportions were found in patients with probable and questionable aPS. The levels of C4bp-S decreased as the levels of aCL, particularly IgG, increased. Stepwise discriminant analysis of natural anticoagulants selected deficiencies of C4bp-S and FPC with increased ATIII as a set of variables with highest predictive power for classification of patients with and without aPS. Thus, deficiencies of natural anticoagulants may occur frequently in patients with SLE.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

[High resolution tridimensional study of the blood vessels of the neck and the intracranial circulation with magnetic resonance angiography].

Magnetic Resonance Angiography (MRA) is a modern vascular imaging technique which allows the noninvasive and direct imaging of vessels. The authors aimed at evaluating the diagnostic accuracy of MRA in the study of pathologic conditions in the neck and intracranial vessels; spatial resolution of the technique was also investigated. Twenty-four healthy volunteers and 82 patients suffering from various diseases of the head and neck vessels were included in the study. First of all, MRA capabilities were investigated in visualizing normal vessels of both neck and intracranial circle. The diagnostic accuracy of the method was then evaluated in the study of vascular diseases, and the results compared with conventional/digital angiographic findings. The comparison demonstrated how stenoses and atherosclerotic plaques tend to be overestimated by MRA because of technical artifacts inherent to the technique itself, whereas vascular ulcerations and aneurysms are frequently underestimated. However, this data was steady and therefore evaluable--the exact knowledge of the artifacts making diagnosis reliable. The diagnostic and technical problems relative to the various vascular diseases are discussed. Finally, several hypotheses of diagnostic iter are suggested.

Angiography, Digital Subtraction↗
PubMed1991

Mass closure of the abdominal wound with delayed absorbable suture in surgery for gynecologic cancer.

There has been a resurgence of interest recently in the optimal method of closure of the midline abdominal wound. The focus has been on the high-risk patient in particular. The controversy centers on interrupted versus continuous fascial closure and the choice of suture material. For three years on a gynecologic cancer service, running mass closure with delayed absorbable suture (Polyglactin) was used. Two hundred fifty-six patients were evaluable for analysis. The minimum follow-up time was two years. There was no wound dehiscence. Fourteen patients (5.5%) developed incisional hernias. The mass closure technique using delayed absorbable suture was effective in very-high-risk patients.

Female↗
PubMed1990

Calreticulin is a candidate for a calsequestrin-like function in Ca2(+)-storage compartments (calciosomes) of liver and brain.

In a search for the non-muscle equivalent of calsequestrin (the low-affinity high-capacity Ca2(+)-binding protein responsible for Ca2+ storage within the terminal cisternae of the sarcoplasmic reticulum), acidic proteins were extracted from rat liver and brain microsomal preparations and purified by column chromatography. No calsequestrin was observed in these extracts, but the N-terminal amino acid sequence of the major Ca2(+)-binding protein of the liver microsomal fraction was determined and found to correspond to that of calreticulin. This protein was found to bind approx. 50 mol of Ca2+/mol of protein, with low affinity (average Kd approx. 1.0 mM). A monoclonal antibody, C6, raised against skeletal-muscle calsequestrin cross-reacted with calreticulin in SDS/PAGE immunoblots, but polyclonal antibodies reacted with native calreticulin only weakly, or not at all, after SDS denaturation. Immuno-gold decoration of liver ultrathin cryosections with affinity-purified antibodies against liver calreticulin revealed luminal labelling of vacuolar profiles indistinguishable from calciosomes, the subcellular structures previously identified by the use of anti-calsequestrin antibodies. We conclude that calreticulin is the Ca2(+)-binding protein segregated within the calciosome lumen, previously described as being calsequestrin-like. Because of its properties and intraluminal location, calreticulin might play a critical role in Ca2+ storage and release in non-muscle cells, similar to that played by calsequestrin in the muscle sarcoplasmic reticulum.

Amino Acid Sequence↗
PubMed1990

Redistribution of synaptophysin and synapsin I during alpha-latrotoxin-induced release of neurotransmitter at the neuromuscular junction.

The distribution of two synaptic vesicle-specific phosphoproteins, synaptophysin and synapsin I, during intense quantal secretion was studied by applying an immunogold labeling technique to ultrathin frozen sections. In nerve-muscle preparations treated for 1 h with a low dose of alpha-latrotoxin in the absence of extracellular Ca2+ (a condition under which nerve terminals are depleted of both quanta of neurotransmitter and synaptic vesicles), the immunolabeling for both proteins was distributed along the axolemma. These findings indicate that, in the presence of a block of endocytosis, exocytosis leads to the permanent incorporation of the synaptic vesicle membrane into the axolemma and suggest that, under this condition, at least some of the synapsin I molecules remain associated with the vesicle membrane after fusion. When the same dose of alpha-latrotoxin was applied in the presence of extracellular Ca2+, the immunoreactivity patterns resembled those obtained in resting preparations: immunogold particles were selectively associated with the membrane of synaptic vesicles, whereas the axolemma was virtually unlabeled. Under this condition an active recycling of both quanta of neurotransmitter and vesicles operates. These findings indicate that the retrieval of components of the synaptic vesicle membrane is an efficient process that does not involve extensive intermixing between molecular components of the vesicle and plasma membrane, and show that synaptic vesicles that are rapidly recycling still have the bulk of synapsin I associated with their membrane.

Animals↗
PubMed1990

The inositol 1,4,5,-trisphosphate receptor in cerebellar Purkinje cells: quantitative immunogold labeling reveals concentration in an ER subcompartment.

The Ca2+ mobilization effect of inositol 1,4,5-trisphosphate, the second messenger generated via receptor-stimulated hydrolysis of phosphatidylinositol 4,5-bisphosphate, is mediated by binding to intracellular receptors, which are expressed in high concentration in cerebellar Purkinje cells. Partially conflicting previous reports localized the receptor to various subcellular structures: elements of ER, both rough and smooth-surfaced, the nuclear envelope, and even the plasma membrane. We have now reinvestigated the problem quantitatively by using cryosections of rat cerebellar tissue immunolabeled with polyclonal monospecific antibodies against the inositol 1,4,5-trisphosphate receptor. By immunofluorescence the receptor was detected only in Purkinje cells, whereas the other cells of the cerebellar cortex remained negative. In immunogold-decorated ultrathin cryosections of the Purkinje cell body, the receptor was concentrated in cisternal stacks (piles of up to 12 parallel cisternae separated by regularly spaced bridges, located both in the deep cytoplasm and beneath the plasma membrane; average density, greater than 5 particles/micron of membrane profile); in cisternal singlets and doublets adjacent to the plasma membrane (average density, approximately 2.5 particles/micron); and in other apparently smooth-surfaced vesicular and tubular profiles. Additional smooth-surfaced elements were unlabeled. Perinuclear and rough-surfaced ER cisternae were labeled much less by themselves (approximately 0.5 particles/micron, two- to threefold the background), but were often in direct membrane continuity with heavily labeled, smooth-surfaced tubules and cisternal stacks. Finally, mitochondria, Golgi cisternae, multivesicular bodies, and the plasma membrane were unlabeled. In dendrites, approximately half of the nonmitochondrial, membrane-bound structures (cisternae, tubules, and vesicles), as well as small cisternal stacks, were labeled. Dendritic spines always contained immunolabeled cisternae and vesicles. The dendritic plasma membrane, of both shaft and spines, was consistently unlabeled. These results identify a large, smooth-surfaced ER subcompartment that appears equipped to play a key role in the control of Ca2+ homeostasis: in particular, in the generation of [Ca2+]i transients triggered by activation of specific receptors, such as the quisqualate-preferring trans(+/-)-1-amino-1,3-cyclopentamedicarboxylic acid glutamatergic receptors, which are largely expressed by Purkinje cells.

Animals↗
PubMed1990

Signal requirements for activation of leukaemic T cells from a chronic lymphocytic leukaemia (T-CLL).

In order to define the signal requirements for leukaemic T cell activation, the proliferation and interleukin-2 (IL-2) production of peripheral lymphocytes from a patient with a HTLV-I-, CD4+, CD45RA+ CD45RO+ CD25- T-CLL were evaluated after the delivery of different stimuli. Unlike resting CD4+ normal T lymphocytes that can be activated only by a two-signal stimulation, T-CLL cells proliferated and released IL-2 in response to a pair of anti-CD2 monoclonal antibodies (MoAbs) or concanavalin A (Con A) in the absence of both accessory cells (AC) and phorbol myristate acetate (PMA). The two stimuli were also able to induce CD25 expression within 12-20 h on the majority of T-CLL cells. A response to anti-CD3 and anti-CD28 MoAbs was detected only in the presence of PMA, similar to that observed in normal resting T lymphocytes matched for phenotype. Both Con A- and CD2-induced proliferation were strongly inhibited by the addition of anti-CD25 MoAb. Furthermore, T-CLL lymphocytes acquired anti-tumour lytic activity after culture in the presence of PMA and ionomycin. We conclude that HTLV1- CD25- T-CLL can be characterized not only by morphological and phenotypical studies but also on the basis of signal requirements for cell activation.

Antibodies, Monoclonal↗
PubMed1990

Chylous pleural effusion in tuberous sclerosis.

We report on a male patient with tuberous sclerosis (adenoma sebaceum and digital fibromas, renal angiomyolipomas and subependymal brain calcifications), who presented with chylothorax. Chest CT scan did not show pulmonary parenchymal alterations, but only a moderate enlargement of the paracaval mediastinal lymph nodes. Tuberous sclerosis with lung involvement presents clinical, radiologic and pathologic manifestations similar to those of lymphangioleiomyomatosis. The pulmonary manifestations of tuberous sclerosis and lymphangioleiomyomatosis have been observed almost exclusively in women, and it has been suggested that they represent opposite ends of a spectrum of presentations of the same entity. Based on these considerations the formation of a chylothorax in a male with tuberous sclerosis constitutes an extremely rare finding.

Chylothorax↗
PubMed1990

Malignant pleural effusions: meaning of pleural-fluid pH determination.

In 36 patients with malignant pleural effusions, we determined the pH and the glucose concentration of the pleural fluid. Twenty-one of 36 patients (58.3%) had a low pH (less than 7.30) and 15 had a normal pH (greater than or equal to 7.30; 7.13 +/- 0.12 vs. 7.37 +/- 0.05; p less than 0.0005). The patients with low pH had significantly lower glucose concentrations than those with normal pH (2.7 +/- 1.4 vs. 6.3 +/- 2.9 mmol/l; p less than 0.0005). Twenty-one of 34 patients (61.7%) had a glucose concentration lower than a cut-off value of 4.4 mmol/l; of these, 17 (81%) had a low pH. The mean survival in the low-pH group was 4.8 +/- 4.4 months, whereas the mean survival in the normal-pH group was 5 +/- 8 months (p greater than 0.4). Twelve of 36 patients (33.3%) were treated with intrapleural Corynebacterium parvum (CBP) injections. Fourteen of 21 low-pH patients (66.6%) survived more than 2 months, and 4 of them are still alive. Six of 15 normal-pH patients (40%) survived more than 2 months, and 1 of them is still alive. Three of the 5 living patients were treated with CBP (2 in the low-pH group and 1 in the normal-pH groups). Our results confirm that pH and glucose concentrations in the pleural fluid of patients with malignant effusions are frequently low. However, the survival and the response to CBP pleurodesis in patients with low-pH malignant effusions are the same as those in patients with normal-pH malignant effusions.

Adolescent↗
PubMed1990

[Caries prevention through a nutritional vehicle].

In order to evaluate the efficacy of fluoridated milk as a cariostatic nutritional product, the biological and technical possibilities of adding fluoride (F) as monofluorophosphate (MFP) to milk were studied, together with a preliminary cost estimation for this procedure. F ingestion by preschool children pertaining to the low and medium-low levels of population was estimated through polls and chemical analyses. The values of F ingestion obtained were in the range of 0.15-0.30 mg/day. The bioavailability of F in those dietary elements which have the highest F concentration was determined. Taking a value of 1.00 for F absorption from sodium fluoride (NaF) in water, relative values of 0.58 and 0.32 were obtained for tea ingestion on a fasting stomach, and together with solid food, respectively. The corresponding value for fish was 0.34. Through another bioavailability experiment it was shown that the absorption of F (from MFP) in milk, is as high as that of F (from NaF) in water. By means of a comparative cost estimation study, it was found that, for the Chilean situation, milk fluoridation is, at least, 1,000 times more economic than water fluoridation. It is concluded that milk fluoridation is an economical and viable alternative for some less developed countries.

Animals↗
PubMed1990

Lengthening of the humerus using the Ilizarov technique. Description of the method and report of 43 cases.

From 1982 to 1986, 43 humeral lengthenings were performed on 29 patients using the Ilizarov technique. Diagnoses included achondroplasia, old septic arthritis, birth palsy, fracture, congenital shortening, and benign neoplasm. The achondroplastic patients (14) had bilateral lengthenings. There were 16 male and 13 female patients aged ten to 36 years (mean, 18 years). The total lengthening in each segment ranged from 5 to 16 cm (mean, 9 cm) and mean treatment time from four to 14 months (mean, eight months). The average follow-up time was 2.7 years (range, 0.5-5.5 years). Functional and aesthetic results were all graded as excellent or good. There were no cases of osteomyelitis or deep infection. Three patients sustained neuropraxias that subsequently resolved completely. There were seven fractures in six patients following removal of the apparatus. Five were treated with casts and two with replication of the apparatus. All healed uneventfully. Humeral lengthening can be safely performed with excellent clinical results using the Ilizarov technique.

Adolescent↗