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Biomedical subjects

A Velasco

Publications and source records attributed to A Velasco.

At least 73 records · Page 4Linked to original sources
PubMed1995

Microglia in normal and regenerating visual pathways of the tench (Tinca tinca L., 1758; Teleost): a study with tomato lectin.

We have studied the microglial cells in the normal and regenerating visual pathways of Tinca tinca (Cyprinid, Teleost) by using the lectin from Lycopersicum esculentum (tomato), which, in our case, has been demonstrated as a specific marker for teleost microglia. In the normal fish, there are tomato lectin positive microglial cells in the retina, optic nerve, and optic tectum. Following optic nerve crush, we observed a more extensive labeling of the microglia in the crushed optic nerve and in the contralateral optic tectum affecting the stratum opticum and stratum fibrosum et griseum superficiale. In both cases, there was an increase of rounded and less ramified microglial cells, and granular cells. This response of a more extensive labeling of microglial cells increases to a maximum at 2-3 weeks after the crush; the density of labeled microglial cells decreases after 3 months after crushing. However, in the retina no changes were observed after optic nerve crush. These results suggest that the microglial cells could play an important role in regeneration of fish optic pathway, as other neuroglial cells do.

Animals↗
PubMed1995

Age-related changes in contractile responses to noradrenaline in isolated blood vessels from rat and rabbit.

1. Age-related changes in vascular function have been studied using rat (1, 6 and 10 months) and rabbit (1 and 6 months) isolated aorta and rat (1, 6 and 10 months) mesenteric perfused artery. 2. The EC50 values of noradrenaline in rat aorta increased with age. Similarly, contractile response to noradrenaline (10(-6) M) and potassium (80 mM) increased with age. In rabbit aorta, contractile responses, both for noradrenaline and potassium, decreased with age. No changes were observed with age in sensitivity to noradrenaline in rat mesenteric perfused artery. 3. The results of the present study suggest that age-related changes may be different for different blood vessels. The sensitivity decrease to noradrenaline in rat aorta involved postreceptor mechanisms.

Aging↗
PubMed1995

Trimeric G proteins regulate the cytosol-induced redistribution of Golgi enzymes into the endoplasmic reticulum.

Streptolysin O-permeabilized cells incubated with a high concentration (5-10 mg/ml) of cytosolic proteins and ATP-generating system exhibit redistribution into the endoplasmic reticulum (ER) of Golgi integral proteins (mannosidase II, galactosyltransferase, TGN 38), detected by immunofluorescence. In addition, mannosidase II is detected in the ER of cells exposed to a high concentration of cytosolic proteins and processed for immunolectron microscopy by immunoperoxidase. The redistribution process requires ATP and is not affected by previous microtubule depolymerization. Ultrastructural observations indicate that Golgi disassembly occurs by budding of coated vesicles. This stage of the process is inhibited by GTP-gamma S, AIF(3-5), transducin beta gamma subunits, and mastoparan, indicating the involvement of trimeric G proteins. At a later stage, vesicles lose their coats and fuse with the ER. This part of the process does not occur in cells incubated at either 15 degrees C or 20 degrees C, or exposed to N-ethylmaleimide. In cells treated with either cholera or pertussis toxin Golgi redistribution into the ER shows a 50-fold lower requirement for cytosolic factors than in untreated cells. These data suggest a regulatory role for both alpha s and alpha i trimeric G proteins in the normal Golgi-ER retrograde transport taking place in intact cells.

Adenosine Triphosphate↗
PubMed1995

Image quality and dose in lumbar spine examinations: results of a 5 year quality control programme following the European quality criteria trial.

The large dose values found for lumbar spine examinations in a centre participating in the European quality criteria trial have been investigated within a 5 year quality control programme. Actions focused mainly on optimizing the focus-to-film distance, tube potential (kV), film optical density and X-ray beam filtration. These actions lead to overall dose reductions of up to 75% in lumbo-sacral joint examinations and prove the need for a regular survey of patient skin doses.

Humans↗
PubMed1995

[Carcinosarcoma of the gallbladder].

The authors present a case of carcinosarcoma of the gallbladder, discussing its possible histological origin, clinical picture, and recommended therapeutic approaches. Only 30 cases have so far been reported. The case described was seen because of a painless large volume mass in the right hypochondrium. She was surgically treated with a complete resection of the gross tumor including a portion of choledochus, followed by chemotherapy. The survival was of 20 months.

Carcinosarcoma↗
PubMed1994

The assessment of constipation in terminal cancer patients admitted to a palliative care unit: a retrospective review.

Constipation is a frequent and distressing complication in patients with advanced cancer. However, very few studies have reviewed the assessment and management of these patients. The purpose of this study was to review the documentation and assessment and diagnosis of constipation in patients admitted to a Palliative Care Unit, and the correlation between those findings and radiological evidence of stool in the colon. The records of 122 consecutive patients admitted to the Palliative Care Unit, Edmonton General Hospital were reviewed in order to assess the physician's and the nurse's record of symptoms, physical findings, and diagnosis and treatment of constipation. All patients also underwent a flat abdominal radiograph that scored for the presence of stool in the colon (0 = no stool; and 12 = stool occupying all the lumen of the four quadrants of the colon). The radiograph was scored blindly by two different physicians. Of 103 evaluable patients, a rectal exam was reported only in 42. Correlation between the assessment by the two physicians' radiograph score was high (0.78, P nd nurses' diagnosis of constipation, the presence of laxative treatment, the number of days since the last bowel movement, and the source of the admission (hospital vs home) were not associated with higher radiological scores for constipation. Assessment is insufficient in this population at high risk for severe constipation. Radiological examination may be necessary for adequate diagnosis in some patients. More research is needed in this area.

Aged↗
PubMed1994

[Pyogenic liver abscess. Experience with 50 cases].

During the last years the diagnosis and treatment of pyogenic liver abscess has changed substantially. The aim of this work is to report a retrospective analysis of 50 patients aged 24 to 87 years old, that presented with a pyogenic liver abscess and were treated in the last 13 years. The sensitivity for diagnosis of ultrasound examination, CAT scan and angiography was 68, 89 and 75% respectively. The origin of the abscess was detected at the biliary tree in 46% and remained unknown in 38%. Thirty one patients were operated, 13 were subjected to percutaneous drainage and 5 were treated only with antimicrobials. Forty percent of patients had a septic complication and 4 (8%) died. Mean hospital stay was 31 days for operated patients and 21 for the rest. The abscess recurred in seven patients and two of these had a gallbladder carcinoma. It is concluded that percutaneous drainage is an alternative to surgical treatment that must be accompanied by a careful diagnostic workup.

Adult↗
PubMed1994

Parvalbumin immunoreactivity in the telencephalic hemispheres of the tench, Tinca tinca.

The distribution of parvalbumin immunoreactivity in the telencephalic hemispheres of the tench (Tinca tinca L.) was studied using a monoclonal antibody and the avidin-biotin immunoperoxidase method. A wide distribution of immunoreactive structures was found in both dorsal and ventral areas of the telencephalic hemispheres. Normally, the parvalbumin-immunostained neurons in the dorsal area were smaller, more weakly stained, and more scattered than those in the ventral one. In the dorsal area, parvalbumin-immunoreactivity was observed in practically all divisions. The highest density of positive somata was found in the lateral nucleus. Density of stained fibres was generally low. Labelling in the ventral area appeared in the ventral and dorsal nuclei, with a high density of both immunoreactive fibres and cell bodies. Neurons were seen close to the ventricle, arranged in two groups of neurons with different sizes and morphologies. The distribution and morphological characteristics of the parvalbuminergic cells were similar to those of previously described GABAergic elements, suggesting a possible colocalization of both substances in the teleost telencephalon, as it has been observed in different telencephalic areas of land vertebrates. On the other hand, significant differences were seen between the distribution of parvalbumin in the telencephalic hemispheres of the tench in comparison with its distribution pattern in supposed homologous structures of the forebrain of amniotes.

Animals↗
PubMed1993

Calbindin D-28K distribution in the retina of the developing trout (Salmo fario L.).

The appearance of calbindin D-28K, a calcium-binding protein, during development of the trout retina was studied by immunohistochemistry. The first calbindin immunoreactive cells appear in the inner nuclear layer at the equator of the embryonic retina at the stage 227 degrees C (around embryonic day 15). Just before hatching, stage 440 degrees C (around embryonic day 30) cells located in the ganglion cell layer and inner nuclear layer, expressed calbindin. This pattern of immunoreactivity was conserved in post-embryonic retinae (alevins 15 days old). In adult retinae the ganglion cells showed a faint immunoreaction; the amacrine cells are markedly fewer and their immunoreaction declined; and the bipolar cells expressed calbindin for the first time. The results obtained in the present work attending to the expression of calbindin, generally conforms with the vitreal to scleral progression of differentiation of the teleost retina. Ganglion, amacrine and bipolar cells undergo further maturation after beginning calbindin expression.

Animals↗
PubMed1993

Circadian rhythms of plasma corticosterone at different times after induction of diabetes. Responses to corticoadrenal stimulation in light and dark phases.

In this study we have tried to determine the effects of streptozotocin-induced (50 mg/kg) diabetes (15 and 30 day duration) on circadian rhythms of plasma corticosterone concentrations and on the responsiveness of the adrenal glands to exogenously administered ACTH at the time of maximum and minimum levels of plasma corticosterone. Rats were kept under controlled lighting 12h light/12h dark (12L/12D) and fed ad libitum. The corticosteroid circadian pattern in control (C) rats is characterized as one in which peak corticosterone concentrations occur at the beginning of the dark phase (activity period), with a decrease over the remainder of the 24h period. Circadian rhythmicity of plasma corticosterone concentration was absent in the diabetic rats 15 days after induction (D15 rats), with higher mean levels than the C. However, in the diabetic rats 30 days after induction (D30 rats) there is a recovery of this rhythm with similar acrophase and amplitude to the C rats. One hour after stimulation by ACTH (5 IU/kg) at the time of maximum and minimum levels of plasma corticosterone, the C rats showed similar plasma corticosterone levels. In the D15 rats, levels of corticosterone in the light phase one hour after ACTH administration were higher than in the dark phase; being lower than C in this phase. The loss of capacity to respond during the dark phase may be due to adrenal blunting in this phase with high levels of plasma corticosterone. In D30 rats, there is a more noticeable loss of capacity for adrenal response in the light than in the dark phase, with values lower than C and D15 rats in both phases. These findings suggest that the duration of diabetes has a significant role in both plasma corticosterone rhythms and adrenal sensitivity to ACTH administration.

Adrenocorticotropic Hormone↗
PubMed1993

The algal community as an indicator of the trophic status of Lake Patzcuaro, Mexico.

An evaluation of water quality and phytoplankton composition position was carried out in order to determine the trophic conditions of Lake Patzcuaro (2035 m above sea level), a high altitude tropical lake. Temperatures ranged from 15 to 23 degrees C. Total phosphorus and inorganic nitrogen showed a seasonal variation; highest values coincided with the rainy season (0.48 and 2.1 mg litre(-1), respectively). Dissolved oxygen ranged from 2 to 7.9 mg litre(-1) at the surface and from 0.6 to 7.3 mg litre(-1) on the bottom, the lowest values being found in shallow zones. Average transparency varied from 0.62 to 1.4 m Secchi depth. Rainfall was a primary factor in seasonal variability as it influenced both physical and biological conditions by contributing to the transport and deposition of silt, which mixed with sinking algal cells. The composition of the surface phytoplankton segregated along five major divisions comprising a total of 49 species. General seasonal patterns of dominance alternated in a sequence beginning with Bacillariophyta, through Chlorophyta to Cyanophyta. Diatoms, the dominant group from February to early June, included Melosira granulata, Stephanodiscus sp., Synedra sp. and Fragilaria sp. During the rainy season (late June to September), Microcystis aeruginosa, Oscillatoria sp., Anabaena sp., Merismopedia sp., Crucigenia cuadrata, Oocystis lacustris, Selenastrum gracile, Mallomonas sp. and Tetraediella sp. were important. Melosira granulata was present throughout the period of study. Spatial and temporal variability in both physical and biological conditions make it difficult to assign a specific trophic state to Lake Patzcuaro. Nevertheless, analysis of the algal community indicates a generally mesotrophic condition.

Journal Article↗
PubMed1993

Distribution of neurokinin A in the cat diencephalon: an immunocytochemical study.

The distribution of neurokinin A-like immunoreactive cell bodies and fibers in the diencephalon of the cat was studied using an indirect immunoperoxidase technique. A high or moderate density of immunoreactive neurons was observed in the nuclei habenularis lateralis, medialis dorsalis, parafascicularis, hypothalamus posterior, area hypothalamica dorsalis, hypothalamus lateralis, periventricularis hypothalami, above the corpus mamillare, and in the perifornical area, whereas scarce immunoreactive perikarya were visualized in the nuclei reuniens, hypothalami ventromedialis, hypothalamus dorsomedialis, and mamillaris lateralis. The highest density of fibers containing neurokinin A was found in the nuclei periventricularis anterior, rhomboidens, centralis medialis, periventricularis hypothalami, and supraopticus. In the regio praeoptica, area hypothalamica dorsalis, hypothalamus posterior, and in the perifornical area a moderate density of immunoreactive fibers was observed, whereas the nuclei habenularis lateralis, medialis dorsalis, mamillaris lateralis, parataenialis, reuniens, habenularis medialis, filiformis, hypothalamus dorsomedialis, hypothalami ventromedialis, arcuatus, and suprachiasmaticus showed a low density of neurokinin A immunoreactive fibers.

Animals↗
PubMed1993

The role of the neurotransmitters acetylcholine and noradrenaline in the pathogenesis of stress ulcers.

1. Adrenergic and cholinergic mechanisms seem to be involved in the pathogenesis of stress ulcers. 2. In this study, gastric ulcers were induced in rats by immobilization and cold. Prior intraperitoneal administration of both anticholinergic (atropine) as well as alpha-blocking medication (phenoxybenzamine) produced a very significant decrease in stress ulcers. 3. Additionally, using the technique of continuous intravenous perfusion in rats, acetylcholine was shown to have a gastric ulcerogenic effect, in contrast to noradrenaline. 4. It is concluded that acetylcholine is the peripheral mediator in stress ulcers, while noradrenaline intervenes at the encephalic level in stress ulcer pathogenesis.

Acetylcholine↗
PubMed1993

Cell type-dependent variations in the subcellular distribution of alpha-mannosidase I and II.

alpha-mannosidases I and II (Man I and II) are resident enzymes of the Golgi complex involved in oligosaccharide processing during N-linked glycoprotein biosynthesis that are widely considered to be markers of the cis- and medial-Golgi compartments, respectively. We have investigated the distribution of these enzymes in several cell types by immunofluorescence and immunoelectron microscopy. Man II was most commonly found in medial- and/or trans- cisternae but showed cell type-dependent variations in intra-Golgi distribution. It was variously localized to either medial (NRK and CHO cells), both medial and trans (pancreatic acinar cells, enterocytes), or trans- (goblet cells) cisternae, or distributed across the entire Golgi stack (hepatocytes and some enterocytes). The distribution of Man I largely coincided with that of Man II in that it was detected primarily in medial- and trans-cisternae. It also showed cell type dependent variations in its intra-Golgi distribution. Man I and Man II were also detected within secretory granules and at the cell surface of some cell types (enterocytes, pancreatic acinar cells, goblet cells). In the case of Man II, cell surface staining was shown not to be due to antibody cross-reactivity with oligosaccharide epitopes. These results indicate that the distribution of Man I and Man II within the Golgi stack of a given cell type overlaps considerably, and their distribution from one cell type to another is more variable and less compartmentalized than previously assumed.

Animals↗
PubMed1993

Evolution of diagnostic radiology in a big hospital during a 5 year period, and the derived collective dose.

An analysis is presented of the trends in the annual number of radiological examinations and in the average effective dose equivalent for each type of examination in a big Spanish hospital. Annual frequencies for each type of examination, annual average effective dose equivalent values for each study group, and the contribution of each examination group to the collective dose are presented. Also, sex and age distributions for several important examinations are given, and their impact on the collective dose is reviewed.

Adolescent↗
PubMed1993

[Hemangiopericytoma: report of 4 cases].

Hemangiopericytoma is an infrequent tumor of vascular origin derived from Zimmermann's pericyte cells. It is generally seen in adults of both sexes and its major risk is late recurrence, that occurs in up to 50% of cases. Its spread pattern is principally hematogenous. The management of the disease is similar to that of other sarcomas. Surgical treatment alone controls the disease in less than 30% of cases and the association of surgery and radiation therapy decrease the risk of local and distant recurrence. We report four cases of hemangiopericytomas, located in the prostate, retroperitoneum, supraclavicular space and lung. The four patients were treated with surgery and radiation therapy, three of them have had no evidence of recurrence after 1.5 to 6 years of follow up and the patient with the tumor located in the lung died one year after the operation.

Adult↗
PubMed1992

Presence of Golgi remnant membranes in the cytoplasm of brefeldin A-treated cells.

Brefeldin A (BFA) rapidly blocks secretion, induces disassembly of the Golgi complex and causes a redistribution of Golgi components into the endoplasmic reticulum (ER). In addition to these effects on the exocytotic pathway, BFA has been shown to induce fusion of endosomal membranes with the trans-Golgi network in some cell types. To better understand the mechanism through which BFA disrupts the exocytotic traffic, we have examined its effects on the ultrastructural organization of the Golgi complex. Within minutes of exposure to BFA, the Golgi cisternae were fragmented into a number of small tubules and vesicles, many of which had a non-clathrin coat on their cytosolic surface. In addition, a complex structure consisting of anastomosing tubules and associated vesicles appeared in the cytoplasm of cells incubated with BFA for 10 min or longer. These tubular networks were permanent, distinct structures separated from the ER cisternae. They contained cis, middle, and trans Golgi proteins as well as the lipid analogue C5-DMB-ceramide. Furthermore, secretory proteoglycans en route through the Golgi were retained in the lumen of the tubular networks. As judged by the endocytosis of cationized ferritin, endosomes do not contribute to the formation of these tubular networks. Reassembly of the Golgi complex after BFA incubation involved fragmentation and reorganization of the tubular networks as well as fusion with vesicles budded from the ER. We conclude that although in the presence of BFA the bulk of Golgi membranes are induced to fuse with the ER, as indicated by the detection of Golgi markers in this organelle, a fraction of these membranes remain in the cytoplasm organized as Golgi remnants.

Animals↗