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Biomedical subjects

J M Ramírez

Publications and source records attributed to J M Ramírez.

At least 19 recordsLinked to original sources
PubMed2006

Violence in mental disorders and community sample: an evolutionary model related with dominance in social relationships.

The major risk determinants of violence are to be young and male, to have low socioeconomic status and suffering substance abuse. This is true whether it occurs in the context of a concurrent mental illness or not; i.e., mental disorders are neither necessary, nor sufficient causes for violence. Intense motivation is a facilitating factor for violence in clinical and non clinical samples. This explains why 'normal' people, are implicated in planned violence at higher rates than mentally ill (e.g. in criminal acts against property). However mentally ill patients are more easily implicated in impulsive violence or in violence without obvious cause due to veiled motivation fuelled by unidentified symptoms. Subjective or real awareness of competitive disadvantage increases motivation for violence (e.g. paranoid, narcissistic symptoms, etc.). Many psychiatric disorders as antisocial disorder, borderline, schizophrenia, have most of the factors that facilitate the appearance of violence. Antisocial disorder is a good model to study determinants of violence in normal samples as it is present in young males that do not have any psychotic symptom, have stable symptomatology, self control under scrutiny, and their motivations are similar to normal samples. Our evolutionary model suggests that there is a non random association of genetic factors (genes, pseudogenes, promoting areas, etc.), that is, a genetic cluster (cluster DO), whose phylogenetic function is to motivate to be the dominant in social relationships. To be the dominant is a major psychological feature present in many social groups of animals, included primates. DO cluster have sense from an evolutionary viewpoint: when expressed in no pathological way it increases inclusive fitness (transmission of the genes of a person genotype whether by oneself or by relatives reproduction). Features of cluster DO in humans are expressed differently according to sex, age, moral education, level of intelligence, etc. Cluster DO has higher phenotypical expression in males and young people. Primary antisocial personality disorder and other related disorders (cluster B personality disorders, disocial, defiant disorder, etc.), are a pathological manifestation of this cluster DO. Some other genetic clusters that causes the genetic liability to some disorders (e.g. attention deficit disorder) are non random associated with cluster DO, thus explaining clinical comorbidity. According to our model, motivation for dominance usually prevails over motivation for material benefit or antinormative behaviour, this explains some incongruent behaviour in antisocial patients not elucidated by other models. Along with the primary expressed feature of dominance of cluster DO there are other secondary features that have been identified by psychobiological studies: novelty seeking, intolerance for frustration, impulsiveness, fearless, aggressiveness, higher threshold for activation of the sympathetic system, lack of empathy, egoism, non acceptance of rules, defiant and rebellious behaviour, manipulation in social interactions, selfishness and deficits in altruism or in social co-operation.

Adult↗
PubMed2006

[A comparative study of choroidal innervation in the human and the rabbit (oryctolagus cuniculus)].

OBJECTIVE: To analyze morphological differences between the choroidal innervation of the human and the rabbit, the latter being a species frequently used as an experimental model of human ocular diseases. METHODS: Twelve human and 12 rabbit choroidal whole mounts were processed using an indirect immunohistochemical technique, peroxidase-anti-peroxidase and antibodies against 200 kD neurofilament. RESULTS: Choroidal nerve fibers were perivascular and intervascular. Perivascular fibers surrounded all arteries forming a network that was more developed in the rabbit. In humans, intervascular fibers were mainly concentrated at the posterior pole where they formed a denser and more highly organized plexus than in the rabbit, which did not exhibit a preferential location for these fibers. Human choroidal ganglion cells were far more numerous than in the rabbit and were concentrated in a circumferential area corresponding to the entrance of the short posterior ciliary arteries of the submacular area. In the rabbit, these cells were restricted to the peripheral choroid. CONCLUSIONS: Some differences were observed between human and rabbit choroidal innervation. The abundance of ganglion cells and their preferential distribution could be necessary to maintain a constant blood flow in the central area of the human choroid. The lack of organization of rabbit choroidal innervation at the posterior pole could be associated with an absence of the macula. These differences, along with peculiarities of retinal vascularization, should be taken into consideration when using the rabbit as an experimental model to study human eye diseases in which regulation of choroidal blood flow is involved.

Animals↗
PubMed2005

Aggression, and some related psychological constructs (anger, hostility, and impulsivity); some comments from a research project.

The purpose of the present study was: first, to offer a few theoretical considerations on the concept of human aggression and its main types; and second, to analyse the relationship between those types of aggression and other related psychological constructs, such as anger, hostility, and impulsivity, summarizing the main empirical results of our research in progress. In order to assess their eventual correlations, several self-report techniques were compared: (a) AQ, used to measure several kinds of aggression, anger, and hostility; (b) CAMA, a questionnaire already used in a variety of cultures, for measuring attitudes toward interpersonal aggression in different instrumental and hostile situations; (c) ASQ, an instrument for measuring experienced anger and its expression in assertive or aggressive ways; and (d) BIS, used to prove three impulsiveness sub-traits: motor, attentional, and non-planning impulsiveness. The different definitions of aggression may be grouped according to whether the primary goal is distress or harm, focusing primarily on the objective infliction of harm, or on the subjective intention of harming. Most classifications in the literature show two kinds of aggression, even if different names are used: Hostile Aggression (among other names it is also known as 'reactive, impulsive, or affective') is an act primarily oriented to hurt another individual; and Instrumental Aggression (also known as 'proactive, premeditated, or predative') is a means or tool for solving problems or for obtaining a variety of objectives. As predicted, there was a positive correlation between experience and expression of anger. Anger involved physiological arousal and prepared for aggression. Anger and impulsiveness were also positively correlated with hostile aggression, but not with instrumental aggression. In the case of impulsiveness, non-planning impulsiveness was positively correlated with some situations related to hostile aggression, such as emotional agitation or lack of communication, but not with instrumental one. Finally, hostility positively correlated with anger and different kinds of aggression, but not its degree of justification. In sum, aggression can be reflected in the different personality constructs, measured by self-reports.

Aggression↗
PubMed2005

Doppler-guided hemorrhoidal artery ligation in the management of symptomatic hemorrhoids.

OBJECTIVE: The aim of this study is to clinically test the efficacy of a new approach for patients having symptomatic grade III and IV hemorrhoids. MATERIAL AND METHOD: 32 patients (17 females) complaining of grade III or IV hemorrhoids were included in the study. A specially designed proctoscope coupled with a Doppler transducer on its tip was used to identify the hemorrhoidal arteries, which were afterwards suture ligated. Operating time as well as per- and post-operative complications were analyzed. Follow-up was planned following discharge after 1 week, 1 month, 6 months and 1 year. RESULTS: Mean operation time was 27 (range 18-43) minutes, and 5 (range 4-7) arteries were located on average. No patient had severe or moderate postoperative pain, with anal discomfort being the main complaint. Rectal bleeding and tenesmus were the commonest post-operative complications. After one year of follow-up, 19 patients were free of symptoms and 6 of them had significant symptom relief. According to grade, the technique failed in just 3 grade III patients, but in as many as 4 grade IV hemorrhoid cases. CONCLUSIONS: Doppler-guided hemorrhoid artery ligation is an easy-to-perform technique that is well accepted by patients and has good results for grade III hemorrhoids.

Adult↗
PubMed2005

The utility of endovaginal sonography in the evaluation of fecal incontinence.

OBJECTIVE: The endoanal sonography in female patients with faecal incontinence is sometimes difficult and can lead to diagnostic errors. The aim of this study is to evaluate the value of endovaginal sonography in such cases. MATERIAL AND METHOD: Thirty female patients complaining of faecal incontinence are included in the study. Anal endosonography was performed in all of them in a single ambulatory session, pictures were taken from all along the anal and results were analyzed afterward. Vaginal endosonography was then performed using the same equipment. Result from both techniques were compared. RESULTS: Endoanal sonography was performed in all 30 patients. In 17 cases no anomalies were found. In 3 patients a simple internal anal sphincter defect was found. One case showed a lateral lesion in both sphincters. Six cases presented anterior external defect and in the rest 3 cases a clear view of the anterior wall was impossible. Vaginal endosonography shows a clear image of the anal canal in 23 out of 30 patients. In two cases changed the results of anal endosonography. CONCLUSION: In the study of faecal incontinence, despite of its technical limitations, endovaginal ultrasound could be of help when the anterior wall of the anal canal is not properly defined.

Adult↗
PubMed2003

A direct contact between astrocyte and vitreous body is possible in the rabbit eye due to discontinuities in the basement membrane of the retinal inner limiting membrane.

Different from most mammalian species, the optic nerve of the rabbit eye is initially formed inside the retina where myelination of the axons of the ganglion cells starts and vascularization occurs. Astrocytes are confined to these regions. The aforementioned nerve fibers known as medullated nerve fibers form two bundles that may be identified with the naked eye. The blood vessels run on the inner surface of these nerve fiber bundles (epivascularization) and, accordingly, the accompanying astrocytes lie mostly facing the vitreous body from which they are separated only by the inner limiting membrane of the retina. The arrangement of the astrocytes around blood vessels leads to the formation of structures known as glial tufts. Fragments (N = 3) or whole pieces (N = 3) of the medullated nerve fiber region of three-month-old male rabbits (Orictolagus cuniculus) were fixed in glutaraldehyde followed by osmium tetroxide, and their thin sections were examined with a transmission electron microscope. Randomly located discontinuities (up to a few micrometers long) of the basement membrane of the inner limiting membrane of the retina were observed in the glial tufts. As a consequence, a direct contact between the astrocyte plasma membrane and vitreous elements was demonstrated, making possible functional interactions such as macromolecular exchanges between this glial cell type and the components of the vitreous body.

Animals↗
PubMed2001

A practical method for the radioisotope labeling of rabbit astrocytes with (3)H-thymidine.

A practical method for the radioisotope labeling aimed at the study of the proliferative behavior of astrocytes was described. It consisted in injecting 20 microCi of (3)H-thymidine into the vitreous body and tracing by autoradiography labeled astrocytes located both inside and outside the retina, e.g. optic nerve and neighboring parts of the central nervous system. The paraffin sections were immunostained for glial fibrillary acidic protein (GFAP) previous to autoradiographic processing. The semiquantitative analysis of labeled astrocytes was carried out on autoradiographs of semithin sections of rabbits killed as early as 6 h and as late as 3 months after the single intravitreal injection of (3)H-thymidine. Compared with the technique of labeling astrocytes by systemic administration (single injection or continuous infusion) of (3)H-thymidine into small animals, the method described herein has the following outstanding features: (i) it is much more economical in terms of the amount of labeled precursor used per animal; (ii) the labeling of the astrocytes is obtained as early as 6 h and remains up to 3 months after injection; (iii) the immunolabeling of the astrocytes is compatible with autoradiography; (iv) it is less risky to the experimental animal and to the environment; (v) it can be used in animals much larger than rats or mice.

Animals↗
PubMed2001

Immunohistochemistry in association with scanning electron microscopy for the morphological characterization and location of astrocytes of the rabbit retina.

The purpose of the present investigation was to establish a method for the morphological characterization and location of the several types of astrocytes in the rabbit retina. Whole retinas were incubated with unlabeled antibody to glial fibrillary acidic protein (GFAP) and, afterwards, treated with secondary antibody labeled according to the requirements for the visualization of the antigen-antibody reaction either with the confocal or transmission electron microscope. Specimens treated similarly to the latter were osmium enhanced and analyzed with scanning electron microscopy (SEM). The different immunohistochemical approaches led to the conclusion that the cells selectively visualized with the SEM are astrocytes. The higher resolution and depth of focus of this instrument allowed a better morphological characterization and a more precise location of the astrocytes in the several levels of the inner portion of the rabbit retina. The method described herein, in which pre-embedding immunohistochemistry for GFAP on rabbit retinas was associated with osmium enhancement and examination with SEM, proved to be reliable and efficient for the morphological characterization and location of astrocytes.

Animals↗
PubMed2001

Changes of astrocytes in retinal ageing and age-related macular degeneration.

Most studies of age-related macular degeneration (AMD) have focused on the outer retina but little has been done on the involvement of astrocytes in this disease. We examined normal (young and old) and pathological (AMD) human retinas for the presence of changes in morphology and distribution of the astrocytes. Electron microscopy and inmunohistochemical techniques (anti-GFAP) were used for this study. Astrocytes in the ageing group showed: (1) higher GFAP immunoreactivity and more cytoplasmic organelles and glial filaments than astrocytes from younger retinas; (2) lipofucsin deposits; (3) a significantly smaller number of cells in the honeycomb astroglial plexus in the ganglion cell layer than in the younger group; and (4) Spaces with no GFAP reactivity in the nerve fiber layer. Changes observed in the AMD group were: (1) the basal membrane of the retinal capillaries was considerably thicker than in normal old individuals; (2) There were numerous non-functional capillaries; (3) There were hypertrophic astrocytes that phagocytosed dead ganglion cells; and (4) There were glial membranes constituted by astrocytes and Müller cells located between the vitreous humour and internal limiting membrane. These observations suggested that the extensive retinal ischaemia that can occur with AMD, together with the loss of astroglial cells accompanying normal ageing, could cause the death of the ganglion cells which cannot be protected from oxidative damage. Extensive ischaemia could cause the astrocytes to migrate to the vitreous humour where there is a metabolic reserve.

Adult↗
PubMed2001

[Application of confocal microscopy in the study of the relationships between astrocytes and blood vessels in the retina].

OBJECTIVE: To study the rabbit retina astrocytes by using immunofluorescence techniques together with the confocal microscopy. MATERIAL AND METHODS: The rabbit retinas were processed with an anti-glial fibrillary acidic protein (anti-GFAP) for astrocyte detection and with propidium lobide for nuclear staining. RESULTS: Confocal microscopy allows for three-dimensional reconstruction of astroglial cells, the performance of double staining procedures with superposition of images corresponding to each chromogen, the exchange of observation axes for each slide and finally the performance of serial optic sections that indicate the exact cell location and their relationship with adjacent structures, eliminating the background signals. CONCLUSIONS: The confocal microscopy provides detailed information about tridimensional morphology and the location of the astrocytes in the rabbit retina. The astrocytes associated with the nerve fiber bundles are located in the nerve fiber layer. The type III perivascular astrocytes are located between the intravitreous capillaries close to the internal limiting membrane of the retina. The type I perivascular astrocytes are found in the retinal face of the intravitreal capillaries, these being the neurons which are the most distant from the retina.

Animals↗
PubMed2000

Human retinal astroglia. A comparative study of adult and the 18 month postnatal developmental stage.

The immunohistochemical location of glial fibrillary acidic protein (GFAP) was used to study the state of maturation of retinal astrocytes from an 18-mo-old infant and to compare it with the situation in the adult. Infant astrocytes showed intense GFAP immunoreactivity in the perikarya and possessed spindle-like enlargements in their processes, while in the adult immunoreactivity in the perikarya was scarce and the spindle-like enlargements were not evident. Two types of astrocyte were observed in adult and child retinas: elongated and star-shaped. In the adult, the star-shaped type tend to be more stylised and to have longer processes than in the infant. In the infant, numerous astrocyte cell bodies were observed over vessels, while in the adult these were scarce. In the infant, the star-shaped astrocytes made up a honeycomb plexus, but this was not fully developed. These results suggest that at 18 mo of postnatal development the retinal astrocytes are still increasing and growing into the astroglial structure found in adults.

Adult↗
PubMed2000

[Apoptosis in ischemic optic neuropathy].

PURPOSE: A study of human eyes with non-arteritic ischaemic optic neuropathy (NAION) to determine whether there is apoptosis and whether this is accompanied by cell necrosis mechanisms. METHODS: Transmission electron microscopy was used to examine the retinas of eyes with NAION. RESULTS: There was a large number of apoptotic ganglion cells. The lesion was not confined to this retinal layer but also affected the inner nuclear layer, where Müller glia with fagocytic capacity were detected. In this layer apoptosis alternated with necrosis in all of the cell types existing in this level: bipolar cells, amacrine cells and horizontal cells. The outer nuclear layer can also suffer lesion, essentially by induction of choroid ischaemia to that level. Again, apoptosis was observed at the photoreceptor level, where there was also death by heterophagy, although this was less frequent. CONCLUSIONS: The behaviour of NAION in humans is similar to that found in experimental models. Apoptosis mechanisms develop, alternating with cell necrosis in the nuclear level.

Aged↗
PubMed1999

Immunohistochemical study of rabbit choroidal innervation.

Immunocytochemical methods with antibodies to the light (68 kDa), medium (160 kDa), and heavy (200 kDa) chain subunits of the neurofilament triplet have been used to visualize neuronal structures in rabbit choroids. Choroidal nerve fibers were present in the suprachoroid and vascular laminae and absent in the choriocapillary layer. These fibers may be classified as perivascular and intervascular. Perivascular fibers surround all arterial and venous blood vessels and form a network; these fibers were labeled with the three NF antibodies, although they were more easily visualized with anti NF-160 and anti NF-200 than anti NF-68. Intervascular fibers formed two groups. The first group consisted of fibers situated between the blood vessels and parallel to the blood vessel wall surface (paravascular fibers); these fibers were better observed using anti NF-160 and NF-200 than anti NF-68. The second group consisted of fibers which travel the entire length of the choroid until they reach the nerve plexus of the ciliary body (long tract fibers). The plexus was observed with anti NF-68, anti NF-160 and anti NF-200; however, the long tract fibers were more clearly visualized with anti NF-160 and anti NF-200 than with anti NF-68. Two types of choroidal cell were also labeled: ganglion cells and melanocytes. Ganglion cells are small, scarce neurons situated in the peripheral choroid; they were labeled with anti NF-160 and anti NF-200. The melanocytes were only labeled with anti NF-200 and they were the only non neuronal structure visualized using antibodies against neurofilaments.

Animals↗
PubMed1998

Reversible denaturation, self-aggregation, and membrane activity of Escherichia coli alpha-hemolysin, a protein stable in 6 M urea.

Escherichia coli alpha-hemolysin (HlyA) is an extracellular protein toxin (107 kDa) whose cell lytic activity may be preserved for months at -20 degreesC in the presence of 6 M urea, although it decays rapidly in urea-free buffers. This paper describes experiments addressed to unravel the role of urea in HlyA stabilization. Urea up to 8 M inhibits the Ca2+-binding and hemolytic activities of the protein, alters its secondary and tertiary structures, and reduces its tendency to self-aggregation. All these changes are largely reversed upon urea removal by dilution or dialysis, suggesting that they are interrelated. Furthermore, the extent of recovery of the native activities and structural features of alpha-hemolysin that follows urea removal increases with the concentration of urea during the previous phase. Thus, it seems that urea elicits the reversible transition of HlyA to a less active but more stable state whose structure differs significantly from that of the native protein. Moreover dialysis equilibration of the protein with buffers containing 3 M urea induces the formation of a molecular form of HlyA 5-10 times more active than the native protein in the absence of urea. This hyperactive intermediate appears to keep the native secondary structure of HlyA, but with a less compact tertiary structure, that increases the number of exchangeable Ca2+ ions under these conditions. Changes in the intrinsic fluorescence of HlyA also support the notion of a conformational change in the high-activity intermediate. The intermediate is only detected when assayed in the presence of Ca2+ and 3 M urea and can bind a large number of calcium ions (approximately 12 vs approximately 3 for the native protein); it shows a large tendency to self-aggregation and presumably, in the presence of membranes, a similar tendency to irreversible insertion, which may be the reason for its high lytic activity.

Amino Acid Sequence↗
PubMed1997

Comparative study of astrocytes in human and rabbit retinae.

Immunohistochemical location of Glial Fibrillary Acidic Protein (GFAP) was used to compare the morphology of astrocytes in vascularized and partially vascularized retinae (human and rabbit, respectively). Astrocytes in human and rabbit retinae were found in the same regions as the blood vessels. These cells in partially vascularized retinae differed from those in vascularized retina in several respects. Firstly, there were six morphological types in rabbit retina and only two in human retina. Secondly, in rabbit retinae there were astrocytes only related to blood vessels called "perivascular astrocytes" which were absent in human retinae. Thirdly, the astrocytes were located in the nerve fiber layer and ganglion cell layer in both types of retinae, but in human retinae these cells could also be seen in the internal nuclear layer. These observations demonstrate that there are many differences between astrocytes in human and rabbit retina, suggesting that rabbit retina could be used with caution as an experimental model in comparative studies with human retina.

Animals↗
PubMed1996

Immunohistochemical study of human optic nerve head astroglia.

Immunocytochemical localization of glial fibrillary acidic protein (GFAP) has been used to study the distribution of astrocytes and their morphology in sections of the optic nerve (ON) of human eye. Although all ON regions presented GFAP immunoreactivity, immunostained tissue was most common in the posterior prelaminar region (PR) and least common in the laminar region (LR). Two shapes of astrocytes were distinguished: thick and thin bodied astrocytes. Astrocytes with thick cell bodies are located in the superficial nerve fiber layer (SNFL), PR, LR and retrolaminar region (RR). Astrocytes with thin cell bodies were found in the SNFL and anterior PR. Sometimes thin bodied astrocytes presented another shape with a long process running parallel to the axons and these were found in the PR and LR. In the SNFL the thin bodied astrocytes accompany the axons and contact the capillaries derived from the central retinal artery. In the anterior PR the thin bodied astrocytes with a stellate shape lie over the vessels forming a sieve through which the axons pass. In the posterior PR, the thick bodied astrocytes form glial tubes that direct axons towards the LR. These astrocytes form a layer in the LR that lines the pores of the lamina cribrosa and separates the connective septa from the axon bundles in the RR. The limiting glial membranes separate the ON tissues from the adjacent tissues and from the course of the central retinal artery and are composed of many thick bodied astrocytes.

Adult↗