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Biomedical subjects

R Chávez

Publications and source records attributed to R Chávez.

At least 37 records · Page 2Linked to original sources
PubMed1995

Purification of a N-acetyl-D-galactosamine specific lectin from the orchid Laelia autumnalis.

From the pseudobulbs of the orchid L. autumnalis a lectin was purified on immobilized porcine mucin with A + H blood group substance. This lectin is a dimeric glycoprotein of M(r) 12,000 with an Sw,20 of 2.2, showing haemagglutinating activity directed mainly to human A1 desialylated erythrocytes. The lectin possesses sugar specificity for N-acetyl-D-galactosamine and also shows high specificity for glycoproteins containing the T (galactose beta 1,3GA1NAc alpha 1,0 Ser/Thr) or the Tn antigen (GalNAc alpha 1,0 Ser/Thr).

ABO Blood-Group System↗
PubMed1994

The effect of cyclosporin A on Hg(2+)-poisoning mitochondria. In vivo and in vitro studies.

The protective effect of cyclosporin A on the damage induced by Hg2+ in kidney mitochondria was studied. Cyclosporin, added in vitro at a concentration of 0.5 microM, reversed the deleterious effects of Hg2+ on transmembrane potential and Ca2+ accumulation. However, when injected in rats, together with Hg2+, cyclosporin failed to protect against Hg2+ poisoning. Due to the low activity of cyclophilin found in kidney mitchondria, it is proposed that the protection of cyclosporin in vitro must be exerted through an independent mechanism different from its binding to cyclophilin.

Amino Acid Isomerases↗
PubMed1994

Participation of the superior ovarian nerve in the regulation of compensatory ovarian hypertrophy: the effects of its section performed on each day of the oestrous cycle.

The effects were analysed of secretion of the superior ovarian nerve on compensatory ovulation and ovarian hypertrophy, in adult rats with the left or right ovaries extirpated during the oestrous cycle and autopsied 6 or 20 days later. Rats with hemiovariectomy or hemiovariectomy plus denervation recovered their oestrous cyclicity between 2 and 3 days after surgery. Six days after hemiovariectomy 14 out of 17 rats ovulated on the expected day of oestrus. All the animals were hemiovariectomized on the day of pro-oestrus. The mean +/- S.E.M. number of ova shed was similar to the group of animals with both ovaries (7.8 +/- 1.2 vs 9.5 +/- 0.2). Compensatory ovarian hypertrophy was observed in the right ovary when left hemiovariectomy was performed on day 2 of dioestrus or pro-oestrus; similar results were observed in the left ovary when the right one was extirpated at oestrus or pro-oestrus. Section of the right superior ovarian nerve in left-hemiovariectomized rats caused a reduction in ovulation rate and number of ova released. Compensatory ovarian hypertrophy was modified in the opposite way by unilateral section of the superior ovarian nerve to the in situ ovary depending on the day of the cycle when hemiovariectomy was performed. Twenty days after treatment, ovulation rate, compensatory ovulation and ovarian hypertrophy were similar in both left- or right-hemiovariectomized rats. Compensatory ovarian hypertrophy increased in all animals with section of the superior ovarian nerve, except when hemiovariectomy was carried out at oestrus or the left ovary was extirpated on day 1 of dioestrus.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Recognition of a CD4+ mouse medullary thymocyte subpopulation by Amaranthus leucocarpus lectin.

We have used the Gal beta(1-->3)GalNAc-specific Amaranthus leucocarpus lectin to isolate a thymus cell subpopulation which is different from that sorted with Arachis hypogaea lectin. The cells recognized by A. leucocarpus lectin were predominantly CD4+, whereas a minor proportion of CD8+ cells (approximately 11%) were also identified. The A. leucocarpus-positive cells were located in the thymus medulla and the cortico-medullary junction. The cortex was negative for A. leucocarpus cells.

Animals↗
PubMed1992

Fluorescamine-induced membrane permeability in mitochondria.

1. Addition of fluorescamine (75 microM) to mitochondria induced an increase in membrane permeability. 2. The leakiness of the inner mitochondrial membrane is characterized by extensive release of accumulated Ca2+, collapse of the transmembrane potential, mitochondrial swelling and efflux of matrix proteins, among them, malate dehydrogenase. 3. These effects were diminished by supplementing the media with 1 mM phosphate, and partially prevented by Mg2+. 4. These results indicate that the primary amino groups of membrane components contribute, partially, to the maintenance of the permeability barrier in mitochondria.

Animals↗
PubMed1989

Effects on oestrous cyclicity and ovulation of unilateral section of the vagus nerve performed on different days of the oestrous cycle in the rat.

The effects of unilateral section of the right or left vagus nerve (SRVN, SLVN) performed on different days of the oestrous cycle of the rat were analysed. Vagal nerve section on the day of oestrus or on day 1 of dioestrus (D1) altered oestrous cyclicity in a more significant way than when it was performed on day 2 of dioestrus (D2) or pro-oestrus (6/58 maintained normal oestrous cycles compared with 32/39 that did not; P less than 0.01). Ovulation rate at oestrus was lower in rats with SLVN than in the sham-operated group (32/47 vs 28/32; P less than 0.05). The number of ova shed by the left ovary was reduced in sham-operated rats and in animals with SRVN and SLVN, whereas the number shed by the right ovary was not modified. The day of the oestrous cycle on which the vagus nerve was cut also influenced the number of ova shed. No changes in plasma levels of FSH at oestrus were observed in animals with SRVN or SLVN. The results indicate that vagal manipulations performed at the beginning of the oestrous cycle (day of oestrus and D1) induce more changes on oestrous cyclicity and ovulation than when they are performed during the second half of the cycle (D2 and pro-oestrus). In addition, the left ovary is more sensitive to neural manipulation than is the right one.

Animals↗
PubMed1987

Differences in the ovulation rate of the right or left ovary in unilaterally ovariectomized rats: effect of ipsi- and contralateral vagus nerves on the remaining ovary.

The possible existence of peripheral asymmetry in the neuroendocrine mechanisms participating in the response of the ovary to gonadotrophins, and the participation of the vagus nerve, was investigated. At oestrus, the ovulation rate (number of ovulating/number of treated rats) of the left ovary in right unilaterally ovariectomized rats was lower than that in the right ovary in left unilaterally ovariectomized rats (42 vs 84%). No differences in the number of ova shed per ovulating animal nor in compensatory ovarian hypertrophy (COH) were observed. Bilateral section of the vagus nerve resulted in reduced COH only in those animals with the left ovary in situ (right unilaterally ovariectomized). Section of the left vagus nerve induced different effects depending upon which ovary was left in situ. When the left ovary was in situ an increase in ovulation rate, COH and number of ova shed was observed; however, when the right ovary was left in place the above three parameters decreased. Section of the right vagus nerve produced a decrease only in COH in both right and left unilaterally ovariectomized animals. It is concluded that in the unilaterally ovariectomized rat the right ovary seems more able to react to compensatory regulatory systems than does the left. The character of the information carried by the left and right vagus nerve is different.

Animals↗
PubMed1985

Glucose stabilization and coronary infarction with artificial pancreas in heart-lung preparation.

In the performance of heart-lung preparations, after 4-8 hours, it is an usual feature to have multiple microinfarctions, and, finally, heart failure and ventricular fibrillation. We have studied glucose, triglycerides and conjugated fructose consumption by the heart-lung preparation and found a very fast glucose depletion (30 to 90 minutes to glucose 0, starting with glucose 120 mg/dl). The depletion has been slower for triglycerides and even slower for conjugated fructose. Ventilation with pure oxygen has not modified itself the coronary deterioration, but if a Biostator has been used in order to maintain the glucose levels at 100-110 mg/dl., the isolated heart-lung does not deteriorate in 16-24 hours, nor show electrical signs of coronary impairment; after this time, the respirator is disconnected and the preparate discarded. The above mentioned experiments demonstrated the need of artificial control of glycemia in isolated organ experiments and suggest the convenience to use more widely the artificial pancreas (Biostator in our case) for better treatment no only in diabetic or pancreatic patients, but also in many circumstances in which the glucose utilization is impaired.

Animals↗
PubMedDate not supplied

Amaranthus leucocarpus lectin recognizes human naive T cell subpopulations.

Amaranthus leucocarpus lectin (ALL) is specific for GalNAc residue found in the inner core of Gal beta 1,3GalNAc alpha 1,O-Ser/Thr disaccharide (T-antigen) or GalNAc alpha 1,O-Ser/Thr (Tn-antigen). Flow cytometric analysis using fluorescein-labeled lectin and monoclonal antibodies against human cell surface markers indicated that 5.7% of mononuclear cells from human healthy donors are recognized by ALL. These cells have the phenotype CD2+CD4+CD19- and most of the lymphocytes recognized are also CD27+, CD45RA+ and CD43+. ALL possesses mitogenic activity on lymphocytes after neuraminidase treatment. Our results indicate that the receptors recognized by ALL could be considered surface markers for naive human T lymphocyte subsets.

Flow Cytometry↗
PubMedDate not supplied

[Advances in the study of immunopathology in atopic disorders].

The atopic diseases are mediated by type I hypersensitivity. These disorders are multifactorial, although, the inherency is probably the most important cause. The disregulation of the Th1/Th2 immune response is one of the predominant factors on the generation and maintenance on the atopic process. We analyze the mechanisms of the regulation of the response Th1/Th2, the recent theories of the disregulation on this response as an etiology, the soluble factors as cytokines, chemokines and their receptors, surface cell markers and transcriptional factors recently mentioned to be important on this disregulation mechanism. Otherwise, we propose some general considerations and perspectives.

Cell Membrane↗