Biomedical subjects

C Escobar

Publications and source records attributed to C Escobar.

At least 37 records · Page 2Linked to original sources

PubMed1997

Photosynthetic electron transport regulates the expression of cytosolic ascorbate peroxidase genes in Arabidopsis during excess light stress.

Exposure of Arabidopsis plants that were maintained under low light (200 mumol of photons m-2 sec-1) to excess light (2000 mumol of photons m-2 sec-1) for 1 hr caused reversible photoinhibition of photosynthesis. Measurements of photosynthetic parameters and the use of electron transport inhibitors indicated that a novel signal transduction pathway was initiated at plastoquinone and regulated, at least in part, by the redox status of the plastoquinone pool. This signal, which preceded the photooxidative burst of hydrogen peroxide (H2O2) associated with photoinhibition of photosynthesis, resulted in a rapid increase (within 15 min) in mRNA levels of two cytosolic ascorbate peroxidase genes (APX1 and APX2). Treatment of leaves with exogenous reduced glutathione abolished this signal, suggesting that glutathione or the redox status of the glutathione pool has a regulatory impact on this signaling pathway. During recovery from photooxidative stress, transcripts for cytosolic glutathione reductase (GOR2) increased, emphasizing the role of glutathione in this stress.

Arabidopsis↗

PubMed1997

Organization of circadian rhythmicity and suprachiasmatic nuclei in malnourished rats.

The present study was aimed at characterizing the effects of low-protein malnutrition (6% casein) on the circadian rhythm of drinking behavior and on suprachiasmatic nuclei immunohistochemistry in Sprague-Dawley rats. Recordings were started at 30 days of age under a 12:12-h light-dark (LD) cycle. At age 150 days, recordings were continued under constant dim red light, and finally the latency to entrain to complete and skeleton photoperiods was established. At the end of the recordings rats were processed for histological analysis. Compared with their controls, malnournished rats exhibited 1) splitting of rhythmicity under LD that 2) condensed to one component in constant dim red light, 3) delayed entrainment to skeleton photoperiod, and 4) precocious entrainment under complete photoperiod. Immunohistochemical analysis showed mainly a decrease in the immunohistochemical detection of vasoactive intestinal polypeptide and glial fibrillar acid protein cells in malnourished animals. These results indicate that in malnourished rats there is a decrease 1) in the coupling force among the oscillators and 2) in the strength of the phase lock between the oscillators and the light-dark cycle.

Animals↗

PubMed1997

[Dysphagia as a symptom of diffuse idiopathic skeletal hyperostosis (Forestier-Rotes disease). A case report and literature review].

Swallowing disorders can be caused by cervical spine diseases, such as diffuse skeletal hyperostosis (DISH). This entity is diagnosed as a cause of dysphagia only after excluding all other possible causes. We report a case in which dysphagia was the initial symptom of DISH. The most important clinical and diagnostic aspects of the disease are discussed.

Aged↗

PubMed1997

[Anatomic features of the middle ear in the gerbil. Scanning electronic microscopic study].

The surgical anatomy of the middle ear was studied in 20 adult gerbils (Meriones unguiculatus) by microdissection and scanning electron microscopy. The most significant finding was a well pneumatized tympanic bulla, which facilitated the identification of useful anatomical landmarks for middle and inner ear dissection. The typical features of middle ear structures in the gerbil are described.

Animals↗

PubMed1996

Development of vestibular and auditory function: effects of hypothyroidism and thyroxine replacement therapy on nystagmus and auditory evoked potentials in the pigmented rat.

The functional development of semicircular canals and some brainstem structures of the auditory system was followed in parallel with time in control and propylthiouracyl-induced hypothyroid pigmented rats by respective recording of postrotatory nystagmus response and auditory evoked brainstem potentials, with the aim of discovering the timing of permanent alterations of these responses in congenital hypothyroidism. A group of hypothyroid rats which under went thyroxine-replacement therapy from postnatal day 12 onward was also included in our studies to corroborate the involvement of thyroid hormones in these effects. Postrotatory nystagmus and auditory evoked responses were absent in congenital hypothyroid rats. In the thyroxine-replaced group postrotatory nystagmus values showed no differences from the control group from postnatal day 28 onward. Auditory evoked potentials in thyroxine-replaced animals could not be elicited at 30 dB, but by increasing the intensity of stimulus to 70 dB, values of latencies of the four waves composing the response were indistinguishable from controls from postnatal day 39 and thereafter. These results show that hypothyroidism affects both semicircular canal and auditory function, the latter more severely than the former, but that these effects can be prevented when thyroxine replacement treatment is started in early stages of postnatal development.

Animals↗

PubMed1995

Structure of an anti-idiotypic Fab against feline peritonitis virus-neutralizing antibody and a comparison with the complexed Fab.

The crystal structure of anti-idiotopic Fab 409.5.3, made against an E2 specific feline infectious peritonitis virus-neutralizing antibody 730.1.4, has been determined in its free from, at 2.9 A resolution by molecular replacement. This antibody, used as an immmunogen, elicits the production of anti-anti-idiotypic antibodies that in turn neutralize the virus. The structure of the uncomplexed Fab was refined using constrained-restrained least squares minimization and simulated annealing in combination with conjugate gradient techniques to a crystallographic R of 0.22 based on 16,482 unique reflections between 20.0 and 2.9 A. The free antiidiotypic Fab shows, when compared to its complexed form, a 5 degrees rotation of its variable light with respect to its variable heavy domain and rearrangement of complementarity determining region loops, which permits optimization of the stereocomplementarity between interacting molecules. This finding supports the induced fit hypothesis for antibody antigen interaction.

Amino Acid Sequence↗

PubMed1995

Surgical combination therapy for vitiligo and piebaldism.

BACKGROUND: Refractory and stable defects of vitiligo and piebaldism may be unresponsive to medical therapy. Melanocyte transplantation can restore the normal pigmentation in some selected patients. OBJECTIVES: To evaluate the efficacy of additional mini-grafting with 1.0-1.2-mm punch grafts to complete the restoration of achromic defects when performing surgical correction of leukoderma. METHODS: Eight patients with refractory stable leukoderma were treated with melanocyte transplantation; three with segmental vitiligo had epidermal shave, by removing the hyperpigmented macules at the periphery of achromic lesions; two others received suction epidermal grafts; and three subjects were treated by in vitro cultured epidermal autografts. All patients received additional mini-grafts in areas of residual achromia. RESULTS: The depigmented defects were 100% restored in seven patients, and in one subject 80% improvement was observed. CONCLUSION: Surgical methods, followed by additional mini-grafting, may be helpful to restore completely the depigmented defects when residual achromia, after treatment with the methods described above, is still present.

Cells, Cultured↗

PubMed1995

Melanocytes in the stria vascularis and vestibular labyrinth of the Mongolian gerbil (Meriones unguiculatus).

Inner ear melanocytes are mainly present in the cochlea, vestibular organ, and endolymphatic sac, but their exact biological function has not been determined. In this investigation, we study the pigment cells in the membranous labyrinth of the gerbil. The inner ear melanocytes of M. unguiculatus show an irregular dendritic shape with cytoplasmic processes. These cells are disposed following the distribution of strial marginal and vestibular dark cells that have an important metabolic activity. Gerbil inner ear melanocytes are characterized by the presence of melanosomes, which are homogeneously dense organelles, of variable size and shape, that are surrounded by a membrane. In these cells, the Golgi apparatus plays a important role in melanin synthesis. When melanocytes were incubated in L-DOPA solution, the vesicles and cisterns of the Golgi apparatus exhibited a positive tyrosinase reaction. An interesting observation is the relation between melanocytes and inner ear capillaries. Sometimes, near to sensory vestibular areas, the melanocytes were in contact with Schwann cells and with myelinated fibres of vestibular nerve. The ultrastructural findings of this investigation are consistent with the hypothesis that melanocytes may have functional significance in the inner ear.

Animals↗

PubMed1995

Dendritic branching of claustral neurons in neonatally undernourished rats.

Golgi-Cox-impregnated neurons of the claustrum were studied in control and undernourished Wistar strain rats at 12, 20, and 40 days of age. A reduced cross-sectional somatic area was observed in the 20-day-old undernourished rats and a significant reduction in the dendritic area was observed in the three ages studied. Dendritic arbor alteration was mainly observed in the number of high order and in the total number of dendritic branches of undernourished rats throughout the study. The data suggest vulnerability of the dendritic claustral growth process during the postnatal period to neonatal undernutrition. These alterations may be associated with telencephalic integrative impairments described in perinatal undernourished rats.

Age Factors↗

PubMed1995

[Loss of cutaneous substances of the foot. Retrograde flaps, apropos of 4 cases].

We report our experience with two retrograde flaps for the treatment of cutaneous tissue loss of the foot. A lateral supramalleolar flap and a medial plantar flap pediculated distally were used, the first to cover the dorsal aspect and the second to cover the forefoot. Indications for local flaps are limited essentially because of the small size. In addition they cannot always be used for local trauma. Retrograde vascularization for the forefoot is an interesting alternative to more invasive salvage procedures involving distant flaps (cross-leg or flee flaps) requiring and uncomfortable position or microsurgery.

Adult↗

PubMed1994

Crystal structure of an idiotype-anti-idiotype Fab complex.

Anti-idiotypic monoclonal antibody 409.5.3 is raised against an antibody that neutralizes feline infectious peritonitis virus. This antibody, used as an immunogen, elicits the production of anti-anti-idiotypic antibodies that in turn neutralize the virus. The crystal structure of the complex between anti-idiotypic Fab 409.5.3 and idiotypic Fab fragment of virus-neutralizing antibody has been solved by molecular replacement using real-space Patterson search and filtering by Patterson correlation-coefficient refinement. The structure has been refined to an R value of 0.21 based on 21,310 unique reflections between 40.0 and 2.9 A. The three-dimensional structure reveals extensive, specific interactions that involve 118 van der Waals contacts and at least 9 probable hydrogen bonds. The two Fabs are rotated 61 degrees with respect to each other around the approximate long axis of the complex and are within 26 degrees being aligned along their major axes.

Amino Acid Sequence↗

PubMed1994

Melanocyte reservoir in vitiligo.

BACKGROUND: Dopa-negative, inactive melanocytes, present in the middle portion of the hair follicle, but also in hair bulbs, have been reported as a source of pigment cells, when repopulation of epidermal melanocytes occurs. A melanocyte reservoir in these anatomical sites has been suggested. Our objective was to investigate the ability of the lower third of the hair follicle (hair bulb) to repigment achromic skin in vitiligo. METHODS: Scalp hair bulbs were transplanted within leukodermic areas in 10 patients with vitiligo. RESULTS: Repigmentation around the grafts was suitable for evaluation in four cases. Dopa-positive (+) cells were seen in the epidermal basal cell layer of the repigmented areas. CONCLUSIONS: Although these findings were observed only in a few patients, they suggest that melanocytes from the implanted lower third portion of the hair follicle (hair bulb) act as a reservoir in this anatomic location and are able to migrate and repigment achromic areas in vitiligo.

Adult↗

PubMed1993

Preliminary crystallographic study of a complex between an Fab of a monoclonal feline peritonitis virus neutralizing antibody and its anti-idiotypic Fab.

A complex between an Fab fragment of an E2 specific feline infectious peritonitis virus neutralizing antibody 730.1.4 and Fab fragment from anti-idiotypic monoclonal antibody 409.5.3, was crystallized from ammonium sulfate using vapor diffusion methods. The complex crystals diffract to about 2.9 A resolution and are of orthorhombic space group P2(1)22(1) with a = 75.2 A, b = 80.6 A and c = 187.6 A. There are two Fab molecules, or one idiotype-anti-idiotype complex, comprising the asymmetric unit. The long 187.6 A c axis suggests that the long axis of the complex might lie along this direction. Although small and radiation-sensitive, crystals are suitable for three-dimensional structural analysis.

Animals↗

PubMed1993

Neonatal undernutrition and amygdaloid nuclear complex development: an experimental study in the rat.

This study describes the morphology of neurons from the basolateral (ABL), central (ACE), and medial (AM) nuclei of the amygdaloid complex in neonatally undernourished (U) and control (C) Wistar strain rats. The cells were impregnated with the Golgi-Cox technique and studied at the ages of 12, 20, and 40 days postnatally. In the U-pups the neurons of the three nuclei displayed a reduced somatic area compared to that of the C-group on Days 12 and 20. However, at 40 days, this difference diminished due to a reduction in the somatic area of the C-group. The dendritic area also appeared reduced on Days 12 and 20 in the U-group, but on Day 40 it reached control values. The neurons from ABL and ACE suffered a significant decrease in the number of dendritic branches due to undernutrition, but the AM nucleus did not show this change. The data suggest different vulnerability of these amygdaloid nuclei to neonatal undernutrition. The findings also suggest that the abnormal emotional response characteristic of perinatal undernourished rats could have a morphological cause.

Aging↗

PubMed1993

[Controlled mobilisation after suture of extensor tendons of the hand. Apropos of 30 consecutive cases].

From January 1988 to May 1991, 30 patients (mean age: 27 years old; range: 15 to 45) sustained 57 tendon injuries in 49 fingers. They were treated by primary repair with assisted post-operative mobilisation by a dynamic splint. Adhesion of extensor apparatus rate was 12 p. cent but only one had a functional impairment. No other complications were noted. At the thumb level (3 out of 49 fingers) the Kapandji-test was respectively at 8.8 and 9/10 without any extensor lack. At the long fingers level TAM was excellent in 91 p. cent of cases, good in 4 p. cent, fair and poor in 2 p. cent. According to Allieu classification results were good and excellent in 9 p. cent of cases. These results were better when injury was localised to or up to zone 5 according to Verdan's classification, and when there was no associated bone nor articular injuries or cutaneous defects. Subjective results were less good (70 p. cent of satisfactory results) because of pain, grip strength lack or disability. Assisted mobilisation allowed intrinsic healing and avoided adhesion when application date and rehabilitation protocol were respected. It was more beneficial for distal and complex injuries.

Adolescent↗

PubMed1992

Treatment of refractory and stable vitiligo by transplantation of in vitro cultured epidermal autografts bearing melanocytes.

BACKGROUND: Previous reports demonstrated the usefulness of in vitro cultured epidermis for repigmenting vitiligo. OBJECTIVE: Our purpose was to determine the potential of in vitro cultured epidermal sheets to treat extensive areas of intractable vitiligo. METHODS: In nine patients with long-standing, stable, and refractory vitiligo, autologous epidermis was cultured in vitro in H-MEM but without growth enhancers or hormones and transplanted onto previously denuded achromic lesions. RESULTS: Repigmentation was achieved to almost 100% in three subjects, 60% improvement was seen in two patients, and 30% to 40% in three additional cases. Only one patient had almost no response. Long-term observations in these patients indicate that repigmentation obtained by this method is permanent. CONCLUSION: Transplantation of in vitro cultured epidermis bearing melanocytes is potentially effective to treat extensive areas of vitiligo, but this method is presently at an experimental stage.

Adult↗

PubMed1991

Characterization of crystals of an Fab fragment of a murine monoclonal antibody.

The Fab fragment of an antibody, made against an E2-specific feline infectious peritonitis virus neutralizing antibody, has been crystallized in a form suitable for X-ray diffraction analysis from PEG 4000 using vapor diffusion methods. The Fab fragment crystals diffract to about 2.9 A resolution and are of triclinic space group P1. Unit cell dimensions, by which the reciprocal lattice can be indexed, are a = 57.16 A, b = 70.85 A, c = 75.81 A, alpha = 85.11 degrees, beta = 121.28 degrees and gamma = 116.33 degrees. There are two Fab fragments comprising the asymmetric unit of the crystals. The presence of a pseudo-mirror plane in the diffraction pattern suggests the presence of at least an approximate dyad axis relating the two Fab fragments within the asymmetric unit.

Animals↗

PubMed1991

Neonatal undernutrition and self-grooming development in the rat: long-term effects.

The effect of neonatal undernutrition on six different self-grooming components was examined in male rats during the pre- and postweaning periods. Rats underfed by the maternal nipple-ligation procedure before weaning did not exhibit significant score differences in the various self-grooming measurements. In contrast, after weaning they showed a significant increment in the duration of face-washing, head-washing, fur licking and body-scratching. In all cases, the total postweaning self-grooming activity was significantly increased in the formerly underfed rats. Present data suggest that neonatal undernutrition may presumably interfere with the sequential maturational processes of central and/or peripheral mechanisms underlying some components of self-grooming behavior.

Aging↗