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Biomedical subjects

R Perez

Publications and source records attributed to R Perez.

At least 199 records · Page 11Linked to original sources
PubMedDate not supplied

Ultrastructural changes in limb distal nerves of rats with alcoholism and/or malnutrition before and after dietary correction.

To study peripheral nerves changes in chronic alcoholism and in malnutrition, we examined ultrastructurally the distal nerve branches of the digits of rats treated with four different dietary schemes, as follows: controls (n = 22), fed standard rodent diet plus water ad libitum; alcoholism (n = 12), fed the standard diet and 2-12% ethanol in drinking water; malnutrition (n = 21), fed with corn tortillas instead of standard diet; and alcoholism and malnutrition combined (n = 22). After 10 months under these conditions, a proportion of animals from each group were sacrificed. The remaining rats of the malnutrition and alcoholism alone groups were deferred a standard diet. The combined alcohol + malnutrition group was subdivided into standard diet, malnutrition and ethanol. After a further 4 months under these new conditions, the animals were sacrificed. Ultrastructural examination of limb distal nerve branches showed that glycogen-like particles were more common in malnourished animals, whereas remyelinating axons were more numerous in ethanol-treated rats. Bands of regeneration were present in both groups, but were more common in animals treated with ethanol. These features decreased significantly when the respective nutritional factor was reversed. The results confirm that ethanol plays a definitive role in the development of alcoholic neuropathy and that malnutrition accentuates, the histopathological abnormalities.

Alcoholism↗
PubMedDate not supplied

Genetic analyses of restriction fragment length polymorphisms using high molecular weight DNA from sperm or lymphocytes embedded in agarose.

A simple and efficient method for determining restriction fragment length polymorphism types on large numbers of individuals using small samples of peripheral blood or sperm cells is described. Whole cells embedded in low gelling/melting temperature agarose were treated with a series of enzyme, detergent, and washing steps to release high molecular weight DNA that was then digested with standard restriction enzymes such as EcoRI and PstI, electrophoresed, blotted, and probed as in normal Southern analyses. The technique should be readily adaptable to any application requiring DNA from small numbers of cells for Southern analyses or pulsed field gel electrophoresis.

Animals↗
PubMedDate not supplied

Inhibition of xylazine induced uterine contractility by clenbuterol and nifedipine.

A study was undertaken in order to determine the effects of xylazine on uterine contractility in goats premedicated with clenbuterol or nifedipine. These drugs inhibit uterine activity by acting as potent tocolytic or uterine relaxant agents. A balloon-tipped catheter was inserted under sedation and local anaesthesia on to a uterine horn in 15 cycling goats in order to record intrauterine pressure changes. Three groups of five goats were used: group I was treated with an intravenous dose of 0.1 mg kg-1 of xylazine. Groups II and III were pretreated with 4 micrograms kg-1 of clenbuterol and 80 micrograms kg-1 of nifedipine, respectively, before administrating the same dose of zylazine. Xylazine increased the frequency and intensity of uterine contractions significantly and the value of the area under the contraction curves was significantly higher than that observed under basal conditions i.e. before drug treatment. In goats premedicated with clenbuterol or nifedipine, the uterotonic effects of xylazine (2858 +/- 217 versus basal contractility: 1241 +/- 173 mm2.5 min-1, P < 0.05) were inhibited for the 30 minutes recording period. These data indicate that clenbuterol and nifedipine can be used as potent tocolytic agents in order to prevent the uterine side effects of xylazine.

Adrenergic alpha-Agonists↗
PubMedDate not supplied

Teleophthalmology link between a primary health care centre and a reference hospital.

We have evaluated a teleophthalmology service linking a primary health care centre and an eye clinic at a reference hospital. General practitioners at the primary care centre serving a population of 15,000 and ophthalmologists at the reference hospital participated in this study. Eye fundus digital images were taken from 278 eye fundi of 139 consecutive patients with clinical conditions that could potentially produce fundus alterations. Fundus images were obtained with a non-mydriatic fundus camera (Canon CR6-45M) and were electronically sent reference hospital where ophthalmologist inspected the images and returned the diagnosis. In 18 patients (13%) the images did not have good enough quality to exclude eye fundus lesions. In 24 patients (17%) clear eye fundus alterations were found in at least one eye. In 14 patients (10%) there were image features suggesting retinal alterations that could not be confirmed by image inspection. Media opacity (13 eyes, 5%, seven patients, 5%) was the most common cause of poor image quality. The most difficult assessment was the evaluation of optic nerve head cupping. Retinal oedema was not observable in the digital images. In our experience teleopthalmology services seem to be an effective alternative for eye fundus diagnosis and patient follow-up.

Computer Communication Networks↗
PubMedDate not supplied

The pathway enabling external sounds to reach and excite the fetal inner ear.

The human fetus in utero is able to respond to sounds in the amniotic fluid enveloping the fetus after about 20 weeks gestation. The pathway by which sound reaches and activates the fetal inner ear is not entirely known. It has been suggested that in this total fluid environment, the tympanic membrane and the round window membrane become 'transparent' to the sound field, enabling the sounds to reach the inner ear directly through the tympanic membrane and the round window membrane. It is also possible that sounds reach the inner ear by means of tympanic membrane--ossicular chain--stapes footplate conduction (as in normal air conduction). There is also evidence that sounds reach the fetal inner ear by bone conduction. Several animal and human models of the fetus in utero were studied here in order to investigate the pathway enabling sounds to reach and activate the fetal inner ear. This included studying the auditory responses to sound stimuli of animals and humans under water. It was clearly shown in all the models that the dominant mechanism was bone conduction, with little if any contribution from the external and middle ears. Based on earlier experiments on the mechanism and pathway of bone conduction, the results of this study lead to the suggestion that the skull bone vibrations induced by the sound field in the amniotic fluid enveloping the fetus probably give rise to a sound field within the fetal cranial cavity (brain and CSF) which reaches the fetal inner ear through fluid communication channels connecting the cranial cavity and the inner ear.

Animals↗
PubMedDate not supplied

The neonate has a temporary conductive hearing loss due to fluid in the middle ear.

Postnatal functional changes in the activity of the ear and auditory pathway in neonatal guinea pigs [from day of birth (postnatal day, PND = 0), PNDs 1-4, 7 and then weekly up to 7 weeks] were studied as a model of maturation of hearing in human neonates. On the day of birth there were signs of a conductive hearing loss: negative middle ear pressure, auditory nerve brainstem evoked response (ABR) threshold elevation, ABR wave 1 latency prolongation and low amplitude otoacoustic emissions. The conductive hearing loss is probably a result of the (amniotic) fluid found in the neonatal middle-ear cavity. Over the next PNDs, this conductive hearing loss was resolved. In order to confirm this neonatal conductive hearing loss and its resolution, saline was instilled into the middle ear of guinea pigs. This induced signs of a conductive hearing loss similar to those seen in the neonatal guinea pigs which disappeared with clearance of this fluid. Therefore it may be concluded that most of the changes in auditory function seen over the first PNDs are due to absorption of amniotic fluid from the middle-ear cavity.

Acoustic Impedance Tests↗