Search PubMed⌕ Search

Biomedical subjects

L Rojas

Publications and source records attributed to L Rojas.

At least 37 records · Page 2Linked to original sources
PubMed1992

Identification of Dirofilaria immitis-infected dogs with a coagglutination assay.

The presence of Dirofilaria immitis excretory-secretory (ES) products was detected in the urine of infected dogs using a coagglutination assay. Urine samples from 30 naturally infected dogs were positive. Seventeen of them were microfilaremic, whereas 13 had become amicrofilaremic after receiving 2 courses of diethylcarbamazine. Urine samples from 20 dogs infected with other parasites, Dipetalonema reconditum (7), Toxocara canis (5), and Ancylostoma caninum (8), and urine samples from 20 healthy dogs were negative. The assay detected 200 ng/ml or more of ES products. This assay is simple, easy to perform with minimum training, and requires no equipment. Therefore it should be useful to detect canine filariasis under field conditions.

Agglutination Tests↗
PubMed1991

Acetylcholine receptor channel gating and conductance involve extracellular disulfide bond(s).

Disulfide bonds are critical determinants of the function of the acetylcholine receptor at the vertebrate neuromuscular junction. In the present study, the role of these bonds in acetylcholine receptor channel gating and conductance was investigated at the single channel level. Disulfide bond reducing agents decreased the single channel conductance of both ligand-gated and spontaneously opening acetylcholine receptor channels, indicating that the observed decrease in conductance is not due to blockade of the channel lumen by agonist molecules. In addition, the reducing agents increased the opening frequency of both liganded and unliganded acetylcholine receptor channels. Use of inside-out patches and both membrane permeant and impermeant reducing agents demonstrated that the disulfide bonds involved are all extracellular. These findings indicate that both channel gating and conductance involve conformational changes in extracellular regions of the acetylcholine receptor.

Animals↗
PubMed1991

Spontaneous openings of large and small conductance acetylcholine receptor channels in Xenopus myocytes.

Spontaneous openings of acetylcholine receptor channels were investigated using Xenopus myotomal muscle cells in culture and patch clamp recording methods. Two classes of channels with conductances close to 40 and 60 pS and reversal potentials near 0 mV were found to open in the absence of agonist. The open time of the low-conductance channel was about 3 times longer than that of the high-conductance channel. Open times were shorter by a factor of 3-5 than those of acetylcholine-activated channels in Xenopus myocytes and showed no significant voltage dependence. These studies indicate that the two predominant classes of acetylcholine receptor channels in this preparation can open spontaneously.

Acetylcholine↗
PubMed1991

The nicotinic acetylcholine receptor channel in embryonic muscle of Xenopus laevis. A program to separate channel types.

The single channel activity of nicotinic acetylcholine receptor (AChR) channels from Xenopus laevis embryonic myotomes in culture, was studied with the patch clamp technique. Two types of single channel activity were observed at low agonist concentration (100 nM ACh-Cl), which were distinguished by their conductance (60 and 40 pS, approximately). Both channel types were recorded simultaneously and therefore to carry out the kinetic analysis, we separate them by using a program exploiting the difference in amplitude of the channels. By using the program CLASS the stationary kinetic characteristics of both types of channels can be obtained separately and evaluated.

Animals↗
PubMed1989

Detection of specific anti-giardia serum antibody by an immunofluorescence test in children with clinical giardiasis.

In 50 of 100 children with clinical giardiasis studied, the presence of Giardia lamblia was proven by stool and/or duodenal aspirate examination; the presence of the parasite was not demonstrated in the rest. Serum antibodies to G. lamblia were investigated in all children by an indirect immunofluorescent test (IIF) with G. lamblia trophozoites as antigen. It was found that all the children with positive duodenal aspirate had positive serology (titers greater than or equal to 1/32). The best correlation between parasitological and serological procedures were in the 1-5-year-old age group, and there was an age dependent increase of the antibody titer. Most of the parasitologically negative children were serologically negative. Our results support the use of IIF as a useful diagnostic procedure in the diagnosis of giardiasis in children.

Adolescent↗
PubMed1988

Acetylcholine modulated potassium channel in the hair cell of the toadfish saccule.

Sensory transduction in the acoustic-lateralis system is modulated by an efferent synapse on the sensory hair cells and afferent fibers. Acetylcholine has been implicated as a neuro-transmitter at this synapse. This work addresses the ionic mechanism of action of acetylcholine on the hair cell of the toadfish saccule using path clamp methods and single channel recording. Acetylcholine and oxotremorine, a muscarinic agonist, were found to increase the open time and opening rate of a high conductance K+ channel in the basolateral walls of the hair cell. This effect is not dependent on the presence of Ca2+ in the extracellular media. The involvement of an intracellular mediator is implicated since bath applied agonist opens K+ channels isolated under the recording pipette.

Acetylcholine↗
PubMed1988

Influence of the patch pipette glass on single acetylcholine channels recorded from Xenopus myocytes.

The type of glass used to fabricate patch pipettes influences the kinetic properties of single-channel currents activated by acetylcholine in Xenopus myocytes. In patches formed with hard glass pipettes, the opening rate decreased in a time-dependent manner. Such decrease was most pronounced for the low-conductance channel. In addition, longer-duration events of this form of channel dropped out faster than shorter-duration events and, as a consequence, the apparent channel open time became shorter during the recording period. These effects were not observed in patches formed with soft glass pipettes.

Animals↗
PubMed1988

Single acetylcholine channel currents recorded from Xenopus myocytes are influenced by the glass of the patch pipette.

The type of glass used to fabricate patch pipettes influences the kinetic properties of single-channel currents activated by acetylcholine in Xenopus myocytes. In patches formed with hard glass pipettes, the opening rate decreased in a time-dependent manner. Such decrease was most pronounced for the low conductance channel. In addition, longer duration events of this form of channel dropped out faster than shorter duration events and, as a consequence, the apparent channel open time became shorter during the recording period. These effects were not observed in patches formed with soft glass pipettes.

Animals↗
PubMed1983

Preliminary evidence of the effect of calcium supplementation on blood pressure in normal pregnant women.

In this study the hypothesis that calcium supplementation during pregnancy can modify blood pressure patterns in a population of normal pregnant women was tested. Thirty-six women with normal single pregnancies, between 20 and 35 years of age, in the second trimester of gestation (15 weeks), were randomly assigned to receive 1 gm of calcium per day (n = 11), 2 gm per day (n = 11), or a placebo (n = 14). No differences were observed at the times of admission into the study (baseline) in demographic and clinical variables or in the calcium intake of each group. Baseline blood pressure measures in several positions also were not different. After the initial blood pressure measures (fifteenth week), five follow-up blood pressure measures were obtained. The supplemented groups had significantly lower diastolic blood pressure than the control subjects between the twentieth and twenty-fourth weeks of gestation. Thereafter, an increase in the control group and the group receiving 1 gm of calcium was observed, but levels were similar at term. On the contrary, patients receiving 2 gm of calcium had blood pressure values that remained significantly lower throughout the third trimester. No differences or clear patterns were observed in the blood levels of calcium, magnesium, phosphorus, and proteins between and within groups during gestation. A possible explanation involving parathyroid hormone is attempted.

Adult↗
PubMed1982

[Acute epiglottitis. Diagnosis and treatment in eight cases (author's transl)].

A revision of acute epiglottitis is carried out with reference to eight cases recorded from 1973 to 1981. The ages of the patients varied from 12 to 35 months, with a female predominance (7:1) and a seasonal pattern occurring in winter months. Authors establish the attitude to be taken when faced to a patient clinically suspected of having acute epiglottitis, its' diagnosis and therapeutic protocol. The use of nasotracheal intubation instead of tracheostomy as the best way of obtaining a free airway in these patients at risk of sudden airway obstruction, is specially stressed.

Acute Disease↗
PubMed1977

Use of the bifurcated needle for BCG vaccination of newborns.

The bifurcated needle vaccination method used successfully against smallpox is a relatively simple technique that can be administered by personnel with only basic preparation and a minimum of training. This fact suggests that it could prove useful in campaigns of BCG vaccination against tuberculosis--especially for vaccination of newborns. With this end in mind, two studies were carried out in Santiago, Chile, to examine previously reported difficulties with the method and to assess its potential as an alternative to the best current method, that of intradermal inoculation. These studies indicated that previously reported variations in the results achieved by different vaccinators could be markedly reduced. However, they also found that the bifurcated needle method did not cause a sufficiently large dose of vaccine to enter the subject--even when fifteen needle strokes and a highly concentrated vaccine (160 mg per ml) were employed. It was thus concluded that although modification of the needle or other changes might ultimately yield satisfactory results, the bifurcated needle technique cannot yet be recommended for BCG vaccination of newborns.

BCG Vaccine↗