Search PubMed⌕ Search

Biomedical subjects

L Fernandez

Publications and source records attributed to L Fernandez.

At least 91 records · Page 5Linked to original sources
PubMed1988

Analysis of the macular pigment by HPLC: retinal distribution and age study.

High performance liquid chromatography (HPCL) has been employed to study the distribution throughout the human retina of zeaxanthin and lutein, the two major components of the macular pigment. Differences between individuals have also been studied with a view to uncovering possible age-related effects. Both pigments were detected in prenatal eyes (approximately 20 weeks gestation) but did not form a visible yellow spot. Generally they were not easily discernible until about 6 months after birth. For 87 donors between the ages of 3 and 95, no dependence on age was observed in the quantity of either pigment. For approximately 90% of these, zeaxanthin was dominant. For the remaining 10%, as well as for the seven youngest donors, all below the age of 2, and in prenatal eyes, lutein was the major pigment. In individual retinas, the lutein:zeaxanthin ratio increased from an average of approximately 1:2.4 in the central 0-0.25 mm to over 2:1 in the periphery (8.7-12.2 mm). The variation in this ratio with eccentricity was linearly correlated with the corresponding rod:cone ratio. A selective mechanism of uptake, which results in cones and rods preferentially acquiring zeaxanthin and lutein, respectively, could explain this correlation.

Adult↗
PubMed1987

Abnormal aggregation accompanies abnormal platelet Ca2+ handling in arterial thrombosis.

The resting levels of cytoplasmic Ca2+ (measured by Quin 2 fluorescence) and dense tubular Ca2+ (measured by chlorotetracycline, CTC, fluorescence) are shown to be higher in platelets from patients with arterial thrombosis than from normal donors. Turbidimetric studies of aggregation of diluted platelet-rich plasma (PRP) at 135 microM Ca2+ showed increased rates of aggregation for patients relative to normal controls. For ADP-stimulated aggregation, increased maximal rates (Vmax) and decreased doses for half-maximal rates were observed. With collagen-stimulated aggregation, patient samples showed only decreased ED50 values relative to normal controls. The changes in these values are linearly correlated with the elevation of resting dense tubular Ca2+ level determined by the calcium-CTC test carried out at 2 mM external Ca2+. For ADP-stimulated aggregation this relationship can be mimicked by pre-incubating normal platelets with subcritical concentrations of the Ca2+ ionophore A23187. These results suggest that elevated cytoplasmic and dense tubular Ca2+ in the "resting state" is a major factor in arterial thrombosis, rendering the platelet more sensitive to the stimulation by physiologic agents.

Adenosine Diphosphate↗
PubMed1986

Importance of correcting isokinetic peak torque for the effect of gravity when calculating knee flexor to extensor muscle ratios.

The purpose of our investigation was to compare, for the hamstring and quadriceps femoris muscles, peak torque values uncorrected for gravity with the peak torque values corrected for gravity and to determine the effect of making this correction on the hamstring to quadriceps femoris muscle peak torque ratio at slow and fast isokinetic speeds. We measured peak torques isokinetically at 60 degrees/sec (slow) and 240 degrees/sec (fast) in 25 female university soccer players. The gravity effect torque (GET) is the torque resulting from the effect of gravity on the combined weight of the leg and dynamometer arm at the precise angle of extension and flexion peak torque. The GET was added to the measured quadriceps femoris muscle peak torque and subtracted from the hamstring muscle peak torque to yield gravity corrected values. Failure to consider GET greatly underestimated quadriceps femoris muscle torque and overestimated hamstring muscle torque and the ratio between these torques at both speeds. Whereas the uncorrected hamstring to quadriceps femoris muscle peak torque ratio increased as speeds went from 60 degrees/sec to 240 degrees/sec, the gravity corrected ratio significantly decreased. Clinicians must remember the importance of making the gravity correction in patients with reduced torque output where the gravitational torque is a greater percentage of the measured torque to ascertain correctly the relative strength of antagonists inversely affected by gravity.

Adolescent↗
PubMed1985

Calcitonin gene-related peptide immunoreactive sensory and motor nerves of the rat, cat, and monkey esophagus.

In the mammalian esophagus calcitonin gene-related peptide (CGRP)-immunoreactive nerves form abundant subepithelial plexuses and penetrate the mucosa. The levels of extractable CGRP in separated epithelial layers are 15.8 +/- 2.4 pmol/g wet wt of tissue (n = 8, mean +/- SEM). Treatment of neonatal rats with capsaicin and ablation of the central portion of the feline nodose ganglion led to a marked reduction in the numbers of CGRP-immunoreactive nerve fibers. The loss of CGRP nerves demonstrated by immunocytochemistry was accompanied by a parallel reduction in the tissue content of CGRP, as measured by radioimmunoassay (1.5 +/- 0.5 pmol/g in capsaicin-treated animals compared with 9.4 +/- 1.9 pmol/g in vehicle-treated controls; p less than 0.0025). These findings indicate the sensory nature of the CGRP-immunoreactive nerves. Substance P-immunoreactive nerve fibers innervated in particular the blood vessels of the lamina propria; very few penetrated the esophageal epithelium and these were only partially depleted after removal of the central portion of the nodose ganglion. The esophageal muscle contained nerves immunoreactive for substance P and, in particular, for CGRP which was also found in the motor end plates of the striated muscle. No changes in the CGRP-containing motor end plates were observed either after treatment of neonatal rats with capsaicin or ablation of cell bodies from the central portion of the nodose ganglion. These nerve fibers may originate from rostral areas of the nucleus ambiguus, where CGRP-immunoreactive motor neurons have previously been described. Thus, our findings reveal dual components, motor and sensory, of the CGRP-containing innervation of the esophagus.

Animals↗
PubMed1985

Cryostat sections with tissue amastigotes of Trypanosoma cruzi as a substrate for Chagas' disease serology.

Sera from 30 chronic chagasic patients together with 52 control samples (34 with other pathological conditions and 18 from normal individuals) were titrated by the indirect immunofluorescent technique (IFA) on Trypanosoma cruzi amastigotes. Acetone-fixed cryostat sections of skeletal muscle of Rockland mice 10 days post-infection with the RA isolate of T. cruzi were used as substrate. Results were compared with titres obtained by conventional IFA on epimastigotes. All 52 control sera had amastigote titres less than or equal to 2 double dilutions (dd) as compared with epimastigote values. Out of the 30 chagasic samples, differences were greater than or equal to 4 dd (less than or equal to 1 log) for 22, 3 dd for 5 and less than or equal to 2 dd for the remaining 3, when comparing amastigote and epimastigote titres. These results show that the use of amastigotes in cryostat sections of infected tissue for performing Chagas' serology in a simple, adequate and sensitive method.

Antibodies↗
PubMed1985

Hepatic acetylator phenotype in bladder cancer patients.

We determined the hepatic acetylator phenotype in 130 patients with transitional-cell carcinoma (urothelioma) of the bladder and, previously in 157 normal control subjects. Eighty-three patients (63.8%) and 90 control subjects (57.4%) were slow acetylators (p greater than 0.05). Patients of both phenotypes did not differ in the consumption of tobacco and coffee. Seventy-five patients were not exposed to occupational risk for bladder cancer and the distribution of acetylator phenotype in them was similar to that of the control group. The other 55 patients had been employed in jobs with an elevated risk for urotheliomas; 41 (74.5%) were slow acetylators, which represented a significant excess over the incidence of slow acetylators in the control group (57.4%) (p less than 0.05); 15 of these patients had worked in jobs with carcinogenic arylamines proven in the workplace environment (11 were slow acetylators). Our results suggest that the slow acetylator phenotype can facilitate the development of urothelioma in individuals with occupational risk.

Acetylation↗
PubMed1984

Rhizobium phaseoli symbiotic mutants with transposon Tn5 insertions.

Rhizobium phaseoli CFN42 DNA was mutated by random insertion of Tn5 from suicide plasmid pJB4JI to obtain independently arising strains that were defective in symbiosis with Phaseolus vulgaris but grew normally outside the plant. When these mutants were incubated with the plant, one did not initiate visible nodule tissue (Nod-), seven led to slow nodule development (Ndv), and two led to superficially normal early nodule development but lacked symbiotic nitrogenase activity (Sna-). The Nod- mutant lacked the large transmissible indigenous plasmid pCFN42d that has homology to Klebsiella pneumoniae nitrogenase (nif) genes. The other mutants had normal plasmid content. In the two Sna- mutants and one Ndv mutant, Tn5 had inserted into plasmid pCFN42d outside the region of nif homology. The insertions of the other Ndv mutants were apparently in the chromosome. They were not in plasmids detected on agarose gels, and, in contrast to insertions on indigenous plasmids, they were transmitted in crosses to wild-type strain CFN42 at the same frequency as auxotrophic markers and with the same enhancement of transmission by conjugation plasmid R68.45. In these Ndv mutants the Tn5 insertions were the same as or very closely linked to mutations causing the Ndv phenotype. However, in two mutants with Tn5 insertions on plasmid pCFN42d, an additional mutation on the same plasmid, rather than Tn5, was responsible for the Sna- or Ndv phenotype. When plasmid pJB4JI was transferred to two other R. phaseoli strains, analysis of symbiotic mutants was complicated by Tn5-containing deleted forms of pJB4JI that were stably maintained.

Bacterial Proteins↗
PubMed1983

Factors associated with prognosis in human breast cancer. I. Predictors for rate of evolution and relapse.

The associations of several clinical factors with general survival, percentage of relapse and survival in the group of patients who relapsed were analyzed in a series of 399 Stage II breast cancer patients operated and irradiated at the Institute of Oncology and Radiobiology in Havana. In another series of 187 patients these associations were studied in regard to the presence of estradiol receptors in the tumors. Factors related to the presence of estrogen receptors were unrelated to the percentage of relapse in long term follow-up. Age and menstrual status were related to the presence of estradiol receptors and to survival inside the group of patients who relapsed but were unrelated to the percentage of relapses. Lymph node status was mainly associated with the percentage of relapses but not related to the presence of estradiol receptors. Other factors (parity and age at first childbirth), related to the presence of receptors, did not clearly influence prognosis. Lactation influenced positively survival inside the relapse group without any clear association with hormone receptors. Results are discussed in terms of a model considering particular host--tumor interaction: The probability of relapse and the speed of evolution of the systemic disease, mutually independent, but determining the prognosis.

Adult↗
PubMed1982

Clinical factors related to the presence of estrogen receptors in breast cancer: a prognostic stratification analysis.

The techniques used for determination of hormone receptors have provided a biochemical basis to the concept of hormone-dependence in breast cancer. By medical experience clinical factors were established for determination of hormonal treatment in breast tumors. The criteria used need now to be re-evaluated in terms of hormone receptor contents. We analysed a group of 155 patients with histologically confirmed breast carcinoma in which estradiol receptor determination was performed. Of these tumors 54% had more than 10 fmol of estradiol per mg protein. Menopause, advanced age, late first childbirth, obesity, early menopause and nuliparity were associated, in that order, with the presence of estrogen receptors in breast tumors. Prognostic stratification analysis brought out polar groups of estrogen receptor contents. Young, premenopausal women with children had only 16% estrogen receptor-positive tumors. Postmenopausal women, either without children or with late first childbirth had as much as 81% of estrogen receptor containing tumors. Clinical variables related to the presence of estrogen receptor positive tumors in the breast cancer population were coincident to risk factors for breast cancer in the healthy population. Possible implications of this coincidences are discussed.

Adult↗
PubMed1981

Spontaneous rupture of an intra-aortic balloon pump.

Circulatory assistance with an intraaortic balloon pump is not free from risks and complications. Among the latter, rupture is extremely rare. We report a case of spontaneous rupture of an intraaortic balloon, which occurred after 29 h of counterpulsation in a patient with cardiogenic shock following an acute myocardial infarction. The probable cause of the rupture was the constant abrasion and eventual perforation of the balloon membrane by a sharp calcified aortic plaque.

Aged↗
PubMed1975

Arbovirus vector ecology studies in Mexico during the 1972 Venezuelan equine encephalitis outbreak.

Virus vector studies were conducted in the States of Durango, Chihuahua, and Tamaulipas, Mexico, in June and July 1972. Apparently only a low level of Venzuelan equine encephalitis (VEE) virus transmission to equines occured at the time of the study, and the infection was restricted to areas which had not experienced overt activity during the preceding year. The low level of infection was associated with a scarcity of mosquitoes. The IB (epidemic) strain of VEE virus was isolated from two pools of Anopheles pseudopunctipennis (Theo.) and the blood of one symptomatic equine. The low mosquito population, the relatively few equine cases observed, and the absence of reports of VEE human disease from the outbreak area suggested VEE virus persistence through a low-level mosquito-equine transmission cycle. Other studies have already indicated that wild vertebrates play no more than a minor role in outbreaks of epidemic VEE. Mosquito collections made in areas of the states of Durango, Chihuahua, and Tamaulipas, where considerable epidemic activity of VEE had occurred in 1971, failed to reveal evidence of VEE virus persistence. Twenty-nine ioslations of other arboviruses were also made in these studies: including 22 of St. Louis encephalitis virus (SLE), 2 of Flanders virus, 1 of Turlock virus, 1 of Trivittatus virus of the California Group, 1 of western equine encephalitis virus (VEE), and 2 (from Santa Rose) which possibly represent a hitherto unknown virus in the Bunyamwera Group. These are the first reports of SLE virus isolations from mosquitoes in Mexico, and the first demonstration of Trivittatus, VEE Turlock and Flanders viruses in Mexico from any source.

Animals↗