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Biomedical subjects

M Vélez

Publications and source records attributed to M Vélez.

At least 19 recordsLinked to original sources
PubMed2001

Patients' answers to a postoperative questionnaire related to laser resurfacing.

To date there is no information that evaluates, from the patient's point of view, the experience of undergoing CO(2) laser skin resurfacing. This article investigates the outcome of laser resurfacing for various cutaneous problems with respect to the patient's expectations and experiences and the surgeon's opinions. Patients were entered into the study prospectively and presented with a questionnaire, at 12 months after treatment, to evaluate the patient's skin resurfacing experience. All patients received standardized preoperative counseling and underwent a standardized surgical protocol, conducted by the same surgeon. Eighty-eight percent of patients considered the result of the laser resurfacing to be very good, and 97% indicated that they had experienced little pain or discomfort. Nevertheless, 77% of patients stated that they would be unwilling to undergo another resurfacing procedure. This discrepancy is most likely the result of the patients' experiences in relation to the degree of erythema afterward. Most patients stated a desire to have more information regarding the procedure, particularly with respect to their experiences concerning postoperative erythema and exudates in the treated area. From the study it can be concluded that patients require extensive preoperative counseling, including a full explanation of all possible sequelae of these procedures to improve the patient's experience.

Aged↗
PubMed2000

[Study and incidence of carcinoma of the larynx in women].

Recent publications show an increase in the frequency of laryngeal carcinoma in women. Previous studies of patients in our health district (1875-1994) showed a male/female ratio of 56/1. However, a retrospective study of all laryngeal carcinomas diagnosed in a recent year (June 1997-May 1998) showed an overall male/female ratio of 10/1. Women are older at time of diagnosis than men (mean 70.33 years). None of the women was a regular drinker and only one smoked. Glottic location and absence of metastatic lymph node enlargement predominated at time of diagnosis.

Adult↗
PubMed1999

Electron microscopy comparison of CO2 laser flash scanning and pulse technology one year after skin resurfacing.

BACKGROUND: The recent adaptation of laser technology in plastic and dermatologic surgery has provided a means to reduce efficiently the irregularities of the surface of the skin. Previous studies have analyzed the short- and medium-term clinical and histologic results of two laser systems: the Sharplan 40C SilkTouch and the 5000C Coherent Ultrapulse with Computer Pattern Generator (CPG). This paper contains the long-term ultrastructural findings observed with the aid of transmission electron microscopy (TEM). MATERIALS AND METHODS: Twenty skin biopsy specimens were taken from ten Caucasion patients, between 54 and 72 years of age, who had undergone facial skin resurfacing with a CO2 laser 1 year previously. The treated areas of the face were divided into two equal parts. One half of the face was treated with the Sharplan SilkTouch laser and the other half with the Coherent Ultrapulse laser. Using TEM, the cell composition of the epidermis was studied ultrastructurally, as were the dermal-epidermal junction (DEJ) and the different fibers and cells in the superficial and middle dermis. RESULTS: On the side treated by the Sharplan laser, little melanin was observed, the DEJ was thicker, and there were abundant collagen fibers well compacted in the dermis. Also present was abundant elastin fiber with scarce interstitial spaces. On the side treated by the Coherent, the melanin was abundant and the DEJ was well structured. There were fibroblasts with lax chromatin in the dermis and collagen fibers in the papillary dermis oriented in a vertical and horizontal manner in relation to the epidermis. There was little elastin. The interstitial spaces were abundant. CONCLUSIONS: The Sharplan laser system seems to provoke a significantly more intense tissue response, with abundant dermal collagen and elastic fibers. This indicates that the Sharplan 40C SilkTouch might produce longer lasting clinical effects.

Aged↗
PubMed1998

Predicting forage indigestible NDF from lignin concentration.

We used chemical composition and in vitro digestibility data from temperate and tropical forages to develop relationships between indices of lignification and forage indigestible NDF. Neutral detergent fiber indigestibility increased nonlinearly as the lignin concentration of the NDF increased. Differences in estimated indigestible NDF using equations developed for a specific forage class (C3 and C4 grasses and legumes) were small and are probably not biologically significant when compared to those estimated from a common equation. Selected equations were compared with the Cornell Net Carbohydrate and Protein System (CNCPS) for the prediction of ADG. The linear equation (2.4 times NDF lignin content) used by the CNCPS and the Beef NRC had some of the largest errors due to mean bias. A log-log model [4.37 x (lignin/NDF)(.84)] provided the best combination of low total prediction error, low mean bias, and minimal error due to regression bias when permanganate lignin was used. A similar equation based on sulfuric acid lignin [6.17 x (lignin/NDF)(.77)] also met the above criteria. These equations then were evaluated with the CNCPS model against animal growth data from diets ranging in forage quality. Regardless of the equation used for predicting unavailable fiber, the CNCPS underpredicted daily gain, with mean biases ranging from -.10 to -.22 kg/d. Regression bias ranged from .13 to .14 kg/d and the coefficients differed from unity (P = .0001). The new equations gave numerically lower energy allowable ADG by steers compared to the linear equation currently used by the CNCPS model. The estimates were lower due to a higher predicted indigestible NDF, which resulted in a lower estimated forage energy value.

Animal Feed↗
PubMed1997

The bacteriophage phi29 head-tail connector imaged at high resolution with the atomic force microscope in buffer solution.

The surfaces of two- and three-dimensional phi29 connector crystals were imaged in buffer solution by atomic force microscopy (AFM). Both topographies show a rectangular unit cell with dimensions of 16.5 nm x 16.5 nm. High resolution images of connectors from the two-dimensional crystal surface show two connectors per unit cell confirming the p42(1)2 symmetry. The height of the connector was estimated to be at least 7.6 nm, a value close to that found in previous studies using different techniques. The 12 subunits of the wide connector domain were clearly resolved and showed a right-handed vorticity. The channel running along the connector had a diameter of 3.7 nm in the wide domain, while it was 1.7 nm in the narrow domain end, thus suggesting a tronco-conical channel shape. Moreover, the narrow connector end appears to be rather flexible. When the force applied to the stylus was between 50 and 100 pN, the connector end was fully extended. At forces of approximately 150 pN, these ends were pushed towards the crystal surface. The complementation of the AFM data with the three-dimensional reconstruction obtained from electron microscopy not only confirmed the model proposed, but also offers new insights that may help to explain the role of the connector in DNA packing.

Bacillus Phages↗
PubMed1996

Possible mechanisms for an irregular vessel coagulation when long laser pulses are used in the treatment of port-wine stains.

The laser treatment of port-wine stains (PWS) has as a main aim the irreversible damage of ectatic vessels. Blood content of the subcutaneous venous plexus in PWS can be increased by a factor of seven or more, compared to that of the normal skin. The venous blood velocity ranges from 0.1-1 mm/s in capillaries to approximately 22 mm/s in larger vessels of about 300 microns in diameter. A PWS, selected for study, was irradiated with a multiline argon laser 488/515 nm wavelength, 1.5 W power, 200 ms pulse duration, 0.5 mm beam diameter and repetition frequency up to 5 Hz. Laser shots were placed adjacently in an area of 1 cm2. Using these parameters, in the case of dilated PWS vessels with an optical penetration depth and thermal diffusion length less than the diameter of the vessel, together with a transit time of blood across the irradiated spot less than the pulse duration, and estimating that during a pulsed laser emission of 200 ms, the blood has travelled a distance of 3-4 mm, there is a strong indication that hemodynamics during irradiation may influence the pattern of coagulation and agglutination. Thrombosis should occur in the case of small vessels and, in larger vessels, the coagulated blood will only partly fill the lumen. The structure developed in the vessel interior may also change continuously with time, as the coagulated material is progressively replaced by fibrotic tissue and the irregular agglutination pattern may be due to inhomogeneity in the absorbed optical energy.

Biophysical Phenomena↗
PubMed1995

Cholesterol effect on the physical state of lipid multibilayers from the platelet plasma membrane by time-resolved fluorescence.

There are indications that the plasma membrane lipid composition and, in particular, the cholesterol/phospholipid (C/PL) ratio, affects platelet function. As a first approximation to the molecular characterization of the effect of cholesterol on the order, fluidity and lateral heterogeneity of the platelet plasma membrane, the steady-state and time-resolved fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH) and trans-parinaric acid (tPnA) has been studied in multibilayer vesicles of phospholipids extracted from human platelet plasma membrane with different cholesterol/phospholipid molar ratios modified in vitro from 0.07 to 0.9. The DPH studies show that the increased presence of cholesterol has a stronger effect on the order than on the fluidity of the bilayer, as has been previously observed in other lipid membranes. On the other hand, from the analysis of the fluorescence kinetics of tPnA we conclude that a higher cholesterol content gives rise to an increase of the heterogeneity of the bilayer, due to a larger fraction of solid-like lipid domains. These domains contain a cholesterol concentration much higher than the macroscopic average value.

Blood Platelets↗
PubMed1995

Reversed metal replicas of freeze-dried proteins to be visualized with the scanning tunneling microscope.

Scanning tunneling microscopy of metal-coated specimens has become a reliable technique that permits direct three-dimensional visualization of structural details at a level at which individual subunits in protein complexes or even single domains of proteins can be resolved. We describe in this paper a variation of the freeze-drying metal coating procedure that allows us to image with the STM the inner side of the metal replica, previously in contact with the protein molecules. We have tested this new approach with two different well characterized protein systems: freeze-dried two-dimensional crystals of bacteriophage phi 29 connector and the vesicle form of two-dimensional crystals of cytochrome oxidase from beef heart mitochondria. The images obtained have very good contrast and provide direct topographic information of the crystal surface, complementing structural information obtained previously with transmission electron microscopy. The resolution limit is imposed by the size (2-3 nm diameter) and corrugation of the metal grains used to prepare the replica and by the randomness of the metal shadowing.

Aluminum Silicates↗
PubMed1994

Improving the results of facial dermal lesions elimination by laser.

Argon laser therapy of superficial pigmented lesions in both young and old people is associated with a risk of complications including delayed wound closure and hypo/hypertrophic scarring. Problems may also occur after treatment of lesions located on the eyelid. To minimize the risk of these problems coagulation of deep tissue should be avoided. We discuss a technique using mercurochrome, a red-colored compound that absorbs the blue and green lines of the argon laser, as a barrier for the irradiated light that eliminates these complications and we provide probable reasons for this technique's effectiveness.

Humans↗
PubMed1992

Monoline argon laser (514 nm) treatment of benign pigmented lesions with long pulse lengths.

A dichroic filter was adjusted in order to make use of the green line of an argon laser for the treatment of pigmented lesions (actinic and senile lentigo, ephelis, café-au-lait marks and spilus nevus). Using a power of 1.5 W, a spot size of 0.5 mm and pulse lengths of 200 or 300 ms, satisfactory elimination of 620 pigmented cutaneous lesions was achieved. Although the pulse lengths used were much longer than the thermal relaxation time of the melanosomes, the histology after treatment showed little damage of adjacent structures. Good restoration of the epidermis and a return of normal pigmentation led to excellent cosmetic results, with few complications.

Cicatrix↗
PubMed1985

Comparative sensitivity of three mosquito cell lines for isolation of dengue viruses.

Comparative studies were carried out on three mosquito cell lines (C6/36 clone of Aedes albopictus, AP-61 from A. pseudoscutellaris, and TRA-284 from Toxorhynchites amboinensis) to determine their sensitivity to dengue virus isolation, growth, and handling characteristics for immunofluorescent testing. Virus isolation rates from human sera were the highest in the TRA-284-SF (a line adapted to serum-free medium), followed by the TRA-284 parental line and AP-61. Virus isolation was the lowest in the C6/36 line. All 3 cell lines were comparable in terms of ease of handling, but C6/36 cells were preferable for detecting infected cells by the direct fluorescent antibody test (DFAT) because of frequent cell clumping in the AP-61 and TRA-284 lines. Early detection of viral antigen of all 4 serotypes in the infected cells by DFAT was dependent upon the virus titre in the serum. The AP-61 and TRA-284-SF cells were the best for early detection and identification of viral antigen. Similarly, both AP-61 and TRA-284 cells were more resistant than C6/36 cells to toxic effects of human sera. Based on the economy of using the serum-free medium, their higher sensitivity for dengue virus isolation, and their ease of handling, it is recommended that the TRA-284-SF cell line be used for routine dengue virus isolation in laboratories with cell culture capability.

Aedes↗
PubMedDate not supplied

Reliability of serum magnesium values during diabetic ketoacidosis in children.

OBJECTIVE: To determine the prevalence of hypomagnesemia in diabetic children during diabetic ketoacidosis and following restitution of acid-base balance. METHODS: Eight consecutive diabetic children, ranging in age from 8 to 16 years, hospitalized in the pediatric intensive care unit with diabetic ketoacidosis from October 1st. through December 31st, 1995. A control group of 33 metabolically stable diabetic children, and a control group of 30 healthy children. Both control groups were similar in composition regarding age and sex to the study group. None of the patients in the study group and none of the controls had Magnesium supplementation given to them during the study period. MEASUREMENTS: Total serum Magnesium concentrations were measured from peripheral venous blood in all 71 patients. For the study group serum Magnesium was determined in a serial fashion: 1. upon admission in diabetic ketoacidosis 2. 24 hours after admission 3. 72 hours after admission RESULTS: The prevalence of hypomagnesemia was 62.4% in patients with diabetic ketoacidosis, (Group 1), 25% in patients after partial correction of ketoacidosis, (Group 2), and none in patients after resolution of ketoacidosis, (Group 3). The prevalence of hypomagnesemia was 6% for the chronic, metabolically stable diabetic control group, (Group 4), but 0% for the non-diabetic control group, (Group 5). Average serum Magnesium levels were significantly lower (p less than 0.05), in patients admitted in diabetic ketoacidosis compared to those of both the diabetic and the non-diabetic control groups. Also average serum Magnesium levels were significantly lower (p less than 0.05), in patients with corrected diabetic ketoacidosis than those of the healthy control group. But there were no significant differences (p = 0.59263) in average serum Magnesium levels between the diabetic control group and the diabetic patients after resolution of ketoacidosis. CONCLUSIONS: In this study the prevalence of hypomagnesemia was documented to be higher than the average described elsewhere for pediatric, adult, and coronary intensive care units. As hypomagnesemia is an indication of Magnesium depletion, we speculate that the transient hypomagnesemia detected in our study group is an expression of a state of Magnesium depletion that is masked by correction of acidosis and the Magnesium shifts associated with it. Consequently serum Magnesium values ought to be considered most reliable during and not after correction of diabetic ketoacidosis. Since Magnesium was not supplemented to any of our patients, the normalization of their serum values must be the result of: a. decreased glycosuria-related urinary losses b. cessation of acidosis-related urinary losses c. Magnesium shifts from intra to extracellular space The high prevalence of hypomagnesemia and the significant lower average serum Magnesium levels in children with diabetic ketoacidosis reveals the magnitude of the problem and the potential for Magnesium depletion that occurs in diabetic children.

Adolescent↗
PubMedDate not supplied

[Becker's myotonia in Peru].

INTRODUCTION: The word myotonia was used for the first time by Strümpell in 1891. Diseases associated with this symptom are called myotonias. They are classified on the basis of their clinical features in: congenita myotonia, paramyotonia congenita, myotonic dystrophy and Schwartz-Jampel syndrome. Becker's myotonia is a generalized congenita nondystrophic myotonia transmitted as an autosomal recessive trait and caused by allelic mutation of the gene encoding the chloride channel CLC-1 of the skeletal muscle fiber surface membrane, localized on chromosome 7q35. At the present time, nondystrophic myotonias are referred as channelopathies. CLINICAL CASE: We describe a case of generalized myotonia in a Peruvian young male, descending of Europeans, without familial history. CONCLUSIONS: We discuss his clinical symptoms, laboratory and electrophysiologic findings, differential diagnosis, and response to the treatment with carbamazepine. We report the first case of Becker's myotonia in Peru.

Adolescent↗
PubMedDate not supplied

[Chin tremor in a peruvian family].

INTRODUCTION: Chin tremor is an uncommon hereditary autosomic dominant disorder, characterized by involuntary, episodic, and repetitive movements involving chin muscles, stimulated by stress. It was first described by Massaro in 1894 like geniospasmo . The most reported cases are from Europeans or Americans families. CLINICAL CASE: A 53 years old man with chin tremor since childhood. CONCLUSIONS: We report the first Peruvian family with chin tremor without European nor American ascendancy with six affected members in four generations.

Chin↗