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Biomedical subjects

G López

Publications and source records attributed to G López.

At least 19 recordsLinked to original sources
PubMed2002

Plasma cell gingivitis.

Plasma cell gingivitis (PCG), an infrequent benign inflammatory condition of unknown etiology, is a type of plasma cell orificial mucositis, which includes a wide spectrum of conditions. We present the case of a 13-year-old girl who had PCG with an erythematous congestive plaque on the anterior maxillary gingiva for 4 years. Occasionally, the lesion became increasingly swollen and painful and bled. Results of a histopathologic examination showed dense plasmacytic infiltrate in the dermis, affecting the dermoepidermal border, with immunohistochemical positivity in the K and A light chains and vascular proliferation. "Lozenge" keratinocytes, "watery" spongiosis, and exocytosis were seen in the epidermis. Laboratory analysis showed notably low levels of both serum IgA and secretory IgA. We consider whether secretory IgA at low levels has an important etiopathogenic role favoring the development of localized subclinical repetitive infections that could lead to chronic PCG.

Adolescent↗
PubMed2001

Synthesis and reactivity of bridging and terminal hydrosulfido palladium and platinum complexes. Crystal structures of [NBu4]2[(Pt(c6F5)2(mu-SH)]2], [Pt(C6F5)2(PPh3)[S(H)AgPPh3]], and [Pt(C6F5)2(PPh3)[S(AuPPh3)2]].

The reactions of the hydroxo complexes [M(2)R(4)(mu-OH)(2)](2)(-) (M = Pd, R = C(6)F(5), C(6)Cl(5); M = Pt, R = C(6)F(5)), [[PdR(PPh(3))(mu-OH)](2)] (R = C(6)F(5), C(6)Cl(5)), and [[Pt(C(6)F(5))(2)](2)(mu-OH)(mu-pz)](2-) (pz = pyrazolate) with H(2)S yield the corresponding hydrosulfido complexes [M(2)(C(6)F(5))(4)(mu-SH)(2)](2-), [[PdR(PPh(3))(mu-SH)](2)], and [[Pt(C(6)F(5))(2)](2)(mu-SH)(mu-pz)](2-), respectively. The monomeric hydrosulfido complexes [M(C(6)F(5))(2)(SH)(PPh(3))](-) (M = Pd, Pt) have been prepared by reactions of the corresponding binuclear hydrosulfido complexes [M(2)(C(6)F(5))(4)(mu-SH)(2)](2-) with PPh(3) in the molar ratio 1:2, and they can be used as metalloligands toward Ag(PPh(3))(+) to form the heterodinuclear complex [(C(6)F(5))(2)(PPh(3))[S(H)AgPPh(3)]], and toward Au(PPh(3))(+) yielding the heterotrinuclear complexes [M(C(6)F(5))(2)(PPh(3))[S(AuPPh(3))(2)]]. The crystal structures of [NBu(4)](2)[[Pt(C(6)F(5))(2)(mu-SH)](2)], [Pt(C(6)F(5))(2)(PPh(3))[S(H)AgPPh(3)]], and [Pt(C(6)F(5))(2)(PPh(3))[S(AuPPh(3))(2)]] have been established by X-ray diffraction and show no short metal-metal interactions between the metallic centers.

Journal Article↗
PubMed2001

Long-term efficiency of catalytic converters operating in Mexico City.

A 1999 ordinance by the Government of Mexico City bans 1993 model-year vehicles from on-road operation if their catalytic converters are not replaced with new ones. To validate the benefits of this action, we examined three issues related to exhaust emissions of vehicles equipped with catalytic converters. After selecting representative fleets of in-use vehicles, a comparison between emissions and catalyst efficiency in cars with two categories of exhaust emission limits was carried out. For that purpose, two fleets were selected, each made up of 10 vehicles run under similar conditions. A third, larger fleet with emissions control systems was used to evaluate and simulate real-world conditions of vehicles in a controlled laboratory. Finally, the aging effect on the catalytic converter was studied on vehicles run for 100,000 km, replacing their old emission control devices for new ones. The 1991-1992 model-year vehicles showed a high percentage of compliance with the corresponding emissions standard (90%) in comparison with 1993 model-year and later vehicles (Tier 0). However, NOx emissions were higher for the newer vehicles. Fifty percent of the 1991-1992 model-year vehicles evaluated under the official inspection/maintenance (I/M) procedure did not meet the regulated emissions standard when the results were compared with those of the U.S. Federal Test Procedure FTP-75. Our results suggest that the replacement of old catalytic converters with new ones will have little effect on decreasing polluting emissions because these vehicles were in very bad mechanical condition. Results of catalytic activity as a function of mileage indicated inefficient catalyst performance for the fleets tested. All pollutant conversions were below 90% efficiency, and they deteriorated by an average of 30% after the vehicles were run for 100,000 km.

Air Pollutants↗
PubMed2001

Dietary fats affect rat plasma lipoprotein secondary structure as assessed by Fourier transform infrared spectroscopy.

This investigation was undertaken to determine by Fourier transform infrared spectroscopy the effects of diets enriched with fish, sunflower or olive oils on the secondary structure of plasma HDL and LDL from rats, as well as the effects on lipid unsaturation and acyl chain lengths. Controls were fed a commercial diet. In HDL, random coil conformation was relatively high in rats fed the fish diet, probably due to the irregular geometry of polyunsaturated fatty acids interacting with apoproteins. Parallel structural behaviors were observed for rats fed control and olive oil diets. The lowest lipid unsaturation level was found in HDL of rats fed olive oil, and acyl chain lengths were slightly increased by the three fats. Rats fed olive oil had the lowest percentage of LDL beta-sheets and these were more abundant in rats fed the fish oil diet. The least lipid unsaturation in LDL was in rats fed the olive oil diet. No significant differences in acyl chain lengths were observed. Certain protein conformational changes and/or apoprotein composition differences due to dietary fat may affect the binding between lipoproteins and their receptors in cells.

Animals↗
PubMed2001

Localization and expression of BCAT during pregnancy and lactation in the rat mammary gland.

During lactation, branched-chain aminotransferase (BCAT) gene expression increases in the mammary gland. To determine the cell type and whether this induction is present only during lactation, female rats were randomly assigned to one of three experimental groups: pregnancy, lactation, or postweaning. Mammary gland BCAT activity during the first days of pregnancy was similar to that of virgin rats, increasing significantly from day 16 to the last day of pregnancy. Maximal BCAT activity occurred on day 12 of lactation. During postweaning, BCAT activity decreased rapidly to values close to those observed in virgin rats. Analyses by Western and Northern blot revealed that changes in enzyme activity were accompanied by parallel changes in the amount of enzyme and its mRNA. Immunohistochemical studies of the mammary gland showed a progressive increase in mitochondrial BCAT (mBCAT)-specific staining of the epithelial acinar cells during lactation, reaching high levels by day 12. Immunoreactivity decreased rapidly after weaning. There was a significant correlation between total BCAT activity and milk production. These results indicate that the pattern of mBCAT gene expression follows lactogenesis stages I and II and is restricted to the milk-producing epithelial acinar cells. Furthermore, BCAT activity is associated with milk production in the mammary gland during lactation.

Animals↗
PubMed2001

[Non classical subtypes of diabetes mellitus].

BACKGROUND: Some adult, obese and diabetic patients, initiate their disease with a severe diabetic ketoacidosis without a precipitating factor and do not require insulin thereafter. These patients are classified as having a "non classical" diabetes mellitus. AIM: To study the clinical, immunological, genetic and metabolic features of patients with non classical diabetes mellitus. PATIENTS AND METHODS: Ten patients (9 men, aged 45 +/- 12 years old) with non classical diabetes mellitus were studied. Anti islet and anti glutamic acid decarboxylase antibodies (ICA and anti GAD), HLA DQ alpha arginine 52 and non aspartic beta 57 were measured. Insulin secretion was measured by C peptide after glucagon injection and with the minimal model of Bergman. The latter model was also used to determine insulin sensitivity. RESULTS: Three patients were immunologically classified as type 1, since they had positive ICA or antiGAD antibodies and type 1 genetics (neutral or susceptible HLA DQ alpha and beta). They had insulin secretion after glucagon stimulus (C peptide ranging from 2.2 to 7.5 pmol/ml), but an almost absent response to a glucose load. They were also insulin resistant (a sensitivity index ranging from 0.05 to 1.67 x 10(-4) min/microU x ml). These three cases could be categorized as latent type 1. The other seven patients were ICA negative and antiGAD negative. Five had a susceptible HLA genotype for type 1 diabetes and two were neutral. All had insulin secretion after glucagon stimulation and a variable response to glucose. Six were insulin resistant (sensitivity index ranging from 0.32 to 1.29 x 10(-4) min/microU x ml). One patient was insulin sensitive (sensitivity index of 3.83 x 10(-4) min/microU x ml). Therefore all these patients were classified as type two diabetics with an atypical debut. CONCLUSIONS: Not all diabetics presenting with a severe diabetic ketoacidosis are type I. Among these, there are subjects with a latent type 1 diabetes or with an atypical type 2 diabetes.

Autoantibodies↗
PubMed2001

[Characterization of the expression and function of SigM an ECF sigma factor in mycobacteria].

The survival of M. tuberculosis within the macrophage depends on its ability to respond to oxidative stress, and the ECF subfamily of sigma factors likely play an important role. We studied SigM, a sigma factor whose gene is located near the origin of DNA replication. In both M. smegmatis and M. bovis BCG, the expression of sigM was induced at high temperature and in stationary phase. Mutants of M. smegmatis without an intact sigM were defective for survival in oxidative stress and also for the induction of thioredoxin reductase activity in oxidative stress. The thioredoxin system reduces disulfide bonds that are formed in oxidative stress. SigM thus appears to regulate thioredoxins and forms part of the bacteria's complex protective responses.

DNA Replication↗
PubMed2000

Bacillus subtilis LrpC is a sequence-independent DNA-binding and DNA-bending protein which bridges DNA.

Genetic evidence suggests that the Bacillus subtilis lrpC gene product participates in cell growth and sporulation. The purified LrpC protein, which has a predicted molecular mass of 16.4 kDa, is a tetramer in solution. LrpC binds with higher affinity ( K (app) approximately 80 nM) to intrinsically curved DNA than to non-curved DNA ( K (app) approximately 700 nM). DNase I footprinting and the supercoiling of relaxed circular plasmid DNA in the presence of topoisomerase I revealed that LrpC induces DNA bending and constrains DNA supercoils in vitro. The LrpC protein cooperatively increases DNA binding of the bona fide DNA-binding and DNA-bending protein Hbsu. LrpC forms inter- and intramolecular bridges on linear and supercoiled DNA molecules, resulting in a large network and DNA compactation. Collectively, these findings suggest that LrpC is an architectural protein and that its activities could provide a means to modulate DNA transactions.

Bacillus subtilis↗
PubMed2000

Langerhans' cell histiocytosis on the vulva.

BACKGROUND: Langerhans' cell histiocytosis (LCH) affecting the vulva alone is rare. At present, there are 51 published cases of LCH affecting the genital area. Of these, only 7 had LCH located in the genital area alone; in these cases, there was no subsequent systemic spread of the disease. A report of the 8th such case is presented with a review of the previous 7 cases. CASE: A 40-year-old white woman presented with a several-month history of pruritic and ulcerous lesions on the vagina which had then spread to the vulva. No tiredness, general malaise, or associated temperature was observed. Physical examination disclosed an erythematous plaque on the labia minora, which was bilateral and slightly infiltrated. The rest of the physical examination brought no other disorders of interest to light. Histological findings were characteristic of LCH. Four cycles of iv vincristine (2 mg/m cycle) 15 days apart did not obtain objective or symptomatic improvement in the vulvar lesions. Therefore, a local and partial extirpation of both labia minora was performed. Eighteen months after surgery, the patient has no symptoms or signs of local recurrence or systemic spread. CONCLUSIONS: Although the occurrence of LCH on the vulva is very unusual, we must bear this possibility in mind when a woman presents atypical chronic lesions on the genital mucosa. In such cases, it is necessary to perform a biopsy on the mucosa, rule out the possibility of systemic disease, and review the patient periodically in order to forestall a possible spread of the disease at any time.

Adult↗
PubMed2000

Marchantin M trimethyl ether.

The title macrocycle, C(31)H(30)O(5), is comprised of two bibenzyl ether moieties linked cyclically by spacers which each consist of two-carbon alkyl chains. The observed conformation of the macrocycle may be partly stabilized by intramolecular C-H.O close contacts. The packing appears to be directed by van der Waals forces. This work explains the occurrence of a signal found in the (1)H NMR spectra of both marchantinquinone and marchantin M trimethyl ether at delta = 5. 49 and 5.56 p.p.m., respectively. The shift in the position of the expected peak can be explained by the proximity of an H atom belonging to one of the aromatic rings to another ring in the same molecule.

Journal Article↗
PubMed2000

Personal-computer-based system for three-dimensional anatomic-physiological correlations during stereotactic and functional neurosurgery.

This paper describes the automatic three-dimensional (3D) graphic possibilities that are supplied by the Neurosurgical Deep Recording System (NDRS) to facilitate anatomic-physiological targeting during stereotactic and functional neurosurgery using depth recording. This software has been developed to substitute the complex electronic equipment ordinarily used for deep brain electrical recording, display and processing by a personal computer. It may also help to improve on-line graphic analysis, automatic management of the recorded information and flexibility to implement different forms of signal analysis. It can automatically show a 2D or 3D representation of the electrode track, with the electrophysiological findings superimposed as well as the corresponding sagittal, coronal and axial views of a brain atlas using automatic scaling. The NDRS has already successfully been applied during more than 300 neurosurgeries in Spain and Cuba, enabling improved targeting accuracy and safety.

Brain Mapping↗
PubMed1999

Crystallization and preliminary X-ray diffraction studies of Streptococcus pyogenes plasmid pSM19035-encoded omega transcriptional repressor.

The transcriptional repressor, omega protein, from the Streptococcus pyogenes broad-host-range plasmid pSM19035 was crystallized at pH 7. 5 and 8.5 by the vapour-diffusion method using PEG 4000 as precipitant. Two crystal forms were obtained; the first belongs to the tetragonal space group P4(1)2(1)2 or P4(3)2(1)2 and the second to the hexagonal space group P6(1) or P6(5). The crystals are most likely to contain one omega protein in the asymmetric unit, with V(m) values of 3.2 and 3.5 A(3) Da(-1), respectively. The crystals diffract X-rays to 2.4 and 2.9 A resolution for the tetragonal and hexagonal systems, -respectively.

Bacterial Proteins↗
PubMed1999

[Heat treatment and dietary fiber effect on protein quality of artichoke and its sub-product].

Blanched (95 degrees C, 5 min), autoclaved (100 degrees C, 5 min) artichoke hearts and their by-product (external leaves and distal portion of stem) were analysed for amino acid composition, "in-vitro" protein digestibility (DIVP), and dietary fiber. Amino acid score of the three samples was in a good agreement with FAO/WHO recommendations including sulphur amino acids. Dietary fiber content was high in all samples, decreasing in autoclaved artichokes that might be relate with the improvement of DIVP. By-product was consider a potential food source because it showed a good amino acid profile and the highest levels of DIVP (76.4%), but fibrouness was also too high (51.6%).

Amino Acids↗
PubMed1999

[Iron bioavailability in food].

The nutritional need for iron in living organisms is derived from the central role that it plays in the energy metabolism of living cells. However, iron exists in almost exclusively in the less soluble oxidised state (Fe III). This has greatly reduce its accessibility. Iron in foods exist in two main forms: haem iron and non-haem iron, which are absorbed by different pathways with different degrees of efficiency depending upon dietary and physiological factors. All these factors increase or reduce the proportion of the total iron in a food or diet that is utilised for metabolism, that is iron bioavailability. Iron deficiency leads to anaemia, one of the most common nutritional deficiency disorders in the world both in industrialised and developing countries. Preventing this illness is based on a gradual growth in our understanding of iron nutrition.

Absorption↗
PubMed1999

[Iron, zinc and copper content of foods commonly consumed in Mexico].

Nutrient composition in foods is necessary for the determination of nutrient intake. Food composition tables used for dietary studies in Mexico do not have information of zinc, iron and copper; when present the values have been extrapolated from laboratory analysis carried out with foods in other countries and regions of the world. In this study zinc, iron, and copper content of 104 plant foods and 32 animal foods was determined. The procedure used was atomic absorption spectrophotometry for the minerals. Foods were grouped into cereals, vegetables, fruits, legumes and animal foods. Zinc content ranged from 0.018 mg/100 g for strawberry to 9.193 mg/100 g for beef. Iron content ranged from 0.113 mg/100 g for yogurt to 19.82 mg/100 g for a commercial cereal which had minerals added during processing. In some foods copper was not found and the highest content was 3.371 mg/100 g in beef liver. This study has provided information on zinc, iron and copper content of the most commonly consumed foods in Mexico.

Animals↗
PubMed1998

B-mode, utero-ovarian and intratumoural transvaginal colour Doppler ultrasonography for differential diagnosis of ovarian tumours.

OBJECTIVES: The aim of this study was to evaluate and compare the use of B-mode transvaginal, utero-ovarian Doppler and intratumoural colour Doppler imaging in the diagnosis of ovarian tumours in order to establish whether they are organic or functional, and malignant or benign in nature prior to surgery. STUDY DESIGN: A series of 213 women between the ages of 15 and 87 presenting ovarian tumours were examined with pulsed and colour Doppler and the functional state of the ovary at the time of the exploration was also established. Size and morphology were evaluated through a new scoring system called sonographic index. This score is calculated as the sum of the points corresponding to tumoural volume (< or = 8 ml = 1 point; > 8 ml and < or = 100 ml = 2 points; > 100 ml = 3 points) and the points corresponding to morphological characteristics (negative echogenicity = 1 point; mixed echogenicity = 2 points; multilocular morphology = 3 points; complex morphology = 4 points; positive echogenicity = 5 points) varying between 2 and 8 points. The flow velocity waveform (FVW) of the utero-ovarian and intratumoural arteries were obtained and analyzed after assessing their resistance indices. Other parameters studied were the presence and location of the colour signal in the intratumoural arteries. RESULTS: Of the total, 84 of the tumours were found to be functional and had disappeared by the time later examinations took place. Surgery was performed in 129 of the patients, and posterior histopathological studies permitted classifying the tumours as benign in 107 cases and malignant in 22. The sonographic index was significantly higher in the organic (4.9 +/- 1.5) and malignant (6.9 +/- 1.0) tumours than in the functional (3.6 +/- 1.5) and the benign (4.1 +/- 1.2) tumours. The utero-ovarian and intratumoural blood flow RIs in the malignant tumours (0.48 +/- 0.12 and 0.43 +/- 0.08, respectively) was significantly lower than in the benign tumours (0.83 +/- 0.12 and 0.58 +/- 0.15, respectively). There were no significant differences in the utero-ovarian and intratumoural blood flow RIs when organic and functional tumours were compared. In all of the malignant tumours a colour signal was identified; it was centrally located in 90% of the cases. A colour signal was observed in 83% of the functional tumours, and in 52% of the organic benign tumours. In the benign tumours the colour signal was peripherally located in 98% of the cases. The variables for sensitivity, specificity, positive predictive value, negative predictive value and precision when organic tumours were diagnosed were 82.9, 65.5, 78.7, 71.4 and 76.1 for a sonographic index where the score was > or = 4; the values for the utero-ovarian RI were 48.4, 90.4, 88.4, 53.6 and 65.1 (cut-off 0.55 > or = RI > or = 0.90); the values for the intratumoural RI were 56.5, 68.6, 54.2, 70.6 and 63.8 (cut-off < or = 0.55). When malignancy was diagnosed these variables were 95.5, 82.2, 38.2, 99.4 and 83.6 for the sonographic index (score > or = 6); 90.9, 98.9, 90.0, 98.9 and 98.1 for the utero-ovarian RI (cut-off < or = 0.55) and 80.0, 66.7, 33.3, 94.1 and 69.0 for the intratumoural RI (cut-off < or = 0.50). The number of false positives diagnosed on the basis of the intratumoural RI decreased when cases that had been evaluated during the luteal phase were excluded from the study. Notwithstanding, the phase of the cycle does not seem to interfere with the diagnosis when utero-ovarian Doppler imaging is used. CONCLUSIONS: B-mode transvaginal ultrasonography and utero-ovarian Doppler velocimetry seem to complement each other to aid in differentiating between organic and functional ovarian tumours. Transvaginal ultrasonography and Doppler imaging provide good results for the diagnosis of malignancy, although the utero-ovarian RI reduces the number of false positives that occur with ultrasonography. Our group, therefore, believes that the combined use of these techniques is beneficial in the clinical d

Adolescent↗
PubMed1998

Naltrexone effects on insulin sensitivity and insulin secretion in hyperandrogenic women.

A total of 12 women (24.2 +/- 1.6 years old, BMI 36.7 +/- 1.5 Kg/m2) with hyperandrogenism (HA) and with normal glucose tolerance test were studied to evaluate the involvement of endogenous opioids in the pathophysiology of insulin secretion and insulin sensitivity in HA by administering naltrexone, an oral opioid receptor antagonist. Six patients received naltrexone orally (75 mg daily) and another six received placebo for 12 weeks (double-blind study). Before and after therapy a frequently sampled intravenous glucose tolerance test (FSIVGTT) was performed. The insulin sensitivity index (SI) was determined by Bergman's program. SHBG, DHEAS, testosterone, free androgen index (FAI) and plasma concentrations of IGF-I and IGFBP-1 were determined in 3 basal samples, before and after therapy. Treatment with naltrexone in hyperandrogenic patients resulted in a decrease in fasting insulin concentrations of 40% and C-peptide concentrations of 50% (p < 0.05). Insulin and C-peptide from the FSIVGTT displayed a similar pattern with a fall in the area under the curve under naltrexone treatment of 34% for insulin and 35% for C-peptide. Insulin sensitivity did not change under naltrexone (1.26 +/- 0.19 vs 1.32 +/- 0.32 10(-4) x min(-1)/(uU/ml)) or placebo (0.95 +/- 0.19 vs 1.12 +/- 0.28 10(-4) x min(-1)/(uU/ml)) administration. However, glucose effectiveness increased significantly with naltrexone (2.231 +/- 0.002 vs 3.354 +/- 0.006 x 10(-2) min(-1)). Glucose (fasting and area under the curve) was not modified significantly after naltrexone administration. Baseline hormone levels were similar in the two groups, and they did not change after long-term treatment with naltrexone or placebo. In conclusion, these results support the hypothesis of elevated opioid tonus and increased insulin secretion as a possible mechanism of hyperinsulinism in a group of hyperandrogenic women of ovarian origin. This alteration could act as an additional factor in the pathogenesis of insulin resistance found in an important proportion of these patients.

Adolescent↗