PubMed Health⌕ Search

Biomedical subjects

L García

Publications and source records attributed to L García.

At least 73 records · Page 4Linked to original sources
PubMed1998

Bone changes in pre- and postmenopausal women with thyroid cancer on levothyroxine therapy: evolution of axial and appendicular bone mass.

The effects of suppressive doses of levothyroxine (LT4) on bone mass are controversial. Our aim was to evaluate the effects on axial and appendicular bone mineral density (BMD) and bone metabolism of long-term LT4 suppressive therapy in women by means of cross-sectional and longitudinal studies, and also to assess the potential influence of menopausal status and LT4 dose. Seventy-six women (aged 47 +/- 13 years, 37 pre- and 39 postmenopausal) on suppressive therapy (67 +/- 34 months duration, mean LT4 dose 168 +/- 41 micrograms/day) from our Thyroid Cancer Unit without previous hyperthyroidism or concomitant hypoparathyroidism were studied. Serum TSH, T3 free T4, calcium, phosphorus, alkaline phosphatase, BGP, iPTH and urinary calcium (uCA) were measured. BMD was measured by dual-energy X-ray absorptiometry (DXA) at lumbar spine, femoral neck, Ward's triangle, ultradistal and distal third radius and expressed as a Z-score. In a subset of 27 women aged 46 +/- 15 years (14 pre- and 13 postmenopausal) a second densitometry scan was performed 27 +/- 5 months later. Patients on suppressive therapy showed a small reduction in BMD at the distal third radius (Z-score: -0.77 +/- 0.98; 95% confidence interval: -1.11, -0.44) without differences between pre- and postmenopausal women. Significant relations with the regimen of suppressive therapy and bone turnover markers were detected except at the lumbar spine. In the longitudinal study a significant although mild reduction in femoral neck BMD was found that correlated with prior T3 and iPTH. In conclusion, our data show a small detrimental effect of cautious LT4 suppressive therapy on bone mass assessed by DXA; it remains to be established whether this increases the prevalence of fractures.

Absorptiometry, Photon↗
PubMed1998

In situ characterization of the Ca2+ sensitivity of large conductance Ca2+-activated K+ channels: implications for their use as near-membrane Ca2+ indicators in smooth muscle cells.

The Ca2+ sensitivity of large conductance Ca2+- and voltage-activated K+ channels (BKV,Ca) has been determined in situ in freshly isolated myocytes from the guinea pig urinary bladder. In this study, in situ denotes that BKV,Ca channel activity was recorded without removing the channels from the cell. By combining patch clamp recording in the cell-attached configuration and microfluorometry of fura-2, we were able to correlate BKV,Ca channel activity with changes in cytoplasmic intracellular [Ca2+] ([Ca2+]i). The latter were induced by ionomycin, an electroneutral Ca2+ ionophore. At 0 mV, the Hill coefficient (nH) and the [Ca2+]i to attain half of the maximal BKV,Ca channel activity (Ca50) were 8 and 1 microM, respectively. The data suggest that this large Hill number was not a consequence of the difference between the near-membrane [Ca2+] ([Ca2+]s) and the bulk [Ca2+]i, indicated by fura-2. High Hill numbers in the activation by Ca2+ of BKV,Ca channels have been seen by different groups (e.g., filled squares in Fig. 4 of Silberberg, S. D., A. Lagrutta, J. P. Adelman, and K. L. Magleby. 1996. Biophys. J. 70:2640-2651). However, such high nH has always been considered a peculiarity rather than the rule. This work shows that a high Ca2+ cooperativity is the normal situation for BKV,Ca channels in myocytes from guinea pig urinary bladder. Furthermore, the Ca50 did not display any significant variation among different channels or cells. It was also evident that BKV,Ca channel activity could decrease in elevated [Ca2+]i, either partially or completely. This work implies that the complete activation of BKV,Ca channels occurs with a smaller increment in [Ca2+]s than previously expected from in vitro characterization of the Ca2+ sensitivity of these channels. Additionally, it appears that the activity of BKV,Ca channels in situ does not strictly follow changes in near-membrane [Ca2+].

Animals↗
PubMed1998

Field studies and cost-effectiveness analysis of vaccination with Gavac against the cattle tick Boophilus microplus.

The control of tick infestations and the transmission of tick-borne diseases remains a challenge for the cattle industry in tropical and subtropical areas of the world. Traditional control methods have been only partially successful and the parasites continue to result in significant losses for the cattle industry. Recently, vaccines containing the recombinant Boophilus microplus gut antigen Bm86 have been developed. These vaccines have been shown to control tick infestations in the field. However, extensive field studies investigating the efficacy and cost-effectiveness of vaccination have not been reported and are needed to appraise the effect of this new approach for tick control. Here is reported the results of the application of Gavac in a field trial including more than 260,000 animals in Cuba. In this study the correlation between the antibody response to vaccination and the effect on ticks fertility is determined. Physiological status of the animals was found to affect the primary response to vaccination but not the antibody titers after revaccination. A cost-effectiveness analysis showed a 60% reduction in the number acaricide treatments, together with the control of tick infestations and transmission of babesiosis, which resulted in savings of $23.4 animal-1 year-1. These results clearly demonstrate the advantage of vaccination and support the application of Gavac for tick control.

Animals↗
PubMed1998

The re-emergence of American visceral leishmaniasis in an old focus in Venezuela: present situation of human and canine infections.

The report of a new autochthonous case of human American Visceral Leishmaniasis (AVL) in 1992 in the village of Guayabita, Aragua State, Venezuela (10 degrees 16'N, 67 degrees 28'W; 500 m asl), led us to undertake an epidemiological study in this locality. A demographic survey was conducted using a structured questionnaire in which data was collected regarding sex, age, occupation, length of residence in the area and migratory history. A leishmanin skin test (LST) was applied and samples of venous blood for counter immunoelectrophoresis (CIEP) and immunofluorescent antibodies (IFAT) tests were drawn. The prevalence of positive LST was 11.4%. The positivity was highest among males and increased with age. Young males seemed to be more exposed to infection than females. Since occupation per se did not seem to account for this association, it may be explained as a gender-associated behavior, leading to different degrees of exposure to sand flies. The canine population was also screened for leishmanial infection. One dog was shown to be parasitologically infected with Leishmania sp. Four out of 71 dogs (5.6%) were positive for FG, CIEP, IFAT and Western Blot and 11 (15.5%) were positive for CIEP. These results suggest that after almost 30 years of epidemiological silence, American visceral leishmaniasis has re-emerged in this focus.

Adolescent↗
PubMed1998

A clinical and histological comparison of flashscanning versus pulsed technology in carbon dioxide laser facial skin resurfacing.

BACKGROUND: Two different carbon dioxide (CO2) laser systems are currently in use for skin resurfacing. The vast majority of lasers use a pulsed beam, like the Coherent 5000C, but Sharplan uses scanning technology. OBJECTIVE: We describe a clinical and histological comparison of these two laser technologies in order to determine if there are differences in the outcome. METHODS: Twenty-two female patients underwent facial skin resurfacing using the Coherent 5000C UltraPulse CPG on one side of the face and the Sharplan Silk Touch on the contralateral side of the face. The clinical appearances were assessed periodically after treatment and punch biopsies were taken preoperatively and after 7, 21, and 90 days. Tissue was stained with Hematoxylin-Eosin, Masson Trichrom, and with the Verhoeff technique. Histological evaluation was performed on randomized samples taken from the same patient. Epidermis/dermis expression, collagen compaction, and elastin fiber quantity were compared to evaluate if any differences existed. RESULTS: The side treated by Coherent healed more rapidly and with excellent cosmesis. Greater erythema was observed on the Sharplan side, but had disappeared at the 90-day evaluation. At this time the quality of the results was similar with no particular difference between the sides treated by the Coherent or the Sharplan lasers. At the histological level, although tissue recovered faster on the Coherent side at the 7-day control, at 90 days the collagen was better compacted and organized on the Sharplan side. Similarly, the quantity of the elastin was significantly more enhanced on the Sharplan side. CONCLUSION: Irradiated laser energy density in relation to time, and the way that it is delivered, should play an important role at the moment of producing collagen shrinkage. The SilkTouch delivers laser energy more aggressively, thereby producing a more intense inflammatory tissue reaction, which results in slower recovery of tissue, compared with the Coherent CPG. More active enhancement of vascularization found in the Sharplan is likely to be the reason for a more effective collagen proliferation and compaction. These changes, together with the increase in elastin in the dermis, may produce longer lasting effects in skin resurfacing.

Adult↗
PubMed1998

Semiology and subtyping of panic disorders.

To date, the quantitative psychopathology of panic disorder (PD) has been less well studied than that of other psychiatric conditions such as schizophrenia or major depression. The aim of the present study was to assess the frequency and factorial grouping of symptoms in a naturalistic sample of PD patients. A total of 274 consecutive cases of PD who contacted an out-patient clinic in Barcelona, Spain were assessed by two experienced interviewers. The assessment instruments included the Structured Clinical Interview for DSM-III-R Upjohn version (SCID-UP-R) and an inventory of panic attack symptoms based on DSM-III-R. Of the patients who presented at the unit during the assessment period, 8.5% presented with PD. Palpitations, shortness of breath, fear of dying and dizziness were the most frequent and intense symptoms reported by the PD patients. Principal-component analysis revealed four factors which accounted for 57% of the variance, including 'cardiorespiratory' (26.1%) and 'vestibular' (15.1%) factors, and two additional factors with mixed symptoms. The frequency of presentation of symptoms was similar to that reported in other studies. However, some discrepancies were observed that may be attributed to transcultural differences as well as to terminological problems and the range of symptoms assessed. These factors may also explain some of the differences found in factor analysis groupings in previous studies. Our findings support the symptom subtyping of PD.

Adolescent↗
PubMed1998

Rapid detection of Actinobacillus actinomycetemcomitans, Prevotella intermedia and Porphyromona gingivalis by multiplex PCR.

The identification of specific periodontal pathogens by conventional methods, mainly anaerobic cultivation, is difficult, time consuming and even sometimes unreliable. Therefore, a multiplex PCR method for simultaneous detection of Actinobacillus actinomycetemcomitans (A.a.), Porphyromona gingivalis (P.g.) and Prevotella intermedia (P.i.) was developed for rapid and easy identification of these specific bacterial pathogens in subgingival plaque samples. In this paper, there is a detailed description of the oligonucleotide primer selection, DNA extraction and PCR conditions and the sequencing of the amplified products. The locus chosen to be amplified is a highly variable region in the 16S ribosomal DNA. For the development of this technique ATCC cultures and pure cultures from subgingival plaque samples taken from periodontitis patients were used. As an internal positive control a recombinant plasmid was developed. This simple DNA extraction procedure and the DNA amplification and visualization of the amplified product permits the detection of the bacteria in a working day. Thus, this multiplex PCR method is a rapid and effective detection method for specific periodontal pathogens.

Aggregatibacter actinomycetemcomitans↗
PubMed1998

Absorption studies of albendazole and some physicochemical properties of the drug and its metabolite albendazole sulphoxide.

In several studies of patients with neurocysticercosis under treatment with albendazole the pharmacokinetic data were difficult to interpret, probably because of slow and erratic drug dissolution response and absorption problems in-vivo. Because there is no information available about the physicochemical properties of the drug, the aim of this work was to explain this erratic behaviour by fully characterizing the solution behaviour of the drug and its metabolite. To accomplish this, the physicochemical properties, pKa and solubility, and in-vitro plasma binding of albendazole and its main metabolite, albendazole sulphoxide, were studied by conventional methods. The intestinal and gastric absorption and dissolution behaviour of albendazole were also studied. The solubility of both compounds is very low. Both are amphoteric molecules with two ionization steps, with pKa values of 10.26 and 2.80 for albendazole and 9.79 and 0.20 for albendazole sulphoxide; low pKa values were obtained by performing linear free energy relationship calculations. On the other hand, protein binding studies showed that albendazole is 89-92% bound to plasma proteins whereas for albendazole sulphoxide the figure is 62-67%. This metabolite is bound by albumin and to alpha1-glycoprotein. Absorption of albendazole occurs along the gastrointestinal tract and is limited by its solubility. Good dissolution profiles were observed when 0.1 M HCl was used as dissolution medium. The results show that 0.1 M HCl enables discrimination between the drug-release characteristics of different products.

Albendazole↗
PubMed1998

Pharmacokinetic interaction in rabbits between a new anticonvulsant, DL-3-hydroxy-3-ethyl-3-phenylpropionamide, and phenytoin.

The effect of phenytoin on the disposition of DL-3-hydroxy-3-ethyl-3-phenylpropionamide (HEPP) has been studied in New Zealand white rabbits. Plasma HEPP levels decreased when the drug was administered with phenytoin. The area under the plasma concentration-time curve was reduced by 56.49% (from 43.23+/-7.0 to 18.81+/-2.03 microg h mL(-1)), the elimination half-life was also significantly (P<0.01) reduced (from 2.68+/-0.35 to 1.04+/-0.07 h) and the clearance was increased (from 0.35 to 0.81 L h(-1) kg(-1)). In-vitro protein binding to bovine serum albumin (BSA) and plasma was evaluated by equilibrium dialysis. Plasma protein binding was low (between 33.69 and 37.43% at concentrations ranging from 6.25 to 100 microg mL(-1)). The compound binds preferentially to albumin with an association constant (Ka) of 3.81 x 10(3) M(-1) at 37 degrees C. The results suggest a pharmacokinetic interaction between phenytoin and HEPP, probably on the drug-metabolizing enzyme system in the liver.

Animals↗
PubMed1998

[Optic neuromyelitis: a necrotizing disease of the central nervous system].

Optic neuromyelitis is characterized by simultaneous or successive necrotizing lesions involving the optic nerves and the spinal cord. We report two females with the disease, aged 30 and 34 years old. In the latter, a neuropathological study was done. Both patients had clinical, neuroradiological and pathological features that differed from those of primary demyelinating syndromes such as multiple sclerosis. These patients illustrate the selectivity of optic nerve and spinal cord lesions. The latter involve mainly pyramidal and Goll tracts while, within the necrotizing lesions of the optic chiasma, the fibers of the unaffected optic nerve are spared. This pattern suggests a selective injury to some population of axons. Blood vessels were not affected in the necrotizing areas and the lesions did not follow a vascular territory, therefore a vascular mechanism causing the disease is unlikely. The clinical and neuropathological features of neuromyelitis optic suggest a selective involvement of some axons.

Adult↗
PubMed1998

[Serum hepatitis B markers in blood donors in Venezuela. What do they mean?].

PURPOSE: The prevalence of serum BH markers is high in our country. In order to assess the factors of impact in this fact a group of blood donors with positive BH markers attending our Service between 1-1-95 and 12-31-96 was evaluated, although the endemic character of the disease may be an obstacle for its recognition. The residual risk of HBV transmission by seronegative transfusions was also evaluated. MATERIAL AND METHODS: The evaluation of donors was performed by surveying identification data, type and frequency of donations and risk factors. The following reagents were used to carry out the bests: Biotest Elisa HbsAgand Heprofile anti HBc, ADI Diagnostics (1995), and Abbott Auzyme Monoclonal and Abbott Corzyme Diagnostic kit. Positive donors were re-evaluated to determine any progression of the disease and they were classified into false positive (FP), chronic carriers (CC), acute hepatitis (AH), naturally immunized (NI), or without evidence of immunity (WI). The residual transfusional risk was calculated by multiplying the adjusted prevalence of HbsAg positive donors by the window period expressed in fractions of a year. RESULTS: Out of 53,338 donations, 5.91% were discarded due to the presence of HBV, 7.5% of them showing significant association with other markers: HCV, Chagas' disease and syphilis. Of all donors 223 (7.54%) returned for re-evaluation, and only 139 (62.33% of them) could be fully evaluated as follows: FP 10.09%, AH 5.76%, CC 7.19%, NI 68.35%, WI 7.91%. Their mean age was 35.73 +/- 9.95 years, and there were 112 males and 12 females. The donations were patient-related in 93.5% of cases, voluntary in 3.22% and coming from mobile units in 3.22% of instances (p = 0.067). Fifth per cent donated for the first time, and the other 50% had donated previously although not in a consecutive way (p = 0.96): 46% were ignorant of their post-donation findings, 37.09% were seemingly negative and 16.12% had positive tests. Of these last, the reasons for donation included defective questioning and information (50%), results not verified (20%) and family/hospital pressure (30%). Homo/bisexuality and drug abuase (not intravenous) were found significant when associated to each other or to promiscuity. Promiscuity attained significant risk value, especially when previous venereal disease or close contact with BH patients were presented (p = 0.0015, p = 0.155, and p = 0.0036, respectively). The residual risk of transmitting HBV by seronegative transfusions was found to be: 1:437. CONCLUSIONS: 1. No risk factors were detected in a half of the cases. 2. The other half, comprising the known seropositive subjects and the promiscuous, homo/bisexual donors and those having close contact with HBV patients, can be discarded predonation. 3. Drug abuse (not intravenous), frequently associated with other risk factors, should discard a donor. 4. History of veneral disease should be considered a risk factor due to its common association to HBV. 5. The residual risk of acquiring HBV post-transfusion is still high. RECOMMENDATIONS: 1. To improve the information provided to donors regarding the risk factors. 2. The interrogation should be simple, direct and deep. 3. To insist in the importance of the donor returning for his/her credentials in the blood bank and to know about any altered results, and to seek medical advice when appropriate. 4. To change related donation into a voluntary and consecutive pattern.

Adult↗
PubMed1998

[How to reduce the prevalence of HIV-positive blood donors].

UNLABELLED: Despite abolishing the policy of giving the results of the serological test as a way to promote blood donation, and also after improving the predonation questionnaire, we still have a high prevalence of HIV positive blood donors. In this paper we try to analyze, interviewing the HIV positive blood donors in our Counselling Clinic from January 1995 to December 1996, why they were accepted. We asked the HIV positive blood donors to fill a form with the following questions: identification, kind and frequency of blood donation, HIV high risk behaviour, awareness of predonation serological status, willingness toward blood donation, awareness of how dangerous the transfusion of HIV contaminated blood is. For the screening we used Abbott HIV1/HIV 3rd generation plus EIA, test and HIV-1 Western Blot Cambridge, Biotest, Worcester MA, for confirmatory assays. During the evaluation period, 53,338 blood donors were attended, 130 (0.24%) were confirmed HIV positive. Only 18/130 (13.84%) assisted to the Counselling Clinic. The mean age was 33.27 +/- 5.35 years old, all males, 15 singles and 3 with stable couples. 6/18 (33.33%) could have been discarded because of physical appearance or because of theirs jobs. "Voluntary Donation" was higher than in the control group (p = 0.0001). Homo/bisexual and promiscuous behaviour (p = 0.0003) were the predominant high risk factors, in this group 55.55% had more than one risk factor. The association with HBV and syphilis was high (p = 0.0001 and p = 0.0005). 5/18 (27.77%) knew they were HIV positive; 3/18 (16.66%) had the suspicion they were HIV positive and 10/18 (55.55%) did not know it; however the risk factors were the same in those groups. In the knew/suspicion group the main reasons for blood donation were: Performing the test once more, 6; failure in the predonation questionnaire, 1; family pressure, 1. In the group that ignored their HIV positivity: ignorance of belonging to a high-risk group, 6; lack of confidence in the interviewer, 3 and failure in the predonation questionnaire, 1. 61.11% knew that the HIV tests were performed on all blood donations and the the positive ones were discarded. No one had knowledge of the window period. CONCLUSIONS: 1. It is necessary to spread more information to the general population about the ways of HIV transmission, the risk factors and its prevention. 2. To make aware all HIV positive or those that suspect they are the HIV positive how dangerous their blood donation could be. 3. Offering the general population a free HIV test and giving the appropriate counselling and support. 4. Improving the questionnaire, assuring that the blood donor could understand the real meaning of the questions and how important his/her truthfulness is. 5. To consider the implementation of the p24 antigen test as mandatory to all blood donations and all the new techniques to avoid HIV transmission. 6. To change the "related" blood donors to the true voluntary, altruistic, blood donor.

Adult↗
PubMed1997

The prevalence of proliferative kidney disease from the kidney and muscle of rainbow and brown trout in Aragón (Spain).

The prevalence and parasite density of PKX (the unknown myxosporean that causes proliferative kidney disease [PKD] of salmonids) were investigated in eight fishfarms in Aragón, Spain. Tissue sections stained with the biotynilated lectin GS-I revealed the presence of this protozoan in only one of the farms. In rainbow trout, the renal prevalence and parasite density peaked in July, but in brown trout the maximum renal prevalence and maximum renal parasite density were reached in May and in July, respectively. In rainbow trout, after the acute phase of the disease, the number of PKX decreases in the kidney but increases in the muscle. In this species of fish, the prevalence and parasite density are much higher in the muscles than in the kidney in October.

Acute Disease↗
PubMed1997

Kinetic characteristics of nucleoside mono-, di- and triphosphatase activities of the periplasmic 5'-nucleotidase of Escherichia coli.

Periplasmic 5'-nucleotidase from Escherichia coli, in addition to the monophosphoesterase activity has a diphosphohydrolase activity, acting on nucleoside di- and triphosphates. We proposed that the monophosphoesterase and diphosphohydrolase activities have their own active site. This proposal is based on the different types of bonds being broken. Chemical modification with selective group reagents did not show differences in the essentiality of some residues, like histidyl, carboxyl and arginyl groups, of these two hydrolytic activities. While kinetic approaches employing the competition plot and unidirectional substrate inhibition point to that diphosphohydrolase activity (ATPase-ADPase) do not share the same active site with monophosphoesterase activity. Western blotting developed with polyclonal anti-placental apyrase antibody revealed a single protein in the periplasmic fraction of 66.5 kDa similar to the Mr of the purified enzyme by isoelectrofocusing.

5'-Nucleotidase↗
PubMed1997

Promoter activities in Vibrio cholerae ctx phi prophage.

Comparison of cholera toxin (CT) production directed by different gene constructs and S1 nuclease mapping revealed the presence of a ctxB-specific promoter within the ctxA coding sequence. Initiation of transcription in this region occurred in wild-type El Tor and classical biotype choleragenic vibrios. We propose that transcription from the ctxB-specific promoter and a stronger ribosomal binding site on the ctxB mRNA synergistically contribute to achieve the correct (5B:1A) subunit stoichiometry. Plasmid pB, a CT promoterless vector expressing only CTB, was used to detect promoter activity by restoration of A-subunit synthesis. Promoter activity expressed in vitro and in vivo was detected upstream of the zonula occludens toxin gene, suggesting that this factor could be produced in vivo to contribute to fluid accumulation. No promoter activity was detected in vitro and in vivo upstream from the accessory cholera enterotoxin gene.

Base Sequence↗