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Biomedical subjects

A Vargas

Publications and source records attributed to A Vargas.

At least 37 records · Page 2Linked to original sources
PubMed2000

Weight loss and growth velocity in obese children after very low calorie diet, exercise, and behavior modification.

UNLABELLED: The prevalence of obesity in American youth is increasing and treatment of the condition is difficult. We have developed a multi-disciplinary weight reduction program that extends over 1 y and includes a very low-calorie diet (VLCD) followed by a hypocaloric diet, exercise, and behavior modification. Based on data collected at baseline, at the end of the acute intervention phase (10-20 wk), and at 1-y evaluation, we assessed the efficacy of this outpatient weight reduction program in treating obese children and adolescents in a follow-up of a series of cases. Furthermore, we examined the impact of the approach on growth velocity and maintenance of weight loss at 1 y. Fifty-six overweight children (aged 7-17 y) were recruited during a period of 18 mo to participate in the weight management program; 52 (93%) completed the acute phase of treatment and 35 (62.5%) successfully completed the 1-y program. There was a significant decrease in body weight and body fat, as assessed by weight determinations and skinfold measurements (p <0.0001; results not corrected for age). The body mass index for the 35 individuals who completed the 1-y program decreased significantly from 32.7 on entry to 28.72 at 1 y (p < 0.0001; results not corrected for age). CONCLUSION: We conclude that a multidisciplinary weight reduction program that combines a VLCD, followed by a balanced hypocaloric diet, with a moderate-intensity progressive exercise program and behavior modification is an effective means for weight reduction in obese children and adolescents.

Adolescent↗
PubMed2000

Age-dependent changes in sperm production, semen quality, and testicular volume in the black-footed ferret (Mustela nigripes).

The black-footed ferret (Mustela nigripes), which was extirpated from its native North American prairie habitat during the 1980s, is being reintroduced to the wild because of a successful captive-breeding program. To enhance propagation, the reproductive biology of this endangered species is being studied intensively. The typical life span of the black-footed ferret is approximately 7 yr. Female fecundity declines after 3 yr of age, but the influence of age on male reproduction is unknown. In this study, testis volume, seminal traits, sperm morphology, and serum testosterone were compared in 116 males from 1 to 7 yr of age living in captivity. Results demonstrated that testes volume during the peak breeding season was similar (P > 0.05) among males 1 to 5 yr of age, reduced (P < 0.05) among males 6 yr of age, and further reduced (P < 0.05) among males 7 yr of age. Motile sperm/ejaculate was similar in males 1 to 6 yr of age but diminished (P < 0.05) in those 7 yr of age. Males at 6 and 7 yr of age produced fewer (P < 0.05) structurally normal sperm than younger counterparts; however, serum testosterone concentrations were not reduced (P > 0.05) in older males. Histological comparison of testicular/epididymal tissue from 5- and 7-yr-old black-footed ferrets confirmed that the interval between these two ages may represent a transitional period to reproductive senescence. In summary, functional reproductive capacity of male black-footed ferrets exceeds that of females by at least 2 yr. Testes and seminal quality are indistinguishable among males 1 to 5 yr of age, with progressive reproductive aging occurring thereafter.

Aging↗
PubMed2000

Dose conversion factor for radon concentration in indoor environments using a new equation for the F-fP correlation.

Since 1994 the radon studies group at the Institut de Tècniques Energètiques (INTE) of the Universitat Politècnica de Catalunya in Barcelona, Spain, has carried out a campaign of continuous measurements of the equilibrium factor (F) and the unattached fraction (f(p)) of radon decay products at four sites which are representative of different environmental characteristics on the Mediterranean littoral of Catalonia, Spain. It has been established that these parameters vary widely, F(0.03-0.87) and f(p) (0-0.72), from one site to another and with time, according to the characteristics of the site and climate. In spite of this variation, the F and f(p) parameters are log-normally or normally distributed. The measurements of F and f(p) show that f(p) is negatively correlated to F by a log-power equation, Ln(1/f(p))=1.90[Ln(1/F)](-0.68), which can be used in all the F range, instead of the commonly used power equation f(p)=aFb suggested by Stranden and Strand and other authors, which fits well for a reduced range of F. Power and log-power equations have been introduced into a simplified dosimetric model in order to estimate the effective dose per unit radon exposure as a function of F. From the log-power equation this value is quite constant and ranged from 9 nSv per Bq m(-3) h to 12 nSv per Bq m(-3) h when F is higher than 0.15. In the case of a lower F factor, a linear function that passes through 0 fits quite well. A value of 12 nSv per Bq m(-3) h is proposed for the Mediterranean littoral of Catalonia as the best estimation.

Air Pollutants, Radioactive↗
PubMed2000

The human leukocyte antigen HLA DRB3*020/DQA1*0501 haplotype is associated with Graves' disease in African Americans.

Information on genetic susceptibility to Graves' disease in African Americans is limited. We studied DRB1, DQB1, DRB3 subtypes, DQA1*0501, DQA1*0201, and CTLA-4 polymorphisms in 49 African American patients with adult onset Graves' disease and 47 racially-matched controls using PCR-based sequence-specific priming methods. There were no significant differences in DRB1 or DQB1 allelic frequencies or CTLA-4 polymorphisms between patients and controls. However, we found that the frequency of DRB3 was significantly increased in the patients (75.5% vs. 57.4%, P = 0.006, X2 = 3.52), especially for the DRB3*0202 subtype (53.1% vs. 23.4, P = 0.003, X2 = 8.91). In this one respect, the finding was in concordance with our previous observations in Caucasian patients with adult-onset Graves' disease. In addition, whereas the frequency of DQA1*0501 was increased (P = 0.018, X2 = 5.63) in our patients, the haplotype of DRB3/DQA1*0501, or DRB3*0202/DQA1*0501 was found to be more strongly associated (P = 0.008, X2 = 7.0; P = 0.0008, X2 = 11.34, respectively). These data suggest that DRB3*0202, particularly when found with DQA1*0501 in a haplotype is a susceptible gene(s) for Graves' disease in adult African Americans. Considering these data with those in Caucasian patients, our results would suggest that the primary Graves susceptible locus is likely DRB3 and not DRB1.

Abatacept↗
PubMed1999

Ring 2 chromosome: ten-year follow-up report.

Côté et al. [1981: Ann Genet 24:231-235] suggested that ring chromosomes without a preceding deletion share a common pattern of phenotypic anomalies, independent of what chromosome is involved. The phenotype of such a "general ring syndrome" consists of growth failure without malformations, few or no minor anomalies, and mild-to-moderate mental retardation. We report on a patient with a ring 2 chromosome with features suggestive of Silver-Russell syndrome at birth and striking postnatal growth retardation with minor intellectual involvement supporting Côté's suggestion. This would be the ninth case of ring 2 chromosome published; the patient is the longest reported survivor, with a 10-year follow-up.

Abnormalities, Multiple↗
PubMed1999

Development of neural crest in Xenopus.

The neural crest is a unique cell population among embryonic cell types, displaying properties of both ectodermal and mesodermal lineages. Most of the recent studies examining the neural crest have been performed in avian embryos. Only in the first half of this century were amphibians extensively used. We first summarize this important older source of information, reviewing studies made since the turn of the century. Due to the increasingly detailed in cellular and molecular knowledge of the early development of Xenopus laevis, the remainder of the review focuses on this species. We describe the route of migration and fate of the neural crest and propose a new model of neural crest induction in which prospective cells are induced independently of the neural plate by a double gradient of a morphogen that patterns the entire ectoderm. This model is also discussed in a more general context in connection with the dorsoventral patterning of the neural tube. Finally, we discuss some ideas concerning neural crest evolution and propose a novel hypothesis about its phylogenetic origin.

Amphibians↗
PubMed1999

Hepatic insulin clearance increases after weight loss in obese children and adolescents.

BACKGROUND: Obesity is a rapidly increasing health problem among US youth. Hyperinsulinemia is associated with obesity and has been found to be a contributory factor for the development of cardiovascular disease in the obese. It has been suggested that hyperinsulinemia of obesity is a result of increased insulin secretion caused by insulin resistance. However, it has been shown in adults that decreased hepatic insulin clearance (HIC) is the primary cause of hyperinsulinemia in this population. METHODS: We studied 15 obese children and adolescents (11 F, 4 M; 8.6 to 18.1 years) before and 10 weeks after their enrollment in a multidisciplinary weight reduction program, which included a protein-sparing modified fast, a moderate intensity progressive exercise program, and a behavior-modification intervention. RESULTS: All patients lost weight (P < 0.05). Measurements of immunoreactive insulin (IRI) and C-peptide reactivity (CPR) were performed before the program and at 10 weeks. IRI levels dropped significantly, whereas CPR levels did not change. CPR/IRI molar ratios, considered an indirect estimation of HIC, rose significantly after weight loss. CONCLUSIONS: Our data suggest that hyperinsulinemia seen in obese children and adolescents is caused by decreased HIC. The cause for this decrease remains unknown, but it is reversible upon weight loss.

Adolescent↗
PubMed1999

Helicobacter pylori infection and insulin requirement among children with type 1 diabetes mellitus.

OBJECTIVE: Helicobacter pylori induces gastric inflammation and the the production of cytokines in infected individuals. Theoretically, this increased production of cytokines could be deleterious for the control of the glycemia of patients with diabetes. This study aimed to describe the insulin requirement among patients with type 1 diabetes and H pylori infection compared with uninfected counterparts. METHODS: Cross-sectional design. Demographic information (age, gender, race, annual family income, and number of individuals per room in the household) and clinical information (age at diagnosis of diabetes, duration of illness, weight, height, compliance with clinical appointments, daily insulin units per kilogram of body weight [IU/kg/d], and glycosylated hemoglobin A level) was obtained from children and adolescents with diagnosis of type 1 diabetes mellitus who were seen at Children's Hospital in New Orleans. A total of 2 mL of blood was also collected and sera were tested for H pylori-specific immunoglobulin G antibodies using an enzyme immunoassay. The daily insulin requirement among infected and uninfected children was compared, and the effect of other variables was evaluated with multiple linear regression. RESULTS: Of the 71 subjects who were evaluated (median age: 11 years), 11 (15.5%) were found to be infected. H pylori infection was more frequent among subjects who were older, who had a lower family income, and who were black. Infected children were found to require more insulin (1.2 vs 0.9 IU/Kg/d) and their glycosylated hemoglobin A level was higher (14.9 vs 11.8) than the level found in uninfected subjects. Multiple linear regression analysis identified H pylori infection duration of illness, race (black), body mass index, and gender (female), to be associated independently with increased daily insulin requirement (IU/kg/d). CONCLUSION: n our study population, children with type 1 diabetes and H pylori infection had an increased daily insulin requirement compared with the requirement of their uninfected peers. The reason for this association requires additional investigation.

Adolescent↗
PubMed1999

[Immunoglobulin rearrangement in the differential diagnosis of primary gastric lymphoma].

BACKGROUND: The traditional methods to distinguish Chronic Follicular Gastritis and Primary Gastric Lymphoma do not allow an adequate definitive diagnosis in a significant number of cases. The molecular Biology diagnostic methods are based on the rearrangement of immunoglobulin genes. The polymerase chain reaction (PCR) specifically amplifies this rearrangement and allows molecular analysis of minimal tissue samples obtained with endoscopical biopsies. AIM: To test the usefulness of this PCR method in the differential diagnosis between Chronic Follicular Gastritis and Primary Gastric Lymphoma. MATERIAL AND METHODS: We analyzed the endoscopical biopsies of six Chronic Follicular Gastritis cases and eight surgically treated Primary Gastric Lymphoma cases, six with the correct diagnosis in the endoscopical biopsies and two with a diagnosis of Chronic Follicular Gastritis. RESULTS: A policlonal immunoglobulin rearrangement was found in the six cases with Chronic Follicular Gastritis. A monoclonal arrangement was found in 5 of 6 biopsies with the diagnosis of Primary Gastric Lymphoma. The same monoclonal rearrangement was observed in the two biopsies incorrectly diagnosed as Chronic Follicular Gastritis. CONCLUSIONS: PCR analysis of immunoglobulin rearrangement is a useful method in the differential diagnosis between Chronic Follicular Gastritis and Primary Gastric Lymphoma.

Chronic Disease↗
PubMed1998

Therapeutic drug monitoring of tobramycin: once-daily versus twice-daily dosage schedules.

OBJECTIVE: To evaluate the effect of dosage regimen (once-daily vs. twice-daily) of tobramicyn on steady-state serum concentrations and toxicity. MATERIALS AND METHODS: Patients undergoing treatment with i.v. tobramycin (4 mg/kg/day) were randomised to two groups. Group OD (n = 22) received a once-daily dose of tobramycin and group TD (n = 21) received the same dose divided into two doses daily. Tobramycin serum concentrations (peak and trough) were measured by enzyme multiplied immunoassay. The renal and auditory functions of the patients were monitored before, during and immediately after treatment. RESULTS: The two groups were comparable with respect to sex, age, body weight and renal function. No statistically significant differences were found in mean daily dose, duration of treatment, or cumulative dose. Trough concentrations were < 2 g/ml in the two groups (100%). Peak concentrations were > 6 microg/ml in 100% of the OD group and in 67% of the TD group (P< 0.01). Mean peak concentrations were markedly different: 11.00+/-2.89 microg/ml in OD vs. 6.53+/-1.45 microg/ml in TD (P< 0.01). The pharmacokinetics parameters were: Ke, (0.15+/-0.03/h in OD vs. 0.24+/-0.06/h in TD), t1/2, (4.95+/-1.41 h in OD vs. 3.07+/-0.71 h in TD), Vd (0.35+/-0.11 l/kg in OD vs. 0.33+/-0.09 l/kg in TD), Cl (0.86+/-0.29 ml/min/kg in OD vs. 1.28+/-0.33 ml/min/kg in TD). Increased serum creatinine was observed in 73% of patients in OD versus 57% of patients in TD, without evidence of nephrotoxicity. In TD group, three patients developed decreased auditory function, of which one presented with an auditory loss of -30 dB, whereas in the OD group only one patient presented decreased auditory function. CONCLUSION: This small study suggests that a once-daily dosing regimen of tobramycin is at least as effective as and is no more and possibly less toxic than the twice-daily regimen. Using a single-dose therapy, peak concentration determination is not necessary, only trough samples should be monitored to ensure levels below 2 microg/ml.

Adolescent↗
PubMed1997

Effect of single point mutations of the human tachykinin NK1 receptor on antagonist affinity.

Molecular modelling and site-directed mutagenesis were used to identify eleven amino acid residues which may be involved in antagonist binding of the human tachykinin NK1 receptor. Recombinant receptors were expressed in mammalian cells using the Semliki Forest virus system. Wild type and mutant receptors showed similar expression levels in BHK and CHO cells, verified by metabolic labelling. Binding affinities were determined for a variety of tachykinin NK1 receptor antagonists in SFV-infected CHO cells. The binding affinity for GR203040, CP 99,994 and CP 96,345 was significantly reduced by mutant Q165A. The mutant F268A significantly reduced the affinity for GR203040 and CP 99,994 and the mutant H197A had reduced affinity for CP 96,345. All antagonists seemed to bind in a similar region of the receptor, but do not all rely on the same binding site interactions. Functional coupling to G-proteins was assayed by intracellular Ca2+ release in SFV-infected CHO cells. The wild type receptor and all mutants except A162L and F268A responded to substance P stimulation.

Animals↗
PubMed1997

Calcium pyrophosphate dihydrate crystal deposition disease presenting as a pseudotumor of the temporomandibular joint.

We report a case of a 66-year-old white woman with calcium pyrophosphate dihydrate (CPPD) crystal deposition disease. The patient related a 2-month history of swelling with tenderness over the left pre-auricular region. A CT scan suggested a synovial chondromatosis. Surgical removal was done and histologic study showed CPPD crystals. This disease rarely involves the temporomandibular joint (TMJ) and is not usually considered in the differential diagnosis. To our knowledge, only 14 cases have been reported in the literature.

Aged↗
PubMed1995

Functional activity of a biotinylated human neurokinin 1 receptor fusion expressed in the Semliki Forest virus system.

The 1.3 S biotinylatable subunit of Proprionibacterium shermanii transcarboxylase complex was fused to the C-terminus of the human neurokinin 1 receptor gene and introduced into the Semliki Forest virus expression vector pSFV1. RNA transcribed from pSFV1-NK1-biot and pSFV-Helper2 was coelectroporated into BHK cells permitting in vivo packaging of recombinant virus. Infection of BHK and CHO cells with SFV-NK1-biot virus yielded high level of the fusion receptor as detected by metabolic labeling, immunoblotting with streptavidin alkaline phosphatase and binding to substance P. Like native receptor, the biotinylated receptor fusion was able to stimulate Ca2+ mobilization in infected CHO cells, indicating functional coupling to guanine-nucleotide-binding proteins.

Animals↗
PubMed1995

Role of metallothionein and cysteine-rich intestinal protein in the regulation of zinc absorption by diabetic rats.

Hyperzincuria and low Zn absorption in diabetic animals and humans have prompted speculation that diabetics are more susceptible to Zn deficiency. There is little information, however, describing the effects of diabetes on the biochemical mechanisms of intestinal Zn transport. We evaluated Zn absorption in streptozotocin-induced diabetic rats based on a model of Zn transport in which cysteine-rich intestinal protein serves as an intracellular carrier that is inhibited by metallothionein (MT). Apparent absorption and retention of Zn and Cu in rats fed a purified diet were measured in a balance study 15-17 d after induction of diabetes. The rate of 65Zn absorption from isolated intestinal segments, molecular distribution of 65Zn in mucosal cytosol, and tissue MT levels were measured on d 20-22. Food consumption, and thus Zn and Cu intake, by diabetic rats was twice that of controls. Although fractional absorption (percent) of Zn and Cu was lower in the diabetic rats, net absorption (micrograms/100 g body weight/d) was higher. The higher net absorption in the diabetic group was offset, however, by higher urinary excretion, so that Zn and Cu retention was similar in both groups of animals. Low fractional absorption is attributable to the down-regulation of intestinal Zn transport, as indicated by the lower rate of 65Zn absorption from isolated intestinal segments in the diabetic rats. Down-regulation of intestinal transport is in turn attributable to higher concentrations of intestinal MT, which resulted in more 65Zn in the mucosal cytosol bound to MT, an inhibitor of Zn transport, and less to cysteine-rich intestinal protein.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Citrate inhibition of rat-kidney cortex phosphofructokinase.

The regulatory properties of citrate on the activity of phosphofructokinase (PFK) purified from rat-kidney cortex has been studied. Citrate produces increases in the K0.5 for Fru-6-P and in the Hill coefficient as well as a decrease in the Vmax of the reaction without affecting the kinetic parameters for ATP as substrate. ATP potentiates synergistically the effects of citrate as an inhibitor of the enzyme. Fru-2,6-P2 and AMP at concentrations equal to Ka were not able to completely prevent citrate inhibition of the enzyme. Physiological concentrations of ATP and citrate produce a strong inhibition of renal PFK suggesting that may participate in the control of glycolysis in vivo.

Adenosine Triphosphate↗