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F Vega

Publications and source records attributed to F Vega.

71 records · Page 4Linked to original sources
PubMed1980

Kinetics of a nucleotide pyrophosphatase in the plasma membrane of the fat cell.

Fat cells from rat and rabbit hydrolyzed externally applied adenosine triphosphate at a rate of about 1.8 nmol times mg(-1) cells times min(-1) corresponding to about 0.3 mumol times mg(-1) protein tinus min(-1). Similar activities were found in cell homogenates. In purified adipocyte plasma membranes the rate of hydrolysis was about 1.8 mumol times mg(-1) protein times min(-1). The hydrolytic activity was dependent on divalent metal ions. Mg(2+), Mn(2+) and Ca(2+) gave highest activities. The activity was maximal at about equimolar concentrations of M(2+) and ATP. Km for MgATP was about 0.23 mM and for CaATP about 0.36 mM. Combinations of Mg(2+) and Ca(2+), or of Mg(2+), Na(+) and K(+) gave similar activities as did Mg(2+) only. At concentrations of 1 mM the following nucleotides were hydrolyzed with a decreasing rate: ATP > ITP > GTP > UTP = CTP. In isolated fat cells the beta-adrenergic drug isoproterenol and insulin slightly increased the rate of hydrolysis of external ATP, while the alpha-effector clonidine was inhibitory. The results suggest that a major portion of the ATP hydrolytic activity of the fat cell plasma membrane represents a nucleotide pyrophosphatase activity with access to externally applied ATP.

Adenosine Triphosphatases↗
PubMedDate not supplied

Treatment of complete and partial obstruction of the nasolacrimal system with polyurethane stents: initial experience.

PURPOSE: To present our experience in the treatment of nasolacrimal occlusion by means of polyurethane stents. METHODS: Forty polyurethane stents were placed under fluoroscopic guidance in 35 consecutive patients with epiphora due to total or partial obstruction of the nasolacrimal system. The set designed by Song was used in all patients. The procedure was performed by introducing a guidewire through the superior punctum into the canaliculus and advancing it across the obstruction into the inferior meatus of the nasal cavity. After pulling out the guidewire, the stent was advanced in retrograde fashion and released into the sac and the nasolacrimal duct. RESULTS: The technical success rate was 100%. The average time for the procedure was 25 min (range 10-60 min). Immediate complications were: mild pain (n = 5), severe pain (n = 1), minimal epistaxis (n = 7), and moderate epistaxis (n = 1). No major complications occurred. The last clinical control revealed complete resolution of epiphora in 35 eyes and partial resolution in four; one patient did not improve. CONCLUSION: This technique for treatment of obstruction of the nasolacrimal system is simple and safe, and may obviate the use of more invasive procedures.

Adult↗
PubMedDate not supplied

Leptin, reproduction and sex steroids.

Leptin is a hormone secreted mainly by the adipose cells with a primary role in the regulation of body weight by establishing a feedback loop between the energy reserves and the hypothalamic centers that control food intake. Recent data suggest that, in addition, leptin interacts with other endocrine systems to provide critical information about the size of the fat stores, acting as a permissive factor that allows the triggering of energy-demanding situations, as the onset of puberty and the reproduction, only when the size of the fuel reserve is large enough to guarantee its success. In addition, leptin appears to play a role during pregnancy and lactation, as it is produced by the placenta and is present in maternal milk. The fact that leptin levels are always higher in females, even after correcting for body fat content, suggests that the interaction between the adipose tissue and the reproductive system is modulated in a different way in males and females by androgenic and estrogenic hormones. In fact, adipose tissue samples taken from male donors are completely refractory in vitro to the action of both estrogens and androgens. On the contrary, dihydrotestosterone, androstenedione and dehydroepiandrosterone-S are potent inhibitors of leptin secretion, while estradiol induces a strong stimulation in adipose tissue taken from women. Testosterone is devoid of activity in either gender.

Animals↗
PubMedDate not supplied

The epidermal growth factor receptor in glioblastoma: genomic amplification, protein expression, and patient survival data in a therapeutic trial.

Human glioblastomas were evaluated for overexpression of the epidermal growth factor receptor (EGFR) in a therapeutic trial with the anti-EGFR antibody EMD 55900. A total of 55 cases were examined by immunohistochemistry using 4 different monoclonal antibodies on frozen or on paraffin sections: EGFR-1 (Amersham), E 62 (Merck), E 30 (Merck), and EMD 55900 (MAB 425, Merck). Definition for inclusion in clinical trials of EMD 55900 was an immunohistochemical overexpression of grade 4+ or 3+ in a scale of 4 grades of staining quality. The use of the 4 different antibodies gave essentially equal results. In 21 cases, the immunohistochemical results were supplemented by molecular genetic analysis of EGFR amplification on the corresponding locus of chromosome 7, using frozen tissue from the same blocks after screening for vital tumor areas. Since no other material was available, the differential polymerase chain reaction technique was applied. Interferon-gamma (IFN-gamma) served as a reference gene. In a preliminary experimental series with cases of known EGFR amplification, a densitometric EGFR/IFN-gamma ratio higher than 3 was determined as indicator for amplification of the EGFR gene. With this experimental approach we were able to identify an amplified EGFR gene in 13 specimens including 2 from recurrent glioblastomas in the same patients. All of these showed an increased immunoreactivity for EGFR protein. The degree of EGFR amplification (EGFR/IFN-gamma ratio as measured by DNA densitometry) showed a positive correlation with the grade of immunohistochemical protein expression, both in regard to the fraction of positive cells and to the overall staining intensity.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies, Monoclonal↗
PubMedDate not supplied

Metabolic and drug distribution studies do not support direct inhibitory effects of metformin on intestinal glucose absorption.

In an attempt to clarify the question of an involvement of the inhibition of intestinal glucose absorption in the mechanism of action of Metformin, we used several experimental approaches: 1 glucose/lactate measurement in rat portal blood in vivo and 2 in the venous effluent of an isolated perfused rat intestinal segment; 3 metabolism of freshly isolated enterocytes in vitro and tissue distribution of 3H-labeled Metformin was investigated both in vivo and in vitro. Metformin applied intraluminally had no significant effect on portal glycaemia after a glucose load, but lactate increased, whereas in vivo only a high Metformin dosage reduced portal glucose appearance significantly. Although high Metformin concentrations were found in gut biopsies, precise histological analysis in the isolated intestine revealed that it was absent from enterocytes; however the drug accumulated in villous lacteals. Intrarterially applied Metformin decreased glucose absorption in the isolated perfused ileo-jejunal segment. These data suggested that vascular Metformin boosted intestinal anaerobic glucose metabolism. Biochemical measurements performed on freshly isolated enterocytes showed that even high Metformin levels did not interfere with cell respiration or with Na+/K+ ATPase activity. Thus, our data agree with other recent reports, suggesting that even at nontherapeutic concentrations Metformin has no relevant inhibitory effect on intestinal glucose absorption. The data are discussed in the frame of previous divergent observations. The results suggest however that Metformin of vascular origin stimulates glucose consumption by the intestine, which then increases lactate output from the gut.

Animals↗
PubMedDate not supplied

[Lymphatic metastases of osteosarcomas].

Osteosarcoma lymph node metastasis are uncommon. This paper shows two patients having osteoblastic osteosarcoma with loco-regional lymph node involvement. In the first case two inguinal and pelvic adenomegalies were found to have tumor metastasis two years and a half after initial diagnosis in a control radiological study. Currently the patient is alive three months after the lymphadenectomy. In the second case, several inguinal high density tumoral nodules were identified during the workup of primary tumor.

Amputation, Surgical↗