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Biomedical subjects

A Panadero

Publications and source records attributed to A Panadero.

12 recordsLinked to original sources
PubMed1999

Cyclin E-cdk2 activation is associated with cell cycle arrest and inhibition of DNA replication induced by the thymidylate synthase inhibitor Tomudex.

Tomudex (ZD1694) is a specific antifolate-based thymidylate synthase inhibitor active in a variety of solid tumor malignancies. Studies were carried out in vitro to evaluate downstream molecular alterations induced as a consequence of the potent and sustained inhibition of thymidylate synthase by Tomudex. Twenty-four hours following the initial 2-h treatment with Tomudex, human A253 head and neck squamous carcinoma cells, not expressing p53 and p21(WAF1), were accumulated with DNA content characteristic of early S phase of the cell cycle with a concomitant reduction of cells in G1 and G2/M phases. The changes in cyclin and cdk protein expression and their kinase activities were examined in control and drug-treated A253 cells. Tomudex treatment resulted in the decrease in p27(kip1) expression, with an increase in cyclin E and cdk2 protein expression and kinase activities 24 h after a 2-h exposure. Although cyclin A protein expression was markedly increased, cyclin A kinase activity was only slightly increased. Cyclin D1, cyclin B, cdk4, and cdc2 protein expression and kinase activities remain constant. Lack of activation of cyclin A- and B-cdc2 was associated with a reduced proportion of cells in G2/M phases. Increased cyclin E-cdk2 protein expression was accompanied by the inhibition of DNA synthesis, with a decrease in E2F-1 expression. These results propose that cyclin E-cdk2 kinase can negatively regulate DNA replication. The studies with dThyd rescue from cyclin E-cdk2 protein overexpression and growth inhibition by Tomudex indicate that increased cyclin E-cdk2 protein expression is associated with effective inhibition of thymidylate synthase and resultant dNTP pool imbalance. Provision of dThyd more than 24 h after exposure to Tomudex allowed cells to replicate DNA for a single cycle back to G1, but did not prevent the profound growth-inhibitory effect manifested in the following 5 days. Tomudex treatment resulted in a time-dependent induction of the megabase DNA fragments, followed by secondary 50- to 300-kb DNA fragmentation. The 50- to 300-kb DNA fragmentation may be derived from the inhibition of DNA synthesis associated with cyclin E-cdk2 activation. These results suggest that the megabase DNA fragmentation is induced as a consequence of inhibition of thymidylate synthase by Tomudex and kilobase DNA fragmentation may correlate with the reduction of p27(kip1) expression and the increase in cyclin E and cdk2 kinase activities. Activation of cyclin E and cdk2 kinases allows cells to transit from G1 to S phase accompanied by the inhibition of DNA synthesis. The changes in cell cycle regulatory proteins associated with growth inhibition and DNA damage by Tomudex are not p53 dependent.

CDC2-CDC28 Kinases↗
PubMed1998

[Common variable immunodeficiency associated with autoimmune thrombocytopenia: anesthetic management].

A 44-year-old man diagnosed of common variable immunodeficiency associated with thrombopenia due to autoimmunity required anesthesia for anal fissure repair and hemorrhoidectomy. Hemostatic complications developed after surgery, with extreme thrombopenia (1,000 platelets/pl) and analytical changes that necessitated administration of six units of platelets from apheresis, as well as immunoglobulins, antifibrinolytic agents (e-aminocaproic acid) and granulocytic colony stimulating factors. Anesthesia for such patients is reviewed, with emphasis on careful management of the airways, preparation of sufficient material for surgery (rapid transfusion equipment, large caliber intravenous catheters, sterile material) and orientation of anesthetic technique toward general anesthesia through a laryngeal mask.

Adjuvants, Anesthesia↗
PubMed1997

Is management of anesthesia in achondroplastic dwarfs really a challenge?

STUDY OBJECTIVE: To review our eight-year anesthetic experience with achondroplastic patients. DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: 15 achondroplastic patients who underwent 53 surgical procedures of orthopedic surgery between 1987 and 1994. INTERVENTIONS: Anesthetic technique, drugs, number of incidents, and complications in the intraoperative and postoperative period were recorded. MEASUREMENTS AND MAIN RESULTS: Adequate premedication before the transfer to the operating room was very useful to reduce anxiety and increase cooperation. Inhalation induction was well tolerated and allowed easy peripheral venous cannulation. Only one patient presented difficulties during intubation (on two occasions). In the other patients, we found small difficulties only during ventilation with a face mask, which was easily corrected by modifying the position of the patient and/or inserting an oropharyngeal airway. No adverse effect was identified for any particular anesthetic drug or technique used. CONCLUSIONS: Although the characteristic deformities of achondroplastic patients can impede the management of anesthesia, in our study we found no special difficulties. Airway complications did not occur. Thus, no specific optimal anesthetic regimen can be recommended.

Achondroplasia↗
PubMed1997

p53 and WAF1 are induced and Rb protein is hypophosphorylated during cell growth inhibition by the thymidylate synthase inhibitor ZD1694 (Tomudex).

In a previous study, we found that treatment of HCT-8 cells with ZD1694, a specific antifolate-based thymidylate synthase inhibitor, resulted in DNA fragmentation. In this study, we have demonstrated the dose- and time-dependent induction of DNA fragmentation accompanied by elevation of p53 and WAF1 protein expression by ZD1694. WAF1 mRNA showed a time-dependent increase, whereas p53 mRNA was not found to be significantly overexpressed. The initial increase in WAF1 mRNA was detected at 4 hr, but increased WAF1 protein expression was detected 8-24 hr after a 2-hr exposure. The amount of total and hypophosphorylated pRb seems to be rising greatly after ZD1694 exposure. The effects of ZD1694 on the expression of E2F1 and formation of the E2F1-Rb complex were investigated after a 2-hr drug exposure (IC90). The results showed a time-dependent decrease in E2F1 mRNA and protein expression; an increase in the abundance of the E2F-Rb complex could be demonstrated beginning 4 hr after drug exposure by a gel shift assay. Kinetic analysis showed increased availability of hypophosphorylated pRb for inhibition of E2F, which could indirectly result from WAF1-induced inhibition cyclin-dependent kinase activity. Whereas thymidylate synthase inhibition by ZD1694 was rapid in onset and maintained for at least 24 hr after drug treatment, drug-induced cellular growth inhibition was significant 24 hr after drug exposure. The increased abundance of hypophosphorylated pRb and binding to transcription factor E2F-1 is consistent with ZD1694-induced cell growth inhibition in HCT-8 cells. Therefore, the observed effect on downstream events after effective inhibition of thymidylate synthase may offer the critical determinants of response to ZD1694.

Adenocarcinoma↗
PubMed1995

Contrasting patterns of DNA fragmentation induced by thymidylate synthase inhibitors, ZD1694 and AG-331.

The patterns of DNA fragmentation were evaluated following a brief exposure (2 h) of the human ileocecal adenocarcinoma cell line, HCT-8, to several specific thymidylate synthase inhibitors, a quinazoline (ZD1694) and benz[cd]indole-containing molecule (AG-331). The magnitude and size of DNA fragmentation induced by the two agents were assessed by alkaline elution for DNA single-strand breaks (ssbs), and by pulsed- and constant-field gel electrophoresis for DNA double-strand breaks (dsbs). Both agents induced dose-dependent DNA dsbs. While AG-331 induced ssbs and dsbs only in nascent DNA, ZD1694 affected both genomic and nascent DNA. The fragments of newly synthesized and genomic DNA, estimated by pulsed-field gel electrophoresis assay, were associated with the bands in the range of 0.05 to 1.1 and 1.1 to 5.7 megabases, respectively. 5-fluoro-2'-deoxyuridine (FdUrd), like ZD1694, produced both mature and nascent DNA fragmentation, whereas only nascent DNA breakage induced by 5-fluorouracil (FUra) was detected, similar to AG-331. The induction of both mature and nascent DNA fragmentation by ZD1694 and FdUrd appears to correlate with the higher, but similar, potency of these agents. Aphidicolin, a DNA polymerase inhibitor, protects from DNA dsbs and cytotoxicity by ZD1694 and AG-331. These observations suggest that replicative DNA synthesis is an important factor in ZD1694- and AG-331-induced DNA fragmentation and, subsequently, cell growth arrest. The results indicate that although the new antimetabolites investigated herein were developed and extensively evaluated as specific and potent thymidylate synthase inhibitors, DNA damage appears to be an important additional determinant of drug effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Antimetabolites, Antineoplastic↗
PubMed1995

Four days' continuous infusion of cisplatin-5-fluorouracil and short daily infusion of high-dose leucovorin as induction chemotherapy for locally advanced head and neck cancer.

Cisplatin-fluorouracil (PF) is the most frequently used combination as induction chemotherapy (CT) for the treatment of locally advanced squamous cell head and neck cancer. This study was designed to evaluate the role of leucovorin (L) in the modulation of the therapeutic activity of PF continuously infused for 4 days. Between June 1990 and June 1992, stage III and IV previously untreated patients received PFL induction chemotherapy followed by surgery, radiotherapy, or both. The chemotherapy consisted of P 25 mg/m2, F 1000 mg/m2 both continuously infused for 4 days and L 250 mg/m2 infused for 2 hours before each daily infusion of PF. PFL was administered every 3 weeks for 4 cycles. The overall response rate at the completion of PFL was 91%, with 54% CR and 37% PR. Locoregional treatment was performed on 68 patients, 11 (16%) underwent surgery, 20 (29%) surgery plus radiotherapy, and 37 (54%) radiotherapy. Complete response status after both induction and locoregional therapy was 71%. Biopsies of the primary tumor or definitive resection specimens immediately after PFL therapy were available in 25 patients in CR. Pathological CR was found in 11 (44%). With a maximum follow-up of 44 months, the overall survival rate is 51% and the median survival has not been reached. PFL is highly active as induction chemotherapy. A randomized comparison between PF and PFL is necessary to define the place of leucovorin modulation in the treatment of head and neck cancer.

Antineoplastic Combined Chemotherapy Protocols↗
PubMedDate not supplied

[Memory and aging: changes in the mammillary body and anterior thalamic nuclei due to age].

Karyometric changes and variation of neuron number in mammillary body and anterior thalamic nuclei, dependent of the age, have been studied in humans and rats. The behaviour of the neurons number is very similar in all studied nuclei of both species: there is a constant and gradual loss of neurons from the first until the last period of the life. The intensity of the neuronal loss, however, is different according the nuclei and is more pronounced in rats than in humans. The evolution of the nuclear area of the human mammillary body is similar to that of the anterior thalamic nuclei: there is a significant decrease until the age of 60-70 years and then begins an increase up to the end of the life. This increase is more intense in the mammillary nuclei than in the thalamic ones. In rats, the behaviour of the mammillary nuclei is different to that of the anterior thalamic nuclei. In the mammillary body there is an increase of the nuclear are until 18 months of age, followed by a decrease until the end of the life. The anterior thalamic nuclei show a double inflexion: first, it appears a marked decrease of the nuclear area during the first 6 months, then the area remains unchanged until the age of 15 months, but from this period up to the end of the 2nd year undergoes an increase and, finally, during the 3 year shows a significant decrease. There is not a complete correlation between neuronal loss and nuclear area increase. Although the neuronal loss is constant during the entire life, the nuclear are increase only in a certain period: in rats during the second year and in humans in the final period of life. The signification of this partial correlation is discussed.

Adolescent↗
PubMedDate not supplied

[Does propofol have advantages over midazolam and isoflurane? Comparative study of 2 total intravenous anesthesia techniques using midazolam and propofol, versus balanced anesthesia with isoflurane].

OBJECTIVES: To compare two techniques for total intravenous anesthesia (TIVA): midazolam-alfentanil-flumazenil and propofol-alfentanil, contrasting them with combined anesthesia (thiopental-isoflurane-alfentanil) and assessing the efficacy of flumazenil in continuous perfusion for preventing resedation in TIVA with midazolam. PATIENTS AND METHODS: The efficacy and clinical tolerance of the 3 anesthetic techniques with propofol, midazolam or isoflurane were studied in 63 patients undergoing elective breast, lumbar or gynecological surgery. Anesthetic induction was achieved with midazolam 0.3 mg/kg-1 (group M), propofol 2.5 mg/kg-1 (group P) or thiopental 3 mg/kg-1 (group I); all patients also received 50 micrograms/kg-1 alfentanil and vecuronium bromide 0.12 mg/kg-1/h-1. Maintenance was achieved with midazolam in perfusion at 0.12 mg/kg-1/h-1 (group M); propofol in perfusion at 7 mg/kg-1/h-1 and a pre-incision dose of 1.5 mg/kg-1 (group P); and isoflurane at 1.15% (group I). The 3 groups also received one pre-incision dose of alfentanil 25 micrograms/kg-1 and post-incision perfusion at 60 micrograms/kg-1/h-1. The infusion of alfentanil was changed by amounts of 20 micrograms/kg-1/h-1 in accordance with the patient's response to surgery. After surgery patients in group M received flumazenil 0.5 mg i.v. over 30 sec and a perfusion of flumazenil 0.5 mg over 60 min. Parameters indicating efficacy were: 1) total dose and timing of alfentanil; 2) number of instances of inadequate anesthesia; 3) peri-operative amnesia; 4) times of awakening and extubation after surgery, and 5) the number of patients in each group who required naloxone. Parameters indicating tolerance were: 1) hemodynamic variables; 2) the number of postoperative desaturations; 3) level of sedation, comprehension and motor coordination and orientation; 4) the "G/g detection" test and the memory recall test; 5) adverse side effects; 6) need for postoperative analgesia, and 7) evaluation of the anesthetic technique. RESULTS: The 3 techniques afforded effective control of hemodynamic response to intubation and surgical incision. Anesthetic maintenance was easy and safe with isoflurane and propofol. Higher doses of alfentanil, however, were needed with midazolam and we found a higher incidence of signs of superficial anesthesia. Reversion of midazolam with flumazenil 0.5 mg i.v. produced earlier awakening, although this was followed later by relapse into hypno-sedation that could not be prevented with a perfusion of flumazenil. Although recovery from anesthesia was slower with propofol than with isoflurane, we observed no differences in level of sedation, motor coordination and postoperative comprehension. Maintenance with isoflurane produced a higher incidence of adverse side effects such as tremors and nausea after surgery. CONCLUSIONS: None of the TIVA techniques proved superior in all the parameters studied during anesthetic maintenance when compared with balanced isoflurane-alfentanil, although the propofol-alfentanil combination was found to be superior to that of midazolam-alfentanil. After anesthesia, however, recovery was better with the association of propofol-alfentanil and adverse side effects were fewer. Flumazenil at the doses used was ineffective for preventing resedation due to midazolam.

Adolescent↗