Cyanobacterial formation of intracellular Ca-carbonates in undersaturated solutions.

Cyanobacteria have long been thought to induce the formation of Ca-carbonates as secondary by-products of their metabolic activity, by shifting the chemical composition of their extracellular environment to conditions favoring mineral precipitation. Some cyanobacterial species forming Ca-carbonates intracellularly were recently discovered. However, the environmental conditions under which this intracellular biomineralization process can occur and the impact of cyanobacterial species forming Ca-carbonates intracellularly on extracellular carbonatogenesis are not known. Here, we show that these cyanobacteria can form Ca-carbonates intracellularly while growing in extracellular solutions undersaturated with respect to all Ca-carbonate phases, that is, conditions thermodynamically unfavorable to mineral precipitation. This shows that intracellular Ca-carbonate biomineralization is an active process; that is, it costs energy provided by the cells. The cost of energy may be due to the active accumulation of Ca intracellularly. Moreover, unlike cyanobacterial strains that have been usually considered before by studies on Ca-carbonate biomineralization, cyanobacteria forming intracellular carbonates may slow down or hamper extracellular carbonatogenesis, by decreasing the saturation index of their extracellular solution following the buffering of the concentration of extracellular calcium to low levels.

Oxygen consumption after flumazenil reversal.

The effect of flumazenil reversal of midazolam-induced anesthesia on whole body oxygen uptake (VO2) was investigated in a double-blind trial in 48 patients (ASA, 1 or 2) undergoing elective surgery under general anesthesia. VO2 was measured in spontaneously breathing patients during recovery from anaesthesia induced with midazolam 0.25 mg.kg-1 and maintained with nitrous oxide 60% in oxygen and halothane. The level of sedation was evaluated by a subjective score. To reverse midazolam-induced anesthesia, patients were randomly allocated to receive placebo or flumazenil (6 micrograms.kg-1). No significant changes in VO2 (160 +/- 53 vs 150 +/- 39 ml.min-1.m-2 or sedation score (2.5 +/- 1.0 vs 2.1 +/- 0.9) were observed in the placebo group. After flumazenil administration, the sedation score significantly (P less than 0.05) improved (2.9 +/- 1.0 vs 1.3 +/- 0.8) whereas no significant change in VO2 was observed (158 +/- 67 vs 157 +/- 61 ml O2.min-1.m-2). These data show that reversal of benzodiazepine effects with flumazenil resulted in no significant change in oxygen uptake.

[Respiratory pattern and activity of the abdominal muscles after upper abdominal surgery]. / Mode ventilatoire et activité des muscles abdominaux après chirurgie sus-ombilicale.

Because only few data is as yet available concerning abdominal muscle activity following upper abdominal surgery, the present study aimed to investigate the pattern of abdominal muscle activity before and after upper abdominal surgery and to relate any changes to differences in abdominal respiratory movements. Eight ASA I patients (5 women, 3 men), mean age 44 +/- 12 yr, undergoing elective cholecystectomy (midline incision) were investigated. The following parameters were measured, with the patients supine and at rest, on the eve of surgery, and 2, 4, 24 and 72 h afterwards: tidal volume (VT), breathing rate (f), inspiratory time (TI), total cycle time (TT), changes in abdominal (Dab) and thoracic (Drc) circumferences, surface electromyograms of the rectus abdominis and obliquus externus abdominis muscles. The ratio (Dab/Dab + Drc) was used as an index of relative abdominal movement. Anaesthetic management was similar for all patients (thiopentone, fentanyl, vecuronium, halothane and N2O). A significant reduction in VT was found between 2 and 24 h postoperatively, with a significant increase in f between 4 and 24 h after surgery. Both these parameters returned to normal values at the 72nd h. Relative abdominal movement was reduced in the immediate postoperative period (2 and 4 h), slowly improving, but remaining lower than normal at 72 h. Muscle tonus was increased at 2 h and returned to normal at the 4th h. This transient increase suggested a residual effect of fentanyl.(ABSTRACT TRUNCATED AT 250 WORDS)

[Monitoring of mixed venous oxygen saturation in aortic surgery: value and limits]. / Monitorage de la SvO2 en chirurgie aortique: intérêt et limites.

This study aimed to determine perioperative changes in mixed venous oxygen saturation (SvO2) in patients undergoing aortic surgery. Continuous SvO2 monitoring was carried out using an Oximetrix pulmonary catheter. Fourteen patients were randomly assigned to 2 groups, group I (n = 7) patients being given a thoracic epidural anaesthetic with a supplementary general anaesthetic, and group II (n = 7) a general anaesthetic as usual. In both groups, SvO2 increased at induction. In group I patients, SvO2 decreased during surgery to less than 60% (n = 2) and less than 70% (n = 4). This fall was corrected by volume loading and intravenous ephedrine. The intraoperative decrease in SvO2 occuring in 2 group II patients was due to a fall in haematocrit in one, and a propranolol infusion in the other. Although patients in group I were all extubated early after the end of surgery (85 +/- 35 min), the lowest value of SvO2 after extubation was always greater than 60%. Patients undergoing aortic surgery under thoracic epidural anaesthesia can be extubated early, without markedly depressing peripheral reserves in oxygen extraction.

[Psychotherapeutic interventions in cancerology]. / Interventions psychothérapiques en cancérologie.

The task of a psychoanalyst working in cancerology is to help patients and families cope with the illness and the treatments by recognizing them all as "subjects" with their own phantoms, desires and personal history. Above all, the cancer patient is concerned by possible losses: loss of an essential body-function, loss of a social and/or economical status and finally loss of life itself. From our experience; we know that relieving pain is not only a question of prescribing the right medication but depends mostly on the way the team is able to recognize fears, conflicts and treat the person globally, offering solutions to solve the problems patients and families meet.

[Role of psychological factors in cancerogenesis and the development of cancerous disease]. / Rôle des facteurs psychologiques dans la cancérogenèse et l'évolution de la maladie cancéreuse.

Psychoanalysts working in cancerology have to face three main difficulties concerning their methodology: the selection of representative populations, the identification of prospective factors and the choice and definition of the data they need to collect. Four examples are given hereafter: a prospective study on the psychogenesis of cancer, the question of cancer-prone personalities, the incidence of psychosocial factors on survival in advanced malignant diseases, and a study focused on bereavement and cancer.