Effects of 1.32-μm Nd-YAG laser on brain thermal and histological experimental data

Considering that the 1.32-μm Nd-YAG laser should have physicothermal properties close to those of the CO₂ laser, a series of experiments were conducted on rat cortex (N = 51). Three laser wavelengths were compared: CO₂ laser (10.6 μm), 1.06-μm Nd-YAG, and 1.32-μm Nd-YAG lasers. For each shot, temperature measurements were recorded with an infrared thermographic videocamera. The digitized signals were figured as thermal profiles and temperature developments. Ninety-five shots were correctly studied and analyzed: CO₂, N = 29; 1.06-μm Nd-YAG, N = 20; 1.32-μm Nd-YAG, N = 46. The histological lesions produced by these three lasers were compared on animals killed 24 hours (N = 20), 8 days (N = 20), and 30 days (N = 5) after the laser impacts. For equivalent densities of energy, the depth of cortical necrosis was comparable for the CO₂ laser (200–250 μm) and the 1.32-μm Nd-YAG laser (210–260μm) whatever the date of death; the 1.06-μm Nd-YAG laser shots were responsible for much more important damage (400–550μm). Because of its important absorption in water and nervous tissue, the authors consider the 1.32-μm Nd-YAG laser most suitable for neurosurgery, particularly because it is conducted through optic fibers, and therefore is easy to handle during neurosurgical procedures.     

Nedocromil sodium inhibits IgE- and IgG-related antigen-induced contraction in guinea-pig trachea

The effects of nedrocromil sodium and disodium cromoglycate were studied on the anaphylactic contraction of guinea-pig trachea in two models of active sensitization (IgE and IgG models). The influence of epithelial removal on the effects of nedocromil sodium and disodium cromoglycate was examined because several studies have shown that the epithelial layer can modulate agonist- or antigen-induced contractile responses. Disodium cromoglycate (10(-4) M) and nedocromil sodium (10(-4) M) provided significant protection against antigen-induced contractions of guinea-pig tracheal smooth muscle in the IgG model. But only nedocromil sodium had an effect at this concentration in the IgG model and was also effective at 10(-5) M in the epithelium-denuded tracheal strips. At this concentration, disodium cromoglycate lost its protective effect. Comparison with the results obtained with FPL-55712, AA-861 and mepyramine suggested that these drugs affect histamine and particularly leukotriene synthesis and/or release by mast cells or other immunocompetent cells. These findings indicate that nedocromil sodium inhibits the IgE- and IgG-related antigen-induced contraction in guinea-pig airways, whereas disodium cromoglycate inhibits only the IgG-related processes. This study supports the hypothesis that these drugs modulate antigen-induced mediator synthesis and/or release from immunocompetent cells.     

Residual Paralysis in the PACU after a Single Intubating Dose of Nondepolarizing Muscle Relaxant with an Intermediate Duration of Action

Background: Residual neuromuscular blockade remains a problem even after short surgical procedures. The train-of-four (TOF) ratio at the adductor pollicis required to avoid residual paralysis is now considered to be at least 0.9. The incidence of residual paralysis using this new threshold is not known, especially after a single intubating dose of intermediate-duration nondepolarizing relaxant. Therefore, the aim of the study was to determine the incidence of residual paralysis in the postanesthesia care unit after a single intubating dose of twice the ED95 of a nondepolarizing muscle relaxant with an intermediate duration of action.

Methods: Five hundred twenty-six patients were enrolled. They received a single dose of vecuronium, rocuronium, or atracurium to facilitate tracheal intubation and received no more relaxant thereafter. Neuromuscular blockade was not reversed at the end of the procedure. On arrival in the postanesthesia care unit, the TOF ratio was measured at the adductor pollicis, using acceleromyography. Head lift, tongue depressor test, and manual assessment of TOF and DBS fade were also performed. The time delay between the injection of muscle relaxant and quantitative measurement of neuromuscular blockade was calculated from computerized anesthetic records.

Results: The TOF ratios less than 0.7 and 0.9 were observed in 16% and 45% of the patients, respectively. Two hundred thirty-nine patients were tested 2 h or more after the administration of the muscle relaxant. Ten percent of these patients had a TOF ratio less than 0.7, and 37% had a TOF ratio less than 0.9. Clinical tests (head lift and tongue depressor) and manual assessment of fade showed a poor sensitivity (11-14%) to detect residual blockade (TOF < 0.9).     

Use of the Cytobrush for concurrent cytology and chlamydia sampling: a comparison of immunofluorescence and culture for detection of chlamydia

Five hundred and thirty-three women attending a genitourinary medicine clinic underwent concurrent cytology and Chlamydia trachomatis screening using a Cytobrush (Medscand AB). In each case, the same Cytobrush was used to give a sample for direct immunofluorescence and culture. 11.1% of samples were positive by immunofluorescence, while 10.6% were positive by culture. This was a close agreement (Kappa = 0.875). The ability of the same instrument to be used for both cytology and chlamydial screening, where direct immunofluorescence is used for detection of chlamydiae, may allow more widespread screening for chlamydia to be practical.     

Molecular system bioenergetics: regulation of substrate supply in response to heart energy demands

This review re-evaluates regulatory aspects of substrate supply in heart. In aerobic heart, the preferred substrates are always free fatty acids, and workload-induced increase in their oxidation is observed at unchanged global levels of ATP, phosphocreatine and AMP. Here, we evaluate the mechanisms of regulation of substrate supply for mitochondrial respiration in muscle cells, and show that a system approach is useful also for revealing mechanisms of feedback signalling within the network of substrate oxidation and particularly for explaining the role of malonyl-CoA in regulation of fatty acid oxidation in cardiac muscle. This approach shows that a key regulator of fatty acid oxidation is the energy demand. Alterations in malonyl-CoA would not be the reason for, but rather the consequence of, the increased fatty acid oxidation at elevated workloads, when the level of acetyl-CoA decreases due to shifts in the kinetics of the Krebs cycle. This would make malonyl-CoA a feedback regulator that allows acyl-CoA entry into mitochondrial matrix space only when it is needed. Regulation of malonyl-CoA levels by AMPK does not seem to work as a master on–off switch, but rather as a modulator of fatty acid import.