Metabolic characteristics of the deltoid muscle in patients with chronic obstructive pulmonary disease.

The purpose of this study was to analyse key enzyme activities of the deltoid muscle (DM) in chronic obstructive pulmonary disease (COPD) patients. The activities of one oxidative enzyme (citrate synthase (CS)), two glycolytic enzymes (lacatate dehydrogenase (LD); and phosphofructokinase (PFK)) and one enzyme related to the use of energy stores (creatine kinase (CK)) were determined in the DM of 10 patients with COPD and nine controls. Exercise capacity (cycloergometry) and the handgrip strength were also evaluated. Although exercise capacity was markedly reduced in COPD (57 +/- 20% predicted), their handgrip strength was relatively preserved (77 +/- 19% pred). The activity of LD was higher in the COPD patients (263.9 +/- 68.2 versus 184.4 +/- 46.5 mmol x min(-1) x g(-1), p<0.01), with a similar trend for CS (67.3 +/- 33.3 versus 46.0 +/- 17.4 mmol x min(-1) x g(-1), p = 0.07). Interestingly, the activity of the latter enzyme was significantly higher than controls if only severe COPD patients were considered (81.8 +/- 31.2 mmol x min(-1) x g(-1), p < 0.01). PFK and CK activities were similar for controls and COPD. Chronic obstructive patients show a preserved or even increased (severe disease) oxidative capacity in their deltoid muscle. This coexists with a greater capacity in the anaerobic part of the glycolysis. These findings are different to those previously observed in muscles of the lower limbs.

Myosin gene expression in the respiratory muscles.

Myosin is one of the basic structural components of skeletal muscles. Its interaction with actin results in muscle contraction. The myosin molecule is composed of two heavy (MyHC) and two light chains (MyLC) that, together with the adenosine triphosphatase (ATPase) activity, determine the functional characteristics of the fibre. Both MyHC and MyLC present different isoforms. The main MyHC isoforms in adult mammals are the slow MyHC (MyHC-I) and fast MyHCs (MyHC-IIa, MyHC-IIb and MyHC-IIx). Muscle fibres can express only one isoform or coexpress different forms. The muscle phenotype is the product of genome plus environmental stimuli. The family of genes that codifies the MyHC isoforms is located in two different clusters, each isoform being encoded by a separate gene. The gene corresponding to slow MyHC is located in chromosome 14, both in humans and in mice. The other genes are positioned in chromosome 17 in humans, and in chromosome 11 in mice. The transcriptional and translational mechanisms that control the expression of MyHC isoforms are not well known, although it is believed that the main regulation is dependent on mechanical signals. These signals are probably mediated by a biochemical messenger. As a general rule, fast MyHC genes seem to be expressed "by default", whereas the slow MyHC gene would be expressed as a response to changes in load. So far, few studies have analysed the in vivo regulation of MyHC gene expression in respiratory muscles. It has recently been reported that breathing against moderate levels of inspiratory resistance quickly induces an increase in the genetic expression of slow MyHC in the diaphragm. This suggests the possibility of eliciting a phenotypic adaptation of respiratory muscles using specific training protocols.

Methacholine induced headache.

A lung function technician developed episodes of headache, probably related to the use of methacholine. The headache disappeared with breathing 100% oxygen. Cholinergic agents are known to induce headaches but the mechanism remains unclear. Vascular factors could be implicated.

Probable pentamidine-induced acute pancreatitis.

OBJECTIVE: To report a case of probable pentamidine-induced acute pancreatitis. CASE SUMMARY: A patient was hospitalized because of fever, dyspnea, and productive cough. Chest X-ray revealed diffuse alveolar infiltrates, and the examination of bronchoalveolar lavage demonstrated the presence of Pneumocystis carinii. Intravenous cotrimoxazole was administered but the patient's condition did not improve. As secondary leukopenia appeared, the treatment was changed to pentamidine isethionate 4 mg/kg/d i.v. On day 5 of this new therapy, the patient experienced abdominal pain, and both blood and urine amylase concentrations raised to 330 U/L and 3960 U/L, respectively. The patient died 48 hours later, and signs of acute pancreatitis were observed in necropsy. DISCUSSION: With reference to a classical method for estimating the probability of adverse drug reactions, a probable relationship between pentamidine therapy and acute pancreatitis was found in this patient. Furthermore, no alternative causes of pancreatitis were present. CONCLUSIONS: It is likely that pentamidine administration in our patient resulted in an acute episode of pancreatitis. Serum and urine amylase concentrations should be monitored in patients receiving this drug.