Involvement of Ca2+ in dopamine release in striatal rat slices by PF9601N and L-deprenyl

Rat striatal slices were incubated 1 hour in Krebs buffer with carbogen by continuous perfusion. When both MAO-B inhibitors PF9601N and l-deprenyl were added in the incubation medium, at 200 microM concentration, a diminution in the dopamine content was observed. The decrease in dopamine content was partially calcium dependent and showed a different mechanism between both compounds. When 1 mM concentration EGTA was added at the Krebs incubation medium without calcium, dopamine content was partially recovered, being not affected in case of l-deprenyl. When 50 microM dantrolene (a calcium vesicular release inhibitor) was added in the Krebs incubation medium without calcium, dopamine was partially recovered for l-deprenyl, being not affected in case of PF9601N. These data indicate that dopamine release is extracellular calcium dependent in case of PF9601N, whereas l-deprenyl depends on calcium intracellular origin.

Neuroprotective aspects of a novel MAO-B inhibitor PF9601N

PF9601N is an acetylenic tryptamine derivative devoid of amphetamine-like properties, that behaves as suicide MAO-B inhibitor more potent than l-deprenyl. It is highly selective towards MAO-B and it neuroprotects from the neurotoxicity induced in C57Bl/6 adult mice by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). PF9601N also shows in vitro antioxidant properties by inhibiting the dopamine autoxidation. A potential therapeutic use in Parkinson's disease treatment is proposed for this compound.

[Metabolic activity of the external intercostal muscle of patients with COPD]

INTRODUCTION

The external intercostal muscle is a relevant contributor to ventilatory work in situations of overloading. Like other respiratory muscles, the external intercostal muscle seems to undergo a process of structural remodeling to adapt to a situation of functional disadvantage. However, findings from published studies of morphology have differed to a certain degree. On the one hand, the proportion of fibers involved in anaerobic metabolism increases; on the other hand, the number of capillaries also increases, an occurrence that would facilitate aerobic metabolism.

OBJECTIVE

This study was designed to analyze the activity of several key enzymes involved in the principal metabolic pathways in the external intercostal muscles of patients with COPD.

METHODOLOGY

We studied 6 patients with COPD (65 +/- 8 years, BMI 23 +/- 3 kg/m2, FEV1 51 +/- 9% ref, RV 184 +/- 38% ref, PaO2 81 +/- 10 mmHg) and 6 control subjects matched for age and anthropometric variables but with normal lung function. External intercostal muscle samples were taken from each patient (fifth intercostal space, non-dominant side). The samples were treated by conventional spectrophotometry to determine enzyme activity as follows: citrate synthase (CS, Krebs cycle), phosphofructokinase (PFK, by common glycolysis), lactate dehydrogenase (LDH, anaerobic glycolysis) and creatine phosphokinase (CPK, use of energy reserves).

RESULTS

Patients with COPD showed greater PFK enzyme activity (93 +/- 25 versus 44 +/- 9 micromol/min/g of fresh weight; p = 0.001) and LDH (308 +/- 42 versus 231 +/- 29 micromol/min/g; p < 0.01) than did control subjects. However, CS and CPK activity was similar in both groups (82 +/- 31 versus 90 +/- 20 micromol/min/g and 4017 +/- 1734 versus 3048 +/- 464 micromol/min/g, respectively), although the latter displayed noteworthy dispersion of values among COPD patients, with levels in some patients being three-fold greater than in controls. RV was directly related to glycolytic enzyme activity (with PFK, r = 0.716, p < 0.01; with LDH r = 0.697, p < 0.05) and PFK and LDH also correlated with each other (r = 0.737, p < 0.01).

CONCLUSIONS

Based on the enzyme activity studied, oxidative activity seems to be conserved in the external intercostal muscle of patients with COPD. Activity in the glycolytic pathway seems to increase and the increase is proportional to the severity of COPD. These findings are probably the expression of a combination of adaptive structural factors.

FA-70, a novel selective and irreversible monoamine oxidase-A inhibitor: effect on monoamine metabolism in mouse cerebral cortex

A series of indolealkylamine derivatives has been previously designed and evaluated with the aim of finding the most potent and selective novel monoamine oxidase (MAO) inhibitors to be used in the therapy of neurological and affective disorders. Among them, FA70, a 5-hydroxy-indolealkylamine derivative, has been characterized in vitro as a potent, irreversible, and mechanism-based inhibitor of the MAO-A isoform. The comparison with clorgyline, analyzed under the same experimental conditions, confirmed FA70 as the most potent MAO-A inhibitor. The ex vivo effect of FA70 on MAO activity in mouse cerebral cortex was similar to that observed in vitro, showing more efficacy than in peripheral tissues. The ex vivo effect of FA70 on amine metabolism also was evaluated after acute and chronic treatment, and the results showed that between both MAO isoforms, MAO-A is the only one responsible for monoamine metabolism in this region of the brain. The ex vivo effect of FA70 on dopamine content was correlated with the activation effect on tyrosine hydroxylase activity, the enzyme responsible for the regulation of the limiting step in catecholamine synthesis.

[The characteristics of the mechanical activity of the respiratory muscles during the diaphragmatic respiration technic]

Noteworthy among breathing training techniques is so-called diaphragmatic breathing. In spite of the technique's name, however, little is known of the functional characteristics of this ventilatory method.

OBJECTIVE

To asses the mechanics of respiratory muscles, particularly diaphragm muscles, during diaphragmatic breathing in patients with severe chronic obstructive pulmonary disease (COPD).

METHODS

Ventilatory pattern and respiratory pressures (abdominal [Pga], intrathoracic [Pes] and transdiaphragmatic [Pdi]) were studied in 10 patients with severe COPD in stable phase (age 69 +/- 6 years, FEV1 33 +/- 12% ref) at baseline and during deep breathing with spontaneous muscle recruitment (SMR) and during breathing training. Measurements were taken with the patient seated and in supine decubitus position.

RESULTS

In seated position ventilatory pattern was similar with SMR and during breathing training. Mean Pdi during airflow, however, was greater during breathing training than with SMR (34.8 +/- 8.0 and 29.3 +/- 9.3 cmH2O, respectively, p < 0.05) for similar levels of Pes. Mechanical effectiveness of the diaphragm expressed as Vt/Pdi) was less during breathing training, however (36.1 +/- 10.4 and 49.5 +/- 15.8 cc/cmH2O, p < 0.05), with no changes in overall efficacy of respiratory muscles (Vt/Pes). In supine decubitus position, ventilatory patterns of SMR and breathing training were similar, although Vt and T1 were slightly higher in the latter (1,065 +/- 305 vs. 1,211 +/- 314 cc, p < 0.01; and 2.76 +/- 1.32 vs. 3.07 +/- 1.23 sec, p < 0.05). Pdi was also higher during breathing training (29.7 +/- 10.2 and 38.0 +/- 10.5 cmH2O, p < 0.05), although accompanied in this case by a higher Pes (21.2 +/- 7.5 to 26.4 +/- 8.4 cmH2O, p < 0.005). In supine decubitus position, the effectiveness of both diaphragm muscles and respiratory muscles overall was similar for both ventilatory modes.

CONCLUSIONS

Breathing training truly involves greater use of the diaphragm, both in seated and supine decubitus positions. Breathing training does not provide greater ventilatory efficacy than SMR, however, in COPD patients.

[Obtaining samples of the human diaphragm during upper laparotomy. A structural analysis]

The diaphragm seems to undergo adaptive structural change in chronic obstructive pulmonary disease. The possibility of obtaining muscle specimens is limited, however, particularly when respiratory function is severely affected.

OBJECTIVE

To assess the viability of a new technique for obtaining diaphragm muscle samples appropriate for structural assessment even from patients with severe functional change, and to study the size of fibers in relation to severity of disease.

METHODS

Fifteen muscle specimens were obtained from patients (aged 57 +/- 15 years) by abdominal laparotomy. All had undergone full lung function testing. Muscle samples were taken during surgery using a new technique involving formation of a tobacco pouch with dome biopsy. The method had been previously validated in animal models. Later, the biopsies were processed to evaluate fiber proportions and sizes (ATPase dyes at different levels of pH).

RESULTS

The 15 patients had a wide range of lung function results (FEV1 22-120% ref); 4 were severely affected (FEV1 < or = 50% ref). Nutritional status was normal in all cases; FEV1/FVC was 67 +/- 13%, RV was 134 +/- 55% ref, maximal mouth pressure (PImmax) was -75 +/- 27 cmH2O, transdiaphragmatic pressure (PIdimax) was 96 +/- 26 cmH2O, DLCO was 87 +/- 26% ref and PaO2 was 89 +/- 14 mmHg. We were able to obtain specimens valid for structural analysis from all patients with no complications. Light type I fibers predominated (54 +/- 9%) and size was normal overall (57 +/- 9 microns minimum diameter [Dm] atrophy index 195 +/- 243, and hypertrophy index 66 +/- 78), with no differences between the two fiber subtypes (Dm 58 +/- 8 microns for type I and 61 +/- 8 microns for type II). Overall size correlated inversely with static volumes (e.g. Dm with RV, r = -0.729, p < 0.01).

CONCLUSIONS

The laparoscopic technique described is simple and safe for use in humans to obtain diaphragm muscle specimens that are valid for morphometric analysis, allowing us to enlarge the range of subjects that can be enrolled for this type of study. The fiber muscles studied are smaller when functional involvement is greater in chronic obstructive pulmonary disease.

Evaluation of nasal prongs for estimating nasal flow

Nasal prongs (NP) connected to a pressure transducer have been suggested as a useful alternative for measuring nasal flow in sleep apnea/hypopnea patients. However, flow measured with NP is expected to be nonlinear. The aim of the present study was to analyze and correct the nonlinearity of nasal flow measurements with NP (VNP). Nasal flow was simultaneously measured with a pneumotachograph (PNT; V) and (NP; VNP) in six healthy subjects during 60 s of breathing at different tidal volumes. Nonlinearity of VNP was assessed by fitting separately, for inspiration and expiration, a Rorher-model equation (VNP x K1 x V + K2 x V2). In addition, we fitted the data to a simpler nonlinear quadratic model (P = K x V2). The main findings were: (1) an excellent fit of the Rorher equation to measured data in all cases; (2) although differences in the Rorher equation coefficients between inspiration and expiration were observed, they were not statistically significant; (3) a substantial intersubject variability was found; and finally, (4) the square root of VNP acceptably fitted the nasal flow data measured by PNT (V) in most cases. We conclude that in order to quantitatively assess nasal flow with NP, data should be corrected for their nonlinear pressure-flow relationships and, that the square root of the flow signal measured with NP is the simplest method of correcting for the observed nonlinearity.

[Muscle relaxants in the morphometric study of the respiratory muscles in human beings]

The morphological examination of respiratory muscle can be affected by muscular contraction following biopsy. Most morphometric studies of respiratory muscles, however, have been carried out without taking into account this factor, the effect of which can be reduced by using relaxants when taking samples. Objective. To examine the effect of using a relaxant in the morphometric analysis of muscle fibers. We examined 31 muscle samples from 7 patients. Immediately after removal, each pipe was divided in half. One was placed in an isotonic physiological solution and the other in a solution of curare 0.02%. Later, both samples were processed for morphometric study with ATP-ase, NADTH and PAS tincture. Morphological data recorded for the different types of fibers included measurement of minimum diameter (Dmin), atrophy and hypertrophy indices (AI and HI) and heterogeneity of distribution (SDDmin). The Dmin was smaller in fibers transported in a curare solution than in those transported in physiological solution (67 +/- 2 microns vs. 71 +/- microns, p < 0.05). The same was true of SDDmin (13 +/- 3 vs. 12 +/- 3, p < 0.05), HI (300 +/- 88 vs. 457 +/- 107, p < 0.05). Likewise, we found a similar direct correlation between size of fibers processed with physiological solution and those processed in curare (Dmin, r = 0.731, p < 0.001; HI, r = 0.827, p < 0.001; SDDmin, r = 0.636, p < 0.0001). The use of relaxants in processing muscle samples prevents contraction and should be used systematically in the morphological analysis of muscle fibers.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Separation and quantification of histamine and N tau-methylhistamine in brain extracts

Histamine and its N tau-methyl derivative can be separated from perchloric acid extracts of rat brain by high performance liquid chromatography on a C18 column under isocratic conditions eluting with 0.1 M sodium phosphate buffer containing 0.19 mM sodium dodecyl sulphate and 25% methanol. Using electrochemical detection, histamine and N tau-methylhistamine can be detected at levels of less than 40 pg/microL tissue extract (less than 1 pmol). The retention times for histamine and N tau-methylhistamine were 15 min and 23 min, respectively, at a flow rate of 1.2 mL/min, and both compounds eluted as acceptably sharp peaks. The concentrations of histamine and N tau-methylhistamine in brain from seven-day-old rats were found to be very similar to those obtained by other analytical procedures.