PubMed Health⌕ Search

Biomedical subjects

B Grassi

Publications and source records attributed to B Grassi.

At least 55 records · Page 3Linked to original sources
PubMed1994

Fatigue and exhaustion in chronic hypobaric hypoxia: influence of exercising muscle mass.

Exhaustive dynamic exercise with large muscle groups in chronic hypobaric hypoxia may be limited by central (nervous) rather than peripheral (metabolic) fatigue. Six males [32 +/- 4 (SD) yr] at sea level (SL) and after 1-mo acclimatization at 5,050 m (HA) performed exhaustive dynamic forearm exercise at a constant absolute load, requiring regional maximum aerobic power at SL, and exhaustive cycle exercise at prevailing maximal O2 uptake (HA approximately equal to 80% SL). Exhaustion time (t(ex)), blood O2 saturation (SaO2), and heart rate (HR) were measured during each exercise bout. Before and after both arm and leg exercise, lactate concentration ([La]), PO2, PCO2, and pH were measured in arterialized blood samples. Integrated electromyogram activity (IEMG) and mean (MPF) and centroid (CPF) power frequencies of the EMG power spectrum during exercise were calculated for forearm flexors and vastus lateralis muscle. t(ex) for forearm exercise at the same absolute load was the same at SL and HA. Similar increases of IEMG (+214% at SL vs. +172% at HA) and decreases of CPF (-13% at SL vs. -16% at HA) and MPF (-22% at SL vs. -21% at HA) were observed. By contrast, at HA, for similar t(ex), leg exercise had to be performed at the same relative (i.e., prevailing maximal O2 uptake) but lower absolute load (approximately equal to 80% of SL).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Adjustment of cardiac output to step exercise in heart transplant recipients.

The maximal rate of O2 uptake (max VO2) during constant-load exercise is markedly reduced (about 30-50%) in heart transplant recipients (HTX) compared to peak aerobic performance of healthy sedentary controls (CTL). In order to evaluate the role of central and peripheral factors for O2 transport and utilization, breath-by-breath measurements of oxygen consumption (VO2) carbon dioxide output (VCO2), and beat-by-beat determination of cardiac output (Q) by transthoracic impedance cardiography were performed during upright submaximal square-wave cycloergometric exercise (50 W, 5 min) in a group of 21 HTX (age: 44 +/- 8 years; 23 +/- 29 months after transplantation, range 1.3-137 months) and 10 CTL (age: 37 +/- 10 years). The steady-state values (+/- SD) at 50 W for HTX and CTL, respectively, were: (VO2) 1.01 L/min +/- 0.10 and 0.98 L/min +/- 0.05 (NS); (VCO2) 1.07 L/min +/- 0.14 and 0.84 L/min +/- 0.06 (P < 0.01); (Q) 15.6 L/min +/- 5.3 and 12.8 L/min +/- 3.6 (NS). Heart rate (HR) in HTX, after an initial 60-90 s delay, increased linearly with time of exercise up to 122/min +/- 11. The half-time of the readjustment of Q at the onset of exercise was, in HTX and CTL respectively: 52 s +/- 16 and 40 s +/- 17 (NS). In spite of the time lag in the readjustment of HR, the Q on-response in HTX is only moderately delayed, indicating that the increase of stroke volume by augmented preload and the Frank-Starling mechanism at the onset of exercise compensates for the lack of autonomic control of the denervated allograft.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Idarubicin is active on MDR cells: evaluation of DNA synthesis inhibition on P388 cell lines.

Multidrug resistance is frequently found in patients affected by hematological malignancies and has been related to a poor prognosis of acute leukemia. In the present paper we report results concerning the activity of idarubicin, an anthracycline derivative, on the leukemic P388 and P388 doxorubicin-resistant cell lines. The results clearly show that idarubicin inhibits DNA synthesis in the resistant cell line more actively than doxorubicin.

Animals↗
PubMed1993

Ventilatory response to exercise after heart and lung denervation in humans.

This study, aimed at investigating some aspects of breathing control at work, was conducted on 8 heart and lung transplant recipients (HLTR) (age 33 +/- 13 years, mean +/- SD; 10 +/- 6 months post-transplantation) and on two control groups, i.e. 11 heart transplant recipients (HTR) and 11 healthy untrained subjects (C). The patients performed a series of 2 to 6 1-min exercise bouts (at 25 or 50 W, corresponding to about 50% of their VO2max) on a bicycle ergometer, followed by a 5 min 25 or 50 W constant load. C exercised both at 50 W (C1) and at 50% of their VO2max (C2). Inspiratory (VI) and expiratory (VE) ventilation, tidal volume (VT), respiratory frequency (fR), end-tidal O2 and CO2 partial pressures (PETO2 and PETCO2 and gas exchange (VO2 and VCO) were measured breath-by-breath. "Phase I" ventilatory response (ph I) was determined as the mean changes of VI, VE, VT, fR, PETO2 and PETCO2, compared to rest, during the first two respiratory cycles following exercise onset. In HLTR ph I did not significantly differ from that of C1 and C2, whereas the response was lower in HTR. VE, VO2 and VCO2 responses during "phase II" (t 1/2 on-) and "phase III" (steady state exercise) were similar in HLTR and in HTR. t 1/2 on- were longer in HLTR and in HTR compared to C1. In 3 HLTR the ventilatory pattern during the 5 min constant loads was similar to that of HTR and C, whereas 4 HLTR presented higher VT and lower fR values. It is concluded that: 1) The ventilatory response to exercise, in all its phases, is substantially preserved despite lung denervation. When slight alterations are found (i.e. the slower phase II), they are presumably of peripheral origin. 2) The normal ph I in HLTR indicates that cardiac and/or pulmonary inputs to the respiratory centers are not involved in its regulation, or that their role can be subserved by other ventilatory control mechanisms.

Adolescent↗
PubMed1993

Plasmatic parameters of fibrin formation and degradation in cancer patients: correlation between fibrinopeptide A and D-dimer.

This investigation was carried out to evaluate fibrin formation and degradation in various types of solid neoplasms by measuring fibrinopeptide A (fpA) in the plasma with a radioimmunoassay and D-dimer (DD) with an enzyme-linked immunosorbent assay in 176 cancer patients; 77 of them showed signs of distant metastasis (M1). FpA and DD were abnormally elevated in 81 and 143 patients respectively. FpA and DD were significantly correlated and unrelated to plasma fibrinogen. Both fpA and DD levels were more elevated in M1 than M0 patients. Coumarin anticoagulants, administered to 32 patients of our series with the aim of preventing cancer growth and dissemination, caused a significant decrease both in fpA and DD levels. Our data provide evidence of increased in vivo fibrin formation and degradation in solid neoplasms: oral anticoagulants can modulate cancer-related hypercoagulation.

Adult↗
PubMed1993

Body composition and maximum alactic anaerobic performance during a one month stay at high altitude.

Prolonged altitude exposure usually leads to considerable weight loss of which a large part is from muscle tissue. This loss reduces maximum alactic anaerobic muscle power. It was hypothesized that most of the weight loss may simply be the result of malnutrition due to lack of palatable food in an uncomfortable environment. To test this hypothesis eight healthy male subjects (age 33.7 +/- 4.6 S.C. yr), well acclimatized to prevent symptoms of acute mountain sickness, were exposed for 4 weeks to an altitude of 5050 m with access to a large choice of palatable food in comfortable conditions. Body weight (with a scale), body composition (from skinfolds), arm muscle plus bone cross-sectional area (Am + b) and muscle plus bone leg volume (Vm+b) (from skinfolds and circumferences), maximum voluntary contraction force of the elbow flexors (MVC, with a load cell) and maximum jumping height (Hmax, on a platform) were measured before departure (SL) and in the first (ALT1), second (ALT2) and fourth week (ALT4) of their altitude sojourn. Three-day dietary records were obtained at SL and at ALT4. Body mass had decreased significantly at ALT2 (-3.8%) and at ALT4 (-4.6%) likely reflecting changes in body water homeostasis. No changes were found in %fat, Am+b, Vm+b, MVC or Hmax. Average dietary intake at SL was 8.96 +/- 1.45 MJ and had increased to 13.59 +/- 3.07 MJ at ALT4. In conclusion, up to an altitude of 5050 m loss of body mass from fat and muscle tissue, and hence impairment of maximum anaerobic muscle power (alactic) appears to be avoidable by food intake matched to energy expenditure. The latter may be achieved simply by proper acclimatization, sufficient comfort and availability of palatable food.

Adipose Tissue↗
PubMed1993

Reversing of chlorambucil resistance by ethacrynic acid in a B-CLL patient.

We evaluated the reversing activity of ethacrynic acid in a B-CLL patient resistant to chlorambucil. The glutathione S-transferase (GST) activity, measured in peripheral blood lymphocytes, resulted extremely elevated. Ethacrynic acid, at pharmacological concentrations, partially reversed chlorambucil resistance and this result appeared related to the increased GST levels.

Aged↗
PubMed1993

Maximal lactic capacity at altitude: effect of bicarbonate loading.

The aim of the present study was to test the hypothesis that the net maximal blood lactate accumulation ([La]max) during heavy exercise in lowlanders acclimatized to chronic hypoxia may be limited by the reduced bicarbonate stores. Six men [age 32 +/- 4 (SD) yr] performed supramaximal exercise until voluntary exhaustion at sea level (204 +/- 54 W) and after sojourning for 1 mo at 5,050 m (175 +/- 23 W), without (C) and with (B) oral sodium-bicarbonate loading (0.3 g/kg body wt). Exhaustion time, arterial blood lactate concentration, arterial pH (pHa), arterial PCO2, and intramuscular pH were measured at rest and after exercise. At sea level, exhaustion time increased from 6.5 +/- 2.8 min in C to 7.5 +/- 2.7 min in B (P < 0.05). At altitude, exhaustion times were similar to the sea level C values and the same in C and B. At sea level, resting pHa increased from 7.41 +/- 0.02 in C to 7.46 +/- 0.03 in B (P < 0.001); the corresponding values at altitude were 7.46 +/- 0.04 and 7.55 +/- 0.03 (P < 0.001). Postexercise pHa at sea level was 7.22 +/- 0.02 in C and 7.25 +/- 0.08 in B (NS). After exercise at altitude, pHa was 7.32 +/- 0.04 and 7.44 +/- 0.03 in C and B, respectively (P < 0.001). [La]max increased from 12.86 +/- 1.45 mM in C to 16.63 +/- 1.76 mM in B (P < 0.01) at sea level and from 6.85 +/- 1.40 mM in C to 7.95 +/- 1.74 mM in B (NS) at altitude.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1993

High muscle blood flow in man: is maximal O2 extraction compromised?

During conventional cycle ergometry, as work rate (WR) is increased toward maximum, O2 extraction increases hyperbolically, typically achieving values of 80-90% at peak O2 uptake (VO2). In contrast, studies using isolated knee-extensor exercise report much higher mass-specific blood flows (Q) and lower maximal O2 extractions (approximately 70%), which have been interpreted as transit time limitation to O2 movement out of the muscle capillary. However, maximal achievable WR levels during conventional cycle ergometry are generally reached (over 10-15 min) after rapid increases in WR, whereas the reported knee-extensor studies have used only more lengthy protocols (45 min). The duration of these protocols may have prevented the attainment of high WR levels and thus high O2 extraction ratios. Accordingly, this investigation examined leg Q and O2 extraction responses during single-leg knee-extensor exercise incremented rapidly (steps of 15-25 W per 2- to 3-min interval), which produced fatigue in 13-15 min. Q and muscle VO2 increased linearly with WR to fatigue with Q-WR and VO2-WR slopes similar to those reported in previous knee-extensor studies. However, with the use of this protocol, very high maximal achievable WR [99 +/- 6 (SE) W] and muscle Q (385 +/- 26 ml.min-1 x 100 g-1) levels were attained, some 80% greater than previously reported. An O2 extraction of 84.6 +/- 2.1% was reached, giving a maximal VO2 of 60.2 +/- 5.8 ml.min-1 x 100 g-1. We conclude that, even under the high Q conditions of single-leg knee-extensor exercise, O2 extraction does not reach a plateau on the basis of short transit times and that previous conclusions to the contrary reflect failure to attain sufficiently high WR levels. Maximal VO2, Q, and O2 extraction in this model have yet to be defined.

Adult↗
PubMed1993

Vitamin D3 administration and multidrug resistance in acute nonlymphoblastic leukemia.

This article reports preliminary results from a pilot study started in 1986 on patients with acute myeloblastic leukemia treated for several months with low-dose arabinosylcytosine and 1(OH)D3. During treatment or at the time of relapse, a monoblastic component was frequently found. A high percentage of patients were P-170-positive. In 2 patients it was possible to show that blasts, previously P-170-negative, became positive after treatment. In these 2 patients, failure of clinical response to antileukemic therapy was associated with this phenotype. The addition of the revertant drug nicardipine to the previously inactive treatment induced a partial response. Thus, previously reported in vitro observations on the differentiating activity of vitamin D3 metabolites, possible induction of multidrug chemoresistance by differentiating agents and the revertant activity of the Ca++ antagonist nicardipine appear to be confirmed in vivo in the reported patients.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Factor analysis and computerized EEG: preliminary data on schizophrenic patients.

Factor Analysis can extract salient features from EEG data and reduce redundancy of multi-channel computerized EEG data. A 16-channel computerized frequency analysis of background brain electrical activity during 3 functional conditions (eyes closed, eyes open and hyperventilation) was carried out in two groups, fifty healthy subjects and twenty-three schizophrenics. The power log-transformed relative values of normal subjects and schizophrenic patients were submitted to Factor Analysis and the resulting factor scores were compared. Schizophrenics showed EEG abnormalities in delta 2, theta 1 and alpha 2 bands for the first factor, accounting for the eyes closed condition, and in theta 2 and beta 2 bands for the second factor, accounting for the eyes open condition. This preliminary study demonstrates the utility of Factor Analysis in managing and comparing computerized EEG data.

Adult↗
PubMed1993

Third generation chemotherapy with P-VABEC for aggressive non-Hodgkin's lymphomas of the elderly.

Between July 1990 and March 1992, 23 elderly patients with intermediate or high-grade non-Hodgkin's lymphomas (NHL) received a combination chemotherapy (P-VABEC: Etoposide, Adriamycin and Cyclophosphamide on days 1, 15, 29, 43, Vincristine and Bleomycin on days 8, 22, 36, 50 and Prednisolone on weeks 1-9). The regimen was administered on an outpatient basis. The median age of the patients was 67 years (range 60-78); 15 were previously untreated, 8 were on second line therapy; 6 patients (44%) had stage IV disease, 19 (83%) B symptoms, 15 (65%) had bulky disease, and (26%) bone marrow involvement. The complete remission (CR) rate was 57%, and the partial remission (PR) rate 43%, with an overall response rate of (100%). No difference in response rate was observed between previously untreated patients and patients treated with P-VABEC as second-line therapy while hematological and clinical toxicity were very mild.

Aged↗
PubMed1993

Activity of different revertant agents on multidrug resistance: in vitro evaluation of their combination.

The revertant activity of different compounds has been assayed on a multidrug-resistant human breast-cancer cell line (MCF 7/Dx). The calcium-channel blocker nicardipine showed the higher revertant ability when compared to cefoperazone or cyclosporin A at concentrations close to the pharmacological range. Interestingly, nicardipine was able to increase the revertant activities of both cefoperazone and cyclosporin A, but these latter were not able to enhance each other over a plateau. However, a limit of about 70% of growth inhibition of the line cultured in the presence of 60 microM doxorubicin seems to be insuperable at the concentrations employed. The combination of the three drugs brings the concentrations of drugs to the point at which the maximum possible inhibition is reached in the pharmacological range, but the complete reversion of chemoresistance is not reached when the doxorubicin is added at the concentration capable of reducing the cell proliferation by 50%.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Gas exchange kinetics in heart transplant recipients.

Submaximal and/or peak levels of oxygen consumption (VO2), pulmonary ventilation (VE), heart rate (HR), stroke volume of heart (SV), cardiac output (Q), muscle blood flow (qm), as well as the kinetics of readjustment of gas exchange, Q and qm (t1/2 VO2on-, t1/2 Qon-, t1/2 qmon-) were determined in 44 heart transplant recipients (HTRs) and in a group of age-, sex-, and physical activity-matched control subjects (CTL) when carrying out rectangular loads (25 to 125 W) on a bicycle ergometer. The increase of SV occurring at work onset appears to compensate in HTRs for the sluggish readjustment of HR so that the rate of readjustment of Q is kept within normal limits. As a consequence, qm, t1/2 q mon-, and t1/2 VO2on- appear to be similar or only moderately delayed in HTRs compared with CTLs. It is concluded that in HTRs, because of constrained maximum HR, only work loads up to 60% of the VO2max of CTLs may be attained; also, owing to the fast readjustment of Q, up to work loads of 75 to 100 W, the rest to work transition phase is not impaired.

Electrocardiography↗
PubMed1991

Peak anaerobic power in master athletes.

The age-related decline in maximal physical performance of healthy subjects may be attributed both to the aging process per se and/or to a progressive reduction in physical activity. In two groups of master athletes, power (P) or endurance (E) trained (n = 115; aged 40-78 years), the degree and rate of the age-related deterioration of the maximal instantaneous muscle power (peak power, Wpeak), and the relative contribution of quantitative (muscle mass) and qualitative factors possibly underlying such deterioration were determined. Two groups of young athletes (n = 20; 17-26 years) and healthy untrained subjects (U, n = 37; 22-67 years) were also tested for comparison. The following two variables were assessed, firstly the lower limb muscle plus bone volume (LMV) by anthropometry, and secondly Wpeak, by means of a standardized vertical jump off both feet, performed on a force platform. The results obtained were that LMV of E and P, as well as of U, was about the same between age 20 and 45 years, whereas at older ages a progressive reduction was observed; the LMV values were higher in P than in E and U.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1991

Energetics of locomotion in African pygmies.

The energy cost of walking (Cw) and running (Cr), and the maximal O2 consumption (VO2max) were determined in a field study on 17 Pygmies (age 24 years, SD 6; height 160 cm, SD 5; body mass 57.2 kg, SD 4.8) living in the region of Bipindi, Cameroon. The Cw varied from 112 ml.kg-1.km-1, SD 25 [velocity (v), 4 km.h-1] to 143 ml.kg-1.km-1, SD 16 (v, 7 km.h-1). Optimal walking v was 5 km.h-1. The Cr was 156 ml.kg-1.km-1, SD 14 (v, 10 km.h-1) and was constant in the 8-11 km.h-1 speed range. The VO2max was 33.7 ml.kg-1.min-1, i.e. lower than in other African populations of the same age. The Cr and Cw were lower than in taller Caucasian endurance runners. These findings, which challenge the theory of physical similarity as applied to animal locomotion, may depend either on the mechanics of locomotion which in Pygmies may be different from that observed in Caucasians, or on a greater mechanical efficiency in Pygmies than in Caucasians. The low Cr values observed enable Pygmies to reach higher running speeds than would be expected on the basis of their VO2max.

Africa↗