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Biomedical subjects

C Bosco

Publications and source records attributed to C Bosco.

At least 37 records · Page 2Linked to original sources
PubMed1995

[Modification of the lipid profile of human placenta by moderate maternal undernutrition].

The lipid composition of human placenta phospholipids, coming from 9 undernourished women that gave birth to low weight newborns and 9 well nourished women, was analyzed using gas-liquid chromatography. Phospholipids of placentas coming from undernourished women, when compared to well nourished women, had significantly lower amounts of w-6 and w-3 fatty acids (40.1 +/- 1.5 vs 42.4 +/- 1.4 and 6.0 +/- 0.7 vs 7.1 +/- 1.3% respectively). The calculated mean melting point was higher in plancetas coming from undernourished women. It these women, the low content of polyunsaturated fatty acids and its replacement by short chain fatty acids was not able to balance the high mean melting points. The relative deficiency of essential fatty acids, the low saturation index and the high mean melting point of undernourished women's placental phospholipids, may suggest a lower membrane fluidity and a subnormal essential fatty acid content of fetal organs, that are essential for normal growth and development.

Analysis of Variance↗
PubMed1994

Seasonal fluctuations of selected physiological characteristics of elite alpine skiers.

The effects of heavy resistance training and jumping exercise were examined during the 1989-1990 season in 12 international level alpine skiers. The athletes were tested before, during, immediately after training and during the period off training (June, July, October 1989, April 1990). Their mechanical behaviour was investigated using firstly squat jumps performed without (SJ) or with low extra loads (20 kg, SJ20kg) and high extra loads (equivalent to body mass on the shoulders, SJbm) and secondly 15-30 s continuous jumping. These tests allowed the assessment of explosive dynamic strength production (SJ and SJ20kg), slow dynamic strength (SJbm) and maximal mechanical power (continuous jumping). The training adopted resulted in specific changes in neuromuscular performance; in fact all the variables studied showed a significant improvement (P < 0.01) from the beginning compared to the end of training. The range of improvement was between 55.4% (SJbm) and 12.5% (average power during 15-s continuous jumping). The enhancement of SJ had become significant by July. Surprisingly, even when no strength or jumping training was performed during the competition period (November-April), no deterioration in the neuromuscular performance was observed, there being no significant difference between the test values obtained in October 1989 and April 1990. It was concluded that the demanding competition programme of alpine skiers may provide a training stimulus adequate to maintain the neuromuscular improvement induced by training throughout the competition season.

Adult↗
PubMed1992

Influence of stretch-shortening cycle on mechanical behaviour of triceps surae during hopping.

Six subjects performed a first series of vertical plantar flexions and a second series of vertical rebounds, both involving muscle triceps surae exclusively. Vertical displacements, vertical forces and ankle angles were recorded during the entire work period of 60 seconds per series. In addition, expired gases were collected during the test and recovery for determination of the energy expenditure. Triceps surae was mechanically modelled with a contractile component and with an elastic component. Mechanical behaviour and work of the different muscle components were determined in both series. The net muscular efficiency calculated from the work performed by the centre of gravity was 17.5 +/- 3.0% (mean +/- SD) in plantar flexions and 29.9 +/- 4.8% in vertical rebounds. The net muscle efficiency calculated from the work performed by the contractile component was 17.4 +/- 2.9% in plantar flexions and 16.1 +/- 1.4% in vertical rebounds. These results suggest that the muscular efficiency differences do not reflect muscle contractile component efficiency but essentially the storage and recoil of elastic energy. This is supported by the relationship (P less than 0.01) found in vertical rebounds between the extra work and the elastic component work. A detailed observation of the mechanical behaviour of muscle mechanical components showed that the strategy to maximize the elastic work depends also on the force-velocity characteristics of the movement and that the eccentric-concentric work of the contractile component does not always correspond respectively to the ankle extension-flexion.

Adult↗
PubMed1991

Muscle enzyme adaptations to added load during training and nontraining hours in rats.

The effects of added load (20% of body mass) on the selected enzyme activities of red and white quadriceps femoris (QF), soleus, and gastrocnemius muscles of rats were studied. The rats were divided into sedentary control (SC), sedentary control with added load (SC+AL), endurance training (ET), and endurance training with added load (ET+AL) groups (n = 10 rats/group). After 6 wk, the SC+AL group had 57% higher (P less than 0.001) beta-glucuronidase (beta-GU) activity and 24% lower (P less than 0.05) citrate synthase activity in white QF than SC. Citrate synthase activity was also decreased in red QF (P less than 0.05) after the added load was used during nontraining hours. The training with added load induced similar but more pronounced changes than normal endurance training, especially in white QF. The ET+AL group demonstrated higher citrate synthase activity in white QF (P less than 0.001) and gastrocnemius (P less than 0.01) and higher malate dehydrogenase activity (P less than 0.05) and beta-GU activity (P less than 0.001) in white QF than the ET group. ET+AL rats also had higher phosphofructokinase (P less than 0.01) and lower creatine kinase (P less than 0.001) activity in white QF than ET rats. In conclusion, the added load without training had minor adaptive influences on muscles. The added load during training hours seemed to be an effective means of influencing the activation and adaptation in muscles that contain fast glycolytic fibers.

Adaptation, Physiological↗
PubMed1991

[The effect of dietary Omega 6 polyunsaturated fatty acids on the activity of enzymes associated with liver mitochondrial and placental function in rats].

Female virgin rats, Wistar strain, divided into three groups of 18 each, were fed either a diet containing 45% of calories as fat (45 g%), the second received low-fat diet (15 g%), before and throughout pregnancy, and the third served as control. For both dietary fat levels, the polyunsaturated to saturated fatty acid (P/S) ratio was adjusted by substitution of saturated fatty acids for corn oil, to provide P/S of 2.0. The control group was fed a diet containing 30% of calories, as fat, with a P/S ratio of 1.0. Rats were sacrificed by decapitation 20 days after mating: fetuses, placenta and liver were then removed and weighed. Liver and placenta mitochondria were isolated. Phospholipids were extracted from mitochondrial membranes, and fatty acid tail composition was determined. Cytochrome c oxidase (a3) and rotenone-insensitive-NADH cytochrome c reductase (NADH cyt c red) in mitochondria subfractions were also assayed. The high-fat diet (45 g%) resulted in an increase in both liver and placental a3, but NADHcyt-c-red, activity did not change. The low fat diet (15 g%) reduced the activity of insensitive rotenone-NADH cytochrome c reductase. The fetal weight of the mothers fed the high-fat diet was higher (p less than 0.001) than in the other groups. No difference in fetal weight was observed between the pregnant groups fed 30% or 15% of calories (fat diets). These results suggest that changes in the fatty acid mitochondrial phospholipids which reflects the composition of dietary fat can result in changes in lipid-dependent function of integral membrane-bound enzymes. Therefore, it can be postulated that the increase of membrane fatty acid Omega 6 enhanced the a3 enzyme activity, which correlated with an increase in fetal growth.

Animals↗
PubMed1989

[Immaturity of syncytial trophoblast in maternal malnutrition. Ultrastructural analysis].

We studied the placental membrane at term in normal females and females with malnutrition not related to associated pathologic processes of pregnancy. Both groups belonged in the low socioeconomic stratum. The fetal aspect of placenta from malnourished females showed signs of immaturity in relation to gestational age, as evidenced by transitional cytotrophoblastic cells in different stages of maturation. The latter appear as a third intermediata layer between cytothropoblast and syncitiotrophoblast.

Female↗
PubMed1989

[Normal term placentae: type of collagen and its disposition around fetal blood vessels detected with the Picro sirius technique].

The chorionic villi tissue of normal term human placentae is made of a highly fibrous extracellular matrix. An increasing amount of fibrous tissue is seen as gestation advances, phenomenon referred as organ aging. Electron microscopy reveals many collagen fibrils close to fibroblasts between the trophoblast and the fetal capillary vessels. A characteristic 67 nm transverse striation produced by the intermixing of tropocollagen and collagen types 1 and 3 is observed. Picrosirius staining under polarized light allowed us to detect abundant type 1 collagen fibers. These were randomly distributed in the stroma but concentrically order around the blood vessels.

Chorionic Villi↗
PubMed1987

Relationship between the efficiency of muscular work during jumping and the energetics of running.

The running economy of seventeen athletes was studied during running at a low speed (3.3 m X s-1) on a motor-driven treadmill. The net energetic cost during running expressed in kJ X kg-1 X km-1 was on average 4.06. As expected, a positive relationship was found between the energetic cost and the percentage of fast twitch fibres (r = 0.60, n = 17, p less than 0.01). In addition, the mechanical efficiency during two different series of jumps performed with and without prestretch was measured in thirteen subjects. The effect of prestretch on muscle economy was represented by the ratio between the efficiency of muscular work performed during prestretch jumps and the corresponding value calculated in no prestretch conditions. This ratio demonstrated a statistically significant relationship with energy expenditure during running (r = -0.66, n = 13, P less than 0.01), suggesting that the elastic behaviour of leg extensor muscles is similar in running and jumping if the speeds of muscular contraction during eccentric and concentric work are of similar magnitudes.

Adult↗
PubMed1987

Effects of rapid weight reduction on force production and vertical jumping height.

The effects of three weight reduction methods on maximal strength, rate of force development, vertical jumping height, and mechanical power were studied in track and field athletes and volleyball players. The three methods were sauna, diet with diuretic, and diuretic alone. The reductions in weight achieved were 3.4%, 5.8%, and 3.8% of body weight after sauna, diet + diuretic, and diuretic, respectively (P less than 0.001). Maximal isometric leg strength and the rate of isometric force development were decreased after the sauna and diet + diuretic treatments. Dehydration caused by the diuretic method alone did not impair neuromuscular performances. As had been expected from theoretical calculations, the rise of the body center of gravity in vertical jumping was slightly improved with all three treatments, the improvement being the greatest following the diuretic treatment (7.1%, P less than 0.001). However, when the work performed was extended for 15 s, an improved power output could be observed only with the diet + diuretic treatment (P less than 0.01). No explanation for the results observed could be made in terms of physiologic parameters.

Adult↗
PubMed1987

The effect of pre-stretch on mechanical efficiency of human skeletal muscle.

The mechanical efficiency of positive work was studied in six subjects performing three different types of exercises. On the first occasion the subjects ran on a motor-driven treadmill at 3.33 m s-1; the second and the third exercises consisted of performing rhythmical vertical jumps for 1 min both in rebound (RJ) and no-rebound (NRJ) conditions. The mechanical efficiency calculated in NRJ, which reflects only the conversion of biochemical energy into mechanical work, was found to be lower than the corresponding observation in RJ, 17.2 vs. 27.8% (P less than 0.001), respectively. These differences could not be explained by only the storage and recoil of elastic energy occurring in RJ compared with NRJ. The calculated extra work delivered 'free' was greater than the potential elastic energy which could be stored within the leg extensor muscles (187 vs. 124 J for each jump, P less than 0.05). It is likely that other factors might be responsible for the extra work found in NRJ. It was suggested that the difference in the length of time to perform positive work between a simple shortening contraction and a stretch-shortening muscular activity could be also responsible for the enhanced efficiency observed in RJ. This suggestion was supported by the high relationship (P less than 0.001) found between the time to perform positive work and the mechanical efficiency measured in jumping and estimated during running.

Adult↗
PubMed1986

The effect of fatigue on store and re-use of elastic energy in slow and fast types of human skeletal muscle.

Stretch-shortening exercises are characterized by enhancement of performance when compared to the work output performed in shortening conditions. There is evidence that fast subjects are unable to re-use great amounts of elastic energy during stretch-shortening cycles performed with slow stretching speed and large stretching length. In the present study, 14 subjects possessing different fibre types in m. vastus lateralis performed vertical jumps with and without preliminary countermovement and with large angular displacement and slow stretching speed The jumping tests were executed before and immediately after fatigue induced by short intense exercises (60 s of continuous rebound jumping). The results indicated that the percentage of re-use of elastic energy was more pronounced in slow subjects compared to fast ones during the test performed before fatigue (28.3% vs. 22.8%). In contrast fast subjects demonstrated a greater percentage re-use of elastic energy than slow ones after fatigue (32% vs. 22.5%). Similarly, the negative relationship observed before fatigue, between the percentage of re-use of elastic energy and percentage of fast twitch fibres (r = 0.50, n = 14, P less than 0.05), was reversed after fatigue (r = 0.55, n = 14, P less than 0.05). The results can be interpreted through differences in sarcomere cross-bridges life-times between fast and slow twitch muscle fibres. The slow twitch-type muscle fibre may be able to retain the cross-bridge attachment for a longer period of time during no fatigued conditions, and therefore it may utilize elastic energy better in slow type ballistic motion. On the other hand, fast twitch type muscle fibres are more affected by fatigue, which might have induced a remarkable decrease of the cross-bridge attachment detachment cycle. Decrease of the cross-bridge rate cycle might allow fast twitch-type muscle fibres to retain longer the elastic energy stored during the stretching phase and then re-use it during positive phase.

Adult↗
PubMed1986

The effect of extra-load conditioning on muscle performance in athletes.

Fourteen sprinters were assigned to an experimental group (N = 7) and a control group (N = 7) in order to study the effects of 3 wk of extra-load conditioning. The extra-load conditioning was achieved by the athletes wearing special vests containing weights (7-8% body mass). The vests were used from morning to evening and during 3-5 training sessions/wk for 3 wk. No changes in the ordinary training regime were allowed, except the use of the vest by the experimental group. A jumping test battery and short running test on a treadmill were utilized to measure explosive power characteristics and the anaerobic performance of the subjects. While the control group showed no changes in any of the variables studied, the experimental subjects significantly improved their jumping heights in squat jumps with and without extra loads; their jumping heights in drop jumps and mechanical power output in 15 s of jumps. No changes in lactate levels or in running times to exhaustion were observed in response to the extra-load conditioning. The improvement of jumping performances could be due to a fast neurogenic adaptation to the new requirements.

Adaptation, Physiological↗
PubMed1985

Adaptive response of human skeletal muscle to simulated hypergravity condition.

The mechanical behaviour of leg extensor muscles of five international-level athletes was evaluated during 13 months training period. Drop jumps, average mechanical power during 15 S continuous jump, and vertical jumps performed with and without extra weights were used to measure explosive power characteristics. The data recorded in vertical jumps was utilized for construction of force-velocity relationship (F-V curve). The athletes did not show improvement in any of the variables studied after 12 months of intensive systematic training programme. It was assumed that the subjects already had reached their upper limit of performance. However, after that the athletes underwent a simulated 3 weeks high-gravity period. The hypergravitational condition was created by wearing a special vest filled with extra loads (11% of BW). The vest was used from morning to evening. No changes in the ordinary training programme were allowed. After the simulated high-gravity conditioning period significant improvement in almost all the variables studied was observed (P less than 0.05-0.001). Vertical jump performance was enhanced from 44.3 to 54.9 cm. The F-V curve remained stable all year but after hypergravity period shifted markedly to the right. The drastic improvement was attributed to be caused by a fast adaptation to the new functional requirements (I.I g). Therefore, once the biological adaptation occurred the mechanical behaviour of the athlete's leg extensor muscle was similar to that which could be experienced in a field at low gravity condition (0.9 g). Adaptive response to the hypergravity conditioning was speculated to occur mainly at neurogenic level and less in myogenic component.

Adaptation, Physiological↗
PubMed1984

The influence of extra load on the mechanical behavior of skeletal muscle.

Eleven international jumpers and throwers engaged in year round training were divided into experimental (n = 6) and control (n = 5) groups. The experimental group was tested before and after a 3 weeks simulated hypergravity period, and again 4 weeks after the hypergravity period. The high gravity condition was created by wearing a vest weighing about 13% of the subjects body weight. The vest was worn from morning to evening including the training sessions, and only removed during sleep. The daily training of all subjects consisted of classical weight training and jumping drills. No changes in the ordinary training program were allowed in the experimental group, except for the use of the vest. Vertical jumps, drop jumps and a 15 s continuous jumping test were used to measure the explosive power characteristics of the subjects. After the hypergravity period the experimental subjects demonstrated significant (5-10%, P less than 0.05-0.01) improvements in most of the variables studied: however, 4 weeks after cessation of the high gravity period they tended to return towards the starting values. No changes were observed in the results of the control group. The improvement observed in the experimental subjects was explained as fast adaptation to the simulated high gravity field. It is suggested that adaptation had occurred both in neuromuscular functions and in metabolic processes.

Adult↗
PubMed1983

A simple method for measurement of mechanical power in jumping.

A simple test for the measurement of mechanical power during a vertical rebound jump series has been devised. The test consists of measuring the flight time with a digital timer (+/- 0.001 s) and counting the number of jumps performed during a certain period of time (e.g., 15-60 s). Formulae for calculation of mechanical power from the measured parameters were derived. The relationship between this mechanical power and a modification of the Wingate test (r = 0.87, n = 12 males) and 60 m dash (r = 0.84, n = 12 males) were very close. The mechanical power in a 60 s jumping test demonstrated higher values (20 W X kgBW-1) than the power in a modified (60 s) Wingate test (7 W X kgBW-1) and a Margaria test (14 W X kgBW-1). The estimated powers demonstrated different values because both bicycle riding and the Margaria test reflect primarily chemo-mechanical conversion during muscle contraction, whereas in the jumping test elastic energy is also utilized. Therefore the new jumping test seems suitable to evaluate the power output of leg extensor muscles during natural motion. Because of its high reproducibility (r = 0.95) and simplicity, the test is suitable for laboratory and field conditions.

Biomechanical Phenomena↗
PubMed1983

Relationship between isokinetic performance and ballistic movement.

The present experiments were carried out to assess the relationship between the mechanical behaviour of the leg extensor muscles in 12 male athletes during activities of a ballistic type and torque production, during: (1) torque production during isokinetic contraction: (2) ballistic type activities (vertical jumps from statis position = SJ, with counter-movement equal CMJ and after a fall from different heights equal DJ) and (3) a new anaerobic test (Bosco 1983a). This consisted of performing continuous jump work for a certain period of time (e.g., 60 s). Both ballistic activities and anaerobic power tests demonstrated the highest relationship with peak torques when this was developed respectively at pi and 4.2 rad x s-1. Peak torque was related to SJ (r = 0.71, p less than 0.01); to CMJ (r = 0.74, p less than 0.005); to best DJ (r = 0.60, p less than 0.05), to 15 s anaerobic power (r = 0.70, p less than 0.01) and 60 s anaerobic power (r = 0.68, p less than 0.01). The power output during ballistic activities was much higher than the power measured during zero acceleration performances. The difference noted was explained in the light of the fact that, when jumping, three different extensor muscle groups in each leg contract with re-use during the concentric phase of elastic energy stored during the eccentric phase. The relationship between isokinetic contraction and ballistic motion is discussed in terms of fiber type recruitment and their velocity dependency.

Acceleration↗
PubMed1983

Mechanical power test and fiber composition of human leg extensor muscles.

The present study was undertaken to assess the relationship between the mechanical power developed during new anaerobic power test and muscular fiber distribution. Ten track and field male athletes were used as subjects, whose muscle fiber composition (m. vastus lateralis) varied from 25 to 58 fast twitch (FT) fibers. The test consisted of measuring the flight time with a special timer during 60 s continuous jumping. A formula was derived to allow the calculation of mechanical power during a certain period of time (e.g., in the present study every 15 s during 60 s of jumping performance). The relationship between the mechanical power for the first 15 s period correlated best with fast twitch (FT) fiber distribution (r = 0.86, p less than 0.005). However, the power output during the successive 15 s periods demonstrated lower correlation with FT, and this relationship became statistically non-significant after 30 s of work. The sensitivity to fatigue of the test was supported by the relationship observed between the decrease of power during 60 s jumping performance and the percentage of FT fibers (r = 0.73, p less than 0.01). Thus, the present findings suggest that muscular performance, as determined by the new jumping test, is influenced by skeletal muscle fiber composition. The new test, which primarily evaluates maximal short term muscular power, also proved sensitive in assessing fatigue patterns during 60 s of strenuous work.

Adult↗