Biomedical subjects

C E Blanco

Publications and source records attributed to C E Blanco.

At least 91 records · Page 5Linked to original sources

PubMed1994

Quality of spontaneous general movements in full-term small for gestational age and appropriate for gestational age newborn infants.

Quality of spontaneous movements was studied in 15 healthy full-term appropriate for gestational age (AGA) and in 15 full-term small-for gestational age (SGA) newborn infants. All general movements with a minimal duration of 20 seconds were judged on different aspects of movement quality. From the general movements in each group (AGA: n = 106; SGA: n = 187), dominant patterns were isolated. In the AGA Group 3 dominant patterns of general movements were present. In the SGA Group 5 dominant patterns of general movements were found. Three of those were identical to the movement patterns in the AGA group, the remaining two patterns were unique for the SGA infants. Our results indicate that the three different types of general movements which constitute the major part of the normal repertoire of healthy full-term infants can be used as a reference for normal spontaneous motor behaviour. The two different types of general movements in the SGA infants might be used to discriminate between healthy and neurologically suspect newborn infants. The difference in movement pattern between AGA and SGA infants might be explained by the effect of intrauterine malnutrition on CNS development.

Apgar Score↗

PubMed1994

Effect of sustained inflations applied directly after cord clamping on lung function in premature newborn lambs.

We studied the possibility of improving lung volume and therefore clinical outcome in premature newborn lambs by increasing the inspiratory volumes during the first minute after birth. Sixteen lambs from eight were delivered by hysterotomy after 130-131 days' gestation. In eight lambs the lungs were inflated with a bag with a sustained inspiratory inflation (SI) of 5 s and expiratory time of 5 s during the first four inflations after cord clamping and then mechanically ventilated. Their siblings did not receive SI and served as a control group. At 8 h postnatally, the SI and control groups showed the following results (mean +/- SEM): mean airway pressure 14.8 +/- 1.8 cmH2O versus 11.9 +/- 1.1 cmH2O, PaO2 41.5 +/- 7.3 kPa versus 31.3 +/- 7.7 kPa, alveolar-arterial oxygen gradient 359 +/- 55 mmHg versus 437 +/- 58 mmHg. Clinical course, incidence of pneumothorax, oxygenation index, total static compliance, parenchymal-alveolar air area ratio or mortality rate were not different. There was no significant difference between the two groups at this time or at any other time during the experiments.

Animals↗

PubMed1994

Cardiovascular changes during sustained lung inflations in premature newborn lambs.

We studied the effect of sustained inspiratory inflations (SI) on the cardiovascular system by measuring mean central venous pressure (MCVP), mean arterial blood pressure (MABP) and heart rate (HR), before and during sustained lung inflations in premature lambs (128-133 days' gestation). SI consisted of four inflations of 5 s at a peak inspiratory pressure of 35 cmH2O, with a mixture of 5% carbon dioxide and 95% oxygen. Each inflation was followed by a positive end-expiratory pressure of 5 cmH2O for 5 s. Percentage change from baseline was -3.88% for MABP and -2.55% for HR during the first inflation. The changes in MCVP fluctuated with each inflation (mean 9.61%; p < 0.01 versus baseline) and deflation (mean -3.87%; p < 0.05 versus baseline). These changes were dependent on the time after birth and the pressure used for SI. The observed cardiovascular changes produced by this procedure are considered clinically relevant when managing premature infants with a high risk of intraventricular haemorrhage.

Animals↗

PubMed1994

Effect of mild hypocapnia on fetal breathing and behavior in unanesthetized normoxic fetal lambs.

We hypothesized that the level of arterial PCO2 (PaCO2) affects the incidence of fetal breathing movements and electrocorticographic (ECoG) states in chronically instrumented fetal sheep. Six fetuses of 128-132 days gestational age were instrumented for recording fetal behavior and for later connection to an extracorporeal membrane oxygenation (ECMO) system to change fetal blood gases. Before ECMO fetal arterial pH and blood gases were pH 7.40 +/- 0.01, PaCO2 42.9 +/- 1.5 Torr, and arterial PO2 (PaCO2) 19.2 +/- 1.7 Torr; during ECMO in normocapnia they were pH 7.37 +/- 0.01, PaCO2 46.1 +/- 0.7 Torr, and PaCO2 27.6 +/- 3.0 Torr; and during ECMO in mild hypocapnia they were pH 7.47 +/- 0.01, PaCO2 35.3 +/- 1.7 Torr, and PaCO2 26.6 +/- 1.7 Torr. The overall incidence of breathing movements, the incidence of breathing movements during low-voltage (LV) ECoG activity, and the mean duration of periods of breathing decreased significantly during hypocapnia. Fetal ECoG activity showed normal cycling during the periods of mild hypocapnia, and the mean duration of LV ECoG periods did not change. During mild hypocapnia, eye movements remained associated with LV ECoG activity and nuchal electromyographic activity remained associated with high-voltage ECoG activity. These results suggest that the presence of breathing movements in fetal life is not only dependent on the behavioral state but also on the level of fetal PaCO2.

Animals↗

PubMed1994

Effect of maternal hypoxemia on behavior in unanesthetized normoxic or mildly hyperoxic fetal lambs.

To determine whether hypoxemia inhibits fetal activity by substances from the mother or placenta, six fetal lambs were chronically instrumented at 128-132 days gestation for extra-corporeal membrane oxygenation (ECMO). Severe maternal hypoxemia (arterial PO2 decreased to 6.00 +/- 0.60 kPa) was produced while fetal arterial PO2 was maintained normoxic or mildly hyperoxic using ECMO. The incidences of fetal breathing movements were 34.8 +/- 3.1% (SE) during baseline before ECMO, 36.8 +/- 3.4% during baseline with ECMO, and 21.4 +/- 3.5% (P < 0.05 compared with baseline with ECMO) during maternal hypoxemia. The durations of periods of breathing were 9.8 +/- 1.2 min before ECMO, 9.3 +/- 1.1 min with ECMO, and 10.5 +/- 1.7 min (P = NS) during maternal hypoxemia. In 7 of 14 maternal hypoxemia experiments, breathing activity stopped too late (7-23 min) to be attributed to maternal hypoxemia. Fetal electrocorticographic activity (P = NS), nuchal electromyographic activity (P = NS), and eye movements were normal before ECMO, with ECMO, and during maternal hypoxemia. Fetal blood pressure and heart rate did not change. We conclude that the inhibition of fetal activity during maternal hypoxemia does not seem to be mediated by release of factors from the maternal side of the placenta or the ewe.

Animals↗

PubMed1994

Maturation of fetal breathing activity.

Spontaneous breathing movements are present during fetal life and they are important for normal development of the lung. Early in gestation they seem to represent free-running activity of the respiratory centers, not controlled by peripheral mechanisms but probably dependent on a tonic CO2 drive. Maturation of sleep states brings into play powerful brainstem inhibitory mechanisms which control FBM. At birth these mechanisms must be overridden to allow the establishment of continuous breathing.

Animals↗

PubMed1993

Postural behaviour of term SGA and AGA newborn infants.

The authors studied the body posture at rest of 15 healthy term infants with birthweights appropriate for gestational age (AGA) and 15 infants who were small for gestational age (SGA). In both groups, there was wide inter-individual variability in postural behaviour. Apart from a preference for a position with all limbs in abduction between 1 and 90 degrees, independent of the degree of flexion or extension and internal/external rotation, no dominant preference posture could be seen for either group. The SGA infants showed a more flexed position of the arms, compared with the AGA group. One of the factors contributing to this difference might be the influence of intra-uterine malnutrition on the development of the central nervous system.

Apgar Score↗

PubMed1993

Effects of partial plasma exchange transfusion on blood flow velocity in large arteries of arm and leg, and in cerebral arteries in polycythaemic newborn infants.

Continuous wave Doppler velocimetry was performed in brachial, femoral and cerebral arteries in four preterm, four small-for-gestational-age (SGA) and eight appropriate-for-gestational age (AGA) polycythaemic newborns before and at 3 and 24 h after partial plasma exchange transfusion and in 18 matched controls at 3 and 24 h after birth. In peripheral arteries, end-diastolic flow velocity was zero in all eight AGA controls, but only in two of the other infants. Consequently, mean flow velocity and red cell transport in AGA controls were significantly lower than in the other five groups, which did not differ. Partial plasma exchange transfusion did not influence flow velocities and red cell transport in peripheral arteries, but normalized the flow velocities in cerebral arteries in all three subgroups of polycythaemic infants, which were lower than in control infants. Cerebral red cell transport in controls increased significantly between 3 and 24 h, and in polycythaemic infants between 0 and 3 h after partial plasma exchange transfusion. In conclusion, reduction in haematocrit had different effects on blood flow velocity and red cell transport of peripheral and cerebral vessels, suggesting that the increased cerebral blood flow velocity after partial plasma exchange transfusion is not simply due to a reduction in viscosity or oxygen content of the blood. The lower peripheral blood flow velocities in normocythaemic AGA infants as compared to all other groups, suggest that the level of maturity is an important determinant for the capacity to regulate blood flow.

Age Factors↗

PubMed1993

The effect of hypocapnia and mechanical pulmonary stress on lung tissue in newborn lambs.

Positive pressure ventilation, using high inspiratory pressures, often causes lung damage. When associated with hypocapnia, it can produce severe focal alveolar alkalosis and can cause damage in areas of low blood flow. A vein-to-vein extracorporeal membrane oxygenator (ECMO) system was used to control blood gases independently of mechanical ventilation in 12 healthy newborn lambs. After connection to the ECMO system, ventilation was started with a peak inspiratory pressure of 35 cm H2O and a positive end-expiratory pressure of 5 cm H2O; the ventilator rate was 40/min with I:E = 1.5 and FiO2 = 1.0. In 6 of the 12 lambs sweep gases through the silicone membrane were regulated to assure arterial normocapnia. The other 6 were ventilated with the same settings and perfused with the same pump flow, but PaCO2 was allowed to fall to hypocapnic levels. The lambs were ventilated for 4 h. Average pH and PaCO2 were 7.62 +/- 0.14 and 2.11 +/- 0.54 kPa, respectively, in the hypocapnic group and 7.39 +/- 0.11 and 4.79 +/- 0.51 kPa in the normocapnic group. After sacrificing the lambs, the lungs were inspected macroscopically and microscopically by computer-assisted morphometry to assess atelectasis and lung edema. Macroscopically there were no hemorrhages, barotrauma or widespread atelectasis of the lungs in either group. The thickness of interlobular lung septa in the right upper lobe was 32.5 +/- 18.0 microns for the hypocapnic group and 29.7 +/- 12.5 microns for the normocapnic group. The parenchymal-alveolar area ratio in the right upper lobe was 28.4 +/- 5.04 and 24.6 +/- 3.75% in the hypocapnic and normocapnic groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Quantitative determination of calcium-activated myosin adenosine triphosphatase activity in rat skeletal muscle fibres.

A quantitative histochemical technique was developed for determining the kinetics of the calcium-activated myosin ATPase (Ca(2+)-myosin ATPase) reaction in rat skeletal muscle fibres. Using this technique, the maximum velocity (Vmax) and the apparent Michaelis-Menten rate constant for ATP (K(app)) of the Ca(2+)-myosin ATPase reaction were measured in type-identified fibres of the rat medial gastrocnemius (MG) muscle. The Vmax and the K(app) of the Ca(2+)-myosin ATPase reaction were lowest in type I fibres and highest (i.e., approx. two times greater) in type IIb fibres. The K(app) in type IIa fibres was similar to that in type I. However, the Vmax was 1.5 times greater in type IIa fibres, compared to type I fibres. Evidence is presented to suggest that the type IIb fibre population in the MG does not represent a single myosin isozyme. In addition, the broad range of Vmax and K(app) values indicates that there is marked heterogeneity in the myosin heavy chain and myosin light chain composition of myosin isozymes among individual fibres.

Animals↗

PubMed1992

State profile in low-risk pre-term infants: a longitudinal study of 7 infants from 32-36 weeks of postmenstrual age.

Spontaneous motor behaviour was longitudinally studied in 7 low-risk preterm infants. The object of this study was to determine whether or not certain recognizable behavioural states exist between 32 and 36 weeks postmenstrual age (PMA), in order to have a well defined recognizable pattern of behaviour during which the preterm infant can be clinically examined. The criteria used to define a behavioural state were: eyes open/closed; crying present/absent; gross body movements present/absent; and respiration regular/irregular. A total of 35 videotapes were made (total time, 99 hours and 25 minutes). For analyzing the data, one second and three-minute windows were used. Our data provide convincing evidence that spontaneous behaviour of preterm infants of 32-36 weeks of PMA can be classified into behavioural states. The variables gross body movements and respiration, are not independent ones. The observed states can be used as a defined clinical condition during which the preterm infants can be clinically examined.

Age Factors↗

PubMed1992

Fetal breathing is not initiated after cord occlusion in the unanaesthetized fetal lamb in utero.

We investigated the role of cord occlusion in the initiation of breathing at birth using an extracorporeal membrane oxygenator system to control fetal blood gases independently of the placenta in 12 chronically instrumented fetal lambs. In group IA (n = 9; exp = 12) PaCO2 was kept constant (5.62 +/- 0.21 to 5.70 +/- 0.23 kPa) during cord occlusion. Group IB (n = 7; exp = 8) were cord occlusion experiments from group IA in which no fetal breathing movements had occurred; CO2 flow to the membrane was increased and fetal PaCO2 rose significantly (5.45 +/- 0.24 to 8.27 +/- 0.56 kPa). In group II (n = 7; exp = 12) PaCO2 was allowed to increase from 5.98 +/- 0.24 kPa to 8.09 +/- 0.48 kPa after cord occlusion. Within 5 min of cord occlusion, FBM did not occur in 11 out of 12 experiments in group IA or in 11 out of 12 experiments in group II. In contrast in group IB breathing did occur in 5 out of 8 experiments. When they occurred, fetal breathing movements were always associated with low voltage electrocortical activity. Our results do not support the hypothesis that the initiation of breathing within 5 minutes of birth is dependent on an inhibitory factor of placental origin. Furthermore these data suggest an association between the presence of breathing and a substantial rise in PaCO2.

Animals↗

PubMed1991

Metabolic variability within individual fibres of the cat tibialis posterior and diaphragm muscles.

Variance in succinate dehydrogenase activity along the transverse and longitudinal axes of fibres from the cat tibialis posterior and diaphragm muscles was determined in order to estimate the three-dimensional distribution of mitochondria within single fibres. The variance (coefficient of variation) in succinate dehydrogenase activity along the transverse fibre axis was greatest in type IIB fibres from both muscles. Intracellular compartmentalization (i.e. subsarcolemmal vs central core differences in succinate dehydrogenase activity) was observed only in type II fibres from the tibialis posterior; the succinate dehydrogenase activity of the subsarcolemmal region was significantly greater than that of the central core. The extent of succinate dehydrogenase variance along the longitudinal fibre axis was dependent on the total length of the fibre segment analyzed, the muscle, and fibre type. The coefficient variation for short fibre segments, i.e. 40 microns, was significantly lower than that for much longer fibre segments (840 microns). Significant differences in the coefficient variation for 840 microns fibre segments were observed between the diaphragm and tibialis posterior muscles. The longitudinal variance in succinate dehydrogenase activity was higher in diaphragm muscle fibres. The succinate dehydrogenase variance along the longitudinal axis of type II fibres was higher in diaphragm muscle fibres. The succinate dehydrogenase variance along the longitudinal axis of type II fibres was significantly greater than that of the type I fibre population. These results indicate that mitochondria are heterogeneously distributed within muscle fibres. Possible functional implications of such intrafibre metabolic variance are discussed.

Animals↗

PubMed1991

Development of respiratory chemoreflexes in response to alternations of fractional inspired oxygen in the newborn infant.

1. We studied the reflex respiratory response to breath-by-breath alternations of fractional inspired oxygen (FI,O2) in full-term human infants delivered either vaginally or by caesarian section at 3-10 h (n = 6), 12-24 h (n = 12), 24-48 h (n = 18), 3-4 days (n = 21) and 5-8 days (n = 7) postnatally. 2. Respiration was measured by inductance plethysmography (Respitrace) and respiratory variables for each breath were calculated on-line by a microcomputer. Test runs (with alternations of FI,O2 between 0.21 and 0.16) and control runs (with an FI,O2 of 0.21) of 50-100 breaths were carried out during quiet sleep. For each respiratory variable the magnitude of the reflex breath-by-breath alternation was compared between control and test runs. 3. There was little respiratory response during control runs at any postnatal age. However, there was a significantly greater response to test runs in all infants studied and at all ages. 4. There were no significant differences in the degree of alternation during test runs between infants of similar postnatal ages delivered by caesarean section and those born vaginally. 5. In all infants the magnitude of the respiratory response increased with postnatal age, presumably reflecting postnatal increases in the hypoxic sensitivity of the peripheral arterial chemoreceptors. 6. The results indicate that in human infants the alternate breath method can be used to detect developmental changes in peripheral chemoreflexes between birth and postnatal day 8.

Cesarean Section↗

PubMed1991

Diaphragm capillarity and oxidative capacity during postnatal development.

In the cat diaphragm, fiber capillarity, cross-sectional area, and succinate dehydrogenase (SDH) activity were measured across the first 6 wk of postnatal development. Fibers were classified as type I, IIa, IIb, or IIc on the basis of staining for myofibrillar adenosinetriphosphatase (ATPase). Capillaries were identified in sections stained for ATPase at pH 4.2. Fiber cross-sectional areas and SDH activities were quantified using an image-processing system. During postnatal development, the proportions of type I fibers increased while type II fibers decreased. At birth, all type II fibers were IIc. From the 1st to the 2nd postnatal wk, the proportion of type IIc fibers decreased while the numbers of IIa and IIb increased. Thereafter the proportion of type IIb fibers continued to increase while the number of IIa steadily declined. At birth, capillarity, cross-sectional areas, and SDH activities of type I and II fibers were low compared with other postnatal age groups. Fiber cross-sectional areas increased progressively with age. The number of capillaries surrounding type I and II fibers increased markedly by the 2nd wk and then continued to increase at a slower rate. The number of capillaries per fiber area reached a peak by the 2nd wk and then declined as fiber cross-sectional area increased. Postnatal changes in capillarity depended on fiber type, being greatest in IIb. SDH activities of type I and II fibers were initially low during the first 2 postnatal wk and then peaked by the 3rd wk. After the 6th wk, fiber SDH activities decreased to adult values. Among the type II fibers, IIb showed the greatest change in SDH activity during early postnatal development.

Adenosine Triphosphatases↗

PubMed1991

Diaphragm muscle fatigue resistance during postnatal development.

Changes in the contractile and fatigue properties of the cat diaphragm muscle were examined during the first 6 wk of postnatal development. Both twitch contraction time and half-relaxation time decreased progressively with age. Correspondingly, the force-frequency curve was shifted to the left early in development compared with adults. The ratio of peak twitch force to maximum tetanic force decreased with age. Fatigue resistance of the diaphragm was highest at birth and then progressively decreased with age. At birth, most diaphragm muscle fibers stained darkly for myofibrillar adenosinetriphosphatase after alkaline preincubation and thus would be classified histochemically as type II. During subsequent postnatal development, the proportion of type I fibers (lightly stained for adenosinetriphosphatase) increased while the number of type II fibers declined. At birth, type I fibers were larger than type II fibers. The size of both fiber types increased with age, but the increase in cross-sectional area was greater for type II fibers. On the basis of fiber type proportions and mean cross-sectional areas, type I fibers contributed 15% of total muscle mass at birth and 25% in adults. Thus postnatal changes in diaphragm contractile and fatigue properties cannot be attributed to changes in the relative contribution of histochemically classified type I and II fibers. However, the possibility that these developmental changes in diaphragm contractile and fatigue properties correlated with the varying contractile protein composition of muscle fibers was discussed.

Adenosine Triphosphatases↗

PubMed1991

Postnatal changes in the distribution of succinate dehydrogenase activities among diaphragm muscle fibers.

The distributions of oxidative capacities among type-identified muscle fibers in the developing cat diaphragm were examined by quantifying succinate dehydrogenase (SDH) activity using a microdensitometric procedure. Animals were studied during the first six weeks of postnatal development and compared to adults. Muscle fiber SDH activities were initially low during the first 2 postnatal wk, then increased to their highest values between 3 and 6 wk. Thereafter, fiber SDH activities declined to adult values. At each age, the distributions of SDH activities for both type I and II fibers were unimodal. Thus, no objective basis exists for subclassifying type II fibers based on differences in oxidative capacity. Fibers could be subclassified as type IIA, IIB, or IIC based on the acid pH lability of ATPase staining. In neonates, approximately 90% of all fibers were classified as type IIC. Thereafter, the proportion of IIC fibers decreased while the proportions of type I, IIA, and IIB increased. Adult fiber type proportions were reached by 6 wk of age. The SDH activity of type I fibers was generally higher than that of type II fibers at all ages, although there was considerable overlap in the distributions of SDH activities among type I and II fibers. The SDH activity of type IIC fibers was also higher than that of either type IIA or IIB during development. Only in the adult diaphragm was the SDH activity of type IIA fibers higher than that of type IIB. At no age could type IIA, IIB, or IIC fibers be discriminated based solely on differences in oxidative capacity.

Adenosine Triphosphatases↗

PubMed1990

Effects of clonidine on breathing movements and electrocortical activity in the fetal lamb.

Clonidine is a recommended antihypertensive for use during pregnancy, although little is known of its fetal effects. This study examines the effects of clonidine on breathing and sleep-state cycling in fetal lambs. Clonidine was infused into a fetal lateral ventricle for up to 24 hours at 128 to 135 days' gestation. Control infusions of artificial cerebrospinal fluid had no effect. Clonidine infusion significantly reduced the incidence and episode duration of fetal breathing for the duration of the infusion period. Cycling of electrocortical activity became irregular and rapid, and the incidence of high-voltage electrocortical activity (equivalent to quiet sleep) was reduced. Fetal heart rate decreased but arterial pressure was unaffected. After infusion the breathing incidence and episode duration both increased significantly compared with control, with continuous high-amplitude breathing for several hours, whereas the incidence of high-voltage electrocortical activity remained low. Because lung development is promoted by fetal breathing, long-term use of clonidine during pregnancy could slow lung development by reducing fetal breathing activity.

Animals↗