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Biomedical subjects

J Stocks

Publications and source records attributed to J Stocks.

At least 181 records · Page 10Linked to original sources
PubMed1980

Activation of the phospholipase A1 activity of lipoprotein lipase by apoprotein C-II.

The effect of apo very low density lipoprotein (apo VLDL) and apoprotein C-II on the phospholipase A1 activity associated with lipoprotein lipase (E.C.3.1.1.3) was studied using purified bovine milk lipoprotein lipase. The enzyme degraded 14C phosphatidylcholine (PC) to 14C 2-acyl lysophosphatidylcholine at a rate of 0.28 +/- 0.01 nmol/min/ml and triolein at a rate of 20.3 +/- 0.4 nmol/min/ml in mixed emulsions of PC and triolein. The phospholipase activity and triacylglycerol lipase activity were both increased by the addition of apo VLDL and apoprotein C-II. After maximal activation, the rate of PC degradation was 1.19 +/- 0.02 nmol/min/ml and triolein degradation 64.4 +/- 0.4 nmol/min/ml. Activation of phospholipase A1 activity and triacylglycerol lipase activity occurred in parallel.

Animals↗
PubMed1980

Effect of nasogastric tubes on nasal resistance during infancy.

Nasal resistance (Rn) and total airways resistance (RAW) during nose breathing were measured in two groups of preterm infants. One group had been fed by nasogastric tube during the neonatal period, while the other had received only orogastric or bottle feeds. There were no significant differences in either Rn or RAW between the two groups, which suggests that for these infants a history of nasogastric tube feeding had no adverse effect on subsequent respiratory function. The acute effects of the nasogastric tube (NGT) were assessed by measuring Rn and RAW with and without the NGT in situ. A significant increase on both Rn and RAW occurred when the NGT was in situ, particularly in white infants, and when the NGT was passed through the larger of the two nostrils.

Airway Resistance↗
PubMed1980

Improved esophageal balloon technique for use in infants.

Esophageal balloons of three different wall thicknesses, two different lengths, and two different diameters were made to assess which type of balloon gave the most consistent and reliable measurements of dynamic compliance (CL) and pulmonary resistance (Rp). The balloons were subjected to in vitro testing to determine their pressure-volume characteristics and working range and then used in infants to compare in vivo results from one balloon to another. The optimal balloon was found to have a length of 35--50 mm, a diameter of 7.6 mm, and a wall thickness of 0.045--0.075 mm. The use of unsuitable balloons or inappropriate volumes of air within the balloon resulted in applied pressures being under-recorded, both in vitro and in vivo, with consequent overestimation of CL and underestimation of Rp during infant lung function tests. Recommendations are made concerning the techniques of making and using esophageal balloons.

Esophagus↗
PubMed1979

Hypertriglyceridaemia associated with an abnormal triglyceride-rich lipoprotein carrying excess apolipoprotein C-III-2.

Two men aged 48 and 35 years with severe hypertriglyceridaemia, glucose intolerance, and a secondary anaemia had more apolipoprotein C-III-2 and less apo C-III-1 on their triglyceride-rich lipoproteins (d less than 1.006) than did types IV or V lipaemic controls. Although the patients' abnormal lipoproteins seemed to produce normal activation of lipoprotein lipase, they did not serve as an efficient substrate for purified lipoprotein lipase. Adipose tissue of case 1 had considerable lipoprotein-lipase activity and the hypertriglyceridaemia responded to dietary therapy (carbohydrate 180 g, fat 80 g, protein 60 g per day, and no alcohol). The haemolytic anaemia improved, but the patient remained glucose intolerant. The abnormal content of apo C-III-2 on the triglyceride-rich lipoproteins, rendering them resistant to clearance by lipoprotein lipase, is believed to have contributed to the patients' severe hypertriglyceridaemia.

Adipose Tissue↗
PubMed1979

Phone rate and the effective planning time hypothesis of stuttering.

Effects on syllable disfluency and phone rate (duration of phones spoken per minute) were compared in 19 adult stutterers under three reading rate conditions: control; slow normally-spoken-word-syllable timed (WS); and phone-prolongation (PP) matched to WS in syllable rate. Both phone rate and syllable disfluency were progressively reduced from control to WS to PP conditions. These results strongly support the discoordination hypothesis that any condition which facilitates initiation of phonation in coordination with articulation and respiration will reduce stuttering. A broader hypothesis is that effective planning time for voice onset coordinations is the common element that explains the power of retarded phone rate, reduction of phonatory complexity, and rhythm virtually to eliminate stuttering.

Adult↗
PubMed1978

Nasal resistance during infancy.

Nasal Resistance (Rn) was measured in 30 Caucasian and 13 Negro infants during the 1st year of life, using an adaptation of the posterior rhinomanometric method. Concurrent measurements of Thoracic Gas Volume (TGV) and Airway Resistance during nose breathing (Raw (n) were made using the plethysmographic technique. The percentage contribution of Rn to Raw (n) was significantly higher in the Caucasian infants (mean 49.2 +/- 7.5 (SD)%), than in the Negro infants (mean 31.1 +/- 6.8 (SD)%), which probably resulted from anatomical differences in nasal structure. In each infant, Rn was subtracted from Raw (n) in order to assess resistance, and its reciprocal, conductance (Gaw), during mouth breathing. A strong linear relationship was found to exist between Gaw (m) and TGV throughout the first year of life (r = 0.92), with no significant difference between Negro and Caucasian infants. Specific Airway Conductance during mouth breathing (SGaw (m) = Gaw (m)/TGV) was found to be considerably higher during infancy than at any other time during life, which may help to at least partially compensate for the fact that newborn infants are obligatory nose breathers.

Airway Resistance↗
PubMed1978

Werdnig-Hoffmann disease. The effects of intrauterine onset on lung growth.

Thoracic gas volume (TGV), resting lung volume at end expiration, was measured by the plethysmographic technique in 9 infants with Werdnig-Hoffmann disease. Five of these infants were considered to have intrauterine onset of the disease; the mother in each case had reported a pronounced reduction in fetal activity during the last trimester of pregnancy, and 4 were found to be hypotonic at birth. The remaining 4 infants appeared normal at birth and did not develop any signs of the disease until between 2 and 12 weeks postnatally. Those with intrauterine onset of disease had a significantly reduced TGV (mean 20.8 ml kg(-1)), whereas those with postnatal onset had normal lung volumes (means 36.1 ml kg(-1)). The reduction in lung volume correlated only with intrauterine onset of disease, and was not related to either the degree of muscle weakness or the duration of disease. There is increasing evidence that fetal breathing movements may be one of the essential prerequisites for normal fetal lung development. It is therefore possible that diminished fetal breathing movements, resulting from weakness of the respiratory musculature in utero, could be responsible for the reduction in lung volume found in those infants with intrauterine onset of the disease.

Humans↗
PubMed1978

Airway resistance in infants after various treatments for hyaline membrane disease: special emphasis on prolonged high levels of inspired oxygen.

Thoracic gas volume, airway resistance (Raw), and dynamic lung compliance (CL) were measured in 48 infants surviving after hyaline membrane disease. Some infants were found to have a small reduction in CL after recovery from the acute phase of the illness but no other abnormalities were detected, irrespective of the type of treatment received. When studied again between the ages of 4 and 10 months, CL had returned to normal, but all infants who had been treated with intermittent positive pressure ventilation (IPPV) during the neonatal period were found to have developed a raised Raw. In contrast, all nonventilated infants, including those who had received up to five days of oxygen therapy in concentrations above 80%, had normal lung function. We conclude that IPPV, and not the increased inspired oxygen concentration, damaged the airways and interfered with their growth.

Airway Resistance↗
PubMed1977

The functional growth and development of the lung during the first year of life.

In this article much of the available data on lung volumes and mechanics in normal infants is assessed and summarized, and growth charts for the various parameters of lung function during the first year of life are presented. There is considerable evidence to show that lung development proceeds in a highly organized manner, and that strong linear relationships exist between lung volume and body size, between dynamic compliance and lung volume, and between airway conductance (the reciprocal of airway resistance) and lung volume. However, the latter relationship is affected both by the race and postconceptional age of the infant. Specific Airway conductance is higher during infancy than at any other time during life, and this gives the newborn infant certain advantages with which to counterbalance both the small size of his lungs and the fact that he is an obligatory nose breather.

Age Factors↗
PubMed1977

Reduced oxidase activity in the caeruloplasmin of two families with Wilson's disease.

Caeruloplasmin has been determined immunologically and by coper oxidase activity in 25 normal subjects, 20 patients with Wilson's disease, and 80 patients with chronic liver disease. Repeated estimation in four patients with Wilson's disease and two heterozygous mothers from two families revealed a consistent reduction in the copper oxidase activity of caeruloplasmin (12-32 units copper oxidase activity/mg caeruloplasmin) relative to the values obtained in normal subjects, patients with chronic liver disease, and other Wilson's disease patients (mean 65-79 units/mg). It is suggested that the functional abnormality in caeruloplasmin observed in these two families is an inherited variant, which does not appear to be due to the presence of a serum inhibitor of copper oxidase.

Adolescent↗
PubMed1977

Specific airway conductance in relation to postconceptional age during infancy.

Thoracic gas volume (TGV) and airway conductance (Gaw) were measured in 69 healthy infants during the 1st yr of life, using an adaptation of the whole body plethysmographic technique in which a heated rebreathing system was used to eliminate temperature differences in respired gas. There was highly significant correlations between TGV and body wt (r=0.99), and between Gaw and TGV (r=0.97) in all the infants. However, the relationship between Gaw and TGV (i.e., specific conductance (SGaw)) was dependent on postconceptional age (PCA) in preterm infants, falling from 0.50 s-1-cmH2O-1 at 31 wk to 0.32 s-1-cmH2O-1 at 40 wk PCA. Gestational age and postnatal age per se did not affect this relationship, showing it to be a maturational event unaffected by the time of birth. After 40 wk, the decrease in SGaw was far more gradual throughout the 1st yr of life. Black and Chinese infants were found to have significantly higher values for SGaw than their White counterparts, which may be due to anatomical differences in nasal structure.

Airway Resistance↗
PubMed1977

A new apparatus for the accurate measurement of airway resistance in infancy.

A new heated rebreathing system has been developed for the measurement of thoracic gas volume (TGV) and airway resistance (Raw) in infants by the plethysmographic technique. The apparatus has a linear response to flow rates between 0-160 ml-s-1, a dead space of 12 ml and a resistance of 5 cmH2O-1-1-S-1 at a flow rate of 60 ml-s-1. The inclusion of pneumatically operated valves in the apparatus is a major improvement over previous methods of occlusion for TGV measurements. The infant is allowed to rebreathe saturated gas at body temperature through the heated system, thus overcoming a potential source of error when measuring Raw in infants. Using this apparatus, the average coefficient of variation was 3.7% for TGV and 5.9% for Raw.

Airway Resistance↗
PubMed1977

Measurement of pulmonary capillary blood flow in infants by plethysmography.

An accurate method for measuring effective pulmonary capillary blood flow (Qc eff) in infants has been developed with an adaptation of the plethysmographic technique. Measurements were made on 19 preterm. 14 small-for-dates, and 7 fullterm normal infants with a constant volume whole body plethysmograph in which the infant rebreathed nitrous oxide. There was a highly significant correlation between Qc eff and body weight, and this relationship was unaffected by premature delivery or intrauterine growth retardation. Mean Qc eff in preterm, small-for dates, and fullterm infants was 203, 208 and 197 ml min-1 kg-1, respectively, with no significant differences between the groups. A significant negative correlation existed between Qc eff and haematocrit in the preterm infants. There was no relationship between weight standardized Qc eff and postnatal age in any of the groups. With this technique, it was possible to readily recognise the presence of rapid recirculation (indicative of shunting) in several of the infants, suggesting that rebreathing methods for the assessment of Qc eff should not be applied indiscriminately during the neonatal period. By taking care to overcome the potential sources of technical error, it was possible to obtain highly reproducible results of Qc eff in infants over a wider age range than has been previously reported.

Body Weight↗