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M T Jones

Publications and source records attributed to M T Jones.

At least 37 records · Page 2Linked to original sources
PubMed1991

Comparison of ultrasonography and oral cholecystography in lithotripsy. II. Determining retreatment.

Both ultrasonography (US) and oral cholecystography (OCG) are being used to evaluate patients after extracorporeal shock wave lithotripsy (ESWL) for gallstones. Criteria for retreatment after the initial ESWL are usually related to the size of the residual fragments. This study examines the efficacy of ultrasound and OCG for determining both the size and number of stone fragments in the gallbladder in an in vitro model and in patients. Ultrasonography and OCG examinations using an in vitro ESWL phantom with ten groups of stones, and on 39 patients, were reviewed independently by three radiologists to determine both the size and number of stone fragments. For the in vitro study, the three readers estimated the correct number of fragments, or the next closest range, in 87% of observations by OCG and in 43% by US. The size of the largest fragment was measured within 1 mm of its actual size in 87% of observations by OCG and 20% by US. Correlation coefficients for the mean measurements of the three readers versus the actual fragment size and number were greater for OCG than for US. For the in vivo study, the three readers agreed in 47% of the OCG versus 32% of US examinations with respect to the number of fragments, and in 65% of OCG compared to 40% of US studies with respect to size of the largest fragment. Multiple statistical analyses demonstrate that these differences are statistically significant. A discrepancy among the readers concerning whether a patient was eligible for retreatment occurred in 15% of OCG as compared to 45% of US studies. Both the in vivo and in vitro studies indicate that there is more interobserver reproducibility for OCG than for US, and that OCG is more reliable in making the decision concerning patient eligibility for retreatment following lithotripsy.

Adult↗
PubMed1991

Hypertonic citrate solution as an alternative to modified Euro-Collins' solution for lung preservation.

In a canine model of acute ischemic lung injury, a hypertonic citrate solution (HTC) widely used for renal preservation in the United Kingdom, was compared with modified Euro-Collins' solution (ECS) currently the most widely clinically used pulmonary perfusate. Ten beagle dogs underwent left thoracotomy and exclusion of the left lung in situ. The lung was flushed with 30 ml/kg of either HTC or ECS and subjected to 60 min of warm ischemia. The circulation to the lung was then restored, the contralateral lung excluded, and the animal ventilated at a fixed FiO2 of 0.4 for 4 hr. Lung function was assessed by arterial oxygenation and hemodynamic measurements and, following sacrifice, by lung weight gain, bronchoalveolar lavage, and ultrastructural studies. Flush perfusion with HTC was associated with significantly less severe reperfusion injury, as determined by superior arterial oxygenation (PaO2 at 1 hr: HTC--152 mmHg [(95% confidence interval) CI] [122-182], ECS--59 [47-70]; PaO2 at 4 hr: HTC--124 [100-149], ECS--51 [42-61]), lower pulmonary vascular resistance index (PVRI at 4 hrs: HTC--838 dynes sec cm-5m-2 [651-1075], ECS--1233 [963-1588]); and lower lung weight (HTC--85 g [66-107], ECS--146 [114-184]). Bronchoalveolar lavage studies demonstrated an influx of neutrophils following reperfusion that was significantly less marked in the HTC group (increase in % neutrophils: HTC 24 [19-29], ECS 77 [72-82]). Lung injury assessed by electron microscopy tended to be less severe in the HTC animals. We conclude that HTC may offer an alternative superior to ECS for lung preservation.

Animals↗
PubMed1991

Lack of effect of fetal administration of cocaine on maternal and fetal plasma adrenocorticotropin, cortisol and lactate concentrations at 127-138 days gestational age.

Few in vivo studies have been done to characterize the effects of cocaine on the maternal and fetal pituitary-adrenal axis during pregnancy. We, therefore, administered cocaine (2 mg.kg-1) intravenously to 6 fetal sheep at 127-138 days of gestation. There was a transient reduction in fetal arterial pO2 with a concomitant increase in pCO2 and a prolonged fall in pH (p less than 0.05) following cocaine injection. No changes were seen in maternal pO2, pCO2 or pH. Maternal adrenocorticotropin (ACTH), cortisol and lactate were not affected by fetal administration of cocaine. Although there was a tendency for fetal plasma ACTH, cortisol and lactate to rise after administering cocaine, the increases were not statistically significant. Previous studies have shown that cocaine administration to the ewe at a similar stage of pregnancy results in increased fetal plasma ACTH concentrations. The results of the present study indicate that cocaine administration to the fetus compromises fetal gas exchange and acid-base balance but the effects on the fetal pituitary-adrenal axis are less pronounced than after maternal administration of cocaine.

Acid-Base Equilibrium↗
PubMed1991

Lack of effect of fetal administration of cocaine on maternal and fetal plasma adrenocorticotropin, cortisol and lactate concentrations at 127-138 days gestational age.

Few in vivo studies have attempted to characterize the effects of cocaine on the maternal and fetal pituitary-adrenal axis during pregnancy. We, therefore, administered cocaine (2 mg.kg-1) intravenously to 6 fetal sheep at 127-138 days of gestation. There was a transient reduction in fetal arterial pO2 with a concomitant increase in pCO2 and a prolonged fall in pH (p less than 0.05) following cocaine injection. No changes were seen in maternal pO2, pCO2 or pH. Maternal plasma adrenocorticotropin, cortisol and lactate were not affected by fetal administration of cocaine. Although there was a tendency for fetal plasma adrenocorticotropin, cortisol and lactate to rise after administering cocaine, the increases were not statistically significant. Previous studies have shown that cocaine administration to the ewe at a similar stage of pregnancy results in increased fetal plasma adrenocorticotropin concentrations. The results of the present study indicate that cocaine administration to the fetus compromises fetal gas exchange and acid base balance, but the effects on the fetal pituitary-adrenal axis are less pronounced than after maternal administration of cocaine.

Adrenocorticotropic Hormone↗
PubMed1991

Effect of maternal cocaine administration on maternal and fetal glucose, lactate, and insulin in sheep.

Although cocaine use during pregnancy is an important cause of perinatal morbidity and mortality, there are no reports of its effect on maternal and fetal carbohydrate metabolism. Six pregnant ewes and their fetuses were instrumented under halothane general anesthesia at 113-119 days' gestation. Between 124-135 days' gestation, the ewes received a single infusion of vehicle or cocaine (1.0 or 2.0 mg/kg) into the jugular vein. At least 24 hours was allowed between successive injections. Maternal and fetal blood samples were drawn at 30 and 20 minutes before and at 5, 15, 30, and 60 minutes after the injection. Both maternal and fetal glucose and lactate concentrations increased (P less than .05) after injection of cocaine at 2.0 mg/kg. There were no significant changes in maternal or fetal plasma insulin concentrations after vehicle or cocaine administration. Induction of hyperglycemia and lactacidemia could be mechanisms whereby cocaine exerts its adverse effects during pregnancy.

Animals↗
PubMed1990

Prediction of oxygen uptake on a bicycle wind-loaded simulator.

The primary purpose of this study was to determine the accuracy of estimating oxygen uptake (VO2) from the flywheel revolution rate of a bicycle wind-loaded simulator. VO2 at four different flywheel revolution rates was measured on a Findlay Road Machine (FRM). Ten male trained cyclists, 10 male untrained cyclists, 10 female trained cyclists and 10 female untrained cyclists served as subjects. Significant curvilinear relationships (P less than 0.01) were found between road speed estimated from flywheel revolution rate and VO2 expressed as 1.min-1, ml.kg-1.min-1, 1.min-1.m-2 (r = 0.97, 0.96, 0.98, respectively). The absolute standard error of the mean VO2 was 0.21 l.min-1 (9.6%), 3.71 ml.kg-1.min-1 (11.5%) and 0.10 l.min-1.m-2 (7.9%), respectively. The relationship between VO2 and speed was similar to that reported during road cycling. To determine the magnitude of between-machine differences in VO2, six subjects randomly performed cycling using two different FMR. Significant (P less than 0.05) differences between machines were found at only the highest speed. The present study indicates that it is possible to accurately predict VO2 from flywheel revolution rate using a FRM. Since the FRM appears to approximate the resistance a cyclist experiences on the road and allows cyclists to use their own bicycle, it provides a good alternative to traditional laboratory ergometers.

Bicycling↗
PubMed1990

Amelioration of lung ischemic injury with prostacyclin.

The single-flush technique of lung preservation is thought to be enhanced by prostaglandin treatment. In order to test this hypothesis, ten beagle dogs underwent thoracotomy and in situ flush perfusion of the excluded left lung with 30 ml/kg of cold, modified Euro-Collins' solution. Group 1 (n = 5) received pretreatment with 30 ng/kg/min of PGI2 by infusion and as an additive to the flush (20 micrograms/L). Group 2 (n = 5) received no PGI2 and served as controls. Following 60 min of warm ischemia, the left lung was reperfused, the contralateral lung excluded, and the animal ventilated at a fixed FiO2 of 0.4 for 4 hr. The severity of reperfusion injury was assessed by arterial oxygenation and hemodynamic measurements and, following sacrifice, by lung weight gain and bronchoalveolar lavage and ultrastructural studies. PGI2 therapy resulted in significant amelioration of reperfusion injury, with superior oxygenation at both 1 and 4 hr (PaO2 at 1 and 4 hr, respectively; PGI2: 145 mmHg +/- 17.0 and 114 +/- 11.2; no PGI2: 59 mmHg +/- 5.8 and 51 +/- 4.5; P less than 0.01 at both times), lower pulmonary vascular resistance index at 4 hr (PVRI; PGI2: 913 dynes sec cm-5m-2 +/- 91; no PGI2: 1239 +/- 68; P less than 0.05) and lower lung weight (PGI2: 76 g +/- 4; no PGI2: 146 +/- 10; P less than 0.001). Bronchoalveolar lavage studies revealed an influx of neutrophils following reperfusion that was less marked in the PGI2 group (increase in % neutrophils; PGI2: 50.4 +/- 6.7; no PGI2: 76.9 +/- 6.0; P less than 0.05). Lung injury score assessed by electron microscopy was lower in the PGI2 group (PGI2: 5.2 +/- 1.1; no PGI2; 8.1 +/- 0.5; P less than 0.05). It is concluded that PGI2 treatment is protective against ischemic lung injury in this model.

Animals↗
PubMed1990

Biliary lithotripsy: in vitro analysis of gallstone fragmentation for equivalent stone volumes.

The relationship between gallstone fragmentation during extracorporeal shock wave lithotripsy (ESWL) and gallstone volume is poorly understood. Clinical results of ESWL show that the highest stone-free rate at 6 months occurs with radiolucent single gallstones 20 mm or less in diameter. In an in vitro study, individual gallstones from cholecystectomy specimens were divided by size and composition into nine single- and nine multiple-stone groups; the stones were then paired on the basis of similar volume. ESWL was performed in a phantom and the size of the largest fragment was measured at 500, 1,000, and 1,500 shock waves. At 1,500 shock waves, sandlike particles were present in six of nine single stones versus two of nine multiple stone groups; the mean size of the largest fragment at 1,500 shock waves was 2.1 mm (single) and 4.4 mm (multiple) in diameter. When corrected for volume, the authors' data suggest that single stones are more easily broken into fragments smaller than 5 mm in diameter than multiple gallstones. The implication, especially when spark-gap technology is used, is that more shock wave energy (ie, an increased number of shock waves at a higher kilovoltage) will be necessary to achieve the same results when treating patients with multiple stones versus a single gallstone with a similar stone volume.

Cholelithiasis↗
PubMed1990

Oxygen consumption and distribution of blood flow in rats climbing a laddermill.

The purpose of this study was threefold: 1) to determine whether untrained rats that refused to run on treadmill would climb on a laddermill (75 degrees incline); 2) to determine O2 consumption (VO2) in untrained rats as a function of laddermill climbing speed; and 3) to determine whether the circulatory response of untrained rats to laddermill climbing is similar to that previously reported for treadmill running at an equivalent VO2. Eighteen female Sprague-Dawley rats that would not perform on a treadmill as part of another study were used to measure VO2 as a function of laddermill speed (5-17 m/min). Data were obtained from all 18 rats; VO2 increased linearly as a function of laddermill speed (r = 0.83, y = 3.0 x + 63.2). Twenty-four female Sprague-Dawley rats that also refused to run on a treadmill were used to measure mean arterial pressure, heart rate, and blood flow distribution (with microspheres) during climbing at 5 and 10 m/min. These exercise intensities were metabolically equivalent to level treadmill running at 45 and 60 m/min (VO2 approximately 78 and 93 ml.min-1.kg-1, respectively). Of the 24 animals, 23 were willing to climb. Mean arterial pressures were higher (approximately 10%) during laddermill climbing than during equivalent treadmill running, but heart rates were the same. General blood flow distribution among muscles as a function of fiber type (with red muscles receiving higher flows) and between muscles and visceral tissues (muscle blood flow increased as a function of exercise intensity while visceral blood flows decreased) were similar to data for rats running on the level.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Distribution of blood flow during exercise after blood volume expansion in swine.

To study the distribution of blood flow after blood volume expansion, seven miniature swine ran at high speed (17.6-20 km/h, estimated to require 115% of maximal O2 uptake) on a motor-driven treadmill on two occasions: once during normovolemia and once after an acute 15% blood volume expansion (homologous whole blood). O2 uptake, cardiac output, heart rate, mean arterial pressure, and distribution of blood flow (with radiolabeled microspheres) were measured at the same time during each of the exercise bouts. Maximal heart rate was identical between conditions (mean 266); mean arterial pressure was elevated during the hypovolemic exercise (149 +/- 5 vs. 137 +/- 6 mmHg). Although cardiac output was higher and arterial O2 saturation was maintained during the hypervolemic condition (10.5 +/- 0.7 vs. 9.3 +/- 0.6 l/min), O2 uptake was not different (1.74 +/- 0.08 vs. 1.74 +/- 0.09 l/min). Mean blood flows to cardiac (+12.9%), locomotory (+9.8%), and respiratory (+7.5%) muscles were all elevated during hypervolemic exercise, while visceral and brain blood flows were unchanged. Calculated resistances to flow in skeletal and cardiac muscle were not different between conditions. Under the experimental conditions of this study, O2 uptake in the miniature swine was limited at the level of the muscles during hypervolemic exercise. The results also indicate that neither intrinsic contractile properties of the heart nor coronary blood flow limits myocardial performance during normovolemic exercise, because both the pumping capacity of the heart and the coronary blood flow were elevated in the hypervolemic condition.

Animals↗
PubMed1990

Effects of training on reproductive tissue blood flow in exercising pregnant rats.

The purpose of this study were to investigate 1) whether treadmill training would attenuate the reduction in reproductive (RBF) and visceral tissue blood flow (VBF) that occurs during an acute bout of submaximal exercise (EX) in pregnant rats and 2) whether fetal number of fetal weight would be affected by training. One group (T) of female rats trained on a treadmill (10 degrees incline, 30 m/min) for 1 h/day 5 days/wk for 10 wk before becoming pregnant. A second group (UT) was run at the same speed and incline for 10 min/day 5 days/wk for 2 wk. T and UT rats were bred until pregnant. Skeletal muscle blood flow, RBF, and VBF were measured at pre-EX and at 1 and 10 min of EX (10 degrees incline, 30 m/min). No differences were observed before or during exercise between the two groups in RBF and VBF, heart rate, or mean arterial pressure. Both groups experienced decreases in VBF (except liver) and RBF from pre-EX to EX. In most muscles skeletal muscle blood flow increased for both groups from pre-EX to EX. Neither group experienced a change in mean arterial pressure from pre-EX to EX, but heart rate increased significantly for both groups. No differences were observed between groups in fetal number, fetal weight, or fetal resorptions. It was concluded that training does not significantly attenuate the reduction in RBF and VBF in pregnant rats that occurs during an acute bout of submaximal EX and that training does not affect fetal weight or fetal number.

Animals↗
PubMed1988

A correlative study of RU38486 biopotency and competition with [3H]dexamethasone for receptors in the rat central nervous system.

Dexamethasone inhibitory action on the release of adrenocorticotrophin has been studied using in vitro anterior pituitary preparations. This inhibition is reversed when the animal is given the antiglucocorticoid compound RU38486 simultaneously with dexamethasone. RU38486 acts at the receptor level and in the cytosolic binding study, it competes with [3H]dexamethasone for the binding sites in pituitary. Such competition is even more pronounced in hypothalamus and hippocampus, indicating that RU38486 also exert its antagonistic action at these sites.

Adrenalectomy↗
PubMed1988

The combined use of sodium valproate and metyrapone in the treatment of Cushing's syndrome.

We have investigated the combined use of metyrapone and sodium valproate in the treatment of five cases of dexamethasone-suppressible Cushing's disease and one case with dexamethasone non-suppressible disease. Metyrapone alone reduced 24 h urinary free cortisol (UFC) and plasma cortisol concentrations. Addition of sodium valproate to metyrapone produced a further reduction in these values in five of six patients with a reduction in plasma ACTH in three of five patients who had dexamethasone-suppressible disease. Plasma 11-deoxycortisol increased markedly on metyrapone. However, addition of valproate produced a further rise in 11-deoxycortisol values in four of five patients including the patient with dexamethasone non-suppressible disease. The results suggest that valproate may be a useful addition to metyrapone in the medical treatment of some patients with Cushing's syndrome and that it may have an action both at the hypothalamus and peripherally.

Adrenocorticotropic Hormone↗
PubMed1988

Plasma corticotrophin-releasing factor (CRF) in normal pregnancy.

Corticotrophin-releasing factor (CRF) was measured directly in maternal plasma using an immunoradiometric assay (IRMA). In the first and second trimester CRF levels were within the non-pregnant range (mean 15 pg/ml). A total of 72 women was followed sequentially from 28 weeks until delivery and CRF levels rose from a median of 20 pg/ml at 28 weeks to 1320 pg/ml at 40 weeks and 1732 pg/ml during labour. There was a strong correlation (rs = 0.81, P less than 0.001) between gestational age and CRF levels. The rate of rise of CRF (pg/ml) per week was associated with weight gain (rs = 0.36, P less than 0.05) but with no other obstetric variable. There was an association between umbilical cord and maternal plasma CRF levels (rs = 0.54, P less than 0.01).

Corticotropin-Releasing Hormone↗
PubMed1988

Plasma corticotrophin-releasing factor (CRF) in abnormal pregnancy.

Maternal plasma levels of cortiocotrophin-releasing factor (CRF) have been measured in abnormal pregnancy states to assess their potential as biochemical markers for at-risk pregnancies. CRF levels were not significantly altered in patients with hydatidiform mole, polyhydramnios or diabetes. CRF levels were elevated in pregnancies complicated by accidental antepartum haemorrhage at 28 weeks (P less than 0.03) but not for the rest of the third trimester. In twin pregnancies CRF levels were significantly raised throughout the third trimester (28-32 weeks, P less than 0.01; 34-36 weeks, P less than 0.001). In patients with pregnancy-induced hypertension (28 weeks, P less than 0.001; 32-36 weeks, P less than 0.001; and 38-40 weeks, P less than 0.01), preterm labour and premature rupture of the membranes (28 weeks, P less than 0.004; 30-32 weeks, P less than 0.002; and 34-36 weeks, P less than 0.001), CRF levels were significantly raised and in some patients levels were elevated 11 weeks before the onset of signs or symptoms. These observations raise the possibility that maternal CRF measurement may be of use as a predictive indicator of certain at-risk pregnancies.

Corticotropin-Releasing Hormone↗
PubMed1988

Influence of prolonged glucocorticoid treatment on intracellular mechanisms involved in ACTH secretion in the rat.

Two chemically characterized peptides, arginine vasopressin (AVP) and corticotrophin-releasing factor-41 (CRF-41), known to stimulate ACTH secretion by interaction with their respective specific receptors on the corticotroph, were shown to cause the accumulation of phosphate esters of inositol (IP) and adenosine 3',5'-monophosphate (cAMP) respectively when added to rat anterior pituitary fragments incubated in vitro. The former 'second messenger' response (IP production) was unaffected in tissues removed from animals treated with prednisolone in the drinking water (1035 mumol/1) for 14 days. On the other hand, the cAMP response, whilst still present, was inhibited by some 50% in tissues taken from such animals. In contrast, pituitary glands from steroid-treated rats failed to respond to challenge with a variety of substances expected to cause the release of ACTH by mimicking or provoking the production of IP or cAMP. Indeed, of the wide range of ACTH secretagogues tested, only the phospholipase A2 activator melittin was able to cause attenuated ACTH release from tissues removed from treated rats. The failure to provoke ACTH release from tissues removed from steroid-treated animals was also seen when submaximal concentrations of CRF-41 or AVP, or hypothalamic extract or 48 mmol K+/1 were used as the stimuli. The staged recovery of the ACTH secretory response and IP and cAMP accumulation in vitro following the withdrawal of prednisolone treatment was also investigated. A cAMP response that did not differ significantly from that of control tissue and a normal ACTH response to K+ and to melittin were all recovered by 3 days after withdrawal, and the response to cholera toxin showed a partial recovery. Responses to all stimuli of ACTH secretion which cause their effect by entering the corticotrophs were normal by 5 days after withdrawal, when the response to CRF-41 was still significantly, and that to AVP still slightly, reduced compared with controls. Surprisingly, restoration of the ACTH response was most delayed when the expectedly most potent extracellular stimulus (hypothalamic extract) was used. In this case, release was still significantly impaired 7 days after steroid withdrawal. The results show that the glucocorticoid acts to compromise several distinct steps in the process whereby extracellular signals such as CRF-41 and AVP cause the secretion of ACTH. The only step that appears to be spared is the generation of IP by AVP.(ABSTRACT TRUNCATED AT 400 WORDS)

Adrenocorticotropic Hormone↗