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Biomedical subjects

R Green

Publications and source records attributed to R Green.

At least 325 records · Page 18Linked to original sources
PubMed1987

Relationship between mean airway pressure, cardiac output, and organ blood flow with normal and decreased respiratory compliance.

We investigated the relation between blood flow and mean airway pressure in two groups of anesthetized newborn piglets. The first group had normal respiratory compliance; the second group had pulmonary surfactant depleted by repeated saline lavage, which decreased static respiratory compliance by 42%. In the normal group, cardiac output decreased linearly from 292 +/- 43 mL/min/kg at 5 cm H2O airway pressure to 134 +/- 37 ml/min/kg at 20 cm H2O airway pressure, a drop of 43% (r2 = 0.79). Blood flow to the heart, kidney, and intestines had a similar decline, but brain, hepatic artery, and adrenal flow were constant. Mean arterial blood pressure did not decrease significantly until the highest airway pressure was reached, whereas sagittal sinus pressure increased as mean airway pressure increased. In contrast, the surfactant-depleted group maintained cardiac output up to a mean airway pressure of 15 cm H2O. At 20 cm H2O, cardiac output fell to 40% of the original value. Blood flow to the heart and kidneys fell at a mean airway pressure of 20 cm H2O; intestinal blood flow decreased beginning at 10 cm H2O. As in the normal piglets, brain, hepatic arterial, and adrenal blood flow were not affected by increasing ventilation pressure. Our data show that positive pressure ventilation in the neonate has important cardiovascular effects that are blunted when respiratory compliance is decreased. More important, because cardiac output decreased prior to a significant decline in arterial blood pressure, these data suggest that in a clinical setting considerable cardiovascular alterations can occur before a decline in arterial blood pressure is detected.

Airway Resistance↗
PubMed1987

Renal tubular function in gestation.

During pregnancy, the filtered load of most ions and small-mol wt solutes increases. Overall, sodium, water, and potassium reabsorption increases, as does excretion of calcium and glucose. Many of the changes occur in the proximal tubule or the loop of Henle. The mechanisms underlying the changes are discussed.

Female↗
PubMed1987

Renal tubular function in the gravid rat.

Pregnancy in the rat is accompanied by enhanced reabsorption of salt and water throughout most, if not all, of the gestational period. Many mechanisms have been suggested but definitive answers are still awaited. The major area of controversy centres around the detection of changes at term. There is general agreement that, at least in mid-gestation, the increase in reabsorption can be attributed to increases in the proximal tubules, the loop of Henle and collecting duct. The contribution of the proximal tubule to the increased reabsorption at term is still uncertain. Enhanced salt and water reabsorption is demonstrated in distal nephron segments irrespective of the stage of gestation. Micropuncture and microperfusion experiments have identified increased reabsorption of water, sodium and chloride in the loop of Henle, but it appears that there is net addition of glucose, urea and potassium to the tubular fluid in this segment which, at least for potassium and glucose, offsets to some extent increased reabsorption by the proximal tubule. Altered renal handling of other solutes (uric acid, calcium and magnesium) also occurs throughout pregnancy but the mechanisms responsible and nephron sites involved remain to be investigated. Attempts to attribute altered reabsorption to direct renal effects of changes in maternal hormones are inconclusive. Prolactin mimics some of the pregnancy-associated increases in reabsorption following chronic administration to male and non-pregnant female rats. These effects might be due to a direct renal action of the hormone or even to the volume expansion following its dipsogenic action.

Animals↗
PubMed1987

The effect of sodium taurocholate on proximal tubular reabsorption in the rat kidney.

Microperfusion of tubules in situ was used to study the direct effect of sodium taurocholate on reabsorption of fluid by the proximal tubule of the rat. Sodium taurocholate (0.1 mmol/l) in the tubular perfusate reduced proximal tubular fluid reabsorption by approximately 30%. Thus, the proximal tubule appears to be a major site at which bile salts cause a natriuresis in the rat, and possibly in obstructive jaundice in man.

Absorption↗
PubMed1987

Effect of dietary sodium chloride and posture on plasma immunoreactive atrial natriuretic peptide concentrations in man.

The effect of changes of dietary sodium chloride intake and posture on plasma atrial natriuretic peptide concentration and renal function was studied in 11 normal human volunteers. Plasma atrial natriuretic peptide concentration was higher in the upright posture on a high than it was on a medium or low salt diet. On the medium and high but not on the low salt diet the concentration increased significantly on adoption of the supine posture. Creatinine, sodium, lithium and fractional lithium clearances, fractional distal sodium excretion and total distal water and sodium reabsorption, which were estimated by the lithium clearance technique, were significantly higher on the high than on the low salt diet. The medium salt intake gave intermediate values. Heart rate while upright was significantly higher on the low than on either the medium or the high salt diets. Systolic blood pressure was unaffected by salt intake. Diastolic blood pressure in the supine position was significantly higher on the low than on the medium or high salt diets. Both plasma noradrenaline concentrations and plasma renin activity were significantly higher on the low than on the high salt diet. Values on the medium salt intake were intermediate. Plasma concentrations of both hormones were higher in the upright than in the supine posture on all three salt intakes. The data are consistent with the hypothesis that atrial natriuretic peptide contributes to the cardiovascular and renal adjustments to changes in dietary sodium chloride, and the possible role of the peptide is discussed.

Adult↗
PubMed1987

Lithium clearance in man: effects of dietary salt intake, acute changes in extracellular fluid volume, amiloride and frusemide.

1. The effects of amiloride and frusemide on lithium clearance were studied during changes in dietary sodium chloride intake and during infusion of 0.9% NaCl in normal human volunteers. 2. Lithium and fractional lithium clearances were less on the low than on the high salt diet. Values for the medium salt diet were intermediate. Acute extracellular fluid volume expansion with 0.9% NaCl infusion and extracellular fluid volume contraction 3-4 h after intravenous frusemide caused lithium and fractional lithium clearances to increase and decrease respectively. 3. Amiloride caused small changes in lithium and fractional lithium clearances on a low salt diet, but was without effect when salt intake was medium or high. 4. Increases in lithium clearance occurred immediately after frusemide irrespective of dietary salt intake and in subjects infused with 0.9% NaCl. Only in salt-depleted subjects did frusemide cause a substantial increase in fractional lithium clearance. Changes induced under other circumstances were small. 5. It is concluded that the lithium clearance method for assessment of proximal tubule salt and water reabsorption can be used with some degree of confidence in certain circumstances (medium and high salt intake as well as in acute volume expansion) but may not be reliable when dietary salt intake is low.

Adult↗
PubMed1987

High-risk aortic aneurysm repair with partial cardiopulmonary bypass.

Two patients with severe cardiac dysfunction and measured left ventricular ejection fractions of 18% and 20% underwent aneurysm repair with the use of femoral vein--femoral artery partial cardiopulmonary bypass. While the aorta was clamped, blood was withdrawn through the venous cannula, and oxygenated blood was delivered to the legs through the arterial cannula. This procedure allowed clamping and unclamping of the aorta to proceed without hemodynamic fluctuation. Intraoperatively, cardiac output, mean arterial pressure, pulmonary artery diastolic pressure, right atrial pressure, pulmonary capillary wedge pressure, and systemic vascular resistance were measured. Both patients recovered, which indicates that this technique may be safely undertaken in the severely compromised patient with cardiac disease.

Aged↗
PubMed1987

Preparation of lipid-free human hemoglobin by dialysis and ultrafiltration.

Dialysis of human red blood cells using a hypotonic solution and a commercial kidney dialysis unit followed by ultrafiltration through 0.1 micron pore hollow fibers provides an easily managed method for isolation of lipid-free hemoglobin. High pressure liquid chromatography analysis of lipid-free hemoglobin (LFHB) indicates 99-100% protein purity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis demonstrated that LFHB migrates as a single band. The process requires hypoosmotic dialysis of human RBC to a final 119-139 (av 132) mosmol/kg osmotic pressure. Additional reduction in osmotic pressure results in irreversible cell lysis which results in lipid contamination of the hemoglobin. Processing one-half liter of packed red blood cells requires 10 h, resulting in an average of 90% hemoglobin recovery.

Dialysis↗
PubMed1987

Uncombable-hair syndrome.

Four children had short, unmanageable, pale blond hair. They had no associated abnormalities and no family histories of abnormal hair. Light microscopy of the hair was normal in three patients, with pili torti present in the fourth. Electron microscopy of hairs from all four children revealed longitudinal grooves in the hair shaft, diagnostic of uncombable-hair syndrome.

Child↗
PubMed1987

Lung water and vascular permeability-surface area in premature newborn lambs with hyaline membrane disease.

Extravascular lung water and vascular permeability-surface area products were measured with a multiple indicator dilution method in 6 premature lambs with hyaline membrane disease 1-5 hours following delivery by cesarean section. The indicators used were 51Cr-labelled erythrocytes, 125I-albumin, 3H-water, and 14C-urea. Results were compared with previously obtained data in newborn lambs without hyaline membrane disease also delivered by cesarean section. Extravascular lung water was significantly higher in lambs with hyaline membrane disease [23.2 +/- 1.0 (SEM) vs. 10.7 +/- 1.4 ml/kg body wt]. Vascular permeability-surface area products for 14C-urea were significantly lower in lambs with hyaline membrane disease (0.30 +/- 0.10 vs 0.78 +/- 0.11 ml/s per kg). It is concluded that extravascular lung water is high in lambs with hyaline membrane disease. Permeability-surface area products for 14C-urea is low in lambs with hyaline membrane disease, which probably indicates a decrease in detectable surface area for exchange due to derecruitment or hypoperfusion of pulmonary exchange vessels in edematous and hypoxic areas of the lungs.

Animals↗
PubMed1987

Specific cross-gender behaviour in boyhood and later homosexual orientation.

Data from a group of males aged 13 to 23, who as children exhibited extensive cross-gender behaviour, was analysed. In boyhood they frequently played with dress-up dolls, role-played as females, dressed in girls' clothes, stated the wish to be girls, primarily had girls as friends, and avoided rough-and-tumble play. The majority of the group evolved a bisexual or homosexual orientation; two types of behaviour, boyhood doll play and female role-playing, were found to be associated with later homosexual orientation. The findings suggest developmental associations between specific types of boyhood cross-gender behaviour and the objects of later sexual arousal.

Child Behavior↗
PubMed1987

Increasing ventilation pressure increases cortical subarachnoid cerebrospinal fluid prostanoids in newborn pigs.

This study examines the responses of pial arterioles and venules to increased mean airway pressure (P aw-) in newborn pigs. We further characterized the changes in cortical subarachnoid cerebrospinal fluid prostanoids with increased P aw-, both before and after cyclooxygenase inhibition with indomethacin. Eight chloralose anesthetized newborn pigs were equipped with closed cranial windows and ventilated with a conventional infant pressure-cycled respirator. Increasing P aw- from 3.2 +/- 0.3 cm water to 14.3 +/- 0.6 cm water did not change pial arteriole or venule diameters. Cerebrospinal fluid prostanoids (6-keto-PGF1 alpha, TxB2, PGE2, and PGF2 alpha), however, were increased reversibly (3- to 5-fold) by increasing P aw-. After indomethacin (5 mg/kg, intravenous) pial arterioles constricted approximately 15% with increased P aw-. These results suggest that increasing ventilation pressure increases brain prostanoid production. Prostanoids appear to inhibit vasoconstriction and may be important in maintaining cerebral blood flow during the stress of mechanical ventilation.

Animals↗
PubMed1987

Impending surgery: the expectations of male coronary patients and their wives.

Waiting to receive coronary graft surgery presents patients and their spouses with a stressful episode which nevertheless holds out the possibilities of symptom relief and improved quality of life. This study examines differences between couples in their experience of waiting, approach to surgery and expectations of treatment benefit. These differences, conceptualized in terms of a theory of adjustment to illness, are discussed in relation to their practical implications for helping patients and spouses to prepare for surgery and its possible outcomes.

Adaptation, Psychological↗
PubMed1987

Lactoferrin binding by leukemia cell lines.

Monocytes and macrophages have receptors for the iron-binding protein lactoferrin. Lactoferrin acts as a potent inhibitor of granulocyte-macrophage colony stimulating factor production when it binds to these cells. Using a rosette assay and immunofluorescence, we have shown that cultured leukemia cells, including the human erythroid leukemia cell line K562, also have lactoferrin binding sites. The number of binding sites on K562 cells was estimated using soluble 59Fe-lactoferrin. Inhibition studies demonstrate that lactoferrin binding sites are distinct and unrelated to receptors for transferrin or the Fc portion of IgG, which are present on K562 cells. However, electrostatic forces may be important for lactoferrin binding, since other polycationic proteins (eg, protamine) inhibit lactoferrin binding. Prior treatment of K562 cells with trypsin nearly abolishes lactoferrin binding. However, these cells recover their ability to bind lactoferrin when trypsin is removed. Unlike transferrin receptors, the expression of lactoferrin binding sites is not regulated by cellular iron status. Cytosine arabinoside arrests the proliferation of K562 cells and simultaneously leads to a reduction in lactoferrin surface binding, suggesting that lactoferrin binding may be dependent on cell proliferation.

Cell Division↗