Biomedical subjects

G Derby

Publications and source records attributed to G Derby.

13 recordsLinked to original sources

PubMed1999

The dynamics of glomerular filtration after Caesarean section.

The objective of this study was to determine whether the glomerular hyperfiltration of pregnancy is maintained even after Caesarean section and, if so, to define the responsible hemodynamics. The dynamics of glomerular filtration were evaluated in 12 healthy women who had just completed an uncomplicated pregnancy and were delivered by Caesarean section. Age-matched but non-gravid female volunteers (n = 22) served as control subjects. GFR in postpartum women was elevated above control values by 41%; 149+/-10 versus 106+/-3 ml/min per 1.73 m2, respectively (P < 0.001). In contrast, corresponding renal plasma flow was the same in the two groups, such that the postpartum filtration fraction was significantly elevated by 20%. Computation of glomerular intracapillary oncotic pressure (piGC) from knowledge of plasma oncotic pressure and the filtration fraction revealed this quantity to be significantly reduced in postpartum women, 20.6+/-1.7 versus 26.1+/-2.0 mmHg in control subjects (P < 0.001). A theoretical analysis of glomerular ultrafiltration suggests that depression of piGC, the force opposing the formation of filtrate, is predominantly or uniquely responsible for the observed postpartum hyperfiltration.

Adult↗

PubMed1998

Nature of glomerular dysfunction in pre-eclampsia.

BACKGROUND: Pre-eclampsia is characterized by hypertension, proteinuria and edema. Simultaneous studies of kidney function and structure have not been reported. We wished to explore the degree and nature of glomerular dysfunction in pre-eclampsia. METHODS: Physiologic techniques were used to estimate glomerular filtration rate (GFR), renal plasma flow and afferent oncotic pressure immediately after delivery in consecutive patients with pre-eclampsia (PET; N = 13). Healthy mothers completing an uncomplicated pregnancy served as functional controls (N = 12). A morphometric analysis of glomeruli obtained by biopsy and mathematical modeling were used to estimate the glomerular ultrafiltration coefficient (Kf). Glomeruli from healthy female kidney transplant donors served as structural controls (N = 8). RESULTS: The GFR in PET was depressed below the control level, 91 +/- 23 versus 149 +/- 34 ml/min/1.73 m2, respectively (P < 0.0001). In contrast, renal plasma flow and oncotic pressure were similar in the two groups (P = NS). A reduction in the density and size of endothelial fenestrae and subendothelial accumulation of fibrinoid deposits lowered glomerular hydraulic permeability in PET compared to controls, 1.81 versus 2.58 x 10(-9) m/sec/PA. Mesangial cell interposition also curtailed effective filtration surface area. Together, these changes lowered the computed single nephron Kf in PET below control, 4.26 versus 6.78 nl/min x mm Hg, respectively. CONCLUSION: The proportionate (approximately 40%) depression of Kf for single nephrons and GFR suggests that hypofiltration in PET does not have a hemodynamic basis, but is a consequence of structural changes that lead to impairment of intrinsic glomerular ultrafiltration capacity.

Adult↗

PubMed1997

Molecular configuration and glomerular size selectivity in healthy and nephrotic humans.

We studied eight healthy volunteers and eight nephrotic subjects to compare the glomerular sieving coefficients (theta) of dextran, a linear polymer of glucopyranose, with those of Ficoll, a spherical polysucrose. Over a molecular radius (rs) interval of 20-70 A, theta for a given Ficoll was uniformly lower than corresponding theta for a dextran of equivalent rs. For each macromolecular species, the theta of molecules with rs > 50 A was selectively enhanced in nephrotic vs. healthy subjects. Analysis of either dextran or Ficoll sieving curves with pore theory revealed the glomerular barrier to have a bimodal pore size distribution: a lower mode of restrictive pores with a lognormal distribution of radii and an upper mode of large shuntlike pores. Nephrotics differed from controls in that the lower mode was broadened and shifted to pores of smaller mean size, but the prominence of shuntlike pores was enhanced by an order of magnitude. Both the mean radius of restrictive pores and the magnitude of the shunt pathway were substantially smaller when estimated from Ficoll than dextran sieving. We interpret the more realistic values for pore parameters derived from Ficoll than dextran sieving to indicate 1) that the normal glomerular barrier prevents albuminuria by virtue of a combination of both charge- and size-selective properties and 2) that a combined impairment of both barrier charge selectivity and size selectively are required to account for the observed level and composition of proteinuria in our nephrotic subjects.

Adult↗

PubMed1988

Occupational exposure to volatile nitrosamines in foundries using the "Ashland" core-making process.

Eight foundries using the "Ashland" process for the production of cores were surveyed to assess the occupational exposure to carcinogenic volatile nitrosamines. Personal and area samples were collected by means of artifact-free cartridges during the core-making and the molding/casting/shake-out operations. Analyses were carried out with gas chromatography/Hall detector and gas chromatography/TEA (thermal energy analyzer) for validation. The core-making workshops had the highest concentration for at least two nitrosamines, N-nitrosodimethylamine (NDMA) and N-nitrosoethylmethylamine (NEMA), but the levels of NDMA never exceeded 0.35 microgram/m3 with an arithmetic mean between 0.23 and 0.02 microgram/m3. In a number of samplings, two other peaks, both on TEA and Hall detector, could not be identified. The foundries per se (molding/casting/shake-out) had lower nitrosamine levels (CNDMAmax = 0.15 microgram/m3, CNDMA less than 0.03 microgram/m3). For the first time NEMA was identified as an industrial contaminant in foundries but its concentration was always lower than that of NDMA. The nitrosamines found were presumably produced from dimethylethylamine (DMEA). Industries producing or using tertiary or secondary amines should be controlled for their possible nitrosamine contamination.

Air Pollutants, Occupational↗

PubMed1988

Coronary artery vasoconstriction routinely occurs after percutaneous transluminal coronary angioplasty. A quantitative arteriographic analysis.

To determine whether percutaneous transluminal coronary angioplasty (PTCA) increases coronary artery luminal dimensions by stretching and injuring ("paralyzing") the smooth muscle of the arterial wall, we prospectively analyzed spontaneous changes and then intracoronary nitroglycerin-induced changes in segmental coronary artery diameters during the first 30 minutes after uncomplicated single-vessel PTCA in 10 patients. Five additional patients received intravenous nitroglycerin throughout the procedure to determine whether nitroglycerin could prevent vasoconstriction after PTCA. All of the patients were maintained on oral doses of diltiazem and aspirin at the time of the study. Coronary arteriography was performed at 2, 5, 15, and 30 minutes after PTCA and then 3 minutes after 300 micrograms i.c. nitroglycerin. Quantitative measurements (computerized edge-detection) were performed at each time, in coronary segments centered in the dilated segment, distal to the dilated segment, and in a control vessel not manipulated with the balloon catheter or guidewire. Progressive vasoconstriction (defined as a loss of diameter that was reversed by intracoronary nitroglycerin) was observed after PTCA in the dilated and distal segments (10 of 10 patients) but not in the control segment. The vasoconstriction in the dilated segment at 30 minutes (mean, 30 +/- 4%) was highly statistically significant compared with vasoconstriction at 2 and 5 minutes after PTCA (p less than 0.001) and compared with the control segment at 30 minutes (p less than 0.005). There was no significant loss of diameter after PTCA in the dilated segment in the five patients who received intravenous nitroglycerin. In conclusion, 1) spontaneous coronary artery vasoconstriction after PTCA occurs routinely at and distal to the site of balloon dilatation despite pretreatment with aspirin and calcium channel blockers; 2) coronary artery vasoconstriction after PTCA is rapidly reversed by intracoronary nitroglycerin and can be prevented by the continuous administration of intravenous nitroglycerin during and after the procedure; 3) these results are incompatible with the hypothesis that PTCA improves coronary luminal dimensions by arterial "paralysis"; and 4) these findings have implications concerning the etiology and prophylaxis of abrupt vessel closure after PTCA.

Aged↗

PubMed1984

Nature of the renal injury following total renal ischemia in man.

The effects of total renal ischemia (TRI) of 15-87 min duration due to suprarenal clamping of the aorta were studied in 15 mannitol-treated patients undergoing abdominal aortic surgery. 15 patients undergoing similar surgery but requiring only infrarenal clamping served as controls. 1-2 h following TRI, GFR was reduced to only 39% of that in controls, 23 +/- 5 vs. 59 +/- 7 ml/min (P less than 0.001). This could not be ascribed to impaired renal plasma flow (RPF), which was mildly reduced to 331 +/- 71 and was not different from the value in controls, 407 +/- 66 ml/min. However, impaired PAH extraction (43 +/- 7%) and isosthenuria, not present in controls, suggest a primary role for tubular injury in lowering GFR at this time. 24 h following TRI, the GFR remained depressed below controls, 45 +/- 8 vs. 84 +/- 8 ml/min (P less than 0.005), while the transglomerular sieving of neutral dextrans was significantly enhanced (radius interval, 24-40 A). A theoretical analysis of transcapillary solute exchange revealed that these findings could be largely explained by a selective reduction of either RPF (-61%) or of transmembrane hydraulic pressure difference (-18%) below control values. Alternately, a combination of these two factors with changes of smaller magnitude could explain the findings. In contrast, a selective increase in oncotic pressure or decrease of the glomerular ultrafiltration coefficient could be excluded as a cause of hypofiltration 24 h after TRI. These observations lead us to suggest that the transient azotemia observed following TRI is due to a self-limited injury to the nephron that is identical to that seen in overt and sustained forms of acute renal failure.

Aged↗

PubMed1984

Dobutamine and dopamine after cardiac surgery: greater augmentation of myocardial blood flow with dobutamine.

Left ventricular hemodynamics, dimensions and coronary sinus blood flows were measured simultaneously after infusions of dobutamine and dopamine. Ten patients were studied 6, 10 to 15, and 24 hr after cardiopulmonary bypass surgery. The dose of each drug was adjusted to increase cardiac output by 25%. Heart rate was held constant with atrial pacing. Dobutamine and dopamine increased peak left ventricular dP/dt from baseline values by 72% vs 58% during the early study, 77% vs 78% in the intermediate study, and 95% vs 79% in the late study (all NS, difference between drugs). Similarly, there were no significant differences in hemodynamic response or in cardiac dimensions after the two drugs in any period. Both drugs increased myocardial oxygen uptake during the intermediate and late studies (32% vs 33% and 34% vs 25%). With dobutamine this increase was matched by a similar increase in coronary blood flow; however, failure of the expected increase in coronary blood flow with dopamine suggested coronary constriction. Although dobutamine and dopamine have similar hemodynamic effects, dobutamine has the advantage of not limiting the increase in coronary blood flow associated with increased oxygen demand.

Catecholamines↗

PubMed1982

Surgery for ventricular tachycardia: efficacy of left ventricular aneurysm resection compared with operation guided by electrical activation mapping.

Sixty-five patients underwent surgery for recurrent ventricular tachyarrhythmias. The 32 patients in group 1 underwent simple left ventricular aneurysm resection. The 33 patients in group 2 underwent myocardial resection or incision guided by intraoperative mapping of the electrical activation sequence. The clinical, hemodynamic and angiographic characteristics of the two groups were similar. Although actuarial survival in the two groups was similar through 24 months, late attrition in group 1 patients has left only 21 +/- 13% (+/- SEM) alive by life-table analysis at 94 months. Arrhythmia recurrence has been greater in group 1 than in group 2. In group 1, 50 +/- 9% of patients at risk at 3 months had recurrences by actuarial analysis. In group 2, only 13 +/- 6% at 1 month, 17 +/- 7% at 3 months and 29 +/- 9% at 24 months relapsed. Death was caused by ventricular tachyarrhythmias in 12 of the 17 patients (71%) who died in group 1, but only three of 12 (25%) who died in group 2. We conclude that surgery of the left ventricle, guided and modified by intraoperative mapping of the electrical activation sequence, frequently eliminates ventricular tachyarrhythmias and may be more effective than blind resection of left ventricular aneurysm.

Electrocardiography↗

PubMed1980

[Incorporation of heptadecanoic acid into liver lipids of Wistar rats (author's transl)].

During perfusions of isolated livers of Wistar rats with heptadecanoic acid, this fatty acid is taken up and rapidly incorporated into cholesterol esters and triacylglycerols which increase in amounts with the duration of the experiment. 2 Large amounts of triheptadocanoylglycerol appear; heterogeneous triacylglycerols (mono- and diunsaturated) with 1 or 2 molecules of heptadecanoic acid) are synthesized. 3 The triacylglycerols with 17 : 0 fatty acid secreted in circulating medium are of the same nature and appear with the same chronology as those previously synthetized by the liver.

Animals↗

PubMed1979

Acute renal failure following cardiac surgery.

In a prospective 6 month study of 204 patients requiring cardiac operations, five (2.5 percent) developed acute renal failure (ARF) and five (2.5 percent) had documented renal dysfunction (RD). Preoperative left ventricular dysfunction and prolonged cardiopulmonary bypass (CPB) were important predictors of subsequent RD/ARF; CPB pressure per se was not. Physiological and clinical studies in 51 selected patients studied over an 18 month period documented the effectiveness of low flow, low pressure CPB in preserving postoperative renal function. Twenty-two patients with nonazotemic postoperative courses demonstrated moderate depression of cardiac function while the glomerular filtration rate (GFR) was normal (98 +/- 30 ml./min/1.73 M.2) within 24 hours of operation. Seventeen high risk patients developed AFF (65 percent mortality rate) and 12 experienced severe RD without ARF (17 percent mortality). ARF (65 percent mortality rate) and 12 experienced severe RD without ARF (17 percent mortality). Eleven patients with ARF and 11 with RD were studied in the early postoperative period; at this time, all 22 patients demonstrated RD with equivalent severe depression of cardiac and renal function. Superposition of further hemodynamic or toxic insults upon ischemic kidneys was usually necessary for ARF to occur.

Acute Kidney Injury↗

PubMed1977

[Release of synthesized lipids by isolated Wistar rat liver perfused by labelled oleic acid and glycerol].

After perfusions with oleic acid (9, 10-3H) and glycerol (1-14C) of isolated livers from wistar Rats, previously subjected to fasting, the study of the TG and PL synthesized by the liver and released in the circulation gives of evidence similar ways of metabolising TG and PL. Two liver pools are present: -- a storage pool, built with slow exchanges of AG of endogenous glycerolipids. In our experiments, the TG: 16 : 0 18 : 1 18: 2 and 16 : 0 18 : 1 18 : 1 and the PL: PE and PC are the glycerolipids of liver constitution: -- a pool of liver secretion. TG and PL are formed according to a rapid de novo synthesis using preferentially the exogenous substrates. They are released in the circulation. In our experiments, the TG secreted are the TG 18 : 1 18 : 1 18 : 1 and 16 : 0 18 : 1 18 : 2, the PL are the PE, AP and LPC.

Animals↗

PubMed1975

[Nutritional value and acceptibility of soy proteins in human diet].

These studies on textured soya protein (TSP) were directed towards the evaluation of its acceptability and nutritional value in man. ACCEPTABILITY. In the beginning, the reaction of adults to the incorporation of 40 g TSP in their daily diet was studied. After a three-week period, no intolerance or fatigue with the regim was shown. In a following study, observations made on young children's attitudes along with quantitative measurements of their food intake were noted during four one-wekk periods: -- period of "imposed diet", without TSP; -- period of imposed diet", with TSP; -- period of "free diet", without TSP; -- period of "free diet", with STP; During the periods of "imposed diets", children could eat only the proposed quantities of foodstuffs. During periods of "free diets", children were able to choose the quantity and sort of food they preferred from the proposed menu. Total protein ingested (differentiating between that of animal and vegetable origin) was calculated for each child from his daily food record. Results show that only one of the twenty-four children systematically refuse soya-containing preparations. Average consumption of soya protein during "free diet" periods was close to the desired level and not significantly different to levels achieved in the "imposed diet" period. The acceptance of TSP by the children was therefore evident. NUTRITIONAL VALUE. The following studies were designed to determine the effects of the replacement of animal protein by TSP (at the maximal levels of its tolerability) in a normal diet. In the first nitrogen balance study, with 10 convalescent subjects, the following protocol was developed: -- the habitual caloric and protein intakes of the subjects was established; -- following a four-day adaptation period, the subjects entered consecutively: a control period at established levels of calories and protein, and a test period in which 20 g of soya protein replaced an equivalent quantity of animal protein. The average nitrogen balances for control and test periods were + 4.49 g and 3.62 g. The difference not being significant at a probability of 5 p. 100. In a second study with 12 adults in good health (6 males and 6 females) soya protein replaced 34-39 p. 100 of the daily protein intake (according to the menu) and the average nitrogen balances in control and test periods were + 0.16 g and 0.91 g. These studies confirm the TSP replacement of animal protein in the normal diet does not affect nitrogen balance and that TSP can make a contribution to the fulfilment protein requierements in man.

Adult↗

PubMed1975

Comparative hemodynamic responses to chlorpromazine, nitroprusside, nitroglycerin, and trimethaphan immediately after open-heart operations.

The hemodynamic effects of intravenous chlorpormazine, nitroprusside, nitroglycerin, and trimethaphan camsylate were studied in 51 patients with high mean arterial pressures immediately after open-heart operations. Chlorpromazine was given by bolus intravenous injection to 24 patients (average dose 10.3 mg); nitroprusside (17 patients), nitroglycerin (8 patients), and trimethaphan (12 patients) were administered by constant intravenous infusion at average doses of 77 mug/min, 59 mug/min, and .097 mg/min, respectively. Measured or derived variables included right atrial pressure, pulmonary artery pressure, left atrial pressure, systemic arterial pressure, heart rate (HR), cardiac index (CI), stroke index (SI), stroke work index (SWI), and systemic vascular resistance index (SVRI). All four vasodilators significantly reduced systemic and intracardiac pressures and SWI (P less than 0.01). Associated changes in left ventricular pumping performance, however, differed importantly between groups. Chlorpromazine caused a significant rise (+19%) in HR with preservation of SI; thus, CI rose significantly (P less than 0.01). Only nitroprusside, however, resulted in enhancement of SI (P less than 0.05) at the lowered left atrial pressure; CI increased by 19% (P less than 0.01), HR rose minimally (6.5%), and calculated SVRI diminished 33% (P less than 0.01). Both nitroglycerin and trimethaphan caused decreases in SI and CI. These results indicate that in general, among the vasodilators studied, nitroprusside is associated with the most favorable hemodynamic responses in early postoperative cardiac surgical patients.

Blood Pressure↗