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Biomedical subjects

P P Lambert

Publications and source records attributed to P P Lambert.

At least 19 recordsLinked to original sources
PubMed1988

Improved Syva MicroTrak Chlamydia trachomatis direct test method.

Recent changes in the MicroTrak Chlamydia trachomatis Direct Specimen Test (Syva Company, Palo Alto, Calif.) have led to improved product performance. The use of the recommended cervical cytology brush can significantly increase the number of endocervical cells collected, and fixation with methanol increases the intensity of elementary-body staining in many specimens.

Chlamydia Infections↗
PubMed1987

The basic proteins of bovine allantoic fluid.

This paper reports the separation of highly cationic proteins (i.e. pI greater than 9.0) of bovine allantoic fluid and their possible pathogenic properties. Experimentally, polycations and cationic proteins of pI greater than 10 induced intravascular coagulation and hemolysis, as well as precipitation of fibrinogen and proteinuria. Bovine allantoic fluid collected at the time of calving contains from 0.6 to 1.3 g of proteins per liter (11 samples). Ion-exchange chromatography, followed by either chromatofocusing or heparin-sepharose-6 beta binding, and, finally, gel filtration separated several fractions and subfractions. These were examined later using polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, and at least ten constituents were visualized. Two components, Mr 34,000, pI 9.7, and Mr 38,000, pI 9.6-9.0, accounted for 33% of the basic proteins present in allantoic fluid and 0.7% of its total protein content. Electrophoretic mobility was unaltered by beta-mercaptoethanol, and periodic acid-Schiff staining was negative. These proteins were not found in ox plasma. The major basic proteins were bound to red cells and platelets. Cell electrophoretic mobility decreased linearly with the logarithm of protein concentration. At concentrations between 10(-6) and 10(-5) M, red cell clumping was rare; hemolysis and platelet agglutination were not observed.

Allantois↗
PubMed1987

PVP-sieving curves as an estimate of glomerular hemodynamics in HgCl2 acute renal failure in the dog.

In the present study, the pathophysiologic role of glomerular hemodynamic factors in the early phase of HgCl2-induced acute renal failure is evaluated in the dog. This model of moderate ARF is characterized by a parallel fall in glomerular filtration rate (delta GFR, -43%) and renal blood flow (delta RBF, -38%) within the first three hours after HgCl2 administration. Glomerular hemodynamics were studied by analysis of PVP-sieving curves. There was a significant shift of these curves upward and to the right during the 3 hours that followed the injection of HgCl2. From this analysis, no arguments for tubular back-leak could be found. Mathematical analysis of the curves revealed a fall in effective filtration pressure (EFP) in presence of an unchanged glomerular ultrafiltration coefficient (Kf) (delta EFP, -40 +/- 4%; p less than 0.01; delta Kf, +5 +/- 1%; p greater than 0.05 vs. control). No major changes occurred in glomerular colloid osmotic pressure. Subsequently, the early fall of GFR in this toxic model of acute renal failure was essentially attributed to a decrease of effective filtration pressure due to either tubular obstruction and/or mainly to renal hemodynamic changes.

Acute Kidney Injury↗
PubMed1984

Pathogenicity of cationized albumin in the dog: renal and extrarenal effects.

The effects of 21 cationized serum albumin samples of various degrees of cationization on renal function were studied in the dog. The samples were perfused intra- aortically to obtain preferential perfusion of the left kidney in 25 dogs. Standard clearance techniques were used, associated in six dogs with sieving studies of 125I-labelled polyvinylpyrrolidone (125I-PVP) and with an extensive morphological study in 15 dogs. Renal effects were observed. (a) Renal effects in left kidneys. The perfusion with weakly cationized albumin (group 1) produced moderate proteinuria associated with the deposition of cationized albumin on the anionic sites of the basement membrane. Glomerular filtration rate (GFR) was unaltered. Perfusion with highly cationized samples (group 2) produced more severe proteinuria and a significant decrease in GFR. Glomerular permeability to 125I-PVP increased. Perfusion with the four samples of highest pI (group 3) was followed by anuria. (b) Renal effects in right kidneys. A retarded mild proteinuria appeared only in group 2 and group 3 animals without alteration of GFR. All the kidneys (group 1 included), with the exception of two (group 3), showed deposition of the protein in the anionic sites. The following extrarenal effects were observed essentially in group 2 and group 3 animals: erythrocyte agglutination and haemolysis, platelet aggregation and thrombocytopenia, and a decrease in plasma fibrogen level due to fibrinogen precipitation. These effects produced progressive obstruction in the glomerular capillaries, thus explaining the occurrence of anuria. The structural damage in group 2 and group 3 left kidneys bears remarkable resemblance to that observed in the fulminant form of the human so-called 'haemolytic-uraemic syndrome'. The neutralization alone of the fixed negative charges in the glomerular wall appears to produce only mild proteinuria, whereas the various extrarenal effects combine to produce more severe proteinuria associated with functional alteration and vascular obstruction.

Acute Kidney Injury↗
PubMed1980

Sieving studies in 'urea-induced nephropathy' in the dog.

1. The intrarenal infusion of concentrated urea after clamping of the renal artery produced immediate proteinuria in the dog. The predominant lesion on ultramicroscopy was destruction of the epithelial layer. Colloidal iron staining showed decreased fixed anionic charges in the capillary wall. 2. Sieving studies with neutral macromolecules such as 125I-labelled polyvinylpyrrolidone and [3H]dextran or an electronegatively charged polymer, [3H]dextran sulphate, showed a moderate increase in permeablility to the neutral tracers and a much more severe alteration of the lectrostatic barrier to the anionic polymer. The fractional clearance of dextran sulphate molecules increased to a greater extent than clearance of neutral dextrans of comparable size. 3. The shape of the curve relating the fractional clearance of dextran sulphate to molecular size is also modified in the contralateral kidney. This may be due to elevated plasma angiotensin II concentrations.

Animals↗
PubMed1976

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. 3. The effects of angiotensin II.

The effects of the intrarenal infusion of synthetic Asn1, val 5 angiotensin II (AII) (from 0.38 to 1 mug min-1) on the determinants of glomerular filtration have been studied. The intracapillary and transcapillary pressure gradients along the capillaries, together with 2 parameters characterizing the porosity of the membrane in terms of pore theory (r, radius of the pores and Ap/1, total pore area per unit of path length) were calculated from the analysis of the sieving curve of I125 PVP molecules (polyvinylpyrrolidone) according to a biomathematical model previously described. AII increased PGC, the intracapillary hydrostatic pressure, but more at the efferent end of the capillaries. Filtration pressure equilibrium was maintained. AII also decreased the water permeability coefficient, Kf. by decreasing Ap/1, r remaining constant. Our results were compared to those obtained from the direct measurements of PGC, using micropuncture techniqles in hydropenic and plasma loaded rats. The complete agreement between the two approaches confirms the validity of the method based on the analysis of the sieving data of neutral macromolecules to calculate the determinants of GFR.

Angiotensin II↗
PubMed1975

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. II. A physiological study in the normal dog.

The two theoretical models proposed previously to calculate the intracapillary and transcapillary glomerular pressure gradients from the sieving of macromolecules such as PVP have been used to analyse in 22 normotensive dogs the sieving curve relating the sieving coefficients, phi, to molecular size (phi: glomerular clearance of PVP fractions/GFR). Neither the "local c2" model-filtrate unmixed at the outer face of the capillaries walls--nor the constant c2 model-filtrate well mixed--allowed to obtain realistic values for the hemodynamical parameters. Indeed with the local c2 model, the best fit between calculated and experimental sieving curves could be obtained only by reversing the intracapillary pressure gradient; conversely the constant c2 model obliged to decrease the intracapillary pressure so abruptly along the capillaries, that retrofiltration took place in the distal parts of the vessels. This difficulty has been overcome by combining the two models; the so-called "hybrid model" considers that the filtrate is well mixed in the vicinity of the urinary pole only. The following results were obtained: 1. PGCa and PGCe (intracapillary pressures at the afferent and efferent extremities of the capillaries) equal to 49.7 +/- 1.03 and 41.8 +/- 1.00 mm Hg respectively. 2. Pressure equilibrium is generally reached at the efferent extremity of the vessels. 3. The slope of PGC (see article) varies inversely to FF. (filtration fraction). 4. The model, however, does not allow to rule out the possibility of retrofiltration.

Animals↗
PubMed1975

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. I. A mathematical model.

Determination of glomerular intracapillary and transcapillary pressure gradients from sieving data. A biomathematical model is described to calculate the intracapillary and transcapillary glomerular pressure gradients from the sieving coefficients (phi: fractional clearances/GFR) of macromolecules such as polyvinylpyrrolidone (PVP). Two differential equations have been developed. The first one calculates local values for GFR in terms of local values for PGC (intracapillary hydrostatic pressure) and pi (oncotic pressure). The second equation calculates the clearance of PVP equimolecular fractions, the sieving equations previously described (24) being used to derive the concentrations of PVP in the filtrate (c2). Two variants of the second equation have been considered, assuming the filtrate in contact with the membrane either "well stirred" or "unstirred" (constant c2 and local c2 gradient models respectively). Computer simulations have been used to illustrate how the sieving curve is modified when the five parameters on which depends the shape of the curve are changed one by one. The sieving curve relates phi to a(s) (hydrodynamically equivalent molecular radius). The determining parameters are: GFP, the mean effective glomerular filtration pressure, epsilon, the slope of the intracapillary pressure, FF, the filtration fraction, Cp0, the protein concentration in arterial plasma and r, the pore radius which is the only structural parameter involved when one assumes the glomerular membrane crossed by cylindrical pores of uniform size and length. The shape of the sieving curve is modified significantly enough by changing GFP, FF and r within reasonable limits, to make it possible to derive GFP and r from experimental sieving data for macromolecules such as PVP or dextrans.

Capillaries↗