The excretion of protein by the mammalian kidney

Women Neuroscientist Disciples of Pío del Río-Hortega: the Cajal School Spreads in Europe and South America

Pio del Rio-Hortega was not only the discoverer of the microglia and oligodendroglia but also possibly the most prolific mentor of all Santiago Ramon y Cajal’s disciples (Nobel awardee in Physiology or Medicine 1906 and considered as the father of modern Neuroscience). Among Río-Hortega’s mentees, three exceptional women are frequently forgotten, chronologically: Pio’s niece Asunción Amo del Río who worked with Río-Hortega at Madrid, Paris, and Oxford; the distinguished British neuropathologist Dorothy Russell who also worked with Don Pío at Oxford; and Amanda Pellegrino de Iraldi, the last mentee in his career. Our present work analyzes the figures of these three women who were in contact and collaborated with Don Pío del Río-Hortega, describing the influences received and the impact on their careers and the History of Neuroscience. The present work completes the contribution of women neuroscientists who worked with Cajal and his main disciples of the Spanish Neurological School both in Spain (previous work) and in other countries (present work).

A recycling anti-transferrin receptor-1 monoclonal antibody as an efficient therapy for erythroleukemia through target up-regulation and antibody-dependent cytotoxic effector functions

Targeting transferrin receptor 1 (TfR1) with monoclonal antibodies is a promising therapeutic strategy in cancer as tumor cells often overexpress TfR1 and show increased iron needs. We have re-engineered six anti-human TfR1 single-chain variable fragment (scFv) antibodies into fully human scFv₂-Fcγ1 and IgG1 antibodies. We selected the more promising candidate (H7), based on its ability to inhibit TfR1-mediated iron-loaded transferrin internalization in Raji cells (B-cell lymphoma). The H7 antibody displayed nanomolar affinity for its target in both formats (scFv₂-Fcγ1 and IgG1), but cross-reacted with mouse TfR1 only in the scFv₂-Fc format. H7 reduced the intracellular labile iron pool and, contrary to what has been observed with previously described anti-TfR1 antibodies, upregulated TfR1 level in Raji cells. H7 scFv₂-Fc format elimination half-life was similar in FcRn knock-out and wild type mice, suggesting that TfR1 recycling contributes to prevent H7 elimination in vivo. In vitro, H7 inhibited the growth of erythroleukemia and B-cell lymphoma cell lines (IC₅₀ 0.1 µg/mL) and induced their apoptosis. Moreover, the Im9 B-cell lymphoma cell line, which is resistant to apoptosis induced by rituximab (anti-CD20 antibody), was sensitive to H7. In vivo, tumor regression was observed in nude mice bearing ERY-1 erythroleukemia cell xenografts treated with H7 through a mechanism that involved iron deprivation and antibody-dependent cytotoxic effector functions. Therefore, targeting TfR1 using the fully human anti-TfR1 H7 is a promising tool for the treatment of leukemia and lymphoma.

Phyllis M. Tookey Kerridge and the science of audiometric standardization in Britain

The provision of standardized hearing aids is now considered to be a crucial part of the UK National Health Service. Yet this is only explicable through reference to the career of a woman who has, until now, been entirely forgotten. Dr Phyllis Margaret Tookey Kerridge (1901-1940) was an authoritative figure in a variety of fields: medicine, physiology, otology and the construction of scientific apparatus. The astounding breadth of her professional qualifications allowed her to combine features of these fields and, later in her career, to position herself as a specialist to shape the discipline of audiometry. Rather than framing Kerridge in the classic 'heroic-woman' narrative, in this article we draw out the complexities of her career by focusing on her pursuit of standardization of hearing tests. Collaboration afforded her the necessary networks to explore the intricacies of accuracy in the measurement of hearing acuity, but her influence was enhanced by her ownership of Britain's first Western Electric (pure-tone) audiometer, which she placed in a specially designed and unique 'silence room'. The room became the centre of Kerridge's hearing aid clinic that, for the first time, allowed people to access free and impartial advice on hearing aid prescription. In becoming the guardian expert and advocate of the audiometer, Kerridge achieved an objectively quantified approach to hearing loss that eventually made the latter an object of technocratic intervention.

Targeting Glioma with a Dual Mode Optical and Paramagnetic Nanoprobe across the Blood-brain Tumor Barrier

In brain tumors, delivering nanoparticles across the blood-tumor barrier presents major hurdles. A clinically relevant MRI contrast agent, GdDOTA and a near-infrared (NIR) fluorescent dye, DL680 were conjugated to a G5 PAMAM dendrimer, thus producing a dual-mode MRI and NIR imaging agent. Systemic delivery of the subsequent nano-sized agent demonstrated glioma-specific accumulation, probably due to the enhanced permeability and retention effect. In vivo MRI detected the agent in glioma tissue, but not in normal contralateral tissue; this observation was validated with in vivo and ex vivo fluorescence imaging. A biodistribution study showed the agent to have accumulated in the glioma tumor and the liver, the latter being the excretion path for a G5 dendrimer-based agent.

Overcoming the challenges in the effective delivery of chemotherapies to CNS solid tumors

Locoregional therapies, such as surgery and intratumoral chemotherapy, do not effectively treat infiltrative primary CNS solid tumors and multifocal metastatic solid tumor disease of the CNS. It also remains a challenge to treat such CNS malignant solid tumor disease with systemic chemotherapies, although these lipid-soluble small-molecule drugs demonstrate potent cytotoxicity in vitro. Even in the setting of a 'normalized' tumor microenvironment, small-molecule drugs do not accumulate to effective concentrations in the vast majority of tumor cells, which is due to the fact that small-molecule drugs have short blood half-lives. It has been recently shown that drug-conjugated spherical lipid-insoluble nanoparticles within the 7-10 nm size range can deliver therapeutic concentrations of drug fraction directly into individual tumor cells following systemic administration, since these functionalized particles maintain peak blood concentrations for several hours and are smaller than the physiologic upper limit of pore size in the VEGF-derived blood capillaries of solid tumors, which is approximately 12 nm. In this article, the physiologic and ultrastructural basis of this novel translational approach for the treatment of CNS, as well as non-CNS, solid cancers is reviewed.

Occurrence of milk proteins in the urine of cows during an extended milking interval

Immunological methods have been used to test samples of urine from 5 cows for the presence of milk proteins. None could be detected when the cows were milked twice daily at the usual intervals, but during an extended milking interval α-lactalbumin was found in the urine of all 5 cows and β-lactoglobulin in the urine of 2 cows. The urine of one cow during and after a milking interval of 39 h contained 1·63 g α-lactalbumin, 1·12 g β-lactoglobulin and a small amount of casein. One of the factors affecting the transfer of these milk constituents from the udder to the urine appears to be their molecular weight.

Proteinuria related to hyperproteinemia in dogs following plasma given parenterally; a renal threshold for plasma proteins

Proteinuria in normal dogs can be produced at will by parenteral injections of dog plasma. As the plasma injections are continued the plasma protein concentration rises and at some point protein begins to appear in the urine. The level of plasma protein concentration at which proteinuria appears in normal dogs ranges from 9.6 to 10.4 gm. per cent. This may be termed the renal threshold for proteinuria. Repeat experiments in the same dog show threshold levels to be practically identical. An interval of days (4 to 26 days) has been noted between the start of plasma protein injections and the appearance of the proteinuria. Larger doses of plasma shorten this interval and the critical plasma protein level is attained sooner. Considerable amounts of protein may appear in the urine—298 gm. protein during a 52 day period in one instance studied—yet the urine clears in 1 to 4 days after cessation of protein injections. Autopsy shows undamaged kidneys. Maximal levels of plasma protein concentration range from 10.0 to 11.5 gm. per cent. The highest levels are usually associated with maximal output of protein in the urine. It seems clear that plasma proteins readily pass cell barriers (or membranes) within the body, including the endothelium and epithelium of the renal glomerulus.

The fate of injected Bence Jones protein

Bence Jones protein injected into rabbits was excreted rapidly into the urine. The excreted protein retained the physicochemical and immunochemical properties of the injected Bence Jones protein. In spite of the rapid excretion, a significant portion of the injected Bence Jones protein was found to be metabolized. After reinjection of radioactive Bence Jones protein into the donor patient, only a little radioactivity was recovered in the urinary protein. The implications of these results are discussed.

The Croonian lecture - Processes of urine formation

I know of no higher honour which can come to an American laboratory than that which is implied in the invitation to a member of its staff to deliver a Croonian lecture before the Royal Society. The obligations which acceptance entails are heavy, particularly so in the present instance, inasmuch as the foundations of knowledge concerning the subject of which I am to speak have been laid by past fellows of this Society and its chief developments have been made by their successors. In accordance with the terms of the Council's invitation, what I shall have to say is based upon a series of connected studies which have been in progress in the Laboratory of Pharmacology of the University of Pennsylvania for more than twenty years and is the product of a succession of collaborations which it has been my privilege to enjoy.

Ultrastructure of canine urinary bladder carcinoma

Luminal and intraepithelial asymmetric unit membrane plaques were found in the urinary bladder urothelium of normal dogs. Tight junctions were found only at the apical poles of the luminal cells. In four dogs with spontaneous urinary bladder carcinomas the asymmetric unit membrane plaques were replaced by symmetric unit membrane. In the neoplastic luminal cells the tight junctions were partially attenuated. Invasive and metastatic neoplastic cells had some tight junction at the stromal interface. Some gap junctions were seen in the normal urothelium but not in the neoplastic cells. The amount of desmosomes in the neoplastic cells varied according to their direction of differentiation (transitional, squamous or glandular).

The morphological basis of the glomerular permeability to proteins

The morphological basis of the glomerular permeability to proteins is reviewed and a survey is given of the studies done with ultrastructural tracer substances. In the normal GCW two structures have been considered important as a possible barrier to macromolecules: the GBM and the epithelial slit pore and slit diaphragm. The currently available evidence indicates that under normal conditions most plasma proteins do not penetrate beyond the subendothelial layer of the GCW. However, it is probable that the epithelial slit diaphragm acts as a secomdary barrier to macromolecules. In glomerular proteinurai the transport of anionic macromolecules through the GCW is increased, but the passage of uncharged macromolecules (PVP, dextran) is less than in the normal glomerulus. The number of anionic sites in the GCW is much smaller than in the normal glomerulus and there is a change in the normal arrangement of the foot processes and a decrease in the number of slit pores. At present, it is still incompletely understood in which way these changes are related to each other. Assuming the presence of focal leaks in the GCW, a possible sequence of events leading to glomerular proteinuria is discussed.

Ochratoxin A and citrinin induced nephrosis in Beagle dogs. I. Clinical and clinicopathological features

Ochratoxin A and citrinin, both mycotoxins, were given separately and combined to young Beagle dogs for 14 days. Ochratoxin A, 0.1 and 0.2 mg/kg, was given by capsule, and citrinin, 5 and 10 mg/kg, was dissolved in ethanol and given by intraperitoneal injection. Clinical signs of toxicosis in dogs given 10 mg/kg citrinin and the higher combined doses included anorexia, retching, tenesmus, weight loss, prostration and death. Severity of the clinical disease and mortality were increased when the mycotoxins were combined, which indicated synergism. The clinicopathological abnormalities reflected renal damage, in that glutamic oxaloacetic transaminase and lactic dehydrogenase increased in the urine of the dogs with clinical signs of poisoning. Serum lactic dehydrogenase was increased in dogs given 10 mg/kg citrinin. Cellular and granular casts, ketones, protein and glucose were in the urine of dogs given large doses of citrinin alone or combined with ochratoxin A. Serum concentrations of sodium, potassium and chloride in the dogs given high doses of each group.

Permselectivity of the glomerular capillary wall: III. Restricted transport of polyanions

The clearance of albumin relative to that of inulin is greatly exceeded by that of uncharged dextrans of the same effective molecular radius (approximately 36A), less than 0.01 vs. 0.20 in normal hydropenic rats. This marked difference in fractional clearances of albumin and neutral dextran suggests that some factor in addition to molecular size retards the transglomerular passage of albumin. Since albumin is a polyanion in physiological solution, we tested the effect of charge on macromolecular permeability by infusing the anionic polymer, dextran sulfate (approximately 2.3 sulfate groups per glycosyl residue), into seven normal hypropenic Munich-Wistar rats. For dextran sulfate with an effective radius of approximately 36A, the fractional clearance was reduced essentially to that found for albumin (approximately 0.01). This enhanced restriction of dextran sulfate, relative to neutral dextran, was also noted for smaller and larger dextran sulfate molecules. These differences in the transport of dextran sulfate vs. dextran suggest electrostatic repulsion of charged macromolecules by some component of the glomerular capillary wall, perhaps the negatively charged sialoprotein which coats glomerular epithelial cells. Loss of this polyanionic coat, as has been reported to occur in proteinuric disorders, might thereby account for the enhanced transmural passage of albumin.

Urinary lactic dehydrogenase isoenzyme 5 in the differential diagnosis of kidney and bladder infections

Urinary lactic dehydrogenase (U-LDH) isoenzyme assays were performed on ch2) as well as normal controls (N = 24). Docuemntation of bladder and kidney infection was accomplished by means of the bladder washout test, culture of ureteric urine (in patients with urinary diversion), kidney function studies including the maximal urine concentration test, clinical symptomatology and radiologic appearance of the urinary tract. Total U-LDH in normal children (10.8 +/- 1 mU/ml) was lower than in patients with bladder (27.0 +/- 3.9 mU/ml) or kidney (226 +/- 67.3 mU/ml) infections (P less than 0.005). In normal children isoenzymes 1 and 2 predominated (LDH-1 migrates fastest to anode -- fast zone pattern). In patients with bladder infections, the isoenzyme patterns varied but the concentration of isoenzyme 5 (3.1 +/- 0.8 mU/ml) was lower (P less than 0.005) than in patients with kidney infections (120 +/- 39 mU/ml). In the latter, isoenzymes 4 and 5 predominated (slow zone pattern). Since overlap between kidney and bladder infections regarding isoenzyme 5 concentrations (at 3 SD) occurred in only one individual (patient 37), a correct differential diagnosis using U-LDH-5 alone would have been possible in 94% of the children with pyelonephritis or 97% of the total patient population (kidney + bladder).

Ochratoxicosis in Beagle dogs. I. Clinical and clinicopathological features

Rice culture of Aspergillus ochraceus that contained ochratoxin A or pure crystalline ochratoxin A was administered orally daily to 23 young male Beagle dogs. Six other young male Beagles served as controls. Most dogs were killed in extremis on or before day 14 after receiving a daily oral dose of ochratoxin A, 0.2–3.0 mg/kg body weight. Consistent clinical features of the mycotoxicosis were anorexia, weight loss, emesis, tenesmus, passage of clots of blood-stained mucus from the rectum, rectal temperature up to 107°F, tonsillitis, dehydration and prostration. The prominent clinicopathological features of the toxicosis were a reflection of renal damage. The urine had a specific gravity as low as 1.004 and contained granular casts, necrotic renal epithelium, and concentrations above normal of protein, glucose, lactic dehydrogenase, isocitric dehydrogenase, leucine aminopeptidase, glutamic-pyruvic transaminase, glutamic-oxalacetic transaminase, and alkaline phosphatase. Serum concentrations of these enzymes did not change. Concentrations of blood urea nitrogen remained, with two exceptions, within the normal range, but the concentrations of blood glucose declined terminally. Serum concentrations of the liver-specific enzyme, γ-glutamyl transpeptidase and sulfabromophthalein dye retention time did not indicate hepatic dysfunction.

Glomerular permeability. Ultrastructural cytochemical studies using peroxidases as protein tracers

1. Glomerular permeability was studied by ultrastructural cytochemistry, using as protein tracers two intravenously injected peroxidases of differing molecular weight. 2. Horseradish peroxidase (molecular weight 40,000) passed rapidly through the endothelial fenestrae, across the basement membrane, and through the epithelial slits into the urinary space. Human myeloperoxidase (molecular weight 160,000 to 180,000) also passed rapidly through the endothelial fenestrae and across the basement membrane, but was impeded at the level of the epithelial slits. Both proteins were taken up in large amounts by the mesangial cells. 3. The present findings indicate that the epithelial slits are the primary filtration barrier responsible for the differential permeability to proteins of varying molecular size. 4. The observations also support the concept that an important function of the mesangial cells is the incorporation and disposal of glomerular filtration residues.

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The object of this study was that of getting additional insight into the mechanism of proteinuria through analysis of the permeability of the glomerular filter for higher molecular weight proteins in patients with proteinuria resulting from diabetic nephropathy. Fifty hospitalized patients with insulin-requiring diabetes mellitus were selected according to the presence of proteinuria and divided into two groups: group I, with or without only minor symptoms of diabetic angiopathy; group II, with moderate to severe diabetic nephropathy and retinopathy grades 1 to 3. In all patients the urinary excretion of haptoglobins (Hp) and of isoagglutins (IA) was measured, as well as the Hp level in the serum and the overall profile of serum and urine proteins. The results indicate that the urinary excretion of Hp and IA could be correlated to some extent with the severity of diabetic nephropathy, whereas the serum level of Hp failed to exhibit any clear-cut anomalies in the presence of diabetic angiopathy. In patients with severe nephropathy, the albumin/globulin ratio in the urine was increased approximately twofold over that in serum, despite a grossly unaltered profile of serum proteins. These results suggest that the "functional pore size" of the renal filter is increased in diabetic nephropathy, but that the mechanism of proteinuria also involves degradation of serum proteins during passage through the kidney.

Renal tubular secretion of human plasma proteins and Bence-Jones protein

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The fate of some alum-precipitated proteins after intramuscular injection

Bovine serum albumin, ovalbumin and rabbit serum albumin, trace-labelled with ¹³¹I and alum-precipitated have been injected intramuscularly into rabbits and the concentration of protein-bound and non-protein-bound ¹³¹I in their plasma and the daily excretion of ¹³¹I in the urine have been determined for periods up to 14 days. Following injection of bovine serum albumin, there is a single peak in the protein-bound ¹³¹I concentration in the plasma 4–6 days later. There are two peaks in the non-protein-bound ¹³¹I concentration in the plasma and the urinary excretion of ¹³¹I, one coincident with the plasma protein-bound ¹³¹I peak, and the other a few days later when there is no protein-bound ¹³¹I in the plasma. It is concluded that the two peaks in plasma non-protein-bound ¹³¹I and urinary ¹³¹I excretion are caused by non-immune and immune phases of catabolism of the antigen. Results of experiments in which alum-precipitated, trace-labelled bovine serum albumin were injected into rabbits in the anamnestic state are consistent with this interpretation. Results after injection of ovalbumin are less clear cut.

About half of an intramuscularly injected dose of alum-precipitated, trace-labelled bovine serum albumin is lost from the legs of mice within 24 hours: thereafter the rate of loss of the protein is much slower.

Renal, Transcapillary, Net Exchange in the Dog

The transcapillary net exchanges of inulin, para-aminohippurate, thiocyanate and heavy water were determined in the renal circulation. It was found that the tracer substances larger than heavy water diffused more freely through renal than through previously studied peripheral or pulmonary capillaries. The results are consistent with the concept of a larger pore size in renal capillaries.

The molecular weights of the proteins of normal and nephrotic sera and nephrotic urine, and a comparison of selective ultrafiltrates of serum proteins with urine proteins

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