The early proximal tubule: a high-capacity delivery-responsive reabsorptive site

1987 ◽  
Vol 252 (4) ◽  
pp. F573-F584 ◽  
Author(s):  
D. A. Maddox ◽  
F. J. Gennari
Keyword(s):  
Proximal Tubule ◽  
High Capacity ◽  
Proximal Convoluted Tubule ◽  
Dynamic State ◽  
Transport Capacity ◽  
Load Dependence ◽  
Almost All ◽  
Early Proximal Tubule

The proximal convoluted tubule is responsible for reclaiming almost all of the filtered bicarbonate, glucose, and amino acids, as well as 40% or more of the filtered sodium, fluid, chloride, and phosphate. Walker and co-workers demonstrated the importance of this nephron segment as a high-capacity transport site in the first mammalian micropuncture studies, and they suggested that the first portion of the proximal tubule played a particularly important role in the ability of the nephron to adapt to variations in filtered load. Since then, many studies using micropuncture and in vivo and in vitro microperfusion techniques have confirmed that the early proximal tubule has a higher transport capacity than the late proximal tubule for a number of solutes. Moreover, at least for bicarbonate, fluid, and chloride, the transport capacity is not static, but is in a dynamic state, adapting in response to changes in filtration. In this review we have focused on the high capacity and load dependence of early proximal bicarbonate and fluid reabsorption. In addition, we summarize the evidence for axial heterogeneity along the proximal convoluted tubule for transport of a variety of other solutes.

H+ gradient-driven dipeptide reabsorption in proximal tubule of rat kidney. Studies in vivo and in vitro

1987 ◽  
Vol 253 (3) ◽  
pp. F448-F457 ◽  
Author(s):  
S. Silbernagl ◽  
V. Ganapathy ◽  
F. H. Leibach
Keyword(s):  
Amino Acids ◽  
Proximal Tubule ◽  
Rat Kidney ◽  
High Capacity ◽  
Peptide Transport ◽  
Transport Systems ◽  
Negative Membrane Potential ◽  
Uptake Process

Microinfusion of glycylsarcosine into superficial nephron sections showed that the dipeptide was reabsorbed mainly in late portions of the rat proximal tubule. In vivo microperfusion data demonstrated a saturable, high-capacity, low-affinity dipeptide reabsorption mechanism that was inhibited by other peptides but not by amino acids or peptidase inhibitors. The reabsorption was enhanced by lowering the luminal pH from 7.5 to 5.5. In vitro studies with rat cortical brush-border vesicles showed that glycylsarcosine uptake was independent of a Na+ gradient and greater uptake occurred when the extravesicular pH was acidic compared with the intravesicular pH. An inward-directed H+ gradient stimulated glycylsarcosine uptake and caused a transient accumulation of the dipeptide inside the vesicles above the equilibrium value. The presence of a proton ionophore abolished the H+ gradient-dependent uptake. An inside-negative membrane potential stimulated the initial uptake of the dipeptide. The uptake process was saturable and inhibited by other peptides but not by amino acids. The vesicle studies also showed that there are at least two peptide transport systems functioning in these vesicles, one a high-affinity, low-capacity type and the other a low-affinity, high-capacity type.

scholarly journals Control of lettuce bottom rot by isolates of Trichoderma spp

2014 ◽  
Vol 40 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Zayame Vegette Pinto ◽  
Matheus Aparecido Pereira Cipriano ◽  
Amaury da Silva dos Santos ◽  
Ludwig Heinrich Pfenning ◽  
Flávia Rodrigues Alves Patrício
Keyword(s):  
Mycelial Growth ◽  
High Capacity ◽  
Dry Weight ◽  
Second Step ◽  
Trichoderma Spp ◽  
In Vivo Experiments ◽  
Bottom Rot ◽  
Trichoderma Isolates

Bottom rot, caused by Rhizoctonia solani AG 1-IB, is an important disease affecting lettuce in Brazil, where its biological control with Trichoderma was not developed yet. The present study was carried out with the aim of selecting Trichoderma isolates to be used in the control of lettuce bottom rot. Forty-six Trichoderma isolates, obtained with baits containing mycelia of the pathogen, were evaluated in experiments carried out in vitro and in vivo in a greenhouse in two steps. In the laboratory, the isolates were evaluated for their capabilities of parasitizing and producing toxic metabolic substances that could inhibit the pathogen mycelial growth. In the first step of the in vivo experiments, the number and the dry weight of lettuce seedlings of the cultivar White Boston were evaluated. In the second step, 12 isolates that were efficient in the first step and showed rapid growth and abundant sporulation in the laboratory were tested for their capability of controlling bottom rot in two repeated experiments, and had their species identified. The majority of the isolates of Trichoderma spp. (76%) showed high capacity for parasitism and 50% of them produced toxic metabolites capable of inhibiting 60-100% of R. solani AG1-IB mycelial growth. Twenty-four isolates increased the number and 23 isolates increased the dry weight of lettuce seedlings inoculated with the pathogen in the first step of the in vivo experiments.In both experiments of the second step, two isolates of T. virens, IBLF 04 and IBLF 50, reduced the severity of bottom rot and increased the number and the dry weight of lettuce seedlings inoculated with R. solani AG1-IB. These isolates had shown a high capacity for parasitism and production of toxic metabolic substances, indicating that the in vitro and in vivo steps employed in the present study were efficient in selecting antagonists to be used for the control of lettuce bottom rot.

Control of glycolysis in vertebrate skeletal muscle during exercise

1996 ◽  
Vol 270 (4) ◽  
pp. R821-R829 ◽  
Author(s):  
U. Krause ◽  
G. Wegener
Keyword(s):  
Gastrocnemius Muscle ◽  
Rana Temporaria ◽  
High Capacity ◽  
Repeated Exercise ◽  
Frog Rana Temporaria ◽  
Time Courses ◽  
Fructose 1,6 Bisphosphate ◽  
Assay Conditions

The gastrocnemius muscle of the frog (Rana temporaria) has a high capacity for anaerobic glycolysis from glycogen. Glycolytic metabolites and effectors of phosphofructokinase, particularly the hexose bisphosphates, were followed in muscle during exercise (swimming between 5 s and 5 min), recovery (rest for up to 2 h after 5 min of swimming), and repeated exercise (swimming for up to 60 s after 2 h of recovery). Glycogen phosphorylase and phosphofructokinase were swiftly activated with exercise. The hexose bisphosphates followed markedly different time courses. Fructose 1,6-bisphosphate was transiently increased in both exercise and repeated exercise. This appears to be an effect rather than a cause of phosphofructokinase activation. Glucose 1,6-biphosphate was accumulated only while phosphofructokinase was active and was unchanged at other times. Fructose 2,6-biphosphate showed a 10-fold transient increase on exercise in rested frogs, almost disappeared from the muscle during recovery, and did not change during repeated exercise. Fructose 2,6-biphosphate is a potent activator of phosphofructokinase in vitro under near physiological assay conditions, and it may serve this function also in vivo during exercise. Glucose 1,6-biphosphate could be an activator of phosphofructokinase in repeated exercise when fructose 2,6-biphosphate is not available.

METABOLISM OF RAM TESTICULAR SPERMATOZOA IN THE PRESENCE OF TESTOSTERONE AND RELATED STEROIDS

1970 ◽  
Vol 65 (3) ◽  
pp. 565-576 ◽  
Author(s):  
J. K. Voglmayr ◽  
R. N. Murdoch ◽  
I. G. White
Keyword(s):  
Aerobic Glycolysis ◽  
Rete Testis ◽  
Glycolytic Metabolism ◽  
Anaerobic Conditions ◽  
Aerobic Conditions ◽  
Testicular Spermatozoa ◽  
Almost All ◽  
Oxidation Of Glucose

ABSTRACT The effects of testosterone* and related steroids on the oxidative and glycolytic metabolism of freshly collected ram testicular spermatozoa and of spermatozoa stored under air in rete testis fluid for 3 days at 3°C have been studied. When freshly collected testicular spermatozoa were incubated with glucose under aerobic conditions only a small proportion of the utilized glucose could be accounted for as lactate. The addition of a number of steroids, including testosterone, androstanedione, 5β-androstanedione, androsterone, epiandrosterone and 5β-androsterone, greatly increased aerobic glycolysis, the oxidation of the substrate and the proportion of the utilized substrate converted to lactic acid. After 3 days storage at 3°C, testicular spermatozoa respired at a greater rate than spermatozoa freshly collected from the testes. Although the stimulating effect of steroids on aerobic glycolysis increased after storage, they depressed rather than stimulated the oxidation of glucose by stored testicular spermatozoa. With the exception of androstanedione, which slightly stimulated glycolysis, storage of testicular spermatozoa for 3 days in the presence of steroids did not significantly influence their subsequent metabolism when washed free of the steroids. Both freshly collected and stored ram testicular spermatozoa displayed a marked Pasteur effect, and utilized more glucose and produced more lactate under anaerobic than under aerobic conditions. In the absence of oxygen the steroids did not stimulate glycolysis to any extent. However, epiandrosterone depressed the glycolysis of freshly collected spermatozoa under anaerobic conditions and after storage, 5β-androsterone had a similar effect. Androstanedione, 5β-androstanedione, epiandrosterone and 5β-androsterone were the most effective steroids in altering the metabolism of testicular spermatozoa and, under almost all conditions of incubation, depressed the synthesis of amino acids from glucose. The results suggest that the effects of testosterone and related steroids in vitro may depend on the age of the spermatozoa after their release from the Sertoli cells; the steroid effects may have important consequences in vivo in relation to sperm maturation.

Effect of ionophore RO 2-2985 on the efflux of calcium from the rat nephron

1978 ◽  
Vol 235 (4) ◽  
pp. F381-F384 ◽  
Author(s):  
H. O. Senekjian ◽  
T. F. Knight ◽  
A. Ince ◽  
E. J. Weinman
Keyword(s):  
Proximal Tubule ◽  
Sodium Phosphate ◽  
Orthophosphoric Acid ◽  
Renal Tubule ◽  
Specific Effect ◽  
Early Proximal Tubule

The effect of the ionophore RO 2-2985 on the efflux of calcium from the renal tubule was studied employing the in vivo microinjection technique. Microinjection solutions contained either RO 2-2985 (E) or its diluent (C). Following microinjections into the early proximal tubule, urinary 45Ca recoveries averaged 10.1 +/- 1.9 (C) and 3.5 +/- 1.4% (E) (P is less than 0.005), while recoveries averaged 32.3 +/- 6.9 (C) and 24.9 +/- 6.5% (E) (P is less than 0.05) following microinjections into the late proximal tubule. To determine if the decreased recovery of calcium was a specific effect, the effect of RO 2-2985 on the efflux of sodium, phosphate, and 3-O-methyl-D-glucose was examined. Compared to controls, RO2-2985 did not affect the urinary recoveries of 22Na, [32P]orthophosphoric acid, or 3-O-methyl-D-[14C]glucose. These studies demonstrate that RO 2-2985 enhances the efflux of calcium microinjected into the proximal portions of the rat nephron.

scholarly journals Medicinal Plants Used for the Traditional Management of Diabetes in the Eastern Cape, South Africa: Pharmacology and Toxicology

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2759 ◽  
Author(s):  
Samuel Odeyemi ◽  
Graeme Bradley
Keyword(s):  
South Africa ◽  
Medicinal Plants ◽  
Scientific Evidence ◽  
Traditional Healers ◽  
Bioactive Molecules ◽  
Eastern Cape ◽  
Insulin Mimetic ◽  
Almost All

The use of medicinal plants for the management of diabetes mellitus is on the rise in the developing countries, including South Africa. There is increasing scientific evidence that supports the claims by the traditional healers. In this review, we compare the families of previously reported anti-diabetic plants in the Eastern Cape by rating the anti-diabetic activity, mode of action and also highlight their therapeutic potentials based on the available evidence on their pharmacology and toxicity. Forty-five plants mentioned in ethnobotanical surveys were subjected to a comprehensive literature search in the available electronic databases such as PubMed, ScienceDirect, Google Scholar and Elsevier, by using “plant name” and “family” as the keywords for the primary searches to determine the plants that have been scientifically investigated for anti-diabetic activity. The search returned 25 families with Asteraceae highly reported, followed by Asphodelaceae and Alliaceae. Most of the plants have been studied for their anti-diabetic potentials in vivo and/or in vitro, with most of the plants having a higher percentage of insulin release and inhibition against carbohydrate digesting enzymes as compared with insulin mimetic and peripheral glucose uptake. Almost all the investigated plants also inhibit oxidative stress as part of their hypoglycemic activity with less toxicity. However, the isolation of their bioactive molecules is still lacking. This review provides a resource to enable thorough assessments of the therapeutic profiles of available medicinal plants used for the management of diabetes in the Eastern Cape, South Africa. Further studies such as the identification of the active ingredients of potent plants still need to be carried out; this may lead to new molecules in drug discovery and development.

scholarly journals Cycle initiation and colony formation in culture by murine marrow cells with long-term reconstituting potential in vivo

Blood ◽  
1996 ◽  
Vol 88 (11) ◽  
pp. 4149-4158 ◽  
Author(s):  
M Trevisan ◽  
XQ Yan ◽  
NN Iscove
Keyword(s):  
Colony Formation ◽  
Interleukin 1 ◽  
Methyl Cellulose ◽  
Culture Conditions ◽  
Liquid Suspension ◽  
Almost All ◽  
Marrow Cells

Abstract This investigation was directed at separating long-term reconstituting (LTR) stem cells in normal murine marrow from hematopoietic precursors detectable in short-term assays in vitro and in vivo, and then at determining whether purified LTR cells could themselves form colonies in culture. To do so, it was first necessary to identify culture conditions that would induce their growth while preserving their long- term reconstituting capacity. Marrow was cultured with various cytokines in liquid suspension for 4 days, after which the surviving LTR activity was quantitated in a competitive in vivo assay. Activity was preserved near input levels with combined murine c-kit ligand (KL), interleukin-1 (IL-1), IL-6, and IL-11. When the cultures also included tritiated or unlabeled thymidine, LTR potential was eliminated, indicating that essentially all LTR cells were induced into cell cycle with these cytokines. To purify them, marrow was sorted on the basis of Ly6A expression and Rhodamine 123 retention. The Ly6AhiRh123ls fraction contained 85% of total recovered LTR activity but only 1% of the recovered cells measured by multilineage colony formation in spleens or in vitro. This fraction was cultured in methyl cellulose with KL, IL-1, IL-6, and IL-11 for 4 to 6 days, after which colonies were isolated and injected into mice. High levels of permanent reconstitution were achievable in sublethally irradiated W41/W41 mice after the injection of a single reconstituting unit, and limiting dilution analysis estimated the frequency of multilineage LTR at 1 in 11,200 unpurified adult marrow cells. In either lethally irradiated normal or sublethally irradiated W41/W41 mice, 1-year lymphomyeloid reconstitutions were obtained from 1 in 65 to 84 colonies of 2 to 16 dispersed cells, but not from larger colonies or those with clumped cells. The results establish that resting marrow LTR cells can be separated from almost all of the more advanced clonogenic cells that are still pluripotential, can be induced to cycle in culture by defined cytokines with preservation of their reconstituting potential, and can be manipulated and assayed efficiently at single-cell and colony levels.

scholarly journals DIPG-07. HIGH THROUGHPUT DRUG SCREENING IDENTIFIES POTENTIAL NEW THERAPIES FOR DIFFUSE INTRINSIC PONTINE GLIOMAS (DIPGs)

2020 ◽  
Vol 22 (Supplement_3) ◽  
pp. iii288-iii288
Author(s):  
Dannielle Upton ◽  
Santosh Valvi ◽  
Jie Liu ◽  
Nicole Yeung ◽  
Sandra George ◽  
...  
Keyword(s):  
High Throughput ◽  
Apoptotic Cell ◽  
Safety Data ◽  
Biologically Active ◽  
Orthotopic Model ◽  
High Throughput Drug Screening ◽  
Diffuse Intrinsic Pontine Gliomas ◽  
Almost All

Abstract DIPGs are the most devastating of all brain tumors. There are no effective treatments, hence almost all children will die of their tumor within 12 months. There is an urgent need for novel effective therapies for this aggressive tumor. We performed a high-throughput drug screen with over 3,500 biologically active, clinically approved compounds against a panel of neurosphere-forming DIPG cells. We identified 7 compounds- auranofin, fenretinide, ivermectin, lanatoside, parthenolide, SAHA and mefloquine- that were confirmed to have potent anti-tumor activity against a panel of DIPG-neurospheres, with minimal effect on normal cells. Using cytotoxicity and clonogenic assays, we found that these drugs were able to inhibit DIPG-neurosphere proliferation and colony formation in-vitro. To determine whether the in-vitro efficacy could be replicated in-vivo, we tested the activity of each of these compounds in an orthotopic DIPG model. Of the agents tested, fenretinide and SAHA were the most active anti-tumor agents, significantly enhancing the survival of tumor bearing animals. Mechanistic studies showed fenretinide enhancing apoptotic cell death of DIPG cells via inhibition of PDGFRa transcription and downregulation of the PI3K/AKT/MTOR pathway. We therefore examined the therapeutic efficacy of fenretinide using a second orthotopic model with PDGFRa amplification. We used two different Fenretinide formulations (LYM-X-Sorb and NanoMicelle) which were found to enhance survival. Fenretinide is clinically available with safety data in children. Validation of the activity of Fenretinide in PDGFRa-amplified or overexpressed DIPGs will lead to the development of a clinical trial, allowing the advancement of fenretinide as potentially the first active therapy for DIPG.

scholarly journals Expression and Role of Parathyroid Hormone-Related Protein in Human Renal Proximal Tubule Cells during Recovery from ATP Depletion

1999 ◽  
Vol 10 (2) ◽  
pp. 238-244
Author(s):  
ADOLFO GARCÍA-OCAÑA ◽  
SUSAN C. GALBRAITH ◽  
SCOTT K. VAN WHY ◽  
KAI YANG ◽  
LINA GOLOVYAN ◽  
...  
Keyword(s):  
Proximal Tubule ◽  
Recovery Period ◽  
Ischemic Injury ◽  
Atp Depletion ◽  
Proximal Tubule Cell ◽  
Pthrp Expression ◽  
Human Proximal Tubule Cell

Abstract. Parathyroid hormone (PTH)-related protein (PTHrP) is widely expressed in normal fetal and adult tissues and regulates growth and differentiation in a number of organ systems. Although various renal cell types produce PTHrP, and PTHrP expression in rat proximal renal tubules is upregulated in response to ischemic injury in vivo, the role of PTHrP in the kidney is unknown. To study the effects of injury on PTHrP expression and its consequences in more detail, the immortalized human proximal tubule cell line HK-2 was used in an in vitro model of ATP depletion to mimic in vivo renal ischemic injury. These cells secrete PTHrP into conditioned medium and express the type I PTH/PTHrP receptor. Treatment of confluent HK-2 cells for 2 h with substrate-free, glucose-free medium containing the mitochondrial inhibitor antimycin A (1 μM) resulted in 75% depletion of cellular ATP. After an additional 2 h in glucose-containing medium, cellular ATP levels recovered to approximately 75% of baseline levels. PTHrP mRNA levels, as measured in RNase protection assays, peaked at 2 h into the recovery period (at four times baseline expression). The increase in PTHrP mRNA expression was correlated with an increase in PTHrP protein content in HK-2 cells at 2 to 6 h into the recovery period. Heat shock protein-70 mRNA expression was not detectable under baseline conditions but likewise peaked at 2 h into the recovery period. Treatment of HK-2 cells during the recovery period after injury with an anti-PTHrP(1-36) antibody (at a dilution of 1:250) resulted in significant reductions in cell number and uptake of [3H]thymidine, compared with nonimmune serum at the same titer. Similar results were observed in uninjured HK-2 cells. It is concluded that this in vitro model of ATP depletion in a human proximal tubule cell line reproduces the pattern of gene expression previously observed in vivo in rat kidney after ischemic injury and that PTHrP plays a mitogenic role in the proliferative response after energy depletion.

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