Urine Formation Research Articles

Topography of the urinary organs in the Baikal seal

The urinary system of aquatic mammals plays an important role in maintaining the body’s homeostasis. Features in the structure and topography of the urinary organs are associated with the habitat and adaptation of the organism of aquatic animals to it. Interest in studying the features of the topography of organs and the structure of the organism as a whole, as well as the organs of urine formation and excretion in particular, is presented by the Baikal seal, given its freshwater lifestyle. The goal was to describe the species-specific features of the topography of the kidneys, ureters, bladder and urethra in male and female Baikal seals. The object of the study was both live individuals and carcasses of the Baikal seal (Phoca sibirica) aged from 1.5 to 3 years. The animals were examined at the Baikal Seal Aquarium LLC and the Irkutsk City Animal Disease Control Station. The cadaver material was collected under the program of the Russian Federal Agency for Fisheries, as well as research and development, experimental design and technological developments (R&D and R&D) from 2014, 2017, 2020. The study material was the organs of the urinary system: kidneys, ureters, bladder, urethra. The studies were carried out using various anatomical methods: autopsy of cadaver material with examination and fixation of syntopy, skeletotopy, holotopy and anatomical dissection, ultrasound diagnostics and multispiral computed tomography.

Non-voltage-gated Ca2+ channel signaling in glomerular cells in kidney health and disease.

Positioned at the head of the nephron, the renal corpuscle generates a plasma ultrafiltrate to initiate urine formation. Three major cell types within the renal corpuscle, the glomerular mesangial cells, podocytes, and glomerular capillary endothelial cells, communicate via endocrine- and paracrine-signaling mechanisms to maintain the structure and function of the glomerular capillary network and filtration barrier. Ca2+ signaling mediated by several distinct plasma membrane Ca2+ channels impacts the functions of all three cell types. The past two decades have witnessed pivotal advances in understanding of non-voltage-gated Ca2+ channel function and regulation in the renal corpuscle in health and renal disease. This review summarizes the current knowledge of the physiological and pathological impact of non-voltage-gated Ca2+ channel signaling in mesangial cells, podocytes and glomerular capillary endothelium. The main focus is on transient receptor potential and store-operated Ca2+ channels, but ionotropic N-methyl-d-aspartate receptors and purinergic receptors also are discussed. This update of Ca2+ channel functions and their cellular signaling cascades in the renal corpuscle is intended to inform the development of therapeutic strategies targeting these channels to treat kidney diseases, particularly diabetic nephropathy.

8-l-Cystinyl Bis(1,8-diazaspiro[4.5]decane) as an Orally Bioavailable l-Cystine Crystallization Inhibitor for Cystinuria.

Cystinuria, a rare genetic disorder, is characterized by defective l-cystine reabsorption from the renal proximal tubule, resulting in abnormally high concentrations of l-cystine and subsequent l-cystine crystallization in urine and stone formation in the urinary tract. Inhibition of l-cystine crystallization by l-cystine diamides such as LH708 (2) represents a promising new approach to prevent stone formation in patients with cystinuria. While 2 shows promising in vivo efficacy and a good safety profile in a Slc3a1-knockout mouse model of cystinuria, further structural modification of 2 led to the discovery of 8-l-cystinyl bis(1,8-diazaspiro[4.5]decane) (LH1753, 3) incorporating a bioisosteric spiro bicyclic diamine 1,8-diazaspiro[4.5]decane for the N-methylpiperazine terminal groups in 2 as a promising candidate with 3 being about 120× more potent than l-cystine dimethyl ester (CDME, 1) and about 2× more potent than 2 in inhibiting l-cystine crystallization. Furthermore, 3 demonstrated good oral bioavailability and in vivo efficacy in preventing l-cystine stone formation in the Slc3a1-knockout mouse model of cystinuria.

Resident macrophages in kidney medulla are critical in cleaning intratubular sedimentary particles

During the passage of the glomerulus filtrate through the renal tubular system, various microscopic sedimentary particles, including mineral crystals resulting from urine concentration, are generated. Dislodging these particles in the intratubular compartment is critical to ensure free flow of filtrate and the final formation of urine. However, it is generally assumed that particle removal is solely attributed to urine flush and whether there is other devoted mechanism is unknown. In this study, we uncovered that most macrophages in the kidney medulla of mice constitutively formed transepithelial protrusions and were “sampling” urine contents, as revealed by high-resolution confocal microscopy. This phenomenon was less pronounced in the cortex. The transepithelial protrusions of medulla macrophages were formed in a transcellular route instead of between epithelial cells, so the overall junctional architecture of tubular epithelium was intact. Juxtatubular macrophages were effcient in sequestering and phagocytosing intraluminal particles through their transepithelial protrusions, and would make transmigration to the tubule lumen to "escort" the excretion of sediment particles, as documented by live two-photon microscopy recording. In accordance, abundant particle-carrying macrophages could be detected in the urine. As such, specifically depleting renal macrophages precipitated kidney stone formation in a hyperoxaluria model. Moreover, naïve mice with underrepresentation of renal macrophages were prone to developing various intratubular sediments. RNA-seq analyses unveiled that medulla macrophages were enriched with genes associated with cell adhesion relative to cortex macrophages. Mechanistically, we found that integrin β1-mediated ligation to the tubular epithelium was crucial to the transepithelial behaviors of medulla macrophages, as evidenced by both pharmacological and genetic approaches. This study unveils a previously unappreciated role of renal medulla macrophages in keeping the tubular system unobstructed by removing intratubular particles. These findings may pave way for developing novel therapeutics for nephrolithiasis. National Natural Science Foundation of China (32170894, 31970898 and 82170441) and the Natural Science Foundation of Zhejiang Province (LZ22C080001). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Neurogenic, non-obstructive urinary retention: diagnosis and treatment

Neurogenic, non-obstructive urinary retention has a varied aetiology. The condition can be caused by central-nervous diseases as well as by disorders of the peripheral nervous system. The formation of residual urine may lead to considerable problems that can have a significant impact on a patient's everyday life. A treatment appropriate for the lower urinary tract dysfunction and suited to the patient's situation in life is only possible if a differentiated diagnostic evaluation has been performed. Both conservative and surgical therapeutic strategies are available, while drug treatment approaches are less relevant. Neuromodulative procedures are particularly suitable for causal treatment of the dysfunction. For patients requiring artificial bladder voiding, intermittent self-catheterization is generally preferable to using an indwelling catheter.

Protein localization of aquaporins in the adult female disease vector mosquito, Aedes aegypti.

The female Aedes aegypti mosquito is a vector for several arboviral diseases, due to their blood feeding behavior and their association with urban communities. While ion transport in Ae. aegypti has been studied, much less is known about mechanisms of water transport. Rapid water and ion excretion occurs in the adult female mosquito post blood meal and involves a set of organs including the midgut, Malpighian tubules (MTs), and hindgut. The MTs are responsible for the formation of primary urine and are considered the most important site for active transport of ions. Within the cells of the MTs, along with various ion transporters, there are aquaporin water channels that aid in the transport of water across the tubule cell membrane. Six aquaporin genes have been molecularly identified in Ae. aegypti (AQP1-6) and found to be responsible for the transport of water and in some cases, small solutes such as glycerol. In this study, we used immunohistochemistry to localize AaAQP1, 2, 4, 5, and 6 in the adult female Ae. aegypti, in non-blood fed and post blood feeding (0.5 and 24hr) conditions. We further examined the main water transporting aquaporin, AaAQP1, using western blotting to determine protein abundance changes in isolated MTs pre- and post-blood feeding. Using fluorescence in situ hybridization, aqp1 mRNA was found exclusively in the principal cells of female MTs. Finally, we used immunogold staining with transmission electron microscopy to determine subcellular localization of AaAQP1 in the Malpighian tubules under non-blood fed conditions. Interestingly, AaAQP1 was found to be predominantly in the principal cells of the MTs, dispersed throughout the brush border; however, there was also evidence of some AaAQP1 localization in the stellate cells of the MTs.

Identification of countercurrent tubule-vessel arrangements in the early development of mouse kidney based on immunohistochemistry and computer-assisted 3D visualization.

Nephron loop-vessel countercurrent arrangement in the medulla provides the structural basis for the formation of concentrated urine. To date, the morphogenesis of it and relevant water and solutes transportation has not been fully elucidated. In this study, with immunohistochemistry for aquaporins (AQP) and Na-K-2Cl co-transporter (NKCC2), as well as 3D visualization, we noticed in embryonic day 14.5 kidneys that the countercurrent arrangement of two pairs of loop-vessel was established as soon as the loop and vessel both extended into the medulla. One pair happened between descending limb and ascending vasa recta, the other occurred between thick ascending limb and descending vasa recta. Meanwhile, the immunohistochemical results showed that the limb and vessel expressing AQP-1 such as descending thick and thin limb and descending vasa recta was always accompanied with AQP-1 negative ascending vasa recta or capillaries and thick ascending limb, respectively. Moreover, the thick ascending limb expressing NKCC2 closely contacted with descending vasa recta without expressing NKCC2. As kidney developed, an increasing number of loop-vessels in countercurrent arrangement extended into the interstitium of the medulla. In addition, we observed that the AQP-2 positive ureteric bud and their branches were separated from those pairs of tubule-vessels by a relatively large and thin-walled veins or capillaries. Thus, the present study reveals that the loop-vessel countercurrent arrangement is formed at the early stage of nephrogenesis, which facilitates the efficient transportation of water and electrolytes to maintain the medullary osmolality and to form a concentrated urine.

Biophysical characterization and insights into the oligomeric nature of CD2-associated protein.

Glomerular podocytes are specialized epithelial cells localized to the blood-urine interface of the kidney. Podocyte slit-diaphragm (SD), a size-and-charge-selective junction, is instrumental in blood ultrafiltration and the formation of protein-free urine. The SD consists of macromolecular complexes of several proteins, such as nephrin, podocin, and CD2-associated protein (CD2AP). CD2AP is an adapter protein and is considered to be crucial for the integrity of SD. Mutations in the SD proteins cause nephrotic syndrome (NS), characterized by proteinuria. SD proteins' structural features must be elucidated to understand the mechanism of proteinuria in NS. In this study, we expressed, purified, and biophysically characterized heterologously expressed human CD2AP. Codon-optimized human CD2AP was expressed in E. coli Rosetta cells. The recombinant protein was induced with 1 mM IPTG and purified by Ni-NTA affinity chromatography. Analytical size-exclusion chromatography, blue native-PAGE, circular dichroism, and fluorescence spectroscopy were performed to decipher the oligomeric nature, secondary structural content, and tertiary packing of CD2AP. Our analysis revealed that CD2AP adopts a predominantly disordered secondary structure despite exhibiting moderate tertiary packing, characterized by low helical and β-sheet content. CD2AP readily assembles into homo-oligomers, with octamers and tetramers constituting the primary population. Interestingly, the inherent flexibility of CD2AP's secondary structural elements appears resistant to thermal denaturation. Frameshift mutation (p.K579Efs*7) that leads to loss of the coiled-coil domain promotes aberrant oligomerization of CD2AP through SH3 domains. We successfully expressed full-length human CD2AP in a heterologous system, wherein the secondary structure of CD2AP is predominantly disordered. CD2AP can form higher-order oligomers, and the significance of these oligomers and the impact of mutations in the context of size-selective permeability of SD needs further investigation.

Review of Structural and Functional Anatomy of Kidney in Ayurvedic Literature with Special Reference to Diseases of the Kidney

Description of organs and their treatment in Ayurvedic texts is very brief. In today’s world when the diseases of organs like kidneys, heart, liver, and brain etc., are becoming very common, Ayurvedic practitioners find these descriptions inadequate to treat patients with such diseases. An effort was made to assess whether critical analysis of references related to kidneys in classical Ayurvedic texts provide inputs to an Ayurvedic Practitioner to understand the pathogenesis of Chronic Kidney Disease (CKD). Tantrayukti based interpretation of references of kidneys in classical Ayurvedic texts establishes that kidneys were known to, and are elaborately described in Ayurveda, with their anatomical details such as embryological origin, name, number, relation with other abdominal organs, location etc. They are known by the name of Vrukka, which are the abdominal organs that are two in number and are described as Basti Marma (which includes the kidneys, ureter, and Bladder) for the purpose of diagnosis, prognosis, and treatment of all urine related diseases. Basti Marma is one of the three Maha Marmas i.e., most important vital organs of the body viz., Shiro (~brain), Hridaya (~heart) and Basti (~bladders). Vrukka (kidney) is formed from the nutritious part of Kapha, Meda and Rakta, gives the inputs to the practitioner to consider the metabolism of these factors in diagnosis and treatment of CKD. Physiology of formation of urine is also elaborately described in Ayurveda. The reference of Sushruta which discusses about Sahastrshaha Sukshma mukhani (~ thousands of minute openings invisible to naked eye) where urine is formed resembles the description of glomerular filtration. Formation and processing by Samaana, role of Jathar Agni, Dhatvagni and Bhutagni in formation of Mutra (~urine), storage and excretion at the level of Bladder, by Apaana is defined clearly, and this description is of immense value for practitioners. Relation of Basti Marma to Kleda (~body fluids) and its pathological connection with specific diseases is also evident. Understanding of various factors viz., Kleda (~body fluids), Marma (~vital organs), Prana (~life force), Oja (~vitality), Kalaa (~Internal membranes) Jathar Agni, Dhatvagni, Bhutagni etc., and their role in pathogenesis of CKD provides Vaidyas with inputs to devise the line of treatment of patients suffering from CKD, taking into consideration the individual condition of each patient.

Urine retention-From the symptom to the structure

Urinary retention describes the inability to urinate. Based on the symptoms and the amount of the initial residual urine formation, a differentiation can be made between acute and chronic forms. The cause can be a subvesical obstruction or a bladder atony. In addition to emergency treatment in the form of initial relief of the strain on the bladder by insertion of a catheter, the indication for a definitive treatment with a clarification of the question whether an acute or chronic event is present is also important. Although the selection of the catheter is subject to few criteria, the further structured approach is complex. Both decision trees are presented in this article.

Implementasi Experiential Learning pada Materi Proses Pembentukan Urine Manusia

Teaching aids in the learning process can help students understand the material being taught. The purpose of this study was to describe the interests and motivation of students after using teaching aids. The teaching aids were developed using the Borg & Gall research model which was limited to five stages, namely information gathering, planning, product draft development, initial field trials, and test results reports. This research was conducted on a small scale involving five students of class VIII. Students' interest in teaching aids is described when students enjoy using teaching aids as learning media, while student motivation is known that students' understanding of the process of forming human urine increases. The students' interest and motivation towards the use of teaching aids from the questionnaire obtained the highest scores of 100%, 96%, 92%, respectively, which indicates that the teaching aids are very good and have a positive influence on student motivation. The results of the small-scale research indicate that the teaching aids developed can attract students' interest and motivation to learn. This reflects the experiential learning process, especially in the material for the process of forming human urine. Keywords: teaching aids, urine formation process, Experiential Learning, motivation

The pinnacle of S. S. Zimnitsky scientific work — nephrology research

The pinnacle of S. S. Zimnitsky scientific heritage is the Zimnitsky, which makes it possible to assess the renal function without invasive procedures and burdening the patient. Proposed a hundred years ago, the Zimnitsky test shows its effectiveness at the present time. S. S. Zimnitsky proposed an original classification of hydronephrosis, described a special form of nephritis and rejected the filtration theory of urine formation, promoting the secretory one. In his purely scientific nephrological articles, S. S. Zimnitsky acts as a sincere and ardent patriot of his great homeland.

A pathogenetic role of posttranslational isoforms of uromodulin

Different biophysical techniques were used to study uromodulin isoforms using experimental models of urine formation (ionic composition, osmolality, pH) in the presence of intact uromodulin and its isoforms isolated from patients with urolithiasis. A model of a medical screening device for persons with preclinical urolithiasis was tested. The concept of targeted therapy of urolithiasis based on the modulation of the properties of uromodulin was put forth.

What Does the Most Celebrated and Pioneer Ottoman Physician, Şanizade Mehmed Ataullah Efendi, Say on Anatomy, Physiology, Diseases, and Surgery of the Urinary System? A Glance at Hamse-i Şanizade or Kanun-ı Şanizade.

Hamse-i Şanizade (Khamse Shānī-zāde) is the most important work of Şanizade Mehmed Ataullah Efendi (1769 or 1771-1826), an Ottoman kadı (qāḍi), physician, historian, polymath, and polyglot, about medicine and consists of 5 books. The first book, Mir'āt al-ebdān fī teshrīḥ a'dā' al-insān, is on anatomy. The second book, Uṣūl al-ṭabī'a, deals with physiology, while the third, Mi'yār al-etıbbā, mentions diseases and their treatments. These books were published together in Istanbul in 1820. A fourth book, Qānūn al-cerrāḥīn, published in Cairo after his death in 1828, discusses surgical treatments of diseases. A fifth book, Mīzān al-edviye, is a pharmacopeia. In this study, we examined the information about urinary system anatomy, physiology, diseases, and their medical and surgical treatments in Hamse-i Şanizade. We examined the first 3 books and the fourth book. The relevant passages were translated into English after being transliterated into the contemporary Turkish alphabet. In the first book, kidney anatomy is discussed under the heading "fī teshrīḥ al-kulā" and bladder anatomy under "fī teshrīḥ al-methāne." In the second book, the formation and excretion of urine are explained in different headings. In the third book, kidney inflammation and its treatment are discussed, with kidney and bladder stones and their medical treatments explained in detail. Finally, the types and treatments of urinary retention are discussed, with types, causes, symptoms, prognosis, and surgical treatments of bladder stones written in detail. In the Ottoman Empire, Hamse-i Şanizade is regarded as one of the first gateways to the West in the field of medicine. It was instrumental in modernizing Ottoman-Turkish medicine and contains and reflects the state-of-the-art knowledge of the time regarding the anatomy, physiology, diseases, and medical and surgical treatments of the urinary system.

Hands-on nephron activity during lecture of urine formation.

Urine formation in the nephron can be a very intimidating concept to students. This straightforward activity, performed by students during the nephron lecture, can help enforce the concepts as they uncover the structures and functions involved in urine formation.NEW & NOTEWORTHY A straightforward activity for students to demonstrate the steps of urine formation and apply it to clinical relevance, this easy-to-develop activity is utilized during lecture for students to tactically "see" how the various parts of the nephron function.

Urine retention-From the symptom to the structure

Urinary retention describes the inability to urinate. Based on the symptoms and the amount of the initial residual urine formation, a differentiation can be made between acute and chronic forms. The cause can be a subvesical obstruction or a bladder atony. In addition to emergency treatment in the form of initial relief of the strain on the bladder by insertion of a catheter, the indication for a definitive treatment with a clarification of the question whether an acute or chronic event is present is also important. Although the selection of the catheter is subject to few criteria, the further structured approach is complex. Both decision trees are presented in this article.

Hydrodynamic model for renal microvascular filtration: Effects of physiological and hemodynamic changes on glomerular size-selectivity.

The first step in renal urine formation is ultrafiltration across the glomerular barrier. The change in its nanostructure has been associated with nephrotic syndromes. Effects of physiological and hemodynamic factor alterations associated with diabetic nephropathy (DN) on glomerular permselectivity are examined through a mathematical model employing low-Reynolds-number hydrodynamics and hindered transport theory. Glomerular capillaries are represented as networks of cylindrical tubes with multilayered walls. Glomerular basement membrane (GBM) is a fibrous medium with bimodal fiber sizes. Epithelial slit fiber spacing follows a lognormal distribution based on reported electron micrographs with the highest resolution. Endothelial fenestrae are filled with fibers the size of glycosaminoglycans (GAGs). Effects of fiber-macromolecule steric and hydrodynamic interactions are included. Focusing on diabetic nephropathy, the physiological and hemodynamic factors employed in the computation are those reported for healthy humans and patients with early-but-overt diabetic nephropathy. The macromolecule concentration is obtained as a finite element solution of the convection-diffusion equation. Computed sieving coefficients averaged along the capillary length agree well with ficoll sieving coefficients from studies in humans for most solute radii. GBM thickening and the loss of the slit diaphragm hardly affect glomerular permselectivity. GAG volume fraction reduction in the endothelial fenestrae, however, significantly increases macromolecule filtration. Increased renal plasma flow rate (RPF), glomerular hypertension, and reduction of lumen osmotic pressure cause a slight sieving coefficient decrease. These effects are amplified by an increased macromolecule size. Our results indicate that glomerular hypertension and the reduction in the oncotic pressure decreases glomerular macromolecule filtration. Reduction of RPF and changes in the glomerular barrier structure associated with DN, however, increase the solute sieving. Damage to GAGs caused by hyperglycemia is likely to be the most prominent factor affecting glomerular size-selectivity.

EXPERIMENTAL MODEL OF NEPHROPATHY IN RATS WITH PROLONGED ANTIMONY INTOXICATION

Introduction. Despite the ample prevalence of antimony in the human environment, there are still no reliable data on its nephrotoxicity. Data from the literature are inconsistent. Materials and methods. The experiments were performed in 2 groups of male Wistar rats weighing 200-250 g. Group 1: intact animals; Group 2: animals with intragastric injection of antimony chloride solution. The solution was injected through a probe into the stomach every day at a dose of 3 mg/kg for one and two months. After the experiment was terminated, the rats were euthanised under thiopental anaesthesia for plasma and renal tissue examination. The basic processes of urine formation, blood electrolyte content (sodium, potassium and calcium) and kidney function were studied under conditions of spontaneous 6-hour diuresis after one and two months. Content of sodium and potassium in biological material was determined by ion-selective method on electrolyte analyzer AEK-1 (Kverti-Med). The concentration of calcium and creatinine in urine and blood plasma, total protein in urine were determined spectrophotometrically. For histological studies, kidney tissue samples were fixed in 10% neutral formalin, then embedded in paraffin, followed by preparation of 7-8 microns thick sections. The sections were stained with hematoxylin and eosin. The sections were studied in transmitted light using a Mikmed-1 microscope at a magnification of 80x200x400. Results. Experiments showed that chronic sulimic intoxication leads to toxic nephropathy, manifested after 2 months of intoxication by a sharp decrease in diuresis due to decreased glomerular filtration rate, impaired electrolyte-excretory function of the kidneys, proteinuria. Morphological examination showed alterative changes: urinary space of glomeruli was enlarged, capillary endothelium with signs of hydropic dystrophy. There was hyaline-drop dystrophy of renal tubule epithelium with partial necrosis. Stroma was edematous, vessels were full of blood with hyalinosis of their walls. Conclusion. Prolonged antimony intoxication leads to nephropathy. Manifestations of the latter after one month and two months of intoxication differ in direction, but are accompanied by marked proteinuria.

INTERPLAY BETWEEN PARAMETERS OF THE HAEMOSTATIC SYSTEM AND URINE FORMATION IN RATS UNDER EXPERIMENTAL MERCURY INTOXICATION. PREVENTIVE OPTIONS

We have explored the effects of melatonin on the interplay between parameters of the haemostatic system and the disruption in basic processes of urine formation under chronic sublimate intoxication. The prophylactic administration of melatonin was performed at a dose of 5 mg/kg along with the intragastric administration of mercury chloride at a dose of 0.5 mg/kg for two months. The use of melatonin helped reduce the Impairment in vascular-platelet and coagulation haemostasis and in the activity of the anticoagulant and fibrinolytic systems, and contributed to the reduction in thrombinaemia. Observed changes correlated with the restoration of urine formation and lipid peroxidation processes and of the activity of antioxidant blood enzymes. The results of the study suggest that melatonin can be recommended for further studies aimed at developing tools for correcting haemostasis associated with exposure to heavy metal compounds.

The Glomerulus According to the Mesangium.

The glomerulus is the functional unit for filtration of blood and formation of primary urine. This intricate structure is composed of the endothelium with its glycocalyx facing the blood, the glomerular basement membrane and the podocytes facing the urinary space of Bowman's capsule. The mesangial cells are the central hub connecting and supporting all these structures. The components as a unit ensure a high permselectivity hindering large plasma proteins from passing into the urine while readily filtering water and small solutes. There has been a long-standing interest and discussion regarding the functional contribution of the different cellular components but the mesangial cells have been somewhat overlooked in this context. The mesangium is situated in close proximity to all other cellular components of the glomerulus and should be considered important in pathophysiological events leading to glomerular disease. This review will highlight the role of the mesangium in both glomerular function and intra-glomerular crosstalk. It also aims to explain the role of the mesangium as a central component involved in disease onset and progression as well as signaling to maintain the functions of other glomerular cells to uphold permselectivity and glomerular health.