-
Clinical Chemistry and Laboratory... Jul 2023Detection of hemoglobin (Hb) and red blood cells in urine (hematuria) is characterized by a large number of pitfalls. Clinicians and laboratory specialists must be... (Review)
Review
Detection of hemoglobin (Hb) and red blood cells in urine (hematuria) is characterized by a large number of pitfalls. Clinicians and laboratory specialists must be aware of these pitfalls since they often lead to medical overconsumption or incorrect diagnosis. Pre-analytical issues (use of vacuum tubes or urine tubes containing preservatives) can affect test results. In routine clinical laboratories, hematuria can be assayed using either chemical (test strips) or particle-counting techniques. In cases of doubtful results, Munchausen syndrome or adulteration of the urine specimen should be excluded. Pigmenturia (caused by the presence of dyes, urinary metabolites such as porphyrins and homogentisic acid, and certain drugs in the urine) can be easily confused with hematuria. The peroxidase activity (test strip) can be positively affected by the presence of non-Hb peroxidases (e.g. myoglobin, semen peroxidases, bacterial, and vegetable peroxidases). Urinary pH, haptoglobin concentration, and urine osmolality may affect specific peroxidase activity. The implementation of expert systems may be helpful in detecting preanalytical and analytical errors in the assessment of hematuria. Correcting for dilution using osmolality, density, or conductivity may be useful for heavily concentrated or diluted urine samples.
Topics: Humans; Hematuria; Peroxidase; Hemoglobins; Erythrocytes; Osmolar Concentration
PubMed: 37079906
DOI: 10.1515/cclm-2023-0260 -
Advances in Physiology Education Dec 2018Understanding osmolarity and tonicity is one of the more challenging endeavors undertaken by students of the natural sciences. We asked students who completed a course...
Understanding osmolarity and tonicity is one of the more challenging endeavors undertaken by students of the natural sciences. We asked students who completed a course in animal physiology to submit an essay explaining what they found most perplexing about this subject, and what in-class activities proved most useful to them. Students had difficulty distinguishing osmolarity from tonicity and determining tonicity based on the solution's composition. The most useful activities were questions requiring simultaneous consideration of both osmolarity and tonicity. Problems that require calculating osmotic concentration and the volumes of body fluid compartments after administration or loss of various solutions emphasize the significance of osmolarity and tonicity in the context of systemic homeostasis and clinical medicine. We hope that our approach to teaching osmolarity and tonicity will prove useful to physiology lecturers who are looking for new ways of introducing this complicated topic to their health professions students.
Topics: Animals; Cell Size; Humans; Learning; Osmolar Concentration; Osmosis; Physiology; Students, Health Occupations; Teaching
PubMed: 30303411
DOI: 10.1152/advan.00094.2018 -
Medical Hypotheses Feb 2019In a natural state, death of the neuronal cells of the central nervous system is a hallmark of the aging process and occurs very insidiously. As we age, a natural loss...
In a natural state, death of the neuronal cells of the central nervous system is a hallmark of the aging process and occurs very insidiously. As we age, a natural loss of the body water occurs simultaneously with a rise in plasma osmolality. When a progressive rise in plasma osmolality occurs with age, it increases the effective viscosity of the circulating blood, and the thickened blood fails to perfuse the body systems and organs. If red blood cells fail to perfuse the central nervous system, the neuronal cells die from hypoxia and a lack of essential nutrients. This process is insidious but unavoidable. Hyperosmolality occurs in all mammals and it is a natural phenomenon of mammalian aging.
Topics: Adult; Aged; Aging; Alzheimer Disease; Body Composition; Body Water; Brain; Central Nervous System; Erythrocytes; Exercise; Female; Hematocrit; Homeostasis; Humans; Infant; Male; Middle Aged; Neurons; Osmolar Concentration; Oxygen; Viscosity; Young Adult
PubMed: 30696601
DOI: 10.1016/j.mehy.2018.12.016 -
Deutsches Arzteblatt International Oct 2023Hydration disturbances are common in old age: the reported prevalence of dehydration in elderly patients ranges from 19% to 89%, depending on the definition and the... (Review)
Review
BACKGROUND
Hydration disturbances are common in old age: the reported prevalence of dehydration in elderly patients ranges from 19% to 89%, depending on the definition and the population in question. However, the clinical assessment of patients' hydration status is difficult. In this review, we discuss the diagnostic value of currently used methods that may or may not be suitable for assessing older patients' hydration status.
METHODS
We conducted a selective literature search for relevant studies concerning patients aged 65 and above. Of the 355 articles retrieved by the initial search, a multistep selection process yielded 30 that were suitable for inclusion in this review.
RESULTS
107 different methods for the diagnostic assessment of dehydration in older persons were evaluated on the basis of the reviewed publications. High diagnostic value, especially for the determination of hyperosmolar dehydration, was found for serum osmolality, serum sodium concentration, inferior vena cava ultrasonography, a history (from the patient or another informant) of not drinking between meals, and axillary dryness. On the other hand, a variety of clinical signs such as a positive skin turgor test, sunken eyes, dry mouth, tachycardia, orthostatic dysregulation, and dark urine were found to be of inadequate diagnostic value.
CONCLUSION
Only five of the 107 methods considered appear to be suitable for determining that a patient is dehydrated. Thus, the available scientific evidence indicates that all clinicians should critically reconsider their own techniques for assessing hydration status in elderly patients. To optimize the clinical assessment of patients' hydration status, there seems to be a need for the rejection of unsuitable methods in favor of either newly developed criteria or of a combination of the best criteria already in use.
Topics: Aged; Humans; Aged, 80 and over; Dehydration; Osmolar Concentration
PubMed: 37583084
DOI: 10.3238/arztebl.m2023.0182 -
Physiology & Behavior Dec 2015Regulation of appropriate osmolality of body fluid is critical for survival, yet there are sex differences in compensatory responses to osmotic challenges. Few studies... (Review)
Review
Regulation of appropriate osmolality of body fluid is critical for survival, yet there are sex differences in compensatory responses to osmotic challenges. Few studies have focused on the role of sex hormones such as estradiol in behavioral responses to increases or decreases in systemic osmolality, and even fewer studies have investigated whether central actions of estrogens contribute to these responses. This overview integrates findings from a series of ongoing and completed experiments conducted in my laboratory to assess estradiol effects on water and NaCl intake in response to osmotic challenges, and on activity in central pathways that mediate such responses.
Topics: Animals; Brain; Drinking; Eating; Estradiol; Humans; Osmolar Concentration; Sodium, Dietary
PubMed: 26074202
DOI: 10.1016/j.physbeh.2015.06.017 -
Contact Lens & Anterior Eye : the... Oct 2023To demonstrate how the likelihood of making a correct diagnosis of dry eye disease varies according to the clinical test methods used. (Review)
Review
PURPOSE
To demonstrate how the likelihood of making a correct diagnosis of dry eye disease varies according to the clinical test methods used.
METHODS
The probability of a person having dry eye, given that they return a positive test, was calculated for a range of standard tests, using the Bayes-Price rule. Global specificity and sensitivity values for each test were estimated by employing the Beta distribution to combine all relevant data obtained from a literature review.
RESULTS
At an assumed prevalence of 11.6%, the single test with the highest probability of a correct diagnosis was corneal staining (probability = 0.28) and the lowest was the ocular surface disease index - OSDI (0.14). The best combination of symptoms with a single test of tear film homeostasis was the 5-item dry eye questionnaire (DEQ-5) + corneal staining (0.42) while OSDI + tear film break up time (TBUT) was the worst (0.23). The simultaneous observation of conjunctival and corneal staining was associated with a probability of 0.49. The probability of a correct diagnosis increased with the number of positive tests, up to a maximum of 0.90 when all of DEQ-5, conjunctival and corneal staining, osmolarity and TBUT were positive.
CONCLUSION
A significant risk of misdiagnosis is associated with using any single test for dry eye disease, or the minimum TFOS DEWS II criterion of symptoms plus any single test of tear film homeostasis. To minimize this risk, the maximum number of tests available should be performed and the results used to inform diagnosis. The simultaneous occurrence of conjunctival and corneal staining should be considered a key outcome and be specified in future guidelines.
Topics: Humans; Dry Eye Syndromes; Bayes Theorem; Tears; Osmolar Concentration; Diagnostic Errors
PubMed: 37544866
DOI: 10.1016/j.clae.2023.102048 -
Medical Hypotheses Dec 2015Alzheimer's disease is a disease that is resulted from increased plasma osmolality both the excessive consumption of animal-based proteins and reduction of sodium... (Review)
Review
Alzheimer's disease is a disease that is resulted from increased plasma osmolality both the excessive consumption of animal-based proteins and reduction of sodium intake, that resulted to increase plasma osmolality. When we are exposed to high animal-based protein diets throughout life, we gradually lose extracellular sodium and the body cannot retain water, resulting in a gradual rise of plasma osmolality. When the neuronal cells of the central nervous system are exposed to high osmolality stress, they produce of phosphorylated tau, APP, and pathologic beta amyloid protein peptides. The BACE 1 protein which influences the cleavage of amyloid precursor proteins (APP) and affects the production of beta amyloid protein peptides, is also increased in a hyperosmotic stress. When pathologic beta amyloid protein peptides are produced, they are degraded by the ubiquitin proteasome proteolytic pathway, and only then are the neurotoxic effects on the central nervous system manifested, leading to Alzheimer's disease.
Topics: Alzheimer Disease; Amyloid Precursor Protein Secretases; Amyloid beta-Protein Precursor; Animals; Aspartic Acid Endopeptidases; Cell Survival; Dietary Proteins; Female; Humans; Male; Mice; Mice, Inbred C57BL; Models, Theoretical; Neurons; Osmolar Concentration; Osmosis; Proteasome Endopeptidase Complex; Sodium; Ubiquitin; tau Proteins
PubMed: 26386488
DOI: 10.1016/j.mehy.2015.09.005 -
Seminars in Dialysis Nov 2017Homeostatic regulation of plasma osmolality (POsm) is critical for normal cellular function in humans. Arginine vasopressin (AVP) is the major hormone responsible for... (Review)
Review
Homeostatic regulation of plasma osmolality (POsm) is critical for normal cellular function in humans. Arginine vasopressin (AVP) is the major hormone responsible for the maintenance of POsm and acts to promote renal water retention in conditions of increased POsm. However, AVP also exerts pressor effects, and its release can be stimulated by the development of effective arterial blood volume depletion. Patients with end-stage renal disease on hemodialysis, particularly those with minimal or no residual renal function, have impaired ability to regulate water retention in response to AVP. While hemodialysis can assist with this task, patients are subject to relatively rapid shifts in volume and electrolytes during the procedure. This can result in the development of transient osmotic gradients that lead to the movement of water from the extracellular to the intracellular space. Hypotension may result-both as a consequence of water movement out of the intravascular compartment, but also from impaired AVP release and inadequate vascular tone. In this review, we explore the evidence for POsm changes during hemodialysis, associations with adverse outcomes, and methods to minimize the rapidity of changes in POsm in an effort to reduce patient symptoms and minimize intra-dialytic hypotension.
Topics: Blood Pressure; Hemodialysis Solutions; Humans; Hypotension; Kidney Failure, Chronic; Neurophysins; Osmolar Concentration; Protein Precursors; Renal Dialysis; Vasopressins; Water-Electrolyte Balance
PubMed: 28691402
DOI: 10.1111/sdi.12629 -
The Journal of Clinical Investigation Jun 2023Maintaining internal osmolality constancy is essential for life. Release of arginine vasopressin (AVP) in response to hyperosmolality is critical. Current hypotheses for...
Maintaining internal osmolality constancy is essential for life. Release of arginine vasopressin (AVP) in response to hyperosmolality is critical. Current hypotheses for osmolality sensors in circumventricular organs (CVOs) of the brain focus on mechanosensitive membrane proteins. The present study demonstrated that intracellular protein kinase WNK1 was involved. Focusing on vascular-organ-of-lamina-terminalis (OVLT) nuclei, we showed that WNK1 kinase was activated by water restriction. Neuron-specific conditional KO (cKO) of Wnk1 caused polyuria with decreased urine osmolality that persisted in water restriction and blunted water restriction-induced AVP release. Wnk1 cKO also blunted mannitol-induced AVP release but had no effect on osmotic thirst response. The role of WNK1 in the osmosensory neurons in CVOs was supported by neuronal pathway tracing. Hyperosmolality-induced increases in action potential firing in OVLT neurons was blunted by Wnk1 deletion or pharmacological WNK inhibitors. Knockdown of Kv3.1 channel in OVLT by shRNA reproduced the phenotypes. Thus, WNK1 in osmosensory neurons in CVOs detects extracellular hypertonicity and mediates the increase in AVP release by activating Kv3.1 and increasing action potential firing from osmosensory neurons.
Topics: Arginine Vasopressin; Homeostasis; Osmolar Concentration; Thirst; Water
PubMed: 37071482
DOI: 10.1172/JCI164222 -
European Biophysics Journal : EBJ Feb 2023In applications of bio-inspired nanoparticles (NPs), their composition is often optimised by including ionizable lipids. I use a generic statistical model to describe...
In applications of bio-inspired nanoparticles (NPs), their composition is often optimised by including ionizable lipids. I use a generic statistical model to describe the charge and potential distributions in lipid nanoparticles (LNPs) containing such lipids. The LNP structure is considered to contain the biophase regions separated by narrow interphase boundaries with water. Ionizable lipids are uniformly distributed at the biophase-water boundaries. The potential is there described at the mean-filed level combining the Langmuir-Stern equation for ionizable lipids and the Poisson-Boltzmann equation for other charges in water. The latter equation is used outside a LNP as well. With physiologically reasonable parameters, the model predicts the scale of the potential in a LNP to be rather low, smaller or about [Formula: see text], and to change primarily near the LNP-solution interface or, more precisely, inside an NP near this interface because the charge of ionizable lipids becomes rapidly neutralized along the coordinate towards the center of a LNP. The extent of dissociation-mediated neutralization of ionizable lipids along this coordinate increases but only slightly. Thus, the neutralization is primarily due to the negative and positive ions related to the ionic strength in solution and located inside a LNP.
Topics: Lipids; RNA, Small Interfering; Nanoparticles; Osmolar Concentration
PubMed: 36810604
DOI: 10.1007/s00249-023-01633-4