Hyperosmotic Fluid Research Articles

Surgical Techniques for Catheter Placement and 5/6 Nephrectomy in Murine Models of Peritoneal Dialysis.

Peritoneal dialysis (PD) is a renal replacement therapy consistent on the administration and posterior recovery of a hyperosmotic fluid in the peritoneal cavity to drain water and toxic metabolites that functionally-insufficient kidneys are not able to eliminate. Unfortunately, this procedure deteriorates the peritoneum. Tissue damage triggers the onset of inflammation to heal the injury. If the injury persists and inflammation becomes chronic, it may lead to fibrosis, which is a common occurrence in many diseases. In PD, chronic inflammation and fibrosis, along with other specific processes related to these ones, lead to ultrafiltration capacity deterioration, which means the failure and subsequent cessation of the technique. Working with human samples provides information about this deterioration but presents technical and ethical limitations to obtain biopsies. Animal models are essential to study this deterioration since they overcome these shortcomings. A chronic mouse infusion model was developed in 2008, which benefits from the wide range of genetically modified mice, opening up the possibility of studying the mechanisms involved. This model employs a customized device designed for mice, consisting of a catheter attached to an access port that is placed subcutaneously at the back of the animal. This procedure avoids continuous puncture of the peritoneum during long-term experiments, reducing infections and inflammation due to injections. Thanks to this model, peritoneal damage induced by chronic PD fluid exposure has been characterized and modulated. This technique allows the infusion of large volumes of fluids and could be used for the study of other diseases in which inoculation of drugs or other substances over extended periods of time is necessary. This article shows the method for the surgical placement of the catheter in mice. Moreover, it explains the procedure for a 5/6 nephrectomy to mimic the state of renal insufficiency present in PD patients.

Fluid Resuscitation in Patients With Severe Burns: A Meta-analysis of Randomized Controlled Trials.

Fluid resuscitation is the mainstay treatment to reconstitute intravascular volume and maintain end-organ perfusion in patients with severe burns. The use of a hyperosmotic or isoosmotic solution in fluid resuscitation to manage myocardial depression and increased capillary permeability during burn shock has been debated. We conducted a systematic review and meta-analysis to compare the efficacies of hyperosmotic and isoosmotic solutions in restoring hemodynamic stability after burn injuries. PubMed, Embase, Cochrane Library, Scopus, and ClinicalTrials.gov registry were searched. Randomized control trials evaluating the efficacy and safety of hyperosmotic and isoosmotic fluid resuscitation in patients with burn injuries were selected. Eligible trials were abstracted and assessed for the risk of bias by two reviewers and results of hemodynamic indicators in the included trials were analyzed. Ten trials including 502 participants were published between 1983 and 2013. Compared with isoosmotic group, the hyperosmotic group exhibited a significant decrease in the fluid load (vol/% total body surface area [TBSA]/weight) at 24 hours postinjury, with a mean difference of -0.54 (95% confidence interval=-0.92 to -0.17). No differences were observed in the urine output, creatinine level, and mortality at 24 hours postinjury between groups. Hyperosmotic fluid resuscitation appears to be an attractive choice for severe burns in terms of TBSA or burn depth. Further investigation is recommended before conclusive recommendation.

The Complex Process of Haemostasis and Interactions due to Hyperosmotic Fluids.

The Complex Process of Haemostasis and Interactions due to Hyperosmotic Fluids.

Falsely Elevated Glucose Concentrations in Peritoneal Dialysis Patients Using Icodextrin.

Peritoneal dialysis (PD) is used as an alternative to hemodialysis in end-stage renal disease (ESRD). Icodextrin has been used as a hyperosmotic agent in PD. The aim of the study was to assess two different point-of-care testing (POCT) glucose strips, affected and not affected by icodextrin, with serum glucose concentrations of the patients using and not using icodextrin. Fifty-two chronic ambulatory peritoneal dialysis (CAPD) patients using icodextrin (Extraneal®) and 20 CAPD patients using another hyperosmotic fluid (Dianeal®) were included in the study. Duplicate capillary and serum glucose concentrations were measured with two different POCT glucose strips and central laboratory hexokinase method. Assay principles of glucose strips were based on glucose dehydrogenase-pyrroloquinoline quinone (GDH-PQQ) and a mutant variant of GDH (Mut Q-GDH). The results of both strips were compared with those of hexokinase method. Regression equations between POCT and hexokinase methods in icodextrin group were y = 2.55x + 1.12 mmol/l and y = 1.057x + 0.16 mmol/l for the GDH-PQQ and Mut Q-GDH methods, respectively. The mean difference between the results of hexokinase and those of GDH-PQQ and Mut Q-GDH in icodextrin group was 3.41 ± 1.56 and 0.72 ± 0.64 mmol/l, respectively. However, the mean differences were found much lower in the control group; 0.64 mmol/l for GDH-PQQ and 0.52 mmol/l for Mut Q-GDH. Compared to GDH-PQQ, glucose strips of Mut Q-GDH correlated better with hexokinase method in PD patients using icodextrin.

Glucocorticoids stimulate endolymphatic water reabsorption in inner ear through aquaporin 3 regulation.

Menière's disease, clinically characterized by fluctuating, recurrent, and invalidating vertigo, hearing loss, and tinnitus, is linked to an increase in endolymph volume, the so-called endolymphatic hydrops. Since dysregulation of water transport could account for the generation of this hydrops, we investigated the role of aquaporin 3 (AQP3) in water transport into endolymph, the K-rich, hyperosmotic fluid that bathes the apical ciliated membrane of sensory cells, and we studied the regulatory effect of dexamethasone upon AQP3 expression and water fluxes. The different AQP subtypes were identified in inner ear by RT-PCR. AQP3 was localized in human utricle and mouse inner ear by immunohistochemistry and confocal microscopy. Unidirectional transepithelial water fluxes were studied by means of (3)H2O transport in murine EC5v vestibular cells cultured on filters, treated or not with dexamethasone (10(-7)M). The stimulatory effect of dexamethasone upon AQP3 expression was assessed in EC5v cells and in vivo in mice. AQP3 was unambiguously detected in human utricle and was highly expressed in both endolymph secretory structures of the mouse inner ear, and EC5v cells. We demonstrated that water reabsorption, from the apical (endolymphatic) to the basolateral (perilymphatic) compartments, was stimulated by dexamethasone in EC5v cells. This was accompanied by a glucocorticoid-dependent increase in AQP3 expression at both messenger RNA (mRNA) and protein level, presumably through glucocorticoid receptor-mediated AQP3 transcriptional activation. We show that glucocorticoids enhance AQP3 expression in human inner ear and stimulate endolymphatic water reabsorption. These findings should encourage further clinical trials evaluating glucocorticoids efficacy in Menière's disease.

Hypernatremia in patients with severe traumatic brain injury: a systematic review.

BackgroundHypernatremia is common following traumatic brain injury (TBI) and occurs from a variety of mechanisms, including hyperosmotic fluids, limitation of free water, or diabetes insipidus. The purpose of this systematic review was to assess the relationship between hypernatremia and mortality in patients with TBI.MethodsWe searched the following databases up to November 2012: MEDLINE, EMBASE, and CENTRAL. Using a combination of MeSH and text terms, we developed search filters for the concepts of hypernatremia and TBI and included studies that met the following criteria: (1) compared hypernatremia to normonatremia, (2) adult patients with TBI, (3) presented adjusted outcomes for mortality or complications.ResultsBibliographic and conference search yielded 1,152 citations and 11 abstracts, respectively. Sixty-five articles were selected for full-text review with 5 being included in our study. All were retrospective cohort studies totaling 5,594 (range 100–4,296) patients. There was marked between-study heterogeneity. The incidence of hypernatremia ranged between 16% and 40%. Use of hyperosmolar therapy was presented in three studies (range 14-85% of patients). Hypernatremia was associated with increased mortality across all four studies that presented this outcome. Only one study considered diabetes insipidus (DI) in their analysis where hypernatremia was associated with increased mortality in patients who did not receive DDAVP.ConclusionsAlthough hypernatremia was associated with increased mortality in the included studies, there was marked between-study heterogeneity. DI was a potential confounder in several studies. Considering these limitations, the clinical significance of hypernatremia in TBI is difficult to establish at this stage.

Whole body acid-base and fluid-electrolyte balance: a mathematical model

A cellular compartment was added to our previous mathematical model of steady-state acid-base and fluid-electrolyte chemistry to gain further understanding and aid diagnosis of complex disorders involving cellular involvement in critically ill patients. An important hypothesis to be validated was that the thermodynamic, standard free-energy of cellular H(+) and Na(+) pumps remained constant under all conditions. In addition, a hydrostatic-osmotic pressure balance was assumed to describe fluid exchange between plasma and interstitial fluid, including incorporation of compliance curves of vascular and interstitial spaces. The description of the cellular compartment was validated by close comparison of measured and model-predicted cellular pH and electrolyte changes in vitro and in vivo. The new description of plasma-interstitial fluid exchange was validated using measured changes in fluid volumes after isoosmotic and hyperosmotic fluid infusions of NaCl and NaHCO3. The validated model was used to explain the role of cells in the mechanism of saline or dilutional acidosis and acid-base effects of acidic or basic fluid infusions and the acid-base disorder due to potassium depletion. A module was created that would allow users, who do not possess the software, to determine, for free, the results of fluid infusions and urinary losses of water and solutes to the whole body.

A New Technique of Expanding the Underdeveloped Scrotum

Sir: Absence of testis often leads to underdevelopment of the scrotum. Tissue expanders1 stretch the underdeveloped scrotum to accommodate a testicular prosthesis. Disadvantages are the need for a second operation, the use of an implant with the risk of infection, the inflation time, repeated visits, and punctures to inflate the expander. A self-inflatable device overcomes these disadvantages. In 1982,2 a self-inflating model was introduced based on a silicone balloon filled with a hyperosmotic fluid, later replaced by hydrogel in 2000,3 commercialized as the OSMED expander (OSMED GmbH, Hartheim, Germany). The expander absorbs body fluids, leading to gradual swelling, providing a predetermined volume and size. The use of an osmotic expander for this indication has never been described before. A 17-year-old boy with bilateral cryptorchidism was treated earlier with bilateral orchidopexy and later with orchidectomy on the right side and scrotal fixation on the left side. The left testis atrophied. Placement of a testicular prosthesis failed. At examination, the testicular implant was fixed in the right inguinal region, with an underdeveloped scrotum without palpable testis (Fig. 1).Fig. 1.: Preoperative situation: migrated testicular prosthesis on the right side and shriveled underdeveloped empty scrotum.A large pocket was created under general anesthesia by an incision high on the scrotal sac. The OSMED rectangular expander with a final volume of 200 ml was inserted. The pocket was closed using a purse-string suture to prevent migration. Drains were not used. The migrated testicular prosthesis was removed. The patient was discharged to home on the first postoperative day. No infection or wound dehiscence, discomfort, or pain was observed at follow-up. Maximum expansion was achieved after 4 weeks, with explantation after 40 days. Two 5-cm testicular implants were fixed at the bottom of the pouch. A 4-month follow-up showed no adverse effects, with a satisfactory result (Fig. 2).Fig. 2.: Satisfactory result after 4 months.By expanding the scrotal tissue, additional scarring from multiple procedures in the past was overcome, providing adequate scrotal soft-tissue coverage. Tissue expansion does not alter the contractility or expansion of the scrotal wall in response to ejaculation, cold, or warmth. Disadvantages of traditional expanders are implant leakage, because of the great mobility of the scrotum, and the need for fillings, risking iatrogenic infections.4 The position of the valve can be troublesome because of the great mobility and limited space. Osmotic expanders overcome many of these disadvantages. The small size of the device reduces operative time, requiring a short incision.5 The final volume of the osmotic expander is defined accurately, facilitating surgical planning. The inflation process is uncontrollable, which can be troublesome in causing, for example, skin ischemia or pain. In our patient, the inflation progress was gradual, without pain or discomfort even at full expansion. At 4-month follow-up, no adverse effects were observed. The testicular prosthesis did not migrate or override and had an aesthetically pleasing result. Scrotal tissues responded well with contraction to cold and relaxation after warm stimuli. In conclusion, we can say that the use of an osmotic expander for expanding the underdeveloped scrotum is a safe, reliable, and easy technique that brings important advantages over the use of traditional expanders. DISCLOSURE The authors have no financial interest to declare in relation to the content of this article. Gregory P. A. Van Eeckhout, M.D. Bert Vanmierlo, M.D. Marc Kioe A. Sen, M.D. Paul Wylock, M.D. Department of Plastic, Reconstructive, and Aesthetic Surgery Johan Braeckman, M.D. Department of Urology Universitair Ziekenhuis Brussel Brussels, Belgium

Downregulation of aquaporins 1 and 5 in nasal gland by osmotic stress in ducklings,Anas platyrhynchos: implications for the production of hypertonic fluid

Using primers against highly conserved regions of mammalian and bird aquaporins in RT-PCR experiments, we amplified products derived from duck (Anas platyrhynchos) nasal gland RNA that were identified as homologues of mammalian and chicken aquaporin 1 and aquaporin 5 cDNAs by sequencing. Using digoxigenin-labelled probes derived from these PCR products in northern blot analyses of mRNA isolated from nasal glands of untreated (naïve) or osmotically stressed ducklings (replacement of drinking water with a 1% NaCl solution), we observed a decrease in aquaporin 1 (AQP1) and aquaporin 5 (AQP5) mRNA abundance (by approximately 40%) during saline adaptation in the animals. Western blot analysis of AQP1 and AQP5 expression in the glands revealed that protein abundance decreased in a similar fashion. Immunohistochemical analysis of AQP1 distribution in cryosections of nasal gland indicated that AQP1 is mainly expressed in endothelial cells of the capillaries, but definitely not in the secretory or ductal cells of the gland. AQP5 distribution in the gland, however, seems to be different, since staining was exclusively observed in apical and basolateral plasma membranes of individual epithelial cells of the primary and central ducts, which collect fluid from the secretory tubules. The observations are consistent with the hypothesis that strongly hyperosmotic fluid is produced by the secretory cells at very low (unstimulated gland) or high (activated gland) rates. In the unstimulated gland, secretions may be diluted by aquaporin-mediated transcellular water flux while passing through the ductal system flushing the glandular ducts, thereby potentially preventing ascending infections. In the activated gland, however, downregulation of aquaporins in capillaries and duct cells may prevent dilution of the initially secreted fluid, enabling the animals to excrete large volumes of a highly concentrated salt solution.

Magnesium secretion by the distal segment of the Malpighian tubules of the black field cricket Teleogryllus oceanicus

The short distal segment of unstimulated Teleogryllus Malpighian tubules secreted hyperosmotic fluid containing primarily Mg (125 mmol l −1), Cl (242 mmol l −1) and Na (43 mmol l −1). Remarkably, the volume secreted by the distal segment in unit time was independent of segment length, i.e. the volume was constant regardless of the length of the segment. Magnesium was secreted at a rate of 75.5 pmol min −1 mm −1; the highest rate recorded for any epithelium. Low concentrations of K (20 mmol l −1) were present but almost no P or S. Ca (2.5 mmol l −1) concentration was higher than in the main segment. The short distal segment secreted 100% of the Mg, 54% of the Cl and 23% of the Na secreted by the whole tubule. The main segment secreted fluid containing primarily K (199 mmol l −1), Cl (149 mmol l −1), Na (104 mmol l −1) and P (48 mmol l −1) with very low concentrations of Ca (1 mmoll −1) and S. The main segment appeared to reabsorb a small fraction of the Mg secreted by the distal segment. The fluid secreted by the whole tubule was isosmotic and alkaline, approximately pH 8.

Influence of intra-osseous infusion of a small volume of hyperosmotic fluid on β-adrenergic function in circulating lymphocytes from bled pigs

Influence of intra-osseous infusion of a small volume of hyperosmotic fluid on β-adrenergic function in circulating lymphocytes from bled pigs

Influence of intra-osseous infusion of a small volume of hyperosmotic fluid on beta-adrenergic function in circulating lymphocytes from bled pigs.

The regulation of beta-adrenergic function in circulating mononuclear leukocytes was evaluated during an episode of haemorrhagic shock treated by intra-osseous infusion of a small volume of hyperosmotic fluid. Two groups of piglets (n = 14) were anaesthetized with ketamine and bled to a mean arterial pressure of 40 mmHg. After 45 min the animals were randomized to receive 100 ml of either hyperosmotic (2.4 mol l-1) or iso-osmotic (0.29 mol l-1) fluid (equal volumes of glucose/sodium chloride) into the tibial bone marrow. Observations of haemodynamic variables and levels of plasma catecholamines and cAMP of circulating mononuclear leukocytes were carried out for 70 min. Infusion of hyperosmotic fluid enhanced the circulatory performance and attenuated the plasma catecholamine release significantly (p < 0.05) compared to the corresponding values in the animals that had iso-osmotic fluid infusion. Measurements of unstimulated and isoprenaline-stimulated cAMP levels in mononuclear lymphocytes indicated that the high plasma catecholamine levels in the iso-osmotic treatment group induced a desensitization of the beta-adrenoceptors 70 min after initiation of the shock. This effect was not seen in animals that had undergone hyperosmotic infusion.

Energy-Dependent Water Vapor Absorption (WVA) in the Pleoventral Cavity of Terrestrial Isopods (Crustacea, Isopoda, Oniscidea): Evidence for Pressure Cycling as a Supplement to the Colligative Uptake Mechanism

Terrestrial isopods (Crustacea, Isopoda, Oniscidea) are capable of active water vapor absorption from subhemolymph water activities. The minimum activity for absorption constitutes the uptake threshold (T), and animals can balance passive losses above the critical equilibrium activity (CEA). Values for Porcellio scaber are 0.889 and 0.913, respectively. Two major mechanisms can explain the uptake process. Maximum attainable uptake fluxes increase linearly with ambient water activity (Aaw) although animals are capable of depressing uptake fluxes below, this curve. Such kinetics are compatible with a steady-state secretion/resorption of hyperosmotic fluid in the pleoventral cavity (PV) and ventilation of ambient air by the pleopodal exopods. At near-threshold activities animals may also reveal sharply augmented uptake fluxes. Comparisons with available data 0on fluid concentrations, and direct observations of pleopodal ventilation, indicate the elevation of Aaw within the PV by pressure cycling. This is confirmed by monitoring pressure fluctuations, coincident with pleopodal ventilations, in an enclosed chamber. Blocking experiments support endogenous secretion/resorption of pleon fluid. Fecal activities are approximately 0.990, discounting a rectal resorption mechanism based on transepithelial activity gradients.

EFFECTS OF HYPERTONIC AND ISOTONIC FLUID INFUSION ON THE FLASH EVOKED POTENTIAL IN RATS

In resuscitation from hemorrhagic shock, very small volumes of hypertonic saline (HS) improve blood pressure while reducing intracranial pressure and edema formation. The effects of hypertonic resuscitation fluids and hypernatremia on electrophysiologic brain function have not been studied. The present study was done in two parts. First we examined the effects of hemorrhagic shock and resuscitation with either 7.5% HS or lactated Ringer's (LR) solution on the flash evoked potential (FEP). Rats were bled to a mean arterial pressure (MAP) of 35 mm Hg for 1 hour, then resuscitated with HS (n = 10) or LR (n = 10) to a MAP of 80 mm Hg for another hour. Resuscitation required 3.8 +/- 0.5 mL/kg HS and 42.9 +/- 7.5 mL/kg LR (p < 0.05). During hemorrhage, FEP latencies increased and amplitudes decreased. During resuscitation, these variables returned toward baseline values. There were no significant differences between groups, although HS tended to restore the FEP better than LR. We next examined the effects on the FEP of hypernatremia and hyperosmolarity produced by two different hyperosmotic fluids. Over a 1-hour period, 16 mL/kg HS (n = 8), 16 mL/kg IsoSal (4.5% saline, 5.9% glucose, 6.4% mixed amino acids; n = 8), or 40 mL/kg LR (n = 8) was infused into normovolemic rats. Plasma sodium levels increased in both hyperosmotic groups (baseline = 145.2 +/- 0.7 mEq/L; after infusion, HS = 202.4 +/- 9.8 mEq/L, IsoSal = 163.3 +/- 4.2 mEq/L; p < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Osmolality and Electrolyte Composition of Pleon Fluid in Porcellio Scaber (Crustacea, Isopqda, Oniscidea): Implications for Water Vapour Absorption

ABSTRACT Active water vapour absorption in Porcellio scaber is associated with the endogenous production of strongly hyperosmotic fluid in the pleoventral chamber (pleoventralraum; PV). Pre-desiccated animals show increased pleon fluid secretion within 1–2 min of transfer to suprathreshold humidities (&amp;gt;87 % relative humidity). The conspicuous increase in fluid volume is accompanied by a rise in osmolality from isosmotic (approximately 750mosmolkg−1) up to as much as 8.2osmol kg−1. Vapour absorption is marked by the onset of metachronal pleopodal ventilation and a subsequent decline in fluid osmolality as uptake fluid approaches equilibrium with ambient water activities. The effects of sealing of the PV by the margins of the depressed pleopods, along with the observation that animals ventilate even when PV fluid activities are somewhat below ambient, suggest that resultant pressure increases may elevate humidity within the PV and thereby augment vapour uptake. Ion-selective microelectrode measurements of Na+, K+, Ca2+ and Cl− concentrations in nanolitre samples of isolated pleon fluid identify Na+ and Cl− as the major osmolytes. Possible preadaptions favouring evolution of vapour absorption in the Oniscidea are discussed.

Cochlear Blood Flow and Microvascular Resistance Changes in Response to Hypertonic Glycerol, Urea, and Mannitol Infusions

The effect of hyperosmotic agents on cochlear blood flow (CBF) was tested in normal guinea pigs and in guinea pigs having prior unilateral operations to ablate the endolymphatic duct. Laser-Doppler-measured CBF was normalized to remove apparent changes related directly to systemic blood pressure. Hyperosmotic fluids were given via venous infusion: glycerol (20% and 40% solutions), urea (10%, 30%, and 40% solutions), and mannitol (40% solution). All agents were dissolved in 0.9% saline and the mixtures were given at a rate of 0.3 to 0.6 mL/min for 5 minutes. Control infusions were of 0.9% saline and isotonic dextran 70 (Pharmacia). All hyperosmotic infusions resulted in similar increases in normalized cochlear blood flow (nCBF) that extended to a maximum of 300% of the baseline value in a dose-dependent way during the infusion time period. Within approximately 30 minutes following infusions, nCBF had returned to baseline levels. Saline infusion alone had little effect on nCBF, but isotonic dextran 70 gave a sustained increase to 122% of the baseline levels. There was no difference between the responses of nCBF in hydropic and normal cochleas for either control or hyperosmotic solutions. Measurements of systemic hematocrit at time intervals during and following the infusions showed that transient reductions of up to approximately 8% (for the maximum osmotic challenge) occurred during the infusion. It is concluded that the hyperosmotic treatments tested here are equally effective for short-term enhancements of nCBF in both normal and hydropic cochleas. The basis of the flow increase is partially rheologic and partially due to a local vasodilation.

Water Vapour Absorption in Terrestrial Isopods

ABSTRACT Continuous and intermittent gravimetric measurements have identified active water vapour absorption (WVA) in three species of terrestrial Isopoda. Water activity thresholds for uptake lie in the range 0.92–0.95. Above the threshold, WVA shows non-saturated kinetics; the rectum apparently serves as a supplementary avenue for fluid resorption during rapid uptake. Standardized uptake fluxes, corrected for vapour pressure deficit, can be varied, allowing animals to balance water losses accurately over long periods. Blocking experiments have localised the ventral pleon as the uptake site. The pleopods display ventilatory cycling during WVA. Cycle frequency increases with humidity, compensating for changes in activity deficit between uptake fluid and air, and allowing uptake rate to be maximised. Freezing-point depression studies reveal hyperosmotic fluid in the ventral pleon. Osmolalities are compatible with prior uptake rates of the specimens studied. WVA would allow terrestrial isopods to regulate their water balance in external activities below the haemolymph activity (approximately 0.99) and above the uptake threshold. Liquid water - an alternative source for hydration - is rapidly absorbed across the hydrophilic cuticle, posing severe danger of drowning.

Osmoregulation in the Field by Salt-Marsh Savannah SparrowsPasserculus sandwichensis beldingi

We studied the osmoregulatory strategy of salt-marsh savannah sparrows (Passerculus sandwichensis beldingi) in the field in Baja California, Mexico, and we compared these birds with a subspecies of savannah sparrow found concurrently in the uplands surrounding the salt marsh. Passerculus sandwichensis beldingi had higher plasma osmolalities (349 vs. 339 mmol/kg), higher ureteral urine osmolalities (577 vs. 477 mmol/kg), higher urine sodium concentrations (126 vs. 74 meq/L), higher urine flow rates (7–10 vs. 1.7 μL/min), and larger kidneys (0.36vs. 0.21 g/pair of kidneys) than the upland sparrows. Other unusual findings in the salt-marsh birds were the presence of substantial volumes of hyperosmotic fluids (up to 811 mmol/kg) in the lower intestine and uric acid extending into the ileum. The rectal epithelium of P. s. beldingi was relatively smooth, with few low apical membrane extensions, whereas that of the upland sparrows had a dense apical microvillous brush border. The maximum urine concentration that we measured in freshly captured P. s. beldingi was 2.7 times plasma osmolality. Our findings suggest an osmoregulatory strategy that includes a high intake of solute, a copious urine flow to excrete this solute load, and, at least at times, substantial refluxing into the intestines of hyperosmotic urinary fluids. This unusual strategy presumably reflects the unusual circumstance of a bird without salt glands living in a salt marsh.

The efficacy of iso- and hyperosmotic fluids as volume expanders in fixed-volume and uncontrolled hemorrhage

Rapid blood volume expansion is the goal in prehospital hemorrhage resuscitation. A comparison was made for fixed volume and uncontrolled hemorrhage between three fluid regimes: Ringer's lactate (RL), Macrodex (MD), or a small volume of a hyperosmotic solution (HSD, 7.5% NaCl/6% dextran 70) followed by RL. A mathematical model was developed to simulate blood volume restoration for these given hemorrhage and resuscitation situations. Model predictions for a fixed hemorrhage (35%) and reinfusion of each fluid regime (1 mL.min-1.kg-1) were found to agree with hematocrit and osmolality changes from experiments on anesthetized rabbits. HSD gave the quickest volume expansion after the controlled hemorrhage, which is a useful experimental model; however, it is not realistic of many trauma injuries. The model suggests for severe uncontrolled hemorrhage that HSD/RL initially hastens the bleed, yet the blood volume expansion is still more effective than RL alone for the first 20 minutes, making it an effective prehospital expander for most urban trauma situations.

The salivary glands of Hyalomma anatolicum anatolicum: Structural changes during attachment and feeding

The histology and ultrastructure of the salivary glands of male and female H.a. anatolicum ticks have been examined m unfed and feeding ticks with special emphasis on aspects related to the feeding process. The salivary glands of H.a. anatolicum consisted of three types of acinus (acinus I, II and III) in females and an additional type IV acinus in males. The type I acinus was agranular and showed slight morphologic changes during feeding. The presence of cells with ultrastructural features characteristic of epithelia involved in the secretion of hyperosmotic fluids supports the hypothesis that these acini secrete hygroscopic saliva during questing stages to absorb water from an unsaturated atmosphere. There were five granular cell types ( a, b, c 1– c 3) in type II acinus, three granular cell types ( d, e, and f) in type III acinus, and one granular cell type ( g) in type IV acinus. The cells a, d and e secreted most of their granules early in feeding and are considered to be cement precursors. The b and c cells appeared to synthesise and secrete their products throughout feeding and so are likely to secrete anticoagulants, enzymes and other pharmacologically active agents required during feeding. The interstitial cells, which were insignificant in acinar types II, III and IV of unfed ticks, became more distinct during feeding. The type III acinus in females showed remarkable cell transformations, during the course of feeding. The ablumenal interstitial cells of type III acinus, in females formed a basal labyrinth of extraordinary complexity by interdigitating with the basolateral membranes of transformed f cells to form a network of extracellular channels to excrete fluid during feeding. There was an enormous increase in the secretory granules of g cells as the feeding advanced. The secretory granules were released by a process of exocytosis, by direct fusion with the apical membranes and through channels connecting several granules.