Low-osmolar Media Research Articles

Symptomatic Intracranial Hemorrhage after Mechanical Thrombectomy - the Difference between Iso-Osmolar and Low-Osmolar Contrast Media.

Symptomatic intracranial hemorrhage (SICH) after mechanical thrombectomy (MT) is generally considered a critical complication. Hemorrhagic transformation after ischemic stroke has also been associated with contrast media administration. The objective of our study was to evaluate correlations between contrast media type and incidence of SICH after MT. Ninety-three consecutive patients (41 men; mean age, 80.2 years; range, 44-98 years) underwent MT reperfusion (expanded thrombolysis in cerebral infarction score, 2a-3) for acute large-vessel occlusion ischemic stroke within 8 h after symptom onset between April 2020 and July 2023 were retrospectively reviewed. Correlations between contrast media type (iso-osmolar or low-osmolar medium) and incidence of SICH were assessed. Contrast media were iso-osmolar in 60 cases or low-osmolar in 33 cases. The overall incidence of SICH was 5.5%. The frequency of SICH was significantly lower in the iso-osmolar group (1.7%) than in the low-osmolar group (12.1%; P = 0.033). Iso-osmolar contrast media was associated with a lower incidence of SICH compared with low-osmolar contrast media in patients after MT.

EPEC-induced activation of the Ca2+ transporter TRPV2 leads to pyroptotic cell death.

The enteropathogenic Escherichia coli (EPEC) type III secretion system effector Tir, which mediates intimate bacterial attachment to epithelial cells, also triggers Ca2+ influx followed by LPS entry and caspase-4-dependent pyroptosis, which could be antagonized by the effector NleF. Here we reveal the mechanism by which EPEC induces Ca2+ influx. We show that in the intestinal epithelial cell line SNU-C5, Tir activates the mechano/osmosensitive cation channel TRPV2 which triggers extracellular Ca2+ influx. Tir-induced Ca2+ influx could be blocked by siRNA silencing of TRPV2, pre-treatment with the TRPV2 inhibitor SET2 or by growing cells in low osmolality medium. Pharmacological activation of TRPV2 in the absence of Tir failed to initiate caspase-4-dependent cell death, confirming the necessity of Tir. Consistent with the model implicating activation on translocation of TRPV2 from the ER to plasma membrane, inhibition of protein trafficking by either brefeldin A or the effector NleA prevented TRPV2 activation and cell death. While infection with EPECΔnleA triggered pyroptotic cell death, this could be prevented by NleF. Taken together this study shows that while integration of Tir into the plasma membrane activates TRPV2, EPEC uses NleA to inhibit TRPV2 trafficking and NleF to inhibit caspase-4 and pyroptosis.

L form bacteria growth in low-osmolality medium.

L form bacteria do not have a cell wall and are thought to require medium of high osmolality for survival and growth. In this study we tested whether L forms can adapt to growth in lower osmolality medium. We first tested the Escherichia coli L form NC-7, generated in 1987 by Onoda following heavy mutagenesis. We started with growth in osmoprotective medium (~ 764 mOsm kg-1) and diluted it stepwise into medium of lower osmolality. At each step the cells were given up to 10 days to adapt and begin growing, during which they apparently acquired multiple new mutations. We eventually obtained a strain that could grow in LB containing only 34 mM NaCl, 137 mOsm kg-1 total. NC-7 showed a variety of morphologies including spherical, angular and cylindrical cells. Some cells extruded a bud that appeared to be the outer membrane enclosing an enlarged periplasm. Additional evidence for an outer membrane was sensitivity of the cells to the compound CHIR-090, which blocks the LPS pathway, and to EDTA which chelates Mg that may stabilize and rigidify the LPS in the outer membrane. We suggest that the mechanical rigidity of the outer membrane enables the angular shapes and provides some resistance to turgor in the low-osmolality media. Interestingly, cells that had an elongated shape underwent division shortly after addition of EDTA, suggesting that reducing the rigidity of the outer membrane under some turgor pressure induces division before lysis occurs. We then tested a well-characterized L form from Bacillus subtilis. L form strain LR-2L grew well with sucrose at 1246 and 791 mOsm kg-1. It survived when diluted directly into 440 mOsm kg-1 but grew poorly, achieving only 1/10 to 1/5 the density. The B. subtilis L form apparently adapted to this direct dilution by rapidly reducing cytoplasmic osmolality.

Evaluation of the safety of patients with pheochromocytoma during enhanced CT examination

[Objective] To assess the safety of patients with pheochromocytoma receiving iodinated contrast media injection during enhanced CT examination.[Methods] The systolic pressure,diastolic pressure,heart rate of 205 patients with suspected diagnosis of adrenal pheochromocytoma were continuously recorded 10 minutes before the examination,and 5 minutes,10 minutes,20 minutes,30 minutes,and 24 hours after the examination.Among them,50 patients whose diagnosis were confirmed by pathology as pheochromocytoma were set as group A.Others were excluded pheochromocytoma and 50 were extracted from them and named as the control group(group B).The changes of blood pressure and heart rate were analyzed at different time points.[Results] The changes of blood pressure and heart rate before and after the examination in two groups showed no significant difference,as well as those at different time points between two groups.[Conclusions] Intravenous injection of low-osmolar iodinated contrast media does not induce changes of blood pressure and heart rate in pheochromocytoma patients.Pheochromocytoma patients have the same safety as patients with other adrenal carcinoma during enhanced CT examination. Key words: Pheochromocytoma; Iodinated contrast media; Safety; Tomography

The Effect Of Iomeprol On Platelet Aggregation And Potential Risk Of Thrombogenecity

Iomeprol is a newer triiodinated nonionic low osmolar monomeric radiographic contrast agent. The physicochemical characteristics of this compound show high water solubility (aqueous solutions of higher iodine concentrations) which allows the formulation of contrast media to have lower osmolalities and viscosities. Lower viscosity values make this contrast agent flow better through catheters, allowing easier manual injection. Its formulation contains 400 mg iodine/ml, the highest concentration so far available on the market for non-ionic contrast media, resulting in better X-ray attenuation and image quality. Although Iomeprol appears to have a favorable profile because of the absence of EDTA (ethylene diamine tetra acetic acid) and the presence of trometamol, hydrochloric acid, water as buffer and stabilizer in its structure, it is still unknown whether this has a distinct advantage on thrombogenicity. In this article, we investigated the potential thrombogenicity of Iomeprol, a non-ionic, low osmolar radiocontrast medium, by measuring its effect on platelet reactivity and noted similarities with other non-ionic low osmolar agents. With the use of ADP, AYPGKF, and collagen stimulation, this contrast agent inhibited platelet aggregation at 50% contrast concentration, whereas the contrast medium did not inhibit aggregation at 10% concentrations. This behavior was similar to other non-ionic agents in its class in terms of platelet reactivity despite its unique properties.

In vitro study of the antimicrobial effects of radiological contrast agents used in arthrography

Aspiration arthrography using an iodinated contrast medium is a useful tool for the investigation of septic or aseptic loosening of arthroplasties and of septic arthritis. Previously, the contrast media have been thought to cause false negative results in cultures when present in aspirated samples of synovial fluid, probably because free iodine is bactericidal, but reports have been inconclusive. We examined the influence of the older, high osmolar contrast agents and the low osmolar media used currently on the growth of ten different micro-organisms capable of causing deep infection around a prosthesis. Five media were tested, using a disc diffusion technique and a time-killing curve method in which high and low inocula of micro-organisms were incubated in undiluted media. The only bactericidal effects were found with low inocula of Escherichia coli and Pseudomonas aeruginosa in ioxithalamate, one of the older ionic media. The low and iso-osmolar iodinated contrast media used currently do not impede culture. Future study must assess other causes of false negative cultures of synovial fluid and new developments in enhancing microbial recovery from aspirated samples.

Contrast-induced nephropathy: current practices among cardiologists

Objective: Contrast-induced nephropathy (CIN) is a serious complication of diagnostic and therapeutic coronary angiography. There are an increasing number of guidelines in the literature to help lessen this complication. Practice patterns in the cardiology community remain relatively unknown. This survey is an effort to better understand such practices. Methods: Questions were written based on the American College of Cardiology (ACC), the American Heart Association (AHA), and the Society of Cardiovascular Angiography and Intervention (SCAI) guidelines to identify cardiologist background and experience. The survey was emailed to 5000 randomly chosen cardiologists in December 2009. Results: A total of 291 responses were received. Among these, 97% reported checking renal function in all patients prior to angiography, 45% checked both estimated glomerular filtration rate (eGFR) and serum creatinine (SCr), 31% checked SCr alone, 19% checked eGFR alone, and 2% checked albumin-to-creatinine (A–C) ratio. Among responding cardiologists, 70% considered eGFR level less than 60 mL/min/1.73 m2 a high risk for CIN whereas 25% considered a level less than 30 mL/min/1.73 m2 a high risk. Thirty percent used only isosmolar media in high-risk patients, 33% used only low osmolar media, and 37% used either one. Conclusions: There is significant diversity in the measures taken by cardiologists to prevent CIN. More studies and clearer guidelines are needed to unify the practices.

Effects of osmolality on sperm morphology, motility and flagellar wave parameters in Northern pike ( Esox lucius L.)

Northern pike ( Esox lucius L.) spermatozoa are uniflagellated cells differentiated into a head without acrosome, a midpiece and a flagellar tail region flanked by a fin structure. Total, flagellar, head and midpiece lengths of spermatozoa were measured and show mean values of 34.5, 32.0, 1.32, 1.17 μm, respectively, with anterior and posterior widths of the midpiece measuring 0.8 and 0.6 μm, respectively. The osmolality of seminal plasma ranged from 228 to 350 mOsmol kg −1 (average: 283.88 ± 33.05). After triggering of sperm motility in very low osmolality medium (distilled water), blebs appeared along the flagellum. At later periods in the motility phase, the tip of the flagellum became curled into a loop shape which resulted in a shortening of the flagellum and a restriction of wave development to the proximal part (close to head). Spermatozoa velocity and percentage of motile spermatozoa decreased rapidly as a function of time postactivation and depended on the osmolality of activation media ( P < 0.05). In general, the greatest percentage of motile spermatozoa and highest spermatozoa velocity were observed between 125 and 235 mOsmol kg −1. Osmolality above 375 mOsmol kg −1 inhibited the motility of spermatozoa. After triggering of sperm motility in activation media, beating waves propagated along the full length of flagella, while waves appeared dampened during later periods in the motility phase, and were absent at the end of the motility phase. By increasing osmolality, the velocity of spermatozoa reached the highest value while wave length, amplitude, number of waves and curvatures also were at their highest values. This study showed that sperm morphology can be used for fish classification. Sperm morphology, in particular, the flagellar part showed several changes during activation in distilled water. Sperm motility of pike is inhibited due to high osmolality in the seminal plasma. Osmolality of activation medium affects the percentage of motile sperm and spermatozoa velocity due to changes in flagellar wave parameters.

Risk of contrast-induced nephropathy in patients with normal renal function: iso-osmolar versus low-osmolar medium

Risk of contrast-induced nephropathy in patients with normal renal function: iso-osmolar versus low-osmolar medium

Regulation of chitin synthase activity in the dimorphic fungus Benjaminiella poitrasii by external osmotic pressure.

The effects of changes in external osmotic pressure on chitin synthase activity of a dimorphic fungus, Benjaminiella poitrasii, have been investigated. Mycelial and yeast cells incubated in medium of low osmolality (distilled water, 0 mOsm) for 10 min had 2-3-fold higher specific activities of native chitin synthase in mixed membrane preparations than cells that had been subjected to a high osmolality medium (1.2 M sorbitol in distilled water, 1612 mOsm). Cells suspended in media of different osmolalities for 10 min were also affected in the extent of germ tube formation. Germ tube formation was highest in cells incubated in low osmolality medium. The addition of protein phosphatase inhibitors (cyclosporin A, 1.2 micrograms/ml; cantharidin, 20 microM) abolished the effect of hypo-osmotic stress on chitin synthase activation of yeast mixed membrane preparations. The presence of protein kinase inhibitors (genistein, 40 micrograms/ml; H-7, 100 microM) and a Ca2+ channel blocker (verapamil, 50 microM) reduced chitin synthase activity to 50-60% of that observed in cells under hypo-osmotic shock. These inhibitors also inhibited germ tube formation. This suggests that chitin synthase activity and yeast hyphal morphogenesis are both subject to regulation by osmotic pressure, phosphorylation and calcium.

The Osmotic Activation of Transporter ProP Is Tuned by Both Its C-terminal Coiled-coil and Osmotically Induced Changes in Phospholipid Composition

Transporter ProP of Escherichia coli (ProPEc) senses extracellular osmolality and mediates osmoprotectant uptake when it is rising or high. A replica of the ProPEc C terminus (Asp468-Arg497) forms an intermolecular alpha-helical coiled-coil. This structure is implicated in the osmoregulation of intact ProPEc, in vivo. Like that from Corynebacterium glutamicum (ProPCg), the ProP orthologue from Agrobacterium tumefaciens (ProPAt) sensed and responded to extracellular osmolality after expression in E. coli. The osmotic activation profiles of all three orthologues depended on the osmolality of the bacterial growth medium, the osmolality required for activation rising as the growth osmolality approached 0.7 mol/kg. Thus, each could undergo osmotic adaptation. The proportion of cardiolipin in a polar lipid extract from E. coli increased with extracellular osmolality so that the osmolality activating ProPEc was a direct function of membrane cardiolipin content. Group A ProP orthologues (ProPEc, ProPAt) share the C-terminal coiled-coil domain and were activated at low osmolalities. Like variant ProPEc-R488I, in which the C-terminal coiled-coil is disrupted, ProPEc derivatives that lack the coiled-coil and Group B orthologue ProPCg required a higher osmolality to activate. The amplitude of ProPEc activation was reduced 10-fold in its deletion derivatives. The coiled-coil structure is not essential for osmotic activation of ProP per se. However, it tunes Group A orthologues to osmoregulate over a low osmolality range. Coiled-coil lesions may impair both coiled-coil formation and interaction of ProPEc with amplifier protein ProQ. Cardiolipin may contribute to ProP adaptation by altering bulk membrane properties or by acting as a ProP ligand.

Gadolinium contrast media are more nephrotoxic than a low osmolar iodine medium employing doses with equal x-ray attenuation in renal arteriography: An experimental study in pigs 1

To investigate in a unilaterally nephrectomized porcine model whether gadolinium contrast media (Gd-CM) are less nephrotoxic than iodine media (I-CM) in x-ray arteriography of a kidney made temporarily ischemic by arterial balloon occlusion. In a noncrossover design, 3 mL of each test solution were injected in eight pigs (mean weight 19 kg) at a rate of 20 mL/min into the right renal artery at the start of a 10-minute period of ischemia. In group 1 (40 pigs) we injected 0.5 M gadopentetate, 0.5 M gadodiamide, 0.5 M iohexol (190 mg I/mL), 0.18 M iohexol (70 mg I/mL; with an x-ray attenuation equal to that of 0.5 M Gd-CM at 80 kV), and saline. In group 2 (24 pigs), we tested 0.18 M iohexol with ischemia and saline with and without ischemia. Gd- and iodine contrast media functioned as markers of glomerular filtration rate (GFR). When saline was tested, a low dose of iohexol (3 mL per pig; 300 mg I/mL) was injected as GFR marker intravenously in group 1 and into the renal artery in group 2. The plasma half-life elimination times of the CM 1-3 hours after injection were used to compare the effects of the different test solutions on GFR. Longer half-life means lower GFR. Group 1: median plasma half-life elimination time of the GFR marker was 3 340 minutes after injection of 0.5 M gadopentetate, 256 after 0.5 M gadodiamide, 179 after 0.5 M iohexol, 143 after 0.18 M iohexol, and 133 minutes after saline. All differences except that between 0.18 M iohexol and saline were statistically significant (P < .01). Group 2: median plasma half-life was 174 minutes after 0.18 M iohexol with ischemia, 196 minutes after saline with ischemia, and 195 minutes after saline without ischemia. There were no significant differences between the test solutions in group 2 (P > .05). In pigs, 0.5 M Gd-CM were more nephrotoxic than both equal-attenuating (70 mg I/mL) and equimolar (190 mg I/mL) concentrations of the I-CM iohexol. These results do not support the "off-label" use of Gd-CM for renal x-ray arteriography in man instead of commercially available concentrations of iodine contrast media at 140, 150 and 180 mg I/mL or diluted to 70 mg I/mL.

EFFECTS OF GENTAMICIN, LIPOPOLYSACCHARIDE, AND CONTRAST MEDIA ON IMMORTALIZED PROXIMAL TUBULAR CELLS

This study was performed to evaluate necrosis, apoptosis, and intracellular calcium levels ([Ca2+]i) in LLC-PK1 (epithelial cell line from pig kidney) induced by GE associated with LPS and a low-osmolality media, Hexabrix (HE).

EFFECTS OF GENTAMICIN, LIPOPOLYSACCHARIDE, AND CONTRAST MEDIA ON IMMORTALIZED PROXIMAL TUBULAR CELLS

Aminoglycosides are widely used in the treatment of gram-negative bacterial infections. Gentamicin (GE) acts mainly in proximal tubular cells, where it is uptake via organic anion transport system and it induces a high incidence of nephrotoxicity, which is characterized by tubular necrosis leading to acute renal failure in 10 to 50% of patients. Gram-negative bacteria have lipopolysaccharide (LPS) which is an endotoxin that causes renal damage. Moreover, many patients are undergone exams using radiologic contrast, which is a risk factor to induce a hemodynamic change in the kidney and to develop acute renal failure. Intracellular calcium [Ca2+]i is involved in renal cellular injury and maybe mediate the effects provoked by these drugs. This study was performed to evaluate necrosis, apoptosis and intracellular calcium levels ([Ca2+]i) in LLC-PK1 (epithelial cell line from pig kidney) induced by GE associated with LPS and a low-osmolality media, Hexabrix (HE).

Regulation of intracellular pH in rat renal inner medullary thin limbs of Henle's loop.

Regulation of intracellular pH (pHi) was studied in isolated rat renal inner medullary thin limbs of Henle's loop in bicarbonate/phosphate-buffered medium with high pCO2, high osmolality ( congruent with670 mosmol/kg H2O; 270 mM urea; 180 mM NaCl), organic osmolytes, and a pH of 6.8 to approximate the physiological in vivo environment. The pH-sensitive fluorescent dye 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein (BCECF) was used to measure pHi. Resting pHi was always acid and significantly more acid in descending thin limb (DTL) cells than in ascending thin limb (ATL) cells from pure or mixed-type thin limbs. Resting pHi was slightly but significantly higher in both DTLs and ATLs in high osmolality ( approximately 670 mosmol/kg H2O) than in low osmolality ( approximately 290 mosmol/kg H2O) medium but not when sucrose replaced urea. In both DTLs and ATLs the rate of recovery of pHi following additional acidification with an NH4Cl pulse was reduced by Na+ removal from the medium and by the addition of 60 microM HOE642 (an inhibitor of the Na+/H+ exchanger, NHE1), 55 microM S1611 (inhibitor of Na+/H+ exchanger, NHE3), 1 microM bafilomycin A1 (an inhibitor of vacuolar H+ -ATPase), or 20 microM Schering 28080 (an inhibitor of H+ -K+ -ATPase) to the medium. Resting pHi was also reduced by 60 microM HOE642, 55 microM S1611, and 20 microM Schering 28080. In both DTLs and ATLs, RT-PCR revealed message for NHE1, NHE3, and vacuolar H+ -ATPase; immunocytochemistry demonstrated the expression of the protein for NHE1 (basolateral membrane), NHE3 (luminal membrane), and H+ -K+ -ATPase (luminal membrane). These data suggest that pHi in rat inner medullary thin limbs is regulated by urea and by basolateral and luminal H+ extrusion via NHE1, NHE3, vacuolar H+ -ATPase, and H+ -K+ -ATPase.

Nucleotide content, oxydative phosphorylation, morphology, and fertilizing capacity of turbot (Psetta maxima) spermatozoa during the motility period

The interdependence between motility, respiration, ATP production, and utilization was investigated in intact spermatozoa of turbot (Psetta maxima), a marine teleost. When spermatozoa were diluted in a hyperosmotic medium (>300 mOsmol/kg), they immediately became motile, and the intracellular concentration of ATP as well as the adenylate energy charge ratio dropped concomitant with the straight-line velocity. The ADP and AMP levels increased from 1.4 to 8.0 nmole/108 cells and from 0.6 to 6.0 nmole/108 cells, respectively. Moreover, 31P-NMR spectra recorded prior to the swimming phase revealed the presence of phosphomonoesters (PMEs) and phosphodiesters (PDEs), intracellular inorganic phosphate (Pi), and phosphocreatine (PCr). At the end of the motility period, PCr, PDE, and PME decreased, while the Pi level increased markedly. Following initiation of motility, O2 consumption of spermatozoa increased from 34.9 to 124.8 O2 nmole/109 spermatozoa/min. FCCP, an uncoupler of oxydative phosphorylation, did not significantly affect the respiratory rate of motile spermatozoa. Ouabain, a specific inhibitor of (Na+/K+)/ATPase, slightly decreased the respiration rate of motile spermatozoa, indicating that the major part of ATP catabolism was linked to dynein ATPase. Inhibitors of the respiratory chain (KCN, NaN3, NaHCO3–, oligomycin) reduced sperm respiration, percentage of motile cells, velocity, and adenylate contents. Following the reactivation of motility of demembranated spermatozoa, KCN, NaN3, NaHCO3– altered the flagellar beat frequency, demonstrating that these respiratory inhibitors possess action sites other than mitochondria. Mitochondrial oxydative phosphorylation is highly requested to produce energy required during motion. Nevertheless it is insufficient to maintain endogenous ATP stores. A second phase of motility was induced by a transfer of exhausted spermatozoa into an ionic medium of low osmolality (200 mOsmol/kg) for 30 min. Spermatozoa, once reactivated in AM, recovered 55% of initial motility and 31% of initial fertilization rate. In hypo-osmotic medium, mitochondrial oxydative phosphorylation also induced ATP regeneration. Following activation of movement, several morphological changes were observed in the mitochondria and the midpiece. Mol. Reprod. Dev. 53:230–243, 1999. © 1999 Wiley-Liss, Inc.

Nucleotide content, oxidative phosphorylation, morphology, and fertilizing capacity of turbot (Psetta maxima) spermatozoa during the motility period.

The interdependence between motility, respiration, ATP production, and utilization was investigated in intact spermatozoa of turbot (Psetta maxima), a marine teleost. When spermatozoa were diluted in a hyperosmotic medium (>300 mOsmol/kg), they immediately became motile, and the intracellular concentration of ATP as well as the adenylate energy charge ratio dropped concomitant with the straight-line velocity. The ADP and AMP levels increased from 1.4 to 8.0 nmole/10(8) cells and from 0.6 to 6.0 nmole/10(8) cells, respectively. Moreover, 31P-NMR spectra recorded prior to the swimming phase revealed the presence of phosphomonoesters (PMEs) and phosphodiesters (PDEs), intracellular inorganic phosphate (Pi), and phosphocreatine (PCr). At the end of the motility period, PCr, PDE, and PME decreased, while the Pi level increased markedly. Following initiation of motility, O2 consumption of spermatozoa increased from 34.9 to 124.8 O2 nmole/10(9) spermatozoa/min. FCCP, an uncoupler of oxidative phosphorylation, did not significantly affect the respiratory rate of motile spermatozoa. Ouabain, a specific inhibitor of (Na+/K+)/ATPase, slightly decreased the respiration rate of motile spermatozoa, indicating that the major part of ATP catabolism was linked to dynein ATPase. Inhibitors of the respiratory chain (KCN, NaN3, NaHCO3-, oligomycin) reduced sperm respiration, percentage of motile cells, velocity, and adenylate contents. Following the reactivation of motility of demembranated spermatozoa, KCN, NaN3, NaHCO3- altered the flagellar beat frequency, demonstrating that these respiratory inhibitors possess action sites other than mitochondria. Mitochondrial oxidative phosphorylation is highly requested to produce energy required during motion. Nevertheless it is insufficient to maintain endogenous ATP stores. A second phase of motility was induced by a transfer of exhausted spermatozoa into an ionic medium of low osmolality (200 mOsmol/kg) for 30 min. Spermatozoa, once reactivated in AM, recovered 55% of initial motility and 31% of initial fertilization rate. In hypo-osmotic medium, mitochondrial oxidative phosphorylation also induced ATP regeneration. Following activation of movement, several morphological changes were observed in the mitochondria and the midpiece.

Effect of low-osmolality nutrient media on growth and culturability of Campylobacter species.

The growth and culturability of Campylobacter jejuni NCTC 11351 and other campylobacters were examined in media having different osmolalities at a range of temperatures (4, 25, and 42 degreesC). The medium osmolalities used ranged from the osmolality of full-strength nutrient medium (modified campylobacter broth having an osmolality of around 254 mosmol) down to 96 mosmol. The following two methods were used to produce media having different osmolalities: dilution of the nutrient medium with distilled water and reformulation of the medium such that the concentrations of various osmolytes were altered while the nutrient content of the medium was unchanged. The results obtained with the two experimental methods were similar, indicating that there was an osmotic threshold effect, such that none of the campylobacters examined (C. jejuni NCTC 11351 and ATCC 33291, Campylobacter lari, and Campylobacter coli) grew in media having osmolalities around 130 mosmol and at temperatures below at 42 degreesC. Conversely, growth occurred in media having osmolalities of around 175 mosmol and above. Osmolar concentrations can be expressed in terms of osmolarity or osmolality. Osmolality is easier to evaluate, is the more commonly used term, and was used in the current study. In nutrient media having low osmolalities (i.e., 130 mosmol and below), the number of CFUs per milliliter declined rapidly regardless of the temperature, and no cells were recovered after 24 h. However, at nongrowth temperatures (25 and 4 degreesC) in higher-osmolality media (175 mosmol and above) a significant population was recovered throughout the experiment (up to 96 h). In low-osmolality nutrient media, the cellular morphology was principally coccoid, while in the early stages of growth in full-strength media the morphology was predominantly rodlike. We propose that the formation of coccoid cells in these experiments was the result of osmotic stress in low-osmolality media. This osmotic effect was apparent regardless of the osmolyte used to reformulate the medium (NaCl, KCl, Na2SO4, NH4Cl, and glucose were used).

Regulation of chitin synthase activity in the dimorphic fungus Benjaminiella poitrasii by external osmotic pressure

The effects of changes in external osmotic pressure on chitin synthase activity of a dimorphic fungus, Benjaminiella poitrasii, have been investigated. Mycelial and yeast cells incubated in medium of low osmolality (distilled water, 0 mOsm) for 10 min had 2–3-fold higher specific activities of native chitin synthase in mixed membrane preparations than cells that had been subjected to a high osmolality medium (1.2 M sorbitol in distilled water, 1612 mOsm). Cells suspended in media of different osmolalities for 10 min were also affected in the extent of germ tube formation. Germ tube formation was highest in cells incubated in low osmolality medium. The addition of protein phosphatase inhibitors (cyclosporin A, 1.2 μg/ml; cantharidin, 20 μM) abolished the effect of hypo-osmotic stress on chitin synthase activation of yeast mixed membrane preparations. The presence of protein kinase inhibitors (genistein, 40 μg/ml; H-7, 100 μM) and a Ca 2+ channel blocker (verapamil, 50 μM) reduced chitin synthase activity to 50–60% of that observed in cells under hypo-osmotic shock. These inhibitors also inhibited germ tube formation. This suggests that chitin synthase activity and yeast hyphal morphogenesis are both subject to regulation by osmotic pressure, phosphorylation and calcium.

Low-osmolar ionic contrast media was better than nonionic media for ischemic complications of angioplasty

Source Citation Grines CL, Schreiber TL, Savas V, et al. A randomized trial of low osmolar ionic versus nonionic contrast media in patients with myocardial infarction or unstable angina undergoing ...