Impact of extracellular-to-intracellular fluid volume ratio on albuminuria in patients with type 2 diabetes: A cross-sectional and longitudinal cohort study

AIMS/INTRODUCTION

Body fluid volume imbalance is common in patients with kidney failure, and is associated with all-cause mortality. This study aimed to investigate the association between fluid volume imbalance and albuminuria in patients with type 2 diabetes mellitus without kidney failure.

MATERIALS AND METHODS

Using data from one cohort study, a baseline cross-sectional study of 432 participants and a longitudinal cohort study of 368 participants who could follow up was carried out. Body fluid imbalance was determined by measuring the extracellular water (ECW)-to-intracellular water (ICW) ratio (ECW/ICW) using bioelectrical impedance analysis. A change in the urinary albumin-to-creatinine ratio (ACR) was defined as the ratio of urinary ACR at follow up to that at baseline. The ECW/ICW ratio was compared with the level of albuminuria.

RESULTS

In this cross-sectional study, the ECW/ICW ratio increased with the level of albuminuria. There was an association between the ECW/ICW ratio and logarithms of urinary ACR after adjusting for covariates (β = 0.205, P < 0.001). Furthermore, the ECW/ICW ratio was associated with a change in the urinary ACR after adjusting for covariates (β = 0.176, P = 0.004) in this longitudinal study. According to the receiver operating characteristic curve, the optimal cut-off point of the ECW/ICW ratio for incident macroalbuminuria, defined as ACR >300 mg/gCr, was 0.648 (area under the curve 0.78, 95% confidence interval 0.58-0.90).

CONCLUSIONS

The ECW/ICW ratio is independently associated with the level of albuminuria in patients with type 2 diabetes mellitus without kidney failure. This reinforces the importance of monitoring fluid balance in patients with type 2 diabetes mellitus.

Extracellular and Intracellular Fluid Shifts on the Onset of Transcutaneous Auricular Vagus Nerve Stimulation

In this paper, we propose multifrequency body impedance measurement technique for monitoring the onset of vagus nerve stimulation. In response to transcutaneous electrical vagus stimulation, changes occur in body fluids i.e. fluid shifts in extracellular and intracellular media that can be assessed by Cole parameters R_e and R_i before and after stimulus, by measuring single side impedance spectroscopy (from 3 kHz to 1 MHz) between wrist and ankle. Following a resting period of 5 minutes in supine position, auricular vagus nerve was stimulated for 3 minutes and BIS performed every 10 seconds, on 23-27 years old, 5 healthy subjects. During the stimulation phase, either an increase or a decrease was observed in extracellular and intracellular fluids. In 3 of the subjects, an ECF decrease of 0.02% per kg was compensated by 0.02 to 0.06% per kg increase in ICF; with a correlation coefficient of -0,70 to -0,79; suggesting fluid shifts between ECF and ICF. With the other 2 subjects, both ECF and ICF decreased by about 0.02% per kg. The study was performed with a limited number of participants; to reach statistically meaningful results measurements will be performed over a larger sample size.

Dehydration of a diver during a hyperbaric chamber exposure with oxygen decompression

OBJECTIVE

An analysis of factors that may indicate both the type and degree of dehydration of a diver's body following a dry chamber hyperbaric exposure.

METHODS

The study was participated by 63 men - professional divers, with extensive diving experience, aged 24-51 years (average age 32.6). The subjects underwent two hyperbaric exposures, one to a pressure of 0.3 MPa and one to a pressure of 0.6 MPa, with oxygen decompression. The exposures were carried out in a hyperbaric chamber pursuant to the decompression tables of the Polish Navy, with the observance of a 24-hour interval between exposures. Blood samples were collected from the participants in order to perform a blood morphology test. Body weight was measured with the bioelectrical impedance method using the Maltron BioScan 920 device.The results were subjected to statistical analysis. The following blood morphology parameters were analyzed: hematocrit (Ht), erythrocyte size (MCV), color index (MCHC) and body weight composition: total water (TBW), extracellular water (ECW), intracellular water (ICW).

RESULTS

The studies have shown that during a hyperbaric exposure in the chamber the diver's body becomes dehydrated, with observable loss of both intracellular water as evidenced by the reduction of hematocrit content and erythrocyte size, as well as extracellular water, with the accompanying increase in the color index.

CONCLUSIONS

Hyperbaric conditions are conducive to the dehydration of the diver's body, however to a degree which does not lead to an occurrence of health hazards. Good care for one's health through proper nutrition and hydration are sufficient preventive and protective measures.

[Study on calculation method of internal and external fluid capacity of human cells based on bioimpedance spectroscopy]

Bioelectrical impedance measurement technology is a non-invasive detection technology for extracting human physiological and pathological information. The analysis method of the relationship between bioimpedance and human physiological parameters is an important part of this technology. In order to calculate the internal and external liquid volume of human cells more accurately, based on the Moissl equation for calculating the internal and external fluid volume of human cells, a segmented human bioimpedance spectrum measurement model and an improved calculation method of intracellular and external fluid capacity were proposed. The measurement and calculation experiments of the intracellular and extracellular fluid volume before and after the human body's water intake were designed and compared with the Moissl calculation method. The results show that the improved calculation method can calculate the intracellular and extracellular fluid volumes more effectively, and the relative error is less than 5%, which may provide new ideas or more accurate methods for the analysis of human body components, facilitating the diagnosis and treatment of diseases.

What dominates the time dependence of diffusion transverse to axons: Intra- or extra-axonal water?

Brownian motion of water molecules provides an essential length scale, the diffusion length, commensurate with cell dimensions in biological tissues. Measuring the diffusion coefficient as a function of diffusion time makes in vivo diffusion MRI uniquely sensitive to the cellular features about three orders of magnitude below imaging resolution. However, there is a longstanding debate, regarding which contribution - intra- or extra-cellular - is more relevant in the overall time-dependence of the MRI-derived diffusion metrics. Here we resolve this debate in the human brain white matter. By varying not just the diffusion time, but also the gradient pulse duration of a standard diffusion MRI sequence, we identify a functional form of the measured time-dependent diffusion coefficient transverse to white matter tracts in 10 healthy volunteers. This specific functional form is shown to originate from the extra-axonal space, and provides estimates of the fiber packing correlation length for axons in a bundle. Our results offer a metric for the outer axonal diameter, a promising candidate marker for demyelination in neurodegenerative diseases. From the methodological perspective, our analysis demonstrates how competing models, which describe different physics yet interpolate standard measurements equally well, can be distinguished based on their prediction for an independent "orthogonal" measurement.

A Randomized Crossover Trial of Dietary Sodium Restriction in Stage 3-4 CKD

BACKGROUND AND OBJECTIVES

Patients with chronic kidney disease (CKD) are often volume expanded and hypertensive. Few controlled studies have assessed the effects of a sodium-restricted diet (SRD) in CKD.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We conducted a randomized crossover trial to evaluate the effect of SRD (target <2 g sodium per day) versus usual diet on hydration status (by bioelectrical impedance spectroscopy) and blood pressure (BP) between May of 2009 and May of 2013. A total of 58 adults with stage 3-4 CKD were enrolled from two academic sites: University of Michigan (n=37) and University of North Carolina at Chapel Hill (n=21); 60% were men, 43% were diabetic, 93% were hypertensive, and mean age was 61 years. Participants followed SRD or usual diet for 4 weeks, followed by a 2-week washout period and a 4-week crossover phase. During the SRD, dieticians provided counseling every 2 weeks, using motivational interviewing techniques.

RESULTS

Whole-body extracellular volume and calf intracellular volume decreased by 1.02 L (95% confidence interval [95% CI], -1.48 to -0.56; P<0.001) and -0.06 L (95% CI, -0.12 to -0.01; P=0.02), respectively, implying decreased fluid content on the SRD compared with usual diet. Significant reductions in urinary sodium (-57.3 mEq/24 h; 95% CI, -81.8 to -32.9), weight (-2.3 kg; 95% CI, -3.2 to -1.5), and 24-hour systolic BP (-10.8 mmHg; 95% CI, -17.0 to -4.6) were also observed (all P<0.01). Albumin-to-creatinine ratio did not change significantly and mean serum creatinine increased slightly (0.1 mg/dl; 95% CI, -0.01 to 0.2; P=0.06). No period or carryover effects were observed. Results were similar when analyzed from phase 1 only before crossover, although P values were modestly larger because of the loss of power.

CONCLUSIONS

In this randomized crossover trial, implementation of SRD in patients with CKD stage 3-4 resulted in clinically and statistically significant improvement in BP and hydration status. This simple dietary intervention merits a larger trial in CKD to evaluate effects on major clinical outcomes.

Association of Plasminuria with Overhydration in Patients with CKD

BACKGROUND AND OBJECTIVES

Hypervolemia is a common feature of patients with CKD and associated with hypertension. Recent work has shown stimulation of sodium retention by urinary plasmin during nephrotic syndrome. However, it is unclear whether plasminuria plays a role in patients with stable CKD and non-nephrotic proteinuria.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

In this cross-sectional study, we analyzed the fluid status of 171 patients with CKD consecutively presenting to our outpatient clinic from 2012 to 2013 using bioimpedance spectroscopy (Body Composition Monitor [BCM]; Fresenius Medical Care, Germany) and its associations to the urinary excretion of plasminogen and plasmin from a spot urine sample. Two-electrode voltage clamp measurements were performed in Xenopus laevis oocytes expressing human epithelial sodium channel to investigate whether plasmin in concentrations found in urine can activate the channel.

RESULTS

Overhydration >5% and overhydration >10% of the extracellular volume were found in 29% and 17% of the patients, respectively, and overhydration was associated with edema, hypertension, higher stages of CKD, and proteinuria. Proteinuria was the strongest independent predictor for overhydration (+0.58 L/1.73 m(2) per 10-fold increase; P<0.001). Urinary excretion of plasmin(ogen) quantified by ELISA correlated strongly with proteinuria (r=0.87) and overhydration (r=0.47). Using a chromogenic substrate, active plasmin was found in 44% of patients and correlated with proteinuria and overhydration. Estimated urinary plasmin concentrations were in a range sufficient to activate epithelial sodium channel currents in vitro. In multivariable analysis, urinary excretion of plasmin(ogen) was associated with overhydration similar to proteinuria.

CONCLUSIONS

Hypervolemia in patients with CKD is strongly associated with proteinuria, even in the non-nephrotic range. Protein-rich urine contains high amounts of plasminogen and active plasmin, rendering plasminuria as a possible link between proteinuria and hypervolemia.

Applicability of vacuum impregnation to modify physico-chemical, sensory and nutritive characteristics of plant origin products--a review

Vacuum impregnation is a non-destructive method of introducing a solution with a specific composition to the porous matrices of fruit and vegetables. Mass transfer in this process is a result of mechanically induced differences in pressure. Vacuum impregnation makes it possible to fill large volumes of intercellular spaces in tissues of fruit and vegetables, thus modifying physico-chemical properties and sensory attributes of products. This method may be used, e.g., to reduce pH and water activity of the product, change its thermal properties, improve texture, color, taste and aroma. Additionally, bioactive compounds may be introduced together with impregnating solutions, thus improving health-promoting properties of the product or facilitating production of functional food.

Precision and within- and between-day variation of bioimpedance parameters in children aged 2-14 years

BACKGROUND & AIMS

Bioimpedance spectroscopy (BIS) offers the possibility to perform rapid estimates of fluid distribution and body composition. Few studies, however, have addressed the precision and biological variation in a pediatric population. Our objectives were to evaluate precision, variation within- and between-days for the BIS-determined parameters total body fluid, extra-cellular fluid, intra-cellular fluid, body cell mass, fat-free mass, extra-cellular resistance, intra-cellular resistance and percentage body fat using a Xitron 4200.

METHODS

All 133 children (81 boys, 52 girls; 2.4-14.9 years) had one series measured on day one (precision population). Forty-four children had a second series on day one (within-day sub-population). Thirty-two children had a series measured on the next day (between-day sub-population). Each measurement series consisted of three repeated measurements. A linear mixed model was used for statistical analysis.

RESULTS

The precision was 0.3-0.8% in children ≥6 years and 0.5-2.4% in children <6 years with a statistically significant difference between the two age-groups (p<0.001). Within-day variation was 1.1-2.8% and between-day variation 2.4-5.7%. Total variation and reference change values are reported.

CONCLUSION

The Xitron 4200 has a very good but age-dependent precision. The median value of three repeated measurements is recommended in order to avoid incorrect measurements.

Comparison of changes of body water measured by using bioelectrical impedance analysis between lercanidipine and amlodipine therapy in hypertensive outpatients

OBJECTIVE

To compare changes of body water measured by using bioelectrical impedance analysis (BIA), between lercanidipine and amlodipine therapy.

MATERIAL AND METHOD

This is a prospective randomized open-label study in hypertensive outpatients. Eighty patients were randomized into two groups; 1) amlodipine 5 mg/d and 2) lercanidipine 10 mg/d. Patients were assessed for changes in total body water (TBW), extracellular water (ECW) and intracellular water (ICW) at week 4 and 8 after treatment.

RESULTS

At baseline body water in both groups were similar. After treatment, both groups did not have significant changes in body water from baseline. Seven patients in amlodipine group (17.5%) and none of lercanidipine group developed edema; p = 0.012. Among those seven patients, TBW, ECW and ICW all increased significantly from baseline.

CONCLUSION

BIA did not detected changes of body water in most patients. However, in patients who developed edema, TBW, ECW and LCW significantly increased from baseline with the greatest changes seen in extracellular compartment.

Disorders of potassium homeostasis: pathophysiology and management

Disorders of potassium homeostasis are common electrolyte abnormalities encountered in hospitalized patients. Hypokalemia and hyperkalemia have been estimated to occur in about 21% and 3% of hospitalized patients, respectively; though the morbidity and mortality associated with the latter is significantly higher. Potassium is a predominantly intracellular ion and the understanding of its dynamics between intra- and extracellular fluid milieus, along with its handling by the kidneys, is important in the diagnosis and treatment of potassium disorders. This article aims to provide a clinically relevant update on management of potassium disorders for internists.

Kinetics and activation energy of recrystallization of intracellular ice in mouse oocytes subjected to interrupted rapid cooling

Intracellular ice formation (IIF) is almost invariably lethal. In most cases, it results from the too rapid cooling of cells to below -40 degrees C, but in some cases it is manifested, not during cooling, but during warming when cell water that vitrified during cooling first devitrifies and then recrystallizes during warming. Recently, Mazur et al. [P. Mazur, I.L. Pinn, F.W. Kleinhans, Intracellular ice formation in mouse oocytes subjected to interrupted rapid cooling, Cryobiology 55 (2007) 158-166] dealt with one such case in mouse oocytes. It involved rapidly cooling the oocytes to -25 degrees C, holding them 10 min, rapidly cooling them to -70 degrees C, and warming them slowly until thawed. No IIF occurred during cooling but intracellular freezing, as evidenced by blackening of the cells, became detectable at -56 degrees C during warming and was complete by -46 degrees C. The present study differs in that the oocytes were warmed rapidly from -70 degrees C to temperatures between -65 and -50 degrees C and held for 3-60 min. This permitted us to determine the rate of blackening as function of temperature. That in turn allowed us to calculate the activation energy (E(a)) for the blackening process; namely, 27.5 kcal/mol. This translates to about a quadrupling of the blackening rate for every 5 degrees C rise in temperature. These data then allowed us to compute the degree of blackening as a function of temperature for oocytes warmed at rates ranging from 10 to 10,000 degrees C/min. A 10-fold increase in warming rate increased the temperature at which a given degree of blackening occurred by 8 degrees C. These findings have significant implications both for cryobiology and cryo-electron microscopy.

[Research and comparative characteristic of the factors determining elasticity of the human skin]

Changes in skin elasticity have been analyzed under different conditions (upon skin stretching, at different thickness of the skin, at different contents of collagen, intercellular and endocellular liquids, upon changes of venous pressure, and during contraction and relaxation of smooth muscles in skin vessels - vasomotions). Elasticity was defined by the acoustic method from the speed of diffusion of a superficial sheared acoustic wave in the skin, by the autoresonant method from the mechanical resonance frequency of skin, and from the vacuum pressure needed for skin site deformation of constant volume. It was shown that the major factors determining the elasticity of skin are it stretching, thickness, and the contents of collagen and liquids in it. The influence on elasticity of venous pressure and the contraction activity of smooth muscles in vessels is not essential. This suggests that the parameters of skin elasticity can be used as indicators of systemic and local lesions of the connective tissue.

Comparison of the body fluid levels in healthy individuals and those with schizophrenia in Japan: Using the bioelectrical impedance method

Polydipsia and water intoxication have been found to be care problems in people with schizophrenia in many countries. This Japanese study measured the body fluid distribution and body fat of 80 males with long standing schizophrenia and compared this to that of 64 healthy males, using bioelectrical impedance spectrum analysis (BIS). Participants with schizophrenia exhibited significantly lower percentages of intracellular fluid and total body fluid, and significantly higher percentages of fat. Moreover, the percentage of extracellular fluid was distributed over a wider range. When the percentage body fluid was compared between the two groups by matching body mass index and body fat, intracellular fluid was significantly lower for those participants with schizophrenia. There findings suggest that nurses and other health professionals need to be very cautious when attempting to modify the excessive drinking of fluids by patients with schizophrenia. In mistakenly trying to prevent water intoxication, they may in fact be contributing to dehydration.

Postoperative metabolic and circulatory responses in patients that express SIRS after major digestive surgery

BACKGROUND/AIMS

Systemic inflammatory response syndrome (SIRS) includes a number of pathologic states because of its loose definition. This study assessed differences in metabolic and circulatory host responses in various patients with SIRS perioperatively.

METHODOLOGY

Fifty-four patients who underwent abdominal surgeries [gastric resection (n=20), colorectal resection (n=24), hepatic resection (n=8)] were divided into two groups: Group A; SIRS (+) on 1 postoperative day (POD), (n=29), B; SIRS (-) on 1 POD, (n=25). The other eight non-operated patients with SIRS caused by infection were enrolled in Group C, as common SIRS. Indirect calorimetry, body impedance measurement to assess water compartments and pulse dye-densitometry for hemodynamic examination were performed in subjects until 14 POD.

RESULTS

The ratio of energy expenditure to basal energy expenditure (%REE) was significantly increased postoperatively, and there were significant differences on %REE from 3 POD to 14 POD between groups A and B. However, %REE in group C was 162+/-23%, which was significantly increased compared with that at 1 POD of groups A (130 +/- 17%) and B (125+/-18%). Cardiac output in group A showed a significant increase until 3 POD compared with that in group B but was significantly lower than that in group C.

CONCLUSIONS

Subjects with common SIRS caused by infection were significantly more hypermetabolic than subjects with postoperative SIRS. Adequate energy intake and circulatory management should be cautiously determined according to the severity of SIRS.

Segment-specific resistivity improves body fluid volume estimates from bioimpedance spectroscopy in hemodialysis patients

Discrepancies in body fluid estimates between segmental bioimpedance spectroscopy (SBIS) and gold-standard methods may be due to the use of a uniform value of tissue resistivity to compute extracellular fluid volume (ECV) and intracellular fluid volume (ICV). Discrepancies may also arise from the exclusion of fluid volumes of hands, feet, neck, and head from measurements due to electrode positions. The aim of this study was to define the specific resistivity of various body segments and to use those values for computation of ECV and ICV along with a correction for unmeasured fluid volumes. Twenty-nine maintenance hemodialysis patients (16 men) underwent body composition analysis including whole body MRI, whole body potassium (40K) content, deuterium, and sodium bromide dilution, and segmental and wrist-to-ankle bioimpedance spectroscopy, all performed on the same day before a hemodialysis. Segment-specific resistivity was determined from segmental fat-free mass (FFM; by MRI), hydration status of FFM (by deuterium and sodium bromide), tissue resistance (by SBIS), and segment length. Segmental FFM was higher and extracellular hydration of FFM was lower in men compared with women. Segment-specific resistivity values for arm, trunk, and leg all differed from the uniform resistivity used in traditional SBIS algorithms. Estimates for whole body ECV, ICV, and total body water from SBIS using segmental instead of uniform resistivity values and after adjustment for unmeasured fluid volumes of the body did not differ significantly from gold-standard measures. The uniform tissue resistivity values used in traditional SBIS algorithms result in underestimation of ECV, ICV, and total body water. Use of segmental resistivity values combined with adjustment for body volumes that are neglected by traditional SBIS technique significantly improves estimations of body fluid volume in hemodialysis patients.

Pharmacological properties of neuronal TTX-resistant sodium channels and the role of a critical serine pore residue

Voltage-gated sodium channels can be characterized by their sensitivity to inhibitors. Na(v)1.5 is sensitive to block by cadmium and extracellular QX-314, but relatively insensitive to tetrodotoxin and saxitoxin. Na(v)1.4 is tetrodotoxin- and saxitoxin-sensitive but resistant to cadmium and extracellular QX-314. Na(v)1.8 and Na(v)1.9 generate slowly inactivating (I(TTXr-Slow)) and persistent (I(TTXr-Per)) currents in sensory neurons that are tetrodotoxin-resistant. Tetrodotoxin sensitivity is largely determined by the identity of a single residue; tyrosine 401 in Na(v)1.4, cysteine 374 in Na(v)1.5 and serine 356 and 355 in Na(v)1.8 and Na(v)1.9. We asked whether Na(v)1.8 and Na(v)1.9 share other pharmacological properties as a result of this serine residue. I(TTXr-Slow) and I(TTXr-Per) were saxitoxin-resistant and resistant to internal QX-314. I(TTXr-Slow) was also resistant to external QX-314 and displayed a approximately fourfold higher sensitivity than I(TTXr-Per) to cadmium. The impact of the serine residue was investigated by replacing tyrosine 401 in Na(v)1.4 with serine (Y401S) or cysteine (Y401C). Both mutants were resistant to tetrodotoxin and saxitoxin. Whereas Na(v)1.4-Y401C displayed an increased sensitivity to cadmium and extracellular QX-314, the serine substitution did not alter the sensitivity of Na(v)1.4 to cadmium or QX-314. Our data indicates that while the serine residue determines the sensitivity of I(TTXr-Slow) and I(TTXr-Per) to tetrodotoxin and saxitoxin, it does not determine their insensitivity to QX-314 or their differential sensitivities to cadmium.

Functionally active t1-t1 interfaces revealed by the accessibility of intracellular thiolate groups in kv4 channels

Gating of voltage-dependent K(+) channels involves movements of membrane-spanning regions that control the opening of the pore. Much less is known, however, about the contributions of large intracellular channel domains to the conformational changes that underlie gating. Here, we investigated the functional role of intracellular regions in Kv4 channels by probing relevant cysteines with thiol-specific reagents. We find that reagent application to the intracellular side of inside-out patches results in time-dependent irreversible inhibition of Kv4.1 and Kv4.3 currents. In the absence or presence of Kv4-specific auxiliary subunits, mutational and electrophysiological analyses showed that none of the 14 intracellular cysteines is essential for channel gating. C110, C131, and C132 in the intersubunit interface of the tetramerization domain (T1) are targets responsible for the irreversible inhibition by a methanethiosulfonate derivative (MTSET). This result is surprising because structural studies of Kv4-T1 crystals predicted protection of the targeted thiolate groups by constitutive high-affinity Zn(2+) coordination. Also, added Zn(2+) or a potent Zn(2+) chelator (TPEN) does not significantly modulate the accessibility of MTSET to C110, C131, or C132; and furthermore, when the three critical cysteines remained as possible targets, the MTSET modification rate of the activated state is approximately 200-fold faster than that of the resting state. Biochemical experiments confirmed the chemical modification of the intact alpha-subunit and the purified tetrameric T1 domain by MTS reagents. These results conclusively demonstrate that the T1--T1 interface of Kv4 channels is functionally active and dynamic, and that critical reactive thiolate groups in this interface may not be protected by Zn(2+) binding.

Endoplasmic reticulum Ca2+ store: regulation of Ca2+ release and reuptake by intracellular and extracellular Ca2+ in pancreatic acinar cells

We investigated the effect of cytosolic and extracellular Ca2+ on Ca2+ signals in pancreatic acinar cells by measuring Ca2+ concentration in the cytosol([Ca2+]c) and in the lumen of the ER([Ca2+]Lu). To control buffers and dye in the cytosol, a patch-clamp microelectrode was employed. Acetylcholine released Ca2+ mainly from the basolateral ER-rich part of the cell. The rate of Ca2+ release from the ER was highly sensitive to the buffering of [Ca2+]c whereas ER Ca2+ refilling was enhanced by supplying free Ca2+ to the cytosol with [Ca2+]c clamped at resting levels with a patch pipette containing 10 mM BAPTA and 2 mM Ca2+. Elevation of extracellular Ca2+ to 10 mM from 1 mM raised resting [Ca2+]c slightly and often generated [Ca2+]c oscillations in single or clustered cells. Although pancreatic acinar cells are reported to have extracellular Ca2+-sensing receptors linked to phospholipase C that mobilize Ca2+ from the ER, exposure of cells to 10 mM Ca2+ did not decrease [Ca2+]Lu but rather raised it. From these findings we conclude that 1) ER Ca2+ release is strictly regulated by feedback inhibition of [Ca2+]c, 2) ER Ca2+ refilling is determined by the rate of Ca2+ influx and occurs mainly in the tiny subplasmalemmal spaces, 3) extracellular Ca2+-induced [Ca2+]c oscillations appear to be triggered not by activation of extracellular Ca2+-sensing receptors but by the ER sensitised by elevated [Ca2+]c and [Ca2+]Lu.

Rhythmic bursting in the cortico-subthalamo-pallidal network during spontaneous genetically determined spike and wave discharges

Absence seizures are characterized by impairment of consciousness associated with bilaterally synchronous spike-and-wave discharges (SWDs) in the electroencephalogram (EEG), which reflect paroxysmal oscillations in thalamocortical networks. Although recent studies suggest that the subthalamic nucleus (STN) provides an endogenous control system that influences the occurrence of absence seizures, the mechanisms of propagation of cortical epileptic discharges in the STN have never been explored. The present study provides the first description of the electrophysiological activity in the cortico-subthalamo-pallidal network during absence seizures in the genetic absence epilepsy rats from Strasbourg, a well established model of absence epilepsy. In corticosubthalamic neurons, the SWDs were associated with repetitive suprathreshold depolarizations correlated with EEG spikes. These cortical paroxysms were reflected in the STN by synchronized, rhythmic, high-frequency bursts of action potentials. Intracellular recordings revealed that the intraburst pattern in STN neurons was sculpted by an early depolarizing synaptic potential, followed by a short hyperpolarization and a rebound of excitation. The rhythmic hyperpolarizations in STN neurons during SWDs likely originate from a subpopulation of pallidal neurons exhibiting rhythmic bursting temporally correlated with the EEG spikes. The repetitive discharges in STN neurons accompanying absence seizures might convey powerful excitation to basal ganglia output nuclei and, consequently, may participate in the control of thalamocortical SWDs.

Improvement of nutritional status as assessed by multifrequency BIA during 15 weeks of refeeding in adolescent girls with anorexia nervosa

In patients with anorexia nervosa (AN), an assessment of changes in body composition and nutritional status is crucial for adequate nutritional management during refeeding therapies. Phase-sensitive multifrequency bioelectrical impedance analysis (BIA) is an inexpensive and noninvasive technique with which to determine nutritional status and body composition. We investigated 21 female adolescents with AN (initial BMI 15.5 +/- 1.1 kg/m(2)) 4 times between wk 3 and 15 of inpatient refeeding and 19 normal-weight, age-matched female controls. From wk 3 to 15, BMI, fat mass, body cell mass (BCM), total body water (TBW), intracellular water (ICW) but not extracellular mass (ECM), and extracellular water (ECW) increased significantly. Reactance (Xc), phase angle (PhA), and the ECM/BCM index as parameters of nutritional status improved significantly in patients and no longer differed from controls in wk 15, although the BMI of patients was significantly lower than those of controls. Changes in the ECM/BCM index were due to accretion of BCM, which was associated with an increase of ICW. Multifrequency phase-sensitive BIA seems to be a promising tool for the assessment of changes in nutritional status and body composition in patients with AN. An individually determined and controlled hyperenergetic diet as part of a multidimensional, interdisciplinary treatment program for eating disorders seems to quickly improve the nutritional status of AN patients.

Dual-energy X-ray absorptiometry lean soft tissue hydration: independent contributions of intra- and extracellular water

Dual-energy X-ray absorptiometry (DEXA) provides a measure of lean soft tissue (LST). LST hydration, often assumed to be constant, is relevant to several aspects of DEXA body composition estimates. The aims of this study were to develop a theoretical model of LST total body water (TBW) content and to examine hydration effects with empirically derived model coefficients and then to experimentally test the model's prediction that, in healthy adults, LST hydration is not constant but varies as a function of extra- and intracellular water distribution (E/I). The initial phase involved TBW/LST model development and application with empirically derived model coefficients. Model predictions were then tested in a cross-sectional study of 215 healthy adults. LST was measured by DEXA, extracellular water (ECW) by NaBr dilution, intracellular water (ICW) by whole body (40)K counting, and TBW by (2)H(2)O dilution. TBW estimates, calculated as ECW + ICW, were highly correlated with (r = 0.97, SEE = 2.1 kg, P < 0.001) and showed no significant bias compared with TBW measured by (2)H(2)O. Model-predicted TBW/LST was almost identical to experimentally derived values (means +/- SD) in the total group (0.767 vs. 0.764 +/- 0.028). LST hydration was significantly correlated with E/I (total group, r = 0.30, SEE = 0.027, P < 0.001). Although E/I increased with age (men, r = 0.48; women, r = 0.37; both P < 0.001), the association between TBW/LST and age was nonsignificant. Hydration of the DEXA-derived LST compartment is thus not constant but varies predictably with ECW and ICW distribution. This observation has implications for the accuracy of body fat measurements by DEXA and the use of TBW as a means of checking DEXA system calibration.

Intracellular machinery for matrix degradation in bone-resorbing osteoclasts

In osteoclasts, TRACP co-localized with cathepsin K in transcytotic vesicles and was activated by cathepsin K in vitro, suggesting that TRACP may degrade organic matrix components in transcytotic vesicles in an event regulated by cathepsin K.

INTRODUCTION

TRACP is an enzyme with unknown biological function. In addition to its phosphatase activity, TRACP is capable of generating reactive oxygen species (ROS). Bone-resorbing osteoclasts contain large amounts of TRACP, and transgenic animal models suggest that TRACP has a role in bone resorption. Osteoclasts resorb bone by secreting acid and lysosomal enzymes such as cathepsin K into an extracellular resorption lacuna between the cell membrane and bone surface. Matrix degradation products are then endocytosed, transcytosed, and secreted through a functional secretory domain in the basolateral membrane facing bone marrow.

MATERIALS AND METHODS

We have studied intracellular localization of TRACP in osteoclasts with antibodies against various known endosomal and lysosomal proteins using confocal microscopy. We also studied co-localization of TRACP with cathepsin K and endocytosed bone matrix components and the effect of cathepsin K digestion on the ROS generating activity of TRACP in vitro.

RESULTS

Double-staining experiments of TRACP with endosomal and lysosomal markers showed that, although some endosomal staining was detected, TRACP was not present in lysosomes. However, TRACP was present in transcytotic vesicles, where it co-localized with cathepsin K. Cathepsin K digestion of TRACP in vitro increased the phosphatase activity by 5.6-fold and the ROS generating activity by 2.0-fold.

CONCLUSIONS

These results suggest that cathepsin K may activate the ROS-generating activity of TRACP in transcytotic vesicles of resorbing osteoclasts, the ROS being targeted to finalize degradation of organic bone matrix components during their transcytosis.

Intracellular and extracellular angiotensin II enhance the L-type calcium current in the failing heart

The influence of intracellular and extracellular angiotensin II (Ang II) on the L-type calcium current of cardiomyocytes isolated from cardiomyopathic hamsters was investigated. The results indicated that Ang II (10(-8) mmol/L), added to the bath, increased the peak inward calcium current (I(Ca)) density by 37+/-3.4% (P<0.05), an effect that depends on the activation of protein kinase C. Intracellular administration of the same dose of Ang II (10(-8) mmol/L) also elicited an increase of peak I(Ca) density but enhanced the rate of I(Ca) inactivation, an effect not seen with extracellular Ang II. Moreover, in control animals, no change in the rate of I(Ca) inactivation was seen with intracellular Ang II. Thapsigargin (1 micromol/L), a potent inhibitor of sarcoplasmic reticulum (SR) ATPase, which depletes the SR, decreased the rate of I(Ca) inactivation elicited by intracellular Ang II, although the cytoplasmic calcium concentration was highly buffered with 10 mmol/L EGTA. These findings might indicate that intracellular Ang II releases calcium from the SR and inactivates I(Ca). The effect of intracellular Ang II on peak I(Ca) was not altered by extracellular losartan (10(-7) mmol/L), supporting the notion that the peptide acted intracellularly. Other studies showed that intracellular Ang I administration (10(-8) mmol/L) enhanced the peak I(Ca) density and the rate of I(Ca) inactivation, an effect that was reduced by intracellular enalaprilat (10(-8) mmol/L). Moreover, intracellular enalaprilat by itself reduced the peak I(Ca) density. These observations might indicate that endogenous Ang II is contributing to I(Ca) modulation in the failing heart.

The extracellular fluid—to—intracellular fluid volume ratio is associated with large-artery structure and function in hemodialysis patients

BACKGROUND

Large-artery derangement is a major risk factor for cardiovascular and all-cause mortality in patients with end-stage renal disease (ESRD). It is not clear how body fluid distribution affects large-artery structure and function in patients with ESRD.

METHODS

One hundred fifty-seven hemodialysis (HD) patients (mean age, 55.9 +/- 15.1 years; 76 men, 81 women) were enrolled. Influence of the extracellular fluid (ECF)-to-intracellular fluid (ICF) ratio derived from bioimpedance spectroscopy on the structure and function of the common carotid artery (CCA) and aorta was analyzed. One hundred forty-four healthy subjects were examined to obtain normal reference values for body fluid compartments. Based on ECF-ICF ratio, 2 groups were identified: ECF-ICF ratio in the 95th percentile or less and ECF-ICF ratio greater than the 95th percentile of age- and sex-stratified normal reference values.

RESULTS

ECF-ICF ratio was significantly related to CCA diameter (r2 = 0.26; P < 0.001), CCA incremental modulus (E(inc); r2 = 0.15; P < 0.001), carotid augmentation index (AGI; r2 = 0.10; P < 0.001), and aortic pulse wave velocity (aPWV; r2 = 0.21; P < 0.001). ECF-ICF ratio remained a significant independent determinant for CCA diameter (model r2 = 0.47; P < 0.001), E(inc) (r2 = 0.29; P < 0.001), aPWV (r2 = 0.51; P < 0.001), and AGI (r2 = 0.40; P < 0.001) when age, sex, mean blood pressure, anthropometrical parameters, HD duration, and status of diabetes mellitus were accounted for. HD patients with an ECF-ICF ratio greater than the 95th percentile had a greater CCA diameter, E(inc), aPWV, and AGI than their counterparts.

CONCLUSION

ECF-ICF ratio is associated with large-artery structure and function in HD patients. Patients with ESRD with a high ECF-ICF ratio are characterized by significant large-artery derangement.

Intracellular correlate of EPSP-spike potentiation in CA1 pyramidal neurons is controlled by GABAergic modulation

The hippocampus has been used extensively as a model to study plastic changes in the brain's neural circuitry. Immediately after high-frequency stimulation to hippocampal Schaffer collateral axons, a dramatic change occurs in the relationship between the presynaptic CA3 and the postsynaptic CA1 pyramidal neurons. For a fixed excitatory postsynaptic potential (EPSP), there arises an increased likelihood of action potential generation in the CA1 pyramidal neuron. This phenomenon is called EPSP-spike (E-S) potentiation. We explored E-S potentiation, using patch-clamp techniques in the hippocampal slice preparation. A specific protocol was developed to measure the action potential probability for a given synaptic strength, which allowed us to quantify the amount of E-S potentiation for a single neuron. E-S potentiation was greatest when gamma-aminobutyric acid (GABA)ergic inhibition was intact, suggesting that modulation of inhibition is a major aspect of E-S potentiation. Expression of E-S potentiation also correlated with a reduced action-potential threshold, which was greatest when GABAergic inhibition was intact. Conditioning stimuli produced a smaller threshold reduction when inhibition was blocked, but some reduction also occurred in the absence of a conditioning stimulus. Together, these results suggest that E-S potentiation is caused primarily through a reduction of GABAergic inhibition, leading to larger EPSPs and reduced action potential threshold. Our findings do not rule out, however, the possibility that modulation of voltage-gated conductances also contributes to E-S potentiation.

Nifedipine-mediated mobilization of intracellular calcium stores increases spontaneous neurotransmitter release at neonatal rat motor nerve terminals

The modulation of spontaneous release of acetylcholine by specific Ca2+ channel blockers was studied at neonatal rat neuromuscular junction. During early postnatal periods (0-4 days), blockers of N- and P/Q-type Ca2+ channels did not affect miniature endplate potential (MEPP) frequency. Unexpectedly, treatment with the L-type Ca2+ channel antagonist nifedipine, although not when treated with isradipine, nitrendipine, or calciseptine, resulted in strong increase in MEPP frequency. The potentiation effect of nifedipine was dose-dependent with a 56-fold maximum effect with 15 microM. The effect decreased during the first two postnatal weeks and disappeared by the third. The effect of nifedipine was not dependent on extracellular Ca2+ and was not altered by the presence of other Ca2+ channel blockers. In contrast, it was abolished by depleting intracellular Ca2+ stores with 2 microM thapsigargin and was partially inhibited by 10 microM ryanodine. In conclusion, we report a new ryanodine receptor-mediated effect of nifedipine on neonatal neuromuscular junction that may indicate the developmental expression of a specific receptor channel that interacts with intracellular Ca2+ stores. This effect of nifedipine should also be considered when using this drug as either a therapeutic or a research tool.

Encoding of progesterone stimulus intensity by intracellular [Ca2+] ([Ca2+]i) in human spermatozoa

Progesterone induces a biphasic Ca(2+) influx and consequent acrosome reaction in human spermatozoa. We have used two procedures to vary the stimulus (dosage and prior receptor desensitization) to investigate the encoding of stimulus strength by intracellular [Ca(2+)] ([Ca(2+)](i)). Acrosome reaction and amplitude (but not kinetics) of the transient [Ca(2+)](i) response (population measurement) showed sigmoidal dose sensitivity over the range 0.3 nM-3 microM, saturating at approximately 300 nM (ED(50) approximately 30 nM). The amplitude of the sustained response saturated at 3 microM. Single-cell imaging showed that the amplitudes of both transient and sustained [Ca(2+)](i) responses were highly dose-dependent, but that their frequency of occurrence and kinetics were largely dose-independent. Fluorimetric measurements confirmed that progesterone-induced [Ca(2+)](i) influx was subject to desensitization, with second and subsequent applications of 3 microM progesterone being ineffective. However, sequential additions of 3 nM, 30 nM and 3 microM progesterone generated transient [Ca(2+)](i) responses at each concentration, the amplitude and duration of the response to 3 microM progesterone being reduced compared with non-pretreated cells. Single-cell imaging revealed that pretreatment had no effect on the proportion of responsive cells, but single-cell responses, similarly to population responses, were smaller and markedly reduced in duration, consistent with an effect of desensitization on a late component of the [Ca(2+)](i) transient. We conclude that the strength of the progesterone stimulus, when varied by dosage or by desensitization, is encoded by an analogue [Ca(2+)](i) signal. Dose dependency of the acrosome reaction is therefore determined not by the number of progesterone-responsive cells but by variation in the probability of exocytosis in a 'constant' responsive population.

Abeta42 generation is toxic to endothelial cells and inhibits eNOS function through an Akt/GSK-3beta signaling-dependent mechanism

The application of beta-amyloid (Abeta) is cytotoxic to endothelial cells, promotes vasoconstriction and impairs nitric oxide (NO) generation or action. However, there is no information on the effect of intracellular Abeta on endothelial cell biology, although recent studies indicate that neuronal Abeta drives Alzheimer's disease pathogenesis. Since the serine-threonine kinase Akt is crucial to both neuronal and endothelial cell survival as well as eNOS activation, we investigated the effects of Abeta expression on Akt-signaling in cultured endothelial cells. Virally-encoded Abeta42 was proapoptotic and inhibitory to Akt phosphorylation in human umbilical vein endothelial cells (HUVECs). Toxicity was characterized by mitochondrial dysfunction, DNA condensation and activation of caspase-3. Substrates downstream of Akt action, GSK-3beta and eNOS, are underphosphorylated in the presence of Abeta. Constitutive activation of Akt reversed Abeta-induced toxicity and stimulated caspase-3 activity, suggesting that inhibition of Akt signaling is functionally significant. These Abeta effects were mediated, in part, through the derepression of GSK-3beta activation and correlated with reductions in NO production. We conclude that intracellular production of Abeta42 is cytotoxic to endothelial cells and that disruption of the Akt/GSK-3beta cell signaling pathway is involved.

Influence of cooling rate on Saccharomyces cerevisiae destruction during freezing: unexpected viability at ultra-rapid cooling rates

The purpose of this work was to study cell viability as a function of cooling rate during freezing. Cooling rate strongly influences the viability of cells during cold thermal stress. One of the particularities of this study was to investigate a large range of cooling rates and particularly very rapid cooling rates (i.e., faster than 20000 degrees C min (-1)). Four distinct ranges of cooling rates were identified. The first range (A(')) corresponds to very slow cooling rates (less than 5 degrees C min (-1)), and results in high cell mortality. The second range (A) corresponds to low cooling rates (5-100 degrees C min (-1)), at which cell water outflow occurs slowly and does not damage the cells. The third range (B) corresponds to rapid cooling rates (100-2000 degrees C min (-1)), at which there is competition between heat flow and water flow. In this case, massive water outflow, which is related to the increase in extracellular osmotic pressure and the membrane-lipid phase transition, can cause cell death. The fourth range (C) corresponds to very high cooling rates (more than 5000 degrees C min (-1)), at which the heat flow is very rapid and partially prevents water exit, which seems to preserve cell viability.

Intracellular glycosylation and development

O-linked N-acetylglucosamine (O-GlcNAc) is a highly dynamic post-translational modification of cytoplasmic and nuclear proteins. Although the function of this abundant modification is yet to be definitively elucidated, all O-GlcNAc proteins are phosphoproteins. Further, the serine and threonine residues substituted with O-GlcNAc are often sites of, or close to sites of, protein phosphorylation. This implies that there may be a dynamic interplay between these two post-translational modifications to regulate protein function. In this review, the functions of some of the proteins that are modified by O-GlcNAc will be considered in the context of the potential role of the O-GlcNAc modification. Furthermore, predictions will be made as to how cellular function and developmental regulation might be affected by changes in O-GlcNAc levels.

Drosophila APC2 and APC1 play overlapping roles in wingless signaling in the embryo and imaginal discs

The regulation of signal transduction plays a key role in cell fate choices, and its disregulation contributes to oncogenesis. This duality is exemplified by the tumor suppressor APC. Originally identified for its role in colon tumors, APC family members were subsequently shown to negatively regulate Wnt signaling in both development and disease. The analysis of the normal roles of APC proteins is complicated by the presence of two APC family members in flies and mice. Previous work demonstrated that, in some tissues, single mutations in each gene have no effect, raising the question of whether there is functional overlap between the two APCs or whether APC-independent mechanisms of Wnt regulation exist. We addressed this by eliminating the function of both Drosophila APC genes simultaneously. We find that APC1 and APC2 play overlapping roles in regulating Wingless signaling in the embryonic epidermis and the imaginal discs. Surprisingly, APC1 function in embryos occurs at levels of expression nearly too low to detect. Further, the overlapping functions exist despite striking differences in the intracellular localization of the two APC family members.

Characterization of two new structural glycoproteins, GP(3) and GP(4), of equine arteritis virus

Equine arteritis virus (EAV) is an enveloped, positive-stranded RNA virus belonging to the family Arteriviridae of the order Nidovirales. Four envelope proteins have hitherto been identified in EAV particles: the predominant membrane proteins M and G(L), the unglycosylated small envelope protein E, and the nonabundant membrane glycoprotein G(S). In this study, we established that the products of EAV open reading frame 3 (ORF3) and ORF4 (designated GP(3) and GP(4), respectively) are also minor structural glycoproteins. The proteins were first characterized by various analyses after in vitro translation of RNA transcripts in a rabbit reticulocyte lysate in the presence and absence of microsomal membranes. We subsequently expressed ORF3 and -4 in baby hamster kidney cells by using the vaccinia virus expression system and, finally, analyzed the GP(3) and GP(4) proteins synthesized in EAV-infected cells. The results showed that GP(4) is a class I integral membrane protein of 28 kDa with three functional N-glycosylation sites and with little, if any, of its carboxy terminus exposed. Both after independent expression and in EAV-infected cells, the protein localizes in the endoplasmic reticulum (ER), as demonstrated biochemically by analysis of its oligosaccharide side chains and as visualized directly by immunofluorescence studies. GP(3), on the other hand, is a heavily glycosylated protein whose hydrophobic amino terminus is not cleaved off. It is an integral membrane protein anchored by either or both of its hydrophobic terminal domains and with no parts detectably exposed cytoplasmically. Also, GP(3) localizes in the ER when expressed independently and in the context of an EAV infection. Only a small fraction of the GP(3) and GP(4) proteins synthesized in infected cells ends up in virions. Most, but not all, of the oligosaccharides of these virion glycoproteins are biochemically mature. Our results bring the number of EAV envelope proteins to six.

Antiviral agents alter ability of HSV-2 to disrupt gap junctional intercellular communication between mammalian cells in vitro

In cultured mammalian cells (Vero), different antiviral agents change to differing degrees the ability of HSV2 to down-regulate gap junctions, each agent having a specific effect. Measured by intracellular electrodes, control cell populations showed 49-51% coupling, uninfected populations treated with acyclovir or SDS averaged 43-51% coupling while populations infected with HSV2 had coupling reduced to 8%. The antiviral agent acyclovir (1 microg/ml), which suppresses viral replication, failed to prevent this down regulation (final coupling ratio of 11%). A plant extract (250 microg/ml) from Pilostigma thonningii offered slightly more protection (final coupling ratio of 22%), while sodium dodecyl sulfate (SDS) (50 microM) afforded nearly complete protection (final coupling ratio of 40%). With SDS there was an initial down regulation to only 16% coupling by 3 h post infection, followed by a recovery of intercellular communication to near control levels by 24 h. While SDS was originally believed to alter the viral coat and prevent entry into the cell, our data are in agreement with recent studies which indicate that SDS treated viruses can enter into host cells, but in a severely diminished condition. Our data also suggest that the gap junction antagonist is brought into the cells as part of the entering virus.

A nucleolar TAR decoy inhibitor of HIV-1 replication

Tat is a critical regulatory factor in HIV-1 gene expression. It mediates the transactivation of transcription from the HIV-1 LTR by binding to the transactivation response (TAR) element in a complex with cyclin T1. Because of its critical and early role in HIV gene expression, Tat and its interaction with the TAR element constitute important therapeutic targets for the treatment of HIV-1 infection. Based on the known nucleolar localization properties of Tat, we constructed a chimeric small nucleolar RNA-TAR decoy that localizes to the nucleoli of human cells and colocalizes in the nucleolus with a Tat-enhanced GFP fusion protein. When the chimeric RNA was stably expressed in human T lymphoblastoid CEM cells it potently inhibited HIV-1 replication. These results demonstrate that the nucleolar trafficking of Tat is critical for HIV-1 replication and suggests a role for the nucleolus in HIV-1 viral replication.

Murine leptin injections increase intracellular fatty acid-binding protein in green sunfish (Lepomis cyanellus)

Green sunfish (Lepomis cyanellus) were injected daily with either murine leptin, phosphate-buffered saline (PBS), or simply handled without injection for 14 days. At the end of the experiment, fish were assayed for intracellular indicators of fatty acid metabolism. Intracellular fatty acid-binding protein (FABP) expression in heart ventricle was twofold higher in the leptin treated group (87.2+/-5.6 Leptin; 47.2+/-6.8 PBS; 28.9+/-3.9 Handled; percent relative expression, Prob.>F<0.001). Two other indicators of intracellular fat metabolism, carnitine palmitoyl transferase activity (CPT) in liver and 3-hydroxyacyl-CoA dehydrogenase (HOAD) in heart were not significantly different among groups, although the trend is for higher values in the leptin treatment (CPT: 0.23+/-0.04 Leptin, 0.11+/-0.04 PBS, 0.10+/-0.03 Handled; U/gm wet weight; Prob.>F=0.08; HOAD: 1.34+/-0.28 Leptin, 0.76+/-0.12 PBS, 0.86+/-0.25 Handled; U/gm wet weight; Prob.>F=0.18). Percent change in total weight, body fat (as a percent of dry weight), cardiosomatic index, and hepatosomatic index were not significantly different among treatments. These results suggest that fish respond to murine leptin injections by increasing fat metabolism, however many of the hallmarks of leptin treatment in mammals (loss of total weight and body fat) were not observed. This lack of response may be due to incompatibility of mouse leptin with fish receptors or an inadequate dose of leptin. We also suggest that leptin's action may be slower in ectotherms due to their lower metabolic rate.

A functional link between the actin cytoskeleton and lipid rafts during budding of filamentous influenza virions

Morphogenesis of influenza virus is a poorly understood process that produces two types of enveloped virion: approximately 100-nm spheres and similar diameter filaments that reach 20 microm in length. Spherical particles assemble at plasma membrane lipid rafts in a process independent of microfilaments. The budding site of filamentous virions is hitherto uncharacterised but their formation involves the actin cytoskeleton. We confirm microfilament involvement in filamentous budding and show that after disruption of cortical actin by jasplakinolide, HA, NP, and M1 redistributed around beta-actin clusters to form novel annular membrane structures. HA in filamentous virions and jasplakinolide-induced annuli was detergent insoluble at 4 degrees C. Furthermore, in both cases HA partitioned into low buoyant density detergent-insoluble glycolipid domains, indicating that filamentous virions and annuli contain reorganised lipid rafts. We propose that the actin cytoskeleton is required to maintain the correct organisation of lipid rafts for incorporation into budding viral filaments.

In vitro efficiency of intra- and extracellular immunization with mouse anti-YGNNV antibody against yellow grouper nervous necrosis virus

Mouse monoclonal antibody (MAb-18) against yellow grouper nervous necrosis virus (YGNNV) coat protein was developed and assayed for its neutralization ability. In the present study, we cloned and sequenced the cDNAs encoding heavy (gamma) and light (kappa) chains by constructing a cDNA library of the MAb-18 hybridoma. Three expression vectors, pCMV-NNV-18H (gamma), pCMV-NNV-18L (kappa), and pCMV-NNV-18HL (both gamma and kappa chains) were constructed and successfully expressed in grouper brain (GB) cells. Western blotting results indicated the secretion of antibody in to the medium with successful folding. Extracellular antibodies secreted by the pCMV-NNV-18HL transfected GB cells, neutralized well with YGNNV and showed the highest neutralization index (log(10) of NI) value 4. A significant reduction of titre (99.9%) was observed, when the intracellularly immunized GB cells were propagated with the YGNNV. These preliminary demonstrations suggest the immunoprophylactic use of plasmid constructs encoding the genes of mouse MAbs and the possibility of producing transgenic pathogen-free spawners and larvae, which contain freely available MAbs against pathogen in the circulation.

Sphingosine 1-phosphate enhances spontaneous transmitter release at the frog neuromuscular junction

Intracellular recordings were made from isolated frog sciatic-sartorius nerve-muscle preparations, and the effects of sphingosine 1-phosphate (S1-P) on miniature endplate potentials (MEPPs) were studied. Extracellular application of S1-P (1 and 30 micro M) had no significant effects on the frequency and amplitude of MEPPs. Delivery into nerve terminals by liposomes containing 10(-5), 10(-4) or 10(-3) M S1-P was associated with a concentration-dependent increase in MEPP frequency of 37, 63 and 86%. The per cent of median MEPP amplitude was not significantly changed, but there was an increase in the number of 'giant' MEPPs. Pre-exposure of the preparations to S1-P 10(-5) but not 10(-8) M entrapped in liposomes for 15 min blocked the effects of subsequent superfusion of S1-P (10(-4) M)-filled liposomes on MEPP frequency. Thus, intracellular S1-P receptors seem to undergo 'desensitization' to higher concentrations of S1-P. The result provides the first evidence that S1-P acting intracellularly but not extracellularly enhances spontaneous transmitter release at the frog neuromuscular junction.

Orientia tsutsugamushi inhibits apoptosis of macrophages by retarding intracellular calcium release

Orientia tsutsugamushi shows both pro- and antiapoptotic activities in infected vertebrate cells. Apoptosis of THP-1 cells induced by beauvericin was inhibited by O. tsutsugamushi infection. Beauvericin-induced calcium redistribution was significantly reduced and retarded in cells infected with O. tsutsugamushi. Antiapoptotic activities of O. tsutsugamushi in infected cells are most probably due to inhibition of the increase in the cytosolic calcium concentration.