Antidiuretic responses to osmotic, ionic or volume stimulation of the brain in the unanesthetized toad, Bufo arenarum Hensel

Single injections of 15 microliter of 1 M NaCl or 2M sucrose into the carotid system of normal unanesthetized toads induced a rapid and significant decrease of urine production. This appears to be the first report on the existence of a Verney-like phenomena in a non-mammalian vertebrate. This antidiuresis was blocked out in the hypophysectomized diencephalic lesioned animal. Concurrently, small volumes (4 microliters) of 1 M NaCl but not 2 M sucrose also induced antidiuresis when injected into the midbrain tegmentum of normal but not of hypophysectomized diencephalic lesioned toads. Larger volumes (6 microliters) of 2 M sucrose were needed to induce a similar antidiuresis in normals. Furthermore, even larger volumes (more than 8 microliters) of any of both solutions were able to induce oliguria in normal as well as in hypophysectomized toads. On the basis of these results, the following conclusion would be drawn: the brain of the toad is able to detect ionic and osmotic stimuli, these stimuli apparently affect different receptors in the brain, the antidiuresis initiated by these mechanisms is dependent on diencephalic integrity.     

Microinjection of Xenopus oocytes: An automated device for volume control in the nanoliter range

Injection of Xenopus oocytes is a technique widely used in studies of gene expression for both qualitative and quantitative analysis of DNA and mRNA. Published methods for controlling and assessing volumes transferred into oocytes are tedious, time consuming, and require considerable expertise. We describe the construction of an apparatus which automatically controls nanoliter injection volumes. For injection volumes from 50 to 10 nl, the mean volume injected into 10 oocytes was within 10% of the expected value and often better, and even for 1-nl injections was within 20% of the expected value. The precision of volume dispensing into individual oocytes decreased with decreasing volume; the standard deviation was about 10–15% of the mean for volumes in the 30- to 50-nl range and about 30–40% of the mean for volumes in the 1- to 2-nl range.     

Quantification of protein surfaces,volumes and atom-atom contacts using a constrained Voronoi procedure

MOTIVATION: Geometric representations of proteins and ligands, including atom volumes, atom-atom contacts and solvent accessible surfaces, can be used to characterize interactions between and within proteins, ligands and solvent. Voronoi algorithms permit quantification of these properties by dividing structures into cells with a one-to-one correspondence with constituent atoms. As there is no generally accepted measure of atom-atom contacts, a continuous analytical representation of inter-atomic contacts will be useful. Improved geometric algorithms will also be helpful in increasing the speed and accuracy of iterative modeling algorithms. RESULTS: We present computational methods based on the Voronoi procedure that provide rapid and exact solutions to solvent accessible surfaces, volumes, and atom contacts within macromolecules. Furthermore, we define a measure of atom-atom contact that is consistent with the calculation of solvent accessible surfaces, allowing the integration of solvent accessibility and inter-atomic contacts into a continuous measure. The speed and accuracy of the algorithm is compared to existing methods for calculating solvent accessible surfaces and volumes. The presented algorithm has a reduced execution time and greater accuracy compared to numerical and approximate analytical surface calculation algorithms, and a reduced execution time and similar accuracy to existing Voronoi procedures for calculating atomic surfaces and volumes.     

Family Poverty Affects the Rate of Human Infant Brain Growth

Living in poverty places children at very high risk for problems across a variety of domains, including schooling, behavioral regulation, and health. Aspects of cognitive functioning, such as information processing, may underlie these kinds of problems. How might poverty affect the brain functions underlying these cognitive processes? Here, we address this question by observing and analyzing repeated measures of brain development of young children between five months and four years of age from economically diverse backgrounds (n = 77). In doing so, we have the opportunity to observe changes in brain growth as children begin to experience the effects of poverty. These children underwent MRI scanning, with subjects completing between 1 and 7 scans longitudinally. Two hundred and three MRI scans were divided into different tissue types using a novel image processing algorithm specifically designed to analyze brain data from young infants. Total gray, white, and cerebral (summation of total gray and white matter) volumes were examined along with volumes of the frontal, parietal, temporal, and occipital lobes. Infants from low-income families had lower volumes of gray matter, tissue critical for processing of information and execution of actions. These differences were found for both the frontal and parietal lobes. No differences were detected in white matter, temporal lobe volumes, or occipital lobe volumes. In addition, differences in brain growth were found to vary with socioeconomic status (SES), with children from lower-income households having slower trajectories of growth during infancy and early childhood. Volumetric differences were associated with the emergence of disruptive behavioral problems.     

Classification and lateralization of temporal lobe epilepsies with and without hippocampal atrophy based on whole-brain automatic MRI segmentation

Brain images contain information suitable for automatically sorting subjects into categories such as healthy controls and patients. We sought to identify morphometric criteria for distinguishing controls (n = 28) from patients with unilateral temporal lobe epilepsy (TLE), 60 with and 20 without hippocampal atrophy (TLE-HA and TLE-N, respectively), and for determining the presumed side of seizure onset. The framework employs multi-atlas segmentation to estimate the volumes of 83 brain structures. A kernel-based separability criterion was then used to identify structures whose volumes discriminate between the groups. Next, we applied support vector machines (SVM) to the selected set for classification on the basis of volumes. We also computed pairwise similarities between all subjects and used spectral analysis to convert these into per-subject features. SVM was again applied to these feature data. After training on a subgroup, all TLE-HA patients were correctly distinguished from controls, achieving an accuracy of 96 ± 2% in both classification schemes. For TLE-N patients, the accuracy was 86 ± 2% based on structural volumes and 91 ± 3% using spectral analysis. Structures discriminating between patients and controls were mainly localized ipsilaterally to the presumed seizure focus. For the TLE-HA group, they were mainly in the temporal lobe; for the TLE-N group they included orbitofrontal regions, as well as the ipsilateral substantia nigra. Correct lateralization of the presumed seizure onset zone was achieved using hippocampi and parahippocampal gyri in all TLE-HA patients using either classification scheme; in the TLE-N patients, lateralization was accurate based on structural volumes in 86 ± 4%, and in 94 ± 4% with the spectral analysis approach. Unilateral TLE has imaging features that can be identified automatically, even when they are invisible to human experts. Such morphometric image features may serve as classification and lateralization criteria. The technique also detects unsuspected distinguishing features like the substantia nigra, warranting further study.     

Photoperiod and testosterone independently affect vocal control region volumes in adolescent male songbirds

Previously, we found that, unlike adults, adolescent male dark-eyed juncos (Junco hyemalis) maintained large Area X volumes despite having low plasma testosterone concentrations. Other studies indicate that photoperiod may act independently of testosterone to modulate vocal control region (VCR) volumes in adult songbirds. In the present study, we investigated the effects of testosterone and photoperiod on the volumes of four VCRs in adolescent male juncos. To test the hypothesis that VCR volumes in these males are testosterone independent, we treated birds exposed to short days with testosterone and later compared their VCR volumes with those of birds exposed to short days without testosterone. To examine whether photoperiod alone could affect VCR volumes independent of testosterone, we measured these volumes in photorefractory birds exposed to long photoperiod without testosterone. Administering testosterone induced singing, yet increased the volume of only one VCR, the robust nucleus of the anterior neostriatum (RA). In contrast, long photoperiod increased several VCR volumes (Area X, higher vocal center, and RA) despite low testosterone levels, but did not induce singing. Our results suggest a limited role for testosterone, but an important role for photoperiod, in controlling VCR volumes in adolescent male juncos. In addition, the results demonstrate that singing behavior can be induced in adolescent males without a concomitant increase in most VCR volumes. © 1998 John Wiley & Sons, Inc. J Neurobiol 36: 550–558, 1998     

Omnidirectional sensory and motor volumes in electric fish

Active sensing organisms, such as bats, dolphins, and weakly electric fish, generate a 3-D space for active sensation by emitting self-generated energy into the environment. For a weakly electric fish, we demonstrate that the electrosensory space for prey detection has an unusual, omnidirectional shape. We compare this sensory volume with the animal's motor volume—the volume swept out by the body over selected time intervals and over the time it takes to come to a stop from typical hunting velocities. We find that the motor volume has a similar omnidirectional shape, which can be attributed to the fish's backward-swimming capabilities and body dynamics. We assessed the electrosensory space for prey detection by analyzing simulated changes in spiking activity of primary electrosensory afferents during empirically measured and synthetic prey capture trials. The animal's motor volume was reconstructed from video recordings of body motion during prey capture behavior. Our results suggest that in weakly electric fish, there is a close connection between the shape of the sensory and motor volumes. We consider three general spatial relationships between 3-D sensory and motor volumes in active and passive-sensing animals, and we examine hypotheses about these relationships in the context of the volumes we quantify for weakly electric fish. We propose that the ratio of the sensory volume to the motor volume provides insight into behavioral control strategies across all animals.     

Multicellular-like compartmentalization of cytoplast in fossil larger foraminifera

Foraminifera are usually between 0.1 and 1 mm in size, thus falling within the range of the largest eukaryotic cells. However, some fossil and extant foraminiferal species reach diameters of more than 100 mm. One hypothesis of how these gigantic sizes could have been attained by these unicellular organisms is the temporary compartmentalization of cytoplasm into smaller volumes of effective metabolism, as reported for several recent species. Evidence of this phenomenon is shown in fossil genera of larger foraminifera belonging to five families of Cretaceous to Oligocene age. Alternative interpretations are discussed.     

Changes in the organization of the neuritic cytoskeleton during nerve growth factor-activated differentiation of PC12 cells: a serial electron microscopic study of the development and control of neurite shape

After exposure to nerve growth factor, PC12 cells differentiate within a period of only a few days into cholinergic sympathetic neurons. Using computer-assisted three-dimensional serial electron microscopic reconstruction, we describe the progressive cytoskeletal and structural changes of PC12 neurites at different stages in their differentiation. Developmental changes in these neurites can be characterized by two major transitions. First, microtubules (MTs), which define the longitudinal axis of the neurite, increase in number leading to a more cylindrical and uniform neurite shape. Second, there are major changes in the relative numbers of other organelle types, which reflect the functional specialization of the neurite. These changes do not in themselves seriously affect shape change of the neurite during development, however the presence of these organelles and their associated obligatory volumes (volumes surrounding organelle) account for well over 50% of the neurite's volume at all stages of development. The MT-MT distances and obligatory volumes associated with the organelles remain constant throughout development. Thus, we can conclude that many of the observed changes seen in developing PC12 neurites are due simply to the production of a greater number of MTs in the cell, and that many of the other important parameters that can be measured and contribute to neurite shape remain constant during development.     

Transpulmonary pressures and lung mechanics with glossopharyngeal insufflation and exsufflation beyond normal lung volumes in competitive breath-hold divers.

Throughout life, most mammals breathe between maximal and minimal lung volumes determined by respiratory mechanics and muscle strength. In contrast, competitive breath-hold divers exceed these limits when they employ glossopharyngeal insufflation (GI) before a dive to increase lung gas volume (providing additional oxygen and intrapulmonary gas to prevent dangerous chest compression at depths recently greater than 100 m) and glossopharyngeal exsufflation (GE) during descent to draw air from compressed lungs into the pharynx for middle ear pressure equalization. To explore the mechanical effects of these maneuvers on the respiratory system, we measured lung volumes by helium dilution with spirometry and computed tomography and estimated transpulmonary pressures using an esophageal balloon after GI and GE in four competitive breath-hold divers. Maximal lung volume was increased after GI by 0.13-2.84 liters, resulting in volumes 1.5-7.9 SD above predicted values. The amount of gas in the lungs after GI increased by 0.59-4.16 liters, largely due to elevated intrapulmonary pressures of 52-109 cmH(2)O. The transpulmonary pressures increased after GI to values ranging from 43 to 80 cmH(2)O, 1.6-2.9 times the expected values at total lung capacity. After GE, lung volumes were reduced by 0.09-0.44 liters, and the corresponding transpulmonary pressures decreased to -15 to -31 cmH(2)O, suggesting closure of intrapulmonary airways. We conclude that the lungs of some healthy individuals are able to withstand repeated inflation to transpulmonary pressures far greater than those to which they would normally be exposed.     

A cost-effective solution to reduce dead volume of a standard dispenser system by a factor of 5

A key trend in high-throughput screening is assay miniaturization to control reagent costs and increase throughput. For this purpose, liquid-handling devices are used that transfer nano-to low-microliter volumes into all currently used microtiter well plates. One drawback of many available dispenser and pipetting systems are high dead volumes. Therefore, the authors were looking for an easy and simple solution to modify their standard liquid-handling device, PerkinElmer's FlexDrop Precision IV, allowing for a dead volume reduction to receive maximum benefit from miniaturized assay formats. Internal reservoirs were developed and constructed by Schering's Technical Development Laboratory (TDL), which are directly connected to the dispenser banks of FlexDrop without tubing. Using these newly built reservoirs, the dead volume was decreased by a factor of 5 in comparison to the manufacturer's reservoirs without compromising liquid-handling parameters such as accuracy and precision. The modified system displayed a high robustness and reliability under routine high-throughput screening conditions.     

Relationship between the volume and proportions of the organoids and cell volume in yeasts]

Populations of yeast Saccharomyces carlsbergensis and Candida quilliermondii were divided into cell classes with different volumes. In each class volumes of nuclei, vacuoles and lipid incorporation were measured. With the increase of cell volumes, volumes of organoides increased too, but the relative volume of nucleus decreased, and the relative volumes of vacuoles and of lipid incorporation increased.     

The partial molar volumes of anesthetics in lipid bilayers

The excess volumes of mixing of benzyl alcohol, halothane, and methoxyflurane in water and in suspensions of several lipid bilayers have been determined at 25 degrees C using a novel excess volume dilatometer. The excess volumes of mixing in water were all found to be negative, whereas in lipid suspensions they were all more positive than those in water alone. From known partition coefficients the partial molar volumes of these three solutes in the lipid bilayers were calculated. These values were all close to the molar volumes of the pure anesthetics, as was a value determined for halothane in olive oil. Halothane was studied in dipalmitoylphosphatidylcholine below its phase transition, and was found to exhibit a much larger excess volume than in any other system we studied. The potency of these three anesthetics was determined in tadpoles. It was calculated that at equi-anesthetic doses these three agents caused an expansion in egg lecithin/cholesterol (2:1) bilayers of 0.21 +/- 0.015%. This result is consistent with the hypothesis that general anesthetics act by expanding membranes.     

Low-volume jet injection for efficient nonviral in vivo gene transfer

The transfer of naked deoxyribonucleic acid (DNA) represents an alternative to viral and liposomal gene transfer technologies for gene therapy applications. Various procedures are employed to deliver naked DNA into the desired cells or tissues in vitro and in vivo, such as by simple needle injection, particle bombardment, in vivo electroporation or jet injection. Among the various nonviral gene delivery technologies jet injection is gaining increasing acceptance because it allows gene transfer into different tissues with deeper penetration of the applied naked DNA. The versatile hand-held Swiss jet injector uses pressurized air to force small volumes of 3 to 10 μL of naked DNA into targeted tissues. The β-galactosidase (LacZ) reporter gene construct and tumor necrosis factor α gene-expressing vectors were successfully jet injected at a pressure of 3.0 bar into xenotransplanted human tumor models of colon carcinoma. Qualitative and quantitative expression analysis of jet injected tumor tissues revealed the efficient expression of these genes in the tumors. Using this Swiss jet-injector prototype repeated jet injections of low volumes (3–10 μL) into one target tissue can easily be performed. The key parameters of in vivo jet injection such as jet injection volume, pressure, jet penetration into the tumor tissue, DNA stability have been defined for optimized nonviral gene therapy. These studies demonstrate the applicability of the jet injection technology for the efficient and simultaneous in vivo gene transfer of two different plasmid DNAs into tumors. It can be employed for nonviral gene therapy of cancer using minimal amounts of naked DNA.     

A framework for whole-cell mathematical modeling

The default framework for modeling biochemical processes is that of a constant-volume reactor operating under steady-state conditions. This is satisfactory for many applications, but not for modeling growth and division of cells. In this study, a whole-cell modeling framework is developed that assumes expanding volumes and a cell-division cycle. A spherical newborn cell is designed to grow in volume during the growth phase of the cycle. After 80% of the cycle period, the cell begins to divide by constricting about its equator, ultimately affording two spherical cells with total volume equal to twice that of the original. The cell is partitioned into two regions or volumes, namely the cytoplasm (Vcyt) and membrane (Vmem), with molecular components present in each. Both volumes change during the cell cycle; Vcyt changes in response to osmotic pressure changes as nutrients enter the cell from the environment, while Vmem changes in response to this osmotic pressure effect such that membrane thickness remains invariant. The two volumes change at different rates; in most cases, this imposes periodic or oscillatory behavior on all components within the cell. Since the framework itself rather than a particular set of reactions and components is responsible for this behavior, it should be possible to model various biochemical processes within it, affording stable periodic solutions without requiring that the biochemical process itself generates oscillations as an inherent feature. Given that these processes naturally occur in growing and dividing cells, it is reasonable to conclude that the dynamics of component concentrations will be more realistic than when modeled within constant-volume and/or steady-state frameworks. This approach is illustrated using a symbolic whole cell model.     

Microdosimetry in 3D realistic mitochondria phantoms: Geant4 Monte Carlo tracking of 250 keV photons in phantoms reconstructed from microscopic images

Mitochondria are considered to be sensitive radiation targets since they control processes vital to the cell’s functioning. These organelles are starting to get attention and some studies are investigating the radiation dose inside them. In previous studies, mitochondria are represented as simple ellipsoids inside the cell not taking into consideration the complexity of their shape. In this study, realistic phantoms are built based on deconvolved widefield fluorescent microscopic images of the mitochondrial networks of fibroblast cells. The phantoms are imported into Geant4 as tessellated volumes taking into account the geometrical complexity of these organelles. Irradiation with 250 keV photons is performed and the lineal energy is calculated. The lineal energy distributions inside the produced phantoms are compared with those calculated inside simple volumes, a sphere and an ellipsoid, where the effect of the shape and volume is clearly seen on lineal energies.     

The cell proliferation kinetics of the EMT6/M/AC mouse tumour at four volumes during unperturbed growth in vivo.

The cell proliferation kinetics of the EMT6/M/AC mouse tumour were determined at four different volumes between 1-5 mm3 and 175 mm3. The decrease in the growth rate between these volumes are mainly due to a decrease in the rate constant for cell production. A small increase in the rate constant for cell loss occurred, but this was thought to be insignificant. The cell loss factor increased from 40% at 1-5 mm3 to over 70% in the 175 mm3 tumours. An increase in the median cell cycle time, from 14-1 hr to 18-5 hr was also found between these same volumes. Results obtained for the NCTC fibrosarcoma and the R-1 rhabdo-myosarcoms indicate that there may be a threshold volume in these sarcomas below which little or no cell loss takes place. This was not found in the EMT6/M/AC tumour.     

Blood volume measurement in baboons: simultaneous estimation of red cell volume and plasma volume

A method is described for frequent sequential blood volume estimation in baboons using 32P for red cell volume measurements and 125I-albumin for simultaneous plasma volume measurements. Values for red cell, plasma, and total blood volumes are reported. Close correlations of the volumes to bodyweight were demonstrated. Circulatory half-lives of the isotopes, determined from disappearance curves, confirmed their suitability for serial measurements in these baboons.     

In vivo pediatric shoulder muscle volumes and their relationship to 3D strength

In the pediatric shoulder, injury and pathology can disrupt the muscle force balance, resulting in severe functional losses. As little data exists pertaining to in vivo pediatric shoulder muscle function, musculoskeletal data are crucially needed to advance the treatment of pediatric shoulder pathology/injury. Therefore, the purpose of this study was to develop a pediatric database of in vivo volumes for the major shoulder muscles and correlate these volumes with maximum isometric flexion/extension, internal/external rotation, and abduction/adduction joint moments. A methodology was developed to derive 3D shoulder muscle volumes and to divide the deltoid into sub-units with unique torque producing capabilities, based on segmentation of three-dimensional magnetic resonance images. Eleven typically developing children/adolescents (4F/7M, 12.0±3.2 years, 150.8±16.7 cm, 49.2±16.4 kg) participated. Correlation and regression analyses were used to evaluate the relationship between volume and maximum, voluntary, isometric joint torques. The deltoid demonstrated the largest (30.4±1.2%) and the supraspinatus the smallest (4.8±0.5%) percent of the total summed volume of all six muscles evaluated. The anterior and posterior deltoid sections were 43.4±3.9% and 56.6±3.9% of the total deltoid volume. The percent volumes were highly consistent across subjects. Individual muscle volumes demonstrated moderate-high correlations with torque values (0.70–0.94, p<0.001). This study presents a comprehensive database documenting normative pediatric shoulder muscle volume. Using these data a clear relationship between shoulder volume and the torques they produce was established in all three rotational degrees-of-freedom. This study furthers the understanding of shoulder muscle function and serves as a foundation for evaluating shoulder injury/pathology in the pediatric/adolescent population.     

Phospholipid membrane bending as assessed by the shape sequence of giant oblate phospholipid vesicles

Vesicle shape transformations caused by decreasing the difference between the equilibrium areas of membrane monolayers were studied on phospholipid vesicles with small volume to membrane area ratios. Slow transformations of the vesicle shape were induced by lowering of the concentration of lipid monomers in the solution outside the vesicle. The complete sequence of shapes consisted of a string of pearls, and wormlike, starfish, discocyte and stomatocyte shapes. The transformation from discocyte to stomatocyte vesicle shapes was analyzed theoretically to see whether these observations accord with the area difference elasticity (ADE) model. The membrane shape equation and boundary conditions were derived for axisymmetrical shapes for low volume vesicles, part of whose membranes are in contact. Calculated shapes were arranged into a phase diagram. The theory predicts that the transition between discocyte and stomatocyte shapes is discontinuous for relatively high volumes and continuous for low volumes. The calculated shape sequences matched well with the observed ones. By assuming a linear decrease of the equilibrium area difference with time, the ratio between the nonlocal and local bending constants is in agreement with reported values.