Determination of total body water by multifrequency bio-electric impedance: development of several models

Multifrequency bio-electronic impedance analysis (MF BIA) measurements are taken from a heterogeneous group of patients, varying in size between obese and slim. The measuring system uses four electrodes: two current and two potential electrodes. Three new models are developed to calculate total body water (TBW) from the BIA data, and the resulting TBW values are compared with TBW determined by D₂O dilution. The results demonstrate that the most simple model provides the best TBW values. For individual patients, TBW can be determined by means of bioimpedance measurement with an accuracy of 3 litres. In the most simple model (model 1), the body is electrically represented by a cylinder, and corrections are made for the amount of fat. This is an extension of the model used by Xitron. In the more advanced models (2 and 3), the body is represented by a cylinder for the trunk, and truncated cones represent the arms and legs. In model 2, ΔTBW amounts to 3 litres. It is shown that the resistance of the trunk is proportional to the square root of the length. In model 3, it is assumed that subcutaneous fat is a poor conductor if electric current. An equation is developed that describes the partition of subcutaneous fat, and the fat layer is then removed from the cones representing arms and legs and from the cylinder that models the trunk.     

Contraluminal transport of organic cations in the proximal tubule of the rat kidney

In order to study the quantitative structure/activity relationship of organic cation transport across the contraluminal side of the proximal renal tubule cell, the stopped-flow capillary microperfusion method was applied and the inhibitory potency (apparent K _i values) of different homologous series of substrates against N ¹-[³H]methylnicotinamide (NMeN⁺) transport was evaluated. Aniline and its ring- or N-substituted analogues as well as the aminonaphthalines do not interact with the contraluminal NMeN⁺ transporter except for the quaternary trimethylphenylammonium and pararosaniline, which bear a permanent positive charge, and for 1,8-bis-(dimethylamino)naphthaline, which forms an intramolecular hydrogen bond. If, however, one or more than one methylene group is interposed between the benzene ring and the amino group, the compounds interact with the contraluminal NMeN⁺ transporter in proportion to their hydrophobicity parameter, i.e. the octanol/water partition coefficient (log octanol). The catecholamines and other hydroxyl-substituted phenylethyl analogues also follow this rule. In addition, the N-heterocyclic pyridine, quinoline, isoquinoline and acridine analogues also interact with the contraluminal NMeN⁺ transporter, when their pK _a values are higher than 5.0, and, an inverse correlation between pK _a and log K _{i, NMeN} was observed. An exception to this rule are those hydroxy compounds of pyridine, quinoline and isoquinoline that show tautomerism. These compounds slightly inhibit NMeN⁺ transport despite low pK _a values. The quaternary nitrogen compounds of aniline and the N-heterocyclic analogues, as far as tested, all interact with the contraluminal NMeN⁺ transporter in relation to their hydrophobicity. The data indicate that the contraluminal NMeN⁺ transporter interacts with N-compounds according to their hydrophobicity and/or according to their basicity (affinity to protons). The reason for deviation of the aniline analogues and the OH-tautomeric heterocyclic N-compounds from this behaviour is discussed.     

Effects of combined entorhinal cortex-hippocampal lesions on locomotor behavior, spontaneous alternation and spatial maze learning in the rat

Male Sprague-Dawley rats with combined lesions to the dorsal and lateral aspects of the entorhinal cortex in one hemisphere and of the contralateral dorsolateral hippocampal formation were compared with both operated and unoperated controls on three different behaviors, monitored across a 53 day postoperative period. The rats with the combined entorhinal cortex-hippocampal lesions (EH) showed transient hyperactivity in the open field, transient reduction in spontaneous alternation levels in an unbaited T-maze and persistent deficits in learning spatial maze problems. The results of the present experiment are discussed in comparison with those from experiments on rats with bilateral hippocampal lesions and those from experiments on rats with bilateral entorhinal cortex lesions. Although some similarities among these findings suggest that these two brain regions probably function in a coordinated fashion with respect to these behaviors, differences in the various syndromes are also discussed.     

Molecular Manipulations of Extracellular Superoxide Dismutase: Functional Importance for Learning

Extracellular superoxide dismutase (EC-SOD) controls the availability of extracellular superoxide (O ₂ ^- ), which is important for a variety of physiological pathways, including the primary means of inactivating nitric oxide (NO). The role of EC-SOD in neurobehavioral function has been until now unexplored. In the current studies, the phenotypic expression of genotypic alterations of EC-SOD production in mice were characterized for spatial learning and memory. Dramatic impairments in spatial learning in the win-shift 8-arm radial maze were seen in both EC-SOD knockout mice and EC-SOD overexpressing mice. The EC-SOD overexpressing mice were further characterized as having significant deficits in a repeated acquisition task in the radial-arm maze, which permitted the dissociation of long and short-term learning. Long-term learning was significantly impaired by EC-SOD overexpression, whereas short-term learning was not significantly affected by EC-SOD overexpression. NO systems have been shown to be importantly involved in learning and memory. This may be important in the current studies because EC-SOD has primary control over the inactivation of NO. We found that EC-SOD overexpressing mice were resistant to the cognitive effects of L-NAME (N^G-nitro-L-arginine methyl ester hydrochloride), an NO synthase inhibitor. Decreased NO catabolism in these mice may have served to counter the effects of NOS inhibition by L-NAME. The current finding that EC-SOD levels that were either higher or lower than controls impaired learning demonstrates that the proper control of brain extracellular (O ₂ ^- ) may be more vital than merely reduction of brain extracelluar (O ₂ ^- ) in maintaining adequate learning function.     

Behavioral Profiles of Genetically Selected Aggressive and Nonaggressive Male Wild House Mice in Two Anxiety Tests

Artificially selected aggressive (SAL) and non-aggressive (LAL) male house mice were tested in a hexagonal tunnel maze and light-dark preference (LD) box to determine if the bidirectional selection for aggressive behavior leads to a coselection for different levels of trait anxiety. The tunnel maze consists of an open, brightly lit central arena surrounded by a complex system of interconnecting tunnels. As in the LD box, animals which spend less time and are less active in the brightly illuminated section of the maze are considered to have higher anxiety levels. In the tunnel maze, the LAL mice showed more exploration and spent more time in the central arena than the SAL animals, but only during the final 2 min of the 6-min test. This reduced preference for the central arena was not due to general inactivity or a failure of the SAL to find the central arena and indicates a higher level of state anxiety in the aggressive animals. In contrast, no anxiety-like differences were found in the LD box, either for the percentage of time spent in the light compartment or for the number of crossings. SAL males actually showed higher levels of moving and rearing, and lower levels of freezing, than did LAL males.     

Analysis of behavioral and hippocampal variation in congenic albino and pigmented BALB mice

Mice of the BALB/c strain are widely used in behavioral research in spite of the albino condition, which can obscure brain-behavior relationships. We have developed a pigmented BALB strain, congenic to BALB/c, which could be more appropriate for neurogenetic studies that aim at identifying the effects of neurological mutations on behavior. Comparison of inbred albino and pigmented congenic BALB arising from the same litters provides a valuable tool for detecting the consequences of the albino mutation on behavioral performances. Preliminary results presented here show that the albino condition does not interfere with the development and patterns of connectivity of mossy fibers in the hippocampus. On the other hand, obvious coat color-linked differences appear for locomotor activity and defecation scores in the open field, pigmented mice being unexpectedlyl less active and more reactive than albino, as if better vision increased their reactions to a novel, anxiogenic environment. Finally, pigmented mice do not show better performances in the radial maze, which confirms that the inability of BALB mice for spatial learning in a highly demanding version of this task cannot be attributed to their inability to process visual information.     

Water diffusion in the different microenvironments of breast cancer

The parameters that characterize the intricate water diffusion in tumors may serve to reveal their distinct pathology. Specifically, the application of diffusion magnetic resonance imaging (MRI) can aid in characterizing breast cancer, as well as monitoring response to therapy. We present here a non-invasive, quantitative MRI investigation, at high spatial resolution, of water diffusion in hormonal dependent MCF7 breast tumors implanted orthotopically in immunodeficient mice. Distinctive MRI protocols were designed in this study, utilizing a broad range of diffusion times and diffusion gradient strengths. Application of these protocols allowed water diffusion in the tissue extracellular and intracellular compartments to be distinguished, and the effect of restricted diffusion and water exchange on the water diffusion in these compartments to be evaluated. Pixel-by-pixel analysis yielded parametric maps of the estimated volume fraction and apparent diffusion coefficient of each compartment. The diffusion of the water in the extracellular microenvironment was approximately two fold slower than that of free water, and in the intracellular compartment was about one order of magnitude slower than that of free water and demonstrated restriction of water diffusion at long diffusion times. Mapping of the water fraction in each compartment was further employed to monitor changes during tumor progression and to assess tumor response to hormonal manipulation with a new antiestrogenic drug, tamoxifen methiodide (TMI). It was found that, in parallel to the growth arrest by this drug, the volume fraction of the slowly diffusing water increased, suggesting a TMI-induced cell swelling. This study can serve as a basis for extending diffusion breast MRI in the clinical setting.     

Stress-induced impairment of inhibitory avoidance learning in female neuromedin B receptor-deficient mice

Neuromedin B (NMB) is a mammalian bombesin (BN)-like peptide that exerts its function via the neuromedin B receptor (NMB-R). The NMB/NMB-R system is involved in stress response, and therefore we examined behavioral properties in female mice lacking NMB-R using a restraint-induced stress paradigm. Thirty minutes of restraint in a wire mesh cage constituted a sufficient stress stimulus for mice as evidenced by elevated blood glucose concentrations in stressed wild-type and NMB-R-deficient mice. Using a one-trial passive avoidance test, stressed NMB-R-deficient mice exhibited a marked reduction in memory performance. NMB-R-deficient mice exhibited elevated spontaneous activity in a novel environment compared to non-stressed mutant mice after 30-min stress, and a similar difference was also observed between stressed/non-stressed wild-type mice. An elevated plus maze test showed that the stress stimulus had no effect on anxiety in either wild-type or NMB-R-deficient mice. Furthermore, pain response of wild-type and NMB-R-deficient mice induced by electric foot shock was not affected under either stressed or non-stressed conditions. These results indicate that impaired memory performance in stressed NMB-R-deficient mice is not a consequence of changes in spontaneous activity, anxiety, or pain response, and suggest that the NMB/NMB-R pathway may play a role in regulating the stress response via the neural system that controls learning and memory.     

Enhanced zinc consumption causes memory deficits and increased brain levels of zinc

Zinc deficiency has been shown to impair cognitive functioning, but little work has been done on the effects of elevated zinc. This research examined the effect on memory of raising Sprague-Dawley rats on enhanced levels of zinc (10 ppm ZnCO3; 0.153 mM) in the drinking water for periods of 3 or 9 months, both pre- and postnatally. Controls were raised on lab water. Memory was tested in a series of Morris Water Maze (MWM) experiments, and zinc-treated rats were found to have impairments in both reference and working memory. They were significantly slower to find a stationary platform and showed greater thigmotaxicity, a measure of anxiety. On a working memory task, where the platform was moved each day, zinc-treated animals had longer latencies over both trials and days, swam further from the platform, and showed greater thigmotaxicity. On trials using an Atlantis platform, which remained in one place but was lowered on probe trials, the zinc-treated animals had significantly fewer platform crossings, spent less time in the target quadrant, and did not swim as close to the platform position. They had significantly greater latency on nonprobe trials. Microprobe synchrotron X-ray fluorescence (microSXRF) confirmed that brain zinc levels were increased by adding ZnCO3 to the drinking water. These data show that long-term dietary administration of zinc can lead to impairments in cognitive function.     

Extensive training in a maze task reduces neurogenesis in the adult rat dentate gyrus probably as a result of stress

It has recently been shown that hippocampal neurogenesis can be modulated either directly or indirectly by ascending cholinergic inputs from the basal forebrain. In the present work, we sought to address whether extended training in a spatial navigation task would affect hippocampal neurogenesis in the presence of a severe and selective cholinergic depletion. Young female rats received stereotaxic injections of the immunotoxin 192 IgG-saporin into the basal forebrain nuclei and/or the cerebellar cortex. Starting from 4 to 5 weeks post-lesion, and for the subsequent 2 weeks, the animals were trained on paradigms of reference and working memory in the water maze and received single daily i.p. injections of bromodeoxyuridine (BrdU) at the end of each testing session. In line with previous observations, a dramatic 80% decrease in neuron proliferation was seen in the dentate gyrus of lesioned animals, as compared to vehicle-injected or intact controls. Interestingly, however, rats subjected to maze training over 2 weeks, irrespective of their learning success, exhibited significantly fewer newborn neurons than matched controls with no maze exposure. Thus, at least for the type of task used here, which has previously been shown to impose a certain degree of stress, extended training and learning does not appear to affect proliferation in the dentate gyrus.