Differential morphology of the superior olivary complex of Meriones unguiculatus and Monodelphis domestica revealed by calcium-binding proteins.

In mammals, the superior olivary complex (SOC) of the brainstem is composed of nuclei that integrate afferent auditory originating from both ears. Here, the expression of different calcium-binding proteins in subnuclei of the SOC was studied in distantly related mammals, the Mongolian gerbil (Meriones unguiculatus) and the gray short-tailed opossum (Monodelphis domestica) to get a better understanding of the basal nuclear organization of the SOC. Combined immunofluorescence labeling of the calcium-binding proteins (CaBPs) parvalbumin, calbindin-D28k, and calretinin as well as pan-neuronal markers displayed characteristic distribution patterns highlighting details of neuronal architecture of SOC nuclei. Parvalbumin was found in almost all neurons of SOC nuclei in both species, while calbindin and calretinin were restricted to specific cell types and axonal terminal fields. In both species, calbindin displayed a ubiquitous and mostly selective distribution in neurons of the medial nucleus of trapezoid body (MNTB) including their terminal axonal fields in different SOC targets. In Meriones, calretinin and calbindin showed non-overlapping expression patterns in neuron somata and terminal fields throughout the SOC. In Monodelphis, co-expression of calbindin and calretinin was observed in the MNTB, and hence both CaBPs were also co-localized in terminal fields within the adjacent SOC nuclei. The distribution patterns of CaBPs in both species are discussed with respect to the intrinsic neuronal SOC circuits as part of the auditory brainstem system that underlie the binaural integrative processing of acoustic signals as the basis for localization and discrimination of auditory objects.

Competitive ligand exchange between Cu-humic acid complexes and methanobactin.

Copper has been found to play a key role in the physiology of methanotrophic micro-organisms, and methane oxidation may critically depend on the availability of Cu. In natural environments, such as soils, sediments, peat bogs, and surface waters, the presence of natural organic matter (NOM) can control the bioavailability of Cu by forming strong metal complexes. To promote Cu acquisition, methanotrophs exude methanobactin, a ligand known to have a high affinity for Cu. In this study, the capability of methanobactin for Cu acquisition from NOM was investigated using humic acid (HA) as a model substance. The kinetics of ligand exchange between Cu-HA and methanobactin was observed by UV-vis spectroscopy, and the speciation of Cu bound to methanobactin was determined by size-exclusion chromatography coupled to an ICP-MS. The results showed that Cu was mobilized from HA by a fast ligand exchange reaction following a second-order rate law with first-order kinetics for both methanobactin and Cu-HA complexes. The reaction rates decreased with decreasing temperature. Equilibrium experiments indicated that methanobactin was not sorbed to HA and proved that methanobactin is competitive with HA for Cu binding by forming strong 1:1 Cu-methanobactin complexes. Consequently, our results demonstrate that methanobactin can efficiently acquire Cu in organic-rich environments.

Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 1. Proton binding.

Proton binding by a soil fulvic acid, humic acid, and a set of size fractions of the humic acid was studied as a function of pH and ionic strength by potentiometric titrations. The negative charge of the humic substances resulting from deprotonation of acidic functional groups generally increased with increasing pH and increasing ionic strength. At any given pH and ionic strength, the fulvic acid fraction exhibited much higher negative charge than the humic acid fraction. For the size-fractionated humic acids, negative charge decreased steadily with increasing apparent molecular weight, as determined by size exclusion chromatography. Observed differences in proton binding by the various humic substances corresponded well to differences in functional group composition, which has been extensively characterized in a previous study using a combination of analytical techniques. The proton binding behavior of the humic substances was described very well by the consistent NICA-Donnan model. However, when all adjustable model parameters were determined using a least-squares minimization technique without introducing parameter constraints, the values of some parameters turned out physically and chemically unreasonable. Therefore, we propose to derive some model parameters from chemical characterization results obtained by size exclusion chromatography and solid-state 13C NMR spectroscopy. Using this approach, we obtained excellent descriptions of all titration data, and the model parameter values were more consistent and chemically reasonable. Our results demonstrate that characterization results of humic substances can be used in NICA-Donnan modeling to reduce the number of free fitting parameters without arbitrary constraints and, thereby, obtaining a more reliable database for environmental modeling.

Relating ion binding by fulvic and humic acids to chemical composition and molecular size. 2. Metal binding.

Binding of Cu(II) and Pb(II) to a soil fulvic acid, humic acid, and two different size fractions of the humic acid was investigated with metal titration experiments at pH 4, 6, and 8. Proton and free metal ion activities in solution were monitored after each titration step using pH and ion selective electrodes (ISE), respectively. The amounts of base required to maintain constant pH conditions were recorded and used to calculate stoichiometric proton-to-metal ion exchange ratios. Despite clear differences in chemical composition and protonation behavior, the fulvic acid and all humic acid fractions exhibited very similar metal binding behavior. Binding of Cu(II) and Pb(II) generally increased with increasing pH and total metal concentration. At low to moderate metal ion concentrations, Cu(II) was bound more strongly to the humic substances than Pb(II). Only at high free metal concentrations, the amounts of metal ions sorbed were higher for Pb(II) than for Cu(II). The molar proton-to-metal ion exchange ratios ranged from 1.0 to 1.8 for Cu(II) and from 0.6 to 1.2 for Pb(II), suggesting that Cu(II) was bound as monodentate and bidentate complexes, while Pb(II) was bound predominantly as monodentate complexes. The metal ion binding data were quantitatively described with the consistent NICA-Donnan model. The best description of an entire multicomponent data set consisting of proton titration, Cu(II), and Pb(II) binding data was achieved when the entire data set was fitted simultaneously. To reduce the number of fitting parameters, results from size exclusion chromatography and solid state 13C NMR spectroscopy were used to estimate two of the NICA-Donnan model parameters. The values of the remaining NICA-Donnan parameters for the humic substances are within a narrow range, suggesting that generalized model parameters may be useful in geochemical modeling involving humic substances.

Reaction-based model describing competitive sorption and transport of Cd, Zn, and Ni in an acidic soil.

Predicting the mobility of heavy metals in soils requires models that accurately describe metal adsorption in the presence of competing cations. They should also be easily adjustable to specific soil materials and applicable in reactive transport codes. In this study, Cd adsorption to an acidic soil material was investigated over a wide concentration range (10(-8) to 10(-2) M CdCl2) in the presence of different background electrolytes (10(-4) to 10(-2) M CaCl2 or MgCl2 or 0.05 to 0.5 M NaCl). The adsorption experiments were conducted at pH values between 4.6 and 6.5 A reaction-based sorption model was developed using a combination of nonspecific cation exchange reactions and competitive sorption reactions to sites with high affinity for heavy metals. This combined cation exchange/specific sorption (CESS) model accurately described the entire Cd sorption data set. Coupled to a solute transport code, the model accurately predicted Cd breakthrough curves obtained in column transport experiments. The model was further extended to describe competitive sorption and transport of Cd, Zn, and Ni. At pH 4.6, both Zn and Ni exhibited similar sorption and transport behavior as observed for Cd. In all transport experiments conducted under acidic conditions, heavy metal adsorption was shown to be reversible and kinetic effects were negligible within time periods ranging from hours up to four weeks.

Transport of Iron Oxide Colloids in Packed Quartz Sand Media: Monolayer and Multilayer Deposition.

The transport and deposition dynamics of hematite (alpha-Fe(2)O(3)) colloids in packed quartz sand media are investigated. Column transport experiments were carried out at various solution ionic strengths, colloid concentrations, and flow velocities. A colloid transport model was proposed that includes the dynamics of blocking as well as multilayer deposition that takes place at high ionic strengths where particle-particle interactions are favorable. Blocking dynamics in the model are described by either Langmuirian adsorption (LA) or random sequential adsorption (RSA). Two important model parameters-the particle-matrix collision efficiency and the ionic strength dependent blocking (excluded area) parameter-are estimated from the colloid breakthrough curves using a nonlinear optimization procedure. The collision (attachment) efficiency for particle-particle interactions, on the other hand, was determined independently from colloid aggregation rate measurements. At very low ionic strength, only monolayer deposition is observed and the RSA model gives a better description of the experimental data than the LA model. At higher ionic strengths, multilayer deposition becomes significant and both models yield comparable results. Calculated maximum surface coverages at low ionic strengths were in good agreement with experimentally observed values obtained by scanning electron microscopy. Copyright 2000 Academic Press.

Absolute Aggregation Rate Constants of Hematite Particles in Aqueous Suspensions: A Comparison of Two Different Surface Morphologies.

Measurements of absolute aggregation rate constants were performed for two samples of well-characterized spheroidal hematite particles with rather different surface morphology. At high ionic strength, the system is in the fast aggregation regime with pH independent rate constants around (1-4) x 10(-18) m3/s. At low ionic strengths, the rate constant is a function of pH and goes through a flat maximum around the point of zero charge (PZC) where fast aggregation conditions are reached. With increasing pH the rate constants increase gradually below the PZC while they decrease very rapidly above the PZC. Above the PZC the rate constants are rather well predicted by the classical DLVO theory. Below the PZC, however, it is necessary to assume a distribution in the surface potentials with a coefficient of variation around 30% to account for the observed behavior. In spite of the pronounced differences in the surface roughness of both hematite samples, their aggregation rate constants are rather similar. Copyright 1997 Academic Press.

Developmental changes of enzymes involved in peptide degradation in isolated rat brain microvessels.

The specific activities of aminopeptidase A (APA), aminopeptidase M (APM), and dipeptidyl-aminopeptidase IV (DP IV) were determined in isolated brain microvessels and in brain homogenate of rats with different ages (between 1 and 8 weeks old). In addition, the blood-brain barrier (BBB)-specific enzymes gamma-glutamyltranspeptidase (gamma-GT) and alkaline phosphatase (ALP) were measured. As similarly described by others, gamma-GT activity increased during this time period by fourfold, whereas ALP increased between weeks 1 and 2 and declined thereafter. DP IV activity increased fivefold during the first 8 weeks after birth and APM activity increased by twofold. A decrease of APA activity was found between weeks 1 and 2 after birth followed by an increase thereafter. The development of aminopeptidase activities responsible for the processing of specific neuropeptides acting on brain microvessels may be important in the development of regulation processes for cerebral blood flow and BBB permeability in the maturing animal.

Age-related pathophysiology of the blood-brain barrier in heat stress.

The possibility that the blood-brain barrier (BBB) might play an important role in the pathophysiology of heat stress (HS) has been examined in young (age 8-9 weeks) and adult (age 24-32 weeks) rats. Exposure of young rats to 4 h HS at 38 degrees C in a biological oxygen demand (BOD) incubator (relative humidity 47-50%, wind velocity 20-26 cm/sec, simulating the environmental conditions of Varanasi, India, during the month of June) resulted in a marked hyperthermia (41.7 +/- 0.23 degrees C) and behavioral symptoms. In these animals there was a profound increase in the permeability of the BBB to Evans blue-albumin (EBA) (464%) and to 131I-sodium iodide (515%), accompanied by a marked increase in the brain water content (4%), of the levels of serotonin (5-hydroxytryptamine, 5-HT) in plasma (687%) and in brain (267%) and a pronounced reduction (30%) in cerebral blood flow (CBF). Morphological examination using light- and electron-microscopy revealed profound neuronal changes associated with a marked increase in glial fibrillary acidic protein (GFAP) and in vimentin immunoreactivities, together with a substantial reduction in myelin basic protein (MBP) immunostaining in the brain. These changes were more pronounced in the brain-stem reticular formation, pons and medulla region. On the other hand, exposure of adult animals to the same intensity of HS resulted in mild or no changes in BBB permeability, content of brain water and 5-HT in the plasma and brain, CBF or other cellular changes.(ABSTRACT TRUNCATED AT 250 WORDS)

On the blood-brain barrier to peptides: specific binding of atrial natriuretic peptide in vivo and in vitro.

Using the intracarotid bolus injection technique, a saturable binding of [125I]atrial natriuretic peptide (ANP) was found in 8 blood-brain barrier (BBB)-protected rat brain regions as well as in the pineal gland, choroid plexus, neurointermediate and anterior lobes of the pituitary, i.e. structures lacking a BBB. The presence of specific ANP binding on the BBB, here shown for the first time by an in vivo approach, was evidenced concomitantly in vitro by incubation of isolated microvessels. A single-class high affinity binding without regional differences was obtained with Kd = 0.23 nM and Bmax = 120 fmol/mg protein. From that a density of 1,400 binding sites per endothelial cell was calculated, thought to be localized predominantly in the luminal membranes. In the in vivo study, the portion of the extracted peptide that, under the conditions used, may have crossed the BBB by passive diffusion amounted to less than 0.4% of the labeled ANP administered. ANP itself did not change the tightness of the BBB to the non-diffusible reference molecule [14C]inulin. In the BBB-free areas, ANP enhanced the inulin space by nearly 50%.

Arginine-vasopressin binding to isolated hippocampal microvessels of rats with different endogenous concentrations of the neuropeptide.

The binding of [125I]arginine-8-vasopressin (AVP) to hippocampal microvessels isolated from brains of normal Wistar rats, animals after water deprivation and heterozygous as well as homozygous diabetes-insipidus rats (Brattleboro strain) were measured. Data from binding experiments from the microvessels of the different groups of animals in each case revealed a single class of high affinity binding sites. However, the binding parameters between the different groups of rats were different. The affinity constants differs by a factor of 5.1, ranging from KD = 1.18 nmol X L-1 (animals after water deprivation) to KD = 6.05 nmol X L-1 (homozygous Brattleboro rats). The binding capacity, differing by a factor of 3.5, ranged from Bmax = 245 fmol X mg-1 to Bmax = 865 fmol X mg-1.

[The x-ray picture of cheirolumbar dysostosis]. / Zur Röntgenologie der cheirolumbalen Dysostose.

Constitutional stenosis of the lumbar vertebral canal and brachycheiria (brachymetacarpia/brachyphalangia) together form cheirolumbar dysostosis (no. 2692 of the Birth Defects Encyclopedia, 1987). Typical findings in the basic type and transitional forms are presented.

Development of hypertension and life span in stroke-prone spontaneously hypertensive rats during oral long-term treatment with various antihypertensive drugs.

In stroke-prone spontaneously hypertensive rats, oral long-term treatment with verapamil, propranolol, hydrochlorothiazide, and dihydralazine attenuated the development of hypertension. The various antihypertensive drugs caused comparable reductions in blood pressure but the calcium antagonist and the beta-receptor blocker prolonged the life span more than the diuretic and vasodilator. The relative heart and lung weights at the time of death were slightly diminished in the verapamil and the high-dose propranolol group. It is assumed that calcium antagonism and beta-receptor blockade prolong the life span, not only due to their blood-pressure-lowering mechanism, but also to the additional protective effects.

[Pippow's syndrome]. / Uber das Pippow-Syndrom.

For the first time since the initial report of aplasia of vertebral joints and brachydactyly occurring in a sibship, a similar family history of this rare dystostosis is presented. The following triad of symptoms is significant: a) hypoplasia of the laminae and of the articular and transverse processes of the vertebrae in the thoracolumbar region; b) cranial shift of the vertebral junctions; and c) brachydactyly. "Pippow's syndrome" and "Pippow's dysostosis" are suggested as possible names for this condition.

Protective effect of the new calcium antagonist anipamil against isoprenaline-induced cardionecrosis in rats.

The new calcium antagonist anipamil (1,7-bis-(3-methoxyphenyl)-3-methylaza-7-cyano-nonadecane) exhibited a pronounced protective effect against isoprenaline-induced myocardial necrosis in rats. Anipamil was administered in single doses of 10 or 20 mg/kg daily for 4 days. 30 mg/kg isoprenaline was given by subcutaneous injection on the 3rd and 4th days of the study. The protective effect of anipamil was assessed by histological investigations, and its effect on the activity of the enzymes succinate dehydrogenase, NADH-NBT reductase, acid phosphatase and glucose-6-phosphate dehydrogenase in experimentally-induced myocardial damage was assessed quantitatively by microphotometry. The protective effect of anipamil against isoprenaline-induced myocardial necrosis was definitely dose-dependent: 10 mg/kg anipamil exhibited a partial protective effect, whilst 20 mg/kg anipamil protected the heart completely.

Vasopressin binds to microvessels from rat hippocampus.

Recent evidence suggests that vasopressin may influence the permeability of the endothelium of brain capillaries. We measured the binding of [125I]arginine-8-vasopressin ([125I]AVP) to microvessels isolated from different regions of the rat brain. The study revealed saturable and specific binding of [125I]AVP to microvessels isolated from hippocampus. Scatchard analysis confirmed a single class of high affinity sites with an equilibrium dissociation constant, Kd, of 3.2 nM and an apparent maximal binding capacity of 205 fmol/mg protein. No binding was observed to microvessels from neocortex and striatum.