Manganese dipyridoxyl diphosphate: MRI contrast agent with antioxidative and cardioprotective properties?

Manganese dipyridoxyl diphosphate (MnDPDP) is a contrast agent for magnetic resonance imaging (MRI) of the liver. Aims of the study were to examine if MnDPDP possesses superoxide dismutase (SOD) mimetic activity in vitro, and if antioxidant protection can be demonstrated in an ex vivo rat heart model. Superoxide (*O-2) and hydroxyl radicals (*OH-) were generated in xanthine oxidase and Fenton reactions. Spin adducts with 5,5-dimethyl-1-pyrroline-N-oxide were detected by electron spin resonance spectroscopy. Contractile function and enzyme release were monitored in rat hearts during hypoxia-reoxygenation. Low microM concentrations of MnDPDP and its metabolite Mn dipyridoxyl ethylene-diamine (MnPLED) dismutated *O-2, but showed no activity in Fenton or catalase reactions. MnDPDP 30 microM improved contractile function and reduced enzyme release in rat hearts during reoxygenation. It is concluded that MnDPDP and MnPLED possess SOD mimetic activities and may thereby protect the heart in oxidative stress.

Proteolysis in human lens epithelium determined by a cell-permeable substrate

PURPOSE

To develop a system for continuous evaluation of proteolytic activity in human lens epithelium and to characterize factors of importance for the regulation of proteolytic activity in lens epithelial cells.

METHODS

Human lens epithelial cells were obtained during cataract surgery. Capsule epithelium specimens consisted of the central parts of the anterior capsule and the underlying lens epithelium. The sample, with the cell-permeable substrate Suc-Leu-Leu-Val-Tyr-7-amino-4-methylcoumarin, was placed in a chamber, which was placed in a thermostat-controlled aluminum block. Fluorescence changes were continuously measured by the fiber optics of the luminometer, which was placed 5 mm above the buffer surface.

RESULTS

After administration of substrate to the medium overlying the cells, the substrate was degraded at a relatively slow rate. Approximately 10 picomoles of amino-4-methylcoumarin were formed per minute. A significant increase of proteolytic activity could be observed after application of 1 microM ionomycin or 2 microM thapsigargin. No leakage of lactate dehydrogenase from the cells was observed during these procedures. Basal proteolytic activity was totally inhibited by the proteasome inhibitor lactacystin. Lactacystin also attenuated the response to ionomycin and thapsigargin.

CONCLUSIONS

Human lens epithelium responds to increased Ca levels from external or internal stores with an increased proteolytic activity that may be mediated by calpain, by the proteasome, or by both. This calcium-dependent change in proteolytic activity may be of importance in the development of cataract.

The haemodynamic effects of iodinated water soluble radiographic contrast media: a review

All classes of iodinated water-soluble radiographic contrast media (RCM) are vasoactive with the iso-osmolar dimers inducing the least changes in the vascular tone. The mechanisms responsible for RCM-induced changes in the vascular tone are not fully understood and could be multifactorial. A direct effect on the vascular smooth muscle cells causing alterations in the ion exchanges across the cell membrane is thought to be an important factor in RCM-induced vasodilatation. The release of the endogenous vasoactive mediators adenosine and endothelin may also play a crucial role in the haemodynamic effects of RCM particularly in the kidney. In addition, the effects of RCM on blood rheology can cause a reduction in the blood flow in the microcirculation. The purpose of this review is to discuss the pathophysiology of the haemodynamic effects of RCM and to offer some insight into the biology of the endothelium and vascular smooth muscle cells as well as the pharmacology of the important vasoactive mediators endothelin and adenosine.

Interaction between heat shock and interleukin 6 stimulation in the acute-phase response of human hepatoma (HepG2) cells

Two characteristic elements of the acute-phase response are an altered pattern of circulating hepatic proteins and fever. Whereas a fever-induced heat shock response could affect expression of acute-phase proteins in the liver, the effects of a modest temperature increase on protein secretion in interleukin-6 (IL-6)-stimulated HepG2 cells were investigated. The response of HepG2 cells to IL-6 stimulation was significantly affected by heat treatment at 40 degreesC. Albumin secretion rates, which were reduced by a factor of 2 in response to either heat shock or IL-6 stimulation alone, were down-regulated by a factor of 4 when IL-6 was administered simultaneously with a continuous 40 degrees C heat shock. IL-6-induced fibrinogen up-regulation was significantly reduced by heat treatment (P < .01), and secretion rates were indistinguishable from control levels after 2 days (P > .10). Unexpectedly, heat shock at 40 degrees C induced a fivefold up-regulation of haptoglobin production in the absence of IL-6. Simultaneous heat shock and IL-6 stimulation caused a synergistic enhancement of haptoglobin expression, with secretion rates increasing up to 30-fold compared with unstimulated control cells. For all three proteins, the interaction between temperature and IL-6 concentration was statistically significant (P < .001). Heat treatment resulted in significant alterations of both the kinetics and sensitivity of IL-6-induced protein synthesis, suggesting a major modification of the mechanism of acute-phase protein regulation at 40 degreesC. In summary, the data show that heat shock can significantly modulate the pattern of acute-phase protein expression and that fever may be an important regulatory factor in the acute-phase response.

Proteolytic cleavage of N-Succ-Leu-Leu-Val-Tyr-AMC by the proteasome in lens epithelium from clear and cataractous human lenses

With ageing, accumulation of modified proteins occur in the lens, forming light scattering aggregates. The multicatalytic proteinase complex, or proteasome, is known to be the major system for removal of damaged proteins in many tissues. In this study we attempted to compare levels of proteasome activity in human lens epithelium from clear vs. cataractous lenses. Normal lenses were obtained from eye donors in a cornea bank and samples from cataractous lenses were obtained from an eye clinic during cataract surgery. Proteolytic activity was quantified using the synthetic peptide substrate N-Succ-Leu-Leu-Val-Tyr-AMC, a substrate often used to measure the chymotrypsin-like activity of the proteasome. Addition of 100 micron lactacystin, a proteasome specific inhibitor, totally inhibited proteolysis, certifying the specificity of the assay. Hydrolysis was detected over time as the appearance of the flourogenic cleavage product and correlated to the area of the epithelium-capsule specimens. Proteolytic cleavage of N-Succ-Leu-Leu-Val-Tyr-AMC by the proteasome was higher in lens epithelium from clear donor lenses as compared to samples from cataractous lenses. Median activity in the latter was only 19% of that in the former, a highly significant difference. There was no difference in activity of the proteasome when looking at cortical vs. non-cortical cataract, nor was there any difference between genders. Regression analysis did not reveal any age-dependent relationship, either in the clear group or in the cataractous group. This work is the first to show differences in proteasome activity between clear and cataractous lenses.

Multiple alpha 2-adrenoceptor signalling pathways mediate pigment aggregation within melanophores

It has previously been shown that alpha 2-adrenoceptors (alpha 2-ARs) mediate pigment granule (melanosome) aggregation in melanophores of the teleost fish Labrus ossifagus. The present investigation scrutinized the signalling mechanisms of melanosome aggregation induced by sympathetic nerve stimulation or by exogenous addition of alpha-AR agonists and cAMP analogues. The following was observed: i) nerve-induced melanosome aggregation was associated with a rapid decrease in the cAMP level; ii) noradrenaline or medetomidine (an alpha 2-AR agonist) caused melanosome aggregation and reduced the cAMP content; iii) RP-8-Cl-cAMP, a membrane-permeating inhibitor of protein kinase A induced melanosome aggregation; and iv) B-HT 920 (an alpha 2-AR agonist) and methoxamine (an alpha 1-AR agonist) induced melanosome aggregation, although they did not reduce cAMP. It has been suggested that in some teleost species alpha 1-ARs mediate melanosome aggregation by increasing the level of intracellular calcium. However, we found that the effect of methoxamine in melanophores from Labrus ossifagus could be blocked by yohimbine (an alpha 2-AR antagonist) but not by equimolar concentration of prazosin (an alpha 1-AR antagonist). Furthermore, 1 microM ionomycin (a calcium ionophore) did not induce melanosome aggregation. Our findings therefore do not indicate that alpha 1-ARs and/or an increase in intracellular calcium mediate melanosome aggregation in Labrus ossifagus. Our results suggest that alpha 2-AR-mediated melanosome aggregation is induced by multiple signalling pathways. One of these involves a reduction in cAMP, but none involves an increase in intracellular calcium.

Postnatal changes in mechanisms mediating acetylcholine-induced relaxation in piglet femoral arteries

We studied the nitric oxide-cGMP pathway in endothelium-dependent relaxation in femoral arterial rings from piglets at different postnatal ages. Responses to acetylcholine (ACh) and sodium nitroprusside (SNP) were examined in phenylephrine-precontracted rings from newborn (10-22-h) and 7 d (7-10-d)-old piglets. Relaxant responses were investigated in endothelium-denuded rings and endothelium-intact controls, and in endothelium-intact rings incubated with the nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine acetate (L-NMMA), indomethacin, or the superoxide anion generator 6-anilinoquinoline-5,8-quinone (LY83583). Arterial rings from both age groups relaxed to a similar degree in response to ACh. Relaxation in rings from newborn piglets was insensitive to NOS inhibition by L-NMMA, whereas in artery rings from 7-d-old piglets, the relaxant response was significantly inhibited by L-NMMA. Incubation with LY83583 gave an inhibition of ACh-induced relaxation very similar to that of L-NMMA. Incubation with indomethacin had no significant effect on ACh-induced relaxation in either age group. Artery rings from both age groups relaxed 100% to SNP; the 7-d-old group was more sensitive than the newborn. NOS inhibition potentiated SNP-induced relaxation in both groups, but the potentiating effect was of greater magnitude in the newborn. Our results indicate a difference in the mechanism(s) underlying ACh-induced relaxation in the femoral artery from newborn and 7-d-old piglets, with an intact relaxant response in rings from the newborn despite NOS inhibition. The SNP results indicate a down-regulated soluble guanylate cyclase in the newborn, possibly related to a difference in basal NO release between the two age groups.

Effects of MnDPDP, DPDP--, and MnCl2 on cardiac energy metabolism and manganese accumulation. An experimental study in the isolated perfused rat heart

RATIONALE AND OBJECTIVES

Recent studies indicate that manganese dipyridoxyl diphosphate (MnDPDP) may function as a slow release agent for manganese ions (Mn++) and that MnDPDP is approximately 10 times less potent than manganese chloride (MnCl2) in depressing cardiac function. The authors examined the possibility that MnDPDP and MnCl2 may influence cardiac metabolism and enzyme release and lead to a tissue accumulation of Mn.

METHODS

Manganese DPDP, DPDP--, or MnCl2 (1000 microM) was infused in isolated rat hearts, which were freeze-clamped at various time intervals during infusion (5 minutes) and recovery (14-minute washout). Enzyme (lactate dehydrogenase) release, tissue high energy phosphates, Mn contents, and physiologic indices were measured at various time intervals.

RESULTS

No significant differences were noted for: lactate dehydrogenase in the treated groups; tissue creatine phosphate (CrP) and adenosine triphosphate in MnDPDP, DPDP--, and control groups; and tissue Mn in DPDP-- and control groups. Manganese-chloride and MnDPDP-treated hearts accumulated and retained Mn in an 8:1 ratio. Manganese chloride depressed cardiac function more effectively than MnDPDP.

CONCLUSIONS

The study has shown that: heart tissue uptake and retention of Mn++ is rapid and effective; MnCl2 is approximately eight times more potent than MnDPDP in promoting these effects; and a rise in tissue Mn content to eight to nine times (MnDPDP) or 60 to 70 times (MnCl2) the normal level does not lead to acute side effects on cardiac energy metabolism, function, and enzyme release. The study indicates that MnDPDP may act like a slow release compound for Mn++ ions.

Extra-lysosomal proteolysis and expression of calpains and calpastatin in cultured thyroid cells

Proteolysis at neutral pH in the soluble fraction of cultured pig thyroid epithelial cells was examined using a synthetic calpain substrate, succinyl-Leu-Tyr-7-amino-4-methylcoumarin. The Ca2+-independent proteolytic activity was largely inhibited by substances known to affect cysteine- and metalloproteases, whereas no or little effects were obtained with inhibitors affecting serine- and aspartic proteases. Addition of Ca2+ did not significantly alter the rate of substrate degradation. Biochemical separation via hydrophobic interaction chromatography and Western blotting demonstrated the presence of both m-calpain (40% of total calpain) and mu-calpain (60%) in confluent thyrocytes. Determination of calpastatin activity indicated a 30 times higher level of the inhibitor as compared to total calpain activity. Western blotting showed the presence of a 110 kD calpastatin form with additional low mol wt forms possibly representing fragmentation products. In immunofluorescent stainings, m-calpain had a diffuse cytoplasmic distribution whereas mu-calpain was located both in the cytoplasm and at the cell-cell contacts. Calpastatin immunoreactivity was mainly granular and located close to the nucleus, although a fibrillar distribution was also observed. The results show the presence of all components of the calpain/calpastatin system and indicate a strict control of calpain activity in cultured thyrocytes. The different subcellular distributions of calpains and calpastatin suggests that they are compartmentalized and require mobilization to interact.

Manganese and the heart: acute cardiodepression and myocardial accumulation of manganese

The aim of study was to assess acute effects of the divalent manganese ion (Mn2+) in an intact but isolated heart preparation. Rat hearts were perfused in the Langendorff mode at constant flow rate. Left ventricular (LV) developed pressure (LVDP). LV pressure first derivatives (LVdp/dt max and min), heart rate (HR) and aortic pressure (AoP) were recorded. Ventricular contents of high energy phosphate compounds (HEP) and Mn metal were measured at the end of experiment. Infusion of MnCl2 for 5 min with perfusate concentrations 1-3000 microM induced an immediate depression of contractile function at and above 30 microM and negative chronotropy at and above 300 microM. These IC50 values were found (microM): LVDP 250; LVdp/dt max 160; LVdp/dp min 120; HR 1000; and increase in AoP 80. Recovery of function during a 14 min washout period was rapid and extensive except for Mn2+ 3000 microM. Somewhat unexpected, Mr2+ 30-1000 microM raised coronary vascular resistance up to about twice the control level, whereas the vasoconstrictory response was overcome at 3000 microM. Mn2+ 3000 microM reduced tissue HEP Ventricular Mn content rose stepwise for perfusate Mn2+ above 1 microM up to about 55 times the control level for perfusate Mn2+ 3000 microM. It is concluded that: acute effects of Mn2+ like depression of contractility and rate is rapidly reversible; and rat hearts accumulate and buffer large amounts of Mn2+ without affecting cardiac function or energy metabolism in the acute stage.

Patients with amyotrophic lateral sclerosis and other neurodegenerative diseases have increased levels of neurofilament protein in CSF

In the present study we describe an ELISA to quantify the light subunit of the neurofilament triplet protein (NFL) in CSF. The method was validated by measuring CSF NFL concentrations in healthy individuals and in two well-characterized groups of patients with amyotrophic lateral sclerosis (ALS) and Alzheimer's disease (AD). The levels were increased in ALS (1,743 +/- 1,661 ng/L; mean +/- SD) and AD (346 +/- 176 ng/L) compared with controls (138 +/- 31 ng/L; p < 0.0001 for both). Within the ALS group, patients with lower motor neuron signs only had lower NFL levels (360 +/- 237 ng/L) than those with signs of upper motor neuron disease (2,435 +/- 1,633 ng/L) (p < 0.05). In a second study patients with miscellaneous neurodegenerative diseases were investigated (vascular dementia, olivopontocerebellar atrophy, normal pressure hydrocephalus, cerebral infarctions, and multiple sclerosis), and the CSF NFL level was found to be increased (665 +/- 385 ng/L; p < 0.0001). NFL is a main structural protein of axons, and we suggest that CSF NFL can be used to monitor neurodegeneration in general, but particularly in ALS with involvement of the pyramidal tract.

Ionic mechanisms contributing to the vasorelaxant properties of iodinated contrast media: a comparison of iohexol and iodixanol in the rabbit isolated aorta

1. We have used rings of rabbit thoracic aorta to investigate the vasorelaxant properties of two different classes of non-ionic iodinated radiographic contrast media (IRCM) and the mechanisms, underlying their mode of action. Iohexol (a triiodinated monomer) was compared with iodixanol (a hexaiodinated dimer). 2. Iohexol and iodixanol both relaxed phenylephrine (0.3 microM) constricted rabbit aorta in a concentration-dependent manner that did not depend on the presence of an intact endothelium. When expressed as a function of iodine concentration, iodixanol caused significantly less relaxation than iohexol. However, the extent of relaxation was similar for both IRCM when expressed on a molar basis. Furthermore, increasing the molarity of the buffer to comparable levels with mannitol evoked only a small (approximately 15%) relaxation of phenylephrine-induced tone. 3. Ouabain (10 microM) significantly inhibited both iohexol- and iodixanol-induced relaxations by approximately 30%. 5-(N-Ethyl-N-isopropyl)-amiloride (EIPA, 100 nM) significantly inhibited iohexol-induced relaxation to the same extent as ouabain, but did not alter the vasorelaxant effect of iodixanol. Co-incubation with ouabain and EIPA had an additive effect in the case of iohexol, increasing inhibition of relaxation to approximately 60%, whereas inhibition of iodixanol-induced relaxation by the combination of ouabain plus EIPA did not differ from that of ouabain alone. 4. Replacing NaCl with N-methyl-D-glucamine (NMDG) to lower extracellular [Na+] and thereby inhibit Na(+)-Ca2+ exchange, attenuated the relaxation evoked by iohexol or by iodixanol (by approximately 25%) in each case. 5. We conclude that iohexol- and iodixanol-induced vasorelaxation in rabbit aorta is mediated through a direct action on vascular smooth muscle that is not simply a consequence of altered osmolality. It involves modulation of the Na(+)-K+ ATPase and, in the case of iohexol, Na(+)-H+ exchange. Both agents also appear to modulate Na(+)-Ca2+ exchange, through direct and/or indirect mechanisms. This is the first study to show specific pharmacological differences between monomeric and dimeric contrast media in vascular smooth muscle.

Increased M-calpain expression in the mesencephalon of patients with Parkinson's disease but not in other neurodegenerative disorders involving the mesencephalon: a role in nerve cell death?

Parkinson's disease is characterized by the loss of dopaminergic neurons in the substantia nigra and, to a lesser extent, the ventral tegmental area and catecholaminergic cell group A8. However, among these dopaminergic neurons, those expressing the calcium buffering protein calbindin are selectively preserved, suggesting that a rise in intracellular calcium concentrations may be involved in the cascade of events leading to nerve cell death in Parkinson's disease. We therefore analysed immunohistochemically the expression of the calcium-dependent protease calpain II (m-calpain) in the mesencephalon of patients with Parkinson's disease, progressive supranuclear palsy or striatonigral degeneration, where nigral dopaminergic neurons degenerate, and matched controls without nigral involvement. Calpain immunoreactivity was found in fibers and neuronal perikarya in the substantia nigra, the ventral tegmental area, catecholaminergic cell group A8 and the locus coeruleus. In patients with Parkinson's disease but not with the other neurodegenerative disorders, m-calpain immunoreactivity was detected in fibers with an abnormal morphology and in Lewy bodies. Sequential double staining revealed that most of these m-calpain-positive fibers and neuronal perikarya co-expressed tyrosine hydroxylase, indicating that most m-calpain neurons are catecholaminergic. Quantitative analysis of m-calpain staining in the substantia nigra and locus coeruleus revealed an increased density of fibers and neuronal perikarya in parkinsonian patients in both structures. These data suggest that increased calcium concentrations may be associated with nerve cell death in Parkinson's disease.

Fertilization and development of mouse oocytes cryopreserved using a theoretically optimized protocol

Rational design of a cryopreservation protocol was demonstrated by using theoretical models of the cryopreservation process to develop an optimal freezing protocol for mouse oocytes. A coupled mechanistic model of the processes of freeze-induced cell dehydration and intracellular ice formation was developed, and cryomicroscopical measurements of intracellular ice formation kinetics were used to determine biophysical parameters required by the model, and to test model predictions of the freezing behaviour of mouse oocytes. A simple phenomenological model for oocyte damage resulting from exposure to concentrated electrolyte and cryoprotectant solutions during cryopreservation was obtained by defining a cost function equal to the duration of the freezing protocol. A two-step freezing protocol was theoretically optimized by using a sequential simplex algorithm to minimize the cost function, subject to the constraint that the predicted probability of intracellular ice formation remain below 5%, yielding a putative optimum at the cooling rate B = 0.59 degrees C/min, and plunge temperature Tp = -67 degrees C. By systematically varying B and Tp about these values in experiments with mouse oocytes cryopreserved in 1.5 M dimethyl sulphoxide, the maximal recovery of intact oocytes with a normal morphology (82%) was obtained for B = 0.5 degrees C/min and Tp = -80 degrees C. Further evaluation of the fertilizability and developmental capacity of oocytes cryopreserved using the optimized protocol yielded cleavage to the 2-cell stage in 65% of oocytes inseminated, and blastocyst formation in 50% of these 2-cell embryos.

Preclinical safety assessment of contrast media: predictive value

The purpose of preclinical tests is to identify the potential benefits and risks of new diagnostic or therapeutic products. Regarding iodinated contrast media (CM), LD50 tests were used extensively in the past. However, from both scientific and ethical perspectives, it is today highly relevant to question the use of LD50 tests. Due to species differences and the very high volume of CM needed to kill half of the animals, such tests are not sensitive enough to differentiate between modern nonionic CM. Further, they are not very predictive in terms of human tolerability. In other tests with more relevant end-points than death, overall tolerance to the new dimeric compound iodixanol (Visipaque), representing the latest step in the development of CM, has been shown to be higher than to the nonionic monomers. Clinical experience has shown that the physiological parameters often stay closer to baseline after Visipaque than after administration of conventional CM.

Long-term storage of tissues by cryopreservation: critical issues

The technique of cryopreservation (maintenance of biological samples in a state of 'suspended animation' at cryogenic temperatures), its potential use in tissue engineering applications and current obstacles to the development of effective cryopreservation methods for tissues are reviewed. A didactic overview of the principles of cryobiology and the methodology of cryopreservation is given, with emphasis on the processes of injury to cells during freezing and thawing, and how these are related to the physicochemical and biophysical changes occurring during cryopreservation. Critical issues relevant to the application of cryopreservation methods to tissues are then addressed, including heat and mass transfer limitations in these bulk systems, intrinsic differences between isolated and cultured cells, and mechanisms of freezing injury unique to tissue systems.

Calpains in the human lens: relations to membranes and possible role in cataract formation

Calpains are Ca-activated neutral proteases present in all cells together with an endogenous inhibitor, calpastatin. Proposed substrates are; cytoskeletal proteins like microtubules and actin, protein kinases such as PKC and membrane-bound enzymes like Ca-ATPase and the Ca-channel. In lenses from different species calpains have been detected in decreasing amounts from the epithelium to the cortex to the nucleus. Several substrates for calpain in the lens have been demonstrated: crystallins, vimentin, actin, beaded filaments and MP26 among others. Both studies on animal models and capsulorhexis indicate that calpains are mainly involved in cortical cataract.

Genetic differentiation in Fomitopsis pinicola (Schwarts: Fr.) Karst studied by means of arbitrary primed-PCR

Genetic variation within and among one Finnish and three Swedish populations of Fomitopsis pinicola (Schwarts: Fr.) Karst. were studied by amplifying DNA from haploid isolates originating from single spore cultures using two arbitrary primers. Analysis offspring from single fruit bodies revealed only three pairs of codominant alleles among 42 variable genetic markers, the remaining 38 segregated independently. Genetic similarity was measured in terms of Euclidean distance. Individuals in the Finnish population tended to form a distinct cluster in the principal component analysis. Variation within and among populations/regions was partitioned by Analysis of Molecular Variance-AMOVA. Within population variation accounted for 91.6% of the total genetic variation. The remaining 7.68% was accounted for by variation between the Finnish population and each of the three Swedish ones. Variation among the Swedish populations accounted for only 0.72% of the total variation. Wright's Fst was 0.17 for all four populations and 0.13 for the three Swedish populations. These relatively low values indicate that there is gene flow among all populations or that they are derived from a common ancestral population. The observed pattern of genetic variation is probably the result of effective spore dispersal and the continuous distribution of this common early successional species.

Increased proteolytic activity in lymphocytes from patients with early onset Alzheimer's disease

The levels of calpains (m-calpain and mu-calpain) in peripheral blood lymphocytes from patients with Alzheimer's disease were determined via Western blotting. The Ca-dependent proteolytic activity and the calpastatin activity were estimated using incubation with exogenous substrate. Evidence was obtained for an increased Ca-dependent proteolytic activity in lymphocytes from patients with early onset Alzheimer's disease. There was also an increased level of membrane-bound mu-calpain in this group of patients. The observed changes may be caused by a general dysregulation of Ca homeostasis in peripheral cells of early onset Alzheimer victims.

Fodrin degradation and subcellular distribution of calpains after neonatal rat cerebral hypoxic-ischemia

Neonatal rats were subjected to transient cerebral hypoxic-ischemia (unilateral occlusion of the common carotid artery + 7.70% O2 for 100 min). Ipsi-and contralateral parietal cerebral cortex was assayed with Western blotting for fodrin breakdown product (FBDP). Calpain immunoreactivity was assayed in the cytosolic fraction (CF) and the membrane and microsomal fraction (MMF). Calpain immunoreactivity decreased bilaterally in the CF during the insult (62-68% of controls) and remained significantly lower during early recovery, whereas the MMF showed no significant changes. This relative redistribution of calpains coincided with the appearance of FBDP in the left, ipsilateral hemisphere, displaying a significantly higher level of FBDP from immediately after the insult until at least 1 day of recovery (204-292% of controls). No significant changes in FBDP could be detected in the right, contralateral hemisphere, indicating that although redistribution of calpains occurred, hypoxia per se did not suffice to initiate fodrin degradation in this model of neonatal hypoxic-ischemia.

Degradation of fodrin and MAP 2 after neonatal cerebral hypoxic-ischemia

Neonatal rats were subjected to transient cerebral hypoxic-ischemia (unilateral occlusion of the common carotid artery + 7.70% O2 for 100 min) and allowed to recover for 3 h, 24 h, 2 days or 14 days. Consecutive tissue sections were stained with antibodies against alpha-fodrin, the 150 kDa breakdown product of alpha-fodrin (FBDP, marker of calpain proteolysis) or microtubule associated protein 2 (MAP 2, marker of dendrosomatic neuronal injury). Cortical tissue pieces were subjected to Western blotting using the antibody against the FBDP. Areas with brain injury displayed a distinct loss of MAP 2 which clearly delineated the infarct. FBDP accumulated in injured and borderline regions ipsilaterally and a less conspicuous, transient increase in FBDP also occurred in the contralateral hemisphere, especially in the white matter. A reciprocal staining pattern could be seen in the cerebral cortex, i.e. loss of MAP 2 and accumulation of FBDP, most pronounced 14 days after the insult. Fodrin and MAP 2 are known calpain substrates, and degradation of these proteins preceded neuronal degeneration, indicating that these proteases may be involved in the early events triggering the cascades leading to neuronal death.

Effects of manganese dipyridoxyl diphosphate, dipyridoxyl diphosphate--, and manganese chloride on cardiac function. An experimental study in the Langendorff perfused rat heart

RATIONALE AND OBJECTIVES

Manganese dipyridoxyl diphosphate (MnDPDP) is a promising contrast agent for magnetic resonance imaging of the liver. The authors explored the possibility that high concentrations of MnDPDP may cause manganese ion (Mn++)-induced side effects on cardiac function.

METHODS

Potential cardiodepression by MnDPDP, DPDP--, and manganese chloride (MnCl2) (100-3,000 mumol/L) was investigated in the isolated rat heart, with left ventricular developed (systolic--end-diastolic) pressure and heart rate as the primary indices of cardiac function.

RESULTS

During 5-minute exposures, 10% and 50% decreases in left ventricular developed pressure were observed for MnDPDP, 250 mumol/L and 1580 mumol/L; DPDP--, less than 100 mumol/L and 1000 mumol/L; MnCl2, 30 mumol/L and 250 mumol/L. Heart rate changes were not observed with MnDPDP. Cardiodepression was reversed within 2 minutes during a 14-minute recovery period for all investigated concentrations of MnDPDP and was less rapid for the highest concentrations of MnCl2.

CONCLUSIONS

Manganese dipyridoxyl diphosphate is well tolerated in the rat heart at concentrations as high as 200 to 250 mumol/L and is approximately 10 times less cardiotoxic than MnCl2. Cardiodepressive effects of MnDPDP in the present rat heart model, perfused in the absence of blood and proteins, are related primarily to the release of free Mn++ ions and in part to the simultaneous release of DPDP--.