Biomedical subjects

J G Richards

Publications and source records attributed to J G Richards.

At least 19 recordsLinked to original sources

PubMed2007

Metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to severe hypoxia.

We examined the metabolic and ionoregulatory responses of the Amazonian cichlid, Astronotus ocellatus, to 20 h exposure to severe hypoxia (0.37 +/- 0.19 mg O(2)/l; 4.6% air saturation) or 8 h severe hypoxia followed by 12 h recovery in normoxic water. During 20 h exposure to hypoxia, white muscle [ATP] was maintained at normoxic levels primarily through a 20% decrease in [creatine phosphate] (CrP) and an activation of glycolysis yielding lactate accumulation. Muscle lactate accumulation maintained cytoplasmic redox state ([NAD(+)]/[NADH]) and was associated with an inactivation of the mitochondrial enzyme pyruvate dehydrogenase (PDH). The inactivation of PDH was not associated with significant changes in cytoplasmic allosteric modulators ([ADP(free)], redox state, or [pyruvate]). Hypoxia exposure caused an approximately 65% decrease in gill Na(+)/K(+) ATPase activity, which was not matched by changes in Na(+)/K(+) ATPase alpha-subunit protein abundance indicating post-translational modification of Na(+)/K(+) ATPase was responsible for the decrease in activity. Despite decreases in gill Na(+)/K(+) ATPase activity, plasma [Na(+)] increased, but this increase was possibly due to a significant hemoconcentration and fluid shift out of the extracellular space. Hypoxia caused an increase in Na(+)/K(+) ATPase alpha-subunit mRNA abundance pointing to either reduced mRNA degradation during exposure to hypoxia or enhanced expression of Na(+)/K(+) ATPase alpha-subunit relative to other genes.

Adaptation, Physiological↗

PubMed2006

Gait variability in people with multiple sclerosis.

Patients with multiple sclerosis (MS) present with varying symptoms that can differ between and within individuals. As new interventions and drug treatments become available to MS patients, it is essential to understand the relationship between fatigue and the variability of functional mobility measures in order to define a meaningful change due to treatment within the MS population. The purpose of this study was to examine the within-day and between-day changes in gait variability for subjects with MS in fresh and fatigued conditions. Walking gait parameters were measured from 20 subjects diagnosed with MS and eight healthy control subjects. Standard deviations of hip, knee and ankle kinematic and kinetic variables were quantified as the measure of variability and analysed with a two-way (group by condition) ANOVA. Results indicated MS subjects had significantly greater hip (P <0.020), knee (P <0.011) and ankle (P <0.034) joint angle variability than control subjects, but variability was not different between conditions. Kinetic variability was not different between groups or conditions. MS subjects in this study walked more slowly than the healthy controls and they also reported more fatigue. Research examining treatment effects within the MS population should account for increased levels of kinematic gait variability.

Adult↗

PubMed2006

Reciprocal expression of gill Na+/K+-ATPase alpha-subunit isoforms alpha1a and alpha1b during seawater acclimation of three salmonid fishes that vary in their salinity tolerance.

The upregulation of gill Na+/K+-ATPase activity is considered critical for the successful acclimation of salmonid fishes to seawater. The present study examines the mRNA expression of two recently discovered alpha-subunit isoforms of Na+/K+-ATPase (alpha1a and alpha1b) in gill during the seawater acclimation of three species of anadromous salmonids, which vary in their salinity tolerance. Levels of these Na+/K+-ATPase isoforms were compared with Na+/K+-ATPase activity and protein abundance and related to the seawater tolerance of each species. Atlantic salmon (Salmo salar) quickly regulated plasma Na+, Cl- and osmolality levels within 10 days of seawater exposure, whereas rainbow trout (Oncorhynchus mykiss) and Arctic char (Salvelinus alpinus) struggled to ionoregulate, and experienced greater perturbations in plasma ion levels for a longer period of time. In all three species, mRNA levels for the alpha1a isoform quickly decreased following seawater exposure whereas alpha1b levels increased significantly. All three species displayed similar increases in gill Na+/K+-ATPase activity during seawater acclimation, with levels rising after 10 and 30 days. Freshwater Atlantic salmon gill Na+/K+-ATPase activity and protein content was threefold higher than those of Arctic char and rainbow trout, which may explain their superior seawater tolerance. The role of the alpha1b isoform may be of particular importance during seawater acclimation of salmonid fishes. The reciprocal expression of Na+/K+-ATPase isoforms alpha1a and alpha1b during seawater acclimation suggests they may have different roles in the gills of freshwater and marine fishes; ion uptake in freshwater fish and ion secretion in marine fishes.

Acclimatization↗

PubMed2005

Ionoregulatory changes in different populations of maturing sockeye salmon Oncorhynchus nerka during ocean and river migration.

We present the first data on changes in ionoregulatory physiology of maturing, migratory adult sockeye salmon Oncorhynchus nerka. Fraser River sockeye were intercepted in the ocean as far away as the Queen Charlotte Islands (approximately 850 km from the Fraser River) and during freshwater migration to the spawning grounds; for some populations this was a distance of over 700 km. Sockeye migrating in seawater toward the mouth of the Fraser River and upriver to spawning grounds showed a decline in gill Na+,K+-ATPase activity. As a result, gill Na+,K+-ATPase activity of fish arriving at the spawning grounds was significantly lower than values obtained from fish captured before entry into freshwater. Plasma osmolality and chloride levels also showed significant decreases from seawater values during the freshwater migration to spawning areas. Movement from seawater to freshwater increased mRNA expression of a freshwater-specific Na+,K+-ATPase isoform (alpha1a) while having no effect on the seawater-specific isoform (alpha1b). In addition, gill Na+,K+-ATPase activity generally increased in active spawners compared with unspawned fish on the spawning grounds and this was associated with a marked increase in Na+,K+-ATPase alpha1b mRNA. Increases in gill Na+,K+-ATPase activities observed in spawners suggests that the fish may be attempting to compensate for the osmotic perturbation associated with the decline in plasma chloride concentration and osmolality.

Analysis of Variance↗

PubMed2004

Limited extracellular but complete intracellular acid-base regulation during short-term environmental hypercapnia in the armoured catfish, Liposarcus pardalis.

Environmental hypercapnia induces a respiratory acidosis that is usually compensated within 24-96 h in freshwater fish. Water ionic composition has a large influence on both the rate and degree of pH recovery during hypercapnia. Waters of the Amazon are characteristically dilute in ions, which may have consequences for acid-base regulation during environmental hypercapnia in endemic fishes. The armoured catfish Liposarcus pardalis, from the Amazon, was exposed to a water P(CO(2)) of 7, 14 or 42 mmHg in soft water (in micromol l(-1): Na(+), 15, Cl(-), 16, K(+), 9, Ca(2+), 9, Mg(2+), 2). Blood pH fell within 2 h from a normocapnic value of 7.90+/-0.03 to 7.56+/-0.04, 7.34+/-0.05 and 6.99+/-0.02, respectively. Only minor extracellular pH (pH(e)) recovery was observed in the subsequent 24-96 h. Despite the pronounced extracellular acidosis, intracellular pH (pH(i)) of the heart, liver and white muscle was tightly regulated within 6 h (the earliest time at which these parameters were measured) via a rapid accumulation of intracellular HCO(3)(-). While most fish regulate pH(i) during exposure to environmental hypercapnia, the time course for this is usually similar to that for pH(e) regulation. The degree of extracellular acidosis tolerated by L. pardalis, and the ability to regulate pH(i) in the face of an extracellular acidosis, are the greatest reported to date in a teleost fish. The preferential regulation of pH(i) in the face of a largely uncompensated extracellular acidosis in L. pardalis is rare among vertebrates, and it is not known whether this is associated with the ability to air-breathe and tolerate aerial exposure, or living in water dilute in counter ions, or with other environmental or evolutionary selective pressures. The ubiquity of this strategy among Amazonian fishes and the mechanisms employed by L. pardalis are clearly worthy of further study.

Acid-Base Equilibrium↗

PubMed2003

Ionoregulatory disruption as the acute toxic mechanism for lead in the rainbow trout (Oncorhynchus mykiss).

The mechanism for acute toxicity of lead (Pb) in rainbow trout (Oncorhynchus mykiss) was investigated at Pb concentrations close to the 96 h LC50 of 1.0 mg dissolved Pb l(-1) (0.8-1.4, 95% C.I.) determined in dechlorinated Hamilton city tap water (from Lake Ontario, hardness=140 mg l(-1) CaCO(3)). Tissue Pb accumulation associated with death was highest in the gill, followed by kidney and liver. Significant ionoregulatory impacts were observed in adult rainbow trout (200-300 g) fitted with indwelling dorsal aortic catheters and exposed to 1.1+/-0.04 mg dissolved Pb l(-1). Decreased plasma [Ca(2+)], [Na(+)] and [Cl(-)] occurred after 48 h of exposure through to 120 h, with increases in plasma [Mg(2+)], ammonia, and cortisol. No marked changes in PaO(2), PaCO(2), pH, glucose, or hematological parameters were evident. Branchial Na(+)/K(+) ATPase activity in juvenile trout exposed to concentrations close to the 96 h LC50 was inhibited by approximately 40% after 48 h of Pb exposure. Calcium ion flux measurements using 45Ca as a radiotracer showed 65% inhibition of Ca(2+) influx after 0, 12, 24 or 48 h exposure to the 96 h LC50 concentration of Pb. There was also significant inhibition (40-50%) of both Na(+) and Cl(-) uptake, measured with 22Na and 36Cl simultaneously. We conclude that the mechanism of acute toxicity for Pb in rainbow trout occurs by ionoregulatory disruption rather than respiratory or acid/base distress at Pb concentrations close to the 96 h LC50 in moderately hard water.

Acid-Base Equilibrium↗

PubMed2003

Exercise and recovery metabolism in the Pacific spiny dogfish (Squalus acanthias).

We examined the effects of exhaustive exercise and post-exercise recovery on white muscle substrate depletion and metabolite distribution between white muscle and blood plasma in the Pacific spiny dogfish, both in vivo and in an electrically stimulated perfused tail-trunk preparation. Measurements of arterial-venous lactate, total ammonia, beta-hydroxybutyrate, glucose, and L-alanine concentrations in the perfused tail-trunk assessed white muscle metabolite fluxes. Exhaustive exercise was fuelled primarily by creatine phosphate hydrolysis and glycolysis as indicated by 62, 71, and 85% decreases in ATP, creatine phosphate, and glycogen, respectively. White muscle lactate production during exercise caused a sustained increase (approximately 12 h post-exercise) in plasma lactate load and a short-lived increase (approximately 4 h post-exercise) in plasma metabolic acid load during recovery. Exhaustive exercise and recovery did not affect arterial PO2, PCO2, or PNH3 but the metabolic acidosis caused a decrease in arterial HCO3- immediately after exercise and during the first 8 h recovery. During recovery, lactate was retained in the white muscle at higher concentrations than in the plasma despite increased lactate efflux from the muscle. Pyruvate dehydrogenase activity was very low in dogfish white muscle at rest and during recovery (0.53 +/- 0.15 nmol g wet tissue(-1) min(-1); n=40) indicating that lactate oxidation is not the major fate of lactate during post-exercise recovery. The lack of change in white muscle free-carnitine and variable changes in short-chain fatty acyl-carnitine suggest that dogfish white muscle does not rely on lipid oxidation to fuel exhaustive exercise or recovery. These findings support the notion that extrahepatic tissues cannot utilize fatty acids as an oxidative fuel. Furthermore, our data strongly suggest that ketone body oxidation is important in fuelling recovery metabolism in dogfish white muscle and at least 20% of the ATP required for recovery could be supplied by uptake and oxidation of beta-hydroxybutyrate from the plasma.

3-Hydroxybutyric Acid↗

PubMed2003

Acute waterborne nickel toxicity in the rainbow trout (Oncorhynchus mykiss) occurs by a respiratory rather than ionoregulatory mechanism.

The acute mechanism of toxicity of waterborne nickel (Ni) was investigated in the rainbow trout (Oncorhynchus mykiss) in moderately hard ( approximately 140 mg l(-1) as CaCO(3)) Lake Ontario water, where the 96-h LC(50) for juvenile trout (1.5-3.5 g) was 15.3 mg (12.7-19.0, 95% C.L.) dissolved Ni l(-1). No marked impact of Ni exposure on average unidirectional or net fluxes of Na(+), Cl(-), or Ca(2+) was observed in juvenile trout exposed for 48-60 h to 15.6 mg Ni l(-1) as NiSO(4). Furthermore, when adult rainbow trout (200-340 g) were fitted with indwelling dorsal aortic catheters and exposed for 117 h to 11.6 mg Ni l(-1) as NiSO(4), plasma ions (Na(+), Cl(-), Ca(2+), and Mg(2+)) were all well conserved. However, mean arterial oxygen tension dropped gradually to approximately 35% of control values. This drop in P(aO(2)) was accompanied by an acidosis primarily of respiratory origin. P(aCO(2)) rose to more than double control values with a concomitant drop in arterial pH of 0.15 units. Acute respiratory toxicity was further evidenced by a significant increase in hematocrit (Ht), and plasma lactate, and a significant decrease in spleen hemoglobin (Hb). Following 117 h of exposure to 11.6 mg Ni l(-1), the gill, intestine, plasma, kidney, stomach, and heart accumulated Ni significantly, with increases of 60, 34, 28, 11, 8, and 3-fold, respectively. Brain, white muscle, liver, and bile did not significantly accumulate Ni. Plasma Ni exhibited a remarkable linear increase with time to levels approximately 30-fold higher than controls. We conclude that in contrast to most other metals, Ni is primarily a respiratory, rather than an ionoregulatory, toxicant at exposure levels close to the 96-h LC(50). The implications of a waterborne metal as an acute respiratory toxicant (as opposed to ionoregulatory toxicants such as Cu, Ag, Cd, or Zn) with respect to toxicity modeling are discussed.

Acid-Base Equilibrium↗

PubMed2002

A combined pharmacological and genetic approach to investigate the role of orphanin FQ in learning and memory.

Using a combination of the selective opioid receptor-like1 (ORL1) receptor agonist, Ro 64-6198, and orphanin FQ/nociceptin (OFQ/N) peptide knockout (KO) mice, the influence of OFQ/N on cognition has been studied in the rodent. In wild type, C57BL/6J mice, Ro 64-6198 (0.3-1 mg/kg i.p.) impaired the acquisition of spatial learning in the Morris water maze, although a mild neurological impairment was evident which complicated precise interpretation. In Lister hooded rats, Ro 64-6198 (6 mg/kg i.p.) produced delay dependent impairments in rats performing either a delayed matching or a delayed nonmatching to position task with only a modest (< 20%) effect on omissions - an effect consistent with a short-term memory impairment. Electrophysiological studies demonstrated an inhibitory effect of OFQ/N on LTP recorded from the CA1 region of wild type mice, but not in ORL1 receptor knockout mice. In contrast to the ORL1 agonist, mice deficient in the OFQ/N peptide showed some evidence of improved spatial learning, fear conditioning and passive avoidance retention. However, CA1 LTP was similar between OFQ/N peptide KO mice and wild type controls. Subsequent receptor radioautography studies demonstrated the presence of ORL1 receptors within various regions of the medial temporal lobe system: i.e. CA1, dentate gyrus molecular layer, subiculum, perirhinal cortex. Taken together, these results suggest a bi-directional effect of OFQ/N containing systems on aspects of cognitive behaviour, particularly those elements associated with hippocampal function. This is consistent with a likely modulatory role of OFQ/N on hippocampal and associated cortical circuitry.

Animals↗

PubMed2002

Donepezil reverses a mnemonic deficit produced by scopolamine but not by perforant path lesion or transient cerebral ischaemia.

The purpose of these studies were threefold. Firstly, to further characterize the effect of perforant path transection on a test of short-term memory: delayed matching (or nonmatching)-to-position [D(N)MTP]. Secondly, to evaluate the effect of a transient cerebral ischaemia in the same task. Both surgical procedures were chosen as they produce a CNS lesion similar to that described in Alzheimer's Disease (AD). Thirdly, the effect of the acetylcholinesterase inhibitor, donepezil (Aricept(R), E2020), on the resulting cognitive impairment was studied. Perforant path transection produced a robust, delay-dependent impairment of choice accuracy in rats performing either a delayed matching- or nonmatching-to-position task. Sample latency was also reduced following lesion, yet the lesion-induced impairment was not affected by increasing the response requirement at the sample stage. An 11-min period of transient ischaemia (two-vessel occlusion model) resulted in almost complete loss of hippocampal CA1 pyramidal cells and a delay-dependent impairment in DMTP performance. However, unlike perforant path lesions, this deficit was unstable and declined in magnitude over the experimental period. Increasing the delay interval restored this deficit. Donepezil, at doses that robustly attenuated a scopolamine (0.06 mg/kg s.c.)-induced DMTP accuracy impairment in naïve, unoperated rats, had no effect against either lesion-induced impairment. The results are considered in terms of the effectiveness of acetylcholinesterase inhibitors in noncholinergic-based preclinical cognitive models.

Alzheimer Disease↗

PubMed2001

Influence of the selective ORL1 receptor agonist, Ro64-6198, on rodent neurological function.

Identification of synthetic agonists and antagonists at orphan receptors represents an important step for understanding their physiological function and therapeutic potential. Accordingly, we have recently described a non-peptide agonist at the opioid receptor like (ORL1) receptor (1S,3aS)-8-(2,3,3a,4,5,6-hexahydro-1H-phenalen-1-yl)-1-phenyl-1,3,8-triazaspiro[4.5]decan-4-one (Ro64-6198; Jenck et al., PNAS 94 (2000) 4938; Wichmann et al., Eur. J. Med. Chem. 35 (2000) 839). We have investigated the effects of this compound in various tests of rodent neurological function, utilising ORL1 knockout mice to examine the pharmacological specificity of Ro64-6198. In male C57BL/6J mice, effects on balance and motor co-ordination were detected following low doses (0.3-1mg/kg IP) of Ro64-6198. At higher doses (1-3mg/kg IP), effects on swim behaviour and hypothermia was observed. At 10mg/kg, each effect became more profound and a severe neurological disturbance appeared, including loss of righting reflex. These effects of Ro64-6198 (10mg/kg IP) were absent in ORL1 receptor knockout mice. In male, hooded Lister rats, Ro64-6198 (6-10mg/kg IP), produced some disturbance of neurological function, including hypoactivity, rotarod performance, grip strength and mild hypothermia. An impairment of food responding under a variable interval (VI) 20s schedule of reinforcement was noted at 3mg/kg. These results confirm Ro64-6198 to be a highly selective pharmacological tool to investigate ORL1 receptor function in vivo and, furthermore, that activation of this receptor is accompanied by a variety of effects on neurological function.

Animals↗

PubMed2001

Improved Semliki Forest virus vectors for receptor research and gene therapy.

We have modified Semliki Forest virus (SFV) vectors to broaden their application range. Here we describe a series of site-directed mutagenesis experiments on the SFV subgenomic 26S promoter to down-regulate the heterologous gene expression. Several mutants showed a dramatic effect on transgene expression levels in BHK cells. The luciferase activity was reduced to approximately 30%, 3%, and 1% compared to the wild type promoter. Similarly, a decrease in beta-galactosidase activity was observed in BHK cells and after injection into the striatum of male Wistar rats. Novel non-cytopathogenic and temperature-sensitive SFV vectors have recently been developed by introduction of point mutations in the viral nonstructural genes nsP2 and nsP4. These vectors do not show the typical shut down of host cell protein synthesis after SFV infections and therefore allow for a substantially prolonged survival of host cells. Both the mutant vectors demonstrating lower and more physiological expression levels and the non-cytopathogenic vectors should be valuable tools for various applications within receptor research. Furthermore, recent studies suggest that SFV vectors can be efficient gene delivery vehicles for gene therapy applications.

Amino Acid Sequence↗

PubMed2001

An evaluation of head movement in backboard-immobilized helmeted football, lacrosse, and ice hockey players.

OBJECTIVE: Improper handling of an unstable neck injury in the prehospital setting may result in iatrogenically induced neurologic injury. Due to helmet design, stabilization of the cervical spine in American football does not require routine removal of the helmet and shoulder pads prior to transport. Adequate data is not available evaluating hockey and lacrosse helmets. This study compares the amount of head movement in American football, lacrosse, and ice hockey helmets during head and neck stabilization procedures. STUDY DESIGN: Prospective. PARTICIPANTS: 12 ice hockey, 9 football, and 9 lacrosse athletes from an National Collegiate Athletic Association Division 1 program. SETTING: On-campus biomechanical laboratory with three HiRes cameras, routinely tested for accuracy. METHODS: Athletes were immobilized on backboards as per protocol. Three motion analysis HiRes cameras follow retroreflective markers placed on the helmet and bite mouthplate to measure relative head and helmet motion. MAIN OUTCOME MEASURES: Helical angles determine the relative range of motion of the head inside the helmets. RESULTS: The mean range of head motion for football players was 4.88 degrees (n = 9, SD 2.07), lacrosse players 6.56 degrees (n = 9, SD 1.61), and ice hockey players 5.54 degrees (n = 12, SD 1.19). These results were not significantly different (p > 0.05). CONCLUSIONS: The rotational head motion seen inside standard immobilized lacrosse and ice hockey helmets is similar to that seen in football helmets. This supports the safety of prehospital stabilization of the potential cervical spine-injured ice hockey and lacrosse athletes with in-line stabilization and helmet in place. Extrapolation of data may not be applicable to other helmet designs, and future studies are needed to determine the safety of emergency procedures in all helmet designs.

Adolescent↗

PubMed2001

Effects of natural organic matter source on reducing metal toxicity to rainbow trout (Oncorhynchus mykiss) and on metal binding to their gills.

Juvenile rainbow trout (Oncorhynchus mykiss, 3 g) were exposed for 74 h in ion-poor (soft) water to a mixed-metal solution in the presence of 4, 6, and 10 mg C/L natural organic matter (NOM). The metals were 0.2 microM Pb, 0.1 microM Hg, 0.1 microM Cd, 1.3 microM Cu, 0.05 microM Ag, and 3.5 microM Co, and the natural organic matter was isolated by reverse osmosis from three sources in southern Ontario, Canada. The six-metal solution alone was extremely toxic to the fish. Increasing concentrations of each NOM increased trout survival, but the NOM having the most allochthonous properties (from Luther Marsh) increased fish survival most, while the NOM having the most autochthonous properties (from Sanctuary Pond, Point Pelee) increased fish survival least. This pattern was reflected in the degree of reduction of Pb and Cu accumulation by the gills. Relatively simple chemical characterization of NOM, such as protein-to-carbohydrate ratios, or optical characterization, such as absorbance-to-fluorescence ratios (e.g., representing aromaticity), may adequately reflect these biologically relevant differences in organic matter quality.

Algorithms↗

PubMed2000

Functional consequences of reduction in NMDA receptor glycine affinity in mice carrying targeted point mutations in the glycine binding site.

We have used site-directed mutagenesis in conjunction with homologous recombination to generate two mouse lines carrying point mutations in the glycine binding site of the NMDAR1 subunit (Grin1). Glycine concentration-response curves from acutely dissociated hippocampal neurons revealed a 5- and 86-fold reduction in receptor glycine affinity in mice carrying Grin1(D481N) and Grin1(K483Q) mutations, respectively, whereas receptor glutamate affinity remained unaffected. Homozygous mutant Grin1(D481N) animals are viable and fertile and appear to develop normally. However, homozygous mutant Grin1(K483Q) animals are significantly lighter at birth, do not feed, and die within a few days. No gross abnormalities in CNS anatomy were detected in either Grin1(D481N) or Grin1(K483Q) mice. Interestingly, in situ hybridization and Western blot analysis revealed changes in the expression levels of NMDA receptor subunits in Grin1(D481N) mice relative to wild type that may represent a compensatory response to the reduction in receptor glycine affinity. Grin1(D481N) mice exhibited deficits in hippocampal theta burst-induced long-term potentiation (LTP) and spatial learning and also a reduction in sensitivity to NMDA-induced seizures relative to wild-type controls, consistent with a reduced activation of NMDA receptors. Mutant mice exhibited normal prepulse inhibition but showed increased startle reactivity. Preliminary analysis indicated that the mice exhibit a decreased natural aversion to an exposed environment. The lethal phenotype of Grin1(K483Q) animals confirms the critical role of NMDA receptor activation in neonatal survival. A milder reduction in receptor glycine affinity results in an impairment of LTP and spatial learning and alterations in anxiety-related behavior, providing further evidence for the role of NMDA receptor activation in these processes.

Animals↗

PubMed2000

Regional and cellular distribution of bleomycin hydrolase mRNA in human brain: comparison between Alzheimer's diseased and control brains.

Genetic polymorphism of human bleomycin hydrolase (hBH) has been reported to be associated with the risk of sporadic Alzheimer's disease (AD). The regional and cellular distribution of mRNA encoding hBH in the brain from controls and patients with AD was examined using in situ hybridization. A hybridization signal, in the form of clusters of single cells, was observed in the white matter. Our results indicate a predominantly astrocytic expression of hBH in the investigated human brain regions. Although the signal intensity was generally reduced in AD brains, the large variability among controls rendered this trend statistically insignificant.

Aged↗

PubMed2000

Controlling polymerization of beta-amyloid and prion-derived peptides with synthetic small molecule ligands.

The Alzheimer beta-amyloid peptide (Abeta) and a fragment of the prion protein have the capacity of forming amyloid-like fibrils when incubated under physiological conditions in vitro. Here we show that a small amyloid ligand, RO-47-1816/001, enhances this process severalfold by binding to amyloid molecules and apparently promote formation of the peptide-to-peptide bonds that join the monomers of the amyloid fibrils. This effect could be antagonized by other ligands, including analogues of RO-47-1816/001, as well as the structurally unrelated ligand Congo red. Analogues of RO-47-1816/001 with low affinity for amyloid did not display any antagonistic effect. In conclusion, these data suggest that synthetic molecules, and possibly also small natural substances present in the brain, may act in a chaperone-like fashion, promoting Abeta polymerization and growth of amyloid fibrils in vitro and possibly also in vivo. Furthermore, we demonstrate that small organic molecules can be used to inhibit the action of amyloid-enhancing compounds.

Amyloid beta-Peptides↗

PubMed2000

Characterization of transgenic mice expressing apolipoprotein E4(C112R) and apolipoprotein E4(L28P; C112R).

Apolipoprotein E (ApoE), which is genetically polymorphic, is a constituent of different lipoproteins. Two variants, ApoE4(C112R) and ApoE4(L28P; C112R) have been linked to the risk of developing Alzheimer's disease. Transgenic mice carrying ApoE4(C112R) (AD71) and ApoE4(L28P; C112R) (AD61) were generated and compared to wild-type mice. The use of glial fibrillary acidic protein as promoter led to transgene expression mainly in glial cells but also in neurons. Transgene protein levels were approximately three-and-a-half-fold that of endogenous ApoE in the glial fibrillary acidic protein-ApoE4(C112R) (AD71) and nearly twofold in the glial fibrillary acidic protein-ApoE4(L28P; C112R) (AD61) mouse lines. Neither transgenic mouse differed from wild-type in cognitive tests at the age of approximately one-and-a-half years. The locomotor activity of AD61 mice was similar to controls, whereas AD71 mice exhibited a clearly reduced level of motor activity. Immunohistological and biochemical brain protein analyses revealed no difference between strains.Thus, in the absence of morphological changes over-expression of ApoE4(C112R) on a background of endogenous mouse ApoE, may result in behavioral deficits while for the ApoE4(L28P; C112R) transgene higher expression might be required or some compensatory mechanisms might protect these animals from the behavioral abnormalities.

Alzheimer Disease↗