Biomedical subjects

R D'Hooge

Publications and source records attributed to R D'Hooge.

At least 19 recordsLinked to original sources

PubMed2006

FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant, a sighted variant of the FVB/N mouse strain suitable for behavioral analysis.

Mice of the FVB/N strain are severely visual impaired as a result of tyrosinase gene defects, leading to a deficiency of the key enzyme for melanin synthesis in skin and eye and of cyclic guanosine monophosphate phosphodiesterase gene defects, which results in albinism (Tyr(c/c)) and retinal degeneration (Pde6b(rd1/rd1)), respectively. Nevertheless, FVB/N mice are commonly used for the generation of transgenic animals because of their large, strong pronuclei and high breeding performance. However, due to visual impairment of the FVB/N animals, the resulting transgenic animals cannot be used in tests that depend on vision, including tests of cognitive behavior. Therefore, we have bred a sighted version of the FVB/N strain by an outcross between FVB/N and 129P2/OlaHsd, followed by repeated backcrosses to FVB/N mice while selecting against albinism and homozygosity of the retinal degeneration mutation. After 11 generations of backcrossing, sighted animals were intercrossed to generate the congenic FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant strain, which is pigmented (Tyr(c-ch)/(c-ch)) and devoid of the genetic predisposition to retinal degeneration. The accurate visual abilities of the FVB.129P2-Pde6b(+) Tyr(c-ch)/Ant mice, for which we propose the name FVBS/Ant, demonstrated a clear visual evoked potential in the presence of normal eye histology and improved performance in the Morris water maze test.

Albinism↗

PubMed2006

Modest phenotypic improvements in ASA-deficient mice with only one UDP-galactose:ceramide-galactosyltransferase gene.

BACKGROUND: Arylsulfatase A (ASA)-deficient mice are a model for the lysosomal storage disorder metachromatic leukodystrophy. This lipidosis is characterised by the lysosomal accumulation of the sphingolipid sulfatide. Storage of this lipid is associated with progressive demyelination. We have mated ASA-deficient mice with mice heterozygous for a non-functional allele of UDP-galactose:ceramide-galactosyltransferase (CGT). This deficiency is known to lead to a decreased synthesis of galactosylceramide and sulfatide, which should reduce sulfatide storage and improve pathology in ASA-deficient mice. RESULTS: ASA-/- CGT+/- mice, however, showed no detectable decrease in sulfatide storage. Neuronal degeneration of cells in the spiral ganglion of the inner ear, however, was decreased. Behavioural tests showed small but clear improvements of the phenotype in ASA-/- CGT+/- mice. CONCLUSION: Thus the reduction of galactosylceramide and sulfatide biosynthesis by genetic means overall causes modest improvements of pathology.

Analysis of Variance↗

PubMed2006

The normal phenotype of Pmm1-deficient mice suggests that Pmm1 is not essential for normal mouse development.

Phosphomannomutases (PMMs) are crucial for the glycosylation of glycoproteins. In humans, two highly conserved PMMs exist: PMM1 and PMM2. In vitro both enzymes are able to convert mannose-6-phosphate (mannose-6-P) into mannose-1-P, the key starting compound for glycan biosynthesis. However, only mutations causing a deficiency in PMM2 cause hypoglycosylation, leading to the most frequent type of the congenital disorders of glycosylation (CDG): CDG-Ia. PMM1 is as yet not associated with any disease, and its physiological role has remained unclear. We generated a mouse deficient in Pmm1 activity and documented the expression pattern of murine Pmm1 to unravel its biological role. The expression pattern suggested an involvement of Pmm1 in (neural) development and endocrine regulation. Surprisingly, Pmm1 knockout mice were viable, developed normally, and did not reveal any obvious phenotypic alteration up to adulthood. The macroscopic and microscopic anatomy of all major organs, as well as animal behavior, appeared to be normal. Likewise, lectin histochemistry did not demonstrate an altered glycosylation pattern in tissues. It is especially striking that Pmm1, despite an almost complete overlap of its expression with Pmm2, e.g., in the developing brain, is apparently unable to compensate for deficient Pmm2 activity in CDG-Ia patients. Together, these data point to a (developmental) function independent of mannose-1-P synthesis, whereby the normal knockout phenotype, despite the stringent conservation in phylogeny, could be explained by a critical function under as-yet-unidentified challenge conditions.

Animals↗

PubMed2004

Effect of NaCN on currents evoked by uremic retention solutes in dissociated mouse neurons.

Uremic retention solutes possibly contribute to neuronal hypoxia/ischemia and its consequences in patients with renal failure. We examined the in vitro effects of several uremic retention solutes on murine central neurons under chemically induced metabolic hypoxia by application of sodium cyanide (NaCN). Whole cell currents were recorded using the tight-seal whole-cell voltage clamp technique. Application of NaCN caused an inward whole-cell current. From all tested toxins, which included several indoles, guanidino compounds, polyamines, purines, phenols, DL-homocysteine, orotate and myoinositol, only creatinine (CTN), guanidine (G) and guanidinosuccinic acid (GSA) produced a significant current in control and hypoxic neurons. Current evoked by GSA was significantly increased in the chemical hypoxic condition, and a synergistic effect of GSA and spermine was observed in hypoxic neurons.

Animals↗

PubMed2003

Nitric oxide in uremia: effects of several potentially toxic guanidino compounds.

Vascular and neurologic impairment remain an important source of morbidity in patients with chronic renal failure (CRF). A portion of CRF patients still suffers from uremic encephalopathy or other signs of nervous system impairment. Several reports demonstrate increased incidence of cardiac infarction and cerebrovascular accidents in CRF patients, even in those with otherwise adequate dialysis treatment [1]. Premature vascular disease, including myocardial infarction, stroke, and peripheral vascular disorder, are the leading causes of death in this population. Although several traditional risk factors for vascular disease and endothelial dysfunction, including smoking, diabetes, dyslipidemia, and hypertension, are often increased in CRF, these factors can only partly explain the high vasculopathy-related morbidity and mortality. Several authors have postulated that CRF-associated atherosclerosis and endothelial dysfunction result from accumulation of certain 'uremic factors,' the identities of which are still a matter of debate. These factors include a variety of guanidino compounds (GCs), which have been shown to be nitric oxide synthase (NOS) modulators both in vitro and in vivo. However, other effects of accumulated uremic GCs have been identified.

Guanidines↗

PubMed2003

Metachromatic leukodystrophy: consequences of sulphatide accumulation.

UNLABELLED: Metachromatic leukodystrophy is a lysosomal lipid storage disorder. It is caused by mutations in the gene for arylsulphatase A, an enzyme involved in the degradation of the sphingolipid 3'-O-sulphogalactosylceramide (sulphatide). This membrane lipid can be found in various cell types, but in particularly high concentrations in the myelin of the nervous system. Patients suffer from progressive, finally lethal, demyelination due to accumulation of sulphatide. In the nervous system, lipid storage not only affects oligodendrocytes but also neurons and, in addition, leads to astrogliosis and activation of microglia. At the cellular level, lysosomal sulphatide storage also affects the lipid composition of myelin itself and has consequences for the amount and localization of particular myelin membrane-associated proteins. Here we review data, largely based on an arylsulphatase A knock-out mouse model of metachromatic leukodystrophy. CONCLUSION: The knock-out mouse model of metachromatic leukodystrophy has provided insights into the histopathological and cellular consequences of sulphatide storage.

Animals↗

PubMed2002

Bone marrow stem cell-based gene transfer in a mouse model for metachromatic leukodystrophy: effects on visceral and nervous system disease manifestations.

Arylsulfatase A (ASA) knockout mice represent an animal model for the lysosomal storage disease metachromatic leukodystrophy (MLD). Stem cell gene therapy with bone marrow overexpressing the human ASA cDNA from a retroviral vector resulted in the expression of high enzyme levels in various tissues. Treatment partially reduces sulfatide storage in livers exceeding 18 ng ASA/mg tissue, while complete reduction was observed in livers exceeding 50 ng ASA/mg tissue. This corresponds to about 80% and 200% of normal enzyme activity. Similar values seem to apply for kidney. A partial correction of the lipid metabolism was detectable in the brain where the galactoerebroside/sulfatide ratio, which is diminished in ASA-deficient mice, increased upon treatment. This partial correction was accompanied by amelioration of neuropathology; axonal cross-sectional areas, which are reduced in deficient mice, were significantly increased in the saphenic and sciatic nerve but not in the optic nerve. Behavioral tests suggest some improvement of neuromotor abilities. The gene transfer did not delay the degeneration occurring in the acoustic ganglion of ASA-deficient animals. The limited success of the therapy appears to be due to the requirement of unexpected high levels of ASA for correction of the metabolic defect.

Animals↗

PubMed2001

Hyperactivity, neuromotor defects, and impaired learning and memory in a mouse model for metachromatic leukodystrophy.

Deficiency of arylsulfatase A (ASA) causes the autosomal recessive lipidosis, metachromatic leukodystrophy (MLD). Performance on tests of activity, motor ability and learning/memory was assessed in ASA-deficient mice and normal controls at 3, 6 and 12 months-of-age. ASA-deficient mice showed consistently increased cage activity in all age groups, whereas open field activity was increased only in the 3-month-old group. Motor coordination and equilibrium, as tested in the rotarod test, was impaired in 12-month-old ASA-deficient mice. Passive avoidance learning was tested in the step-through box. Performance on this test was impaired in the 12-month-old group only. Spatial learning and memory abilities were tested in the Morris water maze. Six-month-old ASA-deficient mice displayed slightly impaired hidden-platform acquisition performance. Three-month-old animals, on the other hand, did not show any acquisition or retention defect on this task, notwithstanding significantly reduced swimming velocity. Acquisition training, both in the hidden- and visible-platform conditions of the Morris water maze, and retention performance during the probe trials were impaired in 12-month-old ASA-deficient mice. The hyperactivity, motor incoordination and slowing, and the age-related learning/memory defects, reported here in ASA-deficient mice, may relate to the decline of neuromotor and cognitive functions in MLD patients, and could be used as correlative or outcome measures in the study of MLD pathophysiology and treatment.

Age Factors↗

PubMed2001

Bone marrow stem cell gene therapy of arylsulfatase A-deficient mice, using an arylsulfatase A mutant that is hypersecreted from retrovirally transduced donor-type cells.

Arylsulfatase A (ASA)-deficient mice represent an animal model for the fatal lysosomal storage disease metachromatic leukodystrophy, which is characterized by widespread intralysosomal deposition of sulfatide. Bone marrow stem cell gene therapy in mice, using a retroviral vector mediating expression of wild-type human ASA, has the potential to ameliorate the visceral pathology, but improves the prevailing brain disease and neurologic symptoms only marginally. One factor that influences the efficacy of bone marrow transplantation therapy in lysosomal storage diseases is the secretion level of the therapeutic enzyme from donor-type cells. Here we test the potential of a hypersecreted glycosylation variant of ASA. Although this mutant lacks mannose 6-phosphate residues it is taken up by cells by a mannose 6-phosphate receptor-independent pathway and causes partial metabolic correction of ASA-deficient mouse cells. Retrovirally mediated transfer of the mutant cDNA into ASA-deficient mice results in the sustained expression of the transgene. Serum levels argue for an increased secretion of the glycosylation mutant also in vivo. Tissue levels were reduced to 2% in liver and up to 40% in kidney compared with animals treated with the wild-type enzyme, indicating reduced endocytosis. Thus, the limited uptake of the variant enzyme outweighs the putative advantageous effect of improved supply. Although the mutant enzyme is able to correct the metabolic defect partially, histological examinations did not reveal any reduction of sulfatide storage in treated animals. Surprisingly, analysis of neurologic symptoms indicated a significant improvement of the gait pattern.

3T3 Cells↗

PubMed2001

The effect of high protein diet on urea and guanidino compound levels in renal insufficient mice.

Nephrectomy in mice provokes a decrease in creatinine clearance (CTN(Cl)) and an increase in urea and specific guanidino compound (GC) concentrations in blood and other tissues. Our purpose was to investigate the influence of high protein diet (HPD) on CTN(Cl), urea and GC levels in NX mice. Mice were nephrectomized or sham-operated and subdivided in groups to study five diet conditions. At the end of each experiment, 10 days and 30 days postsurgery, urine and blood were collected for determination of urea and GCs, including creatinine. HPD resulted in significantly higher CTN(Cl) values in sham-operated mice than those observed in mice under normal protein diet, 10 days as well as 30 days postnephrectomy. HPD induced significant increases in plasma urea, guanidinosuccinic acid, argininic acid and a-keto-delta-guanidinovaleric acid concentration 10 days postsurgery but not 30 days postsurgery. HPD coincided with significantly higher excretion of urea, guanidinosuccinic acid, alpha-keto-delta-guanidinovaleric acid, creatine, argininic acid and gamma-guanidinobutyric acid in sham-operated and nephrectomized mice 10 days postsurgery. Our results show that HPD induces supplementary (to nephrectomy) increases of urea and GCs in the early postsurgery period but not in the later phase.

Animals↗

PubMed2001

Applications of the Morris water maze in the study of learning and memory.

The Morris water maze (MWM) was described 20 years ago as a device to investigate spatial learning and memory in laboratory rats. In the meanwhile, it has become one of the most frequently used laboratory tools in behavioral neuroscience. Many methodological variations of the MWM task have been and are being used by research groups in many different applications. However, researchers have become increasingly aware that MWM performance is influenced by factors such as apparatus or training procedure as well as by the characteristics of the experimental animals (sex, species/strain, age, nutritional state, exposure to stress or infection). Lesions in distinct brain regions like hippocampus, striatum, basal forebrain, cerebellum and cerebral cortex were shown to impair MWM performance, but disconnecting rather than destroying brain regions relevant for spatial learning may impair MWM performance as well. Spatial learning in general and MWM performance in particular appear to depend upon the coordinated action of different brain regions and neurotransmitter systems constituting a functionally integrated neural network. Finally, the MWM task has often been used in the validation of rodent models for neurocognitive disorders and the evaluation of possible neurocognitive treatments. Through its many applications, MWM testing gained a position at the very core of contemporary neuroscience research.

Animals↗

PubMed2001

Endogenous guanidino compounds as uremic neurotoxins.

Epileptic and cognitive symptomatologies are among the most typical manifestations of uremic encephalopathy. Several guanidino compounds (GCs) may play an important role in the etiology of uremic encephalopathy. Four GCs appeared to be highly increased as well in serum, cerebrospinal fluid, and brain of uremic patients, whereas the levels of other metabolically relevant GCs were not or only moderately increased and others were even decreased. These highly increased compounds or "uremic" GCs are creatinine (CTN), guanidine (G), guanidinosuccinic acid (GSA), and methylguanidine (MG). All four compounds were shown to be experimental convulsants in brain concentrations similar to those found in uremic brain. We have described a possible mechanism for the contribution of GCs to uremic hyperexcitability, referring to the in vitro effects of uremic GCs on inhibitory and excitatory amino acid receptors. The excitatory effects of uremic GCs on the central nervous system may be explained by the activation of N-methyl-D-aspartate (NMDA) receptors by GSA, concomitant inhibition of GABA(A) receptors by uremic GCs, and other depolarizing effects. These effects might also indicate the putative contribution of uremic GCs to the etiology of uremic encephalopathy.

Animals↗

PubMed2001

Overexpression of arginase alters circulating and tissue amino acids and guanidino compounds and affects neuromotor behavior in mice.

Arginine is an intermediate of the ornithine cycle and serves as a precursor for the synthesis of nitric oxide, creatine, agmatine and proteins. It is considered to be a conditionally essential amino acid because endogenous synthesis only barely meets daily requirements. In rapidly growing suckling neonates, endogenous arginine biosynthesis is crucial to compensate for the insufficient supply of arginine via the milk. Evidence is accumulating that the intestine rather than the kidney plays a major role in arginine synthesis in this period. Accordingly, ectopic expression of hepatic arginase in murine enterocytes by genetic modification induces a selective arginine deficiency. The ensuing phenotype, whose severity correlates with the level of transgene expression in the enterocytes, could be reversed with arginine supplementation. We analyzed the effect of arginine deficiency on guanidine metabolism and neuromotor behavior. Arginine-deficient transgenic mice continued to suffer from an arginine deficiency after the arginine biosynthetic enzymes had disappeared from the enterocytes. Postweaning catch-up growth in arginine-deficient mice was characterized by increased levels of all measured amino acids except arginine. Furthermore, plasma total amino acid concentration, including arginine, was significantly lower in adult male than in adult female transgenic mice. Decreases in the concentration of plasma and tissue arginine led to significant decreases in most metabolites of arginine. However, the accumulation of the toxic guanidino compounds, guanidinosuccinic acid and methylguanidine, corresponded inversely with circulating arginine concentration, possibly reflecting a higher oxidative stress under hypoargininemic conditions. In addition, hypoargininemia was associated with disturbed neuromotor behavior, although brain levels of toxic guanidino compounds and ammonia were normal.

Amino Acids↗

PubMed2001

Biochemical, histological and behavioral consequences of nephrectomy in young and aged mice.

BACKGROUND: This study investigates the effect of nephrectomy in young and aged mice on some biochemical, histological and behavioural aspects. METHODS: Each age group, 2- and 12-months-old, comprised a sham-operated group, a unilaterally nephrectomized group and a subtotally nephrectomized group. Consequences of nephrectomy were examined 10 days postsurgery on urea and guanidino compound levels in body fluids and brain; the remaining kidney by light-microscopic examination; and learning and memory abilities using the Morris water maze task. RESULTS: Effect of nephrectomy on urea and guanidino compound levels in plasma, urine and brain was significantly more pronounced in the young age group. Some guanidino compounds show a tendency to decrease with aging in the sham-operated group and the two nephrectomized groups. Higher compensatory kidney hypertrophy was found in younger nephrectomized mice whereas in older mice glomerular mesangial expansion was a common feature. Finally, young mice with subtotal nephrectomy displayed a slight but significant impairment in memory and learning; whilst old nephrectomized mice manifested no impairment. CONCLUSIONS: Nephrectomy induces more changes in younger mice than in older mice as observed in higher variation of urea and guanidino compound levels, glomerular volume and kidney hypertrophy and decline in spatial learning and memory.

Age Factors↗

PubMed2001

Restoring the phenotype of fragile X syndrome: insight from the mouse model.

A mouse model for the fragile X syndrome, the most common form of inherited mental retardation, was generated a number of years ago. It shows characteristics compatible with the clinical symptoms of human patients. These include pathological changes such as macroorchidism, behavioral problems, and diminished visuo-spatial abilities. To investigate whether the fragile X syndrome is a potentially correctable disorder, several groups attempted to 'rescue' the knockout mutation by introduction of an intact copy of the FMR1 gene in the knockout mouse. Two different types of rescue mice have been created by injection of constructs based on FMR1 cDNA or on FMR1 genomic DNA. Several pathological, behavioral and cognitive function tests were performed on these two different rescue mouse lines to compare their characteristics with those of the knockout and control littermates. Each rescue line resembled the control in some aspects though neither of the 2 lines was a full 'rescue', e.g. resemble the control in all aspects investigated. Thus, rescue of some aspects of the phenotype has been achieved by introduction of FMR1 constructs in the fragile X knockout mice. The results implicate that, even if FMR1 production is cell type specific, the quantity of the FMRP expression is highly critical as overproduction may have a harmful effect.

Animals↗

PubMed2000

Spatial learning, contextual fear conditioning and conditioned emotional response in Fmr1 knockout mice.

Fmr1 knockout mice are an animal model for fragile X syndrome, the most common form of heritable mental retardation in humans. Fmr1 knockout mice exhibit macro-orchidism and cognitive and behavioural deficits reminiscent of the human phenotype. In the present study additional behavioural and cognitive testing was performed. Knockouts and control littermates were subjected to a spatial learning test using a plus-shaped water maze. Animals had to learn the position of a hidden escape platform during training trials. The position of this platform was changed during subsequent reversal trials. Previously reported deficits in reversal learning were replicated, but we also observed significant differences during the acquisition trials. A plus-shaped water maze experiment with daily changing platform positions failed to provide clear evidence for a working memory impairment, putatively underlying the spatial learning deficits. Two different test settings were used to examine the reported deficit of Fmr1 knockout mice in fear conditioning. Conditioned fear responses were observed in a contextual fear test, and the ability to acquire an emotional response was tested by means of response suppression in a conditioned emotional response procedure. Neither protocol revealed significant differences between controls and knockouts.

Acoustic Stimulation↗

PubMed2000

Impaired cognitive performance in ornithine transcarbamylase-deficient mice on arginine-free diet.

Sparse-fur (spf) mice are a model for the congenital deficiency of ornithine transcarbamylase (OTC), the most common inborn error of urea synthesis in man. In this study, performance of clinically stable spf and control mice (8-10-weeks-old) on two learning tests was assessed under normal Arg(+) or arginine-free Arg(-) diet conditions. Used as an indicator of the metabolic status of the animals, plasma ammonia concentrations were significantly higher in spf than in controls on normal diet, and increased even more during the Arg(-) diet episode. Behaviourally, we found no difference in passive avoidance learning between control and spf mice on Arg(+) diet, whereas in spf mice receiving Arg(-) diet during training, retention performance was significantly reduced. In the hidden-platform water maze, spf mice on Arg(+) diet only showed decreased swimming velocity compared to controls. In mice on Arg(-) diet during the first week of acquisition training, performance on acquisition and retention (probe) trials showed that spf mice experienced more difficulties in actually locating the platform. Visible-platform control experiments only showed a reduction in swimming velocity in spf mice on either diet. We conclude that cognitive performance is impaired in spf mice as a consequence of Arg(-) diet-induced neurochemical alterations.

Ammonia↗

PubMed2000

NG, NG-dimethylarginine and NG, NG-dimethylarginine in renal insufficiency.

Asymmetric NG,NG-dimethylarginine (ADMA) and symmetric NG,NG-dimethylarginine (SDMA) are basic endogenous amino acids with a guanidino group. Our renal distribution study of dimethylarginines clearly indicates that, in mouse and rat, ADMA and SDMA levels are most abundant as protein-incorporated compounds (95%). ADMA represents almost 90% of this protein-incorporated dimethylarginine amount. The four zones studied (cortex, outer and inner stripe of outer medulla, inner medulla) contain more or less the same amount of protein-incorporated dimethylarginine; the concentrations of both free dimethylarginines vary more in the different zones. Plasma and urinary excretion levels in Man, rat and mouse were determined, their changes in renal insufficiency were examined and compared between species. Highly significant negative correlations between both plasma dimethylarginine levels and creatinine clearances were found in Man and rat. The correlation between urinary ADMA excretion levels and creatinine clearances was highly significant and positive in Man and mouse; however, in rat the correlation was negative. In patients with severe renal insufficiency, ADMA clearance was only 9.5% of controls, and that of SDMA only 7.8%. Clearance of ADMA and SDMA in nephrectomized mice was 60.5% and 53.8% of controls, respectively, whereas in nephrectomized rat, ADMA clearance actually increased 5.4 times and that of SDMA did not change significantly. Man, rat and mouse show similarities as well as differences in metabolism.

Aged↗