Biomedical subjects

D Hartmann

Publications and source records attributed to D Hartmann.

At least 37 records · Page 2Linked to original sources

PubMed2001

Sulfatide storage in visceral organs of arylsulfatase A-deficient mice.

The inherited deficiency of arylsulfatase A (ASA) in humans causes lysosomal accumulation of sulfatides in visceral organs and in the nervous system and leads to wide-spread demyelination (metachromatic leukodystrophy, MLD). ASA-deficient mice have previously been generated by means of targeted gene disruption. In the present study, visceral organs of ASA-deficient mice were investigated. A simple technique for the histochemical detection of accumulated sulfatides was elaborated using pre-embedding staining with alcian blue. The gall bladder, intrahepatic bile ducts, exocrine pancreatic ducts, respiratory epithelium and, with low degree, testicular Sertoli cells, showed sulfolipid storage. The storage pattern in the kidney will be described in a separate publication. Hepatocytes, pancreatic islets, adrenal glands, and gastric epithelium were unaffected. Ultrastructurally, the intralysosomal storage material displayed parallel and concentric lamellar patterns. Apart from some differences, the topographic distribution of the sulfatide storage resembled that in human MLD. In addition to being an animal model of the human disease, the ASA-deficient mouse may be useful for investigating the cell biology of sulfolipids in visceral organs.

Animals↗

PubMed2001

[Incarceration of a pancreatic stone fragment in the distal pancreatic duct after ESWL-therapy].

Incarceration of a pancreatic stone fragment in the distal pancreatic duct after ESWL-therapy.A partial or total absence of stones in pancreaticolithiasis therapy can be reached by using ESWL. We report on a patient who happened to get an incarceration of a fragment in the distal pancreatic duct after having been treated by ESWL without a previous sphincterotomy to the ductus Wirsungianus. This emphasizes the recommendation to carry out a papillotomy of the pancreatic main duct before applying ESWL to pancreatic stones.

Calculi↗

PubMed2001

Overlapping functions of lysosomal acid phosphatase (LAP) and tartrate-resistant acid phosphatase (Acp5) revealed by doubly deficient mice.

To date, two lysosomal acid phosphatases are known to be expressed in cells of the monocyte/phagocyte lineage: the ubiquitously expressed lysosomal acid phosphatase (LAP) and the tartrate-resistant acid phosphatase-type 5 (Acp5). Deficiency of either acid phosphatase results in relatively mild phenotypes, suggesting that these enzymes may be capable of mutual complementation. This prompted us to generate LAP/Acp5 doubly deficient mice. LAP/Acp5 doubly deficient mice are viable and fertile but display marked alterations in soft and mineralised tissues. They are characterised by a progressive hepatosplenomegaly, gait disturbances and exaggerated foreshortening of long bones. Histologically, these animals are distinguished by an excessive lysosomal storage in macrophages of the liver, spleen, bone marrow, kidney and by altered growth plates. Microscopic analyses showed an accumulation of osteopontin adjacent to actively resorbing osteoclasts of Acp5- and LAP/Acp5-deficient mice. In osteoclasts of phosphatase-deficient mice, vacuoles were frequently found which contained fine filamentous material. The vacuoles in Acp5- and LAP/Acp5 doubly-deficient osteoclasts also contained crystallite-like features, as well as osteopontin, suggesting that Acp5 is important for processing of this protein. This is further supported by biochemical analyses that demonstrate strongly reduced dephosphorylation of osteopontin incubated with LAP/Acp5-deficient bone extracts. Fibroblasts derived from LAP/Acp5 deficient embryos were still able to dephosphorylate mannose 6-phosphate residues of endocytosed arylsulfatase A. We conclude that for several substrates LAP and Acp5 can substitute for each other and that these acid phosphatases are essential for processing of non-collagenous proteins, including osteopontin, by osteoclasts.

Acid Phosphatase↗

PubMed2001

Implication of APP secretases in notch signaling.

Signaling via notch receptors and their ligands is an evolutionary ancient and highly conserved mechanism governing cell-fate decisions throughout the animal kingdom. Upon ligand binding, notch receptors are subject to a two-step proteolysis essential for signal transduction. First, the ectodomain is removed by an enzyme cleaving near the outer-membrane surface ("site2"). Consecutively, the notch intracellular domain is liberated by a second protease cutting within the transmembrane sequence ("site3"). The intracellular domain is then transferred to the nucleus to act as a transcriptional coactivator. The proteases involved in notch receptor activation are shared with other proteins undergoing regulated intramembrane proteolysis, with intriguing parallels to APP. Specifically, site3 cleavage of Notch, as well as gamma-secretase processing of APP depend both critically on presenilins 1 and 2. Moreover, ADAM 10 and ADAM 17, the proteases proposed to perform site2 cleavage, are also the most probable candidate alpha-secretases to cleave APP. While the biological significance of APP processing remains to be further elucidated, interference with notch signaling has been shown to have severe consequences both in small animal models as well as in humans. Thus, a growing number of long known genetic syndromes like Alagille syndrome or Fallot's tetralogy can be caused by mutations of genes relevant for the notch signaling pathway. Likewise, the anticipated interference of gamma-secretase inhibitors with site3 cleavage may turn out to be a major obstacle for this therapeutic approach to Alzheimer's disease.

ADAM Proteins↗

PubMed2000

Accumulation of autophagic vacuoles and cardiomyopathy in LAMP-2-deficient mice.

Lysosome-associated membrane protein-2 (LAMP-2) is a highly glycosylated protein and an important constituent of the lysosomal membrane. Here we show that LAMP-2 deficiency in mice increases mortality between 20 and 40 days of age. The surviving mice are fertile and have an almost normal life span. Ultrastructurally, there is extensive accumulation of autophagic vacuoles in many tissues including liver, pancreas, spleen, kidney and skeletal and heart muscle. In hepatocytes, the autophagic degradation of long-lived proteins is severely impaired. Cardiac myocytes are ultrastructurally abnormal and heart contractility is severely reduced. These findings indicate that LAMP-2 is critical for autophagy. This theory is further substantiated by the finding that human LAMP-2 deficiency causing Danon's disease is associated with the accumulation of autophagic material in striated myocytes.

Amino Acids↗

PubMed2000

Enzymatic properties, tissue-specific expression, and lysosomal location of two highly homologous rat SULT1C2 sulfotransferases.

We have isolated two highly homologous but distinct rat sulfotransferase cDNAs termed ratSULT1C2 and ratSULT1C2A encoding polypeptides of 297 amino acids each. The amino acid sequence of ratSULT1C2 is 84% identical to the human SULT1C2 and 81% identical to a rabbit SULT1C2 sulfotransferase. ratSULT1C2 and ratSULT1C2A are 92% identical but differ in 22 amino acids. The majority of these amino acid substitutions in ratSULT1C2A is not found in the human and rabbit SULT1C2, which identifies ratSULT1C2 as the orthologue of these sulfotransferases, whereas SULT1C2A is a closely related but distinct enzyme. ratSULT1C2 and 2A sulfotransferases do not sulfonate steroids, dopamine, acetaminophen, or alpha-naphthol, but only p-nitrophenol. Prokaryotically expressed ratSULT1C2A is less active than ratSULT1C2. ratSULT1C2/2A mRNAs are abundant in kidney and less abundant in stomach and liver. The enzymes are expressed as 34-kDa polypeptides in rat kidney, liver, and stomach. In addition, a 28-kDa cross-reacting polypeptide is found in kidney only. Immunohistochemistry revealed expression of ratSULT1C2/2A in the epithelial cells of the proximal tubules of the kidney, bile duct epithelia, hepatocytes, and the epithelium of the gastric mucosal glands. Although the cDNA predicted amino acid sequence identifies both sulfotransferases as cytosolic enzymes, in tissue sections, in the kidney cell line NRK 52, and in transiently transfected BHK cells a considerable fraction of the enzyme was found in a granular perinuclear compartment. Costaining with a lysosomal marker in gastric mucosa tissue sections and cultured cells identifies these structures as lysosomes.

Amino Acid Sequence↗

PubMed2000

ASCA Observation of the Quiescent X-Ray Counterpart to SGR 1627-41.

We present a 2-10 keV ASCA observation of the field around the soft gamma repeater SGR 1627-41. A quiescent X-ray source, whose position is consistent both with that of a recently discovered BeppoSAX X-ray source and with the Interplanetary Network localization for this soft gamma repeater, was detected in this observation. In 2-10 keV X-rays, the spectrum of the X-ray source may be fit equally well by a power-law, blackbody, or bremsstrahlung function, with unabsorbed flux approximately 5x10-12 ergs cm-2 s-1. We do not confirm a continuation of a fading trend in the flux, and we find no evidence for periodicity, both of which were noted in the earlier BeppoSAX observations.

Journal Article↗

PubMed2000

Lupus erythematosus associated with genetically determined deficiency of the second component of the complement.

BACKGROUND: The gene deletion responsible for the type I human complement C2 deficiency was reported in 1992. The purpose of our study is to evaluate clinical and immunological characteristics of 11 patients with lupus erythematosus and type I C2 deficiency. OBSERVATIONS: We observed 5 patients with a homozygous C2 deficiency and 6 with a heterozygous C2 deficiency. Eight patients had systemic lupus erythematosus, 2 had subacute cutaneous lupus erythematosus, and 1 had chronic lupus erythematosus. Photosensitivity was present in 73% of the patients, and 64% tested positive for anti-Ro (SSA) antibodies. Renal involvement that required immunosuppressive therapy was present in 54% of the patients. Ninety percent of the patients tested positive for antinuclear antibodies, and 54% tested positive for anti-double-stranded DNA antibodies. Phenotyping of the fourth component of the complement was performed in 82% of the patients and showed a C4A4B2 phenotype, which is suggestive for the type I C2 deficiency. CONCLUSIONS: Most patients with lupus erythematosus associated with C2 type I deficiency are photosensitive, and this is probably related to the presence of anti-Ro (SSA) autoantibodies. The prognosis for those patients is not better than that for patients with lupus erythematosus in general.

Adolescent↗

PubMed2000

MIC trial: metoprolol in patients with mild to moderate heart failure: effects on ventricular function and cardiopulmonary exercise testing.

UNLABELLED: Beta-blocker therapy results in a functional benefit in patients with heart failure (CHF) due to idiopathic dilated cardiomyopathy (DCM). This study assessed if similar effects were observed in patients with ischemic heart disease (CAD), NYHA II-III after 6 months of therapy with metoprolol. METHODS AND RESULTS: Fifty-two patients with CHF secondary to DCM (26 patients) and CAD (26 patients) and a left ventricular ejection fraction (EF)<40% were enrolled in the placebo-controlled study. The study medication was titrated over 6 weeks, the mean final dosage was 135 mg/day. Three patients died due to cardiogenic shock, two received placebo and one metoprolol. Eight patients did not complete the study due to non-compliance. Metoprolol significantly reduced heart rate at rest and after submaximal and maximal exercise. Vo(2)-max and Vo(2)-AT as well as the 6-min walk test improved significantly after metoprolol treatment. There was a significant increase in EF at rest (27.3-35. 2%), submaximal (28.5-37.7%) and maximal exercise (28.7-40.9%) in the metoprolol-treated patients. No differences were found between patients with CAD and DCM. We also observed reduced left ventricular volumes. CONCLUSION: The additional therapy with metoprolol improved cardiac function and the cardiopulmonary exercise capacity in patients with CHF.

Adrenergic beta-Antagonists↗

PubMed2000

Role of lipase in the regulation of postprandial gastric acid secretion and emptying of fat in humans: a study with orlistat, a highly specific lipase inhibitor.

BACKGROUND AND AIMS: To investigate the importance of lipase on gastric functions, we studied the effects of orlistat, a potent and specific inhibitor of lipase, on postprandial gastric acidity and gastric emptying of fat. METHODS: Fourteen healthy volunteers participated in a double blind, placebo controlled, randomised study. In a two way cross over study with two test periods of five days, separated by at least 14 days, orlistat 120 mg three times daily or placebo was given with standardised daily meals. In previous experiments we found that this dose almost completely inhibited postprandial duodenal lipase activity. Subjects underwent 28 hour intragastric pH-metry on day 4, and a gastric emptying study with a mixed meal (800 kcal) labelled with (999m)Tc sulphur colloid (solids) and (111In)thiocyanate (fat) on day 5. Gastric pH data were analysed for three postprandial hours and the interdigestive periods. RESULTS: Orlistat inhibited almost completely (by 75%) lipase activity and accelerated gastric emptying of both the solid (by 52%) and fat (by 44%) phases of the mixed meal (p<0.03). Orlistat increased postprandial gastric acidity (from a median pH of 3.3 to 2.7; p<0.01). Postprandial cholecystokinin release was lower with orlistat (p<0.03). CONCLUSION: Lipase has an important role in the regulation of postprandial gastric acid secretion and fat emptying in humans. These effects might be explained by lipolysis induced release of cholecystokinin.

Adult↗

PubMed1999

Presenilin 2 deficiency causes a mild pulmonary phenotype and no changes in amyloid precursor protein processing but enhances the embryonic lethal phenotype of presenilin 1 deficiency.

Mutations in the homologous presenilin 1 (PS1) and presenilin 2 (PS2) genes cause the most common and aggressive form of familial Alzheimer's disease. Although PS1 function and dysfunction have been extensively studied, little is known about the function of PS2 in vivo. To delineate the relationships of PS2 and PS1 activities and whether PS2 mutations involve gain or loss of function, we generated PS2 homozygous deficient (-/-) and PS1/PS2 double homozygous deficient mice. In contrast to PS1(-/-) mice, PS2(-/-) mice are viable and fertile and develop only mild pulmonary fibrosis and hemorrhage with age. Absence of PS2 does not detectably alter processing of amyloid precursor protein and has little or no effect on physiologically important apoptotic processes, indicating that Alzheimer's disease-causing mutations in PS2, as in PS1, result in gain of function. Although PS1(+/-) PS2( -/-) mice survive in relatively good health, complete deletion of both PS2 and PS1 genes causes a phenotype closely resembling full Notch-1 deficiency. These results demonstrate in vivo that PS1 and PS2 have partially overlapping functions and that PS1 is essential and PS2 is redundant for normal Notch signaling during mammalian embryological development.

Amyloid beta-Protein Precursor↗

PubMed1999

Neuromotor alterations and cerebellar deficits in aged arylsulfatase A-deficient transgenic mice.

Arylsulfatase A (ASA)-deficient (-/-) mice and ASA(+/+) controls were constructed as a transgenic model for the lysosomal storage disease, metachromatic leukodystrophy (MLD). One-year-old ASA(-/-) mice showed impaired rotarod performance and altered walking pattern characterized by a shorter pace, later evolving into more severe ataxia with tremor in 2-year-old mice. Examination of cerebellar histology showed that 2-year-old ASA(-/-) mice have lost most of the calbindin immunoreactivity from their Purkinje cell dendrites and show simplified dendritic architecture. Additionally, ASA-deficient mice lost a substantial proportion of their Purkinje cells. Recordings of unitary potentials and stimulation of climbing fibers on cerebellar slices from 2-year-old mice indicated that, although the main cerebellar synapses seem to be present and functioning physiologically, the climbing fibers of ASA-deficient mice may have enhanced effects on Purkinje cell activity. It is concluded that ambulatory dysfunctions in ASA(-/-) mice might be explained by an imbalance in the consequences of climbing fiber signals upon Purkinje cell activity due to selective neurodegeneration within the cerebellum.

Aging↗

PubMed1999

Presenilin-1 deficiency leads to loss of Cajal-Retzius neurons and cortical dysplasia similar to human type 2 lissencephaly.

BACKGROUND: Presenilin-1 (PS1) is a transmembrane protein that is located in the endoplasmic reticulum and the cis Golgi apparatus. Missense mutations of PS1 that modify gamma-secretase function, leading to a pathologic processing of amyloid precursor protein, are an important cause of familial Alzheimer's disease. Physiologically, the presenilins are involved in the Notch and Wnt-beta-catenin signaling pathways. RESULTS: PS1-deficient mice develop a cortical dysplasia resembling human type 2 lissencephaly, with leptomeningeal fibrosis and migration of cortical-plate neurons beyond their normal position into the marginal zone and subarachnoid space. This disorder of neuronal migration is associated with the disappearance of the majority of the cells of the marginal zone, notably most of the Cajal-Retzius pioneer neurons, between embryonic days E14 and E18, and is preceded and accompanied by disorganization of Notch-1 immunoreactivity on the neuronal cell membranes. The marginal zone also becomes depleted of the extracellular matrix protein reelin and chondroitin sulfate proteoglycans. At that stage PS1 is transiently expressed in leptomeningeal fibroblasts, which are mandatory for the trophic support of Cajal-Retzius neurons. CONCLUSIONS: In agreement with models in which neuronal migration disorders have been linked to a defect in Cajal-Retzius cells, the loss of most of these cells in PS1-deficient mice leads to cortical dysplasia. Because PS1 is normally expressed in the leptomeninges, and these become fibrotic in the PS1-knockout mice, we favor the hypothesis that the loss of Cajal-Retzius cells is caused by a defective trophic interaction with leptomeningeal cells, possibly involving disruption of Notch signaling.

Amyloid Precursor Protein Secretases↗

PubMed1999

Normal lysosomal morphology and function in LAMP-1-deficient mice.

Lysosomal membranes contain two highly glycosylated proteins, designated LAMP-1 and LAMP-2, as major components. LAMP-1 and LAMP-2 are structurally related. To investigate the physiological role of LAMP-1, we have generated mice deficient for this protein. LAMP-1-deficient mice are viable and fertile. In LAMP-1-deficient brain, a mild regional astrogliosis and altered immunoreactivity against cathepsin-D was observed. Histological and ultrastructural analyses of all other tissues did not reveal abnormalities. Lysosomal properties, such as enzyme activities, lysosomal pH, osmotic stability, density, shape, and subcellular distribution were not changed in comparison with controls. Western blot analyses of LAMP-1-deficient and heterozygote tissues revealed an up-regulation of the LAMP-2 protein pointing to a compensatory effect of LAMP-2 in response to the LAMP-1 deficiency. The increase of LAMP-2 was neither correlated with an increase in the level of lamp-2 mRNAs nor with increased half-life time of LAMP-2. This findings suggest a translational regulation of LAMP-2 expression.

Animals↗

PubMed1999

The function of presenilin-1 in amyloid beta-peptide generation and brain development.

Several mutations in genes that cause the familial form of Alzheimer's Disease (FAD) have been identified. All mutations in the three FAD genes, i.e., amyloid precursor protein (APP), presenilin 1 (PS-1), and presenilin 2 (PS-2) cause an increased production of a longer, more amyloidogenic form of the amyloid peptide corroborating strongly the idea that abnormal processing of APP is central to the pathogenesis. In PS-1 deficient mice, 80% less amyloid peptide was produced. Instead, membrane associated carboxyterminal fragments generated by (alpha- and beta-secretase accumulated suggesting that PS-1 is involved in the gamma-secretase activity cleaving the transmembrane domain of APP after alpha- and beta-secretase cleavage has occured. The clinical mutations in PS-1 which increase the production of betaA41-42 therefore seem to cause a "selective" gain of its normal function. During cortical plate development in PS-1-deficient mice, neurons do not terminate their movement at the outer margin of the cortical plate, but enter the marginal zone and subarachnoid space. These focal heterotopias closely resemble those occuring, e.g., in human lissencephaly type II. The extracellular matrix of the cortical plate and marginal zone was altered as a consequence of a loss of Cajal-Retzius (CR) neurons from the marginal zone. The pathogenesis of this neuronal migration disorder is associated with a reduction and redistribution of notch- immunoreactivity in CR- and cortical plate neurons, a cell surface receptor operative in cell fate selection, which similar to APP is cleaved in its transmembrane domain during activation by a gamma-secretase like protease.

Alzheimer Disease↗

PubMed1999

Targeted disruption of the lysosomal alpha-mannosidase gene results in mice resembling a mild form of human alpha-mannosidosis.

Alpha-mannosidosis is a lysosomal storage disease with autosomal recessive inheritance caused by a deficiency of the lysosomal alpha-mannosidase, which is involved in the degradation of asparagine-linked carbohydrate cores of glycoproteins. An alpha-mannosidosis mouse model was generated by targeted disruption of the gene for lysosomal alpha-mannosidase. Homozygous mutant animals exhibit alpha-mannosidase enzyme deficiency and elevated urinary secretion of mannose-containing oligosaccharides. Thin-layer chromatography revealed an accumulation of oligosaccharides in liver, kidney, spleen, testis and brain. The cellular alterations were characterized by multiple membrane-limited cytoplasmic vacuoles as seen for instance in liver, exocrine pancreas, kidney, thyroid gland, smooth muscle cells, osteocytes and in various neurons of the central and peripheral nervous systems. The morphological lesions and their topographical distribution, as well as the biochemical alterations, closely resemble those reported for human alpha-mannosidosis. This mouse model will be a valuable tool for studying the pathogenesis of inherited alpha-mannosidosis and may help to evaluate therapeutic approaches for lysosomal storage diseases.

Animals↗

PubMed1999

Contribution of 92 kDa gelatinase/type IV collagenase in bronchial inflammation during status asthmaticus.

In order to assess inflammatory features related to severe asthma as compared with mild asthma, we investigated the secretion of 92 kDa gelatinase matrix metalloproteinase (MMP-9) in bronchial lavages of six patients undergoing mechanical ventilation (MV) for status asthmaticus (SA) and in six patients with mild asthma. Ten healthy nonventilated patients and four patients under MV without preexisting respiratory disease were also investigated. Patients with SA were characterized by prominent neutrophilic inflammation (82 +/- 4% versus 10% in mild asthma). On the basis of enzymatic and immunological analysis, results showed an acute 10- to 160-fold increase of 92 kDa gelatinase (MMP-9) concentration in epithelial lining fluid (ELF) from patients with SA, together with activated forms (46 and 26 kDa) of stromelysin-1 matrix metalloproteinase (MMP-3) and detectable concentration of free metallogelatinolytic activity (1-5 micrograms gelatin hydrolyzed/48 h/ml ELF). Concomitant elevated level of tissue inhibitor of metalloproteinase-1 (TIMP-1) was shown only in patients with SA, thus counterbalancing, at least partially, excess of activated 92 kDa gelatinase. Acutely enhanced albumin levels were only observed in patients with SA; in addition, 92 kDa gelatinase and albumin levels were significantly and positively correlated (r = 0.96, p < 0.0001), suggesting that 92 kDa gelatinase may account for increased bronchial permeability in patients with SA. Several arguments support that 92 kDa gelatinase during SA originates both from numerous activated chemoattracted neutrophils and from activated bronchial epithelial cells in response to in situ lung injury. The fact that no relevant change in ELF, albumin, MMP-9, MMP-3, TIMP-1, or laminin degradation products was observed during mild asthma, strongly supports that the mechanism of airway inflammation in SA is quite distinct from that observed in mild asthma.

Adult↗

PubMed1998

Meningeal cells stimulate neuronal migration and the formation of radial glial fascicles from the cerebellar external granular layer.

The cerebellar granule cell layer and partly the Bergmann glial scaffold arise from a secondary subpial proliferative zone, the external granular layer. Their development can be disrupted by selective destruction of meningeal cells. In order to clarify the mechanisms of meningeal control of cortical development, we have investigated the development of early postnatal rat cerebellar slice explants in different coculture set-ups with meningeal cells and other fibroblasts. Fibroblasts of various sources (1) stimulate migration of undifferentiated neurons from the explants by a diffusible factor and (2) trigger the development of a radial phenotype in glial cells by contact-mediated mechanisms involving basal lamina constituents. These data provide further evidence for the involvement of mesenchymal-epithelial interactions in the development of the cerebellar cortex.

Animals↗