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A Aguzzi

Publications and source records attributed to A Aguzzi.

At least 73 records · Page 4Linked to original sources
PubMed2000

Age-related expression of the cellular prion protein in human peripheral blood leukocytes.

BACKGROUND AND OBJECTIVE: Creutzfeldt-Jakob disease typically affects older patients, yet victims of new-variant Creutzfeldt-Jakob disease (nvCJD) are unusually young. Because the cellular prion protein PrP(C) is required for disease development, we investigated age-dependent variability in cell surface PrP(C) expression on various subclasses of human peripheral blood leukocytes (PBL) as a possible susceptibility factor. DESIGN AND METHODS: Three age groups of healthy individuals (mean ages: 6, 33 and 68) were studied by two-color FACS analysis of PBL with fluorescent monoclonal antibodies to PrP(C) and to the lineage markers CD3, CD19, CD4, and CD8. For each subclass marker, surface PrP(C) levels were expressed as mean fluorescence intensity ratios (MFIR) by dividing the geometric mean of the fluorescence of each test antibody by the geometric mean of its isotype-matched control antibody. PrP(C) expression levels in each age and lineage group were compared using appropriate non-parametric tests. RESULTS: We found significant age-related differences in PrP(C) expression on lymphocytes (p=0. 0004). The elderly expressed significantly higher levels than children (p=0.0006) and adults (p=0.0009). PrP(C) expression was also significantly higher in CD3(+) compared to CD19(+ )(p=0.0004) and in CD8(+) compared to CD4(+ )lymphocytes (p=0.0044). INTERPRETATION AND CONCLUSIONS: If PrP(C) expression on PBL were a significant susceptibility factor for nvCJD, young persons would display higher levels. Instead, the elderly expressed the highest amounts of PrP(C) on PBL. This argues against the hypothesis that variability in cell surface expression of PrP(C) in PBL contributes to the exquisite susceptibility of the young to nvCJD.

Adolescent↗
PubMed2000

Organic anion-transporting polypeptides mediate transport of opioid peptides across blood-brain barrier.

Organic anion-transporting polypeptides (Oatps) are a rapidly growing gene family of polyspecific membrane transporters. In rat brain, Oatp1 (gene symbol Slc21a1) and Oatp2 (Slc21a5) are localized at the apical and basolateral domains, respectively, of the choroid plexus epithelium. Furthermore, Oatp2 is strongly expressed at the rat blood-brain barrier (BBB). This study localizes the human OATP (now called OATP-A; SLC21A3) at the BBB in humans. Furthermore, with the Xenopus laevis oocyte system the delta-opioid receptor agonists [D-penicillamine(2,5)]enkephalin (DPDPE) and deltorphin II were identified as new transport substrates of OATP-A. This OATP-A-mediated DPDPE and deltorphin II transport exhibited apparent K(m) values of approximately 202 and 330 microM, respectively, and OATP-A-mediated deltorphin II transport was inhibited by the mu-opioid receptor agonist Tyr-D-Ala-Gly-N-methyl-Phe-glycinol, the endogenous peptide Leu-enkephalin, and the opiate antagonists naloxone and naltrindole. DPDPE also was transported by rat Oatp1 (K(m) approximately 48 microM) and Oatp2 (K(m) approximately 19 microM), whereas deltorphin II was only transported by Oatp1 (K(m) approximately 137 microM). These results demonstrate that OATP-A can mediate transport of the analgesic opioid peptides DPDPE and deltorphin II across the human BBB. Furthermore, because rat Oatp1 and Oatp2 exhibit similar but not identical transport activities as OATP-A, the results generally indicate that members of the Oatp/OATP gene family of membrane transporters play an important role in carrier-mediated transport of opioid peptides across the BBB and blood-cerebrospinal fluid barrier of the mammalian brain.

Aged↗
PubMed2000

Abdominal pain in children: a case of acalculous cholecystitis.

Acalculous cholecystitis is a rare disease in children. Most cases are associated with systemic infections or with autoimmune pathologies, but it may also occur without predisposing factors. A case observed in an otherwise healthy child is reported.

Abdominal Pain↗
PubMed1999

Determination of folate vitamers in food and in Italian reference diet by high-performance liquid chromatography.

A trienzyme treatment (conjugase, alpha-amylase, protease) followed by affinity chromatography and reversed-phase HPLC with UV and fluorescence detection was performed for the quantification of folate vitamers in legumes (chickpea and beans), processed meats (salami Milano and Parma ham) and in an Italian reference diet. This method allowed a good separation of six folate vitamers: 5-methyltetrahydrofolate, 5-formyltetrahydrofolate, folic acid, 10-formylfolic acid, 10-formyldihydrofolate and tetrahydrofolate within 30 min. Recovery, reproducibility and limits of detection of the method are reported. HPLC results were 24-52% lower than the microbiological assay findings.

Chromatography, High Pressure Liquid↗
PubMed1999

PrP-dependent association of prions with splenic but not circulating lymphocytes of scrapie-infected mice.

An intact immune system, and particularly the presence of mature B lymphocytes, is crucial for mouse scrapie pathogenesis in the brain after peripheral exposure. Prions are accumulated in the lymphoreticular system (LRS), but the identity of the cells containing infectivity and their role in neuroinvasion have not been determined. We show here that although prion infectivity in the spleen is associated with B and T lymphocytes and to a lesser degree with the stroma, no infectivity could be detected in lymphocytes from blood. In wild-type mice, which had been irradiated and reconstituted with PrP-deficient lymphohaematopoietic stem cells and inoculated with scrapie prions, infectivity in the spleen was present in the stroma but not in lymphocytes. Therefore, splenic B and T lymphocytes can either synthesize prions or acquire them from another source, but only when they express PrP.

Animals↗
PubMed1999

Ectopic expression of prion protein (PrP) in T lymphocytes or hepatocytes of PrP knockout mice is insufficient to sustain prion replication.

The cellular form of the Prion protein (PrPC) is necessary for prion replication in mice. To determine whether it is also sufficient, we expressed PrP under the control of various cell- or tissue-specific regulatory elements in PrP knockout mice. The interferon regulatory factor-1 promoter/Emu enhancer led to high PrP levels in the spleen and low PrP levels in the brain. Following i.p. scrapie inoculation, high prion titers were found in the spleen but not in the brain at 2 weeks and 6 months, showing that the lymphoreticular system by itself is competent to replicate prions. PrP expression directed by the Lck promoter resulted in high PrP levels on T lymphocytes only but, surprisingly, did not allow prion replication in the thymus, spleen, or brain following i.p. inoculation. A third transgenic line, which expressed PrP in the liver under the control of the albumin promoter/enhancer-albeit at low levels-also failed to replicate prions. These results show that expression of PrP alone is not sufficient to sustain prion replication and suggest that additional components are needed.

Animals↗
PubMed1999

Early induction of angiogenetic signals in gliomas of GFAP-v-src transgenic mice.

Angiogenesis is a prerequisite for solid tumor growth. Glioblastoma multiforme, the most common malignant brain tumor, is characterized by extensive vascular proliferation. We previously showed that transgenic mice expressing a GFAP-v-src fusion gene in astrocytes develop low-grade astrocytomas that progressively evolve into hypervascularized glioblastomas. Here, we examined whether tumor progression triggers angiogenetic signals. We found abundant transcription of vascular endothelial growth factor (VEGF) in neoplastic astrocytes at surprisingly early stages of tumorigenesis. VEGF and v-src expression patterns were not identical, suggesting that VEGF activation was not only dependent on v-src. Late-stage gliomas showed perinecrotic VEGF up-regulation similarly to human glioblastoma. Expression patterns of the endothelial angiogenic receptors flt-1, flk-1, tie-1, and tie-2 were similar to those described in human gliomas, but flt-1 was expressed also in neoplastic astrocytes, suggesting an autocrine role in tumor growth. In crossbreeding experiments, hemizygous ablation of the tumor suppressor genes Rb and p53 had no significant effect on the expression of VEGF, flt-1, flk-1, tie-1, and tie-2. Therefore, expression of angiogenic signals is an early event during progression of GFAP-v-src tumors and precedes hypervascularization. Given the close similarities in the progression pattern between GFAP-v-src and human gliomas, the present results suggest that these mice may provide a useful tool for antiangiogenic therapy research.

Animals↗
PubMed1999

A crucial role for B cells in neuroinvasive scrapie.

Although prions are most efficiently propagated via intracerebral inoculation, peripheral administration has caused kuru [Gajdusek et al, 1966], iatrogenic Creutzfeldt-Jakob disease (CJD) [Gibbs et al, 1997], bovine spongiform encephalitis (BSE), and new variant CJD [Hill et al, 1997; Bruce et al, 1997]. Neurological disease after peripheral inoculation depends on prion expansion within cells of the lymphoreticular system (LRS) [Lasmezas et al. 1996; Wilesmith et al, 1992]. In order to identify the nature of the latter cells, we inoculated a panel of immune deficient mice with prions intraperitoneally. While defects affecting only T lymphocytes had no apparent effect, all mutations affecting differentiation and responses of B lymphocytes prevented development of clinical scrapie. Since absence of B cells and of antibodies correlates with severe defects in follicular dendritic cells (FDCs), the lack of any of these three components may prevent clinical scrapie. Yet, mice expressing immunoglobulins exclusively of the M subclass without detectable specificity for PrPc, and mice with differentiated B cells but lacking functional FDCs, developed scrapie after peripheral inoculation: therefore, differentiated B cells appear to play a crucial role in neuroinvasion of scrapie regardless of B-cell receptor specificity.

Animals↗
PubMed1999

The lack of chromosomal protein Hmg1 does not disrupt cell growth but causes lethal hypoglycaemia in newborn mice.

High mobility group 1 (HMG1) protein is an abundant component of all mammalian nuclei, and related proteins exist in all eukaryotes. HMG1 binds linear DNA with moderate affinity and no sequence specificity, but bends the double helix significantly on binding through the minor groove. It binds with high affinity to DNA that is already sharply bent, such as linker DNA at the entry and exit of nucleosomes; thus, it is considered a structural protein of chromatin. HMG1 is also recruited to DNA by interactions with proteins required for basal and regulated transcriptions and V(D)J recombination. Here we generate mice harbouring deleted Hmg1. Hmg1-/- pups are born alive, but die within 24 hours due to hypoglycaemia. Hmg1-deficient mice survive for several days if given glucose parenterally, then waste away with pleiotropic defects (but no alteration in the immune repertoire). Cell lines lacking Hmg1 grow normally, but the activation of gene expression by the glucocorticoid receptor (GR, encoded by the gene Grl1) is impaired. Thus, Hmg1 is not essential for the overall organization of chromatin in the cell nucleus, but is critical for proper transcriptional control by specific transcription factors.

Animals↗
PubMed1999

Spinal cord pathology and viral burden in homosexuals and drug users with AIDS.

Unless treated with effective antiretroviral therapy many AIDS patients develop a characteristic vacuolar myelopathy of the spinal cord associated with moderate clinical disability. Opinion is divided as to whether vacuolar myelopathy is causally linked to HIV myelitis. To investigate this further, spinal cord pathology was assessed in 41 drug users, 33 homosexual men and 16 other patients, all with AIDS. Previous work has shown that HIV encephalitis is more common in Edinburgh drug users than in homosexual men. In the present study HIV myelitis (10% overall) was more common in drug users (17%) than in homosexual men (3%) (P = 0.05), whereas the incidence of opportunistic infections (7% v. 9%) and lymphomas (2% v. 6%) was comparable in the two groups, but with a slight trend in the reverse direction, reflecting similar findings in the brain. However, moderate or severe vacuolar myelopathy was equally represented in both groups (20% of drug users and 21% of homosexual men). The HIV proviral load, assessed by polymerase chain reaction in frozen samples of thoracic spinal cord in 37 cases, correlated closely with the presence of giant cells and/or with immunocytochemical evidence of productive HIV infection. In 13 cases, the proviral load was measured in cervical, thoracic and lumbar samples and proved to be uniformly high or low in individual cases. This study provides no evidence for direct involvement of HIV, cytomegalovirus, papovavirus or human foamy virus in the pathogenesis of vacuolar myelopathy.

AIDS-Related Opportunistic Infections↗
PubMed1999

Distinct phases of cryogenic tissue damage in the cerebral cortex of wild-type and c-fos deficient mice.

To characterize the development of tissue damage following cryogenic injury to the mouse cortex, the time course of histopathological changes, transcriptional responses and DNA strand breaks following application of a liquid nitrogen-cooled probe to the surface of the parietal bone were assessed. Distinct phases of tissue damage were observed: after 30 min, there was demarcation of a core lesion followed by mainly necrotic cell death starting 2 h after injury. At 12 hours, progressive apoptotic death of scattered cells in the periphery of the core lesion was detected, resembling the penumbra observed in ischaemic stroke. In situ hybridization for c-fos revealed an absence of expression in the core region, suggesting early cessation of transcription. There was strong induction of c-fos in the penumbra 30 min after the lesion, which had spread over the ipsilateral hemisphere at 2 h, possibly caused by peri-infarction depolarization. At later time points, sustained expression of c-fos was observed in some cells in the penumbra. Since a role for c-fos has been postulated in the initiation or execution of apoptotic pathways, the susceptibility of c-fos deficient mice was explored (n=4) in this model. Cryoinjury-induced tissue injury was markedly attenuated in c-fos deficient mice. A model of the phases and mechanisms of cryogenic injury is proposed, which discriminates an early phase characterized by physical changes caused by hypothermia and their immediate consequences (i.e. transcriptional block), an intermediate phase where secondary changes lead to necrosis in the core region, and a final phase of delayed apoptotic cell death in the penumbra.

Animals↗
PubMed1999

Distal axonopathy in peripheral nerves of PMP22-mutant mice.

A partial duplication of chromosome 17 is associated with Charcot-Marie-Tooth disease type 1A (CMT1A), a demyelinating peripheral neuropathy that causes progressive distal muscle atrophy and sensory impairment. Trisomic expression of peripheral myelin protein 22 (PMP22) whose gene is contained within the duplicated region is considered to be responsible for the disease. By using recombinant gene technology in rodents, we had demonstrated previously that PMP22 is sensitive to gene dosage. Homozygous PMP22 knockout (PMP22(0/0)) mice and transgenic animals carrying additional copies of the PMP22 gene develop distinct peripheral polyneuropathies. We have now performed a detailed morphometrical analysis of the L3 roots, quadriceps and saphenous nerves of these PMP22-mutant mice to study whether the myelin and potential axonal deficits are evenly distributed. The L3 roots and the peripheral nerves were chosen as representatives of the proximal and distal segments of the peripheral nervous system. When the roots were compared with the peripheral nerves, myelin deficiencies appeared more severe at the radicular levels, in particular the ventral roots. Decreased numbers of large calibre axons were a prominent feature in the motor branches of both strains of PMP22-mutant mice, and these axonal deficits were more severe distally. Active axonal damage was only observed in the nerves of PMP22(0/0) mice. Despite the distinct effects on myelination and the Schwann cell phenotype that characterize the neuropathies of PMP22-mutant mice, both strains develop a distally accentuated axonopathy as a common disease mechanism which is likely to be responsible for the neurological deficits.

Animals↗
PubMed1999

No complementation between TP53 or RB-1 and v-src in astrocytomas of GFAP-v-src transgenic mice.

Human low-grade astrocytomas frequently recur and progress to states of higher malignancy. During tumor progression TP53 alterations are among the first genetic changes, while derangement of the p16/p14ARF/RB-1 system occurs later. To probe the pathogenetic significance of TP53 and RB-1 alterations, we introduced a v-src transgene driven by glial fibrillary acidic protein (GFAP) regulatory elements (which causes preneoplastic astrocytic lesions and stochastically astrocytomas of varying degrees of malignancy) into TP53+/- or RB-1+/- mice. Hemizygosity for TP53 or RB-1 did not increase the incidence or shorten the latency of astrocytic tumors in GFAP-v-src mice over a period of up to 76 weeks. Single strand conformation analysis of exons 5 to 8 of non-ablated TP53 alleles revealed altered migration patterns in only 3/16 tumors analyzed. Wild-type RB-1 alleles were retained in all RB-1+/-GFAP-v-src mice-derived astrocytic tumors analyzed, and pRb immunostaining revealed protein expression in all tumors. Conversely, the GFAP-v-src transgene did not influence the development of extraneural tumors related to TP53 or RB-1 hemizygosity. Therefore, the present study indicates that neither loss of RB-1 nor of TP53 confer a growth advantage in vivo to preneoplastic astrocytes expressing v-src, and suggests that RB-1 and TP53 belong to one single complementation group along with v-src in this transgenic model of astrocytoma development. The stochastic development of astrocytic tumors in GFAP-v-src, TP53+/- GFAP-v-src, and RB-1+/- GFAP-v-src transgenic mice indicates that additional hitherto unknown genetic lesions of astrocytes contribute to tumorigenesis, whose elucidation may prove important for our understanding of astrocytoma initiation and progression.

Animals↗
PubMed1999

Scrapie pathogenesis in subclinically infected B-cell-deficient mice.

Prion infections can present without clinical manifestations. B-cell deficiency may be a model for subclinical transmissible spongiform encephalopathy, since it protects mice from disease upon intraperitoneal administration of scrapie prions; however, a proportion of B-cell-deficient mice accumulate protease-resistant prion protein in their brains. Here, we have characterized this subclinical disease. In addition, we have studied the possibility that a neurotoxic factor secreted by B cells may contribute to pathogenesis.

Animals↗