Genetic risk factors in young adults with 'cryptogenic' ischemic cerebrovascular disease.

Mutations such as factor V Leiden G1691A (FVL), prothrombin G20210A (FIIM), methylenetetrahydrofolate reductase (MTHFR) C677T, cystathionine beta-synthase (CBS) 844ins68 and endothelial cell protein C receptor (EPCR) 4031ins23 are risk factors for thromboembolism. To assess the role of these mutations in young adults with cerebral ischemia of otherwise undetermined etiology, 93 patients younger than 50 years old with thromboembolic strokes or transient ischemic attacks were studied. One hundred and eighty-six healthy age-matched and sex-matched blood donors served as controls. The FVL mutation was detected in 15/93 patients and 13/186 controls. After adjustment for smoking, arterial hypertension, and hyperlipidemia, the association of the FVL mutation with cerebral ischemia [odds ratio (OR), 3.19; 95% confidence interval (CI), 1.38-7.39] remained significant. One of 93 patients and 6/186 controls were carriers of FIIM (OR, 0.33; 95% CI, 0.04-2.75). We detected the MTHFR TT677 genotype in 9/93 patients and 26/186 controls (OR, 0.66; 95% CI, 0.30-1.47), a CBS 844ins68 mutation in 12/93 patients and 19/186 controls (OR, 1.30; 95% CI, 0.60-2.81), and an EPCR 4031ins23 mutation in 1/93 patients and in no control individual (P = 0.33). In conclusion, in younger adults the FVL mutation is a risk factor for cerebrovascular disease. FIIM, the MTHFR TT677 genotype and the CBS 844ins68 mutation did not contribute to the risk in this group of patients. The EPCR 4031ins23 mutation is very rare, its possible role needs further investigation.

Hydrophilic, pro-drug analogues of T138067 are efficacious in controlling tumor growth in vivo and show a decreased ability to cross the blood brain barrier.

The novel anticancer compound T138067 is an irreversible inhibitor of tubulin polymerization. Amides 3-6 were synthesized using standard methodologies and determined to be significantly less lipophilic than T138067 based on logP calculations. Tubulin polymerization and [(3)H]-T138067 competition assays revealed that these amides are pro-drugs for parent aniline 2. Amides 3-5 showed no detectable signs of crossing the blood brain barrier, while amide 6 was found in extremely small amounts (12 ng/g of brain tissue). Aniline 2, which was formed in vivo from these amides, was found in significantly smaller amounts (approximately 20 to >5000 times) in the brain than when 2 was administered directly. The in vivo efficacy of amide 6 approached that of T138067 and was better tolerated when administered to athymic nude mice bearing MX-1 human mammary tumor xenografts.

A comparative evaluation of the effect of pump type and heparin-coated surfaces on platelets during cardiopulmonary bypass.

Cardiopulmonary bypass (CPB) is associated with hemostatic disorders, mainly due to platelet function defects. In the present prospective study, platelet count and GMP-140 expression on platelets were investigated to comparatively evaluate the impact of different CPB-circuit systems on platelets. The study included 61 patients undergoing coronary artery bypass grafting, randomly assigned to 3 groups. In group A a roller pump, in group B a centrifugal pump, and in group C a centrifugal pump with a Carmeda heparin-coated CPB circuit was applied. Platelet count and GMP-140 expression were analysed pre, during, and following CPB. None of the tested CPB systems did affect platelet count. The percentage of GMP-140-positive platelets increased slightly early during CPB, whereas it decreased significantly postoperatively; group differences were observed between B and C after protamin administration. An advantage of the use of centrifugal pumps and heparin-coated circuits could not be proven with the present set-up. The results suggest that the benefit of the tested systems might depend on the operative procedure and management.

Selective screening for the Factor V Leiden mutation: is it advisable prior to the prescription of oral contraceptives?

The cumulative thrombotic risk of Factor V (FV) Leiden and oral contraceptives (OC) recommends screening for the mutation. Assuming that a family history of thrombosis increases the patient's likelihood of bearing FV Leiden, a selective rather than universal screening would be performed. We studied the utility of a family history of thrombosis for screening of FV Leiden before prescription of OC and, furthermore, the utility of screening even if oral contraception is favoured. 101 patients who had their first and single thromboembolic event while using OC were interviewed. 609 women without any history of thromboembolism recruited by gynecologists completed a standard questionnaire. 101 of these women, age-matched and currently using OC, were selected for a case-control study. Regarding patients with previous thromboembolism, a family history in a first-degree relative had a positive predictive value (PPV) of only 14% for FV Leiden. A PPV of 12% was calculated by investigating the 609 thrombosis-free women. Inherited FV Leiden (odds ratio = 4.9) and acquired risk factors (odds ratio = 10.1) were both found to be the most prominent, but independent additional risks. Nevertheless, FV Leiden carriers, both heterozygotes and homozygotes, did not suffer earlier from thromboembolism than patients without the mutation. In conclusion, family history is an unreliable criterion to detect FV Leiden carriers. Screening for factor V Leiden can be worthwhile even if the advantages of oral contraception are higher assessed than the thrombotic risk. Affected women knowing about their additional risk could contribute to the prevention of thrombosis in risk situations.

PIP: The cumulative thrombotic risk of Factor V Leiden (FVL) and oral contraceptive (OC) use raises the possibility of either selective or universal screening for this mutation before OCs are prescribed. Family history of venous thromboembolism as a criterion to detect FVL carriers was evaluated in a case-control study of 101 women from Bavaria, Germany, who had their first and single thromboembolic event while using OCs and 101 healthy age-matched OC users. A questionnaire was administered to a broader group of 609 OC users without a history of thromboembolism. Analysis of the 609 women revealed a 7.4% prevalence of FVL, but no association between this mutation and a family history of thromboembolism. Among women with a previous thromboembolism, a family history in a first-degree relative had a positive predictive value of only 14% for FVL. The sensitivity of family history was under 50%. 35% of cases compared with 8% of controls carried the FVL mutation. The most significant independent risk factors of thromboembolism were inherited FVL (odds ratio, 4.9) and acquired risk factors--i.e., surgery, leg fractures, distortions, confinement to bed for more than 1 week, or a restricted sitting position more than 6 hours in the 4 weeks before the index date (odds ratio, 10.1). Both heterozygote and homozygote FVL carriers did not suffer earlier from thromboembolism than patients without the mutation. These findings indicate that family history is not an effective predictor of FVL. However, even if the advantages of OC use are greater than the thrombotic risk, screening for FVL may be indicated to permit high-risk women to take preventive action.

Murine leukemia virus-induced neurodegeneration of rats: enhancement of neuropathogenicity correlates with enhanced viral tropism for macrophages, microglia, and brain vascular cells.

A highly neuropathogenic retrovirus, NT40, was generated by serially passaging an infectious molecular clone of Friend murine leukemia virus, FB29, through F344 Fisher rats. NT40 induced severe neurological signs such as reflex abnormalities and ataxia within 4-6 weeks following neonatal inoculation. FB29 led to only very mild neurological dysfunctions with longer incubation periods. Pathological alterations were characterized by mild (FB29) to extensive (NT40) noninflammatory spongiform degeneration, mainly of brain-stem areas. Infectious center assays revealed that viral titers in brain tissues of NT40-infected rats were 100-fold higher than those of FB29-infected animals. Employing immunohistochemistry, in situ hybridization, and flow cytometry, NT40 was found to infect many endothelial cells of brain blood vessels and microglia, whereas FB29 infected only microglia and those to a lower extent. However, when isolated from adult diseased rats, microglial cells turned out in both cases to be nonproductively infected with either FB29 or NT40. Of peripheral organs, we found enhanced levels of NT40 in peritoneal macrophages but not in spleen, thymus, or serum when compared to FB29. Altogether these data suggest that an expanded cellular tropism within the CNS and elevated viral titers in macrophages and microglia correlated with enhancement of neuropathogenicity.

Phenotypic and functional characterization of CD8+ T lymphocytes from the central nervous system of rats with coronavirus JHM induced demyelinating encephalomyelitis.

Intracerebral infection of Lewis (LEW) inbred rats with the neurotropic strain of the murine coronavirus JHM (JHMV) frequently results in a monophasic paralytic disease. In contrast, infection of Brown Norway (BN) inbred rats does not lead to clinical disease. Previous findings indicated that in both rat strains brain-infiltrating leukocytes consisted mainly of CD8+ T lymphocytes. Here, we phenotypically as well as functionally characterised this T cell subset after isolation from the central nervous system (CNS). Using JHMV-infected target cells, MHC class I restricted, cytotoxic T lymphocytes were demonstrated to be present in the leukocyte fraction from the CNS of both, susceptible LEW and disease-resistant BN rats. However, compared to infected, but healthy BN rats, diseased LEW rats generated an enhanced cytotoxic immune response which became most prominent at the maximum of neurological disease. Recently published observations from our laboratory demonstrated a strong virus-specific antibody response in the CNS of BN rats. In LEW rats, however, the response was delayed and of low magnitude. This suggests, that consequences of cytotoxic T lymphocyte action in JHMV-infected CNS tissue largely depend on the efficacy of an accompanying virus-specific humoral immune response.

Effects of adoptive immune transfers on murine leukemia virus-infection of rats.

In a rat model, we have investigated the effects of adoptively transferred virus-specific immune cells on an established retroviral infection of various organs. The experimental design required inoculation of neonatal Fisher rats with a molecular clone of Friend murine leukemia virus (F-MuLV; FB29) which resulted in virus-specific immunotolerance, while infection of adult rats lead to a virus-specific humoral and cellular immune response. Adoptive transfer of virus-specific immune cells from immunized to immunotolerant (i.e., neonatally inoculated) rats was performed at around 15 days postpartum, a time when retroviral titers had already reached high levels in serum, spleen, thymus, and central nervous system (CNS). Seven days post-transfer (dpt), virus titers began to decline by 3-5 logs first in sera and at around 11-15 dpt, in spleens and thymi. Approximately 19 days post-transfer viral titers increased again. In the CNS, viral titers appeared not to change after adoptive transfer, although we observed an influx of activated T-cells and natural killer cells (NK-cells), but not of B-cells, into the CNS as well as an upregulation of major histocompatibility complex class I and II molecules between 8 and 21 dpt on both microglia and other brain cells. From these data we conclude that MuLV-infected cells of lymphoid organs can be eliminated by an antiviral immune response. In the CNS, however, most virus-infected cells escaped an immunological attack in spite of the presence of T- and NK-cells and may thus function as a reservoir for MuLVs.

Resident macrophages (ramified microglia) of the adult brown Norway rat central nervous system are constitutively major histocompatibility complex class II positive.

A flow cytometric phenotype for isolated adult central nervous system (CNS) ramified microglia was previously defined (CD45low CD11b/c+) in the Lewis strain rat, that clearly distinguished these cells from all blood-derived leucocytes, the latter being CD45high. Consistent with the reported lack of major histocompatibility complex (MHC) expression in the CNS, isolated microglia were mostly MHC class II-. Employing these phenotypic criteria, we now show that a proportion of microglia in Brown Norway (BN) strain rats are constitutively MHC class II+. In spinal cord, up to 25% of microglia are distinctly positive and most have some level of expression. In situ staining of MHC class II+ microglial cells in BN rats indicates that positive cells are typical of ramified microglia on the grounds of both morphological appearance and anatomical location. In Lewis (LEW) rats, the few MHC class II-expressing cells isolated from the normal CNS are CD45high blood-derived cells and not resident microglia. After infection of both LEW and BN rats with a neurotropic murine hepatitis virus (MHV-JHM), MHC class II was rapidly upregulated on microglia in the BN but not in the LEW strain. In the latter, inflammatory cells were the predominant MHC class II-expressing population. Nevertheless, most microglia in the LEW strain could, after some delay, be induced to express MHC class II after transfer of an experimental autoimmune encephalomyelitis (EAE)-inducing encephalitogenic T cell line. Paradoxically, strains resistant to EAE (exemplified by the BN) contained more constitutive MHC class II-expressing microglia than susceptible ones, when a variety of strains were examined. The results clearly establish that the normal CNS may contain MHC class II-expressing cells that are a resident rather than a transient blood-derived population. It is significant that this expression is strain related, but there is no evidence that microglial cell constitutive MHC class II expression predisposes to EAE susceptibility.

Human immunodeficiency virus infection in microglia: correlation between cells infected in the brain and cells cultured from infectious brain tissue.

In acquired immunodeficiency syndrome, the lesions of the central nervous system in association with the human immunodeficiency virus are thought to be related to an infection of microglia, although no studies are available in which cultured and physiological characteristics of microglia cells infected in vivo have been examined. In this report, we used brain tissue from a child dying of human immunodeficiency virus infection and show that microglia cells were the main cell population being infected. Moreover, isolated macrophage-like cells from fresh brain material revealed a close resemblance to peripheral blood macrophages in their content of surface and intracellular antigens. No virus particles or viral antigens were produced by these cells during the first week of cultivation. Productive infection was readily apparent, however, by day 30. This finding illustrates the slow nature of the virus life cycle in these cells and the minimal cytopathology that accompanied the infection.

Interaction of a protein with a palindromic sequence from murine rDNA increases the occurrence of amplification-dependent transformation in mouse cells.

muNTS1, an element isolated from the nontranscribed spacer of murine rDNA, increases the occurrence of amplification-dependent transformation in mouse cells when integrated into plasmid DNA containing a selectable marker (Wegner, M., Zastrow, G., Klavinius, A., Schwender, S., Müller, F., Luksza, H., Hoppe, J., Wienberg, J., and Grummt, F. (1989) Nucleic Acids Res. 17, 9909-9932). In an initial attempt to dissect muNTS1 into its structural components we localized part of the transformation increasing activity to a long AT-rich stretch from the 5' region which interacts with HMG-I. Here we identify a second element on muNTS1 which also stimulates the rate of amplification-coupled transformation in cis. It is found in the 3' region of muNTS1 and contains the 11-base pair palindrome ATGGCTGCCAT. It is conserved in the otherwise strongly divergent ribosomal NTS regions from mouse, rat, and man and is also found in the origin/enhancer region of human papovavirus JC. The palindromic sequence interacts specifically with proteins from mouse cell extracts. Protein-DNA interaction was dependent on the presence of zinc ions in the extract. Point-specific mutations within the palindrome reduced protein-DNA complex formation substantially and concomitantly abolished the ability to stimulate the frequency of transformation. The binding activity was purified and shown to consist of two polypeptides with molecular masses of 70 and 73 kDa.

Murine genomic DNA sequences replicating autonomously in mouse L cells.

Plasmids that replicate autonomously in mouse L cells were constructed by inserting random genomic DNA fragments from Ltk- cells into a plasmid containing the HSV-1 thymidine kinase gene with a truncated low-efficiency promoter. HAT resistance was used as a selective marker. The presence of free plasmids in the DNA of transformants was demonstrated by hybridization with a specific plasmid probe, by electron microscopic visualization of circular DNA, and by recovering these plasmids by E. coli transformation. Nineteen different DNA fragments were isolated. They were characterized as murine autonomously replicating sequences by Mbol restriction endonuclease sensitivity, by bromodeoxyuridine substitution, by copy number determination, and by segregation analysis. Sequence analysis of the inserts of nine plasmids revealed a conserved element of 12 bp (CTCATGAGAGGCCAA) in five out of nine autonomously replicating sequences.