The myocilin (MYOC) gene expression in the human trabecular meshwork

PURPOSE

We previously reported a novel cytoskeletal protein with a myosin-like domain which is localized in the ciliary rootlet and basal body of connecting cilium of photoreceptor and hence we named it 'myocilin'. It was soon realized that myocilin is identical to a protein called TIGR (trabecular meshwork inducible glucocorticoid response protein) which was found to be responsible for the pathogenesis of juvenile open angle glaucoma. In this study, we employed in situ RNA hybridization to examine the myocilin (MYOC)/ TIGR gene expression in the trabecular meshworks of glaucomatous and nonglaucomatous eyes.

METHODS

The glaucomatous specimens were obtained by trabeculectomy from the patients with primary open angle glaucoma (POAG), chronic angle closure glaucoma (CACG) and steroid glaucoma, respectively, and the nonglaucomatous specimens were obtained from a victim of traffic accident at autopsy and from a patient with maxillary sinus carcinoma at enucleation for the operation. The in situ RNA hybridization was carried out with digoxigenin-labeled sense and antisense RNA probes.

RESULTS

In all cases, hybridization signals were detected primarily in the trabecular meshwork cells and secondarily in the fibroblast-like cells of corneoscleral wall.

CONCLUSIONS

Myocilin gene is expressed clearly in the trabecular meshwork cells of both glaucomatous and nonglaucomatous eyes.

HTLV-I specific IFN-gamma+ CD8+ lymphocytes correlate with the proviral load in peripheral blood of infected individuals

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurological disease caused by HTLV-I infection. It has been shown that HAM/TSP patients have high proviral loads and an extraordinarily high frequency of circulating CD8 + cytotoxic T lymphocytes specific for HTLV-I in their peripheral blood when compared to asymptomatic HTLV-I carriers (AC). We have previously described an intracellular cytokine detection assay, in which interferon-gamma (IFN-gamma) + CD8 + lymphocytes are specific for HTLV-I in infected individuals. Here, we have established a competitive polymerase chain reaction assay to measure the proviral load of patients and investigate a potential relationship between proviral load and virus-specific CD8 + lymphocytes. Genomic DNA was extracted from peripheral blood lymphocytes (PBL) from eight HAM/TSP patients and seven AC for the measurement of HTLV-I measuring proviral loads. The same PBL were analyzed for intracellular IFN-gamma expression by flow cytometry. In the HAM/TSP patients and AC, the average proviral loads were 34,482 and 9784 copy/microg DNA (P = 0.021), and the average of IFN-gamma + CD8 + lymphocytes in total PBL were 1.47 and 0.08% (P = 0.001), respectively. It was confirmed that HAM/TSP patients have both high proviral loads and increased HTLV-I-specific CD8 + lymphocytes. Furthermore, we found a positive correlation between both factors in the patients with HAM/TSP (P = 0.044) but not in the AC (P = 0.508). These findings suggest that the high number of HTLV-I-specific lymphocytes may result from the increased proviral load in HAM/TSP patients.

Activation of macrophages/microglia with the calcium-binding proteins MRP14 and MRP8 is related to the lesional activities in the spinal cord of HTLV-I associated myelopathy

Macrophages and microglia may play an important role in the pathogenesis of chronic inflammatory process in HTLV-I associated myelopathy (HAM) and tropical spastic paraparesis (TSP). However, the etiology and cellular mechanism of chronic inflammation are poorly understood in HAM/TSP. To help to define the roles of macrophages and microglia we analyzed the various patterns of macrophage and microglia activation in the central nervous system (CNS) of HAM/TSP using several monoclonal antibodies recognizing the different states of activation. The results indicate that a large number of macrophages and microglia express both MRP14 and MRP8 in active-chronic inflammatory lesions of the patients with a short duration of illness (2.5 years). In the patient whose duration of illness was 4.5 years, perivascular and parenchymal macrophages and microglia were reactive for MRP8 but not for MRP14. In contrast, MRP14 and MRP8 were negative on the perivascular and parenchymal macrophages and microglia in inactive-chronic lesions and in controls. This study suggests that (a) activated macrophages and microglia as well as CD4+ T lymphocytes and CD8+ cytotoxic T lymphocytes are main components of the inflammatory process in the CNS in HAM/TSP, (b) activation of macrophages and microglia is related to the amount of HTLV-I proviral DNA in situ.

Rapid detection and identification of two lineages of influenza B strains with monoclonal antibodies

Monoclonal antibodies (Mabs) against influenza B virus were obtained by immunizing mice with B/Nagasaki/1/87, one of the strains of the B/Victoria group. Immunoprecipitation analysis revealed that individual Mabs precipitated the nucleoprotein (NP), the matrix protein (M) or the hemagglutinin protein (HA). By using these Mabs by the peroxidase-antiperoxidase (PAP) staining method, a rapid detection and identification method for influenza B virus was established. Monolayers of Madin-Darby canine kidney cells in microplates were infected with each-strain and incubated for about 24 h, and then were subjected to the PAP staining method using the Mabs as the first antibody. Influenza B virus strains are classified into two major phylogenetic trees, the B/Victoria group and the B/Yamagata group. When anti-NP and anti-M antibodies were used in the PAP staining method, all 13 influenza B virus strains isolated from clinical specimens between 1940 and 1994 were detected regardless of the antigenic drift of the influenza virus. On the other hand, several anti-HA Mabs which reacted specifically with the strains of the B/Victoria group, did not react with any strain of the B/Yamagata group. In the 1996/97 influenza season in Osaka Prefecture in Japan, two antigenically distinct groups of influenza B virus strains were isolated. They belonged to different phylogenetic trees and were clearly distinguishable by the PAP staining method with anti-HA Mabs.

Reduction in HTLV-I proviral load and spontaneous lymphoproliferation in HTLV-I-associated myelopathy/tropical spastic paraparesis patients treated with humanized anti-Tac

Human T-lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a neurological disease that results from an interaction of retroviral infection and immune activation. In this study, five doses (1 mg/kg) of humanized anti-Tac antibody were administered to 9 HAM/TSP patients at weeks 0, 2, 6, 10, and 14. Preliminary immunological studies on HAM/TSP patients treated with humanized anti-Tac indicate that there is a selective down-regulation of activated T cells and a decrease in the HTLV-I viral load in peripheral blood lymphocytes, most likely through the selective removal of HTLV-I-infected, activated CD4+ lymphocytes.

The effect of human beta2-microglobulin on major histocompatibility complex I peptide loading and the engineering of a high affinity variant. Implications for peptide-based vaccines

The ability to directly load cell surface major histocompatibility complex (MHC) class I molecules with peptides provides a potentially powerful approach toward the development of vaccines to generate cell-mediated immunity. We demonstrate that exogenous beta2-microglobulin (beta2m) stabilizes human cell surface MHC I molecules and facilitates their loading with exogenous peptides. Additionally, using three-dimensional crystal structures and known interaction sites between MHC I heavy chains and beta2m, we engineered variants of human beta2m (hbeta2m) with a single serine substitution at residue 55. This alteration was predicted to promote hydrophobic interactions at the MHC I heavy chain/beta2m interface and displace an ordered water molecule. Compared with hbeta2m, the serine to valine substitution at residue 55 had improved ability to bind to cell surface HLA-A1, HLA-A2, and HLA-A3 molecules, facilitate exogenous peptide loading, and promote recognition by peptide-specific T cells. The inclusion of hbeta2m or higher affinity variants when pulsing cells with MHC-restricted peptides increases the efficiency of peptide loading 50-80-fold. Therefore, the inclusion of hbeta2m in peptide-based vaccines may increase cell surface antigen densities above thresholds that allow recognition of peptide antigens by the immune system, particularly for cryptic, subdominant, or marginally antigenic peptides.

Mouse myocilin (Myoc) gene expression in ocular tissues

Human myocilin is identical to TIGR (trabecular meshwork inducible glucocorticoid response) which is responsible for the pathogenesis of juvenile-onset primary open angle glaucoma (GLCIA). We have isolated cDNA for mouse myocilin (Myoc) and investigated mouse myocilin gene expression in ocular tissues with in situ RNA hybridization. Hybridization signals were observed in the iris, ciliary body, trabecular meshwork, sclera, and retina in the mouse eye. The marked signals were seen in trabecular meshwork cells and the anterior portion of sclera. These findings suggest that myocilin mutation could affect the capacity of aqueous outflow and cause elevation of the intraocular pressure which is involved in the pathogenesis of glaucoma.

Demonstration of human T lymphotropic virus type I (HTLV-I) tax-specific CD8+ lymphocytes directly in peripheral blood of HTLV-I-associated myelopathy/tropical spastic paraparesis patients by intracellular cytokine detection

Human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is an inflammatory neurologic disease caused by HTLV-I infection and has been associated with elevated levels of several proinflammatory cytokines in both serum and cerebrospinal fluid. It is unknown what kind of cells secrete these cytokines and if HTLV-I Ags are associated with this phenomenon. Here, we investigated the expression of cytokines in PBL from eight HAM/TSP patients, nine HTLV-I-infected asymptomatic carriers, and seven healthy controls by flow cytometry combined with intracellular cytokine staining. PBL were cultured with brefeldin A without mitogen and IL-2 for 14 h. Under these conditions, CD8+ cells produced proinflammatory cytokines including IFN-gamma, TNF-alpha, and IL-2, which were significantly elevated in HAM/TSP patients. The proportion of CD8+ cells producing IFN-gamma in HAM/TSP patients, asymptomatic carriers, and healthy controls were, on average, 4.9, 0.4, and 0.3%, respectively. IFN-gamma production by these CD8+ cells was suppressed by anti-HLA-class I Ab. Purified CD8+ cells from an HLA-A2 HAM/TSP patient produced IFN-gamma by cocultivation with autologous CD4 cells, the main reservoir of HTLV-I in vivo, or allogenic HLA-A2+ B cells pulsed with a known immunodominant HTLV-I tax peptide. These data suggest that high levels of circulating HTLV-I-specific CD8+ T lymphocytes have the potential to produce proinflammatory cytokines and may promote inflammatory responses to HTLV-I in HAM/TSP patients.

Direct visualization of antigen-specific T cells: HTLV-1 Tax11-19- specific CD8(+) T cells are activated in peripheral blood and accumulate in cerebrospinal fluid from HAM/TSP patients

Human T lymphotropic virus type 1 (HTLV-1) -associated myelopathy/tropic spastic paraparesis is a demyelinating inflammatory neurologic disease associated with HTLV-1 infection. HTLV-1 Tax11-19-specific cytotoxic T cells have been isolated from HLA-A2-positive patients. We have used a peptide-loaded soluble HLA-A2-Ig complex to directly visualize HTLV-1 Tax11-19-specific T cells from peripheral blood and cerebrospinal fluid without in vitro stimulation. Five of six HTLV-1-associated myelopathy/tropic spastic paraparesis patients carried a significant number (up to 13.87%) of CD8(+) lymphocytes specific for the HTLV-1 Tax11-19 peptide in their peripheral blood, which were not found in healthy controls. Simultaneous comparison of peripheral blood and cerebrospinal fluid from one patient revealed 2.5-fold more Tax11-19-specific T cells in the cerebrospinal fluid (23.7% vs. 9.4% in peripheral blood lymphocyte). Tax11-19-specific T cells were seen consistently over a 9-yr time course in one patient as far as 19 yrs after the onset of clinical symptoms. Further analysis of HTLV-1 Tax11-19-specific CD8(+) T lymphocytes in HAM/TSP patients showed different expression patterns of activation markers, intracellular TNF-alpha and gamma-interferon depending on the severity of the disease. Thus, visualization of antigen-specific T cells demonstrates that HTLV-1 Tax11-19-specific CD8(+) T cells are activated, persist during the chronic phase of the disease, and accumulate in cerebrospinal fluid, showing their pivotal role in the pathogenesis of this neurologic disease.

Application of subtype-specific monoclonal antibodies for rapid detection and identification of influenza A and B viruses

We established a rapid method for the identification of influenza A and B virus strains: the peroxidase-antiperoxidase (PAP) staining method with two subtype-specific murine monoclonal antibodies, C179 (H1 and H2 specific) and F49 (H3 specific), and an anti-influenza B virus rabbit polyclonal serum. The types and subtypes of 160 strains were examined, and 158 strains were identified to be the same by the hemagglutination-inhibition (HI) test and the PAP method. In contrast to the results by the HI test, two strains were revealed to be a mixture of two subtypes (H1 and H3) by the PAP method, which was confirmed by plaque cloning. We further analyzed clinical specimens by the PAP method by directly inoculating specimens into Madin-Darby canine kidney cells in microplates. After 40 h of incubation, the types and subtypes of viruses in 52 of 152 specimens were clearly identified. Since the reactivities of the two monoclonal antibodies are not influenced by the antigenic drift of influenza virus, the newly developed method should be applicable not only for rapid diagnosis but also for the epidemiological study of influenza.

Genomic organization of the human myocilin gene (MYOC) responsible for primary open angle glaucoma (GLC1A)

Myocilin is a newly found cytoskeletal protein involved in the morphogenesis of the basal body, a major microtubule organizing center, of the ciliated epithelium. It was recently realized that myocilin is virtually identical to the independently reported protein TIGR (trabecular meshwork-induced glucocorticoid response), which is responsible for the pathogenesis of chromosome 1q-linked primary open angle glaucoma (GLC1A). In this paper, we determined the genomic organization of the myocilin (MYOC/TIGR) gene by analyzing the nucleotide sequence of the BAC clones containing the MYOC/TIGR gene. The MYOC/TIGR gene consists of three exons. Each of the two splice donor and acceptor sites agrees well with the GT/AG rule. Primer sets to amplify each of the three exons are designed. The 5'-flanking region of MYOC gene contains the TGTTCT sequence overlapped with a palindromic sequence TTCTTTTTAAAAAGAA, which appears to be a glucocorticoid responsive element. There is also a unique sequence of dinucleotide repeat [(GT)2AA(GT)4AC(GT)13] which may also serve as a regulatory element. These results should aid in further detection of the MYOC/TIGR gene mutation and in depth understanding of the tissue-specific MYOC gene regulation.

Cloning of the cDNA for a new member of the immunoglobulin superfamily (ISLR) containing leucine-rich repeat (LRR)

We isolated cDNAs for a novel protein with a calculated molecular mass of 46 kDa, containing a leucine-rich repeat (LRR) with conserved flanking sequences and a C2-type immunoglobulin (Ig)-like domain. This novel protein was considered to be a new member of the Ig superfamily and was named ISLR (immunoglobulin superfamily containing LRR). These domains are known to be important for protein-protein interaction or cell adhesion, and therefore it is possible that the novel protein ISLR may also interact with other proteins or cells. Northern blot analysis showed the presence of a 2.4-kb transcript in various human tissues including retina, heart, skeletal muscle, prostate, ovary, small intestine, thyroid, adrenal cortex, testis, stomach, and spinal cord as well as fetal lung and fetal kidney. The ISLR gene was mapped on human chromosome 15q23-q24 by fluorescence in situ hybridization.

Human T cell leukemia virus type I (HTLV-I)-specific CD8+ CTL clones from patients with HTLV-I-associated neurologic disease secrete proinflammatory cytokines, chemokines, and matrix metalloproteinase

Human T cell leukemia virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive neurologic disease characterized by marked degeneration of the spinal cord and the presence of infiltrating CD8+ T cells and macrophages. HAM/TSP patients have very high frequencies of HTLV-I-specific CD8+ CTL in peripheral blood and in cerebrospinal fluid. In this study, we show that HAM/TSP patients also have elevated levels of peripheral blood CD8+ T cells that produce intracellular IFN-gamma. To address the potential role of soluble mediators secreted by CD8+ T cells in the pathogenesis of HAM/TSP, we have analyzed the capacity of a panel of nine HTLV-I-specific CD8+ CTL clones derived from three HAM/TSP patients to secrete cytokines, chemokines, and matrix metalloproteinases. The results demonstrate that the majority of these CTL clones secrete IFN-gamma, TNF-alpha, macrophage-inflammatory protein-1alpha and -1beta, IL-16, and matrix metalloproteinase-9. These findings indicate that HTLV-I-specific CD8+ CTL are an important source of proinflammatory soluble mediators that may contribute significantly to the pathogenesis of HAM/TSP.

Human T cell leukemia virus type I (HTLV-I)-specific CD8+ CTL clones from patients with HTLV-I-associated neurologic disease secrete proinflammatory cytokines, chemokines, and matrix metalloproteinase

Human T cell leukemia virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic, progressive neurologic disease characterized by marked degeneration of the spinal cord and the presence of infiltrating CD8+ T cells and macrophages. HAM/TSP patients have very high frequencies of HTLV-I-specific CD8+ CTL in peripheral blood and in cerebrospinal fluid. In this study, we show that HAM/TSP patients also have elevated levels of peripheral blood CD8+ T cells that produce intracellular IFN-gamma. To address the potential role of soluble mediators secreted by CD8+ T cells in the pathogenesis of HAM/TSP, we have analyzed the capacity of a panel of nine HTLV-I-specific CD8+ CTL clones derived from three HAM/TSP patients to secrete cytokines, chemokines, and matrix metalloproteinases. The results demonstrate that the majority of these CTL clones secrete IFN-gamma, TNF-alpha, macrophage-inflammatory protein-1alpha and -1beta, IL-16, and matrix metalloproteinase-9. These findings indicate that HTLV-I-specific CD8+ CTL are an important source of proinflammatory soluble mediators that may contribute significantly to the pathogenesis of HAM/TSP.

cis-Acting inhibitory elements within the pol-env region of human T-cell leukemia virus type 1 possibly involved in viral persistence

Human T-cell leukemia virus type 1 (HTLV-1) remains latent throughout the life of the carrier, with cells containing the provirus and viral gene expression efficiently down-regulated. On a molecular level, exactly how viruses are down-regulated in vivo remains unresolved. We described here the possibility that down-regulation results from the presence of inhibitory elements within the gag-env region of the provirus in fresh peripheral blood mononuclear cells from carriers. In vitro experiments then revealed that potent cis-acting inhibitory elements (CIEs) are indeed contained in two discrete fragments from the pol region and weaker ones in the env region. The effect of CIEs is relieved by the HTLV-1 posttranscriptional regulator Rex through binding to the Rex-responsive element (RxRE), suggesting that Rex might interfere with pre-mRNA degradation and/or activate the export of mRNA molecules harboring both of the inhibitory elements and RxRE on the same RNA molecule. Thus, we propose the hypothesis that such functions of CIEs may be involved in HTLV-1 persistence.

Chronic sensory ataxic neuropathy and ophthalmoplegia with oculomotor nerve hypertrophy associated with IgM antibodies against gangliosides containing disialosyl groups

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Human BAC library: construction and rapid screening

We have constructed a human genomic bacterial artificial chromosome (BAC) library using high molecular weight DNA from a pre-pro-B cell line, FLEB14-14, with a normal male diploid karyotype. This BAC library consists of 96,000 clones with an average DNA insert size of 110 kb, covering the human genome approximately 3 times. The library can be screened by three different methods. (1) Probe hybridization to 31 high-density replica (HDR) filters: each filter contains 3072 BAC clones which were gridded in a 6 x 6 pattern. (2) Probe hybridization to two Southern blot filters to which 31 HindIII digests of the pooled 3072 BAC clones were loaded. This identifies a particular HDR filter for which further probe hybridization is performed to identify a particular clone(s). (3) Two-step polymerase chain reaction (PCR). First, PCR is applied to DNA samples prepared from ten superpools of 9600 BAC clones each to identify a particular superpool and the second PCR is applied to 40 unique DNA samples prepared from the four-dimensionally assigned BAC clones of the particular superpool. We present typical examples of the library screening using these three methods. The two-step PCR screening is particularly powerful since it allows us to isolate a desired BAC clone(s) within a day or so. The theoretical consideration of the advantage of this method is presented. Furthermore, we have adapted Vectorette method to our BAC library for the isolation of terminal sequences of the BAC DNA insert to facilitate contig formation by BAC walking.

A novel myosin-like protein (myocilin) expressed in the connecting cilium of the photoreceptor: molecular cloning, tissue expression, and chromosomal mapping

We have isolated a human cDNA clone encoding a novel acidic protein of MW 55,000 that we designated "myocilin" since it has homology to myosin and is localized preferentially in the ciliary rootlet and basal body of the connecting cilium of photoreceptor cells. The deduced amino acid sequence of human myocilin showed significant homologies with nonmuscle myosin of Dictyostelium discoideum in the N-terminal region and also with olfactomedin of bullfrog in the C-terminal region. Myocilin contained a leucine zipper-like motif similar to that seen in kinectin and other cytoskeletal proteins. These findings suggest that myocilin is a novel cytoskeletal protein involved in the morphogenesis of ciliated neuroepithelium such as photoreceptor cells. The myocilin gene (MYOC) was mapped to human chromosome 1q23-q24 by fluorescence in situ hybridization.

Neuropathology of HTLV-1-associated myelopathy (HAM/TSP)

In order to clarify pathogenesis of HAM/TSP, we performed a detailed neuropathologic analysis of seven autopsy patients with HAM/TSP. Inflammatory infiltrates of mononuclear cells and degeneration of myelin and axons were noted in the middle to lower thoracic spinal cords and were continuously extended to the entire spinal cord. Horizontal distribution of inflammatory lesions was symmetric at any spinal levels. Immunohistochemical analysis demonstrated T-cell dominance. The numbers of CD4+ T cells and CD8+ T cells were equally present in patients with shorter clinical course. Apoptosis of helper/inducer T cells were observed in the presence of TIA1+ cytotoxic T cells in these active inflammatory lesions. Inflammatory infiltrates were markedly decreased and CD8+/TIA1- T cells were predominated over CD4+ cells in patients with prolonged clinical course. HTLV-1 proviral DNA amounts in the freshly frozen spinal cord measured by quantitative PCR were well correlated with the numbers of infiltrated CD4+ cells. In situ PCR of HTLV-1 proviral DNA using multi-primary pairs demonstrated the presence of HTLV-1 infected cells exclusively in the mononuclear infiltrates of perivascular areas. From these findings, it is suggested that the target of the inflammatory process seen in HAM/TSP lesions may be HTLV-1 infected CD4+ T cells infiltrating the spinal cord.

Human retina-specific amine oxidase (RAO): cDNA cloning, tissue expression, and chromosomal mapping

In search of candidate genes for hereditary retinal disease, we have employed a subtractive and differential cDNA cloning strategy and isolated a novel retina-specific cDNA. Nucleotide sequence analysis revealed an open reading frame of 2187 bp, which encodes a 729-amino-acid protein with a calculated molecular mass of 80,644 Da. The putative protein contained a conserved domain of copper amine oxidase, which is found in various species from bacteria to mammals. It showed the highest homology to bovine serum amine oxidase, which is believed to control the level of serum biogenic amines. Northern blot analysis of human adult and fetal tissues revealed that the protein is expressed abundantly and specifically in retina as a 2.7-kb transcript. Thus, we considered this protein a human retina-specific amine oxidase (RAO). The RAO gene (AOC2) was mapped by fluorescence in situ hybridization to human chromosome 17q21. We propose that AOC2 may be a candidate gene for hereditary ocular diseases.

Chromosomal mapping of a family of human glutamine synthetase genes: functional gene (GLUL) on 1q25, pseudogene (GLULP) on 9p13, and three related genes (GLULL1, GLULL2, GLULL3) on 5q33, 11p15, and 11q24

Glutamine synthetase (GS) is a ubiquitous enzyme that catalyzes the ATP-dependent conversion of glutamate to glutamine using ammonia as the nitrogen source. Using human GS cDNA as a probe, a bacterial artificial chromosome (BAC) library consisting of two-fold coverage of the human genome was screened, and 18 clones were obtained. The restriction analysis of the human insert DNAs provided a basis to divide these 18 BAC clones into five groups, suggesting the existence of a GS gene family in the human genome. PCR analysis using three sets of primers designed from the reported sequences for GS cDNA and a processed pseudogene identified the corresponding BAC clones. Fluorescence in situ hybridization analysis revealed the chromosomal localization of these five genes: the GS gene to 1q25 (GLUL), the processed pseudogene to 9p13 (GLULP), and three related gene to 5q33 (GLULL1), 11p15 (GLULL2), and 11q24 (GLULL3), respectively.

Re-evaluation of myocardial FDG uptake in hyperglycemia

Myocardial [18F] fluorodeoxyglucose (FDG) uptake depends on several metabolic variables in vivo. The effect of different levels of experimentally induced hyperglycemia on myocardial FDG uptake was examined.

METHODS

FDG uptake was studied in young Donryu rats 1 hr after intravenous injection under various pretreatments that increased serum glucose levels. Serum samples were analyzed for glucose, insulin and free fatty acids. Myocardial distribution of FDG was examined with autoradiography.

RESULTS

Administration of glucose (n = 42), triiodothyronine (n = 7), epinephrine (n = 7), dehydroascorbic acid (n = 5) and 4 mg streptozotocin (Szt, n = 10) increased glucose levels to 120-200 mg/dl. Dexamethasone (Dex, n = 34) and 6 mg Szt (n = 6) increased glucose levels to 200-450 mg/dl. Myocardial FDG uptake increased proportionately with increases in serum glucose level up to 200 mg/dl. In severe hyperglycemia (serum glucose: 200-450 mg/dl), however, the FDG uptake decreased and did not correlate with blood glucose level. A study of fractional FDG uptake calibrated by the arterial FDG curve confirmed the same results. Heterogeneous distribution of FDG was observed in the myocardium, both in fasting and in severe hyperglycemic conditions. The pattern of FDG uptake by skeletal muscles was similar to that of the myocardium, although the uptake was lower than that in the myocardium. Changes in insulin and free fatty acids levels could not explain the FDG uptake pattern in severe hyperglycemia. Blood FDG uptake level remained constant regardless of glucose level.

CONCLUSION

Hyperglycemia induced a biphasic pattern of myocardial FDG uptake, common with skeletal muscles. The understanding of myocardial FDG uptake characteristics and their dependence on blood glucose is helpful in interpreting myocardial FDG-PET images.

Mutation rates in LTR of HTLV-1 in HAM/TSP patients and the carriers are similarly high to Tax/Rex-coding sequence

The genomic sequence of human T-cell leukemia virus type 1 (HTLV-1) is highly conserved, although minor sequence variations enable classification of the isolates into several subgroups. We previously reported, however, that the Tax-coding sequence of HTLV-1 genome is highly variable in a random fashion within individuals with HAM/TSP and asymptomatic carriers. Here, we describe frequent base substitutions in the LTR sequence similarly to those in Tax-coding sequence. These observations indicate that frequent mutations are not unique to the sequence encoding the most effective antigen for cytotoxic T lymphocytes, but also seen in the LTR, a non-coding sequence. Thus, frequent mutations seem to occur during the viral replication process rather than the selection of rare mutants by immune surveillance.

Feasibility of fluorine-18-fluorophenylalanine for tumor imaging compared with carbon-11-L-methionine

L-[methyl-11C]methionine (11C-Met) is a useful tracer for tumor imaging with PET. The drawbacks include a short half-life and high physiological accumulation in abdominal organs. To overcome these shortfalls, the feasible use of [18F]fluorophenylalanine (18F-Phe), which shares the same amino acid transport system with Met, for tumor imaging was examined.

METHODS

The time course of tissue distribution of 18F-Phe and the tumor uptake response to radiotherapy were compared with 14C-Met and [3H] thymidine (3H-Thd) in the rat AH109A tumor model. Intratumoral distribution of 18F-Phe was compared with 14C-Met and 14C-Thd using double-tracer macroautoradiography (ARG). We also evaluated whole-body ARG.

RESULTS

Tumor uptake of 18F-Phe peaked at 60 min postinjection and was higher than that of the liver, intestine and kidney but lower than the pancreas. Tumor uptake of 18F-Phe was similar to that of 14C-Met. Tumor-to-blood and tumor-to-muscle ratios were higher in 14C-Met compared with that of 18F-Phe because of the rapid blood clearance of 14C-Met. With whole-body ARG, the tumor was clearly visualized with high contrast. Radiotherapeutic response of tumor uptake of 18F-Phe was as rapid as that with 14C-Met and with 3H-Thd. Intratumoral distribution of 18F-Phe and 14C-Met were identical, and 18F-Phe and 14C-Thd were similar.

CONCLUSION

Fluorine-18-Phe seems to be a potentially useful amino acid tracer for tumor imaging with a longer half-life than 11C, with higher tumor contrast in the abdomen than Met and a similar sensitive response to radiotherapy.

Sequence analysis of human T cell lymphotropic virus type I (HTLV-I) Env genes amplified from central nervous system tissues of patients with HTLV-I-associated myelopathy or leukemia

Human T cell lymphotropic virus type I (HTLV-I) is a retrovirus that has been linked to HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP), a chronic or inflammatory neurological disease with some resemblance to multiple sclerosis. We used the polymerase chain reaction to amplify viral env genes in foci of inflammation and demyelination in the nervous system to adduce additional evidence of the association of HTLV-I with the neuropathological changes in HAM/TSP, and document in this report such an association. We also sought evidence of a distinct viral species in the lesions by amplifying, cloning and sequencing the env genes from tissues sections in which there were pathological changes. We did not find changes in the env gene that correlated with HTLV-I-associated neurological disease vs adult T cell leukemia or with the nervous system vs peripheral blood and lymphoid organs. We did, however, find evidence of extensive mutation and possibly deletions in the env gene in HTLV-I-associated neurological disease. We interpret these findings of increased genetic diversity as a reflection of higher rates of viral replication in HTLV-I-associated myelopathy that support a model of pathogenesis in which increased viral replication activates immune cells that subsequently enter the nervous system and cause injury by immunopathological mechanisms.