Human herpesvirus 6 in hematologic diseases in China

BACKGROUND AND OBJECTIVE

The prevalence and pathogenic role of human herpesvirus 6 (HHV-6) in various benign and malignant hematologic diseases remain largely unknown. The aim of this study was to search for a possible involvement of HHV-6 in the pathogenesis of hematologic diseases.

DESIGN AND METHODS

The presence of HHV-6 DNA sequences was examined by polymerase chain reaction (PCR) in bone marrow mononuclear cells from 241 patients with benign and malignant hematologic diseases in China. Platelet-associated immunoglobulin (PAIg) of 66 idiopathic thrombocytopenic purpura (ITP) patients was measured by competitive enzyme-linked immunosorbent assay. The presence of HHV-6 DNA in sera from 31 ITP patients was examined by PCR. Paired serum samples from 19 ITP patients were analyzed for anti-HHV-6 IgG titers using an indirect immunofluorescence assay.

RESULTS

HHV-6 DNA was detected in 41% and 37.5% of ITP and acute leukemia patients respectively, but in only 6.7% of patients with iron deficiency anemia. HHV-6 positivity for ITP patients with excessive PAIgG was significantly higher than in patients with a normal level of PAIgG. HHV-6 DNA was not detected in any of the serum samples from ITP patients. None of the 19 cases of ITP showed a significant increase in anti-HHV-6 antibody titers during the convalescent phase compared with the onset phase.

INTERPRETATION AND CONCLUSIONS

Our results indicate that HHV-6 infection might be associated with excessive PAIgG in some cases of ITP, and that the virus persists in a latent state. The pathogenic role of HHV-6 in ITP needs to be confirmed by further investigations.

Identification of Mad as a repressor of the human telomerase (hTERT) gene

Activation of telomerase, which has been frequently associated with cellular immortality, may constitute a key step in the development of human cancer. De-repression in the expression of its catalytic subunit hTERT gene has been proposed to directly link to the telomerase activation in tumor cells. Little is known about the mechanism how the hTERT gene is repressed in telomerase-negative mortal cells. This study was conducted, using an expression cloning approach, with the aim of identifying the gene(s) responsible for repressing the hTERT gene expression. Using this genetic screen, we isolated the transcription factor Mad as a repressor. Mutation of its DNA binding sites caused significant de-repression of hTERT promoter activity in mortal cells. This Mad-mediated repression of the hTERT promoter in mortal cells was counteracted by ectopic expression of Myc. The antagonism between Mad and Myc was also observed with an endogenous hTERT promoter. Their potential roles in differential hTERT promoter activities were further supported by the relative amounts of Mad and Myc proteins detected in immortal and mortal cells. Thus, Mad may be a direct negative regulator of hTERT in mortal cells and this repression mechanism can be inhibited by induction of Myc in immortal cells.

Activation of interferon regulatory factor 3 in response to DNA-damaging agents

Genotoxic stress triggers signal transduction pathways that mediate either the protection or apoptosis of affected cells. The interferon regulatory factors (IRFs) are involved in a wide range of host defense mechanisms against environmental stresses. Treatment with DNA-damaging agents, including doxorubicin and UV radiation, caused phosphorylation of the IRF3 transcription factor. Phosphorylation of IRF3 induced its interaction with the transcriptional co-activator cAMP-response element binding protein-binding protein. Furthermore, genotoxic stress-induced phosphorylation of IRF3 resulted in its movement from the cytoplasm to the nucleus, where it activated transcription from its binding site. These observations suggest that IRF3 plays a role in the defensive responses induced by genotoxic stress.

In vivo and in vitro analyses of Myc for differential promoter activities of the human telomerase (hTERT) gene in normal and tumor cells

Induction of the catalytic subunit of human telomerase, hTERT, plays a critical role in the activation of telomerase during tumorigenesis. Here, we isolate the hTERT gene promoter and define the functional promoter region, which is inactive in normal cells but active in tumor cells. Myc directly interacts with the hTERT promoter and activates its transcription both in vivo and in vitro. Activation or repression of Myc can alter hTERT promoter activities in normal or tumor cells. Furthermore, we detect high levels of Myc protein in tumor cells compared with normal cells. The ability of Myc to modulate the activity of the hTERT promoter and, hence, the telomerase enzyme may contribute to its ability to promote tumor formation.

Cellular localization of alpha3beta1 integrin isoforms in association with myofibrillogenesis during cardiac myocyte development in culture

The cellular localization of alpha3beta1 integrin isoforms was examined in cultured neonatal myocytes at selected times during development using double immunofluorescence assays. The distribution of alpha3A subunits began as diffuse and patternless, but as the cells matured, the distribution assumed a sarcomeric banding pattern, and alpha3A appeared to be localized in costameres - sarcolemmal regions adjacent to the Z-disks. Alpha-actinin, a component of the Z-disk, was localized in the same intracellular regions. Temporal analysis of the incorporation of the alpha3A subunit and other myofibrillar proteins into sarcomeres revealed that alpha3A was integrated into sarcomeres following incorporation of alpha-actinin and myosin heavy chain (MHC) but prior to that of desmin. This suggests that alpha3A integrins are incorporated into a pre-existing myofibrillar structure, and it is unlikely that alpha3A integrins participate in the initial assembly of myofibrillar proteins. The alpha3B, beta1A and beta1D subunits were also localized in costameres, where they formed alpha3Abeta1A, alpha3Abeta1D and alpha3Bbeta1A heterodimers. The alpha3Bbeta1D heterodimer, however, was not found in cardiac myocytes. The antisera raised against the cytoplasmic domains of alpha3A, alpha3B, beta1A and beta1D caused disruption of sarcomere structure. Thus, the myofibril-extracellular matrix linkages mediated by isoforms of alpha3beta1 integrin may play a crucial role in the stabilization of myofibril assembly and in the maintenance of sarcomere structure. Co-immunoprecipitation experiments revealed that beta1A, but not beta1D, interacts with the Nck signaling protein, suggesting that Nck participates in downstream signaling triggered by beta1A and that the beta1A-mediated signaling pathway is distinct from that of beta1D.

The structure of the nucleotide-binding site of kinesin

Kinesin is a microtubule-based motor protein responsible for anterograde transport of vesicles and organelles in nerve axons and other cell types. The energy necessary for this transport is derived from the hydrolysis of ATP which is thought to induce conformational changes in the protein. We have solved the X-ray crystal structures of rat brain kinesin in three conditions intended to mimic different nucleotide states: (1) with ADP bound to the nucleotide-binding site, (2) with bound ADP in the presence of AIF(-)4, and (3) with ADP hydrolyzed to AMP by apyrase. In contrast to analogous cases observed in GTP-binding proteins or the muscle motor myosin, the structure of kinesin remained nearly unchanged. This highlights the stability of kinesin's ADP state in the absence of microtubules. Surprisingly, even after hydrolysis of ADP to AMP by apyrase a strong density peak remains at the position of the beta-phosphate which is compatible either with a phosphate or a sulfate from the solvent and appears to stabilize the nucleotide-binding pocket through several hydrogen bonds.

Physical and meiotic mapping of the region of human chromosome 4q11-q13 encompassing the vitamin D binding protein DBP/Gc-globulin and albumin multigene cluster

The vitamin D binding protein/Gc-globulin (DBP) gene is a member of a multigene cluster that includes albumin (ALB), alpha-fetoprotein (AFP), and alpha-albumin/afamin (AFM). All four genes have structural and functional similarities and map to the same chromosomal regions in humans (4q11-q13), mice, and rats. An accurate physical map of the region encompassing these genes is a prerequisite for study of their respective transcriptional regulation and identification of potential shared regulatory elements. By refining the physical and meiotic maps of the 4q11-q13 region and creating a local PAC contig, the order and transcriptional orientations of these four genes were determined to be centromere-3'-DBP-5'-5'-ALB-3'-5'-AFP-3'-5'-AFM3'-telomere. The ancestral DBP gene was separated from the ALB gene by >1.5 Mb. This organization and spacing establishes a foundation for ongoing functional studies in this region.

Induction of GADD45 and JNK/SAPK-dependent apoptosis following inducible expression of BRCA1

The breast cancer susceptibility gene BRCA1 encodes a protein implicated in the cellular response to DNA damage, with postulated roles in homologous recombination as well as transcriptional regulation. To identify downstream target genes, we established cell lines with tightly regulated inducible expression of BRCA1. High-density oligonucleotide arrays were used to analyze gene expression profiles at various times following BRCA1 induction. A major BRCA1 target is the DNA damage-responsive gene GADD45. Induction of BRCA1 triggers apoptosis through activation of c-Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), a signaling pathway potentially linked to GADD45 gene family members. The p53-independent induction of GADD45 by BRCA1 and its activation of JNK/SAPK suggest a pathway for BRCA1-induced apoptosis.

Vitamin D-binding protein gene transcription is regulated by the relative abundance of hepatocyte nuclear factors 1alpha and 1beta

Vitamin D-binding protein (DBP)/Gc-globulin, the major carrier of vitamin D and its metabolites in blood, is synthesized predominantly in the liver in a developmentally regulated fashion. By transient transfection analysis, we identified three regions in the 5'-flanking region of the rat DBP gene, segments F-2, B, and A, that contain tissue-specific transcriptional determinants. Gel mobility shift and DNase I footprinting analyses showed that all three regions contained binding sites for the hepatocyte nuclear factor 1 (HNF1), a transcriptional regulator composed of HNF1alpha and HNF1beta hetero- and homodimers. The activity of the most proximal segment A (coordinates -141 to -43) was DBP promoter-specific, position-dependent, and positively controlled by HNF1alpha. In contrast, the two more distal determinants (segments F-2 and B; coordinates -1844 to -1621 and -254 to -140, respectively) acted as classical enhancers in transfected hepatocyte-derived HepG2 cells; their activities were promoter- and orientation-independent, and disruption of their respective HNF1-binding sites resulted in marked loss of DBP gene expression. Remarkably, the activities of these two distal elements depended upon the relative levels of HNF1alpha and HNF1beta; HNF1alpha had a major stimulatory effect, whereas HNF1beta acted as a trans-dominant inhibitor of HNF1alpha-mediated enhancer activity. These results suggested that the net expression of the DBP gene reflected a balance between the two major HNF1 species; the relative abundance of HNF1alpha and HNF1beta proteins in a cell may thus play a critical role in determining the pattern of gene expression.

The interaction of phospholipid liposomes with bacteria and their use in the delivery of bactericides

Liposomes have been prepared from dipalmitoylphosphatidylcholine (DPPC) incorporating the cationic lipids stearylamine (SA), dimethyldioctadecylammonium bromide (DDAB) and dimethylaminoethane carbamoyl cholesterol (DCchol) and the anionic lipids dipalmitoylphosphatidylglycerol (DPPG) and phosphatidylinositol (PI). Their adsorption to biofilms of skin-associated bacteria (Staphylococcus epidermidis and Proteus vulgaris) and oral bacteria (Streptococcus mutans and sanguis) has been investigated as a function of mole % cationic and anionic lipid. Targeting (adsorption) was most effective for the systems DPPC-chol-SA, DPPC-DPPG and DPPC-PI liposomes to S. epidermidis. The effect of extracellular mucopolysaccharide on targeting was investigated for S. epidermidis biofilms. It was found that targeting increased with the level of extracellular mucopolysaccharide for all liposome compositions studied. The delivery of the oil-soluble bactericide Triclosan and the water soluble bactericide chlorhexidine was studied for a number of liposomal compositions. Superior delivery of both bactericides relative to the free bactericide occurred for DPPC-chol-SA liposomes and for Triclosan delivery by DPPC-DPPG and DPPC-PI liposomes targeted to S. epidermidis at low bactericide concentrations. DPPC-chol-SA liposomes were also effective for delivery of Triclosan to S. sanguis biofilms. Double labelling experiments using [14C]-chlorhexidine and [3H]-DPPC suggested that there was exchange between adsorbed liposomes which had delivered bactericide to the biofilm and those in the bulk solution implying a diffusion mechanism for bactericide delivery.

Enhancement of J6-1 human leukemic cell proliferation by membrane-bound M-CSF through a cell-cell contact mechanism II. Role of an M-CSF receptor-like membrane protein

We have isolated an M-CSF-like membrane-associated growth factor from human leukemic J6-1 cells that can enhance the growth and colony formation of J6-1 cells in vitro. Indirect evidence suggests that this membrane-associated M-CSF-like growth factor may do so by stimulating a corresponding receptor co-expressed on the adjacent J6-1 cells. The objective of this study is to isolate the putative receptor in J6-1 cells by virtue of its ability to bind and thus "block" the growth of J6-1 cells. Based on this approach, we have isolated from the J6-1 cell membrane an inhibitory activity that can inhibit the clonal growth of J6-1 cells. The activity of this inhibitor can be readily neutralized by either anti-M-CSFR MAb or anti-M-CSFR antiserum, suggesting that it is related to M-CSFR, a product of c-fms proto-oncogene. Judging from Sephadex G-200 gel filtration, the molecular weight (MW) of this putative M-CSFR-like inhibitor was estimated to be approx. 150-180 kDa, comparable with that of M-CSFR. The specificity of M-CSFR-like protein to recognize and block membrane-bound M-CSF also was implicated by its ability to upregulate the steady-state levels of c-fms mRNA in J6-1 cells. Besides its antiproliferative activity in vitro, treatment of J6-1 cells with the putative receptor protein before inoculation effectively blocked the growth and tumor formation in vivo by J6-1 cells in a nude mouse model. These findings suggest that the growth and tumor development by J6-1 leukemic cells may involve a contact-mediated "juxtacrine mechanism".

Cloning of a SH3 domain-containing proline-rich protein, p85SPR, and its localization in focal adhesion

A mouse thymus cDNA expression library was screened with monoclonal antibody (mAb), B16-5 which binds to common epitope in SH3 domains of phospholipase C-gamma 1 (PLC-gamma 1) and Nck. We have determined the complete nucleotide sequence of one of several positive clones. The 4,172 bp cDNA clone (GenBank Accession No. U96634) encodes a SH3 domain-containing protein of 646 amino acids. Besides the SH3 domain, the predicted protein has a proline-rich region, nuclear localization signals, and leucine zipper motifs. The expressed protein in Sf9 insect cell exhibits a polypeptide of 85 kDa on SDS-PAGE. The protein is widely distributed in rat tissue with an especially high level of expression in brain and testis. Interestingly, the specific antibodies detected four related proteins of different size (75, 85, 90 and 105 kDa) in brain. In A431 cell, p85SPR is enriched at focal adhesion points indicating that the protein may interact with protein(s) in focal complexes.

Recombinant brain 4-aminobutyrate aminotransferases overexpression, purification, and identification of Lys-330 at the active site

4-Aminobutyrate aminotransferase (4-aminobutyrate: 2-oxoglutarate aminotransferase EC 2.6.1.19) is a key enzyme of the 4-aminobutyric acid shunt. It catalyzes the conversion of 4-aminobutyrate to succinic semialdehyde. In an effort to clarify the structure-function relationships of 4-aminobutyrate aminotransferase, we analyzed 4-aminobutyrate aminotransferase cDNA from pig brain. The inclusion bodies were formed when recombinant 4-aminobutyrate aminotransferase was overexpressed in Escherichia coli. The unfolded overproduced proteins, were purified by hydroxylapatite chromatography in the presence of urea and refolded by a sequential dialysis method. The renatured protein regained its catalytic activity. The lysyl residue at the 330 position of the amino-acid sequence serves as the anchoring site of the cofactor pyridoxal 5'-P. To verify the catalytic site of 4-aminobutyrate aminotransferase, lysine 330 was mutated to arginine by site-specific mutagenesis. Overexpression and purification of the mutated 4-aminobutyrate aminotransferase (K330R) were performed by the same method used the purification of wild-type 4-aminobutyrate aminotransferase. The purified and renatured K330R protein did not show the catalytic activity of wild type 4-aminobutyrate aminotransferase. Furthermore, the mutated protein did not show any absorption band over the spectral range of 320-460 nm characteristic of pyridoxal 5'-P covalently linked to the protein. From the results presented here, it is concluded that lysine 330 is essential for the catalytic function of the aminotransferase.

Gallbladder motility change in late pregnancy and after delivery

OBJECTIVES

The incidence of gallstone disease has increased recently in Korea and there seems to be an increased prevalence of gallstones when in association with pregnancy. Although the pathogenesis is incompletely defined, and altered motility of the gallbladder may contribute to the increased risk of gallstones during pregnancy.

METHODS

We measured gallbladder volume using real-time ultrasonography to find out the mechanism for the changes of gallbladder motility during late pregnancy. Eighteen pregnant women took the gallbladder ultrasonography during their last trimester of pregnancy and after delivery; gallbladder volume and ejection fraction were calculated in each patient.

RESULTS

Fasting gallbladder volumes increased significantly in the last trimester of pregnancy (25.28 +/- 14.26ml) compared with postpartum (17.44 +/- 5.82 ml) (p < 0.05). Gallbladder volumes measured after fatty meals showed more increment in pregnant women (10.13 +/- 7.19 ml) than in those after delivery (4.34 +/- 3.36 ml) (p < 0.005). A significantly reduced gallbladder ejection fraction was found in the pregnant group (60.56 +/- 18.80%) compared with those after delivery (77.48 +/- 13.37%) (p < 0.005).

CONCLUSION

Gallbladder motility in late pregnancy shows significant impairment compared with that in postpartum. Thus, we suggest that gallbladder hypomotility may occur during late pregnancy, and this impairment of gallbladder motility may play an important role in gallstone formation.

The nature of autoantigens targeted in autoimmune endocrine diseases

Autoimmune endocrine diseases result from autoimmune processes involving autoreactive T cells and/or autoantibodies. Considerable progress has been made in elucidating the self- (auto-) antigens involved in these processes. These include tissue-specific membrane receptors, enzymes and secreted hormones. As discussed here by Yao-Hua Song and colleagues, diagnostic and therapeutic applications should now result from these discoveries.

Autoantibodies to the extracellular domain of the calcium sensing receptor in patients with acquired hypoparathyroidism

Acquired hypoparathyroidism (AH) has been considered to result from an autoimmune process but the self-antigens have not been identified. We studied 25 patients with AH, of which 17 had type I autoimmune polyglandular syndrome and 8 had AH associated with autoimmune hypothyroidism. Five of 25 (20%) AH sera reacted to a membrane-associated antigen of 120-140 kD in human parathyroid gland extracts using immunoblot analysis. This is the exact size of the calcium sensing receptor (Ca-SR). The AH sera were then tested by immunoblot using a membrane fraction of HEK-293 cells transfected with Ca-SR cDNA. Eight of 25 (32%) AH sera reacted to a 120-140-kD protein, which closely matched that recognized by the anti-Ca-SR IgG raised in rabbits. The Ca-SR cDNA was translated in vitro into two parts in order to identify the antigenic epitopes. By using this technique, 14 of 25 (56%) AH sera were positive to the extracellular domain of the Ca-SR, whereas none of the AH patients sera reacted to the intracellular domain. The reactivity of the positive sera was completely removed after pre-absorption with the Ca-SR containing membranes. Sera from 50 patients with various other autoimmune diseases as well as 22 normal controls were also tested, and none of them was positive. In conclusion, the Ca-SR has been identified as an autoantigen in AH.

On the structure of microtubules, tau, and paired helical filaments

Microtubules and their associated proteins form the basis of axonal transport; they are degraded during the neuronal degeneration in Alzheimer's disease. This article surveys recent results on the structure of microtubules, tau protein, and PHFs. Microtubules have been investigated by electron microscopy and image processing after labeling them with the head domain of the motor protein kinesin. This reveals the arrangement of tubulin subunits in microtubules and the shape of the tubulin-motor complex. Tau protein was studied by electron microscopy, solution X-ray scattering, and spectroscopic methods. It appears as an elongated molecule (about 35 nm) without recognizable secondary structure. Alzheimer PHFs were examined by FTIR and X-ray diffraction; they, too, show evidence for secondary structure such as beta sheets.

Activation of T lymphocyte subsets by synthetic TSH receptor peptides and recombinant glutamate decarboxylase in autoimmune thyroid disease and insulin-dependent diabetes

We have postulated that a defect in specific antigenic induction of suppressor T lymphocytes may account for the immunoregulatory disorder in autoimmune thyroid disease. In this context, we have measured the proliferative responses of peripheral blood mononuclear cells (PBMC) to the synthetic peptides corresponding to the extracellular domain of the TSH receptor (TSHR) and recombinant glutamate decarboxylase (GAD65) by means of 3H thymidine incorporation. We have also studied the antigenic activation of CD4+ and CD8+ T lymphocytes by measuring human leukocyte antigen-DR (HLA-DR) expression on the cell surface by flow cytometric analysis. PBMC obtained from 47 patients with Graves' disease (GD) [including 19 hyperthyroid GD (hyper GD)], 18 with Hashimoto's thyroiditis (HT), 7 with nontoxic nodular goiter (NG), 18 with insulin-dependent diabetes (IDDM), and 20 normal controls (N), were cultured for 7 days in the presence or absence of the pool peptides representing 3 different segments of TSHR or GAD65 at final concentration of 30 micrograms/mL or 10 micrograms/mL. The proportion of subjects whose PBMC gave a positive proliferative response with a stimulation index (SI) of over 2.3 (i.e. above the mean +2 SD for N) to TSHR peptides was significantly higher in the hyper GD group than among euthyroid GD (eu GD), HT, IDDM, and N group. The corresponding differences in mean SI provided analogous results, showing significant responses above normal in only hyper GD. The CD4+ T lymphocytes from hyper GD group were significantly more activated by TSHR peptides compared to eu GD, HT, IDDM, and N, and this induction correlated to their thyroid hormone levels. Quite differently, the activation of CD8+ T lymphocytes from both hyper GD and eu GD group in response to TSHR peptides was impaired compared to HT, IDDM, and the N group; in contrast to the findings with CD4+ T lymphocytes, this was independent of thyroid hormone levels. On the other hand, while the CD8+ T lymphocytes from GD and N groups were activated equally by GAD65, the activation of CD8+ T lymphocytes from the IDDM group by GAD65 was impaired compared to the GD and N groups. In conclusion, the activation of CD8+ T lymphocytes from GD and IDDM by relevant antigens (i.e. TSHR peptides for GD and GAD65 for IDDM) was impaired, but not by irrelevant antigens (i.e. GAD65 for GD and TSHR peptides for IDDM). There was also a modest stimulation of CD8+ T cells from all groups by tetanus toxoid and cardiac myosin light chain peptide, both irrelevant antigens.(ABSTRACT TRUNCATED AT 400 WORDS)

Insulin immunization of nonobese diabetic mice induces a protective insulitis characterized by diminished intraislet interferon-gamma transcription

We reported previously that daily injections of isophane insulin prevented both hyperglycemia and insulitis in nonobese diabetic (NOD) mice (Atkinson, M., N. Maclaren; and R. Luchetta. 1990. Diabetes. 39:933-937). The possible mechanisms responsible include reduced immunogenicity of pancreatic beta-cells from "beta-cell rest" and induced active immunoregulation to insulin (Aaen, IK., J. Rygaard, K. Josefsen, H. Petersen, C. H. Brogren, T. Horn, and K. Buschard. 1990. Diabetes. 39:697-701). We report here that intermittent immunizations with insulin or its metabolically inactive B-chain in incomplete Freund's adjuvant also prevent diabetes in NOD mice, whereas immunizations with A-chain insulin or with BSA do not. Adoptive transfer of splenocytes from B-chain insulin-immunized mice prevented diabetes in recipients co-infused with diabetogenic spleen cells, an effect that was abolished by prior in vivo elimination of either CD4+ or CD8+ cells. Insulin immunization did not reduce the extent of intraislet inflammation (insulitis); however, it did abolish expression of IFN-gamma mRNA within the insulitis lesions. Immunizations with insulin thus induce an active suppressive response to determinants on the B-chain that converts the insulitis lesion from one that is destructive to one that is protective.

The anatomy of flagellar microtubules: polarity, seam, junctions, and lattice

Although the overall structures of flagellar and cytoplasmic microtubules are understood, many details have remained a matter of debate. In particular, studies of the arrangement of tubulin subunits have been hampered by the low contrast of the tubulin subunits. This problem can now be addressed by the kinesin decoration technique. We have shown previously that the recombinant kinesin head domain binds to beta-tubulin, thus enhancing the contrast between alpha- and beta-tubulin in the electron microscope; this allows one to study the arrangement of tubulin dimers. Here we describe the lattices of the four different types of microtubules in eukaryotic flagellar axonemes (outer doublet A and B, central pair C1 and C2). They could all be labeled with kinesin head with an 8-nm axial periodicity (the tubulin dimer repeat), and all of them showed the B-surface lattice. This lattice is characterized by a 0.92-nm stagger between adjacent protofilaments. The B-lattice was observed on the axonemal microtubules as well as on extensions made by polymerizing porcine brain tubulin onto axonemal microtubules in the proximal and distal directions. This emphasizes that axonemal microtubules serve as high fidelity templates for seeding microtubules. The presence of a B-lattice implies that there must be a helical discontinuity ("seam") in the wall. This discontinuity is now placed near protofilaments A1 and A2 of the A-tubule, close to the inner junction between A- and B-microtubules. The two junctions differ in structure: the protofilaments of the inner junction (A1-B10) are staggered roughly by half a dimer, those of the outer junction (A10-B1) are roughly in register. Of the two junctions the inner one appears to have the stronger bonds, whereas the outer one is more labile and opens up easily, generating "composite sheets" with chevron patterns from which the polarity can be deduced (arrow in the plus direction). Decorated microtubules have a clear polarity. We find that all flagellar microtubules have the same polarities. The orientation of the dimers is such that the plus end terminates with a crown of alpha subunits, the minus end terminates with beta subunits which thus could be in contact with gamma-tubulin at the nucleation centers.

The targeting of phospholipid liposomes to bacteria

Phospholipid liposomes have been prepared from phospholipid mixtures including dipalmitoylphosphatidylcholine/phosphatidylinositol (DPPC/PI) and DPPC/dipalmitoylphosphatidylglycerol (DPPC/DPPG) mixtures and targeted to adsorbed biofilms of the skin-associated bacteria Staphylococcus epidermidis and Proteus vulgaris and the oral bacterium Streptococcus sanguis. The effects of time, liposome concentration and density of bacteria in the biofilm have been studied in detail for Staphylococcus epidermidis. The targeting (as assessed by the apparent monolayer coverage of the biofilms by liposomes) to the biofilms was found to be sensitive to the mol% of PI and DPPG in the liposomes and optimum levels of PI were found for targeting to each bacterium. The use of PI and DPPG-containing liposomes for the delivery of the bactericide, Triclosan, to biofilms of Staphylococcus epidermidis was studied as a function of the amount of Triclosan carried by the liposomes. All the liposome systems tested inhibited the growth of bacteria from the biofilms after brief (2 min) exposure to Triclosan-carrying liposomes. At low Triclosan levels bacterial growth inhibition by Triclosan-carrying liposomes exceeded that by an equivalent level of free Triclosan. After short periods (min) of exposure of biofilms to Triclosan-carrying liposomes the bactericide was shown to preferentially concentrate in the biofilms relative to its liposomal lipid carrier. The results suggest that phospholipid liposomes with appropriately chosen lipid composition have potential for the targeting and delivery of bactericide to bacteria.

Enhancement of J6-1 human leukemic cell proliferation by cell-cell contact: role of an M-CSF-like membrane-associated growth factor MAF-J6-1

Density-dependent cell proliferation and cluster formation are growth phenotypes frequently associated with leukemia cells. The secretion of autocrine growth factor, such as granulocyte-macrophage colony stimulating factor (GM-CSF) and interleukin 1 (IL-1), has been implicated as one possible mechanism in leukemogenesis. In many cases, however, leukemia cells do not appear to produce autocrine growth stimulators. J6-1 is an established human myeloid leukemia cell line that exhibits both density-dependent and cluster-forming growth characteristics. The effect of direct cell-cell contact on J6-1 cell proliferation was investigated. We have isolated from J6-1 cells a membrane-bound factor (designated as MAF-J6-1) that promoted the colony formation by both J6-1 cells and mouse bone marrow CFU-GM. The growth-promoting activity of MAF-J6-1 can be neutralized by either anti-macrophage-CSF (M-CSF or CSF-1) or anti-MAF-J6-1 monoclonal antibodies (MAb), suggesting that MAF-J6-1 is related to M-CSF. Using an immunoblot analysis with anti-MAF-J6-1 MAb, the MW of this membrane-associated factor was estimated to be 80 kDa. Both antibodies also induced a modest growth inhibition on J6-1 cells in vitro. Similarly, addition of exogenous recombinant human M-CSF augmented the colony formation by J6-1 cells, an effect also neutralized by both antibodies. Using an in situ hybridization technique, J6-1 cells were found to express a high level of c-fms proto-oncogene, which encodes the receptor for the M-CSF. Taken together, our results suggest that the membrane-bound MAF-J6-1 promote J6-1 cell proliferation and cluster formation through a 'juxtacrine' mechanism.

The role of tyrosinase in autoimmune vitiligo

Vitiligo is a common depigmenting skin disease, associated with certain autoimmune endocrinopathies, and autoantibodies to several antigens can be found in melanoma cells. We set out to identify the antigens. We examined 26 patients with vitiligo and associated endocrine disease. Of these, 18 patients (77%) and 8 immediate family members had autoantibodies specific for a 69 kDa protein in HTB-70 human melanoma cells that was not seen in control cells. The autoantibody-positive patient sera reacted with recombinant human tyrosinase expressed in Escherichia coli seen by western blots, as did antibodies raised in rabbits against hamster tyrosinase, but not to recombinant tyrosinase-related protein. Not one of 31 normal controls or 8 patients with alopecia or systemic lupus erythematosus had tyrosinase autoantibodies but a small proportion (12%) of 42 patients with autoimmune endocrine disease without a history of vitiligo had them. The results show that tyrosinase, an enzyme important in melanin formation, is a principal autoantigen of autoimmune vitiligo.