Immunologic tolerance maintained by CD25+ CD4+ regulatory T cells: their common role in controlling autoimmunity, tumor immunity, and transplantation tolerance

There is accumulating evidence that T-cell-mediated dominant control of self-reactive T-cells contributes to the maintenance of immunologic self-tolerance and its alteration can cause autoimmune disease. Efforts to delineate such a regulatory T-cell population have revealed that CD25+ cells in the CD4+ population in normal naive animals bear the ability to prevent autoimmune disease in vivo and, upon antigenic stimulation, suppress the activation/proliferation of other T cells in vitro. The CD25+ CD4+ regulatory T cells, which are naturally anergic and suppressive, appear to be produced by the normal thymus as a functionally distinct subpopulation of T cells. They play critical roles not only in preventing autoimmunity but also in controlling tumor immunity and transplantation tolerance.

A molecular marker for chloroquine-resistant falciparum malaria

BACKGROUND

Chloroquine-resistant Plasmodium falciparum malaria is a major health problem, particularly in sub-Saharan Africa. Chloroquine resistance has been associated in vitro with point mutations in two genes, pfcrt and pfmdr 1, which encode the P. falciparum digestive-vacuole transmembrane proteins PfCRT and Pgh1, respectively.

METHODS

To assess the value of these mutations as markers for clinical chloroquine resistance, we measured the association between the mutations and the response to chloroquine treatment in patients with uncomplicated falciparum malaria in Mali. The frequencies of the mutations in patients before and after treatment were compared for evidence of selection of resistance factors as a result of exposure to chloroquine.

RESULTS

The pfcrt mutation resulting in the substitution of threonine (T76) for lysine at position 76 was present in all 60 samples from patients with chloroquine-resistant infections (those that persisted or recurred after treatment), as compared with a base-line prevalence of 41 percent in samples obtained before treatment from 116 randomly selected patients (P<0.001), indicating absolute selection for this mutation. The pfmdr 1 mutation resulting in the substitution of tyrosine for asparagine at position 86 was also selected for, since it was present in 48 of 56 post-treatment samples from patients with chloroquine-resistant infections (86 percent), as compared with a base-line prevalence of 50 percent in 115 samples obtained before treatment (P<0.001). The presence of pfcrt T76 was more strongly associated with the development of chloroquine resistance (odds ratio, 18.8; 95 percent confidence interval, 6.5 to 58.3) than was the presence of pfmdr 1 Y86 (odds ratio, 3.2; 95 percent confidence interval, 1.5 to 6.8) or the presence of both mutations (odds ratio, 9.8; 95 percent confidence interval, 4.4 to 22.1).

CONCLUSIONS

This study shows an association between the pfcrt T76 mutation in P. falciparum and the development of chloroquine resistance during the treatment of malaria. This mutation can be used as a marker in surveillance for chloroquine-resistant falciparum malaria.

Impact of corticotropin-releasing hormone on gastrointestinal motility and adrenocorticotropic hormone in normal controls and patients with irritable bowel syndrome

BACKGROUND

Corticotropin-releasing hormone (CRH) plays a key role in modulating intestinal motility in stressed animals.

AIMS

To evaluate the effect of CRH on intestinal motility in humans and to determine whether patients with irritable bowel syndrome (IBS) have an exaggerated response to CRH.

SUBJECTS

Ten IBS patients diagnosed by Rome criteria and 10 healthy controls.

METHODS

CRH (2 micrograms/kg) was intravenously administered during duodenal and colonic manometry and plasma adrenocorticotropic hormone (ACTH) was measured by radioimmunoassay.

RESULTS

CRH induced motility of the descending colon in both groups (p < 0.001) and induced greater motility indexes in IBS patients than in controls (p < 0.05). CRH produced duodenal phase III motor activity in 80% of the subjects and duodenal dysmotility in 40% of IBS patients. Abdominal symptoms evoked by CRH in IBS patients lasted significantly longer than those in controls (p < 0.05). CRH induced significant increases in plasma ACTH levels in both groups (p < 0.001) and produced significantly higher plasma ACTH levels in IBS patients than in controls (p < 0.001).

CONCLUSION

Human intestinal motility is probably modulated by exogenous CRH. The brain-gut in IBS patients may have an exaggerated response to CRH.

Transplantation of human neural stem cells for spinal cord injury in primates

Recent studies have shown that delayed transplantation of neural stem/progenitor cells (NSPCs) into the injured spinal cord can promote functional recovery in adult rats. Preclinical studies using nonhuman primates, however, are necessary before NSPCs can be used in clinical trials to treat human patients with spinal cord injury (SCI). Cervical contusion SCIs were induced in 10 adult common marmosets using a stereotaxic device. Nine days after injury, in vitro-expanded human NSPCs were transplanted into the spinal cord of five randomly selected animals, and the other sham-operated control animals received culture medium alone. Motor functions were evaluated through measurements of bar grip power and spontaneous motor activity, and temporal changes in the intramedullary signals were monitored by magnetic resonance imaging. Eight weeks after transplantation, all animals were sacrificed. Histologic analysis revealed that the grafted human NSPCs survived and differentiated into neurons, astrocytes, and oligodendrocytes, and that the cavities were smaller than those in sham-operated control animals. The bar grip power and the spontaneous motor activity of the transplanted animals were significantly higher than those of sham-operated control animals. These findings show that NSPC transplantation was effective for SCI in primates and suggest that human NSPC transplantation could be a feasible treatment for human SCI.

Skeletal muscle pathology in X chromosome-linked muscular dystrophy (mdx) mouse

Histological, histochemical, and morphometric analyses were performed chronologically on muscles from mutant mice with X chromosome-linked muscular dystrophy (mdx), and the findings were compared with those in nondystrophic control animals (C57BL/10ScSn). Massive grouped muscle fiber destruction, followed by complete regeneration, occurred abruptly at 20 days of age. There were no preceding changes in body weight, the number and mean diameter of fibers, and fiber type differentiation before the initial episode of muscle fiber necrosis. Muscle fiber necrosis decreased in intensity after 60 days of age. Even after repeated muscle fiber necrosis and regeneration, the most striking finding was that interstitial fibrosis and adipose tissue replacement were minimal, and there was no apparent fiber loss. Since the necrosis was probably well compensated by the active regenerative process, the mdx mice developed no obvious muscle weakness and thus differed from human and other animal muscular dystrophies with the exception of the dystrophic hamster.

Ski is a component of the histone deacetylase complex required for transcriptional repression by Mad and thyroid hormone receptor

The N-CoR/SMRT complex containing mSin3 and histone deacetylase (HDAC) mediates transcriptional repression by nuclear hormone receptors and Mad. The proteins encoded by the ski proto-oncogene family directly bind to N-CoR/SMRT and mSin3A, and forms a complex with HDAC. c-Ski and its related gene product Sno are required for transcriptional repression by Mad and thyroid hormone receptor (TRbeta). The oncogenic form, v-Ski, which lacks the mSin3A-binding domain, acts in a dominant-negative fashion, and abrogates transcriptional repression by Mad and TRbeta. In ski-deficient mouse embryos, the ornithine decarboxylase gene, whose expression is normally repressed by Mad-Max, is expressed ectopically. These results show that Ski is a component of the HDAC complex and that Ski is required for the transcriptional repression mediated by this complex. The involvement of c-Ski in the HDAC complex indicates that the function of the HDAC complex is important for oncogenesis.

A new photoreactivating enzyme that specifically repairs ultraviolet light-induced (6-4)photoproducts

Cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts ((6-4)photoproducts) are the two major classes of cytotoxic, mutagenic and carcinogenic DNA photoproducts produced by ultraviolet light irradiation of cells. The phenomenon of photoreactivation, the reduction of the lethal and mutagenic effects of ultraviolet radiation by simultaneous or subsequent irradiation with near ultraviolet or visible light, has been identified in several organisms and in some cases the enzymes that catalyse this process have been characterized in sufficient detail. CPDs are the only known substrate for the photoreactivating enzymes so far analysed and enzymatic photoreactivation of (6-4)photoproducts has not yet been reported. We report here that an enzyme that catalyses the light-dependent repair of (6-4)photoproduct exists in Drosophila melanogaster. This is, to our knowledge, the first report of such photoreactivating activity specific for (6-4)photoproducts in any organism.

Effect of granulocyte colony-stimulating factor after intensive induction therapy in relapsed or refractory acute leukemia

Background. Although colony-stimulating factors have been shown to accelerate recovery from severe neutropenia after intensive chemotherapy or bone marrow transplantation, their use in acute leukemia has been controversial because in vitro they stimulate leukemic colonies as well as normal granulocyte colonies. Methods. We conducted a prospective, randomized, controlled study to determine the safety and efficacy of recombinant human granulocyte colony-stimulating factor (CSF) after a standard course of intensive therapy in 108 patients with relapsed or refractory acute leukemia (67 with acute myelogenous leukemia, 30 with acute lymphocytic leukemia, 9 in blast crisis from chronic myelogenous leukemia, and 2 with acute leukemia arising from myelodysplastic syndromes). Treatment with granulocyte CSF (200 micrograms per square meter of body-surface area per day in a 30-minute infusion) was begun two days after the end of the chemotherapy and continued until the neutrophil count rose above 1500 per cubic millimeter. Results. Treatment with granulocyte CSF accelerated the recovery of neutrophils significantly (P less than 0.01), shortening it by about a week, but it had no effect on platelet recovery. Although the incidence of febrile episodes was almost the same, documented infections were significantly less frequent in the group treated with granulocyte CSF (P = 0.028). There was no evidence that granulocyte CSF accelerated the regrowth of leukemic cells. Fifty percent of 48 patients in the CSF group who could be evaluated and 36 percent of 50 controls had complete remission. The rate of relapse was almost the same in the two groups. Conclusions. It appears that recombinant human granulocyte CSF is safe in acute leukemia, accelerating neutrophil recovery and thereby reducing the incidence of documented infection without affecting the regrowth of leukemic cells. It should be used with caution, however, pending further confirmation of these early results.

Prognostic value of tumor-associated macrophage count in human bladder cancer

BACKGROUND

We determined the tumor-associated macrophage (TAM) count to investigate its importance in predicting clinical outcome or prognosis in patients with bladder cancer.

METHODS

The TAM count and microvessel count (MVC) were determined immunohistochemically in 63 patients with bladder cancer, including 40 superficial bladder cancers and 23 invasive bladder cancers. To examine the relationship between TAM count and clinical outcome or prognosis in bladder cancer, cystectomy rates, distant metastasis rates, vascular invasion rates and 5 year survival rates were compared between patients with low (< 67) and high (> or = 67) TAM counts.

RESULTS

The TAM count in invasive bladder cancers (154.22+/-11.98) was significantly higher than in superficial bladder cancers (49.05+/-7.76; P<0.0001). The MVC in invasive bladder cancers (71.55+/-10.44) was also significantly higher than in superficial bladder cancers (47.02+/-5.57; P<0.05). There was a positive correlation between TAM count and MVC (r=0.30; P=0.02). Immunohistochemical staining using CD68/horseradish peroxidase monoclonal antibody showed more infiltrating cells in invasive than superficial bladder cancers. Patients with a high TAM count (> or =67) showed significantly higher rates of cystectomy, distant metastasis and vascular invasion than those with a lower TAM count (<67). The 5 year survival rate estimated using the Kaplan-Meier method was significantly lower in patients with a high TAM count than in those with a low TAM count (P<0.0001).

CONCLUSIONS

Our results suggest that determination of TAM count in bladder cancer tissues is of value to predict the clinical outcome or prognosis and to select appropriate treatment strategies in patients with bladder cancer.

Similarity among the Drosophila (6-4)photolyase, a human photolyase homolog, and the DNA photolyase-blue-light photoreceptor family

Ultraviolet light (UV)-induced DNA damage can be repaired by DNA photolyase in a light-dependent manner. Two types of photolyase are known, one specific for cyclobutane pyrimidine dimers (CPD photolyase) and another specific for pyrimidine (6-4) pyrimidone photoproducts[(6-4)photolyase]. In contrast to the CPD photolyase, which has been detected in a wide variety of organisms, the (6-4)photolyase has been found only in Drosophila melanogaster. In the present study a gene encoding the Drosophila(6-4)photolyase ws cloned, and the deduced amino acid sequence of the product was found to be similar to the CPD photolyase and to the blue-light photoreceptor of plants. A homolog of the Drosophila (6-4)photolyase gene was also cloned from human cells.

The tomato DWARF enzyme catalyses C-6 oxidation in brassinosteroid biosynthesis

Brassinosteroids (BRs) are steroidal plant hormones essential for normal plant growth and development. Mutants in the biosynthesis or perception of BRs are usually dwarf. The tomato Dwarf gene (D), which was predicted to encode a cytochrome P450 enzyme (P450) with homology to other P450s involved in BR biosynthesis, was cloned previously. Here, we show that DWARF catalyses the C-6 oxidation of 6-deoxocastasterone (6-deoxoCS) to castasterone (CS), the immediate precursor of brassinolide. To do this, we first confirmed that the D cDNA complemented the mutant light- and dark-grown phenotypes of the extreme dwarf (dx) allele of tomato. To identify a substrate for the DWARF enzyme, exogenous application of BR intermediates to dx plants was carried out. C-6 oxoBR intermediates enhanced hypocotyl elongation whereas the C-6 deoxoBR, 6-deoxoCS, had little effect. Quantitative analysis of endogenous BR levels in tomato showed mainly the presence of 6-deoxoBRs. Furthermore, dx plants were found to lack CS and had a high level of 6-deoxoCS in comparison to D plants that had CS and a lower level of 6-deoxoCS. Confirmation that DWARF catalyzed the C-6 oxidation of 6-deoxoCS to CS was obtained by functional expression of DWARF in yeast. In these experiments, the intermediate 6alpha-hydroxycastasterone was identified, indicating that DWARF catalyzes two steps in BR biosynthesis. These data show that DWARF is involved in the C-6 oxidation in BR biosynthesis.

The Arabidopsis DIMINUTO/DWARF1 gene encodes a protein involved in steroid synthesis

We have identified the function of the Arabidopsis DIMINUTO/DWARF1 (DIM/DWF1) gene by analyzing the dim mutant, a severe dwarf with greatly reduced fertility. Both the mutant phenotype and gene expression could be rescued by the addition of exogenous brassinolide. Analysis of endogenous sterols demonstrated that dim accumulates 24-methylenecholesterol but is deficient in campesterol, an early precursor of brassinolide. In addition, we show that dim is deficient in brassinosteroids as well. Feeding experiments using deuterium-labeled 24-methylenecholesterol and 24-methyldesmosterol confirmed that DIM/DWF1 is involved in both the isomerization and reduction of the Delta24(28) bond. This conversion is not required in cholesterol biosynthesis in animals but is a key step in the biosynthesis of plant sterols. Transient expression of a green fluorescent protein-DIM/DWF1 fusion protein and biochemical experiments showed that DIM/DWF1 is an integral membrane protein that most probably is associated with the endoplasmic reticulum.

Effect of a corticotropin releasing hormone receptor antagonist on colonic sensory and motor function in patients with irritable bowel syndrome

BACKGROUND AND AIMS

Corticotropin releasing hormone (CRH) is a major mediator of the stress response in the brain-gut axis. Irritable bowel syndrome (IBS) is presumed to be a disorder of the brain-gut link associated with an exaggerated response to stress. We hypothesised that peripheral administration of alpha-helical CRH (alphahCRH), a non-selective CRH receptor antagonist, would improve gastrointestinal motility, visceral perception, and negative mood in response to gut stimulation in IBS patients.

METHODS

Ten normal healthy subjects and 10 IBS patients, diagnosed according to the Rome II criteria, were studied. The tone of the descending colon and intraluminal pressure of the sigmoid colon were measured at baseline, during rectal electrical stimulation (ES), and at recovery after administration of saline. Visceral perception after colonic distension or rectal ES was evaluated as threshold values on an ordinate scale. The same measurements were repeated after administration of alphahCRH (10 micro g/kg).

RESULTS

ES induced significantly higher motility indices of the colon in IBS patients compared with controls. This response was significantly suppressed in IBS patients but not in controls after administration of alphahCRH. Administration of alphahCRH induced a significant increase in the barostat bag volume of controls but not in that of IBS patients. alphahCRH significantly reduced the ordinate scale of abdominal pain and anxiety evoked by ES in IBS patients. Plasma adrenocorticotropic hormone and serum cortisol levels were generally not suppressed by alphahCRH.

CONCLUSION

Peripheral administration of alphahCRH improves gastrointestinal motility, visceral perception, and negative mood in response to gut stimulation, without affecting the hypothalamo-pituitary-adrenal axis in IBS patients.

RNA-dependent RNA polymerase activity of the soluble recombinant hepatitis C virus NS5B protein truncated at the C-terminal region

The hepatitis C virus (HCV) NS5B protein encodes an RNA-dependent RNA polymerase (RdRP), which is the central catalytic enzyme of HCV replicase. We established a new method to purify soluble HCV NS5B in the glutathione S-transferase-fused form NS5Bt from Escherichia coli which lacks the C-terminal 21 amino acid residues encompassing a putative anchoring domain (anino acids 2990-3010). The recombinant soluble protein exhibited RdRP activity in vitro which was dependent upon the template and primer, but it did not exhibit the terminal transferase activity that has been reported to be associated with the recombinant NS5B protein from insect cells. The RdRP activity of purified glutathione S-transferase-NS5Bt and thrombin-cleavaged non-fused NS5Bt shares most of the properties. Substitution mutations of NS5Bt at the GDD motif, which is highly conserved among viral RdRPs, and at the clustered basic residues (amino acids 2919-2924 and 2693-2699) abolished the RdRP activity. The C-terminal region of NS5B, which is dispensable for the RdRP activity, dramatically affected the subcellular localization of NS5B retaining it in perinuclear sites in transiently overexpressed mammalian cells. These results may provide some clues to dissecting the molecular mechanism of the HCV replication and also act as a basis for developing new anti-viral drugs.

Transplantation of human tumors in nude mice

Ninety-one human tumors, including various common carcinomas, low-grade malignant tumors, and benign tumors, were transplanted into athymic nude mice. Tumor take was confirmed histologically for 22 neoplasms at the initial transplantation, and 14 serially transplantable tumors were established, including some hitherto unestablished or unreported, such as lung and hepatic cell carcinomas. Among the 91 tumors were 21, 14, and 13 carcinomas of the lung, stomach, and breast, respectively. Transplantability was highest in lung carcinomas (10/21), followed by gastric carcinomas (2/14) and breast carcinomas (1/13). Morphology of original tumors was retained well in most transplanted tumors, but desmoplastic or scirrhous tumors, such as gastric and breast carcinomas, tended to become medullary with a decrease in amount of tumor stroma. The ability to produce mucin in gastric carcinomas or melanin in malignant melanoma was maintained in serially transplantable tumors. In addition, ectopic production of adrenocorticotropin and beta melanocyte-stimulating hormone continued in a transplanted small cell carcinoma of the lung. Preliminary results were obtained on hormone dependency of the transplantable breast carcinoma and on alpha1-fetoprotein in the transplantable hepatic cell carcinoma.

Conversion of normal behavior to shiverer by myelin basic protein antisense cDNA in transgenic mice

Myelin basic proteins (MBPs) are coded by the single gene necessary for myelin formation in the central nervous system of the mouse. An antisense MBP mini-gene was constructed and used to determine the function of antisense DNA in transgenic mice. Several transgenic offspring of a founder transgenic mouse, AS100, were converted from the normal to mutant shiverer phenotype. Antisense MBP messenger RNA was expressed in these mice, and the endogenous MBP messenger RNA, the MBP, and the myelination in the central nervous system were reduced.

The Ski protein family is required for MeCP2-mediated transcriptional repression

DNA methylation is essential for development in the mouse and plays an important role in inactivation of the X chromosome and genomic imprinting. MeCP2 is the founder member of a family of methyl-CpG-binding proteins. MeCP2 directly binds to the co-repressor mSin3, which interacts with class I histone deacetylase, recruiting them to methyl-CpG regions to suppress transcription. Here, we report that MeCP2 directly binds to two co-repressors, c-Ski and N-CoR, in addition to mSin3A, and that the c-Ski, which is encoded by the c-ski proto-onocogene, is required for MeCP2-mediated transcriptional repression. The two regions of c-Ski, including the C-terminal coiled-coil region, interact with the transcriptional repression domain in the center of the MeCP2 molecule. The immunostaining signals for c-Ski and MeCP2 overlap in the nuclear heterochromatin region, suggesting the co-localization of the two proteins. The degree of transcriptional repression mediated by a Gal4-MeCP2 fusion protein was abrogated by overexpression of the putative dominant negative form of c-Ski. Furthermore, injection of antibodies against c-Ski and Sno almost completely abolished the transcriptional repression mediated by the Gal4-MeCP2 fusion protein. These results suggest that the ski gene family is involved in methyl CpG-mediated transcriptional repression.

Distributions of PAX6 and PAX7 proteins suggest their involvement in both early and late phases of chick brain development

We describe here the isolation of chicken PAX6 and PAX7 as members of the PAX gene family expressed in late stages of chick nervous system development. By generating monoclonal antibodies against these PAX molecules, we analyzed their protein distributions in the CNS, neural crest cells and muscle precursor cells. Our detailed description of protein distributions revealed several new features of PAX expression patterns. In particular, PAX6 and PAX7 are expressed in restricted regions in the CNS during early stages. In contrast, at later stages the expression becomes localized to subsets of postmitotic cells in further restricted regions. Such a transition from region-specific expression to cell-specific expression suggests two different roles of these PAX molecules in development: the regionalization and subdivision of the nervous system during early stages, and the differentiation of specific cell populations during late stages.

Hepatitis B virus X protein is a transcriptional modulator that communicates with transcription factor IIB and the RNA polymerase II subunit 5

Hepatitis B virus X protein (HBx) transactivates viral and cellular genes through a wide variety of cis-elements. However, the mechanism is still obscure. Our finding that HBx directly interacts with RNA polymerase II subunit 5 (RPB5), a common subunit of RNA polymerases, implies that HBx directly modulates the function of RNA polymerase (Cheong, J. H., Yi, M., Lin, Y., and Murakami, S. (1995) EMBO J. 14, 142-150). In this context, we examined the possibility that HBx and RPB5 interact with other general transcription factors. HBx and RPB5 specifically bound to transcription factor IIB (TFIIB) in vitro, both of which were detected by either far-Western blotting or the glutathione S-transferase-resin pull-down assay. Delineation of the binding regions of these three proteins revealed that HBx, RPB5, and TFIIB each has two binding regions for the other two proteins. Co-immunoprecipitation using HepG2 cell lysates that express HBx demonstrated trimeric interaction in vivo. Some HBx substitution mutants, which had severely impaired transacting activity, exhibited reduced binding affinity with either TFIIB or RPB5 in a mutually exclusive manner, suggesting that HBx transactivation requires the interactions of both RPB5 and TFIIB. These results indicated that HBx is a novel virus modulator that facilitates transcriptional initiation by stabilizing the association between RNA polymerase and TFIIB through communication with RPB5 and TFIIB.

Nucleus pulposus allograft retards intervertebral disc degeneration

Autogenous implantation of nucleus pulposus or nucleus pulposus cells that were activated by coculture retards intervertebral disc degeneration, but harvesting such grafts causes disc degeneration at the donor site. This study examined whether nucleus pulposus allografts similarly retard disc degeneration and whether such allografting induces immunologic rejection. Japanese White rabbits served as donors and recipients for allografts. Lumbar disc degeneration was induced by aspirating the nucleus pulposus. Two weeks later, intact nucleus pulposus or nucleus pulposus cells were injected and compared with a sham procedure and normal control. The recipients' discs were examined histologically and immunologically at intervals for 16 weeks. Discs receiving an intact nucleus pulposus showed the least degeneration, followed by discs receiving nucleus pulposus cells, both of which were better than no treatment. These findings correlated directly with the intensity of immunochemical staining for Type II collagen. Allogeneic grafts did not induce any appreciable host-versus-graft response. Injection of nucleus pulposus and nucleus pulposus cells retards intervertebral disc degeneration. However, injection of intact nucleus pulposus is more effective than injection of nucleus pulposus cells alone. The intercellular matrix plays an important, but poorly understood, role in preserving intervertebral discs.

Brassinosteroid-6-oxidases from Arabidopsis and tomato catalyze multiple C-6 oxidations in brassinosteroid biosynthesis

Brassinosteroids (BRs) are steroidal plant hormones that are essential for growth and development. It has been proposed that BRs are synthesized via two parallel pathways, the early and late C-6 oxidation pathways according to the C-6 oxidation status. The tomato (Lycopersicon esculentum) Dwarf gene encodes a cytochrome P450 that has been shown to catalyze the C-6 oxidation of 6-deoxocastasterone to castasterone. We isolated an Arabidopsis ortholog (AtBR6ox gene) of the tomato Dwarf gene. The encoded polypeptide has characteristics of P450s and is classified into the CYP85 family. The AtBR6ox and tomato Dwarf gene were expressed in yeast and the ability of the transformed yeast cells to metabolize 6-deoxo-BRs was tested. Metabolites were analyzed by gas chromatography-mass spectrometry. Both enzymes catalyze multiple steps in BR biosynthesis: 6-deoxoteasterone to teasterone, 3-dehydro-6-deoxoteasterone to 3-dehydroteasterone, 6-deoxotyphasterol to typhasterol, and 6-deoxocastasterone to castasterone. Our results indicate that the AtBR6ox gene and the tomato Dwarf gene encode steroid-6-oxidases and that these enzymes have a broad substrate specificity. This suggests that the BR biosynthetic pathway consists of a metabolic grid rather than two separate parallel pathways.

Physicochemical and pharmacokinetic characteristics of plasmid DNA/cationic liposome complexes

The objectives of this study were (i) to characterize the plasmid DNA encoding the chloramphenicol acetyltransferase reporter gene (pCAT) complexed with cationic liposomes (Lipofectin and LipofectACE) in terms of particle size and zeta potential, (ii) to compare pharmacokinetic characteristics, and (iii) to study the hepatic uptake mechanisms. DNA/LipofectACE complexes showed a negative zeta potential of -36 mV at 1:5 w/w ratio, but a positive zeta potential of (19 mV at 1:10 w/w ratio. Lipofectin samples showed a positive zeta potential) of 21-28 mV at these ratios. These preparations showed a wide particle size distribution ranging from 600 to 1200 nm. Following intravenous injection of 1:10 w/w ratio [32P]pCAT/liposome complexes at a dose of 0.1 mg DNA/kg into the tail vein of mice, radioactivity was rapidly eliminated from the plasma and almost 50-60% of the dose was taken up by the liver within 5 min after administration. Plasmid DNA/liposome complexes were predominantly taken up by the liver nonparenchymal cells. The hepatic uptake was inhibited by preceding administration of dextran sulfate (DS), but not by polycytidic acid (poly[C]) and polyinosinic acid (poly[I]), suggesting the involvement of a phagocytic process. We suggest that these complexes are preferentially taken up by the liver nonparenchymal cells mainly via Kupffer cell phagocytosis.