Effects of docosahexaenoic acid on annular lipid fluidity of the rat bile canalicular plasma membrane

The role of docosahexaenoic acid (DHA) in the fluidity of the annular lipid regions and their associated membrane-bound proteins is still not as well understood as that in the global (bulk) lipid regions. We therefore studied the effects of dietary DHA on the relationship between annular and global lipid fluidity and membrane-bound enzymes such as 5'-nucleotidase and Mg(2)+-ATPase in the rat bile canalicular membrane. Dietary DHA caused significant increases in 5'-nucleotidase and Mg(2)+-ATPase activity and in global and annular lipid fluidity, a higher increase in fluidity in the annular lipids than the global lipids, and a decrease in the cholesterol-to-phospholipid molar ratio in the canalicular membrane. Plasma total cholesterol and LDL cholesterol decreased, and fecal cholesterol increased in the DHA-fed rats. No changes were observed in oxidative markers, but glutathione peroxidase increased in the liver with DHA feeding. Annular lipid fluidity, but not global lipid fluidity, correlated remarkably well with DHA, synchronously with the activities of 5'-nucleotidase and Mg(2)+-ATPase. The data indicate that the DHA-induced increase in annular lipid fluidity is responsible for the increases observed in the enzyme activity. We therefore concluded that the increased activity of membrane-bound enzymes and transporters induced by DHA and the concomitant increase in annular lipid fluidity comprise one of the mechanisms involved in DHA-induced clearance of plasma cholesterol.

Regulation of cellular invasion and matrix metalloproteinase activity in HepG2 cell by connexin 26 transfection

We previously reported that connexin (Cx) 26 expression is involved in negative growth control of HepG2 cells established from a human hepatoma. We also found that induction of E-cadherin and subsequent formation of a cell adhesion complex were induced in HepG2 cells by Cx 26 expression. To examine the exact role of Cx 26-induced E-cadherin junctions in regulating appearance of malignant phenotypes of HepG2 cells, we expressed a Cx 26 antisense oligodeoxynucleotide (AS-ODN) in an established HepG2 cell clone that has stable expression of Cx 26 genes. We investigated changes in the expression of E-cadherin, the localization of beta-catenin, and some malignant phenotypes of HepG2 clone after the suppression of Cx 26 expression by AS-ODN treatment. The AS-ODN treatment prevented the expression of Cx 26 and E-cadherin, and the localization of beta-catenin was changed from cytoplasmic membrane to the cytoplasm. In parallel, a morphological change from a monolayer of polygonal cells to multilayered colonies was induced by the treatment, indicating a change of a malignant phenotype of HepG2 cells. The activity of matrix metalloproteinase 9 (MMP-9) was elevated by the AS-ODN treatment. A concomitant increase in invasiveness of the Cx 26-expressing cells by the treatment was also observed in an in vitro assay with Matrigel matrix. These results suggest that the induction of E-cadherin and formation of the cell adhesion complex by Cx 26 expression contribute to the reversal of some malignant phenotypes of HepG2 cells. Furthermore, the Cx 26-dependent expression of E-cadherin leads to reduction of the invasiveness of the cells through suppression of MMP-9 activity.

Anticipatory fall in core temperature in rats acclimated to heat given for various hours at a fixed daily time

Rats were subjected to daily heat exposure limited to a fixed time for 10 consecutive days. An ambient temperature (T(a)) inside an animal room initially set at 24.0 degrees C was raised to 32.0 degrees C, starting at the middle of the dark phase. The high T(a) was maintained for a subsequent 1.5, 3, or 5 h and was then returned to 24.0 degrees C. After the heat exposure schedule, their core temperature significantly fell for about 30 min before and during the period when they had previously been exposed to heat without thermal stimuli. In rats, a time memory for heat exposure could be formed even when the duration of daily heat exposure was short.

Inhibitory effects of nitric oxide on oxidative phosphorylation in plant mitochondria

Plant nitrate reductase (NR) produces nitric oxide (NO) when nitrite is provided as the substrate in the presence of NADH [H. Yamasaki and Y. Sakihama (2000) FEBS Lett. 468, 89-92]. Using a NR-dependent NO producing system, we investigated the effects of NO on the energy transduction system in plant mitochondria isolated from mung bean (Vigna radiata). Plant mitochondria are known to possess two respiratory electron transport pathways-the cytochrome and alternative pathways. When the alternative pathway was inhibited by n-propyl gallate, the addition of NR strongly suppressed respiratory O(2) consumption driven by the cytochrome pathway. In contrast, the alternative pathway measured in the presence of antimycin A was not affected by NO. The extent of the steady-state membrane potential (Deltapsi) generated by respiratory electron transport rapidly declined in response to NO production. The addition of bovine hemoglobin, a quencher of NO, resulted in the recovery of Deltapsi to the uninhibited level. Consistent with its inhibition of Deltapsi, NO produced by NR strongly suppressed ATP synthesis in the mitochondria. These results provide substantial evidence to confirm that the plant alternative pathway is resistant to NO and support the idea that the alternative pathway may lower respiration-dependent production of active oxygens under conditions where NO is overproduced.

Docosahexaenoic acid supplementation-increased oxidative damage in bone marrow DNA in aged rats and its relation to antioxidant vitamins

We compared the influence of docosahexaenoic acid (DHA) supplementation on oxidative DNA damage in bone marrow between young and aged rats. As a marker of oxidative DNA damage, 8-hydroxydeoxyguanosine (8-OHdG) in DNA was analyzed. Young (5-week-old) and aged (100-week-old) female Wistar rats were given DHA (300mg/kg body weight/day) or vehicle (control) orally for 12 weeks. The 8-OHdG in the bone marrow in the aged DHA group was significantly higher than that in the other groups. Vitamin E concentrations, however, did not differ among the groups regardless of the DHA supplementation. Vitamin C (ascorbic acid) concentrations in the aged control group were approximately 1/2 those in the young control group. The concentrations of vitamin C tended to be higher in the young DHA group and lower in the aged DHA group when compared to their respective control groups. Changes in the concentrations of vitamin C and vitamin E in plasma were similar to those in the bone marrow. The activity of hepatic l-gulono- gamma -lactone oxidase, an enzyme responsible for vitamin C synthesis, corresponded well to the concentrations of vitamin C in the bone marrow and the plasma. These results suggest that in aged rats, but not young rats, excess supplementation of DHA induces oxidative DNA damage in bone marrow and that the decrease in vitamin C synthesis in aged rats is involved in the mechanisms of DNA damage.

Induction of a bystander effect in HeLa cells by using a bigenic vector carrying viral thymidine kinase and connexin32 genes

We previously showed that gap junction intercellular communication mediates the bystander effect in anticancer gene therapy with the herpes simplex virus thymidine kinase (HSV-tk) and ganciclovir. Because most cancer cell lines have lost their ability to communicate through gap junctions, we investigated whether we could induce such a communication by transferring a gene for a gap junction. We transfected a vector carrying the HSV-tk (tk) and gap junction (connexin (Cx) 32) genes (Cx32(+)tk(+)) into noncommunicating HeLa cells. We compared the cytotoxicity of ganciclovir with mixtures of these cells and HeLa cells that expressed (Cx32(+)) or did not express (Cx32(-)) the Cx32 gene. The bystander effect was strong when the two mixed cell types expressed Cx32 (i.e., Cx32(+)tk(+) cells and Cx32(+)tk(-) cells). Only 25% of cells survived in this communicating mixture, even when only 10% of the cells were Cx32(+)tk(+). There was also a moderate bystander effect when the Cx32(+)tk(+) cells were mixed with noncommunicating HeLa cells in a 50% ratio. These results demonstrated that the bystander effect is enhanced by Cx32 and suggested that expression of Cx in only one cell type in a mixture can cause a bystander effect. Mol. Carcinog. 30:176--180, 2001.

Body fat distribution and body composition during GnRH agonist therapy

OBJECTIVE

To identify the effects of GnRH agonist therapy on body composition (lean and fat mass components) and body fat distribution.

METHODS

Fifteen women with uterine leiomyomas were given a GnRH agonist (leuprorelin acetate, 3.75 mg) monthly for 4 months. Weight, height, and body mass index (BMI, weight/height) were recorded. Regional and total body composition, trunk-leg fat ratio, bone mineral density of the lumbar spine (L2-L4), and total body were assessed by whole-body scanning with dual-energy x-ray absorptiometry before and after treatment. Uterine volume was measured by transabdominal ultrasonography.

RESULTS

The mean (+/- standard deviation [SD]) lean mass of total body, trunk, and leg decreased significantly (36.3 +/- 4.9 to 35.4 +/- 4.4 kg, P <.01; 18.8 +/- 2.8 to 18.1 +/- 2.8 kg, P <.05; and 11.4 +/- 1.8 to 11.1 +/- 1.6 kg, P <.05; respectively), whereas body fat mass, percentage of body fat, and trunk fat mass increased significantly (20.8 +/- 4.8 to 21.8 +/- 4.6 kg, P <.01; 34.9 +/- 5.9 to 36.5 +/- 5.2%, P <.01; and 8.6 +/- 3.0 to 9.3 +/- 3.0 kg, P <.01; respectively). Trunk-leg fat ratio increased significantly (1.03 +/- 0.32 to 1.12 +/- 0.33, P <.05). Weight, BMI, arm tissue composition (lean and fat mass components), and leg fat mass did not change during 4 months of GnRH agonist therapy. Bone mineral density and uterine volume decreased significantly.

CONCLUSION

Hypogonadism by GnRH agonist therapy induces lean mass loss, increased adiposity overall, and upper body fat accumulation.

Stimulation of intercellular communication of poor-communicating cells by gap-junction-competent cells enhances the HSV-TK/GCV bystander effect in vitro

We have previously shown that gap-junctional intercellular communication (GJIC) appears to play a role in the bystander effect that is observed in anticancer suicide gene therapy mediated by herpes simplex virus (HSV) thymidine kinase (tk) and ganciclovir (GCV). We now report that when connexin-expressing (Cx+) cells are present within a noncommunicating population of cells (Cx-), there is GJIC between the Cx+ and Cx- cells and that due to this stimulation of GJIC, the bystander effect also occurs when the 2 cell types are mixed. We transfected HeLa cells, which do not express any detectable level of connexin, with Cx43. The Cx+ and Cx- HeLa cells were further transfected with the tk gene, giving 4 phenotypes: Cx+tk-, Cx+tk+, Cx-tk+ and Cx-tk-. We observed GJIC between Cx+ and Cx- cells, but not between Cx- and Cx- cells, regardless of the tk genotype. Similarly, we observed the HSV-tk/GCV bystander effect in Cx+tk-/Cx-tk+ and Cx+tk+/Cx-tk- cocultures. The extent of the bystander effect in cocultures of Cx+tk- and Cx-tk+ cells was stronger than in cocultures of Cx+tk+ and Cx-tk- cells when each mixture had the same ratio of Cx+ and tk+ cells. These results suggest that Cx-expressing HeLa cells stimulate GJIC capacity between them and non-Cx-expressing HeLa cells, which mediates the bystander effect in mixtures of Cx+ cells and Cx- cells in vitro. Thus, Cx expression even in only a limited fraction of tumor cells may enhance the efficacy of the HSV-tk/GCV strategy by inducing a bystander effect.

Hepatocyte nuclear factor-1alpha inhibits insulin promoter factor 1-dependent transactivation of the human insulin gene

To investigate the regulational interaction of hepatocyte nuclear factor-1alpha (HNF-1alpha) and insulin promoter factor 1 (IPF1) on insulin gene expression, either or both of the expression vectors carrying each transcription factor were transiently transfected into HeLa cells, RINm5F cells and MIN6 cells together with the luciferase reporter construct driven by a human preproinsulin gene promoter (-1998 to +237) designated as, pINS-1998/luc. IPF1-transfection into HeLa cells strongly stimulated the luciferase activity to 725 fold that of the basal level. In contrast, HNF-1alpha-transfection resulted in only a 6.7 fold increase. In co-transfection experiments, increasing the amount of HNF-1alpha resulted in an 84.5% and 74.4% decrease in IPF1-stimulated luciferase activity in HeLa and RINm5F cells, respectively. Deletion constructs designated as pINS-248/luc, pINS-213/luc and pINS-185/luc were transfected into RINm5F cells to determine the role of the A3 element and its 5' flanking sequence in the inhibitory effect of HNF-1alpha. The results showed that the inhibiting effects of HNF-1alpha with pINS-213/luc and pINS-185/luc were significantly smaller than those with both pINS-1998/luc and pINS-248/luc. Transfection into MN6 cells with pINS-1998/luc in the absence of IPF1 resulted in constitutional transactivation of the insulin gene, and this transactivation was abolished by the co-transfection with HNF-1alpha. The present data indicate that IPF1 rather than HNF-1alpha predominantly transactivates the insulin gene, and that HNF-1alpha inhibits IPF1-dependent insulin gene transactivation mediated through the 5' flanking sequence of the A3 element. It is suggested that HNF-1alpha may be involved in insulin gene expression as a negative regulator.

Reduction of phenoxyl radicals mediated by monodehydroascorbate reductase

Monodehydroascorbate (MDA) reductase catalyzes the reduction of MDA, the only organic radical substrate for the enzyme reported so far. Here, we show that cucumber MDA reductase is also capable of reducing phenoxyl radicals which are generated by horseradish peroxidase (HRP) with H2O2. The addition of MDA reductase plus NADH suppressed the HRP/H2O2 dependent oxidation of quercetin, accompanied by the oxidation of NADH. The quenching of the quercetin radical by MDA reductase plus NADH was confirmed by ESR. MDA reductase with NADH also suppressed the HRP/H2O2 dependent oxidation of hydroxycinnamates, including ferulic acid, coniferyl alcohol, and chlorogenic acid. Thus, the phenoxyl radicals of plant phenols can be reduced to their respective parent phenols by MDA reductase via a mechanism similar to the reduction of MDA.

Peroxynitrite formation by diesel exhaust particles in alveolar cells: Links to pulmonary inflammation

Diesel exhaust particles (DEP) are assumed to be a causal substance for pulmonary inflammation. As peroxynitrite is recently implicated in inflammation and cytotoxity, the hypothesis was tested that instillation of DEP induces formation of peroxynitrite in cells migrated in lung. Rats were intratracheally instilled with DEP suspension (2 mg/0.5 ml/kg) and killed 24 h later. Alveolar cells were collected by broncho-alveolar lavage. Population of alveolar cells increased more than twice by DEP exposure, mainly due to a large increase of neutrophils. Peroxynitrite formation (N(G)-nitro-L-arginine methylester and superoxide dismutase inhibitable chemiluminescence) was detected in alveolar cells from treated rats, and 12-O-tetradecanoylphorbol 13-acetate-stimulation enhanced it. In addition, DEP induced expression of inducible NO synthase mRNA in these cells. But peroxynitrite was not detectable in cells from control. These results indicate that DEP exposure results in peroxynitrite formation in migrated cells, which leads to pulmonary inflammation.

Attenuation of expression of gamma-glutamylcysteine synthetase by ribozyme transfection enhance insulin secretion by pancreatic beta cell line, MIN6

Low levels of intracellular antioxidant enzyme activities as well as glutathione (GSH) concentrations have been described in pancreatic beta cells. We examined the effects of intracellular GSH depletion on insulin secretion and the role of intracellular GSH in signal transduction in beta cell line, MIN6 cells. Anti-gamma-glutamylcysteine synthetase (gamma-GCS) heavy subunit ribozyme was stably transfected to MIN6 cells to reduce intracellular GSH concentration. In the presence of 10 mM glucose, ribozyme-transfected cells (RTC) increased insulin secretion from 0.58 microg/10(6) cells/h in control cells (CC) to 1.48 microg/10(6) cells/h. This was associated with increased intracellular Ca(2+) concentration in RTC, detected by fluo-3 staining. Our results demonstrated that intracellular GSH concentration might influence insulin secretion by MIN6 cells, and suggest that enhanced insulin secretion by beta cells conditioned by chronic depletion of GSH is mediated by increased intracellular Ca(2+) concentration.

Connexin43 suppresses MFG-E8 while inducing contact growth inhibition of glioma cells

Gap junction expression has been reported to control the growth of a variety of transformed cells. We undertook parallel analysis of connexins Cx32 and Cx43 in glioma cells, which revealed potential mechanisms underlying this phenomenon and led to several novel findings. Cx43, but not Cx32, suppressed C6 glioma cell growth. Paradoxically, Cx32 transfection resulted in severalfold more dye transfer than Cx43. However, Cx43 transfectants shared endogenous metabolites more efficiently than Cx32 transfectants. Interestingly, a significant portion of Cx43 permeants were incorporated into macromolecules more readily than those that transferred via Cx32. Cx43 induced contact inhibition of cell growth but in contrast to other reports, did not affect log phase growth rates. Cell death, senescence, or suppression of growth factor signaling was not involved because no significant alterations were seen in cell viability, telomerase, or mitogen-activated protein kinase activity. However, suppression of cell growth by Cx43 entailed the secretion of growth-regulatory factors. Most notably, a major component of conditioned medium that was affected by Cx43 was found to be MFG-E8 (milk fat globule epidermal growth factor 8), which is involved in cell anchorage and integrin signaling. These results indicate that Cx43 regulates cell growth by the modulation of extracellular growth factors including MFG-E8. Furthermore, the ability of a Cx to regulate cell growth may rely on its ability to mediate the intercellular transfer of endogenous metabolites but not artificial dyes.

Nitrite-dependent nitric oxide production pathway: implications for involvement of active nitrogen species in photoinhibition in vivo

Air pollution studies have shown that nitric oxide (NO), a gaseous free radical, is a potent photosynthetic inhibitor that reduces CO2 uptake activity in leaves. It is now recognized that NO is not only an air pollutant but also an endogenously produced metabolite, which may play a role in regulating plant cell functions. Although many studies have suggested the presence of mammalian-type NO synthase (NOS) in plants, the source of NO is still not clear. There has been a number of studies indicating that plant cells possess a nitrite-dependent NO production pathway which can be distinguished from the NOS-mediated reaction. Nitrate reductase (NR) has been recently found to be capable of producing NO through one-electron reduction of nitrite using NAD(P)H as an electron donor. This review focuses on current understanding of the mechanism for the nitrite-dependent NO production in plants. Impacts of NO produced by NR on photosynthesis are discussed in association with photo-oxidative stress in leaves.

Effect of electromagnetic field exposure on chemically induced differentiation of friend erythroleukemia cells

Whether exposure of humans to extremely low frequency electromagnetic fields (ELF-EMF) can cause cancer is controversial and therefore needs further research. We used a Friend erythroleukemia cell line that can be chemically induced to differentiate to determine whether ELF-EMF could alter proliferation and differentiation in these cells in a manner similar to that of a chemical tumor promoter. Exposure of this cell line to 60 Hz ELF-EMF resulted in a dose dependent inhibition of differentiation, with maximal inhibition peaking at 40% and 40 mG (4 microT). ELF-EMF at 10 mG (1.0 microT) and 25 mG (2.5 microT) inhibited differentiation at 0 and 20%, respectively. ELF-EMF at 1.0 (100) and 10.0 G (1,000 microT) stimulated cell proliferation 50% above the sham-treated cells. The activity of telomerase, a marker of undifferentiated cells, decreased 100[times] when the cells were induced to differentiate under sham conditions, but when the cells were exposed to 0.5 G (50 microT) there was only a 10[times] decrease. In summary, ELF-EMF can partially block the differentiation of Friend erythroleukemia cells, and this results in a larger population of cells remaining in the undifferentiated, proliferative state, which is similar to the published results of Friend erythroleukemia cells treated with chemical-tumor promoters.

Type I and type II T cell profiles in chronic myelogenous leukemia

T cell immunity is considered to play an important role in the control of cell growth in chronic myelogenous leukemia (CML) although information regarding the characteristics of T lymphocytes in CML patients is limited. Using flow cytometric analysis of intracellular cytokine expression at the single-cell level, we analyzed helper T and cytotoxic T subsets in 8 CML patients. The percentage of interferon-gamma (IFN-gamma) single-positive CD4 cells (Th1) and that of interleukin-4 (IL-4) single-positive CD4 cells (Th2) was markedly decreased in pretreated CML patients compared to normal controls. In addition, the percentage of IFN-gamma/IL-4 double-positive CD4 cells (Th0) was also reduced. Consequently, the percentage of IFN-gamma/IL-4 double-negative CD4 cells was markedly increased. Similarly, a reduction in IFN-gamma single-positive CD8 cells (Tc1) and IFN-gamma/IL-4 double-positive CD8 cells (Tc0) and an increase in IFN-gamma/IL-4 double-negative CD8 cells were observed in pretreated CML patients. Imbalance of these parameters was markedly improved following cytoreduction therapy. Our findings directly indicate anergic states in CML patients. Determination of the factors that affect Th and Tc profiles may lead to further understanding of immunological states and the development of effective immunotherapy.

Octreotide treatment suppresses malignant somatotrophic pituitary tumor cell growth in rats

We have recently established an in vitro cell line (metastatic mGH3) derived from lymph node metastases of the rat pituitary somatotroph. Here we examined the in vivo effects of octreotide, a somatostatin analog, against malignant pituitary tumors. Wistar-Furth rats (n=8) were inoculated subcutaneously with mGH3 cells while control rats received injections of equal volumes of the vehicle only. Four rats were treated with octreotide three times daily while another group of four rats were treated with saline only. After 6 weeks of treatment, histopathological and immunohistological analyses were performed. The tumor weights of rats treated with octreotide were significantly lighter than those of untreated rats. All rats implanted mGH3, but not administered treatment, developed inguinal lymph node metastases, whereas none of those implanted mGH3 and treated with octreotide developed such metastases. The proportion of PCNA-stained tumor cells was higher in tumors of untreated rats than in those of octreotide-treated rats. However, the proportion of apoptotic cells in the tumor was not different between treated and untreated rats. Our results suggest that octreotide might be potentially effective for invasive and malignant human pituitary tumors by regulating the tumor cell cycle.

[A resected case of lung cancer with an extrapericardial single trunk formed by the left pulmonary veins]

We successfully performed left lower lobectomy in a lung cancer patient with anatomical variation in which left superior and inferior pulmonary veins were connected to the left atrium after foaming an extrapericardial single trunk. When indicating lobectomy, confirming the presence of such anatomical variation is clinically significant to prevent the development of pulmonary edema in the residual lung due to improper division of the single trunk as well as preventing subsequent possibly essential completion pneumonectomy.

Flavonoid-induced expression of a symbiosis-related gene in the cyanobacterium Nostoc punctiforme

The flavonoid naringin was found to induce the expression of hrmA, a gene with a symbiotic phenotype in the cyanobacterium Nostoc punctiforme. A comparative analysis of several flavonoids revealed the 7-O-neohesperidoside, 4'-OH, and C-2-C-3 double bond in naringin as structural determinants of its hrmA-inducing activity.

The somatosensory evoked magnetic fields

Averaged magnetoencephalography (MEG) following somatosensory stimulation, somatosensory evoked magnetic field(s) (SEF), in humans are reviewed. The equivalent current dipole(s) (ECD) of the primary and the following middle-latency components of SEF following electrical stimulation within 80-100 ms are estimated in area 3b of the primary somatosensory cortex (SI), the posterior bank of the central sulcus, in the hemisphere contralateral to the stimulated site. Their sites are generally compatible with the homunculus which was reported by Penfield using direct cortical stimulation during surgery. SEF to passive finger movement is generated in area 3a or 2 of SI, unlike with electrical stimulation. Long-latency components with peaks of approximately 80-120 ms are recorded in the bilateral hemispheres and their ECD are estimated in the secondary somatosensory cortex (SII) in the bilateral hemispheres. We also summarized (1) the gating effects on SEF by interference tactile stimulation or movement applied to the stimulus site, (2) clinical applications of SEF in the fields of neurosurgery and neurology and (3) cortical plasticity (reorganization) of the SI. SEF specific to painful stimulation is also recorded following painful stimulation by CO(2) laser beam. Pain-specific components are recorded over 150 ms after the stimulus and their ECD are estimated in the bilateral SII and the limbic system. We introduced a newly-developed multi (12)-channel gradiometer system with the smallest and highest quality superconducting quantum interference device (micro-SQUID) available to non-invasively detect the magnetic fields of a human peripheral nerve. Clear nerve action fields (NAFs) were consistently recorded from all subjects.

Type I and type II T-cell profiles in aplastic anemia and refractory anemia

Immune-mediated suppression of hematopoiesis has been considered the most important mechanism in the development of idiopathic aplastic anemia (AA) and some types of myelodysplastic syndrome (MDS). Using flow cytometric analysis of intracellular cytokine expression at the single-cell level, we analyzed helper-T (Th) and cytotoxic-T (Tc) subsets in patients with AA and MDS of refractory anemia (RA) subtype. The results showed marked increases in the Th1/Th2 ratio and Tc1/Tc2 ratio in both AA and MDS/RA. Overproduction of cytokines inhibitory to hematopoiesis reported so far might be a reflection of imbalanced development of Th and Tc. Determination of the factors that affect Th and Tc profiles may lead to further understanding of immunological states and the development of effective immunotherapy in AA as well as some types of MDS.

Bystander effect in herpes simplex virus-thymidine kinase/ganciclovir cancer gene therapy: role of gap-junctional intercellular communication

Antitumor suicide gene therapy is one of the emerging strategies against cancer. It consists of the introduction into cancer cells of a gene capable of converting a nontoxic prodrug into a cytotoxic drug. Because this therapeutic gene cannot be easily introduced into the whole cell population of a tumor, the successful eradication of tumors depends on a phenomenon called the "bystander effect," by which the introduced gene can affect even cells in which it is not itself present. From a therapeutic point of view, it may be crucial to enhance this phenomenon through various means to achieve tumor eradication. One such suicide gene, the thymidine kinase gene from the herpes simplex virus, in combination with the prodrug ganciclovir, has been extensively and successfully used in some animal models exhibiting a strong bystander effect. Among the mechanisms involved in this phenomenon, gap junctional intercellular communication (GJIC) is directly involved in the transfer of the toxic metabolites of ganciclovir, which pass directly from herpes simplex virus thymidine kinase-expressing cells to surrounding cells that do not express it. Because GJIC appears to be a mediator of the bystander effect both in vitro and in vivo, here we review possible molecular strategies for enhancing the extent of tumor cell death by increasing the intratumoral GJIC capacity.

Magnetic response of human extrastriate cortex in the detection of coherent and incoherent motion

Although direction selectivity is a cardinal property of neurons in the visual motion detection system, movement of numerous elements without global direction (incoherent motion) has been shown to activate human and monkey visual systems, as does coherent motion which has global direction. We used magnetoencephalography to investigate the neural process underlying responses to these types of motions in the human extrastriate cortex. Both motions were created using a random dot kinematogram and four speeds (0, 0.6, 9.6 and 25 degrees /s). The visual stimuli were composed of two successive motions at different speeds; a coherent motion at a certain speed that changed to incoherent motion at another speed or vice versa. Magnetic responses to the change in motion consisted of a few components, the first of which was always largest. The peak latency of the first component was inversely related to the speed of the preceding motion, but for both motions it was not affected by the speed of the subsequent motion. For each subject, the estimated origin of the first component was always in the extrastriate cortex, and this changed with the speed of the preceding motion. For both motions, the location for the slower preceding motion was lateral to that for the faster preceding motion. Although the latency changes of the two motions differed, their overall response properties were markedly similar. These findings show that the speed of incoherent motion is represented in the human extrastriate cortex neurons to the same degree as coherent motion. We consider that the human visual system has a distinct neural mechanism to perceive random dots' motion even though they do not move in a specific direction as a whole.