Serum midkine levels are increased in patients with various types of carcinomas

The level of expression of midkine (MK), a heparin-binding growth factor, is increased in many types of human carcinomas. An enzyme-linked immunoassay, which utilizes a combination of rabbit and chicken antibodies revealed that serum MK level in the controls (n = 135) was 0.154 +/- 0.076 (mean +/- SD) ng ml(-1)with an apparent cut-off value as 0.5 ng ml(-1). Serum MK level was significantly elevated in the cancer patients (n = 150) (P< 0.001); 87% of the patients showed levels of more than 0.5 ng ml(-1). All ten types of cancer examined showed a similar profile of serum MK level. There was no or weak correlation between C-reactive protein level, a marker of inflammation, and serum MK level. Furthermore, in case of gastric carcinoma and lung carcinoma, patients with stage I carcinoma already showed elevated serum MK levels. The present results indicated that serum MK could serve as a general tumour marker with a good potential for clinical application.

Distribution of nociceptin/orphanin FQ precursor protein and receptor in brain and spinal cord: a study using in situ hybridization and X-gal histochemistry in receptor-deficient mice

Nociceptin/orphanin FQ (N/OFQ) is an opioid-like heptadecapeptide agonist for the opioid receptor homolog, N/OFQ receptor. To explore the precise distribution of the peptide-receptor system, the authors examined the brain and spinal cord from receptor-deficient mice bearing the targeted mutation (morc(m1)), a lacZ insertional mutation in the N/OFQ receptor gene. Precursor protein N/OFQ (preproN/OFQ) mRNA was detected by using in situ hybridization, and the N/OFQ receptor was detected by using X-gal histochemistry. The N/OFQ receptor reflected by lacZ expression was observed at high levels in the dentate gyrus, lateral septum, subparafascicular thalamic nucleus, medial preoptic area, median preoptic nucleus, ventromedial preoptic nucleus, anterior hypothalamic area, paraventricular hypothalamic nucleus, ventromedial hypothalamic nucleus, auditory brainstem nuclei, pontine dorsal tegmentum, and nucleus of the solitary tract. In situ detection of the N/OFQ receptor mRNA by digoxigenin-labeled riboprobes coupled with tyramide signal amplification in normal and wild-type mice resulted in the regional distribution paralleling the lacZ expression in these regions. PreproN/OFQ mRNA was expressed at high levels in the subparafascicular thalamic nucleus, central gray, central tegmental field, auditory brainstem nuclei, caudal spinal trigeminal nucleus, and spinal dorsal horn. Furthermore, variable levels of expression of the peptide and receptor were seen in distinct sites of the brain and spinal cord. These data indicate a correspondence of the peptide and the receptor in local distribution at limbic, hypothalamic, and brainstem sites. Together with concurrent physiologic and behavioral studies in mutant mice, the results suggest functional roles for the N/OFQ system, including the central regulation of learning and memory, hearing ability, water balance, food intake, and blood pressure.

Influence of sodium impurities on arf excimer-laser-induced absorption in CaF2 crystals

The formation of color centers induced by irradiation with ArF excimer lasers in CaF(2) crystals was found to depend strongly on the sodium impurity concentration. Sodium-related color centers were generated by two-photon absorption because the slope of the induced absorption coefficient just after irradiation started was proportional to the square of the laser fluence. The saturation absorption also depended on laser fluence, and a photobleaching induced absorption phenomenon was observed. We concluded that the saturation absorption level was determined by the equilibrium between two-photon excitation and one-photon reverse reaction.

Distribution of cells labelled by a monoclonal antibody (A3) against a cloned cell line derived from a rat malignant fibrous histiocytoma

To pursue the histogenesis of malignant fibrous histiocytoma (MFH), of which the cell of origin is still debated, a monoclonal antibody (A3) was produced against a rat MFH-derived cloned cell line (MT-8). Antigen recognized by A3 was around 80 kDa in molecular weight and was seen on the cytoplasmic membrane of MT-8 cells by immunoelectron microscopy. A3 reacted specifically with MT-8 cells, with another rat MFH-derived cell line (MT-9) and with their induced tumours in syngeneic rats, but not with other rat tumours such as fibrosarcoma, histiocytic sarcoma, malignant meningioma, uterine leiomyosarcoma, endometrial stromal sarcoma, mononuclear cell leukaemia and malignant schwannoma. These findings indicate that A3 has a high specificity for rat MFH cells. In fetuses on gestation days 15, 18 and 20 and in postnatal rats aged 1, 4 and 8 days, A3 reacted with primitive mesenchymal cells in visceral organs and around arteries and bronchi, as well as in the lamina propria of intestinal mucosa, renal interstitium, meninges and perineurium. There were no A3-positive connective tissue cells in organs or other sites in adult rats more than 10 weeks old. It is therefore likely that MFH cells share antigens with primitive mesenchymal cells, which may be multipotent for mesenchymal differentiation. The present study suggests that MFH consists of a population of primitive, undifferentiated mesenchymal cells. A3 also immunolabelled endothelial cells of arteries, venules and pulmonary capillaries in fetal, postnatal and adult rats; vascular endothelial cells in chemically induced hepatic and renal lesions also reacted strongly with A3. However, the significance of endothelial immunoreactivity with A3 remains to be elucidated.

A heparin-binding growth factor, midkine, binds to a chondroitin sulfate proteoglycan, PG-M/versican

Midkine is a heparin-binding growth factor with survival-promoting and migration-enhancing activities. In order to understand the regulation of midkine signaling, we isolated midkine-binding proteoglycans from day 13 mouse embryos, when midkine is intensely expressed. Deglycosylation followed by SDS/PAGE revealed various protein bands; one of these was identified as PG-M/versican by in gel trypsin digestion and sequencing the resulting peptides. PG-M/versican isolated from day 13 mouse embryos bound midkine with a Kd of 1.0 nM. Pleiotrophin/heparin-binding growth-associated molecule, which has a structure related to midkine, was also bound similarly. Digestion with chondroitinase ABC, AC-I or B abolished the binding to midkine. Heparin as well as chondroitin sulfate D and E inhibited the binding. After chondroitinase ABC digestion, the midkine-binding PG-M/versican released 4-sulfated, 6-sulfated, 2, 6-disulfated and 4,6-disulfated unsaturated disaccharides. These results suggest that midkine binds to a polysulfated domain in the chondroitin sulfate chain with a region of dermatan sulfate structure. This proteoglycan may modulate the midkine activity, as binding to midkine can enhance midkine action by concentrating it to the cell periphery or inhibit the action by competing with the binding to a signaling receptor.

Expressions of vascular endothelial growth factor and basic fibroblast growth factor in tumors induced by two different cloned cell lines established from transplantable rat malignant fibrous histiocytoma

In order to establish base-line data on angiogenic factors in development of mesenchymal tumors, expressions of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) in implanted MT-8 and MT-9 tumors, both derived from a transplantable malignant fibrous histiocytoma (MFH) in the F344 rat, were investigated by immunohistochemistry and Western blotting method. MT-8 and MT-9 tumors were developed in syngeneic rats by implant of a tumor tissue fragment. MT-8 tumors were examined on post-implantation (PI) days 3, 6, 9 and 17, and MT-9 tumors were on PI days 9, 14, 17 and 23. The growth of MT-8 tumors was faster than that of MT-9 tumors. Histologically, MT-8 tumors were features of undifferentiated sarcomas, whereas MT-9 tumors exhibited a typical storiform growth pattern of MFH. Immunohistochemically, all cells constituting MT-8 and MT-9 tumors reacted with antibodies to VEGF and bFGF, indicating production of these factors by mesenchymal neoplastic cells. However, there were no marked differences in these immunoreactions between tumors examined. Thus, the bands obtained in the Western blotting methods were densitometrically scanned. The expression levels of VEGF and bFGF gradually increased PI day 3 to 9 in MT-8 tumors and PI day 9 to 17 in MT-9 tumors. On last examination day, the levels of bFGF in both tumors and of VEGF in MT-9 tumors decreased, but the VEGF expression level in MT-8 tumors was still increased. These findings indicated that VEGF and bFGF may contribute cooperatively to angiogenesis in an early growth of mesenchymal tumor development.

Tetrahydrobiopterin inhibits copper-induced oxidation of low density lipoprotein

The effect of tetrahydrobiopterin (BPH4) on Cu2+-induced oxidation of low density lipoprotein (LDL) prepared from rabbit plasma was examined. BPH4 (0.5-10 microM) inhibited the formation of thiobarbituric acid-reactive substances (TBARS) in LDL induced by 5 microM Cu2+ in a dose-dependent manner. BPH4 also suppressed the increase in relative electrophoretic mobility (REM) of LDL in the presence of 5 microM Cu2+. The potency of inhibitions of BPH4 on TBARS formation and REM was the same as or stronger than that of ascorbic acid and alpha-tocopherol, which are known as endogenous inhibitors of LDL oxidation. These results suggest that BPH4 could act as an efficacious endogenous inhibitor of atherogenic LDL modification.

LDL receptor-related protein as a component of the midkine receptor

Midkine (MK) is a heparin-binding growth factor with migration-promoting and survival-promoting activities. To identify signaling receptor(s) of MK, membrane glycoproteins with MK-binding activity were isolated from day 13 mouse embryos by lectin- and MK-affinity chromatography. SDS-PAGE followed by protein sequence analysis revealed the presence of LDL receptor-related protein (LRP) and NCAM in the fraction. The dissociation constant of binding between LRP and MK was 3.5 nM. Receptor-associated protein (RAP), which interfered with the binding, inhibited MK-dependent survival of embryonic neurons. Brushin/megalin, which is also a high molecular weight protein belonging to the LDL receptor family, bound to MK less strongly than LRP. These findings suggest that LRP is a component of the receptor complex for MK.

Kinetics of lymphocytic subsets in chicken tracheal lesions infected with infectious bronchitis virus

The kinetics of T-cells (CD3 positive (+), CD4+ and CD8+ cells) and B-cells (IgG+, IgM+ and IgA+ cells) in chicken trachea were studied immunohistochemically and histopathologically following an intratracheal inoculation of infectious bronchitis virus (IBV). Viral antigen was detected in the cytoplasm of tracheal epithelium from 16 hr to 6 days post-inoculation (p.i.) with a peak on 4 days p.i. A few IgG+, IgM+ and IgA+ cells were detected in the submucosa from 8 hr p.i. Thereafter IgG+ and IgM+ cells were gradually increased in number, and dramatically increased from 3 days p.i., peaked on 4 days p.i., and gradually decreased after 5 days p.i. IgA+ cells were detected in a small number than IgG+ and IgM+ cells during the all experimental period. These B cells mainly existed in the lamina propria, and some cells were recognized in the interepithelial space. After 14 days p.i., small number of IgG+ and IgM+ cells were detected in the germinal center of lymph follicles in the lamina propria. From 24 to 60 hr p.i., a few number of CD3+, CD4+ and CD8+ cells were detected at the perivascular area in the lamina propria. After 3 or 4 days p.i., each positive T-cells increased rapidly in number, and reached on the peak at 5 days p.i. CD3+, CD4+ and CD8+ cells tend to distribute diffusely, perivascular area, and surrounding area of CD4+ cells, respectively. CD4+ cells were dramatically decreased from 7 days p.i., and CD3+ and CD8+ cells were decreased from 14 days p.i. No T-cells were detected in the lymph follicles in the lamina propria.

Glial pathology in development of cerebellar dysplasia in the hereditary cerebellar vermis defect (CVD) rat

The cerebellar vermis defect (CVD) rat is a new neurological mutant characterized by a cerebellar vermis defect and dysplasia in the cerebellum, especially at the cerebellopontine junctions. In this study, the cytokinetics of glia in terms of the development of cerebellar dysplasia in the CVD rat was investigated using glial fibrillary acidic protein (GFAP) and vimentin immunohistochemistry. In the cerebellar hemispheres, dislocation of the Bergmann glia was observed from postnatal day 5 (P5) in lesions with abnormally aggregated external granule cells (EGCs). Rearranging Bergmann glia were often seen around the EGCs penetrating into the white matter. In the cerebellopontine junctional areas, Bergmann glia were induced after penetration of the Purkinje cells, identified with calbindin immunohistochemistry, and EGCs into the pons from P10. Bergmann fibers were frequently arranged perivascularly. In the clusters of Purkinje cells without EGC settlement in the pons, a small number of Bergmann fibers were observed and their alignment was completely disturbed. These findings suggest that morphological changes in the Bergmann glia depend on their contact with Purkinje cells, but that the orientation of their processes may be influenced by EGC settlement. These glial fibers in the CVD rat may play an important role in the aberrant migration of EGCs, resulting in the development of cerebellar dysplasia.

Spontaneous and ethyl-nitrosourea-induced medullomyoblastomas in cerebellar vermis defect (CVD) mutant rats

A 26-week-old female cerebellar vermis defect (CVD) rat, a mutant with cerebellar vermis defect and cerebellar dysplasia, developed a brain tumor about 10 mm in diameter. Histopathologically, the tumor consisted of diffuse proliferation of small round to ovoid cells with hyperchromatic nuclei, occasionally containing round to strap-shaped myoblastic cells. Immunohistochemically, the small round cells expressed neuron-specific enolase and synaptophysin, indicating neuronal differentiation; myoblastic components reacted to desmin, myoglobin, and vimentin. Based on these findings, the case was diagnosed as a medullomyoblastoma (MMB). Furthermore, two cerebella tumors in CVD rats, which were induced by transplacental application of ethyl-nitrosourea, showed histopathology similar to the aforementioned case. MMB is a very rare tumor in humans and animals; thus, it is noteworthy that MMBs developed in CVD rats, involving the dysplastic cerebellum with abnormal migration of external granule cells.

Three-dimensional morphology of the masseter muscle in patients with mandibular prognathism

OBJECTIVE

To compare the morphology of the masseter muscle in patients with mandibular prognathism with that of normal subjects.

METHODS

Three-dimensional X-ray computed tomography (CT) was performed on 69 patients with mandibular prognathism and compared with 91 normal subjects. The angle of the muscle direction in relation to the Frankfurt horizontal plane and the area and the ratio of length of the short to long axes (s/l ratio) on the section perpendicular to the muscle direction were measured.

RESULTS

The mean angle, area and s/l ratio in patients with mandibular prognathism was 76.6 degrees (s.d. 4.4 degrees), 318.3 mm2 (s.d. 77.2 mm2) and 0.312 (s.d. 0.049), respectively. Those of the normal subjects were 65.1 degrees (s.d. 4.4 degrees), 368.3 mm2 (s.d. 97.2 mm2) and 0.393 (s.d. 0.054), respectively. The angle was significantly larger, and the area and s/l ratio were significantly smaller than those of normal subjects (P < 0.001).

CONCLUSION

The morphology of the masseter muscle in mandibular prognathism is significantly different from that of normal subjects. Our results may be helpful in evaluating the results of orthognathic surgery.

FK506 inhibition of histamine release and cytokine production by mast cells and basophils

Histamine release and cytokine production by mast cells and basophils are thought to be closely involved in the pathogenesis of allergic diseases. Some reports show that FK506 (tacrolimus hydrate) inhibited histamine release and cytokine production by mast cells and basophils. However, as the effects of FK506 has not been compared with those of clinically used drugs in those reports, the clinical relevancy of FK506 inhibition remained unclear. In this paper, we compared the actions of FK506 with those of steroids or disodium cromoglycate (DSCG) which has been clinically used. FK506 inhibited histamine release by Brown-Norway rat peritoneal mast cells more potently than steroids and especially DSCG. FK506 also inhibited histamine release by a mast rat basophilic leukemia (RBL)-1 cell line and human peripheral blood basophils, whereas steroids failed to inhibit histamine release by human basophils. FK506 as well as steroids inhibited TNF-alpha and IL-4 production by RBL-1 cells. FK506 was therefore more effective than steroids and DSCG in inhibiting histamine release, and it also had the ability of inhibiting cytokine production by mast cells as steroids do. We concluded that FK506 might regulate allergic diseases via these actions, judging from the viewpoint of clinical relevancy.

Distribution of cells immunopositive for AM-3K, a novel monoclonal antibody recognizing human macrophages, in normal and diseased tissues of dogs, cats, horses, cattle, pigs, and rabbits

The monoclonal antibody AM-3K, which was developed using human pulmonary macrophages as the immunogen, immunocytochemically labels most human macrophages except for blood monocytes and dendritic cell populations. AM-3K also shows cross-reactivity in some animal species. To evaluate the usefulness of AM-3K, the present study investigated the detailed distribution of AM-3K-immunopositive macrophages in normal and diseased tissues of dogs, cats, horses, cattle, pigs, and rabbits. Zamboni's solution-fixed, paraffin-embedded sections were the most available for the immunocytochemistry with AM-3K. In all animal species examined, AM-3K labeled most macrophages in splenic red pulp, lymph node sinuses and thymus, and tissue macrophages in the interstitium of various organs and sites such as the kidneys, lungs, heart, pancreas, intestines, and skin. Alveolar macrophages and perivascular microglial cells were also immunoreactive for AM-3K. Interestingly, Kupffer cells of dogs, cats, and horses were labeled for AM-3K, but those of cattle, pigs, and rabbits were not. Furthermore, in tumor tissues and inflammatory lesions such as liver fibrosis and encephalomalacia that were obtained from dogs, infiltrating macrophages were stained with AM-3K, but not all infiltrating macrophages reacted to AM-3K. In addition, only 30-50% of pulmonary and peritoneal macrophages obtained from cats and dogs were reactive for AM-3K. AM-3K did not react with blood monocytes, dendritic cell populations, and osteoclasts. These observations indicate that AM-3K specifically labels most exudate and tissue macrophages in the animal species examined. However, the expression of antigens recognized by AM-3K on macrophages may be dependent on differential maturation stages or different functions evoked by some conditions. AM-3K immunoreaction products were seen on the cytoplasmic membrane of macrophages by immunoelectron microscopy. AM-3K would be useful for detection of macrophage populations in the animal species examined here.

Neointima formation in a restenosis model is suppressed in midkine-deficient mice

Neointima formation is a common feature of atherosclerosis and restenosis after balloon angioplasty. To find a new target to suppress neointima formation, we investigated the possible role of midkine (MK), a heparin-binding growth factor with neurotrophic and chemotactic activities, in neointima formation. MK expression increased during neointima formation caused by intraluminal balloon injury of the rat carotid artery. Neointima formation in a restenosis model was strongly suppressed in MK-deficient mice. Continuous administration of MK protein to MK-deficient mice restored neointima formation. Leukocyte recruitment to the vascular walls after injury was markedly decreased in MK-deficient mice. Soluble MK as well as that bound to the substratum induced migration of macrophages in vitro. These results indicate that MK plays a critical role in neointima formation at least in part owing to its ability to mediate leukocyte recruitment.

The regulation of prostaglandin and arachidonoyl-CoA formation from arachidonic acid in rabbit kidney medulla microsomes by palmitoyl-CoA

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of palmitic acid (PA) and palmitoyl-CoA (PA-CoA) on the PG and AA-CoA formation from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [14C]-AA in 0.1 M-Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl2 and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. PA (10-100 microM) had no effect on the PG and AA-CoA formation from either 60 or 5 microM AA. PA-CoA (10-100 microM) was without effect on the PG and AA-CoA formation from 60 microM AA, whereas it markedly decreased the PG formation (6-40%) and increased the AA-CoA formation (1.1-2.3-fold) from 5 microM AA, showing that the effects of PA-CoA on the PG and AA-CoA formation change depending on the AA concentration. These results suggest that PA-CoA, but not PA, may regulate the PG and AA-CoA formation at low substrate concentrations (close to the physiological concentration of AA), and that this in-vitro method using 5 microM AA may be useful for clarifying the homeostatic control of the metabolic fate of AA into these two enzymatic pathways.

Epithelial cell kinetics in the inflammatory process of chicken trachea infected with infectious bronchitis virus

All stages of degeneration and regeneration in chicken tracheal epithelium were studied morphologically following an intratracheal inoculation of infectious bronchitis virus (IBV). Viral antigen was detected in the cytoplasm of tracheal epithelium from 1 to 7 days post-inoculation (d.p.i.) with a peak on 3 d.p.i. At 1 d.p.i., almost all epithelial cells were involved in the degeneration. At this time, labelling index of bromodeoxyuridine (BrdU) in the basal cells showed significantly high value compared with control. At 2 and 3 d.p.i., a great number of basal cells were recognized, but the BrdU labelling index tended to decrease. At 4 and 5 d.p.i., the BrdU labelling index of basal cells significantly decreased than 1 d.p.i., and a few number of regenerated immature ciliated epithelia appeared. At 6 to 11 d.p.i., the ciliated columnar epithelia increased rapidly in number, and returned to the normal appearance except for non-ciliated patch by 13 d.p.i. These results suggested that the tracheal epithelial cells infected with IBV degenerated within 24 hours and proliferating activity of basal cells functioned immediately, and 3 to 4 days later, these basal cells were differentiated to the ciliated epithelia.

Midkine rescues Wilms' tumor cells from cisplatin-induced apoptosis: regulation of Bcl-2 expression by Midkine

Midkine (MK) is a heparin-binding growth factor involved in diverse biological phenomena, e.g. neuronal survival, carcinogenesis, and tissue repair. MK expression is detected mainly in the kidney in adult mice. In this study, we show that, at a dose that can induce recoverable renal damage and induce apoptosis, cisplatin (CDDP) transiently suppressed MK expression in mouse kidney. In vitro, CDDP suppressed MK expression and induced apoptosis in cultured G401 cells, a Wilms' tumor cell line. Exogenous MK protein partially rescued G401 cells from CDDP-induced apoptosis. MK enhanced the expression of Bcl-2, but not that of Bcl-x(L), in G401 cells in a dose-dependent manner, and it prevented the Bcl-2 reduction due to CDDP. Moreover, Bcl-2 expression in mouse kidney was also transiently suppressed by CDDP treatment, the expression profile being similar to that of MK. These results imply that MK exerts cytoprotective activity toward a damaging insult, presumably at least in part through enhancement of the expression of Bcl-2.

Midkine binds specifically to sulfatide the role of sulfatide in cell attachment to midkine-coated surfaces

Midkine is a heparin-binding polypeptide which is implicated in the control of development and repair of various tissues. Recognition of sulfate groups in glycosaminoglycans is important for its function. To elucidate further its mechanism of action, the interactions of midkine with sulfated glycolipids were studied. Of various glycolipids and lipids examined, midkine bound strongly to sulfatide and cholesterol-3-sulfate (CHO-3-SO4) in a dose-dependent manner but failed to bind to other standard glycolipids and lipids. The properties of midkine binding to sulfatide and to CHO-3-SO4 differed in their sensitivity to inhibition by anionic polysaccharides, salt concentration and unlabeled midkine. Heparin inhibited midkine binding to sulfatide but weakly inhibited its binding to CHO-3-SO4. Liposomes bearing sulfatide carried out significant interactions with immobilized midkine, whereas those bearing CHO-3-SO4 did not. Incorporation of sulfatide into 32D cells and trypsinized COS cells enhanced 125I-labelled midkine binding, whereas incorporation of ganglioside or galactosylceramide had no effect. Furthermore, sulfatide-incorporated cells enhanced cell attachment to midkine-coated coverslips. These results indicate that midkine binds to sulfatide under physiological conditions and the midkine-sulfatide interaction may be important in controlling cell attachment.

Comparative distribution of GABAergic and peptide-containing neurons in the lateral lemniscal nuclei of the rat

By immunostaining, neurons expressing peptides (dynorphin and corticotropin-releasing factor, CRF) and glutamate decarboxylase (GAD), a GABA-synthesizing enzyme, were precisely mapped in the rat lateral lemniscal nuclei. While GAD neurons were numerous and preferably localized in the dorsal (DLL) and ventral (VLL) nuclei, neurons expressing these peptides were less numerous and localized primarily in the intermediate (ILL) nucleus of the lateral lemniscus. The ILL nucleus was shown to project to the inferior colliculus and to express Fos rapidly in response to peripheral acoustic stimulation, suggesting that the ILL nucleus may take part in non-GABAergic relay of acoustic information in the lateral lemniscus.

Influence of highly curved DNA segments on in vivo topology of plasmids

Recombinant plasmids carrying a highly curved DNA structure are sometimes unstable in Escherichia coli. In order to know the underlying mechanism, several plasmids carrying one or two highly bent DNA segment(s) from the human adenovirus type 2 (Ad2) enhancer and/or origin region of phage lambda replication were systematically constructed and propagated in E. coli. The highly bent DNA segments disturbed the action of DNA topoisomerases: i.e. they were shown to be able to produce an anomalously wide spectrum of linking number topoisomers that tails toward lower supercoiling with a little of the DNA actually positively supercoiled. Furthermore, bent DNA caused multimeric plasmid formation. The linking number topoisomers and multimers seemed to be intermediate topological states of the bent DNA-containing plasmids that would lead to the deletion occurring in them. The nucleotide sequence of a deletion product of a bent DNA-containing plasmid showed that the putative source of the severe topological constraint was entirely eliminated from the plasmid.

Effect of 13-hydroperoxyoctadecadienoic acid on the supply of arachidonic acid for prostaglandin synthesis from arachidonoyl-CoA mediated by the cytosolic or microsomal acyl-CoA hydrolase in rabbit kidney medulla

The effects of 13-hydroperoxyoctadecadienoic acid (13-HPODE) on the cytosolic or microsomal acyl-CoA hydrolase (ACH) activity in rabbit kidney medulla and on the ACH-mediated prostaglandin (PG) formation from arachidonoyl-CoA (AA-CoA) were examined. 13-HPODE (10, 20, and 50 microM) had no effect on the cytosolic ACH activity but significantly inhibited the activity of the microsomal enzyme (43-57% inhibition). PG formation was measured as follows: AA-CoA (20 nmol) was preincubated with the cytosolic or microsomal fraction (as the source of ACH) in the presence or absence of 13-HPODE for 5 min at 37 degrees C, followed by incubation with the microsomal fraction (as the source of PG-synthesizing enzymes), hydroquinone and reduced glutathione for 5 min at 37 degrees C, and the PGs formed were measured by HPLC, with use of 9-anthryldiazomethane for derivatization. 13-HPODE reduced the PG formation when the microsomal fraction, but not the cytosolic fraction, was used as the source of ACH (10, 20, and 50 microM; 28-55% inhibition). These results suggest that 13-HPODE may modulate PG levels in rabbit kidney medulla by inhibiting the microsomal ACH activity.

Nuclear proliferation in syncytia during avian reovirus replication

Cultured chick embryonic fibroblasts formed syncytia after infection with avian reovirus (ARV) strain 58-132. Mitotic figures were occasionally observed within the syncytia. In addition, many nuclei in the syncytia incorporated 5-bromo-2'-deoxyuridine (BrdU), a DNA replication marker, indicating that they were in the S-phase of the cell cycle. These observations suggested that the nuclei within ARV-induced syncytia originated from nuclear endomitosis without cell division, as well as from cell fusion.