Purification and characterization of S-adenosyl-L-methionine: norcoclaurine 6-O-methyltransferase from cultured Coptis japonica cells

S-adenosyl-L-methionine:norcoclaurine 6-O-methyltransferase (norcoclaurine 6-O-methyltransferase), which catalyzes the transfer of the S-methyl group of S-adenosyl-L-methionine to the 6-hydroxyl group of 1,2,3,4-tetrahydro-1-[(4-hydroxyphenyl)methyl]-6,7- isoquinolinediol (norcoclaurine), was purified from cultured Coptis japonica cells and its enzymic properties were characterized. Purified norcoclaurine 6-O-methyltransferase had apparent pI 4.7, a native molecular mass of 95 kDa (determined by gel filtration) and subunit molecular mass of 40 kDa (SDS/PAGE). The enzyme did not require a divalent cation for activity, and the addition of Fe2+, Cu2+, Co2+, Zn2+, Mn2+, or Ni2+ at 5 mM severely inhibited enzyme activity. Neither p-chloromercuribenzoate, N-methylmaleimide nor iodoacetamide inhibited enzyme activity at 1 mM. 5,6-Dihydro-9,10-dimethoxybenzo[g]-1,3-benzodioxolo[5,6-a]qu inolizinium (berberine, the end-product of the biosynthetic pathway in which norcoclurine 6-O-methyltransferase catalyzes an intermediate step) also inhibited the activity by 50% at 10 mM. Norcoclaurine 6-O-methyltransferase methylated both (S)-norcoclaurine and (R)-norcoclaurine and (R,S)-norlaudanosoline. Further characterization of substrate-saturation kinetics and product inhibition of the purified enzyme indicated that norcoclaurine 6-O-methyltransferase follows a bi-bi ping-pong mechanism with Km values of 2.23 mM and 3.95 mM for (R,S)-norlaudanosoline and S-adenosyl-L-methionine, respectively, while Ki values for S-adenosylhomocysteine versus S-adenosyl-L-methionine and (R,S)-norlaudanosoline were 2.1 mM and 0.18 mM, respectively.

[Age-related changes of urinary collagen crosslinks and serum osteocalcin in postmenopausal women]

Urinary collagen crosslinks, lysyl pyridinoline (LP) and hydroxy lysyl pyridinoline (HL), have been shown to be specific parameters of bone degradation, while serum osteocalcin, referred to as bone Gla-protein (BGP), has been used as a sensitive marker of bone formation. The current cross-sectional study was designed to compare between pyridinoline contents in initial fasting urine and serum BGP in postmenopausal women aged 50-90 years. Both LP and HL increased by around 20% and BGP increased by nearly 30% in a later stage of menopause, indicating the possibility that bone turnover did not decline with age as far as could be assessed by these chemical markers. It was of interest that significant correlations of pyridinoline to BGP in the 50s and 60s (r = 0.52 - 0.60, p < 0.05) became insignificant after age 70. Although there is a limitation to these biochemical markers, the present data indicate that the coupling mechanism between bone resorption and formation may become inefficient with aging in postmenopausal women.

Prevention of insulitis and diabetes in beta 2-microglobulin-deficient non-obese diabetic mice

beta 2-Microglobulin (beta 2m)-deficient non-obese diabetic (NOD) mice were established by crossing beta 2m-deficient 129/Sv mice with NOD mice, and used to examine the possible involvement of MHC class I molecules and CD8+ T cells in the development of insulitis and diabetes. In these mice, MHC class I molecules were not expressed, resulting in no generation of CD8+ T cells. None of eight lines of beta 2m-deficient NOD mice (-/-) established developed overt diabetes by 32 weeks, while control littermates (+/+) became diabetic by 22 weeks. histological studies showed no significant lymphocyte infiltration of the islets (insulitis score: 0.03 +/- 0.03) in any of the beta 2m-deficient NOD mice (-/-) compared with littermate NOD mice (+/+) with overt insulitis (1.42 +/- 0.28). These findings support the notion that the expression of MHC class I molecules and/or CD8+ T cells plays an essential role in the infiltration of CD4+ T cells in islets as well as the development of diabetes in NOD mice.

T cell receptor V alpha repertoire of infiltrating T cells in labial salivary glands from patients with Sjögren's syndrome

OBJECTIVE

To analyze the T cell receptor (TCR) V alpha repertoire of infiltrating T cells in labial salivary glands of patients with Sjögren's syndrome (SS).

METHODS

TCR V alpha genes of infiltrating T cells in lips from 2 patients with SS were examined, using the double step inverse polymerase chain reaction. Four and 7 clones encoding the VJC alpha region were established and sequenced, respectively.

RESULTS

All 4 clones used the V alpha 17.1 gene in one patient, while 3 (42.8%) of 7 clones from the other patient used the V alpha 2 family gene (V alpha 2.1, V alpha 2.2, V alpha 2.4), and the other 3 clones used the V alpha 11.1 family gene. A comparison using labial salivary glands and peripheral blood showed that the predominant expression of V alpha 2, V alpha 11.1, and V alpha 17.1 gene segments is specific in the salivary glands.

CONCLUSION

The TCR V alpha repertoire of infiltrating T cells from the lips of 2 patients with SS was relatively restricted in individual patients, thereby suggesting the limited heterogeneity of these cells in salivary glands.

Stage-specific expression of c-myc messenger ribonucleic acid in porcine granulosa cells early in follicular growth

In the present study, the expression of c-myc mRNA in porcine granulosa cells harvested from varying follicle stages was analyzed using northern blot hybridization with a c-myc probe, and compared during follicular growth. Northern blot analysis revealed that porcine granulosa cell RNA obtained from small (1-2 mm) follicles contained an abundance of c-myc transcript of 2.4 kb, the size of which was identical to the c-myc transcript obtained with human early placental RNA used as the control. In contrast to small-follicle granulosa cell RNA, total RNA preparations from either medium (3-5 mm)-follicle granulosa cells or large (6-11 mm)-follicle granulosa cells exhibited no detectable transcripts with the c-myc probe. These results suggest that expression of c-myc mRNA in porcine granulosa cells is limited only at the early stage of follicular growth. The stage-specific expression of c-myc mRNA in granulosa cells early in follicular growth may play a physiological role in the autonomous growth of immature granulosa cells in early folliculogenesis, seemingly independent of pituitary gonadotropic stimulation.

Comparison of intravenous nutrients on gut mucosal proteins synthesis

BACKGROUND

Total parenteral nutrition (TPN) is associated with atrophy of the intestinal mucosa. This study compared the relative effectiveness of a short-chain fatty acid (butyrate), a physical mixture of medium-chain and long-chain triglycerides, structured lipid, and glutamine as components of a TPN regimen, and their ability to support mucosal protein synthesis.

METHODS

Rats were parenterally fed one of six isocaloric (1003 kJ/kg.d-1) and isonitrogenous (1.5 g.kg-1.d-1 of nitrogen) diets for 5 days. Diet 1, glucose 90% and long-chain triglycerides 10% (standard TPN); diet 2, glucose 50% and long-chain triglycerides 50%; diet 3, glucose 50% and a 50/50 physical mixture of long-chain and medium-chain triglycerides 50%; diet 4, glucose 50% and structured lipid 50%; diet 5, glucose 91% and sodium butyrate 9%; and diet 6, same as group 1 except that some of the amino acids were replaced with glycyl glutamine. A control group of rats also underwent catheter placement and were instead fed diet 1 orally for 5 days. Five days after catheterization, all rats were given a 4-hour constant infusion of [U-14C]leucine to determine the mucosal fractional protein synthesis rates.

RESULTS

(1) Mucosal fractional protein synthesis rates were much higher with the oral diet (control) than with any of the intravenous diets. (2) Diet-related differences in the mucosal fractional synthesis rates were found with the jejunum and the proximal and distal colon but not with the ileum. (3) Standard TPN was the least effective diet in supporting mucosal protein synthesis. (4) Structured lipid and butyrate were most effective for the jejunum. (5) For the colon, medium-chain triglycerides and structured lipid were most effective.

CONCLUSION

Standard TPN leads to a decrease in gut mucosal protein synthesis in rats, and this decrease can be partially attenuated by adding nutrients for the gut to the TPN mixture.

Electron microscopic observation of bFGF immunoreactivity in the hippocampus

Light and electron microscopic observation showed two types of neuronal immunostaining for basic fibroblast growth factor in the hippocampal CA2 subfield, where the densest immunoreactive neurons were localized in the brain. One neuronal type showed intense nuclear (eu- and heterochromatin) immunostaining but weak cytoplasmic immunostaining (N-type), and the other showed intense cytoplasmic but no or only faint nuclear immunoreactivity (C-type). The N-type also showed weak immunoreactivity in the perinuclear rough endoplasmic reticulum and contained bFGF mRNA as observed by in situ hybridization histochemistry, showed that this type can produces the bFGF protein. The N-type localized exclusively in the CA2 subfield. The C-type showed strong immunoreactivity on the rER, free ribosomes, and Golgi apparatus, although no clear evidence for bFGF production was observed. The multivesicular bodies, a pathway of endocytosis in hippocampal neurons showed apparent immunoreactivity under EM observation of both of types neurons (Parton et al. J. Cell Biol. 119: 123-137, 1992) suggesting a receptor-mediated type of incorporation of the bFGF.

Lipoprotein(a) is a risk factor for diabetic retinopathy in the elderly

OBJECTIVE

To assess whether serum lipoprotein(a) is a risk factor for diabetic retinopathy in the elderly.

DESIGN

A cross-sectional study.

SETTING

Outpatient diabetic clinic.

PATIENTS

One hundred four noninsulin-dependent diabetic patients (35 males, 69 females). Twenty-three were less than 60 years of age (middle-aged), and 81 were 60 years or older (elderly).

MEASUREMENT

Levels of lipoprotein(a) (Lp(a)) and lipids were measured in fasting serum. HbA1c was also measured as an indicator of diabetic control. Other indicators possibly related to retinopathy were also checked. Retinopathy was estimated by photographs of fundi.

RESULTS

Significantly higher indicators in the group with retinopathy than in the group without were: HbA1c, Lp(a), duration of diabetes, and systolic blood pressure (BP) in the total cases; HbA1c, duration of diabetes, and Lp(a) in the middle-aged; HbA1c, systolic BP, and Lp(a) in the elderly. Multiple logistic regression analysis showed that only HbA1c and Lp(a) were independent risk factors for retinopathy in all cases and in the elderly. The incidence of retinopathy was positively correlated to serum Lp(a) levels.

CONCLUSION

Lp(a) is an independent risk factor for diabetic retinopathy.

HLA-DR+CD3+ and CD8+ cells are increased but CD4+CD45RA+ cells are reduced in the peripheral blood in human scrub typhus

Immunological studies on scrub typhus (ST) have been limited mostly to animals despite the possible difference in the immune responses among the species of the hosts. To investigate in vivo cellular immune responses to ST in humans, we characterized T-cell subsets in the peripheral blood samples from 30 healthy control subjects (HC), 11 patients with nonrickettsial acute infections (NRAI), and 6 patients with ST by a dual labeling method of flow cytometry. In ST, HLA-DR+CD3+ cells were greatly increased compared with those in HC and NRAI (HC, 2.3 +/- 1.3%; NRAI, 4.5 +/- 4.4%; ST, 32.5 +/- 14.7% values are means +/- SD). CD8+ cells were also significantly increased (HC, 29.5 +/- 5.9%; NRAI, 30.5 +/- 9.4%; ST, 44.9 +/- 11.5%), while CD4+CD45RA+ cells were significantly reduced (HC, 23.6 +/- 8.2%; NRAI, 23.3 +/- 12.3%; ST, 12.9 +/- 7.1%) in ST. The unique changes in the T-cell subsets in the peripheral blood samples from the patients with ST support the importance of the cellular immune responses to the natural infection of ST in humans.

Hyperresponsiveness of cardiac muscles to histamine in reserpine-treated guinea pigs

The hyperresponsiveness of cardiac tissue to histamine following treatment with reserpine was pharmacologically characterized. Guinea pig hearts were isolated 24 hours after intraperitoneal administration of 5 mg/kg reserpine. This treatment resulted in a complete depletion of tissue norepinephrine. Reserpine treatment potentiated the positive inotropic response of isolated perfused hearts to histamine at doses ranging from 0.3 to 3 micrograms (23 to 57% increase for reserpine-treated animals vs. 14 to 32% increase for control animals). Isolated left ventricular papillary muscle of reserpine-treated guinea pig hearts also showed hyperresponsiveness to histamine at concentrations of 0.1 microM or greater. The hyperresponsiveness of the papillary muscle contraction of the reserpine-treated animals to histamine was abolished in the presence of 1 microM cimetidine, but not attenuated in the presence of 1 microM diphenhydramine. This hyperresponsiveness was not modified by 1 microM bunazosin or 1 microM propranolol. The results suggest that H2-receptor mediated action plays a role in the hyperresponsiveness of cardiac muscles to histamine.

Interaction of poly(ADP-ribose)polymerase with DNA polymerase alpha

Homogeneously purified poly(ADP-ribose) polymerase (PARP) specifically stimulated the activity of immunoaffinity-purified calf or human DNA polymerase alpha by about 6 to 60-fold. Apparently, poly(ADP-ribosyl)ation of DNA polymerase alpha was not necessary for the stimulation. The effects of PARP on DNA polymerase alpha were biphasic: at very low concentrations of DNA, it rather inhibited its activity, whereas, at higher DNA concentrations, PARP greatly stimulated it. The autopoly(ADP-ribosyl)ation of PARP suppressed both its stimulatory and inhibitory effects. By immunoprecipitation with an anti-DNA polymerase alpha antibody, it was clearly shown that PARP may be physically associated with DNA polymerase alpha. Stimulation of DNA polymerase alpha may be attributed to the physical association between the two, rather than to the DNA-binding capacity of PARP, since the PARP fragment containing only the DNA binding domain showed little stimulatory activity. The existence of PARP-DNA polymerase alpha complexes were also detected in crude extracts of calf thymus.

Characterization of guinea pig estrogen sulfotransferase expressed by Chinese hamster ovary cell-K1 stable transfectants

Estrogen sulfotransferase (EST) activity expressed by Chinese hamster ovary (CHO)-K1 cells stably transfected with a plasmid containing a guinea pig EST complementary DNA insert was subjected to biochemical characterization, and the EST protein was further examined by nondenaturing isoelectric focusing and immunoblot analysis. CHO-K1 cells transfected with the same plasmid without the EST complementary DNA insert as well as untransfected CHO-K1 cells did not demonstrate either EST activity or the presence of an immunologically related protein. The EST expressed by the stably transfected CHO-K1 cells was found to manifest Michaelis-Menten kinetics and would use only estrogenic steroids as substrates, whereas other forms of steroids, such as pregnenolone, dehydroepiandrosterone, cortisol, and testosterone, were not acted on. When 17 beta-estradiol was used as a substrate, sulfonation occurred exclusively at the 3 position; 17-sulfonate was not formed. Thus, the expressed EST acted selectively on the 3-hydroxyl group of phenolic steroids. The apparent Km values for estrone, 17 beta-estradiol, and estriol were 60, 70, and 40 nM, respectively. The maximum velocity (Vmax) determinations for estrone and 17 beta-estradiol were equivalent, whereas the Vmax for estriol was reduced by 33%. Of the three estrogens, only 17 beta-estradiol caused substrate inhibition at a high concentration. Steroid sulfonation requires 3'-phosphoadenosine-5'-phosphosulfate (PAPS) as the active sulfonate donor, and the Km value for PAPS was 1.2 microM. In steroid sulfotransferase reactions, two products are formed: the sulfonated steroid product and the desulfonated cofactor, 3'-phosphoadenosine-5'-phosphate (PAP). The sulfonation of 17 beta-estradiol was inhibited by PAP in a dose-dependent manner. In addition, the Km for PAPS was increased by PAP, whereas the Vmax was unaffected, indicating competitive inhibition (Ki, approximately 0.52 microM). The EST protein expressed by the CHO-K1 cell stable transfectants demonstrated a mol wt of 34 kilodaltons, as determined by sodium dodecyl sulfate-gel electrophoresis. Additionally, when the expressed EST protein was subjected to isoelectric focusing, it was found to consist of multiple charge isoforms. These findings are comparable to what has been previously reported for native guinea pig adrenocortical EST. Furthermore, the charge isoform pattern that was demonstrated for the expressed EST was similar to the pattern observed for the native protein.

Alterations in vascular pattern of the developing palate in normal and spontaneous cleft palate mouse embryos

The alterations in the vascularization of the developing palate were studied through the use of resin cast images of vascular networks in normal and spontaneous cleft lip and palate (CL/Fr) mouse embryos (crown rump [CR] Length 9-18 mm, body wt. 0.11-0.65 g). A more dense vascular plexus was observed in the oral side than in the nasal side before the reorientation of the palatal shelves. Prominent terminal dilatations of the vascular plexus were observed in the extreme medial edge of the elevating palatal shelves which may exert significant force for palatal shelf elevation. The vascular plexus showed a lateral extension. Many small spherical masses of resin were observed in the medial edge of the palatal shelves at the time of medial extension and during fusion, indicating some changes occurring in the capillary wall leading to the resin leakage. In the spontaneous cleft group, a similar vascular pattern was observed, but the greater palatine artery showed discontinuity in the premaxillary region at an early stage. At the same time, terminal dilatations were delayed and frequently absent in the contralateral shelf. After the reorientation of the palatal shelves, the vascular plexus formed an irregular lattice pattern. Dilated vasculature was apparent in the anterior nasopalatine region, indicating the persistence of a more primitive vascular structure in the spontaneous cleft embryos. However, the area where capillary dilatation occurred was different between unilateral and bilateral cleft embryos. In conclusion, blood vessels in the palatal shelves are underdeveloped and remained immature in cleft lip and palate embryos and showed different patterns in the anterior nasopalatine region between unilateral and bilateral cleft embryos. These variant vascular patterns may be due to the inadequate blood supply to the nasopalatine region from the early embryonic stages possibly resulting from the discontinuity of the greater palatine artery.

Differential inhibition of eukaryotic DNA polymerases by halenaquinol sulfate, a p-hydroquinone sulfate obtained from a marine sponge

Halenaquinol sulfate, a p-hydroquinone sulfate obtained from a marine sponge, inhibited the activity of eukaryotic DNA polymerases in varying degrees; the Ki values for DNA polymerases, alpha, beta, delta and epsilon were 1.3, 80, 17.5 and 2.0 microM, respectively, whereas it was less effective against E. coli DNA polymerase I. The inhibition occurred competitively with each of dATP and dTTP, but non-competitively with dCTP, dGTP and the template DNA. Thus, halenaquinol sulfate is demonstrated to be a potential inhibitor of DNA polymerases alpha and epsilon, and be a useful tool for analyzing the dNTP binding sites of DNA polymerases.