Effects of CO2 laser irradiation of the gingiva during tooth movement.

Patients often feel pain or discomfort in response to orthodontic force. It was hypothesized that CO(2) laser irradiation may reduce the early responses to nociceptive stimuli during tooth movement. The distribution of Fos-immunoreactive (Fos-IR) neurons in the medullary dorsal horn of rats was evaluated. Two hrs after tooth movement, Fos-IR neurons in the ipsilateral part of the medullary dorsal horn increased significantly. CO(2) laser irradiation to the gingiva just after tooth movement caused a significant decrease of Fos-IR neurons. PGP 9.5- and CGRP-positive nerve fibers were observed in the PDL of all study groups. The maximum temperature below the mucosa during CO(2) laser irradiation was less than 40 degrees C. It was suggested that CO(2) laser irradiation reduced the early responses to nociceptive stimuli during tooth movement and might not have adverse effects on periodontal tissue.

Construction of Lactobacillus plantarum strain with enhanced L-lysine yield.

AIM: To enhance L-lysine secretion in Lactobacillus plantarum. METHODS AND RESULTS: An S-2-aminoethyl-L-cystein (AEC)-resistant mutant of L. plantarum was isolated, and it produced L-lysine at considerably higher level than the parent strain. Aspartokinase in the mutant has been desensitized to feedback inhibition by L-lysine. The nucleotide sequence analysis of thrA2 that codes for aspartokinase in the mutant predicted a substitution of glutamine to histidine at position 421. L-Lysine-insensitive aspartokinase, together with aspartate semialdehyde dehydrogenase, dihydrodipicolinate synthase, and dihydrodipicolinate reductase genes, was cloned from L. plantarum DNA to a shuttle vector, pRN14, and the genes were then transformed individually into the AEC-resistant mutant and the parent strain. The overexpression of the genes led to the increase in the activity of enzymes they encode in vitro. However, only the strain overexpressing aspartokinase or dihydrodipicolinate synthase produced more L-lysine. CONCLUSIONS: The desensitization of aspartokinase to L-lysine in L. plantarum led to the overproduction of L-lysine. The overexpression of L-lysine-insensitive aspartokinase or dihydrodipicolinate synthase enhanced L-lysine secretion in L. plantarum. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of the L-lysine-overproducing strain of L. plantarum in food or feed fermentation may increase the L-lysine content of fermented products.

Denervation resulting in dento-alveolar ankylosis associated with decreased Malassez epithelium.

Inferior alveolar nerve denervation causes appreciable decreases in the distribution of epithelial rests of Malassez. To explore roles of the Malassez epithelium, we attempted to evaluate possible changes in dento-alveolar tissues surrounding this epithelium by experimental denervation. We found that denervation led to dento-alveolar ankylosis with a decrease in the width of the periodontal spaces. Interestingly, with regeneration of the Malassez epithelium 10 weeks after the denervation, the periodontal space width showed a correspondingly significant increase. These findings suggest that the Malassez epithelium may be involved in the maintenance of periodontal space and that sensory innervation might be indirectly associated with it. In addition, it is of interest that denervation activated root resorption of the coronal root surface and that the consequently resorbed lacunae were repaired by cellular cementum. It is suggested that Malassez epithelium may negatively regulate root resorption and induce acellular cementum formation.

In vivo conversion of a glycan to human compatible type by transformed tobacco cells.

Horseradish peroxidase isozyme C (HRP; EC 1.11.1.7) was used as a model protein to evaluate the capacity of tobacco cells transformed with human beta 1,4-galactosyltransferase (GT6) to modify and galactosylate a foreign glycoprotein. Cells transformed with the HRP gene are designated as BY2-HRP and GT6-HRP, for wild type BY2 and GT6 transformed cells, respectively. Expression of HRP cells was confirmed by isoelectric focusing, peroxidase activity staining, Western blotting, and enzymatic assays. The presence of HRP galactosylated N-glycans in GT6-HRP cells was analyzed by lectin staining, affinity chromatography, and structural analyses of pyridylamino-labeled RCA(120)-bound sugar chains. The structure of Gal(1)GlcNAc(1)Man(5)GlcNAc(2) was proposed based from the results of exoglycosidase digestions and two-dimensional sugar chain mapping. Unlike the HRP produced in BY2-HRP cells, the HRP from GT6-HRP cells has galactosylated glycoproteins that did not bind to the xylose-specific antiserum, suggesting the absence of the beta 1,2-xylose residue in the sugar chain.

Identification of putative gene encoded on ORF16 of the 81 kb contig of Arabidopsis thaliana chromosome III as alpha-mannosidase.

We isolated cDNA corresponding to open reading frame (ORF) 16 of the 81 kb contig of Arabidopsis thaliana chromosome III [Quigley., Nucleic Acids Res., 24, 4313-4318 (1996)] and expressed alpha-mannosidase activity in tobacco suspension-cultured cells, which revealed that ORF16 encodes alpha-mannosidase. We also suggested that Arabidopsis harbors three genes encoding alpha-mannosidase by homology search against the database.

Glycoproteins secreted from suspension-cultured tobacco BY2 cells have distinct glycan structures from intracellular glycoproteins.

Glycan structures of glycoproteins secreted in the spent medium of tobacco BY2 suspension-cultured cells were analyzed. The N-glycans were liberated by hydrazinolysis and the resulting oligosaccharides were labeled with 2-aminopyridine. The pyridylaminated (PA) glycans were purified by reversed-phase and size-fractionation HPLC. The structures of the PA sugar chains were identified by a combination of the two-dimensional PA sugar chain mapping, MS analysis, and exoglycosidase digestion. The ratio (40:60) of the amount of glycans with high-mannose-type structure to that with plant-complex-type structure of extracellular glycoproteins is significantly different from that (ratio 10:90) previously found in intracellular glycoproteins [Palacpac et al., Biosci. Biotechnol. Biochem. 63 (1999) 35-39]. Extracellular glycoproteins have six distinct N-glycans (marked by *) from intracellular glycoproteins, and the high-mannose-type structures account for nearly 40% (Man5GlcNAc2, 28.8%; Man6GlcNAc2*, 6.4%; and Man7GlcNAc2*, 3.8%), while the plant-complex-type structures account for nearly 60% (GlcNAc2Man3Xyl1GlcNAc2*, 32.1%; GlcNAc1Man3Xyl1GlcNAc2 (containing two isomers)*, 6.2%; GlcNAc2Man3GlcNAc2*, 4.9%; Man3Xyl1Fuc1GlcNAc2, 8.3%; and Man3Xyl1GlcNAc2, 3.7%).

Etidronate inhibits human osteoblast apoptosis by inhibition of pro-apoptotic factor(s) produced by activated T cells.

Humoral factors produced by activated T cells are thought to be important in the development of bone loss in patients with rheumatoid arthritis (RA). We investigated the inhibitory effect of etidronate disodium (EHDP) on apoptosis of human osteoblasts induced by supernatants from in vitro activated T cell cultures. Human osteoblastic cell line MG63 cells and human primary osteoblast-like cells were used in the present study as human osteoblasts. T cells were incubated with interleukin-2 and further activated with 1 2-o-tetradecanoyl-phorbol 13-acetate and ionomycin, either in the presence or absence of EHDP. After we carried out the cultivation, we examined the cytotoxicity of cultured T cell supernatants toward MG63 cells and human primary osteoblast-like cells. Supernatants from activated but not resting T cell cultures efficiently induced apoptosis of MG63 cells and primary osteoblast-like cells. Supernatants from activated T cell cultures, incubated with EHDP, exhibited significantly less cytotoxicity than did supernatants incubated in the absence of EHDP. In contrast, the cytotoxicity of activated T cell culture supernatants was not affected by direct treatment of human osteoblasts with EHDP. The concentration of soluble Fas ligand in activated T cell culture supernatants was actually increased by EHDP. However, EHDP did not influence soluble Fas and tumor necrosis factor-alpha concentrations in the supernatant. Furthermore, treatment of human osteoblasts with EHDP did not alter their expression of Bcl-2/Bcl-xL or their sensitivity to anti-Fas immunoglobulin M-induced apoptosis. Our results suggest that EHDP inhibits the production of soluble factor that induces apoptosis of human osteoblasts and thus exhibits a protective action toward human osteoblast apoptosis induced by activated T cell culture supernatants. Although the exact EHDP-regulated molecule that induces apoptosis of human osteoblasts is unknown at present, our study may explain part of the therapeutic action of bisphosphonates in RA complicated by bone loss.

Epithelial rests of Malassez express immunoreactivity of TrkA and its distribution is regulated by sensory nerve innervation.

The periodontal ligament is the connective tissue that fills the space between the tooth and its bony socket. It is abundantly innervated by the sensory and sympathetic nerves. We first investigated the immunoreactivity of TrkA, which is a high-affinity receptor of nerve growth factor (NGF), in the periodontal ligament of rats. Immunoreactivity was observed at the epithelial cells in the cervical and furcation regions of the molars. These epithelial cells, which gather together to form clusters or networks, are known as the epithelial rests of Malassez. Immunoreactivity was not observed in other non-neuronal cells, such as osteoblasts, fibroblasts, odontoblasts, cementoblasts, endothelial cells, and/or osteoclasts. On the basis of these findings, we investigated the possible involvement of sensory nerve innervation in the immunoreactivity of the epithelial cells. Denervation of the inferior alveolar nerve resulted in a marked decrease in the distribution area and size of the clusters of immunoreactive cells compared with those of sham-operated rats. These findings suggest that sensory nerve innervation may have a regulatory role in maintenance of the epithelial rests of Malassez expressing TrkA in the periodontal ligament.

Parathyroidectomy for primary hyperparathyroidism induces positive uncoupling and increases bone mineral density in cancellous bones.

OBJECTIVE: Osteopenia is an important feature of primary hyperparathyroidism (PHP). However, little is known about the change of bone mineral density (BMD) in PHP after surgery. The aim was to investigate the mechanisms of increased BMD after parathyroidectomy in patients with PHP. DESIGN: Prospective observational study. PATIENTS: Ten patients with PHP (7 women, 3 men; mean age 53.2+/-9.1 years). All patients underwent parathyroidectomy for excision of parathyroid adenoma. MEASUREMENTS: BMDs of two cancellous bone-rich sites (L2-L4 lumbar spine and ultra-distal end of the radius, RUD) and one cortical bone-rich site (distal third of the radius, R33%) were measured using dual energy X-ray absorptiometry, before, and 3, 6 and 12 months after surgery. Serum intact PTH, intact osteocalcin, bone type alkaline phosphatase (b-ALP), alkaline phosphatase, calcium, and urinary deoxypyridinoline (Dpd) were measured before, and 1 and 3 days, and 1, 2, 3, 4, 6, 8, 12, and 24 weeks after surgery. RESULTS: Parathyroidectomy resulted in a significant increase in BMDs of L2-L4 and RUD at 3 months postoperatively. Urinary Dpd levels decreased within a few days after surgery, while b-ALP and osteocalcin decreased more slowly throughout the first few months after surgery. The ratio of osteocalcin/Dpd at 1 week after surgery correlated significantly with the percentage change in BMD of L2-L4 at 3 and 6 months after surgery. The ratio of osteocalcin/Dpd at 2 weeks correlated significantly with the percentage change in BMD of L2-L4 at 3, 6 and 12 months after surgery. The preoperative values of osteocalcin, b-ALP, PTH and calcium were positively correlated with the change in BMD of RUD at 3 months and L2-L4 at 12 months, RUD at 6 months, RUD at 3 months and L2-L4 at 12 months, respectively. CONCLUSIONS: In primary hyperparathyroidism patients, the major increase in bone mineral density following parathyroidectomy occurs within 3 months. Parathyroidectomy resulted in a marked increase in bone mineral density of cancellous bones compared to that of cortical bones. The early increase in bone mineral density was due to a preferential activation of bone formation over bone resorption as evidenced by changes in bone metabolic markers. Our results also showed that the preoperative levels of bone metabolic markers may predict the gain in bone mineral density after parathyroidectomy.

Tumor necrosis factor-alpha and interleukin-1beta increase the Fas-mediated apoptosis of human osteoblasts.

Our recent work demonstrated functional Fas expression on human osteoblasts, and the histologic examination of the periarticular osteoporosis region in patients with rheumatoid arthritis (RA) showed apoptosis in osteoblasts. High concentrations of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), and IL-6--which are thought to increase bone resorption--have been determined in RA synovium. We investigated the effect of these cytokines on the Fas-mediated apoptosis of human osteoblasts. The human osteoblastic cell line MG63 and human primary osteoblast-like cells from bone biopsy specimens were used as human osteoblasts. Fas expression on these cells was examined by flow cytometry, and Fas-mediated apoptosis induced by anti-Fas immunoglobulin M (IgM) was determined by a chromium 51 release assay, the presence of cells with hypodiploid DNA, staining with Hoechst 33258 dye, and the detection of DNA fragmentation on agarose gel electrophoresis. The proliferation of osteoblasts was analyzed by a tritiated thymidine incorporation assay. Spontaneous apoptosis was not found on cultured osteoblasts. The apoptosis of human osteoblasts was not induced by TNF-alpha, IL-1beta, or IL-6 alone in the absence of anti-Fas IgM. In addition, proliferation of the cells was not affected by these cytokines. Fas was constitutively expressed on unstimulated osteoblasts, and treatment of these cells with IL-1beta or TNF-alpha significantly augmented Fas expression. Human osteoblasts were committed to apoptosis with anti-Fas IgM, and the treatment of both IL-1beta and TNF-alpha markedly increased Fas-mediated apoptosis. TNF-alpha augmented both Fas expression and Fas-mediated apoptosis more efficiently than did IL-1beta. In addition, an additive effect on both Fas expression and Fas-mediated apoptosis was demonstrated when TNF-alpha and IL-1beta were added to osteoblasts. IL-6 influenced neither Fas expression nor the Fas-mediated apoptosis of osteoblasts. Furthermore, no synergistic effect of IL-6 with IL-1beta or TNF-alpha was observed. IL-1beta, TNF-alpha, or IL-6 did not change Bcl-2 expression. Our results suggest that IL-1beta and TNF-alpha regulate osteoblast cell number by up-regulating the Fas-mediated apoptosis of osteoblasts, one of the putative mechanisms inducing periarticular osteoporosis in patients with RA.

Stable expression of human beta1,4-galactosyltransferase in plant cells modifies N-linked glycosylation patterns.

beta1,4-Galactosyltransferase (UDP galactose: beta-N-acetylglucosaminide: beta1,4-galactosyltransferase; EC 2.4.1. 22) catalyzes the transfer of galactose from UDP-Gal to N-acetylglucosamine in the penultimate stages of the terminal glycosylation of N-linked complex oligosaccharides in mammalian cells. Tobacco BY2 cells lack this Golgi enzyme. To determine to what extent the production of a mammalian glycosyltransferase can alter the glycosylation pathway of plant cells, tobacco BY2 suspension-cultured cells were stably transformed with the full-length human galactosyltransferase gene placed under the control of the cauliflower mosaic virus 35S promoter. The expression was confirmed by assaying enzymatic activity as well as by Southern and Western blotting. The transformant with the highest level of enzymatic activity has glycans with galactose residues at the terminal nonreducing ends, indicating the successful modification of the plant cell N-glycosylation pathway. Analysis of the oligosaccharide structures shows that the galactosylated N-glycans account for 47.3% of the total sugar chains. In addition, the absence of the dominant xylosidated- and fucosylated-type sugar chains confirms that the transformed cells can be used to produce glycoproteins without the highly immunogenic glycans typically found in plants. These results demonstrate the synthesis in plants of N-linked glycans with modified and defined sugar chain structures similar to mammalian glycoproteins.

Structures of N-linked oligosaccharides of glycoproteins from tobacco BY2 suspension cultured cells.

The structures of N-linked sugar chains of glycoproteins expressed in tobacco BY2 cultured cells are reported. Five pyridylaminated (PA-) N-linked sugar chains were derived and purified from hydrazinolysates of the glycoproteins by reversed-phase HPLC and size-fractionation HPLC. The structures of the PA-sugar chains purified were identified by two-dimensional PA-sugar chain mapping, ion-spray MS/MS analysis, and exoglycosidase digestions. The five structures fell into two categories; the major class (92.5% as molar ratio) was a xylose containing-type (Man3Fuc1 Xyl1GlcNAc2 (41.0%), GlcNAc2Man3Fuc1Xyl1GlcNAc2 (26.5%), GlcNAc1Man3Fuc1Xyl1GlcNAc2 (21.7%), Man3 Xyl1GlcNAc2 (3.3%)), and the minor class was a high-mannose type (Man5GlcNAc2 (7.5%)). This is the first report to show that alpha(1-->3) fucosylation of N-glycans does occur but beta(1-->4) galactosylation of the sugar chains does not in the tobacco cultured cells.

Increased Fas-mediated cytotoxicity of CD4-positive T cells in patients with human T-lymphotropic virus type I-associated myelopathy.

Using a 51Cr release assay, we investigated Fas-mediated cytotoxicity of peripheral blood CD4+ T cells of patients with human T-lymphotropic virus type-I (HTLV-I)-associated myelopathy (HAM) against T98G, a glioblastoma cell line which expresses Fas. Cytotoxic activity of CD4+ T cells against T98G was significantly higher in HAM patients than in controls. Moreover, when CD4+ T cells of HAM patients were preincubated with a monoclonal antibody to human Fas ligand (FasL), cytotoxic activity against T98G was significantly suppressed. These results suggest that damage to nervous tissues by the Fas/FasL system is involved in the pathogenesis of HAM.

Inhibitory effect of glucocorticoid for osteoblast apoptosis induced by activated peripheral blood mononuclear cells.

Recent studies suggest a protective effect of glucocorticoid against progression of bone erosion and periarticular osteoporosis in patients with rheumatoid arthritis (RA), although this steroid hormone itself is believed to increase bone loss. To understand the antagonistic effect of glucocorticoid for osteopenic process in RA patients, we examined the effect of dexamethasone on Fas-mediated apoptosis of cultured human osteoblasts induced by either anti-Fas IgM or activated peripheral blood mononuclear cells (PBMC). Human osteoblastic cell line MG63 and primary osteoblast-like cells obtained from biopsy specimens were used in this study. PBMC isolated from healthy donors were cultured with or without recombinant interleukin-2 (rIL-2) followed by 12-O-tetradecanoyl-phorbol 13-acetate (PMA) with ionomycin in the presence or absence of dexamethasone. Fas was functionally expressed on MG63 and primary osteoblast-like cells, and treatment of these cells with dexamethasone affected neither Fas expression nor anti-Fas IgM-induced apoptosis. Activated PBMC expressing membrane-type Fas ligand (mFasL) efficiently killed both MG63 and primary osteoblasts-like cells, and the addition of human Fas chimeric protein (hFas-Fc) significantly diminished the cytotoxicity, indicating that interactions between mFasL of activated PBMC and Fas on human osteoblasts induce apoptosis of the latter. Although dexamethasone did not affect apoptosis of MG63 and primary osteoblast-like cells induced by anti-Fas IgM, treatment of activated PBMC with dexamethasone markedly inhibited both mFasL expression and cytotoxicity of these cells against human osteoblasts, suggesting that dexamethasone preferentially acts not on osteoblasts but PBMC. Cultured supernatants from activated PBMC induced apoptosis of human osteoblasts and the addition of hFas-Fc also inhibited the cytotoxicity of the supernatants. In addition, soluble form FasL (sFasL) was detected in the supernatants of activated PBMC. Furthermore, both the cytotoxicity and sFasL concentration of cultured supernatants of activated PBMC incubated with dexamethasone was significantly lower than that in the absence of dexamethasone. Our data suggest that glucocorticoid suppresses the apoptotic process of osteoblasts by inhibiting the expression of both mFasL and sFasL derived from activated PBMC, mediating a protective effect against periarticular bone loss and bone erosion in inflammatory arthritis such as RA.

Fas and Fas ligand interaction is necessary for human osteoblast apoptosis.

We investigated the cellular and humoral interactions between peripheral blood mononuclear cells (PBMCs) and human osteoblasts, leading to apoptosis of osteoblasts. Human osteoblastic cell line MG63 and human primary osteoblast-like cells obtained from biopsy specimens were used in this study. PBMCs were isolated from healthy donors and cultured with or without stimulation by recombinant interleukin-2 followed by 12-o-tetradecanoylphorbol 13-acetate with ionomycin. Fas was functionally expressed on MG63 and primary osteoblast-like cells. Activated PBMCs expressed Fas ligand (FasL) strongly on their surface and killed MG63 and primary osteoblast-like cells. Cultured supernatants of activated PBMCs also induced apoptotic cell death of MG63 and primary osteoblast-like cells. In contrast, both unstimulated PBMCs and cultured supernatants of unstimulated PBMCs did not induce apoptosis of these cells. Furthermore, the cytotoxic effect and induction of apoptosis against MG63 and primary osteoblast-like cells by activated PBMCs and cultured supernatants were inhibited significantly by human Fas chimeric protein. Our data showed that human osteoblasts expressed Fas fuctionally and both membrane-type and soluble form FasL from activated PBMCs induced apoptosis of these cells, providing the one possible mechanism of bone loss in inflammatory diseases such as rheumatoid arthritis.

Cultured oncogenic osteomalacia tumor cells produce a factor(s) that inhibits osteocalcin production by osteoblastic cells.

A 34-year-old patient was diagnosed with oncogenic osteomalacia associated with hypophosphatemia, low levels of serum 1,25-dihydroxyviamin D [1,25(OH)(2)D], and osteocalcin (OC). Resection of the tumor normalized these blood abnormalities. While such tumors produce a humoral factor(s) that affects phosphate reabsorption by the proximal renal tubules, the direct action of such factor(s) on osteoblast function has not been examined previously. We investigated the effect of conditioned medium of cultured osteomalacia tumor cells on OC production by human osteoblastic cell line, MG-63. The conditiond medium inhibited OC production induced by 1,25(OH)(2)D-3. Our results indicate that the humoral factor(s) produced by the tumor has direct effect on osteoblasts and may contribute to development of the characteristic syndrome.

Influence of Helicobacter pylori infection and the effects of its eradication on gastric emptying in non-ulcerative dyspepsia.

AIM: The aim of the present study was to clarify the effects of Helicobacter pylori infection and its eradication on gastric emptying. SUBJECTS AND METHODS: Out of a total of 52 patients with non-ulcerative dyspepsia, 34 H.pylori-positive patients were enrolled. Antimicrobial drugs for the eradication of H. pylori were administered to 19 out of the 34 H. pylori-positive patients. Gastric emptying was evaluated according to the acetaminophen method. Inflammatory changes and intracellular periodic acid-Schiff-positive substances in the antral mucosa were examined in biopsy specimens. RESULTS: Although gastric emptying was significantly prolonged in the patients with non-ulcerative dyspepsia compared with the control group (P < 0.01), there was no difference in gastric emptying between H. pylori-positive and -negative patients, with all patients showing significantly less gastric emptying than the control group. The H. pylori eradication rate was 58% (11 out of 19) and gastric emptying improved significantly in seven patients whose infection was eradicated and whose dyspeptic symptoms disappeared. The ammonia concentration in gastric juice, inflammatory changes in the gastric mucosa and the index of periodic acid-Schiff-positive substances improved significantly when H. pylori was successfully eradicated compared with patients in whom eradication was unsuccessful. As gut hormones may affect gastroduodenal motility associated with H. pylori infection, we also studied the levels of serum gastrin and cholecystokinin. In the patients whose infection was eradicated, serum gastrin decreased significantly, but the cholecystokinin level did not change significantly, although there was a non-significant trend for cholecystokinin to increase. CONCLUSIONS: These results suggest that delayed gastric emptying is partly associated with H. pylori infection and that the infection may contribute to the development of non-ulcerative dyspepsia.

Attenuation of postmenopausal high turnover bone loss in patients with hypoparathyroidism.

To elucidate the role of PTH in postmenopausal bone loss, we studied 33 postmenopausal patients who received total thyroidectomy due to thyroid carcinoma. Among these patients, 13 were patients with hypoparathyroid function (HPf), and 20 retained normal parathyroid function (NPf) after thyroidectomy. Bone mineral density (BMD), the rate of BMD loss, and incidence of spinal deformity as well as varying bone metabolic markers were analyzed in all patients. The age-matched BMD was clearly higher, and the incidence of spinal deformity was significantly lower in HPf than in NPf. The rate of BMD loss in HPf was significantly lower than in NPf during the early postmenopausal period (within 5 yr after menopause; mean +/- SD, -0.567 +/- 3.05% vs. -2.49 +/- 1.86%/yr, P < 0.05). In contrast, the rates were similar between the two groups during the late postmenopausal period (> 5 yr after menopause). Bone metabolic markers indicated that an accelerated bone turnover occurred during the early postmenopausal period in NPf, but not in HPf. These results suggest that the hypoparathyroid condition provides protection against age-related bone loss. This is due in part to attenuation of the high turnover bone loss that occurs early in menopause.

Decrease in Activity of Glutathione Reductase Enhances Paraquat Sensitivity in Transgenic Nicotiana tabacum.

Transgenic tobacco (Nicotiana tabacum L. cv SR1) with decreased activity of glutathione reductase exhibited enhanced sensitivity to paraquat in the light as evaluated by chlorophyll destruction and electrolyte leakage from leaf discs. This result indicates the involvement of glutathione reductase in the tolerance of plants to photooxidative stress caused by the herbicide.

Suppressive doses of thyroxine do not accelerate age-related bone loss in late postmenopausal women.

To examine whether suppressive doses of thyroxine have any adverse effects on bone, we evaluated various bone metabolic markers (lectin-precipitated alkaline phosphatase, osteocalcin, carboxyl-terminal region of type I collagen propeptide, tartrate-resistant alkaline phosphatase, and urinary excretion of hydroxyproline and pyridinium crosslinks), incidence of vertebral deformity, total body and regional (lumbar spine and radius) bone mineral densities (BMDs), and rates of bone loss in 24 late postmenopausal (more than 5 years after menopause) women who were treated with levothyroxine (L-T4) after total thyroidectomy for differentiated carcinoma. Depending on the clinical records, including serum TSH levels measured by immunoradiometric assay, these patients were divided into two groups. One group of patients was given suppressive doses of L-T4 (TSH < 0.1 mU/L, n = 12) and the other group was given nonsuppressive doses of L-T4 (TSH > 0.1 mU/L, n = 12). There was no difference in bone metabolic markers and incidence of vertebral deformity between the groups. In patients with TSH suppression, Z-scores of BMDs calculated from age-matched healthy women (n = 179, aged 55 to 80) were nearly in the zero range of values (0.077 at total body, 0.228 at lumbar spine, and -0.117 at trabecular region of lumbar spine). The rate of bone loss in TSH-suppressed patients (-0.849 +/- 0.605%/year) was not significantly different from that of nonsuppressed patients (-0.669 +/- 0.659). These prospective and cross-sectional data suggest that long-term levothyroxine therapy using suppressive doses has no significant adverse effects on bone.