Effect of light on carotenoid and lipid production in the oleaginous yeast Rhodosporidium toruloides.

The oleaginous yeast Rhodosporodium toruloides is receiving widespread attention as an alternative energy source for biofuels due to its unicellular nature, high growth rate and because it can be fermented on a large-scale. In this study, R. toruloides was cultured under both light and dark conditions in order to understand the light response involved in lipid and carotenoid biosynthesis. Our results from phenotype and gene expression analysis showed that R. toruloides responded to light by producing darker pigmentation with an associated increase in carotenoid production. Whilst there was no observable difference in lipid production, slight changes in the fatty acid composition were recorded. Furthermore, a two-step response was found in three genes (GGPSI, CAR1, and CAR2) under light conditions and the expression of the gene encoding the photoreceptor CRY1 was similarly affected.

Effects of altered bone remodeling and retention of cement lines on bone quality in osteopetrotic aged c-Src-deficient mice.

Cement lines represent mineralized, extracellular matrix interfacial boundaries at which bone resorption by osteoclasts is followed by bone deposition by osteoblasts. To determine the contribution of cement lines to bone quality, the osteopetrotic c-Src mouse model-where cement lines accumulate and persist as a result of defective osteoclastic resorption-was used to investigate age-related changes in structural and mechanical properties of bone having long-lasting cement lines. Cement lines of osteopetrotic bones in c-Src knockout mice progressively mineralized with age up to the level that the entire matrix of cement lines was lost by EDTA decalcification. While it was anticipated that suppressed and abnormal remodeling, together with the accumulation of cement line interfaces, would lead to defective bone quality with advancing age of the mutant mice, unexpectedly, three-point bending tests of the long bones of 1-year-old c-Src-deficient mice indicated significantly elevated strength relative to age-matched wild-type bones despite the presence of numerous de novo microcracks. Among these microcracks in the c-Src bones, there was no sign of preferential propagation or arrest of microcracks along the cement lines in either fractured or nonfractured bones of old c-Src mice. These data indicate that cement lines are not the site of a potential internal failure of bone strength in aged c-Src osteopetrotic mice and that abundant and long-lasting cement lines in these osteopetrotic bones appear to have no negative impacts on the mechanical properties of this low-turnover bone despite their progressive hypermineralization (and thus potential brittleness) with age.

Factors affecting discontinuation of alendronate treatment in postmenopausal Japanese women with osteoporosis.

BACKGROUND: The main challenge to the long-term treatment of osteoporosis with bisphosphonates has been patient adherence. The purposes of this cohort study were to investigate the 3-year outcome of alendronate treatment in postmenopausal Japanese women with osteoporosis and to identify factors that contributed to the discontinuation of alendronate treatment. METHODS: A total of 72 postmenopausal Japanese women with osteoporosis and aged from 58 to 85 years were treated with alendronate in a 3-year trial. Metacarpal bone mineral density, serum alkaline phosphatase, and urinary cross-linked N-terminal telopeptides of type I collagen were monitored, and factors contributing to the discontinuation of alendronate treatment were determined. RESULTS: Fourteen patients dropped out of the trial. The reasons for dropout were side effects (diarrhea [n = 1], gastric symptoms [n = 9], and inflammation of the mouth [n = 1]) or non-compliance (n = 3). Logistic regression analysis showed that the number of prevalent vertebral fractures was a significant factor affecting the discontinuation of alendronate treatment for the reasons listed above. In 58 patients who continued the 3-year treatment, urinary cross-linked N-terminal telopeptides of type I collagen level was reduced by 44.1% at 3 months and serum alkaline phosphatase level was decreased by 11.6%, 11.8%, and 12.5% at 1, 2, and 3 years, respectively. However, metacarpal bone mineral density did not change significantly. CONCLUSION: Alendronate treatment decreased urinary cross-linked N-terminal telopeptides of type I collagen and serum alkaline phosphatase levels, and maintained metacarpal bone mineral density in postmenopausal Japanese women with osteoporosis. The patients adhered well to alendronate treatment in our clinic. The number of prevalent vertebral fractures was an important factor affecting the discontinuation of alendronate treatment due to side effects and non-compliance.

Five-year alendronate treatment outcome in older postmenopausal Japanese women with osteoporosis or osteopenia and clinical risk factors for fractures.

A retrospective study was conducted to evaluate the outcome of treatment with alendronate (ALN) for 5 years in postmenopausal Japanese women with an increased risk of fractures. Forty postmenopausal Japanese women with osteoporosis or osteopenia and clinical risk factors for fractures (mean age: 75.4 years) were analyzed; 33 patients were treated with alendronate and 7 were treated with alfacalcidol (ALF, controls) in an outpatient clinic run by general practitioners. The metacarpal bone mineral density (BMD) measured using a computed X-ray densitometer, urinary levels of cross-linked N-terminal telopeptides of type I collagen (NTX), and serum levels of alkaline phosphatase (ALP) were monitored during the 5-year treatment period. The urinary NTX and serum ALP levels decreased significantly in the ALN group, compared with the ALF group. The metacarpal BMD was sustained in the ALN group but decreased significantly in the ALF group; the difference between these two groups was also significant. The present study evaluated the outcome of treatment with ALN for 5 years in postmenopausal Japanese women with osteoporosis or osteopenia and clinical risk factors for fractures. ALN successfully suppressed bone turnover and sustained the metacarpal BMD over the 5-year period of treatment in postmenopausal Japanese women with an increased risk of fractures.

Diverse effects of c-src deficiency on molar tooth development and eruption in mice.

C-src deficiency is characterized by osteopetrosis due to impaired bone resorption by hypofunctional osteoclasts and the resultant failure of tooth eruption. In preliminary observations, we frequently encountered erupted molars in c-src deficient mice unlike in other osteopetrotic animals. Here we examine the effects of c-src deficiency on the development of molar teeth with an emphasis on the spatial relation of growing teeth with the surrounding bones. In c-src deficient mice, the magnitude of tooth impaction differed considerably among the types of molars; all maxillary 1st molars were totally impacted deep in the alveolar sockets, whereas most mandibular 1st molars fully erupted into oral cavity. Distribution of osteoclasts in the alveolar bone was identical among all types of molars, and electron microscopy revealed signs of bone resorbing activity in these osteoclasts despite the absence of a ruffled border. From early development, the alveolar space was much narrower in the upper molar tooth germs than in the lower ones in both wild type and homozygous animals, and particularly so in the upper 1st molars. Current observations thus indicate a significant contribution of "hypofunctional osteoclasts" in c-src deficient mice in molar tooth development except for the upper 1st molars, which appear to require highly functional osteoclasts to gain sufficient space for them to grow normally. Taken together, these findings on the seemingly tooth-type specific effects of c-src deficiency on the development and eruption of molar teeth in c-src deficient mice can be attributed to the given differential spatial relation of the respective tooth germs with the surrounding bones in the presence of hypofunctional osteoclasts.

Formation of acellular cementum-like layers, with and without extrinsic fiber insertion, along inert bone surfaces of aging c-Src gene knockout mice.

To investigate the long-term effects of c-src deficiency on skeletal and dental tissues, we examined the lower jaws and long bones of c-src gene knockout (c-src KO) mice by histological and histochemical methods. Numerous multinucleated osteoclasts were distributed throughout the mandible in 5-wk-old c-src KO mice, but by 14 wk they had almost completely disappeared from the alveolar bone, leaving tartrate-resistant acid phosphatase (TRAP)-positive layers along the bone surface. Deposition of osteopontin-positive mineralized tissue, reminiscent of acellular afibrillar cementum (AAC), was confirmed along the TRAP-positive bone surface at 14 wk. The layer progressively thickened up to 21 months. A comparable mineralized layer was noted along the trabeculae of long bones as thickened cement lines. In the periostin-rich areas of jaw bones, but not in the long bones, portions of AAC-like mineralized layers were often replaced with and/or covered by acellular extrinsic fiber cementum (AEFC)-like tissue. These data suggest that the deposition of AAC-like mineralized tissue is a general phenomenon that may occur along inert or slowly remodeling bone surfaces under conditions characterized by reduced bone-resorbing activity, whereas the induction of AEFC-like tissue seems to be associated with the expression of certain molecules that are particularly abundant in the microenvironment of the periodontal ligament.