Risk of subsequent fracture after prior fracture among older women

Among 377,561 female Medicare beneficiaries who sustained a fracture, 10% had another fracture within 1 year, 18% within 2 years, and 31% within 5 years. Timely management to reduce risk of subsequent fracture is warranted following all nontraumatic fractures, including nonhip nonvertebral fractures, in older women.

INTRODUCTION

Prior fracture is a strong predictor of subsequent fracture; however, postfracture treatment rates are low. Quantifying imminent (12-24 month) risk of subsequent fracture in older women may clarify the need for early postfracture management.

METHODS

This retrospective cohort study used Medicare administrative claims data. Women ≥ 65 years who sustained a clinical fracture (clinical vertebral and nonvertebral fracture; index date) and were continuously enrolled for 1-year pre-index and ≥ 1-year (≥  2 or ≥ 5 years for outcomes at those time points) post-index were included. Cumulative incidence of subsequent fracture was calculated from 30 days post-index to 1, 2, and 5 years post-index. For appendicular fractures, only those requiring hospitalization or surgical repair were counted. Death was considered a competing risk.

RESULTS

Among 377,561 women (210,621 and 10,969 for 2- and 5-year outcomes), cumulative risk of subsequent fracture was 10%, 18%, and 31% at 1, 2, and 5 years post-index, respectively. Among women age 65-74 years with initial clinical vertebral, hip, pelvis, femur, or clavicle fractures and all women ≥ 75 years regardless of initial fracture site (except ankle and tibia/fibula), 7-14% fractured again within 1 year depending on initial fracture site; risk rose to 15-26% within 2 years and 28-42% within 5 years. Risk of subsequent hip fracture exceeded 3% within 5 years in all women studied, except those < 75 years with an initial tibia/fibula or ankle fracture.

CONCLUSIONS

We observed a high and early risk of subsequent fracture following a broad array of initial fractures. Timely management with consideration of pharmacotherapy is warranted in older women following all fracture types evaluated.

N-methylated 5-alkenyloxazolium salt transformations

[reaction: see text] In the course of natural product synthetic studies, 5-(4-pentenyl)oxazole and 5-(5-hexenyl)oxazole were N-methylated. The initial N-methylated 5-alkenyloxazolium salt adducts were found to be only intermediates and were ultimately transformed into hydroindole and hydroisoquinoline compounds, respectively.

Functional characterization of five V2 vasopressin receptor gene mutations

COS7 cells were transiently transfected with plasmids encoding mutant forms of the V2 vasopressin receptors corresponding to mutations [Y280C, L292P, R337stop, V277A, and G12E (the latter found in the same kindred with L292P)] recently identified in subjects with X-linked nephrogenic diabetes insipidus (NDI). cAMP response to dDAVP and AVP, saturation binding experiments with [3H]-AVP, immunofluorescence, and indirect ELISA studies were performed to characterize the functional consequences of these mutations. The Y280C, L292P, and R337stop mutant V2 receptors show substantially decreased cell surface expression and are functionally inactive. The V277A mutant receptor, though well expressed at the cell surface as seen by immunofluorescence and ELISA and having a dissociation constant with AVP similar to the wild type receptor, was functionally less active as seen by a substantially decreased receptor number (Bmax) and reduced cAMP stimulation by dDAVP. The G12E mutant was functionally the same as the wild type V2 receptor in both cAMP stimulation and binding. These results provide insight into residues critical for V2 receptor expression and function and also provide direct evidence that Y280C, L292P, R337stop and V277A mutations are the cause of X-linked NDI in affected subjects.

Functional rescue of mutant V2 vasopressin receptors causing nephrogenic diabetes insipidus by a co-expressed receptor polypeptide

Inactivating mutations in distinct G protein-coupled receptors (GPCRs) are currently being identified as the cause of a steadily growing number of human diseases. Based on previous studies showing that GPCRs are assembled from multiple independently stable folding units, we speculated that such mutant receptors might be functionally rescued by 'supplying' individual folding domains that are lacking or misfolded in the mutant receptors, by using a co-expression strategy. To test the feasibility of this approach, a series of nine mutant V2 vasopressin receptors known to be responsible for X-linked nephrogenic diabetes insipidus were used as model systems. These mutant receptors contained nonsense, frameshift, deletion or missense mutations in the third intracellular loop or the last two transmembrane helices. Studies with transfected COS-7 cells showed that none of these mutant receptors, in contrast to the wild-type V2 receptor, was able to bind detectable amounts of the radioligand, [3H]arginine vasopressin, or to activate the G(S)/adenylyl cyclase system. Moreover, immunological studies demonstrated that the mutant receptors were not trafficked properly to the cell surface. However, several of the nine mutant receptors regained considerable functional activity upon co-expression with a C-terminal V2 receptor peptide spanning the sequence where the various mutations occur. In many cases, the restoration of receptor activity by the co-expressed receptor peptide was accompanied by a significant increase in cell surface receptor density. These findings may lead to the design of novel strategies in the treatment of diseases caused by inactivating mutations in distinct GPCRs.

Modulation of linker histones during development in Tetrahymena: selective elimination of linker histone during the differentiation of new macronuclei

Macronuclei of Tetrahymena thermophila contain a typical H1 which has been shown to be missing from micronuclei. Instead, micronuclei contain three unique polypeptides, alpha, beta, and gamma, which are associated with linker regions of micronuclear chromatin. In this report polyclonal antibodies raised against macronuclear H1 are shown to react with alpha, beta, and gamma by immunoblotting analyses. This result suggests that these polypeptides share some common structural feature(s). Also consistent with this result is the finding that both macro- and micronuclei in growing and mating cells stain positively with H1 antibodies by in situ indirect immunofluorescence. However, these analyses demonstrate that the level of linker histone is greatly reduced in the micronucleus of starved cells and in young macronuclear anlagen. These results are in agreement with earlier biochemical studies and together provide strong evidence that dramatic changes in linker histone accompany nuclear differentiation (and dedifferentiation) in Tetrahymena.

Timing of the appearance of macronuclear-specific histone variant hv1 and gene expression in developing new macronuclei of Tetrahymena thermophila

Vegetative cells of the ciliated protozoan Tetrahymena thermophila contain a transcriptionally active macronucleus and a transcriptionally inactive micronucleus. Earlier studies ( Allis , C. D., C. V. C. Glover , J. K. Bowen, and M. A. Gorovsky , 1980, Cell, 20:609-617; and Allis , C. D., Y. S. Ziegler , M. A. Gorovsky , and J. B. Olmsted, 1982, Cell, 31:131-136) demonstrated the existence of a macronuclear-specific histone variant, hv1 , which is enriched in small punctate regions in nucleoli of several mammalian cell lines. These observations suggest that this histone variant is highly conserved in evolution and may be associated with actively transcribed sequences. Despite large differences in structure and function during vegetative growth, macro- and micronuclei are related. During conjugation, the sexual phase of the life cycle in Tetrahymena, postzygotic division products of micronuclei give rise to new micro- and macronuclei, while the old macronucleus moves to the posterior of each cell and is eliminated. In this study using antiserum specific for hv1 , we determined by indirect immunofluorescence the time during conjugation at which hv1 first appears in the developing new macronuclei. In growing, starved, and young mating cells (2-5 h after mixing opposite mating types), only macronuclei are detected with affinity-purified antibodies against hv1 . Newly formed macronuclei are either not stained or only weakly stained in cells in which the old macronucleus is located in the center of the cell. However, new macronuclei are clearly observed in cells in which the old macronucleus has moved to the posterior of the cell (approximately 8 h). During later stages of conjugation (10-16 h), the intensity of hv1 staining in new macronuclei increases with time corresponding to the increasing DNA content of these nuclei. Disappearance of detectable hv1 from old macronuclei begins nearly 1 h after these nuclei reach the posterior cytoplasm (approximately 9-10 h) and is sometimes complete before these nuclei are eliminated from the cells. Autoradiography of cells labeled for brief periods with [3H]uridine shows that new macronuclei begin to synthesize RNA very soon after the second postzygotic division (approximately 8 h). During stages when hv1 is clearly detected in new macronuclei, anlagen are active in RNA synthesis. RNA synthesis in old macronuclei ceases very close to the time when RNA synthesis begins in new macronuclei. Thus, the addition of hv1 coincides closely with the transformation of a transcriptionally inactive germinal nucleus into that of a transcriptionally active somatic nucleus. We suspect that addition of hv1 plays a fundamental role in