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Summary The decline in hip fracture incidence is now accompanied by a further reduction in the likelihood of a recurrent hip fracture among survivors of the first fracture. Introduction Hip fracture incidence is declining in North America, but trends in hip fracture recurrence have not been described. Methods All hip fracture events among Olmsted County, Minnesota residents in 1980-2006 were identified. Secular trends were assessed using Poisson regression, and predictors of recurrence were evaluated with Andersen-Gill time-to-fracture regression models. Results Altogether, 2,752 hip fractures (median age, 83 years; 76% female) were observed, including 311 recurrences. Between 1980 and 2006, the incidence of a first-ever hip fracture declined by 1.37%/year for women (p < 0.001) and 0.06%/year for men (p = 0.917). Among 2,434 residents with a first-ever hip fracture, the cumulative incidence of a second hip fracture after 10 years was 11% in women and 6% in men with death treated as a competing risk. Age and calendar year of fracture were independently associated with hip fracture recurrence. Accounting for the reduction in first-ever hip fracture rates over time, hip fracture recurrence appeared to decline after 1997. Conclusion A recent reduction in hip fracture recurrence is somewhat greater than expected from the declining incidence of hip fractures generally. Additional research is needed to determine the extent to which this can be attributed to improved patient management.

Fluoroquinolones, such as ciprofloxacin, have an adverse effect on growing cartilage and endochondral ossification in children. This study was carried out to determine whether ciprofloxacin also has an adverse effect on the healing of experimental fractures. Sixty male 300-gram Wistar rats were divided equally into three groups, which received ciprofloxacin, cefazolin, or no treatment for three weeks, beginning seven days after production of a closed, nondisplaced, bilateral femoral fracture. The serum concentrations of the ciprofloxacin and the cefazolin were 2.4 and 146 micrograms per milliliter, respectively. Radiographic, histological, and biomechanical studies were used to evaluate fracture-healing. Radiographs revealed significantly more advanced healing of the control fractures compared with the fractures in the ciprofloxacin-treated group (average stage, 2.1 compared with 1.5, p = 0.01). The cefazolin-treated group was not different from the controls with respect to radiographic healing (average stage, 1.8 compared with 2.1, p = 0.18). Torsional strength-testing of fracture callus exposed to ciprofloxacin revealed a 16 percent decrease in strength compared with the controls (284 compared with 338 newton-millimeters, p = 0.04) and a 49 percent decrease in stiffness (twenty compared with thirty-nine newton-millimeters per degree, p = 0.001). The biomechanical strength in the cefazolin-treated group was not different from that of the controls. Fracture calluses in the animals treated with ciprofloxacin showed abnormalities in cartilage morphology and endochondral bone formation and a significant decrease in the number of chondrocytes compared with the controls (0.77 x 10(4) compared with 1.3 x 10(4) cells per square millimeter, p = 0.004). These data suggest that experimental fractures exposed to therapeutic concentrations of ciprofloxacin in serum demonstrate diminished healing during the early stages of fracture repair. The administration of ciprofloxacin during early fracture repair may compromise the clinical course of fracture-healing.

We evaluated the effect of low intensity‐pulsed ultrasound stimulation on rat chondrocytes in vitro using two different 1.0‐MHZ ultrasound signals with spatial and temporal average intensities of 50 or 120 mW/cm2. The pulses had a duration of 200 microseconds and were repeated every millisecond, with corresponding average peak‐pressure amplitudes of 230 or 360 kPa, respectively. Cells were stimulated one, three, or five times for 10 minutes each day starting the third day after plating. One group of cells was exposed to sham ultrasound as a control. The cultures were evaluated for cell proliferation (by [3H]thymidine incorporation and DNA measurement), steady‐state mRNA levels of α1(I) and α1(II) procollagens and aggrecan (by Northern blotting), and proteoglycan synthesis (by [35S]sulfate incorporation). The results revealed that ultrasound causes increases in the level of aggrecan mRNA (p < 0.05) and in proteoglycan synthesis (p < 0.03) after three and five treatments. Expression of mRNA for α1(II) procollagen increased over time, but ultrasound had no stimulatory effect. Expression of mRNA for α1(I) procollagen was initially low and remained unchanged with time. Although cell proliferation increased with time in both groups, there was no statistically significant difference between the cultures treated with ultrasound and the controls (p = 0.1). The in vitro results support our previous in vivo findings that low‐intensity ultrasound stimulates aggrecan mRNA expression and proteoglycan synthesis by chondrocytes, which may explain the role of ultrasound in advancing endochondral ossification, increasing the mechanical strength of fractures, and facilitating fracture repair.

To study regulation of alternative splicing of type II collagen (COL2) pre-mRNA, we constructed a mouse COL2 “minigene” containing genomic sequences spanning exon 1 to exon 4 of COL2 downstream of a cytomegalovirus (CMV) promoter. This minigene was introduced into ATDC5 cells, which undergo chondrocytic differentiation when treated with insulin. Alternative splicing of the COL2 minigene was evaluated by comparing the expression of the two mRNAs transcribed from the minigene to the expression of alternatively spliced transcripts from the endogenous COL2 gene. This analysis suggested that regulation of alternative splicing of pre-mRNAs from the minigene and the endogenous COL2 gene are accomplished by similar mechanisms. We conclude that the cloned genomic fragment contains key sequences necessary for alternative splicing of COL2 pre-mRNA. This system provides a useful model to begin the process of identifying cis- and trans-acting factors that carry out alternative splicing of COL2 pre-mRNA during chondrocyte differentiation.

Osteonectin is a prominent noncollagenous protein of developing bone. A 2150-base-pair cDNA coding for osteonectin, isolated from a bovine bone cell λ gt11 expression library, was sequenced and identified by comparison with protein sequence data. The nucleotide sequence predicts that osteonectin contains 304 amino acids, including a 17-residue signal peptide. Analysis of the deduced protein sequence suggests that the secreted protein contains at least four distinct structural domains. An acidic region at the amino terminus of the protein appears to be a potential hydroxyapatite-binding site. This is followed by a second domain, rich in cysteine, that shows sequence homology with cysteine-rich domains in turkey ovomucoid and other serine proteinase inhibitors. Two sequences homologous with central calcium-binding loops of ``EF hands'' and thus having potential to be high-affinity calcium-binding sites are located in two other domains within the carboxyl-terminal half of the protein. Finally, the osteonectin sequence shows near identity (>90%) with another protein, SPARC (secreted protein, acidic and rich in cysteine), secreted by mouse parietal endoderm. These data suggest that osteonectin, a protein present in bone and other selected tissues, is a multifunctional protein.

An inexpensive monophasic reagent has been developed for the extraction of total RNA from cells or tissues. The main ingredients of the reagent are Phenol, Isoamyl alcohol, Guanidinium isothiocyanate, and Beta-mercaptoethanol (PIG-B). The quality and yield of RNA obtained by this reagent is at par with that obtained by TRIzol, an expensive but widely used monophasic reagent available commercially. The complete composition and method of preparation of PIG-B is provided to aid preparation of the reagent in the laboratory.

Nanomaterials are at the leading edge of the rapidly developing field of nanotechnology. The development of reliable experimental protocols for the synthesis of nanomaterials over a range of chemical compositions, sizes, and high monodispersity is one of the challenging issues in current nanotechnology. In the context of the current drive to develop green technologies in material synthesis, this aspect of nanotechnology is of considerable importance. Biological systems, masters of ambient condition chemistry, synthesize inorganic materials that are hierarchically organized from the nano- to the macroscale. Recent studies on the use of microorganisms in the synthesis of nanoparticles are a relatively new and exciting area of research with considerable potential for development. This review describes a brief overview of the current research worldwide on the use of microorganisms in the biosynthesis of metal nanoparticles and their applications.[PUBLICATION ABSTRACT]

Little is known about bone and cartilage tumors at the molecular level; thus, the identification of genes associated with these tumors may be useful as markers and therapeutic targets. To address this issue and to test the hypothesis that abnormal expression of one or more growth factors in the transforming growth factor‐β superfamily is associated with musculoskeletal neoplasia, degenerate primers based on the conserved sequences in these genes were made for screening tumor samples by reverse transcription‐polymerase chain reaction. First, these primers were used to obtain a comparative profile between a low‐grade chondrosarcoma and its dedifferentiated high‐grade counterpart in the same patient. This experiment identified an amplified DNA product in the high‐grade sample that was identical to osteogenic protein‐1/bone morphogenetic protein‐7. Osteogenic protein‐1 mRNA expression was 17‐fold greater in this high‐grade sample than in the low‐grade one. Osteogenic protein‐1 was highly expressed (three of three) in human osteosarcoma cell lines but was not expressed (zero of four) in normal osteoblast samples. Screening for gene expression of osteogenic protein‐1 in 57 osteosarcomas and chondrosarcomas indicated that 44% (range: 38–52%) of them were positive for osteogenic protein‐1 mRNA. Screening of breast and prostate tumors revealed a similar association with osteogenic protein‐1 mRNA expression.

The enzyme avian myeloblastosis virus reverse transcriptase (AMV-RT) is routinely used for cDNA synthesis, which is generally carried out at temperatures between 37 degrees C and 42 degrees C. We show that this enzyme can support cDNA synthesis, at temperatures as high as 70 degrees C. We have utilized this property of the AMV-RT to improve the specificity of polymerase chain reaction (PCR). Furthermore, this apparently thermophilic property of the enzyme, which is an important constituent of a mesophilic organism, raises intriguing questions regarding evolution of the enzyme structure.

A simple technique for direct sequencing of PCR-amplified templates without purification of the PCR reaction product is presented. This method does not require an additional synthesis step after template amplification, and can generate sequence information form as little as 0.1 fmol of unpurified template.