Treatment of death in the analysis of longitudinal studies of gerontological outcomes

BACKGROUND

Longitudinal studies in gerontology are characterized by termination of measurement from death. Death is related to many important gerontological outcomes, such as functional disability, and may, over time, change the composition of an older study population. For these reasons, treating death as noninformative censoring of a longitudinal outcome may result in biased estimates of regression coefficients related to that outcome.

METHODS

In a longitudinal study of community-living older persons, we analytically and graphically illustrate the dependence between death and functional disability. Relative to survivors, decedents display a rapid decline of functional ability in the months preceding death. Death's strong relationship with functional disability demonstrates that death is not independent of this outcome and, hence, leads to informative censoring. We also demonstrate the "healthy survivor effect" that results from death's selection effect, with respect to functional disability, on the longitudinal makeup of an older study population.

RESULTS

We briefly survey commonly used approaches for longitudinal modeling of gerontological outcomes, with special emphasis on their treatment of death. Most common methods treat death as noninformative censoring. However, joint modeling methods are described that take into account any dependency between death and a longitudinal outcome.

CONCLUSIONS

In longitudinal studies of older persons, death is often related to gerontological outcomes and, therefore, cannot be safely assumed to represent noninformative censoring. Such analyzes must account for the dependence between outcomes and death as well as the changing nature of the cohort.

New approach of testing the effect of heat stress on eggshell quality: mechanical and material properties of eggshell and membrane

1. The effect of high temperature on eggshell quality was investigated by measuring the mechanical and material properties of shell and membranes. 2. Heat exposure resulted in a decrease in zootechnical performance and eggshell thickness, increase in egg breakage, and unchanged egg shape index. 3. The static stiffness (Kstat), dynamic stiffness (Kdyn) and modulus of elasticity of the eggshell were not significantly affected by high temperature. Membrane prolongation increased significantly while membrane attachment strength and breakage strength tended to decrease and increase, respectively. The relationships between these variables were changed by high temperature. 4. Neither Kstat nor Kdyn could give a reasonable explanation for the changed eggshell quality induced by heat stress. The decreased eggshell thickness and changed properties of shell membrane may be responsible, at least partially, for the decreased shell quality of eggs from heat-stressed hens.

Long-term outcome of division of the C8 nerve root for spasticity of the hand in cerebral palsy

Division of the C8 nerve root results in short-term relief of spasticity in the hands of cerebral palsy patients. In the present study, we assessed the long-term outcome of C8 nerve root division. Between March 1997 and January 2002, this procedure was done in 13 patients. All received consistent postoperative functional rehabilitation training. The hands were assessed before operation and at follow-up using the Lazareff grading system. The average follow-up time was 8.6 years. Two hands showed excellent improvement, three limbs showed good improvement and eight hands showed no improvement. No long-term complications occurred in any patient. These results indicate that the long-term outcome of C8 nerve root rhizotomy for the treatment of hand spasticity in CP is generally poor.

Rare-earth ions doped heavy metal germanium tellurite glasses for fiber lighting in minimally invasive surgery

In Er(3+)/Yb(3+) codoped Na(2)O-ZnO-PbO-GeO(2)-TeO(2) (NZPGT) glass fiber, a clear and compact green upconversion amplified spontaneous emission (ASE) trace is observed, and the NZPGT glasses are proved to be a desirable candidate in fabricating low-phonon energy fiber. Intense green upconversion luminescence of Er(3+), balanced green and red upconversion emissions of Ho(3+), and dominant three-photon blue upconversion fluorescence of Tm(3+) have been represented. By varying the excitation power of 974 nm wavelength laser diode, a series of green and white fluorescences have been achieved in Tm(3+)/Er(3+)/Yb(3+) and Tm(3+)/Ho(3+)/Yb(3+) triply doped glass systems, respectively. These results reveal that high-intensity blue, green, and white upconversion ASE fluorescences, which can be adopted for lighting in minimally invasive photodynamic therapy and minimally invasive surgery, are reasonable to be expected in rare-earth doped NZPGT glass fibers.

BRG1 expression is increased in human cutaneous melanoma

BACKGROUND

The SWI/SNF chromatin remodelling complex plays important roles in cellular processes including cell differentiation, cell cycle control and DNA repair. Aberrant expression of SWI/SNF subunits is involved in cancer development. The core subunit of the SWI/SNF complex, SNF5, has been shown to be inactivated in malignant rhabdoid tumours and has been defined as a tumour suppressor. However, the role of the catalytic subunit, BRG1, is not well defined in cancer.

OBJECTIVES

To investigate the role of BRG1 in melanoma development, we examined the expression of BRG1 in melanocytic lesions at different stages and analysed the correlation between BRG1 expression and clinicopathological variables and patient survival.

METHODS

Using tissue microarray and immunohistochemistry, we evaluated BRG1 staining in 48 dysplastic naevi, 90 primary melanomas and 47 metastatic melanomas. We studied melanoma cell proliferative ability with reduced BRG1 expression by small interfering RNA using cell proliferation assay and cell cycle analysis.

RESULTS

We found that BRG1 expression was increased in primary melanoma and metastatic melanoma compared with dysplastic naevi (P<0·0001). We did not find any correlation between BRG1 expression and melanoma patient survival. In addition, we demonstrated that knockdown of BRG1 in melanoma cell lines resulted in significantly reduced cell proliferative ability. This reduced cell proliferation is due to G(1) phase arrest as cyclin D(1) is downregulated upon BRG1 knockdown.

CONCLUSIONS

Our data indicate that BRG1 is significantly increased in human melanoma and is involved in melanoma initiation.

Reduced myoelectric activity in the sphincter of Oddi in a new model of chronic cholangitis in rabbits: an in vivo and in vitro study

BACKGROUND

Chronic cholangitis caused by hepatolithiasis is a common disease in Southeast Asia. Few studies have addressed the effects of chronic cholangitis on cyclic activity of the sphincter of Oddi (SO). In this study, we investigated the changes of myoelectric activity in rabbits with chronic cholangitis in vivo and in vitro.

METHODS

Chronic cholangitis was induced in rabbits by initially introducing three pieces of 2-0 silk suture and sequentially injecting E. coli into the choledochus through the tube in ductus cysticus. In in vivo experiments, myoelectric activity of SO was recorded by a circular electrode through the jejunum stump in conscious animals. In in vitro experiments, the SO was completely isolated and the myoelectric activity was recorded by a circular electrode in a 10-mL organ bath filled with Krebs solution, with or without addition of cholecystokinin-8 (CCK-8), KCl, ionomycin or induction of capacitative calcium entry (CCE).

KEY RESULTS

In comparison with control and non-infected rabbits, the rabbits with chronic cholangitis showed higher levels of alkaline phosphatase and gamma-glutamyltransferase and significant pathological changes including increased inflammatory infiltration and collagen deposition in mucosae or muscular layer. Cyclic myoelectric activity of SO at phases 2 and 3 of migrating motor complex and the excitatory response to CCK-8 were dramatically decreased in animals with chronic cholangitis. Myoelectric activity of SO was also significantly decreased in vitro with or without agonists or with induction of CCE.

CONCLUSIONS & INFERENCES

Myoelectric activity of SO and its response to agonists are decreased in rabbits with chronic cholangitis both in vivo and in vitro.

Vacuum therapy in erectile dysfunction--science and clinical evidence

Vacuum therapy (VT) utilizes negative pressure to distend the corporal sinusoids and to increase the blood inflow to the penis. Depending on its purpose, VT could be used as vacuum constriction device (VCD), with the aid of an external constricting ring which is placed at the base of penis to prevent blood outflow, maintaining the erection for sexual intercourse. Also, as a vacuum erectile device (VED), without the application of a constriction ring, just increases blood oxygenation to the corpora cavernosa and for other purposes. The emerging of phosphodiesterase 5 inhibitors (PDE(5)I) for the treatment of erectile dysfunction (ED) eclipsed VCD as therapeutic choice for ED; however, widespread usage of VED as part of penile rehabilitation after radical prostatectomy and other purposes rekindle the interest for VT. The underlying hypothesis is that the artificial induction of erections shortly after surgery facilitates tissue oxygenation, reducing cavernosal fibrosis in the absence of nocturnal erections, and potentially increases the likelihood of preserving erectile function. Due to its ability to draw blood into the penis regardless of nerve disturbance, VED has become the centerpiece of penile rehabilitation protocols. Herein, we reviewed the history, mechanism, application, side effects and future direction of VT in ED.

Many-body effects in electronic bandgaps of carbon nanotubes measured by scanning tunnelling spectroscopy

Single-walled carbon nanotubes provide an ideal system for studying the properties of one-dimensional (1D) materials, where strong electron-electron interactions are expected. Optical measurements have recently reported the existence of excitons in semiconducting nanotubes, revealing the importance of many-body effects. Surprisingly, pioneering electronic structure calculations and scanning tunnelling spectroscopy (STS) experiments report the same gap values as optical experiments. Here, an experimental STS study of the bandgap of single-walled semiconducting nanotubes, demonstrates a continuous transition from the gap reduced by the screening resulting from the metal substrate to the intrinsic gap dominated by many-body interactions. These results provide a deeper knowledge of many-body interactions in these 1D systems and a better understanding of their electronic properties, which is a prerequisite for any application of nanotubes in the ultimate device miniaturization for molecular electronics, or spintronics.