Sampling density compensation in MRI: rationale and an iterative numerical solution.

Data collection of MRI which is sampled nonuniformly in k-space is often interpolated onto a Cartesian grid for fast reconstruction. The collected data must be properly weighted before interpolation, for accurate reconstruction. We propose a criterion for choosing the weighting function necessary to compensate for nonuniform sampling density. A numerical iterative method to find a weighting function that meets that criterion is also given. This method uses only the coordinates of the sampled data; unlike previous methods, it does not require knowledge of the trajectories and can easily handle trajectories that "cross" in k-space. Moreover, the method can handle sampling patterns that are undersampled in some regions of k-space and does not require a post-gridding density correction. Weighting functions for various data collection strategies are shown. Synthesized and collected in vivo data also illustrate aspects of this method.     

Inflammation in human brain injury: intracerebral concentrations of IL-1alpha, IL-1beta, and their endogenous inhibitor IL-1ra

Following traumatic brain injury (TBI), cascades of inflammatory processes occur. Laboratory studies implicate the cytokines interleukin-1alpha (IL-1alpha) and IL-1beta in the pathophysiology of TBI and cerebral ischemia, whilst exogenous and endogenous interleukin-1 receptor antagonist (IL-1ra) is neuroprotective. We analyzed IL-1alpha, IL-1beta, and IL-1ra in brain microdialysates (100-kDa membrane) in 15 TBI patients. We also analyzed energy-related molecules (glucose, lactate, pyruvate, glutamate, and the lactate/pyruvate ratio) in these brain microdialysates. Mean of mean (+/-SD) in vitro microdialysis percentage recoveries (extraction efficiencies) were IL-1alpha 19.7+/-7.6%, IL-1beta 23.9+/-10.5%, and IL-1ra 20.9+/-6.3%. In the patients' brain microdialysates, mean of mean cytokine concentrations (not corrected for percentage recovery) were IL-1alpha 5.6+/-14.8 pg/mL, IL-1beta 10.4+/-14.7 pg/mL, and IL-1ra 2796+/-2918 pg/mL. IL-1ra was consistently much higher than IL-1alpha and IL-1beta. There were no significant relationships between IL-1 family cytokines and energy-related molecules. There was a significant correlation between increasing IL-1beta and increasing IL-1ra (Spearman r=0.59, p=0.028). There was also a significant relationship between increasing IL-1ra and decreasing intracranial pressure (Spearman r=-0.57, p=0.041). High concentrations of IL-1ra, and also high IL-1ra/IL-1beta ratio, were associated with better outcome (Mann Whitney, p=0.018 and p=0.0201, respectively), within these 15 patients. It is unclear whether these IL-1ra concentrations are sufficient to antagonize the effects of IL-1beta in vivo. This study demonstrates feasibility of our microdialysis methodology in recovering IL-1 family cytokines for assessing their inter-relationships in the injured human brain, and suggests a neuroprotective role for IL-1ra. It remains to be seen whether exogenous IL-1ra or other agents can be used to manipulate cytokine levels in the brain, for potential therapeutic effect.     

Aging aggravates long-term renal ischemia-reperfusion injury in a rat model

Aim

Ischemia-reperfusion injury (IRI) has been considered as the major cause of acute kidney injury and can result in poor long-term graft function. Functional recovery after IRI is impaired in the elderly. In the present study, we aimed to compare kidney morphology, function, oxidative stress, inflammation, and development of renal fibrosis in young and aged rats after renal IRI.

Materials and methods

Rat models of warm renal IRI were established by clamping left pedicles for 45 min after right nephrectomy, then the clamp was removed, and kidneys were reperfused for up to 12 wk. Biochemical and histologic renal damage were assessed at 12 wk after reperfusion. The immunohistochemical staining of monocyte macrophage antigen-1 (ED-1) and transforming growth factor beta 1 (TGF-β1) and messenger RNA level of TGF-β1 in the kidney were analyzed.

Results

Renal IRI caused significant increases of malondialdehyde and 8-hydroxydeoxyguanosine levels and a decrease of superoxide dismutase activity in young and aged IRI rats; however, these changes were more obvious in the aged rats. IRI resulted in severe inflammation and tubulointerstitial fibrosis with decreased creatinine (Cr) clearance and increased histologic damage in aged rats compared with young rats. Moreover, we measured the ratio of Cr clearance between young and aged IRI rats. It demonstrated that aged IRI rats did have poor Cr clearance compared with the young IRI rats. ED-1 and TGF-β1 expression levels in the kidney were significantly higher in aged rats than in young rats after IRI.

Conclusion

Aged rats are more susceptible to IRI-induced renal failure, which may associate with the increased oxidative stress, increased histologic damage, and increased inflammation and tubulointerstitial fibrosis. Targeting oxidative stress and inflammatory response should improve the kidney recovery after IRI.     

Inhibitory effect of icariin on Ti-induced inflammatory osteoclastogenesis

Background

Wear particle-induced periprosthetic osteolysis that results in aseptic loosening is the most common cause of long-term failure after total joint replacement.

Materials and methods

Icariin (ICA), a flavonoid isolated from Epimedium pubescens, inhibits osteoclast formation, but its effects on wear particle-induced inflammatory osteoclastogenesis remains unclear. We investigated the role of ICA in the regulation of osteoclast differentiation in a murine macrophage cell line (RAW264.7), which is stimulated by titanium (Ti) particles and the receptor activator of NF-κB ligand.

Results

ICA effectively inhibited osteoclast formation and bone resorption in the differentiation medium. ICA (10⁻⁷ mol/L) significantly reduced the number of tartrate-resistant acid phosphatase-positive cells compared with the control, and significantly reduced the percentage of the surface covered by resorption lacunae. Quantitative real-time polymerase chain reaction analysis showed that ICA inhibited messenger RNA expression for the receptor activator of nuclear factor-κB, cathepsin K, tartrate-resistant acid phosphatase-positive, and matrix metalloproteinase-9 in RAW264.7 cells stimulated by Ti particles and receptor activator of NF-κB ligand. ICA also reduced pro-inflammatory cytokine expression of interleukin-1β and tumor necrosis factor-α in RAW264.7 cells cultured with Ti particles. In addition, incubation with cholecystokinin-8 showed that ICA had no toxic effects on RAW264.7 cells.

Conclusions

ICA possibly elicited inhibitory effects on inflammatory osteoclastogenesis induced by Ti particles, indicating that ICA may be useful for the prevention and treatment of wear particle-induced osteolysis.     

Pelvic Lymph Node Dissection During Robot-assisted Radical Prostatectomy: Efficacy,Limitations, and Complications—A Systematic Review of the Literature

Context

Pelvic lymph node dissection (PLND) in prostate cancer is the most effective method for detecting lymph node metastases. However, a decline in the rate of PLND during radical prostatectomy (RP) has been noted. This is likely the result of prostate cancer stage migration in the prostate-specific antigen-screening era, and the introduction of minimally invasive approaches such as robot-assisted radical prostatectomy (RARP).

Objective

To assess the efficacy, limitations, and complications of PLND during RARP.

Evidence acquisition

A review of the literature was performed using the Medline, Scopus, and Web of Science databases with no restriction of language from January 1990 to December 2012. The literature search used the following terms: prostate cancer, radical prostatectomy, robot-assisted, and lymph node dissection.

Evidence synthesis

The median value of nodal yield at PLND during RARP ranged from 3 to 24 nodes. As seen in open and laparoscopic RP series, the lymph node positivity rate increased with the extent of dissection during RARP. Overall, PLND-only related complications are rare. The most frequent complication after PLND is symptomatic pelvic lymphocele, with occurrence ranging from 0% to 8% of cases. The rate of PLND-associated grade 3–4 complications ranged from 0% to 5%. PLND is associated with increased operative time. Available data suggest equivalence of PLND between RARP and other surgical approaches in terms of nodal yield, node positivity, and intraoperative and postoperative complications.

Conclusions

PLND during RARP can be performed effectively and safely. The overall number of nodes removed, the likelihood of node positivity, and the types and rates of complications of PLND are similar to pure laparoscopic and open retropubic procedures.     

Mental health outcomes in elderly men with prostate cancer

ObjectiveTo examine the burden of mental health issues (MHI), namely anxiety, depressive disorders, and suicide, in a population-based cohort of older men with localized prostate cancer and to evaluate associations with primary treatment modality.Patients and methodsA total of 50,856 men, who were 65 years of age or older with clinically localized prostate cancer diagnosed between 1992 and 2005 and without a diagnosis of mental illness at baseline, were abstracted from the Surveillance, Epidemiology, and End Results–Medicare database. The primary outcome of interest was the development of MHI (anxiety, major depressive disorder, depressive disorder not elsewhere classified, neurotic depression, adjustment disorder with depressed mood, and suicide) after the diagnosis of prostate cancer.ResultsA total of 10,389 men (20.4%) developed MHI during the study period. Independent risk factors for MHI included age≥75 years (hazard ratio [HR] = 1.29); higher comorbidity (Charlson comorbidity index≥3, HR = 1.63); rural hospital location (HR = 1.14); being single, divorced, or widowed (HR = 1.12); later year of diagnosis (HR = 1.05); and urinary incontinence (HR = 1.47). Black race (HR = 0.79), very high-income status (HR = 0.87), and definitive treatment (radical prostatectomy [RP], HR = 0.79; radiotherapy [RT], HR= 0.85, all P<0.001) predicted a lower risk of MHI. The rates of MHI at 10 years were 29.7%, 29.0%, and 22.6% in men undergoing watchful waiting (WW), RT, and RP, respectively.ConclusionOlder men with localized prostate cancer had a significant burden of MHI. Men treated with RP or RT were at a lower risk of developing MHI, compared with those undergoing WW, with median time to development of MHI being significantly greater in those undergoing RP compared with those undergoing RT or WW.     

Pulmonary protective mechanisms in human infants

The flow of oral and nasal secretions into the pharynx is a recognized source of pulmonary aspiration during sleep in infants and adults alike. Such aspiration probably accounts for many cases of bacterial pneumonia. In infants, swallowing occurs frequently in sleep, and the rate of swallowing appears to be far greater than that of the sleeping adult. Such swallowing during sleep appears to be the major mechanism whereby oral and nasal secretions are transported to the digestive tract. Certain aspects of those swallows, such as "swallow-breaths" and their coordination with the respiratory cycle, have been documented. A brief period of airway closure is always seen during such nonfeeding swallows. Nonfeeding swallows are usually seen during mixed and obstructive apneic spells in preterm infants. The underlying reflex mechanisms responsible for such swallows during apnea are unclear. During ordinary postfeeding regurgitation, upper airway closure and swallowing occur in close temporal sequence. These events appear to be major mechanisms of airway protection during regurgitation. In certain infants, regurgitation and prolonged apnea often occur simultaneously. The mechanism underlying their association is unclear but may involve laryngeal chemoreceptors.