Seasonal effects on human striatal presynaptic dopamine synthesis.

Past studies in rodents have demonstrated circannual variation in central dopaminergic activity as well as a host of compelling interactions between melatonin--a scotoperiod-responsive neurohormone closely tied to seasonal adaptation--and dopamine in the striatum and in midbrain neuronal populations with striatal projections. In humans, seasonal effects have been described for dopaminergic markers in CSF and postmortem brain, and there exists a range of affective, psychotic, and substance abuse disorders that have been associated with both seasonal symptomatic fluctuations and dopamine neurotransmission abnormalities. Together, these data indirectly suggest a potentially crucial link between circannual biorhythms and central dopamine systems. However, seasonal effects on dopamine function in the living, healthy human brain have never been tested. For this study, 86 healthy adults underwent (18)F-DOPA positron emission tomography scanning, each at a different time throughout the year. Striatal regions of interest (ROIs) were evaluated for differences in presynaptic dopamine synthesis, measured by the kinetic rate constant, K(i), between fall-winter and spring-summer scans. Analyses comparing ROI average K(i) values showed significantly greater putamen (18)F-DOPA K(i) in the fall-winter relative to the spring-summer group (p = 0.038). Analyses comparing voxelwise K(i) values confirmed this finding and evidenced intrastriatal localization of seasonal effects to the caudal putamen (p < 0.05, false-discovery rate corrected), a region that receives dopaminergic input predominantly from the substantia nigra. These data are the first to directly demonstrate a seasonal effect on striatal presynaptic dopamine synthesis and merit future research aimed at elucidating underlying mechanisms and implications for neuropsychiatric disease and new treatment approaches.

Surgical Approach to Orbital Floor Fractures: Comparing Complication Rates Between Subciliary and Subconjunctival Approaches.

BACKGROUND: There are multiple approaches to repairing orbital floor fractures. This study compares the postoperative complications of the subciliary and transconjunctival approaches. METHODS: The electronic medical records from 2 hospitals were screened for CPT codes associated with orbital floor reconstruction. A total of 184 patients were identified and included in the study. Patient characteristics and complications were compared by surgical approach. RESULTS: Of the 184 patients, 82 (44.6%) were in the subciliary group and 102 (55.4%) were in the transconjunctival group. The overall postoperative complication rate was 25.5%. The most common of these were diplopia (11.4%), corneal injury (7.1%), proptosis (5.4%), and enopthalmos (4.9%). The complication rate was not statistically significant between the 2 groups. CONCLUSION: Subciliary and transconjunctival approaches to orbital floor repair are equally safe. This study is limited by a smaller sample size, and a larger study will likely be necessary to fully address this question.

Oral glucosamine for 6 weeks at standard doses does not cause or worsen insulin resistance or endothelial dysfunction in lean or obese subjects.

Glucosamine is a popular nutritional supplement used to treat osteoarthritis. Intravenous administration of glucosamine causes insulin resistance and endothelial dysfunction. However, rigorous clinical studies evaluating the safety of oral glucosamine with respect to metabolic and cardiovascular pathophysiology are lacking. Therefore, we conducted a randomized, placebo-controlled, double-blind, crossover trial of oral glucosamine at standard doses (500 mg p.o. t.i.d.) in lean (n = 20) and obese (n = 20) subjects. Glucosamine or placebo treatment for 6 weeks was followed by a 1-week washout and crossover to the other arm. At baseline, and after each treatment period, insulin sensitivity was assessed by hyperinsulinemic-isoglycemic glucose clamp (SI(Clamp)) and endothelial function evaluated by brachial artery blood flow (BAF; Doppler ultrasound) and forearm skeletal muscle microvascular recruitment (ultrasound with microbubble contrast) before and during steady-state hyperinsulinemia. Plasma glucosamine pharmacokinetics after oral dosing were determined in each subject using a high-performance liquid chromatography method. As expected, at baseline, obese subjects had insulin resistance and endothelial dysfunction when compared with lean subjects (SI(Clamp) [median {25th-75th percentile}] = 4.3 [2.9-5.3] vs. 7.3 [5.7-11.3], P < 0.0001; insulin-stimulated changes in BAF [% over basal] = 12 [-6 to 84] vs. 39 [2-108], P < 0.04). When compared with placebo, glucosamine did not cause insulin resistance or endothelial dysfunction in lean subjects or significantly worsen these findings in obese subjects. The half-life of plasma glucosamine after oral dosing was approximately 150 min, with no significant changes in steady-state glucosamine levels detectable after 6 weeks of therapy. We conclude that oral glucosamine at standard doses for 6 weeks does not cause or significantly worsen insulin resistance or endothelial dysfunction in lean or obese subjects.

Decellularized tendon-bone composite grafts for extremity reconstruction: an experimental study.

BACKGROUND: Restoration of biomechanical strength following surgical reconstruction of tendon or ligament insertion tears is challenging because these injuries typically heal as fibrous scars. The authors hypothesize that injuries at the tendon-bone interface would benefit from reconstruction with decellularized composite tendon-bone grafts. METHODS: Tendon-bone grafts were harvested from Sprague-Dawley rats. Grafts subjected to decellularization were compared histologically and biomechanically with untreated grafts ex vivo and in a new in vivo model. Wistar rats underwent Sprague-Dawley allograft reconstruction using a pair-matched design. The rats were killed at 2 or 4 weeks. B-cell and macrophage infiltration was determined using immunohistochemistry, and explants were tested biomechanically. RESULTS: Decellularization resulted in a decrease in cells from 164 ± 61 (untreated graft) to 13 ± 7 cells per high-power field cells (p < 0.005) and a corresponding significant decrease in DNA content, and preserved scaffold architecture of the tendon-bone interface. Biomechanical comparison revealed no difference in failure load (p = 0.32), ultimate tensile stress (p = 0.76), or stiffness (p = 0.22) between decellularized grafts and untreated controls. Following in vivo reconstruction with tendon-bone interface grafts, decellularized grafts were stronger than untreated grafts at 2 weeks (p = 0.047) and at 4 weeks (p < 0.005). A persistent increase in B-cell and macrophage infiltration was observed in both the capsule surrounding the tendon-bone interface and the tendon substance in untreated controls. CONCLUSION: Decellularized tendon-bone grafts display better biomechanical properties at early healing time points and a decreased immune response compared with untreated grafts in vivo.

Human flexor tendon tissue engineering: in vivo effects of stem cell reseeding.

BACKGROUND: Tissue-engineered human flexor tendons may be an option to aid in reconstruction of complex upper extremity injuries with significant tendon loss. The authors hypothesize that human adipose-derived stem cells remain viable following reseeding on human tendon scaffolds in vivo and aid in graft integration. METHODS: Decellularized human flexor tendons harvested from fresh-frozen cadavers and reseeded with green fluorescent protein-labeled pooled human adipose-derived stem cells were examined with bioluminescent imaging and immunohistochemistry. Reseeded repaired tendons were compared biomechanically with unseeded controls following implantation in athymic rats at 2 and 4 weeks. The ratio of collagen I to collagen III at the repair site was examined using Sirius red staining. To confirm cell migration, reseeded and unseeded tendons were placed either in contact or with a 1-mm gap for 12 days. Green fluorescent protein signal was then detected. RESULTS: Following reseeding, viable cells were visualized at 12 days in vitro and 4 weeks in vivo. Biomechanical testing revealed no significant difference in ultimate load to failure and 2-mm gap force. Histologic evaluation showed host cell invasion and proliferation of the repair sites. No increase in collagen III was noted in reseeded constructs. Cell migration was confirmed from reseeded constructs to unseeded tendon scaffolds with tendon contact. CONCLUSIONS: Human adipose-derived stem cells reseeded onto decellularized allograft scaffolds are viable over 4 weeks in vivo. The movement of host cells into the scaffold and movement of adipose-derived stem cells along and into the scaffold suggests biointegration of the allograft.

Physicochemical decellularization of composite flexor tendon-bone interface grafts.

BACKGROUND: Extremity injuries involving tendon attachment to bone are difficult to address. Clinically, tendon-bone interface allografts must be decellularized to reduce immunogenicity. Composite grafts are difficult to decellularize because chemical agents cannot reach cells between tissues. In this study, the authors attempted to optimize tendon-bone interface graft decellularization. METHODS: Human flexor digitorum profundus tendons with attached distal phalanx were harvested from cadavers and divided into four groups. Group 1 (control) was untreated. Group 2 (chemical) was chemically treated with 5% peracetic acid, 0.1% ethylenediaminetetraacetic acid, and 0.1% sodium dodecyl sulfate. Group 3 (low-power) underwent targeted ultrasonication for 3 minutes (22,274 J, 126W) followed by chemical decellularization. Group 4 (high-power) underwent targeted ultrasonication for 10 minutes (88,490 J, 155W) followed by chemical decellularization. Decellularization was assessed histologically with hematoxylin and eosin stain and stains for major histocompatibility complex I stains. Cell counts were performed. The ultimate tensile load of decellularized grafts (group 4) were compared with pair-matched untreated grafts (group 1). RESULTS: Average cell counts were 100 ± 41, 27 ± 10, 12 ± 11, and 6 ± 11 per high-power field for groups 1, 2, 3, and 4, respectively (p < 0.001). Decellularization using physical and chemical treatments (groups 3 and 4) resulted in substantial reduction of cells and major histocompatibility complex I molecules. There was no difference in ultimate tensile load between treated (group4) and untreated (group 1) samples (p > 0.5). CONCLUSIONS: Physicochemical decellularization of tendon-bone interface grafts using targeted ultrasonication and chemical treatment resulted in near-complete reduction in cellularity and maintenance of tensile strength. In the future, these decellularized composite scaffolds may be used for reconstruction of tendon-bone injuries.