Gaussian processes for time-series modelling

In this paper, we offer a gentle introduction to Gaussian processes for time-series data analysis. The conceptual framework of Bayesian modelling for time-series data is discussed and the foundations of Bayesian non-parametric modelling presented for Gaussian processes. We discuss how domain knowledge influences design of the Gaussian process models and provide case examples to highlight the approaches.

Irreversible electroporation for unresectable hepatocellular carcinoma: initial experience and review of safety and outcomes

The aims of this study were to evaluate the safety, feasibility and tumour response of _irreversible electroporation, a non-thermal ablation technique, for the treatment of unresectable hepatocellular carcinoma. The endpoints were safety and local treatment efficacy. Patients with unresectable tumours and tumours not amenable for radiofrequency _ablation because of their vicinity to organs vulnerable to thermal damage such as the bowel or because they were close to large blood vessels that would limit efficacy of ablation due to the heat sink effect were treated with irreversible electroporation using percutaneous _ultrasound and/or computed tomography guided electrode placement between November 2008 and _December 2009. Early, late, minor and major complications were recorded. Tumour response was determined on triphasic helical computed tomography follow-up at one month, then every three months post-procedure. Eleven patients received IRE therapy to 18 HCC lesions (Mean diameter 2.44 ± 0.99 cm; range 1.0-6.1 cm) with five patients having more than one treated HCC. Mean follow-up was 18 months (range 14-24 months). Six patients required repeat treatments for local residual or recurrent disease; two of these also had IRE for distant intrahepatic recurrence. No serious complications were observed despite seven lesions lying adjacent to important structures or organs. Four patients developed transient urinary retention and seven developed transient local post-procedure pain. After IRE therapy, 13 (72%) lesions were completely ablated with 93% success for lesions ≤ 3 cm (13/14). The local recurrence-free period was 18 ± 4 months and the distance recurrence free period was 14 ± 6 months. These preliminary results suggest that IRE is a safe and feasible technique for local ablation of HCC, particularly for lesions less than 3 cm. No major complications were encountered during this study even for tumours close to essential structures or organs.

The significance of reduced kidney function among hospitalized acute general medical patients

BACKGROUND

Inpatient general medical units often look after older patients who have more complex co-morbidity including renal insufficiency. The consequences of renal insufficiency with respect to length of hospital stay (LOS) and mortality have not been well described in hospitalized general medical patients.

AIM

To use a general medical inpatient population to evaluate the impact of reduced kidney function.

DESIGN

Retrospective cross-sectional study.

METHODS

We studied 504 acute medical admissions through an Acute Assessment Unit between February and November 2007. Patients were classified as having chronic kidney disease (CKD), acute kidney injury (AKI), neither (control) or both. LOS, in-hospital mortality and post-discharge survival were evaluated.

RESULTS

Renal impairment was present in 151 patients. Ninety patients had CKD only and 61 had AKI with or without CKD. In-hospital mortality was increased in those with renal impairment compared with controls (9.3 vs. 3.4%; P = 0.006). Within 4 years of admission, 187 (39%) patients had died. Post-discharge mortality was significantly higher in all renal failure populations (hazard ratio: 2.57-4.38; P < 0.01). Adjustment for patient age, gender and Charlson index explained the increased mortality during and after hospital admission but did not explain increased LOS. Only a small proportion (13%) of admitted patients with renal insufficiency had renal disease documented in their discharge summaries.

CONCLUSION

Many general medical inpatients (30%) have reduced kidney function at the time of admission. This study provides validation of the Modification of Diet in Renal Disease equation as a predictor of poor outcomes. Reduced renal function was associated with increased hospital LOS and mortality. Mortality rose with AKI and was explicable on the basis of the patients' age and co-morbidities. Renal insufficiency is documented infrequently in discharge summaries.

Anarchic hand syndrome following resection of a frontal lobe tumor

Anarchic hand syndrome (AHS) is a rare disorder characterized by unwilled, but seemingly purposeful movements of the affected upper limb which are perceived by the patients not to be under their control. It often interferes with goal-directed movements and bimanual tasks. At present there is no effective method of treatment of AHS. We report here a case of AHS following resection of a frontal lobe tumor and describe its effects on the patient's functional activities. The patient used avoidance behavior and mental concentration to overcome the disabling effect of AHS. These strategies appear to be useful in the management of AHS.

The pathogenesis of degeneration of the intervertebral disc and emerging therapies in the management of back pain

This article reviews the current knowledge of the intervertebral disc (IVD) and its association with low back pain (LBP). The normal IVD is a largely avascular and aneural structure with a high water content, its nutrients mainly diffusing through the end plates. IVD degeneration occurs when its cells die or become dysfunctional, notably in an acidic environment. In the process of degeneration, the IVD becomes dehydrated and vascularised, and there is an ingrowth of nerves. Although not universally the case, the altered physiology of the IVD is believed to precede or be associated with many clinical symptoms or conditions including low back and/or lower limb pain, paraesthesia, spinal stenosis and disc herniation.

New treatment options have been developed in recent years. These include biological therapies and novel surgical techniques (such as total disc replacement), although many of these are still in their experimental phase. Central to developing further methods of treatment is the need for effective ways in which to assess patients and measure their outcomes. However, significant difficulties remain and it is therefore an appropriate time to be further investigating the scientific basis of and treatment of LBP.

Advances in compact proton spectrometers for inertial-confinement fusion and plasma nuclear science

Compact wedge-range-filter proton spectrometers cover proton energies ∼3-20 MeV. They have been used at the OMEGA laser facility for more than a decade for measuring spectra of primary D(3)He protons in D(3)He implosions, secondary D(3)He protons in DD implosions, and ablator protons in DT implosions; they are now being used also at the National Ignition Facility. The spectra are used to determine proton yields, shell areal density at shock-bang time and compression-bang time, fuel areal density, and implosion symmetry. There have been changes in fabrication and in analysis algorithms, resulting in a wider energy range, better accuracy and precision, and better robustness for survivability with indirect-drive inertial-confinement-fusion experiments.

Clinical outcome of autologous chondrocyte implantation is correlated with infrared spectroscopic imaging-derived parameters

OBJECTIVE

To investigate whether Fourier transform infrared imaging spectroscopy (FT-IRIS), a modality based on molecular vibrations, is a viable alternative to histology and immunohistochemistry (IHC) for assessment of tissue quality and patient clinical outcome.

METHODS

Osteochondral biopsies were obtained from patients (9-65 months post-surgery) who underwent an autologous chondrocyte implantation (ACI) procedure to repair a cartilage defect (N = 14). The repair tissue was evaluated histologically by OsScore grading, for the presence of types I and II collagen by IHC, and for proteoglycan (PG) distribution and collagen quality parameters by FT-IRIS. Patient clinical outcome was assessed by the Lysholm score.

RESULTS

Improvement in Lysholm score occurred in 79% of patients. IHC staining showed the presence of types I and II collagen in all samples, with a greater amount of collagen type II in the deep zone. The amount and location of immunostaining for type II collagen correlated to the FT-IRIS-derived parameters of relative PG content and collagen helical integrity. In addition, the improvement in Lysholm score post-ACI correlated positively with the OsScore, type II collagen (IHC score) and FT-IRIS-determined parameters. Regression models for the relation between improvement in Lysholm score and either OsScore, IHC area score or the FT-IRIS parameters all reached significance (p < 0.01). However, the FT-IRIS model was not significantly improved with inclusion of the OsScore and IHC score parameters.

CONCLUSION

Demonstration of the correlation between FT-IRIS-derived molecular parameters of cartilage repair tissue and patient clinical outcome lays the groundwork for translation of this methodology to the clinical environment to aid in the management of cartilage disorders and their treatment.

Intraoperative Hyperkalemia: Death in Renal Parathyroidectomy

Objective: Recognize potential life-threatening complications of intraoperative hyperkalemia during parathyroid surgery to control secondary hyperparathyroidism in renal patients. We present a case of a 20-year-old renal patient who died from VF arrest intraoperatively during elective surgery for secondary hyperparathyroidism. Understand the importance of intraoperative potassium monitoring.

Method: Prospective analysis of intraoperative monitoring of potassium levels in patients with CRF undergoing total parathyroidectomy from April 2006 to July 2009 at Hull Royal Infirmary (UK). All patients had postdialysis preoperative potassium levels checked, at least 2 intraoperative levels, and 1 postoperative level.

Results: Twenty-nine patients underwent total parathyroidectomy. A total of 17 out of 29 had intraoperative potassium rises, 55% (95% CI 38-71%) had intraoperative potassium rise above the normal limit (5.3 mM). Six patients (21% (95% CI 10-38%)) required intraoperative treatment with dextrose-insulin infusion. Active intervention was taken for patients who had rises greater than 0.5 mM or active ECG changes. Four patients had increasing potassium levels despite treatment indicating that without treatment these could potentially have been very high. Comparative results of postinduction and first intraoperative potassium levels were a good indicator of potassium rise later and the need for treatment ( P = .003).

Conclusion: Hyperkalemia is a recognized complication within the first 24 hours postparathyroidectomy; however, it can occur more commonly intraoperatively in renal patients with potential devastating effects. Our unfortunate mortality complication has led us to change practice and we advocate active intraoperative monitoring and treatment to prevent such complications.

A pilot study on the effect of short-term consumption of a polyphenol rich drink on biomarkers of coronary artery disease defined by urinary proteomics

Polyphenol rich diets have been associated with a reduced risk of cardiovascular disease. We examined the effect of a polyphenol rich (P-R) drink on biomarkers assessed by urinary proteomics. Thirty nine middle aged and overweight subjects were randomized to P-R drink (n = 20) or placebo (n = 19) in addition to their normal diet. After two weeks urine samples were obtained for assessment of the urinary proteome using capillary electrophoresis coupled to a mass spectrometer. A total of 93 polypeptides were found to be candidates for differential distribution with a nominal p-value <0.05, though these differences did not reach significance when multiple testing was accounted for. Sequences were determined in 19 of these demonstrating that they originate from alpha-1 antitrypsin, collagens, fibrinogen alpha and IgG kappa. Levels of 27 polypeptides were greater than 4-fold different between the two groups. Of these, 7 were previously found to be part of a coronary artery disease (CAD) specific urinary biomarker pattern. Their direction of expression was closer to the healthy state in the P-R drink group and closer to CAD state in the placebo group. Our data suggest that the P-R drink may have beneficial effects on urinary biomarkers of CAD. The data encourage the planning of future prospective studies, aimed at investigating significant effects of polyphenol rich dietary products.

P1-08-15: Pattern of Cardiac Monitoring and Risk of Trastuzumab Associated-Cardiac Dysfunction in a Clinical Practice: A Population Based Study

Background: Adjuvant trastuzumab therapy (ATT) in women with early-stage HER2+ breast cancer has been associated with significant reduction in the disease recurrence and mortality. Cardiac dysfunction (CD) is a known serious adverse effect of ATT. Although periodic cardiac monitoring is recommended during ATT, little is known about pattern of cardiac monitoring and incidence of CD in a clinical setting. The study aimed to determine extent of cardiac monitoring and rate of CD during ATT and to identify factors correlated with CD.

Methods: Medical records of women with localized HER+ breast cancer diagnosed between the years 2005–2007 in the province of Saskatchewan was reviewed. Women with advanced or recurrent disease or if they were treated in the setting of an adjuvant trastuzumab trial were excluded. A logistic regression analysis was performed to determine various clinical variables correlated with CD.

Results: A total 116 eligible women with median age of 54 yrs (range: 27–74) and median BMI of 27 (range: 44–17) were indentified. 40% had a cardiac risk factor & 30% were premenopausal. 51% had node positive & 53% had ER or PR+ breast cancer. 92% received anthracycline-based chemotherapy and 23% received sequential ATT. Of 62 patients with ER/PR+ breast cancer, 61% received adjuvant aromatase inhibitors. Baseline cardiac assessment was performed in 93% women. 98% women underwent periodic cardiac monitoring during ATT, 55% had monitoring performed at the interval of 3–4 months & 82% women had monitoring performed at the interval of 3–6 months. Mean baseline cardiac ejection fraction (EF%) prior to the commencement of chemotherapy and ATT were 65% & 63.9% respectively (p=NS). CD was observed in 32 (28%) women and only 4% were symptomatic. Trastuzumab was interrupted in 34%, and was discontinued in 20% women. Of 32 women with CD, 59% were referred to a cardiologist and 53% were treated with medication. CD was reversible in 84% cases. On multivariate analysis adjuvant aromatase inhibitor therapy was significantly correlated with cardiac dysfunction (Odd ratio 6.9 [95% CI: 1.4−33.0]). During the follow up period 18% women developed recurrent disease and 16% were died.

Conclusions: Our results confirm high compliance with cardiac monitoring, though not as frequently as recommended in the clinical trial setting. Overall the rate of symptomatic decline in cardiac function was similar to the rate reported in the clinical trials, however, a relatively higher incidence of asymptomatic decline in the left ventricle EF% was noted. Among various variables examined, adjuvant aromatase inhibitor therapy was associated with an increased risk of CD.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P1-08-15.

The influence of nutrient supply and cell density on the growth and survival of intervertebral disc cells in 3D culture

The adult human intervertebral disc (IVD) is normally avascular. Changes to the extracellular matrix in degenerative disc disease may promote vascularisation and subsequently alter cell nutrition and disc homeostasis. This study examines the influence of cell density and the presence of glucose and serum on the proliferation and survival of IVD cells in 3D culture. Bovine nucleus pulposus (NP) cells were seeded at a range of cell densities (1.25 × 10(5)-10(6) cells/mL) and cultured in alginate beads under standard culture conditions (with 3.15 g/L glucose and 10 % serum), or without glucose and/or 20% serum. Cell proliferation, apoptosis and cell senescence were examined after 8 days in culture. Under standard culture conditions, NP cell proliferation and cluster formation was inversely related to cell seeding density, whilst the number of apoptotic cells and enucleated "ghost" cells was positively correlated to cell seeding density. Increasing serum levels from 10% to 20% was associated with increased cluster size and also an increased prevalence of apoptotic cells within clusters. Omitting glucose produced even larger clusters and also more apoptotic and senescent cells. These studies demonstrate that NP cell growth and survival are influenced both by cell density and the availability of serum or nutrients, such as glucose. The observation of clustered, senescent, apoptotic or "ghost" cells in vitro suggests that environmental factors may influence the formation of these phenotypes that have been previously reported in vivo. Hence this study has implications for both our understanding of degenerative disc disease and also cell-based therapy using cells cultured in vitro.

The coincidence counting technique for orders of magnitude background reduction in data obtained with the magnetic recoil spectrometer at OMEGA and the NIF

A magnetic recoil spectrometer (MRS) has been built and successfully used at OMEGA for measurements of down-scattered neutrons (DS-n), from which an areal density in both warm-capsule and cryogenic-DT implosions have been inferred. Another MRS is currently being commissioned on the National Ignition Facility (NIF) for diagnosing low-yield tritium-hydrogen-deuterium implosions and high-yield DT implosions. As CR-39 detectors are used in the MRS, the principal sources of background are neutron-induced tracks and intrinsic tracks (defects in the CR-39). The coincidence counting technique was developed to reduce these types of background tracks to the required level for the DS-n measurements at OMEGA and the NIF. Using this technique, it has been demonstrated that the number of background tracks is reduced by a couple of orders of magnitude, which exceeds the requirement for the DS-n measurements at both facilities.

The effect of caloric restriction and glycemic load on measures of oxidative stress and antioxidants in humans: results from the CALERIE Trial of Human Caloric Restriction

Decreasing oxidative stress and increasing antioxidant defense has been hypothesized as one mechanism by which caloric restriction (CR) increases longevity in animals. A total of 46 moderately overweight volunteers (BMI: 25-30 kg/m2), ages 20-42 yr were randomized to either high glycemic (HG) or low glycemic (LG) dietary load CR regimen at either 10% (n=12) or 30% (n=34) of basal caloric intake. All food was provided to participants for 6 mo. Overall, after controlling for CR levels and dietary regimen for 6 mo, plasma glutathione peroxidase activity increased (p=0.04) and plasma protein carbonyl levels decreased (p=0.02) and a non-significant decrease in plasma 8-epi-prostaglandin F2α level was observed (p=0.09). No significant change was observed in other plasma antioxidants such as superoxide dismutase and catalase. These findings indicate that short term CR (10% or 30%) in moderately overweight subjects modulates some but not all measures of antioxidant defense and oxidative stress.

Long-term biomedical and psychosocial outcomes following DAFNE (Dose Adjustment For Normal Eating) structured education to promote intensive insulin therapy in adults with sub-optimally controlled Type 1 diabetes

AIMS

To explore long-term outcomes of participation in a Dose Adjustment For Normal Eating (DAFNE) training course, which provided one-off exposure to structured education in intensive insulin therapy to people with established Type 1 diabetes.

METHODS

A cohort design follow-up of original trial participants at a mean of 44 months (range: 37-51 months) in hospital diabetes clinics in three English health districts. 104 (74%) original participants provided biomedical data; 88 (63%) completed questionnaires including the ADDQoL, measuring impact of diabetes on quality of life (QoL).

RESULTS

At 44 months, mean improvement in HbA(1c) from baseline was 0.36% (9.32+/-1.1% to 8.96+/-1.2%, p<0.01) remaining significant but deteriorated from 12 months (p<0.05). Improvements in QoL seen at 12 months were sustained at 44 (e.g. impact of diabetes on dietary freedom: -1.78+/-2.33 at 44 months versus -4.27+/-2.94, baseline, p<0.0001; versus 1.80+/-2.32 at 12 months, ns). Similar results were obtained using last observation carried forward for patients not supplying follow-up data.

CONCLUSIONS

The impact of a single DAFNE course on glycaemic control remains apparent in the long term, although further interventions will be required to achieve recommended HbA(1c). In contrast, improvements in QoL and other patient-reported outcomes are well maintained over approximately 4 years.

Messenger ribonucleic acid of cerebral nuclei

1. RNA was isolated from crude nuclear preparations and from ribosomes derived from rat brain and liver. Nuclear RNA was obtained by lysis of the nuclei with sodium dodecyl sulphate, followed by denaturation and removal of DNA and protein with hot phenol. 2. Base composition analyses indicated that the cerebral nuclear RNA preparation contained a higher proportion of non-ribosomal RNA than the analogous hepatic preparation. 3. Sucrose-density-gradient analyses revealed a heterogeneous profile for each nuclear RNA preparation, with two major peaks possessing the sedimentation properties of ribosomal RNA (18s and 28s). 4. Template activities of both preparations were widely distributed through the sucrose density gradients. 5. The cerebral nuclear RNA preparation was more active than the hepatic nuclear RNA preparation in promoting amino acid incorporation in cell-free systems from Escherichia coli and rat brain. 6. Cerebral nuclear RNA stimulated amino acid incorporation in a cerebral ribosomal system even in the presence of an excess of purified E. coli transfer RNA. 7. It is concluded that a significant proportion of cerebral nuclear RNA has the characteristics of messenger RNA.

Extracorporeal membrane oxygenation for cardiorespiratory failure in four patients with pandemic H1N1 2009 influenza virus and secondary bacterial infection

We report four patients with pandemic H1N1 2009 influenza virus and secondary bacterial infection who were treated with extracorporeal membrane oxygenation (ECMO) for cardiorespiratory failure. Three of the four patients had profound shock, necessitating support with venoarterial ECMO. Two patients died during ECMO support. The two survivors had prolonged hospital stays, which were complicated by renal failure and limb ischaemia.

The Avon patellofemoral joint replacement: independent assessment of early functional outcomes

We present a prospective review of the two-year functional outcome of 37 Avon patellofemoral joint replacements carried out in 29 patients with a mean age of 66 years (30 to 82) between October 2002 and March 2007. No patients were lost to follow-up. This is the first independent assessment of this prosthesis using both subjective and objective analysis of outcome. At two years the median Oxford knee score was 39 (interquartile range 32 to 44), the median American Knee Society objective score was 95 (interquartile range 90 to 100), the median American Knee Society functional score was 85 (interquartile range 60 to 100), and the median Melbourne Knee score was 28 (interquartile range 21 to 30). Two patients underwent further surgery. Only one patient reported an unsatisfactory outcome. We conclude that the promising early results observed by the designing centre are reproducible and provide further support for the role of patellofemoral joint replacement.

PADMA-28, a traditional tibetan herbal preparation inhibits the respiratory burst in human neutrophils, the killing of epithelial cells by mixtures of oxidants and pro-inflammatory agonists and peroxidation of lipids

Both aqueous and methanolic fractions derived from the Tibetan preparation PADMA-28 (a mixture of 22 plants) used as an anti-atherosclerotic agent, and which is non-cytolytic to a variety of mammalian cells, were found to strongly inhibit (1) the killing of epithelial cells in culture induced by 'cocktails' comprising oxidants, membrane perforating agents and proteinases; (2) the generation of luminol-dependent chemiluminescence in human neutrophils stimulated by opsonized bacteria; (3) the peroxidation of intralipid (a preparation rich in phopholipids) induced in the presence of copper; and (4) the activity of neutrophil elastase. It is proposed that PADMA-28 might prove beneficial for the prevention of cell damage induced by synergism among pro-inflammatory agonists which is central in the initiation of tissue destruction in inflammatory and infectious conditions.

Evaluation of published reports of foam sclerotherapy: what do we know conclusively?

Objectives

The aim was to evaluate the published literature to assess what is conclusively known about optimal technique and outcome for foam sclerotherapy.

Methods

A literature search was performed for randomised controlled trials, meta-analyses and observational studies using appropriate statistical techniques with survival analysis for long-term outcome.

Results

Foam is more effective than liquid for ultrasound-guided sclerotherapy. Both sclerosants commonly used are equally effective for sclerotherapy for small veins. Ultrasound signals appear in the systemic circulation in most patients after foam sclerotherapy but do not appear to be associated with serious complications.

Conclusion

Little else is known about the optimal preparation of foamed sclerosants and the best technique for administering foam for sclerotherapy. Long-term studies are required to determine outcome for various techniques. There is an opportunity for many controlled trials to assess results.

Immunohistochemical study of collagen types I and II and procollagen IIA in human cartilage repair tissue following autologous chondrocyte implantation

This study has assessed the relative proportions of type I and II collagens and IIA procollagen in full depth biopsies of repair tissue in a large sample of patients treated with autologous chondrocyte implantation (ACI). Sixty five full depth biopsies were obtained from knees of 58 patients 8-60 months after treatment by ACI alone (n=55) or in combination with mosaicplasty (n=10). In addition articular cartilage was examined from eight individuals (aged 10-50) as controls. Morphology and semi-quantitative immunohistochemistry for collagen types I and II and procollagen IIA in the repair tissue were studied. Repair cartilage thickness was 2.89+/-1.5 mm and there was good basal integration between the repair cartilage, calcified cartilage and subchondral bone. Sixty five percent of the biopsies were predominantly fibrocartilage (mostly type I collagen and IIA procollagen), 15% were hyaline cartilage (mostly type II collagen), 17% were of mixed morphology and 3% were fibrous tissue (mostly type I collagen). Type II collagen and IIA procollagen were usually found in the lower regions near the bone and most type II collagen was present 30-60 months after treatment. The presence of type IIA procollagen in the repair tissue supports our hypothesis that this is indicative of a developing cartilage, with the ratio of type II collagen:procollagen IIA increasing from <2% in the first two years post-treatment to 30% three to five years after treatment. This suggests that cartilage repair tissue produced following ACI treatment, is likely to take some years to mature.

Pandemic influenza A(H1N1)v in New Zealand: the experience from April to August 2009

Following the detection of imported cases of pandemic influenza A(H1N1)v on 25 April 2009, New Zealand implemented containment measures that appeared to slow establishment of the pandemic during May. The pandemic accelerated markedly in June, reaching a peak within four to six weeks, and has been declining since mid-July. By 23 August there had been 3,179 recorded cases (97.8% reported as confirmed), including 972 hospitalisations, 114 intensive care admissions, and 16 deaths. Influenza-like illness (ILI) surveillance in general practice suggests that 7.5% (95% CI: 3.4-11.2) of the population of New Zealand had symptomatic infection, giving a case fatality ratio of 0.005%. Hospitalisations were markedly higher for Māori (age standardised relative risk (RR)=3.0, 95% CI: 2.9-3.2) and Pacific peoples (RR=6.7, 95% CI: 6.2-7.1) compared with Europeans and others. The apparent decline of the pandemic (shown by all surveillance systems) cannot be fully explained. New Zealand remains in the middle of its traditional influenza season, the influenza A(H1N1)v virus appears relatively infectious, and we estimate that only about 11% of the population have been infected by this novel agent.

Influence of the electrical stimulation of the medial amygdala on adrenocortical sensitivity to adrenocorticotrophin in hypophysectomized rats

The effects of electrical stimulation of medial amygdala on the adrenocortical sensitivity to adrenocorticotrophin (ACTH) were investigated in hypophysectomized rats. The intravenous injection of ACTH increased the rates of 14C transfer from 14C-l-acetate into corticosterone and cortisol in the adrenal slices of hypophysectomized rats. The electrical stimulation of the medial amygdala produced a further increase in the rates of 14C transfer from 14C-l-acetate into corticosterone and cortisol. From these results, it might be suggested that the medial amygdala was capable of enhancing the adrenocortical steroidogenesis in response to ACTH.

Design of an Endoreactor for the Cultivation of a Joint-Like-Structure

To avoid revision surgeries in artificial joint replacements and to allow young people to have a joint replacement, using biological joint replacement created by tissue engineering is a promising alternative. Several research groups have tissue engineered bone [Warnke 2004] and cartilage [Chung 2007] separately. The tissue engineering of a joint, consisting of bone and cartilage is the next frontier. The present study focuses on the design of a novel device, named Endoreactor, that is employing the mechanosensitivity of cells to create a joint-like-structure (JLS) consisting of a bone and cartilage sandwich, similar to an amphiarthrosis, by applying a mechanical loading regime to a stem cell seeded scaffold construct during endocultivation. This way, the patients who will eventually need the new joint will serve as their own bioreactor, having the joint grow in their own body. In the JLS, the outside layers are designed to become bone, using a 6 mm thick scaffold with high stiffness. The center layer is a 4 mm thick scaffold which is compliant so as to experience more strain than the outside scaffolds to stimulate cartilage formation. Compression is realized by placing the JLSs between the long links of a kite-shaped four-bar linkage. This Endoreactor is powered by natural body motion through connection to the musculoskeletal system of the host, which in the experimental phase is a Gottingen minipig. The loading frequency and rest versus active time is dictated by the activity level of the minipig. This results in a natural loading pattern that is employed for the stimulation of cartilage formation in the JLS. A tensile force created during ambulation is converted into compressive action between the two long links of the mechanism. A mechanical stop limits the motion. This way controlled intermittent dynamic compression between 2.5% and 12.5% is realized in the cartilage layer of the JLS. All functions are integrated into a single piece compliant mechanism which is produced out of titanium using 3D rapid prototyping by selective laser melting technology. The mechanism can be fitted with cages that hold the scaffolds for bone and cartilage in place and protect them from external loads while being implanted. A safety spring was added to accommodate for large actuation excursions. A number of prototypes were produced and tested for fatigue, plastic deformation, failure load, and displacements of the long links at the JLS locations under different axial loads. These tests confirmed the proper mechanical functioning of the Endoreactor. Work with animal models making use of the device to culture an amphiarthosis-like joint is foreseen in the near future. This work was carried out at part of MYJOINT: Living Bioreactor—Growing a New Joint in a Human Back, EU FP6-2004-NEST-C-1, Proposal No. 028861.