Effects of unisegmental disc compression on adjacent segments: an in vivo animal model

It is controversial whether fusion of discs in the spine leads to increased degeneration on the remaining discs or whether the degenerative changes are merely a part of the inevitable natural history process. To determine the effects of unisegmental compression and subsequent recovery on adjacent segments, we studied histology, radiology and intradiscal pressure using an in vivo rabbit model. Fifteen New Zealand rabbits were divided in to three groups of five. In the first group, the intervertebral disc L4–L5 of the lumbar spine was axially loaded for 28 days with an external loading device. In the second group, the intervertebral disc was compressed for 28 days and allowed to recover for an equal amount of time, with the loading device removed. Five animals underwent a sham operation, in which the external loading device was situated, but their discs remained unloaded for 28 days. The intradiscal pressure was determined in the loaded discs as well as in the cranial and caudal adjacent discs. Lateral radiographs were taken from each subjected intervertebral disc with adjacent vertebral bodies and the cranial and caudal adjacent segments. The compressed discs showed lower intradiscal pressure in comparison with the control group, which remained unloaded. In the cranial and caudal discs adjacent to the loaded discs the average intradiscal pressure was similar to the unloaded controls. The loaded discs demonstrated a significant decrease in disc space. No discs adjacent to the loaded discs changed in height. The lamellar architecture of the inner, middle, and outer annulus became more disorganized in the loaded discs. The nucleus pulposus showed increase of mucoid degeneration and increased cell death. Intervertebral discs from the control group and the adjacent discs to the compressed discs maintained their normal morphology. This study shows that mechanical loading of discs in the spine can cause rapid degeneration. Adjacent discs, however, did not change in terms of radiology, intradiscal pressure, or histology.     

Arterioarterial prosthetic loop: a new approach for hemodialysis access

OBJECTIVES: In this report we present a novel procedure that uses an arterioarterial prosthetic loop (AAPL) with the proximal axillary or the femoral artery as a vascular access for hemodialysis in patients who have inadequate vascular conditions for creating an arteriovenous fistula or graft. METHODS: Between April 1996 and September 2004, 34 patients received 36 AAPLs as vascular access, either as an axillary chest loop (n = 31) or as a femoral loop (n = 5). In this procedure the artery is ligated between the anastomoses to direct flow through the AAPL. Data from all patients undergoing the procedure were prospectively collected. RESULTS: The indication for an AAPL was the unsuitability of large deep veins in 64%, steal syndrome in 11%, the combination of only a suitable femoral vein and severe peripheral arterial disease in 22%, and congestive heart failure in 3%. All AAPLs were cannulated 18 +/- 4 days postoperatively. Mean follow-up was 31 months (range, 1 to 83). Primary patency was 73% and secondary patency was 96% at 1 year; these rates at 3 years were 54% and 87%, respectively. The rate of all interventions for the maintenance of AAPL function was 0.47 procedures per patient year. Four grafts were abandoned. More than 11,000 hemodialyses with proven efficiency were performed. CONCLUSIONS: The AAPL is an unusual but useful and easy-to-perform alternative procedure to create vascular access for hemodialysis. It can provide survival for strictly selected patients in whom conventional vascular access is not possible. The axillary chest AAPL is preferred.     

Autoimmune responses against renal tissue proteins in long-term surviving allograft recipients

Major histocompatibility complex antigens (MHC) are classical targets of recipient responses to allotransplants. However, the role of an immune response directed against autologous graft tissue determinants is poorly defined. In this study, we investigated (i) whether autologous kidney tissue extract can induce an immune response to autologous kidney proteins in normal rats, and (ii) if a similar autologous response develops in the long-term surviving LEW.1A recipients of an MHC-mismatched LEW.1W kidney (RT1^u to RT1^a). LEW.1A rats immunized with allo- or syngeneic soluble kidney extracts developed a T-cell response to self antigens as shown by the frequency of specific IFN-γ-producing T cells from LEW.1A rats in the presence of extracts (ELISPOT). In contrast, they responded only marginally to dominant RT1^u determinants. The ELISPOT against fractions of soluble autologous kidney extracts separated by an FPLC gel-filtration system indicated a preferential response to megalin, a high molecular weight protein that has been shown to be involved in experimental Heymann nephritis. In a model of long-term kidney allograft survival by anti-CD28 administration, recipients also developed humoral but not cellular responses to megalin. Our data suggest that autoimmune processes develop in long-term surviving kidney allograft recipients.     

Abnormal expression of Col X, PTHrP, TGF-β, bFGF, and VEGF in cartilage with Kashin–Beck disease

The purpose of the current study was to investigate the abnormal expression of Col X, PTHrP, TGF-β, bFGF, and VEGF in cartilage from patients with Kashin–Beck disease (KBD) to understand the pathogenesis of chondronecrosis in KBD. Articular cartilage and growth plate cartilage collected were divided into four groups: control children (8 samples, 5 cases), KBD children (19 samples, 9 cases), control adults (8 samples, 6 cases), and KBD adults (16 samples, 15 cases). The presence of PTHrP, TGF-β₁, bFGF, VEGF, and collagen X in articular cartilage and in growth plate cartilage was analyzed by immunohistochemistry. Articular cartilage and growth plate were each divided in three zones, and the rate of positive cells was counted by light microscope for cytoplasmic and pericellular staining. Results showed that (1) in KBD children, Col X expression was lower in the deep zone of growth plate cartilage than in normal children; in articular cartilage of KBD adults, however, collagen X expression was higher in the middle zone compared to the controls; (2) staining for bFGF, PTHrP, TGF-β₁, and VEGF in KBD adult patients was prominent in the chondrocyte clusters and the eroded surface of articular cartilage, and the percentage of chondrocyte staining was significantly higher than in control samples (t = 3.64–10.34, df = 12 for children and 19 for adults, P = 0.002–0.0001); and (3) the enhanced PTHrP, TGF-β₁, and VEGF staining in the deep and middle zone of KBD articular cartilage correlated with the high incidence of chondronecrosis in the middle zone (48.5% ± 10.2%) and deep zone (70.6% ± 27.0%) of adult KBD cartilage. In conclusion, Col X expression was reduced in areas of chondrocyte necrosis in the deep zone of KBD articular cartilage, indicating changes in terminal chondrocyte differentiation. PTHrP, TGF-β₁, and VEGF expression was significantly altered and indicated degenerative changes in KBD cartilage, which initially resemble those occurring in osteoarthritis, but lead eventually to chondronecrosis, an event not observed in osteoarthritis.     

Plasma angiotensin II concentrations in diabetic ketoacidosis and in hyperosmolar non-ketotic hyperglycemia

Summary Plasma angiotensin II concentrations were measured in 14 patients in diabetic ketoacidosis and in two patients with hyperosmolar non-ketotic hyperglycemia, before treatment and again when blood glucose control was restored. In the ketoacidosis group plasma angiotensin II before treatment was markedly raised in all patients with otherwise uncomplicated diabetes, but was within the normal range in some patients with long-term complications such as neuropathy, retinopathy and nephropathy. Mean angiotensin II before treatment was significantly higher in otherwise uncomplicated patients than in those with long-term complications. However, plasma angiotensin II decreased with improved control in all. Angiotensin II levels did not correlate with indices of rehydration such as changes in blood urea, packed cell volume and calculated changes in plasma volume. There was, however, a significant negative association between pretreatment angiotensin II and pH. Two patients with hyperosmolar non-ketotic hyperglycemia were more dehydrated but less acidotic. Pre-treatment angiotensin II in each was well below the mean of the ketoacidosis group. These data are further evidence that the renin-angiotensin system may be impaired in diabetics with long-term complications. In addition, they suggest that factors other than fluid depletion are also important in activating the renin-angiotensin system in uncontrolled diabetes.     

Evaluation of a novel automated non-invasive pulse pressure variation algorithm

In mechanically ventilated patients, Pulse Pressure Variation (PPV) has been shown to be a useful parameter to guide fluid management. We evaluated a real-time automated PPV-algorithm by comparing it to manually calculated PPV-values. In 10 critically ill patients, blood pressure was measured invasively (IBP) and non-invasively (CNAP^® Monitor, CNSystems Medizintechnik, Austria). PPV was determined manually and compared to automated PPV values: PPV_manIBP vs. PPV_autoIBP was ?0.19±1.65% (mean bias±standard deviation), PPV_manCNAP vs. PPV_autoCNAP was ?1.02±2.03% and PPV_autoCNAP vs. PPV_manIBP was ?2.10±3.14%, suggesting that the automated CNAP^® PPV-algorithm works well on both blood pressure waveforms but needs further clinical evaluation.     

Non-random Mating and Convergence Over Time for Mental Health, Life Satisfaction, and Personality: The Nord-Trøndelag Health Study

Earlier studies have shown evidence for various sources of observed spousal similarity regarding different traits and characteristics. We explored the relative contribution of non-random mating and convergence to spouse similarity with respect to global mental health, life satisfaction, optimism, and type A personality. We used population-based data collected for the Nord-Trøndelag Health Study (1984–1986) and prospective registry information about when and with whom people entered into marriage/cohabitation between 1970 and 2000 for 19,599 married/cohabitating couples and 1,551 future couples that entered into marriage/cohabitation during the 16 years after data collection. Couples were categorized by interval between data collection and entry into marriage/cohabitation. Age-adjusted polychoric correlations calculated for each group were used as the dependent variables in non-linear, segmented regression analysis, with time since or until marriage/cohabitation as the independent variable. Initial correlations between partners-to-be were low to moderate, typically around one-half of the values estimated in existing couples, indicating both non-random mating and early convergence. There appeared to be moderate divergence during the first 20 years of marriage/cohabitation and moderate convergence during the rest of life.