A histological study on polyactive® for the prevention of peridural adhesions after spinal surgery: an experimental study in dogs with a 3 months follow-up

In the present study the potential of Polyactive^® bilayer sheets in the prevention of scar tissue formation after spinal surgery was investigated. Eight adult beagle dogs underwent 3 laminectomies at three levels (L2, L4 and L6). According to a randomized implantation schedule a Polyactive^® sheet or autogenous fat graft was placed in the defect. The third site served as a control without implant. After 4 or 12 weeks (4 dogs per period) the dogs were sacrificed and histological sections were prepared. The Polyactive^® treated defects showed partial closure by newly formed bone. The Polyactive^® was encapsuled by a thin fibrous tissue layer. Ventral to the defect, dense fibrous tissue was present which was separated from the dura by the Polyactive^® sheet in all cases. In some cases fibrous tissue was present between the implant capsule and the dura. In the fat graft group there were no signs of closure of the defect but most sites showed fibrous tissue at the edges of the graft, which was in 4 sites continous with the dura mater. Fibrosis and degeneration of the fat grafts were seen. All control defects showed partial closure by newly formed bone, and ventral to the defect extensive fibrous tissue, which was in 50% continous with the dura mater. Other sections showed loose connective tissue in contact with the dura mater. It is concluded that Polyactive^® has a potential as a mechanical barrier in the prevention of adhesions between the dorsal spinal muscles and the dura mater.     

Hyperdynamic circulation of cirrhotic rats: role of substance P and its relationship to nitric oxide

BACKGROUND: It has been suggested that excessive formation of nitric oxide (NO) is responsible for the hyperdynamic circulation observed in portal hypertension. Substance P is a neuropeptide partly cleared by the liver and causes vasodilatation through the activation of the endothelial NO pathway. However, there are no previously published data concerning the plasma level of substance P in cirrhotic rats and its relationship to NO. METHODS: Plasma concentrations of substance P and nitrate/nitrite (an index of NO production) were determined in control rats and cirrhotic rats with or without ascites using an enzyme-linked immununosorbent assay and a colorimetric assay, respectively. In addition, systemic and portal hemodynamics were evaluated by a thermodilution technique and catheterization. RESULTS: Cirrhotic rats with and without ascites had a lower systemic vascular resistance (2.6 +/- 0.2 and 3.9 +/- 0.4 mmHg ml(-1) x min x 100 g body weight, respectively) and higher portal pressure (14.6 +/- 0.6 and 11.3 +/- 1.8 mmHg) than control rats (6.5 +/- 0.3 mmHg x ml(-1) x min x 100 g BW and 6.8 +/- 0.2 mmHg, respectively, P < 0.05), and cirrhotic rats with ascites had the lowest systemic vascular resistance. Plasma levels of nitrate/nitrite progressively increased in relation to the severity of liver dysfunction (control rats, 2.7 +/- 0.5 nmol/ml; cirrhotic rats without ascites, 5.6 +/- 1.3 nmol/ml; cirrhotic rats with ascites, 8.3 +/- 2.2 nmol/ml; P < 0.05). Cirrhotic rats with ascites displayed higher plasma values of substance P (57.7 +/- 5.9 pg/ml) than cirrhotic rats without ascites (37.9 +/- 3.1 pg/ml, P < 0.05) and control rats (30.1 +/- 1.0 pg/ml, P < 0.05). There was no significant difference in plasma substance P values between control rats and cirrhotic rats without ascites (P > 0.05). No correlation was found between plasma levels of substance P and nitrate/nitrite (r = 0.318, P > 0.05). CONCLUSIONS: Excessive formation of NO may be responsible, at least partly, for the hemodynamic derangements in cirrhosis. Although substance P may not participate in the initiation of a hyperdynamic circulation in cirrhosis, it may contribute to the maintenance of the hyperdynamic circulation observed in cirrhotic rats with ascites.     

Correlates of alcohol use and misuse in fourth-grade children: psychosocial, peer, parental, and family factors

To determine level of alcohol use/misuse and to examine correlates of these behaviors, 1,314 fourth-grade students were surveyed. The questionnaire included 55 items concerning tolerance of deviance, deviant self-image, self-efficacy, susceptibility to peer pressure, personal and peer approval of alcohol use, peer adjustment, parent nurturance and monitoring, family adjustment, parental permissiveness, peer use of alcohol, and exposure to alcohol. The items were factor analyzed and indices constructed. The indices generally had acceptable alpha coefficients (alpha = .61-.91); two exceptions were peer adjustment (alpha = .51) and parental permissiveness (alpha = .42). Tolerance of deviance, deviant self-image, susceptibility to peer pressure, personal and peer approval, peer use and exposure by peers, and parental permissiveness were positively correlated with alcohol use/misuse. Self-efficacy, child-parent interactions, family adjustment, and peer adjustment were negatively correlated with alcohol use/misuse. Implications for the design of family-based alcohol use/misuse prevention programs are discussed.     

The use of low-osmolar contrast agents: technological change and defensive medicine

The escalating cost of medical care in the United States, especially in the past decade, has resulted in efforts to identify the factors contributing to rising costs. One factor often assumed to cause higher medical costs is the physician's fear of liability for not using the latest available technology. In this article, we report the results of a case study we conducted to better understand the relationship between the introduction and use of one particular technology, low-osmolar contrast agents, and liability concerns. Our study suggests that both clinicians and administrators are primarily guided by the medical benefits of low-osmolar contrast agents, and that liability concerns, although widespread, are of secondary importance. The inability to control this and similar technologies is likely to put a far greater strain on the nation's health care resources than is the practice of defensive medicine. These findings may be helpful to health policy makers, physicians, administrators, and legislators considering choices for health care reform in general and for medical liability reform in particular.     

Low-temperature phase diagram of the heavy-fermion superconductor UPt3

The transition to the superconducting state of UPt₃ has been studied in specific-heat experiments on polycrystalline and single-crystalline samples in dependence of heat treatment, purity of starting materials and deviations from stoichiometry, as well as on substituted compounds. The concepts behind the splitting of the transition in two anomalies that are 60 mK apart are critically reviewed. The superconducting phase diagram in the B-T plane has been studied with the use of a sensitive dilatometric technique. The three superconducting phases meet at a tetracritical point and all four phase lines are of second order. From the length anomalies at the phase boundaries the pressure derivatives of the phase lines have been determined and the most stable phase under uniaxial pressure along the c-axis has been identified.     

Evolution of the serum amyloid A (SAA) protein superfamily

The serum amyloid A (SAA) superfamily comprises a number of genes and proteins characterized from a range of mammalian species. The majority of members described to date are dramatically induced during the acute-phase response, suggesting an important short-term beneficial role in the response to tissue injury and inflammation. However, important disease associations have also been proposed for certain SAAs during chronic inflammation. The nomenclature of many of the superfamily members has been the result of comparisons with previously reported sequences implying disease association and/or functional relatedness between such members. The evolutionary relationships of the SAA superfamily members have been investigated by comparisons at both the amino acid and the nucleotide level. The results indicate that all members of the superfamily within a species have been undergoing concerted evolution. This has important implications in ascribing functions and disease associations to individual SAA superfamily members and indicates that designations should not be based on the extent of amino acid identity alone but should be made only following direct experimental observation of the proteins themselves.