Mechanismus der photopolymerisation des styrols, 4. Zur rolle der photo-(4π + 2π)-addukte als kettenüberträger und zur kinetik der photopolymerisation in gegenwart überlagerter,thermischer prozesse

The photopolymerization of styrene was investigated at 25°C, by following the variations in the rate of polymerization and the degree of polymerization with the light intensity, J_M, at different wavelengths of the exciting light (λ_e = 313 nm, λ_e = 335 nm). The corresponding data were analyzed in terms of the formalism between the rate R_P and the viscosity average degree of polymerization P _η. The kinetic evaluation shows that at least at small fractions of the absorbed light and at short duration of the irradiation the stabilization of the growing chain radicals will occur predominantly by bimolecular termination processes and not by chain transfer. This must be attributed to the fact that among the four theoretically possible isomeric photo-(4π + 2π)-intermediates (I) 1-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1a and 1b ) and 2-phenyl-1,2,3,8a-tetrahydronaphthalene (diastereomers 1 ′ a and 1 ′ b ) the photostationary concentration [ 1a ]_∞ of the most reactive chain transfer agent 1a is—as a result of its very small quantum yield of formation ( φ_1a ? φ_1b + φ_1′a + φ_1′b )—extremely low and contributes only a few percent to the total photo-steady-state concentration of I. At higher temperatures (T > 25°C) and at small fractions of the absorbed light J_M/J_o (λ_e = 335 nm), the rate of photopolymerization R_P is controlled by the contributions of two independent routes of initiation: (1) the rate R, which accounts for the photo-free radical formation of the photo-intermediates I, and 2 the rate R, which is derived from the photoinduced free radical generation of the thermally produced Diels-Alder adducts 1a and 1b . As a further aspect of this analysis the results give strong evidence that the endo adduct 1a , when electronically excited, enters into a very efficient radical forming process, contrary to the other isomers 1b , 1 ′ b , and 1 ′ a , which seem to be mainly deactivated by their individual retro-Diels-Alder decompositions and will not enter into free radical formation to any noticeable extent: φ_S ^1a ? (φ_S ^1b + φ_S ^{1 ′ b} + φ_S ^{1 ′ a} ) An explanation of the very different stereodynamic behaviour is given.     

Terminal rearrangements in the genome of adenovirus type 12 mutants adapted to growth in two human tumor cell lines

After serial passage of adenovirus type 12 in cells of the human melanoma line Nki4 virus mutants with enhanced growth potential have been isolated which carry additional sequences of regularly increasing size at the right end of the genome. DNA sequence analysis was performed'to characterize these genomic alterations as well as those of the previously described Ad12 $\text{C}\text{4}\text{1}$ mutants adapted to growth in the human carcinoma cell line $\text{C}\text{4}\text{1}$ (I. Kruczek, E. Schwarz, and H. zur Hausen (1981)Int. J. Cancer27, 139–143). Duplication of the inverted terminal repetition (ITR) emerged as the common feature of the right terminal alterations of all the mutant genomes analyzed. The sequences present between the ITR repeats were of either right-end or left-end origin, the latter suggesting that left-end sequences comprising the ITR and parts of the adjacent unique sequences have been transferred to the right end of the genome. The different sizes of the additional sequences in Ad12 Nki-4 DNA could be explained by varying degrees of amplification of a basic additional sequence of 342 base pairs.     

Detection of methicillin-resistant Staphylococcus aureus and simultaneous confirmation by automated nucleic acid extraction and real-time PCR

A molecular assay for the simultaneous detection of a Staphylococcus aureus-specific gene and the mecA gene, responsible for the resistance to methicillin in staphylococci, was evaluated. The assay included an automated DNA extraction protocol conducted with a MagNA Pure instrument and real-time PCR conducted with a LightCycler instrument. The performance and robustness of the assay were evaluated for a suspension of methicillin-resistant S. aureus (MRSA) strain with a turbidity equivalent to a McFarland standard of 0.5, which was found to be the ideal working concentration. The specificity of the new molecular assay was tested with a panel of 30 gram-negative and gram-positive bacterial strains other than MRSA. No cross-reactivity was observed. In a clinical study, 109 isolates of MRSA were investigated. All clinical MRSA isolates gave positive results for the S. aureus-specific genomic target, and all but one were positive for the mecA gene. In conclusion, the new molecular assay was found to be quick, robust, and laborsaving, and it proved to be suitable for a routine molecular diagnostic laboratory.     

Regulation of tissue-degrading factors and in vitro invasiveness in progression of breast cancer cells

Hormone-independent growth and invasiveness represent phenotypic properties acquired during early progression of breast cancer. We compared human mammary adenocarcinoma cells, MCF-7, which are estrogen-dependent and poorly metastatic, with the estrogen-independent and highly metastatic subline, MCF7/LCC1, with regard to expression of tissue-degrading factors of the matrix metalloproteinase (MMP)-and urokinase (uPA)-dependent degradative pathways, as well as for their in vitro invasive properties. Both cell lines showed low constitutive mRNA expression of the MMP inhibitor TIMP-1. Baseline expression of TIMP-2 mRNA was also very low in MCF-7 cells, whereas the MCF7/LCC1 level was much higher (~10- fold). Furthermore, both cell lines revealed low constitutive capacity to migrate in an in vitro invasion assay. Treatment with 12-O-tetradecanoylphorbol-13-acetate (TPA; 100 nM) induced the mRNAs for TIMP-1 as well as for MMP-1, MMP-9, the uPA receptor, and the uPA inhibitor PAI-1, am ongst which only the responses of MMP-9 and PAI-1 were cell-specific. The mRNA levels of MMP-9 and PAI-1 were ~10-fold and ~15-fold higher in MCF7/LCC1 cells compared to MCF-7 cells. The secretion of immuno-reactive PAI-1 was considerably elevated (. 20-fold) in TPA-treated MCF7/LCC1 cells, whereas the TPA-dependent level of 92-kDa MMP-9 was only ~2-fold higher in MCF7/LCC1 cells than in MCF-7 cells. In both cell lines treatment with TPA was associated with an increase (~10-fold) in in vitro migration, which in the MCF7/LCC1 cells was significantly attenuated by a reconstituted basement membrane extract (Matrigel). These data suggest that TPA-responsive in vitro invasive properties that are probably associ-ated with PAI-1 expression may co-vary with progression from hormone-dependent to -independent breast cancer. © Rapid Science 1998     

Depressive symptoms and disability in acute and chronic back pain patients

Depression and level of disability are evaluated in acute and chronic low back pain (LBP) patients. To assess the possibility that some somatic symptoms are confounded with pain, the items of the Beck Depression Inventory arc divided into a cognitive-affective and somatic subscale. The sample consisted of 37 chronic LBP patients. 41 acute LBP patients, and 28 healthy participants. The level of disability was assessed by the Oswestry Low Back Pain Disability Questionnaire. Chronic LBP patients, but not acute LBP patients, have more depressive symptoms than controls. Additionally, chronic LBP patients report more somatic symptoms of depression (e.g.. emo ltional and self disturbance complaints) than cognitive-affective symptoms. Finally, correlation statistics reveal significant relations between the level of disability and depression scores. Whereas chronic patients show a significant correlation between the somatic subscale and level of disability, in acute patients the cognitive-affective subscale is significantly related to the level of disability. The findings suggest careful consideration of whether somatic symptoms of depression are related to pain when using self-report measurements of depression in pain patients. The separation of cognitive-affective and somatic symptoms of depression to evaluate pain problems seems appropriate.     

Radiopharmacokinetics and radiation dose from 99mTc-HM-PAO (Preliminary report)

Whole body retention measurements were performed in volunteers after i.v. injection of ^99mTc-HM-PAO (Ceretec^®). The organ accumulation was measured in mice and data were transferred to standard man according to ICRP. Absorbed dose calculations were made with these data by using the concept of absorbed fractions (MIRD method). In man, the whole body retention and the retention in the brain could be calculated by direct measurement, absorbed doses to the other organs could only be derived from animal data. The absorbed dose to the brain derived from human data (10.3 Gy/MBq) is greater by a factor of 2 than that derived from animal data. The highest absorbed dose was received by the thyroid (24.4 Gy/MBq), the absorbed dose to the ovaries, testes and whole body ranged from 2.8 to 4.2 Gy/MBq.Dedicated to Professor Dr. Guenter Liess on the occasion of his 65th anniversary     

Risk factors for Epstein–Barr virus reactivation after renal transplantation: Results of a large,multi-centre study

Epstein–Barr virus (EBV) reactivation is a very common and potentially lethal complication of renal transplantation. However, its risk factors and effects on transplant outcome are not well known. Here, we have analysed a large, multi-centre cohort (N = 512) in which 18.4% of the patients experienced EBV reactivation during the first post-transplant year. The patients were characterized pre-transplant and two weeks post-transplant by a multi-level biomarker panel. EBV reactivation was episodic for most patients, only 12 patients showed prolonged viraemia for over four months. Pre-transplant EBV shedding and male sex were associated with significantly increased incidence of post-transplant EBV reactivation. Importantly, we also identified a significant association of post-transplant EBV with acute rejection and with decreased haemoglobin levels. No further severe complications associated with EBV, either episodic or chronic, could be detected. Our data suggest that despite relatively frequent EBV reactivation, it had no association with serious complications during the first post-transplantation year. EBV shedding prior to transplantation could be employed as biomarkers for personalized immunosuppressive therapy. In summary, our results support the employed immunosuppressive regimes as relatively safe with regard to EBV. However, long-term studies are paramount to support these conclusions.     

Rapid rise in plasma glucagon induced by acute cold exposure in man and rat

The effect of acute cold exposure on the concentration of glucagon in the blood was investigated in man and in intact and adrenalectomized rats.In man fasted overnight acute cold exposure, which caused a twofold increase in O₂-consumption resulted in a rapid rise in plasma glucagon. The levels of insulin and blood glucose remained unaltered, while the concentration of serum free fatty acids and -hydroxybutyrate increased.In fasted intact rats acute cold exposure lead to similar effects. A close parallelism between the rise in plasma glucagon and the concentration of hepatic cycloAMP was observed. Adrenalectomy did not impair the cold induced rise in plasma glucagon and hepatic cycloAMP.It is concluded that acute cold exposure caused a rapid rise in the concentration of plasma glucagon leading to an increase in the concentration of hepatic cycloAMP, thus enhancing the rate of hepatic gluconeogenesis and ketogenesis. As these alterations were similar in the absence of glucocorticoids and medulla-derived catecholamines, it is suggested that glucagon may play a role in the metabolic adaptation to acute cold exposure.     

Time-resolved fluorometric assay for the detection of endostatin in chromatographically separated extracts of natural peptides

We present a heterogeneous non-competitive immunological detection assay for peptide and protein antigens from crude extracts of biological sources. This time-resolved fluoroimmunoassay (TR-FIA) has been designed in a solid-phase mode using 96-well microtiter plates. Using the rare-earth metal europium as a fluorescent marker, a highly sensitive, selective and efficient procedure was developed. This technique prevents from interferences of intrinsic protein fluorescence which is highly important for antigen measurement in complex matrices. The TR-FIA has been applied for the detection of circulating forms of the potential anti-tumor agent endostatin, a C-terminal fragment of collagen XVIII, and its close homolog collagen XV (restin) from hemofiltrate. Endostatin was detected with a limit of detection of 3 ng (150 fmol/well) and a broad dynamic range from 10-1000 ng/well.