Crosslinked polyimide foams derived from poly(imidepropylene oxide) copolymers

A new route for the synthesis of high glass transition temperature, thermally stable polymer foams has been developed, using compositionally asymmetric microphase-separated block copolymers where the minor component (poly(propylene oxide)) is thermally labile and the major component (polyimide) is thermally stable. The minor component decomposes to low molecular weight species upon heating, and the decomposition products diffuse out of the film, leaving behind pores embedded in a matrix of the thermally stable component. In this study, the polyimide block was crosslinked with ethynyl functionalities to obtain a stable porous structure. The decomposition of the propylene oxide in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild conditions were required to avoid rapid depolymerization of the propylene oxide and plasticization of the polyimide matrix. The foams showed pore sizes with diameters up to a micrometer in size as well as the expected reduction in the mass density.     

A geometric model for evaluating the effects of inter-fraction rectal motion during prostate radiotherapy

A geometric model is presented which allows calculation of the dosimetric consequences of rectal motion in prostate radiotherapy. Variations in the position of the rectum are measured by repeat CT scanning during the courses of treatment of five patients. Dose distributions are calculated by applying the same conformal treatment plan to each imaged fraction and rectal dose-surface histograms produced. The 2D model allows isotropic expansion and contraction in the plane of each CT slice. By summing the dose to specific volume elements tracked by the model, composite dose distributions are produced that explicitly include measured inter-fraction motion for each patient. These are then used to estimate effective dose-surface histograms (DSHs) for the entire treatment. Results are presented showing the magnitudes of the measured target and rectal motion and showing the effects of this motion on the integral dose to the rectum. The possibility of using such information to calculate normal tissue complication probabilities (NTCP) is demonstrated and discussed.     

Virulence Differences in Mice of Type A and B Histoplasma capsulatum Yeasts Grown in Continuous Light and Total Darkness

Type B yeasts were more virulent for mice than type A under most experimental conditions. Mice infected with type B yeasts grown in the light lived significantly longer than those with type B yeasts grown in the dark. Virulence differences of type A yeasts grown in continuous fluorescent light versus total darkness were not statistically significant.     

Potential modifier role of the R618Q variant of proalpha2(I)collagen in type I collagen fibrillogenesis: in vitro assembly analysis

An arginine to glutamine substitution in the triple helix of proalpha2(I)collagen (R618Q) was first reported in a patient with a variant of Marfan syndrome and later identified in conjunction with a second mutation in a patient with osteogenesis imperfecta (OI). The presence of the R618Q proalpha2(I)collagen allele in unaffected or mildly affected family members suggests that the R618Q allele is either a non-affecting polymorphism or a potential genetic modifier. Conservation of arginine618 across species and fibrillar collagen types suggests it is functionally significant. To investigate the functional significance of the R618Q proalpha2(I)collagen allele, we isolated type I collagen from cultured dermal fibroblasts of control and two unrelated individuals heterozygous for the R618Q proalpha2(I)collagen allele and evaluated helical stability and fibrillar assembly. Type I collagen thermal stability analyzed by protease susceptibility and CD spectroscopy demonstrated no statistical difference between control and R618Q containing collagen molecules. In vitro fibril assembly analyses demonstrated that R618Q containing collagen exhibits rapid fibrillar growth with minimal fibril nucleation phase. Further, electron microscopy demonstrated that the diameter of assembled R618Q containing collagen fibrils was approximately 20% of control collagen fibrils. These findings suggest the R618Q variant does not impact triple helical stability but has a role in collagen fibril assembly, supporting the hypothesis that the R618Q proalpha2(I)collagen variant is a modifier of connective tissue structure/function and is potentially involved in disease pathogenesis.     

Exercise-induced metallothionein expression in human skeletal muscle fibres

Exercise induces free oxygen radicals that cause oxidative stress, and metallothioneins (MTs) are increased in states of oxidative stress and possess anti-apoptotic effects. We therefore studied expression of the antioxidant factors metallothionein I and II (MT-I + II) in muscle biopsies obtained in response to 3 h of bicycle exercise performed by healthy men and in resting controls. Both MT-I + II proteins and MT-II mRNA expression increased significantly in both type I and II muscle fibres after exercise. Moreover, 24 h after exercise the levels of MT-II mRNA and MT-I + II proteins were still highly increased and the MT-II mRNA expression reached a 15-fold increase. As expected, immunohistochemical detection of malondialdehyde (MDA) and nitrotyrosine (NITT) showed that formation of free radicals and oxidative stress were clearly increased in exercising muscle peaking shortly after the end of exercise in both type I and II muscle fibres. This is the first report demonstrating that MT-I + II are significantly induced in human skeletal muscle fibres following exercise. As MT-I + II are antioxidant factors that protect various tissues during pathological conditions, the MT-I + II increases post exercise may represent a mechanism whereby contracting muscle fibres are protected against cellular stress and injury.     

Near-haploid clones in a malignant fibrous histiocytoma

Near-haploid solid tumors are very rare. In a storiform-pleomorphic malignant fibrous histiocytoma (MFH) of bone, we found three cell populations: one with a near-haploid, a second with a near-diploid, and a third with a near-tetraploid chromosome number. The near-haploid cells had few structural rearrangements: i(12p) and t(13q21q) in one clone, and these two and an additional t(19;?)(p11;?) in another clone. One structurally normal copy of all chromosomes was also present, except that the only chromosome 13 was involved in the t(13q21q). There were also two near-diploid clones, one without the t(19;?) and one with a single copy of this derivative chromosome. This is the first MFH reported to have a near-haploid modal chromosome number, and also the first tumor with i(12p) among bone and soft tissue tumors.     

Antigen-binding peripheral blood lymphocytes in guinea-pigs immunized with human thyroglobulin in BCG

Guinea-pigs were immunized with an emulsion of human thyroglobulin (Tg) and BCG vaccine in Freund's incomplete adjuvant. Peripheral blood lymphocytes binding Tg and purified protein derivative of mammalian tuberculin (PPD) labelled with ¹²⁵I were demonstrated with an autoradiographic technique. The percentage of these cells was compared with the size of the delayed hypersensitivity (DH) skin reactions to Tg and PPD, and Tg antibody titres at intervals up to 35 days after immunization. The individual responses to Tg showed the time course of primary immune reactions although they did not parallel each other closely. By contrast, a depression of cutaneous DH to PPD was observed in spite of the presence of substantial numbers of ¹²⁵I-PPD-binding peripheral blood lymphocytes. In non-immune guinea-pigs, approximately 2·8% of peripheral blood lymphocytes bound ¹²⁵I-PPD whereas <0·1% bound ¹²⁵I-Tg.

The significance of antigen-binding lymphocytes in the immune response is discussed, and it is suggested that the presence of a substantial pool of antigen-binding lymphocytes in unprimed may be of importance in the induction of DH.

     

Studies on gonococcus infection. XVI. Purification of Neisseria gonorrhoeae immunoglobulin A1 protease.

A protease which cleaves human immunoglobulin A1 (IgA1) has been purified from broth cultures of Neisseria gonorrhoeae. This IgA1 protease is produced by pilated and nonpilated gonococci throughout their growth cycles. A combination of ammonium sulfate precipitation, column chromatography, and either isoelectric focusing or affinity chromatography was utilized to obtain an enzyme preparation that showed approximately 3,800-fold purification and exhibited two bands (65,000 and 70,000 daltons) by analytical polyacrylamide electrophoresis in the presence of sodium dodecyl sulfate and reducing conditions. IgA1 protease activity is dependent on divalent cations and is heat labile. Detection and quantitation of IgA protease activity utilized an assay in which [125I]IgA1 is incubated with protease preparations and the cleavage products are analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.     

PC-based system for collection and analysis of physiological data

A personal computer based system for data acquisition and analysis appropriate to physiological experiments is described in detail. The system is independent of the details of the analog signal generation. The software, written in C, is modular and easily portable to other PC systems. The system is capable of: (a) sampling many analog signals at an appropriate rate (100 Hz), (b) storing large quantities of digitized data, (c) analysing digitized waveforms to obtain signal parameters, and (d) storing signal parameters in a format suitable for statistical analysis. Computer processed cardiopulmonary data are compared with data derived from standard ICU equipment.