Effect of vitamin A deficiency on oxalate uptake by rat intestinal brush border membrane vesicles (BBMV) and its contribution towards urolithiasis

The intestinal uptake of [14C]oxalate, [14C]glyoxylate, and [14C]glycolate are studied in brush border membrane vesicles (BBMV) isolated from vitamin A-deficient and pair-fed control rats. The data obtained indicate that oxalate and its precursors are transported across the BBMV by passive diffusion. The intestinal uptake of glyoxylate and glycolate remains unaltered in vitamin A deficiency, while uptake rate of oxalate was significantly increased (p less than 0.01) in vitamin A-deficient rats as compared to pair-fed controls. In conclusion, the results indicate that vitamin A deficiency leads to hyperabsorption of oxalate through the gut.     

Heterotopic heart transplantation: a radiographic review

Heterotopic heart transplantation can be performed in the presence of high pulmonary vascular resistance. The authors call attention to a rare, but potentially life-saving procedure.     

Cyclophosphamide-induced cytogenetic effects in mouse bone marrow and spleen cells in in vivo and in vivo/in vitro assays

Sister chromatid exchange (SCE) and chromosomal aberration studies have been used to monitor human populations for genotoxic exposure to chemical substances. These monitoring techniques involve collection of blood and/or bone marrow from the exposed subjects and culturing cells for one or two cell cycles with various treatments in culture. The results obtained from such in vivo/in vitro studies may lead to an over- or underestimation of the damage that could occur in vivo. In the present study, which uses a mouse model, the in vivo/in vitro cytogenetic assays (SCEs and chromosomal aberrations) have been compared with similar in vivo systems in bone marrow and spleen cells treated with various doses of cyclophosphamide (CPA). The results indicate a significant difference in CPA-induced cytogenetic endpoints between in vivo and in vivo/in vitro conditions in both organs. However, linear relationships were found between CPA dose and cytogenetic end point analyzed under both conditions. Based on these results it appears that the in vivo/in vitro assay is a useful technique for indicating potential in vivo damage of chemicals.     

Photon energy dependence of the sensitivity of radiochromic film and comparison with silver halide film and LiF TLDs used for brachytherapy dosimetry

There is a new radiochromic film, a highly uniform, thin (100-microns) detector whose sensitive layer (6 microns thick) changes from colorless to blue by dye polymerization without processing, upon exposure to ionizing radiation. Because the dose gradients around brachytherapy sources are steep, the high spatial resolution offered by film dosimetry is an advantage over other detectors such as thermoluminescent dosimeters (TLDs). This compares the photon energy dependence of the sensitivities of GafChromic film, silver halide verification film (Kodak X-Omat V Film), and lithium fluoride TLDs (Harshaw), over the photon energy range 28 keV to 1.7 MeV, which is of interest in brachytherapy. Sensitivity of the radiochromic film is observed to decrease by about 30% as effective photon energy decreases from 1710 keV (4-MV x rays) to 28 keV (60-kV x rays, 2-mm A1 filter). In contrast, the sensitivity of verification film increases by 980% and that of LiF TLDs increases by 41%. The variation of the sensitivity of radiochromic film with photon energy is considerably less than that for silver halide film and similar to that for LiF TLDs, but in the opposite direction. Radiochromic film, like LIF TLDs, does not exhibit the drastic sensitivity changes below 127 keV that silver halide film exhibits. Dose distribution in the immediate vicinity of a high activity (370 GBq) brachytherapy 192Ir source has been mapped using radiochromic film and is presented to illustrate the applicability of this new technology to brachytherapy dosimetry.     

Effect of lymphocyte mediators on macrophages in vitro. A correlation of morphological and cytochemical changes

Sephadex purified PPD and Con A induced mediator rich fractions (MRF) were applied to guinea-pig macrophages cultured in vitro. At varying times after the addition of the MRF, cells were removed from culture for morphological study and for cytochemical tests. Respiratory enzyme activity and lysosomal acid phos-phatase activity were estimated and the former was quantitated using an integrating microdensitometer. Early changes, 1 hr after MRF contact, were observed and subsequent alterations in activity up to 48 hr after the addition of MRF were also seen. These changes have been related to the inhibition of migration and subsequent `activation' of the macrophages which has been observed morphologically at times up to 3 weeks after MRF addition.

It is suggested that alterations in the cytochemistry of the macrophages after MRF contact could help explain changes in the behaviour of the cells under these experimental conditions.

     

Linkage analysis of SLE susceptibility: confirmation of SLER1 at 5p15.3

We detected a novel susceptibility gene, SLER1, for systemic lupus erythematosus (SLE) at 5p15.3.(1) This finding was based on a selected subgroup of SLE families, where two or more family members have had alleged rheumatoid arthritis (SLE-RA). The main objective of this study was to replicate the linkage at 5p15.3 based on an independent data set of 88 SLE-RA families. Heterogeneity in the genetic model led us to use a nonparametric allele-sharing method. Since our a priori hypothesis of linkage at 5p15.3 was fixed, we genotyped six markers at the linked region. Our new results replicate the initial linkage at 5p15.3 (Zlr=2.58, P<0.005, LOD=1.45). Moreover, evidence of linkage was sustained when analysis was restricted to the subset of SLE families who had 3 or more individuals with alleged RA (Zlr=3.32, P=0.008, LOD=2.40) The results of our previous findings, together with these new results, confirm the SLER1 linkage at 5p15.3. Our results also demonstrate the utility of clinically defined subgroup analysis for detecting susceptibility loci for complex genetic diseases, such as SLE.     

Dose distributions produced by shielded applicators using 241Am for intracavitary irradiation of tumors in the vagina.

Dosimetric characteristics of shielded vaginal applicators containing encapsulated 241Am sources are investigated in this work. Encapsulated 241Am sources emit primarily 60-keV photons which are more effectively shielded by thin layers of high atomic number materials than the 662-keV photons from 137Cs sources. With 241Am, it is possible to achieve almost unidirectional irradiation of localized vaginal tumors. The drastic decrease in irradiation volume on the contralateral side (uninvolved with tumor) is observed to decrease dose by up to 20%, even in the forward direction (unshielded side toward the tumor) of the applicator. A possible explanation for the observed effects of shields in both the forward and backward directions is the reduction of scattered photon fluence due to absorption of photons in the lead shield via photoelectric effect. Current theoretical models do not include this perturbation effect caused by shields on brachytherapy applicators.