NMR chemical shift imaging

Chemical shift imaging combines the spatial information provided by a conventional nuclear magnetic resonance (NMR) image with the chemical shift spectral information provided by NMR spectroscopy. In order to preserve the chemical shift information and provide a spatial map simultaneously, new NMR imaging methods have been developed. In general, these methods have taken two forms: (a) three-dimensional techniques which add an extra axis of information--chemical shift spectral data--to a planar (2-D) image; and (b) two-dimensional techniques which, in certain circumstances, allow one to use techniques only slightly different from conventional ones to obtain high-resolution images of particular chemical shift species. Each of these methods offers unique challenges to the imager, as well as special advantages. In particular, three-dimensional techniques offer the opportunity to visualize the chemical shift spectra explicitly, while two-dimensional techniques allow for rapid imaging times and high spatial resolution. Most of the work in chemical shift imaging to date has focused on 1H, 31P, and 23Na. The high concentration of water and lipids in biological tissue has made the proton especially amenable to study, and the ability to sample other proton-containing compounds (such as lactate) in the face of high concentration lipid and water is now being explored. The potential use of chemical shift imaging techniques in the research and clinical settings is currently under investigation.     

Distribution of mesalazine enemas in active and quiescent ulcerative colitis.

BACKGROUND: The efficacy of mesalazine enemas depends on intraluminal concentration of the drug and is therefore limited by the enema distribution in the colon. Active ulcerative colitis changes colon motility and this leads to uncertainty about enema spread. AIM: To assess the influence of disease activity on enema distribution, we conducted a physician-blinded, longitudinal study of the retrograde spread of three mesalazine enemas. METHODS: Thirty-one patients with mild to moderate ulcerative colitis were subdivided into three groups, and treated with 2 g mesalazine in 30 mL (group I, n = 10), 4 g mesalazine in 60 mL (group II, n = 12) or 1 g mesalazine in 100 mL (group III, n = 9). All patients received oral mesalazine 500 mg t.d.s. Enemas were labelled by adding 10 MBq (99mTc)technetium-sulphur colloid. Anterior scintigraphic images were taken at the start of the study and after 12 weeks of therapy; retrograde spread was assessed by calculating the percentage of the enema in each colonic segment. RESULTS: The activity score of ulcerative colitis diminished significantly after 12 weeks of treatment, but five patients dropped out of the study. At the start of treatment enema activity in group I was mainly concentrated in the sigmoid (99%); in group II activity was found in the rectum (9%), the sigmoid (61%) and the descending colon (15%); in group III activity was distributed between the sigmoid (66%) and descending colon (25%). The colonic distribution of mesalazine enemas was not influenced by disease activity. CONCLUSION: Volume, but not disease activity, is the important determinant of retrograde colonic spread of mesalazine enemas in ulcerative colitis.     

GAP JUNCTION CHANNELS GATING AND PERMSELECTIVITY: THERE ROLES IN CO-ORDINATED TISSUE FUNCTION

1. The gating and permselective properties of gap junction channels are important parameters to determine in delineating their role in co-ordinated tissue function. This is of particular relevance in non-excitable tissues. 2. In the present study gating characteristics of rCx43 are demonstrated. The mean open times are of the order of 0.45-1.1 s. These values are extraordinarily large. 3. The permselectivity of a variety of gap junction channels is also illustrated to show the poor selectivity properties of gap junctions and, hence, their potential to allow the permeation of second messenger molecules. 4. Gating and permselectivity, along with diffusion modelling, produce a picture for gap junction channels that is consistent with physiologically relevant modulation or regulation of gap junction channel patency.     

Multiplanar arc boost radiation therapy for prostate cancer

Localized prostatic carcinoma may be treated with either radical surgery or radiation therapy. Radiation therapy techniques for localized prostatic carcinoma include mega-voltage external irradiation or interstitial implantation, usually with iodine-125 seeds. Two external-beam techniques, multiplanar arc and biplanar arc, are additional options for the treatment of localized prostatic carcinoma. Film dosimetry measurements were made in pelvic phantoms to compare the isodose distributions of various external-beam radiation therapy techniques for boost treatment of prostate target volumes. Idealized calculations were performed to determine the isodose distribution of an I-125 implant. A comparison of these techniques shows that the multiplanar and biplanar arc techniques produce isodose distributions that may be useful in the treatment of prostate carcinoma.     

Biosynthesis of phosphatidylinositol-glycan (PI-G)-anchored membrane proteins in cell-free systems: PI-G is an obligatory cosubstrate for COOH-terminal processing of nascent proteins.

It is generally recognized that nascent proteins destined to be processed to a phosphatidylinositol-glycan (PI-G)-anchored membrane form contain a hydrophobic signal peptide at both their NH2 and COOH termini. In previous studies we showed that rough microsomal membranes (RM) prepared from CHO cells can carry out COOH-terminal processing. We have now investigated RM prepared from many additional cell types, including frog oocytes, B cells, and T cells, and found that all are competent with respect to COOH-terminal processing. Exceptions were certain mutant T cells that had been shown to be defective at various steps of PI-G anchor biosynthesis [Sugiyama, E., De Gasperi, R., Urakaze, M., Chang, H.-M., Thomas, L. J., Hyman, R., Warren, C. D. & Yeh, E. T. H. (1991) J. Biol. Chem. 266, 12119-12122]. In one such defective mutant, COOH-terminal processing activity of RM could be restored either by transfecting the intact cells with the gene for the deficient step in PI-G synthesis or by adding PI-G extracts to the RM in vitro. Cleavage of the COOH-terminal signal peptide in the RM is therefore dependent on the presence of intact PI-G incorporated into the mature protein.     

Signet-ring cell oligodendroglioma – report of two cases and discussion of the differential diagnosis

Two cases of oligodendroglioma consisting largely of signet-ring cells were analyzed histopathologically, immunohistochemically and at the ultrastructural level. The signet-ring cells were negative for a panel of tumor lineage markers including glial fibrillary acidic protein, and were negative for Ki-67 (MIB-1 immunohistochemistry). In contrast with the abundance of lysosomal structures reportedly present in the so-called eosinophilic granular cells in oligodendrogliomas, degenerating mitochondria were mainly seen in the cytoplasm of the signet-ring cells. The differential diagnosis of the oligodendroglial signet-ring cell tumors occurring in children and in adults is discussed. Received: 26 August 1996 / Revised, accepted: 11 November 1996     

Spinal compression fractures in osteoporotic women: patterns and relationship to hyperkyphosis

A prospective study of thoracic and lumbar spinal fracture distribution and its relationship to thoracic kyphosis was performed in 87 women with osteoporosis. Anterior wedge fractures were most commonly seen in the midthoracic spine and about the thoracolumbar junction, whereas central compression fractures were most common from the first to the fourth lumbar levels. Solitary wedge fractures did not occur above the seventh thoracic vertebra, suggesting that a cause other than osteoporosis must be suspected in any patient with an isolated high thoracic fracture. Analysis of the spinal radiographs obtained in an additional 16 women without osteoporosis revealed that both forms of fracture were unusual in this small group with normal spinal mineralization. The number of anterior wedge fractures in the thoracic spine correlated (r = .546) with the degree of thoracic kyphosis. However, 19% of the women with no thoracic fractures still had thoracic hyperkyphosis. The authors conclude that the hyperkyphosis of osteoporotic women is related to anterior compression fractures but also has contributing nonskeletal factors.     

Cross-species bone marrow transplantation: evidence for tolerance induction, stem cell engraftment, and maturation of T lymphocytes in a xenogeneic stromal environment (rat----mouse)

Transplantation of untreated F344 rat bone marrow into irradiated B10 mouse recipients (non-TCD F344----B10) to produce fully xenogeneic chimeras resulted in stable xenogeneic lymphoid chimerism, ranging from 82% to 97% rat. Survival of animals was excellent, without evidence for GVH disease. The specificity of tolerance which resulted was highly donor-specific; MHC disparate third party mouse and rat skin grafts were promptly rejected while donor-specific F344 grafts were significantly prolonged (MST greater than 130 days). Multi-lineage rat stem cell-derived progeny including lymphoid cells (T- and B-lymphocytes), myeloid cells, erythrocytes, platelets, and natural killer (NK) cells were present in the fully xenogenic chimeras up to 7 months after bone marrow transplantation. Immature rat T-lymphocytes matured and acquired the alpha/beta T-cell receptor in the thymus of chimeras in a pattern similar to normal rat controls, suggesting that immature T-lymphocytes of rat origin could interact with the murine xenogeneic thymic stroma to undergo normal maturation and differentiation. This model may be useful to study the mechanisms responsible for the induction and maintenance of donor-specific transplantation tolerance across a species barrier.