Megavoltage imaging with low Z targets: implementation and characterization of an investigational system

The poor quality of stereotactic radiotherapy portal images is a limiting factor in precise image registration. To alleviate this problem, a low atomic number (Z) target was implemented on our Siemens MXE linear accelerator. This investigational system was used to assess the performance of various target materials by filming an aluminum contrast object. Beryllium, carbon and conventional target materials were studied. The bremsstrahlung spectra of these materials were simulated using Monte Carlo techniques. These spectra were used to calculate the dependence of narrow beam contrast on phantom thickness for verification of the data measured from film. A Monte Carlo simulation of the beryllium spectrum in a wide beam geometry was used to evaluate the effect of phantom-to-film distance on contrast. Although the same degree of contrast improvement with distance was not realized in practice, the improvement in image quality rivaled that achieved using a scatter reduction grid. A comparison of conventional localization images of the head and neck of an anthropomorphic phantom with images produced with a beryllium or carbon target and a mammography film and screen system supports earlier suggestions that the technique is clinically useful.     

Lack of effect of a selective vasopressin V1A receptor antagonist SR 49,059, on potentiation by vasopressin of adrenoceptor-mediated pressor responses in the rat mesenteric arterial bed

The vasopressin receptor subtype involved in the enhancement by vasopressin of adrenoceptor-mediated vasoconstriction was investigated in rat isolated perfused mesenteric arteries. [Arg8]vasopressin (1-10 nM) dose-dependently increased the perfusion pressure and enhanced the pressor response to the adrenoceptor agonist methoxamine (40 nmol) or electrical stimulation of periarterial nerves (16 Hz), at the concentration of 10 nM of [Arg8]vasopressin up to 4 and 3 fold, respectively. During prolonged exposure (45 min) the direct vasoconstrictor effect of [Arg8]vasopressin (10 nM) rapidly declined whereas the potentiation of methoxamine-induced vasoconstriction was maintained. The selective vasopressin V1A receptor antagonist SR 49,059 (1-3 nM) and the non-selective V1A/B and oxytocin receptor antagonist [deamino-Pen1,Tyr(Me)2,Arg8]vasopressin (15-45 nM) inhibited the direct vasoconstrictor action of [Arg8]vasopressin but had no effect on the enhancement of the pressor response to methoxamine or electrical stimulation. The V1B receptor agonist [deamino-Cys1,beta-(3-pyridyl)-D-Ala2,Arg8]vasopressin (100-1000 nM) and the V2 receptor agonist [deamino-Cys1,D-Arg8]vasopressin (1-10 nM) were devoid of any pressor activity and did not potentiate methoxamine-evoked vasoconstriction. In contrast, [1-triglycyl,Lys8]vasopressin (100 - 1000 nM) potentiated the methoxamine responses without per se inducing vasoconstriction. In arteries precontracted with methoxamine (7.5 microM) pressor responses to [Arg8]vasopressin (3-10 nM) were not inhibited by a dose of SR 49,059 (3 nM) which abolished the peptide's vasoconstrictor effect under control conditions. These data show that the direct vasoconstrictor effect of [Arg8]vasopressin is mediated by V1A receptors while the enhancement of adrenoceptor-mediated pressor responses is insensitive to V1A, V1B, and oxytocin receptor antagonists and is not mimicked by selective agonists of V1B and V2 receptors. In conclusion, an unusual interaction of vasopressin with V1A receptors, or even the existence of a novel receptor subtype, has to be considered.     

Solution structure of the heparin-binding domain of vascular endothelial growth factor

Tricorn protease was previously described as the core enzyme of a modular proteolytic system displaying multicatalytic activity. Here we elucidate the mode of cooperation between Tricorn and its interacting factors, and we identify two additional factors, F2 and F3, closely related aminopeptidases of 89 kDa. In conjunction with these three factors, Tricorn degrades oligopeptides in a sequential manner, yielding free amino acids. We have been able to reconstitute a proteolytic pathway comprising the proteasome, Tricorn, and its interacting factors, F1, F2, and F3, which converts proteins efficiently into amino acids. Therefore, it is quite likely that Tricorn also acts in vivo downstream of the proteasome and, in cooperation with its interacting factors, completes protein catabolic pathways.     

Computerized documentation for a rural nursing intervention project

Complex traits are generally taken to be under the influence of multiple genes, which may interact with each other to confer susceptibility to disease. Statistical methods in current use for localizing such genes essentially work under single-gene models, either implicitly or explicitly. In genomic screens for complex disease genes, some of the marker loci must be in tight linkage with disease susceptibility genes. We developed a general multi-locus approach to identify sets of such marker loci. Our approach focuses on affected sib pair data and employs a nonparametric pattern recognition technique using artificial neural networks. This technique analyzes all markers simultaneously in order to detect patterns of locus interactions. When applied to previously published sib pair data on type I diabetes, our approach finds the same genes as in the published report in addition to some new loci. For a specific two-locus model of inheritance, the power of our approach is higher than that of the currently used analysis standard.     

A home-based exercise program for nondisabled older adults

OBJECTIVES: This paper describes a videotaped, home-based, strength training program, titled Strong-for-Life and reports on its effectiveness in improving muscle strength, psychological well-being, and health status in a sample of older persons. DESIGN AND SETTING: We enrolled 102 nondisabled, community-dwelling older people aged 66 to 87, identified from the Medicare beneficiary list, into a randomized, controlled trial. MEASUREMENTS: Effectiveness was based on change in isokinetic upper and lower extremity muscle strength, psychologic well-being, and health status. RESULTS: Results revealed several statistically significant short-term benefits after 12 to 15 weeks of exercise, especially for men. Younger older adults demonstrated a 10% improvement in knee extensor strength relative to control subjects. Older male exercisers achieved significant differences relative to controls in perceived anger, tension, and overall social functioning. Male exercisers, in general, achieved significant improvement in perceived vigor. Women did not report psychological benefits following participation in the program. CONCLUSION: Study results reveal that the Strong for Life program, designed to be widely disseminated to the nondisabled older population, has many short-term positive benefits.     

PET in breast cancer

In mid-summer 1997, just as the United States National Cancer Institute was acknowledging that the nuclear bomb tests at the Nevada Test Site may ultimately cause up to 75,000 cases of thyroid cancer in people who were living in the USA in the 1950s and 1960s, the Australian authorities were mooting the possibility that the Maralinga test sites in South Australia should become a tourist attraction. Some Aboriginal tribal leaders welcomed this proposed use when the 20 million Pounds 'clean-up' being paid for by the United Kingdom government as some compensation for using the area for its weapons tests in the 1950s and 1960s is completed. This paper surveys the attempts to clean up the site of UK nuclear weapons tests in the 1950s, not least by attempting to vitrify vast tracts of desert.     

Stable reintroduction of wild-type P53 (MTmp53ts) causes the induction of apoptosis and neuroendocrine-like differentiation in human ductal pancreatic carcinoma cells

Pancreatic ductal adenocarcinoma is one of the major causes of cancer mortality in the industrialized world, having among the poorest prognosis of any malignancy. Mutations or alterations in the p53 tumor suppressor gene/protein are observed in 50-70% of these cancers, yet little information is available regarding the phenotypic effects of restoration of wild-type (wt) p53 function in pancreatic ductal carcinoma cells. The consequences of stable reintroduction of wt p53 on apoptosis and differentiation was examined in a poorly differentiated pancreatic carcinoma cell line (Panc-1), possessing only mutant (mt) p53 (codon 273 mutation). Cells were transfected with a temperature-sensitive mouse p53val135 (tsp53) vector under additional control of a genetically-modified metallothionein promoter. This tsp53 has a 'mt' phenotype at 37.5 degrees C, and a 'wt' phenotype at 32.5 degrees C and the presence of 100 microM ZnCl2. Stable expression of wt p53 caused upregulation of the p21/WAF1 gene, and G1 growth arrest as shown by flow cytometry and BrdU labeling. Additionally, apoptosis was induced 8-12 post-induction in the majority of the cells (60-70%), as demonstrated by morphological changes, in situ TdT labeling and internucleosomal laddering. However, a subpopulation (30%) of the transfectants survived this apoptotic fate. Unlike the epithelial parental Panc-1 cells, these cells exhibited the appearance of a neuroendocrine-like phenotype with extensive branch-like processes, and marked cytoplasmic and cytoskeletal immunostaining for tau-2, synaptophysin, and chromogranin A. These studies suggest that stable and regulated expression of wt p53 can have multiple phenotypic consequences (apoptosis and altered differentiation to a neuroendocrine-like phenotype) in poorly-differentiated pancreatic carcinoma cells.     

Spontaneous resolution of nonimmune hydrops in a fetus with a cystic adenomatoid malformation

BACKGROUND: Blood bank recommendations specify that Ringer's lactate solution (LR) should be avoided while transfusing blood. However, there are few studies either evaluating or quantifying increased coagulation during rapid infusion of LR and blood. DESIGN AND METHODS: Whole blood (WB, n = 25) and packed red blood cells (PRBC, n = 26) were rapidly admixed with normal saline (NS), Lactate solution and LR with 1 g (LR-1), 2 g (LR-2), and 5 g (LR-5) CaCl2/L solutions for assessment of infusion time, filter weight, and clot formation. RESULTS: No significant differences in infusion time or filter weight using WB or PRBC with NS or LR were seen. No significant difference in clot formation between NS and LR with WB or PRBC was found, but the presence of visible clot was increased in the LR-5 group (P = 0.013, WB, and P = 0.002, PRBC). CONCLUSION: A comparison of LR and NS with rapid infusion rates of blood showed no significant difference between infusion time, filter weight and clot formation. Blood bank guidelines should be revised to allow the use of LR in the rapid transfusion of PRBC.     

Ectopic expression of metallothionein-III causes pancreatic acinar cell necrosis in transgenic mice

Mice express four distinct metallothioneins (MTs) that have similar metal-binding properties. MT-I and MT-II are expressed coordinately in most organs, whereas MT-III is expressed predominantly in a subset of neurons and MT-IV is expressed in certain stratified epithelia. The restricted expression of MT-III suggests that it may severe a specialized function. To test this hypothesis, transgenic mice were generated that express MT-III in the wider expression domain of MT-I. Similar transgenic lines expressing extra MT-I under the same regulation were generated as controls for the effect of over-expression of MT. Transgenic mice that express MT-III ectopically frequently die at 2-3 months of age. The pancreata of moribund mice were abnormally small and histological examination, at various ages, revealed a progressive degeneration of the acinar cells. At early stages multifocal acinar cell eosinophilia and swollen nuclei were seen and this pathology progressed to multifocal acinar cell necrosis and fibrosis. The terminal stages were characterized by a loss of the acinar compartment, leaving the islets embedded in a fibrotic remnant. Other organs of these mice were grossly and histologically normal. All organs examined from mice expressing excess MT-I were unremarkable even though expression of either MT-I or MT-III transgenes resulted in similar accumulations of zinc and copper in the pancreata. This study indicates that pancreatic acinar cells are unusually sensitive to chronic expression of MT-III. The mechanism by which MT-III disrupts pancreatic function is unclear, but the results provide further evidence that MT isoforms exhibit distinct properties and probably serve distinct biological functions.