Ischemic proctosigmoiditis

Rectal ischemia is rare because of excellent collateral supply. Although rectosigmoid ischemia is usually accompanied by more proximal colonic involvement, it may occur alone. METHODS: A retrospective review of all patients diagnosed as having colonic ischemia at the Mayo Clinic from 1976 to 1991 was performed. Clinical, endoscopic, radiological, and pathological data were obtained from patient charts. Patients with involvement of the rectosigmoid colon extending to no more than 30 cm above the dentate line on endoscopy were included in the study. A single radiologist reviewed CT scans and aortograms, and a single pathologist reviewed tissue specimens. RESULTS: Ten of 328 patients with ischemic colitis had isolated ischemic proctosigmoiditis. Six patients had acute ischemia (i.e., symptom duration of less than 4 wk), and four had chronic ischemia (symptoms for 4 wk or longer). Ischemic proctosigmoiditis affects elderly patients with atherosclerosis. An identifiable precipitating factor, such as a major illness or hemodynamic disturbance, was identified in four of six patients with acute ischemic proctosigmoiditis and in one of four patients with chronic ischemic proctosigmoiditis. CT revealed rectal wall thickening and/or perirectal stranding. Angiography may demonstrate atheromatous disease of the aortoiliac vessels. Acute and "chronic" presentations had similar histopathological changes. CONCLUSIONS: Ischemic proctosigmoiditis is rare. In contrast to generalized colonic ischemia, patients with acute rectal ischemia often have clearly identifiable precipitating factors. Conservative management is appropriate for uncomplicated acute ischemic proctosigmoiditis. Patients with chronic ischemic proctosigmoiditis. Patients with chronic ischemic proctosigmoiditis may develop bowel perforation necessitating a proctectomy or colonic diversion. Recognition of this entity and differentiation from idiopathic inflammatory bowel disease is important to determine appropriate therapy.     

Magnesium enhances function of postischaemic human myocardial tissue

OBJECTIVES: The effect of Mg2+ on the developed force and concentrations of high energy phosphate metabolites in isolated human atrial trabeculae has been investigated. METHODS: Human atrial trabeculae, obtained from right atrial appendages of patients undergoing cardiac surgery requiring cardiopulmonary bypass, were dissected at room temperature in modified Krebs-Henseleit buffer containing 1.2 or 16 mM Mg2+, mounted on muscle stands, and rewarmed to 34 degrees C in the same buffer. After 30 minutes, their mechanical function was assessed. At the end of the protocol, trabeculae were fast frozen for measurement of concentrations of metabolites of high energy phosphates. RESULTS: Trabeculae collected and rewarmed in 16 mM Mg2+ Krebs-Henseleit buffer showed significantly higher mean developed force (0.59(SEM 0.10) g, p < 0.01) than those rewarmed in 1.2 mM Mg2+ Krebs-Henseleit buffer (0.32(0.03) g). Trabeculae that had a developed force > or = 0.8 g, a resting force < or = 0.7 g, and a cross sectional area < or = 1 mm2 ("functional" trabeculae) were selected for further comparison. New reverse phase high performance liquid chromatography techniques developed for the analysis of small samples (0.5-5 mg dry weight) were used to measure nucleotide, nucleoside, and creatine compounds. Total adenylate (ATP+ADP+AMP) concentrations in trabeculae revived in the presence of 16 mM Mg2+ (15.4(1.1) mumol.g-1 dry weight) were significantly higher (p < 0.01) than in those revived with 1.2 mM Mg2+ (11.8(1.0) mumol.g-1), but lower (p < 0.01) than in trabeculae fast frozen immediately after removal from the patient (22.6(1.0) mumol.g-1). There were no significant differences in NAD and total creatine (phosphocreatine+creatine) concentrations between the three groups. CONCLUSIONS: The presence of high Mg2+ during the rewarming of human atrial trabecular preparations maintains a significantly higher developed force and a significantly higher total adenylate pool than does collection and rewarming with normal concentrations of Mg2+.     

The synthesis of elastin, collagen, and glycosaminoglycans by high density primary cultures of neonatal rat aortic smooth muscle. An ultrastructural and biochemical study

Primary cultures of neonatal rat aortic smooth muscle cells inoculated at high densities (1 X 10(6) cells/25 cm2 Falcon flask) with adequate nutrient media and pH control grow rapidly and form multilayers of cells with typical "hill and valley" organization. After 10 days growth insoluble elastin formation could be visualized by phase contrast microscopy as small particles which grew rapidly to become larger irregular refractile aggregates and later coalesced to form larger aggregates and small fibres. With light and electronmicroscopy, elastin was the predominant matrix protein formed, with the "hill regions" of cultures containing abundant elastin aggregates and some collagen. In 2-week-old cultures differentiation could be observed within the cell multilayer. The older deeper cells contained more protein synthesis organelles and myofilaments and were in close association with large often coalescing elastin aggregates; compared to younger more superficial cells which contained more free polyribosomes less myofilaments, and were associated with fewer and small elastin aggregates. In older cultures this differentiation was not apparent; the cells contained many myofilaments, dense bodies, and lysosomes. Elastin aggregates and newly formed elastic fibres were abundant in the matrix. Quantitative analysis of insoluble elastin formation in the cell layer during the 4-week culture period indicated continuous biosynthesis and deposition which paralleled that of desmosine formation. Amino-acid analysis of a hot alkali insoluble residue (regarded as elastin) from 30-day-old cultures gave a profile identical with neonatal rat aortic elastin in vivo. Insoluble collagen formation in the cell layer tended to plateau after the log phase of growth was completed (10 days). Proteoglycans were found predominantly in the supernatant media. Glycosaminoglycan analysis revealed a profile of dermatan sulphate (32%), chondroitin 4-sulphate (43%), keratan and heparan sulphate (30%), with only a trace of hyaluronic acid. This study indicates that primary cultures of neonatal rat aortic smooth muscle cells remain differentiated in culture and have the unique capacity to continue to synthesize and deposit large amounts (mg) of insoluble elastin which aggregate and from elastic fibres in vitro.     

Comparative structural and immunochemical properties of leghaemoglobins

Circular dichroism studies on leghaemoglobins from snake bean, lupin, serradella and other plants show that, in common with soybean (reported earlier) they have a similar overall polypeptide chain conformation and haem environment and orientation. Immunochemical studies, on the other hand, suggest that the antigenic determinants on the surface of the leghaemoglobins vary considerably. Thus, firstly the alpha-helix content of the leghaemoglobins as a class is very similar (60-65%) and approaches that of the myoglobins, secondly, the sign, magnitude and shape of their circular dichroism spectra in the near ultraviolet, Soret and visible regions suggest close similarities in the environment and orientation of a structurally important tryptophan residue and of the haem moiety, and thirdly, there is comparatively weak haem-protein interaction. The extent of immuno cross-reactivity was found to be best deomonstrated using the Farr radioimmunoassay procedure. The results were (a) 5 leghaemoglobins from one plant (soybean) crossreacted completely but with varying affinities. (b) The extent of cross reactivity between leghaemoglobins from different plants was compared to that within a single plant; the reaction of antiserum to a soybean leghaemoglobin with a serradella leghaemoglobin was weak, with a snake bean leghaemoglobin still weaker (and incomplete) while lupin leghaemoglobins showed no cross reactivity at all. (c) The "rapid" attenuation of cross reactivity among different plant leghaemoglobins is explicable in terms of the extensive amino acid substitutions which have been demonstrated in the literature and in the present studies. (d) In view of this rapid divergence it is not surprising that sperm whale and horse heart myoglobins showed no cross reactivity with soybean leghaemoglobins. In summary, amino acid substitutions in the leghaemoglobin family are conformationally but not immunochemically conservative.     

An Examination of Indicators of Engineering Students' Success and Persistence

Student success and persistence within the major and university were examined through hierarchical linear and logistic regression analyses for two cohorts of engineering students. Indicators of success and persistence were based on theoretical and empirical evidence and included both cognitive and noncognitive variables. Cognitive variables included high school rank, SAT scores, and university cumulative grade point average. Noncognitive factors included academic motivation and institutional integration. Outcome variables included grade point average, enrollment at the university, and status as an engineering major. Gender differences also were evaluated. Several significant relationships among the variables were found. For instance, increased levels of motivation were significantly related to continuing in the major. Implications and directions for future research are discussed.     

Use of Stable Isotopes to Trace Municipal Wastewater Effluents into Food Webs within a Highly Developed River System

Many anthropogenic inputs, such as municipal wastewater effluents (MWWEs), affect stable isotope signatures (δ¹³C and δ¹⁵N) at the base of exposed food webs creating spatial patterns reflecting their incorporation into aquatic food webs. The Grand River in southern Ontario, Canada, is a heavily modified, rapidly urbanizing river that assimilates wastewater from 30 municipal wastewater treatment plants. Stable isotope analysis was applied to resident aquatic invertebrates and fish influenced by three different wastewater outfalls in early, middle, and late summer to determine how values shifted seasonally and with differing effluent quality. There was a slight increase in δ¹³C in both invertebrates and fish in late summer downstream from the three outfalls, but it is difficult to separate effects of the effluents from downstream gradients. Downstream of two of the three outfalls, the δ¹⁵N tended to increase relative to upstream, while the remaining effluent, of the poorest quality, decreased δ¹⁵N values of both invertebrates and fish. Spatial trends in stable isotopes became more pronounced as the summer progressed with the greatest between‐site differences occurring in late summer. This study reflects the complex nutrient dynamics associated with MWWE inputs to rivers and contributes to our understanding and application of stable isotope analysis in impacted lotic ecosystems. Copyright © 2014 John Wiley & Sons, Ltd.     

Correcting temperature-sensitive protein folding defects

Recently, we found that different low molecular weight compounds, all known to stabilize proteins in their native conformation, are effective in correcting the temperature-sensitive protein folding defect associated with the deltaF508 cystic fibrosis transmembrane regulator (CFTR) protein. Here we examined whether the folding of other proteins which exhibit temperature-sensitive folding defects also could be corrected via a similar strategy. Cell lines expressing temperature-sensitive mutants of the tumor suppressor protein p53, the viral oncogene protein pp60src, or a ubiquitin activating enzyme E1, were incubated at the nonpermissive temperature (39.5 degrees C) in the presence of glycerol, trimethylamine N-oxide or deuterated water. In each case, the cells exhibited phenotypes similar to those observed when the cells were incubated at the permissive temperature (32.5 degrees C), indicative that the particular protein folding defect had been corrected. These observations, coupled with our earlier work and much older studies in yeast and bacteria, indicate that protein stabilizing agents are effective in vivo for correcting protein folding abnormalities. We suggest that this type of approach may prove to be useful for correcting certain protein folding abnormalities associated with human diseases.