Diagnosing the irritable bowel syndrome.
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Colonic Diseases, Functional↗
Biomedical subjects
R C Smith
Publications and source records attributed to R C Smith.
Inhibition by thiols of copper(II)-induced oxidation of oxyhemoglobin.
The ability of thiols, 2-imidazolethiones and uric acid to protect bovine oxyhemoglobin from copper(II)-induced oxidation to methemoglobin was investigated. The oxidation of oxyhemoglobin by Cu(II) proceeded in two phases: (1) an initial rapid reaction (less than 30 s) followed by (2) a slower reaction that carried it to completion. Thiols, including N-acetyl-L-cysteine, DL-dithiothreitol, reduced glutathione, DL-homocysteine, 2-mercaptoethanol and 2- and 3-mercaptopropionic acid, whose sulfhydryl groups were slowly oxidized by Cu(II) (with the exception of 2-mercaptopropionic acid), protected oxyhemoglobin in both phases of the reaction. Other thiols, including L-cysteine, cysteamine, and D-penicillamine, whose sulfhydryl groups were readily oxidized by Cu(II), protected hemoglobin initially, but within 2-4 min, the rate of methemoglobin formation was the same as Cu(II)-treated oxyhemoglobin. 2-Mercaptoimidazole and 1-methyl-2-mercaptoimidazole, which complex Cu(II) and inhibit Cu(II)-catalyzed oxidation of ascorbic acid, also protected hemoglobin in the initial phase, but not in the second phase. Uric acid, L-ergothioneine, and thiourea did not protect oxyhemoglobin in either the fast or slow phase. Cu(II) may have a coordination site involved in the oxidation of hemoglobin that is not blocked by the 2-imidazolethiones, uric acid, or the oxidized thiols. It is concluded that certain thiols that complex Cu(II) and are not rapidly oxidized will protect oxyhemoglobin from Cu(II)-induced oxidation, but the thiols are no longer effective once they are oxidized.
Animals↗
Xyloglucan endotransglycosylase, a new wall-loosening enzyme activity from plants.
1. Cell-free extracts of all plants tested contained a novel enzyme activity (xyloglucan endotransglycosylase, XET) able to transfer a high-Mr portion from a donor xyloglucan to a suitable acceptor such as a xyloglucan-derived nonasaccharide (Glc4Xyl3GalFuc; XG9). 2. A simple assay for the enzyme, using [3H]XG9 and based on the ability of the [3H]polysaccharide product to bind to filter paper, is described. 3. The enzyme was highly specific for xyloglucan as the glycosyl donor, and showed negligible transglycosylation of other polysaccharides, including CM-cellulose. 4. The Km for XG9 was 50 microM; certain other 3H-labelled xyloglucan oligosaccharides also acted as acceptors, and certain non-radioactive xyloglucan oligosaccharides competed with [3H]XG9 as acceptor; the minimum acceptor structure was deduced to be: [formula: see text] 5. The pH optimum was approx. 5.5 and the enzyme was less than half as active at pH 7.0. The enzyme was slightly activated by Ca2+, Mg2+, Mn2+, spermidine, ascorbate and 2-mercaptoethanol, and inhibited by Ag+, Hg2+, Zn2+ and La3+. 6. XET activity was essentially completely extracted by aqueous solutions of low ionic strength; Triton X-100, Ca2+, La3+, and Li+ did not enhance extraction. Negligible activity was left in the unextractable (cell-wall-rich) residue. 7. The enzyme differed from the major cellulases (EC 3.2.1.4) of pea in: (a) susceptibility to inhibition by cello-oligosaccharides, (b) polysaccharide substrate specificity, (c) inducibility by auxin, (d) requirement for salt in the extraction buffer and (e) activation by 2-mercaptoethanol. XET is therefore concluded to be a new enzyme activity (xyloglucan: xyloglucan xyloglucanotransferase; EC 2.4.1.-). 8. XET was detected in extracts of the growing portions of dicotyledons, monocotyledons (graminaceous and liliaceous) and bryophytes. 9. The activity was positively correlated with growth rate in different zones of the pea stem. 10. We propose that XET is responsible for cutting and rejoining intermicrofibrillar xyloglucan chains and that it thus causes the wall-loosening required for plant cell expansion.
Carbohydrate Sequence↗
Ozone depletion: ultraviolet radiation and phytoplankton biology in antarctic waters.
The springtime stratospheric ozone (O3) layer over the Antarctic is thinning by as much as 50 percent, resulting in increased midultraviolet (UVB) radiation reaching the surface of the Southern Ocean. There is concern that phytoplankton communities confined to near-surface waters of the marginal ice zone will be harmed by increased UVB irradiance penetrating the ocean surface, thereby altering the dynamics of Antarctic marine ecosystems. Results from a 6-week cruise (Icecolors) in the marginal ice zone of the Bellingshausen Sea in austral spring of 1990 indicated that as the O3 layer thinned: (i) sea surface- and depth-dependent ratios of UVB irradiance (280 to 320 nanometers) to total irradiance (280 to 700 nanometers) increased and (ii) UVB inhibition of photosynthesis increased. These and other Icecolors findings suggest that O3-dependent shifts of in-water spectral irradiances alter the balance of spectrally dependent phytoplankton processes, including photoinhibition, photoreactivation, photoprotection, and photosynthesis. A minimum 6 to 12 percent reduction in primary production associated with O3 depletion was estimated for the duration of the cruise.
Antarctic Regions↗
Synthesis and modification of D7 protein during Xenopus oocyte maturation.
The Xenopus maternal mRNA D7 is translationally repressed during oogenesis, only becoming recruited into polysomes during oocyte maturation, with D7 protein being detectable for the first time prior to germinal vesicle breakdown (GVBD). The synthesis of D7 protein was found to be induced by a variety of maturation-promoting agents including cyclin, c-mos and crude preparations of MPF. D7 protein induced by all these agents is post-translationally modified and exists as a number of variants of differing molecular weight. In contrast to endogenous D7 mRNA, D7 RNA injected into the stage VI oocyte is efficiently translated, resulting in the accumulation of predominantly unmodified D7 polypeptides, which become increasingly modified during oocyte maturation to produce a pattern of polypeptides similar to those derived from endogenous D7 mRNA. Thus, the system that results in the post-translational modification of the D7 protein is itself activated during oocyte maturation. The nature of the protein modification is not known but does not appear to be phosphorylation. The translation of exogenous D7 RNA in the stage VI oocyte does not lead to translational derepression of endogenous D7 mRNA.
Animals↗
Ventricular dysrhythmias in patients undergoing coronary artery bypass graft surgery: incidence, characteristics, and prognostic importance. Study of Perioperative Ischemia (SPI) Research Group.
To determine the incidence and characteristics of ventricular dysrhythmias (premature ventricular contractions greater than 30/min, ventricular tachycardia greater than or equal to 3 beats, and ventricular fibrillation) and whether a relationship exists between ventricular tachycardia and myocardial ischemia in patients undergoing coronary artery bypass graft surgery, we continuously monitored 50 patients for 10 perioperative days using two-lead electrocardiography. Electrocardiographic changes consistent with ischemia were defined as a reversible ST depression greater than or equal to 1.0 mm, or ST elevation greater than or equal to 2.0 mm from baseline, lasting at least 1 minute. Ventricular dysrhythmias developed in 10% of patients preoperatively and in 16% intraoperatively before bypass surgery. The highest incidence occurred postoperatively, with ventricular dysrhythmias developing in 66% of patients (22% to 44% of patients on any postoperative day 0 to 7). Premature ventricular contractions were greater than 30/hr in 6% of patients preoperatively, in 8% intraoperatively before bypass, and in 34% postoperatively (6% to 23% of patients on any postoperative day). Twenty-nine patients (58%) developed 76 verified episodes of greater than or equal to 3 beats of ventricular tachycardia. Ventricular tachycardia occurred in 6% of patients preoperatively (four episodes), in 8% of patients intraoperatively prior to bypass (four episodes), and 54% of patients postoperatively (5% to 21% on any postoperative day). No patient developed ventricular fibrillation. All postoperative ventricular tachycardia episodes (after tracheal extubation) were asymptomatic. Postoperatively, 48% of patients developed ischemia, compared with 12% preoperatively and 10% intraoperatively before bypass surgery. Only 5 of 68 (7%) postoperative ventricular tachycardia episodes occurred within 3 hours of an ischemia episode.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Sensitivity and specificity of the Manning criteria.
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Colonic Diseases, Functional↗
Cross-arch bar splint.
This article describes the use of a round bar connector that will aid the preservation of bone support for two isolated mandibular canines when a fixed partial denture replacing the anterior teeth is contraindicated. If the removable partial denture is constructed with only the two lone-standing canines as abutments, the removable partial denture will move occlusally and gingivally during function, thereby generating forces that may cause bone loss. By the addition of a straight round bar connecting the two canine crowns, the abutments are splinted together and masticatory forces are directed along the long axes of the teeth.
Bite Force↗
Denture tooth selection: an analysis of the natural maxillary central incisor compared to the length and width of the face. Part I.
A project was devised by the removable prosthodontic faculty to determine clinically if there is a correlation between the length and width of the maxillary central incisor on a cast and the length and width of the face. A millimeter gauge was used to measure the lengths and widths of the maxillary incisor on a cast. The Trubyte tooth indicator was selected to measure the length and width of the face. This tooth indicator is designed for calibration of the 16 to 1 ratio between facial dimension and maxillary central incisors.
Adult↗
Denture tooth selection: an analysis of the natural maxillary central incisor compared to the length and width of the face: Part II.
This is the second part of a project conducted by the Removable Prosthodontic Faculty to compare the length and width of the maxillary central incisor with the length and width of the face. In this article, gender of the students was the main consideration. Three hundred fifty men and 138 women students participated in the project.
Adult↗
The acute appendicitis syndrome: psychological aspects of the inflamed and non-inflamed appendix.
The aetiological importance of stressful life events and psychological characteristics was assessed amongst 280 appendicectomy patients of whom 80% were classified with 'acutely inflamed' (organic) appendicitis and 20% with 'non-inflamed' (non-organic) appendicitis. Patients were compared with a community comparison group. Specific characteristics of life stressors, namely severe goal frustration for organic patients and severe threat for non-organic patients, were the best predictors of patient outcome. Whilst psychological characteristics were not useful in discriminating between patients, depression in particular, was clearly associated with both conditions, with 38% of non-organic and 28% of organic patients with depression scores in the clinical range. As the patient's clinical depression status failed to modify the effect of the life stress predictors, it was concluded that life stress played an important role in the development of the patients GI symptoms, irrespective of their clinical depression status.
Adolescent↗
Changes in light scatter and width measurements from the human lens cortex with age.
Light scatter and width measurements of the anterior cortical layers of the human lens were made in 50 eyes of 50 subjects using computerised linear scanning densitometry of Scheimpflug images. It was demonstrated that the amount of light scatter increased with age in all of the three major zones and that zone C3 showed the most marked increase. Most lens growth occurs in zone C2 with C3 showing little increase in width once it has become established. Zone C1 showed a tendency to decrease in width with age. In addition it was shown that the C3 zone, which is not present at birth and during early childhood, appears as a distinct layer during the second decade of life. Its scattering properties continue to increase throughout life, exceeding all other zones after approximately 30 years of age, in the absence of cataract. Possible explanations for the lens zone pattern are discussed.
Adolescent↗
Fast spin-echo MR imaging of the female pelvis. Part I. Use of a whole-volume coil.
In this prospective study, axial and sagittal magnetic resonance (MR) images were obtained with T2-weighted conventional spin-echo (CSE) and fast spin-echo (FSE) sequences in 34 consecutive female patients who underwent clinical pelvic MR examination at 1.5 T. The MR images from each patient were compared side by side, blindly and independently, by two radiologists experienced in MR imaging who used a standardized score sheet for anatomic and pathologic findings. The FSE sequences were rated superior significantly more often than the CSE sequences in most categories of findings (P less than .05), including overall image quality and reduction of motion artifact. The examination time for the FSE sequences was 1 minute 46 seconds versus an examination time of 9 minutes 14 seconds for the CSE sequences. (Both CSE and FSE sequences provided 18 sections.) It is concluded that the FSE sequence provides T2-weighted anatomic and pathologic information superior to that provided by the CSE sequence and requires substantially less imaging time.
Adolescent↗
Multicoil high-resolution fast spin-echo MR imaging of the female pelvis.
A fast spin-echo pulse sequence was combined with multiple surface coils used simultaneously in the form of a "multicoil" in magnetic resonance imaging studies of the female pelvis. This combination allowed maximal resolution with maintenance of the signal-to-noise ratio (S/N) at an acceptable level, and the S/N with the multicoil system was substantially better than that achieved with a body coil. Excellent image quality and demonstration of anatomic detail were afforded by use of this technique.
Adolescent↗
The Babinski response and periodic limb movement disorder.
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Circadian Rhythm↗
Inadequate adrenergic response to disopyramide-induced hypoglycemia.
OBJECTIVE: To report a case of disopyramide-induced hypoglycemia and to discuss the observed inadequate adrenergic response in this patient. Risk factors, possible etiologies, and preventive measures are also discussed. DATA SOURCES: References from case reports and review articles as identified by MEDLINE. DATA SYNTHESIS: A wide variety of drugs has been implicated as causing hypoglycemia. The mechanism for drug-induced hypoglycemia is known for the majority of these agents. Case reports of disopyramide-induced hypoglycemia have been reported in the literature, but the mechanism of action is unclear. We report a case of disopyramide-induced hypoglycemia in which counter-regulatory hormones, serum insulin, and C-peptide concentrations were obtained. From these data, it appears that disopyramide-induced hypoglycemia results from endogenous insulin secretion, with concomitant inadequate counterregulatory response. CONCLUSIONS: Although a rare occurrence, disopyramide-induced hypoglycemia is potentially life-threatening. Patients at risk for this reaction need to be identified prior to the institution of disopyramide therapy. Patients at risk for hypoglycemia should be monitored while on disopyramide and disopyramide blood concentrations should be maintained at the lower end of the therapeutic range, or alternative agents should be considered.
Aged↗
Value of lipid- and water-suppression MR images in distinguishing between blood and lipid within ovarian masses.
The distinction between blood and lipid in ovarian masses on MR imaging is important in the differential diagnosis of these lesions. However, this is often difficult on routine MR images because both blood and lipid within tumors can have the same signal intensity as subcutaneous fat. Accordingly, we studied the value of lipid- and water-suppression MR images in making this distinction in 16 patients (21 lesions). As proved by surgery (six patients) or laparoscopy (10 patients), there were 16 endometriomas, one hemorrhagic leiomyosarcoma, and four lipid-containing mature cystic teratomas. The signal intensity in all 17 hemorrhagic lesions was greater than that of subcutaneous fat on lipid-suppression images and less than that of fat on water-suppression images. This compared with the signal intensity of the four lesions that contained lipid, in which the signal intensity was similar to that of subcutaneous fat on both the lipid- and water-suppression images. Thus, the lipid- and water-suppression MR images allowed an accurate distinction between the two. Our experience suggests that the appearance of blood and lipid in ovarian tumors is sufficiently different on lipid- and water-suppression MR images to allow an accurate distinction between the two. The two techniques should be useful in the differential diagnosis of such lesions by MR imaging.
Adipose Tissue↗
Periodic limb movement disorder is associated with normal motor conduction latencies when studied by central magnetic stimulation--successful use of a new technique.
This study prospectively tested the hypothesis that patients with periodic limb movement disorder (PLMD) have longer motor conduction latencies than normals. Six healthy adults, 13 patients with PLMD, and 8 patients with long-term multiple sclerosis (MS) had recordings of motor conduction latencies during wake and sleep. MS subjects were included only to show that we could detect prolongation of central conduction; nonMS subjects were used to test the hypothesis. Subjects had no other medical or sleep problems. A novel magnetic stimulator, the Cadwell MES-10, was discharged over the vertex and the C7 cervical spine. It triggered compound muscle action potentials that were recorded in the abductor digiti minimi in the hand. The conduction latencies were the total conduction time (TCT), measured vertex to hand, and the peripheral conduction time (PCT), measured C7 to hand. The difference was the central conduction time (CCT). Only TCT could be obtained during sleep. Supporting the use of TCT as an indirect measure of central conduction was that, in all waking subjects, TCT correlated with CCT (r = 0.91, p = 0.001) but not with PCT. Reliabilities during wake and sleep were 0.95 or higher for TCT and PCT measurements. Waking CCT was greater in MS subjects (13.77 milliseconds) than those without MS (9.21 milliseconds), p = 0.001. Sleeping TCT was much less impressive in distinguishing MS subjects [27.08 milliseconds in nonrapid eye movement (NREM) sleep; 28.64 milliseconds in rapid eye movement (REM) sleep] from nonMS subjects (24.45 milliseconds in NREM; 24.84 milliseconds for REM), p = 0.07 for NREM and p = 0.04 for REM.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗