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PubMed2000

Open-loop accommodation in emmetropia and myopia.

PURPOSE: To investigate the influence of method of measurement and refractive error on the open-loop accommodation response. METHODS: Open-loop accommodation was measured in darkness (dark accommodation, DA) and using a pinhole pupil (pinhole accommodation, PA) in emmetropic subjects (EMMs, n = 63), subjects with late-onset myopia (LOMs, n = 50) and subjects with early onset myopia (EOMs, n = 51). Further a control experiment examined the differences between DA and bright-field accommodation (BA) conditions in a subset of subjects. All measurements of open-loop accommodation were carried out monocularly using a Canon R1 infra-red optometer in static recording mode. All myopic subjects were fully corrected using soft contact lenses. RESULTS: A significant variation (p < 0.001) in open-loop accommodation was found between DA and PA, but no variation in open-loop level was observed between the three refractive groups. There was no interaction between these two factors. No significant difference was found between the BA level and DA level in any of the refractive groups. CONCLUSIONS: Open-loop accommodation response positions vary according to the experimental conditions employed during measurement. No refractive group differences in the open-loop response were apparent.

Accommodation, Ocular↗
PubMed1975

Enteric colibacillosis: evaluation of strains of Escherichia coli utilizing the ligated loop technique in gnotobiotic swine.

The enteropathogenicity of 6 strains of Escherichia coli was evaluated via the ligated loop technique in 15 gnotobiotic swine 3 to 4 weeks old. Strain enteropathogenicity in gnotobiotic swine, as determined on the basis of visual loop distention and light microscopic evaluation of intestinal sections, compared favorably with that reported in conventional swine, except that jejunal loops of gnotobiotic swine may be somewhat less sensitive to certain strains. In addition, postoperative mortality rate among gnotobiotic pigs was greater than that reported in conventional pigs. Two types of aberrant loop reactions were observed during the experiment. The 1st, and the more commonly encountered type, was due to the leakage of enteropathogenic organisms or enterotoxin from one loop to another; this was considered to be a true false-positive reaction. The 2nd type of unexpected positive reaction occurred in 2 sacs inoculated with the nonenteropathogenic strain 115. This latter reaction may have represented either a reversion of the organism to its previous enteropathogenic state or a unique reaction of the gnotobiotic intestine to this strain. False-positive loops were not identified in any other sacs, whether inoculated or not. Results of these experiments support the hypothesis that false-positive loops originate from naturally occurring infection.

Animals↗
PubMed2001

Changes of cooperativity between N-methylscopolamine and allosteric modulators alcuronium and gallamine induced by mutations of external loops of muscarinic M(3) receptors.

To clarify the involvement of specific domains of muscarinic receptors in the action of allosteric modulators, muscarinic M(3) receptors (on which allosteric interactions are weak) were genetically modified to become more similar to M(2) receptors (on which allosteric interactions are strong) and were expressed in COS-7 cells. Affinity for allosteric modulator gallamine was enhanced 25- to 50-fold by modifications of the third external loop (o3) and the negative effect of gallamine on the affinity for classical antagonist N-[(3)H]methylscopolamine ([(3)H]NMS) was augmented. Affinity for alcuronium became 3-fold higher after the o3 loop of M(3) receptors was made identical with the o3 loop of M(2) receptors, and alcuronium acquired positive influence on the affinity for [(3)H]NMS. This is the first instance of inducing positive cooperativity on muscarinic receptors by genetic manipulation. Transferring whole o2 loop from M(2) to M(3) receptors substantially enhanced affinities for gallamine and alcuronium without augmenting their negative action on [(3)H]NMS binding. In contrast, effects of simply adding two negative charges into the o2 loop of M(3) receptors were small. Removal of Arg from o1 loop abolished the negative effect of gallamine but not of alcuronium on [(3)H]NMS binding at equilibrium. Data point to an important role of o3 loop in the mechanism of the positive and negative cooperativity between [(3)H]NMS and alcuronium and gallamine, respectively, and in the binding of both modulators to M(2) receptors and reveal independence between mutation-induced changes in the affinity for a modulator and in the magnitude and direction of the allosteric effect of the modulator.

Alcuronium↗
PubMed2001

[Mass optimization of thermal network model of coupled dual-loop thermal control system in spacecraft].

OBJECTIVE: To deal with the mass optimization of thermal control system as well as environmental control and life support system (ECLSS) of manned spacecraft. METHOD: The thermo-hydraulic network composed of coupled liquid dual-loop and gas loops was studied. Physical and mathematical models were established and used for flow, heat transfer and mass calculation in the network. The influences of various operational and structural parameters on the mass were analyzed. RESULT: There were optimal pipe diameters for internal loop and external loop; there existed an upper limit of flow rate in the internal loop and lower limit in the external loop; there were also optimal flow rates in the loops and optimal exit temperature of the radiator. CONCLUSION: Reasonable design of these parameters were very important for reducing the system mass.

Air Conditioning↗
PubMed1992

Loop electrosurgical excision procedure of the transformation zone and colposcopically directed punch biopsy in the diagnosis of cervical lesions.

OBJECTIVE: To estimate the disagreement between the histologic reports at colposcopically directed punch biopsy of the cervix and subsequent loop excision of the transformation zone, and to assess the indications for loop excision in current practice. METHODS: The histologic diagnoses from loop electrosurgical excision procedures and concurrent colposcopically directed punch biopsies were compared in 337 consecutive women undergoing loop excision in a 5-year period. RESULTS: Disagreement between punch biopsy and loop excision was recorded in 190 cases (56.4%). The undercall and overcall rates for punch biopsy were 14 and 42.4%, respectively. Undercall at punch biopsy occurred in 24 of 46 cases of cervical intraepithelial neoplasia (CIN) III and in one microinvasive cancer diagnosed at loop excision, and disagreement was within one grade of CIN in 16 cases. CONCLUSIONS: Loop electrosurgical excision allows further and more accurate histologic examination of the transformation zone and should be the standard assessment procedure in all cases of CIN II detected at punch biopsy and whenever cytology or colposcopy suggests the risk of punch biopsy undercall. Immediate treatment by local destruction should not be performed, to avoid underestimation of the severity of the lesion.

Biopsy↗
PubMed2004

[Gastrectomy with end-loop jejunogastroplasty in stomach cancer].

Experience with surgical treatment of 147 patients after gastrectomy with jejunogastroplasty and creation of end-loop esophageal-intestinal anastomosis is analyzed. Original methods of jejunogastroplasty are based on end-loop construction of esophageal-intestinal anastomosis simulating anatomic-functional analog of lost cardia and pylorus and replacing reservoir function of the stomach. One year and later after surgery 83 patients with end-loop esophageal-intestinal anastomosis and 73 patients with anastomosis were examined. It is demonstrated that jejunogastroplasty with end-loop anastomosis is characterized by low frequency (6%) and degree of reflux-esophagitis. Passage of food through duodenum in end - loop jejunogastroplasty decreases frequency and degree of demping-syndrome. Active isolating function of end-loop anastomosis was demonstrated with x-ray and manometric methods. Primary jejunogastroplasty with end-loop anastomosis leads to reduction of frequency and severity of postoperative pathological syndromes and permits to improve quality life of operated patients.

Adult↗
PubMed1990

Chromosomes of amphibian oocytes as a model for gene expression: significance of lampbrush loops.

Amphibian lampbrush chromosome loops exhibit morphological variability in their RNP matrix. The biological significance of such variability remains unknown. In order to approach this problem, the structural organization of each RNP matrix type was analyzed in relation to transcriptional and post-transcriptional processes. First, autoradiographic and transcription inhibition studies in conjunction with macromolecular spread analysis revealed a particular transcription pattern in the most typical loops, i.e. the globular loops. This pattern was characterized by asynchronous variations in RNA synthesis in the different transcription units present in a given loop. Second, morphological and experimental studies provided evidence that the typical morphologies of different RNP matrices were interconvertible and that the differences between the different RNP matrices resulted from various degrees of tightness in packaging of transcription products. In particular, analysis of thermic-shock-induced changes in the structure of lampbrush chromosomes enabled us to visualize the progressive disorganization of dense RNP matrices into globular, granular and normal matrices. Furthermore, these studies suggested that changes in post-transcriptional processes might play a determining role in the specific morphology of the loops. In particular, the kinetics of each of these different processes, related to one another and/or proteins specific to one or another of these processes, might determine the morphological appearance of the loops. The immunological approach revealed that specific nuclear proteins might therefore interfere with each of these processes. Third, the problem of a possible relationship between the specific morphologies of lateral loops and the expression of particular DNA sequences was approached at the molecular level.

Animals↗
PubMed2006

[Blocking the gastrin/cholecystokinin-B receptor autocrine loop influences the growth and apoptosis of human gastric cancer cells].

OBJECTIVE: To study whether gastrin/cholecystokinin-B (CCK-B) receptor autocrine loop exists in human gastric cancer cells and the effects of gastrin/CCK-B receptor autocrine loop on the growth and apoptosis of human gastric cancer cells. METHODS: Human gastric cancer cells of the line SGC-7901 were cultured. The expression of gastrin and CCK-B was detected by RT-PCR, immunocytochemistry and radioimmunoassay. Antibody against gastrin was added so as to block the autocrine loop to observe the growth rate, cell cycle and apoptosis by 3-(4.5-dimethylthiazol-z-yl) -2, 5-diphenyl tertrazolium blue (MMT) colorimetric assay and flow cytometry (FCM). RESULTS: The SGC-7901 cells co-expressed gastrin and CCK-B receptor mRNAs, confirmed by sequencing, thus forming gastrin/the CCK-B receptor autocrine loop. After the blocking of the autocrine loop by antibody against gastrin, the cell growth rate and the number of cells residing in the S-phase of the cell cycle decreased and the apoptotic rate increased in an antibody concentration-dependent manner. CONCLUSION: Human gastric cancer SGC-7901 cells possess the gastrin/the CCK-B receptor autocrine loop. Blocking the autocrine loop inhibits the cell proliferation and promotes the cell apoptosis.

Actihaemyl↗
PubMed1990

[Experiences with a subcutaneous, fully resorbable bridge in construction a double loop ileo- and colostomy].

Our experience with the subcutaneous absorbable bridge for constructing a temporary loop ileostomy and loop colostomy is described. The use of this subcutaneous absorbable bridge in 15 patients - 6 with loop ileostomy and 9 with loop colostomy - was almost without complications. The absorbable bridge is a progress for maturation of the stoma and for immediate postoperative as prospective fitting of a watertight appliance. The actual trend substituting the temporary loop colostomy by the loop ileostomy may be advanced by the unlimited use of the subcutaneous absorbable bridge for constructing a temporary loop ileostomy.

Adult↗
PubMedDate not supplied

Finger-loops, oncogenes, and metals. Claude Passmore Brown memorial lecture.

Certain DNA-binding proteins that regulate gene expression contain single or multiple copies of short polypeptide sequences, approximately 30 residues long, consisting of combinations of four Cys or His residues at defined spacing, so that Zn++ is complexed in tetrahedral coordination with the respective thiol-sulfur and/or imidazole-nitrogen atoms. The Zn++ ion evidently serves as a strut that stabilizes folding of the domain into a 'finger-loop', which is capable of site-specific binding to double-stranded DNA. This article reviews the evidence (a) that finger-loop domains have been highly conserved during evolution, (b) that they furnish one of the fundamental mechanisms for regulating gene expression, and (c) that a metal ion (e.g., Zn++) is required for binding of finger-loops to DNA and for their biological functions. The authors' search of amino acid sequences of 38 transforming proteins identified possible finger-loop domains in the myc, fms, fps, raf-1, rfp, src, syn, yes, erbA, int-1, and TGF-alpha gene-products. The search incidentally revealed possible finger-loop domains in human insulin receptor, which may provide a mechanistic explanation for recent observations that insulin, after binding to its cell surface receptor, is translocated to hepatocyte nuclei and becomes bound to chromatin. Zn++-coordination sites in finger-loop domains are proposed as potential targets for metal toxicity; substitution of Ni++, Co++, or Cd++ for Zn++ in finger-loops of transforming proteins is suggested as an hypothetical mechanism for metal carcinogenesis.

Amino Acid Sequence↗
PubMed1984

[Assessment of cardiac function by left heart catheterization: an analysis of left ventricular pressure-volume (length) loops].

The mechanical property of the cardiac muscle has been classically analyzed in two ways; shortening of muscle fiber, and the development of tension within the muscle. In the ejecting ventricle, left ventricular (LV) function can be analyzed by the analogous two-dimensional framework of pressure-volume loops, which are provided by plotting the instantaneous volume against corresponding LV pressure. The integral pressure with respect to volume allows to assess a total external ventricular work during ejection. The diastolic pressure-volume relations reflect a chamber stiffness of the ventricle. Force-velocity relations also provide an useful conceptual framework for understanding how the ventricle contracts under given afterload, with modification of preload. In the presence of coronary artery disease, the regional nature of left ventricular contractile function should be defined as well as the global ventricular function as described above, because the latter is determined by the complex interaction of dysfunction of the ischemic myocardium and of compensatory augmentation of shortening of the normally perfused myocardium. We utilized a computer technique to analyze the local wall motion of the ischemic heart by cineventriculography. The boundaries of serial ventricular images are automatically traced and superimposed using the external reference system. Radial grids are drawn from the center of gravity of the end-diastolic image. Measurement of length of each radial grid throughout cardiac cycle provides the analysis of movement of the ventricle at a particular point on the circumference. Using phasic pressure obtained simultaneously with opacification as the common parameter, segmental pressure-length loops are constructed simultaneously at various segments. The loops are similar over the entire circumference in the normal heart, being rectangular in morphology and with synchronous behavior during contraction and relaxation. However, the marked distortion of pressure-length loops with clockwise rotation or figure of eight inscription is observed in the ischemic segments. Systolic work of the ischemic segment diminishes dramatically, and the loops exhibit varying degrees of inclination. The control segment loops also show an inclination to the opposite direction of the ischemic loops. These differences are presumably related to the local redistribution of the myocardial tension during systole in the ischemic ventricle. Thus, the method described should be of particular value in assessing the regional myocardial function in the ischemic ventricle and effects of various interventions which modify ischemia.

Cardiac Catheterization↗
PubMed1984

[Dynamic urinary flow images in patients with ileal loop diversion assessed by I-123-hippuran scintigraphy. Detection of ileoureteral reflux].

To evaluate upper urinary tract and ileal loop functions, dynamic urinary flow studies using I-123 hippuran were performed in 52 kidneys of 27 patients with ileal loop urinary diversion. Analysis of regional renograms enabled easy assessment of the cortical, pelvic and loop functions. Normal pattern was found in 33 cortices (63.5%), 22 pelvis (45.8%) and 14 loops (51.9%). Most of the abnormal findings in the upper urinary tract were delayed excretion and/or retention of the pelvic and ureteral urines. Diagnosis of ileoureteral reflux under normal physiological circumstances was made to compare the pelvic and loop curves. Small peaks and/or irregular spike waves observed in the down slope of the pelvic curve concurrently with the increased activity of the loop curve indicate a production of the ileoureteral reflux associated with ileal movement. This reflux was noted in 22 of the 27 cases (81.5%). Bilateral reflux was evident in 3 cases, and unilateral reflux in 19 cases. Ileoureteral reflux was noticed in 14 of the 15 cases (90%) in which retrograde loopography was performed. Although bilateral reflux was found in 8 cases, the hippuran study revealed bilateral in only one case, unilateral in 5 and no reflux in 2. Thus, I-123 hippuran scintigraphy consisting of sequential renal images, loopograms and regional renograms enables the diagnosis of ileoureteral reflux and obstructive uropathies and is a useful tool to detect functional complications of the upper urinary tract in patients with ileal loop diversion.

Adult↗
PubMed1983

Pancreato-biliary-duodenal interposition of isolated jejunal loop in the surgical treatment of selected cases of chronic pancreatitis.

Eight patients suffering from symptoms of chronic pancreatitis with dilation of Wirsung's and common bile ducts were selected for a double biliary and pancreatic diversion by interposition of two jejunal loops between these ducts and the duodenum. In three patients a single loop was used, performing an anastomosis on the proximal end to the Wirsung duct about 45 centimeters below the anastomosis between the common duct and the jejunum. The distal end of this loop was anastomosed end-to-side to the duodenum. In five patients two different jejunal loop were used. While the proximal end of one loop was anastomosed to the Wirsung duct, the proximal end of the second loop was anastomosed to the common bile duct. End-to-side anastomosis was then performed between the distal end of both loops and the duodenum. There were no deaths or serious complications. The minimum follow-up was twelve months and the maximum three and half years, all the patients being without symptoms and with normalization of the laboratory tests three months after operation.

Chronic Disease↗
PubMed1993

Loop substitution as a tool to identify active sites of interleukin-1 beta.

By computer analysis of the amino acid sequence of human interleukin-1 beta (IL-1 beta) and of the human type I IL-1 receptor (IL-1RI), we have identified two hydropathically complementary peptides (Fassina, G., Roller, P. P., Olson, A. D., Thorgeirsson, S. S., and Omichinski, J. G. (1989) J. Biol. Chem. 264, 11252-11257) capable of binding to each other. The sequence of the IL-1 beta peptide corresponds to that of residues 88-99 (loop 7 of the crystal structure of mature IL-1 beta) of mature IL-1 beta, one of the exposed and highly charged regions of the molecule. The substitution of this loop with an amino acid sequence of the same length but different hydropathic profile generates a mutant with drastically reduced binding activity to IL-1RI. In contrast, the binding affinity to the type II IL-1R (IL-1RII) is the same as that of wild type IL-1 beta. The results show that 1) loop 7 is part of the binding site of IL-1 beta to IL-1RI, but not to IL-1RII. 2) The structure of the mutant protein is not grossly altered except locally at the position of the substituted loop. 3) The substitution of amino acids by site-directed mutagenesis of the loop 7 region generates mutants with binding affinity constants slightly lower than that of wild type IL-1 beta and not comparable to that of the loop substitution analogue. 4. All mutants analyzed, including the loop substitutions, are biologically active, confirming the structural integrity of the proteins. We propose a binding site in which the cooperation of several low energy bonds extended over a wide area results in a high affinity complex between IL-1 and the type I receptor.

Amino Acid Sequence↗
PubMed1993

Structure-function relationships of lipoprotein lipase: mutation analysis and mutagenesis of the loop region.

The molecular models of two microbial lipases and human pancreatic lipase (PL) have suggested the existence of common structural motifs including a buried active site shielded by an amphipathic surface loop. In an effort to explore the role of residues comprising the loop of lipoprotein lipase (LPL), we have used site-directed mutagenesis to generate three new LPL variants. In variant LPLM1 we deleted 18 amino acids leaving a loop of only 4 residues which resulted in an LPL protein inactive against triolein substrates. In contrast, two other LPL variants with only partial deletions, involving the apical section of the loop [LPLM2 (-8 amino acids) and LPLM3 (-2 amino acids)] manifested normal lipolytic activity. These findings indicate a critical requirement for the maintenance of charge and periodicity in the proximal and distal segments of the LPL loop in normal catalytic function. This is further highlighted by the detection of a mutation in the proximal section of the loop in a patient with LPL deficiency at position 225 which results in a substitution of threonine for isoleucine. The intact catalytic activity of the partial deletion variants (LPLM2 and LPLM3) further suggests that the apical residues of the loop contribute minimally to the functional motifs of the active site. We support this postulate by showing that the conserved glycine in the apical turn section (G229) can be substituted by glutamine, lysine, proline, or threonine without significantly affecting catalytic activity.

Base Sequence↗
PubMed1995

Pelvic pouch-anal anastomoses: pros and cons about omission of mucosectomy and loop ileostomy. A study of 60 patients.

Pelvic pouches were constructed in 60 consecutive patients from 1987 to 1991. The first 30 patients underwent mucosectomy and construction of handsewn reservoirs, and ileoanal anastomoses protected by loop ileostomy (group A). In the following 12 patients (group B1) J pouches and ileoanal anastomoses were constructed by total stapling technique without mucosectomy, with a loop ileostomy. In the last 18 patients the loop ileostomy was omitted (group B2). A comparison between group A and B and between group B1 and B2 was made concerning anaesthesia time, hospital stay, blood transfusions, postoperative complications and pouch function at 2 and 12 months. It was found that the stapling technique (group B) reduced anaesthesia time considerably and reduced the need of blood transfusions. Postoperatively thromboembolic episodes and signs of adrenal insufficiency were seen only in the handsewn group, while postoperative febrile conditions were more common in the stapled groups. Ileo-anal dehiscence occurred in two patients without loop ileostomy. Treatment by establishment of a loop ileostomy, local irrigation and administration of antibiotics were successful, the anastomoses healed within 2 weeks and there was no further complications before or after loop closure. Omitting the loop ileostomy saved the patient a further operation and reduces hospital stay and sick leave. After two months of pouch function, patients with handsewn pouches had a lower number of bowel movements (5.5/24 h and 0.8 during the night) than patients with stapled pouches (8.0/24 h and 1.9 during the night). At 12 months, however, the difference between the groups of patients had diminished.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1997

Identification of 2'-hydroxyl groups required for interaction of a tRNA anticodon stem-loop region with the ribosome.

Synthetic RNA stem loops corresponding to positions 28-42 in the anticodon region of tRNA(Phe) bind efficiently in an mRNA-dependent manner to ribosomes, whereas those made from DNA do not. In order to identify the positions where ribose is required, the anticodon stem-loop region of tRNA(Phe) (Escherichia coli) was synthesized chemically using a mixture of 2'-hydroxyl- and 2'-deoxynucleotide phosphoramidites. Oligonucleotides whose ribose composition allowed binding were retained selectively on nitrocellulose filters via binding to 30S ribosomal subunits. The binding-competent oligonucleotides were submitted to partial alkaline hydrolysis to identify the positions that were enriched for ribose. Quantification revealed a strong preference for a 2'-hydroxyl group at position U33. This was shown directly by the 50-fold lower binding affinity of a stem loop containing a single deoxyribose at position U33. Similarly, defective binding of the corresponding U33-2'-O-methyl-substituted stem-loop RNA suggests that absence of the 2'-hydroxyl group, rather than an altered sugar pucker, is responsible. Stem-loop oligoribonucleotides from different tRNAs with U33-deoxy substitutions showed similar, although quantitatively different effects, suggesting that intramolecular rather than tRNA-ribosome interactions are affected. Because the 2'-hydroxyl group of U33 was shown to be a major determinant of the U-turn of the anticodon loop in the crystal structure of tRNA(Phe) in yeast, our finding might indicate that the U-turn conformation in the anticodon loop is required and/or maintained when the tRNA is bound to the ribosomal P site.

Anticodon↗
PubMed1997

Predictive factors used to justify hysterectomy after loop conization: increasing age and severity of disease.

OBJECTIVE: To determine the interpretability and significance of the traditional factors used to predict residual dysplasia in hysterectomy specimens after loop conization. MATERIALS AND METHODS: Loop electrosurgical cervical conization was performed on 372 patients. Ninety three women had a hysterectomy within 6 months of the loop conization. Residual disease was defined as cervical intraepithelial neoplasia or cancer in the hysterectomy specimen. RESULTS: Of the 93 patients having a subsequent hysterectomy, 36 (38.7%) has residual disease in their hysterectomy specimen. The mean age of the patients with residual disease in the post loop conization hysterectomy specimen was 42.22. The mean age of those free of residual disease was 29.42. By multivariate analysis, dysplasia involving the ectocervical margin (p = 0.34) and the endocervical margin (p = 0.35) was not predictive of disease in the hysterectomy specimens. Endocervical curettage (p = 0.005), glandular involvement (p = 0.01), loop conization pathology findings (p < 0.05) and cytological examination (p < 0.001) were predictive of residual dysplasia. CONCLUSIONS: Cytological reports, increasing age, severity of disease, gland involvement and endocervical curettage were the only factors that accurately predicted residual dysplasia. The presence or absence of dysplasia in the loop conization, ectocervical margin and endocervical margin was not predictive of residual dysplasia in post loop conization hysterectomy specimens.

Adult↗