Low duty-cycle pulsed irradiation reduces magnetization transfer and increases the inhomogeneous magnetization transfer effect

Intense off-resonant RF irradiation can lead to saturation of the macromolecular pool magnetization and enhance bound pool dipolar order responsible for the inhomogeneous magnetization transfer (ihMT) effect, but the intensity of RF power in human imaging studies is limited by safety constraints on RF heating. High RF intensities can still be achieved if applied in short pulses with low duty-cycle. Here we investigate the benefits of low duty-cycle irradiation for MT and ihMT studies with both theoretical and experimental methods. Solutions for pulsed irradiation of a two-pool model including dipolar order effects were implemented. Experiments were conducted at 3 T in the brain and through the calf of healthy human subjects. 2D echo planar images were acquired following a preparation of RF irradiation with a 2 s train of 5 ms pulses repeated from between 10 to 100 ms for duty-cycles (DCs) of 50% to 5%, and at varying offset frequencies, and time averaged RF powers. MT and ihMT data were measured in regions of interest within gray matter, white matter and muscle, and fit to the model. RF irradiation effects on signal intensity were reduced at 5% relative to 50% DCs. This reduced RF effect was much larger for single than dual frequency irradiation. 5% DC irradiation reduced single and dual frequency MT ratios but increased ihMT ratios up to 3 fold in brain tissues. Muscle ihMT increased by an even larger factor, depending on the frequency and applied power. The model predicted these changes with duty-cycle. The model fit the data well and constrained model parameters. Low duty-cycle pulsed irradiation reduces MT effects and markedly increases dipolar order effects. This approach is an attractive method to enhance ihMT signal-to-noise ratio and demonstrates a measurable ihMT effect in muscle tissue at 3 T under acceptable specific absorption rates. The effects of duty-cycle changes demonstrated in a separate MT/ihMT preparation provide a route for new applications in magnetization-prepared MRI sequences.

Interpretation of magnetization transfer from inhomogeneously broadened lines (ihMT) in tissues as a dipolar order effect within motion restricted molecules

Comparison of off-resonance saturation with single and dual frequency irradiation indicates a contribution of inhomogeneously broadened lines to magnetization transfer in tissues. This inhomogeneous magnetization transfer (ihMT) phenomenon can be exploited to produce images that highlight tissues containing myelin, in vivo. Here, a model for ihMT is described that includes dipolar order effects from magnetization associated with motion-restricted macromolecules. In this model, equal irradiation at positive and negative frequency offsets eliminates dipolar order and achieves greater saturation than irradiation at a single offset frequency using the same power. Fitting of mouse and human volunteer brain data at different irradiation powers and offset frequencies was performed to assess the relevance of the model and approximate tissue parameters. A key parameter in determining ihMT signal was found to be the relaxation time T1D associated with the dipolar order reservoir and the fraction f of the semi-solid, bound magnetization that possessed a nonzero T1D. Indeed, better fits of myelinated tissue were achieved when assuming f≠1. From such fits, estimated T1Ds of mice in the white matter, (34±14) ms, were much longer than in muscle, T1D=(1±1) ms and the average f from white matter volunteer data was 2.2 times greater than that in grey matter. The combination of f and longer T1Ds was primarily responsible for the much higher ihMT in myelinated tissues, and provided explanation for the species variation. This dipolar order ihMT model should help guide future research, pulse sequence optimization, and clinical applications.

Plant spacing and weed control affect sunflower stalk insects and the girdling behavior of Dectes texanus (Coleoptera: Cerambycidae)

We conducted a 2-yr study to determine the effects of crop density and weeds on levels of damage caused by stalk-boring insects in rain-fed sunflowers in west-central Kansas. Weed-free sunflower had higher seed weight and oil content in 2007, but not in 2006, but weeds did not affect infestation by stalk-boring insects in either year. High-density sunflower had lower estimated seed yield per unit area than low-density sunflower in both years, but percentage oil was slightly greater in the high-density treatment in 2006. Sunflowers were more heavily infested by larvae of Ataxia hubbardi Fisher, Cylindrocopturus adspersus (Leconte), and Pelochrista womanana (Kearfott) in 2006 than in 2007, ostensibly as a result of being planted earlier. Larvae of Dectes texanus LeConte appeared unaffected by planting date and were present in > 70% of plants in both years. Conditions during the period of crop maturity were much drier in 2006 than in 2007 and were associated with higher seed oil content and earlier and faster progression of stalk girdling by D. texanus larvae in both low- and high-density plots. There was also a strong effect of plant density on girdling behavior that seemed to be mediated by effects on soil moisture. Stalk girdling began earlier in high-density plots and a larger proportion of plants were girdled compared with low-density plots on all sampling dates in both years. Certain cultural tactics, in particular reduced plant spacing, have potential to delay the onset of girdling behavior by D. texanus larvae and thus mitigate losses that otherwise result from the lodging of girdled plants.

Intraguild predation among ladybeetles and a green lacewing: do the larval spines of Curinus coeruleus(Coleoptera: Coccinellidae) serve a defensive function?

Laboratory experiments examined interspecific interactions between larvae of three coccinellid species, Curinus coeruleus Mulsant (Chilocorinae), Harmonia axyridis Pallas and Olla v-nigrum (Mulsant) (Coccinellinae), and between these and larvae of the green lacewing, Chrysoperla rufilabris (Burmeister). Larvae of C. coeruleus, although defended on their dorsal surface with long spines, had the smallest mandibles, were the slowest-moving, and the least successful in interspecific larval combat. The long spines of third instar C. coeruleusappeared to reduce their palatability as food to H. axyridis and O. v-nigrum larvae in choice tests with dead larvae, but were not an effective defence against these species in Petri dish arenas. Larvae of O. v-nigrum had a smooth dorsal surface, were intermediate in terms of mandible size, but were the fastest moving, a trait that benefited their survival in intraguild combat. Larvae of H. axyridis were intermediate with respect to dorsal spines and speed of movement, but had the largest mandibles. This species was the most effective intraguild combatant among the coccinellids and the only one to successfully compete against C. rufilabris larvae of similar age. The speed, manoeuverability and long mandibles of C. rufilabris enabled them to impale coccinellid larvae at a relatively safe distance. The spines of C. coeruleus larvae impeded laterally oriented attacks by C. rufilabris, but did not provide sustained protection from repeated attacks. Success in these interactions appeared largely a function of offensive weaponry (mandible size and morphology) and speed of movement, although the role of dorsal spines as defensive structures was not ruled out. Rates of larval cannibalism were highest for C. rufilabris and largely mirrored the level of aggression observed in interspecific combat for each species.

IPM-compatibility of foliar insecticides for citrus: indices derived from toxicity to beneficial insects from four orders

A series of compounds representing four major pesticide groups were tested for toxicity to beneficial insects representing four different insect orders: Coleoptera (Coccinellidae), Hemiptera (Anthocoridae), Hymenoptera (Aphelinidae), and Neuroptera (Chrysopidae). These materials included organophosphates (methidathion, esfenvalerate and phosmet), carbamates (carbofuran, methomyl and carbaryl), pyrethroids (bifenthrin, fenpropathrin, zeta-cypermethrin, cyfluthrin and permethrin) and the oxadiazine indoxacarb. Toxicity to coccinellid and lacewing species was assessed by treating 1st instar larvae with the recommended field rate of commercial products, and two 10 fold dilutions of these materials, in topical spray applications. Adult Aphytis melinus Debach and 2nd instar Orius insidiosus (Say) were exposed to leaf residues of the same concentrations for 24 h. ANOVA performed on composite survival indices derived from these data resolved significant differences among materials with respect to their overall toxicity to beneficial insects. Cyfluthrin, fenpropathrin and zeta-cypermethrin all increased the developmental time of the lacewing and one or more coccinellid species for larvae that survived topical applications. Bifenthrin increased developmental time for two coccinellid species and decreased it in a third. Indoxacarb (Avaunt WG, DuPont Corp.) ranked highest overall for safety to beneficial insects, largely because of its low dermal toxicity to all species tested. Zeta-cypermethrin (Super Fury), FMC Corporation) received the second best safety rating, largely because of its low toxicity as a leaf residue to A. melinus and O. insidiosus. Phosmet (Imidan 70W, Gowan Co.) and methidathion (Supracide 25W, Gowan Co.) ranked high for safety to coccinellid species, but compounds currently recommended for use in citrus such as fenpropathrin (Danitol 2.4EC, Sumimoto Chem. Co.) and carbaryl (Sevin XLR EC, Rhone Poulenc Ag. Co.) ranked very low for IPM-compatibility based on their relatively high toxicity to all species tested.

Colonic bicarbonate output as a test of disease activity in ulcerative colitis

No available test objectively measures impairment of function of the inflamed colonic mucosa in ulcerative colitis. To study function we assessed rectal bicarbonate output by rectal dialysis in the presence of water and bacterial fatty acid (n-butyrate) in 21 controls, 18 patients with acute ulcerative colitis, 12 patients with ulcerative colitis in remission, and 12 patients with other forms of colitis. In acute ulcerative colitis, compared with controls, bicarbonate output and pH was reduced (p less than 0.001); stimulated bicarbonate output with bacterial fatty acid (incremental bicarbonate output) was reduced by 80% in acute ulcerative colitis (p less than 0.01). Results indicate that bicarbonate output is a useful and selective test of mucosal function in acute ulcerative colitis. A diminished incremental bicarbonate output with n-butyrate supports the view of inadequate oxidation of bacterial fatty acids in vivo by the mucosa in ulcerative colitis. Whether the test will prove to be an index of prognosis or will aid choice between medical or surgical therapy requires further study.

Clinical evaluation of the 14C-Triolein Breath Test: a critical analysis

Twenty-two hospital patients without gastrointestinal symptoms and fourteen patients with clinically suspected fat malabsorption were studied using the 14C-Triolein Breath Test and three day fecal fat estimation. The 14C-Triolein Breath Test was 100% sensitive and 86% specific for fat malabsorption. Three day fecal fat estimations were 86% sensitive and 91% specific. These data confirm the high sensitivity and specificity obtained using the 14C-Triolein Breath Test. The speed and convenience of the 14C-Triolein Breath Test plus acceptable sensitivity and specificity make this a practical screening test to detect fat malabsorption.

Gastrointestinal endoscopy: some perspectives

Remarkable technological advances of fibreoptic endoscopy in the past two decades have produced important improvements in diagnosis and treatment of gastrointestinal and hepatobiliary disorders. These advances must be kept in perspective; continuing, critical assessment of their contribution to the management of patients is desirable. Endoscopy can have adverse effects on the total performance of departments of gastroenterology, on gastroenterology as a discipline, and even on the status of the medical profession in the community. Gastroenterologists need to show proficiency of performance and integrity of practice. Control may be achieved by certification delineation of privileges, peer review, public accountability, and realistic financial returns for procedures. Records of a department of gastroenterology indicate that some control may be achieved by insistence on a consultation before decision on endoscopy. This may be a desirable alternative to endoscopy on demand. Undue emphasis on technology runs some risk of destroying the proper practice of consultant medicine.

A comparison of diazepam and phenoperidine in premedication for upper gastrointestinal endoscopy: a randomized double blind controlled study

A variety of agents are used as premedication for upper gastrointestinal endoscopy (U.G.E.). To our knowledge, no double blind studies have been performed to compare their value. In this study phenoperidine (2 mg i.v.) was compared with diazepam (t mg i.v.) in 200 consecutive patients undergoing elective U.G.E. The study was randomized and double blind in regard to both endoscopists and patients. All patients were given atropine (0.4 mg i.v.) and a throat spray with 2% amethocaine. Patients who needed supplemental medication were given diazepam and excluded from final analysis. A graded questionnaire was recorded by endoscopists and patients after U.G.E., and a further anonymous questionnaire was returned by patients four days later. Statistical analysis revealed that phenoperidine was superior at facilitating intubation and providing more relaxation as judged by the endoscopist. Patient questionnaires, four days after U.G.E., indicated less distress during intubation and examination with phenoperidine. Nausea, vomiting, amnesia and phlebitis were uncommon after either phenoperidine or diazepam.

The effect preloads of amino acid on shortterm satiety

The effect of a preload of an amino acid preparation on food intake in man was assessed in eight subjects. Each subject was given a small dose of amino acids or placebo 1/2 h before being presented with a meal. This was done in a blind, randomized fashion on five occasions for each preparation to each subject. The mean food intake of the subjects when receiving the amino acid preparation was 10% (p less than 0.01) less than the intake when receiving the placebo. When the subjects were grouped according to their variation from ideal weight, a 22.5% reduction in food intake was observed in group I (n = 4) who were greater than 5% above the ideal weight for height ratio (p less than 0.001). A 1.75% increase (NS) was seen in group II (n = 4) whose weight was within 5% of their ideal weight. These results demonstrate a modulation of satiety by small caloric doses of amino acids in overweight subjects.

A problem of management in Whipple's disease

A patient with Whipple's disease did not respond to appropriate antibiotic treatment. A therapeutic response was obtained by a combination of tetracycline and prednisolone.

Fractionated dose cholecystography: a comparison between iopanoic acid and sodium ipodate

Two randomised groups of 100 subjects each, undergoing oral cholecystography, were given either a 6 g fractionated dose of iopanoic acid (Telepaque) or sodium ipodate (Biloptin) to determine the relative merits of this dose schedule. Exclusions to the study were pregnancy and iodine sensitivity. Calculi or abnormal gallbladder opacification were present in 45% of subjects. Both agents were equally effective in demonstrating abnormalities, although bile duct visualisation was better using iopanoic acid (P less than 0.05). Of 46 subjects with abnormal cholecystograms subsequently undergoing surgery, all had the diagnosis confirmed. Side effects occurred in 63% of all subjects, being twice as common in those taking iopanoic acid (P less than 0.01). Sodium ipodate in a large fractionated dose is favoured because of the lower occurrence of side effects without loss of diagnostic accuracy.

Thyroid, renal, and hepatic function tests following cholecystography with high-dose contrast agents

Serum biochemical tests were observed for about three weeks following oral cholecystography with fractionated high doses (6 g) of iopanoic acid (Telepaque) or sodium ipodate (Biloptin) in 24 and 29 patients, respectively. Both agents produced similar effects. No significant changes were seen in renal or hepatic function except for a mild increase in bilirubin on day 22. Serum urate decreased 10% on day 4, but the change was not significant. On days 4 and 11, there were significant increases in thyroid-stimulating hormone, thyroxine and free thyroxine index, and a moderate fall in triiodothyronine. Reverse triiodothyronine increased sharply on day 4. The pattern of changes observed suggests that these contrasts interfere with the extrathyroidal deiodination of iodothyronines. The temporary rise in thyroxine and free thyroxine index exceeded reference ranges in about half of all subjects, but they remained clinically euthyroid. Thyroid function tests should be interpreted with caution within three weeks of cholecystography.

Iron deficiency anaemia--a prospective study

A prospective study was performed over 15 months to determine the cause of iron deficiency in adult males and postmenopausal females attending a general hospital. The laboratory computer identified all subjects with a haemoglobin less than 10.6 g/dl and a mean corpuscular volume less than 86 fl. Patients becoming anaemic after trauma or recent surgery were excluded. The iron status of each patient was assessed by serum iron studies, serum ferritin or sternal marrow aspiration. Reduced red cell indices and blood film morphology were not diagnostic of iron deficiency. Of 215 patients assessed, about half (103) were found to be iron replete. This group had a variety of disorders--malignancy, chronic inflammation, chronic renal and non-malignant haematological diseases. The other group of 104 patients satisfied criteria for iron deficiency, and 100 of these were investigated further. The cause of iron deficiency was found in all but three subjects. Inadequate dietary intake was a contributing factor in over half of the patients and 40 regularly took salicylates. Investigation defined a source of chronic gastrointestinal blood loss in most instances.

Gastrointestinal pitfalls

Gastrointestinal symptoms account for 15 to 30 per cent of patients presenting to first contact doctors. The disorders causing these are many and varied--some are rare but most are common. While a considerable depth of knowledge is necessary to suspect, diagnose and treat the rarer diseases, it is the common conditions which constitute the major problems in everyday practice. These problems usually result from inadequate clinical assessment, from a lack of logical thought, from incorrect teaching in undergraduate years and from an uncritical application of therapeutic methods which are not based on scientific fact.

The Mallory-Weiss lesion: a five-year experience

A retrospective survey has been made of patients with the Mallory-Weiss lesion who presented with upper gastrointestinal tract bleeding during the period 1972 to 1976. The lesion was diagnosed endoscopically in 78 cases, representing 7.7% of the total number of patients admitted with upper gastrointestinal tract bleeding. Patients ranged in age from 18 to 86 years (mean 43 years). The male-female ratio was 3:1. A history of retching and vomiting clearly preceded the bleeding in 60 patients. Significant alcohol intake within 48 hours of bleeding was reported in 53% of patients. Other upper gastrointestinal tract conditions, or migraine, may have induced vomiting in some instances. Previously known Mallory-Weiss lesions were rare (two patients), but 21% of patients had well documented past upper gastrointestinal tract bleeding from other causes. The tears were situated at the cardio-oesophageal junction in 47% of patients and were entirely gastric in 30%; 23% were oesophageal. Blood replacement was required in 31 patients (40%), and 16 of these were transfused with five or more units. Of those patients requiring transfusion, half had other significant pathological lesions. The mean hospital stay was four days and prolonged stay in hospital was usually necessary only in the presence of other disease. In no instance was surgery required primarily to control bleeding from mucosal tears. This study suggests that the Mallory-Weiss lesion is a relatively common cause of upper gastrointestinal tract bleeding, but that it is usually a benign condition, unless it complicates some other disorder.

The significance of widening of the presacral space at contrast radiography in inflammatory bowel disease

The width of the presacral space was measured prospectively at various levels in 100 persons without organic colonic or rectal disease who had barium enema X-ray examinations. A standard technique was employed. The most consistent measurement was obtained at the level opposite the S3-S4 disc space; readings varied between 2 mm and 16 mm. Using 16 mm as the upper limit of normal, and a similar technique of barium enema examination, the width of the presacral space at the S3-S4 disc level was measured in 66 patients with inflammatory bowel disease (ulcerative colitis--49; Crohn's colitis--17). The width did not correlate with the severity of the disease process as indicated by sigmoidoscopic examination in proximity in time to the radiological examination. There was a relationship between increased width of the presacral space and the duration of the disease process.

Obstruction of the gastrointestinal tract by foreign bodies in adults

Foreign bodies may become impacted because of congenital or acquired narrowing of the gastrointestinal tract or owing to unusual physical characteristics of the ingested material. Active intervention is necessary when impaction is complicated by intestinal obstruction or perforation or when the foreign body is composed of a toxic substance.

Alpha1-antitrypsin deficiency--a literature review and a case report of a patient with chronic obstructive airways disease and cirrhosis

A patient who manifested both pulmonary and hepatic disease associated with alpha1-antitrypsin deficiency is described. The biological function of alpha1-antitrypsin is discussed, as well as the inheritance of deficiency states and the spectrum of disorders which may ensue. Severe deficiency of alpha1-antitrypsin has been linked with pulmonary emphysema in adult life, progressive liver disease in childhood, adult cirrhosis but rarely with both pulmonary and liver disease.

Colonoscopy and bacteraemia

A prospective study was performed on 35 patients undergoing colonoscopy. Aerobic and anaerobic blood cultures before, during and after the investigation failed to demonstrate bacteraemia in any instance.

Endoscopic diagnosis of metastatic disease of the stomach and duodenum

The commonest tumours which metastasise to the upper gastrointestinal tract are from malignant melanoma, carcinoma of the breast and lung. Over a period of 12 months, three persons with known malignant disease were submitted to endoscopy by reason of upper gastrointestinal symptoms which could have been due to associated non-malignant disease. Two patients had known malignant melanoma and one a carcinoma of the breast. In each instance, endoscopy and biopsy demonstrated evidence of metastatic disease.

Pancreatitis and renal disease

Pancreatitis has been described previously following renal transplantation, but not in association with chronic renal failure. Analysis of 168 patients with renal transplants revealed five who developed pancreatitis, three of whom died. All five were on treatment with prednisone and azathioprine. Four patients were seen with definite attacks of pancreatitis and chronic, stable renal failure from a variety of causes. None had received immunosuppressive agents, prednisone nor thiazide diuretics, but two were on regular frusemide. One patient was on maintenance dialysis, which could not be related directly to the pancreatitis. In either group alcohol ingestion, cholethiathiasis, or hypercalcaemia was not a factor. This diagnosis of pancreatitis was established on clinical grounds and serum amylast levels of greater than 900 iu/1. Similar serum amylast elevation was not found ina random group of patients with chronic renal failure. Hyperlipidaemia was not present in any patient with pancreatitis. Although hypercalcaemia and primary hyperparathyroidism was not found in the transplant and non-transplant subjects, elevated serum parathormone levels have been described in uraemic patients with normocalcaemia. Hyperparathyroidism may be a factor in the development of pancreatitis in reanl failure. Pancreatitis carries a significant mortality risk in renal transplantation. The four non-transplanted patients have survived, despite recurrent attacks of pancreatitis.

Gastric ulceration within hiatus hernia

A retrospective analysis has been made of 19 persons with gastric ulceration in hiatus hernias. Eleven patients presented with acute upper gastrointestinal haemorrhage and three with chronic anaemia. Seventeen had experienced previous abdominal discomfort or heartburn. Diagnosis of ulceration was achieved by endoscopy in 16 instances and by radiography in six instances. A chronic ulcer was found in 10 patients, a discrete acute ulcer in three and multiple erosions in six. Twelve of the hernias were sliding in type and irreducible, in contrast to previous reports that gastric ulceration is most frequent in paracoesophageal hernias. Conservative management resulted in complete healing of the ulcer in the majority of patients. Continued bleeding or failure of the ulcer to heal necessitated surgical intervention in six patients.

Bleeding mucosal lesions in the upper gastrointestinal tracts of patients with oesophageal varices and hepatic cirrhosis

Thirty panendoscopic examinations were carried out on 24 patients with oesophageal varices and hepatic cirrhosis who presented with gastrointestinal hemorrhage. A mucosal lesion, focal or diffuse, was found in the upper gastrointestinal tract in all but three instances. The findings confirmed previous reports that hemorrhage in patients with oesophageal varices frequently occurs from a source other than variceal. This study has also demonstrated that where hemorrhage occurs from oesophageal varices, erosions of the oesophageal mucosa may play a major role in its pathogenesis.

Bacterial flora in the duodenum of patients after biliary fenestration

Fasting duodenal aspirates were studied in 15 patients with a biliary fenestration, 5 patients with a single duodenal diverticulum, 1 patient with a biliary fenestration and duodenal diverticulum, and 11 control subjects. A colonic type of bacterial flora, consisting of coliforms, Clostridium welchii, and Streptococcus faecalis, was found in 10 patients with biliary fenestration, 4 patients with a duodenal diverticulum, the patient with a fenestration and duodenal diverticulum, and in 1 of the control subjects. A high incidence of deconjugation of biles salts (10 out of 15 patients) and of steatorrhoea (8 out of 15 patients) was noted in the patients with biliary fenestration, as well as in those with a duodenal diverticulum (5 and 3 patients out of 5 respectively). Above-normal serum-folate levels were observed in 3 subjects with coliform colonization.

It is possible that vague abdominal symptoms which may be experienced by patients after biliary fenestration, may be due to the presence of an abnormal bacterial flora in the duodenum.