Absorbed dose measurements in dual energy X-ray absorptiometry (DXA)

In this study a predominantly film dosimetric method was used to measure the effective dose from posteroanterior (PA) lumbar spine and proximal femur scans performed on a Lunar DPX-L machine. Because of the very low dose rate in scanning mode, the depth dose data were determined using a stationary detector configuration. The characteristic curve for the film (Kodak TMAT-H) was obtained and depth dose measurements were made using slabs of "solid water". The film was calibrated using a superficial X-ray unit (calibrated against a standard traceable to a national standard). To assess the change in film response with beam hardening at depth, the film was exposed to calibration beams of different half value layer (HVL). The HVL of the DXA beam was determined for surface and depth doses using aluminium filters and a diamond detector (an energy independent device). All measurements were performed three times. Beam size was measured using film, and the scan areas and times were determined by scanning phantoms. The dose from a scan was calculated using Dsc = DTscAb/Asc, where D = dose rate (stationary), Tsc = scan time, Ab = beam area, and Asc = scan area. Organ doses were determined using an anatomical atlas and ICRP 23 female reference. All film measurements had good precision (coefficient of variation < 4%). There was little variation in film sensitivity with change in HVL (< 1% change for the first three HVLs) and consequently no corrections were applied to the depth dose data. Skin entrance dose was 11.5 microGy. Effective dose in females was 0.19 microSv for the PA lumbar spine. For the proximal femur scan, the effective dose was 0.14 microSv (ovaries included) and 0.023 microSv (ovaries excluded) for pre-menopausal and pos-menopausal women, respectively.

Oxidation of Anthracene and Benzo[a]pyrene by Laccases from Trametes versicolor

The in vitro oxidation of the two polycyclic aromatic hydrocarbons anthracene and benzo[a]pyrene, which have ionization potentials of <=7.45 eV, is catalyzed by laccases from Trametes versicolor. Crude laccase preparations were able to oxidize both anthracene and the potent carcinogen benzo[a]pyrene. Oxidation of benzo[a]pyrene was enhanced by the addition of the cooxidant 2,2(prm1)-azinobis(3-ethylbenzthiazoline-6-sulfonate) (ABTS), while an increased anthracene oxidizing ability was observed in the presence of the low-molecular-weight culture fluid ultrafiltrate. Two purified laccase isozymes from T. versicolor were found to have similar oxidative activities towards anthracene and benzo[a]pyrene. Oxidation of anthracene by the purified isozymes was enhanced in the presence of ABTS, while ABTS was essential for the oxidation of benzo[a]pyrene. In all cases anthraquinone was identified as the major end product of anthracene oxidation. These findings indicate that laccases may have a role in the oxidation of polycyclic aromatic hydrocarbons by white rot fungi.

Effects of increasing solid component size of a mixed solid/liquid meal on solid and liquid gastric emptying

This study evaluated the hypothesis that an increase in the volume of the solid component of a mixed solid/nutrient liquid meal will result in more rapid emptying of the solid but slower liquid emptying. Eight normal volunteers were studied on two occasions after ingesting a meal containing 150 ml of 10% dextrose with either 100 g(small) or 400 g (large) of ground beef. Subjects ingested the solid component before the liquid. For the solid component, the lag phase was longer for the larger meal (56 vs. 31 min, P < 0.001). However, the absolute emptying rate for the proximal stomach and the postlag emptying rate of solid from the total stomach, when expressed as kilocalories per minute, were greater with the larger meal (P < 0.002). The lag phase was prolonged (P < 0.03) and the rate of emptying of liquid from the total and proximal stomach was slower (P < 0.001) in the large compared with the small meal. The total amount of energy delivered to the duodenum (from solid and liquid components) after the solid lag phase was greater for the larger meal (4.8 vs. 2.5 kcal/min, P < 0.002). These results indicate that an increase in the volume of the solid component of a mixed solid/liquid meal 1) prolongs the lag phase but accelerates the postlag emptying rate of solid and 2) retards intragastric distribution and emptying of liquid.

Structure and inhibition of plasmepsin II, a hemoglobin-degrading enzyme from Plasmodium falciparum

Plasmodium falciparum is the major causative agent of malaria, a disease of worldwide importance. Resistance to current drugs such as chloroquine and mefloquine is spreading at an alarming rate, and our antimalarial armamentarium is almost depleted. The malarial parasite encodes two homologous aspartic proteases, plasmepsins I and II, which are essential components of its hemoglobin-degradation pathway and are novel targets for antimalarial drug development. We have determined the crystal structure of recombinant plasmepsin II complexed with pepstatin A. This represents the first reported crystal structure of a protein from P. falciparum. The crystals contain molecules in two different conformations, revealing a remarkable degree of interdomain flexibility of the enzyme. The structure was used to design a series of selective low molecular weight compounds that inhibit both plasmepsin II and the growth of P. falciparum in culture.

The functional relationships between hiatal hernia and reflux esophagitis

The purpose of this research was to investigate functional studies by which the hiatal hernia (HH) may be relevant to a reflux esophagitis (RE). Group I consisted of healthy controls who were endoscopically normal (n = 21). Group II consisted of patients with hiatal hernia but no reflux esophagitis (n = 8). Group III had patients with hiatal hernia with reflux esophagitis (n = 9). Group IV had patients with reflux esophagitis but no hiatal hernia (n = 16). Esophageal manometry, ambulatory 24 hour intraesophageal pH monitoring, acid clearance test, and gastric emptying scan were performed in each of the patients. The contraction amplitude at 3 cm above the lower esophageal sphincter did not differ significantly among the four groups, but the mean lower esophageal sphincter pressure was significantly decreased in group II. The DeMeester score in ambulatory 24 hour intraesophageal pH monitoring was significantly higher in group III compared with the controls. No significant difference among the groups was found with respect to acid clearance. Total and proximal gastric emptying times (T1/2) were significantly delayed in group III. We found that hiatal hernia combined with delayed gastric emptying may bear a relationship to the multifactorial origins of reflux esophagitis, and we suggest a rationale for using prokinetic agents as the therapeutic regimen in patients with HH complicated by RE.

Crystallization and preliminary crystallographic data for an FMN-dependent nitroreductase from Escherichia coli B

An FMN-dependent nitroreductase enzyme isolated from Escherichia coli B has been crystallized in a form suitable for high-resolution structural analysis. The crystals belong to the tetragonal space group P4(1)2(1)2 or its enantiomorph P4(3)2(1)2 with cell parameters a = b = 57.74 A, c = 275.51 A and two molecules per asymmetric unit. Diffraction extends to beyond 1.9 A.

Image analysis of 2D gels: considerations and insights

2D gel experiments require computer based analysis when the number of gels exceed four and quantitative information is required. Computer based systems should first perform the required tasks and should do so with enough ease and logic that users in a biological laboratory can easily use it on an intermittent basis. Considerations for analysis systems including input device specifications needed, computer hardware configurations and software tools are discussed and compared to the application requirements. The components of this system are then examined as a whole to envision how the total solution should function optimally in an biological laboratory.

Lithium carbonate in chronic schizophrenia--a brief trial of lithium carbonate added to neuroleptics for treatment of resistant schizophrenic patients

The value of lithium carbonate as an adjunctive treatment of resistant schizophrenia was tested in a 4-week clinical trial using a single-blind, randomized, consent design. Treatment and control groups were drawn from a population of detained patients in an English special (maximum security) hospital. The 2 groups were comparable in terms of age, sex, severity of symptoms, length of hospitalization and concurrent neuroleptic dosage. The addition of lithium carbonate to the treatment regimen did not result in symptomatic improvement in patients completing the treatment protocol. The ethical and practical difficulties raised by the trial are discussed.

Role of the proximal and distal stomach in mixed solid and liquid meal emptying

The role of the proximal and distal stomach in the emptying of solids and liquids from the stomach remains unclear. We have used a dual isotope technique to quantify proximal and distal stomach emptying of a solid (100 g of 99mTc labelled liver/ground beef) liquid (either 200 ml of normal saline (eight subjects) or 25% dextrose (seven subjects) labelled with 113mIn-diethylenetriaminepenta-acetic acid) mixed meal. A manometric catheter simultaneously measured antral, pyloric, and duodenal motor activity. The liquid component dispersed rapidly throughout the stomach and emptied after a minimal lag period. The emptying of the 25% dextrose was delayed compared with the saline. This delay was associated with increased retention of the liquid in the distal stomach, a significant increase in localised phasic pyloric contractions, and a suppression of antral contractions. The solid component initially resided wholly within a proximal stomach reservoir area. Solids then redistributed from proximal to distal stomach during the emptying of liquid from the stomach. Dextrose delayed gastric emptying of solids compared with saline by increasing the solid lag period and retention in the proximal stomach. There was no significant difference between saline and dextrose meals in the distal stomach retention of solid or in the linear rate of emptying after the lag period. We conclude that, contrary to general opinion, the proximal stomach plays an important role in the control of gastric emptying of solids while the distal stomach is important in the emptying of nutrient liquids.

Effect of cisapride on delayed gastric emptying in gastro-oesophageal reflux disease

Some patients with gastro-oesophageal reflux disease have delayed gastric emptying. This study investigates the effect of cisapride on gastric emptying in 34 patients with proved reflux and delayed gastric emptying of solids. They were enrolled in a double blind controlled crossover study. Placebo or cisapride (10 mg) tablets were given three times a day for three days followed by further assessment of gastric emptying. The protocol was repeated with the crossover tablet. Gastric emptying was assessed by a dual radionuclide technique. The percentage of a solid meal remaining in the stomach at 100 minutes (% R100 minutes) and the time taken for 50% of the liquid to empty (T50 minutes) were calculated and analysed by the Wilcoxon matched pairs signed ranks test and expressed as medians (ranges). For gastric emptying of solids the initial % R100 minutes (70 (60-100)%) was not significantly different from placebo (71 (35-100)%). After cisapride treatment a significant acceleration (p less than 0.001) in gastric emptying occurred (% R100 minutes, 50.5 (28-93)%). Similarly with gastric emptying of liquids, the initial T50 minute value was 26.5 (12-82) minutes, after placebo the value was 28 (11-81) minutes, but this was significantly accelerated with cisapride (p less than 0.03) to 22.5 (6-61) minutes. The acceleration in gastric emptying occurred in the proximal portion of the stomach for gastric emptying of both solids and liquids suggesting that this is the principal site of action of cisapride. We conclude that cisapride significantly accelerates gastric emptying of both solids and liquids in patients with gastro-oesophageal reflux disease and delayed gastric emptying.

Comparative effects of duodenal and ileal intubation on gastric emptying and postprandial antral, pyloric, and duodenal motility

The influence of gastric and small-intestinal intubation on fed patterns of antropyloroduodenal motility and gastric emptying of a solid meal has been investigated in normal volunteers. In 10 subjects a manometric assembly was passed as far as the fourth part of the duodenum; in 8 other subjects the terminal ileum was intubated; and a further 8 subjects were not intubated. The manometric assemblies were similar, apart from their length, and both incorporated a sleeve/side hole assembly located across the pylorus. All subjects ingested a meal of 100 g 99mTc-labelled liver/ground beef. There was no significant difference in either the lag phase or the linear emptying phase of gastric emptying between the control and duodenal intubation groups. The emptying phase of the test meal, but not the lag phase, was slower (p less than 0.01) in the ileal intubation group than in the non-intubated and duodenal intubation groups. There were fewer (p less than 0.01) antral pressure waves in the ileal than in the duodenal intubation group. We conclude that ileal but not duodenal intubation has an important inhibitory influence on gastric emptying and antral motility.

A two-dimensional acrylamide gel electrophoresis/computer software approach to decoding the human genome

The human genome sequencing initiative is sure to be an expensive and time-consuming project. To maximize the quality of the initial thrust, it is necessary to concentrate on sequencing those genes that are actively involved in crucial biological processes, both normal and otherwise. To identify the protein products of these genes, we propose the use of two-dimensional acrylamide gel electrophoresis and powerful computer software. The two-dimensional gels can then be scaled to yield sufficient amounts of the protein for direct amino acid sequence analysis. The amino acid sequence then provides the direct link back to the gene.

Motor mechanisms associated with slowing of the gastric emptying of a solid meal by an intraduodenal lipid infusion

The aim of this study was to define better the motor phenomena associated with the slowing of gastric emptying by a duodenal lipid infusion. Antral, pyloric and duodenal motility were recorded in 10 healthy subjects with a manometric assembly which incorporated multiple perfused side-holes and a sleeve sensor positioned astride the pylorus. The gastric emptying of a standard solid meal and the distribution of the ingesta between the proximal and distal stomach were monitored with a radionuclide technique. A triglyceride emulsion was infused into the duodenum for 45 min once 25% of the meal had emptied. The infusion caused significant slowing in the rate of gastric emptying (P less than 0.01). This slowing in gastric emptying was associated with the suppression of pressure waves in the distal antrum (P less than 0.01) and proximal duodenum (P less than 0.01), the induction of pressure waves isolated to a narrow pyloric segment (P less than 0.01), and a redistribution of ingesta from the distal to proximal stomach. These findings suggest that pressure waves isolated to the pylorus, changes in the intragastric distribution of ingested food, and changes in proximal duodenal motility may all act in concert with changes in antral motility to regulate the gastric emptying of solids.

Computer-analysed 2-D electrophoresis

A service is now available for analysing 2-dimensional gels and comparing them to existing databases, broadening the number of laboratories which can study protein expression using the technique.

Protein database development: identification of glycosylated and phosphorylated proteins in unfractionated rat fibroblast lysates

In this paper, techniques are demonstrated for unambiguously mapping phosphoproteins and glycoproteins into a protein database of unfractionated fibroblast proteins. These methods allow for precise registration of subsets of proteins with the image of total proteins. The methods are also applicable to database mapping of antigens identified by indirect immunodetection methods and receptor molecules identified with photoaffinity ligands.

Relationship of the motor activity of the antrum, pylorus, and duodenum to gastric emptying of a solid-liquid mixed meal

The postprandial motor activity of the antrum, pylorus, and duodenum in 15 healthy volunteers was compared with the profiles of emptying of the solid and liquid components of a meal. The liquid component of the meal emptied rapidly in an exponential manner, whereas the solid remained in the fundus of the stomach until approximately 80% of the liquid had emptied and then emptied in a linear manner. The onset of solid emptying was associated with an increase in the rate of occurrence of antral pressure waves (p less than 0.05), and the half-time for solid emptying (t1/2 - lag period) was inversely correlated (p less than 0.05) with the rate of coordinated contractions involving the antrum. The substitution of 25% dextrose in normal saline as the liquid component of the meal increased the half-time for liquid emptying from a median of 8 to 40 min (p less than 0.01), increased the lag period for solid emptying from 40 to 87 min (p less than 0.01), and increased the rate of occurrence of isolated pyloric pressure waves during the solid lag phase from 7 to 58/h (p less than 0.05), but did not affect the slope of solid emptying or the rate of coordinated contractions involving the antrum during the solid emptying period.

Proximal, distal and total stomach emptying of a digestible solid meal in normal subjects

The gastric fundus and antrum probably play different roles in the emptying of solids and liquids in man, but there is little information about the intragastric distribution of food. We have used a new radionuclide technique to quantify proximal, distal and total stomach emptying of a digestible solid meal (100 g of 99Tcm-labelled liver/ground beef given with 150 ml of 10% dextrose) in 13 normal subjects. A proximal reservoir area was seen after consumption of the meal, and used to define the proximal stomach region. A line drawn immediately below this area divided the total stomach region into proximal and distal stomach. Emptying from the total stomach exhibited two phases--an initial lag period (median 41 min, range 21-57 min), followed by approximately linear emptying. Redistribution of food from the proximal to the distal stomach was a major component of the lag period in 11 of the 13 subjects. In the remaining two subjects, redistribution was rapid (proximal 50% emptying time of 4 and 10 min) and antral retention was the major component of the lag period. In seven subjects, a region of reduced activity (contraction band) was seen. The midpoint of this band closely approximated to the line used to divide proximal and distal stomach. We suggest that a contraction band may be responsible for the proximal gastric reservoir seen after meal consumption and plays an important role in the redistribution and emptying of digestible solid food from the stomach. There is considerable variation between normal subjects in the rate of transfer of digestible solid food from the proximal to the distal stomach.

Gastric and esophageal emptying in dystrophia myotonica. Effect of metoclopramide

Gastric and esophageal emptying were measured using scintigraphic techniques in 16 patients with dystrophia myotonica and in 22 normal volunteers. Gastric emptying of a solid meal was slower than the normal range (defined as the mean +/- two standard deviations obtained in the normal volunteers) in 15 of the 16 patients, and gastric emptying of the liquid meal was slower than the normal range in 10 of the patients. Esophageal emptying was also markedly delayed in patients, with 15 of 16 patients having an emptying time longer than the normal range. There was no relationship between gastrointestinal symptoms, or the severity of the peripheral (skeletal) muscle weakness, and either gastric or esophageal emptying. Oral administration of metoclopramide resulted in a significant improvement in gastric emptying of the solid meal and a nonsignificant trend toward more rapid liquid emptying, but no change in esophageal emptying. These results indicate that there is a very high prevalence of gastric and esophageal smooth muscle dysfunction in dystrophia myotonica and that gastroparesis is likely to be a treatable cause of morbidity in this disease.

Abnormalities of gastric and esophageal emptying in polymyositis and dermatomyositis

Gastric and esophageal emptying were assessed using scintigraphic techniques in 13 patients with polymyositis or dermatomyositis and in 13 normal volunteers. Esophageal emptying was significantly delayed in patients, with 8 of 13 patients being outside the normal range. Gastric emptying was also markedly slower in patients than in controls, with 8 patients being outside the normal range for solid emptying and 8 patients beyond the normal range for liquid emptying. The 5 patients with dysphagia all had delayed esophageal emptying, but both gastric and esophageal emptying were delayed in some asymptomatic patients. There was a significant correlation between esophageal emptying and both solid and liquid gastric emptying in the patients. Both gastric and esophageal emptying correlated with the severity of the peripheral (skeletal) muscle weakness. These results indicate that profoundly delayed gastric and esophageal emptying are common in polymyositis and dermatomyositis, implying frequent malfunction of the smooth muscle of the upper gastrointestinal tract in this disease.

Effect of increasing the caloric/osmotic content of the liquid component of a mixed solid and liquid meal on gastric emptying in obese subjects

A dual isotope scintigraphic technique was used to assess the effect of increasing the caloric content of the liquid component of a mixed solid and liquid meal on gastric emptying in control and obese subjects. For the two test meals used gastric emptying of solid was significantly slower in the obese subjects compared to the control subjects. In both obese and control subjects the substitution of 25 per cent dextrose for water as the liquid component of the meal resulted in a significant delay of both solid and liquid emptying. The magnitude of this change was similar in obese and control subjects. The results suggest that the duodenal receptor mechanisms which slow gastric emptying are not defective in obesity.