Dual-energy micro-CT of the rodent lung.

The purpose of this work is to investigate the use of dual-energy micro-computed tomography (CT) for the estimation of vascular, tissue, and air fractions in rodent lungs using a postreconstruction three material decomposition method. Using simulations, we have estimated the accuracy limits of the decomposition for realistic micro-CT noise levels. Next, we performed experiments involving ex vivo lung imaging in which intact rat lungs were carefully removed from the thorax, injected with an iodine-based contrast agent, and then inflated with different volumes of air (n = 2). Finally, we performed in vivo imaging studies in C57BL/6 mice (n = 5) using fast prospective respiratory gating in end inspiration and end expiration for three different levels of positive end expiratory pressure (PEEP). Before imaging, mice were injected with a liposomal blood pool contrast agent. The three-dimensional air, tissue, and blood fraction maps were computed and analyzed. The results indicate that separation and volume estimation of the three material components of the lungs are possible. The mean accuracy values for air, blood, and tissue were 93, 93, and 90%, respectively. The absolute accuracy in determining all fraction materials was 91.6%. The coefficient of variation was small (2.5%) indicating good repeatability. The minimum difference that we could detect in material fractions was 15%. As expected, an increase in PEEP levels for the living mouse resulted in statistically significant increases in air fractions at end expiration but no significant changes at end inspiration. Our method has applicability in preclinical pulmonary studies where changes in lung structure and gas volume as a result of lung injury, environmental exposures, or drug bioactivity would have important physiological implications.

Iron deficiency enhances cholesterol gallstone formation.

BACKGROUND: Cholesterol gallstones occur most commonly in multiparous women, but the causes for this phenomenon remain unclear. This same patient population is prone to chronic iron deficiency anemia. In addition, iron is known to play an important role in hepatic enzyme metabolism. Therefore, we tested the hypotheses that iron deficiency would alter hepatic cholesterol metabolism and enhance gallstone formation. METHODS: Forty adult prairie dogs were fed either a control iron-supplemented (200 ppm), an iron-deficient (8 ppm), a 0.4% cholesterol iron-supplemented (200 ppm), or a 0.4% cholesterol iron-deficient (8 ppm) diet. After 8 weeks gallbladder bile, serum, and liver were harvested. Gallbladder bile was examined for cholesterol crystals and gallstones. Bile lipids and hepatic enzymes were measured, and a cholesterol saturation index (CSI) was calculated. RESULTS: Animals receiving the iron-deficient diet were more likely to have cholesterol crystals in their bile than were animals on the control diet (80% vs. 20%; p < 0.05). Animals on the 0.4% cholesterol iron-deficient diet had more cholesterol crystals per high-powered field (79 +/- 10 vs. 49 +/- 9; p = 0.07), a higher molar % cholesterol (6.0 +/- 0.3 vs 4.4 +/- 0.5; p < 0.05), and a higher CSI (1.27 +/- 0.10 vs. 0.91 +/- 0.07; p < 0.05) compared to animals receiving the 0.4% cholesterol iron supplemented diet. The 7 alpha-hydroxylase levels were lower in the animals on the iron-deficient diet compared to those receiving the control diet (0.42 +/- 0.08 vs 1.17 +/- 0.40 pmol/mg per minute; p = 0.07). CONCLUSIONS: These data suggest that an iron-deficient diet (1) alters hepatic enzyme metabolism, which, in turn, (2) increases gallbladder bile cholesterol and promotes cholesterol crystal formation. We conclude that iron deficiency plays a previously unrecognized role in the pathogenesis of cholesterol gallstone formation in women.

An outbreak of food-borne enterotoxigenic Escherichia coli diarrhoea in England.

An outbreak of diarrhoea with abdominal pain occurred among members of the staff of a school and their guests after a social function at which a cold buffet was served. Sixty people attended the function and 43 subsequently completed questionnaires. Of these, 27 had diarrhoea. The median incubation period was 36 h and the range 12-66 h. Food history analysis showed an association between diarrhoea and eating curried turkey mayonnaise. Stool specimens from 13 of those who developed diarrhoea were examined: Escherichia coli 06.H16 (producing heat-stable and heat-labile enterotoxins) was found in nine specimens and E. coli 027.H20 (producing heat-stable enterotoxin) in 11 specimens. Eight patients had both strains and only one was negative for enterotoxigenic E. coli. Food samples were not available for examination. Enterotoxigenic E. coli should be considered as a possible cause in well-defined outbreaks of food-borne diarrhoea with abdominal pain.

Changing trends in the management of gallstone disease.

BACKGROUND: Day case cholecystectomy is increasingly becoming a management option for elective cases while "same admission" cholecystectomy is now considered a favorable option in the treatment of acute cholecystitis. To assess the advent of these changes in our surgical practice, a retrospective analysis of our experience is presented. METHODS: All patients undergoing cholecystectomy between January 2000 and January 2001 were analyzed according to admission status, operation type, conversion rate, complications, and nonsurgical intervention. RESULTS: 156 patients underwent cholecystectomy and 152 charts were retrieved. Laparoscopic cholecystectomy was performed on 95% of patients with a conversion rate of 9%. Morbidity for the series was 12.5%, including one common bile duct injury (0.6%). Day case and acute cholecystectomy comprised 67% of our cholecystectomy practice. CONCLUSIONS: Our findings suggest that there is an increasing trend toward shortening the hospital stay of patients undergoing laparoscopic cholecystectomy. This does not appear to have had a deleterious effect on outcome.

Surgical informatics on the Internet: any improvement?

PURPOSE: The Internet is a popular, but ungoverned, source of medical information. This study tracked the change in performance of commonly available search engines and the quality of medical data therein over a four-year period. METHODS: We compared the accuracy of information on a commonly performed surgical procedure (vasectomy) using six standard search engines in a four-year period and with two recently developed search engines. The top 25 ranked sites cited by each search engine were scored for description of the procedure, post-operative instructions, complications and unproven associations. RESULTS: There was no improvement in quality of individual sites over the study period. Additionally, the hit rate of search engines remained poor with 27 sites cited (40%) in 2002 either irrelevant or unavailable. DISCUSSION: Few useful sites with accurate information on surgical procedures are available on the Internet and simple search strategies fail to identify site quality or relevancy. CONCLUSION: At present, the Internet cannot be recommended as a reliable resource for many aspects of health information for patients. The onus is on health-care providers to provide high quality sites and direct patients to these sources of reliable information

Comparison of pentobarbital alone and pentobarbital in combination with lidocaine for euthanasia of dogs.

Pentobarbital alone, pentobarbital plus 1% lidocaine solution, pentobarbital plus 2% lidocaine solution, and pentobarbital plus 3% lidocaine solution were each used to euthanatize 6 dogs. For each dog, time between the beginning of injection of the euthanasia solution and each of the following events was recorded: collapse, onset of apnea, flat-line electrocardiogram, flat-line electroencephalogram, loss of palpable heartbeat, and loss of palpable pulse. Any signs of pain or discomfort were also recorded. There were no significant differences among groups except for time to flat-line electrocardiogram. Dogs euthanatized with pentobarbital alone had significantly longer times than did dogs euthanatized with pentobarbital in combination with any of the lidocaine concentrations. We concluded that pentobarbital in combination with lidocaine was a reasonable alternative to pentobarbital alone when euthanatizing dogs.

Lung imaging in rodents using dual energy micro-CT.

Dual energy CT imaging is expected to play a major role in the diagnostic arena as it provides material decomposition on an elemental basis. The purpose of this work is to investigate the use of dual energy micro-CT for the estimation of vascular, tissue, and air fractions in rodent lungs using a post-reconstruction three-material decomposition method. We have tested our method using both simulations and experimental work. Using simulations, we have estimated the accuracy limits of the decomposition for realistic micro-CT noise levels. Next, we performed experiments involving ex vivo lung imaging in which intact lungs were carefully removed from the thorax, were injected with an iodine-based contrast agent and inflated with air at different volume levels. Finally, we performed in vivo imaging studies in (n=5) C57BL/6 mice using fast prospective respiratory gating in end-inspiration and end-expiration for three different levels of positive end-expiratory pressure (PEEP). Prior to imaging, mice were injected with a liposomal blood pool contrast agent. The mean accuracy values were for Air (95.5%), Blood (96%), and Tissue (92.4%). The absolute accuracy in determining all fraction materials was 94.6%. The minimum difference that we could detect in material fractions was 15%. As expected, an increase in PEEP levels for the living mouse resulted in statistically significant increases in air fractions at end-expiration, but no significant changes in end-inspiration. Our method has applicability in preclinical pulmonary studies where various physiological changes can occur as a result of genetic changes, lung disease, or drug effects.

Investigations on X-ray luminescence CT for small animal imaging.

X-ray Luminescence CT (XLCT) is a hybrid imaging modality combining x-ray and optical imaging in which x-ray luminescent nanophosphors (NPs) are used as emissive imaging probes. NPs are easily excited using common CT energy x-ray beams, and the NP luminescence is efficiently collected using sensitive light based detection systems. XLCT can be recognized as a close analog to fluorescence diffuse optical tomography (FDOT). However, XLCT has remarkable advantages over FDOT due to the substantial excitation penetration depths provided by x-rays relative to laser light sources, long term photo-stability of NPs, and the ability to tune NP emission within the NIR spectral window. Since XCLT uses an x-ray pencil beam excitation, the emitted light can be measured and back-projected along the x-ray path during reconstruction, where the size of the X-ray pencil beam determines the resolution for XLCT. In addition, no background signal competes with NP luminescence (i.e., no auto fluorescence) in XLCT. Currently, no small animal XLCT system has been proposed or tested. This paper investigates an XLCT system built and integrated with a dual source micro-CT system. Two novel sampling paradigms that result in more efficient scanning are proposed and tested via simulations. Our preliminary experimental results in phantoms indicate that a basic CT-like reconstruction is able to recover a map of the NP locations and differences in NP concentrations. With the proposed dual source system and faster scanning approaches, XLCT has the potential to revolutionize molecular imaging in preclinical studies.

Phase-selective image reconstruction of the lungs in small animals using Micro-CT.

Gating in small animal imaging can compensate for artifacts due to physiological motion. This paper presents a strategy for sampling and image reconstruction in the rodent lung using micro-CT. The approach involves rapid sampling of free-breathing mice without any additional hardware to detect respiratory motion. The projection images are analyzed post-acquisition to derive a respiratory signal, which is used to provide weighting factors for each projection that favor a selected phase of the respiration (e.g. end-inspiration or end-expiration) for the reconstruction. Since the sampling cycle and the respiratory cycle are uncorrelated, the sets of projections corresponding to any of the selected respiratory phases do not have a regular angular distribution. This drastically affects the image quality of reconstructions based on simple filtered backprojection. To address this problem, we use an iterative reconstruction algorithm that combines the Simultaneous Algebraic Reconstruction Technique with Total Variation minimization (SART-TV). At each SART-TV iteration, backprojection is performed with a set of weighting factors that favor the desired respiratory phase. To reduce reconstruction time, the algorithm is implemented on a graphics processing unit. The performance of the proposed approach was investigated in simulations and in vivo scans of mice with primary lung cancers imaged with our in-house developed dual tube/detector micro-CT system. We note that if the ECG signal is acquired during sampling, the same approach could be used for phase-selective cardiac imaging.

Apolipoprotein(a) inhibits the conversion of Glu-plasminogen to Lys-plasminogen: a novel mechanism for lipoprotein(a)-mediated inhibition of plasminogen activation.

BACKGROUND: Elevated plasma concentrations of lipoprotein(a) [Lp(a)] are associated with an increased risk for thrombotic disorders. Lp(a) is a unique lipoprotein consisting of a low-density lipoprotein-like moiety covalently linked to apolipoprotein(a) [apo(a)], a homologue of the fibrinolytic proenzyme plasminogen. Several in vitro and in vivo studies have shown that Lp(a)/apo(a) can inhibit tissue-type plasminogen activator-mediated plasminogen activation on fibrin surfaces, although the mechanism of inhibition by apo(a) remains controversial. Essential to fibrin clot lysis are a number of plasmin-dependent positive feedback reactions that enhance the efficiency of plasminogen activation, including the plasmin-mediated conversion of Glu-plasminogen to Lys-plasminogen. OBJECTIVE: Using acid-urea gel electrophoresis to resolve the two forms of radiolabeled plasminogen, we determined whether apo(a) is able to inhibit Glu-plasminogen to Lys-plasminogen conversion. METHODS: The assays were performed in the absence or presence of different recombinant apo(a) species, including point mutants, deletion mutants and variants that represent greater than 90% of the known apo(a) isoform sizes. RESULTS: Apo(a) substantially suppressed Glu-plasminogen conversion. Critical roles were identified for the kringle IV types 5-9 and kringle V; contributory roles for sequences within the amino-terminal half of the molecule were also observed. Additionally, with the exception of the smallest naturally-occurring isoform of apo(a), isoform size was found not to contribute to the inhibitory capacity of apo(a). CONCLUSION: These findings underscore a novel contribution to the understanding of Lp(a)/apo(a)-mediated inhibition of plasminogen activation: the ability of the apo(a) component of Lp(a) to inhibit the key positive feedback step of plasmin-mediated Glu-plasminogen to Lys-plasminogen conversion.

The microbiological contamination of equipment processed by the HSDU.

The microbiological hazard to staff of used instruments and equipment when returned to the HSDU appears to be small providing reasonable precautions are taken (Parsons et al, 1985). Nevertheless, little evidence is available on the contamination of used equipment or the efficiency of cleaning and disinfection methods.

Effects of long-term lithium administration on renal structure and function in rats. A distinctive tubular lesion.

Because lithium salts are widely used for long-term therapy of affective disorders and have been recently implicated as a cause of tubulointerstitial renal disease, we have undertaken experiments designed to establish the site of the early and late pathologic lesions and to determine their correlation with the lithium-induced concentrating defect. Male Wistar rats given a semisynthetic diet that contained lithium carbonate, 90 mEq/kg dry weight, developed serum lithium levels in the human therapeutic range; pair-fed controls received sodium carbonate. Within 3 weeks, treated rats developed marked polyuria, with elevation of free water clearance and vasopressin-resistant diabetes insipidus. Early morphologic changes were confined to the cortical collecting tubules and, possibly, contiguous portions of distal tubules. The tubules were dilated and irregularly lined with cells that had bulging or thinned basophilic cytoplasm, enlarged nuclei, sometimes basal vacuolization, and a few mitoses. These changes were evident at 3 weeks and progressed through the end of the observation period at 18 weeks. The proliferative component of the lesion was demonstrated by the finding of a significant and specific increase in 3H-thymidine uptake by nuclei of collecting/distal tubules of lithium-treated rats. The lesion, but not the increased thymidine uptake, extended into the medullary collecting ducts at 9 and 18 weeks. Although occasional intratubular mononuclear cells were seen at 9 and 18 weeks, no interstitial inflammation or fibrosis was seen. These tubular epithelial lesions were not seen in the kidneys of Brattleboro rats or glucose-treated Wistar rats despite comparable polyuria. We suggest that this early, persistent, and reproducible lesion, characterized by reactive and proliferating tubular cells in the cortical collecting tubules, predisposes the kidney to injury from otherwise mild or insignificant insults and may explain the sporadic occurrence of serious tubulointerstitial disease in patients on long-term lithium therapy.

Evaluation of commercially available preservatives for laboratory detection of helminths and protozoa in human fecal specimens.

Formalin and mercuric chloride-based low-viscosity polyvinyl alcohol (LV-PVA) are widely used by most diagnostic parasitology laboratories for preservation of helminth eggs and protozoan cysts and trophozoites in fecal specimens. Concerns about the toxicity of formalin and the difficulty of disposal of LV-PVA are powerful incentives to use alternate preservatives. Such alternatives have been marketed by several companies and are often presented as one-vial, non-mercuric chloride fixatives that aim at performing the same role as formalin and PVA combined. We compared five, one-vial commercial preservatives, two from Meridian Diagnostics, Inc. (Ecofix and sodium acetate-acetic acid-formalin), and one each from Scientific Device Laboratories, Inc. (Parasafe), Alpha Tec Systems, Inc. (Proto-fix), and Streck Laboratories, Inc. (STF), with 10% formalin and LV-PVA. Fecal specimens obtained from patients in a Brazilian hospital were aliquoted within 12 h of collection into the seven preservatives mentioned above and were processed after 1 month at the Centers for Disease Control and Prevention. Direct and concentrated permanent smears as well as concentrates for 20 positive specimens (a total of 259 processed samples) were prepared, stained according to the manufacturers' instructions, examined, and graded. Positive specimens contained one or more parasites with stages consisting of eggs, larvae, cysts, and a few trophozoites of Giardia intestinalis. Criteria for assessment of the preservatives included the quality of the diagnostic characteristics of helminth eggs, protozoan cysts, and trophozoites, ease of use, and cost. Acceptable alternatives to formalin for wet preparations were found. Ecofix was found to be comparable to the traditional "gold standard" LV-PVA for the visualization of protozoa in permanent stained smears. This study suggests that more acceptable alternatives to the traditional formalin and LV-PVA exist.