Ethnic differences in success at application for consultant posts among United Kingdom physicians from 2011 to 2019: a retrospective cross-sectional observational study

OBJECTIVES

To identify associations between success following application for consultant physician posts and demographic factors.

DESIGN

Logistic regression analysis of nationwide survey data.

SETTING

United Kingdom (UK) physicians with a recent certificate of completion of training (CCT).

PARTICIPANTS

All UK trainee physicians who received a CCT between 2010 and 2019 were surveyed. Respondents were excluded if they had not applied for a consultant post or if application data were incomplete.

MAIN OUTCOME MEASURES

The primary outcome measure was success over the entire consultant application process, i.e. shortlisted and offered the post following the first application. Secondary outcomes were: shortlisted following first application and offered a consultant post at first interview.

RESULTS

From 7037 CCT holders surveyed, 50.7% responded. While 1198 (59.7%) respondents were white, 760 (37.9%) were from minority ethnic groups and 50 (3.5%) were of unknown ethnicity. Primary medical qualification (PMQ) country was the UK in 75.3% (n = 1512). On multivariable logistic regression analysis the independent negative associations with success were: minority ethnicity (odds ratio [OR] 0.55, 95% confidence interval [CI] 0.43-0.71); p < 0.001) vs. white; PMQ from Europe (OR 0.47, 95% CI 0.28-0.79; p = 0.004) or Asia (OR 0.68, 95% CI 0.49-0.96; p = 0.027) vs. UK PMQ; year of CCT 2012 (OR 0.40, 95% CI 0.24-0.68; p = 0.001), 2013 (OR 0.39, 95% CI 0.23-0.65; p < 0.001), and 2014 (OR 0.26, 95% CI 0.15-0.43; p < 0.001) vs. 2019. Specialties associated with lower success rates included Cardiology, Endocrinology, Genitourinary medicine, Palliative care, Renal and Respiratory, compared to Acute medicine.

CONCLUSIONS

Minority ethnic group candidates for consultant physician posts had lower success rates compared to white candidates after correction for important variables including specialty, time from and country of PMQ. This finding requires further evaluation to identify the causes for this variation.

Constraining Ion-Scale Heating and Spectral Energy Transfer in Observations of Plasma Turbulence

We perform a statistical study of the turbulent power spectrum at inertial and kinetic scales observed during the first perihelion encounter of the Parker Solar Probe. We find that often there is an extremely steep scaling range of the power spectrum just above the ion-kinetic scales, similar to prior observations at 1 A.U., with a power-law index of around -4. Based on our measurements, we demonstrate that either a significant (>50%) fraction of the total turbulent energy flux is dissipated in this range of scales, or the characteristic nonlinear interaction time of the turbulence decreases dramatically from the expectation based solely on the dispersive nature of nonlinearly interacting kinetic Alfvén waves.

Animal industry and veterinary science in eastern New Guinea: World War II to Independence, 1975

We have described the efforts of the Australian administration of the Territory of Papua and New Guinea (TPNG) to establish a veterinary service and viable animal industries. These efforts began with planning before the end of World War II in 1945 and continued until independence in 1975. Whereas pre-war cattle had mostly been used to control grass on plantations, post-war, the objective was to use the country's extensive, unoccupied grasslands for cattle production. During this period, the cattle population increased from 4000 to more than 150,000. The greatest success was achieved in herds with crosses of Bos indicus and Bos taurus owned by expatriates. The only serious disease constraint on production was myiasis due to Chrysomya bezziana, a parasite throughout New Guinea and South-east Asia. Attempts were made to increase the productivity of the indigenous pig population. Success was limited by a failure to manage inadequate nutrition and internal parasites and to fully understand the cultural aspects of pig ownership. Similar problems inhibited chicken production in villages. The serious viral infections of pigs and birds were absent from TPNG, but a border with Indonesian Papua represents a potential route for the incursion of animal diseases exotic to both Papua New Guinea and to Australia.

Quantification of Trichoderma afroharzianum, Trichoderma harzianum and Trichoderma gamsii inoculants in soil, the wheat rhizosphere and in planta suppression of the crown rot pathogen Fusarium pseudograminearum

AIMS

Develop quantitative assays (qPCR) to determine the detection threshold limits, colonization and persistence of Trichoderma gamsii, Trichoderma afroharzianum and T. harzianum inoculants in cropping soils, the wheat rhizosphere and their in planta suppressive efficacy against the crown rot pathogen Fusarium pseudograminearum.

METHODS AND RESULTS

Trichoderma qPCR primers were designed from the internal transcribed spacer region of 5.8S rDNA and from sequences of DNA fragments diagnostic for each inoculant genotype. The minimum detection thresholds of qPCR assays varied between 1 × 10³ (log 3) and 8 × 10⁴ (log 4·9) conidia (genome) equivalents per gram of soil for multi- and single-copy target sequences, respectively and were independent of soil type. There was a strong correlation (r > 0·974) between culture-dependent and culture-independent (qPCR) quantification methods. In wheat bioassays, Trichoderma inoculants colonized rhizosphere soils and wheat roots at 56-112 days postemergence to a depth of 20 cm but were more abundant (P < 0·001) at 0-10 cm root depth, means ranging from 2 × 10² (log 2·3) to 4 × 10⁵ (log 5·6) conidia equivalents per gram of rhizosphere soil or root tissue. Inoculants reduced (P < 0·001) F. pseudograminearum biomass in wheat crown and root tissue by up to 5754-fold and increased (P = 0·008) plant biomass, relative to the pathogen control.

CONCLUSIONS

The qPCR assays provided sensitive and accurate assessment of wheat root and rhizosphere soil colonization of Trichoderma inoculants. Strains persisted through to grain maturity at levels shown to significantly suppress F. pseudograminearum in planta.

SIGNIFICANCE AND IMPACT OF THE STUDY

The qPCR assays developed here were used to determine the wheat rhizosphere dynamics of T. harzianum, T. afroharzianum and T. gamsii inoculants and their suppressive efficacy against F. pseudograminearum in planta. These assays can be applied to monitor inoculant dynamics in suppressing crown rot and other wheat root diseases in the field.

Randomized controlled study of the prediction of diminutive/small colorectal polyp histology using didactic versus computer-based self-learning module in gastroenterology trainees

BACKGROUND AND AIM

The aim of this randomized trial was to evaluate the performance of self-training versus didactic training in order to increase the diagnostic accuracy of diminutive/small colonic polyp histological prediction by trainees.

METHODS

Sixteen trainees reviewed 78 videos (48 iSCAN-OE and 30 NBI) of diminutive/small polyps in a pretraining assessment. Trainees were randomized to receive computer-based self-learning (n = 8) or didactic training (n = 8) using identical teaching materials and videos. The same 78 videos, in a different randomized order, were assessed. The NICE (NBI International Colorectal Endoscopic) and SIMPLE (Simplified Identification Method for Polyp Labeling during Endoscopy) classification systems were used to classify diminutive/small polyps.

RESULTS

A higher proportion of high-confidence predictions of polyps was made by the self-training group versus the didactic group using both the SIMPLE classification (77.1% [95% CI 73.4-80.3] vs 69.9% [95% CI 66.1-73.5%] [P = 0.005]) and the NICE classification (77% [95% CI 73.2-80.4%] vs 69.8% [95% CI 66-73.4%] [P = 0.006]). When using NICE, sensitivity of the self-training group compared with the didactic group was 72% versus 83% (P = 0.0005), and the accuracy was 66.1% versus 69.1%. The training improved the confidence of participants and SIMPLE was preferred over NICE.

CONCLUSION

Self-learning for the prediction of diminutive/small polyp histology is a method of training that can achieve results similar to didactic training. Availability of adequate self-learning teaching modules could enable widespread implementation of optical diagnosis in clinical practice.

The FIELDS Instrument Suite for Solar Probe Plus: Measuring the Coronal Plasma and Magnetic Field, Plasma Waves and Turbulence, and Radio Signatures of Solar Transients

NASA's Solar Probe Plus (SPP) mission will make the first in situ measurements of the solar corona and the birthplace of the solar wind. The FIELDS instrument suite on SPP will make direct measurements of electric and magnetic fields, the properties of in situ plasma waves, electron density and temperature profiles, and interplanetary radio emissions, amongst other things. Here, we describe the scientific objectives targeted by the SPP/FIELDS instrument, the instrument design itself, and the instrument concept of operations and planned data products.

Peer-led training and assessment in basic life support for healthcare students: synthesis of literature review and fifteen years practical experience

BACKGROUND

In 1995, the University of Birmingham, UK, School of Medicine and Dentistry replaced lecture-based basic life support (BLS) teaching with a peer-led, practical programme. We present our 15-yr experience of peer-led healthcare undergraduate training and examination with a literature review.

METHODS

A literature review of healthcare undergraduate peer-led practical skills teaching was performed though Pubmed. The development of the Birmingham course is described, from its inception in 1995-2011. Training methods include peer-led training and assessment by senior students who complete an European Resuscitation Council-endorsed instructor course. Student assessors additionally undergo training in assessment and communication skills. The course has been developed by parallel research evaluation and peer-reviewed publication. Course administration is by an experienced student committee with senior clinician support. Anonymous feedback from the most recent courses and the current annual pass rates are reported.

RESULTS

The literature review identified 369 publications of which 28 met our criteria for inclusion. Largely descriptive, these are highly positive about peer involvement in practical skills teaching using similar, albeit smaller, courses to that described below. Currently approximately 600 first year healthcare undergraduates complete the Birmingham course; participant numbers increase annually. Successful completion is mandatory for students to proceed to the second year of studies. First attempt pass rate is 86%, and close to 100% (565/566 students, 99.8%) following re-assessment the same day. 97% of participants enjoyed the course, 99% preferred peer-tutors to clinicians, 99% perceived teaching quality as "good" or "excellent", and felt they had sufficient practice. Course organisation was rated "good" or "excellent" by 91%. Each year 3-4 student projects have been published or presented internationally. The annual cost of providing the course is currently £15,594.70 (Eur 18,410), or approximately £26 (Eur 30) per student.

CONCLUSIONS

This large scale, peer-led BLS course demonstrates that such programmes can have excellent outcomes with outstanding participant satisfaction. Peer-tutors and assessors are competent, more available and less costly than clinical staff. Student instructors develop skills in teaching, assessment and appraisal, organisation and research. Sustainability is possible given succession-planning and consistent leadership.

Measurement of the airway surface liquid volume with simple light refraction microscopy

In the cystic fibrosis (CF) lung, the airway surface liquid (ASL) volume is depleted, impairing mucus clearance from the lung and leading to chronic airway infection and obstruction. Several therapeutics have been developed that aim to restore normal airway surface hydration to the CF airway, yet preclinical evaluation of these agents is hindered by the paucity of methods available to directly measure the ASL. Therefore, we sought to develop a straightforward approach to measure the ASL volume that would serve as the basis for a standardized method to assess mucosal hydration using readily available resources. Primary human bronchial epithelial (HBE) cells cultured at an air-liquid interface develop a liquid meniscus at the edge of the culture. We hypothesized that the size of the fluid meniscus is determined by the ASL volume, and could be measured as an index of the epithelial surface hydration status. A simple method was developed to measure the volume of fluid present in meniscus by imaging the refraction of light at the ASL interface with the culture wall using low-magnification microscopy. Using this method, we found that primary CF HBE cells had a reduced ASL volume compared with non-CF HBE cells, and that known modulators of ASL volume caused the predicted responses. Thus, we have demonstrated that this method can detect physiologically relevant changes in the ASL volume, and propose that this novel approach may be used to rapidly assess the effects of airway hydration therapies in high-throughput screening assays.

Acute regulation of the epithelial sodium channel in airway epithelia by proteases and trafficking

Effective clearance of inhaled pathogens is the primary innate defense mechanism in the lung, and requires the maintenance of a proper airway surface liquid (ASL) volume to facilitate ciliary beat and optimize mucociliary clearance. Na(+) absorption via the epithelial sodium channel (ENaC) is tightly regulated and, together with chloride movement, provides the optimal osmotic gradients to absorb excessive fluid in the airway lumen while preventing excessive ASL dehydration, which would compromise mucus clearance from the lung. To absorb excessive fluid from the luminal surface, a local mechanism of ENaC activation allows for an increase in Na(+) absorption at times when the ASL volume is expanded. To help define these regulatory mechanisms, we examined the effects of ASL volume expansion on ENaC activity in primary human bronchial epithelial (HBE) cell cultures. We found that ENaC activity increases dramatically after rapid dilution of endogenous ASL. Approximately 35% of the increase in Na(+) absorption was attributable to activation of ENaC by proteases. The remainder of the increase in Na(+) current was prevented when membrane trafficking was disrupted with brefeldin A, nocodazole, or myosin light chain kinase inhibitors, demonstrating that trafficking is involved with ENaC regulation in the airway. These findings demonstrate that Na(+) absorption in the airway is acutely modulated by the coordinated trafficking of channels to the luminal surface and by the proteolytic activation of ENaC in response to ASL volume expansion.

Safety and immunogenicity profile of the concomitant administration of ZOSTAVAX and inactivated influenza vaccine in adults aged 50 and older

OBJECTIVES

To evaluate the safety and immunogenicity of ZOSTAVAX administered concomitantly with inactivated influenza vaccine or sequentially in adults aged 50 and older.

DESIGN

Randomized, blinded, placebo-controlled study.

SETTING

Thirteen U.S. and seven European study sites.

PARTICIPANTS

Three hundred eighty-two concomitantly, 380 sequentially vaccinated subjects.

INTERVENTION

The concomitant vaccination group received influenza vaccine and ZOSTAVAX at separate injection sites on Day 1 and placebo at Week 4. The nonconcomitant vaccination group received influenza vaccine and placebo at separate injection sites on Day 1 and ZOSTAVAX at Week 4.

MEASUREMENTS

Primary safety endpoints: vaccine-related serious adverse experiences (AEs) within 28 days postvaccination (PV); and diary card-prompted local and systemic AEs. Primary immunogenicity endpoints: geometric mean titer (GMT) and geometric mean fold rise (GMFR) from baseline of varicella-zoster virus (VZV) antibody (Ab) at 4 weeks PV according to glycoprotein enzyme-linked immunosorbent assay (gpELISA) and GMT of influenza Ab for the three vaccine strains (2005-2006 influenza season) at 4 weeks PV according to hemagglutination inhibition assay. Secondary immunogenicity endpoint: influenza seroconversion rates (SCRs).

RESULTS

No serious AEs related to ZOSTAVAX were observed during the study. VZV Ab GMTs 4 weeks PV for the concomitant and sequential groups were 554 and 597 gpELISA U/mL, respectively. The estimated VZV Ab GMT ratio was 0.9 (95% confidence interval (CI)=0.8-1.0), indicating noninferior (P<.001 for the null hypothesis of GMT ratio <0.67) responses. Estimated VZV Ab GMFR from baseline in the concomitant group was 2.1 (95% CI=2.0-2.3), indicating acceptable fold rise. Estimated GMT ratios (concomitant/sequential) for influenza strains A(H1N1), A(H3N2), and B were 0.9 (95% CI=0.8-1.1), 1.1 (95% CI=0.9-1.3), and 0.9 (95% CI=0.8-1.1), respectively, and SCRs were comparable across both groups, with more than 85% achieving titers of 1:40 or greater, meeting regulatory criteria.

CONCLUSION

ZOSTAVAX and influenza vaccine given concomitantly are generally well tolerated in adults aged 50 and older. Ab responses were similar whether ZOSTAVAX and influenza vaccine were given concomitantly or sequentially.

The effect of Penicillium fungi on plant growth and phosphorus mobilization in neutral to alkaline soils from southern Australia

The phosphate solubilizing fungi Penicillium radicum, Penicillium bilaiae (strain RS7B-SD1), and an unidentified Penicillium sp. designated strain KC6-W2 were tested for their ability to increase the growth and phosphorus (P) nutrition of wheat, medic, and lentil in three soils of neutral to alkaline pH reaction. The strongest plant growth promoting (PGP) strain was Penicillium sp. KC6-W2, which stimulated significant increases in shoot growth and dry mass in seven of the nine experiments conducted. Levels of PGP by Penicillium sp. KC6-W2 ranged from 6.6% to 19% and were associated with increased uptake of P to the shoot. The PGP properties of Penicillium sp. KC6-W2 were evident on each of the three different plant species and soil types, a level of reliability not observed in other strains tested. Inoculation of seed with P. radicum increased lentil growth by 5.5% (P < 0.05) in soil from Tarlee but did not affect plant growth in the eight other experiments. Inoculation of plant seed with P. bilaiae RS7B-SD1 resulted in significant PGP in two of the nine experiments conducted. However, when significant, stimulation of PGP by P. bilaiae RS7B-SD1 was strong and resulted in increases in medic dry matter (19%) and lentil shoot dry matter (15%). A soil microcosm experiment investigated the effect of Penicillium fungi on cycling of soil P. Penicillium bilaiae RS7B-SD1 was the only fungus to significantly increase HCO3-extractable P (23% increase; P < 0.05). Production of phosphatase enzymes was not associated with increased HCO3-extractable P. Addition of carbon in the form of ryegrass seed significantly increased microbial respiration and movement of P to the microbial biomass (P < 0.05), but these parameters were irrespective of Penicillium treatment. This work has established the potential for use of Penicillium inoculants to increase plant growth on alkaline soils in Australia. The role of Penicillium fungi in plant P uptake and soil P cycling requires further exploration.

Navigator motion correction of diffusion weighted 3D SSFP imaging

Diffusion weighted (DW) 3D steady state MR (SSFP) head imaging technique using navigator echo's motion correction is presented. This new scheme enables acquisition of DW images even at regions where severe susceptibility is present. Another advantage is the moderate gradient performance requirements. DW imaging methods are sensitive to any kind of motion, thus, most of these methods might suffer from bulk motion artifacts. The common solution to avoid motion artifacts in a 2D DW SSFP acquisition is multi averaging. To avoid the time consuming multi averaging, the new scheme, described here, utilizes navigator echo's motion correction to remove respiratory bulk motion artifacts. At some brain regions, where the motion is governed by blood or CSF pulsation, the navigator motion correction fails. At these regions the correction is an interpolation of corrections from regions where the motion is particularly of the respiratory type. The combination of a 3D sequence with a navigator echo motion correction, enables acquisition of 10 DW slices within a time of 0:50-2:30 min.

Genetic diversity and biological control activity of novel species of closely related pseudomonads isolated from wheat field soils in South Australia

Rhizobacteria closely related to two recently described species of pseudomonads, Pseudomonas brassicacearum and Pseudomonas thivervalensis, were isolated from two geographically distinct wheat field soils in South Australia. Isolation was undertaken by either selective plating or immunotrapping utilizing a polyclonal antibody raised against P. brassicacearum. A subset of 42 isolates were characterized by amplified 16S ribosomal DNA restriction analysis (ARDRA), BIOLOG analysis, and gas chromatography-fatty acid methyl ester (GC-FAME) analysis and separated into closely related phenetic groups. More than 75% of isolates tested by ARDRA were found to have >95% similarity to either Pseudomonas corrugata or P. brassicacearum-P. thivervalensis type strains, and all isolates had >90% similarity to either type strain. BIOLOG and GC-FAME clustering showed a >70% match to ARDRA profiles. Strains representing different ARDRA groups were tested in two soil types for biological control activity against the soilborne plant pathogen Gaeumannomyces graminis var. tritici, the causative agent of take-all of wheat and barley. Three isolates out of 11 significantly reduced take-all-induced root lesions on wheat plants grown in a red-brown earth soil. Only one strain, K208, was consistent in reducing disease symptoms in both the acidic red-brown earth and a calcareous sandy loam. Results from this study indicate that P. brassicacearum and P. thivervalensis are present in Australian soils and that a level of genetic diversity exists within these two novel species but that this diversity does not appear to be related to geographic distribution. The result of the glasshouse pot trial suggests that some isolates of these species may have potential as biological control agents for plant disease.

A keyhole echo planar hybrid imaging technique

A hybrid keyhole imaging method is presented which demonstrates the combination of two distinctly different MR imaging techniques. In this work single shot EPI was used as a dynamic update scan for a conventional high resolution gradient echo acquisition. Problems associated with the integration of MR data from distinctly different imaging techniques are addressed. Illustration is provided by way of diffusion weighted imaging. This novel development requires further investigation which need not be limited to the hybridization of strictly Cartesian based scanning methods.

Rapid iterative reconstruction for echo planar imaging

A rapid automated method for reconstructing echo planar imaging (EPI) data has been developed and is shown to improve image quality by suppressing the troublesome ghost artifact. The algorithm can be applied without prior knowledge obtained from either reference scans or operator intervention. It first estimates, then improves iteratively, the parameters for a linear phase correction applied directly to the complex image data derived from odd and even echoes. The theory used to derive the criteria employed in the iteration provides insight into mechanisms that allow the process to work. Magn Reson Med 42:541-547, 1999.

Modular gradient coil: A new concept in high-performance whole-body gradient coil design

A new concept in high-performance MR gradient coil design is presented which we have called the Modular Gradient Coil (MGC). This novel design approach results in an actively shielded whole-body gradient coil containing multiple and independent elements, integrated onto a single former, for generating gradient fields along each of the three axes (x, y, and z). These elements can be energized in a number of configurations, using a single gradient power supply unit (PSU), to generate a whole range of gradient performance levels. The design criteria for the MGC also include a requirement to prohibit peripheral nerve stimulation in all of its modes of operation. This requirement is achieved, while simultaneously providing high performance, by specifying different volumes of gradient linearity for each of the operating modes. Magn Reson Med 42:561-570, 1999.

The modular (twin) gradient coil--high resolution, high contrast, diffusion weighted EPI at 1.0 Tesla

The modular (twin) gradient coil is a novel and effective approach to obtaining flexible and high power gradient performance without (i) peripheral nerve stimulation and (ii) the need for resonant or expensive high voltage gradient power supply units (PSU). This whole-body gradient system contains, on the same former, two independent sets of gradient coils, the conventional coil set and the short-body coil set. Each gradient axis is able to operate, independently, in any one of three modes. The third, combined, mode is realized by connecting the conventional coils and short-body coils in series. Through careful design of the shape and size of the linear volume of each mode of operation, the modular gradient coil is able to utilize the power, from a single gradient PSU, more efficiently and more appropriately, as determined by the application. In the short-body and combined modes the gradient fields are linear over a volume suitable for whole head/neck, liver and cardiovascular applications. In the conventional mode, a reduced performance is possible but over a much larger (conventional) imaging volume. Utilizing a semi-conductor switching arrangement it is possible to switch between modes in as little as 1 ms. By mixing different modes of operation on different gradient axes it is possible to utilize more efficiently, and safely, the properties of gradient performance best suited to the sequence requirements. Diffusion weighted EPI (DW-EPI) is a particular technique that demands the extremes of gradient system performance in terms of both amplitude and slew rate. DW-EPI has been implemented, using the modular gradient system, on a 1.0 Tesla whole-body MRI system. The preliminary results presented here serve to illustrate the advantages of the modular gradient coil in of itself as well as the direct benefits it provides for DW imaging at 1.0 Tesla.

Accumulation of unconjugated bilirubin in cholesterol pellets implanted in swine gallbladders

BACKGROUND & AIMS

Most cholesterol gallstones have a pigmented center, but it is unclear whether its presence is primary or secondary. This study was performed to determine if bilirubin would accumulate in a gallstone model consisting of cholesterol pellets.

METHODS

Cholesterol was compressed into pellets at 2500 psi, producing a pellet that behaved like human cholesterol gallstones in regard to penetration of solutes into the stone. Pellets were implanted into gallbladders of pigs and harvested after 4 weeks. Bilirubin species were measured by high-performance liquid chromatography.

RESULTS

The proportions of bilirubin species in bile were not changed by the presence of pellets, i.e., diconjugates (mean +/- SD, 1.9% +/- 1.0% vs. 0.7% +/- 0.8%), monoconjugates (83.8% +/- 5.5% vs. 87.8% +/- 6.6%), and unconjugated bilirubin (14.2% +/- 5.3% vs. 11.5% +/- 5.6%) were similar at the time of implantation and removal. The cut surfaces of the pellets were pigmented. Pellets contained 5.46 +/- 1.38 micrograms bilirubin/g sample at harvesting, and 98.6% +/- 2.3% of bilirubin in pellets was unconjugated. In in vitro studies, there was a large increase in unconjugated bilirubin in the bile. Pellets also became pigmented in vitro, but there was considerable variability in the bilirubin species present in the pellets.

CONCLUSIONS

Unconjugated bilirubin accumulates in cholesterol pellets and pigments them. This provides a mechanism by which cholesterol gallstones could become secondarily pigmented.

Echo-volumar imaging (EVI) at 0.5 T: first whole-body volunteer studies

Improvements in the echo-volumar imaging (EVI) technique and its application in whole-body studies are described. Using an in-house built 0.5 T echo-planar imaging system, complete modulus three-dimensional image data are acquired in 102 ms with real-time display. Hardware limitations have restricted the maximum array size achievable to 64 x 32 x 8 voxels. Representative voxel dimensions are x = 6.0 mm; y = 4.0 mm, and z = 10.0 mm. Results on human volunteers are presented, showing cardiac, liver, and bladder images. Also shown are the first EVI gastric filling and emptying results.

The influence of prostaglandin E1 on platelet adherence and injury in preserved rat liver allografts

We have previously shown that part of the injury sustained by cold-preserved livers on reperfusion is the consequence of platelet adhesion to sinusoidal endothelium. The purpose of the present study was to determine whether prostaglandin E1 (PGE1) can reduce the injury and if so, how to maximize this beneficial effect. Rat livers were cold-preserved in University of Wisconsin solution for 30 hours then subjected to 1-hour warm ischemia after which they were reperfused at 37 degrees C with oxygenated Krebs-Henseleit solution with or without isolated platelets. PGE1 was used to treat the donor liver during harvesting, cold preservation, and reperfusion. In some studies, PGE1 was used to pretreat platelets before exposing them to the liver, and in other studies, both liver and platelets were treated. Pretreatment of platelets with paraformaldehyde, which inactivates them, or ADP, which activates them, was also studied. Treatment of livers with PGE1 significantly decreased preservation injury when livers were reperfused in the absence of platelets. However, when platelets were added to the perfusate, prior treatment of the liver with PGE1 had relatively minor beneficial effects. Pretreatment of platelets alone with PGE1 was also beneficial, but again the effect was small. However, when both liver and platelets were treated with PGE1 there was a highly significant decrease in the extent of liver injury and platelet adhesion. Perfusate transaminase levels were lower, bile flow was improved, and histologically, livers appeared less injured. Pretreatment of platelets with paraformaldehyde produced similar results to pretreatment with PGE1. When platelets were preactivated with adenosine diphosphate, extensive hepatic injury occurred upon reperfusion despite PGE1 treatment of the liver. PGE1 can lessen preservation-reperfusion injury impressively when administered to both liver and platelets but has little effect when platelets have been preactivated.

Cholesterol microcrystals associated with concanavalin A-binding glycoproteins contribute artifactually to nucleating activity assays

Concanavalin A (Con A) affinity chromatography is the standard procedure to separate cholesterol nucleating biliary proteins from lipids and pigment. We observed that even after extensive washing following application of bile, lipid contaminants remain. We have determined the contribution of lipid contamination to cholesterol nucleation and assessed a modified procedure to remove lipids from the column. Human gallbladder bile was spiked with [3H]cholesterol and [14C]phospholipid and applied to two sets of Con A-Sepharose columns. One column was washed in the usual manner with Tris-HCl buffer and the other with buffer containing 10 mM taurocholate prior to eluting bound glycoproteins with alpha-D-methylmannopyranoside. Eluted proteins were added to heated abnormal bile at a final concentration of 250 micrograms/ml to study the effect on cholesterol nucleation. A separate aliquot (20 microliter) of the protein solutions was counted for radioactivity. Cholesterol nucleating activity was less in samples from columns washed with 10 mM taurocholate than in samples from columns not washed with the bile salt. Lipid radioactivity was associated with Con A-binding proteins prepared without taurocholate, but not in those prepared with taurocholate wash. Light microscopy revealed the presence of cholesterol microcrystals and vesicles in some Con A-binding protein preparations prepared without a taurocholate wash. However, pellets from ultracentrifuged Con A preparations prepared without a bile salt wash revealed cholesterol crystals in all samples (n = 6). Washing with taurocholate did not affect recovery of protein mass and appearance of bands on SDS-PAGE gel showed an identical pattern in the two groups. This modified procedure to prepare potential nucleating proteins from gallbladder bile should eliminate erroneous results that may arise due to lipid contamination.

A rapid, simple high capacity cholesterol crystal growth assay

Cholesterol crystal "nucleation time", more recently referred to as cholesterol crystal observation time, is defined as the first appearance of cholesterol crystals from isotropic crystal-free biles on light microscopy. This test is used to assess the potency of nucleating agents. Crystal appearance has conventionally been determined by polarizing light microscopy and crystal growth by counting the number of crystals. In this study we adapted a spectrophotometric method to a microtiter plate reader to generate cholesterol crystal growth curves. Model biles were prepared with a cholesterol saturation of 1.2 to 1.3 and total lipid concentration of 10.7 g/dl (taurocholate, 125 mM; cholesterol, 16.8-18.4 mM; phospholipid, 43 mM). Pronucleating IgM samples were used to establish and validate the assay. Cholesterol crystal growth curves were generated by reading absorption at 630 nm daily on a Dynatech microplate reader. Results were correlated to cholesterol crystal counts as determined by polarizing light microscopy. Standard curves generated from absorbencies of known masses of cholesterol crystals were used to quantify the mass of cholesterol crystals formed over the observation period. The assay was applied to known pronucleating biliary immunoglobulins. Results obtained were similar to our previous report that biliary IgM is more potent than biliary IgG. We conclude that using microplates and a microtiter plate reader provides a rapid high capacity method for detecting cholesterol crystal growth to assess potential nucleating agents in nucleation assays.

Evidence of preservation injury to bile ducts by bile salts in the pig and its prevention by infusions of hydrophilic bile salts

Preservation injury to bile ducts is a serious problem in liver transplantation, especially when preservation exceeds 12 hours. The authors hypothesized that the injury was caused by contact of bile ducts with bile salts during cold preservation and might be preventable by infusion of more hydrophilic bile salts. Swine livers were harvested after intraportal infusions of saline (control), of the hydrophobic bile salt taurodeoxycholate, or of the hydrophilic bile salts tauroursodeoxycholate or dehydrocholate. The effect of infusing a combination of hydrophilic and hydrophobic bile acids was also studied. Bile samples were taken before and during the infusions. Then livers were perfused with UW solution, ducts were flushed retrograde with UW, and livers were stored at 0 to 1 degree C for 20 hours. Bile ducts were harvested after preservation, and coded microscopic slides of the specimens were examined by light microscopy. There was large variability in baseline bile salt concentration. Injury after preservation consisted of sloughing and pyknosis of surface and glandular epithelium. The histologic injury score determined after preservation was directly related to bile salt concentration in bile ducts at the time of flushing. During bile salt infusions, the infused bile salt replaced most or all of the other bile salts present in bile. Severe postpreservation injury of intrahepatic ducts occurred after taurodeoxycholate infusions, but injury was minimal when either of the two hydrophilic bile salts was infused. The mixture of bile acids produced intermediate results. Retrograde flushing with UW does not prevent injury to intrahepatic ducts. The authors conclude that the injury is caused by contact with bile salts, is dependent on bile salt concentration and composition, and is preventable.

Active acoustic screening: reduction of noise in gradient coils by Lorentz force balancing

We have designed and constructed a quiet gradient set with restricted access for the combined purposes of evaluating the principles of active acoustic screening, recently introduced by Mansfield, Glover, and Bowtell, and for EPI studies of the head at 3.0 T. The design utilizes the return paths of the conductors in a closed arc loop arrangement to eliminate net Lorentz forces thereby attenuating acoustic noise especially at low frequency. This design should significantly reduce the dangers to patients of high noise levels, especially in high field magnetic resonance imaging systems.

Effect of deoxycholate on immunoglobulin G concentration in bile: studies in humans and pigs

Because an increase in biliary deoxycholate levels seems to be a risk factor for cholesterol gallstone formation, we determined the relationship between deoxycholate levels and levels of the pronucleating protein, immunoglobulin G (Ig) in human gallbladder bile. Patients with cholesterol gallstones had a higher concentration of biliary IgG compared with a pigmented stone group and control patients. This was associated with the simultaneous presence of two conditions in the cholesterol stone group, supersaturated bile and a high deoxycholate/cholate ratio. The other patient groups met only one of the two conditions. Next, animal studies were performed to determine if model biles mimicking the two conditions could affect IgG secretion by the gallbladder. Gallbladders were exposed in vivo and then in an Ussing chamber to model biles. The voltage clamp technique was used to monitor functional integrity of the preparation. Three different model biles were tested: (1) taurodeoxycholate (TDC), 80%; taurocholate (TC), 20%; and cholesterol saturation index (CSI), 1.2; (2) TDC, 20%; TC, 80%; and CSI, 1.2; and (3) TDC, 80%; TC, 20%; and CSI, 0.6. IgG concentrations became significantly higher in group 1 than in the other two groups. The concentration of mucous glycoprotein was also significantly greater in group 1 when compared with group 2. Plasma cells were increased in number in mucosal and submucosal layers in group 1. We conclude that cholesterol supersaturated model bile with high content of TDC induces gallbladder epithelial alterations, which increase the luminal concentration of IgG and mucous glycoprotein.

The effects of hepatic preservation at 0 degrees C compared to 5 degrees C: influence of antiproteases and periodic flushing

The optimal preservation temperature for liver allografts is unknown. We evaluated the effect of small differences in preservation temperature, 5 degrees C vs 0 degrees C, on outcome of prolonged preservation. Livers of Wistar rats were preserved at these temperatures in UW solution for 40 h. Function was studied during reperfusion on the isolated perfused rat liver system at 37 degrees C. To compare the effects of a small reduction in temperature with known beneficial strategies, the effects of including antiproteases and periodic flushing of the graft with UW solution during cold preservation at 5 degrees C were also studied. Aspartate transaminase (AST) and alanine transaminase release after 4 h of reperfusion were much higher in the livers stored at 5 than at 0 degrees C (P < 0.0005). Addition of antiproteases to the preservation solution or periodic flushing reduced AST release but neither treatment at 5 degrees C was as good as simple storage at 0 degrees C. Cumulative bile production after 4 h of reperfusion was significantly greater in the 0 degrees C preserved group than in liver at 5 degrees C or 5 degrees C with periodic flushing. The addition of antiproteases resulted in slightly increased bile production (not significant). Platelets and WBCs in the perfusate decreased during reperfusion. This effect was more pronounced in the 5 degrees C preserved livers than in those stored at 0 degrees C. Antiproteases in the preservation solution appeared to inhibit platelet and WBC loss. Perfusate flow was significantly higher in the 0 degrees C group. We conclude that small differences in preservation temperature even at these low temperatures are important in postreperfusion liver function.

Avoiding peripheral nerve stimulation: gradient waveform criteria for optimum resolution in echo-planar imaging

Adaptation of Mansfield and Harvey's theory of magnetically induced neural stimulation indicates that, for trapezoidal gradient waveforms and at the relatively low modulation frequencies commonly used in echo-planar imaging, an increase in rise time even to the point of creating a triangular waveform can prove advantageous over the use of simple sinusoidal modulation. For example, a higher image resolution is in principle possible before the neural stimulation limit is reached. For higher modulation frequencies and fast ramp trapezoidal waveforms, the peak gradient can be lower than that for a sinusoidal waveform by a factor approaching 2/pi for equal resolution. This means that by using a multimode resonant gradient drive, the amplifier power requirements are greatly relaxed. The signal sampling bandwidth required is also lower, because, due to the trapezoidal nonlinear sample pattern, sample points are spaced linearly during the waveform plateaus.

Fetal weight estimation by echo-planar magnetic resonance imaging

Fetal weight was estimated in utero in eleven singleton pregnancies by measurement of fetal volume with echo-planar imaging (EPI), a form of magnetic resonance imaging, and by ultrasound measurements. EPI estimates of fetal volume were closely correlated with actual birthweight (R = 0.97). The median difference (expressed as a percentage of actual birthweight) between actual and EPI-estimated birthweights was 3.0% (range 0.6-9.9); this discrepancy was significantly smaller than that found for ultrasonographic estimates (6.5% [1.7-17.8]; p < 0.01).

Resonant trapezoidal gradient generation for use in echo-planar imaging

Two passive filter circuit designs are compared which enable series resonant trapezoidal drive of the modulated read gradients used in both echo-planar and echo-volumar imaging. Using simple circuit simulation software, details of the expected power requirements and performance have been evaluated for peak operating currents of up to 1000 A. The circuits evaluated were of a 7th order design incorporating a 110 microH gradient coil operating at fundamental frequencies between 800 Hz and 2000 Hz. Results indicate that the simpler circuit design is not necessarily the most efficient. In addition, by suitable modification of the input waveform algorithm, it can be shown that the shape of the resonant gradient waveform may be varied entirely under software control from triangular to trapezoidal, the minimum ramptime being specified by the highest harmonic accommodated in the circuit. The energy storage, non-dissipative nature of the circuit design also means that the gradient ramptime is effectively independent of amplifier power capabilities, making a fast rise trapezoidal waveform as easy to implement as either triangular or sinusoidal waveforms. Using the approach outlined above, trapezoidal gradient modulation at peak current amplitudes in excess of 320 A and risetimes less than 60 microseconds have been easily produced in this laboratory for use in echo-planar imaging and for investigations into ways of optimising gradient performance before the onset of peripheral nerve stimulation.

A three-year follow-up of children imaged in utero with echo-planar magnetic resonance

A 3-year follow-up study was carried out on 20 children examined in utero with echo-planar magnetic resonance imaging when fetal compromise had been demonstrated or was suspected. There was no demonstrable increase in the occurrence of disease or disability (including hearing deficit) that could be related to echo-planar imaging techniques.

Role of platelets in hepatic allograft preservation injury in the rat

Cold preservation of liver allografts injuries hepatic sinusoidal lining cells. This injury is exacerbated on reperfusion, in part because of adhesion of leukocytes. Platelets also adhere to activated endothelial surfaces. In this study we examined the role of platelets in preservation injury. Our specific aim was to determine whether the degree of platelet adhesion on reperfusion of preserved rat livers was related to duration of cold or warm ischemia and whether platelet adhesion resulted in injury to allografts. We also examined the effect of prior activation of platelets on adhesion and injury. Rat livers were preserved at 1 degree C for different time periods in University of Wisconsin solution and then reperfused for 3 hr on the isolated perfused rat liver system with Krebs-Henseleit solution to which unactivated isolated rat platelets were added. Other livers were rewarmed before reperfusion or reperfused with activated platelets. Platelets were lost from the circulation in all studies; the percentage reduction of circulating platelets was dependent on the length of preservation. The initial platelet concentration did not affect the rate of reduction of platelets in the circuit. Rewarming before reperfusion increased platelet adherence, and prior activation also increased adherence. With electron microscopy we determined that platelets adhered in small aggregates to endothelial cells or endothelial cell remnants. Adherent platelets appeared more activated and contained fewer granules than did unperfused platelets. Liver injury as measured by release of transaminases into perfusate was worsened by longer periods of cold preservation and by addition of rewarming to the protocol. The presence of platelets under these circumstances aggravated injury. Prior activation of platelets also increased the extent of injury. These studies show that platelets have an important role in cold preservation-reperfusion injury.

Prediction of the outcome of transplantation in man by platelet adherence in donor liver allografts. Evidence of the importance of prepreservation injury

We examined platelet adhesion in thirty human donor livers to determine if the degree of platelet adhesion could predict outcome of transplantation. Wedge liver biopsies were taken at the start of the donor operation (biopsy 1) and 1 hr after reperfusion in the recipient (biopsy 2). Biopsies were stained with a monoclonal antibody against platelet glycoprotein Ib and graded for platelet adhesion. Hematoxylin and eosin-stained sections were examined for polymorphonuclear leukocyte adhesion and necrosis. Platelet adhesion was much more frequent and extensive than expected in biopsy 1. Nine of 30 biopsies showed moderate or high-grade platelet adhesion. Thus in this study endothelial cell damage was present in about one-third of donors before the donor operation. The injury was not detectable by routine microscopic or clinical examination or biochemical tests. The degree of platelet adhesion in biopsy 1 predicted development of PMN adhesion and necrosis in biopsy 2 and postoperative transaminase concentrations and prothrombin times in recipients. During preservation and implantation some livers converted from low to either moderate or high grades of platelet adhesion. The grade of platelet adhesion in biopsy 2 predicted postoperative outcome as measured by transaminase and PT levels. Patients whose platelet grade converted to a higher level during preservation and implantation did not do as well as patients who remained at a low adhesion grade. These findings strongly suggest that the degree of platelet adhesion is an important determinant in assessing outcome and may provide a means of measuring the status of liver allografts prior to transplantation.

Evidence of the existence of a soluble mediator of cold preservation injury

A study was designed to determine whether soluble mediators of injury are released during cold preservation. A first set of livers consisting of three groups was stored in cold Euro-Collins solution. These were a control group stored for 10 min (group 1), an experimental group stored for 16 hr (group 2), and an "antiprotease" group to which a cocktail of antiproteases had been added, which was also stored for 16 hr (group 3). The preservation solution in these livers was washed out at the end of preservation, and this effluent was concentrated and infused into a second set of livers that were all cold-stored for 4 hr. Then, the second-set livers were either perfused-fixed at 4 degrees C with universal fixative or reperfused at 37 degrees C for 180 min in the isolated perfused rat liver (IPRL). Morphometric assessment of sinusoidal lining cells (SLC) on light and electron microscopy showed an increased degree of microcirculatory injury in livers preserved with concentrates from livers of the experimental group. On light microscopy, only 2.2 +/- 0.4% (mean +/- SD) of the SLC had a normal flattened morphology compared with 11.9 +/- 2.0% in the control group, and 10.7 +/- 2.3% of the SLC appeared completely detached from the underlying hepatocytes compared with 2.6 +/- 0.8% in the control group, the differences being statistically significant (P < 0.05). This injury was prevented by the addition of antiproteases to EC solution. Similar results were obtained in the IPRL model, in which a number of typical changes related to cold preservation injury were noted in livers preserved with concentrates from the experimental group. Compared with controls, livers preserved with concentrates from the experimental group had early and significant alterations in markers of microcirculatory injury, including a reduction in portal flow and an increase in creatinine kinase-BB isoenzyme release, followed by an increase in perfusate transaminases, LDH, and a decrease in bile production. Again the injuries were largely prevented by the addition of antiproteases. There were no differences among groups in the degree of white cell and platelet adherence during reperfusion. Experiments using UW solution showed similar results, indicating that the soluble mediator(s) is not specific for a particular preservation solution. These observations are consistent with the hypothesis that soluble mediators are produced during the hypothermic period, and are responsible for a significant part of cold preservation injury, and that proteolytic reactions are involved in this type of injury.

Limits to neural stimulation in echo-planar imaging

Simple electrical circuits are used to model neural stimulation. The stimulation current is evaluated for a variety of magnetically induced waveforms and for sinusoidal stimulation as a function of frequency. Experimental results obtained using a small scale magnetic stimulator show that the transient response rather than the steady-state behavior determines the stimulation characteristics thus suggesting a nonlinear model. We show that a nonlinear circuit changes a steady-state current solution into a repeated transient solution and thereby better explains our experimental results. Our model also shows that for very short times and high frequencies, contrary to the current widely held view, neural stimulation is independent of the magnetic field switching rate dB/dt, but depends on the final magnetic field value, Bm. At lower frequencies and rise-times, there may be a small advantage in using square wave over sine wave gradient modulation for whole body echo-planar imaging (EPI). It is found that the peak stimulation fields Bm, for both sinusoidal and trapezoidal waveforms are equal for equal risetimes. This means that for a given image array size and imaging time, trapezoidal modulation EPI ultimately can be made to operate below the neural triggering threshold while the equivalent sine modulation EPI version transcends the threshold.

Effect of human biliary immunoglobulins on the nucleation of cholesterol

We have previously identified that either biliary immunoglobulin IgA or IgM is a pronucleating protein which can accelerate the precipitation of cholesterol from bile. In this study we purified the biliary immunoglobulins (IgA, IgG, and IgM) to homogeneity by affinity chromatography to investigate the relative cholesterol nucleating potency of each immunoglobulin. Each immunoglobulin was added to slow nucleating heated abnormal biles in a dose-response manner to give a final concentration of protein in the range of 62.5-625 micrograms/ml bile. Cholesterol-nucleating activity was measured by noting the first day of cholesterol crystal formation as well as the number of crystals formed over the observation period. Biliary IgM and IgG appear to be more potent pronucleators than IgA. Isolated serum IgM from patients with Waldenstrom's macroglobulinemia as well as serum IgG from patients with and without cholesterol gallstones were shown to have pronucleating activity and acted in a dose-response manner. Commercial IgG unlike commercial IgM retains nucleating activity. The concentration of biliary immunoglobulins was measured by an enzyme-linked immunoassay (ELISA) in the gallbladder bile of patients with and without cholesterol gallstones. Biliary IgG concentrations in bile were higher in cholesterol gallstones patients than in pigmented gallstone patients and controls. We conclude that immunoglobulins particularly IgG and IgM are important pronucleating proteins and could play a role in the pathogenesis of cholesterol gallstones.

Lymphocyte adherence in the reperfused rat liver: mechanisms and effects

Leukocyte adhesion may play a central role in the pathogenesis of preservation-reperfusion injury to liver grafts. We previously showed that lymphocyte adhesion to sinusoids is dependent on the length of cold ischemia. In the present study we examined the mechanisms of lymphocyte adherence after harvesting combined with a short and a long preservation time. The effects of lymphocyte adherence on liver function were also examined. Rat livers were stored at 1 degrees C in University of Wisconsin solution for 45 min or 30 hr and then reperfused at 37 degrees C in the isolated perfused rat liver with isogeneic lymphocytes in an asanguineous perfusate. The role of reactive oxygen intermediates was investigated with allopurinol, a vitamin E analog and ascorbate or superoxide dismutase and catalase. For us to determine the role of Kupffer cells, Kupffer cell blockade was produced by gadolinium chloride. Leukotriene B4 effects were examined with the lipooxygenase inhibitor, nordihydroguaiaretic acid. We evaluated the possible presence of mechanical obstruction by studying flow rates and the circulation of red blood cells. We examined the role of adhesion molecules by pretreating lymphocytes with trypsin or neuraminidase and by exposing livers to arabinogalactan. We investigated the effects of lymphocyte adhesion on liver function by comparing perfusate liver enzymes in livers reperfused with and without lymphocytes, with trypsinized lymphocytes and with an increased number of lymphocytes. Allopurinol significantly reduced hypoxanthine degradation, and nordihydroguaiaretic acid inhibited leukotriene B4 release into the perfusate. The ability of gadolinium chloride to inhibit Kupffer cells was shown by colloid carbon uptake. In livers harvested and preserved for 45 min, lymphocytes decreased about 40% during reperfusion. In livers preserved for 30 hr, the reduction was significantly greater (about 80%). Lymphocyte adherence was lessened in livers preserved for 45 min by all three of the reactive oxygen intermediate protectants and by gadolinium chloride. In contrast, neither reactive oxygen intermediate protectants nor gadolinium chloride reduced adherence in livers preserved for 30 hr. Nordihydroguaiaretic acid had no effect in livers preserved for either 45 min or 30 hr. Portal flow in livers preserved for 45 min and 30 hr was similar, suggesting an absence of mechanical obstruction, and this finding was supported by a complete absence of red cell trapping. Trypsinization of lymphocytes and exposure of livers to arabinogalactan significantly lessened lymphocyte adherence in livers preserved for 30 hr but not in those preserved for 45 min.(ABSTRACT TRUNCATED AT 400 WORDS)

Rapid donor liver nutritional enhancement in a large animal model

Organ donors are typically subject to acute hyponutrition that might affect postpreservation liver function. Livers from nutritionally supplemented rats function better after preservation than livers from fasted rats. We have developed a method to glycogenate the liver of large animals in the temporal context of a human donor liver operation and have studied the fate of glycogen stores during preservation. Starved anesthetized pigs were infused with a hexose solution (glucose, fructose or galactose) by way of the superior mesenteric vein for 3 hr. Regular porcine insulin was infused to maintain a hyperglycemic hyperinsulinemic arterial glucose clamp at 12 to 16 mmol/L. Liver biopsy specimens and blood samples were taken before infusion and hourly. At 3 hr the liver was excised, stored for 24 hr at 1 degrees C in University of Wisconsin solution and biopsied. It was then placed at 20 degrees C for 1 hr to simulate the reimplantation stage of transplantation. Glycogen and nucleotide levels were measured, and results were corrected for starch in the University of Wisconsin solution. A 20% glucose infusion produced rapid hepatic glycogenation without side effects. Greater glycogenation was obtained with 20% fructose but at the cost of lactic acidosis and a fall in pH. A combination of 15% glucose and 5% fructose produced intermediary glycogenation without significant side effects. Galactose (20%) was less efficient than glucose alone. The addition of alanine and glutamine (20 mmol/L) did not significantly improve glycogenation. Metabolism of glycogen at 1 degree C did occur. Glycogen content fell 0.15% +/- 0.05% dry weight liver per hour during cold preservation and 5.49% +/- 2.15% per hour during ischemic rewarming.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of intraportal glucose infusion on hepatic glycogen content and degradation, and outcome of liver transplantation

Recent animal studies suggest that nutritional repletion may improve function of liver allografts, and the authors have found that intraportal glucose infusion in pigs produces rapid and substantial hepatic glycogenation. A controlled prospective randomized study in 32 patients was done to determine glycogen content and degradation in human livers during transplantation, and the effect of intraportal glucose-insulin infusions during the donor operation on these variables and on outcome of transplantation. Peripheral blood glucose concentrations were "clamped" at 14 mmol/L during the glucose-insulin infusion. Liver biopsies were taken at various stages of the procedure. Liver glycogen decreased 2.0 +/- 1.2 g/100 g dry weight liver (mean +/- standard error of the mean) in controls, but increased 6.8 +/- 1.8 g/100 g dry weight in glucose-infused donors. In both groups there was glycogen degradation during periods of cold preservation, anoxic rewarming, and after reperfusion with portal blood. Degradation rates were greater in the glucose-infused group than in controls in all three periods (p less than 0.05). Despite wide variation in postoperative aspartate aminotransferase (AST) levels among recipients in both groups, the difference in peak postoperative AST levels approached significance (p = 0.06). In addition, peak AST levels were closely correlated to anoxic rewarming time in both groups, but the slope of the relationship was much lower (3834 versus 734, p less than 0.01) in the glucose-infused group. Thus at anoxic rewarming times over 90 minutes, glycogenation was protective of liver function. Peak postoperative AST was significantly correlated to glycogen degradation in the cold preservation and rewarming periods in the glucose-infused group only. Intraoperative glucose infusions in humans can reglycogenate the liver, increase glycogen degradation, and improve certain outcome measures in liver transplantation.

A method for sequential excision biopsies of rat liver in an isolated perfused system

We describe a simple method of performing sequential excision biopsies during liver reperfusion in the isolated perfused rat liver. After hepatectomy, four ligatures (5.0 silk) tied with a slip knot are placed around the pedicles of: (1) the inferior and (2) the superior parts of the caudate lobe, as well as (3) the inferior and (4) the superior parts of the right lateral lobe. At the time of biopsy, the prepared 5.0 silk ties are tightened with sufficient force to occlude the vascular pedicle, preventing leakage of circulating perfusate. The procedure provides four biopsies of more than 350 mg each without alteration of perfusate transaminases and tissue ATP contents. The total tissue removed by this method comprises 20-25% of the whole liver weight.

Effect of colectomy on bile composition, cholesterol crystal formation, and gallstones in patients with ulcerative colitis

Bile composition and the presence of cholesterol crystals in bile were studied in bile samples obtained at the time of surgery in patients with ulcerative colitis. Some patients were sampled before colectomy and others at a second operation months to years after a colectomy. Patients in the precolectomy group were found to have bile composition similar to control patients without gallstones, and few had crystals in their bile. In the postcolectomy group, cholesterol concentrations were very high, all biles were supersaturated, and almost all patients had cholesterol crystals in their bile. These findings are similar to those found in persons with cholesterol gallstones. Twenty patients have been followed for at least 3 years after colectomy and to date three have formed cholesterol gallstones.

Immunoglobulins as nucleating proteins in the gallbladder bile of patients with cholesterol gallstones

The gallbladder bile of patients with cholesterol gallstones contains pronucleating proteins which accelerate precipitation of cholesterol crystals from bile. In this study we have improved the purification procedure developed earlier for these nucleating proteins and have now identified the nature of these proteins. Gallbladder bile from patients with cholesterol gallstones was applied to concanavalin A affinity columns. The ConA-binding glycoprotein fractions containing the nucleating proteins were then separated by FPLC (fast protein liquid chromatography) using a Superose 12 gel filtration column. Nucleating activity was detected in the high molecular weight (FPLC-1) as well as in the low molecular weight fractions (FPLC-3). Investigation of the high molecular weight fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by electroelution and amino acid sequencing suggested that these proteins were immunoglobulins. Immunostaining of Western blots with specific monoclonal antibodies identified the presence of immunoglobulin (Ig) M and IgA in the FPLC-1 fraction. These immunoglobulins were further purified by affinity chromatography employing an antibody exchanger (ABx) column which specifically binds immunoglobulins. There was no reduction in the cholesterol nucleating activity in the Abx-bound fraction compared to FPLC-1. Additional studies showed that the FPLC-1 fraction was significantly more potent than the ConA glycoproteins from either rapid and slow nucleating biles. Also the number of crystals formed was significantly greater in the FPLC-1 fraction isolated from cholesterol gallstone biles than from the FPLC-1 fraction from control patient biles. Commercially obtained IgM and IgA had no effect on nucleation, but IgM isolated from the serum of patients with Waldenstrom's macroglobulinemia did accelerate the nucleation of cholesterol. We conclude that the IgM and possibly IgA are pronucleating proteins and may be important in the pathogenesis of cholesterol gallstones in man.

Correlation of donor nutritional status with sinusoidal lining cell viability and liver function in the rat

We have demonstrated that the sinusoidal lining cell injury sustained by rat liver allografts during hypothermic storage is a critical determinant of graft viability. The present study was designed to examine the effect of donor nutritional status on hepatic microcirculation and graft function. Rat livers from four nutritional groups (group I, fasted; group II, fed; group III, intraperitoneal glucose; and group IV, fed plus intraperitoneal glucose) were excised and stored for 24 hr in Marshall's isotonic citrate solution. Then the livers were perfused under anoxic conditions with trypan blue. The percentage of nonviable SLC in each group was 26.7 +/- 8.1, 24.9 +/- 7.9, 17.6 +/- 6.9, and 5.9 +/- 1.9 in groups I, II, III, and IV respectively; i.e., there was a significant improvement in SLC viability with nutritional repletion in group IV. Electron microscopy was performed on livers from groups I and IV following 30-hr preservation in University of Wisconsin solution and after 16-hr preservation in Marshall's isotonic citrate solution. Biopsies were taken at the end of storage and after 1 hr of reperfusion at 37 degrees C. At the end of preservation group IV livers contained glycogen and had much more normal liver ultrastructure than group I livers. After reperfusion there was partial recovery of normal SLC morphology in both groups and depletion of glycogen in group IV. Liver function was studied on the isolated perfused rat liver system at 37 degrees C following 30-hr storage in UW solution. Transaminase release into the perfusate was significantly lower in nutritionally repleted livers than in livers from fasted animals. A significant reduction in perfusate platelet count occurred only in livers from fasted animals. The results show that nutritional repletion can reduce the injury of cold preservation to both hepatocytes and endothelial cells and improve liver function in the postpreservation period.

Pathogenesis of cholesterol gallstones

Cholesterol gallstone disease is extremely common. Three major stages are recognized for stone formation, namely bile that becomes supersaturated with cholesterol, cholesterol nucleation leading to crystal formation and finally retention of the crystals in the gallbladder resulting in stone formation. Supersaturation is common but nucleation into crystals probably requires protein nucleating factors. Impaired motility of the gallbladder causes crystal retention and is probably very important in stone formation.

Albumin absorption and protein secretion by the gallbladder in man and in the pig

To study albumin absorption by the gallbladder in man, an in vitro model was first established in the pig and compared with in vivo function in the same species. Water and electrolyte transport and 125I-albumin absorption and protein secretion in vivo and in vitro were compared. Then similar in vitro studies were performed on human gallbladders obtained at surgery. The in vivo study in the pig was performed without disturbing the gallbladder except to tie a cannula in the cystic duct end. The in vitro model was identical in the pig and human gallbladders. Gallbladders were excised using a technique causing minimal injury and anoxia. They were oxygenated on both mucosal and serosal surfaces in a temperature-controlled environment. Luminal and external bath test solutions consisted of modified Ringers bicarbonate with added glucose; luminal solutions also contained 125I-albumin from different species, depending on the study. Active absorption of sodium and water occurred in both types of studies in the pig but in vivo absorption rates were considerably greater than in vitro rates. Albumin absorption in vivo was substantial; although present in vitro, the absorption of albumin was diminished relatively more than electrolyte transport rates. Protein secretion rates into the gallbladder were similar in vitro and in vivo. The results of studies in the human gallbladders in vitro were similar to the pig, except albumin absorption was greater. Some human gallbladders were obtained from control patients and some from patients with cholesterol gallstones. There were no significant differences between the two groups for any of the variables studied; however, the numbers were small and some control gallbladders were not normal gallbladders.

Biliary cholesterol transport and precipitation: introduction and overview of conference

Cholesterol is secreted into bile as cholesterol-phospholipid vesicles. The cholesterol and phospholipid are subsequently exposed to the bile salts contained in the bile, which leads to the process of micellation. Two situations may arise depending on whether there is enough bile salt in proportion to cholesterol to complete this "maturation" process. If the cholesterol saturation is low, at equilibrium the bile salts will have completely micellized the vesicles. On the other hand, if bile is saturated with cholesterol, the micellation process is incomplete and vesicles and micelles will be present at equilibrium. The residual vesicle in this latter situation may have a higher cholesterol/phospholipid ratio because of the greater propensity of phospholipid to be micellized. This situation may result in cholesterol nucleation. The mechanism of nucleation from vesicles and the possible role of nucleating and antinucleating proteins in this process have been discussed.

Bile sampling, processing and analysis in clinical studies

Obtaining a proper bile sample for investigative purposes is of utmost importance to obtain valid results. Bile can be collected by direct aspiration of the gallbladder, by duodenal intubation or by T-tube drainage. The optimal method of collection depends on the investigative question, as well as on the resources available to the investigator. The procedures for obtaining, processing and analyzing human bile (gallbladder and hepatic) are summarized, pointing out the disadvantages and pitfalls that may occur.