Changes in Rat Adipocyte and Liver Glucose Metabolism Following Repeated Restraint Stress

Rats exposed to repeated restraint weigh less than controls even 8 weeks after stress. Stress-induced weight loss is lean tissue, but the post-stress difference in weight between control and restrained rats is lean and fat mass. Whole-body glucose clearance is enhanced 1 day after stress, but adipocyte glucose utilization is inhibited and muscle glucose transport is unchanged. The studies described here demonstrated that glucose transport was increased in both restrained and pair-fed rats, but that glycogen synthesis was increased only in restrained rats, which may account for the improved whole-body glucose clearance. Adipocyte glucose transport was inhibited and adipose plasma membrane β-adrenergic receptor number was increased 1 day post-stress in restrained rats when weight loss was lean tissue, but were not different from control rats 5 days post-stress, when both fat and lean tissue were reduced. Thus, repeated restraint induces reversible changes in adipocyte metabolism that may represent a transition from the catabolic state of stress to a new energetic equilibrium in rats that maintain a reduced body weight for an extended period of time.

MAPK/ERK2 phosphorylates ERG at serine 283 in leukemic cells and promotes stem cell signatures and cell proliferation

Aberrant ERG (v-ets avian erythroblastosis virus E26 oncogene homolog) expression drives leukemic transformation in mice and high expression is associated with poor patient outcomes in acute myeloid leukemia (AML) and T-acute lymphoblastic leukemia (T-ALL). Protein phosphorylation regulates the activity of many ETS factors but little is known about ERG in leukemic cells. To characterize ERG phosphorylation in leukemic cells, we applied liquid chromatography coupled tandem mass spectrometry and identified five phosphorylated serines on endogenous ERG in T-ALL and AML cells. S283 was distinct as it was abundantly phosphorylated in leukemic cells but not in healthy hematopoietic stem and progenitor cells (HSPCs). Overexpression of a phosphoactive mutant (S283D) increased expansion and clonogenicity of primary HSPCs over and above wild-type ERG. Using a custom antibody, we screened a panel of primary leukemic xenografts and showed that ERG S283 phosphorylation was mediated by mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) signaling and in turn regulated expression of components of this pathway. S283 phosphorylation facilitates ERG enrichment and transactivation at the ERG +85 HSPC enhancer that is active in AML and T-ALL with poor prognosis. Taken together, we have identified a specific post-translational modification in leukemic cells that promotes progenitor proliferation and is a potential target to modulate ERG-driven transcriptional programs in leukemia.

PRKACA mediates resistance to HER2-targeted therapy in breast cancer cells and restores anti-apoptotic signaling

Targeting HER2 with antibodies or small molecule inhibitors in HER2-positive breast cancer leads to improved survival, but resistance is a common clinical problem. To uncover novel mechanisms of resistance to anti-HER2 therapy in breast cancer, we performed a kinase open reading frame screen to identify genes that rescue HER2-amplified breast cancer cells from HER2 inhibition or suppression. In addition to multiple members of the MAPK (mitogen-activated protein kinase) and PI3K (phosphoinositide 3-kinase) signaling pathways, we discovered that expression of the survival kinases PRKACA and PIM1 rescued cells from anti-HER2 therapy. Furthermore, we observed elevated PRKACA expression in trastuzumab-resistant breast cancer samples, indicating that this pathway is activated in breast cancers that are clinically resistant to trastuzumab-containing therapy. We found that neither PRKACA nor PIM1 restored MAPK or PI3K activation after lapatinib or trastuzumab treatment, but rather inactivated the pro-apoptotic protein BAD, the BCl-2-associated death promoter, thereby permitting survival signaling through BCL-XL. Pharmacological blockade of BCL-XL/BCL-2 partially abrogated the rescue effects conferred by PRKACA and PIM1, and sensitized cells to lapatinib treatment. These observations suggest that combined targeting of HER2 and the BCL-XL/BCL-2 anti-apoptotic pathway may increase responses to anti-HER2 therapy in breast cancer and decrease the emergence of resistant disease.

Abstract P5-08-01: Systematic interrogation of resistance to HER2-directed therapy identifies a survival pathway activated by PRKACA and PIM1

Amplification and/or overexpression of the receptor tyrosine kinase HER2 occurs in 20-25% of breast cancers, and is associated with poor prognosis. Targeting of HER2 with drugs such as trastuzumab, lapatinib, or pertuzumab has led to clinical benefit in patients with both metastatic and early-stage HER2-amplified breast cancer. However, resistance and disease progression always occurs in patients with metastatic disease, and many patients with early-stage breast cancer experience recurrences despite adjuvant anti-HER2 therapy. As such, understanding the mechanisms of resistance to anti-HER2 therapy has important clinical implications.

Recent studies have identified mutations in PIK3CA, the gene encoding the catalytic subunit of Phosphatidylinositol 3 kinase (PI3K), as one mechanism of resistance to trastuzumab. However, such mutations are present in only a fraction of trastuzumab-resistant breast cancers. We therefore sought to uncover novel mechanisms of resistance to anti-HER2 therapy through an unbiased screen for kinases and kinase-related molecules that are able to rescue HER2-amplified breast cancer cells from HER2 inhibition.

We utilized a library of nearly 600 lentivirally-delivered open reading frames (ORFs) to constitutively express the coding sequence of each molecule individually in HER2-amplified BT474 breast cancer cells in arrayed high-throughput format. We conducted two parallel screens for the ability of each of these molecules to rescue cells from anti-HER2 therapy: one in which we treated the cells with a lapatinib-like drug that inhibits the kinase activity of HER2 and EGFR, and one in which we lentivirally delivered a short hairpin RNA that suppresses expression of HER2.

We identified those ORFs that restored viability of BT474 cells to greater than two standard deviations above the median of all ORFs in each screen. Multiple members of the MAPK and PI3K signaling pathways scored in both screens, serving to validate the approach. In addition, the survival kinases PIM1 and PRKACA scored robustly. Mechanistic studies suggest that these kinases may confer resistance by restoring the phosphorylation of, and thereby inactivating, the pro-apoptotic protein BAD. Consistent with this finding, overexpression of Bcl-xl, which is inhibited by BAD, also conferred resistance to lapatinib in HER2-amplified breast cancer cells. Furthermore, pharmacological blockade of Bcl-xl and Bcl-2 with ABT-263 enhanced lapatinib-induced killing of HER2-amplified breast cancer cells in vitro, and partially abrogated the rescue conferred by both PRKACA and PIM1. These findings suggest that combined inhibition of HER2 and the anti-apoptotic molecules Bcl-xl and Bcl-2 could enhance tumor cell eradication and prevent or delay the emergence of resistant disease.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-08-01.

Use of the entero-test, a novel approach for the noninvasive capture of biliary metabolites in dogs

Preclinical information on the biliary metabolites of a drug candidate is typically obtained through the collection of bile after surgical cannulation of the bile duct. In this study, we describe a novel approach using the Entero-Test, a simple device that facilitates the noninvasive sampling of duodenal bile. The Entero-Test was used to collect bile from six fasted dogs that had been dosed either orally with simvastatin (SV) or intravenously with simvastatin hydroxy acid (SVA), compounds that have been previously reported to undergo extensive metabolism and biliary secretion in the dog. The devices, consisting of a weighted gelatin capsule containing 90 cm of a highly absorbent nylon string, were swallowed by each dog with the proximal end of the string taped to the animal's face. Once the weighted string had reached the duodenum, gallbladder contraction was stimulated to release bile. Each bile-stained string was then retrieved via the mouth and, after solvent extraction, samples were analyzed for drug-related material by ultraperformance liquid chromatography-mass spectrometry and NMR spectroscopy. Numerous metabolites of SV and SVA were observed, and, in general, the major metabolites have been reported previously from studies with bile duct-cannulated animals dosed with [14C]SV or [14C]SVA. The results from this study demonstrate the utility of deploying the Entero-Test in absorption, distribution, metabolism, and elimination studies to provide information on the nature of biliary metabolites, which, on occasion, may be sufficient to negate the need for more invasive sampling techniques. The benefits and limitations of the technique are discussed.

Effectiveness of the Liberator? in reducing predation on wildlife by domestic cats

We evaluated the effectiveness of the commercial collar-worn product the Liberator? in reducing the number of vertebrates pet cats bring home. Fifteen cats identified by their owners as hunters bringing home at least one prey animal per fortnight were included in the study, which was carried out in Perth, Western Australia over six weeks in November/December 2006 (southern hemisphere late spring/early summer). Each cat spent three weeks wearing a Liberator? and three weeks without it and the number of prey brought home by the cat during each period was recorded by its owner. Participating cats caught 91 prey (37 birds, 44 mammals and 10 herpetofauna). The Southern Brown Bandicoot was the only prey species of conservation concern. Liberators? made no statistically significant difference in the number of cats catching prey, but did reduce the overall number of prey caught. Cats wearing Liberators? caught only 38% of all birds, 40% of all herpetofauna and 30% of all mammals captured during the study. Despite this positive result several product failures occurred, so owners wishing to reduce predation by their cats will need to decide whether the Liberator? is a cost-effective option.

The EuroPhysiome, STEP and a roadmap for the virtual physiological human

Biomedical science and its allied disciplines are entering a new era in which computational methods and technologies are poised to play a prevalent role in supporting collaborative investigation of the human body. Within Europe, this has its focus in the virtual physiological human (VPH), which is an evolving entity that has emerged from the EuroPhysiome initiative and the strategy for the EuroPhysiome (STEP) consortium. The VPH is intended to be a solution to common infrastructure needs for physiome projects across the globe, providing a unifying architecture that facilitates integration and prediction, ultimately creating a framework capable of describing Homo sapiens in silico. The routine reliance of the biomedical industry, biomedical research and clinical practice on information technology (IT) highlights the importance of a tailor-made and robust IT infrastructure, but numerous challenges need to be addressed if the VPH is to become a mature technological reality. Appropriate investment will reap considerable rewards, since it is anticipated that the VPH will influence all sectors of society, with implications predominantly for improved healthcare, improved competitiveness in industry and greater understanding of (patho)physiological processes. This paper considers issues pertinent to the development of the VPH, highlighted by the work of the STEP consortium.

Web-based tools for quantitative renal physiology

We present the development strategy and present state of progress on an interactive website project for quantitative renal physiology: a) a quantitative kidney database (QKDB), and b) an interactive website presenting mathematical models covering the major aspects of renal physiology. QKDB will house data for quantitative evaluation of hypotheses of renal function, from the cellular, through the epithelial and tubular, to whole organ levels. It will thus facilitate comparisons among different species and under various experimental conditions. It will include especially: transport parameters, tubular concentrations and flow rates along the various nephron segments, and anatomical details, in human kidneys, in experimentally studied species, and in model epithelia, such as cultured cells and amphibian skin and urinary bladder. The modeling resource will provide an interactive user interface to a collection of published models at all levels of renal physiology, enabling non-modelers to exploit the models, altering key parameters according to hypotheses of their own and visualizing the simulation results, thus permitting quantitative exploration of new hypotheses. Implementation will be facilitated by translation of the models into a common markup language such as CellML (cell markup language) and SBML (systems biology markup language). There will thus be a modular separation of model descriptions from their numerical solution methods.

Corrosion of cemented titanium femoral stems

Cemented titanium stems in hip arthroplasty are associated with proximal cement-stem debonding and early failure. This was well publicised with the 3M Capital hip. However, corrosion in this setting has been reported with only one stem design and is less widely accepted.

We present a series of 12 cemented titanium Furlong Straight Stems which required revision at a mean of 78 months for thigh pain. At revision the stems were severely corroded in a pattern which was typical of crevice corrosion. Symptoms were eliminated after revision to an all-stainless steel femoral prosthesis of the same design. We discuss the likely causes for the corrosion. The combination of a titanium stem and cement appears to facilitate crevice corrosion.

The pulmonary physician in critical care. Illustrative case 1: cystic fibrosis

The case history of a patient with CF admitted to an ICU is presented and the appropriateness of intensive care management for patients with CF is discussed. Issues relevant to the ICU care of patients with CF are highlighted.

A brief history of theories concerning the mammalian urine concentrating mechanism

The mechanism by which the mammalian kidney creates the osmotic gradient necessary for urine concentration remains an open question. We present a brief survey of the give-and-take between theory and experiment on this question over the last half century. We start with the introduction of the countercurrent multiplier paradigm in 1951. We finish with a description of a recent suggestion that the explanation for the enigmatic inner medullary osmotic gradient may reside in the very metabolism of the inner medullary cells, which are required by the region's hypoxia to obtain their ATP largely from anaerobic glycolysis and which thus, by the same token, furnish net osmoles to the medullary interstitium by converting glucose to lactate.

Antioxidants inhibit indoleamine 2,3-dioxygenase in IFN-gamma-activated human macrophages: posttranslational regulation by pyrrolidine dithiocarbamate

Induction of the heme-containing indoleamine 2,3-dioxygenase (IDO) by IFN-gamma is implicated in anti-microbial and pro-inflammatory activities of human macrophages. Antioxidants can modulate the expression of immune and inflammatory genes, and pyrrolidine dithiocarbamate (PDTC) is a frequently used antioxidant to inhibit the transcription factor NF-kappaB. Here we show that IFN-gamma treatment of human monocyte-derived macrophages (hMDMs) increased the proportion of oxidized glutathione. PDTC attenuated this increase and inhibited IDO activity, although it increased IDO protein expression and did not affect IDO mRNA expression and enzyme activity directly. Other antioxidants, 2-ME, ebselen, and t-butyl hydroquinone, inhibited IDO protein expression. Similar to PDTC, the heme biosynthesis inhibitor succinylacetone (SA) and the iron-chelator pyridoxal isonicotinoyl hydrazone inhibited cellular IDO activity without affecting protein expression, whereas addition of hemin or the heme precursor delta-aminolevulinic acid increased IDO activity. Also, incubation of IFN-gamma-activated hMDM with delta-[(14)C]-aminolevulinic acid resulted in the incorporation of label into immunoprecipitated IDO, a process inhibited by PDTC and SA. Furthermore, supplementation of lysates from PDTC- or SA-treated hMDM with hemin fully restored IDO activity to control levels, and hemin also reversed the inhibitory action of SA but not PDTC in intact cells. Together these results establish a requirement for de novo heme synthesis for IDO activity in IFN-gamma-activated hMDM. They show that, similar to other pro-inflammatory proteins, the activity of IDO is modulated by antioxidants though in the case of PDTC this takes place posttranslationally, in part by limiting the availability of heme for the formation of holo-IDO.

Transmetatarsal amputation: an 8-year experience

This study retrospectively reviews an 8-year consecutive series of transmetatarsal amputation (TMA) for forefoot ischaemia in diabetic and non-diabetic patients. Forty-one patients had TMA. Peri-operative mortality was 17% (7/41). A healed stump was achieved in 19 patients (46%) and 18 of these patients were independently mobile, or mobile with sticks. Non-diabetic patients (8/12) healed significantly better than diabetics (11/29). Median time to healing was 7 months (range 3-20 months). All non-healed survivors had a higher amputation (14 below-knee, 1 Syme's). A healed TMA gives good mobility, but prediction of who will heal after operation is unreliable. Time to healing is often lengthy, and failed healing results in higher amputation. These issues need to be fully discussed with the patient who is considered for TMA.

Dietary cosupplementation with vitamin E and coenzyme Q(10) inhibits atherosclerosis in apolipoprotein E gene knockout mice

Intimal oxidation of LDL is considered an important early event in atherogenesis, and certain antioxidants are antiatherogenic. Dietary coenrichment with vitamin E (VitE) plus ubiquinone-10 (CoQ(10), which is reduced during intestinal uptake to the antioxidant ubiquinol-10, CoQ(10)H(2)) protects, whereas enrichment with VitE alone can increase oxidizability of LDL lipid against ex vivo oxidation. In the present study, we tested whether VitE plus CoQ(10) cosupplementation is more antiatherogenic than either antioxidant alone, by use of apolipoprotein E-deficient (apoE-/-) mice fed a high-fat diet without (control) or with 0.2% (wt/wt) VitE, 0.5% CoQ(10), or 0.2% VitE plus 0.5% CoQ(10) (VitE+CoQ(10)) for 24 weeks. None of the supplements affected plasma cholesterol concentrations, whereas in the VitE and CoQ(10) groups, plasma level of the respective supplement increased. Compared with control, plasma from CoQ(10) or VitE+CoQ(10) but not VitE-supplemented animals was more resistant to ex vivo lipid peroxidation induced by peroxyl radicals. VitE supplementation increased VitE levels in aorta, heart, brain, and skeletal muscle, whereas CoQ(10) supplementation increased CoQ(10) only in plasma and aorta and lowered tissue VITE: All treatments significantly lowered aortic cholesterol compared with control, but only VitE+CoQ(10) supplementation significantly decreased tissue lipid hydroperoxides when expressed per parent lipid. In contrast, none of the treatments affected aortic ratios of 7-ketocholesterol to cholesterol. Compared with controls, VitE+CoQ(10) supplementation decreased atherosclerosis at the aortic root and arch and descending thoracic aorta to an extent that increased with increasing distance from the aortic root. CoQ(10) significantly inhibited atherosclerosis at aortic root and arch, whereas VitE decreased disease at aortic root only. Thus, in apoE-/- mice, VitE+CoQ(10) supplements are more antiatherogenic than CoQ(10) or VitE supplements alone and disease inhibition is associated with a decrease in aortic lipid hydroperoxides but not 7-ketocholesterol.

A modelling study of feedforward activation in human erythrocyte glycolysis

Though feedforward activation (FA) is a little known principle of control in metabolic networks, there is one well-known example; namely, the activation of pyruvate kinase (PK) by fructose-1,6-biphosphate (FBP) in glycolysis. The effects of this activation on the enzyme's kinetics are well characterised, but its possible role in glycolytic control has not been determined, and, experimentally, there is as yet no direct way of modifying the enzyme to remove just the FBP activation without affecting other aspects of the enzyme's kinetics. Given this limitation, we used a detailed numerical simulation of human erythrocyte glycolysis to simulate the effects of selective removal of the activation of PK by FBP on steady-state metabolite concentrations and on the dynamic response of glycolytic flux to a sudden increase of the cell's demand for ATP. Our modelling results predict that in the absence of FA steady-state levels of metabolites within the activation loop, i.e. from FBP to phosphoenolpyruvate, would be four- to thirteen-fold higher than normal, whereas levels of ATP and metabolites outside the loop, i.e. glucose-6-phosphate, fructose-6-phosphate and pyruvate, would be lower than normal. Existing clinical evidence in a patient with haemolytic anaemia, correlated with a lack of activation of PK by FBP (Paglia D.E., Valentine W.N., Holbrook C.T., Brockway R., Blood (1983) 62 972-979), is consistent with this prediction. In response to changing demand for ATP, the model predicts that the corresponding change of glycolytic flux would entail changes of metabolite concentrations in the absence of FA, but that in its presence the levels of metabolites within the activation loop remain essentially unperturbed. Thus, our results suggest that by stabilising metabolite pools in the face of variable glycolytic flux, FA may serve to avoid perturbations of the oxygen affinity of haemoglobin (sensitive to the levels of 2,3-phosphoglycerate) and of cell osmolality that would otherwise occur during variations in the cell's demand for ATP. In addition, by significantly raising the steady-state setpoint of intermediate metabolite pools, the productivity index (ratio of glycolytic flux to total metabolites in the pathway) of glycolysis would fall almost four-fold in the absence of forward activation.

Relative reactivities of N-chloramines and hypochlorous acid with human plasma constituents

Hypochlorous acid (HOCl), the major strong oxidant produced by the phagocyte enzyme myeloperoxidase, reacts readily with free amino groups to form N-chloramines. Since different N-chloramines have different stabilities and reactivities depending on their structures, we investigated the relative reactivities of three model N-chloramines and HOCl with human plasma constituents. TheN-chloramines studied were N(alpha)-acetyl-lysine chloramine (LysCA, a model of protein-associated N-chloramines), taurine chloramine (TaurCA, the primary N-chloramine produced by activated neutrophils), and monochloramine (MonoCA, a lipophilic N-chloramine). Addition of these chlorine species (100--1000 microM each) to plasma resulted in rapid loss of thiols, with the extent of thiol oxidation decreasing in the order TaurCA = LysCA > MonoCA = HOCl. The single reduced thiol of albumin was the major target. Loss of plasma ascorbate also occurred, with the extent decreasing in the order HOCl > LysCA > TaurCA > MonoCA. Experiments comparing equimolar albumin thiols and ascorbate showed that while HOCl caused equivalent loss of thiols and ascorbate, theN-chloramines reacted preferentially with thiols. The chlorine species also inactivated alpha(1)-antiproteinase, implicating oxidation of methionine residues, and ascorbate provided variable protection depending on the chlorine species involved. Together, our data indicate that in biological fluids N-chloramines react more readily with protein thiols than with methionine residues or ascorbate, and thus may cause biologically relevant, selective loss of thiol groups.

MIRD Pamphlet no. 18: Administered cumulated activity for ventilation studies

There has been no consensus on a standard calculational approach regarding the concept of administered activity in ventilation studies involving inhaled radioisotope gas or radioaerosols. This is caused in part by a lack of knowledge regarding the actual activity that enters the lung space (as opposed to activity introduced into the delivery system) and to the extended administration times (t(a)) associated with delivery protocols.

METHODS

This pamphlet reviewed the three primary ventilation procedures, including rebreathing-system protocols, continuous-flow generator output techniques, and radioaerosol delivery systems.

RESULTS

For each technique, an analytic expression has been derived for a new parameter called lung administered cumulated activity, A(L)(0,t(a)), which is the cumulated activity in the lungs during the administration phase. In addition, another potentially useful parameter has been defined-the mean administered activity for ventilation procedures, which normalizes the administered cumulated activity in the lung over the administration period and may serve to standardize descriptions of protocols between patients and institutions. Examples are provided that illustrate these new concepts for typical ventilation protocol administration parameters.

CONCLUSION

The models presented can be employed to evaluate lung administered cumulated activity for use in ventilation dose estimate reports as a function of explicit variables (e.g., spirometer volume, generator output rate, wash-in half-time, administration time). In practice, it is recommended that dose estimate reports be based on measurements of cumulated activity in the lung over the administration period and normalized to this administered cumulated activity.

Minimizing radiation dose for pediatric body applications of single-detector helical CT: strategies at a large Children's Hospital

Adjustments of the standard helical CT protocols for adults can result in reduced radiation dose when imaging children. It is the radiologist's responsibility to critically evaluate the CT techniques used at their institution. Adjustments to CT protocols should be made to choose the appropriate mA and pitch when imaging children.

Advantages and disadvantages of pinless external fixation

The AO pinless external fixator (PEF) uses trocar tipped clamps to grip the outer tibial cortex rather than pins to transfix it. Its main advantage is to avoid further contamination of the medullary canal in open tibial fractures where a nail may subsequently be used. We tested the anatomical safety of this device and its effect on plastic surgical procedures compared with a standard unilateral external fixator (UEF).The PEF and UEF were placed on two amputated limbs which were then dissected. Structures at risk were traced on ten cadaver limbs. We found that important anatomical structures were endangered by the PEF and that safe zones could not always be defined. The UEF avoided these structures. Plastic surgical approaches were made more difficult by the PEF which imposed limitations on local flap design and endangered the arterial perforators which supply them. We conclude that safety is compromised by the PEF because margins for error are small. It poses additional problems in soft tissue reconstruction and highlights the need for co-operation between plastic surgical and orthopaedic teams in choice of fixation device.

Randomised controlled trial of atraumatic versus standard needles for diagnostic lumbar puncture

OBJECTIVE

To compare the ease of use of atraumatic needles with standard needles for diagnostic lumbar puncture and the incidence of headache after their use.

DESIGN

Double blind, randomised controlled trial.

SETTING

Investigation ward of a neurology unit in a university hospital.

PARTICIPANTS

116 patients requiring elective diagnostic lumbar puncture.

INTERVENTIONS

Standardised protocol for lumbar puncture with 20 gauge atraumatic or standard needles.

OUTCOME MEASURES

The primary end point was intention to treat analysis of incidence of moderate to severe headache, assessed at one week by telephone interview. Secondary end points were incidence of headache at one week analysed by needle type, ease of use by operator according to a visual analogue scale, incidence of backache, and failure rate of puncture.

RESULTS

Valid outcome data were available for 97 of 101 patients randomised. Baseline characteristics were matched except for higher body mass index in the standard needle group. By an intention to treat analysis the absolute risk of moderate to severe headache with atraumatic needles was reduced by 26% (95% confidence interval 6% to 45%) compared with standard needles, but there was a non-significantly greater absolute risk of multiple attempts at lumbar puncture (14%, -4% to 32%). Higher body mass index was associated with an increased failure rate with atraumatic needles, but the reduced incidence of headache was maintained. The need for medical interventions was reduced by 20% (1% to 40%).

CONCLUSIONS

Atraumatic needles significantly reduced the incidence of moderate to severe headache and the need for medical interventions after diagnostic lumbar punctures, but they were associated with a higher failure rate than standard needles.

Increased sputum amino acid concentrations and auxotrophy of Pseudomonas aeruginosa in severe cystic fibrosis lung disease

BACKGROUND

Pseudomonas aeruginosa may undergo a phenotypic change from the wild (prototrophic) type to an auxotrophic phenotype in the course of respiratory infection in patients with cystic fibrosis. The clinical significance of this is unclear. A study was undertaken to investigate whether the presence of auxotrophs of P aeruginosa in the sputum of patients with cystic fibrosis correlated with severity of respiratory disease, and whether increased sputum concentrations of amino acids were associated with the emergence of these forms.

METHODS

Sixty adult patients with cystic fibrosis, colonised by P aeruginosa, were recruited and baseline clinical data including lung function were recorded. Serial sputum samples were obtained before, during, and after infective exacerbations where possible. These samples were used for routine microbiological culture, assessment of auxotrophy of P aeruginosa, measurement of amino acid content, and neutrophil elastase assay.

RESULTS

Auxotrophy was common in patients with cystic fibrosis and 20 (33%) had a mean percentage auxotroph count of more than 50% total cfu/ml. The mean percentage auxotroph count was inversely correlated with forced expiratory volume in one second (FEV(1); tau = -0.194, p = 0.031). The median sputum amino acid concentration of the group was 12.5 mmol/l (range 0.13-40.6). The mean amino acid concentration in 33 subjects during infective exacerbations was 18.2 mmol/l (95% CI 15.1 to 21.3) compared with 12.3 mmol/l (95% CI 9.8 to 14.8) when well (p = 0.001). The amino acid content of sputum was inversely correlated with FEV(1) (tau = -0.253, p = 0.005).

CONCLUSIONS

P aeruginosa frequently exhibits auxotrophy in patients with cystic fibrosis, particularly in those with severe underlying pulmonary disease. The sputum amino acid content of patients with cystic fibrosis is high during infective exacerbations and correlates with pulmonary disease severity.

Error analysis of classic colonic transit time estimates

Estimates of colonic transit times (CTT) through the three colonic segments, right colon, left colon, and rectosigmoid, are commonly based on radiopaque markers. For a given segment, CTT is usually calculated from just the number of markers visible in that segment on abdominal X-rays. This procedure is only strictly valid for the theoretical, but unrealistic, case of continuous marker ingestion (i. e., not for a single or once-daily ingestion). CTT was analyzed using the usual estimate of the mean CTT of one marker and also using a new, more realistic estimate based on the kinetic coefficients of a three-compartment colonic model. We directly compared our compartmental approach to classic CTT estimates by double-marker studies in six patients. We also retrospectively studied CTT in 148 healthy control subjects (83 males, 65 females) and 1,309 subjects with functional bowel disorders (irritable bowel syndrome or constipation). Compared with the compartmental estimates, the classic approach systematically underestimates CTT in both populations, i.e., in patients and in healthy control subjects. The relative error could easily reach 100% independent of the site of colonic transit delay. The normal values of total CTT are then 44.3+/-29.3 instead of 30.1+/-23.6 h for males and 68.2+/-54.4 instead of 47.1+/-28.2 h for females.

Inner medullary lactate production and accumulation: a vasa recta model

Since anaerobic glycolysis yields two lactates for each glucose consumed and since it is reported to be a major source of ATP for inner medullary (IM) cell maintenance, it is a likely source of "external" IM osmoles. It has long been known that such an osmole source could theoretically contribute to the "single-effect" of the urine concentrating mechanism, but there was previously no suggestion of a plausible source. I used numerical simulation to estimate axial gradients of lactate and glucose that might be accumulated by countercurrent recycling in IM vasa recta (IMVR). Based on measurements in other tissues, anaerobic glycolysis (assumed to be independent of diuretic state) was estimated to consume approximately 20% of the glucose delivered to the IM. IM tissue mass and axial distribution of loops and vasa recta were according to reported values for rat and other rodents. Lactate (P(LAC)) and glucose (P(GLU)) permeabilities were varied over a range of plausible values. The model results suggest that P(LAC) of 100 x 10(-5) cm/s (similar to measured permeabilities for other small solutes) is sufficiently high to ensure efficient lactate recycling. By contrast, it was necessary in the model to reduce P(GLU) to a small fraction of this value (1/25th) to avoid papillary glucose depletion by countercurrent shunting. The results predict that IM lactate production could suffice to build a significant steady-state axial lactate gradient in the IM interstitium. Other modeling studies (Jen JF and Stephenson JL. Bull Math Biol 56: 491-514, 1994; and Thomas SR and Wexler AS. Am J Physiol Renal Fluid Electrolyte Physiol 269: F159-F171, 1995) have shown that 20-100 mosmol/kgH(2)O of unspecified external, interstitial, osmolytes could greatly improve IM concentrating ability. The present study gives several plausible scenarios consistent with accumulation of metabolically produced lactate osmoles, although only to the lower end of this range. For example, if 20% of entering glucose is consumed, the model predicts that papillary lactate would attain about 15 mM assuming vasa recta outflow is increased 30% by fluid absorbed from the nephrons and collecting ducts and that this lactate gradient would double if IM blood flow were reduced by one-half, as may occur in antidiuresis. Several experimental tests of the hypothesis are indicated.

Molecular action of vitamin E in lipoprotein oxidation: implications for atherosclerosis

The oxidation theory of atherosclerosis proposes that the oxidative modification of low-density lipoproteins (LDL) plays a central role in the disease. Although a direct causative role of LDL oxidation for atherogenesis has not been established, oxidized lipoproteins are detected in atherosclerotic lesions, and in vitro oxidized LDL exhibits putative pro-atherogenic activities. alpha-Tocopherol (alpha-TOH; vitamin E), the major lipid-soluble antioxidant present in lipoproteins, is thought to be antiatherogenic. However, results of vitamin E interventions on atherosclerosis in experimental animals and cardiovascular disease in humans have been inconclusive. Also, recent mechanistic studies demonstrate that the role of alpha-TOH during the early stages of lipoprotein lipid peroxidation is complex and that the vitamin does not act as a chain-breaking antioxidant. In the absence of co-antioxidants, compounds capable of reducing the alpha-TOH radical and exporting the radical from the lipoprotein particle, alpha-TOH exhibits anti- or pro-oxidant activity for lipoprotein lipids depending on the degree of radical flux and reactivity of the oxidant. The model of tocopherol-mediated peroxidation (TMP) explains the complex molecular action of alpha-TOH during lipoprotein lipid peroxidation and antioxidation. This article outlines the salient features of TMP, comments on whether TMP is relevant for in vivo lipoprotein lipid oxidation, and discusses how co-antioxidants may be required to attenuate lipoprotein lipid oxidation in vivo and perhaps atherosclerosis.

Redox reactions related to indoleamine 2,3-dioxygenase and tryptophan metabolism along the kynurenine pathway

The heme enzyme indoleamine 2,3-dioxygenase (IDO) oxidizes the pyrrole moiety of L-tryptophan (Trp) and other indoleamines and represents the initial and rate-limiting enzyme of the kynurenine (Kyn) pathway. IDO is a unique enzyme in that it can utilize superoxide anion radical (O2*- ) as both a substrate and a co-factor. The latter role is due to the ability of O2*- to reduce inactive ferric-IDO to the active ferrous form. Nitrogen monoxide (*NO) and H2O2 inhibit the dioxygenase and various inter-relationships between the nitric oxide synthase- and IDO-initiated amino acid degradative pathways exist. Induction of IDO and metabolism of Trp along the Kyn pathway is implicated in a variety of physiological and pathophysiological processes, including anti-microbial and anti-tumor defense, neuropathology, immunoregulation and antioxidant activity. Antioxidant activity may arise from O2*- scavenging by IDO and formation of the potent radical scavengers and Kyn pathway metabolites, 3-hydroxyanthranilic acid and 3-hydroxykynurenine. Under certain conditions, these aminophenols and other Kyn pathway metabolites may exhibit pro-oxidant activities. This article reviews findings indicating that redox reactions are involved in the regulation of IDO and Trp metabolism along the Kyn pathway and also participate in the biological activities exhibited by Kyn pathway metabolites.

Antioxidant activities and redox regulation of interferon-gamma-induced tryptophan metabolism in human monocytes and macrophages

This article summarises studies supporting the proposal that induction of L-tryptophan (Trp) degradation along the kynurenine pathway in human monocytes and macrophages by interferon-gamma (IFN gamma) represents a novel extracellular antioxidant defence that acts to prevent inadvertent oxidative damage to host tissue during inflammation. The studies show that formation and release of the aminophenolic antioxidant 3-hydroxyanthranilic acid (3-HAA) is responsible for the ability of IFN gamma-primed human macrophages to inhibit the oxidation of low density lipoprotein (LDL); an event implicated as an important event in atherogenesis. 3-HAA efficiently inhibits LDL oxidation by acting as an aqueous oxidant scavenger and a synergist for LDL-associated vitamin E. Indoleamine 2,3-dioxygenase activity (IDO) is the initial and rate limiting enzyme of Trp degradation along the kynurenine pathway. Nitric oxide inhibits IDO activity in IFN gamma-primed human macrophages and this may represent a physiological regulatory mechanism of the dioxygenase during inflammation.

Nasal and exhaled nitric oxide is reduced in adult patients with cystic fibrosis and does not correlate with cystic fibrosis genotype

STUDY OBJECTIVES

Inducible nitric oxide synthase (iNOS) is upregulated in a number of inflammatory lung conditions, and exhaled nitric oxide (NO) concentration is increased. However, previous studies in children with cystic fibrosis (CF) have shown that exhaled NO is reduced. The purpose of this investigation was to study exhaled NO concentration in adults with CF, and to investigate the effect of CF genotype and respiratory tract infection on this measurement.

DESIGN

Exhaled and nasal NO levels were measured in 54 adult CF subjects and 37 healthy nonsmoking age-matched subjects using a chemiluminesence analyzer. Spirometry (FEV(1) and FVC), CF genotype, and bacterial colonization were also recorded.

SETTING

This study was conducted at a national CF center.

RESULTS

The mean age of patients was 26.9 years, and the mean FEV(1) was 50.5% predicted (range, 17 to 104%). Nasal NO in the CF patients (mean, 520 parts per billion [ppb]; confidence interval [CI], 452 to 588) was significantly lower (p < 0.001) than in control subjects (987 ppb; CI, 959 to 1,015). Exhaled NO was significantly lower (p < 0. 001) in CF patients (5.0 ppb; CI, 4.1 to 6.1) than in control subjects (7.3 ppb; CI, 6.8 to 7.8). FEV(1) did not correlate with nasal or exhaled NO. No association was observed between genotype and NO values or colonization with Pseudomonas aeruginosa.

CONCLUSIONS

Despite the airway inflammation that is characteristic of CF, both nasal and exhaled NO were reduced. There was no association with genotype or infection status. As NO has bacteriostatic effects and may augment mucociliary clearance, this observation may be of clinical importance.

Helicobacter pylori uptake and efflux: basis for intrinsic susceptibility to antibiotics in vitro

We previously demonstrated (M. M. Exner, P. Doig, T. J. Trust, and R. E. W. Hancock, Infect. Immun. 63:1567-1572, 1995) that Helicobacter pylori has at least one nonspecific porin, HopE, which has a low abundance in the outer membrane but forms large channels. H. pylori is relatively susceptible to most antimicrobial agents but less susceptible to the polycationic antibiotic polymyxin B. We demonstrate here that H. pylori is able to take up higher basal levels of the hydrophobic fluorescent probe 1-N-phenylnaphthylamine (NPN) than Pseudomonas aeruginosa or Escherichia coli, consistent with its enhanced susceptibility to hydrophobic agents. Addition of polymyxin B led to a further increase in NPN uptake, indicative of a self-promoted uptake pathway, but it required a much higher amount of polymyxin B to yield a 50% increase in NPN uptake in H. pylori (6 to 8 microg/ml) than in P. aeruginosa or E. coli (0.3 to 0.5 microg/ml), suggesting that H. pylori has a less efficient self-promoted uptake pathway. Since intrinsic resistance involves the collaboration of restricted outer membrane permeability and secondary defense mechanisms, such as periplasmic beta-lactamase (which H. pylori lacks) or efflux, we examined the possible role of efflux in antibiotic susceptibility. We had previously identified in H. pylori 11637 the presence of portions of three genes with homology to potential restriction-nodulation-division (RND) efflux systems. It was confirmed that H. pylori contained only these three putative RND efflux systems, named here hefABC, hefDEF, and hefGHI, and that the hefGHI system was expressed only in vivo while the two other RND systems were expressed both in vivo and in vitro. In uptake studies, there was no observable energy-dependent tetracycline, chloramphenicol, or NPN efflux activity in H. pylori. Independent mutagenesis of the three putative RND efflux operons in the chromosome of H. pylori had no effect on the in vitro susceptibility of H. pylori to 19 antibiotics. These results, in contrast to what is observed in E. coli, P. aeruginosa, and other clinically important gram-negative bacteria, suggest that active efflux does not play a role in the intrinsic resistance of H. pylori to antibiotics.

Expression of Acidothermus cellulolyticus endoglucanase E1 in transgenic tobacco: biochemical characteristics and physiological effects

The expression of the Acidothermus cellulolyticus endoglucanase E1 gene in transgenic tobacco (Nicotiana tabacum) was examined in this study, where E1 coding sequence was transcribed under the control of a leaf specific Rubisco small subunit promoter (tomato RbcS-3C). Targeting the E1 protein to the chloroplast was established using a chloroplast transit peptide of Rubisco small subunit protein (tomato RbcS-2A) and confirmed by immunocytochemistry. The E1 produced in transgenic tobacco plants was found to be biologically active, and to accumulate in leaves at levels of up to 1.35% of total soluble protein. Optimum temperature and pH for E1 enzyme activity in leaf extracts were 81 degrees C and 5.25, respectively. E1 activity remained constant on a gram fresh leaf weight basis, but dramatically increased on a total leaf soluble protein basis as leaves aged, or when leaf discs were dehydrated. E1 protein in old leaves, or after 5 h dehydration, was partially degraded although E1 activity remained constant. Transgenic plants exhibited normal growth and developmental characteristics with photosynthetic rates similar to those of untransformed SR1 tobacco plants. Results from these biochemical and physiological analyses suggest that the chloroplast is a suitable cellular compartment for accumulation of the hydrolytic E1 enzyme.

Follicular or Hürthle cell neoplasm of the thyroid: can clinical factors be used to predict carcinoma and determine extent of thyroidectomy?

BACKGROUND

Fine-needle aspiration biopsy (FNAB) and frozen section exam are of limited or no value in distinguishing benign and malignant follicular or Hürthle cell neoplasms of the thyroid gland.

METHODS

Patients who underwent thyroidectomy for treatment of a follicular or Hürthle cell neoplasm between 1990 and 1998 were identified and evaluated for age, gender, head and neck irradiation, nodule size, and cytologic atypia to determine whether clinical factors were predictive of carcinoma.

RESULTS

Of the 352 patients evaluated for nodular thyroid disease, 75 (21%) underwent thyroidectomy after an indeterminate FNAB finding, 66 with follicular and 9 with a Hürthle cell neoplasm. Seventeen (23%) of the patients had carcinoma-follicular variant of papillary (10), follicular (6), and Hürthle cell (1). Carcinoma was diagnosed in 15 of 64 women and 2 of 11 men (P > .05). The mean age was 43 +/- 21 years and 50 +/- 16 years, respectively, in patients with and without carcinoma (P > . 05). Three patients had previous neck irradiation and none had carcinoma. Mean nodule size was 4.2 +/- 2.7 cm and 4.3 +/- 3.5 cm, respectively, in patients with and without carcinoma (P > . 05). Cytologic atypia was present in 8 of 17 patients with carcinoma and 20 of 58 patients without carcinoma (P > .05).

CONCLUSIONS

Clinical factors were not helpful in predicting carcinoma in patients with an indeterminate FNAB finding and thus cannot be used to reliably select patients for more extensive thyroidectomy.

Intravascular irradiation using Re-186 liquid-filled balloon catheters: correlation between experimental and theoretical studies

PURPOSE

Optimization of intravascular radiation to reduce stenosis following coronary angioplasty requires the ability to predict the patterns of radiation dose distribution. This investigation evaluated the agreement between Monte Carlo simulations and experimental radiation dose measurements for a radioisotope liquid-filled balloon catheter in a tissue equivalent phantom.

METHODS AND MATERIALS

Direct measurements of the radiation dose from Re-186 liquid-filled balloons were made using thermoluminescent dosimeters (TLDs) and radiochromic film. Monte Carlo simulations were carried out using the Monte Carlo N-Particle code system (MCNP4B).

RESULTS

The Monte Carlo generated dose values agreed with the experimentally determined results within the statistical uncertainty. A slightly higher penetration was indicated by regression analysis for the TLD data relative to the MCNP4B prediction that may be due to experimental configuration anomalies. For this balloon catheter, approximately 55 mCi of Re-186 will deliver 15 Gy at a 0.5 mm depth in tissue equivalent material in 5 min.

CONCLUSIONS

Correlation between experimentally measured dose values and Monte Carlo computation supports the position that MCNP4B simulations constitute a valuable tool for investigating various clinical therapy designs. The agreement between Monte Carlo calculations and experiments provide confidence in applying MCNP4B to more sophisticated geometries of interest, and other methods of intravascular radiation dose delivery.

Cloning and expression of Trichoderma reesei cellobiohydrolase I in Pichia pastoris

Pichia pastoris was transformed with the Trichoderma reesei cbh1 gene, and the recombinant enzyme was purified and analyzed kinetically and by circular dichroism. The P. pastoris rCBH I was recognized by MoAb raised to T. reesei CBH I but was found in multiple molecular weight species on SDS-PAGE gels. Carbohydrate content determination and SDS-PAGE western analysis indicated that the recombinant protein was hyperglycosylated, although a species very similar in molecular weight to the T. reesei enzyme could be isolated chromatographically. The P. pastoris rCBH I also demonstrated activity toward soluble and insoluble substrates (i.e., pNPL and Sigmacell), although at a level significantly lower than the wild-type enzyme. More seriously, the yeast-expressed enzyme showed non-wild-type secondary structure by circular dichroism. We conclude that P. pastoris may not serve as an adequate host for the site-directed mutagenesis of T. reesei CBH I.

MIRD Pamphlet No. 14 revised: A dynamic urinary bladder model for radiation dose calculations. Task Group of the MIRD Committee, Society of Nuclear Medicine

The constant-volume urinary bladder model in the standard MIRD Pamphlet No. 5 (Revised) phantom has recognized limitations. Various investigators have developed detailed models incorporating more physiologically realistic features, such as expanding bladder contents and residual volume, and variable urinary input rate, initial volume and first void time. We have reviewed these published models and have developed a new model for calculation of radiation absorbed dose to the urinary bladder wall incorporating these aspects.

METHODS

The model consists of a spherical source with variable volume to simulate the bladder contents and a wall represented by a spherical shell of constant volume. The wall thickness varies as the source expands or contracts. The model provides for variable urine entry rate (three different hydration states), initial bladder contents volume, residual volume and first void time. The voiding schedule includes an extended nighttime gap during which the urine entry rate is reduced to one-half the daytime rate.

RESULTS

Radiation-absorbed dose estimates have been calculated for the bladder wall surface (including photon and electron components) and at several depths in the wall (electron component) for 2-18F-fluoro-2-deoxy-D-glucose, 99mTc-diethylenetriaminepentaacetic acid (DTPA), 99mTc-HEDP, 99mTc-pertechnetate, 99mTc-red blood cells (RBCs), 99mTc-glucoheptonate, 99mTc-mercaptoacetyltriglicine chelator (MAG3), 99mTc-methylene diphosphonate (MDP), 99mTc-hexamethylpropylene amine oxime (HMPAO), 99mTc-human serum albumin (HSA), 99mTc-MIBI (rest and stress), 123I-/124I-/131I-OIH, 123I/131I-NaI, 125I-iothalamate, 111In-DTPA and 89Sr-SrCl.

CONCLUSION

The new model tends to give a higher radiation absorbed dose to the bladder wall surface than the previous models. Large initial bladder volumes and higher rates of urine flow into the bladder result in lower bladder wall dose. The optimal first voiding time is from 40 min to 3 hr postadministration, depending on radiopharmaceutical. The data as presented in tabular and graphic form for each compound provide guidance for establishing radiation absorbed dose reduction protocols.

MIRD pamphlet no. 16: Techniques for quantitative radiopharmaceutical biodistribution data acquisition and analysis for use in human radiation dose estimates

This report describes recommended techniques for radiopharmaceutical biodistribution data acquisition and analysis in human subjects to estimate radiation absorbed dose using the Medical Internal Radiation Dose (MIRD) schema. The document has been prepared in a format to address two audiences: individuals with a primary interest in designing clinical trials who are not experts in dosimetry and individuals with extensive experience with dosimetry-based protocols and calculational methodology. For the first group, the general concepts involved in biodistribution data acquisition are presented, with guidance provided for the number of measurements (data points) required. For those with expertise in dosimetry, highlighted sections, examples and appendices have been included to provide calculational details, as well as references, for the techniques involved. This document is intended also to serve as a guide for the investigator in choosing the appropriate methodologies when acquiring and preparing product data for review by national regulatory agencies. The emphasis is on planar imaging techniques commonly available in most nuclear medicine departments and laboratories. The measurement of the biodistribution of radiopharmaceuticals is an important aspect in calculating absorbed dose from internally deposited radionuclides. Three phases are presented: data collection, data analysis and data processing. In the first phase, data collection, the identification of source regions, the determination of their appropriate temporal sampling and the acquisition of data are discussed. In the second phase, quantitative measurement techniques involving imaging by planar scintillation camera, SPECT and PET for the calculation of activity in source regions as a function of time are discussed. In addition, nonimaging measurement techniques, including external radiation monitoring, tissue-sample counting (blood and biopsy) and excreta counting are also considered. The third phase, data processing, involves curve-fitting techniques to integrate the source time-activity curves (determining the area under these curves). For some applications, compartmental modeling procedures may be used. Last, appendices are included that provide a table of symbols and definitions, a checklist for study protocol design, example formats for quantitative imaging protocols, temporal sampling error analysis techniques and selected calculational examples. The utilization of the presented approach should aid in the standardization of protocol design for collecting kinetic data and in the calculation of absorbed dose estimates.

Radiation dosimetry in nuclear medicine

Radionuclides are used in nuclear medicine in a variety of diagnostic and therapeutic procedures. A knowledge of the radiation dose received by different organs in the body is essential to an evaluation of the risks and benefits of any procedure. In this paper, current methods for internal dosimetry are reviewed, as they are applied in nuclear medicine. Particularly, the Medical Internal Radiation Dose (MIRD) system for dosimetry is explained, and many of its published resources discussed. Available models representing individuals of different age and gender, including those representing the pregnant woman are described; current trends in establishing models for individual patients are also evaluated. The proper design of kinetic studies for establishing radiation doses for radiopharmaceuticals is discussed. An overview of how to use information obtained in a dosimetry study, including that of the effective dose equivalent (ICRP 30) and effective dose (ICRP 60), is given. Current trends and issues in internal dosimetry, including the calculation of patient-specific doses and in the use of small scale and microdosimetry techniques, are also reviewed.

A role for reduced coenzyme Q in atherosclerosis?

Substantial evidence implicates oxidative modification of low density lipoprotein (LDL) as an important event contributing to atherogenesis. As a result, the elucidation of the molecular mechanisms by which LDL is oxidized and how such oxidation is prevented by antioxidants has been a significant research focus. Studies on the antioxidation of LDL lipids have focused primarily on alpha-tocopherol (alpha-TOH), biologically and chemically the most active form of vitamin E and quantitatively the major lipid-soluble antioxidant in extracts prepared from human LDL. In addition to alpha-TOH, plasma LDL also contains low levels of ubiquinol-10 (CoQ10H2; the reduced form of coenzyme Q10). Recent studies have shown that in oxidizing plasma lipoproteins alpha-TOH can exhibit anti- or pro-oxidant activities for the lipoprotein's lipids exposed to a vast array of oxidants. This article reviews the molecular action of alpha-TOH in LDL undergoing "mild" radical-initiated lipid peroxidation, and discusses how small levels of CoQ10H2 can represent an efficient antioxidant defence for lipoprotein lipids. We also comment on the levels alpha-TOH, CoQ10H2 and lipid oxidation products in the intima of patients with coronary artery disease and report on preliminary studies examining the effect of coenzyme Q10 supplementation on atherogenesis in apolipoprotein E knockout mice.

MIRD pamphlet No. 17: the dosimetry of nonuniform activity distributions--radionuclide S values at the voxel level. Medical Internal Radiation Dose Committee

The availability of quantitative three-dimensional in vivo data on radionuclide distributions within the body makes it possible to calculate the corresponding nonuniform distribution of radiation absorbed dose in body organs and tissues. This pamphlet emphasizes the utility of the MIRD schema for such calculations through the use of radionuclide S values defined at the voxel level. The use of both dose point-kernels and Monte Carlo simulation methods is also discussed. PET and SPECT imaging can provide quantitative activity data in voxels of several millimeters on edge. For smaller voxel sizes, accurate data cannot be obtained using present imaging technology. For submillimeter dimensions, autoradiographic methods may be used when tissues are obtained through biopsy or autopsy. Sample S value tabulations for five radionuclides within cubical voxels of 3 mm and 6 mm on edge are given in the appendices to this pamphlet. These S values may be used to construct three-dimensional dose profiles for nonuniform distributions of radioactivity encountered in therapeutic and diagnostic nuclear medicine. Data are also tabulated for 131I in 0.1-mm voxels for use in autoradiography. Two examples illustrating the use of voxel S values are given, followed by a discussion of the use of three-dimensional dose distributions in understanding and predicting biologic response.

Bilateral trigger thumbs in identical twins

Bilateral trigger thumbs in 4-year-old identical male twins are reported. To the authors' best knowledge, this is the first true description of this condition in identical twins. All four thumbs were treated by surgical release of the A1 pulley, with good results. The causes proposed for congenital and acquired trigger thumb are discussed, and it is concluded that the cases described here support a genetic predisposition to the condition.

The MIRD perspective 1999. Medical Internal Radiation Dose Committee

The MIRD schema is a general approach for medical internal radiation dosimetry. Although the schema has traditionally been used for organ dosimetry, it is also applicable to dosimetry at the suborgan, voxel, multicellular and cellular levels. The MIRD pamphlets that follow in this issue and in coming issues, as well as the recent monograph on cellular dosimetry, demonstrate the flexibility of this approach. Furthermore, these pamphlets provide new tools for radionuclide dosimetry applications, including the dynamic bladder model, S values for small structures within the brain (i.e., suborgan dosimetry), voxel S values for constructing three-dimensional dose distributions and dose-volume histograms and techniques for acquiring quantitative distribution and pharmacokinetic data.

Cycles and separations in a model of the renal medulla

This study gives the first quantitative analysis of net steady-state transmural fluxes of water, urea, and NaCl in a numerical model of the rat renal medulla in antidiuresis, revealing the model's predictions of water, urea, and NaCl cycling patterns. These predictions are compared both to in vivo micropuncture data from the literature and to earlier qualitative proposals (e.g., K. V. Lemley and W. Kriz. Kidney Int. 31: 538-548, 1987) of cycling and exchange patterns based on medullary anatomy and available permeability and transport parameter measurements. The analysis is based on our most recent three-dimensional model [X. Wang, S. R. Thomas, and A. S. Wexler. Am. J. Physiol. 274 (Renal Physiol. 43): F413-F424, 1998]. In general agreement with earlier proposed patterns, this analysis predicts the following: 1) important water short-circuiting from descending structures to ascending vasa recta in most medullary regions, 2) massive urea recycling in the upper inner medulla, 3) a progressive increase of the ratio of urea to total osmoles along the corticopapillary axis, 4) urea dumped from the collecting ducts (CD) into the deep papilla is returned to the cortex essentially via outer medullary short vasa recta, bearing witness to a shift from the long descending limbs and vasa recta of the inner medulla (IM) to short structures in the outer medulla (OM). The analysis also shows that the known radial heterogeneity of the inner stripe (IS) implies unequal osmolalities in long descending limbs, vasa recta, and CDs entering the IM across the OM/IM border and explains the model's unorthodox osmolality profile along the CD. In conflict with micropuncture evidence of a doubling of urea flow in superficial Henle's loops (SHL) between the end proximal and early distal tubule (T. Armsen and H. W. Reinhardt. Pflügers Arch. 326: 270-280, 1971), the model predicts net urea loss from SHL due to the model's inclusion of nonneglible measured urea permeability of medullary thick ascending limbs [M. A. Knepper, Am. J. Physiol. 245 (Renal Fluid Electrolyte Physiol. 14): F634-F639, 1983]. We present a suite of adjusted model permeabilities that improves agreement with the micropuncture data on this point. In conclusion, this modeling analysis of solute and water recycling serves as a quantitative check on qualitative propositions in the literature and allows closer critical comparison of model behavior with published experimental results than was heretofore possible.

Methicillin-resistant Staphylococcus aureus: impact at a national cystic fibrosis centre

In many patient populations there has been a progressive increase in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA). We examined the prevalence and consequences of acquiring MRSA in the adult cystic fibrosis (CF) population at Royal Brompton. Patients who became colonized by MRSA between 1965 and 1997 were identified from an existing database and case-notes were reviewed. Clinical and microbiological data were recorded. Twenty-six patients became colonized with MRSA during this period. Median age at acquisition was 23.4 years (range 11.8-43.3 years) and median FEV1 (percent predicted) was 28.9% (range 12-81%). Twenty patients (77%) had an FEV1 of < or = 40% predicted MRSA was probably acquired by four patients at Royal Brompton. In 17 patients isolates wer first identified whilst under the care of a total of 11 other institutions. Since the first case of MRSA infection in 1982, there has been an increase in prevalence to a current rate of nine cases in the first seven months of 1997. The commonest site of colonization was the lower airway (96%); the nose (23%) and skin sites (15%) were more rarely affected. Duration of colonization was frequently brief with nine cases (35%) lasting less than one month. The identification of MRSA appeared to be of little clinical significance, and did not generally affect outcomes. Only three patients were MRSA positive at the time of death, and in only one of these was MRSA considered a possible contributing factor.

Hydrolysis of cellulose using ternary mixtures of purified cellulases

The saccharification of microcrystalline cellulose by reconstituted ternary mixtures of purified cellulases (one endoglucanase and two cellobiohydrolases) has been studied over the entire range of mixture compositions. Ternary plots are used to compare the performance of five synthetic mixtures drawn from the cellulase systems of Acidothermus cellulolyticus, Trichoderma reesei, Thermomonospora fusca, and Thermotoga neapolitana. Results reveal that at least one synthetic mixture utilizing enzymes from three different organisms delivers performance competitive with that of a "native" (i.e., co-evolved) ternary system drawn exclusively from T. reesei. This heterologous system, consisting of the endoglucanase E1 from A. cellulolyticus and the exoglucanases CBHI from T. reesei and E3 from T. fusca, is forgiving from the system-design point of view, in that it delivers high saccharification rates over a wide range of mixture compositions.