Computed tomography vs cardiovascular magnetic resonance imaging derived extracellular volume fraction in patients with stable new-onset chest pain

Background

Computed tomography (CT) is increasingly recognised as a diagnostic modality across a range of cardiovascular conditions and is now first-line for the investigation of stable new-onset chest pain. Determination of the myocardial extracellular volume fraction (ECV) has been shown to correlate well with the identification and prognostication of disease. Cardiovascular magnetic resonance (CMR) imaging remains the gold standard for the measurement of myocardial ECVCMR using T1-mapping, but there is increasing evidence for the use of ECV by cardiac CT (ECVCT).

Purpose

To assess the performance of ECVCT against the reference standard of ECVCMR.

Methods

Patients with a history of chest pain and no previously documented coronary disease referred for invasive angiography were recruited as part of the EVINCI Heart-QIT study. A cohort of these patients (n=33) underwent CMR at 1.5T (Siemens Aera, Siemens Healthcare, Erlangen/Germany) with T1 mapping of a mid-ventricular short axis slice (by MOdified Look-Locker Inversion recovery [MOLLI]) before and 15 minutes after a bolus of gadolinium contrast (0.1 mmol/kg gadoterate meglumine), followed by whole-heart ECVCT quantification (Somatom Force, Siemens Healthcare, Erlangen/Germany) using a 5-min post-iodine-contrast acquisition protocol. To account for data clustering on a patient level and volumetric discrepancy on a modality level, comparisons were made using mid-ventricular pooled ECVCT and ECVCMR. Bland-Altman analysis was used to determine the limits of agreement and identify systematic differences between both measures.

Results

A total of 33 patients (70% male, mean age 56.8±12.6yr) underwent the combined CMR and CT. ECVCMR and ECVCT were then analysed retrospectively (Figure 1). The average pooled ECV for the 6 mid-ventricular segments for CMR and CT were (27.6±2.4 and 26.8±2.2 respectively). Bland-Altman analysis demonstrated a marginally higher CMR-ECV (0.8±2.1) vs CT-ECV, which is in keeping with the longer delay-time encountered in CMR protocols (Figure 2).

Conclusions

ECVCT obtained from 5-minute post-contrast CT protocols show good agreement with ECVCMR in a stable chest pain patient cohort.

Funding Acknowledgement

Type of funding sources: Private grant(s) and/or Sponsorship. Main funding source(s): Siemens Helthineers Educational Grant Figure 1. CMR (L) and CT (R) ECV mapsFigure 2. Bland-Altman plot

Consensus exercise identifying priorities for research in the field of general surgery of childhood in the UK

BACKGROUND

The evidence base underlying clinical practice in children's general surgery is poor and high-quality collaborative clinical research is required to address current treatment uncertainties. The aim of this study was, through a consensus process, to identify research priorities for clinical research in this field amongst surgeons who treat children.

METHODS

Questions were invited in a scoping survey amongst general surgeons and specialist paediatric surgeons. These were refined by the study team and subsequently prioritized in a two-stage modified Delphi process.

RESULTS

In the scoping survey, a total of 226 questions covering a broad scope of children's elective and emergency general surgery were submitted by 76 different clinicians. These were refined to 71 research questions for prioritization. A total of 168 clinicians took part in stage one of the prioritization process, and 157 in stage two. A 'top 10' list of priority research questions was generated for both elective and emergency general surgery of childhood. These cover a range of conditions and concepts, including inguinal hernia, undescended testis, appendicitis, abdominal trauma and enhanced recovery pathways.

CONCLUSION

Through consensus amongst surgeons who treat children, 10 priority research questions for each of the elective and emergency fields have been identified. These should provide a basis for the development of high-quality multicentre research projects to address these questions, and ultimately improve outcomes for children requiring surgical care.

SLC6A3 coding variant Ala559Val found in two autism probands alters dopamine transporter function and trafficking

Emerging evidence associates dysfunction in the dopamine (DA) transporter (DAT) with the pathophysiology of autism spectrum disorder (ASD). The human DAT (hDAT; SLC6A3) rare variant with an Ala to Val substitution at amino acid 559 (hDAT A559V) was previously reported in individuals with bipolar disorder or attention-deficit hyperactivity disorder (ADHD). We have demonstrated that this variant is hyper-phosphorylated at the amino (N)-terminal serine (Ser) residues and promotes an anomalous DA efflux phenotype. Here, we report the novel identification of hDAT A559V in two unrelated ASD subjects and provide the first mechanistic description of its impaired trafficking phenotype. DAT surface expression is dynamically regulated by DAT substrates including the psychostimulant amphetamine (AMPH), which causes hDAT trafficking away from the plasma membrane. The integrity of DAT trafficking directly impacts DA transport capacity and therefore dopaminergic neurotransmission. Here, we show that hDAT A559V is resistant to AMPH-induced cell surface redistribution. This unique trafficking phenotype is conferred by altered protein kinase C β (PKCβ) activity. Cells expressing hDAT A559V exhibit constitutively elevated PKCβ activity, inhibition of which restores the AMPH-induced hDAT A559V membrane redistribution. Mechanistically, we link the inability of hDAT A559V to traffic in response to AMPH to the phosphorylation of the five most distal DAT N-terminal Ser. Mutation of these N-terminal Ser to Ala restores AMPH-induced trafficking. Furthermore, hDAT A559V has a diminished ability to transport AMPH, and therefore lacks AMPH-induced DA efflux. Pharmacological inhibition of PKCβ or Ser to Ala substitution in the hDAT A559V background restores AMPH-induced DA efflux while promoting intracellular AMPH accumulation. Although hDAT A559V is a rare variant, it has been found in multiple probands with neuropsychiatric disorders associated with imbalances in DA neurotransmission, including ADHD, bipolar disorder, and now ASD. These findings provide valuable insight into a new cellular phenotype (altered hDAT trafficking) supporting dysregulated DA function in these disorders. They also provide a novel potential target (PKCβ) for therapeutic interventions in individuals with ASD.

Macrolide Resistance from the Ribosome Perspective

Macrolides are important antibiotics used in treatment of respiratory tract infections in humans. Although some of these compounds have been in use for 50 years, it has not been until the last few years that their mechanism of action and the nature of ribosomal-based resistance could be more fully understood. With the advent of robust crystals of ribosomal 50S subunits, and structural resolution of macrolides and ketolides complexed to either Haloarcula marismortui or Deinococcus radiodurans 50S, the ability to dissect the binding modes and understand resistance at the level of the ribosome became possible. This review article compares the binding features of 14-, 15-, and 16-membered macrolides to that of ketolides telithromycin and ABT-773 as revealed at the atomistic level. Attempts to understand how modifications to 23S rRNA and/or mutations in ribosomal proteins L4 and L22 that have been found to confer resistance in Streptococcus pneumoniae, Streptococcus pyogenes, and Haemophilus influenzae are told from the perspective of the ribosome.

CJ-15,801, a novel antibiotic from a fungus, Seimatosporium sp

A novel antibiotic, CJ-15,801 (I), was isolated from the fermentation broth of a fungus, Seimatosporium sp. CL28611. The structure was determined to be a pantothenic acid analog having an alpha,beta-unsaturated carboxylic acid moiety by spectroscopic analyses. The compound inhibits the growth of multi-drug resistant (MDR) Staphylococcus aureus strains with MIC ranging from 6.25 to 50 microg/ml.

A new antibiotic CJ-17,665 from Aspergillus ochraceus

A new antibiotic, CJ-17,665 (I) was isolated from the fermentation broth of Aspergillus ochraceus, CL41582. It inhibits growth of multi-drug resistant Staphylococcus aureus, Streptococcus pyogenes, and Enterococcus faecalis, with MICs of 12.5, 12.5 and 25 microg/ml, respectively. The structure contains a diketopiperazine and an indole N-oxide moiety that is unusual in natural products.

New pyrrolizidinone antibiotics CJ-16,264 and CJ-16,367

Two new antibiotics, CJ-16,264 (I) and CJ-16,367 (II), were isolated from the fermentation broth of an unidentified fungus CL39457. These antibiotics have a pyrrolizidinone skeleton, first discovered in fungi. Compounds I and II inhibit the growth of Gram-positive multi-drug resistant bacteria and some Gram-negative strains such as Moraxella catarrhalis and Escherichia coli with altered permeability (imp). Comparison of an antibacterial profile between the two compounds suggested that the gamma-lactone portion of I is important for the activity.

Identification of an erm(A) erythromycin resistance methylase gene in Streptococcus pneumoniae isolated in Greece

In a serotype 11A clone of erythromycin-resistant pneumococci isolated from young Greek carriers, we identified the nucleotide sequence of erm(A), a methylase gene previously described as erm(TR) in Streptococcus pyogenes. The erm(A) pneumococci were resistant to 14- and 15-member macrolides, inducibly resistant to clindamycin, and susceptible to streptogramin B. To our knowledge, this is the first identification of resistance to erythromycin in S. pneumoniae attributed solely to the carriage of the erm(A) gene.

Two new mechanisms of macrolide resistance in clinical strains of Streptococcus pneumoniae from Eastern Europe and North America

Resistance to macrolides in pneumococci is generally mediated by methylation of 23S rRNA via erm(B) methylase which can confer a macrolide (M)-, lincosamide (L)-, and streptogramin B (S(B))-resistant (MLS(B)) phenotype or by drug efflux via mef(A) which confers resistance to 14- and 15-membered macrolides only. We studied 20 strains with unusual ML or MS(B) phenotypes which did not harbor erm(B) or mef(A). The strains had been isolated from patients in Eastern Europe and North America from 1992 to 1998. These isolates were found to contain mutations in genes for either 23S rRNA or ribosomal proteins. Three strains from the United States with an ML phenotype, each representing a different clone, were characterized as having an A2059G (Escherichia coli numbering) change in three of the four 23S rRNA alleles. Susceptibility to macrolides and lincosamides decreased as the number of alleles in isogenic strains containing A2059G increased. Sixteen MS(B) strains from Eastern Europe were found to contain a 3-amino-acid substitution ((69)GTG(71) to TPS) in a highly conserved region of the ribosomal protein L4 ((63)KPWRQKGTGRAR(74)). These strains formed several distinct clonal types. The single MS(B) strain from Canada contained a 6-amino-acid L4 insertion ((69)GTGREKGTGRAR), which impacted growth rate and also conferred a 500-fold increase in MIC on the ketolide telithromycin. These macrolide resistance mechanisms from clinical isolates are similar to those recently described for laboratory-derived mutants.

A SPECT study of the effect of vagal nerve stimulation on thalamic activity in patients with epilepsy

The mechanism by which vagal nerve stimulation (VNS) exerts an anticonvulsant effect in humans is unknown. This study used (99m)Tc-HMPAO single photon emission tomography (SPECT) to examine the effects of VNS on regional cerebral activity in thalamic and insular regions. Seven subjects with epilepsy who had been receiving vagal nerve stimulation for at least 6 months underwent SPECT scanning with simultaneous scalp electroencephalographic (EEG) recording. Subjects were studied in two states; during VNS activity and during a comparison condition of VNS inactivity. A region of interest analysis demonstrated that rapid cycling stimulation (7 seconds on, 12 seconds off) was associated with relatively decreased activity in left and right medial thalamic regions. No systematic stimulation-related changes were observed on visual or spectral analysis of EEG data. The thalamus is involved in modulation of ongoing cortical EEG activity in animals. Our results support the hypothesis that VNS may exert an antiepileptic action by an effect on thalamic activity.

Mutations in 23S rRNA and ribosomal protein L4 account for resistance in pneumococcal strains selected in vitro by macrolide passage

The mechanisms responsible for macrolide resistance in Streptococcus pneumoniae mutants, selected from susceptible strains by serial passage in azithromycin, were investigated. These mutants were resistant to 14- and 15-membered macrolides, but resistance could not be explained by any clinically relevant resistance determinant [mef(A), erm(A), erm(B), erm(C), erm(TR), msr(A), mph(A), mph(B), mph(C), ere(A), ere(B)]. An investigation into the sequences of 23S rRNAs in the mutant and parental strains revealed individual changes of C2611A, C2611G, A2058G, and A2059G (Escherichia coli numbering) in four mutants. Mutations at these residues in domain V of 23S rRNA have been noted to confer erythromycin resistance in other species. Not all four 23S rRNA alleles have to contain the mutation to confer resistance. Some of the mutations also confer coresistance to streptogramin B (C2611A, C2611G, and A2058G), 16-membered macrolides (all changes), and clindamycin (A2058G and A2059G). Interestingly, none of these mutations confer high-level resistance to telithromycin (HMR-3647). Further, two of the mutants which had no changes in their 23S rRNA sequences had changes in a highly conserved stretch of amino acids ((63)KPWRQKGTGRAR(74)) in ribosomal protein L4. One mutant contained a single amino acid change (G69C), while the other mutant had a 6-base insert, resulting in two amino acids (S and Q) being inserted between amino acids Q67 and K68. To our knowledge, this is the first description of mutations in 23S rRNA genes or ribosomal proteins in macrolide-resistant S. pneumoniae strains.

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.

Appetitive behavior, compulsivity, and neurochemistry in Prader-Willi syndrome

Advances in genetic research have led to an increased understanding of genotype-phenotype relationships. Excessive eating and weight gain characteristic of Prader-Willi syndrome (PWS) have been the understandable focus of much of the research. The intense preoccupation with food, lack of satiation, and incessant food seeking are among the most striking features of PWS. It has become increasingly clear that the behavioral phenotype of PWS also includes symptoms similar to obsessive compulsive disorder, which in all probability interact with the incessant hunger and lack of satiation to engender the intense preoccupation and food seeking behavior that is characteristic of this disorder. Several lines of evidence suggest that genetic material on chromosome 15 may alter synthesis, release, metabolism, binding, intrinsic activity, or reuptake of specific neurotransmitters, or alter the receptor numbers and/or distribution involved in modulating feeding. Among the likely candidates are GABAnergic, serotonergic, and neuropeptidergic mechanisms. This review summarizes what is known about the appetitive behavior and compulsivity in PWS and discusses the possible mechanisms underlying these behaviors. MRDD Research Reviews 2000;6:125-130.

mefE is necessary for the erythromycin-resistant M phenotype in Streptococcus pneumoniae

Recently, it was shown that a significant number of erythromycin-resistant Streptococcus pneumoniae and Streptococcus pyogenes strains contain a determinant that mediates resistance via a putative efflux pump. The gene encoding the erythromycin-resistant determinant was cloned and sequenced from three strains of S. pneumoniae bearing the M phenotype (macrolide resistant but clindamycin and streptogramin B susceptible). The DNA sequences of mefE were nearly identical, with only 2-nucleotide differences between genes from any two strains. When the mefE sequences were compared to the mefA sequence from S. pyogenes, the two genes were found to be closely related (90% identity). Strains of S. pneumoniae were constructed to confirm that mefE is necessary to confer erythromycin resistance and to explore the substrate specificity of the pump; no substrates other than 14- and 15-membered macrolides were identified.

Detection of erythromycin-resistant determinants by PCR

Erythromycin resistance determinants include Erm methylases, efflux pumps, and inactivating enzymes. To distinguish the different mechanisms of resistance in clinical isolates, PCR primers were designed so that amplification of the partial gene products could be detected in multiplex PCRs. This methodology enables the direct sequencing of amplified PCR products that can be used to compare resistance determinants in clinical strains. Further, this methodology could be useful in surveillance studies of erythromycin-resistant determinants.

Glycylcyclines bind to the high-affinity tetracycline ribosomal binding site and evade Tet(M)- and Tet(O)-mediated ribosomal protection

N,N-dimethylglycylamido (DMG) derivatives of 6-demethyl-6-deoxytetracycline and doxycycline bind 5-fold more effectively than tetracycline to the tetracycline high-affinity binding site on the Escherichia coli 70S ribosome, which correlates with a 10-fold increase in potency for inhibition of E. coli cell-free translation. The potencies of DMG-doxycycline and DMG-6-demethyl-6-deoxytetracycline were unaffected by the ribosomal tetracycline resistance factors Tet(M) and Tet(O) in cell-free translation assays and whole-cell bioassays with a conditional Tet(M)-producing E. coli strain.

Streptococcus pneumoniae and Streptococcus pyogenes resistant to macrolides but sensitive to clindamycin: a common resistance pattern mediated by an efflux system

Macrolide-resistant Streptococcus pyogenes isolates from Finland, Australia, and the United Kingdom and, more recently, Streptococcus pneumoniae and S. pyogenes strains from the United States were shown to have an unusual resistance pattern to macrolides, lincosamides, and streptogramin B antibiotics. This pattern, referred to as M resistance, consists of susceptibility to clindamycin and streptogramin B antibiotics but resistance to 14- and 15-membered macrolides. An evaluation of the macrolide-lincosamide-streptogramin B resistance phenotypes among our streptococcal strains collected from 1993 to 1995 suggested that this unusual resistance pattern is not rare. Eighty-five percent (n = 66) of the S. pneumoniae and 75% (n = 28) of the S. pyogenes strains in our collection had an M phenotype. The mechanism of M resistance was not mediated by target modification, as isolated ribosomes from a pneumococcal strain bearing the M phenotype were fully sensitive to erythromycin. Further, the presence of an erm methylase was excluded with primers specific for an erm consensus sequence. However, results of studies that determined the uptake and incorporation of radiolabeled erythromycin into cells were consistent with the presence of a macrolide efflux determinant. The putative efflux determinant in streptococci seems to be distinct from the multicomponent macrolide efflux system in coagulase-negative staphylococci. The recognition of the prevalence of the M phenotype in streptococci has implications for sensitivity testing and may have an impact on the choice of antibiotic therapy in clinical practice.

Clinical strain of Staphylococcus aureus inactivates and causes efflux of macrolides

Searching through a collection of 124 Staphylococcus aureus clinical strains, we found one isolate, strain 01A1032, that inactivates 14- and 16-membered macrolides. The products of inactivation were purified from supernatant fluids of cultures exposed to erythromycin for 3 h and were found to be identical to products of inactivation from Escherichia coli strains that encode either an EreA or EreB esterase. Further, strain 01A1032 was shown to be resistant to azithromycin, a 15-membered macrolide, by an alternate mechanism, efflux. Thus, strain 01A1032 harbors determinants encoding an esterase activity that hydrolyzes 14- and 16-membered macrolides and a macrolide efflux system.

Doctors, nurses, and training in the administration of intravenous drugs

To assess the knowledge of staff and the effect of formal training on house officers we conducted telephone questionnaires of 40 house officers and 18 nurses. The following points were assessed: knowledge of dilution of drugs; knowledge of the rate at which drugs should be given; and the rate at which drugs were given. Appropriately trained nurses had greater knowledge than 'untrained' house officers. In all, 17/18 (94%) nurses compared with 9/18 (50%) house officers knew the correct rate at which to give ampicillin (P = 0.0036, Fisher's exact test); 14/18 (78%) nurses and 1/18 (6%) house officers said they gave ampicillin at the correct rate (P < 0.001); 13/18 (72%) nurses and 7/18 (39%) house officers said they gave ranitidine at the correct rate (P = 0.037). Only 1 of the 10 house officers who knew how rapidly to administer ampicillin said they took the correct length of time; 6 of the 10 who knew how rapidly to give ranitidine said they gave it at the correct rate. Training improves the knowledge of house officers, but other factors besides lack of knowledge (possibly lack of time) adversely affect delivery of intravenous drugs.

No more 'routine' chest radiographs in patients with proximal femoral fractures?

The proportion of abnormal chest radiographs in patients admitted following a femoral neck fracture was assessed. Significant abnormalities were found in 14%. In all these cases chest radiography was indicated. No abnormality was unexpected clinically.

Dehydration: burden or benefit to the dying patient?

Significant numbers of patients die each year from malignant disease. The question of whether or not to administer artificial hydration therapy to the patient who is in the last few days of life has been discussed for some time. Some health care professionals contend that a reduced fluid intake, which often accompanies the dying process, may result in a potentially painful and distressing state of dehydration, requiring preventative measures of fluid replacement therapy. In contrast, other clinicians suggest that artificial hydration is often of no proven benefit in the context of the dying and may impose additional physical and psychological burdens on the patient. This paper investigates the advantages and disadvantages of artificial hydration therapies in terms of the symptom distress experienced by the terminally ill cancer patient. Its aim is to promote discussion about this vital aspect of patient care.

A comparison of four commercial systems used to measure whole-body electrical impedance

Four commercial whole-body impedance measuring systems (Holtain, RJL, Bodystat and EZcomp) were compared on two separate occasions for a group of normal subjects. The first set of readings in 21 subjects demonstrated a significant difference of approximately 6% between the Holtain measurement and the higher readings from the Bodystat or RJL systems. The differences between the RJL and Bodystat readings were much less (mean difference 0.6%). Similar differences between the Holtain and EZcomp or Bodystat measurements were demonstrated on a second occasion for a group of 11 subjects. Given that these devices operate by supplying a constant current, the differences may be explained by the results from a series of measurements on a whole-body resistance simulator in which it appears that for skin contact resistance > 200 omega the Holtain device is unable to sustain a constant current and therefore records a lower impedance than the true value.

Quality of life: verification and use of a self-assessment scale in two patient populations

The study described further evaluates the use of the Holmes & Dickerson linear analogue self-assessment scale in assessing the quality of life of both in-patients and out-patients undergoing radiotherapy for the treatment of malignant disease. The scale is shown to be feasible for use in both clinical settings and to be both reliable and valid. It is quick to use, easy to score and demonstrates marked differences between the patient populations. These differences are discussed and supported on clinical grounds. The results emphasize the fact that cancer patients cannot be regarded as a homogeneous group and highlight the need for care to be planned on an individual basis. Similarly, the need for a means by which individual response can be assessed is demonstrated. It is suggested that this self-assessment technique may be of considerable value in such assessment.

Traumatically intruded permanent incisors: a study of treatment and outcome

Twenty-nine traumatically intruded permanent maxillary incisors from 20 patients were examined, treated and monitored for 2 years. There was a higher proportion of males than females. The teeth intruded furthest were more frequently extracted. Those which were surgically repositioned were more frequently retained and were associated with marginal bone loss significantly less frequently than those which were passively observed, while external root resorption occurred in similar proportions in both groups. A significantly higher proportion of those teeth that were delayed in presentation were subsequently extracted, and a similar trend was found for those with immature roots at the time of the initial examination.

Isotope computed tomography using cone-beam geometry: a comparison of two reconstruction algorithms

A CT scanner has been constructed specifically to determine the three-dimensional distribution of bone mineral in the medullary cavities of the radius, ulna and femur. A source of x-rays (153Gd) and a multiwire proportional counter (MWPC) are mounted at opposite ends of a diameter of an annular mounting. The limb is placed on the axis of rotation of the annulus and a series of two-dimensional transmission projections are obtained at equal angular spacings over 360 degrees. The distribution of bone mineral is reconstructed from the projections either by the method of maximum entropy (ME) or by convolution and back projection (CBP). These two methods have been evaluated by reconstructing a single slice of a phantom, representing the forearm, from projections simulated by computer. With a clinically acceptable exposure time, the mean medullary densities of the ulna and radius were determined with systematic errors of less than 3.5% (ME) and 11% (CBP), although for the latter method of reconstruction the systematic error was reduced to less than 2% by increasing the number of views. The mean medullary densities of the ulna and radius were determined with precisions better than 2.5% (ME) and 3.5% (CBP).

Tomographic reconstruction from experimentally obtained cone-beam projections

Direct reconstruction in three dimensions for two-dimensional projection data has been achieved by cone-beam reconstruction techniques. In this paper explicit formulas for a cone-beam convolution and back-projection reconstruction algorithm are given in a form which can be easily coded for a computer. The algorithm is justified by analyzing tomographic reconstructions of a uniformly attenuating sphere from simulated noisy projection data. A particular feature of this algorithm is the use of a one-dimensional rather than two-dimensional convolution function, greatly speeding up the reconstruction. The technique is applicable however large the cone angle of data capture and correctly reduces to the pure fan-beam reconstruction technique in the central section of the cone. The method has been applied to data captured on a cone-beam CT scanner designed for bone mineral densitometry.

Escherichia coli outer membrane protein K is a porin

Protein K is an outer membrane protein found in pathogenic encapsulated strains of Escherichia coli. We present evidence here that protein K is structurally and functionally related to the E. coli K-12 porin proteins (OmpF, OmpC, and PhoE). Protein K was found to cross-react with antibody to OmpF protein and to share 8 out of 17 peptides in common with the OmpF protein. Strains that are OmpC porin- and OmpF porin- and contain protein K as their major outer membrane protein have increased rates of uptake of nutrients and a faster growth rate relative to the parental porin- strain. The protein K-containing strains are at least 1,000-fold more sensitive to colicins E2 and E3 than is the porin -deficient strain. These data suggest that protein K is a functional porin in E. coli. The porin function of protein K was also demonstrated in vitro, using black lipid membranes. Protein K increased the conductance in these membranes in discrete, uniform steps characteristic of channels with a size of about 2 nS.

Shwachman's syndrome. A review of 21 cases

21 patients (10 male, 11 female) aged between 11 months and 29 years with Shwachman's syndrome are reviewed. All patients had exocrine pancreatic insufficiency. Haematological features included neutropenia in 19 (95%), anaemia in 10 (50%), and thrombocytopenia in 14 (70%); one patient developed erythroleukaemia. Severe infections occurred in 17 (85%) from which 3 (15%) died. Only one child exceeded the 3rd centile for height, and growth retardation was particularly evident in the older patients. All had skeletal abnormalities or delayed skeletal maturation, or both. Metaphyseal dyschondroplasia affected 13 of the older patients and was associated with skeletal deformities. Eight of 9 children under 2 1/2 years had rib abnormalities. Respiratory function tests in children under 2 years demonstrated reduced thoracic gas volume and chest wall compliance. Older patients had reduced forced expiratory volume and forced vital capacity. Neurological assessment showed developmental retardation or reduced IQ assessments, or both, in 85% of patients studied. Other neurological abnormalities included hypotonia, deafness, and retinitis pigmentosa. Neonatal problems had been present in 16 (80%) of the patients and 5 were of low birthweights. Hepatomegaly with biochemical evidence of liver involvement occurred in the younger patients and resolved with age. Other associated features included dental abnormalities, renal dysfunction, an icthyotic maculopapular rash in 13 (65%), delayed puberty, diabetes mellitus, and various dysmorphic features. These findings stress the diverse manifestations of the syndrome and extend knowledge on a number of aspects. Sibship segregation ratios support an autosomal mode of inheritance and an hypothesis for the pathophysiological basis of this syndrome is advanced.

Thenar hypoplasia with associated radiologic abnormalities

We report on five patients who presented with unilateral or bilateral hypoplasia of the thenar eminence. X rays of the affected limbs showed varying degrees of malformation and underdevelopment of the thumb phalanges and first metacarpal bone, and of the carpal bones at the base of the thumb, indicating a developmental abnormality. Our electrodiagnostic findings were compatible with this interpretation. We suggest that this condition is part of the clinical spectrum of radial club hand (radial dysplasia) and that when seen in adults, its recognition is important in the differential diagnosis of carpal tunnel syndrome.

Hypophosphatasia. Review of 24 cases

Radiographic analysis of 24 cases of hypophosphatasia (H) from 9 Paediatric Centres was performed. 3 cases were of neonatal (lethal), 18 cases of infantile (severe) and 3 cases of late (benign) type. Some of the patients were in reality borderline cases between these groups. In the authors' material all the patients showed radiographic signs of the disease. These were divided into diagnostic, characteristic and suggestive features. All of the patients had in common generalised (usually irregular) osteoporosis, generalised (usually irregular) metaphyseal changes, craniostenosis (13 of 18 infantile cases) or widened cranial sutures and ofter bowing of the long bones. Besides the well know radiographic features of hypophosphatasia some less well known, rare or 'new' ones such as, 1. spurs of the long bones (Bowdler sign), 2. distal femoral central metaphyseal defects and epiphyseal defects, 3. S-like deformities of the tibiae, 4. abnormal shape of the distal phalanges of the fingers, 5. multiple rib fractures and slender bones, 6. wedging of the lower thoracic and upper lumbar vertebrae, 7. partial premature fusion of the epiphyses, 8. nephrocalcinosis, 9. loss of lamina dura around the teeth, 10. variation in radiographic appearances of a pair of siblings with lethal form, and, 11. rapid changes in roentgen appearances. are discussed. In two of our patients (siblings) phosphoethanolamine was undetectable in the urine. The authors doubt if a normal skeletal survey may be present at any stage in any of the three major types of hypophosphatasia.