The sh2-R allele of the maize shrunken-2 locus was caused by a complex chromosomal rearrangement.

KEY MESSAGE: The mutant that originally defined the shrunken - 2 locus of maize is shown here to be the product of a complex chromosomal rearrangement. The maize shrunken-2 gene (sh2) encodes the large subunit of the heterotetrameric enzyme, adenosine diphosphate glucose pyrophosphorylases and a rate-limiting enzyme in starch biosynthesis. The sh2 gene was defined approximately 72 years ago by the isolation of a loss-of-function allele conditioning a shrunken, but viable seed. In subsequent years, the realization that this allele, termed zsh2-R or sh2-Reference, causes an extremely high level of sucrose to accumulate in the developing seed led to a revolution in the sweet corn industry. Now, the vast majority of sweet corns grown throughout the world contain this mutant allele. Through initial Southern analysis followed by genomic sequencing, the work reported here shows that this allele arose through a complex set of events involving at least three breaks of chromosome 3 as well as an intra-chromosomal inversion. These findings provide an explanation for some previously reported, unexpected observations concerning rates of recombination within and between genes in this region.

Ultrastructural features of chromatin nu bodies.

Spread chromatin fibers and isolated chromatin fragments prepared from chicken erythrocyte nuclei were stained with dilute aqueous uranyl acetate. High-resolution electron micrographs reveal two new morphological features exhibited by many of the chromatin nu bodies: (a) lateral association of the nu body with the connecting strand, and (b) a centrally stained spot approximately 15 A wide, possibly corresponding to a hole or crevice within the nu body.

Chromatin fragments resembling v bodies.

Fragments of chromatin resembling the spheroid chromatin units (v bodies) have been isolated from formaldehyde-fixed and sonicated chicken erythrocyte nuclei. Ultracentrifugal analyses demonstrated that monomer v bodies have a molecular weight of about 300,000 per particle, exhibit a protein to DNA ratio (by weight) of 1.22:1, and contain a DNA fragment with a molecular weight of approximately 140,000 per v body.

Trabeculectomy training in England: are we safe at training? Two year surgical outcomes.

OBJECTIVES: To define the safety profile of trainee trabeculectomy surgery in the United Kingdom. Surgical exposure for trainees in England is limited due to service requirements, the European working time directive constraints and increasing sub-specialisation of glaucoma surgery. Limited knowledge exists on the outcomes of supervised glaucoma surgery. The aim is to determine the safety of supervised trabeculectomy surgery performed by trainee ophthalmologists. METHODS: Retrospective case note review of all patients that had trabeculectomy surgery with MMC by consultant and trainee surgeons across multiple UK centres. All eyes have 2-year follow up. Success was determined using WGA guidelines. Two-tailed p values were obtained using Fisher's exact test to ascertain statistical significance between groups. MAIN OUTCOME MEASURES: intraocular pressure, visual acuity, success and failure rates. RESULTS: 324 eyes were reviewed. 211 (66.4%) cases were performed by glaucoma consultants, 107(33.6%) by trainee ophthalmologists. The majority of eyes in each group were undergoing surgery for POAG. Post-operative IOP control showed no significant difference between consultant and trainee groups at year 1 and year 2. Success rates showed no significant difference between consultant and trainee cases. Failure rates at year 1 showed a significant difference between the two groups. No significant difference was seen at year 2. The trainee group had significantly more complications, when compared with the consultant group. Snellen visual acuity loss was not statistically significant between the two groups at the 2 year time point. CONCLUSIONS: The outcomes of supervised trainee trabeculectomy compare favourably with consultant cases after 2 year follow up. Trainee cases had higher complication rates than consultant cases. Bleb leaks are a common complication of trainee cases, where closer supervision may be required. There is potential for surgical simulation to help increase the success of such cases. These findings may encourage trainee participation in glaucoma surgery.

Prospective evaluation of postoperative pain in cats undergoing ovariohysterectomy by a midline or flank approach.

Twenty entire female cats were randomly assigned to two groups of 10; the cats in one group underwent ovariohysterectomy by a midline approach and the cats in the other group by a flank approach. Cats were assessed for signs of pain and scores were assigned pre- and postoperatively. There was a tendency for the cats neutered by a flank approach to be in more pain postoperatively (P=0.05). The final pain score for cats in either group was equal to or lower than their baseline score.

Dissecting the self-assembly kinetics of multimeric pore-forming toxins.

Pore-forming toxins are ubiquitous cytotoxins that are exploited by both bacteria and the immune response of eukaryotes. These toxins kill cells by assembling large multimeric pores on the cell membrane. However, a quantitative understanding of the mechanism and kinetics of this self-assembly process is lacking. We propose an analytically solvable kinetic model for stepwise, reversible oligomerization. In biologically relevant limits, we obtain simple algebraic expressions for the rate of pore formation, as well as for the concentration of pores as a function of time. Quantitative agreement is obtained between our model and time-resolved kinetic experiments of Bacillus thuringiensis Cry1Ac (tetrameric pore), aerolysin, Staphylococcus aureus α-haemolysin (heptameric pores) and Escherichia coli cytolysin A (dodecameric pore). Furthermore, our model explains how rapid self-assembly can take place with low concentrations of oligomeric intermediates, as observed in recent single-molecule fluorescence experiments of α-haemolysin self-assembly. We propose that suppressing the concentration of oligomeric intermediates may be the key to reliable, error-free, self-assembly of pores.

Solution structure and dynamics of the single-chain hepatitis C virus NS3 protease NS4A cofactor complex.

The backbone assignments, secondary structure, topology, and dynamics of the single-chain hepatitis C virus NS3 protease NS4A cofactor complex have been determined by NMR spectroscopy. Residues I34 to S181 of NS3 and the central three residues of the NS4A cofactor were assigned and the secondary structure was verified for these residues. In several X-ray structures of NS4A-bound NS3 protease, residues 1 to 28 are stabilized by crystal packing, which allows for the formation of the A0 strand and alpha0 helix. In solution, these N-terminal residues are largely unassigned and no evidence of a well-structured A0 strand or alpha0 helix was detected. NOEs between residues in the E1-F1 loop (containing D81) and the alpha1 helix (containing H57) together with the detection of a D81-H57 hydrogen bond indicate that in solution the catalytic triad (D81, H57, S139) of the protease is better ordered in the presence of the NS4A cofactor. This is consistent with the earlier crystallographic results and may explain the observed increase in catalytic activity of the enzyme due to NS4A binding. A model-free analysis of our relaxation data indicates substantial exchange rates for residues V51-D81, which comprise the upper part of the N-terminal beta-barrel. A comparison of chemical-shift differences between NS3 protease and the NS3 protease-NS4A complex shows extensive chemical-shift changes for residues V51-D81 indicating that non-local structural changes occur upon NS4A binding to the NS3 protease that are propagated well beyond the protease-cofactor interaction site. This is consistent with crystallographic data that reveal large structural rearrangements of the strand and loop regions formed by residues V51-D81 as a result of NS4A binding. The coincidence of large exchange rates for the NS3 protease-NS4A complex with chemical-shift differences due to NS4A binding suggests that residues V51-D81 of the NS3 protease NS4A complex are in slow exchange with a NS4A-free conformation of NS3 protease.

Quantitative Trait Loci Conditioning Resistance to Phaeosphaeria Leaf Spot of Maize Caused by Phaeosphaeria maydis.

Phaeosphaeria leaf spot (PLS) is a potentially important disease of maize (Zea mays) that has appeared in winter breeding nurseries in southern Florida. Inbred lines related to B73 are particularly susceptible to Phaeosphaeria leaf spot, whereas inbreds related to Mo17 are highly resistant. A previous study of the inheritance of resistance to Phaeosphaeria leaf spot in the cross B73 × Mo17 found that resistance is highly heritable and controlled by mostly additive gene action at three or four loci. In this study, we used 158 recombinant inbred (RI) lines derived from the cross B73 × Mo17 to map quantitative trait loci (QTL) governing resistance. The RI lines along with the parent inbred lines and the F1 were evaluated for PLS resistance in replicated trials over two winter growing seasons in southern Florida. Using the composite interval mapping (CIM) function of PLABQTL software, five QTL on four different chromosomes were found to control PLS resistance in Mo17. In addition, the × additive interaction between two of these QTL was found to be significant. Our results are in close agreement with the previous study, where generation mean analysis was used to study the inheritance of resistance to PLS.

Progesterone, glucocorticoid and estradiol receptors in MCF-7 cells bind to chromatin.

MCF-7 cells contain progesterone, estradiol and glucocorticoid receptors. Following addition of these hormones to the growth medium of the cells, hormone-receptor complexes were found to sediment with chromatin fragments produced by trace digestion with micrococcal nuclease. The binding in all cases could be competed by excess unlabeled hormone. In each case the fragments with which the hormone-receptor complexes were associated tended to be smaller than the bulk chromatin fragments, indicating a greater sensitivity of those chromatin regions to the nuclease. The mononucleosomes released by more extensive digestion with micrococcal nuclease contained different amounts of each of the three hormone-receptor complexes. Progesterone could usually be detected on mononucleosomes only after very brief sedimentation analyses, whereas glucocorticoid- and estradiol-labeled mononucleosomes were stable during long centrifugations. Comparison of glucocorticoid- and estradiol-labeled mononucleosomes indicated that their sedimentation rates differed from one another and from bulk nucleosomes. Estradiol nucleosomes from MCF-7 cells and rat uterus (Senior and Frankel, 1978) sediment significantly faster than bulk nucleosomes, while glucocorticoid nucleosomes from MCF-7 cells and rat hepatoma cells sediment with, or even fractionally slower than, bulk nucleosomes.

The utility of the TDx test in the assessment of fetal lung maturity.

Accurate assessment of fetal lung maturity is essential in the management of high-risk obstetric patients. New rapid techniques have been developed to supplement time-consuming chromatographic methods. We compared one of these newer methods, the TDx-FLM, to the standard tests for fetal pulmonary maturity. There was an excellent correlation between the TDx and the lecithin-sphingomyelin ratio (r = 0.78). Although a TDx value of 70 or greater is considered mature, we found a value of 50 or greater predictive of fetal lung maturity in 100% of cases, and have chosen to redefine a mature value as 50 or greater in our institution. This value has greatly enhanced the clinical applicability of the test, allowing use of a large number of specimens from the previously poorly understood and often disregarded borderline category.

"I don't believe in needles": qualitative aspects of a study into the uptake of infant immunisation in two English health authorities.

This paper presents qualitative data to emerge from a largely quantitative case-control study of the uptake of infant immunisation in two District Health Authorities in the North West of England. It was hypothesised that problems arising from transport and time-space constraints would distinguish the parents of those children who had missed appointments from those who had attended. However, most of these difficulties were experienced equally by both groups and so could not solely account for different immunisation behaviour. Rather, the groups could be distinguished further by their differing attitudes towards, and knowledge of, infant immunisation based on a wide range of personal experiences. The paper argues that it is a mistake to label parental decision-making as 'irrational' when one takes into account the interaction between personal experience, differing levels of advice and the impact of constraints, notably gender role constraints, as they affect women with young children.

Urban-rural mortality differentials: controlling for material deprivation.

This paper investigates the relationship between premature mortality and material deprivation, and the differences in this relationship between urban and rural areas. We examine, given comparable measures of affluence or deprivation, whether residual differences exist between urban and rural areas for all-causes of death and, separately, for cancers, circulatory and respiratory diseases. Using 1990-92 mortality data for the 908 wards of Wales we apply statistical analyses based on tabular data and parametric Poisson regression models. Contrasts are sought between six urban and rural categories defined in terms of settlement sizes and the employment structure of rural areas. Inequalities in all-cause premature mortality are widest in the cities, narrowest in the deeper rural areas, and of intermediate and comparable value in other areas of Wales. This is largely a reflection of the different distributions of material deprivation in these areas. After controlling for differences in socio-economic characteristics, using deprivation measures, the tendency for lower mortality in deeper rural areas is substantially reduced. Residual mortality differences between urban and rural areas are shown to be dependent on the way deprivation is measured and the disease group under study. For cancers there are no residual mortality differences, while for respiratory and circulatory diseases some of the residual variation can be accounted for by employment variables, particularly previous employment in the coal mining industry.

Identification and Mapping of Quantitative Trait Loci Conditioning Resistance to Southern Leaf Blight of Maize Caused by Cochliobolus heterostrophus Race O.

ABSTRACT A random set of recombinant inbred (RI) lines (F2:7) derived from the cross of the inbred lines Mo17 (resistant) and B73 (susceptible) were evaluated for resistance to southern leaf blight (SLB) caused by Cochliobolus heterostrophus race O. The RI lines were genotyped at a total of 234 simple sequence repeat, restriction fragment length polymorphism, or isozyme loci. Field plots of the RI lines were inoculated artificially with an aggressive isolate of C. heterostrophus race O in each of two growing seasons in North Carolina. Lines were rated for percent SLB severity two (1996) or three (1995) times during the grain-filling period. Data also were converted to area under the disease progress curve (AUDPC) and analyzed using the composite interval mapping option of the PLABQTL program. When means of disease ratings over years were fitted to models, a total of 11 quantitative trait loci (QTLs) were found to condition resistance to SLB, depending upon which disease ratings were used in the analyses. When the AUDPC data were combined and analyzed over environments, seven QTLs, on chromosomes 1, 2, 3, 4, 7, and 10 were found to come from the resistant parent Mo17. An additional QTL for resistance on chromosome 1 came from the susceptible parent B73. The eight identified QTLs accounted for 46% of the phenotypic variation for resistance. QTL x environment interactions often were highly significant but, with one exception, were the result of differences in the magnitude of QTL effects between years and not due to changes in direction of effects. QTLs on the long arm of chromosome 1 and chromosomes 2 and 3 had the largest effects, were the most consistently detected, and accounted for most of the phenotypic variance. No significant additive x additive epistatic effects were detected. These data support earlier reports of the polygenic inheritance of resistance to SLB of maize.

Assessment of the Abbott IMx assay system for the measurement of human chorionic gonadotropin levels in the treatment of ectopic pregnancy.

The rapid, accurate determination of serum human chorionic gonadotropin (beta-hCG) levels in the 900- to 2000-IU/L range is a critical element in the treatment of patients with suspected ectopic pregnancy. Using the Abbott IMx system (Abbott Laboratories, North Chicago, Ill), beta-hCG levels can be determined on an undiluted sample up to 1000 IU/L. A sample with beta-hCG level greater than 1000 IU/L is automatically diluted and the diluted sample redetermined. Unfortunately, employing a 1:200 fixed dilution can produce a working sample that contains an beta-hCG concentration that does not fall on a linear portion of the standard curve (<7.5 IU/L). This results in a calculated beta-hCG concentration (200 x observed value) that has high error (coefficient of variation up to 21.8%). Additionally, interfering substances in the reagents, which vary in quantity from lot to lot of reagents, further confound accurate beta-hCG determination by the system. Consequently, the Abbott IMx assay system cannot be used as recommended by the manufacturer for routine measurement of serum beta-hCG in the 900- to 2000-IU range. An alternate protocol employing at 1:10 dilution would allow a more accurate beta-hCG determination.

Postanaesthetic cerebral necrosis in five horses.

After being anaesthetised for between one hour 40 minutes and seven hours, five adult horses developed acute neurological signs and extensive cerebrocortical necrosis. Four of them had had abdominal surgery for colic and one had had repeated orthopaedic interventions. Between five hours and seven days after the surgery, all five horses suddenly developed severe signs of a predominantly prosencephalic disturbance: bilateral blindness with normal pupillary light responses, abnormal behaviour varying from propulsive pacing to head pressing profound lethargy and generalised seizures. They were euthanased between 24 hours and three weeks after the onset of these signs. In three of the cases a gross examination of the brain revealed patchy malacia of the cerebral grey matter and some discolouration of the adjacent white matter. Microscopical examination revealed lesions that varied from laminar neuronal necrosis in the grey matter of the cerebral cortex to more diffuse necrosis of the cortex and underlying white matter. Four of the five cases had had a period of hypercapnea while anaesthetised, and two of them (and possibly a third) had also had hypoxaemia.

Spatial and temporal variation of mortality and deprivation 2: statistical modelling.

"Building on the tabular analyses exemplified in our first paper and widely used in the medical literature, we use generalised linear models to provide a formal, statistical approach to the analysis of mortality and deprivation relationships, and their change over time. Three types of fixed effects model are specified and estimated with the same ward-level data sets for Wales examined in our first paper. They are: Poisson models for analysing mortality and deprivation at a single cross section in time; repeated-measures Poisson models for analysing mortality-deprivation relations, not only at cross sections in time, but also their changes over time; and logit models focusing on temporal changes in mortality-deprivation relationships. Nonlinear effects of deprivation on mortality have been explored by using dummy variables representing deprivation categories to establish the connection between formal statistical models and the tabular approach"

Spatial and temporal variation of mortality and deprivation. 1: widening health inequalities.

"In this paper we examine the relationship between premature mortality and material deprivation both over time (the intercensal period, 1981-91) and over space (for the population in wards and ward groups in Wales). Our focus is on the methods of analysis for small area...multiple cross-section mortality data and their application to the substantive issue of the persistent and widening inequalities in Wales.... We examine all-cause deaths and mortality by specific disease classes for groups (quintiles) of wards ranked according to standard measures of material deprivation. Although there have been reductions in premature mortality across all deprivation groups in Wales, over the decade, the gap has widened between the most and least deprived areas."

The genetic architecture of maize (Zea mays L.) kernel weight determination.

Individual kernel weight is an important trait for maize yield determination. We have identified genomic regions controlling this trait by using the B73xMo17 population; however, the effect of genetic background on control of this complex trait and its physiological components is not yet known. The objective of this study was to understand how genetic background affected our previous results. Two nested stable recombinant inbred line populations (N209xMo17 and R18xMo17) were designed for this purpose. A total of 408 recombinant inbred lines were genotyped and phenotyped at two environments for kernel weight and five other traits related to kernel growth and development. All traits showed very high and significant (P < 0.001) phenotypic variability and medium-to-high heritability (0.60-0.90). When N209xMo17 and R18xMo17 were analyzed separately, a total of 23 environmentally stable quantitative trait loci (QTL) and five epistatic interactions were detected for N209xMo17. For R18xMo17, 59 environmentally stable QTL and 17 epistatic interactions were detected. A joint analysis detected 14 stable QTL regardless of the genetic background. Between 57 and 83% of detected QTL were population specific, denoting medium-to-high genetic background effects. This percentage was dependent on the trait. A meta-analysis including our previous B73xMo17 results identified five relevant genomic regions deserving further characterization. In summary, our grain filling traits were dominated by small additive QTL with several epistatic and few environmental interactions and medium-to-high genetic background effects. This study demonstrates that the number of detected QTL and additive effects for different physiologically related grain filling traits need to be understood relative to the specific germplasm.