An "epidemic" model of sexual intercourse prevalences for black and white adolescents

In adolescence (12-16 years), the prevalence of sexual intercourse increases each year. To explain the increasing yearly prevalences, we propose a recursive equation model of onset of adolescent sexual intercourse. The model allows for an "epidemic" process (the transmission of sexuality from a nonvirgin to a virgin) and a nonepidemic process (two virgins progressing to sexual intercourse). The model also requires that virgin females be pubertally mature before they will progress to sexual intercourse. Adequate fits were obtained to the intercourse prevalences for both black and white respondents. Comparisons of alternative models established that the full model was superior to models that omitted either the nonepidemic process or the requirement of females' pubertal maturation. The model was able to fit both white and blacks simultaneously, assuming equal transition probabilities in both races. Hence, we propose the hypothesis that race differences in sexual intercourse prevalence may be strongly influenced by the age of initiation of the "epidemic" process and by race difference in females' rates of pubertal maturation. The results suggested that most new cases of sexual intercourse arose from the epidemic process and that males were more prone to progress to intercourse, given an opportunity.     

Retrovirus-mediated insertional mutagenesis: phagemid rescue of flanking DNA by selecting plasmid ori

A method for screening recombinant lambda libraries was devised to select phage containing genomic regions containing provirus insertions of retroviruses that carry the kanamycin and G418 resistance factor neo and the origin of replication derived from pBR322 (oripBR). Such recombinants are phagemids, able to replicate as bacteriophages or as plasmids under lambda repressor control. lambda repressor was cloned into a plasmid derived from pSC101 that is compatible with pBR322-derived phagemids. A strain carrying this plasmid may be used to select phagemids derived from a single proviral insertion with 100% efficiency from complex recombinant libraries. Homologous recombination between proviral long terminal repeats was observed at a rate of 10(-4)/plaque-forming unit in recABC+ strains. Despite this frequency, intact phagemids are easily recovered as phage after temperature shift to 42 degrees C. Since oripBR itself is a selectable marker in this system, the method could be applied to recover any sequence carrying the ori sequence from pBR322.     

The Advocacy for Pedestrian Safety Study: Cluster Randomised Trial Evaluating a Political Advocacy Approach to Reduce Pedestrian Injuries in Deprived Communities

Objective

To determine whether advocacy targeted at local politicians leads to action to reduce the risk of pedestrian injury in deprived areas.

Design

Cluster randomised controlled trial.

Setting

239 electoral wards in 57 local authorities in England and Wales.

Participants

617 elected local politicians.

Interventions

Intervention group politicians were provided with tailored information packs, including maps of casualty sites, numbers injured and a synopsis of effective interventions.

Main outcome measures

25–30 months post intervention, primary outcomes included: electoral ward level: percentage of road traffic calmed; proportion with new interventions; school level: percentage with 20 mph zones, Safe Routes to School, pedestrian training or road safety education; politician level: percentage lobbying for safety measures. Secondary outcomes included politicians’ interest and involvement in injury prevention, and facilitators and barriers to implementation.

Results

Primary outcomes did not significantly differ: % difference in traffic calming (0.07, 95%CI: −0.07 to 0.20); proportion of schools with 20 mph zones (RR 1.47, 95%CI: 0.93 to 2.32), Safe Routes to School (RR 1.34, 95%CI: 0.83 to 2.17), pedestrian training (RR 1.23, 95%CI: 0.95 to 1.61) or other safety education (RR 1.16, 95%CI: 0.97 to 1.39). Intervention group politicians reported greater interest in child injury prevention (RR 1.09, 95%CI 1.03 to 1.16), belief in potential to help prevent injuries (RR 1.36, 95%CI 1.16 to 1.61), particularly pedestrian safety (RR 1.55, 95%CI 1.19 to 2.03). 63% of intervention politicians reported supporting new pedestrian safety schemes. The majority found the advocacy information surprising, interesting, effectively presented, and could identify suitable local interventions.

Conclusions

This study demonstrates the feasibility of an innovative approach to translational public health by targeting local politicians in a randomised controlled trial. The intervention package was positively viewed and raised interest but changes in interventions were not statistically significance. Longer term supported advocacy may be needed.

Trial Registration

Current Controlled Trials ISRCTN91381117     

Hinging of rabbit myosin rod

The question of hinging in myosin rod from rabbit skeletal muscle has been reexamined. Elastic light scattering and optical rotation have been used to measure the radius of gyration and fraction helix, respectively, as a function of temperature for myosin rod, light meromyosin (LMM), and long subfragment 2 (long S-2). The radius of gyration vs temperature profile of myosin rod is shifted with respect to the optical rotation melting curve by about -5 degrees C. Similar studies on both LMM and long S-2 show virtually superimposable profiles. To correlate changes in the secondary structure with the overall conformation, plots of radius of gyration vs fraction helix are presented for each myosin subfragment. Myosin rod exhibits a marked decrease in the radius of gyration from 43 nm to approximately 35 nm, while the fraction helix remains at nearly 100%. LMM and long S-2 did not show this behavior. Rather, a decrease in the radius of gyration of these fragments occurred with comparable changes in fraction helix. These results are interpreted in terms of hinging of the myosin rod within the LMM/S-2 junction.     

Sialylation of urinary prothrombin fragment 1 is implicated as a contributory factor in the risk of calcium oxalate kidney stone formation

Urinary glycoproteins are important inhibitors of calcium oxalate crystallization and adhesion of crystals to renal cells, both of which are key mechanisms in kidney stone formation. This has been attributed to glycosylation of the proteins. In South Africa, the black population rarely form stones (incidence < 1%) compared with the white population (incidence 12-15%). A previous study involving urinary prothrombin fragment 1 from both populations demonstrated superior inhibitory activity associated with the protein from the black group. In the present study, we compared N-linked and O-linked oligosaccharides released from urinary prothrombin fragment 1 isolated from the urine of healthy and stone-forming subjects in both populations to elucidate the relationship between glycosylation and calcium oxalate stone pathogenesis. The O-glycans of both control groups and the N-glycans of the black control samples were significantly more sialylated than those of the white stone-formers. This demonstrates a possible association between low-percentage sialylation and kidney stone disease and provides a potential diagnostic method for a predisposition to kidney stones that could lead to the implementation of a preventative regimen. These results indicate that sialylated glycoforms of urinary prothrombin fragment 1 afford protection against calcium oxalate stone formation, possibly by coating the surface of calcium oxalate crystals. This provides a rationale for the established roles of urinary prothrombin fragment 1, namely reducing the potential for crystal aggregation and inhibiting crystal-cell adhesion by masking the interaction of the calcium ions on the crystal surface with the renal cell surface along the nephron.     

β-glucuronidase as a marker for clonal analysis of tomato lateral roots

In higher plants, the root-shoot axis established during embryogenesis is extended and modified by the development of primary and lateral apical meristems. While the structure of several shoot apical meristems has been deduced by combining histological studies with clonal analysis, the application of this approach to root apical meristems has been limited by a lack of visible genetic markers. We have tested the feasibility of using a synthetic gene consisting of the maize transposable elementActivator (Ac) inserted between a 35S CaMV promoter and the coding region of a -glucuronidase (GUS) reporter gene as a means of marking cell lineages in roots. The GUS gene was activated in individual cells byAc excision, and the resulting sectors of GUS-expressing cells were detected with the histochemical stain X-Gluc. Sectors in lateral roots originated from bothAc excision in meristematic cells and from parent root sectors that bisect the founder cell population for the lateral root initial. Analysis of root tip sectors confirmed that the root cap, and root proper have separate initials. Large sectors in the body of the lateral root encompassed both cortex and vascular tissues. The number of primary initial cells predicted from the size and arrangement of the sectors observed ranged from two to four and appeared to vary between roots. We conclude that transposon-based clonal analysis using GUS expression as a genetic marker is an effective approach for deducing the functional organization of root apical meristems.     

Assay of acyl-CoA:monoglyceride acyltransferase from rat small intestine using continuous recording spectrophotometry

Acyl-CoA:monoglyceride acyltransferase in microsomal preparations from the small intestine of the rat has been measured by means of continuous recording spectrophotometry. The reaction of 5,5'-dithiobis(2-nitrobenzoic acid) with CoA has been employed for this assay and optimal conditions for the reaction have been defined. One of the substrates, palmitoyl-CoA, inhibits the reaction even in modest concentrations. This inhibition is largely prevented by the addition of bovine serum albumin to the incubation medium. The reliability of the assay method was confirmed by comparison with the more cumbersome assay method that uses radioactive substrate.     

Hyperconservation of the putative antigen recognition site of the MHC class I-b molecule TL in the subfamily Murinae: evidence that thymus leukemia antigen is an ancient mammalian gene

"Classical" MHC class I (I-a) genes are extraordinarily polymorphic, but "nonclassical" MHC class I (I-b) genes are monomorphic or oligomorphic. Although diversifying (positive) Darwinian selection is thought to explain the origin and maintenance of MHC class I-a polymorphisms, genetic mechanisms underlying MHC class I-b evolution are uncertain. In one extreme model, MHC class I-b loci are derived by gene duplication from MHC class I-a alleles but rapidly drift into functional obsolescence and are eventually deleted. In this model, extant MHC class I-b genes are relatively young, tend to be dysfunctional or pseudogenic, and orthologies are restricted to close taxa. An alternative model proposed that the mouse MHC class I-b gene thymus leukemia Ag (TL) arose approximately 100 million years ago, near the time of the mammalian radiation. To determine the mode of evolution of TL, we cloned TL from genomic DNA of 11 species of subfamily Murinae: Every sample we tested contained TL, suggesting this molecule has been maintained throughout murine evolution. The sequence similarity of TL orthologs ranged from 85-99% and was inversely proportional to taxonomic distance. The sequences showed high conservation throughout the entire extracellular domains with exceptional conservation in the putative Ag recognition site. Our results strengthen the hypotheses that TL has evolved a specialized function and represents an ancient MHC class I-b gene.     

Tissue and subcellular immunolocalisation of enzymes of lignin synthesis in differentiating and wounded hypocotyl tissue of French bean (Phaseolus vulgaris L.)

Antisera raised againstl-phenylalanine ammonia-lyase (PAL), cinnamate-4-hydroxylase (C4H), and a cationic cell-wall peroxidase, which had all been purified from suspension-cultured cells of French bean, have been used to carry out immunogold localisations in the growing plant. Immunoglobulin-G fractions were prepared from each antiserum and used to study the distribution of the enzymes in differentiating and wounded hypocotyls by immunogold techniques and visualisation by both light and electron microscopy. Following silver enhancement to amplify the signal, proteins were detected by confocal microscopy in both developing (pre-xylem/ phloem) and later metaxylem stelar tissue.l-Phenylalanine ammonia-lyase and C4H also accumulated in cells adjacent to metaxylem, presumably involved in maintaining a supply of phenylpropanoid precursors to the enucleated xylem for further lignin synthesis. In these cells, PAL subunits were cytosolic although some were associated with endomembrane. Cinnamate-4-hydroxylase was wholly associated with membrane and particularly high concentrations were found in the Golgi bodies. The cationic peroxidase accumulated in xylem at sites of secondary thickening and in the middle lamella. The three proteins are also involved in defensive lignification. Thus when visualised by light microscopy, PAL and C4H were seen to accumulate to high levels throughout the cell types in wound sites and especially in the epidermal cells. An even more intense general distribution was found upon hyperinduction of wounded cells with-aminooxy--phenylpropionic acid. At the subcellular level, PAL was found to be localised in the cytosol in the wounded cells; however, because of the loss of membrane through mechanical damage, association with membrane structures, particularly endoplasmic reticulum, in unwounded cells is not entirely ruled out. Cinnamate-4-hydroxylase was associated with membranes when these were preserved. In wounded tissue, the peroxidase was found at the growing edges of tylose-like structures in the vascular xylem.Abbreviations AOPP -aminooxy--phenylpropionic acid - C4H cinnamic acid-4-hydroxylase - CHS chalcone synthase - GRP glycine-rich glycoprotein - HRGP hydroxyproline-rich glycoprotein - Ig immunoglobulin - PAL phenylalanine ammonia-lyase G.P.B. thanks the Agicultural and Food Research Council for support.     

Ultrastructural cytology of the cyclic corpus luteum of the cow

Corpora lutea (CL) from cows on day 12 of the oestrous cycle were studied by electron microscopy to investigate whether, and how, different subpopulations of luteal cells can be identified in tissue sections. Tissues from 6 CL were examined, and nucleated profiles of luteal cells were classified as large, medium or small on the basis of their areas in electron micrographs. Cut-off points for area categories for large, medium and small-sized cells were based on diameters of greater than 25, 20-25 and less than 20 microns, respectively, if the measured areas were converted to a circular shape after correction for shrinkage. The only qualitative features which distinguished cells of large size from those of small size were the presence of clusters of secretory granules, and of exocytosis of these granules, in large cells only. However, these features were observed in only 59% of large cells, probably primarily due to sampling limitations in single sections. Other qualitative features which have been regarded as diagnostic of large or small luteal cells were observed in cells in all size categories. It was concluded that large and small luteal cells in the cyclic CL of the cow are distinguishable by their ultrastructural features. However, these data do not support the recent suggestion that the mid-cycle CL of the cow contain two subpopulations of large luteal cells in approximately equal numbers.