Patterns of sequence variation in the mitochondrial D-loop region of shrews

Direct sequencing of the mitochondrial displacement loop (D-loop) of shrews (genus Sorex) for the region between the tRNA(Pro) and the conserved sequence block-F revealed variable numbers of 79-bp tandem repeats. These repeats were found in all 19 individuals sequenced, representing three subspecies and one closely related species of the masked shrew group (Sorex cinereus cinereus, S. c. miscix, S. c. acadicus, and S. haydeni) and an outgroup, the pygmy shrew (S. hoyi). Each specimen also possessed an adjacent 76-bp imperfect copy of the tandem repeats. One individual was heteroplasmic for length variants consisting of five and seven copies of the 79-bp tandem repeat. The sequence of the repeats is conducive to the formation of secondary structure. A termination-associated sequence is present in each of the repeats and in a unique sequence region 5' to the tandem array as well. Mean genetic distance between the masked shrew taxa and the pygmy shrew was calculated separately for the unique sequence region, one of the tandem repeats, the imperfect repeat, and these three regions combined. The unique sequence region evolved more rapidly than the tandem repeats or the imperfect repeat. The small genetic distance between pairs of tandem repeats within an individual is consistent with a model of concerted evolution. Repeats are apparently duplicated and lost at a high rate, which tends to homogenize the tandem array. The rate of D- loop sequence divergence between the masked and pygmy shrews is estimated to be 15%-20%/Myr, the highest rate observed in D-loops of mammals. Rapid sequence evolution in shrews may be due either to their high metabolic rate and short generation time or to the presence of variable numbers of tandem repeats.      

Isogenic P-fimbrial deletion mutants of pyelonephritogenic Escherichia coli: the role of α Gal(1–4)β Gal binding in virulence of a wild-type strain

Escherichia coli strains causing acute pyelonephritis often express multiple fimbrial types and haemolysin, which may contribute to their ability to adhere to, and interact with, kidney epithelial cells. Strain CFT073, a pap⁺, sfa⁺, pil⁺, hly⁺ pyelonephritis strain, previously established as virulent in the CBA mouse model of ascending urinary tract infection and cytotoxic for cultured human renal epithelial cells, was selected for construction of isogenic strains. From a gene bank of this strain, two distinct copies of the pap operon were isolated. The two P-fimbrial determinants were sub-cloned into pCVD442, a positive selection suicide vector containing the sacB gene of Bacillus subtilis. Deletion mutations were introduced into each of the two constructs, within papEFG of one operon and papDEFG of the other. Suicide vectors carrying pap deletions were mobilized from E. coli SM10 lambda pir into CFT073 (Nal^R) and cointegrates were passaged on non-selective medium. The first pap mutation was identified by screening a Southern blot of DNA from sucrose-resistant colonies using a papEFG probe. This mutant retained the MRHA⁺ phenotype since a second functional copy of pap was still present. A double pap-deletion mutant, UPEC76, confirmed by Southern blotting, was unable to agglutinate human type O erythrocytes or α Gal(1–4)β Gal-coated latex beads. CBA mice (N =100) were challenged transurethrally with 10⁵, 10⁶, 10⁷, or 10⁹ cfu of strains CFT073 or UPEC76. After one week, quantitative cultures of urine, bladder, and kidney were done and histologic changes were examined. No substantive differences in organism concentration or histological findings between parent and mutant were detected in urine, bladder, or kidney at any challenge concentration. We conclude that adherence by P fimbriae of uro-pathogenic E. coli strain CFT073 plays only a subtle role in the development of acute pyelonephritis in the CBA mouse model.     

Congenital anterior abdominal wall defects in England and Wales 1987-93: retrospective analysis of OPCS data.

OBJECTIVES: Analysis of incidence and characteristics of congenital abdominal wall defects, with special reference to the differences between the incidence of gastroschisis and exomphalos (omphalocele). DESIGN: Retrospective analysis using data from the Office of Population Censuses and Surveys (recoded to differentiate exomphalos and gastroschisis) and the National Congenital Malformation Notification Scheme. SETTING: England and Wales, 1987 to 1993. RESULTS: 1043 congenital anterior abdominal wall defects were notified within the seven year study period. Of these, 539 were classified as gastroschisis, 448 as exomphalos, 19 as "prune belly syndrome," and 37 as "unclassified." Gastroschisis doubled in incidence from 0.65 in 1987 to 1.35 per 10,000 total births in 1991, with little further change; the incidence of exomphalos decreased from 1.13 to 0.77 per 10000 births. The overall incidence of notified congenital abdominal wall defects was 2.15 per 10000 total births. Gastroschisis was associated with a lower overall maternal age than exomphalos and with a significantly lower proportion of additional reported congenital malformations (5.0%) than in the cohort with exomphalos (27.4%) (odds ratio 0.14, 95% confidence interval 0.09 to 0.22; P < 0.001). The sex ratio of the two cohorts was the same. The incidence of gastroschisis and exomphalos was higher in the northern regions of England than in the south east of the country. CONCLUSIONS: The national congenital malformation notification system showed an increasing trend in the incidence of fetuses born with gastroschisis and a progressive decreasing incidence of exomphalos in England and Wales between 1987 and 1993. Although the reasons for this are likely to be multifactorial, a true differential change seems likely. The observed increase in incidence of gastroschisis relative to exomphalos and the differentiation in maternal age have implications for resource management within the NHS and warrant further epidemiological monitoring. Regional differences may be due to a dietary or environmental factor, which requires further study.     

大鼠胼胝体内神经肽Y免疫反应阳性纤维的发育

本实验用免疫组织化学ＡＢＣ法研究了大鼠胼胝体内神经肽Ｙ免疫反应阳性（ＮＰＹ－ＩＲ）纤维的生后发育。结果发现,许多ＮＰＹ－ＩＲ纤维在大鼠出生时便存在于胼胝体内。ＮＰＹ－ＩＲ胼胝体纤维的密度在生后１周内继续逐渐增高,在第２周内达到最高峰。之后,ＮＰＹ－ＩＲ胼胝体纤维的密度逐渐下降,至第３周末时接近成年时的水平,即仅有少量ＮＰＹ－ＩＲ纤维存在于胼胝体内。这些结果提示在大鼠早期生后发育过程中许多ＮＰＹ－ＩＲ胼胝体纤维是暂时性的,其作用可能与大脑皮质的机能发育有关。     

Prostacyclin analogues inhibit canine parietal cell activity and cyclic AMP formation

To assess further the mechanism by which prostacyclin inhibits acid secretion, the actions of two stable prostacyclin analogues on parietal cell function and cyclic AMP formation were tested using enzymatically dispersed cells from canine fundic mucosa. Accumulation of ¹⁴C-aminopyrine (AP) was used as an index of parietal cell response to stimulation. The 16-phenoxy derivative of PGI₂ inhibited accumulation of AP stimulated by histamine (10 μM), with 50% inhibition (ID₅₀) at 10 nM. 6_β-PGI₁ also inhibited the action of histamine (ID₅₀ 0.5μM) but failed to block stimulation by carbachol or the dibutyryl derivative of cyclic AMP (dbcAMP). In similiar concentrations to those producing inhibition of histamine-stimulated AP accumulation, the 16-phenoxy analogue and 6_β-PGI₁ inhibited histamine-stimulated cyclic AMP generation by parietal cells. At 100 fold higher concentrations, 6_β-PGI₁ stimulated cyclic AMP formation, presumably in non-parietal cells. Even in high concentrations the 16-phenoxy analogue failed to increase cyclic AMP formation by mucosal cells. These data indicate that the stable prostacyclin analogues are potent, direct inhibitors of histamine-stimulated parietal cell function and that it is the inhibition, rather than the stimulation, of cyclic AMP formation that is linked to the antisecretory actions of these prostanoid compounds.     

Investigation of the vascular actions of arachidonate lipoxygenase and cyclo-oxygenase products on the isolated perfused stomach of rat and rabbit

The vascular actions of several prostanoids and arachidonate lipoxygenase products were investigated on the gastric circulation of rat and rabbit perfused with Kreb's solution. Under resting conditions, prostacyclin and PGE₂ produced small decreases in perfusion pressure with prostacyclin being the more potent. During vasoconstriction induced by infusion of noradrenaline, vasopressin or angiotensin II, prostacyclin was 20–40 times as active as PGE₂ as a gastric vasodilator in rat or rabbit stomach. PGF_2α was a less potent vasoconstrictor than noradrenaline, while the epoxy-methano endoperoxide analogue produced a long-lasting vasoconstriction. The putative metabolite, 6-oxo-PGE₁ was less active than prostacyclin as a vasodilator, having comparable activity to PGE₁, whereas 6-oxo-PGF_1α had very little activity. The endoperoxide, PGH₂ reduced perfusion pressure, this effect being inhibited by concurrent infusion of 15-HPETE. The vasodilation induced by arachidonic acid was likewise reduced by 15-HPETE, and abolished by indomethacin infusion. The arachidonate lipoxygenase hydroperoxides were vasodilator in the gastric circulation, the rank order of potency being 12-HPETE > 11-HPETE > 5-HPETE > 15-HPETE in both rat and rabbit stomach. It is possible that such vasoactive lipoxygenase products, may play modulator roles in the gastric mucosa.     

Platelet and cardiovascular activity of the hydantoin BW245C, a potent prostaglandin analogue

The platelet anti-aggregating, cardiovascular and gastro-intestinal actions of a hydantoin prostaglandin analogue, BW245C have been compared with prostaglandin and PGD₂ several species. In human plasma , BW245C was 0.2 times as active as prostacyclin and 8 times as active as PGD₂ in inhibiting platelet aggregation. In rat and rabbit plasma, BW245C was only weakly active but was more potent in sheep and horse plasma. Since the acivity of PGD₂ varied in a parallel fashion, BW245C may interactive with PGD₂ binding sites on platelets. The potency of BW245C as a vasodepressor also varied between species, being 0.5, 0.1, 0.06 and < 0.02 times as active as prostacyclin in the aneasthetised dog, monkey, rat and rabbit respectively.The relative activity of BW245C as an inhibitor of platelet aggregation was more comparable, being 0.08, 0.04 and 0.05 times as active as prostacyclin following intravenous infusion in the rabbit dog and monkey respectively. In the rabbit, BW245C was a highly selective platelet inhibitor with minimal cardiovascular actions, whereas in the dog and monkey, BW245C lowered BP in anti-aggregating doses. The potent platlet anti-aggregating actions of BW245C following parenteral or oral administration makes this hydantoin a potentially-useful anti-thrombotic prostaglandin analogue.     

Correlation between adult transformation and aldehyde oxidase staining pattern in wing discs ofApterous genotypes inDrosophila melanogaster

Summary The aldehyde oxidase staining pattern in wing discs ofDrosophila melanogaster bearing the genotypesap ^blt /ap ^blt andap ^blt andap ^blt /ap ⁷³ⁿ showns changes from the wild-type pattern. Extensive areas of the presumptive dorsal posterior wing blade, which are normally unstained, have enzyme activity in these mutants. In wings of these genotypes, dorsal posterior structures are replaced by dorsal anterior wing structures. A strong correlation has been found between the frequencies of various staining patterns in the discs and the extent of transformation in the cuticular structures of the wing, which is consistent with the idea that aldehyde oxidase activity can be used as an indicator in the wing disc of this transformation. Unlike the homoeotic mutationengrailed, apterous has not been interpreted as a selector gene yet the work reported here shows thatapterous alleles can cause changes resembling those of theengrailed phenotype both in aldehyde oxidase staining behaviour and in the cuticular transformation.     

Fine structural and cytochemical studies of human diploid fibroblasts arrested in an essentially nonmitotic state.

Human diploid fibroblasts can be maintained in vitro in an arrested, essentially nonmitotic state for extended periods of time by reducing the serum concentration in the medium from 10 to 0.5%. Arrested cells can be induced to re-enter the proliferative state by subcultivation in medium containing 10% serum. Fine structure, acid phosphatase, cytochrome oxidase, and extracellular carbohydrates in arrested cells were examined and compared to cultures growing in 10% serum and to cells transferred to 10% serum after 21 days in 0.5% serum. Cells in 10% serum posessed a well-developed Golgi complex, extensive rough endoplasmic reticulum, mitochondria containing transverse cristae, and many free ribosomes in the cytoplasm. In arrested cells, Golgi complexes were rarely observed, the number of both free and membrane-bound ribosomes was reduced, the number of cristae per mitochondria was decreased and the amount of demonstrable cytochrome oxidase activity was diminished. There was an accumulation of intercellular carbohydrate components. After subcultivation with medium containing 10% serum, arrested cells regained the ultrastructural characteristics of cells continuously cultured at this serum level; however, the amount of intercellular carbohydrate remained elevated. These results indicate that distinct yet reversible changes occur in the subcellular morphology and organization of cells maintained in an essentially nonmitotic state. This arrested state may be a close approximation to the situation as it occurs in vivo in expanding cell populations.