Evaluating perinatal mortality rates: effects of referral and case mix.

OBJECTIVE--To evaluate perinatal mortality rates as a method of auditing obstetric and neonatal care after account had been taken of transfer between hospitals during pregnancy and case mix. DESIGN--Case-control study of perinatal deaths. SETTING--Leicestershire health district. SUBJECTS--1179 singleton perinatal deaths and their selected live born controls among 114,362 singleton births to women whose place of residence was Leicestershire during 1978-87. MAIN OUTCOME MEASURE--Crude perinatal mortality rates and rates adjusted for case mix. RESULTS--An estimated 11,701 of the 28,750 women booked for delivery in general practitioner maternity units were transferred to consultant units during their pregnancy. These 11,701 women had a high perinatal mortality rate (16.8/1000 deliveries). Perinatal mortality rates by place of booking showed little difference between general practitioner units (8.8/1000) and consultant units (9.3-11.7/1000). Perinatal mortality rates by place of delivery, however, showed substantial differences between general practitioner units (3.3/1000) and consultant units (9.4-12.6/1000) because of the selective referral of high risk women from general practitioner units to consultant units. Adjustment for risk factors made little difference to the rates except when the subset of deaths due to immaturity was adjusted for birth weight. CONCLUSION--Perinatal mortality rates should be adjusted for case mix and referral patterns to get a meaningful result. Even when this is done it is difficult to compare the effectiveness of hospital units with perinatal mortality rates because of the increasingly small subset of perinatal deaths that are amenable to medical intervention.     

Chromosomal localization of uroplakin genes of cattle and mice

The asymmetric unit membrane (AUM) of the apical surface of mammalian urinary bladder epithelium contains several major integral membrane proteins, including uroplakins IA and IB (both 27 kDa), II (15 kDa), and III (47 kDa). These proteins are synthesized only in terminally differentiated bladder epithelial cells. They are encoded by separate genes and, except for uroplakins IA and IB, appear to be unrelated in their amino acid sequences. The genes encoding these uroplakins were mapped to chromosomes of cattle through their segregation in a panel of bovine x rodent somatic cell hybrids. Genes for uroplakins IA, IB, and II were mapped to bovine (BTA) Chromosomes (Chrs) 18 (UPK1A), 1 (UPK1B), and 15 (UPK2), respectively. Two bovine genomic DNA sequences reactive with a uroplakin III cDNA probe were identified and mapped to BTA 6 (UPK3A) and 5 (UPK3B). We have also mapped genes for uroplakins 1A and II in mice, to the proximal regions of mouse Chr 7 (Upk1a) and 9 (Upk2), respectively, by analyzing the inheritance of restriction fragment length variants in recombinant inbred mouse strains. These assignments are consistent with linkage relationships known to be conserved between cattle and mice. The mouse genes for uroplakins IB and III were not mapped because the mouse genomic DNA fragments reactive with each probe were invariant among the inbred strains tested. Although the stoichiometry of AUM proteins is nearly constant, the fact that the uroplakin genes are unlinked indicates that their expression must be independently regulated. Our results also suggest likely positions for two human uroplakin genes and should facilitate further analysis of their possible involvement in disease.     

Ovarian interstitial tissue of the wood mouse, Apodemus sylvaticus

The ovary of the wood mouse contains an unusually large amount of interstitial tissue which appears to develop from undifferentiated cells of the ovarian stroma and also by transformation of theca or granulosa cells of atretic follicles. The cells are characterized by the presence of smooth endoplasmic reticulum, rounded mitochondria with tubular cristae, and abundant, large (1.5 micron diameter) lipid droplets containing cholesterol and its esters. 3 beta-Hydroxysteroid dehydrogenase activity occurs in the interstitial cells. Their ultrastructural characteristics suggest that the cells are not very active, but their abundance and the considerable amount of steroid hormone precursor they contain may compensate for low secretory activity and they may be an important and (from a developmental viewpoint) early source of steroid hormone.     

Nest site selection by yellow-faced honeyeaters Lichenostomus chrysops

When choosing subsequent nest sites, species that produce multiple broods in a single breeding season have the option of dispersing from a site where they previously suffered depredation, i.e., a predator-avoidance tactic. In our study on yellow-faced honeyeaters Lichenostomus chrysops it was found that 89% of nest failures were attributed to nest depredation, the primary cause of reproductive failure. Pairs re-nested further from depredated nesting attempts than from successful nesting attempts and progressively higher above the ground as the breeding season progressed. Pairs nesting in dioecious Coprosma quadrifida plants only nested in non-fruiting male plants. Artificial nests were used to test the hypothesis that nest height and plant preferences were strategies to reduce the risk of depredation. There was no evidence that either higher nests or nests in non-fruiting C. quadrifida achieved reduced levels of depredation during 14 days of artificial nest exposure. Specific nest site characteristics were not found to be associated with nest outcome for either natural or artificial nests. Our study provides further evidence that species may choose a diverse range of nest sites in order to avoid predators from developing specific search images and then, following depredation, compensate by rapidly re-nesting away from the failed attempt.     

Internal initiation of translation of hepatitis C virus RNA: the ribosome entry site is at the authentic initiation codon.

Hepatitis C viral (HCV) RNA includes an internal ribosome entry segment (IRES) that extends some 30 nt into the coding region and promotes internal initiation of translation at the authentic initiation codon at nt 342. The 5'-boundary of this IRES was mapped by in vitro translation and transfection assays and was found to lie between nt 42 and 71. Within these IRES boundaries there are, in most HCV strains, three AUG triplets upstream of the authentic initiation site. Although the first, 5'-proximal, of these is absolutely conserved, a mutational analysis showed that it is not a functional initiation codon. In particular, the G residue could be substituted provided compensatory mutations were made to maintain base pairing. The other two upstream AUGs are not absolutely conserved, and mutation of the third (5'-distal) had little effect on IRES activity. When an additional AUG codon was introduced by single-site mutation just upstream of the authentic initiation codon, it was found to be used when most of the IRES had been deleted to generate an RNA translated by the scanning ribosome mechanism, but was not used in the background of the full-length IRES when internal initiation is operative. These results argue that the IRES promotes direct ribosome entry immediately at, or indeed very close to, the authentic initiation codon, and that the upstream AUGs do not serve as ribosome entry sites.     

Malignant cerebral glioma--I: Survival,disability, and morbidity after radiotherapy.

OBJECTIVE: To describe survival, disability, and morbidity after radiotherapy for malignant glioma. DESIGN: Two year prospective study with home interviews with patients and relatives. SETTING: Seven neurosurgical and radiotherapy centres in London. SUBJECTS: 105 patients aged 21 to 75: 59 had biopsy; 46 had partial macroscopic resection; 92 received radiotherapy; and 13 received steroids alone. MAIN OUTCOME MEASURES: Survival, time free from disability, and changes in disability after treatment. RESULTS: Six and 12 month survival for radiotherapy patients was 70% and 39%, respectively. Age, World Health Organisation clinical performance status, extent of surgery, and history of seizures before diagnosis each influenced survival. The Medical Research Council prognostic index was also significantly related to survival. Multivariate analysis showed that initial clinical performance status was the most important component of the index. Most (80%; 49/61) patients with a clinical performance status of 0, 1, or 2 lived at least six months before becoming permanently disabled. Most patients who had initially had a good clinical performance status (0-2) and who were alive six months after radiotherapy (68%; 36/52), however, had experienced either clinical deterioration or severe tiredness after treatment. In 17% (9/52) of these some permanent loss of function remained. These adverse effects were associated with increasing radiotherapy dose. Severely disabled patients (clinical performance status 3 or 4) gained little benefit. CONCLUSION: Severely disabled patients gain little physical benefit from radiotherapy, whereas those not so disabled may experience considerable adverse effects.     

The elongation of amylose and amylopectin chains in isolated starch granules

The aim of this work was to investigate the conditions required for amylose synthesis in starch granules. Although the major granule-bound isoform of starch synthase - GBSSI - catalyses the synthesis of amylose in vivo, ¹⁴C from ADP[¹⁴C]glucose was incorporated primarily into a specific subset of amylopectin chains when supplied to starch granules isolated from pea (Pisum sativum L.) embryos and potato (Solanum tuberosum L.) tubers. Incubation of granules with soluble extracts of these organs revealed that the extracts contained compounds that increased the incorporation of ¹⁴C into amylose. These compounds were rendered inactive by treatment of the extracts with α-glucosidase, suggesting that they were malto-oligosaccharides. Consistent with this idea, provision of pure malto-oligosaccharides to isolated granules resulted in a dramatic shift in the pattern of incorporation of ¹⁴C, from amylopectin chains to amylose molecules. Comparison of the pattern of incorporation in granules from wild-type peas and lam mutant peas which lack GBSSI showed that this effect of malto-oligosaccharides was specifically on GBSSI. The significance of these results for understanding of the synthesis of amylose and amylopectin in storage organs is discussed.     

Purification and characterisation of an intracellular carbonic anhydrase from the unicellular green alga Coccomyxa

An intracellular carbonic anhydrase (CA; EC 4.2.1.1) was purified and characterised from the unicellular green alga Coccomyxa sp. Initial studies showed that cultured Coccomyxa cells contain an intracellular CA activity around 100 times higher than that measured in high-CO₂-grown cells of Chlamydomonas reinhardtii CW 92. Purification of a protein extract containing the CA activity was carried out using ammonium-sulphate precipitation followed by anion-exchange chromatography. Proteins were then separated by native (non-dissociating) polyacrylamide gel electrophoresis, with each individual protein band excised and assayed for CA activity. Measurements revealed CA activity associated with two discrete protein bands with similar molecular masses of 80 +5 kDa. Dissociation by denaturing polyacrylamide gel electrophoresis showed that both proteins contained a single polypeptide of 26 kDa, suggesting that each 80-kDa native protein was a homogeneous trimer. Isoelectric focusing of the 80-kDa proteins also produced a single protein band at a pH of 6.5. Inhibition studies on the purified CA extract showed that 50% inhibition of CA activity was obtained using 1 M azetazolamide. Polyclonal antibodies against the 26-kDa CA were produced and shown to have a high specific binding to a single polypeptide in soluble protein extracts from Coccomyxa cells. The same antiserum, however, failed to cross-react with soluble proteins isolated from two different species of green algae, Chlamydomonas reinhardtii and Chlorella vulgaris. Correspondingly, antisera directed against pea chloroplastic CA, extracellular CA from C. reinhardtii and human CAII, showed no cross-hybridisation to the 26-kDa polypeptide in Coccomyxa. The 26-kDa protein was confirmed as being a CA by N-terminal sequencing of two internal polypeptide fragments and alignment of these sequences with that of previously identified CA proteins from several different species.Abbreviations CA carbonic anhydrase - CCM CO₂-concentrating mechanism - IEF isoelectric focusing - Rubisco ribulose-l,5-bisphosphate carboxylase/oxygenase We would like to thank Drs. Cecilia Forsman, Inga-Maj Johansson and Nalle Jonsson for their valuable advice concerning the isolation of CA. This work was supported by the Swedish Natural Research Council and Seth M. Kempes Memorial foundation.