Showing papers by "University of Leicester published in 1990"

The list of threatening experiences : the reliability and validity of a brief life events questionnaire

Abstract: During the 23 years since the original work of Holmes & Rahe, research into stressful life events on human subjects has tended towards the development of longer and more complex inventories. The List of Threatening Experiences (LTE) of Brugha et al., by virtue of its brevity, overcomes difficulties of clinical application. In a study of 50 psychiatric patients and informants, the questionnaire version of the list (LTE-Q) was shown to have high test-retest reliability, and good agreement with informant information. Concurrent validity, based on the criterion of independently rated adversity derived from a semistructured life events interview, making use of the Life Events and Difficulties Scales (LEDS) method developed by Brown & Harris, showed both high specificity and sensitivity. The LTE-Q is particularly recommended for use in psychiatric, psychological and social studies in which other intervening variables such as social support, coping, and cognitive variables are of interest, and resources do not allow for the use of extensive interview measures of stress.

Paleozoic accretion and Cenozoic redeformation of the Chinese Tien Shan Range, central Asia

Abstract: The Tien Shan Range in central Asia contains two late Paleozoic sutures. The older, southern suture marks the collision of a passive margin at the north of the Tarim block and an active continental margin; subduction under the latter was to the north. The younger, northern suture separates a northern Carboniferous island arc from an active continental margin developed over a south-dipping subduction zone. The subduction direction under the island arc is unknown. Mesozoic elastics were deposited over the doubly sutured orogen. Rate and energy of sedimentation waned until deposition of Oligocene conglomerates above a regional unconformity-interpreted as marking the onset of deformation induced by the India-Asia collision. Molasse deposition accelerated in Pliocene and Quaternary time, and deposition continues today as active thrusts generate relief. Paleozoic structures control the gross divergence of Cenozoic thrusts across the orogen.

Islet isolation assessment in man and large animals.

Abstract: Recent progress in islet isolation from the pancreas of large mammals including man, accentuated the need for the development of precise and reproducible techniques to assess islet yield. In this report both quantitative and qualitative criteria for islet isolation assessment were discussed, the main topics being the determination of number, volume, purity, morphologic integrity andin vitro andin vivo function tests of the final islet preparations. It has been recommended that dithizone should be used as a specific stain for immediate detection of islet tissue making it possible to estimate both the total number of islets (dividing them into classes of 50 µ diameter range increments) and the purity of the final preparation. Appropriate morphological assessment should include confirmation of islet identification, assessment of the morphological integrity and of the purity of the islet preparation. The use of fluorometric inclusion and exclusion dyes together have been suggested as a viability assay to simultaneously quantitate the proportion of cells that are intact or damaged. Perifusion of islets with glucose provides a dynamic profile of glucose-mediated insulin release and of the ability of the cells to down regulate insulin secretion after the glycemic challenge is interrupted. Although perifusion data provides a useful guide to islet viability the quantity and kinetics of insulin release do not necessarily predict islet performance after implantation. Therefore, the ultimate test of islet viability is their function after transplantation into a diabetic recipient. For this reason,in vivo models of transplantation of an aliquot of the final islet preparation into diabetic nude (athymic) rodents have been suggested. We hope that these general guidelines will be of assistance to standardize the assessment of islet isolations, making it possible to better interpret and compare procedures from different centers.

Game theoretic models of mixed oligopoly

Abstract: . In this paper we review various models that have been proposed for the study of mixed oligopoly, that is markets in which private and public firm compete on equal basis using only market instruments.

X-ray reflection from cold matter in the nuclei of active galaxies

Abstract: THE evidence accumulated over the past few years for strong soft X-ray emission from active galactic nuclei1–3 has been interpreted as black body emission from the innermost stable region of an accretion disk feeding the putative black hole at the centre of the active nucleus, a view given strong support by the rapid variability of some soft X-ray components4. More recently, new X-ray data from the Exosat and Ginga satellites have revealed a second indicator of optically thick matter in the vicinity of the active nucleus, in the form of an iron K-fluorescence line at ≈6.4 keV (refs 5–8). We report the discovery of two further common features of continuum absorption and reflection, revealed in a composite spectrum from twelve Ginga observations of Seyfert-type active galactic nuclei. Most of these spectral features are shown to be well modelled by reprocessing of the hard X-ray power-law continuum in a slab (or perhaps a disk) of cold matter. There is also evidence for a substantial line-of-sight column of photoionized material.

Percutaneous transluminal angioplasty of occlusions of the femoral and popliteal arteries by subintimal dissection.

Abstract: A technique for recanalization of femoral and popliteal arterial occlusions by intentional subintimal dissection is described. Recanalization with this technique was attempted in 71 occlusions of the femoro-popliteal segment with a mean length of 11.4 cm. Primary technical success was achieved in 54 (76%) cases, with complications occurring in 4 (5.6%). Of 44 successful cases reviewed at a mean follow up of 6 months, 37 (84%) were either asymptomatic or improved. The technique has proved to be an effective method of treating occlusions of the femoral and popliteal arteries with an acceptable complication rate. It may allow successful angioplasty where the standard intraluminal method fails, particularly when reconstructive surgery is the only option.

Extra-pair paternity and intraspecific brood parasitism in wild zebra finches Taeniopygia guttata, revealed by DNA fingerprinting

Abstract: The frequency of extra-pair parentage in a wild population of zebra finches Taeniopygia guttata was examined by DNA fingerprinting. A total of 25 families, comprising 16 pairs of parents and 92 offspring (in broods of 1 to 6) were examined. Ten cases of extra-pair parentage, presumed to constitute intraspecific brood parasitism, were detected (10.9% of offspring or 36% of broods), including one possible instance of ‘quasi-parasitism’ (parasitism by a female fertilized by the male nest owner). The average number of parasitic eggs per clutch detected by fingerprinting was 1.10±0.32 SD, very similar to the one egg difference in average clutch size between parasitised (6.0±0.82) and unparasitised nests (5.0±0.95). Two cases of extra-pair paternity (EPP) were detected among 82 offspring whose maternity was confirmed: 2.4% of offspring, or 8% of broods. In both cases EPP accounted for only a single offspring within a brood. Behavioural observations show that EPP occurs through extra-pair copulation rather than rapid mate switching. The results are discussed in the light of what is known about the fertile period and sperm precedence patterns in this species.

Phytochrome, a family of photoreceptors with multiple physiological roles

Abstract: (...) This article reviews the regulation of development by phytochrome and discusses evidence from physiological studies of wild type, mutant and transgenic plants consistent with the proposal that different members of the phytochrome family have different photosensory roles. (...)

Modulation of ATP-sensitive K+ channels in skeletal muscle by intracellular protons.

Abstract: Since their discovery in cardiac muscle, ATP-sensitive K+(KATP) channels have been identified in pancreatic beta-cells, skeletal muscle, smooth muscle and central neurons. The activity of KATP channels is inhibited by the presence of cytosolic ATP. Their wide distribution indicates that they could have important physiological roles that may vary between tissues. In muscle cells the role of K+ channels is to control membrane excitability and the duration of the action potential. In anoxic cardiac ventricular muscle KATP channels are believed to be responsible for shortening the action potential, and it has been proposed that a fall in ATP concentration during metabolic exhaustion increases the activity of KATP channels in skeletal muscle, which may reduce excitability. But the intracellular concentration of ATP in muscle is buffered by creatine phosphate to 5-10 mM, and changes little, even during sustained activity. This concentration is much higher than the intracellular ATP concentration required to half block the KATP-channel current in either cardiac muscle (0.1 mM) or skeletal muscle (0.14 mM), indicating that the open-state probability of KATP channels is normally very low in intact muscle. So it is likely that some additional means of regulating the activity of KATP channels exists, such as the binding of nucleotides other than ATP. Here I present evidence that a decrease in intracellular pH (pHi) markedly reduces the inhibitory effect of ATP on these channels in excised patches from frog skeletal muscle. Because sustained muscular activity can decrease pHi by almost 1 unit in the range at which KATP channels are most sensitive to pHi, it is likely that the activity of these channels in skeletal muscle is regulated by intracellular protons under physiological conditions.

A new mechanism of granite emplacement: intrusion in active extensional shear zones

Abstract: ONE of the principal ways in which continental crust grows is by the incorporation, from deeper within the Earth, of large volumes of granitic magma A 'space problem' exists1 as to how these magmas are accommodated in the crust Traditionally two main emplacement mechanisms have been emphasized: 'forceful' intrusion, whereby buoyancy-driven magmas physically push the crust aside, creating granitic diapirs and balloons; and 'passive' emplacement characterized by replacive mechanisms such as cauldron subsidence and stoping Although more recent work2,3 has demonstrated that space for granites may be created within bends and offsets of large transcurrent faults, the simple view of either forceful or passive still fails to account for the intrusive mechanisms of many granites Here we report the discovery of a new igneous intrusion mechanism In the superbly exposed Proterozoic continental crust of South Greenland we have observed that rapakivi granite was intruded as large-scale sheets along ductile extensional shear zones that were active during emplacement In such a process the space problem seems to be simply resolved

Discourse: Definitions and contradictions

Abstract: With the question ‘What is “discourse”?’ as the starting point, this chapter addresses ways of identifying particular discourses, and attends to how these discourses should be distinguished from texts. The emergence of discourse analysis within psychology, and the continuing influence of linguistic and post-structuralist ideas on practitioners, provide the basis on which discourse-analytic research can be developed fruitfully. This chapter discusses the descriptive, analytic and educative functions of discourse analysis, and addresses the cultural and political questions which arise when discourse analysts reflect on their activity. Suggestions for an adequate definition of discourse are proposed and supported by seven criteria which should be adopted to identify discourses, and which attend to contradictions between and within them. Three additional criteria are then suggested to relate discourse analysis to wider political issues.

Alkaliphiles: Ecology, diversity and applications

Abstract: Organisms with pH optima for growth in excess of pH8, usually between 9 and 10, are properly defined as alkaliphiles (or sometimes alkalophiles). Most of the organisms described to date as growing under very alkaline conditions are prokaryotes, comprising a heterogeneous collection of eubacteria (including cyanobacteria) with a few examples of archaebacteria. With the exception of the alkaliphilic archaebacteria (which are also halophilic), few of the isolates have been comprehensively classified. However, it is clearly that may different taxa are represented amongst the alkaliphiles, and that some of these at least are likely to be new taxa. Alkaliphiles can be isolated from ‘normal’ environments such as garde soil, presumably because there are transient alkaline conditions generated in such environments by biological activity, but a relatively restricted range of types results from the exploration of such environments (often Bacillus spp.). Naturally-occurring stable alkaline environments such as eutrophic soda (Na2CO3) lakes harbour a much wider range of types. A similarity wide range of types may exist in oligotrophic Ca(OH)2-dominated ground water in certain parts of the world. Alkaliphilic microorganisms have already made a large impact in the application of biotechnology for the manufacture of mass market consumer products. “Biological detergents” contain enzymes that have usually been obtained from alkaliphilic or alkalitolerant bacteria. The current proportion of total world enzyme production destined for the laundry detergents market comfortably exceeds 25%, and there are other possible applications in food and waste treatment industies. To date, most commercially available enzymes are derived from a few bacterial taxa (notably Bacillus spp.) and we have been very conservative in our choice of environments in which to look for new products. It is reasonable to suppose that soda lakes (and other alkaline environments) will yield a wealth of new organisms with useful commercial properties.

Object-oriented data modelling for spatial databases

Abstract: Data modelling is a critical stage of database design. Recent research has focused upon object-oriented data models, which appear more appropriate for certain applications than either the traditional relational model or the entity-relationship approach. The object-oriented approach has proved to be especially fruitful in application areas, such as the design of geographical information systems which have a richly structured knowledge domain and are associated with multimedia databases. This article discusses the key concepts in object-oriented modelling and demonstrates the applicability of an object-oriented design methodology to the design of geographical information systems. In order to show more clearly how this methodology may be applied, the paper considers the specific object-oriented data model IFO. Standard cartographic primitives are represented using IFO, which are then used in the modelling of some standard administrative units in the United Kingdom. The paper concludes by discussing current r...

Structure and function of haemolysin B,P-glycoprotein and other members of a novel family of membrane translocators.

Abstract: Recent studies have identified two sub-families of highly conserved polypeptides in a wide variety of organisms concerned with the transport of many different compounds, specific for each transport protein. Both families, represented by HisP and HlyB, respectively, have in common a highly conserved, approximately 25 kD domain, containing an ATP-binding site. The HisP sub-family essentially consists of cytoplasmic proteins which couple energy to the import of small substrates through cytoplasmic membrane permeases in Gram-negative bacteria. The HlyB (P-glycoprotein) sub-family, on the other hand, contains a second large domain which apparently acts as the transmembrane translocator itself, which in most cases drives the secretion of a variety of compounds. These membrane domains share a number of structural features which also serve to distinguish these proteins as a closely related group. Nevertheless, the compounds secreted by the HlyB sub-family include large polypeptides, polysaccharides and a variety of anti-tumour drugs. We describe here the properties of each of these remarkable proteins and we speculate on their possible mechanism of action.

HSP12, a new small heat shock gene of Saccharomyces cerevisiae: Analysis of structure, regulation and function

Abstract: We have isolated a new small heat shock gene, HSP12, from Saccharomyces cerevisiae. It encodes a polypeptide of predicted Mr 12 kDa, with structural similarity to other small heat shock proteins. HSP12 gene expression is induced several hundred-fold by heat shock and on entry into stationary phase. HSP12 mRNA is undetectable during exponential growth in rich medium, but low levels are present when cells are grown in minimal medium. Analysis of HSP12 expression in mutants affected in cAMP-dependent protein phosphorylation suggests that the gene is regulated by cAMP as well as heat shock. A disruption of the HSP12 coding region results in the loss of an abundant 14.4 kDa protein present in heat shocked and stationary phase cells. It also leads to the induction of the heat shock response under conditions normally associated with low-level HSP12 expression. The HSP12 disruption has no observable effect on growth at various temperatures, nor on the ability to acquire thermotolerance.

Pharmacological treatment of urinary incontinence.

Abstract: Urinary incontinence (UI) is a major problem especially to the elderly. The only absolute indications for drug therapy in this condition are infection and atrophic urethritis. Other causes of UI should be treated with behavioural remedies and physiotherapy. If these measures are impractical or fail to improve the condition, then we would recommend additional drug therapy.

Reflection signals and the perception by phytochrome of the proximity of neighbouring vegetation

Abstract: . Spectral photon distributions, red:far-red ratios (i.e. R:FR) and phytochrome photoequilibria (i.e. Pfr/Ptotal) were measured at various distances from artificial canopies composed of mustard or tobacco plants. Measurements were compared for radiation propagated predominantly vertically downwards and radiation propagated predominantly horizontally. Reflection signals from the artificial canopies were computed and shown to consist of a depletion of radiation over the 400–690 nm wavelength range, and an enhancement of radiation over the 690–800 nm range. R:FR and Pfr/Ptotal increased gradually with distance from the canopies, with significant depressions of both parameters evident at least as far as 30 cm from the vegetation stands. It is concluded that, in principle at least, detection of spectral quality differences by phytochrome would allow not only the presence but also the proximity of neighbouring plants to be perceived. Proximity perception is proposed as an ecologically valuable mechanism through which plants may be able to gauge their anticipatory responses to incipient shading according to the challenge posed by the nearness of neighbouring plants.

Muscarinic-receptor-mediated changes in intracellular Ca2+ and inositol 1,4,5-trisphosphate mass in a human neuroblastoma cell line, SH-SY5Y.

Abstract: This study reports increased intracellular Ca2+ and inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] in response to muscarinic-cholinergic stimulation of human neuroblastoma (SH-SY5Y) cells. Carbachol stimulation leads to a rapid increase in intracellular Ca2+ and Ins(1,4,5)P3 mass, both reaching a peak at around 10 s and then declining to a new maintained phase significantly above basal. Dose-response analysis of peak and plateau phases of intracellular Ca2+ shows different agonist potencies for both phases, carbachol being more potent for the plateau phase. The plateau-phase intracellular Ca2+ was dependent on extracellular Ca2+, which is admitted to the cell through a non-voltage-sensitive Ni2(+)-blockable Ca2+ channel. Using a Mn2+ quench protocol, we have shown that Ca2+ entry occurs early during the discharge of the internal stores. The plateau phase (Ca2(+)-channel opening) is dependent on the continued presence of agonist, since addition of atropine closes the Ca2+ channel and intracellular Ca2+ declines rapidly back to basal. We also failed to detect a refilling transient when we added back Ca2+ after intracellular Ca2+ had reached a peak and then declined in Ca2(+)-free conditions. These data strongly suggest that muscarinic stimulation of SH-SY5Y cells leads to a rapid release of Ca2+ from an Ins(1,4,5)P3-sensitive internal store and a parallel early entry of Ca2+ across the plasma membrane.

Heterogeneity of [3H]inositol 1,4,5-trisphosphate binding sites in adrenal-cortical membranes. Characterization and validation of a radioreceptor assay.

Abstract: 1. The characterization of a radioreceptor assay for determining Ins(1,4,5)P3 concentration in tissue extracts is described which utilizes the binding of [3H]Ins(1,4,5)P3 to an adrenal-cortex membrane fraction. 2. Analysis of [3H]Ins(1,4,5)P3 binding by isotope dilution demonstrated an apparent single population of binding sites (KD 3.65 +/- 0.18 nM, Bmax. 872 +/- 70 fmol/mg of protein). Specific binding of [3H]Ins(1,4,5)P3 was enhanced at alkaline pH values (maximum at pH 8.5), with complete loss of specific binding at pH less than 6. These binding sites displayed strict stereo- and positional specificity for Ins(1,4,5)P3, with L-Ins(1,4,5)P3, Ins(1,3,4)P3 and DL-Ins(1,3,4,5)P4 causing 50% displacement of specific [3H]Ins(1,4,5)P3 binding (IC50 values) at concentrations of 14 +/- 3 microM, 3.0 +/- 0.3 microM and 0.53 +/- 0.03 microM respectively. 3. Kinetic analysis of binding data, however, revealed a high-affinity [3H]Ins(1,4,5)P3 binding site (KD 0.052 nM) in addition to the lower-affinity site (KD 2.53 nM) already demonstrated in displacement studies. 4. It is shown that the presence of the high-affinity site can be exploited to increase the sensitivity of the [3H]Ins(1,4,5)P3 radioreceptor assay, allowing accurate detection of 20 fmol of Ins(1,4,5)P3 in 300 microliters of tissue extract. 5. Further validation of the specificity of the above assay for Ins(1,4,5)P3 was provided by incubating tissue extracts with either a 5-phosphatase or 3-kinase preparation. It was shown that identical loss occurred of both Ins(1,4,5)P3 mass and [3H]Ins(1,4,5)P3, added to parallel incubations. 6. The ability of the assay to measure basal and agonist-stimulated increases in Ins(1,4,5)P3 concentration has been demonstrated with rat cerebral cortex and bovine tracheal smooth-muscle slices and a range of cultured and isolated cell preparations.

Regulation of gene expression

Abstract: 1. Pseudo-operator sequences may be located in (or inserted into) plant genomes and utilised to drive expression of foreign genes. These pseudo-operator sequences are nucleotide sequences which are present at a suitable location in a gene at which repressor binding will lead to inhibitation or enhancement of gene expression. The disclosed technique permits the design of altered specificity repressors, which bind the pseudo-operators.

Childhood sexual experiences with adults reported by women with eating disorders: an extended series

Abstract: A total of 158 women presenting with clinical eating disorders have been investigated using a self-report questionnaire and subsequent interview concerning their recollections of sexual experiences with adults before the age of 16 and later adverse sexual experiences. About a third reported events in childhood and over half described some adverse experiences. It may be that these experiences are relevant to the subsequent illness in some cases, but greater certainty must await further research. In the meantime, inquiring about such matters would seem to be advisable in the assessment and therapy of eating-disordered patients.

Estimating the cumulative probability of failure data points to be plotted on Weibull and other probability paper

Abstract: Using both an exact technique and Monte Carlo simulations to estimate the cumulative probability of failure of the ith of n identically stressed samples, it is shown that the approximation F(i,n)=(i-0.3)/(n+0.4) is considerably more accurate than other commonly used approximations. The significance of this in the interpretation of electrical breakdown tests is demonstrated. >

Results of the United Kingdom children's cancer study group's malignant germ cell tumor studies

Abstract: The United Kingdom Children's Cancer Study Group's malignant germ cell tumor studies were undertaken to establish standard protocols for investigating, staging, and treating children, and to study the efficacy of new drug combinations and the value of serial measurement of serum alphafetoprotein (AFP) and human chorionic gonadotrophin (HCG). Boys with Stage I testicular tumors were treated by orchidectomy alone, whereas, after appropriate surgery, chemotherapy was recommended for children with more advanced testicular tumors or with tumors at other sites. From 1979 to 1987, 126 children aged 0 to younger than 16 years with malignant germ cell tumors were registered. They were similar to patients in other large pediatric series with respect to sites of origin, age at presentation in relationship to primary site, histology, female predominence for sacrococcygeal site, and presence of associated malformations (present in 17%). Serum AFP was measured in 123 patients and was elevated in 115, whereas HCG was raised in 19 of 77. Monitoring by serial AFP measurement proved valuable in assessing response to therapy and in early detection of tumor recurrence. When treatment results were assessed in February 1988, 101 of 122 patients were alive (four who received nonprotocol chemotherapy were excluded). Forty-four patients had been cured by surgery alone (41 with testicular tumors, two with ovarian tumors, and one with sacrococcygeal tumor). All of the remaining 78 children received chemotherapy. The initial low dose vincristine, actinomycin, and cyclophosphamide (LDVAC) regimen proved ineffective, actuarial survival at 5 years follow-up being 8% (12 patients), and a regimen of cisplatin, vinblastine, and bleomycin (PVB) caused unacceptable toxicity, with actuarial survival at 5 years follow-up being 67% (nine patients). Five-year actuarial survival was 87% for 17 children given high dose VAC with or without doxorubicin and 84% for 33 given bleomycin, etoposide, and cisplatin (BEP). All 7 children given various combinations of these regimens survived. Excluding the 12 LDVAC cases, patient survival by site was as follows: testis (59 patients, 100%); vagina, uterus, and prostate (four patients, 100%); ovary (25 patients, 88%); thorax (five patients, 40%), and other (four patients, 67%). Similarly, patient survival by stage was Stage I (62,97%), Stage II (14,86%); Stage III(18,83%); and Stage IV (16,72%). Survival by histology was analysed only in cases for which histologic review had been done the LDVAC cases were excluded. Survival was 99% for 68 patients with yolk sac tumors, 75% for eight patients with immature teratomas, 70% for 11 patients with mixed tumors, and 50% for four patients with germinomas. There was no relationship between outcome and initial AFP level or between outcome and the level of HCG.

Ecology and Management of Lake Naivasha, Kenya, in Relation to Climatic Change, Alien Species' Introductions, and Agricultural Development

Abstract: Lake Naivasha is an important freshwater resource for Kenya's foreign-currency-earning agriculture and tourism, and for water-supply. It has always experienced extensive water-level fluctuations as a consequence of irregular rainfall patterns that are affected by continental-scale climatic events, and its communities — particularly of aquatic plants — were adapted to these changes.

Clock mutations alter developmental timing in Drosophila.

Abstract: The developmental time of period mutants in Drosophila melanogaster was monitored under different environmental conditions. We observed that the pers mutants, which have short 19 h circadian cycles, develop faster from eggs to adult than the wild-type: perL mutants, which have long 28 h circadian rhythms, complete development more slowly than the wild-type. These results suggest that endogenous timers may be involved in regulating the development time of D. melanogaster.