Showing papers by "University of Liverpool published in 1988"

Endothelium-derived relaxing factor release on activation of NMDA receptors suggests role as intercellular messenger in the brain.

Abstract: In the vascular system, endothelium-derived relaxing factor (EDRF) is the name of the local hormone released from endothelial cells in response to vasodilators such as acetylcholine, bradykinin and histamine. It diffuses into underlying smooth muscle where it causes relaxation by activating guanylate cyclase, so producing a rise in cyclic GMP levels. It has been known for many years that in the central nervous system (CNS) the excitatory neurotransmitter glutamate can elicit large increases in cGMP levels, particularly in the cerebellum where the turnover rate of cGMP is low. Recent evidence indicates that cell-cell interactions are involved in this response. We report here that by acting on NMDA (N-methyl-D-aspartate) receptors on cerebellar cells, glutamate induces the release of a diffusible messenger with strikingly similar properties to EDRF. This messenger is released in a Ca2+-dependent manner and its activity accounts for the cGMP responses that take place following NMDA receptor activation. In the CNS, EDRF may link activation of postsynaptic NMDA receptors to functional modifications in neighbouring presynaptic terminals and glial cells.

The new stereological tools: disector, fractionator, nucleator and point-sampled intercepts and their use in pathological research and diagnosis

Abstract: The new stereological methods for correct and efficient sampling and sizing of cells and other particles are reviewed. There is a hierarchy of methods starting from the simplest where even the microscopic magnification may be unknown to the most complex where typically both section thickness and the magnification must be known. Optical sections in suitably modified microscopes can be used to improve the ease and speed with which even the most demanding of these methods are performed. The methods are illustrated by practical examples of applications to a wide range of histological entities including synapses, neurons and cancer cells, glomerular corpuscles and ovarian follicles.

Modelling tropical deforestation: A study of GCM land-surface parametrizations

Abstract: Tropical deforestation, by changing land surfaces, may have important consequences for the climate system. Predicting even the local, immediate effects of replacing tropical broadleaf forest with impoverished grassland has been difficult, because the land-surface parametrization schemes used previously in climate models have been inadequate. The forest canopy is particularly important for the surface-energy budget in tropical regions, and models neglecting the occurrence of such a canopy may give an unrealistic partitioning between various surface-energy fluxes. Inclusion of a land-surface scheme with a vegetation canopy into a version of the National Center for Atmospheric Research (NCAR) Community Climate Model (CCM) with a diurnal as well as a seasonal cycle permits an exploratory study of the possible effects of tropical deforestation. In a 13-month integration that assumes that all of the Amazon tropical forest in South America is replaced by impoverished grassland, surface hydrological and temperature effects dominate the response. Reduced mixing and less interception and evaporation from the canopy cause runoff to increase and surface temperatures to rise by 3–5 K. The period of driest soil is increased in the model from one month to several, but the possibility that this change is random cannot be excluded. Increased temperatures and drier soil could have a detrimental impact on survival of the remaining forest and on attempts at cultivation in deforested areas. The land-surface model, driven in a stand-alone mode by prescribed atmospheric conditions and with an imposed seasonal cycle of rainfall, mimics the seasonal cycle of soil moisture and runoff found in the CCM. Hence, it is used to estimate the relative contribution of the various changes imposed to simulate deforestation in the CCM with respect to the model's response at the surface. The change in surface roughness interacting with the canopy hydrology is evidently a major factor in determining the surface response to deforestation. However, the response to change in roughness is less pronounced for simpler models.

The role of reflexivity in feminist psychology

Abstract: The implications of a number of forms of reflexivity are explored for feminist work within psychology. “Personal” and “functional” reflexivity raise issues relating the identity of the researcher and the form/function of the research, while “disciplinary” reflexivity entails analysis of the nature and influence of the field of enquiry. It is argued that reflexivity, particularly of the disciplinary form, is a potentially powerful agent for change within traditional academic disciplines, such as psychology, in that it can be self-consciously applied to advance the feminist challenge.

Spatial and temporal aspects of cell signalling

Abstract: As new techniques are developed to measure intracellular messengers it becomes increasingly apparent that there is a remarkable spatial and temporal organization of cell signalling. Cells possess a small discrete hormone-sensitive pool of inositol lipid. In some cells such as Xenopus oocytes and Limulus photoreceptors this phosphoinositide signalling system is highly concentrated in one region of the cell, so establishing localized calcium gradients. Another example is the hydrolysis of inositol lipids in eggs at the point of sperm entry resulting in a localized increase in Ins(1,4,5) P 3 and calcium which spreads like a wave throughout the egg. In hamster eggs this burst of calcium at fertilization recurs at 1-3 min intervals for over 100 min, a particularly dramatic example of spontaneous activity. Spontaneous oscillations in intracellular calcium exist in many different cell types and are often induced by agonists that hydrolyse inositol lipids. We have made a distinction between oscillations that are approximately sinusoidal and occur at a higher frequency where free calcium is probably continuously involved in the oscillatory cycle and those where calcium falls to resting levels for many seconds between transients. In the former case, the oscillations are thought to be induced through a cytoplasmic oscillator based on the phenomenon of calcium-induced calcium release. Such oscillations can be induced in Xenopus oocytes after injection with Ins(1,4,5) P 3 . A receptor-controlled oscillator based on the periodic formation of I ns (1,4,5) P 3 is probably responsible for the generation of the widely spaced calcium transients. The function of such calcium oscillations is currently unknown. They may be a reflection of the feedback interactions that operate to control intracellular calcium. Another possibility emerged from observations that in some cells the frequency of calcium oscillations varied with agonist concentration, suggesting that cells might employ these oscillations as a way of encoding information. One advantage of using such a frequency-dependent mechanism may lie in an increase in fidelity, especially at low agonist concentrations. Whatever these functions might be, it is clear that uncovering the mechanisms responsible for such oscillatory activity will greatly enhance our understanding of the relation between the phosphoinositides and calcium signalling.

Reliability of ratings of perceived effort regulation of exercise intensity.

Abstract: This study assessed the reliability of ratings of perceived exertion (RPE) for the prescription of exercise intensity during cycling. Ten healthy men (21 to 62 years) and six women (25 to 50 years) attended the laboratory four times, 5 to 7 days apart. On the first visit each subject's maximal oxygen uptake was measured and, subsequently, they cycled at constant work rates based on their perception of ratings 9, 13 and 17 of the Borg 6-20 scale by regulating the resistance of the ergometer without reference to the instrument display panel. Analysis of variance revealed no significant between-trial differences with regard to oxygen uptake (VO2) or heart rate for men or women. The relative exercise intensities corresponding to the 3 ratings of exertion did not differ between men and women. Between-trial correlations for VO2 were highest for visits two and three at RPE levels 9 and 13 (r = 0.83 and r = 0.94) and consistently high (r = 0.92 or greater) for the three trials at RPE17. These data suggest that RPE is a useful frame of reference for the regulation of high levels of exercise intensity in healthy men and women. Small amounts of practice with the scale improve its applicability at lower exercise levels.

The Impact of Maternal Depression on Young Children

Abstract: Depression in mothers of young children is a common condition, and is highly associated with disturbance in the children and with later reading delay. A group of depressed and control women with children aged two and three was interviewed and observed at home and the children assessed. The depressed women had more difficult backgrounds and more current adversity than the controls. They played and talked as much with their children, but the quality of interaction was less satisfactory, with poorer‘meshing’, more distress and more unresolved conflict. Social policy and service implications are discussed.

Analysis of the dental morphology of Plio-Pleistocene hominids. IV. Mandibular postcanine root morphology.

Abstract: The subocclusal morphology of 168 permanent mandibular premolars (N = 77) and molars (N = 91) of Plio-Pleistocene hominids has been investigated The taxonomic allocation of the teeth, which represent at least 46 individuals, was based on nondental evidence Specimens were allocated to one of two major taxonomic categories, (EAFROB or EAFHOM), East African Homo erectus (EAFHER), or their taxonomic affinity was regarded as 'unknown' (N = 17) Information about the root system was derived from radiography and direct observation Morphometric data were in the form of nine linear and two angular measurements based on eighteen reference points Root form was also assessed using a scheme which recognised four classes of root morphology Data were compared using both univariate and multivariate techniques, including Principal Component and Canonical Variate analysis Posterior probabilities derived from the latter were used (in a two-taxon design model) to assess the affinities of the 'unknown' specimens The variation in hominid mandibular premolar root form was interpreted as two morphoclines, based on the presumed primitive condition of the P3 (with mesiobuccal and distal roots, 2R: MB and D) and P4 (with mesial and distal root, 2R: M and D) root systems One trend apparently leads towards root reduction (ie P3 = 1 R; P4 = 1 R), and the other to root elaboration (ie P3 and P4 = 2R: M and D) The extreme form of the latter is the 'molarisation' of the premolar roots seen in EAFROB Despite major differences in root form there was relatively little taxonomic variation in root metrics, except for a more robust distal root system in EAFROB Molar root form showed little interspecific variation except for M2 in which the roots in EAFROB were larger and more robust, with differences in root height being greater for the distal than for the mesial roots Root form and metrics enable four of the 'unknown' specimens (KMN-ER 819, 1482, 1483 and 1801) to be tentatively allocated to EAFHOM, and a single specimen, KMN-ER 3731, to EAFROB Published assessments of the root morphology of the 'robust' australopithecines from Swartkrans suggest that the premolar root form of Australopithecus (Paranthropus) robustus is not obviously intermediate between the presumed ancestral condition, and the 'molarised' mandibular premolar root systems of Australopithecus (Paranthropus) boisei

A method of obtaining a retrovirus-containing fraction from retrovirus-containing cells

Abstract: The present invention relates to a method of obtaining a retrovirus-containing fraction, and in particular, though not exclusively, to obtaining a retrovirus containing fraction from mononuclear cells containing a retrovirus. The method of forming a retrovirus-containing fraction from mononuclear cells containing said virus comprises, preparing a suspension of separated mononuclear cells in a culture medium, incubating said culture and separating the culture supernatant from said incubated culture, characterized in that an effective amount of a glucocorticoid or of a leukemia or viral inducing drug is added to the suspension before and/or during the incubation of said cultures, and if desired separating a retrovirus containing fraction from the separated supernatant.

Hypoxemia during sleep in Duchenne muscular dystrophy.

Abstract: Overnight polysomnography after acclimatization was performed on 14 patients with Duchenne muscular dystrophy (mean age, 18.3 yr; mean VC, 1.24 L). Despite their lack of sleep-related symptoms and normal daytime blood gas tensions, periods of hypopnea and/or apnea (H/A) were observed in all patients (mean frequency 9.6/h; range, 3.7 to 17.0; mean duration 23.1; range of means, 16 to 36 s). In 9 patients, between 0.5 and 12.3 oxygen desaturations of > 5% occurred per hour, with falls from a mean SaO2 baseline of 95.4 ± 0.6% (SEM) to a mean nadir of 74.2 ± 3.9% (range, 58 to 90). This desaturating group (n = 9) showed longer and more frequent H/A than did the 5 nondesaturators; the proportion of REM sleep occupied by H/A was 37.7 ± 3.8% in the desaturating group compared with only 15.1 ± 5.1% in the remainder (p < 0.01). The severity of sleep-disordered breathing could not be reliably predicted from daytime pulmonary function test results, and only maximal static expiratory pressure appeared significantly l...

A 72 kD trophoblast glycoprotein defined by a monoclonal antibody.

Abstract: A novel trophoblast cell surface antigen has been defined by a monoclonal antibody 5T4, raised following immunisation with wheat germ agglutinin (WGA) purified glycoproteins from deoxycholate (DOC) solubilised human syncytiotrophoblast plasma membrane (StMPM). The distribution of the antigen was determined by indirect immunoperoxidase staining of sections of normal organ and placental tissues as well as immunofluorescence and radiobinding assays with a wide variety of cell lines representing differing normal and tumour cell types. In frozen sections of normal full term placenta, 5T4 is strongly expressed only by the syncytiotrophoblast, some extravillous cytotrophoblast and the amniotic epithelium. The 5T4 antigen is apparently not expressed by any maternal component of the placenta nor is it detected in adult liver, lung, bronchus, heart, testis, ovary, brain, or muscle. The antigen is apparently expressed by several specialised epithelia. Immunoprecipitation of radiolabelled StMPM indicated that 5T4 molecules are glycoproteins of mol. wt of approximately 72 kD on SDS-PAGE. 5T4 antigen is selectively expressed by diverse tumour cell lines, including those of developmental origin. The molecular characteristics, relatively restricted normal tissue distribution and expression by certain tumour cell types make this antigen worthy of future study for use as a diagnostic marker of malignancy.

Body image in anorexia nervosa.

Abstract: The term ‘body image’ is used to refer to the picture we have in our minds of the size, shape and form of our bodies; and to our feelings concerning the size, shape and form of our bodies, and its constituent parts.

Differential distribution of beta-tubulin isotypes in cerebellum.

Abstract: We describe the structure and expression of a mammalian beta-tubulin isotype (M beta 6) that is weakly expressed in testis but is abundant in developing brain, with transcripts declining to lower levels in the adult brain. The expression of M beta 6 was undetectable in any other mouse tissue examined. A serum specific for this isotype was prepared using a cloned fusion protein as immunogen. M beta 6 is one of five known beta-tubulin isotypes expressed in brain, and using the anti-M beta 6 serum along with sera, anti-M beta 2, anti-M beta 3/4 and anti-M beta 5, previously characterized, we have examined the pattern of expression of beta-tubulin isotypes in rat cerebellum. The isotypes each have characteristic cell-type specific patterns of localization in cerebellum. M beta 2, M beta 3/4 and M beta 5 are present in both neuronal and non-neuronal cells, but in contrast M beta 6 was only detectable in neurons in tissue sections and in dissociated cerebellar cell culture. The majority of sequence differences among the beta-tubulin isotypes lie at the carboxy terminus, the region of beta-tubulin involved in MAP binding. In the case of M beta 2 and M beta 6, the patterns of expression are similar or identical to the patterns of expression of MAP3 and MAP1A respectively. These results suggest that beta-tubulin isotypes may contribute to the determination of the specific association of MAPs with microtubules of diverse function. However, the strict subcellular segregation of other MAPs in brain may be determined by other factors.

Online text retrieval via browsing

Abstract: Browsing refers to information retrieval where the initial search criteria are generally quite vague. The fundamentals of browsing are explored as a basis for the creation of an intelligent computer system to assist with the retrieval of online information. Browsing actions via a computer terminal are examined, together with new methods of accessing text and satisfying user queries. Initial tests with a prototype system illustrated the use of different retrieval strategies when accessing online information of varying structure. The results suggest the construction of a more intelligent processing component to provide expanded capabilities for content extraction and navigation within text documents.

Renal Pathology and Proteinuria Determine Progression in Untreated Mild/Moderate Chronic Renal Failure

Abstract: The progression of renal failure was analyzed in 108 patients with mild to moderate renal impairment, none of whom had received any form of dietary protein, phosphate restriction or immunosuppressive treatment. The reciprocal of plasma creatinine was plotted against time using a minimum of six plasma creatinine values taken over at least six months (mean 13 values over 41 months). Plots indicated there was linear deterioration in 70 patients, non-linear deterioration in 15 and stable renal function in 24. Progressive renal failure was common in patients with glomerulonephritis, diabetic nephropathy, chronic pyelonephritis and polycystic kidney disease. Most patients with hypertensive nephrosclerosis, analgesic nephropathy and renal impairment following acute renal failure were stable. Among those with progressive impairment the mean rates of deterioration were significantly faster for patients with glomerulonephritis and diabetic nephropathy compared to those with chronic pyelonephritis, polycystic kidney disease and undiagnosed renal disease (p less than 0.01). Hence the underlying renal pathological changes appear to be important in determining progression of renal failure and also the subsequent rate of deterioration. For those with linear progression of renal failure there was a significant correlation between 24-h urinary protein excretion and the rate of deterioration. This relationship held for glomerulonephritis and chronic pyelonephritis as separate diagnostic groups only. Proteinuria, therefore, may be a useful prognostic index for the rate of progression of established renal failure. Calcium phosphate product correlated poorly with the rate of deterioration. We were unable to demonstrate a relationship between spontaneous protein intake and deterioration of renal function. However, patients prescribed high protein diets were not included in dietary analysis and we cannot, therefore, exclude the possibility that a high dietary protein intake may accelerate renal failure. Similarly we were unable to show a significant relationship between blood pressure and progression of renal failure although there were weak correlations between mean arterial pressure and rate of deterioration for chronic pyelonephritis and glomerulonephritis.

Hypotheses of peripheral and central mechanisms underlying occupational muscle pain and injury.

Abstract: In an overview of the problem of occupational muscle pain the evidence indicates that injury is more common the greater the load and the worse the posture in which the work is performed. The commonest are backstrains or ligament or joint damage due to overuse. Fatigue is associated with alterations in energy metabolites in muscle while pain is often due to microscopical damage to the cellular architecture. The progress of pathological changes in muscle following occupational injury may be similar to those seen in primary fibromyalgia (fibrositis) because of a final common pathway involving calcium-induced secondary damage. Occupational muscle pain frequently occurs in the muscles supporting the upper limb girdle and head in workers engaged in repetitively performing skilled manipulations or activities requiring high or sustained mental concentration. It is suggested that both occupational myalgia of this kind may be due to an imbalance in the use of muscles for postural activity (holding or supporting fine movements) compared to phasic use in dynamic work. While there are undoubtedly muscular indications of damage these may be secondary to alterations in (unconscious) central motor control mechanisms.

A reappraisal of anterior cruciate ligament disease in the dog

Abstract: A study of 11 1 cases of cranial cruciate ligament disease, seen over a three year period has been made. Fifty-five of these dogs were under four years of age (average age 21.4 months) and most were of the larger breeds, particularly the rottweiler (25 per cent). The onset of clinical signs was sudden in 53 per cent and gradual in 47 per cent of these cases; bilateral disease was present in 31 per cent. The severity of the lameness was variable. The pathogenesis of the disease appears to involve a gradual stretching, partial rupture and eventually a complete rupture of the cranial cruciate ligament. The term cruciate disease has been used to cover this spectrum of ligament pathology and the clinical signs can appear at any stage during this ligament degeneration. Slight anterior drawer .movement can often be detected during the earlier stages of stretching and partial rupture but this can only be appreciated under general anaesthesia. Osteoarthritis is initiated during the early stages and may be well established by the time the cruciate completely tears. The predisposition to cruciate disease in these young dogs of the larger breeds is difficult to explain but may be related to inadequate exercise during puppyhood.

Variability in Salt Tolerance of Nine Spring Wheat Cultivars

Abstract: The biotic approach to overcome salinity problems has recently received a considerable attention from many workers throughout the world. However the identification of existing crop varieties which have enhanced salt tolerance is clearly of considerable value for exploitation of saline soils for agriculture. Salt tolerance of the nine spring wheat cultivars Bounty, Jerico, LU 26S, Minaret, Sonora 64, Timmo, Toban 66, Tonic, and Wembley was assessed at germination, and at maturity using solution and sand culture techniques. No consistent correlation was found between tolerance assessed at these two growth stages in any of the cultivars except Wembley. The salt tolerant cultivar LU 26S had significantly higher germination percentage and germination rate than the other cultivars, but was intermediate in yield. By contrast cv. Tobari 66 had low germination percentage, intermediate germination rate, but had a higher yield than the other cultivars particularly at the highest salt level. The cv. Wembley had low values in all the characters studied and thus appeared to be very salt sensitive compared with the other cultivars. There was not any consistent relationship between yield characters and ionic content in these cultivars. A general selection criterion based upon whole plant performance for assessment of salt tolerance in wheat is proposed. Zusammenfassung Variabilitat der Salztoleranz von neun Som-merweizensorten Die Salztoleranz von neun Sommerweizensor-ten: Bounty, Jerico, LU 26S, Minaret, Sono-ra 64, Timmo, Tobari 66, Tonic and Wembley wurden bezuglich des Keimens und der Aus-reife untersucht. Bei den gepruften Sorten wa-ren mit Ausnahme von Wembley keine Bezie-hungen bezuglich der Salztoleranz fur diese beiden Entwicklungsphasen festzustellen. Die Sorte LU 26S wies hohere Keimprozente und Keimraten auf als andere Sorten, ergab aber nur einen mittleren Ertrag. Die Sorte Tobari 66 hatte niedrige Keimprozente, eine mittle-re Keimrate und hohere Ertrage als andere Sorten; dies gait insbesondere fur eine hohe Salzgehaltstufe. Die Sorte Wembley erschien dagegen sehr sensitiv in bezug auf die Salzver-traglichkeit in alien untersuchten Eigenschaf-ten. Es konnte kein konsistentes Verhaltnis zwischen den Ertragseigenschaften und dem Ionengehalt nachgewiesen werden.