Showing papers by "Monash University published in 1988"

Design and development of an experimental wrought aluminum alloy for use at elevated temperatures

Abstract: A new wrought aluminum alloy has been designed having high room temperature strength (e.g., 0.2 pct P.S. 520 MPa) combined with improved creep resistance at temperatures in the range 150° to 220 °C. The alloy is A1-6.3 pct Cu-0.5 pct Mg-0.5 pct Ag-0.5 pct Mn-0.2 pct Zr and it is hardened by a new precipitate which forms on the {111} planes and appears to be highly stable at elevated temperatures. Details are given of the principles underlying the development of the alloy and of the preliminary assessment that has been made of mechanical properties. The alloy, or compositions close to it, also has potential for welded applications.

Primary genetic control of somatic sexual differentiation in a mammal

Abstract: The classical view of mammalian sexual differentiation is that a gene on the Y chromosome transforms the indifferent gonad into a testis. The Leydig cells then secrete androgen which stimulates the development of the male reproductive tract, and the Sertoli cells secrete Mullerian inhibitory substance which inhibits the development of the female reproductive tract. In the absence of a testis, the Mullerian duct develops into the Fallopian tubes, uterus and vagina. Thus the whole of sexual differentiation is thought to be hormonally mediated as a consequence of this initial genetic determination of gonadal sex. We have found evidence in a marsupial mammal for extensive sexual dimorphisms which precede any morphological differentiation of the gonads. Thus the classical view of mammalian sexual differentiation may have over-emphasized the role of testicular hormones, and overlooked earlier genetic effects.

A survival study of patients with scleroderma diagnosed over 30 years (1953-1983): the value of a simple cutaneous classification in the early stages of the disease.

Abstract: A longitudinal study was carried out on 177 patients with scleroderma between 1953 and 1983. Patients were classified into 3 types according to the extent of skin sclerosis within one year of presentation: Type 1 with sclerodactyly only; Type 2, skin stiffness proximal to the metacarpophalangeal joints but sparing the trunk; and Type 3, diffuse skin stiffness including the trunk. Ten year survival was 71% in Type 1, 58% in Type 2 and 21% in Type 3. Quality of life was best in Type 1, intermediate in Type 2 and worst in Type 3. Nailfold capillary abnormalities did not discriminate between the types, but anticentromere antibody correlated strongly with Type 1. The simple subdivision of scleroderma based on the early extent of clinical skin involvement has been found to be useful in predicting longterm outcome in this highly variable disease.

Breast feeding, birth spacing and their effects on child survival

Abstract: It has long been known that breastfeeding inhibits female fertility and that it is a factor in restricting population growth. But just how important is it?

Sex determination in marsupials: evidence for a marsupial-eutherian dichotomy.

Abstract: In this paper, we review briefly the current state of knowledge about sexual differentiation in eutherian mammals, and then describe the situation in detail in two marsupial species: the North American opossum and the tammar wallaby. The conventional explanation for the genesis of all male somatic sexual dimorphisms in mammals is that they are a consequence of the systemic action of testicular hormones. In the absence of testes, the embryo will develop a female phenotype. We present evidence for the tammar wallaby that calls into question the universal applicability of this hormonal theory of mammalian sexual differentiation. We have shown that extensive somatic sexual dimorphisms precede by many days the first morphological evidence of testicular formation, which does not occur until around the third day of pouch life. Male foetuses, and pouch young on the day of birth, already have a well-developed gubernaculum and processus vaginalis, paired scrotal anlagen, and a complete absence of mammary anlagen, whereas female foetuses and newborn pouch young have a poorly developed gubernaculum and processus vaginalis, no scrotal anlagen, and well-developed mammary anlagen. Because it seems unlikely that the male gonad could begin hormone secretion until after the Sertoli and Leydig cells are developed, our results strongly suggest that some sexually dimorphic somatic characteristics develop autonomously, depending on their genotype rather than the hormonal environment to which they are exposed. We have been able to confirm the hormonal independence of the scrotum, pouch and mammary gland by administering testosterone propionate daily by mouth to female pouch young from the day of birth; although the Wolffian duct was hyperstimulated, there was no sign of scrotal development, or pouch or mammary inhibition. When male pouch young were treated with oestradiol benzoate in a similar fashion, there was hyperstimulation of the Mullerian duct and inhibition of testicular migration and development, but no sign of scrotal inhibition or pouch or mammary development. Our results in the tammar wallaby are consistent with the earlier studies on the opossum, whose significance was not appreciated at the time. Further evidence in support of this hormonal independence comes from earlier studies of spontaneously occurring intersexes in several species of marsupial, including the opossum and the tammar wallaby. An XXY individual had intra-abdominal testes and complete masculinization of the male reproductive tract internally, but externally there was a pouch and mammary glands and no scrotum.(ABSTRACT TRUNCATED AT 400 WORDS)

Connections of the primary auditory cortex in the common marmoset, Callithrix jacchus jacchus.

Abstract: The afferent and efferent connections of the primary auditory cortex (AI) of common marmosets were traced following small injections of wheat germ agglutinin conjugated with horseradish peroxidase (WGA-HRP) made at best frequency (BF)-defined sites in the AI. After the injections the animals remained anesthetized for 15–23 hours; they were then perfused transcardially with fixative and the brains were processed for WGA-HRP reaction product. Examination of the disposition of labelled material revealed the following results. First, patches of terminal labelling, and to a lesser extent retrograde labelling, were found outside the injection site in the ipsilateral cortex rostral and caudal to the AI. Second, the region of the contralateral cortex corresponding to the injection site contained labelled terminals throughout the depth of the cortex; labelled neurons were found in the middle layers. Third, in each experiment a discrete region of the medial geniculate body (MG) contained retrogradely labelled neurons interspersed with anterogradely labelled terminals. These regions had a banded appearance, were found in the dorsal and rostral half of the MG, and shifted in location progressively dorsal and as the injection site BF increased. The presence of projection zones rostral and caudal to the AI of marmosets, and the disposition of the MG sources of projection in relation to BF, are similar to observations made on other New World monkeys. The ipsilateral corticocortical projections confirm electrophysiological evidence suggesting the existence of auditory fields rostral and caudal to the AI. The thalamocortical auditory system of the marmoset appears relatively simple, with a comparatively undifferentiated MG projecting to a cortical auditory system dominated by a large AI.

Distribution of the murine plasma cell antigen PC-1 in non-lymphoid tissues.

Abstract: PC-1 is an alloantigen of murine plasma cells. Its close association with secretory function in lymphoid cells previously raised the question of whether PC-1 was part of the secretory apparatus. In addition to its expression on lymphocytes, PC-1 had been known to be present in liver, brain, and kidney, although the data were derived almost entirely from bulk absorption studies of polyclonal alloantisera, and virtually nothing was known about the nature of the cells expressing PC-1 in these organs. If PC-1 was functionally involved in the secretory process. it might be expected to be present at secretory sites within these and other organs. We now report the results of an immunohistochemical survey of the distribution of PC-1 in a variety of non-lymphoid organs, using a mAb. The PC-1 Ag was found in a small number of highly discrete locations that were mostly, but not exclusively, associated with epithelia. Sites of strong expression included the distal convoluted tubule of the kidney, ducts of the salivary glands, epididymis, proximal part of the vas deferens, and chondrocytes. The PC-1 glycoprotein was also found in the capillaries of the brain, but did not appear to be present in capillaries elsewhere, a pattern that is strikingly similar to that of the receptor for the iron transport protein, transferrin. Negative sites included the thyroid, pancreas, choroid plexus, smooth and striated muscle, stomach, small and large intestine, gall bladder, renal glomeruli, testis, and seminal vesicles. These results are not consistent with a generalized role for PC-1 in secretion, but are compatible with a role in a specialized subset of macromolecular transport events.

Experimental manipulation of sexual differentiation in wallaby pouch young treated with exogenous steroids

Abstract: We have investigated the effects of androgen or oestrogen treatment of female or male tammar wallabies from the day of birth, when the gonads are histologically undifferentiated, to day 25 of pouch life, when the gonads and the Wolffian and Mullerian ducts have differentiated and the testes have migrated through the inguinal canal. Female tammars treated with testosterone propionate (24–50 mg kg-1 day-1) orally for 25 days had enlarged Wolffian and Mullerian ducts. Mammary and pouch development, however, was indistinguishable from that of control females. The treatment had no apparent effect on ovarian development, or on ovarian position in the abdomen. The phallus of males and females was similar in size, and neither experimental treatment had a significant effect on its size at day 25. Male tammars treated with oestradiol benzoate (1.2–2.5 mg kg-1 day-1) orally for 25 days had gross hypertrophy of the urogenital sinus. Testicular morphology was abnormal; many of the germ cells appeared necrotic, the seminiferous tubules were of reduced diameter, and there were few Leydig cells and increased amounts of fibrous tissue between the tubules. The cortex of these gonads contained some areas which had an ovarian appearance, lacking tubules and containing numerous germ cells. The Mullerian ducts of control males had regressed, but this was prevented by oestrogen treatment, suggesting an inhibition of either Mullerian Inhibiting Substance (MIS) production or its action. Normal testicular migration was inhibited in treated males; the testes remained high in the abdomen, similar in position to the ovaries of control females, whilst control males all had testes in the inguinal region. The gubernaculum and processus vaginalis of control males extended into the scrotum, but in treated males they terminated outside it. Oestrogen treatment had no effect on the size of the scrotum and did not induce mammary or pouch development. These experiments show that marsupials, like eutherians, have a dual hormonal control of Wolffian and Mullerian development. By contrast, the initial development of the mammary glands, pouch, gubernaculum and scrotum does not appear to be under hormonal control and is therefore likely to be autonomous and dependent on genotype.

Market Distortions and Benefits from Research

Abstract: The benefits from cost-reducing research and their distribution under a range of price policies are compared with those that would arise in the absence of the policies. While any price policy affects the distribution of research benefits, the net national or world benefits may be reduced, lef unchanged, or increased, depending on the nature of the policy and the significance of the country in the world market for the commodity. Some implications for decisions on price policies and for distortions in incentives for the allocation of resources to research are raised.

False pyroclastic textures in altered silicic lavas, with implications for volcanic-associated mineralization

Abstract: There is strong emphasis in recent literature that Zn-Cu-Pb massive sulfide deposits associated with felsic volcanism (the kuroko-type deposits) are directly related to submarine calderas formed by large submarine pyroclastic eruptions. Altered silicic volcanic rocks with the appearance of welded and nonwelded pyroclastic flow deposits, volcaniclastic debris flows, and massive- to thin-bedded tuffaceous rocks form a major component of a Silurian succession that hosts Zn-Cu-Pb massive sulfide deposits at Benambra, southeastern Australia. However, critical evaluation of rock textures indicates that these silicic volcanic rocks are mainly lavas and associated autoclastic facies with remarkably deceptive false pyroclastic and volcaniclastic textures, including apparent pumice fiamme and glass shards. Intercalated sediments indicate that most of the silicic volcanics were emplaced in subaqueous settings ranging from relatively shallow water to deep marine.The false textures were produced mainly in originally glassy lava by the combined effects of devitrification, perlitic fracture, and pervasive hydrothermal alteration. These processes are related to the emplacement and cooling history of individual lavas and to a regional, essentially synvolcanic, hydrothermal system. Tectonic foliation of the more altered and mechanically weakened rocks has led to partial dismembering of phenocrysts and groundmass fabrics, thereby further enhancing clastic appearance.Subsequent to recognition of widespread false pyroclastic textures at Benambra, similar features have been identified in three other Australian massive sulfide districts. These results suggest that a reinvestigation of host rocks is warranted at other deposits where submarine pyroclastics are documented. Noncaldera settings combining subsidence in an extensional volcano-tectonic basin, passive submarine lava effusion within the basin, and ambient sedimentation derived from basin margins (including resedimented pyroclastic debris) may be more relevant models in a number of massive sulfide districts.

Approaches to the teaching of STS in science education

Abstract: The Science, Technology and Society movement is a movement within higher and school education that seeks to bring the science education of students at these respective levels more closely to their needs as members of increasingly technological societies. As far as school science education is concerned, two parallel developments have been occurring since the mid 1970s. The first is an evolving conception of the ways in which these interactions between Science, Technology and Society may be dealt with in science education. The other is the development of text and other curriculum materials that provide assistance for teachers wishing to teach science with these emphases. This paper outlines these two developments and brings them together by using an epistemological typology from the first to classify the varieties of curriculum materials now available.

Student Performance in First Year Tertiary Accounting Courses and Its Relationship to Secondary Accounting Education

Abstract: Prior research into this issue in the U.S. and U.K. has utilized a variety of research designs and methods of testing and has produced conflicting empirical results. This Australian study develops a model of student performance which incorporates variables for academic ability, previous accounting knowledge, and mathematics background. The model allows for interactions between some of these variables. Results are tested using a multiple regression form of extended ANCOVA. The findings indicate that the hypothesis that performance in first year accounting is independent of secondary accounting education can be rejected at high levels of significance for all four years studied, both for student marks and rankings and also for aggregate marks as well as course components. The results are contrasted with previous research and the potential implications of these findings are discussed.

Advances in the physiology of inhibin and inhibin-related peptides.

Abstract: Originally, the term ‘inhibin’ was given to a proposed non-steroidal factor produced by the gonad (McCullagh, 1932) which specifically reduced pituitary follicle stimulating hormone (FSH) secretion and whose production was in turn stimulated by FSH in a classical endocrine ‘negative feedback’ system (Franchimont et al., 1979). Inhibin secretion was envisaged to reflect the adequacy of gametogenesis and thus a decline in inhibin secretion would allow an appropriate increase in FSH levels. There exists strong indirect evidence for the inhibin hypothesis in man relating to conditions in which FSH levels vary inversely with ovarian folliculogenesis or seminiferous tubule function; in some instances with monotrophic elevations of FSH, in others with elevations of FSH and LH; whilst in all cases the sex steroid levels are normal. Direct evidence supporting the inhibin hypothesis is plentiful in animals whilst in man data relating to the trophic effect of FSH on ovarian inhibin production (Channing, et al., 1984; McLachlan et al., 1986a) and the reciprocal relationship between the two hormones in women is accumulating (McLachlan et al., 1987a, c). The field of inhibin research has recently seen enormous advances. Inhibin was purified from the ovarian follicular fluid (FF) of several species (Robertson et al., 1985; Miyamoto, et al., 1985; Ling et al., 1985; Rivier et al., 1985; Leversha et al., 1987) and found to be a glycoprotein consisting of two disulphide linked subunits termed u and either PA or PB. This material must be distinguished from non-gonadal proteins isolated from seminal plasma (Sheth et al., 1984; Seidah et al., 1984a) which share few physiological and no structural similarities and are not of gonadal origin. The structures of porcine (Mason et al., 1985) bovine (Forage et al., 1986) human (Mason et al., 1986; Stewart et al., 1986) and rat (Shimasaki et al., 1987) inhibin have been deduced by molecular cloning techniques.

The selective removal of pachytene spermatocytes using methoxy acetic acid as an approach to the study in vivo of paracrine interactions in the testis.

Abstract: Testicular weight and morphology, serum gonadotropins, intratesticular levels of testosterone and ABP levels in testicular interstitial fluid were studied in adult rats at intervals of 1 to 70 days after a single oral dose of 650 mg/kg methoxy acetic acid. At 3 days, this treatment resulted in the selective loss or depletion of pachytene and later spermatocytes from seminiferous tubules at all stages other than VIII to XI of the spermatogenic cycle. At later times this lesion was expressed as an absence mainly of round (14 days) or elongated (21 days) spermatids from the majority of seminiferous tubules. Other than these changes, spermatogenesis did not appear to be affected by treatment and was qualitatively normal in all tubules at 70 days after treatment. As deduced from cell counts at 3 days posttreatment, the initial action of methoxy acetic acid was restricted to late zygotene spermatocytes (stage XII) and pachytene spermatocytes at all stages other than early- to mid-stage VII. Levels of FSH in serum and those of ABP in testicular interstitial fluid indicated that Sertoli cell function was altered in rats treated with methoxy acetic acid. Both were increased at 1 to 3 days posttreatment, returned to normal at 7 to 14 days but were increased again at 21 days before finally returning to control levels at 28 days. In contrast, the levels of testosterone in serum, isolated seminiferous tubules and testicular interstitial fluid were unaffected by treatment, as also were the serum levels of LH. The two periods of increase in FSH and ABP levels coincided with the times of greatest decrease (approximately 20%) in testicular weight, and may be related either to the type of germ cell missing from the affected tubules and/or to the stage of the cycle of the affected (or unaffected) tubules. These data suggest that chemicals such as methoxy acetic acid may prove useful in the study of paracrine interactions in vivo.

Drug and fatty acid effects on serum thyroid hormone binding.

Abstract: We directly compared the competitor potency for serum T4 binding of 11 nonsteroidal antiinflammatory drugs; the diuretics furosemide, ethacrynic acid, and bumetanide; diphenylhydantoin; the cholecystographic contrast agents iopanoate and ipodate; and six long-chain nonesterified fatty acids (NEFA) using equilibrium dialysis. To avoid artefacts that occur in competitor studies with diluted serum or isolated binding proteins, we used undiluted normal serum, with drugs added at concentrations that achieved high therapeutic total and free serum levels at equilibrium. Drug addition was based on the measured free fraction of each drug in serum. The free T4 fraction in normal serum (Tris buffer, pH 7.4; 37 C) was between 1.40 X 10(-4) and 1.53 X 10(-4). Drug-induced increases in T4 free fraction were: fenclofenac, 90%; aspirin, 62%; meclofenamic acid, 39%; diflunisal, 37%; mefenamic acid, 31%; and furosemide, 31%. Significant increases of 7-15% occurred with diclofenac, flufenamic acid, phenylbutazone, and diphenylhydantoin. Indomethacin, ketoprofen, tolmetin, ethacrynic acid, bumetanide, iopanoate, and ipodate were inactive at the concentrations studied. Addition of 2.0 mmol/L oleic acid had a negligible effect, but 3.5 mmol/L oleic acid inhibited T3 and T4 binding significantly. Other long chain NEFA (addition of 1.5 mmol/L) gave increases in free T4 fraction as follows: arachidonic acid, 26%; linolenic acid, 23%; and linoleic acid, 11%. Stearic and palmitic acids were inactive. The effect of 5 mmol/L oleic acid in serum could be reproduced by addition of 0.5 mmol/L to serum diluted 1:10, indicating that protein binding of NEFA is the major determinant that limits their competitor potency. These findings provide a basis for anticipating which potential inhibitors may cause important changes in serum thyroid hormone binding. The time course of such effects will be influenced by the pharmacokinetics of the inhibitor itself as well as the equilibrium findings described here.

Multiresistant Staphylococcus aureus: genetics and evolution of epidemic Australian strains

Abstract: Molecular and genetic analysis of multiresistant isolates of Staphylococcus aureus from widely separated hospitals in Australia has demonstrated that these are clearly related, and that the predominant strains possess up to three different plasmids, which fall into the following classes: (i) small 1.6 kb plasmids, such as pSK3, which are phenotypically cryptic, (ii) 4.5 kb chloramphenicol resistance plasmids, such as pSK2, and (iii) the pSK1 family of multiresistance plasmids, which range in size from 20 to 42 kb and variously encode resistance to antiseptics and disinfectants, trimethoprim (Tpr), penicillin (Pcr) and the aminoglycosides gentamicin, tobramycin and kanamycin (Gmr Tmr Kmr). Gmr Tmr Kmr is encoded on the pSK1 family plasmids by transposon Tn4001, which was also detected on the chromosomes of some clinical isolates. Tn4001 is composed of inverted repeats of the insertion sequence IS256; these repeats flank a Gmr Tmr Kmr sequence encoding for a 57,000 dalton bifunctional protein with aminoglycoside acetyltransferase [AAC(6')] and phosphotransferase [APH(2")] activities. A Tn4001-like structure, which is defective in transposition but encodes for a Gmr Tmr Kmr determinant homologous with that on Tn4001, occurs on conjugative plasmids from strains isolated in North America. Physical studies indicate that Pcr, via a beta-lactamase, and Tpr, via a trimethoprim-insensitive dihydrofolate reductase (DHFR), are also encoded on the pSK1 family by transposons; these transposons have been designated Tn4002 and Tn4003, respectively. Tn4003 is flanked by direct repeats of the insertion sequence IS257. The evolution of the pSK1 family of multiresistance plasmids is traced through the transposition and genetic rearrangement of resistance determinants. Transposition and genetic rearrangement have also contributed to the evolution of a multiresistant chromosome in Staph. aureus. In the majority of contemporary multiply resistant Staph. aureus strains the determinants for resistance to erythromycin (Emr), fusidic acid, methicillin (Mcr), minocycline, rifampicin, spectinomycin, streptomycin, sulphonamides, tetracycline (Tcr), cadmium (Cdr), and mercury (Hgr) are chromosomally encoded; these strains also possess chromosomally encoded Pcr, via a beta-lactamase. Evidence indicates that some of these determinants, Pcr, Cdr, Hgr, and Tcr, were plasmid encoded in isolates collected from Australian hospitals prior to 1970. Through transposition and site-specific integration, they have since been acquired by the chromosome in more recent Staph. aureus strains.(ABSTRACT TRUNCATED AT 400 WORDS)

Glomerular Procoagulant Activity in Human Proliferative Glomerulonephritis

Abstract: Mechanisms for initiation of glomerular fibrin deposition were studied using renal tissue obtained from two patients with rapidly progressive, crescentic glomerulonephritis. Histological examination showed extensive glomerular monocyte infiltration and fibrin deposition in both patients. Sonicated cell suspensions of isolated glomeruli from these patients contained markedly augmented levels of procoagulant activity (PCA) compared with the levels found in normal glomeruli. This PCA was characterized as tissue factor by its functional dependence on Factors VII and V, independence of Factors VIII and XII, inhibition by concanavalin A and phospholipase C, and association with cell membranes. Its coagulant activity was also inhibited by a specific monoclonal anti-human tissue factor antibody. Tissue factor could be identified in glomeruli from these two patients by indirect immunofluorescence using this antibody. These studies implicate extrinsic pathway activation via tissue factor in intraglomerular deposition of fibrin in these patients. Activated monocytes, known to be a potent source of procoagulant activity and seen in large numbers within glomeruli from these patients, are a likely source of this tissue factor.

Offset approximation of uniform B-splines

Abstract: A simple and efficient method is developed for generating offset curves interactively using a set of control knots for a uniform cubic B-spline.

Mathematical Programming Models for Cutting-Stock Problems in the Clothing Industry

Abstract: The cutting-stock problem in the clothing industry does not conform to the classical representation of such problems. Waste minimization is only a subsidiary objective. The overall objective is to maximize long-run profitability, but operational planning requires limiting consideration to a series of problems covering short planning periods. This requires a more complex objective to incorporate interaction between periods. Production constraints with unique characteristics occur in the laying, cutting and sewing operations. The conventional pattern-design problem is dealt with by use of a commercial computer-aided graphical design system. The question addressed in this paper is how to combine such patterns so as to satisfy the various objectives and constraints. This leads to both integer and quadratic formulations of appropriate mathematical programming models.

Asymmetric Hydrocyanation of a Range of Aromatic and Aliphatic Aldehydes

Abstract: A range of aryl, alkyl and heterocyclic aldehydes have been treated with hydrogen cyanide in the presence of the 'Inoue' catalyst, (R,R)- or (S,S)-cyclo [phenylalanylhistidyl]. Most aryl aldehydes with electron-donating substituents in the m- or p-positions give high enantiomeric excess (e.e.) values (≥80%) but aryl aldehydes with strong electron-withdrawing substituents gave moderate e.e. values (≤50%). These moderate values are believed to be due to partial racemization of the product cyanohydrins in the presence of the mildly basic catalyst. In contrast to the reactions of aryl aldehydes , reactions of alkyl aldehydes and of ketones gave low e.e. values (≤30%) and an explanation is proposed.

Dynamics of heterotrophic succession in carrion arthropod assemblages : A comment on Schoenly and Reid (1987).

Abstract: Schoenly and Reid (1987) analyzed eleven sets of data on the temporal changes in arthropod community composition on carcasses to ascertain whether invertebrate succession on carrion proceeded \" . . . as a sequence of discrete faunal seres, or as a continuum of gradual changes . . . \" (Schoenly and Reid 1987:193). Parenthetically, we consider that the term 'sere ' should not be confused with 'seral stage' or ' s tep ' ; Odum (1971:251) defines 'sere' as \" the whole sequence of communities that replaces one another in a given area\" and 'seral stages' as \" the relatively transitory communities\" that comprise a sere. One of Schoenly and Reid's lines of approach relied upon results derived from a multivariate statistical technique commonly called polar ordination (PO). This technique entails computation of a samples-by-samples dissimilarity matrix (usually percentage dissimilarity, Bray and Curtis 1957) followed by the selection of the two most dissimilar samples to serve as poles or end-points of an ordination axis that, hopefully, defines a major direction of community variation (Gauch 1982). However, such endpoint selection can pose problems because the greatest dissimilarity may occur between more than one pair of samples and because the procedure may choose outliers which will fail to spread the samples in ordination space (Bray and Curtis 1957, Gauch 1982). Alternatively, end-points may be deliberately selected based upon expectations of a gradient (e.g. xeric to mesic), rendering interpretation relatively straightforward (Bray and Curtis 1957). Schoenly and Reid (1987) chose the day of first species arrival and the last day taxa were recorded as end-points of the first axis in an effort to obtain a temporal gradient along the X-axis. Appropriate end-point selection is crucial to the success of PO (Bray and Curtis 1957; Beals 1984). Schoenly and Reid (1987) observed that \" the first and last days of carrion faunal succession reflected erratic changes in similarity . . . \" and yet they used these points as the end-points of their

Lung liquid secretion, flow and volume in response to moderate asphyxia in fetal sheep.

Abstract: The effects of moderate fetal asphyxia, induced by constriction of the maternal common internal iliac artery, on lung liquid secretion, tracheal fluid efflux and lung liquid volume have been investigated in unanaesthetized fetal sheep (111-142 days) in utero. During periods of fetal asphyxia the percent oxygen saturation, PO2, pH, and PCO2 of fetal carotid arterial blood changed from 57.2 +/- 1.3% (mean +/- SEM), 22.9 +/- 0.6 mmHg, 7.35 +/- 0.01 and 45.6 +/- 1.0 mmHg to 26.3 +/- 0.5% (P less than 0.001), 14.7 +/- 0.2 mmHg (P less than 0.001), 7.28 +/- 0.02, (P less than 0.001) and 47.8 +/- 0.4 mmHg (P less than 0.02), respectively. Fetal asphyxia, over 6 h, decreased the efflux of tracheal fluid from 7.07 +/- 0.47 ml/h to 3.97 +/- 0.36 ml/h (P less than 0.01) and, over 4 h, decreased the rate of lung liquid secretion from 9.42 +/- 1.76 ml/h to 4.91 +/- 1.54 ml/h (P less than 0.005), whereas it had no significant effect on lung liquid volume. The incidence of fetal breathing movements decreased from 52.9 +/- 2.5% to 22.6 +/- 3.5% during 6-h periods of fetal asphyxia. Thus, although fetal asphyxia decreased the net production of lung liquid, lung liquid volume was maintained probably, because the net efflux of fluid from the lungs via the trachea decreased to a similar extent.

HAEMODYNAMIC AND HEART RATE REFLEX RESPONSES TO PROPOFOL IN THE RABBIT Comparison with Althesin

Abstract: Propofol was administered to eight rabbits by constant i.v. infusion at 0.2, 0.4 and 0.6 mg kg−1 min−1 to produce light sedation. The lowest does was compared with an infusion of Althesin 0.1 mg kg−1 min−1. The rabbits had been previously implanted with aortic and vena caval perivascular balloon cuffs to examine the baroreceptor-heart rate reflex and an aortic thermistor catheter for cardiac output (CO) measurements. A silastic catheter was placed in the pericardial sac so that the cardiac nerves could be blocked with local anaesthetic. Mean arterial pressure (MAP) was well maintained with all anaesthetic infusions. At the lower doses of propofol, CO increased by 20% (P

Chondrocyte antioxidant defences: The roles of catalase and glutathione peroxidase in protection against H2O2 dependent inhibition of proteoglycan biosynthesis

Abstract: The production of hydrogen peroxide by polymorphonuclear cells is suspected as being a cause of cellular damage during acute inflammation. In our study, the kinetics by which hydrogen peroxide suppressed proteoglycan synthesis in cartilage explant culture suggested that the damage occurred at the level of core protein synthesis. Chondrocytes were also shown to contain both catalase and the glutathione peroxidase/reductase systems, which were both involved in the removal of 10(-4) M H2O2. Interruption of either of these peroxide metabolizing systems markedly sensitized cartilage to a greater inhibition of synthesis by H2O2. Inhibition of catalase (with 3-amino 1,2,4 triazole or azide) was found to depress synthesis further, possibly because of exposure to higher steady state levels of H2O2. Inhibition of glutathione reductase (with 1,3-bis-(choloroethyl)-1-nitrosurea) did not expose tissue to higher steady state levels of H2O2, but this treatment decreased the intrachondrocyte level of reduced glutathione which may explain the increased damage obtained in the presence of H2O2. These results support the concept that effective H2O2 metabolizing systems are important in the maintenance of normal biosynthetic rates in cartilage during inflammation.

3-D Shape Measurement By Active Triangulation Using An Array Of Coded Light Stripes

Abstract: A 3-D shape measurement system using multiple light stripe active triangulation is described. The system employs a liquid crystal light valve mounted in a conventional projector to code, or label, an array of 64 stripes of light projected onto the scene to be measured. The scene is viewed by a camera displaced from the projector. Firstly the stripes are located to an accuracy of approximately 0.1 pixel in an image digitized with all the stripes turned on. The stripes are then coded by the projection of a sequence of six patterns of stripes using the light valve. In each pattern the intensity of each stripe, on or off, indicates one bit in a six bit code assigned to the stripe. Each located stripe can therefore be identified by determining the six bit number defined by its intensity in the images of the coding patterns. Once the stripes have been identified triangulation can be performed.

Using Generalizability Theory in Counseling and Development.

Abstract: (1988). Using Generalizability Theory in Counseling and Development. Measurement and Evaluation in Counseling and Development: Vol. 21, No. 2, pp. 81-90.