Showing papers by "Monash University published in 1982"

Light experience and asymmetry of brain function in chickens.

Abstract: Asymmetry of brain function has been demonstrated for several non-human species1, most clearly in the avian brain2,3. In the chicken, a single treatment of the left forebrain hemisphere during the first week of life after hatching with either cycloheximide or the putative neurotransmitter, glutamate, subsequently causes retarded visual and auditory learning, and elevated attack and copulation responses3–5. Similar treatment of the right hemisphere is without effect. The cellular mechanisms by which these pharmacological agents may alter brain development and so reveal lateralization have already been discussed in detail6,7. It is commonly assumed that lateralization of brain function in humans and other species is inherited either genetically1,8 or cytoplasmically9. However, Rogers and Anson have suggested previously3 that light experience may have an important role in establishing lateralization in the chicken forebrain, because after day 17 of incubation the embryo is oriented in the egg such that the left eye is occluded by the chicken's wing and body while the right eye is next to the air sac and exposed to light input (refs 10,11 and J. V. Zappia and L.J.R., in preparation). Because the optic nerves decussate completely and most of the information reaching each tectum is processed by its ipsilateral forebrain hemisphere, it is possible that light entering the right eye stimulates developmental processes in the left hemisphere in advance of the right3. If so, chickens hatched from eggs incubated in darkness should fail to show functional asymmetry of the forebrain. I now report that this is indeed the case for asymmetrical control of attack and copulation.

Cognitive research and the design of science instruction

Abstract: The utilization of cognitive psychological theory and findings from research to inform the design of instruction is illustrated in this paper Physics learning studies demonstrate that students' pre‐instructional world knowledge is often logically antagonistic to the principles of Newtonian mechanics taught in introductory physics Under these conditions psychological theory predicts that learning will be inhibited, a prediction consistent with both the experiences of physics teachers and the results of empirical investigation Informed by cognitive research on problem solving, semantic memory, and knowledge acquisition, instruction has been designed to encourage the reconciliation of world knowledge and physics content among beginning physics students

Accumulation of heavy metals in unicellular algae

Abstract: A model for metal uptake by microorganisms based on surface adsorption has been developed, and then applied to the uptake of cadmium by Chlorella vulgaris. A linear equilibrium relationship between metal in the solution and that adsorbed on the cell surface is assumed and confirmed at low cadmium concentrations by short-term uptake experiments. When it incorporates a description of cell growth, the model predicts an initial rapid uptake and a subsequent slow uptake. Such behavior has often been observed in experiments with growing microorganisms. This indicates that the slow uptake, sometimes thought to be active or metabolic, could be due to the simultaneous effects of growth and surface adsorption. The model shows that initial metal uptake is fast and approaches equilibrium within a few seconds. This prediction is in agreement with experimental results in a batch system: Equilibrium is reached before the first samples are taken (at 10 min) and there is then no measurable change until growth provides a significant increase in cell surface (after several hours). Thus the equilibrium constant can be calculated from experimental results of uptake at 10 min. The equilibrium is found to be affected by phosphate concentration; the amount of cadmium adsorbed on the cell decreases as the concentration of phosphate is increased. Long-term uptake experiments in growing cultures show a greater metal accumulation than predicted by the adsorption model, suggesting the involvement in the slow long-term uptake of some mechanism other than adsorption. This is confirmed by experiments in which uptake in cultures exposed to cadmium throughout the growth period is compared with short-term uptake in similar cultures grown in the absence of cadmium. The modeling approach to metal adsorption provides a basis for further development. A model combining description of adsorption and of intracellular accumulation is necessary to provide a more complete description. Such a model, with precise definitions of system parameters and means of evaluating these parameters from experimental results, will be a powerful tool in investigation of metal uptake by microorganisms.

Successful fertilisation of human oocytes in vitro: concentration of estradiol-17s, progesterone and androstenedione in the antral fluid of donor follicles.11

Abstract: Oocytes and matched samples of follicular fluid were obtained from 156 pre-ovulatory follicles in 125 women 26--36 h after either administration of hCG or the onset of an endogenous LR surge. Concentrations of estradiol-17 beta (E2), progesterone (P) and androstenedione (A4) in the fluid of individual donor follicles were measured and related to the success of fertilisation of oocytes in vitro and the incidence of pregnancies after embryo transfer. Oocytes which gave rise to successful pregnancies were obtained from follicles which contained greater concentrations of E2 and a higher ratio of E2:P than did oocytes from which pregnancy did not result. These data provide direct evidence in support of the hypothesis that estrogenic follicles are the sole source of ova which undergo fertilisation and subsequently give rise to pregnancy in women.

Careless Errors Made by Sixth-Grade Children on Written Mathematical Tasks.

Abstract: Mathematics teachers are aware of careless errors. They know that they themselves have often obtained incorrect answers to problems they knew how to do. Further, most of them have at some time advised students to take more care when attempting mathematical problems. But what are careless errors? And which personality and cognitive characteristics, if any, tend to be associated with students who make careless errors on mathematical tasks? This article addresses these two questions. Recent research by Newman (1977), Casey (1979), Clements (1980), Watson (1980), and Clarkson (Note 1) suggests that when schoolchildren attempt standard mathematical pencil-and-paper tasks the number of careless errors they make is about the same as the number of errors due to systematic weaknesses in process skills. However, while there is a large and growing literature on process skills errors, and especially on errors due to the application of inappropriate or faulty arithmetical processes (Brown & Burton, 1978; Clement, 1977; Cox, 1975; Davis, McKnight, Parker, & Elrick, 1979; McAloon, 1979), the literature on careless errors is relatively sparse. This, together with the increasing tendency for writers to maintain that most, or perhaps even all, mathematical errors are systematic (see, for example, Brown & Burton, 1978, p. 157; Cole, Gay, Glick, & Sharp, 1971, pp. xii-xiii; Davis & McKnight, 1979, p. 103; Ginsburg, 1977, pp. 50-68; Radatz, 1979, p. 170), suggests that there is a need for research into careless errors in mathematics. In the present study an operational definition of careless errors is provided and used in an investigation into the mathematical errors made by 50 sixth-grade children.

Ultrastructure of cortical granule release and zona interaction in monospermic and polyspermic human ova fertilized in vitro

Abstract: Cortical granule release and interaction with the zona pellucida are reported in monospermic and polyspermic fertilized ova and early human embryos cultured in vitro. Twenty-seven preovulatory oocytes from women with tubal or idiopathic infertility were recovered by laparoscopy, after induction of follicular maturation with clomid and human chorionic gonadotropin. These were then inseminated with husband's or donor sperm, cultured for 3–72 hr, routinely fixed in glutaraldehyde/osmium and examined ultrastructurally. Evidence of cortical granule release was observed in all ova and embryos investigated and their contents were identified either at the egg surface or in the perivitelline space or interacting with the inner zona, apparently reinforcing its structure. The latter is very likely the morphological expression of the zona reaction. Delayed release was seen in certain regions of normally fertilized ova and particularly in polyspermic ova, where massive “explosions” of granules occurred. This was attributed to delayed cortical maturation. The mechanics of release were similar in both monospermic and polyspermic ova. Spontaneous dehiscence was also described in one injured unfertilized oocyte. The significance of the cortical and zona reactions as an effective block to polyspermy at the level of the inner zona, which becomes more impenetrable to supplementary sperm, is discussed.

Steroid-Induced Vasoconstriction: Glucocorticoid Antagonist Studies

Abstract: Two currently used steroids (clobetasone butyrate and betamethasone valerate) reproducibly cause vasoconstriction on topical application to human forearm skin. Progesterone, deoxycorticosterone, testosterone, and estradiol, even at 100- to 200-fold higher concentrations, cause no vasoconstriction when applied alone. Applied with clobestasone butyrate, testosterone and estradiol are without antagonist effect; in contrast, both progesterone and deoxycorticosterone antagonize the vasoconstrictor response in a dose-related fashion, with a half-maximal effect at 20-30 times the concentration of clobetasone. Neither progesterone nor deoxycorticosterone affects the vasoconstriction produced by the intradermal injection of epinephrine. In most glucocorticoid-responsive systems, progesterone and deoxycorticosterone are glucocorticoid antagonists, and estradiol and testosterone are inactive. We interpret these studies as evidence that the vasoconstrictor effects of topical steroids are mediated by occupancy of classical glucocorticoid receptors, rather than by nonspecific pharmacological mechanisms.

Ultrastructural observations on cortical granules in human follicular oocytes cultured in vitro

Abstract: The fine structure, distribution, and fate of cortical granules in human oocytes cultured in vitro are reported. Follicular maturation in women with blocked Fallopian tubes was induced by clomiphene citrate and human chorionic gonadotropin, and preovulatory eggs were obtained by improved methods of laproscopy and oocyte recovery. These oocytes were then inseminated and cultured in a modified Ham's F10 medium for 3 to 72 hr to assess their fertilizability. Cortical granules were observed in all 17 unfertilized oocytes investigated, which had completed various stages of meiotic maturation. A marked increase in their numbers was observed in oocytes cultured for 3 to 6 hr. There was no evidence of spontaneous cortical granule release in any of the oocytes studied. It is concluded that cortical maturation expressed by proliferation of cortical granules is as significant a criterion as nuclear maturation in assessing maturity and fertilizability of oocytes cultured in vitro. A short sojourn in culture before insemination could improve chances of normal fertilization and embryo development, which has been recently achieved in our laboratory.

Inhibition of Adenylate Cyclase by Angiotensin II in Rat Renal Cortex

Abstract: Adenylate cyclase of rat renal cortex was inhibited by angiotensin II (All). Inhibition required Na+ (100–200 mM) and GTP (10-5-10-4 M) and was opposed by the receptor antagonist (1-sarcosine, 8-isoleucine]AII. The EC50 value (±SE) for inhibition by All was 3.7 ± 1.2 nM, and the maximum inhibition (±SE) was 23 ±3%. Inhibition was specific for All, since both AI and AIII, at concentrations up to 1 μM, were ineffective in producing inhibition. The maximum decrease (±SE) in adenylate cyclase activity was from 2.45 ± 0.08 to 1.78 ± 0.1 pmol·min/mg protein. A similar absolute decrease was observed when adenylate cyclase was stimulated by calcitonin, vasopressin, or isoproterenol. The inhibition of PTH-stimulated activity [16.7 ± 0.5 (±SE) to 12.2 ± 0.7 pmol·min/mg protein) was significantly greater than the inhibition of basal activity. Therefore, at least some of the inhibitory angiotensin receptors are coupled to adenylate cyclase molecules which also coupled to receptors for PTH

Purification and Chemical Characterisation of Membrane Glycoproteins from Rat Thymocytes and Brain, Recognised by Monoclonal Antibody MRC OX 2

Abstract: The MRC OX 2 monoclonal antibody recognises antigens present on rat thymocytes, brain, follicular dendritic cells in lymphoid organs, vascular endothelium, some smooth muscle and B-lymphocytes. The OX 2 antigens recognised by this antibody were purified from brain and thymus, by solubilisation with sodium deoxycholate, affinity chromatography with MRC OX 2 antibody and gel filtration. The purified brain and thymocyte OX 2 antigens were glycoproteins with apparent Mr 41000 and 47000 respectively as determined by polyacrylamide gel electrophoresis in sodium dodecyl sulphate. Rabbit antisera raised against the purified antigens were analysed by radioimmunoassay and immunoperoxidase-staining of tissue sections. The brain and thymocyte OX 2 antigens were antigenically very similar to those on the other tissues. This indicates that the unusual pattern of distribution was not the result of fortuitous cross-reaction of the MRC OX 2 antibody, as the rabbit sera would be expected to recognise more determinants on the antigen than that recognised by the monoclonal antibody. The amino acid compositions of brain and thymus OX 2 antigens were very similar but with no distinguishing features. Carbohydrate compositions showed that the OX 2 antigens were highly glycosylated, with brain OX 2 antigen containing 24% and thymocyte OX 2 antigen 33% by weight of carbohydrate. Both OX 2 antigens contained carbohydrate residues typical of structures N-linked to asparagine but lacked galactosamine, indicating the absence of O-linked structures. Thymocyte OX 2 contained higher levels of galactose and sialic acid but less fucose than brain OX 2. Similar differences had been observed for brain and thymocyte Thy-1 antigens and were also observed in pooled glycoproteins purified by lentil affinity chromatography from these tissues, reflecting overall differences in the patterns of glycosylation in the two tissues. The OX 2 antigens showed many similarities to Thy-1 antigens in their odd patterns of distribution, characteristic migration on polyacrylamide gels in sodium dodecyl sulphate, and carbohydrate compositions. It is possible that OX 2 antigens, like Thy-1 antigens, have homologies with immunoglobulin domains. A possible role for OX 2 antigens in cell interactions necessary for tissue organisation is discussed.

Effect of angiotensin-converting enzyme inhibition on circulating and local kinin levels

Abstract: Angiotensin-converting enzyme kininase II reduces bradykinin metabolism in vitro and in vivo. However, consistent changes in circulating bradykinin levels after the angiotensin-converting enzyme inhibitor captopril have not been reported. The kallikrein-kinin system has been suggested to be a local hormonal system concerned with regional blood flow, and hence circulating levels may not reflect local tissue levels of kinins. Anesthetized dogs given captopril had a significant increase in urinary kinin excretion without a change in circulating bradykinin levels or in urinary kallikrein. These changes in renal kinins were accompanied by a decrease in blood pressure and renal vasodilation. The hypotension and renal vasodilation produced by captopril were not attenuated either by pretreatment with the angiotension receptor antagonist Sar 1 -lleu 8 -angiotensin II or by reduction of endogenous prostaglandin production with indomethacin. Postischemic renal vasodilation after temporary renal artery occlusion was also associated with increased urinary kinin levels. These results demonstrate that captopril effectively inhibits renal angiotensinconverting enzyme and that the renal kallikrein-kinin system may play an important role in regulating the renal vasculature and may contribute to the renal hemodynamic effects of captopril. Many polypeptide hormone membrane receptors are self-regulated by endogenous tissue concentrations of the peptide hormone. Infusions of bradykinin into rats reduced specific bradykinin receptors. A similar decrease in bradykinin receptor numbers without change in receptor affinity was demonstrated after captopril administration. These results provide indirect evidence that angiotensin-converting enzyme/kininase inhibition by captopril increases local tissue concentration of kinins, which may contribute to the hypotensive effect.

Closure of "Wind-Induced Lock-In Excitation of Tall Structures"

Abstract: Circular and square tower models were tested in a boundary layer wind tunnel. At close to the critical reduced velocity and particularly at low values of structural damping, displacement dependent lock-in excitation was found to cause large increases in cross-wind displacement response, especially for the circular tower, in a suburban type wind model. Critical cross-wind response amplitudes were determined from the response characteristics. These response amplitudes represent the level of cross-wind response of a structure above which the response can not be accounted for by the random wake excitation process and that lock-in excitation is significant. A prediction procedure, which consists of a random excitation model and a sinusoidal lock-in excitation model, is described. Cross-wind response predicted by these models agreed well with the measured response.

"The monster nuisance of all": landowners, alkali manufacturers, and air pollution, 1828-64.

Abstract: A ir pollution has a long history Londoners have complained of the Smoke from sea coal from the thirteenth century onwards1 but the development of a steam-powered, coal-burning technology in the eighteenth and nineteenth centuries created pollution problems of a new order of magnitude. Coal output rose from roughly ii million tons in i8oo to almost 50 million tons in i850 and its combustion in furnaces, steam engines, and domestic hearths created smoke palls which came to be regarded as the inevitable accompaniment to industrial activity. Wordsworth described the industrial town: "O'er which the smoke of unremitting fires/Hangs permanent ")2 The new chemical industries worsened the situation by adding new, noisome, and often toxic elements to the atmosphere; because of their impact, the eminent scientist Lyon Playfair argued that airborne emissions from alkali manufacture were "the monster nuisance of all".3 Industrial-pollution is perhaps the least studied consequence of the Industrial Revolution. Almost fifty years ago Lewis Mumford pointed out that the first mark of "paleotechnic industry" was pollution of the air and the second, pollution of waterways,4 but apart from noting the aesthetic and health implications of dirt and smoke, historians have not followed up his pioneering work. This neglect is unwarranted because many Victorians were affected by pollution, some seriously so. A few were in a position to protect themselves and in doing so they imposed significant restraints upon the freedom of manufacturers and also expanded the sphere of government involvement in the economy. This article looks at one such episode where the interests of alkali manufacturers came into conflict with those of neighbouring landowners. It traces attempts by landowners and others to win some redress for their grievances which began at the end of the i820s and culminated in i863 with the passage of the Alkali Act. This remarkable measure placed the property of manufacturers under the supervision of the state in order to protect the property of landowners, and most conspicuously the property of large, wealthy land-

Attitudes to the fetus among primigravidae.

Abstract: . Thirty primigravidae took part in a prospective study of attitudes to the fetus, carried out by means of a series of semi-structured, tape-recorded interviews. The degree of development of the fetus was grossly underestimated in the first trimester. By mid-pregnancy their ideas about the fetus had become more accurate and all gave realistic descriptions by 36 weeks gestation. Although most women had difficulty in believing that the fetus really existed in early pregnancy, a minority already had an established relationship with the fetus by 8–12 weeks of gestation. Maternal fetal “attachment'’was present in 63% of women by 18–22% weeks and 92% by 36 weeks gestation.

Ruthenium carbonyl complexes. I. Synthesis of [Ru(CO)2(bidentate)2]2+ complexes

Abstract: The complexes RU(CO)2Cl2L [L = 1,l0-phenanthroline (phen) or 2,2'-bipyridyl (bpy)] react with silver carboxylates to yield Ru(CO)2(OCOR)2L derivatives (R = Me or CF3). Reactions of Ru(CO)2(OAc)2L and Ru(CO)2(OAc)2(phen) with trifluoroacetic and trifluoromethanesulfonic acid give Ru(CO)2(OCOCF3)2L and Ru(CO)2(OSO2CF3)2(phen) respectively. In acetonitrile, Ru(CO)2(OAC)2L complexes react with trifluoromethanesulfonic acid to give [Ru(CO)2(MeCN)2L] (O3SCF3)2. The complexes [RU(CO)2L2]2+, [Ru(CO)2(phen)(bpy)]2+, and [Ru(C02(phen)(tmp)]2+ (tmp = 3,4,7,8-tetramethyl-1,l0-phenanthroline) have been prepared by reaction of [Ru(CO)2- (MeCN)2L]2+ and/or Ru(CO)2(OSO2CF3)2 phen with an excess of the appropriate bidentate ligand. A similar series of reactions has yielded Ru(C0)2(OAc)2(py)2, [Ru(CO)2(MeCN)2(py)2] (O3SCF3)2, and [RU(CO)2(py)2L]2+ from Ru(CO)2Cl2(py)2. Stereochemical assignments have been made for all complexes.

Familial Euthyroid Thyroxine Excess: Characterization of Abnormal Intermediate Affinity Thyroxine Binding to Albumin*

Abstract: The abnormal high capacity T4 binding site of familial euthyroid T4 excess was separable from prealbumin and T4-binding globulin but not from albumin. We therefore compared T4 binding by albumin preparations isolated from the sera of normal and affected subjects. By equilibrium dialysis, albumin from affected subjects showed an extra T4 binding site (Kd ∼ 50 nM) in addition to the T4 binding sites of normal albumin (Kd ∼ 4 μM). Comparison of the estimated capacity of the additional site (200 μM) with the molar concentration of albumin suggested that only about one third of albumin molecules from affected subjects contained the extra binding site. Estimates of affinity and capacity were used to derive combining powers for the diverse classes of serum T4 binding sites. From these estimates, it appears that the presence of the abnormal site accounts for the approximate doubling of normal mean total T4 (from ∼ 100 nM or 7.7 μg/dl to ∼ 200 nM or 15.5 μg/dl), in order to maintain a normal free T4 in the face of...

Cellular immune mechanisms in human glomerulonephritis: The role of mononuclear leucocytes

Abstract: Our understanding of the pathologic processes leading to injury in human glomerulonephritis remains limited. Several mediation pathways have been suggested from observations of human biopsies and studies of experimental glomerulonephritis in animals, although the pathogenic mechanism of injury in many situations is obscure. However cells of the monocyte/macrophages series can be identified within glomeruli in glomerulonephritis, especially in more aggressive forms of the proliferative disease in humans. Experimental studies have confirmed the capacity of these cells to induce injury; thus, the role of monocytes as a mediator of glomerular injury is now established. Indirect evidence suggests that T cell-dependent mechanisms may also be involved in glomerulonephritis, but more data are needed to define the extent to which sensitised mononuclear leucocytes participate in the pathogenesis of human glomerulonephritis.

Australian corporate dividend policy: empirical evidence

Abstract: This paper provides Australian evidence on the validity of the lintner (1956) dividend model. This model suggests corporate dividends are a function of current and past earnings. Regression tests are carried out. In these tests the basic Lintner model performs better than some other dividend models examined. In addition, the ability of the model to predict dividend changes is examined and compared to forecasts of various naive models. The forecasting test results generally indicate that a simple no-change model predicts as well as more complex regression models.

Ultrastructural Observations on the Penetration of Human Sperm into the Zona Pellucida of the Human Egg In Vitro

Abstract: Sperm penetration into the zona of 46 human eggs was examined by electron microscopy. Preovulatory oocytes were aspirated at laparoscopy and inseminated by methods which produced normal pregnancies. These were routinely fixed 3–72 hours after insemination and examined for zona penetration. The mechanism of zona penetration was similar in the non-activated oocytes, fertilized ova, and embryos obtained, and resembled that which was reported in most mammals. Sperm were tightly bound to the zona by their plasma membranes. Both acrosome-reacted and unreacted sperm were seen in the cumulus and entering the zona. The acrosome reaction involved multiple fusions and vesiculation of the plasma and outer acrosome membranes. Fine and coarse vesiculation was observed, and the sperm digested a clear pathway through the zona. Sperm were rarely seen in the inner zona and never seen in the perivitelline space of monospermic ova, but freely penetrated these regions in polyspermie ova. A block to polyspermy seemed to operate at the level of the inner zona. Morphologic evidence for the involvement of the inner acrosome membrane in the acrosome reaction and a possible sequence of events in zona penetration is presented. The findings confirm most of late Professor Pierre Soupart's work on zona penetration.

Late Cenozoic pollen spectra from the Atherton Tableland, north-eastern Australia

Abstract: Pollen analysis of samples from a short sediment sequence on the Atherton Tableland, of Late Tertiary or Early Pleistocene age, provides the first evidence of existing vegetation within the region prior to about 100,000 years B.P. Comparison of fossil samples with modern pollen spectra suggests the presence of a submontane rainforest existing under a temperature regime some 3°C cooler than present. A number of ancient taxa including Nothofagus and several conifers, present in the fossil samples, no longer exists within the region. An attempt is made to explain their decline within an area that harbours a great diversity of rainforest species including many primitive angiosperms. Unfavourable climatic conditions combined with aspects of the dispersal ecology of the taxa would have been important contributing factors.

Estimation of automobile speed under day and night conditions.

Abstract: Passenger subjects estimated automobile speed while traveling along an unlit freeway under day and night conditions. A visual occluding device allowed a 1-s glimpse of the road ahead when a judgment was required. Although subjects underestimated speeds, their judgments were more accurate at night than during the day.