Seasonal variation in standing crop,density and leaf growth rate of the seagrass, Heterozostera tasmanica, in western Port and Port Phillip Bay,Victoria, Australia

Standing crop, density and leaf growth rate of Heterozostera tasmanica (Martens ex Aschers.) den Hartog along with light, temperature, nutrient and sediment characteristics were determined monthly for fifteen months at three study sites in Western Port and one site in Port Phillip Bay, Victoria, Australia. Erect vegetative stems of H. tasmanica were frequently branched, were present throughout the year and accounted for 25–60% of the above-sediment biomass, with the stem proportion higher during winter than summer. At three of the four sites there was a unimodal seasonal pattern in which minimum leaf standing crop (27–61 g dry wt. m^?2), density (600–2000 leaf cluster m^?2) and leaf productivity (0.34–0.77 g dry wt. m^?2 day^?1) generally occurred during winter (June–August) and maximum leaf standing crop (105–173 g dry wt. m^?2), density (2700–5000 leaf cluster m^?2) and leaf productivity (2.6–4.2 g dry wt. m^?2 day^?1) occurred during summer (December–February). A bimodal seasonal pattern with minimum standing crop and density during midsummer occurred at one site. This anomalous seasonal pattern may be due to exposure and desiccation stress during spring low tides. At the site receiving the lowest irradiance, standing crop, density and annual leaf production also were lowest, but length and width of leaves, shoot height and leaf growth rate per leaf cluster were the highest of the four study sites. On average, each leaf cluster at any one of the study sites produced 30–31 leaves per year with mean leaf turnover rates of 1.3–1.7% day^?1. Annual leaf production of H. tasmanica ranged from 410 to 640 g dry wt.m^?2 at the four sites.     

Effects of in situ light reduction on density and growth of the seagrass Heterozostera tasmanica (Martens ex Aschers.) den Hartog in Western Port,Victoria, Australia

Neutral density screens were used to reduce the level of irradiance available to an intertidal population of Heterozostera tasmanica (Martens ex Aschers.) den Hartog in Western Port, Victoria, Australia. When irradiance was reduced to 9 and 2% of control (ambient) levels, death of all leaf clusters of H. tasmanica resulted within 2 to 10 months. Reduction of irradiance to 35 and 25% of control levels resulted in a 25–50% decrease in leaf cluster density for the duration of the experiment (14 months). As irradiance level decreased leaf length increased (leaf length at 9% irradiance was twice leaf length in control areas) while leaf growth rate and leaf width remained the same. It is suggested that leaf growth rate per leaf cluster remains the same under reduced irradiance because of decreased likelihood of self-shading by surviving leaf clusters and increased surface area per leaf cluster. Density decreased more rapidly during summer than during winter at reduced light levels. This response may be due to an increase in the plant's light compensation point because of increased respiration at summer temperatures. Information on the lower limits of vertical distribution H. tasmanica in Western Port and Port Phillip Bay, Victoria together with the experimental irradiance reduction data suggests that H. tasmanica requires a minimum of ≈ 5% of surface irradiance for survival.     

Activity of sperm and fertility in the potato moth, Phthorimaea operculella

In this investigation, two kinds of sperm (apyrene and eupyrene) were found in the potato moth. At each mating, a single spermatophore containing both types of sperm was passed to the female. Sperm storage was observed in males in the duplex and in the females in the spermatheca. The fertility of eggs was greater than 90 per cent. Sperm survival in females was from one to 12 days after mating, as determined by egg hatching. Parthenogenesis was absent.     

The centrifugal horizontal cells in the lobula plate of the blowfly, Phaenicia sericata

Intracellular recordings combined with iontophoretic injection of Procion Yellow M4RAN were used to study the anatomy and physiology of the centrifugal horizontal cells (CH-cells) in the lobula plate of the blowfly, Phaenicia sericata.Anatomy: The CH-cells comprise a set of two homolateral, giant visual interneurones (DCH, VCH) at the rostral surface of each lobula plate. Their extensive arborizations in the lobula plate possess bulbous swellings (boutons terminaux). The arborization of one cell (DCH) covers the dorsal, and the arborization of the other cell (VCH) the ventral half of the lobula plate. Their axons run jointly with those of the horizontal cells through the chiasma internum and the optic peduncle. Their protocerebral arborization possesses spines; they form a dense network together with the axonal arborization of the horizontal cells, a second type of giant homolateral cell most sensitive to horizontal motion. The protocerebral arborization of the CH-cells gives rise to a cell body fibre which traverses the protocerebrum dorsally to the oesophageal canal. The cell body lies on the contralateral side laterally and slightly dorsally to the oesophageal canal in the frontal cell body layer.Physiology: The CH-cells respond with graded potentials to rotatory movements of their surround. Cells in the right lobula plate respond with excitation (excitatory postsynaptic potentials, membrane depolarization) to clockwise motion (contralateral regressive, ipsilateral progressive), and with inhibition (inhibitory postsynaptic potentials, membrane hyperpolarization) to counterclockwise motion in either or both receptive fields; CH-cells respond to motion presented to the ipsilateral and/or contralateral eye. Cells of the left lobula plate respond correspondingly to the reverse directions of motion. Vertical pattern motion and stationary patterns are ineffective.The heterolateral H1-neurone elicits excitatory postsynaptic potentials in the DCH-cell; these postsynaptic potentials are tightly correlated 1:1 to the preceding H1-action potentíal. The delay between the peak of the action potential and the beginning of the DCH-postsynaptic potential is 1.15 msec, agreeing very well with the value reported previously for the blowfly, Calliphora (Hausen, 1976a). The synaptic input and output connections of the CH-cells are discussed.     

Changes in macrophage status in vivo during infection with and immunity to Leishmania enriettii

The changing status of peritoneal macrophages in guinea pigs infected with Leishmania enriettii has been examined. It was possible to demonstrate that, at certain times during a primary infection and following attempted reinfection of immune animals, the response of peritoneal macrophages to lymphokine contact in vitro was altered. At these times the harvested cells appeared to behave in vitro as if they had been at least partially activated in vivo before removal. They were unresponsive to lymphokine in the migration inhibition assay, and contact with lymphokine in culture caused a rapid increase in the level of glucose oxidation in these cells. It is suggested that changes in the response of macrophages to lymphokine in vitro may be one way of monitoring activation in vivo.     

Limiting laws and counterion condensation in polyelectrolyte solutions: V. Further development of the chemical model

Counterion binding to polyelectrolyte chains is formulated as a chemical reaction M^z(free) → M^z(bound). Expressions for the chemical potentials of free and bound counterions are set equal to obtain the reaction equilibrium. The results are equivalent to those in the previous paper of this series. An additional result obtained here is that a polyion holds its bound counterion layer with a strength on the order of 100 $\text{kcal}\text{(mole cooperative unit)}$. The method is then applied to the calculation of the polarizability along the chain due to the bound (condensed) counterions.     

A prestaining method for the quantitative assay of proteins on polyacrylamide gels

Dyes have been synthesised¹, which make it possible to prestain proteins prior to electrophoresis on polyacrylamide gels. After discussing the criteria which have to be fulfilled by the dyes, their method of application is described. The method has been tested on a number of selected acidic and basic proteins and also on peptide obtained by the digestion of bovine serum albumin with cyanogen bromide. Excellent reproducibility, stoichiometry and a sensitivity of 0.2 μg with some proteins has been obtained.     

Heavy-metal toxicity in the cyanobacterium Nostoc Linckia

The effects of HgCl₂, NiCl₂ and CoCl₂ on Nostoc linckia (Roth) Born. et Flah. were studied. Low level (0.2 p.p.m.) of mercury increased heterocyst frequency, stimulated nitrate reductase and ammonium uptake, but significantly inhibited acetylene-reducing and glutamine-synthetase activities. In contrast, NiCl₂ and CoCl₂ greatly inhibited all of the above processes.     

In vitro stimulation of cell death in the moulting glands of Oncopeltus fasciatus by 20-hydroxyecdysone

The moulting glands of the milkweed bug, Oncopeltus fasciatus, normally degenerate just before the time of ecdysis to an adult (day 7 of the fifth instar). Morphologically normal cell death can be prematurely stimulated in vitro by 20-hydroxyecdysone. Breakdown is triggered by a 24-hr period of exposure to 20-hydroxyecdysone, but an additional incubation period is required before clear signs of degeneration are manifested. Glands removed after the onset of endogenous ecdysteroid secretion degenerate in vitro in the absence of added hormones. Thus, in the moulting glands of Oncopeltus, ecdysteroids appear to act as an important trigger for metamorphic cell death.     

Hyperpigmented patches in the skin of the newt Notophthalmus viridescens

In the integument of the red-spotted newt there occasionally appear patches of skin which are at the same time melanistic and iridescent. Such hyperpigmented patches have been found on the back, on the tail and on the dorsal surface of both fore and hind limbs. Cytological examination of several such areas revealed the presence of large numbers of chromatophores distributed throughout the dermis. The majority of the chromatophores consisted of atypically large and dendritic melanophores, which contained typical pigment granules. The iridescence resulted from a high incidence of iridophores. Xanthophores also were found in considerable abundance. This extensive and apparently random intermingling of melanophores, iridophores and xanthophores in limited areas constitutes a striking exception to the usual distributional patterns of pigment cells in this animal.     

A kinetic and structural comparison of chorismate mutase/prephenate dehydratase from mutant strains of Escherichia coli K12 defective in the PheA gene

Three classes of mutant strains of Escherichia coli K12 defective in pheA, the gene coding for chorismate mutase/prephenate dehydratase, have been isolated: (1) those lacking prephenate dehydratase activity, (2) those lacking chorismate mutase activity, and (3) those lacking both activities. Chorismate mutase/prephenate dehydratase from the second class of mutants was less sensitive to inhibition by phenylalanine than wild-type enzyme and, along with the defective enzyme from the third class of mutants, could not be purified by affinity chromatography on Sepharosyl-phenylalanine. Pure chorismate mutase/prephenate dehydratase protein was prepared from two strains belonging to the first class. The chorismate mutase activity of these enzymes is kinetically similar to that of the wild-type enzyme except for a two- to threefold increase in both the K_a for chorismate and the K_is for inhibition by prephenate. In both cases only one change in the tryptic fingerprint was detected, resulting from a substitution of the threonine residue in the peptide Gln·Asn·Phe·Thr·Arg. This suggests that this residue is catalytically or structurally essential for the dehydratase activity.     

The diversion of dimethylailylpyrophosphate from polyisoprenoid to cyclopiazonic acid biosynthesis in Penicillium cyclopium westling

During the production of α-cyclopiazonic acid (αCA) by Penicillium cyclopium, dimethylallyltransferase (EC. 2.5.1.1.) T, isopentenyl pyrophosphate isomerase (EC. 5.3.3.2) I, and a prenyl-aryltransferase, S, which produces β-cyclopiazonic acid (βCA) are all induced at the same time. This last enzyme appears maximally before the highest rate of α- or βCA production. Both transferases are not utilized to their maximum capacity, and the production of their end products seems to bear no relationship to their concentrations. Other controls therefore must play an important role in the utilization of their common substrate dimethylallylpyrophosphate (DMAPP). There are two possible control systems: (a), a direct competition by S and T for DMAPP; and (b), control by compartmentation. The first possiblility is the more likely, in view of some of the controls that could apply to the deflection. The three enzymes were separated so that possible controls on the deflection of DMAPP from polyisoprenoids could be studied. They all possessed a subunit structure and exhibited maximum molecular weithts (in the absence of divalent cations and presence of a thiol reductant) of 96 000 (S) and 64 000 (I and T) daltons. Mg²⁺ caused a diminution in size to 75 000 (S) and 50 000 (I and T) daltons. Mg²⁺ had the same effect on I and T but caused major disruptive changes to S. These effects were reversible by addition of EDTA. S was quite specific for DMAPP and cycloacetoacetyl-l-tryptophan (cAATrp) and exhibited Michaelis constants as follows; K_m^cAATrp, 6.0μM and K_m^DMAPP 2.0 μM. It had no obvious requirement for a divalent cation and had an isoelectric point of 5.3. I had a K_m of 6.7 μM and an isoelectric point of 4.5, and either Mg²⁺ or Mn²⁺ was essential. The Michaelis constants for T could not be given but its isoelectric point was 5.1. The enzyme carried out the two reactions normally associated with it (i.e., two additions of IPP to produce farnesyl pyrophosphate) and required Mg²⁺ to do so. The pH optima for S, I, and T were 6.5–7.5, 6.0, and 8.0 respectively. The early and major controlling factor was the appearance of the cosubstrate of S, cAATrp. Other factors were: (a), the appearance of αCA which inhibited T more effectively than S; (b), the removal of free Mn²⁺ and Mg²⁺, both essential for I and T but not for S, possibly brought about by chelation with cAATrp, α- and βCA; (c), the observed low pH of 6.0 when the activity of S was unaltered, I was at its highest, and T exhibited 50% of its maximum; and (d), an activation of I by low physiological levels of βCA and cAATrp which would enhance the rate of appearance of DMAPP to react with an existing pool of cAATrp.     

Discussion on the state of water in the myofilament lattice and other biological systems, based on the fact that the usual concepts of colloid stability can not explain the stability of the myofilament lattice

Application of the usual concepts of colloid stability shows that the in vivo spacings between the myofilaments, making up the contractile part of the muscle myofibrils, correspond to energies of 10(-4) to 10(-1) kT. Refinements in the calculations of the electrostatic and Van der Waals-London energies do not significantly modify these values. Therefore, theory does not predict the observed stability of the myofilament lattice. It is shown that the interfilament water very likely plays an active role in the myofilament lattice. More generally, the structure of water in living cells is probably different from that of bulk water.     

Effects of ovariectomy and estradiol replacement therapy upon the sexual and aggressive behavior of the greater galago (Galago crassicaudatus crassicaudatus)

The effects of ovariectomy and estradiol treatment upon sexual and aggressive behavior were studied in a prosimian primate, the greater galago. Ovariectomized galagos were sexually unreceptive and frequently aggressive, but retained their sexual attractiveness to males. When females were treated with estradiol monobenzoate, however, their aggression and refusals of males' mounting attempts decreased markedly. Although males mounted these females, they usually failed to copulate, possibly because the females did not perform certain postural adjustments which assist males to intromit. Estradiol benzoate alone, even in large doses, does not fully restore patterns of mating behavior in ovariectomized female greater galagos. These observations on a prosimian primate are in striking contrast to the results of similar work on Old World monkeys and chimpanzees.     

Chemotaxis in the Florida spiny lobster, Panulirus argus

The relative importance of input from chemoreceptors on the medial versus the lateral antennular flagellae of the spiny lobster, Panulirus argus, in olfactory orientation is examined. Ablation experiments show that input from the lateral filament, specifically the aesthetase tuft of the lateral filament, is necessary and sufficient to trigger searching behaviour in this organism when stimulated with a gradient of dilute shrimp extract. P. argus locates the odour source by using this lateral filament input in both tropotactic and klinotactic comparisons of odour intensities.     

Spectroscopic studies on the copper(II) complexes of carnosine

Carnosine complexes with copper(II) ions were studied with magnetic resonance techniques over a wide range of ligand to metal ratios at various pH values. Water proton relaxation rates increased with decreasing carnosine to copper ratios until a molar ratio of 48 was reached. Over the ratio range of 48–2 carnosine molecules per copper ion, the relaxation rate decreased so that in the 2:1 carnosine-copper(II) complex, the water-copper(II) distance was estimated to be 1.92 Å. Proton NMR studies revealed the broadening of imidazole proton lines at high mole ratios followed by other histidyl protons as the ratio decreased. The β-alanyl methylene protons were the last to be broadened by the addition of copper(II) ions. Carbon to copper(II) distances were determined for the carnosine to copper mole ratios of 500:1 and 5000:1. EPR spectra obtained at 93°K revealed the probable existence of four carnosine imidazoles as the sole coordinated ligands to copper(II) at high dipeptide-to-metal ratios (>10). At mole ratios below four, nuclear hyperfine lines characteristic of both monomeric and dimeric carnosine-copper(II) forms were observed. These results reveal that imidazole from carnosine is the sole ligand contributed to copper(II) for coordination over the pH range 5 to 7 at high carnosine to copper(II) ratios     

A field study of the headbob displays of male green iguanas (Iguana iguana): Variation in form and context

Headbob displays play an important role in the social behaviour of male green iguanas (Iguana iguana). Four types of headbobs were identified, and the variability in form and context were determined from quantitative analyses of displays filmed in the field. The Roll is a conspicuous advertisement display. The Shudder, the most variable in form, occurred during close contact between males and females. The Roll-shudder is intermediate between the Roll and Shudder in its form and use. The Signature Bob, the most stereotyped display in form, punctuates much activity and is the most variable in contextual use. This display encodes species identity, and possibly individual identity. The conspicuous nature of the headbob displays was enhanced by the intensified colour of territorial males, and by the selection of highly visible display posts. This system of visual displays is viewed as the product of related sets of constraints, including the iguanas' physical capacities, the forest environment, and the social environment.     

Effects of aspirin on renal sodium excretion, blood pressure, and plasma and extracellular fluid volume in salt-loaded rats

The effect of aspirin administration and presumed blockade of prostaglandin synthesis on renal sodium excretion, plasma and extracellular fluid volumes, and blood pressure were examined in rats on a high sodium intake. After acute salt loading aspirin treated rats showed an impaired sodium excretion, while no changes in glomerular filtration rate were observed. In chronically loaded rats (7 weeks) administration of aspirin induced significant increases in both plasma and extracellular fluid volume, but no significant changes in blood pressure were found. The results are consistent with the hypothesis that prostaglandins mediate renal sodium excretion and therefore participate in extracellular fluid volume regulation.