Collective effects in traffic on bi-directional ant trails

Motivated by recent experimental work of Burd et al., we propose a model of bi-directional ant traffic on pre-existing ant trails. It captures in a simple way some of the generic collective features of movements of real ants on a trail. Analysing this model, we demonstrate that there are crucial qualitative differences between vehicular- and ant-traffics. In particular, we predict some unusual features of the flow rate that can be tested experimentally. As in the uni-directional model a non-monotonic density-dependence of the average velocity can be observed in certain parameter regimes. As a consequence of the interaction between oppositely moving ants the flow rate can become approximately constant over some density interval.     

Protein mapping of the salivary complex from a hematophagous leech

The salivary complex of leeches contains many components able to modulate physiological mechanisms, such as coagulation and fibrinolysis, and it is composed by the salivary glands and proboscis, encompassing two different proteomes. The bidimensional electrophoretic pattern of the salivary complex from the Haementeria depressa leech revealed a total of 352 spots, 103 in common with the muscular tissue and 249 exclusive from the salivary complex as detected by silver staining; these spots showed isoelectric points from 3.5 to 9.5 and covered an apparent molecular weight range from 10 to 105 kDa. The following isoforms of proteins were identified by mass spectrometry analysis: antiplatelet protein, myohemerythrin and carbonic anhydrase. Since the leeches were not fed for about 2-3 months to stimulate the secretion of proteins that facilitates the blood metabolism, these most abundant proteins in the salivary complex excised from leeches, are expected to play a role during feeding and might have some anti-hemostatic properties. Furthermore, by zymography, a gelatinolytic and a fibrinolytic protein were identified.     

Characterization of Hexose Transporter for Facilitated Diffusion of the Tonoplast Vesicles from Pear Fruit

Tonoplast vesicles were prepared from the flesh tissue of maturepear fruit. Sugar uptakes into the vesicles determined by twodifferent methods, the membrane and the gel filtration methods,were quite similar. The uptake was highest for glucose and subsequently,in order, for fructose, sucrose and sorbitol. It was not stimulatedby addition of ATP, although the vesicles could create a protongradient. However, the uptakes were significantly inhibitedby p-chloromercuribenzene sulphonate (PCMBS, SH-reagent andinhibitor of sugar transporter). Further, the PCMBS-sensitiveuptakes of glucose and fructose saturated with their increasedconcentrations. Thus, these PCMBS-sensitive uptakes are mediatedby the transporter of facilitated diffusion. The uptakes ofglucose or fructose each had two K_m values. K_m values for glucosewere 0.35 and 18 mM, and those for fructose were 1.6 and 25raM. The uptake of 0.2 mM glucose was inhibited by 2 mM fructoseand that of 2 mM fructose was inhibited by 2 mM glucose, butneither was inhibited by sucrose or sorbitol. O-methyl-glucose(OMG) also inhibited both the glucose and fructose uptakes.Therefore, the same transporter may mediate both glucose andfructose uptakes at lower concentrations; this hexose transportsystem differed from the sucrose and sorbitol transport systems. ¹Research Fellow of the Japan Society for the Promotion of Science. ²Present address: Faculty of Agriculture, Tohoku University,1-1 Tsutsumidori-Amamiyamachi, Aoba-ku, Sendai, 981 Japan.     

Cannibalism and interspecific predation in two predatory ladybirds in relation to prey abundance in the field

Life tables for two predatory ladybirds,Coccinella septempunctata andHarmonia axyridis, were constructed in two years in which prey abundance differed. The prey aphid,Aphis gossypii, was abundant on its primary host from late May to late June. Females ofH. axyridis andC. septempumctata laid their eggs during the increase and peak in aphid abundance. The oviposition period ofC. septempunctata started before and was shorter than that ofH. axyridis. In both species, intraguild predation and/or cannibalism of the egg and fourth instar stages, but rarely of other developmental stages, were observed. Fourth instar larvae ofH. axyridis had to complete their development when aphids were scarce more frequently than those ofC. septempunctata. The highest frequency of intra- and interspecific predation was of fourth instarH. axyridis larvae. In terms of intraguild predation, the larvae ofH. axyridis preyed on larvae ofC. septempunctata, but the reverse was not observed. Percentage survival from egg to adult inH. axyridis was higher than inC. septempunctata in both years, and least in both species in the year of low aphid abundance. These results suggest that prey abundance influenced the frequency of cannibalism and intraguild predation, which were important in structuring this guild of ladybirds.     

Stress tolerance of pressure-shocked Saccharomyces cerevisiae

Pressure shock treatment induced synthesis of heat shock protein (hsp104) and tolerance against various stresses such as high temperature, high pressure and high concentration of ethanol in Saccharomyces cerevisiae. The optimum pressures that induced maximal tolerance against these stresses were in the range of 50–75 MPa and depended on the type of stress. However, pressure shock did not stimulate trehalose production in the cells. © Rapid Science Ltd. 1998     

Biochemical values of blood serum in the female silvered leaf-monkey,Presbytis cristatus

Thirteen days after capture, the blood serum of eight anesthetized female leaf-monkeys,Presbytis cristatus (3.86 kg of mean body weight), were analyzed for hematocrit (35.6±6.7 %), total protein (6.7±0.8 g/dl), albumin (3.61±0.77 g/dl), α-1 globulin (0.13±0.04 g/dl), α-2 globulin (0.73±0.18 g/dl), β globulin (0.87±0.27 g/dl), γ globulin (1.36±0.55 g/dl), A/G ratio (1.23±0.38), Na (161±6.14 mEq/l), K (5.61±0.74 mEq/l), LDH (575±257 IU/l), GOT (93±67 IU/l), GPT (34±33 IU/l), CPK (250±200 IU/l), ALP (613±633 IU/l), LAP (115±68 IU/l), γ-GTP (28±30 IU/l), TG (47±24 mg/dl), T-Cho (141±31 mg/dl), BUN (29.0±5.7 mg/dl), T-bil (0.21±0.07 mg/dl), and IP (3.4±2.0 mg/dl).     

Methylation imprinting was observed of mouse mo-2 macrosatellite on the pseudoautosomal region but not on chromosome 9

Mouse mo-2 macrosatellites consisting of 31-bp tandem repeat units are mainly located at two loci in the C57BL/6 genome, one being at the centromere-distal telomeric region of chromosome 9 and the other at the pseudoautosomal (PA) region of chromosomes X and Y. The two clustes constitute approximately 300 kb and 150 kb, respectively. Southern analysis of a methylation-sensitive enzyme, HpaII-digested DNA showed that the mo-2 macrosatellites are detected as more than 30 polymorphic bands. Comparison of those bands between reciprocally crossed F₁ mice revealed that approximately 20% of the allele-specific fragments exhibit different band intensities depending on the sex of the parent of origin. The differential methylation is observed in the mo-2 macrosatellite on the PA region but not in that on chromosome 9. Several fragments including the 3.4-kb fragment without internal HpaII site are more clearly detected when paternally derived, suggesting that the male-derived macrosatellite is undermethylated. Interestingly the difference is much more remarkable in inter-subspecific F₁ mice between C57BL/6 and MSM than F₁ between C57BL/6 and C3H/He. This suggests the presence of a modifier(s) that affect(s) the methylation of mo-2 in the MSM genome.     

Turgor Regulation in a Brackish Water Charophyte, Lamprothamnium succinctum III. Changes in Cytoplasmic Free Amino Acids and Sucrose Contents during Turgor Regulation

Cytoplasm and cell sap of Lamprothamnium succinctum were analyzedseparately for the contents of free amino acids and sucroseto find whether they contribute to turgor regulation. In thevacuole, both amino acids and sucrose were found to be minorcomponents contributing to the generation of osmotic pressure.Their amounts were almost insensitive to changes in externalosmotic pressure. In the cytoplasm, both amino acids and sucrosein the cytoplasm contributed about 20% to the osmotic pressure.Hypotonic treatment did not affect the contents of either, buthypertonic treatment, while not affecting the amino acid contents,caused a significant increase in sucrose content. The cytoplasmicsucrose content increased linearly with an increase in externalosmotic pressure, accounting for 40% of the increased osmoticpressure. ¹ Present address: Department of Biology, Osaka Medical College,Sawaragi-cho, Takatsuki, Osaka 569, Japan ² Present address: Department of Applied Physiology, NationalInstitute of Agrobiological Resources, Yatabe, Tsukuda, Ibaragi305, Japan (Received November 25, 1986; Accepted March 18, 1987)