Substrate particle size affects pit building decision and pit size in the antlion larvae Euroleon nostras (Neuroptera: Myrmeleontidae)

Abstract. The larvae of the antlion Euroleon nostras are pit-builders, constructing pitfall traps in loose sand. The number of pits and the pit diameter are recorded when larvae are kept in substrates with different particle sizes. The most convenient pit-building sand fractions are two fractions with fine sand (≤ 0.23 mm; 0.23–0.54 mm). The largest pits are constructed in sand with a particle size of 0.23–0.54 mm. In this sand fraction, larvae of all three instars most readily build pits. No pits are constructed in sand with a particle size greater than 1.54 mm. First- and second-instar larvae avoid building pits in substrates of particle size 1–1.54 mm, but third-instar larvae construct pits in this sand fraction. It is assumed that the antlion is capable of distinguishing between substrate types and this hypothesis is tested by giving larvae the choice of building a pit in one of four particle-size fractions. Larvae of all three instars prefer to build pits in the fraction with a particle size of 0.23–0.54 mm. Only third-instar larvae build pits in all four fractions, but only occasionally in the coarser fraction.     

Plant coated vesicles

Abstract. Coated vesicles are organelles frequently encountered in many plant cell types often in association with the plasma membrane, Golgi apparatus, partially coated reticulum and multivesicular bodies. They are readily identified by a characteristic cage or basket composed of interlocking triskelions of the protein clathrin which are bound to the surface of the vesicle membrane. Although their transport function has been well studied and characterized in mammalian systems, the possible importance of coated vesicles as transport organelles in plant cells is only just beginning to be explored. In this review, the authors describe the structure of higher plant coated vesicles and discuss their possible involvement in the endocytosis of marcromolecules, in exocytosis and in the intracellular transport of material between cytoplasmic compartments. Their possible role in maintaining the macromolecular composition of the plasma membrane whilst allowing recycling of excess lipid bilayer and their potential application as vehicles for the introduction of foreign macromolecules into plant cells are discussed.     

Determination of the trophic state by qualitative and quantitative phytoplankton analysis in two gravel pit lakes

The phytoplankton of two gravel pits with comparable nutrient concentrations but different chlorophyll-a concentrations and phytoplankton biovolume was investigated qualitatively and quantitatively over a period of two years. This study deals with the phytoplankton-rich ‘Rotter See’ and the phytoplankton-poor ‘Paulsmaar’, both South of Cologne. The trophic state of both lakes was determined comparatively according to Ryding &; Rast (1989) and the categories used by Brettum (1989). The results were compared with each other. The trophic lake index according to Hörnström (1981) was modified slightly and subsequently determined for both lakes. A combination of qualitative and quantitative phytoplankton analysis made a proposal of a rehabilitation for the Rotter See possible.     

The mechanism of water-stress-induced embolism in two species of chaparral shrubs

The mechanism of water-stress-induced embolism of xylem was investigated in Malosma laurina and Heteromeles arbutifolia, two chaparral shrub species of southern California. We tested the hypothesis that the primary cause of xylem dysfunction in these species during dehydration was the pulling of air through the pores in the cell walls of vessels (pores in pit membranes) as a result of high tensions on xylem water. First, we constructed vulnerability-to-embolism curves for (i) excised branches that were increasingly dehydrated in the laboratory and (ii) hydrated branches exposed to increasing levels of external air pressure. Branches of M. laurina that were dehydrated became 50% embolized at a xylem pressure potential of -1.6 MPa, which is equal in magnitude but opposite in sign to the +1.6 MPa of external air pressure that caused 50% embolism in hydrated stems. Dehydrated and pressurized branches of H. arbutifolia reached a 50% level of embolism at -6.0 and +6.4 MPa, respectively. Secondly, polystyrene spheres ranging in diameter from 20 to 149 nm were perfused through hydrated stem segments to estimate the pore size in the vessel cell walls (pit membranes) of the two species. A 50% or greater reduction in hydraulic conductivity occurred in M. laurina at perfusions of 30, 42, 64 and 82 nm spheres and in H. arbutifolia at perfusions of 20 and 30 nm spheres. Application of the capillary equation to these pore diameters predicted 50% embolism at xylem tensions of -2.2 MPa for M. laurina and -6.7 MPa for H. arbutifolia, which are within 0.7 MPa of the actual values. Our results suggest that the size of pores in pit membranes may be a factor in determining both xylem efficiency and vulnerability to embolism in some chaparral species. H. arbutifolia, with smaller pores and narrower vessels, withstands lower water potentials but has lower transport efficiency. M. laurina, with wider pores and wider vessels, has a greater transport efficiency but requires a deeper root system to help avoid catastro-phically low water potentials.     

The wound response of the siphonous green algal genusCaulerpa III: Composition and origin of the wound plugs

Summary A complex, higly sulphated glucoxylomannogalactan has been extracted in a yield of about 1% dry weight fromC. simpliciuscula. This polysaccharide is similar in composition to sulphated polysaccharides previously isolated from otherCaulerpa species (Mackie andPercival, 1961). The most likely location of this compound in the unwounded cell is in the vacuole. This polysaccharide appears as the major component in wound plugs, forming a viscoelastic barrier between the protoplasm and the external environment. The properties of the sulphated polysaccharide were studied in an effort to understand the physiology and mechanism of wound plug formation.     

Identification of a novel function of the clathrin-coated structure at the plasma membrane in facilitating GM-CSF receptor-mediated activation of JAK2

It is well known that ligand binding to the high-affinity GM-CSF receptor (GMR) activates JAK2. However, how and where this event occurs in a cellular environment remains unclear. Here, we demonstrate that clathrin- but not lipid raft-mediated endocytosis is crucial for GMR signaling. Knockdown expression of clathrin heavy chain or intersectin 2 (ITSN2) attenuated GMR-mediated activation of JAK2, whereas inhibiting clathrin-coated pits or plagues to bud off the membrane by the dominant-negative mutant of dynamin enhanced such event. Moreover, unlike the wild-type receptor, an ITSN2-non-binding mutant of GMR defective in targeting to clathrin-coated pits or plagues [collectively referred to as clathrin-coated structures (CCSs) here] failed to activate JAK2 at such locations. Additional experiments demonstrate that ligand treatment not only enhanced JAK2/GMR association at CCSs, but also induced a conformational change of JAK2 which is required for JAK2 to be activated by CCS-localized CK2. Interestingly, ligand-independent activation of the oncogenic mutant of JAK2 (JAK2V617F) also requires the targeting of this mutant to CCSs. But JAK2V617F seems to be constitutively in an open conformation for CK2 activation. Together, this study reveals a novel functional role of CCSs in GMR signaling and the oncogenesis of JAK2V617F.     

Urinary and air biomonitoring of occupational exposure to benzene in oil pit workers

Abstract

The purpose of this study is to evaluate the personal exposure to benzene and its relationship with biomonitoring and quantitative risk assessment among the personnel working and living near oil pits. This study was conducted in one of oil subsidiary companies in Kharg in 2017. Airborne benzene exposure was evaluated over 8-h periods during work-shift by using personal active samplers. Urinary O-Cresol levels were determined using GC-FID for separation and detection. The highest mean concentration of airborne benzene was at monitoring location, A (0.53?ppm), monitoring location H (0.59?ppm) in the spring, monitoring location M (0.72?ppm) and monitoring location P (0.8?ppm) in the summer, which was more than suggested by the American Conference of Governmental Industrial Hygienists. No direct linear relationship was found between the concentration of airborne benzene, age, work experience, urinary creatinine, and O-Cresol in this study (p?>?.05). No significant difference was observed between urinary O-Cresol and benzene in occupational groups and different seasons (p?>?.05). The highest mean quantitative risk of cancers was observed in summer (1.21?±?0.47). According to the results of this study, urinary biomarker O-Cresol is not a suitable measure for evaluating exposure to environmental benzene.     

Le Paléolithique supérieur de la région centre de l’île de Honshû

Tokai area is situated in the middle of Japan and has various configurations of ground. The eastern area has thick natural layers with volcanic ash which has been supplied from Mt. Fuji. About five chronological stages of Paleolithic culture from trapeze and edge-ground axe culture to microlith culture through backed blade culture have been found in the layers. These stages of Paleolithic culture are indicators of chronological studies in Tokai area. On the other hand, it is difficult to advance chronological studies in the middle east, middle, and west areas, because they have little thickness of layers with volcanic ash. However, different Paleolithic artifacts are found in top and bottom layers which put the AT layer between at Tsubakibora Site in Gifu Prefecture, and they have helped very much chronological studies of Paleolithic culture in the west area. Here is the first result of Paleolithic studies in Tokai area with artifacts which have been found on the forth layer of scoriae at Idemaruyama Site are dated about 35,000 years, one of the oldest Paleolithic culture in Japan. In addition, some lines of pits which were dated 30,000 years were found at Hatsunegahara Site, and they provided valuable data to study Paleolithic hunting. Finally, a holed pendant which had 10 notches on one side was unearthed from Fujiishi Site, and it was dated 19,000 years ago. At Terada and Hino Site, a flat big stone which had carvings was found, though the shape and use were seemed to be different from the pendant at Fujiishi Site.     

Nuove segnalazioni di funghi entomogeni

Abstract

New records of entomogenous fungi. — New records of six entomogenous fungi, three Ascomycetes (Cordyceps lloydii Fawcett, C. memorabilis Ces., C. riverae Pacioni) and three Deuteromycetes (Akantomyces aranearum (Petch) Mains, Hirsutella citriformis Speare, Troglobiomyces guignardii (Maheu) Pacioni) are given. The new records allow to expand the known area of distribution of these parasites, to confirm the particular condition for fructification needed by some of them and to give new details for the less common species.