MARINICHLORELLA KAISTIAE GEN. ET SP. NOV. (TREBOUXIOPHYCEAE,CHLOROPHYTA) BASED ON POLYPHASIC TAXONOMY1

We describe three coccoid green algal strains belonging to a new genus and species, Marinichlorella kaistiae Z. Aslam, W. Shin, M. K. Kim, W.‐T. Im et S.‐T. Lee, in seawater samples from the South Sea of Korea. These strains were maintained at 25°C–30°C under a 12:12 light:dark (L:D) photoregime in an ASN‐III medium at a pH of 7.5. These strains were tolerant of high salinity (7.5% NaCl) (w/v) and temperature (40°C). Molecular phylogenetic analyses using 18S rRNA gene sequence data resolved these organisms to a clade separate from green coccoid algae with similar morphology. The DNA–DNA hybridization results demonstrated very low relatedness of these organisms to phylogenetically related species of the genera Chlorella and Parachlorella. The molar guanine + cytosine content (G + C mol%) of the genomic DNA of these organisms ranged from 64.7 to 69.1 mol%. Based on molecular phylogeny, DNA–DNA hybridization, and other morphological studies, we propose a new taxon, Marinichlorella kaistiae, to describe these strains and classify them in the family Chlorellaceae. The type strain is KAS007^T (= KCTC AG10303^T = IAM C‐620^T).     

Effect of rotational use of insecticides on pyrethroids resistance in Helicoverpa armigera (Lep.: Noctuidae)

Abstract:  To investigate fluctuation in susceptibility to insecticides in the field, natural populations of Helicoverpa armigera were collected from the same field in the region of Multan, Pakistan in 2002 and 2003. The populations were examined against pyrethroids (viz. cypermethrin, esfenvalerate and fenpropathrin) and new insecticides (viz. spinosad, abamectin and indoxacarb). In 2002, the resistance ratio (RR) of cypermethrin and esfenvalerate was significantly higher than fenpropahrin compared with susceptible population. The susceptibility to cypermethrin, esfenvalerate and fenpropathrin increased significantly in 2003; however, the RR for cypermethrin was about half the RR (38) of esfenvalerate (101) and fenpropathrin (89). The toxicity of spinosad, abamectin and indoxacarb was identical in both years. In the field experiments, abamectin was more effective than other compounds tested whereas fenpropathrin, cypermethrin and esfenvalerate had similar toxicity. These results might have important implications in resistance management and suggest that the rotational use of spinosad, abamectin and indoxacarb could help to avoid the development of multiple resistant in H. armigera .     

The extended multidomain solution structures of the complement protein Crry and its chimeric conjugate Crry-Ig by scattering,analytical ultracentrifugation and constrained modelling: implications for function and therapy

Complement receptor-related gene/protein y (Crry) is a cell membrane-bound regulator of complement activation found in mouse and rat. Crry contains only short complement/consensus repeat (SCR) domains. X-ray and neutron scattering was performed on recombinant rat Crry containing the first five SCR domains (rCrry) and mouse Crry with five SCR domains conjugated to the Fc fragment of mouse IgG1 (mCrry-Ig) in order to determine their solution structures at medium resolution. The radius of gyration R(G) of rCrry was determined to be 4.9-5.0 nm, and the R(G) of the cross-section was 1.2-1.5 nm as determined by X-ray and neutron scattering. The R(G) of mCrry-Ig was 6.6-6.7 nm, and the R(G) of the cross-section were 2.3-2.4 nm and 1.3 nm. The maximum dimension of rCrry was 18 nm and that for mCrry-Ig was 26 nm. The neutron data indicated that rCrry and mCrry-Ig have molecular mass values of 45,000 Da and 140,000 Da, respectively, in agreement with their sequences, and sedimentation equilibrium data supported these determinations. Time-derivative velocity experiments gave sedimentation coefficients of 2.4S for rCrry and 5.4S for mCrry-Ig. A medium-resolution model of rCrry was determined using homology models that were constructed for the first five SCR domains of Crry from known crystal and NMR structures, and linked by randomly generated linker peptide conformations. These trial-and-error calculations revealed a small family of extended rCrry structures that best accounted for the scattering and ultracentrifugation data. These were shorter than the most extended rCrry models as the result of minor bends in the inter-SCR orientations. The mCrry-Ig solution data were modelled starting from a fixed structure for rCrry and the crystal structure of mouse IgG1, and was based on conformational searches of the hinge peptide joining the mCrry and Fc fragments. The best-fit models showed that the two mCrry antennae in mCrry-Ig were extended from the Fc fragment. No preferred orientation of the antennae was identified, and this indicated that the accessibility of the antennae for the molecular targets C4b and C3b was not affected by the covalent link to Fc. A structural comparison between Crry and complement receptor type 1 indicated that the domain arrangement of Crry SCR 1-3 is as extended as that of the CR1 SCR 15-17 NMR structure.     

Organization of seminiferous epithelium in primates: relationship to spermatogenic efficiency,phylogeny, and mating system

The succession in time and space of specific germ cell associations, denoted as spermatogenic stages, is a typical feature of mammalian spermatogenesis. The arrangement of these stages is either single stage (one spermatogenic stage per tubular cross-section) or multistage (more than one spermatogenic stage per tubular cross-section). It has been proposed that the single-stage versus multistage arrangement is related to spermatogenic efficiency and that the multistage arrangement is typical for hominids. In the present work, the arrangement of spermatogenic stages and the spermatogenic efficiency of 17 primate species, comprising Strepsirrhini (Prosimians: Lemuriformes, Lorisiformes), Platyrrhini (New World primates), Catarrhini (Old World primates), and Hominoidea (great apes and humans), were analyzed comparatively by quantitative histological and flow cytometric means. We found a predominant single-stage tubular organization in the Strepsirrhini, indicating that the single-stage form represents the ancestral state. The highest degree of multistage complexity was found in Hominoidea (except orangutan) and in Platyrrhini, but not in Catarrhini. Hence, no direct relationship between single-stage/multistage tubular topography and phylogeny could be established across primates. In fact, the tubule arrangement seen in Platyrrhini and Catarrhini primates is the reverse of what might be expected from phylogeny. Interestingly, spermatogenic efficiency was similar in all species. We found no correlation between single-stage/multistage arrangement and spermatogenic efficiency or mating system. We speculate that the presence of a single-stage/multistage organization might simply reflect germ cell clonal size. Our findings further indicate that sperm competition in primates is not reflected at the level of testicular function.     

Multiple levels of Notch signal regulation (review)

Notch is a vitally important signalling receptor controlling cell fate determination and pattern formation in numerous ways during development of both invertebrate and vertebrate species. An intriguing pathway for the Notch signal has emerged where, after ligand-dependent proteolysis, an intracellular fragment of the receptor itself translocates to the nucleus to regulate gene expression. The nuclear activity of the Notch intracellular domain is linked to complexes regulating chromatin organization through histone deacetylation and acetylation. To allow the Notch signal to be deployed in numerous contexts, many different mechanisms have evolved to regulate the level, duration and spatial distribution of Notch activity. Regulation occurs at multiple levels including patterns of ligand and receptor expression, Notch-ligand interactions, trafficking of the receptor and ligands, and covalent modifications including glycosylation, phosphorylation and ubiquitination. Several Notch regulatory proteins have conserved domains that link them to the ubiquitination pathway, and ubiquitination of the Notch intracellular domain has recently been linked to its degradation. Different proteolytically derived isoforms of Notch have also been identified that may be involved in alternative Notch-dependent signals or regulatory mechanisms, and differences between the four mammalian Notch homologues are beginning to be appreciated.     

Comparative Induction of Nitrate and Nitrite Uptake and Reduction Systems by Ambient Nitrate and Nitrite in Intact Roots of Barley (Hordeum vulgare L.) Seedlings

The induction by ambient NO3- and NO2- of the NO3- and NO2- uptake and reduction systems in roots of 8-d-old intact barley (Hordeum vulgare L.) seedlings was studied. Seedlings were induced with concentrations of NaNO3 or NaNO2 ranging from 0.25 to 1000 [mu]M. Uptake was determined by measuring the depletion of either NO3- or NO2- from uptake solutions. Enzyme activities were assayed in vitro using cell-free extracts. Uptake and reduction systems for both NO3- and NO2- were induced by either ion. The Km values for NO3- and NO2- uptake induced by NO2- were similar to those for uptake induced by NO3-. Induction of both the uptake and reduction systems was detected well before any NO3- or NO2- was found in the roots. At lower substrate concentrations of both NO3- and NO2- (5-10 [mu]M), the durations of the lag periods preceding induction were similar. Induction of uptake, as a function of concentration, proceeded linearly and similarly for both ions up to about 10 [mu]M. Then, while induction by NO3- continued to increase more slowly, induction by NO2- sharply decreased between 10 and 1000 [mu]M, apparently due to NO2- toxicity. In contrast, induction of NO3- reductase (NR) and NO2- reductase (NiR) by NO2- did not decrease above 10 [mu]M but rather continued to increase up to a substrate concentration of 1000 [mu]M. NO3- was a more effective inducer of NR than was NO2-; however, both ions equally induced NiR. Cycloheximide inhibited the induction of both uptake systems as well as NR and NiR activities whether induced by NO3- or NO2-. The results indicate that in situ NO3- and NO2- induce both uptake and reduction systems, and the accumulation of the substrates per se is not obligatory.     

Effect of light and glucose on the induction of nitrate reductase and on the distribution of nitrate in etiolated barley leaves

Barley seedlings grown in the dark with 10 mm KNO(3) have low levels of nitrate reductase activity even though large amounts of No(3) (-) accumulate in the leaves. When the leaves are excised and transferred to the light, there is an increase in nitrate reductase activity both in the presence and absence of exogenous NO(3) (-). When the leaves are transferred to a glucose solution (0.05 m) but kept in the dark, induction of nitrate reductase activity occurs only when fresh NO(3) (-) is added to the system.In dark-grown leaves, there are small traces of NO(3) (-) in a "metabolic pool." Addition of glucose does not alter this distribution. Light, on the other hand, results in an appreciable accumulation of NO(3) (-) in the metabolic pool. There is a linear correlation between nitrate reductase activity and the size of the metabolic NO(3) (-) pool. Our results thus suggest that NO(3) (-) accumulates in a storage pool when seedlings are grown in continuous darkness. The transfer of this NO(3) (-) to an active metabolic pool is mediated by light but not by glucose. We believe that this transfer of NO(3) (-) leads to the induction of nitrate reductase. When NO(3) (-) is included in the medium, both light and glucose increase its incorporation into the metabolic pool. The results suggest two mechanisms for regulating the metabolic NO(3) (-) pool: (a) a transfer from the storage pool which requires light; and (b) a transfer from the external medium which requires either glucose or light.     

Comparative Kinetics and Reciprocal Inhibition of Nitrate and Nitrite Uptake in Roots of Uninduced and Induced Barley (Hordeum vulgare L.) Seedlings

Nitrate and NO₂⁻ transport by roots of 8-day-old uninduced and induced intact barley (Hordeum vulgare L. var CM 72) seedlings were compared to kinetic patterns, reciprocal inhibition of the transport systems, and the effect of the inhibitor, p-hydroxymercuribenzoate. Net uptake of NO₃⁻ and NO₂⁻ was measured by following the depletion of the ions from the uptake solutions. The roots of uninduced seedlings possessed a low concentration, saturable, low K_m, possibly a constitutive uptake system, and a linear system for both NO₃⁻ and NO₂⁻. The low K_m system followed Michaelis-Menten kinetics and approached saturation between 40 and 100 micromolar, whereas the linear system was detected between 100 and 500 micromolar. In roots of induced seedlings, rates for both NO₃⁻ and NO₂⁻ uptake followed Michaelis-Menten kinetics and approached saturation at about 200 micromolar. In induced roots, two kinetically identifiable transport systems were resolved for each anion. At the lower substrate concentrations, less than 10 micromolar, the apparent low K_ms of NO₃⁻ and NO₂⁻ uptake were 7 and 9 micromolar, respectively, and were similar to those of the low K_m system in uninduced roots. At substrate concentrations between 10 and 200 micromolar, the apparent high K_m values of NO₃⁻ uptake ranged from 34 to 36 micromolar and of NO₂⁻ uptake ranged from 41 to 49 micromolar. A linear system was also found in induced seedlings at concentrations above 500 micromolar. Double reciprocal plots indicated that NO₃⁻ and NO₂⁻ inhibited the uptake of each other competitively in both uninduced and induced seedlings; however, K_i values showed that NO₃⁻ was a more effective inhibitor than NO₂⁻. Nitrate and NO₂⁻ transport by both the low and high K_m systems were greatly inhibited by p-hydroxymercuribenzoate, whereas the linear system was only slightly inhibited.     

Upper esophageal sphincter function during gastroesophageal reflux events revisited

Upper esophageal sphincter (UES) function during gastroesophageal reflux events is not completely elucidated because previous studies addressing this issue yielded conflicting results. We reexamined the UES pressure response to intraluminal esophageal pressure and pH changes induced by reflux events. We studied 14 healthy, asymptomatic volunteers (age 49 +/- 6 yr) and 7 gastroesophageal reflux disease patients (age 48 +/- 5 yr). UES pressure, intraesophageal pressure, and pH were monitored at the distal, middle, and proximal esophagus concurrently in the supine position 1 h before and 2 h after a 1,000-calorie meal. A total of 321 reflux events were identified by the development of abrupt reflux-induced intraesophageal pressure increase (IPI); 285 events occurred in patients and 36 in control subjects. In control subjects 33 of 36 and in patients 252 of 285 IPI events were associated with a pH drop. Among patients and control subjects, 99% and 100%, respectively, of all IPI events irrespective of pH drop were associated with abrupt increase in UES pressure (34 +/- 2 and 27 +/- 6 mmHg, respectively). The average percentage of maximum UES pressure increase over prereflux values ranged between 66% and 96% (control subjects) and 34% and 122% (patients). IPIs induced by both acidic and nonacidic reflux events evoke strong UES contractile responses.