Photosynthesis of submersed macrophytes in acidified lakes II. Carbon limitation and utilization of benthic CO2 sources

Photosynthetic characteristics of carbon-dioxide limitations were analyzed for leaf tissue in a Cartesian-diver system, in which irradiance could be stringently controlled, and with whole plants in electrode macrosystems for submerged macrophytes (Juncus bulbosus L., Sphagnum auriculatum Schimp. var. inundatum (Russow) M. O. Hill) and other benthic moss and algae (Drepanocladus, Batrachospermum, and an algal mat) from acidified lakes. Light compensation points were extremely low for Juncus (1.5–6 μE m^?2 s^?1) and Sphagnum (3–10), and higher for shallow-inhabiting Batrachospermum (22–33). Leaf tissue, whole plants, and algal populations were rapidly limited by CO₂ availability under closed submersed, acidified conditions (pH 4–6).Controlled and in situ experiments were performed, in which the rooting tissue of Juncus bulbosus was partitioned from the leaves and the rates of photosynthetic carbon fixation of the foliage, utilizing dissolved inorganic ¹⁴C-carbon from the water, were analyzed under different conditions of CO₂ enhancement in the rhizosphere of the sediments. Results demonstrated that: (a) from 25 to 40% of the carbon fixed in the leaves can originate from the rhizosphere, diffuse to the leaves via internal gas lacunae, and be fixed photosynthetically; (b) photosynthetic utilization of CO₂ from the water surrounding the leaves is reduced markedly when the CO₂ concentration of the rhizosphere was increased by direct additions of CO₂, bacteria, or organic compounds (glucose, acetate) that stimulate bacterial growth. Shifts to predominance of submersed benthic primary producers with low light compensation points and adapted to acidified lakes are related in part to circumvention of carbon limitation in the water by utilization of enhanced CO₂ availability in the rhizosphere and at the sediment—water interface from bacterial degradation of organic matter, and in part to physiological mechanisms that conserve and recycle CO₂ of respiration and photorespiration.     

Design and synthesis of novel dihydropyridine alpha-1a antagonists.

A series of analogs of SNAP 5150 containing heteroatoms at C2 or C6 positions is described. Herein, we report that the presence of alkyl substituted heteroatoms at the C2(6)-positions of the dihydropyridine are well tolerated. In addition, 15 inhibited the phenylephrine induced contraction of dog prostate tissue with a Kb of 1.5 nM and showed a Kb (DBP, dogs, microg/kg)/Kb (IUP, dogs, microg/kg) ratio of 14.8/2.5.     

Untersuchungen zur Insektizidresistenz der Haferlaus (Rhopalosiphum padi (L.))

Cabbage plants grown in a field experiment were sprayed with E.C. formulations of malathion, pirimiphos methyl and prothiofos at the rates of 570, 600 and 750 gm a.i. per feddan, residues of the three insecticides were analysed by GLC. Results revealed that initial deposits was varied; the highest deposit was that of malathion followed by pirimiphos methyl, and the lowest initial deposit was that of prothiofos. Initial deposits on inner leaves were less than the outer leaves.

Prothiofos showed more persistence than malathion, the least persistent toxicant was pirimiphos‐methyl. Persistence of the toxicants was lower on inner leaves, probably owing to lower initial deposits.

Deposits were within the permissible limits after 12, 12 and 15 days for malathion, pirimiphos‐methyl and prothiofos respectively, while on inner leaves, these intervals were 6, 8 and 12 days for the same insecticides respectively.     

Peroxidase and polyphenol oxidase activity in malformed mango inflorescence caused byFusarium moniliforme var.subglutinans

Peroxidase and polyphenol oxidase activities in malformed mango inflorescences of ‘Himsagar’ and ‘Bombay green’ oultivars wore found to be increased considerably following infection byFusarium moniliforme var.subglutinans. Whether such increased activities were due to their synthesis by the pathogen or the host, or both, was not studied although it was found that the pathogen was incapable of producing the enzymesin vitro. The activities of both the enzymes in infected tissues were found to increase considerably during the experimental period. It was found that activities of polyphenol oxidase were inhibited in the presence of sodium diethyldithiocarbamate and phenylthiourea; the former acted as chelating agent of Cu of the enzymes and the latter as a competitive inhibitor. Similarly, peroxidase activity was found to be inhibited by cycloheximide which acted as inhibitor of enzyme protein synthesis. The fact that the ‘Himsagar’ cultivar showed greater enzyme activity than the ‘Bombay green’ cultivar possibly suggests its higher resistance to the pathogen.     

Ergebnisse von Untersuchungen über die Effektivtemperatursummen einzelner Entwicklungsstadien der Getreidehähnchen (Lema spp.)

Various methodical approaches for the discovery and selection of virus-resistant potato forms are analysed. The optimum methods and conditions of PVM, PVY and PVX plant inoculation by evaluation to immunity are revealed, a possibility of realisation of complex inoculations on Lycopersicon esculentum Mill. (cv Nevsky) infected by PVM + PVX mixture, what accelerates an evaluation and increases its efficiency. The necessity of the controlled infectious backgrounds creation by evaluation of potato selection material for field (relative resistance to PVM + PVY + PVX complex) is shown.     

The impact of extra-pair mating behavior on hybridization and genetic introgression

Hybridization and genetic introgression can be associated with secondary contact between closely related species. Previous models have examined the ecological and demographic conditions leading to hybridization and introgression, but few have examined the role of behavior. Alternative mating behaviors are common throughout the animal kingdom but have rarely been recognized as a potential mechanism for hybridization. We developed an individual-based genetic model to examine the hypothesis that extra-pair copulations (EPCs) can lead to hybridization and genetic introgression even when assortative mating preferences are intact. Our model showed that female choice, whether pre- or post-copulation, reinforced species boundaries and that hybrids were relatively uncommon when no EPCs occurred. However, when EPCs were introduced into the model, the proportion of hybrids in the population depended on the strength of female mate or sperm choice, the strength of male pursuit of EPCs, and habitat-induced effects on the species composition of the neighborhood. As predicted, male pursuit of EPCs caused extensive introgression, but female preference for conspecific paternity reinforced species differences. Inclusion of mitochondrial markers of species identity revealed significant effects of interspecific and intersexual behavior during EPCs on the direction of introgression. These results suggest that an alternative mating tactic may have major effects on the level of genetic homogenization and can cause local extinction of a species.     

Aminoacyl-tRNA synthetase families and their significance to the origin of the genetic code

A correlation of various aspects of the protein structures and substrate and mechanistic specificities of the aminoacyl-tRNA synthetases has led to the identification of at least one family of enzymes probably derived from a common ancestral synthetase. While strong correlations exist only in one part of the array of 64 codons comprising the Genetic Code, this itself may be interpreted as a meaningful pattern, most consistent with a development of the present code from earlier codes containing fewer amino acids and fewer available codons. Specifically, strong correlations in the enzymes whose cognate tRNAs respond to codons containing a central pyrimidine, including the enzyme family of Ile-, Phe-, Val-, Met-, and Leu-tRNA synthetases, suggests that these enzymes evolved last, and that, therefore, an earlier version of the Genetic Code was comprised solely of codons containing a central purine. It is suggested that further study of the historical interrelationships of these enzymes could lead to a fairly detailed picture of how the Genetic Code developed.     

Combined Surgical Approach to Young Adults with Hip Dysplasia and Concomitant Intra-Articular Pathology Using Intra-Abdominal Monitoring

BackgroundCombined hip arthroscopy and periacetabular osteotomy (PAO) allows for treatment of intra-articular hip pathology with simultaneous correction of acetabular version and femoral head coverage in patients with symptomatic hip dysplasia. Currently, scant data is available to surgeons regarding optimal technique, sequence of repair, perioperative management, and the use of intra-abdominal monitoring in patients undergoing these combined procedures. The purpose of this study is to describe a two-surgeon, muscle-sparing, approach for sequential hip arthroscopy and PAO for the treatment of adults with acetabular dysplasia and concomitant intra-articular hip pathology.MethodsIn this article, we present the indications for combined hip arthroscopy and PAO, in addition to patient set-up and positioning. A detailed discussion of hip arthroscopy and a muscle sparing PAO techniques are then presented, with overview of a novel intra-abdominal pressure monitoring technique and post-operative rehabilitation protocol.ResultsThrough technical refinement and experience, our indications and protocol for the treatment of patients with symptomatic acetabular dysplasia with concomitant intra-articular hip pathology involves a refined and reproducible, two surgeon procedure utilizing hip arthroscopy followed by PAO. The use of intra-abdominal monitoring allows for assessment of intra-peritoneal pressures to monitor for the development of abdominal compartment syndrome secondary to fluid extravasation.ConclusionThe performance of concomitant hip arthroscopy and PAO for concurrent hip dysplasia and intra-articular hip pathology represents an increasingly common approach in hip preservation surgery. The hip arthroscopy and muscle-sparing PAO protocol using intra-abdominal monitoring described here serves to further refine and advance the indications and technical aspects of this challenging procedure.Level of Evidence: V