Experiments on the carboxylase of pea roots

It is known that vitamin B1 is a growth factor for numerous bacteria and fungi including the yeasts (see the summary in Koser and Saunders (1938)). It has also been demonstrated that vitamin B1 is essential for the growth of the isolated roots of higher plants (Bonner, 1937; Robbins and Bartley, 1937). Because of this general vitamin B1 requirement of living organisms, it would seem a priori probable that the vitamin plays a role in some basic cellular process. That this is indeed the case was shown conclusively by the work of Peters and coworkers (see Peters and O’Brien (1938)) and of Lohmann and Schuster (1937). The latter workers found that the prosthetic group of yeast carboxylase is vitamin B1 pyrophosphate. In the case of yeast, vitamin B1 is, then, a constituent of a respiratory enzyme and vitamin B1 pyrophosphate is hence commonly referred to as “cocarboxylase,” a terminology used throughout this paper. Although considerable information is available concerning the rôle of vitamin B1 as a growth factor for roots, there is little known about the carboxylase of such roots. The present work was undertaken with the hope of elucidating possible relationships between vitamin B1 and the carboxylase of pea roots

Inhibitor specificity of amine oxidase

Although at the present time it appears clear that amine oxidase oxidation of adrenalin, or other o-diphenolic pressor amines such as were studied by Richter (6), does not play a significant physiological role, it is equally clear that the inactivation of aliphatic amines, phenethylamine and probably 4-hydroxyphenethylamine (tyramine), does predominantly take place by amine oxidase oxidation. In view of the evidence from the experiments of Ewins and Laidlaw (8) and a later study by Guggenheim and Löffler (9), such amine oxidations chiefly occur in the liver. In the present studies, an attempt was made to value quantitatively the inhibition of some of these particular type compounds by certain types of amines which are not themselves oxidized by the enzyme system (see Alles and Heegaard (10))

Substrate specificity of amine oxidase

The tyramine oxidase activity of liver extracts found by Hare (1), the aliphatic amine oxidase activity of brain, kidney, and liver extracts observed by Pugh and Quastel (2), and the adrenalin oxidase activity of similar extracts noted by Blaschko, Richter, and Schlossman (3) were brought under a common enzyme view-point by the latter authors. They were able to show (4) that extracts of brain, instestine, kindey, and liver from a number of mammals or representatives of the birds, reptiles, amphibians, and fishes all acted to absorb oxygen in the presence of several amine substrates. Hare (1) had shown that tyramine and phenethylamine form ammonia in the course of such oxidations, and Richter (5) showed that an ethylamino and a dimethylamino compound, as well as a number of methylamino and amino compounds, all yield the corresponding alkyl-amines or ammonia in the enzymic oxidation. The conslusion that the demonstrated variey of such enzymic activity can be acribed to the presence of a single type pf amine oxidase was dependent in large part on observations that the relative activities of a preparation from one source on a series of substrates bear some relation to the relative activities exhibited by a preparation from another source. Further evidence depended on the action of certain amines as inihibitors and apparent competition between substrates when two oxidizable substrates are present in the system. The degree to which relative activities of different enzyme preparations were constant in a series of substrates was not good in the data reported, and the fact that Hare (1) had not been able to note activity of the liver preparations she used upon adrenalin as the substrate appeared to require special explanations

A visit to Gunung Nyiut in West Kalimantan

Almost no ornithological fieldwork has been done in the montane regions of Kalimantan in recent decades (Holmes & Burton 1987). We spent 10 days from 28 August to 6 September 1986 observing birds in Gunung Nyiut Wildlife Refuge, West Kalimantan (110(1 E, 1°N) and hope that our records . will contribute to the distributional knowledge of the avifauna of Borneo

Impact of SDN Controllers Deployment on Network Availability

Software-defined networking (SDN) promises to improve the programmability and flexibility of networks, but it may bring also new challenges that need to be explored. The purpose of this technical report is to assess how the deployment of the SDN controllers affects the overall availability of SDN. For this, we have varied the number, homing and location of SDN controllers. A two-level modelling approach that is used to evaluate the availability of the studied scenarios. Our results show how network operators can use the approach to find the optimal cost implied by the connectivity of the SDN control platform by keeping high levels of availability.Comment: Department of Telematics, NTNU, Tech. Rep., March 201

The birds of Bukit Tigapuluh, Southern Riau, Sumatra

A study was made of the avifauna of the Bukit Tigapuluh area in Riau and Jambi Provinces, Sumatra in July-September 1991. This is the first major study of the lowland bird fauna of mainland Riau in this century. A total of 193 bird species was recorded, including 18 species listed as globally threatened. Extensions to known ranges were made for 26 species of which 25 were new to Riau and 3 to Jambi- Data were also provided on 5 species for which there were no recent Sumatran records: Crestless Fireback Pheasant Lophura erythropthalma. Garnet Pitta Pitta granatina, Striped Wren-babbler Kenopia striata. Large Wren-babbler Napothera macrodactyla and Chestnut-capped Thrush Zoothera interpres. In addition, information on breeding was provided for 51 species, of which 22 species were not previously documented to breed in Sumatra

Effects of simulated environmental changes on growth and growth form in a late snowbed population of pohlia wahlenbergii (Web. et Mohr) Andr

In a factorial field experiment we increased the temperature (OpenTop Chambers) and nutrients (nitrogen, phosphorus, and potassium[NPK]) to simulate predicted future climate changes and studiedthe growth response of the acrocarpous bryophyte Pohliawahlenbergii (Bryaceae) in a wet snowbed environment. The speciesshows a positive growth-length response to added nutrients andincreased temperature. The stronger response to nutrientsindicates a strong limitation of nutrients in the snowbedenvironment. There was an immediate response to nutrienttreatment, whereas the temperature response was delayed. Thegrowth response shows a clear interaction between temperature andnutrients. The immediate positive growth response is interpretedas a function of the wet habitat, since water makes the addednutrients immediately available to the plants. The growth formchanged toward a more lax (loose) and desiccation-intolerant formwith added nutrients. In a climate change scenario based on theseresults we hypothesize that bryophyte response will depend on thewater availability from precipitation and from meltwater. In adrier environment we predict that bryophytes will become moreconstrained toward areas with a high continuity of meltwater,whereas increased precipitation may compensate for any changes ingrowth form, which would be positive for bryophytes