Field metabolic rates and water influxes of two sympatric Gerbillidae:Gerbillus allenbyi andG. pyramidum

Summary Two primarily granivorous rodents of Old World deserts,Gerbillus allenbyi (mean adult body mass=26 g) andG. pyramidum (mean adult body mass=40 g), coexist in sandy habitats in the northwestern Negev desert. Both species are burrow dwellers and are nocturnal; however, in their overall distributions,G. pyramidum occurs in more extreme deserts than doesG. allenbyi. In comparing field metabolic rate (FMR) and water influx of the twoGerbillus species, we considered two alternative hypotheses: (1) given the difference in their overall distributions,G. pyramidum has a lower FMR and water influx thanG. allenbyi, and (2) given the similarity in their diets, and that we worked with sympatric populations, FMR and water influx are similar. The latter alternative proved to be correct. Field metabolic rates in summer were 7.29 kJ · g^-0.51 · day^-1 forG. allenbyi and 7.74 kJ · g^-0.51 · day^-1 forG. pyramidum, values that were 69.3% and 74.5%, respectively, of those predicted for rodents of their body masses. Summer water influx ofG. allenbyi was 0.167 ml · g^-0.90 · day^-1 and that ofG. pyramidum was 0.144 ml · g^-0.90 · day^-1; these values were 79.4% and 68.6%, respectively, of water influxes predicted for rodents of their body masses. When compared allometrically, there were no interspecific differences in any of the measurements.     

A Role for the Surrounding Fruit Tissues in Preventing the Germination of Tomato (Lycopersicon esculentum) Seeds : A Consideration of the Osmotic Environment and Abscisic Acid

During tomato seed development the endogenous abscisic acid (ABA) concentration peaks at about 50 d after pollination (DAP) and then declines at later stages (60-70 DAP) of maturation. The ABA concentration in the sheath tissue immediately surrounding the seed increases with time of development, whereas that of the locule declines. The water contents of the seed and fruit tissues are similar during early development (20-30 DAP), but decline in the seed tissues between 30 and 40 DAP. The water potential and the osmotic potential of the embryo are lower than that of the locular tissue after 35 DAP also. Seeds removed from the fruit at 30, 35, and 60 DAP and placed ex situ on 35 and 60 DAP sheath and locular tissue are prevented from germinating. Development of 30 DAP seeds is maintained or promoted by the ex situ fruit tissue with which they are in contact. Their germination is inhibited until subsequent transfer to water, and germination is normal, i.e. by radicle protrusion, and viable seedlings are produced, compared with 30 DAP seeds transferred directly to water; more of these seeds germinate, but by hypocotyl extension, and seedling viability is very poor. Isolated seeds at 35 and 60 DAP re-placed in contact with fruit tissues only germinate when transferred to water after 7 d. At 30 DAP, isolated seeds are insensitive to ABA at physiological concentrations in that they germinate as if on water, albeit by hypocotyl extension. At higher concentrations germination occurs by radicle protrusion. Osmoticum prevents germination, but there is some recovery upon subsequent transfer to water. Seeds at 35 DAP are very sensitive to ABA and exhibit little or no germination, even upon transfer to water. The response of the isolated seeds to osmoticum more closely approximates that to incubation on the ex situ fruit tissues than does their response to ABA. This is also the case for isolated 60 DAP seeds, whose germination is not prevented by ABA, but only by the osmoticum; these seeds are inhibited when in contact with ex situ fruit tissues also. It is proposed that the osmotic environment within the tissues of the tomato fruit plays a greater role than endogenous ABA in preventing precocious germination of the developing seeds.     

Expression of the mosquitocidal toxins of Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis by recombinant Caulobacter crescentus, a vehicle for biological control of aquatic insect larvae.

In the quest for effective control of mosquitoes, attention has turned increasingly to strains of the bacteria Bacillus sphaericus and Bacillus thuringiensis subsp. israelensis, which produce potent toxins with specific mosquitocidal activities. However, sedimentation of the bacterial spores limits the duration of effective control after field application of these bacilli. We describe here the cloning of genes encoding the 51.4- and 41.9-kDa toxins from B. sphaericus 2297, the 100-kDa toxin from B. sphaericus SSII-1, and the 130-kDa toxin from B. thuringiensis subsp. israelensis into the broad-host-range plasmid pRK248 and the transfer of these genes for expression in Caulobacter crescentus CB15. The recombinant C. crescentus cells were shown to be toxic to mosquito larvae. Caulobacter species are ubiquitous microorganisms residing in the upper regions of aquatic environments and therefore provide the potential for prolonged control by maintaining mosquitocidal toxins in larval feeding zones.     

Distribution of alginate gene sequences in the Pseudomonas rRNA homology group I-Azomonas-Azotobacter lineage of superfamily B procaryotes.

Chromosomal DNA from group I Pseudomonas species, Azotobacter vinelandii, Azomonas macrocytogens, Xanthomonas campestris, Serpens flexibilis, and three enteric bacteria was screened for sequences homologous to four Pseudomonas aeruginosa alginate (alg) genes (algA, pmm, algD, and algR1). All the group I Pseudomonas species tested (including alginate producers and nonproducers) contained sequences homologous to all the P. aeruginosa alg genes used as probes, with the exception of P. stutzeri, which lacked algD. Azotobacter vinelandii also contained sequences homologous to all the alg gene probes tested, while Azomonas macrocytogenes DNA showed homology to all but algD. X. campestris contained sequences homologous to pmm and algR1 but not to algA or algD. The helical bacterium S. flexibilis showed homology to the algR1 gene, suggesting that an environmentally responsive regulatory gene similar to algR1 exists in S. flexibilis. Escherichia coli showed homology to the algD and algR1 genes, while Salmonella typhimurium and Klebsiella pneumoniae failed to show homology with any of the P. aeruginosa alg genes. Since all the organisms tested are superfamily B procaryotes, these results suggest that within superfamily B, the alginate genes are distributed throughout the Pseudomonas group I-Azotobacter-Azomonas lineage, while only some alg genes have been retained in the Pseudomonas group V (Xanthomonas) and enteric lineages.     

Problems associated with the use of tetraethylammonium to test for monosynaptic connexions.

Several investigators of the molluscan nervous system have used TEA, injected into presynptic neurones, to determine whether the connexions made by these neurones are monosynaptic. The increase in spike duration produced by the TEA causes an increase in transmitter release, and hence an increase in the amplitude of the postsynaptic potential if the connexion is direct. If the connexion is indirect, the spike in an intercalated neurone will not be affected by the TEA, and the postsynaptic response will remain constant. Experiments described here show that TEA can cross electrotonic junctions in the gastropod mollusc Planorbis corneus. They also show that each TEA-prolonged presynaptic impulse may produce more than one postsynaptic impulse. A larger postsynaptic potential could therefore be produced by presynaptic injection of TEA in the case of an indirect connexion. This indicates that care must be taken when interpreting the results of experiments using TEA to test for monosynaptic connexions.     

Facies distribution patterns of some marine benthic faunas in early paleozoic platform environments

Worldwide Late Cambrian—Silurian lithofacies patterns indicate that the platforms of that time were sites of accumulation of two essentially different rocks suites: the platform carbonate rocks and the platform terrigenous rocks. Most of the platform rocks accumulated as sediments in shallow marine environments similar to those of the present but far more widely spread.Present-day marine benthic faunas are distributed in depth zones which are primarily controlled by temperature. Faunas tend to occur in substrate-related discrete clusters (communities) within each life zone; similar substrates in different depth zones commonly have different faunal associations. Individual phyletic stocks may encounter environmental optimum or near-optimum conditions in certain areas, that commonly are revealed by an abundance of species and individuals within species in each stock. Environmental optimum conditions depend upon availability of food that may be utilized, modes of feeding of the animals present, water motion, and substrate, among other factors. Organisms in past seas were distributed in patterns similar to those of the present.Carbonate platforms were particularly widespread during the latest Cambrian—Early Ordovician. Intertidal environments spread widely across those platforms during that time and characteristic faunal associations developed in them. Saukiid and related tribolites dominated latest Cambrian carbonate platform intertidal faunas. The Early Ordovician carbonate platform intertidal was dominated by archeogastropod-nautiloid cephalopod faunas. These animals were joined by tabulate corals and certain brachiopods during the latter part of the Ordovician and Silurian as prominent faunal elements in the carbonate platform intertidal—shallow subtidal. Cruziana and related trace fossils, bivalves, and certain tribolites (notably homalonotids and dalmanitids) dominated most terrigenous platform intertidal—shallow subtidal faunas of the Ordovician and Silurian.Articulate brachiopods (primarily orthoids, strophomenoids, and rhynchonelloids) appear to have been relatively prominent during the Early Ordovician in shallow subtidal environments on both carbonate and terrigenous platforms and to have spread down the bathymetric gradient into increasingly deeper subtidal areas of both platforms during the latter part of the Ordovician. Tribolites dominated faunas in relatively moderate to deep subtidal environments on both platforms during the early part of the Ordovician. They were gradually replaced by brachiopods in first the shallower, and later the deeper subtidal as dominant members of the faunas. Brachiopods (primarily pentameroids and spiriferoids) dominated nearly all Silurian warm-water subtidal environments from the shallow subtidal to the edges of the platforms.Platform uplifts in the Middle Ordovician and glacio-eustatic sea-level fluctuations in the Late Ordovician caused environmental changes across the platforms that were accompanied by marked replacements among marine benthic faunas in all environments. The distribution of Ordovician carbonate platforms and glacial deposits suggests that an Ordovician polar region may have been close to present-day equatorial Africa and that Ordovician warm temperate-tropical regions lay close to the present-day North Pole.     

REGIONAL DISTRIBUTION OF AMINO ACIDS IN HUMAN BRAIN OBTAINED AT AUTOPSY

Abstract— Contents (μmol/g wet wt.) of 35 free amino acids and related compounds were measured in 12 different regions of each of five human brains. Specimens were obtained at autopsy from patients who died suddenly without previous brain disease. These data may serve for later comparison with contents of amino compounds in similar regions of the brains of patients dying with various neurological or psychiatric disorders.
There were marked and consistent differences in the regional distribution of the following eight compounds: γ-aminobutyric acid, homocarnosine, glutamic acid, aspartic acid, taurine, cystathionine, glycerophosphoethanolamine, and phosphoethanolamine. These differences suggest that some of these compounds may have special physiological roles, including the possible mediation of synaptic transmission.
Human brain contains two previously unreported compounds, the mixed disulphide of cysteine and glutathione and α-(γ-aminobutyryl)-lysine. The latter dipeptide occurs in much higher concentrations in human brain than in the brains of lower mammals.