Subgroups in theHordeum patagonicum complex (Poaceae)

Seeds of theHordeum patagonicum complex were collected from the field and grown in the greenhouse. The aim was to take a sample of members of the complex, and on the basis of the phenotypic similarities in some morphological and physiological characters, determine whether distinct groups exist. When cluster analyses, to generate hypotheses, and orthodox statistical procedures, for hypotheses obtained a priori, were applied to the reproductive morphology, germination and flowering patterns, onlyH. patagonicum subsp.magellanicum, out of the five recognized taxa, could be distinguished consistently. The remaining four taxa, which overlapped considerably, could be re-formed into three groups whose centroids were different but whose ranges of variation were not distinct from each other. We conclude that the highly cross-compatible members of theH. patagonicum complex, first defined as species and later redefined as subspecies are probably no more than biotypes.     

Analytical determination of orthophosphate in water

Methods for orthophosphate determination and the problems of interferences are reviewed.An important group of methods utilizes the phosphomolybdate complex. The complexation step, the reduction step and the extraction step are treated separately and alternative procedures compared.Another group of methods uses ion association complexes; they are primarily used in physiology and not commonly used in water analyses today.Enzymatic methods for orthophosphate analysis in natural waters have been developed lately and are ready for application in selected waterbodies.Flame spectroscopic, fluorometric, gas chromatographic, ion exclusion chromatographic, inductively coupled plasma and other methods are also shortly presented.Radiobiological bioassays for orthophosphate are also available.In conclusion it was emphasized that the most common and reliable technique still is the molybdenum blue method as modified by Murphy & Riley (1962).The need for more specific and sensitive methods is particularly strong in investigations of phosphorus turnover and phosphorus limitation in natural waters. For these purposes the enzymatic phosphatase methods has advantages due to their specificity for orthophosphate and they might offer an alternative to the molybdenum blue method.     

The determination of fresh organic carbon weight from formaldehyde preserved macrofaunal samples

Methodologies are presented whereby the fresh organic carbon weight of formaldehyde preserved macrofaunal samples may be estimated. Length-organic carbon weight regressions were determined for the four numerically dominant bivalves in Narragansett Bay, Rhode Island (Nucula annulata, Yoldia limatula, Mulinia lateralis, and Pandora gouldiana) and one commercially important, but less abundant species (Mercenaria mercenaria). Constants were determined to convert the dry weight of preserved softbodied organisms (polychaetes, oligochaetes, amphipods, etc.) to fresh (unpreserved) organic carbon weight. These results can be used by investigators studying the energetics of benthic communities similar to those in Narragansett Bay.     

Restriction endonuclease mapping of ribosomal RNA genes: Sequence divergence and the origin of the tetraploid treefrog Hyla versicolor

Hyla chrysoscelis (2n=24) and H. versicolor (2n=48) are a diploid-tetraploid species pair of treefrogs. Restriction endonuclease mapping of ribosomal RNA (rRNA) gene repeat units of diploids collected from eastern and western populations reveals no differences within rRNA gene coding regions but distinctive differences within the nontranscribed spacers. A minimum of two physical maps is required to construct an rRNA gene map for the tetraploid, whose repeat units appear to be a composite, with about 50% of the elements resembling the western diploid population and about 50% resembling the eastern population. These results imply that this population of the tetraploid species may have arisen from a genetically hybrid diploid. Alternatively, the dual level of sequence heterogeneity in H. versicolor may reflect some type of gene flow between the two species. The coding region of the rRNA genes in the tetraploid differs from that in either diploid in about 20% of all repeat units, as exemplified by a BamHI site located near the 5 terminus of the 28 S rRNA gene. If the 20% variant class of 28 S rRNA gene coding sequences is expressed, then there must be two structural classes of ribosomes; if only the 80% sequence class is expressed, then a genetic control mechanism must be capable of distinguishing between the two different sequence variants. It is postulated that the 20% variant sequence class may be correlated with a partial functional diploidization of rRNA genes in the tetraploid species.This research was supported, in part, by NSF Grants CDP-8002341 and PRM-8106947 and by faculty research grants from Miami University to J.C.V.     

The number of nucleotides required to determine the branching order of three species,with special reference to the human-chimpanzee-gorilla divergence

Summary A mathematical theory for computing the probabilities of various nucleotide configurations among related species is developed, and the probability of obtaining the correct tree (topology) from nucleotide sequence data is evaluated using models of evolutionary trees that are close to the tree of mitochondrial DNAs from human, chimpanzee, gorilla, orangutan, and gibbon. Special attention is given to the number of nucleotides required to resolve the branching order among the three most closely related organisms (human, chimpanzee, and gorilla). If the extent of DNA divergence is close to that obtained by Brown et al. for mitochondrial DNA and if sequence data are available only for the three most closely related organisms, the number of nucleotides (m^*) required to obtain the correct tree with a probability of 95% is about 4700. If sequence data for two outgroup species (orangutan and gibbon) are available, m^* becomes about 2600–2700 when the transformed distance, distance-Wagner, maximum parsimony, or compatibility method is used. In the unweighted pair-group method, m^* is not affected by the availability of data from outgroup species. When these five different tree-making methods, as well as Fitch and Margoliash's method, are applied to the mitochondrial DNA data (1834 bp) obtained by Brown et al. and by Hixson and Brown, they all give the same phylogenetic tree, in which human and chimpanzee are most closely related. However, the trees considered here are gene trees, and to obtain the correct species tree, sequence data for several independent loci must be used.     

Enhanced Phosphorylation of Tyrosine Hydroxylase at More Than One Site Is Induced by 56 mM K+ in Rat Pheochromocytoma PC 12 Cells in Culture

Incubation of rat pheochromocytoma PC12 cells with dibutyryl cyclic AMP or 56 mM K+ is associated with increased activity and enhanced phosphorylation of tyrosine hydroxylase in situ. Following incubation of the PC12 cells with 32Pi, rapid isolation of the tyrosine hydroxylase, and tryptic digestion of the enzyme, two distinct 32P-peptides can be identified after paper electrophoresis. 56 mM K+ increases 32Pi incorporation into both of these peptides, whereas dibutyryl cyclic AMP increases 32Pi incorporation into only one of these peptides. The rate of increase in the incorporation of 32Pi into these two peptides in cells treated with 56 mM K+ is similar. The phosphorylation of tyrosine hydroxylase in PC12 cells occurs exclusively on serine residues. These results suggest that tyrosine hydroxylase in PC12 cells is phosphorylated on serine residues at two or more distinct sites after 56 mM K+ -induced depolarization. Since only one of these sites is phosphorylated by cyclic AMP-dependent protein kinase, activation of tyrosine hydroxylase by 56 mM K+ may involve phosphorylation by multiple protein kinases in rat pheochromocytoma PC12 cells.     

Distribution and analysis of plasmids inStreptococcus thermophilus

Summary In a survey of 35 strains ofStreptococcus thermophilus, 13 strains were found to harbor plasmid DNA. Most of these strains contained plasmid species varying in size from 2.2 to 7.15 kilobases. Only three strains had more than one plasmid species. Each of the nine distinct types of plasmid DNAs identified had two or more unique recognition sites for restriction endonucleases. The characteristics of the indigenous cryptic plasmids ofS. thermophilus may allow their development as cloning vectors useful in the genetic engineering of this species and other streptococci that are important in food production     

Seasonal Fluctuations of Globodera tabacum solanacearum as Estimated by Two Soil Extraction Techniques

Two soil extraction methods were compared to determine their efficiency in recovering cysts and juveniles of a tobacco cyst nematode, Globodera tabacum solanacearum. The methods were equally efficient when extracting nematodes from soil samples seeded in the laboratory; however, there was a significant extraction method × month interaction when the methods were used to estimate field soil populations over 2 years. The centrifugal sugar flotation method recovered greater numbers of cysts when densities were near 400 cysts/100 cm³ soil and greater numbers of juveniles in all samples. The sugar flotation method recovered greater numbers of cysts during months when densities were less than 400 cysts/100 cm³ soil. Numbers of cysts and juveniles were lowest in June and July following land tillage in May. A soil freeze in January 1982 may have been responsible for unusually high numbers of recovered cysts in February and March 1982, a pattern that did not occur in 1983.     

Development of a high-frequency transforming vector for Aspergillus nidulans

The pyr4 gene of Neurospora crassa, which codes for orotidine-5'-phosphate decarboxylase, is capable of transforming an Aspergillus nidulans pyrG mutant by chromosomal integration, despite low homology between the transforming DNA and the recipient genome. Integration of pFB6, a plasmid carrying pyr4 and capable of replication in Escherichia coli, was not observed at the pyrG locus. The efficiency of transformation was considerably enhanced (50-100 fold) by inclusion in the transforming vector of a 3.5-kb A.nidulans chromosomal sequence, ans1. Although this sequence was isolated on the basis of replicating activity in Saccharomyces cerevisiae, there was no evidence for such activity in A.nidulans. Part of the ans1 fragment appears to be reiterated in the A.nidulans genome, though it is not yet clear whether this is directly responsible for the high transformation frequency. The efficiency of transformation of A.nidulans by plasmids bearing ans1, using an improved protocol, was approx. 5 X 10(3) stable transformants per microgram of plasmid DNA.