Age Structure and Community Diversity of Nematodes Associated with Maize in Iowa Sandy Soils

Age structure of nematode populations around maize growing in sandy soils in Iowa was studied at soil depths of 0-15and 15-30 cm for 2 years. Numbers of Longidorus breviannulatus were generally greater at 0-15 cm than at 15-30 cm deep until mid to late season. The decline in numbers of females as the season progressed indicates that fecundity slowed and is evidence of only one generation per year. Peak populations of Pratylenchus scribneri and Xiphinema americanum occurred in late August or early September. Adults of Hoplolaimus galeatus were few in the roots but common in the soil, indicating that fertilization occurred mostly in the soil. Numbers of P. scribneri were generally greater at the lower depth, especially late in the season. Community diversity (H'') was less when nematode biomass was used instead of numbers. Numbers of H. galeatus did not decline over the winter. Numbers of L. breviannulatus, P. scribneri, and X. americanum declined significantly over the winter, but not between spring cultivation and planting.     

Attachment and multiplication,morphology and protein production of human fetal primary liver cells cultured in hormonally defined media

In Vitro Cellular &; Developmental Biology - Plant -     

Levels of chromosomally encoded Umu proteins and requirements for in vivo UmuD cleavage

Summary Most of the inducible mutagenesis observed in Escherichia coli after treatment with many DNA damaging agents is dependent upon the products of the umuD,C operon. RecA-mediated proteolytic processing of UmuD yields a carboxyl-terminal fragment (UmuD) that is active for mutagenesis. Processing of UmuD is therefore a critical step in the fixation of mutations. In this paper we have analyzed the requirements for UmuD processing in vivo. Standard immuno-detection assays, coupled with a sensitive chemiluminescence detection assay, have been utilized to probe levels of chromosomally encoded Umu proteins from whole-cell E. coli extracts. We found that the derepression of additional SOS gene products, other than RecA, was not required for UmuD processing. Moreover, efficient cleavage of UmuD was observed only in the presence of elevated levels of activated RecA, suggesting that efficient processing would occur only under conditions of severe DNA damage. Detection of chromosomally encoded Umu proteins has allowed us, for the first time, to measure directly the cellular steady-state levels of these proteins under various SOS inducing conditions. UmuD was present at 180 copies per uninduced cell and was measured at 2400 copies per cell in strains that lacked a functional repressor. Induced levels of UmuC were approximately 12-fold lower than UmuD with 200 molecules per cell. These levels of cellular UmuC protein suggest that it functions through specific protein-DNA or protein-protein interactions, possibly as a lesion recognition protein or by interacting with DNA polymerase III.     

Sexual dimorphism in the early Miocene species ofProconsul from the Kisingiri Formation of east Africa: A morphometric examination using multivariate statistics

This paper examines the pattern(s) of sexual dimorphism within the upper dentition ofProconsul specimens from the early Miocene of east Africa. These fossils are compared against the corresponding dentition ofPan troglodytes andGorilla gorilla using principal components and cluster analyses. This paper demonstrates that both sexes ofPan andGorilla are characterized by their own distinctive shape patterns. It is also demonstrated that someProconsul specimens examined here display a pattern that is dissimilar from otherProconsul specimens also examined. This suggests that at least two species ofProconsul may have to be recognized as having lived in this region during the early Miocene. The identification of distinct patterns withinProconsul also suggests that their overall shape and size range are more similar toPan than toGorilla.     

Control of Enterococcus faecalis sex pheromone cAD1 elaboration: Effects of culture aeration and pAD1 plasmid-encoded determinants

Aeration of plasmid-free Enterococcus faecalis strains resulted in an 8- to 16-fold decrease in sex pheromone cAD1 activity in culture filtrates. Levels of two unrelated pheromones, cPD1 and cAM373, were unaffected by culture aeration. Aeration also resulted in a decrease in the expression of conjugative transfer functions observed in cells containing pAD1 traB mutations, verifying a link between traB function and pheromone “shutdown.” Tests with a series of pAD1 mini-plasmids indicated that the product of the traB gene was involved in, but not sufficient for, pheromone shutdown; the cooperation of one or more other gene products encoded within the pheromone response control region was required.     

Purification of ribulose 1,5-bisphosphate carboxylase/oxygenase and of carboxysomes from Thiobacillus thyasiris the putative symbiont of Thyasira flexuosa (Montagu)

The bacterial symbionts of many marine invertebrates contain ribulose 1,5-bisphosphate (RuBP) carboxylase but apparently no carboxysomes, polyhedral bodies containing RuBP carboxylase. In the few cases where polyhedral bodies have been observed they have not been characterised enzymatically. Polyhedral bodies, 50–90 nm in diameter, were observed in thin cell sections of Thiobacillus thyasiris the putative symbiont of Thyasira flexuosa and RuBP carboxylase activity was detected in both soluble and particulate fractions after centrifugation of cell-free extracts. RuBP carboxylase purified 90-fold from the soluble fraction was of high molecular weight and consisted of large and small subunits, with molecular weights of 53,110 and 11,100 respectively. Particulate RuBP carboxylase activity was associated with polyhedral bodies 50–100 nm in diameter, as revealed by density gradient centrifugation and electron microscopy. Therefore, the polyhedral bodies were inferred to be carboxysomes. Native electrophoresis of isolated carboxysomes demonstrated a major band which comigrated with the purified RuBP carboxylase and three minor bands of lower molecular weight. Sodium dodecyl-sulphate (SDS) gel electrophoresis of SDS-dissociated carboxysomes demonstrated nine major polypeptides two of which were the large and small subunits of RuBP carboxylase. The RuBP carboxylase subunits represented 21% of the total carboxysomal protein. The most abundant polypeptide had a molecular weight of 40,500. Knowledge of carboxysome composition is necessary to provide an understanding of carboxysome function.Abbreviations FPLC fast performance liquid chromatography - IB isolation buffer - PAGE polyacrylamide gel electrophoresis - RuBP carboxylase - ribulose 1,5-bisphosphate carboxylase/oxygenase - SDS sodium dodecyl-sulphate     

The bacteriophage Mu transposase protein can form high-affinity protein-DNA complexes with the ends of transposable elements of the Tn 3 family

The 37 kb transposable bacteriophage Mu genome encodes a transposase protein which can recognize and bind to a consensus sequence repeated three times at each extremity of its genome. A subset of this consensus sequence (5'-PuCGAAA(A)-3') is found in the ends of many class II prokaryotic transposable elements. These elements, like phage Mu, cause 5 bp duplications at the site of element insertion, and transpose by a cointegrate mechanism. Using the band retardation assay, we have found that crude protein extracts containing overexpressed Mu transposase can form high-affinity protein-DNA complexes with Mu att R and the ends of the class II elements Tn 3 (right) and IS101. No significant protein-DNA complex formation was observed with DNA fragments containing the right end of the element IS102, or a non-specific pBR322 fragment of similar size. These results suggest that the Mu transposase protein can specifically recognize the ends of other class II transposable elements and that these elements may be evolutionarily related.