Cloning of the Zea mays controlling element Ac from the wx-m7 allele

Summary The cloning of the controlling element Ac from the wx-m7 allele of Zea mays is described. The cloned fragment carries a 4.3 kb insertion that by restriction analysis is indistinguishable from the Ac insertion in Ac wx-m9. It is located approximately 2.5 kb upstream of the Ac wx-m9 insertion. Offprint requests to: P. Starlinger     

Influence of Nutrient Concentrations on MPN Quantification and Enrichment of Nitrate-Reducing Fe(II)-Oxidizing and Fe(III)-Reducing Bacteria from Littoral Freshwater Lake Sediments

The application of culture-dependent studies to quantify Fe-metabolizing microorganisms from the environment is a necessity, as there are so far no universal functional marker genes for application in culture-independent studies. Media composition can vary between studies, therefore, we determined the effects of three different growth media on the quantification (MPNs) and identity (via cloning and sequencing of dominant DGGE bands) of nitrate-reducing Fe(II)-oxidizers and lactate- or acetate-oxidizing Fe(III)-reducers from a lacustrine sediment: low sulphate freshwater medium (FWM), sterile filtered bicarbonate-buffered lake water (BLW) and a mixture of both (MIX). We consistently found fewer cells in the BLW than in the FWM and the MIX. The DGGE banding patterns of the microbial communities enriched in different media types clustered together according to the e^? donor and acceptor couples and not according to the medium used. Thus, although the medium composition significantly influenced the quantification and thereby conclusions on the abundance and potential significance of the targeted group within the ecosystem, biodiversity assessments through enrichment cultures were less influenced by the medium, but instead were affected by the type and concentration of the e^? donor/acceptor.     

Organization of multispecific DNA methyltransferases encoded by temperate Bacillus subtilis phages.

B. subtilis phage rho 11s codes for a multispecific DNA methyltransferase (Mtase) which methylates cytosine within the sequences GGCC and GAGCTC. The Mtase gene of rho 11s was isolated and sequenced. It has 1509 bp, corresponding to 503 amino acids (aa). The enzyme's Mr of 57.2 kd predicted from the nucleotide sequence was verified by direct Mr determinations of the Mtase. A comparison of the aa sequence of the rho 11s Mtase with those of related phages SPR and phi 3%, which differ in their methylation potential, revealed generalities in the building plan of such enzymes. At least 70% of the aa of each enzyme are contained in two regions of 243 and 109 aa at the N and C termini respectively, which are highly conserved among the three enzymes. In each enzyme, variable sequences separate the conserved regions. Variability is generated through the single or multiple use of related and unrelated sequence motifs. We propose that the recognition of those DNA target sequences, which are unique for each of the three enzymes, is determined by these variable regions. Evolutionary relationships between the three enzymes are discussed.     

A method for assaying orotate phosphoribosyltransferase and measuring phosphoribosylpyrophosphate

An orotate phosphoribosyltransferase, OPRTase, assay method which relies upon binding reactant [3H]orotic acid and product [3H]orotidine-5'-monophosphate to polyethyleneimine-impregnated-cellulose resin and collecting on a GFC glass fiber filter is presented. Elution with 2 X 5 ml of 0.1 M sodium chloride in 5 mM ammonium acetate removes all of the orotate and leaves all of the product orotidine monophosphate (OMP) bound so that it may be measured in a scintillation counter. It was found that the addition of 10 microM barbituric acid riboside monophosphate to the reaction mixture prevented the conversion of OMP to UMP and products of UMP. The assay is suitable for measurement of OPRTase activity with purified enzyme or in crude homogenates. A modification of this scheme using commercially available yeast OPRTase and 10 microM of unlabeled OMP provides an assay for phosphoribosylpyrophosphate with a sensitivity such that 10 pmol of PRPP may be measured.     

Leydig cell mitoses in human testes bearing early germ cell tumors

Summary Numerous mitoses were noted in testicular tissue from adult men with early germ cell tumors. More than 15 Leydig cells undergoing mitosis were found in the interstitial compartment. The presence of specific crystalline intracytoplasmatic inclusions demonstrated for the first time that differentiated Leydig cells are capable of proliferation. Occasionally cells are difficult to discriminate during mitosis. To establish reference criteria, the light- and electron-microscopic features of the following mitotic cells were examined: Leydig cells, fibroblasts, perivascular cells, peritubular cells, and lymphocytes. Supplementary mitoses in germ cell tumors and in a case of Leydig cell tumor were investigated. In the literature, only single reports of mitoses in Leydig cells are available. The frequent incidence of Leydig cell mitosis in early germ cell tumors may be due to the presence of growth-promoting factors in the testicular tissue.     

EPR characterization of the iron-sulfur-containing NADH-ubiquinone oxidoreductase of the Escherichia coli aerobic respiratory chain

The energy coupled NADH-ubiquinone (Q) oxidoreductase segment of the respiratory chain of Escherichia coli GR19N has been studied by EPR spectroscopy. Previously Matsushita et al. [(1987) Biochemistry 26, 7732-7737] have demonstrated the presence of two distinct NADH-Q oxidoreductases in E. coli membrane particles and designated them NADH dh I and NADH dh II. Although both enzymes oxidize NADH, only NADH dh I is coupled to the formation of the H+ electrochemical gradient. In addition to NADH, NADH dh I oxidizes nicotinamide hypoxanthine dinucleotide (deamino-NADH), while NADH dh II does not. In membrane particles we have detected EPR signals arising from four low-potential iron-sulfur clusters, one binuclear, one tetranuclear, and two fast spin relaxing g perpendicular = 1.94 type clusters (whose cluster structure has not yet been assigned). The binuclear cluster, temporarily designated [N-1]E, shows an EPR spectrum with gx,y,z = 1.92, 1.935, 2.03 and the Em7.4 value of -220 mV (n = 1). The tetranuclear cluster, [N-2]E, elicits a spectrum with gx,y,z = 1.90, 1.91, 2.05 and an Em7.4 of -240 mV (n = 1). These two clusters have been shown to be part of the NADH dh I complex by stability and inhibitor studies. When stored at 4 degrees C, both clusters are extremely labile as is the deamino-NADH-Q oxidoreductase activity. Addition of deamino-NADH in the presence of piericidin A results in nearly full reduction of [N-2]E within 17 s. In membrane particles pretreated with piericidin A, the cluster [N-1]E is only partly reducible by deamino-NADH and shows an altered line shape.(ABSTRACT TRUNCATED AT 250 WORDS)     

New ecological information onScytalina cerdale (Pisces: Scytalinidae) from a central California rocky intertidal zone

Synopsis New information regarding the ecology ofScytalina cerdale was obtained over a four year period as a consequence of a long-term marine ecological study at the Diablo Canyon Power Plant (DCPP), San Luis Obispo County, California. Twenty intertidal fish surveys were conducted at approximately quarterly intervals, between March 1979 and June 1983, at three separate rocky shore locations (stations). During each survey, a total of 108 square meters (36 m² per station) was searched for fish during periods of low tide. A total of 280S. cerdale were collected, identified, measured, and released back into the same 4 m² area, from the same intertidal station (Diablo Cove), throughout the study period. This limited intertidal occurrence most likely reflectsS. cerdale microhabitat requirements; a combination of intertidal elevation (mean = +0.3 MLLW), substratum specificity (loose gravel, 5–10mm size range, overlying a base of sand and shell fragments), and degree of wave exposure (semi-protected). Throughout the study,S. cerdale was seasonally more abundant during summer months (June through August) and less abundant during winter months (November through February). The only exception to this abundance trend followed the 1982 winter storms, which coincided with an El Niño event, whenS. cerdale abundance uncharacteristically dropped during the subsequent 1983 spring and summer surveys. Mean total lengths did not vary greatly, reflecting the absence of early juvenile fishes, and relatively high mean fish densities (3.5 fish per m² for 20 surveys) were recorded. Qualitative comparisons betweenS. cerdale abundance and seasonal changes in water temperature indicated an inverse relationship. Gravid females, demersal egg masses, and early juvenile individuals were never observed during the four years of the study. This suggests that unlike most other intertidal fishes, particularly other blennioids,S. cerdale may not utilize the intertidal zone for reproductive and recruitment purposes; Diablo Canyon is the most southerly reported distribution for this intertidal species, and therefore, may not entirely represent the species' biology as a whole.     

Sequential order of target-recognizing domains in multispecific DNA-methyltransferases.

In the multispecific DNA(cytosine-5)-methyltransferases (Mtases) of Bacillus subtilis phages SPR and phi 3T the domains responsible for recognition of DNA methylation targets CCA/TGG, CCGG, GGCC (SPR) and GCNGC, GGCC (phi 3T) represent contiguous sequences of approximately 50 amino acids each. These domains are tandemly arranged and do not overlap. They are part of a 'variable' segment within the enzymes which is flanked by 'conserved' amino acids, which are very similar amongst bacterial monospecific and the multispecific Mtases studied here. These results follow from a mutational analysis of the SPR and phi 3T Mtase genes. They further support our concept of a modular enzyme organization, according to which variability of type II Mtases with respect to target recognition is achieved by a combination of the same enzyme core with a variety of target-recognizing domains.     

Labor specialization and the formation of markets for food in a Shipibo subsistence economy

Traditionally, the Shipibo economy was subsistence-based with shifting cultivation supplying calories, principally in the form of plantains and root crops, while fishing and hunting provided animal proteins to the diet. Some men, who recently began producing rice for sale in regional markets, now allocate less time to wild food procurement. Moreover, this trend has been accompanied by the nucleation of households, a growing cash market for agricultural labor, and the intravillage sale of faunal foods. This paper shows that with cash cropping, some Shipibo now freely distribute less food to others in relation to the amount they produce. To account for this change, a theory is developed based on time allocation and patterns of economic behavior reported throughout the Amazon. This theory is then applied to explain specialization and the formation of cash markets for food labor among the Shipibo.