Ultrastructure of oesophageal appendages ("peptonephridia") in enchytraeids (Annelida: Clitellata)

Abstract. Although the oesophageal appendages in the four enchytraeids Enchytrueus crypticus, Fredericia strinta, Buchholzia appendiculata , and Achaeta sp. are quite different from one another in shape and position, their histology and ultrastructure are basically the same. These are intestinal appendages, the lumina of which distally end blind and proximally open into the oesophagus. Almost all of the few cells in their single-layered epithelium have a microvillous, cilia-free border at the apex, facing towards the lumen, and basally comprise an extremely extensive labyrinth. The presence of the latter, composed of very thin cell processes, and of numerous mitochondria identifies the organs as energy-producing and -consuming, transport-active structures. Their possible function as a food-moistening organ or osmoregulatory organ is discussed, and they are compared with other intestinal appendages in enchytraeids and other oligochaetes.     

Identification and partial characterization of a latent ATP,Mg-dependent protein phosphatase in rabbit skeletal muscle cytosol

Summary Fractionation of rabbit skeletal muscle cytosol on Aminohexyl-Sepharose has resulted in the identification of a latent ATP, Mg-dependent protein phosphatase whose catalytic subunit is in the active conformation, but is inhibited by the presence of more than one modulator unit. The partially purified enzyme is converted to an inactive, kinase F_A-dependent form upon incubation at 30°C unless modulator-specific polyclonal antibodies are added to the preparation. The immunoglobulins also relieve the inhibition which is responsible for the low basal phosphatase activity of the enzyme, and they counteract all of the heat-stable inhibitor activity present in the preparation. Addition of free catalytic subunit abolishes the inhibition of the latent enzyme in a dose-dependent way, but cannot prevent the inactivation process. The inactivated phosphatase and the original latent enzyme exhibit the same apparent M _r in sucrose density-gradient centrifugation (70 000) and in gel filtration (110 000).Abbreviations PMSF Phenylmethanesulphonyl Fluoride - TLCK L-l-chloro-3-(4-tosylamido)-7-amino2-heptanone-hydrochloride - TPCK L-l-chloro-3-(4-tosvlamido)-4-phenyl-2-butanone     

Selectivity of juxtaposition between cup-shaped lactotrophs and gonadotrophs from rat anterior pituitary in culture

Summary Semi-thin sections of three-dimensional reaggregates from adult female rat pituitary, cultured in serum-free defined medium, were stained for prolactin, gonadotropin, thyrotropin, growth hormone and S-100, using the double immunolabelling technique. The frequency of juxtaposition between lactotrophs and gonadotrophs was enumerated and compared with the expected frequency at random distribution of polygonal cell profiles in a hexagonal configuration. The proportions of lactotrophs and gonadotrophs in the aggregate sections were determined using stereometrical analysis. The observed frequency of juxtaposition did not differ significantly from the expected frequency. Hence, no reason was found to assume a selective adhesion between lactotrophs and gonadotrophs in adult female rat pituitary reaggregates. A constant proportion of lactotrophs was found to meet the criteria of a cup-shaped morphology, and 70%±9% (mean ±S.D.) of these so-called cupshaped lactotrophs were found to be juxtaposed at their concave side to gonadotrophs. Administration of 0.01 nM 17-oestradiol to the culture medium resulted in a significant reduction of the proportion of cup-shaped lactotrophs but did not affect the selectivity of juxtaposition to gonadotrophs. The selectivity of juxtaposition between cup-shaped lactotrophs and gonadotrophs may be the morphological correlate of the functional relationship between these cells, which are known to be involved in an intra-pituitary paracrine communication system.     

A new pollen type,C-banded and fluorochrome counterstained chromosomes,and evolution inGuatteria and related genera (Annonaceae)

Guatteria, Guatteriopsis, Guatteriella andHeteropetalum share the same conspicuous pollen type which is new for theSpermatophyta. It is zonoaperturate with a folded aperture region and an extremely reduced exine. First chromosome counts and karyotype analyses forGuatteriopsis (4 species investigated) andGuatteriella (1 species) are identical with those ofGuatteria (19 species seen): 2n = 28. The genome is characterized by diploidization and partly telocentric chromosomes. Sequentially Giemsa C- and fluorochrome banded chromosomes and interphase nuclei are described. The cuticular folding pattern is distinct forHeteropetalum only. Growth forms and ecology are reported for many species. The evolutionary pattern of theGuatteria group is discussed and compared with other genera and families.     

Extreme differences in charge changes during protein evolution

Summary The maintenance of a proper distribution of charged amino acid residues might be expected to be an important factor in protein evolution. We therefore compared the inferred changes in charge during the evolution of 43 protein families with the changes expected on the basis of random base substitutions. It was found that certain proteins, like the eye lens crystallins and most histones, display an extreme avoidance of changes in charge. Other proteins, like phospholipase A2 and ferredoxin, apparently have sustained more charged replacements than expected, suggesting a positive selection for changes in charge. Depending on function and structure of a protein, charged residues apparently can be important targets for selective forces in protein evolution. It appears that actual biased codon usage tends to decrease the proportion of charged amino acid replacements. The influence of nonrandomness of mutations is more equivocal. Genes that use the mitochondrial instead of the universal code lower the probability that charge changes will occur in the encoded proteins.     

Chromosomal evolution withinPiperaceae

Chromosome numbers for 26 different species of the generaPiper, Peperomia andPothomorphe (Piperaceae) are reported. The basic chromosome numbers are 2n = 26, x = 13 (Piper, Pothomorphe) and 2n = 22, x = 11 (Peperomia), polyploid series are characteristic forPiper andPeperomia. Piper has the smallest chromosomes and prochromosomal interphase nuclei,Peperomia the largest ones and mostly reticulate to euchromatic nuclei.Pothomorphe is intermediate in both characters. The karyomorphological differences betweenPothomorphe andPiper underline their generic separation. Interspecific size variation of chromosomes occurs inPiper andPeperomia. Infraspecific polyploidy was observed inPiper betle. C-banding reveals different patterns of heterochromatin (hc) distribution between the genera investigated. The genome evolution is discussed.     

The extracellular nuclease of Serratia marcescens: studies on the activity in vitro and effect on transforming DNA in a groundwater aquifer microcosm

A quantitative endonuclease assay, which relies on the introduction of single and double strand breaks into supercoiled plasmid DNA, was used to study the activity of the extracellular nuclease of Serratia marcescens SM6 in buffer and in groundwater. The parallel enzyme concentration-dependent production of relaxed and linear plasmid molecules suggests that the nuclease produces single and double strand breaks in duplex DNA. Bovine serum albumin stimulated the nuclease activity towards DNA and RNA and increased the stability of the enzyme against thermal inactivation. The DNase activity at 4 °C and 50 °C was almost half of that at the optimum temperature (37 °C). The nuclease was active in groundwater, although the specific activity was lower than in buffer. In a groundwater aquifer microcosm, mineral-adsorbed transforming DNA was substantially less accessible to the nuclease than was dissolved DNA. The data suggest that the extracellular nuclease of Serratia marcescens may contribute to DNA turnover in the environment and that adsorption of DNA to minerals provides protection against the nuclease.Abbreviations GW groundwater GWA groundwater aquifer     

Bacterial genome mapping by two-dimensional pulsed-field gel electrophoresis (2D-PFGE)

Macrorestriction mapping is often the first step toward a thorough physical and genetic characterization of a bacterial genome. The problem of deducing the order of partially or completely digested macrorestriction fragments to yield a physical genome map may readily be solved by applying twodimensional pulsed-field gel electrophoresis (2D-PFGE) techniques. These powerful methods are quick and technically easy to perform; specifically, they are independent of DNA probes and should therefore be applicable to any bacterial species irrespective of its prior genetic characterization. In this article, detailed step-by-step protocols are given to set up, run, and evaluate 2D pulsed-field gels. Two basic methods are described: partial/complete 2D gels of one restriction enzyme and complete/complete 2D gels of two different restriction enzymes. Other topics include preparation of bacterial genomic DNA, screening for suitable rare-cutting restriction enzymes and determination of optimal running conditions. Accompanied by many notes, these protocols are meant to offer the novice a sound and rapid access to these important methods.