Molecular and genetic studies on the euchromatin-heterochromatin transition region of the X chromosome of Drosophila melanogaster

A recombinant Charon 4 bacteriophage has been isolated on the basis of RNAs which are enriched in the head of the adult Drosophila melanogaster and hence are likely to be of neural origin. The cloned insert maps to the near vicinity of the uncoordinated locus in polytene chromosome band 19E8. This band is within the transition zone between the euchromatic and heterochromatic regions of the X chromosome, a region which has been well characterized cytogenetically. The insert contains both repetitious and low copy number sequences, some of which vary extensively in both frequency and restriction fragment size between different laboratory strains. One particular family of moderately repeated sequences occurs predominantly in divisions 19 and 20 of the X chromosome and perhaps the distally located X heterochromatin. The molecular landscape surrounding the initial entry point contains many repeated sequences and is thus unlike those observed in most published chromosomal walks. The possible significance of the presence of repeated sequence families in the distinct properties of this region are discussed.     

Structural properties of barley nucleosomes

The structural properties of barley oligonucleosomes are investigated and compared to those of rat liver oligomers. Extraction of barley chromatin was performed using mild nuclease digestion of isolated nuclei leading to a low ionic strength soluble fraction. Oligonucleosomes were fractionated on sucrose gradients and characterized for DNA and histone content. Physico-chemical studies (sedimentation, circular dichroism and electric birefringence) showed that barley oligonucleosomes exhibit properties very close to those of the H1-depleted rat liver counterparts. Moreover, in situ, barley linker DNA was more sensitive to micrococcal nuclease digestion than that of rat liver. These results suggest that barley oligonucleosomes show a less compact structure than their rat liver counterparts and appear to be in contradiction with the very condensed organization of barley chromatin previously suggested.     

Increase in proteinase activity in the cellular slime mould Polysphondylium pallidum induced by bacteria

Abstract Polysphondylium pallidum strain PPHU8 grown in association with bacteria contains aspartic and cysteine proteinases. When myxamoebae were grown in axenic medium the contribution of cysteine proteinases was much lower. The proteinase activity could be altered by addition of heat-killed bacteria to axenically growing cells. This was detected as an increase in the specific activity towards N -benzoyl-L-prolyl-L-phenylalanyl-L-arginine- p -nitroanilide, a cysteine proteinase substrate, and by the appearance of cysteine proteinase bands after electrophoretic analysis. The changes were inhibited by cycloheximide, azide and dinitrophenol. All the available evidence suggests that they are due to the de novo synthesis of cysteine proteinases.     

Cation effects on the nonlinear electrical properties of DNA solutions

The nonlinear electrical properties of DNA solutions were measured when different monovalent cations were added to DNA. The influence of different parameters has been examined: fundamental frequency, field strength, and concentration. A linear relationship between the harmonic current I_h and the DNA concentration is shown, even for higher concentration values (400 mg/l.). The frequency dispersion of I_h has the same shape for all the cations and the low-frequency amplitude of I_h increases in the following order: Li⁺ < Na⁺ < K⁺ < NH < Cs⁺. The nonlinear polarizability values are compared with the linear ones determined using the very low field electric birefringence technique. Both linear and nonlinear values are of the same order of magnitude. It is thought that the nonlinear electrical property of high-molecular-weight DNA mainly results from the deformation of the DNA coils by the electric field.     

Quantitative and qualitative assay of amniotic-fluid acetylcholinesterase in the prenatal diagnosis of neural tube defects

Summary In 110 amniotic fluids the specific acetylcholinesterase was determined quantitatively and qualitatively. In the quantitative assay there were a considerable number of false positives and false negatives, although the mean value of the normal controls differed significantly from that of neural tube defect pregnancies. By the electrophoretic separation of acetylcholinesterase, however, all fluid samples with borderline alpha-fetoprotein levels or fetal blood contamination could be correctly classified. With the exception of one skin-covered spina bifida all neural tube defects in the second trimester could be identified by this method. The second fast-moving band characteristic of the specific acetylcholinesterase was also present in abdominal wall defects and intrauterine death.     

The mucus-trap hypothesis on feeding of aquatic nematodes and implications for biodegradation and sediment texture

Summary Many aquatic nematodes continuously produce with their caudal and pharyngeal glands a slimy trace consisting of sticky, elastic threads which give an acid mucopolysaccharide reaction. Along these traces small particles adhere firmly thus making the traces visible at low magnifications. By creeping repeatedly on their traces the nematodes produce burrows and solid, branched concretions in fine sediments. By these activities soft bottoms acquire a particular framework texture which perhaps may, for instance in the deep sea, enable an interstitial, non-boring microfauna to thrive.The authors suppose that the copious mucus secretion of nematodes is mainly involved in nutrition and they present an hypothesis on the assumed mode of feeding (mucus-trap hypothesis): With their mucus threads these nematodes entrap small detritus particles, bacteria, and macromolecules which subsequently are browsed together with the mucus. The combination of an adhesive mucus thread and the particular mouth construction in nematodes represents a highly elaborated collecting and sorting system for food acquisition. In addition, decomposition processes of organic material coated by the mucus may contribute to a secondary food source which is controlled by nematodes. Feces are embedded within the mucus, and their remaining nutrient content may be subjected to a later re-utilization.     

Linear contour length dependence of electrical polarizability of nucleosomal DNA fragments: implications for the flexibility of DNA

The transient electric birefringence of monodisperse oligonucleosomal DNA ranging from 145 to 990 base pairs has been studied. The orientation of fragments can be described in terms of an induced dipole moment with a small contribution of a permanent dipole. The electrical polarizability delta alpha was found to increase linearly with the DNA contour length. This unexpected dependence might result from a bent structure of DNA already considerable for very short segments. The observed delta alpha values agree with a segmental orientation of rigid subunits of length 13-18 nm as estimated in the elastic model of DNA with a kink angle of about 41 degrees.     

Observations on the effects of protease inhibitors on the suppression of experimental allergic encephalomyelitis

Inhibitors of proteolytic enzymes were tested for their ability to suppress the clinical signs and CNS lesions produced by injection of purified myelin in complete Freund's adjuvant into Lewis rats. Pepstatin or a series of neutral protease inhibitors including aprotinin, soybean trypsin inhibitor, leupeptin, antipain, transaminomethyl cyclohexane carboxylic acid (AMCA), -amino caproic acid (EACA) nitrophenyl guanidino benzoate (NPGB),d- andl-polylysine, or a new commercial protease inhibitor, dipropionyl Rhein (DPR) were injected daily beginning on day 7 after immunization of rats with myelin. Aprotinin and soybean trypsin inhibitor exacerbated the symptoms and lesions of experimental allergic encephalomyelitis (EAE), leupeptin and antipain had no effect, and the plasminogen activators AMCA, EACA, NPGB, as well as poly-l- and poly-d-lysine and DPR suppressed various aspects of EAE. The measurement of acid protease as a biochemical method for quantitation of the degree of cellular infiltration into the CNS is proposed, and the results with the various treatments presented. AMCA and NPGB may exert their effects at the site of entrance of the lymphoid cells into the CNS.