Central nervous projections of mechanoreceptors in the spider Cupiennius salei Keys.

Summary The basic organization of sensory projections in the suboesophageal central nervous system of a spider (Cupiennius salei Keys.) was analyzed with anterograde cobalt fills and a modified Golgi rapid method. The projections of three lyriform slit sense organs and of tactile hairs located proximally on the legs are described and related to central nerve tracts. There are five main longitudinal sensory tracts in the central region of the suboesophageal nervous mass arranged one above the other. Whereas the three dorsal ones contain fibers from the lyriform organs, the two ventral ones contain axons from the hair receptors. Axons from all three lyriform organs have typical shapes and widely arborizing ipsilateral intersegmental branches and a few contralateral ones. The terminal branches of the afferent projections from identical lyriform organs on each leg form characteristic longitudinal pathways, typical of each organ: U-shaped, O-shaped, or two parallel bundles. The terminations of the hair sensilla are ipsilateral and intersegmental. Two large bilaterally arranged longitudinal sensory association tracts receive inputs from all legs including the dense arborizations from tactile hairs, lyriform organs, and other sense organs. These tracts may serve as important integrating neuropils of the suboesophageal central nervous system.     

Assay of deoxyribonucleic acid homology using a single-strand-specific nuclease at 75 C.

We investigated the conditions under which a crude preparation of endonuclease S1 gives maximal hydrolysis of denatured deoxyribonucleic acid (DNA) while giving minimal hydrolysis of native DNA. The hydrolysis was measured by filtering and determining the acid-insoluble reaction product using 3H-labeled substrates. We also investigated various parameters in making this measurement. Under appropriate conditions (in 1 mM ZnSO-4, 0.168 M NaCl at pH 4.8) denatured DNA is hydrolyzed within 3% of completion whereas native DNA is essentially unaffected. The reaction was applied to assay plasmid DNA homoand heteroduplexes for which the method proves to be simple, fast, and reproducible.     

Detection of cell-bound immunoglobulins by a radioisotopic micro-mixed hemadsorption reaction with technetium-99m-labeled erythrocytes.

The mixed hemadsorption (MHA) reaction detects antibodies reactive with cell surface antigens by means of antiglobulin-coated indicator erythrocytes. We have developed a radioisotopic modification which employs sheep erythrocytes (SRBC) that have been prelabeled with technetium-99m (99mTc), a high specific acitivity metastable gamma-emitter of short half life. The 99mTc MHA reaction was performed on human and murine cells cultured in Micro-test II plated with six replicate wells per serum dilution. Antibody activity in species-specific xenoantisera and mono- and polyspecific alloantisera was detected in high titer. The sensitivity of 99mTc micro-mixed hemadsorption was 2 times that of the visual assessment of mixed hemadsorption, 100 to 200 times that of the 125-I-mixed antiglobulin reaction and 500 to 1000 times more sensitive than indirect immunofluorescence. The assay system was applied successfully to confirm the species of origin of a panel of previously karyotyped human and mouse cell lines. Our results indicate that the 99mTc micro-mixed hemadsorption method is a rapid, sensitive, quantitative test for the detection of cell surface antigens and membrane reactive antibodies.     

Initial kinetics of DNA degradation by chicken crude acid deoxyribonuclease

The ability of the crude acid DNase extracted from chicken erythrocytes to degrade native DNA into rod-like sub-units of 5.5 ±0.5×10⁵ daltons, has previously been attributed to a narrow specificity of the enzyme (1).     

Microfiber reinforcement of an arthropod cuticle

Summary 1. According to its fine structure arthropod cuticle is a laminated composite material. The exoskeleton of a spider is surveyed in an electron microscopical study as to the characteristics of its fiber reinforcement.2. Five types of fiber arrangement are distinguished, ranging from unidirectional to continuously rotating fiber orientation and with three types combining elements of both of these extreme cases. The unidirectional type is rare and its occurrence confined to the innermost part of the walking leg endocuticle and to parts of articular membranes. Quite contrary a continuous and regular rotation of fiber direction is common. In hard cuticle (exocuticle) this type of reinforcement is found exclusively.3. Lamellar width, indicating a 180° rotation of the fiber direction, varies within wide limits. Variation is due to varying numbers of fiber layers and the amount of directional change between them (ca. 0.6–24°, type E).4. The diameter of the chitin/protein microfiber amounts to ca. 35 Å. Its length measured up to 1,5 m in the preparations. A periodicity of ca. 80 Å is noted. The precision of fiber alignment within the cuticle is high.5. In the cuticle of the opisthosoma and the articular membranes endocuticular lamellae are taking a wavy course, which is interpreted to be in relation to the cuticle's softness.6. The mechanical implications of both an increasing number of fiber directions in a composite material and of the different types of fiber reinforcement found in the spider cuticle are demonstrated by a calculation of the directional properties of the moduli of elasticity in tension and shear. The predictable strong influence of both the fiber content and the binder material's E-modulus on the mechanical properties of cuticle is illustrated.7. Instead of a trajectorial design a continuous rotation of the fiber orientation is found in all exocuticles. Thus the spider does not make use of the special advantage (high strength/weight ratio) of unidirectional fiber arrangement in places where it seemed most likely.Many thanks are due to Ms. H. Tscharntke for expert assistance with electron microscopy and photographic work. Dipl.-Ing. F. Och and Dr. G. Haberl (Messerschmitt-Bölkow-Blohm GmbH, Ottobrunn) provided the calculations for Figs. 14 and 15. Their generous help is gratefully acknowledged. Dr. K. Frahm (Universität München, Fakultät f. Tiermedizin) kindly shared his densitometer. Ms. F. Althaus carefully carried out the drawings.     

Deoxynucleoside-sensitive mutants of Salmonella typhimurium

Summary Thymineless mutants ofSalmonella typhimurium which are able to grow with low added concentrations of thymine (20 M) fall into two classes on the basis of growth on deoxyribose as sole carbon source. Those which can grow are deoxyribomutase negative and those which cannot are deoxyriboaldolase negative. The former class are inhibited by deoxynucleosides and this provides a method for discriminating between different classes oftlr mutants ofEscherichia coli K12, which cannot utilize deoxyribose as a carbon source. It is suggested that the sensitivity of deoxyriboaldolase negative strains is due to the accumulation of deoxyribose-5-phosphate. The data also indicate that deoxyribose-5-phosphate is the inducer of thymidine phosphorylase. It seems that one or both of the deoxyribose phosphates is the toxic compound, and that reversal of inhibition by ribonucleosides is due to inhibition of the enzymes catalysing their formation from deoxynucleosides. We propose that the symbolsdrm anddra be used to denote the structural genes for deoxyribomutase and deoxyriboaldolase respectively.