Straight Tail Research Articles

Irreversible binding to the receptor of bacteriophages T5 and BF23 does not occur with the tip of the tail.

Treatment of purified tails of bacteriophage T5 with 0.05% sodium dodecyl sulfate specifically removed pb2, a protein of 108,000 molecular weight (108K), from the tail. Although these tails were devoid of the single straight tail fiber, they still inhibited adsorption of T5 to Escherichia coli cells. Reconstitution of these tails with pb2 increased the efficiency of inhibition of T5 adsorption. Treatment of tails with 0.1% sodium dodecyl sulfate removed, in addition to pb2, a protein of 67K from phage T5 and one of 60K from phage BF23. These tails failed to inhibit phage adsorption, and no reconstitution was achieved. Reconstitution of T5 tails with pb2 from BF23, and of BF23 tails with pb2 from T5, did not alter the host receptor specificity of the tails. Binding of untreated T5 tails to small FhuA receptor particles revealed that binding occurred with the conical part of the tail and that pb2 was most likely released from the tail upon binding. From these results and from recent observations with T5-BF23 hybrid phages (K.J. Heller, Virology 139:11-21, 1984), we conclude that the receptor-binding proteins of T5 and BF23 are the 67K and 60K proteins, respectively, and that they are not located at the tip of the tail but rather at or near the site where the straight tail fiber is attached to the conical part of the tail.

VV 5-32-63/64: THE "SUPERMASSIVE DOUBLE GALAXY" IN ABELL 1775 REVISITED.

ABSTRACT Spectroscopy is presented for galaxies in A 1775, the cluster containing VV 5-32-63/64, an apparent double galaxy which has long been considered a gravitationally bound system with supermassive components (10 to the 13th solar masses). However, this model has run afoul of recent radio observations, which detected an extremely long straight radio tail emanating from the eastern galaxy in the pair. The present observations indicate that if both galaxies are members of the same cluster, the cluster radial-velocity dispersion (1522 km/sec) is large enough to account for the velocity difference between the two VV galaxies (1650 km/sec). It is therefore suggested that the VV galaxies are not gravitationally bound and need not be supermassive. The large velocity dispersion measured for A 1775 also strains suggested velocity dispersion vs X-ray luminosity relations for clusters of galaxies, as A 1775 has not yet been detected at X-ray wavelengths.

Isolation of high-density mutants and identification of nonessential structural proteins in bacteriophage T5: Dispensability of L-shaped tail fibers and a secondary major head protein

High-density mutants of bacteriophage T5 were isolated by CsCl isopycnic centrifugation. In all of the mutants isolated, at least one or two phage structural proteins were found to be lost, while no extra inserted or duplicated DNA segments could be found. By morphological examination using an electron microscope and physiological tests, it was shown that one of the proteins lost in the high density mutants corresponded to the structural protein (or one of the structural proteins) of the L-shaped tail fiber and that, in the presence of a straight tail fiber, all L-shaped tail fibers were dispensable to adsorption to bacteria and subsequent DNA injection. A secondary major head protein was also shown to be nonessential.

Body Form and Locomotion in Sharks

A revised interpretation of the mode of action of the heterocercal tail in sharks shows that the upturned tail axis tends to produce a thrust directed downwards behind the centre of balance of the fish and thus gives a moment turning the head upwards. This is countered in two ways—by the rotation of the tail along its longitudinal axis during each lateral beat, and through the action of the ventral hypochordal lobe. The shape of the tail and the mode of action of the tail in all sharks so far considered reflects a balance between these three factors, in all of them the net effect being the production of a forward thrust from the tail that passes directly through the centre of balance of the fiish. There is normally therefore no tendency for the fish to turn around the centre of balance in a sagittal plane but there is a net sinking effect that is countered by the planning effect of the pectoral fins and the ventral surface of the head. A study of 56 species of sharks shows that the tail is constructed according to a remarkably consistent common plan, the extremes being the high angled rather symmetrical tail of pelagic sharks such as hums, Lamna and Rhincodon and the straight tails of benthic sharks such as Ginglymostoma in which a ventral hypochordal lobe is absent. When the general body shape of sharks, including the position of insertion of the median and paired fins and the pattern of growth of fin surface areas is considered, the uniformity of the shark body plan and locomolor function is further emphasised. Four patterns of body form in sharks are recognised: 1) The fast swimming pelagic sharks and the whale sharks have a tail with a high aspect ratio, a conical head, a lateral fluke on the caudal peduncle. 2) The generalised sharks typified by the Carcharhinidae, have lower heterocercal angles, a flattened ventral surface on the head and lack the caudal fluke. 3) The demersal sharks typified by the catsharks (Scyliorhinidae) have a very low, almost straight tail. The ventral hypochordal lobe is absent and the first dorsal fin is posterior in position. 4) The squalomorph sharks are distinct in the absence of the anal fin, presence of a marked epicaudal lobe in the tail and often an elevated insertion of the pectorals. The anal and second dorsal fins are always the smallest fins and the pectorals grow at the fastest rate. In general there is an inverse relationship between size and rale of growth of all fins and the ventral surface of the head. In hammerheads the growth data confirms that the head has a significant planing action in swimming. The pectoral, second dorsal and anal fins show an extreme constancy of position of insertion in all sharks studied. The locomotor mechanism of sharks is adapted for an efficient cruising swimming but at the same time, the potential instability in the sagittal plan allows for the production of turning moments that are used in attack and feeding.

Products ♦ Processes ♦ Materials ♦ Equipment

McMurdo has added a straight tail Printed Circuit Board contact to their range of Dee connectors. Tail lengths are suitable for mounting on 0.062 in (1.5 mm) or on 0.093 in (2.3 mm) thick boards. Connectors are available with 9,15,25,37 or 50 contacts. Body shells and contacts are compatible with International standards.

Distribution and properties of muscle spindles in the caudal segmental muscles of the rat together with some comparisons with hind limb muscle spindles.

The afferent activity in sensory nerve fibres was recorded when lateral segmental muscles of the rat tail were stimulated mechanically. The muscles were then examined histologically and the muscle spindle content established. The distribution of spindles along the tail length and their innervation pattern was obtained. The overall ratio of primary to secondary endings was approximately two to one. Most single spindles (67% of sample) were intermediate; parallel (dual) spindles (29% of sample) usually combined a simple with an intermediate spindle; complex spindles were rare.The maximum muscle extension during tail‐bending movements was a submaximal stimulus to tail spindles; there was no resting discharge in the straight tail position in the absence of fusimotor stimulation.The spindle endings were compared with those in rat hind limb muscles in terms of dynamic index, vibration sensitivity, spindle complexity and conduction velocity of afferent fibres. In all four aspects the tail values were more restricted in range; all caudal spindle endings had lower dynamic indices, lower vibration sensitivity and lower afferent conduction velocities than those found in primary endings in the three hind limb muscles examined (peroneus longus, peroneus brevis and gastrocnemius lateralis). A positive correlation between spindle afferent conduction velocity and vibration sensitivity of caudal spindle endings was recognized, and the possible role of afferent fibre size in determining spindle properties discussed.

Physical properties of phage 299

Phage 299, on equilibrium sedimentation in CsCl, gives 3 major bands whose relative proportions depend on growth conditions. One band is whole heads without tails, the other two are infectious phage of differing degrees of disarray and stability. Electron micrographs show that the infectious phage has a head about 60 nm across, probably icosahedral in shape, and a straight tail of approximately 140 nm in length. The tail assemblies appear defective and incomplete. Sedimentation in a sucrose gradient of the DNA extracted from phage 299 is monodisperse with a molecular weight of 20.6±1.5×106 daltons based on comparison with λ and 186 phage DNA’s. The DNA has a base composition of 51.7% guanine and cytosine as determined by bouyant density in CsCl. A comparison of its denaturation behavior by analysis of the hyperchromic shift at 260 nm with that of phage P2 suggests a considerable number of common characteristics, and an absence of a low guanine and cytosine portion on the part of 299 which amounts to approximately 10% of the total DNA.

Four New Species of Dorylaimellus Cobb, 1913 (Nematoda: Belondiroidea) From North India

Four new species of Dorylaimellus, D. rosae n. sp., D. pruni n. sp., D. paralongicaudatus n. sp. and D. processus n. sp. are described and figured. D. rosae is distinctive by its dorsally convex and ventrally straight tail with rounded terminus and striated sub-cuticle. D. pruni is characterized in possessing short, broadly rounded tail, sub-cuticle striated only near head and tail, distinct hemizonid and unusually broad lateral chord. D. paralongicaudatus can be differentiated by its smooth sub-cuticle, long elongate-conoid tail with rounded terminus; D. processus by its conoid tail with a short process ending in sub-acute terminus.

A NEW HELIOSTAT FOR DARK‐GROUND MICROSCOPY

SYNOPSISSunlight dark ground microscopy with a simple heliostat has revealed a straight tail as the origin of the flagella of most motile bacteria. This tail changes into helices (“flagella”). These show specific wavelengths, with “biplicity” and take part in agglutination. All this has also been recorded cinemicrographically on 16 mm film. Among other subjects studied and filmed with this sunlight technique were bacterial motility, other types of bacterial flagella, including those of Spirilla and Vibrios, and the effect of bacteriophage and penicillin on certain bacteria.A description is here given of a new more elaborate heliostat which will throw a brighter and steadier beam of sunlight into the microscope, thus improving and facilitating further observations of which preliminary results are given here.

Trends in aeronautical science and engineering: Tercentenary lecture delivered by Sir Arnold Hall, F. R. S., at 10.15 a.m. on Monday 25 July ig6o at the Royal Institution

The Lecture reviewed some of the advances in scientific understanding which had influenced aeronautical engineering in the past ten years, and are likely to influence it in the coming decade. The shape of aircraft had changed from the traditional straight wing and tail configuration to the swept-back wing, and delta-wing form. These changes were guided by understanding of the influence of compressibility in the air, and of the effects due to the presence of shock waves at speeds near and above that of sound. Particularly significant among these effects is the interaction between shock waves and the boundary layer, which has strong influence on the lift and drag forces in steady flow, and introduces unsteady flow effects which in some circumstances can be self-exciting. Several of these effects were illustrated, and discussed and the design procedures to bring them under control outlined.

The wavelengths of helical bacterial flagella.

SUMMARY: During normal movement most motile bacteria carry a straight tail, which, when the movement slows, stiffens into helical structures commonly called flagella. The helices of many kinds of bacteria were photographed with a sunlight dark-ground microscope, and their wavelengths measured. Mean values and standard deviations were calculated for each strain and then for the species. ‘Biplicity’ (two wavelengths per bacterium, one twice the other) was observed frequently. Each strain appears to have its own constant wavelengths. The wavelength differs in different kinds of bacteria from 0·60 to 5·058μ., the distribution over the various species not revealing a distinct pattern nor any obvious correlation with other characteristics. The wavelength is affected by temperature, pH value, and colloid content of medium. These features, and the effects of drying, make stained preparations useless for measuring.

THE SPECTRUM OF COMET MRKOS (1955 E)

Direct photographs of Comet Mrkos were made with the Curtis Schmidt from June IS to 23, and objective prism plates with the combined 4and 6-degree prisms from June 25 to 29. A period of good seeing and exceptional transparency partially compensated for the low altitude of the comet (10° to 15°). During this period the comet was approximately 0 . 7 A.U. from the sun and 1.2 A.U. from the earth.1 On direct photographs made with the plate/filter combinations 103a-O/Schott GG5 and 103a-E/Wratten 22, the tail has two principal components. A broad, fan-shaped tail is bounded on its advancing edge by a rather well-defined, roughly parabolic envelope. Superposed on this broad fan is a narrow, straight tail, which can be traced to a distance of 1-9 from the head, and which is inclined about 3° to the projection of the radius vector sun-comet in the sense opposite that of the motion of the comet. The observed length of the projection of the straight tail on the sky corresponds to 6 million km. The diameter of the head on the perpendicular to the radius vector is at least 150,000 km. A reproduction of one of the 103a-O/GG5 plates has appeared elsewhere.2

Shape of bacterial flagella.

IN orthodox bacteriology all flagella are curly. With the exception, however, of spirilla, which possess unchanging horny-looking curly appendages (Fig. 1) directly derived from the cell wall1, motile bacteria usually go forward with a fuzzy-looking straight tail (Fig. 2) and a twisting body2. Under various, probably adverse, conditions this straight tail tends to stiffen into a straight clear-cut rod but more often into a clear-cut helix3. The straight tail of Fig. 3 actually became the helix of Fig. 4, and the helix of Fig. 5 also arose from a straight tail. The helices may show two different but characteristic wave-lengths in the same bacterium, one always exactly twice the other as in Figs. 4 and 5, for which phenomenon ‘biplicity’ would appear a suitable term3.

Halley's Comet in 1909–11

AN exhaustive discussion of the phenomena of Halley's comet and its envelopes, based on the examination of a large number of photographs taken at the Lick Observatory, at its Chile station, and at Mount Wilson, Johannesburg, Helwan, Kodaikanal, Cordoba, Yerkes, Tokyo, and Beirut, is given by Nicholas T. Bobrovnikoff in a memoir on “Halley's Comet in its Apparition of 1909–1911”; which appears in Lick Observatory Publications, Part 2. The outward motion of luminous patches in the tail was studied, and the repulsive force deduced, the assumption being made that the hyperbolic orbits of these objects were in the same plane as the orbit of the comet?s nucleus. The resultant repulsive force was calculated in 31 cases; in 3 cases it exceeded 1,000 times gravity; in 4 cases it was between 100 and 1,000 times; in 6 cases it was between 50 and 100 times. The two tails of the comet on May 29, 1910, are traced on page 457 of the memoir. That of Bredichin?s type I is nearly straight, the indicated repulsive force ranging from 9 to 16; the tail of type II is highly curved, the repulsive force being only 0?1 to 0?2. The presence of this curved tail explained the surprising fact that a tail could be seen in the morning sky for some time after the nucleus and straight tail had become evening objects. On account of the curvature of the tail, the author is doubtful whether the earth passed through any portion of it; in any event only the outlying portions could have been traversed.

Observations of Halley's Comet

THERE is little more to record of Halley's comet yet; as a popular spectacle, in England”, its appearance has been somewhat of a failure, and we shall have to wait some little time before the results obtained by astronomers in different countries are available. Some amount of resentment has been expressed in the popular Press at the feeble appearance of the famous comet, but it should be clearly understood that it is our hazy summer skies and the brightness of our northern twilight that are to blame. In a letter to Prof. Turner Mr. Knox Shaw, of the Helwan Observatory, describes it as really a glorious sight, about May 11, far exceeding in its glory comet 1910a; it then had a straight tail 38° long. Yet at Helwan there were only three fine nights during” the first fortnight in May.

A Rare Phenomenon

LAST Friday, the 11th, my attention was called at 9 p.m. to a most remarkable appearance in the sky. It consisted of a luminous band stretching from the eastern horizon to the west, and passing a little to the south of the zenith. It was first seen here at 8.20, and began as a luminous ray coming up from the west, but when I first saw it, it had extended as described from west to east. It was like a straight tail of a large comet with its head below the horizon, or the track of the beam from a powerful electric search light. Its eastern end lay a little to the south of the Pleiades, which were just rising; and in the west it passed through Corona Borealis. The night was a brilliant starlight one, and small stars could be seen through the luminous band. It was seen in the Co. Kildare, 50 miles from here, and there it passed through the zenith also, which would show that it was at a great altitude. It gradually faded away, and was gone at 9.30. It would be of interest to know if it was observed in other parts of the country.