Paired Arrangement Research Articles

Proposed Fossil Insect Modification to Fossil Mammalian Bone from Plio-Pleistocene Hominid-Bearing Deposits of Laetoli (Northern Tanzania)

Intensive predepositional bone modification is described from fossil vertebrate remains. The bone material is derived from terrestrial Pliocene deposits exposed in the Laetoli area (Northern Tanzania), which represents predominantly vulcanoclastic material. The modifications described are shallow grooves with a U-shaped profile, as seen using scanning electron microscopy. The grooves form clusters of radially arranged grooves with 3–8 mm diameter that randomly cover bone surfaces forming broad surface erosion and lining subcortical cavities in the compact bone. Because of the paired arrangement of isolated grooves constituting the clusters, the modifications are attributed to yet unknown insects. Termites are tentatively suggested as possible producers of the marks.

Serine Acetyltransferase from Escherichia coli Is a Dimer of Trimers

Equilibrium sedimentation studies show that the serine acetyltransferase (SAT) of Escherichia coli is a hexamer. The results of velocity sedimentation and quasi-elastic light scattering experiments suggest that the identical subunits are loosely packed and/or arranged in an ellipsoidal fashion. Chemical cross-linking studies indicate that the fundamental unit of quaternary structure is a trimer. The likelihood, therefore, is that in solution SAT exists as an open arrangement of paired trimers. Crystals of SAT have 32 symmetry, consistent with such an arrangement, and the cell density function is that expected for a hexamer. Electron microscopy with negative staining provides further evidence that SAT has an ellipsoidal subunit organization, the dimensions of the particles consistent with the proposed paired trimeric subunit arrangement. A bead model analysis supports the view that SAT has a low packing density and, furthermore, indicates that the monomers may have an ellipsoidal shape. Such a view is in keeping with the ellipsoidal subunit shape of trimeric LpxA, an acyltransferase with which SAT shares contiguous repeats of a hexapeptide motif.

A Study of Floral Morphological Diversity in Phytolacca (Phytolaccaceae) Based on Early Floral Ontogeny

The floral ontogeny of four species of Phytolacca (P. acinosa, P. clavigera, P. dodecandra, and P. americana) shows major differences in the number and position of stamens and carpels. Five sepals are always formed in a 2/5 sequence. The number of stamens is mostly eight, with a sequential initiation: six outer stamens are arranged in three pairs opposite sepals 1-3; single stamens stand opposite sepals 4-5, except for P. americana, where all antesepalous stamens are positioned in pairs (10 stamens rather than eight). The stamens of the first, second, and third pair arise simultaneously as independent entities. The stamens of the third pair occasionally arise sequentially and are displaced in relation to the third sepal. Stamens opposite sepals 4 and 5 follow sequentially. The delayed plastochron of the stamens opposite sepal 3 indicates that the pentamerous flower has been derived from a trimerous precursor. Phytolacca dodecandra has 10 stamens arising in a different sequence: the five inner stamens are alternisepalous and the five outer, antesepalous, thus resembling diplostemony. The alternisepalous stamens correspond positionally to the two pairs opposite sepals 1-2 in other species, plus one stamen between sepals 3 and 5. The outer antesepalous stamens appear later and correspond to single stamens opposite sepals 3-4-5 in the other species, with two extra stamens opposite sepals 1-2. In other species a variable number of outer stamens may arise centrifugally in alternate whorls. The number of carpels corresponds with the number of stamens in the inner androecial whorl. Each carpel consists of a free abaxial part and an adaxial, continuous ovule-bearing part. Our data of the androecial ontogeny refute the existence of diplostemony in the Phytolaccaceae, with P. dodecandra occupying a pivotal position. It is suggested that the paired arrangement of stamens in Phytolacca is a basic condition in the family and is not the result of dédoublement. The centrifugal initiation of outer stamens is believed to reflect a reversal in the direction of stamen initiation and is not linked with a secondary stamen multiplication.

Effect of magnetic pole arrangement on core loss in laminated high-speed magnetic journal bearings

Power losses in magnetic journal bearings as compared to rolling element or fluid film bearings are very low and normally negligible. However, as operating conditions become more severe, the power losses in magnetic bearings must be considered. This paper examines the effect of magnetic pole arrangement on the core loss of a magnetic journal bearing at high-speed and high-flux-density operation. Experimental core loss results are presented for rotational speeds up to 3.1 million DN and flux densities up to 1.60 T. These results are for a magnetic bearing constructed of cobalt iron. The results are compared to existing results for low-speed operation of silicon iron magnetic journal bearings. Results show that a paired pole arrangement gives a slightly less core loss than an alternating pole arrangement, and that this advantage is not necessarily negligible at high speeds and high flux densities for the cobalt iron bearing.

Study of magnetic susceptibility & lattice parameters of CeNiInH x systems

In the present work we report the study of magnetic susceptibility and lattice parameter measurements of CeNiInH x system with x= 0.0, 0.5, 0.6, 0.67, 0.75, 1.0 and 1.6. It has been revealed that the occurence of paired arrangement of proton in the host material is associated with the electronic phase change of CeNiIn system accompanied with a drastic change in the lattice parameters.

Immunocytochemical localization of CCAP, a novel crustacean cardioactive peptide, in the nervous system of the shore crab, Carcinus maenas L.

Polyclonal antibodies were raised in rabbits against synthetic crustacean cardioactive peptide (CCAP) conjugated to bovine thyroglobulin, and were used to map CCAP-immunoreactive structures in the central nervous system of Carcinus maenas. As expected, the neurohemal pericardial organs (PO) displayed abundant immunoreactivity in nerve fibers and terminals. In addition, immunoreactive neurons were demonstrated in other parts of the nervous system. At least some of them do not appear to terminate in neurohemal structures and may have a non-endocrine, as yet unknown function. Immunoreactive perikarya with a diameter of 25–30 μm occur in the brain. They project into the optic and antennary neuropil, and into the eyestalk. One cell was found in the medulla terminalis of the eyestalk and in the connective ganglion, respectively. From the latter, axonal branches could be traced into the brain and the thoracic ganglia (TG). In the TG, small-diameter perikarya give rise to extensive networks of varicose fibers. Some of the perikarya occur in a characteristic paired arrangement with larger CCAP-immunoreactive somata (diameter 40–50 μm). These pairs of one small and one large cell occur in all mouthpart and leg segments of the TG, except the abdominal ganglia (AG), where only large cells were found. The main projections of the large neurons comprise one or more fibers in each of the seven segmental nerves (SN), leading to neurosecretory terminals in the PO. The fibers in the SN are joined by branches of an ascending axonal tract from the large perikarya in the AG. The large-type perikarya are considered to be the principal source of CCAP in the PO. The optic ganglia in the eyestalk, except the medulla terminalis, the neurohemal sinus gland and the stomatogastric nervous system are devoid of CCAP-immunoreactivity.

Growth and Estrous Activity of Rats Fed Adequate and Deficient Levels of Phosphorus

Female Sprague-Dawley rats were fed two levels of phosphorus ad libitum and in a paired feeding arrangement to yield the following three treatments: 1) adequate phosphorus (0.40%) ad libitum intake, 2) low phosphorus (0.04%) ad libitum intake and 3) adequate phosphorus pair-fed with the low phosphorus group. Feed intake, growth rate and feed conversion in rats fed 0.04% phosphorus ad libitum and in pair-fed control rats were lower (P < 0.01) than in rats fed 0.40% phosphorus ad libitum. Seventy-five percent of the rats exhibited normal estrous cycles, as indicated by vaginal smears, throughout the 105-d period regardless of dietary phosphorus level. Breeding efficiency and number of pups per litter were not altered by dietary treatment. However, compared to either phosphorus-adequate group, dams fed 0.04% phosphorus weaned fewer (P < 0.05) pups and pup survival to 45 d of age was lower (P < 0.05). Average daily gain postweaning was 67% lower for pups in the phosphorus-deficient group than for those in either phosphorus-adequate group. Phosphorus deficiency in rats does not alter estrous cycles but reduces pup survivability postnatally.

Crystal structure of an inhibitor and a model for inhibition of replicative DNA synthesis

6-( p-Hydroxyphenylhydrazino)-uracil is an antimicrobial agent that selectively blocks replicative DNA synthesis in Bacillus subtilis by inhibiting DNA polymerase III. The drug crystallizes as a monoclinic monohydrate, space group C2 c , with a = 23.920(6) A ̊ , b = 5.587(3) A ̊ , c = 17.466(5) A ̊ , β = 101.45(8) ° , and eight hydrated molecules per cell. Three-dimensional X-ray diffraction data were collected. The structure was solved by Patterson methods and refined to an R value of 6.8% for the 1651 data. The geometry of the uracil ring is unusual. The bond distances suggest that a resonance form involving a positively charged hydrazino nitrogen and a negatively charged carbonyl oxygen, O(4), makes a large contribution to the valence bond structure of this compound. The exocyclic C(6)N bond is short (1.335 Å), the C(6)C(5) bond distance is 1.371 Å, which is longer than in uracil, and the C(5)C(4) distance (1.396 Å) is short. The uracil ring, the linked hydrazino nitrogen, and the hydrogen on this nitrogen are in the same plane. Each uracil group is hydrogen bonded to a nearly coplanar uracil across a center of symmetry. The water molecule is also near the plane of these paired bases and forms a hydrogen bond with the uracil-linked hydrazino NH group. This paired base arrangement and the restricted rotation about the exocyclic C(6)N link that constrains the hydrazino NH group to lie near the uracil plane suggest a model for the interaction of the drug with template-primer DNA. The drug acts when cytosine is the base to be copied in the template strand, and the drug is competitive with dGTP. Both cytosine and guanine can be accommodated with little distortion of the crystal structure geometry in a manner compatible with the known geometry of DNA. The structural and biochemical aspects of the model for drug action are discussed.

SWEETNESS PERCEPTION IN RELATION TO SOME TEXTURAL CHARACTERISTICS OF HYDROCOLLOID GELS

AbstractThe apparent sweetness of five different hydrocolloid gels prepared with equal amounts of sodium Sucaryl varied significantly (P &lt; 0.01) when tested in a multiple paired arrangement by seven trained judges. Results from four replications consistently showed sweetness to be the greatest in carrageenan gels and the least in cornstarch gels. It was intermediate in low methoxyl pectin, agar and gelatin gels. Concentrations of gelling agents were selected to produce gels comparable in hardness. Characterization of mechanical textural properties with the GF‐Zenken Texturometer showed that gels of cornstarch and gelatin were more cohesive, springy, chewy and gummy than those of agar, low methoxyl pectin and carrageenan (P &lt; 0.01). These findings suggested that gels which take more effort to disintegrate limit taste perception. Multiple regression analyses showed that the measured mechanical textural parameters accounted for 52.3% of the variability in sweetness scores suggesting that other characteristics may also play a role. Inspection of correlation coefficients of sweetness with single textural parameters showed no one characteristic as a dominating influence over sweetness.

Binding of cytidine triphosphate to aspartate transcarbamylase

Equilibrium dialysis studies reveal that cytidine triphosphate (CTP) binds to a total of six sites on native aspartate transcarbamylase (ATCase) from E. coli. Analysis of the binding curves suggests that there are two discrete classes of CTP binding sites on each native ATCase molecule. Two models are discussed in which a paired arrangement of regulatory chains in the native enzyme leads to heterogeneous binding of CTP. One model assumes that the folding of polypeptide chains in the regulatory dimer produces two CTP binding sites which are physically different and differ in their intrinsic affinities for CTP. Alternatively, interference between CTP molecules binding to identical CTP sites on each regulatory dimer may cause the two sites to bind the ligand with different affinities.

Fluorescence and electron microscopic evidence for the dual innervation of the iris sphineter muscle of the rabbit.

The sphincter zone of the rabbit iris sometimes contains terminals with small granular vesicles. These terminals correspond to yellowish-green fluorescent structures in the sphincter zone. The paired arrangement of a terminal containing these vesicles and one full of agranular vesicles might indicate dual innervation of sphincter muscles by sympathetic and parasympathetic fibers. The sympathetic component probably exerts an inhibitory action on the sphincter muscles.

Effect of Pressure on the Spectra of Certain Complexes of Cu++, Co+++, and Fe++

The effect of pressure is as measured on the spectra of four Cu++ salts, and on K3COF6 and FeSiF6·6H2O. The four Cu++ salts have varying degrees of distortion from octahedral (or tetrahedral) symmetry. For the Tutton's salt (the more distorted octahedral complexes) there were measurably larger effects on the shift and especially on the intensity of the transition. The Co3+ and Fe++ systems were compared to investigate the possibility of crossover from spin free to spin paired arrangement in the former. From the data it is estimated that this should occur at 220–250 kbar.

The molecular and crystal structure of cellulose triacetate

AbstractAn x‐ray diffraction study has been made of cellulose triacetate II. Small films of highly crystalline triacetate with good fibrous orientation and a fair degree of biaxial orientation have been prepared by repeated rolling at successively higher temperatures between 160 and 215°C. The x‐ray diffraction patterns exhibited several new reflections which made it possible to determine the unit cell. It has been found that cellulose triacetate II has four cellobiose acetate residues in a pseudo‐orthorhombic cell with a = 24.5, b = 11.56, and c = 10.43 A. Pairs of these residues are related by twofold screw axes in the c or fiber‐axis direction. The paired arrangement seems to be determined by a fitting of the natural zigzagging shape of the cellulose backbone which is exaggerated by the presence of the secondary acetyl groups. The glucose residues of such a pair are parallel and inclined at about 45° with respect to the a axis. A neighboring chain pair points in the opposite direction and the median planes of the cellobiose units of two such pairs are approximately mutually perpendicular. To accommodate this type of packing, one half of the primary acetyl groups must be twisted sharply out of the median plane of the parent glucose residues. A second statistical model which basically is very similar is also considered. There do not appear to be any strong interactions between chains.

The Chromosome Complexes in Goat (&lt;i&gt;Capra hircus&lt;/i&gt;) and Sheep (&lt;i&gt;Ovis aries&lt;/i&gt;) and Their Relationship

The chromosomes of goat and sheep were investigated from the comparative standpoint in male germ cells. The observations were carried out on the testicular material derived from two breeds in the goat and three breeds in the sheep. So far as the scope of the present study is concerned, there was found, either in the goat or in the sheep, no visible and appreciable difference in the chromosomes among the breeds under consideration, not only in the number but also in the other external morphological features of chromosomes.The number of chromosomes in goat was found to be 60 in diploid and 30 in haploid. All the chromosomes are comprised in the rod-shaped elements of simple telomitic type, and they are placed in the paired arrangement into 29 homologous pairs of autosomes which form a closely graded seriation, and an unequal pair of the X and Y chromosomes. The X chromosome is quite prominent in being the largest of all and displays distinguishable characteristics. The Y element is represented by the smallest one in the group, which is very conspicuous in existence on account of its minute size. The X assumes a characteristic tripartite structure showing two constrictions.The chromosome number in sheep was determined as 54 for diploid and 27 for haploid. After the morphological analysis it was revealed that the diploid complement of the sheep consists of three homologous pairs of atelomitic V-shaped chromosomes, 23 homologous pairs of telomitic rod-shaped ones occurring in a graded series, and an unequal pair of the X and Y which are quite identical in their morphological features to those found in the goat.Evidence furnished by a close morphological comparison of chromosomes between the goat and the sheep sufficiently indicates that a closely related karyological relationship occurs between these two forms, which is very suggestive of the fact that the ancestral sheep and the ancestral goat probably took their origins from a common ancestor.