SYMMETRY IN EQUISETUM

Bierhorst , David W. (Cornell U., Ithaca, N. Y.) Symmetry in Equisetum. Amer. Jour. Bot. 46(3) : 170-179. Illus. 1959.—A total of 118 leaf whorls and corresponding nodes from a total of 9 species of Equisetum were studied in serial cross-section. The number of whorls having the same leaf number as the 2 adjacent ones was 67. The size of the arc measured in degrees of circumference occupied by each leaf, as well as its position relative to leaves of adjacent whorls were measured. The disposition of the internodal and trans-nodal vascular strands was determined for each of the nodes. The average per cent deviations from theoretical leaf size within whorls were: whorls not involved in change in leaf number, 3.9; those with fewer leaves than the one below, 9.5; those with more leaves than one above, 7.1; those with more leaves than one below, 9.4; those with different leaf number from the 2 adjacent ones, 12.5. In Equisetum, it is a general rule that (1) a leaf which falls directly above a leaf in the next whorl where the younger whorl possesses fewer leaves than the older one is usually the largest leaf within its whorl, (2) a leaf which falls directly below a leaf in the next younger whorl where the younger whorl possesses fewer leaves than the older one is usually the smallest leaf within its whorl, (3) a leaf which falls directly above a leaf in the next older whorl where the younger whorl possesses a greater number of leaves than the older one is usually the smallest leaf in its whorl, and (4) a leaf which falls directly below a leaf in the next younger whorl where the younger whorl possesses a greater number of leaves than the older one is usually the largest leaf within its whorl. The numerous variations in the disposition of vascular tissue associated with changes in leaf number are described. Double leaf traces which originate in various ways are common, as well as vertical strands traversing the nodes. The leaf trace system is considered to be determined by the number, position, and relative sizes of leaf primordia. The disposition of the trans-nodal protoxylem seems to be determined to a large extent by the proximity of the leaf traces above and below the node.     

Canine reproduction: I. Reaction of animals to collection of semen and insemination procedures

Two methods of semen collection were attempted on ten untrained dogs of several breeds. Manual manipulation as described proved most reliable for untrained dogs. Electro-ejaculation was attempted unsucessfully with twelve additional dogs.Two methods of insemination were compared. Equipment found most satisfactory is described and a modification suggested.     

Ultrastructural differentiation of the epithelium and mucous glands of the esophagus in the chick embryo

Esophagi of White Leghron chick embryos, six days to hatching, were fixed in 5% glutaraldehyde in a cacodylate-sucrose buffer, postfixed in 1% OsO₄, dehydrated and embedded in Araldite. Tissues were sectioned with glass knives and viewed with a Philips EM 100C. The epithelium in early stages of development is characterized by small intercellular spaces, few cell processes and few desmosomes. In contrast the differentiated epithelium contains numerous cell processes, large intercellular spaces and numerous desmosomes. Mucin appeared in the mucous glands at 17 days.     

Measurement of PGE2 as the methyl oxime by radioimmunoassay using a novel iodinated label

A radioimmunoassay has been developed for prostaglandin E2 (PGE2) using methyl oxime (MOX) derivatisation and a novel 125Iodine radiolabel. PGE2-methyl oxime (PGE2-MOX) is coupled through an imide linkage to proline in a pro-gly-tyr or similar peptide rather than through the conventional amide linkage to histamine or tyrosine methyl ester. The main advantage of this method is that the imide linkage in the label does not resemble the amide link used in the original antigen and the conjugate is therefore readily displaced by the natural PGE2. This overcomes the traditional difficulty encountered in hapten RIAs where the antiserum has a higher affinity for the label than it has for the compound to be measured. The assay that has been developed using these modifications and a solid-phase second antibody separation step, is both sensitive (with a lower detection limit of 0.5 pg/tube), reliable and simple and has the advantage that methyl oximation of the sample protects the PGE from degrading prior to and during the assay.     

Streaming potential of intact wet bone

The conversion of mechanical loads to bioelectrical signals in bone have been suggested to control repair and remodeling. These signals in wet bone are attributed to the electrokinetic behavior where mechanical forces cause electrical signals due to motion of an ion carrying extracellular fluid in the bone matrix (streaming potentials). Streaming potential experiments were performed on control and chemically treated intact wet bone plugs in aphosphate and phosphate buffers to examine the contribution of bone constituents to the electrokinetic behavior of bone tissue. Data indicate that the organic constituents of bone dominate streaming potentials. Slopes of streaming potential vs pressure are related to the electrokinetic (zeta) potential. The slopes should be analyzed in the low pressure region where data is mainly linear. Comparisons of estimated zeta potentials from streaming potentials with existing data obtained by particle electrophoresis showed similar trends.