Morphology of the antennary gland exit duct in ecological and phylogenetic series of talitroid Amphipoda (Crustacea)

The form of the proximal segments of antenna two peduncle and of the antennary gland exit duct on peduncle article two has been examined in 16 species of amphipod crustaceans (including 14 species of Talitridae). Gammarus duebeni (Gammaridae), regarded as exemplifying the norm for aquatic amphipods, has a very distinctive fluted exit duct emanating from a pronounced gland cone. The talitroid Hyale nilssoni was regarded as a typical representative of the hyalid-like ancestors of the Talitridae. It also has a gland cone, but the exit duct of the antennary gland is a thin-walled, collapsible cone. The two proximal articles of antenna two peduncle are much reduced in Talitridae. Only the second may retain a degree of mobility. No gland cone remains. The structure of the urinary exit duct in seven species of simplidactylate landhoppers (Bousfield's Gp IVa) was very similar to the hyalid condition. Beachfleas (Gp II) have strengthened, often sculpted ducts. whilst sandhoppers (Gp III) have no protruding exit duct at all. Only one species of Gp IVb (cuspidactylate) landhopper ( Tasmanorchestia sp.) was investigated and it has an exit duct similar in form to that of the beachfleas (Gp II). Neorchestia plicibranchiata (a Gp IVa species), however, already known to be an anomalous species, has unusually elongate urinary ducts (for a Gp IVa species). These observations lend support to the notion that the landhoppers are a polyphyletic grouping and that the sandhoppers are a very isolated ecomorphological grouping within the family.     

A NEW METHOD OF POLARIZATION MICROSCOPIC ANALYSIS : I. Scanning with a Birefringence Detection System

A new method of polarized light analysis is described in which a highly sensitive electronic detector specific for birefringence is used to identify the crystalline axes of an object and then measure its phase retardation due to birefringence. The microscopic system employed in the method consists of an electronic birefringence detection system (BDS), a microscope with strain-free lenses, and a driven stage for passing the specimen at appropriate velocities across the image of an aperture placed at the field stop and imaged in the specimen plane by the condenser. The detector registers retardations directly as voltage at a constant deflection sensitivity of ca. 1.1 v per angstrom unit over a range of 120 angstrom units. The basal rms noise level is 0.002 A for a spot 36 µ in diameter formed by a 95 x, N. A. 1.25 objective pair, and increases in proportion to the reciprocal of the diameter of the scanning spot. The increase in noise with high resolution scanning can be offset by increasing the instrumental time constant, which is adjustable in decades between 0.004 and 0.4 seconds. A number of difficult problems in high extinction polarization microscopy are avoided by the use of modulated light and a rapid electronic detector. For example: (a) The measured distribution of birefringence is unaffected by the usual diffraction anomaly; therefore polarization rectifiers are not required. (b) The detector is selective for birefringence, so that there is no problem in separating contrast due to different optical properties (e.g. dichroism, light scattering). (c) The speed and sensitivity are both increased by between one and two orders of magnitude over that attainable by visual or photographic methods, thereby rendering a vast number of weakly birefringent, light-scattering, and motile objects readily analyzable for the first time with polarized light.     

Cyclic peptides and depsipeptides from cyanobacteria: A review

An elaborate array of structurally-novel and biologically-active cyclic peptides and depsipeptides are found in blue-green algae (cyanobacteria). Several of these compounds possess structures that are similar to those of natural products from marine invertebrates. Most of these cyclic peptides and depsipeptides, such as the microcystins and the lyngbyatoxins, will probably only be useful as biochemical research tools. A few, however, have the potential for development into useful commercial products. For example, cryptophycin-1, a novel inhibitor of microtubule assembly fromNostoc sp GSV 224, shows impressive activity against a broad spectrum of solid tumors implanted in mice, including multidrug-resistant ones, and majusculamide C, a microfilament-depolymerizing agent fromLyngbya majuscula, shows potent fungicidal activity and may have use in the treatment of resistant fungal-induced diseases of domestic plants and agricultural crops.     

Visualizing and quantifying natural selection

Modern methods of analysis are enabling researchers to study natural selection at a new level of detail. Multivariate statistical techniques can Identify specific targets of selection and provide parameter estimates that fit into equations for evolutionary change. A more Intuitive understanding of the form of selection can be provided through graphical representation of selection surfaces. Combinations of quantitative and visual analyses are providing researchers with new insights into the details of natural selection in the wild.     

Identification of alcaligin as the siderophore produced by Bordetella pertussis and B. bronchiseptica.

The siderophores produced by iron-starved Bordetella pertussis and B. bronchiseptica were purified and were found to be identical. Using mass spectrometry and proton nuclear magnetic resonance, we determined that the siderophore produced by these organisms was identical to alcaligin, a siderophore produced by Alcaligenes denitrificans.     

Intestinal floras of populations that have a high risk of colon cancer.

The fecal floras of polyp patients, Japanese-Hawaiians, North American Caucasians, rural native Japanese, and rural native Africans were compared. The polyp patients and Japanese-Hawaiians were considered to be groups at high risk of colon cancer, and the rural native Japanese and rural native Africans were considered to be groups at low risk. The North American Caucasians were found to have a flora composition intermediate between these two groups. Fifteen bacterial taxa from the human fecal flora were significantly associated with high risk of colon cancer, and five were significantly associated with low risk of colon cancer. Total concentrations of Bacteroides species and, surprisingly, Bifidobacterium species were generally positively associated with increased risk of colon cancer. Some Lactobacillus species and Eubacterium aerofaciens, which also produces major amounts of lactic acid, showed closest associations with low risk of colon cancer.     

The cosmid CSSM25 assigns syntenic group U2 to bovine Chromosome 9 and is localized to ovine Chromosome 8

The cosmid-derived microsatellite CSSM 25 has previously been shown to map to bovine syntenic group U2 by link-age and hybrid somatic cell analysis. We have mapped the cosmid by fluorescent in situ hybridization to bovine Chromosome (Chr) 9q17-21 and ovine Chr 8q17-21 and hence assign U2 to Chr 9 in cattle. Bovine Chr 9 and ovine Chr 8 show strong banding pattern homology, and the localization of CSSM 25 to the same region confirms the strong conservation of gene locations on these chromosomes.