Characteristics of the first meiotic division in hamster hybrids obtained by backcrossing Phodopus sungorus and Phodopus campbelli]

Spermatocytes of fertile, subfertile, and sterile hamster hybrids obtained by backcrossing Phodopus sungorus and Ph. campbelli were analyzed under light and electron microscopes. Light microscopy showed that early meiosis was blocked in pachitene in the spermatocytes of sterile hybrids. The X and Y chromosomes were dissociated in metaphase I in several fertile and subfertile animals. Electron microscopic analysis of the synaptonemal complex (SC) revealed a disturbed synapsis of sex chromosomes and autosomes in all hybrids. Dissociation of the sex chromosomes, terminal and interstitial asynapsis, and interlocking of autosomes were observed. Disturbed synapsis in hybrids was assumed to result from the difference between Ph. sungorus and Ph. campbelli in not only their chromosomes, but their genes as well.     

Priming effect of calcium ionophores on phorbol ester-induced respiratory burst in mouse peritoneal neutrophils.

The abilities of three calcium ionophores (A23187, 4-bromo-A23187, and ionomycin) to modulate the respiratory burst of neutrophils induced by phorbol ester and to increase the concentration of free intracellular Ca2+ ([Ca2+]i) were compared. The production of reactive oxygen species (ROS) was determined by luminol-dependent chemiluminescence and [Ca2+]i was determined with the Fura-2 fluorescent probe. A23187 (0.05-2 microM) and ionomycin (0.001-0.5 microM) but not 4-bromo-A23187 amplified 3-4-fold the respiratory burst induced by phorbol ester. The integral response (total production of ROS over 6 min) had a bell-shaped dependence on the concentration of ionomycin and A23187 with increase and decrease at low and high concentrations of the ionophores, respectively. The maximal effect was found at 0.5 microM ionomycin and 2 microM A23187, these concentrations resulting in transient increases in [Ca2+]i to 1776 +/- 197 and 955 +/- 27 nM, respectively. The ionophores had no effect in calcium-free media, though they increased [Ca2+]i to approximately 400 nM through the mobilization of intracellular Ca2+. In cells with exhausted stores of Ca2+, the addition of 1.5 mM Ca2+ combined with phorbol ester amplified twofold the production of ROS. The inhibition of phospholipase A2 with 4-bromophenacyl bromide significantly decreased the production of ROS. Thus, the entrance of Ca2+ and generation of arachidonic acid under the influence of phospholipase A2 are necessary for the ionophore-induced priming of production of ROS during cell activation with phorbol esters.     

First record of lily thrips, Liothrips vaneeckei Priesner, in Australia (Thysanoptera: Phlaeothripidae)

The first Australian record of the lily thrips, Liothrips vaneeckei Priesner, is reported from a bulb farm in Warragul South, Victoria. It is an occasional pest of Lilium bulbs, both in the field and in storage, particularly in the USA and several European countries, and is also infrequently found in considerable numbers on the corms of orchids.     

Structural organization and evolution of t-complex in Mus genus

Modern data on the structure and evolution of the t complex are discussed. The t complex is a series of inversions in the proximal region of murine chromosome 17; it contains a set of genes that determine its predominant transmission to the offspring of heterozygous males. Variants of structural organization of this genetic system (t haplotypes) have been found in wild populations of four species of genus Mus (M. domesticus, M. musculus, M. molossinus, and M. castaneus), but not in representatives of other, evolutionarily remote species of this genus. The so-called vertical, horizontal, and introgressive hypotheses are discussed of the origin and evolution of the t complex. Based on population genetic studies and molecular analysis a new hypothesis on the origin of the t-complex is put forward. This hypothesis is a synthesis between the vertical and horizontal models and assumes that all known t haplotypes had a common ancestral chromosome 17 carrying a proximal inversion.