Identification and morphometric evaluation of the synapses of optic nerve afferents in the optic tectum of the axolotl (Ambystoma mexicanum)

Summary The terminals of retinal afferents in the tectum of the axolotl have been identified ultrastructurally using techniques of horseradish peroxidase-filling and degeneration. The mitochondria in filled structures show a characteristic electron-lucent matrix. After both eyes have been removed, terminals with light mitochondria disappear from the area known to receive an optic input. In this area the presence of light mitochondria is almost always diagnostic of the retinal origin of a bouton. The synapses are similar to those assumed to be of retinal origin in other vertebrates. Detailed morphometric analysis has been carried out on identified optic synapses in the optic tectum of the axolotl.     

Pulsed-field gel electrophoresis typing of Hafnia alvei isolated from chub-packed and retail ground beef

Thirty-eight isolates of Hafnia alvei were characterized by biochemical profiles, ribotyping and pulsed-field gel electrophoresis (PFGE) patterns. The isolates were recovered from chub-packed (19 isolates) or retail (nine isolates) ground beef, or were obtained from culture repositories (10 isolates). Biochemical profiling differentiated the 38 isolates into five groups and a commercial ribotyping method recognized 11 groups, whereas PFGE differentiated the same 38 isolates into 19 groups. These data substantiate that PFGE is a highly discriminatory tool for establishing the relatedness among Hafnia alvei strains.     

The rates of dissociation and reassociation of the subunits of human chorionic gonadotropin

A large change in quantum yield of the fluorescent probe 1,8-anilinonaphthalene sulfonate is produced when it combines with the glycoprotein hormone, human chorionic gonadotropin. A method of analyzing for the hormone in the presence of its subunits has been developed based on the finding that the subunits have no effect on 1,8-anilinonaphthalene sulfonate fluorescence. Quantitative rates of dissociation and recombination can be obtained with very small concentrations of hormone since fluorescence measurements are fast and sensitive. The effects of temperature, pH, and urea concentration on the rate of human chorionic gonadotropin dissociation have been measured. The rates of recombination of subunits have been studied as a function of temperature, pH, and KCl concentration. Human chorionic gonadotropin is stable in water to pH 12 and pH 4.5 at 37 °C.     

3,5,4′-trihydroxystilbene as a phytoalexin from groundnuts (Arachis hypogaea)

Cis and trans-resveratrol (3,5,4′-trihydroxystilbene) have been isolated from the infected hypocotyls of Arachis hypogaea and implicated as phytoalexins.     

Differentiation of three serovars of Malassezia furfur

Malassezia furfur strains were isolated from the clinically normal skin of 10 volunteers by swabbing four different sites (forehead, ear, back and chest). The strains could be divided into three basic groups on the basis of cultural characteristics. Both unabsorbed and absorbed specific rabbit antisera were prepared against nine of the strains, and both species and group specific antigens could be demonstrated. Serologically, three group specific surface antigens could be identified which corresponded to the three groups identifiable on cultural characteristics. The relevance of these findings to previous in vitro results is discussed.     

Tissue- and stage-specific control of homeotic and segmentation gene expression in Drosophila embryos by the polyhomeotic gene

The distributions of the products of the homeotic genes Sex combs reduced (Scr) and Ultrabithorax (Ubx) and of the segmentation genes, fushi tarazu (ftz), even skipped (eve) and engrailed (en) have been monitored in polyhomeotic (ph) mutant embryos. None of the genes monitored show abnormal expression at the blastoderm stage in the absence of zygotic ph expression. Both Scr and Ubx are ectopically expressed in the epidermis of ph embryos, confirming the earlier proposal, based on genetic analysis, that ph+ acts as a negative regulator of Antennapedia (ANT-C) and bithorax (BX-C) complex genes. At the shortened germ band stage, en is also ectopically expressed, mainly in the anterior region of each segment. In contrast to these effects in the epidermis, the expression of en, Ubx, Scr and ftz is largely or completely suppressed in the central nervous system, whereas eve becomes ectopically expressed in most neurones.