Catecholaminergic contributions to the neuronal machinery of the olfactory bulb: aftoradiographic, immunohistochemical and evoked feild potential studies

aftographic exeperiments on the localization of radiolabelednoradrenaline, dopamine and dopa, as well as immunohistochemicalstudies on hydroxylase-like activity, are summarized and comparedin both rat and turtle olfactory bulbs. Evoked field potentialstudies on effects of dopamine are also discussed. The histochemicalstudies suggest that dopaminergic periglomerular neurons arethe most significant cellular component of the catecholaminergicsystem in the olfactory bulb of both species. Scattered fluorescentcell group was also present in the internal plexiform layerand superficial granule cell layer of the turtle olfactory bulb.Other fibres, not related to intrinsic bulbar neuronal cellbodies, were also labeled, mostly in the granule cell layerbut also in the external plexiform layer. These might belongto a centrifugal catecholaminergic system from brain stem neurons.In the in vitro turtle olfactory bulb, dopamine and apomorphinedepressed the amplitude of field potentials evoked by a singlevolley in the olfactory nerve or lateral olfactory tract, andreduced the depression and latency of reponses when paired volleywere delivered. It is suggested that catecholaminergic systemsplay a key role in modulating mitral cell activity through actionsin both superficial (glomerular) and deep (granule) layers.This may involve direct actions, or other, non-catecholaminergicinterneurons.     

Sex differences in antipredator tail-waving displays of the diurnal yellow-headed gecko Gonatodes albogularis from tropical forests of Colombia

Many vertebrate species show display behaviors when predators are in their vicinity. Some of these displays may inform the predator of the improbability of capturing the prey (i.e., pursuit-deterrent displays) and are potentially advantageous to both predator and prey. Here we present data on a tail display performed by Gonatodes albogularis, a diurnal tropical gecko. We performed transect surveys in three habitats near Bogotá in Colombia. Geckos detected during transects were approached by the observer in a standardized way, and details of their tail-waving displays were recorded. In control recordings animals were watched from a distant site without approaching them. Results showed sexual differences in tail-waving display: when approached by the observer, males performed this behavior more frequently than females. We found no significant differences between males and females in flight-initiation distances and height above the substratum when they were initially located. Results also showed that males displayed more frequently when approached than when the simulated predator remained stationary. We interpret these results as evidence that the display functions as a pursuit-deterrent signal to potential predators. However, as some tail displays were performed in the presence of conspecifics, the display may also have a social function.     

Callus formation and plantlet regeneration from protoplasts derived from suspension cultures of wheat (Triticum aestivum L.)

Protoplasts were isolated from anther-derived suspension cultures of commercial wheat (Triticum aestivum L. cv. Chris). The protoplasts were released enzymatically and isolated by centrifugation on a sucrose cushion. The isolated protoplasts were initially cultured in a liquid medium in the dark. Numerous microcalli were produced under these conditions, some of which differentiated into globular embryos. Upon transfer to a solid medium and exposure to 16h/8h light/dark cycle, the protocalli proliferated and many of the somatic embryos matured. Complete plantlets were obtained and maintained in sterile culture.Abbreviations 2,4-D 2,4-Dichlorophenoxyacetic acid - MES 2-[N-morpholino] ethanesulfonic acid     

Physiological characteristics of the tympanic organ in noctuoid moths

Summary The tympanic organ ofSpodoptera frugiperda, Mocis latipes, Erebus odorata (Noctuidae) andMaenas jussiae (Arctiidae) was stimulated with acoustic stimuli of 20 kHz, 45 ms and 5 s duration, and intensities ranging from 30 to 100 dB. The electric activity of the auditory receptors was recorded at the tympanic nerve with a stainless steel hook electrode. In all of these moth species there is an intensity range (ca. 20 dB) in which the response of each auditory receptor (A₁ and A₂ cells) to 45 ms pulses varies in a linear relation to the logarithm of stimulus intensity. For intensities higher than this value, depending on the species and the cell analysed, the spike discharge may continue to increase, may saturate or may diminish (Fig. 2). InE. odorata andM. latipes the A₁-cell response shows a decrease for stimulus intensities higher than 30 dB above the threshold. In the former species there is a statistically significant linear relation between the A₂-cell response and the decrease of the A₁-cell response, but this is not the case inM. latipes (Fig. 3). The similarity of the responses ofE. odorata to those described inEmpyreuma pugione (Coro and Pérez 1984) suggest that also in this noctuid species one may assume that the A₂ cell inhibits the A₁ receptor. In all of these moth species there is a maximum firing rate of the auditory cells at the beginning of the response to pure tones of 5 s and an exponential decrease of their discharge frequency with the course of time (Fig. 5). The analysed species differ in the adaptation rates of their auditory receptors. In all of these species the A₂ cell adapts more rapidly than the A₁ cell. In most of these species the stimulus intensity influences the adaptation rate of the auditory receptors (Fig. 7). These results are compared with data obtained by other authors, and it is concluded that there are more interspecific differences in the physiological characteristics of the auditory receptors in noctuoid species than those reported so far.Abbreviation AP action potential     

Evidence for X-Linkage of Steroid Sulfatase in the Mouse: Steroid Sulfatase Levels in Oocytes of XX and XO Mice

The steroid sulfatase (STS) levels in mature oocytes of XX and XO mice were assayed along with lactate dehydrogenase (LDH), an autosomal marker, and glucose-6-phosphate dehydrogenase (G6PD), a known X-linked gene. LDH levels in XX and XO oocytes were equal, whereas STS and G6PD levels were approximately twice as high in XX oocytes as in XO oocytes. These results indicate that the STS gene is X-linked in the mouse just as it is in humans. Assays of STS in kidney tissue of XX and XO mice indicated dosage compensation for the gene, which is different from that observed in humans.     

Characterization of Mutants of Escherichia coli Temperature-Sensitive for Ribonucleic Acid Regulation: an Unusual Phenotype Associated with a Phenylalanyl Transfer Ribonucleic Acid Synthetase Mutant

A mutant strain AA-522, temperature-sensitive for protein synthesis, was isolated from a stringent strain (CP-78) of Escherichia coli K-12. The mutant strain has a relaxed phenotype at the nonpermissive growth temperature. Protein synthesis stops completely at 42 C, whereas the rate of ribonucleic acid (RNA) synthesis is maintained at 20% of the 30 C rate. Sucrose-gradient centrifugation analysis of RNA-containing particles formed at 42 C indicated the presence of “relaxed particles.” These particles possess 16S and 23S RNA and are precursors to normal 50S and 30S ribosomal subunits. A search for the temperature-sensitive protein responsible for the halt in protein synthesis implicated phenylalanyl transfer RNA (tRNA) synthetase. Essentially no enzyme activity is detected in vitro at 30 or 40 C. Analysis of phenylalanyl tRNA synthetase activity in revertants of strain AA-522 indicated the presence of intragenic suppressor mutations. Revertants of strain AA-522 analyzed for the relaxed response at 42 C were all stringent; strain AA-522 was stringent at 30 C. These data indicate that a single mutation in phenylalanyl tRNA synthetase is responsible for both a block in protein synthesis and the relaxed phenotype at 42 C.     

Acridine Sensitivity of Bacteriophage T2H in Escherichia coli

Normally acridine-sensitive, Escherichia coli-T2H complexes are rendered acridine-resistant if the infecting bacteriophage mutant is either pr or q. If these pr or q mutants are treated to produce sensitive revertants, one obtains a mutation at any of several dye-sensitizing (ds) sites in the early enzyme region of the T2 map. The ds mutants are nonspecific suppressors because they reduce the resistance of complexes containing either pr or q to proflavine. The ds mutants are not identical in action, since some make pr or q sensitive to proflavine and quinacrine, and others, to proflavine alone. Two ds mutants have r to r(+) mutation patterns which differ, depending upon whether or not the ds is coupled with r7 (an rII mutant). The mutation patterns of r(+) to r are the same for both ds mutants and for wild type. We suggest that dye sensitization may consist of alterations of early enzymes so as to produce slightly different forms of deoxyribonucleic acid which are in turn dyesensitive.     

A nonselective cation channel activated by membrane deformation in oocytes of the ascidianBoltenia villosa

Summary Cell-attached patch clamp recordings from unfertilized oocytes of the ascidianBoltenia villosa reveal an ion channel which is activated by mechanical deformation of the membrane. These channels are seen when suction is applied to the patch pipette, but not in the absence of suction or during voltage steps. The estimated density of these stretch-activated channels is about 1.5/m², a figure equal to or greater than the density of known voltage-dependent channels in the oocyte. Ion substitution experiments done with combined whole-cell and attached patch recording, so absolute potentials are known, indicate that the channel passes Na⁺, Ca²⁺ and K⁺, but not Cl^–. The channel has at least two open and two closed states, with the rate constant that leaves the longer-lived closed state being the primary site of stretch sensitivity. External Ca²⁺ concentration affects channel kinetics: at low calcium levels, long openings predominate, whereas at high calcium virtually all openings are to the short-lived open state. In multiple channel patches, the response to a step change in suction is highly phasic, with channel open probability decreasing over several hundred milliseconds to a nonzero steady-state level after an initial rapid increase. This channel may play a role in the physiological response of cells of the early embryo to the membrane strains associated with morphogenetic events.