Persistence of maternal isoenzyme patterns of the lactate dehydrogenase and phosphoglucomutase system during early development of hybrid trout

Developmental changes in the isoenzyme patterns of LDH and PGM during early embryogenesis (until hatching) in two trout species (Salmo trutta and Salmo irideus) as well as in their reciprocal interspecific hybrids are reported, completing a previous study which had commenced from hatching onward (Hitzeroth et al., 1968). Isoenzymes of both systems occur in unfertilized eggs and in embryos from fertilization onward. Until about the Augenpunkt stage, the isoenzyme patterns remain unchanged and are identical to the patterns of unfertilized eggs; the reciprocal hybrids correspond to the respective maternal species. Additional isoenzymes appearing for the first time at about the Augenpunkt stage in the interspecific hybrids show the same electrophoretic mobility as those in the animals of the respective maternal species at this developmental stage. It is discussed whether the appearance of additional isoenzymes characterizes the activation of maternally derived alleles of the embryonic genome, or whether maternally derived cytoplasmic factors are responsible for the occurrence of these additional bands.Supported by the Deutsche Forschungsgemeinschaft.     

Interspecific hybridization betweenDaphnia hyalina,D. galeata,andD. cucullata and seasonal abundances of these species and their hybrids

The three cladoceran speciesDaphnia hyalina, D. galeata, andD. cucullata frequently coexist in the lakes of northern Germany. Although there are some problems in distinguishing them morphologically, they are easily determined by gelelectrophoresis: each species carries a different allele at the glutamate oxaloacetate transaminase (GOT) locus. Animals morphologically intermediate between two species are heterozygous for the alleles carried by the species they resemble. This pattern is in agreement with the findings at other loci, where also diagnostic alleles exist. These findings are most easily explained by interspecific hybridization between the three species. No evidence is found for backcrosses involving hybrids ofD. cucullata, whereas some backcrosses betweenD. hyalina, D. galeata, and their hybrids are found in some lakes. In four lakes the seasonal abundances of the three species and their hybrids are determined.     

Changes in sperm plasma membrane lipid diffusibility after hyperactivation during in vitro capacitation in the mouse

We have used the technique of fluorescence recovery after photobleaching to measure the diffusibility of the fluorescent lipid analogue, 1,1'-dihexadecyl 3,3,3',3'-tetramethylindocarbocyanine perchlorate on the morphologically distinct regions of the plasma membranes of mouse spermatozoa, and the changes in lipid diffusibility that result from in vitro hyperactivation and capacitation with bovine serum albumin. We found that, as previously observed on ram spermatozoa, lipid analogue diffusibility is regionalized on mouse spermatozoa, being fastest on the flagellum. The bovine serum albumin induced changes in diffusibility that occur with hyperactivation are also regionalized. Specifically, if we compare serum incubated in control medium, which maintains normal motility, with those hyperactivated in capacitating medium, we observe with hyperactivation an increase in lipid analogue diffusion rate in the anterior region of the head, the midpiece, and tail, and a decrease in diffusing fraction in the anterior region of the head.     

Rules of evidence in psychophysiological investigations

Conventional rules encourage an investigator to focus primarily on quantifiable data. In psychophysiological studies, however, the most relevant data may be nonquantifiable, at least at the present time. Behavior, visceral or general, does not necessarily depend on the quantity of a particular stress, but rather is the result of a complex interactive central processing of afferent signals, reflecting more the relevance of actuating factors than their quantitative features. Thus, the rules of evidence must ask not only for measurement, when possible, but for context as well and for data on related intangibles that determine the significance of an experience to an affected individual. Such an inquiry requires the perspicacity of a skilled and disciplined observer. As the practiced ear of a well-trained cardiologist can draw reliable anatomical inferences from listening to the heartbeat, so the eyes and ears of an educated physician should be able to determine the significance of events to his patient with a fair degree of reliability. Both the physician and the cardiologist, however, must deal with the potential distortion brought on by their own biases. Despite problems of bias, lack of replicability, and the need to persist in efforts toward precise measurement, progress continues in understanding the contribution of psychosocial stresses to a variety of gastrointestinal, cardiovascular, respiratory, cutaneous, and other bodily disturbances and the pathways and neurohumoral mechanisms whereby they are mediated. The agenda now calls for developing new strategies for dealing with the powerful intangibles that activate the mechanisms. Meanwhile, as Robert Morrison once cautioned, "We must not expect a science to know more than it does."     

‘Switching-off’ of an auditory interneuron during stridulation in the acridid grasshopperChorthippus biguttulus L.

Summary In freely moving grasshoppers of the speciesChorthippus biguttulus compound potentials were recorded from the neck connectives with chronically implanted hook electrodes. The spikes of one large auditory interneuron, known as the G-neuron (Kalmring 1975a, b) were clearly distinguishable in the recordings and the neuron was identified by its physiology and morphology. In quiescent grasshoppers the G-neuron responds to auditory and vibratory stimuli, but responses to both stimuli are suppressed during stridulation in males (Fig. 1, top, Fig. 7). When a male's wings were removed so that the stridulatory movements of its hindlegs produced no sound, the suppression of the G-neuron response still occurred (Fig. 1, bottom). When proprioceptive feedback from the hindlegs was reduced, by forced autotomy of the legs, the switching-off remained incomplete (Fig. 3) (production of stridulatory patterns was inferred on the basis of electromyograms from the relevant thoracic musculature). Imposed movement of the hindlegs, on the other hand, suppressed the G-neuron response in a graded fashion, depending on the frequency of the movement (Figs. 4 and 5). These experiments suggest that the switching-off is brought about by a combination of proprioceptive feedback and central efferences. The switching-off phenomenon could either protect the grasshopper's auditory pathway from undesired effects of overloading by its own intense song (e.g. self-induced habituation as described by Krasne and Wine 1977) and should therefore apply for most auditory neurons. Alternatively it could prevent escape reflexes from being triggered by stridulatory self-stimulation and consequently might apply only for neurons involved in such networks (as the G-neuron might be).     

On the binding of dolichol by human serum

The presence of a dolichol binding system is demonstrated in human serum. The dolichol binding exhibits normal saturation kinetics with an apparent affinity constant Kd of 6.9 X 10(-6) M. Optimal binding is obtained at pH 7.4 and 5 degrees C. After binding the [3H]dolichol cannot be chased by unlabelled dolichol. The selectivity is examined by competition studies showing that only dolichyl derivatives equally compete for binding sites. From buoyant density centrifugation and gel filtration it is deduced that the dolichol binding is due to a serum protein fraction, displaying the characteristics of VLDL.