Bacterial endocarditis with obstruction of the right atrioventricular orifice and the pulmonary outflow trace in an African monkey (Cercopithecus aethiops).

A 7 to 8-year-old male African green monkey (Cercopithecus aethiops) was found moribund in his cage. Fluid and antibiotic therapy were administered, but the monkey dies 2 hours later. At necropsy, large septic mural thrombi obstructed the right atrioventricular orifice and the pulmonary outflow tract, and smaller septic thrombi were attached to the leaflets of the pulmonary and mitral valves. Staphylococci were isolated from the large thrombus occluding the atrioventricular orifice. Large abscesses were present in the upper and lower lobes of the right lung, and small, wedge shaped infarcts were present in the lungs and kidneys. The clinical and pathologic findings were consistent with a rapidly progressive form of bacterial endocarditis. This was the only case of vegetative bacterial endocarditis seen at this instituion in 700 necropsies of nonhuman primates.     

Sacciform cells in the skin of teleost fish

The fine structure of sacciform gland cells of the epidermis is described in the number of species of teleost fish. In some of these the cell type had either not been found, or not recognized as such, before. Some histological and histochemical results are also reported. Despite considerable differences in the histochemistry and in the morphology of the sacciform cells over the range of species studied, some features of the fine structure are constant and can be used as diagnostic characters. The nucleus is peripheral, and there is a large membrane-limited lumen, into which the secretion is released from membrane-bounded vacuoles at the margin of the cytoplasm. It is probable that the secretion originates mainly in channels of endoplasmic reticulum which become swollen to form the vacuoles. Most sacciform cells open at the surface of the skin by an apical pore, but some have not been seen to open. The classification of the various unicellular glands of teleosts is discussed and it is concluded that attempts to categorise them by the nature of the secretion alone are unsatisfactory.     

Neuroethology has pregnant agendas

Two of the many agendas of neuroethology are illustrated with examples. The first issue is what cells or assemblies of cells and what patterns of activity are sufficient to accomplish recognition of ethologically important stimulus configurations and initiation of behavioral action. The theme is the opportunities available in relatively neglected approaches to these objectives. As an example, the approach is developed of gentle microstimulation of loci in the brain where cells have been found to be responsive to complex, natural stimuli, under conditions conducive to the performance of tell-tale behavior. Other approaches include: (a) microinjection of modulatory substances into regions with such complex recognition cells, and (b) recording in efficient and informative ways, by using multiple electrode arrays, registering wideband activity, in behaving animals. The second issue is what brain and behavior differences has evolution produced between major taxa at distinct grades of complexity. Emphasized are our relative ignorance of basic aspects of connectivity, physiology and cognitive capacities in the major grades and the probability of surprises from new studies that employ comparison. Accepted: 29 January 1999     

Postsynaptic potentials in pacemaker cells: A correlate of behavior in command cells of an electric fish

Intracellular recordings were made from pacemaker-command cells of the electric organ discharge (EOD) of the weakly electric fish Eigenmannia virescens. The fish was immobilized with gallamine triethiodide (Flaxedil) which silenced the EOD. A simulated EOD of this fish (ca. 300 Hz) and a sine wave simulating a neighbor, a few Hz higher (+ΔF) or lower (-ΔF) were introduced into the bath to elicit the “jamming avoidance response” (JAR), monitored through the pacemaker potential. We observed that accompanying the JAR there is a minute hyperpolarizing postsynaptic potential (hpsp) superimposed on the pacemaker potential. A shift in the phase of the hpsp occurs with a change in the sign of ΔF, and therefore of the JAR. Assuming that the behaviorally correlated hpsp is inhibitory, it suggests that mutual inhibition may play a role in regulating the synchronous firing frequency of command neurons, which are electrically coupled with one-another. Scheich and Bullock (1974) proposed a neuronal scheme for the JAR in which they suggest that two systems (P and T) operate together in the nervous system. The T system affects the pacemaker cells at a precise, variable phase of the pacemaker cycle. Although the present results indeed reveal a shift in the hpsp with a change in the sign of ΔF, the actual significance of this shift remains to be evaluated. The unexpected direction of the shift suggests either that the hpsp is excitatory at the phases when it occurs, or that effectiveness of inhibition decreases at later phases in this case instead of increasing as in other cases, or that the hpsp opposes the JAR. The parallel P system is probably more important in explaining the JAR, acting by a DC level control rather than a phase control.     

Differences in the androgen response between two mouse species

Renal weight and beta-glucuronidase activity are two of several well-characterized androgen-responsive parameters in Mus musculus. A similar sexual dimorphism was not reported for a second mouse species, Mus caroli, however. Since this was not associated with a general absence of androgen action, we considered whether a localized defect in androgen receptors or a difference in renal androgen-responsive endpoints in the two species existed. Only minor differences in the characteristics of renal androgen receptors from the two species were found when they were analyzed by two different methods. These differences were not thought to be sufficient to account for the apparent renal androgen unresponsiveness. No differences were found in androgen receptors from brain. Subsequently, a third renal endpoint, ornithine decarboxylase activity, was found to respond to androgen stimulation in Mus caroli. Control of renal androgen action in these two mouse species thus differs at the level of genetic regulatory elements.     

Crop rotation

Crop rotation has been used for thousands of years. During the 1950s and early 1960s, it was felt that synthetic fertilizers and pesticides could forever replace crop rotation without loss of yield, but that opinion has changed. The current consensus is that crop rotation increases yield and profit and allows for sustained production. For example, maize, in a 2‐year rotation with soybean, yields 5 to 20% more than continuous maize, and no amount of fertilizer or pesticide can compensate completely for that difference. It is not well understood what causes the rotation effect, but improvements in soil physical properties and soil organic matter probably play a beneficial role in rotations that include multiple years of sod, pasture, or hay. Short rotations such as maize‐soybean actually result in a degradation in those same factors, yet the rotation effect still is realized. Recent information suggests that soilborne pathogens may be responsible for the yield depression seen with continuous monoculture.