The recovery of the reactivity of the auditory system in the dolphin Tursiops truncatus to paired acoustic stimuli with different spectra]

Recovery cycles of the auditory brainstem responses were studied in the bottle-nosed dolphin, Tursiops truncatus, using paired acoustic clicks. The recovery time was longer if both clicks had identical spectra (50% recovery at 0.9 ms), as compared with that of different spectra (50% recovery at 0.35 ms). These results can explain a different recovery time of evoked responses after an artificial sound and after own locating one.     

Assimilation of animal fats by yeasts and synthesis of protein by continuous cultivation in a complex nutrient medium

Under the conditions of continuous cultivation studies were carried out on a mixed culture (association) with two strains of yeasts: Candida sp., assimilating animal fats, and Candida scottii, assimilating reducing sugars. A complex nutrient medium of wood hydrolysate was used. It was established that in this medium, at a rate of dilution of D = 0.25 h^?1, the mixed culture assimilates the fats and the sugars simultaneously. As a result of this the yield of absolutely dry yeasts with regard to the total sum of fats and sugars amounts to 71% in the case of incineration fat and to 82% in the case of technical pork fat. The contents of protein, amino acids, lipids and ashy substances in the yeasts obtained from a medium with fats do not differ substantially from those obtained from the same medium without fats.     

Occurrence and seasonal variation of 19-norcholest-4-en-3-one and 3 beta-monohydroxy sterols in the Californian gorgonian, Muricea californica

The first natural occurrence of 19-norcholestenone is reported, together with 17 sterols and one other delta 4-3-ketone in the extracts of the Californian gorgonian, Muricea californica (Aurivillius). Six additional demethyl sterols and five additional 4-monomethyl sterols which remain unidentified were also detected. Lipid extracts of M. californica from a winter and summer collection were split by various chromatographic methods into free sterol, steryl ester, and steryl conjugate fractions. Sterol compositions (determined by CG and CG-MS) of each fraction, subsequent to hydrolysis, are tabulated and discussed with respect to plausible origins of observed variations. The possible relationship of the Muricea 19-nor-steroidal ketone to other naturally occurring 19-nor-steroids is discussed.     

Nephrotoxic effect of the specific brain serotonin depletor para-chlorophenylalanine

Brain serotonin depletion induced by peripheral parachlorophenylalanine (pCPA) is frequently used to evaluate the role of the central serotoninergic system in the regulation of a number of physiological functions, including the secretion of renin by the kidney. We found that due to the treatments applied in the protocol used for the investigation of pCPA effect on renin and vasopressin secretion in rats (300 mg/kg i.p. 64 and 40 h before sacrifice) renal injury was induced as well. Typical changes indicating acute renal failure were observed--an initial polyuria, natriuresis and body mass loss, succeeded by oliguria, decreased glomerular filtration rate, and salt and creatinine retention. Morphological changes in the glomeruli included a thickening of the basal membranes, a confluence and a reduced number of podocyte pedicles. A slight to moderate granular degeneration was observed in epithelial cells of the proximal convoluted tubule, combined with mitochondrial changes--an increase in number, matrix disorganization, and myelin degeneration. In conclusion, the renal function changes after i.p. pCPA may be due not to brain serotonin depletion-alone, but also to nephrotoxic effect.     

ABR frequency tuning curves in dolphins

Tone-tone masking was used to determine auditory brain-stem response tuning curves in dolphins (Tursiops truncatus) in a simultaneous-masking paradigm. The Q ₁₀ of the curves was as large as 16–19 in the frequency range 64–128 kHz. In the range 45–16 kHz, Q ₁₀ decreased proportionally to the frequency with the bandwidth of the curves being constant, about 3.5–4 kHz at the 10-dB level. Tuning curves below 45 kHz are supposed to reflect broad spectral bandwidth of the probe's effective part which is no longer than 0.5 ms, irrespective of actual probe duration. Tuning curves above 64 kHz are supposed to reflect the real frequency tuning of the dolphin's auditory system.Abbreviations ABR auditory brain stem response - AP action potential     

Biochemical changes accompanying the long-term starvation of Micrococcus luteus cells in spent growth medium

Changes in the biochemical properties of Micrococcus luteus cells were studied during the transition to a dormant state after incubation in an extended stationary phase. The overall DNA content after 150 days of starvation was similar to its initial level, while the RNA content decreased by 50%. Total lipids and protein, phospholipids and membrane proteins declined rapidly within the first 1–10 days of starvation. After 180 days of starvation, cells contained 43% of the protein and 35% of the lipid initially present. Starvation for 120 days resulted in the loss of phosphatidylglycerol and, to some extent, of phosphatidylinositol, giving a membrane whose phospholipids consisted mainly of cardiolipin. The membrane fluidity declined during starvation, as judged by diphenyl hexatriene fluorescence anisotropy measurements. Oxidase activities declined to zero within the first 20–30 days of starvation, while the dehydrogenases and cytochromes were more stable. The activities of some cytoplasmic enzymes were lost very rapidly, while NADPH-linked isocitrate dehydrogenase had 30% of its initial activity after 120 days of starvation. For all parameters tested there were significant fluctuations during the first 10–20 days of starvation, which may reflect cryptic growth in the culture.Abbreviations MPN Most probable number - DPH Diphenyl hexatriene