Biomedical subjects
Publications and source records attributed to G Harnischfeger.
An aqueous extract of Orthosiphonis folium, given orally, enhances considerably ion excretion in rat to a level comparable to that obtained with furosemide. No aqueretic action is observed. The increased ion excretion is not due to the potassium content of the starting material.
Single-unit responses to tonal stimulation with interaural disparities were recorded in the nuclei of the superior olivary complex (SOC) and the central nucleus of the inferior colliculus (ICC) of the echolocating bat, Molossus ater. Seventy-six units were recorded from the ICC and 74 from the SOC; of the SOC units, 31 were histologically verified in the medial superior olive (MSO), 10 in the lateral superior olive (LSO), and 33 in unidentified areas of the SOC. Best frequencies (BFs) of the units ranged from 10.3 to 89.6 kHz, and Q10 dB values ranged from 2 to 70 dB. Most ICC neurons responded phasically to stimulus onset and were either inhibitory/excitatory [I/E; (53)] or excitatory/excitatory [E/E; (21)] units. In the MSO, 23 units responded tonically and 7 phasically on, 18 were E/E or E/OF (facilitatory for other input) units, and 11 were I/E neurons. All LSO neurons responded in a "chopper" fashion, and the binaural neurons were E/I units. In E/E units the excitatory response to binaural stimulation was frequently larger than the sum of the monaurally evoked responses. Many neurons with E/I or I/E inputs had very steep binaural impulse-count functions and were sensitive to small interaural intensity differences. Twenty-eight units (24%) responded with a change in firing rate of at least 20% to interaural time differences of +/- 500 microseconds. Within this sample, 11 units (8 from ICC, 2 from MSO, and 1 from SOC) were sensitive to interaural time differences of only +/- 50 microseconds. Of these 11 units, 10 were I/E units responding phasically only to stimulus onset and were also sensitive to intensity differences (delta I), being suppressed completely by the inhibitory input over a delta I range of 20 dB or less. Of 117 units tested in the ICC and SOC nuclei, 86 units (76%) were not sensitive to interaural time disparities within +/- 500 microseconds. Because the BFs of these units sensitive to interaural transient time differences (delta t) ranged between 18 and 90 kHz, responses were elicited by pure tones, and responses did not change periodically with the period equal to that of the stimulus frequency, we conclude that the neurons reacted to interaural differences of stimulus-onset time (transient time difference) but not to phase differences (ongoing time difference). Sensitivity to interaural time differences was also correlated with interaural intensity differences.(ABSTRACT TRUNCATED AT 400 WORDS)
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Mapping of auditory area in the cerebellar vermis and hemispheres of little brown bats, Myotis lucifugus, shows that a large area of the bat's cerebellum contains units responding to acoustic stimuli. These units had latencies between 4 and 34 msec and best frequencies between 33.0 and 92.5 kHZ. The Q10-dB values of their tuning curves ranged from 2.0 to 19.7. Most of the units studied fired only a few impulses during a stimulus with minimum thresholds between 22 and 90 dB SPL. Units in the cerebellar vermis tend to have higher best frequencies and shorter latencies than those in the cerebellar hemispheres. However, there is no evidence of clear tonotopic organization therein.
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Cooling of chloroplasts to--196 degrees C can under certain circumstances lead to an erroneous analysis of energy distribution. After minimizing influences of sample geometry and effects of plastid concentration it is shown that externally induced membrane change leads to an increase in the ratio F740/F687 of the fluorescence emission spectrum. Similar alterations can be observed by variation of the rate of cooling the plastids to 77 K, expecially if whole chloroplasts are used. The differences in emission ratios are indicative also of changes in initial energy distribution between the photosystems, given here by the value alphaN. This is inferred from experiments with either osmotically induced thylakoid disturbances or those effected through a slow cooling process. The circumstances and the significance of these observations are discussed.
The Alcian blue method for extracellular marking of recording sites has been improved by filling the glass micropipettes with 3% Alcian blue 8GX or 8GS in 3M KCl buffered to pH 5.2 with 0.05M Potassium acetate. By filling the microelectrodes with a strong electrolyte (3M KCl) the same low resistances (5--25 M omega) and recording properties as conventional micropepettes are preserved. Currents of 0.5--1 microA for 1--3 min passed through the different electrode connected as anode, resulted in coloured spots of 10--100 micrometers in diameter. There was a positive correlation between the amount of curren passed, and the size of the spots. The localization of the electrode tips was successful in more than 80% of all cases. The dyemarks remained for at least 5 cays in vivo and resisted many histological procedures.
4-Phenylspiro [furan-2(3H),1-phtalan]3,3'-dione (fluorescamine) was used to covalently modify amino groups of thylakoids. Subsequently its effect on parameters of energy transfer and phosphorylating activity was assessed. While electron transport, the extent of proton uptake, 515 nm change and 9-aminoacridine quench were relatively resistant to such treatment, the functions connected to coupling factor 1, namely ATP formation by acid/base transition, ATPase activity and photophosphorylation were affected much earlier. Photophosphorylation appears to be the most sensitive. The data are interpreted as indicating an involvement of free amino groups in energy transfer.
Short illumination with white light of dark-maintained Anacystis nidulans prior to immersion in liquid nitrogen resulted in a marked change of fluorescence emission characteristics at 77 K. The fluorescence of Photosystem II-associated membrane bound pigments increases, while the emission due to phycobilins decreases. This effect seems to be due to a light-dependent alteration in the extent of contact between phycobilisomes and thylakoids, since the effect is reversible in the dark and is abolished by short glutaraldehyde fixation. The preillumination effect is not inhibited by DCMU. Emission spectra obtained with actively growing and CO2-starved cells indicate that the light-dependent increase in energy transfer from phycobilins to chlorophyll depends upon the physiological state of the cells.
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