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Biomedical subjects

A Sundby

Publications and source records attributed to A Sundby.

28 records · Page 2Linked to original sources
PubMed1978

Plasma levels of testosterone in bulls. Response to repeated HCG injections.

Administration of 6000 IU HCG to 4 bulls was followed by an elevation of plasma testosterone lasting for 9-13 days. When HCG administration was repeated, the testosterone response was shortened to 4-6 days in 3 bulls due to the formation of antibodies against HCG. The appearance of HCG antibodies coincided with a sharp decrease in the plasma testosterone level, indicating that Leydig cells have to be under continuous HCG stimulation to maintain increased testosterone production. No antibody against bovine LH was detected in the plasma samples containing antibodies against HCG. In one bull the response following the second HCG injection was similar to the plasma testosterone pattern following the first. No antibodies against HCG were found in this bull. Five bulls received 750 IU HCG twice. Following the period with elevated plasma testosterone levels, subnormal levels were observed after both injections. One injection led to decreased levels without development of antibodies against HCG while the second HCG injection led to subnormal testosterone levels concomitant with measurable antibodies against HCG.

Animals↗
PubMed1975

Long-term effect of HCG on plasma testosterone in bulls.

The spontaneous diurnal variation of peripheral plasma testosterone concentrations in four bulls was established and then the long-term effect of a single intravenous or intramuscular injection of HCG on testosterone levels was studied. Intravenous and intramuscular HCG injections produced, within 1/2 hr and 3 hr, respectively, a rapid rise of testosterone to levels equivalent to the highest values seen in the diurnal pattern. A second increase of up to x2 to x3 the highest values of the diurnal cycle was observed 2 days after the injection of HCG, and the testosterone level remained high for at least 3 to 4 days after plasma levels of HCG were no longer detectable. The pattern of diurnal variation after HCG revealed an attenuation of the extensive spontaneous variation and high levels with only slight fluctuations were maintained.

Animals↗
PubMedDate not supplied

Effect of human fibrin adhesive on the ear. An electrophysiological study of auditory function in the guinea pig correlated to light and electron microscopy of middle ear mucosa and inner ear structures.

The effect of human fibrin adhesive applied to the middle ear has been studied in guinea pig. Auditory function was measured using acoustically evoked brainstem responses. Middle and inner ear structures were studied with light, transmission and scanning electron microscopy. A transitory conductive hearing loss was observed, but after 8 weeks the auditory function appeared normal. Microscopy of the middle and inner ear failed to show any tissue damage.

Animals↗
PubMedDate not supplied

Impedance changes elicited by electrocutaneous stimulation.

Electrical stimulation of the skin in the cavum conchae is followed by bilateral changes in the acoustic impedance of the ear due to reflex contraction of the stapedius muscle. A stimulator and a special surface electrode for electrical stimulation of the skin have been developed. The apparatus produces square-wave constant-current pulses independent of the electrical impedance of the electrode and the skin, and its hazard-proof. The effect of five independently variable stimulus parameters upon the elicited impedance changes has been examined in order to find a stimulus producing a large and reproducible impedance change without causing discomfort to the subject. Although a pronounced habituation phenomenon tends to mask the cause to effect relation of the various parameters, the results indicate that an appropriate stimulus is a pulse train of 0.5 s duration, consisting of individual pulses of a frequency of 200 Hz and 1 ms duration. The stimulus is applied at 10-second intervals.

Acoustic Stimulation↗