Biomedical subjects

H A Dengerink

Publications and source records attributed to H A Dengerink.

At least 19 recordsLinked to original sources

PubMed1993

Substance P increases cochlear blood flow without changing cochlear electrophysiology in rats.

Carotid artery infusions of substance P yielded reductions in systemic blood pressure and elevations in cochlear blood flow (CoBF), measured via laser Doppler flowmeter, with no alterations in cochlear action potentials or cochlear microphonics in Wistar-Kyoto rats. Additionally, direct micro-infusions of substance P into the anterior inferior cerebellar artery, which contributes to the local vascular perfusion of the cochlea, yielded elevations in CoBF with no changes in systemic blood pressure. Pretreatment with a specific substance P receptor antagonist, ([D-Pro2,D-Trp7,9]SP) via the carotid artery or the anterior inferior cerebellar artery, diminished subsequent substance P-induced vascular responses. These results suggest that endogenous substance P, like other vasoactive peptides, may interact with a substance P-specific receptor population in the cochlea and may therefore participate in the ongoing regulation of CoBF. These findings also support the premise that vasodilatory hormones, along with vasoconstrictive agents, may be involved in the autoregulation of CoBF.

Action Potentials↗

PubMed1992

The interaction of smoking and noise on temporary threshold shifts.

Four separate experiments examined the effects of cigarette smoking on temporary threshold shifts (TTS) following noise exposure. One experiment compared smokers and non-smokers after the subjects had abstained from smoking for at least 6 h. A second experiment tested only smokers who smoked a cigarette just before noise exposure, during the noise exposure and in a control condition during which they did not smoke. A third experiment tested only non-smokers who were exposed to noise after chewing nicotine gum or after a control condition in which they rested without chewing the gum. A fourth experiment tested smokers and non-smokers in one condition which required them to smoke a cigarette just prior to noise exposure and in another condition which prevented them from smoking. The results indicate that smokers consistently evidence slightly smaller TTS than do non-smokers. Non-smokers evidenced significantly greater TTS at one frequency after they had chewed nicotine gum than when they had not. These results suggest that the smaller TTS associated with cigarette smoking is related to both the chronic and the acute effects of smoking and that these effects may be more attributable to carbon monoxide than to nicotine.

Adolescent↗

PubMed1992

Noise levels from toys and recreational articles for children and teenagers.

This study examined the noise level emitted by toys and recreational articles used by children and teenagers. The results indicate that many of the items tested emit sufficiently intense noise to be a source of noise induced hearing loss in school-age children. While the baby toys provided noise exposure within the limits of national regulations, they are most intense in a frequency range that corresponds to the resonance frequency of the external auditory canal of very young children. Hobby motors emit noise that may require protection depending upon the length of use. Fire-crackers and cap guns emit impulse noises that exceed even conservative standards for noise exposure.

Adolescent↗

PubMed1991

The influence of intra-arterial infusion of arginine vasopressin on cochlear blood flow in the rat.

Intra-arterially infused arginine vasopressin (AVP) elevated systemic blood pressure (BP) in the Sprague-Dawley rat according to a dose-response pattern while cochlear blood flow (CoBF), as measured by laser Doppler flowmetry, was elevated only at the highest dose. Skin blood flow (SBF) decreased significantly with AVP infusion. The local infusion of AVP into the anterior inferior cerebellar artery (AICA), which supplies the common cochlear artery, produced significant dose-dependent reductions in CoBF with no changes in systemic blood pressure. Pretreatment of the local cochlear supplying vessels with an AVP-specific V1 receptor antagonist attenuated subsequent AVP-induced decreases in CoBF, thereby demonstrating specificity of the response. These results suggest that CoBF is reasonably stable in response to systemic AVP infusion until blood pressure exceeds an elevation from base level of approximately +60 mm Hg. One of the mechanisms responsible for this autoregulatory response may be vasoconstriction mediated by the interaction of vasoactive peptides such as AVP and its receptors located in the vasculature of the inner ear or in the more peripheral vessels directly supplying the cochlea.

Animals↗

PubMed1991

Effects of hydroxyethyl starch, nimodipine, and propylene glycol on cochlear blood flow.

A primary goal of pharmacologic treatment for otopathologies of vascular origin is to elevate cochlear blood flow (CoBF), thus facilitating the transport of oxygen and nutrients without compromising perfusion pressure in other tissues. In the present investigation, significant increases in CoBF were measured during intra-arterial infusion of the plasma expanding agent, hydroxyethyline starch (HES), and the vasodilator nimodipine, in anesthetized adult male guinea pigs. There were no changes in systemic blood pressure during the infusion of HES or nimodipine. Intra-arterial infusion of propylene glycol (PG), which is used as a nonaqueous solvent, produced inconsistent CoBF effects accompanied by initial decreases in systemic blood pressure with subsequent increases. It is concluded that nimodipine and HES are very promising agents for inducing increases in CoBF, whereas PG produced inconsistent effects on CoBF while elevating blood pressure, thus compromising its potential usefulness in the treatment of otopathologies.

Animals↗

PubMed1991

Effects of perilymph volume adjustments on cochlear blood flow in the guinea pig.

Previous research suggests a potential relationship between perilymphatic pressure (Pp) and cochlear blood flow (CBF); however, the alterations in Pp necessary to produce changes in CBF have not been adequately described or quantified. The effects of perilymph volume changes on systemic blood pressure (BP) and CBF were presently investigated in the guinea pig cochlea. Five microliters of perilymph were displaced in each of three conditions: viz. evacuation of 5 microliters from the cochlea; replacement of these 5 microliters; and finally the addition of 5 microliters of artificial perilymph into the cochlea. All perilymph volume adjustments were completed in 1-microliter increments during which changes in CBG and BP were recorded. Significant alterations in CBF were observed during 1-microliter perilymph volume adjustments in each condition with no significant changes in systemic BP. The results from this study support our hypothesis that an inverse relationship exists between CBF and Pp in that decreases in perilymph volume yielded elevations in CBF while increases in perilymph volume yielded reductions in CBF.

Animals↗

PubMed1990

Pentoxifylline increases cochlear blood flow while decreasing blood pressure in guinea pigs.

The effects of pentoxifylline on cochlear blood flow (CoBF) were investigated in anesthetized guinea pigs by laser Doppler flowmetry and intravital microscopy red blood cell velocity measurement. Intra-arterial infusion of pentoxifylline (3, 4, and 5 mg/kg/min) produced dose-dependent reductions in blood pressure, accompanied by significant elevations in CoBF that were not dose-dependent. These results are in general agreement with previous findings from our laboratory utilizing normotensive and spontaneously hypertensive rats, however, in contrast with rats, guinea pigs revealed an initial decrease in CoBF followed by an increase. Also, pentoxifylline produced relatively smaller elevations in CoBF in guinea pigs as compared with those previously reported in rats. Taken together these results support the hypothesis that pentoxifylline increases vascular perfusion by decreasing blood viscosity and increasing the plasticity of red blood cells.

Animals↗

PubMed1990

Androgenic effects on angiotensin II-induced blood pressure and cochlear blood flow changes in rats.

Ovariectomized, castrated, and sham-castrated rats pretreated with oil or testosterone were intra-arterially infused with saline and three doses of angiotensin II while blood pressure and cochlear blood flow were measured. The results indicated a positive dose-response relationship for blood pressure and cochlear blood flow. Sham-castrated males had higher mean blood pressure responses than castrated males, followed by ovariectomized females. Cochlear blood flow responses were higher in the sham-castrated males than the ovariectomized females, followed by the castrated males. In comparison to the male groups, the ovariectomized females evidenced the lowest, middle, and highest cochlear blood flow responses to the three increasing doses of angiotensin II. Testosterone pretreatment facilitated angiotensin-induced cochlear blood flow elevations in all three angiotensin doses. These results suggest that endogenous and exogenous androgens may alter blood pressure and/or cochlear blood flow responses to angiotensin II via different mechanisms.

Angiotensin II↗

PubMed1989

The effects of intracerebroventricularly administered angiotensin II on blood pressure and cochlear blood flow in rats and guinea pigs.

Guinea pigs and Sprague-Dawley rats were intracerebroventricularly (icv) infused with various doses of angiotensin II (AII) in order to investigate central control of and species differences in cochlear blood flow (CBF) and blood pressure (BP). The results indicated a positive dose-response relationship between icv infusions of AII for BP and CBF in members of both species. This relationship was more predictable in the guinea pig than in the rat. In addition, responses to similar AII doses between species indicated that: a) BP elevations were significantly greater in the rat than in the guinea pig, b) CBF elevations were not significantly different between the rats and guinea pigs, and c) CBF was more highly correlated with BP in the guinea pig than in the rat. These results suggest that different relationships may exist between BP and CBF in rats and guinea pigs.

Angiotensin II↗

PubMed1989

Autoregulation of cochlear blood flow in normotensive and spontaneously hypertensive rats following intracerebroventricularly mediated adjustment of blood pressure.

Previous studies in our laboratory (Quirk et al., 1988) noted significantly impaired elevations in cochlear blood flow (CoBF) during systemic infusion of the potent vasoconstrictive agent angiotensin II (AII) in the spontaneously hypertensive rat (SHR) as compared with the normotensive Wistar-Kyoto (WKY) rat, despite similar increases in systemic blood pressure. We interpreted these results to suggest that SHRs have an exaggerated autoregulatory mechanism that controls blood supply to the cochlear vessels. However, an alternative explanation for these findings concerns the potential influence of the elevated baseline blood pressure of the SHR on CoBF. Specifically, if there is an absolute threshold blood pressure that triggers an autoregulatory response in the cochlea, then the SHRs would reach that threshold sooner than normotensive animals because they begin at a baseline blood pressure that is well above that of the WKY rat. The present study addressed this possibility by pharmacologically reducing SHR blood pressure to WKY baseline blood pressure and raising WKY to SHR baselines, followed by the infusion of previously utilized doses of AII. The results are consistent with previous findings and support our interpretation of an exaggerated autoregulation of cochlear blood supplying the SHR.

Angiotensin II↗

PubMed1989

Cochlear blood flow autoregulation in Wistar-Kyoto rats.

Wistar-Kyoto rats (WKY) were intra-arterially infused with angiotensin II (AII) or phenylephrine for 10 min. Both vasoactive compounds produced an initial increase in cochlear blood flow (CoBF) as measured by laser Doppler flowmetry, followed by a slow steady return to baseline, despite sustained elevations in systemic blood pressure. These results suggest autoregulation of CoBF in the WKY rat. In a second experiment. All was infused directly into the anterior inferior cerebellar artery (AICA) which feeds the cochlear artery. Significant reductions in CoBF were noted without changes in systemic blood pressure. Pretreatment with the specific angiotensin-receptor antagonist, sarthran (Sar1, Thr8-AII), diminished subsequent AII-induced reductions in CoBF. These results indicate that AII binding to vascular receptors may induce vasoconstriction in the supplying vessels of the cochlea, and thus, the interaction of blood-borne AII and vascular angiotensin receptors may participate in the autoregulation of CoBF.

Angiotensin II↗

PubMed1988

Blood pressure in resting, anesthetized and noise-exposed guinea pigs.

This study investigated blood pressure in guinea pigs while they were 1) alert and free moving, 2) anesthetized with different anesthetics, and 3) exposed to continuous, 115 dB SPL white noise under anesthesia. The animals were prepared with a carotid artery catheter and permitted to recover for 48 h before blood pressure levels were measured. Mean arterial blood pressure in the resting, unrestrained guinea pig was 64 mmHg (+/- 1.38 S.E.). Ketamine Hydrochloride (Ketamine) significantly decreased, and Fentanyl-Citrate significantly increased, blood pressure. Fentanyl-Droperidol produced no substantial blood pressure change. Guinea pigs anesthetized with Fentanyl-Citrate and Fentanyl-Droperidol demonstrated significant blood pressure increases when exposed to noise, with the Fentanyl-Citrate group showing a greater response. Animals anesthetized with Ketamine Hydrochloride exhibited no significant blood pressure changes when exposed to the noise.

Anesthetics↗

PubMed1988

Angiotensin II-induced changes in cochlear blood flow and blood pressure in normotensive and spontaneously hypertensive rats.

Previous investigations in our laboratory have measured significant increases in the circulating levels of the potent vasoconstrictive hormone, angiotensin II (AII; 26 and 64 pg/100 microliters plasma, normal and noise exposed, respectively), during and following noise exposure in the alert rat (Wright et al., 1981). In the present study, these levels were approximated through intra-arterial infusion in the anesthetized spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto (WKY) rat. Laser Doppler flowmeter measurements of cochlear blood flow (CBF) indicated that despite equivalent AII-induced elevations in systemic blood pressure, CBF in the SHR did not increase to the levels measured in the WKY. Pretreatment with the specific angiotensin receptor antagonist sarile, (Sar1,Ile8-AII), reduced AII-induced elevations in systemic blood pressure in members of both strains, but did not change the overall pattern of CBF. These results indicate that SHRs may have a compromised cochlear circulation that is refractory to increases in systemic blood pressure.

Angiotensin II↗

PubMed1988

The effects of pentoxifylline on cochlear blood flow in normotensive and spontaneously hypertensive rats.

Normotensive and spontaneously hypertensive rats (SHRs) were given arterial infusions of saline and pentoxifylline in doses of 1.5, 2.0, and 3.0 mg/kg/min. Blood pressure decreased in a dose related fashion with increasing doses of pentoxifylline. Cochlear blood flow, measured via laser Doppler flowmeter, increased with infusion of pentoxifylline in members of both rat strains, but to a greater extent in SHRs than in normotensive animals. The mechanism of action appears to be decreased red blood cell rigidity which allows increased penetration of red blood cells into microvessels of the cochlea.

Animals↗

PubMed1988

Changes in pure-tone thresholds and temporary threshold shifts as a function of menstrual cycle and oral contraceptives.

The present study examined the effects of exogenous and endogenous ovarian hormones on auditory functioning in young women. Fluctuations in pure tone thresholds and temporary threshold shifts (TTS) at 4 kHz and 6 kHz were assessed across the menstrual cycle. A group of normally cycling, ovulatory women and a group of women using Ortho Novum 7/7/7, a tri-phasic oral contraceptive, were tested during menstruation, at ovulation, and during the luteal phase of their menstrual cycle. A group of men served as controls and were tested at 3 similarly spaced intervals. Only the normally cycling women had significant cyclic fluctuations in auditory sensitivity, displaying poorer thresholds at 4 kHz during the menstrual phase than at the time of ovulation or during the luteal phase. In addition, normally cycling women were found to have significantly less TTS at 6 kHz during the menstrual phase than women using oral contraceptives.

Adult↗

PubMed1987

Ovarian steroid and vasoconstrictor effects on cochlear blood flow.

Ovariectomized rats received intra-arterial infusions of phenylephrine and nicotine. Estrogen treatment for five days prior to these challenges diminished laser Doppler measures of cochlear blood flow (CBF) responses to phenylephrine and blood pressure responses to nicotine. Progesterone enhanced CBF responses to both phenylephrine and nicotine; combined progesterone and estrogen treatment enhanced blood pressure responses to phenylephrine. These results suggest that ovarian steroid-mediated cardiovascular effects may influence cochlear blood flow and potentially hearing functions.

Animals↗

PubMed1987

Noise-induced temporary threshold shifts: the effects of anticipatory stress and coping strategies.

Temporary Thresholds Shifts were assessed in five groups from before to after 5-minute exposure to 110 dB SPL white noise and in one additional group without noise exposure. In each group the baseline conditions were designed to elevate psychological stress via anticipation of the noise and venipuncture procedures. In the three experimental groups, procedures to reduce psychological stress were employed: Information, Relaxation, and Behavioral Avoidance. Manipulation checks supported the effectiveness of these arousal-reducing interventions. Temporary threshold shifts were considerably greater in two of the experimental conditions than in the noise-exposed control conditions.

Adaptation, Psychological↗

PubMed1987

The influence of subjective factors on temporary threshold shifts after exposure to music and noise of equal energy.

The present study examined the influence of subjective factors on temporary threshold shifts (TTS) after exposure to noise and music. Two groups of subjects, those who indicated liking and those who indicated disliking pop/rock music, were exposed to both noise and music on separate occasions. Subjects who liked the music exhibited less TTS following music than noise. They also exhibited less TTS in music than the subjects who disliked the music. Those who disliked the music evidenced greater magnitude of TTS in music than noise.

Attitude↗