Biomedical subjects

M Versluis

Publications and source records attributed to M Versluis.

4 recordsLinked to original sources

PubMed2001

Snapping shrimp make flashing bubbles.

Snapping shrimp produce a loud crackling noise that is intense enough to disturb underwater communication. This sound originates from the violent collapse of a large cavitation bubble generated under the tensile forces of a high-velocity water jet formed when the shrimp's snapper-claw snaps shut (Fig. 1). Here we show that a short, intense flash of light is emitted as the bubble collapses, indicating that extreme pressures and temperatures of at least 5,000 K (ref. 4) must exist inside the bubble at the point of collapse. We have dubbed this phenomenon 'shrimpoluminescence' - the first observation, to our knowledge, of this mode of light production in any animal - because of its apparent similarity to sonoluminescence, the light emission from a bubble periodically driven by ultrasound.

Animals↗

PubMed2001

Spiraling bubbles: how acoustic and hydrodynamic forces compete.

Experiments to study the effect of acoustic forces on individual bubbles in shear flows have been carried out. In the system that we have used, the competition between acoustic and fluid dynamical forces results in a spiraling bubble trajectory. This dynamics is modeled by expressing the balance between Bjerknes and hydrodynamic forces in terms of an ordinary differential equation model, to which a separation of time scales is applied. The success of this model shows that the simple force-balance approach is still meaningful when bubbles are subjected to sound fields.

Journal Article↗

PubMed2000

How snapping shrimp snap: through cavitating bubbles.

The snapping shrimp (Alpheus heterochaelis) produces a loud snapping sound by an extremely rapid closure of its snapper claw. One of the effects of the snapping is to stun or kill prey animals. During the rapid snapper claw closure, a high-velocity water jet is emitted from the claw with a speed exceeding cavitation conditions. Hydrophone measurements in conjunction with time-controlled high-speed imaging of the claw closure demonstrate that the sound is emitted at the cavitation bubble collapse and not on claw closure. A model for the bubble dynamics based on a Rayleigh-Plesset-type equation quantitatively accounts for the time dependence of the bubble radius and for the emitted sound.

Air↗

PubMed1982

Opposite interactions between alpha- and beta-endorphin fragments with dopamine mediated responses on the rat rectum in vitro.

Dopamine causes a dose-dependent contraction of the rat rectum in vitro followed by a relaxation. This contraction can be inhibited by apomorphine and phenylephrine. This inhibition can be attenuated by the beta-endorphin (beta E) fragments 2-17 (des-Tyr1-gamma-endorphin, DT gamma E) and 6-17 (des-enkephalin-gamma-endorphin, DE gamma E). beta E 6-17 seems to be the shortest sequence with full activity in this respect since a shorter fragment (beta E 10-17) was less effective. The atypical neuroleptics oxypertine, sulpiride, and clozapine, the classic neuroleptic haloperidol and metoclopramide have a similar action to DE gamma E. The peptides and atypical neuroleptics do not affect the dopamine response per se while the classic neuroleptics haloperidol and metoclopramide enhance the dopamine response. The effects of the alpha-type endorphins are opposite to those of the gamma-type endorphins, since des-Tyr1-alpha-endorphin (DT alpha E, beta E 2-16) and des-enkephalin-alpha-endorphin (DE alpha E, beta E 6-16) enhance the phenylephrine-induced decreased responsiveness to dopamine. Structure-activity studies revealed that the active moiety of the alpha-endorphin fragments probably resides in the 6-9 region. In addition the alpha-type endorphins directly inhibit the dopamine response. It is concluded that the rat rectum may be used to analyse neuroleptic-like action. In this model alpha- and gamma-endorphin fragments may directly or indirectly influence the interaction of dopamine with the rectum. Because of the strong similarities between the effects of gamma-type endorphins and that of neuroleptics the results support the purported neuroleptic-like action of gamma-type endorphins. The influence of alpha-type endorphins and gamma-type endorphins on the apomorphine or phenylephrine induced decreased responsiveness to dopamine, although opposite, seems to be mediated by an influence on different dopamine sensitive systems.

Acetylcholine↗