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Biomedical subjects

J Vellinger

Publications and source records attributed to J Vellinger.

5 recordsLinked to original sources
PubMed2000

Multistage electrophoresis system for the separation of cells, particles and solutes.

It is common to operate equilibrium-based separation methods, such as distillation and extraction, as multistage unit operations, in which equilibrium is presumably achieved within each stage. Two rate-based separation processes, free electrophoresis and magnetic particle separation, have now been operated in multistage mode. Preparative free electrophoresis of particles and solutes has resisted scale-up and is confined to a narrow range of ionic compositions. Natural convection induced in electrophoresis buffers by Ohmic heating has been a strong deterrent and has led to such measures as radial electrophoresis in Couette flow, free-flow electrophoresis, low-gravity electrophoresis, density gradient electrophoresis, and reorienting density gradient electrophoresis, to name a few. The short vertical electrophoresis path exploited in the last-mentioned forms the basis for multistage electrophoresis. A thin-layer countercurrent distribution apparatus was designed and constructed so that up to 20 fractions could be collected on the basis of electrophoretic mobility by applying an electric field. The mixture to be separated starts in a bottom cavity, and successive top cavities collect fractions as separand particles or molecules are electrophoresed upward out of the bottom cavity. Mathematical models of this process were developed, and experiments were performed to verify the predictions of the models by collecting and counting particles in each cavity after fractionation.

Animals↗
PubMed1996

Microgravity in the STS-29 space shuttle discovery affected the vestibular system of chick embryos.

Out of 32 embryos flown (16 @ E2 + 16 @ E9) for 5 days, 16 survived. All sixteen E2 were dead at landing. Eight were opened and eight were incubated at 1.0G. Autopsy showed that 4 E2 survived over 24 hours in space. Eight E14 hatched without anatomical malformations, and 8 E14 were fixed. The height of the macular epithelia was 31 mu m (mean) in control and 26 mu m in flight chicks. The cross-sectional area of macular nuclei of control was 17 mu m(2) for hair cells and 14 mu m(2) in supporting cells. In flight, cross-sectional area was 17 mu m(2) in hair cells and 15 mu m(2) in supporting cells (n=250). The shape factor of cartilage cells (1.0 = perfect circle) between control (mean = 0.70) and flight (mean = 0.72), and the area of cartilaginous cells between controls (mean = 9 mu m(2)) and flight (mean = 9 mu m(2)) did not differ (n=300). The nuclei of support cells were closer to the basement membrane in flight than in control chicks. The immunoreactivity of otoconia with anti keratan, fibronectin or chrondroitin sulfate was not different between flight and control ears. There were more afferent fibers inside the macular epithelia of flight (p<0.05) than control. Three of 8 flight animals had elevated vestibular thresholds (VT), with normal mean response amplitudes and latencies. Modified afferent innervation patterns requiring weeks to compensate are sufficient to elevate VT, and should be investigated further. Other reversible (sublethal) microgravity effects on sensory epithelia (vacuoles, swelling, etc) require quantification.

Animals↗
PubMed1993

Effects of microgravity on vestibular ontogeny: direct physiological and anatomical measurements following space flight (STS-29).

Does space flight change gravity receptor development? The present study measured vestibular form and function in birds flown as embryos for 5 days in earth orbit (STS-29). No major changes in vestibular gross morphology were found. Vestibular response mean amplitudes and latencies were unaffected by space flight. However, the results of measuring vestibular thresholds were mixed and abnormal responses in 3 of the 8 flight animals raise important questions.

Action Potentials↗
PubMedDate not supplied

Normal vestibular function in chicks after partial exposure to microgravity during development.

Sixty-four fertilized chicken eggs, half at developmental Day 2 and half at Day 9, were exposed to micro-gravity for 5 days aboard the shuttle. Postflight examination showed that none of the Day 2 flight embryos had survived, whereas the Day 9 flight group and both groups of synchronous ground control embryos appeared viable. One-half of the Day 9 flight and ground control embryos were dissected and the temporal bones preserved in acetone for morphological examination. The other half was allowed to hatch to examine vestibularly related behavioral changes. Morphology of the lagenar otoconia was evaluated by scanning electron microscopy. Behavioral changes were accessed by a battery of reflex tests and recordings of spontaneous and vestibularly driven head movements. The results from both the morphological and behavioral studies showed no consistent difference between the flight and the control animals. Several hypotheses may account for this negative result. Because all the Day 2 embryos failed to survive, the remaining Day 9 chicks may have passed the critical developmental period of the chick's vestibular system. Also, the reexposure of the developing chick embryo to earth's 1-g environment may have masked any adverse behavioral effects that exposure to Microgravity may have caused.

Animals↗