Biomedical subjects

V Frenkel

Publications and source records attributed to V Frenkel.

6 recordsLinked to original sources

PubMed2001

Visualizing normal and defective bone development in zebrafish embryos using the fluorescent chromophore calcein.

Zebrafish have recently become a model of choice among developmental biologists. This unique model enables both modern molecular and genetic studies to be carried out to identify genes involved in a wide variety of developmental processes. The success of the genetic approach depends largely on the application of an easy and effective screening method to identify interesting mutants. In order to develop a method for visualizing skeletal structures in zebrafish embryos that would be suitable for screening skeletal mutants, we investigated the use of the fluorescent chromophore calcein, which binds specifically to calcified skeletal structures. By using this method, we followed the development of the skeletal structures in zebrafish embryos from day 1 to day 21 postfertilization, and analyzed the effect of bone morphogenetic protein-2 (BMP2) on axial skeleton development. We found the development of the calcified skeletal structure to appear in a progressive fashion from head to tail. Calcified structures in the head (i.e., the jaw) developed first, which were then followed by the axial skeleton in the trunk. Interesting to note was that there appeared to be two domains in the calcification of vertebrae within the axial skeleton. The first three vertebrae were in the first domain; the rest being in the second domain. Compared with Alcian blue staining, we found that calcein staining indeed labels calcified skeletal structures, and, moreover, it is a more sensitive and inclusive method for visualizing skeletal structures. To determine whether calcein staining could also be used to detect abnormal bone development, we ectopically expressed BMP2 in zebrafish notochord cells. We demonstrated that ectopic expression of BMP2 in notochord cells inhibited the development of the axial skeleton. Together, these results clearly demonstrated the sensitivity of calcein staining for visualizing bone structures in developing zebrafish embryos and its effectiveness for screening for mutants that have bone structure defects.

Alcian Blue↗

PubMed2001

Preliminary investigations of ultrasound induced acoustic streaming using particle image velocimetry.

Particle image velocimetry was used to investigate ultrasound-induced acoustic streaming in a system for the enhanced uptake of substances from the aquatic medium into fish. Four distinct regions of the induced streaming in the system were observed and measured. One of the regions was identified as an preferential site for substance uptake, where the highest velocities in proximity to the fish surface were measured. A positive linear relationship was found between the ultrasound intensity and the maximum streaming velocity, where a unitless geometric factor, specific to the system, was calculated for correcting the numerical relationship between the two parameters. The results are part of a comprehensive study aimed at improving mass transdermal administrations of substances (e.g. vaccines, hormones) into fish from the aquatic medium.

Acoustics↗

PubMed2000

Ultrasound-facilitated transport of silver chloride (AgCl) particles in fish skin.

Electron-dense nano-particles in aqueous suspension were administered by immersion into the epidermis of fish using ultrasound in the therapeutic range. Enhanced permeability of the tissues to the particles was achieved by acoustic cavitation, which induced a controlled level of necrosis in the outer cell layers, and by non-cavitational exposures, which widened intercellular spaces of non-necrosed tissue in deeper regions of the epidermis. Both particle concentration and penetration depth were quantified using transmission electron microscopy. While cavitation-induced perforation was necessary for particles to penetrate into the tissues, non-cavitational exposures during immersions increased the particle flux towards the skin surface, as well as the diffusion rate of the particles within the epidermis and their depth of penetration. The technique described above may potentially be applied for non-stressful, mass-administration of substances into aquatic animals, as well as the relatively new field of ultrasound-facilitated delivery in moist epithelial tissues in humans.

Animals↗

PubMed2000

Ultrasound-induced intercellular space widening in fish epidermis.

Transmission electron microscopy was employed to determine the effects of therapeutic ultrasound (US) (I(sata) < or =2.2 W cm(-2), 3 MHz), sonicated at different angles and durations, on the external epithelia of fish skin. Sonication at 1.7 W cm(-2) (90 s), where the ultrasonic beam was perpendicular to the skin surface, produced minor intercellular space widening (ICSW), as well as the disruption of desmosomes connecting between the cells. Increasing the intensity to 2.2 W cm(-2) increased ICSW, the extent of which was positively correlated to the duration of exposure (30 to 90 s). Perpendicular sonication produced ICSW, almost exclusively between cells of the two outermost cell layers, parallel to the skin surface. Sonicating at 45 degrees (2.2 W cm(-2), 90 s) produced ICSW in deeper cell layers in the tissues, in which the spaces were at seemingly random orientations. Mucous cells and macrophages were also found to be damaged, as were apoptotic epidermal cells. The suggested mechanism for ICSW is the formation of transverse (shear) waves at the interface between the aquatic medium and the skin surface. The waves, which are damped out within a few cell layers, give rise to shear stresses that, in turn, cause strains that act to separate between cells and damage some of the relatively weaker cells.

Animals↗

PubMed1999

Ultrasound-induced cavitation damage to external epithelia of fish skin.

Transmission electron microscopy was used to show the effects of therapeutic ultrasound (< or = 1.0 W/cm2, 1 MHz) on the external epithelia of fish skin. Exposures of up to 90 s produced damage to 5 to 6 of the outermost layers. Negligible temperature elevations and lack of damage observed when using degassed water indicated that the effects were due to cavitation. The minimal intensity was determined for inducing cellular damage, where the extent and depth of damage to the tissues was correlated to the exposure duration. The results may be interpreted as a damage front, advancing slowly from the outer cells inward, presumably in association with the slow replacement of the perforated cell contents with the surrounding water. This study illustrates that a controlled level of microdamage may be induced to the outer layers of the tissues.

Animals↗

PubMed1999

Prognostic significance of apoptosis regulators in breast cancer.

Dysregulation of normal programmed cell death mechanisms plays an important role in the pathogenesis and progression of breast cancer, as well as in responses of tumors to therapeutic intervention. Overexpression of anti-apoptotic members of the Bcl-2 family such as Bcl-2 and Bcl-X(L) has been implicated in cancer chemoresistance, whereas high levels of pro-apoptotic proteins such as Bax promote apoptosis and sensitize tumor cells to various anticancer therapies. Though the mechanisms by which Bcl-2 family proteins regulate apoptosis are diverse, ultimately they govern decision steps that determine whether certain caspase family cell death proteases remain quiescent or become active. To date, approximately 17 cellular homologs of Bcl-2 and at least 15 caspases have been identified in mammals. Other types of proteins may also modulate apoptotic responses through effects on apoptosis-regulatory proteins, such as BAG-1-a heat shock protein 70 kDa (Hsp70/Hsc70)-binding protein that can modulate stress responses and alter the functions of a variety of proteins involved in cell death and division. In this report, we summarize our attempts thus far to explore the expression of several Bcl-2 family proteins, caspase-3, and BAG-1 in primary breast cancer specimens and breast cancer cell lines. Moreover, we describe some of our preliminary observations concerning the prognostic significance of these apoptosis regulatory proteins in breast cancer patients, contrasting results derived from women with localized disease (with or without node involvement) and metastatic cancer.

Antineoplastic Agents↗