PubMed Health⌕ Search

Biomedical subjects

A Rollins

Publications and source records attributed to A Rollins.

9 recordsLinked to original sources
PubMed2001

Photothermal coagulation of blood vessels: a comparison of high-speed optical coherence tomography and numerical modelling.

Optical-thermal models that can accurately predict temperature rise and damage in blood vessels and surrounding tissue may be used to improve the treatment of vascular disorders. Verification of these models has been hampered by the lack of time- and depth-resolved experimental data. In this preliminary study, an optical coherence tomography system operating at 4-30 frames per second was used to visualize laser irradiation of cutaneous (hamster dorsal skin flap) blood vessels. An argon laser was utilized with the following parameters: pulse duration 0.1-2.0 s, spot size 0.1-1.0 mm, power 100-400 mW. Video microscopy images were obtained before and after irradiations, and optical-thermal modelling was performed on two irradiation cases. Time-resolved optical coherence tomography and still images were compared with predictions of temperature rise and damage using Monte Carlo and finite difference techniques. In general, predicted damage agreed with the actual blood vessel and surrounding tissue coagulation seen in images. However, limitations of current optical-thermal models were identified, such as the inability to model the dynamic changes in blood vessel diameter that were seen in the optical coherence tomography images.

Animals↗
PubMed1998

A novel fiber-optic pH sensor incorporating carboxy SNAFL-2 and fluorescent wavelength-ratiometric detection.

A fiber-optic pH sensor was prepared using the self-referencing fluorescent pH probe carboxy seminaphtho-fluorescein (SNAFL-2). The ratio of the emission from the base form of this dye and the emission near the isoemissive point is insensitive to variations in the excitation intensity and photobleaching. The carboxy SNAFL-2 and a photoaffinity crosslinker, 4-azido-2,3,5,6-tetrafluorobenzoic acid, succinimidyl ester, were attached onto poly(acrylamide-co-vinylamine) to form a hydrophilic functional membrane for the fiber-optic sensor. Photo crosslinking was used to create a crosslinked pH-sensing membrane and covalently bind the membrane onto the surface of the PMMA optical fiber. The fluorescent properties of the membrane-fiber conjugate have been determined. The membrane is stable, and the pH sensor shows a fast response time and excellent resolution in a wide pH range of 3 to 11.

Biocompatible Materials↗
PubMed1997

Protein kinase C isozyme-mediated cell cycle arrest involves induction of p21(waf1/cip1) and p27(kip1) and hypophosphorylation of the retinoblastoma protein in intestinal epithelial cells.

The molecular mechanisms underlying protein kinase C (PKC) isozyme-mediated control of cell growth and cell cycle progression are poorly understood. Our previous analysis of PKC isozyme regulation in the intestinal epithelium in situ revealed that multiple members of the PKC family undergo changes in expression and subcellular distribution precisely as the cells cease proliferating in the mid-crypt region, suggesting that activation of one or more of these molecules is involved in negative regulation of cell growth in this system (Saxon, M. L., Zhao, X., and Black, J. D. (1994) J. Cell Biol. 126, 747-763). In the present study, the role of PKC isozyme(s) in control of intestinal epithelial cell growth and cell cycle progression was examined directly using the IEC-18 immature crypt cell line as a model system. Treatment of IEC-18 cells with PKC agonists resulted in translocation of PKC alpha, delta, and epsilon from the soluble to the particulate subcellular fraction, cell cycle arrest in G1 phase, and delayed transit through S and/or G2/M phases. PKC-mediated cell cycle arrest in G1 was accompanied by accumulation of the hypophosphorylated, growth-suppressive form of the retinoblastoma protein and induction of the cyclin-dependent kinase inhibitors p21(waf1/cip1) and p27(kip1). Reversal of these cell cycle regulatory effects was coincident with activator-induced down-regulation of PKC alpha, delta, and epsilon. Differential down-regulation of individual PKC isozymes revealed that PKC alpha in particular is sufficient to mediate cell cycle arrest by PKC agonists in this system. Taken together, the data implicate PKC alpha in negative regulation of intestinal epithelial cell growth both in vitro and in situ via pathways which involve modulation of Cip/Kip family cyclin-dependent kinase inhibitors and the retinoblastoma growth suppressor protein.

Animals↗
PubMed1977

Epidemiological studies of female prisoners. IV. Homosexual behavior.

The existence of homosexual behavior in female offenders is investigated not only as an adaptive process but as an established behavior existing prior to detention. Ninety-five prisoners from the Framingham Institution for Women were included: 26 were self-reported homosexuals, 42 were considered homosexuals by prision staff, and 27 were nonhomosexuals. Suicidal thoughts, suicidal attempts, psychiatric problems during menstruation, and a history of violent crimes against persons were characteristic of the homosexual group, whereas a history of crimes against self and property as well as history of alcoholism were common in the nonhomosexual group. Violet behavior together with suicidal attempts in homosexual female prisoners support the hypothesis that aggressive impulses may be expressed either externally or toward the self, the problem being one of impairment in control mechanisms. The findings also suppor the idea that violent behavior, as shown by this group of incarcerated homosexual females, is multidetermined. The factors that influence its appearance and expression could include a history of family violence, impulse control as children, neurological abnormality, sex role identification problems, biochemical abnormalities (manifested as menstrual irregularities), and impulse control problems as adults. A better understanding of human violence must be based on the recognition of the multidimensional nature of the problem using the tools and insights from many disciplines.

Adaptation, Psychological↗
PubMed1977

Parental loss, depression and violence. III. Epidemiological studies of female prisoners.

Information was obtained from 95 incarcerated female prisoners on their history of violence, on their feelings of depression, their suicide attempts, and on their history of loss of parents. The data revealed that the loss of father before the age of 10 years was more highly correlated with signs of depression in these women prisoners than was loss of mother. Women who reported at least one suicide attempt in the past were significantly more depressed on the self-report measure of depression than the other women, and were more likely to be judged as violent on the basis of several independent indices. The results support the hypothesis that violence toward others and suicidal behavior are part of the same phenomenon of impairment in control mechanisms.

Depression↗