Biomedical subjects

A Feyerabend

Publications and source records attributed to A Feyerabend.

5 recordsLinked to original sources

PubMed1990

Mapping regional cerebral vascular transit time by simultaneous determination of local cerebral blood flow and local cerebral blood volume.

We developed a method for autoradiographic mapping of regional cerebral transit time (CTT) by simultaneously measuring local cerebral blood flow (LCBF) and local cerebral blood volume (LCBV). Previously described single-tracer techniques for determination of LCBF and LCBV were modified for dual-tracer, 99mTc and 14C, autoradiography and used to create digital images of LCBF and LCBV from the same brain sections in a series of normal rats. The images were aligned and ratio images (LCBV/LCBF) were then generated which reflected CTT. Regional cerebral transit time was found to vary significantly through-out the brain in a pattern only partially related to that of blood flow. Such CTT heterogeneity could cause errors in implementation of kinetic models which assume uniform or monovariant distributions of vascular transit time.

Animals↗

PubMed1990

Gamma camera image acquisition, display, and processing with the personal microcomputer.

The authors evaluated the potential of a microcomputer for direct acquisition, display, and processing of gamma camera images. Boards for analog-to-digital conversion and image zooming were designed, constructed, and interfaced to the Macintosh II (Apple Computer, Cupertino, Calif). Software was written for processing of single, gated, and time series images. The system was connected to gamma cameras, and its performance was compared with that of dedicated nuclear medicine computers. Data could be acquired from gamma cameras at rates exceeding 200,000 counts per second, with spatial resolution exceeding intrinsic camera resolution. Clinical analysis could be rapidly performed. This system performed better than most dedicated nuclear medicine computers with respect to speed of data acquisition and spatial resolution of images while maintaining full compatibility with the standard image display, hard-copy, and networking formats. It could replace such dedicated systems in the near future as software is refined.

Gamma Cameras↗

PubMed1989

Ultra-high-speed teleradiology with ISDN technology.

A solid-state, personal computer-based, image digitization and transmission system was developed that uses integrated services digital network (ISDN), a technology under development for ultra-high-speed data transmission over normal phone lines. Thousands of images have been transmitted to a site more than 15 miles away, with data rates exceeding 56,000 bits or 7,000 bytes (1 byte = 8 bits) per second with nearly perfect accuracy. Present modification of the system hardware and software should increase the data rate to 128,000 bits, or 16,000 bytes, per second. With this rate of transmission, remote radiologic image transmission should become a practical, routinely available diagnostic tool.

Computer Communication Networks↗

PubMed1989

Two-compartment, two-sample technique for accurate estimation of effective renal plasma flow: theoretical development and comparison with other methods.

Discordance between effective renal plasma flow (ERPF) measurements from radionuclide techniques that use single versus multiple plasma samples was investigated. In particular, the authors determined whether effects of variations in distribution volume (Vd) of iodine-131 iodohippurate on measurement of ERPF could be ignored, an assumption implicit in the single-sample technique. The influence of Vd on ERPF was found to be significant, a factor indicating an important and previously unappreciated source of error in the single-sample technique. Therefore, a new two-compartment, two-plasma-sample technique was developed on the basis of the observations that while variations in Vd occur from patient to patient, the relationship between intravascular and extravascular components of Vd and the rate of iodohippurate exchange between the components are stable throughout a wide range of physiologic and pathologic conditions. The new technique was applied in a series of 30 studies in 19 patients. Results were compared with those achieved with the reference, single-sample, and slope-intercept techniques. The new two-compartment, two-sample technique yielded estimates of ERPF that more closely agreed with the reference multiple-sample method than either the single-sample or slope-intercept techniques.

Humans↗

PubMed1980

Identification and partial purification of human tumor nucleolar antigen 54/6.3.

The present study was designed to characterize the human tumor nucleolar antigens found first in the HeLa cells and subsequently in a broad range of human cancers. For visualization of the antigens, HeLa cell nucleolar or nuclear protein fractions were analyzed on 4% polyacrylamide isoelectric focusing gels. The gels were incubated with rabbit antisera to HeLa cell nucleoli and then with fluorescein- or peroxidase-conjugated goat anti-rabbit immunoglobulin G. With this technique, two major nucleolar antigens (focusing at pH 6.3 and pH 6.1) were identified. These antigens were also found in the Namalwa cell, but not in human liver cells. Purification of the antigen(s) was achieved by selective extraction of Namalwa cell nuclei with 10 mM Tris-HCl (pH 8), 40 to 100% ammonium sulfate precipitation, diethylaminoethyl cellulose chromatography in which the antigen was eluted with 0.15 M NaCl buffer (DE-0.15M fraction), and use of isoelectric focusing gels. The immunostained bands (HuAg 6.3 and HuAg 6.1) and the bright nucleolar immunofluorescence of the HeLa cells were not observed after the antisera were preabsorbed with the DE-0.15M fraction. The immunostained bands (HuAg 6.3 and HuAg 6.1) and the nucleolar immunofluorescence of the HeLa cells were also observed when isoelectric focusing gels were incubated with antiserum from rabbits immunized with the DE-0.15M fraction. On the sodium dodecyl sulfate second dimension of the two-dimensional polyacrylamide gel electrophoresis, the antigen(s) migrated as single spots with appraent molecular weights of 54,000.

Antigens, Neoplasm↗