PubMed Health⌕ Search

Biomedical subjects

T Simmons

Publications and source records attributed to T Simmons.

29 records · Page 2Linked to original sources
PubMed1986

Electrode configurations for a respiratory impedance measurement suitable for rate responsive pacing.

A rate responsive cardiac pacemaker will benefit the patient only if the input parameter is a reliable indicator of exercise. Part of the reliability is dependent upon selection of the best physiological parameter and part is dependent upon the measurement technique. Twenty-six patients have been studied in order to ascertain the best measurement configuration for an intravascular impedance respiratory monitor. Four electrode configurations have been examined at rest and during exercise. The results have been compared using measures of sensitivity and specificity. The ideal configuration requires that a current field be established between the right ventricular blood and the pacemaker case. And, that voltage sensing be done between an electrode in the SVC and the pacemaker case.

Electrodes↗
PubMed1978

Uptake and early fate of metaphase chromosomes ingested by the Wi-L2 human lymphoid cell line.

Aspects of the ingestion and early intracellular fate of homologous. [3H]-thymidine-labeled chromosomes (donor) were studied in recipient Wi-L2 cells in the absence of reutilized radioactivity. As much as 67% of the cell-associated radioactivity was resistant to hydrolysis by DNase I after 4 h of incubation. Cell fractionation and electron microscope autoradiography indicated that chromosome uptake was rapid, into both cytoplasmic and nuclear fractions and was facilitator and dose dependent. Sedimentation analysis demonstrated that at 4 h donor DNA of approximate single-strand mol wt of 1--6 X 10(6), as compared to 6--12 X 10(6) for chromosomal DNA, was recoverable in cell fractions. By 6 h, a significant portion of the nucleus-associated donor DNA was converted into material of higher mol wt, although no evidence was found for integration into recipient DNA. Cytoplasmic donor DNA continued to be degraded. An average number of chromosome equivalents of nucleus-associated donor DNA to recipient cell nuclei of 1--4 was obtained and its relationship to the lower frequency of chromosome-mediated gene transfer is discussed.

Cells, Cultured↗
PubMed1975

Rectal diverticula.

Eight cases of rectal diverticula are discussed with reference to the etiological, clinical and radiological findings. Males predominated 3:1 and the average number of diverticula in each patient was 2. Diverticulosis of the remaining colon, especially the sigmoid segment, always accompanied rectal diverticula. The average diameter of rectal diverticula was larger than that of the colonic: 2.5 cm vs. 0.5-1.0 cm. Rectal diverticula may be confused with a carcinoma at endoscopy. Surgical treatment becomes necessary if the diverticulum progresses to abscess formation and perforation.

Aged↗
PubMed1973

Nuclear envelope-associated resumption of RNA synthesis in late mitosis of HeLa cells.

The restitution of RNA synthesis in cultures progressing from metaphase into interphase (G(1)) has been investigated in synchronized HeLa S(3) cells by using inhibitors of macro-molecular synthesis and the technique of electron microscope autoradiography. The rate of incorporation of radioactive uridine into RNA approached interphase levels in the absence of renewed protein synthesis. In contrast, maintenance of this rate in G(1) was dependent upon renewed protein synthesis. Restoration of synthesis of heterogeneous nuclear RNA occurred under conditions that inhibited production of ribosomal precursor RNA. In autoradiographs of individual cells exposed to radioactive uridine, silver grains were first detected after nuclear envelope reformation at the periphery of the chromosome mass but before chromosomal decondensation. These data are consistent with the following interpretation. Multiple RNA polymerase activities persist through mitosis and are involved in the initiation of RNA synthesis in early telophase at sites on the nuclear envelope.

Autoradiography↗
PubMedDate not supplied

Bizarre parosteal osteochondromatous proliferation: case report and review of the literature.

Bizarre parosteal osteochondromatous proliferation of bone (BPOP) is a benign lesion that is occasionally misinterpreted as a malignant process. The original reports described lesions exclusively in the hands and feet. However, subsequent reports have included additional sites in the long bones, skull, and maxilla. The differential diagnosis of BPOP includes numerous benign and malignant lesions. The benign differential diagnosis includes osteochondroma and reactive processes. The most important malignant differential diagnosis is parosteal osteosarcoma. We present a case of an 11-year-old boy with recurrent BPOP and review the literature. We discuss the differential diagnosis and pathogenesis of the lesion.

Bone Neoplasms↗
PubMedDate not supplied

Signal-averaged electrocardiography for detection of ventricular tachycardia using fast Fourier transform filtering on a standard ECG cart.

Signal-averaged electrocardiography has been advocated as a technique to predict the occurrence of ventricular tachycardia, especially in patients with ischemic heart disease. We studied a heterogeneous population of 77 patients referred for electrophysiologic testing using a recently developed fast Fourier transform filtering system available as part of a standard electrocardiography cart. The sensitivity, specificity, and positive predictive accuracy of this system were consistent with those previously determined using bidirectional Butterworth filters or finite impulse response filtering techniques. This new filtering approach in generation of signal-averaged ECG data for detection of ventricular tachycardia has promise but will require use in larger groups to establish its true clinical value.

Electrocardiography↗