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Biomedical subjects

S H Lewis

Publications and source records attributed to S H Lewis.

9 recordsLinked to original sources
PubMed1998

Effects of tissue anisotropy on the spectral characteristics of ultrasonic backscatter measured with a clinical imaging system.

In this paper, we report the effects of inherent tissue anisotropy on the spectral properties of backscattered ultrasound when measured with a commercially-available imaging system. We insonified five specimens of bovine tendon immersed in a water tank and rotated in 10 degrees increments while being imaged with a Hewlett-Packard Sonos 1500 system. The backscattered RF signals corresponding to each angle of insonification were digitized and the spectral characteristics of the backscattered ultrasound were determined. The mean anisotropy, defined as the average difference between values at perpendicular and parallel insonification, for band-limited estimates of backscattered power, centroid frequency, upper-band to lower-band power ratio, and upper-band to total-band power ratio were found to be 24.6 +/- 1.1 dB, 142 +/- 27 kHz, 32 +/- 13%, and 22 +/- 5%, respectively (mean +/- SE). The magnitude of each of these backscatter spectral parameters was larger at perpendicular insonification compared with the corresponding values at parallel insonification, consistent with previous measurements of the inherent anisotropy of ultrasonic attenuation and backscatter in tissue.

Animals↗
PubMed1998

The placenta and its significance in neonatal outcome.

The placenta should not be overlooked as a source of much valuable diagnostic information. Close evaluation of the placenta and its attached membranes may reveal further information. Essential data may be obtained from pathologic examination, and if questions exist, specimens should be retained with proper care.

Amniotic Band Syndrome↗
PubMed1997

Comparison of integrated backscatter values obtained with acoustic densitometry with values derived from spectral analysis of digitized signals from a clinical imaging system.

Time-domain-based integrated backscatter values obtained with the use of acoustic densitometry (AD) were compared with values determined from a spectral-based analysis of the radio-frequency (RF) signals with a modified Hewlett-Packard Sonos 1500 imaging system. Integrated backscatter images of five specimens of bovine tendon were acquired in the AD acquisition mode, and the corresponding signals related to the backscattered RF were digitized for each angle of insonification as the specimens were rotated in 10-degree increments. The integrated backscatter images were analyzed with the AD analysis package, and the corresponding values determined from the RF power spectra were obtained from the digitized ultrasonic signals. Good agreement was found between the two methods over the entire range of measured values. The mean anisotropy in the measured integrated backscatter (mean +/- standard error) was found to be 27 +/- 2 dB for time-domain-based analysis and 25 +/- 2 dB for RF spectral-based analysis.

Acoustics↗
PubMed1990

HIV-1 in trophoblastic and villous Hofbauer cells, and haematological precursors in eight-week fetuses.

AIDS in children is usually caused by vertical transmission of human immunodeficiency virus type 1 (HIV-1). Aborted eight-week fetal and placental tissue from HIV-1 positive and negative (enzyme-linked immunosorbent assay and Western blot) women was analysed by immunocytochemistry and in-situ hybridisation. Maternal decidual leucocytes, villous trophoblastic derivatives, villous mesenchymal cells, and embryonic blood cell precursors in tissues from seropositive patients all stained for HIV-1 antigen and hybridised for nucleic acids. These observations suggest that a cytological pathway for vertical transmission of HIV-1 is established by eight weeks gestational age.

Adult↗
PubMed1990

Benign mesenchymoma of the round ligament. A report of two cases with immunohistochemistry.

Benign mesenchymomas are tumors composed of an admixture of two or more mature mesenchymal tissue types. Clinically and histologically they are benign lesions. However, they are seldom encapsulated and therefore may recur locally if incompletely excised. The authors report on two benign mesenchymomas composed of mature fat, thin-walled small and medium size vessels, and spindle cells demonstrated to be smooth muscle by immunohistochemical studies. They were diagnosed in women in their 50s. Both were located in the round ligament of the uterus. One was discovered incidentally during hysterectomy, and the other was unusually large, being diagnosed preoperatively as a retroperitoneal liposarcoma. Most round ligament tumors are leiomyomas or fibromas. To the authors' knowledge, this is the first report of benign mesenchymomas occurring in this location.

Adnexa Uteri↗
PubMed1988

Correlation of karyotype and immunophenotype in childhood acute lymphoblastic leukemia.

To correlate leukemic cell karyotype with immunophenotype, we studied 364 children with acute lymphoblastic leukemia (ALL). A prognostically favorable cytogenetic feature, hyperdiploidy greater than 50 chromosomes, was found in 33% of cases classified as common ALL antigen positive (CALLA+) early pre-B (common) ALL, in contrast to 18% of pre-B cases (P = .012), 5% of T cell cases (P less than .001), and none of the B cell cases (P less than .001) or cases of CALLA negative (CALLA-) early pre-B ALL (P = .002). The frequency of translocations, an adverse cytogenetic feature, was significantly lower in CALLA+ early pre-B ALL cases (35%) than in B cell (100%; P less than .0001), pre-B (59%; P less than .001), or CALLA- early pre-B (62%; P = .016) cases. Thus, patterns of chromosomal change differ widely among the major immunophenotypic groups of ALL and may account for reported differences in responsiveness to treatment.

Antigens, Neoplasm↗
PubMed1979

Tumorigenicity of embryonal carcinoma as an assay to study control of malignancy by the murine blastocyst.

A bioassay, based on tumorigenicity, has been developed to determine the mechanism whereby the blastocyst of the mouse controls malignant expression of embryonal carcinoma. The assay is based upon the incidence of tumors obtained when known numbers of cells of the 402AX strain of embryonal carcinoma are injected into strain 129 mice, compared to the incidence obtained when the same number of embryonal carcinoma cells are incorporated into Swiss-Webster blastocysts that are then injected in strain 129 animals. The results indicate that the blastocyst can regulate one embryonal carcinoma cell consistently; it may have a slight effect on three, but it cannot regulate four or five of them. The position of the embryonal carcinoma cell in the blastocyst is important. Regulation occurs if the embryonal carcinoma cell is placed in the blastocoele cavity, but enhancement of tumorigenicity is obtained if it is placed between the zona pellucida and the trophectoderm. By contrast, the blastocyst is unable to regulate a single B-16 melanoma cell placed in the blastocoele cavity, indicating a degree of specificity for the regulatory process.

Animals↗