Biomedical subjects

L Avruch

Publications and source records attributed to L Avruch.

8 recordsLinked to original sources

PubMed1992

The fetal acetabulum. A histomorphometric study of acetabular anteversion and femoral head coverage.

To study the development of the acetabulum in the early fetal period, 39 embryologic specimens were reviewed in detail. Histologic serial sections were made through 47 hips in the transverse plane. Measurements of acetabular anteversion and femoral head coverage revealed that both parameters depend on the exact level of sectioning. However, when measured at the level of the maximum diameter of the femoral head, they did not show significant variation through the embryonic and early fetal stages (six to 20 weeks). This is in contradistinction to the late fetal period. The hip does remain covered during this early fetal period. Congenital dislocation of the hip is not an early developmental condition. This accounts for the absence of any reports of hip dislocations in the first half of gestation.

Acetabulum↗

PubMed1991

Morphometry of the human thigh muscles. A comparison between anatomical sections and computer tomographic and magnetic resonance images.

The present study examined the relative accuracy and precision of MR and CT procedures for determining the CSA of individual muscles from the human thigh. Serial AN, CT and MR cross-sections were obtained from three cadaveric lower limbs. The MR measurements provided accurate and precise values for the CSAs of most thigh muscles, generally within +/- 7.5% of the AN standard. In contrast, CT tended systematically to overestimate the AN CSA by 10-20%. Retest procedures indicated that highly reliable measurements could be obtained from both MR and CT images. However, subjective interpretations of boundaries between closely apposed muscle bellies, particularly for muscles with more than one head, were necessary for resolving entities in the imaging records and this decreased the relative accuracy of MR and CT measures. Interestingly, MR records demonstrated an incomplete septum between vastus lateralis and vastus intermedius more prominently than AN cross-sections. The novel cross-validation procedures used in this study also highlighted several system-based errors in the MR records that, if undetected and left uncorrected, would have seriously biased the morphometric data obtained with this technique. In general, MR provides high resolution images of the human thigh muscles which may be used to obtain valid measures of the CSA of these structures.

Cadaver↗

PubMed1986

Fast-field-echo MR imaging with Gd-DTPA: physiologic evaluation of the kidney and liver.

To determine if magnetic resonance imaging with Gd-DTPA could be used to assess renal and hepatic perfusion and possibly function, a fast-field-echo technique was used to perform sequential imaging of the kidney and liver of five subjects. Sixteen 3-second images of the same section were obtained at 13-second intervals immediately after Gd-DTPA administration, and again at 30 or 50 minutes after injection. From these images, curves of renal and hepatic signal versus time were generated. In each case the renal signal intensity peaked within 2 minutes and decreased to 60% or less by 3.4 minutes, and 35% or less by 50 minutes. Hepatic curves peaked within 2 minutes and approached initial levels by 30 minutes. These results suggest that transit and clearance of the contrast agent can be imaged by this technique.

Humans↗

PubMed1985

The ring-down artifact.

"Ring-down" is an ultrasound artifact that appears as a solid streak or a series of parallel bands radiating away from abdominal gas collections. Using an in vitro system of bubbles in water or gelatin, it was found that the ring-down artifact originated from the center of a cluster of four bubbles (bubble tetrahedron), three on top and one nestled beneath. Entrapped between the bubbles is a horn- or bugle-shaped fluid collection that we theorize emits a continuous sound wave back to the transducer when struck by an ultrasound pulse. Electronic processing by the scanner converts this continuous sound wave into the series of bands seen in the ring-down artifact.

Gases↗

PubMed1985

Pitfalls to avoid: the right paraspinal pseudotumor.

Fat in the fissure for the ligamentum teres, if abundant and sagittally oriented, will outline the right margin of the lateral segment of the left lobe of liver. This produces the appearance of a right paraspinal mass on plain abdominal radiographs. The nature of the anatomical relationships has been demonstrated using computed tomography.

Adipose Tissue↗

PubMed1976

The induced biosynthesis of 7-dehydrocholesterols in yeast: potential sources of new provitamin D3 analogs.

The effect of low concentrations of a specifically designed sterol-24-transmethylase inhibitor, 25-aza-24, 25-dihydrozymosterol (10) on sterol production in Saccharomyces cerevisiae was examined. The synthesis of cholesta-5,7,22,24-tetraen-3beta-ol (4), its 7,22,24 analog (15) and the 7,24 analog (5) coupled with the availability of zymosterol (6) and cholesta-5,7,24-3beta-ol (3) derivatives facilitated a search for these sterols in cultures treated with this inhibitor. When S. cerevisiae was grown in the presence of 1.3 and 5 muM 10, it produced no ergosterol but accumulated zymosterol (6), cholesta-5,7,22,24-tetraen-3beta-ol (4) and related C27 sterols (3 and 5). These results indicate blockage of the side chain methylation that normally occurs during the biosynthesis of ergosterol in yeast by compound 10 is efficient. The cholesta-5,7,22,24-tetraen-3beta-ol is a close structural analog of provitamin D3 (7-dehydrocholesterol). The inhibited yeast thus provides a source of a potentially new provitamin D3 substitute.

Aerobiosis↗

PubMed1975

Nuclear demethylation and C-24 alkylation during ergosterol biosynthesis in Saccharomyces cerevisiae.

The role of 4,4-dimethylzymosterol (3), 4,4-dimethylfecosterol (4) and 31-norlanosterol (5) in the biosynthesis of ergosterol in Saccharomyces cerevisiae has been investigated. The synthesis of 4 and 5 coupled with the availability of 3 facilitated a search for these sterols in commercial yeast sterol concentrates, fresh laboratory grown yeast and fresh brewery grown yeast. Sterol 4 was not detected in any of these mixtures whereas 5 was found in the first and last and 3 was present in all three sources investigated. Investigation of incorporation of [2-3H]lanosterol into 3, 4 and 5 revealed significant incorporation into 3 but neither 4 nor 5. This observation suggests the principle pathway for ergosterol biosynthesis initially involved 1 leads to 3 leads to 7. Incubation of a mixture of [2,4-3H]zymosterol and [26,27-14C]lanosterol with S. cerevisiae revealed that during the initial phases of aerobic growth the major route from 7 to ergosterol involves zymosterol (11) but as 11 accumulates 4 alpha-methyl-24-methylenezymosterol (8) assumes equal importance.

Chromatography, Gas↗

PubMedDate not supplied

Gadolinium-DTPA and MR imaging of pituitary adenoma: a preliminary report.

Gadolinium-DTPA MR imaging (Gd-MR), unenhanced MR imaging, and contrast-enhanced CT studies were compared prospectively in six patients with surgically confirmed pituitary adenomas and three patients without sellar pathology to determine the utility of Gd-MR in the diagnosis of pituitary adenoma. In normal patients, the pituitary gland, cavernous sinus, and infundibulum enhanced by T1 shortening after gadolinium. In adenoma patients, two of four focal lesions identified with contrast-enhanced CT were identified with Gd-MR, and one was identified with unenhanced MR. The earliest short repetition-time sequence performed after gadolinium injection was best for focal lesion detection. Normal cavernous sinus enhancement by gadolinium made identification of cavernous sinus extension of adenoma difficult. Infundibulum displacement was better seen with contrast-enhanced CT (two vs one); however, unenhanced and Gd-MR were better than contrast-enhanced CT for demonstrating chiasmal compression (four vs three). Contrast-enhanced CT, Gd-MR, and plain MR were equally able to identify gland enlargement, sellar floor erosion, and abnormalities of the diaphragma sellae. In this preliminary series, we found Gd-MR to be promising for imaging adenomas; however, modifications in Gd-MR technique including thinner slices and immediate scanning after gadolinium injection are necessary for the best detection of focal lesions.

Adenoma↗