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Biomedical subjects

B Shaffer

Publications and source records attributed to B Shaffer.

24 records · Page 2Linked to original sources
PubMed1969

Nonsense mutations affecting the his4 enzyme complex of yeast.

The his4 region of yeast contains the information necessary for the catalysis of three steps in the histidine biosynthetic pathway. The three activities specified by this region remain physically associated during gel filtration and ultracentrifugation and after extensive purification. Nonsense mutations in the "operator distal" his4C region lower the molecular weight of the two proximal activities. The proximal activities can, therefore, function without the his4C portion of the protein(s). These observations are compatible with the following three possibilities. The his4 region codes for: (1) an aggregate of three proteins forming a multiprotein complex; (2) a single protein with three catalytic activities; and (3) a single protein which is cleaved to form three proteins which remain associated.

Chromatography, Gel↗
PubMedDate not supplied

Release and reattachment of the coracoacromial ligament: a cadaveric study.

The purpose of this study was to examine the anatomy and ability to reattach the coracoacromial ligament (CAL) after acromioplasty. Twenty-eight fresh cadaveric shoulder specimens were dissected, and the CAL dimensions and pattern of attachment were examined. The ability to reattach the CAL to the anterior acromion after acromioplasty was investigated, comparing release along the anterior acromion (traditional anterior acromioplasty) versus subperiosteal elevation from the acromial undersurface. The influence of CAL length, acromial "type," and amount of acromioplasty on reattachment were examined. In 96% of the specimens (27 of 28) confluent medial and lateral bands of the CAL insertion along the acromion precluded "selective" release. The ability to anatomically reattach the CAL was directly related to the method of ligament release (anterior release versus subperiosteal elevation) (p < 0.0001). When directly released from along the anterior acromion, the CAL could not be anatomically reattached in any specimen. Nonanatomic reattachment to a more medial anterior acromial insertion site, however, was possible in 22 (79%) of 28 specimens. Reattachment required an average medial positioning of 60% (range 16% to 88%) along the anterior acromion from the anterolateral tip. Six (21%) specimens could not be reattached despite attempted medial positioning. In contrast, when subperiosteally elevated from the anterior inferior acromion, the CAL was reattachable in all specimens, anatomically in 26 (93%) of 28. The two nonanatomic reattachments required medially reattaching the ligament's normal acromial insertion by an average of 30%. There was no relationship between specimen sex, age, presence of rotator cuff tear, type of acromion, and CAL reattachment. The confluent anatomy of the CAL does not permit "selective" release of discretely identifiable portions of the CAL (i.e., the lateral band). In cases in which CAL restoration is important, careful subperiosteal elevation from the acromial undersurface will facilitate anatomic reattachment. Standard release of the CAL from the anterior acromion precludes anatomic, and in some cases any, reattachment of the CAL.

Acromion↗
PubMedDate not supplied

Preoperative sizing of meniscal allografts in meniscus transplantation.

The purpose of this study was to determine the accuracy of radiographic and magnetic resonance imaging techniques in preoperative sizing for allograft meniscus transplantation. Twelve cadaveric knee specimens underwent sequential radiographs, magnetic resonance imaging scans, and arthrotomy. Meniscus dimensions were measured in multiple planes for the purpose of determining accuracy of imaging studies in comparison with actual meniscus dimensions. Overall, magnetic resonance imaging proved only slightly more accurate than conventional radiography. The mean difference between magnetic resonance imaging measurements and actual meniscus dimensions was 2.25 +/- 2.04 mm. The mean difference between radiographic measurements and actual meniscus dimensions was 2.35 +/- 1.79 mm. Neither imaging technique was accurate for measuring individual meniscus dimensions, with only 35% of images measuring within 2 mm of actual meniscus dimensions. Using less stringent criteria for accuracy (within 5 mm), radiography and magnetic resonance imaging were 79% and 83% reliable, respectively. Failure to obtain true anteroposterior or lateral images (15 degrees of external and internal rotation) increased measurement inaccuracy. Intraobserver agreement was significantly higher for magnetic resonance imaging than for radiography. Further research into the development of alternative techniques for more reliable meniscus sizing and better understanding of the tolerance for meniscus size mismatch is necessary.

Anthropometry↗