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Biomedical subjects

M Schiffer

Publications and source records attributed to M Schiffer.

126 records · Page 7Linked to original sources
PubMed1969

Mechanism of estrogenic action in acromegaly.

In four acromegalic patients, estrogen therapy did not significantly alter the mean values of basal radioimmunoassayable plasma growth hormone. In two patients, estrogen therapy did not qualitatively alter the lack of reduction of plasma growth hormone levels after oral administration of glucose, nor did it reduce in these patients the response of plasma growth hormone to insulin-induced hypoglycemia. In one of the patients, insulin sensitivity with respect to glucose and the hypoglycemia-induced growth hormone rise seemed greater during estrogen therapy. Despite the absence of demonstrable reductions inplasma growth hormone level under varying experimental circumstances, the administration of estrogen resulted in reduction of urinary calcium and hydroxyproline excretion, in reduction of radiocalcium bone accretion rates and exchangeable pools, in reduction of serum phosphorus, and in more negative nitrogen balances. The experimental data therefore suggest that estrogen may be a peripheral antagonist of the effects of excessive growth hormone secretion in acromegaly.

Acromegaly↗
PubMed1968

Correlation of amino acid sequence and conformation in tobacco mosaic virus.

Correlation of the amino acid sequence with the conformation in tobacco mosaic virus protein is considered in this article. After division of the sequence into groups with helical or nonhelical potential, the segments likely to be helical were related to the X-ray diffraction patterns obtained by Franklin, Caspar, Holmes, and Klug. The approximate locations of these segments within the known boundaries of the subunit were predicted from the radial distribution and helical projection of electron density. As a result of these assignments, the number of possible conformations was also reduced for the nonhelical segments. The structure of the subunit was simulated by flexible models of rubber and electrical tubing, as well as by space-filling Corey-Pauling-Koltun models. These models were used to locate the protein segments impinging upon the ribonucleic acid of the virus. The two pairs of carboxyl groups believed to be responsible for the binding of lead were also tentatively identified on these models as aspartic acid residues 64 and 66 (first pair) and glutamic acid residues 131 and 145 (second pair).

Amino Acid Sequence↗
PubMed1967

Use of helical wheels to represent the structures of proteins and to identify segments with helical potential.

The three-dimensional structures of alpha-helices can be represented by two-dimensional projections which we call helical wheels. Initially, the wheels were employed as graphical restatements of the known structures determined by Kendrew, Perutz, Watson, and their colleagues at the University of Cambridge and by Phillips and his coworkers at The Royal Institution. The characteristics of the helices, discussed by Perutz et al. (1965), and Blake et al. (1965), can be readily visualized by examination of these wheels. For example, the projections for most helical segments of myoglobin, hemoglobin, and lysozyme have distinctive hydrophobic arcs. Moreover, the hydrophobic residues tend to be clustered in the n +/- 3, n, n +/- 4 positions of adjacent helical turns. Such hydrophobic arcs are not observed when the sequences of nonhelical segments are plotted on the wheels. Since the features of these projections are also distinctive, however, the wheels can be used to divide sequences into segments with either helical or nonhelical potential. The sequences of insulin, cytochrome c, ribonuclease A, chymotrypsinogen A, tobacco mosaic virus protein, and human growth hormone were chosen for application of the wheels for this purpose.

Amino Acid Sequence↗
PubMedDate not supplied

Toxemia of pregnancy: cerebral CT findings.

Four patients with pregnancy-induced hypertension (preeclampsia-eclampsia) and neurological dysfunction unrelated to intracranial hemorrhage, cerebral venous thrombosis, or preexisting neurological disorder had cranial CT performed during their hospitalization. Three patients had diffuse white matter hypodensities with associated mass effect. The fourth patient had bilateral, asymmetric hypodensities confined to the basal ganglia. Computed tomography is useful in establishing an early diagnosis of the complicating neurological disorder as well as in providing a better understanding of the physiopathological changes seen in the brain in this condition.

Adult↗