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Biomedical subjects

L C Williams

Publications and source records attributed to L C Williams.

49 records · Page 3Linked to original sources
PubMed1979

The amino acid sequence of fragment A, an enzymically active fragment of diphtheria toxin. I. The tryptic peptides from the maleylated protein.

Six tryptic peptides ranging in size from 3 to 126 residues were isolated from maleylated Fragment A of diphtheria toxin after tryptic hydrolysis. These peptides accounted for all 193 residues found by amino acid analysis. After demaleylation, the six peptides were purified by chromatography on Sephadex G-50, coupled with paper chromatography and electrophoresis, and were analyzed by various methods. The compositions and properties of the peptides are reported. Almost 70% of the residues were positioned within these peptides.

Adenosine Diphosphate Sugars↗
PubMed1979

The amino acid sequence of fragment A, an enzymically active fragment of diphtheria toxin. II. The cyanogen bromide peptides.

Cyanogen bromide cleavage of Fragment A from diphtheria toxin at the four methionines present in each molecule resulted in five major peptides which were isolated and studied by sequence methods. These five peptides of 4, 11, 14, 63, and 101 residues account for all 193 residues in Fragment A and provide overlaps for the tryptic peptides from the maleylated protein. Two additional peptides were isolated and shown to be shorter forms (8 and 10 residues) of the COOH-terminal cyanogen bromide peptide (11 residues).

Adenosine Diphosphate Sugars↗
PubMed1979

The amino acid sequence of fragment A, an enzymically active fragment of diphtheria toxin. III. The chymotryptic peptides, the peptides derived by cleavage at tryptophan residues, and the complete sequence of the protein.

Fragment A (21,145 daltons in its longest known form) may be derived from diphtheria toxin (60,000 daltons) by mild tryptic digestion and reduction. Purified Fragment A consists of a mixture of 3 molecules of 190, 192, and 193 residues; the first 190 residues are in common and correspond to the NH2-terminal region the toxin. All three species of Fragment A are active in catalyzing ADP ribosylation of elongation factor 2, an essential component of protein synthesis. This reaction inactivates the factor and is responsible for the toxin's action in inhibiting protein synthesis in animal cells. It is believed that Fragment A or similar enzymically active fragments released into the cytosol of toxin-treated cells mediate this inhibition. The complete amino acid sequence of Fragment A has been determined from 32 chymotryptic peptides, three peptides derived by chemical cleavage of Fragment A at its 2 tryptophan residues, five cyanogen bromide peptides, and six tryptic peptides from the maleylated protein.

Adenosine Diphosphate Sugars↗
PubMed1979

Identification of interacting amino acids at the histone 2A--2B binding site.

Histones 2A and 2B of calf thymus were cross-linked within intact nuclei by UV irradiation. This procedure induces the formation of covalent cross-links between noncovalently interacting residues in the histones of native chromatin. Tryptic peptide and partial sequence analysis of the cross-linked product has shown that the covalent linkage is between tyrosine-37, -40, or -42 (we have not yet determined which) of H2B and proline-26 of H2A. We conclude that these residues constitute part of the hydrophobic H2A--H2B binding domain within the nucleosomes of native chromatin.

Amino Acid Sequence↗
PubMed1979

Labetalol in severe and resistant hypertension.

1 The efficacy of labetalol in the treatment of severe hypertension (diastolic greater than or equal to 115 mm Hg) was studied retrospectively. Ten patients were followed for more than 6 months. At 6 months, eight were well controlled and the mean dose in those was 975 mg daily. Four of these were receiving labetalol alone; two were on labetalol and diuretic only. 2 Three patients were resistant to doses of 1600, 1800 and 2400 mg daily respectively; two of these were controlled with increased doses of vasodilator drugs. In two cases labetalol had produced large falls in the standing BP while not influencing the supine BP. 3 Three other resistant patients were seen, of whom one merely required an increase in dose to 2200 mg daily and the addition of a diuretic. Both the others were elderly, had severe vascular disease, and suffered disabling postural hypotension on a dose of labetalol which did not influence the supine BP. 4 Labetalol can control severe hypertension. There remain patients whose supine BP is not influenced by a dose of labetalol which produces marked postural hypotension.

Adult↗
PubMed1976

Technic of deep hypothermia and circulatory arrest in the neonate and infant.

Most congenital heart anomalies now can be surgically corrected in a neonate or very young infant. Because their hearts are so small, it is advantageous to work in a bloodless and motionless operative field. Deep hypothermia with circulatory arrest provides this setting. Physiologic problems associated with hypothermia are minimized by inducing general vasodilatation with large doses of methylprednisolone. Surface cooling is done with ice blankets and small sandwich bags filled with crushed ice. The patient's temperature gradually falls to 75.2 F (24 C). After median sternotomy, core cooling can be used to bring the patient's temperature to the desired 68 F (20 C). Circulatory arrest is produced by draining blood into the reservoir and cross-clamping the great vessels and venae cavae. It can be maintained for up to 60 minutes. In infants over six months and over 6 kg (13.2 lb), moderate hypothermia 77 F (25 C) and low perfusion (1/4-1/3 of normal) with short periods (10 to 15 minutes) of circulatory arrest improve operative conditions and allow correction of the most complicated congenital heart defects.

Blood Volume↗
PubMed1971

In vitro susceptibility of strains of Pseudomonas pseudomallei to rifampin.

Reported high activity of rifampin for Pseudomonas pseudomallei could not be verified by extensive in vitro tests conducted with 31 recently isolated strains. Minimal inhibitory concentrations of rifampin were 25 mug/ml for three strains and greater than 25 mug/ml for 28 strains. Rifampin had relatively poor in vitro activity when compared with tetracycline drugs and chloramphenicol antibiotics now commonly used for treating melioidosis.

Chloramphenicol↗