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Biomedical subjects

Y Burstein

Publications and source records attributed to Y Burstein.

At least 91 records · Page 5Linked to original sources
PubMed1979

Thrombocytosis and increased circulating platelet aggregates in newborn infants of polydrug users.

Thirty-three prospectively studied neonates born to mothers using methadone plus other drugs developed significant thrombocytosis by the second week of life compared to platelet counts performed during the first week. This increase persisted for over 16 weeks, with a further short-lived significant peak at 10 weeks of age. Platelet counts exceeding 1,000,000/mm3 were found in seven infants. Thrombocytosis was not related to withdrawal symptoms or treatment (phenobarbital or paregoric). No thrombocytosis was found in 36 normal control infants up to eight weeks of life. Twenty-eight of the study group infants were evaluated for circulating platelet aggregates. Thirteen patients had a normal aggregate index and a mean platelet count of 468,000/mm3; 15 patients had increased aggregates and mean platelet count of 754,000/mm3. The risk for increased circulating platelet aggregates correlated directly with an increase in platelet count. Thrombocytosis and increased circulating platelet aggregates may be factors in the pathogenesis of the focal infarcts, and subarachnoid and germinal plate hemorrhages, described at autopsy in infants of addicted mothers.

Amphetamine↗
PubMed1979

Messenger RNA of opsin from bovine retina: isolation and partial sequence of the in vitro translation product.

Opsin, the apoprotein of the visual pigment rhodopsin, is synthesized on membranes of the rough endoplasmic reticulum and subsequently passes through the Golgi apparatus to the rod outer segment. This pathway parallels the early stages of biosynthesis of some secretory proteins and viral membrane glycoproteins. Most of these proteins are initially synthesized as precursor molecules with a short-lived hydrophobic extra peptide segment at the NH(2) terminus. Therefore we investigated whether or not the immediate translation product of opsin mRNA contains a similar short-lived NH(2)-terminal extra peptide. The mRNA coding for opsin was isolated from bovine retina polysomes precipitated by antibodies to opsin. The mRNA directed the cell-free synthesis of a protein comparable in size to opsin that was specifically precipitated by anti-opsin antibodies. Sequence analyses of the immunoprecipitated protein labeled with six radioactive amino acids (Met, Asn, Pro, Phe, Tyr, Val) provided the following result: [Formula: see text] (X is unknown). This partial sequence of the cell-free product corresponds exactly to the published NH(2)-terminal segment of native opsin (21 residues long) and extends beyond this region. Met-1 was shown to be the initiator methionine residue, because only the initiator [(35)S]Met-tRNA(1) (Met)-not the internal [(35)S]Met-tRNA(2) (Met)-donated the NH(2)-terminal methionine. This finding essentially rules out the possibility that Met-1 was preceded by a peptide that was rapidly cleaved. Thus opsin, and not a precursor, is the immediate product of opsin mRNA translation.

Amino Acid Sequence↗
PubMed1979

Primary structure of the NH2-terminal extra piece of the precursor to human placental lactogen.

The cell-free translation product of human placental lactogen mRNA is a precursor molecule larger than the mature hormone that circulates in plasma. To determine the structure of pre-placental lactogen, the poly(A)-rich RNA fraction of term placenta was isolated and translated in a wheat germ cell-free system. The mRNA programmed the synthesis of a major protein, 3000 daltons larger than placental lactogen, that was specifically precipitated by hormone antibodies. The immunoprecipitated protein was labeled separately with 20 radioactive amino acids and subjected to sequence analysis. The results showed the synthesis of pre-placental lactogen in which an extra piece 25 residues long preceded the NH2 terminus of the mature protein. The structure of the extra piece is as follows: Met-Pro-Gly-Ser-Arg-Thr-Ser-Leu-Leu-Ala-Phe-Ala-Leu-Leu-Cys-Leu-Pro-Trp-Leu-Gln-Glu-Ala-Gly-Ala-. Met1 is the initiator residue because only initiator [35S]Met-tRNAMet1, but not internal [35S]Met-tRNA2Met, donated NH2-terminal methionine. The structure of the extra piece showed little homology with that of unrelated hormones but striking homology (64%) with the extra piece of rat pre-growth hormone. Most amino acid substitutions involved a single base change in the codon. Mature human placental lactogen and rat growth hormone have 59% homology in sequence. Thus, our findings provide additional evidence to support the common evolutionary origin of these hormones, not only of the mature proteins but also of the extra piece segments.

Amino Acid Sequence↗
PubMed1979

Amino acid sequence of the biosynthetic precursor to a human hormone.

The radiosequencing method used to determine the structure of precursors of hormones and other secretory proteins was reviewed. Determination of the primary structure of the hydrophobic Xp of the biosynthetic precursor to hPL was described. This is the first human hormone whose precursor structure has been determined completely by this method. Comparison of the sequence we determined with the sequence of rat pre-growth hormone deduced from the structure of its coding DNA revealed striking homology of the Xp regions. These findings support coevolutionary development of the DNA for both the Xp segment and mature protein regions of these related hormones.

Amino Acid Sequence↗
PubMed1978

Increase in platelet aggregation following a rise in plasma free fatty acids.

Platelet aggregation was studied following intravenous injection of heparin to nine healthy adults. Heparin is known to produce an increase in the concentration of free fatty acids (FFA) within 10 minutes of intravenous injection. A significant correlation was found between the intensity of primary platelet aggregation and changes in plasma FFA levels. No correlation was found between plasma FFA levels and the intensity of secondary platelet aggregation.

Fatty Acids, Nonesterified↗
PubMed1977

Glutamine as a precursor to N-terminal pyrrolid-2-one-5-carboxylic acid in mouse immunoglobulin lambda-type light chains. Amino acid-sequence variability at the N-terminal extra piece of lambda-type light-chain precursors.

The mRNA molecules coding for three mouse immunoglobulin lambda-type light (L) chains (MOPC-104E lambda(1), RPC-20 lambda(1), MOPC-315 lambda(2)) programme the cell-free synthesis of precursors larger than the mature proteins. Radioactive amino acid-sequence analyses of each of the three precursors labelled with [(3)H]alanine, [(3)H]serine, [(3)H]glutamine, [(3)H]glutamic acid and [(3)H]threonine showed that an extra piece, at least 18 residues long, is linked to the N-terminus of the mature L-chains. The N-terminal extra-peptide segment may be 19 residues long, since analyses of precursors labelled with [(35)S]methionine indicated an additional N-terminal methionine residue which was recovered in low yields. Presumably this is the initiator methionine, which is known to be short lived in eukaryotes. The mature forms of MOPC-104E, RPC-20 and MOPC-315 lambda L-chains are blocked at the N-termini by pyrrolid-2-one-5-carboxylic acid (pyroglutamic acid). Sequence analyses of precursors labelled with [(3)H]glutamine and [(3)H]glutamic acid showed incorporation only of glutamine in a position that matches with the position of pyrrolid-2-one-5-carboxylic acid in the mature forms of all three precursors, and incorporation of glutamic acid in other positions. The data showed the absence of glutamine-glutamic acid interconversion, since the radioactive peaks obtained from either (3)H-labelled amino acid were discrete, and free from cross-contamination. These results prove that glutamine is the precursor amino acid of pyrrolid-2-one-5-carboxylic acid at the N-termini of the mature MOPC-104E lambda(1), RPC-20 lambda(1) and MOPC-315 lambda(2) L-chains. Thus the formation of pyrrolid-2-one-5-carboxylic acid by cyclization of glutamine is a post-translational event which occurs after, or concomitant with, cleavage of the extra piece from the precursor to yield the mature L-chain. The variable (V) regions (110 amino acid residues) of mouse lambda L-chains are quite similar: when compared with that of MOPC-104E lambda(1) chain, the V-region of RPC-20 lambda(1) chain differs in one residue, and the V-region of MOPC-315 lambda(2) chain differs in 11 residues. The partial sequence data show that the N-terminal extra pieces of the two lambda(1) L-chain precursors have, so far, identical partial sequences; the extra piece of the lambda(2) L-chain precursor differs from these in at least three out of 19 positions.

Amino Acid Sequence↗
PubMed1977

Amino acid sequence of the NH2-terminal extra piece segments of the precursors of mouse immunoglobulin lambda1-type and kappa-type light chains.

The mRNA molecules coding for mouse immunoglobulin light (L) chains direct the cell-free synthesis of precursors in which extra peptide segments precede the amino termini of the mature proteins. The results of amino acid sequence analyses of two precursors labeled with 20 radioactive amino acids enabled unambiguous determination of the complete primary structure of the extra piece segments. The complete sequences (and sizes) of the NH2-terminal extra pieces are: in MOPC-104E lambda1 L-chain precursor, Met-Ala-Trp-Ile-Ser-Leu-Ile-Leu-Ser-Leu-Leu-Ala-Leu-Ser-Ser-Gly-Ala-Ile-Ser (19 residues); in MOPC-41 kappa L-chain precursor, Met-Asp-Met-Arg-Ala-Pro-Ala-Gln-Ile-Phe-Gly-Phe-Leu-Leu-Leu-Leu-Phe-Pro-Gly-Thr-Arg-Cys (22 residues). The extra pieces in the precursors of MOPC-104E (lambda1), MOPC-41 (kappa), and MOPC-321 (kappa) L-chains differ extensively from each other in their amino acid sequence (65-73%). In addition to this sequence heterogeneity, the extra pieces are characterized by a high percentage of hydrophobic residues: 69% in the MOPC-104E lambda1 L-chain precursor (this report), 73-75% in the kappa L-chain precursors [Schechter, I. & Burstein, Y. (1976) Proc, Natl. Acad. Sci. USA 73, 3273-3277]. The marked hydrophobicity of the extra piece suggests that it may favor interaction of the precursor with cell membranes, in a manner similar to the function of the "hydrophobic domain" of membrane-bound proteins. We propose two possible targets for interaction: (i) the endoplasmic membranes, where the NH2-terminal extra piece is cleaved from the precursor to yield mature protein destined for secretion; (ii) the cell surface membrane, where the intact precursor is anchored by virtue of the hydrophobic extra piece to serve as the antigen-recognizing receptor.

Amino Acid Sequence↗