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Biomedical subjects

I Schechter

Publications and source records attributed to I Schechter.

At least 91 records · Page 5Linked to original sources
PubMed1976

Partial amino-acid sequence of the precursor of an immunoglobulin light chain containing NH2-terminal pyroglutamic acid.

Analyses of amino-acid sequences of the total cell-free products programmed by the mRNA of MOPC-104E gamma light (L)-chain show that over 95% of the products have sequences of a distinct protein that correspond to the L-chain precursor. In this precursor an extra piece is coupled to the NH2-terminus of the mature L-chain. Analyses of products labeled with [3H]alanine, [3H]leucine, and [3H]proline demonstrate that the extra piece is composed of at least 18 residues. Analyses of [35S]methione-labeled product indicate that the extra piece may contain an additional NH2-terminal methionine, which is detected in about 10% of the molecules. Partial recovery of the NJ2-terminal methionine (alanine, leucine, and proline are recovered in yields close to theoretical, greater than 95%) suggests that it is the initiator methionine, which is known to be short lived in eukaryotes due to rapid hydrolysis. Thus, the extra piece seems to be 19 residues in length, and it contains one methionine at the NH2-terminus, three alanines at positions 2, 12, and 17, and five leucines at positions 6, 8, 10, 11, and 13. The close gathering of leucine residues, as well as their abundance (26%), suggest that the extra piece would be quite hydrophobic. Hydrophobicity seems to be a general property of the extra piece, since similar clusters of leucine were found in the precursors of 3 KL-chains (Burstein, Y. & Schechter, I. (1976) Biochem. J. 157, 145-151). The NH2-terminus of the mature MOPC-104E gamma L-chain is blocked by pyroglutamic acid. The fact that in the precursor a peptide segment precedes this NH2-terminus establishes that pyroglutamic acid is not the initiator residue for synthesis of the L-chain. Apparently, the pyroglutamic acid is formed by cyclization of glutamic acid or glutamine during cleavage of the extra piece to yield the mature L-chain.

Amino Acid Sequence↗
PubMed1976

Marked hydrophobicity of the NH2-terminal extra piece of immunoglobulin light-chain precursors: possible physiological functions of the extra piece.

mRNAs coding for mouse immunoglobulin light chains direct the cell-free synthesis of precursors in which extra peptide segments precede the NH2-termini of the mature proteins. The abundance (18-30%) of leucine residues in the extra piece indicates that it is quite hydrophobic [Schechter and Burstein (1976) Biochem. Biophys, Res. Commun. 68, 489]. Accordingly, we have determined the positions of all hydrophobic residues by sequencing two k-type light (L)-chain precursors that were labeled with: [3H]Ala, [3H]Val, [3H]Leu, [3H]Ile, [3H]Thr, [3H]Pro, [3H]Phe, [3H]Tyr, [3H]Trp, [35S]Met, and [35S]Cys. The partial sequences (and sizes) of the extra pieces obtained are: in MOPC-321 precursor, Met-X-Thr-X-Thr-Leu-Leu-Leu-Trp-Val-Leu-Leu-Leu-Trp-Val-Pro-X-X-Thr-X-(20 residues; X is unknown); in MOPC-41 precursor, Met-X-Met-X-Ala-Pro-Ala-X-Ile-Phe-X-Phe-Leu-Leu-Leu-Leu-Phe-Pro-X-Thr-X-Cys- (22 residues). Despite the fact that these extra pieces differ extensively in sequence (68%), both of them are highly enriched with hydrophobic residues (75% in MOPC-321, 73% in MOPC-41). This marked hydrophobicity suggests that the extra piece favors interaction of the precursor with cell membranes, in a manner similar to the function of the "hydrophobic domain" of membrane-bound proteins (e.g., glycophorin). We propse that the hydrophobic extra piece directs most precursor molecules to the endoplasmic reticulum, where they are cleaved to yield mature L chain destined for scretion; a few precursor molecules escape cleavage and are embedded in the cell surface to serve as the antigen-recognizing receptor. The probability that the Leu-Leu-Leu-Trp-Val sequence occurs by change is 1.6 X 10(-8). Therefore, the data provide evidnece for duplication of a short DNA segment in the structural gene coding for the MOPC-321 precurosr. Duplication with inversion is also indicated from inverted repetition of the Phe-Lue-Leu sequence in the extra piece of the MPOC-41 precursor.

Amino Acid Sequence↗
PubMed1975

Partial amino acid sequence of the precursor of immunoglobulin light chain programmed by messenger RNA in vitro.

The five proteins programmed in a cell-free system by a mouse kappa light chain messenger RNA were labeled with [3H]leucine and subjected to amino acid sequence analyses. In all five proteins, 20 amino acid residues precede the amino terminus of the mature protein, indicating that there is one major point for the initiation of messenger RNA translation. The abundance (30 percent) of leucine residues in the extra piece (leucine at positions 6, 7, 8, 11, 12, and 13) indicates that this moiety is hydrophobic. Furthermore, it seems that the precursor may have an additional extra piece at the carboxyl terminus.

Amino Acid Sequence↗
PubMed1975

Prolonged retention of glutaraldehyde-treated skin homografts in humans.

Treatment of cadaver skin homografts in vitro with glutaraldehyde significantly prolonged their average retention time from 10.9 to 21.8 days in 21 patients with burns and/or extensive soft tissue injuries. The glutaraldehyde-treated homografts serve as a useful non-viable wound cover. They remain adherent to the wound bed for prolonged periods and support the formation of granulation tissue favourable for the subsequent acceptance of autografts. Toxic symptoms or allergic reactions were not noticed in any of the recipients. Treatment of the skin with glutaraldehyde is simple to perform, requires minimal laboratory equipment, and is not time consuming.

Aldehydes↗
PubMed1975

Region of immunoglobulin light-chain mRNA transcribed into complementary DNA by RNA-dependent DNA polymerase of avian myeloblastosis virus.

The mRNA coding for a kappa-type immunoglobulin light (L)-chain and its complementary DNA (cDNA) hybridize with a Crt1/2 of 2.6 x 10(-4) moles of ribonucleotide x liter-1 x sec, forming well-matched duplexes (melting temperature Tm equals 89 degrees). The molecular weight of the cDNA is about 280,000 (840 nucleotides) as determined by alkaline sucrose gradient centrifugation and from the extent of protection of the mRNA by the cDNA from ribonuclease digestion. The cDNA anneals with kappa-type mRNAs of the same and different subgroups with comparable Crt1/2 values, but not with a lambda-type mRNA. Thus, one kappa-type cDNA can be used to quantify the mRNAs coding for all kappa-type L-chains. The values of cDNA hybridized at saturation with various kappa-type mRNAs indicate that: (1) the cDNA is complementary to the entire constant region and to about half of the variable (V)-region; (2) V-regions of similar amino-acid sequence are coded by a similar nucleotide sequence; (3) the nucleic acid probe to one V-region may anneal and quantify V-region genes of members of the same subgroup.

Avian Leukosis Virus↗
PubMed1975

Prolonged retention of glutaraldehyde-treated skin allografts and xenografts: immunological and histological studies.

Glutaraldehyde (GA)-treated skin allografts and xenografts (from mice, rats and guinea-pigs) behave in the same way as judged from retention time, gross inspection, microscopic examination, and assays for graft antigenicity. The GA-treated grafts are retained for long periods of time (an increase by more than 6-fold as compared to untreated grafts), they are tightly bound to the recipient, they are initially soft but become progressively stiffer with minimal shrinkage in size, and remain free from infection. The histology shows that the grafts are nonviable and fixed by the GA, they are avascularized but the general structure of the skin (epidermis, adnexa and dermis) is preserved for about 3 months. The antigenicity of the GA-treated grafts is very poor, actually it is undetectable. They do not elicit the formation of cytotoxic antibodies, and animals sensitized by untreated allografts retain the GA-treated allografts similarly to normal unsensitized recipients. The lack of transplantation immunity is also indicated by the fact that GA-treated isografts behave and are rejected similarly to GA-treated allografts and xenografts. Microscopic examination suggests that the mechanism of rejection of GA-treated grafts is similar to that operating in the rejection of an inert foreign body. The marked prlongation in the retention of Ga-treated skin grafts and their properties justify investigations on the applicability of these grafts in clinical practice.

Aldehydes↗
PubMed1975

Prognostic factors in rehabilitation after severe head injury. Assessment six months after trauma.

After initial neurosurgical treatment, 40 patients who regained consciousness 1 to 90 days after major cerebral trauma, were admitted for rehabilitation. Six months after their injury they were assessed in terms of: 1) Locomotor function, 2) Intellectual performance, 3) Communication disorder, and 4) behaviour disturbances. The usefulness of these parameters as prognostic factors in rehabilitation is discussed. Eight patients without significant disabilities in all 4 parameters returned to normal life. Patients who showed locomotor, communicative and behaviour impairment but no gross intellectual deficits, were considered capable of being retrained. The poorest prospects for social and vocational rehabilitation were found in 15 patients with cognitive defects.

Adult↗
PubMed1973

Biologically and chemically pure mRNA coding for a mouse immunoglobulin L-chain prepared with the aid of antibodies and immobilized oligothymidine.

The mRNA coding for a mouse immunoglobulin L-chain was prepared from MOPC-321 myeloma polysomes specifically precipitated with antibodies directed against L-chains, followed by chemical purification on oligo(dT)-cellulose. Biological purity (capacity to program the synthesis only of L-chain) was calculated to be >/=95%. This value was based on the estimation of contamination by non-L-chain mRNA activities that were present in large abundance in RNA preparations extracted from the total polysome population. A similar degree of purity was calculated from the extent of precipitation of myeloma and nonmyeloma polysomes with anti-L-chain and non-L-chain antibodies. Chemical purity (95%) was determined from the amount of rRNA in the mRNA preparation by scanning of appropriate gels. In a cell-free system, the purified mRNA directed the synthesis of two precursors heavier than L-chain by about 1300 and 4700 daltons. Cell-free products labeled with 10 [(14)C]aminoacids yielded 27 out of 28 expected L-chain tryptic peptides and four additional peptides. Most probably the latter were derived from extra pieces in the precursors, and the apparent loss of one peptide was due to modifications at the N-terminus. The main fraction of L-chain mRNA was composed of two species of about 420,000 and 450,000 daltons. These molecules are much larger than that required to code for a mature L-chain (calculated about 250,000). The additional nucleotide mass can be accounted for in part for the coding of the extra piece (about 50,000) and in part for the polyadenylate moiety.

Animals↗