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Biomedical subjects

J Applebaum

Publications and source records attributed to J Applebaum.

17 recordsLinked to original sources
PubMed1992

Treatment of superficial cutaneous pigmented lesions by melanin-specific selective photothermolysis using the Q-switched ruby laser.

The Q-switched ruby laser at 694 nm, a wavelength well absorbed by melanin relative to other optically absorbing structures in skin, causes highly selective destruction of pigment-laden cells. In addition, the 20-nsec pulse duration produced by this laser approximates the thermal relaxation time for melanosomes, thereby confining the energy to the target. This new laser system produces clinically significant fading of superficial cutaneous pigmented lesions in patients, without complications such as hypertrophic scarring or changes in the normal skin pigmentation, often seen with conventional laser systems or other therapeutic methods. In ongoing clinical trials at our facility, excellent results have been obtained for lentigines, café-au-lait macules, nevus spilus, Becker's nevi, and ephelides (freckles), without skin scarring or textural or permanent pigment changes. The purpose of this report is to (1) describe the theoretical considerations that can be understood and used by a nonlaser-oriented practitioner involved in achieving selective removal of superficial cutaneous pigmented lesions, and (2) describe the practical application of the device to the clinical management of patients.

Female↗
PubMed1990

The roles of tyrosines 24, 31, and 60 in the high affinity binding of insulin-like growth factor-I to the type 1 insulin-like growth factor receptor.

A series of insulin-like growth factor I (IGF-I) structural analogs in which one or more of the three tyrosine residues were replaced with nonaromatic residues were produced and their binding properties characterized. The single point mutations, [Leu24]IGF-I, [Ala31]IGF-I, and [Leu60]IGF-I result in an 18-, 6-, or 20-fold loss in affinity, respectively, for the type 1 IGF receptor. Multiple mutations, [Ala31,Leu60]IGF-I, [Leu24, Ala31]IGF-I, [Leu24, Leu60]IGF-I, or [Leu24, Ala31, Leu60]IGF-I result in a 520-, 240-, 1200-, or greater than 1200-fold loss in affinity, respectively, at the type 1 IGF receptor. In contrast, none of the analogs display greater than a 2-fold loss in affinity for the acid-stable human serum binding proteins. At the insulin receptor, [Ala31]IGF-I and [Leu24]IGF-I are equipotent to and 5-fold less potent than IGF-I, whereas [Leu60]IGF-I and the multiple mutation analogs are inactive up to 10 microM. Analogs [Leu24]IGF-I, [Ala31]IGF-I, and [Leu24, Ala31]IGF-I are equipotent to IGF-I at the type 2 IGF receptor, whereas all analogs containing Leu60 demonstrate little measurable affinity at this receptor. Thus, Tyr24, Tyr31, and Tyr60 are involved in the high affinity binding of IGF-I to the type 1 IGF receptor, while Tyr60 is important for maintaining binding to the type 2 IGF receptor.

Amino Acid Sequence↗
PubMed1990

Flashlamp-pumped pulsed dye laser therapy for poikiloderma of Civatte.

The use of pulsed yellow light from a flash-lamp-pumped pulsed dye laser has provided a successful form of therapy to remove both the telangiectasias and irregular pigmentation associated with poikiloderma of Civatte. The short pulse duration and specificity of the interaction between yellow light and hemoglobin permit this technique to be performed on the thin skin of the neck without textural changes or scarring. Furthermore, use of the large beam diameter of this laser system allows for rapid treatment of large areas in a short period of time.

Humans↗
PubMed1990

Clinical management of port-wine stain in infants and young children using the flashlamp-pulsed dye laser.

The flashlamp-pulsed dye laser (FLPDL) at 585 nm, a wavelength well absorbed by oxyhemoglobin, causes highly selective vascular injury. In addition, the 450 microsecond pulse duration produced by this laser approximates the thermal relaxation time for dermal blood vessels thereby confining the energy to the target. This new laser effects excellent lightening of port-wine stain (PWS) in infants and young children without the adverse complications of hypertrophic scarring, permanent pigmentation abnormality, or textural changes, complications often seen with conventional laser systems. The FLPDL now permits treatment of this patient population expected to gain the most benefit from early laser therapy in a much safer manner, before the psychological complications of being a "marked" person develop. The purpose of this report is to: (1) describe the theoretical considerations behind achieving selective removal of PWS that can be understood and used by a nonsurgically-oriented practitioner; and (2) describe the practical application of the device used in the clinical management of infants and young children.

Child, Preschool↗
PubMed1989

The C region of human insulin-like growth factor (IGF) I is required for high affinity binding to the type 1 IGF receptor.

We have produced and characterized the binding properties of three structural analogs of human insulin-like growth factor I (hIGF-I). These analogs are [1-62]hIGF-I, an analog lacking the carboxyl-terminal 8-amino acid D region of hIGF-I; [1-27, Gly4, 38-70]hIGF-I, an analog in which residues 28-37 of the C region of hIGF-I are replaced by a 4-reside glycine bridge; and [1-27,Gly4,38-62]hIGF-I, an analog with the C region glycine replacement and a D region deletion. The removal of the D region of hIGF-I has little effect on binding to the type 1 and type 2 insulin-like growth factor (IGF) receptors. [1-62]hIGF-I has 2-fold higher affinity for the insulin receptor and 4-fold higher affinity for IGF serum-binding proteins. The replacement of the C region of hIGF-I with a four-glycine span results in a 30-fold loss of affinity for the type 1 IGF receptor. However this analog has near normal affinity for the type 2 IGF receptor, the insulin receptor, and IGF serum-binding proteins. Incorporating the C region glycine replacement and the D region deletion into one analog does not affect binding to either the type 2 receptor or to IGF serum-binding proteins. As predicted from the single deletion analogs [1-27,Gly4,38-62]hIGF-I has reduced affinity for the type 1 IGF receptor (approximately 40-fold) and increased affinity for the insulin receptor (5-fold). These data indicate that determinants in the C region of hIGF-I are involved in maintaining high affinity binding to the type 1 IGF receptor and that neither the C region nor the D region are required for high affinity binding to the type 2 IGF receptor or to IGF serum-binding proteins.

Amino Acid Sequence↗
PubMed1989

Structural analogs of human insulin-like growth factor (IGF) I with altered affinity for type 2 IGF receptors.

We have used site-directed mutagenesis of a synthetic gene for insulin-like growth factor (IGF) I to prepare three analogs in which specific residues in the A region are replaced with the corresponding residues in the A chain of insulin. The analogs are [Ile41, Glu45, Gln46, Thr49, Ser50, Ile51, Ser53, Tyr55, Gln56]IGF I (A chain mutant), in which residue 41 is changed from threonine to isoleucine and residues 42 to 56 of the A region are replaced, [Thr49, Ser50, Ile51]IGF I, and [Tyr55, Gln56]IGF I. These analogs are all equipotent to IGF I at the type 1 IGF receptor in human placental membranes, and in stimulating the incorporation of [3H]thymidine into DNA in the rat vascular smooth muscle cell line A10. However, the A chain mutant and [Thr49, Ser50, Ile51]IGF I have greater than 20-fold lower relative affinity for the type 2 IGF receptor of rat liver membranes, respectively. In contrast, [Tyr55, Gln56]IGF I has 7-fold higher affinity than IGF I for the type 2 IGF receptor. Residues 49, 50, and 51 in IGF I are Phe-Arg-Ser and are strictly conserved in IGF II. Residues 55 and 56 of IGF I and the corresponding residues in IGF II are Arg-Arg and Ala-Leu, respectively. Thus, the presence of the charged residues at these positions in IGF I appears to be responsible, in part, for the lower affinity of IGF I for the type 2 IGF receptor. In addition to the alterations in affinity for the type 2 IGF receptor, the A chain mutant has a 7-fold increase in affinity for insulin receptors, and [Thr49, Ser50, Ile51]IGF I has a 4-fold lower affinity for acid-stable human serum binding protein. These data strongly suggest that specific determinants in the A region of IGF I are important for maintaining binding to the type 2 IGF receptor, and that these determinants are different from those required for maintaining high affinity for the type 1 IGF receptor.

Amino Acid Sequence↗
PubMed1988

Expression, purification and characterization of recombinant human insulin-like growth factor I in yeast.

Insulin-like growth factor I (IGF-I) is a 70 amino acid (aa) protein that is structurally similar and functionally related to insulin. We have inserted a synthetic gene coding for human IGF-I into a Saccharomyces cerevisiae expression vector utilizing the MF alpha 1 promoter and pre-pro leader peptide. This vector directs the expression and secretion of native, biologically active growth factor. Cleavage of the pre-pro alpha factor leader sequence in vivo results in the secretion of a 70-aa recombinant IGF-I molecule with the native N-terminal glycine residue. Human IGF-I purified from yeast culture supernatant is equipotent to serum-derived IGF-I in inhibiting [125I]IGF-I binding to type-I IGF receptors and crude human serum-binding proteins. Recombinant IGF-I is also equipotent to human IGF-I in the stimulation of DNA synthesis in rat aortic smooth-muscle cells. In contrast, yeast recombinant IGF-I is less potent than serum-derived IGF-I in binding to type-2 IGF receptors. The ability to produce native, biologically active IGF-I in yeast will allow the elucidation of binding domains through the expression and characterization of specific structural analogs.

Gene Expression Regulation↗
PubMed1988

Structural analogs of human insulin-like growth factor I with reduced affinity for serum binding proteins and the type 2 insulin-like growth factor receptor.

Four structural analogs of human insulin-like growth factor I (hIGF-I) have been prepared by site-directed mutagenesis of a synthetic IGF-I gene and subsequent expression and purification of the mutant protein from the conditioned media of transformed yeast. [Phe-1,Val1,Asn2, Gln3,His4,Ser8, His9,Glu12,Tyr15,Leu16]IGF-I (B-chain mutant), in which the first 16 amino acids of hIGF-I were replaced with the first 17 amino acids of the B-chain of insulin, has greater than 1,000-, 100-, and 2-fold reduced potency for human serum binding proteins, the rat liver type 2 IGF receptor, and the human placental type 1 IGF receptor, respectively. The B-chain mutant also has 4-fold increased affinity for the human placental insulin receptor. [Gln3,Ala4]IGF-I has 4-fold reduced affinity for human serum binding proteins, but is equipotent to hIGF-I at the types 1 and 2 IGF and insulin receptors. [Tyr15,Leu16]IGF-I has 4-fold reduced affinity for human serum binding proteins and 10-fold increased affinity for the insulin receptor. This peptide is also equipotent to hIGF-I at the types 1 and 2 IGF receptors. The peptide in which these four-point mutations are combined, [Gln3,Ala4,Tyr15,Leu16]IGF-I, has 600-fold reduced affinity for the serum binding proteins. This peptide has 10-fold increased potency for the insulin receptor, but is equipotent to hIGF-I at the types 1 and 2 IGF receptors. All four of these mutants stimulate DNA synthesis in the rat vascular smooth muscle cell line A10 with potencies reflecting their potency at the type 1 IGF receptor. These studies identify some of the domains of hIGF-I which are responsible for maintaining high affinity binding with the serum binding protein and the type 2 IGF receptor. In addition, these peptides will be useful in defining the role of the type 2 IGF receptor and serum binding proteins in the physiological actions of hIGF-I.

Amino Acid Sequence↗
PubMed1988

Mutants of human insulin-like growth factor I with reduced affinity for the type 1 insulin-like growth factor receptor.

Four mutants of human insulin-like growth factor I (hIGF I) have been purified from the conditioned media of yeast transformed with an expression vector containing a synthetic gene for hIGF I altered by site-directed mutagenesis. hIGF I has the sequence Phe-23-Tyr-24-Phe-25 which is homologous to a region in the B-chain of insulin. [Phe23,Phe24,Tyr25]IGF I, in which the sequence is altered to exactly correspond to the homologous sequence in insulin, is equipotent to hIGF I at the types 1 and 2 IGF and insulin receptors. [Leu24]IGF I and [Ser24]IGF I have 32- and 16-fold less affinity than hIGF I at the human placental type 1 IGF receptor, respectively. These peptides are 10- and 2-fold less potent at the placental insulin receptor, respectively. [Leu24]IGF I and [Ser24]IGF I have similarly reduced affinities for the type 1 IGF receptor of rat A10 and mouse L cells. Thus, the importance of the interaction of residue 24 with the receptor is conserved in several species. In three cell-based assays, [Leu24]IGF I and [Ser24]IGF I are full agonists with reduced efficacy compared to hIGF I. Desoctapeptide [Leu24]IGF I, in which the loss of aromaticity at position 24 is combined with the deletion of the carboxyl-terminal D region of hIGF I, has 3-fold lower affinity than [Leu24]IGF I for the type 1 receptor and 2-fold higher affinity for the insulin receptor.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1988

Serum half-life and biological activity of mutants of human insulin-like growth factor I which do not bind to serum binding proteins.

We have characterized the biological properties of two mutants of human insulin-like growth factor I (IGF-I) which, as we have shown previously, have normal affinity for the type I IGF receptor, but drastically reduced affinity for the acid-stable components of human serum binding proteins. [Phe-1,Val1,Asn2,Gln3,His4,Ser8,His9,Glu12 ,Tyr15,Leu16]IGF I (B-chain mutant) and [Gln3,Ala4,Tyr15,Leu16]IGF I have 1000 and 500 times lower affinity than IGF-I for the native 150K binding protein in adult rat serum. Like IGF-I, these two peptides migrate as monomers during size exclusion chromatography on TSK 125. [125I]IGF-I, [125I]B-chain mutant, and [125I] [Gln3,Ala4,Tyr15,Leu16]IGF-I have in vivo serum half-lives of 100, 27.5, and 26.9 min, respectively, after iv injection. These data suggest that serum binding protein-bound peptide is cleared from the serum more slowly than free peptide. The tissue distributions of [125I]IGF-I and [125I]B-chain mutant are similar 10 min after dosing, with more than 80% of the tissue-sequestered intact radioactive peptides in the kidney. Despite decreased serum half-lives, the B-chain mutant and [Gln3,Ala4,Tyr15,Leu16]IGF-I are, respectively, 4 times and twice as active as IGF-I in stimulating the incorporation of [14C]glucose into glycogen in rat diaphragm in vivo. This effect of IGF-I is thought to be mediated by the type 1 IGF receptor in muscle, since the same doses of peptide that stimulated glycogen synthesis more than 30-fold did not stimulate the incorporation of [14C]glucose into total lipid in adipose tissue, an effect known to be mediated by the insulin receptor. These data support the hypothesis that serum- or tissue-derived binding proteins impair the ability of IGF-I to exert its effects through the type 1 IGF receptor in vivo.

Adipose Tissue↗
PubMed1987

Expression of a synthetic gene encoding human insulin-like growth factor I in cultured mouse fibroblasts.

A synthetic gene encoding human insulin-like growth factor I (hIGF-I) was assembled and inserted into an expression vector containing the cytomegalovirus immediate early (CMV-IE) transcriptional regulatory region and portions of the bovine growth hormone gene. The recombinant plasmid encodes a 97 amino acid fusion protein containing the first 27 amino acids of the bovine growth hormone precursor and the 70 amino acids of hIGF-I. This plasmid, when transiently introduced into cultured mouse fibroblasts, directs synthesis of the fusion protein, subsequent proteolytic removal of the bovine growth hormone signal peptide, and secretion of hIGF-I into the culture medium. Conditioned medium from transfected cells inhibits binding of 125I-labeled IGF-I to type I IGF receptors on human placental membranes and to acid-stable human serum carrier proteins. The recombinant hIGF-I produced is biologically active, as monitored by the stimulation of DNA synthesis in vascular smooth muscle cells.

Amino Acid Sequence↗
PubMed1986

Osteogenesis induced by bone matrix is inhibited by inflammation.

This study was designed to examine the effect of inflammatory reaction elicited by percutaneous tube on bone induction. Inflammation was provoked by different types of biomaterials. In order to evaluate incorporation of percutaneous tubes, bone matrix and subcutaneous tissue, demineralizing bone matrix was implanted in the subcutaneous tissue of rats and was exposed to interaction with inflammatory conditions. Inhibition to the induction of cartilage and bone by the inflammatory process could be clearly demonstrated. It is suggested that the low pH levels, typical to enzymes operative in inflammation are a direct cause for inhibition of chondro and osteogenesis. The process of calcification is characterized by the activation of enzymes in high pH levels.

Animals↗
PubMed1985

Cloning and expression of Clostridium pasteurianum galactokinase gene in Escherichia coli K-12 and nucleotide sequence analysis of a region affecting the amount of the enzyme.

The Clostridium pasteurianum galactokinase gene was cloned by complementation, of the galK locus, into Escherichia coli. Restriction enzyme analysis subcloning and Tn5 mutagenesis indicated that the gene was located on a 1.8 X 10(3) base-pair ClaI-Sau3A fragment that encoded a polypeptide of approximately 40 Mr. Although the C. pasteurianum and the E. coli galactokinases have similar subunit molecular weights, Southern hybridization analysis indicated no strong homology between their genes. Even though this clone showed a low level of galactokinase expression, the Gal+ phenotype, provided by the clostridial galactokinase, was unstable in E. coli, and the gene was frequently inactivated by the spontaneous acquisition of insertion sequences. A second clone containing this gene on a large restriction fragment was isolated by hybridization. This clone was unable to grow on galactose-containing media due to the overproduction of galactokinase. Comparison of the plasmids from these two clones revealed that the second contained an additional 300 base-pairs located at one end of the galactokinase gene. Appropriate operon fusions with a promoter-less E. coli galactokinase gene indicated that these additional 300 base-pairs had promoter activity in E. coli. The DNA sequence of this region which lies upstream of the C. pasteurianum galactokinase gene was determined and compared with that from several clones producing high, low or undetectable amounts of galactokinase. The reasons for the high and low level expression and for the instability of the C. pasteurianum galactokinase in E. coli are discussed. The presence of the galactokinase suggests that galactose is used in C. pasteurianum through the Leloir pathway via galactose 1-phosphate.

Base Sequence↗