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Biomedical subjects

D Chang

Publications and source records attributed to D Chang.

At least 181 records · Page 10Linked to original sources
PubMed1992

Identification of a nuclear localization sequence in the polyomavirus capsid protein VP2.

A nuclear localization signal (NLS) has been identified in the C-terminal (Glu307-Glu-Asp-Gly-Pro-Gln-Lys-Lys-Lys-Arg-Arg-Leu318) amino acid sequence of the polyomavirus minor capsid protein VP2. The importance of this amino acid sequence for nuclear transport of newly synthesized VP2 was demonstrated by a genetic "subtractive" study using the constructs pSG5VP2 (expressing full-length VP2) and pSG5 delta 3VP2 (expressing truncated VP2, lacking amino acids Glu307-Leu318). These constructs were transfected into COS-7 cells, and the intracellular localization of the VP2 protein was determined by indirect immunofluorescence. These studies revealed that the full-length VP2 was localized in the nucleus, while the truncated VP2 protein was localized in the cytoplasm and not transported to the nucleus. A biochemical "additive" approach was also used to determine whether this sequence could target nonnuclear proteins to the nucleus. A synthetic peptide identical to VP2 amino acids Glu307-Leu318 was cross-linked to the nonnuclear proteins bovine serum albumin (BSA) or immunoglobulin G (IgG). The conjugates were then labeled with fluorescein isothiocyanate and microinjected into the cytoplasm of NIH 3T6 cells. Both conjugates localized in the nucleus of the microinjected cells, whereas unconjugated BSA and IgG remained in the cytoplasm. Taken together, these genetic subtractive and biochemical additive approaches have identified the C-terminal sequence of polyoma-virus VP2 (containing amino acids Glu307-Leu318) as the NLS of this protein.

Amino Acid Sequence↗
PubMed1992

The use of additive and subtractive approaches to examine the nuclear localization sequence of the polyomavirus major capsid protein VP1.

A nuclear localization signal (NLS) has been identified in the N-terminal (Ala1-Pro-Lys-Arg-Lys-Ser-Gly-Val-Ser-Lys-Cys11) amino acid sequence of the polyomavirus major capsid protein VP1. The importance of this amino acid sequence for nuclear transport of VP1 protein was demonstrated by a genetic "subtractive" study using the constructs pSG5VP1 (full-length VP1) and pSG5 delta 5'VP1 (truncated VP1, lacking amino acids Ala1-Cys11). These constructs were used to transfect COS-7 cells, and expression and intracellular localization of the VP1 protein was visualized by indirect immunofluorescence. These studies revealed that the full-length VP1 was expressed and localized in the nucleus, while the truncated VP1 protein was localized in the cytoplasm and not transported to the nucleus. These findings were substantiated by an "additive" approach using FITC-labeled conjugates of synthetic peptides homologous to the NLS of VP1 cross-linked to bovine serum albumin or immunoglobulin G. Both conjugates localized in the nucleus after microinjection into the cytoplasm of 3T6 cells. The importance of individual amino acids found in the basic sequence (Lys3-Arg-Lys5) of the NLS was also investigated. This was accomplished by synthesizing three additional peptides in which lysine-3 was substituted with threonine, arginine-4 was substituted with threonine, or lysine-5 was substituted with threonine. It was found that lysine-3 was crucial for nuclear transport, since substitution of this amino acid with threonine prevented nuclear localization of the microinjected, FITC-labeled conjugate.

Amino Acid Sequence↗
PubMed1992

Factors influencing milk insufficiency and its long-term health effects: the Bedouin Infant Feeding Study.

Women who breastfeed have frequently reported milk insufficiency as the reason for introducing the bottle, but no one has addressed its potential long-term health effects. This paper described the factors associated with milk insufficiency versus another reason for introducing the bottle and its potential health effects based on an analysis of a prospective cohort study of 1005 Bedouin Arab women who delivered healthy newborns in 1981 and 1982. By two months postpartum, 72% introduced the infant to the bottle with 72% reporting milk insufficiency as the reason for introducing the bottle. The percentage of milk insufficiency declined with increasing age of the infant. Based on multiple logistic regression analyses, birth season was statistically significantly associated with the odds ratio (OR) of milk insufficiency versus another reason for introducing the bottle during the first two months. Women who delivered in the spring-summer had an increased OR = 1.65 of reported milk insufficiency compared with those who delivered during the rest of the year. Parity was directly related to the OR = 1.04 of milk insufficiency (but just missed significance) during one to two months and was statistically significantly associated with the OR = 1.12 of reported milk insufficiency during 3-18 months. The rates of stunting after the infant was introduced to the bottle and the duration of breastfeeding did not differ by reason for introducing the bottle. Thus the high frequency of reported milk insufficiency was not associated with adverse health effects.

Adolescent↗
PubMed1992

An analysis of errors in kinematic parameters associated with in vivo functional radiographs.

A pair of functional radiographs, taken at each end of the range of motion, are used to determine spinal motions. Graphic construction and computer-assisted methods are available for the radiographic analysis. The later provides many more motion parameters. A study of lumbar spine lateral radiographs was conducted to determine errors in the motion parameters due to spinal level, radiographic quality, and errors in the two digitizing instruments. Significant differences were found in the errors due to the two digitizers when the same radiographic pair was redigitized several times. There were only minimal differences, however, between the digitizers when the radiographic films were remarked and redigitized. The error ranges (2 x SD) for the motion parameters were 1) rotation = +/- 1.25 degrees; 2) translation of the inferior posterior vertebral body corner = +/- 0.86 degrees; and 3) coordinates for the center of rotation = +/- 4.3 mm. Both the spinal level and radiographic quality affected the magnitude of errors in all motion parameters.

Computer Graphics↗
PubMed1992

p105, the NF-kappa B p50 precursor protein, is one of the cellular proteins complexed with the v-Rel oncoprotein in transformed chicken spleen cells.

Active NF-kappa B-like transcription complexes are multimers consisting of one or two members of a family of proteins related to the c-Rel proto-oncoprotein. We have isolated a chicken cDNA encoding p105, the precursor protein for the p50 subunit of NF-kappa B. Sequence analysis shows that chicken p105 is approximately 70% identical to the mouse and human p105 proteins, containing the Rel homology domain in its N-terminal 370 amino acids and several ankyrinlike repeats in the C-terminal portion of the protein. The Rel homology domain is particularly highly conserved between chicken and mammalian p50, and an in vitro-synthesized, truncated chicken p105 protein, containing sequences that correspond to the predicted p50 protein, bound to a consensus kappa B site in an electrophoretic mobility shift assay. In v-Rel-transformed chicken spleen cells, v-Rel is found in high-molecular-weight complexes which include cellular proteins of approximately 124 kDa (p124) and 115 kDa (p115). Here we report that in vitro-produced p105 comigrates with p124 from v-Rel-transformed spleen cells and that p105 and p124 appear to be identical by partial proteolytic mapping with V8 protease. Furthermore, both p105 and p50 can complex directly with v-Rel and chicken c-Rel in vitro. However, in vitro association with p105 by v-Rel does not necessarily correlate with transformation, since one nontransforming v-Rel mutant can associate with p105 in vitro.

Amino Acid Sequence↗
PubMed1992

Maternal recall of infant feeding events is accurate.

STUDY OBJECTIVE: Retrospective infant feeding data are important to the study of child and adult health patterns. The accuracy of maternal recall of past infant feeding events was examined and specifically the infant's age when breast feeding was stopped and formula feeding and solid foods were introduced. DESIGN AND SETTING: The sample consisted of Bedouin Arab women (n = 318) living in the Negev in Israel who were a part of a larger cohort participating in a prospective study of infant health and who were delivered of their infants between July 1 and December 15, 1981. Data from interviews conducted 12 and 18 months postpartum were compared to the standard data collected six months postpartum. MAIN RESULTS: As length of recall increased there was a small increase in the mean difference, and its standard deviation, between the standard and recalled age when breast feeding was stopped and formula feeding and solid foods were started. Recall on formula feeding was less accurate than recall on solid foods and breast feeding. In particular, among those 61% reporting formula use at the six month interview, 51% did not recall introducing formula when interviewed at 18 months. The odds ratio (95% CI) of stunting versus normal length for age for formula fed versus breast fed infants based on recall data (OR = 2.07; 95% CI 0.82-5.22) differed only slightly from those based on the standard data (OR = 2.21; 95% CI 0.77-6.37). The accuracy of a mother's recall varied with her child's nutritional status at the time of the interview, but not with other sociodemographic, infant, or interviewer characteristics. CONCLUSIONS: Retrospective infant feeding data based on maternal recall of events up to 18 months in the past can be used with confidence in epidemiological studies. However, data on formula feeding may not be as accurate as data on breast feeding and solid food feeding, and accuracy may decrease as length of recall increases.

Bottle Feeding↗
PubMed1992

The metabolism of acitretin and isoacitretin in the in situ isolated perfused rat liver.

1. The metabolism of acitretin and its 13-cis isomer, isoacitretin, has been investigated in the in situ isolated perfused rat liver in order to differentiate the action of the liver from that of the gut on the metabolism of these isomers. 2. Acitretin undergoes alpha-oxidation, chain shortening O-demethylation, and glucuronidation in the perfused rat liver. 3. Isoacitretin undergoes glucuronidation as the major, almost exclusive, route of metabolism in the perfused rat liver. 4. The difference in the hepatic metabolism of the cis and trans isomers of this retinoid may explain the differences in their pharmacokinetics, and may help in understanding the pharmacokinetics of related retinoids.

Acitretin↗
PubMed1992

Early events of polyoma infection: adsorption, penetration and nuclear transport.

Polyoma virions have different attachment proteins which are responsible for hemagglutination of erythrocytes and attachment to cultured mouse kidney cells (MKC). Virion binding studies demonstrated that MKC possess specific (productive infection) and nonspecific (nonproductive) receptors. Empty polyoma capsids have hemagglutination activity and bind to non-specific MKC receptors, but they are not capable of competing for specific virion cell receptors or preventing productive infection. Isoelectric focusing of the virion major capsid protein, VP1, separated this protein into six species (A through F). These species had identical amino acid sequences, but differed in degree of modification (phosphorylation, acetylation, sulfation and hydroxylation). Evidence based upon precipitation with specific antisera supports the view that VP1 species E is required for specific adsorption and that D and F are required for hemagglutination. The virion attachment domain has been localized to an 18 kilodalton fragment of the C-terminal region of VP1. Monopinocytotic vesicles containing 125I-labeled polyoma virions were isolated from infected MKC. A crosslinker was used to bind the MKC cell receptor(s) covalently to VP1 attachment protein, and a new 120 kilodalton band was identified by SDS-PAGE. An anti-idiotype antibody prepared against a neutralizing polyoma monoclonal antiody was used to identify a putative 50 kilodalton receptor protein from a detergent extract of MKC, as well as from MKC membrane preparation.

Adsorption↗
PubMed1991

Effect of probenecid on the pharmacokinetics and pharmacodynamics of procainamide.

Renal tubular transport of organic anions and cations is assumed to be mutually exclusive. However, results of a number of in vitro and in vivo studies suggest an interaction between the organic anion, probenecid, and various organic cations in the proximal renal tubule. To evaluate the clinical importance of such an interaction, the authors investigated the pharmacokinetics and pharmacodynamics of procainamide, an organic cation with a low therapeutic index that is excreted in part by active secretion in the proximal tubule, in the presence and absence of probenecid. In a randomized crossover study, six healthy subjects received a single 750-mg IV dose of procainamide, with and without prior probenecid administration (2 g orally). Blood and urine samples were obtained and pharmacokinetic parameters of procainamide were determined in each treatment period. QT intervals were measured from ECG recordings that were obtained at blood collection times for pharmacodynamic evaluation. Coadministration of probenecid did not result in any significant change in the overall disposition of procainamide. In particular, renal clearance was not significantly different (488 +/- 95 mL/min without probenecid vs. 478 +/- 69 mL/min in the presence of probenecid). Our data suggest an interaction between probenecid and procainamide in the proximal renal tubule does not exit. Reasons for this lack of interaction are discussed.

Adult↗
PubMed1991

Human surfactant protein D: SP-D contains a C-type lectin carbohydrate recognition domain.

Lung surfactant protein D (SP-D) shows calcium-dependent binding to specific saccharides, and is similar in domain structure to certain members of the calcium-dependent (C-type) lectin family. Using a degenerate oligomeric probe corresponding to a conserved peptide sequence derived from the amino-terminus of the putative carbohydrate binding domain of rat and bovine SP-D, we screened a human lung cDNA library and isolated a 1.4-kb cDNA for the human protein. The relationship of the cDNA to SP-D was established by several techniques including amino-terminal microsequencing of SP-D-derived peptides, and immunoprecipitation of translation products of transcribed mRNA with monospecific antibodies to SP-D. In addition, antibodies to a synthetic peptide derived from a predicted unique epitope within the carbohydrate recognition domain of SP-D specifically reacted with SP-D. DNA sequencing demonstrated a noncollagenous carboxy-terminal domain that is highly homologous with the carboxy-terminal globular domain of previously described C-type lectins. This domain contains all of the so-called "invariant residues," including four conserved cysteine residues, and shows high homology with the mannose-binding subfamily of C-type lectins. Sequencing also demonstrated an amino-terminal collagenous domain that contains an uninterrupted sequence of 59 Gly-X-Y triplets and that also contains the only identified consensus for asparagine-linked oligosaccharides. The studies demonstrate that SP-D is a member of the C-type lectin family, and confirm predicted structural similarities to conglutinin, SP-D, and the serum mannose binding proteins.

Amino Acid Sequence↗