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Biomedical subjects

M Chang

Publications and source records attributed to M Chang.

At least 181 records · Page 10Linked to original sources
PubMed1985

Purification and partial sequencing of bovine liver alkaline phosphatase.

Bovine liver alkaline phosphatase has been purified to homogeneity by procedures that include reverse-phase HPLC. The pure enzyme has an apparent Mr of 160,000 and is composed of what appears to be two identical monomers of Mr 82,000. About 80% of the material yielded the amino-terminal sequence Leu-Val-Pro-Glu-Lys-Glu-Lys-Asp-Pro-?-Tyr-?-Arg-Asp-Gln-Ala-Gln. The minor component was extended at the amino terminus by two residues that have not yet been identified, i.e., ?-?-Leu-Val-Pro-Glu-Lys-Glu-Lys-Asp-Pro-?-Tyr-?-Arg-Asp-Gln-Ala-Gln.

Alkaline Phosphatase↗
PubMed1984

The major rat heart glutathione S-transferases are anionic isozymes composed of Yb size subunits.

The GSH S-transferases from rat heart cytosol has been purified by S-hexylglutathione-linked Sepharose-6B affinity chromatography. The majority (approximately 80%) of these GSH S-transferases are anionic isozymes which can be resolved further by DEAE-cellulose column chromatography and isoelectric focusing. They are mainly composed of Yb size (Mr = 27,000) subunits with different substrate specificity patterns from the rat liver anionic GSH S-transferases. The major cationic GSH S-transferases from liver are not expressed in rat heart. Although some cationic GSH S-transferases from rat heart can be purified by CM-cellulose column chromatography they are composed of major subunits of Yb electrophoretic mobility.

Aging↗
PubMed1984

Use of high-performance liquid chromatography for preparing samples for microsequencing.

A method has been developed for the microsequencing of protein at subnanomole levels. The protein is carboxymethylated and freed of salts and reagents by reversed-phase chromatography prior to automated Edman degradation on a gas-phase sequencer. The carboxymethylated protein can also be fragmented chemically or enzymatically for further sequence analysis. The analytical techniques used to monitor the progress of the reactions all have picomole level sensitivity.

Amino Acid Sequence↗
PubMed1984

The persisting pseudomelanoma problem.

We reviewed 6,169 cases in which whole eyes were submitted to the Armed Forces Institute of Pathology (AFIP), Washington, DC, between January 1970 and December 1980. We sought to determine whether there had been any change in the frequency of incorrect diagnoses of malignant melanoma since two previous studies had been conducted at the AFIP. Of 744 eyes with clear media submitted with the clinical diagnosis of malignant melanoma, the rate of incorrect diagnosis was 6.4% (48 of 744 cases). During the 11-year study, the rate of incorrect diagnoses declined from 12.5% to 1.4%. Despite that overall decrease, the locations and frequency of simulating lesions were comparable with those found in the two previous studies. We believe our current findings reflect a significant increase in diagnostic accuracy among clinicians practicing outside of major academic centers.

Choroid Neoplasms↗
PubMed1984

Characterization of small amounts of peptides and proteins.

The use of microchemical methods for the characterization of both natural and recombinant proteins of biomedical importance is discussed. The methods include gel electrophoresis, high-performance liquid chromatography, protein fragmentation, amino acid analysis and automated Edman degradation. Each procedure is applicable at the picomole level.

Journal Article↗
PubMed1984

Retinal arteriolar occlusions following amniotic fluid embolism.

Amniotic fluid embolism is a serious complication of pregnancy resulting in death in the majority of patients. Particulate matter originating in the amniotic fluid has been identified at autopsy in the lung, kidney, and brain. A patient is presented who survived amniotic fluid embolism and developed bilateral retinal arteriolar occlusions, presumably based on entrapment of particulate matter originating in amniotic fluid. Her clinical course and ophthalmic findings are reviewed, and the relationship between amniotic fluid embolism and retinal vascular occlusion is discussed.

Adult↗
PubMed1983

Bacterial periorbital and orbital cellulitis in childhood.

The clinical features, microbiologic data, complications, and treatment in 137 children with periorbital cellulitis and 21 children with orbital cellulitis is presented. Periorbital cellulitis was more frequent (87%) than orbital cellulitis (13%). Periorbital cellulitis is a heterogeneous disease that may complicate trauma of the eyelids, external ocular infection, and upper respiratory infection. Children with periorbital cellulitis related to trauma or external infection tended to be less than 5 years old with negative blood cultures (99%) and positive cultures of percutaneous aspirates (42%); while children with periorbital cellulitis related to upper respiratory infection also tended to be less than 5 years of age, but blood cultures were frequently positive (42%) and cultures of percutaneous aspirates were usually negative (92%). Three children in the latter group developed meningitis. Intravenous antibiotic alone was effective treatment in most patients (90%). Orbital cellulitis was more frequent in children older than 5 years and frequently associated with sinusitis (90%). Blood and skin cultures were usually negative. Intravenous antibiotics alone were effective management in many patients (62%), but a significant proportion required paranasal sinus or orbital surgery (38%).

Bacterial Infections↗
PubMed1983

Pig brain contains cholecystokinin octapeptide and several cholecystokinin desoctapeptides.

A sequential method employing methanol extraction of the COOH-terminal fragment of cholecystokinin (CCK) from pig brain followed by HCl extraction of the more basic CCK peptides was used as the first step in purification of these peptides. Recovery was monitored with two different assays, one directed to the COOH terminus of CCK and the other to the NH2 terminus. The amino acid content and sequence were determined for each of five peptides after purification. The only peptide containing COOH-terminal immunoreactivity was CCK-octapeptide (CCK8). The other four peptides did not contain CCK8 and had lost one or two additional amino acids, perhaps as a consequence of the action of carboxypeptidases. These peptides were shown to be CCK33-desnonapeptide, CCK39-desnonapeptide and -desdecapeptide, and a large molecular weight precursor, CCK58-desnonapeptide, containing 19 amino acids (Ala-Val-Gln-Lys-Val-Asp-Gly-Glu-Ser-Arg-Ala-His-Leu-Gly-Ala-Leu-Leu-Ala-Arg) NH2-terminal to CCK39. The three NH2-terminal fragments of CCK58, CCK39, and CCK33 were about equally prominent. The brain, unlike the gut, appears to cleave CCK8 rapidly from a precursor peptide but to process the NH2-terminal portions of the molecule more slowly and incompletely.

Amino Acid Sequence↗
PubMed1983

Transient retinal striae.

Transient retinal folding was observed in a 28-year-old woman presenting with bilateral uveal inflammation. These retinal striae resolved within 5 weeks as the anterior uveal inflammation responded to topical cycloplegic and corticosteroid therapy. Ultrasonographic findings demonstrated choroidal thickening as a contributing factor in the production of these temporary retinal folds. We present this unusual case since transient retinal folding has been rarely documented, and as far as we are aware, has not been previously investigated by ultrasonography.

Adrenal Cortex Hormones↗
PubMed1982

Intestinal absorption of amino acid derivatives: importance of the free alpha-amino group.

The intestinal absorption of L-lysine-p-nitroanilide, L-alanine-p-nitroanilide, and glycine-p-nitroanilide was studied in the presence of competitive inhibitors in a perfused rat intestine. It ws observed that L-lysine-p-nitroanilide absorption was inhibited by L-lysine methyl ester and L-arginine-beta-naphthylamide but not by N alpha-acetyl-L-lysine methyl esters. L-Alanine-p-nitroanilide absorption was inhibited by L-alinine methyl ester but not by beta-alanine methyl ester. It was further observed that N alpha-benzoyl-L-arginine-p-nitroanilide and N alpha-succinyl-L-phenylalanine-p-nitroanilide were poorly absorbed. It was concluded that the peptidase in the brush border region that serves as the hydrolysis site requires a free alpha-amino group (an aminopeptidase), and that passive absorption of these compounds occurs only to a small extent.

Amino Acids↗
PubMed1982

Age at marriage and fertility in Taiwan.

"This study is concerned with the effects of age at marriage on fertility in Taiwan, with the primary objective of understanding the nature and causes of the recent upsurge of the...birth rate." Data are taken from the population register for the period 1975 to 1978 and from two fertility surveys undertaken in 1967 and 1976. It is found that the increase in the birth rate between 1975 and 1978 was primarily due to a large increase in the proportion and number of women aged 25 to 29. It was also due, in part, to an increase in the age at marriage. The effects of shifts in marriage duration, improved fecundability, and increases in premarital pregnancy are also considered. The author suggests that a further decline in fertility is unlikely in the near future unless there are changes in traditional family values, son preference, and number of children desired. (summary in CHI)

Age Distribution↗
PubMed1981

Mechanistic studies on reactions of bacterial methionine gamma-lyase with olefinic amino acids.

Methionine gamma-lyase (EC 4.4.1.11), which catalyzes the formation of methanethiol, alpha-ketobutyrate, and ammonia from L-methionine (eq 1), promotes the oxidative deamination of several four- and five-carbon olefinic amino acids (1-5). With the exception of vinylglycine (1), the Vmax rates of keto acid formation from the unsaturated substrate analogues are substantially lower than that for processing of methionine to alpha-ketobutyrate; vinylglycine is deaminated to ketobutyrate and ammonia with a Vmax twice that for L-methionine turnover. L-Allylglycine, L-2-amino-3-trans-pentenoate, and L-2-amino-3-cis-pentenoate (2, 4, 5) are all converted to 2-keto-pentanoic acid (alpha-ketovalerate). L-2-Amino-3-cis-pentenoate (5) is also a time-dependent, irreversible inactivator of the enzyme. None of the other substrate analogues tested appears to inactivate the enzyme. Spectral analysis of the enzymatic reaction with cis isomer 5 reveals the formation of a high-wavelength chromophore (lambda max = 550 nm ) which implies that a beta, gamma-unsaturated pyridoxal p-quinoid (VI) accumulates. No such absorbing species appears to form during the reaction of trans isomer 4 with methionine gamma-lyase. But a 550-nm chromophore develops when both 4 and 5 are reacted with Al(NO3)3 and pyridoxal methochloride in methanolic KOH. It would appear that the geometry of the protein and the olefinic amino acid as an intermediate enzyme-substrate adduct controls the kinetics of reaction, such that azaallylic isomerization becomes selectively rate determining for reaction with 5. When this isomerization is slow, an accumulating Michael-type acceptor (VI) could lead to the observed irreversible inactivation of the enzyme.

Alkenes↗