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Biomedical subjects

N Chang

Publications and source records attributed to N Chang.

At least 55 records · Page 3Linked to original sources
PubMed1984

An autopsy case of rheumatoid arthritis with aortic steno-insufficiency, angina pectoris and severe heart failure.

Although nonspecific pericarditis, myocarditis, valvulitis, and coronary arteritis are known as cardiac lesions that accompany rheumatoid arthritis (RA), there have been few reports of the occurrence of clinically severe valvular disease. We report here the case of 69-year-old man with a 25-year history of RA who died of acute left-sided heart failure complicating to aortic steno-insufficiency and angina pectoris. Autopsy findings revealed the coincidence of a congenital bicuspid aortic valve with chronic inflammation, fibrosis and calcification; eccentric hypertrophy and myocardial fibrosis of the left ventricle; 75% luminal narrowing of the proximal portion of the coronary artery due to atherosclerosis, and narrowing of the small arteries of the cardiac muscle due to angitis. It is deduced that the coronary artery lesions, aortic valve lesions and myocardial lesions were aggravated by the bicuspid aortic valve, changes with ageing and corticosteroid therapy.

Aged↗
PubMed1983

Continuous direct tissue oxygen tension measurement by a new method using an implantable silastic tonometer and oxygen polarography.

A new method of tissue oxygen tension measurement that is suitable for human use has been described. An implanted Silastic tube tonometer is combined with polarographic oxygen electrodes. The techniques of preparation, insertion, and measurement have been described. The advantages and disadvantages of this method have been considered in relation to established methods of tissue oxygen tension measurement. The method is suitable for clinical use and can be used to aid clinical decision-making.

Oxygen↗
PubMed1983

Direct measurement of wound and tissue oxygen tension in postoperative patients.

An implanted Silastic catheter technique was used to measure partial pressure of oxygen in mastectomy wounds and needle-induced wounds in the subcutaneous tissue of the arms of 33 postoperative patients to assess tissue-wound oxygenation and perfusion on the day of operation and daily through postoperative day five. Characteristic patterns were observed. Wound hypoxia was common and most pronounced after abdominal, vascular, and cardiac procedures. It was most severe immediately after operation. Tissue hypoxia was not easily detected by clinical evaluation and was unknowingly tolerated by experienced surgeons. The relationship between arterial and tissue PO2 is biphasic and presumably curvilinear at the lower range of PaO2 and rises linearly even above the point of full saturation of hemoglobin. Supplemental bolus fluid infusion elevated depressed tissue PO2 in 19 out of 19 measurements, implicating hypovolemia as a common cause of postoperative tissue hypoxia. Measurements of tissue oxygen tension, coupled with a single arterial oxygen determination, constitute a clinically useful means of monitoring tissue perfusion.

Abdomen↗
PubMed1982

Comparison of the effect of bacterial inoculation in musculocutaneous and random-pattern flaps.

The response of musculocutaneous and random-pattern flaps to bacterial inoculation was studied in dogs by intradermal injection of bacteria and deposition of bacteria into stable wound spaces created by wound cylinders. No difference could be demonstrated in the susceptibility to bacterial challenge in the different portions of the musculocutaneous flap and in normal skin. A larger area of necrosis was observed in the random-pattern flaps, and the distal part was significantly more susceptible to necrosis. While the musculocutaneous flaps recovered rapidly from the bacterial inoculation, necrosis was observed in the random-pattern flaps. The bacterial count increased in the wound spaces surrounded by the random-pattern flaps, leading to full-thickness flap necrosis. The bacterial count decreased in the wound spaces surrounded by musculocutaneous flaps; there was evidence of healing around the wound cylinders. The musculocutaneous flap demonstrates a greater resistance to bacterial inoculation than the random-pattern flap on both its cutaneous and muscular surfaces.

Animals↗
PubMed1981

An interference phenomenon associated with a measles virus SSPE isolate (Halle).

A measles virus (Halle SSPE isolate) induced ring plaque phenomenon (concentric rings of living and dead cells) has been shown to be associated with the temperature-dependent production of interfering particles. The interfering particles have been purified by potassium tartrate linear gradient centrifugation and have buoyant densities of 1.15 g/ml (M particle) and 1.06 g/ml (L particle) respectively. Both interfering particle population have been shown to decrease the yield of wild-type measles virus from infected cells by 50% when co-infection experiments were performed. Neither the M or L particle population interfered with the growth of VSV in the same host-cell system.

Animals↗
PubMed1979

The mechanism of the irreversible inhibition ofrat liver phenylalanine hydroxylase due to treatment with p-chlorophenylalanine. The lack of effect on turnover of phenylalanine hydroxylase.

The administration of a single dose of p-chlorophenylalanine (360 mg/kg) to rats leads to the irreversible loss of 90% of hepatic phenylalanine hydroxylase activity after 24 h. This loss of activity is not the result of either an alteration in the overall structure of the enzyme, as determined by its antigenicity, or in the total immunologically reactive protein in the liver, as tested with a specific antiserum prepared against native phenylalanine hydroxylase. Neither the rate of synthesis nor the rate of degradation of phenylalanine hydroxylase is changed by p-chlorophenylalanine (pClPhe) treatment. The half-life for the enzyme is about 2 days in control and in pClPhe-treated rats. In addition, there is no detectable incorporation of pClPhe into the phenylalanine hydroxylase molecule itself.

Animals↗
PubMed1979

Preliminary characterization of bovine pineal prolactin releasing (PPRF) and release-inhibiting factors (PPIF) activity.

Bovine pineal glands were subjected to extraction with dilute acetic acid, gel filtration on Sephadex G-25 and subsequent ultrafiltration through Diaflo membranes PM10, UM2 and UM05. Various fractions derived at each step were tested for the presence of substances which stimulate or inhibit prolactin secretion in vitro and in vivo. Both prolactin releasing (PPRF) and release-inhibiting (PPIF) activities were observed. PPRF activity was present in certain fractions derived from Sephadex G-25 and in the PM10 residue (MW congruent to less than 10,000). Whereas both the UM2 residue (MW greater than 1000) and UM05 filtrates (MW less than 500) was seen to inhibit pituitary prolactin release in vitro, the UM05 residue (MW greater than 500 and less than 1000) inhibited prolactin release in vivo, possibly by stimulating the secretion of the hypothalamic prolactin inhibiting factor. On the basis of its inactivation by trypsin it was concluded that PPIF may be a peptide or contain a peptide moiety indispensible for its biological activity. Experiments are in progress to characterize pineal prolactin-regulating activities and to elucidate further the physiological role of the pineal gland in the regulation of prolactin secretion.

Animals↗
PubMed1978

Purification of infectious pancreatic necrosis (IPN) virus and comparison of polypeptide composition of different isolates.

Infectious pancreatic necrosis (IPN) virus was partially purified by freon extraction of infected CHSE-214 cells and concentrated by polyethylene glycol (PEG) precipitation of virus from the medium. Both methods resulted in virus concentrates that could be further purified by two CsCl gradient centrifugations with little loss of infectivity. A Recovery of 80 to 100% of the virus infectivity was obtained and over 100-fold concentration of viral infectivity was achieved by these methods. This purification was used to compare 10 isolates of IPN virus with regard to their physiochemical properties by electron microscopy, buoyant density in CsCl, and sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the purified virions. Electron-microscopic observations showed that the virus isolates were identical in that they were isometric, hexagonal in profile, and had a particle diameter of 71 nm. The buoyant densities of the virus isolates in CsCl were found to be 1.33 g/ml. SDS-gel electrophoresis of the virus isolates revealed the presence of three polypeptides of molecular weight 50, 30, and 27 x 10(3) designated as VP50, VP30, and VP27, respectively.

Animals↗
PubMed1976

In vitro activation of rat liver phenylalanine hydroxylase by phosphorylation.

Essentially pure phenylalanine hydroxylase from rat liver can be activated between 2.5- and 3.0-fold by treatment with Mg2+, ATP, protein kinase, and cyclic AMP. The activation is seen when the hydroxylase is assayed in the presence of tetrahydrobiopterin, but not in the presence of 2-amino-4-hydroxy-6,7-dimethyltetrahydropteridine. In the presence of [gamma-32P]ATP, activation is accompanied by incorporation of 32P into the protein to the extent of 0.7 mol/mol of hydroxylase subunit (Mr = 50,000). Cehmical analysis of the untreated enzyme shows that it already contains about 0.3 mol of Pi/mol of hydroxylase. These results suggest that the activity of the hydroxylase may be regulated by phosphorylation.

Adenosine Triphosphate↗
PubMed1976

Hepatic phenylalanine 4-monooxygenase is a phosphoprotein.

Phenylalanine hydroxylase [phenylalanine 4-monooxygenase; EC 1.14.16.1; L-phenylalanine, tetrahydropteridine:oxygen oxidoreductase(4-hydroxylating)] isolated from rat liver is a phosphoprotein containing approximately 0.31 mumol of protein-bound phosphate per mumol of subunit (50,000 molecular weight). When the enzyme is further phosphorylated in the presence of ATP and a 3'5'-cyclic-AMP-dependent protein kinase (EC 2.7.1.37; ATP:protein phsophotransferase), an additional 0.7 mumol of phosphate per mumol of subunit is introduced, bringing the total phosphate content up to about 1 mumol/mumol of subunit. This phosphorylation of the enzyme in vitro is accompanied by a 2.6-fold increase in hydroxylase activity when the activity is assayed in the presence of tetrahydrobiopterin. Partial proteolytic digestion of phenylalanine hydroxylase, which previously had been shown to activate the enzyme 20- to 50-fold [Fisher, D.B. & Kaufman, S. (1973) J. Biol. Chem. 248, 4345-4353], removes almost all of the phosphate from the enzyme.

Animals↗