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Biomedical subjects

P Chang

Publications and source records attributed to P Chang.

At least 235 records · Page 13Linked to original sources
PubMed1991

Fluorocarbon/lecithin emulsions: identification of EYP-coated fluorocarbon droplets and fluorocarbon-empty vesicles by freeze-fracture electron microscopy.

Freeze-fracture has been used to examine perfluorodecalin/egg yolk phospholipid emulsions (70:8, w/v%) destined to be used as injectable oxygen carriers. The fluorocarbon displays a specific granular aspect upon freeze-fracture which makes it readily recognizable and allows the distinction between two populations of objects on the micrographs: fluorocarbon droplets and water-filled lipid vesicles.

Egg Yolk↗
PubMed1991

Interactions of triply phosphorylated human beta-casein: fluorescence spectroscopy and light-scattering studies of conformation and self-association.

Structural changes of triply phosphorylated human beta-casein, caused by shifts in temperature between 5 and 40 degrees C, were studied using intrinsic and extrinsic fluorescence, fluorescence polarization, turbidity, and light scattering measurements. Intrinsic fluorescence declined between 5 and 20 degrees C then rose between 25 and 40 degrees C, indicative of a shift of the tryptophan fluor toward a more nonpolar environment. The fluorescence of the extrinsic probe, 8-anilino-1-naphthalene-sulfonic acid (ANS), increased only slightly between 5 and 25 degrees C, and then more sharply between 25 and 40 degrees C, suggesting a change in conformation leading to a change in either the dissociation constant, Kd, or the number of ANS binding sites, N. The presence of Ca+2 ions did not significantly alter the pattern of changes of intrinsic and extrinsic fluorescence with changing temperature. For ANS binding, values of Kd and N were calculated by two different procedures, each based upon different assumptions. The results point to increased exposure of hydrophobic surfaces with increased temperature, strongly supportive of conformational changes. Although more opportunity for hydrophobic interaction leads to increased protein-protein association, turbidity and light-scattering also suggest ion bridge formation between protein molecules. A comparison of the primary sequences of beta-caseins from six species reveal residues that are common in all species examined and thus are pivotal in protein folding and conformation, intermolecular hydrophobic interactions and ion bridge formation with Ca+2 and inorganic phosphate.

Amino Acid Sequence↗
PubMed1991

Regional extraction of circulating norepinephrine, DOPA, and dihydroxyphenylglycol in humans.

Dihydroxyphenylglycol (DHPG) is the main intraneuronal metabolite of the sympathetic neurotransmitter, norepinephrine (NE), and dihydroxyphenylalanine (DOPA) the immediate product of the rate-limiting step in catecholamine biosynthesis. Simultaneous measurements of regional rates of appearance (spillovers) of NE, DOPA, and DHPG in plasma have the potential to provide unique information about aspects of sympathoneural function but have not actually been measured in humans. In the present study, spillovers of DHPG, DOPA, and NE in the heart, head, leg, and lungs, were estimated from regional extraction fractions of infused [3H]-1-NE, DHPG, and [13C6]DOPA or unlabelled DOPA in humans during cardiac catheterization. There was little cardiac extraction of DHPG (7 +/- SEM 2%) or DOPA (8 +/- 4%) but substantial extraction of NE (69 +/- 4%). Values for cardiac spillover of DHPG and DOPA therefore were similar to values for the arteriovenous increment times plasma flow (arteriovenous production rate), whereas the cardiac spillover of NE averaged about 7-times the NE arteriovenous production rate. Cardiac DHPG spillover (28 +/- 3 ng/min) exceeded the spillovers of NE (9 +/- 2 ng/min) and DOPA (15 +/- 4 ng/min). In contrast, cranial DOPA spillover (159 ng/min) exceeded those of NE and DHPG by 8- and 2-fold and accounted for about 1/10 of the total spillover of DOPA into arterial plasma. In the femoral vascular bed, arteriovenous production rates of NE and DHPG were unrelated to femoral spillovers of NE and DHPG. Arterial and regional clearances of [13C6]DOPA were similar to those of unlabelled DOPA. The results suggest that (1) endogenous NE, DOPA, and DHPG all are released into the bloodstream by the heart, head, and limbs of humans; (2) DHPG and DOPA are not co-released with NE; (3) cardiac arteriovenous production rates of DOPA and DHPG can be used to indicate cardiac spillover of these catechols, whereas the cardiac NE arteriovenous production rate substantially underestimates cardiac NE spillover; and (4) estimates of limb spillover of NE and DHPG require concurrent measurements of the corresponding regional clearances.

Arteries↗
PubMed1991

Experimental and clinical free cutaneous transfers in the dog.

Various reconstructive techniques have been applied to the management of difficult wounds in the dog. Wounds in the distal extremities and on the face are hard to manage by conventional methods. A free cutaneous flap, based on the superficial cervical vessels, was developed and used in a series of experimental and clinical cases. Six of eight experimental orthotopic transfers survived. The two failures were thought to be related to technical error. The seven flaps, used in clinical cases, all survived and successfully resolved the dogs' clinical problems.

Animals↗
PubMed1991

Tar, CO and delta 9THC delivery from the 1st and 2nd halves of a marijuana cigarette.

Previous in vitro studies suggest that, with successive puffs from a marijuana cigarette, delta-9-THC becomes concentrated in the remaining uncombusted portion of the cigarette. These observations are consistent with the common practice of smoking marijuana cigarettes to a smaller butt length than that to which tobacco cigarettes are smoked. The purpose of the present study was to compare the delivery of delta-9-THC, as well as total insoluble smoke particulates (tar) and carbon monoxide, from the distal ("first") versus the proximal ("second") halves of a standard marijuana cigarette during "natural" smoking of marijuana. On 4 separate days, ten habitual marijuana users smoked nearly all or approximately 1/2 of a standard marijuana cigarette (83 mm length; 800-900 mg; 1.24% THC), as follows: day 1, "whole" cigarette (60 mm smoked, leaving a 23-mm butt); day 2, "first" half (first 30 mm); day 3, "second" half (second 30 mm) after the "first" half was presmoked with a syringe; and day 4, "second" half after the "first" half was excised. A previously described smoking apparatus (20) was used for measurement of puff volume and inhaled tar. Puff volume and number were allowed to vary spontaneously (provided that the specified length of cigarette was consumed), while inhaled volume (1.5 liters), breathholding time (14 s) and interpuff interval (30 s) were held constant. Blood samples were withdrawn prior to smoking and serially after completion of smoking for analysis of blood carboxyhemoglobin (COHb) and serum delta-9-THC. Heart rate was measured before and 5 min after smoking. Subjects rated their level of "high" 20 min after completion of smoking.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbon Monoxide↗
PubMed1991

Distribution of type A and type B EBV in patients with nasopharyngeal carcinoma.

The subtypes of Epstein-Barr virus (EBV) according to EBNA 2 genes were investigated in 53 nasopharyngeal carcinoma (NPC) biopsies in Taiwan by polymerase chain reaction (PCR) and by Southern blot hybridization method. EBV DNA was found present in all NPC biopsies. Type A was the predominant type and comprised of 94.3% of the EBV of NPC. Type B or coinfection of type A and type B comprised of only 3.8% and 1.9% respectively.

Adult↗
PubMed1991

Complete functional recovery after 24-hour heart preservation with University of Wisconsin solution and modified reperfusion.

Successful long-term myocardial preservation is dependent on optimizing conditions during arrest, storage, and reperfusion. Neonatal piglet hearts were arrested and stored in University of Wisconsin solution (UW) at 4 degrees C for 24 hours and reperfused on a blood-perfused, adult animal-supported isolated circuit. Results were compared with nonischemic continuously perfused control hearts (group 1, n = 5). The initial 10 minutes of reperfusion in groups 2-4 was modified by aspartate/glutamate-enriched leukocyte-depleted blood cardioplegia (group 2, n = 7), leukocyte depletion alone (group 3, n = 9), and aspartate/glutamate-enriched blood cardioplegia alone (group 4, n = 6). After 10 minutes, perfusion was continued with unmodified whole blood. In group 5 (n = 9), unmodified whole blood was used for initial reperfusion as well as subsequent perfusion. The stroke work index was determined 60 minutes after reperfusion. Biopsies for high-energy phosphates, myocardial water content, and electron microscopy were obtained after functional assessment. The stroke work index at left ventricular end-diastolic pressure of 9 mm Hg did not differ between groups 1 and 2 (19.0 +/- 1.4 x 10(3) and 19.0 +/- 1.5 x 10(3) [mean +/- SEM] erg/g, respectively). These were both different from group 5 (13.3 +/- 0.8 x 10(3) erg/g, p less than 0.05). Group 3 showed improved function (15.7 +/- 0.7 x 10(3) erg/g), but this did not reach statistical significance when compared with group 5. No difference was found between groups 4 and 5. Myocardial water content, high-energy phosphate levels, and ultrastructure were similar in all groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1991

The role of imaging in prostate cancer.

For patients with prostate cancer, diagnostic imaging can play three roles: screening, staging, and monitoring. Bayesian analysis dictates that if the prior probability of cancer is relatively low or if the consequences of a false-positive result are unacceptable, the test must be optimally specific. If the prior probability of cancer is high or if the consequences of missing it are unacceptable, the test must be optimally sensitive. For screening, the consequences of a miss are slight, and the consequences of labeling an insignificant cancer significant are serious. Thus, a very specific test is required. No current imaging modality fulfills this criterion. For staging, the prior probability of significant disease is relatively high, and the consequences of a miss serious, so a very sensitive test is required. Transrectal sonography, plus biopsy under sonographic control, fulfills this criterion for local disease, as does a bone scan for bone metastases. For monitoring, the prior probability is high, and the consequences of a miss serious, so a very sensitive test is needed. The bone scan is sensitive for bone metastases. Although CT is not sensitive for detecting lymph node metastases, it has practical clinical advantages over other imaging modalities for monitoring purposes in that it can detect disease in multiple structures at once. It is the only test that can monitor prostate size, the size of the lymph nodes, and whether hydronephrosis or liver metastases are present all in the scope of one examination.

Diagnostic Imaging↗
PubMed1990

Interactions of triply phosphorylated human beta-casein: monomer characterization and hydrodynamic studies of self-association.

The triply phosphorylated form of human beta-casein comprises about 15% of that fraction and is thus a significant component about midway between the two extremes of zero and five phosphoryls. Its partial specific volume, v, of 0.74 +/- 0.01 and absorbancy, E1% 1 cm, 280 nm, of 6.2 +/- 0.2 are almost identical to the other human beta-caseins. Equilibrium dialysis gave an average of 3.1 +/- 0.4 major Ca2+ binding sites at 37 degrees C with Kdiss = 8.6 x 10(-4) M. Sedimentation and viscosity at low temperatures or in 3.3 M urea suggested a prolate ellipsoidal monomer with 1.4 g H2O/g protein, 10 nm in length and 1.4 nm in width. The concentrated charge of the phosphoryls may be near one end of the ellipsoid, allowing the molecules to align with the flow in the viscometer at low concentration but, due to intermolecular electrostatic interactions, not when concentration is high. This would provide a reason for the heretofore unexplained curvature in the plots of reduced viscosity, eta red, vs beta-casein protein concentration. Self-association increased with temperature. At 37 degrees C in low salt buffer, s20,W was 16 S, which increased to about 33 S as ionic strength, I, was increased to 0.2 and above. At the same time, eta red in low salt buffer decreased from about 22 ml/g at 4 degrees C to a constant value of about 5 ml/g above 23 degrees C. A similar value for eta red at 37 degrees C, which was almost independent of protein concentration, was obtained at I greater than 0.25, giving an extrapolated intrinsic viscosity value of [eta] = 4.0 ml/g. Using this value and assuming a spherical aggregate, calculations suggest a radius of 9 nm with about 48 monomers and 0.86 g H2O/g protein.

Calcium↗
PubMed1990

The role of imaging in screening for prostate cancer. A decision analysis perspective.

Using Bayesian and decision analytical concepts, we can define the ideal characteristics of any screening test for cancer of the prostate: high specificity, reasonably high sensitivity, noninvasiveness, low cost, and low interobserver variability. Computed tomography (CT) fails as a test, since it cannot show the internal structure of the prostate; MRI is too expensive and has an unacceptably poor specificity. Transrectal sonography does have many desirable characteristics, including relatively high sensitivity and, if no biopsy is done, low cost and noninvasiveness. But it has an unacceptably low specificity for early, clinically significant lesions: over half of all patients tested will have a positive result, requiring a confirming biopsy, which means that transrectal sonography will in the end be too invasive and too expensive. Therefore, we cannot recommend transrectal sonography as a primary screening tool for cancer of the prostate at this time.

Costs and Cost Analysis↗
PubMed1990

Effects of molecular oxygen, oxidation-reduction potential, and antioxidants upon in vitro replication of Treponema pallidum subsp. pallidum.

The effects of various concentrations of dithiothreitol, molecular oxygen, and several antioxidants upon the in vitro replication of Treponema pallidum were studied. The optimal dithiothreitol concentration was between 0.65 and 1.62 mM, and the optimum oxygen concentration was 3.0% +/- 0.5% in both the presence and absence of additional antioxidants. It was discovered that the reduced sulfhydryl concentration and the oxidation-reduction potential of the medium were stabilized after 5 days. The water-soluble antioxidants cobalt chloride, cocarboxylase, mannitol, and histidine were individually tested for their ability to increase treponemal growth in vitro. The optimum concentrations for these antioxidants were 21 nM, 4.3 nM, 0.55 mM, and 0.23 mM, respectively. When combined at these concentrations, the mixture of antioxidants stimulated the in vitro replication of T. pallidum. The number of treponemes in cultures with the antioxidants averaged a 59-fold increase, compared with a 43-fold increase in cultures lacking the antioxidants. It was further demonstrated that histidine and mannitol were the most critical components of this mixture. Catalase and superoxide dismutase were investigated for their ability to promote the growth and maintain viability of T. pallidum in tissue culture. The optimum concentrations for these enzymes were 10,000 U/liter and 25,000 U/liter, respectively. When these enzymes and the above antioxidants were combined and added to a chemically reduced modified Eagle medium, the treponemes increased an average of 70-fold, compared with an average of 35-fold in cultures lacking them. Furthermore, this medium, T. pallidum culture medium, supported the replication of T. pallidum at oxygen concentrations from 5 to 7% with little loss in yield or viability. The lipid-soluble antioxidants vitamin A and vitamin E acetate were also shown to enhance the in vitro growth of T. pallidum in this medium.

Antioxidants↗
PubMed1990

Gallbladder contractility in patients with spinal cord injuries: a sonographic investigation.

Approximately 30% of all patients who have spinal cord injuries have gastrointestinal symptoms. One cause is gallstone disease; indeed the literature suggests that gallstones are more common in patients with spinal cord injuries because these patients have impaired contractility of the gallbladder with a reduced ejection fraction. To test this hypothesis, we obtained gallbladder sonograms in 30 patients with spinal cord injuries (16 quadriplegics and 14 paraplegics) and in 32 uninjured age-matched control subjects. Four patients and four asymptomatic control subjects had gallstones and were excluded. The remaining 26 patients and 28 control subjects fasted for 12 hr. Longitudinal and transverse sonograms of the gallbladder were made immediately before the ingestion of 25 g of fat, and at 10, 20, 30, 45, and 60 min thereafter. Gallbladder volumes were measured by using the ellipsoid method. Resting and residual volumes and the emptying times were determined and the ejection fractions were calculated. The ejection fractions were significantly lower (p = .003) in the patients than in the control subjects because the resting volumes were lower than in the control subjects (p = .013). However, the emptying times and residual volumes were the same in the two groups. We conclude that gallbladder contractility is normal in patients with spinal cord injuries and that the lower ejection fraction found in such patients is due to a smaller resting volume.

Adult↗
PubMed1990

Effect of helium and heliox on glutamate decarboxylase activity.

The activity of glutamate decarboxylase (GAD) in pure helium at 6.8 MPa was significantly enhanced when compared to GAD activity in air at 0.1 MPa (906 vs. 602 nmol.h-1.mg-1 protein, respectively). No significant difference was found between GAD activities in heliox at 6.8 MPa (0.87% O2 at 6.8 MPa) and in air at 0.1 MPa. On the other hand, the activities in heliox at 0.1 MPa (0.87% O2 at 0.1 MPa) and air at 0.1 MPa were significantly different (655 and 446 nmol.h-1.mg-1 protein, respectively). These data indicate that pressures up to 6.8 MPa do not affect the GAD-catalyzed synthesis of gamma-aminobutyric acid, but that the enzyme, as previously reported, is sensitive to low levels of oxygen.

Animals↗
PubMed1990

Effect of PCO2-adjusted pH on the neonatal heart during hypothermic perfusion and ischemia.

The effect of pH regulation on the function of the isolated neonatal heart during continuous hypothermic perfusion and arrest was tested in 3- to 6-day-old piglet hearts. Three groups of hearts were perfused from an adult support pig, with pH varied by a carbon dioxide/oxygen gas exchanger and temperature controlled by a heat exchanger. After control function studies were obtained at normothermia with a pH of 7.4, the hearts were cooled over 15 minutes to 10 degrees C. Hypothermic perfusion was maintained for 1 hour, followed by rewarming to 37 degrees C. In group 1 (n = 5), the alpha stat (neutral) model, the blood perfusate was maintained at a pH of 7.4 (calculated at 37 degrees C). In group 2, the alkaline model, the pH was maintained at 7.9, and in group 3, the pH-stat (acid) model, the pH was maintained at 7.0. In addition, the effect of 1 hour of hypothermic ischemia after hypothermic perfusion at a pH of 7.0 was evaluated in five hearts (group 4). After rewarming no significant difference was noted in functional recovery (group 1 = 93% +/- 5%, group 2 = 92% +/- 6%, group 3 = 96% +/- 5%, and group 4 = 95% +/- 2%), oxygen consumption, coronary resistance, lactate extraction, and myocardial extravascular water content. We conclude that neonatal heart function is resistant within the range of this study to changes in pH caused by changes in carbon dioxide tension during hypothermic perfusion and ischemia.

Acid-Base Equilibrium↗
PubMed1990

[Therapeutic effect of yupingfeng san and shengmai yin on Coxsackie B viral myocarditis].

A "LDH release method" was used to determine NK cell activity in 30 cases of Coxsackie B viral myocarditis and contrasted with 20 normal volunteers. About 80% cases revealed NK cell activity deficiency. Among them, the NK activity of 24 cases (80%) was less than 14%; and 15 cases (50%) less than 10%. After Yupingfeng San and Shengmai Yin treatment for 2-3 months, their NK cell activity was elevated from 12.26 +/- 1.31% to 31.99 +/- 4.23% (P less than 0.001). At the same time, their clinical manifestations and EKG changes were improved or returned to normal.

Adult↗