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Biomedical subjects

P Chang

Publications and source records attributed to P Chang.

At least 271 records · Page 15Linked to original sources
PubMed1987

Desensitization of renal vasopressin-stimulated adenylate cyclase by a vasopressor and antidiuretic antagonist, [1-(beta-mercapto-beta,beta-cyclopentamethylenepropionic acid),2-(O-ethyl)-D-tyrosine, 4-valine]arginine vasopressin.

Desensitization of the renal antidiuretic (V2) receptor has been regarded as agonist-specific. We found that a vasopressor and antidiuretic (V1V2) antagonist d(CH2)5DTyr(Et)VAVP induced desensitization of the receptor and that a vasopressor (V1) antagonist d(CH2)5Tyr(Me)AVP, which is a weak antidiuretic (V2) agonist, counteracted the potent desensitizing action of 1-deamino-8-D-arginine-vasopressin and endogenous arginine vasopressin.

Adenylyl Cyclases↗
PubMed1987

Mutual interactions between speech and finger movements.

Speech output and finger movements were recorded as right-handed males repeated a syllable while making cyclical finger movements in three experimental conditions: (2) maintaining constant amplitude in both response systems; (b) alternating speech amplitude while attempting to maintain constant finger movement amplitude; and (c) alternating finger movement amplitude while attempting to maintain constant speech amplitude. Observations showed that output of the two response systems was coupled (one syllable was uttered with each finger movement) and entrained in amplitude (the amplitude pattern of the response that the subject attempted to keep constant followed that of the concurrently-active amplitude-modulated response). These interactions were bidirectional and were present with both left-handed and right-handed finger movements. The interactions are more extensive and subtle than mere interference wtih one response system by the other, and apparently do not depend on anatomical overlap of the responding neural systems.

Journal Article↗
PubMed1987

Myocardial protection in the neonatal heart. A comparison of topical hypothermia and crystalloid and blood cardioplegic solutions.

UNLABELLED: Myocardial protection achieved during 2 hours of ischemic arrest was evaluated in 45 isolated, blood perfused, neonatal (1 to 5 days) piglet hearts. Comparisons were made among five methods of myocardial protection: Group I, topical cooling; Group II, hyperosmolar (450 mOsm) low-calcium (0.5 mmol/L) crystalloid cardioplegia; Group III, St. Thomas' Hospital cardioplegia; Group IV, cold blood cardioplegia with potassium (21 mmol/L), citrate-phosphate-dextrose (calcium level 0.6 mmol/L), and tromethamine; and Group V, cold blood cardioplegia with potassium alone (16 mmol/L) (calcium level 1.2 mmol/L). Hemodynamic recovery (percent of the preischemic stroke work) after 30 and 60 minutes of reperfusion was 82.9% and 86.7% in Group I, 35.7% (p less than 0.0001) and 43.7% (p less than 0.0001) in Group II, 76.1% and 77.7% in Group III, 67.4% (p less than 0.05) and 60.6% (p less than 0.05) in Group IV, and 110.7% and 100.6% in Group V. CONCLUSIONS: Topical cooling is an effective method of myocardial protection in the neonate. Cold blood cardioplegia with potassium alone and a normal calcium level provides optimal functional recovery. The improved protection obtained with both crystalloid and blood cardioplegia with normal calcium levels suggests an increased sensitivity of the neonatal heart to the calcium level of the cardioplegic solution.

Animals↗
PubMed1986

Effect of sodium nitroprusside on the biophase concentration of D-tubocurarine at the neuromuscular junction.

D-Tubocurarine (DTC) at an intravenous dose of 250 micrograms/kg, or at an intra-arterial dose of 25 micrograms/kg, produced about a 50% block on the twitch tension of the indirectly stimulated tibialis anterior muscle of anaesthetized cats. The DTC-induced neuromuscular block was abolished if it was given intravenously but not intra-arterially, 30 min after the commencement of sodium nitroprusside (SNP) infusion (5 micrograms/kg per min) when there was a maximum decrease in blood pressure. The results indicate that the biophase concentration of DTC at the neuromuscular junction may be decreased as a consequence of the vasodilation induced by SNP leading to a reduced transport of the blocker to the site of action.

Animals↗
PubMed1986

Expandable intrahepatic portacaval shunt stents in dogs with chronic portal hypertension.

A canine experimental model was used to investigate the feasibility of using balloon-expandable portacaval shunts in humans with chronic portal hypertension. Intrahepatic portacaval shunts were created in nine dogs with stable portal hypertension previously induced by intraportal injections of polyvinyl alcohol (Ivalon). Embolic material was injected periodically through a subcutaneous port that allowed repeated access to the portal system. Shunts were placed 14 weeks after the last embolization. A shunt patency rate of 100% was observed up to 48 weeks. Low portacaval pressure gradient and high shunt flow accounted for the good results.

Animals↗
PubMed1985

Interactions in human casein systems: self-association of fully phosphorylated human beta-casein.

Human beta-casein was separated according to the extent of phosphorylation and the fully phosphorylated moiety was characterized. Fully phosphorylated human beta-casein makes up to 13-15% of the beta-casein fraction. It has a partial specific volume, v, of 0.754 +/- 0.008 and an absorbancy, E1(1%)cm,280 nm of 6.4 +/- 0.2. Sedimentation and viscosity data yield a solvation of 2.9 g H2O/g protein and an axial ratio of about 5 for the monomer. This would be consistent with a prolate ellipsoid of 10 nm length and 2 nm width. There is one strong binding site for Ca2+ for each organic phosphate ester in the molecule. The protein will precipitate at room temperature upon the addition of either 10 mM Ca2+ or greater than 1 M NaCl. Increasing the temperature from 4 to 37 degrees C causes an apparent conformational change and an increase in protein aggregation which is further increased by the addition of NaCl at this temperature until a limiting size is reached at about 0.25 M NaCl. This limiting size polymer contains 95-105 monomers and is nearly spherical with a radius of about 15 nm and a solvation of 3 g H2O/g protein. If this polymer were the submicelle of human casein, it could account for the abnormally high solvation of human casein micelles but their small average size would be more difficult to reconcile without additional information concerning K-casein association. The addition of Ca2+ to the system introduces association patterns which are more complex and not easily assessed.

Amino Acids↗
PubMed1985

A marker of animal-vegetal polarity in the egg of the sea urchin Paracentrotus lividus. The pigment band.

We have examined the subequatorial accumulation of pigment granules (the so-called 'pigment band') in the egg of the sea urchin Paracentrotus lividus, which constitutes an unambiguous marker of animal-vegetal polarity. Most of the reddish pigment granules are situated at the periphery of the egg. They exhibit occasional saltatory movements and can aggregate into large patches. Pigment granules are retained as a band in the isolated cortex when the egg surface complex is isolated by shearing eggs attached to polylysine-coated surfaces with calcium-free isotonic solutions. Pigment granules remain as the main vesicular component of fertilized egg cortices or of unfertilized egg cortices perfused with calcium to provoke cortical granule exocytosis. They may be anchored to the isolated cortex through associations with the plasma membrane and with an extensive subsurface network of rough endoplasmic reticulum (rough ER). Pigment granules contain antimonate-precipitable calcium and, in this respect and many others, resemble acidic vesicles recently identified in the cortex of unpigmented sea urchin eggs. We discuss the similarities observed between granules and acidic vesicles in various urchin egg species and their possible functions.

Actin Cytoskeleton↗
PubMed1985

Characterization of hydroxyl radical-induced damage after sparsely and densely ionizing irradiation.

The extent of hydroxyl radical mediated cell inactivation was measured for a variety of particle beams ranging from 8.5 Me V/u neon ions to 570 Me V/u argon ions. In general, the fraction of the total radiosensitivity caused by OH decreases from close to 60 per cent at low ionization density or low linear energy transfer (low LET) to close to 25 per cent at high LET for aerobically irradiated mammalian cells. The extent of OH induced cell lethality can be explained in terms of LET infinity only for low energy or low atomic number particles where fragmentations and complicated track structures do not contaminate the characteristic particle LET. For example, at a calculated LET infinity of 100 ke V/micron, the OH mediated fraction of the total radiation damage is about 25 per cent for low energy carbon but close to 40 per cent for high energy carbon ions. For low energy charged nuclei of approximately the same energy, as the 5.4-13.4 MeV/u He, Li, C and Ne ions in this report, there is a predictable diminution of the OH mediated effect with increasing LET infinity; however, the biological effect cannot be predicted accurately from calculated LET infinity values for high energy particle irradiation, nor indeed from a variety of low energy charged particles of quite different energies (incident velocities). This illustrates the unsuitability of using LET as a unifying parameter, except under specific circumstances. As more is learned about the energy deposition for energized charged particles in terms of track structure (core and penumbra), it may be possible to characterize the radiobiological data with a better physical parameter than LET infinity.

Animals↗
PubMed1985

Incidence of malignancy in peripheral lymph node biopsy.

A review was made of 62 lymph node biopsy procedures during a 12-month period, from January 1, 1982, to December 31, 1982. The overall diagnostic yield was 56.5 per cent. Malignant lymph nodes were found in 53.2 per cent of cases. Seventy-two and two-tenths per cent (72.2%) of all malignant lymph nodes were metastatic carcinoma, including 6.1 per cent of metastatic lymph nodes with unknown primary. Twenty-seven and three-tenths per cent (27.3%) of all malignant lymph nodes belonged to the lymphoma-leukemia group. Among all the superficial lymph node regions, enlarged supraclavicular lymph nodes are associated with the highest incidence (75%) of malignancy. Clinical features associated with high incidence malignancy were: age greater than 55 years (75.8%), duration of less than 1 month (66.6%)--particularly, with a history of previous malignancy (91.7%). The anatomic knowledge of regional lymphatic drainage is essential in localizing the primary lesion of a metastatic lymph node.

Adolescent↗
PubMed1984

Overfill of common piggyback admixture solutions.

The average final volume of 23 commonly used piggyback solutions was determined. Polyvinyl chloride (PVC) containers filled with 0.9% sodium chloride injection or 5% dextrose injection in 50 ml and 100 ml sizes were used for 20 of the piggybacks. A total of ten samples of each drug and dose were measured by draining the entire contents into a graduated cylinder and measuring the volume. The mean volumes, standard deviations, and ranges for each drug and dose were calculated. The volume found in each sample exceeded the volume in the original PVC container by at least 20% in the 50 ml size and 11% in the 100 ml size. The greatest percentage volume difference was 62% in the 50 ml size and 28% in the 100 ml size. The FasPak and the two Viaflex Plus Ready-To-Use containers, which did not require the use of the 50 and 100 ml PVC containers, had a percentage volume difference of 2.6%, 2.2%, and 3.4%, respectively. This information demonstrates the fact that the final volumes of some piggyback admixtures are significantly greater than that which may be presumed from the admixture label.

California↗
PubMed1983

Estimation of mixed venous oxygen saturation.

Pulmonary artery oxygen saturation (PA) was measured directly and estimated from venal cavae samples in 175 adults without intracardiac shunts to ascertain which of four formulas (MV1, MV2, MV3, or MV4) best estimated mixed venous oxygen saturation. Because the formula MV1, which favored IVC samples, most closely approximated pulmonary artery saturation, we recommend its use to estimate systemic flow in patients with left-to-right shunts. In addition, a difference between directly measured PA and calculated MV1 of 6% or greater indicates the presence of a left-to-right shunt in 97% of cases.

Adolescent↗
PubMed1983

Reciprocal day/night relationship between serotonin oxidation and N-acetylation products in the rat pineal gland.

Pineal tryptophan, serotonin [5-hydroxytryptamine (5-HT)], N-acetylserotonin, melatonin, 5-hydroxyindoleacetic acid, 5-hydroxytryptophol, 5-methoxytryptophol, and 5-methoxyindoleacetic acid were measured by high pressure liquid chromatography with electrochemical detection. A complete analysis required less than the equivalent of two rat pineal glands. Samples were obtained at eight time points. A reciprocal physiological relationship was found between oxidation and N-acetylation products of 5-HT. 5-HT and the oxidation products 5-hydroxyindoleacetic acid, 5-hydroxytryptophol, 5-methoxytryptophol, and 5-methoxyindoleacetic acid decreased at night, when the N-acetylation products N-acetylserotonin and melatonin increased. These observations are consistent with the hypothesis that circadian changes in the N-acetylation of 5-HT by indoleamine N-acetyltransferase is the major factor controlling circadian changes in the amounts of 5-HT, and 5-HT oxidation and N-acetylation products in the rat pineal gland.

Acetylation↗
PubMed1982

Metastatic melanoma of unknown primary.

A retrospective study of 166 patients with metastatic melanoma of unknown primary was performed. These were selected from 3805 cases of melanoma in Memorial Sloan-Kettering Cancer Center from 1949 through 1975 (an incidence of 4.4%). There were 109 male and 57 female patients, 75 with Stage II disease and 91 with Stage III. The site of predominant involvement in Stage II patients was the axilla (47%). Five- and ten year survival rates of Stage II patients were 46% and 41%, respectively. The only factor that was shown to influence their survival was the delay (three months or more) of radical lymphadenectomy after initial histologic diagnosis. As expected, the prognosis of Stage III patients was very poor. Our study showed that patients with metastatic melanoma of unknown primary followed a similar clinical course as the Stages II and III patients with overt primary lesion. Stage II patients could expect a reasonable survival, the treatment of choice being prompt radical regional lymphadenectomy.

Adolescent↗
PubMed1982

Partial digestion of neurophysins with proteolytic enzymes: unusual interactions between bovine neurophysin II and chymotrypsin.

Bovine neurophysin II was partially digested by chymotrypsin and by chymotrypsin followed by carboxy-peptidase B to produce large fragments collectively representing deletions of residues 1-5 and 91-95. All such fragments were capable of binding peptides to the principal hormone-binding site of neurophysin with normal or near-normal affinity, indicating that residues 1-5 and 91-95 do not directly participate in binding. In addition, preliminary results with thermolysin-derived fragments suggested that residue 6 does not participate in peptide binding. During the course of chymotrypsin studies, it was demonstrated that bovine neurophysin II behaves as a transient competitive inhibitor of chymotrypsin; for neurophysin-peptide complexes, Ki congruent to 8 x 10(-6) M. This inhibition is dependent on neurophysin conformation and is relieved by the anomalous preferential splitting by chymotrypsin of Arg-Arg and Phe-Pro bonds near the carboxyl terminus of neurophysin II. It is suggested that this phenomenon might reflect the interaction of neurophysin II with a chymotrypsin-related enzyme in the pituitary. One approach used in the study of binding properties of proteolytically modified neurophysin was affinity chromatography; the preparation and properties of a conveniently prepared affinity column for neurophysin are described.

Chromatography, Affinity↗