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Biomedical subjects

H Chang

Publications and source records attributed to H Chang.

At least 253 records · Page 14Linked to original sources
PubMed1987

Effects of ubiquinones on spontaneous membrane hyperpolarizations in a cloned monkey kidney cell line.

The effects of ubiquinones on spontaneous membrane hyperpolarizations in JTC-12 cells were examined. There were three types of spontaneous hyperpolarizations; rhythmic, sporadic and oscillatory types. The oscillatory type was not observed in the standard medium, whereas it was observed in sodium-free medium or in the medium containing 300 nM coenzyme Q10. The number of the cells showing spontaneous hyperpolarizations significantly increased in the medium containing coenzyme Q10 (47.7%) as compared to the control (18.9%). However, coenzyme Q1 (500 nM) showed no effects.

Animals↗
PubMed1987

Platelet imipramine binding in patients with panic disorder and major familial depression.

Platelet 3H-imipramine binding was investigated in 15 normal subjects, 17 patients with major depressive disorder and 43 patients with panic disorder, to further study the relationship between depressive and anxiety disorders. Whereas patients with major depression had a significantly lower mean Bmax value than healthy volunteers, mean Bmax values in patients with panic disorder did not differ significantly from normal controls. Furthermore, apparently normal Bmax values were observed even in those panic disorder patients who had concurrent major depression or a past history of depression. Thus, despite previous findings of an overlap between panic and depressive disorders, the present results suggest that the two syndromes may have distinct neurochemical substrates.

Adult↗
PubMed1987

Stimulation and inhibition of lipolysis in isolated rat adipocytes: evidence for age-related changes in responses to forskolin and PGE1.

The ability of a number of hormones to activate cellular responses in a variety of cells declines with age. The mechanisms responsible for these alterations are complex and incompletely understood. Rat adipocytes have served as an important model to study blunted responses to stimulatory hormones which function by activating cAMP accumulation. We have previously found that the blunted lipolytic response of adipocytes from older rats to the beta adrenergic receptor agonist isoproterenol appeared to be due to a lessened ability of isoproterenol to activate cAMP accumulation. Further, the blunted response to isoproterenol was apparently caused by an accentuated inhibition of lipolysis, mediated by adenosine receptors activated by endogenously released adenosine. The present studies were designed to test and extend those conclusions. We have utilized forskolin to augment the cAMP accumulation that occurs in the presence of isoproterenol. Isoproterenol-activated lipolysis was greater in adipocytes from 2 month old rats compared with those from 12 month old rats (603 +/- 32 vs 450 +/- 29 nmol/10(5) cells/hr, P less than 0.01). However, in the presence of forskolin (10(-6) M), there was no significant difference in the response to isoproterenol between the two groups (646 +/- 23 vs 615 +/- 29 nmoles/10(5) cells/hr). As we had seen previously, the adenosine receptor agonist phenylisopropyladenosine more effectively inhibited lipolysis in the adipocytes from older rats. We now also find that PGE1 more efficaciously inhibits lipolysis in the cells from older rats. These data confirm that diminished cAMP accumulation in adipocytes from older rats appears to be a rate-limiting alteration in the regulation of lipolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1987

Age-related changes in rat muscle glycogen synthase activity.

This study was designed to evaluate effects of aging on glycogen synthase activity in rat skeletal muscle. Total enzyme activity was shown to be significantly, (p less than .001) lower in tensor fascia latae, biceps femoris, and soleus muscle obtained from 24-month-old compared with 2-month-old rats. Similarly, values for the active form of enzyme were significantly lower, (p less than .001) in all three muscle types of 24-month-old compared with 2-month-old rats. This age-related decline in glycogen synthase activity was not due to a reduction in the affinity of the enzyme for its activator (glucose-6-phosphate) and was independent of the concentration of substrate (UDP-glucose) in the assay system. Because similar age-related changes were seen when enzyme activity was expressed per milligram of muscle protein or per gram of muscle tissue, the fall in enzyme activity was not a simple function of an age-related decline in muscle mass. Glycogen levels also were reduced significantly in tensor fascia latae, biceps femoris, and soleus of 24-month-old rats compared with 2-month-old rats, p less than .001. These results document an age-related change in a key enzyme regulating glycogen metabolism in muscle.

Aging↗
PubMed1987

The gene for galactosyltransferase maps to mouse chromosome 4.

The chromosomal localization of the gene for UDP-galactosyltransferase (glycoprotein 4-B-galactosyltransferase, EC 2.4.1.38) has been determined to be on mouse chromosome 4 by the use of mouse X hamster somatic cell hybrids. It has been proposed that galactosyltransferase is associated with the mouse T/t complex which has been localized to mouse chromosome 17. These results show that galactosyltransferase is not encoded within the T/t complex.

Animals↗
PubMed1987

Survival rates and properties of sickle cell anemia red cells treated with nitrogen mustard.

A machine for the extracorporeal delivery of covalent anti-sickling agents has been described by Babb and coworkers and this therapeutic modality has been found feasible by others. We report here, further evaluation of nitrogen mustard (HN2), for possible use in the extracorporeal therapy of sickle cell anemia. Heparinized aliquots of whole blood from three patients with sickle cell disease were treated extra-corporeally with HN2 (0.65 mg/ml); the excess HN2 was neutralized with thiosulfate, and the blood was returned to the donor after labelling with 51Cr. HN2 produced an average 51Cr T1/2 which was 160% of control values. Fractionation of labelled red cells into different densities (ages) revealed that the main effect of HN2 was on the younger cell population which was characterized by a 51Cr T1/2 increase of 300% over the untreated blood. Further, "in vitro" studies were conducted to establish the effects on the SS red cells that could be expected from the treatment with HN2 at the concentrations used. Solubility determination (Csat) of deoxy hemoglobin S gels demonstrated that HN2 markedly inhibited the polymerization of HbS, was significantly more effective than potassium cyanate, and is among the most potent anti-sickling agents thus far reported. The viscosity of deoxygenated sickle red cells in a cone plate viscometer was markedly reduced by HN2, and hemodynamic studies using the microvasculature of an isolated rat mesoappendix demonstrated a reduction of peripheral resistance and an increase in flow rate when deoxygenated sickle cells pre-treated with HN2 were tested. At the highest concentration of HN2 (2 mg/ml), the peripheral resistance and the flow rates of deoxygenated cells attained levels found with oxygenated sickle blood. O2 affinity was partially corrected in the HN2 treated HbSS red cells. -SH reactivity of the red cell membrane was not affected by HN2. Among the added advantages of HN2 for extra-corporeal use is its rapid reaction rate, the lack of significant change of the O2 equilibrium at the concentration tested and the fact that the unreacted compound can be readily detected and neutralized. For these reasons HN2 is well suited for extra-corporeal treatment of sickle cell anemia for those patients with a severe form of the disease.

Anemia, Sickle Cell↗
PubMed1986

Identification of three new Ig lambda-like genes in man.

Three new human lambda L chain-like Ig genes are identified by restriction enzyme and nucleotide sequence analysis. Two genes, 14.1 and 16.1, have intact J and C regions, and are potentially functional, with open reading frames. A third gene, 18.1, is a pseudogene. The evolutionary lineage of these genes compared to the known functional locus lambda C1-lambda C6 can be surmised from Southern blot and nucleotide homologies. This study demonstrates that the human lambda gene family is more complex than previously recognized.

Amino Acid Sequence↗
PubMed1986

The human galactosyltransferase gene is on chromosome 9 at band p13.

The structural gene for galactosyltransferase (glycoprotein 4-B-galactosyltransferase, EC 2.4.1.38) was localized to human chromosome 9 band p13 by chromosome in situ hybridization using a cloned bovine galactosyltransferase cDNA probe. This chromosomal location is at the same position to which galactose-1-phosphate uridyltransferase, an enzyme which provides the nucleotide sugar substrate (UDP-galactose) for galactosyltransferase, has been mapped.

Animals↗
PubMed1986

Bovine galactosyltransferase: identification of a clone by direct immunological screening of a cDNA expression library.

A 1.3-kilobase cDNA clone (7A) coding for bovine galactosyltransferase (glycoprotein 4-beta-galactosyltransferase, EC 2.4.1.38) was isolated from a lambda gt11 expression library by immunological screening with monospecific polyclonal antisera to the affinity-purified bovine enzyme. The nucleotide sequence of this clone predicts an open reading frame that starts at the 5' end of the insert and codes for a polypeptide of 334 amino acids with Mr 37,645. Based on a Mr of 57,000 for the membrane-bound enzyme this clone accounts for approximately 61% of the coding sequence. Portions of the predicted amino acid sequence matched the six tryptic peptides isolated from affinity-purified bovine galactosyltransferase. Clone 7A hybridizes to a 4.8-kilobase bovine mRNA and identifies multiple EcoRI restriction fragments in bovine, murine, and human DNA.

Amino Acid Sequence↗
PubMed1986

Contiguous thin multisection MR imaging by two-dimensional Fourier transform techniques.

Section thickness in two-dimensional Fourier transform (FT) imaging is dependent on gradient strength and the shape of the radio-frequency pulses used to excite the nuclei. By manipulation of these parameters, it is possible to obtain 2.5-mm-thick sections in contiguous, multisection imaging. Because this method is efficient in imaging with long repetition times (TR), it effectively complements three-dimensional FT thin-section imaging techniques, which require imaging with short TRs. Fifteen double-echo, contiguous images of 0.9 X 0.9 X 2.5-mm resolution were obtained in 17.1 minutes for a TR of 2 seconds.

Fourier Analysis↗
PubMed1986

Desensitization of adenosine receptor-mediated inhibition of lipolysis. The mechanism involves the development of enhanced cyclic adenosine monophosphate accumulation in tolerant adipocytes.

Adipocytes contain adenosine receptors, termed A1 receptors, which inhibit lipolysis by decreasing adenylate cyclase activity. The inhibition of lipolysis by adenosine agonists in vivo acutely suppresses the plasma concentrations of free fatty acids (FFA) and triglycerides. We have found that infusions of the adenosine receptor agonist phenylisopropyladenosine (PIA) initially decreases plasma FFA concentrations; however, with prolonged exposure (6 d), rats become very tolerant to the effects of the drug. Adipocytes isolated from epididymal fat pads from PIA-infused rats have altered lipolytic responses. When lipolysis is stimulated with a relatively high concentration of isoproterenol (10(-7) M), PIA does not inhibit lipolysis in adipocytes from the infused animals. However, PIA inhibits isoproterenol-stimulated cyclic AMP (cAMP) accumulation in adipocytes from the infused rats although with decreased sensitivity compared with controls. The explanation for the impaired antilipolytic effect appears to be due to the fact that isoproterenol-stimulated cAMP accumulation is markedly increased in cells from infused rats. Indeed, basal lipolysis and lipolysis stimulated with lower concentrations of isoproterenol (10(-9), 10(-8) M) are effectively inhibited by PIA. cAMP accumulation is greatly increased in adipocytes from infused rats when stimulated by isoproterenol, ACTH, and forskolin. The results have some striking analogies to changes induced in nerve cells by prolonged exposure to narcotics. These data suggest that tolerance to PIA develops in adipocytes as a consequence of enhanced cAMP accumulation.

Adenosine Deaminase↗