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Biomedical subjects

C Lin

Publications and source records attributed to C Lin.

At least 55 records · Page 3Linked to original sources
PubMed1985

Relationship between production of epidermal growth factor receptors, gene amplification, and chromosome 7 translocation in variant A431 cells.

Synthesis of the epidermal growth factor (EGF) receptor has been analyzed in a series of variant A431 human epidermoid carcinoma cell clones reported to contain different amounts of EGF binding sites. The amount of EGF receptor protein, quantitated by immunoaffinity chromatography, and EGF receptor mRNA, quantitated by cDNA hybridization, were closely correlated to the extent of EGF receptor gene amplification. This correlation existed in variants selected for reduced EGF receptors and in revertants from those variants with increased EGF receptors. There was also a correlation between the frequency of translocation of chromosome 7, containing the EGF receptor gene, and EGF receptor protein. These results support gene amplification as the mechanism enhancing A431 cell EGF receptor protein and determining growth responses.

Carcinoma, Squamous Cell↗
PubMed1979

Reduction of GTP activation of adenylate cyclase system by its coupling to hormone receptor.

We have examined the characteristics of the adenylate cyclase system from control and butyrate-treated cells. Butyrate treatment results in both an increased number of catecholamine receptors and an induction of a response to the hormone, as reported previously (Tallman, J.F., Smith, C.C., and Henneberry, R.C. (1977) Proc. Natl. Acad. Sci. U.S.A. 74, 873-877); in addition, we found that the same treatment reduces the degree of activation of adenylate cyclase by GTP. We have demonstrated in two cell types that this decrease in GTP activation is inversely related to the degree of induction of the hormone response. Furthermore, in plasma membranes isolated from butyrate-treated cells, the hormone receptor is sensitive to GTP; i.e. GTP reduces the affinity of isoproterenol for the receptor. We propose that these changes reflect an interaction between the beta-adrenergic receptor and the nucleotide regulatory component and that this interaction represents, at least in part, the process of coupling. Several possible mechanisms which can account for the change in GTP activation are discussed in terms of our current understanding of the regulation of the adenylate cyclase system.

1-Methyl-3-isobutylxanthine↗
PubMed1976

Routine amnioscopy at term.

A controlled study for the management of antepartum meconium-stained amniotic fluid (MSAF) detected by amnioscopy performed in a total of 508 patients is presented. The incidence of antepartum MSAF was 2.2%, while intrapartum MSAF was found in 15% of cases. A significant incidence of depressed neonates was found in the latter group. Patients with antepartum MSAF had no perinatal losses, whether managed expectantly or by oxytocin induction. Immediate operative intervention (ie, cesarean section) is not warranted. Observations on FHR patterns, fetal pH, and Apgar scores of these patients are presented.

Apgar Score↗
PubMed1975

Electron microscopy of albumin synthesis.

Albumin molecules appeared to be synthesized in the light hepatocytes of rats by bound polysomers on rough and endoplasmic reticulum and the nuclear envelope. The molecules were discharged directly into the cytosol, then to the external cellular spaces. This conclusion failed to support the current theory from biochemical studies that albumin is synthesized by bound ribosomes, discharged into the cisternae of rough endoplasmic reticulum, and transported to the smooth endoplasmic reticulum and then to the Golgi apparatus. In addition to the liver, positive syntheic activities were observed in the aorta, kidney, and hepatoma cells of rat. Earlier investigators have reported that only liver cells can synthesize albumin.

Albumins↗
PubMed1975

An empirical method of grouping genotypes based on a linear function of the genotype-environment interaction.

The regression approach for analysing genotype-environmental interaction is extended to include the grouping of genotypes. An unweighted pair-group cluster analysis was applied to a special dissimilarly index, derived from the test statistic for differences among regressions. The resulting groups reflect the general pattern of response to the various environments. The data of Yates and Cochran (1938) were used to illustrate the clustering process.

Environment↗
PubMed1975

Calcitonin inhibition of bone cell metabolism in vivo: an experimental study in dogs.

Calcitonin (CT) has been shown to act by decreasing the output of calcium from the bone, but the precise mechanism that brings about this change is still not fully understood. The present investigation was designed to study the effect of CT on the metablic activity of bone cells, utilizing changes in oxygen consumption and carbon dioxide production as indices of tissue metabolism. Arterio-venous gradients of calcium, inorganic phosphate, hydroxyproline, oxygen, carbon dioxide and hydrogen ions were studied across the canine femur. The results showed that the hypocalcemic action of CT was accompanied by a corresponding decrease in free hydroxyproline output from the bone, demonstrating that decreased bone resorption was responsible for the fall in plasma calcium levels. Reduced oxygen consumption and decreased carbon dioxide production by the bone showed that CT acted by inhibiting the metabolic activity of bone cells in vivo. It is speculated that CT may have acted by depressing mitochondrial respiration.

Animals↗
PubMed1975

Ureteral obstruction from metastatic breast carcinoma.

Metastases from carcinoma of the breast may involve one or both ureters, and may be a clinically important phenomenon. Two cases are presented and the autopsy experience with 181 cases of metastatic breast carcinoma is reviewed. Ureteral involvement was demonstrated in 8.3% of the cases. Bilateral metastases were common.

Adenocarcinoma↗
PubMedDate not supplied

Cysteinyl methyl ester of AVP(4-8), a potent agonist on the maintenance of passive avoidance in rats.

A series of short AVP analogs with D- or L-arginine forming the C-terminal was synthesized, and their peripheral effects, i.e., vasoconstrictor and antidiuretic activities, and behavioral effects in enhancing retention in passive avoidance in rats were evaluated. We found that: 1) AVP(4-8) and its cysteinyl methyl ester were more potent in the behavioral response than its D-Arg homologs; 2) the methyl ester derivative was the most effective analog in this behavioral test among the peptides we synthesized, with a potency 40 times as high as AVP; 3) neither the D- nor the L-Arg short derivatives of AVP showed any peripheral effects up to a dose thousands of times greater than AVP. The results support the contention that arginine in the short analogs plays an important role in their behavioral response associated with a relatively steady peptide conformation.

Amino Acid Sequence↗
PubMedDate not supplied

Pit-1-dependent expression of the receptor for growth hormone releasing factor mediates pituitary cell growth.

In Snell (dw) and Jackson (dwJ) dwarf mice, mutations in the gene encoding Pit-1, a tissue-specific POU-domain transcription factor, lead to the absence of somatotroph, lactotroph and thyrotroph cells. Pre-somatotroph proliferation is stimulated by increased intracellular levels of cyclic AMP, normally induced by growth hormone releasing factor (GRF; refs 7-17). Here we report the cloning of mouse and rat complementary DNAs encoding a new member of the seven-transmembrane-helix, G-protein-coupled receptor family restricted to the pituitary gland, which mediates increases in intracellular cAMP and cAMP-dependent gene transcription in response to GRF. The receptor is expressed in a spatial and temporal pattern corresponding precisely to growth hormone gene expression, and neither is expressed in dw/dw mice. The pituitary hypoplasia in these mice thus appears to be due, at least in part, to the absence of GRF receptor, which is in turn due to the absence of functional Pit-1.

Amino Acid Sequence↗
PubMedDate not supplied

Correlation of 14C-griseofulvin metabolism in rat liver microsomes, isolated perfused rat livers, and in rats with bile duct cannulas.

The metabolism of 14C-griseofulvin has been compared in rat liver microsomes, isolated perfused rat livers, and rats with bile duct cannulas. In all three preparations, 4-desmethylgriseofulvin and 6-desmethylgriseofulvin were the major metabolites. The ratio of total 4-desmethylgriseofulvin to 6-desmethylgriseofulvin formed was 1.20, 0.89, and 1.01 in liver microsomes, isolated perfused livers, and rats with bile duct cannulas, respectively. After a 7-min incubation with liver microsomes, most (96%) of the griseofulvin remained unchanged. Only small amounts of 4-desmethylgriseofulvin (1.26%) of dose) and 6-desmethylgriseofulvin (1.05% of dose) were formed. In isolated perfused liver, most of the drug (59% of dose) was excreted into bile within 4 hr, primarily as 4-desmethylgriseofulvin (24% of dose) and 6-methylgriseofulvin (24% of dose). In animals with bile duct cannulas, 65% of the dose was excreted into bile and 18% of the dose into urine within 4 hours. In bile, 32% of the dose was excreted as 4-desmethylgriseofulvin and 20% of the dose as 6-desmethylgriseofulvin, whereas in urine the drug was excreated predominantly as 6-desmethylgriseofulvin (13% of dose) with only a small amount of 4-desmethylgriseofulvin (1% of dose), during the first 4 hr. These results show that there is good correlation in the metabolic fate of 14C-griseofulvin in the liver microsomes, isolated perfused liver, and rats with bile duct cannulas. In addition to the similar ratio of 4-desmethylgriseofulvin to 6-desmethylgriseofulvin, there is also an agreement in the extent of metabolism and biliary excretion in isolated perfused liver and in rats with bile duct cannulas, which suggests that the isolated perfused liver is an important technique for studying drug metabolism in animals.

Animals↗
PubMedDate not supplied

Isolation and identification of the major metabolite of albuterol in human urine.

The major urinary metabolite of albuterol in man was isolated and purified by ion-exchange chromatography and countercurrent distribution. On the basis of proton magnetic resonance, infrared, and mass-spectral analysis, enzymic hydrolysis, and assay of inorganic sulfate after acid hydrolysis, the metabolite has been identified as the 4'-O-sulfate ester of albuterol.

Albuterol↗