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Biomedical subjects

L Cheng

Publications and source records attributed to L Cheng.

At least 415 records · Page 23Linked to original sources
PubMed1985

Phosphate excretion in uremic rats: effects of parathyroidectomy and phosphate restriction.

As progressive renal failure develops, phosphate excretion per functioning nephron increases, thus preserving homeostasis. To test whether dietary phosphate supply might contribute to the regulation of renal phosphate excretion in the uremic setting, groups of male Sprague-Dawley rats that were either parathyroidectomized (PTX) or sham PTX (S-PTX) and either five-sixths nephrectomized (Nx) or sham Nx (S-Nx) were studied following a 4-wk dietary regimen consisting of 0.1 or 0.7% phosphate. For Nx rats fed the 0.7% phosphate diet the fractional excretion of phosphate (FEPi) was enhanced (47 +/- 6 vs. 21 +/- 3%) and the maximum tubular reabsorption of phosphate per milliliter GFR (TmPi/GFR) was suppressed (1.65 +/- 0.19 vs. 2.33 +/- 0.19 mumol/ml). FEPi was unchanged by PTX in these Nx animals (42 +/- 6 vs. 47 +/- 6%). TmPi/GFR remained suppressed in PTX, NX animals when compared with S-Nx, PTX controls (3.38 +/- 0.33 vs. 5.07 +/- 0.41 mumol/ml). For rats fed the 0.1% phosphate diet Nx did not affect TmPi/GFR in either S-PTX (5.40 +/- 0.43 vs. 4.97 +/- 0.34 mumol/ml) or PTX (7.03 +/- 0.23 vs. 6.98 +/- 0.21 mumol/ml) animals. For both S-Nx and Nx animals the effects of PTX and dietary phosphate restriction on TmPi/GFR were independent and additive. In all groups of animals, tubular reabsorption of phosphate per milliliter GFR (TRPi/GFR) dropped acutely with continued infusion of phosphate once TmPi/GFR was achieved. Thus, a resetting of TRPi/GFR occurs among Nx rats in response to both chronic dietary phosphate deprivation and acute intravenous phosphate loading.(ABSTRACT TRUNCATED AT 250 WORDS)

Absorption↗
PubMed1985

Chronic active hepatitis of hepatitis B and non-A, non-B etiology. Immunohistochemical localization of hepatitis B core antigen in a series of needle biopsies.

Hepatitis B core antigen (HBcAg) was immunohistochemically demonstrated in 19 of 30 needle liver biopsies (63%) of chronic active hepatitis (CAH) from 15 of 24 patients (63%) whose serum contained hepatitis B surface antigen (HBsAg). The percentage of hepatocytes with nuclear and/or cytoplasmic immunoreactivity was quantified in each biopsy specimen, and these percentages were then compared with the amount of HBsAg and the degree of inflammation within the biopsy specimen. The percentage of HBcAg-positive hepatocytes in a biopsy specimen was greatest in those specimens that contained the most HBsAg, although this finding was not statistically significant. The percentage of HBcAg-positive hepatocytes was greatest in those specimens having the least inflammatory activity, and this was statistically significant (P less than .01). Also, the percentage of biopsy specimens containing HBcAg was increased in those groups with lesser inflammatory activity (P less than .01). By staining for both HBcAg and HBsAg, the detection rate of hepatitis B (HB)-related antigens rose to 27 of 30 biopsies (90%) in 22 of 24 patients (92%).

Biopsy, Needle↗
PubMed1984

Sodium gradient-dependent calcium uptake in renal basolateral membrane vesicles. Effect of parathyroid hormone.

The Na+/Ca2+ exchange system in rat renal cortex basolateral membrane vesicles was studied. Uptake and efflux of Ca2+ in the membrane vesicles were stimulated by trans-Na+. The enhancement of Ca2+ uptake by the intravesicular greater than extravesicular Na+ gradient was inhibited by ionophores that dissipated the gradient, and was increased by an outside negative membrane potential. Na+-dependent Ca2+ uptake was saturable with respect to both Ca2+ and Na+. A [Ca2+]0.5 of 8 microM was calculated. The relationship between Na+ concentration and rate of Ca2+ efflux was sigmoidal; a [Na+]0.5 of 15 mM and a Hill coefficient of 2.5 were estimated. Removal of parathyroid glands from the rats resulted in a 40% decrease in the Na+-dependent Ca2+ uptake. Infusion of parathyroid hormone (the synthetic tetratriacontapeptide) into these animals fully restored the activity. The isolated basolateral membrane possessed parathyroid hormone-sensitive adenylate cyclase. These findings may suggest a mechanism by which parathyroid hormone regulates the reabsorption of Ca2+ in the kidney.

Adenylyl Cyclases↗
PubMed1984

Renal adaptation to phosphate load in the acutely thyroparathyroidectomized rat: rapid alteration in brush border membrane phosphate transport.

The sustained in vivo infusion of phosphate into thyroparathyroidectomized rats resulted, after 1 h, in a marked decrease in net phosphate reabsorption, even though the plasma concentration of phosphate continued to rise. This response to phosphate infusion was expressed at the level of the proximal tubule brush border membrane. Within 40 min of the initiation of the infusion the Na+-dependent phosphate uptake system in isolated membrane vesicles was decreased. Phosphate uptake in the absence of Na+, Na+-dependent D-glucose uptake, and 22Na+ uptake were not affected. These findings demonstrate the locus of this parathyroid hormone-independent adaptation and indicate the rapidity with which the membrane transport system is regulated.

Adaptation, Physiological↗
PubMed1983

Pulmonary carcinoids. Immunohistochemical demonstration of brain-gut peptides.

Antisera raised against serotonin, gastrin, somatostastin, motilin, bombesin, calcitonin, secretin, glucagon, ACTH, neurotensin, and pancreatic polypeptide carboxyterminal hexapeptide were employed to immunohistochemically stain seven pulmonary carcinoids. Argentaffin and argyrophil stains were also performed on all cases. Serotonin-like immunoreactivity was present in four tumors, pancreatic polypeptide-like immunoreactivity in four tumors, bombesin-like immunoreactivity in two tumors and ACTH-like immunoreactivity in one tumor. The cells shown to contain neuroendocrine products constituted a minority cell population in all tumors except the ACTH-immunoreactive tumor. This study suggests that pulmonary carcinoids, like their abdominal counterparts, contain a variety of neuroendocrine products, and may produce more than one neuroendocrine product. Serotonin and pancreatic polypeptide-like immunoreactivity were the most prevalent neuroendocrine products demonstrable in this study.

Adult↗
PubMed1983

The neuroendocrine products of intestinal carcinoids. An immunoperoxidase study of 35 carcinoid tumors stained for serotonin and eight polypeptide hormones.

The intestinal carcinoid tumors of 26 patients were stained for the presence of serotonin, gastrin, somatostatin, motilin, secretin, glucagon, pancreatic polypeptide, ACTH, and neurotensin. Argentaffin and argyrophil stains were also performed in all cases. Thirty-five separate tumors (counting metastases and multiple primaries) from the 26 patients were studied. Serotonin was present in 30 of the 35 tumors. Nineteen tumors contained serotonin only. Fourteen tumors contained multiple neuroendocrine products. One tumor contained gastrin only. One tumor did not stain immunohistochemically, but was argyrophilic. Metastatic deposits were studied in nine patients. Some metastases produced the identical neuroendocrine products as the primary tumor, whereas others produced either additional or fewer hormones than the primary tumor. Moreover, different metastases from the same primary tumor were observed to produce different hormones. Argyrophilic cells were present in all cases and were much more numerous than cells staining by immunohistochemistry. Argyrophilic cells probably contain monoamines and polypeptide hormones in addition to those studied in this series. The argyrophil stain was the best general stain in this study for the demonstration of neuroendocrine cells. Argentaffin staining was negative in ten cases that were serotonin positive and two argentaffin positive cases were serotonin negative. The carcinoid syndrome, as clinically defined by the presence of flushing and diarrhea, was noted in five patients, all of whom had serotonin-containing small bowel carcinoids. Endocrine-related symptoms were not clinically appreciated in the remaining patients.

Adolescent↗
PubMed1983

Cytochemical and competitive protein binding assays for estrogen receptor in breast disease. A comparative study of 62 cases.

Estrogen receptor content of breast lesions was estimated using a fluorescent cytochemical technique and a competitive protein binding assay. Of 48 cancers examined, an equal proportion contained significant quantities of receptor by either method (62.5%). The concordance between methods for individual patients was also 62.5%. A greater proportion (26%) of patients younger than 45 years of age had receptor-positive cancers using the cytochemical method than were found by the biochemical method (10%). Benign breast disease was also studied using the fluorescent cytochemical method. A greater proportion of lesions containing estrogen receptors was found compared with that cited in the literature for the competitive protein-binding assay. Because of the methodologic simplicity of the fluorescent cytochemical method, further study for routine use is indicated.

Adenofibroma↗
PubMed1983

A colonic adenocarcinoma with argentaffin cells. An immunoperoxidase study demonstrating the presence of numerous neuroendocrine products.

A well-differentiated colonic adenocarcinoma containing large numbers of gastrointestinal neuroendocrine cells is presented. The presence of neurosecretory granules was confirmed by electron microscopy. Immunocytochemistry showed large numbers of serotonin-containing tumor cells and lesser numbers of somatostatin, gastrin, motilin, secretin and neurotensin-containing cells. Some of these hormones are not normally present in the colon in significant numbers of cells. The presence of several cell types within a single tumor supports the concept that the normal epithelial cells of the gastrointestinal mucosa are derived from a common endodermal stem cell. There exists a spectrum of tumors ranging from the classical adenocarcinoma to the classical carcinoid, and this report identifies the position of this case within that spectrum.

Adenocarcinoma↗
PubMed1983

Phosphate uptake by renal membrane vesicles of rabbits adapted to high and low phosphorus diets.

Renal adaptation to changes in phosphate intake was studied by comparing phosphate uptake by proximal tubule brush border membrane vesicles from rabbits on a relatively high or low phosphorus diet. The low phosphorus diet increased Na+ gradient-dependent phosphate uptake. Uptake in the absence of Na+ and in the presence of Na+, but no gradient, was not significantly affected. The phosphorus diet did not alter Na+ gradient-dependent D-glucose and L-proline uptake. The low phosphorus diet increased Vmax; affinity for phosphate was not appreciably changed. At all concentrations of extravesicular Na+, phosphate uptake was higher in membrane vesicles from animals fed the low phosphorus diet; the kinetics of the phosphate uptake system, with respect to Na+, was also altered by the change in dietary phosphate. These findings suggest that adaptation involves an alteration in the rate of translocation of the Na+-phosphate carrier when energized by a Na+ gradient driving force rather than a change in the number of Na+-phosphate carrier sites. With membrane vesicles from rabbits fed a low phosphorus diet, phosphate uptake increased several-fold when the pH of the uptake medium was raised, whereas with membrane vesicles from animals fed a high phosphorus diet the enhancement of uptake with alkalinization was relatively small. Irrespective of the diet, divalent phosphate was the probable preferred species for transport. Dietary adaptation was associated, however, with an alteration in the pH dependency of the transport system per se. These findings provide evidence that the adaptation of the kidney phosphate transport system to dietary phosphate load involves an intrinsic change in the Na+-phosphate carrier.

Animals↗
PubMed1982

Acinar-endocrine cell tumor of the pancreas. Report of a pancreatic tumor containing both zymogen and neuroendocrine granules.

A case of pancreatic tumor with features of both an acinar cell and an endocrine cell tumor is presented. The histologic appearance of the tumor by light microscopy was consistent with the appearance of either an islet cell tumor or an acinar cell tumor. Electron microscopy revealed two distinct populations of membrane bound granules within the same tumor cells; namely, a small granule measuring 100-200 nanometers in diameter with a narrow halo separating it from the granule membrane, and a large granule measuring 400-500 nanometers in diameter and having a closely applied membrane. The smaller granules have the characteristic appearance of gastroenteropancreatic (GEP) endocrine-cell granules. The large granules are greater in size than neuroendocrine granules, their morphologic structure is most consistent with that of zymogen granules, and a positive lipase stain supported the presence of zymogen granules within the tumor. The occurrence of both neuroendocrine and zymogen granules within the same cell has been previously described in the "intermediate cell" of the pancreas, but not to our knowledge in a tumor of the pancreas. The finding of both endocrine and exocrine granules within a single cell indicates a histogenetic relationship between the pancreatic endocrine and exocrine cells, and may represent the first reported case of a neoplastic proliferation of intermediate cells.

Adenoma, Islet Cell↗