PubMed Health⌕ Search

Biomedical subjects

R Chang

Publications and source records attributed to R Chang.

At least 19 recordsLinked to original sources
PubMed1992

Genomic structure and chromosomal mapping of the murine CD40 gene.

The B cell-associated surface molecule, CD40, is likely to play a central role in the expansion of Ag-stimulated B cells, and their interaction with activated Th cells. In our study we have isolated genomic clones of murine CD40 from a mouse liver genomic DNA library. Comparison with the murine CD40 cDNA sequence revealed the presence of nine exons that together contain the entire murine CD40 coding region, and span approximately 16.3 kb of genomic DNA. The intron/exon structure of the CD40 gene resembles that of the low affinity nerve growth factor receptor gene, a close homolog of both human and murine CD40. In both cases the functional domains of the receptor molecules are separated onto different exons throughout the genes. Southern blot analysis demonstrated that murine CD40 is a single copy gene that maps in the distal region of mouse chromosome 2.

Amino Acid Sequence↗
PubMed1992

Inhibitory effect of green tea on the growth of established skin papillomas in mice.

In 10 separate experiments, mice with established chemically induced or UV light-induced skin papillomas were treated continuously with green tea in the drinking water or with i.p. injections of a green tea polyphenol fraction or (-)-epigallocatechin gallate three times a week for 4-10 weeks. Partial tumor regression or > 90% inhibition of tumor growth, as measured by changes in tumor volume per mouse, was observed in 5 experiments, and marked inhibition of tumor growth (46-89%) was observed in 5 additional experiments. Treatment of the mice with green tea or green tea constituents had an inhibitory effect on body weight increases in several but not all of the studies. Examination of the data from all ten experiments revealed that complete tumor regression occurred in 14 of 346 papilloma-bearing mice (4%) that were treated with green tea in the drinking water or with i.p. injections of green tea constituents, whereas none of the 220 papilloma-bearing control mice treated with only vehicle exhibited complete tumor regression. These observations indicate that oral administration of green tea, i.p. administration of a green tea polyphenol fraction, or i.p. administration of (-)-epigallocatechin gallate inhibited the growth and/or caused the regression of established experimentally induced skin papillomas.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1992

Developmental patterns of ganglioside sialosylation coincident with neuritogenesis in cultured embryonic chick brain neurons.

Chick brain precursor neurons were observed to introduce sialic acid biosynthetically into only three specific gangliosides: monosialosyl lactosyl ceramide (GM3), disialosyl lactosyl ceramide (GD3), and disialosyl gangliotrihexosyl ceramide (GD2), when sialic acid was labeled metabolically by its obligate precursor, [3H] ManNAc. Sialosyl donor CMP-[3H]NeuAc supplied in the culture medium gave rise uniquely to surface-labeled GD3. Thus sialosyl transferase/GD3 synthase activity is expressed both intraneuronally and in the neuronal exofacial surface. Upon epidermal growth factor-induced onset of neurite outgrowth, labeled complex sialosyl gangliotetrahexosyl ceramide species of gangliosides began to appear in the embryonic neuronal plasma membrane. However, intraneuronal and exofacial sialosyl transferase/GD3 synthase activities remained constant, with or without neurite outgrowth. Moreover, simpler species of gangliosides maintained a steady quantitative sialosyl level (1.6 +/- 0.2 micrograms of sialic acid/mg of protein), whereas more complex species completely absent before neurite outgrowth accrued and reached 4.8 +/- 0.9 micrograms of sialic acid/mg of protein with full neurite development. This analysis of developmental patterns of ganglioside sialosylation has provided evidence that stable neurite outgrowth depends upon generation by the neuron of special plasma membrane with a massive content of complex higher species of gangliosides.

Animals↗
PubMed1992

Ly-1 B (B-1) cells are the main source of B cell-derived interleukin 10.

We have previously reported (O'Garra, A. et al., Int. Immunol. 1990, 2:821) that murine B lymphomas and purified normal peritoneal B cells produce interleukin (IL) 10. We now show that this production of IL 10 B cells correlates with the presence of Ly-1 (B-1) B cells, in both normal and diseased mice. Using a semi-quantitative modification of the polymerase chain reaction, we show that IL 10 expression is detectable in peritoneal B cells but only becomes apparent in splenic B cells of aged mice of which a high proportion are Ly-1+. Furthermore, the expression of IL 10 is constitutive in splenic B cells from mice carrying the Ly-1+ BCL1 lymphoma. Since IL 10 is a potent regulator of in vitro immune function, its production by Ly-1 lineage B (B-1) cells raises the possibility that this subset of B cells may regulate their own development and/or the function of other immunocompetent cells.

Aging↗
PubMed1992

The effects of peptide histidine isoleucine on antral gastrin and somatostatin.

The present studies were directed to determine whether peptide histidine isoleucine (PHI) affects expression of the gastrin and somatostatin genes and whether such effects may be functionally linked. In separate experiments, the effects of PHI on medium gastrin and somatostatin concentrations, the incorporation of 35S-labelled amino acids into newly synthesized gastrin and somatostatin, and steady state gastrin and somatostatin mRNA were determined. PHI inhibited basal expression of the gastrin gene at all levels examined, while no significant effect on basal somatostatin gene expression could be detected. PHI also decreased carbachol-stimulated antral gastrin release and simultaneously increased somatostatin release. However, in contrast to its structural analogues, secretin and gastric inhibitory peptide, the immunoneutralization of endogenous somatostatin by the administration of specific antibodies did not affect significantly the capacity of PHI to inhibit gastrin release into the culture medium stimulated by carbachol. The results of these studies indicate that PHI exerts a physiological inhibitory effect on antral gastrin cells and that this inhibition may occur at several steps along the biosynthetic pathway. In addition, unlike its structural analogues, PHI inhibition of carbachol-stimulated gastrin release is not functionally linked to its stimulatory effects on somatostatin release.

Animals↗
PubMed1992

The assessment of nursing caries and its relationship to high caries in the permanent dentition.

The prevalence of nursing caries has been found to be high in populations of Native American children, unlike other US population groups. Comparisons among studies are difficult because a variety of operational definitions of the syndrome have been used. This study had two goals. First, a retrospective dental record audit was conducted for a Native American population attending Head Start in 1977-78, to compare the prevalence rates of nursing caries obtained by using different nursing caries classification schemes. Second, we studied the relationship of prior nursing caries to current high caries level determined by a clinical exam in the same children approximately ten years later (N = 88). As expected, different classification schemes yielded different prevalence rates. Classification of nursing caries by buccal or lingual caries in the maxillary incisors found 45 percent of the children with the disorder, vs 61 percent if measured by three or more carious maxillary incisors, or 76 percent if two or more carious maxillary incisors. Nursing caries in these Head Start children, defined by caries on the buccal or lingual surfaces of the maxillary incisors, showed no increased risk of greater than or equal to 5 DMFT at age 15. The Head Start children classified as having nursing caries by two or more, or three or more, decayed maxillary anterior teeth had relative risks (RR) of 1.6 (95% Cl 1.1, 2.4) and 1.4 (95% Cl 1.0, 1.9) for high caries (DMFT greater than or equal to 5) ten years later, whereas the RR for children with a dmft greater than or equal to 5 was 2.4 (95% Cl 1.4, 4.3).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Pulmonary metastases: MR imaging with surgical correlation--a prospective study.

The sensitivity of magnetic resonance (MR) imaging for detection of pulmonary metastases in 11 patients scheduled for thoracotomy and curative resection of metastases was evaluated with a prospective, controlled study. MR imaging performed at 0.5 T was compared with chest radiography, computed tomography (CT), and thoracotomy in 12 cases. (One patient had two separate occurrences of pulmonary metastases.) All images were interpreted in blinded fashion. When all MR sequences were interpreted together, MR imaging enabled correct identification of all patients with pulmonary nodules (100%). CT enabled detection of at least one nodule in all 12 cases (100%) by design; the sensitivity of chest radiography was only 64%. For individual nodules, MR imaging was at least as sensitive as CT (P2 less than .25 [two-sided value]) and significantly more sensitive than chest radiography (P2 less than .01). Among all MR sequences, short inversion time inversion-recovery sequences had the highest sensitivity for detection of individual nodules (82%).

Adult↗
PubMed1992

Corticotropin-secreting carcinoid tumors of the thymus: diagnostic unreliability of thymic venous sampling.

Three patients with Cushing syndrome due to ectopic production of corticotropin underwent total thymectomy on the basis of elevated concentrations of corticotropin in selective samples from thymic veins but in the absence of a radiographically detectible thymic mass. In one patient, radiologic examination demonstrated hyperplasia of neuroendocrine cells staining positively for corticotropin throughout the thymus but no discrete mass. This patient had complete remission after total thymectomy. The other two patients had no evidence of an intrathymic source of corticotropin, and both had persistent Cushing syndrome. Elevated levels of corticotropin in thymic vein samples may reflect corticotropin production by pulmonary bronchial carcinoid tumors, mediastinal metastases, thymic carcinoids, or diffuse hyperplasia of intrathymic neuroendocrine elements. In the absence of a demonstrable intrathymic mass, corticotropin gradients in thymic veins do not reliably indicate a thymic source of corticotropin and should not necessarily be used as a basis for exploratory thoracotomy or blind thymectomy.

Adrenocorticotropic Hormone↗
PubMed1992

Distinction between hyperaldosteronism due to bilateral hyperplasia and unilateral aldosteronoma: reliability of CT.

Hyperaldosteronism due to a unilateral adenoma must be distinguished from hyperaldosteronism due to bilateral hyperplasia to enable the proper choice between surgical treatment (for adenoma) or medical treatment (for hyperplasia). To compare the efficacy of computed tomography (CT) and adrenal venous sampling, both examinations were performed in 24 patients with primary aldosteronism. All patients with a diagnosis of adenoma based on findings at venous sampling underwent adrenalectomy. The CT-based diagnosis was unilateral aldosteronoma in 17 patients and hyperplasia in seven patients. On the basis of venous sampling, unilateral adenoma was diagnosed in 22 patients; this diagnosis was confirmed by means of unilateral adrenalectomy in 21 patients. The most common error was diagnosis of hyperplasia based on the presence of bilateral nodules on CT scans: In six of seven patients with such a diagnosis, venous sampling and subsequent surgery revealed a unilateral adenoma. In hyperaldosteronism with multiple bilateral nodules, CT cannot reliably permit distinction between hyperplasia and adenoma.

Adenoma↗
PubMed1992

Neurologic complications of petrosal sinus sampling.

Petrosal sinus sampling has been described as an innocuous, essentially risk-free procedure. The authors report on two patients from two different institutions who sustained brain stem injury as a result of petrosal sinus sampling and two other patients in whom brain stem injury was avoided. Major neurologic complications have occurred in only 0.2% of procedures (one of 508) performed at the National Institutes of Health and in 0.5% of a subset of these procedures (one of 184) that were performed with a specially designed petrosal sinus catheter. The cause of these complications is unclear but is presumed to be localized venous hypertension. Tip-deflector catheter-guide-wire systems, if available, are recommended for petrosal sinus sampling. Inadequate data exist to permit recommendation of any other catheter. Brain stem injury is preventable if the catheter is withdrawn at the earliest sign of even a minor, seemingly insignificant problem. Subtle symptoms and signs that may not appear to be neurologic may herald a clinical catastrophe if not heeded.

Adult↗
PubMed1992

EDRF inhibition augments pulmonary hypertension in intact newborn lambs.

There is increasing evidence that resting pulmonary vascular tone is mediated by the release of endothelium-derived relaxing factors (EDRF). However, the importance of EDRF release during pulmonary hypertension is unknown. Therefore, in eight newborn lambs we studied the effects of both N omega-nitro-L-arginine (an inhibitor of EDRF synthesis) and L-arginine (a precursor of EDRF synthesis) during pulmonary hypertension induced either by the intravenous infusion of U-46619 (a thromboxane A2 mimic) or by hypoxia. After pretreatment with N omega-nitro-L-arginine, the increases in pulmonary arterial pressure produced by U-46619 (102.0 +/- 34.9% vs. 144.8 +/- 28.6%, P less than 0.05) and by hypoxia (35.6 +/- 17.3% vs. 91.4 +/- 24.8%, P less than 0.05) were significantly augmented. However, after pretreatment with L-arginine, the increases in pulmonary arterial pressure produced by U-46619 (107.0 +/- 21.4% vs. 62.6 +/- 22.6%, P less than 0.05) and hypoxia (44.3 +/- 18.3% vs. 9.2 +/- 11.7%, P less than 0.05) were significantly attenuated. These results suggest that during pulmonary hypertension, EDRF is released to limit the increase in pulmonary arterial pressure and that L-arginine availability becomes rate limiting for further EDRF synthesis and release.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Prospective study of the use of intraarterial secretin injection and portal venous sampling to localize duodenal gastrinomas.

BACKGROUND: Duodenal gastrinomas producing Zollinger-Ellison syndrome (ZES) are rarely imaged on preoperative studies. Measurement of serum gastrin levels by transhepatic portal venous sampling (PVS) or by sampling from hepatic veins after intraarterial secretin injection have been advocated as useful tests to identify these tumors before operation. METHODS: As part of a prospective study, selective intraarterial secretin injection has been performed in 36 consecutive patients with ZES, PVS has been performed in 30 of these patients, and the results have been compared. RESULTS: Gastrinomas were found at laparotomy in 33 of 36 patients (92%). Duodenal tumors were found in 18 patients (50%). The remaining patients had liver, pancreatic, or nodal disease (n = 15). Thirty-two of 36 patients (89%) had positive results with intraarterial secretin injection study, whereas 18 of 30 (60%) had a positive PVS gradient (p = 0.02, Fisher's exact test). The most common positive gradient with intraarterial secretin injection was found with injections of the gastroduodenal artery, and the most common positive gradient with PVS was found in the inferior pancreaticoduodenal (IPDV) or superior pancreaticoduodenal vein (SPDV). Fourteen of 18 (78%) patients with duodenal gastrinomas had a positive GDA injection, whereas five of 18 (28%) without duodenal tumors had a positive GDA injection (p = 0.006). Five of 16 patients with duodenal gastrinomas had a positive gradient in the IPDV or SPDV, whereas four of 14 without duodenal tumors had a positive gradient in the IPDV or SPDV (not significant). CONCLUSIONS: Intraarterial secretin injection is more sensitive than PVS at localizing duodenal gastrinomas and should replace PVS in patients with ZES and occult tumors.

Adult↗
PubMed1991

Insulinomas: localization with selective intraarterial injection of calcium.

To facilitate the noninvasive preoperative localization of islet cell tumors less than 15 mm in diameter, the authors examined the use of calcium as an insulin secretagogue in an arterial stimulation venous sampling (ASVS) technique. In four patients with episodic hypoglycemia, calcium gluconate (0.01-0.025 mEq Ca2+/kg) was injected directly into branches of the celiac plexus (gastroduodenal, splenic, and hepatic arteries) and the superior mesenteric artery. In all patients, serum levels of insulin rose abruptly in blood samples taken from the right hepatic vein 30 and 60 seconds after the infusion of calcium into the artery supplying the tumor; injection into an artery not supplying the tumor did not result in a similar rise. Accurate localization of the insulinomas was verified at surgery in three patients. In the fourth patient, who did not undergo surgery, arteriographic results were positive for insulinoma at the predicted site. On the basis of these results, the authors believe noninvasive ASVS may replace invasive portal venous sampling as the most effective method for the localization of occult insulinomas.

Angiography↗
PubMed1991

L-Arginine, a precursor of EDRF in vitro, produces pulmonary vasodilation in lambs.

There is increasing evidence that resting pulmonary vascular tone is mediated in part by the release of endothelium-derived relaxing factors (EDRF). Because L-arginine may be a precursor for EDRF synthesis, we studied the pulmonary vasodilating effects of L-arginine at rest and during pulmonary hypertension in 16 intact newborn lambs. At rest, the intravenous infusions of L-arginine (150 mg/kg) had no hemodynamic effects. However, during pulmonary hypertension induced by hypoxia or the infusion of U-46619 (a thromboxane A2 mimic), L-arginine decreased pulmonary arterial pressure by 22 and 27%, respectively (P less than 0.05). The decrease in pulmonary arterial pressure produced by L-arginine was blocked by methylene blue, a guanylate cyclase inhibitor, and augmented by Zapranast, a guanosine 3',5'-cyclic monophosphate (cGMP) phosphodiesterase inhibitor (-17.9 vs. -31.2%, P less than 0.05). In addition, L-arginine partially reversed the pulmonary hypertension induced by N omega-nitro-L-arginine, a competitive EDRF synthesis inhibitor, but D-arginine had no hemodynamic effects. This study suggests that L-arginine produces pulmonary vasodilation by increasing cGMP concentrations, supporting the in vitro hypothesis that L-arginine is a precursor for EDRF synthesis, whose availability may become rate limiting during pulmonary hypertension.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1991

Intravascular streaming during carotid artery infusions. Demonstration in humans and reduction using diastole-phased pulsatile administration.

Intra-arterial carotid artery chemotherapy for malignant gliomas is limited by focal injuries to the eye and brain which may be caused by poor mixing of the drug with blood at the infusion site. This inadequate mixing can be eliminated in animal models with diastole-phased pulsatile infusion (DPPI) which creates 1-ml/sec spurts during the slow blood flow phase of diastole. Before treatment with intracarotid cisplatin, 10 patients with malignant gliomas were studied to determine whether intravascular streaming occurs after intracarotid infusion in humans, and if so, if it is reduced with DPPI. Regional cerebral blood flow (rCBF) studies were performed by intravenous injection of H2(15)O and positron emission tomography. This was followed by supra- or infraophthalmic internal carotid artery (ICA) injections of H2(15)O with either continuous infusion or DPPI. Local H2(15)O concentration in the brain was determined and the images of radiotracer distribution in the continuous infusion and DPPI studies were compared to the rCBF images. Intravascular streaming of the infusate was identified by a heterogeneous distribution of the infused H2(15)O in brain compared to rCBF. Extensive and variable intravascular streaming occurred in three patients who received infusions into the supraophthalmic segment of the ICA. Some brain areas received up to 11 times the expected radiotracer delivery, while other regions received as little as one-tenth. This streaming pattern was markedly reduced or eliminated by DPPI. In the five patients who received infraophthalmic infusions, a minimally heterogeneous distribution of the infusate was detected. The authors conclude that extensive intravascular streaming accompanies supraophthalmic ICA infusions in patients. The magnitude of streaming can be substantially reduced or eliminated with DPPI. Those who perform intra-arterial infusion should consider using DPPI to assure uniform drug delivery to brain.

Analysis of Variance↗
PubMed1991

[Preliminary studies on subtypes of respiratory syncytial virus in China].

An analysis of subtypes of 9 respiratory syncytial (RS) viruses isolated from Guangzhou and Nanjing areas of china was carried out with eight Sweden RS-subtype specific monoclonal antibodies (MAbs) and 7 internal anti-RS MAbs. All these MAbs directed against respectively the large Glycoprotein (G), fusion protein (F), nucleoprotein (NP), and phosphoprotein (P) components of the prototype Long strain of RS virus. The patterns of the reactions of these MAbs to the nine isolated strains of RS virus were compared with indirect immunofluorescence assay (IFA), alkaline phosphoesterase-anti alkaline phosphoesterase (APAAP) enzyme-linked assay and Western blotting. The antigenic variations were founded among the strains of RS virus, and two subtypes allocated to the subtype A and B of RS virus by using the eight RS-subtype specific MAbs. Seven out of the 9 isolated strains of RS virus belonged to the subtype A, and two were being to the subtype B. The antigenic diversities were also founded within the same subtype, and the main pronounced difference were observed on the G glycoprotein by using the internal anti-RS MAbs. These findings are potentially important both for vaccine development and for the understanding of clinical and epidemiological characteristics of RS virus.

Antigenic Variation↗
PubMed1990

Gastrinomas: localization by means of selective intraarterial injection of secretin.

Small doses (30 U) of secretin were injected directly into the splenic, gastroduodenal, hepatic, and superior mesenteric arteries of 13 patients with Zollinger-Ellison syndrome who were undergoing angiography to localize gastrin-secreting tumors of the islet cells. Blood samples from the right hepatic vein and a peripheral vein were drawn before and 30, 60, 120, and 210 seconds after each intraarterial secretin (IAS) injection. A 50% rise in gastrin level in the 30-second sample from the hepatic vein localized the gastrinoma to the head, body, or tail of the pancreas, depending on the artery into which secretion was injected. IAS results were positive in seven of 13 patients (54%); selective angiography was positive in five of 13 (38%); and the combined study, selective angiography with IAS injection, was positive in 10 of 13 (77%). Portal venous sampling was positive in six of 13 (46%). Selective IAS injection, combined with angiography, is the most sensitive study for localizing gastrinomas and avoids percutaneous transhepatic catheterization for portal venous sampling.

Adult↗