Biomedical subjects

J Ong

Publications and source records attributed to J Ong.

At least 109 records · Page 6Linked to original sources

PubMed1987

Cushing's syndrome due to ectopic proopiomelanocortin gene expression by islet cell carcinoma of the pancreas.

Expression of proopiomelanocortin (POMC) was studied in a male patient with Cushing's syndrome and ectopic production of ACTH by a pancreatic carcinoma. Plasma ACTH levels (greater than 200 pg/ml) were elevated, and elevated serum cortisol and urinary free cortisol were partially suppressed to 25% of basal levels by high-dose dexamethasone. Petrosal and jugular vein sampling did not yield a gradient of ACTH. Immunohistochemical staining of tumor tissue removed at pancreatectomy was positive for ACTH and beta endorphin, and negative for corticotropin-releasing factor (CRF). Tumor cells cultured in vitro secreted ACTH and beta-endorphin, which comigrated with their respective radiolabeled standards on gel chromatography. Hydrocortisone suppressed in vitro ACTH secretion and CRF (100 nM) stimulated ACTH by 50% during 72 hours of incubation. Agarose gel electrophoresis of poly-(A) mRNA extracts of tumor tissue followed by hybridization with 32P-cDNA for POMC revealed 2 distinct RNA species. The major RNA species (about 1.0 kb) was smaller than authentic pituitary POMC mRNA (about 1.1 kb); a larger precursor band also was visualized, suggesting either processing or degradation of tumor-POMC mRNA. Cytoplasmic dot blot hybridization of tumor mRNA with POMC cDNA yielded a positive signal with increasing amounts of RNA blotted. Immunohistochemistry and radioimmunoassay (RIA) of ACTH, in vitro regulation of ACTH secretion, and expression of POMC mRNA species by this tumor document expression of the human POMC gene by an islet carcinoma associated with Cushing's syndrome.

Adenoma, Islet Cell↗

PubMed1987

An enzyme-linked immunoassay for lipoprotein lipase.

Polyclonal antibodies against bovine milk lipoprotein lipase (LPL) were used to generate an enzyme-linked immunosorbent assay (ELISA) for rat LPL. The antibodies to LPL were affinity purified on bovine LPL columns and were shown to be specific for LPL by immunoprecipitation and enzyme inhibition. The solid-phase ELISA was sensitive from 1.0 to 20 ng/ml of LPL and paralleled enzyme activity. Denatured rat LPL showed the same LPL mass as undenatured samples, allowing LPL mass to be quantitated effectively in a variety of rat tissue extracts.

Adipose Tissue↗

PubMed1987

Uptake inhibitors potentiate gamma-aminobutyric acid-induced contractile responses in the isolated ileum of the guinea-pig.

The gamma-aminobutyric acid (GABA)-induced contractile responses in the guinea-pig isolated ileum, maintained in Krebs-bicarbonate solution (pH 7.4, 37 degrees C), were significantly potentiated by inhibitors of GABA uptake, with a greater potentiation of the responses in the presence of (+/-)-cis-3-aminocyclohexane-carboxylic acid (ACHC) greater than L-2,4-diaminobutyric acid (DABA) greater than (+/-)-nipecotic acid greater than beta-alanine, whilst simultaneous addition of DABA with beta-alanine caused a greater potentiation of the GABA-induced responses than did nipecotic acid with beta-alanine, or any of the uptake blockers applied alone. The concentration-response curves for the GABA-induced ileal contraction were shifted to the left in the presence of the uptake inhibitors, this shift being more prominent over the lower concentration range of GABA (1-20 microM). By contrast, contractile responses to muscimol or 3-amino-1-propanesulphonic acid (3APS) were not potentiated by the uptake blockers, neither were their concentration-response curves altered. Bicuculline methochloride shifted the GABA concentration-response curve to the right, whilst picrotoxinin both shifted the concentration-response curve for GABA to the right and depressed the maximum response. In the presence of the uptake inhibitors, the rightward shift of the concentration-response curves for GABA induced by bicuculline was less than that induced by bicuculline alone. The rightward shift with picrotoxinin was similarly reduced in the presence of the uptake inhibitors, without altering the depression of the maximum by picrotoxinin. Bicuculline caused a rightward shift of the concentration-response curves for 3APS and muscimol, with the curve for 3APS most affected. Picrotoxinin similarly shifted the concentration-response curves for 3APS and muscimol but depressed the maximum, with the curve for 3APS again being most affected. None of the inhibitors of GABA uptake influenced the concentration-response curves for 3APS or muscimol in the presence of bicuculline or picrotoxinin. 5. In conclusion, a saturable GABA uptake system is present in the enteric nervous system of the guinea-pig intestine, where neuronal GABA uptake appears to predominate over glial uptake.

Animals↗

PubMed1987

Bicarbonate-dependence of responses to ethylenediamine in the guinea-pig isolated ileum: involvement of ethylenediamine-monocarbamate.

gamma-Aminobutyric-acid (GABA)-mimetic responses were induced by ethylenediamine (EDA) in the isolated ileum of the guinea-pig maintained in bicarbonate buffered Krebs-Henseleit (KBC) solution, pH 7.4, 37 degrees C, the responses consisting of a contraction followed by a relaxation. There were no such responses to EDA in bicarbonate-free phosphate buffered (KPO) or HEPES buffered (KHO) Krebs solution, gassed with 100% O2, pH 7.4, 37 degrees C, yet the ileum responded to GABA in bicarbonate-free Krebs solution. Similar GABA-mimetic responses were induced by EDA in the isolated ileum maintained in bicarbonate-free KPO or KHO modified Krebs solution, gassed with O2, if HCO3- (5mM) was first added immediately before the test dose of EDA (0.1-1 mM), the threshold [HCO3-]being 2 mM for EDA-induced responses in these preparations. However, ileal GABA-mimetic responses were induced in bicarbonate-free KPO or KHO solutions by EDA that had been pretreated with carbon dioxide, where the final [HCO3-]in the bath did not exceed 25 microM. Ethylenediamine monocarbamate (synthetic EDAC) released [3H]-GABA from preloaded segments of ileum maintained in bicarbonate-free KPO or KHO solution containing amino-oxyacetic acid and beta-alanine, the release being sensitive to 3-mercaptopropionic acid which prevents GABA release. EDA itself did not evoke any such release in the absence of bicarbonate, but released [3H]-GABA from segments maintained in KBC solution. 4 GABA-mimetic responses were induced by EDAC in the isolated ileum maintained in bicarbonate-free KPO solution, as was a delta-aminovalerate-sensitive depression of ileal twitch responses elicited by transmural stimulation, all of which were also sensitive to 3-mercaptopropionic acid. 5 It is concluded that GABA-mimetic responses to EDA in the isolated ileum of the guinea-pig, maintained in normal Krebs bicarbonate medium, result from the release of endogenous GABA by ethylenediamine monocarbamate formed through the rapid reaction of EDA with the carbon dioxide of bicarbonate buffered Krebs solution. Furthermore, in the ileum, HCO3 ions per se are not necessary for this GABA-releasing property of EDA if the latter is first converted to the monocarbamate, since syntheticethylenediamine monocarbamate elicits ileal GABA-mimetic responses in the total absence of bicarbonate.

Animals↗

PubMed1987

Detection of latency-related viral RNAs in trigeminal ganglia of rabbits latently infected with herpes simplex virus type 1.

Using a combination of in situ hybridization and Northern (RNA) blot analysis, we investigated herpes simplex virus type 1 (HSV-1) transcriptional activity in an ocular rabbit model of HSV-1 latency. Radioactively labeled cloned fragments, representing virtually the entire HSV-1 genome, were individually hybridized to RNA in sections of trigeminal ganglia taken from rabbits during the latent phase of infection with HSV-1 (McKrae). Our results suggest that two discrete latency-related RNAs (LR-RNAs) may be present. The LR-RNAs were localized mainly in the nuclei of neurons. The more abundant LR-RNA was detected in approximately 3% of all neurons examined and was designated major LR-RNA. The other LR-RNA, designated minor LR-RNA, was detected in approximately 0.3% of neurons from latently infected rabbits. The genes for the LR-RNAs mapped in the vicinity of the immediate-early gene ICP0 (also designated IE110). The gene for the major LR-RNA partially overlapped the left (3') end of the ICP0 gene. In situ hybridization with single-stranded RNA probes showed that this LR-RNA was of complementary sense to that of ICP0 mRNA. Northern blot analysis gave an approximate size for this LR-RNA of 1.8 to 2.2 kilobases. The minor LR-RNA mapped to or near the right (5') end of the ICP0 gene. The detection of LR-RNAs suggests the possibility that these RNAs or their products may play significant roles in the initiation and/or maintenance of HSV-1 latency.

Animals↗

PubMed1987

Insulin-like growth factor I induces c-fos messenger ribonucleic acid in L6 rat skeletal muscle cells.

Insulin-like growth factor I (IGF-I) mediates growth promotion of GH on specific target cells. As other growth factor action has been associated with oncogene induction, we examined whether IGF-I activated cellular oncogenes in L6 rat muscle cells, known target cells of IGF-I stimulatory action. Quiescent cells were incubated in serum-free defined medium with IGF-I (Amgen recombinant analog, Thr59) from 5 min to 4 h. 32P-Labeled DNA was first prepared from IGF-I-treated cell poly(A) RNA using avian myeloblastosis virus reverse transcriptase. This labeled probe was hybridized against a blot containing 12 different immobilized oncogene DNAs. The v-fos DNA showed a positive hybridization signal, indicating the presence of c-fos mRNA sequences. Northern analysis with [32P]v-fos DNA revealed a major c-fos mRNA species (2.2 kilobases) induced by treatment of cells with IGF-I (100 ng/ml) or fetal calf serum (15%) for 45 min. We, therefore, measured c-fos induction by cytoplasmic RNA blot hybridization. IGF-I (6.25 ng/ml) stimulated c-fos mRNA 4-fold. Maximum stimulation (18-fold) was seen with 100 ng/ml IGF-I. Peak c-fos induction occurred after 30-min exposure to IGF-I and remained elevated for up to 2 h. Treatment of cells with a high dose of insulin (100 nM) also resulted in a modest (27%) increase in relative levels of c-fos mRNA. The results show that c-fos mRNA is induced by IGF-I in L6 cells. This novel observation suggests that IGF-I action at least in part may be mediated by c-fos, a cellular oncogene thought to play a critical role in cell differentiation and proliferation.

Animals↗

PubMed1987

Insulin-like growth factor I gene expression in GH3 rat pituitary cells: messenger ribonucleic acid content, immunocytochemistry, and secretion.

Insulin-like growth factor I (IGF-I) is present in multiple tissues and cell types. Expression of the IGF-I gene was examined in GH3 cells, a rat pituitary tumor cell line secreting GH and PRL. Increasing concentrations of RNA extracts of GH3 cells yielded a linear increase in hybridization intensity with a 32P-labeled mouse IGF-I cDNA probe. Northern analysis of GH3 cells poly(A) RNA revealed IGF-I mRNA transcripts 1.3, 5.3, and 7.7 kilobases in size. Poly(A) RNA extracts of BALBc/3T3 fibroblasts, a cell line dependent on exogenous somatomedins for DNA synthesis, and of JEG-3 cells, a choriocarcinoma cell line, did not hybridize with the IGF-I cDNA probe. GH3 cells showed positive immunoperoxidase staining using a rabbit anti[Thr59]IGF-I antibody which was largely blocked by prior incubation of the antibody with excess IGF-I. Negligible background peroxidase activity was present in cells incubated with a rabbit nonimmune serum and PBS. Furthermore, BALBc/3T3 fibroblasts showed only weak specific staining with the IGF-I antibody. Finally, GH3 cells secreted IGF-I into the culture medium in a time-dependent fashion, while neither 3T3 nor JEG-3 cells produced detectable medium levels of the peptide after 72 h of incubation. As IGF-I is known to inhibit GH production by the pituitary, the data shown suggest that locally produced IGF-I may regulate GH secretion in an autocrine or paracrine fashion.

Animals↗

PubMed1986

Caprolactam-barbiturate interaction at the GABAA receptor complex in the guinea-pig intestine.

4,6,6-Trimethylcaprolactam antagonised GABAA receptor-mediated contractile responses in guinea-pig isolated ileum, displacing the GABA dose-response curve to the right in a non-parallel manner, and causing a depression of the maximum response. Pentobarbitone not only potentiated the GABAA receptor-mediated contractions but also reversed this non-competitive antagonism by 4,6,6-trimethylcaprolactam, shifting the dose-response curve for GABA to the left and restoring the maximum response. It is conclude that this caprolactam acts at the picrotoxin-barbiturate site on the Cl(-)-ionophore complex.

Animals↗

PubMed1986

gamma-Aminobutyric acid-dependent motility induced by avermectin B1a in the isolated intestine of the guinea pig.

In the isolated ileum of the guinea pig, neurally mediated rhythmic longitudinal mechanical activity was induced by avermectin, a macrolide anthelmintic that releases gamma-aminobutyric acid (GABA) and modulates the GABAA-receptor-ionophore complex. This avermectin-induced activity was dependent on GABA, being reduced or abolished by bicuculline, a GABAA-receptor antagonist, and by 3-mercaptopropionic acid which prevents neural GABA release. These results provide additional direct evidence that GABA is a functional neurotransmitter in the myenteric plexus of the guinea pig intestine, evidently involved in the regulation of intestinal motility.

3-Mercaptopropionic Acid↗

PubMed1986

Expression of the myc cellular proto-oncogene in human thyroid tissue.

The expression of cellular oncogenes was examined in human thyroid tissue. Four thyroid adenomas and three thyroid carcinomas expressed c-myc oncogene mRNA transcripts, which were not expressed in normal thyroid tissues. Agarose gel electrophoresis of poly(A) RNA extracts of adenoma tissues followed by hybridization with v-myc DNA yielded two distinct c-myc mRNA species [2.1 and 4.0 kilobases (kb)]. Thyroid cancer tissue poly(A) RNA revealed a predominant larger c-myc mRNA species (approximately 6 kb) and a smaller 2.1-kb species. After enzymatic dispersion of thyroid adenoma cells, cytoplasmic dot blot hybridization of immobilized thyroid adenoma RNA extracts with the v-myc cDNA probe showed stimulation of c-myc mRNA expression by TSH in a dose- and time-dependent manner. After 72-h pretreatment with serum-free medium, the quiescent adenoma cells yielded a negligible hybridization signal which was stimulated by TSH (10 mU/ml) after 6 h of treatment. Although normal cultured thyroid cells did not contain detectable c-myc mRNA, TSH also stimulated the myc protooncogene expression in a time-dependent manner in normal thyroid cells. These results demonstrate the expression of c-myc mRNA in human thyroid tumors and the in vitro induction of c-myc mRNA in both normal and adenoma thyroid cell cultures by TSH.

Adenocarcinoma, Papillary↗

PubMed1984

Evidence that 5-hydroxytryptamine does not mediate GABA-induced contractile responses in the guinea-pig proximal ileum.

Segments of the isolated proximal ileum of the guinea-pig were set up in the organ bath to record longitudinal muscle contractions. Both gamma-aminobutyric acid (GABA) and 5-hydroxytryptamine induced neurally mediated cholinergic contractile responses; desensitization to 5-HT did not consistently depress contractile responses to GABA, whilst quipazine antagonized the neuronal responses induced by 5-HT without affecting responses to GABA. It is thus concluded that 5-HT does not mediate GABA-induced responses in the ileum.

Acetylcholine↗

PubMed1984

Evidence for a physiological role of GABA in the control of guinea-pig intestinal motility.

Rhythmic neurally mediated spontaneous relaxations of the longitudinal muscle in the isolated ileum of the guinea pig are modified by GABA antagonism. Bicuculline methochloride, a GABAA-receptor antagonist, and picrotoxinin, a Cl--ionophore blocker, as well as GABA desensitization reduced or most often abolished these naturally occurring periodic spontaneous relaxations, indicating a physiological involvement of GABA in the control of intestinal motility. The possible mechanism whereby GABA may induce such relaxations is discussed in relation to GABA actions in the enteric nervous system where GABA is a neurotransmitter.

Animals↗

PubMed1984

Potentiation of GABAA-receptor-mediated responses by barbiturates in the guinea-pig ileum.

In the isolated ileum of the guinea-pig, gamma-aminobutyric acid (GABA) elicited both GABAA- and GABAB-receptor-mediated responses. Barbiturates significantly potentiated the GABAA receptor-induced contractions over the lower dose range of applied GABA (less than 50 microM), without affecting the GABAB-receptor-induced 'after-relaxation', their relative potencies being thiopentone (ThP) greater than pentobarbitone (PB) greater than barbitone (Bb) greater than phenobarbitone (PhB). Also, higher doses of ThP, PB and Bb elicited bicuculline- and picrotoxinin-sensitive GABA-like contractions. PB shifted the dose-response curve for GABA in the presence of bicuculline methochloride to the left without altering the slope or the dose ratio, and not only displaced the dose-response curve for GABA in the presence of picrotoxinin but also restored the slope and the maximum response towards that of the control GABA-induced response. These results further characterise the GABAA-receptor sites of the guinea-pig enteric nervous system, where GABA is evidently a neurotransmitter.

Animals↗

PubMed1984

Evidence that ethylenediamine acts in the isolated ileum of the guinea-pig by releasing endogenous GABA.

Ethylenediamine (EDA) released [3H]-gamma-aminobutyric acid ([3H]-GABA) in a dose-dependent manner from the isolated preloaded ileum of the guinea-pig maintained in Krebs-bicarbonate solution (pH 7.4, 37 degrees C), in the presence of beta-alanine and amino-oxyacetic acid (AOAA) to prevent GABA uptake into glial cells and catabolism. This release was reversibly prevented by 3-mercaptopropionic acid (3-MPA), also in a dose-dependent manner. In the isolated ileal preparations of the guinea-pig maintained in Krebs-bicarbonate solution, EDA induced a dose-dependent transient, cholinergic contractile response (GABAA-receptor-mediated effect), followed by an 'after-relaxation' (GABAB-receptor-mediated effect). EDA also induced a transient contraction superimposed on repetitive twitch responses to electrical transmural stimulation of the cholinergic neurones, followed by a depression of the twitch contractions. This GABAA-receptor-mediated contraction was antagonized by bicuculline methochloride and picrotoxinin, whilst the GABAB-receptor-mediated 'after-relaxation', and depression of cholinergic twitch contractions, was susceptible to antagonism by delta-aminovaleric acid. The pA2 value for bicuculline methochloride antagonism of EDA was estimated to be 5.8, identical with that for GABA. 3-Mercaptopropionic acid also prevented these pharmacological actions induced by EDA without affecting responses to GABA, 3-aminopropranesulphonic acid, muscimol, baclofen or the twitch responses to transmural stimulation. It is concluded that EDA releases both [3H]-GABA and endogenous GABA in the guinea-pig ileum, thus providing further evidence that GABA is a transmitter in the enteric nervous system.

3-Mercaptopropionic Acid↗

PubMed1983

Interactions between GABA and 5-hydroxytryptamine in the guinea-pig ileum.

In isolated segments of the guinea-pig ileum, there was: (a) an early, short-lived (less than 20 s) depression by gamma-aminobutyric acid (GABA) of contractile responses to 5-hydroxytryptamine (5-HT), acetylcholine(ACh), or nicotine, also seen with 3-amino-1-propanesulphonic acid (3APS) or muscimol in place of GABA, and sensitive to bicuculline, picrotoxinin or piretanide, and (b) a delayed, longer-lasting (30 s-1 min) depression of responses to 5-HT and nicotine, but not exogenously applied ACh, also seen with baclofen and only antagonised by delta-aminovaleric acid (DAVA). At 25 degrees C, all these effects were still observed but slowed, whilst at 37 degrees C after cold storage (6 degrees C) overnight, the early, short-lived depression was reduced or eliminated, yet the delayed depression was enhanced. It is concluded that the early, short-lived depression is mediated through GABAA-receptor sites, and the delayed, longer-lasting depression through GABAB-receptor sites on neurones of the myenteric plexus; effects consistent with GABA being a neurotransmitter in the enteric nervous system.

Acetylcholine↗

PubMed1982

GABAA- and GABAB-receptor-mediated modification of intestinal motility.

The actions of gamma-aminobutyric acid (GABA) and its analogues, 3-amino-1-propanesulphonic acid (3APS) and baclofen, have been investigated using isolated segments of the guinea-pig ileum and distal colon. GABA and 3APS, but not baclofen, induced GABAA-receptor mediated effects; prompt, dose-dependent contractions of the ileum which were antagonised by bicuculline, picrotoxinin, piretanide, tetramethylenedisulphotetramine, atropine and tetrodotoxin. Baclofen and GABA, but not 3APS, induced a dose-dependent GABAB-receptor mediated depression of electrically elicited twitch contractions of the ileum, unaffected by the GABAA-receptor antagonists or by antagonism of adenosine, adrenergic, opiate or nicotinic receptors. In the distal colon, baclofen and GABA caused a bicuculline- and picrotoxinin-insensitive depression of spontaneous cholinergic contractions. Desensitization to GABA and baclofen, and cross-desensitization to both agonists was observed. Combined antagonism of GABAA-receptors and desensitization to baclofen slowed pellet expulsion to the same extent as GABA desensitization alone, indicating that both GABAA- and GABAB-receptor sites are involved in this modification of peristalsis by GABA.

Animals↗

PubMed1982

Memory-for-Designs, intelligence, and achievement of educable mentally retarded children.

Relationships between Memory-for-Designs test, Wechsler Intelligence Scale for Children (WISC), and Wide Range Achievement Test (WRAT) were determined for classes of 12 and 14 educable mentally retarded children. Rank-difference rs showed that Memory-for-Designs errors correlated significantly with WISC Verbal IQs (-0.78), WISC Performance IQs (-0.85), and WISC Full Scale IQs (-0.96) for Class 1, and with WRAT Reading (-0.79) and WRAT Arithmetic (-0.70) for Class 2, implying that Memory-for-Designs may supplement the other tests in placement of children into educable mentally retarded classes. The high r (-0.96) between Memory-for-Designs and WISC Full Scale IQs indicates that a major component in intelligence is visual memory, which accounts for 84% of the variance of intelligence and suggests the possibility of improving intelligence through visual memory training in the schools.

Achievement↗

PubMed1981

Southeastern Asian refugees' presbyopia.

The onset and terminal stages of presbyopia, the loss of amplitude of accommodation of the eye associated with old age, of the Southeastern Asian refugees were investigated. Subjects examined in a 6-mo. period in an optometric practice are included. A +1.00 D add was used to define onset of presbyopia, and +2.00 to 2.50 D, the terminal stage. Only those age 42 yr. and below were analyzed, a total of 184 subjects. Of these 68 required a +1.00 D or larger add. chi 2 test of an obvious increase in add requirement from ages 30-34 to 35-39 yr. was significant, meaning that the onset of presbyopia begins at the age of 35 yr. Age 42 yr. was considered the most probable age to be the terminal stage. An unusual feature, presbyopia occurring below age 35 yr., was noted. Thus, the earlier onset and terminal stages of presbyopia of the Southeastern Asian refugees support the notion of the regional, ethnic, and environmental influences in the development of presbyopia.

Adolescent↗