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S L Chew

Publications and source records attributed to S L Chew.

At least 37 records · Page 2Linked to original sources
PubMed2001

Predictors of the outcome of surgical treatment in acromegaly and the value of the mean growth hormone day curve in assessing postoperative disease activity.

Acromegaly is associated with increased morbidity and mortality unless serum GH levels are persistently less than 5 mU/L ( approximately 2 ng/mL) after treatment. Transsphenoidal surgical resection is the best available treatment for restoring GH to such "safe" levels; however, criteria for the assessment of the response to treatment are not uniform. To determine the clinically most useful method of assessing disease activity postoperatively and identify predictors of a favorable response to surgical treatment, we have analyzed 67 patients with acromegaly who underwent transsphenoidal surgery between 1993 and 1998. We used three different definitions of a satisfactory or safe response: 1) a postoperative mean GH less than 5 mU/L obtained from averaging five serum GH values obtained throughout one day; 2) a random single GH less than 5 mU/L; or 3) a serum insulin-like growth factor I (IGF-I) level within the normal range. Relying on a single GH measurement alone, 9 of the 23 patients with a single postoperative mean GH level less than 5 mU/L obtained at least one GH value of more than 5 mU/L (false positive rate, 28%) and 8 of the patients with a postoperative mean GH value of more than 5 mU/L obtained a single GH value of less than 5 mU/L (false negative rate, 15%). Postoperatively, a significant increase in the fluctuation of random GH values around the mean was observed in patients who were rendered safe (coefficient of variation, from 26 +/- 2% to 53 +/- 6%; P < 0.001) compared with patients with persistence of inadequately controlled disease. However, 13% (3 of 23) of patients with mean postoperative GH levels of less than 5 mU/L had elevated serum IGF-I levels postoperatively, and 17% (8 of 44) of patients with mean serum GH levels more than 5 mU/L had postoperative IGF-I levels within the normal range. There was no difference in the rate of agreement between mean GH less than 5 mU/L and normalization of IGF-I in relation to the interval since operation when IGF-I levels were measured. Preoperative tumor size and pretreatment mean GH levels were the major determinants of the outcome of surgery, as patients who were rendered safe had significantly lower preoperative mean GH levels than patients who were not cured (median, 31 mU/L vs. 78.5 mU/L, P < 0.01). IGF-I levels were weakly correlated with tumor size and could not be used to predict the patients who would be rendered safe. Preoperative PRL levels were higher in patients who failed to achieve a surgical satisfactory outcome [498 mU/L (187-857) vs. 196 mU/L (136-315), P < 0.01]. In summary, although single random GH values and IGF-I values are both significantly correlated with mean GH levels, they should not be used as an alternative to averaging several GH values to assess disease activity, because of the pulsatile nature of GH secretion and the multiple factors that may influence serum IGF-I. Because significant discrepancies occur, particularly postoperatively, mean GH levels remain the more reliable indicator of surgical outcome and disease activity. As there is considerably more evidence relating long-term prognosis to serum GH levels than to IGF-I and discrepancies occur between GH levels and IGF-I, we suggest that mean serum GH levels and single IGF-I levels, measured early in the postoperative period, are currently the best biochemical guide to the adequacy of surgery and, hence, the need for further treatment.

Acromegaly↗
PubMed2001

Nuclear post-transcriptional control of gene expression.

The mammalian nucleus has considerable control over nascent transcripts. The basic mechanisms of post-transcriptional processing are well understood and recently some of the principles underlying the regulation of nuclear processing events have been elucidated. Here we review the recent progress in identification of signalling pathways that modulate the action of key RNA-binding proteins which regulate splicing, and the mechanisms of action of the C-terminal domain of RNA polymerase II that co-ordinate transcription with nuclear mRNA processing events.

Alternative Splicing↗
PubMed2000

Expression and protein-binding studies of the EEN gene family, new interacting partners for dynamin, synaptojanin and huntingtin proteins.

EEN, identified initially as a fusion partner to the mixed-lineage leukaemia gene in human leukaemia, and its related members, EEN-B1 and EEN-B2, have recently been shown to interact with two endocytic molecules, dynamin and synaptojanin, as well as with the huntingtin protein. In the present study, we show that the expression of the EEN gene-family members is differentially regulated. Multiple-spliced variants were identified for EEN-B2. In the brain, EEN-B1 and EEN-B2 mRNA are preferentially expressed in the cerebellar Purkinje and granule cells, dentate gyrus cells, hippocampal pyramidal neurons and cerebral granule cells. The expression patterns of EEN-B1 and EEN-B2 mRNA in the brain overlap with those of dynamin-I/III, synaptojanin-I and huntingtin, whereas the ubiquitous expression of EEN is consistent with that of dynamin-II. In testes, members of the EEN family are co-expressed with testis-type dynamin and huntingtin in Sertoli cells and germ cells respectively. Our results on the overlapping expression patterns are consistent with the proposed interaction of EEN family members with dynamin, synaptojanin and huntingtin protein in vivo. Although all three EEN family members bind to dynamin and synaptojanin, EEN-B1 has the highest affinity for binding, followed by EEN and EEN-B2. We also demonstrate that amphiphysin, a major synaptojanin-binding protein in brain, can compete with the EEN family for binding to synaptojanin and dynamin. We propose that recruitment of the EEN family by dynamin/synaptojanin to clathrin-coated pits can be regulated by amphiphysin.

Alternative Splicing↗
PubMed2000

An exonic splicing silencer in the testes-specific DNA ligase III beta exon.

Alternative pre-mRNA splicing of two terminal exons (alpha and beta) regulates the expression of the human DNA ligase III gene. In most tissues, the alpha exon is expressed. In testes and during spermatogenesis, the beta exon is used instead. The alpha exon encodes the interaction domain with a scaffold DNA repair protein, XRCC1, while the beta exon-encoded C-terminal does not. Sequence elements regulating the alternative splicing pattern were mapped by in vitro splicing assays in HeLa nuclear extracts. Deletion of a region beginning in the beta exon and extending into the downstream intron derepressed splicing to the beta exon. Two silencing elements were found within this 101 nt region: a 16 nt exonic splicing silencer immediately upstream of the beta exon polyadenylation signal and a 45 nt intronic splicing silencer. The exonic splicing silencer inhibited splicing, even when the poly-adenylation signal was deleted or replaced by a 5' splice site. This element also enhanced polyadenylation under conditions unfavourable to splicing. The splicing silencer partially inhibited assembly of spliceo-somal complexes and functioned in an adenoviral pre-mRNA context. Silencing of splicing by the element was associated with cross-linking of a 37 kDa protein to the RNA substrate. The element exerts opposite functions in splicing and polyadenylation.

Base Sequence↗
PubMed2000

The interaction between EEN and Abi-1, two MLL fusion partners, and synaptojanin and dynamin: implications for leukaemogenesis.

The mixed lineage leukaemia gene, MLL (also called HRX, ALL-1) in acute leukaemia is fused to at least 16 identified partner genes that display diverse structural and biochemical properties. Using GST pull down and the yeast two hybrid system, we show that two different MLL fusion partners with SH3 domains, EEN and Abi-1, interact with dynamin and synaptojanin, both of which are involved in endocytosis. Synaptojanin, a member of the inositol phosphatase family that has recently been shown to regulate cell proliferation and survival, is also known to bind to Eps15, the mouse homologue of AF1p, another fusion partner of MLL. Expression studies show that synaptojanin is strongly expressed in bone marrow and immature leukaemic cell lines, very weakly in peripheral blood leukocytes and absent in Raji, a mature B cell line. We found that the SH3 domains of EEN and Abi-1 interact with different proline-rich domains of synaptojanin while the EH domains of Eps15 interact with the NPF motifs of synaptojanin. In vitro competitive binding assays demonstrate that EEN displays stronger binding affinity than Abi-1 and may compete with it for synaptojanin. These findings suggest a potential link between MLL fusion-mediated leukaemogenesis and the inositol-signalling pathway.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Sustained reduction in circulating cholesterol in adult hypopituitary patients given low dose titrated growth hormone replacement therapy: a two year study.

OBJECTIVE: To study the effects of short (6 months) and longer-term (up to 24 months) growth hormone (GH) replacement therapy using a dose titration regimen, on lipid and glucose metabolism in GH-deficient, hypopituitary adults. DESIGN: On-going open study of GH treatment up to 24 months. Measurements were performed at baseline and at 6, 12, 18 months and 2 years during therapy (data shown at 6 months and 2 years only). Using a dose titration regimen the median GH dose used to achieve and maintain IGF-I levels above the median, but below the upper limit of the age-related reference range (median IGF-I 202.5 microg/l, range 76-397 microg/l), was 1.2 IU daily (range 0.4-3 IU) [0.8 IU/day, males; 1.6 IU/day, females]. PATIENTS: Ninety GH-deficient hypopituitary adults (54 female, median age 48 years, range 19-79 years) entered the study and 24 (14 female, median age 45 years, range 32-79 years) have concluded the 2 year period of assessment. MEASUREMENTS: Body mass index (BMI), waist and hip circumference ratio (WHR), fasting lipids, glucose and glycated haemoglobin (HbA1c) levels were measured at 6 month intervals during GH therapy. RESULTS: Using the dose titration regimen, compared to pretreatment values, total and low density lipoprotein (LDL)-cholesterol levels were significantly lower at 6 months (mean +/- SEM, 5.61+/-0.1 vs. 5.25+/-0.1, and 3.85+/-0.19 vs. 3.43+/-0.26, respectively, P<0.05), and were maintained throughout the study. Male patients had significantly lower pretreatment total and LDL cholesterol levels than females (mean +/- SEM, 5.33+/-0.16 mmol/l vs. 5.7+/-0.12 mmol/l and 3.8+/-0.23 mmol/l vs. 3.92+/-0.29 mmol/l, respectively, P< 0.05). A decrease in total cholesterol was confined to patients with pretreatment total cholesterol levels above 5.8 mmol/l; patients with the highest pretreatment cholesterol levels (> 6.4 mmol/l) obtained the greatest cholesterol reduction (mean +/- SEM, 7.13 +/- 0.14 mmol/l vs. 5.76+/-0.31 mmol/l, P<0.05). A cholesterol-lowering effect of GH therapy was evident in patients who had elevated pre-GH total cholesterol levels even if they were already receiving and continuing lipid lowering medication (mean +/- SEM, 5.62+/-0.22 vs. 5.03+/-0.285, P<0.05). A modest increment in high density lipoprotein (HDL)-cholesterol was evident at 18 months but there was no significant change in triglycerides at any time point. Fasting plasma glucose increased significantly at 6 months but remained within the reference range. Glycated haemoglobin increased significantly at 6 months and was maintained throughout the study; one patient developed frank diabetes mellitus while receiving treatment. There was a weak but significant correlation between the increment in glycated haemoglobin and pretreatment BMI (r = + 0.215, P<0.05). CONCLUSION: The effect of GH on lowering total and low density lipoprotein-cholesterol is more prominent in patients with higher pretreatment cholesterol levels and is evident even in patients receiving other lipid-lowering medication. A modest increment in mean fasting glucose (within the reference range) and mean glycated haemoglobin persisted throughout the study. One patient developed diabetes mellitus. A GH replacement regimen using low dose and careful titration to avoid elevated IGF-I levels and adverse effects is associated with sustained beneficial effects on circulating lipids.

Adult↗
PubMed2000

Optimal dosage interval for depot somatostatin analogue therapy in acromegaly requires individual titration.

BACKGROUND: The recent introduction of the depot somatostatin analogues octreotide LAR and lanreotide represent major advances in the medical treatment of acromegaly. However, it is uncertain whether the recommended dose intervals of 4 weeks and 10-14 days, respectively, are applicable to all patients. AIMS: To determine the optimum intervals between depot injections of either octreotide LAR and lanreotide for the suppression of serum GH and IGF-I in patients with acromegaly. Twenty-seven patients with acromegaly were randomly allocated to receive either three injections at 4 week intervals of octreotide LAR (n = 18) or five injections at 14 day intervals of lanreotide (n = 11); two patients participated in both arms. Prior to the first injection, at 4 and 6 weeks after the last injection of LAR, and at 10, 14 and 21 days after the last injection of lanreotide, serum mean GH and IGF-I levels were measured. RESULTS: In the LAR-treated group, at 4 and 6 weeks after the third injection 13 patients (72%) and 12 patients (67%), respectively, had a mean GH < 5 mU/l. IGF-I was normalized in 12 and 11 patients at these times. In the lanreotide-treated group, five (45%), four (36%) and three (27%) patients, respectively, had a GH < 5 mU/l at 10, 14 and 21 days after the last injection and eight, six and five patients had a normal serum IGF-I. CONCLUSION: There is marked variability in individual patient responses to depot somatostatin analogues. The establishment of optimal drug intervals requires careful assessment. For octreotide LAR many patients may be as adequately controlled with 6 weekly injections as with 4 weekly injections. It is important to measure serum GH profiles at intervals after initiating therapy with these drugs to individualize doses for each patient and hence minimize cost.

Acromegaly↗
PubMed2000

Exonic splicing enhancer motif recognized by human SC35 under splicing conditions.

Exonic splicing enhancers (ESEs) are important cis elements required for exon inclusion. Using an in vitro functional selection and amplification procedure, we have identified a novel ESE motif recognized by the human SR protein SC35 under splicing conditions. The selected sequences are functional and specific: they promote splicing in nuclear extract or in S100 extract complemented by SC35 but not by SF2/ASF. They can also function in a different exonic context from the one used for the selection procedure. The selected sequences share one or two close matches to a short and highly degenerate octamer consensus, GRYYcSYR. A score matrix was generated from the selected sequences according to the nucleotide frequency at each position of their best match to the consensus motif. The SC35 score matrix, along with our previously reported SF2/ASF score matrix, was used to search the sequences of two well-characterized splicing substrates derived from the mouse immunoglobulin M (IgM) and human immunodeficiency virus tat genes. Multiple SC35 high-score motifs, but only two widely separated SF2/ASF motifs, were found in the IgM C4 exon, which can be spliced in S100 extract complemented by SC35. In contrast, multiple high-score motifs for both SF2/ASF and SC35 were found in a variant of the Tat T3 exon (lacking an SC35-specific silencer) whose splicing can be complemented by either SF2/ASF or SC35. The motif score matrix can help locate SC35-specific enhancers in natural exon sequences.

Animals↗
PubMed2000

Insulin-like growth factor I and the development of colorectal neoplasia in acromegaly.

Patients with acromegaly are at increased risk of colorectal neoplasia and, by analogy with high-risk nonacromegalic patients, may require regular colonoscopic screening. However, it is unknown whether the risk is equal in all patients or whether some should be regarded as carrying a particularly high risk. The aims of this study were: 1) to establish the natural history of colorectal neoplasia in acromegaly; 2) to establish which patients are at increased risk of developing neoplasia; and 3) to elucidate the influence of insulin-like growth factor I (IGF-I) in adenoma formation. A prospective colonoscopic evaluation of the development of new premalignant adenomas in the colon was performed in 66 patients with biochemically proven acromegaly who had previously undergone colonoscopic screening and removal of all visible polyps. Twenty-five patients (38%) had a total of 37 polyps detected at the second colonoscopy: nine (14%) had at least one adenoma, and 18 (27%) had one or more hyperplastic polyps (2 patients had both). The development of new adenomas, but not hyperplastic polyps, was associated both with elevated serum IGF-I (P < 0.005) and, to a lesser extent, with a previous adenoma at the original colonoscopy (P < 0.07). In summary, patients with acromegaly and in whom serum IGF-I remains elevated and/or who have had a previous adenoma should be regarded as having an especially high risk for the development of subsequent colorectal neoplasia. Serum IGF-I seems to be implicated in the development of colorectal neoplasia in acromegaly, although the exact mechanisms remain uncertain.

Acromegaly↗
PubMed1999

Evidence for the function of an exonic splicing enhancer after the first catalytic step of pre-mRNA splicing.

Exonic splicing enhancers (ESEs) activate pre-mRNA splicing by promoting the use of the flanking splice sites. They are recognized by members of the serine/arginine-rich (SR) family of proteins, such as splicing factor 2/alternative splicing factor (SF2/ASF), which recruit basal splicing factors to form the initial complexes during spliceosome assembly. The in vitro splicing kinetics of an ESE-dependent IgM pre-mRNA suggested that an SF2/ASF-specific ESE has additional functions later in the splicing reaction, after the completion of the first catalytic step. A bimolecular exon ligation assay, which physically uncouples the first and second catalytic steps of splicing in a trans-splicing reaction, was adapted to test the function of the ESE after the first step. A 3' exon containing the SF2/ASF-specific ESE underwent bimolecular exon ligation, whereas 3' exons without the ESE or with control sequences did not. The ESE-dependent trans-splicing reaction occurred after inactivation of U1 or U2 small nuclear ribonucleoprotein particles, compatible with a functional assay for events after the first step of splicing. The ESE-dependent step appears to take place before the ATP-independent part of the second catalytic step. Bimolecular exon ligation also occurred in an S100 cytosolic extract, requiring both the SF2/ASF-dependent ESE and complementation with SF2/ASF. These data suggest that some ESEs can act late in the splicing reaction, together with appropriate SR proteins, to enhance the second catalytic step of splicing.

Adenosine Triphosphate↗
PubMed1999

Pineal nitric oxide synthase, but not heme oxygenase, mRNA is suppressed by continuous exposure to light.

We have previously shown that exposure of rats to constant light (LL) induced a decrease in NO synthase (NOS) activity in the pineal gland. We report here that the use of the sensitive technique of RT-PCR has demonstrated that mRNA for neuronal NOS is present in the pineal, and that it is photoneurally regulated. There was a marked decrease in pineal neuronal NOS mRNA levels in continuous light conditions, similar to the changes seen in NOS enzyme activity. Inducible NOS was not present in the pineal, and there was evidence that the photoregulatable form was not endothelial NOS. The mRNA for two isoforms of heme oxygenase, the enzyme responsible for the generation of the putative neuromodulator carbon monoxide, was also present in the pineal, but neither isoform was photoregulated. Using immunodetection, it was not possible to identify the presence of NOS protein, other than to a minimal extent, even though NOS activity was clearly present. NADPH-diaphorase staining and in situ hybridization were carried out in an attempt to identify the precise location of neuronal NOS message. A strong NADPH-diaphorase reaction was present in sympathetic nerve fibers of the pineal, but pinealocytes showed no or only very weak labelling. In situ hybridization was also unable to identify neuronal NOS message in pinealocytes. These data thus also suggest the possible presence of a pineal-specific NOS isoenzyme.

Animals↗
PubMed1999

T-STAR/ETOILE: a novel relative of SAM68 that interacts with an RNA-binding protein implicated in spermatogenesis.

RBM is an RNA-binding protein encoded on the Y chromosome in mammals and is expressed only in the nuclei of male germ cells. Genetic evidence from infertile men implicates it in spermatogenesis, but its function is unknown. Of a number of potential partners for RBM identified by a yeast two-hybrid screen with testis cDNA, the most frequent isolates encoded a novel RNA-binding protein, termed T-STAR, that is closely related to SAM68, an Src-associated protein of unknown function. The mouse homologue was also cloned and designated étoile. It mapped to chromosome 15, while T-STAR mapped to the syntenic region on human chromosome 8. T-STAR/étoile is expressed primarily in the testis; in rat germ cells, the expression of both T-STAR/étoile and SAM68 is regulated during meiosis. Transfection of T-STAR/étoile fused with green fluorescent protein into HeLa cells caused an accumulation of protein in a novel compartment of the nucleus, adjacent to the nucleolus but distinct from the peri-nucleolar compartment. RBM and other hnRNP G family members are candidate downstream targets for regulation by T-STAR/ETOILE and SAM68.

3T3 Cells↗
PubMed1998

Acute and subacute effects of endotoxin on hypothalamic gaseous neuromodulators.

Although two-way communication between the hypothalamus and the immune system in now well established, particularly for the hypothalamo-pituitary-adrenal axis, the role of the gaseous neurotransmitters nitric oxide (NO) and carbon monoxide (CO) is much less well understood in terms of hypothalamic function. These agents are an important part of the peripheral inflammatory response; and their synthetic enzymes, NO synthase (NOS) and heme oxygenase (HO), respectively, have been localized to the hypothalamic PVN and SON. The induced generation of both NO and CO leads to the suppression of CRH and vasopressin, the major stimulators of the HPA. Thus, the addition of hemin to hypothalamic explants is maximally active at 1 microM in attenuating the release of CRH and vasopressin, and this dose is also most effective in generating biliverdin and associated CO. CO generation is also able to stimulate cyclooxygenase to produce prostaglandin E2, an established intermediary in the cytokine-stimulated activation of the HPA. Finally, inducible NOS mRNA is specifically induced in the hypothalalmus in response to endotoxin, in parallel to interleukin-1. These data provide increasing evidence in favor of NO and CO as counterregulatory agents in the HPA response to immune activation.

Animals↗
PubMed1998

Expression of the growth hormone secretagogue receptor in pituitary adenomas and other neuroendocrine tumors.

Synthetic GH secretagogues (GHSs; GH-releasing peptides and their nonpeptide mimetics) stimulate GH release, activate the hypothalamo-pituitary-adrenal axis, and release PRL in vivo. Patients with acromegaly show an exuberant GH response to GHSs, whereas patients with pituitary-dependent ACTH-secreting tumors show an exaggerated rise in ACTH and cortisol. We, therefore, studied the presence of GHS receptor (GHS-R) messenger ribonucleic acid (RNA) in 38 human pituitary tumors of different cell types, 3 ectopic ACTH-secreting tumors, a pancreatic gastrinoma, 3 insulinomas, and a non-secreting thymic carcinoid as well as in 7 normal pituitary glands. Certain pituitary tumors were also studied by in vitro cell culture with measurement of secreted GH, ACTH, PRL, FSH, LH, alpha-subunit, and TSH. RNA was extracted from tissue samples and, after RT, a duplex PCR reaction with primers for the GHS-R gene and for the housekeeping gene glyceraldehyde-3-phosphate dehydrogenase was performed, allowing semiquantitation of GHS-R expression. All the somatotroph adenomas (n = 8) showed a 2-10 times higher expression of the GHS-R gene compared to normal pituitaries. Higher than normal expression was shown in 5 of 18 tumors from patients with ACTH-secreting pituitary adenomas and in 1 of 3 ectopic ACTH-secreting carcinoid tumors. Two of the pituitary ACTH-secreting adenoma samples showed completely absent expression of the GHS-R, 8 showed expression similar to that of normal pituitary tissue, and 3 of the corticotroph adenoma tissue samples and 2 ectopic ACTH-secreting tumors showed a very low level of expression. One of 4 prolactinoma samples showed a high level of expression, 1 showed expression similar to that of normal pituitary, and 2 samples showed a very low level of expression. Nonfunctioning pituitary adenoma samples showed either absent or very low level expression of the GHS-R. The pancreatic gastrinoma sample showed expression similar to that of normal pituitary tissue, whereas 3 insulinomas showed low level expression of the GHS-R gene; a nonsecreting thymic carcinoid tumor showed no detectable expression. In summary, although GHS-R messenger RNA is abundant in human somatotroph adenomas, it is also present in other pituitary adenomas, particularly ACTH-secreting tumors. These findings may explain the in vivo responses to GHSs in patients harboring such tumors. It also appears from our study that GHS-R may be expressed in other neuroendocrine tumors.

Acromegaly↗
PubMed1998

Caudal morphine in paediatric patients: a comparison of two different doses in children after major urogenital surgery.

We compared the duration of postoperative analgesia and the occurrence of side-effects of two different doses of caudal morphine in children undergoing major urogenital surgery. Fifty-two children aged between 1 and 12 years were randomly selected to receive caudal morphine, either 25 micrograms.kg-1 (Group A) or 50 micrograms.kg-1 (Group B) with 0.5 ml kg-1 of 0.25% plain bupivacaine immediately before surgery. They were monitored for 24 hours in a high dependency area for known complications of epidural morphine. There was no significant difference in postoperative analgesia between the two doses of caudal morphine. Clinically significant respiratory depression or sedation was not detected in either group. The occurrence of vomiting and pruritus was similar in both groups. Urinary retention was not recorded as all children had an indwelling catheter as required by the surgical procedure. We concluded that 25 micrograms.kg-1 of caudal morphine is as effective as 50 micrograms.kg-1 for providing postoperative analgesia in children undergoing urogenital surgery.

Analgesics, Opioid↗
PubMed1997

Induction of nitric oxide synthase and interleukin-1beta, but not heme oxygenase, messenger RNA in rat brain following peripheral administration of endotoxin.

Previous studies have suggested that both nitric oxide (NO) and carbon monoxide (CO) are important modulators of the inflammatory response, while more recent data have implicated both gases as regulators of hypothalamic neuroendocrine function, particularly the hypothalamo-pituitary-adrenal axis. We have, therefore, investigated the modulation of the transcripts for the synthetic enzymes for both NO and CO following the intraperitoneal administration of lipopolysaccharide, serotype B5 055, over the course of 24 h. The mRNA for type I or neuronal nitric oxide synthase (nNOS), and type II or inducible (iNOS), and heme oxygenase1 ('inducible') and heme oxygenase2 ('constitutive'), were reverse transcribed to cDNA, amplified by the polymerase chain reaction, and then quantified using a co-amplified internal standard, beta-actin. This allowed for assessment of relative changes in transcript concentration. In addition, these were compared to changes in expression of the cytokine, IL-1beta. Finally, absolute levels of the synthetic enzyme transcripts were assessed by means of co-amplification in the presence of varying amounts of mutant templates in a competitive PCR reaction. Our data revealed rapid induction of IL-1beta, iNOS and HO1 in the liver, returning to baseline at 24 h. In the hypothalamus, all transcripts were present under basal conditions, but only IL-1beta and iNOS were induced by the LPS. We conclude that hypothalamic IL-1beta and iNOS can be induced by a non-lethal dose of endotoxin, and are, thus, in a position to mediate certain of the neuroendocrine consequences to inflammatory stress.

Animals↗
PubMed1997

Metastatic parathyroid carcinoma in the MEN2A syndrome.

We report a patient with a metastatic parathyroid carcinoma and medullary carcinoma of the thyroid. This patient represents a variation of the multiple endocrine neoplasia syndrome (MEN) type 2A. There was no evidence of a phaeochromocytoma. The case illustrates the difficulties that may be encountered in localising the source of PTH secretion; the patient underwent four unsuccessful exploratory operations of the neck and mediastinum before further investigations revealed a single metastatic deposit of parathyroid carcinoma involving the first thoracic vertebra. PCR amplification and sequencing of the RET oncogene from the metastatic parathyroid carcinoma and genomic DNA revealed a heterozygous mutation (Cys634Tyr) in exon 11, as has previously been described to occur in MEN 2A. In addition, loss of tumour heterozygosity was demonstrated at loci from chromosomes 1, 2, 3p, 13q and 16p. This represents the first report of a parathyroid carcinoma in a MEN2A patient, in which the multiple allelic deletions are consistent with the generalised losses observed in aggressive tumours.

Carcinoma↗