Biomedical subjects
Publications and source records attributed to D N Papachristou.
Loop colostomy is traditionally prevented from retracting into the peritoneal cavity by a rod or other supporting device. The rod can be safely replaced by a single suture. The technique facilitates fitting of the ostomy bag and eliminates the need to remove the supporting element later on.
Somatostatin (SS) and neuropeptide Y (NPY) are coproduced in a subpopulation of neurons that are selectively resistant to NMDA neurotoxicity. We have previously reported that quinolinic acid (QUIN), an NMDA receptor agonist, augments SS mRNA in cultured fetal rat cortical neurons. This study examines coregulation of SS and NPY by QUIN and NMDA in cultured cortical neurons and compares the effects of these agents with those of forskolin and phorbol 12-myristate 13-acetate (PMA), known to activate SS and NPY gene transcription by protein kinase A- and protein kinase C-dependent mechanisms. In addition, transcriptional regulation of the SS gene was investigated by acute transfection of cortical cultures with an SS promoter-chloramphenicol acetyltransferase (CAT) construct. QUIN and NMDA displayed dose-dependent fourfold augmentation of levels of mRNA for SS but not for NPY. In contrast, forskolin and PMA increased both SS and NPY mRNA levels. QUIN- and NMDA-mediated induction of SS mRNA was blocked by the NMDA receptor antagonist (-)-2-amino-5-phosphonovaleric acid and displayed regional brain specificity because it was not observed in fetal hypothalamic cell cultures. In time course studies, the effects of QUIN/NMDA on SS mRNA occurred after a latency of 8 h, indicating a delayed effect. Cortical cells transfected with pSS-750 CAT showed three- to fourfold stimulation of CAT activity with forskolin but not by QUIN or NMDA. These data reveal a dose-dependent, tissue-specific, NMDA receptor-mediated stimulation of SS but not NPY mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
The somatostatin (SS) gene is transcriptionally regulated via the cyclic AMP (cAMP) response element (CRE), located in the proximal promoter (-41 to -48 bp). We have previously reported that glucocorticoids induce dose-dependent cell-specific alterations in the steady-state SS mRNA level. Here we have investigated direct transcriptional control of the SS gene by glucocorticoids. We have examined transcriptional interaction between glucocorticoids and the cAMP signalling pathway and mapped the 5' upstream regulatory region of the SS gene involved in glucocorticoid transactivation. Transcriptional regulation was determined by analysis of chloramphenicol acetyltransferase (CAT) activity in PC12 rat pheochromocytoma cells and A126-1B2 (protein kinase A-deficient mutant PC12) cells, by acute transfection of 5' flanking SS DNA (- 750, -250 and -71 bp) ligated to the reporter (CAT) gene. Dexamethasone (DEX) induced a dose-dependent 2.2-fold stimulation of SS gene transcription in PC12 cells, but not in A126-1B2 cells. Other steroid and thyroid hormones tested, and retinoic acid, were ineffective, while cAMP and forskolin stimulated gene transcription 4-5-fold in PC12 cells but not in A126-1B2 cells. DEX exerted an additive effect on cAMP-induced gene transcription. Deletion of the promoter from -750 to -71 bp (but not from -750 to -250 bp) abolished all stimulatory effects of DEX without affecting cAMP responsiveness. Mutation of the CRE abrogated both DEX- and cAMP-dependent gene enhancement. Gel electrophoretic mobility shift assays confirmed that the -250 to -71 bp region of the SS promoter (but not the -71 to +55 bp domain) binds specifically to a glucocorticoid response element-sensitive nuclear protein(s) from PC12 cells, suggesting a putative glucocorticoid receptor interaction with SS promoter DNA. We conclude that glucocorticoids regulate SS gene transcription positively. Glucocorticoid-induced transactivation shows dependence on protein kinase. A activity, and may be mediated via protein-protein interaction between the glucocorticoid receptor and the CRE binding protein. DNA sequences upstream from the CRE between -250 and -71 bp in the SS promoter appear to be the target of glucocorticoid action.
The drug cysteamine (CHS) induces a profound loss of somatostatin-14 (SS-14) biological and immunological (SS-14 LI) activity from somatostatin cells in vivo and in vitro. The present study was designed to determine (i) whether CHS induced loss of somatostatin is accompanied by secondary increases in SS-mRNA perhaps through loss of autoinhibition of somatostatin cells; (ii) whether CHS exerts additional direct effects on SS gene regulation. CHS was administered to rats in vivo or applied in vitro to primary cultures of rat islet cells, rat islet somatostatin-producing tumor cells (1027 B2), and endogenous or in vitro synthesized SS-mRNA. In vivo administration of CHS led to 80% reduction in tissue SSLI by 4 h. These changes were accompanied by significant alterations in SS-mRNA that were both tissue-specific and time-dependent. The pattern in brain and intestine was typified by a significant 60% increase in SS-mRNA at 2 h followed by a gradual reduction to approximately 55% of control at 8 h. Stomach showed a significant 95% increase in SS-mRNA at 4 h followed by a 37% decrease by 8 h. Pancreatic SS-mRNA displayed a sustained 25-65% reduction for 8 h. Pretreatment of islet cell cultures with CHS reproduced the in vivo findings with pancreas viz. decreased SSLI (80-90% of control) accompanied by a parallel reduction in SS-mRNA (40-50% of control) sustained from 2-72 h. CHS also induced a reduction in immunoreactive insulin and insulin mRNA in cultured islet cells. As with normal islet cells, CHS treatment of 1027 B2 islet tumor cells led to a profound and sustained decrease in SSLI and SS-mRNA. These changes occurred in the absence of any alteration in intracellular cAMP levels. CHS was without effect when incubated directly with SS-mRNA isolated from 1027 B2 cells or with in vitro synthesized SS-mRNA. We conclude that in addition to its effect on SSLI, CHS also induces time- and tissue-dependent alterations in SS-mRNA. The mechanism of CHS action on SS-mRNA is complex and may involve both an indirect effect secondary to loss of somatostatin autoinhibition (to account for SS-mRNA increases) and/or a direct inhibition of SS gene expression (to explain SS-mRNA reduction). The precise site of direct CHS action on SS gene regulation remains to be defined.(ABSTRACT TRUNCATED AT 400 WORDS)
Although a number of previous studies have suggested that glucocorticoids influence somatostatin (SS) function at the peptide level in some tissues and SS mRNA levels in thyroid tumor cells, there has been no systematic investigation of the effects of glucocorticoids on SS gene expression in normal tissues. In the present study, we have examined the effect of dexamethasone (DEX) on SS secretion and gene expression in rat tissues using as models DEX-treated rats in vivo, primary cultures of rat islet and cerebrocortical cells, and a SS-producing rat islet tumor cell line (1027B2). In vivo DEX administration (0.5 mg/kg) for 3 or 8 days augmented SS-mRNA 2- to 3-fold in peripheral tissues (stomach, pancreas, and jejunum), but reduced it by 50-60% in brain. The DEX effect was time dependent, being more pronounced after 8 days than after 3 days of treatment. In all tissues, SS mRNA levels returned to control values 2 weeks after cessation of DEX. Changes in tissue content of immunoreactive SS paralleled those in SS mRNA. In cultured rat islet cells, 18-h incubation with DEX induced dose-dependent biphasic effects on immunoreactive SS and SS mRNA; low doses (10(-10) M) were stimulatory, and high doses (10(-8)-10(-5) M) were inhibitory. Insulin secretion displayed dose-dependent stimulation by DEX, whereas glucagon release was inhibited. The effect of DEX on SS mRNA levels in primary cultures of brain cells was solely inhibitory. 1027B2 cells responded to DEX with augmented immunoreactive SS secretion and SS mRNA levels at low concentration (10(-10) M), followed by a dose-dependent inhibition of both parameters with increasing DEX concentrations. We conclude that glucocorticoids exert significant effects on SS peptide production and steady state mRNA levels in normal SS-producing tissues in vivo, in vitro, and in cultured 1027B2 cells. The glucocorticoid effect is time and dose dependent, tissue specific, and at least in part due to a direct action of the steroid hormone on SS-producing cells.
One of the systems proposed to mediate the reinforcing effects of ethanol is the endogenous opioid system. The objective of the present studies was to investigate the effects of various concentrations of ethanol on the release of beta-endorphin (beta-EP) by the hypothalami of mice showing either high (C57BL/6) or low (DBA/2) voluntary ethanol consumption. Results indicated that the release of beta-EP, either under basal conditions or in the presence of ethanol, was higher from the hypothalami of the C57BL/6 than of the DBA/2 mice. After exposure to various concentrations of ethanol, it was observed that for both strains of mice, low concentrations of ethanol (10, 20 and 25 mM) induced a more pronounced increase in the release of hypothalamic beta-EP than high concentrations of ethanol (30 and 60 mM) leading to an inverse U-shaped dose-response curve. Maximum release for both strains of mice was obtained at 20 mM ethanol. High-performance liquid chromatography analysis indicated that beta-EP 1-31 in the nonacetyl, opiate active form was the major form of the beta-EP-sized peptides released by the hypothalami of both strains of mice. The tissue content of beta-EP-like peptides was similar in the hypothalami of both strains of mice; however, the content of pro-opiomelanocortin mRNA was significantly higher in the hypothalami of the C57BL/6 mice. These genetically determined differences in the basal activity and in the response of the hypothalamic beta-EP system to ethanol may be partially responsible for the different ethanol consumption exhibited by these two strains of mice.
Striatal atrophy in Huntington's disease (HD) is characterized by selective preservation of a subclass of neurons colocalizing NADPH-diaphorase (NADPH-d), somatostatin (SS), and neuropeptide Y (NPY), which have been reported to show three- to fivefold increases in SS-like immunoreactivity (SSLI) and NPY content. Since HD brain is capable of producing excessive quantities of the excitotoxin quinolinic acid (Quin), an N-methyl-D-aspartate (NMDA) receptor agonist, and since experimental Quin lesions show neuronal loss with sparing of NADPH-d/SS/NPY neurons, it has been suggested that Quin may be important in the pathogenesis of HD. In the present study we determined whether Quin stimulates SS gene function in cultured cortical cells known to be rich in NADPH-d/SS/NPY neurons. Cultures of dispersed fetal rat cortical cells were exposed to Quin (1 and 10 mM) with or without (-)-2-amino-5-phosphonovaleric acid (APV; 0.5 mM), an NMDA receptor antagonist, NMDA (0.2 and 0.5 mM), and glutamate (Glu; 0.5 mM). Medium and cellular SSLI was determined by radioimmunoassay and SS mRNA by Northern analysis with a cRNA probe. Quin induced significant (p less than 0.01) 1.6- and 2.5-4 fold increases in SSLI and SS mRNA accumulation, respectively, which were abolished by APV. Release of SSLI into the culture medium was stimulated two- to fivefold by Quin over a 2- to 20-h period. The increase in SS mRNA produced by Quin was time and dose dependent. A similar dose-dependent increase in SS mRNA comparable with that observed with Quin was induced by NMDA.(ABSTRACT TRUNCATED AT 250 WORDS)
To investigate cAMP-dependent regulation of somatostatin secretion and gene expression in the islets of Langerhans, we have correlated the effects of forskolin, theophylline, and (Bu)2cAMP (dbcAMP) on the secretion of somatostatin-like immunoreactivity (SLI), cAMP generation, and somatosatin mRNA (S-mRNA) accumulation by cultured rat islet cells and a rat somatostatin-producing islet tumor cell line (1027 B2). Additionally, we have compared these effects with those of phorbol esters. Forskolin induced large acute increases in cAMP levels in islet cells, whereas theophylline produced modest sustained elevations in cAMP. During 4-h exposure to islets cells, forskolin, theophylline, and dbcAMP produced time- and dose-related increases of up to 14-fold in SLI release and up to 5-fold in S-mRNA levels. The rate of increase in S-mRNA paralleled secretion and occurred with the following order of potency: forskolin greater than dbcAMP greater than theophylline. The analog 1,9-dideoxyforskolin, which is unable to activate adenylyl cyclase, produced a small increase in SLI release without affecting S-mRNA. The effects of short term increases in islet cAMP levels and SLI release on long term changes in S-mRNA accumulation were investigated in a 48-h study with forskolin. Pretreatment of islet cells for 30 min with forskolin evoked large acute increases in cAMP levels and SLI release. S-mRNA rose in a biphasic pattern, with an acute increase at 30 min followed by a secondary increase at 12-48 h. In 1027B2 cells, forskolin and theophylline generated large increases in cAMP levels. Despite this, the two agents as well as dbcAMP produced only slight (20-35%) stimulation of SLI release and S-mRNA accumulation. Phorbol 12-myristate 13-acetate and phorbol 12,13-dibutyrate evoked dose-dependent stimulation of SLI secretion of up to 4-fold from islet cells without altering S-mRNA. Both secretion and S-mRNA were unresponsive to phorbol esters in 1027 B2 cells.(ABSTRACT TRUNCATED AT 400 WORDS)
In streptozocin-induced diabetes in rats, there is a marked increase in the content and release of immunoreactive somatostatin (SLI) from the pancreas and upper gut. To elucidate whether these SLI changes are associated with alterations in somatostatin gene transcription, we measured somatostatin mRNA (SmRNA) accumulation in these and other SLI-producing tissues. Pancreas, stomach, jejunum, hypothalamus, and cerebral cortex were removed from control rats, 6-wk-diabetic rats, and diabetic rats treated with insulin for 6 wk. Total RNA was isolated by centrifugation through CsCl and fractionated on agarose gels. A sensitive radiodensitometric hybridization assay was used to determine SmRNA levels in absolute amounts by in vitro synthesized sense-strand RNA as a quantitative standard and antisense cRNA as a specific probe. SLI was determined by radioimmunoassay. SmRNA exhibited size heterogeneity between the different control and diabetic tissues. A 2- to 3-fold increase in total SmRNA was found in pancreas and stomach of the diabetic rats that suppressed toward normal with insulin treatment. These two tissues also exhibited significant 1.6- to 2.6-fold increases in SLI, respectively. The remaining tissues showed no diabetes-related changes in SLI or SmRNA. We conclude that in insulinopenic diabetes, tissue SLI and SmRNA accumulation undergo parallel changes; are increased in pancreas and upper gut, reflecting augmented somatostatin synthesis; are reciprocally related to insulin acting directly or indirectly on somatostatin-producing cells; and are unchanged in the lower gut and brain, suggesting tissue-specific regulation of somatostatin gene transcription in diabetes.
Total extrathoracic esophagectomy was performed in 16 patients with neoplasms arising in the thoracic and cervical esophagus and the hypopharynx. The procedure was combined with posterior mediastinal gastric pull up in all but two patients who had previous gastrectomy and were managed with colon interposition. Splenectomy was avoided in all patients. Although, in the presence of TNM stage III and IV disease, the procedure was performed mostly for palliation, it resulted in only two deaths and it led to rapid initiation of oral alimentation. Extrathoracic esophagectomy constitutes a safe and simple alternative to other ablative or palliative procedures in the treatment of hypopharyngeal and esophageal malignancies.
Two techniques are presented that can be used for reconstruction of full-thickness defects of the cheek. Defects involving a small area of mucosa can be reconstructed with an anteriorly based neck-pectoral skin flap in combination with primary closure of the mucosa. Defects involving a large part of the mucosa can be managed with a deltopectoral flap in combination with a pectoralis major myocutaneous flap. The two techniques have been applied with satisfactory results in a group of patients with neoplasms of the cheek.
In order to investigate the effects of 6 weeks' neuroleptic treatment on the pituitary-thyroid axis in 25 male schizophrenic patients, and the diurnal variation in the thyrotropin (TSH) and prolactin (PRL) responses to thyrotropin-releasing hormone (TRH) in these patients, the TRH stimulation test was performed in each of them at 14.00 and 24.00 h of the same day, both before and after 6 weeks' treatment with neuroleptics (chlorpromazine or fluspirilene). Also, serum thyroxine (T4), in vitro radioactive triiodothyronine uptake (RT3 U) and free-thyroxine index (FTI) values were estimated from the pre-TRH blood sample. We found no evidence of diurnal variation in the TSH response to TRH in the schizophrenic patients, before or after 6 weeks' neuroleptic treatment. Only drug-free schizophrenic patients had significantly higher PRL responses to TRH at 14.00 h than those at 24.00 h. After 6 weeks' neuroleptic treatment, schizophrenic patients tended to have lower FTI values; also, they had significantly higher basal TSH and PRL values, as well as significantly augmented TSH and PRL responses to TRH, in comparison to their pretreatment values. These findings render possible the diagnosis of subclinical hypothyroidism in neuroleptic-treated schizophrenic patients.
In order to construct a colorectal anastomosis with the EEA or the Russian stapler, one must tie the colonic and the rectal stump on the instrument with two pursestring sutures. A modified circular stapler equipped with hooks eliminates the need to insert sutures. The instrument constructs a double row anastomosis at a minimal cost because it operates with cheap staples that are inserted manually. Its preliminary evaluation in clinical practice showed that it facilitates considerably low anterior resection.
A retrospective study was made of 41 patients treated for gastric myosarcoma to identify prognostic factors that influence results. The adjusted five- and ten-year survival rates were 56% and 43% respectively, with no significant difference between leiomyosarcoma and malignant leiomyoblastoma. A histopathologic grade of malignancy could be assigned to each tumor according to the degree of hypercellularity, nuclear abnormality, mitotic rate and other characteristics. High histopathologic grade, large tumor size (greater than 5 cm diameter) and invasion of adjacent organs adversely affected prognosis. Five-year survival after curative treatment was: 100% (9/9) for small tumors, of which six were treated by wedge gastric resection; 67% (8/12) for large tumors, mostly after subtotal gastrectomy; and 0% for tumors that invaded adjacent organs, despite extended resections. It is concluded that the management of gastric myosarcomas can be planned according to these prognostic factors and that multimodal therapy of tumors with adverse factors warrants consideration.
Intrahepatic dissection in ablative liver surgery can be accomplished easily and safely with a jet of normal saline generated by a standard agricultural electric sprayer. The jet washes away the intrahepatic parenchyma leaving the ducts and vessels undamaged and easily controlled during dissection. The technique, applied in 45 lobectomies in the dog and in 4 liver resections in man, reduced blood loss.
A retrospective study involving 174 patients with adenocarcinoma of the gastric fundus treated with proximal subtotal (PS), extended proximal subtotal (EPS), total (T), and extended total (ET) gastrectomy showed that 1)there were no statistically significant differences in operative mortality between the four gastrectomy types; 2)ET was associated with a significantly lower incidence of local recurrence than T (P less than 0.05) and PS (P less than 0.001); 3)ET resulted in a significantly higher survival rate than PS or T (P less than 0.01) when the three procedures were applied in patients who had TNM stage I and II tumors; 4)patients with stage III and IV tumors did poorly regardless of gastrectomy type. The study implies that intraoperative tumor staging might identify stage I and II patients who benefit the most from radical surgery and those with stage III and IV tumors who should receive palliative surgery.
Subungual melanoma, a rare and easily misdiagnosed neoplasm, affected 52 patients. The lesion usually appeared as a dark spot under the nail, causing its destruction at a later stage. Diagnosis was missed by primary care physicians in 42% of the cases. Management in the hospital consisted of amputation of the involved finger or toe with or without regional node dissection. The study indicated that proper amputation should be at the tarsometatarsal or the carpometacarpal level. It also showed the node dissection should best be performed at the time of amputation, regardless of whether the nodes are clinically involved or not. Besides nodal metastasis, prognosis is adversely affected by nail destruction caused by the tumor. Subungual melanomas of the fingers have a better prognosis.
This is a retrospective study comparing the results of distal subtotal (DST), total (T), and extended total (ET) gastrectomy in a group of 143 patients with adenocarcinomas of the antrum. Of those, 52 had TNM stage I and II tumors and 91 had stage II and IV tumors. Operative mortality was 10% with DST, 23% with T, and 16% with ET. The incidence of recurrence of the tumor at the gastrectomy site was 26% for DST, 27% for T, and only 9% for ET. In stages I and II, the difference of recurrence in favor of ET was significant (P less than 0.05). Analysis of survival data without TNM staging showed no significant difference between the three procedures. TNM staging indicated that that surgical treatment, regardless of procedure, salvaged only five out of 91 stage III and IV patients. The choice of procedure made a difference only in stages I and II, where ET was associated with a significantly higher survival than DST (P less than 0.02). The study suggested that intraoperative staging might be of value in selecting the proper type of gastrectomy. This could be accomplished with node sampling because tumor size corresponds poorly with TNM stage.