Synergistic activity of gamma-linolenic acid and cytotoxic drugs against pancreatic adenocarcinoma cell lines

BACKGROUND

Gamma-linolenic acid (GLA) is growth inhibitory both in vitro and in vivo, at doses non-toxic to non-cancer cells. Chemotherapeutic agents have limited activity in pancreatic cancer. Interactions between GLA and cytotoxic drugs have not previously been investigated; any synergy might improve the therapeutic effect of these agents.

AIM

To investigate possible interactions between GLA and 5-fluorouracil (5-FU) or gemcitabine against pancreatic cancer cell lines in vitro.

METHODS

Two pancreatic cancer cell lines were exposed to GLA alone and in combination with 5-FU or gemcitabine. Residual viable biomass was measured using the MTT assay and the results analysed by the median effect method of Chou and Talalay [Adv Enzyme Regul 1984;22:27-55].

RESULTS

GLA concentrations of 3.9- 125 microg/ml had a synergistic or additive growth inhibitory effect on all tested concentrations of gemcitabine. Synergism was demonstrated between GLA and 5-FU only at concentrations of 62.5-125 microg/ml of 5-FU.

CONCLUSION

GLA has a synergistic effect with gemcitabine at concentrations that correspond to in vivo therapeutic doses. GLA with 5-FU is synergistic only at a tight range of high concentrations of 5-FU. GLA lacks toxic side effects and may be useful in combination with gemcitabine.

A randomised clinical trial to assess the effect of total enteral and total parenteral nutritional support on metabolic, inflammatory and oxidative markers in patients with predicted severe acute pancreatitis (APACHE II > or =6)

BACKGROUND

Total enteral nutrition (TEN) within 48 h of admission has recently been shown to be safe and efficacious as part of the management of severe acute pancreatitis. Our aim was to ascertain the safety of immediate TEN in these patients and the effect of TEN on systemic inflammation, psychological state, oxidative stress, plasma glutamine levels and endotoxaemia.

METHODS

Patients admitted with predicted severe acute pancreatitis(APACHE II score >5) were randomised to total enteral (TEN; n = 8) or total parenteral nutrition (TPN; n = 9). Measurements of systemic inflammation (C-reactive protein), fatigue (visual analogue scale), oxidative stress (plasma thiobarbituric acid-reactive substances), plasma glutamine and anti-endotoxin IgG and IgM antibody concentrations were made on admission and repeated on days 3 and 7 thereafter. Clinical progress was monitored using APACHE II score. Organ failure and complications were recorded.

RESULTS

All patients tolerated the feeding regime well with few nutrition-related complications. Fatigue improved in both groups but more rapidly in the TEN group. Oxidative stress was high on admission and rose by similar amounts in both groups. Plasma glutamine concentrations did not change significantly in either group. In the TPN group, 3 patients developed respiratory failure and 3 developed non-respiratory single organ failure. There were no such complications in the TEN group. Hospital stay was shorter in the TEN group [7(4-14) vs. 10 (7-26) days; p = 0.05] as was time to passing flatus and time to opening bowels [1 (0-2) vs. 2 (1-5)days; p = 0.01]. The cost of TEN was considerably less than of TPN.

CONCLUSION

Immediate institution of nutritional support in the form of TEN is safe in predicted severe acute pancreatitis. It is as safe and as efficacious as TPN and may be beneficial in the clinical course of this disease.

Deficiencies of micronutrients, altered bowel function, and quality of life during late follow-up after pancreaticoduodenectomy for malignancy

BACKGROUND/AIM

A previous study in our unit showed an inadequate dietary intake of fat-soluble vitamins and energy after pancreaticoduodenectomy (PD). This study was designed to determine whether deficiencies in dietary intake of micronutrients lead to nutritional deficiencies and to examine the impact of dietary advice on nutrition, bowel function, and quality of life.

METHODS

Ten patients who had undergone PD for malignant disease more than 6 months previously were studied at baseline and follow-up 8 weeks apart. Dietary intakes of energy, fat, and micronutrients were assessed by analysis of weighed food diaries, and serum vitamins and trace elements were measured at each visit. Quality of life questionnaires (EORTC QLQ30 and PAN 26) were answered, and a clinical assessment of the bowel function was made. Targeted dietary intervention was given, where indicated, and its impact on the study parameters was assessed at the second clinic visit.

RESULTS

The patients were generally well nourished. Dietary deficiencies of fat-soluble vitamins were detected (vitamin A, n = 2; vitamin D, n = 10; vitamin E, n = 2), but these correlated with serum deficiency only for vitamin A. The selenium intake was borderline or insufficient in 6 patients' diet, with serum deficiencies in 4. Despite normal intakes of iron and zinc, half the patients showed serum deficiency. The bowel function was an important factor in quality of life, and symptoms improved in 3 patients with enzyme supplements and antidiarrhoeal medication.

CONCLUSIONS

PD patients appear to be prone to a predictable set of micronutrient deficiencies that may be compounded by insufficient dietary intake. The bowel function is important to these patients, and it should be optimized with aggressive enzyme replacement. Dietary intervention appears to make little short-term impact in the areas studied.

Genomic profiles and predictive biological networks in oxidant-induced atherogenesis

Atherogenic stimuli trigger complex responses in vascular smooth muscle cells (VSMCs) that culminate in activation/repression of overlapping signal transduction cascades involving oxidative stress. In the case of benzo[a]pyrene (BaP), a polycyclic aromatic hydrocarbon present in tobacco smoke, the atherogenic response involves interference with redox homeostasis by oxidative intermediates of BaP metabolism. The present studies were conducted to define genomic profiles and predictive gene biological networks associated with the atherogenic response of murine (aortic) VSMCs to BaP. A combined oxidant-antioxidant treatment regimen was used to identify redox-sensitive targets during the early course of the atherogenic response. Gene expression profiles were defined using cDNA microarrays coupled to analysis of variance and several clustering methodologies. A predictor algorithm was then applied to gain insight into critical gene-gene interactions during atherogenesis. Supervised and nonsupervised analyses identified clones highly regulated by BaP, unaffected by antioxidant, and neutralized by combined chemical treatments. Lymphocyte antigen-6 complex, histocompatibility class I component factors, secreted phosphoprotein, and several interferon-inducible proteins were identified as novel redox-regulated targets of BaP. Predictor analysis confirmed these relationships and identified immune-related genes as critical molecular targets of BaP. Redox-dependent patterns of gene deregulation indicate that oxidative stress plays a prominent role during the early stages of BaP-induced atherogenesis.

Imaging of neuroendocrine tumors of the pancreas

BACKGROUND

Neuroendocrine tumors of the pancreas are uncommon neoplasms of the pancreas that can occur sporadically or in association with various syndromes such as multiple endocrine neoplasia type 1 (MEN I). Patients can present with a specific clinical syndrome related to biochemically functioning tumors or with nonspecific symptoms related to mass effect or metastases. The size, function, consistency, and malignant behavior of neuroendocrine tumors are integrally related. Imaging has a major role in the preoperative localization of the primary tumor and detection of metastases. Several techniques are available including ultrasound, endoscopic ultrasound, computed tomography (CT), MR, somatostatin receptor scintigraphy, angiography, and arterial stimulation with venous sampling; each with unique advantages and limitations. The reported performance for these techniques vary widely, and as a result, recommended imaging algorithms are controversial. Recent technical advances in ultrasound, CT, and MRI have occurred that may improve the sensitivity of some of the techniques. Further improvements are likely in the future. In this chapter we will review imaging techniques used to study the pancreas as it relates to the detection of neuroendocrine tumors, imaging findings of these tumors using various imaging modalities, and the advantages, limitations and results obtained with each technique.

Non-compliance with national guidelines in the management of acute pancreatitis in the United kingdom

BACKGROUND

Deficiencies and lack of standardisation of the management of acute pancreatitis in the UK have been reported. National UK guidelines for the management of acute pancreatitis were published in 1998. However, implementation of national guidelines in other areas has been patchy, suggesting that evaluation of the uptake of the pancreatitis guidelines would be appropriate.

AIM

Identification of current practice in the management of acute pancreatitis as reported by consultant surgeons, in order to determine how effectively the UK guidelines have been introduced into practice.

METHODS

A questionnaire was posted to 1,072 full members of the Association of Surgeons of Great Britain and Ireland. It consisted of 13 questions that aimed to identify the surgeon's practice in the management of patients with acute pancreatitis in relation to key points in the UK guidelines. We compared the practice of hepatobiliary and pancreatic (HBP) vs. non-HBP specialists, and teaching vs. non-teaching hospital surgeons using the chi(2) test.

RESULTS

Of 538 responses (50%), 519 were from consultant surgeons. 59 did not look after patients with acute pancreatitis and 89 (17%) had a HBP interest. There were differences between the recommendations in the guidelines and reported practice, particularly in the use of critical care resources and referral to specialist units. Of consultants looking after acute pancreatitis 371 (72%) were non-HBP specialists. There were significant overall differences between the practice of HBP specialists and non-specialists: in severity assessment (Glasgow and C-reactive protein vs. Ranson criteria); indication and timing of requesting computed tomography (routinely at 7-10 days vs. when clinically indicated); nutritional support (enteral feeding vs. no support), and in common bile duct assessment prior to cholecystectomy (intra-operative cholangiography vs. endoscopic retrograde cholangiopancreatography). There was no significant difference between practice in teaching and non-teaching hospitals.

CONCLUSION

Implementation of national guidelines for the management of acute pancreatitis was greater in the practice of HBP specialists than non-specialists. This has implications for the rationale of creating guidelines, and for the strategies associated with their introduction.

Body composition, muscle function and psychological changes in patients undergoing operation for hepatic or pancreatic disease

BACKGROUND

There is currently a dearth of data with respect to changes in body composition, physiological function and pSychological state in patients undergoing operative treatment for pancreatic or hepatic disease although marked changes in these variables have been reported in colorectal surgical patients.

METHODS

In 36 patients (37 operations) we have studied the effect of a pancreatic or hepatic operation (with and without nutritional support) on body fat and body protein (assessed by Dual energy X-ray absorptiometry (DEXA) and anthropometry), respiratory function (measured by spirometry and vitalography), voluntary muscle function (measured by hand dynamometry) and psychological state (measured by use of the hospital anxiety and depression score and visual analogue scale for fatigue) over a 1-week period postoperatively.

RESULTS

On the 3rd postoperative day there were significant changes in: grip strength 307 (135-499) to 249 (85-461) N; FEV1 2.28 (0.48-3.98) to 1.02 (0-2.42) litres/min; FVC 2.90 (0.75-5.02) to 1.28 (0.22-3.31) litres; anxiety score 7 (0-17) to 6 (1-20); depression score 3 (0-10) to 5 (0-20), and fatigue 3.9 (0.4-10) to 6.8 (1.0-9.7). These persisted on day 7 by which time mid-arm circumference and total body fat (by DEXA) had fallen from 30.1 (21.1-45.0) to 29.5 (20.2-43.2) cm, and 20.7 (5.8-53.7) to 20.4 (6.6-53.5) kg, respectively.

CONCLUSION

We conclude that operative treatment for pancreatic or hepatic disease has an adverse effect on body composition, physiological function and psychological state.

Body composition, physiological function and psychological changes in patients with predicted severe acute pancreatitis

BACKGROUND

Serious sepsis and major blunt trauma have adverse effects on body composition, physiological function and psychological state. The effect of severe acute pancreatitis on these groups of variables has not yet been reported.

METHODS

We have studied the effect of predicted severe acute pancreatitis (admission APACHE II score > or = 6) on body fat and mid arm muscle circumference (assessed by dual-energy X-ray absorptiometry and anthropometry), respiratory function (measured by spirometry and vitalography), voluntary muscle function (measured by hand dynamometry) and psychological state (measured by use of the hospital anxiety and depression score and visual analogue scale for fatigue) on admission, and three and seven days thereafter.

RESULTS

The median APACHE II score of the 15 patients (7 men) in this study was 10 (6-13). The patients showed significant improvement in respiratory function (FEV1 1.3, 1.6, 2.3 litres/s, p < 0.01; FVC 1.5, 2.0, 2.9 litres, p < 0.01; PEFR 304, 372, 409 litres/min, p = 0.01 but no change in voluntary muscle function (210, 205, 213 N, p = 0.41) over the 7-day study period. Psychological state improved in terms of fatigue (2.4, 4.2, 7.0, p < 0.01) and depression (6, 9, 4, p = 0.12) but not in anxiety (8, 6, 7, p = 0.07). Body fat measured by DEXA (17.3 kg on admission, 16.7 kg on day 7, p = 0.13) and the mid upper arm muscle circumference (262, 248, 251 mm, p = 0.10) did not change implying that energy and nitrogen balance over the 7-day study period was achieved.

CONCLUSION

Predicted severe acute pancreatitis has an adverse effect on respiratory function and psychological state similar to that observed in serious sepsis. Improvement in these variables is apparent over 7 days of effective treatment. Further research is indicated to examine the effect of nutritional support on these variables.

Detection of flat lesions in the colon with CT colonography

BACKGROUND

We investigated whether flat lesions of the colon could be detected on computed tomographic colonography (CTC).

METHODS

CTC and conventional colonoscopy were performed on 547 consecutive patients. A subset of 22 polyps was described as flat on colonoscopy (n = 16) or CTC (n = 6) and are the basis of this report. CTC was performed with a standard technique (5-mm collimation, 3-mm reconstruction intervals). Patients were scanned in supine and prone positions. Examinations were randomly assigned and reviewed in a blinded fashion by two of three radiologists. Prospective interpretations were recorded. All patients had conventional colonoscopy, which served as the gold standard.

RESULTS

Twenty-two flat lesions ranging from 0.4 to 3.5 cm were histologically classified as adenomatous (n = 8) or hyperplastic (n = 14). The sensitivities for detecting all flat lesions and flat adenomas by each reviewer were 43% and 100%, 65% and 100%, and 15% and 13%, respectively. "Double reading" resulted in detection of 68% of all lesions and 100% of adenomas. Of the seven hyperplastic polyps missed by both reviewers, four were identified retrospectively.

CONCLUSION

Flat lesions of the colon represent an important source of false negative CTC examinations. Awareness of their morphology can assist radiologists in finding most of these challenging lesions.

Apoptosis and proliferation of acinar and islet cells in chronic pancreatitis: evidence for differential cell loss mediating preservation of islet function

BACKGROUND

Chronic pancreatitis is characterised clinically by early exocrine insufficiency, with diabetes mellitus occurring as a late phenomenon. This is mirrored pathologically by extensive acinar cell destruction and islet preservation. The mechanisms underlying this differential rate of cellular destruction are unknown.

AIMS

To test the hypothesis that acinar loss and islet preservation in chronic pancreatitis occurs due to differential epithelial kinetics and investigate the role of inflammatory cells and cell cycle associated molecules.

METHODS

Archival tissue from six chronic pancreatitis cases was compared with six normal controls using TUNEL and immunohistochemistry for CD3, CD20, CD68, MIB-1, Bcl-2, Bax, Fas, Fas ligand, retinoblastoma protein (Rb), and tissue inhibitor of metalloproteinases 1 (TIMP-1) and 2 (TIMP-2).

RESULTS

The acinar cell apoptotic index (AI) and proliferation index were higher in chronic pancreatitis than controls. T lymphocytes diffusely infiltrated fibrous bands and acini but rarely islets. Acinar Bcl-2 expression exceeded islet expression in chronic pancreatitis and controls while Bax was strongly expressed by a subset of islet cells and weakly by centroacinar cells. Islet Fas and Fas ligand expression exceeded acinar expression in chronic pancreatitis and controls. Acinar Rb expression was higher in chronic pancreatitis than in controls. Islets in chronic pancreatitis and controls showed intense TIMP-1 and TIMP-2 expression.

CONCLUSION

Apoptosis plays a significant role in acinar loss in chronic pancreatitis. Acinar Bcl-2 and islet Bax expression indicates complex AI control. Increased acinar Rb expression in chronic pancreatitis may differentially promote acinar loss. Fas ligand expression may be restricted to islet cell membranes through TIMP-1 expression and inhibit islet damage by promoting apoptosis of cytotoxic T lymphocytes.

A phase II trial of marimastat in advanced pancreatic cancer

Pancreatic cancer has a poor response to conventional chemotherapy and radiotherapy. Inhibition of matrix metalloproteinase activity involved in tumour invasion and metastases is a novel biological approach for cancer treatment. This multicentre phase II clinical trial assessed marimastat, an oral matrix metalloproteinase inhibitor, in patients with advanced pancreatic cancer. A total of 113 patients received marimastat for 28 days at 100 mg b.d. (n = 9), 25 mg o.d. (n = 90) or 10 mg b.d. (n = 14). Patients with a response to treatment could continue marimastat beyond 28 days. Of 113 patients, 90 (80%) completed the 28-day study and 83 (73%) continued treatment. The principal side effect was arthralgia in 14 (12%) patients at 28 days and 33 (29%) patients over the whole study. There were 31 patients (27%) who required dose modification. Of 76 patients with evaluable CA19-9 levels, 23 (30%) showed no increase or fall in CA19-9. Of 83 patients with radiologically assessable disease, 41 (49%) had stable disease. The median survival was 245 days for those with a stable or falling CA19-9 level 128 days in those with rising CA19-9. The overall survival was 3.8 months. 5.9 months for stage II, 4.7 months for stage III and 3 months for stage IV disease. Of 90 patients, 46 (51%) had stabilization or reduction in pain, mobility and analgesia scores. Further development and clinical evaluation of matrix metalloproteinase inhibitors for the treatment of pancreatic cancer is warranted.

Roles of norepinephrine and ATP in sympathetically evoked vasoconstriction in rat tail and hindlimb in vivo

In anesthetized rats, we characterized the contributions of norepinephrine (NE) and ATP to changes in tail and hindlimb (femoral) vascular resistances (TVR and FVR, respectively) evoked by three patterns of sympathetic stimulation: 1) couplets (2 impulses at 20 Hz), 2) short trains (20 impulses at 20 Hz), and 3) a natural irregular pattern previously recorded from a sympathetic fiber innervating the rat tail artery. All stimuli evoked greater changes in TVR than FVR. Judging from the effects of the alpha-adrenoceptor antagonist phentolamine, the purinergic receptor antagonist suramin, or alpha,beta-methylene ATP (which desensitizes P2X receptors), we propose that NE has a major role in the constriction evoked by the couplet, as well as by the short train and by the low- and high-frequency components of the natural pattern, but that considerable synergy occurred between the actions of ATP and NE. This contrasts with previous in vitro studies that indicated that ATP dominates vascular responses evoked by sympathetic stimulation with a few impulses at low frequency and that NE dominates responses to longer trains or at high frequencies.

Feasibility of planar virtual pathology: a new paradigm in volume-rendered CT colonography

Planar virtual pathology (PVP) is an isometric rendering method for examining the CT colonography dataset, which renders the colon in discrete colonic segments. Ten patients with 36 polyps were evaluated using traditional 2D axial, 2D multiplanar reformatted, and 3D endoluminal images as well as PVP. PVP displayed 13 of 17 (76%) polyps of >1 cm, whereas 11 of 17 (65%) were detected using traditional rendering methods. PVP may be a useful adjunct in detecting additional polyps at CT colonography.

CT colonography without cathartic preparation: feasibility study

PURPOSE

To evaluate methods for contrast material labeling of stool in the unprepared colon for computed tomographic (CT) colonography and to determine their sensitivity for polyp detection.

MATERIALS AND METHODS

Fifty-six patients with suspected or known polyps were assigned to five groups. Two to seven doses of 225 mL of dilute contrast material were orally administered during 24 or 48 hours. Transverse CT images were assessed for effectiveness of stool labeling. Colonoscopy was performed in all patients and was the standard. Two radiologists blinded to prior imaging and colonoscopic results assessed polyp detection.

RESULTS

For each group, average stool labeling scores and ranges were as follows: 24 hour two dose, 16% and 8%-21%; 24 hour five dose, 53% and 27%-66%; 48 hour four dose, 38% and 22%-48%; 48 hour six dose, 68% and 54%-77%; and 48 hour seven dose, 88% and 75%-98%. Sensitivity for the two radiologists for the identification of patients with polyps 1 cm or larger for each group was as follows: 24 hour two dose, 50% and 67%; 24 hour five dose, 100% and 100%; 48 hour four dose, 58% and 75%; 48 hour six dose, 56% and 67%; and 48 hour seven dose, 100% and 80%.

CONCLUSION

Ingestion of contrast material adequately labels stool for lesion identification; a 48-hour lead time and multiple doses of contrast material are required. Sensitivity for polyp detection in patients with adequate stool labeling approaches the sensitivity for polyp detection in prepared colons.

Haemobilia

BACKGROUND

This review aims to establish whether increased use of invasive procedures and the trend toward conservative management of major trauma has resulted in an increased incidence of haemobilia.

METHOD

A Medline (http://igm.nlm.nih.gov/)-based search of the English language literature from January 1996 to December 1999 inclusive was performed using the keywords haemobilia, hemobilia, haematobilia and hematobilia. The presentation, aetiology, investigation, management and outcome of 222 cases were reviewed.

RESULTS

Two-thirds of cases were iatrogenic while accidental trauma accounted for 5 per cent. Haemobilia may be major, constituting life-threatening haemorrhage, or minor; it may present many weeks after the initial injury. Diagnosis is most commonly confirmed by angiography. Management is aimed at stopping bleeding and relieving biliary obstruction; 43 per cent of cases were managed conservatively and 36 per cent were managed by transarterial embolization (TAE). Surgery was indicated when laparotomy was performed for other reasons and for failed TAE. The mortality rate was 5 per cent.

CONCLUSIONS

Although the incidence of iatrogenic haemobilia has risen considerably, the bleeding is often minor and can be managed conservatively. When more urgent intervention is required, TAE is usually the treatment of choice. There is no evidence that the conservative management of accidental liver trauma increases the risk of haemobilia.

A reverse genetic analysis of components of the Toll signaling pathway in Caenorhabditis elegans

BACKGROUND

Both animals and plants respond rapidly to pathogens by inducing the expression of defense-related genes. Whether such an inducible system of innate immunity is present in the model nematode Caenorhabditis elegans is currently an open question. Among conserved signaling pathways important for innate immunity, the Toll pathway is the best characterized. In Drosophila, this pathway also has an essential developmental role. C. elegans possesses structural homologs of components of this pathway, and this observation raises the possibility that a Toll pathway might also function in nematodes to trigger defense mechanisms or to control development.

RESULTS

We have generated and characterized deletion mutants for four genes supposed to function in a nematode Toll signaling pathway. These genes are tol-1, trf-1, pik-1, and ikb-1 and are homologous to the Drosophila melanogaster Toll, dTraf, pelle, and cactus genes, respectively. Of these four genes, only tol-1 is required for nematode development. None of them are important for the resistance of C. elegans to a number of pathogens. On the other hand, C. elegans is capable of distinguishing different bacterial species and has a tendency to avoid certain pathogens, including Serratia marcescens. The tol-1 mutants are defective in their avoidance of pathogenic S. marcescens, although other chemosensory behaviors are wild type.

CONCLUSIONS

In C. elegans, tol-1 is important for development and pathogen recognition, as is Toll in Drosophila, but remarkably for the latter rôle, it functions in the context of a behavioral mechanism that keeps worms away from potential danger.

Growth hormone in neural tissues of the chick embryo

Growth hormone (GH) gene expression predominantly occurs in the pituitary gland, although it also occurs in many extrapituitary sites, including the brain. The cellular location and ontogeny of neural GH production is, however, largely unknown. This has therefore been determined during chick embryogenesis. In chicks, the brain develops from the neural tube at embryonic day (ED) 3. At this age, the divisions of the brain (the telencephalon, diencephalon, mesencephalon, metencephalon and myelencephalon) have intense GH immunoreactivity (GH-IR) (detected by two polyclonal antibodies and a monoclonal antibody for chicken GH). The otic and optic vesicles were also strongly GH immunoreactive, as were the Vth (semi-lunar), VIIth (facial), VIIIth (acoustic) and IXth (glossopharyngeal) nerve ganglia. This GH-IR was specific for GH and was lost when the antibodies were preabsorbed with recombinant chicken GH. The widespread distribution of GH-IR in the neural tissues of ED 3 embryos was mirrored by the distribution of GH receptor (GHR) immunoreactivity, detected by an antibody raised against the chicken GHR. In ED 6/ED 7 embryos, the neural retina of the eye and the epithelial and lens fiber cells were intensely stained for GH-IR, as was Rathke's pouch and the wall of the diencephalon. In contrast, only a few scattered cells were immunoreactive in the surrounding mesoderm. At ED 14, the GH-IR in the brain was restricted to specific tissues and cells. For instance, immunoreactive cells were present in the molecular and pyramidal layers of the cerebral cortex, in the gray matter of the cerebellum, in the choroid plexus, and in the walls of the ventricles. In summary, GH- and GHR-like proteins are abundant in neural tissues of the chick during the first third of incubation, becoming discretely localized to specific tissues and cells during later incubation. The localization of GH and GHR in these tissues, prior to the ontogeny of plasma GH, suggests autocrine or paracrine roles for GH during early embryogenesis.