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A Andrew

Publications and source records attributed to A Andrew.

At least 19 recordsLinked to original sources
PubMed2000

Nickel-induced plasminogen activator inhibitor-1 expression inhibits the fibrinolytic activity of human airway epithelial cells.

One cause of debilitating pulmonary fibrosis is inhalation of insoluble metals. Human epidemiological and animal studies have associated inhalation of nickel dusts with increased incidence of pulmonary fibrosis. However, specific mechanisms for nickel-induced pulmonary fibrosis have yet to be elucidated. The current studies examine the hypothesis that particulate nickel promotes pulmonary fibrosis by inhibiting the fibrinolytic cascade. Since the urokinase-type plasminogen activator (uPA) initiates this cascade, this hypothesis was tested by investigating the effects of noncytotoxic levels of nickel subsulfide on the balance of uPA expression relative to expression of its inhibitor, PAI-1, in cultured human bronchial epithelial cells (BEAS-2B). Exposure to the metal decreased secreted uPA protein levels and activity without affecting uPA mRNA levels. In contrast, these same exposures stimulated transcription of PAI-1, causing prolonged increases in both mRNA and protein levels. Despite partial recovery of uPA protein levels, uPA activity remained depressed for more than 48 h after exposure to nickel due to the continued increase in PAI-1 expression. These data indicate that particulate nickel inhibits the fibrinolytic cascade by increasing the ratio of plasminogen inhibitor to activator. Sustained loss of uPA activity may contribute to nickel-induced pulmonary fibrosis in exposed populations.

Bronchi↗
PubMed1999

Authors' reply

Explore the source record for details and available documents.

Journal Article↗
PubMed1999

Gut endocrine cells in birds: an overview, with particular reference to the chemistry of gut peptides and the distribution, ontogeny, embryonic origin and differentiation of the endocrine cells.

This review deals with gut endocrine cells in birds. It focuses on both morphological and developmental aspects of these cells, which were included members of Pearse's APUD series. They comprise many cell types, which, in birds as in mammals, produce serotonin and a range of regulatory peptides. The chemical structure of most avian gut peptides has been established. These peptides and their functions are outlined here. The types and distribution of avian gut endocrine cells are detailed and compared with the situation in mammals. In birds, ultrastructural work has been limited to certain types of gut endocrine cell and not as widely applied as in mammals. However, immunocytochemistry has found widespread application in studies on birds: the hatching chick and also the adult chicken and certain other species such as the quail and duck have been studied. Gut endocrine cells showing immunoreactivity for the following peptides/serotonin have been identified: somatostatin, pancreatic polypeptide (PP), peptide YY, glucagon, secretin, vasoactive intestinal peptide, gastrin, cholecystokinin (CCK), neurotensin, motilin, gastrin-releasing peptide, substance P, enkephalin and serotonin. The colocalization of different peptides (including chromogranins) and of peptides and serotonin in the same gut endocrine cells is reviewed: notable amongst such associations are glucagon with PP and gastrin/CCK with neurotensin in the same cells. On morphological grounds cells have been identified as endocrine in avian gut from at least 9 days of incubation. Immunocytochemical studies show the majority of the various types first to appear between 12 to 14 days of incubation, with substantial numbers being recorded from 17 days onwards. Experimental studies on chicken and quail embryos have determined the embryonic origin of gut endocrine cells: evidence is unequivocal that such cells arise from the endoderm, not the neural crest, other ectoderm or the mesoderm. Studies on avian embryos have also contributed to our knowledge of mechanisms controlling the differentiation of gut endocrine cells: evidence shows that gut mesenchyme plays an important role in provoking (or inhibiting) the development of gut endocrine cells and there are indications that the endocrine cell pattern in gut is established early and that an axially-derived factor may be important in this process. The kinds of genetic mechanism possibly involved are mentioned but full elucidation of the processes concerned is awaited. A better understanding of the formation of endocrine tumours of the gut should result from the findings.

APUD Cells↗
PubMed1998

The origin of gut and pancreatic neuroendocrine (APUD) cells--the last word?

The evidence that gut and pancreatic endocrine cells are not derivatives of the neural crest is overwhelming: yet this conclusion is still not universally accepted. In this editorial attention is drawn to the body of experimental evidence which points conclusively to gut and pancreatic endocrine cells arising from endoderm, not the neural crest, the neurectoderm or neuroendocrine programmed epiblast.

APUD Cells↗
PubMed1998

Effects of tri-iodothyronine (T3), insulin, insulin-like growth factor I (IGF-I) and transforming growth factor beta1 (TGFbeta1) on the proportion of insulin cells in cultured embryonic chick pancreas.

With a view to ultimately identifying factors involved in the development of pancreatic insulin cells, we have cultured dorsal pancreatic buds from 5-day chick embryos on a basement membrane matrix (Matrigel) in a serum-free medium supplemented with selected factors. The endodermal components of the buds were freed of almost all the mesenchyme so as to eradicate as much as possible of this source of some such factors. In 7-day cultures, insulin and glucagon cells were demonstrated immunocytochemically; numbers of insulin cells were expressed as a percentage of insulin plus glucagon cell counts. Our standard medium contained insulin. Addition of tri-iodothyronine to this medium did not increase the proportion of insulin cells, but in combination with raised concentrations of glucose and essential amino acids it improved somewhat the marked increase previously recorded for these nutrient conditions. Omission of insulin from the standard medium greatly reduced the proportion of these cells; substitution of insulin by insulin-like growth factor I increased the proportion considerably more than did insulin. To test for an overall effect of growth factors, explants were cultured in standard medium on Matrigel containing reduced amounts of growth factors: the proportion of insulin cells proved to be increased over that reached on normal Matrigel. The suspicion that transforming growth factor beta1, a component of Matrigel, might act to reduce the proportion of insulin cells was tested and found to be correct. It is suggested that the different factors studied here may affect either or both of proliferation and determination in the differentiation pathway of insulin vis-à-vis glucagon cells.

Animals↗
PubMed1995

Evidence for oestrogenic regulation of heat shock protein expression in human endometrium and steroid-responsive cell lines.

Gene amplification with target-specific primers (reverse-transcription polymerase chain reaction (RT-PCR)) was used to monitor the relative expression of oestrogen and progesterone receptor mRNAs alongside the mRNAs for heat shock proteins HSP 90 alpha, HSP 90 beta and HSP 70a in normal samples of human endometrial tissue over the whole menstrual cycle and in short-term cultures of steroid-responsive (T47-D) and unresponsive (HRT-18) cell lines exposed to oestradiol and progesterone over a 24-h incubation period. In endometrium, oestrogen and progesterone receptors followed the expected patterns of expression at the protein level during the menstrual cycle and also showed a positive correlation of expression with each other throughout (r = 0.514). Of the HSPs only HSP 90 alpha expression correlated positively with oestrogen receptor (r = 0.687), while HSP 70a expression, which peaked in the late secretory stage, displayed a significantly inverse correlation with HSP 90 beta expression (r = -0.526). All p values < 0.05. In T47-D cell cultures, oestrogen receptor expression was stimulated transiently by oestradiol (10(-7) mol/l) and more persistently by progesterone (10(-7) mol/l). Progesterone receptor expression was depressed by progesterone and weakly stimulated by oestradiol. HSP 70a and HSP 90 alpha expression were stimulated by oestradiol. Progesterone generally depressed HSP 90 alpha expression and simultaneous addition of both oestradiol and progesterone to the culture medium was antagonistic to HSP 90 alpha expression. No clear effect of agonist addition on HSP mRNA expression was apparent in the HRT-18 cultures. A possible mechanism for observed oestrogenic effects on HSP expression is put forward.

Actins↗
PubMed1994

Distribution of serotonin-immunoreactive gut endocrine cells in chicks at hatching. Examination of possible co-localisation with peptides reveals unexpected cross-reactivity of substance P antiserum with serotonin.

Serotonin-immunoreactive, i.e. enterochromaffin (EC) cells were found to be widely distributed in the intestine of the newly hatched chick but sparse in the stomach, and being particularly abundant in the duodenum, upper ileum and rectum. Although in birds, as in mammals, EC cells are most abundant in the intestine, in the stomach they are far sparser than in mammals. Comparison of adjacent sections immunostained for serotonin and a peptide provided no evidence that EC cells in the hatching chick contain motilin or substance P, and that at least the great majority of bombesin-immunoreactive cells contain no serotonin: it is apparent that the mammalian pattern of distribution of peptides in EC cells does not occur in the chick, at least at hatching. Cross reaction of an antiserum to substance P with serotonin was discovered, suggesting the need for a review of existing evidence for co-localisation of this peptide with serotonin.

Animals↗
PubMed1994

Failure of insulin cells to develop in cultured embryonic chick pancreas: a model system for the detection of factors supporting insulin cell differentiation.

Little being known about factors necessary for insulin cell differentiation, we tested the chance observation that these cells were virtually absent from collagen gel cultures of embryonic avian pancreas in which the other pancreatic endocrine cells were numerous. Five-day dorsal buds stripped of their enveloping mesenchyme were embedded in gel and overlaid by a defined medium containing serum, then cultured for 7 days. Immunocytochemical evaluation showed a very low proportion of insulin cells. Substitution of the gel by a polyamino acid coating slightly increased the proportion. In an attempt to test for ability of insulin cell formation to recover, we transferred explants first cultured in collagen gel to polyamino-acid-coated dishes for a further 7 days. No improvement resulted. In controls grown for 14 days on a polyamino acid coating, insulin cells disappeared completely. We conclude that collagen gel does not support survival and differentiation of chick embryonic insulin cells and that the medium used is lacking in some essential factor(s). Determination of their identity should prove possible by exploitation of this model.

Amino Acids↗
PubMed1994

Observer variation in the assessment of chronic gastritis according to the Sydney system.

The main aims of the Sydney system for the classification of gastritis are to improve uniformity in histopathological reporting and to provide a flexible matrix of rules for grading the histological features. We sought to determine the level of interobserver agreement between pathologists in the application of the Sydney system. Three histopathologists independently examined H & E, alcian blue/PAS and modified Giemsa stained sections of two antral and two corpus gastric biopsies from 69 consecutive dyspeptic patients. After elimination of five unsuitable cases, each observer graded chronic inflammation, polymorph activity, atrophy, intestinal metaplasia and Helicobacter pylori density in the antrum and corpus on a 0-3 scale according to the Sydney system criteria. The pairwise agreement on final diagnosis and the overall and conditional agreement on histological grades were examined by kappa statistics. Agreement on the final diagnosis ranged from 83-94% with kappa values of 0.699 ('good') to 0.887 ('excellent'). Conditional probability of agreement on a diagnosis of H. pylori positive gastritis was 99%, but wider disagreements were apparent in the recognition of H. pylori negative gastritis, reactive gastritis and even normal biopsies. Overall agreement for grade ranged from 70% for antral atrophy to 94% for intestinal metaplasia in the corpus with 'moderate' or 'good' kappa values. We conclude that the diagnostic and grading criteria described in the Sydney system can be applied consistently by histopathologists. The findings underline its potential usefulness in routine practice.

Biopsy↗
PubMed1994

PCR in situ hybridisation detection of HPV 16 in fixed CaSki and fixed SiHa cell lines.

AIMS: To investigate the feasibility of using fixed cells with the polymerase chain reaction (PCR) in situ hybridisation and to investigate possible reasons for reaction failure. METHODS: Fixed SiHa and CaSki cells were used in an experimental model of PCR in situ hybridisation for the detection of low and intermediate copy number viral infection in fixed cells. RESULTS: PCR in situ hybridisation was able to detect one to two copies of human papillomavirus (HPV) 16 in SiHa cells, using small fragment amplicons (120 base pairs), confirming the high detection sensitivity and flexibility of the technique. Problems were encountered with localisation of PCR amplified product in CaSki cells (200-300 copies of HPV 16 per cell) owing to diffusion of product post amplification. Overall, 40% of reactions were successful, which confirms the current unreliability of the technique. Within cell preparations, about 50% of cells contained amplified product. CONCLUSION: PCR in situ hybridisation represents the marriage of two revolutionary molecular pathological techniques. However, it is currently unreliable, with reaction failure common. Standardised, dedicated equipment is urgently required if the technique is to achieve universal acceptance. In the future, the technique may be used to detect chromosomal translocations in human tumours and to study cellular gene expression.

Base Sequence↗
PubMed1993

Subinvolution of the uteroplacental arteries: an immunohistochemical study.

Subinvolution of uteroplacental arteries is a well-recognized cause of hemorrhage in the postpartum period. Although the physiological changes in these arteries during pregnancy are well documented, the sequence of events in normal involution is largely unknown. A recent immunohistochemical study has raised the possibility of an abnormal interaction between maternal uterine cells and fetal trophoblast in subinvolution. An indirect immunoperoxidase technique was used to compare deposition of complement components and immunoglobulin in subinvoluted and normally involuted uteroplacental arteries in 25 cases of postpartum hemorrhage. Deposits of C1q, C3d, C4, and C9 were detected within the walls of normally involuted vessels, whereas deposition of C1q, C3d, and C4 was absent in subinvoluted vessels; C9 was detected only focally. Deposition of immunoglobulins G, A, and M mirrored those described for complement components. The results suggest that immunological factors are necessary for the process of normal involution of uteroplacental arteries and are deficient in subinvoluted vessels.

Arteries↗
PubMed1993

Origin and differentiation of gut endocrine cells.

The epithelium of the digestive tract contains endocrine cells which produce serotonin and an array of regulatory peptides. It is now irrefutably established that gut endocrine cells are not of neural crest nor even of neurectodermal origin. Furthermore, the proposal that they might originate from neuroendocrine-programmed epiblast has been retused by recent evidence that they share the endodermal stem cell pool with the other epithelial cells of the gut. Based on the available evidence, a working hypothesis for the differentiation of gut endocrine cells has been developed. It is proposed that initially the developing gut acquires an underlying tendency to differentiate into intestine: the endoderm has the potential to form a wide range of endocrine cell types. A little later, some influence operative over the length of the presumptive gut imposes a regionally specific pattern on the tract. This process concerns morphogenesis and pre-selection of the range and proportions of the endocrine cell types. Thereafter, the mesenchyme feeds to the endoderm confirmatory signals reinforcing this pre-selected regional pattern of endocrine cells. Once the different endocrine cell types have started to differentiate, their maturation is effected by circulating factors which include glucocorticoid hormone: this process is mediated by the mesenchyme. Other factors concerned at various stages of gut endocrine cell differentiation could be other hormones, growth factors and or components of extracellular matrix: such factors are still untested in this context.

Animals↗
PubMed1992

Can a non-gut mesenchyme support differentiation of gut endocrine cells?

This experiment was designed to find out if endoderm lacks an intrinsic ability to give rise to gut endocrine cells, and, if not, whether differentiation of endocrine cells can be supported by mesenchyme from a source outside the digestive tract. Heterospecific combinations of proventricular endoderm and flank mesenchyme from chick and quail embryos at 3.25-4 days of incubation were grown as chorio-allantoic grafts to a final incubation age of 21 days. Re-associated proventricular endoderm and mesenchyme served as controls. The proventricular endoderm induced some smooth muscle in the flank mesenchyme but the latter did not support as advanced glandular morphogenesis as did proventricular mesenchyme. Nevertheless, endocrine cells differentiated in experimental as in control grafts and at similar frequencies. The various types were distinguished immunocytochemically by their contained peptides; the range of types found was specific for the proventriculus. Hence it is concluded not only that the particular non-gut mesenchyme used does support differentiation of gut endocrine cells, but also that the determination of the progenitors of endocrine cells, and the selection of the range of types destined to differentiate in a particular part of the digestive tract under normal circumstances, occurs early in development--before 3.25 days of incubation in the case of the proventriculus.

Animals↗
PubMed1990

Intestinal mesenchyme provokes differentiation of intestinal endocrine cells in gizzard endoderm.

The gizzard (muscular stomach) of chicks is deficient in endocrine cells at hatching. It has previously been shown that proventricular types and proportions of endocrine cells can be induced in gizzard endoderm under the influence of proventricular (glandular stomach) mesenchyme. In order to test its capacity to form nongastric endocrine cell types, gizzard endoderm of 3.75- to 5-day chick embryos was combined with mesenchyme from the small intestine of 3.5- to 4-day quail embryos. The combinations were grown as chorio-allantoic grafts until they attained an incubation age comparable to that of hatching chicks. Controls comprised reassociated endoderm and mesenchyme of chick gizzard and of quail intestine. In the experimental grafts, morphogenesis was predominantly intestinal but some grafts showed gizzard-like features, particularly if the endoderm had been provided by older donors. All intestinal endocrine cell types, including those also found in the normal proventriculus (serotonin-, glucagon-, pancreatic polypeptide-, neurotensin- and somatostatin-immunoreactive cells) differentiated in experimental grafts, some even where morphogenesis was gizzard-like. Hence progenitors of not only gastric, but also intestinal, endocrine cells are indeed present in gizzard endoderm. The possibility that gizzard mesenchyme is inhibitory to endocrine cell differentiation is mooted. Motilin- and secretin-immunoreactive cells, which are characteristic of the intestine but not of the proventriculus of chicks at hatching, were respectively sparse or absent when the endoderm was derived from older donors. Thus the ability of gizzard endoderm to differentiate into nongastric endocrine cell types declines before its capacity to form gastric types. The unexpected appearance of gastrin-releasing peptide (GRP)-immunoreactive cells, a proventricular type not found in normal chick intestine, suggests that the intestinal mesenchyme, at least in this instance, was exercising a permissive role.

Animals↗
PubMed1989

Differentiation of endocrine cells in chick allantoic epithelium combined with pancreatic mesenchyme.

Allantoic endoderm of 3-day chick embryos was combined with pancreatic mesenchyme of 5-day embryos and cultured as chorio-allantoic grafts for a total of 14 days. Recombinations of endoderm and mesenchyme of the pancreas and of the allantois served as controls. The usual types of endocrine cells differentiated in the pancreatic controls, none in the allantoic controls. In experimental grafts simple columnar epithelium with goblet cells and a sucrase-positive brush border developed; a few insulin cells and endocrine cells typical of the intestine differentiated. Hence allantoic endoderm has endocrine potentiality not realised in vivo, where its own mesenchyme may be inhibitory.

Allantois↗
PubMed1988

Differentiation of intestinal and ectopic endocrine cells from avian gastric and pancreatic endoderm.

The chorio-allantoic grafts analysed were prepared from avian proventricular endoderm combined with its own or pancreatic mesenchyme and from re-associated pancreatic layers. Intestine developed ectopically in some grafts: in these, endocrine cells typical of intestine differentiated irrespective of the source of the endoderm or mesenchyme. In addition, endocrine cells inappropriate for the surrounding histology were detected in small numbers in grafts of all categories. Clearly it is not the mesenchyme that is responsible but perhaps some aspect of the procedure, which may relate to stressful stimuli thought to provoke intestinal metaplasia. The differentiation of inappropriate cells aids in understanding the occurrence of ectopic endocrine tumours.

Animals↗