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I M Varndell

Publications and source records attributed to I M Varndell.

35 records · Page 2Linked to original sources
PubMed1985

Elevated levels of vasoactive intestinal peptide in the eye and urinary bladder of diabetic and prediabetic Chinese hamsters.

The eyes and urinary bladder of non-diabetic, prediabetic and diabetic Chinese hamsters were evaluated by radioimmunoassay and immunocytochemistry to determine the content and distribution of vasoactive intestinal peptide (VIP). The average concentration of VIP was increased in the eyes of all diabetic (pmol/g = 68%, pmol/organ = 50%) and prediabetic (pmol/g = 152%, pmol/organ = 115%) hamsters compared with age-matched non-diabetic animals. Immunocytochemistry showed that the elevation of VIP was primarily related to greater intensity of fluorescence of the nerve fibres in the vasculature of the choroid. The average content of VIP in the urinary bladder was greater in diabetic animals only on the basis of pmol/organ (135%) and in prediabetics on the basis of pmol/g (87%) compared with non-diabetic animals. Qualitative immunocytochemistry suggested that the elevated level of VIP was related to a larger distribution of nerve fibres in the urinary bladder of diabetic hamsters. The high level of VIP in the eyes and urinary bladder of diabetic and prediabetic hamsters is an interesting observation which should receive further study to determine whether it is an aetiological agent underlying the pathogenesis of ophthalmic complications and neurogenic bladder or the result of some pathological process which affects these organs.

3-Hydroxybutyric Acid↗
PubMed1985

Ultrastructural localization of chromogranin: a potential marker for the electron microscopical recognition of endocrine cell secretory granules.

Using a monoclonal antibody (LK2H10) directed against human chromogranin, we have been able to localize this soluble glycoprotein to the matrix of secretory granules from a wide variety of endocrine cells. In the gut, enterochromaffin, enteroglucagon, glucose-dependent insulinotropic peptide, gastrin, and neurotensin-containing cells exhibit chromogranin immunoreactivity. In our system, chromogranin-immunoreactive material was restricted to the halo of human pancreatic glucagon-containing secretory granules within A-cells. Chromogranin immunoreactivity was also localized to secretory granules in phaeochromocytomas, gastrinomas, medullary carcinomas of the thyroid and a carotid body tumour (chemodectoma). Chromogranin is proposed as a potential marker for the ultrastructural recognition of endocrine cell secretory granules.

Adolescent↗
PubMed1985

Localization of glucagon-like peptide (GLP) immunoreactants in human gut and pancreas using light and electron microscopic immunocytochemistry.

The distribution of peptide immunoreactivities predicted from the sequence of the human preproglucagon gene in enteroglucagon (EG; glicentin-like immunoreactant-containing) cells of the human gut and A cells of the pancreas has been determined by light and electron microscopic immunocytochemistry. At light microscopy the application of peroxidase-antiperoxidase and immunogold-silver staining methods has revealed that glucagon-like peptide (GLP-1 and GLP-2) immunoreactivities coexist with a glicentin-related immunodeterminant in human colorectal EG cells and pancreatic A cells. Using single and double colloidal gold probe electron immunocytochemistry, we have been able to show the coexistence of glicentin, GLP-1, and GLP-2 immunoreactivities within single EG cell secretory granules. No morphologic segregation of the proglucagon immunoreactants was observed in EG cells of the colonic mucosa. In pancreatic A cells we have localized GLP-1, GLP-2, and glucagon-[16-29] immunoreactivities solely to the electron-dense core of the secretory granules, whereas glicentin-related immunoreactivity was restricted to the electron-lucent halo. The results obtained in the present study have shown that the peptide immunoreactivities predicted from cDNA sequencing of the human preproglucagon gene are indeed expressed in colorectal EG and pancreatic A cells. The topographical segregation of immunoreactivities in the A cell secretory granule shows that antigenic determinants derived from the C-terminal portion of proglucagon are stored with glucagon in the core of the secretory granule.

Colon↗
PubMed1984

Visualisation of messenger RNA directing peptide synthesis by in situ hybridisation using a novel single-stranded cDNA probe. Potential for the investigation of gene expression and endocrine cell activity.

The neuropeptide tyrosine precursor (pre-pro-NPY) messenger RNA (mRNA) has been localised in formaldehyde-fixed human phaeochromocytoma tissue using a sensitive in situ hybridisation procedure and a novel single-stranded cDNA probe. The reaction product was revealed by avidin-biotin-peroxidase complex and streptavidin-gold complex with silver enhancement. This technique may be applied for the determination of biosynthetic activity of endocrine and neuronal cell bodies. This is largely due to its rapidity by comparison with conventional autoradiographic procedures, to the permanence of the reaction product and to the sensitivity of the visualisation steps.

Adrenal Gland Neoplasms↗
PubMed1984

Peptide YY (PYY) immunoreactivity is co-stored with glucagon-related immunoreactants in endocrine cells of the gut and pancreas.

In this study we report the localisation of PYY immunoreactivity in intestinal mucosa endocrine (EG) cells containing glucagon-related peptides and also in foetal pancreatic A cells of rat and man. Radioimmunoassay of human foetal pancreatic extracts revealed the presence of PYY immunoreactivity, the concentration of which declined with age (from 65.42 pmol/g at week 20 to 17.0 pmol at week 40; correlation coefficient = -0.893), in contrast to the amount of glucagon which remained statistically constant throughout the same foetal period. The identity of this PYY immunoreactive material with the original 36 amino acid porcine peptide has been shown by high pressure liquid chromatography (HPLC).

Adult↗
PubMed1984

Neuropeptide tyrosine (NPY) immunoreactivity in norepinephrine-containing cells and nerves of the mammalian adrenal gland.

The application of immunocytochemistry at both light and electron microscopic levels has revealed neuropeptide tyrosine (NPY)-immunoreactive material to be localized to norepinephrine-containing endocrine cells in the adrenal medulla and also to varicose nerve fibers penetrating the adrenal cortex of several mammalian species, including horse, cat, rat, guinea pig and mouse. Correlative electron microscopic immunostaining has revealed that enkephalin and NPY immunoreactivities are co-localized to the same norepinephrine-containing secretory granules. High concentrations of NPY have been extracted from the mouse adrenal gland (1243.7 +/- 122.8 pmol NPY/g wet tissue; mean +/- SE). Chromatographic analysis has shown the extracted material to correspond with pure natural NPY.

Adrenal Medulla↗
PubMed1983

Intracellular topography of immunoreactive gastrin demonstrated using electron immunocytochemistry.

Gastrin (G)-producing cells from the mammalian gastric antrum have been investigated using computer-assisted morphometry and a novel double colloidal gold-labeled-immunoglobulin electron immunocytochemical procedure. Correlation analysis of human antral G-cells indicates (p less than 0.001) that a single population of granules exists with small (160 nm) electron-dense and large (240 nm) electron-lucent forms representing the extremes. Non-crossreacting region-specific antisera have been used to visualize G-17 and G-34 (progastrin) to the small electron-dense granules and G-17 to the other intermediate forms. From the results we propose a topographic segregation of immunoreactive gastrins within 2 apparently distinct granule subclasses and suggest that this may represent the pathway of granule maturation.

Adult↗
PubMed1983

Immunocytochemical evidence for the presence of gamma 1-MSH-like immunoreactivity in pituitary corticotrophs and ACTH-producing tumours.

The presence of gamma 1-MSH has been demonstrated in bovine neuro-intermediate lobe by biochemical methods, thus suggesting that this peptide is cleaved from the cryptic region of pro-opiocortin. In this study we report the localisation of gamma 1-MSH-like immunoreactivity in the adenohypophysis of man, ox, pig, dog and guinea-pig using immunocytochemical procedures at both light and electron microscope levels. Antisera recognising the C-terminal Arg-Phe-amide and the C-terminal penta-peptide-amide of gamma 1-MSH have been used throughout this study. The immunostaining was found in all endocrine cells of the pars intermedia (where present) and in scattered cells of the pars distalis identified as corticotrophs. No gamma 1-MSH immunoreactivity was detected in rat adenohypophysis. In addition, 7 ACTH-producing tumours (1 pituitary adenoma and 6 ectopic) were investigated and shown to contain gamma 1-MSH immunoreactive cells.

ACTH Syndrome, Ectopic↗
PubMed1983

Double immunogold staining method for the simultaneous ultrastructural localization of regulatory peptides.

Recent studies have suggested that the morphological characteristics of secretory granules contained within endocrine cells and nerves may be determined largely by their chemical composition. The use of the immunogold staining (IGS) method, which is based on the adsorption of colloidal gold to immunoglobulins, has been used in our laboratory to demonstrate a wide range of intracellular antigens at both the light and electron microscope levels. In this study we have applied a modification of the IGS method for the simultaneous detection of two separate antigens in a single tissue section, using a variety of region-specific antisera to different peptides. Peptide antisera were raised in rabbits or in guinea pigs and these were applied simultaneously or sequentially to grid-mounted ultrathin tissue sections. Antigenic sites were visualized at the electron microscope level using antisera raised in goats, adsorbed to gold particles of 12, 20, or 40 nm. Using this technique we have attempted to investigate the coexistence of multiple antigens in single tissue sections, in particular in single granules; the topographic distribution of molecular forms within one single granule or granule population; the heterogeneity of peptidergic neurons and also the heterogeneity of peptide content in morphologically similar granules. The double immunogold staining procedures described here have proved to be extremely effective for the simultaneous ultrastructural localization of two antigens (peptide-peptide; peptide-propeptide) on a single tissue section. The further development of this technique may provide useful information on neuroendocrine cell dynamics in normal and diseased states.

Animals↗
PubMed1983

Neurotensin-like immunoreactivity in a subpopulation of noradrenaline-containing cells of the cat adrenal gland.

RIA of cat adrenal tissue extracts revealed a neurotensin-like immunoreactive material concentrated within the medulla of the gland (mean +/- SEM neurotensin concentration, 15.2 +/- 3.6 pmol/g whole gland; 47.9 +/- 18.4 pmol/g microdissected medulla). This immunoreactive material was found to elute in the region of synthetic neurotensin, thus indicating a similarity to the tridecapeptide originally isolated from bovine hypothalamus. Using immunocytochemical procedures at both light and ultrastructural levels, a neurotensin-like immunoreactive material was localized to a subpopulation of noradrenaline-containing cells quite distinct from the previously described enkephalin-immunoreactive chromaffin cells. Correlative ultrastructural observations have identified three morphologically distinct types of chromaffin cells in the medulla, indicating a marked heterogeneity within the noradrenaline cell population. The finding of neurotensin-like immunoreactivity in noradrenaline-containing cells of the cat adrenal medulla provides further evidence in support of the postulated existence of heterogeneous subpopulations of noradrenaline-containing cells and suggests a possible functional interrelationship between neurotensin and catecholamine.

Adrenal Glands↗
PubMed1983

Immunocytochemical localisation of katacalcin, a calcium-lowering hormone cleaved from the human calcitonin precursor.

Katacalcin is a newly discovered calcium-lowering hormone predicted from the nucleotide sequence of a cloned cDNA derived from human calcitonin mRNA. The aim of the study was to localise katacalcin by immunocytochemistry at both light and electron microscope levels. Antisera to synthetic katacalcin and calcitonin were used to investigate 8 cases of medullary thyroid carcinoma and 6 normal human thyroids (3 adult and 3 fetal). We have been able to demonstrate the co-localisation of these peptides in normal and neoplastic C-cells in all cases studied. Our results suggest that peptide sequences predicted by recombinant DNA technology can be localised using immunocytochemistry and that the combination of these techniques may have applications in diagnostic pathology.

Calcitonin↗
PubMed1982

Electron immunocytochemical localization of enkephalin-like material in catecholamine-containing cells of the carotid body, the adrenal medulla, and in pheochromocytomas of man and other mammals.

Enkephalin-like immunoreactivity has been localized to electron-dense secretory granules of cat and piglet carotid bodies and adrenal medullae, horse adrenal medulla, and also to human adrenal medulla and pheochromocytomas using a gold-labeled antibody technique performed at the electron microscopic level. The same granules were also demonstrated to exhibit dopamine-beta-hydroxylase-like immunoreactivity, which suggests a granular colocalization of amines and peptides in catecholamine-storing cells.

Adrenal Gland Neoplasms↗
PubMedDate not supplied

Radioimmunoassay of alpha rat atrial natriuretic peptide.

Specific antibodies to alpha 1-28 atrial natriuretic peptide have been raised and used for radioimmunoassay of tissue extracts and for light and electron microscopic immunocytochemistry. The radioimmunoassay has been used to quantitate ANP-immunoreactivity in normal rat heart and hypothalamus and immunocytochemistry to demonstrate its localisation in specific tissue structures. Gel chromatography and high pressure liquid chromatography confirm that the majority of ANP-like immunoreactivity in the atria exists as high molecular weight forms. Rat hypothalamus contains immunoreactive ANP; the concentration per gram of tissue being 2-4 thousand fold less than that of the cardiac atria. The supraoptic region of the hypothalamus did not have a significantly different concentration of ANP-like immunoreactivity from the hypothalamic region as a whole. Immunocytochemical staining with ANP antiserum revealed the cardiac ANP-immunoreactivity to be concentrated around the nuclear poles within the cytoplasm of atrial muscle cells. Electron microscopic study of atrial cells stained with the immunogold technique confirmed the localisation of the ANP immunoreactivity to electron-dense secretory granules. The highest density of regional immunoreactive staining was in the subepicardial area, the lowest in the interatrial septum. The finding that the highest quantities of ANP immunoreactivity occur in areas subjected to the greatest distensional forces supports the hypothesis that atrial stretch is a stimulus to the release of this peptide from cells.

Animals↗
PubMedDate not supplied

Immunogold staining procedure for the localisation of regulatory peptides.

The use of protein A- and IgG-conjugated colloidal gold staining methods for the immuno-localisation of peptide hormones and neurotransmitters at light- and electron microscope level are described and discussed. Bright-field and dark-ground illumination modes have been used to visualise the gold-labelled antigenic sites at the light microscope level. Immunogold staining procedures at the ultrastructural level using region-specific antisera have been adopted to localise specific molecular forms of peptides including gastrin (G17 and G34), glucagon and pro-glucagon, insulin and pro-insulin, in normal tissue and in tumours of the gastroenteropancreatic system. Similar methods have been used to demonstrate the heterogeneity of p-type nerves in the enteric nervous system. Vasoactive intestinal polypeptide (VIP) has been localised to granular sites (mean +/- S.D. granule diameter = 98 +/- 19 nm) in nerve terminals of the enteric plexuses and in tumour cells of diarrhoeogenic VIP-producing neoplasias (mean +/- S.D. granule diameter = 126 +/- 37 nm) using immunogold procedures applied to ultraviolet-cured ultrathin sections. Co-localisation of amines and peptides in carotid body type I cells and in chromaffin cells of normal adrenal medulla and phaeochromocytomas has also been demonstrated. Advantages of the immunogold procedures over alternative immunocytochemical techniques are discussed.

Animals↗
PubMedDate not supplied

Co-localization of neuropeptide tyrosine (NPY) and its C-terminal flanking peptide (C-PON).

Neuropeptide tyrosine (NPY) is one of the most abundant and widespread peptides in the mammalian nervous system. Recent isolation and sequencing of the DNA encoding NPY has predicted the existence of a 97 amino acid precursor peptide. Proteolytic processing of this precursor could yield three separate peptide products, an N-terminal signal peptide, neuropeptide tyrosine and a 30 amino acid C-terminal flanking peptide (C-PON). Here, we present evidence that the predicted C-flanking peptide of NPY is widely distributed in both the central and peripheral nervous systems of several mammalian species including man, and has an identical distribution to NPY. It was also demonstrated, using correlative light microscopic immunostaining on serial sections and double electron microscopic immunocytochemistry, that C-PON and NPY immunoreactivities are co-localized in neuronal cell bodies of the brain cortex, sympathetic ganglion cells, norepinephrine-containing granules of the adrenal medulla and in human pheochromocytoma tumor cells.

Adrenal Gland Neoplasms↗
PubMedDate not supplied

Ultrastructure and electron immunocytochemistry of insulin-producing B-cell tumors from transgenic mice: comparison with counterpart human tumors.

This paper reports on an ultrastructural and electron-microscopic immunocytochemical study of pancreatic B cells from normal mice, pancreatic B cells and derivative tumors from transgenic mice, and tissue from human pancreatic B-cell tumors. In normal and neoplastic B cells from both species, typical immature and mature beta-granules (with spherical cores of variable density) were observed, whereas typical beta-granules with a crystalloid core were only present in human B cells (normal and tumor). A small number of atypical granules were found in distinct neoplastic cells which contained no typical beta-granules. The atypical granules were smaller (100-200 nm diameter) than typical beta-granules (250-450 nm diameter) seen in other cells. Immunoreactivity for proinsulin was localized only to immature granules, whereas insulin and C-peptide immunoreactivities were demonstrated in atypical, immature, and mature granules. In transgenic mouse and human B-cell tumors, insulin immunoreactivity was consistently weaker than the immunostaining for C-peptide. An intragranular, topographic segregation of immunoreactive C-peptide was observed in a population of transgenic tumor cells. Our results showed similarities in antigenic distribution and only slight differences in morphology between human and mouse B cells. Therefore, the transgenic mouse system may prove to be an effective model for studying mammalian B-cell tumorigenesis.

Adenoma, Islet Cell↗