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J F Morris

Publications and source records attributed to J F Morris.

At least 91 records · Page 5Linked to original sources
PubMed1994

Human islet amyloid polypeptide accumulates at similar sites in islets of transgenic mice and humans.

The cellular mechanisms responsible for conversion of islet amyloid polypeptide (IAPP) into insoluble amyloid deposits in non-insulin-dependent diabetes mellitus (NIDDM) are not clear. Overexpression of IAPP and the amino acid sequence of human IAPP (hIAPP) have both been implicated. To examine factors involved in amyloid formation, transgenic mice expressing the hIAPP or rat IAPP (rIAPP) gene were generated. These mice had elevated plasma IAPP concentrations, and they were normoglycemic and normoinsulinemic. No amyloid deposits were detected by light microscopy. To examine the ultrastructure of islets, pancreatic tissue was studied from hIAPP and rIAPP transgenic mice and from age-matched control mice by immunoelectron microscopy. IAPP was immunolocalized in beta-cell secretory granules of all mice, and the COOH- and NH2-terminal flanking peptides of hIAPP were localized in beta-cell granules of hIAPP mice. Accumulations of nonfibrillar perivascular IAPP-immunoreactive material were found between capillaries and beta-cells in hIAPP transgenic mice but not in rIAPP transgenic or control mice. Similar nonfibrillar masses were identified in islets of an NIDDM patient. Secondary lysosomes in beta-cells and macrophages of hIAPP transgenic mice showed dense labeling for IAPP. We suggest that hIAPP is degraded more slowly than rIAPP or mouse IAPP by beta-cell lysosomes. Accumulations of IAPP in islet perivascular spaces may represent the early stages of islet amyloid formation.

Aged↗
PubMed1993

Physical and functional interaction between WT1 and p53 proteins.

WT1 is a tumor-suppressor gene expressed in the developing kidney, whose inactivation leads to the development of Wilms tumor, a pediatric kidney cancer. WT1 encodes a transcription factor which binds to the EGR1 consensus sequence, mediating transcriptional repression. We now demonstrate that p53, the product of a tumor-suppressor gene with ubiquitous expression, physically associates with WT1 in transfected cells. The interaction between WT1 and p53 modulates their ability to transactivate their respective targets. In the absence of p53, WT1 acts as a potent transcriptional activator of the early growth response gene 1 (EGR1) site, rather than a transcriptional repressor. In contrast, WT1 exerts a cooperative effect on p53, enhancing its ability to transactivate the muscle creatine kinase promoter.

Animals↗
PubMed1992

Antigen presentation for T cell interleukin-2 secretion is a late acquisition of neonatal B cells.

The ability of B lymphocytes to process and present antigen to helper T cells is essential to initiate T cell-B cell interactions in humoral immune responses. Here we describe the developmental acquisition of the antigen-presenting function of B cells as measured by the ability of B cells to stimulate a T cell hybrid to interleukin (IL)-2 secretion. Neonatal splenic B cells are not adult-like in their ability to process and present the model protein antigen pigeon cytochrome (Pc), which enters the B cell through fluid-phase pinocytosis, until 21 to 28 days of life. The ability of neonatal B cells to process and present antigen which enters the cell bound to surface Ig is not adult-like until 28 days of age. When neonatal B cells acquire antigen-presenting cell (APC) function, surface IgM facilitates antigen processing. The delayed acquisition of APC function cannot be accounted for solely by a deficiency in major histocompatibility complex MHC class II, ICAM-1, or LFA-1 as neonatal B cells express adult levels of these molecules by 7-14 days after birth. Moreover, the ability of neonatal B cells to present a peptide fragment of Pc which does not require processing is adult like by day 14. Furthermore, neonatal B cells are capable of binding, internalizing and degrading radiolabeled antigen, suggesting a more subtle level of regulation. In contrast to neonatal B cells, immature B cells in the adult bone marrow and adult B cells undergoing antigen-driven differentiation to memory B cells, as defined by the loss of the J11D marker, are competent to process and present antigen resulting in T cell IL-2 secretion. Thus, developing B cell subpopulations in the adult and in the neonate can be distinguished. Only neonatal B cells are deficient in their ability to stimulate T cells to IL-2 production.

Animals↗
PubMed1992

Tunicamycin, puromycin and brefeldin A influence the subcellular distribution of neuropeptides in hypothalamic magnocellular neurones of rat.

Magnocellular neurones in the supraoptic nuclei of normal Long Evans and homozygous Brattleboro rats were examined electron-microscopically after intracisternal injections of tunicamycin, puromycin, or brefeldin A. Moderate (50 micrograms) or high (200 micrograms) doses of tunicamycin caused the formation of electron-dense filamentous accretions in the endoplasmic reticulum (ER) cisterns of vasopressin neurones, but only the high dose of tunicamycin also caused accretions to form in the ER of some oxytocin neurones. Immunogold labelling of ultrathin sections from tunicamycin-treated rats revealed that, in about 5% of vasopressin neurones, the accretions could be immunogold-labelled for vasopressin and its associated neurophysin. However, in the majority of vasopressin neurones, the sections required trypsinisation before immunolabelling of the accretions could be detected. Small accretions in the ER of oxytocin neurones did not label for oxytocin or its neurophysin without prior trypsinisation, whereas larger accretions in other oxytocin cells could be labelled without prior trypsin treatment. Administration of puromycin resulted in the formation of small ER accretions in both vasopressin and oxytocin neurones. These accretions were immunolabelled with antisera, respectively, to vasopressin and oxytocin, but neurophysin-immunoreactivity was in most cases absent and was not revealed by treatment with trypsin, suggesting that neurophysin-immunoreactive epitopes were absent from truncated peptides forming the accretions. Brefeldin A caused dilatation of ER cisterns and disruption of the Golgi apparatus in both oxytocin and vasopressin neurones, but did not cause accretions to form in the ER.

Animals↗
PubMed1992

V3 loop region of the HIV-1 gp120 envelope protein is essential for virus infectivity.

The mechanism by which HIV-1 mediates cell fusion and penetrates target cells, subsequent to receptor (CD4) binding, is not well understood. However, neutralizing antibodies, which recognize the principal neutralizing determinants of the gp120 envelope protein (the V3 loop region, residues 296 to 331), have been shown to effectively block cell fusion and virus infectivity independent of the initial gp120-CD4 binding. To investigate the role of the V3 loop in an HIV infection, a series of site-specific mutations were introduced into the HIV-1 envelope gene. Specifically, each residue (312 to 315) in the strongly conserved tetrapeptide sequence, GPGR, which is positioned in the center of the V3 loop domain was individually altered. The processing, transport, and CD4 binding properties of the mutant envelope proteins were comparable to those of the wild-type protein, however, none of the mutants were able to form syncytia in the HeLa-T4 assay. Molecular HIV-1 clones containing mutations altering the G312, G314, or R315 residues produced noninfectious virions, whereas a clone with a P313A mutation was found to be infectious. These results demonstrate that certain V3 loop mutations can be lethal and clearly indicate that this region of the HIV-1 gp120 protein is essential for virus infectivity.

Amino Acid Sequence↗
PubMed1992

Immuno-electron microscopic evidence for two different types of partial somatic repair of the mutant Brattleboro vasopressin gene.

In homozygous Brattleboro rats a frame-shift mutation in the vasopressin gene prevents secretion of vasopressin by magnocellular neurosecretory neurons and thus causes diabetes insipidus. Whereas most "vasopressin" neurons in Brattleboro homozygotes apparently lack vasopressin and its associated neurophysin and glycopeptide, some isolated cells overcome the mutation and "revert" to producing readily detectable amounts of vasopressin. We describe here two morphologically and immunocytochemically distinct subsets of such "revertant" cells. One subset contain, in their rough endoplasmic reticulum cisterns, electron-dense aggregates immunoreactive for vasopressin, for parts of oxytocin-neurophysin, and for CP14 (a peptide with a sequence deduced from the mutated precursor), but not for vasopressin-associated glycopeptide ("glycopeptide") or vasopressin-neurophysin. In Brattleboro heterozygotes, which have one mutant and one normal copy of the vasopressin gene, morphologically similar revertant cells exist; the aggregates in the rough endoplasmic reticulum of these cells do not immuno-label for CP14, but the cells do produce 160-nm neurosecretory granules immunoreactive for vasopressin, vasopressin-neurophysin and glycopeptide. In Brattleboro homozygotes, the second, more abundant subset of neurons which recover vasopressin immunoreactivity also express vasopressin-associated glycopeptide and CP14 but not oxytocin-neurophysin; both glycopeptide and CP14 are restricted to the rough endoplasmic reticulum but do not form aggregates. We conclude that two different somatic repairs of the Brattleboro mutation can occur. We propose that, in aggregate-containing neurons, exons B and C have been exchanged between the vasopressin and oxytocin genes; glycopeptide-immunoreactive neurons have either undergone mismatch repair or exchanged exon B.

Animals↗
PubMed1992

Basal metabolic rate in adults with growth hormone deficiency and in patients with acromegaly: relationship with lean body mass, plasma insulin level and leucocyte sodium pump activity.

1. The relationship of lean body mass, plasma insulin concentration and leucocyte active sodium transport with basal metabolic rate was investigated in 24 adults with growth hormone deficiency before and after treatment with recombinant human growth hormone and in 10 patients with untreated acromegaly. 2. Based on total-body potassium determined by whole-body 40K counting, patients with acromegaly had increased lean body mass, whereas lack of growth hormone was associated with decreased lean body mass. 3. By indirect calorimetry, patients with acromegaly had increased basal metabolic rates and patients with growth hormone deficiency had decreased values when expressed as percentages of values predicted from the WHO/FAO/UNU equations. Basal metabolic rate expressed in terms of lean body mass was similar in acromegaly and growth hormone deficiency, but was higher than normal in both patient groups. 4. The leucocyte ouabain-sensitive sodium efflux rate constant was decreased in both patients with acromegaly and patients with growth hormone deficiency, and there was no correlation with basal energy expenditure, fasting plasma insulin level or serum growth hormone level. 5. There was no increase in the sodium efflux rate constant in patients with growth hormone deficiency after 1 month on treatment with recombinant human growth hormone. 6. Apparent differences in basal metabolic rate in growth hormone deficiency and acromegaly are due to changes in lean body mass. Both adults with growth hormone deficiency and patients with acromegaly have increased energy expenditure, probably owing to changes in fuel metabolism which are not reflected in the leucocyte sodium pump activity.

Acromegaly↗
PubMed1992

Defective alloantigen-presenting capacity of 'Langerhans cell histiocytosis cells'.

The functional activity of skin cells derived from an infant who died of multisystem Langerhans cell histiocytosis (LCH) was examined. Involved and non-involved skin was obtained at postmortem examination within three hours of death; normal epidermal Langerhans cells and 'LCH cells' were separated by means of dispase digestion. The functional activity of different populations of CD1a positive cells was assessed using the conventional six day allogeneic mixed cell reaction. Compared with Langerhans cells from a healthy control, LCH cells showed minimal functional activity. However, Langerhans cells from non-involved skin showed normal and Langerhans cells overlying involved skin showed augmented functional activity. These findings suggest that LCH is a disease in which abnormal Langerhans cells accumulate and/or proliferate in various tissues but it does not affect the entire Langerhans cell population.

Antigens, CD↗
PubMed1991

Transcriptional repression mediated by the WT1 Wilms tumor gene product.

The wt1 gene, a putative tumor suppressor gene located at the Wilms tumor (WT) locus on chromosome 11p13, encodes a zinc finger-containing protein that binds to the same DNA sequence as EGR-1, a mitogen-inducible immediate-early gene product that activates transcription. The transcriptional regulatory potential of WT1 has not been demonstrated. In transient transfection assays, the WT1 protein functioned as a repressor of transcription when bound to the EGR-1 site. The repression function was mapped to the glutamine- and proline-rich NH2-terminus of WT1; fusion of this domain to the zinc finger region of EGR-1 converted EGR-1 into a transcriptional repressor.

Amino Acid Sequence↗
PubMed1991

Widespread release of peptides in the central nervous system: quantitation of tannic acid-captured exocytoses.

Tannic acid methods have been applied to capture the exocytosis of peptide-containing granules from peptidergic neurons. The captured exocytoses have been quantitated to assess the proportion and amount of peptide released at different parts of the neuronal membrane. Examination of hypothalamic synaptic boutons shows that only about one-half of the peptidergic vesicles is exocytosed into the synaptic cleft and also that exocytosis also occurs from undilated peptidergic axons. Study of the magnocellular neurosecretory system reveals that all parts of their extensive terminal arborization appear to be equally capable to exocytose peptide. Only about one-half of their peptide is released from their nerve endings, which about the capillaries. The remainder is released much deeper in the lobules of secretory tissue where its principal target(s) could be the pituicytes and/or neurosecretory axons. Dendrites of magnocellular neurons are also capable of releasing peptide by exocytosis and dendrites could release sufficient oxytocin and vasopressin to account for the peptide known to be released into the hypothalamus. We conclude that peptidergic neurons release substantial amounts of peptides from all of their processes and that this must be taken into account when considering what functions those peptides might serve.

Animals↗
PubMed1991

Membrane routing during exocytosis and endocytosis in neuroendocrine neurones and endocrine cells: use of colloidal gold particles and immunocytochemical discrimination of membrane compartments.

The hypothesis that the retrieval of membranes of neurohypophysial neurosecretory granules (NSG) and small electron-lucent microvesicles occurs by different routes was tested by incubating neurohypophysial neurosecretosomes with colloidal gold particles of various sizes. Neurosecretosomes derived from normal Long Evans rats and incubated in media of normal ionic composition endocytosed a few small (less than 25 nm) gold particles into 40-50 nm electron-lucent microvesicles. After depolarisation, more small gold particles were found in microvesicles, and small and large (greater than 25 nm) gold particles in vacuoles. Oxytocin-containing neurosecretosomes derived from Brattleboro rats, which contain 160 nm-diameter NSG, endocytosed gold particles in a pattern indistinguishable from that of neurosecretosomes from Long Evans rats. However, neurosecretosomes derived from defective vasopressin neurones of Brattleboro rats, which contain microvesicles, small vacuoles, and a few 100 nm dense-cored vesicles, but no 160 nm NSG, endocytosed only small colloidal gold particles. Early after depolarisation the gold particles were present only in microvesicles, but later some could be found in vacuoles and lysosome-like structures. Immunogold cytochemistry using a polyclonal antiserum raised against microvesicle-rich neurosecretosomes derived from Brattleboro rats labelled microvesicles in the posterior pituitary strongly, NSG weakly, and vacuoles to a variable extent. These data together indicate that, after exocytosis, the membranes of NSG are recaptured as large vacuoles. Microvesicles are exocytosed and endocytosed separately.

Animals↗
PubMed1991

Localisation of islet amyloid polypeptide and its carboxy terminal flanking peptide in islets of diabetic man and monkey.

Islet amyloid polypeptide is a normal constituent of islet Beta cells and is derived from a larger precursor by removal of flanking peptides at the carboxy (C) and amino (N) terminals. The role of these flanking peptides in the formation of amyloid in Type 2 (non-insulin-dependent) diabetes mellitus and in insulinomas is unknown. The C-terminal flanking peptide of islet amyloid polypeptide was localised by immunocytochemistry in human and monkey pancreatic islets from Type 2 diabetic and non-diabetic individuals by use of specific polyclonal antisera. Immunoreactivity for the C-terminal peptide was found in insulin-containing cells in both diabetic and non-diabetic tissue: no antibody binding was detected in islet amyloid of Type 2 diabetic man or of monkeys although a positive reaction occurred with antisera for islet amyloid polypeptide. The C-terminal peptide was localised by immunogold electron microscopy in the insulin granules in both diabetic and non-diabetic individuals but, unlike islet amyloid polypeptide, was not detected in lysosomes. The absence of immunoreactivity for the C-terminal peptide in amyloid suggests that incomplete cleavage of this flanking peptide from islet amyloid polypeptide is not a factor in the formation of islet amyloid.

Adult↗