Showing papers by "Luis M. Montuenga published in 1999"

Adrenomedullin binding protein in the plasma of multiple species: characterization by radioligand blotting.

Abstract: Frequently, peptide hormones circulate in plasma associated with specific binding proteins that modify the clearance and biochemical activities of the peptide. Our experimental approach was to use 125I-ligand blotting procedures to probe for the presence of specific adrenomedullin (AM) binding proteins (AMBPs). Plasma proteins from chick, calf, dog, goat, guinea pig, human, mouse, pig, rabbit and sheep blood were separated electrophoretically in 10% nonreducing SDS-polyacrylamide gels and transferred to nitrocellulose. Nonspecific binding of tracer was blocked on the nitrocellulose with a hydrolyzed casein matrix. Blots were probed with synthetic human 125I-AM. Autoradiogram scanning of blots revealed a mixture of 140- and/or 120- kD protein complexes that bound 125I-AM in all species tested. Binding of the ligand was specific as judged by a linear competitive displacement of the tracer binding from human, bovine and pig plasma AMBP bands with increasing concentrations of nonlabelled AM in the binding buf...

Expression of adrenomedullin and proadrenomedullin n-terminal 20 peptide in human and rat prostate

Abstract: SUMMARY Adrenomedullin (AM) and proadrenomedullin N-terminal 20 peptide (PAMP) are two recently discovered hypotensive peptides translated from the same message transcript (preproAM mRNA). In this article we report the presence of AM, PAMP, and their mRNA in human and rat prostate and of AM receptor mRNA in rat prostate. PreproAM mRNA was found in the epithelium of normal human and rat prostate glands by in situ hybridization. In humans, it was mainly expressed in the basal cells. In rat, its expression was higher in the ducts than in the acini of all the prostate lobes. Immunocytochemistry identified a similar distribution pattern for AM compared with its mRNA but showed different locations for AM and PAMP immunoreactivity. The former was widespread in the epithelia, whereas the latter was almost exclusively found in neuroendocrine cells. In rat, Western blot analysis confirmed the presence of high levels of AM peptide in the ventral lobe and of its precursor in the ventral and dorsolateral lobes. Immunoreactivity for serotonin, chromogranin A, PAMP, and AM defined four subpopulations of prostate neuroendocrine-like cells in rat, a cell type that has not been previously described. (J Histochem Cytochem 47:1167‐1177, 1999)

Underlying disease stress augments plasma and tissue adrenomedullin (AM) responses to endotoxin: colocalized increases in AM and inducible nitric oxide synthase within pancreatic islets.

Abstract: Rapid onset metabolic impairments accompany the initiation of the acute phase response to many disease stresses, whereas more chronic metabolic perturbations may prolong the recovery period. In the present experiment the application of a mild endotoxin challenge [lipopolysaccharide (LPS)] alone or additive to a chronic subclinical parasitic infection (Sarcocystis cruzi; LPS 1 PI) in calves was used as a model to investigate and define a dynamic axis coordinated between adrenomedullin (AM) and nitric oxide in response to immune challenge. Plasma AM and NO2/NO3 concentration responses after LPS (0.45 mg/kg, iv) were rapid in onset and of higher magnitude and longer duration in PI 1 LPS calves than in those challenged with LPS alone. The post-LPS increase in plasma insulin was significantly greater in PI 1 LPS than in LPS; following refeeding of calves, insulin secretion was most blunted in PI 1 LPS calves, consistent with the inhibitory effects of NO and AM on insulin secretion. A more chronic response to the immune challenge (organ specific) was in evidence in tissues harvested 24 h after LPS challenge. Where lung and liver showed no immunostaining for inducible nitric oxide (iNOS), iNOS immunostaining was present in the pancreas, localized to islets only. The percentages of iNOS-immunopositive cells in islets were 1.7%, 21%, 6.7%, and 24% for control (C; saline infused), PI, LPS, and PI 1 LPS calves, respectively. AM immunostaining was not evident in the liver and was present, but not differentially affected by treatment, in airway epithelium in the lung. The number of islet cells with positive immunostaining for AM was increased in LPS, PI, and PI 1 LPS calves. The percentages of AM-immunopositive cells in islets were 8%, 27%, 20%, and 33% for C, PI, LPS, and PI 1 LPS, respectively. Immunostaining for AM and iNOS was colocalized with cells positive for pancreatic polypeptide. By triple label confocal fluorescence immunocytochemistry, colocalization of intense AM and iNOS immunostaining was confirmed in peripheral islet cells. A weaker, more diffuse iNOS signal was also apparent in insulin-containing cells in PI 1 LPS. We conclude that chronic low level infection potentiates the severity of metabolic perturbations that arise with additive sudden onset immune challenge, as can occur with bacterial toxins. These metabolic disturbances are reflected in and possibly mediated by early onset increases in plasma tumor necrosis factor-a, insulin, and AM and up-regulated iNOS activity. These acute complications rapidly progress into a more chronic state characterized by diminished insulin response to feeding stimulus and colocalized increases in pancreatic islet AM and iNOS. The pancreatic responses in AM and iNOS may play a major role in mediating prolonged disturbances in nutrient use by tissues through their influences on temporal patterns of pancreatic hormone secretion during chronic illness. (Endocrinology 140: 5402‐5411, 1999)

The Role of Adrenomedullin as a Growth Regulatory Peptide in the Normal and Malignant Setting

Abstract: Adrenomedullin (AM) is a recently discovered pluripotent peptide initially isolated from a human adrenal gland tumor (pheochromocytoma). Adrenomedullin has been shown to have an ancient origin with immunoreactive species found in mammals, birds, reptiles, amphibians, fish, and echinoderms (starfish). Given its highly conserved evolutionary expression, AM is thought to play a critical role in species survival. This peptide has been shown to mediate a variety of physiological functions, of which its involvement in growth regulation will be the central focus of this paper. In the following text, we will review the cited literature in this area and include our own observations regarding AM expression in carcinogenesis, embryogenesis, and wound repair. Adrenomedullin will be shown to induce both growth promotion or growth suppression depending on the target cell examined and the surrounding nutritional environment in which the analysis was done. Its implied role as a mitogen, angiogenic factor, and apoptosis survival factor will be critiqued and evaluated relative to its importance in the cell proliferation process. Finally, we will review the antimicrobial effect AM has on several human pathogens ( E s cherichia coli and Candida albicans) and demonstrate its participation in the host immune response system as a first line defense peptide.

Pigment Epithelium-Derived Factor (PEDF) in the Retina

Abstract: Pigment epithelium-derived factor (PEDF) was first described as a secreted product of human fetal retinal pigment epithelial (RPE) cells in culture with a potent neuronal differentiating activity on human retinoblastoma Y-79 cells.1 It was reported that PEDF at nanomolar concentrations induces a morphological differentiation of Y-79 cells, characterized by the elongation of neurite-like processes and the expression of neuronal markers, e.g., neuron-specific enolase and the 200-kDa neurofilament subunit.2 It was shown later that PEDF can also induce the differentiation of cells from another human retinoblastoma, the Weri cells.3 While its role in vivo on retina cells is not known yet, its origin and these activities suggest that PEDF may play a role as a neurotrophic factor for the retina. In this regard, evidence of its effects on neurons from the CNS and PNS is accumulating rapidly and supports the notion that PEDF is a multipotent neurotrophic factor that acts upon various types of neurons and from different species. For example, it promotes the survival of rat cerebellar granule cell (CGC) neurons in culture,4 including protection against glutamate neurotoxicity5 and against both natural and induced apoptosis in vitro;6 it promotes survival and differentiation of developing avian and murine spinal motor neurons.7 Given the important biological activities of PEDF, it is of interest to investigate its mechanism of action on the retina. Therefore, the overall objective of this review will be to discuss the biochemistry of PEDF in the context of a potential use as a relevant neurotrophic factor for the retina.