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Biomedical subjects

K G Bensch

Publications and source records attributed to K G Bensch.

At least 37 records · Page 2Linked to original sources
PubMed1985

Synthesis of extracellular matrix glycoproteins by cultured microvascular endothelial cells isolated from the dermis of neonatal and adult skin.

We examined the synthesis of extracellular matrix macromolecules by human microvascular endothelial cells isolated from the dermis of neonatal (foreskin) and adult (abdominal) skin. Electron microscopy showed that both cell types produced an extracellular matrix that was strictly localized to the subendothelial space. The subendothelial matrices were initially deposited as a single discontinuous layer of filamentous, electron-dense material that progressively became multilayered. Biosynthetic studies indicated that 2-4% of the newly synthesized protein was deposited in the subendothelial matrices by both cell types. Approximately 15-20% of the radiolabeled protein was secreted into the culture medium, and the remainder was confined to the cellular compartment. Biochemical and immunochemical analyses demonstrated the extracellular secretion of type IV collagen, laminin, fibronectin, and thrombospondin by the newborn and adult cells. Whereas type IV collagen was the predominant constituent of the matrix, fibronectin was secreted into the medium, with only small amounts being deposited in the matrix. Thrombospondin was a major constituent of the matrix produced by the newborn foreskin cells but was virtually absent in the matrix elaborated by the adult cells. However, both cell types did release comparable amounts of thrombospondin into their medium. Immunoperoxidase staining for type IV collagen revealed a fibrillar network in the subendothelial matrices produced by both adult and neonatal cells. In contrast, thrombospondin, which was detected only in the matrix of newborn cells, exhibited a spotty and granular staining pattern. The results indicate that the extracellular matrices synthesized by cultured human microvascular endothelial cells isolated from anatomically distinct sites and different stages of development and age are similar in ultrastructure but differ in their macromolecular composition.

Aging↗
PubMed1985

Gastrin releasing peptide in human neuroendocrine tumours.

Neuroendocrine tumours of the lung and gut are known to possess bombesin-like immunoreactivity. The recent observation that gastrin releasing peptide (GRP), a 27 amino acid peptide isolated from the porcine intestine, may be the mammalian analogue of bombesin led us to look for this peptide in a variety of human neoplasms. Formalin-fixed tissues from 85 tumours were examined by the immunoperoxidase technique, using specific antisera to the GRP molecule (1-27) and the GRP fragment (1-16). Intense cytoplasmic GRP immunoreactivity was seen in thyroid medullary carcinomas (3/3), carcinoids of lung, pancreas, and intestine (22/36), and paragangliomas (2/3). Less frequent staining was present in pulmonary small cell (oat cell) carcinomas (1/8) and pituitary adenomas (1/6). Complete absence of immunoreactivity was observed in three phaeochromocytomas, five Merkel cell tumours, six neuroblastomas and 15 non-neuroendocrine tumours. Normal neuroendocrine cells of the thyroid (C-cells) and bronchial mucosa (Kulchitsky cells) exhibited GRP immunoreactivity; nerve fibres from all sites failed to demonstrate staining for GRP. In each positive case, the pattern of staining for GRP (1-27) and GRP (1-16) was identical, although the GRP (1-16) immunostaining was weaker. These findings indicate that bombesin immunoreactivity in human neuroendocrine cells and tumours is attributable to GRP-like molecules and that GRP is a useful marker of neuroendocrine differentiation in many tumours.

Adenoma↗
PubMed1985

Age-related changes in turnover and concentration of a subset of thorax polypeptides from Drosophila melanogaster.

Six polypeptides from Drosophila melanogaster were analyzed by two-dimensional polyacrylamide gel electrophoresis for age-related changes in protein turnover and protein concentration. The protein samples, from thoraces of 6 day (young), 26 day (middle) and 45 day (old) flies, were compared using autoradiography for [35S]methionine labeled proteins and silverstaining for unlabeled preparations. The combination of these two techniques has permitted determination of the relative turnover rate as well as the steady-state concentration of these proteins as a function of age. The autoradiographs reveal that all of the analyzed proteins decrease in turnover rate whereas the absolute protein concentrations, as determined from the silverstained gels, show a decrease for three proteins, no change for two, and an increase in one protein with age. These findings show a remarkable quantitative heterogeneity of ageing changes in proteins, but absence of alterations in the fidelity of the translation of these polypeptides.

Aging↗
PubMed1985

Comparison of the effect of two and six week exposure to 80% and 100% oxygen on the lung of the newborn mouse: a quantitative SEM and TEM correlative study.

Prolonged inhalation of 80% oxygen, in contrast to 100% oxygen, has generally been assumed not to lead to significant pulmonary impairment. Two and six week old C57BL mice were systematically assessed by transmission and scanning electron microscopy for structural changes in the lung caused by inhalation of 80% and 100% oxygen from the first day of life, and the injury was quantitated morphometrically. Six weeks of continuous inhalation of 80% oxygen resulted in diffuse fibrosis of the gas exchanging parts of the lung superimposed on which were, in the 100% oxygen exposed mice, foci of coarse scarring. Lowering the inspired oxygen concentration from 100% to 80% appeared to reduce the mucosal injury more than the interstitial fibrotic response. This suggests that the most persistent alteration caused by chronic supplemental oxygen exposure below 80% will be interstitial fibrosis.

Animals↗
PubMed1985

The role of ascorbic acid in senile cataract.

The reductone ascorbic acid, present in the crystalline lens in concentrations higher than those of glucose, is capable of undergoing nonenzymatic "browning" in the presence of lenticular proteins. We studied the nonenzymatic browning with ascorbate in model systems employing bovine serum albumin and lens crystallins. When bovine serum albumin, alpha-crystallin, or gamma-crystallin was incubated with [14C]ascorbic acid, the formation of yellow and then brown condensation products appeared to correlate with increasing protein-associated radioactivity. The fluorescence spectrum of these products was similar to that of homogenates of human cataractous lenses. We suggest that the nonenzymatic reaction of lens crystallins with ascorbic acid may contribute, at least in part, to the color changes of aging lenses and to the physical lenticular deterioration leading to senile cataract. High dietary intake of ascorbic acid did not affect the fluorescence spectrum of murine lenses; thus, we assume that the speed and extent of the lenticular browning reactions must depend on a deterioration of other factors of the multicomponent antioxidant system of the eye.

Anaerobiosis↗
PubMed1985

Gastrin releasing peptide is a selective mitogen for small cell lung carcinoma in vitro.

Human small cell lung carcinoma (SCLC) cells have been shown to contain significant levels of a bombesin-immunoreactive peptide. The 27-amino acid peptide, gastrin releasing peptide (GRP), has recently been shown to be responsible for the bombesin-like immunoreactivity found in SCLC cells. Among four lung cancer cell lines examined in vitro, GRP exhibited mitogenic activity for two SCLC subtypes, but not for a squamous carcinoma or adenocarcinoma lung cell line. The mitogenicity of the GRP molecule has been isolated to the carboxyterminal fragment, designated GRP 14-27, which is in part homologous to bombesin. The aminoterminal fragment, GRP 1-16, is no homologous to bombesin and exhibits no mitogenic activity. Thus, GRP may be an important growth regulating or autocrine factor in human SCLC.

Carcinoma, Small Cell↗
PubMed1984

Complete inhibition of transferrin recycling by monensin in K562 cells.

Monensin blocks human transferrin recycling in a dose-dependent and reversible manner in K562 cells, reaching 100% inhibition at a noncytocidal dose of 10(-5) M, whereas transferrin recycling is virtually unaffected by noncytocidal doses of chloroquine. The intracellular pathway of human transferrin in K562 cells, both in the presence and absence of 10(-5) M monensin, was localized by indirect immunofluorescence. Monensin blocks transferrin recycling by causing internalized ligand to accumulate in the perinuclear region of the cell. The effect of 10(-5) M monensin on human transferrin kinetics was quantitatively measured by radioimmunoassay and showed a positive correlation with immunofluorescent studies. Immunoelectron microscopic localization of human transferrin as it cycles through K562 cells reveals the appearance of perinuclear transferrin-positive multivesicular bodies within 3 min of internalization, with subsequent exocytic delivery of the ligand to the cell surface via transferrin-staining vesicles arising from these perinuclear structures within 5 min of internalization. Inhibition of ligand recycling with 10(-5) M monensin causes dilated transferrin-positive multivesicular bodies to accumulate within the cell with no evidence of recycling vesicles. A coordinated interaction between multivesicular bodies and the Golgi apparatus appears to be involved in the recycling of transferrin in K562 cells. Cell-surface-binding sites for transferrin were reduced by 50% with 10(-5) M monensin treatment; however, this effect was not attenuated by 80% protein synthesis inhibition with cycloheximide, supporting the idea that the transferrin receptor is also recycled through the Golgi.

Cell Line↗
PubMed1984

Basal lamina formation by cultured microvascular endothelial cells.

The production of a basal lamina by microvascular endothelial cells (MEC) cultured on various substrata was examined. MEC were isolated from human dermis and plated on plastic dishes coated with fibronectin, or cell-free extracellular matrices elaborated by fibroblasts, smooth muscle cells, corneal endothelial cells, or PF HR9 endodermal cells. Examination of cultures by electron microscopy at selected intervals after plating revealed that on most substrates the MEC produced an extracellular matrix at the basal surface that was discontinuous, multilayered, and polymorphous. Immunocytochemical studies demonstrated that the MEC synthesize and deposit both type IV collagen and laminin into the subendothelial matrix. When cultured on matrices produced by the PF HR9 endodermal cells MEC deposit a subendothelial matrix that was present as a uniform sheet which usually exhibited lamina rara- and lamina densa-like regions. The results indicate that under the appropriate conditions, human MEC elaborate a basal lamina-like matrix that is ultrastructurally similar to basal lamina formed in vivo, which suggests that this experimental system may be a useful model for studies of basal lamina formation and metabolism.

Animals↗
PubMed1984

Gastrin-releasing peptide immunoreactivity in intestinal carcinoids.

Human neuroendocrine tumors are known to demonstrate immunoreactivity to the amphibian peptide bombesin. The recent observation that gastrin-releasing peptide (GRP), a 27 amino acid peptide first isolated from porcine intestine, may be the mammalian analog of bombesin led us to look for this peptide in intestinal carcinoid tumors. Formalin-fixed tissues from 20 of these tumors were examined by the immunoperoxidase technic, using specific antisera to the GRP molecule (1-27) and the GRP fragment (1-16). Intense diffuse cytoplasmic immunoreactivity was observed in carcinoids from the small intestine (7/10), appendix (4/5), and colon (1/5). In each positive case, the pattern of staining for GRP (1-16) and GRP (1-27) was identical. These findings indicate that bombesin-like immunoreactivity in human intestinal carcinoid tumors is attributable to GRP-like molecules and that GRP is a useful marker for neuroendocrine differentiation.

Adult↗
PubMed1984

Acromegaly and Zollinger-Ellison syndrome secondary to an islet cell tumor: characterization and quantification of plasma and tumor human growth hormone-releasing factor.

A young woman with acromegaly and Zollinger-Ellison syndrome associated with a GH-releasing factor (GRF)- and gastrin-secreting metastatic islet cell carcinoma was studied by means of specific antisera which recognize various regions of the GRF molecule. Using specific immunohistochemical techniques, the tumor cells were shown to contain GRF, gastrin, and gastrin-releasing peptide, but not GH. During a 4-h period, plasma GRF levels averaged 5.6 +/- 1.4 ng/ml (+/- SD), while GH levels averaged 148 +/- 71 ng/ml. GH secretion was pulsatile and increased after TRH administration. GRF RIAs may be useful in establishing the diagnosis of acromegaly secondary to the ectopic secretion of GRF.

Acromegaly↗
PubMed1984

Growth-hormone-releasing factor immunoreactivity in human endocrine tumors.

Seventy-three human tumors and adjacent nonneoplastic tissues were analyzed immunohistochemically for the presence of growth-hormone-releasing factor (GRF). Four of 9 pancreatic endocrine tumors, 2 of 3 appendiceal carcinoids, and 1 of 5 cecal carcinoids were immunoreactive for GRF. One of the GRF-containing pancreatic tumors was associated with acromegaly. Histologically, the growth patterns of these tumors were variable, and the distribution of immunoreactive cells was patchy and irregular. There were no normal cells that contained GRF. These results indicate that GRF production by human tumors is more common than previously thought, although clinical acromegaly may not be apparent in patients who harbor such neoplasms.

Acromegaly↗
PubMed1984

Gastrin-releasing peptide, a mammalian analog of bombesin, is present in human neuroendocrine lung tumors.

Several reports have indicated that the amphibian peptide bombesin is present in oat-cell carcinoma of the human lung. The recent observation that gastrin-releasing peptide (GRP), a 27-amino acid peptide isolated from porcine intestine, may be the mammalian analog of bombesin led the authors to look for this peptide in human pulmonary tumors. Examination of 36 human lung tumors (8 carcinoids, 8 oat-cell carcinomas, and 20 non-oat-cell carcinomas) by immunohistochemistry and radioimmunoassay demonstrated the presence of high, although variable, levels of GRP in neuroendocrine tumors, and not in other histologic types. These findings indicate that bombesin immunoreactivity in human lung tumors should be attributed to GRP or GRP-like molecules and that GRP may be a useful marker of neuroendocrine differentiation.

Animals↗
PubMed1983

Bicyclic ring formation is not necessary for the (auto)oxidation of ascorbic acid.

The oxidation rates of ascorbic acid and several of its derivatives have been examined in order to delineate the role of bicyclic ring formation in the autooxidation of ascorbic acid. The compounds evaluated and their respective oxidation rates at pH 7.4 are in uM X min-1: ascorbate, 0.70; 5 methyl 3,4 dihydroxytetrone, 0.65; D-iso ascorbate, 0.73; and ascorbyl palmitate, 0.64. These data do not support the contention that bicyclic ring formation is required for the oxidation of ascorbic acid because both 5 methyl 3,4 dihydroxytetrone and ascorbyl palmitate, neither of which can form the bicyclic intermediate, have oxidation rates similar to that of ascorbate. Furthermore, evidence is presented which suggests that ionization of the oxygen on C3 of ascorbic acid is an obligatory initial step in ascorbic acid autooxidation.

Ascorbic Acid↗
PubMed1983

Factors controlling the in vitro growth pattern of human microvascular endothelial cells.

Monolayer cultures of endothelial cells of human dermal microvascular origin were exposed to a variety of culture conditions and in vitro differentiation of the cells assessed by light and electron microscopic examination. Restoration of a cytologic and fine structural appearance which resembled most closely that present in vivo was possible by raising the intracellular cAMP level. These cells formed junctional complexes seen in uncontracted microvessels and specialized attachment sites at their basal cell membrane, contained a complex network of bundled micro- and intermediate filaments and numerous Weibel-Palade bodies and accumulated electron-opaque deposits between the cells and the culture dish surface.

Capillaries↗
PubMed1983

Effect of amino acids, peptides and related compounds on the autooxidation of ascorbic acid.

The autooxidation rate of ascorbic acid (AA) at 10(-5) M under aerobic conditions at pH 7.4 was found to be 1.16 mumol/min/l. A number of compounds at low concentrations were found to inhibit this oxidation rate. These were in order of effectiveness: EDTA (10(-6) M) greater than Mercaptoethanol greater than aminoethyl cysteine, oxidized glutathione greater than glycylglycylhistidine greater than glycylhistidyllysine greater than 3-methyl histidine approximately histidine greater than histamine greater than hypertensin greater than cysteic acid greater than imidazole greater than glutamine greater than hydroxyproline, and lysine. All other amino acids and peptides examined had little or no effect on the autooxidation rate of ascorbic acid. Ascorbate solutions, treated with Chelex-100 (divalent chelating resin) or containing low concentrations of EDTA (10(-7) M) did not show a significant reduction of the rate of autooxidation. Of particular interest was the finding that 3-methyl histidine had a significant inhibitory effect on ascorbic acid oxidation whereas 1-methyl histidine had no effect. These data suggest that ascorbic acid forms complexes with certain compounds and that this interaction stabilizes ascorbic acid against auto-oxidation.

Amino Acids↗
PubMed1983

Conformational changes of serum albumin induced by ascorbic acid.

Bovine serum albumin (BSA) was found to inhibit the autooxidation of ascorbic acid (AA) at physiologic pH. The spontaneous oxidation rate of AA at 1 X 10(-5) M was 0.87 mumol X L-1 min-1. In the presence of 1 microM BSA, the rate is 15% of the spontaneous rate (0.13 mumol X L-1 X min-1). The u.v. difference spectrum of the AA:BSA complex reveals a decrease in absorbance at 204 nm. These data provide evidence that AA binds to BSA and induces a conformational change in the BSA molecule.

Animals↗