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Biomedical subjects

G Schultz

Publications and source records attributed to G Schultz.

At least 181 records · Page 10Linked to original sources
PubMed1992

Transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and protein levels in human placentas from early, mid, and late gestation.

OBJECTIVE: Human placenta expresses receptors for transforming growth factor-alpha and epidermal growth factor throughout pregnancy. Experiments were performed to determine whether epidermal growth factor or transforming growth factor-alpha might be synthesized by placental cells and act through an autocrine mechanism to influence functioning of placental cells in vivo. STUDY DESIGN: Human placentas from early, mid, and late gestations were analyzed for transforming growth factor-alpha and epidermal growth factor messenger ribonucleic acid and proteins. Polyadenylic acid-positive ribonucleic acid was isolated from placentas from 10, 11, 13, 21, 32, 38, 39, and 40 weeks of gestation and analyzed by Northern analysis for hybridization with complementary deoxyribonucleic acid probes specific for epidermal growth factor or transforming growth factor-alpha. Levels of immunoreactive epidermal growth factor and transforming growth factor-alpha were measured by specific radioimmunoassays in pools of placentas from early, mid, and late gestations, and levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein were measured by radioreceptor assay. RESULTS: All placentas had a strong transforming growth factor-alpha hybridization band at 4.5 kb and a weak epidermal growth factor hybridization band at 5.2 kb. High levels of transforming growth factor-alpha immunoreactive protein (90 to 180 ng/mg protein) and low levels of immunoreactive epidermal growth factor (3 to 9 pg/mg protein) were detected in pools of placentas from early, mid, and late gestations. High levels of epidermal growth factor and transforming growth factor-alpha receptor-active protein (250 ng/mg protein) were also detected. CONCLUSION: Human placentas contain relatively high levels of immunoreactive and receptor-active transforming growth factor-alpha, as well as transforming growth factor-alpha messenger ribonucleic acid, throughout gestation. This finding suggests that transforming growth factor-alpha may act by an autocrine system to influence human placental cell function in vivo.

Blotting, Northern↗
PubMed1992

Effect of transforming growth factor beta on postoperative adhesion formation and intact peritoneum.

Transforming growth factor beta (TGF beta) is an extremely potent chemoattractant for macrophages, mononuclear leukocytes, and fibroblasts. It also acts as a potent stimulant for collagen and fibronectin synthesis and inhibits epithelial cell growth. TGF beta plays an important role in healing many types of wounds, but its role in peritoneal adhesion formation is not known. These studies were performed to determine if TGF beta could affect postoperative wound healing in a rat model. In the first experiment, 20 rats were divided into two groups and received either 2 micrograms TGF beta or control diluent IP daily for 5 days after surgical injury to the uterine horns. The severity of the adhesions were graded 2 weeks postoperatively using a score of 0-3. The TGF beta group showed a higher adhesion score at 2 weeks compared to control, 2.9 +/- 0.34 and 1.6 +/- 0.61, respectively (P less than 0.001). On H&E stained sections of the adhesions, there was an increase in the number of both inflammatory cells and fibroblasts in the TGF beta-treated animals. A comparison trial of bone-derived TGF beta (a gift from Collagen Corporation, Palo Alto, CA) versus recombinant TGF beta (a gift from Oncogen, Seattle, WA) versus control using the same protocol as above showed that both sources of TGF beta were more effective in promoting postoperative adhesions when compared to controls, and there was no difference between TGF beta groups, 3.0 +/- 0 for both TGF beta groups, and 2.2 +/- 0.91 for control (P less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Role for the submandibular gland in modulating pulmonary inflammation following induction of systemic anaphylaxis.

Previous studies have shown that bilateral decentralization of the superior cervical ganglia (SCG; decentralization) attenuates allergen-induced pulmonary inflammatory responses in male rats sensitized to the nematode Nippostrongylus brasiliensis. The present report examines the neuronal and glandular mechanisms mediating the protection against pulmonary inflammation afforded by decentralization. Tissues and organs innervated by the SCG are responsible for this protection since, in a manner similar to decentralization, bilateral removal of the SCG (ganglionectomy) reduced anaphylaxis-induced accumulation of inflammatory cells in bronchoalveolar lavage fluid. Removal of the submandibular gland (sialadenectomy) did not modify the severity of the pulmonary inflammation, but concurrent sialadenectomy and decentralization abolished the protective effect of decentralization. Thus, we postulate that cervical sympathetic nerves tonically inhibit release of anti-inflammatory factors from submandibular glands. No relationship was found between noradrenaline and serotonin content of submandibular glands and the degree of protection against pulmonary inflammation offered by decentralization and ganglionectomy. Both decentralization and ganglionectomy appeared to increase the level of transcripts that encode immunomodulatory growth factors (nerve growth factor and epidermal growth factor) in submandibular glands, but these denervations evidently did not modify the transcripts for TGF beta 2. Systemic inflammatory events are regulated by the central nervous system at a level superior to the SCG probably through modulation of immunoregulatory factors in submandibular glands.

Anaphylaxis↗
PubMed1992

Inhibition of Ca(2+)-induced calcitonin secretion by somatostatin: roles of voltage dependent Ca2+ channels and G-proteins.

Somatostatin has recently been applied therapeutically for hypercalcitonemia in patients with calcitonin-producing tumours. Using calcitonin-secreting cells (C-cells) of the medullary thyroid carcinoma cell line rMTC 44-2, we investigated the inhibitory action of somatostatin on calcitonin release, cytosolic Ca2+ and Ca2+ channel currents. The Ca(2+)-induced rises of the cytosolic Ca2+ and calcitonin secretion were greatly inhibited by somatostatin or its stable analogue octreotide. The effects of somatostatin were pertussis toxin-sensitive. Under voltage clamp conditions, C-cells exhibited slowly inactivating Ca2+ channel currents. Bath application of 100 nM somatostatin reversibly reduced the Ca2+ channel current by about 30%. The Ca2+ channel current and its inhibition by somatostatin were not affected by intracellularly applied cyclic AMP. Moreover, pretreating the cells with pertussis toxin had no effect on the control Ca2+ channel currents but greatly abolished its inhibition by somatostatin. The data show that somatostatin suppresses the Ca(2+)-stimulated calcitonin secretion by inhibiting voltage-dependent Ca2+ channel currents and by lowering cytosolic Ca2+. These actions of somatostatin involve pertussis toxin-sensitive G-proteins and occur independently of changes in the cyclic AMP concentration.

Animals↗
PubMed1992

Immunological identification of G protein alpha- and beta-subunits in tail membranes of bovine spermatozoa.

Heterotrimeric G proteins are believed to play important roles as signal transducing components in various mammalian sperm functions. To assess the distribution of G proteins in bovine sperm tails, we purified membranes by hypoosmotic swelling of bovine spermatozoa followed by disruption of plasma membranes in a homogenizer and various centrifugation steps. Electron microscopy revealed highly purified membranes of bovine sperm tails. Subsequently, antisera against synthetic peptides were used to identify G proteins in immunoblots. An antiserum directed against the C-terminal decapeptide of Gi3 and detecting all known pertussis toxin-sensitive alpha-subunits, reacted specifically with a 40-kDa protein. In contrast, various other specific peptide antisera against alpha-subunits did not detect any G protein in enriched tail membranes. An antiserum recognizing the beta 2-subunit of G proteins and an antiserum reacting with both beta 1- and beta 2-subunits identified a 35-kDa protein in sperm tail membranes. In contrast, antisera against the 36-kDa beta 1-subunit did not detect any relevant proteins in the membrane fraction. Neither G protein alpha-subunits nor G protein beta-subunits were found in the cytosol. Our results suggest that G proteins in membranes of tails of bovine spermatozoa most likely belong to a novel subtype of G protein alpha-subunits, whereas the putative beta-subunit could be identified as a beta 2-subunit.

Adenosine Diphosphate Ribose↗
PubMed1992

Growth factors and corneal endothelial cells: III. Stimulation of adult human corneal endothelial cell mitosis in vitro by defined mitogenic agents.

Human corneal endothelial cells (HCEC) do not mitose extensively in vivo after damage to the endothelial layer. However, HCEC will divide in vitro if cultured under appropriate conditions. We measured the ability of various sera, plasma, growth factors, and nutritional substances to stimulate mitosis of HCEC during 5 days of organ culture after a central freeze injury to the endothelium. Supplementation of a chemically defined medium (CDM) with 20% fetal human serum (FHS) induced significantly higher numbers of mitotic figures or labeled nuclei of human or cat corneas compared with paired corneas cultured in CDM alone. Furthermore, addition of 20% FHS produced more labeled nuclei than did addition of 20% fetal bovine serum or 20% adult human serum. Dialyzed fetal human serum failed to stimulate mitosis, indicating that one or more components of fetal human serum with molecular weight less than 12,000 are essential for mitosis. Human plasma also failed to stimulate mitosis, but an extract of human platelets significantly stimulated high levels of nuclear labeling, suggesting that growth factors contained in platelet granules were responsible for serum-stimulated mitosis of HCEC. Addition of 100 nM epidermal growth factor (EGF) or 10 microM insulin to CDM supplemented with low levels of adult human serum (0.5%) stimulated significantly higher numbers of labeled nuclei compared with paired corneas cultured with 0.5% adult human serum. Supplementation of corneal storage media (K-Sol and CSM) with a mixture of chemically defined agents consisting of EGF, insulin, transferrin, selenium, linoleic acid, and albumin stimulated significantly higher numbers of labeled nuclei compared with paired corneas cultured in the unsupplemented corneal storage media.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1992

Effects of growth factors on corneal wound healing.

Healing of ocular surface wounds is a complex process involving migration, mitosis, and differentiation of epithelial and stromal cells. Endogenously produced peptide growth factors such as epidermal growth factor (EGF), transforming growth factor alpha (TGF-alpha), or transforming growth factor beta (TGF-beta) may play key roles in the natural wound healing process. Lacrimal gland cells were reported to synthesize and secrete EGF into tear fluid where it may enhance healing of corneal epithelial and stromal injuries by an exocrine pathway. EGF stimulated DNA synthesis of epithelial cells and stromal fibroblasts in culture, stimulated synthesis of fibronectin by epithelial cells and was chemotactic for human epithelial and stromal cells. Human corneal epithelial cells also synthesized TGF-alpha which may influence epithelial cells by an autocrine pathway. TGF-beta, which is a potent inducer of lysyl oxidase mRNA levels in cultures of human scleral fibroblasts, may be the factor most responsible for inducing synthesis of corneal extracellular matrix components after an injury. Treatment of epithelial injuries ocular surface wounds with exogenous peptide growth factors also accelerated healing in rabbits and primates. Treatment of severe ocular surface injuries caused by alkali with a combination of EGF, fibronectin, a synthetic collagenase inhibitor, and Aprotinin significantly blocked ulceration and enhanced epithelial regeneration. Clinical trials of topical treatment of EGF for ocular surface wounds suggest that peptide growth factors may be a valuable adjuvant for treatment of ocular surface wounds.

Animals↗
PubMed1992

The prostacyclin analogues, cicaprost and iloprost, increase cytosolic Ca2+ concentration in the human erythroleukemia cell line, HEL, via pertussis toxin-insensitive G-proteins.

In the human erythroleukemia cell line, HEL, prostaglandin E2 (PGE2) and the stable prostacyclin analogue, iloprost, increase cytosolic Ca2+ concentration ([Ca2+]i) via pertussis toxin-sensitive and -insensitive pathways. Unlike iloprost, the stable prostacyclin analogue cicaprost (ZK 96480), is devoid of agonistic properties at prostaglandin E2 receptors. We compared the effects of cicaprost, iloprost and PGE2 on [Ca2+]i in HEL cells. Cicaprost, iloprost and PGE2 were similarly potent to increase [Ca2+]i in HEL cells. However, unlike the effects of PGE2, those of the prostacyclin analogues were not inhibited by pertussis toxin. The prostaglandins studied increased [Ca2+]i through both mobilization from internal stores and Ca2+ influx from the extracellular space. Prostacyclin analogue- and PGE2-induced rises in [Ca2+]i were desensitized in a homologous manner. Additionally, there was cross-desensitization between cicaprost and iloprost, but not between the prostacyclin analogues and PGE2. Our data suggest that in HEL cells (i) cicaprost and iloprost act through prostacyclin receptors and (ii) that these receptors couple to pertussis toxin-insensitive heterotrimeric regulatory guanine nucleotide-binding proteins, (iii) resulting in an increase in [Ca2+]i by Ca2+ mobilization from internal stores and sustained influx.

Calcium↗
PubMed1991

Thyrotropin-releasing hormone induces opposite effects on Ca2+ channel currents in pituitary cells by two pathways.

Thyrotropin-releasing hormone (TRH) stimulates pituitary secretion by steps involving a cytosolic Ca2+ rise. We examined various pathways of Ca2+ elevation in pituitary GH3 cells. By using the patch clamp technique in the whole-cell configuration and Ba2+ as divalent charge carrier through Ca2+ channels, TRH (1 microM) reversibly reduced the current by about 55%. This hormonal effect was prevented by infusing guanine 5'-[beta-thio]diphosphate (GDP[beta S]) intracellularly but not by pretreating the cell with pertussis toxin (PT). Since PT-insensitive guanine nucleotide-binding regulatory (G) proteins are known to mediate a hormone-stimulated inositol trisphosphate-mediated Ca2+ release from intracellular stores, we assume that the inhibitory effect of TRH on Ba2+ currents through Ca2+ channels is caused by the increased intracellular Ca2+. To prevent a Ca(2+)-release-dependent inhibition of Ca2+ channels, we preincubated GH3 cells in a medium free of divalent charge carriers and measured the Na+ current through Ca2+ channels. When fura-2 was used as indicator for the cytosolic Ca2+, TRH induced a release from intracellular stores only once and had no effect on the intracellular Ca2+ concentration during further applications. In line with this observation, TRH initially reduced the Na+ current through Ca2+ channels but stimulated it during subsequent applications. The stimulation was sensitive to GDP[beta S] and was abolished by pretreatment with PT, suggesting that the stimulatory action of TRH is mediated by a G protein different from the one that functionally couples the receptor to phosphatidylinositol 4,5-bisphosphate hydrolysis. In conclusion, the present data suggest that TRH increases the intracellular Ca2+ concentration by two interacting pathways, that release from intracellular stores causes a secondary blockage of Ca2+ channels, and that, especially with empty intracellular Ca2+ stores, Ca2+ channels are stimulated by a PT-sensitive G protein.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Molecular cloning and expression of a new alpha-subunit of soluble guanylyl cyclase. Interchangeability of the alpha-subunits of the enzyme.

A cDNA coding for a new subunit of soluble guanylyl cyclase with a calculated molecular mass of 81.7 kDa was cloned and sequenced. On the basis of sequence homology, the new subunit appears to be an isoform of the alpha 1-subunit and was designated alpha 2 as the new subunit is very similar to the alpha 1-subunit in the middle and C-terminal part; it is quite diverse in the N-terminal part. Preceding experiments had shown that coexpression of the alpha 1- and beta 1-subunits is necessary to obtain a catalytically active guanylyl cyclase in COS cells [(1990) FEBS Lett. 272, 221-223]. The finding that the alpha 2-subunit was able to replace the alpha 1- but not the beta 1-subunit in expression experiments demonstrates the interchangeability of the alpha-subunit isoforms of soluble guanylyl cyclase.

Amino Acid Sequence↗
PubMed1991

Assignment of G-protein subtypes to specific receptors inducing inhibition of calcium currents.

The inhibition of voltage-dependent Ca2+ channels in secretory cells by plasma membrane receptors is mediated by pertussis toxin-sensitive G proteins. Multiple forms of G proteins have been described, differing principally in their alpha subunits, but it has not been possible to establish which G-protein subtype mediates inhibition by a specific receptor. By intranuclear injection of antisense oligonucleotides into rat pituitary GH3 cells, the essential role of the Go-type G proteins in Ca(2+)-channel inhibition is established: the subtypes Go1 and Go2 mediate inhibition through the muscarinic and somatostatin receptors, respectively.

Animals↗
PubMed1991

Brain nitric oxide synthase is a biopterin- and flavin-containing multi-functional oxido-reductase.

Brain nitric oxide synthase is a Ca2+/calmodulin-regulated enzyme which converts L-arginine into NO. Enzymatic activity of this enzyme essentially depends on NADPH and is stimulated by tetrahydrobiopterin (H4biopterin). We found that purified NO synthase contains enzyme-bound H4biopterin, explaining the enzymatic activity observed in the absence of added cofactor. Together with the finding that H4biopterin was effective at substoichiometrical concentrations, these results indicate that NO synthase essentially depends on H4biopterin as a cofactor which is recycled during enzymatic NO formation. We found that the purified enzyme also contains FAD, FMN and non-heme iron in equimolar amounts and exhibits striking activities, including a Ca2+/calmodulin-dependent NADPH oxidase activity, leading to the formation of hydrogen peroxide at suboptimal concentrations of L-arginine or H4biopterin.

Amino Acid Oxidoreductases↗
PubMed1991

Sequence homologies between guanylyl cyclases and structural analogies to other signal-transducing proteins.

The cyclic GMP-forming enzyme guanylyl cyclase exists in cytosolic and in membrane-bound forms differing in structure and regulations. Determination of the primary structures of the guanylyl cyclases revealed that the cytosolic enzyme form consists of two similar subunits and that membrane-bound guanylyl cyclases represent enzyme forms in which the catalytic part is located in an intracellular, C-terminal domain and is regulated by an extracellular, N-terminal receptor domain. A domain of 250 amino acids conserved in all guanylyl cyclases appears to be required for the formation of cyclic nucleotide, as this homologous domain is also found in the cytosolic regions of the adenylyl cyclase. The general structures of guanylyl cyclases shows similarities with other signal transducing enzymes such as protein-tyrosine phosphatases and protein-tyrosine kinases, which also exist in cytosolic and receptor-linked forms.

Adenylyl Cyclases↗
PubMed1991

Identification of the G-protein alpha-subunit encoded by alpha o2 cDNA as a 39 kDa pertussis toxin substrate.

A novel form of the Go alpha-subunit (alpha o2) has been identified by molecular cloning (Hsu et al., J. Biol. Chem. 265, 11220-11226, 1990). An antibody was generated against a synthetic peptide corresponding to a region of the protein encoded by alpha o2 cDNA. The antibody reacted with an apparently single 39 kDa protein in membrane preparations of rodent brain and with a 39 kDa pertussis toxin substrate in membranes of rodent neuroendocrine and pituitary cells. A previously produced antibody raised against a region common to proteins encoded by alpha o2 cDNA and the previous cloned alpha o1 cDNA (Itoh et al., Proc. Natl. Acad. Sci. USA 83, 3776-3780, 1986) recognized proteins of 39 and 40 kDa in preparations of bovine, porcine and rodent brain and pertussis toxin substrates of 39 and 40 kDa in membranes of rodent neuroendocrine and pituitary cells. We conclude that the 39 kDa Go alpha subunit is encoded by alpha o2 cDNA.

Amino Acid Sequence↗
PubMed1991

Evidence for opioid receptor-mediated activation of the G-proteins, Go and Gi2, in membranes of neuroblastoma x glioma (NG108-15) hybrid cells.

In membranes of neuroblastoma x glioma (NG108-15) hybrid cells, the photoreactive GTP analog, [alpha-32P] GTP azidoanilide, was incorporated into 39-41-kDa proteins comigrating in urea-containing sodium dodecyl sulfate-polyacrylamide gels with immunologically identified G-protein alpha-subunits, i.e. a 39-kDa Go alpha-subunit, a 40-kDa Gi2 alpha-subunit, and a 41-kDa Gi alpha-subunit of an unknown subtype. The synthetic opioid, D-Ala2,D-Leu5-enkephalin (DADLE), stimulated photolabeling of the 39-41-kDa proteins. In the presence of GDP, which increased the ratio of agonist-stimulated to basal photolabeling, DADLE at a maximally effective concentration stimulated photolabeling of the 39- and the 40-kDa protein 2-3-fold. Somatostatin, adrenaline, and bradykinin were less potent than DADLE and, to varying degrees, stimulated photolabeling of the 40-kDa protein more than that of the 39-kDa protein. Prostaglandin E1 was inactive. The present data represent direct evidence for an activation of endogenous Go and Gi2 via opioid receptors and other receptors in the native membrane milieu.

Alprostadil↗
PubMed1991

EGF and TGF-alpha in wound healing and repair.

Wound healing is a localized process which involves inflammation, wound cell migration and mitosis, neovascularization, and regeneration of the extracellular matrix. Recent data suggest the actions of wound cells may be regulated by local production of peptide growth factors which influence wound cells through autocrine and paracrine mechanisms. Two peptide growth factors which may play important roles in normal wound healing in tissues such as skin, cornea, and gastrointestinal tract are the structurally related peptides epidermal growth factor (EGF) and transforming growth factor alpha (TGF-alpha). EGF/TGF-alpha receptors are expressed by many types of cells including skin keratinocytes, fibroblasts, vascular endothelial cells, and epithelial cells of the GI tract. In addition, EGF or TGF-alpha are synthesized by several cells involved in wound healing including platelets, keratinocytes, and activated macrophages. Healing of a variety of wounds in animals and patients was enhanced by treatment with EGF or TGF-alpha. Epidermal regeneration of partial thickness burns on pigs or dermatome wounds on patients was accelerated with topical application of EGF or TGF-alpha, and EGF treatment accelerated healing of gastroduodenal ulcers. EGF also increased tensile strength of skin incisions in rats and corneal incisions in rabbits, cats, and primates. Additional research is needed to better define the roles of EGF, TGF-alpha and their receptor in normal wound healing, to determine if alterations have occurred in the EGF/TGF-alpha system in chronic wounds, and optimize vehicles for effective delivery of peptide growth factors to wounds.

Amino Acid Sequence↗
PubMed1991

Differential inhibition and potentiation of chemoattractant-induced superoxide formation in human neutrophils by the cell-permeant analogue of cyclic GMP, N2,2'-O-dibutyryl guanosine 3':5'-cyclic monophosphate.

Human neutrophils possess a superoxide (O2-)-forming NADPH oxidase which is activated by the chemoattractants, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (fMet-Leu-Phe), complement C5a, platelet-activating factor and leukotriene B4. We studied the roles of cAMP and cGMP in the regulation of O2- formation using the cell-permeant analogues of cyclic nucleotides, N6,2'-O-dibutyryl adenosine 3':5'-cyclic monophosphate (Bt2cAMP) and N2,2'-O-dibutyryl guanosine 3':5'-cyclic monophosphate (Bt2cGMP). Bt2cAMP inhibited O2- formation induced by these chemoattractants to similar extents. Bt2cGMP as low as 10 mumol/l significantly inhibited O2- formation induced by fMet-Leu-Phe at a submaximally effective concentration (50 nmol/l), and Bt2cGMP was more effective in diminishing O2- formation than Bt2cAMP. In contrast, Bt2cGMP did not affect O2- formation induced by fMet-Leu-Phe at a maximally effective concentration (1 mumol/l). Bt2cGMP (0.1 and 1 mmol/l) enhanced O2- formation induced by 0.1 mumol/1 C5a by 23% and 49%, respectively, and Bt2cGMP antagonized inhibition of O2- formation caused by Bt2cAMP. Bt2cGMP inhibited platelet-activating factor-induced O2- formation to a lesser extent than Bt2cAMP and had no effect on that induced by leukotriene B4. Bt2cAMP and Bt2cGMP had no effect on O2- formation induced by NAF, gamma-hexachlorocyclohexane, phorbol myristate acetate, A 23187 and arachidonic acid. Our data suggest that: 1. Bt2cAMP generally inhibits chemoattractant-stimulated O2- formation. 2. Bt2cGMP inhibits fMet-Leu-Phe- and platelet-activating factor-stimulated O2- formation but potentiates C5a-induced O2- formation.(ABSTRACT TRUNCATED AT 250 WORDS)

Bucladesine↗