Beta 1 integrin ligation stimulates tyrosine phosphorylation of phospholipase C gamma 1 and elevates intracellular Ca2+ in pancreatic acinar cells.

We have recently reported increased tyrosine (TYR) phosphorylation of a number of pancreatic acinar cell proteins following antibody ligation of beta 1 integrins (Wrenn and Herman, Biochem, Biophys. Res. Commun. 208, 1995, 978-984). Concurrent with this TYR phosphorylation was a marked activation of protein kinase C (PKC). This led us to investigate phospholipase C gamma 1 (PLC gamma 1), a key enzyme responsible for diacylglycerol generation, as a target for integrin-mediated TYR phosphorylation. Staining with antiphosphotyrosine antibodies revealed increased TYR phosphorylation of immunoprecipitated PLC gamma 1 prepared from beta 1 integrin-ligated acinar cells. Subsequent stripping and reprobing of Western blots with polyclonal anti-PLC gamma 1 was confirmatory. Over this same time period, intracellular [Ca2+] increased from < 100 nM to 600 nM, further suggesting a functional relevance of integrin-linked phosphorylation as a regulatory mechanism in exocrine pancreas.

Dynamic changes in the locus control region of erythroid progenitor cells demonstrated by polymerase chain reaction.

The locus control region (LCR) far upstream of the human beta-like globin genes is defined by the preferential chromatin accessibility/DNase I hypersensitivity of four constituent DNA sites HS4, 3, 2, and 1. In an attempt to understand the mechanism of LCR function during early stages of erythropoiesis, a new polymerase chain reaction (PCR) method has been developed to examine the chromatin structure/DNase I hypersensitivity of the LCR in progenitor cells logistically available in limited cell numbers. In erythroid progenitors as well as in multipotent cells with erythroid potential, hypersensitive sites HS4, 3, 2, and 1 were present and the chromatin structure of the LCR was accessible. Moreover, the chromatin structure of the LCR underwent dynamic changes during erythropoiesis. In early erythroid progenitors, the HS2 site was more accessible than the HS3 site. In more mature erythroid progenitors, HS2 became less accessible than HS3 and the other sites. The results indicate that the transcriptional program of the globin genes is encoded, at least in part, in the chromatin accessibility of the LCR. This globin program was apparently initiated in multipotent cells and maintained in erythroid progenitors. Furthermore, the program could be modulated in response to cellular changes accompanying differentiation of the progenitor cells.

Integrin-linked tyrosine phosphorylation increases membrane association of protein kinase C alpha in pancreatic acinar cells.

Ligation of beta 1 integrin receptors resulted in increased tyrosine phosphorylation of at least five proteins (Mrest = 110, 85, 55, 30 and 24 kD) from rat pancreatic acinar cells. Increased protein kinase C (PKC) activity and elevated amounts of immunoreactive PKC alpha were demonstrated in membrane fractions from integrin-ligated acinar cells. Membrane translocation of PKC alpha was confirmed using scanning confocal laser microscopy in immunocytochemical preparations of acinar cells following beta 1 integrin ligation. These studies establish the presence of a beta 1 integrin-linked protein tyrosine phosphorylation system in exocrine pancreatic cells and provide evidence for integrative activity of this system with PKC, a primary signalling pathway of central importance in these cells.

Nitric oxide participates in the regulation of pancreatic acinar cell secretion.

The role of nitric oxide (NO) in the regulation of exocrine secretion was investigated in isolated rat pancreatic acini. NO synthase activity was detected in the extract of acini and purified by ion-exchange and 2',5'-ADP agarose chromatographies. Enzyme activity was determined by conversion of 3H-arginine to 3H-citrulline, by measurement of nitrite (a breakdown product of NO) and by generation of cyclic GMP. Treatment of acini with L-arginine increased nitrite as well as cyclic GMP and amylase release, which were prevented by the nitric oxide synthase inhibitors N-monomethyl-arginine [NMMA] and NG-nitro-L-arginine [NNA]. These nitric oxide inhibitors also blocked carbachol-induced amylase release as well as elevation of acinar cell cyclic GMP. NNA was a potent inhibitor of carbamylcholine-induced amylase release (est. Ki = 2.2 uM). Nitric oxide apparently participates significantly in the overall control of pancreatic acinar cell secretory function.

Transforming growth factor-beta: signal transduction via protein kinase C in cultured embryonic vascular smooth muscle cells.

Transforming growth factor-beta (TGF-beta), an ubiquitous regulatory peptide, has diverse effects on the differentiation and behavior of vascular smooth muscle cells (VSMC). However, the molecular mechanism through which TGF-alpha exerts its effects remains obscure. We investigated the phosphoinositide/protein kinase C [PKC] signaling pathway in the action of TGF-beta on cultured embryonic avian VSMC of differing lineage: a) thoracic aorta, derived from the neural crest; and b) abdominal aorta, derived from mesenchyme. The second messenger responsible for activation of PKC is sn-1,2-diacylglycerol [DAG]; TGF-beta increased the mass amounts of DAG in the membranes of neural crest-derived VSMC concurrent with translocation of PKC from the soluble to the membrane fraction, but TGF-beta had no effect on the DAG or PKC of mesenchyme-derived VSMC. TGF-beta potentiated the growth of platelet-derived growth factor (PDGF)-treated, neural crest-derived VSMC; but abolished PDGF-induced growth of mesenchymal cells. It is concluded that molecular and functional responses of VSMC to TGF-beta are heterogeneous and are functions of the embryonic lineage of the VSMC.

Environmental interactions of Sulphlex pavement.

Sulphlex, a mixture of elemental sulfur and plasticizers, has been considered for use as an asphalt substitute in road construction. Because this material contains substantial quantities of elemental sulfur, it is a potential substrate for growth of sulfur-oxidising bacteria. Experiments, performed to determine the susceptibility of Sulphlex in Sulphlex-containing media to degradation by Thiobacillus thiooxidans, resulted in breakdown of the Sulphlex material and concomitant production of acid. In concurrent studies, plants were grown in Sulphlex-amended soils. These plants exhibited higher sulfur content and reduced productivity as compared with plants grown in unamended soils, indicating that Sulphlex was being broken down in the soil and that the breakdown products were apparently having a detrimental effect on plant productivity. These experiments indicate that naturally occurring sulfur-oxidising bacteria have the potential to break down Sulphlex paving material, resulting in adverse effects on both the structural integrity of the pavement and the local environment.

Antihistamine update.

Antihistamines are a diverse group of drugs, each possessing the ability to inhibit various actions of histamine. Because they act principally through competitive inhibition of the histamine receptor, they are helpful as a means of preventing rather than reversing these actions. As a result of a resurgence of interest in antihistamine therapy during the past decade, a new class of H1 blockers, clinically devoid of sedative and anticholinergic effects, has evolved. Thus, the choice of antihistamine can now be based on the side effects profile as well as the clinical profile. As we continue to develop a better understanding of these newer agents, we will be able to select more rationally the antihistaminic agent most appropriate to the specific disorder. Used judiciously, the antihistamines available today have a broad application of therapeutic uses, with few significant side effects.

Congenital self-healing reticulohistiocytosis. A new entity in the differential diagnosis of neonatal papulovesicular eruptions.

A case of congenital self-healing reticulohistiocytosis is described. The case is different from those previously described because papulovesicles, rather than the papulonodules that are usually characteristic of this disease, predominated. All lesions regressed within 2 months of presentation, and at 2-year follow-up, the patient continues to develop normally without recurrence of the eruption or progression to internal organ involvement. Electron microscopic examination revealed numerous Langerhans' granules admixed with myelinlike laminated dense granules characteristic of this disease. The unique physical presentation in this case, as well as the criteria used to differentiate this disorder from the more malignant forms of histiocytosis and other childhood papulovesicular eruptions, is emphasized.

Diaphoresis and Meniere's disease.

The effect of diaphoresis on patients with Meniere's disease (labyrinthine hydrops) previously has not been reported. With the use of two distinct activities to produce diaphoresis, we were able to document substantial transient improvements in pure-tone threshold, speech-reception threshold, and speech discrimination concurrent with a decrease in tinnitus and fullness in two patients with unilateral Meniere's disease that had been diagnosed previously by the glycerin test. The two diaphoretic activities were (1) strenuous exercise, including periodic visits to the sauna, and (2) passive activity consisting of repetitive visits to the sauna. Glycerin, an osmotic diuretic, produces similar temporary beneficial effects primarily in patients in the fluctuant hearing stage of Meniere's disease. The glycerin test is being used in several clinics as an adjunct for the diagnosis of endolymphatic hydrops.

Static compliance of the eardrum in Meniere disease.

A recent study compared the acoustic impedance values in the affected and unaffected ears of patients with unilateral Meniere disease, and suggested that the higher impedance measured in the affected ears was due to increased intralabyrinthine pressure (endolymphatic hydrops). The present study does not support these findings. This conclusion is based on the static compliance of 17 patients with unilateral Meniere disease, measured during the glycerin test. Glycerin, an osmotic diuretic, produces transient improvements in pure-tone threshold and/or speech discrimination in the affected ear only. Orally administered glycerin is thought to cause these improvements by reducing endolymphatic hydrops. We were unable to find any change in static complicance after glycerin ingestion. Also no difference between the affected and unaffected ears, either before or after glycerin, was noted.