Oxidative DNA damage induced by silica in vivo

Occupational exposure to silica has often been associated with the development of pulmonary fibrosis and, occasionally, lung cancer. Their development may be mediated by oxidant-induced cellular injury. The short- and long-term effects of a single intratracheal instillation of silica in rats (10 mg/200 microliters/saline per rat) was assessed by measuring 8-hydroxy-2'-deoxyguanosine (oh8dG) levels in lung tissue and peripheral blood leukocytes. Cell differentials, reduced glutathione (GSH), and superoxide dismutase (SOD), lipid peroxide, and total phospholipids in peripheral blood and/or bronchoalveolar lavage fluid (BALF) were also measured. The pulmonary oh8dG levels increased approximately 2.24- 2.86-fold from 1 to 5 days after exposure to silica. It was still elevated 1 and 4 weeks after installation, but the difference was no longer statistically significant. The oh8dG levels in peripheral blood leukocytes were never significantly different, but they were generally higher than in the controls. The low SOD levels in the BALF of exposed rats in the early stage and the higher GSH levels in the late stage may represent protective reactions against the generation of oxygen species. A significant increase in oh8dG levels in lung tissue suggested the possible carcinogenicity of silica.

Different features of Ca2+ oscillations in differentiated and undifferentiated hepatocyte doublets

Cytosolic free Ca2+ ([Ca2+]i) oscillations are postulated to play a critical role in cellular proliferation. By using doublets of normal rats (NR) and those 18 hours after two-thirds hepatectomy (PHR), we investigated cytosolic free Ca2+ ([Ca2+]i) responses in liver regeneration. Normal rat hepatocyte doublets that retain their bile canaliculi are polarized and well differentiated. PHR doublets, which also retain their bile canaliculi, were characterized as undifferentiated by (1) decreased canalicular secretion of fluorescein-isothiocyanate-labeled glycocholate; (2) increased labeling index of hepatocytes in BrdU staining (approximately 30%); and (3) impaired transfer of fluorescent dye injected into one cell of the pair to the other. Addition of phenylephrine to NR and PHR doublets in the presence of extracellular Ca2+ resulted in [Ca2+]i oscillations or a nonoscillatory-sustained increase in [Ca2+]i followed by a gradual return to the baseline. Extracellular Ca2+ was not required for [Ca2+]i oscillations but was necessary for a sustained increase in [Ca2+]i. Simultaneous addition of prazosin, alpha 1-receptor blocker, to doublets immediately abolished these [Ca2+]i responses. The [Ca2+]i level in each of the adjacent cells was synchronous in sustained increase in [Ca2+]i but asynchronous in [Ca2+]i oscillations. As the phenylephrine concentration was increased (1 to 100 mumol/L), oscillations were replaced by a sustained increase in [Ca2+]i in NR doublets. In contrast, in PHR doublets, oscillations remained, whereas the frequency of oscillations increased in a dose-dependent manner. These results indicate that the mechanisms of phenylephrine-evoked [Ca2+]i responses are different in differentiated and undifferentiated doublets and that the frequency modulation of [Ca2+]i oscillations may be involved in the intracellular signal transduction in the cellular proliferation process during liver regeneration.

Changing pattern of agitated impaired mental status in patients with advanced cancer: association with cognitive monitoring, hydration, and opioid rotation

In late 1990, it became standard practice at the palliative care unit of the Edmonton General Hospital to regularly administer the Mini-Mental State Questionnaire (MMSQ) and to undertake opioid rotation and hydration upon detection of cognitive failure. We retrospectively reviewed the charts of 117 and 162 patients admitted in 1988-1989 and 1991-1992, respectively, to assess the impact of these maneuvers on the prevalence of agitated impaired mental status (IMS). All patients underwent regular cognitive assessment in 1991-1992 versus none in 1988-1989. Seventy-three percent of patients received hydration in the second period versus 32% in the first (P < 0.01). The frequency of opioid rotation was also greater in the second period (41% versus 21%, P < 0.001). The incidence of agitated IMS decreased from 26% in 1988-1989 to 10% in 1991-1992 (P < 0.001). This was reflected by a lower mean dose of the major drug used to treat this condition, haloperidol (3.6 +/- 2.4 versus 5.6 +/- 3.8 mg/day, P < 0.01), and less frequent use of other neuroleptics and benzodiazepines (0.12 versus 0.38 prescriptions per patient, P < 0.01) in the second period. Our data suggest that routine cognitive monitoring, opioid rotation, and hydration may reduce the incidence of agitated IMS in terminal cancer patients.

Long-term enhancement of dopamine release by high frequency tetanic stimulation via a N-methyl-D-aspartate-receptor-mediated pathway in rat striatum

We studied the effects of high frequency tetanic stimulation of the striatum on the KCl (20 mM)-evoked dopamine release in rat striatal slices. The KCl-evoked dopamine release was potentiated by high frequency tetanic stimulation (10-20 Hz) of the striatum including the corticostriatal fibers, and this potentiation was observed until 3 h after high frequency tetanic stimulation. Potentiation of dopamine release after high frequency tetanic stimulation was induced not only by KCl but also by glutamate in Mg(2+)-free medium, N-methyl-D-aspartate in Mg(2+)-free medium, and by DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid. 2-amino-5-phosphovalerate, 3-[(+/-)-2-carboxypiperazine-4-yl]-propyl-1-phosphonate or dibenzocycloheptaneimine, N-methyl-D-aspartate receptor inhibitors, abolished enhancement by tetanus, whereas, 6,7-dinitroquinoxaline-2,3-dione, an antagonist of DL-alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid ionotropic receptors, or L-2-amino-4-phosphonobutyrate, an antagonist of glutamate metabotropic receptors, showed no effect. Moreover, pretreatment with glutamate or N-methyl-D-aspartate in the absence of Mg2+ also facilitated dopamine release evoked by KCl concentrations. When extracellular Ca2+ was removed from the medium during pretreatment, potentiation by glutamate disappeared. We conclude that activation of N-methyl-D-aspartate receptors on dopaminergic nerve terminals in the striatum produces the long-term changes in efficacy of the response to KCl or glutamatergic agents. That is, plastical phenomena could exist at presynaptic levels between glutamatergic neurons and dopaminergic neurons in striatum.

Topographic EEG changes due to hypobaric hypoxia at simulated high altitude

Multichannel human EEG signals were studied topographically in subjects exposed to an atmosphere of reduced air pressure in a chamber in which high-altitude conditions were simulated. EEG signals from 16 electrodes placed on the scalp were recorded simultaneously with electrocardiography and vertical eye movement. Baseline records were first obtained at sea level (PRE 0 m), and then at reduced air pressures corresponding to the altitudes of 3000 m, 4000 m, and 6000 m, respectively, and after returning to sea level (POST 0 m). A complete set of EEG records under all 6 conditions was obtained in 5 of the 15 subjects, and under 5 conditions (all except the 6000 m condition) in 3 other subjects. The spectral powers of 1 min epochs of the multichannel EEG signal under each altitude condition were compared to that at PRE 0 m using analysis of variance. Under the 3000 m condition, the spectral power of the 10-11 Hz components was significantly decreased and, with increasing altitude, significant decrease of spectral power was observed in a wider range of the alpha frequency band. Under the 6000 m condition, the decrease of spectral power of the alpha band in the posterior brain areas was -7 dB compared to the baseline. In contrast, the spectral power of the theta frequency band in anterior brain areas increased significantly in the 5000 m and 6000 m conditions. At the POST 0 m condition after return from the 5000 m condition (without exposure to the 6000 m condition), the EEG showed recovery to the level of the baseline PRE 0 m condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Acquired hypochromic and microcytic sideroblastic anaemia responsive to pyridoxine with low value of free erythrocyte protoporphyrin: a possible subgroup of idiopathic acquired sideroblastic anaemia (IASA)

Patients with idiopathic acquired sideroblastic anaemia (IASA) usually show macrocytic or normocytic anaemia and increased free erythrocyte protoporphyrin (FEP). The mean cell haemoglobin concentration is normal or slightly low. Here we report a pyridoxine-responsive IASA patient with microcytic and hypochromic anaemia and low FEL level; these features are usually seen in cases of hereditary sideroblastic anaemia. Microcytosis increased during therapy. There may be a subgroup of IASA with microcytic and hypochromic anaemia, low normal FEP and some response to pyridoxine like hereditary sideroblastic anaemia.

Effect of a high alpha-linolenate and high linoleate diet on membrane-associated enzyme activities in rat brain--modulation of Na+, K+- ATPase activity at suboptimal concentrations of ATP

Semi-purified diets supplemented with either a high alpha-linolenate (n - 3) (perilla) oil or a high linoleate (n - 6) (safflower) oil were fed to rats through two generations. Rats fed safflower oil showed a decrease in docosahexaenoic acid (n - 3) and a compensatory increase in docosapentaenoic acid (n - 6) in all the brain regions and organelles examined, when compared with rats fed perilla oil. As reported previously, the safflower oil-fed rats exhibited inferior learning ability compared with the perilla oil-fed rats (N. Yamamoto et al., J. Lipid Res. 28, 144 (1987)). Using brains of rats in these dietary groups, the activities of several enzymes, Na+ , K+-ATPase, Ca2+-ATPase, 5'-nucleotidase, 2',3'-cyclic nucleotide phosphodiesterase, acetylcholinesterase, and choline acetyltransferase in membranes, were compared. The 5'-nucleotidase activity in cortex and hippocampus, and the Na+, K+-ATPase activity in myelin decreased slightly but significantly in the safflower oil group. None of the other membrane-associated enzyme activities in all the brain regions and organelles examined was affected significantly by the dietary fatty acids under optimal assay conditions in vitro. However, in the safflower oil group, the Na+, K+-ATPase activity of synaptosomes at a suboptimal concentration of ATP was 78% that in the perilla oil group. These results suggest that relatively large changes in the proportions of n - 3 and n - 6 polyunsaturated fatty acids in brain membranes caused by dietary manipulation do not provoke significant alterations in most membrane-bound enzyme activities. However, a small but significant change in Na+, K+-ATPase activity at a suboptimal concentration of ATP may be implicated in the altered learning behavior reported earlier.

[Experimental studies on the influence of duodenal contents on the mucosa of gastric remnant]

Using the PCNA staining method, we examined the histopathological changes and cytokinetics on the gastric mucosa of the gastric remnant at the anastomosis 10, 20 and 50 weeks after gastrectomy. We conducted the distal gastrectomy in rats and divided them into three groups: Group 1, in which "a sham" operation was performed; Group 2, in which reflux of duodenum fluids was prevented by Roux-en Y anastomosis; and Group 3, in which reflux of duodenum fluids was allowed by gastro-jejunal anastomosis. Adenocarcinoma developed only at the anastomosis of the afferent loops in animals of Group 3 directly exposed to duodenum fluid. The PCNA labeling index at the anastomosis of the afferent loop was high from the early stages. In addition, labeling index tended to increase gradually, and PCNA positive cells were diffusely scattered, which indicated acceleration of cytosis. From these results, we concluded that the reflux of duodenum fluid was essential for the development of cancer in the remnant stomach. Moreover, cytosis was closely related to the development of epithelial cancer of the gastric mucosa at the anastomosis of the remnant stomach.

Immunohistochemical study of calpain and its endogenous inhibitor in the skeletal muscle of muscular dystrophy

A calcium-dependent proteinase (calpain) has been suggested to play an important role in muscle degradation in Duchenne muscular dystrophy (DMD). In immunohistochemical studies, calpain and its endogenous inhibitor (calpastatin) were located exclusively in the cytoplasm in normal human muscles. The intensity of the staining was stronger in type 1 than in type 2 fibers. Quantitative immunohistochemical study showed an increase of calpain in biopsied muscles from the patients with DMD and Becker muscular dystrophy. Abnormal increases in calpain and calpastatin were demonstrated mainly in atrophic fibers, whereas necrotic fibers showed moderate or weak immunoreactions for the enzymes. Opaque fibers and hypertrophic fibers were negative. Not all dystrophin-deficient muscle fibers necessarily showed a strong reaction for calpain. We suggest that calpain may play an important role in muscle fiber degradation, especially in the early stage of muscle degradation in muscular dystrophy.

Changes of cytokeratin and involucrin expression in squamous cell carcinomas of the skin during progression to malignancy

The detection of cytokeratins in neoplastic tissues by immunohistochemical methods has numerous diagnostic and investigative applications, because cytokeratins are usually conserved in tumour cells during malignant transformation. Recently, however, it has been reported that progression to malignancy is associated with commencement of expression of low-molecular-weight cytokeratins. In the present study, 42 specimens from 35 cases of squamous cell carcinoma (SCC) of the skin were analysed by immunohistochemical techniques, using polyclonal anti-involucrin antibody and a panel of monoclonal antikeratin antibodies, in order to investigate the nature and differentiation of SCCs. The expression of cytokeratins and involucrin in well-differentiated SCCs was similar to that in normal epidermis. In contrast with well-differentiated SCCs, the expression of differentiation-specific cytokeratins and involucrin was diminished in the immature tumour cells in proportion to the malignancy of the SCCs. Some antibodies, however, stained all tumour cells, irrespective of the degree of malignancy. Furthermore, expression of simple epithelial and non-cornifying stratified squamous epithelial cytokeratins was observed in atypical tumour cells of poorly differentiated SCCs. It is of interest that similar expression was noted in many tumour cells in the lymph node metastases and in some tumour cells in the primary cutaneous lesions. Cytokeratin expression similar to that in normal epidermal keratinocytes was conserved in well-differentiated SCCs, but the expression of cytokeratins changed during progression to malignant transformation. The expression of simple epithelial or non-cornifying stratified squamous epithelial cytokeratins in cutaneous SCCs may be a marker for their capability of invasion and metastatic potential.

Granulocyte macrophage-colony stimulating factor-dependent replication of polyoma virus replicon in hematopoietic cells. Analyses of receptor signals for replication and transcription

Granulocyte macrophage-colony stimulating factor (GM-CSF) stimulates proliferation of various hematopoietic cells. Using cytoplasmic deletion mutants of the human GM-CSF receptor (hGMR) beta subunit and tyrosine kinase inhibitors, we previously showed that distinct signaling pathways of hGMR are involved in the induction of c-fos/c-jun mRNAs and of c-myc mRNA/cell proliferation. We used polyoma virus (Py) replicon to analyze the initiation of DNA replication induced by hGM-CSF in mouse BA/F3 pro-B cells expressing hGMR. hGM-CSF efficiently stimulated Py replication in the presence of Py enhancer and Py large T antigen supplied in trans. Analyses of Py enhancer mutants revealed that hGM-CSF promoted Py replication and activated transcription of the Py early promoter through the PEA3/PEBP5 region of Py enhancer. The membrane proximal region of hGMR beta subunit is required for activation of PEA3/PEBP5-dependent replication which is also required for activation of DNA synthesis in the host cells. In contrast, a more distal region which is essential for activation of c-fos and c-jun genes is required for the PEA3/PEBP5-dependent transcription of Py early promoter. These results indicate that distinct signaling pathways of hGMR are required to activate PEA3/PEBP5-dependent replication and transcription although the same enhancer is required for both activities.

Spectral analyses of R-R interval and systolic blood pressure in diabetic autonomic neuropathy

We studied autonomic nervous system function using the principle of maximum entropy (ME) to perform spectral analyses of the R-R interval and systolic blood pressure in 32 diabetic patients and 40 healthy controls. The R-R interval and systolic blood pressure were measured using a continuous, noninvasive monitoring system. The power spectra of both the R-R interval (RR) and systolic blood pressure (SYS) were obtained using ME and the areas of two frequency components were measured: a low- (LFC) and a high-frequency component (HFC). The RR-LFC, RR-HFC and SYS-LFC of diabetic patients were significantly smaller than those of healthy controls. The results of the spectral analyses in diabetic patients correlated with neither disease duration nor nephropathy, while the SYS-LFC showed significant correlations with both retinopathy and the delay in median motor nerve conduction velocity. In the mild autonomic neuropathy group, the RR-LFC and SYS-LFC were not differ from those of healthy controls or patients without autonomic neuropathy. However, the RR-HFC was significantly smaller than that of healthy controls or patients without atonomic neuropathy. In the setting of mild diabetic autonomic neuropathy, it was suggested that cardiac parasympathetic dysfunction preceded both alpha and beta sympathetic dysfunction.

Alveolar air/tissue interface and nuclear magnetic resonance behavior of normal and edematous lungs

The alveolar air/tissue interface markedly affects the NMR properties of lungs by causing an NMR signal loss as a result of internal (tissue-induced) magnetic field inhomogeneity. The signal loss can be measured as the difference in NMR signal intensity (difference signal delta) between a pair of images obtained using temporally symmetric and asymmetric spin-echo sequences. Previous data indicate that the difference signal measured at an asymmetry time of 6 ms (delta 6ms) is very low in degassed lungs and increases markedly with alveolar opening. Theoretically, the NMR behavior of edematous lungs is expected to differ from that of normal nondegassed lungs because alveolar flooding and collapse are equivalent to partial (regional) degassing. To test this prediction, we measured delta 6ms in normal and edematous (oleic acid-injured) excised unperfused rat lungs at 5, 10, 20, 30, and 0 (full passive deflation) cm H2O inflation pressure (PL). Lung volume changes were estimated from NMR lung water density (pH2O) measurements. In normal lungs, delta 6ms did not vary with PL. In edematous lungs delta 6ms was, as predicted, significantly lower than normal at 5 and 10 cm H2O PL but rose markedly (to about normal) as PL was further increased. Upon subsequent deflation from 30 to 0 cm H2O PL, delta 6ms did not vary significantly or decreased. On the basis of our theoretical models, the data could be interpreted as reflecting the loss of alveolar air/tissue interface as a result of alveolar flooding and the relative contributions of airspace recruitment and distension to the lung volume changes. Histologic and morphometric data obtained from the same lungs supported this interpretation.(ABSTRACT TRUNCATED AT 250 WORDS)

[A case of nephrotic syndrome mimicking membranoproliferative glomerulonephritis (MPGN) and associated with reactive hemophagocytic syndrome after renal death]

We report a case of nephrotic syndrome which mimicked membranoproliferative glomerulonephritis (MPGN) and was associated with hemophagocytic syndrome after renal death. A 41-year-old Japanese man was referred to our hospital because of nephrotic syndrome in February 1979. He had no signs, symptoms nor laboratory data suggestive of liver damage. He was diagnosed as idiopathic MPGN and administered prednisolone and cyclophosphamide (total dose of about 50,000mg). He developed end-stage renal disease, and dialysis therapy was initiated in February 1992. Simultaneously, he was diagnosed as hepatitis C virus (HCV)-positive liver cirrhosis. In August 1994, he died because of reactive homophagocytic syndrome, which occurred in the setting of immunosuppression due to chronic renal failure, liver cirrhosis, and sesecondary diabetes. In this case, we can not deny the possibility that radical therapeutic intervention against "idiopathic MPGN" had a negative effect on the clinical course of chronic HCV infection.

Effect of a novel cholecystokinin receptor antagonist, FK480, administered intraduodenally, on pancreatic secretion in rats

The effect of a new cholecystokinin (CCK)-A receptor antagonist, FK480, developed in Japan, on pancreatic exocrine secretion stimulated by exogenous CCK and intraduodenal casein was investigated in vivo when administered to anesthetized rats intraduodenally, and its CCK antagonistic activity was compared with that of CR 1505. Intraduodenal administration of FK480 at graded doses of 0.0016-1.0 mg/kg-h produced dose-dependent inhibition of pancreatic juice volume and amylase output stimulated by intravenous infusion of CCK-8 at a dose of 0.06 micrograms/kg-h. The half-maximal inhibitory dose (ID50) of FK480 for CCK-8-stimulated amylase secretion was 0.025 mg/kg-h, whereas the ID50 of CR 1505 was 5.2 mg/kg-h, indicating that FK480 is 208 times more potent than CR 1505. Moreover, intraduodenal FK480 (0.2 mg/kg-h) significantly suppressed pancreatic juice volume and amylase output augmented by intraduodenal infusion of casein (400 mg/h). It is concluded that FK480 administered intraduodenally has a significant, potent inhibitory action on the exocrine pancreas stimulated by exogenous CCK and intraduodenal casein.

Granulomatous lesions caused by Pseudomonas aeruginosa in the ostrich (Struthio camelus)

Granulomatous lesions were observed in imported ostriches aged 3 months. Clinically, the birds showed lassitude, incoordination, and inappetence. At necropsy, yellowish white nodules often accompanied by a pseudodiphtheritic membrane were found in the oral, pharyngeal, tracheal and air sac mucosae, the lungs, oesophageal serosa, and abdominal peritoneum. Histopathological examination revealed purulent granulomatous lesions containing central bacterial colonies with an outer shell and club formation. The bacteria were small Gram-negative bacilli, which showed positive immunohistochemical staining for Pseudomonas aeruginosa. The bacterial colonies were positive for chicken IgM. Clubs around the colonies were negative for P. aeruginosa and chicken IgM. Such findings have not previously been reported in the ostrich.

Immunological responses to polyvalent canine vaccines in dogs

The immunological responses to commercially available polyvalent vaccines in dogs were examined. There was a tendency in decreased lymphocyte counts on day 7 in the puppy and adult dogs. There was a significant increase in the blastogenesis of lymphocytes on day 7 and 21 in puppies, whereas no significant changes were seen in the adult dogs. Delayed type hypersensitivity (DTH) responses to phytohemagglutinin (PHA) and canine parvo-virus (CPV) vaccine monitored 0, 3, 8 weeks after vaccination produced strong reactions, in particular those to CPV vaccine rose significantly after vaccination and maintained the higher responses for at least 2 months. Therefore, it is considered that vaccination is immunomodulative rather than immunosuppressive and that DTH responses to PHA and CPV vaccine are helpful to monitor non-specific and specific immune functions in vivo.

Dietary high-linoleate safflower oil is not hypocholesterolemic in aged mice after a long-term feeding--comparison with lard, perilla oil and fish oil

Aged mice (6 months of age) fed a conventional diet were shifted to diets containing 10% lard, high-linoleate safflower seed oil, high alpha-linolenate perilla seed oil or high-docosahexaenoate fish oil. A significant increase in whole body cholesterol (/g wt) was seen within 30 d after the shift (rapid response), followed by a gradual decrease in 60 to 120 d (slow response); similar changes occurred in all the dietary groups. Shortly after the shift, the serum cholesterol concentrations increased to higher levels in the lard and safflower oil groups than in the other groups, and the levels at 120 d were in the group order of safflower oil > lard > perilla oil > fish oil. Rapid and slow responses to dietary shifts were also seen in hepatic cholesterol levels (/g wt), which were higher in the lard group than in the other groups at 120 d. The arterial cholesterol contents of the fish oil group tended to be less than in the other groups at 120 d. Thus in aged mice after a relatively long-term feeding (> one tenth of the life-span), safflower oil was not hypocholesterolemic as compared with lard and other omega 3-rich oils. Long-term feeding of fish oil maintained serum cholesterol concentrations at lower levels than feeding with safflower oil or lard and without accumulating cholesterol in the aorta, liver or whole body; perilla oil was also hypocholesterolemic but to a lesser degree than fish oil.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical localization of keratins and involucrin in solar keratosis and Bowen's disease

The present study was conducted to determine the patterns of immunohistochemical characterization of keratin (K) and involucrin in solar keratosis and Bowen's disease in order to clarify the abnormal differentiation or maturation of the tumor cells in these precancerous epithelial dermatoses. Seventeen human anti-cytokeratin antibodies and an anti-involucrin antibody were used to examine 15 cases of solar keratosis and 18 cases of Bowen's disease. Formalin-fixed and paraffin-embedded sections were stained with these antibodies by the avidin-biotin-peroxidase technique. In solar keratosis, keratin and involucrin distribution was similar to that in normal epidermis, whereas in Bowen's disease the keratin distribution varied among individual cases. The dyskeratotic cells in Bowen's disease showed a reduction or loss of staining with these antibodies, and they were occasionally positive for keratin 19. These observations suggest that there is a difference in keratin and involucrin expression between solar keratosis and Bowen's disease and that the atypical cells of Bowen's disease exhibit a diversity of differentiation.

A lysophosphoinositide-specific phospholipase C distinct from other phospholipase C families in rat brain

Distinct phospholipase C activities capable of hydrolyzing lysophosphatidylinositol (lysoPI-PLC) or phosphatidylinositol (PI-PLC) have been demonstrated in rat brain membranes. Treatment of brain membranes with 1 M NaCl or 1% sodium cholate solubilized a majority of PI-PLC activity from the membranes, whereas a significant level of lysoPI-PLC activity still remained membrane-associated. Most of the lysoPI-PLC activity was recovered in a 0.5% sodium deoxycholate-0.25 M NaCl extract which contained only low levels of PI-PLC activity. Using the separated fractions, differences between lysoPI-PLC and the known PI-PLC isoforms were examined. A specific peptide inhibitor of PI-PLC, which was previously shown to interact with active site regions common to known PI-PLC activity. Immunoblot analysis of both the lysoPI-PLC-rich and PI-PLC-rich fractions revealed that an antiserum against PI-PLC delta 1 cross-reacted with other PI-PLC isoforms, but not significantly with lysoPI-PLC. Furthermore, lysoPI-PLC was more resistant to sulfhydryl reagents than was PI-PLC. Our results indicate that lysoPI-PLC is an enzyme distinct from PI-PLC and that lysoPI-PLC possesses a different active site than known PI-PLC isoforms.

High affinity chimeric human granulocyte-macrophage colony-stimulating factor receptor carrying the cytoplasmic domain of the beta subunit but not the alpha subunit transduces growth promoting signals in Ba/F3 cells

Granulocyte-macrophage colony-stimulating factor receptor (GMR) is composed of two distinct subunits alpha and beta, and the cytoplasmic domains of both subunits are essential to transduce signals. We further analyzed the role of the cytoplasmic domain of each subunit by constructing chimeric subunits, designated alpha/beta and beta/alpha, by exchanging cytoplasmic domains of the alpha and beta subunits of hGMR. Reconstituted high-affinity chimeric hGMRs, hGMR(alpha/beta,beta/alpha) and hGMR(alpha/beta,beta), as well as the wild type hGMR(alpha,beta), transduced signals in Ba/F3 cells. These observations indicate that the original configuration between the extracellular and the cytoplasmic domains of the hGMR(alpha,beta) subunits is not obligatory, and that hGMR(alpha/beta,beta) transduced signals through the cytoplasmic domain of the beta subunit in an oligomeric form, without involvement of the cytoplasmic domain of the alpha subunit.