Development of a versatile high-throughput mutagenesis assay with multiplexed short read NGS using DNA-barcoded supF shuttle vector library amplified in non-SOS E. coli

A forward mutagenesis assay using the supF gene has been widely employed for the last several decades in studies addressing mutation frequencies and mutation spectra associated with various intrinsic and environmental mutagens. In this study, by using a supF shuttle vector and non-SOS-induced Escherichia coli with short-read next-generation sequencing (NGS) technology, we present an advanced method for the study of mutations, which is simple, versatile, and cost-effective. We demonstrate the performance of our newly developed assay via pilot experiments with ultraviolet (UV) irradiation, the results from which emerge more relevant than expected. The NGS data obtained from samples of the indicator E. coli grown on titer plates provides mutation frequency and spectrum data, and uncovers obscure mutations that cannot be detected by a conventional supF assay. Furthermore, a very small amount of NGS data from selection plates reveals the almost full spectrum of mutations in each specimen and offers us a novel insight into the mechanisms of mutagenesis, despite them being considered already well known. We believe that the method presented here will contribute to future opportunities for research on mutagenesis, DNA repair, and cancer.

Expression and action of hepatocyte growth factor in bovine endometrial stromal and epithelial cells in vitro

Hepatocyte growth factor (HGF) is a pleiotropic growth factor that acts on various epithelial cells. The objectives of this study were to determine whether HGF altered the proliferation and prostaglandin (PG) secretion of bovine endometrial stromal and epithelial cells in vitro. We also observed HGF and HGF receptor (c-met) mRNA expression in cultured bovine endometrial stromal and epithelial cells by RT-PCR. Stromal and epithelial cells obtained from cows in early stage of the estrous cycle (days 2-5) were cultured in DMEM/Ham's F-12 supplemented with 10% calf serum. The cells were exposed to HGF (0-10 ng/ml) for 2, 4, or 6 days. HGF significantly increased the total DNA in epithelial (P < 0.05), but not stromal cells. In another experiment, when the cells reached confluence, the culture medium was replaced with fresh medium with 0.1% BSA containing HGF 0-100 ng/ml and the cells were cultured for 24 hr. The HGF stimulated PGF2alpha secretion in epithelial, but not stromal cells. RT-PCR revealed that mRNA of HGF is expressed only in stromal cells, and that c-met mRNA is expressed in both stromal and epithelial cells. These results suggest that HGF plays roles in the proliferation and the regulation of secretory function of bovine endometrial epithelial cells in a paracrine fashion.

Glutathione-S-transferase-pi expression regulates sensitivity to glutathione-doxorubicin conjugate

We have reported that glutathione-doxorubicin conjugate (GSH-DXR) exhibited potent cytotoxicity against tumor cells and inhibited glutathione-S-transferase (GST) enzyme activity. In order to determine whether or not the expression of GST-pi lowered the cytotoxicity of GSH-DXR, cytocidal activity of the conjugate was examined using tumor cells in which the level of GST-pi expression was regulated by transfecting GST-pi cDNA in the correct or reverse direction and comparing with that of DXR. Enhancement of GST-pi expression by transfecting GST-pi sense cDNA into human hepatoblastoma HepG2 cells in which GST-pi expression was extremely low caused an increase in GST activity from 0.26 to 55.0 nmol/mg/min and a marked reduction in transfectant sensitivity to GSH-DXR to 1/120 (0.15-18 nM IC50) although the sensitivity to DXR was slightly decreased to 1/2.6 (380-990 nM IC50). By contrast, a high GST-pi-expressing human colon cancer cell line, HT29, showed a decrease in GST enzyme activity from 72.0 to 45.9 nmol/mg/min after transfecting GST-pi antisense cDNA and a marked improvement in transfectant sensitivity to GSH-DXR was observed (28-2.9 nM IC50) compared with the transfectant sensitivity to DXR (1020-320 nM IC50). Additionally, the expression of GST-pi in HepG2 cells caused a decrease in GSH-DXR-induced activation of caspase-3, which was an apoptotic marker, whereas the suppression of GST-pi in HT29 cells showed an increase in caspase-3 activation. These results suggested that the cytocidal efficacy of GSH-DXR, but not that of DXR, was controlled by the level of GST-pi expression in the cells.

Temperature sensitivity in peroxisome assembly processes characterizes milder forms of peroxisome biogenesis disorders

Peroxisome biogenesis disorders (PBDs) contain various clinical phenotypes; Zellweger syndrome (ZS), neonatal adrenoleukodystrophy (NALD), and infantile Refsum disease (IRD), decreasing in the clinical severity in this order. We found that all IRD cell lines and some NALD lines belonging to several different complementation groups are temperature-sensitive in peroxisome assembly; that is, they lacked catalase-positive peroxisomes at 37 degrees C, but do gain the peroxisomes at 30 degrees C. We identified heterozygous mutations E55K/R119Stop in the PEX2 gene of an IRD patient of complementation group F. The E55K mutation was the direct cause of the temperature-sensitivity because similar phenotypes could be transferred to PEX2-defective CHO cells by transfecting the mutant gene. Thus, temperature-sensitive peroxisome assembly is representative of milder forms of PBDs.

Catalase-less peroxisomes. Implication in the milder forms of peroxisome biogenesis disorder

We established a Chinese hamster ovary cell line having a temperature-sensitive phenotype in peroxisome biogenesis. This mutant (65TS) was produced by transforming a PEX2-defective mutant, Z65, with a mutant PEX2 gene, PEX2(E55K), derived from a patient with infantile Refsum disease, a milder form of peroxisome biogenesis disorder. In 65TS, catalase was found in the cytosol at a nonpermissive temperature (39 degrees C), but upon the shift to a permissive temperature (33 degrees C), catalase gradually localized to the structures containing a 70-kDa peroxisomal membrane protein, PMP70. In contrast to catalase, other matrix proteins containing typical peroxisome targeting signals, acyl-CoA oxidase and peroxisomal 3-ketoacyl-CoA thiolase, were co-localized with PMP70 in most cells, even at 39 degrees C. We found that these structures are partially functional peroxisomes and named them "catalase-less peroxisomes." Catalase-less peroxisomes were also observed in human fibroblasts from patients with milder forms of peroxisome biogenesis disorder, including the one from which the mutant PEX2 gene was derived. We suggest that these structures are the causes of the milder phenotypes of the patients. Temperature-dependent restoration of the peroxisomes in 65TS occurred even in the presence of cycloheximide, a protein synthesis inhibitor. Thus, we conclude that in 65TS, catalase-less peroxisomes are the direct precursors of peroxisomes.

A case of acute myocardial infarction associated with topical use of minoxidil (RiUP) for treatment of baldness

A 45-year-old Japanese man with paroxysmal atrial fibrillation (AF) developed acute anteroseptal myocardial infarction (MI). He had used 1% topical minoxidil (RiUP) once a day for 4 months before the onset of MI for treatment of baldness. Coronary angiography demonstrated severe stenosis at the proximal portion of the left anterior descending coronary artery with a tilling defect. Electrocardiographic monitoring revealed paroxysmal AF and sinus bradycardia with sinus arrests, suggestive of sick sinus syndrome. Topical minoxidil is now widely used for the treatment of male pattern baldness. Although it may be difficult to relate topical use of minoxidil to myocardial ischemia, a greater awareness of its toxicity will be necessary, and patients with cardiovascular disorders should be excluded from the therapy.

[Anesthetic management for placement of tracheobronchial stents in patients with airway stenosis]

We report the anesthetic management for stents placement in patients with tracheobronchial stenosis. The subjects were 6 patients with lung cancer and one patient with tracheal invasion of esophageal cancer. Anesthesia was induced with propofol, fentanyl and vecuronium, and maintained with propofol and vecuronium. After intubation, tracheostomy was performed. The patients were kept apnic during insertion of stents. Three patients had dynamic stents inserted from tracheostomy site and one orally. Three patients had Dumon stents inserted orally, but the procedure in one patient was cancelled because her stent could not be placed at appropriate position. We recommend the anesthetic management through the tracheostomy site for the placement of Dumon tubes or dynamic stents.

Characterization of Vibrio parahaemolyticus manganese-resistant mutants in reference to the function of the ferric uptake regulatory protein

In many bacteria, the ferric uptake regulatory protein (Fur) has a central role in the negative regulation of genes affected by iron limitation. In this study, Vibrio parahaemolyticus strains carrying mutations in the fur gene encoding Fur were isolated by the manganese selection method to assess the function of Fur in connection with alternations in the coordinate expression of the siderophore vibrioferrin (VF) and iron-repressible outer membrane proteins (IROMPs). Ten out of 25 manganese-resistant mutants constitutively produced VF and expressed at least two IROMPs irrespective of the iron concentration in the medium. PCR-direct DNA sequencing of the fur genes in these mutants identified four different point mutations causing amino acid changes. Moreover, a fur overexpressing plasmid was constructed to prepare antiserum against V. parahaemolyticus Fur. Western blotting with this antiserum revealed that the intracellular abundance of the wild-type Fur was not significantly affected by the iron concentrations in the growth medium, and that the Fur proteins of the mutant strains occurred at substantially smaller amounts and/or migrated more rapidly in sodium dodecyl sulfate-polyacrylamide gel electrophoresis than the wild-type Fur. These data afford an additional insight into the structure-function relationship of Fur and imply its involvement in the iron acquisition systems of V. parahaemolyticus, although it is yet unknown whether its action on the target genes is direct or indirect.

Formation of peroxisomes from peroxisomal ghosts in a peroxisome-deficient mammalian cell mutant upon complementation by protein microinjection

Most mammalian cell strains genetically deficient in peroxisome biogenesis have abnormal membrane structures called ghosts, containing integral peroxisomal membrane protein, PMP70, but lacking the peroxisomal matrix proteins. Upon genetic complementation, these mutants regain the ability of peroxisome biogenesis. It is postulated that, in this process, the ghosts act as the precursors of peroxisomes, but there has been no evidence to support this. In the present study, we investigated this issue by protein microinjection to a mutant Chinese hamster ovary cell line defective of PEX5, encoding a peroxisome-targeting signal receptor. When recombinant Pex5p and green fluorescent protein (GFP) carrying a peroxisome-targeting signal were co-injected into the mutant cells, the GFP fluorescence gathered over time to particulate structures where PMP70 was co-localized. This process was dependent on both Pex5p and the targeting signal, and, most importantly, occurred even in the presence of cycloheximide, a protein synthesis inhibitor. These findings suggest that the ghosts act as acceptors of matrix proteins in the peroxisome recovery process at least in the PEX5 mutant, and support the view that peroxisomes can grow by incorporating newly synthesized matrix proteins.

[Airway management in a patient with lower lip squamous cell carcinoma after radical surgical resection]

General anesthesia was scheduled in a patient who had undergone radical surgical resection because of his lower lip squamous cell carcinoma. His oral area had been reconstructed drastically and this pathological change indicated difficulties of mask fitting, mask ventilation and laryngoscopic intubation. Before induction of general anesthesia, we performed fiberbronchoscopic transnasal awake intubation. The patient's condition was stable during both intubation and operation. At the end of anesthesia, the tracheal tube was removed after the patient had become fully awake and had recovered completely from neuromuscular brockade. In conclusion, it is important to evaluate and recognize the difficult airway preoperatively. When this is suspected, awake intubation should be chosen to secure and guarantee the airway.

[Application of continuous intra-arterial blood gas monitoring system "Paratrend 7" for pulmonary lavage of a patient with alveolar proteinosis]

We applied a continuous intra-arterial blood gas monitoring system (Paratrend 7) to a patient with pulmonary alveolar proteinosis during pulmonary lavage. Lavage was performed under general anesthesia with one lung ventilation. We inserted the sensor of Patatrend 7 through a 20 G catheter into the radial artery, and monitored pH, PaCO2 and PaO2 continuously throughout the procedure. SpO2 and EtCO2 were also monitored. Saline 1000-1500 ml was instilled and drained repeatedly by volume limited methods. PaO2 values by Paratrend 7 increased during instillation and decreased during drainage of the irrigating fluid. In contrast, PaCO2 value by Paratrend 7 decreased slightly during instillation and increased during drainage. The change of SpO2 was almost the same as that by Paratrend 7, but the response time of pulse oxymetry was a little quicker than Paratrend 7. During the lavage procedure, respiratory and circulatory condition changed very rapidly, and it is necessary to monitor blood gas change intensively. Paratrend 7 is useful as a perioperative monitoring system, but pulse oxymetry might be sufficient during pulmonary lavage considering its cost.

[The efficiency of intermittent antegrade warm blood cardioplegia]

We studied the effects of modified Calafiore technique that is intermittent antegrade warm blood cardioplegia including potassium solution and oxygenated with normothermic cardiopulmonary bypass. From January 1996 to March 1997, 45 patients who had undergone elective coronary artery bypass grafting were assigned retrospectively to two groups. Warm group: 25 patients received intermittent antegrade warm blood cardioplegia with normothermic cardiopulmonary bypass. Cold group: 20 patients received intermittent antegrade cold blood cardioplegia with slight hypothermic cardiopulmonary bypass. Preoperative variables were similar in both groups. The rate of sinus rebeating after aorta declamping with DC was lower in warm group than in cold group [warm group 2/25 (8%) versus cold group 8/20 (40%); P < 0.05]. The levels of CK and CK-MB were significantly lower in warm group than in cold group on postoperative day 0. On postoperative day 0 and day 1, the dosage of cathecholamines were significantly less for the warm group than in the cold group. Perioperative events of IABP, PMI and neurological dysfunction were not statistically different. These results show that intermittent antegrade warm blood cardioplegia is a safe and effective method for myocardial protection. But it requires further assessment.

[Propofol anesthesia for a patient with insulinoma]

We experienced the anesthetic management of a 47-year-old woman with insulinoma. Removal of the tumor was performed under propofol, nitrous oxide, and epidural anesthesia. We tried the continuous infusion of glucose to maintain normal blood glucose level and to avoid intraoperative hypoglycemic event. The blood glucose and immunoreactive insulin (IRI) level were measured intermittently. After the removal of the insulinoma, the IRI level decreased rapidly to the normal range. In this case, neither hyperglycemic nor hypoglycemic episode was observed. The perioperative course was uneventful. Propofol has not been shown to significantly affect the release of insulin and glucose regulation. This case suggests that under the condition of continuous glucose infusion and blood glucose monitoring, propofol is an useful anesthetic agent for a patient with insulinoma.

[Prophylactic effect of nicorandil on perioperative coronary spasm]

The prophylactic effect of nicorandil on perioperative coronary spasm (CS) in CABG was examined retrospectively. The subjects were 313 patients who had undergone elective CABG. The patients were divided into two groups a control group receiving single administration of nitroglycerine (N = 196) and a nicorandil group receiving both nitroglycerine and nicorandil (4 mg.h-1-8 mg.h-1) (N = 107). The two groups were compared. The incidence of CS was 14 cases (7.1%) in the control group and 6 cases (5.6%) in the nicorandil group, demonstrating a significant difference. With the dose and the administration method employed in this study, no prophylactic effect of nicorandil on perioperative CS has been demonstrated.

Investigation of the mechanism of alcohol-induced bronchial asthma

BACKGROUND

Many Japanese patients with asthma experience episodes or exacerbation of asthma after alcohol consumption. This phenomenon is not seen in Caucasians and is specific to Asians. This has been thought to be attributable to a difference in alcohol metabolism, in particular the metabolism of acetaldehyde, between Asians and Caucasians.

METHODS

An oral ethanol challenge test, a leukocyte histamine release test, and an ELISA for detection of IgE specific to acetaldehyde-human serum albumin conjugate were carried out in 42 adults with bronchial asthma and nine healthy adults.

RESULTS

Fifty-five percent of the patients with asthma responded to the ethanol challenge and showed a 20% or greater reduction in forced expiratory volume in 1 second. Blood acetaldehyde and plasma histamine levels were significantly higher in responders than in nonresponders. The leukocyte histamine release test revealed no ethanol-induced histamine release. Acetaldehyde, on the other hand, was found to induce histamine release in a volume-dependent manner. The histamine release was significantly higher in the asthma group (both responders and nonresponders) than in the healthy control group. ELISA did not detect any IgE specific to acetaldehyde-human serum albumin conjugate.

CONCLUSION

Alcohol-induced bronchial asthma seems to develop as follows. Alcohol elevates blood acetaldehyde levels, which leads to degranulation of mast cells (or basophils). The resultant release of chemical mediators, such as histamine, induces asthma.

A clinical study of mortality due to asthma

BACKGROUND

Despite identification of the pathophysiologic mechanisms of asthma and improvement in therapy, asthma mortality has not decreased in recent years.

OBJECTIVE

The pathophysiology and asthma-related death preventive measures were investigated with a physician-based questionnaire survey.

METHODS

Questionnaires were sent to physicians primarily involved in treating asthma in Nagasaki Prefecture, Japan. The clinical characteristics of 32 patients who died of asthma (fatal cases) from 1984 to 1992 were compared with those of 17 patients with severe asthma who survived as a result of treatment by mechanical ventilation (nearly fatal cases).

RESULTS

The number of deaths due to asthma increased in the last 2 years. Fatal cases and nearly fatal cases included patients with severe asthma as well as patients with mild asthma. Analysis of the clinical histories of patients judged to have died suddenly revealed the presence of persistent wheezing in these patients for a few days prior to the fatal episode. Airway obstruction was more marked and bronchial hyperresponsiveness was greater in fatal cases compared with those of a group of 70 patients without a history of nearly fatal acute asthma.

CONCLUSIONS

The following measures may help prevent asthma deaths. Both patients and physicians should realize that even mild episodes can lead to severe, even fatal acute asthma. The severity of asthma should be evaluated not only by symptoms and peak expiratory flow rates but also bronchial hyperresponsiveness. Treatment should include reduction of bronchial hyperresponsiveness using oral or inhaled corticosteroids.

Mechanism on insulin-like action of vanadyl sulfate: studies on interaction between rat adipocytes and vanadium compounds

When rats with streptozotocin (STZ)-induced diabetes were given a daily intraperitoneal (i.p.) injection of VOSO4 (+4 oxidation state of vanadium), their serum glucose dropped from hyperglycemic level to normal level within 2d and serum free fatty acid (FFA) level also dropped to normal level. Vanadium was incorporated in most organs as well as in the adipose tissues, as detected by neutron activation analysis (NAA). The mechanism for the insulin-like action vanadium in terms of FFA release from isolated rat adipocytes was investigated: (1) Vanadyl (IV) and vanadic (III) ions normalize the FFA release in the adipocytes treated with epinephrine; (2) vanadate (V) ion treated with ascorbic acid, cysteine or glucose is effective in normalizing the FFA release but vanadate ion alone has no effect on FFA release; (3) vanadyl ion is incorporated into the adipocytes, while vanadate ion is not, as indicated by ESR spectroscopy; and (4) vanadyl ion can act on the glucose transporter, as indicated by experiments using cytochalasin B which is an inhibitor of this transporter. From these results, the normalization of both serum glucose and FFA levels by vanadyl ion was concluded to be due to the incorporation of vanadyl ion into the adipocytes, in which the metal ion acts on the glucose transporter and induces both the promotion of glucose uptake and the decrease of FFA release form peripheral adipocytes. The vanadyl state was suggested to be a possible pharmacologically active form of vanadium allowing the insulin-like action.(ABSTRACT TRUNCATED AT 250 WORDS)

[Six cases of allergic bronchopulmonary aspergillosis]

Six cases of allergic bronchopulmonary aspergillosis (ABPA) were evaluated. In four cases, diagnosis and steroid therapy were delayed, which resulted in irreversible pulmonary dysfunction. The important points for early diagnosis were: (1) Differentiation from pulmonary tuberculosis, (2) the presence of bronchial asthma was not essential for diagnosis, and (3) fungi other than Aspergillus fumigatus might cause this syndrome.

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor binds human recombinant IL-1 (alpha and beta) and inhibits IL-1 actions in vitro and in vivo

A synthetic peptide corresponding to 86-93 of the human type I IL-1 receptor and its analogues bound human recombinant (hr) IL-1 (alpha and beta) and inhibited dose-dependently both Con A-stimulated proliferation of mouse spleen cells and hrIL-1 beta-stimulated formation of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells in rat bone marrow cell cultures. Furthermore, hrIL-1 beta-induced mouse paw edema was dose-dependently inhibited by systemic administration (ip) of the synthetic peptide. These results suggest that one of the IL-1 binding sites of the human type I IL-1 receptor comes to the region of 86-93 and the synthetic peptide having the ability to bind hrIL-1 (alpha and beta) blocks the biological activities of exogenous hrIL-1 beta and endogenous mouse IL-1.

A gene coding for a zinc finger protein is induced during 12-O-tetradecanoylphorbol-13-acetate-stimulated HL-60 cell differentiation

ETR103 cDNA was cloned as an immediate early gene in the course of macrophagic differentiation of HL-60 cells stimulated by TPA (12-O-tetradecanoylphorbol-13-acetate). The induction by TPA was immediate-early (within 30 min) and transient. This gene was not induced by vitamin D3 or by retinoic acid, which stimulates differentiation of HL-60 cells to the monocytic or granulocytic lineage, respectively. The ETR103 mRNA was induced by TPA in lymphoid or myeloid leukemia cell lines of several maturation stages. The induction by TPA seems to proceed by a protein kinase C-mediated mechanism, on the basis of the results obtained by using protein kinase C inhibitor (H-7), protein kinase C activator (diC8), and an activator of protein kinase A (dibutyryl cAMP). Okadaic acid, an inhibitor of protein phosphatases, also induced the ETR103 mRNA expression. The nucleotide sequence of the ETR103 cDNA reveals that ETR103 encodes a human zinc finger-containing transcription factor identical to Egr-1 and 225, which is homologous to mouse Egr-1, Zif/268, Krox-24, and TIS8, or to rat NGFI-A.

Effects of glutathione depletion on the synthesis of proteoglycan and collagen in cultured chondrocytes

We studied the effect of the depletion of glutathione on the synthesis of proteoglycan and collagen in cultured chick chondrocytes. When the cultured chondrocytes were incubated with 1 mM buthionine sulfoximine (BSO), a specific inhibitor of gamma-glutamyl-cysteine synthetase, the intracellular glutathione level markedly dropped within 12 h with no loss of cell viability. Incorporation of 35SO2-4 into proteoglycan was lowered in the presence of BSO. When the 35S-labeled proteoglycans were separated into two fractions by glycerol density gradient centrifugation, the inhibitory effect of BSO on the synthesis of proteoglycan was greater in the fast-sedimenting proteoglycan fraction, which consisted mainly of cartilage specific large proteoglycan (PG-H), than in the slowly sedimenting proteoglycan fraction. The inhibition by BSO of the synthesis of core protein-free glycosaminoglycan chains primed by p-nitrophenyl-beta-D-xyloside was smaller than the inhibition of the synthesis of proteoglycan. Analysis of glycosaminoglycans labeled with [3H]glucosamine indicated that the treatment of chondrocytes with BSO resulted in a small increase in the proportion of synthesis of hyaluronic acid to the synthesis of total glycosaminoglycan. The incorporation of [3H]proline into collagen was also inhibited by BSO. Sodium dodecyl sulfate polyacrylamide gel electrophoresis of the 3H-labeled collagen showed that, in the presence of BSO, processing of Type II collagen appeared to slow down and the proportion of Type X collagen synthesis was reduced.

Expression of a novel immediate early gene during 12-O-tetradecanoylphorbol-13-acetate-induced macrophagic differentiation of HL-60 cells

Human promyelocytic leukemia cell line, HL-60, undergoes macrophagic differentiation when it is stimulated with TPA (12-O-tetradecanoylphorbol-13-acetate). We have cloned ETR101 cDNA whose mRNA was induced immediate early (30 min) and transiently by TPA. The mRNA is superinduced by addition of the protein synthesis inhibitor cycloheximide. The sequence of ETR101 cDNA (1826 base pairs) reveals that (i) it will encode a protein of 223 amino acids with a formula molecular weight of 24,200, (ii) the amino acid sequence is highly homologous to mouse chx1 protein whose mRNA was found recently to be enhanced in activated T lymphocytes in response to cycloheximide, (iii) the amino acid sequence is also weakly homologous to jun family gene products, and (iv) in the mRNA 3'-flanking region, there is a unique GUUUG sequence which is complementary to a part of B1 repetitive sequence and may be involved in mRNA degradation. ETR101 mRNA is induced by TPA in a wide variety of leukemia cells including myeloid, T-lymphoid, and B-lymphoid lineages. We have found that this mRNA is also induced by okadaic acid, a protein phosphatase inhibitor, and that TPA or cycloheximide act synergistically with okadaic acid. In addition, the induction is inhibited by protein kinase C inhibitors. Therefore, ETR101 mRNA level is controlled, either directly or indirectly, by protein phosphorylation.

Cation channels from ciliary membrane of Tetrahymena reconstituted into planar lipid bilayer. Comparison between the channels from the wild T. thermophila and from its mutant which does not show ciliary reversal

Cation channels in ciliary membrane vesicles from wild type Tetrahymena thermophila and from its mutant which does not show ciliary reversal or avoiding reaction were reconstituted into a planar lipid bilayer. Since the mutant does not produce the regenerative Ca2+ action potential, the mutation was expected to have occurred at the Ca-channel in the ciliary membrane. In the sample from the mutant, the channel most frequently observed was selective for cations over anions. The single channel conductance shows Michaelis-Menten type dependency on the cation concentration. The maximum conductance and dissociation constants (in parenthesis) for K+, Mg2+, Ca2+, and Ba2+ were 371 pS (23.3 mM), 17 pS (0.49 mM), 18 pS (0.52 mM), and 25 pS (0.82 mM), respectively, when the anion was gluconate. The properties of the corresponding channel from the wild type are similar to those from the mutant. No essential difference was detected, which indicates that the predominant channel is not the putative Ca channel responsible for the avoiding reaction of Tetrahymena. Some other channels than the predominant channel were also observed.