Photocurrent measurements of the purple membrane oriented in a polyacrylamide gel

When illuminated, oriented purple membranes isolated from Halobacterium halobium give a photoelectric effect. The frequency response of a photocurrent measuring system for purple membranes oriented and immobilized in a polyacrylamide gel is analyzed from DC to 100 MHz. The waveform of the photocurrent can depend on both the sample conditions (including bathing solution) and the measuring system (electrode and ammeter) at both the low and high frequency ends. In the DC-1 kHz range (millisecond signals), the apparent lifetime of the photocurrent component is distorted if the electrode is not platinized and if the conductivity of the bathing solution is not low. In the 1 kHz to 1 MHz range (microsecond signals), the frequency response is flat under most conditions. In the MHz range (nanosecond signals), the apparent lifetime of the photocurrent component will be distorted if the conductivity of the bathing solution is not high and if the input impedance of the ammeter is not low and constant throughout the frequency range. With our optimized apparatus, we could measure the photocurrent components from oriented purple membrane with lifetimes from 70 ms to 32 ns without distortion by the measuring system.

Transition of environmental polarity of tyrosine-76 of Trimeresurus flavoviridis phospholipase A2 upon active site ligand binding

Modification of Trimeresurus flavoviridis phospholipase A2 with a 5-fold molar excess of tetranitromethane produced 40% active mononitrotyrosyl phospholipase A2 in which Tyr-76 was specifically nitrated. This is in contrast to the case of mammalian pancreatic phospholipases A2 where Tyr-70 but not Tyr-76 was nitrated. When Ca2+ was bound to T. flavoviridis mononitrotyrosyl phospholipase A2, nitrated tyrosine (Tyr(NO2))-76 moved from a less polar site to a polar site with the decrease of the pKa value of its hydroxyl group. Nitration of Tyr-76 did not influence the binding affinity to Ca2+. Addition of laurylphosphorylcholine to mononitrotyrosyl phospholipase A2 in the presence of Ca2+ caused the movement of Tyr(NO2)-76 from a polar environment to a less polar environment with the rise in the pKa value. Tyrosine-76 is located in the site whose environmental polarity is affected by the binding of the ligands to the active site. As Tyr-76 is located in the site not proximal to the active site, it could be assumed that the conformational change induced by the binding of the ligands extends to the region remote from the active site in T. flavoviridis phospholipase A2. This might provide evidence of long-range diffusional coupling between remote sites in the noncooperative globular protein.

Inverse correlation between combined mutagenicity in Salmonella typhimurium and strength of coordinate bond in mixtures of cobalt(II) chloride and 4-substituted pyridines

Cobalt(II) chloride (CoCl2), non-mutagenic by itself, has been tested for mutagenic activity in the presence of 4-substituted pyridines in the test strains of Salmonella typhimurium. CoCl2 was found to be mutagenic in strains TA1537 and TA2637, when combined pyridine, with methyl isonicotinate, 4-methyl-pyridine, 4-ethylpyridine, 4-chloropyridine or 4-bromopyridine. Mixtures of CoCl2 and isonicotinic acid, 4-cyanopyridine, 4-aminopyridine, or 4-dimethylaminopyridine exhibited no mutagenicity. Judging from the spectral observations, such combined mutagenicity may be due to the formation of moderate to weak complexes between these compounds and the Co(II) cation.

The guinea-pig step cycle: X-ray cinematographic analysis of the forelimb during pharmacologically induced "stepping automatism"

"Stepping automatism" has generally been studied in mesencephalic or spinal cats and has been induced electrically with the animal on a treadmill (Shik and Orlovsky 1976). Derivatives of 4-R-2,2,5,5-tetrakis (trifluoromethyl)-imidazoline (SIS = Substances capable of Inducing Stepping) I-IV (Liu 1985, Liu et al. 1984) can induce regular "stepping automatism" in guinea pigs. The present paper concerns the guinea-pig step cycle of the forelimb during SIS II-induced "stepping automatism" analysed with the use of X-ray cinematography and electromyography (EMG) studies in suspended animals. Results show that the flexion phase (F E1) and the extension phase (E2 E3) of the SIS-induced step cycle are quite comparable to those of the normal step cycle in other quadrupedal animals walking on the ground. The excursions of elbow, shoulder and scapula joints are all in phase in F and E3, whereas the scapula is largely out of phase with the elbow and shoulder during E1 and E2. It is surprising that during SIS II-induced locomotion in guinea pigs suspended in the air, "yield" could be seen in both, the elbow and the shoulder joints.

Effect of cooling of the culmen of the cerebellar vermis on chemically induced stepping in guinea pigs

A regular 'stepping automatism' was induced via our recently reported SIS (substances capable of inducing stepping) in guinea pigs. Reversible cooling (5-0 degrees C) or partial ablation of the culmen of the cerebellar vermis could facilitate SIS-induced stepping, whereas electrical stimulation (300 microA up) of the same region could attenuate or abolish stepping. Cooling could only facilitate, but not trigger stepping movements. The above-mentioned facilitation was most prominent in those guinea pigs that exhibited a weak stepping automatism. Cooling of the lateral part of the culmen of the cerebellar vermis and hemisphere mainly facilitated stepping of the ipsilateral forelimb. When the interfacial temperature between the cooling probe and tentorium cerebelli was appropriate (5-0 degrees C), cooling could mimic the effects of ablation to a great extent.

Studies on Ricinus communis lectin--carbohydrate interaction by means of affinity electrophoresis

The affinity gel electrophoresis of lectins purified from the seeds of Ricinus communis was studied. The mobilities of lectins on the gel showed various degree of retardation with their affinity toward their macromolecular ligand-agarose. Ricinus agglutinin which possessed the strongest affinity was retarded strongly, ricin C, and ricin B moderately, and ricin A, weakly. The concentrations of free moving ligand-galactose to reduce the retardation were also correlated very well with the potencies of affinities of lectins toward the ligand. The Kd values calculated from the retardations were 4.32 microM, 18.32 microM, 28.13 microM and 52.88 microM for ricinus agglutinin, ricin C, ricin B and ricin A respectively. Affinity gel electrophoresis was found to be a simple and quick method for studying the interaction of lectins with their ligands.

Studies on the antitumor lectins isolated from the seeds of Ricinus communis (castor bean)

Three toxic proteins and one agglutinin were purified from the seeds of Ricinus communis by a simple and fast method using Sepharose 4-B affinity chromatography followed by Sephadex G-100 gel filtration. The weakly adsorbed ricins A and B were retarded and eluted with the buffer from the affinity chromatographic column, while ricin C and ricinus agglutinin had to be eluted with 0.1 M galactose. The molecular weights of ricins A, B, and C were about 62,000 and that of ricinus agglutinin was 120,000, estimated by amino acid compositions and SDS gel electrophoresis. They all possessed two non-identical subunits: A and B chains linked by one disulfide bond. Their LD50 values were 4, 28, 14 and 112 micrograms per kg body weight of mice for ricins A, B and C and ricinus agglutinin, respectively. The amino acid compositions of the three toxins and their A and B subunits were very similar, but not identical, while ricinus agglutinin showed a different composition. Ricin A is a newly isolated lectin which has a strong inhibitory effect on the growth of tumor cells. By using cell cultures, it was demonstrated that the tumor cells were more sensitive to lectin than non-transformed cells, and that this could be caused by the higher binding affinity of lectin to tumor cells than to non-transformed cells.

Transformation of Halogen-, Alkyl-, and Alkoxy-Substituted Anilines by a Laccase of Trametes versicolor

The laccase of the fungus Trametes versicolor was able to polymerize various halogen-, alkyl-, and alkoxy-substituted anilines, showing substrate specificity similar to that of horseradish peroxidase, whereas the laccase of Rhizoctonia praticola was active only with p -methoxyaniline. The substrate specificities of the enzymes were determined by using gas chromatography to measure the decrease in substrate concentration during incubation. With p -chloroaniline as the substrate, the peroxidase and the Trametes laccase showed maximum activity near pH 4.2. The transformation of this substrate gave rise to a number of oligomers, ranging from dimers to pentamers, as determined by mass spectrometry. The product profiles obtained by high-pressure liquid chromatography were similar for the two enzymes. A chemical reaction was observed between p -chloroaniline and an enzymatically formed dimer, resulting in the formation of a trimer. All three enzymes oxidized p -methoxyaniline to 2-amino-5- p -anisidinobenzoquinone di- p -methoxyphenylimine, but only the T. versicolor laccase and the peroxidase caused the formation of a pentamer (2,5-di- p -anisidinobenzoquinone di- p -methoxyphenylimine). Our results demonstrate that in addition to horseradish peroxidase, a T. versicolor laccase can also polymerize aniline derivatives.

Differential effects of abrin on normal and tumor cells

The effects of the plant toxin abrin on normal mouse embryonic fibroblasts (MEF), an untransformed mouse cell line (NIH 3T3), and two mouse tumor cell lines (LMTK- and S-180) were studied. Measurements of cell growth and colony formation showed that MEF and S-180 cells were more sensitive to abrin intoxication than NIH 3T3 and LMTK- cells. Also, the effects of abrin on the inhibition of [3H]leucine and [3H]thymidine incorporation were more evident in MEF and S-180 cells. The basis for these varying responses to abrin by the four different cells was examined. The number of abrin binding sites per cell was determined from [125I]abrin binding studies: NIH 3T3 and LMTK- cells had significantly fewer abrin binding sites than MEF and S-180 cells. The fate of the [125I]abrin after internalization was examined by gel electrophoresis and autoradiography. A pattern of time-dependent degradation was observed, degradation being more rapid in NIH 3T3 and S-180 cells than in LMTK- and MEF cells. We conclude that the varying responses of different cells to the toxin abrin may be due to several factors, including the relative number of abrin binding sites on the cell surface and the rate of degradation of the toxin once internalized. The results also show that the sensitivities of the cells to abrin do not necessarily correlate with their normal or neoplastic state.

Synthesis of delta sleep-inducing peptide (DSIP) and its physiological activity

Protected nonapeptide--Delta Sleep-Inducing Peptide (DSIP) formula: see text has been synthesized by classical method. The product has been treated with TFA and purified on DEAE-Sephadex-A25 column, pure free nonapeptide obtained and alpha to beta transposition of Asp-residue found to be absent. It has been assayed by electrophoresis at pH 3.8, microcrystallinecellulose TLC and HPLC. The physiological activities of synthetic DSIP are performed on rabbits by using intravenous administration or mesodiencephalic ventricular infusion. Its function of intensifying delta and sigma waves on rabbit's electroencephalogram (EEG) is evident. There is no concomitant increase of delta- and sigma-enhancing effect following mesodiencephalic ventricular infusion of 10 or 20 times higher than 5 microgram/rabbit doses. Results of 6-day consecutive intravenous administration (50 microgram/kg) indicate that there is no obvious sign of adaptation to DSIP. Results suggest that the physiological function of endogenous sleep-inducing peptide is different from that of general sleeping draught.

Hypoxia, calcium, and contracture as mediators of myocardial enzyme release

During calcium-free perfusion, anoxic contracture of myocardial cells causes cells to separate at intercalated disks and leads to an energy-independent enzyme release in the absence of active transmembrane calcium fluxes. It is proposed that contracture mediates membrane damage and enzyme release in cells sensitized to the calcium paradox.

[HLA and childhood asthma (author's transl)]

In order to study the relationship between human leukocyte antigens (HLA) and the occurrence of childhood bronchial asthma in Chinese, HLA typings were done, by using commercially available HLA immunoplates (Behring, West Germany), in 99 children with allergic bronchial asthma who attended the allergy clinic of the Department of Pediatrics, National Taiwan University Hospital and had been receiving hyposensitization. The results showed: (1) There was no difference in the frequency of HL-A antigens between patients and normals, (2) while HLA-B5 appeared more frequently in patients than in normals (relative risk 2.28-3.18, chi 2 = 15.39, p less than 0.001), HLA-B17 was less often seen in patients than in normals (relative risk 0.19, chi 2 = 33.49 p less than 0.001). It is, therefore, concluded that in Chinese, individuals carrying HLA-B5 have higher chance to be affected by bronchial asthma and those carrying HLA-B17 are less likely to become asthmatics in their childhood.

Pulmonary function in a typical case of Pickwickian syndrome

Pulmonary function was studied in a patient with Pickwickian syndrome, before and after a weight reduction of 160 kg which was brought about by jejunoileal bypass surgery. After weight reduction, there was an increase in alveolar ventilation, lung volumes and respiratory flow rates. Arterial blood oxygen tension, arterial oxygen saturation, arterial carbon dioxide tension and pH also showed a significant improvement towards normal. These findings indicate that reduction of body weight is beneficial for Pickwickian syndrome patients. The improvement of pulmonary function was probably due to the improvement of the patient's respiratory mechanics.

Asymmetric diphenol formation by a fungal laccase

A laccase isolated from the fungus Rhizoctonia praticola catalyzed the cross-coupling of two differently halogenated phenols. When 2,4-dichlorophenol and 4-bromo-2-chlorophenol were incubated together with the enzyme, three dimers were formed and isolated by thin-layer chromatography. The molecular weights of these compounds were determined by mass spectrometry as 322, 410, and 366, which correspond with the respective dimers of each of the phenols and with a hybrid formed from both, tentatively assigned the structure 3,3',5'-trichloro-5-bromo-2,2'-diphenol. Gas chromatography-mass spectrometry analysis of these products and of their methylated derivatives lent support to these structural assignments.

Characterization of an enzyme from Rhizoctonia praticola which polymerizes phenolic compounds

An extracellular phenol oxidase from the fungus Rhizoctonia praticola which polymerizes various xenobiotic phenols was isolated and characterized. The enzyme was purified by DEAE-cellulose and Sephadex G-200 chromatography followed by preparative polyacrylamide gel electrophoresis. Atomic absorption and EPR spectroscopy indicated the presence of copper, and SDS gel electrophoresis revealed a molecular weight of 78,000. With 2,6-dimethoxyphenol as substrate, the enzyme showed a pH optimum of 6.7--6.9, and a temperature optimum of 40 degrees C. According to these and additional characteristics it appears that the enzyme belongs to the class of laccases.

Fungal degradation of 1-naphthol

The biological degradation of 1-naphthol was studied during growth, with replacement cultures and cell extracts of the fungus Fusarium solani. Radioactivity of 1-naphthol-1-14C disappeared partially during growth, but it was completely dissipated by cell-extract activity. More than 80% of 14CO2 evolved was collected after 60 min incubation in a cell-extract experiment. The active enzymes seem to be constitutive inasmuch as 1-naphthol was metabolized with cells which were not cultured on an inducing substrate. No difference in activity could be observed between cell-free extracts prepared from spores or mycelium of the fungus.

Rates of infection with Japanese encephalitis virus of two culicine species of mosquito in Taiwan

The role of Culex annulus as a Japanese-encephalitis (JE) vector has been drawing increasing attention recently. In this small trial, the rate of JE virus infection in C. annulus was compared with that in C. tritaeniorhynchus summorosus in the north-western coastal area of Taiwan, where both species are common as JE vectors. In order to increase the recovery rate of the virus, the mosquitos were artificially incubated at 26-28 degrees C for 10 days after collection. Two out of 6 C. t. summorosus pools and 7 out of 31 C. annulus pools, collected during a 17-day period in June 1969, were positive for JE virus. The results strongly suggest that one of the factors determining the severity of virus emergence in Taiwan is the total density of both species during the critical period of emergence of viraemic amplifiers: the relative prevalence of the two species of mosquito seems to be less important.