Role of water receptor in the frog

To elucidate the role of the water receptor in the frog (Rana catesbeiana), reflex activities elicited by its excitation were studied. Application of tap water to the oral mucosa depressed the rhythmical movement of gorge (buccal) respiration, accompanied by an elevation of the inner pressure of the oral cavity (buccal pressure). Tonic reflex discharges were elicited in the nerves innervating the submental and submaxillary muscles, which close the nostrils, the pterygoid and the profound portion of the major masseter muscles, which produce a strong bite, and the geniohyoid and hyoglossus muscles, which elevate buccal pressure. These muscles, except for the pterygoid, also participate in the rhythmical movement of gorge respiration as expiratory muscles. Rhythmical movements in the minor masseter and sternohyoid muscles, which act as inspiratory muscles in gorge respiration, were depressed by the water stimulation of the oral mucosa. These findings indicate that the water receptor plays a role in the interruption of gorge respiratory movements, accompanied by an elevation of buccal pressure.     

Benthic foraminiferal fauna during the time of the Indian-Asian contact, in southern Balochistan, Pakistan

Cretaceous and early Paleocene benthic foraminifera were studied from one section along the western Gaj River, southern Balochistan, Pakistan, to reconstruct the paleoenvironment of the Tethys Sea during the Indian-Asian contact. We recognize three lithostratigraphic units in ascending order: the Mughal Kot Formation, the Pab Sandstone, and the Jamburo Group. Both the Maastrichtian Mughal Kot Formation, which consists of shale with grey marly limestone, and the Maastrichtian Pab Sandstone, which consists of quartzose sandstone, indicate an open ocean environment as they have diversified planktic and benthic foraminiferal assemblages. The Maastrichtian-Paleocene Jamburo Group, consisting of dark grey, calcareous shale and marlstone with some sulfide grains, is characterized by low diversities of benthic assemblages. The change to the lower diversities may be associated with the development of poor circulation of deeper water that was caused by narrowing of the Tethys Sea.The Trochammina spp. Assemblage from the Jamburo Group, which can be correlated with flysch-type agglutinated foraminiferal assemblages, has a low benthic species diversity, indicating an unfavorable condition for calcareous foraminifera because of the development of oxygen-depleted water. The absolute abundance of agglutinated specimens shows a remarkable change from low numbers in the Maastrichtian to high ones in the Paleocene. The benthic foraminiferal evidence supports the hypothesis that the collision of the Asian and Indian plates occurred near the end of the Cretaceous.     

Application of bacterial magnetic particles as novel DNA carriers for ballistic transformation of a marine cyanobacterium

Summary Bacterial magnetite particles (BMPs) of 50 to 100nm diam were used as DNA carriers for the ballistic transformation of the marine cyanobacteriumSynechococcus. BMPs were bombarded into the cyanobacterial cells at several bombardment velocities using a particle gun. Successful transformation and gene expression were confirmed by Southern hybridization and CAT assay, respectively. The BMPs were also observed in the cyanobacterial cells by transmission electron microscopy. These results suggested that BMPs can be used as carriers for introducing DNA into bacterial cells.     

Photomicrobial sensors for selective determination of phosphate

A photomicrobial sensor consisting of immobilized Chlorella vulgaris and an oxygen electrode has been developed for selective determination of phosphate. When 40 mM phosphate was added to the sensor system, the photocurrent increased to a maximum under light irradiation with a response time of 1 min. The current increased with increasing phosphate concentration in the range 8–70 mM. Selectivity of the sensor was satisfactory. Good agreement was obtained between the phosphate concentrations in lake water determined by the photomicrobial sensor and by conventional colorimetry (correlation coefficient 0.96).     

Photomicrobial electrode for selective determination of sulphide

Summary A photomicrobial electrode, which uses the photosynthetic bacteria Chromatium sp. in conjunction with a hydrogen electrode, was developed for the determination of sulphide. The response time of the photomicrobial electrode was 5–10 min. A linear relationship was obtained between the current of the electrode and the sodium sulphide concentration below 3.5 mM. The minimum detectable concentration of sodium sulphide was 0.4 mM. Selectivity of the sensor is satisfactory. A good agreement was obtained between the photomicrobial electrode and the ethylene blue method (correlation coefficient: 0.90).     

Possible participation of Ca2+, Mg2+-dependent endonuclease in liver DNA fragmentation after N-methyl-N-nitrosourea treatment

We examined the fragmentation of DNA treated with N-methyl-N-nitrosourea under conditions in which Ca2+, Mg2+-dependent endonuclease is active. The molecular mass of DNA found in mouse liver slices treated with methylnitrosurea in the presence of Ca2+ plus Mg2+ was 4 X 10(5) Da. Similar results were obtained with a reconstituted system containing partially purified Ca2+, Mg2+-dependent endonuclease and methylnitrosurea-treated DNA. The enzyme extensively cleaved methylnitrosurea-treated DNA, compared with non-treated DNA. The methylnitrosurea-treated nuclear proteins obtained from mouse liver nuclei had no effect on the DNA fragmentation by the enzyme. Using closed-circular DNA treated with methylnitrosurea, the enzyme produced single-strand cuts in the DNA, as was seen in non-treated, closed-circular DNA, however, the rate of hydrolysis was increased. Ca2+, Mg2+-dependent endonuclease thus warrants further investigation, with regard to the precise mechanism of extensive degradation of DNA in cells treated with carcinogenic alkylating agents.     

UV Irradiation induces an activity which stimulates Simian virus 40 rescue upon cell fusion.

UV irradiation of African green monkey cells greatly stimulated efficiency of simian virus 40 induction from simian virus 40-transformed Syrian hamster cells after cell fusion. The maximum inducing activity was observed at 15 to 20 h after irradiation but remained only transiently. The addition of cycloheximide after UV irradiation eliminated the stimulation of the activity.     

Some Characteristics of Protein Kinases in Lemna paucicostata

The three protein kinases of Lemna paucicostata that are separableby DEAE-Sephacel chromatography have been designated PI, PIIand PIII [Kato et al. (1983) Plant & Cell Physiol. 24: 841].The optimum pH for the PI and PII enzymes was 7.5 and for thePHI enzyme 7.0. The activities of these enzymes were stimulatedby divalent cations, the maximum stimulation being producedby 5 nw Mg^{2 $} for PI, by 3 mM Co^{2 $} for PII and by 1 mM Mn^2$ for PIII. The cytokinins; benzyladenine, kinetin and zeatin,inhibited the activity of the PIII enzyme. The molecular weightsof the PI and PII enzymes did not change after incubation withcAMP even though their activities were regulated by this compound. (Received October 17, 1983; )     

Separation of keratinocytes by density gradient centrifugation for DNA cytofluorometry

Summary A method for the separation of guinea pig epidermal keratinocytes, in which the Feulgen-stainable material suffers minimal damage, has been investigated. The principal stage involves trypsin treatment of the epidermal sheet, stripped from the dermis with ethylenediamine tetraacetic acid. The epidermal cells thus isolated are separated into three groups by centrifugation on a continuous colloidal silica (Percoll) density gradient. The resulting arrangement of the keratinocytes in the centrifuge tube corresponds to their arrangement in situ, with basal cells at the bottom and the more differentiated cells above. By morphological examination, it can be shown that relatively pure fractions of basal cells, spinous cells, and granular cells are obtained by this method. With respect to DNA distribution pattern, there was good agreement between that of keratinocytes separated by the microdissection-ultrasonic irradiation method, or by the chymotrypsin method as reported previously by us, and that obtained by the present method.