Up‐regulation of Tyrosinase Gene by Nitric Oxide in Human Melanocytes

Ultraviolet light (UV) radiation causes skin‐tanning, which is thought to be mediated by stimulating the release of melanogenic factors from keratinocytes as well as other cells. Nitric oxide (NO) has been reported to be generated after UV radiation and to stimulate melanocytes as one of the melanogens. In a previous experiment by another group on melanogenesis induced by NO, increases in both tyrosinase activity and tyrosinase protein levels were observed after daily stimulation of NO for 4 days. In the present study, we investigated tyrosinase gene expression within the first 24 hr of NO‐induced melanogenesis. Tyrosinase mRNA expression was found to be induced 2 hr after a single treatment with S‐nitroso‐N‐acetyl‐ l ‐arginine. An increase of tyrosinase activity was also detected time‐dependently within the 24‐hr period, accompanied by an increase of tyrosinase protein levels. The induction of mRNA expression was suppressed by a cyclic guanosine 3′,5′‐monophosphate (cGMP)‐dependent protein kinase (cGMP/PKG) inhibitor. These results suggest that the enhancement of tyrosinase gene expression via the cGMP pathway may be a primary mechanism for NO‐induced melanogenesis.     

Two new species of Petunia (Solanaceae) from southern Brazil

Two new species of Petunia Jussieu from Santa Catarina and Rio Grande do Sul states in Brazil are described and compared with the other seven specieS. A key and synopsis of all the species of Petunia are provided     

INTERACTION OF GIBBERELLIN A3, AND INORGANIC PHOSPHATE IN TOBACCO SEED GERMINATION

1. Investigation was made on the influence of inorganic phosphateupon the germination of positively photoblastic tobacco seed(Nicotiana tabacum L. var. uirginica (AGDH.) COM. "Bright Yellow")induced by GA₃, GA₃M, kinetin, red light, and ammonium saltsof various organic acids.
2. Inorganic phosphate increases theGAs-induced germination, andinhibits the germination causedby ammonium citrate, while itdoes not influence the germinationbrought about by GA₃M, kinetin,and red light.
3. The optimumpH for the GA₃-induced germination lies in the acidicpH range,indicating that the undissociated form of GA₃ is operative.The stimulatory effect of phosphate is, however, not ascribedmerely to the pH control in the mediurr. Phosphate exerts somespecific influence for which the presence of the free carboxylgroup of GAs is required.
4. The observed contrasting effectsof phosphate on the GA₃-inducedgermination (i.e., acceleration),on the one hand, and on theammonium citrate-induced germination(i.e., inhibition), onthe other, were explained by assumingthat the phosphate effectsultimately consist in acceleratingthe uptake of the carboxylicacid into the seeds.
5. GA₃M alsohas an activity of inducing the germination of tobaccoseedwithout light.

¹Present address: Department of Vegetable Crops, Universityof California, Davis, California, U.S.A. (Received March 12, 1962; )     

Involvement of Nitric Oxide in UVB‐Induced Pigmentation in Guinea Pig Skin

Ultraviolet (UV) B irradiation evokes erythema and delayed pigmentation in skin, where a variety of toxic and modulating events are known to be involved. Nitric oxide (NO) is generated from l ‐arginine by NO synthases (NOS). Production of NO is enhanced in response to UVB‐stimulation and has an important role in the development of erythema. NO has recently been demonstrated as a melanogen which stimulates melanocytes in vitro, however, no known in vivo data has been reported to support this finding. In this study, we investigated the contribution of NO with UV‐induced pigmentation in an animal model using an NOS inhibitor. UVB‐induced erythema in guinea pig skin was reduced when an NOS inhibitor, l ‐NAME (N‐nitro‐ l ‐arginine methylester hydrochloride), was topically applied to the skin daily, beginning 3 days before UVB‐irradiation. Delayed pigmentation and an increased number of DOPA‐positive melanocytes in the skin were markedly suppressed by sequential daily treatment with l ‐NAME. Furthermore, melanin content 13 days after UVB‐irradiation was significantly lower in skin treated with l ‐NAME than in the controls. In contrast, d ‐NAME (N‐nitro‐ d ‐arginine methylester hydrochloride), an ineffective isomer of l ‐NAME, demonstrated no effect on these UV‐induced skin responses. These results suggest that NO production may contribute to the regulation of UVB‐induced pigmentation.     

Fatty Acids in Buckwheat are Growth Inhibitors

Four fatty acids, palmitic, stearic, arachidic and behenic acids,were identified (using gas chromatography-mass spectrometry)from buckwheat seedlings. These fatty acids at a concentrationof 250 ppm caused a slight but significant inhibition in growthof rice seedlings. Fagopyrum cymosum, fatty acid, growth inhibitor     

INDOLE-3-ACETIC ACID IN CHICK EMBRYOS

The occurrence of IAA, a plant-growth-regulating substance of the auxin group, was investigated in developing chick embryos. Paperchromatography followed by the Avena curvature test revealed the presence of a substance with auxin activity and the same Rf as IAA. This substance was identified as IAA by combined gas chromato-graphy-mass spectrometry. The amount of IAA in a unit weight of embryo was almost identical during embryo development, the total amount of IAA in an embryo increasing as it developed. The amount of IAA in the whole egg was also examined and it was found that an egg incubated for 9 days at 37°C contained a larger amount of IAA than one not incubated.     

Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis(Megaloptera: Corydalidae)

SUMMARY 1. Seasonal change in the respiration of the dobsonfly larva, Protohermes grandis ,was studied by measuring the oxygen consumption rate (resting metabolism) bimonthly for 2 years. The respiratory rate of the larva was significantly lower during the summer season when the stream temperature rose to 30°C.
2. Summer depression of respiration was confirmed by measuring the rate of carbon dioxide evolution. The mean value of the respiratory quotient was estimated to be 0.76 ± 0.05 SE. The larva is believed to conserve energy by this reduction in respiratory rate,
3. In other seasons, however, the larva maintained a higher respiratory rate and remained active even in the winter when the stream temperature decreased near to 0°C. In fact, significant growth in weight occurred from mid-October to late March.
4. This acclimation to temperature may enable the efficient allocation of energy during the long larval period (3 years) in streams which have large annual fluctuations in temperature.     

Specific Kilting of Human Melanoma Cells With an Efficient 10B-Compound on Monoclonal Antibodies

We previously established methods which have enabled us to target a sufficient number of ¹⁰B atoms on human melanoma cells to destroy them by thermal neutron irradiation. Monoclonal antibodies were here used as vector of ¹⁰B atoms on the target cell. Thermal neutrons require at least 10⁹¹⁰B atoms to destroy the cell. In order to accumulate an adequate number of ¹⁰B atoms on target cells, our first approach was to make an effective compound that contains 12 atoms of ¹⁰B in a molecule. The second step was to conjugate the compound with an avidin molecule (¹⁰B₁₂-avidin). One molecule of the ¹⁰B₁₂-avidin carries about 30 atoms of ¹⁰B. This ¹⁰B₁₂-avidin can be specifically targeted on human melanoma cells by biotinated monoclonal antibodies specific for the cells. Furthermore, the number of ¹⁰B atoms on target cells can be augmented by a hapten-antihapten monoclonal antibody system. The cultured human melanoma cells treated with these methods were damaged by thermal neutron irradiation. This is the first study that indicates thermal neutrons do injure target cells boronated by monoclonal antibodies.     

Light-dependent oxygen uptake by non-living, chlorophyll-containing particles obtained from oceanic environments

Chlorophyll-containing, non-living particles obtained from oceanicenvironments showed a light-dependent oxygen uptake reaction.Activity was found in marine samples rich in diatom cells andcell fragments, though particles originating from dinoflagellatesshowed only insignificant activity. The same reaction was seenin sonic-disrupted and washed cell fragments of cultured Phaeodactylumtricomutum. The reaction did not require extra electron donors or electroncarriers, even in particles washed thoroughly with buffer. Add-backof the soluble fraction had no effect. The action spectrum ofthe reaction indicated that only light absorbed by chlorophyllswas effective though the sample also contained carotenoids. Based on the data obtained we inferred that the O₂ uptake reactionis the same as that caused by the action of isolated chlorophyllsand, that a water-insoluble compound(s) contained in the samplesserved as electron donor. A possible contribution of this reactionto the O₂ economy in oceanic environments is discussed. (Received January 30, 1971; )