An Improved Modification of Permanganate Oxidation of Eumelanin That Gives a Constant Yield of Pyrrole-2,3,5-Tricarboxylic Acid

Microanalysis of eumelanin is based on the formation of pyrrole-2,3,5-tricarboxylic acid (PTCA) on permanganate oxidation followed by its HPLC determination. A problem in this method was that the oxidation gave concave, exponential curves when the amounts of PTCA formed were plotted against the amounts of sample oxidized. The problem has been mostly overcome by adding a homogenate of 5 mg of a mouse liver to the oxidation medium. Sepia melanin, C57BL black mouse hair, B16 mouse melanoma, and MM418 human melanoma cells were oxidized in the absence or presence of the liver homogenate. The yields of PTCA increased about 1.5-fold by adding the liver homogenate and the calibration curves became linear or almost linear. With the improved method the PTCA values from various types of samples can be reliably compared.     

A field evaluation of the sexual competitiveness of sterile melon flies, Dacus (Zeugodacus) cucurbitae

ABSTRACT.

• 1 The sexual competitiveness of sterile melon fly males [Ducus (Zeugodacus) cucurbitue Coquillett] was estimated under field conditions.
• 2 The value of competitiveness was about 0.8 for flies in the fifth to tenth generation from the beginning of mass-rearing, but decreased to about 0.2 in the eighteenth generation.
• 3 The sexual competitiveness estimated using laboratory data was near unity even in the final stage of our study.
• 4 It was concluded that the field evaluation of sexual competitiveness is essential to determine the quality of the insects reared for purposes of pest control.

     

Electrical Properties of Toad Oocytes During Maturation and Activation

The full-grown oocytes of the toad Bufo bufo japonicus , whether in follicular layer or not, had a membrane potential of about -50 mV in De Boer's solution (DB), but underwent a deep hyper-polarization of up to -90 mV when pretreated with Ca, Mg-free EDTA-solution. Regardless of the magnitude of their resting potentials, the defolliculated oocytes exposed to progesterone underwent a gradual depolarization before the germinal vesicle breakdown and retained membrane potential at a level of -10 mV until 18 hr post hormone treatment (PHT), the stage of the second meiotic metaphase. A positive-going activation potential of a magnitude of 70 mV was recorded in the oocytes when pricked at 18 hr PHT as well as in uterine eggs 3–5 min after insemination. A low magnitude of activation potential in response to pricking was recorded in 63% of the oocytes at 13 hr PHT, and premature oocytes exhibiting the activation potential always underwent cortical granule breakdown (CGBD) and perivitelline space formatión. Oocytes where the germinal vesicle had been removed before the hormone treatment exhibited an activation potential and underwent CGBD in response to pricking at 18 hr PHT, whereas those pulse-treated with cycloheximide (10 μg/ml) during the 8–11 hr PHT exhibited neither of these cortical responses. These results indicate that the syntheses of proteins independent of germinal vesicle taking place at 9–11 hr PHT enable the oocytes to undergo cortical responses.     

Influences of Sex,Castration, and Androgens on the Eumelanin and Pheomelanin Contents of Different Feathers in Wild Mallards

In mallards the bright nuptial plumage of the drake represents the neutral, sex hormone-independent coloration of the species that both sexes eventually exhibit after castration. We compared the pheo- and eumelanin contents of feathers from the head, breast, flank, and under-tail coverts in five groups of mallards after the post-nuptial molt in summer: intact hens, intact drakes, castrated drakes, castrated drakes injected with testosterone during the spring, and castrated drakes injected with 5α-dihydrotestosterone during the spring. In the head feathers and under-tail coverts, the gonadal hormones of the intact birds and the testosterone injections into castrates significantly reduced the eumelanin content, tended to increase the pheomelanin content, and, thereby, changed the melanin type from eumelanic in the untreated castrates to mixed melanic in the other three groups. The eumelanin contents of the flank feathers did not differ among the groups, but the pheomelanin contents at this site was significantly elevated in the two intact groups and the testosterone-treated compared to the uninjected castrates. Again, the melanin type changed from eumelanic in the castrates to mixed melanic in the other three groups. The high pheomelanin content of the breast feathers in the castrated birds was significantly reduced in the hens, intact drakes, and testosterone-injected castrates with a concomitant tendency for elevated eumelanin contents. At this site, a change occurred from pheomelanic to mixed melanic. 5α-dihydrotestosterone was clearly less effective than testosterone in affecting the melanin contents in castrates and resulted in an intermediate coloration. The differing effects of the two androgens might be a result of differences in their conversion to estrogens.     

Light Microscopic Observations of Infraciliature and Morphogenesis in Six Species of Rumen Ostracodinium Ciliates

Infraciliature and morphogenesis of six rumen ciliates, Ostracodinium mammosum, O. munham, O. dilobum, O. rugoloricatum, O. iwawoi, and O. tiete are described from pyridinated silver carbonate-impregnated specimens. These six Ostracodinium have a similar polybrachykinety arrangement, distinct from that of other ophryoscolecid ciliates and intermediate between those of O. gracile and 0. damaliscus. Buccal infraciliature is composed of three polybrachykineties, a kinety loop, and paralabial kineties. Small dorso-adoral polybrachykinety, slender vestibular polybrachykinety, and kinety loop are characteristic. Dorsal infraciliature consists of the dorsal polybrachykinety that extends laterally along the dorsal side of the body. Morphogenesis is different from that of O. gracile, because the right end of ventral primordium extends dorsally to grow into a right primordium without separation.     

STIMULATION OF COLLAGEN SYNTHESIS IN RAT CARDIAC FIBROBLASTS BY EXPOSURE TO HYPOXIC CULTURE CONDITIONS AND SUPPRESSION OF THE EFFECT BY NATRIURETIC PEPTIDES

Synthesis of type I and type III collagens by rat cardiac fibroblasts was stimulated when the cells were cultured under 95% N₂/5% CO₂for one hour followed by incubation under normoxic conditions for 24 hours. The stimulative effect was attenutated by the presence of atrial natriuretic peptide (ANP, 10⁻⁶m) or brain natriuretic peptide (BNP, 10⁻⁶m) in the culture medium. Northern blot analysis indicated that α1(I) and α1(III) collagen mRNA levels were also increased by hypoxia, and decreased with the addition of ANP or BNP in a dose-dependent manner. These results indicate interaction between intracellular signals of a physical stimulus (hypoxic stress) and those of a chemical one (ANP or BNP) and demonstrate that both signals regulate collagen synthesis by cardiac fibroblasts at the levels of the mRNAs. The results also suggest that natriuretic peptides produced by cardiomyocytesin vivomay function as paracrine factors that play a role in the prevention of cardiac fibrosis in ischaemic heart diseases.