Effects of Host Cell Density on Cell Infection Level in Antheraea eucalypti (Lepidoptera: Saturniidae) Cell Cultures Persistently Infected with Nosema bombycis (Microsporida: Nosematidae)

ABSTRACT. Spores of Nosema bombycis Y9101, isolated from the beet armyworm, Spodoptera exigua , were primed with an alkaline solution and inoculated into Antheraea eucalypti cell cultures. Infected cells were subcultured every five days at three cell densities (2.5 × 10³, 5.0 × 10³, and 1.0 × 10⁴ cells/cm²). A difference was observed in the spread of N. bombycis Y9101 infection between low-density and higher-density cultures of host cells. The host cell density did not affect the productivity of secondary infective forms of the parasite. The principal factor determining the rate of microsporidian infection in vitro was the number of host cells existing within the reach of extruded short-coiled polar tubes from spores germinated intracellularly.     

A New Method for Inoculation of Poor Germinator, Nosema sp. NIS M11 (Microsporida: Nosematidae), into an Insect Cell Culture

ABSTRACT. Spores of Nosema sp. NIS M11, primed with 0.1 N KOH solution, were mixed with either physiological salt solutions or IPL-41 medium, an insect cell culture medium, for germination. In the latter medium, only a few spores germinated, while high percentages of spore germination were obtained in physiological salt solutions, particularly in Rinaldini's solution. By using the salt solutions as inoculation media, KOH-primed NIS M11 spores were inoculated into the Spodoptera frugiperda SF21AEII cell line. The initial infection levels were consistently higher than that obtained by using IPL-41 medium. Among the salt solutions, Rinaldini's solution, containing KCl in place of NaCl, gave the highest percentage of initial cell infection. Increased osmolarity of salt solutions did not improve the efficiency of spore germination and infection of N. sp. NIS M11.     

The Inhibitory Effect of Glabridin from Licorice Extracts on Melanogenesis and Inflammation

Glabridin is the main ingredient in hydrophobia fraction of licorice extract affecting on skins. In this study, we investigated inhibitory effects of glabridin on melanogenesis and inflammation using cultured B16 murine melanoma cells and guinea pig skins. The results indicated that glabridin inhibits tyrosinase activity of these cells at concentrations of 0.1 to 1.0 μg/ml and had no detectable effect on their DNA synthesis. Combined analysis of SDS-polyacrylamide gel electrophoresis and DOPA staining on the large granule fraction of these cells disclosed that glabridin decreased specifically the activities of Tl and T3 tyrosinase isozymes. It was also shown that UVB-induced pigmentation and erythema in the skins of guinea pigs were inhibited by topical applications of 0.5% glabridin. Anti-inflammatory effects of glabridin in vitro were also shown by its inhibition of superoxide anion productions and cyclooxygenase activities. These data indicated that glabridin is a unique compound possessing more than one function; not only the inhibition of melanogenesis but also the inhibition of inflammation in the skins. By replacing each of hydroxyl groups of glabridin with others, it was revealed that the inhibitory effect of 2′-O-ethyl glabridin was significantly stronger than that of 4′-O-ethyl-glabridin on melanin synthesis in cultured B16 cells at the concentration of 1.0 mg/inl. With replacement of both of two hydroxyl groups, the inhibitory effect was totally lost. Based on these data, we concluded that two hydroxyl groups of glabridin are important for the inhibition of melanin synthesis and that the hydroxyl group at the 4’ position of this compound is more closely related to melanin synthesis.     

Development of Melanocyte Progenitors in Murine Steel Mutant Neural Crest Explants Cultured With Stem Cell Factor,Endothelin-3, or TPA

Stem cell factor (SCF) has been suggested to be indispensable for the development of neural crest cells into melanocytes because Steel mutant mice (i.e., Sl/Sf¹) have no pig-mented hairs. On the other hand, it has been demonstrated that the addition of endothelin 3 (ET-3) or TPA to neural crest cell cultures can induce melanocyte differentiation without addition of extrinsic SCF. In this study, we excluded the influence of intrinsic SCF by using SI/SI mouse embryos to study more precisely the effects of natural cytokines, such as extrinsic soluble SCF or ET-3, or chemical reagents, such as TPA or cholera toxin. We found that SCF is supplied within the wild-type neural crest explants and that ET-3 cannot induce melanocyte differentiation or proliferation without SCF. These results indicate that SCF plays a critical role in survival or G1/S entry of melanocyte progenitors and that SCF initially stimulates their proliferation and then ET-3 accelerates their proliferation and differentiation. TPA has the ability to elicit neural crest cell differentiation into melanocytes without exogenously added SCF but it is not as effective as SCF because many more melanocytes developed in the wild-type neural crest explants cultured with TPA.     

Life history traits related to resource partitioning between synhospitalic species of Colocasiomyia (Diptera, Drosophilidae) breeding in inflorescences of Alocasia odora (Araceae)

Abstract.

• 1 Two closely related species of Colocasiomyia alocasiae (Okada) and C.xenalocasiae (Okada) (Diptera, Drosophilidae) breed in inflorescences of Alocasia odora C. Koch (Araceae), a hermaphroditic understorey clonal herb.
• 2 The two drosophilid species form a synhospitalic pair in Okinawa with alocasiae breeding in the upper half of the inflorescence and xenalocasiae breeding in the lower half.
• 3 C.alocasiae also has the following combination of life history traits: small body size, many eggs, and early reproductive maturity. In contrast, xenalocasiae can be described as having larger body size, fewer eggs, and delayed reproductive maturity.
• 4 Resource partitioning between the two species on the same host may be affected by these life history traits which are associated with their larval habitats.

     

Respiratory aspects of Rhodotorula mucilaginosa

The absorption spectrum of intact cels of Rhodotorula mucilaginosaexhibits three absorption peaks for carotenoids and a Soretband for cytochrome(s). The difference spectrum between thereduced and oxidized states indicates there are components ofcytochrome b, c(c₁) and a+a₃. However, the respiratory aspectof this strain differs significantly from that of baker's yeast,Saccharomyces cerevisiae. The respiratory capacity is strikinglyenhanced in the transition from the lag to the logarithmic phaseof growth, and is accompanied with a special increase in cytochromeoxidase. Addition of TMPD (plus ascorbate) in the presence ofglucose barely affects oxygen consumption of the cells duringthis period, whereas it markedly affects consumption in oldercells. Sodium azide slightly inhibits respiration in the courseof growth, except during this limited transitional period. Azide-insensitiverespiration is also seen in the mitochondrial fraction preparedfrom cells grown to the stationary state. A similar situationis found with antimycin A. Morphological investigations were carried out electron-microscopicallyon the cells of different growth stages. (Received September 16, 1969; )     

Genetic and acoustic population structuring in the Okinawa least horseshoe bat: are intercolony acoustic differences maintained by vertical maternal transmission?

The origin and meaning of echolocation call frequency variation within rhinolophid bats is not well understood despite an increasing number of allopatric and sympatric examples being documented. A bimodal distribution of mean regional call frequency within the Okinawa‐jima Island population of Rhinolophus cornutus pumilus (Rhinolophidae) provided a unique opportunity to investigate geographic call frequency variation early in its development. Individual resting echolocation frequencies, partial mitochondrial DNA D‐loop sequences and genotypes from six microsatellite loci were obtained from 288 individuals in 11 colonies across the entire length of the island, and nearby Kume‐jima Island. Acoustic differences (5–8 kHz) observed between the north and south regions have been maintained despite evidence of sufficient nuclear gene flow across the middle of the island. Significant subdivision of maternally inherited D‐loop haplotypes suggested a limitation of movement of females between regions, but not within the regions, and was evidence of female philopatry. These results support a ‘maternal transmission’ hypothesis whereby the difference in the constant frequency (CF) component between the regions is maintained by mother–offspring transmission of CF, the restricted dispersal of females between regions and small effective population size. We suggest that the mean 5–8 kHz call frequency difference between the regions might develop through random cultural drift.