Antimelanoma Activity of Chloroquine,an Antimalarial Agent With High Affinity for Melanin

The antimalarial agent chloroquine is known for high affinity for melanin. This 4-aminoquinoline derivative was examined for anti-melanoma activity and uptake into melanoma cells. Chloroquine inhibited growth of cultured melanoma cells; the effect was much greater to a moderately pigmented cell line HMV-II than to a nonpigmented HMV-I. Treatment with chloroquine at a dose of 62 mg/kg i.p. for 12 days prolonged by 71% the life span of mice bearing B16 melanoma, while 24-day treatment at 31 mg/kg resulted in a 81% increase in life span. HMV-II cells showed a two-fold increase in up-take of chloroquine as compared with HMV-I cells. Chloroquine, 24 hr after administration to mice implanted s.c. with B16 melanoma, was selectively accumulated in the pigmented tissues, melanoma and eyes. Other nonpigmented tissues such as the liver, lung, and kidney showed rapid uptake (within 1 hr) and release. These results suggest that chloroquine is toxic to pigmented melanoma cells, the process being partly mediated by binding to melanin     

Effect of climate change over the past half century on the distribution,extent and NPP of ecosystems of Inner Mongolia

The response of natural vegetation to climate change is of global concern. In this research, changes in the spatial pattern of major terrestrial ecosystems from 1956 to 2006 in Inner Mongolia of China were analyzed with the Holdridge Life Zone (HLZ) model in a GIS environment, and net primary production (NPP) of natural vegetation was evaluated with the Synthetic model, to determine the effect of climate change on the ecosystem. The results showed that climate warming and drying strongly influenced ecosystems. Decreased precipitation and the subsequent increase in temperature and potential evapotranspiration caused a severe water deficiency, and hence decreased ecosystem productivity. Climate change also influenced the spatial distribution of HLZs. In particular, new HLZs began to appear, such as Warm temperate desert scrub in 1981 and Warm temperate thorn steppe in 2001. The relative area of desert (Cool temperate desert scrub, Warm temperate thorn steppe, Warm temperate desert scrub, Cool temperate desert and Warm temperate desert) increased by 50.2% over the last half century, whereas the relative area of forest (Boreal moist forest and Cool moist forest) decreased by 36.5%. Furthermore, the area of Cool temperate steppe has continuously decreased at a rate of 5.7% per decade; if the current rate of decrease continues, this HLZ could disappear in 173 years. The HLZs had a large shift range with the mean center of the relative life zones of desert shifting northeast, resulting a decrease in the steppe and forest area and an increase in the desert area. In general, a strong effect of climate change on ecosystems was indicated. Therefore, the important role of climate change must be integrated into rehabilitation strategies of ecosystem degradation of Inner Mongolia.     

EFFECT OF PROLACTIN ON THE TADPOLE TAIL FIN. III. EFFECT OF PROLACTIN ON THE HYDROXYLATION OF PROTOCOLLAGEN-PROLINE OF THE TAIL FIN

The fact that bovine prolactin stimulates the collagen synthesis of the tadpole tail fin was confirmed by the present experiments, in which specific radioactivity of ¹⁴C-hydroxyproline hydroxylated from the incorporated ¹⁴C-proline was measured by the method different from that of the previous report (Y oshizato and Y asumasu , 1970). Stimulatory effect of prolactin on the incorporation of ¹⁴C-proline into the collagen fraction did not disappear even under the conditions, where the activity of protocollagen-proline hydroxylase was inhibited by α,α'-dipyridyl. In fact prolactin had not a significant effect on the activity of the emzyme. It, therefore, is concluded that the hormone promotes the incorporation of ¹⁴C-proline into collagen without affecting the hydroxylation step of the protein synthesis.     

Role of Wall-bound β-Glucanases in Regulating Tip-growth of Lilium longiflorum Pollen Tubes

β-Glucanases were found in the cell wall of Lilium longiflorum Thunb. pollen tubes grown in vitro . The activity of β-glucanases was, in a certain extent, decreased by nojirimycin, an inhibitor of glucosidase. Pollen germination percentage reduced dramatically when nojirimycin was applied in the culture medium. In case that nojirimycin was added at 0 or 1 h after the onset of incubation, the inhibition rate was 99.6% and 91.4%, respectively. When 3 mmol/L of nojirimycin was applied in the liquid medium at 0, 1, 1.5 and 2 h after the onset of incubation, the growth of pollen tubes was interrupted, which resulted in the morphological change of the pollen tubes such as the newly grown portion of pollen tubes being bent, curved and swollen. Tracing the growth pattern of the individual pollen tube grown in semi-solid medium by video microscopy, the authors demonstrated that pollen tube growth rate was strongly inhibited by nojirimycin at concentrations ranged from 0.003 to 3 mmol/L. Moreover, the cytoplasmic arrangement and the morphology of the pollen tubes were also affected by nojirimycin. The growth inhibition brought about by nojirimycin was reversible. These results indicated that β-glucanases, which degrade 1,3-β-glucan and/or 1,4-β-glucan or 1,3:1,4-β-glucan constructed in the cell wall, are involved in pollen germination and pollen tube growth. It provides new insight into an understanding of the contribution of β-glucanases to the cell wall extensibility and the crucial role of cell wall in regards to the regulation of pollen tube growth.     

CHANGES IN THE MELANOPHOROTROPIC FUNCTION OF THE PITUITARY GLAND ACCOMPANYING BLINDNESS IN XENOPUS LAEVIS DAUDIN

A number of cases of blindness appeared among a group of cultured Xenopus laevis. The blind toads lacked eyeballs and optic nerves and were consistently dark in color. Similar anatomical changes in the head and pigmentation were produced experimentally by removing the eyeballs of tadpoles or young adult toads. The dark pigmentation of blind Xenopus: was shown to be due to the continuous release of MSH from the pars intermedia of the pituitary, since hypophysectomy led to the complete blanching of the dermal and epidermal melanophores. MSH activity in the pars intermedia of blind toads was extremely high in comparison with that of normal animals. No special difference with respect to the general growth and behaviour was found between normal and blind Xenopus, which suggests that the pituitary functions other than that of the pars intermedia are not affected by the state of the optic nerves. These observations suggest that the retrogressive degeneration of the optic nerves exerts a profound effect on the secretory activity of the pars intermedia via the hypothalamic controlling center.     

FORMATION OF GERM CELL-LIKE CELLS IN THE PERITONEAL EPITHELIUM OF THE TESTES OF ESTROGEN-TREATED ADULT MALES OF THE JAPANESE RED-BELLIED NEWT, CYNOPS PYRRHOGASTER PYRRHOGASTER

Columnar cells of the peritoneal epithelium in slender cords of the testes were examined in normal and estradiol benzoate-treated Japanese red-bellied newt, Cynops pyrrhogaster pyrrhogaster, by light and electron microscopy. In normal newts, the peritoneal epithelium covering the slender cord consists of columnar cells, which contain extraordinarily large, oval or spindle-shaped nuclei with conspicuous indentations. The nucleus contains chromatin granules and the cytoplasm is filled with numerous tonofilaments. The primordial germ cells are scattered throughout the slender cord, and each cell is surrounded by a few follicle cells. Between the germ cells and follicle cells there are microvilli-like processes. The nucleus of primordial germ cells is multilobate and has electron lucent areas, dispersed chromatin and several electron-dense nucleoli. In the lighter cytoplasm, the nuage material is found very near to nuclear pores, and is frequently seen among the mitochondria. The nucleolus-like body is not associated with other organelles. The primary spermatogonia have bilobate nuclei. It is remarkable that most of the cytoplasmic organelles are found in the deep nuclear indentations. The nuage material and nucleolus-like body are well developed in the cytoplasm. After treatment of newts with estradiol benzoate for one year, four types of cells can be distinguished in the peritoneal epithelium. One type is quite different from the columnar cells. These newly appeared cells are large and light in appearance. Their nucleus is highly lobate, and contains dispersed chromatin and several nucleoli with compact electron dense material in its periphery. The cells are characterized by the presence of nuage material and nucleolus-like bodies in the cytoplasm. There are microvilli-like processes between these cells and adjacent elongated cells. These ultrastructural characteristics of the light cells are very similar to those of primordial germ cells and/or primary spermatogonia in normal testes. These findings suggest that the light cells which appear in the peritoneal epithelium of the testes on administration of estrogen may be germ line cells.     

EFFECT OF PLASTOCYANIN ON PHOTOPHOSPHORYLATION IN ISOLATED CHLOROPLASTS

The effect of addition of plastocyanin on photophosphorylationin isolated chloroplasts was studied in comparison with itseffect on photoreduction. Catalytic amounts of added plastocyaninstimulated the HILL reaction with NADP as oxidant, but the photophosphorylationcoupled to this reaction was not influenced by the additionof plastocyanin. The addition of NH₄+ or the complete phosphorylatingsystem did not affect the plastocyanin-induced increase in rateof the photoreduction. The rate of photoreduction of NADP, FMN,or indigo carmine in the presence of DPIP and ascorbate wasmuch accelerated by added plastocyanin, but these reactionswere not coupled to ATP formation. As reported earlier, isolated chloroplasts can utilize plastocyaninas oxidant in the HILL reaction. This reaction was found tobe accompanied by ATP formation, but the efficiency in thiscase was somewhat lower than in photophosphorylation coupledto the HILL reaction with the usual oxidants. The possible mechanism of these reactions is described brieflyand a scheme for reactions of plastocyanin in the electron transferin chloroplasts is presented. (Received July 20, 1965; )     

In Vitro Regression of Tadpole Tail by Thyroid Hormone

DERBY successfully maintained the tail of tadpole ( Rana pipiens) in vitro over a period of 2 weeks in a physiological salt solution (1). When we tried to apply DERBY'S methods of the tissue culture to tadpoles of bullfrog, Rana catesbeiana , it was found that the tissue regressed spontanously without stimulation of thyroid hormone. Several different media were examined in order to select a better culture medium for the bullfrog tadpole tissues. RPMI-1640 medium supplemented with insulin and transferrin was found to be satisfactory for this aim. With this improved medium, the interaction between the epidermis and the mesenchyme has been investigated during the hormone-induced tadpole tail regression and the epidermal dependence of the mesenchyme regression was demonstrated by the following three experiments. (i) Some of surgically prepared mesenchymes regressed in responce to thyroid hormone. In these cases the mesenchymes were revealed to be contaminated with the remaining epidermal cells. (ii) Complete removal of the epidermis was accomplished by the chemical treatment. The mesenchyme thus obtained ("nude tail fin") was insensible to thyroid hormone. (iii) "Skin conditioned medium" (SCM) was prepared by culturing the skin in the presence and absence of thyroid hormone. Nude tail fin regressed when cultured in the SCM containing thyroid hormone.     

Actin Degradation in the Metamorphosing Bullfrog Tadpole Tail

Degradation of tail muscle proteins was investigated during metamorphosis of Rana catesbeiana , tadpole. Regressing tail muscle contained actomyosin which was comparable to that of non-regressing tail muscle in its physico-chemical character, althouth the actomyosin content of the former tissue decreased as compared to the latter. However, when muscle proteins were extracted in the SDS-containing medium (TSM) and analyzed by SDS-polyacrylamide gel electrophoresis, we found that the protein band corresponding to actin disappeared completely during the late climax stage of metamorphosis. Detailed studies on this phenomenon showed that the apparent absence of actin on SDS-polyacrylamide gel electrophoresis was dependent upon the metamorphic stages of the tadpoles investigated. When TSM extract from the premetamorphic tadpole tail muscles which contained actin was incubated with the same extract from tadpoles of the climax stage, actin derived from premetamorphic tadpole disappeared on gel electrophoresis, indicating that tail muscle tissues of the climax stages contain the actin-degrading enzyme. Characterization of the enzyme was performed with a crude extract using actin prepared from rabbit thigh muscle as a substrate. Actin degrading activity showed incubation time- and temperature-dependency and the activity decreased gradually when the extract was preheated at increasing temperatures with the complete inactivation at 100°C. The major degradation products of actin hydrolysis by the enzyme had a Mr=28,000 and 14,000 which indicated the enzyme splits actin at a specific point. The activity had an optimum pH of 7.5 and was inhibited by leupeptin and iodoacetate and required the presence of a thiol reagent.     

Elimination of a specialised facultative symbiont does not affect the reproductive mode of its aphid host

Abstract.  1. Microorganisms that manipulate the reproduction of their hosts through diverse mechanisms including the induction of parthenogenesis are widespread among arthropods.
2. The pea aphid, Acyrthosiphon pisum , shows a variation in its reproductive mode, with lineages reproducing by cyclical parthenogenesis (obligate alternation of parthenogenetic and sexual generations each year) and others by obligate parthenogenesis (continuous asexual reproduction all year round). In addition, the pea aphid harbours, along with Buchnera the primary aphid endosymbiont, several facultative symbionts whose prevalence differs among host populations.
3. The possible influence of a Rickettsia facultative symbiont on the reproductive mode of its host was tested on two pea aphid clones by comparing the response of infected and uninfected individuals with the same genetic background to conditions that typically induce the production of sexual morphs.
4. No significant effect of the Rickettsia infection was found on the type of reproductive morphs produced (sexual vs. asexual) or on their quantities for the two clones.
5. However, the Rickettsia had a detrimental effect on the fitness of its aphid host, in apparent contradiction to the high prevalence of this symbiont in some host populations. It is suggested that this negative impact may disappear under specific environmental conditions, transforming a parasitic association into a mutualistic one.