Regulation of cell lineage specification by the retinoblastoma tumor suppressor.

Early studies of the retinoblastoma gene (RB) have uncovered its critical role as a regulator of the G(1)/S cell cycle phase progression. Surprisingly, genetic approaches in mammals and nematodes have also shown RB controls cell lineage specification and aspects of differentiation. The RB gene product accomplishes this by diverse mechanisms such as by interacting with tissue-specific transcription factors, enhancing RNA interference, and modifying chromatin structure. We review recent studies uncovering novel mechanisms by which RB works in several cell lineages and we provide perspectives on how these new findings might relate to RB tumor suppression.

Analysis of Epstein-Barr virus gene expression upon phorbol ester and hydroxyurea treatment by real-time quantitative PCR.

Epstein-Barr virus (EBV) has the potential to undergo latent and lytic pathways during infection. However, expression of many of the viral genes during the lytic-latent transition remains unclear. In this study, we investigated the effects of 12-O-tetradecanoylphorbol-13-acetate (TPA) and hydroxyurea (HU), two commonly used modulators of EBV life cycle, on the expression profiles of the entire genome of EBV persistent infected in B95-8 cells. After treatment with TPA for 48 h, the copy number of EBV genome in the cells increased about 2.5 fold, whereas HU treatment resulted in a reduction to approximately two-thirds of the original level. Except a small set of genes, the amounts of EBV mRNA are generally less abundant than that of beta-actin. The expression of a large fraction of the 80 EBV genes was found to be activated after TPA treatment with a noticeable increase of 19 and 21 fold, respectively in BSLF1 and BBLF4. In contrast, treatment of the B95-8 cells with HU, a nucleotide synthesis inhibitor, dramatically suppressed the expression of EBV lytic genes. In summary, we have demonstrated that real-time quantitative PCR is a reliable method to monitor the influence of drug-treatment in EBV genes regulation. Our results also provide a basis for further investigation on how the virus coordinates its own gene expression during latent-lytic pathway transition.

[Studies on the establishment of malarial animal model of short-term relapse. III. Combined therapy with pyronaridine-artemether-chloroquine for parasitemia clearance].

To establish a Plasmodium cynomolgi-monkey model of short-term relapse, different antimalarials have been used to inhibit recrudescence so as to elude the confusion between the two different onsets. When a single dose of effective schizonticides pyronaridine, artemether or chloroquine was administered, recrudesence readily occurred. This paper reports the results of the combined therapy with the above three drugs. Seven rhesus monkeys from Guangxi Autonomous Region infected with Plasmodium cynomolgi from Vietnam by blood transmission were rapidly cured by combined therapy with pyronaridine 6 mg/kg-artemether 100 mg/kg-chloroquine 10 mg/kg (PAC-1) once daily for 3 days. The average time of parasite clearance was 3.43 +/- 0.89 d and the curvilinear regression equation of parasite density after treatment was Y = 10(3.94-0.83X). Severe side effects of the gastrointestinal tract occurred during the course of treatment, though no recrudescence was found after 300-400 days. To reduce the side effects, another test was carried out in 3 monkeys and the dosage regimen was modified to pyronaridine 6 mg/kg-artemether 10 mg/kg-chloroquine 20 mg/kg (PAC-2) once daily for 3 days. There was no obvious side effect in the tested monkeys and the parasites were cleared during a mean time of 2.67 +/- 0.58 d and the curvilinear regression equation of parasite density was Y = 10(3.7-1.46X). No recrudescence was detected in the animals during a follow-up of 180 days. The study shows that PAC-2 regimen of the combined therapy is effective for parasitemia clearance and might be adopted for establishment of the monkey model of short-term relapse.

[Studies on the establishment of malarial animal model of short-term relapse. IV. Short-term relapse in rhesus monkeys infected with sporozoites of Plasmodium cynomolgi].

The present paper reports that the short-term relapse could be artificially made by the application of the experimental method, and thus we established the monkey model of the short-term relapse. According to the experimental design, when the parasitemia was detected in rhesus monkeys infected with sporozoites of Plasmodium cynomolgi, a combined therapy of pyronaridine 6 mg/kg body weight, artemether 10 mg/kg and chloroquine 20 mg/kg once daily for 3 days was carried out to clear the erythrocytic parasite and then the short-term relapse was observed in the animal follow-up for 100 days. The combined therapy was given again when relapse occurred. One onset of relapse occurred on 47 days after therapy in monkey M194 infected with sporozoites 11 x 10(3). In M195 infected with sporozoites 55 x 10(4), relapses occurred for 3 times on 30, 37 and 51 days respectively after medication, but during a follow-up period of 200 days, no relapse was shown in M192 and M193 infected with sporozoites 50 and 55 x 10(2), respectively. The results showed that the frequency of the short-term relapse was relative to the sporozoites inoculation, and sporozoites less than 11 x 10(3) were not suitable for making short-term relapse in animal model. No long term relapse could be seen in all the 4 monkeys until 400 days. Under existing conditions that the relapse was generally explained with hypnozoite assumption, the establishment of animal model of short-term relapse could be tenable.(ABSTRACT TRUNCATED AT 250 WORDS)

[Studies on the establishment of malarial animal model of short-term relapse. II. The phenomenon of sustained special ring form parasitemia in Plasmodium cynomolgi infection].

Our previous report that the EE merozites of Plasmodium cynomolgi from Vietnam continuously released from the liver to the blood circulation was further demonstrated in this report. Monkeys were given pyronaridine 24 mg/kg.d x 6 after being inoculated intravenously with 32 x 10(5) sporzoites of P. cynomolgi. Thick blood film examination was conducted two times daily till the day when trophozoites were detected. Under the residual action of blood schizontocied, a special ring form parasitemia at low patasite-density was detected for more than 30 days. As the ring forms of P. cynomolgi were demonstrated to be susceptible to pyronaridine in our previous experiments, it might be inferred that these ring forms derived from EE merozites released not for once but continuously for 30 days or longer.

[Studies on the establishment of malarial animal model of short-term relapse. I. Asynchronous growth of exoerythrocytic schizonts of Plasmodium cynomolgi].

A monkey was infected with sporozoites of Plasmodium cynomolgi from Vietnam. Parasitemia was detected on the 8th day with a starting density of 17/100 white blood cells. 22 hours after that time, many EE schizonts appeared with an average density of 3.74 +/- 0.66 per mm3 hepatic tissue in liver biopsy specimens from the monkey. Most of the EE schizonts were immature and grew at an uneven rate, having an average diameter of 34.22 +/- 7.28 microns but some of them even remained 15.75 +/- 2.47 microns in diameter similar to the EE schizonts on the 6th day. The results showed that the EE schizonts of Plasmodium cynomologi were asynchronous in growth. The authors suggest that the release of merozoites from liver might be a successive process for many times, and not to be completed at a time.

[Localization of the antigen in erythrocytic stages of Plasmodium yoelii by immuno-electron microscopy].

In this study, the antigen recognized by the protective McAb M26-32 in erythrocytic stages of P. yoelii was localized by immuno-electron microscopy with LR Whithe resin embedding and colloidal gold probe cytochemical techniques. The results indicated that the antigen which reacts specifically to McAb M26-32 was mainly localized within the cytoplasm of early and late trophozoites, schizonts and merozoites, being the common antigen of asexual blood stages of the plasmodium. The amount of the antigen was on the increase during the development of trophozoite, while a portion of the antigen might be transported outward by exocytosis of the parasites and then be localized in the cytoplasm of the infected erythrocytes adjacent to the parasites.

[Study on the exoerythrocytic forms of Plasmodium yoelii yoelii in rats and mice].

SD rats and three strains of mice were infected with Plasmodium yoelii yoelii By265 strain by intravenous inoculation of sporozoites via tail vein. Liver tissues were taken 42 hours after infection and serial sections were made and stained by Colophonium-Giemsa method for microscopic examination. The ratio of the average value of major diameter/minor diameter of exoerythrocytic(EE)schizonts of Plasmodium yoelii yoelii in rats and mice of ICR/JCL, C57BL, KM strains was 35.81 +/- 4.56 microns/29.72 +/- 4.08 microns, 28.08 +/- 4.66 microns/23.66 +/- 4.44 microns, 28.14 +/- 4.16 microns/23.63 +/- 3.77 microns, 23.80 +/- 2.42 microns/21 +/- 0 microns, respectively. The results showed that the development of EE schizonts of Plasmodium yoelii yoelii was not synchronous. The EE schizonts in the rat liver were surrounded by Kupffer cells, monocytes and monocyte-derived macrophages. Since the parasitemia disappeared rapidly in rats, and EE schizonts were not well developed in KM strain, it may be considered that ICR/JCL and C57BL strains are more suitable as vertebrate host in Plasmodium yoelii yoelii-Anopheles stephensi system model (Figs. 1-9).

Sexual dimorphism in Laccopithecus robustus, a late miocene hominoid from China.

Laccopithecus robustus is a siamang-sized fossil ape from the Miocene site of Lufeng, China. The species is known from a partial cranium, numerous mandibles, and scores of isolated teeth. This species shows striking dental similarities to Pliopithecus from the Miocene of Europe and a number of cranial similarities to extant gibbons. Laccopithecus differs from extant gibbons and resembles other fossil and extant apes in showing marked sexual dimorphism in the size and shape of the canines and anterior lower premolars. Evidence for sexual differences in either the size or shape of other teeth is less clear. There is some evidence for a sexual size dimorphism based on the variability of molar teeth.