Molecular characterizations of two begomoviruses infecting Vinca rosea and Raphanus sativus in India

Dear Editor Samples of Vinca rosea and Raphanus sativus leaves showing typical leaf curling were collected from gardens and fields of Bhatinda,Punjab (India).An expected product of ～550 bp in size was amplified from total DNA extracts of symptomatic leaf samples with universal primers on the coat protein region of begomoviral DNA-A component.Moreover,DNA β were also detected in both V.rosea and R.sativus using β satellite universal primers.This is the first report of a β satellite associated with V.rosea in India.The presence of begomoviruses was also confirmed by Southern blot analysis using cloned DNA-A probe of Papaya leaf curl virus.Sequence analysis of viruses infecting V.rosea (Vinca yellow vein virus) and R.sativus (Raphanus sativus leaf curl Bhatinda virus) showed 74％ and 84％ nucleotide sequence identity with Papaya leaf curl virus,respectively.     

Effect of Vinca rosea extracts in treatment of alloxan diabetes in male albino rats

Administration of aqueous extracts of V. rosea flower and leaf have been found to regulate the blood sugar level in alloxan diabetic male albino rats. V. rosea therapy not only produced blood glucose homeostasis but also reversed changes in carbohydrate, protein, lipid metabolisms and metabolic and pathologic changes that took place in pancreatic islet cells, liver and kidney following a single dose (150 mg/kg body weight) of alloxan monohydrate. B-cell secretory activity resumed near-normalcy as evidenced by near-normal serum insulin concentration and electron-microscopic study proving that V. rosea manifests its beneficial activity through B-cell rejuvenation, regeneration and stimulation.     

THE SPERMATOGONIAL STEM CELL POPULATION IN ADULT RATS

Radioautographed whole mounted seminiferous tubules from adult rat testes were used to analyse undifferentiated type A spermatogonia at various intervals up to 81 hr following a single injection of ³H-TdR. the data obtained led to the identification of the spermatogonial stem cell and to the formulation of a new model for spermatogonial renewal and differentiation. Undifferentiated type A cells were morphologically alike, but were topographically classified as (1) isolated or (2) paired and aligned. Although labeled isolated A cells were scattered over most stages of the seminiferous epithelium, their proliferative activity varied with the stage; their labeling index was 20-30% in stages I and II, but less than 1% in stages VII and VIII. By tracing the labeled divisions of isolated A spermatogonia in time, it was seen that some daughter cells became separated from one another to form two new isolated cells, while others remained together as paired A spermatogonia. Analysis of two successive waves of labeled mitoses revealed that most paired A spermatogonia continued to proliferate forming four aligned A cells, many of which divided again to produce a chain of eight and so on. the greatest incidence of labeling among paired and aligned A spermatogonia occurred in stages XIII-III. In stage I, where the labeling index was 50%, the calculated proliferative fraction was 1 for these spermatogonia. Between stages II and V, they began to leave mitotic cycle, and during stage V this entire cohort morphologically transformed into A₁ spermatogonia. Labeled metaphase curves for undifferentiated A spermatogonia were distinct from any of the curves previously constructed for the six classes of differentiating spermatogonia, especially because of particularly long S and G₂ phases in the former. the cell cycle time of paired and aligned A cells was 55 hr, compared to an average of 42 hr for differentiating types A₂ to B.     

Immunohistochemical distribution of sulfhydryl oxidase in the human testis

Summary Sulfhydryl oxidase (SOx) is an enzyme that catalyzes the oxidation of sulfhydryl compounds. It is present in mitochondria of certain testicular cells at specific stages of functional activation. In the mature human testis moderate SOx immunoreactivity is found in Leydig cells, and lacking in Sertoli and in peritubular cells. The A_dark spermatogonia usually contain immuno-reactive mitochondria, while in A_pale spermatogonia immunoreactivity is mostly low. In stage V of spermatogenesis, A_pale spermatogonia were found containing immunoreactive material. Leptotene (stages IV and V) and zygotene (stage VI) primary spermatocytes display a moderate immunoreaction. It is strongest in pachytene spermatocytes of stages I–IV, decreases in stage V, and is low during diakinesis and in secondary spermatocytes. Late spermatids usually show a stronger immunoreactivity than early spermatids. At stage V of spermatogenesis the late spermatids contain only few immunoreactive particles. Spermatozoa are free of SOx-immunoreactive mitochondria. In residual bodies small amounts of SOx-immunoreactive particles are seen. Compared to rat and hamster testis, SOx immunoreactivity of the human testis is less clearly stage-dependent and it is not confined to certain germ cell stages. As deduced from the findings in patients with spermatogenic disorders, the SOx immunoreactivity of spermatogonia in human testis seems to be of diagnostic relevance.     

Kinetics of spermatogenesis in megachiropteran bat, Rousettus leschenaulti (Desmarset): seminiferous epithelial cycle, frequency of stages, spermatogonial renewal and germ cell degeneration.

The paper describes in detail the cytomorphology of different types of germ cells, the 10 typical cellular associations or stages of the cycle of seminiferous epithelium (CSE), frequency of appearance of these stages, pattern of spermatogonial stem cell renewal and per cent degeneration of various germ cells in R. leschenaulti. Of the 14 steps of spermiogenesis (stained with PAS-haematoxylin) the first 10 were associated with the stages I-X, whereas, the remaining were found in association with one of the first six stages. The frequency of appearance of the various stages ranged from 3.84% (stage V) to 19.84% (stage I). These observations indicate that stage V is of shortest duration and stage I is of the longest duration in the bat. Five types of spermatogonia (A1, A2, A3, In and B) were identified based on their shape, size and nuclear morphology. Type A spermatogonia are oval with a large nucleus containing 1 or 2 nucleoli. The chromatin showed progressive condensation from A1 to A3 so that the latter appeared darkest among all the A type spermatogonia. The In type derived from A3 are smaller but appear darker than A3 due to heterochromatin crusts along the inner border of the nucleus. The B type spermatogonia derived from In are round and possess single nucleolus. The B type spermatogonia divided mitotically before entering meiosis or the actual production of the primary spermatocytes. The various spermatogonia divided mitotically at fixed stages of the cycle giving rise to their next generations.(ABSTRACT TRUNCATED AT 250 WORDS)     

The ultrastructure of the nuclei and the behaviour of the sex chromosomes of human spermatogonia

Summary The nuclear structure of human spermatogonia has been studied with electron microscopical and histochemical methods. Type B spermatogonia have chromatin clumps without any special ultrastructure and several nucleoli. Five different types of nuclear bodies, and besides, a nuclear vacuole, have been observed in type A spermatogonia. Type I bodies are typical nucleoli consisting of three regions: amorphous, fibrillar and granular. Type II, III and V are considered to be atypical nucleoli. Type IV bodies are small chromatin condensations. Type I bodies are the only ones in which RNA was demonstrated by light histochemical techniques and no PAS positive material was found inside the nuclei. The absence of any special ultrastructure in the chromatin from spermatogonia, and the small mass of the chromatin condensations, show that the human X chromosome and perhaps the Y chromosome are not heteropycnotic in the interphasic nuclei of human spermatogonia.Abbreviations Used RNA ribonucleic acid - gonia spermatogonia This work has been supported by a grant (No. 2623) of the Consejo Nacional de Investigaciones Cientificas y Tecnicas, and partially by a grant (C.M. 6522) from the Population Council.We wish to thank Professor R. E. Mancini for his suggestions during this investigation and his support for its achievement, and to Dr. J. C. Lavieri for providing the biopsies.     

Spermatogenesis and related plasma androgen levels in Atlantic halibut (Hippoglossus hippoglossus L.)

Spermatogenesis in male Atlantic halibut (Hippoglossus hippoglossus L.) was investigated by sampling blood plasma and testicular tissue from 15-39-month-old fish. The experiment covered a period in which all fish reached puberty and completed sexual maturation at least once. The germinal compartment in Atlantic halibut testis appears to be organized in branching lobules of the unrestricted spermatogonial type, because spermatocysts with spermatogonia were found throughout the testis. Spermatogenesis was characterized histologically, and staged according to the most advanced type of germ cell present: spermatogonia (Stage I), spermatogonia and spermatocytes (Stage II), spermatogonia, spermatocytes and spermatids (Stage III), spermatogonia, spermatocytes, spermatids and spermatozoa (Stage IV), and regressing testis (Stage V). Three phases could be distinguished: first, an initial phase with low levels of circulating testosterone (T; quantified by RIA) and 11-ketotestosterone (11-KT; quantified by ELISA), spermatogonial proliferation, and subsequently the initiation of meiosis marked by the formation of spermatocytes (Stage I and II). Secondly, a phase with increasing T and 11-KT levels and with haploid germ cells including spermatozoa present in the testis (Stage III and IV). Thirdly, a phase with low T and 11-KT levels and a regressing testis with Sertoli cells displaying signs of phagocytotic activity (Stage V). Circulating levels of 11-KT were at least four-fold higher than those of T during all stages of spermatogenesis. Increasing plasma levels of T and 11-KT were associated with increasing testicular mass throughout the reproductive cycle. The absolute level of, or the relation between, testis growth and circulating androgens were not significantly different in first time spawners compared to fish that underwent their second spawning season. These results provide reference levels for Atlantic halibut spermatogenesis.     

SPERMATOGONIAL CHALONE(S): EFFECT ON THE PHASES OF THE CELL CYCLE OF TYPE A SPERMATOGONIA IN THE RAT

Adult rats with X-irradiated testes were used to analyze the effect of the spermatogonial chalone(s) on the phases of the cell cycle of type A spermatogonia. Twelve days after irradiation, the animals were used in two experiments designed to test the existence of hypothetical G₂ and S phase chalones. For the G₂ assay, rats injected twice with testicular extract (Group I), liver extract (Group II) or physiological saline (Group III) were killed 10 hr after the initial injection. Mitoses of type A, Intermediate and type B spermatogonia were counted in whole mounts of dissected seminiferous tubules. To test for an S phase inhibitor, two groups of rats were given multiple injections of either testicular extract (Group IV) or saline solution (Group V). Twenty-two hr after the first injection they were injected with [³H]thymidine and killed 2 hr later. Silver grains over labelled type A nuclei were counted in radioautographed sections of testes from these animals. The average grain counts were identical in Groups IV and V, indicating that the testicular extract did not affect type A spermatogonia during the S phase. Counts of type A mitoses in Groups I, II and III revealed that in the animals injected with the testicular extract (Group I) the number of divisions was 50% lower than in the control groups (Groups II and III). In contrast, mitotic activity of differentiating spermatogonia (In + B) was similar in all three groups of animals. This result is attributed to a testicular chalone which specifically inhibits type A spermatogonia during the G₂ phase of the cell cycle. Indirect evidence for a G₁ spermatogonial chalone is also presented, as a result of an analysis of published data (Clermont & Mauger, 1974).     

DNA double-strand breaks and gamma-H2AX signaling in the testis

Within minutes of the induction of DNA double-strand breaks in somatic cells, histone H2AX becomes phosphorylated at serine 139 and forms gamma-H2AX foci at the sites of damage. These foci then play a role in recruiting DNA repair and damage-response factors and changing chromatin structure to accurately repair the damaged DNA. These gamma-H2AX foci appear in response to irradiation and genotoxic stress and during V(D)J recombination and meiotic recombination. Independent of irradiation, gamma-H2AX occurs in all intermediate and B spermatogonia and in preleptotene to zygotene spermatocytes. Type A spermatogonia and round spermatids do not exhibit gamma-H2AX foci but show homogeneous nuclear gamma-H2AX staining, whereas in pachytene spermatocytes gamma-H2AX is only present in the sex vesicle. In response to ionizing radiation, gamma-H2AX foci are generated in spermatogonia, spermatocytes, and round spermatids. In irradiated spermatogonia, gamma-H2AX interacts with p53, which induces spermatogonial apoptosis. These events are independent of the DNA-dependent protein kinase (DNA-PK). Irradiation-independent nuclear gamma-H2AX staining in leptotene spermatocytes demonstrates a function for gamma-H2AX during meiosis. gamma-H2AX staining in intermediate and B spermatogonia, preleptotene spermatocytes, and sex vesicles and round spermatids, however, indicates that the function of H2AX phosphorylation during spermatogenesis is not restricted to the formation of gamma-H2AX foci at DNA double-strand breaks.     

Potential ofVinca rosea extracts in modulating trace element profile

Diethylnitrosamine (DEN) was used as cancer-inducing agent in the experimental animals.Vinca rosea extract was supplemented with the drinking water as a chemopreventive agent. After 4 wk of treatment, animals were sacrificed and livers were excised. Nuclei and mitochondria were separated by differential centrifugation. The proton-induced X-ray emission technique has been used as the analytical method. Elemental analysis were performed for whole liver, nuclei, and mitochondria.V. rosea plant parts were also analyzed for elemental contents. Treatment with DEN caused an increase of Ni, Zn, and Cr levels in the whole liver and nuclei. There is an increase in Fe concentration in the liver, although the level decreased in mitochondria. The concentrations of Br and Ca were unchanged in the liver as a whole, but there were substantial increases of Br in nuclei and mitochondria, whereas Ca levels depleted drastically in these two organelles.Vinca extracts were effective in reverting the changes in the elemental concentration in the hepatic tissue as a whole, but were not that effective at subcellular levels.     

Impact of UV-B radiation on Clonostachys rosea germination and growth

Sensitivity to UV-B radiation is one of the main limitations of biological control of plant pathogens in the field. The effect of UV-B radiation on germination and leaf tissue colonization by the biological control agent Clonostachys rosea was evaluated. There were variations among C. rosea strains in sensitivity to UV-B radiation. The most tolerant strain (LQC62) had relative germination of about 60?% after irradiation of 4.2?kJ?m(-2). The deleterious effects of UV-B radiation on C. rosea colonization were overcome by higher conidial concentration. In addition, the tolerance of C. rosea conidia was higher when irradiated over leaf disks compared to agar media, and this is very important information to determine the dose and spray strategies for applying C. rosea in the field.     

红景天提取物提高高强度跑台运动小鼠的抗氧化能力

为了考察红景天提取物对高强度跑台运动小鼠的抗氧化能力的影响,本研究将30只昆明小鼠随机分成对照组、模型组和红景天提取物组,每组10只。红景天提取物组小鼠按照500 mg/kg bw的剂量灌胃红景天提取液(2 m L)。对照组和模型组小鼠灌胃等体积的蒸馏水,共灌胃4周。采用硫酸蒽酮比色法检测小鼠肝脏和肌肉组织糖原的含量;采用硫代巴比妥酸比色法检测小鼠骨骼肌组织中的丙二醛(MDA)水平;采用RT-PCR和Western blotting检测骨骼肌组织中的超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)的表达水平;采用苏木精和伊红(HE)染色评价骨骼肌病理改变。研究显示,模型组小鼠的跑台运动时间显著低于红景天提取物组(61.32 min vs 83.22 min,p<0.05);与模型组相比,红景天提取物组小鼠骨骼肌的炎性细胞浸润明显减轻,肌纤维排列明显改善;红景天提取物组的肝糖原和肌糖原含量均显著高于模型组;红景天提取物组小鼠骨骼肌组织中的MDA水平显著低于模型组;红景天提取物组的SOD、GSH-Px和CAT m RNA和蛋白表达水平均显著高于模型组;红景天提取物可通过上调抗氧化酶表达来增加抗氧化能力,减弱骨骼肌损伤,并增加机体的抗疲劳能力。     

Serotonin involvement in Rhodiola rosea attenuation of nicotine withdrawal signs in rats

Rhodiola rosea has been used for centuries in the traditional medicine to stimulate nervous system, to enhance physical and mental performance and to treat fatigue. It is known that administration of Rhodiola rosea extract elicits antidepressant activity, but the mechanism of action still remains unclear. Evidence from animal models and human studies show that nicotine reduces symptoms of depression and that nicotine cessation induces depressive-like symptoms. We investigated the effects of Rhodiola rosea on nicotine withdrawal signs. Nicotine dependence was induced by subcutaneous nicotine injection (2mg/kg, four times daily) for 14 days. Another group of animals treated with nicotine (for 14 days) and successively with Rhodiola rosea extract was co-administered with selective 5-HT receptorial antagonist WAY 100635 (1mg/kg). After nicotine withdrawal animals were evaluated for behavioural parameters (locomotor activity, abstinence signs, marble burying test), diencephalic serotonin metabolism and serotonin receptor-1A expression. Results show a significant increase of 5-HT content in N treated with R. rosea, with a significant increase of serotonin receptor 1A, suggesting an involvement of serotonin in beneficial effects of R. rosea on suffering produced by nicotine withdrawal.     

Low temperature promotes annexin V expression in newt testis

We examined the effect of low temperatures on annexin V expression in newt testis. When newts were transferred to a low temperature (12 degrees C), up-regulation of annexin V protein was observed in secondary spermatogonia. In primary spermatocytes, high levels of annexin V expression were observed at both 12 degrees C and 22 degrees C, but at 12 degrees C the protein was localized in part of the cytoplasm of primary spermatocytes. These results indicate that in newt testis annexin V is a cold-sensitive protein, suggesting the possibility that annexin V might have a cold stress-related function in newt germ cells.     

小RNA深度测序技术分析西瓜花叶病毒蜀葵分离物

蜀葵病毒病害的发生对其生长造成严重影响,明确蜀葵病毒病害的种类及变异进化对蜀葵病毒病害的防治具有重要意义。利用小RNA深度测序技术对具有明显脉明、花叶症状的蜀葵叶片进行鉴定。结果发现,感病蜀葵被西瓜花叶病毒(Watermelon mosaic virus, WMV)、锦葵脉明病毒(Mala vein cleaning virus, MVCV)和一种新的RNA病毒[暂命名为蜀葵病毒1号(Althaea rosea virus1, ArV1)]所侵染。为进一步明确WMV蜀葵分离物(WMV-Tg)的进化关系,对病毒WMV-Tg全基因组进行扩增,获得全长为10 046个核苷酸序列(nt)。序列分析结果显示,WMV-Tg与已报道的WMV分离物基因组核苷酸序列的同源性为83.3%～90.2%。系统进化关系表明,WMV-Tg与WMV-Pg聚为一簇,亲缘关系最近。对蜀葵WMV-Tg来源的小RNA(WMV-derived small interfering RNAs, WMV-vsiRNAs)的长度分布、5′碱基偏好性、极性分布以及热点区分布的分析,有助于加深对WMV-vsiRNAs的了解,并为进一步研究病毒来源的小RNA(virus-derived small interfering RNAs, vsiRNAs)在抗病毒防御中的功能,以及为蜀葵病毒病的防治奠定理论基础。     

两株产生免疫抑制剂的小双孢菌分离株的鉴定

从江苏无锡土壤中分离到两株玫瑰小双孢菌SIPI226和SIPI207,经形态、化学分析、Ribotyping及16S rRNA分析,两菌株细胞壁含meso\|DAP、磷酸类脂PIV、无枝菌酸,醌为MK9(H0,H2,H4),G+C mol%分别为683和694。经初步鉴定为玫瑰小双孢菌的两个新亚种：玫瑰小双孢菌无锡亚种(Microbispora rosea subsp. wuxiensis)和玫瑰小双孢菌鼋头渚亚种(Microbispora rosea subsp. yuantouzhuensis)。菌株SIPI226和SIPI207分别为玫瑰小双孢菌无锡亚种和玫瑰小双孢菌鼋头渚亚种的典型菌株。     

Distribution of type A spermatogonia in the mouse is not random

The distribution of type A spermatogonia was studied using drawings of cross-sectioned tubules at various stages of the spermatogenic cycle of perfusion-fixed, epoxy-embedded mouse testis. Spermatogonia were classified as either positioned opposite the interstitium or opposite the region where two tubules make contact or in a defined, intermediate region at which the two tubules diverged. At stage V, the population of type A spermatogonia, comprised of A(s) through A(al) cells, is randomly positioned around the periphery of the seminiferous tubule. The A(s) through A(al) population becomes nonrandomly distributed beginning at stage VI, being located primarily in regions where the tubule opposes the interstitium, and remains nonrandom through stage III of the next cycle. The A(1) spermatogonia of stage VII, derived from most A(pr) and A(al) spermatogonia, and the A(2) spermatogonia of stage IX, derived from the A(1) spermatogonia, are also nonrandomly positioned opposing the interstitium. However, the A(3) population of stage XI becomes randomly distributed around the tubule. To our knowledge, these are the first data to show that the more primitive spermatogonial types (A(s) to A(al)) move to specific sites within the seminiferous tubule. Division of the regularly spaced, more primitive spermatogonia (A(s) to A(al)) leads to the spread of their progeny (A(1) to A(4)) laterally along the base of the seminiferous tubule. The lateral spread from more or less evenly spaced foci ensures that spermatogenesis is conducted uniformly around the entire tubule. The data also suggest that the position of a seminiferous tubule in the mouse is stabilized in relationship to other seminiferous tubules.     

Differential expression of annexin V during spermatogenesis in the newt Cynops pyrrhogaster

 In order to isolate genes whose expression is up-regulated after the initiation of meiosis, we screened a cDNA expression library of newt testes with antiserum against homogenates of testes derived from the spermatogonial and spermatocyte stages. We report the isolation of spermatocyte-specific cDNA clones encoding a newt homologue of the calcium-dependent phospholipid-binding protein, annexin V. Northern blot analysis showed that newt annexin V mRNA was 1.7 kb in length and was expressed strongly in testes, but weakly in other organs. In situ hybridization revealed that the expression of newt annexin mRNA was barely observed in spermatogonia, but increased significantly in leptotene-zygotene primary spermatocytes and reached a maximum level in pachytene spermatocytes and round spermatids. The newt annexin V cDNA predicted a 323-amino acid protein and had a 68% homology to human annexin V. The predicted amino acid sequence contained a conserved 4-fold internal repeat of approximately 70 residues like other annexin proteins. Immunoblot analysis using the monoclonal antibody against newt annexin V showed that the protein was expressed scarcely in spermatogonia but was abundantly expressed in stages from primary spermatocytes to spermatids; this pattern was consistent to that of the mRNA. Immunohistochemical analysis revealed that newt annexin V was localized in the cytoplasm of the spermatogenic cells, but not in somatic cells such as Sertoli cells or pericystic cells. These results indicate that the expression of newt annexin V is up-regulated in the spermatogenic cells after the initiation of meiosis and suggest that newt annexin V plays an important role in spermatogenesis. Received: 8 December 1995 / Accepted: 12 February 1996 Edited by H. Shimada/D. Tautz     

Ability of Clonostachys rosea to Establish and Suppress Sporulation Potential of Botrytis cinerea in Deleafed Stems of Hydroponic Greenhouse Tomatoes

The ability of Clonostachys rosea to establish and persist in deleafed tomato stems and to suppress sporulation potential of Botrytis cinerea was investigated in plots of hydroponic tomatoes in commercial greenhouses. Leaves near lower fruit clusters were removed according to standard practice and deleafed portions of the stems were treated with C. rosea , iprodione or water. Inoculum of B. cinerea was from natural infections. Stem lesions were not produced by the pathogen during the trials. Development of C. rosea and B. cinerea in stems was estimated indirectly by quantifying sporulation on excised stem tissues that were incubated on an agar medium containing paraquat. Incidence and area of sporulation of C. rosea on tissue pieces were high (76-99%) and moderately high (33-79%), respectively, when stems were treated with the agent at 0, 6, 24 or 48 h after deleafing and sampled 11 to 75 days later. In various instances, the agent also sporulated on tissues from water controls and iprodione treatments, apparently after interplot transmission. In most instances, incidence and area of sporulation of B. cinerea on tissue pieces were high (83-100%) and moderate to high (35-76%), respectively, in the water controls, but moderate (31-44%) and moderate to low (5-34%), respectively, for stems treated with C. rosea at 0 to 48 h after deleafing and sampled after 11-75 days. Without exception, C. rosea suppressed B. cinerea as or more effectively than iprodione. Correlations between inoculum density of C. rosea (0-10 6 conidia mL -1 ) and sporulation potential of B. cinerea in deleafed stems were strongly negative in each of three tests ( r = -0.95 to -0.99). Conidial suspensions and a talc formulation of C. rosea were of similar effectiveness against B. cinerea . We conclude that C. rosea persisted and suppressed sporulation potential of B. cinerea in deleafed tomato stems for at least 11 weeks after application.     

The actomyosin cytoskeleton of amoebae of the cellular slime molds acrasis rosea and protostelium mycophaga: structure, biochemical properties, and function

In amoebae of the cellular slime molds (mycetozoans) Acrasis rosea and Protostelium mycophaga, bundles of F-actin radiate from the endoplasm-ectoplasm interface into the pseudopodia, where G-actin is also located. We conclude that these actin bundles form a core scaffold driving pseudopod extension which is subsequently completed by filling with a more loosely organized meshwork of F-actin. Some bipolar, elongate amoebae of A. rosea also contained long bundles of F-actin that traverse the cells lengthwise and remotely resemble stress fibers. Rodlets of F-actin were scattered in the body of amoebae of A. rosea or formed star-shaped or polygonal complexes near or around contractile vacuoles, where they may play a role in contraction. In total protein extracts analyzed by SDS-PAGE and immunoblots the actins migrated like the rabbit skeletal muscle control. The relative proportion of actin in total protein extracts was 7.9% for A. rosea and 34.5% for P. mycophaga. We detected four or five isoactins in extracts of both species and we determined that the genome of each species contains approximately six actin genes. Whether they are all expressed or if posttranslational modifications occur remains to be determined. Myosin II was enriched in actomyosin extracts; its Mr was 187.8 kDa for A. rosea and 220.7 kDa for P. mycophaga. Cell models ("ghosts") contracted upon the addition of ATP. We conclude that amoebae of A. rosea and P. mycophaga, although behaving differently from those of Dictyostelium discoideum, contain the basic repertoire of molecules that enable pseudopod extension by actin polymerization and ATP-induced contraction of the cell cortex. Copyright 1998 Academic Press.