Spire2 and Rab11a synergistically activate myosin-5b motor function

Cellular vesicle long-distance transport along the cytoplasmic actin network has recently been uncovered in several cell systems. In metaphase mouse oocytes, the motor protein myosin-5b (Myo5b) and the actin nucleation factor Spire are recruited to the Rab11a-positive vesicle membrane, forming a ternary complex of Myo5b/Spire/Rab11a that drives the vesicle long-distance transport to the oocyte cortex. However, the mechanism underlying the intermolecular regulation of the Myo5b/Spire/Rab11a complex remains unknown. In this study, we expressed and purified Myo5b, Spire2, and Rab11a proteins, and performed ATPase activity measurements, pulldown and single-molecule motility assays. Our results demonstrate that both Spire2 and Rab11a are required to activate Myo5b motor activity under physiological ionic conditions. The GTBM fragment of Spire2 stimulates the ATPase activity of Myo5b, while Rab11a enhances this activation. This activation occurs by disrupting the head-tail interaction of Myo5b. Furthermore, at the single-molecule level, we observed that the GTBM fragment of Spire2 and Rab11a coordinate to stimulate the Myo5b motility activity. Based on our results, we propose that upon association with the vesicle membrane, Myo5b, Spire2 and Rab11a form a ternary complex, and the inhibited Myo5b is synergistically activated by Spire2 and Rab11a, thereby triggering the long-distance transport of vesicles.

A new C19-diterpenoid alkaloid in Aconitum georgei Comber

Nine diterpenoid alkaloids were isolated from Aconitum georgei Comber belonging to the genus Aconitum in Ranunculaceae family. Their structures were determinated by using HR-ESI-MS and 1 D/2D NMR spectra as geordine (1), yunaconitine (2), chasmanine (3), crassicauline A (4), forestine (5), pseudaconine (6), 14-acetylalatisamine (7), austroconitine B (8), and talatisamine (9). Among them, compound 1 is a previously undescribed aconitine-type C19-diterpenoid alkaloid, and compounds 3, and 5-9 have not previously been isolated from this species. The results of in vitro experiments indicated that new compound 1 possesses mild anti-inflammatory activity, which inhibited the production of NO in LPS-activated RAW 264.7 cells with an inhibition ratio of 29.75% at 50 μM.

H2 S works synergistically with rhizobia to modify photosynthetic carbon assimilation and metabolism in nitrogen-deficient soybeans

Hydrogen sulfide (H₂ S) performs a crucial role in plant development and abiotic stress responses by interacting with other signalling molecules. However, the synergistic involvement of H₂ S and rhizobia in photosynthetic carbon (C) metabolism in soybean (Glycine max) under nitrogen (N) deficiency has been largely overlooked. Therefore, we scrutinised how H₂ S drives photosynthetic C fixation, utilisation, and accumulation in soybean-rhizobia symbiotic systems. When soybeans encountered N deficiency, organ growth, grain output, and nodule N-fixation performance were considerably improved owing to H₂ S and rhizobia. Furthermore, H₂ S collaborated with rhizobia to actively govern assimilation product generation and transport, modulating C allocation, utilisation, and accumulation. Additionally, H₂ S and rhizobia profoundly affected critical enzyme activities and coding gene expressions implicated in C fixation, transport, and metabolism. Furthermore, we observed substantial effects of H₂ S and rhizobia on primary metabolism and C-N coupled metabolic networks in essential organs via C metabolic regulation. Consequently, H₂ S synergy with rhizobia inspired complex primary metabolism and C-N coupled metabolic pathways by directing the expression of key enzymes and related coding genes involved in C metabolism, stimulating effective C fixation, transport, and distribution, and ultimately improving N fixation, growth, and grain yield in soybeans.

Macrostines A and B: Tetracyclic fisicoccane from the fungus Periconia macrospinosa WTG-10

Two previous unreported fusicoccane diterpenoids macrostines A and B, together with seven known compounds were isolated from an extract of the fungus Periconia macrospinosa WTG-10. Their structures were elucidated by detailed analysis of spectroscopic data, NMR calculations with DP4+, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra or X-crystallography. Macrostines A and B showed no cytotoxicity, antimicrobial activity and inhibitory effect on nitric oxide production in LPS-activated RAW264.7 macrophages. Compound 9 showed moderate activity against Bacillus subtilis.

Polyketides with antimicrobial activities from Penicillium canescens DJJ-1

Two undescribed polyketides canecines A-B, one unreported cyclopentenone canecine C, together with 12 known compounds were isolated from an extract of the fungus Penicillium canescens DJJ-1. Their structures were elucidated by detailed analysis of spectroscopic data, NMR calculations with dJ-DP4 or DP4+, and their absolute configurations were further determined by quantum chemical calculations of ECD spectra or X-crystallography. Canecine A was a grisan polyketide featuring a dimethyltetrahydro-4H-furo[2,3-b]pyran. Canecine A exhibited significant inhibitory activity against Candida albicans with an MIC value of 1 μg/mL and showed inhibitory effect on nitric oxide production in LPS-activated RAW264.7 macrophages. These results enrich the structural diversities of polyketides from endophytic fungi.

Investigations of specialised metabolites of endophyte Diaporthe destruens hosted in Illigera orbiculata C. Y. Wu

A chemical investigation of the endophytic fungus Diaporthe destruens from the Hernandiaceae plant Illigera orbiculata C. Y. Wu collected from southern Yunnan Province, China, led to the isolation of six undescribed compounds, including two azaphilone analogs, which are a pair of epimers (13R-hydroxy-chermesinone A and 13S-hydroxy-chermesinone A); a pyrrole derivative (1-(4-(methoxymethyl)-1H-pyrrol-3-yl)ethan-1-one); an isoindolone derivative (4-hydroxy-6-methoxyisoindolin-1-one); a benzylbenzene derivative (destruensine A) and a conjectural fragment of polyketide ((2R,4R)-2-(methoxymethyl)pentane-1,4-diol) along with nine known compounds. Their structures were elucidated by spectroscopic methods and HRESIMS, and the absolute configurations were further confirmed by electronic circular dichroism (ECD) and chemical derivatization. The antimicrobial activities, anti-acetylcholinesterase activities, antiproliferation, and NO production inhibitory effects of compounds 1-15 were evaluated.

[Advances in Hippo signaling pathway in oral squamous cell carcinoma]

Oral squamous cell carcinoma (OSCC) is a common cancer that develops from oral epithelial cells, it has a high incidence, mortality and teratogenic rate, which poses a serious threat to people's life and health.The Hippo signaling pathway plays a key role in tumorigenesis, regulation of stem cell homeostasis, tissue regeneration, and organ size control. In OSCC, activation of Hippo signaling pathway can inhibit malignant biological behavior, epithelial mesenchymal transformation and distant metastasis of tumors, and improve the survival rate of patients. Considering the importance of the Hippo signaling pathway in the development of cancer, this paper summarized the composition and regulatory mechanism of Hippo pathway, elaborated the role of Hippo signaling pathway in the occurrence and development of OSCC.At the same time, make a simple generalization about the potential therapeutic approaches and strategies to reduce the risk of drug resistance for OSCC patients targeting this pathway.

The LKB1-like Kinase Elm1 Controls Septin Hourglass Assembly and Stability by Regulating Filament Pairing

Septins form rod-shaped hetero-oligomeric complexes that assemble into filaments and other higher-order structures, such as rings or hourglasses, at the cell division site in fungal and animal cells [1-4] to carry out a wide range of functions, including cytokinesis and cell morphogenesis. However, the architecture of septin higher-order assemblies and their control mechanisms, including regulation by conserved kinases [5, 6], remain largely unknown. In the budding yeast Saccharomyces cerevisiae, the five mitotic septins (Cdc3, Cdc10, Cdc11, Cdc12, and Shs1) localize to the bud neck and form an hourglass before cytokinesis that acts as a scaffold for proteins involved in multiple processes as well as a membrane-diffusible barrier between the mother and developing bud [7-9]. The hourglass is remodeled into a double ring that sandwiches the actomyosin ring at the onset of cytokinesis [10-13]. How septins are assembled into a highly ordered hourglass structure at the division site [13] is largely unexplored. Here we show that the LKB1-like kinase Elm1, which has been implicated in septin organization [14], cell morphogenesis [15], and mitotic exit [16, 17], specifically associates with the septin hourglass during the cell cycle and controls hourglass assembly and stability, especially for the daughter half, by regulating filament pairing and the functionality of its substrate, the septin-binding protein Bni5. This study illustrates how a protein kinase regulates septin architecture at the filament level and suggests that filament pairing is a highly regulated process during septin assembly and remodeling in vivo.

The cargo adaptor proteins RILPL2 and melanophilin co-regulate myosin-5a motor activity

Vertebrate myosin-5a is an ATP-utilizing processive motor associated with the actin network and responsible for the transport and localization of several vesicle cargoes. To transport cargo efficiently and prevent futile ATP hydrolysis, myosin-5a motor function must be tightly regulated. The globular tail domain (GTD) of myosin-5a not only functions as the inhibitory domain but also serves as the binding site for a number of cargo adaptor proteins, including melanophilin (Mlph) and Rab-interacting lysosomal protein-like 2 (RILPL2). In this study, using various biochemical approaches, including ATPase, single-molecule motility, GST pulldown assays, and analytical ultracentrifugation, we demonstrate that the binding of both Mlph and RILPL2 to the GTD of myosin-5a is required for the activation of myosin-5a motor function under physiological ionic conditions. We also found that this activation is regulated by the small GTPase Rab36, a binding partner of RILPL2. In summary, our results indicate that RILPL2 is required for Mlph-mediated activation of Myo5a motor activity under physiological conditions and that Rab36 promotes this activation. We propose that Rab36 stimulates RILPL2 to interact with the myosin-5a GTD; this interaction then induces exposure of the Mlph-binding site in the GTD, enabling Mlph to interact with the GTD and activate myosin-5a motor activity.

Regulation of class V myosin

Class V myosin (myosin-5) is a molecular motor that functions as an organelle transporter. The activation of myosin-5's motor function has long been known to be associated with a transition from the folded conformation in the off-state to the extended conformation in the on-state, but only recently have we begun to understand the underlying mechanism. The globular tail domain (GTD) of myosin-5 has been identified as the inhibitory domain and has recently been shown to function as a dimer in regulating the motor function. The folded off-state of myosin-5 is stabilized by multiple intramolecular interactions, including head-GTD interactions, GTD-GTD interactions, and interactions between the GTD and the C-terminus of the first coiled-coil segment. Any cellular factor that affects these intramolecular interactions and thus the stability of the folded conformation of myosin-5 would be expected to regulate myosin-5 motor function. Both the adaptor proteins of myosin-5 and Ca2+ are potential regulators of myosin-5 motor function, because they can destabilize its folded conformation. A combination of these regulators provides a versatile scheme in regulating myosin-5 motor function in the cell.

The Globular Tail Domain of Myosin-5a Functions as a Dimer in Regulating the Motor Activity

Myosin-5a contains two heavy chains, which are dimerized via the coiled-coil regions. Thus, myosin-5a comprises two heads and two globular tail domains (GTDs). The GTD is the inhibitory domain that binds to the head and inhibits its motor function. Although the two-headed structure is essential for the processive movement of myosin-5a along actin filaments, little is known about the role of GTD dimerization. Here, we investigated the effect of GTD dimerization on its inhibitory activity. We found that the potent inhibitory activity of the GTD is dependent on its dimerization by the preceding coiled-coil regions, indicating synergistic interactions between the two GTDs and the two heads of myosin-5a. Moreover, we found that alanine mutations of the two conserved basic residues at N-terminal extension of the GTD not only weaken the inhibitory activity of the GTD but also enhance the activation of myosin-5a by its cargo-binding protein melanophilin (Mlph). These results are consistent with the GTD forming a head to head dimer, in which the N-terminal extension of the GTD interacts with the Mlph-binding site in the counterpart GTD. The Mlph-binding site at the GTD-GTD interface must be exposed prior to the binding of Mlph. We therefore propose that the inhibited Myo5a is equilibrated between the folded state, in which the Mlph-binding site is buried, and the preactivated state, in which the Mlph-binding site is exposed, and that Mlph is able to bind to the Myo5a in preactivated state and activates its motor function.

Identification of the Isoform-specific Interactions between the Tail and the Head of Class V Myosin

Vertebrates have three isoforms of class V myosin (Myo5), Myo5a, Myo5b, and Myo5c, which are involved in transport of multiple cargoes. It is well established that the motor functions of Myo5a and Myo5b are regulated by a tail inhibition mechanism. Here we found that the motor function of Myo5c was also inhibited by its globular tail domain (GTD), and this inhibition was abolished by high Ca(2+), indicating that the tail inhibition mechanism is conserved in vertebrate Myo5. Interestingly, we found that Myo5a-GTD and Myo5c-GTD were not interchangeable in terms of inhibition of motor function, indicating isoform-specific interactions between the GTD and the head of Myo5. To identify the isoform-specific interactions, we produced a number of Myo5 chimeras by swapping the corresponding regions of Myo5a and Myo5c. We found that Myo5a-GTD, with its H11-H12 loop being substituted with that of Myo5c, was able to inhibit the ATPase activity of Myo5c and that Myo5a-GTD was able to inhibit the ATPase activity of Myo5c-S1 and Myo5c-HMM only when their IQ1 motif was substituted with that of Myo5a. Those results indicate that the H11-H12 loop in the GTD and the IQ1 motif in the head dictate the isoform-specific interactions between the GTD and head of Myo5. Because the IQ1 motif is wrapped by calmodulin, whose conformation is influenced by the sequence of the IQ1 motif, we proposed that the calmodulin bound to the IQ1 motif interacts with the H11-H12 loop of the GTD in the inhibited state of Myo5.

Cervical cytology ASCUS patients with HPV detection and clinical value

OBJECTIVE

Patients whose cervical cytological exams produced a result of atypical squamous cells of undetermined significance (ASCUS) were asked to undergo human papillomavirus (HPV DNA) genotyping detection to assess the role of HPV infection in ASCUS.

MATERIALS AND METHODS

This study included 1,219 patients with ASCUS that were randomly divided into two groups. The first group contained 618 patients. These participants underwent colposcopy with cervical biopsy. The remaining 601 underwent colposcopy and biopsy with HPV DNA detection.

RESULTS

Out of the 56,000 patients with ASCUS who underwent ThinPrep cytology test (TCT) de- tection in the authors' hospitals' gynecological outpatient clinics, 1,604 were diagnosed with ASCUS (2.86%). Among the 1,219 patients with ASCUS, the rate of detection of cervical intraepithelial neoplasia (CIN) and cancerization was 22.89% (279/1,219). Among the 601 patients who underwent HPV testing, 182 were positive for high-risk HPV (30.28%). Among HPV-positive samples, the most common high-risk types were HPV16, and HPV58. The most common low-risk types were HPV6 and HPV 11. The rate of detection among high- risk patients who were positive for HPV and cervical carcinoma with intraepithelial neoplasia was 70.88% (129/182). The rate of detection for HPV-negative patients with cervical cancer with intraepithelial neoplasia was 11.55% (47/407). The rate of detection of high-risk HPV was higher than among patients who had not undergone HPV detection and among patients who were negative for HPV (p < 0.05).

CONCLUSION

The results of cervical cytological examination showed that the manner of progression from inflammation to cancer could differ considerably. HPV DNA examination is an effective means of categorizing and managing ASCUS.

Tuning Crystal Phase and Emission Properties of Upconversion Nanocrystals Through Lanthanide Doping

Infrared-to-visible upconversion fluorescent nanocrystals of Yb³⁺/Er³⁺-codoped NaYF₄ and Yb³⁺/Er³⁺/Gd³⁺-tridoped NaYF₄ were synthesized using a modified coprecipitation process. X-ray diffraction and transmission electron diffraction scans of the nanocrystals confirmed that Gd³⁺ doping caused a phase transition to occur in the nanocrystals, changing them from a cubic to a hexagonal phase. Hexagonal phase Yb³⁺/Er³⁺/Gd³⁺-tridoped NaYF₄ nanocrystals displayed much stronger and sharper upconversion luminescence, and larger intensity ratios of red over green emissions relative to their cubic phase counterparts. The influence of the crystal phase on the upconversion emission properties was explored by use of excitation power dependence curves, dynamic fluorescence and Raman spectra. The results suggest that the cubic-to-hexagonal phase transition decreases the crystal field symmetry, and then enhances upconversion luminescence intensity by relaxing forbidden selection rules. The conversion into the hexagonal phase also increases the number of phonon modes, and consequently improves the phonon-assisted energy transfer efficiency from Yb³⁺ to Er³⁺, thus facilitating the output of red emissions.

None detectable retrograde transport of Chinese botulinum toxin type A in mice by single intramuscular injection

Botulinum toxin type A (BoNT/A) can specifically cleave synaptosomal associated protein of 25 kDa (SNAP-25) into cleaved SNAP-25 (cl.SNAP-25), thus blocking the synaptic transmission in motor end plate and resulting in paralysis. It has been widely applied in clinical for treatment of various conditions characterized by muscle hyperactivity, such as dystonia and spasticity. BoNT/A is used locally, with little diffusion. Its paralyzing role is considered to be restricted to the nerve muscle junction, or close to the injection site. Recently, more and more studies, however, have suggested that BoNT/A also has central effects. In addition, some investigators have demonstrated that BoNT/A enters into central nervous system via retrograde transport after local intramuscular administration. The retrograde axonal transport of Chinese BoNT/A (CBoNT/A) was studied in this paper, which was rare in report. And the results showed that cl.SNAP-25 appeared not only at the injection site but also in contralateral muscle. Retrograde transport, however, was non-existent or too little to be detected in our study.

Oligonucleotide microarray analysis reveals dysregulation of energy-related metabolism in insulin-sensitive tissues of type 2 diabetes patients

Impaired insulin action within skeletal muscle, adipose tissue, and the liver is an important characteristic of type 2 diabetes (T2D). In order to identify common underlying defects in insulin-sensitive tissues that may be involved in the pathogenesis of T2D, the gene expression profiles of skeletal muscle, visceral adipose tissue, and liver from autopsy donors with or without T2D were examined using oligonucleotide microarrays and quantitative reverse transcriptase-PCR. Compared with controls, 691 genes were commonly dysregulated in these three insulin-sensitive tissues of humans with T2D. These co-expressed genes were enriched within the mitochondrion, with suggested involvement in energy metabolic processes such as glycolysis and gluconeogenesis, fatty acid beta oxidative, tricarboxylic acid cycle, and electron transport. Genes related to energy metabolism were mostly downregulated in diabetic skeletal muscle and visceral adipose tissue, while they were upregulated in the diabetic liver. This observed dysregulation in energy-related metabolism may be the underlying factor leading to the molecular mechanisms responsible for the insulin resistance of patients with T2D.

[Influence of organochlorine pesticides in wastewater on the soil along the channel]

Nine profile soil samples and two sewage water samples were collected from Xiaodian sewage irrigation area in Taiyuan city, concentrations of organochlorine pesticides (OCPs) were determined by the gas chromatography coupled with electron capture detector (GC-ECD) to analyze the influence of the leakage of sewage water. The result shows that OCPs in sewage water were mainly composed of HCHs. Concentrations of DDTs and other organochlorine pesticides were very low or out of the detection limit. Concentrations of sigmaOCPs and HCHs in eight profiles near irrigation channels to some extend decreased with the increasing of the linear distance off the channel, which shows influences of the leakage of sewage water on the soil nearby. Concentrations of HCHs clearly decreased with the increasing of soil depth in most profile soils. For the horizontal direction, concentrations of HCHs also decreased with the increasing of the linear distance off the channel. The correlation between HCHs and TOC was positive, but no correlation between pH and HCHs was found.

[Vertical distribution and possible sources of polycyclic aromatic hydrocarbon in sewage area soil]

Nine profile soil samples were collected from Xiaodian sewage irrigation area, Taiyuan city, China. The concentrations of 16 polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography equipped with a mass spectrometry detector (GC/ MS). The rank order of the average concentrations of PAHs in the 0-10 cm upper soil layer was background area < swamp area < groundwater irrigation area < sewage irrigation area. The concentrations of PAHs in most profile soils decreased with the increase of depth, and the PAHs were mainly accumulated in the surface soil layer (0-40 cm). 4-6 rings of PAHs were mainly accumulated in the 0-50 cm soil layer, and the accumulation capacity in groundwater-irrigation area was better than that in sewage irrigation area. The correlation between different rings of PAHs and TOC was positive (r(max) = 0.791, P = 0), and the same situation was found for PAHs and sand (r(max) = 0. 882, P = 0). The correlation between PAHs and pH was negative (r(min) = -0.1, P = 0.702). The main source of PAHs in the surface soil layer (0-40 cm) of study area was coal combustion. There were two pollution ways of PAHs in soil, one was settled into soil directly, the other was first settled into water and absorbed on the surface of solid particles, and then got enrichment in soil as irrigation water flew.

Calmodulin bound to the first IQ motif is responsible for calcium-dependent regulation of myosin 5a

Myosin 5a is as yet the best-characterized unconventional myosin motor involved in transport of organelles along actin filaments. It is well-established that myosin 5a is regulated by its tail in a Ca(2+)-dependent manner. The fact that the actin-activated ATPase activity of myosin 5a is stimulated by micromolar concentrations of Ca(2+) and that calmodulin (CaM) binds to IQ motifs of the myosin 5a heavy chain indicates that Ca(2+) regulates myosin 5a function via bound CaM. However, it is not known which IQ motif and bound CaM are responsible for the Ca(2+)-dependent regulation and how the head-tail interaction is affected by Ca(2+). Here, we found that the CaM in the first IQ motif (IQ1) is responsible for Ca(2+) regulation of myosin 5a. In addition, we demonstrate that the C-lobe fragment of CaM in IQ1 is necessary for mediating Ca(2+) regulation of myosin 5a, suggesting that the C-lobe fragment of CaM in IQ1 participates in the interaction between the head and the tail. We propose that Ca(2+) induces a conformational change of the C-lobe of CaM in IQ1 and prevents interaction between the head and the tail, thus activating motor function.

NO serves as a signaling intermediate downstream of H₂O₂ to modulate dynamic microtubule cytoskeleton during responses to VD-toxins in Arabidopsis

Although hydrogen peroxide (H₂O₂) and nitric oxide (NO) can act as an upstream signaling molecule to modulate the dynamic microtubule cytoskeleton during the defense responses to Verticillium dahliae (VD) toxins in Arabidopsis, it is not known the relationship between these two signaling molecules. Here, we show that VD-toxin-induced NO accumulation was dependent on prior H₂O₂ production, NO is downstream of H₂O₂ in the signaling process, and that H₂O₂ acted synergistically with NO to modulate the dynamic microtubule cytoskeleton responses to VD-toxins in Arabidopsis.

Hydrogen peroxide modulates the dynamic microtubule cytoskeleton during the defence responses to Verticillium dahliae toxins in Arabidopsis

The molecular mechanisms of signal transduction of plants in response to infection by Verticillium dahliae (VD) are not well understood. We previously showed that NO may act as an upstream signalling molecule to trigger the depolymerization of cortical microtubules in Arabidopsis. In the present study, we used the wild-type, and atrbohD and atrbohF mutants of Arabidopsis to explore the mechanisms of action of H(2)O(2) signals and the dynamic microtubule cytoskeleton in defence responses. We demonstrated that H(2)O(2) may also act as an upstream signalling molecule to regulate cortical microtubule depolymerization. The depolymerization of the cortical microtubules played a functional role in the signalling pathway to mediate the expression of defence genes. The results indicate that H(2)O(2) modulates the dynamic microtubule cytoskeleton to trigger the expression of defence genes against V. dahliae toxins (VD-toxins) in Arabidopsis.

Cortical microtubule as a sensor and target of nitric oxide signal during the defence responses to Verticillium dahliae toxins in Arabidopsis

The molecular mechanisms of signal transduction of plants in response to Verticillium dahliae (VD) are not known. Here, we show that Arabidopsis reacts to VD-toxins with a rapid burst of nitric oxide (NO) and cortical microtubule destabilization. VD-toxins treatment triggered a disruption of cortical microtubules network. This disruption can be influenced by NO production. However, cortical microtubule disruptions were not involved in regulating the NO production. The results indicated that NO may act as an upstream signalling molecule to trigger the depolymerization of cortical microtubule. Cortical microtubules may act as a target of NO signal and as a sensor to mediate the activation of PR-1 gene expression. These results suggested that NO production and cortical microtubule dynamics appeared to be parts of the important signalling system and are involved in the defence mechanisms to VD-toxins in Arabidopsis.

Verticillium dahliae toxin induced alterations of cytoskeletons and nucleoli in Arabidopsis thaliana suspension cells

In plant cells, cytoskeletons play important roles in response to biotic and abiotic stresses. However, little is known about the dynamics of cytoskeletons when cells are attacked by unphysical stress factors such as elicitors and toxins. We report here that the toxin of Verticillium dahliae (VD toxin) induced changes of microfilaments (MFs) and microtubules (MTs) in Arabidopsis thaliana suspension-cultured cells. When cells were treated with a low concentration of VD toxin, MFs were disrupted ordinally from the cortex to the perinuclear region, and then recovered spontaneously; but the MTs persisted. The MFs in the perinuclear region showed more resistance to VD toxin than the cortical ones. In contrast, when cells were treated with a high concentration of VD toxin, MFs and MTs were disrupted sooner and more severely and did not recover spontaneously. Treatments with high concentrations of VD toxin also induced changes of nucleoli. At the early stages of treatment, a nucleus had a single ring-shaped nucleolus. At the later stages, multiple smaller and more brightly fluorescing nucleoli emerged in a single nucleus. Disrupted MFs could be recovered by removing the VD toxin before the ring-shaped nucleoli appeared. All these results showed that MFs and MTs play important roles in the early defense responses against VD toxin in Arabidopsis suspension cells. The cytoskeletons may be used as sensors and effectors monitoring the defense reactions. The changes of nucleoli induced by VD toxin should be important characteristics of cell death.

Effect of shear stress on cultivation of Bacillus thuringiensis for thuringiensin production

Cultivation of Bacillus thuringiensis for thuringiensin production is a mixed-growth-associated system. Cultivation conditions should be different during the cell growth stage and production stage. In this study, agitation speed and aeration rate were varied during the exponential growth phase and stationary phase in order to investigate the effect of shear stress via agitation on cultivation of B. thuringiensis for thuringiensin production. It was found that shear stress had a significant effect on thuringiensin production during the stationary phase. By decreasing the agitation speed during the stationary phase, product formation was increased up to 43%.

In vivo assembly of rhodopsin from expressed polypeptide fragments

Rhodopsin folding and assembly were investigated by expression of five bovine opsin gene fragments separated at points corresponding to proteolytic cleavage sites in the second or third cytoplasmic regions. The CH(1-146) and CH(147-348) gene fragments encode amino acids 1-146 and 147-348 of opsin, while the TH(1-240) and TH(241-348) gene fragments encode amino acids 1-240 and 241-348, respectively. Another gene fragment, CT(147-240), encodes amino acids 147-240. All five opsin polypeptide fragments were stably produced upon expression of the corresponding gene fragments in COS-1 cells. The singly expressed polypeptide fragments failed to form a chromophore with 11-cis-retinal, whereas coexpression of two or three complementary fragments [CH(1-146) + CH(147-348), TH(1-240) + TH(241-348), or CH(1-146) + CT(147-240) + TH(241-348)] formed pigments with spectral properties similar to wild-type rhodopsin. The NH2-terminal polypeptide in these rhodopsins showed a glycosylation pattern characteristic of wild-type COS-1 cell rhodopsin and was noncovalently associated with its complementary fragment(s). Further, the CH(1-146) + CH(147-348) rhodopsin showed substantial light-dependent activation of transducin. We conclude that the functional assembly of rhodopsin is mediated by the association of at least three protein-folding domains.

[Surgical treatment of rectal carcinoid--report of 60 cases]

From 1973 to 1989, 60 patients with rectal carcinoid, as discovered by mass screening, were treated. It accounted for 0.02% of subjects screened and was the first among all G-I carcinoids. 96.7% of patients were asymptomatic and 86.6% were located within 8 cm of the anus. All were treated by surgery and none has died of this disease. The frequency of positive stump was 27% as observed in 31 specimens by local resection. Extended local resection still gave a positive residual rate of 9.4%. The authors believe that extended local resection is indicated even for small lesions less than 0.5 cm across.

Mitogenic response of rat Schwann cells to fibroblast growth factors is potentiated by increased intracellular cyclic AMP levels

Rat sciatic nerve Schwann cells either do not proliferate, or proliferate very slowly, in medium containing 10% fetal bovine serum (FBS). They were previously shown to respond only to a limited number of mitogens associated with cells of central and peripheral nervous systems, which appeared to be distinct from FGFs and PDGF, and to agents that raise intracellular cAMP levels. In a basal medium consisting of 75% DMEM, 25% Ham's F-12, 5 nM sodium selenite, 50 microM 2-amino ethanol, and 2 mM histidine, supplemented with 5% FBS, we showed that aFGF, bFGF, and PDGF were all capable of stimulating Schwann cell growth and the stimulation was greatly potentiated by forskolin and dibutyryl-cAMP. In addition, pretreating culture surface with purified matrix proteins such as laminin, fibronectin, or type 1 collagen, was necessary for obtaining a better cellular response to the mitogenesis of these growth factors even in 10% FBS. Our results clearly indicated that providing a suitable medium and substratum, aFGF, bFGF and PDGF are mitogens for rat sciatic nerve Schwann cells in medium with and without forskolin or dibutyryl-cAMP.