The Yeast Protein Kinase Sch9 Functions as a Central Nutrient-Responsive Hub That Calibrates Metabolic and Stress-Related Responses

Yeast cells are equipped with different nutrient signaling pathways that enable them to sense the availability of various nutrients and adjust metabolism and growth accordingly. These pathways are part of an intricate network since most of them are cross-regulated and subject to feedback regulation at different levels. In yeast, a central role is played by Sch9, a protein kinase that functions as a proximal effector of the conserved growth-regulatory TORC1 complex to mediate information on the availability of free amino acids. However, recent studies established that Sch9 is more than a TORC1-effector as its activity is tuned by several other kinases. This allows Sch9 to function as an integrator that aligns different input signals to achieve accuracy in metabolic responses and stress-related molecular adaptations. In this review, we highlight the latest findings on the structure and regulation of Sch9, as well as its role as a nutrient-responsive hub that impacts on growth and longevity of yeast cells. Given that most key players impinging on Sch9 are well-conserved, we also discuss how studies on Sch9 can be instrumental to further elucidate mechanisms underpinning healthy aging in mammalians.

The nutrient-responsive CDK Pho85 primes the Sch9 kinase for its activation by TORC1

Yeast cells maintain an intricate network of nutrient signaling pathways enabling them to integrate information on the availability of different nutrients and adjust their metabolism and growth accordingly. Cells that are no longer capable of integrating this information, or that are unable to make the necessary adaptations, will cease growth and eventually die. Here, we studied the molecular basis underlying the synthetic lethality caused by loss of the protein kinase Sch9, a key player in amino acid signaling and proximal effector of the conserved growth-regulatory TORC1 complex, when combined with either loss of the cyclin-dependent kinase (CDK) Pho85 or loss of its inhibitor Pho81, which both have pivotal roles in phosphate sensing and cell cycle regulation. We demonstrate that it is specifically the CDK-cyclin pair Pho85-Pho80 or the partially redundant CDK-cyclin pairs Pho85-Pcl6/Pcl7 that become essential for growth when Sch9 is absent. Interestingly, the respective three CDK-cyclin pairs regulate the activity and distribution of the phosphatidylinositol-3 phosphate 5-kinase Fab1 on endosomes and vacuoles, where it generates phosphatidylinositol-3,5 bisphosphate that serves to recruit both TORC1 and its substrate Sch9. In addition, Pho85-Pho80 directly phosphorylates Sch9 at Ser726, and to a lesser extent at Thr723, thereby priming Sch9 for its subsequent phosphorylation and activation by TORC1. The TORC1-Sch9 signaling branch therefore integrates Pho85-mediated information at different levels. In this context, we also discovered that loss of the transcription factor Pho4 rescued the synthetic lethality caused by loss of Pho85 and Sch9, indicating that both signaling pathways also converge on Pho4, which appears to be wired to a feedback loop involving the high-affinity phosphate transporter Pho84 that fine-tunes Sch9-mediated responses.

Pib2 as an Emerging Master Regulator of Yeast TORC1

Cell growth is dynamically regulated in response to external cues such as nutrient availability, growth factor signals, and stresses. Central to this adaptation process is the Target of Rapamycin Complex 1 (TORC1), an evolutionarily conserved kinase complex that fine-tunes an enormous number of cellular events. How upstream signals are sensed and transmitted to TORC1 has been intensively studied in major model organisms including the budding yeast Saccharomyces cerevisiae. This field recently saw a breakthrough: the identification of yeast phosphatidylInositol(3)-phosphate binding protein 2 (Pib2) protein as a critical regulator of TORC1. Although the study of Pib2 is still in its early days, multiple groups have provided important mechanistic insights on how Pib2 relays nutrient signals to TORC1. There remain, on the other hand, significant gaps in our knowledge and mysteries that warrant further investigations. This is the first dedicated review on Pib2 that summarizes major findings and outstanding questions around this emerging key player in cell growth regulation.

TORC1 Determines Fab1 Lipid Kinase Function at Signaling Endosomes and Vacuoles

Organelles of the endomembrane system maintain their identity and integrity during growth or stress conditions by homeostatic mechanisms that regulate membrane flux and biogenesis. At lysosomes and endosomes, the Fab1 lipid kinase complex and the nutrient-regulated target of rapamycin complex 1 (TORC1) control the integrity of the endolysosomal homeostasis and cellular metabolism. Both complexes are functionally connected as Fab1-dependent generation of PI(3,5)P₂ supports TORC1 activity. Here, we identify Fab1 as a target of TORC1 on signaling endosomes, which are distinct from multivesicular bodies, and provide mechanistic insight into their crosstalk. Accordingly, TORC1 can phosphorylate Fab1 proximal to its PI3P-interacting FYVE domain, which causes Fab1 to shift to signaling endosomes, where it generates PI(3,5)P₂. This, in turn, regulates (1) vacuole morphology, (2) recruitment of TORC1 and the TORC1-regulatory Rag GTPase-containing EGO complex to signaling endosomes, and (3) TORC1 activity. Thus, our study unravels a regulatory feedback loop between TORC1 and the Fab1 complex that controls signaling at endolysosomes.

Multilayered Control of Protein Turnover by TORC1 and Atg1

The target of rapamycin complex 1 (TORC1) is a master regulator of cell homeostasis, which promotes anabolic reactions and synchronously inhibits catabolic processes such as autophagy-mediated protein degradation. Its prime autophagy target is Atg13, a subunit of the Atg1 kinase complex that acts as the gatekeeper of canonical autophagy. To study whether the activities of TORC1 and Atg1 are coupled through additional, more intricate control mechanisms than simply this linear pathway, we analyzed the epistatic relationship between TORC1 and Atg1 by using quantitative phosphoproteomics. Our in vivo data, combined with targeted in vitro TORC1 and Atg1 kinase assays, not only uncover numerous TORC1 and Atg1 effectors, but also suggest distinct bi-directional regulatory feedback loops and characterize Atg29 as a commonly regulated downstream target of both TORC1 and Atg1. Thus, an exquisitely multilayered regulatory network appears to coordinate TORC1 and Atg1 activities to robustly tune autophagy in response to nutritional cues.

TORC1 specifically inhibits microautophagy through ESCRT-0

Nutrient starvation induces the degradation of specific plasma membrane proteins through the multivesicular body (MVB) sorting pathway and of vacuolar membrane proteins through microautophagy. Both of these processes require the gateway protein Vps27, which recognizes ubiquitinated cargo proteins at phosphatidylinositol 3-phosphate-rich membranes as part of a heterodimeric complex coined endosomal sorting complex required for transport 0. The target of rapamycin complex 1 (TORC1), a nutrient-activated central regulator of cell growth, directly phosphorylates Vps27 to antagonize its function in microautophagy, but whether this also serves to restrain MVB sorting at endosomes is still an open question. Here, we show that TORC1 inhibits both the MVB pathway-driven turnover of the plasma membrane-resident high-affinity methionine permease Mup1 and the inositol transporter Itr1 and the microautophagy-dependent degradation of the vacuolar membrane-associated v-ATPase subunit Vph1. Using a Vps27^7D variant that mimics the TORC1-phosphorylated state of Vps27, we further show that cargo sorting of Vph1 at the vacuolar membrane, but not of Mup1 and Itr1 at endosomes, is sensitive to the TORC1-controlled modifications of Vps27. Thus, TORC1 specifically modulates microautophagy through phosphorylation of Vps27, but controls MVB sorting through alternative mechanisms.

A spatially and functionally distinct pool of TORC1 defines signaling endosomes in yeast

The evolutionarily conserved target of rapamycin complex 1 (TORC1) regulates cell growth in a homeostatic manner by tuning anabolic and catabolic processes in response to nutritional and hormonal cues. Interestingly, rather than being localized at the plasma membrane as perhaps expected for an integrator of extracellular signals, TORC1 mainly localizes at vacuolar (in yeast) and lysosomal (in more complex eukaryotes) membranes where it seems optimally placed to sense both the nutrient status within the cytoplasm and the vacuolar/lysosomal compartment. How TORC1 controls downstream targets that are distant from the vacuole/lysosome, is currently poorly understood. In this context, we recently identified and characterized 2 spatially and functionally distinct pools of TORC1 in the budding yeast Saccharomyces cerevisiae: one at the vacuole that promotes protein synthesis, and another one at endosomes that inhibits protein degradation. Thus, our findings highlight the presence of spatially separated pools of TORC1 that are commissioned with functionally specific tasks within cells. In addition, they pinpoint the existence of signaling endosomes in yeast, which raises numerous new questions that are warranted to direct future research in this area.

Extensive first-principles molecular dynamics study on Li encapsulation into C60 and its experimental confirmation

The aim of increasing the production ratio of endohedral C₆₀ by impinging foreign atoms against C₆₀ is a crucial matter of the science and technology employed towards industrialization of these functional building block materials. Among these endohedral fullerenes, Li⁺@C₆₀ exhibits a wide variety of physical and chemical phenomena and has the potential to be applicable in areas spanning the medical field to photovoltaics. However, currently, Li⁺@C₆₀ can be experimentally produced with only ∼1% ratio using the plasma shower method with a 30 eV kinetic energy provided to the impinging Li⁺ ion. From extensive first-principles molecular dynamics simulations, it is found that the maximum production ratio of Li⁺@C₆₀ per hit is increased to about 5.1% (5.3%) when a Li⁺ ion impinges vertically on a six-membered ring of C₆₀ with 30 eV (40 eV) kinetic energy, although many C₆₀ molecules are damaged during this collision. On the contrary, when it impinges vertically on a six-membered ring with 10 eV kinetic energy, the production ratio remains at 1.3%, but the C₆₀ molecules are not damaged at all. On the other hand, when the C₆₀ is randomly oriented, the production ratio reduces to about 3.7 ± 0.5%, 3.3 ± 0.5%, and 0.2 ± 0.03% for 30 eV, 40 eV, and 10 eV kinetic energy, respectively. Based on these observations we demonstrate the possibility of increasing the production ratio by fixing six-membered rings atop C₆₀ using the Cu(111) substrate or UV light irradiation. In order to assess the ideal experimental production ratio, the ⁷Li solid NMR spectroscopy measurement is also performed for the multilayer randomly oriented C₆₀ sample irradiated by Li⁺ using the plasma shower method combined with inductively coupled plasma atomic emission spectroscopy (ICP-AES). Time-of-flight mass spectroscopy measurements are also performed to cross check whether Li⁺@C₆₀ molecules are produced in the sample. The resulting experimental estimate, 4% for 30 eV incident kinetic energy, fully agrees with our simulation results mentioned above, suggesting the consistency and accuracy of our simulations and experiments.

Functional mapping of yeast genomes by saturated transposition

Yeast is a powerful model for systems genetics. We present a versatile, time- and labor-efficient method to functionally explore the Saccharomyces cerevisiae genome using saturated transposon mutagenesis coupled to high-throughput sequencing. SAturated Transposon Analysis in Yeast (SATAY) allows one-step mapping of all genetic loci in which transposons can insert without disrupting essential functions. SATAY is particularly suited to discover loci important for growth under various conditions. SATAY (1) reveals positive and negative genetic interactions in single and multiple mutant strains, (2) can identify drug targets, (3) detects not only essential genes, but also essential protein domains, (4) generates both null and other informative alleles. In a SATAY screen for rapamycin-resistant mutants, we identify Pib2 (PhosphoInositide-Binding 2) as a master regulator of TORC1. We describe two antagonistic TORC1-activating and -inhibiting activities located on opposite ends of Pib2. Thus, SATAY allows to easily explore the yeast genome at unprecedented resolution and throughput.

DOI:http://dx.doi.org/10.7554/eLife.23570.001

Genes are stretches of DNA that carry the instructions to build and maintain cells. Many studies in genetics involve inactivating one or more genes and observing the consequences. If the loss of a gene kills the cell, that gene is likely to be vital for life. If it does not, the gene may not be essential, or a similar gene may be able to take over its role.

Baker’s yeast is a simple organism that shares many characteristics with human cells. Many yeast genes have a counterpart among human genes, and so studying baker’s yeast can reveal clues about our own genetics. Michel et al. report an adaptation for baker’s yeast of a technique called “Transposon sequencing”, which had been used in other single-celled organisms to study the effects of interrupting genes. Briefly, a virus-like piece of DNA, called a transposon, inserts randomly into the genetic material and switches off individual genes. The DNA is then sequenced to reveal every gene that can be disrupted without killing the cell, and remaining genes are inferred to be essential for life.

The approach, named SATAY (which is short for “saturated transposon analysis in yeast”), uses this strategy to create millions of baker’s yeast cells, each with a different gene switched off. Because the number of cells generated this way vastly exceeds the number of genes, every gene will be switched off by several independent transposons. Therefore the technique allows all yeast genes to be inactivated several times in one single experiment. The cells can be grown in varying conditions during the experiment, revealing the genes needed for survival in different situations. Non-essential genes can also be inactivated beforehand to uncover if any genes might be compensating for their absence.

In the future, this technique may be used to better understand human diseases, such as cancer, since many disease-causing genes in humans have counterparts in yeast.

DOI:http://dx.doi.org/10.7554/eLife.23570.002

Ypk1 and Ypk2 kinases maintain Rho1 at the plasma membrane by flippase-dependent lipid remodeling after membrane stresses

The plasma membrane (PM) is frequently challenged by mechanical stresses. In budding yeast, TORC2-Ypk1/Ypk2 kinase cascade plays a crucial role in PM stress responses by reorganizing the actin cytoskeleton via Rho1 GTPase. However, the molecular mechanism by which TORC2-Ypk1/Ypk2 regulates Rho1 is not well defined. Here, we found that Ypk1/Ypk2 maintain PM localization of Rho1 under PM stress via spatial reorganization of the lipids including phosphatidylserine. Genetic evidence suggests that this process is mediated by the Lem3-containing lipid flippase. We propose that lipid remodeling mediated by the TORC2-Ypk1/Ypk2-Lem3 axis is a backup mechanism for PM anchoring of Rho1 after PM stress-induced acute degradation of phosphatidylinositol 4,5-bisphosphate [PI(4,5)P₂], which is responsible for Rho1 localization under normal conditions. Since all the signaling molecules studied here are conserved in higher eukaryotes, our findings might represent a general mechanism to cope with PM stress.

Unsolved mysteries of Rag GTPase signaling in yeast

The target of rapamycin complex 1 (TORC1) plays a central role in controlling eukaryotic cell growth by fine-tuning anabolic and catabolic processes to the nutritional status of organisms and individual cells. Amino acids represent essential and primordial signals that modulate TORC1 activity through the conserved Rag family GTPases. These assemble, as part of larger lysosomal/vacuolar membrane-associated complexes, into heterodimeric sub-complexes, which typically comprise two paralogous Rag GTPases of opposite GTP-/GDP-loading status. The TORC1-stimulating/inhibiting states of these heterodimers are controlled by various guanine nucleotide exchange factor (GEF) and GTPase-activating protein (GAP) complexes, which are remarkably conserved in various eukaryotic model systems. Among the latter, the budding yeast Saccharomyces cerevisiae has been instrumental for the elucidation of basic aspects of Rag GTPase regulation and function. Here, we discuss the current state of the respective research, focusing on the major unsolved issues regarding the architecture, regulation, and function of the Rag GTPase containing complexes in yeast. Decoding these mysteries will undoubtedly further shape our understanding of the conserved and divergent principles of nutrient signaling in eukaryotes.

Zds1/Zds2-PP2ACdc55 complex specifies signaling output from Rho1 GTPase

Zds1/Zds2–PP2A^Cdc55 forms a complex with Rho1 GTPase and specifies Rho1 signaling outcome by regulating Rho1 GAPs in budding yeast.

Budding yeast Rho1 guanosine triphosphatase (GTPase) plays an essential role in polarized cell growth by regulating cell wall glucan synthesis and actin organization. Upon cell wall damage, Rho1 blocks polarized cell growth and repairs the wounds by activating the cell wall integrity (CWI) Pkc1–mitogen-activated protein kinase (MAPK) pathway. A fundamental question is how active Rho1 promotes distinct signaling outputs under different conditions. Here we identified the Zds1/Zds2–protein phosphatase 2A^Cdc55 (PP2A^Cdc55) complex as a novel Rho1 effector that regulates Rho1 signaling specificity. Zds1/Zds2–PP2A^Cdc55 promotes polarized growth and cell wall synthesis by inhibiting Rho1 GTPase-activating protein (GAP) Lrg1 but inhibits CWI pathway by stabilizing another Rho1 GAP, Sac7, suggesting that active Rho1 is biased toward cell growth over stress response. Conversely, upon cell wall damage, Pkc1–Mpk1 activity inhibits cortical PP2A^Cdc55, ensuring that Rho1 preferentially activates the CWI pathway for cell wall repair. We propose that PP2A^Cdc55 specifies Rho1 signaling output and that reciprocal antagonism between Rho1–PP2A^Cdc55 and Rho1–Pkc1 explains how only one signaling pathway is robustly activated at a time.

Electrical transport properties of fullerene peapods interacting with light

In this paper, we investigate the transport properties of field-effect transistors (FETs) based on various kinds of fullerene (C(60), C(70), and C(84)) peapods. The encapsulation of various fullerenes inside single-walled carbon nanotubes (SWNTs) is characterized by TEM and Raman spectroscopy. Our results indicate that the transport characteristics of p-type SWNTs are extremely sensitive to the encapsulation of various kinds of fullerene. In the absence of light illumination, the threshold voltage of p-type SWNTs shifts towards positive values after C(60) and C(70) encapsulation, and ambipolar transport characteristics are observed for C(84) peapods. The photoinduced electron transfer phenomenon is observed for fullerene peapods under light illumination. The optical response for C(60) and C(70) peapod FET devices is reflected in a shift of threshold voltage towards negative values, and a recoverable characteristic is observed when light is off. After a long period of light illumination, in contrast to p-type C(60) and C(70) peapods, an n-type transport characteristic is observed on C(84) peapods.

Isolation of hyperactive mutants of mammalian target of rapamycin

The mammalian target of rapamycin (mTOR) is a Ser/Thr kinase that plays essential roles in the regulation of a wide array of growth-related processes such as protein synthesis, cell sizing, and autophagy. mTOR forms two functionally distinct complexes, termed the mTOR complex 1 (mTORC1) and 2 (mTORC2); only the former of which is inhibited by rapamycin. Based on the similarity between the cellular responses caused by rapamycin treatment and by nutrient starvation, it has been widely accepted that modulation in the mTORC1 activity in response to nutrient status directs these cellular responses, although direct evidence has been scarce. Here we report isolation of hyperactive mutants of mTOR. The isolated mTOR mutants exhibited enhanced kinase activity in vitro and rendered cells refractory to the dephosphorylation of the mTORC1 substrates upon amino acid starvation. Cells expressing the hyperactive mTOR mutant displayed larger cell size in a normal growing condition and were resistant to cell size reduction and autophagy induction in an amino acid-starved condition. These results indicate that the activity of mTORC1 actually directs these cellular processes in response to nutrient status and confirm the biological functions of mTORC1, which had been proposed solely from loss-of-function analyses using rapamycin and (molecular)genetic techniques. Additionally, the hyperactive mTOR mutant did not induce cellular transformation of NIH/3T3 cells, suggesting that concomitant activation of additional pathways is required for tumorigenesis. This hyperactive mTOR mutant will be a valuable tool for establishing physiological consequences of mTOR activation in cells as well as in organisms.

Cesium-filled single wall carbon nanotubes as conducting nanowires: scanning tunneling spectroscopy study

Metal-filled single wall carbon nanotubes (SWCNTs) are examined for possible application to conducting wires in nanoelectronics architecture. The local electronic structure of SWCNTs partially filled with cesium atoms is studied with scanning tunneling spectroscopy. The conduction and valence bands are shifted downward with two localized states in the gap at the location where the Cs atoms are filled. From a first-principles calculation, we confirm that these two gap states are bound states originating from the two lowest conduction bands.

Light represses conidiation in koji mold Aspergillus oryzae

In the filamentous fungus Aspergillus oryzae, there has been no report on photoreaction. Here we investigated the effect of light in A. oryzae and found that conidiation was repressed by white light. This reaction is contrary to that of other Aspergilli, which show abundant conidiation under light. Moreover, red light also caused reduced conidiation. Genome sequencing of A. oryzae indicated the existence of homologs of some light-related genes in other filamentous fungi. To approach the molecular mechanism of this photoresponse, the effect of red light on the expression level of several genes putatively responsible for conidiation or photoperception, i.e., brlA, a gene known to be required for conidiation, AofphA, the putative homolog of the A. nidulans phytochrome gene fphA, and AoveA, the putative homolog of the negative regulator gene in conidiation in A. nidulans, was examined. These three genes showed no significant response to red light at the transcriptional level. The results indicate that A. oryzae perceives and responds to red light in a manner independent of the transcriptional regulation of these genes.

Collective mode properties in a paired fullerene-ion plasma

A pair-ion plasma without electrons consisting of C60+ and C60- is generated through the processes of electron-impact ionization, electron attachment, and magnetic filtering. Properties of electrostatic modes propagating along magnetic-field lines are experimentally investigated by externally exciting them with two types of electrodes. It is found that four kinds of wave modes exist and a frequency spectrum of phase lag between the density fluctuations of C60+ and C60- is unique in comparison with ordinary electron-ion plasmas. One of the modes is an ion acoustic wave which is divided into two branches at around the ion cyclotron frequency in the presence of a backwardlike mode joining them. The phase lag of the ion acoustic wave strongly depends on the frequency, while those for the other ion plasma and intermediate-frequency waves are constant at pi independent of the frequency.

Synthesis and electronic properties of ferrocene-filled double-walled carbon nanotubes

Double-walled carbon nanotubes (DWNTs) are filled with ferrocene molecules by a vapour diffusion method for the first time. The as-synthesized ferrocene-filled DWNTs are characterized by transmission electron microscopy (TEM), energy-dispersive x-ray spectrometry (EDX) and Raman spectroscopy. Electronic properties of double-walled carbon nanotubes (DWNTs) filled with ferrocene molecules are studied by fabricating them as the channels of field-effect transistor (FET) devices. Our results reveal that electronic properties of ferrocene-filled DWNTs are greatly modified due to the charge transfer between ferrocene molecules and DWNTs. In addition, after ferrocene molecules are decomposed inside DWNTs, electronic properties of DWNTs exhibit a further change due to Fe encapsulation, and unipolar n-type semiconducting DWNTs are consequently obtained.

Absorption and penetration of left-hand polarized waves related to polarization reversal causing electron cyclotron resonance

Propagation and absorption of electromagnetic waves with electron cyclotron resonance (ECR) frequency are investigated for the case of inhomogeneously magnetized plasmas, when the left-hand polarized wave (LHPW) is selectively launched. The LHPW with axisymmetric-azimuthal and second-order radial modes is absorbed near the ECR point at any radial position, which is caused by the polarization reversal to the right-hand polarized wave. On the other hand, it is clarified that the LHPW with fundamental radial mode penetrates the ECR point without polarization reversal. In addition, it is theoretically suggested that polarization reversal can partially occur in the plasma column for the case of nonaxisymmetric modes.

Electrostatic waves in a paired fullerene-ion plasma

Three kinds of electrostatic modes are experimentally observed to propagate along magnetic-field lines for the first time in the pair-ion plasma consisting of only positive and negative fullerene ions with an equal mass. It is found that the phase lag between the density fluctuations of positive and negative ions varies from 0 to pi depending on the frequency for ion acoustic wave and is fixed at pi for an ion plasma wave. In addition, a new mode with the phase lag about pi appears in an intermediate-frequency band between the frequency ranges of the acoustic and plasma waves.

Polarization-reversal-induced damping of left-hand polarized wave on electron cyclotron resonance

The left-hand polarized wave, which has been believed not to be related to electron cyclotron resonance (ECR), is for the first time demonstrated to be damped near the ECR point in an inhomogeneously magnetized plasma as a result of the polarization reversal to the right-hand polarized wave. The polarization reversal is found to be caused by the existence of the boundary between a plasma and a vacuum region, the local point of which shifts depending on the plasma column radius. This phenomenon is quantitatively explained in terms of the dispersion relation including the effect of the radial boundary condition.

Drift-wave instability excited by field-aligned ion flow velocity shear in the absence of electron current

The drift wave is observed to be destabilized by a magnetic-field-aligned ion flow velocity shear in the absence of field-aligned electron drift flow in laboratory experiments using a concentrically three-segmented plasma source. The fluctuation amplitude increases with increasing a shear strength, but the instability is found to be gradually stabilized when the shear strength exceeds a critical value. The destabilizing and stabilizing mechanisms are well explained by a plasma kinetic theory including the effect of radial density gradient.

Changes in expressions of proinflammatory cytokines IL-1beta, TNF-alpha and IL-6 in the brain of senescence accelerated mouse (SAM) P8

The senescence-accelerated mouse (SAM) is known to be a murine model for accelerated aging. The SAMP8 strain shows age-related deterioration of learning and memory at an earlier age than control mice (SAMR1). In the present study, we investigated the changes in expressions of interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in the brain of SAMP8. In the hippocampus of 10 months old SAMP8, the expression of IL-1 mRNA was significantly elevated in comparison with that of SAMR1. In both strains of SAMs, increases in IL-1beta protein in the brain were observed at 10 months of age compared with 2 and 5 months. The only differences found between the strain in protein levels were at 10 months and were elevations in IL-1beta in the hippocampus and hypothalamus, and in TNF-alpha and IL-6 in the cerebral cortex and the hippocampus in SAMP8 as compared with SAMR1. However, lipopolysaccharide-induced increases in the expression of these cytokines in brain did not differ between SAMP8 and SAMR1. Increases in expression of proinflammatory cytokines in the brain may be involved in the age-related neural dysfunction and/or learning deficiency in SAMP8.

[Evaluation of reserved hepatic function in patients with hepatobiliary tumor by 99mTc-GSA: effect of hyperbilirubinemia and usefulness of regional reserved hepatic functional imaging]

The evaluation of the reserved hepatic function was performed by 99mTc-galactosyl serum albumin (99mTc-GSA) in seventy patients with hepatobiliary tumor. The dynamic study was performed to evaluate global reserved hepatic function following the intravenous bolus injection of 99mTc-GSA, and the hepatic single photon emission computed tomography (SPECT) was obtained to assess the regional reserved hepatic function. The functional hepatic index (LHL15) was derived from liver time-activity data, and it was compared with serum total-bilirubin level, serum albumin level and plasma disappearance rate of indocyanine green (ICG15). In the patients with hepatocellular carcinoma, LHL15 value agreed well with ICG15 value, serum total-bilirubin level, and serum albumin level. Moderate or severe hepatic dysfunction was observed at 65.4% of these patients. In the patients with cholangiocellular carcinoma, a discrepancy of LHL15 value and ICG15 value was observed. Increment of the ICG15 value was correlated with that of the serum total-bilirubin level, whereas the correlations was not observed between the LHL15 value and the serum total-bilirubin level. These results indicate that 99mTc-GSA scintigraphy can evaluate the reserved hepatic function without the embellishment of jaundice. This method is useful for assessing the global and regional reserved hepatic function.

The functional hepatic volume assessed by 99mTc-GSA hepatic scintigraphy

The accuracy of measurement of the functional hepatic volume by single photon emission computed tomography (SPECT) with 99mTc-galactosyl serum albumin (99mTc-GAS) was evaluated. 99mTc-GSA planar scintigraphic images were obtained dynamically and the hepatic SPECT imaging was then performed in 25 patients with hepatobiliary tumors. The patients were divided into 4 groups with normal hepatic function, and mild, moderate and severe hepatic dysfunction. The functional hepatic volume determined by SPECT was compared with the morphological hepatic volume determined by compute tomography. The ratio of the hepatic volumes obtained by the two methods was calculated. The mean hepatic volume ratio was 96.6 +/- 2.3% in the normal hepatic function group and 95.9 +/- 2.2% in the mild dysfunction group (n.s.). In both the moderate and severe hepatic dysfunction groups, the hepatic volume ratio was smaller than that in the normal group (87.9 +/- 5.2%, p < 0.0001, and 71.9 +/- 7.6%, p < 0.0001, respectively). There was a linear correlation between the hepatic volume ration and various indices of reserve hepatic function, such as LHL15 (r = 0.83, p < 0.0001), HH15(r = 0.74, p < 0.0001), and ICG15 (r = 0.75, p < 0.0005). These results indicate that the hepatic volume ratio is proportional to the severity of hepatic dysfunction, and suggest that the functional hepatic volume measured with 99mTc-GSA faithfully reflects the functioning hepatocyte mass. 99mTc-GSA scintigraphy and hepatic SPECT therefore provide information regarding global and regional reserve hepatic function.

The role of thallium-201 single photon emission tomography in the investigation and characterisation of brain tumours in man and their response to treatment

The aim of this study was to characterise brain tumour type and treatment response in relation to the uptake of thallium-201. 201T1 single photon emission tomography (SPET) was performed in 58 patients with brain tumours. Fifty-six patients were utilised for the statistical comparison of the early and delayed 201T1 indices expressed as the ratio of tumour to contralateral cerebral hemisphere uptake. The retention index of 201T1 in the tumour tissue calculated from the early and delayed scans was also analysed. Furthermore, in 56 patients with 58 brain tumours, a comparison was made of the diagnostic value of high 201T1 uptake and gadolinium diethylene triamine penta-acetic acid (Gd-DTPA) enhancement on MRI scans. Although high 201T1 uptake was observed in viable malignant gliomas, brain metastases, meningiomas and malignant teratoma, the viable malignant gliomas could not be differentiated from brain metastases and extracerebral tumours by means of 201T1 indices. 201T1 SPET failed to diagnose a viable ring-enhanced tumour with a thin rim and small tumours of less than 1.5 cm in diameter visualised by Gd-DTPA-enhanced MRI. In spite of this, 201T1 SPET appears to be effective for determination of the malignant viability of tumours.

[Bone dynamic study--evaluation for factor analysis of hip joint]

Factor analysis was applied to dynamic study of Tc-99m MDP for the evaluation of hip joint disorders. Fifteen patients were examined; eight were normal, six were osteoarthritis in which one accompanied synovitis was included, and one was aseptic necrosis on the head of the femur. In normals, according to the Tc-99m MDP kinetics, three factor images and time-activity curves were obtained which were named as blood vessel, soft tissue, and bone factor images and curves. In the patient with osteoarthritis, increased accumulation of the hip joint was shown in bone factor image only. But in one patient, who took osteoarthritis with synovitis, marked accumulations of the Tc-99m MDP appeared not only on the bone factor image but also on the soft tissue. Operation revealed thickening synovial tissue around the hip joint, caused by inflammatory process. In follow-up studies of the patient with aseptic necrosis on the head of the left femur, excessive accumulations, which were seemed in his left hip joint on both bone and soft tissue factor images at first, were decreased respondently to the treatment of this lesion. In conclusion, the factor analysis was useful for differencial diagnosis of the hip joint disorders and observation of the clinical course of the hip joint disorders.

Neuron-specific enolase as a serum marker for immature teratoma and dysgerminoma

Neuron-specific enolase (NSE) was measured with an enzyme-immunoassay in sera from 54 patients with malignant (24 cases) and benign (30 cases) germ cell tumors of ovarian origin. Serum NSE contents were clearly raised above control value (greater than 10 ng/mg) in 4 of 8 patients with immature teratomas and 5 of 6 with dysgerminomas. NSE was also measured in nine cell lines of germ cell tumors. Among these cell lines, high NSE contents were detected in the cell extracts and culture supernatants from PA-1 and Tera-II lines. In immunohistochemical study, widespread positive staining for NSE was shown in dysgerminomas, whereas the immunostaining was confined to neural elements in both an immature teratoma and xenograft tumors derived from PA-1 and Tera-II lines in nude mice. These findings suggest that serum NSE measurements are of diagnostic value not only for immature teratomas but also for dysgerminomas.