Tumor-specific migration routes of xenotransplanted human glioblastoma cells in mouse brain

The migration of neural progenitor cells (NPCs) to their final destination during development follows well-defined pathways, such as along blood vessels. Cells originating from the highly malignant tumor glioblastoma (GBM) seem to exploit similar routes for infiltrating the brain parenchyma. In this report, we have examined the migration of GBM cells using three-dimensional high-resolution confocal microscopy in brain tumors derived from eight different human GBM cell lines xenografted into immunodeficient mice. The primary invasion routes identified were long-distance migration along white matter tracts and local migration along blood vessels. We found that GBM cells in the majority of tumors (6 out of 8) did not exhibit association with blood vessels. These tumors, derived from low lamin A/C expressing GBM cells, were comparatively highly diffusive and invasive. Conversely, in 2 out of 8 tumors, we noted perivascular invasion and displacement of astrocyte end-feet. These tumors exhibited less diffusive migration, grew as solid tumors, and were distinguished by elevated expression of lamin A/C. We conclude that the migration pattern of glioblastoma is distinctly tumor cell-specific. Furthermore, the ability to invade the confined spaces within white matter tracts may necessitate low expression of lamin A/C, contributing to increased nuclear plasticity. This study highlights the role of GBM heterogeneity in driving the aggressive growth of glioblastoma.

CSIG-04. BMP4 INDUCTION OF A SENESCENCE-LIKE PHENOTYPE IN HUMAN GLIOBLASTOMA CELLS IS PARTIALLY DEPENDENT ON P21

Bone morphogenetic protein 4 (BMP4) was initially suggested as a potential differentiation-inducing factor to be used in the therapy of glioblastoma. We and others have however demonstrated that the response is reversible, variable among patient samples, and heterogeneous within the same cell line. To deepen our knowledge on how BMP4 affects different types of glioblastoma cells, we treated phenotypically different clones from the same patient tumor—a multitherapy-sensitive/proneural-like (SENS/PN) clone and a multitherapy-resistant/mesenchymal-like (RES/MES) clone—with BMP4. In the SENS/PN clone, BMP4 turned on a mesenchymal-related gene program, whereas this response was less prominent in the RES/MES clone. Untreated SENS/PN cells were smaller than RES/MES cells, but both clones responded to BMP4 by cell size enlargement. Increase in cell size has been suggested to precede senescence; young cells are smaller than old cells that eventually enter replicative senescence. BMP4 induced a senescence-like phenotype in a subpopulation of cells, demonstrated by induction of senescence-associated (SA)-β-gal, p21 up-regulation, lamin B1 down-regulation, as well as increased lysosomal mass and granularity. This was more pronounced in the RES/MES clone than in the SENS/PN clone, and it was dependent on canonical SMAD signaling. Senolytic treatment ablated the SA-β-gal positive cells and reduced the p21 level at the population level. Targeted deletion of p21 abolished BMP4-induced SA-β-gal and increase in cell growth, while lamin B1 down-regulation remained, demonstrating that p21 signaling is crucial for one part of the senescence induction by BMP4. We are currently further investigating a connection between cell size, mesenchymality and senescence. We hypothesize that large mesenchymal-like cells are closer to senescence than smaller proneural cells within the cell culture. A combination of senescence-induction and senolytic treatment may open treatment opportunities to target therapy-resistant glioblastoma cells.

Modeling glioblastoma heterogeneity as a dynamic network of cell states

Tumor cell heterogeneity is a crucial characteristic of malignant brain tumors and underpins phenomena such as therapy resistance and tumor recurrence. Advances in single-cell analysis have enabled the delineation of distinct cellular states of brain tumor cells, but the time-dependent changes in such states remain poorly understood. Here, we construct quantitative models of the time-dependent transcriptional variation of patient-derived glioblastoma (GBM) cells. We build the models by sampling and profiling barcoded GBM cells and their progeny over the course of 3 weeks and by fitting a mathematical model to estimate changes in GBM cell states and their growth rates. Our model suggests a hierarchical yet plastic organization of GBM, where the rates and patterns of cell state switching are partly patient-specific. Therapeutic interventions produce complex dynamic effects, including inhibition of specific states and altered differentiation. Our method provides a general strategy to uncover time-dependent changes in cancer cells and offers a way to evaluate and predict how therapy affects cell state composition.

Growth-Inhibitory Activity of Bone Morphogenetic Protein 4 in Human Glioblastoma Cell Lines Is Heterogeneous and Dependent on Reduced SOX2 Expression

Glioblastoma multiforme continues to have a dismal prognosis. Even though detailed information on the genetic aberrations in cell signaling and cell-cycle checkpoint control is available, no effective targeted treatment has been developed. Despite the advanced molecular defects, glioblastoma cells may have remnants of normal growth-inhibitory pathways, such as the bone morphogenetic protein (BMP) signaling pathway. We have evaluated the growth-inhibitory effect of BMP4 across a broad spectrum of patient samples, using a panel of 40 human glioblastoma initiating cell (GIC) cultures. A wide range of responsiveness was observed. BMP4 sensitivity was positively correlated with a proneural mRNA expression profile, high SOX2 activity, and BMP4-dependent upregulation of genes associated with inhibition of the MAPK pathway, as demonstrated by gene set enrichment analysis. BMP4 response in sensitive cells was mediated by the canonical BMP receptor pathway involving SMAD1/5/9 phosphorylation and SMAD4 expression. SOX2 was consistently downregulated in BMP4-treated cells. Forced expression of SOX2 attenuated the BMP4 sensitivity including a reduced upregulation of MAPK-inhibitory genes, implying a functional relationship between SOX2 downregulation and sensitivity. The results show an extensive heterogeneity in BMP4 responsiveness among GICs and identify a BMP4-sensitive subgroup, in which SOX2 is a mediator of the response. IMPLICATIONS: Development of agonists targeting the BMP signaling pathway in glioblastoma is an attractive avenue toward a better treatment. Our study may help find biomarkers that predict the outcome of such treatment and enable stratification of patients.

Mesenchymal transition and increased therapy resistance of glioblastoma cells is related to astrocyte reactivity

Grade IV astrocytoma/glioblastoma multiforme (GBM) is essentially incurable, partly due to its heterogenous nature, demonstrated even within the glioma-initiating cell (GIC) population. Increased therapy resistance of GICs is coupled to transition into a mesenchymal (MES) cell state. The GBM MES molecular signature displays a pronounced inflammatory character and its expression vary within and between tumors. Herein, we investigate how MES transition of GBM cells relates to inflammatory responses of normal astroglia. In response to CNS insults astrocytes enter a reactive cell state and participate in directing neuroinflammation and subsequent healing processes. We found that the MES signature show strong resemblance to gene programs induced in reactive astrocytes. Likewise, astrocyte reactivity gene signatures were enriched in therapy-resistant MES-like GIC clones. Variable expression of astrocyte reactivity related genes also largely defined intratumoral GBM cell heterogeneity at the single-cell level and strongly correlated with our previously defined therapy-resistance signature (based on linked molecular and functional characterization of GIC clones). In line with this, therapy-resistant MES-like GIC secreted immunoregulatory and tissue repair related proteins characteristic of astrocyte reactivity. Moreover, sensitive GIC clones could be made reactive through long-term exposure to the proinflammatory cytokine interleukin 1 beta (IL1β). IL1β induced a slow MES transition, increased therapy resistance, and a shift in DNA methylation profile towards that of resistant clones, which confirmed a slow reprogramming process. In summary, GICs enter through MES transition a reactive-astrocyte-like cell state, connected to therapy resistance. Thus, from a biological point of view, MES GICs would preferably be called 'reactive GICs'. The ability of GBM cells to mimic astroglial reactivity contextualizes the immunomodulatory and microenvironment reshaping abilities of GBM cells that generate a tumor-promoting milieu. This insight will be important to guide the development of future sensitizing therapies targeting treatment-resistant relapse-driving cell populations as well as enhancing the efficiency of immunotherapies in GBM. © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Abstract 3843: LSD1 modulation by allosteric ligands

LSD1 has emerged as a potential therapeutic target for a number of cancer types (e.g. AML, SCLC, colorectal, breast, liver, prostate, glioblastoma, Ewing sarcoma), as well as sickle cell anaemia and Alzheimer’s disease. Irreversible LSD1 catalytic inhibitors have shown limited clinical efficacy in AML and SCLC, while solid tumours are largely unaddressed. This is in contrast to LSD1 knockdown with impact on a wide range of cancers, indicating that LSD1 functions other than enzymatic should be targeted.

We have developed novel small molecules that modulate LSD1 via an allosteric site - without inhibiting its enzymatic function - inducing a 60% reduction of nuclear LSD1 levels. The sensitivity profile in a cancer cell line panel is unique and dissimilar to >300 diverse reference compounds. In vitro efficacy is observed in glioma-initiating clones that are highly resistant to standard-of-care temozolimide as well as catalytic LSD1 inhibitors. Efficacy in the sub-µM range is observed with other solid tumour models, e.g. prostate cancer. The compounds exhibit synergy (Bliss independence >40%) with HDAC inhibitors as evaluated by viability in cellular cancer models, including lung, liver and glioblastoma.

Pharmacokinetic studies show good blood-brain-barrier penetration and oral availability of the allosteric LSD1 modulator BEA-17. A repeat dose of 25 mg/kg was well tolerated by NOD SCID mice, leading to µM level accumulation in the brain. Results from orthotopic glioblastoma PDX models, and in vivo hollow-fiber models of other solid tumours will be presented, as well as mechanistic insights from biophysical assays and gene expression analysis.

Citation Format: Wei B. Emond, Matthis Geitmann, Malin Jarvius, Konrad Koehler, Per Källblad, Mia Niklasson, Vendela Parrow, Rajiv Sawant, Maria Sjöberg, Johan Winquist, Anna Segerman, Ulf Bremberg. LSD1 modulation by allosteric ligands [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3843.

COMBImage2: a parallel computational framework for higher-order drug combination analysis that includes automated plate design, matched filter based object counting and temporal data mining

BACKGROUND

Pharmacological treatment of complex diseases using more than two drugs is commonplace in the clinic due to better efficacy, decreased toxicity and reduced risk for developing resistance. However, many of these higher-order treatments have not undergone any detailed preceding in vitro evaluation that could support their therapeutic potential and reveal disease related insights. Despite the increased medical need for discovery and development of higher-order drug combinations, very few reports from systematic large-scale studies along this direction exist. A major reason is lack of computational tools that enable automated design and analysis of exhaustive drug combination experiments, where all possible subsets among a panel of pre-selected drugs have to be evaluated.

RESULTS

Motivated by this, we developed COMBImage2, a parallel computational framework for higher-order drug combination analysis. COMBImage2 goes far beyond its predecessor COMBImage in many different ways. In particular, it offers automated 384-well plate design, as well as quality control that involves resampling statistics and inter-plate analyses. Moreover, it is equipped with a generic matched filter based object counting method that is currently designed for apoptotic-like cells. Furthermore, apart from higher-order synergy analyses, COMBImage2 introduces a novel data mining approach for identifying interesting temporal response patterns and disentangling higher- from lower- and single-drug effects. COMBImage2 was employed in the context of a small pilot study focused on the CUSP9v4 protocol, which is currently used in the clinic for treatment of recurrent glioblastoma. For the first time, all 246 possible combinations of order 4 or lower of the 9 single drugs consisting the CUSP9v4 cocktail, were evaluated on an in vitro clonal culture of glioma initiating cells.

CONCLUSIONS

COMBImage2 is able to automatically design and robustly analyze exhaustive and in general higher-order drug combination experiments. Such a versatile video microscopy oriented framework is likely to enable, guide and accelerate systematic large-scale drug combination studies not only for cancer but also other diseases.

COMBImage: a modular parallel processing framework for pairwise drug combination analysis that quantifies temporal changes in label-free video microscopy movies

BACKGROUND

Large-scale pairwise drug combination analysis has lately gained momentum in drug discovery and development projects, mainly due to the employment of advanced experimental-computational pipelines. This is fortunate as drug combinations are often required for successful treatment of complex diseases. Furthermore, most new drugs cannot totally replace the current standard-of-care medication, but rather have to enter clinical use as add-on treatment. However, there is a clear deficiency of computational tools for label-free and temporal image-based drug combination analysis that go beyond the conventional but relatively uninformative end point measurements.

RESULTS

COMBImage is a fast, modular and instrument independent computational framework for in vitro pairwise drug combination analysis that quantifies temporal changes in label-free video microscopy movies. Jointly with automated analyses of temporal changes in cell morphology and confluence, it performs and displays conventional cell viability and synergy end point analyses. The image processing algorithms are parallelized using Google's MapReduce programming model and optimized with respect to method-specific tuning parameters. COMBImage is shown to process time-lapse microscopy movies from 384-well plates within minutes on a single quad core personal computer. This framework was employed in the context of an ongoing drug discovery and development project focused on glioblastoma multiforme; the most deadly form of brain cancer. Interesting add-on effects of two investigational cytotoxic compounds when combined with vorinostat were revealed on recently established clonal cultures of glioma-initiating cells from patient tumor samples. Therapeutic synergies, when normal astrocytes were used as a toxicity cell model, reinforced the pharmacological interest regarding their potential clinical use.

CONCLUSIONS

COMBImage enables, for the first time, fast and optimized pairwise drug combination analyses of temporal changes in label-free video microscopy movies. Providing this jointly with conventional cell viability based end point analyses, it could help accelerating and guiding any drug discovery and development project, without use of cell labeling and the need to employ a particular live cell imaging instrument.

Abstract 4175: Targeting of a mesenchymal profile in order to sensitize multitherapy resistant glioblastoma clones

The overall aim of this study was to find ways to sensitize treatment resistant glioma-initiating cell (GIC) clones to conventional therapy. Heterogeneity is substantial in glioblastoma multiforme (GBM) and through establishment of clonal GIC cultures from patient biopsies we have demonstrated a wide variety in the responses to drugs and radiation. A multitherapy resistance phenotype was linked to proneural-mesenchymal transition (PMT) in the transcriptome. The variety in therapy response was observed as a continuum of phenotypes. The distribution of phenotypes resembled a normal distribution and multitherapy resistance was associated with low DNA methylation grade in promoter regions of mesenchymal master regulators (FOSL2, RUNX1). Our data thus implied that the transition is bi-directional and epigenetically regulated (Segerman et al, Cell Reports - accepted in principle).

To investigate if spontaneous changes in drug and radiation response occur, we have derived subclones from a resistant clone. Both subclones with higher and lower therapy resistance than the parental clone were generated. Also molecularly the subclones largely reconstituted the original clonal variation.

PMT shows similarities to epithelial-mesenchymal transition (EMT), which is induced by extrinsic factors. We therefore specifically analyzed the gene expression data for signaling receptors differentially expressed in resistant vs. sensitive clones as well as cognate ligands. To estimate the importance of a particular signaling pathway, expression of co-receptors and ligands was taken into account. We found several cases of coherent upregulation of receptor and ligand indicative of autocrine loops. Regarding pathways that appeared to be overactive in resistant vs. sensitive clones, there was a prominent overlap with EMT. It was also apparent that several pathways were activated concomitantly.

We are currently focusing on identifying combinations of drugs (and antibodies) that sensitize resistant clones to conventional treatment through modulation of cell signaling patterns. In the initial screen temozolomide (TMZ) response is used as an indicator of achieved sensitization. The strategy is to iteratively combine primarily antagonists of signaling receptors connected to resistance. We are also exploring the effect of stimulating pathways with apparently higher activity in sensitive clones (e.g. addition of ligands).The concept of sensitizing glioma and other types of cancer cells by targeting the mesenchymal character through usage of e.g. signaling receptor inhibitors is not new and has shown promise. Indeed, our preliminary data look encouraging.

In conclusion, our data show that multitherapy resistance is connected to a plastic cell-state. Also, receptors and ligands that are differentially expressed in resistant and sensitive clones engage pathways regulating EMT.

Citation Format: Mia Niklasson, Malin Jarvius, Caroline Haglund, Efthymia Chantzi, Tobias Bergström, Frida Nyberg, Annika Hermansson, Mårten Fryknäs, Mats Gustafsson, Bo Segerman, Rolf Larsson, Bengt Westermark, Anna Segerman. Targeting of a mesenchymal profile in order to sensitize multitherapy resistant glioblastoma clones [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4175. doi:10.1158/1538-7445.AM2017-4175

Simultaneous Multiplexed Measurement of RNA and Proteins in Single Cells

Significant advances have been made in methods to analyze genomes and transcriptomes of single cells, but to fully define cell states, proteins must also be accessed as central actors defining a cell's phenotype. Methods currently used to analyze endogenous protein expression in single cells are limited in specificity, throughput, or multiplex capability. Here, we present an approach to simultaneously and specifically interrogate large sets of protein and RNA targets in lysates from individual cells, enabling investigations of cell functions and responses. We applied our method to investigate the effects of BMP4, an experimental therapeutic agent, on early-passage glioblastoma cell cultures. We uncovered significant heterogeneity in responses to treatment at levels of RNA and protein, with a subset of cells reacting in a distinct manner to BMP4. Moreover, we found overall poor correlation between protein and RNA at the level of single cells, with proteins more accurately defining responses to treatment.

The Human Glioblastoma Cell Culture Resource: Validated Cell Models Representing All Molecular Subtypes

Glioblastoma (GBM) is the most frequent and malignant form of primary brain tumor. GBM is essentially incurable and its resistance to therapy is attributed to a subpopulation of cells called glioma stem cells (GSCs). To meet the present shortage of relevant GBM cell (GC) lines we developed a library of annotated and validated cell lines derived from surgical samples of GBM patients, maintained under conditions to preserve GSC characteristics. This collection, which we call the Human Glioblastoma Cell Culture (HGCC) resource, consists of a biobank of 48 GC lines and an associated database containing high-resolution molecular data. We demonstrate that the HGCC lines are tumorigenic, harbor genomic lesions characteristic of GBMs, and represent all four transcriptional subtypes. The HGCC panel provides an open resource for in vitro and in vivo modeling of a large part of GBM diversity useful to both basic and translational GBM research.

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The HGCC resource contains 48 annotated human GBM cell lines and an interactive database

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The GBM cell lines are propagated in stem cell conditions and display GSC characteristics

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The HGCC resource provides cell lines of all molecular (TCGA) subtypes

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All data connected with the HGCC cell lines can be accessed at hgcc.se

RETRACTED: Vulnerability of glioblastoma cells to catastrophic vacuolization and death induced by a small molecule

Glioblastoma multiforme (GBM) is the most aggressive form of brain cancer with marginal life expectancy. Based on the assumption that GBM cells gain functions not necessarily involved in the cancerous process, patient-derived glioblastoma cells (GCs) were screened to identify cellular processes amenable for development of targeted treatments. The quinine-derivative NSC13316 reliably and selectively compromised viability. Synthetic chemical expansion reveals delicate structure-activity relationship and analogs with increased potency, termed Vacquinols. Vacquinols stimulate death by membrane ruffling, cell rounding, massive macropinocytic vacuole accumulation, ATP depletion, and cytoplasmic membrane rupture of GCs. The MAP kinase MKK4, identified by a shRNA screen, represents a critical signaling node. Vacquinol-1 displays excellent in vivo pharmacokinetics and brain exposure, attenuates disease progression, and prolongs survival in a GBM animal model. These results identify a vulnerability to massive vacuolization that can be targeted by small molecules and point to the possible exploitation of this process in the design of anticancer therapies.

Platelet-derived growth factor over-expression in retinal progenitors results in abnormal retinal vessel formation

Platelet-derived growth factor (PDGF) plays an important role in development of the central nervous system, including the retina. Excessive PDGF signaling is associated with proliferative retinal disorders. We reported previously that transgenic mice in which PDGF-B was over-expressed under control of the nestin enhancer, nes/tk-PdgfB-lacZ, exhibited enhanced apoptosis in the developing corpus striatum. These animals display enlarged lateral ventricles after birth as well as behavioral aberrations as adults. Here, we report that in contrast to the relatively mild central nervous system phenotype, development of the retina is severely disturbed in nes/tk-PdgfB-lacZ mice.

In transgenic retinas all nuclear layers were disorganized and photoreceptor segments failed to develop properly. Since astrocyte precursor cells did not populate the retina, retinal vascular progenitors could not form a network of vessels. With time, randomly distributed vessels resembling capillaries formed, but there were no large trunk vessels and the intraocular pressure was reduced. In addition, we observed a delayed regression of the hyaloid vasculature. The prolonged presence of this structure may contribute to the other abnormalities observed in the retina, including the defective lamination.

Enlarged lateral ventricles and aberrant behavior in mice overexpressing PDGF-B in embryonic neural stem cells

Platelet-derived growth factor (PDGF) is important in central nervous system (CNS) development, and aberrant expression of PDGF and its receptors has been linked to developmental defects and brain tumorigenesis. We previously found that neural stem and progenitor cells in culture produce PDGF and respond to it by autocrine and/or paracrine signaling. We therefore aimed to examine CNS development after PDGF overexpression in neural stem cells in vivo. Transgenic mice were generated with PDGF-B under control of a minimal nestin enhancer element, which is specific for embryonic expression and will not drive adult expression in mice. The resulting mouse showed increased apoptosis in the developing striatum, which suggests a disturbed regulation of progenitor cells. Later in neurodevelopment, in early postnatal life, mice displayed enlarged lateral ventricles. This enlargement remained into adulthood and it was more pronounced in male mice than in transgenic female mice. Nevertheless, there was an overall normal composition of cell types and numbers in the brain and the transgenic mice were viable and fertile. Adult transgenic males, however, showed behavioral aberrations and locomotor dysfunction. Thus, a tightly regulated expression of PDGF during embryogenesis is required for normal brain development and function in mice.

Maintenance of clonal diversity in Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae). I. Fluctuating seasonal selection moulds long-term coexistence

The deterministic maintenance of clonal diversity in thelytokous taxa can be seen as a model for understanding how environmental heterogeneity both can stabilize genetic diversity and can allow coexistence of competing species. We here analyze the temporal fluctuations in clonal diversity in the thelytokous Lonchopterid fly, Dipsa bifurcata (Fallén, 1810), at four localities in Sweden over an 8-year period. Estimated fitness values for clones are cyclical, synchronous among populations and correlated with seasonal changes in the environment. Differential winter viability and emergence from overwintering along with differential reproductive rate during the summer appear to be the selective mechanisms by which long-term clonal diversity is maintained. In a companion paper (Tomiuk et al, 2004), we present a model for the maintenance of clonal diversity through the mechanism of differential diapause among clones, utilizing fitness values estimated from the data presented here. In general, our results imply that fluctuating seasonal fitnesses can maintain stable genetic polymorphism within populations, as well as coexistence between closely related competitors, when coupled with differences in diapause phenology.

Maintenance of clonal diversity in Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae). II. Diapause stabilizes clonal coexistence

We analyze a selection model analogous to a one-locus, two-allele haploid system that can explain recurrent seasonal changes in diversity for communities with diapausing species or populations with diapausing clones. The model demonstrates the potential influence of differential diapause on the stability of species and clonal coexistence and, by extension, on the maintenance of genetic polymorphism in general. Using estimates of clonal fitness values from populations of the parthenogenetic spear-winged fly Dipsa bifurcata (Fallén, 1810) (Diptera: Lonchopteridae), the model explains the long-term stable oscillation of clonal frequencies exhibited by these populations. In general, clones or species that share the same spatial habitat can persist in stable coexistence if there are differences not only in their temporarily fluctuating fitness values but also in their dormancy patterns.

Insulin insensitivity and delayed transcapillary delivery of insulin in oophorectomized rats treated with testosterone

The importance of transcapillary insulin delivery as a regulated step was explored in an insulin resistant rat model. Oophorectomized female rats were exposed to testosterone (OVX + T) for 8 weeks and examined with insulin clamps, muscle microdialysis, and analyses of insulin distribution kinetics. The results were compared with those obtained in sham-operated control rats. After OVX + T, onset of glucose uptake in skeletal muscle was significantly (P < 0.001-0.05) delayed compared with controls as measured by the glucose infusion rate (GIR) during a euglycaemic, hyperinsulinaemic clamp (5 mU kg-1 min-1). The increase in interstitial insulin concentrations was also significantly (P < 0.05) delayed (15-20% lower) in OVX + T treated rats compared with control rats, but to such a small magnitude that this alone could not explain the late onset of the insulin effect. Skeletal muscle capillary density, examined histochemically, was diminished (P < 0.01-0.001) by 20-25% after treatment with OVX + T compared with control animals, as was the peripheral blood flow (P < 0.05) by 40-45%, measured with the microsphere technique. Insulin binding was reduced in proportion to the reduced (P < 0.01) vascular surface area by OVX + T treatment. Transcapillary transport rate of insulin, measured by comparisons of the kinetics of inulin and insulin spaces in muscle with time, tended (ns) to be lower after OVX + T compared with control rats (30-40%) as a reflection of the lower capillary surface area. The data suggest that the delayed onset of insulin action after OVX + T results from combined defects in the muscle cell at a postreceptor level and, to a lesser extent, from retarded transcapillary delivery of insulin.

Muscle glucose uptake is effectively activated by ischemia in type 2 diabetic subjects

It has previously been shown that Wortmannin, a phosphatidylinositol 3-kinase inhibitor, inhibits glucose transport activated by insulin but not by ischemia, suggesting the importance of an activating mechanism that bypasses the insulin signal. To evaluate the relevance of this insulin-independent pathway in insulin-resistant subjects, the ability of ischemia to stimulate glucose uptake was investigated in 9 patients with type 2 diabetes and in 9 healthy control subjects (fasting glucose level 9.4 +/- 0.8 vs. 5.1 +/- 0.1 mmol/l, P < 0.001, in type 2 diabetic patients and control subjects, respectively; fasting insulin level insulin 8.1 +/- 2.6 vs. 4.5 +/-0.7 mU/l, P < 0.05, respectively) matched for sex, age, and BMI. Arterial plasma and interstitial concentrations of glucose and lactate (measured by subcutaneous and muscle microdialysis) were recorded in the forearm before, during, and after ischemia induced locally for 20 min. During ischemia, the muscle interstitial glucose concentration decreased significantly from 7.7 +/- 0.6 to 5.4 +/- 0.4 mmol/l (P < 0.01) and from 4.4 +/- 0.3 to 3.6 +/- 0.3 mmol/l (P < 0.05) in type 2 diabetic patients and control subjects, respectively. The arterial-interstitial (A-I) glucose concentration difference was 1.7 +/- 0.6 and 0.7 +/- 0.3 mmol/ at basal, and it increased significantly to 3.5 +/- 0.7 (P < 0.01) and 1.4 +/-0.3 mmol/l (P < 0.05) during ischemia in each group, respectively. Interstitial lactate increased significantly during ischemia from 0.8 +/- 0.1 to 1.1 +/- 0.1 mmol/l (P < 0.05) and from 0.5 +/- 0.1 to 0.9 +/- 0.2 mmol/l (P < 0.05), respectively. The A-I glucose concentration difference was abolished immediately postischemia and regained after approximately 15 min, whereas high interstitial lactate levels remained elevated throughout the study. Subcutaneous interstitial glucose concentrations remained unchanged during ischemia and postischemia in both groups, whereas the interstitial lactate concentration in adipose tissue increased during ischemia from 1.4 +/- 0.2 to 2.0 +/- 0.2 mmol/l (P < 0.05) and from 1.1 +/- 0.1 to 1.8 +/- 0.3 mmol/l (P < 0.05) in type 2 diabetic patients and control subjects, respectively. Plasma glucose and lactate levels were unchanged in both groups during the study period. The results show that in muscle, but not in adipose tissue, glucose uptake is efficiently activated by ischemia in insulin-resistant type 2 diabetic subjects, suggesting the activation of a putative alternative pathway to the insulin signal in muscle cells.

Effects of exercise on insulin distribution and action in testosterone-treated oophorectomized female rats

Administration of testosterone (T) to oophorectomized (Ovx) female rats is followed by severe insulin resistance, localized to postreceptor cellular events in the muscle. In this study, intervention by exercise was introduced to examine whether circulatory adaptations are involved in insulin resistance. Two groups of Ovx rats were studied: one group was given T (Ovx+T); another group had free access to running wheels (Ovx+T+Ex). In addition, one control group (sham operated) was studied. Insulin sensitivity was measured with the euglycemic hyperinsulinemic clamp technique (submaximal) for 150 min. Muscle interstitial glucose and insulin concentrations were measured by microdialysis. The measurements showed that, in Ovx+T rats, the onset of insulin action was significantly (P < 0.05) slower during the first 95 min of the clamp compared with that in Ovx+T+Ex and controls. Muscle interstitial concentrations of insulin but not glucose were lower in both Ovx+T and Ovx+T+Ex rats than in controls throughout the clamp. It was concluded that physical exercise prevented the slow onset of insulin action in Ovx+T rats without changing the distribution time of muscle interstitial insulin. The results indicate that hyperandrogenicity is characterized by delayed muscle insulin action. Physical exercise reverses these defects without any beneficial effect on muscle interstitial insulin concentrations.

Modulation of vestibular function by nociceptin/orphanin FQ: an in vivo and in vitro study

The effects of nociceptin (orphanin FQ) on medial vestibular nucleus (MVN) neurons in vitro, and on vestibulo-ocular reflex (VOR) function in vivo, were investigated in order to determine the role of 'opioid-like orphan' (ORL1) receptors in modulating vestibular reflex function in the rat. Nociceptin (100 nM-1 microM) potently inhibited the spontaneous discharge of the majority (86%) of MVN neurons tested in the rat dorsal brainstem slice preparation in vitro. This inhibition was dose-dependent and persisted after blockade of synaptic transmission in low Ca2+/Co2+ medium. The inhibitory effects were insensitive to the opioid antagonist naloxone, but were effectively antagonised by the selective ORL1 receptor antagonist, [Phe1Psi(CH2-NH)Gly2]Nociceptin(1-13)NH2. The majority of MVN neurons ( approximately 70%) were inhibited by both nociceptin and the delta-opioid receptor agonist, [D-ala2, D-leu5]-enkephalin (DADLE), while a minority of cells (approximately 30%) were selectively responsive either to DADLE or to nociceptin, but not both. Co-application of nociceptin and DADLE to neurons that were responsive to both agonists, resulted in an inhibitory response that was the same as or less than the inhibition evoked by either agonist alone. Intracellular whole-cell patch clamp recordings from identified Type A and Type B MVN cells showed that both these cell types are responsive to nociceptin, which induced membrane hyperpolarisation and decrease in input resistance consistent with its known effects on membrane K currents in other cell types. In alert rats, i.c.v. injection of nociceptin caused a significant decrease in the gain of the hVOR and resulted in a prolongation of post-rotatory nystagmus in darkness. The decrease in VOR gain and the increase in the VOR time-constant was significant even at low doses of nociceptin which did not cause other observable behavioural effects. These findings demonstrate that endogenously released nociceptin may have a hitherto unexplored role in the functional modulation of the neural pathways that mediate vestibular reflexes in vivo.

Induction of insulin resistance by glucosamine reduces blood flow but not interstitial levels of either glucose or insulin

To study the effects of a glucosamine infusion on skeletal muscle metabolism, microdialysis was performed in the medial femoral muscle in Sprague-Dawley rats during a euglycemic-hyperinsulinemic clamp (insulin infusion 18 mU x kg(-1) x min(-1)). During steady-state clamping conditions (70 min), an infusion of glucosamine (30 micromol x kg(-1) x min(-1)) or saline was given for 240 min. Blood flow was measured by the microsphere technique at the end of the clamp. An approximately 36% (P < 0.001) reduction in the glucose infusion rate was seen after 170 min in the glucosamine-treated rats compared with control rats. There were no significant differences in interstitial or plasma levels of either insulin or glucose between the two groups. Both interstitial (2.31 +/- 0.18 vs. 1.71 +/- 0.24 mmol/l, P < 0.05) and arterial plasma lactate concentrations (1.29 +/- 0.09 vs. 0.79 +/- 0.09 mmol/l, P < 0.01) were significantly higher in control rats compared with glucosamine-treated rats. Blood flow was significantly reduced in hind limb femoral muscles in the glucosamine-treated rats compared with control rats. The most pronounced reduction in blood flow was seen in the Soleus muscle (27.6 +/- 3.4 vs. 14.7 +/- 2.0 ml x 100 g(-1) x min(-1), P < 0.01). These results demonstrate that induction of insulin resistance by glucosamine results in a reduction of the blood flow rate as well as the uptake of glucose and the production of lactate in skeletal muscle. As a result of the inhibited glucose metabolism, the interstitial glucose concentration was unchanged despite the reduced blood flow after glucosamine administration. The data suggest the importance of regulation of blood flow by nonoxidative metabolism of glucose in resting muscle.

Induction of rat muscle insulin resistance by epinephrine is accompanied by increased interstitial glucose and lactate concentrations

Muscle glucose uptake and lactate release during beta-adrenergic stimulation by epinephrine (epi) and beta-adrenergic blockade by propranolol (prop) were investigated during an euglycaemic hyperinsulinaemic (30 pmol x kg(-1) x min(-1)) with or without added somatostatin (0.1 microg/min; pancreatic) clamp in female rats. To assess the interstitial insulin, glucose and lactate concentrations, microdialysis was done in the medial femoral muscle in both legs. The influence of muscle skeletal blood flow on interstitial insulin, glucose and lactate was examined with the microsphere technique, using 57Co-microspheres. Epinephrine decreased glucose infusion rate by about 75% (p < 0.0001) and increased concentrations of interstitial glucose by about 35% (p < 0.001) and lactate by about 65% (p < 0.01). Plasma insulin concentration increased during beta-adrenergic stimulation by about 25% (p < 0.05) whereas the interstitial insulin concentration was unchanged. Muscle blood flow in the hindlimb was considerably enhanced by about 130%, (p < 0.001) by epinephrine. Infusion of propranolol totally abolished all the above effects induced by epinephrine. The data show that insulin resistance and vasodilation induced by beta-adrenergic stimulation with epinephrine is accompanied by increased interstitial glucose as well as lactate concentrations in muscle. The increased interstitial glucose concentration is the result of a decreased cellular uptake of glucose together with an increased capillary delivery of glucose by vasodilation. It is concluded that the severe cellular resistance to insulin induced by epinephrine could not be overcome either by the increased insulin secretion or by vasodilation.

Audiological disturbances caused by long-term exposure to industrial solvents. Relation to the diagnosis of toxic encephalopathy

Sixty workers, consecutively admitted due to suspicion of solvent-induced chronic toxic encephalopathy (CTE), were investigated with pure-tone audiometry, determination of speech recognition of monosyllabic words and distorted speech and cortical response audiometry (CRA). Eighteen workers not exposed to occupational solvents and noise were also investigated. The scores in the distorted speech test were significantly lower and the CRA latencies were significantly longer in the solvent group than in the control group. There was no difference between the groups in the pure-tone and monosyllabic speech recognition tests. In the solvent group, 19 subjects had one or several pathological audiological test results (values exceeding the mean result of the control group by 2 SD). Independently of the audiological examination all the workers in the solvent group underwent the traditional clinical assessment of CTE, which is based on symptoms, history of exposure, clinical neurological examination and a neuropsychological investigation. They were classified in three groups--CTE, incipient CTE and non-CTE. There was no correlation between these groups and the audiological test results. A previous report on vestibular pathology in the same group of subjects and the present investigation on hearing deficits suggest that long-term exposure to solvents causes disturbances of the central pathways in the otovestibular system. Hitherto, no attention has been paid to these disturbances in the definition of the CTE syndrome.

Imprinting of female offspring with testosterone results in insulin resistance and changes in body fat distribution at adult age in rats

In women, a relative hyperandrogenicity is statistically associated with insulin resistance and centralization of body fat, which are predictors for the development of non-insulin-dependent diabetes mellitus. The aim of this study was to evaluate the effect of androgenization of newborn female rats on insulin sensitivity at adult age. To mimic the neonatal androgen peak normally observed in male rats, female pups were administered one high dose of testosterone (T) subcutaneously within 3 h after birth. They were then given back to their mothers and followed to adult age. At the end of the week 9, tail samples were taken, showing no differences in fasting plasma concentrations of glucose, lactate, insulin, or free fatty acids between T-treated rats and controls. Plasma concentrations of T and progesterone were significantly lower in the T-treated rats, whereas no differences were found in the levels of corticosterone, estradiol, insulin-like growth factor I, or ACTH. After 10 wk, insulin sensitivity was studied with hyperglycemic and euglycemic hyperinsulinemic (5 mU insulin/kg/min) clamp techniques. The T-treated rats showed insulin resistance with both techniques, which was overcome with time and increasing insulin concentrations during the clamp measurements. The T-treated rats were also heavier and had increased relative weights of skeletal muscles and the spleen. Parametrial, retroperitoneal, and inguinal adipose tissues decreased in weight while mesenteric adipose tissue tended to increase, resulting in an approximately 30-50% larger mesenteric than other adipose tissues. It is concluded that neonatal T imprinting of female rats is followed by insulin resistance, changes in adipose tissue distribution, and an enlarged lean mass, without elevation of circulating T. Similar changes are seen in adult female rats or women receiving T.

Are deficits in the equilibrium system relevant to the clinical investigation of solvent-induced neurotoxicity?

OBJECTIVES

The diagnosis of solvent-induced chronic toxic encephalopathy is commonly based on case histories of exposure to solvents, symptoms, and deficits on psychometric tests. It has previously been demonstrated that long-term solvent-exposed workers have disturbances of the equilibrium system. The correlation between these disturbances and the diagnosis of chronic toxic encephalopathy has been analyzed in the present study.

MATERIAL AND METHODS

Sixty men, consecutively admitted due to the suspicion of this syndrome, were investigated and classified into 3 groups--solvent-induced chronic toxic encephalopathy, incipient chronic toxic encephalopathy and nonchronic toxic encephalopathy. They were all examined using an otoneurological test battery, including analysis of saccades, smooth pursuit, visual suppression of the vestibular ocular reflex, and dynamic posturography.

RESULTS

Compared with healthy referents several of the subjects, even in the nonchronic toxic encephalopathy group, showed a reduced visual suppression ability, a prolonged latency of saccades, and pathological posturographic results. Some otoneurological tests correlated with the duration of exposure and the results of psychometric tests representing memory and perceptual skills. Nevertheless, there was no significant group correlation between the otoneurological findings and the diagnosis of chronic toxic encephalopathy.

CONCLUSION

Disturbances revealed by an otoneurological investigation have so far not been considered in the diagnosis of chronic toxic encephalopathy. Our results indicate that an otoneurological test battery adds worthwhile information about lesions within the brainstem-cerebellar complex not revealed by a psychometric investigation.

Are the effects of toluene on the vestibulo and opto-ocular motor system inhibited by the action of GABAB antagonist CGP 35348?

The acute effects of toluene and a selective GABAB-antagonist, CGP 35348, on the vestibulo and opto-ocular motor (VOOM) system in rats were investigated by recording of compensatory eye-movements during vestibular and optokinetic stimulations. It has previously been demonstrated that toluene enhances the performance of the basic vestibulo-oculomotor reflex (VOR) and depresses the effects of the visual input to this reflex. It has been proposed that these effects are caused by alterations of the GABA-transmission system in the cerebellum. It has now been demonstrated that the exaggerating effects of toluene on the VOR, tested by angular horizontal acceleration/deceleration of the animals in darkness, are inhibited by CGP 35348 in a dose related way. On the contrary, the depressing effects on the visual input, tested by optokinetic stimulation, by angular acceleration/deceleration with a simultaneous conflicting visual stimulation and by eliciting saccades, could not be prevented by CGP 35348. The results support the hypothesis that toluene causes some of the effects on the VOOM system by influence on the GABA-transmission. The findings are in agreement with a recent report of increased levels of extracellular GABA in the cerebellar cortex during exposure to toluene.

Macrovascular causes underlying otoneurological disturbances

In the diagnostic procedure for patients with symptoms and signs indicating VIIIth nerve or brain stem disturbances, the possible presence of tumors, infarcts, bleedings or microvascular loops are taken into account. Ten patients with vertigo, balance disorders, tinnitus or unilateral hearing loss proved to have a similar cause underlying the disturbances. They ranged in age from 51 to 80 years and had a duration of their symptoms of 1-10 years. In the test battery audiology, electronystagmography, broad-frequency rotatory testing and dynamic posturography were used. No uniform pattern was present. The results showed VIIIth nerve as well as CNS signs. Trigeminal neuralgia and hemifacial spasm were observed. CT, NMR or angiography were performed. The common finding for these patients were ectatic vertebral and/or basilar arteries. The size and position of the vessels indicated that compression of the VIIIth nerve or brainstem was the cause underlying their disturbances. To exclude that macrovessels appear in patients without neurotological symptoms and signs 300 consecutive NMR investigations in patients referred for other than neurotogic indications were scrutinized. In these patients no macrovessels were found. The findings indicate that ectatic vessels may cause disturbances mimicking a pontine angle tumor, Meniere's disease and other peripheral or central conditions with inner ear symptoms, vertigo and balance disorders. Arterial loops in the pontine angle may give indications for microvascular surgery, but the big ectatic vertebral and basilar arteries may offer surgical decompression possibilities, though with large risks.

Effects of GABAB activation and inhibition on vestibulo-ocular and optokinetic responses in the pigmented rat

The effects of the GABAB agonist baclofen and the GABAB antagonist CGP 35348, given separately or simultaneously, on the central vestibular system of pigmented rats have been evaluated. Drugs were administered either intramuscularly or intracerebroventricularly. Eye movements were recorded during vestibular, optokinetic and combined visual-vestibular stimulation. Activation of the GABAB receptors by baclofen caused a dose related disturbance of the system, manifested by (1) a decrease of the optokinetic gain, (2) a reduced ability to suppress nystagmus during conflicting vestibular and visual input, and (3) a disability to maintain the eccentric eye position upon a spontaneous saccade. All these effects could be inhibited in a dose-dependent fashion by CGP 35348, suggesting that the findings are specifically related to the GABAB receptor. Given separately, the antagonist did not affect the mentioned parameters. During horizontal acceleratory/deceleratory stimulation in darkness baclofen caused a biphasic pattern in the dose-response curves. Small amounts of baclofen caused an increase of the gain and of the duration of poststimulatory nystagmus, while high doses had a depressive action on the same parameters. The stimulating effect of baclofen could be inhibited or even reversed by CGP 35348, which has a depressive effect per se, similar to the effects of baclofen given in the upper range of doses.

Effects of toluene, styrene, trichloroethylene, and trichloroethane on the vestibulo-and opto-oculo motor system in rats

The acute effects of inhalation of four solvents on the central vestibular system of rats were analyzed by recording eye movements upon different stimuli. The dose-response relationship was investigated. Optokinetic stimulation was obtained by placing the animals in front of a surrounding visual pattern, moving at different velocities. The slow-phase eye velocity (SPV) of nystagmus was calculated and divided by the stimulus velocity, giving the gain. All the solvents caused a decrease of the gain. Vestibular stimulation was performed on a turntable by an angular acceleration/deceleration in darkness. The SPV and the duration of the post-stimulatory nystagmus were calculated. The shape of the SPV dose-response curves differed among the four solvents. Toluene, styrene, and trichloroethylene prolonged the duration of nystagmus while trichloroethane did not. A conflicting vestibular and optokinetic stimulation was performed by an angular acceleration/deceleration with a surrounding visual pattern moving with the turntable. All solvents decreased the ability to cancel nystagmus, elicited by vestibular stimulation in conflict with a visual input. Quick movements of the eyes, saccades, were elicited by tactile stimulation. Toluene, styrene, and trichloroethylene changed the generation of the saccades while trichloroethane did not. Most of the findings indicate a common site of action in the central vestibular system, viz, the cerebellar-vestibular circuit. However, within this domain, there are evident differences in the effects among the solvents. This findings, together with previous results obtained in other experimental models of the central nervous system (CNS), suggest that different solvents should be considered as individual compounds.(ABSTRACT TRUNCATED AT 250 WORDS)

The Influence of Visual and Somatosensory Input on the Vestibulo-Oculomotor Reflex of Pigmented Rats

Eye movements were recorded in the pigmented rat during vestibular, optokinetic and combined visual-vestibular stimulation. The dominant time constant in pigmented rats, tested during angular vestibular stimulation in darkness, is about two times longer than the cupular time constant. The gain and the duration of nystagmus, achieved by angular vestibular stimulation, can be enhanced by visual impulses. This is most evident during an optokinetic temporonasal stimulation, but is also seen with a nasotemporal stimulation. A mere optokinetic monocular stimulation without a synchronous vestibular excitation causes nystagmus only when the stimuli has a temporonasal direction. The duration of nystagmus, achieved by angular vestibular stimulation, is prolonged by disturbances of the neck proprioceptive system. This is more evident during a simultaneous visual input than in darkness. The ability to cancel nystagmus during conflicting vestibular and optokinetic impulses is well developed in the pigmented rat.

The effect of toluene on the vestibulo- and opto-oculomotor system in rats, pretreated with GABAergic drugs

Toluene, an aromatic solvent, prolongs the duration of nystagmus induced by a rotatory acceleration or by an optokinetic stimulation in the pigmented rat. Baclofen, an agonist of GABAB receptors, and 4,5,6,7-tetrahydroisoxazolo[5,4-c]-pyridin-3-ol (THIP), an agonist of GABAA receptors are able to block this toluene effect on the vestibular system. On the contrary diazepam, which by itself causes an evident reduction of the duration of acceleratory nystagmus, is not able to block the toluene effect. The results indicate that the toluene effect is related to GABA transmission and that the solvent interacts by a rather receptor specific mechanism of action.

Vestibular disturbances after neck muscle sectioning in rat

The nystagmus response to rotatory acceleration was investigated in rats. The stimulus was exerted by a turntable accelerated 13.3%/sec2 for 9 seconds and after 1-2 minutes decelerated accordingly. Eye movements were recorded using the search coil technique. The duration of postrotatory nystagmus and speed of slow component velocity gain were recorded. After unilateral neck muscle sectioning no change appeared. After bilateral sectioning the nystagmus response was increased with a remaining high gain and prolonged response duration. The experiments show the influence by the muscles on the velocity storage mechanism.

Activity in the corpora lutea resulting from sterile matings in Clethrionomys glareolus: a histochemical study

The capacity for steroid production in the corpora lutea (CL) of bank voles was examined by enzyme histochemistry for 3 beta-hydroxysteroid dehydrogenase. The results revealed similar activity in the CL resulting from sterile matings and the CL of pregnancy 2 days after mating. Six days after mating, the CL of pregnancy showed a strong reaction, while there was almost no reaction in the CL from sterile matings, which were clearly regressed at this time. It is suggested that the CL from sterile matings produce progesterone before regression and that this progesterone may prime the luteotrophic complex, increasing fertility of subsequent matings.