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Abstract Background In recent years, the interest in Al[18F]F as a labeling agent for Positron Emission Tomography (PET) radiotracers has risen, as it allows for fast and efficient fluorine-18 labeling by harnessing chelation chemistry. The introduction of Restrained Complexing Agent (RESCA) as a chelator has also shown that chelator-based radiolabeling reactions can be performed in mild conditions, making the radiolabeling process attractively more facile than most conventional radiofluorination methods. The aim of the study was to establish optimized conditions for Al[18F]F labeling of Affibody molecules using RESCA as a complexing agent, using Z09591 and Z0185, two Affibody proteins targeting PDGFRβ and TNFα, respectively, as model compounds. Results The Al[18F]F labeling of RESCA-conjugated Z09591 was tested at different temperatures (rt to 60 °C) and with varying reaction times (12 to 60 min), and optimal conditions were then implemented on RESCA-Z0185. The optimized synthesis method was: 1.5–2.5 GBq of cyclotron produced fluorine-18 were trapped on a QMA cartridge and eluted with saline solution to react with 12 nmol of AlCl3 and form Al[18F]F. The respective RESCA-conjugated Affibody molecule (14 nmol) in NaOAc solution was added to the Al[18F]F solution and left to react at 60 °C for 12 min. The mixture was purified on a NAP5 size exclusion column and then analyzed by HPLC. The entire process took approximately 35 min, was highly reproducible, indicating the efficiency and reliability of the method. The labeled compounds demonstrated retained biological function for their respective targets after purification. Conclusions We present a general and optimized method for Al[18F]F labeling of RESCA-conjugated Affibody molecules, which can be widely applied to this class of peptide-based imaging agents. Moreover, radiochemical yields were improved when the labeling was conducted at 37 °C or above. In vitro and in vivo assessment of the respective tracers was promising, showing retained binding capacity as well as moderate defluorination, which is usually regarded as a potential downside for RESCA-conjugated tracers. Graphical abstract

Abstract Background Alveolar macrophages activation to the pro-inflammatory phenotype M1 is pivotal in the pathophysiology of Ventilator-Induced Lung Injury (VILI). Increased lung strain is a known determinant of VILI, but a direct correspondence between regional lung strain and macrophagic activation remains unestablished. [68Ga]Ga-DOTA-TATE is a Positron Emission Tomography (PET) radiopharmaceutical with a high affinity for somatostatin receptor subtype 2 (SSTR2), which is overexpressed by pro-inflammatory-activated macrophages. Aim of the study was to determine, in a porcine model of VILI, whether mechanical strain correlates topographically with distribution of activated macrophages detected by [68Ga]Ga-DOTA-TATE uptake. Methods Seven anesthetized pigs underwent VILI, while three served as control. Lung CT scans were acquired at incremental tidal volumes, simultaneously recording lung mechanics. [68Ga]Ga-DOTA-TATE was administered, followed by dynamic PET scans. Custom MatLab scripts generated voxel-by-voxel gas volume and strain maps from CT slices at para-diaphragmatic (Para-D) and mid-thoracic (Mid-T) levels. Analysis of regional Voxel-associated Normal Strain (VoStrain) and [68Ga]Ga-DOTA-TATE uptake was performed and a measure of the statistical correlation between these two variables was quantified using the linear mutual information (LMI) method. Results Compared to controls, the VILI group exhibited statistically significant higher VoStrain and Standardized Uptake Value Ratios (SUVR) both at Para-D and Mid-T levels. Both VoStrain and SUVR increased along the gravitational axis with an increment described by statistically different regression lines between VILI and healthy controls and reaching the peak in the dependent regions of the lung (for strain in VILI vs. control was at Para-D: 760 ± 210 vs. 449 ± 106; at Mid-T level 497 ± 373 vs. 193 ± 160; for SUVR, in VILI vs. control was at Para-D: 2.2 ± 1.3 vs. 1.3 ± 0.1; at Mid-T level 1.3 ± 1.0 vs. 0.6 ± 0.03). LMI in both Para-D and Mid-T was statistically significantly higher in VILI than in controls. Conclusions In this porcine model of VILI, we found a topographical correlation between lung strain and [68Ga]Ga-DOTA-TATE uptake at voxel level, suggesting that mechanical alteration and specific activation of inflammatory cells are strongly linked in VILI. This study represents the first voxel-by-voxel examination of this relationship in a multi-modal imaging analysis.

Summary: Non-invasive assessment of fibrogenic activity, rather than fibrotic scars, could significantly improve the management of fibrotic diseases and the development of anti-fibrotic drugs. This study explores the potential of an Affibody molecule (Z09591) labeled with the Al(18)F-restrained complexing agent (RESCA) method as a tracer for the non-invasive detection of fibrogenic cells. Z09591 was functionalized with the RESCA chelator for direct labeling with [18F]AlF. In vivo positron emission tomography/magnetic resonance imaging scans on U-87 tumor-bearing mice exhibited high selectivity of the resulting radiotracer, [18F]AlF-RESCA-Z09591, for platelet-derived growth factor receptor β (PDGFRβ), with minimal non-specific background uptake. Evaluation in a mouse model with carbon tetrachloride-induced fibrotic liver followed by a disease regression phase, revealed the radiotracer’s high affinity and specificity for fibrogenic cells in fibrotic livers (standardized uptake value [SUV] 0.43 ± 0.05), with uptake decreasing during recovery (SUV 0.29 ± 0.03) (p

Abstract Background Beta-cell replacement methods such as transplantation of isolated donor islets have been proposed as a curative treatment of type 1 diabetes, but widespread application is challenging due to shortages of donor tissue and the need for continuous immunosuppressive treatments. Stem-cell-derived islets have been suggested as an alternative source of beta cells, but face transplantation protocols optimization difficulties, mainly due to a lack of available methods and markers to directly monitor grafts survival, as well as their localization and function. Molecular imaging techniques and particularly positron emission tomography has been suggested as a tool for monitoring the fate of islets after clinical transplantation. The integral membrane protein DGCR2 has been demonstrated to be a potential pancreatic islet biomarker, with specific expression on insulin-positive human embryonic stem-cell-derived pancreatic progenitor cells. The candidate Affibody molecule ZDGCR2:AM106 was radiolabeled with fluorine-18 using a novel click chemistry-based approach. The resulting positron emission tomography tracer [18F]ZDGCR2:AM106 was evaluated for binding to recombinant human DGCR2 and cryosections of stem-cell-derived islets, as well as in vivo using an immune-deficient mouse model transplanted with stem-cell-derived islets. Biodistribution of the [18F]ZDGCR2:AM106 was also assessed in healthy rats and pigs. Results [18F]ZDGCR2:AM106 was successfully synthesized with high radiochemical purity and yield via a pretargeting approach. [18F]ZDGCR2:AM106 retained binding to recombinant human DCGR2 as well as to cryosectioned stem-cell-derived islets, but in vivo binding to native pancreatic tissue in both rat and pig was low. However, in vivo uptake of [18F]ZDGCR2:AM106 in stem-cell-derived islets transplanted in the immunodeficient mice was observed, albeit only within the early imaging frames after injection of the radiotracer. Conclusion Targeting of DGCR2 is a promising approach for in vivo detection of stem-cell-derived islets grafts by molecular imaging. The synthesis of [18F]ZDGCR2:AM106 was successfully performed via a pretargeting method to label a site-specific covalently bonded fluorine-18 to the Affibody molecule. However, the rapid washout of [18F]ZDGCR2:AM106 from the stem-cell-derived islets graft indicates that dissociation kinetics can be improved. Further studies using alternative binders of similar classes with improved binding potential are warranted.

Abstract Background Platelet-derived growth factor receptor beta (PDGFRβ) is a receptor overexpressed on activated hepatic stellate cells (aHSCs). Positron emission tomography (PET) imaging of PDGFRβ could potentially allow the quantification of fibrogenesis in fibrotic livers. This study aims to evaluate a fluorine-18 radiolabeled Affibody molecule ([18F]TZ-Z09591) as a PET tracer for imaging liver fibrogenesis. Results In vitro specificity studies demonstrated that the trans-Cyclooctenes (TCO) conjugated Z09591 Affibody molecule had a picomolar affinity for human PDGFRβ. Biodistribution performed on healthy rats showed rapid clearance of [18F]TZ-Z09591 through the kidneys and low liver background uptake. Autoradiography (ARG) studies on fibrotic livers from mice or humans correlated with histopathology results. Ex vivo biodistribution and ARG revealed that [18F]TZ-Z09591 binding in the liver was increased in fibrotic livers (p = 0.02) and corresponded to binding in fibrotic scars. Conclusions Our study highlights [18F]TZ-Z09591 as a specific tracer for fibrogenic cells in the fibrotic liver, thus offering the potential to assess fibrogenesis clearly. Graphical abstract

Abstract Purpose In the characterization of severe lung diseases, early detection of specific inflammatory cells could help to monitor patients’ response to therapy and increase chances of survival. Macrophages contribute to regulating the resolution and termination of inflammation and have increasingly been of interest for targeted therapies. [68Ga]Ga-DOTA-TATE is an established clinical radiopharmaceutical targeting somatostatin receptor subtype 2 (SSTR 2). Since activated macrophages (M1) overexpress SSTR 2, the aim of this study was to investigate the applicability of [68Ga]Ga-DOTA-TATE for positron emission tomography (PET) imaging of M1 macrophages in pulmonary inflammation. Methods Inflammation in the pig lungs was induced by warm saline lavage followed by injurious ventilation in farm pigs (n = 7). Healthy pigs (n = 3) were used as control. A 60-min dynamic PET scan over the lungs was performed after [68Ga]Ga-DOTA-TATE injection and [18F]FDG scan was executed afterward for comparison. The uptake of both tracers was assessed as mean standardized uptake values (SUVmean) 30–60-min post-injection. The PET scans were followed by computed tomography (CT) scans, and the Hounsfield units (HU) were quantified of the coronal segments. Basal and apical segments of the lungs were harvested for histology staining. A rat lung inflammation model was also studied for tracer specificity using lipopolysaccharides (LPS) by oropharyngeal aspiration. Organ biodistribution, ex vivo autoradiography (ARG) and histology samples were conducted on LPS treated, octreotide induced blocking and control healthy rats. Results The accumulation of [68Ga]Ga-DOTA-TATE on pig lavage model was prominent in the more severely injured dorsal segments of the lungs (SUVmean = 0.91 ± 0.56), compared with control animals (SUVmean = 0.27 ± 0.16, p

Fibrosis accompanies various pathologies, and there is thus an unmet medical need for non-invasive, sensitive, and quantitative methods for the assessment of fibrotic processes. Currently, needle biopsy with subsequent histological analysis is routinely used for the diagnosis along with morphological imaging techniques, such as computed tomography (CT), magnetic resonance imaging (MRI), and ultrasound (US). However, none of these imaging techniques are sufficiently sensitive and accurate to detect minor changes in fibrosis. More importantly, they do not provide information on fibrotic activity on the molecular level, which is critical for fundamental understanding of the underlying biology and disease course. Molecular imaging technology using positron emission tomography (PET) offers the possibility of imaging not only physiological real-time activity, but also high-sensitivity and accurate quantification. This diagnostic tool is well established in oncology and has exhibited exponential development during the last two decades. However, PET diagnostics has only recently been widely applied in the area of fibrosis. This review presents the progress of development of radiopharmaceuticals for non-invasive detection of fibrotic processes, including the fibrotic scar itself, the deposition of new fibrotic components (fibrogenesis), or the degradation of existing fibrosis (fibrolysis).

Abstract Biomarkers for the measurement of islets of Langerhans could help elucidate the etiology of diabetes. Synaptic vesicle glycoprotein 2 A (SV2A) is a potential marker reported to be localized in the endocrine pancreas. [11C]UCB-J is a novel positron emission tomography (PET) radiotracer that binds to SV2A and was previously evaluated as a synaptic marker in the central nervous system. Here, we evaluated whether [11C]UCB-J could be utilized as a PET tracer for the islets of Langerhans in the pancreas by targeting SV2A. The mRNA transcription of SV2A was evaluated in human isolated islets of Langerhans and exocrine tissue. In vitro autoradiography was performed on pancreas and brain sections from rats and pigs, and consecutive sections were immunostained for insulin. Sprague–Dawley rats were examined with PET-MRI and ex vivo autoradiography at baseline and with administration of levetiracetam (LEV). Similarly, pigs were examined with dynamic PET-CT over the pancreas and brain after administration of [11C]UCB-J at baseline and after pretreatment with LEV. In vivo radioligand binding was assessed using a one-compartment tissue model. The mRNA expression of SV2A was nearly 7 times higher in endocrine tissue than in exocrine tissue (p

Abstract Due to the wide scale of inflammatory processes in different types of disease, more sensitive and specific biomarkers are required to improve prevention and treatment. Cluster of differentiation 69 (CD69) is one of the earliest cell surface proteins expressed by activated leukocytes. Here we characterize and optimize potential new imaging probes, Affibody molecules targeting CD69 for imaging of activated immune cells. Analysis of candidates isolated in a previously performed selection from a Z variant E. coli library to the recombinant extracellular domain of human CD69, identified one cross-reactive Z variant with affinity to murine and human CD69. Affinity maturation was performed by randomization of the primary Z variant, followed by selections from the library. The resulting Z variants were evaluated for affinity towards human and murine CD69 and thermal stability. The in vivo biodistribution was assessed by SPECT/CT in rats following conjugation of the Z variants by a DOTA chelator and radiolabeling with Indium-111. A primary Z variant with a Kd of approximately 50 nM affinity to human and murine CD69 was identified. Affinity maturation generated 5 additional Z variants with improved or similar affinity. All clones exhibited suitable stability. Radiolabeling and in vivo biodistribution in rat demonstrated rapid renal clearance for all variants, while the background uptake and washout varied. The variant ZCD69:4 had the highest affinity for human and murine CD69 (34 nM) as well as the lowest in vivo background binding. In summary, we describe the discovery, optimization and evaluation of novel Affibody molecules with affinity for CD69. Affibody molecule ZCD69:4 is suitable for further development for imaging of activated immune cells.

The progressive loss of beta-cell mass is a hallmark of diabetes and has been suggested as a complementary approach to studying the progression of diabetes in contrast to the beta-cell function. Non-invasive nuclear medicinal imaging techniques such as Positron Emission Tomography using radiation emitting tracers have thus been suggested as more viable methodologies to visualize and quantify the beta-cell mass with sufficient sensitivity. The transmembrane G protein-coupled receptor GPR44 has been identified as a biomarker for monitoring beta-cell mass. MK-7246 is a GPR44 antagonist that selectively binds to GPR44 with high affinity and good pharmacokinetic properties. Here, we present the synthesis of MK-7246, radiolabeled with the positron emitter fluorine-18 for preclinical evaluation using cell lines, mice, rats and human pancreatic cells. Here, we have described a synthesis and radiolabeling method for producing [18F]MK-7246 and its precursor compound. Preclinical assessments demonstrated the strong affinity and selectivity of [18F]MK-7246 towards GPR44. Additionally, [18F]MK-7246 exhibited excellent metabolic stability, a fast clearance profile from blood and tissues, qualifying it as a promising radioactive probe for GPR44-directed PET imaging.

Imaging and radiotherapy targeting the glucose-dependent insulinotropic polypeptide receptor (GIPR) could potentially benefit the management of neuroendocrine neoplasms (NENs), complementing clinically established radiopharmaceuticals. The aim of this study was to evaluate a GIPR-targeting positron emission tomography (PET) radioligand with receptor-specific binding, fast blood clearance, and low liver background uptake. The peptide DOTA-bioconjugate, C803-GIP, was developed based on the sequence of the endogenous GIP(1-30) and synthetic exendin-4 peptides with selective amino acid mutations to combine their specificity for the GIPR and in vivo stability, respectively. The 68Ga-labeled bioconjugate was evaluated in vitro in terms of binding affinity, specificity, and internalization in HEK293 cells transfected with the human GIPR, GLP1, or GCG receptors and in sections of human insulinoma and NENs. In vivo binding specificity, biodistribution, and tissue background were investigated in mice bearing huGIPR-HEK293 xenografts and in a pig. Ex vivo organ distribution, pharmacokinetics, and dosimetry were studied in normal rats. [68Ga]Ga-C803-GIP was stable and demonstrated a high affinity to the huGIPR-HEK293 cells. Binding specificity was demonstrated in vitro in frozen sections of NENs and huGIPR-HEK293 cells. No specific uptake was observed in the negative controls of huGLP1R and huGCGR cells. A novel rationally designed PET radioligand, [68Ga]Ga-C803-GIP, demonstrated promising binding characteristics and specificity towards the GIPR.

Introduction Glucagon-like peptide-1 (GLP-1) increases insulin secretion from pancreatic beta-cells and GLP-1 receptor (GLP-1R) agonists are widely used as treatment for type 2 diabetes mellitus. Studying occupancy of the GLP-1R in various tissues is challenging due to lack of quantitative, repeatable assessments of GLP-1R density. The present study aimed to describe the quantitative distribution of GLP-1Rs and occupancy by endogenous GLP-1 during oral glucose tolerance test (OGTT) in pigs, a species that is used in biomedical research to model humans.Research design and methods GLP-1R distribution and occupancy were measured in pancreas and gastrointestinal tract by ex vivo autoradiography using the GLP-1R-specific radioligand 177Lu-exendin-4 in two groups of pigs, control or bottle-fed an oral glucose load. Positron emission tomography (PET) data from pigs injected with 68Ga-exendin-4 in a previous study were used to retrieve data on biodistribution of GLP-1R in the gastrointestinal tract.Results High homogenous uptake of 177Lu-exendin-4 was found in pancreas, and even higher uptake in areas of duodenum. Low uptake of 177Lu-exendin-4 was found in stomach, jejunum, ileum and colon. During OGTT, there was no increase in plasma GLP-1 concentrations and occupancy of GLP-1Rs was low. The ex vivo autoradiography results were highly consistent with to the biodistribution of 68Ga-exendin-4 in pigs scanned by PET.Conclusion We identified areas with similarities as well as important differences regarding GLP-1R distribution and occupancy in pigs compared with humans. First, there was strong ligand binding in the exocrine pancreas in islets. Second, GLP-1 secretion during OGTT is minimal and GLP-1 might not be an important incretin in pigs under physiological conditions. These findings offer new insights on the relevance of porcine diabetes models.

Abstract The glucagon receptor (GCGR) is emerging as an important target in anti-diabetic therapy, especially as part of the pharmacology of dual glucagon-like peptide-1/glucagon (GLP-1/GCG) receptor agonists. However, currently, there are no suitable biomarkers that reliably demonstrate GCG receptor target engagement. Methods Two potent GCG receptor peptide agonists, S01-GCG and S02-GCG, were labeled with positron emission tomography (PET) radionuclide gallium-68. The GCG receptor binding affinity and specificity of the resulting radiopharmaceuticals [68Ga]Ga-DO3A-S01-GCG and [68Ga]Ga-DO3A-S02-GCG were evaluated in HEK-293 cells overexpressing the human GCG receptor and on frozen hepatic sections from human, non-human primate, and rat. In in vivo biodistribution, binding specificity and dosimetry were assessed in rat. Results [68Ga]Ga-DO3A-S01-GCG in particular demonstrated GCG receptor-mediated binding in cells and liver tissue with affinity in the nanomolar range required for imaging. [68Ga]Ga-DO3A-S01-GCG binding was not blocked by co-incubation of a GLP-1 agonist. In vivo binding in rat liver was GCG receptor specific with low non-specific binding throughout the body. Moreover, the extrapolated human effective doses, predicted from rat biodistribution data, allow for repeated PET imaging potentially also in combination with GLP-1R radiopharmaceuticals. Conclusion [68Ga]Ga-DO3A-S01-GCG thus constitutes a first-in-class PET tracer targeting the GCG receptor, with suitable properties for clinical development. This tool has potential to provide direct quantitative evidence of GCG receptor occupancy in humans.

Abstract Background The G-protein-coupled receptor 44 (GPR44) is a beta cell-restricted target that may serve as a marker for beta cell mass (BCM) given the development of a suitable PET ligand. Methods The binding characteristics of the selected candidate, AZ12204657, at human GPR44 were determined using in vitro ligand binding assays. AZ12204657 was radiolabeled using 11C- or 3H-labeled methyl iodide ([11C/3H]CH3I) in one step, and the conversion of [11C/3H]CH3I to the radiolabeled product [11C/3H]AZ12204657 was quantitative. The specificity of radioligand binding to GPR44 and the selectivity for beta cells were evaluated by in vitro binding studies on pancreatic sections from human and non-human primates as well as on homogenates from endocrine and exocrine pancreatic compartments. Results The radiochemical purity of the resulting radioligand [11C]AZ12204657 was > 98%, with high molar activity (MA), 1351 ± 575 GBq/μmol (n = 18). The radiochemical purity of [3H]AZ12204657 was > 99% with MA of 2 GBq/μmol. Pancreatic binding of [11C/3H]AZ12204657 was co-localized with insulin-positive islets of Langerhans in non-diabetic individuals and individuals with type 2 diabetes (T2D). The binding of [11C]AZ12204657 to GPR44 was > 10 times higher in islet homogenates compared to exocrine homogenates. In human islets of Langerhans GPR44 was co-expressed with insulin, but not glucagon as assessed by co-staining and confocal microscopy. Conclusion We radiolabeled [11C]AZ12204657, a potential PET radioligand for the beta cell-restricted protein GPR44. In vitro evaluation demonstrated that [3H]AZ12204657 and [11C]AZ12204657 selectively target pancreatic beta cells. [11C]AZ12204657 has promising properties as a marker for human BCM.

Diabetes is a chronic metabolic disease affecting over 400 million people worldwide and one of the leading causes of death, especially in developing nations. The disease is characterized by chronic hyperglycemia, caused by defects in the insulin secretion or action pathway. Current diagnostic methods measure metabolic byproducts of the disease such as glucose level, glycated hemoglobin (HbA1c), insulin or C-peptide levels, which are indicators of the beta-cell function. However, they inaccurately reflect the disease progression and provide poor longitudinal information. Beta-cell mass has been suggested as an alternative approach to study disease progression in correlation to beta-cell function, as it behaves differently in the diabetes physiopathology. Study of the beta-cell mass, however, requires highly invasive and potentially harmful procedures such as pancreatic biopsies, making diagnosis and monitoring of the disease tedious. Nuclear medical imaging techniques using radiation emitting tracers have been suggested as strong non-invasive tools for beta-cell mass. A highly sensitive and high-resolution technique, such as positron emission tomography, provides an ideal solution for the visualization of beta-cell mass, which is particularly essential for better characterization of a disease such as diabetes, and for estimating treatment effects towards regeneration of the beta-cell mass. Development of novel, validated biomarkers that are aimed at beta-cell mass imaging are thus highly necessary and would contribute to invaluable breakthroughs in the field of diabetes research and therapies. This review aims to describe the various biomarkers and radioactive probes currently available for positron emission tomography imaging of beta-cell mass, as well as highlight the need for precise quantification and visualization of the beta-cell mass for designing new therapy strategies and monitoring changes in the beta-cell mass during the progression of diabetes.

There is an unmet medical need for non-invasive, sensitive, and quantitative methods for the assessment of fibrosis. Herein, an improved collagelin analogue labelled with gallium-68 for use with positron emission tomography (PET) is presented. A cyclic peptide, c[CPGRVNleHGLHLGDDEGPC], was synthesized by solid-phase peptide synthesis, conjugated to 2-(4,7-bis(2-(tert-butoxy)-2-oxoethyl)-1,4,7-triazonan-1-yl)acetic acid, and labelled with gallium-68. High performance liquid chromatography (HPLC) was used for the quality and stability assessment of the collagelin analogue. Non-specific organ distribution, blood clearance, and excretion rates were investigated in healthy mice and rats using ex vivo organ distribution analysis and dynamic in vivo PET/CT. Mice with carbon tetrachloride (CCl4) induced liver fibrosis were used for the investigation of specific binding via in vitro frozen section autoradiography, ex vivo organ distribution, and in vivo PET/CT. A non-decay corrected radiochemical yield (48 ± 6%) of [68Ga]Ga-NOTA-PEG2-c[CPGRVNleHGLHLGDDEGPC] ([68Ga]Ga-NO2A-[Nle13]-Col) with a radiochemical purity of 98 ± 2% was achieved without radical scavengers. The 68Ga-labelling was regioselective and stable at ambient temperature for at least 3 h. The autoradiography of the cryosections of fibrotic mouse liver tissue demonstrated a distinct heterogeneous radioactivity uptake that correlated with the fibrosis scores estimated after Sirius Red staining. The blood clearance and tissue washout from the [68Ga]Ga-NO2A-[Nle13]-Col was fast in both normal and diseased mice. Dosimetry investigation in rats indicated the possibility for 4–5 PET/CT examinations per year. Radiolytic stability of the collagelin analogue was achieved by the substitution of methionine with norleucine amino acid residue without a deterioration of its binding capability. [68Ga]Ga-NO2A-[Nle13]-Col demonstrated a safe dosimetry profile suitable for repeated scanning.

Type 2 diabetes (T2D) is a complex and heterogeneous disease which affects millions of people worldwide. The classification of diabetes is at an interesting turning point and there have been several recent reports on sub-classification of T2D based on phenotypical and metabolic characteristics. An important, and perhaps so far underestimated, factor in the pathophysiology of T2D is the role of oxidative stress and reactive oxygen species (ROS). There are multiple pathways for excessive ROS formation in T2D and in addition, beta-cells have an inherent deficit in the capacity to cope with oxidative stress. ROS formation could be causal, but also contribute to a large number of the metabolic defects in T2D, including beta-cell dysfunction and loss. Currently, our knowledge on beta-cell mass is limited to autopsy studies and based on comparisons with healthy controls. The combined evidence suggests that beta-cell mass is unaltered at onset of T2D but that it declines progressively. In order to better understand the pathophysiology of T2D, to identify and evaluate novel treatments, there is a need for in vivo techniques able to quantify beta-cell mass. Positron emission tomography holds great potential for this purpose and can in addition map metabolic defects, including ROS activity, in specific tissue compartments. In this review, we highlight the different phenotypical features of T2D and how metabolic defects impact oxidative stress and ROS formation. In addition, we review the literature on alterations of beta-cell mass in T2D and discuss potential techniques to assess beta-cell mass and metabolic defects in vivo.

A validated imaging marker for beta-cell mass would improve understanding of diabetes etiology and enable new strategies in therapy development. We previously identified the membrane-spanning protein GPR44 as highly expressed and specific to the beta cells of the pancreas. The selective GPR44 antagonist MK-7246 was radiolabeled with carbon-11 and the resulting positron-emission tomography (PET) tracer [11C]MK-7246 was evaluated in a pig model and in vitro cell lines. The [11C]MK-7246 compound demonstrated mainly hepatobiliary excretion with a clearly defined pancreas, no spillover from adjacent tissues, and pancreatic binding similar in magnitude to the previously evaluated GPR44 radioligand [11C]AZ12204657. The binding could be blocked by preadministration of nonradioactive MK-7246, indicating a receptor-binding mechanism. [11C]MK-7246 showed strong potential as a PET ligand candidate for visualization of beta-cell mass (BCM) and clinical translation of this methodology is ongoing.

Introduction: [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 (previously published as [68Ga]Ga-DO3A-VS-Cys40-S01-GCG) has shown high-affinity specific binding to the glucagon receptor (GCGR) in vitro and in vivo in rats and non-human primates in our previous studies, confirming the suitability of the tracer for drug development applications in humans. The manufacturing process of [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 was automated for clinical use to meet the radiation safety and good manufacturing practice (GMP) requirements. Methods: The automated synthesis platform (Modular-Lab PharmTrace, Eckert & Ziegler, Eurotope, Germany), disposable cassettes for 68Ga-labeling, and pharmaceutical-grade 68Ge/68Ga generator (GalliaPharm®) used in the study were purchased from Eckert & Ziegler. The parameters such as time, temperature, precursor concentration, radical scavenger, buffer concentration, and pH, as well as product purification step, were investigated and optimized. Process optimization was conducted with regard to product quality and quantity, as well as process reproducibility. The active pharmaceutical ingredient starting material DO3A-VS-Cys40-Tuna-2 (GMP-grade) was provided by Sanofi Aventis. Results: The reproducible and GMP-compliant automated production of [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 with on-line documentation was developed. The non-decay-corrected radiochemical yield was 45.2 ± 2.5% (n = 3, process validation) at the end of the synthesis with a labeling synthesis duration of 38 min and a quality controlincluding release procedure of 20 min. The radiochemical purity of the product was 98.9 ± 0.6% (n = 17) with the total amount of the peptide in the preparation of 48 ± 2 µg (n = 3, process validation). Radionuclidic purity, sterility, endotoxin content, residual solvent content, and sterile filter integrity tests met the acceptance criteria. The product was stable at ambient temperature for at least 2 h. Conclusion: The fully automated GMP-compliant manufacturing process was developed and thoroughly validated. The resulting [68Ga]Ga-DO3A-VS-Cys40-Tuna-2 was used in a clinical study for accurate quantification of GCGR occupancy by a dual anti-diabetic drug in vivo in humans.

The positron emission tomography (PET) ligand [ 11 C]carfentanil is a selective agonist for μ-opioid receptors and has been used for studying μ-opioid receptors in the human brain. However, it is unknown if [ 11 C]carfentanil binding differentiates between subtype receptors μ 1 and μ 2 . In this study, we investigated whether μ 1 and μ 2 can be studied separately through receptor subtype–selective inhibition of [ 11 C]carfentanil by pharmacologic intervention. [ 11 C]Carfentanil binding characteristics on rat brain sections were assessed either alone or in the presence of the μ-receptor inhibitor cyprodime or the μ 1 -specific inhibitor naloxonazine. [ 11 C]Carfentanil binding in the living rat brain was similarly studied by small animal PET/computed tomography during baseline conditions or following displacement by cyprodime or naloxonazine. Autoradiography binding studies on rat brain sections demonstrated that [ 11 C]carfentanil has higher affinity and binding potential for μ 1 than for μ 2 . [ 11 C]Carfentanil binding to μ 2 in vivo could not be detected following specific blocking of μ 1 , as predicted from the low binding potential for μ 2 as measured in vitro. [ 11 C]Carfentanil binding is preferential for μ 1 compared to μ 2 in vitro and in vivo. Clinical studies employing [ 11 C]carfentanil are therefore likely biased to measure μ 1 rather than μ 2 .

Objectives: Fibrosis is involved in many chronic diseases. It affects the functionality of vital organs, such as liver, lung, heart and kidney. Two novel imaging agents for positron emission tomography (PET) imaging of fibrosis have previously pre-clinically demonstrated promising target binding and organ distribution characteristics. However, the relevant disease monitoring in the clinical setup would require multiple repetitive examinations per year. Thus, it is of paramount importance to investigate the absorbed doses and total effective doses and thus, the potential maximum number of examinations per year. Methods: Two cyclic peptide (c[CPGRVMHGLHLGDDEGPC]) analogues coupled via an ethylene glycol linker (EG2) to either 2-(4,7-bis(2-(tert-butoxy)-2-oxoethyl)-1,4,7-triazonan-1-yl)acetic acid (NO2A-Col) or 4-(4,7-bis(2-(tert-butoxy)-2-oxoethyl)-1,4,7-triazacyclononan-1-yl)-5-(tert-butoxy)-5-oxopentanoic acid (NODAGA-Col) were labelled with 68Ga. The resulting agents, [68Ga]Ga-NO2A-Col and [68Ga]Ga-NODAGA-Col, were administered in the tail vein of male and female Sprague–Dawley rats (N = 24). An ex vivo organ distribution study was performed at the 5-, 10-, 20-, 40-, 60- and 120-min time points. The resulting data were extrapolated for the estimation of human organ and total body absorbed and total effective doses using Organ Level Internal Dose Assessment Code software (OLINDA/EXM 1.1) assuming a similar organ distribution pattern between the species. Time-integrated radioactivity in each organ was calculated by trapezoidal integration followed by a single-exponential fit to the data points extrapolated to infinity. The resulting values were used for the residence time calculation. Results: Ex vivo organ distribution data revealed fast blood clearance and washout from most of the organs. Although the highest organ absorbed dose was found for kidneys (0.1 mGy/MBq), this organ was not the dose-limiting one and would allow for the administration of over 1460 MBq per year for both [68Ga]Ga-NO2A-Col and [68Ga]Ga-NODAGA-Col. The total effective dose was the limiting parameter with 0.0155/0.0156 (female/male) mSv/MBq and 0.0164/0.0158 (female/male) mSv/MBq, respectively, for [68Ga]Ga-NO2A-Col and [68Ga]Ga-NODAGA-Col. This corresponded to the total amount of radioactivity that could be administered per year of 643 and 621 MBq before reaching the annual limit of 10 mSv. Thus, up to six examinations would be possible. The residence time and organ absorbed doses in liver and spleen were higher for [68Ga]Ga-NODAGA-Col as compared to [68Ga]Ga-NO2A-Col. Conclusion: The limiting parameter for the administered dose was the total effective dose that would allow for at least six examinations per year that might be sufficient for adequate disease monitoring in longitudinal studies and a routine clinical setup.

Islet transplantation is an attractive treatment for selected patients with brittle type 1 diabetes. In the clinical setting, intraportal transplantation predominates. However, due to extensive early islet cell death, the quantity of islets needed to restore glucose homeostasis requires in general a minimum of two donors. Moreover, the deterioration of islet function over time results in few insulin-independent patients after five-year followup. Specific obstacles to the success of islet transplantation include site-specific concerns for the liver such as the instant blood mediated inflammatory reaction, islet lipotoxicity, low oxygen tension, and poor revascularization, impediments that have led to the developing interest for alternative implantation sites over recent years. Within preclinical settings, several alternative sites have now been investigated and proven favorable in various aspects. Muscle is considered a very promising site and has physiologically properties and technical advantages that could make it optimal for islet transplantation.

The effects of forest fertilizers on Calluna vulgaris, Vaccinium vitis-idaea, Cladina arbusculua, Cladina rangiferina and Cladina stellaris were studied during an eleven-year experimental period in Vasterbotten, Sweden. The study site was situated in the boreal region and was part of a 130 years old Pinus sylvestris stand. The forest type is mainly the dry dwarf-shrub type. Thirty-two demarcated plots (20 m x 20 m) were grouped into eight blocks, each containing four plots. In 1979 and 1985 fertilizations with ammonium nitrate equiavalent to 150 kg N/ha, with ammonium nitrate equiavalent to 250 kg N/ha and with urea equiavalent to 150 kg N/ha were carried out. Field sampling wad done in late July 1979, 1980, 1982, 1984, 1985, 1986, 1988 and 1990. Main parameters studied were coverage, height and standing crop. Effects were visible already after one growing season. All treatments had a positive effect on the growth of C. vulgaris and V. vitis-idaea. Doses around or over 150 kg N/ha, gave a clearly negative effect (range 23% - 73%) on the standing crop of Cladina spp. for a period of time exceeding eleven years compared to the control standing crop.

During recent years, soil scarification has become a standard procedure for improving seed beds after logging. Around 57 000 ha were treated, primarily through harrowing and ploughing, in the counties of Vâsterbotten and Norbotten during 1985. The positive effects of scarification, from a forestry point of view, are improved access to plant nutrients, raised soil temperatures and reduces surface moisture. The aim of the present study was to describe long-term changes in the ground vegetation following scarification. Harrowing affects 45-55% of the plant cover while ploughing affects 65-90%. 10 years after ploughing and harrowing about 20% of the surface is still without vegetation. Real long-term effects remain in dispute. It has been claimed that ploughing, at least, may lead to irreversible changes.

Abstract: Early in the era of atmospheric nuclear weapon tests, the reindeer was found to be an interesting animal concerning the transfer of environmental radioactive contaminants to man via the production of contaminated reindeer meat. The reason for the high transfer factors for some radionuclides is the feeding habits of the reindeer with a substantial intake of lichens, especially in the wintertime. One effect of the seasonal changes in feeding is also a considerable cyclic, seasonal variation in radiocesium content of soft tissues. The effective half-life of radiocesium was determined to about 30 days in an experiment where a herd of reindeer was moved form a high (>20 kBq/m2137Cs) to a low (

The entire Swedish reindeer area was to some extent contaminated by radionuclides after the accident at Chernobyl, USSR, in 1986.

Includes the following reviews: pp. 76-77. Elisabeth Ahlsén. Magnusson, E. & Nauclér, K. (eds.), Reading and Spelling Disabilities: Linguistic Etiology. pp. 77-80. Mats Mobärg. Lewin, E. & Lewin, A.E., The Thesaurus of Slang. pp. 81-82. Norman Vance. Bryans, R., Ulster: A Journey through the Six Counties. + McKittrick, D., Despatches from Belfast. pp. 82-83. Stephen Medcalf. Wetherbee, W., Geoffrey Chaucer, The Cantebury Tales. pp. 83-84. Jeremy Lane. Taylor, D.J., A Vain Conceit: British Fiction in the 1980s. pp. 84-86. Britt-Marie Kylander. Wahlman, B. (projektledare) m.fl., Franska ordboken. p. 87. Olof Eriksson. Livres nouveaux. pp. 87-88. Marie-Rose Blomgren. Merle, P., Dictionnaire du Français branché suivi du Guide du français tic et toc. pp. 89-91. Gunnar Magnusson. Krumm, H.-J. (Hrsg.), Handbuch Fremdsprachenunterricht. pp. 92-93. Gustav Korlén. Duden, Deutsches Universalwörterbuch. 2 Aufl. pp. 93-94. Evald Johansson. Freund, F. & Sunqvist, B., Tysk grammatik, övningsbok och Tysk grammatik, övningsbok, facit. pp. 95-97. Birgit Stolt. Graf von Krockow, C., Die Stunde der Frauen. Bericht aus Pommern 1944-47. + Gräfin von Maltzan, M., Schlage die Trommel und fürchte dich nicht. pp. 97-99. Michael Opitz. Janka, W., Schwierigkeiten mit der Wahrheit. pp. 99-101. Annelise Stawström. Köningsdorf, H., Lichtverhältnisse. pp. 101-103. Christiane Baumann. Bleisch, N., Kontrollverlust. p. 104. Helmut Müssener. Internat. Deutschlehrerverg (Hrsg.), Dem Frieden entgegen. Ein Lesebuch mit 100 Texten aus fünf Jahrhunderten. p. 104. Helmut Müssener. Peters, J. (Hrsg.), Zweimal Stockholm-Berlin 1946. Briefe nach der Rückkehr: Jürgen Peters und Wolfgang Steinitz. Mit Nachfragen an Robert Rompe und Jürgen Kuszynski.

A model for long-term analysis of the influence of timber production on lichens for reindeer grazing (Cladina, Alectoria, Bryoria spp and others) in Sweden is presented. The annual production of and demand for lichens are estimated and compared. Production of these lichens is presumed to set the upper limit for the reindeer population. Reindeer graze on both ground and tree lichens, which both must be accessible in sufficient amounts and at the right times of the year if reindeer husbandry is to succeed without supplementary feeding. The model is based mainly on existing data, and uses are estimations from the National Forest Survey and the Hugin system for calculation of longterm potential cut (Bengtsson, 1981). Geographically the study is limited to Vasterbotten and Norrbotten, the northernmost counties in Sweden, where most reindeer husbandry in Sweden is located, and where reindeer grazing takes place over almost the whole area. The calculations cover a period of one hundred years from 1980, and are based on a timber production programme which relies more on «multiple use» than the current Swedish forest policy (Bengtsson, 1986). The annual production of ground lichens is calculated by multiplying the area covered with ground lichens by their increment as estimated from their rate of biomass increase, which in turn depends on site factors and age of the stand. The estimation of the area is based on data from the National Forest Survey. Sample plots with ground lichens are assumed to maintain lichens during the whole hundred year period. Areas with stands that have been thinned within ten years and stands younger than 20 years are excluded due to logging residues from thinnings and packed snow. Some of the remaining area cannot practically be utilized for reindeer grazing. Representatives of three communities of reindeer herders classified 212 plots from the National Forest Survey with ground lichens and assessed that 3/4 of the plots can be utilized. The reduction was because of location (near buildings, roads, railroads, and recreation facilities), or because the area with lichens was too small and isolatéd. Demand for ground lichens is calculated as the daily demand for ground lichens by the reindeer multiplied by the number of days every year that reindeer depend on this forage. Figures used are based upon estimations from persons with great experience of reindeer farming. The annual production of tree lichens consists of two parts, i.e., tree lichens within reach of the reindeer, and tree lichens which become accessible after falling down from the trees onto the snow. Forest stands dominated by conifers and older than one hundred years are assumed to bear tree lichens. This area is also reduced to 75 per cent for reasons of practical accessibility. Annual production of lichens in reach of the reindeer is then estimated as the area multiplied by the increment rate of the biomass. One quarter of the annually fallen tree lichens is assumed to be available as fodder during late winter/early spring. The demand for tree lichens is principally estimated in the same way as for ground lichens, but the number of days per years is lower because tree lichens are mainly considered to be fodder in distress periods. Two sources of uncertainty are present in the results, namely the influence of factors not included in the models, and the influence of uncertainty in factors included in the models. The models used to estimate production and demand obviously imply simplifactions of true relations. These simplifications are mainly due to a basic lack of knowledge, one example being that variation, i.e. in volume per hectare, might very well influence the production of lichens, but is not taken into consideration in the models. One example of uncertainty in data used is the increment rate of lichen fodder. Another example is the estimation of biomass of lichens, here based upon investigations (Eriksson, unpubl.) with other purposes than to provide data about grazing availability in the large geographic regions used in this study. The possibilities for drawing reliable conclusions will increase when better estimations of input data and relationship are available. The geographic division into four regions is a result of the design of the National Forest Survey. However, great differences may be present within these geographic areas, each containing a number of communities of reindeer herders. Thus, results are not applicable to single communities of reindeer herders. The study illustrates a method of revealing how lichen fodder for reindeer will develop in relation to timber production. The results of the calculations, however, are too uncertain to allow reliable conclusions to be drawn. Nonetheless, the results indicate that in some areas there is already a shortage of lichen fodder for the number of reindeer assumed in this study. The calculations hint that production will decrease in the future. These indications should motivate more research in this topic. If the results of this study are accurate and if forestry develops according to the assumptions, the owners of the reindeer will have to continue or increase the supplementary feeding and/or reduce the number of reindeer significantly. They will also have to utilize all of the areas that are possible to graze, even if some of them today are considered to be of marginal value for reindeer grazing. Another way to improve the balance of production and demand is to adjust forest management on areas with lichens to a greater extent than has been done in the timber production alternative analysed in this study. Virkesproduktionens inverkan på renskotselns lavbete - En metodstudie. Abstract in Swedish / Sammanfattning: En modell for långsiktig analys av virkesproduktionens inverkan på renskotselns lavbete(Cladina, Alectoria, Bryoria spp mfl) i Sverige presenteras. Modellen beråknar årlig produktion och behov av lavbete, ef^ersom tillgången på dessa lavar bedoms begrånsa renpopulationen. Både tråd- och marklavar betas av renarn£| och måste finnas tillgångliga i tillråcklig mångd och vid rått tidpunkt under året om renskotseln skall klara sig utan stodutfordring. Modellen bygger huvudsakligen på redan existerande data. Skattningarna av areal gors med data från riksskogstaxeringen och från beråkningar med Hugin-systemet for långsiktiga analyser av avverkningsmojlighe-terna (Bengtsson, 1981). Studien begrånsas geografiskt till Norr- och Våsterbottens lån. Beråkningarna gors for en hun^raårsperiod med start 1980, och bygger på ett virkesproduktionsprogram i A VB-85 som syftar till mera mångbruk an dagens skogspolitik (Bengtsson, 1986). Den årliga produktionen av marklav skattas som produkten av mångden marklav per hektar, dess till-våxtprocerit och arealen med marklav. Mångden marklav per hektar beror av ståndortsforhållanden och bes-tåndsåldern. Skattningen av arealen baseras på uppgifter från riksskogstaxeringen. Provytor med marklav antas vara laybårande under hela prognosperioden. Provytor dår beståndsåldern år lågre ån 20 år, samt provytor som i awerkningsberåkningen rojts eller gallrats under senaste tioårsperiod råknas dock bort. Orsaken år att snopacknirig och kvarlåmnade stammar och ris forsvårar eller omojliggor for renen att komma åt laven. Hela den återstående arealen kan dock inte nytt jas for planerad renskotsel. Representanter for tre samebyar bedomd)e 212 av riksskogstaxeringens provytor med marklav med avseende på om de kan nytt jas for planerad renskotsel. Resultatet blev att 3/4 av provytorna ansågs kunna utnyttjas. Provytor råknades bort på grund av belågenlhet nåra byggnader, vågar, jårnvågar och friluftsanlåggningar, eller pga att arealen med marklav var for liten och isolerad for att kunna utnyttjas. Behovet av marklav beråknas som produkten av det genomsnittliga dygnsbehovet for en ren, antalet renar samt det ailital dagar per år som renarna bedoms ha behov av detta foder. De två senare uppgifterna grundas på uppskattningar av personer med stor erfarenhet av renskotsel. Den årliga produktionen av trådlavar består dels av lavtillvåxten i det betningsbara hojdintervallet, dels av trådlav som faller ner på snon. Barrdominerade bestånd aldre ån hundra år antas vara trådlavbårande, men åven denna areal reduceras med hånsyn till praktisk tillgånglighet. Årlig produktion av trådlav inom råckhåll for renen skattas som produkt av mångden trådlav, dess tillvåxtprocent och arealen. Av den trådlav som årli-gen faller n)er på marken antas en fjårdedel vara tillgånglig under vårvintern. Efterfrågan på trådlav beråknas på i princip samma sått som efterfrågan på marklav, men antal betningsda-gar per år åk lågre eftersom trådlav huvudsakligen år ett visserligen hogkvalitativt och låttillgångligt, men dock nodfoder. Resultaten år osåkra av två huvudorsaker. Dels pga inverkan av faktorer som inte ingår i modellen, dels osåkerhetejn i de faktorer som ingår i modellen. Modellen innehåller uppenbart forenklingar av verkliga samband. Dessa forenklingar beror huvudsakligen på viss brist på grunddata. Mojligheterna att dra såkre slutsatser kommer att oka i takt med båttre kunskap om utnyttjade samband och uppgifter. Den geografiska indelningen i lånsdelar beror på utformningen av riksskogstaxeringen. Forhållandena kan givetvis variera inom dessa lånsdelar, som var och en består av ett flertal samebyar. Resultaten får således inte tillåmpas på enskilda samebyar. Studien visar på en metod for att belysa hur renskotselns lavbete kommer att utvecklas i relation till virkes-produktionen. Resultaten år dock allt for osåkra for att man skall kunna dra några såkra slutsatser. Resultaten antyder emellertid att for vissa områden finns redan i dag en brist på lavbete for den renpopulation som kalkylerats med i denna studie. Beråkningarna antyder att produktionen av lavbete kommer att minska i framtiden, vilket bor motivera mer forskning inom området. Om resultaten i denna studie år riktiga och om det virkesproducerande skogsbruket utvecklas enligt exemplet, måste renågarna fortsåtta med eller utoka stodutfodringen och/eller minska antalet renar betydligt. De tvingas också utnyttja alla betningsbara områden, åven sådana som for nårvarande anses vara marginella. Ett annat sått att forbåttra balansen år att modifiera det virkesproducerande skogsbruket på arealer med lavbete i storre utstråckning ån vad som gors i det alternativ som analyseras hår. Puuntuotannon vaikutus jäkälälaitumiin. Abstract in Finnish / Yhteenveto: Artikkelissa esitetåån pitkånaikavålin analyysimalli puuntuotannon vaikutuksista ruotsin jåkålå-laitumille (Cladina, Alectoria, Bryoria spp. ym.). Koska jåkålien saantia pidetåån porojenlukumååråå rajoittava, laskee malli jåkålålaidunten vuotuisen tuoton ja tarpeen. Porot laiduntavat sekå puussa ettå maassa kasvavia jåkåliå, ja nitå molempia on oltava saatavilla, sekå tarvittava måårå, ettå oikeaan aikaan vuodesta, jos poronhoito aikoo selviytyå ilman tukiruokintaa. Malli rakentuu pååsiassa jo aikaisemmin hankittuihin tietoihin. Pinta-ala arviot tehdåån valtakunnanmetsånarvioinnin tietojen, ja hakkuumahdollisuuksien pitkånaikavålin analysoimiseksi perustetun Hugin-systeemin laskelmien avulla (Bengtsson, 1981). Maantieteellisesti tutkielma rajoittuu Norrbotte-nin ja Våsterbottenin lååneihin. Laskelmat tehdåån sadanvuoden aikavålille alkaen 1980, perustuen yhteen AVB-85:en puuntuotantoohjelmaan, joka tåhtåå tåmånpåivåistå laajempaan metsien moninaiskåyttoon (Bengtsson, 1986). Vuotuinen maassa kasvavien jåkålien tuotanto arvioidaan jåkålien hehtaarimåårien, sen kasvuprosentin ja pinta-alan tulona. Jåkålien måårå hehtaaria kohti on riippuvainen kasvupaikan ja metsikon iåstå. Pinta-ala arviot perustuvat valtakunnanmetsånarvioinnin tietoihin. Jåkålåå kasvavien koealojen odotetaan pitåvån jåkå-låkasvustonsa koko prognoosiajan. Koealat, joissa metsikon ikå on alle 20 vuotta, sekå koealat, jotka hak-kuulaskelmissa on perattu tai harvennettu viimeisen kymmenen vuoden aikana, on jåtetty huomioimatta. Syynå tåhån on lumenpakkaantuminen, sekå jåljelle jåtetyt rungot ja oksat, jotka vaikeuttavat tai tekevåt po-rojen jåkålån saannin mahdottomaksi. Vuotuinen puussa kasvavien jåkålien tuotanto koostuu, osittain poron ulottuvilla olevasta, ja osittain lu¬melle putoavasta jakålåstå. Yli sata vuotta vanhojen havupuuvaltaisten metsikkojen oletetaan tuottavan puussa kasvavia jåkåliå, mutta myos tåmå pinta-ala pienenee kåytånnon syistå. Vuotuinen poronulottuvilla puussa kasvavien jåkåliå tuotanto arvioidaan jåkålån måårån, sen kasvuprosentin ja pinta-alan tulona. Yksi neljånnesosa siitå vuosittain lumelle tippuvasta jåkålåmååråstå oletetaan olevan saatavilla kevåttalvella. Puussa kasvavien jåkålien kysyntå lasketaan periaatteessa samalla tavoin kuin maassa kasvavien jåkålien ky-syntå, paitsi ettå vuorokausien måårå vuodessa on pienempi, koska puussa kasvavavien jåkålien katsotaan på-åasiassa olevan håtåravintoa. Tulokset ovat epåvarmoja kahdesta pååsyystå. Osittain niiden tekijoiden vuoksi, jotka eivåt sisålly malliin, osittain niiden tekijoiden epåtarkkuudesta, jotka sisåltyvåt malliin. Malli sisåltåå selviå todellisten yhteyksien yksinkertaistamisia. Nåmå yksinkertaistamiset johtuvat pååasiassa perustietojen puutteesta. Esimerkkinå voidaan mainita, ettå metsån tila muuttuu paljolti prognoosikauden aikana. Tåtå vaihtelua esimerkiksi puus-tossa ei kuitenkaan mallissa huomioida. Esimerkki niiden tekijoiden epåtarkkuudesta, jotka sisåltyvåt malliin, on jåkålålaidunten kasvuprosentti. Toinen esimerkki on jåkålåmåårien arviot, jotka tåsså perustuvat tutkielmiin (Eriksson, julkaisematon), joilla on ollut toinen tarkoitusperå kuin tåsså tutkimuksessa kåsiteltåvien lååninosien laiduntamahdollisuuksien arvioiminen. Mahdollisuudet varmojen johtopååtosten tekoon lisååntyvåt yhdesså parempien perustietojen myotå kåytetyistå yhteyksistå ja tiedoista. Maantieteellinen jako lååninosiin johtuu valtakunnanmetsånarvioinin rakenteesta. Olosuhteet voivat tie-tysti vaihdella nåiden lååninosien sisållå, joista jokainen sisåltåå useamman paliskunnan. Tuloksia ei siis saa tulkita paliskunta kohtaisesti. Tutkielma esittåå tavan valoittaa kuinka porohoidon jåkålålaitumet kehittyvåt suhteessa puuntuotantoon. Tulokset ovat kuitenkin liian epåvarmoja, jotta niistå voitaisiin vetåå varmoja loppupååtelmiå. Tulokset viittaavat kuitenkin, ettå tietyillå alueilla on jo talla hetkellå pula jåkålålaitumista niillå poromåårillå, joilla tassa tutkielmassa on laskettu. Laskelmat viittaavat, ettå tuotanto våhenee tulevaisuudessa, minkå pitåisi motivoida laajempaa tutkimukseen tållå alueella. Jos tulokset tåsså tutkimuksessa ovat oikeat ja jos puuntuotannollinen metsåtalous kehittyy esimerkin mu-kaisesti, pitåå poronomistajien jatkaa tai lisåtå tukiruokintaa ja/tai våhentåå porojen lukumååråå huomatta-vasti. He joutuvat my os hyodyntåmåån kaikki laiduntamiskelpoiset alueet, my os sellaiset jotka tållå hetkellå ovat våhemmån tårkeitå. Toinen tapa par ant aa tasapainoa on sopeuttaa jåkålåalueiden puuntuotannollinen metsåtalous suuremmassa måårin kuin tåsså analysoitavassa vaihtoehdossa tehdåån.