Influence of microenvironment on engraftment of transplanted β-cells

Pancreatic islet transplantation into the liver provides a possibility to treat selected patients with brittle type 1 diabetes mellitus. However, massive early β-cell death increases the number of islets needed to restore glucose homeostasis. Moreover, late dysfunction and death contribute to the poor long-term results of islet transplantation on insulin independence. Studies in recent years have identified early and late challenges for transplanted pancreatic islets, including an instant blood-mediated inflammatory reaction when exposing human islets to the blood microenvironment in the portal vein and the low oxygenated milieu of islets transplanted into the liver. Poor revascularization of remaining intact islets combined with severe changes in the gene expression of islets transplanted into the liver contributes to late dysfunction. Strategies to overcome these hurdles have been developed, and some of these interventions are now even tested in clinical trials providing a hope to improve results in clinical islet transplantation. In parallel, experimental and clinical studies have, based on the identified problems with the liver site, evaluated the possibility of change of implantation organ in order to improve the results. Site-specific differences clearly exist in the engraftment of transplanted islets, and a more thorough characterization of alternative locations is needed. New strategies with modifications of islet microenvironment with cells and growth factors adhered to the islet surface or in a surrounding matrix could be designed to intervene with site-specific hurdles and provide possibilities to improve future results of islet transplantation

Metabolizam anorganskog olova u profesionalno eksponiranih ljudi

Decay rates of blood lead levels in 29 lead workers after end of exposure were analysed mathematically with an exponential two-compartment model. The slow pool had a median half-time of about 5 years, the fast one about one month, but with a considerable inter-individual variation. Lead levels in finger-bone, as determined in 73 active and retired workers by an X-ray fluorescence method, ranged from less than 20 up to 135 mg/kg. There was an increase of finger-bone lead level with increasing exposure time (maximum about 10 mg/kg/year), but the variation between individuals was considerable. In retired workers there was an association between lead levels in finger-bone and blood; an increase of 100-150 mg/kg corresponded to about 1.5 µmol/l. Bone lead levels in biopsies from vertebral spinous processes of 28 lead workers were often lower or higher than in finger-bone, suggesting at least two bone lead pools. Lead level in bone may be practically useful to determine the extent of »internal« lead exposure by mobilization from the skeleton.Napravljena je matematička analiza smanjenja razine olova u 29 radnika pomoću modela s dva kompartmenta. Spori dio kompartmenta imao je vrijeme polovičnog nestanka od otprilike pet godina, a brzi od otprilike jedan mjesec. Postojale su značajne individualne varijacije. Razina olova u falangama kretala se između 20 i 135 mg/kg, kao što je utvrđeno fluorescentnom metodom s X-zrakama u 73 aktivna i umirovljena radnika. Razina olova u kosti rasla je s vremenom ekspozicije s maksimumom od 10 mg/kg. U umirovljenih radnika postojala je povezanost između koncentracije olova u kosti i one u krvi. Povećanje od 100 do 150 mg/kg u kosti odgovaralo je otprilike 1.5 µmol/L. Koncentracija olova u spinalnim nastavcima kralješaka bila je često veća ili manja od one u falangama, što upućuje na postojanje barem dvaju kompartmenta. Razina olova u kosti može poslužiti u praktične svrhe za procjenu moguće interne ekspozicije olovu mobiliziranjem iz skeleta

Nickel-doped agarose gel phantoms in MR imaging

A method for the production of a tissue-mimicking phantom material for MR imaging is described. The material consists of a nickel-doped agarose gel. The T1 and T2 values of the gel can be varied independently by changing the relative amounts of nickel and agarose. Practically any T1 and T2 combination of clinical interest can be obtained. The long-term stability was studied and found to be good. The relaxation times were estimated using an MR analyzer. The accuracy and the reproducibility of these measurements were evaluated and found to be reassuring. Gel phantoms were also scanned in an MR unit. The signal strength of an inversion recovery sequence was evaluated using the gel phantoms in order to verify their usefulness. These measurements were compared to theory with good agreement. Furthermore, tissue-equivalent phantoms were made. Gels resembling gray matter, white matter, and CSF were scanned. Comparisons with clinical in vivo scans, as well as calculated levels were made. It is anticipated that the gel phantoms described here will be useful in quality assurance as well as in pulse sequence optimization

Metabolizam anorganskog olova u profesionalno eksponiranih ljudi

Decay rates of blood lead levels in 29 lead workers after end of exposure were analysed mathematically with an exponential two-compartment model. The slow pool had a median half-time of about 5 years, the fast one about one month, but with a considerable inter-individual variation. Lead levels in finger-bone, as determined in 73 active and retired workers by an X-ray fluorescence method, ranged from less than 20 up to 135 mg/kg. There was an increase of finger-bone lead level with increasing exposure time (maximum about 10 mg/kg/year), but the variation between individuals was considerable. In retired workers there was an association between lead levels in finger-bone and blood; an increase of 100-150 mg/kg corresponded to about 1.5 µmol/l. Bone lead levels in biopsies from vertebral spinous processes of 28 lead workers were often lower or higher than in finger-bone, suggesting at least two bone lead pools. Lead level in bone may be practically useful to determine the extent of »internal« lead exposure by mobilization from the skeleton.Napravljena je matematička analiza smanjenja razine olova u 29 radnika pomoću modela s dva kompartmenta. Spori dio kompartmenta imao je vrijeme polovičnog nestanka od otprilike pet godina, a brzi od otprilike jedan mjesec. Postojale su značajne individualne varijacije. Razina olova u falangama kretala se između 20 i 135 mg/kg, kao što je utvrđeno fluorescentnom metodom s X-zrakama u 73 aktivna i umirovljena radnika. Razina olova u kosti rasla je s vremenom ekspozicije s maksimumom od 10 mg/kg. U umirovljenih radnika postojala je povezanost između koncentracije olova u kosti i one u krvi. Povećanje od 100 do 150 mg/kg u kosti odgovaralo je otprilike 1.5 µmol/L. Koncentracija olova u spinalnim nastavcima kralješaka bila je često veća ili manja od one u falangama, što upućuje na postojanje barem dvaju kompartmenta. Razina olova u kosti može poslužiti u praktične svrhe za procjenu moguće interne ekspozicije olovu mobiliziranjem iz skeleta

Dosimeter gel and MR imaging for verification of calculated dose distributions in clinical radiation therapy

A dosimeter gel, based on an agarose gel infused with a ferrous sulphate solution and evaluated in a magnetic resonance scanner, was used for complete verification of calculated dose distributions. Two standard treatment procedures, treatment of cancer in the urinary bladder and treatment of breast cancer after modified radical mastectomy, were examined using pixel-by-pixel and dose volume histogram comparison. The dose distributions calculated with the dose planning system was in very good agreement with the measured ones. However, in the case of the more complicated breast cancer treatment, some discrepancies were found, mainly at the beam abutment region. This may be explained by field displacements errors and by a small limitation of the dose planning utilising small electron beams in this region. The dosimeter gel system have proven to be a useful tool for dosimetry in clinical radiation therapy applications