Biomedical subjects

F Palm

Publications and source records attributed to F Palm.

15 recordsLinked to original sources

PubMed2003

Reactive oxygen species cause diabetes-induced decrease in renal oxygen tension.

AIMS/HYPOTHESIS: Augmented formation of reactive oxygen species (ROS) induced by hyperglycaemia has been suggested to contribute to the development of diabetic nephropathy. This study was designed to evaluate the influence of streptozotocin (STZ)-induced diabetes mellitus, as well as the effects of preventing excessive ROS formation by alpha-tocopherol treatment, on regional renal blood flow, oxygen tension and oxygen consumption in anaesthetized Wistar Furth rats. METHODS: Non-diabetic and STZ-diabetic rats were investigated after 4 weeks with or without dietary treatment with the radical scavenger DL-alpha-tocopherol (vitamin E, 5%). A laser-Doppler technique was used to measure regional renal blood flow, whilst oxygen tension and consumption were measured using Clark-type microelectrodes. RESULTS: Renal oxygen tension, but not renal blood flow, was lower throughout the renal parenchyma of diabetic rats when compared to non-diabetic control rats. The decrease in oxygen tension was most pronounced in the renal medulla. Renal cellular oxygen consumption was markedly increased in diabetic rats, predominantly in the medullary region. Diabetes increased lipid peroxidation and protein carbonylation in the renal medulla. Treatment with alpha-tocopherol throughout the course of diabetes prevented diabetes-induced disturbances in oxidative stress, oxygen tension and consumption. The diabetic animals had a renal hypertrophy and a glomerular hyperfiltration, which were unaffected by alpha-tocopherol treatment. CONCLUSIONS/INTERPRETATION: We conclude that oxidative stress occurs in kidneys of diabetic rats predominantly in the medullary region and relates to augmented oxygen consumption and impaired oxygen tension in the tissue.

Animals↗

PubMed2003

High-resolution MR technique allowing visualization of the course of the inferior alveolar nerve along cystic processes.

Magnetic resonance imaging is not established in the preoperative diagnosis of mandibular cystic lesions; therefore, no attempts have been made thus far to evaluate the course of the mandibular neurovascular bundle along the process. However, the radiologist can detect the neurovascular bundle along the cystic lesion by high-resolution MR imaging and convey this information to the maxillofacial surgeon. This reduces the risk of intraoperative damage of the nerve. The examination of the neurovascular bundle can easily be integrated in a tumor MRI protocol of the jaw if the slice orientation is adapted to the course of the mandibular canal.

Cysts↗

PubMed2003

[Topography of the inferior alveolar nerve in relation to cystic processes of the mandible in dental MRI].

PURPOSE: Cystic processes are changing the course of the inferior alveolar nerve in the mandible. This study evaluates the possibility of demonstrating the relationship between space-occupying processes and the course of the neurovascular bundle. MATERIALS AND METHODS: Thirteen patients with cystic processes in the mandible (9 keratocystic lesions, 1 eosinophilic granuloma, 1 plasmocytoma, 2 adamantinomas) were examined by MRI (1.5-T magnet, 8-cm surface coil, PD-gradient-echo-sequences in sagittal and coronal orientation, without enhancement) and the results retrospectively evaluated. RESULTS: The entire course of the nerve could be delineated in all patients. In six patients with minor cystic processes, the nerve was identified in both sagittal and coronal orientation. In seven patients with major cystic lesions, only parts of the nerve were detected in either image orientation, but the nerve could be visualized in its entire length by evaluating coronal and sagittal images side by side. CONCLUSION: It is possible to delineate the inferior alveolar nerve in its entirety along pathologic mandibular lesions. For large cystic lesions, this requires the evaluation of both coronal and sagittal sections of multidirectional MRI.

Adolescent↗

PubMed2003

Altered response in renal blood flow and oxygen tension to contrast media in diabetic rats.

PURPOSE: To investigate the effect of the contrast medium (CM) iopromide on renal microcirculation and oxygen tension in non-diabetic control and streptozotocin-diabetic Wistar Furth rats. MATERIALS AND METHODS: Oxygen tension was measured with Clark-type microelectrodes and blood flow with laser-Doppler flow probes. In order to differentiate between an acutely increased blood glucose concentration and a long-term diabetic state, some of the non-diabetic control rats were intravenously infused with glucose. RESULTS: CM decreased the medullary oxygen tension in control (non-diabetic normoglycemic) rats ( approximately 35%) but not in diabetic rats. Medullary blood flow in control rats increased after CM administration and remained elevated, while it was unchanged in the diabetic rats. In response to CM, glucose-infused control rats responded similarly to control animals in medullary oxygen tension, but similarly to diabetic rats in medullary blood flow. Contrary to in control rats, medullary oxygen tension was unchanged in diabetic animals after CM administration. CONCLUSION: Streptozotocin-diabetic rats have an altered response to intravenous injection of the CM iopromide compared to non-diabetic rats. The unaltered medullary oxygen tension, seen in the diabetic group after injection of CM, suggests that non-hemodynamic mechanisms are responsible for the increased frequency of renal failure commonly seen among diabetic patients.

Animals↗

PubMed2003

Et-A receptor antagonist BQ123 prevents radiocontrast media-induced renal medullary hypoxia.

PURPOSE: Renal vasoconstriction with resultant tissue hypoxia, especially in the renal medulla, has been suggested to play a role in contrast media (CM)-induced nephropathy. Endothelin (ET) is released into the blood stream following CM injection and has been proposed as a potential mediator through its vasoconstrictive properties. MATERIAL AND METHODS: To investigate the possible protective influence of ET-receptor antagonists against CM-induced reduction in renal function, we studied the effects of injection of iopromide with and without pretreatment with BQ123 (ET-A antagonist) or BQ788 (ET-B antagonist) on renal superficial cortical flow (CBF), outer medullary blood flow (OMBF) and outer medullary oxygen tension (pO2) in normal rats. RESULTS: Administration of CM (1600 mg I/kg b.w.) did not affect CBF in any of the groups. However, a transient decrease in OMBF occurred, which was unaffected by both BQ123 and BQ788. Also a transient decrease in outer medullary pO2 was induced by CM administration. The pO2 reduction was significantly smaller after pretreatment with BQ123, than after injection of CM alone or together with BQ788, and pO2 returned more rapidly to the control level. Neither receptor antagonist had an effect on CM-mediated increases in electrolyte excretion. CONCLUSION: In the normal rat, activation of ET-A receptors is partly involved in the depression of outer medullary pO2 caused by injection of iopromide. However, the decrease in OMBF after iopromide injection is not mediated by ET receptors. The beneficial effects of the ET-A receptor antagonist on CM-induced changes in outer medullary pO2 seem therefore not primarily mediated on the hemodynamic level but may rather involve tubular transport mechanisms.

Animals↗

PubMed2003

MR imaging of traumatic lesions of the inferior alveolar nerve in patients with fractures of the mandible.

BACKGROUND AND PURPOSE: The objective of this study was to assess whether MR imaging can image the neurovascular bundle in patients with fractures of the mandible. In addition, an attempt was made to evaluate whether MR images provide information regarding the continuity of the inferior alveolar nerve before surgery and regarding signal intensity changes after trauma. METHODS: We analyzed preoperative MR images of 23 patients with mandibular fractures. Object-oriented sagittal view proton density- and T1-weighted sequences (before and after the administration of contrast agent) were used not only in an attempt to obtain purely qualitative information regarding nerve continuity in the neurovascular bundle (inferior alveolar nerve, artery, vein) but also to perform quantitative region-of-interest measurements of signal intensities at four defined measurement sites. The measurements were compared with those obtained for a patient population with healthy mandibles. RESULTS: It was possible to interpret MR images in 21 cases. MR imaging findings showed that the neurovascular bundle had been cut in two patients and was intact in the remaining 19 patients. These MR imaging findings were confirmed intraoperatively in all cases. Although we found no significant signal intensity differences between patients with intact nerves and patients with cut nerves, we found significant differences between patients with mandibular fractures and patients with unremarkable mandibles. CONCLUSION: It is possible to diagnose the interruption of nerve continuity by using MR imaging. Signal intensity measurements in the neurovascular bundle provide no information regarding nerve continuity.

Adolescent↗

PubMed2002

Unaltered oxygen tension in rat pancreatic islets despite dissociation of insulin release and islet blood flow.

The present study investigated the importance of a tightly regulated islet blood flow for an optimal oxygenation of the islet tissue during different demands for insulin release. Glucose and/or a non-specific nitric oxide synthase inhibitor (L-NNA) were infused intravenously in non-pretreated or vagotomized rats and the animals were subjected to measurements of islet blood flow, oxygen tension and serum insulin concentrations. Islet blood flow was measured using a non-radioactive microsphere technique, tissue oxygen tension was recorded with Clark microelectrodes and insulin concentrations were determined by enzyme-linked immunosorbent assay technique. Administration of L-NNA (0.3 mg kg(-1) min(-1)) for 10 min halved basal islet blood flow, but did not affect serum insulin concentrations. Glucose administration (10 mg kg(-1) min(-1)) induced a marked increase in islet blood flow, which could be prevented by vagotomy or L-NNA. The serum insulin concentrations increased in all glucose-infused animals. The islet tissue oxygen tension remained similar in all animals despite these interventions. Reasons other than oxygenation of the islet tissue must explain the normally existing tight regulation of islet blood flow.

Animals↗

PubMed2001

A composite polymer/tricalcium phosphate membrane for guided bone regeneration in maxillofacial surgery.

The aim of the study was the development of a resorbable membrane for guided bone regeneration (GBR) with improved biocompatibility, which should be stiff enough to avoid membrane collapse during bone healing. Combining a bioactive ceramic with a resorbable polymer may improve the biocompatibility and osteoconductivity of resorbable devices. The present article describes the preparation, the mechanical properties, and the in vitro degradation characteristic of a composite membrane made of poly(L, DL-lactide) and alpha-tricalcium phosphate in comparison to a membrane made of pure poly(L, DL-lactide). The tensile strength and the elastic modulus as well as the molecular weight of the membranes were measured after in vitro degradation in buffer at 37 degrees C up to 28 weeks. The initial tensile strength of the composite and the polymer membrane was 37.3 +/- 2.4 MPa and 27.7 +/- 2.3 MPa and the elastic modulus 3106 +/- 108 MPa and 3101 +/- 104 MPa, respectively. The mechanical properties remained constant up to 8 weeks and then decreased slowly until week 28. The molecular weight of both membranes decreased steadily from 170,000 D to 30,000 D. It was concluded that the mechanical requirements for a membrane for GBR were fulfilled by the composite membrane.

Absorbable Implants↗

PubMed2001

Changing dopaminergic activity through different pathways: consequences for renal sodium excretion, regional blood flow and oxygen tension in the rat.

Dopamine (DA) is an intrarenal natriuretic hormone involved in sodium homeostasis, but the regulation of renal dopaminergic tonus is unclear. We evaluated different pathways for elevating DA tonus to determine which are important for the ability of the kidney to produce natriuresis and studied the accompanying effects on regional renal blood flow and oxygen tension. Thus, we compared the effects of a catechol-O-methyl transferase (COMT)-inhibitor, an unspecific monoamine oxidase (MAO)-inhibitor, a D1-like receptor agonist and a DA precursor in anaesthetized rats. Sodium excretion increased sixfold after COMT inhibition, eightfold after administration of the D1-like agonist, whereas it was similar to control after MAO inhibition and infusion of DA precursor. Urinary dopamine excretion increased 42% by COMT inhibition, 55% by MAO inhibition and 12-fold after DA precursor, but remained unchanged after infusion of the D1-like agonist. The D1-like receptor agonist led to a 38% increase in the cortical blood flow and a 21% increase in outer medullary blood flow. Regional renal blood flow was unaffected by all other treatments. Cortical and outer medullary oxygen tension was unaffected in all treatment groups. To conclude, the natriuretic and haemodynamic properties of an elevation in DA tonus depends on the route by which the elevation occurred. Systemic administration of a D1-like receptor agonist, results in a natriuretic response which, as opposed to the natriuresis seen after COMT inhibition, coincides with an increase in renal cortical and outer medullary blood flow. Precursor delivery or MAO inhibition did not change neither urinary sodium excretion nor renal blood flow.

3,4-Dihydroxyphenylacetic Acid↗

PubMed2001

Surgically repaired cleft lips depicted in paintings of the late Gothic period and the Renaissance.

Paintings and drawings by Lucas Moser, Leonardo da Vinci, Albrecht Dürer, and Jacob Cornelisz van Oostsanen suggest that they employed people who had had cleft lips operated on as models for their works of art. Created between 1431 and 1520, the portraits show diagnostic facial profiles with a curved nasal dorsum, short columella, maxillary retrusion, and pseudoprogenia. The first medical illustration of cleft lip surgery was published in 1564 by Ambroise Paré. It was therefore late Gothic and Renaissance artists who depicted the conspicuous signs of surgically treated patients with cleft lip more than 130 years before the surgeons.

Art↗

PubMed2001

Glucose-regulated pulsatile insulin release from mouse islets via the K(ATP) channel-independent pathway.

OBJECTIVE: Regulation of insulin release by glucose involves dual pathways, including or not inhibition of ATP-sensitive K(+) channels (K(ATP) channels). Whereas the K(ATP) channel-dependent pathway produces pulsatile release of insulin it is not clear whether the independent pathway also generates such kinetics. DESIGN AND METHODS: To clarify this matter, insulin secretion and cytoplasmic Ca(2+) ([Ca(2+)](i)) were studied in perifused pancreatic islets from ob/ob mice. Insulin release was measured by ELISA technique and [Ca(2+)](i) by dual-wavelength fluorometry. RESULTS: Insulin secretion was pulsatile (0.2--0.3/min) at 3 mmol/l glucose when [Ca(2+)](i) was low and stable. Stimulation with 11 mmol/l of the sugar increased the amplitude of the insulin pulses with maintained frequency and induced oscillations in [Ca(2+)](i). Permanent opening of the K(ATP) channels with diazoxide inhibited glucose-stimulated insulin secretion back to basal levels with maintained pulsatility despite stable and basal [Ca(2+)](i) levels. Increase of the K(+) concentration to 30.9 mmol/l in the continued presence of diazoxide and 11 mmol/l glucose restored the secretory rate with maintained pulsatility and caused stable elevation in [Ca(2+)](i). Simultaneous introduction of diazoxide and elevation of K(+) augmented average insulin release almost 30-fold in 3 mmol/l glucose with maintained pulse frequency. Subsequent elevation of the glucose concentration to 11 and 20 mmol/l increased the release levels. After prolonged exposure to diazoxide, elevated K(+) and 20 mmol/l glucose, the pulse frequency decreased significantly. CONCLUSIONS: Not only glucose signaling via the K(ATP) channel-dependent but also that via the independent pathway generates amplitude-modulated pulsatile release of insulin from isolated islets.

ATP-Binding Cassette Transporters↗

PubMed2001

Markedly decreased oxygen tension in transplanted rat pancreatic islets irrespective of the implantation site.

In this study, we syngeneically transplanted islets to three different implantation sites of diabetic and nondiabetic rats, then 9-12 weeks later we measured the blood perfusion and compared the tissue partial pressure of oxygen (PO2) levels of these transplanted islets to endogenous islets. Modified Clark microelectrodes (outer tip diameter 2-6 microm) were used for the oxygen tension measurements, and islet transplant blood perfusion was recorded by laser-Doppler flowmetry (probe diameter 0.45 mm). The islet graft blood perfusion was similar in all islet grafts, irrespective of the implantation site. In comparison, the three implantation organs (the kidney cortex, liver, and spleen) differed markedly in their blood perfusion. There were no differences in islet graft blood perfusion between diabetic and nondiabetic recipients. Within native pancreatic islets, the mean PO2 was approximately 40 mmHg; however, all transplanted islets had a mean PO2 of approximately 5 mmHg. The oxygen tension of the grafts did not differ among the implantation sites. In diabetic recipients, an even lower PO2 level was recorded in the islet transplants. We conclude that the choice of implantation site seems less important than intrinsic properties of the transplanted islets with regard to the degree of revascularization and concomitant blood perfusion. Furthermore, the mean PO2 level in islets implanted to the kidney, liver, and spleen was markedly decreased at all three implantation sites when compared with native islets, especially in diabetic recipients. These results are suggestive of an insufficient oxygenization of revascularized transplanted islets, irrespective of the implantation site.

Animals↗

PubMed2001

Transient glomerular hyperfiltration in the streptozotocin-diabetic Wistar Furth rat.

The glomerular hemodynamic response to streptozotocin (STZ)-induced experimental diabetes differs depending on metabolic control and rat strain used. The present study characterize the glomerular filtration rate (GFR) and other renal parameters, weekly up to eight weeks of diabetes in STZ-diabetic Wistar Furth rats. The STZ-treated rats became diabetic within 24 h after treatment and retained a blood glucose concentration of 20-25 mmol/l throughout the experimental period. The GFR was transiently increased during the first 3-5 weeks after induction of diabetes, but thereafter did not differ from control animals. The renal weight increased by approximately 50% during the first week after induction of diabetes, thereafter no further increase in weight occurred. The urinary flow rate and urinary osmolar excretion were approximately 10 times higher in diabetic animals when compared to non-diabetic animals. Although they remained markedly higher than in non-diabetic animals, both the urinary flow rate and the urinary osmolar excretion peaked after 3 weeks of diabetes and thereafter tended to decrease. The urinary sodium and potassium excretions did not differ between non-diabetic and diabetic animals. We conclude that the transient increase in the GFR seen in the human disease, occurs in Wistar Furth rats, which is in contrast to a majority of other rat strains, where the GFR is persistently increased.

Animals↗

PubMed2000

Chronically decreased oxygen tension in rat pancreatic islets transplanted under the kidney capsule.

BACKGROUND: A factor of potential importance in the failure of islet grafts is poor or inadequate engraftment of the islets in the implantation organ. This study measured the oxygen tension and blood perfusion in 1-, 2-, and 9-month-old islet grafts. METHODS: The partial pressure of oxygen was measured in pancreatic islets transplanted beneath the renal capsule of diabetic and nondiabetic recipient rats with a modified Clark electrode (outer tip diameter 2-6 microm). The size of the graft (250 islets) was by purpose not large enough to cure the diabetic recipients. The oxygen tension in islets within the pancreas was also recorded. Blood perfusion was measured with the laser-Doppler technique. RESULTS: Within native pancreatic islets, the partial pressure of oxygen was approximately 40 mm Hg (n=8). In islets transplanted to nondiabetic animals, the oxygen tension was approximately 6-7 mm Hg 1, 2, and 9 months posttransplantation. No differences could be seen between the different time points after transplantation. In the diabetic recipients, an even more pronounced decrease in graft tissue oxygen tension was recorded. The mean oxygen tension in the superficial renal cortex surrounding the implanted islets was similar in all groups (approximately 15 mm Hg). Intravenous administration of glucose (0.1 gxkg(-1)x min(-1)) did not affect the oxygen tension in any of the investigated tissues. The islet graft blood flow was similar in all groups, measuring approximately 50% of the blood flow in the kidney cortex. CONCLUSION: The oxygen tension in islets implanted beneath the kidney capsule is markedly lower than in native islets up to 9 months after transplantation. Moreover, persistent hyperglycemia in the recipient causes an even further decrease in graft oxygen tension, despite similar blood perfusion. To what extent this may contribute to islet graft failure remains to be determined.

Animals↗

PubMed2000

Engraftment and growth of transplanted pancreatic islets.

Transplantation of pancreatic islets may provide a cure for type 1 diabetes. However, this treatment can currently be offered only to very few patients. To improve transplantation success we need to understand better the mechanisms of how the implanted islets survive, grow and/or maintain adequate function. We herein report on our studies to evaluate the factors responsible for the engraftment, i.e. revascularization, reinnervation etc., of transplanted islets and relate these factors to the metabolism and growth of the islets. Graft metabolism can be monitored by microdialysis probes that allow for the measurement of minute amounts of islet metabolites and hormonal products. Growth of the endocrine cells can be stimulated both in vitro before implantation and in vivo post-transplantation. Another problem is rejection of transplanted islets, which may be overcome by the microencapsulation of islets. The knowledge gained by the present studies will enable us to elucidate the optimal treatment of islets to ensure a maximal survival of the transplanted islets, and may be applied also to clinical islet transplantation.

Animals↗