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Biomedical subjects

L Jansson

Publications and source records attributed to L Jansson.

At least 109 records · Page 6Linked to original sources
PubMed1996

Root surface etching at neutral pH promotes periodontal healing.

The purpose of the present investigation was to examine whether an etching agent operating at neutral pH (EDTA) can enhance healing compared to a low pH etching agent (citric acid) in an animal model. Maxillary molars and premolars, in total 32 teeth, in 4 monkeys were divided between test (EDTA or citric acid treatment) and matched control groups. Periodontal surgery on both palatal and buccal roots using the dehiscence model was performed with or without root surface etching. Healing results were evaluated histomorphometrically after 8 weeks. The statistically significant differences between EDTA treated surfaces (n=15) and control surfaces (n=11) were approximately 10% less failure (gingival recession and periodontal pocket), 10 to 15% more total histological attachment (long epithelial junction, connective tissue and reparative cementum), approximately 20% less long epithelial junction and approximately 20% more connective tissue in roots etched with EDTA. The statistically significant differences between citric-acid-treated surfaces (n=14) and control surfaces (n=11) were approximately 10% more connective tissue and 15% less long epithelial junction in the citric acid etched roots. Thus, etching with EDTA appeared to improve healing, avoiding the superficial necrotizing effect on exposed periodontal tissues by citric acid documented in previous studies. Although etching at present is not routinely applied in conventional periodontal therapy, future potential applications of etching at neutral pH may include exposure of the collagenous matrix of dentin for retention of biologically active substances, such as growth factors. Such treatment may be argued to produce a biocompatible surface more conducive to periodontal membrane cell colonization after removal of root-surface- associated smear without compromising the vitality of the surrounding periodontium.

Acid Etching, Dental↗
PubMed1996

Pancreatic islet blood flow in normal and obese-hyperglycemic (ob/ob) mice.

The present study evaluated whether a microsphere technique could be used for islet blood flow measurements in anesthetized mice. When this was confirmed, we applied the technique in different strains of mice. Approximately 9 x 10(4) microspheres could be given without interfering with mean arterial blood pressure. Mixing of the microspheres with arterial blood was adequate, and the extraction of microspheres in capillary beds was nearly 100%. In NMRI mice whole pancreatic blood flow was estimated to be 0.54 +/- 0.11 ml.min-1.g pancreatic tissue-1 and islet blood flow to be 18 +/- 4 microliters.min-1.g pancreas-1 (n = 12 animals per experiment), whereas corresponding values in lean C57Bl/6 mice were twice as high. In C57Bl/6 mice glucose (3 g/kg iv) doubled islet blood flow without affecting whole pancreatic blood flow, whereas no effect was seen after an equimolar dose of 3-O-methylglucose. In obese-hyperglycemic C57Bl/6 mice, islet blood flow was more than five times higher than in the lean C57Bl/6 mice when expressed as blood flow per gram pancreas. However, when islet blood perfusion was corrected for islet weight, it was lower in the obese than in the lean mice, suggesting an impaired ability in obese mice to increase blood flow in concert with the increased islet mass. This may contribute to the insufficient insulin secretion and resulting hyperglycemia seen in these animals.

Animals↗
PubMed1996

Diet-induced obesity and pancreatic islet blood flow in the rat: a preferential increase in islet blood perfusion persists after withdrawal of the diet and normalization of body weight.

The aim of the present study was to evaluate the effects of diet-induced obesity on pancreatic islet blood perfusion in normal Wistar rats. Furthermore, we investigated to what extent any obesity-associated changes in islet blood flow could be reversed after reversion to a normal diet with normalization of body weight. Young adult female Wistar rats were offered a palatable mixed high-caloric diet (cafeteria diet) in addition to standard pelleted chow. Age-matched control rats received standard pelleted chow only. After 4 weeks the diet-treated rats had a body weight of approximately 15% more than that of the controls. All diet-treated rats had decreased glucose tolerance and increased serum insulin concentrations, but basal blood glucose concentrations were similar in anesthetized diet-treated and control rats. Whole pancreatic and islet blood flow rates were measured with a microsphere technique. The islet blood flow as well as fractional islet blood flow were increased (P < 0.01) in rats fed the cafeteria diet, while blood perfusion of the whole pancreas was similar to that of the control rats. In a second experiment, rats received the cafeteria diet for 4 weeks and were then fed standard pelleted food alone for another 3 weeks, while controls received standard diet for 7 weeks. After this period total body weight, retroperitoneal fat pad weight and glucose tolerance were similar to those of the controls. Whole pancreatic blood flow was unchanged as compared with that of control rats. However, both islet blood flow (P < 0.01) and fractional blood flow (P < 0.01) were increased. We conclude that diet-induced obesity in rats is associated with decreased glucose tolerance, hyperinsulinemia and a specific increase in absolute and fractional islet blood perfusion. This increase persists for at least 3 weeks after the diet is withdrawn despite normalization of body weight and glucose tolerance.

Animals↗
PubMed1995

Transplantation of fetal porcine pancreas to diabetic or normoglycemic nude mice. Evidence of a rapid engraftment process demonstrated by blood flow and heat shock protein 70 measurements.

The aims of the present investigation were to study the blood flow rate in transplanted fetal porcine islet-like cell clusters (ICC) with laser-Doppler flowmetry and to evaluate the influence of hyperglycemia on this process. In order to investigate the degree of stress in transplanted beta cells during engraftment, the amount of heat shock proteins (HSP) or stress proteins was measured. ICC were prepared from the fetal porcine pancreas by employing a tissue culture technique. A total volume of 6 microliters (approximately 750) ICC was transplanted under the left kidney capsule of either normo- or hyperglycemic C57BL/6J nude mice. The blood flow to the xenogeneic islet graft and the adjacent kidney parenchyma were measured with laser Doppler flowmetry (LDF). Within 2 hr after transplantation (day 0) or 3, 6, 9, 12 (both normo- and hyperglycemic recipients), 15, 40, or 85 (only normoglycemic recipients) days after implantation of ICC into the nude mice, the hsp70 contents of the grafts were analyzed by means of an immunoassay. Revascularization of the subcapsular ICC graft was initiated rapidly, and 3 days posttransplantation the nutritional blood supply constituted 70% of the adjacent kidney blood flow. This figure increased with time after implantation until the ICC graft had equal or even higher blood perfusion than the adjacent kidney parenchyma. Hyperglycemia in recipients did not affect the revascularization process. Hsp analysis from ICC in culture demonstrated a surprisingly high content of hsp70. However, 3-9 days after transplantation the hsp70 content was markedly reduced in both the normo- and hyperglycemic group and then remained low in both groups. Thus, the present study showed that ICC transplanted into normo- or hyperglycemic nude mice were rapidly revascularized, and that the production of hsp70 was lowered already 3 days after transplantation when compared with cultured ICCs.

Adenosine↗
PubMed1995

A novel pathway for vitamin A signaling mediated by RXR heterodimerization with NGFI-B and NURR1.

In addition to its role as a 9-cis retinoic acid receptor, RXR has an important role in the regulation of multiple hormonal pathways through heterodimerization with nuclear receptors. Here, we show that two orphan receptors, NGFI-B and NURR1, which have been shown previously to interact with DNA as monomers, also can heterodimerize with RXR. These heterodimers bind selectively to a class of retinoic acid response elements composed of direct repeats spaced by 5 nucleotides. In this respect they are similar to heterodimers formed between RXR and the receptor for all-trans retinoic acid, RAR. However, whereas RXR is inhibited in the RXR-RAR heterodimer, NGFI-B/NURR1 promote efficient activation in response to RXR ligands and therefore shift RXR from a silent to an active heterodimerization partner. These data show that NGFI-B and NURR1 can increase the potential of RXR to modulate gene expression in a ligand-dependent manner by allowing a distinct class of direct repeats to serve as specific RXR response elements. Because expression of both NGFI-B and NURR1 is rapidly induced by various growth factors, these findings also suggest a novel mechanism for convergence between vitamin A or retinoid and growth factor signaling pathways.

Base Sequence↗
PubMed1995

The blood flow in pancreatico-duodenal grafts in rats: inhibition of nitric oxide synthase preferentially decreases islet blood flow.

In this study normoglycemic inbred Wistar-Furth rats were implanted with a syngeneic pancreatico-duodenal graft, i.e. a denervated pancreas. The blood flow to the intact native pancreas and to the transplanted gland was measured with a microsphere technique in anesthetized rats 2 weeks after transplantation. The animals were given an intravenous injection with saline alone, NG-nitro-L-arginine (25 mg/kg body weight) or sodium nitroprusside (10 micrograms/kg body weight) 10 min before blood flow measurements. Administration of NG-nitro-L-arginine increased mean arterial blood pressure and caused a pronounced decrease in whole pancreatic blood flow in both the native and transplanted gland. The islet blood flow was more markedly decreased by NG-nitro-L-arginine in both the native and transplanted pancreas, and constituted about 4% of whole pancreatic blood flow compared with 10% in the control animals. Sodium nitroprusside markedly decreased mean arterial blood pressure, but did not affect pancreatic or islet blood flow in any of the glands. It is concluded that inhibition of nitric oxide synthase causes a preferential decrease in islet blood flow both in the native pancreas and in the transplanted pancreas. This suggests that nitric oxide which affects islet blood flow is mainly endothelial-derived, and does not emanate from external nervous fibers.

Amino Acid Oxidoreductases↗
PubMed1995

No role of interleukin-4 in CD23/IgE-mediated enhancement of the murine antibody response in vivo.

Antigen-specific IgE up-regulates the specific IgM, IgG1, IgG2a and IgE response in vivo when given to mice together with antigen. The enhancement is mediated by the low-affinity receptor for IgE, Fc epsilon RII or CD23, as demonstrated both in CD23-deficient mice and by blocking CD23 with anti-CD23 monoclonal antibodies. A possible mechanism behind the regulatory effects of CD23 is that the IgE/CD23/antigen complex is endocytosed by B cells, leading to increased antigen processing and presentation on major histocompatibility complex (MHC) class II molecules to T helper cells. In the present study we have found that the expression of CD23 is reduced fivefold on splenic B cells in mice genetically deficient for IL-4. When IL-4-deficient mice and normal littermates were immunized with 2,4,6-trinitrophenyl (TNP)-specific IgE followed by bovine serum albumin (BSA)-TNP or with BSA-TNP alone, the BSA-specific IgG1 and IgG2a responses were equally well augmented by IgE in all mice. In addition, a low but significant IgE response was seen even in the IL-4-deficient mice. Thus, enhancement of the antibody response through IgE and CD23 occur in the absence of IL-4 and is not dependent on CD23 up-regulation.

Animals↗
PubMed1995

Spreading of the immune response to different myelin basic protein peptides in chronic experimental autoimmune encephalomyelitis in B10.RIII mice.

B10.RIII mice develop chronic and relapsing experimental autoimmune encephalomyelitis (EAE) after immunization with the myelin basic protein (MBP) peptide 89-101 (VHFFKNIVTPRTP). To investigate the basis for the chronicity of the disease, the subsequent development of an immune responses to other parts of the MBP protein were investigated. Onset of disease occurs 9-25 days after immunization with MBP89-101. T cell responses towards a series of MBP peptides were assessed in an enzyme-linked immunospot assay detecting single cells secreting IFN-gamma. There were responses not only to MBP89-101, but also towards peptides derived from sequences outside of MBP89-101. These peptides were of two kinds: those with sequences completely outside the 89-101 stretch of MBP; and those sharing a short sequence with MBP89-101 depending on alternative splicing of MBP mRNA. Immunization with these peptides also produced chronic EAE and a spreading of the immune response to other MBP peptides. Immunization with stepped peptides around the relevant region (MBP87-110) showed that peptides sharing a 6-amino-acid motif induced EAE after immunization. After MBP89-101 peptide immunization, T cells isolated from lymph nodes did not cross-react in vitro to the other peptides sharing this motif. We suggest that one mechanism for the development of relapses during the disease course is the recruitment of new T cells with specificity for MBP peptides not derived from the peptide used for immunization. This is the first time such a mechanism has been demonstrated in a chronic autoimmune disease model.

Amino Acid Sequence↗
PubMed1995

When the severely ill elderly patient refuses food. Ethical reasoning among nurses.

Forty registered nurses (RNs) regarded as "good and experienced" in either cancer or dementia care, were asked about their decision to feed or not feed a severely ill elderly woman (a hypothetical case). In order to compare ethical reasoning in the two groups of nurses and to illuminate what it means to RNs to face a situation where the patients can/cannot decide for themselves, a phenomenological hermeneutic approach was used for the analysis. Both groups saw themselves as the advocate for their patients but in different ways. The RNs who talked about a mentally alert patient emphasized that they encouraged their patient to speak up for herself, while the RNs who talked about a severely demented patient emphasized that they tried very hard to interpret their patient's vague and unclear communicative cues and to act as her advocate, especially in relation to physicians. Transcending experiences of dying relatives and patients as well as role models helped them to achieve their ambition of putting themselves in the patient's shoes in order to respect and understand her or his wish and/or what was best for them. The majority of RNs strongly rejected active euthanasia.

Adult↗
PubMed1995

Pancreatic polypeptide and splanchnic blood flow in anesthetized rats.

The aim of the study was to evaluate the effects of pancreatic polypeptide (PP) on splanchnic blood flow in anesthetized rats. For this purpose, either PP dissolved in saline (225, 450, or 900 pmol/kg body weight/h) or saline alone was infused at a rate of 2 ml/h for 30 min. Immediately after the infusion the blood flow to the whole pancreas, islets, duodenum, and colon was measured with a microsphere technique. The highest dose of PP caused a small decrease in mean arterial blood pressure. The two lowest doses decreased duodenal blood flow, but did not affect the blood perfusion to the other investigated organs. The highest dose of PP decreased the blood flow to the pancreas, islets, and duodenum, did not affect colonic blood flow. No change in the fraction of whole pancreatic blood flow diverted through the islets could be seen after PP administration. It is concluded that administration of high doses of PP induces a general splanchnic vasoconstriction.

Anesthesia↗
PubMed1995

Facial expressions of patients with dementia: a comparison of two methods of interpretation.

Two methods of interpreting the videotaped facial expressions of four patients with severe dementia of the Alzheimer type were compared. Interpretations of facial expressions performed by means of unstructured naturalistic judgments revealed episodes when the four patients exhibited anger, disgust, happiness, sadness, and surprise. When these episodes were assessed by use of a modified version of the Facial Action Coding System, there was, in total, 48% agreement between the two methods. The highest agreement, 98%, occurred for happiness shown by one patient. It was concluded that more emotions could be judged by means of the unstructured naturalistic method, which is based on an awareness of the total situation that facilitates imputing meaning into the patients' cues. It is a difficult task to find a balance between imputing too much meaning into the severely demented patients' sparse and unclear cues and ignoring the possibility that there is some meaning to be interpreted.

Aged↗
PubMed1995

Identification of murine loci associated with susceptibility to chronic experimental autoimmune encephalomyelitis.

B10.RIII mice develop chronic and relapsing experimental autoimmune encephalomyelitis (EAE) after immunization with the myelin basic protein (MBP) peptide 89-101. The disease is associated with the major histocompatibility complex (MHC) (eae1). We have now investigated the importance of non-MHC regions for the EAE susceptibility in a cross between RIIIS/J and B10.RIII mice which share the MHC region but differ in disease susceptibility. Linkage analysis using microsatellite markers spanning the genome identified a region (eae2) on chromosome 15 which showed linkage to disease (P = 0.0002). Our data also suggest linkage to a second region (eae3) on chromosome 3 (P = 0.0024), and provide evidence for locus interactions between eae2 and eae3. These results provide clues to the genetic basis of multiple sclerosis.

Amino Acid Sequence↗
PubMed1995

Long-time etching at low pH jeopardizes periodontal healing.

The purpose of the present investigation was to examine whether the immediate necrotizing effects of low pH etching agents also impair periodontal healing in the long-term perspective. It was concluded that long-time etching (3 min) at low pH of root surfaces surrounded by vital periodontal issues resulted in impaired periodontal healing. In contrast, short-time etching appeared to promote connective tissue formation by preventing epithelialization of the periodontal wound despite its low pH. However, clinical inferences should be drawn with caution from the present results, since healing results recorded at 8 weeks may not prove to be stable, especially for those cases sensitive to the immediate influence of marginal infection such as connective tissue attachments and epithelial junctions, unless optimal oral hygiene is maintained. Furthermore, the choice of acid may be of importance.

Acid Etching, Dental↗
PubMed1995

The influence of endodontic infection on progression of marginal bone loss in periodontitis.

The purpose of the present investigation was to determine magnitude and rate of proximal radiographic attachment loss in relation to endodontic infection in periodontally involved teeth. The investigation was conducted as a retrospective longitudinal study on a periodontitis-prone randomly selected referral population, including 175 single-rooted, root-filled teeth in 133 patients. An observation period of at least 3 years was required. Periapical conditions of the selected sample at baseline and re-examination were evaluated on radiographs, independently by 3 investigators. Each single-rooted, root-filled tooth of the sample was given a score according to the combined registrations. Radiographic attachment level was measured as the distance between the most coronal point of the alveolar bone and the apex at the mesial and distal sides of the tooth, and expressed as relative radiographic attachment level (RRAL) (radiographic attachment level at baseline/root length) at proximal sites for every tooth. Multiple regression analysis was used to study change in RRAL over time. Teeth in periodontitis-prone patients with progressing periapical pathology indicating a continuous root canal infection were found to lose comparatively more radiographic attachment than teeth with no signs of periapical pathology or teeth with an established periapical destruction which subsided during the observation period. An approximate 3-fold amplification of the rate of marginal proximal radiographic bone loss by endodontic infection in periodontitis-prone patients was found with an average 0.19 mm/year, while 0.06 mm/year was lost for teeth without endodontic infection or subsiding endodontic involvement.

Adult↗
PubMed1995

Endodontic pathogens in periodontal disease augmentation.

Periapical pathology indicating endodontic infection, when present in periodontitis-affected teeth, has recently been shown to be correlated to marginal periodontal breakdown. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The aim of the present investigation was to assess the effects of endodontic pathogens on marginal periodontal wound healing on root surfaces devoid of cementum but surrounded by healthy periodontal membrane. Significant differences between infected and non-infected teeth were found with respect to pathological pocket and connective tissue: The experimental defects were covered by approximately 20% more pocket epithelium in infected teeth while defects in non-infected teeth showed approximately 10% more connective tissue coverage. It was concluded, that an intra-canal infection of endodontic pathogens stimulates epithelial downgrowth along denuded dentin surfaces with marginal communication. Extrapolated to the clinical situation, endodontic infections in periodontitis-prone patients may augment periodontitis propagation.

Animals↗
PubMed1995

pH effects on experimental wound healing of human fibroblasts in vitro.

The aim of the present study was to examine to what extent pH affects human fibroblast repopulation of an experimental wound in vitro laying special emphasis on cell migration, DNA synthesis, and alterations in cell morphology. Wounds were simulated in vitro by partially scraping off monolayers of human embryonic diploid lung fibroblast and human periodontal ligament fibroblast-like cells respectively. The wounded monolayers were cultured at pHs ranging from 7.2 to 8.4. The experiments were evaluated by autoradiography as well as light and scanning electron microscopic techniques. A significant, approximately linear, decrease was noted both in cell migration into and DNA synthesis in the experimental wounds as a result of pH increase. The surviving cells in the wounds showed cytoplasmatic vacuoles and blebbing at pH levels above 7.8. Clinical implications of these results for endodontic calcium hydroxide treatment are that hydroxyl ions, diffusing through root dentin, may interfere with vital cell functions necessary for healing on the root surface.

Adult↗
PubMed1995

Endodontic pathogens: propagation of infection through patent dentinal tubules in traumatized monkey teeth.

Periapical pathology indicating endodontic infection, when present in marginal periodontitis-affected teeth, has recently been shown to be an aggravating factor in progression of marginal destruction. This has been associated with patency of dentinal tubules in the tooth cervix, an area normally devoid of cementum following periodontal therapy. These studies are, however hampered by that only circumstantial evidence such as presence of periapical destruction have been applied as criteria of endodontic infection. The purpose of the present investigation was to study to what extent a predefined selection of endodontic pathogens inoculated in the root canal can influence periodontal pathology and healing in areas of the root covered by or devoid of cementum, using root resorption as a histomorphometric marker. Exposed dentine surfaces, in the present study showed significantly larger areas of resorption in infected roots compared to non-infected roots, while cementum surfaces showed an almost identical distribution of tissue reactions regardless of root canal infection or not. It was concluded that endodontic pathogens or their products were not able to penetrate the cementum barrier. The significantly larger areas of resorption on exposed dentine surfaces in infected roots compared to non-infected roots indicated that endodontic pathogens or their products could spread through dentinal tubules to a root surface void of cementum. Extrapolated to the marginal situation this indicated that endodontic pathogens in the root canal might be able to aggravate marginal infection in areas of root devoid of cementum.

Animals↗