Biomedical subjects

S Lindskog

Publications and source records attributed to S Lindskog.

At least 73 records · Page 4Linked to original sources

PubMed1994

Differential periodontal temperature measurements in the assessment of periodontal disease activity: an experimental and clinical study.

The difference in surface temperatures between the bottom of periodontal pockets and the attached gingiva adjacent to the openings of the pockets were determined both in monkeys with experimental marginal periodontitis, and clinically in patients with marginal periodontitis. For this purpose a custom-made, temperature-measuring device was developed which enabled immediate recording of temperature differences as well as periodontal pocket depths, bleeding, and attachment levels. The measurements were performed periodically. The differential temperature measurements were correlated to change in periodontal attachment over time. It was shown that differential periodontal temperatures are well correlated to change in periodontal attachment over time. It was furthermore concluded that differential periodontal temperature measurements have the potential of serving as a predictor of activity of marginal periodontitis. However, more extensive data are required to assess the sensitivity and specificity of the method.

Animals↗

PubMed1994

Root surface texture after different scaling modalities.

Root surface texture after scaling with hand instruments, ultrasonic scalers (Amdent 830 and Cavi-Med 2000), and a sonic scaler (Titan-S) was assessed in vitro. The experimental material consisted of 48 extracted human teeth divided into six groups. Root surface texture was assessed with scanning electron microscopy (SEM). Hand and sonic instrumentation produced large grooves and removed cementum evident at a magnification of x 70, while the root surface alterations after ultrasonic instrumentation were not detectable below a magnification of x 500. The working principle of each scaling instrument in relation to its effect on the root surface was discussed.

Dental Cementum↗

PubMed1994

Oral hairy leukoplakia: pathogenetic aspects and significance of the lesion.

Oral hairy leukoplakia in HIV-seropositive persons is considered as a highly serious sign and places the patient in the AIDS-related complex group according to the classification recommended by the Centers for Disease Control. Epstein-Barr virus (EBV) is thought to be the cause. Based on the investigation of 14 of our own cases and a review of the literature, we conclude that so called hairy leukoplakia does not have a specific histopathologic pattern. Identical lesions can be caused by fungus infection, or biting and other kinds of mechanical irritation. Both fungal infection and EBV infection have been proven in a high percentage of the lesions. However, EBV has been found also in apparently normal oral mucosa. This questions the assumption that the virus is the cause of the lesions. In our investigation the presence of "hairy leukoplakia" did not reflect the clinical status of the patient. The best indicator of the clinical status was the T-lymphocyte subset CD4+ number in the peripheral blood. It appears that low CD4+ counts, candidiasis and the presence of replicating EBV in the epithelial cells are parallel markers of increasing immunodeficiency.

Adult↗

PubMed1994

The micromorphology in vivo of the buccocervical region of premolar teeth in young adults. A replica study by scanning electron microscopy.

The buccal surfaces of premolar teeth are common sites of gingival recession, generally attributed to overzealous oral hygiene. Scanning electron microscopy (SEM) of replicas made from dental impressions was applied to document the micromorphology of the buccocervical region of all premolar teeth in 27 dentally healthy, young adults. The SEM observations were correlated with clinical examination. Of the 216 sites, one-third, predominantly the maxillary first premolars, had gingival recession, but fewer than 50% were clinically discernible. The exposed roots were devoid of cementum, and the dentinal surface was smear-like or dotted with tubular apertures from which droplets of fluid extruded. SEM of replicas of gingiva, recorded as clinically healthy, frequently showed signs of inflammation: fluid exudate and distortion of gingival contour by swelling. The cervical enamel of healthy and affected sites showed characteristic periodic fissure-like cracks, probably enamel tufts. The high frequency of subclinical gingival recession, exposed cervical dentin, and gingival inflammation in dentally healthy young adults, in the absence of abrasion of hard or soft tissues, indicates the need to review conventional concepts of initiation of buccal recession and root exposure.

Adult↗

PubMed1994

Quality of periodontal healing. I: Review of the literature.

This summary focuses on quality of healing following periodontal surgical and non surgical procedures. It is based on a survey of the literature on clinical, radiographic and histological assessment as well as on 3 recent studies on the quality of periodontal healing published in this Journal.

Alkaline Phosphatase↗

PubMed1994

Quality of periodontal healing. II: Dynamics of reparative cementum formation.

The purpose of the present study was to follow the formation of mineralised tissue (reparative cementum) on instrumented root surfaces. Twenty-four permanent maxillary and mandibular laterals from six, 3-4-year-old monkeys (macaca fascicularis) were used in the experiment. The incisors were gently extracted and the periodontal membrane (PDM) and cementum on the mesial surface of the roots removed to a distance of 1-2 mm from both the cemento-enamel junctions and the apices of the roots. The teeth were subsequently replanted. Ankylosis was seen both after 3 and 5 wks, although to a lesser degree at 5 wks to be virtually absent at 10 wks. It appeared that the resorptive activity predominant at 5 wks had removed the ankylotic fusion. After 10 weeks, a remaining layer of mineralised tissue, commonly referred to as reparative cementum was seen to cover the denuded dentine surfaces in the present study. It appeared not to be firmly attached to the root surface and did not show a normal cementum-morphology in polarised light. It had a multi-layered appearance resembling alveolar bone tissue and the connective tissue fibres adjacent to the reparative mineralised tissue-layer were not functionally oriented but rather parallel to the root surface. It was concluded that the formation of this mineralised tissue (rearative cementum) was the result of a transient ankylosis.

Alveolar Bone Loss↗

PubMed1994

Quality of periodontal healing. III: Periodontal width following long epithelial junction or reparative cementum formation.

The purpose of the present study was to compare the width of the periodontal space following two different marginal periodontal healing reactions (long epithelial junction and connective tissue healing involving formation of reparative cementum) with the width of normal periodontium, either intact or following reattachment. Twelve permanent lateral incisors in monkeys from a previous experimental study on periodontal wound healing on denuded surfaces were selected based on strict healing criteria. The periodontal width was measured histomorphometrically and compared to the periodontal width on the contra lateral side of the same root where reattachment had taken place and with the width of normal periodontal space of neighbouring untreated teeth. The mean periodontal width for both after formation of a long junctional epithelium and reparative cementum were significantly larger than the control width, approximately 290%. This may be taken as evidence of an impaired functional adaptation of the reparative tissue compared to a reestablished or normal periodontal membrane.

Animals↗

PubMed1994

Quality of periodontal healing. IV: Enzyme histochemical evidence for an osteoblast origin of reparative cementum.

The aim of the present study was to map the distribution of healing gingival and periodontal connective tissue well as osteoblastic activity in marginal periodontal wound healing using activity of alkaline phosphatases as markers. Activity of non-specific alkaline phosphatase (NSAP) was abundant in periodontal but not in gingival connective tissue. Activity of vanadate-resistant alkaline phosphatase (VRAP) had a preferential localisation to periosteal and endosteal bone surfaces but was not detectable in cementoblasts along root surfaces. However, following spontaneous marginal healing of exposed dentine surfaces, activity of VRAP was also found on healing dentine surfaces. It was concluded that osteoblasts rather than cementoblasts form reparative cementum on exposed dentine surfaces during marginal periodontal healing.

Alkaline Phosphatase↗

PubMed1993

Proton transfer in the catalytic mechanism of carbonic anhydrase. Effects of placing histidine residues at various positions in the active site of human isoenzyme II.

The maximal rate of CO2 hydration catalyzed by human carbonic anhydrase II (carbonate hydro-lyase, EC 4.2.1.1) is limited by proton transfer steps involving the acid-base function of His-64. To test whether or not the precise location of this proton transfer group is critical, histidine residues were placed in various positions in the active site of the enzyme. Thus, four double mutants were made, all with His-64 replaced by Ala-64, and with a histidine residue replacing Asn-62, Ala-65, Asn-67 or Thr-200. The results show that the mutants with His-62, His-67 and His-200, but not the mutant with His-65, yield significantly higher kcat values for CO2 hydration than the single mutant with Ala-64, indicating that His-62, His-67 and His-200 can contribute to proton transfer between the metal center and the reaction medium. However, the average proton transfer efficiency of these histidines is only about 5% of that of His-64 in the unmodified enzyme.

Binding Sites↗

PubMed1993

Blockade of galanin-induced inhibition of insulin secretion from isolated mouse islets by the non-methionine containing antagonist M35.

The neuropeptide galanin occurs in pancreatic adrenergic nerves and has been suggested to be the adrenergic mediator of the stress-induced inhibition of insulin release. To study its physiological function, we recently synthesized a galanin-like galanin receptor antagonist, galantide. However, this antagonist contains a methionine moiety, and is therefore easily oxidized. We have now synthesized another galanin antagonist which does not contain methionine. This peptide, M35, is a chimeric 21 amino acid peptide in which galanin-(1-13) is coupled to bradykinin-(2-9). M35 (10 microM to 1 pM) had no effect by itself on glucose (11.1 mM)-stimulated insulin secretion in isolated mouse islets, but potently counteracted the inhibitory action of galanin (100 nM). The lowest effective dose of M35 was 10 nM. M35 did not counteract the inhibitory action of clonidine (1 microM) or somatostatin (1 microM) on insulin secretion. Furthermore, M35 displaced 125I-monoiodo-[Tyr26]galanin from membranes of insulin producing RINm5F cells. The displacement curve fitted to a two-site model in which 60% of label bound with a K1 of 0.1 +/- 0.01 nM and 40% with a K2 of 3 +/- 0.5 nM. In conclusion, M35 is a specific, non-methionine-containing galanin receptor antagonist on insulin-producing cells.

Amino Acid Sequence↗

PubMed1993

Importance of the conserved active-site residues Tyr7, Glu106 and Thr199 for the catalytic function of human carbonic anhydrase II.

The catalytic mechanism of carbonic anhydrase includes the reaction of a zinc-bound hydroxide ion with the CO2 substrate. This hydroxide ion is part of a hydrogen-bonded network involving the conserved amino acid residues Thr199, Glu106 and Tyr7. To investigate the functional importance of these residues, a number of site-specific mutants have been made. Thus, Thr199 has been changed to Ala, Glu106 to Ala, Gln and Asp, and Tyr7 to Phe. The effects of these mutations on catalyzed CO2 hydration and ester hydrolysis have been measured, as well as the binding of some inhibitors. The results show that the CO2 hydration activity of the mutant with Phe7 is only marginally reduced, whereas the esterase activity is larger than that of unmodified enzyme. It is concluded that Tyr7 is not a functionally required element of the hydrogen-bonded network. The CO2 hydration activity (kcat as well as kcat/Km) and the esterase activity of the mutant with Ala199 are reduced about 100-fold. The affinity for the sulfonamide inhibitor, dansylamide, is only slightly reduced while the mutant has an enhanced affinity for bicarbonate and the anionic inhibitor, SCN-. The activities of the mutants with Ala106 and Gln106 are also reduced. The reduction of the esterase activity is about 100-fold, while kcat for CO2 hydration has decreased by a factor of 1000. The parameter kcat/Km is only about one order of magnitude smaller for these mutants than for the unmodified enzyme. The binding of dansylamide and another sulfonamide inhibitor, acetazolamide, are about 20-times weaker to the mutant with Gln106 than to unmodified enzyme. These results suggest important roles for Thr199 and Glu106 in carbonic anhydrase catalysis. The mutant with Asp106 is almost fully active suggesting that the structure has undergone a compensatory change to maintain the interaction between residue 106 and Thr199.

Amino Acid Sequence↗

PubMed1993

Crystallographic analysis of Thr-200-->His human carbonic anhydrase II and its complex with the substrate, HCO3-.

A complex of carbonic anhydrase (CA) with one of its substrates, bicarbonate, has been studied crystallographically. Human isoenzyme II was mutated at position 200 from threonine to histidine, which results in higher affinity for bicarbonate. The HCO3- ion binds in the active site to the zinc ion as a pseudo-bidentate ligand which gives the metal a coordination geometry between tetrahedral and trigonal bipyramide. The water/hydroxide normally bound with tetrahedral coordination to the zinc is probably replaced by the OH group of the bicarbonate ion. The importance of residues Thr-199 and Glu-106 in controlling the binding orientation of HCO3- is discussed as well as the catalytic mechanism. Both the complex as well as the uncomplexed mutant were studied at 1.9 A resolution.

Bicarbonates↗

PubMed1993

Structural analysis of the zinc hydroxide-Thr-199-Glu-106 hydrogen-bond network in human carbonic anhydrase II.

The significance of the zinc hydroxide-Thr-199-Glu-106 hydrogen-bond network in the active site of human carbonic anhydrase II has been examined by X-ray crystallographic analyses of site-specific mutants. Mutants with Ala-199 and Ala-106 or Gln-106 have low catalytic activities, while a mutant with Asp-106 has almost full CO2 hydration activity. The structures of these four mutants, as well as that of the bicarbonate complex of the mutant with Ala-199, have been determined at 1.7 to 2.2 A resolution. Removal of the gamma atoms of residue 199 leads to a distorted tetrahedral geometry at the zinc ion, and a catalytically important zinc-bound water molecule has moved towards Glu-106. In the bicarbonate complex of the mutant with Ala-199 one oxygen atom from bicarbonate binds to zinc without displacing this water molecule. Tetrahedral coordination geometries are retained in the mutants at position 106. The mutants with Ala-106 and Gln-106 have a zinc-bound sulfate ion, whereas this sulfate site is only partially occupied in the mutant with Asp-106. The hydrogen-bond network seems to be "reversed" in the mutants with Ala-106 and Gln-106. The network is preserved as in native enzyme in the mutant with Asp-106 but the side chain of Asp-106 is more extended than that of Glu-106 in the native enzyme. These results illustrate the importance of Glu-106 and Thr-199 for controlling the precise coordination geometry of the zinc ion and its ligand preferences which results in an optimal orientation of a zinc-bound hydroxide ion for an attack on the CO2 substrate.

Carbonic Anhydrases↗

PubMed1993

Relationship between periapical and periodontal status. A clinical retrospective study.

The purpose of the present investigation was to explore possible relationships between clinical periodontal status in periodontally involved teeth with and without endodontic infection. The investigation was conducted as a retrospective study on a consecutive referral population. The periapical conditions in endodontically-involved single-rooted teeth from a selected patient sample were evaluated and correlated to their periodontal status. There was a significant correlation between periapical pathology and vertical bony destructions. An intra-individual comparison between pocket depth in teeth with and without periapical pathology showed that periapical pathology was significantly correlated to an increased pocket depth in the absence of a vertical bony destruction. It was concluded that an endodontic infection, evident as a periapical radiolucency, promotes periodontal pocket-formation on an instrumented marginal root surface and, consequently, should be regarded as a risk factor in periodontitis progression and be given appropriate consideration in periodontal treatment planning.

Adult↗

PubMed1993

Periodontal healing in teeth with periapical lesions. A clinical retrospective study.

The purpose of the present investigation was to compare clinical periodontal healing in periodontally involved teeth with and without pulpal pathosis. The investigation was conducted as a retrospective study on a consecutive referral population. The periapical conditions in endodontically involved single-rooted teeth from a selected patient sample were evaluated and correlated with their periodontal healing pattern. Multiple regression analysis of the registered variables showed that initial mean pocket depth and time elapsed after treatment significantly influenced change in pocket-depth. Non-surgical treatment of periodontal pockets exceeding 2.5 mm in teeth with horizontal marginal defects, over the observation period, showed significantly reduced mean pocket depth reduction in teeth with periapical pathology compared to teeth without periapical pathology. It was, furthermore, evident that proximal restorations, abutments for fixed bridges and root fillings with and without dowels did not significantly influence pocket depth reduction in the present material. It was concluded, based on the present results, that a root-canal infection, evident as a periapical radiolucency, if left untreated may in the long term perspective result in retarded or impaired periodontal healing following periodontal therapy and, consequently, should be given appropriate consideration when coordinating endodontic therapy and periodontal treatment.

Adult↗

PubMed1993

Successive removal of periodontal tissues. Marginal healing without plaque control.

The aim of the present study was to compare periodontal healing after successive removal of periodontal tissue components, from the alveolar bone to the dentin surface. The prevailing tissue reaction when adhering PDM was left on the exposed roots was that most of the bone tissue that had been removed from the buccal surfaces had regenerated and the integrity of the PDM between the new alveolar bone and cementum surface had been reestablished. On exposed etched cementum surfaces, 2 prevailing healing results were recorded. In half the number of the roots, the root surfaces were covered by connective tissue with fibers running parallel to the root surfaces in a capsule-like arrangement. The other prevailing reaction was a thin epithelial cell-lining running parallel to the root surfaces in close contact or partly penetrating the adjacent connective tissue. On exposed denuded dentin surfaces, gingival retraction was a constant finding, associated with an epithelial cell-lining of varying thickness sometimes with rete pegs and cyst-like formations. Gingival retraction was also a constant finding on etched dentin surfaces. This was associated with pathological pockets outlined by epithelial cell-layers of varying thicknesses. The significance of these findings were discussed with special emphasis on dynamics of recurrent periodontitis.

Acid Etching, Dental↗

PubMed1993

The amelocemental junction in young premolar teeth. A replica study by scanning electron microscopy.

To investigate the validity of traditional data on the frequency of various relationships of root cementum to coronal enamel at the amelocemental junction, the relationship in 50 young premolar teeth extracted on orthodontic indications was documented, using replica techniques for scanning electron microscopy (SEM), combined with polarization microscopy of thin ground sections (< 40 microns). Of 200 surfaces, 30 were excluded because of damage during specimen preparation. Replicas of the other 170 surfaces were photographed at 20x and 80x in SEM and classified as having an edge-to-edge relationship of enamel to cementum in 76% and an overlap of cementum onto the cervical enamel in 14%. What appeared to be a gap between enamel and cementum at low magnification (10%) was seen at high magnification to be a ditch or trough in the cementum: no gaps with exposed dentin were observed in SEM. Polarization microscopy of ground sections of the original specimens confirmed the SEM classification. In this material, the edge-to-edge relationship of enamel to cementum predominated: overlapping of cementum onto the enamel was less prevalent than previously reported. The methods applied in this study circumvented some major sources of artefact formation due to shrinkage during specimen preparation, which may previously have caused misinterpretation of 'gap' relationships.

Bicuspid↗

PubMed1993

Development of periapical lesions.

The purpose of the present study was to follow the development of periapical lesions both radiographically and histologically in infected teeth with open and sealed root canals. The mandibular premolars from five adult monkeys were used in the experiment. Sealed infected teeth developed radiographic signs of periapical pathosis significantly earlier than unsealed teeth. Although, histological signs of pathology could be seen periapically at earlier observation periods, sealed teeth consistently developed these changes earlier than unsealed teeth. Furthermore, the histological periapical pathology differed somewhat between the two groups in that unsealed teeth showed a multi-focal diffuse pattern of spreading.

Animals↗