Effect of hypophysectomy on dentin production in maxillary incisors in the rat

abstract — The effect of hypophysectomy on the dentin production and on the longitudinal growth of the maxillary incisors of female rats 60–105 d of age was determined In- the tetracycltne technique. In normal rats, the highest rate of dentin apposition amounted to about 23μm per clay in the middle part of the tooth with lower values in apical and incisal directions. Because of incisal attrition, the tooth was exchanged in about 55 d, corresponding to a longitudinal growth rate of'about 400μm per day. After hypophysectomy, the rate of dentin production was reduced to about 60%, with a considerable variation depending on the position of the odontoblasts along the tooth. The longitudinal growth rate was reduced to about 50% of normal. As the length of the tooth was the same within the period studied, this resulted in a slower transfer of the odontoblasts along the tooth and a time delay of about 55 d before they reached the incisal part of the tooth. The total dentin production of the odontoblasts in the hypophysectomized animals was the same as in normals. Compared with the effect of hypophysectomy on the rate of longitudinal bone growth and cortical bone remodeling, the effect on the dentin production and longitudinal growth of the incisors is less pronounced, indicating differences in sensitivity to hormones between the different cell systems.     

Morphometric analysis of occlusal groove-fossa-system in mandibular third molar

Abstract – Based on serially cut 200-μm-thick sections from 21 human mandibular third molars, a quantitative characterization was made of the morphology in the mesial and distal interlobal groove. Two parameters were used: depth of interlobal groove and structure angle. The interlobal groove depth varied between 0.13 and 0.55, taken in relation to the maximum crown height. The structure angle varied between 2° and 170°. If the structure angle was ≤25°, the interlobal groove was classified as a fissure; if the angle was >25°, the interlobal groove was classified as a groove. Only in 18% of the sections did the interlobal groove manifest itself as a fissure. The study demonstrates that it was possible unambiguously to describe the two-dimensional profile of interlobal grooves by groove depth and structure angle.     

Somatostatin inhibition of phospholipase G activity in isolated rat pancreatic islets

We have assessed the effect of somatostatin on the phospholipase C activity in isolated rat pancreatic islets. The phospholipase C activity was measured as the generation of inositol 1,4,5-trisphosphate and its metabolite inositol 1,3,4-trisphosphate from the hydrolysis of polyphosphoinositides. Inositol phosphates were measured using anion-exchange fast protein liquid chromatography analysis of extracts from islets prelabelled with myo-[³H]inositol. Somatostatin (1–1000 nmol l^-1) significantly inhibited the glucose-induced (12 mmol l^-1) phospholipase C activity in a concentration-dependent manner. The Ca²⁺ channel blocker verapamil (25 μmol l^-1) also inhibited the glucose-induced (12 mmol l^-1) phospholipase C, whereas the combination of somatostatin and verapamil did not induce any additional inhibition. At 3.3 mmol l^-1 glucose, the hypoglycaemic sulphonylurea, tolbutamide (1 mmol l^-1), increased the phospholipase C activity. This effect was reversed by somatostatin (100 nmol l^-1). Tolbutamide did not further increase the glucose-induced (12 mmol l^-1) phospholipase C activity. However, the somatostatin inhibition of glucose-induced (12 mmol l^-1) phospholipase C was reversed by tolbutamide. The activator of adenylyl cyclase, forskolin (20 μmol l^-1), did not exert any effect on the PLC-inhibition of somatostatin, whereas forskolin alone inhibited the phospholipase C activation at 12 mmol l^-1 glucose. Our study demonstrates that somatostatin inhibits the hydrolysis of polyphosphoinositides in pancreatic islets, apparently via a mechanism dependent on Ca²⁺ and not on cAMP.     

Comparison of Threshold Values Between Steroid and Nonsteroid Unipolar Memhrane Leads

The aim of this study was to evaluate whether steroid membrane leads can reduce pacing thesholds and thereby save energy as compared to nonsteroid membrane leads. The study was a random sample, double blind test consisting of 90 patients between 49–94 years of age admitted to seven hospitals in Europe for pacemaker implantation. The two leads compared in this study had contoured activated carbon tips covered with ion exchange membranes. The leads were identical except that 30 μg of dexa-methasone was dissolved in the ion exchange membrane of one of the leads. Normal lead implant procedures were used. Follow-up procedures were conducted at 2 weeks and 1,3,6, and 12 months after lead implantation. The pulse generator was programmed to an amplitude of 2.5 or 5 V and a duration of 0.5 msec. The stimulation threshold was measured using the VARIO function. The threshold was measured a total of three times in order to determine the presence of microdislocations. At the 2- and 4-week follow-ups, the stimulation threshold was significantly lower for the steroid leads than for the membrane leads without steroid (0.54 ± 0.19 vs 0.76 ± 0.25 V, P = 0.0005; and 0.59 ± 0.19 vs 0.74 ± 0.26 V, P = 0.005), but after 3 months, the threshold values were almost the same for both leads.     

The Hemodynamic Importance of Atrial Systole: A Function of the Kinetic Energy of Blood Flow?

The relative importance of atrial systole on left ventricular filling was investigated at rest and during exercise in 25 patients with dual chamber pacemakers. The mean blood flow velocity over the atrial valve, the velocities of the rapid filling phase (E), the active filling phase (A), and the E/ A ratio were determined for pulsed Doppler-echocardiography. The patients were first examined at rest during AV sequential pacing (DVI) at 70 and 104 beats/mm. The investigation was subsequently repeated during atrial synchronous pacing (VDD) at rest and during supine submaximal exercise at workloads adjusted to achieve heart rates corresponding to those during DVI pacing. The mean blood flow velocity at rest did not differ between DVI and VDD pacing at 70 beats/mm (0.46 vs 0.49 m/sec). When (he resting heart rate was increased to 104 beats/min (DVI) the mean blood flow velocity increased to 0.56 msec (P < 0.001). At a corresponding heart rate during exercise (VDD) the velocity increased to 0.70 msec (P < 0.001). At a resting heart rate of 70 beats/min the E/A ratio (n = 14) did not differ significantly between DVI and VDD pacing. With an increased resting heart rate (DVI) the E/A ratio decreased from 0,94 ± 0.45 to 0.78 ± 0.18; NS. When the heart rate increased during exercise (VDD) the E/A ratio increased from 0.75 ± 0.14 to 0.97 ± 0.16; P < 0.001. There was a positive correlation between the increase of the mean blood flow velocity and the increase of the E/A ratio during exercise (r = 0.69, P < 0,01). No such correlation was found when the heart rate was changed at rest. Thus, the importance of atrial systole on ventricular filling diminishes during exercise in accordance with increasing blood flow velocity, which by physical principles is related to the kinetic energy. The relative importance of atrial systole is hence inversely correlated to the kinetic energy of the blood flow.     

Correlative light microscopic and scanning electron microscopic study of completely and incompletely orthokeratinized rat oral epithelium

Abstract – Using light microscope (LM) and scanning electron microscope (SEM) a study of the surface morphology of rat oral epithelium was undertaken. A good correlation was found between the LM and SEM findings in the demonstration of the characteristic differences in surface structure between completely and incompletely orthokeratinized areas of the rat oral epithelium. Completely keratinized epithelium (hard palate and attached gingiva) shows a surface layer of orderly arranged, closely approximated and overlapping cells. The individual cell surface shows a honeycomb pattern of interconnecting ridges surrounding depressions or micropits. Incompletely keratinized epithelium (buccal mucGsaT alveolar sulci, gingival crest and interpapillary area of the dorsum of the tongue) shows a very uneven, corrugated surface layer. There is considerable loss of cell cohesion with the formadoo of wide intercellular clefts. The individual cell surface is characterized by microplicatioris of irregular size and arrangement. The findings of the present investigation are discussed in the light of an idea previously put forward by the authors that a correlation exists between surface morphology of the keratinized rat oral mucosa and colonization and penetration of Candida organisms in experimental candidosis.     

Oral mucous membrane lesions in children treated with bone marrow transplantation

Abstract – Oral mucous membrane lesions were studied in 54 children below 12 yr of age treated with allogeneic bone marrow transplantation mainly because of hematological malignancies. Sixty-two percent of the children exhibited a wide range of oral side effects during therapy. Lesions observed during the first 2 wk prior to engraftment of the donor marrow were related to the chemo- and radiotherapy given. Oral ulcerations were seen in 34% of the children. Children given methotrexate as graft-versus-host disease (GVHD) prophylaxis exhibited oral ulcerations significantly (P<0.05) more often than those given cyclsporin. Oral lesions related to acute GVHD were only observed in two patients. Reactivating herpes simplex virus infection was seen in 35% of the children who were seropositive prior to BMT. An extensive oral candidiasis was observed in 15% of the patients. All six children with a chronic GVHD exhibited changes in the oral mucosa 2–4 yr after transplantation such as erythma of the mucous membranes, tongue atrophy and also lichenoid changes in the buccal mucosa.