Mutual wear evaluation of resin composites when opposing enamel and dentin.

Mutual wear rates of resin composites and both superficial and deep layers of enamel and dentin were investigated by means of an in vitro wear test. Occlusal surfaces of extracted molars were ground flat to respective layers of enamel and dentin. Hemispherical-shaped styli (n = 8) made of microfilled and microhybrid composites were placed perpendicular to the finished tooth surface (600 grit) in the presence of tap water, and a two-body wear test (75 N load and 1.2 Hz) was performed for 100,000 cycles. The wear depths on both tooth and composite specimens were determined, and the data were statistically analyzed by two-way ANOVA and Boneferroni test (p < 0.05). The values of deep and superficial dentin specimens against Esthet-X (530.2 +/- 213.0 microm and 717.4 +/- 309.6 microm) were significantly greater than those against Epic-TMPT (34.1 +/- 17.6 microm and 29.3 +/- 10.8 microm). The values of Esthet-X against dentin were the smallest (2.4-2.6 microm), followed by those of the same material against enamel (5.5-6.1 microm), and those of Epic-TMPT against enamel (7.2-7.9 microm). It was concluded that the wear rates of dentin varied with the type of composite used while those of enamel showed the consistency.

Antigen sampling by intestinal M cells is the principal pathway initiating mucosal IgA production to commensal enteric bacteria.

Secretory IgA (SIgA) directed against gut resident bacteria enables the mammalian mucosal immune system to establish homeostasis with the commensal gut microbiota after weaning. Germinal centers (GCs) in Peyer's patches (PPs) are the principal inductive sites where naive B cells specific for bacterial antigens encounter their cognate antigens and receive T-cell help driving their differentiation into IgA-producing plasma cells. We investigated the role of antigen sampling by intestinal M cells in initiating the SIgA response to gut bacteria by developing mice in which receptor activator of nuclear factor-κB ligand (RANKL)-dependent M-cell differentiation was abrogated by conditional deletion of Tnfrsf11a in the intestinal epithelium. Mice without intestinal M cells had profound delays in PP GC maturation and emergence of lamina propria IgA plasma cells, resulting in diminished levels of fecal SIgA that persisted into adulthood. We conclude that M-cell-mediated sampling of commensal bacteria is a required initial step for the efficient induction of intestinal SIgA.

Trochanteric sciatic neuropathy.

A patient with severe weakness, atrophy, and sensory loss of the right leg had a focal right sciatic neuropathy. The sciatic nerve was enlarged at the level of the lesser trochanter, excessively firm, and multistranded; its stimulation threshold was focally increased. Biopsied fascicles had reduplicated perineurial leaflets, many Renaut bodies, and an abnormal unimodal spectrum of small-diameter fibers. We postulate that the lesion was induced by the combination of an underlying prominent lesser trochanter and sitting on hard benches.

Assessment of nerve regeneration and adaptation after median nerve reconnection and digital neurovascular flap transfer.

Six patients with median nerve severance (five sutured) were studied after an interval of 1.8 to 35 years to assess residual neurologic deficit, misdirected axonal regrowth, and adaptation to faulty reinnervation. Mild motor impairment was confirmed by the smaller thenar muscle action potentials and isometric muscle twitches from supramaximal stimulation of the median nerve. Sensory impairment was supported by the increased thresholds of vibratory (p = 0.003) and touch-pressure (p = 0.004) detection thresholds of the pulp of index fingers and decreased amplitudes of sensory nerve action potentials. A tactile hemidigit localization test revealed that localization was not significantly different from that on the contralateral side but perceptual territory was increased. This increase is best explained by misdirected axon regrowth without CNS adaptation. Long-standing faculty tactile digit localization in neurovascular skin flaps from finger to thumb also was demonstrated--further evidence that CNS adaptation is imperfect when sensory nerves to digits are relocated.

Soft-tissue coverage for the treatment of osteomyelitis of the lower part of the leg.

For treatment of chronic osteomyelitic wounds of the lower part of the leg, a three-stage approach is necessary: (1) adequate debridement of bone and soft tissue, (2) control of infection by open packing with frequent dressing changes and use of intravenously administered antibiotics, and (3) healthy soft-tissue coverage and obliteration of dead space. If the bone is unstable, it can be immobilized temporarily by means of external fixation. Bone grafting can be accomplished by use of conventional bone grafting after healing of the soft tissues, a vascularized bone graft, or open bone grafting. Soft-tissue coverage is provided by a local muscle flap or a free muscle flap. We prefer to cover the muscle with a skin graft. The muscle flaps described in this article obliterate dead space, provide soft-tissue coverage, act as a bed for skin grafts, and improve the vascularity of the wound.

Rehabilitative operation for motor neuron disease: tendon transfer for segmental muscular atrophy of the upper extremities.

Segmental spinal muscular atrophy of adolescence is a clinical syndrome that can be distinguished from the more common forms of motor neuron disease. A patient with this syndrome who was no longer able to care for herself is described. After selective tendon transfers in her right upper extremity, she has been able to perform many of the activities of daily living. This improved function has been maintained for more than 2 years. We suggest that transfer of tendons and muscles may be indicated in selected patients with slowly progressive muscular atrophy.

Skeletal reconstruction by vascularized bone transfer: indications and results.

The indications for and the results of 60 consecutive microvascular bone transfers performed at our institution during a 50-month period are reviewed. All 60 patients were followed up for at least 1 year. The overall primary union rate was 67%, and the eventual union rate was 77%. The most frequent indication for the procedure was long-bone reconstruction after limb-salvage wide local resection of a malignant tumor. We achieved the best results with limb reconstruction after resection of a malignant tumor and with recipient sites that involved the forearm or mandible. In contrast, our results were least favorable with reconstruction after resection for chronic osteomyelitis and with reconstruction of defects of the shoulder girdle. Overall, vascularized bone transfer seems to be a valuable reconstructive technique for management of clinical problems that involve massive skeletal defects.

Interaction of endothelial eccrine mechanisms and human adrenomedullin on vascular resistance in canine bone.

Adrenomedullin is a novel peptide known to be one of the most potent vascular smooth muscle relaxing agents in vivo. The aim of this study is to investigate the effect of adrenomedullin in relation to nitric oxide, prostaglandins and endothelium-derived hyperpolarized factor (EDHF). A 0.1-ml bolus of 1 nmol human adrenomedullin is a potent inhibitor of the pressor response to exogenous norepinephrine infusion in an ex vivo canine tibia perfusion model for a duration of at least 70 min (P < 0.005). This attenuation of vascular smooth muscle contraction occurs even when nitric oxide production is blocked by NG-monomethyl-L-arginine acetate (L-NMMA) infusion and EDHF is blocked by tetraethylammonium infusion, although the effect is of shorter duration (at least 10 min). Indomethacin as well does not affect the suppression of norepinephrine-induced vascular smooth muscle contraction. Based on these data, human adrenomedullin has both nitric oxide- and EDHF-dependent mechanism as well as a nitric oxide- and EDHF-independent mechanism.

The effects of acidosis and alkalosis on long bone vascular resistance.

This study used an ex vivo perfusion model to investigate the direct effects of acidosis and alkalosis on the vascular resistance of the canine tibia. Baseline vascular resistance (BVR) and the vascular smooth muscle response to bolus doses of norepinephrine (NE) (0.025-3.2 nmol) and periarterial sympathetic nerve stimulation (NS) (10-25 Hz: 9 V, 2 ms pulses, 10 s) were studied. In Group I, these parameters were measured at normal pH (duration 7.34-7.44) and then during acidosis (pH 7.2-7.33). In Group II, they were measured at normal pH and then during alkalosis (pH 7.47-7.58). In Group III (control), they were measured serially at a normal pH. Alkalosis increased BVR by 56% (p < 0.0001). Acidosis attenuated (18% reduction) and alkalosis enhanced (66% increase) the vasoconstrictor action of NE (p < 0.0001). Acidosis also attenuated (11% reduction) the effect of sympathetic NS (p = 0.012). It is concluded that perfusion pH influences the sensitivity of long bone resistance vessels to circulating NE and sympathetic NS. Thus, local concentration of hydrogen ions may provide bone with a mechanism to autoregulate blood flow.

The effects of ischemia on long bone vascular resistance.

An in vitro canine tibia model was used to assess the effects of 48 h of hypothermic (4 degrees C) ischemia on bone vascular resistance and on responsiveness of intraosseous blood vessels to circulating norepinephrine. Three groups of bones were studied: Group I (n = 11), 48 h hypothermic ischemia; Group II (n = 11), 48 h hypothermic ischemia with pretreatment with allopurinol and oxypurinol; and Group III (n = 10), no ischemia. Resting vascular resistance in both ischemic groups (79 and 74 mmHg/ml/min) was significantly higher (p less than 0.0001) than in the nonischemic group (22 mmHg/ml/min). Effects of norepinephrine on vascular resistance were significantly greater in both ischemic groups (p less than 0.004). In all three groups, acetylcholine infusion attenuated the increases in perfusion pressure caused by norepinephrine. This demonstrates secretion of endothelial-mediated relaxing factors (EDRF) and prostaglandin for up to 48 h of hypothermic ischemia. As no significant differences were detected between the two ischemic groups, this study failed to demonstrate any protective effect of xanthine oxidase inhibitors.

Endothelial control of long bone vascular resistance.

This in vitro study investigates whether intraosseous endothelial cells can regulate long bone blood flow by secretion of vasodilator prostaglandin and EDRF (endothelium-derived relaxing factor). Canine tibia were perfused through the nutrient artery at a constant flow rate, and the increases in perfusion pressure caused by standard doses of norepinephrine were recorded first under control conditions and then during acetylcholine infusion. Acetylcholine attenuated the norepinephrine pressure responses (-62 +/- 3%). This attenuating effect of acetylcholine was partially abolished by inhibition of prostaglandin synthesis (-20 +/- 6%) and completely abolished by inhibition of EDRF synthesis (+73 +/- 43%) or combined inhibition of prostaglandin and EDRF synthesis (+134 +/- 30%). These results are statistically significant (p less than 0.0001) and suggest that both EDRF and vasodilator prostaglandin are synthesized by intraosseous endothelial cells, and can modify long bone vascular resistance. Thus, as in other organs, intraosseous endothelial cells may provide bone with an autoregulatory control mechanism and enable it to respond to a diverse group of vasodilator stimuli.

Effect of ischemic storage on endothelium in canine bone.

The limits of room temperature (24 degrees C) and hypothermic (4 degrees C) storage for preservation of endothelial eccrine function were investigated with use of an ex vivo perfusion apparatus model of the cannulated canine tibia. Norepinephrine-induced contraction of smooth muscles in both the presence and absence of acetylcholine was compared, with and without selective blockade of endothelial-derived relaxing factor (EDRF). At room temperature, release of EDRF deteriorated after 24 h and was absent after 48 h of storage. At 4 degrees C, endothelial eccrine activity appeared unimpaired for as long as 72 h of storage. From 96-192 h of storage at 4 degrees C, release of EDRF was suggested, but with an attenuation of its effect on smooth muscle. At 216 and 504 h of storage at 4 degrees C, no endothelial eccrine activity was demonstrated.

Failure of perfusion with oxygenated Krebs-Ringer solution to preserve the eccrine function of the vascular endothelium in bone.

An ex vivo canine tibia preparation was perfused at a constant rate with aerated (95% O2-5% CO2) Krebs-Ringer solution for 24 h. Bolus injections of norepinephrine (0.125-0.5 micrograms) were given and then acetylcholine (5 x 10(-5) M) was used to stimulate endothelial production of smooth muscle relaxing factors. Following 1 h of perfusion the addition of acetylcholine resulted in significant attenuation of the response to norepinephrine (p < 0.001). After 4 h perfusion acetylcholine did not attenuate the norepinephrine response, but addition of L-arginine (the precursor of endothelial-derived relaxing factor) resulted in significant attenuation in the presence of acetylcholine (p < 0.005). At 6, 12, and 24 h the acetylcholine did not attenuate the norepinephrine response. It is concluded that normothermic, continuous perfusion with oxygenated Krebs-Ringer solution results in normal endothelial eccrine activity up to 1 h. Following this period there is substrate depletion but endothelial eccrine function can be demonstrated for up to 4 h. At 6 h this function cannot be demonstrated, suggesting degradation of the functional integrity of the endothelium.

Blood flow evaluation of vascularized bone transfers in a canine model.

Blood flow in vascularized bone transfers was evaluated in a canine model. Cortical bone blood flow was determined in undisturbed control bone, vascularized heterotopic bone transfers, and nonvascularized cortical bone grafts by means of the radionuclide-labeled microsphere technique. Four animals were studied at 2 days, three at 1 week, eight at 2 weeks, four at 4 weeks, and three at 6 weeks postoperatively. In the 2-day animals, the vascularized bone transfers exhibited intermediate levels of blood flow (1.4 +/- 0.4 ml/100 g of bone/min) compared with undisturbed control bone (2.7 +/- 0.5 ml/100 g of bone/min) and conventional cortical bone grafts (0.0 +/- 0.0 ml/100 g of bone/min). At 1 week postoperatively, the differences in blood flow values of the vascularized transfers (1.7 +/- 0.7 ml/100 g of bone/min) and control bone (1.4 +/- 1.0 ml/100 g of bone/min) and of the nonvascularized grafts (0.2 +/- 0.1 ml/100 g of bone/min) and control bone (1.6 +/- 1.1 ml/100 g of bone/min) were no longer significant. At 2 weeks postoperatively, blood flow had increased in both graft groups. At 4 weeks postoperatively, the bone blood flow values in the vascularized transfers (4.8 +/- 1.4 ml/100 g of bone/min) were significantly greater than the bone blood flow in control specimens (1.6 +/- 0.5 ml/100 g of bone/min) and conventional cortical bone grafts (2.5 +/- 2.0 ml/100 g of bone/min).(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of human adrenomedullin on a canine tibial perfusion model in the absence of vascular endothelium.

The effect of human adrenomedullin was investigated using an ex vivo perfused canine tibial model in the absence of vascular endothelium. Adrenomedullin is a novel peptide with known vasodilator properties. In this model, a 0.1 ml bolus injection of 10(-5) M of either acetylcholine or adrenomedullin decreased vascular resistance in tibial preparations precontracted with prostaglandin F2 alpha by 88.3 +/- 3.0% and 92.8 +/- 2.8%, respectively, in the presence of vascular endothelium. Conversely, a 0.1 ml bolus injection of 10(-5) M acetylcholine produced a constrictor response after removal of vascular endothelium. A 0.1 ml bolus injection of 10(-5) M adrenomedullin decreased the baseline perfusion pressure in a dose-dependent manner for a duration of 20 minutes and also attenuated the pressor response to exogenous norepinephrine injection for at least 10 minutes compared with the control study (p < 0.05) in the absence of vascular endothelium. These data suggest that human adrenomedullin relaxes blood vessels in bone by a direct action on vascular smooth-muscle cells. In addition, the attenuation effect of human adrenomedullin on pressor responses to exogenous norepinephrine injection is independent of vascular endothelium.

Dose-dependent variations in blood flow evaluation of canine nerve, nerve graft, tendon, and ligament tissue by the radiolabeled-microsphere technique.

This study evaluates the dose-dependent accuracy of the radionuclide-labeled microsphere technique for blood flow evaluation in nerve, tendon, and ligament. In eight dogs, blood flows were determined for nerve, nerve graft, tendon, and ligament tissue by simultaneous injection of high- and low-dose microspheres with different radiolabels. The results demonstrated no significant differences in blood flow as measured from the small number of microspheres (less than 400) and the high number (more than 400) for nerve and tendon tissue. For nerve tissue, microsphere counts of 50 to 100, 100 to 200, 200 to 300, and more than 300 produced mean percentage errors of 12.74% (n = 5, SEM = 4.52), 5.45% (n = 13, SEM = 1.22), 10.22% (n = 6, SEM = 4.37), and 17.08% (n = 12, SEM = 3.30), respectively. For tendon tissue, the same microsphere subdivisions had mean percentage errors of 7.47% (n = 4, SEM = 2.66), 3.63% (n = 6, SEM = 1.34), 15.54% (n = 4, SEM = 4.43), and 12.91% (n = 1), respectively. For ligament tissue, percentage errors were consistently higher; microsphere counts of 30 to 100, 100 to 200, and 200 to 300 produced mean errors of 20.14% (n = 4, SEM = 6.38), 18.66% (n = 4, SEM = 6.24), and 25.78% (n = 2, SEM = 1.97), respectively. Although there was no direct relationship between percentage error and number of microspheres retrieved, we suggest that microsphere counts in the range of 100 to 200 should be considered acceptable for nerve and tendon in the canine. Ligament tissue seems to be less well suited to the microsphere technique; however, further study is warranted.

Effect of human adrenomedullin on vascular resistance of the canine tibia.

An ex vivo model of a perfused canine tibia was used to investigate the effect of human adrenomedullin, a novel peptide with known vasodilator properties, on the vascular resistance of bone. Human adrenomedullin has a potent and long-lasting vasodilator effect in the canine tibia following precontraction of vascular smooth muscle by infusion of prostaglandin F2 alpha. A 0.1 ml bolus injection of 10(-5) M human adrenomedullin suppressed the pressor response of the canine tibia preparation to an infusion of norepinephrine by 43-52% for a duration of 100 minutes. An injection of 10(-6) adrenomedullin suppressed the pressor response to an infusion of norepinephrine by 22-23% for a duration of 40 minutes. These data suggest that human adrenomedullin may be a potent and long-acting vascular smooth-muscle relaxant in bone.

Preservation of bone graft vascularity with the University of Wisconsin cold storage solution.

The preservation of the microcirculation of bone has been evaluated with use of an in vitro canine tibia perfusion model. The production of relaxing factors by the osseous vascular endothelium was used as a metabolic marker for viability. This endothelial eccrine function was preserved for 5 days (120 h) by cold storage without continuous perfusion after a washout with the University of Wisconsin (UW) solution. This synthetic perfusate was superior to Krebs Ringer solution (p < 0.05), but storage without perfusion failed to prevent a significant rise in vascular resistance. Two techniques were effective for the preservation of bone vascularity for 24 h: washout with UW solution followed by nonperfusion cold (4 degrees C) storage, and vascular washout with mannitol solution followed by continuous hypothermic (5 degrees C) microperfusion (0.03 ml/min) with UW solution. The most consistent, and lowest, vascular resistance was produced by the microperfusion technique. However, UW solution does not consistently prevent an increase in vascular resistance with hypothermic ischemia. This technique may prove useful for the preservation of vascularized bone grafts, but it needs to be evaluated in a transplantation model.

Adrenergic control mechanisms of blood flow in a vascularized canine tibial allograft.

A vascularized canine tibial allograft was used to study the alpha-adrenoreceptor subtypes of the microcirculation of bone. Bone transplantation was performed on six dogs, and the bone blood flow was estimated with the use of serial injections of radiolabeled 15 microns microspheres. After microvascular anastomosis, the mean cortical blood flow in the allografted tibia was 3.6 +/- 2.1 ml/100 g/min. Alpha 1-adrenoreceptor blockade, with prazosin, caused an increase in normalized blood flow in five allografts and a slight decrease in one allograft. The mean increase was 32 +/- 48%, but this was not statistically significant (p < 0.2). The addition of an alpha 2-adrenoreceptor blockade, with rauwolszin, resulted in a significant increase (132 +/- 88%) in normalized blood flow in all allografts (p < 0.02). This ex vivo experiment confirms that both alpha 1 and alpha 2 adrenergic mechanisms play a role in controlling bone blood flow in centrally denervated allografts.

The effect of hypothermic ischemia on the alpha-adrenergic mechanisms of the canine tibia vascular bed.

The effect of hypothermic ischemia on alpha-1 and -2 adrenergic receptor mediated vasoconstriction has been studied in an in vitro perfused canine tibia preparation. Bones were perfused at a constant rate with aerated (95% O2, 5% CO2) modified Krebs Ringer solution and the effect of bolus injections of norepinephrine (0.025-6.4 nmol) on the perfusion pressure was studied. For all bones the first dose-response curve was produced under control conditions. In one group the second dose-response curve was generated during a constant infusion of prazosin (alpha-1 adrenergic antagonist); in another it was produced during a constant infusion of rauwolscine (alpha-2 adrenergic antagonist); in the control group it was generated under control conditions. The results demonstrate that, after 48 h of hypothermic ischemia, alpha-1 adrenergic-mediated vasoconstriction was significantly attenuated (p less than 0.001). However, alpha-2 adrenergic-mediated vasoconstriction was unaffected by increasing periods of hypothermic ischemia.