Load transfer and periprosthetic fractures after total hip arthoplasty: Comparison of periprosthetic fractures of femora implanted with cementless distal-load or proximal-load femoral components and measurement of the femoral strain at the time of implantation.

BACKGROUND: Little is known about the causes and mechanisms underlying periprosthetic fractures around femoral components particularly in relation to the stem design. In an in vitro study 20 pairs of fresh cadaveric femora were loaded to fracture axially and transversally. FINDINGS: When proximal femoral strain was measured at the time of impaction of cementless stems the load transfer was determined by the underlying anatomy rather than by the shape of the stem, so that the so-called "load transfer" properties - proximal or distal - ascribed to stem designs are a myth. The axial-load and the transverse-load model were then exposed to loads to failure (fracture) and showed a biphasic pattern throughout independent of the impact direction. In the second phase, the fracture phase proper, the bone behaved like a brittle solid. Failure occurred very rapidly within less than 5 milliseconds. The forces to failure were between 2 and 11 kN. Most of the fractures (82.5%) occurred above the stem tip. INTERPRETATION: Note that the study was confined to early preosteointegration fractures. Neither the stem design nor the impact direction, i.e. on the knee or on the side of the hip, was related to the fracture morphology.

Elevated transforming growth factor-beta 1 (TGF-ß1) levels in human fracture healing.

INTRODUCTION: Transforming growth factor-beta 1(TGF-ß1) is a regulatory protein, involved in bone fracture healing. Circulating TGF-ß1 levels have been reported to be a predictor of delayed bone healing and non-union, suggesting active relationship between tissue and circulating TGF-ß1 in fracture healing. The purpose of this study was to analyse TGF-ß1 local and serum concentrations in fracture healing to further contribute to the understanding of molecular regulation of fracture healing. PATIENTS AND METHODS: Serum samples of 113 patients with long bone fractures were collected over a period of 6 months following a standardised time schedule. TGF-ß1 serum concentrations were measured using ELISA. Patients were assigned to 2 groups: Group 1 contained 103 patients with physiological healing. Group 2 contained 10 patients with impaired healing. Patients in both groups were matched. One patient of the group 2 had to be excluded because of missing match partner. In addition, fracture haematoma from 11 patients of group 1 was obtained to analyse local TGF-ß1 concentrations. 33 volunteers donated serum which served as control. RESULTS: TGF-ß1 serum concentrations increased during the early healing period and were significantly higher in patients with physiological healing compared to controls (P=0.04). Thereafter, it decreased continuously between weeks 2 and 8 and fell again after week 8. TGF-ß1 serum concentrations in patients with physiological healing were significantly higher at week 24 compared to controls (P=0.05). In non-unions, serum concentrations differed significantly from those of controls at week 6 (P=0.01). No significant difference in between patients with physiological and impaired fracture healing was observed. Fracture haematoma contained significantly higher TGF-ß1 concentrations than peripheral serum of the patients (P=0.017). CONCLUSION: Elevated levels of TGF-ß1 in haematoma and in serum after bone fracture especially during the entire healing process indicate its importance for fracture healing.

Growth factor release in extra- and intramedullary osteosynthesis following tibial fracture.

INTRODUCTION: Recent studies indicate alterations of local and systemic growth factor level during fracture healing. As a result, osteogenic and angiogenic growth factors allow us to monitor fracture healing on a molecular level. We hypothesised that closed intramedullary (IM) reaming and nail fixation, in contrast to open reduction and internal plate fixation (ORIF), could exert an effect on the cellular elements present in the intramedullary canal, leading to increased release of mediators. The purpose of the study was to investigate whether different osteosynthesis techniques influence the released quantity of cytokines. PATIENTS AND METHODS: A total of 34 patients with tibia fractures treated with IM fixation and 19 patients treated with ORIF were included in the study. In addition to clinical and radiological examination, serum concentrations of transforming growth factor beta 1(TGF-ß1), macrophage-colony stimulating factor (M-CSF) and vascular endothelial growth factor (VEGF), were analysed at 1, 2, 4, 6, 8, 12, and 24 weeks after surgery. RESULTS: Expression of TGF-ß1 and M-CSF was increased during the first 2 weeks of fracture healing in patients treated with the IM fixation technique compared with those treated by ORIF. After 24 weeks, M-CSF levels in patients with IM fixation were clearly higher. Conversely, VEGF levels were higher during the first 2 weeks of fracture healing in patients treated by ORIF compared with IM fixation. However, these results were not significant. CONCLUSION: Our results show that 1 week after surgery neither reamed IM fixation nor ORIF of the tibia could increase the expression of VEGF, M-CSF and TGF-ß1 in its favour.

Concomitant endothelin-1 overexpression in lung transplant donors and recipients predicts primary graft dysfunction.

Primary graft dysfunction (PGD) causes significant morbidity following lung transplantation (LTX). Mortality is high in PGD and therapeutic strategies are limited. To investigate whether endothelin-1 (ET-1) that mediates increased vascular permeability and edema formation in lung grafts can predict PGD, ET-1 mRNA expression was examined in lung tissue biopsies of 105 donors and recipients obtained shortly before LTX. Serum ET-1 concentration was assessed by ELISA. PGD grade was diagnosed and scored by oxygenation and radiological characteristics according to ISHLT guidelines. PGD grade 3 developed in 11% of patients. ET-1 mRNA expression was significantly increased in both donor (p < 0.0001) and recipient (p = 0.01) developing PGD as compared to no PGD group. Pretransplant ET-1 serum concentrations were elevated in recipients with PGD as compared to no PGD group (p < 0.0001), although serum ET-1 was not different between donors whose grafts developed PGD grades 0-3. In regression analysis, concomitant elevated donor tissue ET-1 and recipient serum ET-1 predicted PGD grade 3. This study indicates that pretransplant ET-1 mRNA overexpression in donors associated with elevated pretransplant serum ET-1 in recipients contribute to PGD development and that their assessment might be beneficial to predict PGD and to identify recipients who could benefit from a targeted ET-1 blockade.

Serum matrix metalloprotease-1 and vascular endothelial growth factor--a predict cardiac allograft rejection.

Cardiac allograft rejection is currently diagnosed from endomyocardial biopsies (EMB) that are invasive and impractical to repeat. A serological marker could facilitate rejection monitoring and minimize EMB-associated risks. We investigated the relation of serum matrix metalloprotease (MMP)-1 and vascular endothelial growth factor (VEGF)-A concentrations to cardiac allograft rejection, using 1176 EMBs and serum samples obtained from 208 recipients. Acute cellular rejection was diagnosed in 186 EMBs. Mean week 1 and week 2 serum MMP-1 concentrations predicted rejection (p = 0.001, AUC = 0.80). At the optimal cut-off level of >or=7.5 ng/mL, MMP-1 predicted rejection with 82% sensitivity and 72% specificity. Initial serum MMP-1 <5.3 ng/mL (lowest quartile) was associated with rejection-free outcome in 80% of patients. Both MMP-1 (p < 0.001, AUC = 0.67-0.75) and VEGF-A (p < 0.01, AUC = 0.62-0.67) predicted rejection on the next EMB, while rejection at EMB was identified only by VEGF-A (p < 0.02, AUC = 0.70-0.77). Patients receiving combined cyclosporine-A and everolimus had the lowest serum MMP-1 concentrations. While serum MMP-1 predicts rejection-free outcome and VEGF-A identifies rejection on EMB, both markers predict rejection in follow-up of cardiac transplant recipients. Combination of serum MMP-1 and VEGF-A concentration may be a noninvasive prognostic marker of cardiac allograft rejection, and could have important implications for choice of surveillance and immunosuppression protocols.

Donor myocardial HIF-1alpha is an independent predictor of cardiac allograft dysfunction: a 7-year prospective, exploratory study.

Knowledge on interplay between the cardiac molecular response to transplantation-induced stress and primary graft dysfunction (PGD) is limited. A cDNA array identified HIF-1, EGR-1, NAB-2, VEGF-A and uPA as mediators of cardiac tissue response to transplantation-induced stress. mRNA expression of these molecules was measured in left ventricular biopsies from 200 donors before and after aortic cross-clamping and at 10-, 30- and 60-min reperfusion by real-time RT-PCR. HIF-1alpha expression at two time points was significantly associated with PGD, as shown by univariate analysis, receiver operating characteristic curve and multivariate logistic regression. At a cut-off level of 200 arbitrary units, HIF-1alpha after aortic cross-clamping in donors (78% sensitivity, 83% specificity) and at 10-min reperfusion (85% sensitivity, 83% specificity) identified PGD. HIF-1alpha demonstrates the potential to be a predictive marker for PGD; however, as multiple factors were tested at different time points, prospective evaluation is clearly necessary to confirm this observation.

Recipient vascular endothelial growth factor serum levels predict primary lung graft dysfunction.

Primary graft dysfunction (PGD) is a severe complication in lung transplantation. Therapeutic strategies are limited and there exist no predictive markers for PGD. To investigate whether vascular endothelial growth factor (VEGF) that regulates vascular permeability could predict PGD, pretransplant VEGF serum concentrations were measured in 150 lung transplant patients and 12 controls by ELISA. PGD was scored from 0 to 3 using chest radiographs and PaO(2)/FiO(2) ratios according to the International Society for Heart and Lung Transplantation guidelines. The mean graft ischemia time was 5 h 47 min and the donors' PaO(2)/FiO(2) ratios were >300. PGD grades 0-3 occurred in 23%, 44%, 21%, and 11% of patients, respectively. Pre-operative VEGF serum concentrations were significantly higher in PGD grade 3 (p < 0.0001) versus grade 0-2 and controls. VEGF concentrations significantly predicted PGD grade 3 versus 0-2 in logistic regression analysis (p < 0.0001) and receiver operating analysis (AUC = 0.778). At a cut-off level of > or =650 pg/mL VEGF had 86% sensitivity and 62% specificity to identify PGD grade 3 versus 0-2. Pre-operative VEGF serum concentrations could identify lung transplant recipients with high PGD risk.

Upregulation of vascular endothelial growth factor receptors is associated with advanced neuroblastoma.

BACKGROUND: Angiogenesis is essential for tumor growth and relies on the production of angiogenic factors. Vascular endothelial growth factor (VEGF) is a major regulator of angiogenesis that binds to tyrosine kinase receptors Flt-1 and KDR. The interaction of VEGF and its receptors at gene and protein levels in neuroblastoma remains widely unknown. METHODS: Tumor biopsy specimens and serum were obtained from 37 neuroblastoma patients; adrenal biopsy sections and sera of 7 normal children served as controls. Biopsy specimens were examined by real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting; serum was analyzed by enzyme-linked immunosorbent assay (ELISA). VEGF-A(165), B, C, Flt-1, and KDR were analyzed. RESULTS: VEGF isoforms and its receptors' mRNA were expressed in neuroblastoma and control tissues. Whereas the ligands were increased in stages III and IV, the receptors were upregulated in stage III only. At protein level, VEGF-B and C, Flt-1, and KDR were not detectable in tissue lysates, whereas VEGF-A was increased in stages III and IV. Serum VEGF protein levels were upregulated in stage III. CONCLUSIONS: VEGF-A(165) is one of the major angiogenesis regulators among the ligands' family of VEGF, whereas its receptors KDR, and most probably Flt-1, may contribute to a poor prognosis (angiogenic) phenotype, as indicated by their upregulated MRNA levels in stage III neuroblastoma. VEGF-A(165) mainly contributes to increased serum VEGF levels and may serve as a diagnostic tool in advanced-stage neuroblastoma.

Valvular density alone cannot account for sites of chronic venous insufficiency and ulceration in the lower extremity.

OBJECTIVE: Class 6 chronic venous stasis is associated with abnormal venous hemodynamics and ulceration. Ulcers primarily occur over bones and tendon prominences but very rarely over muscular compartments. We hypothesized that the anatomical distribution of venous stasis ulcers in the lower extremity is related to a lower density of venous valves. METHODS: The venous vasculature of six normal human legs was cast with resin, and their microvenous valvular anatomy was examined. Skin samples were obtained from the skin overlying the 1) Achilles' tendon, 2) anterior tibia, 3) medial malleolus, 4) lateral malleolus, 5) dorsal surface of the foot, 6) planta pedis, 7) dorsal aspect of the great toe; and from the skin regions overlying the 8) gastrocnemius, 9) tibialis anterior, and 10) peroneus muscles. The valvular and venous densities were determined in a scanning electron microscope, normalized to the size of specimens, and the valvular index was calculated. Analysis of variance with Bonferroni t-test was used to compare the valvular index between the regions. RESULTS: Venous valves were observed in all tissue regions. The diameter of veins with valves ranged from 18 microm to 803 microm. The valvular index for regions overlying bones/tendons (i.e., regions 1-7) was significantly higher versus those overlying muscular regions (i.e., regions 8-10) (p < 0.05). The valvular index was not different (p = 0.51) when regions 1 and 2 (where ulcers almost never occur) were compared to regions 3, 4, 5, 6, and 7 (where ulcers frequently occur); nor were there differences between the vascular indexes of regions overlying muscle. The largest venous valves were observed in the plantar region, and the smallest-sized ones were present in the peroneal region. CONCLUSIONS: This study shows that the density of venous valves is actually higher in regions of the human lower extremity overlying bones and tendons, where venous stasis ulcers are common, than those overlying muscular areas, where ulcers are rarely seen. Thus, valvular quantity alone cannot account for the higher clinical incidence of ulceration. It is likely that muscular pumping and/or valvular quality are important factors in preventing the development of venous stasis and ulceration in the lower extremity.

Impact of cardiac transplantation on molecular pathology of ET-1, VEGF-C, and mitochondrial metabolism and morphology in dilated versus ischemic cardiomyopathic patients.

Little is known about the long-term impact of cardiac transplantation on activity and modifications of endothelin (ET)-1 system, vascular endothelial growth factor (VEGF), and mitochondrial metabolism and morphology in patients with ischemic cardiomyopathy (ICM) versus dilated cardiomyopathy (DCM). Messenger RNA (mRNA) expression levels of ET-1, endothelin converting enzyme (ECE)-1, VEGF-C, carnitine palmitoyltransferase (CPT)-1, and carnitine acetyltransferase (CARAT), as well as the number of normal, edematous, and degenerated mitochondria were assessed in left ventricular biopsies of 21 patients with DCM and 20 with ICM (New York Heart Association class III-IV) before and up to 3 months after cardiac transplantation. Cardiac samples of donated, nonfailing hearts served as controls (n=10). In cardiac biopsies of both ICM and DCM patients, ET-1, VEGF-C, CPT-1, and CARAT mRNA were up-regulated, whereas ECE-1 mRNA was down-regulated (P<0.05). Degenerated mitochondria had the highest number in both groups, followed by normal and edematous mitochondria. After cardiac transplantation, in ICM patients impaired gene expression levels decreased to, or below, normal levels, and the number of normal mitochondria increased (P<0.05). In implanted hearts of DCM patients, however, up-regulated ET-1 transcript levels persisted and the number of normal mitochondria decreased, whereas the number of degenerated mitochondria increased (P<0.05), and edematous mitochondria remained unchanged in number. These results show that cardiac transplantation corrects the impaired hemodynamic and echocardiographic parameters in both groups, whereas in DCM, the molecular pathology of ET-1 system and mitochondria persists. Therefore, it is more likely that these changes are the cause rather than a consequence of DCM.

Selective downregulation of VEGF-A(165), VEGF-R(1), and decreased capillary density in patients with dilative but not ischemic cardiomyopathy.

Cardiomyopathy (CM) comprises a heterogeneous group of diseases, including ischemic (ICM) and dilative (DCM) forms. The pathogenesis of primary DCM is not clearly understood. Recent studies in mice show that vascular endothelial growth factor (VEGF) is involved in ICM. Whether VEGF plays a role in human CM is unknown. We examined the mRNA and protein expression of VEGF and its receptors in hearts of patients with end-stage DCM and ICM and in healthy individuals using real-time polymerase chain reaction and Western blotting. Number of capillaries, area of myocytes, and collagen were calculated in cardiac biopsies using transmission electron microscopy. In DCM, except for VEGF-C, mRNA transcript levels of VEGF-A(165), VEGF-A(189), and VEGF-B and the protein level of VEGF-A and VEGF-R(1) were downregulated compared with controls (P:<0.05). However, in ICM, mRNA transcript levels of VEGF isoforms and protein levels of VEGF-C were upregulated. The vascular density was decreased in DCM but increased in ICM compared with controls (P:<0. 05). Muscular hypertrophy was not different for ICM and DCM, although DCM had more collagen (P:<0.05). Blunted VEGF-A and VEGF-R(1) protein expression and downregulated mRNA of the predominant isoform of VEGF-A, VEGF-A(165), to our knowledge shown here for the first time, provide evidence that the VEGF-A defect in DCM is located upstream. Whether downregulation of certain VEGF isoforms in DCM is a cause or consequence of this disorder remains unclear, although upregulated VEGF levels in ICM are most likely the result of ischemia.

Pulmonary lymphatic filling is increased in spontaneously hypertensive rats.

Extravascular lung liquid must rely on tissue-space pressure gradients to drive it into the lymphatics because the fluid is outside the lymphatic contractile pumping and valve control. Focal tissue pressure changes could result from muscular contraction in the blood vessel walls. Perivascular lymphatics usually lie within the adventitia of pulmonary blood vessels, and are generally more noticeable in veins than arteries. Spontaneously hypertensive rats have exaggerated focal pulmonary venous muscle (venous sphincters). These muscular tufts are often near initial lymphatics; if their contraction was important for lymph transport, spontaneously hypertensive rats could have more lymphatic filling in the areas of the pulmonary venous sphincters than normotensive rats. Because the focal muscularity is found in pulmonary veins more than arteries, veins may have more focal lymphatic filling than arteries. To test these hypotheses, lung histology and vascular and lymphatic casts of spontaneously hypertensive and normotensive rats were examined. Contracted venous sphincters were found on 108 of 127 veins with lymphatics in the spontaneously hypertensive rats and 5 of 41 in the normotensive rats P<0.01). The spontaneously hypertensive rats had deeper venous contractions and more lymphatic filling around both arteries and veins (P<0.01). In the hypertensive rats, the venous was greater than the arterial lymphatic filling (P<0.01). On the pleural surface, hypertensive rats also had greater lymphatic filling than controls (P<0.01). This anatomic evidence suggests that pulmonary venous sphincters are associated with focal lymphatic filling, and perivascular muscle action might be a component of the pulmonary lymphatic system.

Auditory ossicle abnormalities and hearing loss in the toothless (osteopetrotic) mutation in the rat and their improvement after treatment with colony-stimulating factor-1.

Osteopetrosis describes a group of skeletal metabolic diseases of heterogeneous etiology and varied severity that produces a generalized accumulation of skeletal mass, the result of reduced bone resorption. Inherited in a variety of species including humans, the most severe forms are lethal. Among common features are progressive blindness and deafness of controversial etiologies for which there are no universally effective treatments. We have studied the auditory responsiveness and auditory ossicle quantitative histomorphology and temporal bone vasculature in the toothless (tl) rat, a lethal osteopetrotic mutation with few osteoclasts, very low bone turnover, and limited angiogenesis in the axial skeleton. Compared with normal littermates, 3-week-old mutants showed significantly reduced auditory responsiveness, a hearing loss due to abnormalities in both form and tissue composition of the stapes, and little capillary sprouting in the vascular bed of the temporal bone. Treatment of mutants with colony-stimulating factor 1 (CSF-1), known to greatly reduce sclerosis in the axial skeleton, significantly improved hearing, stapedial form and tissue composition, and angiogenesis in the temporal bone. In normal rats, the stapes consisted of 89.3% bone, 9.1% mineralized cartilage, and 0.8% porosity. In osteopetrotic rats, the stapes consisted of 48.3% bone, 35.9% mineralized cartilage, and 15.9% porosity, while after CSF-1 treatment, the bone content increased to 55.2%, cartilage was decreased to 21.7%, and porosity increased to 23.0%, respectively. This is the first demonstration of an auditory abnormality in an osteopetrotic animal mutation and shows that the hearing loss in tl rats can be significantly improved following treatment with CSF-1.

Morphometry of human coronary arterial trees.

BACKGROUND: Some groups, including ours, have been generating arterial tree models using constrained constructive optimization (CCO). Arterial trees have been grown to arbitrary resolution without input of anatomical data. We performed this study to learn about the shortcomings that might have resulted from neglecting the anatomical data in CCO models. METHODS: In a total of 450 segments obtained from 4 human cast hearts, the ratio ofbifurcating daughter segment radii (O < Sbif = r(2)/r(1) < 1) was examined, which corresponds to the split of the total flow of the mother segment. For any complete bifurcation, where the radii of the parent segments and the radii of daughters were known, the area expansion ratio was computed (Aexp = [r(1)2 + r(2)2]/r(parent)2). RESULTS: The bifurcating ratio was found to be distributed in a nonnormal fashion, with a median of 0.76. The average area expansion ratio Aexp, characterizing the change of cross-sectional area of the vasculature from proximal to distal, was 0.93+/-0.26. The 'rate of branching' (d(i)/(d(0)) was defined by the segment diameter relative to the diameter of the root segment. Averaging the rate of branching over segments within each bifurcation level resulted in a decreasing function of bifurcation level. CONCLUSIONS: This article provides new experimental data on branching geometry of coronary arteries (i.e., the trees evaluated in this study are purely delivering rather than conveying). Based on these facts, we suggest that the analytical bifurcation law in CCO might be replaced by the bifurcation rule obeyed on a stochastic basis only.

Morphological and clinical aspects of scapular fasciocutaneous free flap transfer for treatment of venous insufficiency in the lower extremity.

We have recently shown that free scapular fasciocutaneous flaps transferred to the lower extremities of patients with chronic venous insufficiency and cutaneous ulcers have resulted in improvement in venous refilling times measured by photoplethysmography in the flap areas and that recurrent ulceration does not recur for up to 7 years. We hypothesized that the transferred flaps contained valves in their microvascular bed, which facilitated venous return, and using scanning electron microscopy of vascular corrosion casts and light and transmission electron microscopy of tissue sections prepared from human dorsal thoracic fascia, we showed that valves were most abundant in veins with a luminal diameter of 30-120 microm (59.3% of 905 valves). The depth of these valves increased with venous diameter, but the size of valve sinuses was not different for individual valves. Except for veins > 1,000 microm in diameter, there was no significant difference in the number of valves in different parts of an individual flap or between different flaps. Most valves were bicuspid; only in the vein Category 30-120 microm were unicuspid valves encountered. Valves were sometimes located in series in a short segment of a vein; occasionally they were found at the merging of two veins. Transmission electron microscopy showed that valve leaflets had collagen fibers that ascended toward the tip of the leaflet and were occasionally accompanied by elastic fibers. Myofibroblasts were regularly present in the valve leaflets. The present report reviews and updates these anatomic data about the human scapular region, focusing on venous valvular microstructure, and suggests that the high number of smaller-size valves contributes to improved hemodynamic of the leg and thus the clinical success of free scapular flaps used to treat cutaneous ulcerations in the lower extremity.

Sphincters of canine hepatic sublobular veins respond to endothelin-1 and 3.

The dog has been used repeatedly as a model in liver transplantation research. The microcirculation and its regulatory mechanisms play a crucial role during ischemia and reperfusion. Little is known about the role of venous sphincters in regulating blood flow in the dog liver. Hence, we performed this study to elucidate their potential role in regulating local blood flow. In 14 dogs mean systemic (MSP) and mean portal venous pressure (MPP) were measured. Light and electron microscopy (scanning and transmission) of tissue sections and vascular corrosion casts were used to elucidate the microvascular morphology. Immunocytochemistry was applied to identify smooth muscle cells and the innervation of venous sphincters. Endothelins 1 and 3 were injected to find whether the hepatic venous sphincters are sensitive to these vasoactive agents. Tufts of smooth muscle cells were found in the sublobular veins (SLV; 100 to 250 microm in diameter), that reduced the luminal diameters of veins by 34%. Nerve endings were not observed close to these venous sphincters. The MSP and MPP were 75.3+/-2.4 mmHg and 8.9+/-0.95 mmHg, respectively. Treatment with 1.0 microg/kg of endothelin-1 (ET-1) significantly increased the MSP, the MPP and the percentage of focal venous sphincter contraction by 39% (105+/-4.7 mmHg), 43% (12.8+/-1.7 mmHg) and 57% (53.5+/-4.7), respectively (P <0.01). Treatment with ET-3 caused a significant (P <0.01) decrease in the MSP, the MPP and the percentage of sphincter contraction by 19% (61.0+/-2.2 mmHg), 39% (5.8+/-2.9 mmHg) and 38% (20.9%+/-3.15). Sinusoids did not contain sphincters. Hepatic arterioles and central veins were not affected by ET-treatment. The contraction of SLV sphincters correlated with increases in MPP (r=0.81, P <0.01) and was related to the MSP (r=0.67, P <0.01). These data show that the smooth muscle sphincters in SLV of the dog liver are involved in the local regulation of blood flow and that these sphincters are stimulated by non-neurogenic mechanisms. These sphincters contract in response to ET-1 and relax in response to ET-3. Since ET-1 is released during and/or causes inflammation, e.g., during ischemia and reperfusion, its antagonists might be of benefit during transplantation reperfusion of liver.

Endothelin-1 causes luminal constrictions in rat cochlear veins.

Serum levels of the vasoconstrictor endothelin-1 (ET-1) increase in ischemia and systemic hypertension. We examined the effects of ET-1 on the cochlear microvasculature. Blood vessels were cast with methacrylate in adult male Wistar Kyoto rats, 10 min after intravenous injection of ET-1 (1.0 microg/kg); control animals received saline. Systemic blood pressure was recorded continuously. ET-1 increased the average systolic pressure by 18% and average diastolic pressure by 22% (P < 0.01). Scanning electron microscopy of cast vessels showed multiple circumscribed luminal constrictions on: (1) postcapillary venules; (2) collecting veins; (3) where collecting veins merged with the spiral modiolar vein; (4) on the spiral modiolar vein itself. Circumscribed constrictions in arteries were not observed. In ET-1 injected animals focal contractions of collecting veins reduced luminal width by 13.4% +/- 2.9 (P < 0.01). In control rats, constrictions on venous casts were minimal and constrictions on arteries were not observed. The present study shows that ET-1 is involved in local control of cochlear blood flow in that it focally contracts cochlear veins. It is suggested that this might be due to the high affinity of ET-1 receptors and/or the large number of ET-1 receptors on contractile cells in venous walls.

Morphologic sites for regulating blood flow in the exocrine pancreas.

The exocrine pancreas has a lobular structure and an intricate capillary network supplies the lobules. Casts of these capillaries are either straight and of constant width, provided with many shallow crests, or undulating and of varying diameter, provided with bulges and deeper constrictions. The mean capillary cast diameter is 6.32 microns (SD 0.53) and 3.91 microns (SD 0.84) at constriction sites. The first type corresponds to non-fenestrated capillaries, makes 24% of capillaries and is more frequently provided with pericytes (2.7 +/- 0.9 pericytes per capillary profile). The second type corresponds to fenestrated capillaries, comprises 76% of the capillaries and is less frequently provided with pericytes (1.5 +/- 0.6 pericytes per capillary profile). The endothelial cells of capillaries regularly form intermediate junctions and microvilli and contain microtubuli and cytoplasmic filaments. Intravital observations show that capillaries are capable of contracting and narrowing the capillary lumen. This contractility is accomplished by endothelial cells both at and apart from their nuclear regions while pericytes never contracted spontaneously during our in vivo observations. The capillary diameters estimated by intravital measurements, 3.53 microns (SD 1.05), are similar to cast measurements but differ at constricted segments from cast measurements. Flow reduction shows more variability in smaller capillaries and the flow is more reduced in capillaries of 5 microns diameter to about 40% of open capillaries vs. 68% in capillaries with 7.5 microns diameter. Veins are either provided with smooth muscle sphincters or with valves. These results indicate that corrosion casting accurately shows the geometry of capillaries. However, where the capillaries are drastically constricted, they might not be filled and therefore may be underestimated during measurements. Since none of the intravital luminal constrictions are small enough to reduce flow (smaller than 1 micron luminal diameter) and because many constrictions are effective to reduce flow, we conclude that capillaries of the exocrine pancreas are always capable of maintaining continuous blood flow yet can influence blood perfusion. The presence of venous valves in association with venous sphincters constitutes a new situation concerning blood drainage regulation in the exocrine pancreas.

Localization of endothelin-1 and endothelin-3 in the cochlea.

The distribution of endothelin-1 (ET-1) and endothelin-3 (ET-3) was studied by indirect immunostaining of decalcified guinea pig and rat cochleae. No species differences were observed. Perikarya and processes of spiral ganglion cells were highly reactive for both ET-1 and ET-3. The epithelial lining of the cochlear duct stained for ET-1 and ET-3, but reactivity for ET-1 was higher in the lining cells of the inner sulcus, Claudius', and Hensen's cells, while the tympanic covering layer of the basilar membrane stained stronger for ET-3 compared to ET-1. In the stria vascularis, all cell types stained for ET-3, while marginal cells were more reactive for ET-1. Spiral ligament fibroblasts were reactive for ET-1, but not for ET-3. Connective tissue cells of the spiral limbus stained for both endothelins. The region of synapses on outer hair cells reacted for ET-1 and ET-3 but sensory cells remained unstained. Endothelins are discussed to act as modulatory peptides, possibly interfering with nitric oxide, prostaglandins, and atrial natriuretic peptide in the lateral cochlear wall (lateral cochlear wall, i.e. stria vascularis and spiral ligament). The occurrence of endothelins in cochlear neurons suggest their potential role as neurotransmitters.