Embryonic lethality and vascular defects in mice lacking the Notch ligand Jagged1. (17/4225)

The Notch signaling pathway is an evolutionarily conserved intercellular signaling mechanism essential for embryonic development in mammals. Mutations in the human JAGGED1 ( JAG1 ) gene, which encodes a ligand for the Notch family of transmembrane receptors, cause the autosomal dominant disorder Alagille syndrome. We have examined the in vivo role of the mouse Jag1 gene by creating a null allele through gene targeting. Mice homozygous for the Jag1 mutation die from hemorrhage early during embryogenesis, exhibiting defects in remodeling of the embryonic and yolk sac vasculature. We mapped the Jag1 gene to mouse chromosome 2, in the vicinity of the Coloboma ( Cm ) deletion. Molecular and complementation analyses revealed that the Jag1 gene is functionally deleted in the Cm mutant allele. Mice heterozygous for the Jag1 null allele exhibit an eye dysmorphology similar to that of Cm /+ heterozygotes, but do not exhibit other phenotypes characteristic of Cm /+ mice or of humans with Alagille syndrome. These results establish the phenotype of Cm /+ mice as a contiguous gene deletion syndrome and demonstrate that Jag1 is essential for remodeling of the embryonic vasculature.  (+info)

Developmental expression of aquaporin 1 in the rat renal vasculature. (18/4225)

Aquaporin 1 (AQP-1) is a water channel protein that is constitutively expressed in renal proximal tubule and descending thin limb cells as well as in endothelial cells of the descending vasa recta. Studies in the developing rat kidney have demonstrated that AQP-1 is expressed in renal tubules before birth. However, nothing is known about the expression of AQP-1 in the renal vasculature during kidney development. The purpose of this study was to establish the distribution of AQP-1 in the renal vasculature of the developing rat kidney and follow the differentiation of the vascular system during kidney development. Kidneys from 16-, 17-, 18-, and 20-day-old fetuses and 1-, 4-, 7-, 14-, 21-, and 28-day-old pups were preserved and processed for immunohistochemical studies using a preembedding immunoperoxidase procedure. AQP-1 immunoreactivity was detected using affinity-purified rabbit polyclonal antibodies to AQP-1. AQP-1 was expressed throughout the arterial portion of the renal vasculature of the fetal and neonatal kidney from gestational age 17 days to 1 wk after birth. AQP-1 immunoreactivity gradually disappeared from the renal vasculature between 1 and 2 wk of age and remained only in the descending vasa recta. In contrast, AQP-1 immunoreactivity was not observed in lymphatic vessels until 3 wk of age and persisted in the adult kidney. AQP-1 was also expressed in a population of interstitial cells in the terminal part of the renal papilla at 3 wk of age as well as in the adult kidney. The transient expression of AQP-1 in the arterial portion of the renal vasculature in the developing rat kidney suggests that AQP-1 is important for fluid equilibrium and/or drainage in the developing kidney or, alternatively, plays a role in the regulation of growth and/or branching of the vascular tree during kidney development.  (+info)

Validation of diameter measurements by ultrasound: intraobserver and interobserver variations assessed in vitro and in fetal sheep. (19/4225)

OBJECTIVES: Blood flow evaluation in the fetus is hampered by inaccuracy in the measurement of vessel diameter. The impact of biological variation on reproducibility studies is unknown. The present study evaluated diameter measurements carried out with modern ultrasound equipment by assessing inter- and intraobserver variations. DESIGN: Repeated measurements analyzed by a general factorial model of analysis of variance. METHODS: Three observers measured repeatedly (six or more times for each tube and session) silicone tube implants (0.6, 2.2 and 6 mm), applying ultrasound imaging in eight fetal sheep, and the same silicone tubes in vitro. Analysis of variance was carried out on 199 observations made in vitro and 537 in vivo. RESULTS: The upper 95% confidence limit for the intra- and interobserver variations was higher for measurements made in vivo than in vitro. It was highest for the largest diameter and varied between 0.10 and 0.38 mm. When the diameter was determined as an average of repeated measurements, the error was reduced: six measurements in vivo had upper 95% confidence limits for intraobserver variation of 0.04 and 0.09 mm for diameters of 0.6 and 6 mm, respectively. CONCLUSIONS: The results show that ultrasound diameter measurements have a high reproducibility even for vessels of small dimensions when repeated measurements are taken with high-frequency ultrasound under favorable conditions. The low variation described in the present investigation of silicone tubes, compared to previous studies, suggests that diameter changes of living vessels represent a separate source of measurement variation.  (+info)

Adenosine 5'-triphosphate and neuropeptide Y are co-transmitters in conjunction with noradrenaline in the human saphenous vein. (20/4225)

1. Human saphenous veins were used to assess the cooperative participation of adenosine 5-triphosphate (ATP), neuropeptide Y (NPY), and noradrenaline (NA) in the vasomotor responses elicited following electrical depolarization of the perivascular nerve terminals. Rings from recently dissected human biopsies were mounted to record isometric muscular contractions; the motor activity elicited in the circular muscle layer following electrical depolarization (2.5-20 Hz, 50 V, 0.5 msec) were recorded. 2. Incubation of the biopsies with either 100 nM tetrodotoxin (TTX) or 1 microM guanethidine abolished the vasomotor response elicited by electrical nerve depolarization. The independent application of either ATP or NA to vein rings induced concentration-dependent contractions. 3. Tissue incubation with 30 microM suramin or 10 nM prazosin produced 10 fold rightward displacements of the alpha,beta-methylene ATP and NA concentration-response curves respectively. NPY contracted a limited number of biopsies, the vasoconstriction elicited was completely blocked by 1 microM BIBP 3226. A 5 min incubation of the biopsies with 10-100 nM NPY synergized, in a concentration-dependent fashion, both the ATP and the ATP analogue-induced contractions. Likewise, tissue preincubation with 10 nM NPY potentiated the vasomotor responses evoked with 20-60 nM NA. 4. Neither suramin, BIBP 3226, nor prazosin was individually able to significantly modify the derived frequency-tension curves. In contrast, the co-application of 30 microM suramin and 10 nM prazosin or 30 microM suramin and 1 microM BIBP 3226, elicited a significant (P<0.01) downward displacement of the respective frequency-tension curves. 5. The simultaneous application of the three antagonists-30 microM suramin, 1 microM BIBP 3226 and 10 nM prazosin-caused a significantly greater displacement of the frequency-tension curve than that achieved in experiments using two of these antagonists. 6. Electrically-evoked vasomotor activity is blocked to a larger extent by tissue incubation with 2.5 microM chloroethylclonidine and 30 microM suramin rather than with 10 nM 5 methyl urapidil and 30 microM suramin. As a result, the alpha1-adrenoceptor involved in the vasomotor activity has tentatively been associated with the alpha1B adrenoceptor family subtype. 7. Results support the physiological role of ATP in sympathetic neurotransmission. The present results are consistent with the working hypothesis that human sympathetic vasomotor reflexes involve the coordinated motor action of ATP, NPY, and NA acting on vascular smooth muscle cells. The present results support the concept of sympathetic co-transmission in the human saphenous vein.  (+info)

Embryonic death of Mek1-deficient mice reveals a role for this kinase in angiogenesis in the labyrinthine region of the placenta. (21/4225)

Mek is a dual-specificity kinase that activates the extracellular-signal-regulated (Erk) mitogen-activated protein (MAP) kinases upon agonist binding to receptors. The Erk MAP kinase cascade is involved in cell-fate determination in many organisms. In mammals, this pathway is proposed to regulate cell growth and differentiation. Genetic studies have shown that although a single mek gene is present in Caenorhabditis elegans, Drosophila and Xenopus, two mek homologs, Mek1 and Mek2, are present in the mammalian cascade. In the present study, we describe a mutant mouse line in which the mek1 gene has been disrupted by insertional mutagenesis. The null mutation was recessive lethal, as the homozygous mutant embryos died at 10.5 days of gestation. Histopathological analyses revealed a reduction in vascularization of the placenta that was due to a marked decrease of vascular endothelial cells in the labyrinthine region. The failure to establish a functional placenta probably explains the death of the mek1-/- embryos. Cell-migration assays indicated that mek1-/- fibroblasts could not be induced to migrate by fibronectin, although the levels of Mek2 protein and Erk activation were normal. Re-expression of Mek1 in the mutant mouse embryonic fibroblasts (MEFs) restored their ability to migrate. Our findings provide genetic evidence that establishes the unique role played by Mek1 in signal transduction. They also suggest that mek1 function is required for normal response to angiogenic signals that might promote vascularization of the labyrinthine region of the placenta.  (+info)

Changes in vascular basement membrane in the endometrium of Norplant users. (22/4225)

Progestogen-only contraception is almost invariably associated with changes in menstrual bleeding patterns. Changes in the endometrial vasculature, and in particular an increase in vascular fragility, may contribute to this bleeding. In this study, endometrial vascular density and endothelial cell basement membrane components were examined using immunohistochemistry before and after insertion of Norplant. Endometrial vascular density was increased from a mean (+/- SEM) of 189.6 +/- 7.0 vessels/mm2 during the control cycle to 253.9 +/- 80.7 vessels/mm2 at 2-13 weeks of Norplant exposure, and to 212.7 +/- 12.9 vessels/mm2 at 14-42 weeks. During the control cycle, a mean of 161.4 +/- 4.5 vessels/mm2 stained for collagen IV (85% of all vessels), while at 2-13 weeks, 144.5 +/- 13.0 vessels/mm2 stained for collagen IV (57% of all vessels) (t ratio = 2.08, P = 0.0057). By 14-42 weeks, 71% of vessels (151.0 +/- 9.8) vessels/mm2 were surrounded by collagen IV. This was not significantly different from control values (t ratio = 2.03). Endometrial vascular laminin was also reduced following Norplant insertion, from a mean of 176.0 +/- 4.2 vessels/mm2 in the control cycle (93% of vessels), to 156.3 +/- 6.7 vessels/mm2 at 2-13 weeks of exposure (57% of vessels) (t ratio = 2.08, P = 0.01). By 14-42 weeks of exposure to Norplant, 162.5 +/- 9 vessels/mm2 (76%) stained for laminin. This was not significantly different from control values (t ratio = 2.04). Endometrial vascular heparan sulphate proteoglycan (HSPG) was reduced from 58.6 +/- 3.0 vessels/mm2 during the control cycle (31% of vessels) to 43.6 +/- 5.6 vessels/mm2 (only 17% of vessels) at 2-13 weeks (t ratio = 2.08, P = 0.025). At 14-42 weeks, only 19% of vessels stained for HSPG (41.3 +/- 5.8 vessels/mm2; t ratio = 2.04, P = 0.009).  (+info)

Examination on biological activities and fates of new steroids, steroid-17-yl methyl glycolate derivatives. (23/4225)

A variety of acyl derivatives based on the "antedrug" concept were synthesized to evaluate their biological activities, in vitro fate in human serum and examine pharmacokinetics in rats. Among the prepared compounds, acetyl and pivaloyl derivatives (8 and 9) showed strong to vasoconstrictive activity in human, exceeding that of dexamethasone. In rats, topical administration of the compound 8 significantly reduced oxazolone-induced ear edema compared to that of control. These activities were almost equal to that of prednisolone, however 9 did not show any suppression of the oxazolone-induced edema. The in vitro half-lives of 8 and 9 in human serum were 18.2 and 43.8 hours, respectively. Prednisolone and dexamethasone were extremely stable under the used conditions. When compound 8 was intravenously administrated to rats, its metabolites, 20(R)-methyl dexamethasonate (4) and carboxylic acid (18), were found in the systemic blood. The total body clearance of 8 was 1734 ml x hr(-1) x kg(-1), which was about 12 times larger than that of dexamethasone. On the other hand, 9 was found to be metabolized instantaneously to methyl prednisolonate (1) in systemic serum. Acetyl derivative 8 derived from dexamethasone may thus be useful as a topical steroid which offers the advantage of a low potential for systemic and local side effects.  (+info)

The importance of surgeon volume and training in outcomes for vascular surgical procedures. (24/4225)

PURPOSE: Mortality and morbidity rates after vascular surgical procedures have been related to hospital volume. Hospitals in which greater volumes of vascular surgical procedures are performed tend to have statistically lower mortality rates than those hospitals in which fewer procedures are performed. Only a few studies have directly assessed the impact of the surgeon's volume on outcome. Therefore, the purpose of this study was to review a large state data set to determine the impact of surgeon volume on outcome after carotid endarterectomy (CEA), lower extremity bypass grafting (LEAB), and abdominal aortic aneurysm repair (AAA). METHODS: The Florida Agency for Health Care Administration state admission data from 1992 to 1996 were obtained. The data included all nonfederal hospital admissions. Frequencies were calculated from first-listed International Classification of Diseases-9 codes. Multiple logistic regression was used to test the significance on outcome of surgeon volume, American Board of Surgery certification for added qualifications in general vascular surgery, hospital size, hospital volume, patient age, and gender. RESULTS: During this interval, there were 31,172 LEABs, 45,744 CEAs, and 13,415 AAAs performed. The in-hospital mortality rate increased with age. A doubling of surgeon volume was associated with a 4% reduction in risk for adverse outcome for CEA (P =.006), an 8% reduction for LEAB, and an 11% reduction for AAA ( P =.0002). However, although hospital volume was significant in predicting better outcomes for CEA and AAA procedures, it was not associated with better outcomes for LEAB. Certification for added qualifications in general vascular surgery was a significant predictor of better outcomes for CEA and AAA. Certified vascular surgeons had a 15% lower risk rate of death or complications after CEA (P =.002) and a 24% lower risk rate of a similar outcome after AAA (P =.009). However, for LEAB, certification was not significant. CONCLUSION: Surgeon volume and certification are significantly related to better patient outcomes for patients who undergo CEA and AAA. In addition, surgeons with high volumes demonstrated consistently lower mortality and morbidity rates than did surgeons with low volumes. Hospital volume for a given procedure also is correlated with better outcomes.  (+info)