Nanostructure of Poly(Acrylic Acid) Adsorption Layer on the Surface of Activated Carbon Obtained from Residue After Supercritical Extraction of Hops.

The nanostructure of poly(acrylic acid) (PAA) adsorption layer on the surface of mesoporous-activated carbon HPA obtained by physical activation of residue after supercritical extraction of hops was characterized. This characterization has been done based on the analysis of determination of adsorbed polymer amount, surface charge density, and zeta potential of solid particles (without and in the PAA presence). The SEM, thermogravimetric, FTIR, and MS techniques have allowed one to examine the solid surface morphology and specify different kinds of HPA surface groups. The effects of solution pH, as well as polymer molecular weight and concentration, were studied. The obtained results indicated that the highest adsorption on the activated carbon surface was exhibited by PAA with lower molecular weight (i.e., 2000 Da) at pH 3. Under such conditions, polymeric adsorption layer is composed of nanosized PAA coils (slightly negatively charged) which are densely packed on the positive surface of HPA. Additionally, the adsorption of polymeric macromolecules into solid pores is possible.

Haldane's rule revisited: do hybrid females have a shorter lifespan? Survival of hybrids in a recent contact zone between two large gull species.

Haldane's rule predicts that particularly high fitness reduction should affect the heterogametic sex of interspecific hybrids. Despite the fact that hybridization is widespread in birds, survival of hybrid individuals is rarely addressed in studies of avian hybrid zones, possibly because of methodological constraints. Here, having applied capture-mark-recapture models to an extensive, 19-year-long data set on individually marked birds, we estimate annual survival rates of hybrid individuals in the hybrid zone between herring (Larus argentatus) and Caspian (Larus cachinnans) gulls. In both parental species, males have a slightly higher survival rate than females (model-weighted mean ± SE: herring gull males 0.88 ± 0.01, females 0.87 ± 0.01, Caspian gull males 0.88 ± 0.01, females 0.87 ± 0.01). Hybrid males do not survive for a shorter time than nonhybrid ones (0.88 ± 0.01), whereas hybrid females have the lowest survival rate among all groups of individuals (0.83 ± 0.03). This translates to a shorter adult (reproductive) lifespan (on average by 1.7-1.8 years, i.e. ca 25%) compared with nonhybrid females. We conclude that, in line with Haldane's rule, the lower survival rate of female hybrids may contribute to selection against hybrids in this hybrid zone.

Development of parasitic Maculinea teleius (Lepidoptera, Lycaenidae) larvae in laboratory nests of four Myrmica ant host species.

Maculinea butterflies are social parasites of Myrmica ants. Methods to study the strength of host ant specificity in the Maculinea-Myrmica association include research on chemical and acoustic mimicry as well as experiments on ant adoption and rearing behaviour of Maculinea larvae. Here we present results of laboratory experiments on adoption, survival, development and integration of M. teleius larvae within the nests of different Myrmica host species, with the objective of quantifying the degree of specialization of this Maculinea species. In the laboratory, a total of 94 nests of four Myrmica species: M. scabrinodis, M. rubra, M.ruginodis and M. rugulosa were used. Nests of M. rubra and M. rugulosa adopted M. teleius larvae more readily and quickly than M. ruginodis colonies. No significant differences were found in the survival rates of M. teleius larvae reared by different ant species. Early larval growth of M. teleius larvae differed slightly among nests of four Myrmica host species. Larvae reared by colonies of M. rugulosa which were the heaviest at the beginning of larval development had the lowest mean larval body mass after 18 weeks compared to those reared by other Myrmica species. None of the M.teleius larvae was carried by M. scabrinodis or M. rubra workers after ant nests were destroyed, which suggests a lack of integration with host colonies. Results indicate that Myrmica species coming from the same site differ in their ability to adopt and rear M. teleius larvae but there was no obvious adaptation of this butterfly species to one of the host ant species. This may explain why, under natural conditions, all four ants can be used as hosts of this butterfly species. Slight advantages of particular Myrmica species as hosts at certain points in butterfly larval development can be explained by the ant species biology and colony structure rather than by specialization of M. teleius.

Impaired PTPN13 phosphatase activity in spontaneous or HPV-induced squamous cell carcinomas potentiates oncogene signaling through the MAP kinase pathway.

Human papillomaviruses (HPVs) are a causative factor in over 90% of cervical and 25% of head and neck squamous cell carcinomas (HNSCCs). The C terminus of the high-risk HPV 16 E6 oncoprotein physically associates with and degrades a non-receptor protein tyrosine phosphatase (PTPN13), and PTPN13 loss synergizes with H-Ras(V12) or ErbB2 for invasive growth in vivo. Oral keratinocytes that have lost PTPN13 and express H-Ras(V12) or ErbB2 show enhanced Ras/RAF/MEK/Erk signaling. In co-transfection studies, wild-type PTPN13 inhibited Ras/RAF/MEK/Erk signaling in HEK 293 cells that overexpress ErbB2, EGFR or H-Ras(V12), whereas an enzymatically inactive PTPN13 did not. Twenty percent of HPV-negative HNSCCs had PTPN13 phosphatase mutations that did not inhibit Ras/RAF/MEK/Erk signaling. Inhibition of Ras/RAF/MEK/Erk signaling using MEK inhibitor U0126 blocked anchorage-independent growth in cells lacking PTPN13. These findings show that PTPN13 phosphatase activity has a physiologically significant role in regulating MAP kinase signaling.

Total hip replacement in renal transplant patients.

Avascular necrosis of the femoral head creates considerable morbidity in successful renal transplant recipients who are generally young and expect active lifestyles. Total hip replacement is considered the treatment of choice in these patients, but surgeons may be wary because of a supposed increase in the risk of infection and other complications. A review of the literature reveals that cemented hip arthroplasty provides good to excellent functional outcomes for renal transplant patients. Most authors have found that the risk of infection is not increased despite chronic immunosuppression, but the rates of general complications are and should be anticipated and treated. There is a high rate of early failure in these patients because of their young age and diffuse osteopenia as a result of secondary hyperparathyroidism related to the underlying renal disease and chronic steroid use. Recent studies have found that despite decreased bone stock in these patients, porous-coated prostheses are not contraindicated.

Influence of the absolute configuration on pharmacological activity of antihypertensive and antiarrhythmic drugs.

Chirality is a fundamental property of biological systems and reflects the underlying asymmetry of matter. Interactions of drugs with receptors, enzymes or binding sites have long been known to be stereoselective, and it is increasingly recognized that both pharmacodynamic and pharmacokinetic events contribute to the overall clinically observed stereoselectivity. The pharmacological activity may reside only in one enantiomer, while the second one may be inactive or have desirable or undesirable activity. Two isomers may be nearly identical both in qualitative and quantitative aspects of pharmacological activity. The activity of particular enantiomers may differ only at the quantitative level. It is also possible that a particular enantiomer displays qualitatively different mode of action than the second one. This review describes the influence of the absolute configuration on pharmacological activity of the selected currently used or being under investigation drugs acting on cardiovascular system, especially as the antihypertensive and antiarrhythmic agents.

Evaluation of sex hormone levels and some metabolic factors in men with coronary atherosclerosis.

BACKGROUND: Because of the great controversy over the role of androgens in the pathogenesis of atherosclerosis, we investigated the relationship between serum sex hormone levels and angiographically confirmed coronary artery disease in men. MATERIAL AND METHODS: We investigated 86 men aged 40-60 years, 56 with coronary artery disease and 30 healthy men, matched by age, as a control group. Body mass index and waist to hip ratio were calculated and total body fat mass and percentage of abdominal deposit were investigated by dual-energy X-ray absorptiometry (Dpx (+) Lunar, USA). The serum levels of sex hormones and insulin were measured using commercial radioimmunoassay and IRMA (by SHBG) kits (DPC, USA). The serum levels of lipids and glucose were assessed by means of enzymatic methods. RESULTS: Men with coronary artery disease had lower total testosterone levels (17.01+/-6.42 vs. 19.37+/-6.58 nmol/l; p < 0.05), testosterone/estradiol ratio (228.5+/-88.5 vs. 289.8+/-120.1; p < 0.05) and free androgen index (FAI) (59.49+/-14.79 vs. 83.03+/-25.81; p < 0.0001), and higher levels of estrone (49.5+/-27.7 vs. 36.6+/-12.7 pg/ml) than men in the control group. Moreover, men with coronary artery disease were more insulin-resistant than controls and had an atherogenic lipid profile. There was an inverse correlation (p < 0.05) between testosterone level and serum level of glucose (r = -0.29), triglycerides (r= -0.37), body mass index (r= -0.55), waist (r = - 0.43), total body fat mass (r = - 0.3) and fasting insulin resistance index. A significant positive association (p < 0.05) was found between testosterone and the quantitative insulin sensitivity check index and high density lipoprotein cholesterol level in serum (r = 0.26). CONCLUSIONS: Low levels of total testosterone, testosterone/estradiol ratio and free androgen index and higher levels of estrone in men with coronary artery disease appear together with many features of metabolic syndrome and may be involved in the pathogenesis of coronary atherosclerosis.

Redox signaling of the arteriolar myogenic response.

Arteriolar vascular smooth muscle cells (VSMCs) are mechanosensitive, constricting to elevations in transmural pressure (P(TM)). The goal of the present study was to determine using mouse isolated tail arterioles and arteries whether oxidant signaling regulates this myogenic response. In response to P(TM) elevation, VSMCs of arterioles but not arteries generated constriction and increased reactive oxygen species (ROS) activity (using the H(2)O(2)-sensitive probe dichlorodihydrofluorescein). Arterioles had increased expression of NADPH oxidase components compared with arteries. Inhibition of NADPH oxidase, using mice with targeted impairment of enzyme components (p47(phox) or rac1) or diphenyleneiodonium, prevented the pressure-induced generation of ROS. When ROS activity was inhibited, either by inhibiting NADPH oxidase or with N-acetylcysteine, the myogenic constriction was abolished. The myogenic constriction was also inhibited by catalase, which inactivates H(2)O(2), but was unaffected by a cell-permeant mimic of superoxide dismutase (MnTMPyP). alpha(1)-Adrenergic constriction was not associated with altered ROS activity and was not affected by inhibition of NADPH oxidase or ROS. Exogenous H(2)O(2) constricted VSMCs of arterioles but not arteries. Thus, NADPH oxidase and ROS, in particular H(2)O(2), contribute to the myogenic response of arteriolar VSMCs.

Determinants of terminal mesenteric artery resistance during the first postnatal month.

Experiments were conducted to delineate the vascular effector systems that contribute to setting mesenteric vascular tone in swine during the first postnatal month. Terminal mesenteric arteries (TMA), which function as resistance vessels, were studied in vitro with a microvascular perfusion system allowing independent pressure and flow manipulation. When pressure was varied 0-100 mmHg in the absence of flow, TMA from 1-day-old animals demonstrated myogenic vasoconstriction, whereas TMA from 40-day-old animals did not. In 1- but not 40-day-old TMA, the endothelin A (ET(A)) receptor antagonist BQ-610 shifted the pressure-diameter curve upward, whereas the ET(B) receptor antagonist BQ-788 and the L-arginine analog N(G)-monomethyl-L-arginine (L-NMMA) shifted the curve downward; in all instances, myogenic vasoconstriction was preserved. Flow eliminated myogenic vasoconstriction in 1-day-old TMA, i.e., diameter increased as a function of pressure. The effect of BQ-610 was lost under flow conditions; however, BQ-788 and N-acyl-L-Trp-3,5-bis-(trifluoromethyl) benzyl ester, an antagonist specific to the substance P neurokinin-1 (NK(1)) receptor, shifted the pressure-diameter curve downward in the presence of flow, whereas L-NMMA restored myogenic vasoconstriction. Adding flow had no effect on the pressure-diameter relationship in 40-day-old TMA. Other blocking agents, including prazosin, losartan, indomethacin, and charybdotoxin, had no effect on the pressure-diameter relationship in either age group under flow or no-flow conditions. Constitutive production of nitric oxide (NO) and endothelin-1 participates in setting resistance in 1-day-old TMA, and important stimulants to NO production include flow and activation of ET(B) and NK(1) receptors. In contrast, 40-day-old TMA act as passive conduits in which the elastic properties of the vessel are the primary determinant of diameter.

Relationship between flow rate and NO production in postnatal mesenteric arteries.

We studied mesenteric arterial arcades from 3- and 35-day-old swine to determine the relationship between perfusate flow rate and release of nitric oxide (NO) into mesenteric effluent. Mesenteric arterial arcades were perfused under controlled-flow conditions with a peristaltic pump using warm oxygenated Krebs buffer. Basal rates of NO production were 43.6 +/- 4.2 vs. 12.1 +/- 2.5 nmol/min in 3- vs. 35-day-old mesentery during perfusion at in vivo flow rates (9 vs. 20 ml/min, respectively). Rate of NO production was directly related to flow rate over a wide range of flows (5-40 ml/min) in 3- but not 35-day-old mesentery. Both age groups demonstrated a brisk, albeit brief, increase in NO production in response to infusion of NO-dependent vasodilator substance P (10(-8) M/min). Tyrosine kinase inhibitor herbimycin A and L-arginine analog L-NMMA significantly attenuated flow-induced increase in NO production, and phosphatase inhibitor phenylarsine oxide increased magnitude of flow-induced increase in NO production in 3-day-olds. Removal of extracellular Ca(2+) and depletion of intracellular Ca(2+) stores (Ca(2+)-free Krebs with EGTA plus thapsigargin) had no effect on NO production in either group. Thus, basal rate of NO production is greater in mesenteric arterial arcades from 3- than from 35-day old swine, a direct relationship between flow rate and NO production rate is present in mesentery from 3- but not 35-day-olds, and phosphorylation events are necessary for this interaction to occur.

Age-dependent changes in the postnatal intestinal microcirculation.

Significant changes occur in intestinal hemodynamics during the transition from fetal to newborn life and then again during the first postnatal month. Most importantly, basal vascular resistance substantially decreases following birth. It then decreases further between postnatal days 1 and 3, plateaus, and then begins a slow, progressive increase between postnatal days 12 and 30. The basal rate of intestinal blood flow mirrors the changes in vascular resistance in an inverse manner. The postnatal changes in vascular resistance appear to be mediated, in large part, by an increase in the constitutive and stimulated production of nitric oxide. Most importantly, the diameter of terminal mesenteric arteries (150-300 microm diameter) in newborn (i.e., 1 day old) swine is determined by three intrinsic vascular control systems: endothelial production of nitric oxide and endothelin, and the inherent myogenic response of vascular smooth muscle. In contrast, these vessels in older subjects (i.e., 35 days old) are primarily passive in nature and fail to demonstrate significant diameter change in response to blockade of endogenous nitric oxide production or endothelin receptors, or applied perturbations of pressure or flow rate. The circulatory physiology of the perinatal and newborn intestine is exceptional when compared to the adult condition inasmuch as several hemodynamic variables change quite dramatically between fetal and neonatal life and during the first postnatal month. The unique hemodynamic conditions that characterize the perinatal and newborn intestine appear to be part of the overall physiological transition that occurs as the fetus, once born, replaces the placenta with his gastrointestinal tract to obtain nutrition. The goal of this review is to describe the circulatory physiology of the perinatal and newborn intestine, with a particular emphasis on those portions of the intestinal microcirculation that have thus far been studied. First, however, it is important to discuss the age-dependent changes that occur within the intestinal circulation during perinatal and early newborn life.

Role of endothelin-1 in regulation of the postnatal intestinal circulation.

Newborn intestine is uniquely prone to vasoconstriction in response to a wide variety of perturbations. To test the hypothesis that endothelin (ET)-1 is an important factor in this process, we determined the effects of exogenous ET-1 administration and blockade of endogenous ET-1 in vivo and in vitro in 3- and 35-day-old swine. Intramesenteric artery administration of exogenous ET-1 to vascularly isolated in vivo gut loops (10(-9) M/kg bolus) caused vasoconstriction and reduced gut O(2) uptake similarly in these age groups. Selective blockade of ET(A) or ET(B) receptors with BQ-610 or BQ-788, respectively, in vascularly isolated in vivo gut loops had no effect on gut vascular resistance or O(2) uptake in either age group; within in vitro gut loops, BQ-610 significantly increased vasoconstriction when perfusion pressure was reduced below baseline, but only in 3-day-old animals; i.e., it impaired the autoregulatory response to perfusion pressure reduction. Exogenous ET-1 significantly decreased capillary perfusion within in vitro gut loops, as evidenced by a decrease in capillary filtration coefficient, but only in 3-day-old animals; furthermore, blockade of endogenous ET-1 activity with BQ-610 significantly enhanced capillary filtration coefficient in 3-day-old animals and increased O(2) extraction ratio. ET-1 did not depress intestinal metabolic rate, as evidenced by its effect on the O(2) uptake-blood flow relationship; it did compromise tissue oxygenation because of its effects on intestinal O(2) transport. ET-1 concentration in mesenteric venous effluent exceeded arterial concentration, but only in 3-day-old intestine, suggesting production of ET-1 by newborn intestine. We conclude that ET-1 exerts an age-dependent effect on intestinal hemodynamics in postnatal intestine, having a greater impact in 3- than in 35-day-old intestine.

Heparin-binding epidermal growth factor-like growth factor protects rat intestine from ischemia/reperfusion injury.

BACKGROUND: We have shown previously that heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is cytoprotective for intestinal epithelial cells exposed to hypoxia in vitro. We now examine the effects of HB-EGF on the recovery of small intestine from ischemic injury in vivo. METHODS: Segmental intestinal ischemia of 60-min duration was produced in adult rats by occlusion of a first-order branch of the superior mesenteric artery. Recombinant HB-EGF (100 microg) was injected intraluminally into the proximal small bowel after 45 min of ischemia in experimental animals, and buffered saline was injected in control animals. Animals were sacrificed after 48 h, and the affected bowel was resected, processed, and examined microscopically, with histologic grading of the ischemic injury. Additional animals were allowed to recover for up to 1 month to evaluate mortality differences. RESULTS: Intraluminal administration of HB-EGF resulted in significantly decreased extent and severity of ischemia/reperfusion injury, with significantly decreased grade of injury in the HB-EGF-treated compared with nontreated animals (average injury grade 0.66 compared with 2.44, respectively). Moreover, the mortality rate was significantly lower in the HB-EGF-treated animals compared with nontreated animals (0% vs 25%, respectively). HB-EGF-treated animals had increased weight gain in the postischemia recovery period. CONCLUSIONS: We conclude that HB-EGF, given intraluminally, reduces both the amount and the severity of ischemia/reperfusion injury in the small bowel, reduces the mortality associated with intestinal ischemia, and may enhance intestinal recovery. The in vitro and in vivo cytoprotective effects of this growth factor suggest that it may, in the future, be clinically useful in treating patients with intestinal ischemia.

Effects of sustained low-flow perfusion on the response to vasoconstrictor agents in postnatal intestine.

This laboratory has previously reported that sustained reduction of blood flow in newborn intestine causes a triphasic increase in vascular resistance that occurs over 3-4 h and that these changes are mediated, in part, by loss of endothelial nitric oxide (NO) production. This study examines the effects of exposure to sustained low-flow perfusion on the subsequent response to three contractile agonists: ANG II, norepinephrine (NE), and endothelin-1 (ET-1). Gut loops from 3- and 35-day-old swine were exposed to low-flow conditions in vivo (i.e., reduction of flow to approximately 50% of baseline) for 30 min or 5 h. Thereafter, they were removed to an extracorporeal perfusion circuit for in vitro hemodynamic assessment; alternatively, the mesenteric artery perfusing the gut loop was removed and cut into rings for assessment of isometric tension development. Gut loops from 3-day-old subjects exposed to low-flow conditions demonstrated significantly increased contractile responses to ANG II, NE, and ET-1; also, mesenteric artery rings from these gut loops demonstrated a significant reduction of the ED50 for all three agonists. Similar changes were not observed in intestine or mesenteric artery rings from older subjects. Sustained blockade of endogenous NO synthesis with NG-monomethyl- L-arginine duplicated the effects of exposure to sustained low-flow perfusion. It appears that sustained reduction of blood flow in newborn intestine decreases constitutive NO production, which in turn causes a generalized enhancement of the contractile efficacy of ANG II, NE, and ET-1.

Effects of systemic hypotension on postnatal intestinal circulation: role of angiotensin.

Systemic hypotension causes a greater degree of vasoconstriction in intestine from 3- than from 35-day-old postnatal swine. To determine the basis for this age-dependent difference, systemic hypotension (pressure reduction to approximately 50% of baseline) was induced by creating pericardial tamponade in postnatal swine instrumented to allow measurement of intestinal hemodynamics and oxygenation in vivo. Hypotension caused gut vascular resistance to increase 77 +/- 6% in 3-day-old subjects but only 18 +/- 3% in 35-day-old subjects. Prior blockade of alpha1-receptors with phentolamine, vasopressin receptors with [d(CH2)5,D-Phe2,Ile4,Ala9-NH2]AVP, or surgical denervation of the gut loop had no effect on hypotension-induced gut vasoconstriction. Losartan, which blocks angiotensin AT1 receptors, significantly attenuated hypotension-induced gut vasoconstriction in both age groups. BQ-610, which blocks endothelin ETA receptors, also limited the magnitude of vasoconstriction but only in younger subjects. This effect may have been consequent to an interaction between endothelin and angiotensin, inasmuch as a subpressor concentration of endothelin increased the contractile response to angiotensin in mesenteric artery rings. The substantial rise in 3-day-old gut vascular resistance was partly consequent to a locally mediated vasoconstriction that occurred in response to pressure and/or flow reduction during hypotension, as evidenced by the significant attenuation of this constriction when blood flow was held constant by controlled-flow perfusion to the gut loop during hypotension. Intestinal O2 uptake was compromised to a significantly greater degree in 3- than in 35-day-old subjects during hypotension. This difference was primarily due to the inability of younger intestine to increase O2 extraction in the face of reduced blood flow and may be mediated, in part, by an effect of angiotensin II on intestinal capillary perfusion.

Effects of sustained flow reduction on postnatal intestinal circulation.

Studies were conducted to determine the effect of mechanically induced sustained flow reduction on intestinal hemodynamics and oxygenation in 3- and 35-day-old swine. In vitro gut loops were perfused under controlled-pressure conditions from an oxygenated blood reservoir at age-appropriate perfusion pressures; pressure was rapidly reduced to a level that lowered flow rate to approximately 50% of its baseline value, and pressure was then kept at that level for 2 h. In 3-day-old intestine, vascular resistance (Ri) increased by 20% immediately after pressure and flow reduction but then stabilized for 3-4 min; thereafter, flow began to decrease despite maintenance of perfusion pressure, so that Ri increased an additional 15% by 30 min after flow reduction. Flow continued to diminish over the next 90 min, though at much slower rate. Intestine from 35-day-old swine demonstrated an immediate increase in Ri after pressure and flow reduction, but thereafter Ri increased very little. The protocol was repeated within in vitro gut loops perfused under controlled-flow conditions, and within autoperfused, innervated gut loops developed in vivo and similar observations were made in both preparations. In 3-day-old intestine, pretreatment with the L-arginine analog Nomega-monomethyl-L-arginine (10(-4) M) had no effect on the immediate rise in resistance occurring in the first 1 min but substantially attenuated the subsequent slow, progressive rise noted thereafter. Pretreatment with the angiotensin 1A receptor antagonist losartan (2 x 10(-6) M) had no effect on hemodynamic changes during the first 60 min after mechanical perfusion pressure reduction but attenuated the very slight increase in resistance noted during the final 60 min of the protocol. The postnatal intestinal circulation demonstrates progressive vasoconstriction when its flow rate is mechanically reduced in a sustained manner, and this effect is age specific, occurring in 3- but not 35-day-old swine. These changes in gut vascular resistance may be consequent to loss of nitric oxide production and/or local production of angiotensin.

Postnatal changes in gut hemodynamics: a possible role for substance P.

Studies were conducted in young postnatal swine to determine if substance P (SP) participates in the regulation of postnatal intestinal hemodynamics and oxygenation. SP was present in homogenates of whole intestine from postnatal swine in an age-dependent manner as follows: 1 day old and never fed, 126 +/- 35; 3 days old and fasted, 148 +/- 30; and 14 days old, 51 +/- 10 pg/mg protein (P < 0.01, 14- vs. 1- or 3-day-olds). Phenylephrine-precontracted rings of mesenteric artery from 3-day-old subjects mounted for tension recording within buffer-filled myographs demonstrated brisk relaxation in response to SP (EC50, 2 x 10(-10) M). This relaxation was eliminated by mechanical removal of the endothelium or blockade with the L-arginine analog NG-monomethyl-L-arginine (L-NMMA) and was significantly attenuated by pretreatment with N-acyl-L-Trp-3,5-bis-(trifluoromethyl) benzyl ester (NATB), a highly selective NK-1 receptor antagonist (pA2 5 x 10(-10) M). Infusion of exogenous SP into the mesenteric artery of innervated in vivo gut loops reduced intestinal vascular resistance 35% and increased tissue oxygen uptake 40% in both 3- and 14-day-old subjects. By contrast, blockade of the NK-1 receptor for SP with NATB increased intestinal vascular resistance 19% in 3-day-old subjects but only 5% in 14-day-old subjects (P < 0.01). SP-induced changes in gut vascular resistance were significantly attenuated by prior coinfusion of NATB or L-NMMA, indicating that the peptide exerted this vascular effect via theNK-1 receptor, which is linked to endothelial cell nitric oxide synthase. Both NATB and L-NMMA attenuated flow-induced dilation within pump-perfused in vitro gut loops from 3-day-old subjects. SP appears to participate in the regulation of the newborn intestinal circulation, especially during the first days after birth.

Segmental intestinal ischemia: an improved method of producing small bowel injury.

Previous animal models of intestinal ischemia-reperfusion have been successful in causing considerable mucosal damage, cellular destruction and sepsis. However, this often results in the death of the animal, making it impossible to examine the effects of modulators of the ischemic event. The sequence of morphologic and physiologic changes in the bowel from such injuries continues to be an area of intense examination. We have studied these changes by producing segmental intestinal ischemia in vivo in a rat model. By occluding a first-order branch of the superior mesenteric artery (SMA) and by selectively ligating terminal collateral branches, reproducible segmental intestinal ischemia was achieved. Bowel damage ranged from alterations in the villus structure to frank hemorrhagic necrosis of the intestinal wall. This model allows the study of hypoperfusion injury to the small intestine without total SMA occlusion, thus reducing the overall mortality.

Pressure and flow characteristics of terminal mesenteric arteries in postnatal intestine.

The responses of buffer-perfused terminal mesenteric arteries from 3- and 35-day-old swine to manipulation of intravascular pressure and flow rate were determined. Under in vivo conditions, these vessels demonstrated age-dependent differences in resting diameter (182 vs. 301 microns in 3- vs. 35-day-old swine). A proximal-to-distal pressure gradient was present in vessels from both age groups (delta 13 vs. delta 16 mmHg in 3- vs. 35-day-old swine), suggesting their functional role as resistance vessels. Vessels were mounted within an in vitro perfusion apparatus that allowed independent regulation of inflow and outflow pressure. Vessels from both age groups demonstrated the development of active tone in response to an incremental rise in pressure, applied in the absence of flow. However, myogenic vasoconstriction was only observed in younger arterioles. Similarly, both groups demonstrated dilation in response to a flow stimulus generated in the absence of a net change in intravascular pressure, although the magnitude of this response was significantly greater in younger vessels (+27 vs. +7% in 3- vs. 35-day-old swine). The dilatory response to flow was eliminated by NG-monomethyl-L-arginine (10(-4)M) but restored by coadministration of L-arginine (10(-3)M). Myogenic vasoconstriction was overridden by flow-mediated dilation in terminal mesenteric arteries from 3- but not 35-day-old swine after concomitant application of pressure and flow stimuli. We conclude that the hemodynamic characteristics of terminal mesenteric arteries are age dependent in postnatal swine.

The effects of ischemia-reperfusion on endothelial cell function in postnatal intestine.

The goal of these experiments was to determine whether the perturbation of ischemia-reperfusion has an age-dependent effect on subsequent endothelial cell production of nitric oxide. Three- and 35-d-old swine in the experimental group were exposed to 1-h partial ischemia (90% flow reduction) and 2-h reperfusion in vivo by creation and then removal of a mesenteric artery coarctation. Control subjects underwent exposure of the mesenteric artery only. After reperfusion, gut vascular resistance had increased 44 +/- 6% in 3-d-old, but had decreased 41 +/- 4% in 35-d-old subjects. At the completion of the in vivo portion of the protocol mesenteric artery was removed, and nitric oxide production was estimated in vitro, by measuring cGMP production by vessel segments or by measuring relaxation of phenylephrine-precontracted rings, both after stimulation of nitric oxide production by substance P or the calcium ionophore A23187. Compared with control, mesenteric artery segments from 3-d-old subjects demonstrated reductions in basal, substance P-stimulated (10(-8) M) and A23187-stimulated (10(-7) M) cGMP accumulation of 50 +/- 7%, 66 +/- 6% and 78 +/- 7%. Mesenteric artery segments from 35-d-old subjects demonstrated increases in basal, substance P-stimulated, or A23187-stimulated cGMP accumulations of 114 +/- 14%, 92 +/- 8%, or 78 +/- 9%. Compared with control, I/R rings from 3-d-old subjects demonstrated reductions in substance P-induced (10(-8) M) or A23187-induced (10(-7) M) relaxations of 56 +/- 7% or 30 +/- 7%. In contrast, 35-d-old ischemia-reperfusion rings demonstrated increases in substance P- or A23187-induced relaxation of 36 +/- 8% or 98 +/- 11%. It is concluded that ischemia-reperfusion has an age-dependent effect on endothelial production of NO within in vitro postnatal mesenteric artery and that these changes mirror the effects of ischemia-reperfusion on gut vascular resistance in vivo.