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Biomedical subjects

P A Vincent

Publications and source records attributed to P A Vincent.

At least 19 recordsLinked to original sources
PubMed1996

ATP-MgCL2 reduces intestinal permeability during mesenteric ischemia.

ATP-MgCl2 has been demonstrated to have beneficial attributes in numerous models of organ ischemia. In this study we examined whether ATP-MgCl2 could decrease permeability in ischemic segments of rat ileum. Ileal segments (nonischemic and ischemic) from the same rat were cannulated and perfused, and the plasma to lumen clearance of 51Cr-EDTA was measured. Ischemia increased permeability from a baseline value of 0.59 +/- 0.14 (mean +/- SEM in ml/min/g dry wt of intestine) to 1.10 +/- 0.14 at 90 min (n = 12), significantly higher than that of the nonischemic segments (0.55 +/- 0.07) at 90 min (P < 0.05). This was associated with a significant reduction in blood flow from 0.84 +/- 0.08 (n = 4) (mean +/- SEM ml/min/g wet wt of intestine) to 0.16 +/- 0.06 (n = 4) (P < 0.05) as measured by labeled microspheres. Rats receiving ATP-MgCl2 (100 micromol) (n = 8) pretreatment showed no increase in clearance over 90 min (baseline 0.69 +/- 0.07; 90 min 0.70 +/- 0.07) and no significant difference in blood flow from untreated ischemic segments (0.21 +/- 0.9) (n = 4). Tissue ATP levels determined enzymatically were significantly reduced by 5 min postischemia to 4.19 +/- 0.35 (n = 7) (P < 0.05) from a control value of 6.77 +/- 0.77 micromol/g dry wt (n = 14). ATP levels remained depressed at 30 min (3.45 +/- 0.35) and 90 min (3.38 +/- 0.26). ATP-MgCl2 treatment did not significantly alter these tissue ATP levels. These data indicate that ATP-MgCl2 prevents the increase of 51Cr-EDTA permeability during ischemia without alterations in tissue ATP levels or increases in intestinal blood flow.

Adenosine Triphosphate↗
PubMed1996

Thrombin increases fluid flux in isolated rat lungs by a hemodynamic and not a permeability mechanism.

Alpha-Thrombin increases endothelial protein permeability in vitro and induces weight gain in the isolated perfused lung. The objectives of this study were to determine whether thrombin increases endothelial permeability of the isolated perfused rat lung and whether a change in permeability or hemodynamics mediates the gain in lung weight. Endothelial protein permeability was assessed by regression analysis of 125I-labeled albumin clearance vs. fluid flux to determine the permeability-surface area product (PS) and the reflection coefficient (sigma). Thrombin (5 x 10(-8) or 5 x 10(-7) M) did not alter protein permeability from the control values of PS and sigma. Thrombin caused an overall increase in transvascular fluid flux, as depicted by a gain in lung weight. Pulmonary arterial and capillary pressures and arterial and venous resistances increased by 10 min after thrombin injection, and lung weight decreased due to arterial constriction. From 10 to 50 min, pressures and resistances decreased, but capillary pressure and venous resistance decreased to a lesser extent and, as a result, lung weight increased. Pretreatment with BQ-123, an endothelin-receptor antagonist, attenuated the sustained increases in pressures and resistances and the rate of lung weight gain. Indomethacin, a cyclooxygenase inhibitor, had no effect. These findings indicate that the increase in lung weight induced by thrombin results from an elevation of capillary pressure mediated, in part, by endothelin and is not due to an increase in endothelial protein permeability of the isolated perfused rat lung.

Animals↗
PubMed1995

Extracellular matrix incorporation of normal and NEM-alkylated fibronectin: liver and spleen deposition.

The incorporation of plasma fibronectin (pFn) into the extracellular matrix (ECM) is believed to influence tissue integrity, wound repair, and vascular permeability. In vitro, matrix assembly of Fn requires the binding of soluble Fn to cell-associated matrix assembly sites. Alkylation of human pFn (HFn) with N-ethylmaleimide (NEM) prevents the initial binding of Fn to matrix assembly sites as well as its in vitro incorporation into the ECM as reflected by detergent-insoluble 125I-labeled Fn (pool II Fn). We determined the kinetics of Fn matrix incorporation in tissue and whether NEM treatment of rat pFn (NEM-RFn) would limit its in vivo incorporation into ECM by analysis of pool I [deoxycholate (DOC) soluble] and pool II (DOC insoluble) 125I-Fn in tissues after its intravenous injection into rats. After intravenous injection, tissue incorporation of normal rat 125I-pFn was especially intense in liver and spleen, in agreement with the large amount of endogenous Fn detected in the matrices of these organs. Tissue deposition of plasma-derived 125I-RFn in liver and spleen peaked by 4 h, with significant (P < 0.01) loss over 24 h, indicating turnover of matrix Fn. Tissue localization of normal 125I-RFn in liver, lung, spleen, heart, and intestine was greater (P < 0.05) than 125I-NEM-RFn at 4 h. Normal HFn, but not NEM-HFn, was incorporated into tissues and colocalized with endogenous Fn in the matrix. To identify the cells mediating the intense incorporation of pFn into liver ECM, we compared matrix assembly of 125I-HFn by cultured fibroblasts, hepatocytes, and hepatic Kupffer cells. With fibroblasts, 125I-HFn in pool I reached steady state by 3 h, whereas 125I-HFn in pool II exceeded that in pool I by 6 h and continued to increase over 24 h. With hepatocytes, pool I 125I-HFn reached steady state by 1 h, and a progressive increase (P < 0.05) of 125I-HFn in pool II was observed over 24 h. Kupffer cells were not able to incorporate significant amounts of 125I-HFn into matrix. NEM-HFn displayed limited incorporation into ECM by both fibroblast and hepatocyte cultures. These novel observations suggest that the interaction of soluble pFn with matrix assembly sites is necessary to its in vivo incorporation into the ECM.

Alkylation↗
PubMed1995

Fibronectin attenuates increased endothelial monolayer permeability after RGD peptide, anti-alpha 5 beta 1, or TNF-alpha exposure.

Endothelial permeability can be altered by tumor necrosis factor-alpha (TNF-alpha), a cytokine released in association with inflammation-induced tissue injury. In the subendothelial matrix, fibronectin (Fn) influences endothelial cell adhesion by the interaction of integrins with RGD and non-RGD attachment sites in Fn. We compared the effect of TNF-alpha, RGD-containing peptides (GRGDSP), or antibody to alpha 5 beta 1-integrins on the protein permeability of bovine lung endothelial monolayers as assessed by transendothelial 125I-labeled albumin clearance. We also examined the influence of purified human plasma fibronectin (hFn) on this permeability response. TNF-alpha, RGD peptides, and antibodies to alpha 5 beta 1-integrins elicited a dose- and time-dependent increase in protein permeability as well as a reorganization and/or disruption of the endogenous Fn matrix. A control RGE peptide (GRGESP) as well as immunoglobulin G purified from nonimmune rabbit serum did not increase endothelial protein permeability or disrupt the endogenous fibrillar Fn pattern in the matrix. Likewise, a LDV peptide derived from the alternatively spliced type III connecting segment (IIICS) within bovine Fn (bFn) was unable to increase permeability of the bovine endothelial monolayer. Co-incubation of purified soluble hFn (300 or 600 micrograms/ml) with either TNF-alpha, the RGD peptide, or the antibody to alpha 5 beta 1-integrins prevented the increase in endothelial permeability. This protective effect was also observed when the purified hFn (600 micrograms/ml) was added after the TNF-alpha-induced increase in endothelial permeability had taken place. Immunofluorescent analysis confirmed the incorporation of the hFn into the subendothelial matrix and its co-localization with the endogenous bFn. The similar alteration of the subendothelial matrix after exposure to RGD peptides, anti-alpha 5 beta 1-antibodies, or TNF-alpha, coupled with the ability for hFn to attenuate the permeability increase typically elicited by all three agents, suggests that disruption of cell-matrix interactions may be the mechanism by which TNF-alpha alters endothelial permeability.

Animals↗
PubMed1994

Delayed elevation of ED1-cellular fibronectin in plasma following postsurgical bacteremia.

Fibronectin (Fn) exists in both a soluble form in plasma and lymph as well as an insoluble form in the extracellular matrix. Matrix-localized cellular fibronectin (cFn) contains extra domains (ED1 and/or ED2) not found in plasma Fn (pFn). Very little (< 1-2%) ED1-containing cFn exists in normal blood, and its rapid release into plasma and/or lymph is believed to reflect acute vascular injury. We used a polyclonal antibody to sheep pFn and a monoclonal antibody to ED1 domain of cFn to measure both pFn and ED1-cFn in relationship to lung lymph flow (QL), lung lymph-to-plasma (L/P) total protein concentration ratio, and lung protein clearance (LPC). Unanesthetized sheep (n = 7) were injected intravenously with Pseudomonas aeruginosa (5 x 10(8)) at both 2 and 7 days following surgical preparation of a lung lymph fistula. After both bacterial challenges, we observed an early increase in QL and a small decline in the L/P ratio (0-2 h), reflecting increased fluid filtration in the presence of an intact vascular barrier. This was followed by a further increase (P < 0.05) in QL; an elevation in the L/P ratio; and a marked (P < 0.05) increase in LPC over 3-6 h, indicative of an increase in lung endothelial protein permeability. Before the first bacterial infusion, ED1-cFn in plasma was 9.97 micrograms/ml or approximately 2% of the total Fn antigen in plasma; whereas ED1-cFn in lung lymph was 6-8% of total lymph Fn.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Isoproterenol decreases protein permeability in edematous isolated rabbit lungs: estimation of PS and sigma.

The objective of the present study was to determine whether the ability of the beta-adrenergic agonist isoproterenol to attenuate pulmonary edema occurs via a permeability and/or hemodynamic mechanism. In isolated perfused rabbit lungs, the restrictive property of the vascular barrier to the movement of fluid and protein was assessed by measurements of the capillary filtration coefficient (Kf) and the transvascular clearance of 125I-labeled albumin, respectively. Regression analysis of albumin clearance vs. transvascular fluid flux was performed to estimate the permeability-surface area product (PS) and the reflection coefficient (sigma) by use of the linear or nonlinear flux equation. Arterial, capillary, and venous pressures and resistances, weight gain, and the wet-to-dry weight ratio were also assessed. Isoproterenol (8 ng.ml-1.min-1) attenuated the arachidonic acid (4 mg)-induced increases in fluid flux, wet-to-dry weight ratio, albumin clearance, and PS and the decrease in sigma. Isoproterenol had no effect on the increase in Kf, and there was no correlation between capillary pressure and fluid flux in any of the four groups. Regression analysis revealed that the non-linear flux equation provided estimates of PS and sigma that more accurately described the statistical differences in albumin clearance among the groups studied than the linear flux equation. These findings demonstrate that isoproterenol attenuated the increased transvascular flux of albumin in edematous lungs by modifying the protein permeability of the vascular barrier.

Animals↗
PubMed1993

Steroid priming promotes oxytocin-induced norepinephrine release in the ventromedial hypothalamus of female rats.

In vivo microdialysis was used to detect norepinephrine (NE) release in the ventromedial hypothalamus of estradiol (E2)- or E2 plus progesterone (P)-treated female rats injected with 1.0 IU of oxytocin (OXY). Dialysates were collected before and after OXY administration on 3 consecutive days and analyzed for NE content by high performance liquid chromatography with electrochemical detection. After the last sample was collected on day 1, animals were injected with 3 micrograms E2 benzoate or oil. On day 3, E2-primed animals received 200 micrograms of P and control females received oil prior to OXY administration. OXY administration did not induce NE release on day 1. When OXY was administered to animals that received E2 approximately 20 h earlier, increased release of NE was not consistently seen. In contrast, E2-primed animals that received P on day 3 displayed significant increases in the release of NE after OXY administration compared to their own basal levels and to NE levels in control animals. To distinguish whether E2 priming is sufficient to promote OXY-induced release of NE without the addition of P, NE content of VMH dialysates in a second group of animals was examined following exposure to vehicle or E2 alone. When OXY was administered 24 or 48 h after estrogen priming, only 1 of 4 E2-primed females had modestly elevated dialysate NE levels. To evaluate the interactions between OXY and NE in the regulation of reproductive behavior, lordosis responses were observed in hormone-primed female rats receiving systemic injections of OXY, the alpha 1-adrenoceptor antagonist prazosin, or both OXY and prazosin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Incorporation of fibronectin into matrix decreases TNF-induced increase in endothelial monolayer permeability.

Plasma fibronectin, a dimeric adhesive protein in blood, incorporates into the subendothelial and interstitial matrix in the lung especially during vascular injury. Fibronectin in the matrix is believed to influence cell-cell interaction and endothelial cell adhesion to the collagen-rich extracellular matrix. We previously observed that addition of purified soluble human plasma fibronectin (hFn) to cultured pulmonary endothelial monolayers attenuates the increase in protein permeability of such monolayers exposed to tumor necrosis factor-alpha (TNF-alpha). In the current study, we determined the specificity of this permeability response to fibronectin by comparing hFn to two other purified adhesive proteins in human plasma, i.e., vitronectin (Vn) and fibrinogen (Fg). We also determined whether matrix incorporation was essential for this hFn-mediated protective response by comparing normal intact hFn to either hFn alkylated with N-ethylmaleimide (NEM) or to purified 160/180-kDa hFn fragments, since these alternate forms of fibronectin are believed to exhibit limited ability to incorporate into matrix. Calf pulmonary artery endothelial (CPAE) monolayers (3-4 days postseeding) were exposed to human recombinant TNF-alpha for 18 h at a medium concentration of 200 U/ml followed by assessment of protein permeability using transendothelial 125I-labeled albumin clearance. Dimeric hFn (600 micrograms/ml) significantly (P < 0.05) reduced the TNF-induced increase in endothelial monolayer permeability. Vn or Fg, added at equal molar concentrations to the hFn, were unable to attenuate endothelial permeability. Immunofluorescent analysis utilizing antibodies specific to either hFn, human Vn, or human Fg revealed incorporation of the exogenous hFn into the extracellular matrix, but no matrix incorporation of Vn or Fg. Both NEM-treated dimeric hFn as well as purified 160/180-kDa fragments of hFn, which cannot incorporate into the matrix, were also unable to prevent the TNF-induced increase in protein permeability. Thus the ability for soluble hFn to reduce the TNF-induced increase in lung endothelial monolayer permeability was specific and dependent on its incorporation into the extracellular matrix.

Animals↗
PubMed1993

Release of ED1 fibronectin from matrix of perfused lungs after vascular injury is independent of protein synthesis.

Fibronectin (Fn) is an adhesive protein found in the plasma and extracellular tissue matrix. Locally synthesized tissue or cellular Fn (cFn) has extra domains (ED1 and ED2) not present in liver synthesized plasma Fn (pFn). In the lung, Fn is found in the endothelial and epithelial basement membranes, as well as in the interstitial matrix. Utilizing murine monoclonal antibodies to ED1 of cFn, we studied the release of total Fn as well as ED1-Fn into the plasma-free perfusate of the isolated perfused rabbit lung in relation to changes in lung weight due to fluid accumulation after oxidant (H2O2) challenge. Both parameters were also studied after addition of cycloheximide (20 micrograms/ml perfusate) to the perfusion medium to inhibit lung protein synthesis. After continuous H2O2 challenge (11 nmol.ml buffer-1.min-1), there was a 2.25 +/- 0.62 g increase in lung weight over 60 min. Measurement of 125I-labeled albumin clearance at 20 min after the start of H2O2 infusion confirmed an increase in lung endothelial protein permeability after H2O2 treatment. Fn antigen was released into the perfusate as early as 15 min after oxidant challenge. By 60 min, total perfusate Fn increased in H2O2-treated lungs (n = 6) to 2.10 +/- 0.48 micrograms/ml compared with only 0.35 +/- 0.09 micrograms/ml in normal control lungs (n = 5). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of nonreduced samples revealed that the Fn released consisted of primarily intact (440 kDa) Fn as well as Fn fragments. A rapid release of ED1-Fn paralleled the increased release of total Fn.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Effect of fibronectin on permeability of normal and TNF-treated lung endothelial cell monolayers.

Fibronectin is found in a soluble form in plasma and lymph and in an insoluble form in the extracellular matrix. Plasma fibronectin can incorporate into the tissue pool of fibronectin where its adhesive properties may influence cell-cell interaction, cell adhesion to a collagenous matrix, and vascular integrity. Elevation of plasma fibronectin can attenuate the increase in lung vascular permeability in sheep during postoperative gram-negative bacteremia, and plasma fibronectin deficiency can magnify the increase in lung vascular permeability with postoperative sepsis. Using pulmonary endothelial monolayers, we determined if exogenous human plasma fibronectin (pFn) would influence the protein permeability of pulmonary endothelial monolayers as determined by transendothelial clearance (microliters/min) of 125I-albumin after they were exposed to human recombinant tumor necrosis factor-alpha. Treatment of endothelial monolayers with tumor necrosis factor (TNF) (200 U/ml) for 18 h resulted in a significant (P < 0.05) increase in protein permeability. Addition of intact purified human plasma fibronectin to normal confluent endothelial monolayers to yield a medium concentration of 300, 600, and 900 micrograms/ml for 18 h had no effect on baseline protein permeability. In contrast, whereas addition of lower amounts of human plasma fibronectin (300 micrograms/ml) did not attenuate the TNF-induced increase in monolayer permeability, the higher concentrations of 600 or 900 micrograms pFn/ml significantly decreased (P < 0.05) protein permeability. The ability of soluble plasma fibronectin to attenuate the TNF-induced increase in endothelial protein permeability required an incubation time of at least 2-3 h, perhaps due to a lag time required for its incorporation into the extracellular matrix.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Immunofluorescent analysis of plasma fibronectin incorporation into the lung during acute inflammatory vascular injury.

Incorporation of plasma fibronectin into tissues is believed to influence endothelial cell-cell interaction, as well as endothelial cell adhesion to matrix. We used immunofluorescent microscopy coupled with tissue extraction of noncovalently incorporated fibronectin to delineate the time course for matrix incorporation of soluble plasma-derived fibronectin into the lung of sheep during postoperative bacteremia. Adult sheep were surgically prepared with both lung and peripheral lymph fistulas. Sheep were anesthetized 2 days following surgery and injected intravenously with a sublethal dose of live Pseudomonas aeruginosa, which consisted of 5 x 10(8) live organisms suspended in 0.9% saline. Bacterial infusion elicited a 300% increase in lung transvascular protein clearance but no increase in peripheral transvascular protein clearance. Purified dimeric human plasma fibronectin (hFn), used as an "immunologic marker," was then infused intravenously (100 mg/sheep) into two additional groups of sheep (nonbacteremic control group and bacteremic experimental group) and allowed to mix with the plasma pool of endogenous soluble sheep fibronectin (sFn). Incorporation of the plasma-derived hFn into the lung matrix and its distribution in relation to endogenous sheep fibronectin in the matrix was assessed by dual-label immunofluorescence using antibodies specific to either sFn or hFn. Human fibronectin from the vascular compartment codistributed with endogenous sheep fibronectin in the lung matrix. Moreover, its deposition into the lung was markedly increased in postoperative bacteremic sheep compared with nonbacteremic control sheep. Increased hFn deposition in the lung with bacteremia was clearly apparent within 2 h. The hFn deposited in the lung was nonextractable using a heparin-urea tissue extraction buffer, suggesting its rapid covalent cross-linking and incorporation into the lung matrix. Microscopic analysis of serial lung biopsies revealed focal areas of inflammation with an intense mononuclear infiltrate into the lungs by 2 h in the bacteremic sheep. Interstitial edema and vascular endothelial injury were observed by 4 h, with alveolar edema apparent over 6 to 8 h. Thus, postoperative bacteremia results in a rapid incorporation of plasma fibronectin into the lung matrix. This may be a physiologic mechanisms to stabilize the integrity of the lung vascular barrier.

Animals↗
PubMed1993

Why do NICU nurses not refeed gastric residuals prior to feeding by gavage?

The purpose of this study was to determine why NICU nurses do not refeed gastric residuals to preterm infants prior to feeding by gavage. To gather the data, we delivered questionnaires to all 75 NICU registered nurses at a southeastern regional hospital. The nurses were told the study was to learn "about nursing practice in relation to gavage feedings." Thirty-five percent (26) of the questionnaires were completed and returned within the two-week data collection period. Although the literature recommends refeeding gastric aspirates to premature infants prior to gavage feedings, only two (8 percent) of the respondents indicated that they do this at least half the time. Many (54 percent) indicated that they knew refeeding residuals benefited preterm infants. However, more than half (58 percent) selected "doctors in this hospital do not order" as their rationale for not refeeding. More studies with larger sample sizes need to be done to assess accurately the reasons that nurses do not refeed gastric residuals. The findings of this study suggest (1) inservice educational programs should be developed regarding the value of refeeding residuals and (2) nurses' awareness of their decision-making ability should be increased.

Decision Making↗
PubMed1992

Simultaneous measurement of fluid and protein permeability in isolated rabbit lungs during edema.

Fluid conductance and protein permeability have been studied in isolated perfused lung models of pulmonary edema. However, previous studies have not investigated changes of both fluid conductance and protein permeability in the same isolated lung preparation after injury. Arachidonic acid (AA) metabolites are involved in the inflammatory processes that lead to the development of pulmonary edema. The hemodynamic effects of AA have been well established; however, controversy exists concerning the ability of AA to alter the permeability of the pulmonary microvasculature to fluid and protein. The purpose of this study was to simultaneously determine whether transvascular fluid conductance and protein permeability are increased in isolated perfused rabbit lungs with pulmonary edema induced by AA. Indomethacin (80 microM) was added to the perfusate to inhibit the hemodynamic effects of AA and produce a pressure-independent model of pulmonary edema. Fluid conductance was assessed by determination of the capillary filtration coefficient (Kf), and protein permeability was evaluated by measurement of 125I-albumin clearance. The injection of AA (3 mg/200 ml of perfusate) into the pulmonary arterial catheter resulted in an increase in lung weight over the remaining 30-min experimental period. Kf (microliter.s-1 x cmH2O-1 x g dry lung-1) was increased (P < 0.05) in AA-treated lungs at 10 and 30 min post-AA injection when compared with control lungs and baseline values (determined 10 min before AA injection). Albumin clearance was also greater (P < 0.05) in lungs that received AA. 125I-albumin clearance was measured at different rates of fluid flux produced by elevation of venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Albumins↗
PubMed1991

Effects of non-competitive NMDA receptor antagonists on reproductive and motor behaviors in female rats.

MK-801 and dextrorphan, selective non-competitive antagonists at N-methyl-D-aspartate (NMDA) receptors, were used to evaluate the effect of NMDA receptor blockade on sexual and motor behaviors in female rats. Ovariectomized rats were treated with estradiol benzoate (EB) for 48 or 72 h followed by progesterone (P) 3.5-4 h before testing the animals for sexual receptivity. After testing for estrous responsiveness, the effect of NMDA antagonists on several motor behaviors was also assessed. Lordosis frequency and intensity were inhibited in animals that received 0.5 mg/kg MK-801 30 min before EB; the same dose of MK-801 was relatively ineffective when administered 24 h after EB. In neither case did MK-801-treated females differ from controls when motor behaviors were assessed after mating tests. When 30 mg/kg dextrorphan, a short-acting NMDA antagonist, was administered 15 min before P, sexual behavior was not blocked. However, both 0.05 mg/kg MK-801 and 30 mg/kg dextrorphan suppressed ongoing female sexual behavior within 30 min in animals made receptive with EB and P. These deficits in sexual behavior were associated with changes in motor performance. MK-801 (0.1 mg/kg) and dextrorphan (30 mg/kg) abolished movement in the vertical dimension (e.g. jumping and rearing). By contrast, the drugs increased movement in the longitudinal (locomotion) and lateral (circling) dimensions. At 0.2 mg/kg, MK-801 blocked movement in both the vertical and longitudinal dimensions; however, it failed to block circling. Only at 0.4 mg/kg did MK-801 inhibit lateral movements and righting reflexes.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Incorporation of circulating fibronectin into various tissues during sepsis: colocalization with endogenous tissue fibronectin.

We studied the plasma clearance and tissue incorporation of intravenously infused purified human plasma fibronectin into various tissues during a period of acute lung vascular injury induced by lethal postoperative bacteremia in sheep. Lung, liver, spleen, and heart tissue were examined for both endogenous sheep tissue fibronectin as well as the experimentally infused human fibronectin using dual-label immunofluorescence. Awake sheep (n = 4) received a postoperative iv infusion of 5 x 10(9) live Pseudomonas over a 60-min infusion interval. Bacterial challenge was started 2 hr after starting the iv fibronectin infusion of purified human plasma fibronectin (100 mg iv bolus; 4 hr iv at 100 mg/hr). Human fibronectin displayed a biphasic rate of clearance from the plasma with entrance into lymph. Human fibronectin readily incorporated in all tissues studied, including the lung which was the focus of vascular injury. Analysis of tissue sections by dual-label immunofluorescence indicated that the exogenous human fibronectin colocalized with the endogenous sheep fibronectin. Thus, the plasma fibronectin concentration may influence the lung vascular barrier due to its incorporation into the tissue pool of fibronectin. Moreover, the plasma may serve as a reservoir for soluble fibronectin which can enter and colocalize with the insoluble tissue pool of fibronectin in various tissues.

Animals↗
PubMed1991

Intracranial dialysis and microinfusion studies suggest that morphine may act in the ventromedial hypothalamus to inhibit female rat sexual behavior.

The present investigation examined the neural sites and mechanisms of opiate inhibition of female sexual behavior. Systemic administration of morphine (10 mg/kg) significantly reduced ovarian steroid-induced estrous behavior in female rats. This behavioral inhibition was prevented when the opiate receptor antagonist naloxone (5 mg/kg) was administered 30 min prior to morphine. Bilateral infusion of morphine directly into the ventromedial hypothalamus (VMH) also inhibited hormone-dependent estrous behavior for at least 2 hr. Furthermore, naloxone infusion into the VMH 20 min before behavior testing reduced the inhibitory effects of systemically administered morphine on lordosis. These results suggest that morphine may inhibit female sexual behavior by acting directly on the VMH, the primary site at which ovarian steroids facilitate this behavior. In a separate experiment we used in vivo brain microdialysis to test the hypothesis that morphine inhibits lordosis by interfering with norepinephrine (NE) neurotransmission in the VMH. In control rats, the onset of mating was associated with increased NE release in the VMH. Morphine-treated animals displayed neither behavioral estrus nor elevated NE release from the VMH when tested with stimulus males. These data are consistent with the hypothesis that morphine suppresses NE release in the VMH. Nevertheless, mechanisms other than or in addition to attenuation of hypothalamic NE release may contribute to the inhibitory effects of morphine on lordosis.

Animals↗
PubMed1991

Kinetics of plasma fibronectin: increased lung tissue incorporation after postoperative bacteremia.

Fibronectin is an adhesive glycoprotein that may influence the permeability of the vascular barrier. We compared the plasma disappearance of purified human fibronectin (hFn) and its incorporation into lung tissue in control nonbacteremic and bacteremic sheep after surgery to determine the influence of postoperative bacteremia on the plasma clearance and lung deposition of hFn. Lymph fistulas were surgically prepared 48 h before either saline or bacterial challenge to allow for collection of timed samples of plasma, lung lymph, and peripheral lymph. On the day of the study, the sheep were anesthetized and given either 5 X 10(8) Pseudomonas aeruginosa in saline or saline alone. In parallel, they were infused intravenously with 100 mg of hFn, and the hFn concentration in plasma, lymph, and tissue extracts was subsequently determined by enzyme-linked immunosorbent assay over an 8-h experimental interval. Localization of endogenous sheep fibronectin (sFn) and the injected hFn in serial lung tissue samples was determined by dual-label immunofluorescence. In nonbacteremic control sheep, plasma hFn levels declined with an initial rapid slope (t1/2 = 0.53 +/- 0.19 min), followed by a second, gradual slope (t1/2 = 21.7 +/- 2.5 h), whereas the concentration of hFn in lung lymph and peripheral lymph rose exponentially with time. In bacteremic sheep, the early plasma disappearance of hFn was similar, but the second phase of plasma clearance was faster (t1/2 = 7.4 +/- 0.3 h). Lung tissue from control and bacteremic sheep contained the same level of extractable hFn. However, tissue extraction followed by immunofluorescence microscopy indicated that lung tissue from bacteremic sheep contained more nonextractable hFn than lung tissue from nonbacteremic sheep. Thus postoperative bacteremia that elicits acute lung vascular injury will increase the plasma disappearance of hFn and its incorporation into the lung tissue.

Animals↗