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T M Saba

Publications and source records attributed to T M Saba.

At least 73 records · Page 4Linked to original sources
PubMed1986

Clearance and tissue distribution of fibronectin in septic rats: relationship to synthetic rate.

Fibronectin is a glycoprotein found in a soluble form in plasma and in an insoluble form in many tissues. We evaluated the influence of postoperative intraperitoneal sepsis on the clearance, tissue distribution, and synthesis of plasma fibronectin in rats (300-400 g). Experimental sepsis was induced by cecal ligation following laparotomy, whereas control animals underwent laparotomy (5 cm) alone. At 24 and 48 h after laparotomy, plasma fibronectin levels were normal. After laparotomy plus cecal ligation, plasma fibronectin increased by 47% at 24 h and remained elevated (52% above 0 time) at 48 h. At 24 h postsurgery the disappearance and tissue distribution of 75Se-plasma fibronectin and 75Se-plasma albumin was evaluated. Tissue distribution was quantified at 2 and 24 h after intravenous injection of both tracer proteins in separate groups. Both fibronectin and albumin demonstrated an initial distribution between vascular and extravascular sites and then a progressive decrease in plasma. In control (laparotomy) rats the half-life (t1/2) for plasma clearance of 75Se-plasma fibronectin was 25.33 +/- 2.53 h compared with 13.21 +/- 0.78 h in the septic rats. Septic rats manifested decreased sequestration of 75Se-fibronectin at the area of surgical incision (laparotomy), increased sequestration at the focus of intraperitoneal infection, and increased uptake in the nonviable portion of the cecum. The synthetic rate for plasma fibronectin in laparotomized control rats was 3.03 +/- 0.29 mg X 100 g-1 X 24 h-1, whereas after laparotomy plus cecal ligation the synthetic rate increased to 4.58 +/- 0.35 mg X 100 g-1 X 24 h-1. In contrast the synthetic rate for albumin decreased from 84.70 +/- 1.66 mg X 100 g-1 X 24 h-1 in controls to 52.38 +/- 1.77 mg X 100 g-1 X 24 h-1 in the septic animals. Thus intraperitoneal sepsis in the rat will enhance the vascular clearance, alter the distribution, and increase the synthetic rate for plasma fibronectin.

Animals↗
PubMed1986

Comparative effect of circulating bacterial or nonbacterial particulates on plasma fibronectin: relationship to lung deposition of blood-borne foreign particles.

Reticuloendothelial (RE) phagocytic function and plasma fibronectin are altered early after trauma and during septic shock. Since fibronectin-coated particles will tend to aggregate if not efficiently phagocytized, we hypothesized that elevated fibronectin levels during hepatic and/or splenic RE depression could potentiate the lung deposition of blood-borne foreign microparticles. To evaluate this concept, we measured plasma fibronectin, hepatic RE function, and tissue deposition of blood-borne colloids in rats after they were injected with nonbacterial and bacterial particulates. Rats were injected intravenously with gelatin-coated colloids (50 mg/100 gm) to simulate blood-borne collagenous tissue debris after trauma, or with live Pseudomonas aeruginosa (1 X 10(9)/rat) to simulate bacterial entrance into the blood with sepsis, or with both to simulate sepsis after trauma. Phagocytic function was evaluated by liver and spleen uptake of gelatinized 125I RE test emulsion. Fibronectin was quantified by electroimmunoassay. There was an acute 60-80% decrease in plasma fibronectin 2 hr following either colloid or colloid coupled with bacterial infusion. Bacterial infusion alone elicited only a mild 20% decrease in fibronectin by 2 hr. By 24 hr, restoration of fibronectin levels was observed in all groups with hyperfibronectinemia observed in animals challenged with Pseudomonas. Following colloid alone, liver uptake of the RE test particle was acutely depressed at 2 hr in association with an acute depletion of fibronectin, but at 24 hr the RE depression persisted even with normalization of fibronectin. In contrast, with only bacteremia, the rebound elevation of fibronectin was associated with increased hepatic RE function. In rats given both colloid and Pseudomonas, the hyperfibronectinemia (60-100% above controls) at 24 hr coexisted with inadequate liver phagocytic uptake ability. This resulted in a significant 20-fold (P less than 0.05) increment in lung localization of the blood-borne test microparticles. Thus, hyperfibronectinemia without a parallel increase in liver phagocytic ingestive ability may actually enhance lung localization of blood-borne microparticles, which have a high affinity for fibronectin.

Animals↗
PubMed1986

Plasma fibronectin.

Plasma fibronectin deficiency and reticuloendothelial phagocytic dysfunction are observed in critically ill and septic surgical, trauma or burn patients with multiple organ failure. They also appear to amplify altered lung vascular permeability with sepsis or intravascular coagulation. This article highlights important aspects of plasma fibronectin which may relate to the aetiology of multiple organ failure in the septic injured patient.

Capillary Permeability↗
PubMed1985

Lung vascular injury with protease infusion. Relationship to plasma fibronectin.

Fibronectin exists in a soluble form in plasma and in an insoluble form in tissues. Plasma fibronectin can modulate phagocytic function as well as incorporate into the tissue matrix where it is believed to influence microvascular integrity and tissue repair. The temporal alterations in plasma and lung lymph fibronectin were studied in relation to increased pulmonary vascular permeability induced by protease infusion. The acute sheep lung lymph fistula model was used. A 39% decrease in plasma fibronectin (control = 421 +/- 67 micrograms/ml) was observed 2.5 hours (255 +/- 43 micrograms/ml) after protease infusion. There was an elevation of lymph fibronectin early after protease infusion, followed by a progressive decline. Concomitant with the decrease in plasma fibronectin, an increase in lymph flow (QL) of greater than 200% (from a control of 6.7 +/- 1.0 ml/hr to 13.9 +/- 1.4 ml/hr) was observed within 2.5 hours. Also, there was a sustained elevation in the total protein lymph/plasma concentration (L/P) ratio, which was maximal at 2.5 hours. The transvascular protein clearance (TVPC = QL X L/P) was 4.5 +/- 0.7 ml/hr at the control period and 13.1 +/- 2.0 ml/hr by 2.5 hours. This was indicative of increased flux of protein-rich fluid across the pulmonary endothelial barrier. Lung vascular permeability stabilized after 2.5 hours as manifested by a slowly declining L/P ratio. Thus, plasma fibronectin deficiency may contribute to the etiology of increased lung vascular permeability with protease infusion. Since the progressive decline in plasma fibronectin was not reflected in a proportional increase in lymph fibronectin, plasma fibronectin may have sequestered in tissues such as the lung, or perhaps in reticuloendothelial cells during the injury phase. Whether the progressive decrease in plasma fibronectin reflects its incorporation into the endothelial barrier matrix where it may mediate stabilization of the pulmonary microvascular barrier remains to be determined.

Animals↗
PubMed1985

Human plasma fibronectin effect on serum-mediated uptake of Pseudomonas aeruginosa PA 1348A by human granulocytes.

The effect of human plasma fibronectin on human granulocyte (PMN) phagocytosis of one strain of Pseudomonas aeruginosa (PA 1348A) was examined in a previously defined optimal phagocytic assay. Normal and fibronectin-deficient serum demonstrated similar rates of bacterial uptake by PMNs. Complement depletion of both sera inhibited phagocytosis. Addition of purified fibronectin did not alter phagocytosis. These findings strongly support the conclusion that fibronectin neither promotes nor inhibits opsonization for phagocytosis of this strain of P. aeruginosa.

Blood Bactericidal Activity↗
PubMed1985

Lung fluid and protein flux during postoperative sepsis.

Pulmonary microvascular injury during sepsis after injury appears to be amplified with plasma fibronectin deficiency, but the degree of injury relative to the extent of sepsis has not been defined. We evaluated pulmonary vascular permeability in sheep as influenced by various levels of postoperative Pseudomonas sepsis during a period of plasma fibronectin deficiency. The hemodynamic response to Pseudomonas was very similar regardless of the intensity of septic challenge and characterized by systemic arterial hypotension, decreased cardiac output, and pulmonary arterial hypertension. In contrast, increased pulmonary microvascular permeability was observed with increments in the bacterial challenge. Thus, lung protein clearance (LPC) or so called pulmonary transvascular protein clearance (TPC) used as an index of lung vascular permeability was 9.1 +/- 1.9 ml/hr, 15.1 +/- 1.7 ml/hr, and 19.3 +/- 3.0 ml/hr 2 hr after low (3 X 10(9) i.v.; 1 X 10(10) i.p.), medium (3 X 10(9) i.v.; 3 X 10(10) i.p.), and high (5 X 10(9) i.v.; 5 X 10(10) i.p.) dose Pseudomonas challenges, respectively. Thus, the extent of the altered pulmonary microvascular integrity in sheep during sepsis after surgery in the presence of fibronectin deficiency is dependent on the degree of bacterial sepsis. In addition, infusion of cryoprecipitate was an effective means of reversing the plasma fibronectin deficiency. Accordingly, this may be used as a model to investigate the mechanism of altered lung fluid balance during postoperative septic shock and the effect of fibronectin on this response.

Animals↗
PubMed1984

Fibronectin-enhanced attachment of gelatin-coated erythrocytes to isolated hepatic Kupffer cells.

The phagocytic process is a combination of a sequence of events which includes a recognition attachment phase and a subsequent internalization phase. The present study was designed to investigate the effect of plasma fibronectin on the attachment and ingestion of gelatinized sheep erythrocytes to isolated rat Kupffer cells in a monolayer assay. Kupffer cells were isolated by sequential collagenase-pronase digestion followed by metrizamide density gradient centrifugation and subsequent adherence to plastic. Classification as Kupffer cells was confirmed by the presence of functional Fc receptors, a positive peroxidase reaction, and phagocytic activity. Purified plasma fibronectin as well as rat serum containing fibronectin promoted attachment of gelatinized fixed sheep erythrocytes to Kupffer cells in a dose-dependent manner, whereas fibronectin-deficient serum did not. Heparin did not enhance the fibronectin-mediated attachment or ingestion of gelatinized sheep erythrocytes at lower particle doses, whereas at higher particle doses heparin augmented the response. These results indicate that fibronectin can enhance the binding and ingestion of foreign gelatin-coated particulates by Kupffer cells.

Animals↗
PubMed1984

Effect of acute plasma fibronectin depletion on tissue fibronectin levels: analysis by a new fluorescent immunoassay.

Plasma fibronectin modulates reticuloendothelial (RE) phagocytosis of cellular and tissue debris, fibrin microaggregates, and gelatin-coated particulates. An antigenically related, but more insoluble form of fibronectin is found in various tissues and suspected to play a role in vascular permeability, cell adhesion, and wound healing. The current study developed a fluorescent immunoassay which could be utilized for the quantification of tissue fibronectin following its extraction from tissues. Additionally, the changes in tissue fibronectin induced by the intravenous injection of gelatin-coated colloids in rats (300-350 g), which acutely depletes the plasma fibronectin level, were also investigated. Injection of gelatinized RE test lipid emulsion (50 mg/100 g) depleted the plasma fibronectin at 2 hr (80-85% depletion) followed by rebound restoration within 24 hr as quantified by either electroimmunoassay or fluorescent immunoassay. RES system clearance of the test particles from the blood resulted in an acute elevation in fibronectin extractable from the liver with a normalization by 48 hr. In contrast, assay of tissue fibronectin following a single extraction revealed a decrease in lung extractable fibronectin within 2 hr following RE blockade which persisted for 24-48 hr. Extractable fibronectin in spleen and renal tissue was unaltered by RE blockade. This microfluorescent immunoassay may provide a sensitive method to quantify fibronectin in small aliquots of tissue. Increased hepatic fibronectin most likely reflects interiorization of plasma fibronectin during Kupffer cell clearance of the test particles. Decreased lung extractable fibronectin may alter lung vascular sensitivity to a subsequent septic and/or intravascular coagulation stress. Thus, similar to the labile nature of plasma fibronectin, the concentration of fibronectin in various tissues, can undergo dynamic alterations.

Animals↗
PubMed1984

Reversal of fibronectin and opsonic deficiency in patients. A controlled study.

Plasma fibronectin is an opsonic glycoprotein which augments reticuloendothelial phagocytic clearance of nonbacterial particulates. We evaluated the influence of intravenous infusion of plasma cryoprecipitate on circulating immunoreactive fibronectin and associated opsonic activity at 0.5, 2.0, 4.0, 10, and 21 hr postinfusion in septic (n = 8) and nonseptic (n = 6) surgical and/or trauma patients with documented plasma fibronectin deficiency. The study was a randomized, double-blind, crossover clinical protocol in which fibronectin-poor (0.116 +/- 0.025 mg/ml) cryoprecipitate extracted plasma (placebo) was compared to fibronectin-rich (2.139 +/- 0.161 mg/ml) plasma cryoprecipitate. Septic injured patients (149.37 +/- 17.11 micrograms/ml) had lower (p less than 0.05) plasma fibronectin levels than nonseptic injured patients (212.17 +/- 7.14 micrograms/ml) and both were less (p less than 0.05) than normal (330 +/- 30 micrograms/ml). As tested in vitro with a peritoneal macrophage monolayer assay, cryoprecipitate manifested opsonic activity related to its fibronectin concentration. Intravenous infusion of fibronectin rich cryoprecipitate reversed both the immunoreactive fibronectin and opsonic deficiency, while infusion of the placebo at a comparable total protein load did not reverse either deficient parameter. Reversal of fibronectin deficiency was more sustained in nonseptic injured patients as compared to septic injured patients. Thus, reversal of opsonic deficiency in septic and nonseptic injured patients is observed after infusion of plasma cryoprecipitate and not with infusion of fibronectin deficient plasma at comparable protein loads. Also, cryoprecipitate extracted plasma may serve as an appropriate control solution for randomized studies evaluating the therapeutic value of fibronectin-rich plasma cryoprecipitate.

Adolescent↗
PubMed1984

Clearance from the vascular compartment of endogenously labelled plasma fibronectin.

Plasma fibronectin is a large molecular weight glycoprotein which may have both opsonic and structural adhesive roles. Fibronectin deficiency has been documented in patients especially early after trauma or burn as well as during sepsis following injury. In this study, the disappearance of fibronectin from the blood was studied in rats utilizing plasma fibronectin metabolically labelled with 75Se-selenomethionine. After injection of 75Se-selenomethionine, the maximum specific activity of endogenously labelled plasma fibronectin, the observed at 4 hours. Thereafter, it declined in a non-monoexponential fashion in association with depletion of the precursor. Labelled 75Se fibronectin was purified from donor rat plasma by gelatin-sepharose affinity chromatography. It retained its electrophoretic mobility, gelatin adherence, and opsonic activity similar to that of unlabelled plasma fibronectin. Following intravenous injection of 75Se plasma fibronectin, its disappearance from plasma manifested two phases. The first was an initial fast disappearance of a small amount of fibronectin, reflecting distribution between plasma and interstitial compartments. The second was a slower disappearance phase with a half-time (T 1/2) of at least 15 hours. Infusion of gelatin-coated particles, which are rapidly cleared by RE cells in the liver and spleen, enhanced the disappearance of 75Se fibronectin from the plasma. These data suggest that the normal rate of fibronectin disappearance from the vascular space is quite fast. Utilization of this experimental approach may provide valuable data on fibronectin kinetics as influenced by trauma and burn.

Animals↗
PubMed1984

Depressed reticuloendothelial clearance of platelets in rats after trauma.

Platelet microembolization may contribute to microcirculatory and organ damage following trauma and shock. It is hypothesized that posttraumatic reticuloendothelial depression predisposes to such microembolization by failure to clear altered platelets from the circulation. The present study evaluated the short-term (1 h) clearance and organ localization of radiolabeled homologous damaged platelets in normal rats and in rats following sublethal Noble-Collip drum trauma. Platelets were collected in citrated platelet-rich plasma from normal rats and labeled with 51Cr in citrated saline. Platelets were altered by repeated centrifugation in protein-free medium. These platelets differed functionally and morphologically from normal platelets. Disappearance of iv injected damaged platelets conformed to a two-compartment exponential clearance. Velocity of clearance in the rapid compartment correlated with hepatic platelet localization, whereas velocity of clearance in the second compartment correlated with splenic platelet localization. Clearance rate of the rapid compartment was depressed at 1 h after trauma and elevated at 24 h. These changes were associated with a decrease in hepatic platelet localization at 1 h and an increase above normal at 24 h. Splenic platelet localization was decreased by 3 h following trauma. Pulmonary platelet localization was increased at all times following trauma. It is concluded that the posttrauma state is associated with a defect in the reticuloendothelial system clearance of altered platelets, which may augment embolization of platelets in the lung.

Animals↗
PubMed1984

Mechanism of acute depletion of plasma fibronectin following thermal injury in rats. Appearance of a gelatinlike ligand in plasma.

Plasma fibronectin was depleted within 15 min following sublethal burn, followed by partial recovery at 8 h and complete restoration by 24 h in anesthetized rats. Radiolabeled 75Se-plasma fibronectin, injected intravenously before burn, was rapidly sequestered in burn skin as well as the liver. Fibronectin levels at 2 h postburn as detected by immunoassay vs. 75Se-plasma fibronectin indicated that more fibronectin was in the plasma than detected by electroimmunoassay. Crossed immunoelectrophoretic analysis of fibronectin in early postburn plasma demonstrated a reduced electrophoretic mobility of the fibronectin antigen. Addition of heparin or fibrin, both of which have affinity for fibronectin, to normal plasma was unable to reproduce this altered fibronectin electrophoretic pattern. In contrast, addition of gelatin or native collagen to normal plasma reproduced the abnormal electrophoretic pattern of fibronectin seen in burn plasma. Extracts of burned skin, but not extracts of normal skin, when added to normal plasma, elicited a similar altered electrophoretic pattern for fibronectin. By gel filtration, fibronectin in burn plasma had an apparent molecular weight approximately 40% greater than that observed in normal plasma. These data suggest the release into the blood of a gelatinlike ligand from burned skin, which complexes with plasma fibronectin. Thus, fibronectin deficiency acutely postburn appears mediated by (a) its accumulation at the site of burn injury; (b) its removal from the circulation by the liver; and (c) its presence in the plasma in a form that is less detectable by immunoassay.

Animals↗
PubMed1984

Von Willebrand factor (VIII R:Ag), fibronectin, and insulin-like growth factors I and II in diabetic retinopathy and nephropathy.

We have measured plasma von Willebrand factor (VWF) as the factor VIII-related antigen, plasma fibronectin, and two of the serum somatomedins, insulin-like growth factor I (IGF I) and IGF II, in 51 diabetic patients and 25 nondiabetic control subjects. VWF was significantly higher in the diabetic group than in the controls (173 +/- 9% SEM versus 101 +/- 9%, P less than 0.001), as has been reported by others. However, within the diabetic group there was no significant difference in VWF between those patients without retinopathy, those with background or proliferative retinopathy, or those with macular edema. There was also no difference in VWF between the diabetic subjects with and those without proteinuria. These results rule against a previously advanced hypothesis that the increase in VWF in patients with diabetes is secondary to microangiopathy. No significant difference was observed in fibronectin, IGF I, or IGF II between the diabetic and control groups, between the diabetic group without retinopathy and the retinopathic subgroups, and between the diabetic subjects with and without proteinuria. In the diabetic patients, there was no correlation between diabetic control as assessed by glycosylated hemoglobin and glycosylated serum protein, and the plasma levels of VWF, fibronectin, IGF I, or IGF II. The results of this study strongly suggest that neither plasma VWF, fibronectin, IGF I, nor IGF II plays an important primary role in the pathogenesis of diabetic microvascular disease, although one or more of these factors might play a permissive role.

Adult↗
PubMed1984

Leukocyte involvement in pulmonary localization of blood-borne microparticulates: relationship to altered lung fluid balance.

The lung lymph fistula preparation in sheep was used to study the influence of localization of blood-borne foreign microparticulates in the lung on lymph flow (Qlym); lymph-to-plasma total protein concentration ratios (L/P); pulmonary transvascular protein clearance (Qlym X L/P); and pulmonary hemodynamics. Test particles small enough to readily pass through capillary beds were infused intraarterially to avoid acute lung vascular injury by macroembolism. In sheep, tissue distribution patterns demonstrated that by 15 min after intravenous infusion of the gelatinized reticuloendothelial (RE) test lipid emulsion (0.8-1.0 micron) or gelatinized colloidal carbon (250 A), 30-35% of the injected particle dose localized in the lung, with approximately 15-22% in RE cell-rich organs such as the liver. Particle infusion resulted in an acute neutropenia in the absence of a decline in platelets. Electron microscopy revealed that the increased particulate localization in the lung reflected particle uptake by marginated phagocytic cells as well as the presence of microaggregates within the vascular space. Lung localization of both particulates resulted in approximately a 200-300% increase in both lymph flow and transvascular protein clearance. The hemodynamic response coupled with the pattern of transvascular protein clearance in relationship to lymph flow suggests that the alterations in fluid and protein flux were due to both an increase in microvascular pressure as well as an increase in lung vascular permeability. Marginated phagocytic cells which rapidly ingest the blood-borne foreign test particles may contribute to the altered lung fluid balance seen with the entrance of foreign or abnormal microparticulates in the blood.

Animals↗
PubMed1983

Correction of serum opsonic defects after burn and sepsis by opsonic fibronectin administration.

Opsonic fibronectin modulates reticuloendothelial (RE) uptake of nonbacterial particulates, as well as some bacterial strains, and may thus play an important role in host defense against sepsis after burn injury. We evaluated the relationship between burn injury, sepsis, and opsonic fibronectin levels in rats, as well as the ability to reverse the acute opsonic deficiency after burn injury by administration of purified opsonic fibronectin. Burn injury resulted in an acute (within one hour) depletion of opsonic fibronectin (from 341 +/- 30 to 98 +/- 7 mg/L) that was correctable by administration of purified opsonic fibronectin when accompanied by moderate sepsis, while burn injury plus severe sepsis (level, 168 +/- 30 mg/L) limited attempted restoration of normal opsonic levels (level, 121 +/- 18 mg/L). The in vitro serum opsonic deficit was partially correctable (from 2.2% to 6.7% of the injected dose per 100 mg), while in vivo RE functional deficits could not be corrected. We conclude that the acute postburn deficiency in opsonic fibronectin is amenable to repletion therapy; however, many additional factors may contribute to acute RE failure after burn injury.

Animals↗
PubMed1983

Actin-induced reticuloendothelial phagocytic depression as mediated by its interaction with fibronectin.

Circulating fibronectin, also known as opsonic alpha 2 surface binding glycoprotein or cold-insoluble globulin, modulates phagocytosis of tissue debris, fibrin microaggregates, and gelatin-coated colloids by the reticuloendothelial (RE) system. Opsonically active fibronectin has an actin binding site and a demonstrated in vitro affinity for actin. Since actin potentially released into blood and tissue fluids following tissue injury could complex with fibronectin, the present study evaluated the effect of actin on plasma opsonic activity and Kupffer cell phagocytosis. Intravenous injection of actin did not acutely decrease plasma immunoreactive fibronectin levels although fibronectin levels increased at 6, 12, and 24 hr postinjection. However, intravenous actin injection did depress RE phagocytic activity in vivo as measured by decreased blood clearance of test colloid and impaired hepatic uptake of colloid particles as well as retention of the particles in the circulation. In vitro, preincubation of plasma with actin depressed the opsonic activity of plasma with respect to its ability to support phagocytosis, but such treatment of plasma did not alter the detection of fibronectin by immunoassay. Utilizing purified fibronectin with demonstrated opsonic activity, it was also observed that actin interaction with fibronectin would block its biological ability to enhance phagocytosis. This effect appeared to be mediated at the humoral level, since no direct depressant effect of actin on Kupffer cell function was observed. Thus, actin, if released into the blood following injury, may contribute to bioassayable opsonic fibronectin deficiency and phagocytic dysfunction, but this disturbance would remain undetectable by immunoassay of fibronectin levels.

Actins↗