Search PubMed⌕ Search

Biomedical subjects

T M Saba

Publications and source records attributed to T M Saba.

At least 91 records · Page 5Linked to original sources
PubMed1983

Lung vascular permeability after reversal of fibronectin deficiency in septic sheep. Correlation with patient studies.

Plasma fibronectin deficiency and opsonic dysfunction exist in critically ill septic surgical, trauma, and burn patients with multiple organ failure. Fibronectin deficiency can be reversed by infusion of fresh plasma cryoprecipitate. The influence of therapy with human cryoprecipitate on lung vascular permeability in septic sheep with plasma fibronectin deficiency following surgery was evaluated. Additionally, selected studies on pulmonary function in septic surgical and trauma patients after infusion of plasma cryoprecipitate were completed. In patients, ventilation-perfusion balance appeared to improve as measured by the multiple inert gas elimination technique. With the lung lymph fistula preparation in fibronectin deficient sheep, infusion of human plasma cryoprecipitate (10 units; 250 ml) delayed the onset and minimized the increase in lung vascular permeability during postoperative Pseudomonas sepsis (5 X 10(9) bacteria, I.V.; 5 X 10(10) bacteria, I.P.). For example, in a first group of sheep, the transvascular protein clearance (TPC) at 2 hrs in septic sheep (n = 4) treated with only saline (volume control) was 20.1 +/- 3.1 ml/hr, compared to 11.23 +/- 0.83 ml/hr in the sheep (n =a 4) treated with fibronectin-rich cryoprecipitate (p less than 0.05). In a second group of sheep, cryoprecipitate depleted of fibronectin by affinity chromatography was used as the control solution. It also did not manifest this protective effect with respect to lung vascular permeability. Thus, at 2 hrs the lymph flow (Qlym) was 30.2 ml/hr and the transvascular protein clearance (TPC) was 18.0 ml/hr in septic sheep given fibronectin-deficient cryoprecipitate. In contrast, in the fibronectin-rich cryoprecipitate treated sheep, the Qlym was 14.8 ml/hr and the TPC was 8.12 ml/hr. It is suggested that fibronectin may influence lung vascular integrity during sepsis following surgery and trauma.

Adolescent↗
PubMed1983

Fibronectin levels during intraperitoneal inflammation.

Fibronectin is a high-molecular-weight opsonic protein known to influence macrophage uptake of nonbacterial particulate matter. The concentration of fibronectin in serum and the quantity of fibronectin in the inflamed peritoneal space were examined in rats after intraperitoneal casein injection. Fibronectin levels were studied in relation to the opsonic activity of the serum, as assayed by the uptake of gelatin-coated. 51Cr-labeled, fixed sheep erythrocytes by adherent peritoneal macrophage monolayers. Intraperitoneal inflammation resulted in a marked increase in peritoneal fluid fibronectin that lasted throughout a 4-day observation period. The opsonic activity of serum also increased after casein challenge at 24, 48, and 72 h. The elevation in the level of fibronectin in the peritoneal space appeared to coincide with or closely precede the maximal increase in concentration of inflammatory peritoneal macrophages. After casein injection, when serum immunoreactive fibronectin increased, an enhancement in phagocytic clearance of blood-borne gelatin-coated test particles was also observed. It is suggested that the elevation of fibronectin in blood during intraperitoneal inflammation may mediate enhanced liver phagocytic function. The increased amount of fibronectin in the inflamed peritoneal space may also influence the phagocytic activity of peritoneal macrophages.

Animals↗
PubMed1983

Kinetics of endogenously labeled plasma fibronectin: incorporation into tissues.

Fibronectin exists in a soluble form in plasma and lymph as well as in a relatively insoluble form in tissues. The disappearance of endogenously labeled fibronectin from plasma and its subsequent extravascular localization was studied over a 38-h period in normal rats (350-400 g) utilizing plasma fibronectin labeled in vivo with 75Se-selenomethionine. For comparative analysis, 125I-albumin was utilized in these dual isotopic experiments. After the simultaneous injection of 75Se plasma fibronectin (20 nCi) and 125I-albumin (2 microCi), all measured tissues demonstrated accumulation of both radiolabeled proteins in extravascular sites. Plasma fibronectin demonstrated a rather specific and high affinity for liver and spleen, which are enriched with reticuloendothelial cells. Albumin manifested the expected washout from extravascular sites, whereas fibronectin primarily displayed retention in tissues. The plasma disappearance of 75Se-labeled fibronectin was well described by two exponentials: an early phase with a half time of 0.52 h and a later phase with a half time of 21 h. To account for tissue retention of labeled fibronectin, a two-compartment kinetics model was required that included loss from the extravascular exchangeable compartment. Analysis of the disappearance kinetics and fibronectin distribution allowed estimation of the fractional turnover rate, pool size, and mean residence time. Accordingly the total rate of loss for plasma fibronectin was 0.51-0.54 mg/h. The calculated pool size of the soluble form of fibronectin was 15.5-16.3 mg. The mean residence time for exchangeable fibronectin was 29.6-29.9 h. These findings suggest that plasma fibronectin can be incorporated within the insoluble pool of fibronectin in tissues.

Animals↗
PubMed1983

Normal fibronectin levels as a function of age in the pediatric population.

Fibronectin is an important non-immune opsonic protein influencing phagocytic clearance of blood-borne nonbacterial particulates which may arise in association with septic shock, tissue injury, and intravascular coagulation. In the present study, serum fibronectin was measured by both electroimmunoassay as well as rapid immunoturbidimetric assay in healthy children (n = 114) ranging in age from 1 month to 15 years in order to delineate the temporal alterations in fibronectin with age. Normal adult serum fibronectin concentrations are typically 220 micrograms/ml +/- 20 micrograms/ml. Serum concentration is 35-40% lower than normal plasma concentration due to the binding of fibronectin to fibrin during clot formation. Children between 1-12 months of age had significantly (P less than 0.05) lower serum fibronectin levels than children between the ages of 1-15 years. Progressive elevation in fibronectin levels was observed within the last 8 months of the first year of age. Fibronectin levels in children older than 1 year of age remained constant up to 15 years and were within the lower limit of the normal adult concentration. No significant (P greater than 0.05) difference in serum fibronectin was observed between male and female children at all age groups. Fibronectin levels thus, increase during the first year of age and normal levels of this blood protein in the infant are less than the normal range for adults.

Adolescent↗
PubMed1983

Influence of septic peritonitis on circulating fibronectin, immunoglobulin, and complement: relationship to reticuloendothelial phagocytic function.

This study was designed to quantify the changes in the major serum opsonins--ie, fibronectin, IgG, and C3--during Staphylococcus aureus and Escherichia coli peritonitis as they may functionally relate to RES phagocytic function. Both forms of peritonitis were characterized by acute depletion of fibronectin, IgG, and C3 within 6 h. By 24 h, C3 levels had returned to control levels in both groups. IgG levels remained depressed 24 h following the induction of E coli peritonitis but had normalized by 24 h after Staph aureus challenge. In contrast, fibronectin was markedly elevated by 24 h with both E coli and Staph aureus peritonitis. Hepatic RES phagocytic function was significantly stimulated following induction of either Staph aureus or E coli peritonitis. The rapid increase in fibronectin as well as RES activation during septic peritonitis may represent a generalized host-defense response.

Animals↗
PubMed1983

Amplification of the opsonic activity of fibronectin by a plasma factor lacking gelatin affinity.

The opsonic activity of plasma fibronectin is important in modulating the reticuloendothelial system (RES) phagocytic removal of a variety of endogenous and exogenous particulate material from the vascular compartment. Purification of plasma-opsonic fibronectin by affinity chromatography with gelatin-Sepharose revealed that although in vitro hepatic Kupffer cell phagocytosis was absolutely dependent upon the presence of fibronectin, the purified fibronectin evaluated in concentrations similar to that found in plasma (350-450 micrograms/ml) supported phagocytosis at a level two- to threefold less than that observed in whole plasma. In contrast, the combination of purified fibronectin with small aliquots of opsonically inactive fibronectin-free plasma restored normal opsonic activity as assessed by liver slice bioassay and enhanced fibronectin-mediated attachment of gelatinized particulate to isolated Kupffer cells in vitro. Evidence is presented in this study that there exists in plasma a macromolecular species that amplifies the opsonic activity of fibronectin in a dose-related manner. This amplification or cofactor activity is nondialysable and has a molecular weight greater than 12,000. Inactivation of the amplification activity present in affinity-absorbed plasma can be achieved by heating the fibronectin-free plasma at 60 degrees C for 20 min, supporting the hypothesis that the cofactor is a protein. The amplification response is dose related, suggesting that the mechanism of its action is stoichiometric rather than catalytic. Evidence is presented that partial purification of the cofactor can be achieved by (NH4)2SO4 precipitation at 4 degrees C. Purification of this cofactor will provide an opportunity to evaluate its role in the altered opsonic states known to exist after trauma, burn, and sepsis.

Animals↗
PubMed1983

Alterations of fibronectin and reticuloendothelial phagocytic function during adaptation to experimental shock.

Fibronectin is a large molecular weight glycoprotein that participates in opsonization as well as in adhesive structural tissue support. The effect of repetitive low grade traumatic shock on circulating fibronectin, opsonic activity, and RES phagocytic function was studied in rats during the process of adaptation to trauma. Enhanced hepatic Kupffer cell phagocytic activity was observed in rats that were resistant to trauma. During the adaptation process, serum fibronectin levels, as measured by immunoassay, were altered markedly and manifested a pattern of acute deficiency early post-trauma followed by rebound and sustained elevation of fibronectin greatly in excess of control levels. At the time adaptation to trauma was achieved, the circulating fibronectin was within the normal range. In an in vitro system, livers from adapted rats exhibited increased phagocytic ability. The data suggest that Kupffer cell activation occurs during the development of adaptation to trauma and that increased hepatic RE activity accounts for the overall increase in RES clearance seen in the trauma-adapted animals. Since repetitive low grade trauma, which can lead to adaptation, will cause immunoreactive opsonic fibronectin levels to become substantially higher than normal throughout much of the duration of the adaptation protocol, it is possible that this excessive circulating fibronectin represents a means by which local conditioning of blood vessels to trauma may be achieved. Most likely, this would be due to incorporation of the circulating fibronectin into the insoluble tissue fibronectin pool, which has been recently shown to take place. The findings suggest that RES function and fibronectin may be factors influencing trauma tolerance.

Adaptation, Physiological↗
PubMed1982

Opsonic fibronectin deficiency and sepsis. Cause or effect?

Opsonic fibronectin is known to modulate macrophage (RE cell) and neutrophil Phagocytic function. Its depletion has been documented following trauma, burn, and operation in patients with rapid restoration of normal levels unless bacteremia and/or wound sepsis intervenes. Sepsis is associated with a secondary phase of opsonic fibronectin deficiency. We have observed in burn patients that this secondary phase of opsonic fibronectin depletion following trauma and burn is seen two to three days prior to the onset of clinical sepsis, raising the question of whether this deficiency sensitized the host to the subsequent development of sepsis or whether its deplection was merely an unsuspected sensitive indication of preclinical sepsis. To address the possibility that opsonic fibronectin deficiency might lower resistance to sepsis, Sprague-Dawley rats (200 gm) were partially depleted (35%) of their opsonic fibronectin prior to intraperitoneal inoculation with Staphylococcus aureus. Mortality to S. aureus peritonitis was significantly (p < 0.05) increased in animals with fibronectin deficiency. Furthermore, in control animals, nonsurvival was also associated with significantly (p < 0.05) lower initial fibronectin levels than survival. However, peritonitis itself also resulted in an early (within one hour) depletion of opsonic fibronectin followed by a marked "hyperopsonemia" within 12 hours in both groups. Thus, opsonic fibronectin depletion decreases resistance to sepsis, and the development of sepsis itself will initiate opsonic fibronectin deficiency. Host defense against infection may depend on early restoration and maintenance of normal opsonic fibronectin levels following trauma, burn, and operation, as well as the ability of the host to mount an appropriate hyperopsonemic elevation of fibronectin levels in response to infection.

Animals↗
PubMed1982

Comparative influence of blood-borne nonbacterial particles and Staphylococcus aureus on fibronectin, complement and immunoglobulin.

Opsonic fibronectin deficiency has been documented in septic injured patients and suspected to reflect acute depletion due to blood-borne nonbacterial particulates. In the present study, the comparative effect of intravenous infusion of heat-killed Staphylococcus aureus or gelatin-coated nonbacterial test particles on immunoreactive fibronectin, IgG and C3 was investigated. These two test particles were selected because of their known dependence upon adequate opsonization for efficient RES phagocytic removal. The intravenous injection of gelatin-coated RE test lipid emulsion (50 mg/100 gm body weight) resulted in an acute depletion of serum fibronectin with no major alteration in circulating IgG or C3. This selective depletion of fibronectin was followed by a rapid restoration and elevation of fibronectin level within 24 hours. In contrast, intravenous infusion of heat-killed S. aureus (1 X 10 11/rat) resulted in an acute depletion of fibronectin and C2 within 60 minutes. The deficiency of these opsonic proteins after bacterial challenge was followed by elevation of fibronectin and normalization of C2. IgG was not significantly changed at any time. The decline in fibronectin and C3 was greater with an increase in bacterial dose. These studies emphasize the specificity of the opsonic deficiency induced by gelatin-coated particles. Additionally, the suggest that opsonic deficiency with S. aureus bacteremia may be, in part, functionally related to disturbances of fibronectin. The role of fibronectin deficiency in documented states of opsonic deficiency with sepsis warrants consideration.

Animals↗
PubMed1982

Fibronectin deficiency and intestinal transvascular fluid balance during bacteremia.

Reticuloendothelial (RE) clearance dysfunction, which can be induced by opsonic fibronectin deficiency, has been correlated with organ failure during sepsis. We investigate the role of opsonic fibronectin deficiency and RE blockade in modulating alterations in intestinal transvascular fluid balance induced by Pseudomonas bacteremia using an isolated, innervated, and autoperfused canine small intestinal segment. Intravenous infusion of gelatin-coated particles was used to induce fibronectin deficiency and RE blockade. Lymph flow and lymph/plasma (L/P) protein concentration ratios were stable following intravenous challenge with bacteria or gelatin-coated particles. In contrast, lymph flow increased and L/P ratio decreased significantly when bacteremia coexisted with particle-induced opsonic fibronectin deficiency and RE blockade. This elevation in lymph flow and decline in L/P ratio was associated with normal vascular permeability to albumin, IgG, and IgM. The increase in intestinal fluid flux during bacteremia with RE blockade appears to be due to an increase in microvascular hydrostatic pressure and not to an increase in vascular permeability. These findings emphasize a potentially important role for fibronectin and associated RE system function as determinants of fluid filtration during sepsis.

Animals↗
PubMed1982

Opsonic fibronectin is necessary for optimal serum-mediated phagocytosis of Staphylococcus aureus by human neutrophils.

Opsonic fibronectin is known to mediate reticuloendothelial (RE) cell and neutrophil uptake of nonbacterial particulates. In a recent study opsonic fibronectin deficiency following burn preceded the onset of sepsis, leading us to hypothesize a role for this protein in antibacterial defense. To test this hypothesis we compared pooled normal human serum to fibronectin-depleted serum in its ability to opsonize and promote phagocytosis of Staphylococcus aureus by human neutrophil monolayers. Phagocytosis and intracellular killing were evaluated using acridine orange staining and ultraviolet (UV) microscopy. Human serum depleted of opsonic fibronectin by gelatin-sepharose affinity chromatography manifested a marked reduction in its ability to support phagocytosis of S aureus by human neutrophils. Reconstitution of fibronectin-deficient human serum with purified human plasma fibronectin restored its opsonic activity. The direct interaction of fibronectin with the bacteria was shown by mixing and/or incubation of the bacteria with normal serum followed by centrifugation and removal of the bacteria. This resulted in a marked (P less than 0.05) depletion (adsorption) of the fibronectin from the serum. Fibronectin appears not to act independently, but was an important cofactor in the ability for serum to stimulate phagocytosis. Thus, plasma fibronectin may be an important protein essential for maximal opsonic activity of serum. Its depletion following trauma and burn may undermine RE cell and neutrophil defense against infection and bacteremia, thus contributing to organ failure during septic shock.

Fibronectins↗
PubMed1982

Effect of bilateral nephrectomy on plasma fibronectin levels: its influence on acute fibronectin response to trauma and RE blockade.

Plasma fibronectin is important to reticuloendothelial (RE) function and resistance to experimental shock. However, the factors that regulate its level have remained undefined. The present study evaluated the concept that the kidneys may play a role in the modulation of plasma fibronectin levels. Immunoreactive and opsonically active fibronectin in blood over a 28-hour period following bilateral nephrectomy was assessed in male rats (250-350 gm) by electroimmunoassay, peritoneal macrophage monolayer assay, and liver slice bioassay. Controls consisted of sham-operated rats. An acute 25%-30% fibronectin deficiency was detected within the initial 1-2 hours posttrauma in both experimental and control rats. Thereafter, a significant (P less than 0.05) increase in immunoreactive fibronectin developed by 24 hours which was much greater after bilateral nephrectomy as compared to controls (P less than 0.05). With the peritoneal macrophage assay or with the liver slice assay, the plasma or serum from bilateral nephrectomized rats has greater opsonic activity as compared to controls. This corresponded to increased hepatic RE phagocytic function in vivo after nephrectomy. In the 24-hour postnephrectomized rats, fibronectin decreased acutely after RE blockade or traumatic shock (NCD) indicating it was biologically active. These data suggest that the kidneys may participate in regulating the blood level of this protein, which has a role in reticuloendothelial system function and shock resistance.

Animals↗
PubMed1981

Defects in peripheral oxygen utilization following trauma and shock.

Following shock and trauma, there may be capillary block or stasis that sets up a neurohumoral response, causing further capillary constriction and ischemia. This ischemia may not result in tissue hypoxia, as functioning capillaries may still exist near the damaged areas. Following resuscitation, however, a reperfusion syndrome causing massive tissue edema, endothelial swelling, and further capillary blocking may lead to tissue hypoxia. We used isolated canine hind limb as a model of the peripheral circulation in a series of experiments that showed that interstitial edema alone did not reproduce the defect in peripheral oxygen utilization. On the other hand, both reperfusion syndrome and microembolization were able to reproduce this response. Hypertonic mannitol and imidazole reversed this defect following either reperfusion syndrome or microembolization, respectively. These data suggest that resuscitated posttrauma patients suffering from defects in peripheral oxygen utilization probably owing to microembolization, reperfusion and tissue edema, which may be treated by specific therapy.

Animals↗
PubMed1981

Ventilation-perfusion relationships with high cardiac output in lobar atelectasis.

Pulmonary gas exchange was evaluated in 10 anesthetized mechanically ventilated dogs. Cardiac output (QT) was increased approximately 50% by opening peripheral arteriovenous fistulas. With both lungs ventilated, increasing QT increased mixed venous O2 both pressure (PO2) and pulmonary arterial pressure, but neither shunt fraction nor the distribution of ventilation-perfusion was consistently altered. During left lung atelectasis, increasing QT again increased mixed venous PO2 and pulmonary arterial pressure, but two different responses in shunt-like perfusion were measured. In four dogs, left lung atelectasis caused a shunt fraction of 46 +/- 6% that was not changed by high QT (P greater than 0.05). In six dogs, atelectasis caused a shunt fraction of 24 +/- 3% during normal QT that increased to 42 +/- 2% during high QT (P less than 0.001). Dogs whose shunt fraction during atelectasis was high and unchanged by QT had lower arterial pH (7.24 +/- 0.03) than dogs whose shunt fraction was initially lower and was increased with QT (7.36 +/- 0.02) (P less than 0.01). We conclude that increased QT can worsen shunt flow during lobar atelectasis when hypoxic vasoconstriction has been effective in limiting perfusion to the collapsed region at normal levels of QT.

Animals↗