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G D Niehaus

Publications and source records attributed to G D Niehaus.

16 recordsLinked to original sources
PubMed2005

Real-time microbe detection based on director distortions around growing immune complexes in lyotropic chromonic liquid crystals.

We describe director distortions in the nematic liquid crystal (LC) caused by a spherical particle with tangential surface orientation of the director and show that light transmittance through the distorted region is a steep function of the particle's size. The effect allows us to propose a real-time microbial sensor based on a nontoxic lyotropic chromonic LC (LCLC) that detects and amplifies the presence of immune complexes. A cassette is filled with LCLC, antibody, and antigen-bearing particles. Small and isolated particles cause no macroscopic distortions of the LCLC. Upon antibody-antigen binding, the growing immune complexes distort the director and cause detectable optical transmittance between crossed polarizers.

Antigen-Antibody Complex↗
PubMed1998

Quantifying rat pulmonary intravascular mononuclear phagocytes.

Cells of the mononuclear phagocyte system (MPS) protect the host by clearing effete and foreign particulates from the circulation. The current study was designed to identify, quantify, harvest, and provide a partial functional characterization of the systemic host-defense cell located in the pulmonary microvasculature of the rat. Critical colloid doses of test particulates (monastral blue B [MBB] or polystyrene beads) were infused intra-arterially into anesthetized rats so that phagocytically active pulmonary intravascular phagocytes could be identified. Morphologic characterization of in situ phagocytes was performed using electron microscopy. The number of active phagocytes was then determined using tissue samples processed for light microscopy. Finally, sequential perfusion of the pulmonary vasculature with buffer, chelating agent, and collagenase allowed elution and preliminary functional characterization of the pulmonary intravascular mononuclear phagocyte (PIMP). Electron microscopy demonstrated that both mononuclear phagocytes and neutrophils contributed to pulmonary sequestration of circulating particulates. Light microscopy showed that the microvasculature of each alveolus contained 0.50+/-0.19 active mononuclear phagocytes and 0.14+/-0.12 active neutrophils. A chelation/collagenase elution technique was then used to harvest the PIMP. Histologic evaluation of the postperfusion lungs indicated that 80% of the active phagocytes were removed by the technique. In total, the elution fluids contained 2.63+/-1.04 x 10(7) cells, with 1.60+/-0.78 x 10(7), 0.49+/-0.17 x 10(7), and 0.54+/-0.26 x 10(7) of those cells being mononuclear phagocytes, neutrophils, and lymphocytes, respectively. Functionally, the mononuclear phagocyte population exhibited a spectrum of phagocytic activities, with 51.5+/-19.5% of the cells being inactive, 33.9+/-13.4% exhibiting moderate phagocytic activity, and 14.6+/-9.8% demonstrating intensive phagocytic capacity. The current study provides the first quantified demonstration that mononuclear phagocytes are primarily responsible for sequestering blood-borne foreign particulates in the pulmonary circulation of the rat. Approximately 2 x 10(7) PIMP existed in the lungs of 300 gram rats. The functionally heterogeneous mononuclear phagocytes exhibited phagocytic capacities ranging from avidly phagocytic (14.6+/-9.8%) through moderately active (33.9+/-13.4%) to inactive. The lung microvasculature's large pool of inactive mononuclear phagocytes may provide a recruitable mechanism to allow significant increases in clearance of circulating particulates. A resident pool of activatable mononuclear phagocytes might explain previous clinical observations of increased particulate localization in the lung microvasculature of septic patients.

Animals↗
PubMed1998

Ultrastructural and cytochemical evaluation of sepsis-induced changes in the rat pulmonary intravascular mononuclear phagocytes.

Sepsis stimulates an increase in the number and activity of mononuclear phagocytes in systemic host-defence organs. The present study was conducted to define the ultrastructural and cytochemical characteristics of the mononuclear phagocytes that sequester in the lung microvasculature of septic rats. Fourteen rats were challenged with a single intraperitoneal injection of saline (0.5 ml/100 g), E. coli (2 x 10(7)/100 g) or glucan (4 mg/100 g), and euthanased 2, 4, or 7 d later. The lungs were inflation fixed and processed for transmission electron microscopy. Cellular morphology was used to identify the intravascular mononuclear phagocytes and acid phosphatase (AcPase) expression was monitored as an index of cellular differentiation and activation. Control rats contained a limited number of monocytes in the pulmonary vasculature. In contrast, large numbers of activated mononuclear phagocytes were seen in the microvasculature within 48 h of treatment with either microbial product. The recruited pulmonary intravascular mononuclear phagocytes (PIMP) exhibited AcPase-reactive Golgi complexes, accumulation of secretory vesicles and other features of cell activation consistent with enhanced biosynthetic activity. Subsequent electron microscopy, conducted 4 and 7 d posttreatment, suggested that a progressive decline in the number and activity of PIMPs then occurred. In order to quantify the sepsis-induced accumulation of AcPase-positive PIMP, the experimental challenges were repeated in 11 rats and, 48 h later, tissue samples were evaluated by light microscopy for tartrate-insensitive acid phosphatase. Control rats exhibited 0.148 +/- 0.107 AcPase-positive PIMP/alveoli. E. coli and glucan challenged animals exhibited significant (P < 0.01) increases in AcPase-positive mononuclear phagocytes, with 0.782 +/- 0.073 and 0.636 +/- 0.170 PIMP/alveoli respectively. The results demonstrate that focal sepsis stimulates a significant, but transient, recruitment of activated mononuclear phagocytes into the rat pulmonary microvasculature.

Acid Phosphatase↗
PubMed1993

Effect of peak inspiratory pressure on the filtration coefficient in the isolated perfused rat lung.

Positive inspiratory pressure- (PIP) ventilated, isolated rat lungs become edematous when perfused at rates approximately the normal cardiac output. The study was conducted to test the hypothesis that high peak inspiratory pressures contribute to the edema development. Five isolated lungs were perfused at a rate of 24.4 +/- 2.2 ml.min-1.100 g body wt-1 with 40% whole blood (diluted with saline containing 4.0 g/100 ml bovine serum albumin) and ventilated with peak pressures ranging from 0 to 20 mmHg. The lungs exhibited edema at PIP values > 9.3 mmHg. The stable pulmonary vascular pressure and resistance suggested that the edema may have resulted from a PIP-induced increase in microvascular permeability. In a second study, the stability of the preparation was evaluated during a 3-h test period. Seven lungs were ventilated at a peak inspiratory pressure of 8.0 mmHg and perfused at 26.8 +- 1.7 ml.min-1 x 100 g body wt-1. Microvascular integrity was maintained for approximately 2 h as indicated by filtration coefficient measurements of 0.175 +/- 0.068, 0.197 +/- 0.066, and 0.169 +/- 0.067 g.min-1 x mmHg-1 x 100 g-1 at 25, 70, and 115 min, respectively, after initiation of the study. The results suggest that isolated rat lungs perfused at rates that parallel normal rat cardiac output and ventilated at low peak inspiratory pressures provide a viable mechanism for evaluation of the pathophysiology of microvascular injury.

Animals↗
PubMed1990

Administration of a synthetic antiprotease reduces smoke-induced lung injury.

Our previous studies suggest that a neutrophil-mediated inflammatory injury causes a major fraction of the pulmonary edema that occurs after smoke inhalation. Because activated neutrophils extrude cytotoxic proteases, the current study was conducted to evaluate the role of proteases in the pulmonary microvascular injury. Twelve sheep, instrumented for collection of lung lymph, were insufflated with cotton smoke. The sheep were treated 30 min after smoke inhalation with either gabexate mesilate (an inhibitor of serine proteases) or vehicle. Smoke inhalation resulted in an increased protease activity in the lung interstitium, as evidenced by decreases in both antiprotease activity and immunoreactive alpha 2-macroglobulin. Intravenous infusion of gabexate mesilate prevented the decrease in antiprotease activity. The protease inhibitor significantly attenuated the smoke-induced increase in transvascular fluid and protein flux, with untreated animals exhibiting 460% increases in flux compared with 180% in the inhibitor treated sheep. The protease inhibitor also eliminated the functional degradation in gas exchange that was observed in the untreated sheep. These studies strongly suggest that an increase in pulmonary proteolytic enzyme activity is responsible for a significant fraction of the degradation in microvascular integrity and gas exchange that is associated with smoke inhalation injury.

Animals↗
PubMed1988

The effect of leukocyte depletion on smoke inhalation injury in sheep.

Leukocytes and the production of oxygen radicals and proteolytic enzymes have been implicated in the pathogenesis of lung injury after smoke inhalation. We investigated the mechanism responsible for this form of pulmonary damage in chronically prepared sheep previously made leukopenic with intra-arterial infusions of nitrogen mustard (mechlorethamine hydrochloride). A control air insufflated group (sham: n = 6), a cotton smoke insufflated group (smoke: n = 12), and a leukopenic cotton smoke insufflation group (smoked + depleted: n = 6) were compared. Although both smoke insufflation groups had equivalent smoke exposure, which was indexed by carboxyhemoglobin, the smoked + depleted group had significant attenuation in the increases in pulmonary artery pressure, pulmonary vascular resistance, and pulmonary lymph flow. The PaO2 to FiO2 ratio (P:F) did not fall to the same extent, nor was there a fall in PaO2. The production of oxygen radicals, which was measured as plasma-conjugated dienes, and the consumption of antiprotease, as measured by alpha 2-macroglobulin levels in lung lymph, were not changed in the smoked + depleted group, whereas it was elevated in the smoked group. We conclude that circulating leukocytes and the release of oxygen radicals and proteolytic enzymes contribute to the lung injury, pulmonary microvascular permeability increase, and pulmonary edema seen after smoke inhalation.

Animals↗
PubMed1986

The pulmonary lesion of smoke inhalation in an ovine model.

Inhalation injury was induced in chronically instrumented sheep (n = 9) by insufflating them with smoke from burning cotton cloth. Sham animals (n = 9) were insufflated with air. There were no temporal changes in any measured parameter of the sham animals. Smoke induced a depression in PaO2. There was a threefold elevation in protein-rich pulmonary lymph which was sustained for over 48 hours. The lymph-to-plasma oncotic pressure ratio was increased. The cardiac index, left atrial pressure, and pulmonary arterial pressure remained unchanged in both groups. After smoke inhalation, the interstitial levels of neutrophils increased while interstitial antiprotease activity was depressed. The lung lymph concentration of 6-keto prostaglandin F1a, the major metabolite of prostacyclin, was increased. These data suggest that the pulmonary injury following smoke inhalation is the result of an increase in lung microvascular permeability to protein with resultant pulmonary edema. The mechanisms responsible for these changes appear to be related to direct injury to the tracheobronchial tree by cytotoxic agents in the smoke; polymorphonuclear leukocytes; and, possibly, eicosanoids.

6-Ketoprostaglandin F1 alpha↗
PubMed1985

Thrombin-induced alterations in lung fluid balance in awake sheep.

We examined the effect of fibrinolysis depression on thrombin-induced pulmonary microembolism in awake sheep prepared with chronic lung lymph fistulas. Fibrinolysis was depressed by an intravenous infusion (100 mg) of tranexamic acid [trans-4-(Aminomethyl)cyclohexanecarboxylic acid]. Pulmonary microembolism was induced by an intravenous infusion of alpha-thrombin (80 NIH U/kg) in normal (n = 7) and in tranexamic acid-treated (n = 6) sheep. Thrombin immediately increased pulmonary lymph flow (Qlym) in both groups. The increased Qlym was not associated with a change in the lymph-to-plasma protein concentration (L/P) ratio in the control group and with a small decrease in the tranexamic acid-treated group. The increases in Qlym and pulmonary transvascular protein clearance (Qlym X L/P ratio) in the tranexamic acid-treated group were greater and sustained at four- to fivefold above base line for 10 h after the thrombin and remained elevated at twofold above base line even at 24 h. In contrast, Qlym and protein clearance were transiently increased in the control group. The mean pulmonary arterial pressure (Ppa) and pulmonary vascular resistance (PVR) increased after thrombin in tranexamic acid-treated group; the increases in Ppa and PVR in the control group were transient. Protein reflection coefficient as determined by the filtration independent method decreased after thrombin in tranexamic acid-treated sheep (n = 5), indicating an increased vascular permeability to proteins. We conclude that prolongation of microthrombi retention in the pulmonary circulation results in an increased vascular permeability to proteins. Both increased vascular permeability and vascular hydrostatic pressure are important determinants of the increases in Qlym and transvascular protein clearance after thrombin-induced pulmonary microembolism.

Amino Acids↗
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

The pathophysiology of smoke inhalation injury in a sheep model.

This study describes an experimental model of smoke inhalation injury in sheep, in which the same pathophysiologic alterations occur as with clinical inhalation in man. Both the patients and the experimental sheep develop diffuse pulmonary mucosal sloughing, pulmonary edema, and a decrease in systemic oxygen tension. The results of this study indicate that the pulmonary edema is the result of an increase in microvascular permeability, characterized by increases in lung lymph flow (Qlym), lymph-to-plasma protein concentration ratio (L/P), and transvascular protein flux (Qlym X lung lymph protein concentration), while pulmonary vascular pressures remain constant. Neutrophil degranulation may contribute to the increased microvascular permeability.

Animals↗
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

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↗
PubMed1981

Influence of gelatin on bioassayable and immunoreactive opsonic fibronectin.

Plasma fibronectin has a high affinity for denatured collagen (gelatin) and exerts an opsonic influence on phagocytosis of test colloids and clearance of tissue debris by macrophages. This study evaluated the effect of in vitro and in vivo interaction of gelatin with plasma on measurable bioassayable opsonic activity and immunoreactive fibronectin. Incubation of human, dog, sheep, and rat plasma with gelatin prior to in vitro assay decreased (P less than 0.05) the ability of plasma to augment particle uptake in the liver slice bioassay. Incubation of plasma with gelatin also decreased the concentration of fibronectin that could be detected by electroimmunoassay. Intravenous infusion of gelatin into rats, dogs, and sheep resulted in an acute depression in both bioassayable and immunoreactive opsonic observations suggest that deficits of opsonic fibronectin as documented in injured patients by bioassay and electroimmunoassay may not be exclusively related to actual depletion of fibronectin from blood but may be, in part, due to binding of fibronectin to blood-borne material post-trauma, i.e., collagenous tissue debris, whose presence in plasma may limit its detection by both assays.

Adult↗
PubMed1980

Reticuloendothelial clearance of blood-borne particulates: relevance to experimental lung microembolization and vascular injury.

The rapid increase in sheep lung vascular permeability observed during Pseudomonas aeruginosa bacteremia may be due to embolization of the pulmonary microvasculature by bloodborne particulates. Since alterations in lung microvascular permeability during mild septicemia in sheep may reflect inefficient RES phagocytic clearance of bacteria as well as products of bacterial induced intravascular coagulation, the opsonic and phagocytic aspects of RES function in sheep (30-50 kg) were compared to other species. RES function was evaluated by both the clearance and relative organ uptake of gelatinized I(131) RE test lipid emulsion and gelatinized colloidal carbon. Immunoreactive opsonic a(2)SB glycoprotein levels were determined by electroimmunoassay. The phagocytic index for RES clearance of the gelatinized (500 mg/kg) test lipid in sheep was 0.019 +/- 0.002 corresponding to a half-time of 16.65 +/- 1.74 minutes. With colloidal carbon (64 mg/kg), the phagocytic index in sheep was 0.080 +/- 0.026, corresponding to a half-time of 6.16 +/- 1.99 minutes. The per cent of injected lipid emulsion (%ID) in major RE organs, on a total organ basis (TO), was: liver = 15.69 +/- 1.65%; spleen = 2.09 +/- 0.78%. Localization in the lung = 31.39 +/- 6.2%. The per cent of carbon localized in major RE organs (%ID/TO) was: liver = 21.37 +/- 1.9%; spleen = 1.95 +/- 0.55%. Localization in the lung = 32.70 +/- 4.55%. In contrast, clearance and organ distribution of the blood-borne test microparticles in rats and dogs at the same relative challenging dose revealed a much more intense and rapid liver and spleen RES uptake with minimal lung localization (1-2%). Immunoreactive opsonic protein concentrations varied greatly with species and directly correlated with efficiency of RES function. Levels observed were: dog = 1285 +/- 135 microg/ml; mouse = 1077 +/- 67 microg/ml; rat = 400 +/- 31 microg/ml; human = 297 +/- 10 microg/ml; and sheep = 184 +/- 13 microg/ml. After intravenous particulate challenge, circulating immunoreactive opsonic protein in the sheep was depleted (p < 0.05) rapidly with partial recovery at 24 hours and mild rebound hyperopsonemia at 48 hours. This pattern is in contrast to the rapid restoration seen in dog and rat within three to six hours postchallenge. Thus, in sheep, the extensive pulmonary localization of blood-borne microparticles appears related to inefficient RES clearance function mediated by a relative deficiency of circulating opsonic protein (plasma fibronectin).

Animals↗
PubMed1980

Influence of opsonic fibronectin deficiency on lung fluid balance during bacterial sepsis.

Lung microvascular permeability in sheep increases during Pseudomonas bacteremia. The sheep's low plasma opsonic fibronectin concentration and associated inefficient reticuloendothelial clearance of blood-borne particulates may contribute to the response of increased lung vascular permeability during sepsis. The present study investigated the influence of sepsis on lung fluid balance in sheep with and without opsonic glycoprotein (plasma fibronectin) deficiency. Using the lung lymph fistula preparation in sheep, we made measurements of lung lymph flow (QLYM), lymph-to-plasma protein concentration ratios (L/P), pulmonary hemodynamics, and extravascular lung water content. Deficiency of opsonic fibronectin resulted in a minimal increase in lymph flow with no change in transvascular protein clearance (QLYM X L/P). Pseudomonas sepsis with or without fibronectin deficiency resulted in a stable L/P and a transient increase in pulmonary arterial pressure, which declined to a new steady state. Although sepsis resulted in a 100% elevation (P < 0.05) in lymph flow and transvascular protein clearance, sepsis in the presence of fibronectin deficiency induced a sustained 300--400% increase in lymph flow and a 300% increase in transvascular protein clearance. Thus opsonic fibronectin deficiency exaggerates the increased lung vascular permeability during sepsis.

Animals↗