Edge-on adsorption of multi-chain functional alkanes stabilizes noncovalent monolayers on MoS2.

Modified long-chain alkanes are often used to functionalize graphene and MoS2 noncovalently, with the goal of controlling the substrate electronic structure or interactions with the environment. Alkyl chain adsorption enthalpy is lower on MoS2 than on graphite; the decreased molecule-substrate interaction strength suggests utility for monolayer structures that increase stability through other means. Previously, we have found that diyne phospholipid monolayers on HOPG are more stable toward solution processing than monolayers of single-chain amphiphiles. Here, we show that this is also true for assembly on MoS2, but that the additional stability appears to arise from edge-on adsorption, producing monolayers in which alkyl chains form two stacked layers on the substrate.

Expression of the phenotypic abnormality of platelet-type von Willebrand disease in a recombinant glycoprotein Ib alpha fragment.

The platelet GP Ib-IX receptor supports platelet adhesion and activation by binding to vWf in the exposed subendothelial matrix. An abnormal GP Ib-IX complex exists in platelet-type or pseudo-von Willebrand disease and has a characteristic increased affinity for soluble vWf resulting in impaired hemostatic function due to the removal of larger vWf multimers from the circulation. Genetic studies within an afflicted family have demonstrated that the disease is linked to a Gly233-->Val amino acid substitution within the alpha-subunit of the oligomeric GP Ib-IX complex (Miller, J.L., D. Cunningham, V.A. Lyle, and C. L. Finch. 1991. Proc. Natl. Acad. Sci. USA. 88:4761-4765). To evaluate the functional consequences of this mutation, we constructed a recombinant analogue of the alpha-subunit of GP Ib containing Val233. Experiments comparing molecules with either Gly233 or Val233 revealed that the Val substitution generates a molecule with increased affinity for vWf. The recombinant fragment reproduces the functional abnormality of the GP Ib-IX complex in platelet-type von Willebrand disease, thus establishing the molecular basis of the bleeding disorder within this family. Moreover, it becomes apparent that structural elements responsible for the regulation of hemostasis through modulation of vWf affinity for platelets reside within the alpha-subunit of the GP Ib-IX complex.

Point mutation in a leucine-rich repeat of platelet glycoprotein Ib alpha resulting in the Bernard-Soulier syndrome.

Leucine-rich repeats are a conserved structural motif, of yet undefined significance, found in a group of proteins from different species. Among these are the four components of the human platelet glycoprotein Ib-IX-V complex, a membrane receptor that performs an essential role in the thrombogenic function of platelets by interacting with the adhesive protein, von Willebrand factor. We have found that a single amino acid substitution (Ala156-->Val) within one of the six leucine-rich repeats in the alpha-subunit of glycoprotein Ib results in a variant form of the congenital bleeding disorder, Bernard-Soulier syndrome, characterized by giant dysfunctional platelets. Genetic studies of the propositus and his family members were complemented by immunological and functional analysis of expressed recombinant GP Ib alpha fragments to demonstrate that the observed mutation is the cause of defective von Willebrand factor binding. These studies define the molecular basis of the Bernard-Soulier syndrome within this family and demonstrate that structural integrity of a leucine-rich repeat is necessary for normal function of the glycoprotein Ib-IX-V receptor complex and, possibly, for normal platelet morphology.

Dimerization of glycoprotein Ibα is not sufficient to induce platelet clearance.

UNLABELLED: ESSENTIALS: Many anti-glycoprotein (GP)Ibα antibodies induce platelet clearance in a dimer-dependent manner. Characterization of monoclonal antibodies that bind the mechanosensitive domain (MSD) of GPIbα. An anti-MSD antibody binds two copies of GPIbα in platelets but does not induce platelet clearance. The prevailing clustering model of GPIbα signaling is incorrect or needs revision. BACKGROUND: The mechanism of platelet clearance is not clear. Many antibodies binding the membrane-distal ligand-binding domain of glycoprotein (GP)Ibα induce rapid clearance of platelets and acute thrombocytopenia, which requires the bifurcated antibody structure. It was thought that binding of these antibodies induced lateral dimerization or clustering of GPIbα in the plasma membrane, which leads to downstream signaling and platelet clearance. However, many antibodies targeting GPIbß and GPIX, which are associated with GPIbα in the GPIb-IX complex, do not induce platelet clearance, which is in contradiction to the clustering model. OBJECTIVES: To test whether dimerization or clustering of GPIbα is sufficient to transmit the signal that leads to platelet clearance. METHODS: We have recently raised several mAbs targeting the mechanosensitive domain (MSD) of GPIbα. Binding of these anti-MSD antibodies was characterized with biochemical methods. Their ability to stimulate platelets and induce platelet clearance in mice was assessed. RESULTS AND CONCLUSION: Infusion of anti-MSD antibodies does not cause thrombocytopenia in mice. These antibodies show no detectable effects on platelet activation and aggregation in vitro. Further biochemical investigation showed that the anti-MSD antibody 3D1 binds two copies of GPIbα on the platelet surface. Therefore, lateral dimerization of GPIbα induced by antibody binding is not sufficient to initiate GPIb-IX signaling and induce platelet clearance. Our results suggest that a factor other than or in addition to clustering of GPIbα is required to induce platelet clearance.

Drosophila melanogaster male germ line-specific transcripts with autosomal and Y-linked genes.

We have identified of set of related transcripts expressed in the germ line of male Drosophila melanogaster. Surprisingly, while one of the corresponding genes is autosomal the remainder are located on the Y chromosome. The autosomal locus, at 77F on chromosome arm 3L, corresponds to the previously described transcription unit 18c, located in the first intron of the gene for an RI subunit of cAMP-dependent protein kinase. The Y chromosome copies have been mapped to region h18-h19 on the cytogenetic map of the Y outside of any of the regions required for male fertility. In contrast to D. melanogaster, where Y-linked copies were found in nine different wild-type strains, no Y-linked copies were found in sibling species. Several apparently Y-derived cDNA clones and one Y-linked genomic clone have been sequenced. The Y-derived genomic DNA shares the same intron/exon structure as the autosomal copy as well as related flanking sequences suggesting that it transposed to the Y from the autosomal locus. However, this particular Y-linked copy cannot encode a functional polypeptide due to a stop codon at amino acid position 72. Divergence among five different cDNA clones ranges from 1.5 to 6% and includes a large number of third position substitutions. We have not yet obtained a full-length cDNA from a Y-linked gene and therefore cannot conclude that the D. melanogaster Y chromosome contains functional protein-coding genes. The autosomal gene encodes a predicted polypeptide with 45% similarity to histones of the H5 class and more limited similarity to cysteine-rich protamines. This protein may be a distant relative of the histone H1 family perhaps involved in sperm chromatin condensation.

The Drosophila Eip78C gene is not vital but has a role in regulating chromosome puffs.

We have generated a number of chromosomal aberrations that disrupt the early-late ecdysone-induced 78C puff gene (Eip78C, ecdysone-induced protein, FlyBase name for the E78 gene of Stone and Thummel 1993), which encodes the two members of the nuclear hormone receptor superfamily Eip78C-A and Eip78C-B. The aberrations include deletions of the ligand-binding/dimerization domain of both, inversions that split Eip78C-A but retain residual Eip78C-B expression, and a small deletion specific for Eip78C-B. We find that wild-type Eip78C functions are completely dispensable for normal development under laboratory conditions. However, we show that Eip78C-B is required for the maximal puffing activity of a subset of late puffs (63E and 82F) since these puffs are reduced in size in Eip78C-B mutant backgrounds. Paradoxically the same late puffs are reduced, as well as at least one other, when the Eip78C-B cDNA is overexpressed from a heat shock promoter. These data indicate either that Eip78C function is redundant or that it plays a subtle modulating role in the regulation of chromosome puffing.

Nuclear hormone receptors and the Drosophila ecdysone response.

In Drosophila several members of the nuclear hormone receptor super-family are involved in regulating developmental pathways mediated by the steroid hormone ecdysone. At least seven genes encode a set of receptors which are expressed in a complex overlapping temporal and tissue-specific pattern. The variety of Drosophila receptors invites comparisons with mammalian systems and suggests that different receptors may interact to regulate developmental decisions. Once again the humble fruit fly is providing a genetic framework for understanding complex regulatory systems which have been conserved during evolution.

Cell sorting using a universally applicable affinity chromatography matrix: solid-phase anti-fluorescein isothiocyanate antibody.

Procedures are described for fractionating cells utilizing a universally applicable cellular affinity chromatography matrix. The affinity matrix consists of immunoabsorption purified goat anti-fluorescein isothiocyanate antibody coupled to large derivatized polyacrylamide beads. This matrix may, in principle, be used to isolate any cell subpopulation provided it has a fluorescein-labeled ligand on its surface. In this report the matrix was used to isolate viable purified fractions of mouse surface Ig-positive cells, Lyt1 cells, and mouse lymphocytes that bind the lectin soybean agglutinin. A preliminary experiment using the anti-FITC beads suggested that this technique can provide a fraction of cells enriched in antigen binding cells. Cell populations isolated by this technique retain their ability to respond to in vitro mitogen stimulation, as well as their ability to be maintained in cell culture following fractionation. Additional experiments using a column consisting of goat anti-rabbit Ig antibody coupled to the same support material are also reported.

Distribution of glycoconjugates in the human retinal internal limiting membrane.

The internal limiting membrane (ILM), or basal lamina, of the neural retina is located between the end feet of retinal Müller cells and the vitreous cortex. Recent studies of ILM substructure and histochemistry suggest that the ILM lamina rara externa, a region of the ILM likely to mediate vitreoretinal adhesion, is rich in noncollagen glycoconjugates. To characterize the spatial distribution and temporal expression of ILM glycoconjugates further, fetal and adult human retinas were examined using lectin histochemistry. Eyes from early fetal (13-15 weeks of gestation), midfetal (17-20 weeks of gestation), late fetal (23-26 weeks of gestation), full-term (38-41 weeks of gestation), early adult (17-20 yr of age), and late adult (57-84 yr of age) stages were examined. Although a number of significant observations pertaining to the distribution and temporal expression of ILM-associated glycoconjugates are described, two may have a significant relationship to vitreoretinal adhesion. In contrast to laminin and fibronectin, which are detectable throughout the retinal ILM at both young and older adulthood, erythrina cristagalii (ECA), a lectin with high binding affinity for galactose beta (1,3) N-acetyl-glucosamine, binds strongly to the ILM of young eyes but does not bind to the ILM of eyes from older donors. In addition, dolichos bifloris (DBA), a lectin with high binding affinity for N-acetylgalactosamine, does not bind to the ILM at early fetal stages, but binds at the midfetal stage, a time which corresponds with the onset of tertiary vitreous elaboration. More significantly, the DBA-binding glycoconjugate is neural retina ILM specific; it is not present in the basal lamina of the ciliary epithelium. Based on the known oligosaccharide composition of nonocular forms of human laminin, fibronectin, and collagen type I, and on the distribution of these molecules in the basal laminas of both the retina and ciliary epithelium, the authors conclude that the molecule bound by DBA has not been identified previously as a component of the ILM. Further characterization of ILM-associated molecules will be important to understand vitreoretinal adhesion and clinical disorders where adhesion is anomalous.

A method for improved biometry of the anterior chamber with a Scheimpflug technique.

A new method is described for obtaining cross-sectional images of the anterior chamber. Photographs are obtained with a Scheimpflug slit-lamp camera. After cornea, iris, and lens surfaces are digitized, mathematical corrections are made for the camera distortion and for the refractive effects of the cornea. The reproducibility and accuracy of the method were tested and found to be adequate for clinical study of human eyes in physiologic or diseased states.

Optic disc, foveal, and extrafoveal damage due to surgical separation of the vitreous.

OBJECTIVE: To evaluate the morphologic outcomes resulting from surgical vitreoretinal separation in young adult primates. MATERIALS AND METHODS: Vitrectomy and mechanical separation of the vitreous from the internal limiting lamina (ILL) of the posterior retina and surface of the optic disc were performed on 25 young adult cynomolgus monkey eyes in vivo. Lectin histochemical studies were used to evaluate the vitreoretinal interface. Morphologic outcomes were tabulated. RESULTS: In 11 of 25 eye regions, residual vitreous remained attached to the ILL in some of the regions. Localized ILL breaks or separation of the ILL from the neural retina was noted in 9 eyes. Retinal tissue loss, including avulsion of the ganglion cell, inner plexiform, or inner nuclear layers, was observed in 7 eyes. Avulsion of axon bundles in the optic disc was noted in 9 eyes. Significantly, partial- or full-thickness foveal tears were noted in 11 eyes. Based on the surgeons' intraoperative observations, small superficial optic disc or retinal hemorrhages were observed in 3 of 25 eyes. None of the eyes on which a vitrectomy alone was performed showed ILL damage, or retinal or optic disc tissue loss. CONCLUSION: Damage may occur to the optic disc, fovea, and extrafoveal retina as a result of surgical separation of the vitreous from the retina in young adult primates. CLINICAL RELEVANCE: These data support the contention that surgically induced damage at the level of the vitreoretinal interface may help explain the visual field defects noted after surgery to close full-thickness macular holes. These data also support the need for developing additional modalities to assist in vitreous separation, thereby reducing the risk of traumatic complications associated with purely mechanical procedures.

Chondroitin sulfate-induced generation of epiretinal membranes.

Previous investigations have examined the role of serum and retinal pigment epithelium-derived factors in the elaboration of epiretinal membranes. Alternatively, the contribution of the insoluble interphotoreceptor matrix, known to contain chondroitin-sulfate-containing proteoglycans, in the generation of epiretinal membranes, has not been evaluated, to our knowledge. To investigate the potential role of chondroitin sulfates in eliciting epiretinal membranes, chondroitin sulfate glycosaminoglycans were injected into the vitreous cavity of rabbits. Examination demonstrated epiretinal membranes in 86% of eyes receiving chondroitin-6-sulfate. Temporal development of chondroitin sulfate glycosaminoglycan-induced epiretinal membranes was categorized into three distinct stages: a preretinal cell stage 1 to 3 weeks following injection, a glial "tuft" stage at 3 to 6 weeks, and a "mature" complex membrane stage at 6 weeks or later. Our results suggest that intravitreal administration of chondroitin sulfate glycosaminoglycan, components of insoluble interphotoreceptor matrix proteoglycans, may elicit the generation of epiretinal membranes, even in the absence of retinal disruption.

Insoluble interphotoreceptor matrix in human vitreous after rhegmatogenous retinal detachment.

PURPOSE: To determine whether insoluble interphotoreceptor matrix is present in the vitreous of human eyes after rhegmatogenous retinal detachment. METHODS: Vitreous aspirates were collected from 12 eyes of 12 patients during retinal reattachment surgery or membrane peeling for rhegmatogenous retinal detachment-related macular epiretinal membranes between 1 day and 5 months after patients' initial rhegmatogenous retinal detachment symptoms. The aspirates were pelleted by centrifugation, embedded in acrylamide, sectioned, and incubated with fluorescein isothiocyanate-conjugated peanut agglutinin and an interphotoreceptor matrix-specific polyclonal antibody, designated 1-89B. RESULTS: Before surgery, 11 of 12 eyes exhibited pigment in the anterior vitreous (Shafer's sign). Morphologic and histochemical characteristic profiles of insoluble interphotoreceptor matrix domains, bound by fluorescein isothiocyanate-conjugated peanut agglutinin or polyclonal antibody 1-89B, or both, were identified in vitreous aspirates from 11 of 12 patients. CONCLUSIONS: The results of this study provide evidence that insoluble interphotoreceptor matrix constituents gain access to the vitreous after rhegmatogenous retinal detachment. Furthermore, insoluble interphotoreceptor matrix may remain in the vitreous for several months without being degraded.

Vitrectomy for complicated retinal detachments secondary to branch retinal vein occlusions.

Combined rhegmatogenous and traction retinal detachments associated with branch vein occlusions occurred in five eyes of five patients between Jan. 1, 1986 and Dec. 31, 1987. Four patients underwent surgery with pars plana vitrectomy and intravitreal gas, with or without scleral buckling. One patient refused treatment. All operated on eyes had attached retinas at a mean follow-up of seven months. Because posterior traction plays an important role in these unusual detachments, consideration should be given to pars plana vitrectomy and air-fluid exchange rather than scleral buckling alone.

Predictors of scleral rupture and the role of vitrectomy in severe blunt ocular trauma.

We reviewed retrospectively 40 eyes that had received blunt trauma and had been explored for scleral rupture. Twenty-nine eyes had scleral rupture. Of these 29, ten had ruptures seen preoperatively. Nineteen had occult ruptures. The preoperative findings predictive of scleral rupture were a visual acuity of light perception or no light perception, an intraocular pressure of less than 10 mm Hg, hyphema, and chemosis. Of the 29 ruptures, 27 involved the superior hemisphere and 25 involved the anterior hemisphere of the globe. Ten of 29 eyes (34%) with scleral rupture and eight of 11 eyes (73%) without rupture achieved a final visual acuity of 5/200 or better over an average follow-up period of 6.7 months. Factors prognostic of ambulatory vision for eyes with ruptured and intact globes included an initial visual acuity of 5/200 or better, absence of scleral rupture, and a rupture length of less than 11 mm in eyes with ruptures. The vitrectomized eyes also had a better result, suggesting that early pars plana vitrectomy is of benefit in selected rupture cases.

Location, substructure, and composition of basal laminar drusen compared with drusen associated with aging and age-related macular degeneration.

PURPOSE: To determine whether basal laminar drusen differ in their location, ultrastructure, or composition from drusen associated with aging and age-related macular degeneration. METHODS: A paraffin-embedded block from an eye of a patient with basal laminar drusen was obtained. Sections were examined immunohistochemically using a battery of antibodies and lectins directed against drusen-associated proteins and glycoconjugates, respectively. Thin sections were examined by electron microscopy and compared with eyes with age-related macular degeneration. RESULTS: Drusen in the eye with basal laminar drusen are located between the basal lamina of the retinal pigment epithelium and the inner collagenous layer of Bruch membrane, just as they are in age-related macular degeneration. Two distinct ultrastructural phenotypes are observed in the eye with basal laminar drusen; their substructure is indistinguishable from drusen phenotypes in age-related macular degeneration. Both basal laminar drusen and drusen associated with age-related macular degeneration are bound by the lectins Ricinis communis agglutinin and Arachis hypogea agglutinin (after neuraminidase digestion) and by antivitronectin, anti-HLA-DR, anti-serum amyloid P, and anti-C5 antibodies, but not by antibodies directed against basement membrane-associated heparan sulfate proteoglycan, laminin, fibrinogen, or collagen type IV. CONCLUSIONS: These data support the notion that cuticular or basal laminar drusen are similar to, and perhaps indistinguishable from, drusen associated with age-related macular degeneration and are not nodular or diffuse thickenings of Bruch membrane, as previously suggested. Thus, we suggest basal laminar drusen is a misnomer. This clinical phenotype should be identified as "early adult onset, grouped drusen" or by the eponym "Gass syndrome." Features of basal laminar drusen, such as uniform drusen size, clustered distribution, and angiographic features, do not appear to be related to differences in drusen location, composition, or substructure.

The effect of oral antiplatelet agents on tissue plasminogen activator-mediated thrombolysis in a rabbit model of thromboembolic stroke.

OBJECTIVE: The success of thrombolytic therapy in acute stroke relies on timely reperfusion. The current study examines the efficacy of antiplatelet agents as adjuvants for thrombolytic therapy. METHODS: Using an established rabbit model of clot embolization and a randomized blinded design, rabbits (n = 8 in each group) were orally pretreated daily for 5 days with adjuvant aspirin (1 mg/kg of body weight or 20 mg/kg), ticlopidine (100 mg/kg), or vehicle (sodium carbonate). On the 6th day, tissue plasminogen activator (6.3 mg/kg administered intravenously over 2 h), was initiated 1 hour after embolization. RESULTS: In all groups, cerebral blood flow (CBF) was reduced to < 10 ml/100 g/min immediately after clot embolization. After the initiation of tissue plasminogen activator (t-PA), there was significant restoration of CBF in the control (t-PA only) and ticlopidine groups (P < 0.05) only. Restoration of CBF generally correlated with brain infarct size (percent hemisphere, mean +/- standard error of the mean), which was 18.0 +/- 7.0 in the t-PA only group versus 11.0 +/- 3.3, 26.5 +/- 5.8, and 21.5 +/- 3.4 in the ticlopidine, low-dose aspirin, and high-dose aspirin groups, respectively (ticlopidine versus aspirin, P < 0.05). Clot lysis was identical in the control and ticlopidine groups, with 6 of 8 animals demonstrating complete clot lysis. Aspirin antagonized clot lysis in a dose-related manner, with low-and high-dose aspirin groups noting clot lysis in four of eight and two of eight animals, respectively. CONCLUSIONS: Pretreatment with ticlopidine significantly reduced brain infarct size when compared with aspirin treatment (P < 0.05). Moreover, whereas ticlopidine treatment did not affect clot lysis or CBF relative to t-PA alone, aspirin therapy resulted in antagonism of clot lysis and was associated with a more modest restoration of blood flow. This study provides a background for a more comprehensive understanding of the balance of thrombogenicity and thrombolysis and may assist in the development of novel therapies to expedite cerebrovascular patency and reduce ischemic and reperfusion-mediated neuronal injury.

16(R)-hydroxyeicosatetraenoic acid, a novel cytochrome P450 product of arachidonic acid, suppresses activation of human polymorphonuclear leukocyte and reduces intracranial pressure in a rabbit model of thromboembolic stroke.

OBJECTIVE: Activated polymorphonuclear leukocytes (PMNs) have been suggested to contribute to the development of increased intracranial pressure (ICP). We recently demonstrated that human PMNs produce a novel cytochrome P450-derived arachidonic acid metabolite, 1 6(R)-hydroxyeicosatetraenoic acid [16(R)-HETE], that modulates their function. It was thus of interest to examine this novel mediator in an acute stroke model. METHODS: 16-HETE was assessed initially in a variety of human PMN and platelet in vitro assays and subsequently in an established rabbit model of thromboembolic stroke. A total of 50 rabbits completed a randomized, blinded, four-arm study, receiving 16(R)-HETE, tissue plasminogen activator, both, or neither. Experiments were completed 7 hours after autologous clot embolization. The primary end point for efficacy was the suppression of increased ICP. RESULTS: In in vitro assays, 16(R)-HETE selectively inhibited human PMN adhesion and aggregation and leukotriene B4 synthesis. In the thromboembolic stroke model, animals that received 16(R)-HETE demonstrated significant suppression of increased ICP (7.7 +/- 1.2 to 13.1 +/- 2.7 mm Hg, baseline versus final 7-h time point, mean +/- standard error), compared with either the vehicle-treated group (7.7 +/- 0.9 to 15.8 +/- 2.6 mm Hg) or the tissue plasminogen activator-treated group (7.6 +/- 0.6 to 13.7 +/- 2.1 mm Hg). The group that received the combination of 16(R)-HETE plus tissue plasminogen activator demonstrated no significant change in ICP for the duration of the protocol (8.6 +/- 0.6 to 11.1 +/- 1.2 mm Hg). CONCLUSION: 16(R)-HETE suppresses the development of increased ICP in a rabbit model of thromboembolic stroke and may serve as a novel therapeutic strategy in ischemic and inflammatory pathophysiological states.

Activation of complement by tissue plasminogen activator, but not acute cerebral ischemia, in a rabbit model of thromboembolic stroke.

Although complement activation is associated with tissue injury during inflammatory and ischemic states, complement activation in states of acute cerebral ischemia before and after administration of tissue plasminogen activator (TPA) has not yet been examined and is the focus of this investigation. Twenty-four New Zealand White rabbits weighing 3 to 3.5 kg were used for this study. Of these, 20 were subjected to intracranial autologous clot embolization via the internal carotid artery. Three hours postembolization, rabbits received an intravenous infusion of TPA (6.3 mg/kg, 20% bolus with the remainder infused over a 2-hour interval; 12 animals) or vehicle (eight animals). All animals were observed for a total of 7 or 8 hours postembolization. These two groups were compared to a cohort undergoing sham operation with subsequent TPA infusion (four animals). Plasma samples to quantify complement component C5 hemolytic activity (C5H5O) were obtained at the following time points: 30 minutes before and after clot embolization; 1 hour before and 1 hour after the initiation of therapy with TPA or vehicle and at the completion of the protocol; 7 to 8 hours after clot embolization. The C5 activation was not detected as the result of acute cerebral ischemia. However, animals receiving TPA with or without concomitant clot embolization exhibited C5 activation as assessed by a reduction in C5 hemolytic function, both 1 hour after initiation of TPA infusion (78.7 +/- 10.3% and 77.5 +/- 9.9% of baseline value, respectively; mean +/- standard error of the mean [SEM]) and at the end of the protocol, 2 hours after the completion of the TPA infusion (72.5 +/- 8.8% and 53.3 +/- 8.1%, respectively; mean +/- SEM, p < 0.05, each group). This study supports the conclusion that TPA, but not acute cerebral ischemia, may activate the complement cascade in this rabbit model of thromboembolic stroke.

Rapid (0.5 degrees C/min) minimally invasive induction of hypothermia using cold perfluorochemical lung lavage in dogs.

OBJECTIVE: Demonstrate minimally invasive rapid body core and brain cooling in a large animal model. DESIGN: Prospective controlled animal trial. SETTING: Private research laboratory. SUBJECTS: Adult dogs, anesthetized, mechanically ventilated. INTERVENTIONS: Cyclic lung lavage with FC-75 perfluorochemical (PFC) was administered through a dual-lumen endotracheal system in the new technique of 'gas/liquid ventilation' (GLV). In Trial-I, lavage volume (V-lav) was 19 ml/kg, infused and withdrawn over a cycle period (tc) of 37 s. (effective lavage rate V'-lav=31 ml/kg/min.) Five dogs received cold (approximately 4 degrees C) PFC; two controls received isothermic PFC. In Trial-II, five dogs received GLV at V-lav=8.8 ml/kg, tc=16 s, V'-lav=36 ml/kg/min. MEASUREMENTS AND MAIN RESULTS: Trial-I tympanic temperature change was -3.7+/-0.6 degrees C (SD) at 7.5 min, reaching -7.3+/-0.6 degrees C at 18 min. Heat transfer efficiency was 60%. In Trial-II, efficiency fell to 40%, but heat-exchange dead space (VDtherm) remained constant. Lung/blood thermal equilibration half-time was <8 s. Isothermic GLV caused hypercapnia unless gas ventilation was increased. At necropsy after euthanasia (24 h), modest lung injury was seen. CONCLUSIONS: GLV cooling times are comparable to those for cardiopulmonary bypass. Heat and CO(2) removal can be independently controlled by changing the mix of lavage and gas ventilation. Due to VDtherm of approximately 6 ml/kg in dogs, efficient V-lav is >18 ml/kg. GLV cooling power appears more limited by PFC flows than lavage residence times. Concurrent gas ventilation may mitigate heat-diffusion limitations in liquid breathing, perhaps via bubble-induced turbulence.