Louis G. D'Alecy

Validation of Volume–Pressure Recording Tail-Cuff Blood Pressure Measurements

BACKGROUND The American Heart Association has recommended tail-cuff blood pressure measurement for high-throughput experimental designs, including mutagenesis screens and genetic crosses. However, some tail-cuff methods show good agreement with radiotelemetry and others do not, indicating that each tail-cuff method requires independent validation. METHODS We validated the volume-pressure recording (VPR) tail-cuff method by comparison to simultaneous radiotelemetry measurements. RESULTS Bland-Altman analysis of 560 cycles from 26 independent measurement sessions showed good agreement between VPR and radiotelemetry measurements, with tail-cuff measurements being 0.25 mm Hg lower than telemetry measurements on average. However, the VPR method was less accurate, compared to radiotelemetry, at extreme high and low (i.e., <110 or >180 mm Hg) systolic blood pressures (SBPs). CONCLUSIONS We conclude that the VPR tail-cuff method provides accurate blood pressure measurements over the physiological range of blood pressure in mice.

Cardiopulmonary-cerebral resuscitation with 100% oxygen exacerbates neurological dysfunction following nine minutes of normothermic cardiac arrest in dogs

This study investigated the effects of normoxic (FIO2 = 0.21), hyperoxic (FIO2 = 1.0), and hyperoxic (FIO2 = 1.0) plus antioxidant pretreatment (tirilazad mesylate) [corrected] resuscitation on neurologic outcome following 9 min of normothermic (39 +/- 1.0 degrees C) cardiac arrest. Physiologic variables including arterial blood gases and neurologic outcome, which was assessed using a standardized scoring system, were followed over a 24-h period following resuscitation from cardiac arrest. Hyperoxically resuscitated dogs sustained significantly worse neurological deficit at 12 and 24 h (mean scores: 39 +/- 3 and 49 +/- 8, respectively) than did antioxidant pretreated hyperoxically resuscitated dogs (mean scores: 22 +/- 1, P = 0.0007 and 22 +/- 1, P = 0.004, respectively) and normoxically resuscitated dogs (mean scores: 28 +/- 4, P = 0.025 and 33 +/- 8, P = 0.041 respectively). These data suggest that oxidant injury has a major role in central nervous system dysfunction following successful resuscitation from 9 min of cardiac arrest. Also, resuscitation from cardiac arrest with hyperoxic FIO2s may contribute to and further exacerbate neurologic dysfunction.

Protection from cerebral ischemia by brain cooling without reduced lactate accumulation in dogs.

Hypothermia protects tissue function in ischemia. This study determined if selective brain cooling inhibits cerebral cortical lactate accumulation and thus accounts for imporved neurologic outcome after complete cerebral ischemia in dogs. The brain was selectively cooled (hippocampal temperature 33 degrees C) by nasal lavage with water at 5 degrees C. Control dogs received nasal lavage with water at 39 degrees C. Mean +/- SEM rectal temperature in both groups was 39 +/- 1 degree C prior to ischemia. Selective brain cooling before and during 10 minutes of cardiac arrest was associated with significantly improved neurologic function and 100% survival, whereas normothermic cardiac arrest produced marked neurologic dysfunction and 100% mortality. Cerebral cortical lactate accumulation was measured in a complementary series of dogs exposed to the same two treatments but with the addition of six cerebral cortical brain biopsies taken before, during, and immediately after cardiac arrest. Brain and rectal temperatures of dogs in the brain biopsy protocol were similar to those of dogs in the recovery protocol. There was no difference detected in cerebral lactate accumulation during ischemia between brain-cooled and control dogs. Thus, reduction in cortical brain lactate during ischemia cannot account for the postischemic functional protection afforded by preischemic selective brain cooling.

Insulin administration protects neurologic function in cerebral ischemia in rats.

Hyperglycemia exacerbates neurologic damage in clinical and experimental central nervous system ischemia. The purpose of our study was to determine if insulin administration before significantly alters neurologic deficit and survival after ischemia using a newly developed rat cerebral ischemia model. One hour before the onset of ischemia, 40 200-300-g Sprague-Dawley rats received intraperitoneal injections of either 1 ml normal saline or 0.4, 0.5, or 0.6 units regular insulin in 1 ml normal saline. Rats were then intubated and ventilated with 1-1.5% halothane. The aortic arch was exposed, and snares were placed on the innominate, left carotid, and left subclavian arteries. A 20-minute occlusion was begun, and anesthesia was discontinued. Baseline plasma glucose concentration was similar (p = 0.48, Students t test) in both groups, but it subsequently was significantly lower in the 0.4 unit insulin-treated group up to 4 hours after occlusion (p less than or equal to 0.0035, Students t test). Neurologic deficit was scored on a 50-point scale (0 = normal, 50 = severe deficit) 1, 4, 18, and 24 hours after occlusion. In the 0.4 unit insulin-treated group the neurologic deficit score was significantly lower than in the saline-treated group 1, 4, 18, and 24 hours after occlusion (p less than or equal to 0.005, Students t test). Survival was significantly higher (p = 0.001) in the 0.4 unit insulin-treated (1.7 unit/kg dose) group than in the saline-treated group. No rats died when preocclusion plasma glucose concentration was between 65 and 175 mg/dl.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of the aminosteroid U74006F after cardiopulmonary arrest in dogs.

The oxygen free radical-induced lipid peroxidative reactions that occur during resuscitation from normothermic cardiac arrest may contribute to the degree of neurologic dysfunction sustained. A blinded, randomized experimental trial was performed to determine whether U74006F, a potent inhibitor of lipid peroxidation, reduces morbidity and 24-hour mortality after 10 minutes of normothermic cardiopulmonary arrest; ventricular fibrillation was induced by electrical stimulation in 24 open-chest, halothane-anesthetized dogs, and circulation was reestablished by direct cardiac compressions, administration of a standardized drug regime, and internal countershocks. When spontaneous circulation was restored, a bolus injection of 1.5 mg/kg U74006F (n = 12) or 25 mM citrate vehicle (n = 12) was infused intravenously in 15 minutes and an infusion was continued at 0.125 mg/kg/hr for the next 12 hours. In the drug-treated group, plasma U74006F concentration averaged 0.13 microgram/ml between 3 and 12 hours after cardiac arrest. By 24 hours after arrest, 10 of 12 (83%) vehicle-treated dogs had died but only four of 12 (33%) U74006F-treated dogs had died (p = 0.017). U74006F-treated dogs survived significantly longer (mean +/- SEM 22 +/- 1 hr) than vehicle-treated dogs (18 +/- 1 hr), with significantly better neurologic function 1, 2, and 24 hours after arrest. Plasma fatty acid hydroperoxide concentrations 12 hours after arrest were 88 +/- 81 pmol/ml in U74006F-treated and 241 +/- 49 pmol/ml in vehicle-treated dogs (p less than 0.05). Vitamin E concentrations were significantly higher in the plasma of U74006F-treated dogs 2, 3, and 6 hours after arrest compared with vehicle-treated dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Sympathetic Control of Cerebral Blood Flow in Dogs

The effect of sympathetic stimulation on cerebral blood flow was investigated in dogs anesthetized with chloralose. A preparation has been developed for the moment-to-moment measurement of cerebral venous outflow with an electromagnetic flow transducer. The brains arterial supply was left undisturbed. The sympathetic innervation of the cerebral vessels was stimulated at the stellate ganglion (3−9 v, 3 msec, and 1, 3, 6, 10, and 15 Hz for 60 or 90 seconds). Stimulation at 15 Hz resulted in an average decrease in cerebral blood flow of 79.7%. During stimulation the arterial oxygen tension decreased from 93.2 to 84.9 mm Hg, the arterial carbon dioxide tension increased from 32.9 to 34.6 mm Hg, and arterial pH fell from 7.392 to 7.378. These changes in blood gas variables all opposed the observed vasoconstriction. Interactions between intracranial pressure and sympathetic cerebral vasoconstriction were evaluated by measuring cerebrospinal fluid pressure and cerebral venous outflow pressure. Stimulation of the left sympathetic stellate ganglion produced a 64% decrease in cerebral blood flow and an 8 mm Hg increase in intracranial pressure. Infusion of saline into the cisterna magna, raising intracranial pressure to 47 mm Hg, produced a 3% decrease in cerebral blood flow. Opening the cerebrospinal fluid space and thus fixing intracranial pressure at zero (atmospheric pressure) did not alter the cerebral blood flow response to sympathetic stimulation. It was concluded that stimulation of the sympathetic stellate ganglion resulted in cerebral vasoconstriction which was independent of changes in arterial PCO2, Po2, and pH and was also independent of changes in cerebrospinal fluid pressure.

Pleiotropic Phenotype of a Genomic Knock-In of an RGS-Insensitive G184S Gnai2 Allele

ABSTRACT Signal transduction via guanine nucleotide binding proteins (G proteins) is involved in cardiovascular, neural, endocrine, and immune cell function. Regulators of G protein signaling (RGS proteins) speed the turn-off of G protein signals and inhibit signal transduction, but the in vivo roles of RGS proteins remain poorly defined. To overcome the redundancy of RGS functions and reveal the total contribution of RGS regulation at the Gαi2 subunit, we prepared a genomic knock-in of the RGS-insensitive G184S Gnai2 allele. The Gαi2G184S knock-in mice show a dramatic and complex phenotype affecting multiple organ systems (heart, myeloid, skeletal, and central nervous system). Both homozygotes and heterozygotes demonstrate reduced viability and decreased body weight. Other phenotypes include shortened long bones, a markedly enlarged spleen, elevated neutrophil counts, an enlarged heart, and behavioral hyperactivity. Heterozygous Gαi2+/G184S mice show some but not all of these abnormalities. Thus, loss of RGS actions at Gαi2 produces a dramatic and pleiotropic phenotype which is more evident than the phenotype seen for individual RGS protein knockouts.

Paraplegia in the rat induced by aortic cross-clamping: Model characterization and glucose exacerbation of neurologic deficit

Spinal cord damage caused by ischemia is a serious, underappreciated, and relatively refractory problem in clinical practice. Research is hampered by a lack of experimental models that appropriately mimic clinical situations. A new model of paraplegia in the rat is presented and evaluated by standard neurologic deficit scoring (1, 4, 18, and 24 hours after occlusion) and by computerized activity monitoring (1 and 18 hours after occlusion). Rats underwent temporary occlusion of the thoracic aorta for 10, 15, or 20 minutes. Experimental groups received glucose (2 gm/kg) and demonstrated a significant elevation in blood glucose (p = 0.001) and were significantly more neurologically impaired at all four time periods (p less than or equal to 0.005) than the ischemic control group, which received equivalent volumes of normal saline solution. Significant differences in neurologic deficit were noted with direct clinical examination and computerized activity monitoring. With the use of the latter system, statistical differences were detected in total distance traveled and number of vertical movements. We conclude the following: (1) Paraplegia is reliably and reproducibly achieved in this rat model; (2) because of the rats more extensive behavioral repertoire when compared with other models of spinal ischemia (e.g., rabbit), more end points can be monitored and more subtle behavioral deficits discerned; (3) computerized activity monitoring can distinguish varying degrees of neurologic deficit and correlates with clinical neurologic deficit scoring; and (4) glucose exacerbates paraplegia in this model.

Murine prolylcarboxypeptidase depletion induces vascular dysfunction with hypertension and faster arterial thrombosis

Prolylcarboxypeptidase (PRCP) activates prekallikrein to plasma kallikrein, leading to bradykinin liberation, and degrades angiotensin II. We now identify PRCP as a regulator of blood vessel homeostasis. β-Galactosidase staining in PRCP(gt/gt) mice reveals expression in kidney and vasculature. Invasive telemetric monitorings show that PRCP(gt/gt) mice have significantly elevated blood pressure. PRCP(gt/gt) mice demonstrate shorter carotid artery occlusion times in 2 models, and their plasmas have increased thrombin generation times. Pharmacologic inhibition of PRCP with Z-Pro-Prolinal or plasma kallikrein with soybean trypsin inhibitor, Pro-Phe-Arg-chloromethylketone or PKSI 527 also shortens carotid artery occlusion times. Aortic and renal tissues have uncoupled eNOS and increased reactive oxygen species (ROS) in PRCP(gt/gt) mice as detected by dihydroethidium or Amplex Red fluorescence or lucigenin luminescence. The importance of ROS is evidenced by the fact that treatment of PRCP(gt/gt) mice with antioxidants (mitoTEMPO, apocynin, Tempol) abrogates the hypertensive, prothrombotic phenotype. Mechanistically, our studies reveal that PRCP(gt/gt) aortas express reduced levels of Kruppel-like factors 2 and 4, thrombomodulin, and eNOS mRNA, suggesting endothelial cell dysfunction. Further, PRCP siRNA treatment of endothelial cells shows increased ROS and uncoupled eNOS and decreased protein C activation because of thrombomodulin inactivation. Collectively, our studies identify PRCP as a novel regulator of vascular ROS and homeostasis.

Avian febrile response.

The febrile response of the pigeon (Columba livia) was characterized for comparison with our present day understnading of mammalian fever. 2. When injected with live Pasteurella multocida the birds became febrile and died. 3. Varying doses of dead bacteria produced a complex dose‐dependent febrile response. 4. Antipyretics effectively attenuated the febrile response to dead bacteria. 5. The similarities of reptilian, avian and mammalian fever suggest a common origin and perhaps a similar adaptive role of fever in increasing host survival during bacterial infection.