Craig S. DeBruyn

A new major histocompatibility complex class I b gene expressed in the mouse blastocyst and placenta

Abstract Because of the role major histocompatibility complex (MHC) class I b molecules may play during mouse embryonic development, we thought it would be interesting to search for additional MHC class I b molecules that might be expressed in preimplantation embryos, and in particular in the trophoblastic lineage. We therefore screened a mouse preimplantation blastocyst cDNA library for MHC class I sequences. This search led to the identification and characterization of a new MHC class I b gene, blastocyst MHC. Sequences identical to the exons and 3′ untranslated region of this gene have been found in many laboratory mouse strains, as well as in the related mouse species Mus spreciligus. The presence of this gene in mouse strains of different MHC class I haplotypes argues that blastocyst MHC is a unique, newly-described gene rather than a new allele of a previously described mouse MHC class I gene. Blastocyst MHC has the structure of an MHC class I b gene, with the six exons characteristic of T-region genes. It is linked to H2-D. The amino acid sequence encoded by this gene maintains all the features of a functional antigen-presentation domain. The blastocyst MHC gene, like the human class I b gene HLA-G, is expressed at the blastocyst stage and in the placenta, and may be the mouse analog for HLA-G.

Magnesium sulfate decreases maternal blood pressure but not uterine blood flow during epidural anesthesia in gravid ewes.

The purpose of this study was to determine whether administration of magnesium sulfate decreased maternal blood pressure during epidural anesthesia in gravid ewes. Twenty-two experiments were performed in 11 chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included: 1) T = 0: magnesium sulfate 4 g intravenously over 5 min followed by an infusion of magnesium sulfate at 4 g/h, or normal saline iv followed by an infusion of normal saline alone; 2) T = 135 min: 500 ml normal saline intravenously over 12 min; and 3) T = 150 min: epidural administration of 2% lidocaine. The initial bolus of magnesium sulfate slightly decreased maternal mean arterial pressure (MAP) but increased uterine artery blood flow (UBF). The increase in UBF was accompanied by an increase in fetal PaO2 at 145 min in the magnesium sulfate group but not in the control group. At 165 min (i.e., 15 min after the epidural injection of lidocaine), epidural lidocaine resulted in a median sensory level of T-10 in the magnesium sulfate group and T-11 in the control group. During epidural anesthesia, maternal MAP was lower (P = 0.001) in the magnesium sulfate group than in the control group. At 165 min, maternal MAP was 18 +/- 3% below baseline (P = 0.0001) in the magnesium sulfate group but did not differ significantly from baseline in the control group. Maternal cardiac output and UBF did not differ from baseline after epidural injection of lidocaine in either group.(ABSTRACT TRUNCATED AT 250 WORDS)

Ephedrine remains the vasopressor of choice for treatment of hypotension during ritodrine infusion and epidural anesthesia.

Background:Historically, ephedrine has been the vasopressor of choice for treatment of most cases of hypotension in obstetric patients. However, the choice of vasopressor in the parturient receiving a β-adrenergic agent for tocolysis has not been evaluated extensively. The current study evaluated whether ephedrine or phenylephrine better restores uterine blood flow and fetal oxygenation during ritodrine infusion and epidural anesthesia-induced hypotension in gravid ewes. Methods:Fourteen chronically instrumented gravid ewes between 0.8 and 0.9 timed gestational age were used. On separate days, each animal underwent the experimental protocol with one of three agents: ephedrine, phenylephrine, and normal saline-control. The experimental protocol was as follows: (1) at time zero, intravenous infusion of ritodrine was begun; (2) at 120 min, 2% lidocaine was given epidurally to achieve a sensory level of at least T6; and (3) at 135 min, an intravenous bolus of either ephedrine, phenylephrine, or normal saline-control was given, followed by a continuous intravenous infusion of the same agent for 30 min. In the ephedrine and phenylephrine experiments, the rate of infusion was adjusted to maintain maternal mean arterial pressure close to baseline. Results:Ritodrine infusion alone significantly increased maternal heart rate and cardiac output in all three groups. Epidural anesthesia during ritodrine infusion significantly decreased maternal mean arterial pressure, heart rate, cardiac output, uterine blood flow, and fetal arterial oxygen tension for each of the three groups. Both ephedrine and phenylephrine restored maternal mean arterial pressure to baseline, as designed. Ephedrine significantly increased uterine blood flow and fetal arterial oxygen tension when compared with normal saline-control, but phenylephrine did not. Phenylephrine significantly increased uterine vascular resistance when compared with normal saline-control, but ephedrine did not. Conclusions:Although ephedrine and phenylephrine provided similar restoration of maternal mean arterial pressure, ephedrine was superior to phenylephrine in restoring uterine blood flow during ritodrine infusion and epidural anesthesia-induced hypotension in gravid ewes. Also, ephedrine, but not phenylephrine, significantly improved fetal oxygenation, when compared to normal saline-control.

Which Vasopressor Should Be Used To Treat Hypotension during Magnesium Sulfate Infusion and Epidural Anesthesia

Ephedrine restores and/or protects uterine blood flow and fetal well-being in laboratory animals. In contrast, alpha 1-adrenergic agonists worsen uterine blood flow and fetal condition. We previously demonstrated that magnesium sulfate (MgSO4) attenuates the detrimental effects of phenylephrine on uterine vascular resistance in gravid ewes. Therefore, we performed this study to determine whether ephedrine or phenylephrine better restores and protects uterine blood flow and fetal oxygenation during epidural anesthesia-induced hypotension in hypermagnesemic gravid ewes. Twelve chronically instrumented gravid ewes were each used for three experiments: 1) ephedrine, 2) phenylephrine, and 3) normal saline (NS)-control. For each experiment the protocol was as follows: 1) at time zero, intravenous infusion of MgSO4 was begun; 2) at 150 min a thoracic level of epidural anesthesia was achieved with 2% lidocaine; and 3) at 165 min, an intravenous infusion of ephedrine, phenylephrine, or NS was begun and continued through 195 min. Epidural anesthesia uniformly decreased maternal mean arterial blood pressure (MAP), heart rate, cardiac output, uterine blood flow, and fetal PO2 in each of the three groups. Both ephedrine and phenylephrine restored maternal MAP to baseline, as expected from the experimental design. Ephedrine significantly increased cardiac output and uterine blood flow when compared with NS-control, but phenylephrine did not. Phenylephrine significantly increased uterine vascular resistance when compared with NS-control, but ephedrine did not. As a result, fetal pH and PO2 were significantly greater during ephedrine infusion than during infusion of NS-control. Fetal pH was stable during ephedrine infusion, but it continued to decrease during phenylephrine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Epidural Anesthesia Worsens Uterine Blood Flow and Fetal Oxygenation during Hemorrhage in Gravid Ewes

Recent studies suggest that epidural anesthesia initiated before hemorrhage may improve survival and acid-base status in laboratory animals. However, studies of hemorrhagic shock in nonpregnant animals may not be applicable to less severe hemorrhage in pregnant animals. The purpose of this study was to determine whether epidural anesthesia alters maternal and fetal hemodynamic and acid-base responses to hemorrhage in gravid ewes. Twenty-four experiments were performed in twelve chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included: 1) T = 0 min: normal saline 500 ml intravenously; 2) T = 15 min: epidural administration of 0.5% bupivacaine (epidural group) or normal saline (control group); 3) T = 30 min: epidural administration of additional 0.5% bupivacaine (epidural group only) if the sensory level of anesthesia was below T10; 4) T = 45 min: maternal hemorrhage 20 ml/kg over 55 min; and 5) T = 110 min: transfusion of collected maternal blood over 55 min. At 45 min (i.e., 30 min after the epidural injection of bupivacaine), epidural bupivacaine resulted in a median sensory level of T9 in the epidural group. At that time, maternal mean arterial pressure was less (P less than 0.05) in the epidural group than in the control group (14 +/- 2% below baseline versus 4 +/- 1% above baseline, respectively). Maternal mean arterial pressure, heart rate, cardiac output, and uterine blood flow, and fetal PO2 and pH all were significantly less during hemorrhage (P less than 0.05) in the epidural group than in the control group.(ABSTRACT TRUNCATED AT 250 WORDS)

Does calcium chloride help restore maternal blood pressure and uterine blood flow during hemorrhagic hypotension in hypermagnesemic gravid ewes

Magnesium sulfate worsens maternal hypotension and fetal oxygenation during hemorrhage in gravid ewes. The purpose of this study was to determine whether calcium chloride administration is a useful adjunct to blood transfusion during hemorrhagic hypotension in hypermagnesemic gravid ewes. Sixteen experiments were performed in eight chronically instrumented animals between 0.8 and 0.9 of timed gestation. The experimental sequence included (a) T = 0: magnesium sulfate 4 g IV; (b) T = 5: infusion of magnesium sulfate 4 g/h IV; (c) T = 90: maternal hemorrhage 20 mL/kg over 55 min; (d) T = 147: calcium chloride 10 mg/kg or normal saline (NS-control) 0.1 mL/kg IV; (e) T = 160: transfusion of collected maternal blood over 55 min. Magnesium sulfate alone slightly decreased maternal mean arterial pressure (P = 0.002) and increased uterine blood flow (P = 0.0001) in both groups before hemorrhage. During hemorrhage, maternal mean arterial pressure, cardiac output, and uterine blood flow, and fetal PO2 and pH all decreased sharply (P = 0.0001). Cardiac output increased (P = 0.0005) modestly just after the intravenous bolus of calcium chloride. Maternal mean arterial pressure was significantly higher (P = 0.03) during transfusion in the calcium chloride group than in the NS-control group, but only after mean arterial pressure was near baseline measurements. Maternal uterine blood flow and fetal PO2 and pH responses over time were similar in the two groups. We conclude that intravenous administration of calcium chloride (10 mg/kg) transiently increased cardiac output during hemorrhagic hypotension and slightly increased mean arterial pressure during transfusion in hypermagnesemic gravid ewes.(ABSTRACT TRUNCATED AT 250 WORDS)