Granzyme A Produced by γ9δ2 T Cells Activates ER Stress Responses and ATP Production, and Protects Against Intracellular Mycobacterial Replication Independent of Enzymatic Activity

Mycobacterium tuberculosis (Mtb), the pathological agent that causes tuberculosis (TB) is the number one infectious killer worldwide with one fourth of the world's population currently infected. Data indicate that γ₉δ₂ T cells secrete Granzyme A (GzmA) in the extracellular space triggering the infected monocyte to inhibit growth of intracellular mycobacteria. Accordingly, deletion of GZMA from γ₉δ₂ T cells reverses their inhibitory capacity. Through mechanistic studies, GzmA's action was investigated in monocytes from human PBMCs. The use of recombinant human GzmA expressed in a mammalian system induced inhibition of intracellular mycobacteria to the same degree as previous human native protein findings. Our data indicate that: 1) GzmA is internalized within mycobacteria-infected cells, suggesting that GzmA uptake could prevent infection and 2) that the active site is not required to inhibit intracellular replication. Global proteomic analysis demonstrated that the ER stress response and ATP producing proteins were upregulated after GzmA treatment, and these proteins abundancies were confirmed by examining their expression in an independent set of patient samples. Our data suggest that immunotherapeutic host interventions of these pathways may contribute to better control of the current TB epidemic.

Mechanistic investigations of Granzyme A-mediated γ9δ2 T cell TB protective effects

One fourth of the world population is infected with Mycobacterium tuberculosis (Mtb). Currently, BCG strains are the only vaccines available to protect against tuberculosis (TB). Our lab has identified γδ T cells that secrete Granzyme A (GzmA) with TB protective effects. GzmA when released by TB-specific γδ T cells has been shown to inhibit the intracellular replication of the pathogen. To elucidate the mechanism(s) involved in this inhibition, the lab has purified human GzmA. The effects of this highly purified GzmA on mycobacterial replication inside human macrophages are being investigated using systems biology. A 2D-DIGE proteomic approach of PBMC-adherent cells has been performed to identify putative pathways involved in the control of mycobacterial replication. Our preliminary analysis of two PPD+ volunteers indicates that ER-stress responses (HSPA5, HSP90B1, P4HB, PDIA3) and purinergic channel receptor activation (ATP5B/C1/D/H/O) may be important for GzmA-mediated intracellular mycobacterial inhibition. Verification of these results is being performed to confirm the overall mechanism, and to exclude unrelated signals. Elucidation of the detailed pathways involved in pathogen clearance could lead to the development of novel chemotherapeutic and/or immunotherapeutic approaches for control of Mtb infection.

On differences in the equation-of-state for a selection of seven representative mammalian tissue analogue materials

Tissue analogues employed for ballistic purposes are often monolithic in nature, e.g. ballistic gelatin and soap, etc. However, such constructs are not representative of real-world biological systems. Further, ethical considerations limit the ability to test with real-world tissues. This means that availability and understanding of accurate tissue simulants is of key importance. Here, the shock response of a wide range of ballistic simulants (ranging from dermal (protective/bulk) through to skeletal simulant materials) determined via plate-impact experiments are discussed, with a particular focus on the classification of the behaviour of differing simulants into groups that exhibit a similar response under high strain-rate loading. Resultant Hugoniot equation-of-state data (U_s-u_p; P-v) provides appropriate feedstock materials data for future hydrocode simulations of ballistic impact events.

WEDGE: an anticoagulant thrombin mutant produced by autoactivation

BACKGROUND

The production of therapeutically relevant proteases typically involves activation of a zymogen precursor by external enzymes, which may raise regulatory issues about availability and purity. Recent studies of thrombin precursors have shown how to engineer constructs that spontaneously convert to the mature protease by autoactivation, without the need for external enzymes.

OBJECTIVES

Autoactivation is an innovative strategy that promises to simplify the production of proteases of therapeutic relevance, but has not been tested in practical applications. The aim of this study was to provide a direct test of this strategy.

METHODS

An autoactivating version of the thrombin mutant W215A/E217A (WE), which is currently in preclinical development as an anticoagulant, was engineered.

RESULTS AND CONCLUSIONS

The autoactivating version of WE can be produced in large quantities, like WE made in BHK cells or Escherichia coli, and retains all significant functional properties in vitro and in vivo. The results serve as proof of principle that autoactivation is an innovative and effective strategy for the production of trypsin-like proteases of therapeutic relevance.

Evaluation of aminohydantoins as a novel class of antimalarial agents

Given the threat of drug resistance, there is an acute need for new classes of antimalarial agents that act via a unique mechanism of action relative to currently used drugs. We have identified a set of druglike compounds within the Tres Cantos Anti-Malarial Set (TCAMS) which likely act via inhibition of a Plasmodium aspartic protease. Structure-activity relationship analysis and optimization of these aminohydantoins demonstrate that these compounds are potent nanomolar inhibitors of the Plasmodium aspartic proteases PM-II and PM-IV and likely one or more other Plasmodium aspartic proteases. Incorporation of a bulky group, such as a cyclohexyl group, on the aminohydantion N-3 position gives enhanced antimalarial potency while reducing inhibition of human aspartic proteases such as BACE. We have identified compound 8p (CWHM-117) as a promising lead for optimization as an antimalarial drug with a low molecular weight, modest lipophilicity, oral bioavailability, and in vivo antimalarial activity in mice.

On the effects of lateral gauge misalignment in shocked targets

Plate-impact experiments have been used to interrogate the influence of gauge alignment on the shock response of wire-element lateral manganin stress gauges in PMMA and aluminium targets. Embedded gauges were progressively rotated relative to the target impact face. Peak stress and lateral gauge rise-times were found be proportional (negatively and positively, respectively) to the resolved angle of the embedded gauge element. However, lateral stress gradients behind the shock were found to be relatively insensitive to gauge alignment. In addition, investigation of the effects of release arrival showed no connection to either peak stress or behaviour behind the shock.

Crystal structure of fatty acid amide hydrolase bound to the carbamate inhibitor URB597: discovery of a deacylating water molecule and insight into enzyme inactivation

The endocannabinoid system regulates a wide range of physiological processes including pain, inflammation, and cognitive/emotional states. URB597 is one of the best characterized covalent inhibitors of the endocannabinoid-degrading enzyme fatty acid amide hydrolase (FAAH). Here, we report the structure of the FAAH-URB597 complex at 2.3 A resolution. The structure provides insights into mechanistic details of enzyme inactivation and experimental evidence of a previously uncharacterized active site water molecule that likely is involved in substrate deacylation. This water molecule is part of an extensive hydrogen-bonding network and is coordinated indirectly to residues lining the cytosolic port of the enzyme. In order to corroborate our hypothesis concerning the role of this water molecule in FAAH's catalytic mechanism, we determined the structure of FAAH conjugated to a urea-based inhibitor, PF-3845, to a higher resolution (2.4 A) than previously reported. The higher-resolution structure confirms the presence of the water molecule in a virtually identical location in the active site. Examination of the structures of serine hydrolases that are non-homologous to FAAH, such as elastase, trypsin, or chymotrypsin, shows a similarly positioned hydrolytic water molecule and suggests a functional convergence between the amidase signature enzymes and serine proteases.

Preparative and analytical chromatography of pegylated myelopoietin using monolithic media

Monolithic media were compared with Q- and SP-Sepharose high performance chromatography for preparative purification and with Q- and SP-5PW chromatography for analysis of a pegylated form of myelopoietin (MPO), an engineered hematopoietic growth factor. The use of either monolithic or Sepharose based supports for preparative chromatography produced highly purified pegylated MPO with the monolithic media demonstrating peak resolution and repeatability at flow rates of 1 and 5 ml/min resulting in run times as much as five-fold shorter compared to Sepharose separations. The monolithic disks also resulted in 10-fold shorter run times for the analytical chromatography, however, their chromatographic profiles and peak symmetry were not as sharp compared to their Q-5PW and SP-5PW counterparts.

Behaviors Producing Photodispersal in Stentor coeruleus¶

The ciliate Stentor coeruleus exhibits photodispersal, that is, these cells swim away from light sources and collect in dimly lighted areas. We imaged and reconstructed the tracks of 48 Stentor to determine which swimming behaviors produced their photodispersal. We observed that their photodispersal is not due to a change in their swimming speed but rather to a change in the frequency with which they reorient their swimming direction. Therefore, their photodispersal must be due to either (1) a gradual reorientation of the organism's swimming direction determined by the direction of the light beam (phototaxis) or (2) multiple randomly directed reorientations in swimming direction that occur less frequently when the cell is swimming away from the light source (biased random walk). Sixteen (19%) of the 83 observed forward swimming tracks lasting three or more seconds exhibited a gradual bending away from the light source consistent with a phototaxis. However, most tracks were interrupted repeatedly by abrupt reorientations resulting from ciliary reversals and "smooth turns" that caused cells to reorient through 5.4 times as many degrees as were needed to direct them away from the light source. When cells were swimming away from the light source, their probability of reorienting was reduced and photodispersal resulted.

Mammalian cell production and purification of progenipoietin, a dual-agonist chimaeric haematopoietic growth factor

One member of the progenipoietin (ProGP) family of engineered proteins, ProGP-2, is a chimaeric dual cytokine receptor agonist, expressed in mammalian cells, that stimulates both human fetal liver tyrosine kinase-3 (Flt3) and the granulocyte-colony-stimulating-factor (G-CSF) receptor. The production of ProGP-2 on a small and large scale using either anti-(Flt3 ligand) antibody-affinity chromatography, or a combination of (NH4)2SO4 fractionation, anion-exchange chromatography, hydrophobic-interaction chromatography and preparative reverse-phase chromatography is described. ProGP-2 was produced in hollow-fibre reactors containing stably transfected NS0 cells. The productivity of ProGP-2 was initially high, but was found to decrease 3-4-fold over time. When the yield of ProGP-2 decreased, the combination of three conventional chromatography steps was required to meet protein purity similar to that achieved by the anti-(Flt3 ligand) chromatography method. In addition, a protease activity was observed in conditioned media from the hollow-fibre reactors that resulted in increased degradation of ProGP-2 that was removed by hydrophobic-interaction chromatography at higher pH. Together the results demonstrated a method for production and purification of ProGP-2 for additional studies on its haematopoietic activity.

Partial cloning of putative G-proteins modulating mechanotransduction in the ciliate stentor

Signal transduction systems known to utilize G-proteins in higher eukaryotes undoubtedly evolved prior to the development of metazoa. Pharmacological evidence indicates that the ciliates Paramecium, Stentor, and Tetrahymena all utilize signaling systems similar to those found in mammals. However, there has been relatively little direct evidence for the existence of G-proteins in ciliates. Since highly conserved heterotrimeric G-proteins form the basis of receptor-coupled signal transduction systems in a wide variety of metazoa, it is of interest to know if these important signaling molecules were early to evolve and are present and functionally important in a wide variety of unicellular organisms. We have previously shown that mechanotransduction in Stentor is modulated by opiates in a manner that may involve pertussis toxin-sensitive G-proteins. Here we utilize drugs known to interact with G-proteins to further test for the involvement of these important signaling molecules in Stentor mechanotransduction. We present behavioral and electrophysiological data demonstrating that putative G-proteins in Stentor decrease mechanical sensitivity by modulating the mechanotransduction process. In addition, we report the partial cloning of 4 G-protein alpha-subunits from Stentor. We confirm that these clones are of Stentor origin and are transcribed. Furthermore, we employ antisense oligodeoxynucleotide-mediated knockout to demonstrate that these ciliate G-proteins exert a modulatory influence on Stentor behavior, and that a G1/G0-like clone mediates the inhibitory action of beta-endorphin on mechanotransduction.

The effects of maternal indomethacin therapy on human fetal branch pulmonary arterial vascular impedance

OBJECTIVE

To examine whether maternal indomethacin therapy affects human fetal pulmonary arterial vascular impedance without constriction of the ductus arteriosus and to determine the changes in the pulmonary arterial vascular impedance in the presence of ductal constriction.

STUDY DESIGN

In this cross-sectional study, 52 normal fetuses without maternal medication (control group), 33 fetuses without ductal constriction (Study group I) and 11 fetuses with ductal constriction (Study group II) during maternal indomethacin therapy between 24 and 34 weeks of gestation were examined by Doppler echo-cardiography. Blood velocity waveforms across the proximal right or left pulmonary artery were obtained and the pulsatility index (PI) of the proximal pulmonary arteries was calculated.

RESULTS

In the control group, the proximal pulmonary artery PI was higher (p < 0.0001) at 24-25 weeks (n = 7) (3.73 +/- 0.33; mean +/- SD) than at 33-34 week of gestation (n = 11) (2.98 +/- 0.27). The PI was constantly greater (p < 0.005) in Study group I than in the control group. However, in this group the mean average weekly decrease in the PI of the proximal pulmonary arteries was similar to that in the control group. After 26 weeks of gestation, the PI values in Study group II were significantly higher than in the control group (27 weeks: 4.12 vs. 3.34 (p < 0.005); 30 weeks: 4.48 vs. 3.14 (p < 0.0001); 34 weeks: 4.96 vs. 3.00 (p < 0.0001), respectively).

CONCLUSIONS

Human fetal pulmonary arterial vascular impedance is increased by maternal indomethacin therapy even without ductal constriction. In the presence of ductal constriction, the magnitude of the increase in the vascular impedance is related to the gestational age.

Regional hemodynamic effects of dopamine in the sick preterm neonate

OBJECTIVE

To study the effects of dopamine on renal, mesenteric, and cerebral blood flow in sick preterm neonates.

STUDY DESIGN

The pulsatility index was used to assess the dopamine-induced changes in renal, mesenteric, and cerebral blood flow by means of color Doppler ultrasonography in 23 nonhypotensive preterm neonates (birth weight: 981 +/- 314 g; postnatal age: <2 days). Dopamine was given at a dose of 6.1 +/- 3.0 microgram/kg per minute to combat oliguria, impaired peripheral perfusion, or both. Blood flow velocity measurements were made before and during dopamine administration, with each patient serving as his or her own control subject.

RESULTS

Dopamine significantly increased blood pressure and urine output. Dopamine decreased the pulsatility index in the renal artery (2.98 +/- 1.18 vs 1.68 +/- 0.45; P <.05) while the pulsatility index in the superior mesenteric and medial cerebral artery was not affected. Thus renal blood flow increased while mesenteric and cerebral blood flow remained unchanged during dopamine treatment. The increase in renal blood flow was independent of the blood pressure changes.

CONCLUSIONS

These findings suggest a functionally mature renal, but not mesenteric, vasodilatory dopaminergic response in the preterm neonate. The observations also indicate the lack of an effect of low- to medium-dose dopamine on cerebral hemodynamics in the nonhypotensive preterm neonate.

Reactivity of the human fetal pulmonary circulation to maternal hyperoxygenation increases during the second half of pregnancy: a randomized study

BACKGROUND

The aims of the present study were to determine whether maternal hyperoxygenation affects human fetal pulmonary circulation and whether there is a gestational age-related response in the fetal pulmonary circulation to maternal hyperoxygenation during the second half of gestation.

METHODS AND RESULTS

Twenty women between 20 and 26 weeks of gestation and 20 women between 31 and 36 weeks of gestation with normal singleton pregnancies were randomized to receive either 60% humidified oxygen or medical compressed air (room air) by a face mask. Fetal aortic and pulmonary valve; ductus arteriosus (DA); and right (RPA), left (LPA), and distal (DPA) pulmonary artery blood velocity waveforms were obtained by Doppler ultrasound before, during, and after maternal administration of either 60% oxygen or room air. Left and right ventricular cardiac outputs, DA volume blood flow, and RPA and LPA volume blood flows (Qp) were calculated. Foramen ovale volume blood flow (left ventricular cardiac output-Qp) was estimated. Pulsatility index (PI) values of DA, RPA, LPA, and DPA were calculated. Maternal hyperoxygenation did not change any of the measured fetal parameters between 20 and 26 weeks, whereas between 31 and 36 weeks, the PI values of RPA, LPA, and DPA decreased (P<.0001) and the PI of DA increased (P<.0001). In addition, Qp increased (P<.001), and DA volume blood flow (P<.01) and foramen ovale volume blood flow (P<.03) decreased. Left and right ventricular cardiac outputs were unchanged. All changes returned to baseline after maternal hyperoxygenation was discontinued.

CONCLUSIONS

Reactivity of the human fetal pulmonary circulation to maternal hyperoxygenation increases with advancing gestation; this suggests that fetal pulmonary circulation is under acquired vasoconstriction at least after 31 to 36 weeks of gestation.

Human fetal right ventricular ejection force under abnormal loading conditions during the second half of pregnancy

Our objective was to determine whether abnormal loading conditions can modify human fetal right ventricular ejection force during the second half of pregnancy. By Doppler echocardiography, we studied 73 normal fetuses between 19 and 41 weeks of gestation, 27 fetuses with hypoplastic left heart syndrome (chronic volume overload) between 18 and 38 weeks of gestation, 14 fetuses with mild to moderate constriction of the ductus arteriosus (pulsatility index (PI) between 1.0 and 1.9) and seven fetuses with severe constriction (PI < 1.0) or occlusion of the ductus arteriosus (relatively acute pressure overload) between 28 and 34 weeks of gestation. In the normal and ductal constriction/occlusion groups, blood velocity waveforms were recorded at the level of the aortic and pulmonary valves, and in the group with hypoplastic left heart syndrome at the level of the pulmonary valve. The ventricular ejection forces were calculated. In the normal group, right (RVEF; r = 0.91, p < 0.0001) and left (LVEF; r = 0.86, p < 0.0001) ventricular ejection forces increased and were equal during the second half of gestation. In the group with hypoplastic left heart syndrome the RVEF increased (r = 0.76, p < 0.0001) with advancing gestation. The RVEF (p < 0.0005) and its average weekly increase (p < 0.0001) were greater in the hypoplastic left heart syndrome group than in the normal group. In the group with mild to moderate ductal constriction, both ventricular ejection forces were similar to those of the normal group. The RVEF (p < 0.003) and its average weekly increase (p < 0.03) were lower in the group with severe ductal constriction or occlusion than in the normal group. The LVEF did not differ from that of the normal group We conclude that chronic volume overload increases and relatively acute pressure overload decreases human fetal RVEF. The right ventricular performance is modified by abnormal loading conditions.

Role of the pulmonary circulation in the distribution of human fetal cardiac output during the second half of pregnancy

BACKGROUND

By using Doppler echocardiography, we determined the normal distribution of human fetal combined cardiac output (CCO) from the left and right ventricles. We also established weight-indexed pulmonary and systemic vascular resistances (Rpi and Rsi, respectively) and changes during the second half of pregnancy.

METHODS AND RESULTS

Blood flows at the aortic and pulmonary valve annuli (LVCO and RVCO, respectively), right and left pulmonary arteries (QP), and ductus arteriosus (QDA) were calculated in 63 normal fetuses. Foramen ovale blood flow (QFO = LVCO-QP) was estimated. From 20 to 30 weeks of gestation, the proportion of QP of the CCO increased (from 13% to 25%, P < .001), while the proportion of QFO decreased (from 34% to 18%, P < .001). After 30 weeks, the proportions of QP and QFO were unchanged. At 38 weeks, the proportion of RVCO (60%) was higher (P < .05) than that of LVCO (40%). The proportion of QDA did not change significantly. The correlation between RVCO calculated from blood flow through the pulmonary valve and from QDA and QP was good (r = .97, P < .0001). RPi (P < .001) decreased from 20 to 30 weeks of gestation. From 30 to 38 weeks, RPi increased (P < .0001). Rsi increased (P < .001) from 20 to 38 weeks. The ratio of RPi to RSi decreased (P < .01) from 20 to 30 weeks and later remained unchanged.

CONCLUSIONS

The human fetal pulmonary circulation has an important role in the distribution of cardiac output.

Fetal branch pulmonary arterial vascular impedance during the second half of pregnancy

OBJECTIVE

Our purpose was to establish normal physiologic parameters in the fetal proximal and distal branch pulmonary arterial vascular impedance during the second half of pregnancy and to analyze relationships between proximal and distal pulmonary arterial blood velocity waveforms.

STUDY DESIGN

In this cross-sectional study 100 uncomplicated singleton pregnancies were studied by pulsed color Doppler techniques between 18 and 41 weeks of gestation (median 30 weeks). Both right and left proximal (immediately after the bifurcation of the main pulmonary artery) and distal (beyond the first bifurcation of the branch pulmonary artery) pulmonary artery blood velocity waveforms were recorded and pulsatility index values were calculated. Peak systolic velocities and time-to-peak-velocity intervals were measured. Time-to-peak-velocity intervals were also analyzed at the level of aortic and pulmonary valves and at the ductus arteriosus. Right and left pulmonary artery diameters and right lung length were measured.

RESULTS

In both right and left proximal and distal pulmonary arteries pulsatility index values decreased (p < 0.0001) and the peak systolic velocities (p < 0.003) and time-to-peak-velocity intervals (p < 0.0001) increased during the second half of pregnancy. In the proximal pulmonary arteries the pulsatility index values decreased linearly until 34 to 35 weeks of gestation and in the distal pulmonary arteries until 31 weeks of gestation. Thereafter they remained unchanged. In pulmonary arteries time-to-peak-velocity intervals were shorter (p < 0.01) than at the pulmonary valve level. There were no significant differences between the right or left pulmonary arteries in the pulsatility index values, peak systolic velocities, time-to-peak-velocity intervals, or pulmonary artery diameters. In the proximal pulmonary arteries the pulsatility index values (p < 0.02) and peak systolic velocities (p < 0.0001) were higher and time-to-peak-velocity intervals (p < 0.0001) were longer than in the distal pulmonary arteries. There was a 2.5-fold increase in pulmonary artery diameters and right lung length.

CONCLUSIONS

Fetal branch pulmonary arterial vascular impedance decreases significantly during the second half of pregnancy. The linear decrease in vascular impedance during the second trimester and in the beginning of the third trimester may be related to the growth of the lung and the increase in the number of resistance vessels. During the latter part of the third trimester pulmonary vascular impedance does not decrease further.

Genetic studies reveal that myristoylCoA:protein N-myristoyltransferase is an essential enzyme in Candida albicans

MyristoylCoA:protein N-myristoyltransferase (Nmt) catalyses the co-translational, covalent attachment of myristate (C14:0) to the amino-terminal glycine residue of a number of eukaryotic proteins involved in cellular growth and signal transduction. The NMT1 gene is essential for vegetative growth of Saccharomyces cerevisiae. Studies were carried out to determine if Nmt is also essential for vegetative growth of the pathogenic fungus Candida albicans. A strain of C. albicans was constructed in which one copy of NMT was partially deleted and disrupted. A Gly-447-->Asp mutation was introduced into the second NMT allele. This mutation produced marked reductions in catalytic efficiency at 24 and 37 degrees C, as judged by in vitro kinetic studies of the wild-type and mutant enzymes which had been expressed in, and purified from, Escherichia coli. The growth characteristics of isogenic NMT/NMT, NMT/delta nmt, and nmt delta/nmtG447D C. albicans strains were assessed under a variety of conditions. Only the nmt delta/nmtG447D strain required myristate for growth. This was true at both 24 and 37 degrees C. Palmitate could not substitute for myristate. Incubation of nmt delta/nmtG447D cells at 37 degrees C in the absence of myristate resulted in cell death as observed by the inability to form colonies on media supplemented with 500 microM myristate. Studies in an immunosuppressed-mouse model of C. albicans infection revealed that the NMT/delta nmt strain produced 100% lethality within 7 d after intravenous administration while the isogenic nmt delta/nmtG447G strain produced no deaths even after 21 d. These observations establish that Nmt is essential for vegetative growth of C. albicans and suggest that inhibitors of this acyltransferase may be therapeutically useful fungicidal agents.

Doppler in non-immune hydrops fetalis

Fetal ultrasound studies were performed on 24 fetuses with non-immune hydrops to evaluate echocardiographic and cardiovascular Doppler parameters that may be useful in assessing hemodynamics and in predicting outcome. Of all cardiovascular parameters analyzed, only the presence of abnormal pulsations in the umbilical vein (p < 0.001) was found to be significantly different between the 11 survivors and 13 non-survivors. In a smaller subset of 12 fetuses, in whom inferior vena caval waveforms were recorded, survivors (n = 6) had a significantly lower percentage of retrograde flow in the inferior vena cava (p < 0.001) and higher inferior vena caval E/V velocity ratio (p < 0.001) than non-survivors (n = 6). Sixteen of the 24 cases examined had abnormal umbilical venous pulsations; 12 of the 16 (75%) died including all fetuses with hydrops due to twin-to-twin transfusion or congenital heart disease. When fetuses with pulsatile flow in the umbilical vein were compared with fetuses with normal umbilical venous flow, the following significant differences were found: lower right and left ventricular output velocities, larger inferior vena caval diameter, decreased shortening fractions of the right and left ventricles, and lower peak velocities at the aortic and pulmonary valves and in the ductus arteriosus.

Is tube-escape learning by protozoa associative learning?

The ciliate protozoa, Stentor and Paramecium, have been reported to escape from the bottom end of narrow capillary tubes into a larger volume of medium with increasing rapidity over the course of trials. This change in behavior has been considered an apparent example of associative learning. This decrease in escape time is not due to a change in the protozoa's environment, their swimming speed, frequency of ciliary reversals, or the proportion of time spent forward or backward swimming. Instead, most of the decrease results from a decrease in the proportion of time spent in upward swimming. However, a similar decrease in upward swimming occurs when the task is altered to require escape from the upper end of the capillary tubes. Because the protozoa exhibit the same change in behavior regardless of the reinforcing stimulus, tube-escape learning is not associative learning.

Diastolic function of the fetal heart during second and third trimester: a prospective longitudinal Doppler-echocardiographic study

To generate normal charts of fetal cardiac inflow velocities and to assess physiologic changes of ventricular diastolic function, velocity waveforms of tricuspid and mitral valves were studied longitudinally in 49 fetuses in 4 week intervals from 14 weeks gestation to term. Doppler tracings were analyzed for: peak early (E) and peak late (A) inflow velocities, time velocity integral (TVI) of total inflow and A-wave velocity waveforms and heart rate corrected isovolemic relaxation time. E- and A-velocity as well as total- and A-wave-TVI of both valves increased significantly with gestational age (P < 0.001). Heart rate and A/E ratio decreased significantly with gestational age (P < 0.001). The ratio of A-wave TVI to total TVI of both valves and heart rate corrected isovolemic relaxation time (IVR) was constant suggesting unchanged diastolic function. This study provides normal charts for fetal cardiac inflow velocities. After 14 weeks of gestation all inflow velocities and their respective TVI's increased linearly in the growing fetal heart. There was evidence that diastolic function did not change. Area ratios and IVR should be used to determine changes in ventricular diastolic function, rather than velocity ratios.

Is tube-escape learning by protozoa associative learning?

The ciliate protozoa, Stentor and Paramecium, have been reported to escape from the bottom end of narrow capillary tubes into a larger volume of medium with increasing rapidity over the course of trials. This change in behavior has been considered an apparent example of associative learning. This decrease in escape time is not due to a change in the protozoa's environment, their swimming speed, frequency of ciliary reversals, or the proportion of time spent forward or backward swimming. Instead, most of the decrease results from a decrease in the proportion of time spent in upward swimming. However, a similar decrease in upward swimming occurs when the task is altered to require escape from the upper end of the capillary tubes. Because the protozoa exhibit the same change in behavior regardless of the reinforcing stimulus, tube-escape learning is not associative learning.

Pharmacokinetic and galactopoietic response to recombinant variants of bovine growth hormone

Two studies were designed to examine the pharmacokinetic and galactopoietic potency of three molecular variants of recombinant-derived bovine GH (rbGH): [Met1, Leu127]-bGH, [Ala1, Val127]-bGH and [Ala1, Val127, His133]-bGH. Histidine substitution for arginine at residue 133 of rbGH was shown to impart thrombin resistance. In a Latin square design, nine lactating Holstein cows received a 25 mg rbGH bolus infusion via the jugular vein followed by frequent blood sampling over the next 12 h. The serum GH concentration data were found to fit a two-compartment open model. Neither primary nor secondary kinetic parameter estimates differed significantly (P > 0.05) among the three rbGH variants. Thus, the disposition of GH concentration at time t was described by the equation C(t) = (1295.5 micrograms/l) (e-(0.11/min)(t)) + (317.3 micrograms/l)(e-(0.03/min)(t)). Overall averages were: area under the curve = 27.1 mg.min per l, clearance = 0.15 litres/min per 100 kg and volume of distribution of the central compartment = 2.59 litres/100 kg. The t 1/2 for the two compartments averaged 8.2 and 29.1 min. In the second study, 36 lactating Holstein cows received i.m. injections of one of four oil-based formulation treatments: control vehicle or 500 mg of one of the three rbGH variants every 14 days for 42 days. Average and maximum serum GH concentrations and area under the curve estimates were increased by approximately 3-6 micrograms/l, 5-15 micrograms/l and 40-90 micrograms.day per 1 respectively. Ala1, Val127 rbGH treatments elicited greater blood GH concentrations than [Met1, Leu127]-bGH when administered in an oil-based formulation. Blood GH responses did not directly translate into milk response differences, possibly due to differences in biopotency or receptor availability. Thrombin resistance resulting from substitution of histidine at position 127 of rbGH did not affect blood GH pharmacokinetic parameters or milk response over other rbGH variants.

A comparative analysis of the kinetic mechanism and peptide substrate specificity of human and Saccharomyces cerevisiae myristoyl-CoA:protein N-myristoyltransferase

Human myristoyl-CoA:protein N-myristoyltransferase (hNmt) catalyzes the transfer of myristate from CoA to the amino-terminal Gly residue of a number of cellular proteins involved in signal transduction pathways, to structural and nonstructural proteins encoded by retroviruses, hepadnaviruses, picornaviruses, and reoviruses, as well as to several transforming tyrosine kinases. hNmt has been purified 230-fold from an erythroleukemia cell line. The monomeric enzyme has no associated methionyl aminopeptidase activity. To determine the enzyme's kinetic mechanism, we examined the effect of covariation of subsaturating concentrations of myristoyl-CoA and peptide substrate on initial velocity. Double-reciprocal plots excluded a double displacement (ping-pong) mechanism. Product inhibition studies indicated that CoA was a noncompetitive inhibitor against myristoyl-CoA and a mixed-type inhibitor against peptide substrates. Together these results are consistent with a sequential ordered mechanism where, in a typical catalytic cycle, myristoyl-CoA binds to apoenzyme before peptide followed by release of the CoA and then myristoylpeptide products. This kinetic mechanism is identical to that described for Saccharomyces cerevisiae N-myristoyl-transferase (Nmt1p) and emphasizes the impact that regulation of myristoyl-CoA pool size and accessibility may have in modulating protein N-myristoylation in these two species. Comparative studies of the peptide substrate specificities of hNmt and Nmt1p using a panel of 12 octapeptides revealed distinct differences in their tolerance for amino acid substitutions at positions 3, 4, 7, and 8 of parental peptides derived from the amino-terminal sequences of known N-myristoyl-proteins. This finding contrasts with our recent observation that the acyl-CoA substrate specificities of hNmt and Nmt1p are highly conserved and suggests that these differences in peptide recognition provide an opportunity to develop species-specific enzyme inhibitors.

Comparison of the acyl chain specificities of human myristoyl-CoA synthetase and human myristoyl-CoA:protein N-myristoyltransferase

Human myristoyl-CoA synthetase and myristoyl-CoA:protein N-myristoyltransferase (hNmt) have been partially purified from an erythroleukemia cell line. Their substrate specificities were examined using two in vitro assays of enzyme activity together with a panel of C7-C17 saturated fatty acids plus 72 myristic acid analogs containing oxygen, sulfur, ketocarbonyl, ester, amide, cis and trans double bonds, triple bonds, and para-substituted phenyl groups. There is an inverse relationship between the polarity and the activity of C14 fatty acid substrates of myristoyl-CoA synthetase. Surveys of tetradecenoic and tetradecynoic acids suggest that myristate is bound to the synthetase in a bent conformation with a principal bend occurring in the vicinity of C5-C6. The synthetase can tolerate a somewhat wider range of physical chemical properties in acyl chains than can the monomeric hNmt. However, like myristoyl-CoA synthetase, there is an inverse relationship between acyl chain polarity and the activities of hNmt's acyl-CoA substrates. Moreover, the acyl chain of myristoyl-CoA appears to be bound to hNmt in a bent conformation with bends located in the vicinity of C5 and C8. The acyl chain specificities of both enzymes make them well suited to utilize efficiently any cellular pools of 5Z-tetradecenoic and 5Z,8Z-tetradecadienoic acids and their CoA derivatives. This feature may account for the recent observation that in some mammalian cell lineages, certain N-myristoyl-proteins are heterogeneously acylated with these C14 fatty acids. Finally, the acyl-CoA binding sites of human and Saccharomyces cerevisiae Nmts appear to have been highly conserved. Given their overlapping yet distinct peptide substrate specificities, development of species-specific inhibitors of Nmts should probably focus on structural features recognized in the enzymes' peptide substrates rather than in the acyl chain of their acyl-CoA substrates.

Left ventricular assistance without thoracotomy: mediastinal and transseptal approaches to the left heart

Two methods to cannulate the left atrium for initiating mechanical left ventricular circulatory assistance using a centrifugal pump were investigated in 25 sheep. A modified Dennis transatrial septal approach produced flow rates of 88.6 +/- 14 mL.kg-1.min-1 through 21F catheters inserted during fluoroscopy through the jugular vein. In 8 animals the septal perforation was plugged after decannulation with a modified Rashkind umbrella plug. Fibroendothelial tissue covered the plug by 4 week. In 7 other animals, the septal defect was not plugged. The septal defect reached pinpoint size by 2 weeks and was completely closed by 4 weeks. In 10 sheep, the left atrium was cannulated from the neck through the mediastinum. Left ventricular assistance flow averaged 71.6 +/- 14 mL.kg-1.min-1. Mean blood loss during 1 hour of left ventricular assistance was 47 mL. In 8 animals, the atrial perforation was plugged with a mean blood loss of 253 +/- 194 mL. In 2 animals, the perforation was intentionally not plugged; mean blood loss was 700 mL. All animals survived. The modified Dennis transatrial method is recommended as a safe, expeditious, cost-effective method to implement left ventricular assistance without thoracotomy. The mediastinal approach, which is technically possible in humans, is more difficult but feasible. Left ventricular assistance has been proven to be the most effective way to rest the failing, ejecting left ventricle. Implementation without thoracotomy potentially expands applications of left ventricular assistance for temporary support of patients with severe manifestations of ischemic heart disease.

Diagnosis, transport, and outcome in fetuses with left ventricular outflow tract obstruction

Between March 1986 and April 1990, 22 consecutive fetuses (at gestational ages of 21 to 38 weeks) with a suspected diagnosis of critical (ductus-dependent) left ventricular outflow tract obstruction on fetal echocardiogram were referred to our center for delivery and surgical treatment. Diagnoses were hypoplastic left heart syndrome (n = 16), valvular aortic stenosis (n = 2), common atrioventricular canal with subaortic stenosis (n = 3), and single ventricle with subaortic stenosis (n = 1). Postnatal echocardiography revealed that fetal echocardiography was correct in predicting left ventricular outflow tract obstruction to be critical in all but one patient, for a positive predictive value of 96%. Of the 21 patients with true, critical left ventricular outflow tract obstruction, 17 patients underwent cardiac surgery as neonates (birth to 6 days of age, median 2 days); 13 (or 77%) survived and were discharged from the hospital. In addition, one patient underwent successful balloon aortic valvotomy for critical valvular aortic stenosis but later died of sepsis. Lethal chromosomal and congenital abnormalities should be sought and are contraindications for this approach. In utero transport of fetuses with suspected critical left ventricular outflow tract obstruction to a neonatal cardiac surgical center can result in improved neonatal condition and may improve overall survival.

Acute fetal ductal occlusion in lambs

To assess fetal right ventricular and hemodynamic responses to acute occlusion of the ductus arteriosus, the pulmonary pressure, right and left ventricular output, and right ventricular dimensions of five fetal lambs were measured with simultaneous echocardiographic monitoring. Ductal occlusion resulted in a rise in pulmonary arterial pressure, a decrease in right ventricular output of 68%, an increase in left ventricular output of 18%, and a fall in combined cardiac output of 34%. The right ventricular systolic dimension increased, and the shortening fraction decreased from 0.41 to 0.14. Tricuspid regurgitation started within two heartbeats after ductal occlusion and resolved as soon as the occlusion was released. Acute fetal ductal occlusion imposes a marked increase in the right ventricular afterload, resulting in reversible triscuspid regurgitation.

Doppler echocardiography of fetal ductus arteriosus constriction versus increased right ventricular output

A prospective longitudinal study from 121 examinations of 41 normal pregnant women showed that fetal ductal flow velocities increased with gestational age. These normal data were compared with data in three groups of fetuses with altered ductal flow velocities: 22 fetuses (mean gestational age 31.3 weeks) had ductal constriction due to maternal indomethacin treatment; 10 fetuses (mean gestational age 27.9 weeks) had been exposed to terbutaline, a positive inotropic agent and 14 fetuses (mean gestational age 33.3 weeks) had hypoplastic left heart syndrome. In normal fetuses maximal systolic, mean and end-diastolic ductal flow velocities increased linearly (p less than 0.0001). The pulsatility index did not change (mean +/- 2 SD: 2.46 +/- 0.52). Fetuses with ductal constriction had higher maximal, mean and end-diastolic flow velocities and a significantly lower pulsatility index than did normal fetuses (1.25 +/- 0.76; p less than 0.0005). Six of 10 fetuses of the terbutaline group and 8 of 14 fetuses with hypoplastic left heart syndrome had increased maximal flow velocity, but normal or only mildly elevated mean flow velocity. The pulsatility index in fetuses during terbutaline therapy and with hypoplastic left heart syndrome was significantly higher than in normal fetuses (3.11 +/- 0.46 and 3.09 +/- 0.7, respectively, vs. 2.46 +/- 0.52; p less than 0.0005). Fetal ductal waveform analysis was necessary to distinguish fetal ductal constriction from increased right ventricular output. These measurements may be helpful in the diagnosis of left-sided outflow obstruction and assessment of fetal hemodynamic data.

Venous Doppler ultrasonography in the fetus with nonimmune hydrops

Eighteen pregnancies with nonimmune hydrops fetalis were referred for fetal echocardiography to rule out congenital heart disease. In 14 of these cases, pulsating blood velocities were recorded in the umbilical vein, which in a normal population had a nonpulsatile blood velocity pattern. The four cases without pulsations in the umbilical vein were found to have intrauterine viral infections. In the last 10 cases examined, the umbilical venous pulsations were found to reflect abnormal central venous pulsations during atrial systole suggesting increased fetal central venous pressure. Right ventricular shortening fraction was significantly decreased in the group with umbilical venous pulsations compared with those without (0.18 versus 0.32, p less than 0.05). All the fetuses without venous pulsations survived, but only four of the 14 with pulsations survived (p less than 0.05). The results suggest that blood velocity recordings in the umbilical and central veins of the fetus can give valuable clinical information with regard to the presence of fetal congestive heart failure and differentiate between this physiologic state and other causes of nonimmune hydrops fetalis. This may have implications for fetal diagnostic work-up and prognosis.

Premature constriction of the ductus arteriosus

Prostaglandin synthetase inhibition in the fetus may induce constriction of the ductus arteriosus. Clinical experience is now accumulating that proves that this potential complication is reversible and that it is easily diagnosed by Doppler echocardiography.

Purification and characterization of pituitary bovine somatotropin

Bovine somatotropin (bST) has been isolated from pituitary glands and compared in a variety of chemical analyses and bioassays with somatotropin derived from recombinant Escherichia coli. Comparison of pituitary extracts and purified bST by Western blot analysis of two-dimensional gels suggested that the immunoreactive somatotropin species present in the extract were also present in the purified material, with no significant losses or degradation as a result of the purification method. NH2-terminal sequence analysis indicated the presence of equal quantities of Ala-Phe-Pro-Ala-Met-Ser-Leu-Ser- and Phe-Pro-Ala-Met-Ser-Leu-Ser- sequences. The Met-Ser-Leu-Ser-NH2-terminal sequence, a degradation product observed in NIH standard lots, was not detected. Assay of bioactivity in a bovine liver receptor-binding assay and in a female rat growth assay showed pituitary bST and recombinant methionyl-bovine somatotropin to be equipotent. Tryptic maps and sequence analysis of pituitary-derived somatotropin suggest the presence of isoaspartate derivatization at Asp128.

Localization of mechanoreceptors in the protozoan, Stentor coeruleus

Mechanoreceptor channels were localized by using the ligands, tubocurarine (TC), decamethonium (Deca), and gallamine (Gall), which have been shown to bind specifically to these channels. The binding of radioactively labeled TC (TC*) was found to be directly proportional to the cell surface area suggesting that the channels are uniformly distributed over the cell surface. Intracellular TC and Gall injections did not depress mechanical stimulus sensitivity though these drugs did depress sensitivity when applied extracellularly at the same concentrations; therefore, the ligand binding sites are on or near the external surface of the cell. Autoradiographs revealed that radioactively labeled Deca (Deca*) bound to the pigmented stripes but not to the ciliary stripes or membranellar band. Further, Stentor induced to shed their membranellar band through exposure to 8% urea were more sensitive to mechanical stimuli than were controls; therefore, the membranellar cilia do not appear to contain mechanoreceptor channels. Collectively, these data indicate that the mechanoreceptor channels are located in the somatic surface covering the pigmented stripes. The density of mechanoreceptor channels in the plasma membrane covering the somatic surface is tentatively estimated to be between 5500 and 14,500 microns-2 based on the density of TC* binding, the apparent number of TC molecules binding per mechanoreceptor channel, and data suggesting that only one fifth to one fourth of the bound TC* is bound to structures in the plasma membrane.

Habituation in Stentor: a response-dependent process

The contractile protozoan Stentor coeruleus habituates during repetition of the mechanical stimulus used to elicit the initial contractions. This decrement in response probability was found to be highly correlated with a reduction in receptor potential amplitude, while the amplitude of the action potentials that triggered the contractions did not change. When mechanical stimulation elicited receptor potentials and not action potentials, the receptor potential did not habituate significantly. Conversely, action potentials repetitively elicited by current pulses habituated animals to mechanical stimuli. Similarly, voltage steps used to simulate action potentials produced pronounced decrements in receptor currents recorded from voltage-clamped cells, while mechanical stimulation produced only small decrements. Thus, habituation depends primarily on action potential production, while mechanical stimulation itself makes a much smaller, but significant, contribution. The temporal relation between mechanical stimuli and action potentials, when both occur, is inconsequential in determining the rate and degree of habituation produced.

Habituation in Stentor: produced by mechanoreceptor channel modification

Habituation in Stentor was shown in the previous paper (Wood, 1988) to result from a progressive diminution in mechanoreceptor potential amplitude during the course of repetitive mechanical stimulation. The source of this diminution was analyzed in the present studies by eliciting mechanoreceptor currents from control and habituated cells under voltage clamp control. The I-V plots obtained have a voltage-dependent region between -60 and -20 mV, and a linear voltage-independent region between -20 and 20 mV, with a reversal potential near 20 mV. The slope of the linear region did not change as a result of habituation indicating that the maximum mechanoreceptor current, and hence the total number of mechanoreceptor channels, was the same in control and habituated cells. The mechanoreceptor current reversal potential was changed by only a few millivolts, from 21.6 to 17.2 mV, leaving the driving force term for the mechanoreceptor current at resting potential relatively unchanged. On the other hand, the voltage-dependent region of the I-V plot became significantly steeper after habituation (9.6 mV/e-fold change) compared to its value before habituation (12.3 mV/e-fold change). This shift in voltage dependence is sufficient to explain the diminution in receptor potential amplitude seen during normal recordings at resting potential. The importance of the voltage-dependent characteristic of the mechanoreceptor channels to the habituation process was corroborated by the observation that the amplitude of receptor potentials elicited from cells depolarized by current pulses habituated to only a very limited degree while receptor potentials elicited at resting potential underwent marked habituation.(ABSTRACT TRUNCATED AT 250 WORDS)

An improved method for measurement of common tricyclic antidepressant drugs and their metabolites using normal phase HPLC

A sensitive HPLC method that allows the simultaneous determination of imipramine, amitriptyline and their desmethyl metabolites, using a 10 cm straight silica cartridge column with a mobile phase consisting of 0.004% perchloric acid in methanol is presented. Detection of the eluent is at 210 nm. The drugs are back-extracted from serum, giving both a good recovery and sensitivity of at least 5 micrograms/L. This method has proved to be extremely robust and reliable, with coefficients of variation around 3% being reported.

The mechanism of tubocurarine action on mechanoreceptor channels in the protozoan Stentor coeruleus

(+)-Tubocurarine (TC) decreases the probability that the protozoan, Stentor coeruleus Ehrenberg, will contract in response to mechanical stimulation, because it selectively depresses mechanoreceptor currents. Resting membrane properties and action potentials are not significantly altered by the drug. Stentor incubated in media containing radioactively labelled TC (TC*) retain TC* after extensive washing despite a rather high apparent KD (19.7 mumol l-1). The incubation curve for TC* binding exhibits an initial exponential rise followed by a linear increase. Wash-out of bound TC* and elimination of the exponential component of the incubation curve is observed if the TC* incubation is followed by a 5-s exposure to 8% urea; therefore, the exponential component represents a reversible binding process. TC* binding in the exponential component is highly correlated (r less than −0.96) with the depression in receptor current and response probability when incubation time, drug concentration and drug (gallamine, TC, decamethonium and succinylcholine) are varied. These correlations suggest that the exponential binding is to functional mechanoreceptors. Mechanoreceptor currents are decreased by hyperpolarization and increased by depolarization, indicating that the mechanoreceptor channel is voltage-dependent. At hyperpolarized potentials the channels are in a form (the U form) which cannot be opened by mechanical stimulation; at depolarized potentials they are in a form (the R form) which can be opened. TC appears to bind to the U form with higher affinity than to the R form, since depolarization reduces the amount of bound TC* and relieves the depression of mechanoreceptor current produced by TC.

Sensitivity of carcinogen-treated DNA to inactivation by ultraviolet radiation

The DNA of bacteriophage SPO2c12 was treated with methylmethane sulfonate (MMS), beta-propiolactone (BPL), 2-anthramine (AA) or benzo[a]pyrene (BP) and then exposed to 254-nm radiation. Competent Bacillus subtilis host cells were transfected with DNA subjected to the carcinogen-UV treatment or with DNA treated with carcinogen only. Survival curves were obtained for loss of plaque-forming ability as a function of UV dose. The UV sensitivity of DNA treated with MMS, BPL or AA was not significantly different from that of untreated DNA. The results indicate that in competent B. subtilis the pathways for repair of alkylating agent damage and for repair of UV damage are probably different.

Effect of supercoiling on the abortive initiation kinetics of the RNA-I promoter of ColE1 plasmid DNA

An analysis of the effect of DNA supercoiling on transcription of the RNA-I promoter of ColE1 has been undertaken using the abortive initiation assay developed by McClure (McClure, W. R., Cech, C. L., and Johnston, D. E. (1978) J. Biol. Chem. 253, 8941-8948). A tau plot was constructed, enabling the equilibrium constant for closed complex formation (KI) and the isomerization rate constant (k2) to be determined. The effect of supercoiling on RNA-I is an apparent 100-fold increase in the isomerization rate, k2, with little or no effect on KI. This is the first reported abortive initiation analysis of RNA-I transcription which serves in the regulation of plasmid replication.

The N-ethylmaleimide-sensitive cysteine residue in the pH-dependent subunit interactions of malate dehydrogenase

The specific chemical modification by N-ethylmaleimide of a cysteine residue at pH 5.0 in porcine heart mitochondrial malate dehydrogenase (L-malate:NAD+ oxidoreductase, EC 1.1.1.37) has been shown to result in an enzymatically inactive, monomeric product, which does not reassociate at pH 7.5 to yield the native dimer. In this report, an investigation of proton release and uptake upon NADH binding to the native enzyme and to the N-ethylmaleimide-modified enzyme has implicated the above cysteine residue as being directly linked to the pH-dependent subunit dissociation of mitochondrial malate dehydrogenase. The results are consistent with the view that the modified cysteine residue is not located at the subunit interaction site, although it is probably near this site. A recent study from this laboratory has demonstrated that the monomeric enzyme obtained at pH 5.0 exists in a conformation which is enzymatically inactive and which has an enhanced intrinsic protein fluorescence. Interpretation of protein fluorescence data has suggested that the N-ethylmaleimide modification results in inactivation of the enzyme by preventing the pH-induced conformational change to the active dimer. However, NADH is able to induce reassociation of the N-ethylmaleimide-modified enzyme at pH 7.5 but not at pH 5.0. This reassociation at pH 7.5 is accompanied by a significant regain of enzymatic activity, indicating that NADH binding is able to partially overcome the negative effect of the cysteine modification on the pH-dependent subunit reassociation of mitochondrial malate dehydrogenase.