Evidence of mobilization of hobo transposons in a P-element mutagenesis screen

In Drosophila melanogaster, mutations in Su(var) and En(var) loci either suppress or enhance position effect variegation, respectively. Towards the cloning of these genes we have induced, recovered, and characterized a series of Su(var) mutations located on the third chromosome. These mutations were recovered from a P-element mutagenesis scheme in which the third chromosome P[ry+ delta 2-3](99B) element would provide transposase in trans to mobilize a single nonautonomous P transposon, P[pUCHSNeo](9C), located on the X chromosome. Although this cross scheme induces mobilization of the X-chromosome P transposons and its subsequent reinsertion onto the autosomes, none of the Su(var) mutations recovered could be associated with P-transposon insertions. Further investigation of these mutations by in situ hybridization showed that another mobile element that can be mobilized in hybrids, hobo, was associated with these mutations. We conclude that the mobilization and reinsertion of the hobo elements, through an inadvertent hybrid HE dysgenic cross, is most likely responsible for the Su(var) mutations recovered from this P-element mutagenesis. The association of hobo element with this Su(var) locus will facilitate its cloning and offers the possibility of hobo transposon tagging other Su(var) loci.

Deletion between directly repeated DNA sequences measured in extracts of bacteriophage T7-infected Escherichia coli

An in vitro system based upon extracts of bacteriophage T7 infected Escherichia coli was used to study genetic deletions and to examine the importance of DNA replication in the deletion process. When T7 genomes with gene 1.3 inactivated by a 43-bp insert of random sequence DNA bracketed by 11-bp direct repeats were replicated in vitro the inserts were deleted with a frequency of about 10(-5) deletions per genome replication. Under conditions where deletion could take place only by recombination between direct repeats on distinct DNA molecules deletion frequency was at least an order of magnitude lower. These data demonstrate the utility of the in vitro system as a means for examining deletion mechanisms and underscore the importance of DNA replication in deletions.

Transvaginal sonography in the diagnosis and management of cervical incompetence

Cervical incompetence remains a controversial area in obstetric management. The development of transvaginal sonography has resulted in a clearer image of the internal cervical os, a development which may indirectly have beneficial effects on outcome. However, the rapid development of cervical dilatation in some cases necessitates frequent ultrasound monitoring.

[Preliminary study of changes in plasma prostaglandin E1 in rats with experimental "schizophrenia"]

We referred to Borison's method of making the model schizophrenia. Rats were injected d-amphetamine intraperitoneally once a day so that the schizophrenia models were established within four weeks. After five weeks, rats with schizophrenia were treated with chlorpromazine. Contents of plasma prostaglandin E1(PGE1) in rats were determined before and after treatment respectively. This study demonstrated that contents of plasma PGE1 in rats receiving amphetamine for four weeks were higher than those in control animals (P < 0.05). At this time, male rats' stereotypy scores were 3.5 and female stereotypy scores 5. But contents of plasma PGE1 in rats with schizophrenia approached those in control animals with giving amphetamine once a day continuously. Contents of plasma PGE1 decreased in rats with schizophrenia receiving chlorpromazine.

Restriction fragment length polymorphism of hsp70 gene, localized in the RT1 complex, is associated with hypertension in spontaneously hypertensive rats

Previous studies from our laboratory have demonstrated that the intermediate phenotype of thermosensitivity is present in hypertensive mice and rats. Increased expression of hsp70 caused by increased transcription rate was demonstrated in vivo, in organs, and in cultured cells from spontaneously hypertensive rats and hypertensive mice. In this study, a polymorphism of this gene was revealed with BamHI enzyme by using a human hsp70 probe. A 4.4-kb fragment was visualized in normotensive rats (Brown-Norway BN.lx and Sprague-Dawley), and a 3.0-kb fragment was found in spontaneously hypertensive rats (SHR) of three different origins and in Wistar and Buffalo rats. Both fragments were present in the Wistar-Kyoto rat strain. The present study mapped the polymorphism of hsp70 into the RT1 complex in BN.1K and SHR.1N congenic strains. The hsp70 restriction fragment length polymorphism is associated with a blood pressure difference of 15 mm Hg in recombinant inbred strains. These results justify the search for a mechanism by which hsp70 could influence blood pressure.

The effect of the length of direct repeats and the presence of palindromes on deletion between directly repeated DNA sequences in bacteriophage T7

The frequency of genetic deletion between directly repeated DNA sequences in bacteriophage T7 was measured as a function of the length of the direct repeat. The non-essential ligase gene (gene 1.3) of bacteriophage T7 was interrupted with pieces of synthetic DNA bracketed by direct repeats of various lengths. Deletion of these 76 bp long inserts was too low to be measured when the direct repeats were less than 6 bp long. However, the frequency of deletion of inserts with longer direct repeats increased exponentially as the length of the repeats increased from 8 to 20 bp. When inverted repeats (palindromes) were designed in the midst of the insert there was essentially no increase in deletion frequency between 10 bp direct repeats. But, the same palindromic sequences increased the deletion frequency between 5 bp direct repeats by at least two orders of magnitude. Thus, in this system homology at the endpoints is a more important determinant of deletion frequency than is the presence of palindromes between the direct repeats.

Effects of nimodipine on the production of thromboxane A2 following total global cerebral ischemia

To clarify the contribution of vasoconstrictor prostaglandins to the hypoperfusion state typically following total global cerebral ischemia, 14 mongrel dogs were subjected to 11 minutes of global cerebral ischemia. They were then randomly assigned to receive either no treatment or an intravenous bolus of the calcium channel blocker nimodipine, 10 micrograms/kg, 15 minutes after ischemia followed by a continuous infusion of nimodipine, 1.0 micrograms/kg/min. Thromboxane (Tx) A2 production, as measured by cerebral venous levels of TxB2 (the stable metabolite of TxA2) increased similarly in the two groups. In contrast to previous studies, mean postischemic cerebral blood flow did not increase sufficiently in the nimodipine-treated group to achieve statistical significance. These data suggest that the improved neurological outcome associated with nimodipine treatment following global cerebral ischemia does not relate to reduced levels of the prostaglandin precursor arachidonate.

Absence of prostaglandin changes associated with protamine administration in patients with pulmonary hypertension

In patients with pre-existing pulmonary hypertension, severe pulmonary vasoconstriction has been observed following protamine administration. Thromboxane A2, a potent vasoconstrictor, is capable of producing increases in pulmonary vascular resistance, and animal studies suggest that heparin-protamine complexes stimulate thromboxane A2 synthesis. This study assessed the effect of protamine administration on hemodynamics and on plasma thromboxane A2 and its biologic antagonist, prostacyclin, by serial measurement of the stable metabolites, thromboxane B2 and 6-keto-prostaglandin F1 alpha, respectively. Ten adults with pulmonary artery hypertension undergoing elective mitral valve replacement were studied. After termination of cardiopulmonary bypass, baseline hemodynamic measurements were obtained and arterial blood for prostanoid analysis was sampled. Hemodynamic and prostanoid measurements were obtained 5, 10, 15, and 30 minutes after the protamine infusion began. Prostanoid levels were performed by double antibody radio-immunoassay. No significant hemodynamic changes occurred and no significant changes in prostanoid levels were observed. It is concluded that in patients with pulmonary hypertension, heparin-protamine complexes do not consistently raise circulating thromboxane levels, and the relationships among prostanoids, pulmonary hypertension, and systemic hypotension are still not clear.

Inhibition of thromboxane A2 production does not improve post-ischemic brain hypoperfusion in the dog

In a canine model of global brain ischemia, six dogs received a selective thromboxane A2 synthetase inhibitor, UK 38,485 (dazmagrel) before the ischemic event; six received a saline placebo. Cerebral blood flow (CBF), systolic and diastolic arterial pressure, cardiac output, pH, PaCO2, PaO2, and arterial and jugular-vein thromboxane B2 (a stable metabolite of thromboxane A2) and 6-keto PGF1 alpha (a stable metabolite of prostacyclin) were measured at baseline, after release of aortic and venae caval occlusion and at intervals up to 120 min thereafter. Treated animals showed nearly complete post-ischemic inhibition of thromboxane B2 production; control animals showed increases in jugular venous thromboxane B2. Arterial and jugular venous levels of 6-keto PGF1 alpha were significantly higher in treated animals at most post-ischemic intervals. CBF in both groups was similar to baseline values at time 0, then declined similarly in both groups by 30 min to approximately equal to 35% of baseline values where it remained thereafter. There were no significant differences in other variables at any interval. We conclude that inhibition of thromboxane A2 production does not alter post-ischemic brain hypoperfusion.

Methylprednisolone on circulating eicosanoids and vasomotor tone after endotoxin

Acute pulmonary and systemic vasomotor changes induced by endotoxin in dogs have been related, at least in part, to the production of eicosanoids such as the vasoconstrictor thromboxane and the vasodilator prostacyclin. Steroids in high doses, in vitro, inhibit activation of phospholipase A2 and prevent fatty acid release from cell membranes to enter the arachidonic acid cascade. We, therefore, administered methylprednisolone (40 mg/kg) to dogs to see if eicosanoid production and the ensuing vasomotor changes could be prevented after administration of 150 micrograms/kg of endotoxin. The stable metabolites of thromboxane B2 (TxB2) and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) were measured by radioimmunoassay. Methylprednisolone by itself did not alter circulating eicosanoids but when given 2.5 h before endotoxin not only failed to inhibit endotoxin-induced eicosanoid production but actually resulted in higher circulating levels of 6-keto-PGF1 alpha (P less than 0.05) compared with animals receiving endotoxin alone. Indomethacin prevented the steroid-enhanced concentrations of 6-keto-PGF1 alpha after endotoxin and prevented the greater fall (P less than 0.05) in systemic blood pressure and systemic vascular resistance with steroid plus endotoxin than occurred with endotoxin alone. Administration of methylprednisolone immediately before endotoxin resulted in enhanced levels (P less than 0.05) of both TxB2 and 6-keto-PGF1 alpha but with a fall in systemic blood pressure and vascular resistance similar to the animals pretreated by 2.5 h. In contrast to the early steroid group in which all of the hypotensive effect was due to eicosanoids, in the latter group steroids had an additional nonspecific effect. Thus, in vivo, high-dose steroids did not prevent endotoxin-induced increases in eicosanoids but actually increased circulating levels of TxB2 and 6-keto-PGF1 alpha with a physiological effect favoring vasodilation.

The antioxidant activity of alpha-tocopherol-bovine serum albumin complex in micellar and liposome autoxidations

A comparison is made of the antioxidant activity of a water-soluble form of alpha-tocopherol complexed with bovine serum albumin (alpha-T X BSA) with that of micellar alpha-tocopherol and aqueous 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylate (Trolox) to inhibit autoxidation of linoleic acid in sodium dodecyl sulfate micelles. The peroxyl radical trapping ability of alpha-T X BSA compares favorably with that of alpha-tocopherol and Trolox, and all three can be used in quantitative measurements of the susceptibility of the micellar substrate to undergo autoxidation: the oxidizability, for reactions initiated in the micellar phase by di-tertbutylhyponitrite (DBHN) or in the aqueous phase by azobisamidinopropane hydrochloride (ABAP). alpha-Tocopherol and Trolox are also effective antioxidants to inhibit DBHN- or ABAP-initiated autoxidations of dilinoleoylphosphatidylcholine (DLPC) liposomes prepared as multilamellar or unilamellar bilayers characterized by 31P NMR spectra. The oxidizability of DLPC liposomes is determined by various combinations of water-soluble and lipid-soluble initiators and the antioxidants, alpha-tocopherol and Trolox. In contrast, alpha-T X BSA does not effectively trap peroxyl radicals when it is added after initiation of autoxidation in the lipid phase (DBHN) or in the aqueous phase (ABAP). The radical trapping ability of alpha-T X BSA becomes evident if it is mixed with the DLPC for some hours before initiation. This result is interpreted in terms of diffusion of alpha-tocopherol from the bound alpha-T X BSA form to the liposome before it exhibits antioxidant activity.

Regional blood flow and pulmonary thromboxane release after sublethal endotoxin infusion in sheep

Fifteen minutes after intravenous Escherichia coli endotoxin (EN) infusion the sheep lung transiently releases into the systemic circulation up to 12 micrograms of thromboxane A2 (TxA2)/min measured by radioimmunoassay as its metabolite thromboxane B2 (TxB2). To determine whether lung thromboxane release alters regional blood flow (RBF) we injected microspheres before and 20, 30, and 100 minutes after EN infusion in 13 awake sheep. In seven untreated control sheep (group 1) pulmonary vascular resistance (PVR) increased threefold at 20 and 30 minutes after EN infusion, coinciding with a large transpulmonary blood concentration gradient of TxB2. There was no measured RBF change to any systemic tissue or organ except the right ventricle at 20 minutes after EN infusion, when blood flow per gram of tissue doubled. In six sheep (group 2) treated with intravenous ibuprofen before EN infusion there was no increase in PVR, plasma TxB2, or blood flow to the right ventricle, and no difference of RBF to any other organ or tissue when compared to group 1. TxA2 is a potent local pulmonary vasoconstrictor but it rapidly hydrolyzes. Its short half-life and the circulatory delay in systemic arterial delivery prevent TxA2 from acting as a circulating vasoconstrictor.

Thromboxane and prostacyclin (epoprostenol) during exercise in diffuse pulmonary fibrosis

Plasma thromboxane A2, a vasoconstrictor, and plasma prostacyclin (epoprostenol), a vasodilator, were assessed by double-antibody radioimmunological assay of their respective stable circulating metabolites, thromboxane B2 (TxB2) and 6-ketoprostaglandin F1 alpha, in 9 patients with severe diffuse pulmonary fibrosis (DPF), who were known to become hypo-oxaemic during exercise, and in 9 healthy volunteers. In the 7 patients with the most severe DPF, mean arterial PO2 fell from 68 mm Hg at rest to 51 mm Hg at peak aerobic exercise, and mean TxB2 increased to twice the value at rest. The 9 controls remained oxygen saturated throughout exercise; their mean TxB2 did not change during aerobic exercise, but during anaerobic exercise increased to twice the value at rest, and increased further during recovery. There were no significant changes in 6-keto-prostaglandin F1 alpha in either group. The selective release of TxB2 during aerobic exercise in hypo-oxaemic patients suggests that thromboxane mediates hypoxic pulmonary vasoconstriction. Its release in normal man during anaerobic exercise may reflect a more general response to the metabolic changes of tissue hypoxia.

Thromboxane and pulmonary hypertension following E. coli endotoxin infusion in sheep: effect of an imidazole derivative

We assessed the effect of a specific thromboxane synthetase inhibitor (an imidazole derivative) on pulmonary hemodynamics and the concentrations of TxB2 (TxA2), 6-keto-PGF1 alpha (PGI2), and PGF2 in pulmonary lymph and transpulmonary blood samples following intravenous administration of E. coli endotoxin (1 microgram/kg) in sheep. In control animals the rise in pulmonary artery pressure correlated with increases in plasma and lymph TxB2 concentrations and large transpulmonary concentration gradients of this metabolite were measured. In imidazole treated animals both pulmonary hypertension as well as increases in plasma and lymph TxB2 concentrations were substantially reduced. In contrast, peak concentrations of 6-keto-PGF1 alpha (PGI2) and PGF2 alpha were severalfold higher than those measured in control animals. This suggests a shunting of endoperoxide metabolism towards prostacyclin and primary prostaglandins and documents the specificity of the thromboxane synthetase inhibitor. Our study provides evidence that endotoxin-induced pulmonary hypertension is mediated by pulmonary synthesis of TxA2.

Role of thromboxane and prostacyclin in pulmonary vasomotor changes after endotoxin in dogs

Cyclooxygenase inhibitors prevent the pulmonary vasomotor changes in response to low-dose endotoxin. We, therefore, explored the role of two highly vasoactive prostanoids, thromboxane A(2), a vasoconstrictor, and prostacyclin, a vasodilator, in the transient pulmonary vasoconstriction and subsequent loss of alveolar hypoxis vasoconstriction (AHPV) that follows endotoxin. AHPV was tested in the dog with a double-lumened endotracheal tube allowing ventilation of one lung with nitrogen as a hypoxic challenge while the other lung was ventilated with oxygen to maintain systemic oxygenation. Relative distribution of perfusion to the two lungs was assessed with intravenous (133)Xe and external scintillation detectors. The stable metabolites of thromboxane and prostacyclin, i.e., thromboxane B(2) and 6-keto-prostaglandin F(1alpha) were measured in plasma with radioimmunoassay. 15 mug/kg i.v. of endotoxin induced no rise in pulmonary vascular resistance (PVR), but prevented AHPV so that the initial 33% (+/-2 SEM) decrease in perfusion to the hypoxic lung became only a 2% (+/-1) decrease. Circulating levels of thromboxane and prostacyclin concurrently rose (P < 0.01) from nondetectable levels to 380 pg/ml (+/-40) and 360 pg/ml (+/-130). 150 mug/kg of endotoxin induced a transient rise in PVR from 4.09 to 9.00 mm Hg/liter per min in association (r = 0.89, P < 0.01) with a sharp rise in thromboxane levels to 4,460 pg/ml (+/-1,350) whereas prostacyclin levels were elevated less markedly to 550 pg/ml (+/-400). Prostaglandin F(2alpha), another vasoconstrictor, was not elevated. 30 min after endotoxin when PVR was again base line and AHPV lost, thromboxane fell significantly (P < 0.01) to 2,200 pg/ml (+/-1,100) whereas prostacyclin remained elevated at 360 pg/ml (+/-135), a level similar to that seen when 15 mug/kg of endotoxin induced loss of AHPV. Indomethacin prevented the rise in thromboxane and prostacyclin after endotoxin as well as the changes in pulmonary vasomotor tone. Thus, a complex interaction between thromboxane and prostacyclin is involved in the pulmonary vasomotor response to low-dose endotoxin.