NOS inhibition restores renal responses to atrial distension during pregnancy

Nitric oxide (NO) biosynthesis increases during pregnancy and has been shown to suppress baroreceptor activity. The renal response to a simulated increase in circulating blood volume (atrial distension) is also attenuated at this time. We hypothesized that blocking NO biosynthesis during pregnancy would restore the renal response. Female rats were implanted with indwelling intracardiac balloons and central venous cannulas. After recovery, they were mated, and on day 14 of pregnancy, osmotic minipumps containing the NO synthase inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) or its inactive enantiomer N(G)-nitro-D-arginine methyl ester (D-NAME) (120 mg/2 ml at 10 microg/min) were implanted. In response to atrial distension (1 h), urine output increased in the D- and L-NAME-treated virgin rats. During pregnancy (day 20), this response was attenuated in the D-NAME-treated, but not the L-NAME-treated, animals, i.e., after a simulated increase in circulating blood volume, inhibition of NO biosynthesis restored the renal response of pregnant rats to that seen in virgin animals. We conclude that, during normal pregnancy, increased NO biosynthesis blunts the reflex renal response to atrial distension.

Distribution of 4a-hydroxytetrahydropterin dehydratase in rat tissues Comparison with the aromatic amino acid hydroxylases

A 4a-carbinolamine intermediate is generated stoichiometrically during the tetrahydrobiopterin-dependent phenylalanine hydroxylation reaction catalyzed by phenylalanine hydroxylase. The dehydration of the carbinolamine is catalyzed by the enzyme, 4a-hydroxytetrahydropterin dehydratase. We have now examined the distribution of the dehydratase activity in various rat tissues by activity measurements and by immunoblot analysis to explore the possibility that the dehydratase may also play a role in tyrosine and tryptophan hydroxylation. The only two tissues that express relatively high dehydratase activity are liver and kidney, which are also the only two tissues that express phenylalanine hydroxylase activity. The dehydratase activity was generally very low in those tissues which contain high levels of tyrosine and tryptophan hydroxylase activity, except for the pineal gland. These results suggest that the dehydratase may not play an important role in the regulation of the synthesis of those neurotransmitters which are derived from the hydroxylated aromatic amino acids.

Splenorenal reflex regulation of arterial pressure

During the course of our studies into the control of fluid extravasation from the splenic vasculature, we found that intrasplenic inhibition of NO biosynthesis caused an increase in systemic blood pressure. The present experiments were designed to investigate the mechanisms underlying this novel observation. There was an increase in mean arterial pressure when the nonspecific NO inhibitor N(G)-monomethyl-L-arginine (L-NMMA) was infused via the splenic artery but not when the same dose was administered systemically. Conversely, blood pressure decreased after intrasplenic but not systemic administration of the NO donor S-nitroso-N-acetyl-D,L-penicillamine. There was no pressor response to intrasplenic administration of either the inducible or neuronal NO synthase inhibitors N-[3-(aminomethyl)-benzyl] aceramidine and L-N(5)-(1-imino-3-butenyl)-ornithine. The pressor response to L-NMMA was abolished by denervation of either the spleen or the kidney and by pretreatment with the ACE inhibitor enalapril. We propose that the spleen influences systemic blood pressure through a reflex pathway comprising splenic afferent nerves and renal sympathetic control of renin release.

Influence of a short or long abstinence period on semen parameters in the ejaculate of patients with nonobstructive azoospermia

OBJECTIVE

To compare the effect of a short (4 days) or a long (14 days) abstinence period on sperm retrieval by extended sperm preparation in patients with nonobstructive azoospermia scheduled for testicular biopsy and intracytoplasmic sperm injection (ICSI).

DESIGN

A prospective case control study.

SETTING

Male infertility clinic in a university hospital.

PATIENT(S)

Fifty male patients with nonobstructive azoospermia, scheduled for testicular biopsy for ICSI.

INTERVENTION(S)

Diagnosis of nonobstructive azoospermia and a thorough microscopic search for sperm cells (extended sperm preparation).

MAIN OUTCOME MEASURE(S)

The number of sperm cells collected, sperm motility, and total motile sperm count after short and long abstinence periods.

RESULT(S)

There was a significant difference between long and short abstinence with an increase in sperm count (log-to-log transformed analysis of variance P<.025) and total motile sperm (P<.025 analysis of variance, P<.02 paired Student's t-test) in the former group, but no significant change in sperm motility (Wilcoxon and paired Student's t-test). In 18 patients, sperm concentration and sperm motility were similar in a second collection, done after the same abstinence period, compared with the same parameters in the first sample. When at least 10 motile sperm were defined as the cutoff number, allowing ICSI without testicular biopsy, no significant differences were found between the two abstinence periods. No clinical or laboratory male characteristic could predict the detection of 10 motile sperm by extended sperm preparation either after a short or a long abstinence period.

CONCLUSION(S)

Sperm count and total motile sperm were increased after a long abstinence period, with no change in sperm motility. No additional advantages were conferred by long abstinence as opposed to short abstinence when 10 motile sperm were defined as the cutoff number for ICSI. The recommended period of abstinence for extended sperm preparation and ICSI, whether short or long, should be individualized for each patient.

Atrial natriuretic factor increases splenic microvascular pressure and fluid extravasation in the rat

The spleen is an important site of atrial natriuretic factor (ANF)-induced fluid extravasation into the systemic lymphatic system. The mechanism underlying this process was studied in a blood-perfused (1 ml min(-1)) rat spleen using the double occlusion technique. To ensure that our observations were spleen specific, a similar protocol was repeated in the hindquarters. Rat ANF(1-28), infused into the splenic artery of anaesthetized male rats, caused a dose-dependent (0.3-59 pmol min(-1)) increase in microvascular pressure from 11.3 +/- 0.7 to 14.9 +/- 0.5 mmHg and in post-capillary resistance from 7.2 +/- 0.6 to 10.1 +/- 1.1 mmHg ml(-1). ANF elicited no change in splenic pre-capillary resistance or in hindquarter haemodynamics. Intrasplenic ANF (6.5 pmol min(-1)) caused a sustained increase in intrasplenic fluid efflux from 0.1 +/- 0.1 to 0.3 +/- 0.1 ml min(-1), and in capillary filtration coefficient (Kf) from 1.2 +/- 0.5 to 2.4 +/- 0.6 ml mmHg-1 min-1 (100 g tissue)-1. Mechanical elevation of splenic intravascular pressure (from 11.3 +/- 0.7 to 22.4 +/- 0.2 mmHg) significantly increased intrasplenic fluid extravasation (from 0.4 +/- 0.3 to 1.4 +/- 0.3 ml min(-1)). The natriuretic peptide receptor-C (NPRC)-specific agonist C-ANF(4-23) (12.5 and 125 pmol min(-1)) did not alter splenic intravascular pressure or pre-/post-capillary resistance. The ANF antagonist A71915 (8.3 and 83 pmol min-1), which blocks ANF-stimulated cGMP production via natriuretic peptide receptor-A (NPRA), inhibited the ANF-induced changes in splenic microvascular pressure and post-capillary resistance. It is concluded that ANF enhances the extravasation of isoncotic fluid from the splenic vasculature both by raising intrasplenic microvascular pressure (increased post-capillary resistance) and by increasing filtration area. The constrictive activity of ANF on the splenic vasculature is mediated through NPRA.

Adrenomedullin increases fluid extravasation from the splenic circulation of the rat

1. We studied the effect of adrenomedullin (ADM) on fluid efflux from the splenic vasculature into extravascular spaces. 2. Splenic arterial infusion of ADM (1, 3 and 9 ng min(-1); n = 9, 11 and 10, respectively) caused a dose-dependent increase in intrasplenic fluid efflux (+0.6 +/- 0.3 (saline) vs. +2.0 +/- 0.3 ml min(-1) (9 ng min(-1) ADM), P < 0.05), and in splenic (venous minus arterial) haematocrit (+0.8 +/- 0.1 (saline, n = 6) vs. +3.1 +/- 0.3 % (9 ng min(-1) ADM, n = 7), P < 0.05). There was no change in splenic weight (0.99 +/- 0.02 (saline, n = 6) vs. 0.99 +/- 0.02 g (9 ng min(-1) ADM, n = 7), P > 0.05). 3. There was no change in MAP before (97.5 +/- 2.2 mmHg), during (98.4 +/- 3.4 mmHg), or after (100.2 +/- 2.2 mmHg) intrasplenic infusion of ADM (9 ng min(-1)) (n = 11, P < 0.05). 4. ADM (9 ng min(-1)) caused an increase in intrasplenic microvascular pressure (11.3 +/- 0.3 (saline, n = 5) vs. 13.0 +/- 0.3 mmHg (9 ng min(-1) ADM, n = 6), P < 0.05). 5. ADM (1 x 10(-11) to 1 x 10(-6) M) induced greater vasorelaxation of isolated preconstricted splenic resistance arteries than veins (maximal relaxation: 60 +/- 0.9 (artery, n = 9) vs. 43 +/- 1.7 % (vein, n = 8), P < 0.05). L-NMMA (10(-4) M) partially inhibited the ADM-induced relaxation in splenic arteries (maximal relaxation: 38 +/- 3 (ADM + L-NMMA, n = 5) vs. 60 +/- 3 % (ADM + D-NMMA, n = 5), P < 0.05). 6. It is concluded that ADM increases fluid efflux from the splenic vasculature by differentially reducing pre- vs. post-capillary resistance, thus increasing intrasplenic microvascular pressure.

Effect of 5α-pregnan-3α-ol-20-one on nitric oxide biosynthesis and plasma volume in rats

Plasma 5α-pregnan-3α-ol-20-one (pregnan) levels and nitric oxide (NO) biosynthesis increase during pregnancy. These factors have independently been implicated in the control of blood pressure and volume. We wished to determine whether pregnan might be responsible both for the increase in NO biosynthesis and for the increase in plasma volume observed during pregnancy. Virgin female Long-Evans rats were implanted with indwelling cannulas and maintained on a low nitrate/nitrite diet. After the rats recovered from surgery, 500 μg of pregnan or vehicle were given daily for 2 days. NO biosynthesis and plasma volume were measured in conscious animals before and after treatment. Pregnan caused a significant increase in NO biosynthesis (1.9 ± 0.8 μmol/24 h, n = 10) compared with the vehicle-treated control group (0.3 ± 0.4 μmol/24 h, n = 10, P < 0.05). Similarly, there was a significant increase in plasma volume in the pregnan-treated group (0.7 ± 0.2 ml/100 g, n = 11) compared with the vehicle-treated control group (0.2 ± 0.1 ml/100 g, n = 11, P < 0.05). These results confirm that pregnan can mimic pregnancy by its ability to increase both NO biosynthesis and plasma volume.

Splenic denervation worsens lipopolysaccharide-induced hypotension, hemoconcentration, and hypovolemia

During lipopolysaccharide (LPS)-induced endotoxemia, increased intrasplenic fluid efflux contributes to a reduction in plasma volume. We hypothesized that splenic sympathetic nerve activity (SSNA), which increases during endotoxemia, limits intrasplenic fluid efflux. We reasoned that splenic denervation would exaggerate LPS-induced intrasplenic fluid efflux and worsen the hypotension, hemoconcentration, and hypovolemia. A nonlethal dose of LPS (150 microg x kg(-1) x h(-1) for 18 h) was infused into conscious male rats bearing transit time flow probes on the splenic artery and vein. Fluid efflux was estimated from the difference in splenic arterial inflow and venous outflow (A-V). LPS significantly increased the (A-V) flow differential (fluid efflux) in intact rats (saline -0.01 +/- 0.02 ml/min, n = 8 vs. LPS +0.21 +/- 0.06 ml/min, n = 8); this was exaggerated in splenic denervated rats (saline -0.03 +/- 0.01 ml/min, n = 7 vs. LPS +0.41 +/- 0.08 ml/min, n = 8). Splenic denervation also exacerbated the LPS-induced hypotension, hemoconcentration, and hypovolemia (peak fall in mean arterial pressure: denervated 19 +/- 3 mmHg, n = 10 vs. intact 12 +/- 1 mmHg, n = 8; peak rise in hematocrit: denervated 6.7 +/- 0.3%, n = 8 vs. intact 5.0 +/- 0.3%, n = 8; decrease in plasma volume at 90-min post-LPS infusion: denervated 1.08 +/- 0.15 ml/100 g body wt, n = 7 vs. intact 0.54 +/- 0.08 ml/100 g body wt, n = 8). The exaggerated LPS-induced hypovolemia associated with splenic denervation was mirrored in the rise in plasma renin activity (90 min post-LPS: denervated 11.5 +/- 0.8 ng x ml(-1) x h(-1), n = 9 vs. intact 6.6 +/- 0.7 ng x ml(-1) x h(-1), n = 8). These results are consistent with our proposal that SSNA normally limits LPS-induced intrasplenic fluid efflux.

Effect of nitric oxide on basal and stretch-induced release of atrial natriuretic factor (ANF) from isolated perfused rat atria

We investigated the effect of the NO donor SNAP (6.7 nM) on basal and stretch-induced ANF release from isolated perfused rat atria. There was no significant difference in basal ANF secretion between the vehicle- and SNAP-infused atria (SNAP: 388+/-63 pg. 100 microl(-1), n = 13 vs. vehicle: 349+/-26 pg. 100 microl(-1), n = 5). Atrial distention caused an increase in ANF secretion in both the buffer- and SNAP-treated groups. SNAP greatly attenuated the stretch-induced increase in ANF (SNAP: 225+/-7 pg. 100 microl(-1), n = 5 vs. vehicle: 448+/-72 pg. 100 microl(-1), n = 13, P < 0.05). The compliance of atria treated with SNAP was lower than that of the vehicle-perfused atria (P < 0.05). Thus, although SNAP appeared to attenuate stretch-induced ANF secretion, there was in fact no significant difference in the ratio of Delta[ANF] to Deltaintraluminal volume (SNAP: 5.8+/-1.3 pg. 100 microl(-1). microl(-1) vs. vehicle: 8.2+/-1.4 pg. 100 microl(-1). microl(-1).). In conclusion, we found no evidence that NO alters the control of basal or stretch-induced ANF secretion. NO can however reduce ANF release by shifting the pressure-volume curve, so that a given increase in atrial pressure is associated with a smaller increase in intraluminal volume and reduced atrial distention.

Nitric oxide increases fluid extravasation from the splenic circulation of the rat

We hypothesized that nitric oxide (NO) contributes to intrasplenic fluid extravasation by inducing greater relaxation in splenic resistance arteries than veins such that intrasplenic microvascular pressure (P(C)) rises. Fluid efflux was estimated by measuring the difference between splenic blood inflow and outflow. Intrasplenic infusion of the NO donor S-nitroso-N-acetylpenicillamine (SNAP) (0.3 microg. 10 microl(-1). min(-1)) caused a significant increase in intrasplenic fluid efflux (baseline: 0.8 +/- 0.4 ml/min, n = 10 vs. peak rise during SNAP infusion: 1.3 +/- 0.4 ml/min, n = 10; P < 0.05). Intrasplenic P(C) was measured in the isolated, blood-perfused rat spleen. Intrasplenic infusion of SNAP (0.1 microg. 10 microl(-1). min(-1)) caused a significant increase in P(C) (saline: 10.9 +/- 0.2 mmHg, n = 3 vs. SNAP: 12.2 +/- 0.2 mmHg, n = 3; P < 0.05). Vasoreactivity of preconstricted splenic resistance vessels to sodium nitroprusside (SNP) (1 x 10(-12)-1 x 10(-4) M) and SNAP (1 x 10(-10)-3 x 10(-4) M) was investigated with the use of a wire myograph system. Significantly greater relaxation of arterioles than of venules occurred with both SNP (%maximal vasorelaxation: artery 96 +/- 2.3, n = 9 vs. vein 26 +/- 1.9, n = 10) and SNAP (%maximal vasorelaxation: artery 50 +/- 3.5, n = 11 vs. vein 32 +/- 1.7, n = 8). These results are consistent with our proposal that differential vasoreactivity of splenic resistance arteries and veins to NO elevates intrasplenic P(C) and increases fluid extravasation into the systemic lymphatic system.

Assessment of structured socioeconomic effects on health

Social epidemiologists study effects of variables such as education or income on health outcomes. Because other factors may influence both the exposure and the outcome, adjustments are commonly made in an effort to estimate the "independent" effect of exposure. The validity of common adjustment strategies when estimating the outcome distribution under hypothetical interventions of the exposure is potentially compromised by structured relations between covariates, observed and unobserved. These considerations of covariate structure may be particularly important for the study of "distal" socioeconomic factors that affect health through specified intermediates, therefore making standard adjustments in social epidemiology potentially problematic. Two related approaches have been proposed for defining and estimating causal effects in light of covariate structure: Robins' g-computation algorithm and Pearl's non-parametric structural equations. We review the conceptual foundation for these techniques, and provide a heuristic example using data from the National Longitudinal Mortality Study (NLMS) to demonstrate the extent to which selected causal effects (contrasts between hypothetical intervention regimens) are sensitive to structured relations among measured and unmeasured covariates, even in very simple systems.

Mutagenesis of the regulatory domain of phenylalanine hydroxylase

The regulatory domain of phenylalanine hydroxylase (PAH, EC ) consists of more than 100 amino acids at the N terminus, the removal of which significantly activates the enzyme. To study the regulatory properties controlled by the N terminus, a series of truncations and site-specific mutations were made in this region of rat PAH. These enzymes were expressed highly in Escherichia coli and purified through a pterin-conjugated Sepharose affinity column. The removal of the first 26 amino acids of the N terminus increased the activity by about 20-fold, but removal of the first 15 amino acids increased the activity by only 2-fold. Replacing serine-29 of rat PAH with cysteine from the same site of human PAH increased the activity by more than 4-fold. Mutation of serine to other amino acids with varying side chains: alanine, methionine, leucine, aspartic acid, asparagine, and arginine also resulted in significant activation, indicating a serine-specific inhibitory effect. But these site-specific mutants showed 30--40% lower activity when assayed with 6-methyl-5,6,7,8-tetrahydropterin. Stimulation of hydroxylase activity by preincubation of the enzyme with phenylalanine was inversely proportional to the activation state of all these mutants. Combined with recent crystal structures of PAH [Kobe, B. et al. (1999) Nat. Struct. Biol. 6, 442-448; and Erlandsen, H., Bjorgo, E., Flatmark, T. & Stevens, R. C. (2000) Biochemistry 39, 2208-2217], these data suggest that residues 16-26 have a controlling regulatory effect on the activity by interaction with the dihydroxypropyl side chain of (6R)-5,6,7,8-tetrahydrobiopterin. The serine/cysteine switch explains the difference in regulatory properties between human and rat PAH. The N terminus as a whole is important for maintaining rat PAH in an optimum catalytic conformation.

Effect of adrenomedullin on placental arteries in normal and preeclamptic pregnancies

Adrenomedullin is a potent vasodilatory peptide with plasma levels that increase during pregnancy. Although fetoplacental adrenomedullin levels are reported to increase in preeclampsia, maternal plasma levels may be elevated or decreased, or they may resemble those in normal pregnancy. In other hypertensive conditions, adrenomedullin increases. Therefore, we hypothesized that maternal plasma adrenomedullin levels would be higher in hypertensive pregnancies than in normotensive pregnancies and that the higher placental resistance found in preeclamptic pregnancies results from blunted activity of adrenomedullin on the vasculature. Adrenomedullin concentrations in plasma from women with normotensive pregnancies, gestational hypertension, and preeclampsia were determined by radioimmunoassay. Stem villous arteries from normotensive and preeclamptic pregnancies were dissected and mounted on a wire myograph system. Arteries were first preconstricted to 80% of their maximum constriction with U46619, a thromboxane A(2) mimetic, and exposed to cumulative doses of adrenomedullin (1x10(-)(9) to 3x10(-)(7) mol/L). Contrary to our hypothesis, there were no significant differences in maternal plasma adrenomedullin levels among patients with normal pregnancies, gestational hypertension, and preeclampsia. Adrenomedullin significantly relaxed arteries from both normal and preeclamptic placentas, but there was no significant difference between the 2 groups. During normal pregnancy, adrenomedullin may contribute to the low placental vascular resistance. This pathway appears to be intact in preeclampsia. We conclude that the increased placental vascular resistance observed in preeclampsia is due neither to reduced adrenomedullin secretion nor to an attenuated vascular responsiveness. Moreover, unlike other hypertensive disorders, there is no compensatory rise in circulating adrenomedullin levels.

Long-term results of intestinal transplantation for pseudo-obstruction in children

PURPOSE

The aim of this study was to determine long-term results of intestinal transplantation in children with pseudo-obstruction, particularly when stomach and colon are not part of the allograft.

METHODS

The authors conducted a case-record review of all children who underwent transplantation at our center for a primary diagnosis of pseudo-obstruction. Supplementary information was obtained from outpatient charts, computerized database, and telephone survey of parents.

RESULTS

Six small bowel and 3 liver-small bowel transplants were carried out in 8 patients between 1993 and 1999. Median follow-up is 40 months (range, 13 to 73 months). Median age at transplantation was 2.7 years (range, 0.7 to 12.8 years). Median graft survival in this series is 15 months (range, 1 day to 71 months). Stomach and colon were excluded from all allografts. Two children died 5 and 368 days after transplant and 2 graft losses occurred in 1 patient. Two children had lymphoproliferative disease; both are alive with functioning grafts. Five survivors with functioning grafts receive full enteral feedings at home. Four of the 5 have had ileostomies closed, and 3 have normal bowel movements.

CONCLUSIONS

Intestinal transplantation without stomach or colon provides children with chronic intestinal pseudo-obstruction with a good quality of life. The underlying disease poses special challenges in management.

Dr(a) (Cromer-related blood group antigen)-incompatible renal transplantation

BACKGROUND AND OBJECTIVES

Cromer system antigens, a series of blood group antigens of very high frequency, are not considered to be clinically significant in transfusion. In renal transplantation only the ABO blood group antigens are considered essential. The Drori blood group antigen is present in serum and has been found to reside on the renal tubular basement membrane and Bowman's capsule. The effect of anti-Dra on the renal parenchyma has not been evaluated.

MATERIALS AND METHODS

A unique case of renal transplantation of an incompatible Dr(a+) kidney to a Dr(a-) patient with anti-Dra in her serum is presented.

RESULTS

Graft function was immediately good. The titer of anti-Dra remained unchanged following transplantation.

CONCLUSION

The successful outcome of a case of a Drori (Dra)-incompatible kidney transplantation confirmed the lack of clinical significance of the anti-Dra relating to transplantation.

Timed-kill curves for Cryptococcus neoformans isolated from patients with AIDS

Infection with Cryptococcus neoformans is an increasing problem in immunocompromised patients, particularly those with acquired immune deficiency syndrome (AIDS). Amphotericin B and fluconazole are currently acceptable therapies for cryptococcal meningitis; however, their effects remain suboptimal and recurrence or treatment failure is still a problem. Antifungal susceptibility testing may be an important tool for guiding therapy, but for C. neoformans, a reliable method is still not available. This retrospective study evaluated minimal inhibitory concentration (MIC) for amphotericin B and fluconazole, and minimal fungicidal concentration (MFC) and timed-kill curves for amphotericin B against 16 clinical isolates of C. neoformans obtained from AIDS patients with cryptococcal meningitis. No correlation between clinical outcome and MIC was observed for amphotericin B. In selected cases, the MFC seemed to be a better predictor of outcome than MIC. In this study, amphotericin B timed-kill curves appeared to show a correlation with clinical outcome of the 16 patients with AIDS-associated cryptococcal meningitis. These in vitro tests must be further evaluated in prospective studies to confirm their potential usefulness for guiding cryptococcal meningitis therapy.

Vascular endothelial growth factor (VEGF) in breast cancer: comparison of plasma, serum, and tissue VEGF and microvessel density and effects of tamoxifen

The assessment of angiogenesis in breast cancer is of importance as a key indicator of survival and response to therapy. Circulating vascular endothelial growth factor (VEGF) measurements may provide a less subjective analysis than microvessel density (MVD) or immunohistochemical analysis of VEGF expression; however, most studies have used serum, which is now known to largely reflect platelet-derived VEGF concentrations. This study examined for the first time both plasma (VEGFp) and serum (VEGFs) VEGF concentrations in 201 blood samples from pre- and postmenopausal healthy controls and from patients with benign breast disease, localized breast cancer, breast cancer in remission, or metastatic breast cancer and related these to other clinicopathological markers. VEGFp but not VEGFs concentrations of patients with localized disease were significantly elevated compared with normal controls (P = 0.016). Patients with metastatic disease had higher VEGFp and VEGFs levels than normal controls (P < 0.001, P = 0.044 respectively), and higher VEGFp, but not VEGFs, than patients with benign disease (P = 0.009) and patients with localized disease (P = 0.004). However, the highest VEGFp and VEGFs concentrations were seen in patients in remission compared with normal controls (P < 0.001 and P = 0.008, respectively). VEGFp concentrations in patients in remission were also higher than in patients with benign disease (P = 0.01) or patients with localized disease (P = 0.005). Tamoxifen treatment was significantly associated with higher circulating and platelet-derived VEGF levels. Circulating VEGF did not correlate with any clinicopathological factor, including MVD or VEGF expression. VEGF expression was significantly correlated with estrogen receptor status and inversely correlated with tumor grade. MVD correlated with tumor size. Tamoxifen-induced increases in VEGF may be important in clinical prognosis or associated pathologies.

Noninvasive prediction of pulmonary artery pressure in patients with isolated ventricular septal defect

Management of patients with isolated ventricular septal defect (VSD) requires information regarding pulmonary artery pressure (PAP). The purpose of this study was to evaluate the individual predictive value of noninvasive methods for assessment of PAP and to determine if any combination of techniques significantly improved their predictive power. We reviewed the clinical history, electrocardiogram, and echocardiogram of 31 patients (age 1.9 +/- 1. 73 years) who underwent catheterization for isolated VSD. Noninvasive data were compared for patients with mean PAP <20 mmHg (group 1) and those with mean PAP > or =20 (group 2) at catheterization. Fourteen (45%) patients were in group 1 and 17 (55%) in group 2. Doppler estimation of VSD gradient, right ventricular hypertrophy by echocardiogram, interventricular septal orientation, and VSD size had predictive value for elevated mean PAP (p < 0.01). All patients (n = 6) with normal findings in all four variables had normal PAP. All patients (n = 12) with at least three of four abnormal findings had elevated PAP. Six patients in group 1 had at least one variable that incorrectly predicted high PAP, whereas 3 patients with normal findings on three of the four variables nevertheless had elevated PAP. No single noninvasive variable accurately predicted PAP in all cases. However, normal findings for all four significant variables did predict normal PAP and suggest that cardiac catheterization is unnecessary in that setting. However, any other combination of normal and abnormal findings for the four significant variables did not reliably predict PAP and such patients may require catheterization to directly measure PAP.

Effect of nitric oxide synthase inhibition on cardiovascular and hormonal regulation during pregnancy in the rat

Recent studies have shown that nitric oxide (NO) biosynthesis increases in pregnancy and that inhibition of nitric oxide synthase (NOS) induces some pathological processes characteristic of preeclampsia. The current project sought to study the effect of the NOS inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 10 microg x min(-1), sc for 7 days) on plasma volume, plasma atrial natriuretic factor (ANF), plasma endothelin-1 (ET), and plasma renin activity (PRA) during gestation in conscious rats. NOS inhibition caused mean arterial pressure to increase in both virgin and 21-day pregnant rats. Plasma volume fell in the pregnant rats [L-NAME, 4.5 +/- 0.3 mL x 100 g(-1) body wt. (n = 7) vs. D-NAME, 6.8 +/- 0.2 mL x 100 g(-1) body wt. (n = 10); P < 0.05] but not in the virgin rats [L-NAME, 4.3 +/- 0.1 mL x 100 g(-1) body wt. (n = 6) vs. D-NAME, 4.8 +/- 0.2 mL x 100 g(-1) body wt. (n = 8)]. There was no effect of NOS inhibition on plasma ANF levels or PRA in either the virgin or pregnant rats. However, L-NAME did decrease plasma ET levels in the pregnant rats [L-NAME, 19.6 +/- 1.6 pg x mL(-1) (n = 8) vs. D-NAME, 11.6 +/- 2.5 pg x mL(-1) (n = 9); P < 0.05]. Our results confirm that NO is involved in cardiovascular homeostasis in pregnancy; NOS inhibition selectively reduces plasma volume in pregnant rats, thus mimicking a major pathophysiological perturbation of preeclampsia. However, it does not induce the hormonal changes characteristic of preeclampsia, namely the decrease in PRA and increase in plasma ET and ANF levels.

Effect of nitric oxide synthase inhibition on cardiovascular and hormonal regulation during pregnancy in the rat

Recent studies have shown that nitric oxide (NO) biosynthesis increases in pregnancy and that inhibition of nitric oxide synthase (NOS) induces some pathological processes characteristic of preeclampsia. The current project sought to study the effect of the NOS inhibitor Nω-nitro-L-arginine methyl ester (L-NAME, 10 µg·min-1, sc for 7 days) on plasma volume, plasma atrial natriuretic factor (ANF), plasma endothelin-1 (ET), and plasma renin activity (PRA) during gestation in conscious rats. NOS inhibition caused mean arterial pressure to increase in both virgin and 21-day pregnant rats. Plasma volume fell in the pregnant rats [L-NAME, 4.5 ± 0.3 mL·100 g-1 body wt. (n = 7) vs. D-NAME, 6.8 ± 0.2 mL·100 g-1 body wt. (n = 10); P < 0.05] but not in the virgin rats [L-NAME, 4.3 ± 0.1 mL·100 g-1 body wt. (n = 6) vs. D-NAME, 4.8 ± 0.2 mL·100 g-1 body wt. (n = 8)]. There was no effect of NOS inhibition on plasma ANF levels or PRA in either the virgin or pregnant rats. However, L-NAME did decrease plasma ET levels in the pregnant rats [L-NAME, 19.6 ± 1.6 pg·mL-1 (n = 8) vs. D-NAME, 11.6 ± 2.5 pg·mL-1 (n = 9); P < 0.05]. Our results confirm that NO is involved in cardiovascular homeostasis in pregnancy; NOS inhibition selectively reduces plasma volume in pregnant rats, thus mimicking a major pathophysiological perturbation of preeclampsia. However, it does not induce the hormonal changes characteristic of preeclampsia, namely the decrease in PRA and increase in plasma ET and ANF levels.

Key words: plasma volume, preeclampsia, endothelin, atrial natriuretic factor, plasma renin activity.