Contextual factors influencing the implementation of the obstetrics hemorrhage initiative in Florida.

OBJECTIVE: The purpose of this study was to explore the multilevel contextual factors that influenced the implementation of the Obstetric Hemorrhage Initiative (OHI) among hospitals in Florida. STUDY DESIGN: A qualitative evaluation was conducted via in-depth interviews with multidisciplinary hospital staff (n=50) across 12 hospitals. Interviews were guided by the Consolidated Framework for Implementation Research and analyzed in Atlas.ti using rigorous qualitative analysis procedures. RESULT: Factors influencing OHI implementation were present across process (leadership engagement; engaging people; planning; reflecting), inner setting (for example, knowledge/beliefs; resources; communication; culture) and outer setting (for example, cosmopolitanism) levels. Moreover, factors interacted across levels and were not mutually exclusive. Leadership and staff buy-in emerged as important components influencing OHI implementation across disciplines. CONCLUSION: Key contextual factors found to influence OHI implementation experiences can be useful in informing future quality improvement interventions given the institutional and provider-level behavioral changes needed to account for evolving the best practices in perinatology.

Prenatal diagnosis of sub-microscopic partial trisomy 10q using chromosomal microarray analysis in a phenotypically abnormal fetus with normal karyotype.

Partial trisomy of the 10q region was originally reported in 1979 [1]. For 25 years, the diagnosis was made microscopically based on large, visible insertions in the region identified by karyotype analysis. Previous case reports have included both unbalanced translocations and large duplications/insertions in the 10q region [2]. Probands with partial trisomy 10q syndrome often have an abnormal phenotype that may include developmental delay [3-5], craniofacial abnormalities [3, 5], talipes (clubfoot) [2], microcephaly [2-4], or congenital heart disease [2-6]. Prenatal diagnoses by karyotype have been made following ultrasound diagnosis of sacrococcygeal teratoma [7], renal pyelectasis [3, 8-10], and other fetal abnormalities [4]. In this case, we report the first prenatal diagnosis of partial trisomy 10q (10q22.3-10q23.2) with a normal karyotype and an abnormal chromosomal microarray analysis (CMA). This is the smallest copy number variant (CNV) (7.5 Mb) in the 10q22.3-10q23.2 regions yet reported.

Clinical value of postnatal autopsy and genetics consultation in fetal death.

The aim of the present study was to investigate the clinical use of postnatal autopsy and genetics consultation in cases of fetal death in a teaching hospital. A retrospective analysis of medical records including pathology and genetics reports was performed in all cases of fetal death in which a woman delivered at Ben Taub General Hospital, Houston, Texas over a 2-year period. Cases were excluded when gestational age of the fetus was less than 20 weeks. Fetuses were only included when the 1- and 5-min Apgar scores were 0 and 0, respectively. There were 139 fetal deaths and 12,209 live born infants during the study period (stillbirth rate 1.125%). Although pathology services were used in 96.2%, a genetics consultation was obtained in only 12% of cases. Fetal autopsy provided a certain cause of fetal death in 19.4%, a probable cause for death in 36.3%, and was inconclusive in 44.3%. Among the cases in which a genetics consultation was obtained, a certain and probable cause for fetal death was found in 20% and 20% of cases, respectively. The utilization of genetics consultation was found to be independent of multiple clinical variables examined including ultrasound data, identification of maceration, and training level of resident. Our data show a frequent use of pathologic examination in cases of fetal death and an infrequent use of genetics consultation services. The request for genetics consultation seemed to have been made at random.

Angiotensinogen and endothelial nitric oxide synthase gene polymorphisms among Hispanic patients with preeclampsia.

OBJECTIVE: We sought to establish an association between preeclampsia and the methionine to threonine polymorphism at amino acid residue 235 (Met235Thr) in angiotensinogen in a Hispanic population. We looked for a relationship between this allele and the allele in the endothelial nitric oxide synthase gene (NOS3) that produces the A form (NOS3*A) with respect to preeclampsia. STUDY DESIGN: Clinical data were collected from 87 patients with preeclampsia and 53 control subjects. Patients and controls were genotyped for the angiotensinogen polymorphism allele (AGT*T) and the NOS3*A polymorphism. We then compared patients with preeclampsia and control subjects and investigated disease severity within the preeclampsia group as a function of genotype. RESULTS: The AGT*T allelic frequencies among patients with preeclampsia and control subjects were 0.72 and 0.70, respectively (P =.84). The blood pressure of patients with an AGT*T allele who also carried a NOS3*A allele was higher at earlier gestational ages (r = -0.052; P =.02). Analysis suggested that the systolic blood pressure differences were due to gestational age effects and the presence of a NOS3*A allele (P <.10). CONCLUSION: The AGT*T allele was not associated with the development of preeclampsia. Independently of the presence of an AGT*T allele, the NOS3*A allele was associated with a higher blood pressure at an earlier gestational age.

Influence of the angiotensinogen gene on the ovulatory capacity of mice.

OBJECTIVE: The tissue-bound ovarian renin-angiotensin system (OVRAS) is critically involved in ovulation in humans and rodents. Mice with disruption and overexpression of the angiotensinogen gene (Agt) have been previously generated. We investigated the influence of varying Agt gene expression on the ovulatory capacity and early embryonic development in mice. DESIGN: Observational study of genetically altered mice and their response to a superovulation protocol. SETTING: Academic research institution. ANIMAL(S): Mice with varying copy numbers of Agt (one copy: n = 48; two copies: n = 51; three copies: n = 20; four copies: n = 24). INTERVENTION(S): Superovulation protocol, oocyte culture. MAIN OUTCOME MEASURE(S): Number of oocytes harvested, early embryonic development of zygotes, evaluation of ovarian histology, serum estradiol measurements. RESULT(S): The mean number of oocytes harvested was greatest in wild-type mice (two copies of Agt, 39.9 +/- 14) with a reduction of ovulatory capacity in mice overexpressing Agt (three copies [34.8 +/- 11.7] and four copies [31.2 +/- 12.4], P =.026). Mice with one copy of Agt showed a slight decrease of ovulatory capacity compared to wild-type mice (35.8 +/- 15.2, P =.29). Ovarian histology, serum estradiol levels, and early embryonic development were independent of the Agt genotype. CONCLUSION(S): Overexpression of Agt was associated with reduced ovulatory capacity, but with none of the other parameters that were evaluated. These findings support an important role of the ovarian renin-angiotensin system in the process of follicular rupture.

Analysis of guanidinoacetate and creatine by isotope dilution electrospray tandem mass spectrometry.

Guanidinoacetate methyltransferase (GAMT) deficiency is a disorder of creatine metabolism characterized by low plasma creatine concentrations in combination with elevated guanidinoacetate (GAA) concentrations. Although rare, GAMT deficiency has been identified in children with seizures, extrapyramidal movements, developmental delay, myopathies and behavioral abnormalities. Treatment with creatine monohydrate has been proven to be effective. We describe an isotope dilution electrospray tandem mass spectrometry (ES-MS/MS) assay for the simultaneous determination of plasma GAA and creatine using multiple reaction monitoring (MRM), d(3)-creatine as the internal standard and derivatization of GAA and creatine as butyl-esters. We analysed plasma of 16 healthy adults and 20 healthy children as well as three affected children. Plasma GAA concentrations were 5.02+/-1.84 micromol/l (mean+/-S.D.) in adults, 3.91+/-0.76 micromol/l in children age 5-10 years and 11.57, 15.16, 14.36 micromol/l in children with GAMT deficiency. Plasma creatine concentrations were 34.7+/-15.25 micromol/l in adults, 58.96+/-22.30 micromol/l in children and 5.37, 8.15, 403.5 micromol/l in two untreated children and one treated child with GAMT deficiency, respectively. GAA can also be reliably measured from filter cards, which is sufficient to make the correct diagnosis while creatine is consistently falsely elevated probably secondary to liberation of red cell creatine. In nine healthy newborn infants, GAA concentrations from filter cards were 4.83+/-1.43 and 5.04+/-1.84 micromol/l in 16 healthy adults. We conclude that isotope dilution ES-MS/MS is ideal for rapid high-throughput diagnosis of GAMT deficiency both from plasma and filter paper cards. Using this technique neonatal screening is feasible for this treatable inborn error of creatine metabolism.

Placental expression and serum levels of cytokeratin-18 are increased in women with preeclampsia.

OBJECTIVE: To evaluate placental expression and serum cytokeratin-18 in women with preeclampsia. METHODS: Serum cytokeratin-18 was evaluated in 44 women with preeclampsia and 44 healthy pregnant women using an immunoradiometric assay. Placental expression of cytokeratin-18 was investigated in specimens from 23 women with preeclampsia and 20 healthy pregnant women by immunohistochemistry. RESULTS: Median serum cytokeratin-18 in women with preeclampsia and healthy pregnant women was 106.7 and 76.0 U/L, respectively (P =.02). Among women with preeclampsia, serum cytokeratin-18 was significantly associated with severity of disease (P =.001) and showed a sensitivity (standard error) and specificity (standard error) of 85% (7%) and 65% (12%), respectively. In placental specimens, the cytoplasm of the syncytiotrophoblast stained positive for cytokeratin-18 with strong and widespread staining in 83% and 45% of placental specimens of women with preeclampsia and healthy pregnant women, respectively (P =.01). CONCLUSION: Elevated serum cytokeratin-18 values are associated with disease severity in women with preeclampsia. Our data provide additional evidence that the placenta might be the source of the elevated serum cytokeratin-18 values in women with preeclampsia.

Polymorphisms within the interleukin-1 beta gene cluster and preeclampsia.

OBJECTIVE: To identify associations between polymorphisms within the interleukin-1 beta gene cluster, all of which increase protein expression, and preeclampsia. METHODS: We genotyped a Hispanic population (69 women with preeclampsia and 47 controls) for two polymorphisms of the interleukin-1 beta gene (promoter region and exon 5) and one polymorphism of the interleukin-1 receptor antagonist gene in intron 2. Clinical data were collected from medical records. Values are given as means or medians. Statistical power to identify a difference in occurrence of interleukin-1 beta promoter, interleukin-1 beta exon 5, and interleukin-1 receptor antagonist gene polymorphisms in women with preeclampsia compared with controls was 21%, 15.9%, and 30.9%, respectively. RESULTS: We found no association between any single polymorphism and occurrence of preeclampsia. Among women with preeclampsia, those with polymorphism of interleukin-1 receptor antagonist gene had higher mean systolic blood pressure (BP) at admission (178 +/- 33.4 versus 159 +/- 19.5 mmHg, P =.039). When all three polymorphisms combined were evaluated, women with preeclampsia and at least three mutant alleles (n = 8) had higher mean systolic BP at admission (182 +/- 30 versus 160 +/- 20.5 mmHg, P =.009) and increased alanine aminotransferase (67 [10--1024] versus 20 [3--407] IU/L, P =.04) and aspartate aminotransferase (119 [25--2239] versus 24 [4--489] IU/L, P =.002). At admission, BP in controls was independent of any polymorphism identified. CONCLUSION: Although the power of this study was limited, our data do not support a role for polymorphisms of the interleukin-1 beta and interleukin-1 receptor antagonist genes in the pathogenesis of preeclampsia among Hispanic women. Our findings do suggest that polymorphisms within the gene cluster might influence severity of preeclampsia.

Perinatal development of endothelial nitric oxide synthase-deficient mice.

The purpose of this study was to evaluate the influence of endothelial nitric oxide synthase (eNOS) deficiency on fetal growth, perinatal survival, and limb development in a mouse model with a targeted mutagenesis of the Nos3 gene. Wild-type (Nos3+/+) and eNOS-deficient fetuses (Nos3-/-) were evaluated on Gestational Day (E)15 and E17, and newborn pups were observed on Day 1 of life (D1). The average term duration of pregnancy was 19 days. For the evaluation of postnatal development, a breeding scheme consisting of Nos3+/- x Nos3+/- and Nos3-/- x Nos3-/- mice was established, and offspring were observed for 3 wk. Southern blotting was used for genotyping. No significant differences in fetal weight, crown-rump lengths (CRL), and placental weight were seen between Nos3+/+ and Nos3-/- fetuses on E15. By E17, Nos3-/- fetuses showed significantly reduced fetal weights, CRL, and placental weights. This difference in body weight was also seen throughout the whole postnatal period. In pregnancies of Nos3-/- females, the average number of pups alive on D1 was significantly decreased compared to either E15 or E17. Placental histology revealed no abnormalities. On E15, E17, and D1, Nos3(-/-) fetuses demonstrated focal acute hemorrhages in the distal limbs in 0%, 2.6%, and 5.7%, respectively, of all mutant mice studied on the respective days. Bone measurements showed significantly shorter bones in the peripheral digits of hindpaws of Nos3-/- newborns. We conclude mice deficient for eNOS show characteristically abnormal prenatal and postnatal development including fetal growth restriction, reduced survival, and an increased rate of limb abnormalities. The development of this characteristic phenotype of eNOS-deficient mice dates back to the prenatal development during the late third trimester of pregnancy.

Endothelial-derived nitric oxide and angiotensinogen: blood pressure and metabolism during mouse pregnancy.

The regulation of blood pressure during pregnancy involves several biological pathways. Candidate genes implicated in hypertensive diseases during pregnancy include those of the renin-angiotensin system and nitric oxide synthase (NOS). We evaluated blood pressure and metabolic characteristics during pregnancy in mutant mice. These included mice with a null mutation in the endothelial NOS (eNOS) gene (Nos3(-/-)), four copies of the angiotensinogen gene (Agt(2/2)), and mutations in both genes [four copies of Agt and heterozygous deficient for eNOS (Agt(2/2)Nos3(+/-)), four copies of Agt and homozygous deficient for eNOS (Agt(2/2)Nos3(-/-))]. Blood pressure measurements of nulliparous females from mutant strains were compared with two common laboratory strains C57Bl6/J and SV129 throughout their first pregnancy. Serum and urine analysis for the evaluation of renal and liver physiology were measured in the prepregnant state and during the third trimester of pregnancy. Throughout pregnancy blood pressures in all mutant strains were higher compared with controls. Agt(2/2)Nos3(-/-) showed the highest blood pressures and C57Bl6/J the lowest. Control mice, but not mutant mice, showed a second trimester decline in blood pressure. No immediate differences were noted regarding behavioral characteristics, renal or liver function parameters. Mice deficient for eNOS, mice with overexpression of Agt, and mice with mutations in both genes demonstrated higher blood pressure throughout pregnancy. There was no evidence of renal dysfunction, liver dysfunction, or hemolysis among any of the strains studied. We conclude that Nos3 and Agt are important genes in the regulation of blood pressure during pregnancy.

An endothelial nitric oxide synthase gene polymorphism is associated with preeclampsia.

OBJECTIVE: We sought to test the hypothesis that a polymorphism of the endothelial nitric oxide synthase gene (NOS3) is associated with preeclampsia. METHODS: We collected and performed polymerase chain reaction (PCR) on genomic DNA from pregnant patients with and without preeclampsia. Patient history and clinical course were evaluated. MAIN OUTCOME MEASURE(S): Frequency of the intron 4 polymorphism of NOS3 (designated allele A) among patients with preeclampsia compared with controls. Clinical features of patients with preeclampsia and the A allele compared with those patients with preeclampsia who did not have the A allele. RESULTS: The frequency of the A allele was 0.10 among controls versus 0.39 among patients with preeclampsia (p < 0.01). The odds ratio of developing preeclampsia when at least one A allele was present was 6.5 [95% confidence interval (CI): 2.1-19.7]. After adjusting for ethnic variation, the odds ratio increased to 7.2 (95% CI: 2.0-25.5). Among patients with preeclampsia, systolic blood pressure at the time of admission was higher for patients with at least one A allele compared with patients homozygous for the B allele (168 versus 156 mm Hg; p = 0.03), independent of gestational age (p = 0.01). CONCLUSION: These data provide evidence for an association between NOS3 and preeclampsia. In defined ethnic groups, this NOS3 may offer predictive information regarding the subsequent development of preeclampsia and its clinical course.

Placental expression and serum concentrations of cytokeratin 19 in preeclampsia.

OBJECTIVE: To evaluate cytokeratin 19 as a serum marker of preeclampsia. METHODS: Serum cytokeratin 19 levels were measured in 46 women with preeclampsia and 46 controls matched for gestational age and parity, using an immunoradiometric assay. Cytokeratin 19 was evaluated immunohistochemically in placental specimens from 28 healthy pregnant women and 24 women with preeclampsia. RESULTS: Cytokeratin 19 was identified in the syncytiotrophoblast in 13 (46. 4%) of 28 and 23 (95.8%) of 24 placental specimens from controls and women with preeclampsia, respectively (P =.03). Median serum levels of cytokeratin 19 in controls and women with preeclampsia were 1.7 (range 0.3-4.7) microg/mL and 2.7 (range 0.8-8.2) microg/mL, respectively (P <.001). Cytokeratin 19 significantly influenced the odds of presenting with preeclampsia (P <.001) and the odds of developing severe disease (P <.001). Serum cytokeratin 19 correlated inversely with fetal birth weight (Kendall tau-b correlation coefficient = -0.2, P =.007). Compared with healthy pregnant women, women with severe preeclampsia had significantly higher and more rapidly increasing cytokeratin 19 serum levels throughout the third trimester (P <.001). CONCLUSION: Placental stimulation of cytokeratin 19, and release of it into maternal circulation, seem to be a feature of preeclampsia. Correlations with clinical characteristics suggest that cytokeratin 19 is a marker of disease severity.

Genetic contributions of the endothelial nitric oxide synthase gene to ovulation and menopause in a mouse model.

OBJECTIVE: To investigate the influence of the endothelial nitric oxide synthase gene (Nos3) on ovulatory capacity and reproductive senescence. DESIGN: Prospective, controlled study. SETTING: Academic research institution. SUBJECT(S): Laboratory mice with targeted mutagenesis of Nos3. INTERVENTION(S): Hyperstimulation protocol, oocyte culture, and ovarian histology using wild-type (Nos3(+/+); n = 20), heterozygous (Nos3(+/m); n = 39), and homozygous deficient (Nos3(m/m); n = 11) female mice; observation of reproductive outcomes. MAIN OUTCOME MEASURE(S): Number and survival of oocytes; onset of menarche and menopause. RESULT(S): The mean number of superovulated oocytes (18 +/- 36 vs. 41 +/- 4) and the 48-hour overall survival rate of embryos (65% vs. 81%) were significantly reduced for Nos3(m/m) female mice compared with Nos3(+/+) female mice. Nos3(m/m) females showed a significantly reduced number and size of antral follicles and corpora lutea compared with wild-type controls. Compared with Nos3(+/m) x Nos3(+/m) breedings, Nos3(m/m) x Nos3(m/m) breedings showed a higher female age at first litter (76.2 +/- 10.3 vs. 107.8 +/- 26.6 days), fewer litters (10.5 +/- 3.6 vs. 7. 8 +/- 4.2), and a lower female age at reproductive senescence (400.2 +/- 64.5 vs. 332.1 +/- 27.4 days), respectively. CONCLUSION(S): Our data suggest that Nos3 deficiency is associated with reduced ovulatory capacity and impaired early embryonic viability and that it influences the onset of menarche and menopause.

Nitric oxide release and contractile properties of skeletal muscles from mice deficient in type III NOS.

Skeletal muscle constitutively expresses both the type I (neuronal) and type III (endothelial) isoforms of nitric oxide synthase (NOS). We tested the functional importance of type III NOS using skeletal muscles with similar levels of type III NOS expression (diaphragm and soleus) from wild-type, heterozygous, and type III NOS-deficient littermate mice. Muscles were incubated at 37 degrees C in Krebs-Ringer solution. NO accumulation in the medium was measured by chemiluminescence; force-frequency and fatigue characteristics were measured using direct electrical stimulation. Diaphragm and soleus released NO at similar rates during passive incubation; these rates increased during active contraction. NO release by type III NOS-deficient muscle was not different from that of wild-type muscle under any condition tested. Force-frequency and fatigue characteristics also were unaffected by genotype. Because type III NOS deficiency did not alter function, we conclude that NO effects previously observed in wild-type muscle are likely to be mediated by type I NOS.

Genetic control of fertility and embryonic waste in the mouse: A rolefor angiotensinogen.

The purpose of this study was to evaluate the impact of angiotensinogen gene (Agt) deficiency on reproductive fitness in a rodent model. Mice with 0 (Agt(-/-)), 1 (Agt(-/+)), and 2 (Agt(+/+)) copies of Agt were bred according to the following schemes: 1) Agt(-/-) x Agt(-/-), 2) Agt(-/+) x Agt(-/+), 3) Agt(+/+) x Agt(+/+), and 4) Agt(+/+) female symbol x Agt(-/+) male symbol. There were 4 breeding pairs per scheme. Breedings were time mated. Mice and litters were weighed daily. Southern blotting was used for genotyping. We found that Agt(-/-) breeding pairs had fewer litters (2 [range 1-2] vs. 4 [range 3-5]; P = 0.01), fewer pups per litter (4 [range 1-7] vs. 6 [range 1-10]; P = 0.006), and longer interpregnancy intervals (43 days [range 31-44] vs. 35.5 days [range 22-58]; P = 0.04) compared to wild-type controls. The ratio of postcoital plugs to subsequent litters was 4.0 and 1.2 for Agt(-/-) and Agt(+/+) breedings, respectively (P = 0.03). Median maternal weights during all trimesters of pregnancy were significantly lower for Agt-deficient mice compared to wild-type controls. Among Agt(-/+) x Agt(-/+) breedings, the proportions of Agt(+/+) (n = 17), Agt(-/+) (n = 38), and Agt(-/-) (n = 4) offspring differed significantly from the expected 1:2:1 Mendelian inheritance pattern (P = 0.03). Neonatal survival among the offspring derived from the Agt(-/-) x Agt(-/-) breeding scheme was significantly reduced (P = 0. 001). We conclude that Agt deficiency is associated with an in utero lethal effect, decreased fertility, and impaired neonatal survival.

Molecular and clinical characterization of a patient with duplication of 1p36.3 and metopic synostosis.

Chromosome 1p duplications are rare. There have been only 11 reported cases of isolated 1p duplication, all of which were proximal, interstitial duplications. We present a patient with a terminal duplication of 1p (1p36.3). To our knowledge, this is the first such reported case. Our patient presented with metopic synostosis, rectal stenosis, atrial septal defect, and mildly delayed gross motor development. Molecular characterization using microsatellite marker analysis and fluorescence in situ hybridization (FISH) revealed an area of duplication between p58 and D1S2893, approximately 13 cM in size. We compare our patient's clinical findings with the clinical phenotype found in patients with the corresponding deletion of 1p36.3 and discuss the role of gene dosage in other deletion/duplication syndromes.

Limb reduction defects in endothelial nitric oxide synthase-deficient mice.

Nitric oxide synthases are a family of enzymes capable of converting L-arginine to L-citrulline with the subsequent release of nitric oxide (NO). NO has been shown to have multiple biologic effects depending on the isoform responsible for its production and its tissue of origin. Murine endothelial nitric oxide synthase (eNOS) is encoded by Nos3, located on mouse chromosome 5. NO produced from this isoform causes vascular smooth muscle relaxation. Other investigators have shown that the administration of nonspecific inhibitors of nitric oxide synthases to pregnant rats induces limb reduction defects. However, mice deficient in Nos3 have not previously been noted to show such abnormalities. To explore the importance of eNOS during development, we produced mice deficient in eNOS using embryonic stem cell technology. Limb reduction defects were seen in approximately 10% of the null animals. We also observed increased neonatal loss of homozygous deficient pups. One functional copy of Nos3 eliminates the risk of limb defects observed in our mouse strain. These findings have implications for understanding genetic predisposition to sporadic limb reduction defects in humans.

Combined malonic and methylmalonic aciduria with normal malonyl-coenzyme A decarboxylase activity: a case supporting multiple aetiologies.

We identified a patient who excreted large amounts of methylmalonic acid and malonic acid. In contrast to other patients who have been described with combined methylmalonic and malonic aciduria, our patient excreted much larger amounts of methylmalonic acid than malonic acid. Since most previous patients with this biochemical phenotype have been reported to have deficiency of malonyl-CoA decarboxylase, we assayed malonyl-CoA decarboxylase activity in skin fibroblasts derived from our patient and found the enzyme activity to be normal. We examined four isocaloric (2000 kcal/day) dietary regimes administered serially over a period of 12 days with 3 days devoted to each dietary regimen. These diets were high in carbohydrate, fat or protein, or enriched with medium-chain triglycerides. Diet-induced changes in malonic and methylmalonic acid excretion became evident 24-36 h after initiating a new diet. Total excretion of malonic and methylmalonic acid was greater (p < 0.01) during a high-protein diet than during a high-carbohydrate or high-fat diet. A high-carbohydrate, low-protein diet was associated with the lowest levels of malonic and methylmalonic acid excretion. Perturbations in these metabolites were most marked at night. On all dietary regimes, our patient excreted 3-10 times more methylmalonic acid than malonic acid, a reversal of the ratios reported in patients with malonyl-CoA decarboxylase deficiency. Our data support a previous observation that combined malonic and methylmalonic aciduria has aetiologies other than malonyl-CoA decarboxylase deficiency. The malonic acid to methylmalonic acid ratio in response to dietary intervention may be useful in identifying a subgroup of patients with normal enzyme activity.

Regionalization of endothelium-dependent relaxation in the thoracic aorta of pregnant and nonpregnant guinea pigs.

Regional variation in the response of the thoracic aorta to contractile agonists has previously been demonstrated. Since the net contractile response reflects the interaction between smooth muscle activation and the release of endothelial substances, we hypothesize that agonist-stimulated release of endothelium-derived nitric oxide (NO) also varies along the length of the thoracic aorta. The distribution of thoracic aorta estrogen receptors is also regionalized. Since pregnancy augments the release of endothelium-derived NO by acetylcholine (ACh) in some arterial beds, we further hypothesize that pregnancy enhances the stimulated release of NO from the thoracic aorta. Aortae were removed from nonpregnant and near term pregnant guinea pigs and cut into ring segments numbered sequentially proximal to distal. The rings were suspended at their optimal passive tension and submaximally contracted with prostaglandin F2 alpha. Endothelium-derived NO-dependent relaxation to ACh increased moving proximal to distal along the aorta independent of pregnancy and ACh relaxation was unaffected by pretreatment with physostigmine to inhibit cholinesterase. The magnitude of the relaxation to carbachol among the different segments was similar to ACh. Pregnancy decreased the ED50 for ACh of segments from the middle and distal segments of the thoracic aorta. Relaxation to the NO donor sodium nitroprusside and the nonreceptor-mediated endothelium-dependent relaxing agent A23187 was uniform along the length of the aorta and independent of pregnancy. These experiments demonstrate regional variation in the stimulated release of endothelium-derived NO in the guinea pig thoracic aorta which is increased by pregnancy.