Gum arabic glycoprotein contains glycomodules of both extensin and arabinogalactan-glycoproteins.

Gum arabic glycoprotein (GAGP) is a large molecular weight, hydroxyproline-rich arabinogalactan-protein (AGP) component of gum arabic. GAGP has a simple, highly biased amino acid composition indicating a repetitive polypeptide backbone. Previous work (Qi, W., Fong, C., Lamport, D.T.A., 1991. Plant Physiology 96, 848), suggested small (approximately 11 residue) repetitive peptide motifs each with three Hyp-arabinoside attachment sites and a single Hyp-arabinogalactan polysaccharide attachment site. We tested that hypothesis by sequence analysis of the GAGP polypeptide after HF-deglycosylation. A family of closely related peptides confirmed the presence of a repetitive 19-residue consensus motif. However, the motif: Ser-Hyp-Hyp-Hyp-Thr-Leu-Ser-Hyp-Ser- Hyp-Thr-Hyp-Thr-Hyp-Hyp-Leu-Gly-Pro-His, was about twice the size anticipated. Thus, judging by Hyp-glycoside profiles of GAGP, the consensus motif contained six Hyp-arabinosides rather than three and two Hyp-polysaccharides rather than one. We inferred the glycosylation sites based on the Hyp contiguity hypothesis which predicts arabinosides on contiguous Hyp residues and arabinogalactan polysaccharides on clustered non-contiguous Hyp residues, i.e. the GAGP motif would consist of arabinosylated contiguous Hyp blocks flanking two central Hyp-polysaccharides. We predict this rigidifies the glycoprotein, enhances the overall symmetry of the glycopeptide motif, and may explain some of the remarkable properties of gum arabic.

Effect of nitric oxide and carbon monoxide on uterine contractility during human and rat pregnancy.

OBJECTIVE: We sought to study the effects of authentic nitric oxide and carbon monoxide on the contractile activity of pregnant human and rat myometrium. STUDY DESIGN: Strips were prepared from uterine biopsy specimens of 10 pregnant, nonlaboring women at term gestation undergoing cesarean delivery. In addition, rings were prepared from the uteri of pregnant rats at midterm (day 14) and at term (day 22) gestation (n = 10-12). The tissues were mounted in organ chambers filled with Krebs-Henseleit solution continuously aerated with 5% carbon dioxide in air (37 degrees C, pH approximately 7.4) for isometric tension recording. The effects of nitric oxide and carbon monoxide gases on spontaneous contractile activity were studied. Responses to hemin (hemoxygenase substrate), which produces endogenous carbon monoxide, were also examined. Responses to nitric oxide and carbon monoxide were also studied in aortic and tail artery rings from pregnant rats after contraction with phenylephrine. RESULTS: Nitric oxide significantly inhibited contractility of human myometrium at term (area under the concentration-response curve, 145.36 +/- 30.02 vs 40.56 +/- 22.81 in controls; P <.05) and rat myometrium at midterm gestation (264.23 +/- 47.86 vs 121.82 +/- 23.50; P <.05) but not at term. No statistically significant inhibition was induced in human or rat myometrium by carbon monoxide, whereas hemin significantly attenuated contractility in human myometrium at term and in rat myometrium at midterm gestation (P <. 05). Nitric oxide, carbon monoxide, and hemin relaxed aortic and tail artery rings. CONCLUSIONS: Authentic nitric oxide inhibits rat uterine contractile activity at midterm gestation but not at term. However, nitric oxide inhibits human myometrium activity at term. Authentic carbon monoxide does not appear to modulate uterine contractility, whereas hemin may have some inhibitory properties.

Electrolytic generation of oxygen partially explains electrical enhancement of tobramycin efficacy against Pseudomonas aeruginosa biofilm.

The role of electrolysis products, including protons, hydroxyl ions, reactive oxygen intermediates, oxygen, hydrogen, and heat, in mediating electrical enhancement of killing of Pseudomonas aeruginosa biofilms by tobramycin (the bioelectric effect) was investigated. The log reduction in biofilm viable cell numbers compared to the numbers for the untreated positive control effected by antibiotic increased from 2.88 in the absence of electric current to 5.58 in the presence of electric current. No enhancement of antibiotic efficacy was observed when the buffer composition was changed to simulate the reduced pH that prevails during electrolysis. Neither did stabilization of the pH during electrical treatment by increasing the buffer strength eliminate the bioelectric effect. The temperature increase measured in our experiments, less than 0.2 degree C, was far too small to account for the greatly enhanced antibiotic efficacy. The addition of sodium thiosulfate, an agent capable of rapidly neutralizing reactive oxygen intermediates, did not abolish electrical enhancement of killing. The bioelectric effect persisted when all of the ionic constituents of the medium except the two phosphate buffer components were omitted. This renders the possibility of electrochemical generation of an inhibitory ion, such as nitrite from nitrate, an unlikely explanation for electrical enhancement. The one plausible explanation for the bioelectric effect revealed by this study was the increased delivery of oxygen to the biofilm due to electrolysis. When gaseous oxygen was bubbled into the treatment chamber during exposure to tobramycin (without electric current), a 1.8-log enhancement of killing resulted. The enhancement of antibiotic killing by oxygen was not due simply to physical disturbances caused by sparging the gas because similar delivery of gaseous hydrogen caused no enhancement whatsoever.

Employment and health-risk behaviors among pregnant adolescents.

STUDY OBJECTIVE: To compare health-risk behaviors, maternal, and neonatal outcomes of pregnant adolescents less than 18 years old who reported employment more than 15 hours per week with those who did not report working. We hypothesized that working teens compared with nonworking adolescents would report higher rates of health-risk behaviors. METHODS: A structured interview was conducted at the first prenatal visit and the medical chart was reviewed to extract pregnancy (pregnancy-induced hypertension, preterm labor with hospitalization, and preterm delivery) and neonatal outcomes (low birthweight, small for gestational age, and admission to the neonatal intensive care unit). The study was conducted at an outpatient maternal and child health clinic at a university teaching hospital. A total of 384 white (n=111), African American (n=151), and Mexican American (n=99) adolescents, aged 12 to 17 years, who initiated care between January 2, 1992, and December 31, 1994, and delivered an infant at our institution were consecutively sampled. A structured interview assessed various health-risk behaviors including age at first intercourse, substance use (tobacco, alcohol, and other illicit drug use), and number of sexual partners. Medical records were reviewed to obtain information on pregnancy complications (pregnancy-induced hypertension, preterm delivery, and preterm labor with hospitalization) and negative birth outcomes (infant birthweight and neonatal intensive care admission). RESULTS: Controlling for chronological age, logistic regression analyses found that adolescents reporting employment at their first prenatal visit (n=40) compared with those not employed at this visit (n=331) were more likely to be characterized by school enrollment, higher economic status, partner employment, partner alcohol use, and a longer relationship with the father of their baby. Multivariate logistic regression found that employed females were 4.6 times more likely to deliver a small-for-gestational-age infant. CONCLUSIONS: Employment reported at the time of the first prenatal visit does not appear to be associated with an increase in health-risk behaviors or obstetric complications, but a relationship between working more than 15 hours and small-for-gestational-age delivery was detected.

Pneumonia in pregnancy.

Pneumonia occurs in the pregnant population with a frequency equal to that in the general population. However, its course is often more virulent, and mortality rates from certain pathogens may be high. The pregnant woman is more susceptible to injury to the respiratory tract due to a number of factors. These include alterations in the immune system which involve cell-mediated immunity and mechanical and anatomical changes involving the chest and abdominal cavities. The cumulative effect is decreased tolerance of hypoxia and acute changes in pulmonary mechanics. The spectrum of pathogens is similar to that for nonpregnant individuals, and the management of pneumonia in pregnancy does not differ in general from the nonpregnant state. However, careful attention should be paid to the fetoplacental unit with delivery generally indicated for obstetric purposes only. Issues that also need to be addressed include effects of certain infections, medications, fever, and hypoxia on the developing fetus.

Effects of intravascular transfusion for red cell alloimmunization on fetal arterial blood pressure.

OBJECTIVE: To evaluate the effects of intravascular transfusion (IVT) on the fetal umbilical arterial pressure (UAP) in pregnancies complicated by red cell alloimmunization. STUDY DESIGN: UAP and amniotic fluid pressures (AFP) were measured immediately before and after IVT. Mean UAP was calculated by computing 1/3 (systolic blood pressure - diastolic blood pressure) + diastolic blood pressure. The fractional increase in fetoplacental blood volume with transfusion was calculated by dividing the net volume of blood transfused by the sum of the net volume transfused and the fetoplacental volume based on the estimated fetal weight by ultrasound. Statistical techniques included paired t-test, and the Pearson product correlation. Significance was defined as p < 0.05. RESULTS: The fetal umbilical artery was punctured during a total of 27 procedures in 21 patients. Pre- and posttransfusion mean UAPs were recorded in 16 of these procedures. Mean UAP increased from 34.0 +/- 14.2 mm Hg pretransfusion to 38.6 +/- 12.8 mm Hg posttransfusion (p = 0.34). There was no correlation between the fractional change in fetoplacental blood volume and the calculated difference between pre- and posttransfusion blood pressure. Bradycardia occurred during 5 procedures (31.2%). Fetal demise occurred after 2 procedures (12.5%). CONCLUSION: IVT appears to have a minimal effect on the fetal UAP. Fetal bradycardia occurs in a significant percentage of these cases.

The effect of intrauterine transfusion on fetal bilirubin in red cell alloimmunization.

OBJECTIVE: To evaluate the change in fetal serum bilirubin levels in response to intrauterine transfusion for red cell alloimmunization. METHODS: The records of 37 patients who underwent more than one intrauterine transfusion were reviewed. The following indices were extracted: pre- and post-transfusion fetal hematocrit, total and direct serum bilirubin, reticulocyte count, Kleihauer-Betke test results, volumes of intravascular and intraperitoneal transfusions, and the source used for transfusion. The data were compared for interval 1 (transfusion 1 to 2) and interval 2 (transfusion 2 to 3). The rates of change in bilirubin, reticulocyte count, and percent fetal cells on the Kleihauer-Betke test were defined as the differences between the initial values of one transfusion and the initial values of the next transfusion divided by the number of days between transfusions. Analysis of variance, sign-rank test, and linear regression analysis were used when appropriate. P < .05 was significant. RESULTS: The median number of intrauterine transfusions for each patient was 3 (range 2-8). Gestational ages ranged from 22 to 37 weeks. Total bilirubin remained above the 97.5 percentile for gestational age in all but five patients. There was a significant decrease in reticulocyte count and fetal cells on the Kleihauer-Betke test, and an increase in hematocrit with serial intrauterine transfusions. Bilirubin increased significantly after the first intrauterine transfusion (3.9 versus 5.0 mg/dL) and remained elevated thereafter. CONCLUSION: Fetal total serum bilirubin remains elevated with repeated intrauterine transfusions in fetal alloimmunization. Total bilirubin should not be used to evaluate fetal hematologic responses to the transfusions.

Neonatal outcome after active perinatal management of the very premature infant between 23 and 27 weeks' gestation.

OBJECTIVE: To record the effect of aggressive perinatal management on neonatal outcome in the very premature infant. METHODS: A retrospective chart review of 114 infants born between 23 and 27 weeks' gestation, managed by one perinatal transport service at one hospital between July 1989 and December 1993. Fetuses > 23 weeks' gestation were considered viable and were managed with tocolytics, antibiotics, and surfactant at the discretion of the treating physician. Morbidity and mortality rates in the first 6 months, including stillbirths were analyzed. A major neurologic condition was defined as ultrasonographic evidence of grade 3 or 4 intraventricular hemorrhage or periventricular leukomalacia. RESULTS: Both neonatal mortality rate and the incidence of stillbirths decreased with advancing gestational age. Of 24 infants born at 23 weeks' gestation, 33% were stillborn and 13% were alive at 6 months. This survival rate improved to 48% for infants delivered at 24 weeks' gestation, and to 68%, 75%, and 71% for those delivered at 25, 26, and 27 weeks' gestation, respectively. The percentage of infants who survived without a major neurologic condition increased with advancing gestational age at delivery from 13% at 23 weeks' gestation to 40% at 24 weeks, 48% at 25 weeks, 70% at 26 weeks, and 71% at 27 weeks. The incidence of retinitis of prematurity, respiratory complications, and days spent in the hospital decreased with greater gestational age. CONCLUSIONS: An active plan of management for all gestations of > 23.9 weeks seems appropriate.