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Biomedical subjects

B C Calhoun

Publications and source records attributed to B C Calhoun.

At least 37 records · Page 2Linked to original sources
PubMed1998

Use of a focussed teen prenatal clinic at a military teaching hospital: model for improved outcomes of unmarried mothers.

We evaluated the utility of a focussed, multidisciplinary adolescent clinic in improving perinatal outcomes. The study population included all delivering unmarried teenagers (13-19 years) from January 1, 1993 to December 31, 1995 attending the focussed adolescent obstetrical clinic compared to a similar cohort of married teenagers (13-19 years), married 20-24 year-old patients, and unmarried 20-24 year-old patients. There were no statistical differences in chorioamnionitis, intrauterine growth retardation (IUGR), postpartum haemorrhage, maternal weight gain, mean gestational age at delivery, preterm delivery rates (<37 weeks), low birth-weight (<2,500 g), Caesarean delivery, postterm delivery rates (>41 weeks), macrosomia (>4,000 g), placental abruption, chronic hypertension, alcohol use, Apgar scores or stillbirth rates or neonatal death rates among the 4 groups studied. Statistical differences were noted in mean delivery weights (p<0.05), preeclampsia (p<0.004), gestational diabetes (p<0.01), history of substance abuse (p<0.0001), tobacco use (p<0.0001), and forceps delivery rates (p<0.004). However, in the teen cohort none of these differences appeared to adversely affect perinatal outcomes in our patients. The focussed, adolescent obstetrical clinic appears to provide perinatal morbidities equal to a low-risk, general population generating better than expected outcomes for pregnant teenagers.

Adolescent↗
PubMed1998

Rab11a redistributes to apical secretory canaliculus during stimulation of gastric parietal cells.

Previous investigations in several systems have demonstrated that Rab3 family members redistribute to soluble fractions on fusion of secretory granules with target plasma membranes. Rab proteins are then recycled back onto mature secretory vesicles after reinternalization of the membrane. Although this cycle is well established for Rab3, far less is known about redistribution of other Rab proteins during vesicle fusion and recycling. In the gastric parietal cell, Rab11a is associated with H-K-ATPase-containing tubulovesicles, which fuse with the apical plasma membrane (secretory canaliculus) in response to agonists such as histamine. We have analyzed distribution of Rab11a and other tubulovesicle proteins in resting and histamine-stimulated rabbit parietal cells. Stimulation of isolated gastric glands in the presence of 100 microM histamine and 100 microM 3-isobutyl-1-methylxanthine did not cause a significant increase in soluble Rab11a. H-K-ATPase, Rab11a, Rab25, syntaxin 3, and SCAMPs increased immunoreactivity in stimulus-associated vesicles prepared from rabbits treated with histamine compared with those from ranitidine-treated animals. The large GTPase dynamin was found in both vesicle preparations, but there was no change in amount of immunoreactivity. Immunofluorescence staining of resting and histamine-stimulated primary cultures of parietal cells demonstrated redistribution of H-K-ATPase and Rab11a to F-actin-rich canalicular membranes. Dynamin was present on canalicular membranes in resting and stimulated cells. These results indicate that Rab11a does not cycle off the membrane during the process of tubulovesicle fusion with the secretory canaliculus. Thus Rab11a may remain associated with recycling apical membrane vesicle populations.

1-Methyl-3-isobutylxanthine↗
PubMed1997

Two Rab proteins, vesicle-associated membrane protein 2 (VAMP-2) and secretory carrier membrane proteins (SCAMPs), are present on immunoisolated parietal cell tubulovesicles.

The tubulovesicles of gastric parietal cells sequester H+/K+-ATPase molecules within resting parietal cells. Stimulation of parietal cell secretion elicits delivery of intracellular H+/K+-ATPase to the apically oriented secretory canaliculus. Previous investigations have suggested that this process requires the regulated fusion of intracellular tubulovesicles with the canalicular target membrane. We have sought to investigate the presence of critical putative regulators of vesicle fusion on immunoisolated gastric parietal cell tubulovesicles. Highly purified tubulovesicles were prepared by gradient fractionation and immunoisolation on magnetic beads coated with monoclonal antibodies against the alpha subunit of H+/K+-ATPase. Western blot analysis revealed the presence of Rab11, Rab25, vesicle-associated membrane protein 2 (VAMP-2) and secretory carrier membrane proteins (SCAMPs) on immunoisolated vesicles. The same cohort of proteins was recovered on vesicles immunoisolated with monoclonal antibodies against SCAMPs and VAMP-2. In contrast, whereas immunoreactivities for syntaxin 1A/1B and synaptosome-associated protein (SNAP-25) were present in gradient-isolated vesicles, none of the immunoreactivity was associated with immunoisolated vesicles. The observation of VAMP-2 and two Rab proteins on immunoisolated H+/K+-ATPase-containing tubulovesicles supports the role for tubulovesicles in a regulated vesicle fusion process. In addition, the presence of SCAMPs along with Rab11 and Rab25 implicates the tubulovesicles as a critical apical recycling vesicle population.

Amino Acid Sequence↗
PubMed1997

Fetoplacental vascular tone during fetal circuit acidosis and acidosis with hypoxia in the ex vivo perfused human placental cotyledon.

OBJECTIVES: Our purpose was to determine the effects of acidosis and acidosis-hypoxia on fetoplacental perfusion pressure and its response to angiotensin II. STUDY DESIGN: Perfused cotyledons from 14 placentas were studied with either an acidotic fetal circuit perfusate (n = 7) or an acidotic-hypoxic fetal circuit perfusate (n = 7). Each cotyledon's fetal vasculature was initially perfused under standard conditions and bolus injected with 1 x 10(-10) moles of angiotensin II. Fetoplacental perfusate was then replaced with either an acidotic medium (pH 6.90 to 7.00 and Po2 516 to 613 mm Hg) or an acidotic-hypoxic medium (pH 6.90 to 7.00 and Po2 20 to 25 mm Hg) followed by an angiotensin II injection. The vasculature was subsequently recovered with standard perfusate and again injected with angiotensin II. Perfusion pressures within each group were compared by one-way analysis of variance, and results were expressed as mean pressure +/- SEM. RESULTS: Resting fetoplacental perfusion pressure did not change when the fetal circuit perfusate was made acidotic (28 +/- 1 mm Hg vs 25 +/- 2 mm Hg) or acidotic-hypoxic (26 +/- 2 mm Hg vs 25 +/- 2 mm Hg). The maximal fetoplacental perfusion pressure achieved in response to angiotensin II did not differ with an acidotic perfusate (41 +/- 2 mm Hg vs 38 +/- 1 mm Hg) or with an acidotic-hypoxic perfusate (39 +/- 2 mm Hg vs 36 +/- 2 mm Hg). CONCLUSIONS: In the perfused placental cotyledon fetoplacental perfusion pressure and pressor response to angiotensin II are not affected by fetal circuit acidosis or acidosis-hypoxia. This suggests that neither fetal acidosis nor fetal acidosis combined with hypoxia has a direct effect on fetoplacental vascular tone.

Acidosis↗
PubMed1997

The fetoplacental pressor effects of low-dose acetylsalicylic acid and angiotensin II in the ex vivo cotyledon model.

OBJECTIVE: Our purpose was to investigate perfusion pressure changes ex vivo induced by angiotensin II on fetoplacental vasculature pretreated with low-dose acetylsalicylic acid. STUDY DESIGN: Two cotyledons from each of 12 placentas were perfused. The intervillous space of one cotyledon was infused with acetylsalicylic acid (5 x 10(-5) mol/L) similar to the serum concentration of women receiving daily low-dose aspirin therapy (60 to 81 mg). The control cotyledon was infused with an equivalent amount of normal saline solution. Two doses of angiotensin II, 1 x 10(-11.5) and 1 x 10(-10) moles, were injected as boluses into the chorionic arteries of each cotyledon. A 3 x 10(-7) mole dose of angiotensin II was also injected into the intervillous space. Statistical analysis was performed with analysis of variance, and results are expressed as mean pressure change in millimeters of mercury +/- SEM. RESULTS: Perfusion pressure response did not vary between cotyledons pretreated with acetylsalicylic acid and control cotyledons when 3 x 10(-7) moles of angiotensin II was injected into the intervillous space (8.0 +/- 1.9 mm Hg vs 9.8 +/- 1.6 mm Hg, p = 0.59). There were no differences between cotyledons in pressure response to 1 x 10(-11.5) moles of angiotensin II injected into the fetal circuit (5.9 +/- 0.8 mm Hg vs 6.7 +/- 0.9 mm Hg, p = 0.51). However, in the cotyledons pretreated with acetylsalicylic acid there was a decrease in the pressor response to 1 x 10(-10) moles of angiotensin II (14.1 +/- 1.4 mm Hg vs 21.5 +/- 3.3 mm Hg, p = 0.05). CONCLUSIONS: Low-dose aspirin infused into the intervillous space decreases vasoconstriction elicited by angiotensin II in the fetoplacental compartment. This suggests that maternal low-dose aspirin therapy has effects in the fetoplacental circulation in addition to its effects in the maternal circulation.

Angiotensin II↗
PubMed1997

Perinatal hospice: a response to partial birth abortion for infants with congenital defects.

This article discusses decisions involving whether to terminate late-term pregnancies when fetal anomalies have been detected. Partial-birth abortion performed on fetuses with chromosomal abnormalities, while performed under the guise of reducing suffering, threatens the best interests of the mother and infant. An alternative for parents faced with the decision to terminate their pregnancy is perinatal hospice. Perinatal hospice recognizes the value of bringing these infants to term by treating them as beings conceived with a tangible future. This alternative is preferred because of post-termination psychological distress and because biblical teachings emphasize the dignity and worth of each fetus. Perinatal hospice supports parents through their grief when their infant dies and maximizes the opportunity for authentic mourning.

Abortion, Eugenic↗
PubMed1996

A somatodendritic distribution of Rab11 in rabbit brain neurons.

Comparisons of subcellular targeting in neurons and epithelial cells have led to suggestions that apical epithelial antigens localize to axons and nerve terminals. We have studied the distribution in brain of the small GTP-binding protein, Rab11, which is localized to apical vesicular populations in epithelial cells. Sections of rabbit brain were examined by immunohistochemistry using a monoclonal antibody against rabbit Rab11. Rab11 immunoreactivity was present exclusively in neurons. In all regions examined, including forebrain, cerebellum, thalamus and brainstem, Rab11 immunoreactivity was observed in cell bodies and dendrites. No staining was observed in hippocampal neurons. These results indicate that the distribution of Rab11 does not support previous suggestions that apical epithelial markers should localize to axons and synaptic endings.

Animals↗
PubMed1996

Compound presentation resulting from the forward-roll technique of external cephalic version: a possible mechanism.

Limited reports exist about the frequency of compound presentation after external cephalic version. A compound hand and foot presentation is reported after external cephalic version in a woman desiring vaginal birth after cesarean delivery. We report a mechanism by which a forward roll during external cephalic version may predispose an infant in complete breech position to a compound foot presentation.

Adult↗
PubMed1996

The effects of hemodialysis on total intrauterine volume.

Our objective was to assess the effects of maternal fluid shifts during hemodialysis on the amniotic fluid volume. Ultrasound estimation of the total intrauterine volume before and after dialysis was performed between 23 and 26 weeks in a 30-year-old woman with progressive IgA glomerulonephropathy. The total intrauterine volume was reduced after each episode of dialysis. The mean decrease in the amniotic fluid volume was 116.6 ml (range 17.8-287.1 ml), which represented a 1.5-31.1% change in the total intrauterine volume (p = 0.004). The reduction was linearly related to the amount of maternal fluid removed during hemodialysis. The reduction in the total intrauterine volume was best estimated by the equation: -6.618 + (32.582) (weight loss in kilograms). Hemodialysis during pregnancy results in linear amniotic fluid shifts related to the amount of maternal fluid removed during dialysis. Given these findings, care must be taken to limit the volume of maternal fluid removed during hemodialysis, especially in pregnancies complicated by early gestation, intrauterine growth retardation, or oligohydramnios.

Adult↗
PubMed1995

External cephalic version at a military teaching hospital: predictors of success.

The purpose of this prospective study was to analyze our experience with external cephalic version under tocolysis. This included an expected (1) high success rate of version, (2) infrequent occurrence of reversion, (3) reduction in the incidence of intrapartum breech presentation, avoiding the need for Caesarean delivery, and (4) predictors of success in our series. The study spanned the period from 1985 to 1993, enrolling 113 subjects who presented to our OB/GYN Department with any type of breech presentation at 37 weeks' gestation or greater and met the following criteria: (1) absence of labour or ruptured membranes, (2) singleton pregnancy, (3) absence of medical or obstetrical complications and amniotic fluid index of greater than 8 cm. After a reassuring fetal assessment, IV terbutaline was given prior to an attempt at version. The results revealed a 46% (53 or 113) version success rate with a 4% (2 of 53) reversion within a week after procedure. There was a 2% (2 of 113) complication rate, with 1 being a minor incident of fetal bradycardia that responded easily to intrauterine resuscitation. One major complication occurred with placental abruption during the attempt, which required immediate Caesarean delivery. Predictors of success in our series included: multiparity, fundal/posterior placenta, and fetal head and spine on the corresponding side of the maternal sagittal plane. External cephalic version in a controlled setting can be a safe procedure for residents in training that lowers Caesarean delivery rate for breech presentation.

Cesarean Section↗
PubMed1995

The effects of antenatal steroid use in premature rupture of membranes.

We sought to determine if antepartum steroid treatment offers any clinical benefits to patients with premature rupture of membranes. One hundred and forty-five maternal-neonatal pairs were studied. Forty-five maternal-neonatal pairs with premature, preterm rupture of membranes received steroids during 24-35 weeks' gestation. One hundred maternal-neonatal pairs received no antenatal steroids. The 2 groups were identical with regard to gestational age at rupture of membranes, gravity, parity, race, fetal gender, socioeconomic status, smoking, and preterm labour risk factors. Study of the data revealed that maternal chorioamnionitis was less frequent in the steroid group (p < 0.001). Bronchopulmonary dysplasia (oxygen dependent at discharge at term gestational age) was less frequent in the steroid group (p < 0.05). The remainder of the data revealed no statistically significant differences in preterm delivery rate, necrotizing enterocolitis, respiratory distress syndrome, intraventricular haemorrhage rate or severity of haemorrhage, hospital days, latency to delivery, or ventilator days. Antepartum steroid use in preterm rupture of membranes appears to offer clinical benefit in premature infants by lessening the rate of bronchopulmonary dysplasia in those infants receiving antepartum steroids.

Betamethasone↗
PubMed1995

Emergency management of sudden puerperal fever.

The development of fever during the puerperium is a relatively common complication. Although the primary source of these fever usually stems from the genital tract, a thorough evaluation of the febrile puerperal patient for other sites of infection is necessary before initiating antibiotic therapy. Increased awareness of factors that predispose a patient to postpartum infection has significantly reduced maternal morbidity and mortality.

Emergency Medicine↗
PubMed1995

Urinary incontinence procedures performed at a military teaching hospital.

PURPOSE: This study provides follow-up of primary modified Pereyra needle urethropexy procedures performed with permanent suture by residents at a military teaching hospital. METHOD: Review of all resident-performed primary Pereyra urethropexy procedures performed at Keesler Medical Center (KMC) from December 1990 through April 1994. RESULTS: The results from 34 primary Pereyra needle urethropexy procedures, with 24 patients less than 2 years from surgery and mean follow-up of 19.5 months, demonstrated that 21/24 had improvement in their incontinence. This gives an 88% success rate at less than 2 years. We had 10 patients more than 2 years from surgery, with mean follow-up of 38 months, and 6/10 with continence. The overall success rate was 27/34 (79%). We noted that on preoperative evaluation, 5/7 failures were found to have urethral closing pressures of < 20 cm H2O (8-18). One of the late failures was found to have had no cystometrics performed and no demonstrable stress urinary incontinence. Her procedure was termed "prophylactic." Removing 6/7 failures for incomplete evaluation or use of less appropriate procedure, we find 27/28 patients (96%) with successful results. The presence of low urethral pressure (< 20 cm H2O) was a significant factor in the failures regardless of timing (< 2 years vs. > 2 years) (p < 0.04). There was no difference in parity, estrogen use, urgency component, age, socioeconomic status, associated operative procedures, postoperative infection, or complications noted between successful and unsuccessful Pereyra urethropexy as a primary method of genuine stress incontinence surgery. CONCLUSION: The primary Pereyra needle urethropexy had an overall success rate of 79% (27/34). Allowing for properly evaluated and treated patients, we find 96%(27/28) success. It appears that the primary modified Pereyra vaginal urethropexy with permanent suture is an easily taught and superior method of primary surgical treatment of stress urinary incontinence in a military training program.

Adult↗
PubMed1995

Management of immune thrombocytopenia purpura at a military medical center.

OBJECTIVE: To investigate whether fetal platelets in immune thrombocytopenia purpura (ITP) may be predicted by antepartum assessment. METHODS: A prospective analysis was conducted of 28 pregnant women with ITP out of 8,056 deliveries. Of the 28 patients, 13 were evaluted by fetal scalp sampling and 11 were evaluated by percutaneous umbilical blood sampling (PUBS). RESULTS: The mean fetal and maternal platelet counts prior to delivery were 146,000 and 176,000, respectively. The mean fetal and maternal platelet counts after delivery were 245,000 and 149,000, respectively. Fetal cord platelet counts could not be predicted by maternal platelet count, the presence/absence of maternal direct/indirect anti-platelet antibodies, steroid therapy, or history of splenectomy. PUBS for fetal platelet assessment correlated well with fetal postdelivery counts. CONCLUSIONS: Patients with ITP rarely exhibit complications. No antepartum characteristic enhances reliable prediction of neonatal outcome. Method of delivery should be based on obstetric guidelines.

Adolescent↗
PubMed1994

Early genetic amniocentesis and its relationship to respiratory difficulties in paediatric patients: a report of findings in patients and matched controls 3-5 years post-procedure.

This study evaluates the long-term pulmonary complications of 25 children from a prospective, matched-control, pilot study evaluating short-term complications of early (11-14 weeks' gestation) versus traditional (15 weeks' gestation and later) genetic amniocentesis. Five children in the early amniocentesis group were found to have various respiratory difficulties, a morbidity rate comparable to that of paediatric patients in the general population. These data identify the need for larger, multicentre trials.

Amniocentesis↗