Mandibular biomechanics and development of the human chin

The development of the chin, a feature unique to humans, suggests a close functional linkage between jaw biomechanics and symphyseal architecture. The present study tests the hypothesis that the presence of a chin changes strain patterns in the loaded mandible. Using an anatomically correct 3-D model of a dentate mandible derived from a CT scan image, we analyzed strain patterns during incisal and molar biting. We then constructed a second mandible, without a chin, by 'defeaturing' the first model. Strain patterns of the second model were then compared and contrasted to the first. Our main finding was that chinned and non-chinned mandibles follow closely concordant patterns of strain distribution. The results suggest that the development of the human chin is unrelated to the demands placed on the mandible during function.

Microhardness and Ca:P ratio of carious and Carisolv™ treated caries-affected dentine using an ultra-micro-indentation system and energy dispersive analysis of x-rays — A pilot study

BACKGROUND

This study aimed to evaluate microhardness and chemical analysis of carious and caries-affected dentine. The hypothesis tested was that calcium:phosphorous (Ca:P) ratios correlate with microhardness values.

METHODS

Four carious human third molars were sectioned through the caries lesion in the mesiodistal longitudinal plane. One half of each lesion underwent carious dentine removal using Carisolv gel. The cut surfaces were polished, microhardness tested using an Ultra-Micro-Indentation System (UMIS) and elemental analysis performed using energy dispersive analysis of x-rays (EDAX).

RESULTS

The microhardness of carious dentine decreased gradually towards the cavity floor, but that for caries-affected dentine showed more variation with depth, having a mean hardness of (0.63 +/- 0.18) GPa. Ca:P ratios of carious dentine varied among the four specimens. The mean Ca:P ratio of caries-affected dentine was 1:2.03 +/- 0.08. The hypothesis was accepted for active lesions.

CONCLUSIONS

The use of Carisolv to excavate carious tissue can be as effective as rotary instrumentation.

Mid-trimester endovaginal sonography in women at high risk for spontaneous preterm birth

CONTEXT

Although shortened cervical length has been consistently associated with spontaneous preterm birth, it is not known when in gestation this risk factor becomes apparent.

OBJECTIVE

To determine whether sonographic cervical findings between 16 weeks' and 18 weeks 6 days' gestation predict spontaneous preterm birth and whether serial evaluations up to 23 weeks 6 days' gestation improve prediction in high-risk women.

DESIGN, SETTING, AND PARTICIPANTS

Blinded observational study performed between March 1997 and November 1999 at 9 university-affiliated medical centers in the United States in 183 women with singleton gestations who previously had experienced a spontaneous birth before 32 weeks' gestation.

OBSERVATION

Certified sonologists performed 590 endovaginal sonographic examinations at 2-week intervals. Cervical length was measured from the external os to the functional internal os along a closed endocervical canal. Funneling and dynamic cervical shortening were also recorded.

MAIN OUTCOME MEASURE

Spontaneous preterm birth before 35 weeks' gestation, analyzed by selected cutoff values of cervical length.

RESULTS

Forty-eight women (26%) experienced spontaneous preterm birth before 35 weeks' gestation. A cervical length of less than 25 mm at the initial sonographic examination was associated with a relative risk (RR) for spontaneous preterm birth of 3.3 (95% confidence interval [CI], 2.1-5.0; sensitivity = 19%; specificity = 98%; positive predictive value = 75%). After controlling for cervical length, neither funneling (P =.24) nor dynamic shortening (P =.054) were significant independent predictors of spontaneous preterm birth. However, using the shortest ever observed cervical length on serial evaluations, after any dynamic shortening, the RR of a cervical length of less than 25 mm for spontaneous preterm birth increased to 4.5 (95% CI, 2.7-7.6; sensitivity = 69%; specificity = 80%; positive predictive value = 55%). Compared with a single cervical measurement at 16 weeks' to 18 weeks 6 days' gestation, serial measurements at up to 23 weeks 6 days significantly improved the prediction of spontaneous preterm birth in a receiver operating characteristic curve analysis (P =.03).

CONCLUSIONS

Cervical length assessed by endovaginal sonography between 16 weeks' and 18 weeks 6 days' gestation, augmented by serial evaluations, predicts spontaneous preterm birth before 35 weeks' gestation in high-risk women.

Preliminary studies on the optimum shape of dental bridges

Several pre-existing anterior and posterior dental bridge models using Finite elements and the new ceramic material In-Ceram have been developed. The mechanical behaviour of these models has been compared with optimised profiles obtained from a newly developed evolutionary algorithm known as Evolutionary Structural Optimisation (ESO). The results show that the mechanical behaviour of the bridges was mainly restricted by the properties of the porcelain veneer and the design of the bridges themselves. For the case of the anterior bridge, it was found that there existed a specific thickness of veneer that minimised the maximum principal stress. This was related to peak stresses that occurred at the bridge surface. Peak stresses also occurred in the material interface between the In-Ceram and the veneer. These extreme stresses were attributed to the notch size and shape. For the case of the posterior bridge, it was concluded that the shape of the bottom of the Pontic tooth is crucial in reducing the magnitude of the maximum principal tensile stress. The ESO process produced bridge designs which have uniformly stressed bridge surfaces, and which also have significantly lower maximum principal tensile stresses compared to the pre-existing designs (up to 44%).

Thermal expansion coefficient of titanium casting

A reliable measurement of the thermal expansion coefficient (alpha) value is required to achieve a positive thermal mismatch between metal and porcelain for porcelain-fused to metal crowns. Heating rate and specimen conditions may significantly influence the alpha value and the effects of these factors were studied. Commercially pure cast titanium rods, 'as cast' and sandblasted, were heated at various conditions. According to this study, the discrepancy of alpha values between heating and cooling conditions was insignificant when the heating (cooling) rate was reduced to 1 degrees C min(-1). It was revealed that alpha values obtained from 1 degrees C min(-1) cooling rates should be utilized. Dental porcelain with an alpha value lower than 8.5 x 10(-6) degrees C will be suitable for titanium-ceramic applications.

Osteoporosis influences the early period of fracture healing in a rat osteoporotic model

Osteoporotic fractures commonly occur in the elderly. Although current therapies are aimed at the prevention and treatment of osteoporotic fractures, studies examing the fracture healing process in osteoporotic bone are limited. We produced an osteoporotic rat model by ovariectomy (ovx) and maintained a low calcium diet (LCD) in order to evaluate the influence of osteoporosis on fracture healing. Callus formation and strength was monitored over a 3 week period by histological and biomechanical assessment. Data collected simultaneously on a group of rats undergoing sham surgery (sx) were used for comparison. A 40% reduction in fracture callus cross-sectional area and a 23% reduction in bone mineral density in the healing femur of the ovx rats was observed on day 21 following fracture as compared with the sx group (p < 0.01). Biomechanical data from the healing femur of the ovx rats revealed a fivefold decrease in the energy required to break the fracture callus, a threefold decrease in peak failure load, a twofold decrease in stiffness and a threefold decrease in stress as compared with the sx group (p < 0.01, respectively). Histomorphological analysis revealed a delay in fracture callus healing with poor development of mature bone in the ovx rats. This study provides physical evidence of altered fracture healing in osteoporotic bone, which may have important implications in evaluating the effects of new treatments for osteoporosis on fracture healing.

Cytology of mucinous carcinoma of breast: a report of 28 cases with histological correlation

Pure mucinous carcinoma (MC) of the breast is a relatively uncommon variant of breast carcinoma with distinctive histological and cytological features. In this study we have analysed fine needle aspiration (FNA) cytological material from 28 cases of MC of breast and correlated the cytomorphological features with histopathology. The 28 patients consisted of 27 females and one male patient. 14 patients were Chinese, 10 were Indian and four were Malay. Their ages ranged from 38 to 90 with a mean at 52 years. The left breast was involved in 17 and the right in 11 cases. The duration of the lump varied from two weeks to 10 years. The cytological picture was characterized by abundant extracellular mucin giving a "sea of mucin" or "whirlpools of mucin" effect, in which were seen floating clusters of tumour cells with relatively bland cytological features. Myxo-vascular fragments were seen in 12 cases. Dissociated tumour cells showed a plasmacytoid appearance with eccentric nuclei. In four cases, the mucin was scanty in amount and the cellularity was high while in two cases, the cellularity was very low. Psammoma bodies were seen in cytological smears in one case. Histological study of excision or mastectomy specimens confirmed all 28 cases to be pure MC. Knowledge of the distinctive cytomorphological appearance of MC would enable correct identification of these lesions as malignant and prompt treatment that could further enhance the survival of these prognostically good breast cancers.

The hardness and modulus of elasticity of primary molar teeth: an ultra-micro-indentation study

OBJECTIVE

Baseline information on the mechanical properties of and the effect of load upon dental hard tissue is important in the development of successful dental materials. Existing methods of measuring such properties of tissue are subject to significant experimental error. This study reports on the use of an Ultra-Micro-Indentation System (UMIS) to measure the hardness and elastic modulus of primary enamel and dentine.

METHODS

Primary molar teeth were sectioned, set in resin and polished. Thirty indentations were made in enamel and dentine using a Berkovitch indentor, 15 of which were subject to a load of 50mN and 15 to a load of 150mN. An automated computerised system converted the force/penetration graph for each indentation in to a hardness vs depth graph from which values for the mean hardness and elastic modulus were calculated.

RESULTS

Primary enamel had a mean hardness of 4.88+/-0.35GPa whilst the hardness of dentine was 0.92+/-0.11GPa The elastic modulus for enamel was 80.35+/-7.71GPa and that of dentine 19.89+/-1.92GPa. Using linear regression analysis a significant relationship could be shown between the hardness and the elastic modulus for both enamel and dentine when loaded to 150mN but only for dentine at 50mN (P<0.05). In general the elasticity of tooth structure increased as the hardness increased.

CONCLUSION

The UMIS offers a simple and reproducible method of measuring basic mechanical properties of small samples of enamel and dentine.

Characterisation of tribochemically assisted bonding of composite resin to porcelain and metal

OBJECTIVE

The fracture of bonded ceramic to metal restorations remains a problem in clinical dental practice. The use of resin based composites to repair such fractures is generally unsatisfactory. Tribochemical technology creates a surface layer of small silica particles fused to the surface substrate. Such a layer potentially improves adhesion of resin to both alloy and porcelain. Adhesion between two substrates is traditionally studied using shear or tensile bond strength tests. However, the highest stress at bond failure may not represent the real bonding characteristics correctly. An alternative method is to describe the bonding characteristics by determining the strain energy release rate for a given interface. This study compares the bonding characteristics of a resin to gold/porcelain interface using a tribochemical coating process with those of a control group using simple gritblasting.

METHODS

Pre-cracked specimens were subjected to load-unload cycles using a simple four point bending test and the resultant strain energy release rates were calculated.

RESULTS

Tribochemically pretreating the porcelain resulted in a significant increase in the resultant strain energy release rate from 42.72+/-3.65J/m(2) for the controls to 61.35+/-6.26J/m(2). Likewise there was a significant improvement in the strain energy release rate for the gold/composite interface from 27.31+/-3.00J/m(2) to 42.13+/-4.83J/m(2).

CONCLUSIONS

Tribochemical technology offers significant potential advantages for clinical dental practice.

Cytologic appearances in invasive lobular carcinoma of the breast. A study of 21 cases

OBJECTIVE

To examine the fine needle aspiration cytologic features of invasive lobular carcinoma of breast and to discuss problems that may occur in cytodiagnosis.

STUDY DESIGN

Fine needle aspiration cytologic smears from 21 cases of invasive lobular carcinoma (ILC) of breast were subjected to detailed cytomorphologic analysis. Features studied included pattern of cells, size of cells, nuclear placement, pleomorphism, presence of intracytoplasmic lumina (ICL) and signet ring cells.

RESULTS

Cellularity was generally moderate or high, and the pattern was predominantly or partly dissociated in 86% of cases. Rosettelike pattern was discerned in alveolar-type ILC. Cell size was usually small or intermediate, with nuclei placed eccentrically in most cases. ICLs with or without signet ring cells were present in 12 cases (57%).

CONCLUSION

A cytologic picture consisting of predominantly dissociated small or intermediate-sized tumor cells with eccentric nuclei, with some of the cells showing ICLs, is highly suggestive of ILC. Indian file pattern, another characteristic feature of ILC, is, however, focal and inconsistent. Variant patterns of ILC may show other cytologic features, such as rosettelike pattern (alveolar variant of ILC) or large cell pattern (pleomorphic variant of ILC) and may consequently be difficult to categorize on cytologic smears.

The value of cytology in granulomatous mastitis: a report of 16 cases from Malaysia

BACKGROUND

Granulomatous mastitis is a rare condition of the breast that can mimic a carcinoma. There are characteristic histological features, the most important of which is a predominantly lobular inflammatory process. It must be differentiated from known causes of granulomatous inflammation, such as tuberculosis.

METHODS

In the present paper, the clinical and pathological features of 16 patients with granulomatous mastitis seen over a 3-year period in the University Hospital, Kuala Lumpur, are described.

RESULTS

A clinical suspicion of malignancy was present in 10 cases. One of the patients was nulliparous. One had an associated hyperprolactinaemia, while two had systemic lupus erythromatosis. One of the patients was pregnant at the time of presentation. Four patients had localized lumps excised, five were treated conservatively because the lesion was too extensive to resect, and seven patients required drainage procedures for abscess formation.

CONCLUSION

Awareness of this condition is important because it mimics a carcinoma, and surgery may not be the best treatment for recurrent disease.

Serologic and molecular investigations of a chimera

A chimeric individual possesses two or more genetically distinct cell populations. Although the chimerism may not be evident in all gene systems, various loci display greater numbers of alleles than genetically "normal" individuals. The proposita was referred for further laboratory investigation due to a mixed-field ABO blood group reaction following routine antenatal testing. Various molecular (HLA class II, ABO genotyping, and 10 short tandem repeat [STR] microsatellites) and serologic (HLA class I and red cell blood groups) typing techniques were employed to investigate a number of polymorphic loci located on different chromosomes. Chimerism was identified in 8 out of the 14 chromosomes tested: chromosome 1 (Duffy), 6 (HLA class I and II), 9 (ABO), 11 (HUMTH01), 12 (HUMPLA2A1), 15 (HUMFES/FPS), 18 (Kidd) and 21 (D21S11). The proposita was determined to be a probable dispermic chimera, based on the results of the serology and molecular studies.

Fine-needle aspiration cytology of metastatic nasopharyngeal carcinoma

Over a 32-month period at the University Hospital, Kuala Lumpur, we were able to study the cytological appearance of metastatic nasopharyngeal carcinoma (NPC) in 17 cases. This comprised 14 males and three females of which 13 were Chinese, three were Malay, and one was Indian. Their ages ranged from 27 to 64 years. Histological correlation was available in all the patients in the form of nasopharyngeal biopsies, and they were classified as per the World Health Organization classification into types I, II, and III NPC. Smears from type II NPC showed good cellularity with mainly clustered and occasionally dissociated cells, with focal columnar appearance, vesicular nuclei, prominent nucleoli, and variable amounts of cytoplasm. Clusters of malignant cell closely associated with lymphoid cells and dissociation of malignant cells were more characteristic of type III NPC. FNA cytology is now applied extensively to the diagnosis of head and neck tumours and knowledge of the cytomorphology of NPC would greatly aid in pinpointing the primary of this tumour which is notorious for presenting with early nodal metastasis.

A place called HOPE: group psychotherapy for adolescents of parents with HIV/AIDS

Project HOPE is a psychosocial support program for noninfected children of HIV-positive parents. The challenges of starting and implementing the program's psychotherapy group for grieving adolescents, and clinical examples of group process and effective interventions in group leadership, are described. Four stages in group development are explicated--safety, dependency, counterdependency, and independence--paralleling the adolescent separation-individuation process.

Identification of beta-L-gulose as the sugar moiety of the main polar lipid Thermoplasma acidophilum

The main polar lipid (MPL) of Thermoplasma acidophilum has been purified and its structure determined. NMR, mass spectrometry, and capillary gas chromatography-mass spectrometry experiments have shown that the previously unidentified sugar moiety of MPL is the rare sugar L-gulose. MPL is thus a tetraether lipid with cyclopentane rings and head groups of phosphoglycerol, as previously reported, and beta-L-gulopyranose. Further, MPL is also the dominant lipid found in lipid extracts from another species of the Thermoplasma genus, T. volcanium, suggesting that L-gulose may represent a dominant sugar moiety of the polar lipids biosynthesized by this archaeobacterial genus. Minor phospholipids were tentatively identified as diether and hydroxydiether analogs of phosphatidylglycerol, and phosphatidylinositol.

The preterm prediction study: maternal stress is associated with spontaneous preterm birth at less than thirty-five weeks' gestation. National Institute of Child Health and Human Development Maternal-Fetal Medicine Units Network

OBJECTIVE

Our purpose was to determine whether various measures of poor psychosocial status in pregnancy are associated with spontaneous preterm birth, fetal growth restriction, or low birth weight.

STUDY DESIGN

Anxiety, stress, self-esteem, mastery, and depression were assessed at 25 to 29 weeks in 2593 gravid women by use of a 28-item Likert scale. Scores for each psychosocial subscale were determined, and an overall psychosocial score was calculated. Scores were divided into quartiles, and the lowest quartile scores were used to define poor psychosocial status. The percent spontaneous preterm birth, low birth weight, and fetal growth restriction in women with low and high psychosocial scores were compared. Logistic regression analyses provided the odds ratios and 95% confidence intervals.

RESULTS

Analyses revealed that stress was significantly associated with spontaneous preterm birth and with low birth weight with odds ratios of 1.16, p = 0.003, and 1.08, p = 0.02, respectively, for each point on the scale. A low score on the combined scale or on any subscale other than stress did not predict spontaneous preterm birth, fetal growth restriction, or low birth weight. After multivariate adjustment was performed for psychosocial status, substance use, and demographic traits, black race was the only variable significantly associated with spontaneous preterm birth, fetal growth restriction, and low birth weight; stress and low education were associated with spontaneous preterm birth and low birth weight.

CONCLUSION

Stress was associated with spontaneous preterm birth and low birth weight even after adjustment for maternal demographic and behavioral characteristics. Black race continues to be a significant predictor of spontaneous preterm birth, fetal growth restriction, and low birth weight even after adjustment for stress, substance use, and other demographic factors.

Ribavirin as therapy for chronic hepatitis C. A randomized, double-blind, placebo-controlled trial

OBJECTIVE

To evaluate ribavirin, an oral antiviral agent, as therapy for chronic hepatitis C.

DESIGN

Randomized, double-blind, placebo-controlled study.

SETTING

Clinical Center of the National Institutes of Health, a tertiary referral research hospital.

PATIENTS

29 patients with chronic hepatitis C who received oral ribavirin (600 mg twice daily) for 12 months and 29 controls with chronic hepatitis C who received placebo for 12 months.

MEASUREMENTS

Effects of therapy were evaluated by measuring serum aminotransferase and hepatitis C virus (HCV) RNA levels before, during, and for 6 months after therapy and by histologic examination of liver specimens before and at the end of treatment.

RESULTS

Patients treated with ribavirin had a prompt decrease in serum aminotransferase levels (54% overall) compared with levels before treatment and levels in controls (5% decrease). Serum aminotransferase levels became normal or nearly normal in 10 patients treated with ribavirin (35% [95% CI, 18% to 54%]) but in no controls (0% [CI, 0% to 12%]). Aminotransferase levels remained normal in only 2 patients after ribavirin therapy was discontinued (7% [CI, 1% to 23%]). Serum HCV RNA levels did not change during or after therapy. Liver biopsy specimens showed a decrease in hepatic inflammation and necrosis among ribavirin-treated patients whose aminotransferase levels became normal.

CONCLUSIONS

Ribavirin has beneficial effects on serum aminotransferase levels and histologic findings in the liver in patients with chronic hepatitis C, but these effects are not accompanied by changes in HCV RNA levels and are not sustained when ribavirin therapy is discontinued. Thus, ribavirin alone for periods as long as 12 months is unlikely to be of value as therapy for chronic hepatitis C.

A silver stain protocol for proteins yielding high resolution and transparent background in sodium dodecyl sulfate-polyacrylamide gels

A simple, sensitive silver staining method for sodium dodecyl sulfate polyacrylamide gel electrophoresis has been developed which yields high resolution of proteins with a transparent background. The method includes the incorporation of a water wash after a short fixation step in ethanol/ acetic acid and prior to glutaraldehyde cross-linking, which appears to be necessary for the high resolution staining of protein bands and the low background staining.

Expectant management of preterm premature rupture of the membranes

OBJECTIVES

Our purpose was to (1) evaluate expectant management of preterm premature rupture of the membranes between 20 and < 36 weeks' gestation and (2) compare outcomes in service and private populations.

STUDY DESIGN

The study included only singleton pregnancies prospectively managed between 20 and < 36 weeks' gestation with proved preterm premature rupture of the membranes. None of the patients received prophylactic antibiotics, tocolytics, or steroids, and none of the neonates received surfactant or had lethal anomalies. Patients (n = 511) were divided into private (n = 194) and staff (n = 317) categories, but all were managed identically.

RESULTS

Approximately 50% of patients were delivered within 48 hours. Infection is more likely with preterm premature rupture of membranes before 28 weeks' gestation (p = 0.001), as is fetal death associated with infection (p < 0.001). Other findings in this study were (1) no significant differences in evaluated outcomes between private and staff patients, except that significantly more vaginal deliveries occurred in staff patients, (2) a prolongation of pregnancy > or = 7 days in 12.9% of patients, (3) a significant increase in the rate of maternal infection if preterm rupture of membranes occurred before 28 weeks' gestation, (4) a significant increase in fetal and neonatal deaths if preterm premature rupture of membranes occurred before 28 weeks, and (5) an increased probability of survival whose rate of increase is dependent on the gestational age at which preterm premature rupture of membranes occurred. For babies weighing < 1500 gm at birth compared with controls, babies delivered of mothers not having preterm premature rupture of membranes, 1-year follow-up revealed (1) a significantly lower incidence of pulmonary interstitial emphysema and cerebral palsy in the study group delivered before 28 weeks' gestation, (2) a significantly lower incidence in bronchopulmonary dysplasia in the study group delivered after 28 weeks' gestation, and (3) no significant differences in the incidence of intraventricular hemorrhage, pneumothorax, or Bayley Mental Developmental Index < 68 between those delivered before or after 28 weeks' gestation.

CONCLUSION

Over 47.8% of the patients continued their pregnancy beyond 48 hours, and in 12.9% of cases expectant management of preterm premature rupture of membranes prolonged the pregnancy by > or = 7 days. The maternal infection rate is greater before 28 weeks' gestation and is associated with higher fetal-neonatal mortality. Status has little impact on outcome. Expectant management is not detrimental to quality of survival. Survival probability increases at a more rapid rate with preterm premature rupture of membranes after 22 weeks of gestation.

Effects of maternal ingestion of low-dose aspirin on the fetal cardiovascular system

OBJECTIVE

Our purpose was to assess fetal central and regional hemodynamics in normal fetuses using two-dimensional, range-gated pulsed Doppler echocardiography in pregnant women on chronic baby aspirin regimen (87 mg).

STUDY DESIGN

Fifteen fetuses exposed to maternal chronic ingestion of baby aspirin were compared with 26 control fetuses. Longitudinal studies of the umbilical artery waveform and blood flow through the fetal right and left ventricles were obtained every 4 weeks during gestation in a group of fetuses exposed to daily maternal intake of 87 mg of aspirin. Pulsed Doppler waveforms were obtained below the tricuspid and mitral valves, at the level of the descending aorta (below the ductus), and at the level of the fetal renal artery as it enters the kidney. All tracings were recorded on a strip chart and analyzed with a digital light-pen and graphic overlay system. Peak systolic velocity and minimal diastolic velocity were obtained for the umbilical and fetal renal artery. Peak flow velocity and velocity time integral of the pulsed Doppler waveforms of the atrioventricular valves were calculated. Acceleration time/ejection time ratio was obtained for the descending aorta.

RESULTS

No significant differences were found among the two groups in either central or regional circulation.

CONCLUSION

Chronic daily maternal ingestion of baby aspirin does not significantly affect the central and regional circulation of the fetus.

Effect of inflammation of enteric nerves. Cytokine-induced changes in neurotransmitter content and release

The results of our previously published work provide evidence of inflammation-induced functional disturbances in the enteric nervous system. Data presented in this paper describe our preliminary results indicating that the altered function in enteric nerves in the nematode-infected rat model of intestinal inflammation is mediated by interleukin-1. This is based on the ability of the exogenous cytokine to mimic changes observed in the model, and on the ability of a specific IL-1 antagonist to attenuate these changes. In addition, we have identified mechanisms underlying the actions of IL-1 in the myenteric plexus. Our data are consistent with a direct interaction between the cytokine and neural membranes. In addition, the delayed effect of IL-1 beta on neurotransmitter release appears to be due to the release of endogenous IL-1, most likely from macrophage-like cells in the myenteric plexus (Fig. 3). If such cells possess receptors for neuropeptides, as has been found with macrophages elsewhere in the gut, a neuroimmune axis would exist in the myenteric plexus. Thus, the finding of a source of IL-1 in the plexus of the noninflamed intestine invites speculation on a neuromodulatory role of the cytokine within the enteric nervous system.

Atrial natriuretic factor concentrations during pregnancy and in the postpartum period

Atrial natriuretic factor (ANF) is a hormone that regulates fluid and electrolyte homeostasis. Increased intra-atrial pressure or atrial distention, which might occur secondary to intravascular volume expansion, stimulate the secretion of ANF by human atrial myocytes. During normal human pregnancy, there is a progressive increase in total intravascular fluid volume. Thus, we asked the following question: Does this physiologic adaptation to pregnancy result in an increase in ANF concentrations? Concentrations of alpha-human ANF (alpha-hANF) were measured by a specific radioimmunoassay in venous blood samples obtained longitudinally in the first, second, and third trimesters of pregnancy, during the intrapartum period, in the early postpartum period, and 6 to 8 weeks postpartum from 11 normal women who had no antepartum, intrapartum, or postpartum complications. Maternal circulating alpha-hANF levels were not different from those seen in the nonpregnant state. However, higher alpha-hANF concentrations were noted in the early postpartum period. Although the hypervolemia of normal pregnancy is not associated with higher alpha-hANF concentrations, other possibilities (such as increased ANF clearance, dilutional effects) need to be investigated. Finally, the etiology for the transient increase in alpha-hANF levels in the early postpartum period remains to be elucidated.

Uteroplacental Doppler flow velocity waveform indices in normal pregnancy: a statistical exercise and the development of appropriate reference values

In a prospective cross-sectional study, we examined 154 normal pregnant women and measured the systolic to diastolic (S/D) ratio and resistance index (RI) in the umbilical artery and both uterine arteries. Placental location with respect to laterality was determined by real-time ultrasound. In patients with unilateral placental location, each uterine artery was evaluated according to its relationship with the placenta. Doppler flow velocity waveforms were obtained by a continuous wave Doppler device. Kolmogorov D tests revealed that RI values follow gaussian distribution, but that S/D values were markedly skewed to the right. There was a significant negative linear relationship between gestational age and umbilical artery RI and a significant negative curvilinear relationship between gestational age and umbilical artery (S/D (r = 0.83, p less than 0.001; and r = -0.79, p less than 0.001, respectively). Confidence bands for umbilical artery RI were developed based on the linear model with gestational age (fitted umbilical artery RI = 0.97199 - 0.01045*gestational age). Confidence bands for umbilical artery S/D were derived from the corresponding RI values by means of the functional relationship S/D = 1/(1 - RI). The RI and S/D values of the uterine arteries declined until 24 to 25 weeks' gestation and remained unchanged thereafter. This relationship, however, was not statistically significant (r = -0.10, p = 0.22). The placental uterine artery is different from the nonplacental quantitatively and qualitatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Ammonia and related amino acids in the pathogenesis of brain edema in acute ischemic liver failure in rats

The pathogenesis of brain edema in acute liver failure is poorly understood. We have previously shown that rats with ischemic acute liver failure (portacaval anastomosis followed by hepatic artery ligation) exhibit brain edema and intracranial hypertension, with swelling of cortical astrocytes as the most prominent neuropathological abnormality. Because ammonia has been shown to induce swelling of astrocytes in vivo and in vitro, we examined the relationship between brain ammonia, amino acids generated from ammonia metabolism and brain water content in this model. Four groups of animals were studied: rats subjected to two sham operations, rats subjected to portacaval anastomosis and a sham operation, rats subjected to a sham operation and hepatic artery ligation and rats subjected to portacaval anastomosis and hepatic artery ligation. The last group of animals was studied at three progressive stages of encephalopathy. Cortical gray matter water increased from 80.26% +/- 0.22% (sham + sham) to 82.46% +/- 0.06% (last stage of devascularization). In cerebral cortex, brain ammonia increased to a maximum of 5.4 mmol/L. Glutamine, generated in glial cells from ammonia and glutamate, increased sixfold to 24 mmol/L and remained at this level throughout all stages of encephalopathy. Alanine, which may be generated from the transamination of glutamine, increased in parallel to the increase in water (r = 0.80, n = 15). In this model of fulminant liver failure and associated brain edema, brain ammonia increases to levels associated with in vitro swelling of brain slices and glial cells. The accumulation of osmogenic aminoacids such as glutamine and alanine may contribute to the selective astrocyte swelling seen in this condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Interrelationship and clinical significance of increased resistance in the uterine arteries in patients with hypertension or preeclampsia or both

OBJECTIVES

This study was designed to evaluate the clinical significance of the Doppler flow velocity waveform analysis of the two uterine arteries on an individual basis and in combination expressed as the mean uterine artery.

STUDY DESIGN

We evaluated uterine artery resistance by means of continuous wave Doppler ultrasonography in 123 pregnant women with chronic hypertension, preeclampsia, or both. The placental location was determined by real-time ultrasonography. Clinical outcomes were compared according to uterine artery abnormalities. The Doppler flow studies were not used in patient management.

RESULTS

In patients with unilateral placentas (n = 67) the placental uterine artery was found to be a better predictor of poor pregnancy outcome than the nonplacental artery and the mean of the two arteries. There was a strong degree of correlation between abnormal nonplacental uterine artery and abnormal mean of uterine artery (r = 0.75, p less than 0.001), and there was a moderate degree of correlation between abnormal placental uterine artery and abnormal mean uterine artery (r = 0.46, p less than 0.001). Uterine artery discordance (left-right uterine artery systolic/diastolic ratio) was mostly the result of an abnormal nonplacental uterine artery (r = 0.74, p less than 0.0001) and not the result of an abnormal mean uterine artery (r = 0.44, p less than 0.003); the degree of discordance did not relate to pregnancy outcome. Unilateral placental location was associated with longer stays in neonatal intensive care units and more perinatal deaths.

CONCLUSION

Because of the differences between the two uterine arteries, we conclude that for proper interpretation of uterine artery flow velocity waveforms, the placental location should be known and each vessel analyzed individually.

Uteroplacental Doppler flow velocity waveform analysis correlates poorly with glycemic control in diabetic pregnant women

We examined 65 pregnant women with gestational (n = 31) and insulin dependent (n = 34) diabetes mellitus in order to evaluate the clinical usefulness of Doppler flow velocity waveform analysis in these pregnancies. Umbilical and uterine artery flow velocity waveforms were obtained during the third trimester with a continuous wave Doppler device. Quality of maternal glycemic control was evaluated by hemoglobin (Hb) A1 measurements at the time of delivery in 61 patients and by mean capillary blood sugars during the third trimester of pregnancy in four patients. There was no difference in various clinical and Doppler parameters between patients with good glycemic control and those with poor control. In contrast, the same clinical and Doppler parameters were significantly different in patients with preeclampsia than in those without preeclampsia, regardless of glycemic control. There was a poor positive linear correlation (r = 0.30, p less than 0.02) between maternal HbA1 and umbilical artery flow velocity waveforms (systolic/diastolic ratio). Proteinuria correlated better with umbilical artery systolic/diastolic ratio (r = 0.49, p less than 0.001). We conclude that Doppler flow velocity waveform analysis may be clinically useful only in diabetic pregnancies complicated by preeclampsia.

Interrelationship between atrial natriuretic factor concentrations and acute volume expansion in pregnant and nonpregnant women

The secretion of atrial natriuretic factor by human atrial myocytes is stimulated by increased intraatrial pressure or atrial distention. To determine whether acute intravascular volume expansion affects atrial natriuretic factor concentrations during pregnancy, circulating atrial natriuretic factor levels were measured in pregnant women at term (before elective cesarean section) and nonpregnant control subjects before and during intravenous infusion of lactated Ringer's solution (approximately 30 ml/kg). Venous plasma concentrations of alpha-human atrial natriuretic factor were determined by a specific radioimmunoassay. A significant increase in alpha-human atrial natriuretic factor levels in nonpregnant subjects was seen. Pregnant women did not show a significant response to a similar stimulus. Finally, basal alpha-human atrial natriuretic factor levels in pregnant and nonpregnant women were not different. Volume expansion (long-term or short-term) in normal human pregnancy may not be sensed by atrial volume sensors, possibly because it is accommodated by an enlarged maternal vascular compartment.

Effect of placental laterality on uterine artery resistance and development of preeclampsia and intrauterine growth retardation

We studied 153 pregnant women with normal pregnancies and 147 women with complicated pregnancies (diabetes, hypertensive disorders, and intrauterine growth retardation) to evaluate the association of placental location and the development of preeclampsia, intrauterine growth retardation, and uterine artery resistance. The placental location was determined by real-time ultrasonography, and the uterine artery resistance was determined by continuous-wave Doppler flow velocity waveform analysis. In the presence of preeclampsia or intrauterine growth retardation, up to 75% of the patients had unilaterally located placentas and 25% central placentas, whereas in the absence of these two conditions only 51% of the patients had unilateral and 49% central placentas (p less than 0.02). In patients with unilateral placentas, the incidence of preeclampsia and intrauterine growth retardation was 2.8-fold and 2.7-fold greater than in patients with central placentas (p less than 0.03 and p less than 0.01). Among all patients unilateral placental location was more likely to be associated with abnormal artery flow velocity waveforms than central placental location (p less than 0.001). We conclude that unilateral placental location may predispose to the development of preeclampsia and intrauterine growth retardation by its effect on uterine artery resistance.

Vaginal pH: a marker of preterm premature rupture of the membranes

Preterm premature rupture of the membranes (PROM) is a common predecessor of preterm or low birth weight (LBW) birth, yet the risk of preterm PROM is presently unpredictable. Numerous infectious organisms that change the normal vaginal milieu have been associated with preterm PROM. Because these organisms alter vaginal pH, the use of pH was evaluated as a potential marker for women at increased risk for preterm PROM. Among 115 women at high risk for an LBW birth, those with a mean vaginal pH above 4.5 had a threefold increased risk of preterm PROM as compared with those with a mean pH of 4.5 or lower. Vaginal pH may be a useful marker to predict a woman's risk for preterm PROM.

Ammonia-induced swelling of rat cerebral cortical slices: implications for the pathogenesis of brain edema in acute hepatic failure

The pathogenesis of brain edema in fulminant hepatic failure is incompletely understood. Our previous studies in models of this disease suggest the presence of a cytotoxic mechanism; as cortical astrocytes appeared predominantly swollen, we hypothesized that ammonia, metabolized to glutamine solely within this cell, could play a role in brain water accumulation. We determined ammonia levels in different brain regions of rats after hepatic devascularization, a model previously shown to exhibit brain edema. Concentrations of 2.5 mM were observed in the edematous cerebral cortex. We then added several concentrations of ammonium chloride to the first cortical brain slice, a preparation used to study cytotoxic brain edema. At a final bath concentration of ammonia of 5 and 10 mM, swelling could be detected: a decrease in the space of distribution of inulin was seen at the 10 mM concentration, suggesting intracellular water accumulation. Neuropathologically, astrocytes appeared involved even at subswelling doses of ammonia. Octanoic acid, at a 10 mM concentration, also resulted in demonstrable swelling. Ammonia, at concentrations in the incubation bath that approach the levels seen in an in vivo model of brain edema, results in water accumulation of cortical brain slices. Toxins implicated in the pathogenesis of hepatic encephalopathy, such as ammonia and octanoic acid, may, result in brain water accumulation.

Correcting umbilical artery flow velocity waveforms for fetal heart rate is unnecessary

We prospectively examined 55 normal pregnant women between 32 and 41 (means = 37) weeks' gestation. Five measurements of the umbilical artery peak-systolic/end-diastolic frequency ratio were obtained from each patient during one examination. Comparison of the fetal heart rate and the umbilical artery peak-systolic/end-diastolic frequency ratios between pregnancies less than 37 and greater than 37 weeks' gestation revealed no difference. Subsequently a total of 256 measurements were analyzed as one group. Plotting the individual peak-systolic/end-diastolic frequency ratios against the corresponding fetal heart rates revealed a moderate negative linear correlation: y = 4.15-0.012x, r = -0.36 and p less than 0.04. When only heart rates between 120 to 160 beats/min were plotted against peak-systolic/end-diastolic frequency ratios, a weaker correlation was found (r = -0.33, p = 0.15). The difference (mean +/- SD) between the obtained and the corrected peak-systolic/end-diastolic frequency ratios was 4.4% +/- 3.2%. The 95th percentile of the obtained peak-systolic/end-diastolic frequency ratio was 3.35 and the corrected ratio was 3.27. Averaging of the five measurements obtained from each patient for all 55 patients decreased the 95th percentile value to 3.09 whereas the same procedure for the corrected peak-systolic/end-diastolic frequency ratios decreased it to 3.07. We conclude that although there is a statistically significant negative linear correlation between the fetal heart rate and the umbilical artery peak-systolic/end-diastolic frequency ratio, this relationship is not clinically significant.

Oxytocin, vasopressin, and prolactin responses associated with nipple stimulation

Nipple stimulation by pregnant women close to term results in oxytocin release, as reflected by increased levels of oxytocin in peripheral plasma. This appears to be a specific response, and it does not involve either vasopressin or prolactin release.

Systemic tocolysis for premature labor is associated with an increased incidence of pulmonary edema in the presence of maternal infection

Our hypothesis is that systemic tocolysis of patients in premature labor is associated with a higher incidence of pulmonary edema in the presence of maternal infection. Over a 64-month period, medical records of all patients with a diagnosis at discharge of pulmonary edema or congestive heart failure were reviewed. There were 27 cases of pulmonary edema, 16 of which (59.3%) were associated with treatment of preterm labor. The incidence of pulmonary edema in patients receiving systemic tocolysis for treatment of preterm labor was significantly higher than that in our general obstetric population (3.04% versus 0.05%). Of the 527 patients receiving tocolysis, there was evidence of maternal infection in 52. The incidence of pulmonary edema was higher in the presence of maternal infection than in its absence (11/52 or 21% versus 5/475 or 1%, p = 0.0000). We conclude that there is a very strong association between the development of pulmonary edema and the presence of maternal infection in patients being treated for premature labor with systemic tocolysis.

Nonpalpable breast lesions at biopsy. A detailed analysis of radiographic features

Several studies have demonstrated that mammographic screening of asymptomatic women results in a lower mortality rate where breast cancer is concerned. Often, screening mammograms reveal a nonpalpable radiographic abnormality and the diagnosis must be determined by an excisional biopsy after radiographic needle localization. The mammographic features associated with 179 nonpalpable breast abnormalities biopsied after radiographic needle localization were carefully characterized. There were 41 carcinomas (23%) in the series. The aim of this study was to determine which radiographic findings, if any, strongly portend the presence of either a malignant or benign lesion. Mammographic features that were commonly associated with malignancy include a change from a previous mammogram, a distortion of the surrounding architecture, the association of a soft tissue density and calcifications, and the presence of more than ten calcifications in the lesion. The radiographic abnormalities which were more commonly associated with benign disease include well-defined densities without calcifications, asymmetric densities without calcifications, and abnormalities consisting solely of a focus of mammographic calcifications that have fewer than ten concretions. The incidence of malignancy in lesions having these mammographic characteristics was only 5.5%. On the basis of these results alone, no firm threshold for biopsy can be recommended. The risks of deferring biopsy until there is worsening of the mammographic image remains to be determined.

Human fetal breathing response to intravenous glucose is directly related to gestational age

This prospective longitudinal study examined human fetal breathing activity over the second half of pregnancy both in the fasting state and after intravenous glucose administration. There was a linear relationship between gestational age and percent time spent breathing after glucose between 19 and 38 weeks' gestation. However, no such correlation could be demonstrated between gestational age and fetal breathing activity in the fasting state.

Efficacy of combined administration of magnesium sulfate and ritodrine in the treatment of premature labor

Seventy-four patients in preterm labor at 20-35 weeks' gestation were randomly assigned to receive ritodrine (N = 36) or ritodrine plus magnesium sulfate treatment (N = 38) for tocolysis. Ten did not complete therapy and were excluded from analysis. Nineteen of 32 patients (59%) in the ritodrine plus magnesium sulfate group were successfully treated, compared with only 11 of 32 patients (34%) in the ritodrine-only group (P less than .05). Of the 21 patients who failed to respond to the initial ritodrine treatment, 16 received intravenous magnesium sulfate supplemental therapy; 75% of this group were treated successfully. The frequency of adverse maternal and fetal side effects did not differ between the treatment groups. In the combined group compared with the ritodrine group, the dose requirements for ritodrine therapy as well as the total duration of treatment for both ritodrine and magnesium sulfate were reduced significantly. We conclude that concurrent administration of ritodrine and magnesium sulfate is more efficacious than ritodrine alone and does not appear to increase the frequency of adverse side effects.

C-reactive protein: a limited test for managing patients with preterm labor or preterm rupture of membranes?

C-reactive protein has been used to identify patients at high risk for infectious morbidity with preterm labor or preterm rupture of membranes. In this article we report on 104 patients with preterm labor symptoms (n = 45) or preterm rupture of the membranes (n = 59) and serial evaluations of C-reactive protein measured by latex agglutination and laser nephelometry. The simple, inexpensive latex method appears comparable to the laser method in predicting infectious morbidity and can be used clinically. Elevated C-reactive protein values before delivery predict infectious morbidity in only 8% to 29% of patients, and up to 18% of patients with serious infections may be misdiagnosed as having normal C-reactive protein values before delivery.

Variable decelerations during nonstress tests are not a sign of fetal compromise

An examination of 908 fetal heart rate tests of 418 consecutive patients revealed brief variable decelerations in more than 50.7% of the patients. Although an association existed with nuchal cord location found at delivery, no association existed between these variable decelerations and fetal heart rate decelerations during labor, low Apgar scores at birth, or birth weight. We find no evidence to suggest that these brief variable decelerations are a sign of fetal compromise or an indication for obstetric intervention.

Predictors of hospital mortality after out-of-hospital cardiopulmonary resuscitation

Hospital mortality was examined in all patients successfully resuscitated from a witnessed out-of-hospital cardiac arrest due to ventricular fibrillation over a 1-yr period. Variables independently predictive of hospital mortality were a history of congestive heart failure before cardiac arrest, the time between collapse and initiation of CPR, and the time between collapse and restoration of circulation. The latter time was not related to either patient age or clinical history. Thus, hospital mortality was predetermined by prehospital factors, some of which can be changed.