Alternative technique or mitigating strategy for sevoflurane-induced neurodegeneration: a randomized controlled dose-escalation study of dexmedetomidine in neonatal rats

Background

Brain injury in newborn animals from prolonged anaesthetic exposure has raised concerns for millions of children undergoing anaesthesia every yr. Alternative anaesthetic techniques or mitigating strategies are urgently needed to ameliorate potentially harmful effects. We tested dexmedetomidine, both as a single agent alternative technique and as a mitigating adjuvant for sevoflurane anaesthesia.

Methods

Neonatal rats were randomized to three injections of dexmedetomidine (5, 25, 50, or 100 µg kg -1 every 2 h), or 6 h of 2.5% sevoflurane as a single agent without or with dexmedetomidine (1, 5, 10, or 20 µg kg -1 every 2 h). Heart rate, oxygen saturation, level of consciousness, and response to pain were assessed. Cell death was quantified in several brain regions.

Results

Dexmedetomidine provided lower levels of sedation and pain control than sevoflurane. Exposure to either sevoflurane or dexmedetomidine alone did not cause mortality, but the combination of 2.5% sevoflurane and dexmedetomidine in doses exceeding 1 µg kg -1 did. Sevoflurane increased apoptosis in all brain regions; supplementation with dexmedetomidine exacerbated neuronal injury, potentially as a result of ventilatory or haemodynamic compromise. Dexmedetomidine by itself increased apoptosis only in CA2/3 and the ventral posterior nucleus, but not in prefrontal cortex, retrosplenial cortex, somatosensory cortex, subiculum, lateral dorsal thalamic nucleaus, or hippocampal CA1.

Conclusions

We confirm previous findings of sevoflurane-induced neuronal injury. Dexmedetomidine, even in the highest dose, did not cause similar injury, but provided lesser degrees of anaesthesia and pain control. No mitigation of sevoflurane-induced injury was observed with dexmedetomidine supplementation, suggesting that future studies should focus on anaesthetic-sparing effects of dexmedetomidine, rather than injury-preventing effects.

Increased secretion of exopolysaccharide and virulence potential of a mucoid variant of Salmonella enterica serovar Montevideo under environmental stress

During an investigation to increase the recovery of Salmonella enterica from Oregano, an increased expression of exopolysaccharide was induced in Salmonella serovar Montevideo. The atypical mucoid (SAL242S) and the non-mucoid (SAL242) strains of Montevideo were compared and characterized using various methods. Serotyping analysis demonstrated that both strains are the same serovar Montevideo. Electron microscopy (EM) of cultured SAL242S cells revealed the production of a prominent EPS-like structure enveloping aggregates of cells that are composed of cellulose. Mucoid cells possessed a higher binding affinity for Calcofluor than that of the non-mucoid strain. Genotypic analysis revealed no major genomic differences between these morphotypes, while expression analyses using a DNA microarray shows that the mucoid variant exhibited heightened expression of genes encoding proteins produced by the SPI-1 type III secretion system. This increased expression of SPI1 genes may play a role in protecting Salmonella from environmental stressors. Based on these observations, Salmonella serovar Montevideo mucoid variant under stressful or low-nutrient environments presented atypical growth patterns and phenotypic changes, as well as an upregulated expression of virulence factors. These findings are significant in the understanding of survival abilities of Salmonella in a various food matrices.

Comparison between pulsed-wave Doppler- and tissue Doppler-derived Tei indices in fetuses with and without congenital heart disease

OBJECTIVES

The aim of this study was to compare the right (RV) and left (LV) ventricular Tei indices obtained by pulsed-wave Doppler (PD) and tissue Doppler (TD) methods in fetuses with structurally normal and abnormal hearts.

METHODS

This was a retrospective cross-sectional study of 147 fetuses that had a fetal echocardiogram and Tei index measured during a 2-year period. The RV and LV Tei indices were measured using both PD and TD methods. The difference between the two methods of Tei index measurement was tested using paired sample t-test, Pearson correlation coefficient was used to examine their relationship, and the agreement between the methods was tested using Bland-Altman analysis.

RESULTS

A total of 87 fetuses had normal hearts and 60 had a congenital heart defect. Both PD and TD Tei indices were measured successfully from at least one ventricle in 123 cases and from both ventricles in 110 cases. The mean TD Tei index was significantly higher than the mean PD Tei index for both ventricles (P < 0.0001). There was a weak but statistically significant correlation between the PD and TD Tei indices of the right ventricle (r = 0.20, P = 0.029), whereas the PD and TD Tei indices of the left ventricle did not correlate significantly (r = 0.04, P = 0.684). When pairs of Tei indices measured by two different methods (123 pairs for the right ventricle and 111 for the left ventricle) were tested with Bland-Altman analysis, the bias and precision were 0.147 and 0.254, respectively, for the right ventricle, and 0.299 and 0.276, respectively, for the left ventricle.

CONCLUSIONS

Correlation between Tei indices measured by PD and TD methods is weak and the agreement between individual measurements is poor. Therefore, they should not be used interchangeably in the assessment of fetal cardiac function.

Prediction of outcome of fetal congenital heart disease using a cardiovascular profile score

OBJECTIVES

Congestive heart failure in fetuses with congenital heart defects (CHD) is associated with high perinatal mortality. The clinical condition can be characterized by five ultrasound markers that comprise the 10-point cardiovascular profile (CVP) score. Our aim was to assess the value of the CVP score in evaluating the condition and in maintaining surveillance of fetuses with CHD.

METHODS

We evaluated retrospectively 131 singleton pregnancies with a diagnosis of fetal CHD, which had been assessed by serial echocardiographic examinations, during which the CVP score was obtained. Fetal and neonatal outcomes, including perinatal mortality and Apgar scores, were assessed.

RESULTS

Fetuses with a final CVP score <or= 7 were statistically significantly more likely to suffer mortality than were fetuses with a final CVP score >or= 8 (87.5% vs. 15.2% mortality; P < 0.0001, chi square = 24.5). Significance was maintained after controlling for birth weight, lag time between the final examination and delivery and the dichotomized 5-min Apgar score (odds ratio, 22.3; P = 0.024). For low Apgar score and mortality, the CVP score had low sensitivity (0.25 and 0.27, respectively) but high specificity (0.98 and 0.99, respectively). The presence of hydrops and severe cardiomegaly were statistically significantly associated with mortality (P < 0.05).

CONCLUSIONS

Fetuses with CHD and a CVP score below 8 are at risk of perinatal death. The CVP score may be used to assess the severity of fetal CHD and to plan perinatal management.

Cognitive deficits in school-age children with severe short bowel syndrome

BACKGROUND/PURPOSE

Improved therapies for the management of short bowel syndrome (SBS) have resulted in the prolonged survival of many children. By early childhood, the physiological sequelae of severe SBS include delayed physical development and metabolic imbalances. However, little is known about how SBS affects brain development. Although many parents report school problems, no controlled study has evaluated the integrity of the central nervous system in SBS children. The purpose of this study was to investigate the neuropsychological status of school-aged SBS children to determine if there were characteristic cognitive impairments that might be amenable to early therapeutic intervention.

METHODS

SBS children (n = 8; mean age, 116.9 +/- 21 months) were compared with an age-matched cystic fibrosis (CF) control group (n = 8; mean age, 118.1 +/- 14 months). Groups did not differ in age, grade, or absences. Neuropsychological tests with established sensitivity to CNS integrity compared performance over 6 cognitive domains. Emotional status also was measured. Analyses were completed with 2-tailed t tests.

RESULTS

Groups did not differ on tests of intellectual ability and emotional function. Language, memory and learning, and problem-solving testing results indicated no significant group differences. However, the SBS group performed more poorly on measures assessing visual-spatial ability, with P values ranging from .002 to .045. In a subset of subjects, we noted significantly slower left-handed, but not right-handed, performance on measures of finger dexterity and psychomotor speed.

CONCLUSIONS

Although emotional status did not differ from that of children with CF, SBS patients showed visual-spatial deficits in the company of preserved language, attention and memory, and executive skills. The specificity and consistency of these findings suggests that right hemisphere CNS changes may occur in children with SBS. This unexpected finding, coupled with the indication of left-sided psychomotor slowing in right-handed subjects, raises the possibility that actual brain impairment, rather than developmental delay accompanying slowed physical growth, accounts for these findings. Longitudinal studies are needed to further clarify this issue. The educational significance of the results is discussed.

Hamster Leydig cells are less sensitive to ethane dimethanesulfonate when compared to rat Leydig cells both in vivo and in vitro

It has been reported that ethane dimethanesulfonate (EDS) is a Leydig cell toxicant that affects rats and hamsters (Kerr et al., 1987), while, in contrast, the Leydig cells of mice are relatively insensitive to the toxicant. In the rat, there is a rapid decline in levels of testosterone (T) within hours after EDS administration. However, T production, spermiogenesis, and fertility are restored within a few weeks as new Leydig cells are formed from undifferentiated cells in the interstitium of the testis. In an earlier study, we found, as expected, that ejaculated sperm counts (ESCs) reached a nadir 10 days after adult rats were dosed with EDS at 65 mg/kg ip along with serum and testicular T, testis and seminal vesicle weights, and in vitro T production, while, in contrast, EDS at 65 mg/kg had no effect on these endpoints in the Syrian hamster (Gray et al., 1992). In the current study, when EDS was administered to 6, 12, and 18 month old hamsters at 100 mg/kg, it produced subtle effects on serum T and sex accessory gland weights, while dramatic effects were seen in similarly exposed rats. In addition, when testes were examined by light microscopy all treated rats displayed severely reduced Leydig cell numbers, while, in contrast, only one-third of the EDS-treated hamsters were affected, having moderately reduced Leydig cell numbers. In support of the histological data, 3 beta-HSD enzyme activity was reduced by 99% of control in EDS-treated rats, but it was reduced by only 35% of control in EDS-treated hamsters. An in vitro analysis of the effects of EDS on LH-stimulated T production by quartered testes demonstrated that the hamster testis was less sensitive to the direct effects of EDS than the rat testis. The IC50 after 3 hr in culture was greater than 1800 micrograms EDS/ml for the hamster quarter testes, while the IC50 for the rat quarter testes was 320 micrograms EDS/ml. In summary, these results demonstrate in vivo and in vitro that Leydig cells of hamsters are less sensitive to EDS than those of the adult rat.

Chest pain in otherwise healthy children and adolescents is frequently caused by exercise-induced asthma

Chest pain in children and adolescents, unlike in adults, is rarely of cardiac origin and its etiology is frequently unknown. In this age group, chest pain can limit normal activity and sports participation. The reported incidence of exercise-induced asthma in children with chest pain is less than 20%. For this study, 88 otherwise healthy children and adolescents with chest pain followed a treadmill protocol without a warm-up period designed to obtain a target heart rate of 180 or greater during the first several minutes of exercise. Patients maintained this workload for 6 to 8 minutes. Pulmonary function tests performed prior to exercise and at 2, 5, 10, 15, 20, and 25 minutes revealed a decrease in forced expiratory volume in 1 second or peak expiratory flow rate of greater than or equal to 15% in 64 (72.7%) children. Inhaled albuterol resulted in subjective improvement in 97% (35/36) and objective improvement in 70% (25/36) of patients. In otherwise healthy children and adolescents with chest pain, the incidence of exercise-induced asthma seems greater than previously reported. Treatment with bronchodilators may help these patients lead a more active life-style.

Use of synthetic oligonucleotide DNA probes for identification and direct detection of Bacteroides forsythus in plaque samples

Oligonucleotide DNA probes complementary to the hypervariable region of the 16S rRNA of Bacteroides forsythus were tested for their specificity and sensitivity against reference and clinical isolates of 73 different species of bacteria. The probes were used to detect the organism directly from nucleic acid extracts of subgingival plaque samples, and the results were compared with results of detection by culture methods. The data demonstrate that the probes are very specific (100%) and sensitive (100% when they are compared with those obtained by the culture method) and could reliably detect the organism in plaque samples. When a probe to a conserved region of the 16S rRNA (UP9A) was used to estimate the quantity of bacteria present in plaque samples, it gave results comparable to those of culture methods. The data suggest that total microbial load may be a parameter in periodontal disease.

A double-blind, placebo-controlled trial of fluoxetine plus behavior modification in the treatment of obese binge-eaters and non-binge-eaters

To determine whether fluoxetine is effective in the long-term treatment of obesity and whether it is particularly useful in the treatment of obese binge-eaters, the authors randomly assigned 45 obese subjects (22 with binge-eating problems and 23 without binge-eating) to fluoxetine (60 mg/day) or placebo in a 52-week double-blind trial. The 21 subjects who completed the trial made 13 clinic visits and were taught basic behavior modification strategies. Patients treated with fluoxetine plus behavior modification lost significantly more weight than those treated with placebo plus behavior modification. However, the drug did not appear to have a differential benefit for binge-eaters.

Flecainide for supraventricular tachycardia in children

The clinical efficacy, adverse effects and pharmacokinetics of flecainide were evaluated in 16 pediatric and young adult patients with supraventricular tachycardia (SVT). Patients had received an average of 2.8 drugs before flecainide was tried. The following mechanisms of supraventricular arrhythmias were determined in patients by intracardiac electrophysiologic studies: atrioventricular node reentry, 4; reentry through an accessory connection, 7; atrial automatic focus, 2; atrial flutter, 3. Twelve patients had normal cardiac anatomy and 4 had congenital heart disease. Each patient received 2.8 mg/kg/day of flecainide divided into 2 doses 12 hours apart. After 3 days, the dose was increased to 5.6 mg/kg/day if necessary. In 14 patients, serum flecainide concentrations measured 3 to 4 days after beginning therapy ranged from 0.1 to 0.8 micrograms/ml (mean 0.40). Flecainide successfully controlled SVT in 8 of 16 patients. SVT in 3 of 7 patients with accessory connections and in 3 of 4 patients with atrioventricular node reentry was successfully controlled. In 1 of 2 patients with atrial automatic tachycardia, SVT had been completely controlled over 16 months. Only 1 of 3 patients treated for atrial flutter responded. Follow-up for successfully treated patients ranged from 4 to 16 months (median 9). Seven patients continue to take flecainide. None of the patients had clinical congestive heart failure. No drug-related adverse effects were noted on the resting surface electrocardiogram. Flecainide rarely produced proarrhythmic effects in this series. The 2 that were observed were mild and caused no clinical problems. Noncardiovascular side effects also occurred infrequently.(ABSTRACT TRUNCATED AT 250 WORDS)

Methodological issues related to age of onset of obesity

Research related to age of onset of obesity may be hampered by two methodological problems: (a) inconsistencies across studies in the criteria used to define early-onset and maturity-onset obesity and (b) the failure to control for other differences between early-onset and maturity-onset obese patients. Analyzing data from 178 applicants to a behavioral weight control program, this study found that almost twice as many patients were classified as early-onset obese when the division was based on their answer to the question, "Were you overweight as a child or teenager?" than when the division was based on self-reported weight at age 21. Moreover, early-onset obese patients were younger and heavier than those with maturity-onset obesity. Further studies are needed to determine the most reliable and valid means of classifying patients as early- or maturity-onset obese.

Autoregulation of testosterone secretion in perfused rat testes

Infusion of testosterone into the testicular artery, at concentrations comparable to those that occur in the testicular vein in situ, inhibited LH-stimulated testosterone secretion by rat testes perfused in vitro. This inhibition was rapid and dose responsive. In contrast to testosterone, intra-arterial infusion of 5 alpha-androstan-3 alpha, 17 beta-diol, corticosterone and androstenedione failed to inhibit testosterone secretion. The inhibition of testosterone secretion by intra-arterial infusion of testosterone was reversed by either cessation of testosterone infusion or the simultaneous addition of androstenedione to the artificial perfusion medium. Taken together, these results showed that LH-stimulated testosterone secretion by in vitro perfused rat testes was inhibited by a short-loop negative feedback of testosterone.

Mathematical model of steroidogenesis in rat and rabbit testes

The purpose of this study was to develop a mathematical model of testicular steroidogenesis which could not only predict steroid secretion but also could be implemented to test the validity of assumptions used in studies of testicular testosterone biosynthesis in rats and rabbits. Since the two predominant fates of testicular steroids are metabolism and secretion, we hypothesized that the data for construction of the model could be observed testicular steroid secretions and that these data could then be used to elucidate intratesticular steroid conversions. Equations based on steroid secretion by testes perfused in vitro were developed to estimate transition probabilities corresponding to steroid secretion or conversion. The model was tested by comparing the predicted steroid secretion rates with those observed for control testes perfused in vitro. In addition, the transition probabilities determined by the model were used to indicate the predominant series of reactions for converting pregnenolone to testosterone. The results presented herein confirm the capability of the model to predict steroid secretion rates and to predict preferred pathways for testosterone biosynthesis in maximally stimulated testes perfused in vitro. Moreover, the model construction required only algebra and steady-state measurements.

Testosterone and 5alpha-reduced androgen secretion by rabbit testes-epididymides perfused in vitro

Mass spectrometric determinations confirmed that testosterone, 5alpha-androstan-17betaol-3-one, 5alpha-androstan-3alpha, 17beta-diol and 5alpha-androstan-3beta, 17beta-diol were present in venous effluent of in vitro perfused rabbit testes-epididymides. Testosterone, dihydrotestosterone, 3alpha-androstanediol and 3beta-androstanediol were secreted at 3.1 plus or minus 0.9, 0.7 plus or minus 0.2, 0.4 plus or minus 0.1 and 0.6 plus or minus 0.1 mug/h when testes-epididymides were perfused with an artificial medium containing 2.5 ng/ml NIH-LH-S17, ovine. Surprisingly, testosterone constituted only 64% of the total mass of the four androgens secreted. These results probably reflect in vivo androgen secretion since hourly collections of spermatic vein blood from anesthetized rabbits contained 2.7 plus or minus 0.9, 0.8 plus or minus 0.3, 0.15 plus or minus .04 and 0.5 plus or minus 0.2 mug of testosterone, dihydrotestosterone, 3alpha-androstanediol and 3beta-androstanediol, respectively. Once again testosterone constituted only 64% of the total mass of the four androgens.

Formation and secretion of 5alpha-androstan-17beta-ol-3-one, 5alpha-androstan-3alpha,17beta-diol and 5alpha-androstan-3beta,17beta-diol by the perfused rabbit testis epididymis

Rabbit testes epididymides were perfused in vitro at 36.5 C with an artificial medium containing bovine red blooc cells. Three major testosterone metabolites were formed and subsequently elaborated into the venous effluent of testes epididymibdes when testosterone-1,2,6,7-3-H was infused into the artery of the perfused organ. In contrast, testosterone-1,2,6,7-1-H remained unchanged when incubated in the artificial medium under similar conditions. Elution volume from a Sephadex LH-20 column, development in three ascending paper chromatographic (APC) systems, acetylation and development in a fourth APC system followed by gas liquid chromatography (GLC) of the acetylated products tentatively identified the radioactive-metabolites as 5alpha-androstan-17beta-ol-3-one (DHT), 5alpha-androstan-3alpha,17beta-diol (3alphaol) and 5alpha-androstan-3beta,17beta-diol (3beta-ol). The identity of these 5alpha-reduced testosterone metabolites was confirmed by crystallization to constant specific activity in the presence of authentic carrier steroid. These results suggest that DHT and androstanediols formed by perfused rabbit testes epididymides subsequently escape into the venous effluent.