Activities of aminopeptidases in a rat saline model of volume hypertension

Aminopeptidase activity plays a role in the metabolism of several peptides that could be involved in blood pressure control. This activity has been implicated in the pathogenesis of hypertension, essentially in spontaneously hypertensive rats. However, few studies have examined aminopeptidase activities in animal models other than genetic hypertension. To analyze the aminopeptidase response to the specific conditions of the reduced renal mass saline model of arterial hypertension, aminopeptidase A activity (glutamyl- and aspartyl-aminopeptidase), aminopeptidase M activity (alanyl-aminopeptidase), aminopeptidase B activity (arginyl-aminopeptidase), pyroglutamyl-aminopeptidase and cystinyl-aminopeptidase were measured in the neurohypophysis, in the adrenal gland and in serum of this model of hypertension. In the neurohypophysis, there was a significant increase of soluble cystinyl-, alanyl-, arginyl-, pyroglutamyl- and membrane-bound aspartyl-aminopeptidase activities in hypertensive animals. In the adrenal gland, soluble cystinyl-, alanyl-, arginyl- and pyroglutamyl-aminopeptidase activities were also higher in hypertensive rats than in normotensive controls. No differences were found in serum levels of aminopeptidase activities between both groups of animals. A highly significant positive correlation between the neurohypophysis and the adrenal gland was observed for soluble cystinyl- and alanyl-aminopeptidase activities in the model of hypertension, whereas no correlation was observed in normotensive rats. Our results suggest that aminopeptidase activities could be involved in the regulatory response to the reduced renal mass hypertension and also suggest a coordinate response between the adrenal gland and the neurohypophysis, to the specific metabolic conditions of this model of hypertension.

Cross-adaptation and molecular modeling study of receptor mechanisms common to four taste stimuli in humans

Psychophysical cross-adaptation experiments were performed with two carbohydrates, sucrose (SUC) and fructose (FRU), and two sweeteners, acesulfame-K (MOD) and dulcin (DUL). Seven subjects were asked to match concentrations that elicited the same intensity as a sucrose reference (30 g/l). Cross-adaptation levels were calculated as the ratio of isointense concentrations measured for a given stimulus before and under adaptation. On average, cross-adaptation between SUC and FRU is low and apparently reciprocal. By contrast, cross-adaptation between SUC and MOD is clearly non-reciprocal: SUC adapts MOD significantly (24%, P < 0.005), but MOD fails to adapt SUC (2%, P < 0.79). Significant and reciprocal cross-enhancement is observed between DUL and MOD (approximately -20%, P < 0.03), and also between SUC and DUL (approximately -15%, P < 0.08). In parallel, molecular modeling of the four tastants was performed in order to look for the 12 common binding motifs that were isolated on 14 other tastants in a previous study. SUC and FRU each display 10 out of the 12 binding motifs, whereas DUL and MOD only display four and five distinct motifs respectively and do not have any motif in common. Experimental cross-adaptation levels seem to correlate well with the number of motifs that molecules have in common. FRU and SUC share a majority of binding motifs and correlatively show mutual cross-adaptation. Four motifs of MOD are found among the 10 motifs of SUC, which may explain why SUC cross-adapts MOD but not vice versa. By contrast, DUL and MOD do not share any motif and do not cross-adapt. The various molecular mechanisms that may be responsible for cross-adaptation and/or cross-enhancement are discussed in light of our results.

Ventilatory physiology of children and adolescents with anxiety disorders

BACKGROUND

Abnormalities in ventilatory physiology have been noted in adults with panic disorder. We tested the hypothesis that abnormalities in ventilatory physiology differentiate children and adolescents with anxiety disorders from psychiatrically healthy children.

METHODS

Ventilatory physiology was monitored with a canopy apparatus during room-air breathing and 15 minutes of carbon dioxide exposure in 33 children and adolescents comprising 18 probands with an anxiety disorder and 15 psychiatrically healthy children.

RESULTS

During room-air breathing, probands had significantly larger minute ventilation, larger tidal volumes, and more variable breathing patterns than healthy comparisons, but the groups did not differ in end-tidal carbon dioxide or respiratory rate. During carbon dioxide challenge, probands exhibited larger minute ventilation and respiratory rate responses relative to comparisons.

CONCLUSION

These findings on the association between ventilatory physiology and anxiety disorders in children and adolescents are consistent with results from studies of adults with panic disorder.

Analytical evaluation of an improved procedure for measuring thyrotropin

The analytical characteristics of the AxSYM Ultrasensitive hTSH-II (Abbott Laboratories) procedure for quantitation of serum thyrotropin (TSH) concentration were evaluated. Within- and between-run imprecisions, functional sensitivity, analytical interval and relative inaccuracy with respect to the Enzymum-Test TSH (Boehringer Mannheim) were studied. In all cases, the within-run and between-run of coefficients variation were lower than 6.69% and 8.12% respectively. The measurement range was tested with serial dilutions of a serum with a high thyrotropin concentration, and the procedure was found to be linear up to at least 87.0 mIU/l. The functional sensitivity was 0.018 mIU/l. The relative inaccuracy study (Passing-Bablok non-parametric linear regression) produced the following linear equation: (AxSYM) = 1.02. (ES-700)-0.03 mIU/l, with 95% confidence intervals of a (-0.05; -0.01); b (0.98; 1.06).

Natural evolution of nuchal thickness in trisomy-21 fetuses

OBJECTIVE

To assess the natural evolution of nuchal thickness in trisomy-21 fetuses.

METHODS

Serial measurements of nuchal thickness were performed over a 1- to 6-week period in 45 consecutive fetuses with trisomy 21, between the 10th and the 23rd weeks of pregnancy. To avoid a gestational age confounding effect, nuchal thickness also was expressed in standard deviations (SDs) for the corresponding gestational week. In addition, the changes were assessed in terms of the presence of clinical positive thickening, considered as such when the measurement was above 2.5 SD.

RESULTS

A mean increase of 1.8 mm (95% confidence interval [CI] 1.3, 2.3) for nuchal thickness was observed for a mean period of 21 days. When corrected by gestational age, the mean increase of 0.3 SD (95% CI -0.2, 0.9) was found to be not significant. No clinically relevant nuchal thickening changes were recorded (51% versus 69%) at re-examination.

CONCLUSION

Nuchal thickening at re-examination is observed in a similar proportion of trisomy-21 fetuses as when first observed.

Sex differences and in vitro effects of steroids on serum aminopeptidase activities

We studied the possible existence of physiological sex differences in serum aminopeptidase activities in mice, by evaluating the effect of gonadectomy and the in vitro response to the presence in the medium of cholesterol or steroid hormones. Alanyl- and glutamyl-aminopeptidase activities were measured in sera from male, female, orchiectomized and ovariectomized mice, incubated with substrate solutions, and compared with the same groups of serum incubated with substrate solutions including cholesterol, 17-beta-estradiol, testosterone, progesterone or hydrocortisone. Our results demonstrated highly significant sex differences, and an influence of cholesterol and steroid hormones on aminopeptidase activity. Depending on the nature of the aminopeptidase, these enzymes responded in different ways to the presence of these substances and also responded differently to gonadectomy. For alanyl-aminopeptidase activity, but not for glutamyl-aminopeptidase activity, there was a clear difference in response between males and females to incubation of the serum with steroid hormones.

Hemodynamic response to respiratory challenges in panic disorder

This study compares the hemodynamic response to panic disorder subjects with that of normal controls during respiratory challenges. Panic patients meeting DSM-IIIR criteria for panic disorder and normal controls were challenged with room air hyperventilation, 5% CO2 breathing, and 7% CO2 breathing. Measurements of pulse and blood pressure were taken at resting baseline and before and at the end of each respiratory challenge. Panic attack to each challenge was determined by using raters blinded to subject diagnosis and each subject's self-rating of panic. Significantly larger systolic and diastolic blood pressure increases were found in patients who panicked with room air hyperventilation than nonpanicking patients or normal controls. No significant blood pressure differences were found with 7% or 5% CO2 challenges, but higher pulse rates were found in the patient group. It may be possible that panic with room air hyperventilation causes a significant increase in systolic and diastolic blood pressure, or that a subgroup of panic disorder patients has a hyperactive vascular response to hypocapnia. These patients panic with room air hyperventilation and develop greater vasoconstriction and/or increased blood pressure response.

Changes in serum osteocalcin levels in the follow-up of kidney transplantation

Serum osteocalcin, total alkaline phosphatase, intact parathyroid hormone (PTH), creatinine, calcium, and phosphate were determined in 23 kidney cadaveric allograft recipients, immediately before and 0.5, 1, 3 and 6 months after surgery. Immunosuppressive treatment was based on low doses of corticosteroids and cyclosporin combined with antilymphoblast globulin. The decrease in serum creatinine was accompanied by falling PTH concentrations. Serum osteocalcin levels were higher than normal before kidney transplantation and diminished at 0.5 and 1 month after surgery. Significant increases in serum osteocalcin concentrations were observed 3 and 6 months after kidney transplantation with a significant correlation with alkaline phosphatase levels. The increase in serum osteocalcin levels observed in our transplanted patients is not related with a parallel increase in serum creatinine levels nor with an increment in PTH levels; it seems to reflect an increase in the osteoblastic activity, which is not altered by steroid therapy.

Effects of the antipsychotic drug sulpiride on reproductive hormones in healthy premenopausal women: relationship with body weight regulation

Metabolic and endocrine abnormalities secondary to hyperprolactinemia, such as hypogonadism and hyperandrogenicity, may be involved in the excessive body weight gain induced by antipsychotic drugs in women. The present study was conducted in healthy premenopausal women, in order to detect an endocrine imbalance secondary to antipsychotic drug administration, which, if sustained in the long term, might be involved in the development of obesity. After a control menstrual cycle, sulpiride (200 mg/day) or placebo was nonblindly administered for 28 days; blood lipids and the serum levels of the following hormones which are involved in body weight regulation were assessed at days 3, 10, 20 and 26 of the cycle: prolactin (PRL), 17-beta estradiol (E2), progesterone (P4), follicle stimulating hormone (FSH), luteinizing hormone (LH), free testosterone (T5), dehydroepiandrosterone sulfate (DHEAS), cortisol, tyrotropic hormone (TSH), tetraiodothyroxine (T4), and the areas under the insulin and glucose tolerance curve. During sulpiride administration, the following changes were observed when compared to placebo administration: PRL levels were significantly increased; E2 levels were significantly reduced at days 10 and 20; P4 levels were significantly reduced at day 20, and the area under the glucose tolerance curve was significantly increased. The other variables were not significantly affected. The body weight gain was higher during sulpiride than during placebo administration, but it did not reach statistical significance, perhaps because the period of treatment was too short. The decrease in the serum levels of E2 during sulpiride administration is probably secondary to hyperprolactinemia. It affects the E2/T5 ratio in the direction of increasing the androgenic activity, as observed in women with well-established obesity. This effect, along with a genetic predisposition, increased appetite, hypoactivity and ignorance of proper dietary habits, may explain the excessive weight gain and obesity observed in women during chronic treatment with sulpiride and other antipsychotic agents.

Respiratory psychophysiology of panic disorder: three respiratory challenges in 98 subjects

OBJECTIVE

Respiratory abnormalities may play a central role in the pathophysiology of panic disorder. The current study was undertaken to examine the respiratory response in the largest series of subjects to date during three respiratory challenges that used improved methodology.

METHOD

Fifty-nine patients with DSM-III-R panic disorder and 39 normal volunteers were challenged with 5% and 7% CO2 inhalation and room air hyperventilation separated by room air breathing with continuous spirometry.

RESULTS

Patients with panic disorder were more sensitive to the anxiogenic effects of CO2 than were normal subjects, and CO2 was a more potent stimulus to panic than hyperventilation. Patients increased their respiratory rate more quickly during CO2 inhalation than did comparison subjects, and this increase preceded the panic attacks. Patients who panicked in response to 5% CO2 demonstrated continued rise in end-tidal CO2, while the end-tidal CO2 of the comparison groups stabilized. Low end-tidal CO2 and high variance in minute ventilation at baseline predicted panic attacks during CO2 inhalation. Following CO2 or hyperventilation challenges, respiratory rate dropped sharply, while tidal volume remained elevated longer in patients than in comparison subjects.

CONCLUSIONS

The findings confirm the greater behavioral and physiological sensitivity of patients with panic disorder to CO2 inhalation and identify a series of respiratory abnormalities. Panic attacks in panic disorder may be explained by inefficient compensatory mechanisms, primarily of respiratory rate.

Renal aminopeptidase activities in animal models of hypertension

Aminopeptidase activity (AP) has been implicated in the metabolism of renal and circulating vasoactive peptides. This activity is involved in the pathogenia of hypertension, essentially in spontaneously hypertensive rats. However, no other animal models, which develop hypertension by other different ways, have been used to study the possible role of aminopeptidase activity. To investigate the role of this activity in the pathogenesis of hypertension, angiotensinase A activity (glutamyl-AP and aspartyl-AP), aminopeptidase M activity (alanyl-AP), aminopeptidase B activity (arginyl-AP), pyroglutamyl-AP, and cystinyl-AP were measured in the serum and kidney of two experimental animal models of renovascular hypertension: Goldblatt two-kidney one clip (G2K-1C) and low renal mass rats (LRM). No differences were found in serum levels of AP in LRM or G2K-1C in comparison with their respective controls. In LRM rats there was a significant decrease in membrane-bound angiotensinase A (glutamyl-AP), arginyl-AP and alanyl-AP activities. In G2K-1C rats there was a significant decrease in soluble and membrane-bound angiotensinase A activity (aspartyl-AP). Our results suggest that AP activities play a role in the regulation of renal vasoactive peptides, and respond differently depending on the cause of hypertension.

Laparoscopic versus open Nissen fundoplication: outcome of surgery in monozygotic twins

Differences in outcome and cost of laparoscopic and open surgery are continuously being evaluated. Two-year-old monozygotic twin boys with a previous history of prematurity, severe gastroesophageal reflux disease, and intractable reactive airway disease were each scheduled to undergo a laparoscopic Nissen fundoplication (LNF) on the same day. Current medications for both patients included albuterol, cromolyn sodium, dexamethasone, ranitidine, and metoclopramide. In the first case, the laparoscopic procedure was converted to an open Nissen fundoplication (ONF) to gain expeditious control of bleeding from a short gastric vessel close to the spleen. The second patient underwent LNF without complication. Operative time for each patient was 3.5 h. The postoperative length of stay for each patient was 6 days (ONF) and 4 days (LNF). The total hospital charges were $21,931 (ONF) and $19,108 (LNF). The first patient (ONF) was readmitted later on the day of discharge (postoperative day 6) for vomiting and was discharged after 24 h with no further treatment. The subsequent course of each patient was similar. At a 6-week follow-up visit, both patients were tolerating a regular diet with weight gain and dramatic improvement in pulmonary symptoms.

Limited effectiveness of femur and humerus shortening as markers of Down syndrome in early midtrimester fetuses

This is a prospective screening study addressed to assess the value of femur and humerus shortening in the prenatal detection of Down syndrome. Prior to amniocentesis, 1,543 consecutive pregnancies between 13 and 18 weeks were studied. Femur and humerus shortening were assessed with the use of 6 different ratios, and then correlated with the karyotype obtained in amniotic fluid. Sensitivities achieved for Down syndrome with femur ratios were lower than those using humerus (17-22 vs. 43%) for similar false-positive rates (7-8 vs. 6-8%). The most effective ratio was the observed-to-expected humerus length with 43% sensitivity for a 6% false-positive rate. Combining femur and humerus measurements did not substantially improve the prediction obtained using the best humeral ratio. In conclusion, femur and humerus shortening appears to be of limited value in the detection of Down syndrome.

Umbilical Doppler velocimetry in fetuses with trisomy 18 at 10-18 weeks' gestation

The aim of our study was to obtain measurements of the umbilical artery pulsatility index (PI) in pregnancies before invasive procedures for prenatal diagnosis, in order to investigate its potential prognostic value in predicting trisomy 18. We performed a prospective study including 1785 consecutive women from 10 to 18 weeks with singleton pregnancies undergoing chorionic villus sampling (n = 559) or genetic amniocentesis (n = 1226) in our unit. Doppler measurements were performed transvaginally (tenth to 13th week of gestation) or transabdominally (14th to 18th week of gestation) immediately before the invasive procedure. In 7 out of 10 fetuses subsequently diagnosed as trisomy 18, the PI was above the 95th centile, providing a detection rate of 70 per cent, a specificity of 95.1 per cent, a positive predictive value of 7.7 per cent, and a negative predictive value of 99.8 per cent. When the 90th percentile was assayed as a cut-off, the efficacy of PI as a marker of trisomy 18 yielded a sensitivity of 90 per cent and a specificity of 90.4 per cent, with a positive predictive value of 5.2 per cent and a negative predictive value of 99.9 per cent. We suggest that although the use of a single PI measurement for screening purposes needs to be confirmed by further investigation, trisomy 18 fetuses show an abnormal increase in umbilical PI in the first half of pregnancy, and its relation to the early onset of fetal growth retardation needs to be further explored.

Interobserver variability of midtrimester fetal nuchal thickness

OBJECTIVE

To assess the interobserver variability of ultrasound measured fetal nuchal thickness (NT).

STUDY DESIGN

NT was measured in 103 consecutive early midtrimester pregnancies (13-18 weeks) by three ultrasonographists with different levels of expertise, in our Prenatal Unit. Measurements were obtained prior to amniocentesis, blindly in relation to other examiners' values. The Lin's concordance correlation coefficient and the Kappa statistics were used to assess concordance between observed values.

RESULTS

Mean differences between pairs of observers ranged from 0.44 to 0.57 mm. A higher concordance correlation between measurements was obtained between the more experienced observers (r = 0.77 versus r = 0.51). When assigning cases with a NT > or = 5 mm to a group at risk for Down's syndrome, a high concordance between experienced ultrasonographists was observed (98% agreement; kappa = 0.90).

CONCLUSIONS

Interobserver variability in NT was acceptable between experienced ultrasonographists.

Brachycephaly is ineffective for detection of Down syndrome in early midtrimester fetuses

The aim of this study was to assess the value of fetal brachycephaly in the detection of Down syndrome at 13-18 weeks of pregnancy. The cephalic index (CI) was determined in 555 consecutive chromosomally normal fetuses, and in 38 chromosomal abnormalities, prior to amniocentesis. A CI > 0.85 was observed in 14% (2/14) of the fetuses with Down syndrome and in 11% of the normal fetuses. In conclusion, our data show that brachycephaly is not a useful marker for Down syndrome in early midtrimester fetuses.

Criteria for fetal nuchal thickness cut-off: a re-evaluation

An attempt has been made to establish a more effective cut-off criterion for nuchal thickness (NT) and to assess the optimal gestational period for the prediction of trisomies 21 and 18. Reference intervals were established for NT from the tenth to the 18th week, using either gestation-specific centiles or the parametric method. The measurements in 47 consecutive trisomy 21 and 18 trisomy 18 cases were plotted against these intervals. Assaying different cut-off criteria for both the centile and the parametric methods, sensitivities and false-positive rates for each gestational week were calculated and then compared with the commonly applied 'two-stepped' cut-off method (3 mm early, 6 mm later). The parametric method, based on a progressive rise, with +2.5 SD for the corresponding gestational week as a cut-off value, showed the best performance (likelihood ratio 38) in the prediction for trisomy 21. The optimal gestational age was the 12-18 week period, with an overall sensitivity of 62 per cent (23/37) for an average false-positive rate of 0.7 per cent. For trisomy 18, the most effective cut-off was also +2.5 SD, and 10-13 gestational weeks as the optimal period, achieving 86 per cent (6/7) sensitivity for a 1.9 per cent false-positive rate.

Combining nuchal translucency with umbilical Doppler velocimetry for detecting fetal trisomies in the first trimester of pregnancy

OBJECTIVE

The aim of our study was to evaluate whether the combined use of umbilical artery pulsatility index (UAPI) and nuchal translucency (NT) measurements would be useful in the prediction of fetal chromosomal abnormalities at 10 to 13 weeks of gestation.

DESIGN

A prospective study.

POPULATION AND METHODS

Five hundred and fifty-three consecutive women with singleton pregnancies between 10 and 13 weeks of gestation, who underwent chorionic villus sampling at our institution. UAPI and fetal NT thickness were measured immediately before the invasive procedure. Pregnancies in which structural malformations had been detected by ultrasound were excluded.

RESULTS

Using the 95th centile and 3 mm as the cutoffs for UAPI and NT, respectively, the detection rate for all chromosomal anomalies was 84.2%, with a false positive rate (1-specificity) of 6.6%, a positive predictive value of 31.3%, and a negative predictive value of 99.4%. Out of the 553 tested pregnancies 502 had both parameters within the normal range and only three of them (0.6%) were chromosomally abnormal; in six of the eight cases (75%) in which both parameters were abnormal a chromosome anomaly was present. Of the 43 cases in which only one parameter was abnormal, 10 were chromosomally abnormal (23.2%).

CONCLUSIONS

Our results suggest that the presence of chromosomal anomalies may be strongly suspected when an increased NT thickness (NT > or = 3 mm) is associated with an abnormally high UAPI at 10 to 13 weeks of gestation. The number of cases studied is small, however, and these conclusions are tentative and preliminary. The value of a single measurement of NT and UAPI for screening purposes needs to be substantiated by further investigation.

Prediction of myotonic dystrophy clinical severity based on the number of intragenic [CTG]n trinucleotide repeats

We carried out a genotype-phenotype correlation study, based on clinical findings in 465 patients with myotonic dystrophy (DM), in order to assess [CTG] repeat number as a predictive test of disease severity. Our analysis showed that the DM subtypes defined by strict clinical criteria fall into three different classes with a log-normal distribution. This distribution is useful in predicting the probability of specific DM phenotypes based on triplet [CTG] number. This study demonstrates that measurement of triplet expansions in patients' lymphocyte DNA is highly valuable and accurate for prognostic assessment.

Stress fractures. Current concepts of diagnosis and treatment

The stress fracture is a common injury seen by healthcare professionals caring for athletes. They have been described in numerous areas of the skeletal system and in multiple sports. However, they are most commonly seen in the lower extremities, with running the reported cause in most cases. Stress fractures result from repetitive, cyclic loading of bone which overwhelms the reparative ability of the skeletal system. Mechanically, three events may lead to stress fractures. First, the applied load can be increased. Secondly, the number of applied stresses can increase. Finally, the surface area over which the load is applied can be decreased. Diagnosis requires thorough clinical evaluation with a high index of suspicion for stress fractures. History must focus on examining the athletes training regimen, especially any changes in distance, running surface and type of shoe. Physical examination varies depending on the location of the stress fracture. Ultrasound is a possible adjunct to the physical examination. Initial plain radiological evaluation may be normal, especially early in the course of a stress fracture. Further radiological evaluation may be necessary to make a definitive diagnosis. Repeating plain radiographs, bone scintigraphy, magnetic resonance imaging and computerised tomography are all possible options. Treatment options begin with rest and cessation of the precipitating activity. This should be 'active rest' in which the athlete continues to exercise depending on the site of the fracture. The athlete should be evaluated from a biomechanical point of view and any abnormalities dealt with prior to rehabilitation. Possible adjuncts to treatment include pneumatic braces and electromagnetic field therapy. There are specific stress fractures that must be considered at-risk for complications of healing. The treatment of these fractures begins with immobilisation and may require surgery pending response to therapy. Stress fractures occur more frequently in female athletes in relation to their male counterparts. There is a demonstrated relationship to eating disorders, amenorrhea and osteoporosis, or the female athlete triad. Thus, stress fractures in the female athlete requires additional investigation into those areas. The diagnosis and treatment of stress fractures is a challenge for the physician caring for the athlete. It requires a high index of suspicion combined with a strong knowledge of the at-risk stress fractures and their complications. Accurate and timely diagnosis is required to prevent possible costly and disabling complications.

Population pharmacokinetics of amikacin in critically ill patients

The pharmacokinetic parameters of amikacin were determined in a population of 20 adults and 36 pediatric patients admitted into an intensive care unit. Amikacin was administered by repeated intravenous infusion over 0.5 h (600 to 1,350 mg for adults; 70 to 1,500 mg for children). The number of administrations ranged from 2 to 17, and the number of samples collected from each patient ranged from 2 to 70. The population enrolled in the study had large variabilities in age (0.5 to 85 years), weight (6 to 95 kg), height (72 to 187 cm), creatinine clearance rate (18 to 110 ml/min), blood urea nitrogen concentration (1.5 to 15 mmol/liter), and total protein concentration (30 to 91 g/liter). The mean population parameters and their interindividual variabilities were obtained for an initial group of 44 patients (16 adults and 28 children). A two-compartment model was fitted to the population data by using the computer program P-PHARM. Model selection was guided by evaluation of the minimum objective function and the weighted residuals. The population analysis has been performed with the complete set of the collected data, including the individual serum amikacin concentration together with the individual estimate of the creatinine clearance values. The potential sources of variability in the population parameters were investigated by using patients' age, height, weight, creatinine clearance, blood urea nitrogen concentration, and total protein concentration as covariables. A test group of 12 additional patients (4 adults and 8 children) was used to evaluate the predictive performances of the population parameters. The individual pharmacokinetic parameters were computed by a Bayesian fitting procedure. From the resulting individualized values of the parameters, the concentrations of amikacin in the serum of the patients were calculated. To evaluate the performance of the Bayesian estimation, the experimental concentrations were compared with the predicted ones. The Bayesian approached developed in the study accurately predicts amikacin concentrations in serum and allows for the estimation of amikacin pharmacokinetics parameters, minimizing the risk of bias in the prediction. This was demonstrated in patients with both stable and unstable renal functions.

Early midtrimester fetal nuchal thickness: effectiveness as a marker of Down syndrome

OBJECTIVE

Our purpose was to assess the validity of nuchal thickness in the prediction of Down syndrome in early midtrimester fetuses.

STUDY DESIGN

In 1543 consecutive pregnancies undergoing amniocentesis, primarily for advanced maternal age, nuchal thickness was prospectively measured between 13 and 18 weeks and then correlated with the karyotype obtained from amniotic fluid.

RESULTS

With the cutoff value suggested in the literature (> or = 6 mm), 33.3% (6/18) of the cases of Down syndrome would be detected for a 0.1% (2/1424) false-positive rate, with a positive predictive value adjusted to a prevalence of Down syndrome in the general population of 1:3. To increase the sensitivity of the method, the threshold was lowered to 5 mm, achieving a sensitivity of 77.8% (14/18) for a 2.1% (30/1424) false-positive rate and an adjusted positive value of 1:19.

CONCLUSIONS

In early midtrimester fetuses decreasing the nuchal thickness threshold to 5 mm substantially enhances the detection of Down syndrome with a reasonable false-positive rate.

Immediate changes in umbilical blood flow after transcervical chorionic villus sampling performed by biopsy forceps

Transvaginal ultrasonography with colour Doppler was used to evaluate the immediate changes on the fetal heart rate (FHR) and the fetal umbilical artery pulsatility index (PI) after chorionic villus sampling (CVS). This prospective study included 279 consecutive singleton pregnancies, between 10 and 13 weeks, of women who underwent transcervical CVS in our institution. All Doppler measurements were obtained transvaginally before and immediately after CVS. Structural malformations detected by ultrasound were excluded. Student's t- and Wilcoxon texts were performed for statistical analysis. The results showed no significant decrease in FHR (mean 1.04 beats, t = 1.68, P = 0.94) and a significant elevation of umbilical artery PI (mean 0.12, t = - 6.51, P < 0.001) post-CVS. This difference was only significant in procedures performed at less than 11 weeks' gestation, since there was no significant change for those procedures performed thereafter. These preliminary data suggest that acute fetal haemodynamic changes are induced by CVS and may have clinical effects. Hypotheses on possible vascular mechanisms are discussed. Colour Doppler could widen the possibilities for more accurate in vivo assessment and research on CVS-related placental injury.