Risk factors for late preterm and term stillbirth: A secondary analysis of an individual participant data meta-analysis

OBJECTIVE

Identify independent and novel risk factors for late-preterm (28-36 weeks) and term (≥37 weeks) stillbirth and explore development of a risk-prediction model.

DESIGN

Secondary analysis of an Individual Participant Data (IPD) meta-analysis investigating modifiable stillbirth risk factors.

SETTING

An IPD database from five case-control studies in New Zealand, Australia, the UK and an international online study.

POPULATION

Women with late-stillbirth (cases, n = 851), and ongoing singleton pregnancies from 28 weeks' gestation (controls, n = 2257).

METHODS

Established and novel risk factors for late-preterm and term stillbirth underwent univariable and multivariable logistic regression modelling with multiple sensitivity analyses. Variables included maternal age, body mass index (BMI), parity, mental health, cigarette smoking, second-hand smoking, antenatal-care utilisation, and detailed fetal movement and sleep variables.

MAIN OUTCOME MEASURES

Independent risk factors with adjusted odds ratios (aOR) for late-preterm and term stillbirth.

RESULTS

After model building, 575 late-stillbirth cases and 1541 controls from three contributing case-control studies were included. Risk factor estimates from separate multivariable models of late-preterm and term stillbirth were compared. As these were similar, the final model combined all late-stillbirths. The single multivariable model confirmed established demographic risk factors, but additionally showed that fetal movement changes had both increased (decreased frequency) and reduced (hiccoughs, increasing strength, frequency or vigorous fetal movements) aOR of stillbirth. Poor antenatal-care utilisation increased risk while more-than-adequate care was protective. The area-under-the-curve was 0.84 (95% CI 0.82-0.86).

CONCLUSIONS

Similarities in risk factors for late-preterm and term stillbirth suggest the same approach for risk-assessment can be applied. Detailed fetal movement assessment and inclusion of antenatal-care utilisation could be valuable in late-stillbirth risk assessment.

Association between habitual snoring, middle ear disease, and speech problems in young children with non-syndromic cleft palate anomalies

The purpose of this study was to investigate the association between habitual snoring (HS), middle ear disease (MED), and speech problems in children with cleft palate. This cross-sectional study included children aged 2.0-7.9 years with non-syndromic cleft palate anomalies. Parents completed the Pediatric Sleep Questionnaire and a questionnaire about MED. Audiograms and speech assessment were also conducted. Ninety-five children were enrolled; 15.2% of families reported HS, 97.6% MED, and 17.1% speech problems. HS (37.5% vs 10.3%, P = 0.007) and early episodes of MED (92.3% vs 58.2%, P = 0.021) were more likely to be reported for children with isolated cleft palate when compared to those with cleft lip and palate. Children with cleft lip and palate had a higher frequency of MED with effusion compared to those with Robin sequence (86.4% vs 57.1%, P = 0.049). The odds ratio for HS in children with ≥1 episode of MED in the last year was 7.37 (95% confidence interval 1.55-35.15, P = 0.012). There was a trend for children with speech problems reported by parents to have HS (30.8% vs 11.5%, P= 0.076). Anatomical factors play a role in the frequency of upper airway symptoms in children with cleft palate. A recent history of at least one episode of MED was associated with an increased frequency of HS.

Exposure-response relationship for ramucirumab from the randomized, double-blind, phase 3 REVEL trial (docetaxel versus docetaxel plus ramucirumab) in second-line treatment of metastatic non-small cell lung cancer

PURPOSE

Ramucirumab plus docetaxel improved survival in REVEL, a randomized phase 3 trial for patients with Stage IV non-small cell lung cancer after standard platinum-based chemotherapy. This exploratory analysis evaluated the exposure-response relationship of ramucirumab from REVEL.

METHODS

Patients received ramucirumab (10 mg/kg) or placebo plus docetaxel (75 mg/m2) every 3 weeks. Pharmacokinetic samples were collected. A population pharmacokinetic analysis predicted ramucirumab minimum concentration after first-dose administration (Cmin,1) and average concentration at steady state (Cave,ss). Predicted Cmin,1 and Cave,ss were used to evaluate the relationship between ramucirumab exposure and efficacy and safety, respectively. Exposure-efficacy was assessed by Kaplan-Meier and Cox regression analyses; exposure-safety was assessed by ordered categorical analyses.

RESULTS

Analyses included 376 patients treated with ramucirumab plus docetaxel and 366 patients treated with placebo plus docetaxel (364 for safety population). After adjusting for corresponding prognostic factors, the association between overall survival (OS) and Cmin,1 was statistically significant (p = 0.0110), although progression-free survival (PFS) showed a marginal association (p = 0.0515). At high ramucirumab exposures (Cmin,1), greater improvements (smaller hazard ratios) were seen for OS and PFS when stratified by Cmin,1 exposure quartiles. A statistically significant correlation was observed between ramucirumab Cave,ss and grade ≥ 3 febrile neutropenia and hypertension.

CONCLUSIONS

An association was observed between ramucirumab exposure and efficacy. Higher ramucirumab exposure was associated with improved clinical outcomes and increased toxicity in this analysis. Two exposure-response prospective randomized trials are being conducted to address causation (NCT02443883 and NCT02514551), with encouraging preliminary results (Ajani et al. in Ann Oncol 28:abstr 698P, 2017).

Diagnostic potential of the peptide-mediated magnetic separation (PMS)-phage assay and PMS-culture to detect Mycobacterium avium subsp. paratuberculosis in bovine milk samples

Controlling the spread of Johne's disease, caused by Mycobacterium avium subsp. paratuberculosis (MAP), in domestic livestock is challenging. Current diagnostic methods lack sufficient sensitivity to detect subclinically infected animals, and thus, better diagnostic methods are needed. This study was carried out to investigate the diagnostic potential of two novel peptide-mediated magnetic separation (PMS)-based tests-a PMS-phage assay and PMS-culture-both of which have been developed and optimized to detect viable MAP cells in bovine milk. Individual milk samples (50 ml) were obtained from 105 "non-infected" and 40 "MAP-infected" animals (classified as such on the basis of prior faecal culture and serum-ELISA results) in three dairy herds and tested in parallel by the PMS-phage assay and PMS-culture. Diagnostic sensitivity (DSe) and specificity (DSp) of the PMS-phage and PMS-culture methods were determined relative to the MAP infection status of the animal contributing the milk sample. The PMS-based tests applied individually showed moderate DSe (PMS-culture 0.250 and PMS-phage assay 0.325) and high DSp (0.962 and 1.000, respectively). When results of the two PMS-based tests were combined, DSe increased substantially to 0.525, and the DSp was calculated to be 0.962. It was concluded that combined application of the PMS-phage assay and PMS-culture provided the most complete picture regarding the presence of viable MAP in bovine milk samples. A comprehensive validation of the PMS-based assays relative to currently used diagnostic methods (faecal culture and serum-ELISA) would be the next step in assessment of the diagnostic potential of these novel PMS-based methods.

Exposure-response relationship of ramucirumab in patients with advanced second-line colorectal cancer: exploratory analysis of the RAISE trial

PURPOSE

To characterize ramucirumab exposure-response relationships for efficacy and safety in patients with metastatic colorectal cancer (mCRC) using data from the RAISE study.

METHODS

Sparse pharmacokinetic samples were collected; a population pharmacokinetic analysis was conducted. Univariate and multivariate Cox proportional hazards models analyzed the relationship between predicted ramucirumab minimum trough concentration at steady state (C min,ss) and survival. Kaplan-Meier analysis was used to evaluate survival from patients in the ramucirumab plus folinic acid, 5-fluorouracil, and irinotecan (FOLFIRI) treatment arm stratified by C min,ss quartiles (Q). An ordered categorical model analyzed the relationship between C min,ss and safety outcomes.

RESULTS

Pharmacokinetic samples from 906 patients were included in exposure-efficacy analyses; samples from 905 patients were included in exposure-safety analyses. A significant association was identified between C min,ss and overall survival (OS) and progression-free survival (PFS) (p < 0.0001 for both). This association remained significant after adjusting for baseline factors associated with OS or PFS (p < 0.0001 for both). Median OS was 11.5, 12.9, 16.4, and 16.7, and 12.4 months for ramucirumab C min,ss Q1, Q2, Q3, Q4, and placebo group, respectively. Median PFS was 5.4, 4.6, 6.8, 8.5, and 5.2 months for ramucirumab C min,ss Q1, Q2, Q3, Q4, and placebo group, respectively. The risk of Grade ≥3 neutropenia was associated with an increase in ramucirumab exposure.

CONCLUSIONS

Exploratory exposure-response analyses suggested a positive relationship between efficacy and ramucirumab exposure with manageable toxicities in patients from the RAISE study with mCRC over the ranges of exposures achieved by a dose of 8 mg/kg every 2 weeks in combination with FOLFIRI.

The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales: coastal processes, land-use change and air quality

We present results from the OP3 campaign in Sabah during 2008 that allow us to study the impact of local emission changes over Borneo on atmospheric composition at the regional and wider scale. OP3 constituent data provide an important constraint on model performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty. Model studies of land-use change confirm earlier work, indicating that further changes to intensive oil palm agriculture in South East Asia, and the tropics in general, could have important impacts on air quality, with the biggest factor being the concomitant changes in NO(x) emissions. With the model scenarios used here, local increases in ozone of around 50 per cent could occur. We also report measurements of short-lived brominated compounds around Sabah suggesting that oceanic (and, especially, coastal) emission sources dominate locally. The concentration of bromine in short-lived halocarbons measured at the surface during OP3 amounted to about 7 ppt, setting an upper limit on the amount of these species that can reach the lower stratosphere.

A carpet-based mechanism for direct antimicrobial peptide activity against vaccinia virus membranes

Antimicrobial peptides have activity against a wide variety of biological membranes and are an important component of innate immunity in vertebrate as well as invertebrate systems. The mechanisms of action of these peptides are incompletely understood and a number of competing but not necessarily mutually exclusive models exist. In this study we examined the virucidal activity of four peptides, the human cathelicidin derived LL37, Xenopus alanine-substituted Magainin-2 amide, uperin-3.1, and a cecropin-LL37 hybrid against vaccinia virus. The peptides were shown to be differentially virucidal but all were shown to attack the viral envelope, with LL37 being the most effective and uperin-3.1 the least. Density gradient analysis of the treated virions indicated the virus outer membrane was efficiently removed by peptide action and suggests a mechanism of direct virus inactivation that is consistent with the carpet model for peptide-mediated membrane disruption. Interestingly, the least effective peptide uperin-3.1 was equally effective as the others at inducing susceptibility to neutralizing antibody. This suggests that in addition to direct killing by a carpet-based mechanism, the peptides may simultaneously operate a different mechanism that exposes sequestered antigen without membrane removal.

Eosinophil-nerve interactions and neuronal plasticity in rat gut associated lymphoid tissue (GALT) in response to enteric parasitism

Intestinal lymphoid tissues and Peyer's patches (PP) are innervated sites of immune surveillance in the gastrointestinal tract. Following infection with F. hepatica, neuronal hyperplasia and significantly increased eosinophil and mast cell trafficking to colonic PP sites were evident in rat tissues. Nerve-eosinophil associations were significantly elevated in infected colon and colonic PP, as were colonic tissue levels of the circulatory recruitment factors IL-5 and eotaxin. Increased immunoreactivity for neuronal plasticity markers GAP-43 and neural cell adhesion molecule (NCAM) was also found in infected tissues. Such neuronal alterations in the PP during enteric parasitism may have functional consequences on particular or pathogen uptake.

Sleep in children with attention deficit/hyperactivity disorder

Attention-deficit hyperactivity disorder (ADHD) is one of the most common psychological disorders in children. Sleep disturbances are also very prevalent among the pediatric age range and can lead to substantial behavioral and cognitive consequences that may mimic ADHD. Conversely, children with ADHD may suffer from significant sleep disturbances that may originate in the biochemical disturbances that underlie their deficits in executive function and attention. This review addresses both these issues and provides a concise yet timely assessment of the potential links between sleep disorders and ADHD.

Brain asymmetries in autism and developmental language disorder: a nested whole-brain analysis

We report a whole-brain MRI morphometric survey of asymmetry in children with high-functioning autism and with developmental language disorder (DLD). Subjects included 46 boys of normal intelligence aged 5.7-11.3 years (16 autistic, 15 DLD, 15 controls). Imaging analysis included grey-white segmentation and cortical parcellation. Asymmetry was assessed at a series of nested levels. We found that asymmetries were masked with larger units of analysis but progressively more apparent with smaller units, and that within the cerebral cortex the differences were greatest in higher-order association cortex. The larger units of analysis, including the cerebral hemispheres, the major grey and white matter structures and the cortical lobes, showed no asymmetries in autism or DLD and few asymmetries in controls. However, at the level of cortical parcellation units, autism and DLD showed more asymmetry than controls. They had a greater aggregate volume of significantly asymmetrical cortical parcellation units (leftward plus rightward), as well as a substantially larger aggregate volume of right-asymmetrical cortex in DLD and autism than in controls; this rightward bias was more pronounced in autism than in DLD. DLD, but not autism, showed a small but significant loss of leftward asymmetry compared with controls. Right : left ratios were reversed, autism and DLD having twice as much right- as left-asymmetrical cortex, while the reverse was found in the control sample. Asymmetry differences between groups were most significant in the higher-order association areas. Autism and DLD were much more similar to each other in patterns of asymmetry throughout the cerebral cortex than either was to controls; this similarity suggests systematic and related alterations rather than random neural systems alterations. We review these findings in relation to previously reported volumetric features in these two samples of brains, including increased total brain and white matter volumes and lack of increase in the size of the corpus callosum. Larger brain volume has previously been associated with increased lateralization. The sizeable right-asymmetry increase reported here may be a consequence of early abnormal brain growth trajectories in these disorders, while higher-order association areas may be most vulnerable to connectivity abnormalities associated with white matter increases.

Dissociations of cerebral cortex, subcortical and cerebral white matter volumes in autistic boys

High-functioning autistic and normal school-age boys were compared using a whole-brain morphometric profile that includes both total brain volume and volumes of all major brain regions. We performed MRI-based morphometric analysis on the brains of 17 autistic and 15 control subjects, all male with normal intelligence, aged 7-11 years. Clinical neuroradiologists judged the brains of all subjects to be clinically normal. The entire brain was segmented into cerebrum, cerebellum, brainstem and ventricles. The cerebrum was subdivided into cerebral cortex, cerebral white matter, hippocampus-amygdala, caudate nucleus, globus pallidus plus putamen, and diencephalon (thalamus plus ventral diencephalon). Volumes were derived for each region and compared between groups both before and after adjustment for variation in total brain volume. Factor analysis was then used to group brain regions based on their intercorrelations. Volumes were significantly different between groups overall; and diencephalon, cerebral white matter, cerebellum and globus pallidus-putamen were significantly larger in the autistic group. Brain volumes were not significantly different overall after adjustment for total brain size, but this analysis approached significance and effect sizes and univariate comparisons remained notable for three regions, although not all in the same direction: cerebral white matter showed a trend towards being disproportionately larger in autistic boys, while cerebral cortex and hippocampus-amygdala showed trends toward being disproportionately smaller. Factor analysis of all brain region volumes yielded three factors, with central white matter grouping alone, and with cerebral cortex and hippocampus-amygdala grouping separately from other grey matter regions. This morphometric profile of the autistic brain suggests that there is an overall increase in brain volumes compared with controls. Additionally, results suggest that there may be differential effects driving white matter to be larger and cerebral cortex and hippocampus-amygdala to be relatively smaller in the autistic than in the typically developing brain. The cause of this apparent dissociation of cerebral cortical regions from subcortical regions and of cortical white from grey matter is unknown, and merits further investigation.

The long-term follow-up of women treated for postnatal depression at a specialist day hospital compared to routine primary care

BACKGROUND

Postnatal depression affects approximately 13% of childbearing women. There are very few specialist treatment centres, despite emerging evidence that these units are superior to routine primary care in the short term. We investigated the long-term benefits of treatment for postnatal depression at a specialist day unit, compared to routine primary care.

METHODS

Women who took part in an earlier study of postnatal depression were invited to participate in this follow-up. Self-report questionnaires (the Work, Leisure and Family Life Questionnaire - Modified (WLFQ-M) and the Dyadic Adjustment Scale (DAS)) were administered, together with the revised Clinical Interview Schedule (CIS-R). Information was also obtained regarding subsequent children and depressive episodes since the initial study.

RESULTS

Of the original cohort of 60 women, 23 agreed to participate in the follow-up. There were no significant differences between DAS and WLFLQ-M scores or ICD-10 diagnoses of depressive episode between the women who had previously received specialist care. However, the numbers were small and make conclusions difficult. Qualitative analysis suggests that treatment at a specialist unit is beneficial in the long term.

CONCLUSION

Further, larger studies of the long-term benefits of specialist treatment need to be carried out. (Int J Psych Clin Pract 2002; 6: 199-203 ).

A population approach to enzyme characterization and identification: application to phenacetin O-deethylation

PURPOSE

To determine the enzyme kinetics (EK) and identify the human cytochrome(s) P450 (CYP) involved in the deethylation of phenacetin to acetaminophen using a population-based method.

METHODS

A sparse data set was generated from incubations containing human liver microsomes (n = 19) with phenacetin. Estimates of the EK parameters were obtained by fitting the concentration-velocity data to Michaelis-Menten models by using nonlinear mixed effects modeling. Relationships between the EK parameters and the CYP activities determined for these liver microsomes were examined.

RESULTS

A two-enzyme kinetic model with a saturated, low KM enzyme and an unsaturated, high KM enzyme capable of forming acetaminophen best fit the data. The population estimates of the EK parameters were Vmax1, 911 pmol/min/mg protein; KM1, 11.3 microM; and Cl(int2), 0.4 microl/min/mg. The coefficients of variation for interliver variability in Vmax1 and residual error of the model were 39% and 15%, respectively. When the selective catalytic activities were examined as potential covariates, 7-ethoxyresorufin O-deethylation (CYP1A2) activity was found to be associated with the low KM enzyme, however, the high KM enzyme(s) could not be identified.

CONCLUSIONS

The population approach characterized the EK parameters and identified the low KM enzyme responsible for phenacetin O-deethylation as CYP1A2. Population modeling of EK provides valuable information on inter- and intraliver variability in CYP dependent activities.

Oxygen saturation during the first 24 hours of life

AIM

To determine normative data for arterial oxygen saturation, measured by pulse oximetry (SpO2), in healthy full term infants throughout their first 24 hours of life.

METHODS

Long term recordings of SpO2, pulse waveform, and breathing movements were made on 90 infants. Recordings were analysed for baseline SpO(2), episodes of desaturation (SpO2 </= 80%), apnoeic pauses of >/= four seconds, and periodic apnoea (>/= three apnoeic pauses, each separated by </= 19 breaths).

RESULTS

Median baseline SpO(2) was 98. 3% (range 88.7-100). Longitudinal analysis at four hour intervals showed that SpO2 remained stable until 20-24 hours of age, when it became significantly lower (p < 0.03). Episodic desaturations were identified in 23 recordings. Nine prolonged desaturations (SpO2 </= 80% for >/= 20 seconds) were identified in six recordings. Four desaturations fell to </= 60%. Periodic apnoea was identified in 60% of recordings.

CONCLUSION

The range of SpO2 during the first 24 hours of life is similar to that found previously during the first month of life. The clinical significance of the prolonged episodes of desaturation observed justifies further investigation.

Regulation of factor VIIIa by human activated protein C and protein S: inactivation of cofactor in the intrinsic factor Xase

Factor VIIIa is a trimer of A1, A2, and A3-C1-C2 subunits. Inactivation of the cofactor by human activated protein C (APC) results from preferential cleavage at Arg336 within the A1 subunit, followed by cleavage at Arg562 bisecting the A2 subunit. In the presence of human protein S, the rate of APC-dependent factor VIIIa inactivation increased several-fold and correlated with an increased rate of cleavage at Arg562. (Active site-modified) factor IXa, blocked cleavage at the A2 site. However, APC-catalyzed inactivation of factor VIIIa proceeded at a similar rate independent of factor IXa, consistent with the location of the preferential cleavage site within the A1 subunit. Addition of protein S failed to increase the rate of cleavage at the A2 site when factor IXa was present. In the presence of factor X, cofactor inactivation was inhibited, due to a reduced rate of cleavage at Arg336. However, inclusion of protein S restored near original rates of factor VIIIa inactivation and cleavage at the A1 site, thus overcoming the factor X-dependent protective effect. These results suggest that in the human system, protein S stimulates APC-catalyzed factor VIIIa inactivation by facilitating cleavage of A2 subunit (an effect retarded in the presence of factor IXa), as well as abrogating protective interactions of the cofactor with factor X. (Blood. 2000;95:1714-1720)

Children of parents with mental illness. I: An overview from a nursing perspective

This paper explores the psychosocial consequences of parental mental illness for child mental health and the implications for mental health nursing. The literature on risk and vulnerability to psychosocial disorder, resilience, child protection, disorder prevention and epidemiological data are reviewed. Based upon a health promotion approach, a model for mental health nursing advocacy for families of adult consumers is proposed as an effective means of preventing disorder in subsequent generations.

Preparation of 99Tcm-MAG3: no confirmation that sodium chloride injections from plastic containers affect radiochemical purity

Reports have suggested that when sodium chloride injections from a plastic ampoule are used during the preparation of 99Tcm-mercaptoacetyltriglycine (99Tcm-MAG3), the radiochemical purity of the final product might be reduced. A study was therefore undertaken to examine the effect of sodium chloride injections from five manufacturers on the radiochemical purity and stability of 99Tcm-MAG3. One sodium chloride injection was supplied in a glass vial, three in plastic ampoules and one in a plastic infusion bag. Three batches of sodium chloride injections from each manufacturer were tested. The radiopharmaceutical was prepared at a radioactive concentration of 1.1 GBq in 10 ml according to the instructions of the manufacturer of TechneScan MAG3. Analysis of radiochemical purity was performed by high-performance liquid chromatography immediately after preparation and 6 h later. Using 95% as the minimum acceptable radiochemical purity, all the products were satisfactory over the 6 h test period. No manufacturer's sodium chloride injection was found to have a statistically significant effect on the radiochemical purity. Based on the 15 batches of sodium chloride injection tested, this study cannot confirm that sodium chloride injections from a plastic container affect the radiochemical purity of 99Tcm-MAG3. However, in view of the known sensitivity of some 99Tcm radiopharmaceuticals to external influences, it is probably good practice to test radiochemical purity when new batches of ancillary materials, such as sodium chloride injections, are introduced.

Effect of exposure to 15% oxygen on breathing patterns and oxygen saturation in infants: interventional study

OBJECTIVE

To assess the response of healthy infants to airway hypoxia (15% oxygen in nitrogen).

DESIGN

Interventional study.

SETTINGS

Infants' homes and paediatric ward.

SUBJECTS

34 healthy infants (20 boys) born at term; mean age at study 3.1 months. 13 of the infants had siblings whose deaths had been ascribed to the sudden infant death syndrome.

INTERVENTION

Respiratory variables were measured in room air (pre-challenge), while infants were exposed to 15% oxygen (challenge), and after infants were returned to room air (post-challenge).

MAIN OUTCOME MEASURES

Baseline oxygen saturation as measured by pulse oximetry, frequency of isolated and periodic apnoea, and frequency of desaturation (oxygen saturation < or = 80% for > or = 4 s). Exposure to 15% oxygen was terminated if oxygen saturation fell to < or = 80% for > or = 1 min.

RESULTS

Mean duration of exposure to 15% oxygen was 6.3 (SD 2.9) hours. Baseline oxygen saturation fell from a median of 97.6% (range 94.0% to 100%) in room air to 92.8% (84.7% to 100%) in 15% oxygen. There was no correlation between baseline oxygen saturation in room air and the extent of the fall in baseline oxygen saturation on exposure to 15% oxygen. During exposure to 15% oxygen there was a reduction in the proportion of time spent in regular breathing pattern and a 3.5-fold increase in the proportion of time spent in periodic apnoea (P < 0.001). There was an increase in the frequency of desaturation from 0 episodes per hour (range 0 to 0.2) to 0.4 episodes per hour (0 to 35) (P < 0.001). In 4 infants exposure to hypoxic conditions was ended early because of prolonged and severe falls in oxygen saturation.

CONCLUSIONS

A proportion of infants had episodes of prolonged (< or = 80% for > or = 1 min) or recurrent shorter (< or = 80% for > or = 4 s) desaturation, or both, when exposed to airway hypoxia. The quality and quantity of this response was unpredictable. These findings may explain why some infants with airway hypoxia caused by respiratory infection develop more severe hypoxaemia than others. Exposure to airway hypoxia similar to that experienced during air travel or on holiday at high altitude may be harmful to some infants.

Interacting regions in the A1 and A2 subunits of factor VIIIa identified by zero-length cross-linking

Factor VIIIa is a heterotrimer of A1, A2, and A3-C1-C2 subunits, the activity of which is labile due to a weak affinity interaction of the A2 subunit with the A1/A3-C1-C2 dimer. We have used the zero-length cross-linking reagent, 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide hydrochloride (EDC), to localize regions of interaction within the A1 and A2 subunits. Reaction of factor VIIIa with EDC resulted in the formation of a cross-linked product of approximately 90 kD consisting of the A1 and A2 subunits as judged by Western blotting. Alkaline resistance of this product indicated an amide rather than ester linkage. Factor VIIIa activity decreased as the concentration of cross-linked product increased, suggesting that flexibility in the inter-subunit interaction may be required for proper cofactor function. This product was not formed in the contiguous A1-A2 domains of factor VIII, suggesting that, upon cofactor activation, a conformational change occurs that leads to the formation of a new interdomainal salt bridge(s). Reaction of the EDC-treated factor VIIIa with activated protein C (APC), which cleaves the A1 subunit at Arg336 and bisects the A2 subunit at Arg562, resulted in the formation of an approximately 30 kD product that contains the C-terminus region of A1 covalently linked to the N-terminal half of the A2. The approximately 90 kD cross-linked product was generated after reaction of A2 subunit with A1/A3-C1-C2 dimer but not with A1(336)/A3-C1-C2, a form of the dimer produced by APC cleavage and lacking the C-terminal acidic region of A1. A synthetic peptide corresponding to this acidic region (Met337-Arg372) was found to covalently cross-link to the isolated A2 subunit in 1:1 stoichiometry, suggesting that this region is both necessary and sufficient for the interaction of the A1 and A2 subunits. Sequence analysis of this product suggested that Glu344 in the A1 peptide may contribute to the cross-linkage. These results indicate that activation of factor VIII results in formation of a new ionic linkage(s) localized to the acidic C-terminal region of A1 and the N-terminal half of A2.

Flavonoid-induced gastroprotection in rats: role of blood flow and leukocyte adherence

To elucidate the mechanisms of flavonoid-induced protection against nonsteroidal anti-inflammatory drug (indomethacin)-induced acute gastric damage, the effects of 5-methoxyflavone and 5-methoxyflavanone on the gastric vasculature were compared both in vivo (using laser Doppler flowmetry in anesthetized rats) and in vitro on rat superior mesenteric arteries. The effects of the compounds on indomethacin-induced leukocyte adherence to mesenteric venules were investigated by intravital videomicroscopy. Oral 5-methoxyflavone reduced indomethacin-induced macroscopic damage by 38 to 99% (ED50 = 5.5 mg/kg). Damage was not significantly reduced by 5-methoxyflavanone. Light microscopy studies also demonstrated a reduction in damage severity. 5-Methoxyflavone, but not 5-methoxyflavanone, increased the gastric conductance significantly. The effects on isolated mesenteric arteries correlated with the effects on in vivo conductance. Finally, indomethacin-induced leukocyte adherence was inhibited to a greater extent by 5-methoxyflavone than by 5-methoxyflavanone. In conclusion, the flavonoid 5-methoxyflavone provides gastroprotection against nonsteroidal anti-inflammatory drug-induced gastric damage. A structurally similar compound, 5-methoxyflavanone, demonstrated minimal gastroprotective activity, suggesting that the double bond of 5-methoxyflavone is required for biological activity. The finding that 5-methoxyflavone (but not 5-methoxyflavanone) significantly increased gastric vascular perfusion and reduced leukocyte adherence to mesenteric venules suggests that these mechanisms may contribute to the flavonoid's gastroprotective activity.

Response of Mycobacterium smegmatis to acid stress

Evidence was sought for the existence of an inducible acid tolerance response in Mycobacterium smegmatis. Exposure of M. smegmatis to a sub-lethal, adaptive acidic pH was found to confer a significant level of protection against subsequent exposure to a lethal pH, compared to unadapted cells. Adaptation was dependent on de novo protein synthesis.

Model for the factor VIIIa-dependent decay of the intrinsic factor Xase. Role of subunit dissociation and factor IXa-catalyzed proteolysis

The intrinsic factor Xase complex (FXase) is comprised of a serine protease, FIXa, and a protein cofactor, FVIIIa, assembled on a phospholipid surface. Activity of FXase decays with time and reflects the lability of FVIIIa. Two mechanisms potentially contribute to this decay: (i) a weak affinity interaction between the FVIIIa A2 subunit and Al/A3-Cl-C2 dimer and (ii) FVIIIa inactivation resulting from FIXa-catalyzed proteolysis of the Al subunit. At low reactant concentrations (0.5 nm FVIIIa; 5 nm FIXa), FXase decay is governed by the inter-FVIIIa subunit affinity and residual activity approaches a value consistent with this equilibrium, as judged by reactions containing exogenous A2 subunit. Analysis using a mutant form of FVIII (FVIIIR336I) possessing an altered FIXa cleavage site, showed similar rates of FXase decay (0.12 min(-1)) and confirmed the lack of contribution of proteolysis under these conditions. When the concentration of FIXa was increased 10-fold, the initial rate of decay of FXase containing native FVIIIa increased (0.82 min(-1)) and paralleled the rate of proteolysis of Al subunit. However, the rate of decay of FXase containing the FVIIIaR336I was reduced (0.048 min(-1)) consistent with the elevated concentration of FIXa stabilizing the labile subunit structure of the cofactor. Reconstitution of FVIII with FIXa-cleaved light chain showed that cleavage at the alternate FIXa site (A3 domain) was not inhibitory to FXase. The presence of substrate FX resulted in a 10-fold reduction in the rate of FIXa-catalyzed proteolysis of FVIIIa. These results suggest a model whereby decay of FXase results from both FVIIIa subunit dissociation and FIXa-catalyzed cleavage, dependent upon the relative concentration of reactants, with greater contribution of the former at low values and, in the absence of substrate, greater contribution of the latter at high values.

Arterial oxygen saturation in healthy term neonates

Our objective was to determine arterial oxygen saturation as measured by pulse oximetry (SpO2) in healthy term neonates during their first 4 weeks of life. Overnight recordings of SpO2 (Nellcor N200), photoplethysmographic (pulse) waveforms from the oximeter and breathing movements were performed in 60 term infants. They were studied initially during their 1st week of life (median age 4 days, range 1-7) and then again during their 2nd-4th week (median age 17 days, range 8-27). Median baseline SpO2, measured during regular breathing, was 97.6% (range 92-100) during week 1 versus 98.0% (86.6-100) during week 2-4 (P > 0.05). Episodes of desaturation, defined as a fall in SpO2 to < or = 80% for > or = 4 s, were found in 35% of recordings obtained in week 1 compared to 60% of those obtained in week 2-4 (P < 0.01). Their frequency increased from a median of (0-41) per 12 h of recording at the initial recording to 1 (0-165) at follow up (P < 0.01). Analysis of the data by week of life showed a peak in desaturation frequency in the 2nd week of life. The infants with extreme values at follow-up (e.g. a baseline SpO2 of 86.6%, 5th percentile 91.9%, or a desaturation frequency of 165 per 12 h of recording, 95th percentile 32) had had values well within the normal range during their initial recording (a baseline SpO2 of 94.4%, or a desaturation frequency of 4). Most of the desaturations in the infants with extreme values were associated with periodic apnoea. These results demonstrate only relatively minor developmental changes in oxygenation in term neonates during the first 4 weeks of life. The clinical significance of outlying values, i.e. a low baseline SpO2 or a high number of episodic desaturations, remains to be determined.

CONCLUSION

These healthy term neonates had values for baseline oxygen saturation and desaturation frequency that were not substantially different from those observed in older infants.

Activated protein C-catalyzed proteolysis of factor VIIIa alters its interactions within factor Xase

Factor VIIIa, the cofactor for the factor IXa-dependent conversion of factor X to factor Xa, is proteolytically inactivated by activated protein C (APC). APC cleaves at two sites in factor VIIIa, Arg336, near the C terminus of the A1 subunit; and Arg562, bisecting the A2 subunit (Fay, P., Smudzin, T., and Walker, F. (1991) J. Biol. Chem. 266, 20139-20145). Factor VIIIa increased the fluorescence anisotropy of fluorescein-Phe-Phe-Arg factor IXa (Fl-FFR-FIXa; Kd = 42.4 nM), whereas cleavage of factor VIIIa by APC eliminated this property. Isolation of the APC-cleaved A1/A3-C1-C2 dimer (A1336/A3-C1-C2), and the fragments derived from cleaved A2 subunit (A2N/A2C), permitted dissection of the roles of individual cleavages in cofactor inactivation. Intact A1/A3-C1-C2 dimer increased Fl-FFR-FIXa anisotropy and bound factor X in a solid phase assay, while these activities were absent in the A1336/A3-C1-C2. However, the residues removed by this cleavage, Met337 Arg372, did not directly participate in these functions since neither a synthetic peptide to this sequence nor an anti-peptide polyclonal antibody blocked these activities using intact dimer. CD spectral analysis of the intact and truncated dimers indicated reduced alpha and/or beta content in the latter. The A1/A3-C1-C2 dimer plus A2 subunit reconstitutes cofactor activity and produced a factor VIIIa-like effect on the anisotropy of Fl-FFR-FIXa. However, when A2 was replaced by the A2N/A2C fragments, the resulting fluorescence signal was equivalent to that observed with the dimer alone. These results indicate that APC inactivates the cofactor at two levels within the intrinsic factor Xase complex. Cleavage of either subunit modulates the factor IXa active site, suggesting an essential synergy of interactive sites in factor VIIIa. Furthermore, cleavage of the A1 site alters the conformation of a factor X binding site within that subunit, thereby reducing the affinity of cofactor for substrate.

Synthesis and biological evaluation of substituted flavones as gastroprotective agents

Flavone (1) was found to protect against ethanol-induced gastric damage in rats; however, it is known that certain compounds in the flavone class, including flavone itself, are inducers of hepatic drug metabolizing enzymes. With the hope of identifying gastroprotective flavones that have minimal effects on drug metabolizing enzymes, we have synthesized and evaluated selected flavone analogs. Gastroprotective potency in the ethanol model was retained by methoxy substitution in the 5-position (4) and by methoxy (12) or methyl (14) substitution in the 7-position. A number of substituted analogs of the potent molecule 5-methoxyflavone (4) were also synthesized, and in many cases, these substitutions provided gastroprotective molecules. In order to assess liver enzyme induction potential, two of the gastroprotective flavones, 7-methoxyflavone (12) and 5-methoxy-4'-fluoroflavone (26), were examined for their effect on liver microsomal cytochrome P450 and 7-ethoxyresorufin O-dealkylase (CYP1A) activity. These two compounds caused minimal changes in the cytochrome P450 concentration and were considerably less potent than beta-naphthoflavone as inducers of CYP1A enzyme activity. Furthermore, following oral administration to rats, 5-methoxy-4'-fluoroflavone (26) was found to protect against indomethacin-induced gastric damage. These results indicate that, through appropriate substitution, flavones can be obtained that are gastroprotective but have minimal effects on drug-metabolizing enzymes.

Localization of factor IXa and factor VIIIa interactive sites

The contribution of the catalytic and noncatalytic domains of factor IXa to the interaction with its cofactor, factor VIIIa, was evaluated. Two proteolytic fragments of factor IXa, lacking some or all of the serine protease domain, failed to mimic the ability of factor IXa to enhance the reconstitution of factor VIIIa from isolated A1/A3-C1-C2 dimer and A2 subunit. Both fragments, however, inhibited this factor IXa-dependent activity. Selective thermal denaturation of the factor IXa serine protease domain eliminated its effect on factor VIIIa reconstitution. Modification of factor IXa with dansyl-Glu-Gly-Arg chloromethyl ketone (DEGR-IXa) stabilized this domain, and heat-treated DEGR-IXa retained its ability to enhance factor VIIIa reconstitution. These results indicate the importance of the serine protease domain as well as structures residing in the factor IXa light chain (gamma-carboxyglutamic acid and/or epidermal growth factor domains) for cofactor stabilizing activity. In the presence of phospholipid, the A1/A3-C1-C2 dimer produced a saturable increase in the fluorescence anisotropy of fluorescein-Phe-Phe-Arg chloromethyl ketone-modified factor IXa (Fl-FFR-IXa). This effect was inhibited by a factor IXa fragment comprised of the gamma-carboxyglutamic acid and epidermal growth factor domains. The difference in Fl-FFR-IXa anisotropy in the presence of A1/A3-C1-C2 dimer (delta r = 0.043) compared with factor VIIIa (delta r = 0.069) represented the contribution of the A2 subunit, A peptide corresponding to factor VIII A2 domain residues 558-565 decreased the factor VIIIa dependent-anisotropy of Fl-FFR-IXa to a value similar to that observed with the A1/A3-C1-C2 dimer. These results support a model of multiple interactive sites in the association of the enzyme-cofactor complex and localize sites for the A1/A3-C1-C2 dimer and the A2 subunit to the factor IXa light chain and serine protease domain, respectively.

An investigation of factors that might influence the radiochemical purity and stability of 99mTc-MAG3

Technetium 99m mercaptoacetyltriglycine (99mTc-MAG3) was prepared from a commercial kit by various techniques to assess the effect of a number of variables on radiochemical purity and stability. Its radiochemical purity was determined by high performance liquid chromatography at 0 and 6 h after preparation and was found to be consistently greater than 95%. It has been demonstrated that the radiochemical purity of 99mTc-MAG3 prepared according to the manufacturer's instructions is not influenced by the volume of 99mTc generator eluate used, agitation, the presence of air in the reaction vial or the use of a 99mTc generator eluate with a 99Tc:99mTc ratio of 16:1. A modified method of preparation in which the MAG3 kit is reconstituted with saline before addition of 99mTc-pertechnetate has been shown to yield a satisfactory product and should help to minimise the radiation dose to the fingers of radiopharmacy staff.