A workflow for the detection of antibiotic residues, measurement of water chemistry and preservation of hospital sink drain samples for metagenomic sequencing

BACKGROUND

Hospital sinks are environmental reservoirs that harbour healthcare-associated (HCA) pathogens. Selective pressures in sink environments, such as antibiotic residues, nutrient waste and hardness ions, may promote antibiotic resistance gene (ARG) exchange between bacteria. However, cheap and accurate sampling methods to characterize these factors are lacking.

AIMS

To validate a workflow to detect antibiotic residues and evaluate water chemistry using dipsticks. Secondarily, to validate boric acid to preserve the taxonomic and ARG ('resistome') composition of sink trap samples for metagenomic sequencing.

METHODS

Antibiotic residue dipsticks were validated against serial dilutions of ampicillin, doxycycline, sulfamethoxazole and ciprofloxacin, and water chemistry dipsticks against serial dilutions of chemical calibration standards. Sink trap aspirates were used for a 'real-world' pilot evaluation of dipsticks. To assess boric acid as a preservative of microbial diversity, the impact of incubation with and without boric acid at ∼22 °C on metagenomic sequencing outputs was evaluated at Day 2 and Day 5 compared with baseline (Day 0).

FINDINGS

The limits of detection for each antibiotic were: 3 μg/L (ampicillin), 10 μg/L (doxycycline), 20 μg/L (sulfamethoxazole) and 8 μg/L (ciprofloxacin). The best performing water chemistry dipstick correctly characterized 34/40 (85%) standards in a concentration-dependent manner. One trap sample tested positive for the presence of tetracyclines and sulphonamides. Taxonomic and resistome composition were largely maintained after storage with boric acid at ∼22 °C for up to five days.

CONCLUSIONS

Dipsticks can be used to detect antibiotic residues and characterize water chemistry in sink trap samples. Boric acid was an effective preservative of trap sample composition, representing a low-cost alternative to cold-chain transport.

Detection of early stage pancreatic cancer using 5-hydroxymethylcytosine signatures in circulating cell free DNA

Pancreatic cancer is often detected late, when curative therapies are no longer possible. Here, we present non-invasive detection of pancreatic ductal adenocarcinoma (PDAC) by 5-hydroxymethylcytosine (5hmC) changes in circulating cell free DNA from a PDAC cohort (n = 64) in comparison with a non-cancer cohort (n = 243). Differential hydroxymethylation is found in thousands of genes, most significantly in genes related to pancreas development or function (GATA4, GATA6, PROX1, ONECUT1, MEIS2), and cancer pathogenesis (YAP1, TEAD1, PROX1, IGF1). cfDNA hydroxymethylome in PDAC cohort is differentially enriched for genes that are commonly de-regulated in PDAC tumors upon activation of KRAS and inactivation of TP53. Regularized regression models built using 5hmC densities in genes perform with AUC of 0.92 (discovery dataset, n = 79) and 0.92-0.94 (two independent test sets, n = 228). Furthermore, tissue-derived 5hmC features can be used to classify PDAC cfDNA (AUC = 0.88). These findings suggest that 5hmC changes enable classification of PDAC even during early stage disease.

Early and frequent exposure to antibiotics in children and the risk of obesity: systematic review and meta-analysis of observational studies

Background: This study aimed to systematically evaluate the available evidence on prenatal and early infancy antibiotic exposure and the association with overweight and obesity in later childhood.

Methods: We conducted a comprehensive search of Embase, MEDLINE, and Web of Science for observational studies assessing prenatal and early antibiotic exposure on the risk of overweight and obesity. We independently assessed the risk of bias using the ROBINS instrument and the overall quality of evidence using the GRADE approach.

Results: Our search identified thirteen observational studies including 554,983 participants; most studies were at moderate risk of bias. We found a statistically significant impact of early antibiotic exposure and the risk of being overweight later in childhood (OR 1.18; 95% CI 1.05 to 1.34) (very low quality evidence). We also found that early childhood antibiotic exposure was associated with the risk for childhood obesity (OR 1.14; 95% CI 1.04 to 1.24) (very low quality evidence).

Conclusions: Very low quality evidence suggests that exposure to antibiotics early in life may be associated with an increased risk of being overweight and obese in later childhood.  However, very low quality evidence raises serious questions about the plausibility of prenatal and early infancy antibiotic exposure being causally related to weight in children.

PROSPERO registration: CRD42016050011 (14/12/2016)

Effect of Placental Growth Factor on Trophoblast-Endothelial Cell Interactions In Vitro

Placental growth factor (PlGF) is an important angiogenic factor which has an emerging role in the clinical management of suspected preeclampsia. The role of PlGF in normal placental development is not completely understood and it is uncertain whether PlGF influences trophoblast and endothelial cell interactions central to uterine spiral artery remodelling, especially in variable oxygen conditions. A two-cell model of endovascular invasion was used. Tissue culture plates were coated with Matrigel™, on which fluorescent-labelled uterine microvascular endothelial cells (1 × 10⁵/well) and HTR8/SVNeo cells were co-cultured (1 × 10⁵/well) for 20 h. Co-cultures were treated with recombinant human PlGF (rhPlGF) (10 or 100 ng/mL) and incubated at either 21% O₂ or 2% O₂. Images were captured by fluorescence microscopy and analysed using ImageJ (n = 7). Data was analysed using SPSSv24. Treatment with rhPlGF did not improve integration in co-cultures irrespective of oxygen conditions but increased proliferation in 2% O₂ of both trophoblast and endothelial cells. Expression of angiogenic factors VEGF, sFLT-1, PlGF and CXCL12 in both co-cultures and in isolated trophoblast cells was not altered by rhPlGF treatment. Expression of TLR-3 mRNA in co-cultures was increased by rhPlGF 100 ng/mL at 21% O₂ (p = 0.03). PlGF contributes to trophoblast and endothelial cell proliferation in the setting of physiological hypoxia but does not influence trophoblast and endothelial cell interactions in an in vitro model of spiral artery remodelling. Upregulation of TLR-3 expression in co-cultures may indicate a role for PlGF in the placental inflammatory response.

Abstract 1372: Detection of early stage pancreatic cancer using 5–hydroxymethylcytosine signatures in circulating cell free DNA

Pancreatic cancers are typically diagnosed at late stage where disease prognosis is poor as exemplified by a 5-year survival rate of 8.2%. Earlier diagnosis would be beneficial by enabling surgical resection or earlier application of therapeutic regimens. We investigated the detection of pancreatic ductal adenocarcinoma (PDAC) in a non-invasive manner by interrogating changes in 5-hydroxymethylated cytosines (5hmC) in circulating cell free DNA in the plasma of a PDAC cohort (n=51) in comparison with a non-cancer cohort (n=41). 5hmC profiles from PDAC and non-cancer samples were generated using a previously published modified hMe-Seal protocol that utilizes chemical labeling of 5hmC by β-glucosyltransferase and allows detection of cell free 5hmC from small amounts of cfDNA (1). We found that 5hmC sites are enriched in a disease and stage specific manner in exons, 3’UTRs and transcription termination sites. Our data show that 5hmC density is reduced in promoters and histone H3K4me3 associated sites with progressive disease suggesting increased transcriptional activity. 5hmC density is differentially represented in thousands of genes, and a stringently filtered set of the most significant genes points to biology related to pancreas (GATA4, GATA6, PROX1, ONECUT1) and/or cancer development (YAP1, TEAD1, PROX1, ONECUT1, ONECUT2, IGF1 and IGF2). Regularized regression models were built using 5hmC densities in a comprehensive set of genes with the most variable 5hmC counts and performed with an AUC = 0.94 - 0.96 on training data. We tested the ability to classify PDAC and non-cancer samples with the Elastic net and Lasso models on three independent pancreatic cancer 5hmC data sets (n = 26, 23 and 7) compared with corresponding independent non-cancer cohorts (n =103, 53 and 10), and found validation performance to be AUC = 0.74 - 0.97. The findings suggest that 5hmC changes enable classification of PDAC patients with high fidelity and are worthy of further investigation on larger cohorts of patient samples. Reference: 1. Song, C. - X. et al. 5 - Hydroxymethylcytosine signatures in cell-free DNA provide information about tumor types and stages. Cell Res 27, 1231 (2017).

Citation Format: Francois Collin, Yuhong Ning, Gulfem D. Guler, Tierney Phillips, Erin McCarthy, Aaron Scott, Chris Ellison, Chin-Jen Ku, Kim Chau, Alan Ashworth, Stephen R. Quake, Samuel Levy. Detection of early stage pancreatic cancer using 5–hydroxymethylcytosine signatures in circulating cell free DNA [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 1372.

Lactobacillus reuteri to Treat Infant Colic: A Meta-analysis

CONTEXT

Lactobacillus reuteri DSM17938 has shown promise in managing colic, but conflicting study results have prevented a consensus on whether it is truly effective.

OBJECTIVE

Through an individual participant data meta-analysis, we sought to definitively determine if L reuteri DSM17938 effectively reduces crying and/or fussing time in infants with colic and whether effects vary by feeding type.

DATA SOURCES

We searched online databases (PubMed, Medline, Embase, the Cumulative Index to Nursing and Allied Health Literature, the Database of Abstracts of Reviews of Effects, and Cochrane), e-abstracts, and clinical trial registries.

STUDY SELECTION

These were double-blind randomized controlled trials (published by June 2017) of L reuteri DSM17398 versus a placebo, delivered orally to infants with colic, with outcomes of infant crying and/or fussing duration and treatment success at 21 days.

DATA EXTRACTION

We collected individual participant raw data from included studies modeled simultaneously in multilevel generalized linear mixed-effects regression models.

RESULTS

Four double-blind trials involving 345 infants with colic (174 probiotic and 171 placebo) were included. The probiotic group averaged less crying and/or fussing time than the placebo group at all time points (day 21 adjusted mean difference in change from baseline [minutes] -25.4 [95% confidence interval (CI): -47.3 to -3.5]). The probiotic group was almost twice as likely as the placebo group to experience treatment success at all time points (day 21 adjusted incidence ratio 1.7 [95% CI: 1.4 to 2.2]). Intervention effects were dramatic in breastfed infants (number needed to treat for day 21 success 2.6 [95% CI: 2.0 to 3.6]) but were insignificant in formula-fed infants.

LIMITATIONS

There were insufficient data to make conclusions for formula-fed infants with colic.

CONCLUSIONS

L reuteri DSM17938 is effective and can be recommended for breastfed infants with colic. Its role in formula-fed infants with colic needs further research.

The principle of equipoise in pediatric drug trials

Equipoise is a fundamental ethical principle in the conduct of interventional trials comparing two or more treatment arms. This principle dictates that, at the time of planning and executing such trials, the researchers must have no compelling evidence that one arm is superior to the other arm(s). That means that it is unethical to involve patients in a study where one intervention is convincingly better than the other, as this would mean that a group of patients will receive an inferior option, which may endanger their health. While this principle may be straightforward at the beginning of a trial, there are numerous ways how it may be subsequently disrupted. Presently, most of the literature on equipoise deals with adult patients, with very little experience in children. This paper illustrates the principle of equipoise and the process of defining it. Because the majority of pediatric medications have not been studied adequately and are not labeled for pediatric use, it is often challenging to decide whether equipoise exists for a certain pharmacological treatment. Moreover, the equipoise may dynamically change during the conduct of a study, if new evidence from other studies becomes available.

Probiotics for infantile colic: a randomized, double-blind, placebo-controlled trial investigating Lactobacillus reuteri DSM 17938

OBJECTIVE

To investigate the effectiveness of Lactobacillus reuteri DSM 17938 for the treatment of infantile colic in breastfed Canadian infants, compared with placebo.

STUDY DESIGN

A randomized, double-blind, placebo-controlled trial was conducted involving 52 infants with colic, according to modified Wessel criteria, who were assigned at random to receive L reuteri DSM 17938 (10(8) colony-forming units) (n = 24) or placebo (n = 28) for 21 days. Daily crying and fussing times were recorded in a structured diary, and maternal questionnaires were completed to monitor changes in infant colic symptoms and adverse events.

RESULTS

Total average crying and fussing times throughout the study (from baseline to day 21) were significantly shorter among infants with colic in the probiotic group compared with infants in the placebo group (1719 ± 750 minutes [29 ± 13 hours] vs 2195 ± 764 minutes [37 ± 13 hours]; P = .028) (relative risk, 0.78; 95% CI, 0.58-0.98). Infants given L reuteri DSM 17938 showed a significant reduction in daily crying and fussing times at the end of treatment period compared with those receiving placebo (median, 60 minutes/day [IQR, 64 minutes/day] vs 102 minutes/day [IQR, 87 minutes/day]; P = .045). On day 21, a significantly higher proportion of infants in the L reuteri DSM 17938 group responded to treatment with a ≥50% crying time reduction compared with infants given placebo (17 vs 6, P = .035; relative risk, 3.3; 95% CI, 1.55-7.03).

CONCLUSION

Administration of L reuteri DSM 17938 significantly improved colic symptoms by reducing crying and fussing times in breastfed Canadian infants with colic.

Extracellular quality control in the epididymis

The epididymal lumen represents a unique extracellular environment because of the active sperm maturation process that takes place within its confines. Although much focus has been placed on the interaction of epididymal secretory proteins with spermatozoa in the lumen, very little is known regarding how the complex epididymal milieu as a whole is maintained, including mechanisms to prevent or control proteins that may not stay in their native folded state following secretion. Because some misfolded proteins can form cytotoxic aggregate structures known as amyloid, it is likely that control/surveillance mechanisms exist within the epididymis to protect against this process and allow sperm maturation to occur. To study protein aggregation and to identify extracellular quality control mechanisms in the epididymis, we used the cystatin family of cysteine protease inhibitors, including cystatin-related epididymal spermatogenic and cystatin C as molecular models because both proteins have inherent properties to aggregate and form amyloid. In this chapter, we present a brief summary of protein aggregation by the amyloid pathway based on what is known from other organ systems and describe quality control mechanisms that exist intracellularly to control protein misfolding and aggregation. We then present a summary of our studies of cystatin-related epididymal spermatogenic (CRES) oligomerization within the epididymal lumen, including studies suggesting that transglutaminase cross-linking may be one mechanism of extracellular quality control within the epididymis.

Application of surrogate methods for assessing the bioavailability of PAHs in sediments to a sediment ingesting bivalve

The usefulness of two surrogate methods for rapidly determining the bioavailability of PAHs in hydrocarbon-contaminated marine sediments was assessed. Comparisons are made between the PAHs accumulated by the benthic bivalve, Tellina deltoidalis, and the extractable-PAHs determined using a 6-h XAD-2 resin desorption method and a 4-h gut fluid mimic (GFM) extraction method. There were significant positive relationships between PAH bioaccumulation by the bivalves and sediment PAH concentrations. These relationships were not improved by normalising the sediment PAH concentrations to the organic carbon concentration. The average percentage lipid content of the bivalves was 1.47+/-0.22% and BSAFs for total-PAHs ranged from 0.06 to 0.80 (kgOC/kg lipid). The XAD-2 and GFM methods both extracted varying amounts of PAHs from the sediments. Low concentrations of PAHs were extracted by the GFM method (0.2-3.6% of total-PAHs in sediments) and the GFM results were inadequate for generalising about the bioavailability of the PAHs in the sediments. The XAD-2 method extracted greater amounts of PAHs (3-34% of total-PAHs in sediments), however, the total-PAH concentrations in the sediments provided a better, or equally good, prediction of PAH bioaccumulation by T. deltoidalis. The results indicated that these methods required further development before they can be applied routinely as surrogate methods for assessing the bioavailability of PAHs in sediments. Future research should be directed towards lowering detection limits and obtaining comparative data for a greater range of sediment types, contaminant classes and concentrations, and organisms of different feeding guilds and with different gut chemistry.

Transcatheter closure of persistent arterial ducts with different types of coils

BACKGROUND

Different types of coils have been designed for transcatheter closure of persistent arterial ducts. We compared the efficacy and safety of three types of coils: Gianturco coils (Cook), Cook detachable coils (Cook), and Duct Occlud devices (pfm).

METHODS

Sixty-three patients underwent coil occlusion of arterial ducts between April 1995 and July 2000. The mean age and weight were 4.8+/-3.4 years and 16.5+/-7.6 kg, respectively. The results and complications of ductal occlusion among the three types of coils were compared. Kaplan-Meier analysis was used to assess reduction in the prevalence of residual shunt with time, and multiple regression analysis was performed to identify predictors of complete occlusion.

RESULTS

Coil occlusion of persistent arterial ducts that measured 2. 2 +/- 0.8 mm was feasible in 90% (57/63) of patients. Gianturco coils were used in 29, Duct Occlud devices in 16, and Cook detachable coils in 12 patients. The prevalence of residual shunt at 24 hours, 6 months, 12 months, and 24 months was 42%, 20%, 18%, and 14%, respectively. The reduction in prevalence of residual shunt with time tended to be greater when Gianturco coils were used (P =. 067). Logistic regression identified the use of Gianturco coils to be a significant predictor of complete ductal occlusion on follow-up (P =.04). Pull-through of coils occurred in 4.8% (3/63) and coil embolization in 6.3% (4/63). There was no association between the type of coil and the risk of embolization (P = 1.00).

CONCLUSIONS

Transcatheter occlusion of small persistent arterial ducts with coils is safe and effective. There is no advantage of detachable coils (Cook detachable coils and Duct Occlud devices) over nondetachable Gianturco coils in reducing the risk of embolization. Our findings are in favor of the inexpensive, but more effective, Gianturco coils for occluding small arterial ducts of 3 mm or less.

A novel downstream positive regulatory element mediating transcription of the human high mobility group (HMG) I-C gene

The high mobility group (HMG) I proteins are small, non-histone chromosomal proteins that promote gene activation during development and within rapidly dividing cells. They do so by facilitating enhanceosome formation on inducible genes, via both protein/DNA and protein/protein interactions. The HMG I-C gene is tightly regulated, normally being expressed exclusively during embryonic development. However, HMG I-C expression is also observed frequently in a number of tumor types, and this expression has been shown to contribute to the malignant transformation process. With the aim of dissecting pathways that lead to aberrant expression of HMG I-C in tumor cells, we have analyzed HMG I-C gene regulation in the human hepatoma cell line PLC/PRF/5. One of the two HMG I-C transcripts detected in this cell line originates from a novel downstream initiation site at nucleotide -161 relative to the first methionine. Transcription from the downstream initiation site is mediated by a PRE located between nt -222 and -217. We show here that the Sp1 and Sp3 transcription factors interact with the PRE and transactivate the HMG I-C promoter in a cooperative fashion. This study provides the first characterization of this downstream HMG I-C promoter.

A novel downstream positive regulatory element mediating transcription of the human high mobility group (HMG) I-C gene

The high mobility group (HMG) I proteins are small, non-histone chromosomal proteins that promote gene activation during development and within rapidly dividing cells. They do so by facilitating enhanceosome formation on inducible genes, via both protein/DNA and protein/protein interactions. The HMG I-C gene is tightly regulated, normally being expressed exclusively during embryonic development. However, HMG I-C expression is also observed frequently in a number of tumor types, and this expression has been shown to contribute to the malignant transformation process. With the aim of dissecting pathways that lead to aberrant expression of HMG I-C in tumor cells, we have analyzed HMG I-C gene regulation in the human hepatoma cell line PLC/PRF/5. One of the two HMG I-C transcripts detected in this cell line originates from a novel downstream initiation site at nucleotide -161 relative to the first methionine. Transcription from the downstream initiation site is mediated by a PRE located between nt -222 and -217. We show here that the Sp1 and Sp3 transcription factors interact with the PRE and transactivate the HMG I-C promoter in a cooperative fashion. This study provides the first characterization of this downstream HMG I-C promoter.

Cis-element dependence and occupancy of the human invariant chain promoter in CIITA-dependent and -independent transcription

The major histocompatibility complex (MHC)-associated invariant chain (Ii) associates with the class II alpha/beta heterodimer during its biosynthesis, inhibiting association of endogenous peptides with the peptide-binding cleft. It is therefore not surprising that there are significant similarities in regulatory mechanisms controlling the expression of the structural class II MHC and Ii genes. One important similarity is that both classes of genes can be expressed via CIITA-dependent or -independent mechanisms. In this report, we have dissected CIITA-dependent and -independent transcription of the Ii gene using an isogenic B-LCL cell pair (Jijoye and clone-13) which do or do not express the class II MHC transactivator (CIITA), respectively. Experiments using mutant or deletion constructs of the Ii gene promoter indicate that while both the X-box and li-kappaB1 elements are critical for CIITA-dependent transcription in B lymphocytes, the Ii-kappaBI element is of greater importance for CIITA-independent Ii gene transcription, with the X-box playing a secondary role. Despite these clear differences in cis-element dependence of CIITA-dependent and -independent Ii transcription, there are only subtle differences in the occupancy of these elements in vivo as assessed by genomic footprinting. These differences are restricted to occupancy of the X-box and Y-box, with which the RF-X and NF-Y complexes interact in Ii-positive cells. This difference in the occupancy of the X-box and Y-box in this cell pair indicates that while protein/protein interactions between CIITA and promoter-bound factors stabilize promoter occupancy, these interactions are not absolutely required for occupancy and transcription of the invariant chain gene.

Acute sporadic non-A, non-B, non-C, non-D, non-D, non-E hepatitis

Patients presenting with clinical and laboratory features consistent with a diagnosis of acute non-A, non-B hepatitis were evaluated for evidence of hepatitis C or hepatitis E infection and for evidence of severe or prolonged disease. Antibody to hepatitis C virus (anti-HCV) was detected in 75 of 108 (69%) patients, antibody to hepatitis E virus (anti-HEV) in three patients (3%), and neither antibody in 31 (29%) patients. One patient had both anti-HCV and anti-HEV. HCV RNA was not detected in sera from any of 20 patients with seronegative (non-ABCDE) hepatitis, but in all 10 patients with anti-HCV who were tested by polymerase chain reaction (PCR). Compared with patients with acute hepatitis C, those with non-ABCDE hepatitis had a lower incidence of parenteral risk factors (6% vs. 70%; P < .001), higher peak serum bilirubin levels (45% vs. 5% with peak levels > 15 mg/dL; P < .001), more prolonged jaundice (25% vs. 0% with peak bilirubin >5 weeks after onset; P < .01), more severe prothrombin time abnormalities (26% vs. 0% with >3 second prolongation; P < .001), more severe hypoalbuminemia (39% vs. 9% with albumin <3 g/dL; P < .01), and more frequent major clinical complications (13% vs. 0% with encephalopathy; P < .01; 10% vs. 0% with death or transplant; P = .024). Patients with acute non-ABCDE hepatitis were less likely to develop chronic hepatitis than those with acute hepatitis C (23% vs. 68%; P < .05). Thus, patients with acute non-ABCDE hepatitis are epidemiologically distinct from those with acute hepatitis C and have a significantly more severe acute illness.

IgM antibody response in acute hepatitis C viral infection

IgM antibody against hepatitis C virus (IgM anti-HCV) was measured in serial samples from 15 transfusion recipients in whom posttransfusion chronic non-A, non-B hepatitis (NANBH) developed and three plasmapheresis donors during acute HCV infection using recombinant proteins derived from three immunodominant regions: core, NS-3, and NS-4 (c100). IgM anti-HCV core was detected in 13 of 15 posttransfusion patients. Nine of these patients had transient, acute-phase IgM anti-HCV core detected coincidentally or earlier than active IgG anti-HCV core response. The average duration of IgM anti-HCV core reactivity was 8.1 +/- 3.7 weeks. One patient lacking an IgM anti-HCV core response had detectable IgM anti-HCV NS-3 during the acute phase. Passive transfer of IgM anti-HCV was not observed in these posttransfusion cases, in contrast to the high frequency observed for IgG anti-HCV. Late IgM anti-HCV was detectable against core, c100, and NS-3 in three, two, and one posttransfusion patients, respectively. These data indicate that IgM anti-HCV core is a useful acute-phase marker in HCV infection.

Partitioning and extraction of glucose regulates cerebral glucose utilization in newborn dogs

We investigated the amount of fasting steady-state systemic glucose production utilized by the neonatal canine cerebral cortex. The relationship of systemic glucose production and cerebral glucose utilization were analyzed as functions of cerebral blood flow, cerebral oxygen uptake, and indirect measures of alternate fuel utilization. Fasting arterial blood glucose was 3.36 mM and glucose production was 49.6 mumol/kg/min. Average cerebral blood flow was 0.83 ml/g/min, and cerebral glucose uptake was 0.60 +/- 0.15 mumol/g/min. 36.6% of systemic glucose production was utilized by the cerebral cortex. There were no correlations between systemic glucose production, cerebral blood flow, or cerebral glucose uptake with blood glucose concentration. Furthermore, total cerebral glucose uptake was static across a wide range of glucose levels. Nonetheless, the percent of glucose production used by the brain was an inverse function of systemic glucose production (r = -0.71, p less than 0.001). The cerebral extraction of glucose (27.6 +/- 4.1%) decreased as a function of increasing blood glucose levels (r = -0.51, p less than 0.05), while brain uptake index correlated with increasing systemic glucose production (r = 0.61, p less than 0.02). We can conclude that the canine neonatal cerebral cortex may utilize only 37% of systemic glucose production. At low rates of glucose turnover, a larger proportion of systemic glucose production is allotted to the brain. Mechanisms that may regulate total cerebral glucose influx may be glucose permeability, or the increased extraction of glucose at lower blood glucose levels.