Fully Implantable Arterial Blood Glucose Device for Metabolic Research Applications in Rats for Two Months

BACKGROUND

Chronic continuous glucose monitoring options for animal research have been very limited due to various technical and biological challenges. We provide an evaluation of a novel telemetry device for continuous monitoring of temperature, activity, and plasma glucose levels in the arterial blood of rats for up to 2 months.

METHODS

In vivo testing in rats including oral glucose tolerance tests (OGTTs) and intraperitoneal glucose tolerance tests (IPGTTs) and ex vivo waterbath testing were performed to evaluate acute and chronic sensor performance. Animal studies were in accordance with the guidelines for the care and use of laboratory animals and approved by the corresponding animal care and use committees (Data Sciences International, Eli Lilly).

RESULTS

Results demonstrated the ability to record continuous measurements for 75 days or longer. Bench testing demonstrated a high degree of linearity over a range of 20-850 mg/dL with R(2) = .998 for linear fit and .999 for second order fit (n = 8 sensors). Evaluation of 6 rats over 28 days with 52 daily and OGTT test strip measurements each resulted in mean error of 3.8% and mean absolute relative difference of 16.6%.

CONCLUSIONS

This device provides significant advantages in the quality and quantity of data that can be obtained relative to existing alternatives such as intermittent blood sampling. These devices provide the opportunity to expand the understanding of both glucose metabolism and homeostasis and to work toward improved therapies and cures for diabetes.

Adenine ribo- and deoxyribonucleotide metabolism in human erythrocytes, B- and T-lymphocyte cell lines, and monocyte-macrophages

Ordinarily packaged in DNA, adenine deoxyribonucleotides are preferentially concentrated in erythrocyte and lymphocyte cytosol in adenosine deaminase (adenosine aminohydrolase, EC 3.5.4.4) deficiency. A spectrum of cytosol enzyme activities are defined in terms of reaction velocities, K0.5s, and nucleotide partition after incubation with ribo- and deoxyribonucleotides. AMP and dAMP were dephosphorylated, but only AMP was deaminated in vitro. Although nucleotidase activity is much stronger in lymphocytes, AMP deaminase was the dominant degradative reaction in all erythrocyte and lymphocyte lysates under the conditions specified. For most cytosolic enzymes, ribonucleotides were preferred cofactors, implying that dADP and dATP often may be bystanders at metabolic events. The adenylate kinase-mediated partition of approximately equimolar ribo- and deoxyribonucleotide substrates yielded a very large preponderance of AMP in the monophosphate compartment, the monophosphates alone being directly vulnerable to degradative loss. The adenylate kinase(s) of lymphocytes differed strikingly from those of erythrocytes in reaction velocities with nucleotide cofactors, K0.5s, and in susceptibility to substrate inhibition.

Pyruvate kinase isozyme (PK-Greenville) with defective allosteric activation by fructose-1,6-diphosphate: the role of F-1,6-P modulation in normal erythrocyte metabolism

A child with chronic hemolytic anemia since birth was found to have erythrocyte pyruvate kinase (PK) in a highly unusual form relative to other mutant isozymes when characterized by International Committee for Standardization in Hematology criteria. Most properties of the partially purified isozyme (designated PK-Greenville) were altered minimally, if at all, except for nearly total insensitivity to allosteric activation by fructose-1,6-diphosphate (F-1,6-P). One parent appeared to be heterozygous for a null gene and the other for an allele governing production of the mutant isozyme. Apparent restriction of the molecular defect to ineffective activation kinetics suggests that the F-1,6-P binding site on erythrocyte PK is functionally as well as physically allosteric. The magnitude of the metabolic block at the PK step and the clinical severity indicate that allosteric modulation by F-1,6-P is a crucial property of PK in normal erythrocyte metabolism.