Novel approach for tracking interdisciplinary research productivity using institutional databases.

This study proposes a new practical approach for tracking institutional changes in research teamwork and productivity using commonly available institutional electronic databases such as eCV and grant management systems. We tested several definitions of interdisciplinary collaborations based on number of collaborations and their fields of discipline. We demonstrated that the extent of interdisciplinary collaboration varies significantly by academic unit, faculty appointment and seniority. Interdisciplinary grants constitute 24% of all grants but the trend has significantly increased over the last five years. Departments with more interdisciplinary grants receive more research funding. More research is needed to improve efficiency of interdisciplinary collaborations.

Rewiring of the corticospinal tract in the adult rat after unilateral stroke and anti-Nogo-A therapy.

Adult Long Evans rats received a photothrombotic stroke that destroyed >90% of the sensorimotor cortex unilaterally; they were subsequently treated intrathecally for 2 weeks with a function blocking antibody against the neurite growth inhibitory central nervous system protein Nogo-A. Fine motor control of skilled forelimb grasping improved to 65% of intact baseline performance in the anti-Nogo-A treated rats, whereas control antibody treated animals recovered to only 20% of baseline scores. Bilateral retrograde tract tracing with two different tracers from the intact and the denervated side of the cervical spinal cord, at different time points post-lesion, indicated that the intact corticospinal tract had extensively sprouted across the midline into the denervated spinal hemicord. The original axonal arbours of corticospinal tract fibres that had recrossed the midline were subsequently withdrawn, leading to a complete side-switch in the projection of a subpopulation of contralesional corticospinal tract axons. Anterograde tracing from the contralesional cortex showed a 2-3-fold increase of midline crossing fibres and additionally a massive sprouting of the pre-existing ipsilateral ventral corticospinal tract fibres throughout the entire cervical enlargement of the anti-Nogo-A antibody-treated rats compared to the control group. The laminar distribution pattern of the ipsilaterally projecting corticospinal tract fibres was similar to that in the intact spinal cord. These plastic changes were paralleled by a somatotopic reorganization of the contralesional motor cortex where the formation of an ipsilaterally projecting forelimb area was observed. Intracortical microstimulation of the contralesional motor cortex revealed that low threshold currents evoked ipsilateral movements and electromyography responses at frequent cortical sites in the anti-Nogo-A, but not in the control antibody-treated animals. Subsequent transection of the spared corticospinal tract in chronically recovered animals, treated with anti-Nogo-A, led to a reappearance of the initial lesion deficit observed after the stroke lesion. These results demonstrate a somatotopic side switch anatomically and functionally in the projection of adult corticospinal neurons, induced by the destruction of one sensorimotor cortex and the neutralization of the CNS growth inhibitory protein Nogo-A.

Monoclonal antibody pharmacokinetics and pharmacodynamics.

More than 20 monoclonal antibodies have been approved as therapeutic drugs by the US Food and Drug Administration, and it is quite likely that the number of approved antibodies will double in the next 7-10 years. Antibody drugs show several desirable characteristics, including good solubility and stability, long persistence in the body, high selectivity and specificity, and low risk for bioconversion to toxic metabolites. However, many antibody drugs demonstrate attributes that complicate drug development, including very poor oral bioavailability, incomplete absorption following intramuscular or subcutaneous administration, nonlinear distribution, and nonlinear elimination. In addition, antibody administration often leads to an endogenous antibody response, which may alter the pharmacokinetics and efficacy of the therapeutic antibody. Antibodies have been developed for a wide range of disease conditions, with effects produced through a complex array of mechanisms. This article attempts to provide a brief overview of the main determinants of antibody pharmacokinetics and pharmacodynamics. Clinical Pharmacology & Therapeutics (2008); 84, 5, 548-558 doi:10.1038/clpt.2008.170.

Pharmacokinetics, pharmacodynamics, and platelet binding of an anti-glycoprotein IIb/IIIa monoclonal antibody (7E3) in the rat: a quantitative rat model of immune thrombocytopenic purpura.

The pharmacokinetics, pharmacodynamics, and platelet binding of 7E3, an anti-glycoprotein IIb/IIIa (GPIIb/IIIa) monoclonal antibody, were studied in the rat in an attempt to develop a quantitative animal model of immune thrombocytopenia (ITP). 7E3, a murine IgG1 antibody developed against human GPIIb/IIIa, demonstrated cross-reactivity with rat platelets by flow cytometry and via enzyme-linked immunosorbent assay. The apparent affinity (K(A)) of 7E3-rat platelet binding was 1.2 +/- 0.2 x 10(7) M(-1), with 3.3 +/- 0.3 x 10(4) binding sites per platelet. Following intravenous 7E3 administration (0.8, 4, and 8 mg/kg), plasma concentrations declined in a bi-exponential manner, with a terminal half-life of 61 +/- 5 h and a steady-state volume of distribution of 62 +/- 15 ml/kg. Clearance was dose-dependent, with values ranging from 0.64 +/- 0.08 ml/h/kg (8 mg/kg) to 1.01 +/- 0.08 ml/h/kg (0.8 mg/kg). 7E3 induced a reproducible, severe thrombocytopenia in rats and extended bleeding in a manner consistent with human ITP. Nadir platelet counts were 79 +/- 33, 25 +/- 6, and 17 +/- 2 x 10(6)/ml, for 7E3 doses of 0.8, 4, and 8 mg/kg, respectively. Bleeding times after a 10-mm tail incision ranged from 5 +/- 3 min in control animals to 15 +/- 0 min (the maximum allowed time in this study) in animals receiving 8 mg/kg. Blood volumes lost during bleeding experiments ranged from 30 +/- 24 microl (control) to 349 +/- 358 microl (8 mg/kg). A reproducible, quantitative rat model of ITP has been created; this model is expected to facilitate the evaluation of new treatments for this disease.

An ELISA for quantification of murine IgG in rat plasma: application to the pharmacokinetic characterization of AP-3, a murine anti-glycoprotein IIIa monoclonal antibody, in the rat.

An enzyme-linked immunosorbent assay (ELISA) has been developed to determine concentrations of murine IgG in rat plasma. Specifically, the assay was developed to measure a murine anti-glycoprotein IIIa antibody (AP-3) in rat plasma to facilitate future investigations of AP-3 pharmacokinetics and pharmacodynamics in the rat. The working range of the assay is 15-100 ng ml(-1), corresponding to a limit of quantification of 1.5 microg ml(-1) in rat plasma. The assay was validated with respect to accuracy, precision, and cross-reactivity with both pooled rat and mouse IgG. Intra-assay recoveries of AP-3 in rat plasma ranged from 93 to 103%, with CV% values ranging from 5.2 to 8.5%. Inter-assay recoveries of the plasma AP-3 samples ranged from 107 to 119% with CV% values ranging from 17.7 to 25.1%. The assay has no appreciable cross reactivity with pooled rat IgG and full cross reactivity with pooled mouse IgG, making this an ideal assay to determine plasma pharmacokinetics of mouse antibodies in the rat. The assay was used to determine the pharmacokinetics of AP-3 in a Sprague-Dawley rat.

Highly sensitive high-performance liquid chromatographic assay for methotrexate in the presence and absence of anti-methotrexate antibody fragments in rat and mouse plasma.

Recently, Balthasar and Fung have proposed that anti-methotrexate antibody fragments may be employed to enhance the selectivity of intraperitoneal methotrexate (MTX) therapy. This current work presents a sensitive high-performance liquid chromatographic method for measuring plasma concentrations of total (i.e., bound and unbound) MTX and free (unbound) MTX in rat and mouse plasma, in the presence or absence of therapeutic anti-MTX antibody fragments. The assay involves pre-column derivatization of MTX by sodium hydrosulfite to 2,4-diamino-6-methylpteridine. The limit of quantitation for MTX by this assay was 1.25 ng in rat plasma, mouse plasma and mouse plasma ultrafiltrate, which corresponds to a concentration of 25 ng/ml for a 50 microl sample. The limit of quantitation was found to be 2.5 ng in rat plasma ultrafiltrate (i.e., 50 ng/ml in 50 microl rat plasma ultrafiltrate). The method was shown to be quite accurate, as the mean assayed concentration of quality control samples was within 10% of theoretical values. We have applied the method to the investigation of MTX pharmacokinetics in mice and rats, following the administration of MTX alone or following simultaneous administration of MTX and anti-MTX Fab fragments. The method has been shown to be suitable for the assay of total and free methotrexate in the plasma of these species and will enable the testing of pharmacokinetic hypotheses regarding the influence of anti-MTX Fab fragments on the disposition of MTX.

Application of pharmacodynamic modeling for designing time-variant dosing regimens to overcome nitroglycerin tolerance in experimental heart failure.

PURPOSE: Prolonged continuous administration of nitroglycerin (NTG) leads to hemodynamic tolerance. We used a previously developed pharmacokinetic-pharmacodynamic (PK/PD) model of NTG tolerance in experimental heart failure to test whether dosage regimens, designed from this model, may allow avoidance of tolerance development upon continuous NTG infusion. METHODS: Simulation experiments (using ADAPT II) were performed to evolve a time-variant infusion regimen that would theoretically provide sustained hemodynamic effect (30% reduction in left ventricular end-diastolic pressure, LVEDP) throughout 10 hours of drug dosing. A computer controlled infusion pump was utilized to deliver this time-variant input. Infusion experiments were then conducted in CHF rats to challenge the predictability of the applied PK/PD model. RESULTS: Simulations showed that exponentially increasing input functions provided more sustained LVEDP effects when compared to linear or hyperbolic input functions delivering the same total NTG dose. A computer-selected infusion regimen of 6.56e0.00156 x minutes micrograms/min was anticipated to provide the desired hemodynamic profile in our animal model. Experiments conducted in rats with congestive heart failure (n = 4) confirmed the prediction of sustained hemodynamic effect without tolerance (28 +/- 4% reduction in LVEDP at 10 hrs). CONCLUSIONS: These findings support the utility of our PK/PD model of NTG tolerance in predicting NTG action, and serve as an example of therapeutic optimization through PK/PD considerations.

Inverse targeting of peritoneal tumors: selective alteration of the disposition of methotrexate through the use of anti-methotrexate antibodies and antibody fragments.

We have hypothesized that antidrug antibodies (ADAb) may be employed to impart site-specific alterations in the disposition of drug molecules, potentially allowing for targeted drug therapy. We are specifically interested in minimizing systemic exposure to free drug and systemic toxicities resultant from regional chemotherapy through the intravenous administration of ADAb. In this report, we present the production and purification of anti-methotrexate Fab fragments, and we present investigations of the effects of anti-methotrexate Fab and anti-methotrexate immunoglobulin G on the disposition of methotrexate in the rat. Pharmacokinetic studies revealed that intravenous anti-methotrexate immunoglobulin G (anti-MTX IgG) and anti-methotrexate Fab (anti-MTX Fab) administration produced dramatic alterations in the plasma pharmacokinetics of methotrexate (MTX), following intraperitoneal MTX administration (area under the total MTX concentration vs time curve for anti-MTX IgG relative to control, 420 +/- 90 (p < 0.05); for anti-MTX Fab relative to control, 46 +/- 6.1 (p < 0.05); area under the free MTX concentration vs time curve for anti-MTX IgG relative to control, 0.64 +/- 0.16; for anti-MTX Fab relative to control, 0.45 +/- 0.20 (p < 0.05)). Additional studies conducted in anesthetized rats revealed no significant alterations in the area under the total peritoneal MTX concentration vs time curves, free MTX peritoneal concentration vs time curves, or peritoneal exit rate of MTX in anti-MTX Fab treated animals relative to controls. Therefore, our pharmacokinetic studies demonstrate that ADAb may produce site-specific alterations in drug pharmacokinetics, potentially enhancing the site specificity of drug distribution and drug action following regional chemotherapy.

Pharmacokinetic and pharmacodynamic optimization of intraperitoneal chemotherapy.

Intraperitoneal drug administration has been utilized to increase chemotherapeutic exposure to tumors confined to the peritoneal cavity, such as those found in ovarian, gastric, colo-rectal and mesotheliomal cancers. Extensive pre-clinical and clinical experimentation has been conducted to assess the pharmacokinetic and therapeutic benefits of this mode of therapy. Pharmacokinetic studies have shown that the barrier function of the peritoneal membrane may be utilized to produce large, favorable concentration gradients between peritoneal perfusate and blood. However, most clinical studies so far have demonstrated minimal increases in drug efficacy or decreases in drug toxicities from intraperitoneal drug therapy alone. This paper reviews the application of adjunctive therapies that have been rationally conceived to optimize intraperitoneal drug therapy through the alteration of antineoplastic pharmacokinetics and pharmacodynamics.

High-affinity rabbit antibodies directed against methotrexate: production, purification, characterization, and pharmacokinetics in the rat.

We describe the production, purification, characterization, and disposition of rabbit polyclonal methotrexate antibodies. These antibodies are prepared for subsequent testing of a drug delivery approach to reduce systemic toxicity upon regional administration of methotrexate. The polyclonal antibodies were raised in New Zealand white female rabbits immunized with a methotrexate-bovine serum albumin conjugate. The anti-methotrexate antibodies were sequestered from rabbit serum through the use of a protein-G affinity column which allowed for purification of up to 100 mg of rabbit IgG in 30-40 min. The extent of purification was demonstrated through SDS-PAGE and calculation of specific binding activity relative to total protein concentration. The purified antibodies have been shown to have high affinity (Keq range: 1.8 x 10(8) to 8.75 x 10(9) M-1) and high selectivity for methotrexate. Preliminary pharmacokinetic studies of the purified antibodies in the rat following a 6 mg/kg intravenous infusion (n = 4) indicate a steady state volume of distribution of 38.0 +/- 11.2 mL kg-1, a systemic clearance of 0.92 +/- 0.67 mL kg-1 h-1 and an elimination half life of 28.9 +/- 7.9 h (mean +/- SD).

Utilization of antidrug antibody fragments for the optimization of intraperitoneal drug therapy: studies using digoxin as a model drug.

The direct administration of chemotherapeutic agents into the peritoneal cavity has been investigated as a method to treat cancers residing within the peritoneum. The benefits of i.p. drug administration are limited, however, by the systemic toxicity of antineoplastic drugs which diffuse out of the peritoneum and into the general circulation. We propose that antidrug antibody fragments may be useful in binding chemotherapeutics in the general circulation, thereby reducing the systemic tissue exposure and toxicity resulting from such i.p. therapy. Inasmuch as antibody fragments directed against antineoplastic agents are not available, we tested our hypothesis by using i.v. administered ovine antidigoxin Fab fragments and determined their ability to limit digoxin tissue exposure and toxicity in mice after an i.p. digoxin injection. The rate of digoxin disappearance from the peritoneal cavity and the fraction of digoxin unbound in the peritoneal cavity were also assessed to determine the effect of the antibody fragments on peritoneal exposure. Our results showed that the antidigoxin antibody fragments can greatly decrease digoxin tissue exposure and toxicity without affecting peritoneal exposure, unbound fraction of digoxin in the peritoneum or peritoneal digoxin disappearance rate. Although the utility of drug-binding antibodies and antibody fragments for the treatment of drug intoxication is well known, these results demonstrated the potential ability of antidrug antibody fragments to improve the site-specificity of drug therapy.