Antibodies as carrier proteins

Pre-existing antibodies against a drug substance can significantly alter the pharmacokinetic profile of the drug in the circulation. Rapid clearance, mediated by complement or Fc receptors, occurs for crosslinked immune complexes, but not for complexes containing only one or two antibodies. With antibodies functioning as carrier proteins, monovalent antigens may enjoy a prolonged circulatory half-life, as observed in the case of digoxin, insulin, and various interleukins. While such an effect should be highly sensitive to fluctuations in antibody affinity and titer, it may present a means of extending the circulation of potent but rapidly cleared therapeutic agents. This mini-review attempts to delineate the causal relation between the factors influencing antibody binding and the circulatory life of a therapeutic agent, be it a small drug or a macromolecule.     

Adaptation to hyperglycemia enhances insulin secretion in glucokinase mutant mice

The present study was undertaken to test the hypothesis that exposure to high glucose concentrations enhances insulin secretion in pancreatic islets from glucokinase-deficient mice. Insulin secretion and intracellular calcium ([Ca2+]i) were measured as the glucose concentration was increased from 2 to 26 mmol/l in islets from heterozygous glucokinase (GK)-deficient mice (GK+/-) and their wild-type littermates (GK+/+). Results obtained in islets incubated in 11.6 or 30 mmol/l glucose for 48-96 h were compared. GK+/- islets that had been incubated in 30 mmol/l glucose showed improved although not normal insulin secretory and [Ca2+]i responses to the standard glucose challenge as well as an enhanced ability to sense small amplitude glucose oscillations. These effects were associated with increased glucokinase activity and protein. In contrast, exposure of GK+/+ islets to 30 mmol/l glucose increased their basal insulin secretion but reduced their incremental secretory responses to glucose and their ability to detect small amplitude glucose oscillations. Thus exposure of GK+/- islets to 30 mmol/l glucose for 48-96 h enhanced their ability to sense and respond to a glucose stimulus, whereas similar exposure of GK+/+ islets induced evidence of beta-cell dysfunction. These findings provide a mechanistic framework for understanding why glucokinase diabetes results in mild hyperglycemia that tends not to increase over time. In addition, the absence of one allele of the glucokinase gene appears to protect against glucose-induced beta-cell dysfunction (glucose toxicity).     

Granulocyte-macrophage colony-stimulating factor in patients with neutropenic fever is potent after low-risk but not after high-risk neutropenic chemotherapy regimens: results of a randomized phase III trial

PURPOSE: A randomized unblinded phase III trial was designed to determine the ability of granulocyte-macrophage colony-stimulating factor (GM-CSF) to accelerate recovery from febrile neutropenia induced by chemotherapy. PATIENTS AND METHODS: A total of 68 patients with febrile neutropenia following chemotherapy defined as axillary temperature greater than 38 degrees C and absolute neutrophil count (ANC) less than 1 x 10(9)/L were included. After stratification for high- and low-risk chemotherapy to induce febrile neutropenia, treatment was randomized between GM-CSF at 5 microg/kg/d or control, both being associated with antibiotics. RESULTS: GM-CSF significantly reduced the median duration of neutropenia from 6 to 3 days for ANC less than 1 x 10(9)/L(P < .001) and from 4 to 3 days for ANC less than 0.5 x 10(9)/L (P=.024), days of hospitalization required for febrile neutropenia, and duration of antibiotics during hospitalization. The greatest benefit with GM-CSF appeared for patients who had received low-risk chemotherapy, for which the median duration of ANC less than 1 x 10(9)/L was reduced from 7 to 2.5 days (P < .001) and from 4 to 2 days for ANC less than 0.5 x 10(9)/L (P=.0011), the duration of hospitalization during the study from 7 to 4 days (P=.003), and the duration on antibiotics during hospitalization from 7 to 3.5 days (P < .001). A multivariate analysis, using Cox regression, showed that variables predictive for recovery from neutropenia were GM-CSF (P=.0010) and time interval between the first day of chemotherapy and randomization (P=.030). There was no benefit for GM-CSF when high-risk chemotherapy was considered. CONCLUSION: GM-CSF significantly shortened duration of neutropenia, duration of neutropenic fever-related hospitalization, and duration on antibiotics during hospitalization when febrile neutropenia occurred after low-risk chemotherapy, but not high-risk chemotherapy.     

Use of polymerase chain reaction in clinical diagnostic laboratories in viral hepatitis B and C]

alpha 1-Antitrypsin deficiency has been associated with a variety of vascular disorders including arterial aneurysms, spontaneous extracranial arterial dissections, and arterial fibromuscular dysplasia. We determined the distribution of alpha 1-antitrypsin phenotypes in patients with intracranial arterial dissections, a rare cause of subarachnoid hemorrhage. The study population consisted of 4 consecutive patients with subarachnoid hemorrhage due to spontaneous intracranial arterial dissections. The vertebral artery was involved in 3 patients and the posterior inferior cerebellar artery in 1 patient. Three of these 4 patients were found to have a heterozygous alpha 1-antitrypsin deficiency (PiMZ or PiMS phenotypes). These data support previous studies suggesting that patients with alpha 1-antitrypsin deficiency may be at an increased risk of developing spontaneous arterial dissections.     

What do animal cancer tests tell us about human cancer risk?: Overview of analyses of the carcinogenic potency database

Many important issues in carcinogenesis can be addressed using our Carcinogenic Potency Database, which analyzes and standardizes the literature of chronic carcinogenicity tests in laboratory animals. This review is an update and overview of our analyses during the past 15 years, using the current database that includes results of 5152 experiments on 1298 chemicals. We address the following: 1. More than half the 1298 chemicals tested in long-term experiments have been evaluated as carcinogens. We describe this positivity rate for several subsets of the data (including naturally occurring and synthetic chemicals), and we hypothesize and important role in the interpretation of results for increased cell division due to administration of high doses. 2. Methodological issues in the interpretation of animal cancer tests: constraints on the estimation of carcinogenic potency and validity problems associated with using the limited data from bioassays to estimate human risk, reproducibility of results in carcinogenesis bioassays, comparison of lifetable and summary methods of analysis, and summarizing carcinogenic potency when multiple experiments on a chemical are positive. 3. Positivity is compared in bioassays for two closely related species, rats and mice, tested under similar experimental conditions. We assess what information such a comparison can provide about interspecies extrapolation. 4. Rodent carcinogens induce tumors in 35 different target organs. We describe the frequency of chemicals that induce tumors in rats or mice at each target site, and we compare target sites of mutagenic and nonmutagenic rodent carcinogens. 5. A broad perspective on evaluation of possible cancer hazards from rodent carcinogens is given, by ranking 74 human exposures (natural and synthetic) on the HERP indes.     

Melatonin and exposure to constant light/darkness affects ovarian follicular kinetics and estrous cycle in Indian desert gerbil Meriones hurrianae

Health care providers are becoming increasingly involved with the development of clinical pathways as they take on more of the responsibilities of quality management and resource use. Although clinical pathways that are developed at the national, regional, or specialty organization level provide a framework for reference, locally developed pathways tailor care to patients who are served within an agency or community. As multidisciplinary teams develop pathways for patients with back and spine disorders, they create tangible definitions of quality. Variance tracking systems used in conjunction with pathways provide feedback on patient progress and outcomes. These guidelines have significant potential for the future.     

Cardiopulmonary function at rest and during exercise after resection for bronchial carcinoma

BACKGROUND: Measurements of postoperative spirometric values after pneumonectomy and lobectomy vary considerably, and few researchers have studied the changes in exercise capacity during maximal work after lung resection. The purpose of this study was to describe the postoperative alterations in cardiopulmonary function. METHODS: Ninety-seven consecutive patients with lung malignancy were prospectively examined with maximal exercise test, spirometry, and arterial gas tensions. Fifty-seven patients were reinvestigated 6 months postoperatively. RESULTS: In patients having lobectomy, forced expiratory volume in 1 second decreased 8%, and exercise capacity, expressed by maximal oxygen uptake and maximal work rate, significantly decreased 13%. In patients having pneumonectomy forced expiratory volume in 1 second significantly decreased 23%, but the loss in lung volume was partly compensated as measured by exercise capacity, which decreased only 16%. Generally patients with the smallest preoperative forced vital capacity had the smallest postoperative deterioration expressed in percentages. We found a weak correlation between alterations in maximal oxygen uptake and lung function after resection. CONCLUSIONS: Lobectomy is associated with only minor deterioration of lung function and exercise capacity. Pneumonectomy causes a decrease in pulmonary volumes to about 75% of the preoperative values, partly compensated in better oxygen uptake, which postoperatively was about 85% of the preoperative values. Alteration in forced expiratory volume in 1 second is a poor predictor of change in exercise capacity after pulmonary resection.