Future direction of nanomedicine in gastrointestinal cancer]

Cancer is one of the leading causes of death in human, and among various cancers, gastrointestinal cancers occupy more than 55%. Gastric cancer is the first leading cause of cancer-related mortality in the world and the number of pancreas and colon cancers are increasing remarkably during last two decades which will continue to increase in the future. Even though the clinical importance of gastrointestinal cancers is very high and endless efforts has been made to develop novel diagnostic and therapeutic methods to improve the patient's quality of life and survival, the realistic advance in the actual survival benefit of the cancer patients are still strongly required. Nanotechnology has the power to radically change the way of cancer diagnosis and treatment. Currently, there is a lot of researches on novel nanodevices capable of detecting cancer at its earliest stage, pinpointing its location within the body, and delivering anticancer drugs specifically to the malignant cells. Nanoscale devices can readily interact with biomolecules both on the cell surface and within the cell. In addition, nanoscale devices are already proven that they can deliver therapeutic agents to target cells even within specific organelles. Major areas in which nanomedicine is being developed in cancer include early detection and proteomics, imaging diagnostics and multifunctional therapeutics. Because nanotechnology would provide a technical power and tool that enable new diagnostics, therapeutics, and preventives to keep pace with today's explosion in knowledge in the future, it would be very useful to know the perspectives in the direction of nanotechnology as a major clinician responsible for the patients with gastrointestinal malignancies.     

Particle size and morphology of UHMWPE wear debris in failed total knee arthroplasties--a comparison between mobile bearing and fixed bearing knees.

Osteolysis induced by ultrahigh molecular weight polyethylene wear debris has been recognized as the major cause of long-term failure in total joint arthroplasties. In a previous study, the prevalence of intraoperatively identified osteolysis during primary revision surgery was much higher in mobile bearing knee replacements (47%) than in fixed bearing knee replacements (13%). We postulated that mobile bearing knee implants tend to produce smaller sized particles. In our current study, we compared the particle size and morphology of polyethylene wear debris between failed mobile bearing and fixed bearing knees. Tissue specimens from interfacial and lytic regions were extracted during revision surgery of 10 mobile bearing knees (all of the low contact stress (LCS) design) and 17 fixed bearing knees (10 of the porous-coated anatomic (PCA) and 7 of the Miller/Galante design). Polyethylene particles were isolated from the tissue specimens and examined using both scanning electron microscopy and light-scattering analyses. The LCS mobile bearing knees produced smaller particulate debris (mean equivalent spherical diameter: 0.58 microm in LCS, 1.17 microm in PCA and 5.23 microm in M/G) and more granular debris (mean value: 93% in LCS, 77% in PCA and 15% in M/G).     

Effect of a low-protein diet on doxorubicin pharmacokinetics in the rabbit

Summary Malnutrition involving protein deficiency, which commonly occurs in cancer patients receiving anthracycline treatment, is considered to be a risk factor for the development of cardiotoxicity. Protein deficiency has been shown to impair the metabolism of drugs such as theophylline and acetaminophen. If protein deficiency also impairs anthracycline metabolism, it could explain at least in part the enchanced anthracycline toxicity associated with malnutrition. We tested this idea by determining the effect of a low- protein, isocaloric diet on doxorubicin pharmacokinetics in rabbits. The animals were randomized into two groups for 8–12 weeks. Rabbits in group 1 received a low-protein (5%), isocaloric diet, whereas those in group 2 received a normal-protein (15%) diet. Both groups (group 1,n=15; group 2,n=14) were given 5 mg/kg doxorubicin by i.v. bolus. After doxorubicin injection, blood samples were obtained over the next 52 h for the measurement of doxorubicin and doxorubicinol plasma concentrations by high-performance liquid chromatography (HPLC) with fluorometric detection. The low-protein diet significantly decreased doxorubicin clearance (48±3 vs 59±4 ml min^–1 kg^–1;P<0.05), prolonged the terminal climination half-life (28±2 vs 22±2 h;P<0.05), and increased the area under the plasma concentration/time curve extrapolated to infinity (1722±122 vs 1405±71 ng h ml^–1;P<0.05) as compared with the values determined for rabbits fed the standard rabbit chow (15% protein). The volume of distribution for doxorubicin was not altered by the low-protein diet. In addition, in rabbits fed the the low-portein diet, the terminal elimination half-life of the alcohol metabolite, doxorubicinol was prolonged (52±5 vs 40±2 h;P<0.05). Thus, a low-protein diet causes a reduction in the ability of rabbits to eliminate doxorubicin and possibly its alcohol metabolite doxorubicinol. If a similar alteration in anthracycline pharmacokinetics occurs in malnourished cancer patients, this phenomenon may contribute to their increased risk of developing cardiotoxicity associated with anthracycline therapy.Supported by the Department of Veterans Affairs and the American Heart Foundation     

Fatty acid profiles in response to soybean oil lipid emulsion infusions in essential fatty acid-deficient miniature swine

The ability of soybean oil lipid emulsions to affect essential fatty acid deficiency (EFAD) and plasma fatty acid distribution was studied in neonatal pigs. The test animals were maintained on a fat-free diet prior to administration of lipid emulsion. Plasma and red blood cell (RBC) membrane levels of essential [linoleic (C-18:2 omega 6) and arachidonic (C-20:4 omega 6)] and nonessential [palmitic (C-16, palmitoleic (C-16:1 omega 7), stearic (C-18), and oleic (C-18:1 omega 9)] fatty acids and the triene:tetraene ratio [5,8,11-eicosatrienoic acid (C-20:3 omega 9):arachidonic acid (C-20:4 omega 6)] were monitored to ascertain the establishment of EFAD and its correction. Nonessential fatty acids were studied, as these components of lipid therapy have received little attention. Results indicate that soybean oil emulsions are effective in reversing fatty acid profiles found in EFAD, and both essential and nonessential fatty acids are under strict metabolic control.     

Comparison of the blood-brain barrier and liver penetration of acridine antitumor drugs

Summary The blood-brain barrier penetration of amsacrine and its analogs 9-({2-methoxy-4-[(methylsulfonyl)-amino]phenyl}amino)-,5-dimethyl-4-acridine carboxamide (CI-921) and M-[2-(dimethylamino)ethyl]-acridine-4-carboxamide (AC) was measured in the barbiturate-anesthetized mouse. After intracarotid administration, AC was almost completery extracted (90%) in a single transit through the brain capillaries, whereas CI-921 (20%) and amsacrine (15%) were moderately extracted. AC is retained in the brain; no loss of AC from the brain was apparent at 1, 2, 4, or 8 min after injection. In contrast, after intraportal administration, 75% of the AC, 94% of the CI-921, and 57% of the amsacrine was extracted in a single transit through the hepatic vasculature. Rather than being retained in the mouse liver, these acridine antitumor agents show time-dependent loss (t _1/2=10 min for amsacrine and AC, 24 min for CI-921). We conclude that unlike most antitumor agents, these acridine drugs appear to penetrate the blood-brain barrier readily.This study was supported by the Auckland Medical Research Foundation (New Zealand), by the Medical Research Foundation (New Zealand), by the National Science Foundation (United States/New Zealand Cooperative Science Program), by the United States Veterans Administration, and by NIH grant NS 25554     

Gastric cancer mortality and nitrate levels in Wisconsin drinking water.

The association between nitrate levels in public and private sources of drinking water and gastric cancer mortality in Wisconsin was investigated in a case-control study. All gastric cancer deaths of Wisconsin residents from 1982 through 1985 were compared with deaths from other causes (controls), and nitrate levels in the home drinking water of these residents were determined. Nitrate measures for public sources were obtained from historic nitrate data from municipal sources that existed in 1970. Nitrate measures for private water sources were obtained by testing the wells individually at the existing residences. Controls were matched individually to gastric cancer cases with respect to sex, year of birth, year of death, Wisconsin birth, and Wisconsin residency at the time of death. Matched-pair analyses were performed on the paired data, and the following levels of nitrate-nitrogen exposure were used as indicators of exposure: 0.5, 2.5, 5.0, and 10.0 mg/l. Matched-pair analysis was also performed for which private water supply constituted exposure. Odds ratios and 95% confidence intervals were, respectively, 0.92 (0.75, 1.12); 0.97 (0.74, 1.35); 0.86 (0.69, 1.08); 1.50 (0.12, 18.25); and 1.09 (0.82, 1.47) for exposure to private well-water sources. These results did not indicate an increased risk of gastric cancer at any level.     

Suppression of presynaptic calcium currents by hypoxia in hippocampal tissue slices.

We tested the hypothesis that suppression of inward calcium current in presynaptic terminals is the cause of failure of synaptic transmission early during cerebral hypoxia. Postsynaptic responses in CA1 zone of hippocampal tissue slices were blocked either by the combined administration of 6,7-dinitroquinoxaline-2,3-dione (DNQX) and 3-((+-)-2-carboxypiperazine-4-yl)-propyl-1-phosphonic acid (CPP) or by lowering extracellular calcium concentration ([Ca2+]o). Repetitive orthodromic activation of central neurons caused transient decrease of [Ca2+]o (measured by ion selective microelectrodes) in neuropil, attributable to influx of Ca2+ in presynaptic terminals. Presynaptic [Ca2+]o responses were rapidly and reversibly suppressed when oxygen was withdrawn from hippocampal tissue slices. The 'resting' baseline level of [Ca2+]o declined at first gradually, then precipitously as in spreading depression (SD). Presynaptic volleys during high frequency train stimulation were also depressed somewhat before SD began. We conclude that (1) presynaptic Ca2+ currents fail during hypoxia, perhaps because 'resting' intracellular free Ca2+ activity is increased and, in part, also because of partial failure of presynaptic impulse conduction; (2) the influx of Ca2+ into brain cells in hypoxic spreading depression is not mediated by glutamate/aspartate dependent channels.