Inhibition of vascular endothelial growth factor prevents retinal ischemia-associated iris neovascularization in a nonhuman primate

The antiestrogenic drug tamoxifen induces liver tumors in rats by a genotoxic mechanism. The key step has been proposed to be the formation of a reactive carbocation from the metabolite alpha-hydroxytamoxifen. This compound reacts with DNA in vitro to a small extent (1 in 10(5) DNA bases), giving products identical to those found in rat liver cells treated with tamoxifen. Now we have prepared the more reactive alpha-acetoxytamoxifen, which reacts with DNA in vitro to a much greater extent (1 in 50 bases). The products of this reaction were subjected to 32P postlabeling and shown by both TLC and reverse-phase liquid chromatography to be identical to those isolated from DNA treated with alpha-hydroxytamoxifen and to those found in the liver DNA of rat hepatocytes treated with tamoxifen or of the livers of rats treated with tamoxifen. The major product was also isolated as the nucleoside and characterized by UV, mass, and proton magnetic resonance spectroscopy. It is an adduct of tamoxifen and deoxyguanosine in which the alpha position of tamoxifen is linked covalently to the exocyclic amino group of deoxyguanosine.     

Comparative study of chronic aluminum-induced neurofilamentous aggregates with intracytoplasmic inclusions of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is characterized neuropathologically by chromatolysis, Bunina bodies, hyaline inclusions, skein-like inclusions and axonal spheroids. Aluminum, a known neurotoxin, is the cause of dialysis encephalopathy and is considered to be a causative agent in high incidence foci of ALS in the western Pacific. We have developed an experimental model of motor neuron degeneration in New Zealand white rabbits using chronic low-dose intracisternal administration of aluminum and compared the clinical and neuropathological changes to those of human ALS. Aluminum-inoculated rabbits developed progressive hyperreflexia, hypertonia, limb splaying, gait impairment, muscle wasting, hindlimb paralysis and impaired tonic immobility responses without overt encephalopathic features over a 14-month period. Examination of spinal cords from these animals demonstrated the frequent occurrence and progressive development of anterior horn cell lesions that included small, round, argentophilic perikaryal inclusions similar to hyaline inclusions seen in human ALS. Other inclusions were more condensed and eosinophilic, while still others had neurofibrillary tangle-like morphologies. Axonal spheroids and neuritic thickenings were also prominent and were identical to those seen in human ALS. We believe that the similar and progressive development of neuropathological changes observed in the chronic aluminum-intoxication model, compared to human ALS, warrants further study to aid in understanding the cellular and molecular mechanisms of human motor neuron disease.     

Characterization of the rpoB gene mutations in clinical isolates of rifampicin-resistant Mycobacterium tuberculosis

OBJECTIVES: Characterization and frequency of the rpoB gene mutations associated with rifampin resistance in Mycobacterium tuberculosis clinical isolates in Sevilla. METHODS: Characterization of rpoB mutations in 21 rifampicin-resistant strains of M. tuberculosis isolated during a three-year period (1994-1996) by three different molecular methods: a nonradioactive Single-strand conformation polymorphism (SSCP) analysis, DNA sequence analysis and a commercial method the line probe assay InnoLiPA. RESULTS: Five distinct rpoB mutations were identified. Ser531-->Leu mutation was detected in 14 strains (66.7%), H526-->Asp in 3 strains (14.3%), Ans512-->Ser in 1 strain (4.8%), Glu513-->Leu in 1 strain (4.8%). A nine nucleotide deletion (codon 510-513) was found in one strain (4.8%) while in the remaining resistant strain (4.8%) no mutation was detected. CONCLUSIONS: The frequency of the different mutations found in the rpoB gene, associated with rifampicin resistance in Mycobacterium tuberculosis clinical isolates in Seville, are similar to those previously reported. However, two new mutations has been detected: a nine nucleotide deletion (codon 510-513), and the Asn512-->Ser point mutation. The characterization of the mutations in the rpoB gene could serve as epidemiological marker for the rifampicin resistant clinical isolates of M. tuberculosis.     

Dietary supplementation with carotenoids: effects on alpha-tocopherol levels and susceptibility of tissues to oxidative stress

The ability of dietary supplementation with carotenoids to protect chick tissues against oxidative stress in vitro was examined. Male Leghorn chicks were fed on diets supplemented (100 mg supplement/kg diet) with either beta-carotene, zeaxanthin (beta,beta-carotene-3,3'-diol), canthaxanthin (beta,beta-carotene-4,4'-dione) or alpha-tocopherol, or on a control diet, from 1 d old until 37 d of age. Tissues (liver, heart, skeletal muscle and plasma) were removed and assayed for total carotenoids and alpha-tocopherol content and portions subjected to oxidative stress by incubation of homogenates with cumene hydroperoxide and FeSo4. Animals receiving zeaxanthin and canthaxanthin had significantly greater carotenoid concentrations in liver, heart, muscle and plasma compared with untreated controls (P < 0.05); animals fed on diets supplemented with beta-carotene, or alpha-tocopherol did not have significantly different tissue carotenoid contents compared with untreated controls. alpha-Tocopherol supplementation elevated alpha-tocopherol levels in all tissues examined (P < 0.05). Supplementation with carotenoids did not affect tissue alpha-tocopherol levels, but beta-carotene lowered plasma alpha-tocopherol levels by 50% (P < 0.05). Incubation of plasma or tissue homogenates with oxidant stressors induced lipid peroxidation (production of thiobarbituric-acid reactive substances) in all tissues. Animals given alpha-tocopherol, beta-carotene or zeaxanthin had a reduced susceptibility to oxidant stress in liver compared with unsupplemented controls (P < 0.05), and alpha-tocopherol-supplemented animals had reduced susceptibility in skeletal muscle compared with tocopherol-supplemented animals had reduced susceptibility in skeletal muscle compared with unsupplemented controls (P < 0.05). Canthaxanthin supplementation did not influence the susceptibility to oxidant stress in any tissue examined. These results suggest that zeaxanthin, a carotenoid present in animal and human diets, may have significant activity as an antioxidant against oxidative stress in tissues.     

Medicine taking in Southampton: a second look

1. A 1 in 200 sample of the Southampton electorate were sent a postal questionnaire in January 1993. Of the 756 adults surveyed, 400 (52.9%) returned completed questionnaires. One hundred and eighty-eight (47.0%) of the respondents had been prescribed a medicine within the previous month. 2. Compared with a survey 9 years earlier, medicine taking had increased amongst men (44.1% vs 33.7% NS) and drugs acting on the respiratory system were in more widespread use (19 vs 7 patients P < 0.05). 3. Patterns of storage of medicines were almost identical to those found in 1984. However, methods of disposal were significantly different with 34% of the respondents stating that they would return left-over medicines to the Doctor or Pharmacist compared with 17% in the previous study (P < 0.01). 4. Of those taking medicines 120 (63.8%) had received a manufacturers' information leaflet. Medicines used to treat disorders of the respiratory and cardiovascular systems were most likely to be accompanied by such a leaflet (74% and 70% respectively). 5. Those who received a leaflet were almost all satisfied by it. However, patient awareness of potential side effects remained poor with only 30% being aware of any which their medicine might cause. 6. Despite improvements in attitudes towards medicine taking over time patients awareness of potential adverse effects remains limited. Further research is necessary in order to determine how best to educate patients on this topic.     

Compensating customer-generators: a taxonomy describing methods of compensating customer-generators for electricity supplied to the grid

The increasing popularity of on-site power generation is driving the demand for methods to compensate customer-generators that supply electricity to the grid. Although many practices exist for providing such compensation, confusion surrounds the terms often used to describe such practices (notably, net metering and net billing). To help clarify this situation, the following paper proposes a taxonomy that distinguishes between 16 distinct compensation practices.     

Drug and environmental factors associated with adverse pregnancy outcomes. Part III: Folic acid: pharmacology, therapeutic recommendations, and economics

OBJECTIVE: To review folic acid's mechanism of action, adverse effects, therapeutic recommendations, compliance, and cost. DATA SOURCES: A MEDLINE search was conducted through December 1997. Additional sources were obtained from Current Contents and citations from the references obtained. Search terms included folate, folic acid, neural tube defect, homocysteine, and methylenetetrahydrofolate reductase. STUDY SELECTION: Animal and human studies examining the effects of folate were reviewed. DATA EXTRACTION: Data collected included mechanism of action, safety issues, dosing recommendations, compliance with recommendations, and economics. DATA SYNTHESIS: Folic acid decreases neural tube defect risk through an effect on methionine-homocysteine metabolism. In addition, increased folate intake may reduce cardiovascular morbidity and mortality. Since toxicity is minimal, everyone can potentially benefit from increased folate consumption. To help achieve this, the Food and Drug Administration has mandated that cereal grain be fortified with 140 micrograms of folic acid per 100 g of grain, which will add approximately 0.1 mg of folate to the average diet. Studies recommend supplementing with 0.2 mg to promote optimal homocysteine concentrations and for preventing neural tube defects. CONCLUSIONS: Despite fortification, most women will still receive less folate than the 0.4 mg/d recommended by the Public Health Service. All population groups would benefit from increased folate intake. Current studies indicate 200 micrograms/d may be the minimum effective amount of fortification needed for normalizing homocysteine concentrations and preventing a significant number of neural tube defects; thus, a higher level of food fortification may be warranted.     

Admission to hospitals with on-site cardiac catheterization facilities :impact on long-term costs and outcomes

BACKGROUND: Admission to a hospital with a capability for cardiac procedures is associated with a higher likelihood of referral for a cardiac procedure but not with a better short-term clinical outcome. Whether there are differences in long-term mortality and resource consumption is not clear. We sought to determine whether elderly Medicare patients with acute myocardial infarction admitted to hospitals with on-site cardiac catheterization facilities have lower long-term hospital costs and better outcomes than patients admitted to hospitals without such facilities. METHODS AND RESULTS: As part of the Cooperative Cardiovascular Project pilot in Connecticut, we conducted a retrospective cohort study using data from medical charts and administrative files. The study sample included 2521 patients with acute myocardial infarction covered by Medicare from 1992 to 1993. The cardiac catheterization rate was higher in the hospitals with facilities (38.6% versus 26.9%; P<0.001), but the revascularization rate was similar (20.5% versus 19.5%) during the initial episode of care and at 3 years (29.7% versus 29.7%). Mortality rates were similar for patients admitted to the 2 types of hospitals at 30 days (OR, 1.08; 95% CI, 0.83 to 1.42) and at 3 years (OR, 1.02; 95% CI, 0.83 to 1.26). The adjusted readmission rates were significantly lower among patients admitted to hospitals with cardiac catheterization facilities (OR, 0.76; 95% CI, 0.61 to 0.94). However, the overall mean days in the hospital for the 3 years after admission was 25.9 for patients admitted to hospitals with facilities and 24.6 for the other patients (P=0.234). Adjusting for baseline patient characteristics, there was no significant difference in the 3-year costs between patients admitted to the 2 types of hospitals. CONCLUSIONS: With higher rates of cardiac catheterization and lower readmission rates, patients admitted to hospitals with on-site cardiac catheterization facilities did not have significantly different hospital costs compared with patients admitted to hospitals without these facilities. There was also no significant difference in short- or long-term mortality rates.