Transplanted olfactory ensheathing cells remyelinate and enhance axonal conduction in the demyelinated dorsal columns of the rat spinal cord

Olfactory ensheathing cells (OECs), which have properties of both astrocytes and Schwann cells, can remyelinate axons with a Schwann cell-like pattern of myelin. In this study the pattern and extent of remyelination and the electrophysiological properties of dorsal column axons were characterized after transplantation of OECs into a demyelinated rat spinal cord lesion. Dorsal columns of adult rat spinal cords were demyelinated by x-ray irradiation and focal injections of ethidium bromide. Cell suspensions of acutely dissociated OECs from neonatal rats were injected into the lesion 6 d after x-ray irradiation. At 21-25 d after transplantation of OECs, the spinal cords were maintained in an in vitro recording chamber to study the conduction properties of the axons. The remyelinated axons displayed improved conduction velocity and frequency-response properties, and action potentials were conducted a greater distance into the lesion, suggesting that conduction block was overcome. Quantitative histological analysis revealed remyelinated axons near and remote from the cell injection site, indicating extensive migration of OECs within the lesion. These data support the conclusion that transplantation of neonatal OECs results in quantitatively extensive and functional remyelination of demyelinated dorsal column axons.     

Human metabolism and excretion of cancer chemoprotective glucosinolates and isothiocyanates of cruciferous vegetables

Isothiocyanates and their naturally occurring glucosinolate precursors are widely consumed as part of a diet rich in cruciferous vegetables. When plant cells are damaged, glucosinolates are released and converted to isothiocyanates by the enzyme myrosinase. Many isothiocyanates inhibit the neoplastic effects of various carcinogens at a number of organ sites. Consequently, these agents are attracting attention as potential chemoprotectors against cancer. As a prerequisite to understanding the mechanism of the protective effects of these compounds, which is thought to involve the modulation of carcinogen metabolism by the induction of phase 2 detoxication enzymes and the inhibition of phase 1 carcinogen-activating enzymes, we examined the fate of ingested isothiocyanates and glucosinolates in humans. Recently developed novel methods for quantifying isothiocyanates (and glucosinolates after their quantitative conversion to isothiocyanates by purified myrosinase) and their urinary metabolites (largely dithiocarbamates) have made possible a detailed examination of the fates of isothiocyanates and glucosinolates of dietary crucifers. In a series of studies in normal volunteers, we made these findings. First, in nonsmokers, urinary dithiocarbamates were detected only after the consumption of cruciferous vegetables and condiments rich in isothiocyanates and/or glucosinolates. In sharp contrast, the consumption of noncrucifers (corn, tomatoes, green beans, and carrots) did not lead to the excretion of dithiocarbamates. Moreover, the quantities of dithiocarbamates excreted were related to the glucosinolate/isothiocyanate profiles of the cruciferous vegetables administered (kale, broccoli, green cabbage, and turnip roots). Second, eating prepared horseradish containing graded doses of isothiocyanates (12.3-74 micromol; mostly allyl isothiocyanate) led to a rapid excretion of proportionate amounts (42-44%) of urinary dithiocarbamates with first-order kinetics. The ingestion of broccoli in which myrosinase had been heat-inactivated also led to proportionate but low (10-20%) recoveries of urinary dithiocarbamates. Broccoli samples subsequently treated with myrosinase to produce the cognate isothiocyanates were much more completely (47%) converted to dithiocarbamates. Finally, when bowel microflora were reduced by mechanical cleansing and antibiotics, the conversion of glucosinolates became negligible. These results establish that humans convert substantial amounts of isothiocyanates and glucosinolates to urinary dithiocarbamates that can be easily quantified, thus paving the way for meaningful studies of phase 2 enzyme induction in humans.     

Effects of clonidine in a primed rat model of acute hepatic porphyria

The hypothesis that local release of prostanoids may contribute to the pharmacologic effect of nitroglycerin (NTG) has long been debated. Results of prostanoid blockade by indomethacin on NTG-induced effects, to date, have been inconclusive. To quantitate the effects of intravenous indomethacin on NTG-induced myocardial blood flow by using positron-emission tomography, we conducted a prospective, controlled, parallel-design study comparing patients with coronary artery disease with healthy volunteers. Eight subjects, four Canadian Class II-III coronary artery disease (CAD) with luminal narrowing of > 80% in a minimum of two vessels, and four healthy volunteers were evaluated. Baseline global myocardial blood flow was equivalent between the groups. NTG produced a 49.3 +/- 4.7% increase in myocardial blood flow in healthy volunteers (p = 0.006) and an -0.5 +/- 19.8% decrease in the group with CAD (p = 0.62 between groups). After indomethacin, both groups had a 24% decline in myocardial blood flow (CAD, p = 0.25; healthy, p = 0.03). One patient with CAD had acute ischemia after indomethacin. The study demonstrated that short-term intravenous indomethacin decreases NTG-induced myocardial blood flow to the same degree in both subjects with CAD and healthy individuals. Impairment of myocardial blood flow from this pharmacologic combination may be most important in patients with severe fixed lesions.     

The differentiation of Brucella species by substrate specific tetrazolium reduction

In the development of a tetrazolium reduction assay to replace substrate stimulated oxygen uptake for the identification of Brucella species, nine tetrazolium salts were evaluated. Only the more readily reduced compounds (MTT and INT) detected increased metabolic activity with the more fastidious, slow growing strains and with B. suis strains on L-arginine and DL-ornithine. The assay was optimised with MTT. MTT reduction profiles offered with the medium on which the cells were grown. Cells grown on TSA gave profiles more similar to the published respirometric results than those grown on SDA. The optimal substrate concentration was 0.84 g l-1 and prolonged (> 3 h) exposure to substrate was necessary before adding MTT. MTT concentration was not critical and the OD was proportional to the MTT concentration between 0.03 and > 0.5 g l-1. MTT reduction was linear for 60 min after its addition. The reaction was, therefore, stopped after 60 min by adding formaldehyde solution. The optimised assay was evaluated with 71 strains of Brucella, representing all the species and biovars of the genus. Each strain was assigned to its previously identified species and sub-groups were defined.     

Comparison of the effects of potential parenteral vehicles for poorly water soluble anticancer drugs (organic cosolvents and cyclodextrin solutions) on cultured endothelial cells (HUV-EC)

Left atrial (LA) adaptation during the development of left ventricular (LV) dysfunction is not fully understood. We performed echocardiographic assessment of LA volumes simultaneously with recordings of pulmonary wedge pressures in 60 patients. Twenty patients had no structural or functional LV abnormalities, 20 had a recent myocardial infarction with LV dysfunction, and 20 suffered from congestive heart failure (CHF). Pressure-volume loops were obtained at baseline and during increases in LA pressure produced by normal saline infusion. LA afterload was estimated by the effective LV elastance (E(LV)). Atrioventricular coupling was calculated by the E(LV)/E(es) ratio (where E(es) is the end-systolic elastance). E(es) increased in patients with myocardial infarction (0.80 +/- 0.09 mm Hg/ml, p <0.001), whereas it decreased in patients with CHF (0.22 +/- 0.05 mm Hg/ml, p <0.001) compared with controls (0.61 +/- 0.07 mm Hg/ml). Similarly, stroke workload increased in patients with myocardial infarction (60.7 +/- 7.3 mm Hg x ml, p <0.001), whereas it decreased in patients with CHF (25.4 +/- 2.2 mm Hg x ml, p <0.001) compared with controls (44.8 +/- 5.5 mm Hg x ml). In all patients LA stiffness (slope of the relation of the filling portion of the pressure-volume loop) was increased compared with controls (controls: 0.13 +/- 0.04, patients with myocardial infarction: 0.22 +/- 0.05, and patients with CHF: 0.27 +/- 0.05 mm Hg/ml, p <0.001 for both comparisons). Moreover, the E(LV)/E(es) ratio increased gradually as LV function deteriorated (controls: 1.06 +/- 0.10, patients with myocardial infarction: 1.35 +/- 0.16, and patients with CHF: 6.90 +/- 0.84, p <0.001). Thus, early in heart failure, LA pump function is augmented but LA stiffness increases and work mismatch occurs. With further progression of LV dysfunction, LA pump function decreases as a result of increased afterload imposed on the LA myocardium.     

Heritability of facet-level traits in a cross-cultural twin sample: support for a hierarchical model of personality

The common variance among personality traits can be summarized in the factors of the five-factor model, which are known to be heritable. This study examined heritability of the residual specific variance in facet-level traits from the Revised NEO Personality Inventory. Analyses of raw and residual facet scales across Canadian (183 monozygotic [MZ] and 175 dizogotic [DZ] pairs) and German (435 MZ and 205 DZ pairs) twin samples showed genetic and environmental influences of the same type and magnitude across the 2 samples for most facets. Additive genetic effects accounted for 25% to 65% of the reliable specific variance. Results provide strong support for hierarchical models of personality that posit a large number of narrow traits in addition to a few broader trait factors or domains. Facet-level traits are not simply exemplars of the broad factors they define; they are discrete constructs with their own heritable and thus biological basis.     

Detection of milk antibiotic residues by use of screening tests and liquid chromatography after intramammary administration of amoxicillin or penicillin G in cows with clinical mastitis

OBJECTIVE: To compare results of 6 commercially available milk antimicrobial screening tests with results of liquid chromatography (LC) when testing milk samples from individual cows treated for mild clinical mastitis by intramammary (IMM) infusion with amoxicillin or penicillin G. ANIMALS: 6 cows with noninduced clinical mastitis: 3 treated by IMM infusion with amoxicillin and 3 treated by IMM infusion with penicillin G. PROCEDURE: Composite milk samples were collected before, during, and after treatment. Samples were assayed by use of the screening tests and their results and those of LC were compared. The LC results were assumed to represent the true result. RESULTS: Results of screening tests compared well with results of LC, with agreement of 94%. Positive screening test results for samples containing drug values below the established tolerance or safe level, as evaluated by LC, were obtained from 2 cows in which abnormal milk, as well as marked increases in composite milk somatic cell count, were observed. With the exception of 1 test in 1 cow, all screening tests had negative results at the end of the labeled milk-withholding time. CONCLUSIONS AND CLINICAL IMPLICATIONS: On the basis of results of the limited sample reported, the screening tests appeared to provide good agreement overall, compared with LC results, when testing milk of individual cows treated by IMM infusion with amoxicillin or penicillin G. Positive screening test results for milk samples containing amoxicillin or penicillin G at values below the established tolerance or safe level, as evaluated by LC, may occasionally be obtained.     

Copper-catalyzed oxidation mediates PAF formation in human LDL subspecies. Protective role of PAF:acetylhydrolase in dense LDL

Free radical-mediated oxidation of cholesterol-rich LDL plays a key role in atherogenesis and involves the formation of oxidized phospholipids with proinflammatory biological activity. We evaluated the production of platelet-activating factor (PAF), a potent inflammatory mediator, in human LDL subspecies on copper-initiated oxidation (4 mumol/L CuCl2, 80 micrograms/mL for hours at 37 degrees C). PAF formation was determined by biological assay of HPLC-purified lipid extracts of copper-oxidized lipoproteins; chemical identity was confirmed by gas chromatographic and mass spectrometric analyses. PAF, characterized as the C16:0 molecular species, was preferentially produced in intermediate LDL (d = 1.029 to 1.039 g/mL) (8.6 +/- 5.7 pmol PAF/3 h per mg LDL protein) and light LDL (d = 1.019 to 1.029 g/mL), but was absent from dense LDL particles (d = 1.050 to 1.063 g/mL). As PAF:acetylhydrolase inactivates PAF and oxidized forms of phosphatidylcholine, we evaluated the relationship of lipoprotein-associated PAF:acetylhydrolase to PAF formation. We confirmed that PAF:acetylhydrolase activity was elevated in native, dense LDL (41.5 +/- 9.5 nmol/min per mg protein) but low in LDL subspecies of light and intermediate density (d 1.020 to 1.039 g/mL) (3.5 +/- 1.6 nmol/min per mg protein) [Tselepis et al, Arterioscler Thromb Vasc Biol. 1995;15:1764-1773]. On copper-mediated oxidation for 3 hours at 37 degrees C, dense LDL particles conserved 20 +/- 14% of their initial enzymatic activity; in contrast, PAF:acetylhydrolase activity was abolished in light and intermediate LDL subspecies. Clearly, the elevated PAF:acetylhydrolase activity of dense LDL efficiently diminishes the potential inflammatory role of endogenously formed PAF; nonetheless, formation of proatherogenic lysophospholipids results. In contrast, LDL particles of the light and intermediate subclasses can accumulate PAF on oxidative modification.     

Endoscopic variceal ligation in prophylaxis of first variceal bleeding in cirrhotic patients with high-risk esophageal varices

To determine the efficacy of endoscopic variceal ligation (EVL) in prophylaxis on the rate of first esophageal variceal bleeding, we conducted a prospective, randomized trial in 126 cirrhotic patients with no history of previous upper gastrointestinal bleeding and with esophageal varices endoscopically judged to be at high risk of hemorrhage. The end-points of the study were bleeding and death. Life-table curves showed that prophylactic EVL significantly diminished the rate of variceal hemorrhage (12/62 [19%] vs. 38/64 [60%]; P = .0001) and overall mortality (17/62 [28%] vs. 37/64 [58%]; P = .0011). The 2-year cumulative bleeding rate was 19% (12/ 62) in the EVL group and 60% (38/64) in the control group. The 2-year cumulative mortality rate was 28% (17/62) in the EVL group and 58% (37/64) in the control group. Comparison of Kaplan-Meier estimates of the time to death of both groups showed significantly lower mortality in the ligation group (P = .001). Patients undergoing EVL had few treatment failures and died mainly of hepatic failure. The lower risk in the EVL group was attributed to a rapid reduction of variceal size. Prophylactic EVL was more efficient in preventing first bleeding in patients with good condition (Child A) than in those with decompensated disease (Child B and C). We conclude that prophylactic EVL can decrease the incidence of first variceal bleeding and death over a period of 2 years in cirrhotic patients with high-risk esophageal varices.