Performance of the single intradermal comparative tuberculin test in identifying cattle with tuberculous lesions in Irish herds

The sensitivity of the single intradermal comparative tuberculin test, as applied in the Republic of Ireland, was estimated in 353 cattle with tuberculous lesions. These cattle had been removed from 47 herds which were depopulated owing to chronic or extensive infection with Mycobacterium bovis. The test had a sensitivity of 90.9 per cent, because 321 (90.9 per cent) of the 353 cattle with tuberculous lesions gave a positive or inconclusive result, and 32 gave a negative result. These 32 negative cattle came from 17 (36 per cent) of the 47 depopulated herds.     

MRI demonstration of impairment of the blood-CSF barrier by glucose administration to the thiamin-deficient rat brain

Contrast-enhanced T1-weighted spin-echo magnetic resonance imaging (MRI) has demonstrated that Gd-diethylenetriaminepentaacetate (Gd-DTPA), which normally does not cross the blood-brain or blood-CSF barriers, does so approximately 40 min after administration of glucose to a vitamin B1 deficient rat. The period of the onset of this blood-CSF or blood-brain barrier dysfunction coincides with our previous observations of accumulation of glutamate or glutamate derivatives following an equivalent glucose load under identical conditions of thiamin deficiency, consistent with a relationship between these two observations. The dysfunction was reversed when a thiamin deficient animal was made thiamin replete.     

Sterol utilization and metabolism by Heliothis zea

Heliothis zea (corn earworm), an insect that fails to synthesize sterols de novo, was reared on an artificial diet treated with 18 different sterol supplements. Larvea did not develop on a sterol-less medium. Δ⁵-Sterols with a hydrogen atom, a methylene group, an E-or Z-ethylidene group, or an α- or β-ethyl group (cholesterol, ostreasterol, isofucosterol, fucosterol, sitosterol, and clionasterol, respectively) at position C-24, and Δ⁵-sterols doubly substituted in the side chain at C-24 with an α-ethyl group and at C-22 with a double bond (stigmasterol) supported normal larval growth to late-sixth instar (prepupal: maturity). The major sterol isolated from each of these sterol treatments was cholesterol, suggesting that H. zea operates a typical 24-dealkylation pathway. The sterol requirement of H. zea could not be met satisfactorily by derivatives of 3β-cholestanol with a 9β, 19-cyclopropyl group, gem dimethyl group at C-4, a Δ^5,7-bond or Δ⁸-bond, or by side-chain modified sterols that possessed a Δ²⁵⁽²⁷⁾-24β-ethyl group, Δ²³⁽²⁴⁾-24-methyl group, or 24-ethyl group, or Δ²⁴⁽²⁵⁾-24-methyl or 24-ethyl group. The major sterol recovered from the larvae (albeit developmentally arrested larvae) treated with a nonutilizable sterol was the test compound. Sterol absorption was related to the degree of sterol utilization. The most effective sterols absorbed by the insect ranged from 27 to 66 μg per insect, whereas the least effective sterols absorbed by the insect ranged from 0.6 to 6 μg per insect. Competition experiments using different proportions of cholesterol and 24-dihydrolanosterol (from 9:1 to 1:9 mixtures) indicated that abnormal development of H. zea may be induced on less than a 1 to 1 mixture of utilizable (cholesterol) to nonutilizable (24-dihydrolanosterol) sterols. The results demonstrate new structural requirements for sterol utilization and metabolism by insects, particularly with respect to the position of double bonds in the side chain and functionalization in the nucleus. The novel sterol specificities observed in this study appear to be associated with the dual role of sterols as membrane inserts (nonmetabolic) and as precursors to the ecdysteroids (metabolic).     

Restriction endonuclease profiles of orf virus isolates from the British Isles

A comparison of DNA profiles of representative isolates of orf virus, obtained using four different restriction endonucleases (RE), showed that the enzyme EcoRI could be used to discriminate between wild-type virus isolates and vaccine strains. The enzyme was used to compare the RE profiles of orf virus isolates from 43 outbreaks of orf that occurred in vaccinated flocks between 1988 and 1993; 21 outbreaks yielded wild-type virus, 10 yielded vaccine viruses, three produced both vaccine and wild-type viruses and no clear result was obtained from nine of the outbreaks. From the 21 outbreaks yielding wild-type viruses, 28 orf virus isolates had clear RE profiles and 15 distinct RE profiles were recorded. Usually only one virus type was associated with each outbreak but from two farms, two different wild-type viruses were recovered. No predominant genotype was identified, with four RE profile types being recovered for more than one outbreak. From the more severe form of orf involving the buccal cavities of lambs only wild-type viruses were recovered, with at least four different genotypes being represented.     

Three-dimensional solution structure of alpha-conotoxin MII by NMR spectroscopy: effects of solution environment on helicity

alpha-Conotoxin MII, a 16-residue polypeptide from the venom of the piscivorous cone snail Conus magus, is a potent and highly specific blocker of mammalian neuronal nicotinic acetylcholine receptors composed of alpha3 beta2 subunits. The role of this receptor type in the modulation of neurotransmitter release and its relevance to the problems of addiction and psychosis emphasize the importance of a structural understanding of the mode of interaction of MII with the alpha3 beta2 interface. Here we describe the three-dimensional solution structure of MII determined using 2D 1H NMR spectroscopy. Structural restraints consisting of 376 interproton distances inferred from NOEs and 12 dihedral restraints derived from spin-spin coupling constants were used as input for simulated annealing calculations and energy minimization in the program X-PLOR. The final set of 20 structures is exceptionally well-defined with mean pairwise rms differences over the whole molecule of 0.07 A for the backbone atoms and 0.34 A for all heavy atoms. MII adopts a compact structure incorporating a central segment of alpha-helix and beta-turns at the N- and C-termini. The molecule is stabilized by two disulfide bonds, which provide cross-links between the N-terminus and both the middle and C-terminus of the structure. The susceptibility of the structure to conformational change was examined using several different solvent conditions. While the global fold of MII remains the same, the structure is stabilized in a more hydrophobic environment provided by the addition of acetonitrile or trifluoroethanol to the aqueous solution. The distribution of amino acid side chains in MII creates distinct hydrophobic and polar patches on its surface that may be important for the specific interaction with the alpha3beta2 neuronal nAChR. A comparison of the structure of MII with other neuronal-specific alpha-conotoxins provides insights into their mode of interaction with these receptors.     

Volatile anaesthetics reduce adhesion of blood platelets under low-flow conditions in the coronary system of isolated guinea pig hearts

BACKGROUND: Inhibitory effects of volatile anaesthetics on platelet aggregation have been demonstrated in several studies. However, the influence of volatile anaesthetics on intracoronary platelet adhesion has not been elucidated so far. METHODS: Isolated hearts of guinea pigs were perfused with buffer in the absence or presence of volatile anaesthetics (0.5 and 1 MAC) at constant coronary flow rates of 5 ml/min for 25 min, then 1 ml/min for 30 min and again 5 ml/min for 10 min. Before, during and after low-flow perfusion, a bolus of human platelets was applied into the coronary system. To simulate thrombogenic conditions, 0.3 U/ml human thrombin was infused during low-flow perfusion and reperfusion. The number of platelets sequestered to the endothelium was calculated from the difference between coronary in- and output of platelets. The myocardial production of lactate and consumption of pyruvate and coronary perfusion pressure were also determined. RESULTS: At a flow rate of 5 ml/min only about 3% of the applied platelets did not emerge from the coronary system, in any group. In contrast, 13.1 +/- 1.2% (mean +/- SEM) of infused platelets became adherent in low-flow perfusion in the control group without anaesthetic. The adherence was reduced with each 1 MAC isoflurane (to 6.2 +/- 1.2%), sevoflurane (to 4.4 +/- 0.9%) or halothane (to 3.2 +/- 1.5%) (each P < 0.05 vs. control). Volatile anaesthetic, 0.5 MAC, did not inhibit platelet adhesion to a statistically significant extent in any case. Perfusion pressure and metabolic parameters were not statistically different between the control and the hearts exposed to anaesthetics. CONCLUSION: Volatile anaesthetics in a concentration of 1 MAC can reduce the adhesion of platelets in the coronary system under reduced flow conditions. This action does not arise from vasodilation or inhibition of ischaemic stress.     

Fucoidin reduces coronary microvascular leukocyte accumulation early in reperfusion

BACKGROUND: Leukocytes rapidly accumulate in the heart early in reperfusion after ischemia, contributing to reperfusion injury. The purpose of this study was to determine whether treatment with the selectin blocker fucoidin (FCN) would attenuate early leukocyte retention in coronary venules and capillaries during low flow reperfusion. METHODS: Isolated rat hearts subjected to 30 minutes of 37 degrees C, no-flow ischemia were initially reperfused with blood containing labeled leukocytes, followed by reperfusion with a Krebs red cell solution. The deposition of leukocytes in coronary capillaries and venules was observed using intravital microscopy. Three groups were studied: nonischemic control hearts, untreated postischemic hearts reperfused at low flow, and postischemic hearts reperfused at low flow, where both the hearts and the blood reperfusate were pretreated with FCN (0.36 mg/mL blood). RESULTS: In the ischemia-reperfusion group, we observed a rapid and significant increase in leukocyte accumulation in both capillaries and venules. Treatment with FCN significantly reduced the leukocyte accumulation in both capillaries and venules (p<0.05). In addition, FCN significantly reduced the persistence of leukostasis in both capillaries and venules, indicating that FCN affected a transient adhesion process. CONCLUSIONS: These results suggest that the selectin family of leukocyte-endothelial cell adhesion proteins mediates the initial retention of leukocytes in both coronary capillaries and venules during reperfusion. Selectin blockade may be effective in reducing the contribution of leukocytes to early reperfusion injury.