Comparison of technetium-99m-HMPAO and technetium-99m-ECD cerebral SPECT images in Alzheimer's disease

SPECT has shown increasing promise as a diagnostic tool in Alzheimer's disease (AD). Recently, a new SPECT brain perfusion agent, 99mTc-ethyl cysteinate dimer (99mTc-ECD) has emerged with purported advantages in image quality over the established tracer, 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO). This research aimed to compare cerebral images for 99mTc-HMPAO and 99mTc-ECD in discriminating patients with AD from control subjects.

METHODS

Twenty-four AD patients (mean age +/- s.d. = 68.9 +/- 8.2 yr) and 13 healthy subjects (68.4 +/- 8.0 yr) were scanned sequentially with 20 mCi of each tracer using the CERASPECT system within 1 mo. Scanning began on average 11.5 +/- 2.8 min after 99mTc-HMPAO injection and 41.8 +/- 10.1 min after 99mTc-ECD. A ratio, R, was derived of count densities in "typically affected" brain structures (parietal and temporal association cortices) to "unaffected" structures (cerebellum, basal ganglia, thalamus, occipital cortex, and sensorimotor cortex).

RESULTS

Analysis of variance revealed significant interaction between diagnostic group and radiopharmaceutical (F = 4.71; df = 1.35; p = 0.04), with 99mTc-ECD demonstrating better separation of R values between AD patients and control subjects than 99mTc-HMPAO. Receiver operating characteristic (ROC) analysis, revealed no significant difference in the ability of the two tracers to correctly classify AD patients and control subjects. Both tracers showed high diagnostic accuracy (99mTc-ECD: sensitivity = 100%, specificity = 92%; 99mTc-HMPAO: sensitivity = 100%, specificity = 85%).

CONCLUSION

Technetium-99m-ECD shows greater contrast than 99mTc-HMPAO between affected and unaffected brain structures in AD when patients are compared to age-matched control subjects. Both tracers perform equally well in correctly classifying patients and control subjects.

High molecular weight phospholipase A2 and fatty acids in human colon tumours and associated normal tissue

Human colon tumours usually form more prostaglandins (PGs) than associated normal tissues, but the mechanism(s) are not fully understood. We analysed fatty acid compositions, in particular arachidonate, and measured the amount and the activity of high molecular weight cytoplasmic phospholipase A2 (cPLA2) of these tissues. Total lipids extracted from homogenised surgical specimens were transesterified and fatty acids were analysed by gas chromatography. cPLA2 was separated by SDS-PAGE, Western-blotted, immunoblotted using a specific antibody to cPLA2 and semiquantified following enhanced chemiluminescence using a scanning densitometer. cPLA2 biological activity was also assayed using 1-stearoyl, 2-[1-14C]-arachidonyl, L-3-phosphatidylcholine. Compared with normal mucosa/submucosa, there was more total arachidonate in tumours (P < 0.01), and increased levels of cPLA2 occurred in 6 of 17 tumours. In conclusion, the higher amounts of tumour total arachidonate and the sometimes higher levels of cPLA2, might help to explain why some human colon tumours form increased amounts of PGs.

Safe biotechnology. 7. Classification of microorganisms on the basis of hazard. Working Party "Safety in Biotechnology" of the European Federation Biotechnology

The current systems for classifying human pathogens on the basis of hazard are well developed and their basic criteria are in general agreement one with another. Of more importance, the safety practices based on these classifications have generally been successful. They have enabled extensive research activities, medical practice and industrial production to be conducted on an ever-increasing scale, involving dangerous microorganisms (e.g. in vaccine production and treatment of infected patients) with a very low incidence of adverse effects on the workers involved and the general public. Although the EU has adopted a harmonised list of agents in groups 1-4 there is as yet no complete agreement among member states and individual microbiologists. The purpose of this paper is to present a historical survey and to discuss the current processes for identifying and classifying the hazards posed by the use of microorganisms in research and technology. This is essential in the design of appropriate methods of counteracting potential risks.

Effects of D-myo-Inositol-1,2,6-triphosphate on eicosanoid formation in burned skin

D-myo-Inositol-1,2,6-triphosphate (IP3) has been shown to reduce edema and progressive ischemia following experimental skin burns. The mechanism(s) are not identified but could be related to antiinflammatory effects of the agent. In the present ex vivo study we compared the effects of IP3 with those of saline and indomethacin on eicosanoid formation by normal and burned rat skin. In burned skin IP 3 treatment reduced the release of thromboxane B2 (TXB2) (P < 0.01) and leukotriene B4 (LTB 4) (P < 0.05) but there was only a weak trend for less prostaglandin E (PGE) compared to burned control animals receiving saline. Indomethacin reduced the release of TXB2 (P < 0.01), and PGE (P < 0.001), but not LTB 4 from burned skin compared to skin from saline-treated burned animals. In non-burned skin IP 3 increased the release of PGE (P < 0.01) and LTB 4 (P < 0.01), but did not significantly influence TXB2 accumulation in the incubation fluid compared to the saline-treated group. Indomethacin reduced the release of TXB2 (P < 0.001) and PGE (P < 0.001), but increased LTB 4 (P < 0.001) in normal skin compared to the saline-treated group. In conclusion, IP 3 inhibited the release of TXB2 and LTB 4 from burned skin ex vivo, but increased PGE and LTB 4 release from normal skin. These results suggest that the mode of action of IP 3 differs from that of nonsteroidal antiinflammatory drugs. The effects of IP 3 on the arachidonic acid cascade also seem to differ in burned versus normal skin.

Activity of nimesulide on constitutive and inducible cyclooxygenases

Prostaglandins are pro-inflammatory but are gastroprotective. The gastric mucosa synthesizes prostaglandins mainly via constitutive cyclooxygenase (COX-1), whereas leucocytes have inducible enzyme (COX-2). Nimesulide (CAS 51803-78-2) differentially inhibited prostanoid synthesis in these human tissues as well as with in vitro enzyme assays, and was less potent than indometacin (CAS 53-86-1) on COX-1. Fresh human gastric mucosa was cut finely, washed and pre-incubated (100 mg in 1 ml phosphate buffered saline pH 7.4) with or without nimesulide or indometacin (0.1-100 micrograms/ml; 0 degree C; 30 min). The fluid was replaced with fresh identical solution, incubated (37 degrees C; 30 min) and the solution assayed. Isolated leucocytes from human peripheral blood were incubated (1-1.5 x 10(6), 2 ml Krebs' solution) with or without nimesulide or indometacin (0.1-100 micrograms/ml; 37 degrees C; 1 h), stimulated with lipopolysaccharide (5 micrograms/ml), further incubated for 24 h at 37 degrees C and the medium assayed for the prostanoids PGE, TXB2, 6-keto-PGF1 alpha and the leukotriene LTB4 by radioimmunoassay (RIA). In vitro assays with COX-1 from ram seminal vesicles, or COX-2 from sheep placenta, were performed by pre-incubating the enzymes with vehicle alone (controls) or with drug for 5 min at 37 degrees C. Arachidonate (10 mumol/l) was added and further incubated for 2 min at 37 degrees C. Reactions were terminated and PGE determined by RIA. Both drugs caused concentration-related inhibitions of prostanoid accumulation in incubates of both tissues. Nimesulide reduced PGE accumulation more potently in incubates of stimulated leucocytes than of gastric mucosa. With gastric tissue, nimesulide was less potent than indometacin by approximately 6-22 fold (IC50 for PGE, TXB2, 6-keto-PGF1 alpha, respectively; 14.8 vs 2.5; 12.8 vs 1.0; 31.1 vs 1.4 mumol/l; p < 0.05 to 0.02). With the leucocytes, the concentrations of both drugs, particularly indometacin were not low enough to calculate the IC50. With the in vitro assay, nimesulide (0.01 to 100 mumol/l) did not inhibit PGE formation by COX-1 but caused a concentration-related inhibition of PGE formation by COX-2 (4-60%). These results are consistent with the effective analgesic/anti-inflammatory activity of nimesulide coupled with better gastric tolerance compared to indometacin.

The thermal acclimation of burst escape performance in fish: an integrated study of molecular and cellular physiology and organismal performance

Goldfish (Family Cyprinidae, Carassius auratus) and killifish (Family Cyprinodontidae, Fundulus heteroclitus) were acclimated to 10, 20 and 35 &deg;C for 4 weeks. The thermal acclimation of C-start (escape swimming) performance and the physiological properties of fast twitch muscle fibres that underlie it were investigated in these species at the molecular (myosin isoform expression), biochemical (myofibrillar ATPase activity), cellular (contractile kinetics) and organismal levels of organisation. Peptide maps were obtained for fast muscle myosin heavy chains, isolated from 10 &deg;C- and 35 &deg;C-acclimated fish. Different myosin heavy chain isoforms were expressed in response to a change in acclimation temperature in goldfish, but myosin heavy chain isoform expression was unaffected by acclimation temperature in killifish. Compared with fish acclimated to 35 &deg;C, acclimation to 10 &deg;C increased the activity of fast muscle myofibrillar ATPase assayed at 10 &deg;C fivefold in goldfish and only 50 % in killifish. Muscle twitch contraction time at 10 &deg;C decreased significantly in response to acclimation to 10 &deg;C in both species; however, the magnitude of this response was much greater in goldfish (100 %) than in killifish (30 % or less). In goldfish, these changes in the physiological properties of fast twitch fibres during 10 &deg;C acclimation resulted in a six- to eightfold increase in the speed and turning velocity of fish performing C-starts at 10 &deg;C. By comparison, the somewhat smaller acclimatory response of killifish fast muscle properties was accompanied by only a minor (50 % or less) adjustment in locomotor performance. Thermal acclimatory responses of fast muscle at the molecular, biochemical and cellular levels of organisation are clearly reflected in alterations in organismal escape performance.

The effect of folate on the methotrexate/indomethacin interaction in a murine cancer cell line

1. The effect of folate on the interaction between methotrexate (a folate analogue) and indomethacin has been examined in murine NC carcinoma cells. 2. Conditioning of NC cells to a physiological (20 nM) folate concentration after culture in a high folate concentration increased the response to methotrexate. The sensitivity of these conditioned cells to methotrexate related inversely to the folate concentration. 3. At 20 nM and 2 microM folate, indomethacin 1 micrograms ml-1 potentiated the cytotoxicity of methotrexate 4 and 8 ng ml-1 (both P < 0.03). 4. When NC cells were incubated with [3H]-methotrexate at 20 nM and 2 microM folate, there was a trend for increased tritium accumulation with indomethacin 0.36 micrograms ml-1 (1 microM; P < 0.01). 5. We conclude that the folate concentration can affect the sensitivity of NC cells to methotrexate, although the degree of potentiation of cytotoxicity by indomethacin remains similar.

Interaction between methotrexate and indomethacin on a human normal haemopoietic cell line

1. The interaction between methotrexate and indomethacin has been examined, at a physiological folate concentration (20 nM), on a human normal lymphoblast-like cell line (RPMI 1788) in vitro. 2. Indomethacin (1 microgram ml-1) increased the reduction of lymphoblast growth caused by methotrexate (10-80 ng ml-1). 3. Indomethacin (0.1 and 1 microgram ml-1) potentiated the cytotoxicity of methotrexate (20 and 40 ng ml-1) after 4 days in culture. 4. Indomethacin (0.4 micrograms ml-1) reduced the accumulation of tritium in lymphoblasts incubated with [3H]-methotrexate after 30 min; therefore initial drug accumulation was not responsible for the potentiation seen after 4 days. 5. If indomethacin increases the killing of human cancer cells by methotrexate in vivo, with a smaller potentiation on lymphoblasts, this combination may be beneficial in treating human malignancy.

Comparison of invasive and non-invasive measurement of continuous arterial pressure using the Finapres in patients undergoing spinal anaesthesia for lower segment caesarean section

We have compared arterial pressures measured by an indwelling radial cannula with those obtained non-invasively by the Finapres 2000 (Ohmeda) during spinal anaesthesia for lower segment Caesarean section. The digital outputs of both pressures were recorded using a computerized system. We studied 20 patients, yielding a total of 18,772 data points after elimination of data recorded during arterial flushing and erroneous results from each source. The data analysis demonstrated a normal distribution for differences between the two methods of measurement, and the correlations between invasive and Finapres readings for systolic, diastolic and mean pressures were 0.78, 0.72 and 0.79, respectively, indicating an overall poor reflection of intra-arterial pressure by the Finapres under these circumstances. Some patients and some periods of readings reflected a high degree of precision and little bias. However, unexplained large differences in pressure and trends of change that were out of phase over time occurred frequently. We conclude that the Finapres cannot be recommended as a monitor of arterial pressure in this group of patients in whom sudden hypotension may be a threat to maternal or fetal outcome.

IS WALKING COSTLY FOR ANURANS? THE ENERGETIC COST OF WALKING IN THE NORTHERN TOAD BUFO BOREAS HALOPHILUS

Locomotor mode and the maximal capacity for aerobic metabolism are thought to be co-adapted in anuran amphibians. Species that rely heavily on walking often have high capacities for aerobic metabolism relative to species that rely primarily on saltation. We tested the hypothesis of co-adaptation of gait and aerobic metabolism by investigating the locomotor energetics of Bufo boreas halophilus, a toad that walks, but does not hop. Rates of oxygen consumption during locomotion were measured in an enclosed variable-speed treadmill. The steady-state rate of oxygen consumption (V(dot)O2ss) increased linearly within a range of sustainable speeds [V(dot)O2ss (ml O2 g-1 h-1) = 0.93 x speed (km h-1) + 0.28]. The minimum cost of transport, Cmin (the slope of this relationship), varied significantly among individual toads. When expressed in units of oxygen consumed per distance travelled (ml O2 km-1), Cmin scaled isometrically with body mass: Cmin = 0.69mass1.07. Consequently, mass-specific Cmin (ml O2 g-1 km-1) was uncorrelated with body mass. Variation in Cmin was also unrelated to experimental temperature. Mass-specific Cmin estimates were similar to previous allometric predictions for terrestrial animals of similar size, which contrasts with previous findings for another toad species. Maximum rates of oxygen consumption measured in closed, rotating respirometers were significantly higher than the maximum rates achieved on the treadmill, but lower than those measured previously in other Bufo species. Our results indicate that walking is not necessarily a costly gait for toads and that high maximum rates of oxygen consumption are not associated with reliance on walking within the genus Bufo.

Spinal anaesthesia for caesarean section: comparison of infusions of phenylephrine and ephedrine

Maternal cardiovascular changes and neonatal acid-base status were assessed in 29 healthy women undergoing elective lower segment Caesarean section under spinal anaesthesia. The patients were allocated randomly to one of three groups to receive an i.v. infusion of one of the following: ephedrine 1 mg min-1 (group E1: n = 10), ephedrine 2 mg min-1 (group E2: n = 9), or phenylephrine 10 micrograms min-1 (group P: n = 10). Invasive arterial pressure was monitored continuously and if hypotension occurred (defined as a 20% decrease from baseline, taken after i.v. preload administration), bolus doses of either ephedrine (6 mg in groups E1 and E2) or phenylephrine (20 micrograms in group P) were given. Only four patients became hypotensive in group E2, compared with eight patients in group E1 and nine patients in group P. The total time that the patients remained hypotensive was greatest in group P (P < 0.005), less in group E1 and least in group E2. Neonatal Apgar scores and acid-base profiles were similar in all three groups. In this study, an infusion of phenylephrine 10 micrograms min-1 with bolus doses of 20 micrograms was shown to be significantly less effective in maintaining systolic arterial pressure within 20% limits of baseline compared with an infusion of ephedrine 1 or 2 mg min-1 with bolus doses of 6 mg.

Effect of lignocaine on eicosanoid synthesis by pieces of human gastric mucosa

Lignocaine can affect prostaglandin synthesis in various tissues, and it has anti-inflammatory activity. No studies have been made previously on human isolated gut tissues. When concentrations of 5, 50 and 250 micrograms mL-1 lignocaine were incubated with human gastric mucosa/submucosa at 37 degrees C for 30 min, only the highest concentration reduced the levels of prostaglandin E, thromboxane B2 and 6-keto-PGF1 alpha in the incubates, and leukotriene C4/D4 was unaffected. Therapeutically relevant amounts of lignocaine given parenterally would therefore seem unlikely to alter gastric mucosal prostanoids, but high doses can be given orally because of extensive first-pass metabolism in the liver.

Intrathecal injection of lysine acetylsalicylic acid in the rat: a neurotoxicological study

Lysine acetylsalicylic acid has been reported to induce analgesic effects in humans after intrathecal (i.t.) injection. Before conducting further studies in humans with this drug, it is important to evaluate potential toxicological effects on the spinal cord in animals. In the present study the effects of chronic intrathecal administration of provocative doses of lysine acetylsalicylic acid (L-ASA) on the rat spinal cord were evaluated using light and electron microscopy and a quantitative morphometric method. We also investigated the effects of single doses of the drug on the spinal cord blood flow (SCBF) using the laser-Doppler flowmetry technique. No histopathological changes or differences in number or density of neuronal cells could be seen after chronic administration of L-ASA as compared to controls. The SCBF decreased immediately after i.t. injection of a large dose (4 mg) of L-ASA and returned to predrug levels within 10 min. At the end of the experiment metabolic acidosis was detected, indicating a systemic effect of acetylsalicylic acid. It is concluded that no neurotoxic effects on the spinal cord were seen after chronic i.t. injection of L-ASA. From a neurotoxicological point of view, our findings do not contraindicate the spinal use of L-ASA in humans.

Sexual networking in provincial Thailand

Thailand is currently experiencing a major HIV epidemic, spread primarily through heterosexual contact. Patronage of prostitutes is relatively common. In-depth, open-ended interviews were conducted in a Central Thai province with a purposive sample of 181 urban men who had had sexual relations with at least two different women during the prior year. Additional qualitative information is provided by interviews with 50 women. The most common network pattern for men was a combination of commercial and noncommercial sexual relationships. Men reported that they commonly used condoms when they engaged in sex with prostitutes, but condom use was lowest for men who were the most frequent patrons. In noncommercial, nonmarital relationships, men screen partners for risk rather than practice safe sex, and condom use is generally low. Persons involved in noncommercial sexual networks are largely unaware that their partner may link them to a larger network of sexual contacts and associated risks of HIV infection. Men who have both commercial and noncommercial sexual partners can be found throughout the social strata. A program that focuses only on the closed commercial sex network will address only partially the real risk situations.

Effects of cupric chloride and tamrabhasma, a traditional Indian preparation of copper, on eicosanoid production by human gastric and colonic mucosa

Tamrabhasma is a traditional copper oxide-containing Indian preparation which has anti-ulcer activity. We have studied the effect of tamrabhasma and CuCl2.2H2O on prostaglandin formation by human gastric and colonic mucosa and submucosa, as prostaglandins have mucosal protective activity, and their release may contribute to the anti-ulcer effect. With the gastric mucosa, tamrabhasma 10 micrograms mL-1, but not 0.1 or 1 microgram mL-1, increased prostaglandin E (PGE) concentration by 38% (P < 0.05), with little or no effect on 6-keto-PGF1 alpha, thromboxane B2 or the leukotriene (LT) LTC4/LTD4. CuCl2.2H2O (10 micrograms mL-1) increased 6-keto-PGF1 alpha by 46% (P < 0.05), but 0.1, 1, 50 and 250 micrograms mL-1 did not significantly affect any of the prostanoids, and only the highest concentration reduced the amount of LTC4/LTD4. In the colon mucosa, tamrabhasma (0.1-10 micrograms mL-1) or CuCl2.2H2O (10-50 micrograms mL-1) increased all the prostanoids and this effect was greater than in the gastric mucosa but there was no significant change in LTC4/LTD4. CuCl2.2H2O showed a bell-shaped concentration-effect curve, with no significant effect at lower and higher amounts. Indomethacin (0.1-10 micrograms mL-1) caused a concentration-dependent reduction in the prostanoid amounts. The effect of tamrabhasma was probably not only due to the presence of Cu2+, as tamrabhasma was more effective than CuCl2.2H2O alone; in addition the solubility of CuO is very low. Increased prostanoid levels might explain, at least partly, the gastric mucosal protection by tamrabhasma. The results in the colon, however, raise the possibility that tamrabhasma should be examined for the treatment of inflammatory bowel disease.

A pharmacokinetic study of sulphasalazine and two new formulations of mesalazine

We have examined the pharmacokinetics of enteric coated sulphasalazine compared with two new formulations of mesalazine. These consisted of microgranules of mesalazine coated with Eudragit S in a concentration of either 20 or 25% dry lacquer substance; these in turn were enclosed in capsules coated with Eudragit L. In-vitro dissolution studies of coated microgranules showed that drug release was pH dependent. Studies in 7 normal volunteers showed median peak concentrations of 5-amino-salicylic acid and N-acetyl-5-amino-salicylic acid occurred at about 6 hours with both microgranular preparations, compared with sulphasalazine at 15 h. The microgranule formulation coated with 20% Eudragit S gave serum levels and overall systemic absorption similar to values with sulphasalazine. This new formulation may be of value for delivering mesalazine and other therapeutic agents to the colon.