Malathion toxicity: Effect on the liver of the fish Brachydanio rerio (cyprinidae)

Four-month-old siblings of zebra fish, Brachydanio rerio, were exposed to 0.5, 0.7, 0.9, and 1.1 mg/liter of malathion for 7 days. DNA, RNA, protein, and free amino acid contents and the activities of acid and alkaline phosphatases were monitored in the liver. There was marked inhibition in DNA, RNA, and protein contents and the activities of acid and alkaline phosphatase. Total free amino acid content, however, significantly increased. Seven days withdrawal to freshwater indicated a recovery trend. The probable reasons for various changes are discussed.     

[18F]Fallypride dopamine D2 receptor studies using delayed microPET scans and a modified Logan plot

[¹⁸F]Fallypride PET studies can be used to estimate the nondisplaceable binding potential (BP_ND) in vivo of dopamine D2/D3 receptor-rich regions of the brain. These studies often take considerable time, up to ≥2 h, limiting the throughput. In this work, we investigated whether limited-duration scans performed subsequent to tracer administration yielded stable BP_ND estimates. In particular, we applied a modified version of the Logan plot method on the last 60 min of 120-min data and compared the results to those from analysis of the full data set.MethodsFourteen male Sprague-Dawley rats were injected with [¹⁸F]fallypride intravenously while under isoflurane anesthesia, and dynamic data were acquired on the microPET Focus 220 scanner for 120 min. The distribution volume ratio (DVR=BP_ND+1) was calculated from a Logan plot using 120 min of data and from a modified version using only the last 60 min. Three of these rats were imaged again on a second day to test the reproducibility. A two-tissue compartment model also was used to fit the time–activity curves (TACs) of the 120-min scans to estimate the parameters K₁, k₂, k_on, k₄ and B_max. These parameters were then used to simulate similar TACs while changing k_on to reflect changes in the dopaminergic system. The simulated TACs were used as a means for exploring the differences in DVR estimates between the last 60 min only and the full 120 min of simulated data.ResultsThe average DVR from the full 120-min scans was 13.8±0.9, whereas the average DVR estimated from only the last 60 min of data (DVR′) was 16.3±1.0. The DVR estimates showed good reproducibility in the three rats (mean DVR=13.8±1.5 on Day 1 and DVR=13.8±0.9 on Day 2). The simulations showed that the relationship between DVR′ and DVR estimates follows a semilinear form with varying k_on.ConclusionAlthough the BP_ND estimates are slightly overestimated in a delayed scan mode (i.e., no initial radiotracer uptake measurements) compared to a full scan, this overestimation depends primarily on k₃ (≈k_on×B_max) and has been evaluated in this work for a wide range of k_on values using simulated TACs. In particular, the sensitivity of DVR′ to changes in k_on is similar to that of DVR. This method of delayed scans eliminates the necessity of imaging during the initial uptake of the radiotracer and, thus, can be used to increase the throughput of studies.     

Activation of DA1 receptors by dopamine or fenoldopam increases cyclic AMP levels in the renal artery but not in the superior cervical ganglion of the rat

In the isolated superior cervical ganglion of the rat, activation of either DA1 or DA2 receptors leads to inhibition of ganglionic transmission. Using dopamine as well as relatively selective dopamine receptor agonists and antagonists we have performed electrophysiological as well as biochemical experiments to study the nature of dopamine receptors in this sympathetic ganglion. Fenoldopam, a selective DA1 receptor agonist caused marked inhibition of the compound postganglionic action potential evoked by stimulation of preganglionic nerve. The inhibitory effect of fenoldopam was antagonized by the DA1 receptor antagonist R-sulpiride but not by the DA2 receptor antagonist S-sulpiride. However, the more potent and selective DA1 receptor antagonist SCH-23390 failed to antagonize ganglion blocking effect of fenoldopam indicating that DA1 receptor in sympathetic ganglia is different from that in blood vessels. The superior cervical ganglion also contains DA2 receptors inasmuch as quinpirole, a DA2 receptor agonist, caused inhibition of ganglionic transmission which was antagonized by S-sulpiride but not by R-sulpiride. The existence of both subtypes of dopamine receptor in the superior cervical ganglion was ascertained further as dopamine itself caused inhibition of ganglionic transmission which was antagonized by either S- or R-sulpiride. Again, however, the DA1 receptor antagonist SCH-23390 failed to antagonize the ganglion blocking effect of dopamine. To characterize further the ganglionic DA1 receptor we sought to demonstrate whether or not ganglionic DA1 receptor is linked to the enzyme adenylate cyclase as is known to be the case for peripheral DA1 or central D1 dopamine receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nurses' involvement in international research collaborations

Nurses are becoming increasingly involved in collaborative international research teams. This article describes a European-wide research consortium that is implementing research across Europe. The experiences of members of a cross-national research consortium and some of the challenges are discussed. Cross-national research consortia should pay attention to preparatory, methodological, financial, operational and structural challenges. Ownership of data and dissemination of research findings are also explored. Consortia need to find a balance between a consistent organisational structure and communication styles, and respecting the differences between members of the consortium.     

Spontaneous rupture of the diaphragm.

A 42-year-old man was brought into the Accident and Emergency Department with epigastric discomfort and severe bradycardia. Computerized tomography of the chest revealed spontaneous rupture of the left hemidiaphragm with herniation of small bowel loops.