Cardiovascular and respiratory responses associated with limb autotomy in the blue crab, Callinectes sapidus

Cardiovascular and respiratory variables were recorded in the blue crab, Callinectes sapidus, during injury and subsequent autotomy of a chela. Cardiac function and haemolymph flow rates were measured using a pulsed-Doppler flowmeter. Oxygen uptake was recorded using an intermittent flow respirometry system. Crabs reacted to the loss of a chela with a rapid increase in heart rate, which was sustained for 2 h. Stroke volume of the heart also increased after the chela was autotomized. A combined increase in heart rate and stroke volume led to an increase in cardiac output, which was maintained for an hour after the loss of a chela. There was also differential haemolymph perfusion of various structures. There was no change in perfusion of the anterolateral arteries or posterior and anterior aortae, during injury of the chela or subsequent autotomy. Haemolymph flow rates did increase significantly through the sternal artery during injury and immediately following autotomy of the chela. This was at the expense of blood flow to the digestive gland: a sustained decrease in haemolymph flow through the hepatic arteries occurred for 3 h following autotomy. Fine-scale cardiac changes associated with the act of autotomy included a bradycardia and/or associated cardiac pausing before the chela was shed, followed by a subsequent increase in cardiac parameters. Changes in the cardiovascular physiology were paralleled by an increase in oxygen uptake, which was driven by an increased ventilation of the branchial chambers. Although limb loss is a major event, it appears that only acute changes in physiology occur. These may benefit the individual, allowing rapid escape following autotomy with a subsequent return to normal activity.     

The effect of CaCl2 and verapamil on the binding of cisplatin to cultures of normal and transformed human fibroblasts

Normal and transformed human fibroblasts were treated for either 1 sec or 1 h with the antitumor drug cis-dichlorodiamine platinum (cisplatin). The dose response of drug binding and cell survival was determined for cells treated with the drug in the presence or absence of 3.0 mM CaCl2. The levels of drug initially bound to both cell types was similar and was not affected by the presence of Ca2+. The dividing non-transformed cells were most sensitive to killing by short treatment with cisplatin compared to the transformed cells or the confluent non-transformed cultures. After 1 h of cisplatin treatment, the levels of drug bound to the cells were significantly less than that recovered after the shorter treatment. This time-dependent loss of cisplatin was inhibited both by CaCl2 and by the calcium channel blocking agent, verapamil. The higher levels of cisplatin bound after 1 h in the presence of these agents, however, did not in all cases result in decreased survival; the effects were dependent on cell type and on whether the cells were dividing or confluent. Analysis of cisplatin binding to cell cultures indicated that initially the cisplatin was weakly attached to the pericellular and substratum attached material but that with time, the drug bound to this material decreased. This time-dependent removal from the extracellular matrix was much less in the transformed cell cultures and was inhibited by calcium. We propose that the major site of interaction of cisplatin with these cells is in the extracellular matrix and with time the cultures alter their extracellular matrix to decrease this binding. This removal process appears to involve calcium or calcium transport since CaCl2 and verapamil both block these changes.     

The haplotype distribution of the ΔF508 mutation in cystic fibrosis families in Scotland

Summary The gene defective in cystic fibrosis (CF) has recently been isolated and the major mutation identified. The haplotype distribution of this mutation (ΔF508) has been determined for 215 CF chromosomes in the Scottish population. ΔF508 represents 73% of all CF mutations in this group. There remains considerable linkage disequilibrium between XV2c and KM19 and other mutations in the CF gene.     

Mapping of genes on the linear chromosome of the bacterium Borrelia burgdorferi: Possible locations for its origin of replication

Molecular clones of Borrelia burgdorferi, aetiologic agent of Lyme borreliosis, were isolated and analysed by DNA sequence determination. This procedure yielded B. burgdorferi homologues of gidA, gyrB, gyrA, ftsA and ftsZ. The genes were located on the physical map of the B. burgdorferi linear chromosome. Also mapped were the genes fla and p60 while dnaA was mapped using a heterologous probe. gyrA and gyrB were found to be in tandem and were mapped, along with dnaA at the centre of the chromosome. gidA was located close to the left hand extremity of the chromosome. Because gyrB, dnaA and gidA are normally located within 50 kb of the origin of replication (oriC), we propose two possible sites for oriC in the B. burgdorferi linear chromosome.