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.     

Studies on human uterine cervix and rat uterus using S-, X- and Q-band electron-spin-resonance spectroscopy.

In previous studies we have reported on the detection of a strong e.s.r. signal in samples of normal human cervix; the signal is much reduced or absent in samples of invasive cancer of the cervix. In order to identify the species responsible for the strong signal, we have used X-, S- and Q-band e.s.r. spectroscopy. The major signal that is detectable in ground-up samples of cervix preserved at -196 degrees C has features consistent with the presence of a peroxy free radical. Good agreement with the experimental findings was obtained by computer simulation, using values for the g-tensor of gx = 2.002, gy = 2.005 and gz = 2.036. The peroxy radical is produced on grinding the normal cervix samples to a powder under liquid N2, and appears to be formed by modification of a pre-existing oxygen-containing complex. Control experiments eliminated the possibility that the strong signals seen in frozen powders prepared from normal cervix were artefacts only of the grinding procedure. Experiments with rats in vivo and with cervix samples in vitro are consistent with the conclusion that the peroxy radical is formed by disturbing the cyclo-oxygenase system that is involved in prostaglandin synthesis.     

Atrial natriuretic hormone secretion in patients with renal failure

To study the effects of volume overload and renal failure on plasma levels of immunoreactive atrial natriuretic hormone (IR-ANH), we measured levels of this hormone in normal subjects, in patients with advanced chronic renal failure (CRF) with and without clinically evident volume overload, and in patients with end-stage renal disease (ESRD) treated with chronic hemodialysis. The levels were 13 +/- 2 pmol/l in normal volunteers, 77 +/- 24 pmol/l in patients with CRF without volume overload, and 219 +/- 50 pmol/l in patients with CRF and clinically evident volume overload (analysis of variance, p less than 0.001, alpha = 0.05 compared to normals). In patients with ESRD, the levels of IR-ANH were 145 +/- 46 pmol/l before dialysis and decreased to 87 +/- 31 after dialysis (p less than 0.025). No correlation was found between the decrease in IR-ANH levels and the decrease in weight during dialysis. A significant positive correlation was found between the IR-ANH levels and blood urea nitrogen in patients with CRF (r = 0.658, p less than 0.01). Volume overload appears to be the most important stimulatory factor for ANH secretion in renal failure patients but other mechanisms, especially a decrease in metabolic clearance, may also contribute to elevated plasma levels. The increased secretion of ANH in patients with renal failure may be an important adaptive response to volume overload and hypertension.