X-ray structure study of thermotropic phases in isoacylphosphatidylcholine multibilayers

Structures of lamellar phases in aqueous dispersions of diisoacylphosphatidylcholines (17iPC and 20iPC) were determined by x-ray diffraction methods. In agreement with previous DSC studies, subgel, gel, and liquid crystal phases were observed in each homolog. The subgel Lc(c') phases of both homologs show significant two-dimensional long range order and can be described by rectangular lattices. The dimensions of the two rectangular unit cells differ in that the side chains are canted (approximately 33 degrees) in the 20iPC homolog, while in 17iPC the side chains are normal to the bilayer plane. The gel L beta phases of 17iPC (Tgg = 17-19.5 degrees C) and 20iPC (Tgg = 44 degrees C) are similar but not identical and are consistent with a distorted, pseudohexagonal lattice for the rotationally disordered side chains. The liquid crystal phases of 17iPC (Tgl = 28 degrees C) and 20iPC (Tgl = 52 degrees C) are structurally similar and are typical of lipids with fluid side chains. Significant but different changes occur in the long spacings at Tgg and Tgl for the two homologs. This implies that interfacial states (particularly in the subgel phases) differ in the two homologs below the liquid crystal phase transition temperature.

An evaluation of contractility parameters determined from isometric contractions and micturition studies

In a group of 110 patients of mixed pathology 218 micturitions were investigated. Using an on-line computer, two contractility parameters were calculated: the parameter U/l, which is derived from the isometric pressure rise in the detrusor before micturition actually started, and the parameter wmax, which is derived from flow and pressure during micturition. It was found that neither of the parameters conforms to the definition of an ideal contractility parameter. Both parameters are subject to the influence of the urethral resistance or the degree of neurogenic stimulation of the bladder, and both measure to some degree the actual performance of the detrusor during a given micturition instead of its myogenic properties. Nevertheless, by dividing patients into groups according to these two measured values, it was shown that clinically relevant types of detrusor behaviour can be distinguished.

A fluctuation in plasma melatonin level in the Weddell seal during constant natural light

Blood was collected over a 24-h period from free-living adult Weddell seals that had been exposed to natural constant daylight for some 12 weeks. The plasma melatonin concentration was low throughout the trial (range of means: 30.8-70.4 pg/ml) with the exception of a 3-h period centered on 1700 h local time, when the plasma level rose to a mean of 131.8 pg/ml. The pineal gland of the Weddell seal is thus capable of transient bouts of activity during constant and bright daylight, a situation usually inhibitory to the function of the gland. It is suggested that circadian fluctuations in the intensity of constant light entrain variation in the pineal gland functioning of this seal during summer.

Effects of long-term catheter implantation on the contractile and histological properties of the canine bladder

In beagles, a bladder catheter was surgically implanted and subvesical obstruction was artificially introduced. After 3 months a striking reduction in detrusor contractility measured in vitro was observed, which was associated with a presumptive reduction in the concentration of acetylcholinesterase in the muscle cells and a probable reduction in the mean cell size. In this model the contribution of the catheter to the changes is greater than that of the subvesical obstruction.

Place of the free flow curve in the urodynamic investigation of children

In a group of 210 children, predictions based on the form of the free flow rate curve, obtained without invasive instrumentation, have been compared with the results of a full urodynamic study. If the free flow curve is normal and there is no residual urine, then significant voiding abnormality, whether of functional or anatomical origin, is unlikely. If the free flow curve is abnormal or there is residual urine, then a full urodynamic investigation is indicated in order to determine the cause. A child with a normal free flow curve is more likely to show detrusor instability than a child with an abnormal free flow.

Phenoxybenzamine in prostatic obstruction

A short controlled trial has confirmed that phenoxybenzamine (10 or 20 mg/day) relaxes the resting proximal urethra and reduces the voiding frequency in patients with benign prostatic hypertrophy.

A new method for permanent catheterization in the dog

A new method of enabling urodynamic measurements to be made in the conscious dog is reported. A connecting device is located under the skin on the dog's back, and a catheter passes between this device and the bladder. The system described has proved valuable.

Urodynamic investigation of the wide ureter

Pressure flow studies constitute a valuable advancement in the investigation of wide ureters without reflux. However, these studies do not in themselves allow the determination of the adequacy of urine transport into the bladder. Radiological examination during perfusion is necessary to assess peristalsis and antiperistalsis, to determine the outflow to the bladder and to judge the geometric changes. Case studies reveal that it is difficult to assess the outflow to the bladder from measurements of renal pelvic pressure and of inflow.

The assessment of prostatic obstruction from urodynamic measurements and from residual urine

One hundred and seventeen males over the age of 55 were investigated for possible prostatic obstruction. About half of the cases in this series could have been objectively classified as unobstructed or obstructed from the maximum flow rate alone. In about two-thirds of the cases obstruction could be satisfactorily assessed from the maximum flow rate together with the detrusor pressure at maximum flow. It was not helpful to combine these 2 measurements into a single urethral resistance factor. In the remaining one-third of the cases, obstruction could be objectively assessed only from a plot of detrusor pressure against flow rate throughout micturition. In many of these cases both the pressure and the flow rate were low and the main peculiarity was that the contractile power of the bladder was weak. Residual urine is a sign of an abnormality of bladder function rather than the direct result of urethral obstruction.