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Biomedical subjects

D J Griffiths

Publications and source records attributed to D J Griffiths.

At least 73 records · Page 4Linked to original sources
PubMed1987

Clinical comparison of bladder contractility parameters calculated from isometric contractions and pressure-flow studies.

Parameters describing the contractility of the urinary bladder can be calculated from both isometric contractions and pressure-flow studies. The first method has the advantage of making very little demand either on the patient or on the urodynamicist, and the disadvantage of yielding a parameter that is not clearly related to muscle physiology. The second method demands more from both patient and experimenter but yields straightforward parameters. For a group of 86 patients with mixed pathologic findings, a correlation between the two types of parameters was demonstrated, showing that both methods test, at least partly, the same mechanism.

Adult↗
PubMed1987

Vesicoureteral reflux and lower urinary tract dysfunction: evidence for 2 different reflux/dysfunction complexes.

We examined retrospectively 458 children 2 to 15 years old without neuropathic conditions or a gross anatomical abnormality to determine whether there was an association between lower urinary tract dysfunction and vesicoureteral reflux. We identified 2 different types of reflux/dysfunction complexes with contrasting urodynamic characteristics. One type included bladder instability with powerful voiding contractions of the bladder and reflux that frequently occurred on 1 side only. Reflux nephropathy or the presence of an upper urinary tract abnormality is rare. In the other type the bladder contracted poorly during voiding and overactivity of the urethral closure mechanism often was observed. The bladder usually was stable and the reflux occurred frequently on both sides. Reflux nephropathy or the presence of an upper urinary tract abnormality is relatively common. Direct videourodynamic observations of reflux in a second group of children confirmed the existence of these 2 types of reflux/dysfunction complexes.

Adolescent↗
PubMed1987

Dynamics of the upper urinary tract: I. Peristaltic flow through a distensible tube of limited length.

A theoretical analysis and numerical solutions are presented for viscosity-dominated flow through a uniform, highly distensible tube with a slit-shaped cross section undergoing peristalsis. At flow rates below an intrinsic upper limit to the peristaltic carrying capacity of the tube, provided that there is always at least one peristaltic contraction wave in the tube, two different types of steady peristaltic flow are possible, with well defined boluses separated by regions where the tube is nearly completely occluded (flow with isolated boluses and flow with boluses in contact). Above this limit two other non-steady types of flow are possible, in which the boluses are less well defined and the contraction waves are in general not completely occlusive (flow with leaky boluses and open-tube flow). In flow with isolated boluses, boluses in contact and leaky boluses, the upstream pressure is determined by the mechanical properties (active and passive) of the tube undergoing peristalsis. In open-tube flow it is primarily determined by the resistance of the outlet from the tube.

Animals↗
PubMed1987

Dynamics of the upper urinary tract: II. The effect of variations of peristaltic frequency and bladder pressure on pyeloureteral pressure/flow relations.

The dynamics of pyeloureteral flow is described when there is no peristalsis and for peristalsis of high and intermediate frequencies, on the assumption that the ureter is uniform except in the mid-ureter and at the outlet. The possibility of upstream transmission of bladder pressure variations to the renal pelvis is considered. The overall behaviour depends on three principal variables, the maximum tube pressure in the contraction waves, the intrinsic peristaltic carrying capacity and the peristaltic frequency f, expressed in the form fT where T is the time for a peristaltic contraction wave to sweep through the ureter. At intermediate peristaltic frequencies (fT less than but comparable with one) oscillatory flow patterns can occur, in which periods of peristaltically driven flow alternate with extraperistaltic periods of flow through the open ureter. The kidney is better isolated from bladder pressure variations when the peristaltic frequency is high, but high peristaltic frequency can by itself lead to elevated renal pelvic pressure if the flow rate is high. Experimental observations in pigs are presented to support these conclusions.

Animals↗
PubMed1986

The pineal gland is very large and active in newborn antarctic seals.

The pineal gland of newborn elephant seals and Weddell seals is larger than in adult females. The gland is considerably larger at birth in Weddell seals than in elephant seals. The former experience greater extremes of temperature. Plasma melatonin concentrations in excess of 2000 pg/ml were recorded in the first days of life, compared with 20-50 pg/ml in adults.

Animals↗
PubMed1986

Adenohypophysis of the elephant seal (Mirounga leonina): morphology and seasonal histological changes.

Changes in adenohypophyseal cell populations over a 12-month period were studied in the seasonally breeding elephant seal (24 adult males, 3 adult females, and 5 neonates) at Macquarie Island. The glands were weighed and fixed in formol sublimate. Selected sections were stained with the oxidation-alcian blue-periodic acid Schiff-orange G technique. Gonadotropic, thyrotropic, lactotropic, and somatotropic cells were readily identifiable; whilst corticotropes, inactive secretory cells of all types, and stellate cells were not stained and were counted collectively as chromophobic cells. Hypophyseal weight was low throughout autumn and winter, but increased significantly during the spring breeding season and the summer. Thyrotropes were distributed evenly throughout the pars distalis, but the other secretory cells showed areas of concentration. Acidophils were common peripherally, particularly lactotropes, while gonadotropes were largely confined to the 'basophilic wedge,' a narrow, central superior zone. In males, lactotropic and gonadotropic cells showed significant seasonal changes in number. Gonadotropes were more common in sexually active males than sexually quiescent ones, while lactotrope numbers were much greater at midsummer than midwinter. This lactotrope cycle appeared to be related to photoperiod but unrelated to breeding.

Animals↗
PubMed1986

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.

Adult↗
PubMed1986

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.

Gels↗
PubMed1986

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.

Animals↗
PubMed1986

Urinary bladder function and its control in healthy females.

Recordings in eight healthy female volunteers of bladder (detrusor) pressure and flow rate, obtained during bladder filling and during voiding, both through the urethra and through a catheter, demonstrate that a model of bladder function in which the detrusor muscle is considered as completely passive during filling and fully activated during voiding is inadequate. Assessment of the detrusor contraction strength by a new method (described in APPENDIX A) shows that in ideal normal voidings the contraction strength rises to values of 11-24 W/m2 and is sustained or rises slightly until the bladder is empty. During unstable detrusor contractions, which even in these healthy women are observed during bladder filling and also during inhibited voidings through the urethra, the contraction is weaker. During voidings through a catheter the detrusor contraction is weak, variable, and fades away before the bladder is empty. An elementary feedback analysis demonstrates that the effect of the micturition reflex governing detrusor behavior differs according to whether or not voiding is taking place. The reflex does not lead to a simple on-off mechanism but to a more complex behavior that is consistent with the observations and that appears to be important for the understanding of pathological obstructed micturition.

Adult↗
PubMed1985

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.

Acetylcholinesterase↗
PubMed1984

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.

Aged↗
PubMed1984

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.

Adolescent↗
PubMed1983

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.

Animals↗