Roger Lentle - Academia.edu (original) (raw)

Papers by Roger Lentle

Frontiers in Endocrinology, Nov 21, 2019

Techniques in Coloproctology, 2020

Frontiers in Physiology, 2018

The uses and limitations of the various techniques of video spatiotemporal mapping based on chang... more The uses and limitations of the various techniques of video spatiotemporal mapping based on change in diameter (D-type ST maps), change in longitudinal strain rate (L-type ST maps), change in area strain rate (A-type ST maps), and change in luminous intensity of reflected light (I-maps) are described, along with their use in quantifying motility of the wall of hollow structures of smooth muscle such as the gut. Hence ST-methods for determining the size, speed of propagation and frequency of contraction in the wall of gut compartments of differing geometric configurations are discussed. We also discuss the shortcomings and problems that are inherent in the various methods and the use of techniques to avoid or minimize them. This discussion includes, the inability of D-type ST maps to indicate the site of a contraction that does not reduce the diameter of a gut segment, the manipulation of axis [the line of interest (LOI)] of L-maps to determine the true axis of propagation of a contraction, problems with anterior curvature of gut segments and the use of adjunct image analysis techniques that enhance particular features of the maps.

BJU International, 2019

ObjectivesTo explore and characterize the disposition and dynamics of micromotions in the wall of... more ObjectivesTo explore and characterize the disposition and dynamics of micromotions in the wall of the intact resting teradotoxinized urinary bladder of the rabbit before and after the administration of adrenergic and cholinergic pharmaceutical agents.MethodsSpatiotemporal maps and related intravesical pressure were used to analyse propagating patches of contractions (PPCs) and their component individual myogenic contractions [propagating individual contractions (PICs)] in the wall of the tetradotoxinized urinary bladder.ResultsThe bladder wall exhibited two contractile states that were of similar frequencies to those of the two types of electrophysiological discharge described in previous studies; the first, in which cyclic PPCs predominated, the second in which small irregular PICs predominated. The addition of carbachol increased the size, frequency, speed and distance of propagation of PPCs, whereas the addition of isoprenaline temporarily halted the incorporation of PICs into PP...

Journal of The Royal Society Interface, 2018

The measurement of the viscosity of digesta is complicated by settling and compositional changes ... more The measurement of the viscosity of digesta is complicated by settling and compositional changes that accompany digestion. The current work determined whether the apparent and relative viscosities ( η a and η r ) of digesta could be accurately determined from the actual and maximum solid volume fractions ( ϕ and ϕ max , respectively) using the Maron–Pierce equation. The rheological properties of digesta from the small intestine of six pigs were determined at a shear rate of 1 s −1 at 37°C. A series of suspensions of plant fibre in a Newtonian liquid (70% aqueous fructose) were made at viscosities similar to pig digesta by adjusting ϕ . The relationships between the apparent and relative viscosities ( η a and η r ) and the plant fibre properties; aspect ratio (AR) and ϕ and ϕ max were then determined for digesta and the suspensions. The ARs for the digesta and plant fibre particles were determined using image analysis of scanning electron micrographs and η a from rheometric flow curv...

American Journal of Physiology-Gastrointestinal and Liver Physiology, 2016

We used spatiotemporal mapping of strain rate to determine the direction of propagation and ampli... more We used spatiotemporal mapping of strain rate to determine the direction of propagation and amplitudes of the longitudinal and circumferential components of antrocorporal (AC) contractions and fundal contractions in the rat stomach maintained ex vivo and containing a volume of fluid that was within its normal functional capacity. In the region of the greater curvature the longitudinal and circular components of AC contractions propagated synchronously at right angles to the arciform geometric axis of the stomach. However, the configuration of AC contractions was U shaped, neither the circular nor the longitudinal component of contractions being evident in the upper proximal corpus. Similarly, in the distal upper antrum of some preparations, circumferential components propagated more rapidly than longitudinal components. Ongoing “high-frequency, low-amplitude myogenic contractions” were identified in the upper proximal gastric corpus and on the anterior and posterior wall of the fund...

The Journal of Physiology, 2007

Bait consumption and biology of tammar wallabies in the Rotorua region

Food and Nutrition Sciences, 2013

Food & Function, 2015

Villous movements augmented radial mass transfers and mixing.

, except for brief excerpts in connection with reviews or scholarly analysis. Use in connection w... more , except for brief excerpts in connection with reviews or scholarly analysis. Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden. The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights.

PloS one, 2014

We investigated the passive mechanical properties of villi in ex vivo preparations of sections of... more We investigated the passive mechanical properties of villi in ex vivo preparations of sections of the wall of the distal ileum from the brushtail possum (Trichosurus vulpecula) by using a flow cell to impose physiological and supra-physiological levels of shear stress on the tips of villi. We directly determined the stress applied from the magnitude of the local velocities in the stress inducing flow and additionally mapped the patterns of flow around isolated villi by tracking the trajectories of introduced 3 µm microbeads with bright field micro particle image velocimetry (mPIV). Ileal villi were relatively rigid along their entire length (mean 550 µm), and exhibited no noticeable bending even at flow rates that exceeded calculated normal physiological shear stress (>0.5 mPa). However, movement of villus tips indicated that the whole rigid structure of a villus could pivot about the base, likely from laxity at the point of union of the villous shaft with the underlying mucosa. ...

The Journal of Poultry Science, 2006

The Journal of Poultry Science, 2007

We examined gizzard morphology and diet particle size reduction in broiler chickens fed a wheat-b... more We examined gizzard morphology and diet particle size reduction in broiler chickens fed a wheat-based diet that was o#ered in either a mash or a pelleted form. The pelleted diet had a lower proportion of coarse particles on wet sieving. Birds fed the mash diet had a significantly larger gizzard mass per unit body mass. The gizzards of all birds increased uniformly in size, there being no significant change either in the ratio of content to empty mass or in the ratio of gizzard length to breadth with diet. Thus, there was no tendency for coarse particles to accumulate in the gizzards of bird fed the mash diet. The relative proportion of all classes of particles below *./** mm was increased and the relative proportion of all particle classes above *./** mm was reduced in birds regardless of feed form. The relative increase of particles in all classes below *./** mm was greater in birds fed mash feed. However, digesta exiting the gizzard of birds fed mash diet contained significantly greater amounts of particles of size classes +mm and greater than digesta of those fed the pelleted diet. Thus, whilst the gizzard operates to generally reduce particle sizes above *./** mm and increase those below this size, this reduction is not uniform and likely to be a probabilistic function as it is in the human mouth.

World's Poultry Science Journal, 2007

This review highlights the limited amount of research conducted regarding the optimum particle si... more This review highlights the limited amount of research conducted regarding the optimum particle size of different feeds for efficient poultry production. The current industry practice of using highly processed, pelleted diets masks the influence of particle size, but some reports suggest that the effects of feed particle size on performance may be maintained even after pelleting. There appears to be a general consensus that particle sizes of broiler diets based on maize or sorghum, optimum particle size should be between 600 and 900 μm. Available data clearly show that grain particle size is more critical in mash diets than in pelleted or crumble diets. Although it has been postulated that finer grinding increases substrate availability for enzymatic digestion, there is evidence that coarser grinding to a more uniform particle size improves the performance of birds maintained on mash diets. This counter-intuitive effect may result from the positive effect of feed particle size on giz...

The Journal of Physiology, 2013

Key points Extracellular recording techniques are commonly used to measure bioelectrical activity... more Key points Extracellular recording techniques are commonly used to measure bioelectrical activity. However, the validity of gastrointestinal extracellular recordings has recently been challenged. In this joint experimental and modelling study, slow waves were recorded during contractile inhibition, biphasic and monophasic slow wave potentials were recorded simultaneously, and the biophysical basis of extracellular potentials was modelled with comparison to experimental data. The results showed that in vivo extracellular techniques reliably recorded slow waves in the absence of contractions, and potentials recorded using conventional serosal electrodes (biphasic) were concordant in phase and morphology with those recorded using suction electrodes (monophasic). Modelling further demonstrated that the morphology of experimental recordings is consistent with the biophysics underlying slow wave depolarisation. In total, these results demonstrate that gastrointestinal extracellular record...