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Biomedical subjects

K E Carr

Publications and source records attributed to K E Carr.

At least 73 records · Page 4Linked to original sources
PubMed1984

Etched surfaces of plastic embedded and frozen hydrated gastrointestinal tissue.

Scanning electron microscopy (SEM) is most often used to describe the structure of natural surfaces, but it can also be used to examine surfaces created artificially by sectioning or cryofracture. When plasma etched resin sections are studied, the SEM combines some of the functions of a light microscope and a transmission electron microscope. When etched frozen hydrated tissue is examined the groundwork is laid for the use of X-ray microanalysis for the study of elemental concentrations in tissue unexposed to chemical agents of any kind. Examples are given of the study of jejunum and stomach with these two techniques. The results are integrated with data from conventional SEM images to produce composite diagrams which assist with the interpretation of function and topographical morphology.

Animals↗
PubMed1984

Correlative scanning electron microscopy in gastrointestinal pathology.

Some applications of SEM to the study of gastrointestinal pathology are illustrated and discussed, along with a review of recent literature in this field. Particular emphasis is placed on correlative microscopy, involving, for example, the reprocessing of SEM specimens for LM and TEM, and of LM paraffin blocks for SEM. In terms of diagnosis and prognosis, the relevance of SEM data at present remains quite limited, calling for the further exploration of clinical and diagnostic problems through correlative techniques.

Digestive System↗
PubMed1984

Morphological differences in the response of mouse small intestine to radiobiologically equivalent doses of X and neutron irradiation.

A scale has been developed to describe the effects of radiation on small intestinal villi. The scale has been used to compare the damage done to the villi in the period 0-5 days after irradiation by X-irradiation or neutron irradiation, using 10 Gy X-rays and 5 Gy neutrons, doses which are radiobiologically equivalent when assessed by the microcolony assay method. Use of the scale indicates that the damage done to the villi by neutrons is greater than that produced by X-rays. This has implications for the interpretation of radiobiological equivalent doses (R.B.E.). Resin light microscopy and transmission electron microscopy (T.E.M.) have also been used to examine small intestinal damage after 10 Gy X-irradiation and 5 Gy neutron irradiation. Differences include variations in crypt shape, mitotic activity and the proportion of crypts which are heavily parasitised. As well as the differences in villous shape which have been reflected in the different values on the scoring system, there are also variations in the response of the constituent cells of the epithelial compartment of the villi. In general, the effect of the neutron irradiation is more severe than that of the X-rays, particularly as would be suggested by a simple quantitation of crypt regeneration.

Animals↗
PubMed1983

Effect of bile salt perfusion and intraduct pressure on ionic flux and mucosal ultrastructure in the pancreatic duct of the cat.

Net ionic flux and mucosal ultrastructure were examined following perfusion of the cat pancreatic duct with bicarbonate or sodium taurocholate solutions (5-40 mM). Taurocholate perfusion increased net Cl- gain, net HCO3- loss and net K+ gain and was associated with significant widening of lateral intercellular spaces and increased complexity of intercellular labyrinths. Increased perfusion pressure (30 mm Hg) did not affect flux or ultrastructure during perfusion with bicarbonate but increased net ion flux significantly during perfusion with 40 mM sodium taurocholate. Ultrastructural changes during perfusion of 40 mM taurocholate at increased pressure were not consistent but focal epithelial disruption and cell shedding were seen occasionally. The hypothesis is advanced that taurocholate perfusion triggers physiological transport mechanisms and may make the duct mucosa more vulnerable to other potentially harmful agents. The significance of these changes in the pathogenesis of acute pancreatitis in man remains uncertain and care must be exercised before extrapolating from observed net ion flux data in this animal model.

Animals↗
PubMed1983

Low temperature scanning electron microscope studies of mouse small intestine.

Etched frozen hydrated specimens of mouse small intestine have been examined with low temperature scanning electron microscopy as a preliminary to X-ray microanalysis. Recognizable images have been obtained of most of the known histological features of the gut. Nuclear and cytoplasmic details were often seen. Ice crystal damage was evident, although the degree of artefact depended on the cell type being examined and also varied from cell to cell or within cells. The same specimens were later examined with resin light microscopy and transmission electron microscopy. These two techniques confirmed that preservation was adequate for identification of cells and tissues, although cavities were seen, representing ice crystal damage. These preliminary results indicate that SEM of etched, frozen, hydrated specimens provides adequate identification of cellular detail to allow further work using X-ray microanalysis to be carried out.

Animals↗
PubMed1983

Damage to the surface of the small intestinal villus: an objective scale of assessment of the effects of single and fractionated radiation doses.

Scanning electron microscopy has been used to compare damage to mouse small intestinal mucosa after irradiation with different doses of photons and neutrons. Various stages of the collapse of villous structure seen after radiation include the production of conical and rudimentary villi and a flattened mucosa. A scale is proposed to relate radiation to villous damage. Points from this scale are taken to produce comparative ratios for equivalent damage produced by different radiation conditions. RBE values are quoted for neutron. X and gamma radiation given as single or fractionated irradiation doses and as whole or partial body irradiation. The relationship between the stroma in intravillous pegs and that of the pericryptal compartment is explored.

Animals↗
PubMed1982

Scanning electron microscopy.

The technology of scanning electron microscopy (SEM) is described in brief. Its application to the study of cell and tissue structure is demonstrated and the evolution of the concept of "topographical histology" is discussed. Some current literature on the application of SEM is reviewed under the headings of experimental pathology and human pathology. While SEM has become an indispensable technique for the experimental morphologist, its application to diagnostic pathology and cytology is still at an early exploratory stage.

Animals↗
PubMed1982

Scanning and transmission electron microscopy of the damage to small intestinal mucosa following X irradiation or hyperthermia.

Scanning and transmission electron microscopy (S.E.M. and T.E.M.) and resin histology have been used to investigate the effects on mouse small intestinal villi of heating at 43 degrees C for 20 minutes and of irradiation with 10 Gy X-rays. Damage after irradiation included conical villi and giant cells. Damage after heating included the production of conical and rudimentary villi and the stacking of enterocytes. Individual cells showed signs of abnormalities in their cell membranes, nuclei and cytoplasmic components. The differences in the response after irradiation and hyperthermia are linked to the fact that heating has a primary effect on villous structure, whereas irradiation mainly affects the proliferative pool of crypt cells.

Animals↗
PubMed1981

Scanning electron microscopy, autolysis, and irradiation as techniques for studying small intestinal morphology.

Examination of autolysed control mouse small intestine using scanning electron microscopy has revealed details of the connective tissue components of the mucosa. The cores of the villi are seen collapsed across the intervillous basin. Crypts of Lieberkuhn are seen as tubular channels stretching down from the intervillous basin. Sometimes the crypts are split in two by a connective tissue septum. The mouths of the crypts of Lieberkuhn are, in general, arranged in double rows between the single rows of villi. The ratio of number of crypts to numbers of villi was calculated as 5.01:1. This is close to the figure of 4.53:1, as quoted by Smith & Jarvis (1980) who used differential interference contrast microscopy to investigate the crypt to villus ratio. After radiation, the severe drop in the number of crypt mouths can be clearly seen by the combination of autolysis and scanning electron microscopy: the rows of crypt mouths between the villi have been lost, and many crypt mouths have been occluded by stromal tissue. The arrangement of the crypt mouths and the observation of mucosal abnormalities after irradiation have led to the postulation that cells leaving the crypt mouths move in a spiral manner towards and then up the villous surface: this postulated movement might imply an asymmetry in some properties of enterocytes. The use of scanning electron microscopy in conjugation with autolysis and irradiation has thus forced a critical re-examination of the relationships between crypts and villi.

Animals↗
PubMed1981

Multinucleate giant enterocytes in small intestinal villi after irradiation.

Scanning electron microscopy of the small intestine of the mouse 5 days after X- or neutron irradiation has revealed the formation of giant cells on the villus surface. Correlative light microscopy and transmission electron microscopy have shown that these giant cells are syncytial in nature. Characteristic features of lipid inclusions and apical microvilli suggest tha these syncytia are giant enterocytes. It has also been shown that these giant cells are in contact with the connective tissue core of the villus and have a close contact with the normal enterocytes, thus maintaining mucosal integrity. It is postulated that radiation damage has caused incomplete separation during mitosis and that attempted division occurs outside the crypts of Lieberkuhn.

Animals↗
PubMed1981

Scanning electron microscopy of tissue response to irradiation.

Much of the work done so far with scanning electron microscopy to explore tissue damage by irradiation has used mouse or rat small intestine as a model. Variations are described in the response of this model with time after radiation, with dosage, with the method of irradiation and with the type of radiation. In the mouse, damage is expressed as a progression from normal finger shaped villi through the following stages: lateral villous collapse, vertical villous collapse, conical villi, rudimentary villi and flat mucosa, sometimes with ulceration. The presence of giant enterocytes is described and their relationship to time after radiation is discussed. The response of other organs is compared with that of small intestine and different methods are discussed for the assessment of the surface effects of radiation. A new method is proposed for assessing the relative effects of different types of radiation by defining the dosages required to produce two clearly recognizable effects, vertical villous collapse and conical villi. In conclusion, radiation damage is compared with other mucosal lesions and the areas most needing further work are highlighted.

Animals↗
PubMed1981

The ultrastructure of some gastrointestinal lesions in experimental animals and man.

This has been a brief and necessarily selective review, covering only a few of the numerous experimental and diagnostic uses of electron microscopy in the field of gastroenterology. The roles of experimentalist and diagnostician have emerged in a kind of counterpoint. We have identified the contrasting themes of the controllable laboratory experiment and the uncontrollable experiment of disease; of the three-dimensional image of the surface scanning technique and the two-dimensional world of the thin section. There is harmony, also, in our common concern for morphology and our shared interest in any structural change. Altered morphology, whether in tissue architecture or cellular organisation, may offer a key to the better understanding of altered function. In the future, both the experimental and the diagnostic electron microscopist will come to rely more on correlative procedures, such as the re-processing of specimens for a second look with a different technique. Functional dividends are promised to the morphologist by advances in detector technology and associated techniques such as analytical microscopy. It remains to be seen whether medical benefits will accrue, in terms of a more precise diagnosis or a more effective prognosis in individual cases of human gastrointestinal disease.

Animals↗
PubMed1981

Surface damage in the small intestine of the mouse after X - or neutron irradiation.

Damage after X-irradiation includes lateral villous collapse, progressing after 3 - 5 days to villi which sometimes show signs of vertical collapse. After neutron irradiation vertical villous collapse is established earlier, with less swelling of villous tips. It seems, therefore, that at radiobiologically equivalent doses, neutron and X-irradiation produce different levels of surface damage, with neutron irradiation being the more destructive. Early villous tip damage may perhaps be due to disruption of susceptible cells already at the extrusion zone, or to stromal damage.

Animals↗
PubMed1980

SEM in service pathology: a review of its potential role.

New medical technology evolves through distinct phases. Initial technical proving is followed by a phase of detailed data recording, often with no detailed attempt to fill any specific service requirements. Next an attempt is made to establish correlations with other techniques and results, with a view to defining any unique attributes of the technology in particular fields. Detailed service-related applications are then worked out, but the final adoption of new instrumentation into clinical practice depends not only on the success of its technical performance, but also on its cost-effectiveness. This paper reviews studies of clinically-derived material from the viewpoint of a U.K. diagnostic pathologist. Detailed comparisons are drawn between the evolution of SEM on the one hand and of LM and CTEM on the other. An attempt is made to identify areas of practice in which SEM might make the greatest impact in the foreseeable future. It is proposed that paraffin-embedded tissue in pathology back files may provide a valuable source of investigative material for diagnostic SEM.

Animals↗
PubMed1979

Lack of correlation between villus and crypt damage in irradiated mouse intestine.

It has been observed that scanning electron microscopy is a more sensitive indicator of mucosal damage at low radiation dose levels than conventional quantitative crypt counting techniques. Three different fractionation schedules were subjected to investigation by both of these methods to try to elucidate some features of irradiation damage to the whole of the intestinal mucosa, at dose levels commonly used in clinical practice. Despite variations in the qualitative observations, there was a marked difference in two of the schedules between damage expressed as crypt counts and that described by the qualitative techniques. In the first case high crypt numbers were associated with severe mucosal damage, whereas the second schedule produced a reduced crypt count in association with low damage to the surface mucosa. A third schedule produced results in which there was a general agreement between low crypt numbers and considerable surface mucosal damage. However, observations were made of mucosal formations not previously seen on damaged mucosal surfaces. These resembled the appearance normally associated with the gut of patients suffering from coeliac disease. Variations in the qualitative observations were seen in all the schedules so that their interpretation in terms of perturbation of cellular kinetics is difficult.

Animals↗