The effects of static 3.0 T and 0.5 T magnetic fields and the echo-planar imaging experiment at 0.5 T on E. coli.

Various mutant strains of Escherichia coli have been exposed to a homogeneous static magnetic field of either 0.5 T or 3.0 T and to the time varying magnetic fields found in echo-planar imaging experiments. No evidence of increased DNA damage was detected, even with bacterial strains disabled for DNA repair.

Morphological aspects of chromaffin tissue: the differential fixation of adrenaline and noradrenaline.

The morphological aspects of chromaffin tissue are reviewed, based mainly on our studies on the mouse adrenal gland. Particular attention was focused on the differential fixation of adrenaline and noradrenaline, and on the uptake and storage of [3H]dopa, [3H]dopamine and related substances in the adrenaline-storing (A) and noradrenaline-storing (NA) cells. Scanning electron microscopy combined with the NaOH-maceration method was useful for demonstrating the 3-dimensional organisation of nerve terminals, chromaffin cells, glial elements and vascular elements. In transmission electron microscopy, 3 types of chromaffin cell were distinguished. They were A, NA and SGC (small granule chromaffin) cells. After glutaraldehyde fixation followed by postosmication, A cell granules showed lower electron density, whereas NA cell granules were solid and dark. This difference in appearance between A and NA cells was first explained by the hypothesis that, after glutaraldehyde fixation, most of the adrenaline dissolved, whereas noradrenaline was precipitated in situ. Later, this hypothesis was supported by a series of autoradiographic and radioisotopic assay studies using [3H]dopa, [3H]dopamine and related substances; when [3H]adrenaline occurred, radioactivity in A cells mostly disappeared in the specimen, whereas that in the NA cells remained. At 15-60 min after an i.p. injection of [3H]dopa or [3H]dopamine, the concentration of radioactivity in A cells was higher than that in NA cells. However, in hypophysectomised mice, the radioactivity was low and evenly distributed in these 2 types of chromaffin cell. It was deduced that the carrier activities for extracellular dopa and dopamine were made greater in the A cells than in the NA cells by the pituitary gland. The hypophysectomy effects were restored by i.p. administration of ACTH.

The innervation of the adrenal gland. IV. The source of pre- and postganglionic nerve fibres to the guinea-pig adrenal gland.

The pre- and postganglionic sympathetic innervation of the guinea-pig adrenal medulla was investigated using the retrograde neuronal tracers Fast Blue and WGA-HRP. Labelled preganglionic cell bodies were located in the intermediolateral horn of spinal segments T3-L2, the majority (73.9%) were found between T6-T12 representing 70.2% of the total number of labelled cells; the segment T10 contained the largest number of labelled neurons. Labelled postganglionic cell bodies were found in the paravertebral ganglia between vertebral levels T3-T12 (representing 22.6% of the total labelled neurons), the maximum number was found at T10. In addition, labelled neurons were found in the suprarenal ganglion (representing 7.2%). No labelled cells were found in the coeliac ganglia. The labelled neurons were found ipsilateral to the site of injection into the left adrenal gland. It is concluded that the guinea-pig adrenal gland receives both a pre- and a significant postganglionic sympathetic innervation. The destination of these nerve fibres within the adrenal gland has yet to be determined.

The innervation of the adrenal gland. IV. Innervation of the rat adrenal medulla from birth to old age. A descriptive and quantitative morphometric and biochemical study of the innervation of chromaffin cells and adrenal medullary neurons in Wistar rats.

The innervation of the adrenal medulla has been investigated in normal Wistar rats from birth to old age and ultrastructural findings compared with biochemical markers of the cholinergic innervation of the adrenal gland and catecholamine storage. Morphological evidence of the immaturity of the innervation during the first postnatal week is provided and using quantitative morphometry the innervation of chromaffin cells is shown to reach a mean total of 5.4 synapses per chromaffin cell during the period 26 days to 12 weeks of age. The variation in contents of synaptic profiles is discussed in the light of recent work that demonstrates a major sensory as well as visceral efferent innervation of the gland. Adrenal medullary neurons usually occur in closely packed groups, intimately associated with Schwann cells. Axodendritic and axosomatic synapses on these neurons are described and the likely origin of axonal processes innervating the neurons discussed. In old age the density of innervation remains the same as in young adult animals even though the medulla shows evidence of hyperplasia and hypertrophy of individual chromaffin cells.

Estimation of lung volume in infants by echo planar imaging and total body plethysmography.

Echo planar imaging (an extremely fast method of magnetic resonance imaging) was used to measure lung volume in a group of nine infants, all of whom had had respiratory problems. The mean echo planar imaging estimate of total lung volume was 44 +/- 9 ml/kg. In each case the right lung was larger than the left (ratio 52.8:47.2%). The mean thoracic gas volume was 36 +/- 8 ml/kg. The entire sequence of images of the thorax (about 400) takes five minutes to complete, infants require no sedation, and there are no side effects.

Localisation of chromogranin A and B, met-enkephalin-arg6-gly7-leu8 and PGP9.5-like immunoreactivity in the developing and adult rat adrenal medulla and extra-adrenal chromaffin tissue.

The localisation of chromogranins A and B, met-enkephalin-arg6-gly7-leu8 (met-enk 8) and protein gene product 9.5 (PGP 9.5) in the adrenal medulla and extra-adrenal chromaffin tissue has been studied in the developing rat by immunogold-silver staining. In the adult rat adrenal the cytoplasm of all medullary chromaffin cells showed a positive response with chromogranin A and B; in each case occasional groups of cells with a low reactivity that may have been NA cells were seen. Chromogranin A was first detected in adrenal medullary and extra-adrenal chromaffin cells at 18 days of gestation whilst chromogranin B was not detected in animals younger than 7 days. In 15 days old animals the adrenal medullary response to A and B was of the same intensity as that seen in the adult. Less than 1% of adult medullary chromaffin cells were responsive to met-enk 8 staining and medullary cells were unreactive in the fetus, with only extra-adrenal chromaffin tissue responding prenatally. During the first postnatal week immunoreactive cells appeared in the adrenal medulla in considerably greater proportions than in the adult gland. In contrast, positively stained nerve terminals associated with chromaffin cells and abundant in the adult adrenal were not detected during the first week of life. Immunoreactive nerve terminals were first seen early in the second week of life at a time when positive chromaffin cells were becoming less common. PGP 9.5 was located in all chromaffin cells of the adult adrenal and was readily detected in chromaffin cells in the adrenal and in extra-adrenal locations of the earliest stage examined (E16). Our findings suggest that the ontogenesis of the chromogranin-like immunostaining reflects the maturation of chromaffin granules and the PGP 9.5 immunostaining detected a protein common to cells of neuronal origin and expressed at an early stage of differentiation. The reciprocal relationship between the presence of enkephalins in chromaffin cells and in their presynaptic terminals merits further investigation.

The innervation of the adrenal gland. III. Vagal innervation.

Following the injection of 3-5 microliters of horseradish peroxidase or Fast Blue into the left adrenal medulla, labelling of neurons in the vagal sensory ganglia of rats and guinea-pigs has been demonstrated in all cases. Labelled vagal motor neurons with cell bodies in the dorsal motor nucleus of the vagi have been demonstrated in all cases in the guinea-pig and occasionally in the rat. The possible reasons for this variation are discussed. In both rat and guinea-pig the motor and sensory vagal innervation of the rat adrenal is derived from bilaterally situated cell bodies and the proportion of innervation derived from the two sides is approximately equal but with a slight ipsilateral predominance.

Gastrointestinal tract: dynamic MR studies with echo-planar imaging.

Gastrointestinal (GI) tract motility was depicted in four human volunteers with the high-speed echo-planar imaging technique: modulus blipped echo-planar single-pulse technique (MBEST). Data acquisition times of 64 and 128 msec obviate image degradation due to motion without the need for gut paralysis and allow imaging of the GI tract in real time. Peristaltic patterns of the gastric antrum and proximal small intestine were depicted for fasting and fed subjects and subjects in whom peristalsis had been pharmacologically stimulated. The potential for quantitative measurements of GI tract motion with this new technique was demonstrated.

The natural history of the chromaffin cell--twenty-five years on the beginning.

Aspects of the functional anatomy of the chromaffin cell since 1950 are reviewed--beginning with the identification of noradrenaline in the adrenal gland and the first descriptions of distinct adrenaline- and noradrenaline-storing cells. Reference is made to the identification of specific proteins and neuropeptides in chromaffin cells, of the storage of endogenous and exogenous amines including 5HT. The influence of corticosteroids and nerve growth factor on cell phenotypes is discussed and a plea made for the specific use of descriptive terms with due regard to historical and functional context: this relating particularly to the appropriate labelling of elements as SIF cells. The review includes reference to recent quantitative studies on the rat adrenal medulla and adrenal chromaffin cells and to the innervation of the adrenal medulla by pre- and postganglionic sympathetic neurons, by spinal afferent neurons and by sensory and motor vagal fibers.

Immunohistochemical and biochemical analysis of the development of the noradrenaline- and adrenaline-storing cells in the adrenal medulla of the rat and pig.

The development of the noradrenaline (NA)- and adrenaline (A)-storing cells was examined in the adrenal gland of pre- and postnatal rats and pigs. Cryostat sections were immunostained with antibodies to NA and A. Amine levels were estimated in homogenates of adrenals by ion-pair reversed-phase liquid chromatography with electrochemical detection. 1. In adult animals separate NA- and A-storing cells were found. In the rat A-cells comprised about 80% of the parenchyma of the adrenal medulla. NA-cells, the remaining 20%, were randomly arranged in clusters. In the pig, in contrast, the A- and NA-storing cells were equally distributed, with spherical clusters of NA-cells were surrounded by A-cells. 2. In the earliest developmental stages examined (16th day of gestation in the rat, and 42nd day in the pig) the adrenals only contained NA-immunoreactive cells. In the rat separate NA- and A-storing cells were first noticed 2 or 3 days after birth, whereas in the pig separated cells were already present at the 56th prenatal day (full term at 114th day). 3. In both rat and pig adrenals dopamine (DA), NA and A increased in amount rapidly during development. In the rat this change mainly took place after birth (an increase of 13 times from the 17th day of gestation, and a 100-fold increase from birth to adult age). In porcine adrenal increase of the total amount of amines mainly occurred before birth (200 times between the 42nd day of gestation and birth, whereas only 10 times after birth). 4. In both species DA-levels remained low during pre- and postnatal development. On the contrary, the relative concentrations of NA decreased while that of A increased correspondingly. Again, species differences were noticed: in the rat NA decreased from 90% (17th day of gestation) via 35% (just before birth) to 20% at adult age, while the porcine adrenal showed a more gradual decrease, i.e., from 90% (42nd day of gestation) to 70% (birth) ending up with 50% in the adult stage. 5. The immunohistochemical and biochemical data indicate that, in rat adrenal medulla three phases of development can be distinguished. First, up to the 18th day of gestation, medullary cells synthesize and store only NA. Second, from the 18th day to 2 or 3 days after birth, NA and A are synthesized and stored in a single cell type ("mixed cell type"), and third, NA and A are localized in separate cell types.(ABSTRACT TRUNCATED AT 400 WORDS)

The development and maturation of adrenal medullary chromaffin cells of the rat in vivo: a descriptive and quantitative study.

A descriptive account and morphometric study of the adrenal medulla and adrenal chromaffin cells of Wistar rats aged from birth to 22 months is presented. Distinct adrenaline and noradrenaline-storing types of chromaffin cells are first identified in 4-day-old animals, prior to that time individual cells contain both adrenaline- and noradrenaline-storing granules. Primitive sympathetic cells and phaeochromoblasts occurs up to 2 days postnatally. Mitotic figures occur in chromaffin cells of a maturity and appearance appropriate to age and most frequently in adrenaline-storing cells. The adrenal medulla continues to increase in volume throughout the period and chromaffin cells increase in number and in some cases volume. There is a corresponding increase in neuronal elements. In 22-month-old rats individual cells or groups of chromaffin cells show evidence of hypertrophy and changes in cytoplasmic organelles, in particular lysosomes, rough endoplasmic reticulum and storage granules and vesicles. Some hypertrophied chromaffin cells contain a heterogeneous population of granules suggesting a degree of functional plasticity in some cells in aged rats.

Whole-body echo-planar MR imaging at 0.5 T.

The ultra-high-speed echo-planar imaging technique produces instant snapshot magnetic resonance images in exposure times ranging from approximately 10 to 100 msec. A particular variant, the modulus blipped echo-planar single-pulse technique (MBEST), possesses two advantages: First, it makes the technique experimentally more robust; second, it introduces inherent T2 weighting in the images. The authors have used MBEST with an exposure time of 64 msec to explore the potential range of clinical applications in a series of normal volunteers. Applications include evaluation of the heart, renal function, and gastrointestinal tract. All images were obtained with proton resonances at 22 MHz.

The innervation of the adrenal gland. II. The source of spinal afferent nerve fibres to the guinea-pig adrenal gland.

The sensory innervation of the guinea-pig adrenal medulla was studied using the fluorescent retrograde tracer Fast Blue. Labelled neurons were found in the dorsal root ganglia at segments T3-L2, the greatest contribution arising from T10 representing 15.2% of the total number of labelled cells. Labelling was ipsilateral to the site of injection of tracer into the adrenal medulla and the labelled neurons ranged in size between 6 and 36 microns. The overall size distribution fell into two groups of between 6 and 15 microns and of between 18 and 36 microns. Presumed sensory nerve endings were found in the adrenal medulla associated with chromaffin cells and vascular elements. The nerve endings were ovoid to spherical and densely packed with mitochondria. It is concluded that events occurring in the guinea-pig adrenal medulla, and possibly cortex, are monitored by sensory nerve terminals whose cell bodies lie within dorsal root ganglia. The exact distribution of the sensory nerve terminals within the adrenal gland is yet to be determined.

Improvements in snap-shot nuclear magnetic resonance imaging.

New variants of the ultra-high-speed echo-planar imaging technique have been used to obtain snap-shot images of adult patients and volunteers at 0.1 T. Modified pulsed-gradient sequences together with non-linear signal sampling and activity screened gradients have greatly improved the image quality obtainable by single-shot methods. A particular variant, modulus blipped echo-planar single-pulse technique (MBEST), although slightly slower than the blipped echo-planar single-pulse technique (BEST), is experimentally more robust and incorporates intrinsic T2 weighting. An account of these improvements together with some experimental results is presented.

The innervation of the adrenal gland. I. The source of pre- and postganglionic nerve fibres to the rat adrenal gland.

The sympathetic innervation of the rat adrenal medulla was studied using the fluorescent tracer Fast Blue. Labelled preganglionic cell bodies were located in the intermediolateral horn of the spinal cord at segments T1 and L1; the greatest number was found in T9. The ILp nucleus contained 95%, the ILf nucleus 4%, and the IC nucleus 1% of the total number of labelled preganglionic cells. Labelled postganglionic cell bodies were found in the sympathetic ganglia at levels T4 and T12; the maximum number were located in ganglia at T9 and T10. In addition, labelled cells were found in the suprarenal ganglion. No labelled cells were found in the ganglia of the coeliac plexus. The number of labelled preganglionic cells in the spinal cord accounted for 88.6%, the labelled cells in the sympathetic chain for 8.7% and those in the suprarenal ganglia for 2.7% of the total number of labelled cells found. The detailed distribution within the gland of postganglionic axons has yet to be determined, but it is thought that some are destined for the adrenal cortex.

Blood flow to the adrenal gland of the rat: its distribution between the cortex and the medulla before and after haemorrhage.

This study has investigated the flow of blood to the adrenal gland of the anaesthetised rat under basal conditions and after the induction of haemorrhagic hypotension. By combining the use of radioactive microspheres with subsequent serial sectioning we have been able not only to assess total adrenal blood flow but also to determine its distribution within the gland. In normal anaesthetised rats approximately 7.4% of the adrenal blood flow passes directly to the medulla, the remainder being distributed to the cortex. This proportional flow is also observed immediately after withdrawal of sufficient venous blood to cause a 32% reduction in systolic blood pressure. However, the latter procedure results in a 52% increase in the total blood flow to the gland despite the associated fall in cardiac output.

A quantitative analysis of rat adrenal chromaffin tissue: morphometric analysis at tissue and cellular level correlated with catecholamine content.

A morphometric analysis of normal Wistar rat adrenal medulla following perfusion fixation and Araldite embedding, was correlated with catecholamine levels on fresh tissue, measured by high-performance liquid chromatography. The mean volume of whole adrenal is 13.2 mm3 and the mean medullary volume 1.3 mm3. Volume density estimates showed that the medulla is composed of 63% chromaffin tissue with an adrenaline to noradrenaline storing cell ratio of 4.4:1. The vasculature occupies 20%, neuronal tissue 5% and interstitial tissues 12% of the medulla. A comparison was made of cell volumes, cell numbers and volume and surface density estimates of cytoplasmic organelles in adrenaline and noradrenaline storing cells. The mean cell volume of adrenaline storing cells at 1300 micron3 is larger than that of noradrenaline storing cells at 980 micron3. A single adrenal medulla contains 4.4-5.7 X 10(5) adrenaline cells and 1.5-1.9 X 10(5) noradrenaline cells. Chromaffin granules account for approximately 30% of the volume of the cytoplasm; the numerical density of granules at different sites in the cell was calculated for adrenaline cells. The volume density of mitochondria (4%) and the surface density of mitochondrial membranes (the ratio of outer to inner membrane being approximately 1:2.3) were similar in both cell types. Rough endoplasmic reticulum was the only organelle to show a significant difference in volume and surface density between the two cell types. Adrenaline storing cells have stacks of rough endoplasmic reticulum which have two to three times the surface and volume densities of that found diffusely scattered throughout noradrenaline cells. The adrenaline content of an adrenaline storing cell is 0.14 X 10(-6) microM and that of a granule 3.0 X 10(-12) or 3.8 X 10(-12) mumoles depending on the method of calculation. The noradrenaline content of noradrenaline storing cells can only be calculated on the assumption that all noradrenaline is stored in this cell type though it is likely that some is contained within adrenaline cells. Based on this assumption the noradrenaline content is 0.17 X 10(-6) mumoles per cell and 5 X 10(-12) mumoles per granule. The present study provides baseline morphometric data on the rat adrenal medulla at tissue and cellular level correlated with amine levels in adrenaline and noradrenaline storing cells and granules.

Measurement of T1 by echo-planar imaging and the construction of computer-generated images.

The high-speed echo-planar imaging (EPI) technique is used to obtain rapid T1 and spin density measurements by a two-point method. It is shown that neglect of edge effects in the slice selection procedure leads to significant systematic errors in T1. T1 maps for two young patients, obtained at 4.0 MHz, are presented. The T1 and spin density values obtained are used to produce computer-generated images in inversion recovery simulations. These results demonstrate marked improvement in image contrast without paying the time penalty incurred in real experiments, thereby greatly increasing patient throughput potential.

Transectional echo planar imaging of the heart in cyanotic congenital heart disease.

Echo planar imaging is that form of magnetic resonance imaging which gives very short image acquisition times. The method has been used to produce images of the infant heart which are free of cardiorespiratory motion artefact, despite tachypnoea and tachycardia. EPI transections of the normal heart are compared with transections in truncus arteriosus, tetralogy of Fallot, right heart hypoplasia and transposition of the great arteries. The diagnosis of the cause of cyanosis in these infants was established by the noninvasive EPI method and validation of the findings may be found in transectional postmortem analyses reported in the literature.