Structure of the sensory innervation of the anal canal in the pig. A light- and electron-microscopical study

The sensory innervation of the anal canal of the pig was investigated by light and electron microscopy. The distribution of the different types of sensory nerve endings correlates with the histology of different zones: (1) After the rectal mucosa there was a zone lined with nonkeratinized stratified squamous epithelium. (2) A middle zone was lined with keratinized stratified squamous epithelium. Here the dermis already showed a papillary and reticular layer. (3) The last zone showed hairy skin with a high hair density. The following nerve endings were found: Free nerve endings reached the stratum superficiale in nonkeratinized squamous epithelium and the stratum granulosum in the keratinized squamous epithelium. Dermal free nerve endings were found in all zones near the epithelium and two different types were identified as those derived from C-fibers and those from A-delta-fibers. Merkel nerve endings showed different features depending on their location. Few Merkel-like cells were found in the epithelium of the anal crypts. Typical Merkel Tastscheiben were located at the base of epithelial ridges or pegs in zones 2 and 3. The number of Merkel cells varied up to 200. The myelinated afferent fiber supplied 10-15 Merkel cells. Merkel cells were also found regularly in the outermost layer of the external rooth sheath of hair follicles at about the same level as perifollicular nerve endings. Lamellated corpuscles were found in the dermis of all zones except the cranial part of zone 1, where the anal crypts are located. Generally they consisted of a central nerve terminal which may be branched. Each terminal was surrounded by an inner core of concentrically arranged lamellae of the terminal Schwann cell and one or several inner cores were included in a capsule of perineural cells. The size of the corpuscle, the regularity of the inner core and the number of capsular layers depended on the location of the corpuscle.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of pregnancy on the extrinsic innervation of the guinea pig uterus. A histochemical, immunohistochemical and ultrastructural study

Summary The extrinsic innervation of the guinea pig uterus was studied by immunohistochemical, ultrastructural and enzyme histochemical methods.The extrinsic innervation was organized in two major ways. One consisted of nerve trunks and non-varicose nerve fibres running in the suspensory ligament, and the other of a plexus of varicose nerve fibres surrounding vessels, and non-vessel-related non-varicose nerve fibres in the mesouterus. The use of different neuronal and Schwann cell markers showed that the extrinsic innervation was predominantly adrenergic and contained only few peptidergic nerves. Acetylcholinesterase-positive (cholinergic) nerves were only found around the uterine artery.In late pregnancy, the extrinsic nerves of the mesouterus adjacent to foetus-containing uterine horns underwent pronounced degenerative changes comprising both Schwann cell and axonal structures. In comparison, no changes were found in extrinsic nerves of mesouteri adjacent to non-foetus-bearing uterine horns or in extrinsic nerves in the suspensory ligaments. Further, chemical sympathectomy produced axonal degeneration but no changes in the Schwann cells.In conclusion, the pregnancy-induced nerve degeneration is of a very special type different from that following chemical sympathectomy and represents a local phenomenon related to the conceptus. Hypothetically, this could be of importance for counteracting disturbances in placental blood flow.     

Effect of starvation on somatostatin content of pancreas and gastrointestinal tract of the guinea pig

The effect of 48-hour starvation on the somatostatin contents of the pancreas and gastrointestinal tract was studied in the guinea pig. Somatostatin contents were higher in various portions of the stomach and pancreas of fed guinea pigs than in fed rats and unchanged after 48-hour starvation, in spite of the decreased blood glucose level. These results suggest that somatostatin may not play the same physiological role in nutrient homeostasis of guinea pigs as it does in other species.     

Computer-assisted morphometric study of the innervation of the guinea pig heart

Summary A computer-assisted method is introduced for the morphometric analysis of immunoreactive markers of the innervation of the heart, such as synaptophysin, neuropeptide Y (NPY), neurotensin (NT), substance P (SP), and calcitonin gene-related peptide (CGRP). Video images of stained sections were digitalized and the area density (AD) of the immunoreactive structures was measured by discrimination for grey levels within the myocardium of the right atrium, the perivascular region of epicardial arteries, and the trunk of the bundle of His. Synaptophysin immunoreactivity (IR), which served as a marker for presynaptic vesicles, indicated a dense innervation of the conductive system (AD 1.5241). Marked differences in the pattern of distribution were found between the neuropeptides. The AD of NPY-IR (0.5073) and SP-IR (0.1352) was highest in the perivascular tissue, while NT-IR (0.1628) and CGRP-IR (0.5161) exhibited maximal values in the bundle of His. The computer-assisted morphometric measurement of the AD of immunoreactive markers is suggested to be a suitable method for quantitative studies of the innervation of the heart under normal and experimental conditions.Dedicated to Professor Dr. T. H. Schiebler on the occasion of his 65th birthday     

Computer-assisted morphometric study of the innervation of the guinea pig heart

A computer-assisted method is introduced for the morphometric analysis of immunoreactive markers of the innervation of the heart, such as synaptophysin, neuropeptide Y (NPY), neurotensin (NT), substance P (SP), and calcitonin gene-related peptide (CGRP). Video images of stained sections were digitalized and the area density (AD) of the immunoreactive structures was measured by discrimination for grey levels within the myocardium of the right atrium, the perivascular region of epicardial arteries, and the trunk of the bundle of His. Synaptophysin immunoreactivity (IR), which served as a marker for presynaptic vesicles, indicated a dense innervation of the conductive system (AD 1.5241). Marked differences in the pattern of distribution were found between the neuropeptides. The AD of NPY-IR (0.5073) and SP-IR (0.1352) was highest in the perivascular tissue, while NT-IR (0.1628) and CGRP-IR (0.5161) exhibited maximal values in the bundle of His. The computer-assisted morphometric measurement of the AD of immunoreactive markers is suggested to be a suitable method for quantitative studies of the innervation of the heart under normal and experimental conditions.     

Taste receptors in the gastrointestinal tract. V. Acid sensing in the gastrointestinal tract

Luminal acidity is a physiological challenge in the foregut, and acidosis can occur throughout the gastrointestinal tract as a result of inflammation or ischemia. These conditions are surveyed by an elaborate network of acid-governed mechanisms to maintain homeostasis. Deviations from physiological values of extracellular pH are monitored by multiple acid sensors expressed by epithelial cells and sensory neurons. Acid-sensing ion channels are activated by moderate acidification, whereas transient receptor potential ion channels of the vanilloid subtype are gated by severe acidosis. Some ionotropic purinoceptor ion channels and two-pore domain background K(+) channels are also sensitive to alterations of extracellular pH.     

Culture-independent analysis of gut bacteria: the pig gastrointestinal tract microbiota revisited

The phylogenetic diversity of the intestinal bacterial community in pigs was studied by comparative 16S ribosomal DNA (rDNA) sequence analysis. Samples were collected from a total of 24 pigs representing a variety of diets, ages, and herd health status. A library comprising 4,270 cloned 16S rDNA sequences obtained directly by PCR from 52 samples of either the ileum, the cecum, or the colon was constructed. In total, 375 phylotypes were identified using a 97% similarity criterion. Three hundred nine of the phylotypes (83%) had a <97% sequence similarity to any sequences in the database and may represent yet-uncharacterized bacterial genera or species. The phylotypes were affiliated with 13 major phylogenetic lineages. Three hundred four phylotypes (81%) belonged to the low-G+C gram-positive division, and 42 phylotypes (11.2%) were affiliated with the Bacteroides and Prevotella group. Four clusters of phylotypes branching off deeply within the low-G+C gram-positive bacteria and one in the Mycoplasma without any cultured representatives were found. The coverage of all the samples was 97.2%. The relative abundance of the clones approximated a lognormal distribution; however, the phylotypes detected and their abundance varied between two libraries from the same sample. The results document that the intestinal microbial community is very complex and that the majority of the bacterial species colonizing the gastrointestinal tract in pigs have not been characterized.     

A qualitative and quantitative study of subfractions of the histone H10 in various mammalian tissues.

The histone H10 was examined from seven mammalian species. All tissues were shown to contain two subfractions of H10, except for those of rabbit, in which little or no H10 was found. The subfraction composition was compared quantitatively in different mouse and hamster tissues, with the conclusion that this composition is tissue-specific. It is proposed that the wide occurrence of H10, together with the evidence of no more or less than two subfractions wherever it occurs, and the tissue-specific nature of the ratio of subfractions, signify that these two subfractions have specific individual functions.     

Comparative studies on intrinsic factor and cobalophilin in different parts of the gastrointestinal tract of the pig

The vitamin B₁₂ binders in the pig pyloric mucosa gastric and intestinal juice from the upper gastrointestinal tract were fractionated into only two molecular forms, classified as intrinsic factor and cobalophilin. The unsaturated vitamin B₁₂-binding power due to cobalophilin was lower in the intestinal than in the gastric juice. Electrofocusing revealed that intrinsic factor and cobalophilin in the intestinal juice contained more of the `neutral'-type isoproteins, and the suggestion is made that this is due to enzyme activity. The gastric-juice intrinsic factor contained more acidic isoproteins, which supports the hypothesis that carbohydrate is added on to the polypeptide chain of this protein before it is secreted into gastric juice. The gastric- and intestinal-juice cobalophilins, studied also by electrofocusing, differed from that of pyloric mucosa and they appeared to be of salivary origin. With regard to molecular dimensions there was no significant difference between the intrinsic factors and cobalophilins from all sources studied. All cobalophilins had molecular weights by the formula of Svedberg of approx. 92500, Stokes radii of 4.62nm and sedimentation coefficients of 5.15S. The corresponding values for the intrinsic factors were 63600, 3.57nm and 4.38S. In addition, the intrinsic factors exhibited similar avidities for binding to the solubilized ileal intrinsic-factor receptor. Also the intrinsic factors and cobalophilins, irrespective of their source, bound to the analogous specific xenoantibodies with the same avidity. The present results demonstrate that intrinsic factor remains practically unaltered during its passage through the proximal intestine and render unlikely the speculations made about the presence of an endogenous binder for intrinsic factor as well as the existence of a `pancreatic intrinsic factor'. In addition, they are compatible with the theory that the interference by undegraded cobalophilin may be the reason for the abnormal vitamin B₁₂ absorption observed in patients with pancreatic insufficiency.     

Effect of CCK-8 on myoelectrical activity of the gastrointestinal tract in the conscious miniature pig

In conscious miniature pigs, with implanted electrodes in the wall of the antrum pylori, duodenum, jejunum, and ileum, the influence of IV infusions of CCK-8 (17.5 and 175 pM/kg/min) on gastrointestinal myoelectrical activity was measured. Although both doses under study induced a decrease in antral spike activity, only the higher dose resulted in an overall decrease in integrated myoelectrical activity. In the ileum both doses augmented spiking activity during the infusion, but inhibited electrical activity after the end of the infusion. No response was observed in the duodenum and jejunum. The experiments demonstrate the overall inhibitory effect of CCK-8 on antral electrical activity and its stimulatory influence on ileal smooth muscle.     

Chromogranin A in the human gastrointestinal tract: an immunocytochemical study with region-specific antibodies.

We studied the immunoreactivity of 12 different region-specific antibodies to the chromogranin A (CgA) molecule in the various neuroendocrine cell types of the human gastrointestinal (GI) tract by using double immunofluorescence techniques. These staining results were compared with others obtained with a commercial monoclonal CgA antibody (LK2H10). G (gastrin)-cells showed immunoreactivity to virtually all region-specific antibodies, but with varying frequency. Most intestinal EC (enterochromaffin)- and L (enteroglucagon)-cells were immunoreactive to the antibodies to the N-terminal and mid-portion of the CgA molecule, whereas the EC-cells in the stomach reacted with fewer region-specific antibodies. D (somatostatin)-cells reacted to the CgA 411-424 antibody and only occasionally showed immunoreactivity to the other CgA antibodies. A larger cytoplasmic area was stained with the antibodies to CgA 17-38 and 176-195 than with the other antibodies tested. These differences in staining pattern may reflect different cleavage of the CgA molecule in different cell types and at different regions of the GI tract.