Prenatal development of the human Brunner's glands.

The prenatal development of the human Brunner's glands has been investigated in 23 fetuses from the 10th week of gestation to full-term. At 12 weeks, a few cords of epithelial cells were seen budding from the duodenal mucosa immediately beyond the pyloric sphincter. They represent the initial stage of the development of Brunner's glands. At 16 weeks, Brunner's glands originated as simple tubular downgrowths from the bottoms of the most proximal crypts of the duodenum. The secretory products of the component cells of these primitive tubules contained periodic acid schiff (PAS) positive material which was largely supranuclear in position and resisted digestion by diastase. From 20 weeks to full term, the Brunner's glands developed in a progressive fashion starting in the proximal part of the duodenum near the pyloroduodenal junction. Further tubular downgrowths were added distally, leading to an increase in length of the glandular tissue. The gland showed an increase in size proximally due to elongation and branching of the tubules. At birth, the glandular cells of Brunner's glands resembled those of normal adult in structure and staining reactions. The PAS staining of the cells of the early developed glands (at 12 weeks) was as intense as those of the full-term. The secretory materials of the developed Brunner's glands showed negative reaction with Alcian blue (AB) at pH 2.5 at any stage of development. These results suggest that the mucin secreted by the developed Brunner's glands of human is neutral mucopolysaccharide in nature.

Segmental motor and sensory innervation of muscles in anterior leg compartment as revealed by retrograde transport of horseradish peroxidase.

Horseradish peroxidase (HRP) tracing technique was used to label and localize motor and sensory neurons innervating tibialis anterior, extensor hallucis longus and extensor digitorum longus muscles of the anterior leg compartment of the rat. The tibialis anterior sensory neurons were located in the ipsilateral L4 and L5 spinal ganglia. Cells of origin of tibialis anterior motor endings were also found in the ipsilateral ventral horn of the same cord segments as the labeled sensory ganglia. Extensor hallucis longus sensory neurons were located in L4 to L6 spinal ganglia, while its labeled motor neurons were located in L4 and L5 spinal cord segments. The motor neurons innervating the extensor digitorum longus muscle were located in L4 to L6 spinal cord segments; its sensory neurons were previously localized. All labeled motor and sensory neurons were present on the ipsilateral side. Almost all motoneurons innervating the 3 muscles were present in the dorsolateral nucleus of the ventral horn.

Anatomical variations in the formation of the human oesophageal hiatus.

The formation of the oesophageal hiatus was studied in 50 human diaphragms in which crura and the median arcuata ligaments were carefully dissected and their fibres were carefully traced to the central tendon. In 98% of the cases the right crus was divided into a medial, a middle and a lateral bundle. In 90% the left crus was divided into a medial and a lateral bundle. The medial bundle of the right crus was a constant component in bounding the hiatus. The undivided crura did not contribute to the borders of the hiatus. 5 variations in the formation of the hiatus were observed. In 62% the hiatus was bounded by the 2 crura mainly the right; the left crus shared only in the formation of the posterior border. In 10% the 2 crura contributed equally to the formation of the hiatus; the hiatus was formed by the medial bands. In 10% the hiatus was formed exclusively by the right crus. In 2% the hiatus was formed exclusively by the left crus. In 16% crura had no direct relation to the hiatus except posteriorly and the hiatus was bounded by a V-shaped band from the median arcuate ligament, this finding has not been previously reported. The functional significance of these variations was discussed.

Fluorescence histochemical study of the localisation and distribution of beta-adrenergic receptor sites in the spinal cord and cerebellum of the chicken.

The distribution of beta-adrenergic receptor sites has been studied in chicken spinal cord and cerebellum using a fluorescent analogue of propranolol, 9-amino-acridin-propranolol (9-AAP). In the cervical and lumbar regions of the spinal cord, beta-adrenoceptor sites were concentrated on cell bodies of alpha-motor neurons of the dorsolateral and ventrolateral nuclear groups of the ventral horn. In the thoracic region, they were present on cell bodies of the preganglionic sympathetic nucleus (dorsal commissural nucleus). In the dorsal horn, the receptor sites were present mainly on cell bodies of columna dorsalis magnocellularis. Sparse distribution of fluorescence was present in other regions of the gray matter. In the cerebellum, a dense distribution of beta-adrenergic receptor sites was observed on Purkinje cell bodies and their apical dendrites. Sparse distribution of receptor sites was present on fine ramifications of Purkinje cell dendrites in the molecular layer. Receptor sites were absent in the granule cell layer and the white matter. These observations indicate that alpha-motor neurons, preganglionic sympathetic neurons, neurons of columna dorsalis magnocellularis, and Purkinje cells are adrenoceptive, while granule cells are non-adrenoceptive.

Prenatal development of the human submandibular gland.

The prenatal development of the human submandibular gland has been investigated in 26 fetuses from the 10th week of gestation to full term. At 10-12 weeks, the glandular elements (primitive ducts and acini) were immature and surrounded by a loose mesenchyme. The acinar cell population increased gradually till the age of 32 weeks, and the rate of increase was diminished thereafter. At 16 weeks, intercalated and striated ducts were distinguished and their number increased till the age of 32 weeks when their number seemed to be stabilized. The development of the granular convoluted tubule cells from the proximal segments of striated ducts occupied the later stages of development. They appeared around the age of 20 weeks and proceeded till full term. At birth, the gland appeared devoid of mucous acini and fat cells and the secretory end-pieces were of the serous type. During the second trimester, periodic acid-Schiff- and alcian blue-positive secretory materials appeared in the epithelial cells of both ducts and acini, and in their lumina. This secretory activity was transitory and disappeared around the age of 28 weeks. The possible function of these secretory products is discussed.

The development of the human phreno-oesophageal membrane.

23 human fetal diaphragms were used to study the structural changes of the phreno-oesophageal membrane at the different prenatal ages. 2 human adult diaphragms were used for comparison. This membrane was found to be formed by both the superior and inferior diaphragmatic fasciae. The phreno-oesophageal membrane was mainly formed by the superior fascia at early stages of development and by the inferior at later ages. The collagenous and elastic components of this membrane increased gradually with age. The crural muscle fibres forming the boundary of the oesophageal hiatus at 10 weeks showed gradual regression and was replaced by tendinous fibres. The latter formed secondary insertion in addition to the primary one in the central tendon. The strip of striated muscle, which was occasionally present at the lower end of the oesophagus, could be attributed to failure of recession of the crural muscle bordering the hiatus. The functional significance of the phreno-oesophageal membrane in the process of deglutition and vomiting and for prevention of hiatus hernia is discussed.