Altered responsiveness to parasympathetic activation of submaxillary salivary gland in the heat-acclimated rat

Submaxillary salivary gland responsiveness during the heat acclimation procedure (34 +/- 1 degree C) was studied in the rat. Gland responsiveness was evaluated by measuring saliva flow rate of the anesthetized animals following either parasympathetic nerve stimulation or i.v. application of pilocarpine. A thirty percent decrease in glandular responsiveness for the two modes of stimulation was measured during the first 10 days of acclimation. Following 60 days of acclimation recovery was observed. It is concluded that decreased responsiveness of the heat-acclimated gland is a glandular event. Increased saliva flow occurring at the initial phase of acclimation is apparently due to changes in the thermoregulatory center.     

Early development of parasympathetic nerves in the mouse submandibular gland.

The early development of the parasympathetic nerves of the mouse submandibular gland is described, both in vivo and in culture. Axon outgrowth has been visualized by electron microscopy, supravital staining with methylene blue, and histochemical localization of acetylcholinesterase activity. Axon outgrowth from the submandibular ganglion parallels in time and in space the morphogenesis of the epithelium of the salivary gland. The average rate of axon elongation during the first 2 days of culture is about 500 μm/day. The precision of pattern formation during that period and the high rate of growth indicate that axon outgrowth is not initially random but that its orientation is determined immediately during the process of outgrowth.     

Ultrastructure of the human submaxillary gland

Summary Myoepithelial cells in the human submaxillary gland are stellate in form, with long, tapering processes. They are interposed between the base of the secretory cells and the basement membrane, and are bound to the secretory cells by desmosomes. Their cytoplasm contains numerous myofilaments measuring approximately 40 Å in diameter, which frequently aggregate to form structures similar to the dark bodies seen in smooth muscle cells. The myofilaments are anchored to the plasma membrane by attachment devices. The myoepithelial cells are often accompanied by cells which have a similar shape, but possess an extremely electron-lucent cytoplasm that contains almost no organelles or inclusions. Electron microscopical observations indicate that these cells, termed clear cells, are transformed directly into myoepithelium, since all morphological intergrades between the two cell types have been recognized.This work was supported in part by a grant from the Henry Spenadel Trust. The technical assistance of Mr. Roy R. Keppie and Mrs. Mona Brandreth is gratefully acknowledged.     

Specificity of submaxillary gland sialyltransferases

A method has been developed to determine the activities of specific sialyltransferases by analysis of the products of the reaction. This method, which utilizes high performance liquid chromatography, distinguishes addition of sialic acid to the N-acetylgalactosamine vs. galactose residues of the mucin disaccharide Galβ(1→3)GalNac, and can be used to distinguish formation of the 3′- and 6′-isomers of sialyllactose. For the bovine, ovine, and porcine submaxillary extracts, more than 95% of the activity with asialo ovine submaxillary mucin is due to formation of NeuAc α(2→6)GalNAc. With lactose as the acceptor, more than 95% of the α(2→3) isomer is produced. Activity with asialofetuin is due solely to the O-linked chain, with relative activity toward the galactose vs. GalNAc residues of 0.32, 1.5, and 0.10 for bovine, ovine, and porcine, respectively. The rat submaxillary gland extract showed equal formation of 3′- and 6′-sialyllactose, and very low activity with asialo ovine submaxillary mucin. However, at least 40% of the activity toward the Galβ(1→3)GalNAc disaccharide of asialofetuin was directed toward the GalNAc residue. The relative preference of the N-acetylgalactosaminide α(2→6) sialyltransferase for a monosaccharide vs. a substituted GalNAc may play a role in regulation of chain length during mucin synthesis.     

Crystallization of mouse submaxillary gland renin

Renin isolated from the mouse submaxillary gland has been crystallized and is being subjected to X-ray diffraction analysis.The observed crystalline form has the following unit cell dimensions: $\text{a = 96.4 (1)}\text{A}\text{?}\text{, b = 104.4 (1)}\text{A}\text{?}\text{, c = 77.4 (1)}\text{A}\text{?}\text{, β = 101.2 (1) °}$, space group P2₁, Z = 8 (4 protein molecules in the asymmetric unit).Native data have been recorded at 5 Å resolution with an automatic diffractometer.     

Thyroid gland activity and motor activity during dog ontogenesis]

The locomotor activity (LA) and the level of the protein-bound iodine (PBI) in the blood serum were investigated in 62 puppies at the age of 1--12 months. A parallel elevation of PBI and the LA was observed the first 4 months after birth. The second peak of the LA at the age of 7--9 months was not accompanied by any PBI rise. Inhibition of the thyroid function with mercasolyl increased the LA at the age of 1--3 months and decreased it at the age of 7 months. An increase of the LA one month after thyroidectomy was found at the age of 1 and 3.5 months. The activity of puppies operated on at the age of one month showed a sharp fall after 2--4 months. The data on various effect of thyroid hormones on puppies of different age pointed to the complex relation between the LA and the thyroid gland function.