Five kinds of hormone-producing cells were identified immunohistochemically in the bovine anterior pituitary gland, and their ultrastructures were examined by electron microscopy. The fine structural properties of non-hormone producing cells, agranular folliculo-stellate (FS) cells, were studied at the same time. Growth hormone (GH) cells and prolactin (PRL) cells are oval or spherical in shape and evenly distributed throughout the gland. They have numerous round and electrondense granules, and their mean diameters are almost the same, 460 and 440 nm in GH and PRL cells, respectively. The maximum diameter of secretory granules is 200-900 nm in GH cells and 200--700 nm in PRL cells. Larger secretory granules (more than 700 nm in diameter) arefound only in GH cells and they seem to be one of the fine structural criteria distinguishing GH cells from PRL cells. The thyroid stimulating hormone (TSH) cell is a large and polyhedral shaped cell with many small granules (100-300 nm in diameter, mean: 180 nm). The adrenocorticotropic hormone (ACTH) cell is a large and stellate cell. The diameter of the secretory granules in ACTH cells varies from 150 to 500 nm with the mean of 290 nm. Luteinizing hormone (LH) cells are generally small and oval cells, and they consist of2 subtypes, LH-a and LH-b cells, which have different sizes ofsecretory granules. The LH-a cell has secretory granules with maximum diameter between 175 and 500 nm (mean=300 nm), and the LH-b cell has granules 100 and 325 nm in diameter (mean: 190 nm). The incidence of LH-a cells is higher than that of LH-b cells. The ES cells have a small cell body with cytoplasmic processes protruding between granulated cells. They are characterized by microvilli interdigitating each other in the intracellular pseudolumen, cilia and colloidal material in the follicles. It should be noted that the junctional complexes are frequently found between FS cells, an FS cell and a granulated cell, and between granulated cells.
A cystine aminopeptidase distinct from two major aminopeptidases was isolated from human skeletal muscle extract and its physicochemical properties were compared with those of other enzymes. Two activity peaks hydrolyzing S-benzylcysteine-methylcoumarinamide (S-Bz-Cys-MCA) were separated on DEAE-cellulose. One was shown to be a minor cystine aminopeptidase (CAP), and the other a major aminopeptidase M-like enzyme. The newly-found CAP had the following properties; addition ofCl ions resulted in increased activity, like that seen in aminopeptidase B, the pH optimum was 7.5, and there was no reduction in activity upon addition of 1 mM puromycin and 10 mM EDTA. We discuss the identity of this CAP.
Binding studies revealed the presence of two classes of binding sites for atrial natriuretic peptide (ANP) on hog ciliary bodies and choroid membranes. The curvilinear Scatchard plots were evaluated by nonlinear regression analysis using a twosite model which identified a high affinity site Kd1=73±12 pM and Bmax1=77±7 fmol/mg protein, and a low affinity site Kd2=0.748±0.199 nM and Bmax2= 44±11 fmol/mg protein in ciliary bodies, and a high affinity site Kd1=45±3 pM and Bmax1= 44±2 fmol/mg protein, and a low affinity site Kd2=1.181±0.356 nM and Bmax2=158±44 fmol/mg protein in choroid. Affinity labeling with disuccinimidyl suberate followed by electrophoresis under nonreducing condition and autoradiography show that the peptide binds predominantly to 66,000 dalton species on membrane of ciliary bodies. However, on membrane of choroid, the high molecular size protein (130,000 dalton species) is intensely labeled. The results suggest that a polypeptide of 66,000 dalton represents a component of the high affinity ANP receptor.
Angiotensin II binding sites in human adrenal glands obtained at autopsy were investigated. The tissue sections were incubated with 125I-angiotensin II and analyzed using [3H]-Ultrofilm autoradiography with image analysis coupled to computerized microdensitometry. In addition, a comparison was made with 125I-standards. A single type of specific, high affinity binding sites was found in the zona glomerulosa and medulla. The rank order for inhibition of the binding in the zona glomerulosa and medulla was [Sar1, Ile8]-angiotensin II and Des-Asp1-[Ile8]angiotensin II > native angiotensin II = angiotensin III >>> angiotensin I, αhuman atrial natriuretic polypeptide (ANP-(99-126)), substance P and methionineenkephalin. The possibility that angiotensin II plays a significant role in function of the human adrenal zona glomerulosa and medulla by interacting with specific, high affinity receptors, Warrants further attention.
Interactions between epithelial cells and collagen fibrils were investigated using primary cultures of newborn rat epidermal cells and adult rat hepatic parenchymal cells. Morphology and the rate of DNA synthesis of these cells were regulated by collagen fibrils in a dose-dependent manner. Collagen fibrils at more than 50 μg/cm2 of growth area greatly reduced spreading of the two types of cells. The rate of DNA synthesis of these cells was inversely related to the quantity of the collagen fibrils available to the cell: when cultured on the collagen fibrils at 500 μg/cm2, the rates of synthesis of epidermal and hepatic cells decreased to 42% and 14% of those on the plastic culture dish, respectively. Collagen in a heat-denatured or a native, but non-polymerized form showed no such actions or less effective on the cells, indicating the importance of a fibril formation in the cell to collagen interactions. The transglutaminase activity of epidermal cells and the secretion of albumin by hepatic parenchymal cells increased proportionately to the amounts of collagen fibrils, suggesting that collagen fibrils support to induce and stabilize the expressions of differentiated functions of the epithelial cells.
During anoxic liver perfusion, numerous blebs were formed that protruded from hepatocytes, and their contents were released into the sinusoidal lumen. Cytosolic enzymes such as the cytoplasmic isozyme of aspartate aminotransferase and lactate dehydrogenase leaked into the perfusate after a lag of about 60 min, which was the time required for the formation of blebs. The leakage pattern of the enzymes was similar to that of components of the endoplasmic reticulum and ribosomes, such as glucose-6-phosphatase, RNA and phospholipids, which were present in the blebs. The rate of release of the cytoplasmic isozyme of aspartate aminotransferase depended greatly on the flow rate during perfusion, and no enzyme leaked into the perfusate when the flow rate was slow. The rate of release was greatly accelerated by raising the viscosity of the perfusion fluid. The results indicate that the cytosolic enzymes released from ischemic liver are those present in blebs which protrude into the sinusoidal space and are disrupted by the hydrodynamic force of the blood stream.
Activity of 2’,5’-oligoadenylate (2-5A) synthetase was measured in sera as well as in lymphocytes from humans and mice by a sensitive radioimmunoassay. Low levels of 2-5A synthetase activity were detected reproducibly in the serum and plasma from healthy subjects. The enzyme activity in the serum was 0.3-0.7 pmol/h/ml of serum, which was 1-2% of that in the lymphocytes obtained from 1 ml of blood. Low levels of 2-5A synthetase activity were also detected in the serum from mice. The enzyme activity in mouse serum was increased by administration of interferons or interferon inducers. Changes in the enzyme activity in the serum were generally in accord with those in the lymphocytes. The enzyme activity in the lymphocyte extract was 50-200 times higher than that in the serum when the activity was compared on a protein basis. We further detected 2-5A synthetase activity in the culture supernatant when peripheral mononuclear cells were cultivated in vitro for 24 h; the activity was 0.3-1.0% of that in the cultured cells. The enzyme level in the culture medium was elevated with an increase in the intracellular enzyme level produced by interferons given in vitro.
Lymphocytic infiltration confined to the pancreatic islets is one of the characteristic findings during the diabetic stage of non-obese diabetic (NOD) mice. Electron microscopic observations indicate that lymphocytes come into contact with pancreatic B cells with their villi and sometimes intrude them by cytoplasmic projections. Transmission (TEM) and scanning (SEM) electron microscopy of a mixture of cultured islet cells and T cell-rich splenic lymphocytes from NOD mice revealed a similar manner of contact between both cells in vivo. These observations suggest that immunological mechanisms involving in T lymphocytes may destroy islet cells and lead to the development of overt diabetes in NOD mice.
A new type of spider toxin with histamine-releasing activity was purified from the venom of the Joro spider, Nephila clavata, using high performance liquid chromatography. Three kinds of toxins (Nephilatoxins-7, -8 and -9) were isolated. They all possess the aromatic indole-3-acetyl group connected to N-termini of the hydrophilic and polycationic part constructed of basic amino acids and polyamines. The structural relation to the other spider toxins is discussed.
The effect of mazindol on insulin and glucagon secretion was studied in ventromedial hypothalamic (VMH)-lesioned obese rats with hyperinsulinemia. Three weeks after a VMH or sham operation, the rats were divided into two groups: one was fed a balanced diet containing mazindol (50 mg/kg) and the other was fed a balanced diet without mazindol for 3 weeks. In the VMH rats, mazindol treatment was associated with a significant reduction in body weight and calorie intake, but it had no effect in the sham-operated rats. Furthermore, the fasting plasma insulin level and the arginine-induced insulin secretion from the perfused pancreas of VMH rats treated with mazindol were significantly lower than those in VMH rats without mazindol treatment. In addition, mazindol produced no significant change in the insulin secretion of sham-operated rats either in vivo or in vitro. It is therefore suggested that mazindol suppresses the hypersecretion of insulin in VMH rats through an anorectic effect and/or suppression of vagal hyperactivity.