Ca²⁺-ATPase in the tanycyte ependyma of the third ventricle was investigated in rats using a cytochemical method. Reaction products were detected in the plasma membrane of the tanycytic ependymal lining of the third ventricle and were especially marked at the apical microvilli of its more dorsal part adjacent to the ventromedial nucleus. The positive reaction was dependent on calcium. A difference between the apical and the lateral plasma membrane was observed with respect to substrate specificity. The substitution of ADP for ATP caused no reaction product in the former, while exhibiting activity in the latter. The property of the enzyme seems to be different between the two. Ca²⁺-ATPase in tanycytes may have a role in the active transport of substances and in the regulation of intraventricular and intracellular Ca²⁺ concentrations.

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The postnatal development of peroxidase (PO) activity in laryngeal and tracheal epithelia and glands was histochemically investigated in specific pathogen free (SPF) rats. Tissues were fixed in a cold 1% p-formaldehyde-1.25% glutaraldehyde solution in a 0.1M sodium cacodylate buffer, pH 7.4, for 30min at 4°C, and incubated in a diaminobenzidine-H₂O₂ medium including 2mM KCN for 60min at 37°C.
The laryngeal glands had formed four days after birth, and PO activity was seen in some terminal tubule cells on day 6. Five days after birth, some tracheal epithelial cells invaginated into the matrix and formed glands, which became PO positive on day 11. The distribution of PO activity in the glands on day 14 resembled that of adult rats (3 months). The respiratory tract columnar epithelial cells of SPF rats were entirely devoid of the activity, although these cells started exhibiting positive activity when infected with some microorganisms such as corynebacteria. These results indicated that the glands of the rat respiratory tract are formed and synthesize PO after respiration has occurred, that regional difference seems to be important to gland maturation, and that respiratory tract columnar epithelial cells lack enzyme activity which may be inducible through microorganism infection.

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The ultrastructural localization of nicotinamide adenine dinucleotide phosphatase (NADPase) and thiamine pyrophosphatase (TPPase) or nucleoside diphosphatase (NDPase) activities was studied in the principal cells of the rat epididymis and compared with the pattern produced after monensin treatment.
The NADPase activity was found positive in the intermediate cisternae near the cis side of the Golgi lamellae, to show a difference in compartment from that of TPPase on the trans side. After 60min treatment with monensin, most of the Golgi stacked lamellae exhibited dilation. The swelling occurred in all stacks without preferential effect on any particular Golgi subcompartment. With these enzymes, the characteristic staining patterns on the subcompartments in the Golgi apparatus were basically unchanged after treatment with monensin. However, some of the NADPase positive intermediate cisternae on the cis side of the Golgi apparatus were remarkably dilated.

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The intracellular localization of two peroxisomal enzymes, catalase and acyl-CoA oxidase, in regenerating rat liver after partial hepatectomy has been investigated by means of postembedding protein A-gold immunocytochemical technique. The peroxisomes in regenerating rat liver underwent marked changes in shape and size as revealed by catalase cytochemistry with DAB. By immunoelectron microscopy, all peroxisomes, irrespective of size and configuration were strongly positive for catalase showing numerous gold particles distributed over their matrix sparing the electron dense nucleoid region. Sections incubated with the monospecific antibody against acyl-CoA oxidase showed essentially a similar distribution of gold particles, although the labeling density was weaker than with catalase. In all sections the endoplasmic reticulum and the Golgi complex were negative for both catalase and acyl-CoA oxidase, thus ruling out any involvement of the secretory apparatus in the biosynthesis of those proteins. The uniform distribution of catalase and acyl-CoA oxidase in all peroxisomes (presumably new and old) is consistent with the concept of transfer of matrix proteins from preexisting particles to new ones.
In addition to the localization of catalase in the matrix of peroxisomes, some gold particle aggregates were also noted apparently on ribosomes in the cytoplasmic matrix. Serial section analysis, however, revealed that all cytoplasmic labeling was due to tangentially sectioned peroxisomes, especially those with abnormal shapes. Our observations suggest that the concentration of nascent peroxisomal proteins in the cytoplasm of rat liver cells under physiological conditions is too low to be detectable by the presently available immunocytochemical techniques.

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The ultrastructure and cytochemical localization of Ca²⁺-activated adenosine triphosphatase (Ca²⁺-ATPase) activity of the ovarian surface epithelium in immature rats and in adult rats during the estrous cycle and pregnancy were investigated at both light and electron microscopical levels. In the adult rat ovaries at all stages of the estrous cycle, the intensity of Ca²⁺-ATPase activity and ultrastructure of the surface epithelium were considerably varied in the different regions on the same ovary. The variations in the morphology and Ca²⁺-ATPase activity likely provide evidence for the differences in the functional activity of the surface epithelium, which are related to the topographical connection with adjacent structures of ovarian cortex, i.e., corpus luteum, preovulatory Graafian follicles, interstitium containing small follicles. In the adult rat ovaries at all reproductive stages, the cuboidal or columnar surface epithelial cells were found on the interstitium containing small follicles. In some places, the columnar surface epithelial cells, forming crypts of the epithelium, invaginated into the ovarian proper. This type of surface epithelial cell had well-developed microvilli on its apical membrane, and showed intense Ca²⁺-ATPase activity on its apical and lateral membranes. The squamous surface epithelial cells were found on the surface of corpus luteum and preovulatory Graafian follicles. These cells had a low number of microvilli and less activity of Ca²⁺-ATPase on the apical membrane. In the immature rat ovaries, the surface epithelial cells were in part squamous, in part cuboidal. Both types of surface epithelial cells had few microvilli. Ca²⁺-ATPase activity on the apical membrane was considerably less on all surfaces of the ovaries. It seems that the transport function of the surface epithelium in the immature ovary is not active as compared with the mature ovary.
These results suggest that the surface epithelium may have an active function of local absorption and/or transepithelial transport between pelvic cavity and ovarian proper, and its functional activity is associated with the reproductive function of the ovary.

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Critical electrolyte concentration (CEC) values were determined for DNA and DNA/Hl and DNA/protamine complexes under varying toluidine blue staining conditions and using Mg²⁺ as inorganic cation. CEC values were considered those molarities of MgCl₂ at which green staining was detected microspectrophotometrically. Variation in the CEC values was found with respect to association of nuclear proteins with DNA and the nucleoprotein complex considered. The DNA filaments exhibited the highest range of CEC values, whereas the lowest CEC values were presented by the DNA/protamine complex, especially when the staining solutions were prepared in McIlvaine buffer. The method thus appears to be promising for further studies on differences among DNA/protein complexes in vitro or even in situ.

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Using a peroxidase labeled antibody (Fab'-fragments) method, the subcellular localization of dipeptidyl peptidase IV (DPP IV) in rat kidney and small intestine was examined. In the kidney DPP IV immunoreactivity was primarily confined to the brush border membrane of the proximal tubule cells. Immunoreaction product was also detected on the surface of capillary endothelium of the glomeruli and epithelium of Bowman's capsule. In the small intestine, DPP IV was found to be localized on the external surface of the brush border membrane of enterocytes. DPP IV immunoreactivity was also found in the cytoplasmic vesicles, lysosomes and Golgi apparatus in some enterocytes.
The results of the present study confirmed that DPP IV is a brush border membrane peptidase and suggest that in the kidney and small intestine this enzyme may participate in the digestion or reabsorption process of proline-containing peptides.

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