Movements of the luminal plasma membrane during the early stage of secretion in rat parotid acinar cells were investigated by an immunocytochemical technique using dipeptidyl peptidase (DPP) IV as a marker. In acinar cells stimulated by a single intraperitoneal injection of isoproterenol, numerous pits and tubular invaginations rapidly appeared in the luminal plasmamembrane preceding exocytosis. At a subsequent stage, membranes of these invaginations came into contact and fused with those of secretory granules, and the contents of granules were discharged into the lumen through pits and tubular invaginations. After the termination of discharge, the membrane of emptied granules acquires the property of the luminal plasma membrane with regard to DPP IV immunoreactivity. At later stages of secretion, membranes of discharged granules fused successively with those of neighbouring undischarged granules, resulting in an enlargement of the lumen. The results indicate that the luminal plasma membrane of the acinar cell plays a significant role in the process of secretion in the parotid gland.

The aequorin-Ca²⁺ transient evoked by depolarizing clamp pulses was faster in the fast twitch extensor digitorum longus (e.d.l.) muscle than in the slow twitch soleus muscle of the rat at temperatures examined (15-40°C). The Q₁₀ of the decay time constants were 2.3 and 2.1 for the e.d.l. and soleus, respectively. The potential-amplitude relation of the Ca²⁺ transient in both muscles was sigmoid and tended to plateau at around +50 mV. The maximum amplitude evoked by strong and long pulses was greater in the e.d.l. than in the soleus. The Ca²⁺ transients in both muscles could be evoked in Ca²⁺-free (EGTA) Ringer, indicating that the Ca²⁺ transient is caused by Ca²⁺ released from intracellular stores. During a prolonged depolarization, Ca²⁺ transients gradually declined in both muscles due probably to inactivation of the excitation-Ca²⁺ release coupling process. The decline was faster in the e.d.l. than in the soleus. After denervation, the Ca²⁺ transients in diaphragm muscle became slower in parallel with a slowing of contraction time. It is concluded that the difference in the time course of the Ca²⁺ transient is a factor responsible for the difference in contraction time in mammalian muscles.

The regional distribution of a novel pituitary protein (7B2)-like immunoreactivity (IR7B2) in the rat urogenital tract has been examined by specific radioimmunoassay, and its molecular forms determined by gel permeation and high performance liquid chromatography. While IR-7B2 was present in all regions studied except the seminal vesicle, the highest concentrations of IR-7B2 were found in the ureter, the vagina and the vas deferens. Chromatographic analysis of the ureter extracts using both systems revealed a similar profile of IR-7B2 to that present in the porcine pituitary extracts.

In the cerebellum of jaundiced homozygous (ji) Wistar Gunn rats, specific activity of glutamate decarboxylase (GAD) on a wetweight basison andafterpostnatal day 10was significantly lower than in non-jaundiced heterozygous (j+) rats (2). In the present study, wehaveexaminedthepostnatal developmentofGAD activityin another strain of Gunn rats (Sprague-Dawley Gunn rat). Thejj rats ofthis strain also showeda considerably low rate ofincrease in GAD activity from days 10 to 15 compared withj+ rats. To clarify a histological basis of the impaired development of GAD activity inji rats, the postnatal development of cerebellar y-aminobutyric acid (GABA)ergic neurons was studied immunocytochemically using anti-GABA antiserum raised in rabbits. Golgi andPurkinje cellswere stainedwiththeanti-GABA antiserum atthe dayofbirth in both jj andj+ rats. Many Purkinje cells, which showed some degenerative changesalready at day 1 injj rats, suffered from severe damages at day 10, and disappeared before day 15. Golgi cells also showed some degenerative changes at day 15, though they still maintained their immunoreactivity to the antiserum. Basket cells, which appearedat day 10,weresmallin number injjratsatday15, suggestingthattheyhadbeenseverelydamaged during this period. The results suggest that bilirubin sensitivity ofGABAergic neurons isheterogeneous, anddestruction bybilirubin ofPurkinje andbasketcells before day 15 is mainly responsible for a low rate ofincrease in GAD activity from postnatal days 10 to 15.

Using antisera against growth hormone-releasing factor, cell bodies and axon processes were identified in the hypothalamus and the median eminence of the monkey Macaca irus. Cell bodies were located mainly in the arcuate nucleus and along the third ventricle wall, and occasionally in the ventromedial nucleus. Irnmunostained axons were also observed in the dorsolateral hypothalamus. No immunostained cell bodies were identified in the hypothalamic magnocellular nuclei (paraventricular, supraoptic and suprachiasmatic nuclei). In the median eminence, bundles of fibers were present in the external layer. These cell bodies and fibers did not react with antisera against neurophysin, somatostatin, gonadotropin-releasing hormone, and corticotropin-releasing factor.

We identified a gelsolin-like 84 K M_r protein in the conventional actin preparation from cedures utilizing DNase I affinity column chromatography andhigh performance liquid vertebrate smooth muscle, and purified this protein from bovine aorta by simple　procedures utilizing DNase I affinity column chromatography and high performance liquid chromatography. The 84 K M_r protein reduced the high-shear viscosity of actin filaments, and shortened their lengths in a Ca²⁺-dependent manner, in relatively higher molar ratio to actin (1:100). This effect was almost unprevented by the presence of smooth muscle tropomyosin. In the lower molar ratio to actin (1:10,000), the protein reduced the viscosity of actin filaments at low-shear rates without shortening filaments in the presence of Ca²⁺. This effect was also unprotected by smooth muscle tropomyosin. Synthetic smooth muscle thin filaments consisting of gizzard actin, tropomyosin, and aorta 84 K M_r protein disassembled to shorter fragments in the presence of Ca²⁺ and reversibly assembled into long filaments when Ca²⁺ was removed by EGTA. Since conventional smooth muscle actin preparations contain the 84 K M_r protein, we discussed the necessity of a careful interpretation on the results of actin-myosin interaction with tropomyosin in vitro. Further, the possibility that the 84 K M_r protein plays an important role in some processes during physiological smooth muscle contraction, particularly long-lasting tonic contraction, was discussed.

A scorpion toxin conjugated with biotin and avidin has been used to investigate the location of the voltage-dependent Na-channel in the electric organ of Electrophorus electricus. Distribution of the conjugated scorpion toxin was visualized under a light or an electron microscope by using biotinylated peroxidase and diaminobenzidine. A dense staining was observed on the innervated surface of the electroplax plasmalemma, but not on the non-innervated surface. Electron micrographs at a higher magnification showed that the caveolar invaginations of the innervated membrane surface were also stained. This specific staining was completely blocked by an excess amount of unmodified scorpion toxin or by a high concentration of KCl in the incubation medium.

The plasma membrane of trout sperm was removed by the treatment with Triton X-100 and phosphorylation of sperm protein was analyzed by SDS-polyacrylamide gel electrophoresis after incubating the demembranated sperm with [y-³²P]ATP. When the motility of demembranated sperm was initiated by addition of cAMP, a 15 K protein was strongly phosphorylated within 1 sec, a time period compatible with the normal initiation of sperm motility. When sperm were first allowed to swim and then demembranated, cAMP-dependent phosphorylation of the 15 K protein was not observed. The results suggest that the 15 K protein, completely phosphorylated in 1 sec in the presence of cAMP, triggers the initiation of sperm motility.

Single intraperitoneal administration of cyclophosphamide (200 mg/kg) to male nonobese diabetic (NOD) mice resulted in a significant increase in the incidence of overt diabetes mellitus up to 90% around 2 weeks alter the injection (P<0.005). Daily subcutaneous injections of nicotinamide (500 mg/kg) almost completely prevented the development of cyclophosphamide-induced diabetes mellitus (P<0.005). Pancreatic islets of cyclophosphamide-nicotinamide-treated 19-week-old mice were normal in size, but were slightly or moderately infiltrated by lymphocytes. In contrast, only small-sized islets were left in cyclophosphamide-induced diabetic mice of the same age, and some of these islets were severely affected by insulitis.