Different aspects of membrane differentiation at the inner side (GERL) of the Golgi apparatus in rabbit luteal cells

Synopsis After luteinization, during the growth phase, rabbit luteal cells showed a well-developed Golgi apparatus, which was clearly reduced at the end of pseudo-pregnancy. During this whole period, acid phosphatase was demonstrated in the saccules (g) of the Golgi stack and in the innermost Golgi element (G₂), which may be part of GERL. Between both acid phosphatase-positive compartments, a negative or slightly positive element (G₁) was present paralleling the saccules of the Golgi stack. This element was composed of cisternal (G₁ c) and perforated portions (G₁ p) and directly bordered the thiamine pyrophosphatase-positive saccules of the Golgi stack (g₁–g₂). Arylsulphatase activity was present in two saccules in the middle of the stack (g₃–g₄) and in the innermost Golgi element (G₂). In the acid phosphatase and arylsulphatase reactions the limiting membrane of the lysosomes was more reactive than the matrix. After phosphotungstic acid staining at a low pH, the inner elements of the Golgi apparatus (G₁ and G₂) and the border of the lysosomes were heavily contrasted. The lysosomal matrix and the other Golgi stack saccules were either almost unstained or displayed a clearly lower contrast.It is concluded that the cytochemical difference between Golgi (g) and GERL (G) membranes is most probably the result of a specific process of membrane differentiation, which takes place at G₁. There is also evidence that the lysosomal matrix hydrolases may be formed in the saccules of the Golgi stack. The strongly phosphotungstic acid-positive inner elements are, although more extended, comparable in large part with the GERL elements as described in neurons (Novikoffet al., 1971).     

Immunocytochemical demonstration of dopamine-beta-hydroxylase and cytochrome B561 on the axonal reticulum in bovine sympathetic neurons.

In sympathetic neurons the axonal reticulum can be considered an extension of the secretory pole of the Golgi apparatus. If this tubular system indeed represents the neurosecretory apparatus, it would likely contain on its membranes the enzymes involved in catecholamine synthesis. To test this hypothesis, we investigated the distribution of dopamine-beta-hydroxylase and cytochrome b561 in bovine splenic nerve and nerve terminals in the vas deferens with an immunogold procedure after glycolmethacrylate embedding. Counterstaining with phosphotungstic acid at low pH selectively revealed the axonal reticulum elements. With antibodies against both enzymes, gold labeling was observed over the large dense-cored vesicles, the Golgi-associated axonal reticulum, the reticulum within axons, and the tubular complex at the nerve terminal. From our results it can be concluded that in sympathetic neurons the axonal reticulum represents a tubular neurosecretory system, extending from the Golgi apparatus in the cell soma to the nerve terminal. This concept emphasizes the local production of neurosecretory vesicles and may be of importance in the interpretation of neuronal transmission in normal and diseased states.     

LYSOSOMAL PACKAGING IN DIFFERENTIATING AND DEGENERATING ANURAN LATERAL MOTOR COLUMN NEURONS

The role of the Golgi apparatus and the Golgi-endoplasmic reticulum-lysosome complex (GERL) in the genesis of lysosomes was examined in differentiating and degenerating motor neurons of anuran larvae. Acid phosphatase, aryl sulfatase, and thiolacetic acid esterase were utilized as marker enzymes for the lysosomal system, while nucleoside diphosphatase and thiamine pyrophosphatase labeled the inner saccule(s) of the Golgi apparatus. Reduced osmium tetroxide was routinely deposited in the outer Golgi saccule regardless of the state of neuronal maturation. In all young neurons, the disposition of acid hydrolase reaction product paralleled the formation of GERL, with no lytic activity in the Golgi apparatus per se. Hypertrophy of the Golgi apparatus and GERL was observed in the early phases of degeneration, and both organelles apparently exhibit extensive hydrolytic activity. Dense bodies, autophagic vacuoles, and primary lysosomes were found arising from GERL, while the Golgi apparatus may produce primary lysosomal granules during regression. On the other hand, in differentiating neurons, hydrolytic activity was restricted to GERL and an occasional dense body and autophagic vacuole. These studies illustrate a parallelism between the development of GERL and genesis of primary and secondary lysosomes during neuronal cytodifferentiation, and implicate GERL and possibly the Golgi apparatus in lysosomal packaging in degenerating neurons.     

Electron microscopic demonstration of acid phosphatase activity in the developing and mature heterophils of the chicken

Summary As shown by electron microscopic histochemistry using a modified Gomori lead salt technique, acid phosphatase is present in large dense granules and the Golgi apparatus —but not the light granules—in both immature and mature heterophils in the chicken. The large dense granules appear to form by budding from the Golgi cisternae while the light granules appear to be unassociated with the Golgi apparatus. The findings indicate that the large, dense granules are the lysosomes of the heterophils in the chicken.     

Intracellular localization of basement membrane precursors in the endodermal cells of the rat parietal yolk sac. I. Ultrastructure and phosphatase activity of endodermal cells

The parietal layer of the rat yolk sac includes a 5 microliter thick sheet known as Reichert's membrane that exhibits properties of basement membranes. Its inner side is lined by a single layer of loosely distributed cells referred to as endodermal cells. Both Reichert's membrane and endodermal cells were examined at 13-14 days' gestation with emphasis on the ultrastructure of the Golgi apparatus, the identification of its component parts by specific phosphatase activities, and its possible role in the cells' secretory process. Reichert's membrane is composed of a series of stacked layers similar to basal laminae and composed of a network of fibrils with a diameter of 2-8 nm along which dots are located at irregular intervals. The endodermal cells contain the usual organelles, including interconnected rough endoplasmic reticulum (rER) cisternae and a prominent Golgi apparatus. With the help of phosphatase reactions, the stacks of Golgi saccules were divided into a) "phosphatase-free" saccules, the first ones on the cis or forming side, b) one or two "intermediate" saccules in the middle of the stacks, containing nicotinamide adenine dinucleotide phosphatase activity, c) one or two "last" saccules rich in thiamine pyrophosphatase activity on the trans or mature side, and d) continuing beyond the trans side, the GERL element displaying acid phosphatase activity. The latter is associated with profiles equally rich in acid phosphatase and tentatively considered to be prosecretory granules. Finally, the ectoplasm adjacent to Reichert's membrane displays large, acid phosphatase-containing structures tentatively considered to be secretory granules. Thus, the extensive rER network, the well-compartmentalized Golgi apparatus, and the presence of structures which may be prosecretory and secretory granules indicate that the endodermal cells are well-equipped for the secretion of the components of Reichert's membrane.     

Effect of colchicine on the Golgi complex of rat pancreatic acinar cells

Colchicine administered to adult rats at a dosage of 0.5 mg/100 g of body weight effected a disorganization of the Golgi apparatus in pancreatic acinar cells. The results obtained after various periods of treatment (10 min to 6 h) showed (a) changes in all components of the Golgi complex, and (b) occurrence of large vacuoles that predominated in cytoplasmic areas outside the Golgi region. The alterations in Golgi stacks concerned elements of the proximal and distal side: (a) accumulation of transport vesicles, (b) formation of small, polymorphic secretion granules, and (c) alterations in the cytochemical localization of enzymes and reaction product after osmification. Transport vesicles accumulated and accompanied short, dilated cisternae, which lack mostly the reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase, and osmium deposits after prolonged osmification. After 4 to 6 h of treatment, accumulated transport vesicles occupied extensive cellular areas; stacked cisternae were not demonstrable in these regions. The changes on the distal Golgi side included GERL elements: condensing vacuoles were diminished; they were substituted by small, polymorphic zymogen granules, which appeared to be formed by distal Golgi cisternae and by rigid lamellae. Unusually extended coated regions covered condensing vacuoles, rigid lamellae, and polymorphic secretion granules. A cytochemical distinction between Golgi components and GERL was possible neither in controls nor after colchicine treatment. The cytochemical alterations in Golgi components were demonstrable 20-30 min following administration of colchicine; at 45 min, initial morphological changes--augmentation of transport vesicles and formation of polymorphic zymogen granules--became apparent. 20 min after administration of colchicine, conspicuous groups of large vacuoles occurred. They were located mostly in distinct fields between cisternae of the endoplasmic reticulum, and were accompanied by small osmium--reactive vesicles. Stacked cisternae were not demonstrable in these fields. Vacuoles and vesicles were devoid of reaction products of thiamine pyrophosphatase, inosine diphosphatase, and acid phosphatase. The results provide evidence that formation of stacked Golgi cisternae is impaired after colchicine treatment. The colchicine--induced disintegration of the Golgi complex suggests a regulatory function of microtubules in the organization of the Golgi apparatus.     

Ultrastructural and cytochemical studies of acid phosphatase and trimetaphosphatase in rat peritoneal mast cells developing in vivo

Summary The ultrastructural and cytochemical features of peritoneal mast cells of the rat were studied. Immature mast cells show specific cytoplasmic granules of different sizes, the smaller ones localized in the Golgi region. The rough endoplasmic reticulum and Golgi apparatus are well developed, and mitochondria are numerous. Nuclei show deep indentations. Acid phosphatase is present in the Golgi saccules, in GERL (Golgi apparatus-endoplasmic reticulumlysosome) and in some small granules. It is not present in mature granules. Trimetaphosphatase is present in the Golgi saccules, in GERL, in most immature granules and in some mature granules. These enzymes appear to be transported and packaged into granules by the Golgi apparatus, suggesting that the specific mast cell granules may be a form of lysosome. The results of this study are consistent with the hypothesis that peritoneal mast cells may be derived from macrophage-like precursors.     

Ultrastructural localization of coenzyme A phosphatase (CoA-Pase) activity to the GERL system in secretory ameloblasts of the rat incisor

Enzymatic hydrolysis of the monoester phosphate group from coenzyme A (CoA) was studied in rat incisor ameloblasts by incubating specimens from glutaraldehyde-fixed teeth in a cytochemical medium prepared with acetyl-CoA as substrate and lead ions as capture agent for phosphate. Ameloblasts incubated for 1 hr at 37 degrees C and at pH 5.0 in this medium showed reaction product localized almost exclusively along the trans (mature) aspect of the Golgi apparatus within a network of small granules and interconnecting tubular channels that comprise the GERL system in this cell. Reaction product was otherwise seen in trace amounts only within some Golgi saccules, a few lysosomal dense bodies and, in rare instances, within an occasional focal area of the endoplasmic reticulum. No selective staining of the GERL system was seen in control ameloblasts incubated at either pH 7.2 or pH 9.0 with acetyl-CoA as substrate, or incubated at pH 5.0 with dephospho-CoA as substrate. Control experiments at pH 5.0 also revealed that reaction product selectively stained the GERL system in ameloblasts when other molecules resembling CoA were used as substrate (e.g., crotonyl-CoA, 3'-NADP+), but not when adenosine 3'-monophosphate (3'-AMP) was used as substrate. That is, ameloblasts incubated at pH 5.0 with 3'-AMP showed heavy deposits of reaction product at many sites throughout the cell, including most lysosomal dense bodies, the Golgi saccules, the GERL system, most secretory granules, the nucleus, and extensively throughout the endoplasmic reticulum. These findings suggest that the GERL system of ameloblasts contains a CoA-specific phosphatase activity that may function to convert CoA to dephospho-CoA at acid pH. Biochemical studies included with this investigation further indicate that CoA-Pase activity saturates at exceptionally low concentrations of substrate (KM = 30 microM CoA) compared to other acid-dependent phosphatases.     

CYTOLOGICAL STUDIES ON TWO FUNCTIONAL HEPATOMAS : Interrelations of Endoplasmic Reticulum, Golgi Apparatus, and Lysosomes

The Reuber hepatoma H-35 and Morris hepatoma 5123 have been studied by electron microscopy and by cytochemical staining methods for a number of phosphatases. These studies emphasize the resemblances of the two tumors to rat liver, but they also indicate distinctive features in each of the three tissues. Secretory product accumulates within the cisternae of the Golgi apparatus that dilate to form the Golgi vacuoles. The vacuoles apparently separate, and secretory material undergoes further condensation within them. These "secretory vacuoles" possess acid phosphatase activity and may thus be considered lysosomes. The membranes of the Golgi apparatus are without acid phosphatase activity but show high levels of thiaminepyrophosphatase activity. The endoplasmic reticulum also hydrolyzes thiaminepyrophosphate but at a lower rate; it hydrolyzes the diphosphates of uridine, guanosine, and inosine rapidly. These observations and the electron microscopic images are consistent with the view that the cytomembranes are in a dynamic state of flux, movement, and transformation in the living cell, and that smooth surfaced derivatives of the endoplasmic reticulum become refashioned into the Golgi membranes as the Golgi membranes are being refashioned into those that delimit secretory vacuoles. The variations encountered in the two hepatomas are described. The electron microscope literature dealing with the relations of the Golgi apparatus to secretory granules, on the one hand, and the endoplasmic reticulum, on the other, is reviewed briefly.     

A comparative ultrastructural study of the trigeminal ganglion in the rat and chicken

The neurons of the trigeminal ganglia of the rat and chicken were characterized by means of light microscopic, electron microscopic, and histochemical methods. Light microscopy disclosed four types of neurons, based on the characteristics of Nissl granules: (1) large neurons with diffusely distributed and very fine granules, (2) neurons containing coarse and sparsely distributed Nissl granules, (3) neurons containing dense Nissl granules of varying size, and (4) small neurons with granules concentrated peripherally. Electron microscopy allowed further definition of these four types of neurons by the length and arrangement of flattened cisterns of granular endoplasmic reticulum (gER) and the number of neurofilaments. Type 1 cells were largest, with a mean nuclear area of 139.8 ± 28.3 μm². Type 4 cells were smallest, with a mean nuclear area of 74.6 ± 20.9 μm². The mean nuclear areas of type 2 and 3 cells were intermediate to those of the type 1 and 4 cells. Type 3 and 4 neurons lacked neurofilaments. Four forms of Golgi apparatus were found: (1) large bent grains forming a network throughout the soma, (2) dispersed fine granular deposits, (3) fine or small granules, and (4) coarse bent deposits arranged confluently in the perinuclear zone. In some rat neurons, the concentration of acid phosphatase reaction products suggested a high enzymatic activity, whereas the chicken ganglion cells showed no such concentration. These findings are discussed and compared with the classifications of previous studies.     

The fine localization of acid phosphatase activity in the unvacuolated notochordal cells of the early chick embryo

Summary The electron microscopical localization of acid phosphatase activity was investigated in ultra-thin and semi-thin sections of unvacuolated notochordal cells of chick embryos from stages 9 to 14 (as defined by Hamburger & Hamilton). At stage 9, many notochordal cells show a lightly positive reaction for acid phosphatase activity. Thereafter, the acid phosphatase-positive cells of the notochord increase in number and, at stage 14, the reaction products for the enzyme are distributed throughout almost all the cisternae of the nuclear envelope and a well-differentiated endoplasmic reticulum, the parallel cisternal and reticular parts of the Golgi complex, and various lysosomes in nearly all notochordal cells. In the cisternae of the nuclear envelope and endoplasmic reticulum, the acid phosphatase reaction products are in a fine granular form. In the outermost layer of the cisternal parts of the Golgi complex, faint lead deposits similar to those in the endoplasmic reticulum are found, but in other cisternal and reticular regions which may correspond to the GERL, considerable amounts of reaction products are present. Knob-like projections are also seen protruding from the reticular parts of the Golgi complex. These results suggest that, at least up to stage 14, the notochordal cells are actively synthesizing acid phosphatase which is directly transported from the endoplasmic reticulum to the Golgi complex. The enzyme may be accumulated by the Golgi complex from which primary lysosomes are formed. Furthermore, the pattern of the ultrastructural localization of acid phosphatase activity in embryonic notochordal cells of the chick differs from that of adult cells of other animals.     

Dictyosome polarity and membrane differentiation in outer cap cells of the maize root tip

Outer rootcap cells of maize produce large numbers of secretory vesicles that ultimately fuse with the plasma membrane to discharge their product from the cell. As a result of the fusion, these vesicles contribute large quantities of membrane to the cell surface. In the present study, this phenomenon has been investigated using sections stained with phosphotungstic acid at low pH (PACP), a procedure in plant cells that specifically stains the plasma membrane. In the maize root tip, the PACP also stains the membranes of the secretory vesicles derived from Golgi apparatus to about the same density that it stains the plasma membrane. Additionally, the membranes of the secretory vesicles acquire the staining characteristic while still attached to the Golgi apparatus. The staining progresses across the dictyosome from the forming to the maturing pole, thus confirming the marked polarity of these dictyosomes. Interestingly, the PACP staining of Golgi apparatus is confined to the membranes of the secretory vesicles. It is largely absent from the central plates or peripheral tubules and provides an unambiguous example of lateral differentiation of membranes orthogonal to the major polarity axis. In the cytoplasm we could find no vesicles other than secretory vesicles bearing polysaccharide that were PACP positive. Even the occasional coated vesicle seen in the vicinity of the Golgi apparatus did not stain. Thus, if exocytotic vesicles are present in the maize root cap cell, they are formed in a manner where the PACP-staining constituent is not retained by the internalized membrane. The findings confirm dictyosome polarity in the maize root cap, provide evidence for membrane differentiation both across and at right angles to the major polarity axis, and suggest that endocytotic vesicles, if present, exclude the PACP-staining component.     

Fine structure of the lysosomes in the two types of synoviocytes of normal rat synovial membrane

Summary The lysosomal system of the two types of synoviocytes (A and S) from the knee joint of normal rat synovial membrane was studied by electron-microscopic acid phosphatase cytochemistry. In random sections of the synovial intima lysosomes were more often encountered in the A-cell profiles than in the S-cell profiles. Characteristically, type-A synoviocytes showed many large and medium-sized lysosomes the cytochemical appearance of which varied considerably. No acid phosphatase activity was detectable in the cisternae of the Golgi apparatus or in the Golgi vesicles. In type-S synoviocytes the lysosomes were smaller, and more uniform in cytochemical appearance. Heavy deposits of acid phosphatase reaction product were constantly demonstrated in cisternae of the Golgi apparatus as well as in smooth-walled Golgi vesicles in type-S cells. The findings that type-A and type-S synoviocytes show distinctly different organization of the lysosomal system indicate that the roles of the lysosomes in these two types of cells may be different.     

Golgi apparatus, GERL, and secretory granule formation within neurons of the hypothalamo-neurohypophysial system of control and hyperosmotically stressed mice

The vasopressin-producing neurons of the hypothalamo-neurohypophysial system are a particularly good model with which to consider the relationship between the Golgi apparatus nd GERL and their roles in secretory granule production because these neurons increase their synthesis and secretion of vasopressin in response to hyperosmotic stress. Enzyme cytochemical techniques for acid phosphatase (AcPase) and thiamine pyrophosphatase (TPPase) activities were used to distinguish GERL from the Golgi apparatus in cell bodies of the supraoptic nucleus from normal mice, mice hyperosmotically stressed by drinking 2% salt water, and mice allowed to recover for 5-10 d from hyperosmotic stress. In nonincubated preparations of control supraoptic perikarya, immature secretory granules at the trans face of the Golgi apparatus were frequently attached to a narrow, smooth membrane cisterna identified as GERL. Secretory granules were occasionally seen attached to Golgi saccules. TPPase activity was present in one or two of the trans Golgi saccules; AcPase activity appeared in GERL and attached immature secretory granules, rarely in the trans Golgi saccules, and in secondary lysosomes. As a result of hyperosmotic stress, the Golgi apparatus hypertrophied, and secretory granules formed from all Golgi saccules and GERL. Little or no AcPase activity could be demonstrated in GERL, whereas all Golgi saccules and GERL-like cisternae were TPPase positive. During recovery, AcPase activity in GERL returned to normal; however, the elevated TPPase activity and secretory granule formation seen in GERL-like cisternae and all Golgi saccules during hyperosmotic stress persisted. These results suggest that under normal conditions GERL is the predominant site for the secretory granule formation, but during hyperosmotic stress, the Golgi saccules assume increased importance in this function. The observed cytochemical modulations in Golgi saccules and GERL suggest that GERL is structurally and functionally related to the Golgi saccules.     

Histochemical studies of developing human fetal small intestine

Summary The histochemical characteristics of absorptive and mucus-producing cells have been described in 16 specimens of small intestine from human fetuses between 7 and 22 weeks of age. In the youngest specimens a slight to moderate reaction was found for all enzymes examined which included those known from biochemical or ultrastructural studies to be located predominantly in Golgi apparatus (thiamine pyrophosphatase), surface membrane (alkaline phosphatase, adenosine triphosphatase, leucine aminopeptidase), lysosomes (acid phosphatase), and mitochondria (succinic dehydrogenase). Mucus granules of somehat unusual location and staining properties were also found at this time. A progressive intensification of a majority of these histochemical reactions was observed between 3 and 6 fetal months.These findings indicate that the histochemical apparatus for degradation and absorption of nutrients and for elaboration of protein and mucus is already well established in the human fetus by the end of this 6 month period. It is not known, however, whether these activities occur in utero or whether they contribute significantly to fetal nutrition.     

On the heterogeneous glycosylation of the membranes of the trans Golgi network in rabbit luteal cells

In rabbit luteal cells the transmost element (G2) of the Golgi apparatus bears cytochemical resemblances to the limiting membrane of lysosomes and it was suggested that lysosomal membranes may originate from the above element. But in the normal Golgi apparatus it cannot be made out whether the considered molecules are indeed membrane bound. Perfusing the rabbit ovary with buffer containing monensin or ammonium chloride allowed to vesiculate the trans Golgi network (G2-G1) selectively. Controls showed a well-preserved ultrastructure. Parts of the limiting membrane of the vacuoles derived from the transmost reticulum (G2) were spiny coated and carried an osmiophilic inner layer. They also showed a heavy precipitate for acid phosphatase (AcPase) and were strongly stained with phosphotungstic acid (PTA) at low pH. By neutralizing the acidic groups, involved in the PTA-staining, it was possible to show that the same membranes were more heavily glycosylated. The MvB's and the limiting membrane of lysosomes showed the same staining characteristics. The other membrane domains revealed a gradient in PTA staining and in AcPase activity. It is concluded that the trans Golgi network (G2-G1) is an acidic compartment. The presence of differentially glycosylated membranes reveals a sorting mechanism for membranous components. The highly glycosylated membrane stretches seem to be involved in endocytosis and in the formation of lysosomal membranes.     

The origin of the zymogen granule membrane of the pancreatic acinar cell as examined by ultrastructural cytochemistry of acid phosphatase, thiamine pyrophosphatase, and ATP-diphosphohydrolase activities

Cytochemical distributions of acid phosphatase, thiamine pyrophosphatase, and ATP-diphosphohydrolase activities have been examined on thin sections of rat pancreas and on isolated zymogen-granule membranes. Acid phosphatase was found in the rigid lamellae separated from the Golgi stacked cisternae, in condensing vacuoles, and in the trans-saccules of Golgi apparatus; it was not detected in purified zymogen-granule membranes. Thiamine pyrophosphatase was detected in trans-saccules of the Golgi apparatus, in purified zymogen-granule membranes, and in the plasmalemma of the acinar cell. It was absent in condensing vacuoles. The ATP-diphosphohydrolase activity has a distribution similar to thiamine pyrophosphatase. These observations illustrate the similarity between the trans-saccules of the Golgi apparatus and the membrane of mature zymogen granules and the disparity between the latter membrane and the membrane of the condensing vacuole. They suggest that the condensing vacuole might not be the immediate precursor of the zymogen granule as commonly assumed. An alternative possibility would be that condensing vacuoles would fuse with the trans-saccule (transition) of the Golgi apparatus which in turn would form mature zymogen granules.     

Ultrastructural and ultracytochemical identification of the small granules in basophils from human and animals

The small granules in the basophils obtained from humans and animals were compared ultrastructurally and cytochemically. Cytochemically, there were no qualitative differences among the small granules in the species examined. The small granules in humans, guinea pigs and rabbits were approximately 0.16-0.22 micron, 0.15-0.17 micron, and 0.12-0.16 micron, in diameter, respectively. In all species small granules had a single unit membrane and contained some amorphous material. In immature cells many of the small granules were distributed near the Golgi apparatus, while in the mature cells many of them were found around the periphery of the cell. There were no morphological or cytochemical differences between the small granules of the immature cells and those of the mature cells. The negative reaction in the dialysed iron and high iron diamine methods showed that the small granules did not have acid mucopolysaccharides or sulfated glycoconjugates. The strong reaction of the small granules of all species to the periodic acid-thiocarbohydrazide-silver proteinate (PA-TCH-SP) test, which was especially prominent in rabbit, showed that the small granules have many periodate-reactive neutral glycoconjugates but no acidic glycoconjugates. Enzyme cytochemistry revealed that the small granules are negative for peroxidase and catalase but positive for acid phosphatase.     

Fine structural and histochemical studies on salivary glands of Peripatoides novae-zealandiae (Onychophora) with special reference to acid phosphatase distribution

The Onychophora feed on small arthropods and produce saliva when ingesting prey. Although saliva undoubtedly helps to liquefy the food its constituents have not yet been fully described. The salivary glands, two long tubes of glandular epithelium, are known to secrete a powerful protease, however, besides other enzymes and mucus. In Peripatoides novae-zealandiae there are protein-secreting cells of three types, referred to here as columnar, cuboidal and modified cells, and mucus cells. The anterior two-thirds of the gland show most cell diversity, while the posterior region consists mainly of columnar cells. These are the most numerous elements overall and they probably secrete salivary protease. In thick resin sections the granules of all protein-secreting cells stain strongly with methylene blue. Those of columnar cells are markedly uneven in size and accumulate distally, eventually filling the cytoplasm. More proximal Golgi regions may be discernible. Mucus cells are all of one type and their secretion droplets are stained lightly by methylene blue. The electron microscope shows that distal microvilli, desmosomes and septate junctions are common to all gland cells. In columnar cells, secretory material is contributed by Golgi complexes and by rough endoplasmic reticulum. Early secretory vacuoles containing dense material are seen in the concavity of Golgi regions. They are precursors to larger condensing vacuoles whose contents have a more flocculent appearance, and which may attain 3–4 μm in diameter. These evolve into secretory granules, usually of uneven texture, which are up to 2–5 μm in diameter. Histochemical tests for acid phosphatase show moderate amounts of enzyme throughout the gland. In whole mounts and sections the strongest reaction is in a band of cuboidal cells along the anterior median border. Columnar cells show a diffuse cytoplasmic reaction towards the base and sometimes distal to the nucleus, and mucus cells may also react strongly round the nucleus. Cytoplasm near the lumen shows little reaction. The secretory granules do not appear to contain active enzyme. Under the electron microscope a positive reaction for acid phosphatase is seen in lysosomal derivatives near the base and lateral periphery of gland cells. These bodies are probably autophagic vacuoles and they may contain membranous whorls and possibly old secretion granules. Acid phosphatase is involved also in the elaboration of new secretory granules in both columnar and mucus cells. Dense reaction product is found in a system of interconnected tubules and cisternae near the innermost face of the Golgi complex, which is interpreted as GERL. Acid phosphatase is present in the peripheral zone of adjacent early secretory vacuoles, and interconnections occur between GERL and secretory vacuoles. It is suggested that GERL tubules containing the enzyme may fuse with early secretory vacuoles and release acid phosphatase at their periphery. The acid phosphatase reaction is negative in large condensing vacuoles and most secretory granules. These findings are consistent with what is known from mammalian cells, including those of salivary glands.     

Lysosomes in anterior pituitary corticotrophs of the rat. A combined immunocytochemical and enzyme cytochemical study

E600 resistant non-specific esterase activity or acid phosphatase activity were localized in corticotrophic cells identified by postembedding immunocytochemistry (PAP of protein A-immunogold techniques). The lysosomal system of this cell type consists of dense bodies, of a population of small lysosomes mostly situated at the cell periphery in the vicinity of secretory granules as well as of tubular structures. These latter were located either in the central part of the cytoplasm and probably belonged to the Golgi apparatus or at the cell periphery, partly in the extensions. Small lysosomes occurred to be in continuity with enzyme-containing tubules. In a few structures lysosomal enzyme activity and ACTH immunoreactivity overlapped. Some autophagic vacuoles seemed to contain secretory granule matrix. It is suggested that the concept of crinophagy can be extended to the corticotrophs, though the lysosomal system may be involved in the specific function of this cell type by other mechanisms as well.