Vacuolar Area Research Articles

Aspects of iron nutrition in macroalgaeUlva pertusa (Chlorophyta) under iron stress

Fe, Chlorophyll (Chl) and total nitrogen (TN) content in tissues were measured in Fe-deficient cultures ofUlva. pertusa over a period of 60 days. Photosynthetic carbon fixation rates were studied at the start of and 30 days after Fe-deficiency culture, when the effects of Fe-deficiency on the ultrastructure were also analyzed. The iron content in tissue decreased exponentially during Fe-deficiency (from 726.7 to 31.6 μg/gdw) and simultaneously Chl and TN content declined to 4.35% and 59.9% of their original levels respectively. Maximum carbon fixation rate (50–250 μmol/m2 s) under Fe-deficiency decreased significantly compared with the control (p<0.01) and was 13.6 to 0.365 μg C/cm2 h. Photosynthesis in Fe-deficient cells became light-saturated at lower irradiance than that in control. Ultrastructural observations of Fe-deficient cells showed reductions in chloroplast number, some degeneration of lamellar organization, an increase in vacuolar area, a decrease in mitochondrial matrix density, and variation in accumulation body number and morphology. During Fe-deficiency, the algae growth rate continued to decline and after 6 weeks of iron deficiency, no further growth was detectable. These suggested that the lower growth rate ofUlva. pertusa under Fe-deficiency could be due mainly to nitrogen utilization and inhibition of photosynthesis.

Effects of natural ventilation on leaf ultrastructure of Dianthus caryophyllus L. cultured in vitro

Vessel closure configurations exert direct and indirect control over factors pertaining to the physical boundaries of the mieroenvironment, and induce a typical phenotype in in vitro plant production. Upon modification of the in vitro environment, carnation explants showed a gradation of their ultrastructural characteristics from hyperhydric to normal. A higher degree of development was observed in plants from vessels with higher ventilation compared to ones from vessels with low ventilation rates. The cell walls of epidermal cells from both normal and hyperhydric plants grown in nonventilated vessels were less developed than those from plants grown in ventilated vessels. Cytoplasm of normal plants was dense and generally located in parietal areas. The cytoplasm was even more dense in plants grown in ventilated vessels and acclimated. The degree of thylakoid stacking and distribution were affected by ventilation conditions, being poorly developed with low ventilation. Ultrastructurally, stomata from in vitro plants are ready to carry out their task, although there are significant differences in guard cell size and vacuolar area between acclimated and in vitro plants.

Cytochemical study of the involvement of cell organelles in formation and accumulation of fibrillar amyloid in the pancreas of NORbeta transgenic mice.

Phosphatase ultrastructural cytochemistry was used to evaluate the participation of cytoplasmic organelles in the accumulation of fibrillar amyloid beta (Abeta) in exocrine acinar cells and in macrophages of the pancreas of transgenic mice overexpressing a carboxy-terminal fragment of Abeta protein precursor (ABPP). Nucleoside diphosphatase (NDPase) and glucose-6-phosphatase (G6Pase) were used as cytochemical markers of the endoplasmic reticulum (ER), thiamine pyrophosphatase (TPPase) as a marker of the Golgi apparatus (GA), and acid phosphatase (AcPase) as a marker of lysosomes. Monoclonal antibody 4G8 raised against the 17-24 aa sequence of human Abeta protein was used for immunogold localization of fibrillar Abeta. The results of this study indicate that the formation of Abeta in acinar cells occurs directly in the vacuolar areas of the rough ER (RER) without evident participation of the elements of the GA, whereas an intimate structural relation with primary lysosomes suggests their role in modification or digestion of the deposited amyloid. In macrophages, fibrillar amyloid was present in numerous cytoplasmic vacuoles located frequently in close proximity to flattened saccules of the ER. This structural pattern revealed similarity to that observed previously in microglial cells producing fibrillar PrP amyloid in scrapie-infected mice and Abeta in brains of human elderly patients and in Alzheimer's type brain pathology.

Hydrogen peroxide-induced changes in intracellular pH of guard cells precede stomatal closure.

Epidermal bioassay demonstrated that benzylamine, a membrane-permeable weak base, can mimick hydrogen peroxide (H2O2) to induce stomatal closure, and butyric acid, a membrane-permeable weak acid, can partly abolish the H2O2-induced stomatal closure. Confocal pH mapping with the probe 5-(and-6)-carboxy seminaphthorhodafluor-1-acetoxymethylester (SNARF-1-AM) revealed that H2O2 leads to rapid changes in cytoplasmic and vacuolar pH in guard cells of Vicia faba L, i. e. alkalinization of cytoplasmic areas occur red in parallel with a decrease of the vacuolar pH, and that butyric acid pretreatment can abolish alkalinization of cytoplasmic areas and acidification of vacuolar areas of guard cells challenged with H2O2. These results imply that the alkalinization of cytoplasm via efflux of cytosol protons into the vacuole in guard cells challenged with H2O2 is important at an early stage in the signal cascade leading to stomatal closure.

Infection of Vero cells with Coxiella burnetii phase II: relative intracellular bacterial load and distribution estimated by confocal laser scanning microscopy and morphometry

Coxiella burnetii, the agent of Q fever in man and of coxiellosis in other species, is an intracellular pathogen not yet grown axenically. Confocal laser fluorescence microscopy and morphometry were used to measure relative C. burnetii phase II loads and their intracellular distribution in aldehyde fixed and DAPI stained Vero cell monolayers. The fluorescence of single horizontal optical sections provided useful information on relative loads of bacteria in cells and vacuoles. The relative density of the bacteria in the vacuoles was inferred from ratios of fluorescence to vacuolar section areas. Relative bacterial loads, bacterial densities and section areas of large vacuoles increased exponentially between days 2 and 4 of the infection of γ-irradiated host cells, stabilized between days 4 and 6, and decreased thereafter. Estimated minimum doubling times were higher for the overall complement of the intracellular organisms (about 12 h) than for bacteria that were confined to larger vacuoles (about 10 h).

Delayed irradiation effects on nasal epithelium in patients with nasopharyngeal carcinoma. An ultrastructural study.

The ostiomeatal complex is responsible for the clearance of most sinus secretions. To evaluate the delayed effects of irradiation. this study examined the infundibulum mucosa of 10 patients who developed sinusitis after receiving radiotherapy for nasopharyngeal carcinoma (NPC). Pathologic findings under the light microscope revealed an increased deposition of dense collagenous fibers in the lamina propria. The epithelial cells also transformed into a stratified arrangement and showed gradual reduction of cytoplasmic volume. Ultrastructural observations detected areas of ciliary loss, intercellular and intracellular vacuolation, and ciliary dysmorphism. Most of these pathologic findings were observed even in a patient 23 years after irradiation. The results presented herein suggest that radiotherapy may cause long-term damage to the nasal epithelium that may be responsible for the prolonged sinusitis of irradiated NPC patients.

Development of Vacuoles and Vacuolar H+‐ATPase Activity under Extremely High CO2 Conditions in Chiorococcum littorale Cells

Abstract: The number and cross‐sectional area of vacuoles in Chlorococcum littorale cells visualized with a differential interfer ence fluorescence microscope increased after their transfer from air to 40% CO2. An immunological observation indicated that the level of subunit B of vacuolar H*ATPase also increased under 40% CO2 conditions. The activity of nitrate‐sensitive ATP‐ase associated with the vacuolar membrane was 2–fold higher in 40% CO2‐‐grown cells than in air‐grown cells. The effects of inhi bitors on the ATPase activity confirmed that these activities were derived from vacuolar‐type H‐ATPase. These results sug gest that vacuole development associated with that of vacuolar H+‐ATPase occurred during the acclimatization of C. littorale cells to extremely high CO2 conditions.

Spontaneous and artificial lesions of magnocellular reticular formation of brainstem deteriorate avoidance learning in senescence-accelerated mouse SAM

The role of the magnocellular reticular formation (MGRF) of the brainstem on learning and memory was examined in memory-deficient mice with spontaneous spongy degeneration in the brainstem (senescence-accelerated mouse, SAMP8) and control mice (accelerated-senescence resistant mouse, SAMR 1). SAMP8 showed spontaneous age-related impairment of learning and memory, as determined by passive and active avoidance responses. The deficits of learning and memory function in passive avoidance performances began at two months of age and increased with ageing. In the brains of SAMP8 at one month of age and older, spongy degeneration was mainly observed in the brainstem, while no vacuoles were evident in SAMR1 control (normal ageing mouse) brains in the age range tested (up to 12 months). The vacuolization in SAMP8 was marked in the MGRF, especially in the dorsomedial MGRF. Quantitative analysis of the vacuolization showed that the total area and number of vacuoles in the MGRF increased with age, and they were affected by the degree of deficits in learning and memory. The latency 24 h after footshock in passive avoidance tests decreased with the increase in total area and number of vacuoles in MGRF. The number of shocks in active avoidance tests increased with the increase in total number and area of vacuoles. Thus, learning and memory ability in passive and active avoidance responses deteriorated with enlargement in the vacuolated area in MGRF, and it was assumed that MGRF (especially, the dorsomedial part) possesses functions related to learning and memory. To confirm this notion, behavior and memory tests (passive avoidance and active avoidance tests, open field tests and shock sensitivity measurements) were carried out in SAMR1 mice, whose bilateral dorsomedial MGRF was destroyed electrolytically (MGRF-lesioned mice). The MGRF-lesioned mice showed no difference from sham mice in sensory threshold or open field activity; however, there was severe deterioration in passive avoidance behavior and impairment in the active avoidance performances. From the results in SAMP8 and MGRF-lesioned mice, it was confirmed that MGRF (especially the dorsomedial part) has functions related to learning and memory, and is one part in the learning and memory system of the brain. Thus, SAMP8 can serve as a model of RF-lesioned mice with impaired learning and memory functions.

Multifocal retinopathy of Great Pyrenees dogs.

Forty-four related Great Pyrenees dogs were examined ophthalmoscopically. Focal retinal elevations, multiple gray-tan-pink subretinal patches, and discrete areas of tapetal hyper-reflectivity were seen in 19 dogs, ranging from 13 weeks to 10 years of age. These lesions varied in size from focal spots that were barely visible with the indirect ophthalmoscope to areas that were larger than the optic disc. Complete blood cell counts, serum biochemical profiles, urinalyses, and blood pressure measurements were completed on four affected dogs and all were within normal reference ranges. Photopic and scotopic electroretinography was completed and the a-wave and b-wave amplitudes and latencies were similar for affected and age-matched nonaffected Great Pyrenees and other normal dogs. Electroretinograms that were examined twice during a 3-year period on three affected adult dogs did not reveal significant progressive deterioration of the a or b-wave parameters. Fluorescein angiography was completed on four affected dogs of ages 1 (n = 2), 5, and 6 years. These angiograms were repeated in three of these dogs 1 year later. The blood ocular barrier was intact in these dogs but there was blocked choroidal fluorescence. Postmortem examination, light microscopy, scanning and transmission electron microscopy were performed on three affected puppies and two affected adult dogs. These examinations revealed that the lesions in the puppies were limited to bilateral multiple areas of retinal pigment epithelial vacuolation, hypertrophy, and apparent separation from Bruch's membrane, and multiple serous retinal detachments. The affected adult dogs had focal retinal degeneration and retinal pigment epithelial hypertrophy, hyperplasia and pigmentation. Pedigree analysis and test mating confirm that this condition is inherited, probably as an autosomal recessive trait. This condition develops at approximately 13 weeks of age and the focal areas of retinal detachment and retinal pigment epithelial vacuolation progress to permanent and stable focal areas of retinal degeneration, and retinal pigment epithelial hypertrophy and pigmentation.

Histopathological changes in the pituitary glands of female hamsters infected with the 139H strain of scrapie

Previous studies in hamsters showed that the 139H strain of scrapie injected intracerebrally caused a generalized endocrinopathy and marked hypoglycaemia and hyperinsulinaemia. The low scrapie infectivity levels in the pancreas suggested that the changes noted in that organ were of neuroendocrine origin. In the current study, female weanling Syrian hamsters were inoculated intracerebrally with scrapie strain 139H or 263K, or with homogenate of normal hamster brain. Coronal sections of the pituitary gland were stained with haematoxylin and eosin, Gomori's one-step trichrome, Congo red, thioflavin-S, and antibodies specific for several pituitary hormones. Sections were examined by light microscopy. The hamsters inoculated with scrapie strain 139H showed extensive pituitary vacuolization. Most vacuoles were located in the ventral or ventrolateral parts of the pars distalis. The pituitary glands of 139H-infected hamsters also showed cellular changes, namely, hypertrophy, atrophy and cytoplasmic vesicles. Nuclear changes such as swelling, vesicle formation, chromatin increase, pyknosis, karyorrhexis and karyolysis also occurred. The cellular and nuclear changes were most pronounced in the regions with vacuolation. Hamsters infected with the 263K strain did not show these changes. Immunocytochemical examination suggested that parenchymal cell types which produce different hormones were affected in areas of vacuolation. The changes produced by 139H were not seen in hamsters infected with strain 263K. This study provides the first evidence of cytopathological changes in the pituitary glands of scrapie-infected animals and suggests a relationship between the pituitary changes and the pathological findings in the pancreas and other endocrine organs of 139H-infected hamsters.

Diel changes in gut-cell morphology and digestive activity of the marine copepod Acartia tonsa

Morphometric measurements of the gut cells of the marine calanoid copepod Acartia tonsa were made over a 24 h diel cycle to test the hypothesis that feeding rhythms in this copepod are limited by the cycles of blishter-like cells (B-cells) in the gut. Copepods were collected from Long Island Sound, New York, USA, in June 1991. Experimental treatments included low (1 μg chlorophyll al-1) and high (10 μg chlorophyll al-1) food concentrations. Copepods were fixed and embedded in Epon at six time intervals over the 24 h period, and semi-thin sections through the length of Midgut Zone II were analyzed for gut-cell area and vacuole area, with area measurements integrated to yield estimates of gut-cell volume and vacuole volume. Concurrent measurements of gut fluorescence, a measure of gut fullness, and digestive enzyme activities also were made. A diel cycle in gut fluorescence was observed, most notably in the low-food treatment, which exhibited a 3-fold increase in gut pigments. There was little consistent change in digestive enzyme activities over this time span. Gaps in the gut wall indicative of spent B-cells were observed in 17 of 39 copepods, with no trend over time or food treatment. Generally, only a single gap was seen in any one copepod. B-cells were vacuolated throughout the 24 h period. Morphometric analyses revealed a correlation between gut fluorescence and both maximum vacuole area and vacuole volume, as well as percent vacuolated cell volume, in the low-food treatment. The high-food treatment, which had a relatively smaller increase in gut fluorescence (1.5-fold) during the night cycle, showed no significant increase in vacuole size. B-cells appear to have a life-cycle greater than the diel feeding period, and while B-cell vacuoles respond to the ingested food during the diel cycle, production of B-cells does not appear to be a limiting factor in A. tonsa's feeding cycle.

In Vitro plant cell growth in microgravity and on clinostat

For the study of gravity's role in the processes of plant cell differentiation in vitro, a model “seed-seedling-callus” has been used. Experiments were carried out on board the orbital stations Salyut-7 and Mir as well as on clinostat. They lasted from 18 to 72 days. It was determined that the exclusion of a one-sided action of gravity vector by means of clinostat and spaceflight conditions does not impede the formation and growth of callus tissue; however, at cell and subcellular levels structural and functional changes do take place. No significant changes were observed either on clinostat or in space concerning the accumulation of fresh biomass, while the percentage of dry material in space is lower than in control. Both in microgravity (MG) and in control, even after 72 days of growth, cells with a normally developed ultrastructure are present. In space, however, callus tissue more often contains cells in which the cross-section area of a cells, a nuclei and of mitochondria are smaller and the vacuole area - bigger than in controls. In microgravity a considerable decrease in the number of starch-containing cells and a reduction in the mean area of starch grains in amyloplasts is observed. In space the amount of soluble proteins in callus tissue is 1.5 times greater than in control. However, no differences were observed in fractions when separated by the SDS-PAGE method. In microgravity the changes in cell wall material components was noted. In the space-formed callus changes in the concentration of ions K, Na, Mg, Ca and P were observed. However, the direction of these changes depends on the age of callus. Discussed are the possible reasons for modification of morphological and metabolic parameters of callus cells when grown under changed gravity conditions.

Viral load and its relationship to quinolinic acid, TNF alpha, and IL-6 levels in the CNS of retroviral infected mice.

Mouse models of infection of the central nervous system (CNS) have been used to study retroviral-induced neurologic disease. Ecotropic-neurotropic murine leukemia virus (MuLV) infection of susceptible neonatal mice causes a neurologic disease characterized by progressive hindlimb paralysis. The lesions consist of chronic noninflammatory spongiform change predominantly involving brainstem and spinal cord. Two molecularly cloned strains of MuLV, ts-1, a temperature-sensitive mutant of Moloney MuLV, and pNE-8, derived from a feral mouse isolate Cas-Br-E, were used in this study. Infected mice were sacrificed at regular intervals postinoculation throughout the time-course of disease. The neuropathology was evaluated using standard histological and immunohistopathological techniques. Tissue concentrations of viral proteins and potentially cytotoxic factors were compared with the histopathology in select regions of the CNS. Areas of extensive vacuolation with neuronal and oligodendroglial infection were observed in spinal cord, brainstem, and cerebellum. High titers of infectious virus were observed within CNS lesions, whereas low titers were observed in morphologically uninvolved areas. Western blot analysis revealed abundant production of viral envelope proteins, which correlated well with infectious virus titers. Serum quinolinic acid (QUIN) concentrations in both groups of noninfected and infected mice were similar. However, CNS tissue concentrations of QUIN, TNF alpha, and IL-6 in ts-1 infected mice were significantly higher than in pNE-8 infected or noninfected mice. The difference in concentration of these factors may be the result of greater activation of macrophages/microglia in ts-1 infected mice. During murine retroviral encephalitis, CNS damage may be mediated by direct infection of CNS cells and may be enhanced by indirect effects of neurotoxic factors possibly secreted by infected/activated macrophages.

Platelet morphology in Parkinson's disease: An electron microscopic study

There are no peripheral diagnostic markers for Parkinson's disease (PD). However, recent studies of platelets in PD patients indicate that mitochondrial and monoamine oxidase function may be abnormal. This investigation examines platelets in PD from a morphological standpoint utilizing transmission electron microscopy (EM). Fourteen PD patients (seven treated, seven untreated) and seven age matched controls had platelets separated from other blood components, fixed in a standardized fashion and examined by EM. Platelets (in the activated form because they were collected in glass tubes) were evaluated at magnifications of 15,000 × and 40,000 ×. Abnormalities observed in treated and untreated PD patients included the presence of numerous large intracytoplasmic vacuoles formed from the open canalicular system. Morphometric examination performed at 40,000 × magnification indicated that the mean area of vacuoles and the cytoplasmic volume percent of platelets occupied by vacuoles were significantly greater in PD (p < 0.05) than controls. However, differences observed between treated and untreated PD groups suggest that these changes could be caused by the disease or the treatment or both. No abnormalities were found in relation to mitochondria, storage granules and glycogen. From EM assessment, we conclude that platelets in PD are morphologically abnormal.

The ultrastructure of micropropagated and greenhouse rose plant stomata

Stomata of leaves from in vitro grown rose plantlets remain opened in the dark. The ultrastructure of their guard cells was studied after a 7 h light and a 7 h dark period, and compared to that of functional stomata from plants which have been acclimatized to greenhouse conditions. Qualitative and quantitative observations concerning the shape of the guard cells, mitochondria, plastids and starch grains, demonstrated the similarity in guard cell ultrastructure. The peculiarity of guard cell ultrastructure of in vitro cultured plants was the inability to close in the dark; vacuolar area was 40% of the whole guard cell area during both light and dark period whereas, in guard cells from greenhouse plants, the vacuolar area was 40% of the whole guard cell area during the light and only 25% during the dark period. These results indicate that stomata from in vitro plants are duly developed and possess an ultrastructure suitable for a typical functioning. The inability to close in the dark results from atypical water relation.

Physarum vitronectin-like protein has extensive homology to dihydrolipoamide acetyltransferase.

Physarum vitronectin-like protein with a molecular mass of 70 kDa cross-reacts with anti-bovine vitronectin and promotes cell-spreading (Miyazaki, K. et al. 1992. Exp. Cell Res., 199: 106-110.). The amino-terminal sequence of Physarum vitronectin-like protein is, however, distinct from those of animal vitronectins but shows significant sequence homology with dihydrolipoamide acetyltransferase, a component of pyruvate dehydrogenase complex. We have investigated the structural relationships between Physarum vitronectin-like protein and dihydrolipoamide acetyltransferase by using both antibody and protein-chemical methods. The vitronectin-like protein reacted with both anti-bovine vitronectin IgG and anti-rat pyruvate dehydrogenase complex IgG, indicating that it shares common antigenic determinant(s) with rat pyruvate dehydrogenase complex. Furthermore, sequencing studies of peptides obtained by lysylendopeptidase digestion indicated that internal sequences of Physarum vitronectin-like protein show significant homology with dihydrolipoamide acetyltransferase, but do not show any homology with the primary structures of authentic vitronectins. Immunocytochemistry revealed that the protein is widely localized in cytoplasm and nuclei of Physarum polycephalum, but is not present in the central area of vacuoles. Our results indicate that Physarum vitronectin-like protein is a molecule structurally and immunologically related to dihydrolipoamide acetyltransferase but functionally similar to animal vitronectin, although its localization is unique.

A primary demyelinating disorder of young cattle

The clinical signs and neuropathological changes are described in six Limousin X calves that, at about one month after birth, showed signs of blindness, nystagmus, rotation of the eyes, opisthotonos, hyperprotraction of the forelegs and, in one case, apparent seizures. Pathologically there was necrosis of the optic chiasma and focal areas of myelin sheath vacuolation or demyelination in certain areas of the brain, especially in the cerebellar peduncles. In one animal, kept alive for 7 months, there was remyelination by Schwann cells of some demyelinated axons in the focal cerebellar lesions, while other axons remained demyelinated. There was no evidence of oligodendrocyte remyelination. The cause of the condition was not determined but a genetic association is likely.

Topographic distribution of scrapie amyloid-immunoreactive plaques in chronic wasting disease in captive mule deer (Odocoileus hemionus hemionus)

Chronic wasting disease (CWD), a progressive neurological disorder of captive mule deer, black-tailed deer, hybrids of mule deer and white-tailed deer and Rocky Mountain elk, is characterized neuropathologically by widespread spongiform change of the neuropil, intracytoplasmic vacuolation in neuronal perikarya and astrocytic hypertrophy and hyperplasia. We report the topographic distribution of amyloid plaques reactive to antibodies prepared against scrapie amyloid in CWD-affected captive mule deer (Odocoileus hemionus hemionus). Scrapie amyloid-immunoreactive plaques were found in the cerebral gray and white matter, in deep subcortical nuclei, in isolation or in clusters in areas of vacuolation, and perivascularly, in subpial and subependymal regions. In the cerebellum, immunoreactive amyloid plaques were observed in the molecular, pyramidal and granular layers. Scrapie amyloid-immunoreactive deposits were also seen in neuronal perikarya. Furthermore, amyloid plaques in CWD-affected captive mule deer were alcianophilic at 0.3 M magnesium chloride indicating the presence of weakly to moderately sulfated glycosaminoglycans. Our data corroborate that CWD in captive mule deer belongs to the subacute virus spongiform encephalopathies.

Amiodarone toxicity: II. Desethylamiodarone-induced phospholipidosis and ultrastructural changes during repeated administration in rats

The contribution of desethylamiodarone (DEA), principal metabolite of the antiarrhythmic drug amiodarone, to the major side effects of amiodarone is unclear. The effects of repeated DEA administration to rats on tissue drug accumulation, ultrastructural changes, and phospholipid concentrations were studied. Two groups ( n = 8/group) of male Sprague-Dawley rats (250 g body wt) were administered a 5% aqueous solution of DEA (Dose I, 40 mg/kg/day; Dose II, 60 mg/kg/day) intraperitoneally for 21–23 days, while a third group (control, n = 8) received saline. DEA levels were significantly higher with Dose II compared to Dose I in the lung, liver, kidney, spleen, heart, and serum while the tissue to serum ratios were similar with both doses for all tissues except the heart. DEA administration caused a significant elevation in the lipid phosphorus levels of liver, lung, and alveolar macrophages compared to control levels. A strong positive correlation ( p < 0.01) was found between tissue DEA levels and lipid phosphorus for the above tissues. Electron microscopy revealed the presence of lipid inclusion bodies in liver, lung, and alveolar macrophages of DEA-treated rats. A dose-dependent increase in the percentage of vacuolar surface area was found in the lung and alveolar macrophages. The tissue ultrastructural changes after repeated DEA dosing were qualitatively similar to our previous findings with amiodarone. Increased lung and liver phospholipid levels with repeated DEA doses may result from a potent inhibitory action of DEA on tissue phospholipase A as has been observed by others in in vitro studies.

Comparison of the Rat Pinealocyte Ultrastructure With Melatonin Concentrations During Daytime and at Night

The aim of this study was to investigate the ultrastructure of rat pinealocyte during daytime (1600 h) and at night (0100 h) and to compare these observations with serum melatonin levels in the same animals. In addition, pineal melatonin concentrations were determined in other animals. Both serum and pineal melatonin concentrations were significantly higher at night than during daytime (34 and 21 times, respectively). Sizes of pinealocytes, their nuclei, and nucleoli, as well as cross-sectional areas of mitochondria and granular endoplasmic reticulum were also higher at night than during daytime, whereas areas of lysosomes, Golgi apparatus, and vacuoles containing flocculent material did not differ at the time points studied. In contrast, the number of dense-core vesicles was higher during daytime. The results of the present study show that morphological patterns of higher metabolic activity of the rat pinealocyte at night when compared to those during daytime correlate with melatonin concentrations.