Ultrastructure of rhesus monkey renomedullary interstitial cells.

The fine structure of rhesus monkey renomedullary interstitial cells was studied by electron microscopy. These stellate cells contained variable numbers of lipid droplets, moderate numbers of mitochondria, moderate amounts of rough endoplasmic reticulum, and prominent Golgi zones. In rare instances, apparent release of lipid droplets into the interstitium was observed. The most prominent feature of the interstitial cells was larger nuclear pseudoinclusions which were observed in a high proportion of the animals examined.     

Angiotensinase A in the renomedullary interstitial cells

Aminopeptidase A (angiotensinase A; APA) was demonstrated by histochemical means in the renomedullary interstitial cells of the golden hamster, rat, guinea pig and hare. The highest APA activities were shown in the interstitial cells of the hamster. Ultracytochemical studies of the kidney medulla of the hamster indicated that APA is localized mainly on the cell membranes of interstitial cells. Reaction product was also observed intracellularly in the nuclear membrane region. Besides the interstitial cells, APA was demonstrable ultracytochemically in the endothelial cell membranes of medullary blood vessels. Biochemical studies of APA in the renal medulla of experimental animals (sodium loaded and sodium depleted hamsters) have shown that significant changes of APA activities were available only after sodium loading, namely a decrease of APA activities in comparison to control animals. - APA through its degradation of angiotensin, is presumed, to have a bearing on the angiotensin induced prostaglandin biosynthesis of renomedullary interstitial cells.     

Lipid granularity and topographic characteristics of renomedullary interstitial cells in genetically spontaneous hypertension in rats

Light microscopy was used to study lipid granularity of the renomedullary interstitial cells (IC) in spontaneously hypertensive rats (SHR) aged 4 months and in Wistar rats (control) of the same age. Altogether 2000 IC were examined per animal on an average. The concentric distribution of the granular IC in the renal papilla was demonstrated. Lipid granularity of the IC was discovered to be lowered and the zone of granular IC to be enlarged in the whole papilla in SHR rats as compared with control. Also, the differences were found in lipid granularity of the IC in individual zones of the papilla in both SHR and normotensive animals, which seems likely to indicate different functional significance of the individual parts of the renal papilla.     

Ultrastructure of rat ovarian interstitial gland cells during pregnancy

Summary The fine structure of the interstitial gland of the rat ovary was studied at estrus and on Days 4, 6, 10, 14 and 18 of pregnancy. At estrus, ovarian interstitial cells have small nuclei with dense irregular clumps of heterochromatin. Mitochondria are small and rod-shaped and have predominantely lamellar cristae. Numerous osmiophilic lipid droplets are present. At Days 4 and 6, nuclear heterochromatin is reduced, and nucleoli are larger and complex. Mitochondria are enlarged and often bizarre-shaped and have tubular cristae. Golgi and smooth endoplasmic reticulum are more conspicuous. At Day 10, prominent ultrastructural features include nuclei with conspicuous heterochromatin, smaller mitochondria with both lamellar and tubular cristae, numerous ribosomes and lipid droplets with decreased osmiophilia. At Days 14 and 18, nuclei have increased heterochromatin, mitochondria are small and have lamellated cristae and an increase in the size and number of lipid droplets occurs. These observations suggest that steroidogenic activity of interstitial cells is highest during the first half of pregnancy and regresses during the last half. It is suggested that the interstitial gland is an important ovarian source of pregnancy hormone(s) during the first half of gestation and that LH may modulate steroidogenic activity in this ovarian component.     

Compositional changes in lipid microdomains of air-blood barrier plasma membranes in pulmonary interstitial edema.

We evaluated in anesthetized rabbits the compositional changes of plasmalemmal lipid microdomains from lung tissue samples after inducing pulmonary interstitial edema (0.5 ml/kg for 3 h, leading to approximately 5% increase in extravascular water). Lipid microdomains (lipid rafts and caveolae) were present in the detergent-resistant fraction (DRF) obtained after discontinuous sucrose density gradient. DRF was enriched in caveolin-1, flotillin, aquaporin-1, GM1, cholesterol, sphingomyelin, and phosphatidylserine, and their contents significantly increased in interstitial edema. The higher DRF content in caveolin, flotillin, and aquaporin-1 and of the ganglioside GM1 suggests an increase both in caveolar domains and in lipid rafts, respectively. Compositional changes could be ascribed to endothelial and epithelial cells that provide most of plasma membrane surface area in the air-blood barrier. Alterations in lipid components in the plasma membrane may reflect rearrangement of floating lipid platforms within the membrane and/or lipid translocation from intracellular stores. Lipid traffic could be stimulated by the marked increase in hydraulic interstitial pressure after initial water accumulation, from approximately -10 to 5 cmH2O, due to the low compliance of the pulmonary tissue, in particular in the basement membranes and in the interfibrillar substance. Compositional changes in lipid microdomains represent a sign of cellular activation and suggest the potential role of mechanotransduction in response to developing interstitial edema.     

Ultrastructure of the cells of the ovarian interstitial gland in hypophysectomized rats

Summary The fine structure of the interstitial gland of the ovary was studied in hypophysectomized rats and in hypophysectomized rats after denervation of the ovary or stimulation of the ovarian plexus. Hypophysectomized rats were used to eliminate gonadotropic influences on interstitial cells. In hypophysectomized rats, there was a large amount of intercellular space and cells had irregularly shaped nuclei and a large nuclear-cytoplasmic ratio. Prominent cytoplasmic features included small mitochondria with an electron-dense matrix, rough and smooth endoplasmic reticulum, polysomes and large osmiophilic lipid droplets. Interstitial cells from stimulated ovaries had reduced intercellular space and a reduced nuclear-cytoplasmic ratio. Mitochondria had tubular cristae; smooth endoplasmic reticulum-surrounded lipid droplets, and large polysomes were present. After section of the ovarian plexus, intercellular space was increased and filopodia were numerous. Cytoplasmic features included mitochondria with a dense matrix and indistinct cristae, large electronlucent lipid droplets, and variously sized multivesicular structures. These observations suggest that stimulation of the ovarian plexus in hypophysectomized rats causes regressed cells to assume the fine structural features of active steroidogenic cells. In contrast, interruption of the ovarian nerve supply causes a qualitative and quantitative increase in ultrastructural features characteristic of regressed steroidogenic cells. These responses of interstitial gland cells to denervation and stimulation provide morphological evidence for a functional role for the adrenergic nerves to this ovarian compartment.     

Ovarian interstitial tissue of the wood mouse, Apodemus sylvaticus

The ovary of the wood mouse contains an unusually large amount of interstitial tissue which appears to develop from undifferentiated cells of the ovarian stroma and also by transformation of theca or granulosa cells of atretic follicles. The cells are characterized by the presence of smooth endoplasmic reticulum, rounded mitochondria with tubular cristae, and abundant, large (1.5 micron diameter) lipid droplets containing cholesterol and its esters. 3 beta-Hydroxysteroid dehydrogenase activity occurs in the interstitial cells. Their ultrastructural characteristics suggest that the cells are not very active, but their abundance and the considerable amount of steroid hormone precursor they contain may compensate for low secretory activity and they may be an important and (from a developmental viewpoint) early source of steroid hormone.     

The interstitial cells in the renal medulla of rat,rabbit, and gerbil in different states of diuresis

Summary The inner zone of the renal medulla of rats, gerbils, and rabbits was investigated to determine whether or not there are any characteristic ultrastructural differences between the interstitial cells of these species. The effects on the interstitial cells of water deprivation and water loading were also investigated.In all three species, the Type 1 interstitial cells, the lipid containing cells, were abundant and their distribution and topographical relations as well as their general ultrastructure were similar. The previously reported significantly higher frequency in desert rats could not be confirmed. Although the lipid droplets of the interstitial cells were smaller in gerbils and rabbits when compared to rats, their fine structure was similar. Their electron dense outer zone was sometimes associated with a granular material and/or a lamellar material with a periodicity of about 40 Å resembling phospholipid myelin figures.Water-loaded rats showed a considerable increase in the number of lipid droplets when compared to dehydrated or untreated animals. In contrast, the interstitial cells of waterloaded gerbils and rabbits were depleted of lipid droplets.We are indebted to Professor A.B. Maunsbach for valuable discussions and criticism and to Mrss. Hanne Weiling and Birthe Overgaard for competent technical assistance. The gerbils used in this study were a gift from Leo AB, Helsingborg, Sweden. This study was supported by the Danish Medical Research Council (J. nos. 512-1067, 512-1545, 512-3633)     

Ultrastructural changes in the lungs of neonatal rats intratracheally inoculated with meconium

Meconium aspiration syndrome has been for many years an important cause of neonatal respiratory distress in newborn babies and sporadically reported in animals. This investigation was designed to study the ultrastructural and morphometric changes in the lungs of neonatal rats following the intratracheal inoculation of meconium. Seven-day-old Fischer-344 rats (n = 24) were randomly allocated in two groups. One group was intratracheally inoculated with saline solution and the second group received homologous meconium. Neonates were euthanatized at 1, 3 and 7 postinoculation days (PID) and lungs were examined by light and electron microscopy. Saline solution did not induce any ultrastructural changes in the lung. In contrast, meconium induced deciliation, recruitment of neutrophils and pulmonary alveolar macrophages to the bronchoalveolar space, intravascular sequestration of neutrophils and aggregation of platelets at PID 1 and 3. Other ultrastructural changes at PID 1 and 3 included interstitial edema and escape of red cells and fibrin into the alveolar space and interstitium. Interstitial edema and sequestration of neutrophils were responsible for the significant increase in thickness of alveolar septa. At PID 7 there was hyperplasia and enlargement of type II pneumocytes as well as interstitial proliferation of mesenchymal cells with intra-alveolar fibrosis. It was concluded that intratracheal inoculation of meconium in neonatal rats induces acute ultrastructural changes followed by a reparative response.     

Blockade of alpha-adrenergic receptors by analogues of phosphatidylcholine

The experimental evidence reviewed in this article suggests that the kidneys may have an additional function in regulating blood pressure besides their role in controlling both blood volume by urine formation and the relative state of vasoconstriction by the renin-angiotensin system. That is, the kidneys may have an additional influence upon the vasculature of a hormonal vasodilating system. The interstitial cells of the renal medulla appear to be mediating this activity and lipid compounds have been extracted from the renal medulla which display depressor activity. One such compound, the antihypertensive polar renomedullary lipid (APRL), has been demonstrated to consist of specific alkyl ether analogues of phosphatidylcholine. The vascular responses to these compounds include vasodilation of both arterioles and venules, rapid lowering of arterial blood pressure with little or no tachycardia, increased depressor activity in hypertensive animals, and blockade of vascular smooth muscle alpha 1-adrenergic receptors. Most recently, APRL and a synthetic analogue, 1-0-octadecyl-2-acetyl-sn-glycero-3-phosphorylcholine, have been used to demonstrate alpha-adrenergic receptor blockade on a smooth muscle cell line (DDT1) by radioligand assays. This action may be due to the insertion of these compounds into cell membranes causing subsequent steric interactions and blockade of the alpha-adrenergic receptor.     

Oogenesis in Hydra carnea: A new model based on light and electron microscopic analyses of oocyte and nurse cell differentiation

Oogenesis in Hydra carnea starts with an accumulation of a great number of I-cells in the interstitial spaces of the ectoderm of the body column. One centrally located I-cell becomes the future oocyte, the others differentiate into nurse cells. Presumptive oocyte and nurse cells are not easily distinguishable at that time. The earliest stage of an oocyte we could identify on ultrastructural criteria was in prophase of its first meiotic division. Only at this stage autosynthesis of nutritive substances predominates, the following rapid increase of the oocyte volume relies on the successive adoption of cytoplasmic fragments from nurse cells. Extending fingerlike processes between the epitheliomuscular cells, the oocyte then starts to phagocytose apoptotic nurse cells. Nurse cell differentiation is indicated by the appearance of lipid vesicles in I-cells. As differentiation proceeds glycogen, rEr and Golgi complexes appear and the cells increase due to a continuous production and accumulation of lipid, glycogen and yolk-like electron dense material. Then the loss of cytoplasmic fragments and degenerative changes typical of apoptosis, a morphologically defined form of cell death, converts the nurse cells into apoptotic bodies. The bulk of nurse cells becomes phagocytosed by the oocyte at late stages of their transformation into apoptotic bodies. At the end of oogenesis which in Hydra carnea takes about 4 days, the egg consists for the largest part of apoptotic nurse cells which persist in the developing embryo until hatching.     

Influence of nitrogen stress on Isochrysis galbana strain U4, a candidate for biodiesel production

Lipid accumulation has been investigated in numerous microalgal species to assess their potential with respect to biodiesel production. The present work determines the effect of nitrogen stress on physiological and ultrastructural changes in Isochrysis galbana U4. This study is unique in showing the correlations between growth, lipid production, pigmentation and ultrastructural changes in Isochrysis cells undergoing nitrogen starvation. The continuation of algal growth after the complete depletion of external nitrogen was shown to be supported by internal nitrogen stores, possibly in the pyrenoid. Cell growth ceased and lipid accumulation was initiated after the internal store of nitrogen had become exhausted. The depletion of intracellular nitrogen reservoirs to critical thresholds initiated the onset of the stationary phase, a decline in chlorophyll content and the initiation of lipid and carotenoid accumulation. The most notable ultrastructural changes, upon nitrogen stress, were the accumulation of plastidial and cytoplasmic lipid bodies and the dismantling of the chloroplast. The size of the pyrenoid when external nitrogen became depleted was found to decrease significantly, up to four‐fold. This was attributed to the remobilization of nitrogen from Rubisco. The level of expression of heterochromatin was found to increase when cells were nitrogen starved. This is thought to favor long‐term dormancy in this species because aging cells have been noted to recover rapidly when returned to conditions favorable for growth. The observations of this study are consistent with the hypothesis that the responses of Isochrysis cells to nitrogen starvation are regulated by the internal reserves of nitrogen, and the depletion of these reserves is an important trigger for lipid accumulation in this species. The findings of this study also indicate that Isochrysis galbana U4 is a promising candidate for biodiesel lipid production.     

In vivo differentiation of brown adipocytes in adult mice: an electron microscopic study

The differentiation of brown adipocyte precursor cells was studied in interscapular brown adipose tissue of adult mice by electron microscopy. Different stages of cell differentiation were characterized in situ. Previous autoradiographic studies suggested that interstitial cells represent the precursor cells of fully differentiated brown adipocytes. The present observations provide morphological evidence for a progressive differentiation of interstitial stem cells into mature brown adipocytes. Four typical stages of development were identified: (1) interstitial cells, (2) protoadipocytes, (3) preadipocytes, and (4) mature brown adipocytes. Interstitial stem cells were small spindle shaped cells, situated between brown adipocytes and characterized by a high nuclear-cytoplasmic ratio, the scarcity of organelles, and the absence of lipid inclusions. Protoadipocytes resembled interstitial cells except that they contained a few tiny lipid droplets in their cytoplasm. Preadipocytes had a larger cytoplasm enclosing many mitochondria and lipid droplets; the smooth endoplasmic reticulum was well developed surrounding the lipid droplets, and was closely associated with the mitochondria. Preadipocytes had the typical structure of growing cells, developing long cytoplasmic processes between and around blood capillaries. Mature brown adipocytes represented the final stage of differentiation. Almost all their cellular volume was occupied by lipid droplets and numerous mitochondria with very dense cristae. Brown adipocytes were also characterized by a tight association with blood capillaries, as expected from metabolically active cells requiring oxygen and substrates. These observations provide direct ultrastructural evidence for a progressive differentiation of interstitial cells into brown adipocytes with a continuum of intermediate cellular types.     

Structural and biochemical changes in mitochondria after cisplatin treatment of Dalton’s lymphoma-bearing mice

Cisplatin treatment of tumor-bearing mice and analysis of ultrastructural features of mitochondria in the kidney and Dalton’s lymphoma cells showed the appearance of more roundish mitochondria with thickened membranes. It also caused the reduction in the number and irregularity in the shape of cristae and formation of vacuoles in the mitochondria. After cisplatin treatment, decreased level of protein, succinate dehydrogenase activity, and increased level of lipid peroxidation were noted in Dalton’s lymphoma tumor cells and kidney. Cisplatin-mediated decrease in SDH activity, GSH level and an increase in LPO in the mitochondria of kidney could play an important role to produce nephrotoxicity. However, in DL cells, decrease in cellular GSH could be noteworthy than mt-GSH, along with decrease in SDH activity and increase in LPO in the cisplatin-mediated anticancer activity. These changes could play an important role to produce both the cisplatin-mediated effects i.e. anticancer activity and nephrotoxicity. Cisplatin-induced biochemical and ultrastructural changes in mitochondria after cisplatin treatment should be an important factor in the development of biochemical injury in mitochondria and affecting the overall metabolism in the cells. The findings from the present studies indicate multilevel effect of cisplatin in the cells and do support the earlier view that mitochondria could be a critical target in cisplatin-mediated anticancer activity and toxicity in the hosts.     

Ultrastructural Changes of Rice Pollen Callus Cell Grown on Differentiation Medium

A comparative observation on the rice pollen callus cultured on the medium supplemented with 2 mg/L 2,4-D and omitted 2,4-D but contained 0.5 mg/L kinetin and 0.2 mg/L NAA respectively was made by electron microscope. The callus cells when transferred to the medium containing kinetin show some changes at ultrastructural level. The numbers of mitochondria, plast and ribosome show an increase in some epidermal cells which kept an ability of active division and may be differentiated into a primordial bud. The storage materials such as lipid bodies and starch grains show sharp decrease or disappearance and the degree of vacuolation decrease in the parenchyma cells of internal callus. Besides vessel differentiation, some sieve elements appeared in the callus. The types of callus cell became various and some electron-dense cell occurred. Although above-mentioned ultrastructural changes appeared in callus cells grown under differentiation condition were true but we do not think those are specific mark for differentiating cell. More work is needed with cytochemistry and molecular biological methods to study callus cell differentiation.     

On lipid droplets in renal interstitial cells

Summary By examining Epon sections of the renal papilla, it is demonstrated that a brief period of salt repletion in salt-depleted rats induces a considerable increase in the number of lipid droplets in the renal interstitial cells. It is supposed that this difference indicates that the lipid droplets contain substances which are physiologically important for the kidneys. Possibly, these substances are prostaglandins, which have been demonstrated previously by other authors in extracts from the renal medulla.This work was supported by a grant from the Danish State Research Foundation.The author wishes to acknowledge the support and inspiration given by E. Bojesen, M.D., and P. Leyssac, M.D., the Institute of Experimental Medicine.     

On lipid droplets in renal interstitial cells

Summary By ultracentrifugation of homogenates of rat renal papillae, a low density layer composed of small primary fluorescing lipid droplets was isolated. Probably the isolated lipid material originates mainly from the primary fluorescing lipid droplets of the renal interstitial cells. The isolated lipid droplets were mainly triglycerides, cholesterol esters and free longchain fatty acids. The long-chain fatty acid composition of the main components differed markedly from that of the analogous components of plasma and depot fat. The findings suggest that the complex lipids of the isolated lipid droplets are synthetized by the renal papilla and probably by the renal interstitial cells. The prostaglandin precursor arachidonic acid constitutes a significant fraction of the triglyceride long-chain fatty acids. Usually also small quantities of prostaglandins were present. Altogether the results suggest that the lipid droplets of the renal interstitial cells may function as a storage site for prostaglandin precursor.This work was supported by a grant from the Danish State Research Foundation. — The authors wish to acknowledge the support and inspiration given by E. Bojesen, M.D., Ph.D., the Institute of Experimental Medicine, Division of Endocrinology. — The authors wish to thank Dr. John E. Pike of the Upjohn Company, Kalamazoo, Michigan, for supplying the Prostaglandins used in this study.     

Renal interstitial hyaluronan: functional aspects during normal and pathological conditions

The glycosaminoglycan (GAG) hyaluronan (HA) is recognized as an important structural component of the extracellular matrix, but it also interacts with cells during embryonic development, wound healing, inflammation, and cancer; i.e., important features in normal and pathological conditions. The specific physicochemical properties of HA enable a unique hydration capacity, and in the last decade it was revealed that in the interstitium of the renal medulla, where the HA content is very high, it changes rapidly depending on the body hydration status while the HA content of the cortex remains unchanged at very low amounts. The kidney, which regulates fluid balance, uses HA dynamically for the regulation of whole body fluid homeostasis. Renomedullary HA elevation occurs in response to hydration and during dehydration the opposite occurs. The HA-induced alterations in the physicochemical characteristics of the interstitial space affects fluid flux; i.e., reabsorption. Antidiuretic hormone, nitric oxide, angiotensin II, and prostaglandins are classical hormones/compounds involved in renal fluid handling and are important regulators of HA turnover during variations in hydration status. One major producer of HA in the kidney is the renomedullary interstitial cell, which displays receptors and/or synthesis enzymes for the hormones mentioned above. During several kidney disease states, such as ischemia-reperfusion injury, tubulointerstitial inflammation, renal transplant rejection, diabetes, and kidney stone formation, HA is upregulated, which contributes to an abnormal phenotype. In these situations, cytokines and other growth factors are important stimulators. The immunosuppressant agent cyclosporine A is nephrotoxic and induces HA accumulation, which could be involved in graft rejection and edema formation. The use of hyaluronidase to reduce pathologically overexpressed levels of tissue HA is a potential therapeutic tool since diuretics are less efficient in removing water bound to HA in the interstitium. Although the majority of data describing the role of HA originate from animal and cell studies, the available data from humans demonstrate that an upregulation of HA also occurs in diabetic kidneys, in transplant-rejected kidneys, and during acute tubular necrosis. This review summarizes the current knowledge regarding interstitial HA in the role of regulating kidney function during normal and pathological conditions. It encompasses mechanistic insights into the background of the heterogeneous intrarenal distribution of HA; i.e., late nephrogenesis, its regulation during variations in hydration status, and its involvement during several pathological conditions. Changes in hyaluronan synthases, hyaluronidases, and binding receptor expression are discussed in parallel.     

Possible link between converting enzyme inhibition and renomedullary interstitial cells

The kidney exerts both prohypertensive and antihypertensive functions. Part of the anti-hypertensive function of the kidney is mediated by the renomedullary interstitial cells (RIC), as an endocrine-type function. Six experimental models of hypertension and their relation to the antihypertensive function of the RIC are discussed. It is proposed that the anti-hypertensive function of the RIC may be deficient by the three mechanisms: 1) absence of the cells (as in the renoprival state); 2) severe damage to the cells (as in partial nephrectomy-salt hypertension of the rat and late malignant hypertension of the rabbit); and 3) constraint of the function of these cells (as in angiotensin-salt hypertension due to a lower salt intake). The constraint may result from excessive angiotensin, either by a direct effect or via a hemodynamic mechanism. The converting enzyme inhibitors (CEI) fail to exert their antihypertensive function when the RIC are absent or damaged. Conversely, the CEI are effective in those models associated with intact RIC. CEI appear to exert their antihypertensive action partly through an effect on RIC.     

Ovarian hypercytolipidemia induced by obese (ob/ob) and diabetes (db/db) mutations: basis of female reproductive tract involution II

The diabetes (db/db) and obese (ob/ob) genotype mutations induce a progressive, hypercytolipidemic condition within the ovarian compartments of the female reproductive tract that results in sterility and premature organ involution in C57BL/KsJ mice. The current studies focus on the ultrastructural changes that occur within the ovarian interstitial, thecal, and follicular granulosa cell layers during the progressive expression of these mutations which promote tissue cytolipidemia-induced organoinvolution. Control (normal: +/?), diabetes (db/db), and obese (ob/ob) genotype groups were prepared for high resolution light (HRLM) and transmission electron microscopic (TEM) analysis of ovarian tissue samples collected from 4 (young)- to 20 (aged)-week-old mice, allowing for the progressive influences of the mutational aberrations on tissue structure to be evaluated. Compared to controls, both (ob/ob) and (db/db) mutations induced a dramatic increase in ovarian interstitial, thecal and follicular granulosa cytolipid vacuole accumulations, which increased in density between 4 and 20 weeks of age. Initially, lipid vacuoles aggregated in the interstitial and thecal regions of ovarian follicles in response to the hyperglycemic-hypertriglyceridemic metabolic conditions typical of both (ob/ob) and (db/db) groups. Progressive cytoplasmic movement of the lipid pools established a perinuclear isolation from associated cytoplasmic organelles. Progressive lipid accumulations forced cytoplasmic organelles to peripheral cell compartments and altered the follicular cell profile towards that of adipocyte-like entities relative to controls. The progressive hypercytolipidemia-induced alterations in cell structure disrupted normal tissue continuity, which culminated in premature ovarian organo-involution and female reproductive sterility.