Sclerema neonatorum. Light and electron microscopic studies

Specimens from four cases of sclerema neonatorum were studied by light and electron microscopy. The connective tissue bands of the cutis and subcutis were thickened and alternated with loosely distributed bands in broad, distended areas of basal substance. Extensive areas areas filled with cross-banded structures were observed in the dermis. In the interlobular septa of the subcutaneous and perirenal fat splitting of fibers into microfibrils was visible. Changes in the capillaries and small blood vessels were also noted. Neither fat cells filled with rosettes of needle-like crystals, nor any inflammatory infiltrates of foreign body type giant cells were found in subcutaneous tissue.

Effects of fasting and insulin administration on polyribosome formation in rat epididymal fat cells

Polyribosomes from rat epididymal fat pads may be prepared in a synthetically active state and high yield by quick-freezing the tissue in liquid nitrogen, followed by grinding to a frozen powder. The number of initiated (active) ribosomes is limiting in a cell-free protein synthesis assay derived from the frozen preparation that measures completion of nascent polypeptide chains. When starved rats are killed 30 min after a single injection of insulin (0.8 unit, subcutaneously) there is a shift in the ribosomal distribution pattern (on sucrose density gradients) in the direction of larger polyribosomes. This is accompanied by a 2-fold increase in protein synthetic activity of fat cell ribosomes as measured in vitro. When isolated epididymal fat cells are treated with insulin, with or without added glucose, a 2-fold increase in the rate of incorporation of [3H]leucine into [3H]leucine into trichloroacetic acid-insoluble protein is noted within 40 min. The parallel increases in the number of initiated ribosomes, in their synthetic activity in vitro, and in the apparent protein synthetic activity of the whole cell indicate a rapidly evolving action of insulin at the level of peptide chain initiation.

[L line cell differentiation. Histochemical and electron microscopic studies]

In a medium supplemented with 60 per cent large cattle serum, part of the cell population of L-transformed culture was seen to be differentiated into mature lipocytes. The formation of structures similar to normal fat tissue took place in the same conditions, provided a reduced quantity of the seeded cells was used. The cell differentiation was accompanied with a decrease in acid phosphatase and non-specific esterase activities. The ultrastructural study has demonstrated a suitable preservation of cytoplasmic structures and a domination of the rough cytoplasmic reticulum compared to the control cell cultures where free ribosomes and polysomes predominated.

The polytene chromosomes in the fat body nuclei of Drosophila melanogaster

A photo-map of the polytene chromosomes of fat body nuclei from third instar larvae of Drosophila melanogaster has been constructed and keyed to the revised salivary gland maps of Bridges (1938), Bridges and Bridges (1939) and Bridges (1941 a, b, 1942). Apparent variations in banding pattern are discussed in the light of current studies on polytene chromosome structure and function.

Lysosomal degradation of receptor-bound 125I-labeled insulin by rat adipocytes: its characterization and dissociation from the short-term biologic effects of insulin

In this study we used chloroquine to characterize the interalization and lysosomal degradation of receptor-bound 125I-insulin by rat adipocytes and to determine the role of lysosomal processing of insulin in the short-term biologic effects of the hormone. Chloroquine inhibited the degradation of 125I-insulin bound to adipocytes by both association and disslociation experiments. In the former experiments, chloroquine caused a time- and concentration-dependent increase in specifically bound insulin owing to an increase in intact insulin and a decrease in degradation products, as determined by trichloroacetic acid precipitability and gel chromatographic analysis of material extracted from the cells. In the dissociation experiments, 50 microM chloroquine decreased the rate of degradation by two third, as reflected in the release of degradation to or degraded by isolated plasma membranes, on the degradation of 125I-insulin by proteases in the incubation medium, or on the endocytotic uptake of receptor-bound insulin. Quantitative electron miroscopy, using monomeric ferritin-insulin, showed 50 microM chloroquine doubled the number of lysosomal structures containing ferritin. These findings are consistent with an inhibition by chloroquine of lysosomal degradation of internalized receptor-bound insulin. Chloroquine, at these same concentrations, had no effect on the ability of insulin to stimulate glucose transport and oxidation or to inhibit epinephrine-stimulated lipolysis. In these studies, we show that lysosomal degradation of internalized receptor-bound insulin is not necessary for insulin to cause short-term biologic effects in the adipocyte.

A comparison of basal and insulin-stimulated glucose transport in rat adipocyte plasma membranes

Specific D-glucose transport in plasma membranes prepared from control and insulin-treated rat adipocytes was measured using a recently developed dual isotope ([3H]-D-glucose and [14C]-L-glucose), rapid filtration assay which allowed measurements of initial rates at 1 s and 37 degrees. Plasma membranes from insulin-treated adipocytes showed an increase in glucose transport compared with control cells. Saturation kinetic data revealed that the plasma membranes from insulin-treated and control cells had the same Km (26 mM) for glucose transport, whereas insulin treatment increased the Vmax from 4433 pmol/mg protein/s to 9465 pmol/mg proteins/s. Arrhenius plots showed no difference in the energy of activation between control and insulin-stimulated glucose transport states. The optimum pH of both control and insulin-stimulated glucose transport was 7.4. Lower or higher pHs progressively decreased both control and insulin-stimulated glucose transport proportionately. Calcium in the transport assay media did not affect basal or insulin-stimulated glucose transport. However, omission of calcium from the adipocyte incubation media significantly lowered the insulin stimulation by 24% while basal levels were not significantly affected. Insulin specifically bound to the plasma membrane was carried through the fractionation procedure, but removal of this insulin did not alter the stimulated glucose transport. Glucose transport by plasma membranes from control or insulin-treated adipocytes was equally (percentage) inhibited by N-ethylmaleimide, dithiothreitol, reduced glutathione, or cytochalasin B. No inhibition of control or insulin-stimulated transport was seen with cytochalasin D or oxidized glutathione. The data presented are consistent with insulin causing the formation of new transport sites similar to the existing basal sites.

Myxoid liposarcoma: study of ten cases

The ultrastructure of 10 myxoid liposarcomas from 9 patients is presented. Features closely resembling those of developing fetal adipose tissue were seen in all tumors. THe various cell types identified ranged from undifferentiated cells to typical multivacuolated and univacuolated lipoblasts. In addition, a secretory type mesenchymal cell with distended cisternae of rough endoplasmic reticulum was found in every case as well as intermediate cells with secretory product and lipid accumulation. relative proportions of these types varied from case to case. A prominent feature in all cases was the particular spatial relationship of the abundant capillaries to the various cell types. The undifferentiated cells had perivascular processes with a tendency to envelop the primitive capillaries. These cells progressively enlarged and acquired features of the differentiated cell types as they separated from the lamina. Mitotic activity, when detectable, was prominent in the capillary wall and its vicinity. Lipoblasts resembling those of brown adipose tissue frequently coexisted in the same tumor with others analogous to those of white adipose tissue. Our findings suggest that tumor cells in liposarcoma originate from a dividing population of perivascular mesenchymal cells, in a manner akin to that of developing white adipose tissue.

Complement-mediated production of plasma-membrane vesicles from rat fat-cells

1. Rat isolated fat-cells were coated with rabbit anti-(rat erythrocyte) antibody and incubated with fresh guinea-pig serum for 25 min at 37 degrees C, which resulted in a more than 95% release of the cytosolic enzyme lactate dehydrogenase. 2. Under these conditions fragmentation of the plasma membrane was examined by following the plasma-membrane markers 5'-nucleotidase, adrenaline-sensitive adenylate cyclase and membrane-bound rabbit immunoglobulin G through a differential-centrifugation fractionation procedure. 3. Approx. 50% of the plasma-membrane markers remained associated with triacylglycerol. Of the remainder more than half was pelleted by centrifugation at 10 000 g for 30 min. 4. The 10 000 g supernatant was fractionated by centrifugation on a sucrose density gradient (15-50%, w/w). This procedure resulted in the production of two visible white bands on the density gradient. The bands consisted of vesicles derived from the plasma membrane, since they coincided with peaks of 5'-nucleotidase activity, contained membrane-bound immunoglobulin G and the denser one had adenylate cyclase activity. The phospholipid and protein contents of the vesicles were determined and compared with those in purified plasma membrane. 5. It is suggested that complement-mediated lysis of rat fat-cells caused the production of plasma-membrane vesicles that differ in composition from the whole plasma membrane.

[Mechanisms of regulation of intracellular distribution of Ca2+ in adipose tissue]

The kinetics of influx and efflux of 45Ca and its accumulation by the subcellular membranes of adipose tissue have been studied. The initial rate of Ca2+ efflux does not depend on the intracellular concentration of Na+ and K+. The rate of exchange between intracellular 45Ca and 40Ca of the incubation medium is independent on concentration of Na+ and K+ in the incubation mixture. This suggests the absence of Na,Ca-transmembrane exchange in the adipocytes. The changes in the ratio of intracellular concentration of Na+ and K+ by the factors inhibiting the activity ofNa,K-ATPase cause redistribution of Ca in the intracellular pools of the adipocytes. The lypolytic agents (adrenalin, adrenocorticotropic hormone, caffeine) but not dibutytyl-3' : 5'-AMP, accelerate Ca2+ efflux from the adipocytes. At physiological concentrations of ATP, succinate and Pi the highest Ca-accumulating activity is observed in adipose tissue mitochondria. The highest initial rate of Ca uptake, as in the case of contractile tissues, is detected in the endoplasmic reticulum membranes. In contrast to the plasma membranes and reticulum, in which the Ca-accumulating capacity is independent of ATP concentration up to 0.5 mM, the Ca-accumulating capacity of mitochondria decreases 8--9-fold with a reduction in ATP concentration from 4 down to 1 mM. The physiological significance of this phenomenon in the action mechanism of lipolytic agents, which reduce the ATP content in the adipocytes, is discussed.

Benign lipoblastomatosis: ultrastructure and histogenesis

Ultrastructural study of a case of benign lipoblastomatosis revealed a cellular spectrum which included undifferentiated mesenchymal cells, stellate myxoid cells, fibroblasts, lipoblasts, lipocytes and many intermediate forms. The uni- and multivacuolated fat cells contained membrane and non-membrane bound cytoplasmic vacuoles, predominatly of saturated lipid. Their cytoplasm also contained simple-structured mitochondria devoid of intramatrical or crystalloid bodies. The fine structure of the cellular components of lipoblastomatosis supports the concept that this is a neoplasm related to fetal white fat rather than to brown fat.

Adult metachromatic leukodystrophy. IV. Ultrastructural studies on the central and peripheral nervous system

Ultrastructural studies on the central and peripheral nervous system of 2 patients with adult onset metachromatic leukodystrophy (MLD), dead at the ages of 46 and 51 years, showed MLD-specific inclusions, tufaceous and prismatic structures, a wide spectrum of membranous arrangements within lysosomal residual bodies, and the intimate admixture of sulfatides and other membranous material with lipopigments. Oligodendrocytes and Schwann cells were foremost affected but membranous inclusions could also be verified in neuronal perikarya and astrocytes. The varying ultrastructural spectrum of lysosomal residual bodies in adult onset MLD and the association with lipopigments, chiefly in nerve cells, exceed the fine structural observations on late infantile and juvenile MLD and may reflect morphological differences between these subtypes of MLD that are also known from clinical and biochemical observations.

Glomus tissue in the vicinity of the human carotid sinus

Three of 60 cadavers have shown, in the adventitia or in the adipose tissue from the human carotid sinus region, small islands of tissue richly and typically vascularized and with nerve endings contacting cells like the tissue of the principal carotid body. In two of the cases such 'miniglomera' were single but in the third there were several all on the same side. A modified en bloc silver nitrate reduction stain was used to demonstrate the microvascular arrangements and the nerve endings by light microscopy of serial tangential sections of the carotid bifurcation.

Surface structure changes of rat adipocytes during lipolysis stimulated by various lipolytic agents. A scanning electron microscopic study

A qualitative and quantitative electron microscopic study was performed on rat adipocytes during stimulation of lipolysis by various agents. Scanning electron microscopy of control cells revealed a spherical cell with a textured glycocalyx surface exhibiting small irregular projections. Globular surface evaginations or protrusions measuring 8-18 muM in diameter were seen on cell hemispheres, and there was an average of one protrusion for every two hemispheres examined. Distribution analysis showed that 60 percent of the hemispheres had no protrusions, and 25, 10, and 5 percent of the hemispheres had one, two or three protrusions, respectively. Thin-section and freeze- fracture electron microscopy of the protrusions showed a small triglyceride droplet surrounded by a thin cytoplasmic rim that was continuous with the main cytoplasmic matrix. The glycocalyx coating and plasma membrane extended from the cell surface onto, and over, the protrusion. Scanning microscopy of cells stimulated by lipolytic agents, including epinephrine, adrenocorticotropic hormone, theophylline, and dibutyryl cyclic AMP, revealed a dose-dependent increase in the number of protrusions per cell hemisphere. Maximal concentrations of lipolytic hormones cuase an average 2.5-fold increase in the number of protrusions per hemisphere without changing the average size of the protrusions. Only 40 percent of the stimulated cell hemispheres exhibited no protrusions; over 15 percent of the cells contained three or more; and a number of the protrusions were multilobulate. Insulin prevented the increase in the number of protrusions and the change in distribution caused by the lipolytic hormones but did not prevent the increase caused by theophylline and dibutryl cyclic AMP. The data suggest that the protrusions are a structural feature of the cell and may be related to the lypolytic pathway. These observations may help explain some of the discrepant biochemical data relating to hormonal stimulation of lipolysis.

Normal and experimentally induced lysosomal activity in the larval fat body of Calliphora erythrocephala Meigen

Acid phosphatase activity was demonstrated by EM-cytochemistry in 4 day old third instar larvae of the fly Calliphora erythrocephala Meigen, but not in younger stages. During larval development, the activity increased, reaching a maximum at the onset of pupariation. The reaction product was localized in Golgi vesicles and sacculi, in vacuoles and in protein granules of varying size and composition, confirming the autophagic character of the protein granules. Throughout larval development, the reaction product was restricted to membrane-bound structures and no indications of "free" cytoplasmic activity that might be related to cytolysis were found. Enzyme activity could be evoked by transplanting inactive fat body lobes into host larvae of a later developmental stage. High enzyme activity was induced in these transplants within 18 h. The sites of activity were roughly the same, but a portion of the activity in the transplants was found in the vacuoles. The induction could be inhibited by cyclohexamide.

Transplantation experiments with the fat body of Calliphora: a morphometric study of induced ultrastructural changes

Transplantation of fragments of the anterior fat body lobe of 4 day old feeding stage larvae into one day older hosts, which are at the end of feeding, leads to precocious induction of ultrastructural changes in the transplanted cells of the fat body. These changes include alterations in the mean relative and absolute areas of mitochndria, protein granules, lipid droplets and vacuoles. The extent of intracellular changes induced in the transplants depends on the physiological condition of the host. This confirms that alterations in the internal environment at termination of feeding induce prematamorphic changes in cells of the fat body.

A fine structural survey of the development of the adult fat body of Leptinotarsa decemlineata

The fat body of a female Colorado potato beetle, Leptinotarsa decemlineata, at adult ecdysis, contains a large number of protein granules which are composed of light and dark zones. Part of the light zone in some of these granules is believed to be urate. During the first two days after adult ecdysis, fat body development is not essentially different in females reared either under long- or short-day conditions. Protein granules and large vacuoles disappear and the first cell organelles are regenerated. The effect of the photoperiod on the histological structure of the fat is expressed after these events. In females reared under long-day conditions, the fat body becomes specialized for vitellogenin synthesis. Under short-day conditions, the fat body stores massive amounts of lipid until day 6 after adult ecdysis. Then the first electron-dense protein granules develop near the nucleus, and on day 10 the first autophagic vacuoles are seen. These structure changes are discussed in connection with the known biochemical properties of the adult faty body of Leptinotarsa.

Electron microscopical studies on the genesis of white adipocytes: differentiation of immature pericytes into adipocytes in transplanted preadipose tissue

In order to clarify the relationships between perivascular cells, capillaries and fat cells, with a special reference to the origin of fat cells, we have made a light and electron microscopical study on the developing epididymal adipose tissue of newborn to 5-week-old rats, and also on the differentiating, transplanted epididymal preadipose tissue from 6-day-old rats. Development of epididymal preadipose tissue progressed rapidly 6 or 7 days after birth. The preadipose tissue on the 5th day after transplantation consisted of differentiated areas with many mature fat cells, and of undifferentiated areas in which these cells were scanty. In the differentiated areas of developing epididymal preadipose tissue, both in situ and transplanted, many fat cells seemed to develop in the area immediately adjacent to growing capillaries, but cells intermediate between perivascular cells and preadipocytes were seldom observed. However, in undifferentiated areas of transplanted tissue, we found ultrastructural evidence that immature pericytes of capillaries can differentiate into preadipocytes.

Dexamethasone effect on the phospholipid content of isolated fat cell ghosts from adrenalectomized rats

The lipid composition of sonicated ghosts from isolated fat cells has been investigated. Epididymal fat cells from adrenalectomized rats were incubated with and without 8 x 10(-8) M dexamethasone for 3 h. Phospholipids and cholesterol were isolated from membrane ghosts prepared from these cells. There was a 61% increase in membrane sphingomyelin from cells incubated with dexamethasone (P less than 0.025). No significant change was observed in other phospholipids, cholesterol, or fatty acid components of the phospholipids.

Intermitochondrial bridge junctions in fat body cells of the pre-hatch larvae of the forest tent caterpillar Malacosoma disstria HBN

An electron microscopic feature of fat body cells of diapausing Malacosoma disstria pre-hatch caterpillars, experimentally held at certain controlled time-and-temperature conditions, is an elaborate bridge junction, between mitochondria, strikingly similar in appearance to the septate junction which has frequently been described as occurring between cells of many invertebrate species. It is suggested that the intermitochondrial unctions may well represent elaborate forms of interaction between organelles in order to enhance metabolic efficiency in times of stress.