Mitochondrial Surface Density Research Articles

Morphometric Analysis of the Internal Ultrastructure of Mitochondria of Muscle Tissue in Horsehair Worm Gordionus alpestris (Nematomorpha)

Internal ultrastructure of the muscle tissue mitochondria of horsehair worm Gordionus alpestris (Nematomorpha) was studied using morphometry. Surface area of the inner mitochondrial membrane per unit of the mitochondrial volume, or surface density of the inner mitochondrial membrane, was measured as a main morphometric parameter. The surface density of the inner mitochondrial membrane of the G. alpestris muscle tissue was compared to the respective parameter of the skeletal and cardiac muscle mitochondria. The surface density of the inner mitochondrial membrane of the worm was close to the surface density values of the cardimyocytes of 3-month-old mice and Wistar rats and was slightly higher than the surface density of mitochondria from the skeletal muscle of 3-month-old mice. The functional significance of the well-developed system of mitochondrial membranes of extended mitochondria of the horsehair worm is discussed as a structure necessary to ensure effective functioning of the circomyarian conntractile apparatus in the muscle tissue of the horsehair worm.

Effects of verapamil and timolol on cellular morphometric changes in cat hearts with regional ischaemia.

In twenty-one anaesthetized open chest cats the left anterior descending coronary artery (LAD) was occluded for three hours. Seven cats were pretreated with a bolus injection of Verapamil, followed by a continuous infusion of Verapamil during the ischaemic period. Seven cats were pretreated with a bolus injection of Timolol to a heart rate reduction of 20 beats/min or more and seven cats were given saline. In the latter two groups the cats received a continuous infusion of saline during the period of coronary occlusion. Biopsies were taken from the mid-myocardium of the normal, border and ischaemic zones, as defined by fluorescein staining, and verified by blood flow measurements with radiolabelled microspheres. Standard point counting techniques were used for calculations of fractional volumes of mitochondria, cytoplasm and myofibrils as well as of mitochondrial surface density and surface to volume ratio. We observed a cytoplasmic oedema in the border and ischaemic zones, that was not altered by medical treatment. In the border zone of the control cats there is greater mitochondrial swelling than in the ischaemic zone. This particular swelling is not seen in the treatment groups. However, in the normal and border zones of the verapamil group the mitochondria are smaller when compared with the respective zones in the two other groups, but increases relatively more in size in the border and ischaemic zones. Furthermore, we measured the water content, sarcomere length and per cent heavily damaged cells. These variables were not altered by Verapamil or Timolol in any zone when compared with the respective zones in the control group.

Stereological analysis of peroxisomes and mitochondria in intestinal epithelium of patients with peroxisomal deficiency disorders: Zellweger's syndrome and neonatal‐onset adrenoleukodystrophy

Peroxisomes, participants in lipid metabolism, have been shown to be altered in liver in two metabolic diseases in which long-chain fatty acids accumulate in tissues: Zellweger's syndrome and neonatal adrenoleukodystrophy (ALD). The intestine also plays a role in lipid metabolism, and we have had the opportunity to compare peroxisomes in normal intestinal epithelium with those from patients with Zellweger's syndrome and neonatal ALD at the electron microscopic level by using the combined techniques of cytochemistry and stereological analysis. Peroxisomes were numerous in intestinal epithelium of the normal individuals. They were ellipsoidal in shape with average diameters of 0.37 by 0.56 micron and filled with coarsely granular, DAB+ content. Peroxisomes in the intestinal epithelium of the ALD patient were similar in appearance and number but smaller in size (0.28 by 0.44 micron). Peroxisomes of normal appearance were absent from the intestinal epithelium of patients with Zellweger's syndrome; DAB+ content, however, was observed in rare, membrane-bound structures of much smaller size (0.12 by 0.19 micron). In liver of patients with Zellweger's syndrome, peroxisomes are lacking; in neonatal ALD they are abnormal in appearance and greatly reduced in number. The presence of rare minute peroxisomes in the intestinal epithelium in Zellweger's syndrome and of small peroxisomes in this epithelium in neonatal ALD indicate that peroxisomes in the intestinal epithelium are affected in these diseases, but to a lesser extent than in the liver. In the ALD intestinal epithelium, DAB+ material was also seen in long, sinuous, tubular or cisternal elements intermingled and occasionally in continuity with peroxisomes. It is suggested that these represent the early stages of peroxisome formation, the peroxisomal reticulum as originally envisioned by Lazarow, while the rare structures seen in Zellweger's represent rudiments of such a reticulum. Lamellar inclusions and clear spaces occurred in the cytoplasm adjacent to these structures indicating either that material accumulated there had been extracted during fixation or that these regions are more susceptible to autolysis. Mitochondria are also involved in lipid metabolism and have been reported to be abnormal in Zellweger's tissue. No qualitative differences were observed in the mitochondria of the intestinal epithelia examined in this study. Although quantitation revealed a greater mean volume, number, and surface density of mitochondria in the intestinal epithelia of neonatal ALD, it was not a statistically significant difference in all cases.

Stereologic analysis of ultrastructural changes in cardiomyocytes in adriblastine-induced cardiomyopathy

Both single and graded administration of an anthracycline antibiotic adriablastine at a dose of 20 mg/kg to white rats have resulted in cardiomyocyte volume decrease, dystrophia and lysis of myofibrils, and reduction of mitochondrial surface density volume. Accumulations of myelin bodies of different configuration and diffuse myolysis were observed. Myelin bodies and diffuse myolysis of cardiomyocytes in adriablastine-induced cardiomyopathy are believed to be a morphological sign of lipid peroxidation.

Effects of thyroidectomy on the adrenal cortex zona fasciculata

The effects of surgical thyroidectomy on the ultrastructure of the adrenal fasciculata zona of the adult male rat were investigated. In the thyroidectomized rats, the nucleus presented large heterochromatin patches mainly localized at the nuclear periphery and the nucleolus-associated chromatin; the cytoplasmic alterations were scarce. Morphometric studies showed a significant decrease in the relative volume of the nucleus, nucleolus, and euchromatin and a significant increase in the relative volume of heterochromatin. The numerical density of perichromatin granules counted in material prepared by the EDTA method showed a significant decrease. Concerning the cytoplasmic organelles, the morphometric data only revealed a significant decrease in the relative volume and surface density of mitochondria. The nuclear and mitochondrial volumetric changes induced by surgical hypothyroidism may be related to the absence of the thyroid hormone, nuclei and mitochondria probably being the subcellular targets for the thyroid hormone.

Postnatal development of the rat adrenal cortex: an ultrastructural morphometric study

Adrenals from 12-hr, 4 1/2, 7 1/2, 10-, and 14-day-old rats were used in this study. At 12 hr the cells of the zonae glomerulosa and fasciculata were similar to those of the adult adrenal cortex. The zona juxtamedullaris cells presented round mitochondria with vesicular cristae and very dense matrix and a large endoplasmic reticulum. After this age and until the 14th day, changes were slight and mainly regarding the size of cytoplasmic organelles. Variations in volumetric and surface densities were determined by stereological methods. These showed between 12 hr and 4 1/2 days of life in the three cortex zones a significant decrease of the volumetric densities of mitochondria (except the zona juxtamedullaris) and the endoplasmic reticulum (except in the zona glomerulosa) and a significant increase in the relative volume of the lipid droplets. The surface density of mitochondria decreased in the three zones, and the same parameter for the lipid droplets significantly increased in the zonae glomerulosa and fasciculata. After 4 1/2 days there was, in the three zones, an increase in the volumetric density of the mitochondria and endoplasmic reticulum and an increase in the mitochondrial surface density which were significant in most cases; the volumetric and surface densities of the lipid droplets increased except in the zona juxtamedullaris. These data suggest a decrease in the adrenal metabolic activity during the first days of life, which increases thereafter until reaching normal values.

Stereologic analysis of normal and dystrophic avian αW myofibers

The αW fibers of the posterior latissimus dorsi from normal (NPLD) and dystrophic (DPLD) chicks were analyzed by stereologic methods for electron microscopy. The αW fibers were located in electron micrographs by comparison with adjacent frozen sections where αW fibers were identified by established histochemical criteria. Striking mitochondrial and sarcotubular alterations were detected in dystrophic αW fibers prior to involvement of myofibrils. These changes are interpreted as features of an incipient stage of dystrophy that occur in αW fibers before degenerative changes. The volume fraction of myofibrils from αW fibers of the DPLD was 5% less than that of the NPLD. The volume densities of mitochondria were similar for both types of muscle. Mitochondrial surface density was 30.5% higher in DPLD than in NPLD. The surface-to-volume ratio of mitochondria was also 30.5% higher in DPLD than in NPLD. In DPLD, both surface density and volume density of terminal cisterns were 44% more than in NPLD. Volume density of the longitudinal tubules declined 18%, from 3.58 ± 0.13% in NPLD to 2.93 ± 0.20% in DPLD. The smaller decline in surface density of the longitudinal tubules in the DPLD plus a 14% increase in surface-to-volume ratio indicates that they are fewer in number and narrower in diameter than in the NPLD. Volume density of the transverse tubules was 188% greater and their surface density 162% greater in DPLD than in NPLD.

Ultrastructural studies on the prenatal development of the rat adrenal cortex

The ultrastructural changes observed during the intrauterine life of the rat adrenal cortex are described. Adrenals of rat fetuses from 16 1/2 to 22 1/2 days of gestation were used. Between Days 16 1/2 and 17 1/2 most mitochondria had vesicular and tubular or lamellar cristae, and a few vesicular cristae only; endoplasmic reticulum spaces were large, and there were numerous free ribosomes and scarce lipid droplets. From 18 1/2 to 22 1/2 days of development, adrenal cells showed an increasing number of mitochondria and lipid droplets and a gradual decrease in the area occupied by the reticulum; mitochondria with vesicular cristae became more numerous. Variations in volumetric and surface densities of the cell organelles and the numeric density of mitochondria were assessed by stereological methods. These showed an increase in mitochondrial volume and number at all successive periods studied and an increase in surface density of mitochondria, endoplasmic reticulum spaces, and lipid droplets between 16 1/2 and 17 1/2 and 18 1/2 and 20 1/2 days. Endoplasmic reticulum volumetric density was significantly diminished after 18 1/2 to 20 1/2 days. Since the adrenal organelle changes described herein coincided with the beginning of adrenal steroid secretion, it is suggested that they represent the morphologic counterpart of such metabolic phenomena.

Morphometric analysis of the ultrastructural changes in rat liver induced by the peroxisome proliferator SaH 42-348.

The changes occurring in hepatocytes of F-344 male rats during a 3-wk treatment with a hypolipidemic agent, 1-methyl-4-piperidyl-bis [p-chlorophenoxy]acetate (SaH 42-348), have been evaluated by morphometric and biochemical methods. The twofold increase in liver weight resulted from a significant increase in hepatocyte cytoplasm as well as a moderate increase in the number of liver cells. The peroxisome population and SER played an overwhelming part in the hypertrophy of hepatocytic cytoplasm. The relative volume and the surface density of peroxisomes volume resulted from an increased ninefold and sevenfold, respectively. The increase in the collective peroxisome volume resulted from an increase in both the number and the average volume of peroxisomes. The SER also demonstrated a substantial increase in these values. The relative volume and surface density of mitochondria were not significantly altered in comparison to controls, while these values for RER decreased onefold. Studies on the lobular distribution of cytoplasmic organelles before and during treatment revealed that the relative volume and surface density of peroxisomes and SER increased from periportal to centrilobular cells of the hepatic lobule, whereas mitochondrial values decreased from periportal to centrilobular cells. The RER values were fairly constant in different parts of the hepatic lobule. The increase in peroxisome and SER volume and surface area was first evident within the first 3 days of SaH 42-348 treatment and these values continued to increase, reaching a steady state within 2 wk. The time course of increase in catalase and carnitine acetyltransferase activities correlated with the morphometric data on the peroxisomes. After cessation of SaH 42-348 treatment, the peroxisome values decreased rapidly within the first 3 days and reached control levels within 1 wk. Moderate reduction in SER values occurred after withdrawal of the drug, but these values remained higher than controls even after 2 wk, suggesting that the reduction in the amount of circulating peroxisome proteins may result in empty SER channels. On the 4th day of drug withdrawal a significant increase in the relative volume and surface density of lysosomes was observed, suggesting that these organelles may play some part in the removal of cellular membranes. However, the rapid reduction in peroxisome values after SaH 42-348 withdrawal appears to be due to cessation of enhanced peroxisome protein synthesis.

Environmentally induced changes in mitochondria and endoplasmic reticulum of Saccharomyces carlsbergensis yeast.

The effects of culture environment on the volume density and surface density of mitochondria and endoplasmic reticulum in a facultative yeast were studied. When compared with cells grown aerobically on a nonrepressive substrate, cells grown in the absence of oxygen showed a sharp reduction in both volume density of mitochondria and surface density of the inner mitochondrial membrane (imm) in the remaining mitochondrial profiles. Use of fermentable (repressive) substrates under aerobic conditions restricted the volume density of mitochondria to a much greater extent than the surface density of imm. The range of mitochondrial volume densities in these experiments was 4-11%. Surface density of endoplasmic reticulum (ER) was sensitive to growth rate and in particular to changes in oxygen tension, showing large fluctuations during both anaerobic and aerobic adaptation. These fluctuations in ER are discussed in relation to the known role of this organelle in lipid metabolism.

A comparative morphometric analysis of the effects of thyroxine and acth on the zona fasciculata of rat adrenal cortex

The effects of thyroxine and ACTH on the ultrastructure of cells of the adrenal zona fasciculata were studied by morphometric analysis and compared by two-way analysis of variance. The results indicate that the effects of thyroxine and ACTH are different and independent. The statistically significant differences in effect of thyroxine and ACTH are: thyroxine causes an increase in the volume fraction of mitochondria and a decrease in the volume fraction of endoplasmic reticulum independent of ACTH; thyroxine causes a decrease in surface density of mitochondria and endoplasmic reticulum in the absence of ACTH, but in the presence of ACTH this effect is moderated by an interaction of throxine and ACTH. There were no statistically significant effects of either thyroxine or ACTH on volume fraction or surface density of liposomes.

Ultrastructural alterations produced in rat adrenal by aminoglutethimide. A stereologic and cytochemical study.

The ultrastructure of the zona fasciculata cells of the rat adrenal was examined after aminoglutethimide (Elipten) administration. Eight male adult rats were injected with 20-25 mg/kg per day; five control rats were injected with an equal volume of saline. The rats were sacrificed after 7 days of treatment and adrenal pieces were processed for morphological and cytochemical electron microscopic studies. The volume density and surface density of the cell organelles of treated and control animals were determined by the stereologic methods of Weibel et al. and the values were statistically compared. The identification of cholesterol was carried out in treated and control animals by the Scallen and Dietert method. In Elipten treated rats there was a significant decrease in the volume fraction and surface density of mitochondria, a significant increase in the volume fraction and surface density of endoplasmic reticulum and the Golgi complex. The volume fraction of lipid droplets was increased significantly; their number and surface density were also increased. Peroxisomes were more numerous than in controls but their small number and size did not allow a stereologic study. A greater amount of cholesterol was visible in treated than in control rats, namely in the Golgi complex. The number of lysosomes with acid phosphatase activity was not increased in treated rats when compared with controls. The variations observed were interpreted as due to the inhibition of the conversion of cholesterol to pregnenolone, a step of the steroidogenic pathway. (Endocrinology90: 444, 1972)