Electron Microscopic Morphometric Analysis Research Articles

Structural-functional correlations of diabetic nephropathy

Patient 1. A 30-year-old woman had had type-I (insulin-dependent) diabetes mellitus (IDDM) for 27 years. At the time of evaluation, she weighed 50 kg, was 157 cm tall, and had a blood pressure of 114/80 mm Hg. She had background retinopathy and no clinical neuropathy. Her urine was positive for protein by dipstick and the albumin excretion rate was 2500 /tg/min. Her hemoglobin A1 was 8.9%; serum creatinine, 1.2 mg/dl; and creatinine clearance, 79 mI/mm/i .73 m2. As part of the study of renal structure and function in siblings concordant for IDDM, she underwent a percutaneous renal biopsy. Light microscopy revealed that 30% of the glomeruli were globally sclerosed. The others all had moderately severe diffuse mesangial expansion. Many afferent and efferent glomerular arterioles showed varying amounts of hyalinosis, with some vessel walls completely replaced by the waxy, homogeneous, pink hyaline material. Mild diffuse interstitial expansion was evident, and patchy areas of more marked interstitial fibrosis were found, mainly in association with atrophic tubules or sclerotic glomeruli. Electron microscopic morphometric analysis showed the mesangial volume fraction (that is, fraction of glomerular volume occupied by mesangium [VvMesJ) to be 0.40 (upper limit of normal, 0.22). The VvMes cells measured 0.11 and VvMes matrix 0.26; the ratio of mesangial matrix to total mesangium was 0.65 (normal ratio 0.5). The surface density of the peripheral glomerular basement membrane (that is, the filtration surface per unit of tuft area {SvPGBM]) was 0.087 (lower limit of normal, 0.095) and the GBM width was 661 nm (upper limit of normal, 450 nm). Patient 2. The 28-year-old sister of Patient 1 developed IDDM at age 5. She had no retinopathy or neuropathy. She weighed 60 kg, was 164 cm tall, and had a blood pressure of 102/64 mm Hg. The urine was negative for protein by dipstick; urine albumin excretion rate was 75 g/min. Her hemoglobin A1 was 14%; serum creatinine, 0.9 mg/dl; and creatinine clearance, 71 ml/min/l .73 m2. Light microscopic evaluation of her renal biopsy specimen was similar to that of her sister. Morphometric analysis revealed a VvMes of 0.45, a ratio of mesangial matrix to total mesangium of 0.63, an SvPGBM of 0.83, and a GBM width of 712 nm.

Pathogenetic Mechanisms Involved in Mesangial Interposition in IgA Nephropathy

To investigate the pathogenetic mechanisms of mesangial interposition (MI) in IgA nephropathy, we examined renal biopsy samples from 20 patients with IgA nephropathy. Electron microscopic morphometric analysis showed that cytoplasmic protrusion of mesangial cells (MCs) into endothelial cells (ECs) or capillary lumina, and widening of the lamina rara interna (LRI) were significantly more prominent in glomeruli with MI than in those without. Immunoelectron microscopy revealed that the ratio of positive endothelial staining with a polyclonal antibody against human platelet-derived growth factor (PDGF) BB was significantly higher in capillary loops with MI than in those without. Enhanced capillary staining of fibronectin related to MI was not recognized. These results suggest that MI in IgA nephropathy is caused by factors such as enhancement of cytoplasmic extensibility of the MCs, widening of the LRI and chemotactic influence of PDGF-BB located in the glomerular ECs.

Tamoxifen induces hepatocellular carcinoma in rat liver: A 1-year study with two antiestrogens

The effects of equimolar doses of the triphenylethylene antiestrogens tamoxifen and toremifene on female Sprague-Dawley rat liver were studied in a 52-week toxicity study which included a 13-week recovery period. Liver tumors were found in four out of five rats at the highest dose level of tamoxifen (45 mg/kg per day) after 52 weeks of dosing, and these appeared to be hepatocellular carcinomas in three rats. After the 13-week recovery period all surviving rats in the highest tamoxifen dose group had large liver tumors (diameter up to 2 cm) which appeared to be hepatocellular carcinomas in five out of six rats. No tumor was observed in the toremifene-treated rats (48 mg/kg per day) either after 52 weeks of dosing or after the recovery period. Electron microscopic morphometric analysis after 52 weeks of dosing revealed that at the tamoxifen high dose level, the volume densities of the peroxisomes, mitochondria, and residual bodies were elevated in the nonneoplastic hepatocytes of the rats. In the neoplastic hepatocytes of the tamoxifen-treated rats the volume density of nuclei was slightly elevated. The slight proliferation of peroxisomes and mitochondria might be related to tumor development in the tamoxifen treated rats.

Nerve growth factor (NGF) receptors in a central nervous system glial cell line: upregulation by NGF and brain-derived neurotrophic factor.

The neurotrophic proteins nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) are related in their primary amino acid structures. In this study we investigated the extent to which the low-affinity NGF receptor (LNGFR) in C6 glioma cells can discriminate between the neurotrophins NGF and BDNF. LNGFR-immunoreactivity (IR) was studied in C6 cells treated for 16 hr with NGF (50 ng/ml) or BDNF (10 ng/ml), using immunogold labelling and electron microscopic morphometric analysis. The cells were exposed to the anti-NGFR antibody 192-IgG, followed by immunoglobulin conjugated with colloidal gold. Untreated C6 cells exhibited some surface gold label (positive LNGFR-IR). Cells treated with NGF or BDNF displayed significantly increased LNGFR-IR on all surfaces in terms of gold labeling, which was more pronounced in NGF-treated cells. LNGFR-IR was also localized in coated endocytotic vesicles, in smooth endoplasmic reticulum, and in secondary multivesicular lysosomes in neurotrophin-treated and untreated cells. The increase in LNGFR protein was further substantiated by a correspondingly higher content of LNGFR mRNA detected after 15 hr of either NGF or BDNF treatment. These results suggest that the LNGFR in glial cells can be upregulated by the structurally related neurotrophins NGF and BDNF.

Cytoskeletal elements regulate the distribution of nerve growth factor receptors in PC12 cells.

Nerve growth factor receptor (NGFR)-like immunoreactivity (IR) was studied in PC12 cells treated for 96 hr with NGF (40 ng/ml), using immunogold labeling and electron microscopic morphometric analysis. The cells were exposed to the anti-NGFR antibody 192-IgG, followed by immunoglobulin (IgG) conjugated with colloidal gold. PC12 cells exhibited occasional gold label (positive NGFR-IR) on all surfaces. Cells treated with colcemid (0.05 micrograms/ml) or cytochalasin D (2 micrograms/ml), which limit microtubule (MT) and microfilament (MF) formation, respectively, displayed an increased NGFR-IR in terms of gold labeling. NGFR-IR was also seen on taxol (0.85 micrograms/ml)-exposed cells, an agent that promotes MT assembly. Cells treated simultaneously with cytochalasin D and taxol had a dramatically augmented NGFR-IR on their surfaces, which exceeded levels obtained with either agent alone. Prominent NGFR-IR was localized frequently in coated endocytotic vesicles, in smooth endoplasmic reticulum, and in secondary multivesicular lysosomes, in both treated and untreated cells. The results suggest that a large number of NGFRs (positive NGFR-IR) in PC12 cells are cryptic and not available for ligand binding. Changes in cytoskeletal organization that may affect mobility of integral membrane proteins can modulate the distribution of NGFR-IR on neuronal surfaces.

The mechanism of formation of alveolar pores (Kohn's pores) in neonatal rabbits

The mechanism of the formation of alveolar pores (Kohn's pores) in neonatal male rabbits was studied by scanning electron microscopy and scanning electron microscopic morphometric analysis. The number of alveolar pores per alveolus was increased after birth. About 80 percent of alveolar pores had Type II alveolar epithelial cells on their edges when the rabbits were 1-day old. This percentage decreased thereafter. Circle-like intercellular junctions of Type I cells were frequently observed in or around the alveolar pores and Type II cells frequently attached to these junctions in the early neonatal stage. The alveolar pores with Type II cells which were mainly faced this side of alveolar lumen, and Type II cells which were separated from the pores tended to be found at the points where three or more Type I alveolar epithelial cells gathered in the early neonatal stage. However, alveolar pores with Type II cells which were mainly faced other side of the alveolar lumen, and alveolar pores without Type II cells tended to be found between two Type I cells. At the rims of the pore, crescent-shaped Type II cells located between circle-like intercellular junctions were frequently observed in the early neonatal stage. In conclusion. 1) One of the function of Type II cells is to form the alveolar pores. 2) Alveolar pores are formed by Type II cells which have penetrated into the alveolar wall and faced both sides of the alveolar lumina. Type II cells combine the Type I alveolar epithelial cells of both sides of the alveolar wall and make pores with circle-like intercellular junctions.(ABSTRACT TRUNCATED AT 250 WORDS)

Dendritic and synaptic properties of collicular neurons: A quantitative light and electron microscopical study of Golgi‐impregnated cells

The present study deals with a light- and electron microscopic morphometric analysis of Golgi-impregnated neurons in the superior colliculus of rats with the purpose to unravel inter- and intralaminar differences in their dendritic and synaptic organization. In particular, layer IV was studied and compared with its boundary layers III and V. The results show that collicular cells in layer IV basically form a homogeneous population with respect to the number of primary dendrites, the total length of impregnated dendrites, and the diameter, ellipticity, and orientation of dendritic fields and somata of Golgi-impregnated neurons. Somata of reconstructed small cells in layer III and IV as well as V have all a similar density of about 40 synaptic contacts per 100 microns2 surface. However, the cell bodies of large multipolar cells in layer V have a slightly but significantly larger synaptic density (about 50 per 100 microns2). Dendrites of large and small collicular cells had no significantly different synaptic densities (43 and 48 per 100 microns2, respectively). In conclusion, the present results show only minor dendritic and synaptic differences between individual cells in the same layer, as well as in neighboring layers, which implies a low degree of cellular and synaptic intra- and interlaminar differentiation. It is discussed that this organization differs markedly from that in other visual centers, including the collicular homologue, the tectum of lower vertebrates, and the mammalian visual cortex, where pronounced inter- and intralaminar differentiations exist. Such an organization may provide a framework of laminar specificity by which distinct cell types may select a restricted set of input out of all information available. The present quantitative investigation suggests that a similar framework is not present in the superior colliculus.

DBcAMP stimulates vesicle transport and HRP excretion in isolated perfused rat liver

To clarify the effect of adenosine 3',5'-cyclic monophosphate (cAMP) on the transcytotic vesicle pathway, we measured the biliary excretion of bile acid, phospholipid, and horseradish peroxidase (HRP) in the isolated perfused rat liver (IPRL) with or without infusion of N6,2'-O-dibutyryl-cAMP (DBcAMP). A linear relationship between bile flow and bile acid excretion was observed in both control and DBcAMP-infused livers. DBcAMP increased the y-axis intercept from 1.10 +/- 0.16 to 1.48 +/- 0.19 microliters.min-1.g liver-1 (P less than 0.01) and the slope from 6.5 +/- 1.99 to 10.77 +/- 1.71 microliters/mumol bile acid (P less than 0.01). DBcAMP also increased the biliary excretion of bile acid and phospholipid during a 1.0 mumol/min infusion of taurocholate. When HRP was pulse loaded for 1 min, HRP appeared in bile in early (4-6 min) and late (20-25 min) peaks. DBcAMP markedly increased the late peak of HRP from 0.33 +/- 0.08 to 1.15 +/- 0.32 ng.min-1.g liver-1 (P less than 0.01), a phenomenon blocked by colchicine. An electron-microscopic morphometric analysis indicated that DBcAMP increased both the density and %area of HRP-containing vesicles in the pericanalicular area, compared with controls, 18 min after a 1-min pulse of HRP. DBcAMP had no effect on the uptake rate of HRP in 4-h primary hepatocyte cultures but stimulated biliary excretion of HRP when preloaded in the IPRL. These findings indicate that cAMP regulates excretory function in part by stimulating the microtubule-dependent transcytotic vesicle transport system.

Changes in the concentration of indole‐3‐acetic acid during the growth of etiolated lupin hypocotyls

The longitudinal distribution of unaltered radioactive indole‐3‐acetic acid (IAA), after application of [5‐3H]‐IAA to decapitated etiolated lupin hypocotyls. exhibited a wave‐like pattern similar to that obtained with endogenous IAA. Waves of radioactive IAA were localizated both in the elongation zone and in the non‐growing basal region of the hypocotyl. These IAA waves were transient because of basipetal polar transport and metabolism of IAA.The level of endogenous IAA in different zones of the hypocotyl varied with age, following a wave‐like pattern. During the elongation period of each zone, IAA was parallel to the bell‐shaped curve of the growth rate. In addition, a role in secondary cell wall deposition is suggested for the other IAA wave that appeared after the cell elongation period, since an electron microscopic morphometric analysis of the cell wall showed that the cell wall thickness increased once the cell elongation ceased.As the oscillation of endogenous IAA level occured in both space (distribution along the hypocotyl) and time (variation with age), it is suggested that the level of IAA really depended on the growth status of the cells. The response of the cells to the positional information submitted by the auxin waves as regards the growth status of the cell is discussed.

Morphometric analysis of mitochondria and boutons in the dentate gyrus molecular layer of aged rats

An electron microscopic morphometric analysis of the volume density of mitochondria and boutons in the dentate gyrus molecular layer was carried out in young (3-4 months old) and aged (26-27 months old) Wistar rats. This study showed that the volume fraction of mitochondria per unit volume of the neuropil in aged rats did not differ significantly from that in young animals. The comparison of different zones of the molecular layer (supragranular, inner, middle and outer zone) showed a significant increase in the mitochondrial volume density from the supragranular to the outer zone in both animal groups. These stereologic results are discussed in relation to the histochemical pattern of the mitochondrial enzymes in young and aged rats. Only in the supragranular zone was there a statistically significant difference in the volume density of boutons, i.e. aged rats showed about a 20% higher volume density than did young rats. It is suspected that this increase in bouton volume density could be due to the age-related atrophy of smaller dendritic shafts previously reported in senescent Fischer rats.

Gap junction ultrastructure in rat liver parenchymal cells after in vivo ischemia.

The ultrastructure of gap junctions between rat liver parenchymal cells has been studied after in vivo ischemia, with and without subsequent blood reflow. Freeze fracture replicas were analysed by electron microscopic observation, optical diffraction and morphometric analysis. In control specimens gap junction connexons were widely dispersed and arranged in nearly random fashion over nearly the whole junctional area, with only minute spots of hexagonal connexon arrangement. An ischemic period of 30 min, from which the vast majority of cells are capable of recovery after restoration of the blood supply, usually entails only a slight enlargement of the areas of hexagonally arranged connexons. After 120 min of ischemia without reflow, which results in necrosis of most parenchymal cells, all gap junctions showed a completely hexagonal arrangement of connexons. The numerical density of connexons after 30 and 120 min of ischemia without reflow was significantly higher than in controls, whereas after 30 min of ischemia followed by 2 h of reflow the numerical density had returned to control levels. A fully hexagonal arrangement of gap junction connexons, as occurs after longer periods of ischemia, seems to be related to irreversible cell damage and presumably to metabolic uncoupling of cells. This was preceded by an increase in the numerical density of connexons, which is probably a reversible phenomenon.

Basement membrane thickening of postcapillary venules and capillaries in rheumatoid synovium. Immunoelectron microscopic and electron microscopic morphometric analysis.

Pathologic changes in the basement membrane (BM) of postcapillary venules (PCV) and capillaries in rheumatoid arthritis (RA) synovium were studied by immunoelectron microscopy, using a monoclonal antibody against human type IV collagen, C(IV)22, and by electron microscopic morphometric analysis. The sublining region of RA synovium was classified into lymphocyte-rich areas, transitional areas, and interstitial areas, according to their pattern of cellular infiltration. In lymphocyte-rich areas, the BM of the PCV and capillaries were minimally thickened; disruption of the lamina densa was seldom seen. Transitional areas, which contained macrophages, lymphocytes, and plasma cells, had numerous PCV and capillaries. The BM was markedly thickened and partially multilamellated, and there were many disruptions in the lamina densa. The BM contained degenerated endothelial cells and cell debris. On immunostaining of this BM with monoclonal antibody C(IV)22, type IV collagen stained heavily, mainly in the disrupted lamina densa; this indicates that the thickening was, at least in part, the result of an increase in BM collagen. In uninfiltrated interstitial areas, BM were moderately thickened and multilamellated, and showed few disruptions of the lamina densa; there were similar increases in type IV collagen, but cell debris was seldom observed. Measurement of the BM width, the ratio of BM width to vessel diameter, and the fraction of vascular cross-sectional area occupied by BM demonstrated that the thickness of the BM of both PCV and capillaries was greatest in transitional areas and was smallest in lymphocyte-rich areas (P less than 0.01). Since macrophages and macrophage-derived factors have been found to promote synthesis of BM collagen type IV, and since transitional and interstitial areas are rich in macrophages and histiocytes, respectively, it is suggested that these mononuclear cells and the factors secreted by them play a significant role in the thickening of the BM of PCV and capillaries in RA synovitis.

Catecholamine synapses and contents in the paraventricular hypothalamic nucleus and nucleus tractus solitarius of DOCA-salt hypertensive rats.

Central catecholamine (CA) neurons in the nucleus tractus solitarius (NTS) and paraventricular hypothalamic nucleus (PVN) were studied in Wistar rats that had been unilaterally nephrectomized. The experimental animals were then treated with deoxycorticosterone acetate (DOCA) and salt water. The control animals were treated with the vehicle and tap water. Blood pressure of animals 4 weeks after DOCA/salt treatment was significantly elevated when compared to control rats. Morphologically, CA terminals showed no noticeable changes in the DOCA/salt hypertensive rats. Furthermore, the density of CA terminals either in the NTS or in the PVN of the DOCA/salt hypertensive rats was not statistically different from that of normotensive controls, suggesting that salt does not cause lesions or destruction of CA terminals. However, an extensive electron-microscopic morphometric analysis indicated that there was an enhancement of CA synaptogenesis (expressed by increased synaptic frequency among all CA boutons labeled with 5-hydroxydopamine) in the PVN, but not in the NTS of DOCA/salt hypertensive rats. In addition, the high-performance liquid chromatography revealed decreased CA contents in the PVN, but not in the NTS, of DOCA/salt hypertensive animals. Since synapses are primary sites for neurotransmitter release, the above results collectively suggest that more CA synapses formed in the PVN may reflect a net CA release from CA terminals resulting in the decreased CA content in the axonal terminals. Such an increased CA release and enhanced CA synaptogenesis may consequently enhance CA function in the PVN of hypertensive rats 4 weeks after DOCA/salt treatment, and relate to the development and/or maintenance of hypertension in the DOCA/salt rats.

The toxicological response of the algaAnabaena flos- aquae (cyanophyceae) to cadmium

The toxicological response of the cyanophycean algaAnabaena flos- aquae to cadmium was investigated by three integrated approaches: 1) the determination of the incipient lethal concentration of the metal, 2) study of metal incorporation and cellular compartmentalization using X-ray energy dispersive analysis, and 3) the quantification of intracellular structural changes, after metal exposure, using morphometric analysis. After 96 hr of exposure, the incipient lethal concentration was calculated to be 0.118 ± 0.04 μM cadmium. At concentrations three orders of magnitude higher than the incipient lethal concentration, cadmium was incorporated into both the cellular cytoplasm and the cell's polyphosphate bodies. Cadmium also caused the polyphosphate bodies to lose Mg and Ca, resulting in ionic changes in the elemental composition of these cellular inclusions. The utilization of stereological techniques for electron microscopic morphometric analysis established that all concentrations of cadmium tested caused significant reductions in the surface area of the cell's thylakoids. Cadmium induced changes in the numbers and relative volume of the cell occupied by polyhedral bodies, polyphosphate bodies, lipid inclusions, cyanophycin granules, membrane limited crystalline, inclusions, and changes in the volume of the cell wall layers were also documented. The physiological significance of these findings are discussed in terms of the toxic action of cadmium and the cellular mechanisms for detoxification of cations once they enter the cell.

The development of lesions in the glomerular basement membrane and mesangium after transplantation of normal kidneys to diabetic patients.

Renal allograft biopsies at the time of transplantation (baseline) and 2 yr later were obtained in 6 type I diabetic and 12 nondiabetic patients and studied for glomerular basement membrane (GBM) and mesangial changes. Diabetic patients had significantly greater GBM thickness compared with nondiabetics at 2 yr (P = 0.05, rank sum test), and the increase in GBM thickness comparing baseline and 2-yr biopsies was greater in the diabetic compared with nondiabetic patients (P = 0.005, rank sum test). Similarly, diabetic patients developed significant mesangial thickening by light microscopy while no changes were observed in nondiabetic patients (P = 0.001). Electron microscopic morphometric analysis of the percentage of total mesangium was not different on comparing diabetic and nondiabetic patients at 2 yr. There was an increase in the matrix component of the mesangium in the diabetics at this time, although this did not reach statistical significance (P = 0.06). In addition, the surface density of the peripheral glomerular capillary wall, presumably reflecting mesangial expansion, was decreased in the diabetic and unchanged in the nondiabetic patients (P = 0.005). These studies document, for the first time, the development of GBM and mesangial lesions of diabetic nephropathy in normal living related donor and cadaver kidneys transplanted into diabetic patients and support the hypothesis that these lesions are secondary to the diabetic state.

Studies on vinblastine-induced autophagocytosis in mouse liver. III. A quantitative study.

The microtubule inhibitor vinblastine (25 mg/kg, i.p.) induces autophagocytosis in mouse hepatocytes. The formation of autophagic vacuoles, their contents, and other cellular changes after vinblastine injection in hepatocytes, were studied by light and electron microscopic morphometric analysis. The volume density of autophagic vacuoles increased significantly during the experimental period (24 h). This increase was due to the significant increase in their number, which was approximately 5-fold 4 h, 12 h and 24 h after vinblastine injection. The mean volume of the autophagic vacuoles increased significantly 1 h after vinblastine injection, at which time the formation of new autophagic vacuoles was at its greatest. There was an accumulation of single membrane-limited, obviously older autophagic vacuoles in the cytoplasm. Their volume density was at its maximum 12 h after injection, suggesting a retarded turnover of autophagic vacuoles. The segregation of cytoplasmic components into autophagic vacuoles may not be selective after vinblastine injection. The injurious effects of vinblastine were evident both in light and electron microscopic studies. In the parenchymal cells the Golgi cisternae were dilated and disorganized and the volume density of the Golgi apparatus was significantly decreased 12 h after vinblastine injection. The volume density of lysosomes was increased during the 12 h after vinblastine injection. Vesicles containing very low density lipoprotein particles accumulated in the cytoplasm so that their volume density was significantly increased during the entire experimental period. Vinblastine apparently interfered with the transport and secretion of the very low density lipoproteins from the parenchymal cells.

Characterization of monoaminergic terminals in the neostriatum of neonatal rats: an electron microscopic morphometric analysis.

Monoaminergic (MA) boutons in the neostriatum of neonatal rats were studied by using 5-hydroxydopamine. We found: (a) bouton size averaged 0.6 micron in diameter; (b) terminal density was 68 boutons per 7200 micron2 area; (c) synaptic frequency was 33.2%; and (d) MA neurons constituted 9.2% of all boutons. This population was much lower than that reported in immature neocortex where MA neurons are a major innervation.

Quantitative analyses of neuronal development in the lateral motor column of mouse spinal cord. II. Development of motor neuronal organelles.

The development of organelles within presumptive alpha motor neuronal somata was studied by electron microscopic morphometric analysis. Cells with large nuclei were selected for sampling from the lateral motor column of the brachial spinal cord of mouse embryos ranging in age from embryonic day 11 (E11) through E16. The first objective was to compare the cytodifferentiation of alpha motor neuronal somata among three genetically different strains of mice that differ in the development of forelimb reflex behavior and associated pathway synaptogenesis (Vaughn et al., '75). On the basis of multiple linear regression analyses, no significant differences were found among strains for either the initial levels or rates of cytodifferentiation. As a result, the data were combined for all three strains to analyze organelle changes during early neuronal development. The average areas of perikaryal cytoplasm and nuclei increased significantly. In addition, the relative areas of nucleoli, mitochondria, Golgi complexes, and rough endoplasmic reticulum increased, while the relative areas of heterochromatin and "free" ribosomes decreased. There were significant increases in the number of mitochondria and Golgi complexes per unit area of perikaryal cytoplasm. The average size of mitochondria appeared to increase during development, but was significantly smaller in adult alpha motor neurons than in embryonic specimens. In contrast, the average size of individual Golgi complexes was relatively constant throughout embryonic development, as well as in the adult. In general, the cytodifferentiation of alpha motor neurons appeared to progress in a relatively constant, linear fashion between E11 and E16.

Utilization of morphometric analysis in evaluating response of Plectonema boryanum (Cyanophyceae) to exposure to eight heavy metals.

The techniques of morphometric analysis were used to study the ultrastructural changes induced inPlectonema boryanum (Cyanophyceae) by heavy metal exposure. Four of the test metals (Mn, Zn, Hg, and Cd) produced no changes in overall cell dimensions. Two metals (Pb and Cu) produced significant increases in cell size and two other metals (Co and Ni) caused significant decrease in cell size. Mn, Pb, Co, Ni, and Cd caused significant increases in the surface area of the cell's thylakoids and Ni, Co, Zn, and Hg caused a significant reduction in the volume of the intrathylakoidal spaces. All tested metals except Pb and Mn caused the production of extra intracellular membrane whorls. Pb, Mn, Co, Zn, Hg, Cd, and Ni caused coalescence of cellular lipid while Cu caused a reduction in cellular lipid content. Co caused a reduction in the number of polyhedral bodies and Cd caused an increase in the volume of the cell's polyphosphate bodies. The physiological significance of these findings are discussed in terms of potential toxic action of cations and the cellular mechanisms for the detoxification of cations once they enter the cell. Common mechanisms of both procaryotic and eucaryotic algae are discussed and the utilization of stereological techniques for electron microscopic morphometric analysis is established in studies of metal toxicity at the cellular level.

Electron-microscopic morphometric analysis of mouse liver. II. Effect of ageing and thymus transplantation in old animals

The influence of age and thymus on liver cells has been investigated by performing a complete morphometric analysis. The age-dependence was tested in three groups of mice aged 2, 12, and 24 months, while the action of the thymus was studied on 24-month-old mice grafted with neonatal thymus 30 days before the analysis was performed. Among the investigated parameters, the most considerable changes were found in the mean nuclear volume, which displayed a significant increase during ageing. The thymus was capable of reversing such an age-dependent increase when grafted into old animals. The volume of single hepatocytes also displayed an age-dependent increase which was not corrected by thymus grafting. The data presented suggest that the thymus influences the mitotic activity of the hepatocytes and further support the hypothesis that the thymus also plays an important role in non-immunological processes of ageing.