Development of morphologic heterogeneity of hepatocyte mitochondria in the mouse

The ultrastructure of mitochondria in periportal and perihepatic hepatocytes from newborn, 5-, 10-, and 20-day-old, and adult male ddY mice was analyzed by quantitative electron microscopy. In newborn and 5- and 10-day-old animals, the axial ratio (length per diameter), surface to volume ratio (area of the outer membrane per unit mitochondrial volume), and volume density were not significantly different between periportal and perihepatic cells. In 20-day-old and adult animals, the surface to volume ratio was greater in perihepatic cells than periportal cells, and the volume density was greater in periportal cells than perihepatic cells. The axial ratio became greater in perihepatic cells than periportal cells in adult animals. However, there were no differences in the surface density of the outer membrane, and of the inner membrane and cristae between the cells of both zones in all age groups examined. When the data were expressed as volume and area per cell, the patterns of subacinar distribution and age-related changes differed from the patterns seen in the volume and surface density data mainly in adult animals. This difference was generally caused by the marked increase in hepatocyte volume between 20 days of age and adulthood, especially in perihepatic cells. The results show that differences between mitochondria in periportal cells and those in perihepatic cells in the shape (the axial and surface to volume ratios), volume density, and area of the outer membrane per cell, evident in adult animals, are not present in newborn animals but arise during postnatal development.     

Ultrastructure of the aging myocardium: A morphometric approach

Left ventricular tissue from adult and aging Syrian hamster heart was compared at the ultrastructural level, using both qualitative and morphometric electron microscopy. The aging myocardium often showed indented nuclei, lipid droplets and aggregations of dense bodies. The volume fractions of muscle cells occupied by mitochondria, lipid and lysosomes (including both primary lysosomes and residual bodies) was significantly greater in the old animals, while there was no significant difference in nuclear volume fraction or myofibrillar mass. Sarcoplasmic reticular volume and membrane surface area fell during aging. The area of mitochondrial inner membrane plus cristae per mitochondrial volume also fell. When sarcoplasmic reticular and mitochondrial area were expressed per myofibrillar volume fraction, the sarcoplasmic reticular ratio fell, while the mitochondrial parameter remained constant. Discoordinate aging of cellular components in the mammalian myocardium is proposed.     

Effects of lead inclusion bodies on subcellular distribution of lead in rat kidney: the relationship to mitochondrial function

The effect of Pb pretreatment on the subcellular binding of a tracer dose of 203Pb was studied in kidneys of rats in which intranuclear and cytoplasmic inclusion bodies had been induced by a single ip injection of Pb acetate (50 mg Pb/kg) 6 days earlier. Results of subcellular fractionation studies in rats injected iv with 203Pb 24 hr prior to sacrifice demonstrated that 203Pb activity was about 1.5 times higher in kidney homogenates and mitochondrial fractions of control compared to Pb-pretreated rats. Cytosolic 203Pb activity in control rats was 5 times higher than that in Pb-pretreated rats. In contrast, Pb pretreatment increased the 203Pb binding capacity to the nuclear and inclusion body fractions by 7 and 20 times, respectively, compared with controls. Pb pretreatment decreased total mitochondrial 203Pb binding but resulted in a higher proportion of 203Pb bound to the inner membrane and matrix fractions relative to the controls. After in vitro incubation of control renal mitochondria with 203Pb the binding to inner and outer membranes and matrix fractions increased with increasing concentration of unlabeled lead added to the incubation. Deposits on the inner membrane of isolated mitochondria from Pb-pretreated rats were observed by isotonic ammonium molybdate negative staining and these mitochondria also showed decreased respiratory control ratios (RCRs). Succinate-mediated respiration rates and membrane binding of the fluorescent probe ethidium bromide were not affected by Pb pretreatment. These data indicate that lead influences its own subcellular distribution in the kidney following Pb pretreatment as shown by the increase of nuclear and inclusion body binding and increase of mitochondrial inner membrane and matrix binding of lead. The mitochondrial inner membrane shows a preferential affinity for lead following in vivo treatment which can be correlated with impairment of a specific inner membrane function (depressed RCRs). Lead exposure did not alter the activity of the mitochondrial membranes to undergo energy linked conformational changes.     

Vibration Model for Hypoxic Type of Cell Metabolism Evaluated on Rabbit Cardiomyocytes

Activity of the energy production system in rabbits myocardium was examined under various conditions of whole-body vibration. The energy-dependent response of native mitochondria from rabbit heart was studied polarographically using a Clark closed membrane electrode. In was established that the energy production system in rabbit myocardium was involved in organism’s response to whole-body vibration. Functional changes in myocardial mitochondria were shown to depend on the mode of whole-body vibration (frequency and duration). It manifested in an imbalance between functional activity of FAD- and NAD-dependent components of the respiratory chain. The increase in the frequency and duration of vibration was accompanied by dysfunction of the energy production system in cardiomyocytes. These changes manifested in activation of succinic acid oxidation and inhibition of NAD-dependent components of the mitochondrial respiratory chain. Vibration due to systemic dysregulatory infl uence can be used as a model for studies of both vibration phenomenon realized at the level of the energy production system in organs and tissues and vibroprotective properties of medicinal products.     

The maintenance of mitochondrial size in the rat adrenal cortex zona fasciculata by ACTH

An electron microscopic examination of the rat adrenal cortex reveals changes in the abundance and structure of the mitochondria of the zona fasciculata after hypophysectomy, which are time-dependent and lead to the production of giant (diameter > 1.5μ) mitochondria. These changes were measured in low power fields involving a total thin section area of 850μ² at 4, 7, 11, and 14 days after hypophysectomy. Following hypophysectomy, the number of mitochondria decreases, the volume of lipid droplets increases, the ratio of the surface area of the outer mitochondrial membrane to the mitochondrial volume decreases (indicative of increased size), and the percent of small mitochondria increases. The volume of giant mitochondria, comprising 8% of the total mitochondrial volume in control animals, increases to 65% of the total 7 days after hypophysectomy and to 82% 14 days after hypophysectomy. It has been found that administration of ACTH causes the gradual reversal of these effects of hypophysectomy over a period of 9 days. Mitochondrial partitions, clearly associated with the inner membrane, were observed after hypophysectomy and during ACTH-induced recovery. The evidence suggests that ACTH controls the process of growth and division of the mitochondria. The retarded growth of mitochondria in the absence of ACTH is associated with fusion of existing mitochondria to form giant mitochondria.     

Reduction in energy efficiency induced by expression of the uncoupling protein, UCP1, in mouse liver mitochondria

Uncoupling Protein 1 (UCP1) is an inner mitochondrial membrane protein, uniquely expressed in brown adipocytes, which uncouples the mitochondrial respiration impairing ATP production and energy efficiency. The aim of the present study was to express UCP1 in liver mitochondria using a non-viral system in order to affect energy utilization. The effect of ectopic protein expression on liver energy metabolism, which was evaluated 42 h after DNA transfer, showed that mitochondria expressing UCP1 presented decreased ATP production, lasted more time in membrane potential state 3, and consumed more molecular oxygen to produce the same amount of ATP than the control group. In summary, the successful functionality of the mitochondrial protein, UCP1, after hydrodynamic delivery is a novel and significant finding. This approach could be useful to ectopically express mitochondrial proteins and, in this particular case, to manage metabolic disorders related to energy efficiency and expenditure, such as obesity.     

ATPase activity of kidney mitochondria stimulated by sodium.

ATPase activity of intact mitochondria may be induced by the presence of sodium. Mitochondria obtained from kidney cortex or medulla demonstrate a higher sodium-stimulated ATPase than mitochondria prepared from liver. This difference is not due to a greater capacity of kidney mitochondria for ATP hydrolysis. Sodium-stimulated ATPase activity of mitochondria is not further enhanced by magnesium or potassium, nor is it inhibited by ouabain. Furthermore, the ATPase of submitochondrial particles is not enhanced by the presence of sodium. These results indicate that the ATPase activity of mitochondria which is stimulated by sodium is unrelated to the microsomal Na-K-ATPase. mitochondrial sodium-stimulated ATPase is affected by pH, anionic composition, furosemide, and ethacrynic acid. The demonstration that mitochondrial ATP hydrolysis can be activated by sodium suggests that intracellular sodium may directly influence intracellular energy metabolism.     

Phospholipid composition of liver mitochondria in experimental hemorrhagic shock

Heparin used as an anticoagulant in modeled hemorrhagic shock decreases the phosphatidylcholine and increases the phosphatidylethanolamine contents in the mitochondria. Accumulation of lysophosphatidylcholine in whole mitochondria and their inner membrane is observed in hemorrhagic shock. At the same time, hemorrhagic shock decreases phosphatidylcholine content in the inner and outer mitochondrial membranes and increases phosphatidylethanolamine content in the outer membranes. Modification of phospholipid composition of mitochondrial membranes is a mechanism responsible for impaired energy production in liver mitochondria in hemorrhagic shock. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 124, No. 7, pp. 43–45, July, 1997     

大鼠下丘脑弓状核神经元的衰老性变化

选用青、中年和老年雄性大鼠各１０只，用形态计量学和体视学方法定量分析弓状核神经元年龄性变化。结果发现在老年大鼠弓状核，部分暗型和亮型神经元内粗面内质网排列紊乱、缩短和双层膜间隔增宽，线粒体嵴断裂、肿胀和空泡化，溶酶体，微管和颗粒小泡数减少；与青、中年组比较神经元数分别丢失３７％和２７％，核仁平均体积缩小３０％左右；     

Calf muscle adaptation in intermittent claudication. Side-differences in muscle metabolic characteristics in patients with unilateral arterial disease

The adaptation of enzyme activities, notably in the oxidative metabolism, and of prerequisites for tissue transport of oxygen in the claudication leg was evaluated by comparing muscle biopsies from the gastrocnemius muscle of the claudication and the symptom-free leg of seven patients with unilateral claudication. The claudication leg had higher activities of a marker enzyme for mitochondrial oxidative capacity, citrate synthase (CS), as well as of the MB and the mitochondrial isoenzyme of creatine kinase (CK), which are considered to be involved in the transfer of high energy phosphate from the mitochondria to the resynthesis of ATP in the cytoplasm. The difference between claudication and healthy leg in activities of these CK isoenzymes were well correlated with the corresponding side difference in CS activity. No significant differences between claudication and healthy leg were found in distribution of muscle fibre types or fibre dimension, capillary density or myoglobin content, nor was there any side difference in phosphofructokinase or lactate dehydrogenase. Side differences tended to be greater in those patients with the most advanced obstructive arterial disease as estimated from non-invasive pressure measurements. It is concluded that in reasonably physically-active patients, the mode of ischaemia to which the claudication leg is subjected leads to a metabolic adaptation characterized by increased activities of enzymes involved in the oxidative metabolism, but no significant adaptation of either the conditions for local oxygen transport, as estimated by myoglobin content, and capillary density, or capacity for anaerobic metabolism.     

Optic neuropathies--importance of spatial distribution of mitochondria as well as function

Optic neuropathies such as Leber's hereditary optic neuropathy, dominant optic atrophy and toxic amblyopia are an important cause of irreversible visual failure. Although they are associated with a defect of mitochondrial energy production, their pathogenesis is poorly understood. A common feature to all these disorders is relatively selective degeneration of the papillomacular bundle of retinal ganglion cells resulting central or caecocentral visual field defects. The striking similarity in the pattern of clinical involvement seen with these disparate disorders suggests a common pathway in their aetiology. The existing hypothesis that the optic nerve head has higher energy demands than other tissues making it uniquely dependent on oxidative phosporylation is not satisfactory. First, other ocular tissues such as photoreceptors, which are more dependent on oxidative phosporylation are not affected. Second, other mitochondrial disorders, which have a greater impact on mitochondrial energy function, do not affect the optic nerve. The optic nerve head has certain unique ultra structural features. Ganglion cell axons exit the eye through a perforated collagen plate, the lamina cribrosa. There is a sharp discontinuity in the density of mitochondria at the optic nerve head, with a very high concentration in the prelaminar nerve fibre layer and low concentration behind the lamina. This has previously been attributed to a mechanical hold up of axoplasmic flow, which has itself been proposed as a factor in the pathogenesis of a number of optic neuropathies. More recent evidence shows that mitochondrial distribution reflects the different energy requirements of the unmyelinated prelaminar axons in comparison to the myelinated retrolaminar axons. The heterogeous distribution of mitochondria is actively maintained to support conduction through the optic nerve head. We propose that factors that disrupt the heterogeneous distribution of mitochondria can result in ganglion cell death. Evidence for this comes from studies of cultured cells with the dominant optic atrophy mutation in which mitochondrial distribution is altered and from some forms of hereditary spastic paraparesis which are associated with optic atrophy. The responsible mutations do not affect ATP production until late in the disease but do affect mitochondrial arrangement, again showing that mitochondrial distribution as well as energy production by individual mitochondria may be important in the pathogenesis of ganglion cell death. Greater understanding of the factors localising mitochondria within the ganglion cell axon in particular the interaction with cytoskeleton is required to formulate new treatments. Boosting energy production alone may not be an effective treatment.     

Decline in respiratory control ratio of rat liver mitochondria in old age

Rat liver mitochondria isolated from old animals (27–33 months) showed a clear decline in the state 3 rate of respiration (presence of ADP) compared with mitochondria from mature animals (3–12 months) when using either succinate or NAD⁺-linked substrates.The state 4 rate of respiration (absence of ADP), which is a sensitive indicator of damage to the inner mitochondrial membrane, remained unchanged. Consequently the respiratory control ratio (state 3/state 4) declined.A loss of reserve capacity to maintain the ADP:O ratio was also observed.These observations indicate a decline in energy production in old animals.     

A morphological and immunohistochemical study of the ultimobranchial body in the Japanese lizard and the snake

A morphological and immunohistochemical study of the ultimobranchial body of reptiles Japanese lizard and snake was carried out. The ultimobranchial body of the Japanese lizard was located adjacent to the left arch of the aorta between the trachea and esophagus. It was found as a cluster or group of cells with no capsule. Grimelius' silver impregnation and lead-hematoxylin staining produced positive reactions in some of the clustered cells and follicular cells. The same reaction pattern was observed with anti-calcitonin using the PAP method. The PAP reactions were positive to antiserum against pig calcitonin, but negative to antiserum against synthesized human calcitonin. Furthermore, the PAP reactions were negative to antiserum against tyrosine hydroxylase. The immunofluorescent study of the snake ultimobranchial body revealed that most of the clustered cells and some of the follicular cells were calcitonin-immunoreactive but none was tyrosine hydroxylase-immunoreactive. Certain histological similarities exist between the Japanese lizard ultimobranchial body and snake ultimobranchial body, but the distribution of calcitonin-positive cells were slightly different. In the Japanese lizard, the positive cells were scattered between the foliicles and the number was small. However, most of the cells which formed the cluster in the ultimobranchial body of snake were positive. The findings suggest that the configuration of amino acid in the Japanese lizard calcitonin and snake calcitonin are similar to that of pig calcitonin, and the reptile and the birds is a boundary of the tyrosine hydroxylase existence.     

What of apoptosis is important: The decay process or the causative origin?

Apoptosis is defined as the process of 'programmed cell death' (PCD), during which many cells simultaneously die from within along a very orderly pattern. PCD is as intrinsic for cells as mitosis and is involved in both degenerative and developmental processes of organs and organisms. The pattern of apoptotic cell decay is caused by the total cellular content. Since all body cells possess the same genome, they are similar in many aspects and, therefore, the major processes are nearly identical in all cell types. The same destructive processes also occur continuously in healthy living cells, but then the capacity of repair mechanisms is sufficient to effect cellular integrity. Decay processes become visible, as soon as repair can no more be sufficient. PCD starts as soon as produced energy is permanently insufficient to repress decay. Decreased energy production may arise due to (i) turning off the pivotal tricarbonic acid cycle, (ii) turning off oxidative phosphorylation, (iii) damage of mitochondria, and (iv) inhibition of mitochondrial biogenesis regarding both the mitochondrial and the nuclear part. The consequence of this kind of decreased energy production will be a massive, inefficient fermentative energy production with enormous amounts of lactic acid. Increasing acidity and falling pH will slow down enzymatic activities and thus also intracellular processes. As soon as energy for repair has become insufficient, cellular decay becomes irreversible and the cell will die. Thus, the mitochondrial apoptotic pathway is suggested to arise due to low mitochondrial energy production. For optimal functioning cells need adequate internal conditions and cellular morphology. Cellular morphology depends on (i) the intracellular turgor, (ii) the intracellular cytoskeleton, and (iii) close intercellular contact with neighbour cells. Lack of energy implies decrease of turgor and, consequently, a strong decline of conditions needed for adequate functioning of the cell. Thus, if this lack of energy cannot be repaired in time, it will contribute to cellular decay. Various cellular components or systems that are not directly linked to mitochondria, may be functionally inhibited or damaged and thus contribute to apoptosis. These components or systems that probably constitute the non-mitochondrial pathway are (i) the cellular uptake systems for energy-rich substrates, (ii) extra-mitochondrial enzymes that are involved in non-mitochondrial processes of oxidative energy production, (iii) cytoplasmatic, non-mitochondrial protein synthesis, (iv) the system that regulates osmotic conditions and turgor, and (v) the synthesis and repair of the cytoskeleton. After this careful reflection I am convinced that apoptosis is merely the complex machinery of cellular decay after energy generation has irreversibly stopped. Therefore, apoptosis research for health care should be focussed on processes that hinder energy production. For therapeutic aims research should be focussed on metabolic aspects of energy production and on mitochondrial processes.     

Zona reticularis in aging spontaneously hypertensive rats: a quantitative ultrastructural study of 70- and 95-week-old animals.

The zona reticularis of 70- and 95-week-old female Wistar-Kyoto (WKY) and spontaneously hypertensive (SH) rats was studied by quantitative stereologic techniques. The zona reticularis in the adrenal gland of 70-week-old SH rats was virtually identical to that of 70-week-old WKY rats. In both SH and WKY rats at 95 weeks of age, however, there was hypertrophy of smooth endoplasmic reticulum reflected quantitatively in increased volume and surface area, as compared with that of WKY rats or SH rats at 70 weeks of age. Ninety-five-week-old WKY rats had a significantly greater mitochondrial volume/cell and surface area of mitochondrial membranes than SH rats. Inclusion of lipid droplets within mitochondria was seen in zona reticularis cells from SH and WKY rats at 70 weeks of age; mitochondria-lipid-droplet association was more frequent at 95 weeks of age. The volume of lipofuscin per cell was significantly greater in WKY than in SH rats at 95 weeks of age. Thus, by quantitative techniques, one can see that the zona reticularis of 95-week-old SH rats differs from that of WKY rats, principally in the presence of smaller cells with a smaller surface area of mitochondrial cristae and a reduced volume of mitochondria, lipofuscin, and lipid droplets.     

An ultrastructural study of the hypertrophied human papillary muscle cell with special emphasis on specific staining patterns,mitochondrial projections and association between mitochondria and SR

Summary Biopsy material of the hypertrophied human papillary muscle has been processed according to various electron microscopical techniques in order to study the mitochondrial ultrastructure and the association between mitochondria and sarcoplasmic reticulum (SR).En bloc staining with a Cu-Pb citrate solution resulted in specifically contrasted mitochondrial and sarcotubular membranes, characterized by numerous, discrete, electron-dense particles. The differences in staining patterns between the perinuclear mitochondria and their subsarcolemmal and interfibrillar counterparts suggest differences in chemical properties and/or metabolic activities. The selectively contrasted mitochondrial particles may represent a conglomorate of extrinisic and intrinisic respiratory enzymes and other membrane-associated proteins, while the majority of the electron-dense particles of the sarcotubular membrane may represent positively stained Ca²⁺-pumps. Ultrastructural findings in the present study strongly indicate that the slender mitochondrial projections represent an initial stage in a process leading to the formation of large and pleomorphic mitochondria. Intimate contact between adjacent mitochondria as well as between mitochondria and SR are documented. In the contact regions some of the specifically contrasted particles of the adjacent membranes had fused with each other. It is suggested that these particles represent membrane-bound transport proteins providing a system for interorganelle exchanges of metabolites and/or ions.     

Leukemic mitochondria. III. Acute lymphoblastic leukemia.

Quantitative and qualitative electron microscopic studies were performed on the mitochondria of leukemic lymphoblasts in 6 patients with acute lymphoblastic leukemia. Similar studies were performed on lymphoblasts from lymph nodes obtained from 10 surgical patients without nodal diseases. Significant quantitative differences between normal and leukemic mitochondria were not observed except for a difference in mitochondrial area per cell (P less than 0.05). This was not significant lacking, qualitative diffecrences were observed. These abnormalities included rare giant mitochondria, disrupted mitochondria with virus-like particles, smaller granules in greater abundance, mitochondrial DNA, and contact between the mitochondrion and nucleus during interphase. Fifty-three percent of the leukemic lymphoblasts contained polyribosomes, as compared to 25% of the normal lymphoblasts. The cells with the polyribosomes contained the giant mitochondria. The leukemic lymphoblasts had an appearance similar to transformed lymphocytes resulting from an immunologic stimulus. This suggests that acute lymphoblastic leukemia may be a disease which is associated with an immunologic response. From the available ultrastructural and biochemical data, it would seem that the leukemic lymphoblast is a product of an abnormal metabolism which affects its ability to differentiate. These ultrastructural findings seem to indicate the need for biochemical investigation of leukemic mitochondria. (Am J Pathol 78:49-58, 1975     

Mitochondrial mutations,cellular instability and ageing: modelling the population dynamics of mitochondria

All eukaryotic cells rely on mitochondrial respiration as their major source of metabolic energy (ATP). However, the mitochondria are also the main cellular source of oxygen radicals and the mutation rate of mtDNA is much higher than for chromosomal DNA. Damage to mtDNA is of great importance because it will often impair cellular energy production. However, damaged mitochondria can still replicate because the enzymes for mitochondrial replication are encoded entirely in the cell nucleus. For these reasons, it has been suggested that accumulation of defective mitochondria may be an important contributor to loss of cellular homoeostasis underlying the ageing process.We describe a mathematical model which treats the dynamics of a population of mitochondria subject to radical-induced DNA mutations. The model confirms the existence of an upper threshold level for mutations beyond which the mitochondrial population collapses. This threshold depends strongly on the division rate of the mitochondria. The model also reproduces and explains (i) the decrease in mitochondrial population with age, (ii) the increase in the fraction of damaged mitochondria in old cells, (iii) the increase in radical production per mitochondrion, and (iv) the decrease in ATP production per mitochondrion.     

磁性纳米粒子-抗体复合物分离肝癌线粒体

 摘要：目的 利用人肝癌组织，研究磁性纳米粒子-抗体复合物与传统线粒体分离方法之间的差异。方法 取人肝癌组织，分别采用磁性纳米粒子-抗体复合物和密度梯度离心方法分离线粒体。扫描电镜观察线粒体形态，Western blot检测线粒体蛋白标志物，流式细胞仪分析线粒体膜电位变化。结果 采用磁性纳米粒子-抗体复合物方法分离得到的肝癌组织线粒体结构完整，无胞核、胞膜等组分的污染，几乎没有过氧化物酶体和溶酶体的污染。经流式细胞仪检测，线粒体膜电位稳定。结论 与传统方法相比，磁性纳米粒子-抗体复合物分离方法具备简便易行，分离得到的线粒体结构完整、纯度及活性较高，并且不需要大型设备等优点。     

A study of serum mitochondrial enzymes(mCK, mAST, mMDH) in rotavirus and adenovirus gastroenteritis in pediatric patients]

Rotavirus and adenovirus antigens in feces from 77 cases of gastroenteritis in pediatric patients were examined. Mitochondrial enzymes, mitochondrial creatine kinase(mCK), mitochondrial aspartate amino-transferase(mAST) and mitochondrial malate dehydrogenase(mMDH) activities in their sera were also measured and compared with the results of rotavirus and adenovirus antigens in the feces. Thirty-one cases were rotavirus antigen-negative(rota-negative)/adenovirus antigen-negative(adeno-negative), 5 were rota-negative/adenovirus antigen-positive(adeno-positive), 40 were rotavirus antigen-positive(rota-positive)/adeno-negative, and only one case showed positive for both antigens. The mean activities of these three enzymes were compared among 3 groups except one both positive case mentioned above and control group(n = 105) by Mann-Whitney U-test. The serum mCK activity was significantly higher in rota-positive/adeno-negative patients than in other groups(p < 0.01). On the other hand, no significant differences were observed for mAST and mMDH activities among any groups. It is suggested that these phenomena are caused by the differences of localization of these enzymes in mitochondria, that mCK is located the outer surface of inner membrane of mitochondria, and mAST and mMDH are located on the inner surface. The difference of serum mCK activity between rotavirus infection and adenovirus infection suggests that intestinal epithelial cell injury by rotavirus is stronger than that by adenovirus.