A quantitative histological study of strain-dependent differences in the effects of irradiation on mouse lung during the early phase

Strain differences in the radiation response of mouse lung during the early phase (before 28 weeks postirradiation) were investigated histologically. The nine strains tested were divided into three groups on the basis of the nature of the edema present, the occurrence of hyaline membranes, and the presence of fibrosis. Group 1 mice, three C57 strains, developed hyaline membranes, focal fibrosis, and a protein-rich edema containing fibrin. Group 3, CBA and two C3H strains, had only a protein-poor edema with little fibrin and developed no visible fibrosis. Group 2 mice had both types of edema and small quantities of focal fibrosis. The degree of lung impairment in mice dying of respiratory insufficiency was assessed by scoring lung acini as nonfunctional or open and presumably functional. Over 70% of acini were nonfunctional as a result of airflow obstruction. This was considered sufficient to account for death. Carbon perfusion immediately before sacrifice indicated that all types of lesions were at least partially perfused with blood. Pleural effusions were found in some individuals of two strains. The proportion of nonfunctional acini was similar in mice of the same strain with and without effusions, which would not be expected if the effusions contributed appreciably to respiratory distress in the early phase.     

A quantitative histological study of adrenal development during late gestation and the perinatal period in intact and hypophysectomized fetal sheep

Growth of the sheep adrenal was studied during late gestation and the perinatal period. Adrenals were recovered from 28 fetuses taken at D100 (D0: day of mating), D120, D132 and D144, and in 4 newborn animals 3 days after birth (equivalent to D151). Animals were of the Ile de France breed. Cortex (without capsule) and medulla volumes increased respectively by 7.2 and 2.4 between D100 and D151. The 2 parts had the same volume between D100 and D120; thereafter the cortex became predominant, representing 74% of the whole gland at D151. Hypertrophy and hyperplasia were shown after D132 in the cortex (zona fasciculata); they were observed later after D144 in the medulla (central zone). Fifteen fetuses hypophysectomized at D100 or D120 were recovered at D120 or D144. The lack of pituitary inhibited cortical growth (zona fasciculata) and suppressed hypertrophy and hyperplasia. The medulla continued to grow after hypophysectomy but to a lesser extent than in controls.     

The genetic basis of strain-dependent differences in the early phase of radiation injury in mouse lung.

Substantial differences between mouse strains have been reported in the lesions present in the lung during the early phase of radiation injury. Some strains show only classical pneumonitis, while other strains develop substantial fibrosis and hyaline membranes which contribute appreciably to respiratory insufficiency, in addition to pneumonitis. Other strains are intermediate between these extremes. These differences correlate with intrinsic differences in activities of lung plasminogen activator and angiotensin converting enzyme. The genetic basis of these differences was assessed by examining histologically the early reaction in lungs of seven murine hybrids available commercially after whole-thorax irradiation. Crosses between fibrosing and nonfibrosing parents were uniformly nonfibrosing, and crosses between fibrosing and intermediate parents were uniformly intermediate. No evidence of sex linkage was seen. Thus the phenotype in which fibrosis is found is controlled by autosomal recessive determinants. Strains prone to radiation-induced pulmonary fibrosis and hyaline membranes exhibited intrinsically lower activities of lung plasminogen activator and angiotensin converting enzyme than either the nonfibrosing strains or the nonfibrosing hybrid crosses. The median time of death of the hybrids was genetically determined primarily by the longest-lived parent regardless of the types of lesions expressed.     

A quantitative histological study of adrenal development during the perinatal period in intact and hypophysectomized pigs

Adrenal growth was studied between D70 of gestation (D0: day of mating) and D6 after birth in 33 fetuses and 11 new-born pigs of the Large White breed. Volume, height and mean surface, were estimated by zone, as well as cell number, cell size and nucleocytoplasmic ratio. The volume increased exponentially. In the cortex it was 4.0 mm3, 7.2 mm3, 10.5 mm3, 33.6 mm3, 55.3 mm3 at D70, D94, D106, D113 and D1-D6, respectively, after birth. In the medulla, the volume was 4.0 mm3, 6.3 mm3, 6.9 mm3, 9.6 mm3 and 20.6 mm3 at the same stages. This evolution was due to predominant longitudinal stretching between D94 and D106, then thickening, as shown by the relative variations of the height and the surface. The growth of the cortex corresponded to hyperplasia associated with hypertrophy after D110. In the medulla, hyperplasia predominated until D110; this was followed by hypertrophic phase. Twelve fetuses hypophysectomized at D44 or at D55 were recovered at D94, D106 and D112 at least 50 days after surgery. Hypophysectomy did not affect medullar development (volume and number of cells) but inhibited very significantly the growth of the cortical zone, particularly that of the fasciculata.     

Effect of prenatal gamma irradiation during the late fetal period on the postnatal development of the mouse

Pregnant Swiss albino mice were exposed to 0.3, 0.5, 1.0, or 1.5 Gy of gamma radiation on day 17 of gestation. Sham-exposed controls were examined for comparison. Exposed mice as well as controls were left to complete gestation and parturition. Pups were observed up to age 6 weeks; appearance of physiological markers (pinna detachment, eye opening, fur development, vaginal opening, and testes descent), postnatal mortality, body weight, body length, head length, head width, and tail length were recorded. A significant delay in fur development was observed at 0.3 Gy and in other physiological markers at doses above 0.3 Gy, while a significant increase in mortality and growth retardation occurred only at 1.0 and 1.5 Gy. Although congenital anomalies such as syndactyly and bent tail were observed at doses of 0.5-1.5 Gy, only syndactyly showed a statistically significant increase in frequency. A statistically significant lower body weight was observed during the first week of postnatal life, but body weights increased to normal levels by the second week in animals exposed to doses less than 1.0 Gy. At higher doses, low body weight persisted throughout the postnatal period. Head length and tail length showed a significant decrease from controls at 0.5-1.5 Gy, and the effect was evident from birth to age 6 weeks. But a similar effect on body length and head width was noticed only at 1.0 and 1.5 Gy. These studies indicate that even in the absence of any major morphological changes, normal development of physiological landmarks and postnatal growth can be impaired by fetal irradiation at 17 days p.c. (post coitus). Morphological changes appear to have a threshold between 0.3-0.5 Gy, while physiological marker effects may occur with a lower threshold.     

A quantitative histological study of Golgi II neurons and pale cells in different cerebellar regions of the adult and ageing mouse brain

Two types of medium to large sized neurons are present in the granular layer of the mouse cerebellum. One type has a large nucleus with a prominent nucleolus and a moderate amount of cytoplasm containing Nissl substance. This type corresponds to the classical Golgi II neuron. The second type has a much smaller nucleus (mean diameter 8.4 microns) with a darkly staining nuclear envelope which is almost invariably deeply indented by cytoplasmic intrusions. The nucleolus is smaller and less conspicuous than in Golgi II neurons. These neurons are identical to the pale cells described by Altman and Bayer (1977). The numbers of both types of neuron were estimated in the spinocerebellum, lobus simplex and nodulus in mice aged 6, 15, 22, 25, 28 and 31 months. There was no significant variation in the number of either Golgi II neurons or pale cells with age in any part of the cerebellum. The number of Golgi II neurons per mm3 was similar in all parts of the cerebellum (mean 3560 mm3). This was identical to the mean number of pale cells per mm3 in the spinocerebellum and pontocerebellum but in the nodulus pale cells were much more numerous (mean 41,170 per mm3). It is postulated that pale cells are small Golgi II neurons.     

Role of early and late oestrogenic effects on implantation in the mouse

Oestrogen action in the uterus is expressed in an early phase (Phase I) and a late phase (Phase II). The role of this biphasic oestrogen action in implantation is not clear. To determine the relative importance of Phase I and II responses, triphenylethylene compounds (CI-628, LY-117018, nafoxidine, clomiphene citrate and tamoxifen) and oestrogens (oestriol and oestradiol-17 beta) were used in a physiologically relevant experimental system for studying implantation. All compounds elicited uterine water imbibition to various degrees in ovariectomized-progesterone-treated mice at 6 h (Phase I response) and their effectiveness in inducing implantation in delayed implanting mice correlated with their respective potency to increase uterine wet weight. This suggests that Phase I might be an essential component of oestrogen action in implantation and that the efficiency of a compound to elicit a Phase I response might serve as a predictive indicator of its potential action on implantation.     

Vascular permeability and late radiation fibrosis in mouse lung

It has been suggested that fibrosis which develops after irradiation is caused by increases in vascular permeability. Plasma proteins leak into irradiated tissue where fibrinogen may be converted into fibrin which is gradually replaced by fibrous tissue. Vascular and fibrotic changes in mouse lung were investigated after X irradiation of the right hemithorax. Blood volume and accumulation of extravascular proteins were measured using indium (111In)-labeled red cells, iodinated (131I) albumin, and iodinated (125I) fibrinogen. Tracers were injected 1-47 weeks after irradiation and lungs were excised 24 or 96 hr later to determine radioactivity. The amount of collagen was estimated by measuring the hydroxyproline content. During the first few months after X rays, lung blood volume decreased to a plateau which depended on radiation dose (10-25 Gy). Small increases in extravascular albumin and fibrinogen occurred at 1-12 weeks after 10-25 Gy. Subsequently, protein returned to normal after 10 Gy, remained elevated after 15 Gy, and increased after 20 and 25 Gy. Hydroxyproline per gram of dry irradiated lung was increased at 18 weeks after 15-25 Gy. Subsequently it showed little change although both total hydroxyproline content and dry weight decreased after 20 and 25 Gy. Support for the hypothesis was that hydroxyproline per gram only increased after X-ray doses which caused marked extravasation of protein. There was no evidence, however, for deposition of 125I-fibrin or for a gradual increase in fibrosis corresponding to the prolonged excess of extravascular protein.     

Late functional and biochemical changes in mouse lung after irradiation: differential effects of WR-2721

The radioprotective effect of WR-2721 on late damage after whole thorax irradiation has been studied after split doses of radiation using the standard death and breathing rate assays at monthly intervals between 3 and 15 months after irradiation, as well as two biochemical measurements of injury at 15 months, hydroxyproline (HP), an indicator of tissue fibrosis, and DNA content, an indicator of tissue cellularity. A comparison of HP/lung and breaths per minute (BPM) in each dose group in the WR-2721 and non-WR-2721-treated mice 15 months after irradiation showed that the relationship between these two assays of late lung injury was not the same. There were large dose-related increases in breathing rate corresponding to relatively small changes in HP in the lungs of mice given radiation alone. In contrast, the mice given WR-2721 before irradiation showed large dose-related increases in HP/lung, but BPM remained relatively constant independent of dose. These data suggest then that changes in breathing rate and deaths later than 9 months after whole lung irradiation may not be due to collagen accumulation in the lung. WR-2721 did protect better against late lung functional changes (protection factors (PF) = 1.6) and late deaths (PF = 1.51) than against earlier changes in these same assays (PF = 1.4 and 1.28, respectively). Although the earlier-appearing injury after whole thoracic irradiation is most likely related to lung damage with deaths and increases in breathing rate resulting from pneumonitis, the cause of the late-appearing functional injury in the lung after radiation is not clear. Thus protection of late lung damage measured from either lethality or breathing rate is not related to the prevention of lung fibrosis.     

Quantitative PCR assays for mouse enteric flora reveal strain-dependent differences in composition that are influenced by the microenvironment

The mammalian gastrointestinal (GI) tract is inhabited by over a hundred species of symbiotic bacteria. Differences among individuals in the composition of the GI flora may contribute to variation in in vivo experimental analyses and disease susceptibility. To investigate potential interindividual differences in GI flora composition, we developed real-time quantitative PCR-based assays for the detection of the eight members of the Altered Schaedler Flora (ASF) as representative members of different bacterial niches within the mammalian GI tract. Quantitative and reproducible strain-specific variations in the numbers of the ASF members were observed across 23 different barrier-housed inbred mouse strains, suggesting that the ASF assays can be used as sentinels for changes in GI flora composition. A significant cage effect was also detected. Isogenic mice that cohabited at weaning, whether from the same or different litters, showed little variation in ASF profiles. Conversely, litters split among different cages at weaning showed divergence in ASF profiles after three weeks. Individual ASF profiles, once established, were highly stable over time in the absence of environmental perturbation. Furthermore, cohabitation of different inbred strains maintained most of the interstrain variation in the GI flora, supporting a role of host genetics in determining GI flora composition.     

A quantitative analysis of mitochondria during fetal mouse oogenesis

A quantitative analysis of mitochondrial populations during the meiotic prophase of mouse oogenesis was carried out. The mean absolute area occupied by mitochondria and the mean number of mitochondria per cell increases in a linear fashion from pachytene through dictyate. The mean area occupied by mitochondria increases at pachytene and thereafter. Both small and large aggregations of mitochondria are seen, particularly during the later stages of prophase. Vacuolated mitochondria are present from preleptotene through pachytene. Mitochondria show major dynamic changes throughout fetal mouse oogenesis, which may suggest significant functional activities yet to be elucidated.     

Sex- and strain-dependent histological features of the proximal convoluted tubular epithelium of mouse kidney: association with lysosomes containing apolipoprotein B

In the present study, we performed comparative histological observations of ICR, BALB/c, C57BL/6, C3H/HeN and DBA/2 mice kidneys. Sex and strain differences were observed in the appearance of vacuolar structures of the proximal convoluted tubules (toluidine blue-positive granules in osmium-postfixed epoxy-resin sections). These features were especially remarkable in male DBA/2 mice. The vacuolar structures in male DBA/2 mice showed heterogeneous staining with Sudan B in frozen sections and appeared under an electron microscope as multilammelar giant dense bodies. In addition, these dense bodies showed heterogeneous acid phosphatase reactions. Immunohistochemical analyses of these structures for apolipoprotein B showed strong positive reactions. These results suggested that vacuolar structures in the proximal convoluted tubules, which were remarkable in male DBA/2 mice, were giant lysosomes containing apolipoprotein B.     

Genetics of obesity in KK mouse and effects of A y allele on quantitative regulation

KK mouse is known as a polygenic model for non-insulin-dependent diabetes mellitus with moderate obesity. To identify the quantitative trait loci (QTLs) responsible for the body weight in KK, linkage analysis with 97 microsatellite markers was carried out into 192 F₂ progeny, comprising 93 mice with a/a genotype at agouti locus and 99 mice with A ^y /a genotype, of a cross between C57BL/6J female and KK-A^y (A^y congenic) male, thereby the influence of A ^y allele on the quantitative regulation of body weight was also examined. In F₂ a/a mice, we identified a QTL on Chromosome (Chr) 4, and two loci with suggestive linkage on Chrs 15 and 18. In F₂ A ^y /a mice, a QTL was identified on Chr 6, and two loci with suggestive linkage were identified on Chrs 4 and 16. That the QTL on Chr 4 was held in common between F₂ a/a and F₂ A ^y /a progenies implies that this locus may be a primary component regulating body weight in KK and KK-A^y. These results suggest that the body weight in KK is controlled by multiple genes, and the different combination of loci is involved in the presence of A ^y allele. The QTL on Chr 6 seemed to determine the body weight by controlling fat deposition, because the linkage was identified on body weight and adiposity, and is suggested to be a component involved in the metabolic pathway in obesity caused by the A ^y allele. Received: 16 December 1997 / Accepted: 16 March 1998