Ultrastructure of mitochondria and the endoplasmic reticulum in renal tubules of Dahl salt-sensitive rats

Metabolic and functional abnormalities in the kidney precede or coincide with the initiation of overt hypertension in the Dahl salt-sensitive (SS) rat. However, renal histological injury in SS rats is mild before the development of overt hypertension. We performed electron microscopy analysis in 7-wk-old SS rats and salt-insensitive consomic SS.13BN rats and Sprague-Dawley (SD) rats fed a 4% NaCl diet for 7 days. Long mitochondria (>2 μm) accounted for a significantly smaller fraction of mitochondria in medullary thick ascending limbs in SS rats (4% ± 1%) than in SS.13BN rats (8% ± 1%, P < 0.05 vs. SS rats) and SD rats (9% ± 1%, P < 0.01 vs. SS rats), consistent with previous findings of mitochondrial functional insufficiency in the medulla of SS rats. Long mitochondria in proximal tubules, however, were more abundant in SS rats than in SS.13BN and SD rats. The width of the endoplasmic reticulum, an index of endoplasmic reticulum stress, was significantly greater in medullary thick ascending limbs of SS rats (107 ± 1 nm) than in SS.13BN rats (95 ± 2 nm, P < 0.001 vs. SS rats) and SD rats (74 ± 3 nm, P < 0.01 vs. SS or SS.13BN rats). The tubules examined were indistinguishable between rat strains under light microscopy. These data indicate that ultrastructural abnormalities occur in the medullary thick ascending limbs of SS rats before the development of histological injury in renal tubules, providing a potential structural basis contributing to the subsequent development of overt hypertension.

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Abstract 479: Shortening of Mitochondria and Dilation of Endoplasmic Reticulum in the Medullary Thick Ascending Limb of Dahl Salt-Sensitive Rats

Hypertension ◽

10.1161/hyp.62.suppl_1.a479 ◽

2013 ◽

Vol 62 (suppl_1) ◽

Author(s):

Xiaofeng He ◽

Mingyu Liang

Keyword(s):

Endoplasmic Reticulum ◽

Interstitial Fibrosis ◽

Early Stage ◽

Strain Differences ◽

Structural Basis ◽

Renal Tubules ◽

Thick Ascending Limb ◽

Sprague Dawley ◽

Sd Rats ◽

Induced Hypertension

Functional abnormalities in the kidney appear to precede or coincide with the initiation of salt-induced hypertension in the Dahl salt-sensitive SS rat. However, the structural basis or mechanism of early renal abnormalities, especially in the renal tubules, is poorly understood. We performed electron microscopy analysis in 7 week old SS rats and salt-insensitive consomic SS.13 BN rats and Sprague-Dawley (SD) rats fed a 4% NaCl diet for 7 days. Long mitochondria (>2 μm), an indication of healthy mitochondria, accounted for a significantly smaller fraction of all mitochondria in medullary thick ascending limbs in SS rats (4% ± 1%) than in SS.13 BN rats (8% ± 1%, P<0.05 vs. SS) and SD rats (9% ± 1%, P<0.01 vs. SS). This is consistent with our previous findings of mitochondrial insufficiency in the medulla of SS rats. Long mitochondria in proximal tubules, however, were more abundant in SS rats than in SS.13 BN and SD rats. The width of endoplasmic reticulum, an index of endoplasmic reticulum stress, was significantly greater in medullary thick ascending limbs of SS rats (107 ± 1 nm) than SS.13 BN rats (95 ± 2 nm, P<0.001 vs. SS) and SD rats (74 ± 3 nm, P<0.01 vs. SS or SS.13 BN ). The rat strain differences in ultrastructure were observed even though the tubules were indistinguishable by light microscopy and less than 5% of the kidney area was affected by inflammation, interstitial fibrosis, or tubular casts. These data indicate that ultrastructural abnormalities in the mitochondria and endoplasmic reticulum in the medullary thick ascending limbs occur in the early stage of, and could contribute to, the development of salt-induced hypertension.

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Structural basis of ER-associated protein degradation mediated by the Hrd1 ubiquitin ligase complex

Science ◽

10.1126/science.aaz2449 ◽

2020 ◽

Vol 368 (6489) ◽

pp. eaaz2449 ◽

Cited By ~ 7

Author(s):

Xudong Wu ◽

Marc Siggel ◽

Sergey Ovchinnikov ◽

Wei Mi ◽

Vladimir Svetlov ◽

...

Keyword(s):

Electron Microscopy ◽

Ubiquitin Ligase ◽

Dynamics Simulation ◽

Structural Basis ◽

Cryo Electron Microscopy ◽

Ubiquitin Ligase Complex ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

Simulation Results ◽

Membrane Region

Misfolded luminal endoplasmic reticulum (ER) proteins undergo ER-associated degradation (ERAD-L): They are retrotranslocated into the cytosol, polyubiquitinated, and degraded by the proteasome. ERAD-L is mediated by the Hrd1 complex (composed of Hrd1, Hrd3, Der1, Usa1, and Yos9), but the mechanism of retrotranslocation remains mysterious. Here, we report a structure of the active Hrd1 complex, as determined by cryo–electron microscopy analysis of two subcomplexes. Hrd3 and Yos9 jointly create a luminal binding site that recognizes glycosylated substrates. Hrd1 and the rhomboid-like Der1 protein form two “half-channels” with cytosolic and luminal cavities, respectively, and lateral gates facing one another in a thinned membrane region. These structures, along with crosslinking and molecular dynamics simulation results, suggest how a polypeptide loop of an ERAD-L substrate moves through the ER membrane.

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Comparative Incidences and Biological Outcomes for Thymoma in Various Rat Strains in National Toxicology Program Studies

Toxicologic Pathology ◽

10.1177/0192623319863119 ◽

2019 ◽

Vol 47 (7) ◽

pp. 833-841

Author(s):

Rebecca R. Moore ◽

Hiroaki Nagai ◽

Rodney A. Miller ◽

Jerry F. Hardisty ◽

Neil Allison ◽

...

Keyword(s):

Cause Of Death ◽

Early Mortality ◽

Sprague Dawley ◽

Rat Strains ◽

Fischer 344 ◽

National Toxicology Program ◽

Sd Rats ◽

Biological Outcomes ◽

Long Term Studies

Thymomas from 277 Fischer 344/N (F344/N), 10 Sprague Dawley (HSD:Sprague Dawley SD) (SD), 129 Wistar Han [Crl:WI(Han)] (WH), and 4 Wistar Outbred (WO) rats were reviewed from long-term studies in the National Toxicology Program (NTP) database. The incidence of thymomas in F344/N rats was slightly higher in males than in females, while the incidences in SD and WH rats were higher in females than in males. Only male WO rats were used in NTP studies. Of the 277 thymomas in F344/N rats, 235 (84.8%) were benign and 42 (15.2%) malignant, 14 of which exhibited metastasis. Of the 10 thymomas in SD rats, 5 (50%) were benign and 5 (50%) were malignant, one of which exhibited metastasis. Of the 129 thymomas in WH rats, 126 (98%) were benign and 3 (2%) were malignant, 1 with metastasis. Of the 4 thymomas in WO rats, 3 (75%) were benign and 1 (25%) was malignant, with no metastases. Malignant thymomas in F344/N and WH rats showed a propensity to be the cause of death and to result in early mortality, whereas the benign thymomas were associated less often with decreased survival. No occurrences of this neoplasm were reported to be related to exposure to any test articles.

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Reduced osmotically inactive Na storage capacity and hypertension in the Dahl model

AJP Renal Physiology ◽

10.1152/ajprenal.00323.2001 ◽

2002 ◽

Vol 283 (1) ◽

pp. F134-F141 ◽

Cited By ~ 79

Author(s):

Jens Titze ◽

Holger Krause ◽

Hermann Hecht ◽

Peter Dietsch ◽

Jörn Rittweger ◽

...

Keyword(s):

Water Retention ◽

Storage Capacity ◽

Sprague Dawley ◽

Fluid Accumulation ◽

Rat Strains ◽

Sd Rats ◽

Inactive Form ◽

Dry Ashing ◽

Total Body

Recent evidence suggested that Na can be stored in an osmotically inactive form. We investigated whether osmotically inactive Na storage is reduced in a rat model of salt-sensitive (SS) hypertension. SS and salt-resistant (SR) Dahl-Rapp rats as well as Sprague-Dawley (SD) rats were fed a high (8%)- or low (0.1%)-NaCl diet for 4 wk ( n = 10/group). Mean arterial pressure (MAP) was measured at the end of the experiment. Wet and dry weights, water content, total body Na (TBS), and bone Na content were measured by dessication and dry ashing. MAP was higher in both Dahl strains than in SD rats. In SS rats, 8% NaCl led to Na accumulation, water retention, and hypertension due to impaired renal Na excretion. There was no dietary-induced Na retention in SR and SD rats. TBS was variable; nevertheless, TBS was significantly correlated with body water and MAP in all strains. However, the extent of Na-associated volume and MAP increases was strain specific. Osmotically inactive Na in SD rats was threefold higher than in SS and SR rats. Both SS and SR Dahl rat strains displayed reduced osmotically inactive Na storage capacity compared with SD controls. A predisposition to fluid accumulation and high blood pressure results from this alteration. Additional factors, including impaired renal Na excretion, probably contribute to hypertension in SS rats. Our results draw attention to the role of osmotically inactive Na storage.

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Neuraminidase1 Inhibitor Protects Against Doxorubicin-Induced Cardiotoxicity via Suppressing Drp1-Dependent Mitophagy

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.802502 ◽

2021 ◽

Vol 9 ◽

Author(s):

Yating Qin ◽

Chao Lv ◽

Xinxin Zhang ◽

Weibin Ruan ◽

Xiangyu Xu ◽

...

Keyword(s):

Mitochondrial Fission ◽

Subsequent Development ◽

Control Group ◽

Protective Effects ◽

Sprague Dawley ◽

Beneficial Effects ◽

Myocardial Apoptosis ◽

Sd Rats ◽

Cardio Protection

Anthracyclines, such as doxorubicin (DOX), are among the effective chemotherapeutic drugs for various malignancies. However, their clinical use is limited by irreversible cardiotoxicity. This study sought to determine the role of neuraminidase 1 (NEU1) in DOX-induced cardiomyopathy and the potential cardio-protective effects of NEU1 inhibitor oseltamivir (OSE). Male Sprague–Dawley (SD) rats were randomized into three groups: control, DOX, and DOX + OSE. NEU1 was highly expressed in DOX-treated rat heart tissues compared with the control group, which was suppressed by OSE administration. Rats in the DOX + OSE group showed preserved cardiac function and were protected from DOX-induced cardiomyopathy. The beneficial effects of OSE were associated with the suppression of dynamin-related protein 1 (Drp1)-dependent mitochondrial fission and mitophagy. In detail, the elevated NEU1 in cardiomyocytes triggered by DOX increased the expression of Drp1, which subsequently enhanced mitochondrial fission and PINK1/Parkin pathway-mediated mitophagy, leading to a maladaptive feedback circle towards myocardial apoptosis and cell death. OSE administration selectively inhibited the increased NEU1 in myocardial cells insulted by DOX, followed by reduction of Drp1 expression, inhibition of PINK1 stabilization on mitochondria, and Parkin translocation to mitochondria, thus alleviating excessive mitochondrial fission and mitophagy, alleviating subsequent development of cellular apoptotic process. This work identified NEU1 as a crucial inducer of DOX-induced cardiomyopathy by promoting Drp1-dependent mitochondrial fission and mitophagy, and NEU1 inhibitor showed new indications of cardio-protection against DOX cardiotoxicity.

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Genetic variability in combustion particle-induced chronic lung injury

AJP Lung Cellular and Molecular Physiology ◽

10.1152/ajplung.1997.272.3.l521 ◽

1997 ◽

Vol 272 (3) ◽

pp. L521-L532 ◽

Cited By ~ 10

Author(s):

U. P. Kodavanti ◽

R. H. Jaskot ◽

W. Y. Su ◽

D. L. Costa ◽

A. J. Ghio ◽

...

Keyword(s):

Lung Injury ◽

Airway Epithelium ◽

Intratracheal Instillation ◽

Immunohistochemical Analysis ◽

Lung Damage ◽

Sprague Dawley ◽

Rat Strains ◽

Mrna Isoforms ◽

Sd Rats ◽

Oil Fly Ash

Occupational exposure to anthropogenic particles is associated with lung injury in humans. We hypothesized that residual oil fly ash (ROFA), an emission source particulate, may induce acute lung injury and fibrosis in sensitive rat strains and that fibronectin (Fn) gene expression will correspond to the development of fibrosis. Male Sprague-Dawley (SD), Wistar (WIS), and Fischer 344 (F-344) rats (60 days old) were exposed to saline or ROFA (8.3 mg/kg) by intratracheal instillation and examined for up to 12 wk. Histology indicated focal areas of lung damage showing inflammatory cell infiltration as well as alveolar, airway, and interstitial thickening in all three rat strains during 1-7 days postexposure. Trichrome staining of the lung sections indicated a sporadic incidence of focal alveolar fibrosis at 1, 3, and 12 wk in SD rats, whereas WIS and F-344 rats showed only a modest increase in trichrome staining in the septal areas. Of all Fn mRNA isoforms examined by polymerase chain reaction, only EIIIA(+) was upregulated during 6 h-1 wk in ROFA-exposed SD and WIS rats but not in F-344 rats. In situ hybridization analysis in SD rats revealed Fn mRNA expression by macrophage and alveolar and airway epithelium and within fibrotic areas. Immunohistochemical analysis revealed increased presence of Fn EIIIA(+) protein in the areas of fibrotic injury and basally to the airway epithelium. In summary, Fn EIIIA(+) increases early in the course of particle-induced lung injury and remodeling, which may or may not result in discernible alveolar fibrosis. There is a rat strain variation in ROFA-induced fibrosis and associated Fn EIIIA(+) expression.

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Strain-Specific Nicotinic Modulation of Glutamatergic Transmission in the CA1 Field of the Rat Hippocampus: August Copenhagen Irish Versus Sprague-Dawley

Journal of Neurophysiology ◽

10.1152/jn.01119.2006 ◽

2007 ◽

Vol 97 (2) ◽

pp. 1163-1170 ◽

Cited By ~ 9

Author(s):

Manickavasagom Alkondon ◽

Edna F. R. Pereira ◽

Michelle C. Potter ◽

Frederick C. Kauffman ◽

Robert Schwarcz ◽

...

Keyword(s):

Hippocampal Slices ◽

Female Rats ◽

Differential Sensitivity ◽

Stratum Radiatum ◽

Sprague Dawley ◽

Rat Strains ◽

Glutamatergic Neurons ◽

Sd Rats ◽

Male And Female Rats ◽

Α7 Nachr

Prepulse inhibition (PPI), a measure of sensorimotor gating impaired in patients with schizophrenia, is more sensitive to disruption by apomorphine in prepubertal August Copenhagen Irish (ACI) than Sprague-Dawley (SD) rats. In brain regions including the hippocampus, PPI is modulated by α7* nicotinic receptors (nAChRs) and kynurenic acid (KYNA), a kynurenine metabolite that blocks α7 nAChRs. Here, KYNA levels and nAChR activities were measured in the hippocampi of 10- to 23-day-old ACI and SD rats of both sexes. Hippocampal KYNA levels were not different between ACI and SD rats. In hippocampal slices from both rat strains, choline (10 mM) evoked α7* nAChR-mediated type IA currents in CA1 stratum radiatum (SR) interneurons. In the presence of α7 nAChR antagonists, acetylcholine (ACh, 1 mM) evoked α4β2* nAChR-mediated type II currents. ACh also triggered excitatory postsynaptic currents (EPSCs) that resulted from α3β4* nAChR activation in glutamatergic neurons/axons synapsing onto the interneurons. The magnitude of the nicotinic responses did not differ significantly between male and female rats. Only the magnitude of α3β4* nAChR responses and the frequency of spontaneous EPSCs recorded from CA1 SR interneurons differed between the rat strains, being significantly larger in ACI than SD rats. These results indicate that the α3β4* nAChR activity in glutamatergic neurons/axons and the number of glutamatergic terminals synapsing onto CA1 SR interneurons are larger in prepubertal ACI than SD rats. The differential sensitivity of these rats to PPI disruption by apomorphine may result from strain-specific levels of glutamatergic activity and its strain-specific modulation by α3β4* nAChRs in the hippocampus.

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Characterization and structural basis of a lethal mouse-adapted SARS-CoV-2

Nature Communications ◽

10.1038/s41467-021-25903-x ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Shihui Sun ◽

Hongjing Gu ◽

Lei Cao ◽

Qi Chen ◽

Qing Ye ◽

...

Keyword(s):

Binding Affinity ◽

Receptor Binding ◽

Structural Basis ◽

Rapid Adaptation ◽

Cryo Electron Microscopy ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

And Gender ◽

Related Mortality

AbstractThere is an urgent need for animal models to study SARS-CoV-2 pathogenicity. Here, we generate and characterize a novel mouse-adapted SARS-CoV-2 strain, MASCp36, that causes severe respiratory symptoms, and mortality. Our model exhibits age- and gender-related mortality akin to severe COVID-19. Deep sequencing identified three amino acid substitutions, N501Y, Q493H, and K417N, at the receptor binding domain (RBD) of MASCp36, during in vivo passaging. All three RBD mutations significantly enhance binding affinity to its endogenous receptor, ACE2. Cryo-electron microscopy analysis of human ACE2 (hACE2), or mouse ACE2 (mACE2), in complex with the RBD of MASCp36, at 3.1 to 3.7 Å resolution, reveals the molecular basis for the receptor-binding switch. N501Y and Q493H enhance the binding affinity to hACE2, whereas triple mutations at N501Y/Q493H/K417N decrease affinity and reduce infectivity of MASCp36. Our study provides a platform for studying SARS-CoV-2 pathogenesis, and unveils the molecular mechanism for its rapid adaptation and evolution.

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Elevation of fumarase attenuates hypertension and can result from a nonsynonymous sequence variation or increased expression depending on rat strain

Physiological Genomics ◽

10.1152/physiolgenomics.00063.2017 ◽

2017 ◽

Vol 49 (9) ◽

pp. 496-504 ◽

Cited By ~ 8

Author(s):

Kristie Usa ◽

Yong Liu ◽

Aron M. Geurts ◽

Yuan Cheng ◽

Jozef Lazar ◽

...

Keyword(s):

Sequence Variation ◽

Specific Activity ◽

Tricarboxylic Acid Cycle ◽

Renal Medulla ◽

Brown Norway ◽

Sprague Dawley ◽

Rat Strains ◽

High Salt Diet ◽

Sd Rats ◽

Rat Strain

The activity of fumarase, an enzyme in the tricarboxylic acid cycle, is lower in Dahl salt-sensitive SS rats compared with SS.13BN rats. SS.13BN rats have a Brown Norway (BN) allele of fumarase and exhibit attenuated hypertension. The SS allele of fumarase differs from the BN allele by a K481E sequence variation. It remains unknown whether higher fumarase activities can attenuate hypertension and whether the mechanism is relevant without the K481E variation. We developed SS-TgFh1 transgenic rats overexpressing fumarase on the background of the SS rat. Hypertension was attenuated in SS-TgFh1 rats. Mean arterial pressure in SS-TgFh1 rats was 20 mmHg lower than transgene-negative SS littermates after 12 days on a 4% NaCl diet. Fumarase overexpression decreased H2O2, while fumarase knockdown increased H2O2. Ectopically expressed BN form of fumarase had higher specific activity than the SS form. However, sequencing of more than a dozen rat strains indicated most rat strains including salt-insensitive Sprague-Dawley (SD) rats had the SS allele of fumarase. Despite that, total fumarase enzyme activity in the renal medulla was still higher in SD rats than in SS rats, which was associated with higher expression of fumarase in SD. H2O2 can suppress the expression of fumarase. Renal medullary interstitial administration of fumarase siRNA in SD rats resulted in higher blood pressure on the high-salt diet. These findings indicate elevation of total fumarase activity attenuates the development of hypertension and can result from a nonsynonymous sequence variation in some rat strains and higher expression in other rat strains.

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Material analysis techniques using the ion mill

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100167639 ◽

1996 ◽

Vol 54 ◽

pp. 1034-1035

Author(s):

J. P. Benedict ◽

R. M. Anderson ◽

S. J. Klepeis

Keyword(s):

Polished Surface ◽

Surface Material ◽

Analysis Techniques ◽

Material Analysis ◽

Optical Inspection ◽

Electron Microscopy Analysis ◽

Microscopy Analysis ◽

Argon Ions ◽

The Impact ◽

Scanning Electron

Ion mills equipped with flood guns can perform two important functions in material analysis; they can either remove material or deposit material. The ion mill holder shown in Fig. 1 is used to remove material from the polished surface of a sample for further optical inspection or SEM ( Scanning Electron Microscopy ) analysis. The sample is attached to a pohshing stud type SEM mount and placed in the ion mill holder with the polished surface of the sample pointing straight up, as shown in Fig 2. As the holder is rotating in the ion mill, Argon ions from the flood gun are directed down at the top of the sample. The impact of Argon ions against the surface of the sample causes some of the surface material to leave the sample at a material dependent, nonuniform rate. As a result, the polished surface will begin to develop topography during milling as fast sputtering materials leave behind depressions in the polished surface.

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