Design, synthesis, and evaluation of 2,2'-bipyridyl derivatives as bifunctional agents against Alzheimer's disease

Alzheimer's disease (AD) is a complex multifactorial neurodegenerative disease. Metal ion dyshomeostasis and Aβ aggregation have been proposed to contribute to AD progression. Metal ions can bind to Aβ and promote Aβ aggregation, and ultimately lead to neuronal death. Bifunctional (metal chelation and Aβ interaction) compounds are showing promise against AD. In this work, eleven new 3,3'-diamino-2,2'-bipyridine derivatives 4a-4k were synthesized, and evaluated as bifunctional agents for AD treatment. In vitro Aβ aggregation inhibition assay confirmed that most of the synthesized compounds exhibited significant self-induced Aβ_1-42 aggregation inhibition. Among them, compound 4d displayed the best inhibitory potency of self-induced Aβ_1-42 aggregation with IC₅₀ value of 9.4 µM, and it could selectively chelate with Cu²⁺ and exhibited 66.2% inhibition of Cu²⁺-induced Aβ_1-42 aggregation. Meanwhile, compound 4d showed strong neuroprotective activity against Aβ_1-42 and Cu²⁺-treated Aβ_1-42 induced cell damage. Moreover, compound 4d in high dose significantly reversed Aβ-induced memory impairment in mice.

Abstract 43: Predictive biomarkers of recurrence may not be useful for deescalating treatment of breast ductal carcinoma in situ due to de novo ipsilateral breast carcinoma development

Introduction: Up to 25% of cases of ductal carcinoma in situ (DCIS) recur, and half of these recur as invasive breast cancer (IBC). There is no biomarker to predict which DCIS cases will recur but it has been suggested that a biomarker would allow de-escalation of the current paradigm of treating most patients with surgery and/or radiotherapy. However, we hypothesize that not all recurrences are genetically similar to the primary DCIS (i.e. non-clonal) and therefore arise de novo. To test this we assembled a large recurrence cohort to explore the clonal relatedness of primary-recurrence tumor pairs prior to proposing a predictive biomarker (Gorringe et al Mod Pathol 2015).

Method: We microdissected and extracted DNA from 65 pairs of primary DCIS and recurrences. Half of these recurrences were IBC. We analyzed 21 pairs by targeted sequencing or low-coverage whole-genome sequencing (LCWGS, 2x depth) and 44 pairs with Whole Exome Sequencing (WES, average depth 95x). We similarly analyzed a set of non-recurrent DCIS cases (n=29) treated with wide local excision and with a minimum of 7 years follow-up. No matched normal samples were available. Several approaches were utilized to investigate clonal relatedness using copy number alterations and mutations (when detected), including the Clonality package (Mauguen et al Biometrics 2018), manual breakpoint inspection (Bollet et al JNCI 2008), and clonality indexes (Schultheis et al JNCI 2016). Phylogenetic analyses were carried out by MEDICC2 (Petkovic et al bioRxiv 2021) on WES samples.

Results: 62% of cases were clonal (40/65), 28% were non-clonal. There were 7/65 that were equivocal, although further validation will be performed. There was no significant difference in clonal relatedness whether the recurrence was IBC or DCIS. IBC recurrent cases showed a significantly higher ploidy than the DCIS recurrences. The final phylogenetic analysis with MEDICC2 will be presented, which will take into account any subclonal whole-genome doubling events. Furthermore, clonal primary DCIS showed a significantly higher number of TP53 mutations compared to non-recurrent and non-clonal primaries (p<0.001, Fisher Exact test) and a higher level of copy number events overall.

Conclusion: Detailed molecular analysis of a large cohort of matched DCIS primary and their recurrences using high sequencing resolution showed a substantial proportion of recurrences were not genetically related to the primary DCIS. Our observations raise the question of whether a tumor intrinsic biomarker alone would be sufficient to predict DCIS recurrences.

Citation Format: Tanjina Kader, Sakshi Mahale, Magnus Zethoven, Hugo Saunders, Dorothea Lesche, David Byrne, Siqi Lai, Lauren Tjoeka, Claire Candido, Maree Pechlevanis, Olivia Craig, Jia-Min Pang, Lisa Devereux, Shona Hendry, Eloise House, Sureshni Jayasinghe, Michael Toss, Islam M. Miligy, Emad Rakha, Stephen Fox, Bruce Mann, Ian Campbell, Kylie Gorringe. Predictive biomarkers of recurrence may not be useful for deescalating treatment of breast ductal carcinoma in situ due to de novo ipsilateral breast carcinoma development [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 43.

[Specifications for diagnosis and treatment of non-neonatal tetanus]

Tetanus consists of neonatal tetanus and non-neonatal tetanus. Non-neonatal tetanus remains a serious public health problem, although neonatal tetanus has been eliminated in China since 2012. Non-neonatal tetanus is a potential fatal disease. In the absence of medical intervention, the mortality rate of severe cases is almost 100%. Even with vigorous treatment, the mortality rate is still 30%-50% globally. These specifications aim to regulate non-neonatal tetanus diagnosis and treatment in China, in order to improve medical quality and safety. These specifications introduce the etiology, epidemiology, pathogenesis, clinical manifestations and laboratory tests, diagnosis, differential diagnosis, grading and treatment of non-neonatal tetanus.

The genetic architecture of breast papillary lesions as a predictor of progression to carcinoma

Intraductal papillomas (IDP) are challenging breast findings because of their variable risk of progression to malignancy. The molecular events driving IDP development and genomic features of malignant progression are poorly understood. In this study, genome-wide CNA and/or targeted mutation analysis was performed on 44 cases of IDP, of which 20 cases had coexisting ductal carcinoma in situ (DCIS), papillary DCIS or invasive ductal carcinoma (IDC). CNA were rare in pure IDP, but 69% carried an activating PIK3CA mutation. Among the synchronous IDP cases, 55% (11/20) were clonally related to the synchronous DCIS and/or IDC, only one of which had papillary histology. In contrast to pure IDP, PIK3CA mutations were absent from clonal cases. CNAs in any of chromosomes 1, 16 or 11 were significantly enriched in clonal IDP lesions compared to pure and non-clonal IDP. The observation that 55% of IDP are clonal to DCIS/IDC indicates that IDP can be a direct precursor for breast carcinoma, not limited to the papillary type. The absence of PIK3CA mutations and presence of CNAs in IDP could be used clinically to identify patients at high risk of progression to carcinoma.

Abstract P6-10-21: Evaluation of genomic changes in ductal carcinoma in situ as potential biomarkers of recurrence risk

Routine breast cancer screening has increased detection of pre-invasive lesions such as ductal carcinoma in situ (DCIS). Currently, DCIS cases are mostly treated with wide local excision combined with adjuvant radiotherapy and/or hormonal therapy, even though only 25% of DCIS treated with surgery alone recur with 50% of recurrences being invasive. At present, prediction of recurrence risk is based on histopathological features and patient characteristics but reliable identification of individual recurrence risk is still challenging. Certain genetic aberrations (i.e. copy number variation, somatic mutations) are associated with breast cancer progression. While most recurrences are assumed to be genetically related to the primary tumour (“clonal recurrence”), the prevalence of ipsilateral independent primary events (“non-clonal recurrence”) after treatment for DCIS is uncertain. If this is a substantial proportion of cases, their presence would compromise attempts to find tumour intrinsic biomarkers of recurrence. To enable the discovery of better recurrence biomarkers, this project initially aims to identify cases with primary DCIS and later clonal ipsilateral recurrence.

Sections from formalin-fixed paraffin-embedded blocks from primary DCIS cases and their subsequent recurrences were obtained from Nottingham City Hospital (UK). Two pathologists reviewed representative sections to identify areas for microdissection. Tumour epithelial cells were needle-microdissected and DNA was isolated. Sequencing libraries were prepared using a) a custom capture panel of 110 breast cancer-related genes or b) NEBNext Ultra II for low-coverage whole-genome sequencing (LC-WGS) depending on DNA quality and quantity. Sequencing was then performed on Illumina NextSeq 500 system with an average coverage of a) 400x and b) 1.3x, respectively. Data was processed by an in-house bioinformatics pipeline to detect and filter for high confidence somatic variants. Copy number profiles were obtained using CopywriteR (panel off-target reads), PureCN (panel on-target reads) and Control-FREEC (LC-WGS). Of 33 patients initially ascertained on the basis of a recurrent breast event, 30 had an ipsilateral recurrent tumour after 4.7 years on average, and 24 primary/recurrence pairs had sufficient data available to determine clonality. Eighteen pairs (75%) were classified as clonal by the following criteria: occurring in similar locations, showing a similar or higher tumour grade, and sharing ≥ 3 copy number breakpoints or likely somatic variants in the genes included in the panel. Six pairs (25%) did not meet this criteria and were classified as non-clonal. Preliminary data analysis shows that invasive recurrences (n = 12) were detected on average 3 years later than DCIS recurrences (n = 6), despite constant surveillance. The most commonly observed somatic mutations occurred in the TP53 and PIK3CA genes. Genetic variants in TP53 and PIK3CA were equally common in primary tumours with clonal and non-clonal recurrence. Frequent copy number alterations involved losses on 16q as well as gains on 1q, 8q and 17q, whereat the 8q gain was less profound. The presence of 25% non-clonal recurrences shows that differentiating between clonal and non-clonal recurrences might be crucial for further recurrence risk biomarker discovery. Thus, this project will proceed with comparing genetic variation in primary DCIS with clonal recurrence to DCIS cases without later recurrence. These samples are currently being obtained and analysed.

Citation Format: Dorothea Lesche, Hugo Saunders, Sakshi Mahale, Magnus Zenthoven, Siobhan Huges, Tanjina Kader, Niko Thio, Islam M Miligy, Jia-Min Pang, Andrew R Green, Emad A Rakha, Ian G Campbell, Stephen B Fox, Kylie Gorringe. Evaluation of genomic changes in ductal carcinoma in situ as potential biomarkers of recurrence risk [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P6-10-21.

[Specifications for diagnosis and treatment of non-neonatal tetanus]

Tetanus consists of neonatal tetanus and non-neonatal tetanus. Although neonatal tetanus in China has been eliminated since 2012, non-neonatal tetanus remains a serious public health problem. Non-neonatal tetanus is a potential fatal disease, and the mortality rate of severe cases is almost 100% in the absence of medical intervention. Even with vigorous treatment, the mortality rate is still 30~50% globally. In order to standardize the diagnosis and treatment of non-neonatal tetanus in China, this specification is hereby formulated. This standard includes etiology, epidemiology, pathogenesis, clinical manifestations, laboratory tests, diagnosis, differential diagnosis, classification, grading and treatment of non-neonatal tetanus.

Molecular comparison of interval and screen-detected breast cancers

Breast cancer (BC) diagnosed after a negative mammogram but prior to the next screening episode is termed an 'interval BC' (IBC). Understanding the molecular differences between IBC and screen-detected BCs (SDBC) could improve mammographic screening and management options. Therefore, we assessed both germline and somatic genomic aberrations in a prospective cohort. Utilising the Lifepool cohort of >54 000 women attending mammographic screening programs, 930 BC cases with screening status were identified (726 SDBC and 204 IBC). Clinico-pathological and family history information were recorded. Germline and tumour DNA were collected where available and sequenced for BC predisposition and driver gene mutations. Compared to SDBC, IBCs were significantly associated with a younger age at diagnosis and tumour characteristics associated with worse prognosis. Germline DNA assessment of BC cases that developed post-enrolment (276 SDBCs and 77 IBCs) for pathogenic mutations in 12 hereditary BC predisposition genes identified 8 carriers (2.27%). The germline mutation frequency was higher in IBC versus SDBC, although not statistically significant (3.90% versus 1.81%, p = 0.174). Comparing somatic genetic features of IBC and SDBC matched for grade, histological subtype and hormone receptor revealed no significant differences, with the exception of higher homologous recombination deficiency scores in IBC, and copy number changes on chromosome Xq in triple negative SDBCs. Our data demonstrates that while IBCs are clinically more aggressive than SDBC, when matched for confounding clinico-pathological features they do not represent a unique molecular class of invasive BC, but could be a consequence of timing of tumour initiation and mammographic screening. Copyright © 2019 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Assessing Tumor Angiogenesis in Histological Samples

Tumor neovascularization acquires their vessels through a number of processes including angiogenesis, vasculogenesis, vascular remodeling, intussusception, and possibly vascular mimicry in certain tumors. The end result of the tumor vasculature has been quantified by counting the number of immunohistochemically identified microvessels in areas of maximal vascularity, so-called hot spot. Other techniques have been developed such as Chalkley counting and the use of image analysis systems that are robust and reproducible as well as being more objective. Many of the molecular pathways that govern tumor neovascularization have been identified and many reagents are now available to study these tissue sections. These include angiogenic growth factors and their receptors and cell adhesion molecules, proteases, and markers of activated, proliferating, cytokine-stimulated, or angiogenic vessels, such as CD105. It is also possible to differentiate quiescent from active vessels. Other reagents that can identify proteins involved in microenvironmental influences such as hypoxia have also been generated. Although the histological assessment of tumor vascularity is used mostly in the research context, it may also have clinical applications if appropriate methodology and trained observers perform the studies.

Abstract 2962: LRH-1 expression in breast cancer tissue and its association with phenotype and DNA methylation

Introduction

The LRH-1 gene (NR5A2) located on chromosome 1q codes for a transcription factor implicated in promoting cell proliferation and migration in breast cancer. The gene contains five CpG islands and codes for several mRNA isoforms. However, little is known about its expression in breast cancer tissues. In this study, we examine LRH-1 expression patterns in breast cancer tissue by immunohistochemistry, its association with phenotypic features, and the relationship of DNA methylation with LRH-1 expression.

Methods

LRH-1 immunohistochemical (IHC) staining was performed on tissue microarray sections containing 329 cases of breast cancer (175 ductal carcinoma in situ (DCIS), 154 invasive carcinomas). Methylation was assessed using methylation sensitive high resolution melting assays targeted towards regions in the second and fifth CpG islands of LRH-1. These CpG islands are situated immediately upstream of the transcription start sites of mRNA transcripts 1 and 3, respectively. CpG island 2 (CpG2) methylation was assessed in 96 cases (65 DCIS, 31 invasive carcinoma), methylation of CpG island 5 (CpG5) was assessed in 99 cases (66 DCIS, 33 invasive carcinoma), and methylation data for both CpG islands was obtained in 85 cases (55 DCIS, 30 invasive carcinoma).

Results

IHC staining revealed four patterns of nuclear staining in breast cancer tissues. Nuclear staining was present as either in a finely granular pattern (pattern 1), a sparse punctate pattern (pattern 2), a dense punctate pattern (pattern 2+), or as a coarse granular pattern (pattern 3). Patterns 1 and 2 were considered LRH-1 low and patterns 2+ and 3 were considered LRH-1 high. LRH-1 high staining was significantly associated with adverse phenotypic features including high grade (p<0.0005), non-luminal phenotype (p = 0.003), estrogen receptor (ER) negativity (p = 0.008), progesterone receptor (PgR) negativity (p = 0.003) and HER2 amplification (p = 0.039). The presence of CpG5 methylation together with absent or low levels of CpG2 methylation was significantly associated with LRH-1-high IHC expression (p = 0.033) and aggressive phenotypic features of high grade (p = 0.001), non-luminal intrinsic subtype (p = 0.021), ER negativity (p = 0.010), PgR negativity (p = 0.021), and HER2 amplification (p = 0.043).

Conclusions

This study identifies, for the first time, distinct nuclear IHC staining patterns in breast cancer tissue and the association of LRH-1 IHC-high patterns with aggressive phenotypic features. Differential DNA methylation of two regions is associated with LRH-1 IHC staining pattern, indicating a role for DNA methylation in the control of differential mRNA isoform expression and thus protein expression.

Citation Format: Jia-Min Pang, Ashwini Chand, Kevin Knower, Elena Takano, David Byrne, Evelien Sprenkeler, Ramyar Molania, Ewan Millar, Soon Lee, Sandra O'Toole, Colin Clyne, Alexander Dobrovic, Stephen Fox. LRH-1 expression in breast cancer tissue and its association with phenotype and DNA methylation. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 2962. doi:10.1158/1538-7445.AM2015-2962

Is the trimodal pattern of death after trauma a dated concept in the 21st century? Trauma deaths in Auckland 2004

OBJECTIVE

To determine whether the classical trimodal distribution of trauma deaths is still applicable in a contemporary urban New Zealand trauma system.

METHODS

All trauma deaths in the greater Auckland region between 1 January 2004 and 31 December 2004 were identified and reviewed. Data was obtained from hospital trauma registries, coroner autopsy reports and police reports.

RESULTS

There were 186 trauma deaths. The median age was 28.5 years and the median Injury Severity Score was 25. The predominant mechanisms of injury were hanging (36%), motor vehicle crashes (31.7%), falls (9.7%), pedestrian-vehicle injury (5.4%), stabbing (4.3%), motorcycle crashes (3.2%), and pedestrian-train injury (2.2%). Most deaths were from central nervous system injury (71.5%), haemorrhage (15.6%), and airway/ventilation compromise (3.8%). Multi-organ failure accounted for 1.6% of deaths. Most deaths occurred in the pre-hospital setting (80.6%) with a gradual decrease thereafter.

CONCLUSION

There was a skew towards early deaths. The trimodal distribution of trauma deaths was not demonstrated in this group of patients.

Human leukocyte antigen class II alleles in Caucasian women with primary biliary cirrhosis

In the current study, we investigated human leukocyte antigen (HLA) class II alleles in Caucasian women with primary biliary cirrhosis (PBC), a disease that preferentially affects women. Alleles of DRB1, DQA1, and DQB1 were determined by DNA-based HLA typing for women with PBC (n = 72) and healthy women (n = 381). All study subjects were Caucasian. HLA DRB1*08 was significantly increased in women with PBC compared to healthy women. The increase was primarily due to the DRB1*0801 allele, also the most common DRB1*08 allele among controls. DQB1*04 and DQA1*0401 were significantly increased. DRB1*1501, DQA1*0102, and DQB1*0602 were associated with decreased risk. Analyses conducted comparing parous women with PBC to parous healthy women (n = 68 and n = 282, respectively) yielded similar significant results. Although the DRB1*08-DQA1*0401-DQB1*04 haplotype was significantly associated with PBC, consistent with other studies, this haplotype nevertheless represented only 19% (14/72) of all PBC patients and can account for only a minority of the risk of PBC.

HLA allelic variants encoding DR11 in diffuse and limited systemic sclerosis in Caucasian women

OBJECTIVE

We investigated HLA class II alleles in women with systemic sclerosis (SSc), a rare disease that preferentially affects women.

METHODS

Specific alleles of DRB1, DQA1 and DQB1 were determined by DNA-based HLA typing for women with SSc (n = 102) and healthy women (n = 533). All study subjects were Caucasian. DRB1, DQA1 and DQB1 allele frequencies of women with SSc were compared with those of healthy women.

RESULTS

Among women with SSc, 29.4% (30/102) and among healthy women 10.7% (57/533) had DRB1*11. Allele frequencies were compared for women with SSc and healthy women (each woman has two alleles). The allele frequency of DRB1*11 was 15.7% (32/204 alleles) in SSc women and 5.8% (62/1066 alleles) in healthy women (P = 0.000002). The increase of DRB1*11 was found both in diffuse (P = 0.0001) and limited SSc (P = 0.002) (allele frequencies 15.0 and 17.2%, respectively). Among women with diffuse SSc, there was a disproportionate increase of the DRB1*1104 allele (P = 0.0004) with no increase of DRB1*1101 (P = 1.00). In contrast, in limited SSc the strongest association was with DRB1*1101 (P = 0.008), with a less significant increase of DRB1*1104 (P = 0.04).

CONCLUSIONS

An increase of DRB1*11 in SSc is consistent with other reports. Although present in both diffuse and limited SSc disease subsets, the increase was predominantly due to over-representation of DRB1*1104 in women with diffuse SSc. Women with limited SSc had a preponderance of DRB1*1101, the most common allele in healthy women. DRB1*1104 and DRB1*1101 differ by a single amino acid at position 86, where the former has valine and the latter glycine.

Male microchimerism in women with systemic sclerosis and healthy women who have never given birth to a son

BACKGROUND

Male DNA or cells are often used to measure microchimerism in a woman. In studies of autoimmune diseases male microchimerism is most often attributed to the previous birth of a son.

OBJECTIVE

To determine the frequency of male microchimerism in healthy women or women with systemic sclerosis who had never given birth to a son.

METHODS

Real time quantitative polymerase chain reaction targeting the Y chromosome specific sequence DYS14 was employed to test DNA extracted from peripheral blood mononuclear cells of 26 women with systemic sclerosis and 23 healthy women who had never given birth to a son.

RESULTS

are expressed as the genome equivalent number of male cells per million host cells (gEq/mil).Results: Male DNA was found in 15% of women with systemic sclerosis (range 0 to 23.7 gEq/mil) and in 13% of healthy women (range 0 to 5.1 gEq/mil). Although two women with male DNA had an induced abortion, most had no history of spontaneous or induced abortion (either systemic sclerosis or healthy).

CONCLUSIONS

Microchimerism with male DNA can be found in the circulation of women who have never given birth to a son. Thus sources other than a male birth must be considered when male DNA is used to measure microchimerism. Although other studies are needed, there was no apparent difference in women with systemic sclerosis and healthy women. Possible sources of male DNA include unrecognised male pregnancy or unrecognised male twin, an older male sibling with transfer through the maternal circulation, or sexual intercourse alone.

Toxicity of allyl alcohol in primary cultures of freshly isolated and cryopreserved hepatocytes maintained on hydrated collagen gels

The toxicity of allyl alcohol was compared in freshly isolated and cryopreserved hepatocytes that were either placed in suspension or maintained on hydrated collagen gels in a sandwich configuration. The purpose of this study was to evaluate whether the two types of cells displayed the same sensitivity to allyl alcohol when maintained in vitro over relatively prolonged periods of time. The important differentiated functions of urea synthesis, secretion of albumin, and metabolism of ethoxycoumarin, a model drug substrate, were used as end points of toxicity. Cryopreserved hepatocytes incubated in physiological buffer shortly after removal from liquid nitrogen were more sensitive to allyl alcohol than freshly isolated hepatocytes. In contrast, cryopreserved and freshly isolated hepatocytes maintained on hydrated collagen gels responded identically to allyl alcohol. Thus, the increased sensitivity of cryopreserved hepatocytes in suspension to allyl alcohol is a transient phenomenon that disappears after the cells have been allowed to recover on hydrated collagen gels. Dissipation of the mitochondrial membrane potential by allyl alcohol, as indexed by rhodamine 123 fluorescence, was also the same in freshly isolated and cryopreserved hepatocytes maintained on hydrated collagen matrices. This loss of mitochondrial membrane potential caused by allyl alcohol preceded inhibition of albumin and urea biosynthesis. Collectively, the results indicate that cryopreserved cells maintained on hydrated collagen gels provide a useful system to define the actions of certain hepatotoxic agents over relatively prolonged periods of time in vitro.

Actions of selected hepatotoxicants on freshly isolated and cryopreserved rat hepatocytes

The present study compares the actions of the hepatotoxic agents allyl alcohol, acetaminophen, and carbon tetrachloride on energy metabolism in freshly isolated and cryopreserved rat hepatocytes. After 30 min incubation of freshly isolated hepatocytes at 37 degrees C to allow metabolic equilibration, hepatocytes were supplemented with cryoprotectants and cooled in a stepwise manner to liquid nitrogen temperature. Hepatocytes stored in liquid nitrogen for 2 weeks to 6 months were thawed and centrifuged through Percoll to remove damaged cells. Despite similarities in energy status as indexed by ATP content and the rate of urea synthesis in freshly isolated and cryopreserved hepatocytes, cryopreserved hepatocytes were more sensitive to hepatotoxicants. All three hepatotoxicants caused ATP and rates of urea synthesis to decline to a greater extent in cryopreserved than in freshly isolated hepatocytes. Rates of oxygen uptake were higher in cryopreserved cells than in freshly isolated hepatocytes and declined in cryopreserved cells but not in freshly isolated cells during the initial period of incubation. Rates of mitochondrial respiration stimulated with site-specific substrates were comparable in freshly isolated and cryopreserved cells permeabilized with digitonin. Allyl alcohol and acetaminophen inhibited site-specific respiration to the same extent in both groups of cells. Collectively, these results suggest that increased sensitivity to hepatotoxic agents and elevated oxygen consumption in cryopreserved hepatocytes recovered after storage in liquid nitrogen are related to higher demand for energy in these cells rather than to permanent injury caused by cryopreservation and irreversible uncoupling of oxidative phosphorylation.