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Foveal hypoplasia, optic nerve decussation, and anterior segment dysgenesis (FHONDA) is a rare recessively inherited syndrome first described in 2013. FHONDA is associated with biallelic disease-causing variants in the SLC38A8 gene, which has a strong expression in the photoreceptor layer. To date, 60 different disease-causing variants in the SLC38A8 gene have been described. In this cross-sectional case series, we included three unrelated female patients with FHONDA syndrome who presented with congenital nystagmus and decreased visual acuity from infancy. Best-corrected visual acuity was 20/100 OD and 20/60 OS for Patient 1 (P1) (72 years old); light perception OD and hand motion OS for Patient 2 (P2) (66 years old); and 20/100 OD and 20/100 OS for Patient 3 (P3) (25 years old). While normal retinal pigmentation was seen on P1 and P3, P2 presented retinal features of retinitis pigmentosa, including a pale optic nerve head, vessel thinning, and 360° dense bone spicule hyperpigmentation OU. Spectral-domain optical coherence tomography revealed grade 4 foveal hypoplasia in all patients. In P1 and P2, the novel class IV c.388 + 1G > T p.? variant in SLC38A8 was present in homozygosity; while P3 harboured the novel c.214G > C p.(Gly72Arg) variant in homozygosity, classified as class III. Thus, we expand the mutational spectrum of FHONDA by reporting two novel variants. In addition, we describe features of retinitis pigmentosa for the first time in a patient with biallelic homozygous S LC38A8 variants, thus broadening our understanding of the clinical phenotype associated with this rare syndrome., Competing Interests: Declaration of conflicting interestsThe authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Tick-borne diseases are important for animal and human health, because they can cause death if not diagnosed and treated early. Canine monocytic ehrlichiosis (CME) can cause high morbidity in dog populations. Rocky Mountain Spotted Fever (RMSF) is among the most virulent infectious in humans; dogs are also susceptible to infection. The aims of this study were to evaluate the presence of Ehrlichia canis and Rickettsia spp. infections in domestic dogs, and to identify tick species parasitizing dogs among urban areas of two municipalities (Sobral and Alcântaras) in the Ceará State, Northeastern Brazil. A total of 208 domiciled dogs was sampled. After clinical evaluation, blood samples and ticks were collected and submitted to Real-Time Polymerase Chain Reaction (RT-PCR) targeting E. canis DNA. Serum samples were screened by Indirect Immunofluorescence Assays (IFA) for antibodies against different strains of Rickettsia spp. previously recognized in Brazil. The results of this study indicate the molecular detection of E. canis in the state of Ceará, Brazil, where the proportion of canine infection in Sobral (9.9%) was higher than in Alcântaras (5.6%). Rhipicephalus sanguineus sensu lato was the prevalent tick species infesting the dogs in both municipalities (43.5 and 53.3%, respectively). Our serological results indicate that dogs of the study area were at low risk of exposure to these tick-borne Rickettsia spp. of the spotted fever group. Our study offers epidemiological data of these diseases to better understanding Rickettsiales epidemic and enzootic cycles in the Brazilian semiarid region, improving prevention and control measures., Competing Interests: Declaration of competing interest There were no conflicting interests that could have influenced the conduction of this study., (Copyright © 2024 Elsevier B.V. All rights reserved.)

The bacterial genus Borrelia comprises vector-borne spirochetes that have been classified into three major groups: the relapsing fever group (RFG), the Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner sensu lato group (Bbsl), and the reptile-monotreme group (RMG). All three groups have been associated mainly with ticks and wild animals, especially rodents, birds, and reptiles. Here, we searched for Borrelia infection among 99 vampire bats [Desmodus rotundus (É. Geoffroy)] (Chiroptera: Phyllostomidae) from the Brazilian semiarid region. Through molecular investigation of bat internal organs, haplotypes of a potentially novel Borrelia organism were detected in 5% (5/99) of the bats. Borrelia DNA was detected in the liver, blood, spleen, kidney and brain, suggesting a systemic infection. Phylogenetic analyses inferred from partial sequences of the borrelial rrs and flaB genes indicated that the vampire bat-associated Borrelia sp. of this study form a monophyletic group with a newly reported Borrelia associated with a Colombia bat, distinct from the three main currently recognized groups of Borrelia spp., Bbsl, RFG, and RMG. These novel bat-associated Borrelia spp. from South America might have arisen through an independent event along the borrelial evolutionary history, since previous molecular reports of Borrelia organisms in bats or bat-associated ticks from Africa, Europe, and North America were all classified in the RFG., (© The Author(s) 2022. Published by Oxford University Press on behalf of Entomological Society of America. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Cross-species transmission events and mixed infection of small ruminant lentiviruses (SRLVs) were studied in seven goats and two sheep from three small ruminant mixed flocks from Northeast and Southeast Brazil. Genetic and antigenic analyses with gag/env genes and ELISA multiepitope SU1/SU5 recombinant antigens were carried out, respectively. The genetic analysis of gag and env sequences showed high viral diversity in both species, MVV-like (subtype A1) and CAEV-like B1 in goats, and CAEV-like (subtype B1) in sheep, revealing SRLV interspecies transmission from sheep to goats and vice versa in Brazilian farms. Two Brazilian caprine lentiviruses were segregated in two new genetic clades based on gag analyses, which suggests a new classification into heterogenic genotype A. Furthermore, goat isolates were grouped into subtype A1 and B1 clusters. Cross-reactive antibodies were detected in goats using ELISA with a recombinant antigen carrying SU1 and SU5 immunodominant epitopes; the results showed anti-CAEV and MVV antibodies in goats and anti-CAEV antibodies in sheep. This result can be associated with the high divergence in the V4 region due to SRLV variability. All results confirm cross-species infection of SRLV in Brazilian mixed herds., (Copyright © 2022. Published by Elsevier B.V.)

Objectives . Lower back pain (LBP) is a common health problem worldwide, affecting an increasing number of individuals. Military firefighters (MFFs) face high levels of physical and psychological demands and are commonly exposed to different occupational risk factors. This study aimed to estimate the prevalence of chronic lower back pain (CLBP) in Brazilian enlisted MFFs. Methods . This cross-sectional study was carried out at the Military Firefighters Department of the Brazilian Federal District (Corpo de Bombeiros Militar do Distrito Federal [CBMDF]). The estimated sample size was 608 MFFs. Results . Of the 623 participants, 575 valid and complete questionnaires were analyzed. A total of 183 participants reported CLBP, indicating a point prevalence of 31.8% (95% confidence interval [CI] [28.2, 35.4]). The prevalence of acute and subacute LBP was 9.2% (95% CI [7.1, 11.9]), and 59% (95% CI [54.9, 62.9]) reported no back pain. CLBP was more common among men aged 40-49 years, who were insufficiently active and overweight. Conclusion . Around one-third of the study population reported CLPB. Prevalence estimates of CLPB were greater among men and those between 40 and 49 years old. Our data support the need for programs to prevent and treat CLBP among firefighters.

In Brazil, 19 species of the genus Ornithodoros (Acari: Argasidae) have been reported. The medical and veterinary importance of Ornithodoros ticks has increased substantially in recent decades, with the discovery of various relapsing fever Borrelia infecting Ornithodoros ticks. Herein, argasid ticks were collected during 2019-2020 from caves, abandoned nests and homes in various regions of Ceará State, Brazilian semiarid-Caatinga biome. In total, 289 ticks were collected and identified into five species: Ornithodoros cavernicolous (176 specimens), Ornithodoros fonsecai (81), Ornithodoros mimon (12), Ornithodoros rietcorreai (4), and a fifth species provisionally retained as Ornithodoros sp. Ubajara. Tick identifications were corroborated by a phylogenetic analysis inferred using the 16S rRNA gene. To extend the molecular characterization, DNA samples were tested by an additional PCR assay targeting the nuclear Histone 3 (H3) gene. Because there were no H3 sequences of argasids in GenBank, we extended this PCR assay for additional Ornithodoros species, available in our laboratory. In total, 15 partial sequences of the H3 gene were generated for 10 Ornithodoros species, showing 0% intraspecific polymorphism, and 1.5-11.6% interspecific polymorphism. Phylogenetic analyses inferred segregated Ornithodoros sp. Ubajara as a potential novel species. Our results also highlight the potential of the H3 gene for deeper phylogenetic analyses of argasids. The present study provides new data for argasid ticks of the genus Ornithodoros in the Caatinga biome. Because some of these tick species are human-biting ticks, active surveillance for the incidence of human infection due to Ornithodoros-borne agents is imperative in the Caatinga biome., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The aim of this study was to determine the occurrence of tick-borne pathogens (Ehrlichia canis, Babesia vogeli, Hepatozoon spp. and Rickettsia spp.) in dogs in Vila de Jericoacoara, coastal region of Ceará, Brazil. Blood samples were collected from 153 animals and analyzed using molecular and serological methods. Sixty animals were found to be infected or exposed to at least one of the pathogens studied. Babesia vogeli was the most prevalent pathogen (15%), followed by E. canis (13.7%) and Hepatozoon spp. (11.8%), which was identified as Hepatozoon canis through sequencing. Twenty dogs (13%) were seroreactive to Rickettsia spp. Rhipicephalus sanguineus sensu lato was observed on 11.8% of the animals. There were associations between age (< 3 years old) and positivity for B. vogeli, and between habitation (stray dogs) and positivity for H. canis. There were also associations between anemia and infection with H. canis, and between leukopenia and exposure to Rickettsia spp. No association was detected between clinical alterations and infection with or exposure to the pathogens studied. The results confirmed that pathogens of veterinary importance are circulating in northeastern Brazil and showed that dogs are exposed to Rickettsia species with zoonotic potential, thus indicating a need for vector control measures.

Equine infectious anemia (EIA) is listed by the World Organization for Animal Health (OIE) as one of the equine diseases that must be notified. No effective treatment or vaccine is available. EIA control is based on segregation and euthanasia of positive equids. The disease is caused by the equine infectious anemia virus (EIAV), a member of the genus Lentivirus of the Retroviridae family. Despite the importance of this disease in equids, EIA has been poorly studied in donkeys (Equus asinus). We evaluate the sanitary conditions related to EIAV in donkeys from a shelter of abandoned animals captured on the roads of the Ceará. A total of 124 donkeys were randomly selected, and three horses lived at the same shelter. The animals were clinically evaluated, and a group of the 20 animals was submitted to hematological tests. Three diagnostic tests for EIA were used, agar gel immunodiffusion (AGID), enzyme-linked immunosorbent assay (ELISA) using EIAV recombinant protein gp90 (rgp90) and recombinant protein p26 (rp26) ELISA, and polymerase chain reaction (PCR) for detection of the EIAV tat-gag gene. From the donkeys, only 1 animal was positive using AGID 0.81% (1/124), compared to 21.8% (27/124) in the rgp90 and 10.5% (13/124) in the rp26 ELISA. Proviral DNA was detected by PCR tat-gag in 8.8% (11/124), and phylogenetic analysis confirms that the EIAV sequences of donkeys from the Brazilian Northeast grouped with Pantanal Brazilian sequences. Thus, in light of the results, we conclude that donkeys are carriers of EIAV and could be sources of infection., (Copyright © 2021. Published by Elsevier Inc.)

Ornithodoros tabajara n. sp. is described from laboratory-reared larvae and adult specimens collected in the Brazilian Caatinga. This new species shares the ecological niche with Ornithodoros rietcorreai and is likely associated with colonial rodents of genus Kerodon. However, O. tabajara n. sp. is morphologically easy to distinguish from O. rietcorreai and other Neotropical Ornithodoros by a unique combination of characters: larva with 17 pairs of dorsal setae (seven anterolateral, three central and seven posterolateral), sub-oval dorsal plate, hypostome blunt apically with dentition formula 2/2 along its extension, only one pair of posthypostomal setae, six pairs of sternal setae, posteromedian setae absent, and leave-shaped anal valves; alive adults with whitish islands of mammillae symmetrically distributed on dorsum (not visible in ethanol-preserved specimens), and median disk merging with posteromedian file. A phylogenetic analysis performed with mitochondrial 16S rDNA sequences points O. tabajara n. sp. as O. rietcorreai's sister taxon, which rises the hypothesis of sympatric speciation., (Copyright © 2021 Elsevier GmbH. All rights reserved.)

We conducted a molecular survey for Borrelia spp. in Ornithodoros ticks previously reported as biting humans. We collected specimens in natural ecosystems and inside human dwellings in 6 states in Brazil. Phylogenetic analyses unveiled the occurrence of 4 putatively new species of relapsing fever group borreliae.

Objectives: The objectives of this study were to confirm the prevalence of feline immunodeficiency virus (FIV) infection in domestic cats in the region north of Ceará, Brazil, and to determine the factors associated with infection and the major circulating subtypes of the virus in this area., Methods: Samples from 148 cats were collected and tested using anti-FIV antibody screening, with confirmation of positive results by PCR. Univariate analysis was performed considering the epidemiological characteristics and FIV status. Sequencing and phylogenetic analysis of the gag and pol genes were performed to confirm the FIV subtype., Results: Nine cats (6.1%) tested positive for FIV - one female (0.7%) and eight males (5.4%). Male cats were significantly more likely to be infected ( P <0.05). Phylogenetic analysis of gag and pol gene sequences indicated that the FIV isolates circulating in the study area belonged to subtype B., Conclusions and Relevance: In this study, we demonstrated a low prevalence for FIV in the northwest of Ceará, north-eastern Brazil. Male sex is a significant risk factor for FIV infection and the best predictive factor for FIV status. All isolates examined in this study clustered within subtype B, which is the predominant subtype in Brazil. This is the first report of genetic characterization of FIV in the state of Ceará, Brazil., Competing Interests: Conflict of interest: The authors declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Background: Hyperhomocysteinemia in breast cancer (BC) patients can be a risk factor for thromboembolic events. This study aimed to evaluate homocysteine and its cofators (folic acid and vitamin B12) concentrations and platelet count at diagnosis of BC, 3 and 6 months after the beginning of chemotherapy treatment and to correlate them with clinical data., Methods: Thirty-five BC patients were included; blood samples were obtained by venipuncture. Plasmatic Hcy and cofactors concentrations were measured by competitive chemiluminescent enzyme immunoassay method. Platelet count was done using an automated analyzer. Statistical analysis was performed using the software SPSS., Results: During chemotherapy, homocysteine (P = 0.032) and vitamin B12 (P < 0.001) concentrations increased, while folate and platelets decreased (P < 0.001). Among the clinical data, the menopausal status showed significant positive correlation (P = 0.022) with homocysteine concentration increase., Conclusions: Evaluation of homocysteine concentrations during chemotherapy is extremely important because their levels increase during chemotherapy treatment, thus increasing the risk of thromboembolism development., (© 2014 Wiley Periodicals, Inc.)

Breast cancer remains the second most frequent type of cancer in the world and the first among women, and systemic chemotherapy is an adjuvant therapeutic modality that improves survival in a great part of patients. Women with breast cancer, however, frequently show a higher risk of thromboembolism, an event associated to hyperhomocysteinemia and the presence of circulating tumor cells (CTC). Our aim is to correlate the presence of CTCs, detected by the analysis of CK19 and c-erbB2 gene expressions, and the homocysteine plasma levels in the peripheral blood in patients with breast cancer undergoing chemotherapy. Epithelial marker expression (CK19 and c-erbB2) and homocysteine levels were analyzed in a mononuclear fraction of the peripheral blood and plasma, respectively, obtained from 35 patients diagnosed with breast cancer at diagnosis and throughout chemotherapy treatment. No significant relation between the CK19 and c-erbB2 expressions and hyperhomocysteinemia was observed at any moment of the evaluation throughout the chemotherapy treatment (3 and 6 months after the onset). Among clinical data, only menopausal status showed a statistically significant correlation with homocysteine concentration. Although differences in the expressions of the analyzed epithelial markers were detected at 3 and 6 months of chemotherapy treatment, no relation between plasma homocysteine variations and the CK19 and c-erbB2 gene expressions was found in patients under chemotherapy treatment at any moment of the evaluation, suggesting that chemotherapy affects the expressions of the studied genes independently.

A study of descriptive, exploratory and retrospective study with a quantitative approach is to evaluate the expansion of graduate programs in nursing in the state of Piauí in the period 1973 to 2008. It was researched, aided by a form, all ten institutions of higher education in this period, in Piauí. The results pointed to an expansion of nursing programs in the last 10 years, growth in the period 1973 to 2008 in the order of 1.300%. There was a total of 2,949 licensed nurses per capita showing a relation for Piaui of 0.93 nurse/1.000 inhabitants. From the data of the study there is the potential of Piauí in training nurses, with growth of courses and places. Thus, stirs up to reflection on the part of institutions and professional bodies as to the relative labor market and demand for graduates, quality control and course vacancies offered.

Objectives: understand the Social Representations about needlestick injuries elaborated by Nursing Technicians and analyze how these representations influence their conducts., Method: the data, obtained by interviews, were processed using ALCESTE software and their analysis was based on Serge Moscovici's Social Representations Theory., Results: it was evidenced that, after the accident, these professionals take care of the affected area. Then, they report the accident, motivated by the fear of catching HIV and hepatitis. The different feelings experienced are due to this fear and the way they were forwarded by the institution, reflecting in the cause they attribute to their accident., Conclusions: it was verified that knowledge about the accident as a whole is very incipient in this professional group, demanding continuing education and greater emphasis on this subject in professional training. It is expected that this study draws public authorities and health institutions' attention to the problem and that it modifies Nursing Technicians' Social Representations about percutaneous exposure.

The rapid emergence of AIDS in humans during the period between 1980 and 2000 has led to extensive efforts to understand more fully similar etiologic agents of chronic and progressive acquired immunodeficiency disease in several mammalian species. Lentiviruses that have gene sequence homology with human immunodeficiency virus (HIV) have been found in different species (including sheep, goats, horses, cattle, cats, and several Old World monkey species). Lentiviruses, comprising a genus of the Retroviridae family, cause persistent infection that can lead to varying degrees of morbidity and mortality depending on the virus and the host species involved. Feline immunodeficiency virus (FIV) causes an immune system disease in domestic cats (Felis catus) involving depletion of the CD4+ population of T lymphocytes, increased susceptibility to opportunistic infections, and sometimes death. Viruses related to domestic cat FIV occur also in a variety of nondomestic felids. This is a brief overview of the current state of knowledge of this large and ancient group of viruses (FIVs) in South America.

The purpose of this study was to prepare various 4-substituted N-phenyl-1,2,3-triazole derivatives using click chemistry. The derivatives were screened in vitro for antimicrobial activity against Mycobacterium tuberculosis strain H37Rv (ATCC 27294) using the Alamar Blue susceptibility test. The activity was expressed as the minimum inhibitory concentration (MIC) in μg/mL (μM). Derivatives of isoniazid (INH), (E)-N'-[(1-aryl)-1H-1,2,3-triazole-4-yl)methylene] isonicotinoyl hydrazides, exhibited significant activity with MIC values ranging from 2.5 to 0.62 μg/mL. In addition, they displayed low cytotoxicity against liver cells (hepatoma HepG2) and kidney cells (BGM), thereby providing a high therapeutic index. The results demonstrated the potential and importance of developing new INH derivatives to treat mycobacterial infections.

Feline immunodeficiency virus (FIV) causes a slow progressive degeneration of the immune system which eventually leads to a disease comparable to acquired immune deficiency syndrome (AIDS) in humans. FIV has extensive sequence variation, a typical feature of lentiviruses. Sequence analysis showed that diversity was not evenly distributed throughout the genome, but was greatest in the envelope gene, env. The virus enters host cells via a sequential interaction, initiated by the envelope glycoprotein (env) binding the primary receptor molecule CD134 and followed by a subsequent interaction with chemokine co-receptor CXCR4. The purpose of this study was to isolate and characterize isolates of FIV from an open shelter in São Paulo, Brazil. The separated PBMC from 11 positive cats were co-cultured with MYA-1 cells. Full-length viral env glycoprotein genes were amplified and determined. Chimeric feline × human CD134 receptors were used to investigate the receptor utilization of 17 clones from Brazilian isolates of FIV. Analyses of the sequence present of molecular clones showed that all clones grouped within subtype B. In contrast to the virulent primary isolate FIV-GL8, expression of the first cysteine-rich domain (CRD1) of feline CD134 in the context of human CD134 was sufficient for optimal receptor function for all Brazilian FIV isolates tested., (Copyright © 2011 Elsevier B.V. All rights reserved.)

This study had as objective to apprehend the Social Representation of damage liability of nursing in the invasive procedures elaborated by the professionals of the area. It treats of a qualitaitve research, developed in a public hospital with 64 fellows. The data were produced from the free association words test, processed by software Tri-Deux Mots, being done Correspondence Factorial Analysis. The fellow's representational field indicated favorable attitudes in relation to the invasive procedures stimulus. The conceptions about hospital infection stimulus demonstrated a broad vision of hospital infection problem and its serious consequences. However it was not observed preoccupation and manifestation in the fellow's social representations about the civil responsibilities of Nursing professional.

The number of accidents involving motorcycles has increased in Brazil. The objective of this study was to identify the type of victims of these accidents who were treated at an emergency department in Piauí State, Brazil. The sample included 430 such victims in this quantitative study. Most were male, 15-24 years of age, and from the State of Piauí itself. 301 of the victims were drivers of the motorcycles, 81 were passengers, and 48 were struck or run over by the motorcycles. 76.05% of the accidents occurred from Thursday to Sunday. 80.75% had temporary sequelae, and 53.33% of the accidents occurred at night. In 69.3% of the cases, victims suffered lacerations; 51.4% fractures; 27.44% hematomas; and 20.7% head trauma. Among the accident victims, motorcycle drivers, and those suspected of alcohol consumption, 52.07% were not wearing a helmet at the time of the accident. Most of the victims were discharged from hospital, while 14 died. In conclusion, injuries from motorcycle accidents deserve attention, especially to plan preventive measures to help control their occurrence in the State.

The Arterial Hypertension is considered as a serious Public Health problem that affects most of the world population and presents difficulties to control.This study dealt with the social representations of the women carriers of Arterial Hypertension about what it is like to be carriers of the disease in the family context, and the health services provided by the professionals that care for them and exploring the psychosocial aspects related to their feelings and behavior that might interfere in their treatment and control of the disease. It was performed in Teresina - PI with 25 women assisted in the Health Center. The data collected was organized in a "corpus" and submitted to the ALCESTE software 4.5, which produced three initial context units, showing the manifestations and feelings of the carriers. The social representations influence the process of knowledge production and circulation that guide and define the behavior and conducts of the hypertensive disease carrier.

This study has as objective to describe the experience of being mother of an autistic child. A qualitative approach was accomplished according to the phenomenological concepts of Martin Heidegger. Fourteen mothers of autistic children had been interviewed, with semi-structured questions, tape-recorded and transcribed integrally. The local of data collection was the AMA-PI with data produced in May, 2006. The analysis revealed that mothers who live the facticity of having an autistic child is permeated by negative feelings, faith and solitudeness. Mothers also leave their daily life to live their children's daily live. When assuming their existential condition - to be -in the world and to be mother of a autistic child, they begin to understand how to be capable to fight for their children's well-being, without complaints, demonstrating self-denial, patience and concern.

Historical and social study that aimed at obtaining the social representations about associative practice present at the collective memory of the members from ABEn-PI. Its primary source were 94 minutes of ABEn-PI created from 1959 to 1970 and from 1995 to 2005 and analyzed according to a thematic analysis of categorical content. The social representations obtained were about knowledge, positioning and feelings about nursing teaching, religiosity and honoring and political fights of ABEn. The dissemination of these knowledge, positioning and feelings among the members of the association, showed the spread of social representations determining the behavior of these nurses as ABEn-PI members.

This study aims to draw up a proposal of integration for the fourth term of Nursing from NOVAFAPI. The main focus was to describe the subjects' structure chain, the competencies and abilities to be developed, as well as discuss the methodology and the method of assessment specified and draw up a proposal for the fourth term. A qualitative approach was used, based on the action research referential. The subjects were the faculties and students from the term, plus the coordinator of the course. Its results show there is already the understanding that the integrated curriculum will contribute for the education of subjects more capable of transforming social reality.

Ca2+ and inorganic phosphate-induced mitochondrial swelling and membrane protein thiol oxidation, which are associated with mitochondrial permeability transition, are inhibited by progressively decreasing the incubation medium pH between 7.2 and 6.0. Nevertheless, the detection of mitochondrial H2O2 production under these conditions is increased. Permeability transition induced by phenylarsine oxide, which promotes membrane protein thiol cross-linkage in a process independent of Ca2+ or reactive oxygen species, is also strongly inhibited in acidic incubation media. In addition, we observed that the decreased protein thiol reactivity with phenylarsine oxide or phenylarsine oxide-induced swelling at pH 6.0 is reversed by diethyl pyrocarbonate, in a hydroxylamine-sensitive manner. These results provide evidence that the inhibition of mitrochondrial permeability transition observed at lower incubation medium pH is mediated by a decrease in membrane protein thiol reactivity, related to the protonation of protein histidyl residues.