Conditions Of Acidosis Research Articles

Determination of Solubility and Potential of Acid Production of some Feedstuffs and Investigation of their In Vitro Fermentation in Natural and Induced Acidosis Conditions

Determination of Solubility and Potential of Acid Production of some Feedstuffs and Investigation of their In Vitro Fermentation in Natural and Induced Acidosis Conditions

An Investigation into Rumen Fungal and Protozoal Diversity in Three Rumen Fractions, during High-Fiber or Grain-Induced Sub-Acute Ruminal Acidosis Conditions, with or without Active Dry Yeast Supplementation.

Sub-acute ruminal acidosis (SARA) is a gastrointestinal functional disorder in livestock characterized by low rumen pH, which reduces rumen function, microbial diversity, host performance, and host immune function. Dietary management is used to prevent SARA, often with yeast supplementation as a pH buffer. Almost nothing is known about the effect of SARA or yeast supplementation on ruminal protozoal and fungal diversity, despite their roles in fiber degradation. Dairy cows were switched from a high-fiber to high-grain diet abruptly to induce SARA, with and without active dry yeast (ADY, Saccharomyces cerevisiae) supplementation, and sampled from the rumen fluid, solids, and epimural fractions to determine microbial diversity using the protozoal 18S rRNA and the fungal ITS1 genes via Illumina MiSeq sequencing. Diet-induced SARA dramatically increased the number and abundance of rare fungal taxa, even in fluid fractions where total reads were very low, and reduced protozoal diversity. SARA selected for more lactic-acid utilizing taxa, and fewer fiber-degrading taxa. ADY treatment increased fungal richness (OTUs) but not diversity (Inverse Simpson, Shannon), but increased protozoal richness and diversity in some fractions. ADY treatment itself significantly (P < 0.05) affected the abundance of numerous fungal genera as seen in the high-fiber diet: Lewia, Neocallimastix, and Phoma were increased, while Alternaria, Candida Orpinomyces, and Piromyces spp. were decreased. Likewise, for protozoa, ADY itself increased Isotricha intestinalis but decreased Entodinium furca spp. Multivariate analyses showed diet type was most significant in driving diversity, followed by yeast treatment, for AMOVA, ANOSIM, and weighted UniFrac. Diet, ADY, and location were all significant factors for fungi (PERMANOVA, P = 0.0001, P = 0.0452, P = 0.0068, Monte Carlo correction, respectively, and location was a significant factor (P = 0.001, Monte Carlo correction) for protozoa. Diet-induced SARA shifts diversity of rumen fungi and protozoa and selects against fiber-degrading species. Supplementation with ADY mitigated this reduction in protozoa, presumptively by triggering microbial diversity shifts (as seen even in the high-fiber diet) that resulted in pH stabilization. ADY did not recover the initial community structure that was seen in pre-SARA conditions.

IMPACT OF LACTIC ACIDOSIS ON THE SURVIVAL OF LEWIS LUNG CARCINOMA CELLS

To investigate the effect of lactic acidosis on the survival of Lewis lung carcinoma cells under glucose-deprived conditions. LLC/R9variant of Lewis lung carcinoma cells was cultured in glucose deficit or complete culture medium. Conditions of lactic acidosis, lactosis, and acidosis were generated in glucose deficit medium. Cell survival, cell cycle, apoptosis, autophagy, and the content of glucose, lactate, vascular endothelial growth factor in the culture medium were determined. Light and fluorescent microscopy, flow cytometry, spectrophotometry, and ELISA were used. It has been found that 24h incubation of tumor cells under lactic acidosis caused (i) the reduction of the number of living cells by 33% (p < 0.05) and 56% (p<0.05); (ii) the inhibition of apoptosis by 4.3-fold (p < 0.05) and 3.3-fold (p < 0.05); (iii) the reduction of the rate of glucose consumption by 2-fold (p<0.05) and 2.5-fold (p < 0.05); (iv) an increase of lactate production more than twice (p < 0.05) and 1.6-fold (p<0.05) compared with these indexes under conditions of glucose deficiency or complete glucose-containing medium, respectively. However, on the second day of culture under lactic acidosis, the number of viable cells reached a maximum, in contrast to culture in the complete medium. The number of live cells on the seventh day of culture under lactic acidosis exceeded almost 2-3times (p<0.05) that in the culture under conditions of the glucose deprivation or in complete medium. On the third day under lactic acidosis the autophagolysosomes count was 54% (p <0.05) lower that that under glucose deficit. Lactic acidosis promoted the survival and proliferation of Lewis lung carcinoma cells by energy system reprogramming directed on inhibition of apoptosis and autophagy, a significant decrease in the rate of glucose utilization and activation of glutaminolysis and, consequently, increase of the lactate production rate. Inhibition of lactate production by tumor cells may be considered as a promising approach for more efficient antiangiogenic treatment of cancer.

INDIE-HFpEF (Inorganic Nitrite Delivery to Improve Exercise Capacity in Heart Failure With Preserved Ejection Fraction): Rationale and Design.

URL: http://www.clinicaltrials.gov. Unique identifier: NCT02742129.

Resident Macrophages in Muscle Contribute to Development of Hyperalgesia in a Mouse Model of Noninflammatory Muscle Pain.

Macrophages play a role in innate immunity within the body, are located in muscle tissue, and can release inflammatory cytokines that sensitize local nociceptors. In this study we investigate the role of resident macrophages in the noninflammatory muscle pain model induced by 2 pH 4.0 preservative-free sterile saline (pH 4.0) injections 5days apart in the gastrocnemius muscle. We showed that injecting 2 pH 4.0 injections into the gastrocnemius muscle increased the number of local muscle macrophages, and depleting muscle macrophages with clodronate liposomes before acid injections attenuated the hyperalgesia produced by this model. To further examine the contribution of local macrophages to this hyperalgesia, we injected mice intramuscularly with C34, a toll-like receptor 4 (TLR4) antagonist. When given before the first pH 4.0 injection, C34 attenuated the muscle and tactile hyperalgesia produced by the model. However, when given before the second injection C34 had no effect on the development of hyperalgesia. Then to test whether activation of local macrophages sensitizes nociceptors to normally non-nociceptive stimuli we replaced either the first or second acid injection with the immune cell activator lipopolysaccharide, or the inflammatory cytokine interleukin (IL)-6. Injecting LPS or IL-6 instead of the either the first or second pH 4.0 injection resulted in a dose-dependent increase in paw withdrawal responses and decrease in muscle withdrawal thresholds. The highest doses of LPS and IL-6 resulted in development of hyperalgesia bilaterally. The present study showed that resident macrophages in muscle are key to development of chronic muscle pain. This article presents evidence for the role of macrophages in the development of chronic muscle pain using a mouse model. These data suggest that macrophages could be a potential therapeutic target to prevent transition of acute to chronic muscle pain particularly in tissue acidosis conditions.

Tumor acidosis enhances cytotoxic effects and autophagy inhibition by salinomycin on cancer cell lines and cancer stem cells.

Sustained autophagy contributes to the metabolic adaptation of cancer cells to hypoxic and acidic microenvironments. Since cells in such environments are resistant to conventional cytotoxic drugs, inhibition of autophagy represents a promising therapeutic strategy in clinical oncology. We previously reported that the efficacy of hydroxychloroquine (HCQ), an autophagy inhibitor under clinical investigation is strongly impaired in acidic tumor environments, due to poor uptake of the drug, a phenomenon widely associated with drug resistance towards many weak bases. In this study we identified salinomycin (SAL) as a potent inhibitor of autophagy and cytotoxic agent effective on several cancer cell lines under conditions of transient and chronic acidosis. Since SAL has been reported to specifically target cancer-stem cells (CSC), we used an established model of breast CSC and CSC derived from breast cancer patients to examine whether this specificity may be associated with autophagy inhibition. We indeed found that CSC-like cells are more sensitive to autophagy inhibition compared to cells not expressing CSC markers. We also report that the ability of SAL to inhibit mammosphere formation from CSC-like cells was dramatically enhanced in acidic conditions. We propose that the development and use of clinically suitable SAL derivatives may result in improved autophagy inhibition in cancer cells and CSC in the acidic tumor microenvironment and lead to clinical benefits.

Abstract B38: Melatonin efficacy in breast cancer microenvironment under acidosis

Abstract Breast cancer is the most common neoplasia among women and has been frequently associated to high morbidities and mortalities rates. Cancer progression is strongly influenced by conditions of tumor microenvironment. Rapid tumor growth results in decreased of oxygen intake, restricting metabolic demands in specific regions of tumor. This poor perfusion coupled with preferential anaerobic glycolysis leads to acidification of tumor microenvironment. Survival mechanisms of tumor cells under acidic conditions are not well characterized, but has been shown that adverse conditions in tumor microenvironment can select phenotypes that are able to adapted to survival and growth in low pH conditions, hence resulting in tumor progression. Thus, controlling these adverse conditions in tumor microenvironment is a promising tactic in limiting cancer development. Melatonin, a hormone naturally produced and secreted by pineal gland, appears to play multiple roles in cancer and it is proposed as a possible keeper of an extreme environment hindering the survival of these cells. In this study, the benefits of melatonin treatment on cell viability of breast cancer cell lines under acidosis condition were evaluated. Breast cancer cell lines estrogen receptor (ER)-positive (MCF-7) and ER-negative (MDA-MB-231) were cultured in Dulbecco's Modified Eagle's medium (DMEM) at 37°C in 5% CO2. Cell viability was measured using an MTT assay. Individual wells of a 96-well plate were seeded with 100 µL of medium containing 0.05 x 106 cells and cells were separated into the following groups: Group 1) Cells cultured in pH 7.4 with DMEM (control); Group 2) Cells cultured in pH 6.7 with DMEM supplemented with 25 mmol/L buffer 2- (N-Morpholino) ethanesulfonic acid (MES) for 24 hours, to mimic an acute acidosis in tumor microenvironment; Group 3) Cells cultured with DMEM supplemented with 25 mmol/L MES and treated with 1 mM of melatonin for 24 hours; Group 4) Cells cultured with DMEM supplemented with 25 mmol/L MES for 12 hours and treated with 1 mM of melatonin for an addition 12 hours. After treatments, MTT solution were added to each well, and the plates were incubated at 37°C for an additional 4 hour. To solubilize the MTT formazan crystals, the cells were incubated with dimethyl sulfoxide (DMSO) for 10 minutes and absorbance was measured at 540 nm. Cell viability (%) was calculated for all groups compared to control samples. The results were compared by ANOVA, followed by the Bonferroni test. The results showed that there was a decrease of both MCF-7 and MDA-MB-231 cells viability under acute acidosis conditions (Group 1 vs Group 2, p &amp;lt; 0.05). MCF-7 cells showed 65.36 ± 1.16 % of cell viability while MDA-MB-231 cells showed 52.98 ± 0.90 of cell viability under acidosis conditions (Group 2). Melatonin treatment for 24 hours was effective in reducing cell viability in acidosis conditions, leading to a decrease in MCF-7 cells (Group 3: 52.41 ± 1.32 %) and MDA-MB-231 cells (Group 3: 47.83 ± 0.67 %) when compared with cells under acidosis without treatment (Group 2 vs Group 3, p &amp;lt; 0.05). Furthermore, in both cell lines there was a decrease in cell viability in Group 4 (MCF-7 = 54.24 ± 1.22 %; MDA-MB-231 = 45.60 ± 0.45 %) compared to cells under acidosis (Group 2 vs Group 4, p &amp;lt; 0.05), and no difference was observed when compared with cells under acidosis and treated with melatonin for 24 hours (Group 3 vs Group 4, p &amp;gt; 0.05). In conclusion, our results show that acute acidosis reduces the viability of breast cancer cells and melatonin treatment is effective, leading to decrease the cell viability under acute acidosis.In addition, studies are being madeto evaluate the effectiveness of melatonin also in chronic acidosis conditions, and to investigate its signaling pathways in the extreme tumor microenvironment, in order to confirm potential effectiveness of melatonin in breast cancer in these conditions. Citation Format: Nathália Martins Sonehara, Bruna Victorasso Jardim-Perassi, André de Lima Mota, Marina Gobbe Moschetta, Debora Aparecida Pires de Campos Zuccari, Rubens de Paula, Jr. Melatonin efficacy in breast cancer microenvironment under acidosis. [abstract]. In: Proceedings of the AACR Special Conference: Metabolism and Cancer; Jun 7-10, 2015; Bellevue, WA. Philadelphia (PA): AACR; Mol Cancer Res 2016;14(1_Suppl):Abstract nr B38.

Correlation between Ischemia modified albumin with pH in acidosis and alkalosis: A possible link

Ischemia modified albumin (IMA), a recently developed marker for myocardial ischemia is measured by using albumin cobalt binding (ACB) assay. The correlation between the formation of IMA and alterations in the pH levels are of considerable importance and the same was not clear in the available literature. Based on our literature search, the study was designed to check and compare the levels of IMA and the pH in acidosis and alkalosis patients with those in normal patients. The mean of IMA in patient with acidosis (0.832±0.16) was higher when compared with the normal pH patients (mean 0.71±0.21). The IMA levels in patients of alkalosis were also found higher (mean 0.804±0.19) compared to that of the normal control. It was also observed that the mean of IMA was lower in the patients with alkalosis than the patients with acidosis. When the IMA levels and the pH levels in acidosis and alkalosis patients were correlated, there was a weak negative correlation between pH levels in acidosis and IMA levels. In alkalosis, the correlation was positive but there was no significance in these changes. In conditions of acidosis and alkalosis, where the pH levels are altered which could be one of the factors responsible for increase in the IMA levels. However, the correlation was weak and an increase in the sample size could provide us with a better relation between the levels of pH and IMA.

To study an alteration in biochemical parameters in acute and chronic phase of respiratory acidosis and alkalosis

Introduction: The primary abnormality in respiratory acidosis is retention of CO2 (increased H2CO3) due to impaired alveolar ventilation resulting in a rise in pCO2 causing acidemia. However, respiratory alkalosis occurs when there is decrease in H2CO3 concentration. A fall in pCO2, reduces the ratio of carbonic acid to bicarbonate resulting in alkalemia. Aim: To study variations in biochemical parameters in respect to respiratory acidosis and alkalosis. Material and Methods: The biochemical parameters of respiratory acidosis and alkalosis like blood pH, concentration of CO2, pO2, pCO2, level of HCO3-. Results: The studied components of respiratory acidosis and alkalosis were found to be highly significant in chronic conditions of respiratory acidosis and alkalosis (p

Drug-Induced Metabolic Acidosis.

Metabolic acidosis could emerge from diseases disrupting acid-base equilibrium or from drugs that induce similar derangements. Occurrences are usually accompanied by comorbid conditions of drug-induced metabolic acidosis, and clinical outcomes may range from mild to fatal. It is imperative that clinicians not only are fully aware of the list of drugs that may lead to metabolic acidosis but also understand the underlying pathogenic mechanisms. In this review, we categorized drug-induced metabolic acidosis in terms of pathophysiological mechanisms, as well as individual drugs’ characteristics.

Metabolic Suppression of a Drug-Resistant Subpopulation in Cancer Spheroid Cells.

Inhibition of metabolic features which distinguish cancer cells from their non-malignant counterparts is a promising approach to cancer treatment. Energy support for drug extrusion in multidrug resistance (MDR) is a potential target for metabolic inhibition. Two major sources of ATP-based metabolic energy are partial (glycolysis) and complete (mitochondrial oxidative phosphorylation) oxidation of metabolic fuels. In cancer cells, the balance between them tends to be shifted toward glycolysis; this shift is considered to be characteristic of the cancer metabolic phenotype. Numerous earlier studies, conducted with cells cultured in a monolayer (2-D model), suggested inhibition of glycolytic ATP production as an efficient tool to suppress MDR in cancer cells. Yet, more recent work challenged the appropriateness of the 2-D model for such studies and suggested that a more clinically relevant approach would utilize a more advanced cellular model such as a 3-D model. Here, we show that the transition from the 2-D model (cultured monolayer) to a 3-D model (cultured spheroids) introduces essential changes into the concept of energetic suppression of MDR. The 3-D cell organization leads to the formation of a discrete cell subpopulation (not formed in the 2-D model) with elevated MDR transport capacity. This subpopulation has a specific metabolic phenotype (mixed glycolytic/oxidative MDR support) different from that of cells cultured in the 2-D model. Finally, the shift to the oxidative phenotype becomes greater when the spheroids are grown under conditions of lactic acidosis that are typical for solid tumors. The potential clinical significance of these findings is discussed.

Impact of Saccharomyces cerevisiae fermentation product and subacute ruminal acidosis on production, inflammation, and fermentation in the rumen and hindgut of dairy cows

The effects of a Saccharomyces cerevisiae fermentation product (SCFP) on microbial fermentation in the digestive tract, milk production, and inflammation response were determined in Holstein dairy cows under normal and subacute ruminal acidosis (SARA) conditions. Eight lactating dairy cows with ruminal and cecal cannulas were used in a cross-over design with 5 wk experimental periods. During the first experimental period, cows were randomly assigned to treatment, i.e. SCFP (Original XPC, Diamond V, Cedar Rapids, IA) or control. During the second experimental period, treatments were reversed. Experimental periods were separated by a two-week wash out period. During each period, the 4 cows on the SCFP treatment were supplemented with 14g/d of SCFP in 126g of ground corn, whereas the other four cows received 140g ground corn only. During the first 4 wk of each experimental period, all cows received a basal diet. During week 5 of both experimental periods, a SARA challenge was conducted in all cows by replacing 208g/kg of the basal diet with pellets of ground wheat and barley (50:50 on a weight basis). This SARA challenge increased the duration of rumen pH below 5.6 from 11.1 to 311.1min/d, indicating successful induction of SARA. Inducing SARA reduced milk fat from 3.24 to 2.82%, and lowered the acetate to propionate ratio from 3.07 to 1.74 in rumen fluid, from 5.13 to 4.57 in cecal digesta, and from 4.81 to 4.34 in feces. Induction of SARA increased milk protein content from 3.23 to 3.32%, without a concomitant effect on milk protein yield. Inducing SARA also increased endotoxic lipopolysaccharide (LPS) in rumen fluid, cecal digesta and feces from 15,389 to 123,296 endotoxin units (EU)/mL, from 31,982 to 77,380EU/mL, and from 29,679 to 77, 371EU/mL, respectively. Concentrations of LPS, serum amyloid A, haptoglobin, and LPS-binding protein increased by 215.0, 250.6, 181.6 and 47.5%, respectively, in peripheral blood when SARA was induced. The SCFP did not affect feed intake, yields of milk, milk fat, and milk protein but it reduced the variation in rumen pH during control feeding. During the SARA challenge, SCFP tended to reduce ruminal LPS at 6h after feed delivery, increased milk fat percentage (2.71 vs 2.92%, control vs SCFP), and reduced the extent of SARA-associated inflammation response as indicated by a reduction in the concentration of the pro-inflammatory cytokine tumor necrosis factor α (0.09 vs 0.03ng/mL, control vs SCFP). This shows that SCFP can attenuate some of the impact of SARA on production and health of dairy cows.

Extracellular acidosis impairs P2Y receptor-mediated Ca2+ signalling and migration of microglia

Microglia are the resident macrophage and immune cell of the brain and are critically involved in combating disease and assaults on the brain. Virtually all brain pathologies are accompanied by acidosis of the interstitial fluid, meaning that microglia are exposed to an acidic environment. However, little is known about how extracellular acidosis impacts on microglial function. The activity of microglia is tightly controlled by ‘on’ and ‘off’ signals, the presence or absence of which results in generation of distinct phenotypes in microglia. Activation of G protein coupled purinergic (P2Y) receptors triggers a number of distinct behaviours in microglia, including activation, migration, and phagocytosis. Using pharmacological tools and fluorescence imaging of the murine cerebellar microglia cell line C8B4, we show that extracellular acidosis interferes with P2Y receptor-mediated Ca2+ signalling in these cells. Distinct P2Y receptors give rise to signature intracellular Ca2+ signals, and Ca2+ release from stores and Ca2+ influx are differentially affected by acidotic conditions: Ca2+ release is virtually unaffected, whereas Ca2+ influx, mediated at least in part by store-operated Ca2+ channels, is profoundly inhibited. Furthermore, P2Y1 and P2Y6-mediated stimulation of migration is inhibited under conditions of extracellular acidosis, whereas basal migration independent of P2Y receptor activation is not.Taken together, our results demonstrate that an acidic microenvironment impacts on P2Y receptor-mediated Ca2+ signalling, thereby influencing microglial responses and responsiveness to extracellular signals. This may result in altered behaviour of microglia under pathological conditions compared with microglial responses in healthy tissue.

Abstract PR09: A genome-wide RNAi screen reveals a protective role of decreased lipogenesis under hypoxia

Abstract As solid tumors form, a number of physiological changes occur within the tumor, including low oxygen levels (hypoxia) and an accumulation of lactic acid with concomitant lowered pH levels (lactic acidosis). In order to adapt to and survive in the strong selective pressures imposed by these tumor microenvironment (TME) “stresses”, cancer cells exhibit significant genetic and metabolic changes. While transcriptional responses and signaling events triggered by stresses are well-studied, a systematic genome-wide, forward-genetics screen to identify which genes are critical or restrictive for cell survival in these TME stresses has not been examined. The purpose of this study is to better understand the function of genes that modulate cell survival under TME stresses in order to improve our knowledge of tumor evolution and allow for the development of treatments to specifically target cancer cells under these stresses. We performed a contextual short-hairpin RNA (shRNA) pooled screen in cancer cells cultured under control, hypoxia or lactic acidosis conditions. Genomic DNA was recovered from each condition to amplify the resulting shRNAs by PCR before quantifying them by microarray. A number of criteria were used to select top candidate hits, including multiple shRNAs targeting a single gene needing to pass stringent statistical criteria. We have successfully validated a number of candidate genes with multiple shRNAs. Importantly, our analysis identified HIF-2α (EPAS1) as critical for cells to survive under hypoxia and this result has been validated. One “multiple hairpin hit” was ACACA. This gene encodes acetyl-CoA carboxylase (ACC1), which is the enzyme that mediates the rate-limiting step of de novo lipogenesis by converting acetyl-CoA to malonyl-CoA. Validation experiments showed that inhibition of ACC1 by four different shRNAs protected cells from hypoxia-induced apoptosis in several cell lines. This protective affect was specific to hypoxia, since cells were not protected under lactic acidosis or glutamine deprivation. Further interrogation of related genes revealed that the depletion of ATP citrate lyase (ACLY) also prevented hypoxia-induced apoptosis. ACLY acts upstream of ACC1, converting citrate to acetyl-CoA. Metabolomic and transcriptomic analysis revealed that the silencing of ACC1 or ACLY significantly diminished the expected hypoxia and stress responses of these cells. We hypothesize that the metabolic shift resulting from the depletion of ACC1 or ACLY switches cancer cells from a “nutrient rich/proliferative” state to a “nutrient poor/survival” state, allowing cells to better cope with hypoxia. Consistent with this concept, when the gene signatures of ACC1 or ACLY depletion were used to stratify patients in breast cancer datasets, the inactivation of these genes correlated with reduced proliferative and hypoxia pathways and more favorable outcomes. These results may have important implications for the use of metformin and lipogenic inhibitors in the clinic. Our forward-genetics screen has identified novel genes and biological processes that impact the survival of cancer cells under TME stresses. These findings inform our understanding of the selection of somatic mutations in cancer cells and help reveal potential new therapeutic strategies to selectively target solid human cancers. This abstract is also presented as Poster B1. Citation Format: Melissa M. Keenan, Beiyu Liu, Jianli Wu, Derek Cyr, Joseph Lucas, Deborah M. Muoio, So Young Kim, Jen-Tsan Chi. A genome-wide RNAi screen reveals a protective role of decreased lipogenesis under hypoxia. [abstract]. In: Abstracts: AACR Special Conference on Cellular Heterogeneity in the Tumor Microenvironment; 2014 Feb 26-Mar 1; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2015;75(1 Suppl):Abstract nr PR09. doi:10.1158/1538-7445.CHTME14-PR09

Acidosis slows electrical conduction through the atrio-ventricular node.

Acidosis affects the mechanical and electrical activity of mammalian hearts but comparatively little is known about its effects on the function of the atrio-ventricular node (AVN). In this study, the electrical activity of the epicardial surface of the left ventricle of isolated Langendorff-perfused rabbit hearts was examined using optical methods. Perfusion with hypercapnic Tyrode's solution (20% CO2, pH 6.7) increased the time of earliest activation (Tact) from 100.5 ± 7.9 to 166.1 ± 7.2 ms (n = 8) at a pacing cycle length (PCL) of 300 ms (37°C). Tact increased at shorter PCL, and the hypercapnic solution prolonged Tact further: at 150 ms PCL, Tact was prolonged from 131.0 ± 5.2 to 174.9 ± 16.3 ms. 2:1 AVN block was common at shorter cycle lengths. Atrial and ventricular conduction times were not significantly affected by the hypercapnic solution suggesting that the increased delay originated in the AVN. Isolated right atrial preparations were superfused with Tyrode's solutions at pH 7.4 (control), 6.8 and 6.3. Low pH prolonged the atrial-Hisian (AH) interval, the AVN effective and functional refractory periods and Wenckebach cycle length significantly. Complete AVN block occurred in 6 out of 9 preparations. Optical imaging of conduction at the AV junction revealed increased conduction delay in the region of the AVN, with less marked effects in atrial and ventricular tissue. Thus acidosis can dramatically prolong the AVN delay, and in combination with short cycle lengths, this can cause partial or complete AVN block and is therefore implicated in the development of brady-arrhythmias in conditions of local or systemic acidosis.

Prevalence of Ruminal Lactic Acidosis and Clinical Assessments of Four Therapeutics in Goats of Bangladesh

Acidosis conditions either acute or chronic following ingestion of excessive amounts of readily fermented carbohydrate are great production problems for goat in Bangladesh. This study designed to investigate the prevalence of lactic acidosis and then response to different therapeutic agents. For this purpose, 1,128 goat were examined at outdoor District Veterinary Hospital, Faridpur, Bangladseh for treatment of which 40 goats were found positive for lactic acidosis showing 3.55% prevalence of disease. The highest occurrence found in female (4.64%) of over 3 years age (4.64%) in indigenous goat (2.7%). For therapeutic assessment the forty affected goats were divided into four groups A, B, C and D comprising of 10 animals each. Group A were given magnesium hydroxide 8% w/v at 1 g/kg body weight orally. In group B magnesium hydroxide 8% w/v at a dose as group A combination with 7.5% sodium bicarbonate at the rate of 0.9 ml/Kg body weight intravenously administered. Goat in group D were treated with mixture of ginger, nuxvomica, sodium carbonate, cobalt sulphate, dried ferrous sulphate and thiamin mononitrate at the rate of 1 g/kg body weight orally. Goat of group C treated with combination drugs of group A, B and D. The rectal temperature, pulse rate, respiration rate, was performed before and after treatment. It was found that the highest recovery in group C with an average period of 21 ± 1.8 hours. It was concluded that lactic acidosis is a common disease of goats and its severity can be effectively reduced by using combination drugs.

PH‐Dependent structural ensembles of haptoglobin suppress β2‐microglobulin amyloidosis: role in lysosomal localization and extracellular protein quality control (752.7)

Several diseases involve extracellular deposition of misfolded proteins, which is associated with inflammation and local acidosis. We have investigated the chaperone‐like activity of haptoglobin towards the amyloid aggregation of β2‐microglobulin (β2m) and of α‐synuclein and its role in clearing the amyloid deposits from the extracellular space. At neutral pH, haptoglobin prevents the formation of β2m amyloid fibrils but not that of α‐synuclein. Under conditions of local acidosis, pH 5.5‐6.5, it prevents β2m fibril formation with relatively decreased efficiency. We have investigated the structural and stability aspects of haptoglobin as a function of pH. Between pH 5.5‐8.0, it exists in a continuum of conformational states with subtle perturbation in tertiary structure, moderately exposed hydrophobic surfaces and distinct latent heat of unfolding. Below pH 5.0 it exists in a molten‐globule‐like conformation with no chaperone activity. Live cell imaging and flow cytometry studies show that the species of β2m formed in the presence of haptoglobin are not cytotoxic and readily undergo lysosomal degradation. Analytical ultracentrifugation and dot blot studies reveal that haptoglobin interacts with prefibrillar oligomeric species formed during β2m fibril formation. Thus, haptoglobin is an extracellular chaperone with promising therapeutic implications in extracellular amyloid diseases.

Titratable acidity: A Pitts concept revisited

Titratable Acidity (TA) in urine can be measured directly or calculated from actual and reference pH, by using the pKa2 6,8 for phosphate. In urine, H2PO4− represents the excretion of filtered H2PO4−, filtrated HPO42− being completely reabsorbed by the proximal tubule (the Van Slyke approach). Since excretion of H2PO4− frequently exceeds its glomerular filtration, this approach is considered inadequate by Pitts. He claimed that it is the tubular H+ secretion which converts filtered HPO42− to H2PO4−, thereafter excreted in urine. This is only true under conditions of inorganic acid or neutral phosphate loading, when the maximum tubular phosphate reabsorption (TmPi) is overcharged. In controls, H2PO4− excretion is lower than its glomerular filtration, provided that acid-base status is normal and tubular phosphate reabsorption is below the TmPi. The TmPi is lower than its glomerular filtration, provided that acid-base status is normal and tubular phosphate reabsorption is below the TmPi. When the TmPi is exceeded, a portion of HPO42− escapes proximal reabsorption, reaching the distal tubule where its absorption is precluded, while tubular H+ secretion converts HPO42− to H2PO4−. In man and dog, the attainment of TmPi is evidenced by a FE% of 20%, and only beyond this limit H2PO4− excretion exceeds glomerular filtration. When FE% is lower than 20%, H2PO4− filtration exceeds excretion, HPO42− being completely reabsorbed at the proximal tubule by NaPi-2a and 2c cotransporters. While Van Slyke's approach is always valid, Pitts’ approach is only valid under loading conditions, when the two processes of H2PO4− excretion overlap each other. NH +4 increases inversely to TA excretion in conditions of acidosis and tP restriction, but is independent of TA in Pi-replete dogs, independently of acidosis.

The importance of autophagy regulation in breast cancer development and treatment.

Breast cancer (BC) is a potentially life-threatening malignant tumor that still causes high mortality among women. One of the mechanisms through which cancer development could be controlled is autophagy. This process exerts different effects during the stages of cancer initiation and progression due to the occurring superimposition of signaling pathways of autophagy and carcinogenesis. Chronic inhibition of autophagy or autophagy deficiency promotes cancer, due to instability of the genome and defective cell growth and as a result of cell stress. However, increased induction of autophagy can become a mechanism which allows tumor cells to survive the conditions of hypoxia, acidosis, or chemotherapy. Therefore, in the development of cancer, autophagy is regarded as a double-edged sword. Determination of the molecular mechanisms underlying autophagy regulation and its role in tumorigenesis is an essential component of modern anticancer strategies. Results of scientific studies show that inhibition of autophagy may enhance the effectiveness of currently used anticancer drugs and other therapies (like radiotherapy). However, in some cases, the promotion of autophagy can induce death and, hence, elimination of the cancer cells and reduction of tumor size. This review summarizes the current knowledge on autophagy regulation in BC and up-to-date anticancer strategies correlated with autophagy.

Effects of the acid-tolerant engineered bacterial strain Megasphaera elsdenii H6F32 on ruminal pH and the lactic acid concentration of simulated rumen acidosis in vitro

The aim of this study was to examine the effects of the acid-tolerant engineered bacterial strain Megasphaera elsdenii H6F32 (M. elsdenii H6F32) on ruminal pH and the lactic acid concentrations in simulated rumen acidosis conditions in vitro. A mixed culture of ruminal bacteria, buffer, and primarily degradable substrates was inoculated with equal numbers of M. elsdenii H6 or M. elsdenii H6F32. The pH and lactic acid concentrations in the mixed culture were determined at 0, 2, 4, 6, 8, 10, 12, 14, 16, and 18h of incubation. Acid-tolerant M. elsdenii H6F32 reduced the accumulation of lactic acid and increased the pH value. These results indicate that acid-tolerant M. elsdenii H6F32 could be a potential candidate for preventing rumen acidosis.