Reduced Cell Yield Research Articles

Marrow changes and reduced proliferative capacity of mesenchymal stromal cells from patients with “no-option” critical limb ischemia; observations on feasibility of the autologous approach from a clinical trial

Background aimsApproximately 1 in 3 patients with critical limb ischemia (CLI) are not suitable for surgical or endovascular revascularization. Those “no-option” patients are at high risk of amputation and death. Autologous bone marrow mesenchymal stromal cells (MSCs) may provide a limb salvage option. In this study, bone marrow characteristics and expansion potentials of CLI-derived MSCs produced during a phase 1b clinical trial were compared with young healthy donor MSCs to determine the feasibility of an autologous approach. Cells were produced under Good Manufacturing Practice conditions and underwent appropriate release testing. MethodsFive bone marrow aspirates derived from patients with CLI were compared with six young healthy donor marrows in terms of number of colony-forming units–fibroblast (CFUF) and mononuclear cells. The mean population doubling times and final cell yields were used to evaluate expansion potential. The effect of increasing the volume of marrow on the CFUF count and final cell yield was evaluated by comparing 5 CLI-derived MSCs batches produced from a targeted 30 mL of marrow aspirate to five batches produced from a targeted 100 mL of marrow. ResultsCLI-derived marrow aspirate showed significantly lower numbers of mononuclear cells with no difference in the number of CFUFs when compared with healthy donors’ marrow aspirate. CLI-derived MSCs showed a significantly longer population doubling time and reduced final cell yield compared with young healthy donors' MSCs. The poor growth kinetics of CLI MSCs were not mitigated by increasing the bone marrow aspirate from 30 to 100 mL. ConclusionsIn addition to the previously reported karyotype abnormalities in MSCs isolated from patients with CLI, but not in cells from healthy donors, the feasibility of autologous transplantation of bone marrow MSCs for patients with no-option CLI is further limited by the increased expansion time and the reduced cell yield.

A simple, robust flow cytometry-based whole blood assay for investigating sex differential interferon alpha production by plasmacytoid dendritic cells

Central to sex differences observed in outcome from infection and vaccination is the innate immune response, and specifically production of type I interferons by plasmacytoid dendtiric cells (pDCs), the main producers of IFN-α. Evaluation of IFN-α production by pDCs is therefore critical for studies of innate immune function. However, reliable measurement of pDC IFN-α is hampered by reduced cell yields and cytokine production after cryopreservation or after even short delays in stimulating freshly isolated cells. We here describe a simple yet robust method for measuring IFN-α production in pDCs that preserves cell activation and cytokine production through immediate stimulation of whole blood and subsequent maintenance at 37 °C.

Type I collagen facilitates safe and reliable expansion of human dental pulp stem cells in xenogeneic serum-free culture

BackgroundHuman dental pulp stem cells (DPSCs) are a readily accessible and promising cell source for regenerative medicine. We recently reported that a xenogeneic serum-free culture medium (XFM) is preferable to fetal bovine serum-containing culture medium for ex vivo expansion of DPSCs; however, we observed that, upon reaching overconfluence, XFM cells developed a multilayered structure and frequently underwent apoptotic death, resulting in reduced cell yield. Therefore, we focused on optimization of the XFM culture system to avoid the undesirable death of DPSCs.MethodsWe selected type I collagen (COL) as the optimal coating substrate for the cultureware and compared DPSCs cultured on COL in XFM (COL-XFM cells) to the conventional XFM cultures (XFM cells).ResultsOur results demonstrated that COL coating facilitated significantly higher rates of cell isolation and growth; upon reaching overconfluence, cell survival and sustained proliferative potential resulted in two-fold yield compared to the XFM cells. Surprisingly, after subculturing the overconfluent COL-XFM cultures, the cells retained stem cell behavior including stable cell growth, multidifferentiation potential, stem cell phenotype, and chromosomal stability, which was achieved through HIF-1α-dependent production and uniform distribution of collagen type I and its interactions with integrins α2β1 and α11β1 at overconfluency. In contrast, cells undergoing apoptotic death within overconfluent XFM cultures had disorganized mitochondria with membrane depolarization.ConclusionThe use of COL as a coating substrate promises safe and reliable handling of DPSCs in XFM culture, allowing translational stem cell medicine to achieve stable isolation, expansion, and banking of donor-derived stem cells.

Cryopreservation of Canine Primary Dorsal Root Ganglion Neurons and Its Impact upon Susceptibility to Paramyxovirus Infection.

Canine dorsal root ganglion (DRG) neurons, isolated post mortem from adult dogs, could provide a promising tool to study neuropathogenesis of neurotropic virus infections with a non-rodent host spectrum. However, access to canine DRG is limited due to lack of donor tissue and the cryopreservation of DRG neurons would greatly facilitate experiments. The present study aimed (i) to establish canine DRG neurons as an in vitro model for canine distemper virus (CDV) infection; and (ii) to determine whether DRG neurons are cryopreservable and remain infectable with CDV. Neurons were characterized morphologically and phenotypically by light microscopy, immunofluorescence, and functionally, by studying their neurite outgrowth and infectability with CDV. Cryopreserved canine DRG neurons remained in culture for at least 12 days. Furthermore, both non-cryopreserved and cryopreserved DRG neurons were susceptible to infection with two different strains of CDV, albeit only one of the two strains (CDV R252) provided sufficient absolute numbers of infected neurons. However, cryopreserved DRG neurons showed reduced cell yield, neurite outgrowth, neurite branching, and soma size and reduced susceptibility to CDV infection. In conclusion, canine primary DRG neurons represent a suitable tool for investigations upon the pathogenesis of neuronal CDV infection. Moreover, despite certain limitations, cryopreserved canine DRG neurons generally provide a useful and practicable alternative to address questions regarding virus tropism and neuropathogenesis.

PWE-256 Enhanced radiosensitivity of colorectal cancer cells by targeting BCL-3

Introduction Colorectal cancer remains the second most common cause of cancer related death in the UK. The successful management of rectal cancer has improved significantly with changes to surgical technique and the addition of pre-operative chemo-radiotherapy. A significant proportion of patients fail to respond to neo-adjuvant therapy. BCL-3 expression (an NF-KB homodimeric binding protein) is associated with poor prognosis in colorectal cancer patients, 1 and has been shown to drive expression of Cancer Stem Cell (CSC) markers in colorectal cancer. 2,3,4 Importantly evidence shows that CSCs contribute to tumour development and therapeutic resistance. 5 It was hypothesised that expression of BCL-3 could be driving cell survival after radiation, and therefore represent a novel biomarker for therapeutic response. Method Established colorectal cells lines LS174T and HCA7 were cultured in flasks/plates. Suppression of BCL-3 expression was achieved by transfection with short interfering RNA (siRNA), cells were irradiated with 1–2.5Gy γ-radiation (Cs-137 source). Cell yield and apoptosis were determined. Cell viability was assessed using a crystal violet assay, protein analysis by Western Blotting. Results BCL-3 suppression results in reduced cell yield and increased apoptosis in LS174T and HCA7 cells. Suppression of BCL-3 expression combined with γ-irradiation results in a significant decrease in cell viability of both LS174T (40% reduction in cell viability at 1Gy, p = 0.028; 54% reduction in cell viability at 2.5Gy, p = 0.005) and HCA7 cells (33% reduction in cell viability at 1Gy, p = 0.017; 50% reduction in cell viability at 2.5Gy, p = 0.031). Conclusion We have shown for the first time that suppressing BCL-3 expression results in radio-sensitisation in an in-vitro colorectal cancer model, the mechanisms of which are currently under investigation. Work is underway to validate this research with in-vivo tissue samples; the aim is to determine whether BCL-3 expression levels correlate with therapeutic response to radiotherapy in rectal cancer patients and whether BCL-3 levels could be used to stratify patient treatment. Disclosure of interest None Declared. References Puvvada SD et al . Oncology. 2010;78:181–188 Al-Kharusi, MR et al . Carcinogenesis. 2013;34:1150–1157 Smartt, HJ et al . Gut. 2012;61:1306–1314 Urban BC et al . BCL-3 promotes colorectal tumour cell survival through activation of the AKT signalling pathway. In revision. 2015 Pattabiraman, DR et al . Nature reviews. Drug discovery. 2014;13:497–512

Effect of nitrogenous resource on growth, biochemical composition and ultrastructure of Isochrysis galbana (Isochrysidales, Haptophyta)

SummaryThe nitrogenous resource used to promote algal growth has cost implications for mass culture processes. The present study therefore aimed to determine the effect of different nitrogenous resources (nitrate, ammonium and urea) on various performance parameters (growth, final cell yield, pigmentation, lipid yield and cellular and sub‐cellular characteristics) in Isochrysis galbana. Growth rate was unaffected by nitrogenous resource, but the final cellular yield in the nitrate and urea treatments far exceeded that evident in the ammonium treatments. The reduced cell yield in ammonium treatments and the earlier onset of the stationary phase was brought about by nitrogen‐starvation due to an increase in pH and resultant ammonia volatilization. This starvation initiated an early onset of lipid accumulation, chlorophyll depletion and an increase in the carotenoid to chlorophyll ratio relative to the other nitrogen (N) source treatments. Hence, in spite of being potentially the preferred source of N by algae (due to its reduced state), ammonium‐nitrogen is undesirable for mass culture. The performance parameters of Isochrysis grown in urea (an organic N source) and nitrate (an inorganic N source) were similar, but lipid accrued earlier in cells grown in medium supplemented with urea. This is advantageous for lipid acquisition for the production of biodiesel since it would reduce the duration of photobioreactor runs. Urea is easily available and considerably cheaper than all the other N sources tested and is thus recommended as the nitrogenous resource for large‐scale culture of I. galbana for biodiesel production.

Nutrient starvation effects on the allelochemical potency of Alexandrium tamarense (Dinophyceae)

Batch culture experiments were performed to investigate potential effects of nutrient starvation on the allelochemical potency of the toxic dinoflagellate Alexandrium tamarense. Triplicate cultures with reduced nitrate (−N) or phosphate (−P) seed were compared to nutrient-replete (+N+P) cultures. Total depletion of the dissolved inorganic limiting nutrient, reduced cell quotas, changed mass ratios of C/N/P and reduced cell yield clearly indicate that treatment cultures at stationary phase were starved by either N or P, whereas growth cessation of +N+P cultures was probably due to carbon limitation and/or a direct effect of high pH. Pulsed addition of the limiting nutrient allowed −N and −P cultures to resume growth. Lytic activity of A. tamarense as quantified by a Rhodomonas bioassay was generally high (EC50 around 100 cells mL−1) and was only slightly modulated by growth phase and/or nutrient starvation. Lytic activity per cell increased with time in both +N+P and −P cultures but not −N cultures. P-starved stationary-phase cells were slightly more lytic than +N+P cultures, but this difference may be due to increased cell size and/or accumulation of extracellular compounds. In conclusion, only slight changes but no general and major increase in lytic activity in response to nutrient starvation was observed.

Abstract 3856: Loss fo N or K-Ras B does not mimic the effects of farnesy transferase inhibited osteosarcoma or 293T cells

Abstract Ras proteins are small GTPases that regulate growth, differentiation, survival, and cell death. Prenylation, the addition of either a farnesyl (15 carbon chain lipid) or geranylgeranyl (20 carbon chain lipid) group, allows Ras and other small GTPases to anchor into the plasma membrane, a necessary step for Ras to activate multiple signaling pathways, including the MAPK cascades. The specific CAAX motif at the C terminus of a protein determines whether it can be farnesylated, geranylgeranylated, or both. There are four highly homologous Ras proteins: K-Ras A, K-Ras B, N-Ras, and H-Ras, each containing a CAAX motif that allows farnesylation. K-Ras B and N-Ras can be alternately geranylgeranylated (GGd) if farnesylation is blocked by a specific small molecule (FTI). Oncogenic Ras mutations are found commonly in cancer, and Ras also can be a major mediator of signals initiated by activated receptor tyrosine kinases (RTKs). Since RTK signaling plays a major role in the biology of sarcomas, we were interested in the mechanisms by which FTIs might affect osteosarcoma cell growth and survival. Osteosarcoma cell lines have variable responses to FTI treatment, including reduced proliferation and programmed cell death at a range of concentrations from 1 nM to 100 nM (Hall et al. 2010). Further, 293T fibroblast cells also have decreased cell viability and increased subG1 and G2/M cell cycle arrest with FTI treatment. 293T cells respond similarly to OS187 our most sensitive osteosarcoma cell line. To assess Ras activity in response to FTI, we co-precipitated activated Ras with the Ras target protein Raf, then probed by western for Ras. Surprisingly, Ras activity was increased in response to FTI in both osteosarcoma cell lines and 293T cells. We also found that the activity of downstream effectors, ERK and p38 MAPK, also increased with FTI (Hall et al, 2010). It was unclear whether the changes in cell growth and survival were due to decrease in farnesylated Ras or the increase in geranylgeranylated Ras. To determine if loss of N-Ras or K-Ras B activity could account for reduced cell yield following FTI, we knocked down each of these proteins in our most responsive osteosarcoma cell line, OS187, and in 293T cells. There was no significant difference in cell yield or cell cycle when either of these proteins was knocked down. To determine if alternate prenylation of N or K-Ras B are responsible for decreased cell yield and/or cell cycle arrest, mutant forms of these proteins will need to be transduced into OS187 and 293T cells for further analysis. In conclusion, FTI caused growth inhibition and cell death for both osteosarcoma cells and 293T cells. FTIs increased Ras activation and the activity of downstream effectors. Since knocking out N or K-Ras B did not reproduce any of these effects, the effects of FTI are not due to the loss of farnesylated Ras. These observations suggest that the effects may be due to increased geranylgeranylated N Ras or K-Ras B. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3856. doi:10.1158/1538-7445.AM2011-3856

ERBB Expression in Philadelphia Chromosome-Positive ALL as a Potential Therapeutic Target.

Philadelphia chromosome-positive ALL (Ph+ALL) strikes older children and adults, is difficult to treat and often has poor outcomes with conventional therapies. Tremendous advances have been made in other cancers through identification of essential signaling molecules that can be inhibited by small molecule medicines. ERBB proteins are such targets for several adult carcinomas, including breast and lung cancer. Expression of one member of the ERBB family, Her-2, is associated with chemotherapy resistance in one report of adult B-ALL. We examined the expression, activation status and contribution to growth and survival of ERBB receptors in Ph+ALL cell lines Z33, Z119 and Z181. Phosphorylated Her-2 was detected by western blot in all 3 lines, as was trace amounts of Her-3. Western-blot identified expression of the p80 form of Her-4 in Z119, which correlated with flow cytometry assessment of Her-4. Expression in Z33 of EGFR, detected by western blot, correlated with down-regulation of both EGFR and Her-2 from the cell surface, as assessed by flow cytometry. Internalization of EGFR homo- and hetero-dimers is associated with receptor phosphorylation and active signaling. To assess the physiologic importance of ERBB signaling in Ph+ALL, cells were cultured in the pan-ERBB inhibitor CI-1033 (Pfizer Global Research and Development), which is specific for ERBB family receptors in tissue culture up to 20 μM concentrations. All lines demonstrated reduced cell yield after CI-1033 exposure, with average IC50 of 0.783 for Z119, 1.178 for Z181 and 1.737 for Z33. The increased sensitivity of Z119 to CI-1033 correlated with an increased rate of apoptosis: 3 μM CI-1033 caused a 26% increase in the fraction of sub-diploid Z119 cells at 24 hours, compared to 13% for Z181 and 16% for Z33. Higher sensitivity to ERBB inhibition also correlated with growth factor resistance, since Z33 and Z181 are dependent upon autocrine GM-CSF for growth while Z119 grows independent of known autocrine secretion of hematopoietic growth factors. These data suggest that Ph+ALL cells may acquire GM-CSF independence by relying more on ERBB-derived signals, since these receptors are capable of activating similar second messenger pathways. Our data suggest that, surprisingly, the ERBB family of receptor tyrosine kinases are intact and functioning in Ph+ALL, and inhibition of these signals may provide benefit to Ph+ALL patients, either in combination with imatinib or in patients who develop imatinib resistance.

Carnosine-Induced Changes in the Development of Spermatogenic Epithelial Cells in Senescence Accelerated SAM Mice

Carnosine significantly increased the number of spermatogonia and Sertoli cells in mice prone (SAMP1) and resistant (SAMR1) to accelerated aging and appreciably reduced cell yield in meiosis and spermiogenesis in SAMP1 mice. In experimental SAMP1 mice catastrophic changes in the number of gametes were paralleled by intensive degradation of the spermatogenic epithelium. In SAMR1 mice treated with carnosine highly ordered spermatogenic structure was preserved.

Genetic, physiological and biochemical characterization of multiple methanol methyltransferase isozymes in Methanosarcina acetivorans C2A

Biochemical evidence suggests that methanol catabolism in Methanosarcina species requires the concerted effort of methanol:5-hydroxybenzimidazolylcobamide methyltransferase (MtaB), a corrinoid-containing methyl-accepting protein (MtaC) and Co-methyl-5-hydroxybenzimidazolylcobamide:2-mercapto-ethanesulphonic acid methyltransferase (MtaA). Here we show that Methanosarcina acetivorans possesses three operons encoding putative methanol-specific MtaB and corrinoid proteins: mtaCB1, mtaCB2 and mtaCB3. Deletion mutants lacking the three operons, in all possible combinations, were constructed and characterized. Strains deleted for any two of the operons grew on methanol, whereas strains lacking all three did not. Therefore, each operon encodes a bona fide methanol-utilizing MtaB/corrinoid protein pair. Most of the mutants were similar to the wild-type strain, with the exception of the DeltamtaCB1 DeltamtaCB2 double mutant, which grew more slowly and had reduced cell yields on methanol medium. However, all mutants displayed significantly longer lag times when switching from growth on trimethylamine to growth on methanol. This indicates that all three operons are required for wild-type growth on methanol and suggests that each operon has a distinct role in the metabolism of this substrate. The combined methanol:CoM methyltransferase activity of strains carrying only mtaCB1 was twofold higher than strains carrying only mtaCB2 and fourfold higher than strains carrying only mtaCB3. Interestingly, the presence of the mtaCB2 and mtaCB3 operons, in addition to the mtaCB1 operon, did not increase the overall methyltransferase activity, suggesting that these strains may be limited by MtaA availability. All deletion mutants were unaffected with respect to growth on trimethylamine and acetate corroborating biochemical evidence indicating that each methanogenic substrate has specific methyltransfer enzymes.

Ethanol production from cheese whey permeate by Kluyveromyces marxianus UFV-3: A flux analysis of oxido-reductive metabolism as a function of lactose concentration and oxygen levels

In order to investigate the effect of lactose concentration and oxygen level on the growth and metabolism of Kluyveromyces marxianus UFV-3 in cheese whey permeate, batch cultures were conducted under aerobic, hypoxic, and anoxic conditions, with lactose at initial concentration ranging from 1 to 240 g L −1. The increase in lactose concentration increased ethanol yield and ethanol volumetric productivity, and has reduced cell yield. When lactose concentration was equal or above 50 g L −1 and the oxygen levels were low, the ethanol yield was close to its theoretical value. Maximum ethanol concentrations attained in this study were 76 and 80 g L −1 in hipoxia and anoxia, respectively. The lactose consumption rate in anoxia was greater than in aerobiosis and hipoxia. However, under anoxia, the lactose consumption rate of K. marxianus followed a saturation kinetics, which was not observed in hypoxia and aerobiosis. All oxygen levels investigated, showed a tendency for saturation of the ethanol production rate above 65 g L −1 lactose. Ethanol production rate was also higher on anoxia.

Differential expression of Desulfovibrio vulgaris genes in response to Cu(II) and Hg(II) toxicity.

The response of Desulfovibrio vulgaris to Cu(II) and Hg(II) was characterized. Both metals increased the lag phase, and Cu(II) reduced cell yield at concentrations as low as 50 microM. mRNA expression was analyzed using random arbitrarily primed PCR, differential display, and quantitative PCR. Both Cu(II) and Hg(II) (50 micro M) caused upregulation of mRNA expression for an ATP binding protein (ORF2004) and an ATPase (ORF856) with four- to sixfold increases for Hg(II) and 1.4- to 3-fold increases with Cu(II). These results suggest that D. vulgaris uses an ATP-dependent mechanism for adapting to toxic metals in the environment.

β2-Microglobulin as a negative regulator of the immune system: high concentrations of the protein inhibit in vitro generation of functional dendritic cells

AbstractTwo common features in human immunodeficiency virus infection and acquired immunodeficiency syndrome, rheumatoid arthritis, and hematologic malignancies including multiple myeloma are elevated serum levels of β2-microglobulin (β2M) and activation or inhibition of the immune system. We hypothesized that β2M at high concentrations may have a negative impact on the immune system. In this study, we examined the effects of β2M on monocyte-derived dendritic cells (MoDCs). The addition of β2M (more than 10 μg/mL) to the cultures reduced cell yield, inhibited the up-regulation of surface expression of human histocompatibility leukocyte antigen (HLA)–ABC, CD1a, and CD80, diminished their ability to activate T cells, and compromised generation of the type-1 T-cell response induced in allogeneic mixed-lymphocyte reaction. Compared with control MoDCs, β2M-treated cells produced more interleukin-6 (IL-6), IL-8, and IL-10. β2M-treated cells expressed significantly fewer surface CD83, HLA-ABC, costimulatory molecules, and adhesion molecules and were less potent at stimulating allospecific T cells after an additional 48-hour culture in the presence of tumor necrosis factor-α and IL-1β. During cell culture, β2M down-regulated the expression of phosphorylated mitogen-activated protein (MAP) kinases, extracellular signal-related kinase (ERK), and mitogen-induced extracellular kinase (MEK), inhibited nuclear factor-κB (NF-κB), and activated signal transducer and activator of transcription-3 (STAT3) in treated cells, all of which are involved in cell differentiation and proliferation. Thus, our study demonstrates that β2M at high concentrations retards the generation of MoDCs, which may involve down-regulation of major histocompatibility complex class I molecules, inactivation of Raf/MEK/ERK cascade and NF-κB, and activation of STAT3, and it merits further study to elucidate the underlying mechanisms.

L-pyroglutamate spontaneously formed from L-glutamate inhibits growth of the hyperthermophilic archaeon Sulfolobus solfataricus.

Identification of physiological and environmental factors that limit efficient growth of hyperthermophiles is important for practical application of these organisms to the production of useful enzymes or metabolites. During fed-batch cultivation of Sulfolobus solfataricus in medium containing L-glutamate, we observed formation of L-pyroglutamic acid (PGA). PGA formed spontaneously from L-glutamate under culture conditions (78 degrees C and pH 3.0), and the PGA formation rate was much higher at an acidic or alkaline pH than at neutral pH. It was also found that PGA is a potent inhibitor of S. solfataricus growth. The cell growth rate was reduced by one-half by the presence of 5.1 mM PGA, and no growth was observed in the presence of 15.5 mM PGA. On the other hand, the inhibitory effect of PGA on cell growth was alleviated by addition of L-glutamate or L-aspartate to the medium. PGA was also produced from the L-glutamate in yeast extract; the PGA content increased to 8.5% (wt/wt) after 80 h of incubation of a yeast extract solution at 78 degrees C and pH 3.0. In medium supplemented with yeast extract, cell growth was optimal in the presence of 3.0 g of yeast extract per liter, and higher yeast extract concentrations resulted in reduced cell yields. The extents of cell growth inhibition at yeast extract concentrations above the optimal concentration were correlated with the PGA concentration in the culture broth. Although other structural analogues of L-glutamate, such as L-methionine sulfoxide, glutaric acid, succinic acid, and L-glutamic acid gamma-methyl ester, also inhibited the growth of S. solfataricus, the greatest cell growth inhibition was observed with PGA. We also observed that unlike other glutamate analogues, N-acetyl-L-glutamate enhanced the growth of S. solfataricus. This compound was stable under cell culture conditions, and replacement of L-glutamate with N-acetyl-L-glutamate in the medium resulted in increased cell density.

An insight into insect cell metabolism through selective nutrient manipulation

Nutritional information of insect cell cultures, required for designing strategies to increase protein productivity, is still limited. In this work, nutrient feeding or removal was used to determine the role of selected nutrients and their interactions in insect cell metabolism before viral infection. Glucose, glutamine, tyrosine, and methionine were consumed at the highest rates in batch and fed-batch cultures, and thus were selected to be manipulated. Glucose and glutamine could be replaced by other carbon sources or amino acids, respectively. However, growth was reduced when such alternative sources were utilized, revealing the distinctive role of glucose and glutamine. Glucose and glutamine consumption rates were regulated by their own concentration, although glutamine concentration did not affect glucose consumption rate or vice versa. Excessive glucose or glutamine supply caused energy and carbon wastes, as observed by reduced cell yields and accumulation of by-products, such as alanine. Nevertheless, growth inhibition was attenuated by simultaneous excess of both nutrients, probably because cells had both carbon and ammonia available to deal with toxic by-products in the form of alanine. Other amino acids, such as tyrosine and methionine, were also relevant for maintaining prolonged viability. The importance of an adequate nutrient supply was demonstrated; particularly, the need to maintain glucose and glutamine concentrations just above their critical values.

Comparison of the inhibitory action on Saccharomyces cerevisiae of weak-acid preservatives, uncouplers, and medium-chain fatty acids

This study was initiated to establish whether inhibition of growth of yeasts by medium-chain fatty acids resembled that caused by weak-acid preservatives or uncouplers. Unlike sorbic acid and 2,4-dinitrophenol, decanoic acid caused rapid cell death at its inhibitory concentration. This suggested a mode of action by medium-chain fatty acids, distinct from both weakacid preservatives and uncouplers. Sorbic acid and 2,4-dinitrophenol both increased lag and doubling times, reduced cell yields and inhibitory concentrations of both were highly pH sensitive. The possibility is discussed as to whether weak-acid preservatives and uncouplers share common modes of inhibition.

Comparison of the inhibitory action on Saccharomyces cerevisiae of weak-acid preservatives, uncouplers, and medium-chain fatty acids.

This study was initiated to establish whether inhibition of growth of yeasts by medium-chain fatty acids resembled that caused by weak-acid preservatives or uncouplers. Unlike sorbic acid and 2,4-dinitrophenol, decanoic acid caused rapid cell death at its inhibitory concentration. This suggested a mode of action by medium-chain fatty acids, distinct from both weak-acid preservatives and uncouplers. Sorbic acid and 2,4-dinitrophenol both increased lag and doubling times, reduced cell yields and inhibitory concentrations of both were highly pH sensitive. The possibility is discussed as to whether weak-acid preservatives and uncouplers share common modes of inhibition.

Cryopreservation and storage of embryonic rat mesencephalic dopamine neurons for one year: comparison to fresh tissue in culture and neural grafts

Blocks of embryonic rat ventral mesencephalic tissue containing the developing A8–A10 dopamine (DA) cell groups were cryopreserved and stored for approximately 1 year, at which time this tissue was thawed, dissociated into a cell suspension, and compared to a similar preparation of fresh mesencephalic tissue for viability in tissue culture and neural grafts. Estimates of total cell number immediately prior to plating in culture indicated that cryopreserved tissue yields fewer cells, but when this reduced cell number is compensated for, and equal numbers of cells were plated in culture, approximately equal total numbers of neurons, as well as tyrosine hydroxylase (TH)-positive neurons, were present in cultures from cryopreserved and fresh tissue. Grafting of equal numbers of fresh and cryopreserved mesencephalic cells into the striatum of adult rats with large unilateral lesions of the nigrostriatal DA pathway tended to yield smaller grafts with fewer surviving TH-positive cells with less extensive neuronal processes when tissue was previously cryopreserved. However, grafts derived from freeze-stored tissue provided a similar timecourse and extent of behavioral recovery in amphetamine-induced rotational tests to that provided by fresh tissue grafts. Taken together, our findings indicate that while cryopreservation of mesencephalic tissue has its costs — reduced cell yield in cultures and grafts, and compromised morphology in grafts — sufficient numbers of cryopreserved neurons survive the grafting procedure to ameliorate behavioral signs of DA depletion in the lesioned rat model.

Identification of 2,3-dihydroxybenzoic acid as a Brucella abortus siderophore.

Brucella abortus grown in low-iron medium or in the presence of iron chelators [ethylenediamine-di(o-hydroxyphenylacetic acid) and 2,2-dipyridyl] showed reduced cell yields and released a material positive in chemical and biological assays for catechols. This material was purified from culture fluids of B. abortus 2308 by chromatography on agarose-iminodiacetic acid-Fe3+ and identified as 2,3-dihydroxybenzoic acid (2,3-DHBA) by thin-layer chromatography, paper electrophoresis, and UV-visible nuclear magnetic resonance and mass spectroscopy. No other major catechols were observed at different stages of growth, and 2,3-DHBA was also produced upon iron limitation by representative strains of B. abortus biotypes 1, 5, 6, and 9. Both synthetic 2,3-DHBA and the natural catechol relieved the growth inhibition of B. abortus 2308 by ethylenediamine-di(o-hydroxyphenylacetic acid), and 2,3-DHBA promoted 55Fe uptake by B. abortus 2308 by an energy-dependent mechanism. Two other monocatechols tested, 2,3-dihydroxybenzoyl-Ser and 2,3-dihydroxybenzoyl-Gly, also promoted 55Fe uptake. More complex catechol siderophores (agrobactin and enterobactin), hydroxamate siderophores (aerobactin, ferrichrome, and deferriferrioxamine mesylate [Desferal]), and an EDTA-related siderophore (rhizobactin) failed to mediate 55Fe uptake. B. abortus cells grown in low-iron medium or in medium with iron had similar rates of iron uptake when supplied with 55Fe-2,3-DHBA, and the release of 2,3-DHBA under iron starvation was not associated with the expression of new outer membrane proteins. These results suggest an uptake system in which only the synthesis of the siderophore is regulated by the iron available for growth.