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PubMedDate not supplied

Enhancing oxygen transfer in surface-aerated bioreactors by stable foams.

To enhance oxygen transfer in surface-aeration bioreactors, stabilized foams were generated to increase the gas-liquid interfacial area by slowly introducing coarse bubbles into media containing fetal bovine serum. The bubble sparging rates were so low (i.e., 20 and 50 mL/h) that the contribution to oxygen transfer from these bubbles was due to foaming instead of bubbling. Furthermore, no physical cell damage caused by bubble sparging was observed. Oxygen transfer coefficients, kLa, in the bioreactors were measured in cell-free media. Without the foam-stabilizing agent (i.e., serum), no appreciable change in kLa was observed due to the bubble sparging. On the other hand, with serum, kLa increased with increasing serum content and bubble sparging rate and corresponded well with the degree of foaming. With 10% fetal bovine serum and a bubble sparging rate of 50 mL/h, kLa increased approximately 90% compared with no foaming. The enhancing effect of foam on oxygen transfer in surface aeration bioreactors has been further demonstrated with hybridoma cultures simultaneously grown in three identical bioreactors with and without stabilized foams.

Aerobiosis↗

PubMed1988

Sensory interaction with central 'generators' during respiration in the dogfish.

The activity in sensory and motor nerves of the gills was recorded from selected branches of the vagus nerve in decerebrate dogfish, Scyliorhinus canicula. Vagal motoneuronal activity was observed at the start of the rapid pharyngeal contraction and was followed by sensory nerve activity which preceded the slow expansion phase. Rhythmical vagal motoneuronal activity was still present after all movements had been prevented by curare paralysis although the frequency of the rhythm was higher than in the ventilating fish. Electrical stimulation of vagal sensory fibres had 3 effects on the ventilatory movements. (1) It evoked a reflex contraction of several gill muscles after a latency of about 11 ms. (2) It could reset the respiratory cycle because a stimulus given during expansion delayed the onset of the subsequent contraction. (3) The stimulus could entrain the rhythm if it was given continuously at a frequency close to that of ventilation. The vagal motor rhythm was disrupted by trigeminal nerve stimulation in the paralyzed fish but not if the motor rhythm was being entrained by vagal nerve stimulation. Vagal sensory activity may be important, therefore, in maintaining the stability of the generating circuits.

Animals↗

PubMed1976

Rhythmic swimming activity in neurones of the isolated nerve cord of the leech.

1. Repeating bursts of motor neurone impulses have been recorded from the nerves of completely isolated nerve cords of the medicinal leech. The salient features of this burst rhythm are similar to those obtained in the semi-intact preparation during swimming. Hence the basic swimming rhythm is generated by a central oscillator. 2. Quantitative comparisons between the impulse patterns obtained from the isolated nerve cord and those obtained from a semi-intact preparation show that the variation in both dorsal to ventral motor neurone phasing and burst duration with swim cycle period differ in these two preparations. 3. The increase of intersegmental delay with period, which is a prominent feature of swimming behaviour of the intact animal, is not seen in either the semi-intact or isolated cord preparations. 4. In the semi-intact preparation, stretching the body wall or depolarizing an inhibitory motor neurone changes the burst duration of excitatory motor neurones in the same segment. In the isolated nerve cord, these manipulations also change the period of the swim cycle in the entire cord. 5. These comparisons suggest that sensory input stabilizes the centrally generated swimming rhythm, determines the phasing of the bursts of impulses from dorsal and ventral motor neurones, and matches the intersegmental delay to the cycle period so as to maintain a constant body shape at all rates of swimming.

Action Potentials↗

PubMed1990

Functional interaction among catalytic residues in subtilisin BPN'.

Variants of the serine protease, subtilisin BPN', in which the catalytic triad residues (Ser-221, His-64, and Asp-32) are replaced singly or in combination by alanine retain activities with the substrate N-succinyl-L-Ala-L-Ala-L-Pro-L-Phe-p-nitroanilide (sAAPF-pna) that are at least 10(3) to 10(4) above the non-enzymatic rate [Carter, P., Wells, J.A. Nature (London) 322:564-568, 1988]. A possible source of the residual activity was the hydrogen bond with the N delta 2 of Asn-155 that helps to stabilize the oxyanion generated in the tetrahedral transition state during amide bond hydrolysis by the wild-type enzyme. Replacing Asn-155 by Gly (N155G) lowers the turnover number (kcat) for sAAPF-pna by 150-fold with virtually no change in the Michaelis constant (KM). However, upon combining the N155G and S221A mutations to give N155G:S221A, kcat is actually 5-fold greater than for the S221A enzyme. Thus, the catalytic role of Asn-155 is dependent upon the presence of Ser-221. The residual activity of the N155G:S221A enzyme (approximately 10(4)-fold above the uncatalyzed rate) is not an artifact because it can be completely inhibited by the third domain of the turkey ovomucoid inhibitor (OMTKY3), which forms a strong 1:1 complex with the active site. The mutations N155G and S221A individually weaken the interaction between subtilisin and OMTKY3 by 1.8 and 2.0 kcal/mol, respectively, and in combination by 2.1 kcal/mol. This is consistent with disruption of stabilizing interactions around the reactive site carbonyl of the OMTKY3 inhibitor.(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine↗

PubMed1987

Cytoplasmic bar-like structures of alveolar type II cells: an ultrastructural study in freshly isolated cells from rat lungs.

Bar-like structures are tubular cytoplasmic inclusions found in situ in pulmonary epithelial type II cells of several animal species. The physiological significance and mode of formation of these inclusions are not fully established. In this paper, we describe bar-like structures as found in freshly isolated type II cells from rat lungs. Pulmonary cells were dissociated from the tissue with elastase and separated on a discontinuous density gradient of Percoll. The complete isolation procedure yielded 17 X 10(6) type II cells per animal (purity = 80%). Either from the crude cell suspensions or the purified preparations, only a small fraction of the type II cell population harbored the inclusions (less than 5%). It is shown that the bounding membranes of the bar-like structures can derive from the endoplasmic reticulum, the nuclear membrane, or the Golgi apparatus. Occasional connections with lamellar bodies were observed, and different levels of complexity in the bar-like structures were also found. The apparent rigid conformation and the orientation of the bar-like structures were taken as evidence for a role of the cytoskeleton in their formation. Because the inclusions do not appear to be new organelles or cellular structures performing a specific function, we propose that their formation may be a transient and limited cellular event in normal cells. However, the stabilization and the generation of the osmiophilic structures, as well as their overproduction, may reflect alterations of the normal physiology of the type II cells.

Animals↗

PubMed1990

Cellular interactions in metastasis.

The metastatic cascade is a sequence of events that must be completed for metastases to be established. The realization that tumors are heterogeneous, consisting of many different subpopulations differing in many characteristics, and the belief that there are selective events in the metastatic process have led several laboratories to isolate and characterize variants with both high and low metastatic potential. Typically, the highly metastatic variants have been able to form distant metastases when implanted into the subcutis. Such lines have been popular for studies of metastatic mechanisms and anti-metastatic therapy, but they may be atypical examples, and thus not the best experimental models. Recent studies indicate that normal tissue influences metastasis such that many tumors metastasize only if placed in the orthotopic site. Furthermore, some cells that do not metastasize individually are able to do so in conjunction with other variant subpopulations. Thus, mixtures of tumor cells in the tissue of origin can express a more malignant character. We review possible mechanisms for such influential interactions, as well as the role of cellular interactions in generating heterogeneity and stabilizing tumor characteristics.

Animals↗

PubMed1988

Isolation and characterization of Saccharomyces cerevisiae mutants resistant to T-2 toxin.

T-2 toxin, a trichothecene mycotoxin, inhibits the growth of Saccharomyces cerevisiae. We have isolated nine spontaneous S. cerevisiae mutants resistant to this toxin. The mutants were distinguished from the wild type according to their degree of resistance to T-2 toxin on media with dextrose or glycerol as the carbon source. Generation time, mutation stability and level of cross-resistance to roridin A, another trichothecene, were determined for each mutant. The T-2 toxin resistant mutants were further characterized by subsequent tests involving cross-resistance and collateral sensitivity to chlorampenicol, neomycin, paromomycin, ethidium bromide and thiolutin. Mutants have been placed into three subgroups and the mechanism of T-2 toxin resistance in each group has been postulated. Mutant HK1 is the first S. cerevisiae isolate resistant to roridin A. One particular isolate, mutant HK11, carries a single recessive nuclear mutation. This mutation was termed ttt (for T-2 toxin resistant).

Antifungal Agents↗

PubMed1978

Transfer of genetic information via isolated amphibian metaphase chromosomes.

The metaphase chromosome transfer system of McBride and Ozer (1973) has been adapted to a haploid, euploid, frog cell line. Genes coding for a deoxypyrimidine kinase and an enzyme responsible for a thymidine-specific saturable transport system have each been transferred at frequencies between 10(-6) and 10(-5) transferents per cell treated. Revertants for each of these two genes were observed at frequencies between 10(-8) and 10(-7) revertants per cell tested. Selfing controls showed no transferents. Two colonies were obtained in which cotransfer of both genes may have occurred. Activities of the transferred genes were assayed by incorporation of [3H]thymidine into alkali-stable, acid-precipitable material. Growth properties of 13 transferents in various media were also determined and presence of the appropriate enzymes inferred. These transferents were tested for stability early (25 generations) after transfer and were found to be stable. All 13 transferents possess the normal haploid number of chromosomes (n = 13) with no cytologically detectable chromosomal fragments.

Animals↗

PubMed1992

Round table on epidemiology and control of fox rabies.

The current epizootic of rabies in Europe has as its main host the fox. Oral vaccination of the fox population has proven to be particularly effective. It is clear that the major components for a successful vaccination programme are a potent and stable vaccine, and an effective baiting system; the latter should attract the target animal but no non-target species. Recently, vaccines of increased stability have been generated; amongst these is a vaccinia recombinant virus which expresses rabies virus glycoprotein. Consequently, both attenuated live virus vaccines and a recombinant vaccine are available for routine field vaccination of the fox population.

Animals↗

PubMed1985

Genetic transformation of the phytopathogenic bacteria, Erwinia chrysanthemi.

Erwinia chrysanthemi is an enterobacterium whose phytopathogenicity is due to its pectinolytic and cellulolytic activities. The CaCl2 mediated transformation procedure was successfully applied to two E. chrysanthemi wild type strains. The highest efficiency of transformation of E. chrysanthemi with pBR322 was found using 0.1 M CaCl2, 0.1 M MgCl2 treated cells and a heat pulse at 30 degrees C for 6 min. This yielded about 600 transformants per microgram of pBR322 DNA and 2.3 X 10(-6) per viable cell. Plasmid stability after twenty generations was lower than in E. coli: only 40-60% of the cells retained the plasmid in the absence of selective pressure. Based on this result, cloning in E. chrysanthemi with pBR322 vectors should therefore be possible, making it a potential host for cloning any gene for biomedical or industrial purposes.

Calcium Chloride↗

PubMed2025

Chemoselective Tagging of Protein Methacrylation.

Protein lysine methacrylation (Kmea) is a recently identified post-translational modification whose biofunction remains poorly understood. Until now, there has been no chemical labeling method for Kmea modification, which has severely hindered the discovery and functional studies of methacrylated proteins. Here, we developed a photocatalytic thia-Michael reaction system for the chemoselective labeling of protein methacrylation. By exploiting the dual effect of steric hindrance and the stability of the generated C-center radical, the reaction interference of the structural isomer crotonylation can be efficiently avoided. Based on this reaction, a multifunctional water-soluble benzenethiol-azide probe azDSH was designed and synthesized, and a workflow for the specific labeling, enrichment, and identification of Kmea proteins was developed. Proteomic identification of histone and nuclear protein extracts and whole-cell lysate revealed a number of novel Kmea proteins and modification sites besides histones, such as HMGB1, TdIF2, UHRF1, HNRPD, BRWD1, TAF1, TACC1, and SETD3, providing new targets for the study of epigenetic regulation. This study provides an effective method for the analysis of protein methacrylation modifications in biological systems.

Humans↗

PubMed1991

Familial transmission of alcohol use: IV. A seventeen-year follow-up on the relationships between parent and adult offspring alcohol use; Tecumseh, Michigan.

The sample for this study comprised 190 three member sets of father, mother, and adult son or daughter who were first interviewed in 1960 as part of Cardiovascular Examination I of the Tecumseh Community Health Study. At that time, alcohol data were collected from self-reports for both parents and offspring. In 1977 alcohol data were again collected for the adult offspring only, from self-reports. In 1960 offspring's drinking was significantly related to both fathers' and mothers' drinking and remained so in 1977 despite shifts over time in the proportions of offspring across five alcohol use categories. The majority of offspring did not fall into their parents' category, but the mode by and large reflected the parent category. The majority of offspring of non-drinkers did drink, but at low and not high volume; the majority of offspring of high volume drinkers drank at lower levels than their parents, and were not likely to be life-long abstainers, although they may have become past drinkers. Two non-drinking parents reinforced non-drinking in their adult offspring and two drinking parents reinforced the early onset and persistence of high volume drinking. Among offspring who changed their drinking level between 1960 and 1977, those who had drunk less than their parents were the most likely to have increased their drinking, and those who had drunk more than their parents were the most likely to have decreased their drinking. Patterns observed in this study may be viewed as intrafamilial sources of drinking stability transmitted across generations in a single community.

Adolescent↗

PubMed1989

Monitoring and selection of resistance to pyrethroids in the Australian sheep blowfly, Lucilia cuprina.

Field and laboratory populations of the Australian sheep blowfly, Lucilia cuprina (Wiedemann) (Calliphoridae), were surveyed by bioassay for possible resistance to the synthetic pyrethroids, a group of insecticides under development for blowfly control. A normal distribution of LC50 values was found using deltamethrin, the test pyrethroid, with no indication of specific resistance despite widespread use of deltamethrin on sheep to control the sheep body louse, Damalinia ovis (Schrank) (Trichodectidae). There was no cross-resistance to deltamethrin from existing organophosphate (OP) resistance nor from previous use of DDT. Selection with deltamethrin on a combined field strain, CSF85, increased the LC50 gradually over the first twenty generations until it stabilized at approximately 25x that of the unselected CSF85. This laboratory-induced resistance extended to other pyrethroids, cypermethrin (16x), cyhalothrin (25x) and cycloprothrin (10x), and increased the existing resistance of CFS85 to the OP diazinon (11x) and the carbamate, butacarb (83x).

Animals↗

PubMed1992

Replication origin mutations affecting binding of pSC101 plasmid-encoded Rep initiator protein.

To investigate the role of binding sites for Rep initiation protein in the replication of pSC101, a series of plasmids was constructed which carried different combinations of mutations in three binding sites within the minimal origin of replication. Mutation of all three sites reduced the affinity of purified Rep protein for the origin by 100-fold, as measured by a competition binding assay. Mutations in individual binding sites prevented binding of Rep protein to the mutant site but not to adjacent wild-type sites. Transformation efficiency, copy number, and stability over 150 generations were measured for each of the mutant plasmids. Unlike other similar plasmids related to pSC101, the Rep binding sites were found not to be equivalent. A mutation in the site RS1, proximal to repeated sequences which serve as DnaB helicase entry sites in oriC, had a severe effect on replication activity. A similar mutation in the distal site RS3 caused a reduction in copy number, but the mutant plasmid was stably maintained despite a broadened distribution of copy number within the population. A mutation in the middle RS2 site had no significant effect on pSC101 replication.

Bacterial Proteins↗

PubMed2025

Characterization and purification of Pseudomonas aeruginosa phages for the treatment of canine infections.

BACKGROUND: Pseudomonas aeruginosa is an opportunistic pathogen that causes infections in both human and veterinary medicine, presenting significant challenges in treatment because of biofilm production and its intrinsic resistance. This problem is exacerbated by the increase in acquired antimicrobial resistance. Bacteriophage (phage) therapy has emerged as a promising alternative for treating infection classically treated with antibiotics, offering a targeted approach to combat this infection. This study aimed to evaluate the therapeutic potential of 7 phages, focusing on their suitability for treating canine infections, as well as their purification and safety analysis for therapeutic use. RESULTS: Two self-isolated phages and five provided phages were analysed. All tested phages reduced bacterial load in vitro; however, their efficacy varied across different concentrations. The host range analysis revealed a spectrum between 9.8 and 68.6% of canine clinical P. aeruginosa isolates. In our in vitro tests 3 out of 7 phages were able to significantly reduce the biofilm biomass, achieving reductions up to 93.38%. The sequence analysis did not discover known virulence factors and genes connected to antimicrobial resistance mechanisms. The self-isolated phages were classified as lysogenic, whereas the other phages had a lytic infection cycle. Through the purification of the phages, high-titre phage preparations (> 1011 PFU/ml) were generated with high stability for at least 1.5 years. The tested endotoxin units are below the regulatory limits. CONCLUSION: Investigating phages as alternative treatment option seems promising with lytic phages covering a broad host range and a genomic potential for biofilm degradation. These findings support the development of phage cocktails as a targeted alternative for treating canine P. aeruginosa infections, particularly in cases of antibiotic resistance, and highlight the importance of selecting well-characterized lytic phages for therapeutic efficacy and safety.

Pseudomonas aeruginosa↗

PubMed1976

[The battery-state control. A new possibility for the control of pacemakers. Preliminary report (author's transl)].

After a brief examination of the technical problems of current pacemakers, with special reference to the battery state control, the authors present a new technique for such control. A power stabilizer able to generate a standard pulse of 4.3 in every condition of battery charge has been fitted on the power supply of a fixed rate pacemaker of normal production. By activating (through an external magnet) such apparatus, it is possible with an easy oscilloscopic measurement to obtain the real value of the battery voltage. Thus the comparison with previously taken measurements and the errors connected with the repetition of such measurements can be avoided. The stimulation rate and the pulse duration corresponding to the discharged state of the batteries can also be known in advance. The data obtained from the first two controls are reported.

Arrhythmias, Cardiac↗

PubMed1991

Nonradical oxidants of the phagocyte type induce the activation of plasmatic single chain- urokinase.

Single chain- urokinase (scu-PA) is the proenzyme of the plasminogen activator urokinase (tcu-PA). In human blood scu-PA is of great stability. Activated phagocytes generate large amounts of single chain- urokinase and of reactive oxidants (chloramines and HOCl). Since these cells participate in physiologic fibrinolysis, we were interested in the interaction between plasmatic scu-PA and chloramines. The oxidants dose dependently induce the activation of plasmatic scu-PA. Optimal activation of scu-PA occurs at about 3-5 mmol/l of chloramine-T. The findings suggest a control mechanism of scu-PA stability/activity by oxidatively modifiable plasma proteins, such as alpha-2-antiplasmin. The oxidation mechanism seems to be mediated by singlet molecular oxygen, an excited oxygen species. Basing on this scu-PA/oxidant synergism a sensitive and fast functional assay of scu-PA in human plasma is presented. Plasmatic inhibitors normally interfering with functional scu-PA measurements are inactivated by addition of chloramine-T, imitating the physiological oxidants generated by activated phagocytes. The scu-PA concentration in plasma of n = 36 healthy individuals has been determined to be 5.8 +/- 1.6 ng/ml. The lower detection limit of plasma scu-PA by the procedure described is about 1.5 ng/ml of plasma. By means of this technique scu-PA concentration during thrombolytic therapy can be measured within minutes in undiluted (direct) plasma samples, allowing adjustments of the scu-PA dosage. The present study gives further credence for a role of singlet molecular oxygen, possibly a new type of locally acting hormones (autacoid), in the regulation of the fibrinolytic pathway.

Adult↗

PubMed1991

[Establishment of transplantable HL-60 xenograft lines in athymic nude mice].

In vivo models of HL-60 cells were successfully established as ascites and/or solid forms in nude mice (BALB/c, nu/nu). HL-60 ascites and solid tumor cells produced 100% lethal takes after their 7th transplant generation and were stabilized at serial transplant intervals of 14 and 40 days respectively. Morphological studies demonstrated that the ascites and solid tumor cells exhibited morphological characteristics similar to those of HL-60 cells in vitro. The establishment of transplantable HL-60 xenograft lines provides a potential tool for the screening of effective differentiation inducers.

Animals↗