Biomedical subjects

B Y Chen

Publications and source records attributed to B Y Chen.

At least 19 recordsLinked to original sources

PubMed2007

Roles of mitogen-activated protein kinase pathways during Escherichia coli-induced apoptosis in U937 cells.

Escherichia coli (E. coli) infections play an important and growing role in the clinic. In the present study, we investigated the involvement of members of the mitogen-activated protein kinase (MAPK) superfamily, including extracellular signal-regulated kinase (ERK), c-Jun NH(2)-terminal kinase (JNK) and p38 MAPK, and caspase-3 and 9 activity in E. coli-induced apoptosis in human U937 cells. We found that E. coli induces apoptosis in U937 cell lines in a dose- and time-dependent manner, p38 MAPK and JNK were activated after 10 min of infection with E. coli. In contrast, ERK1/2 was down-regulated in a time-dependent manner. The levels of total (phosphorylation state-independent) p38 MAPK, JNK and ERK1/2 did not change in E. coli-infected U937 cells at all times examined. Moreover, exposure of U937 cells to E. coli led to caspase-3 and 9 activity. For the evaluation of the role of MAPKs, PD98059, SB203580 and SP600125 were used as MAPKs inhibitors for ERK1/2, p38 MAPK and JNK. Inhibition of ERK1/2 with PD98059 caused further enhancement in apoptosis and caspase-3 and 9 activity, while a selective p38 MAPK inhibitor, SB203580 and JNK inhibitor, SP600125 significantly inhibited E. coli-induced apoptosis and caspase-3 and 9 activity in U937 cells. The results were further confirmed by the observation that the caspase inhibitors Z-DEVD-FMK and Z-LEHD-FMK blocked E. coli-induced U937 apoptosis. Taken together, we have shown that E. coli increase p38 MAPK and JNK and decrease ERK1/2 phosphorylation and increase caspase-3 and 9 activity in U937 cells.

Apoptosis↗

PubMed2003

Risk factors of adverse drug reaction caused by nimesulide in Shanghai patients with osteoarthropathy.

The aim of this study was to investigate the risk factors for adverse drug reactions (ADRs) to nimesulide in patients from Shanghai with osteoarthropathy. A retrospective epidemiological study was performed to obtain information (observational variables) on demographics, primary disease, family history of disease, quality of life, dietary habits, lifestyle, use of nonsteroidal anti-inflammatory drugs (NSAIDs) and ADR history of NSAIDs. Univariate and multivariate analyses were performed to establish the relationship between these observational variables and the occurrence of ADRs caused by nimesulide. Among the 726 variables, five risk factors for ADRs to nimesulide were identified. The study showed an increased risk for ADR occurrence with increased scoring of the following four factors: (i) "Concomitant drug therapy" (odds ratio [OR]: 4.66, 95% confidence intervals [CI]: 1.26-17.26, p < 0.05); (ii) "Compared with six months ago, how would you rate your health in general now?" (OR: 1.38, 95% CI: 1.03-1.84, p < 0.05); (iii) "General feeling of health status" (OR: 1.27, 95% CI: 1.03-1.56, p < 0.05) and (iv) "1 expect my health to get worse" (OR: 2.05, 95% CI: 1.22-3.44, p < 0.01). There was a decreased risk for ADR occurrence with increased scoring of the factor "Have you ever suffered from depression that impacted on your life?" (OR: 0.15, 95% CI: 0.03-0.66, p < 0.05). The predictive model for the overall incidence rate of ADRs caused by nimesulide was then established. In conclusion, the predictive model helps to indicate the risk of ADRs to nimesulide and provides clinicians with an alternative method for decision making when prescribing this drug.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed2001

Analgesic activity and opioid receptor selectivity of stereoisomers of ohmefentanyl isothiocyanate.

Ohmefentanyl is a very potent and highly selective agonist for mu-opioid receptors. We now study analgesia, in vitro activity and opioid receptor affinity of the stereoisomers of ohmefentanyl isothiocyanate. We found that some isomers of ohmefentanyl isothiocyanate had a potent analgesic effect and that all isomers except (3R,4S,2'S)-ohmefentanyl isothiocyanate had a more potent inhibitory action on the electrically evoked contractions of mouse vas deferens than of guinea pig ileum. The inhibitory actions could be antagonized by naloxone. However, compared with the activity of the corresponding stereoisomers of ohmefentanyl, these ohmefentanyl isothiocyanates had significantly reduced analgesia and in vitro activity. They also inhibited the binding of [3H]DPDPE ([D-Pen(2),D-Pen(5)]enkephalin) and [3H]DAGO ([D-Ala(2),Mephe(4),Gly-ol(5)]enkephalin) to opioid receptors in mouse brain membranes. The inhibitory effect of stereoisomers of ohmefentanyl isothiocyanate at mu-opioid receptors was markedly lower than that of their parent compounds. The affinity of stereoisomers of ohmefentanyl isothiocyanate for delta-opioid receptors was, however, greater than or equal to that of their corresponding stereoisomers of ohmefentanyl. The results showed that the introduction of an isothiocyanato group into the phenyl ring in position-1 of ohmefentanyl reduced bioactivity and affinity to mu-opioid receptors but that the selectivity of these compounds for delta-opioid receptors was enhanced. Isomer (3R,4S,2'R)-ohmefentanyl isothiocyanate showed highest selectivity for delta-opioid receptors (K(i)(mu)/K(i)(delta)=13.6) and potent analgesic activity (ED(50)=0.25 mg/kg).

Analgesics, Opioid↗

PubMed2001

Identifications, classification, and evolution of the vertebrate alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) receptor subunit genes.

The AMPA receptor (AMPAR), a pharmacologically defined ionotropic glutamate receptor, mediates fast excitatory synaptic transmission in the vertebrate central nervous system. Mammalian and avian AMPARs are assembled from the products of four genes (GRIA1-GRIA4) conserved in their translated sequences and gene organizations. Teleost fish also express AMPAR subunits; however, the AMPAR genes have not been extensively investigated in lower vertebrates. To elucidate the evolution of vertebrate AMPAR genes, reverse-transcriptase PCR-based surveys of subunits expressed in the brains of eight nonmammalian vertebrates were performed. The newly cloned vertebrate AMPAR subunits were classified by their sequence identities to the mammalian AMPAR subunits. The results of molecular and phylogenetic analyses indicated that the members of the AMPAR gene family increased from two in the jawless hagfish to four in the tetrapods and the shark and to more than four in the teleost fish. The sizes of AMPAR gene families correlate well with those of many multigene families observed in various vertebrates. Moreover, all vertebrates expressed at least one AMPAR subunit bearing an arginine (R) at the Q/R site, at which no invertebrate glutamate receptor subunit has been found to have an R residue, suggesting that the low calcium-permeable AMPARs appeared at early evolutionary stages of vertebrate central nervous systems. Uniquely, the loop 1 (L1) regions between hydrophobic domain 1 and hydrophobic domain 2 of the hagfish putative GRIA2 and all the teleost GRIA1 subunits were much longer than those of the remaining known ionotropic glutamate receptor subunits. The length and sequence of the L1 of teleost GRIA1 subunits were heterogeneous, suggesting that the amino acid residues in L1 were not highly selected.

Amino Acid Sequence↗

PubMed2001

Acute toxicity of heavy metals to acetate-utilizing mixed cultures of sulfate-reducing bacteria: EC100 and EC50.

Acid mine drainage from abandoned mines and acid mine pit lakes is an important environmental concern and usually contains appreciable concentrations of heavy metals. Because sulfate-reducing bacteria (SRB) are involved in the treatment of acid mine drainage, knowledge of acute metal toxicity levels for SRB is essential for the proper functioning of the treatment system for acid mine drainage. Quantification of heavy metal toxicity to mixed cultures of SRB is complicated by the confounding effects of metal hydroxide and sulfide precipitation, biosorption, and complexation with the constituents of the reaction matrix. The objective of this paper was to demonstrate that measurements of dissolved metal concentrations could be used to determine the toxicity parameters for mixed cultures of sulfate-reducing bacteria. The effective concentration, 100% (EC100), the lowest initial dissolved metal concentrations at which no sulfate reduction is observed, and the effective concentration, 50% (EC50), the initial dissolved metal concentrations resulting in a 50% decrease in sulfate reduction, for copper and zinc were determined in the present study by means of nondestructive, rapid physical and chemical analytical techniques. The reaction medium used in the experiments was designed specifically (in terms of pH and chemical composition) to provide the nutrients necessary for the sulfidogenic activity of the SRB and to preclude chemical precipitation of the metals under investigation. The toxicity-mitigating effects of biosorption of dissolved metals were also quantified. Anaerobic Hungate tubes were set up (at least in triplicate) and monitored for sulfate-reduction activity. The onset of SRB activity was detected by the blackening of the reaction mixture because of formation of insoluble ferrous sulfide. The EC100 values were found to be 12 mg/L for copper and 20 mg/L for zinc. The dissolved metal concentration measurements were effective as the indicators of the effect of the heavy metals at concentrations below EC100. The 7-d EC50 values obtained from the difference between the dissolved metal concentrations for the control tubes (tubes not containing copper or zinc) and tubes containing metals were found to be 10.5 mg/L for copper and 16.5 mg/L for zinc. Measurements of the turbidity and pH, bacterial population estimations by means of a most-probable number technique, and metal recovery in the sulfide precipitate were found to have only a limited applicability in these determinations.

Acetates↗

PubMed2001

[Effect of Chinese herbal medicine for nourishing yin and removing fire on biosynthesis, secretion and regulative mechanism of gonadotropin-releasing hormone in hypothalamus].

OBJECTIVE: To elucidate the effect of Chinese herbal medicine (CHM) for nourishing Yin and removing fire on the biosynthesis, secretion and regulative mechanism of gonadotropin-releasing hormone (GnRH) in hypothalamus. METHODS: The brain slices of medial basal hypothalamus of adolescent rats, which had been fed with CHM, were incubated. The content of GnRH in incubative liquid was determined during the slices were stimulating with high KC1 to observe the change of GnRH biosynthesis from tonic secretory center of GnRH (arcuate nucleus and ventromedial nucleus) in hypothalamus. The integrated optic density of GnRH positive immunoreactive substance in preoptic area of hypothalamus was determined by immunohistochemistry and image processing to observe the change of GnRH content in pulsative secretory center of GnRH (medial preoptic nucleus) in hypothalamus. The push-pull perfusion of medial preoptic area in hypothalamus was performed. The content of GnRH in serial perfusates was determined by radioimmunoassay (RIA) to observe the change of frequency and amplitude of GnRH pulse releasing from medial preoptic area in hypothalamus. The content of aspartic acid, glutamic acid and gamma-amino butyric acid in the perfusate was determined by high performance liquid chromatography-fluorometry, and the content of beta-endorphic in the perfusate was determined by RIA to observe the change of releasing amount of exciting aminoacid neurotransmitter and beta-endorphin from pulsative secretory center of GnRH (medial preoptic area) in hypothalamus. RESULTS: CHM could markedly reduce the content of GnRH in medial basal hypothalamus (arcuate nucleus and veatromeolial nucleus) and preoptic area (meolical preoptic nucleus) of hypothalamus, and could obviously lower the frequency and amplitude of GnRH pulse releasing from medial preoptic nucleus, It also could markedly decrease the releasing amount of aspartic acid and glutamic acid, while obviously increase the releasing amount of gamma-amino butyric acid and beta-endorphin from medial preoptic area of hypothalamus. CONCLUSION: CHM could markedly reduce the activity of GnRH neurons in hypothalamus through inhibiting the releasing of central exciting aminoacid neurotransmitter and promoting the releasing of central inhibiting aminoacid neurotransmitter and beta-endorphin, thereby, obviously decrease the biosynthesis and secretion of GnRH from tonic and pulsative secretory center of GnRH in hypothalamus. It could be one of chief effective mechanism of CHM in efficiently treating the idiopathic precocious puberty.

Animals↗

PubMed2000

Variable pulmonary responses from exposure to concentrated ambient air particles in a rat model of bronchitis.

Chronic bronchitis may be considered a risk factor in particulate matter (PM)-induced morbidity. We hypothesized that a rat model of human bronchitis would be more susceptible to the pulmonary effects of concentrated ambient particles (CAPs) from Research Triangle Park, NC. Bronchitis was induced in male Sprague-Dawley rats (90-100 days of age) by exposure to 200 ppm sulfur dioxide (SO2), 6 h/day x 5 days/week x 6 weeks. One day following the last SO2 exposure, both healthy (air-exposed) and bronchitic (SO2-exposed) rats were exposed to filtered air (three healthy; four bronchitic) or CAPs (five healthy; four bronchitic) by whole-body inhalation, 6 h/day x 2 or 3 days. Pulmonary injury was determined either immediately (0h) or 18 h following final CAPs exposure. The study protocol involving 0 h time point was repeated four times (study #A, November, 1997; #B, February, 1998; #C and #D, May, 1998), whereas the study protocol involving 18 h time point was done only once (#F). In an additional study (#E), rats were exposed to residual oil fly ash (ROFA), approximately 1 mg/ m(3)x6 h/day x 3 days to mimic the CAPs protocol (February, 1998). The rats allowed 18 h recovery following CAPs exposure (#F) did not depict any CAPs-related differences in bronchoalveolar lavage fluid (BALF) injury markers. Of the four CAPs studies conducted (0 h time point), the first (#A) study (approximately 650 microg/m3 CAPs) revealed significant changes in the lungs of CAPs-exposed bronchitic rats compared to the clean air controls. These rats had increased BALF protein, albumin, N-acetyl glutaminidase (NAG) activity and neutrophils. The second (#B) study (approximately 475 microg/m3 CAPs) did not reveal any significant effects of CAPs on BALF parameters. Study protocols #C (approximately 869 microg/m3 CAPs) and #D (approximately 907 microg/m3 CAPs) revealed only moderate increases in the above mentioned BALF parameters in bronchitic rats exposed to CAPs. Pulmonary histologic evaluation of studies #A, #C, #D, and #F revealed marginally higher congestion and perivascular cellularity in CAPs-exposed bronchitic rats. Healthy and bronchitic rats exposed to ROFA (approximately 1 mg/m3) did not show significant pulmonary injury (#E). Analysis of leachable elemental components of CAPs revealed the presence of sulfur, zinc, manganese, and iron. There was an apparent lack of association between pulmonary injury and CAPs concentration, or its leachable sulfate or elemental content. In summary, real-time atmospheric PM may result in pulmonary injury, particularly in susceptible models. However, the variability observed in pulmonary responses to CAPs emphasizes the need to conduct repeated studies, perhaps in relation to the season, as composition of CAPs may vary. Additionally, potential variability in pathology of induced bronchitis or other lung disease may decrease the ability to distinguish toxic injury due to PM.

Acetylglucosaminidase↗

PubMed2000

Linkage of hiccup with heartbeat.

We explored a possible link between the cardiac cycle and the timing of recurrent hiccups in 10 patients with chronic, intractable hiccups. Recordings made during daytime naps in a sleep laboratory included sleep state; electrocardiogram; and respiration by means of a thermistor to detect airflow, bands around the rib cage and abdomen to assess expansion, and a bipolar surface electrode electromyogram over parasternal intercostal muscles. Hiccups could be detected on the abdominal bands and the parasternal electromyogram. The time of occurrence of each hiccup and each R wave in a continuous tracing of 100 or more hiccups were recorded and analyzed together with semiquantitive estimates of the phase of hiccup respiration. Whereas the hiccup rate ranged from approximately one-third to one-eighth of heart rate and was more variable than heart rate, hiccups showed a tendency, stronger in some subjects than others, to occur in midsystole. Variation in R-wave-R-wave (R-R) interval in association with hiccups was found in five patients. In three of these patients, hiccups were synchronized with respiration so that the cyclic change in R-R interval posthiccup could be explained as sinus arrhythmia, but, in two patients, the hiccups were not synchronized with respiration, so that hiccups are most likely responsible for the variation in heart rate. Also, the variation of R-R interval with hiccups suggests that there is some phasic autonomic efferent activity associated with hiccups.

Aged↗

PubMed2000

[Studies of the genetic polymorphism of Schistosoma japonicum (Chinese mainland strains)].

In order to analyze the interspecies diversity and the extent of diversity among Schistosoma japonicum Chinese mainland strains, the genetic variation on gene level among 6 isolates collected from Jiangxi, Hunan, Hubei, Anhui, Sichuan, Yunnan and a cultured isolate from a laboratory were studied using molecular biological technique. There were only two different bases at position 112 and 143 in 536 bp sequence of 28S rDNA-D2 domain between Anhui and Yunnan isolates, the homology was 99.6%. The result could be explained the reason of why the migration rates of single chain 28S rDNA-D2 domain among the above 7 isolates were the same completely in PCR-SSCP. However, comparing with the sequences of the Philippine isolate of S. japonicum, S. mansoni and S. aematobium, there were 6, 94 and 93 different bases and the homologies were 98.9, 82.5 and 82.7 per cent separately. With 8 restriction endonucleases to analyze the ITS of rDNA obtained by PCR from the 7 isolates, the results showed that only 3 minor bands were different, e.g. 5.3% of total 58 fragments. It was suggested that the ITS of rDNA among 7 isolates were highly conserved. Using randomly amplified polymorphic DNA (RAPD) to analyze the genetic diversity of the genomes of the 7 isolates, the average genetic distance (D) calculated from total 284 amplified fragments was 0.22. The maximum D was 0.30 and existed between Anhui and Yunnan isolates. The minimum D was 0.13 and existed between Sichuan and Yunnan isolates. The clustering analysis of genetic distances showed that the 7 isolates could be gathered in one group. From above three results, it could be considered that the genetic diversity on gene level among S. japonicum Chinese mainland strains was very low.

Animals↗

PubMed1998

PCR cloning and characterization of multiple ADP-glucose pyrophosphorylase cDNAs from tomato.

Four ADP-glucose pyrophosphorylase (AGP) cDNAs were cloned from tomato fruit and leaves by the PCR techniques. Three of them (agp S1, agp S2, and agp S3) encode the large subunit of AGP, the fourth one (agp B) encodes the small subunit. The deduced amino acid sequences of the cDNAs show very high identities (96-98%) to the corresponding potato AGP isoforms, although there are major differences in tissue expression profiles. All four tomato AGP transcripts were detected in fruit and leaves; the predominant ones in fruit are agp B and agp S1, whereas in leaves they are agp B and agp S3. Genomic southern analysis suggests that the four AGP transcripts are encoded by distinct genes.

Amino Acid Sequence↗

PubMed1998

Characterization of bacteriophage lambda Q- mutant for stable and efficient production of recombinant protein in Escherichia coli system.

We previously demonstrated that the lambda system integrated into the host chromosome can overcome the instability encountered in continuous operations of unstable plasmid-based expression vectors. High stability of a cloned gene in a lysogenic state and a high copy number in a lytic state provide cloned-gene stability and overexpression in a two-stage continuous operation. But the expression by the commonly used S- mutant lambda was only twice as high as that of the single copy. To increase the expression in the lambda system, we constructed a Q- mutant lambda vector that can be used in long-term operations such as a two-stage continuous operation. The Q- mutant phage lambda is deficient in the synthesis of proteins involved in cell lysis and lambda DNA packaging, while the S- mutant is deficient in the synthesis of one of two phage proteins required for lysis of the host cell and liberation of the progeny phage. Therefore, it is expected that the replicated Q- lambda DNA containing a cloned gene would not be coated by a phage head and would remain naked for ample expression of the cloned gene and host cells would not lyse easily and consequently would produce larger amounts of cloned-gene products. The beta-galactosidase expression per unit cell by the Q- mutant in a lytic state was about 30 times higher than that in a lysogenic state, while the expression by the commonly used S- mutant in a lytic state was twice as high as that in a lysogenic state. The optimal switching time of the Q- mutant from the lysogenic state to the lytic state for the maximum production of beta-galactosidase was 5.3 h, which corresponds to an early log phase in the batch operation.

Bacteriophage lambda↗

PubMed1998

ADP-glucose pyrophosphorylase is localized to both the cytoplasm and plastids in developing pericarp of tomato fruit.

The intracellular location of ADP-glucose pyrophosphorylase (AGP) in developing pericarp of tomato (Lycopersicon esculentum Mill) has been investigated by immunolocalization. With the use of a highly specific anti-tomato fruit AGP antibody, the enzyme was localized in cytoplasm as well as plastids at both the light and electron microscope levels. The immunogold particles in plastids were localized in the stroma and at the surface of the starch granule, whereas those in the cytoplasm occurred in cluster-like patterns. Contrary to the fruit, the labeling in tomato leaf cells occurred exclusively in the chloroplasts. These data demonstrate that AGP is localized to both the cytoplasm and plastids in developing pericarp cells of tomato.

Chloroplasts↗

PubMed1998

Fresh vs aged benzylpenicillin on non-IgE responses in mice.

AIM: To study whether or not the freshly prepared benzylpenicillin could induce different non-IgE antibody response from aged benzylpenicillin. METHODS: Antibody response was determined by enzyme-linked immunosorbent assay (ELISA). Antigen molecules recognized by antibodies and antigenic cross reactions were tested by hapten inhibition assay. RESULTS: Isotypes of specific non-IgE antibodies induced by freshly prepared benzylpenicillin were mainly IgM, and then IgG and IgA. Some parts of specific antibodies recognized benzylpenicillin molecule and major parts combined with degraded or transforming products. Isotypes of antibodies responsible for cross reaction were mainly IgG between benzylpenicillin and ampicillin and IgM between benzylpenicillin and piperacillin. CONCLUSION: Freshly prepared and aged benzylpenicillin induced different non-IgE antibody response.

Ampicillin↗

PubMed1998

[Effects of electroacupuncture on the expression of estrogen receptor protein and mRNA in rat brain].

In order to show some light on the possible molecular mechanism of the effects of acupuncture on the hypothalamic-pituitary-ovarian axial function, radioimmunoassay (RIA), RNA dot blot and Northern blot, monoclonal antibody immuno-histochemistry and computer image analysis technique were used to study the effects of electroacupuncture (EA) on the blood level of estradiol (E2) and the expression of estrogen receptor protein and mRNA in the ovariectomized rat brain. The results show that ovariectomy induced a decrease of blood E2 level and increase of the expression of estrogen receptor protein and mRNA in the brain. All these effects could be remarkably reversed by previous EA treatment of ovariectomized rats. EA in intact rat, however, had no effects on blood E2 and expression of estrogen receptor. The above results suggest that EA at some effective acupoints may activate the production of body estrogen, resulting in a long term increase or suppression at the level of gene(s) expression and consequent normalization on the dysfunction of hypothalamic-pituitary-ovarian axis.

Animals↗

PubMed1997

Multiple forms of ADP-glucose pyrophosphorylase from tomato fruit.

ADP-glucose pyrophosphorylase (AGP) was purified from tomato (Lycopersicon esculentum Mill.) fruit to apparent homogeneity. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis the enzyme migrated as two close bands with molecular weights of 50,000 and 51,000. Two-dimensional polyacrylamide gel electrophoresis analysis of the purified enzyme, however, revealed at least five major protein spots that could be distinguished by their slight differences in net charge and molecular weight. Whereas all of the spots were recognized by the antiserum raised against tomato fruit AGP holoenzyme, only three of them reacted strongly with antiserum raised against the potato tuber AGP large subunit, and the other two spots (with lower molecular weights) reacted specifically with antisera raised against spinach leaf AGP holoenzyme and the potato tuber AGP small subunit. The results suggest the existence of at least three isoforms of the AGP large subunit and two isoforms of the small subunit in tomato fruit in vivo. The native molecular mass of the enzyme determined by gel filtration was 220 +/- 10 kD, indicating a tetrameric structure for AGP from tomato fruit. The purified enzyme is very sensitive to 3-phosphoglycerate/inorganic phosphate regulation.

Blotting, Western↗

PubMed1997

Acupuncture normalizes dysfunction of hypothalamic-pituitary-ovarian axis.

This article summarizes the studies of the mechanism of electroacupuncture (EA) in the regulation of the abnormal function of hypothalamic-pituitary-ovarian axis (HPOA) in our laboratory. Clinical observation showed that EA with the effective acupoints could cure some anovulatory patients in a highly effective rate and the experimental results suggested that EA might regulate the dysfunction of HPOA in several ways, which means EA could influence some gene expression of brain, thereby, normalizing secretion of some hormones, such as GnRH, LH and E2. The effects of EA might possess a relative specificity on acupoints.

Adrenal Glands↗

PubMed1996

Bioreactor studies on temperature induction of the Q- mutant of bacteriophage lambda in Escherichia coli.

The parasite-host interactions between bacteriophage lambda (denoted as lambda) and Escherichia coli bacteria were studied in different bioreactor systems. Although the replicated lambda-DNA of Q- mutant remains naked for a longer time to reach a high gene expression, the epidemic of lambda-infection and the coevolutionary host-phage relations limit the temperature induction efficiency. The temperature induction is strongly dependent upon the susceptible population density at which lambda-infection is activated. Maximum beta-galactosidase expression occurs at the threshold of the infection system. According to this concept, the lethal level of parasitic lambda to hosts is approx. 5 x 10(6) pfu/ml. Since a higher phage lambda burden is exerted upon host cells at a low ODsh, the system moves towards virulence reduction for total survival. Prey-predator isocline analysis is used to consider the stability of the outcome of infection. The host growth has a destabilizing effect at lower population densities and a stabilization effect at higher population. Based upon the predictions, a substrate enrichment enhances bacterial growth and reporter protein production. However, the operations still need to follow the trajectory of threshold tie line to guarantee maximal productivity. Since the washout of infected cells reduces induction performance in continuous cultures, a batch mode of operation is better than continuous stirred tank reactor (CSTR) mode to achieve high gene expression. The threshold cell density regulates induction performances and therefore produces the optimal gene expression by maintaining maximal viable cells that provide sufficient resources for lambda expression.

Bacteriophage lambda↗

PubMed1996

Random amplified polymorphic DNA markers of the Brassica alboglabra chromosome of a B. campestris-alboglabra addition line.

The alien C-genome chromosome in a Brassica campestris alboglabra monosomic addition line was characterized by random amplified polymorphic DNA (RAPD) analysis. The alien chromosome carried three loci, Ec, Wc and Lap-1C, controlling synthesis of erucic acid, white flower colour and a fast-migrating band of leucine aminopeptidase (Lap-1Cc) respectively. The RAPD analysis revealed 17 markers specific to the alien chromosome. Among 45 offspring plants from the selfed addition line the alien C-chromosome was transmitted to 15 plants, four plants had only parts of this chromosome and the remaining 26 plants did not carry the chromosome.

Alleles↗