Bacterial growth inhibition by overproduction of protein

Multicopy plasmids that have been engineered to produce large quantities of a single gratuitous (non-functional, non-toxic) protein are often problematic. When fully induced, these engineered constructions produce very sick bacteria. The reasons for this may be found in the physiology of wild-type laboratory strains that have been selected to grow at maximum rates with optimal quantities of their proteins. Such bacteria apparently experience the accumulation of gratuitous proteins as an internal shift down and they respond to this with a starvation response. Unlike the shift down associated with a change of growth media, the production of large quantities of gratuitous protein is not associated with a new pre-programmed steady-state of balanced growth. Consequently, the starvation response continues until the bacteria commit suicide by, among other things, destroying their ribosomes.

[Obesity-hypoventilation syndrome]

5 cases with obesity-hypoventilaion syndrome were reported. The clinical manifestations were obesity, palpitation, dyspnea, lethargy, cyanosis, distention of cervical vein, edema, enlargement of liver and hypertension. All of them were initially diagnosed as chronic bronchitis or heart diseases. Pulmonary function test showed restrictive ventilative defect and hypercapnia with hypoxemia. Mouth oclusion pressure at 0.1 second was higher than the normal value. The response to CO2 was decreased. Hypertrophy of right heart was shown in ECG and X-ray film improvement in symptoms and blood gases analyses were found to be associated with body weight decrease in a follow up period of one year.

Endothelium-dependent hyperpolarization of vascular smooth muscle: role for a non-nitric oxide synthase product

There is now a considerable evidence that indicates that there is non-NO/prostanoid mediated vasodilation/hyperpolarization mechanism in a variety of blood vessels from different species. It is argued that a factor, EDHF, is responsible for mediating these cellular events and, like NO, EDHF is synthesized and released, in a Ca(2+)-dependent manner, from endothelial cells and activates vascular K+ channel(s) with the predominant evidence suggesting K(Ca) (iberiotoxin and/or apamin sensitive) though this remains to be absolutely confirmed. A number of studies also indicate that a cytochrome P-450 metabolite of arachidonic acid, namely an epoxyeicosatrienoic acid, may serve as the chemical messenger between endothelial and vascular smooth muscle cells. Evidence confirming that there is chemical transmission between endothelial and vascular smooth muscle cells is, however, minimal. Although significant progress has been recently made, much needs to be discovered concerning the nature, synthesis, release, vascular effects as well as the role of EDHF in normal and diseased vascular tissue.

[Effect of RII on the biological properties of human nasopharyngeal carcinoma cell lines]

N(4-hydroxycarbophenyl) retinamide (RII) is a new synthetic analog of retinoids with low toxicity. Its effect on the biological properties associated with tumor malignant behavior of human nasopharyngeal carcinoma cell lines (HNCs), including CNE-2Z parent cell lines and their variants L2, H2, L4 was studied. RII (10(-5) mol/L) caused detectable morphologic differentiation of HNCs. It inhibited growth of HNCs in vitro and decreased ability of these cells to penetrate matrigel-coated filters by using a reconstituted basement membrane invasion assay. These results suggested that RII might be a kind of useful anticancer drug.

[Apoptosis of tumor cells in lectin-dependent lymphokine-activated killer cell-mediated cytotoxicity]

By using DNA electrophoresis and propidium iodide (PI) staining flow cytometry (FACS) analysis, we studied the mechanisms of lymphokine-activated killer (LAK) cell-mediated cytotoxicity. In the presence of pokeweed mitogen (PWM), human LAK cells induced DNA fragmentation of two leukemic cell lines (U937 cells and Raji cells) and two solid tumor cell lines (SW1116 cells and Hep-2 cells), a hallmark of apoptosis. The reactions were carried out at the effector/target ratio of 1:1 and in 4 hr coculture. Pretreatment with RNA and protein synthesis inhibitors (actinomycin D and cycloheximide) did not prevent the target cells from apoptosis. As the TNF-resistant tumor cell lines such as SW1116 cells and Raji cells were also triggered to apoptosis, other factors than TNF would play the role. DNA-PI staining FACS analysis also suggested that a part of LAK cells underwent apoptosis to some extent during incubation with target cells. The results provide a new way to investigate the mechanisms of cytotoxicity of LAK cells and to enhance the efficacy of adoptive tumor therapy with LAK cells.

Determination of human immunodeficiency virus RNA in plasma and cellular viral DNA genotypic zidovudine resistance and viral load during zidovudine-didanosine combination therapy

Eleven human immunodeficiency virus (HIV)-infected subjects on long-term zidovudine (ZDV) therapy had didanosine (ddI) added to their antiretroviral regimen. HIV RNA in plasma was quantitated by branched-DNA signal amplification assay. Peripheral blood mononuclear cell (PBMC) HIV viral DNA was quantitated by PCR. The relative amounts of wild-type (WT) sequence, ddI resistance-associated codon changes (reverse transcriptase [RT] gene codon 65 K-->R [RT K65R], RT 174V, RT I135K/T/V, and RT M184I/V), and ZDV resistance-associated codon change (RT T215Y/F) from HIV RNA in plasma and RT T215Y/F from PBMC viral DNA were determined by differential hybridization of PCR products from 10 of 11 subjects. All subjects had evidence of RT T215Y/F mutation in both RNA in plasma and PBMC DNA at baseline. Subjects with a mixture of WT and RT T215Y/F HIV RNA in plasma at baseline demonstrated a decline in RNA levels in plasma after the addition of ddI. However, after 6 months of ZDV-ddI therapy, WT HIV RNA in plasma was undetectable in all subjects who had demonstrated a mixture at baseline. Subjects with only RT T215Y/F RNA present in plasma at baseline remained so and demonstrated no decline in RNA levels in plasma. In all subjects, no significant changes in PBMC DNA viral load and RT T215Y/F or WT levels were seen. HIV RNA in plasma demonstrated a significantly higher RT T215Y/F mutant/WT ratio than that of PBMC viral DNA, both at baseline and after ZDV-ddI combination therapy in all subjects. No subjects developed mutations associated with ddI resistance at codons 65, 74, 135, and 184 during this study. This study suggests that determination of relative amounts of RT T215Y/F and WT species from HIV RNA in plasma at baseline may be predictive of virologic response during ZDV-ddI combination therapy.

Ribosome mutants with altered accuracy translate with reduced processivity

We have determined whether or not there is a correlation between the accuracy of tRNA selection and the processivity of translation by mutant ribosomes. In our assay the estimation of processivity was made from a system in which transcription is dependent on T7 RNA polymerase in order to eliminate the influence of transcriptional polarity on our measurements. We found that the processivity of translation is reciprocally correlated to the degree with which mutant ribosomes restrict nonsense suppression events. This is observed when transcription is from both T7 RNA polymerase and Escherichia coli RNA polymerase. In other words, we have confirmed the expected correlation between increased accuracy of tRNA selection and decreased processivity of translation. No such monotonic correlation was obtained with ribosome ambiguity (ram) mutants, though all of these were less processive than wild-type ribosomes. In addition, streptomycin was found to simultaneously stimulate tRNA selection errors and processivity of translation for a mutant that is partially dependent on streptomycin. These data suggest that the growth rates of ribosome mutants are significantly decreased by the degree to which their processivity in translation is affected. Furthermore, we suggest that streptomycin dependence is a phenomenon reflecting the interplay of the restrictive mutation and antibiotic on the processivity of translation.

Inhibitory effects of 2-[(diethylamino)acetyl]-1,2,3,4-tetrahydro-6, 7-dimethoxyl-1-[1'-(6"-methoxy-2"-naphthalenyl)ethyl]-isoquinoline on isolated guinea pig papillary muscle and heart atrium

AIM

To investigate the cardiac actions of 2-[(diethylamino)acetyl]-1,2,3,4-tetrahydro-6, 7-dimethoxyl-1-[1'-(6"-methoxy-2"-naphthalenyl) ethyl]-isoquinoline (CPU57) by comparison with nifedipine and focus on its mechanism of actions.

METHOD

The following were measured and recorded: 1) the rate and contraction of spontaneous beating of the guinea pigs right heart atrium, 2) the isometric tension of the electrically stimulated left heart atrium and the right papillary muscles.

RESULTS

CPU57 had negative inotropic and negative chronotropic actions in isolated heart of guinea pigs as the typical calcium antagonist, nifedipine. However, CPU57 0.01-100 mumol.L(-1) produced less cardiac inhibitory potency than nifedipine and had much stronger negative inotropic action than negative chronotropic action. The decrease in external CaCl2 concentration from 1.5 to 0.3 mmol.L(-1) or increase to 7.5 mmol.L(-1), potentiated or reduced respectively, the inhibitory action of CPU57 on the contraction in paced left heart atrium in normal CaCl2 solution. CPU57 1-10 mumol.L(-1) also inhibited contractile response to CaCl2 in paced left heart atrium with pD2' value of 4.77.

CONCLUSION

CPU57 has calcium antagonism on the heart of guinea pigs.

Central cardiovascular effects of CPU-23, a substituted tetrahydroisoquinoline, in rats

The cardiovascular effects of intracerebroventricular (i.c.v.) injections of low doses of CPU-23, a substituted tetrahydroisoquinoline, were investigated and compared with those of nifedipine in pentobarbital-anaesthetized Sprague-Dawley rats. CPU-23, in doses of 0.2 to 0.5 mg/kg (i.c.v.), which did not elicit any significant cardiovascular responses when injected intravenously, caused a clear-cut and long-lasting decrease of mean arterial pressure (MAP) and heart rate (HR) in a dose-dependent manner. The effects of CPU-23, in a dose of 0.05 mg/kg, were similar to those of nifedipine, a prototype L-type calcium antagonist. The hypotensive effects of CPU-23 were significantly attenuated by bilateral cervical vagotomy. The results strongly suggest that a central component may be involved in the cardiovascular effects of CPU-23 and that dihydropyridine receptor sites in the brain may be involved in the central control of cardiovascular functions.

Gratuitous overexpression of genes in Escherichia coli leads to growth inhibition and ribosome destruction

We attempted to test the idea that the relative abundance of each individual tRNA isoacceptor in Escherichia coli can be altered by varying its cognate codon concentration. In order to change the overall codon composition of the messenger pool, we have expressed in E. coli lacZ with the aid of T7 RNA polymerase so that their respective gene products individually accounted for 30% of the total bacterial protein. Unexpectedly, the maximum expression of either test gene has no specific effect on the relative rates of synthesis of the tRNA species that we studied. Instead, we find that there is a cumulative breakdown of rRNAs, which results in a loss of ribosomes and protein synthetic capacity. After either of the test genes is maximally induced, there is a growing fraction of protein synthesis invested in beta-galactosidase or delta tufB that is matched by a comparable decrease of the fraction of normal protein synthesis. We have also observed enhanced accumulation of two heat shock proteins during overexpression. Finally, after several hours of overexpression of either test protein, the bacteria are no longer viable. These results are relevant to the practical problems of obtaining high expression levels for cloned proteins.

Mechanisms of Argon Retention in Clays Revealed by Laser 40Ar-39Ar Dating

A method for dating clays is important for studies of weathering, diagenesis, hydrocarbon migration, and the formation of major metalliferous deposits. However, many attempts have produced imprecise or inaccurate results. Data from shales show that, contrary to expectations, the (40)Ar-(39)Ar dating technique can be successfully used to determine the diagenetic age of ancient sediments because (39)Ar losses during irradiation are controlled by release from low retentivity sites in illite equivalent to those that have lost radiogenic (40)Ar in nature, rather than by direct recoil as is generally assumed.

[Pathologic characteristics of diffuse alveolar damage induced by paraquat in rat lungs]

Pathologic characteristics and events of paraquat (PQ) induced diffuse alveolar damage were observed by pathohistologic and ultrastructural studies of the lungs of rats, which were given a single intraperitoneal injection of PQ 25mg/kg body weight and sacrificed 6 hours to 45 days later. Results showed that the capillary endothelial and type I epthelial cells were mainly damaged, and associated with interstitial oedema, haemorrhage and hyaline membrane formation of the alveoli, and accentuated alveolitis. The lesions were located in the alveolar structural units and very diffuse in distribution. When the pulmonary damage became irreversible, it then led to fibrosis.

Role of oxygen derivatives in the cytotoxicity and DNA damage produced by asbestos on rat pleural mesothelial cells in vitro

The role of reactive oxygen metabolites in the toxic effects of asbestos on pleural mesothelial cells is not well defined. We exposed rat pleural mesothelial cells (RPMC) to chrysotile and crocidolite fibers (0-40 micrograms/cm2) in the presence or absence of catalase and superoxide dismutase (SOD). Cell injury was measured using the colorimetric 3-4 (5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and DNA damage was evaluated in terms of unscheduled DNA synthesis (UDS). Catalase (100 U/ml) and SOD (250 U/ml) protected RPMC against asbestos-induced cytotoxicity and DNA damage. However, the inactivated enzymes and bovine serum albumin also showed some protection, suggesting that the effect of antioxidant enzymes may be partly related to their protein nature. These results suggest that oxygen derivatives are partly involved in the toxic effects of asbestos on cultures of RPMC. The presence of extracellular proteins may also decrease asbestos-produced toxicity by reducing the degree of RPMC-fiber interaction.

Air samples from a building with asbestos-containing material: asbestos content and in vitro toxicity on rat pleural mesothelial cells

Buildings equipped with asbestos-containing material may release asbestos fibers, the toxicity of which remains uncertain because of the generally low dose level. In 22 air samples collected in a building the asbestos level ranged between 0 and 0.027 f/ml. Both chrysotile and amphiboles were found. There was no association between in vitro cytotoxicity on rat pleural mesothelial cells and asbestos content, but there was a significant correlation with the total amount of particulate material. Four samples exhibited an enhancement of DNA synthesis in cells arrested in G1 with 5 mM hydroxyurea. This is more likely related to the particulate matter associated with asbestos fibers.

Effects of U-50 488H, a kappa-agonist, on action potentials of isolated ventricular papillary muscle of guinea pigs

Trans(+-)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]-benzeneacetamide-methanesulfonate-hydrate (U-50 488H), a specific kappa-agonist, at 1-10 mumol.L-1 caused concentration-dependent reductions in the action potential duration at 50% and 90% of repolarization (APD50 and APD90) without modifying the resting potential (RP), the action potential amplitude (APA) and the maximal upstroke velocity (Vmax). The effects were attenuated by (-)-(1R,5R,9R)-5,9-diethyl-2-(3-furylmethyl)-2L-hydroxy-6,7-benzomorphan (M(r) 2266 BS, 1 mumol.L-1), a specific kappa-antagonist which itself had no effect on the action potentials of the ventricular papillary muscle of guinea pigs, indicating that U-50 488H at 1-10 mumol.L-1 acts via specific cardiac kappa-receptors. At 100 mumol.L-1, U-50 488H not only shortened APD50 and APD90, but also reduced RP, APA, and Vmax, which were not attenuated by Mr 2266 BS (1 mumol.L-1) suggesting that the effects of U-50 488H at 100 mumol.L-1 were probably nonspecific.

Cardiac electric activity of 1-(2-[(6-methoxyl)-naphthylmethyl])-1-methyl-N-piperidinylacethyl-6,7- dimethoxyl-1,2,3,4-tetrahydroisoquinoline in SHR and WKY rats

1-(2-[(6-Methoxyl)-naphthylmethyl)])-1-methyl-N-piperidinylacethyl -6,7- dimethoxyl-1,2,3,4-tetrahydroisoquinoline (CPU-23), a substituted tetrahydroisoquinoline, reduced the voltages of P wave and J point, prolonged PR interval, and slowed sinus rhythm of ECG in spontaneously hypertensive rats (SHR) and age-matched normotensive WKY rats. The effects of CPU-23 on cardiac electric activity were stronger in SHR than in WKY rats (P < 0.05 or P < 0.01). The results suggest that CPU-23 have a calcium antagonistic activity on rat hearts and that calcium antagonists may exert a stronger inhibition of the cardiac electric activity in hypertensive rats than in normotensive rats.

Calcium antagonistic and antiarrhythmic actions of CPU-23, a substituted tetrahydroisoquinoline

1. The effects of CPU-23 (1-(1-[(6-methoxyl)-naphth-2-yl])-propyl-2-(1-piperidine)-acetyl-6 ,7- dimethyoxy-1,2,3,4-tetra-hydroisoquinoline) were studied on mechanical and electrical activities, and intracellular free calcium ([Ca2+]i) of isolated cardiac tissues in order to investigate its spectrum and mechanisms of action in the heart. Its antiarrhythmic and haemodynamic effects in pentobarbitone-anaesthetized rats subjected to coronary artery ligation were also evaluated. 2. CPU-23 at 10(-6)-10(-4) M markedly inhibited slow action potential characteristics in guinea-pig papillary muscles and pace-maker action potential of rabbit sinoatrial node. It affected fast action potential only at 10(-4) M. None of the effects of CPU-23 was reversed by washout for up to 2 h. 3. Like nifedipine and diltiazem, CPU-23 decreased the heart rate of the isolated perfused heart of the rat. However, in contrast to these two classical calcium antagonists which dose-dependently inhibited the force of contraction, CPU-23 inhibited and stimulated the force of contraction at 10(-7)-3 x 10(-6) M and 10(-5) M, respectively. 4. CPU-23 at 10(-6)-10(-5) M inhibited the KCl-induced [Ca2+]i increase in the Ca2+ medium, but did not affect the caffeine-induced [Ca2+]i increase in the Ca(2+)-free medium in isolated ventricular myocytes. 5. CPU-23 at 1-5 mg kg-1 reduced dose-dependently ventricular arrhythmias including ventricular ectopic beats, VT and VF as well as mortality during coronary artery ligation. At 2.5-5 mg kg-1 it even abolished VF, which was accompanied by 100% survival. 6. It is suggested that CPU-23 has calcium antagonistic properties in cardiac tissues. It selectively blocks the transmembrane influx of extracellular Ca2+ through Ca2+ channels, thus reducing the heart rate and developed tension, altering the slow action potential characteristics and producing antiarrhythmic effect against ischaemic arrhythmias.

Quantification and comparison of HIV-1 proviral load in peripheral blood mononuclear cells and isolated CD4+ T cells

HIV proviral load was determined by quantitative DNA polymerase chain reaction (PCR) in peripheral blood mononuclear cells (PBMC) and lymphocyte subsets isolated by cell sorter. Provirus measured in PBMC, when expressed as HIV copy number per million CD4+ cells, resulted in values which approximated those obtained from sorted CD4+ T lymphocytes. A cross sectional analysis of HIV proviral load in CD4+ T cells from 25 previously untreated and 30 zidovudine-treated seropositive patients with CD4+ T-cell counts between 25 and 802/mm3 demonstrated HIV copy numbers ranging from 1 copy per 10,000 cells in early disease to 1 copy per 10 cells in advanced disease. HIV proviral load can be rapidly assayed by PCR to give a reproducible value which varies over a 1,000-fold range and is positively correlated with cell infectivity as measured by a quantitative micrococulture assay. A less technically demanding assay using PBMC as substrate can give similar results to those obtained with sorted CD4+ T cells.

Cardiovascular effects of substituted tetrahydroisoquinolines in rats

1. A series of substituted tetrahydroisoquinolins derived from the cleavage products of tetrandrine were found to inhibit [3H]-nitrendipine binding to rat cerebral cortical membranes. Those compounds which displaced [3H]-nitrendipine binding were also able to inhibit high KCl-induced contraction of rat aorta in vitro. 2. There was a significant correlation between the ability of these tetrahydroisoquinolines to inhibit [3H]-nitrendipine binding and KCl-induced contraction (r = 0.99, P less than 0.001). 3. CPU-23 (1-(1-[(6-methoxy)-naphth-2-yl])-propyl-2-(1-piperidine)-acetyl- 6,7- dimethoxy-1,2,3,4-tetrahydroisoquinoline), one of the most potent compounds identified in this series, behaved as a simple competitive inhibitor at the [3H]-nitrendipine binding site and reduced the apparent affinity but not the maximal number of binding sites in saturation analysis. 4. In contrast to nifedipine which caused hypotension and tachycardia, CPU-23 induced both hypotension and bradycardia in a dose-dependent manner in pentobarbitone-anaesthetized Sprague-Dawley rats, spontaneously hypertensive and age-matched normotensive WKY rats. 5. It is suggested that CPU-23 may exert its cardiovascular effects via interaction with the dihydropyridine binding site on the L-type calcium channel.

[Textual study on traditional Chinese drugs caodoukou and baidoukou]

Through a critical study of herbalogy, it is concluded that the mature seeds of Alpinia zermubet were used as caodoukou in ancient times. The original plant of Yutao recorded in Zhiwu Mingshi Tukao may be the species of Alpinia katsumadai. Baidukou used in ancient times may be the seeds of Alpinia katsumadai found in the south of China, or Amomum compactum and Am. kravanh imported from foreign countries.

Use of mesothelial cell cultures to assess the carcinogenic potency of mineral or man made fibers

Natural mineral fibers may produce pulmonary cancers and mesothelioma. In contrast with lung cancer, the incidence of fiber-induced mesothelioma is not enhanced in smokers compared to non smokers. It is therefore of special interest to use mesothelial cells to study the toxicity of natural or man made mineral fibers. Several years ago, we have developed a method to culture rat pleural mesothelial cells (RPMC). We have first studied the effects of asbestos fibers by the application of in vitro tests formerly developed to determine the genotoxicity and transforming potency of soluble xenobiotics. Moreover, we have determined whether RPMC expressed cytochromes P450 known to metabolize polycyclic aromatic hydrocarbons. This paper reviews the results obtained so far. It has been found that asbestos fibers produced a cell transformation and a genotoxicity characterized by the formation of aneuploid cells, abnormal anaphases, chromosomal aberrations and DNA repair (UDS). In addition, RPMC expressed different forms of cytochromes P450. It is nowadays suggested that the tumorigenic potency of asbestos fibers may be related to the fiber dimensions, to their surface properties and in vivo biopersistence; this term involves the fiber solubility in biological medium and the fiber epuration from the lung by clearance mechanisms. Experiments are now in progress to determine whether the in vitro effects are dependent on the fiber parameters suggested as playing a role in the carcinogenic potency.

Coding assignments of the genome of adult diarrhea rotavirus

Adult diarrhea rotavirus (ADRV) has caused epidemics of diarrhea in China since 1982 and remains the only group B rotavirus associated with widespread disease in humans. We recently characterized the proteins of ADRV and have now proceeded to identify the gene segments encoding each protein. Viral RNA transcripts were synthesized in vitro with the endogenous viral RNA polymerase and separated by electrophoresis in agarose. The individual transcripts were translated in a cell-free system using nuclease-treated rabbit reticulocyte lysates. The translation products were compared with polypeptides found in purified virus and were characterized by SDS-PAGE, immunoprecipitation, and Western blot analysis using antisera to double- and single-shelled virions, virus cores, and monoclonal antibodies. Furthermore, individual RNA transcripts were hybridized to total dsRNA to determine their genomic origin. Based on this analysis, the core polypeptides VP1, VP2 and VP3 are encoded by segments 1, 2, and 3, respectively. The main polypeptides in the inner capsid, VP6, and the outer capsid, VP4 and VP7, are encoded by segments 6, 4, and 8 respectively. Segments 5, 7, and 9 code for 60, 45, and 30 kDa nonstructural polypeptides. Two other nonstructural polypeptides (24 and 25 kDa) are derived from gene segment 11. Gene segment 10 codes for a 26 kDa polypeptide that is precipitated with serum to ADRV and may be a structural protein VP9. With this exception, gene coding assignments of ADRV are comparable to those of the group A rotaviruses. Our results have clear implications for further work in cloning, sequencing, and expression genes of ADRV and can provide direction towards understanding the origin and the evolution of this virus.

Antagonistic effects of dihydropyridines and verapamil on CaCl2 and 5-HT-evoked contraction in porcine coronary artery

In porcine coronary arterial strips, the antagonistic effects of nifedipine (Nif), nimodipine (Nim), nicardipine (Nic), felodipine (Fel), and verapamil (Ver) to CaCl2-evoked contraction in Ca(2+)-free, K(+)-depolarized solution were greater than that to 5-HT. The order of potency (pD2') was Nif (9.1) greater than Fel (8.4) greater than Nim (7.9) greater than Nic (7.8) greater than Ver (7.2) to CaCl2 and Nif (8.3) greater than Nim (7.5) greater than Fel (6.8) greater than Ver (5.6) greater than Nic (5.3) to 5-HT. Ver inhibited 2 components of 5-HT-evoked contraction in Ca(2+)-free solution, but Fel inhibited only extracellular Ca(2+)-dependent contraction, suggesting that their action modes are different.