Disruption of plastid-encoded RNA polymerase genes in tobacco: expression of only a distinct set of genes is not based on selective transcription of the plastid chromosome

Plastids of higher plants operate with at least two distinct DNA-dependent RNA polymerases, which are encoded in the organelle (PEP) and in the nucleus (NEP), respectively. Plastid run-on assays and Northern analyses were employed to analyse gene expression in tobacco mutant plastids lacking the PEP genes rpoA, rpoB or rpoC1. Hybridisation of run-on transcripts to restriction fragments representing the entire tobacco plastid chromosome, as well as to selected plastid gene-specific probes, shows that all parts of the plastid DNA are transcribed in rpo-deficient plastids. In comparison to wild-type chloroplasts, which are characterized by preferential transcription of photosynthesis-related genes in the light, mutant plastids exhibit a different transcription pattern with less pronounced differences in the hybridisation intensities between the individual genes. The analysis of steady-state transcript patterns and transcription rates of selected genes in both types of plastids demonstrates that differences in transcription rates are not necessarily paralleled by corresponding changes in transcript levels. The accumulation of large transcripts in the mutant plastids indicates that processing of primary transcripts may be impaired in the absence of PEP. These data suggest that, contrary to the prevailing view, much of the regulation of NEP-driven plastid gene expression in the rpo-deficient mutants is not based on differential promoter usage but is exerted at post-transcriptional levels.

Molecular, functional and ultrastructural characterisation of plastids from six species of the parasitic flowering plant genus Cuscuta

Plastids of Cuscuta reflexa Roxb., C. subinclusa D. et H., C. gronovii Willd. and C. campestris Yunck. possess thylakoids and contain both chlorophyll a and b in a ratio similar to that of stem tissue of the systematically closely related but 'normal' green Ipomoea tricolor. In contrast, plastids of C. odorata R. et P. and C. grandiflora H.B.K. do not contain any chlorophyll or possess thylakoids. Light-driven electron transport, as measured by oxygen evolution and indicated by analysis of chlorophyll fluorescence, was present in all chlorophyll-containing species. The photosystem II efficiency was low and ranged from 0.511 to 0.687. The plastid rbcL gene could not be detected in C. odorata, but was present in all other tested species. Neither rbcL transcripts nor the large subunit of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco) could be detected in C. odorata and C. grandiflora. Low amounts of the large subunit of Rubisco were detected immunologically in all other Cuscuta species. Apparently, the genus Cuscuta comprises species with different degrees of plastid functionality, ranging from intact chloroplasts, via plastids with impaired protein production and gene expression to plastids with reduced plastome gene content.

Conformational properties of a cyclic peptide bradykinin B2 receptor antagonist using experimental and theoretical methods

The solution conformation of the cyclic peptide J324 (cyclo0,6-[Lys0,Glu6,D-Phe7]BK), an antagonist targeted at the bradykinin (BK) B2 receptor, has been investigated using experimental and theoretical methods. In order to gain insight into the structural requirements essential for BK antagonism, we carried out molecular dynamics (MD) simulations using simulated annealing as the sampling protocol. Following a free MD simulation we performed simulations using nuclear Overhauser enhancement (NOE) distance constraints determined by NMR experiments. The low-energy structures obtained were compared with each other, grouped into families and analyzed with respect to the presence of secondary structural elements in their backbone. We also introduced new ways of plotting structural data for a more comprehensive analysis of large conformational sets. Finally, the relationship between characteristic backbone conformations and the spatial arrangement of specific pharmacophore centers was investigated.

Chiral separations in capillary high-performance liquid chromatography and nonaqueous capillary electrochromatography using helically chiral poly(diphenyl-2-pyridylmethyl methacrylate) as chiral stationary phase

Enantioseparations in nonaqueous capillary electrochromatography (CEC) are reported in this study for the first time, using wide-pore aminopropyl silica gel coated with helically chiral poly(diphenyl-2-pyridylmethyl methacrylate) (PDPM) as chiral stationary phase (CSP). The anodic electroosmotic flow (EOF) in a methanolic solution of ammonium acetate was used for the migration of neutral analytes through the packed bed in the capillaries. Four different techniques, high-performance liquid chromatography (HPLC) in common-size columns, capillary HPLC, pressure-assisted CEC and CEC were compared from the viewpoint of separation parameters. The latter three were performed with the same experimental setup, varying the relative contribution of the pressure-driven and the electrically driven flow to the overall mobility of the analyte. Capillary HPLC offers clear advantages compared to enantioseparations in common-size columns. However, for a given particle size of the packing material, CEC was not obviously advantageous compared to pressure-driven separations.

Expression of p73 and its relation to histopathology and prognosis in hepatocellular carcinoma

BACKGROUND

The protein p73, the first identified homologue of the tumor suppressor gene p53 (also known as TP53), has been shown to induce apoptosis (programmed cell death), but its function in tumor development has not been established. This study was undertaken to investigate the expression of p73 in liver tissue of patients with hepatocellular carcinoma (HCC) and to determine whether this expression has any impact on prognosis.

METHODS

In situ hybridization and immunohistochemistry for the detection of p73 RNA transcripts and protein, respectively, were performed in tissues from 193 patients with curatively (R0-) resected HCC. Patients receiving liver transplantation were excluded. The results obtained were analyzed with respect to their association with pathohistologic stage, Edmondson grade, p53 expression status and several histopathologic factors of possible prognostic value, and, finally, with patient survival.

RESULTS

RNA transcripts encoding p73 were detected by in situ hybridization in tumor cells but not in stromal, endothelial, or inflammatory cells or in cholangiocytes. Transcripts were also found occasionally in non-neoplastic hepatocytes. By immunohistochemistry, we detected p73 protein in 61 (32%) of the 193 carcinomas examined. Positive immunohistochemical staining was confined to the cell nucleus. Univariate survival analysis showed that p73 expression status was statistically significantly related to prognosis (two-sided P<.0001). Patients with p73-positive tumors had a poorer prognosis than those with p73-negative carcinomas. Multivariate Cox survival analysis identified the age of the patient, p73 expression status, co-existing cirrhosis, and Edmondson grade as independent prognostic factors.

CONCLUSION

The protein p73 is overexpressed by a subset of HCCs and could serve as a useful indicator of prognosis in patients with this disease.

Validation of the heat treatment step used in the production of diaspirin crosslinked hemoglobin (DCLHb) for viral inactivation--effect of crosslinking

Two experiments were performed to assess viral inactivation during the crosslinking and heat treatment steps of the DCLHb manufacturing process. Stroma free hemoglobin (SFHb) collected from a large scale manufacturing lot was tested in a 1:680 scaled down system in which the key parameters used in the manufacturing process were replicated. In the first study Porcine Parvovirus (PPV), a non-enveloped virus, was used to assess inactivation, while in the second study Bovine Viral Diarrhea Virus (BVDV), an enveloped virus, was utilized. In both experiments, the SFHb solution was deoxygenated and an aliquot of virus suspension was added. To initiate the crosslinking reaction, a solution of bis (3,5-dibromosalicyl) fumarate (DBBF) in HEPES buffer was added to the test solution. In both experiments the reaction times and the degree of crosslinking were normal. After crosslinking, the reaction mixtures were heated to 74 +/- 1 degrees C over 30 minutes, held at 74 +/- 1 degrees C for 90 minutes, and cooled to less than 10 degrees C over 30 minutes. In each experiment the degree of crosslinking of final product was 100% and yield of hemoglobin recovery was normal. Samples were removed prior to crosslinking, after crosslinking and before, during and after heat treatment for determination of virus titer and evaluation of key process parameters. The results from these experiments were consistent with those obtained from the full scale manufacturing process for the deoxygenation, crosslinking and the heat treatment step during the production of DCLHb. The results of virus assays showed that crosslinking has no effect on viruses and their subsequent inactivation by heat treatment.

[Acceptance of progressive lenses]

BACKGROUND

The wearing of progressive lens poses a problem to two kinds of patients: those who are practically emmetropic and use reading glasses only, and ametropic patients whose eyes have been corrected for years with bifocals. The wearing of progressive lenses is generally not recommended for those presbyopes.

METHODS

A group of individuals (n = 50) underwent refraction, and their addition was adjusted to their work and their age (44-72 years). They were then divided into two groups, one of which (n = 25) was equipped with bifocals (Telarc, Essilor) and the other (n = 25) with progressive lenses (Varilux Comfort, Essilor). After four weeks, the types of glasses were exchanged. After a further four weeks, each group used the original pair of glasses for another week. At the end of this phase, each of the test subjects was asked his opinion in favour of one or the other types of glasses. At each change of glasses, factors such as duration of the adaptation period, assessment of sight, general impression and time of use were recorded.

RESULTS

At the determination of refraction much attention must be given to mildly astigmatic patients in order to optimise the prescription of progressive lenses. Progressive lenses were just as well tolerated by the group of convinced bifocal wearers, even though the familiarisation period took up to two weeks, especially for the older patients. Once the progressive lenses had been accepted, bifocals were generally abandoned for good. This is mainly due to the quality of the progressive lenses, which favour precise vision even in intermediate zones. For most of the individuals who were previously fitted with reading glasses only, the demarcation line between the distant and near parts of the bifocal lens pose major problems. Whereas progressive lenses were accepted as readily as in the group previously fitted with bifocals, about 40% of the total individuals tested refused bifocal lenses.

CONCLUSION

In all, 96% of the participants considered progressive lenses good or very good. All recognised that progressive lenses represent the most aesthetic solution. However, in certain cases bifocal lenses together with progressive lenses remain interesting. For patients who were previously accustomed to reading glasses only, the duration of use of glasses with progressive lenses rose from 40% to 60% of the working day.

[Idiopathic varus gonarthrosis: diminished nociceptive vs. unchanged somatosensory sensitivity]

Neuromuscular control deficits are supposed to contribute to the development of osteoarthritis (OA). Pain measurements were performed to clarify whether nociceptive afferents differ between OA patients and healthy subjects. Thermal pain thresholds were significantly higher in OA subjects as compared to controls, but there was no difference in perceptual thresholds after electrical stimulation. Lateralization, gender, site of OA changes, previous operations, or medication did not affect these findings.

[Aniseikonia reduces binocular summation in the VECP]

The binocular summation effect of human VECP (increase in amplitude from about 4.0 microV to about 5.4 microV) was proved and optimized in 32 subjects. Stimulus parameters: TV steady-state pattern reversal (7.0 Hz); pattern size 1 degree; stimulus contrast 5% (higher stimulus contrasts reduced considerably the selectivity of the binocular summation effect); 96 sweeps averaging (Nicolet Compaq Four); position of electrodes: 10% and 30% above Protuberantia occipitalis externa of nasioninion distance. Aniseikonia of 7 to 52% was generated by means of small Galilei telescopes. Because of comparatively large interindividual variance within the series of subjects, no decrease in binocular VECP amplitude could be demonstrated at an aniseikonia less than 52%. On one woman subject, a significant reduction in amplitude (5% level) at 14%, 26% and 52% aniseikonia was apparent, but not at 7%. Thus, for this subject, it was possible to correlate the results with the clinically known limits of toleration for aniseikonia. This result was confirmed by more than 60% of the subjects in the test group.

Up-regulation of CYP2A5 expression by porphyrinogenic agents in mouse liver

Coumarin 7-hydroxylase (COH) activity is catalyzed by the Cyp2a-5 gene product (CYP2A5 enzyme) in mice. Mouse hepatic CYP2A5 expression is often increased in conditions in which other P450 forms are repressed, e.g. after the administration of heavy metals and other toxic agents known to affect cellular heme balance. In this study, the effect of various porphyrinogenic chemicals on the expression CYP2A5 and the key enzymes in heme metabolism was studied. Administration of single doses of griseofulvin (1000 mg/kg), thioacetamide (10 mg/kg) and aminotriazole (1000 mg/kg) to DBA/2 and C57BL/6 mice produced up to 10-fold increases in hepatic COH catalytic activity. Dramatic, up to 130-fold increases in response to the inducers was observed in the amount of CYP2A5 steady-state mRNA. The mRNA contents of aminolevulinate synthase, ferrochelatase and heme oxygenase were also increased to a variable extent, possibly reflecting feed-back regulatory mechanisms. In D2 mice the CYP2A5 inducing effect of aminotriazole and thioacetamide, but not that of griseofulvin, pyrazole and phenobarbital, was abolished by exogenously administered heme arginate. In the B6 strain heme arginate treatment increased CYP2A5 expression but it did not affect the induction caused by porphyrinogenic agents. These results show that porphyrinogenic agents act as efficient inducers of CYP2A5, and suggest that regulation of the transcription of the Cyp2a-5 gene could in some instances involve heme-sensitive factors.

[Effect of biopterin on the electroretinogram of Long-Evans rats]

Tetrahydrobiopterin (BH4) is an important cofactor in the synthesis of the leading intraretinal catecholamine derivate dopamine. According to Iuvone et al., retinal BH4-tyrosine affinity and dopamine synthesis are influenced by environmental light intensities. So far, no data are available about the in vivo effect of BH4 concentrations on the functional parameters of the retina. ERG recordings were performed after BH4 had been administered for 3 days (10 micrograms and 500 micrograms/day IP). After high-dose application a significant ERG effect was observed in a-, b-amplitudes and latencies, respectively. This is the first observation that BH4 has an in vivo effect on the functional parameters of the retina and is consistent with previous results on retinal dopamine action. This result supports the hypothesis that pterin metabolism plays an important role in the adaptive processes of the retina. It may be discussed as a model for the so far unexplained adaptation of neurons.

Conditioning of Parsley (Petroselinum crispum L.) Suspension Cells Increases Elicitor-Induced Incorporation of Cell Wall Phenolics

The elicitor-induced incorporation of phenylpropanoid derivatives into the cell wall and the secretion of soluble coumarin derivatives (phytoalexins) by parsley (Petroselinum crispum L.) suspension cultures can be potentiated by pretreatment of the cultures with 2,6-dichloroisonicotinic acid or derivatives of salicylic acid. To investigate this phenomenon further, the cell walls and an extracellular soluble polymer were isolated from control cells or cells treated with an elicitor from Phytophthora megasperma f. sp. glycinea. After alkaline hydrolysis, both fractions from elicited cells showed a greatly increased content of 4-coumaric, ferulic, and 4-hydroxybenzoic acid, as well as 4-hydroxybenzaldehyde and vanillin. Two minor peaks were identified as tyrosol and methoxytyrosol. The pretreatment effect is most pronounced at a low elicitor concentration. Its specificity was elaborated for coumarin secretion. When the parsley suspension cultures were preincubated for 1 d with 2,6-dichloroisonicotinic, 4- or 5-chlorosalicylic, or 3,5- dichlorosalicylic acid, the cells exhibited a greatly increased elicitor response. Pretreatment with isonicotinic, salicylic, acetylsalicylic, or 2,6-dihydroxybenzoic acid was less efficient in enhancing the response, and some other isomers were inactive. This increase in elicitor response was also observed for the above-mentioned monomeric phenolics, which were liberated from cell walls upon alkaline hydrolysis and for "lignin-like" cell wall polymers determined by the thioglycolic acid method. It was shown for 5-chlorosalicylic acid that conditioning most likely improves the signal transduction leading to the activation of genes encoding phenylalanine ammonia lyase and 4-coumarate: coenzyme A ligase. The conditioning thus sensitizes the parsley suspension cells to respond to lower elicitor concentrations. If a similar mechanism were to apply to whole plants treated with 2,6-dichloroisonicotinic acid, a known inducer of systemic acquired resistance, one can hypothesize that fungal pathogens might be recognized more readily and effectively.

Neopterin in patients with choroidal melanoma

Neopterin excretion in urine and the serum concentrations of neopterin were compared in 101 patients with a malignant melanoma of the choroid and in a matched group of healthy volunteers. The majority of cases (n = 99) presented an untreated (n = 20) or treated and either partially (n = 33) or completely regressed (n = 47) melanoma of stage I-III without signs of extraocular manifestation at the time of analyses. The incidence of elevated neopterin concentrations in all melanoma patients beyond the upper limit (mean + 2 S.D. of healthy controls) was 16% for both serum and urine. In patients with critical events, for example orbital infiltration or delayed metastatic disease during the subsequent follow-up period (at least 14 months), the neopterin concentrations were at the higher end of distribution. One patient with verified metastatic disease at the time of analysis presented extremely elevated neopterin concentrations in serum (82.3 nmol/l) and urine (1608 mumol/mol creatinine). It seems that the results of neopterin analyses are informative as a prognostic factor for the follow-up of patients with a malignant melanoma of the choroid.

[The effect of triamterene on the ERG of Long-Evans rats]

Dopamine is an important mediator of the neuronal adaptation mechanism of the retina. Tetrahydrobiopterin (BH4) is cofactor of the rate-limiting enzymatic tyrosine-hydroxylase step in the biosynthetic pathway of dopamine. This enzymatic step causes an oxidation of BH4 to dihydrobiopterin (BH2), which is reduced again to BH4 by action of dihydropterin-reductase (DHPR) and dihydrofolate-reductase (DHFR). Triamterene, a pterin derivate, is known to induce DHFR after initial inhibition. Concomitant elevation of retinal BH4 will result in a higher dopamine concentration. ERG changes of Long-Evans rats mediated by this triamterene effect on dopamine concentration were examined after the rats received triamterene with tap water in two experimental series for 5 and 11 days. After 5 days of triamterene administration a significant decrease of scotopic a- and b-wave ERG amplitudes were registered. After 11 days of triamterene application the decrease could be shown to be even more substantial. This effect was completely reversible: 10 weeks after cessation of triamterene supply ERG amplitudes increased to previous levels. The observed transient ERG changes support the concept of biopterin as an mediator of neuronal adaptation mechanisms of the retina.

Influence of exercise on clearance of oxidant stress products and loosely bound iron

The significance of free radical chemistry within the exercise and post-exercise milieu is not yet well understood. It is yet to be determined whether adequate biochemical defense mechanisms exist to protect the organism from oxygen-centered radicals generated by exercise. Rats trained at 70% VO2peak for 6 wk were compared with controls after an exhaustive run. Post-exhaustion urinary malondialdehyde, gastrocnemius loosely bound iron, and susceptibility to oxidant stress were assessed. Exhaustive exercise resulted in a significant (P < 0.05) increase in urinary malondialdehyde, tissue loosely bound iron, and susceptibility to oxidative stress in both control and trained rats. The untrained group's tissue iron and susceptibility to oxidative stress were both significantly greater than trained rats. Electrical stimulation of perfused hindquarters of untrained and trained rats resulted in a significant increase of malondialdehyde into the perfusate. Trained rats cleared the malondialdehyde from the perfusate more rapidly than did the untrained.

Methyl jasmonate conditions parsley suspension cells for increased elicitation of phenylpropanoid defense responses

Pre-incubation of suspension-cultured parsley cells with methyl jasmonate greatly enhances their ability to respond to fungal elicitors by secretion of coumarin derivatives. The effect is most pronounced at relatively low elicitor concentration and also observed for the incorporation of esterified hydroxycinnamic acids and of "lignin-like" polymers into the cell wall. These three responses correspond to defense reactions induced locally when a fungal pathogen attacks plant cells. In contrast, the conditioning of parsley cells by the signal substance methyl jasmonate is reminiscent of the developmental nature of systemic acquired resistance and renders the cells more effective for the elicitor-induced local defense reactions.