Targeting presequence acquisition after mitochondrial gene transfer to the nucleus occurs by duplication of existing targeting signals

We have cloned a gene for mitochondrial ribosomal protein S11 (RPS11), which is encoded in lower plants by the mitochondrial genome, in higher plants by the nuclear genome, demonstrating genetic information transfer from the mitochondrial genome to the nucleus during flowering plant evolution. The sequence s11-1 encodes an N-terminal extension as well as an organelle-derived RPS11 region. Surprisingly, the N-terminal region has high amino acid sequence similarity with the presequence of the beta-subunit of ATP synthase from plant mitochondria, suggesting a common lineage of the presequences. The deduced N-terminal region of s11-2, a second nuclear-encoded homolog of rps11, shows high sequence similarity with the putative presequence of cytochrome oxidase subunit Vb. The sharing of the N-terminal region together with its 5' flanking untranslated nucleotide sequence in different proteins strongly suggests an involvement of duplication/recombination for targeting signal acquisition after gene migration. A remnant of ancestral rps11 sequence, transcribed and subjected to RNA editing, is found in the mitochondrial genome, indicating that inactivation of mitochondrial rps11 gene expression was initiated at the translational level prior to termination of transcription.

[Hypertension and hyperuricemia]

Epidemiological studies show that serum uric acid is positively associated with blood pressure levels and that serum uric acid is also a predictor of the development of hypertension in normotensive adults. Several clinical studies revealed that insulin resistance and/or hyperinsulinaemia is associated with hypertension and higher plasma concentrations of uric acid, triglyceride and plasminogen activator inhibitor 1 and with lower HDL cholesterol concentrations. Abnormalities in membrane transport system of sodium and related ions may be associated with impared urinary excretion of uric acid in hyperuricemic patients with hypertension. Several anti-hypertensive drugs have been shown to increase urinary excretion of uric acid and thereby reduce its serum level. Strict salt restriction and weight loss may cause at least in the short-term, adverse metabolic changes including elevated uric acid levels. In hypertensive patients.

Pituitary adenylate cyclase-activating polypeptide protects rat-cultured cortical neurons from glutamate-induced cytotoxicity

We have investigated the effects of pituitary adenylate cyclase-activating polypeptide with 38 residues (PACAP38) on glutamate-induced neuronal cell death in rat-cultured cortical neurons. The rat-cultured neurons were obtained from E17 day-old embryos and cultured in a chemically defined medium without serum for 10 days, after which more than 95% of the cells were stained by a specific antibody against MAP-2, a specific marker for neurons. The number of viable neurons was identified by the mitochondrial conversion of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) to formazan, which was detected by the associated change in optical density at 570 nm. Glutamate-induced neuronal cell death was suppressed by PACAP38 at concentrations as low as 10(-13) M, and at 10(-11) M maximally suppressed half of the amount of glutamate-induced cell death seen in a control situation (no PACAP38). The dose-response curve was bell-shaped. Dibutyryl cAMP (dbcAMP) also increased the number of neurons that were protected from damage with a bell-shaped dose-response curve suggesting that PACAP exerts its neuroprotective effect through the activation of a cAMP signal transduction system. However, cAMP accumulation in the media of neurons was stimulated by PACAP38 at concentrations as low as 10(-11) M, a much higher concentration than the minimal effective dose of PACAP38 required for protection against glutamate-induced neuronal cell death. Among the three neuropeptides of PACAP38, arginine vasopressin (AVP) and C-type natriuretic peptide (CNP), only PACAP38 exhibited a neurotrophic effect in the glutamate-induced neuronal cell death at the indicated concentrations. These data indicate that PACAP38 is one of the more important neuroprotective factors. The kind of intracellular signal transduction system involved in the neuroprotective effect of PACAP38 still remains to be established.

Induction of Graves-like disease in mice by immunization with fibroblasts transfected with the thyrotropin receptor and a class II molecule

Graves disease is an autoimmune thyroid disease characterized by the presence of antibodies against the thyrotropin receptor (TSHR), which stimulate the thyroid to cause hyperthyroidism and/or goiter. By immunizing mice with fibroblasts transfected with both the human TSHR and a major histocompatibility complex class II molecule, but not by either alone, we have induced immune hyperthyroidism that has the major humoral and histological features of Graves disease: stimulating TSHR antibodies, thyrotropin binding inhibiting immunoglobulins, which are different from the stimulating TSHR antibodies, increased thyroid hormone levels, thyroid enlargement, thyrocyte hypercellularity, and thyrocyte intrusion into the follicular lumen. The results suggest that the aberrant expression of major histocompatibility complex class II molecules on cells that express a native form of the TSHR can result in the induction of functional anti-TSHR antibodies that stimulate the thyroid. They additionally suggest that the acquisition of antigen-presenting ability on a target cell containing the TSHR can activate T and B cells normally present in an animal and induce a disease with the major features of autoimmune Graves.

Variability of mitochondrial subgenomic molecules in the meristematic cells of higher plants

MtDNAs from BY-2 cells and rice root were analyzed by random amplified polymorphic DNA (RAPD) assay and Southern hybridization analysis. A number of differences were observed in the RAPD patterns amplified from mtDNAs sampled at different phases of the BY-2 cell culture. RAPD fragments also varied with the template DNAs derived from various areas of rice root tip. When a RAPD fragment was hybridized to restriction fragments of whole DNAs, isolated from the distal area of the apical meristem and differentiated elongation zone of a root, two distinct stoichiometric differences were observed in the hybridization signals. This suggests that the organization of mt-genome in prototypic cells in the root apical meristem differs from that found in the differentiated cells.

Disturbances of glucose and lipid metabolism in first and second generation Japanese-Brazilians. Japanese-Brazilian Diabetes Study Group

Increased prevalence of self-reported NIDDM in Japanese-Brazilians was reported when compared to Japan. This study aimed at determining the prevalence of NIDDM and IGT in Japanese-Brazilians living in the city of Bauru, São Paulo, Brazil. The impact of western environment on the frequency of obesity, dyslipidemia and hypertension was investigated. All Issei (first generation; n = 238) and a random sample of Nisei (second generation; n = 292), aged 40-79 years, were selected for clinical examination and OGTT (WHO criteria). Age-adjusted prevalence of NIDDM did not differ between men and women for Issei (12.4 vs. 11.6%, respectively), but it became different for Nisei (21.7 vs. 11.4%, P < 0.03) due to an increased rate among men. Increased IGT prevalence was also observed between Issei and Nisei men (8.5 vs. 19.3%, P < 0.03). Issei women had a higher IGT rate than Issei men (27. 3 vs. 8.5%, P < 0.0005). Body mass index (BMI) was higher in the second generation (24.1 +/- 3.6 vs. 23.3 +/- 3.1 kg/m2, P < 0.00005) and also the frequency of obesity, defined as BMI > 25 kg/m2. Comparison of waist/hip ratio by gender showed that only among women, Nisei had lower ratio than Issei (0.90 vs. 0.88, P < 0.05). Nisei had a lower total and LDL-cholesterol than Issei but triglyceride and HDL-cholesterol did not differ. Nisei women (younger than the Issei) had lower triglyceride and total cholesterol. This pattern was not seen between the two generations of men. Considering the mean blood pressure values, Issei and Nisei groups with normal glucose tolerance were not hypertensive. Systolic blood pressure was lower in Nisei and the inverse was found concerning diastolic levels. NIDDM prevalence in Japanese-Brazilians is higher than in Japan and in the general Brazilian population. Besides environment, genetic factors may confer susceptibility to NIDDM when they are exposed to a western environment. Before developing glucose intolerance, disturbances of lipid profile and blood pressure could be detected. Nisei may be more affected due to a longer exposure to an unfavorable environment and these changes seem to occur earlier among men than women.

Hyperphosphorylation of retinoblastoma protein and stimulation of growth by okadaic acid in human pancreatic cancer

Phosphorylation/dephosphorylation of intracellular proteins are important steps in the regulation of cell growth. Okadaic acid, an inhibitor of the serine/threonine protein phosphatases 1 and 2A, is a potent tumor promoter. This effect may be through the inhibition of dephosphorylation (termed "hyperphosphorylation") and subsequent inactivation of tumor-suppressor proteins. We examined whether okadaic acid regulates growth of human pancreatic cancer cells (MIA PaCa-2 and Panc-1) or alters the phosphorylation of the retinoblastoma tumor-suppressor protein. Growth studies, nuclear labeling analyses, and Western blotting for retinoblastoma protein were performed. Okadaic acid stimulated cell growth and induced hyperphosphorylation of the retinoblastoma protein. The growth-stimulatory effect of okadaic acid on these human pancreatic cancer cells may be mediated by inactivation of the growth suppressive effect of the retinoblastoma protein by hyperphosphorylation. These studies suggest that the growth of these human pancreatic cancer cells is still regulated by tumor-suppressor proteins.

A chloroplast-derived sequence is utilized as a source of promoter sequences for the gene for subunit 9 of NADH dehydrogenase (nad9) in rice mitochondria

The chloroplast-derived sequence trnS-rps4/ 3'trnL-trnF-ndhJ-ndhK (4066 bases in length) is present in a region that starts 355 bases upstream of the gene for subunit 9 of NADH dehydrogenase (nad9) in the mitochondrial genome of rice. Northern blot hybridization revealed that three large transcripts of 3.05, 1.62 and 1.05 kb hybridized to strand-specific probes for both the nad9 gene and the chloroplast-derived sequence, indicating that the nad9 gene was transcribed together with the chloroplast-derived sequence. From the results of in vitro capping and ribonuclease protection experiments, as well as primer extension analysis, we identified at least seven sites for the initiation of transcription of nad9 in the chloroplast-derived sequence. All of the initiation sites for transcription of the nad9 gene were located in sequences homologous to chloroplast DNA. Two of seven initiation sites were flanked by a sequence homologous to the consensus promoter motif that includes the CRTA motif (where R is A or G) of the rice mitochondrion. However, the sequences surrounding the other five sites showed only limited similarity to the conserved sequence. It is suggested that all the promoters of the rice nad9 gene exist in a sequence that was transferred from the chloroplast during evolution. Thus, the chloroplast-derived sequence has a novel, significant function in the mitochondrial genome of this higher plant.

MR imaging enhancement with superparamagnetic iron oxide in chronic liver disease: influence of liver dysfunction and parenchymal pathology

PURPOSE

To analyze the influence of liver dysfunction and parenchymal pathology on the accumulation of superparamagnetic iron oxide (SPIO).

METHODS

We evaluated MR images of 13 patients having small hepatic neoplasms before and after administration of SPIO (10 micronol/kg). Biopsy and laboratory data confirmed the presence of severe cirrhosis in two patients, mild cirrhosis in four, chronic hepatitis in five, and normal livers in two. Degrees of liver dysfunction or liver parenchymal pathology were correlated with reductions in signal intensity of the liver and spleen after administration of SPIO. Signal intensity reduction was evaluated using a 1.5 Tesla MR unit.

RESULTS

Response to SPIO of the liver and spleen did not correlate with liver parenchymal pathology, although reductions in signal intensity of the liver were somewhat small in severely cirrhotic livers. There were slight correlations between signal intensity alterations of the liver and laboratory data such as the indocyanine green retention rate (correlation coefficient 0. 47), albumin (0.36), total bilirubin (0.36), and serum glutamic oxaloacetic transaminase (GOT) (0.46). Signal intensity reduction of spleen did not correlate with liver function tests except for serum GOT. In patients with cirrhosis, heterogeneous structures were detected in the nontumorous portions of the liver. However, these did not prevent the diagnosis of small hepatomas.

CONCLUSION

The uptake of SPIO showed some correlation with liver function but not with chronic liver parenchymal pathology. SPIO provided sufficient contrast between tumor and surrounding liver parenchyma among patients with chronic liver disease.

Effect of manidipine and delapril on insulin sensitivity in type 2 diabetic patients with essential hypertension

The open trial was designed to evaluate the effects of long-term antihypertensive treatment with the calcium-channel blocker, manidipine and the angiotensin converting enzyme (ACE) inhibitor, delapril on insulin sensitivity in Japanese non-insulin dependent diabetes mellitus (NIDDM) patients with essential hypertension. We measured the insulin sensitivity index (SI) and the glucose-effectiveness (SG) by the use of Bergman's minimal model method in 18 hypertensive NIDDM patients before and after administration of manidipine (group A) or delapril (group B) for 3 months. Manidipine treatment for 3 months significantly improved SI in group A from 3.35 +/- 0.61 (x 10(-4) min-1 microU-1 ml-1) to 4.70 +/- 1.34 (P < 0.05). Delapril treatment for 3 months also significantly improved SI in group B from 3.56 +/- 1.04 to 5.00 +/- 0.87 (P < 0.05). Manidipine significantly improved SG in group A from 1.60 +/- 0.64 (x 10(-2) min) to 2.19 +/- 0.38 (P < 0.05). Delapril treatment also significantly improved SG in the group B from 1.41 +/- 0.56 to 1.91 +/- 0.35 (P < 0.05). Manidipine and delapril did not affect urinary C-peptide excretion for 24 h in the hypertensive NIDDM patients. Treatment with manidipine or delapril significantly reduced systolic and diastolic blood pressures in the hypertensive NIDDM patients. There were no differences between plasma glucose, serum total triglycerides, and cholesterol or lipoprotein cholesterol fractions, heart rate and body weight after 3 months on manidipine or delapril. This study confirmed the improving effects on SI and SG by long-term treatment with manidipine or delapril in the hypertensive NIDDM patients.

A promiscuous chloroplast DNA fragment is transcribed in plant mitochondria but the encoded RNA is not edited

The RNA editing processes in chloroplasts and mitochondira of higher plants show several similarities which are suggestive of common components and/or biochemical steps between the two plant organelles. The existence of various promiscuous DNA fragments of chloroplast origin in plant mitochondrial genomes allowed us to test the possibility that chloroplast sequences are also edited in mitochondria. An rpoB fragment transferred from chloroplasts to mitochondria in rice was chosen as it contains several editing sites, two of which match sequence motifs surrounding even non-homologous editing sites in both chloroplast and mitochondrial transcripts. Rice chloroplast and mitochondrial rpoB DNA and cDNA sequences were selectively amplified and the editing status of the cDNA sequences was determined. Three of the four potential rpoB editing sites previously detected in maize were found to be edited in the rice chloroplast rpoB transcript, whereas the fourth was found to remain unedited. In mitochondria, however, all four editing sites remain unmodified at the cDNA level. This indicates that the editing processes of higher plant mitochondria and chloroplasts are not identical and that organelle-specific factors are required for eliciting the respective editing events.

Thyrotropin induces G1 cyclin expression and accelerates G1 phase after insulin-like growth factor I stimulation in FRTL-5 cells

We have investigated the mechanism by which TSH pretreatment potentiates insulin-like growth factor I (IGF-I)-induced DNA synthesis in FRTL-5 cells. As previously described, pretreatment with TSH increased IGF-I-induced DNA synthesis, suggesting that the effect of TSH is mediated through the cAMP pathway. TSH and A kinase activators required at least 12 h to precondition cells to respond to IGF-I stimulation. The presence of cycloheximide abolished the effect of TSH to increase IGF-I-induced DNA synthesis. When the time course of thymidine uptake after IGF-I addition was studied, TSH pretreatment increased the maximum DNA incorporation and shortened the G1 phase interval. These results indicated that some proteins induced by TSH are required for the effect of TSH on IGF-I activity, and the proteins are important for cell cycle progression. Cyclins are key regulators of the cell cycle; therefore, we investigated the expression of cyclins D1 and E after TSH stimulation. TSH- and A kinase-activating agents increased the expression of cyclins D1 and E after 24 h. The same amounts of cyclins D1 and E induced by IGF-I were increased after TSH pretreatment. TSH pretreatment induced the expression of G1 cyclin in FRTL-5 cells, and IGF-I caused the accumulation of enough G1 cyclins to drive the cell cycle from G1 to S phase in a short time, which accounts for the effect of TSH on IGF-I induced DNA synthesis.

Fast fluid-attenuated inversion recovery (FAST-FLAIR) of ischemic lesions in the brain: comparison with T2-weighted turbo SE

PURPOSE

We compared fast fluid-attenuated inversion recovery (FAST-FLAIR) images with Turbo SE T2-weighted images to evaluate the detectability of small ischemic lesions in the brain.

MATERIALS AND METHODS

Thirty-six cases of multiple cerebral ischemic lesions were examined with FAST-FLAIR and Turbo SE imaging. The detectability of lesions, ability to discriminate lesions from the cortex, visualization of perivascular space, and visualization of brainstem lesions were compared between the two sequences.

RESULTS

The total number of lesions detected on both sequences was 534 in 36 cases. Six lesions in three cases were detected only on FAST-FLAIR, and one lesion in one case was detected only on the Turbo SE. All the 52 lesions located close to the cortex could be discriminated from the cortex on the FAST-FLAIR images, while 23 of these lesions could not be discriminated on the Turbo SE. Perivascular spaces were not visualized as areas of high signal on the FAST-FLAIR images. Pontine lesions that were visualized in four cases were clearer on the Turbo SE images than on the FAST-FLAIR images.

CONCLUSION

The FAST-FLAIR images were shown to be useful in the detection of ischemic lesions and in distinguishing them from the surrounding normal structures. The FAST-FLAIR sequence is expected to become a new additional routine sequence.

RNA editing of transcripts of the gene for apocytochrome b (cob) in rice mitochondria

RNA editing was examined in rice mitochondrial apocytochrome b (cob) transcripts. Nineteen C-U conversions were found, and most of them changed the polypeptide sequence encoded by genomic DNA sequence. Evidence for partial and excess editing was also found.

Multiple initiation sites for transcription of a gene for subunit 1 of F1-ATPase (atp1) in rice mitochondria

We identified the sites for the initiation of transcription of a gene for subunit 1 of F1-ATPase (atp1) in rice mitochondrial DNA. Capping and ribonuclease protection experiments in vitro, together with primer extension analysis, demonstrated that there were at least eight transcription initiation sites upstream of atp1. One initiation site, expressed most actively, was flanked by a sequence identical to the consensus promotor motif of rice mitochondrial genes. However, the sequences surrounding the other seven initiation sites exhibited no similarity to the consensus sequence.

The gene for a subunit of an ABC-type heme transporter is transcribed together with the gene for subunit 6 of NADH dehydrogenase in rice mitochondria

We previously identified a chloroplast-derived (ct-derived) sequence of 32 base pairs (bp) in rice mitochondrial DNA that includes a part (30 bp; psitrnI) of a gene for isoleucine tRNA (CAU) of the chloroplast. Analyzing the ct-derived psitrnI, we found that an open reading frame (orf240), which was homologous to the gene for a subunit of an ATP-binding cassette-type (ABC-type) heme transporter, namely helC, of Rhodobacter capsulatus, and a gene for subunit 6 of NADH dehydrogenase (nad6) were located upstream of and downstream from the ct-derived psitrnI, respectively. Northern-blot hybridization and analysis by reverse transcription-polymerase chain reaction (RT-PCR) revealed that both orf240 and nad6 were co-transcribed in rice mitochondria. An analysis of PCR-amplified fragments of the region of orf240/nad6 from the DNA of some Gramineae suggests that the arrangement of orf240/nad6 was generated in the mitochondrial genome of the genus Oryza during evolution after its divergence from the other Gramineae. Most of the transcripts of orf240 are edited, with a change from cytidine to uridine, at 35 positions. Editing of the RNA changes 33 amino-acid residues among the 240 encoded amino-acid residues, suggesting that the orf240 gene is functional in rice mitochondria.

Mitochondrial DNA 3394 mutation in the NADH dehydrogenase subunit 1 associated with non-insulin-dependent diabetes mellitus

Mitochondrial DNA (mtDNA) mutation is associated with a subtype of non-insulin-dependent diabetes mellitus (NIDDM). We identified two homoplasmic mtDNA mutations at the positions of 3394 (T-C) and 3423 (G-T) in a NIDDM patient with clinical features of mitochondrial encephalopathy. The mtDNA 3394T-C mutation changed a conserved tyrosine to a histidine in NADH dehydrogenase subunit 1. The frequency of mtDNA 3994 T-C mutation was determined with Polymerase Chain Reaction-Restriction Fragment Length Polymorphism (PCR-RFLP) in general NIDDM patients and nondiabetic control subjects. The mutation was seen in 4.9% of NIDDM patients and 1.3% of nondiabetic controls. It is indicated that the mtDNA 3394 T-C mutation is associated with NIDDM in Japan.

Loss of H19 imprinting in esophageal cancer

Recent articles have reported that loss of imprinting (LOI) of the endogenous gene H19 was frequently found in lung cancer and chorio-carcinoma, common adulthood cancers. Consequently, we examined the status of genomic imprinting of H19 in 29 esophageal and 48 colorectal cancer specimens, and studied its relation to the expression of H19. Of 12 esophageal cancer specimens heterozygous for the RsaI polymorphism, 6 (50%) exhibited LOI of H19, but none of the 18 colorectal cancer specimens heterozygous for the RsaI polymorphism exhibited LOI of H19. The present study suggests that LOI of H19 may play an important role in the pathogenesis of esophageal cancer. Moreover, H19 expression was frequently abundant in both cancers, and all six esophageal cancers carried LOI with overexpressed H19. Therefore, this overexpression of H19 seems to be an important phenomenon for the development of esophageal and colorectal cancer cells.