Exploring the structural assembly of rice ADP-glucose pyrophosphorylase subunits using MD simulation

ADP-glucose pyrophosphorylase plays a pivotal role as an allosteric enzyme, essential for starch biosynthesis in plants. The higher plant AGPase comparises of a pair of large and a pair of small subunits to form a heterotetrameric complex. Growing evidence indicates that each subunit plays a distinct role in regulating the underlying mechanism of starch biosynthesis. In the rice genome, there are four large subunit genes (OsL1-L4) and three small subunit genes (OsS1, OsS2a, and OsS2b). While the structural assembly of cytosolic rice AGPase subunits (OsL2:OsS2b) has been elucidated, there is currently no such documented research available for plastidial rice AGPases (OsL1:OsS1). In this study, we employed protein modeling and MD simulation approaches to gain insights into the structural association of plastidial rice AGPase subunits. Our results demonstrate that the heterotetrameric association of OsL1:OsS1 is very similar to that of cytosolic OsL2:OsS2b and potato AGPase heterotetramer (StLS:StSS). Moreover, the yeast-two-hybrid results on OsL1:OsS1, which resemble StLS:StSS, suggest a differential protein assembly for OsL2:OsS2b. Thus, the regulatory and catalytic mechanisms for plastidial AGPases (OsL1:OsS1) could be different in rice culm and developing endosperm compared to those of OsL2:OsS2b, which are predominantly found in rice endosperm.

The Rice Plastidial Phosphorylase Participates Directly in Both Sink and Source Processes

The plastidial starch phosphorylase (Pho1) functions in starch metabolism. A distinctive structural feature of the higher Pho1 is a 50–82-amino-acid long peptide (L50–L82), which is absent in phosphorylases from non-plant organisms. To study the function of the rice Pho1 L80 peptide, we complemented a pho1− rice mutant (BMF136) with the wild-type Pho1 gene or with a Pho1 gene lacking the L80 region (Pho1ΔL80). While expression of Pho1 in BMF136 restored normal wild-type phenotype, the introduction of Pho1ΔL80 enhanced the growth rate and plant productivity above wild-type levels. Mass spectrometry analysis of proteins captured by anti-Pho1 showed the surprising presence of PsaC, the terminal electron acceptor/donor subunit of photosystem I (PSI). This unexpected interaction was substantiated by reciprocal immobilized protein pull-down assays of seedling extracts and supported by the presence of Pho1 on isolated PSI complexes resolved by blue-native gels. Spectrophotometric studies showed that Pho1ΔL80 plants exhibited modified PSI and enhanced CO2 assimilation properties. Collectively, these findings indicate that the higher plant Pho1 has dual roles as a potential modulator of source and sink processes.

The plastid phosphorylase as a multiple-role player in plant metabolism

The physiological roles of the plastidial phosphorylase in starch metabolism of higher plants have been debated for decades. While estimated physiological substrate levels favor a degradative role, genetic evidence indicates that the plastidial phosphorylase (Pho1) plays an essential role in starch initiation and maturation of the starch granule in developing rice grains. The plastidial enzyme contains a unique peptide domain, up to 82 residues in length depending on the plant species, not found in its cytosolic counterpart or glycogen phosphorylases. The role of this extra peptide domain is perplexing, as its complete removal does not significantly affect the in vitro catalytic or enzymatic regulatory properties of rice Pho1. This peptide domain may have a regulatory function as it contains potential phosphorylation sites and, in some plant Pho1s, a PEST motif, a substrate for proteasome-mediated degradation. We discuss the potential roles of Pho1 and its L80 domain in starch biosynthesis and photosynthesis.

Re-programming of gene expression in the CS8 rice line over-expressing ADPglucose pyrophosphorylase induces a suppressor of starch biosynthesis

The CS8 transgenic rice (Oryza sativa L.) lines expressing an up-regulated glgC gene produced higher levels of ADPglucose (ADPglc), the substrate for starch synthases. However, the increase in grain weight was much less than the increase in ADPglc levels suggesting one or more downstream rate-limiting steps. Endosperm starch levels were not further enhanced in double transgenic plants expressing both glgC and the maize brittle-1 gene, the latter responsible for transport of ADPglc into the amyloplast. These studies demonstrate that critical processes within the amyloplast stroma restrict maximum carbon flow into starch. RNA-seq analysis showed extensive re-programming of gene expression in the CS8 with 2073 genes up-regulated and 140 down-regulated. One conspicuous gene, up-regulated ~15-fold, coded for a biochemically uncharacterized starch binding domain-containing protein (SBDCP1) possessing a plastid transit peptide. Confocal microscopy and transmission electron microscopy analysis confirmed that SBDCP1 was located in the amyloplasts. Reciprocal immunoprecipitation and pull-down assays indicated an interaction between SBDCP1 and starch synthase IIIa (SSIIIa), which was down-regulated at the protein level in the CS8 line. Furthermore, binding by SBDCP1 inhibited SSIIIa starch polymerization activity in a non-competitive manner. Surprisingly, artificial microRNA gene suppression of SBDCP1 restored protein expression levels of SSIIIa in the CS8 line resulting in starch with lower amylose content and increased amylopectin chains with a higher degree of polymerization. Collectively, our results support the involvement of additional non-enzymatic factors such as SBDCP in starch biosynthesis.

Mechanism Underlying Heat Stability of the Rice Endosperm Cytosolic ADP-Glucose Pyrophosphorylase

Rice grains accumulate starch as their major storage reserve whose biosynthesis is sensitive to heat. ADP-glucose pyrophosphorylase (AGPase) is among the starch biosynthetic enzymes severely affected by heat stress during seed maturation. To increase the heat tolerance of the rice enzyme, we engineered two dominant AGPase subunits expressed in developing endosperm, the large (L2) and small (S2b) subunits of the cytosol-specific AGPase. Bacterial expression of the rice S2b with the rice L2, potato tuber LS (pLS), or with the mosaic rice-potato large subunits, L2-pLS and pLS-L2, produced heat-sensitive recombinant enzymes, which retained less than 10% of their enzyme activities after 5 min incubation at 55°C. However, assembly of the rice L2 with the potato tuber SS (pSS) showed significantly increased heat stability comparable to the heat-stable potato pLS/pSS. The S2b assembled with the mosaic L2-pLS subunit showed 3-fold higher sensitivity to 3-PGA than L2/S2b, whereas the counterpart mosaic pLS-L2/S2b showed 225-fold lower sensitivity. Introduction of a QTC motif into S2b created an N-terminal disulfide linkage that was cleaved by dithiothreitol reduction. The QTC enzyme showed moderate heat stability but was not as stable as the potato AGPase. While the QTC AGPase exhibited approximately fourfold increase in 3-PGA sensitivity, its substrate affinities were largely unchanged. Random mutagenesis of S2b^QTC produced six mutant lines with elevated production of glycogen in bacteria. All six lines contained a L379F substitution, which conferred enhanced glycogen production in bacteria and increased heat stability. Modeled structure of this mutant enzyme revealed that this highly conserved leucine residue is located in the enzyme's regulatory pocket that provides interaction sites for activators and inhibitors. Our molecular dynamic simulation analysis suggests that introduction of the QTC motif and the L379F mutation improves enzyme heat stability by stabilizing their backbone structures possibly due to the increased number of H-bonds between the small subunits and increased intermolecular interactions between the two SSs and two LSs at elevated temperature.

RNA-Binding Protein RBP-P Is Required for Glutelin and Prolamine mRNA Localization in Rice Endosperm Cells

In developing rice (Oryza sativa) endosperm, mRNAs of the major storage proteins, glutelin and prolamine, are transported and anchored to distinct subdomains of the cortical endoplasmic reticulum. RNA binding protein RBP-P binds to both glutelin and prolamine mRNAs, suggesting a role in some aspect of their RNA metabolism. Here, we show that rice lines expressing mutant RBP-P mislocalize both glutelin and prolamine mRNAs. Different mutant RBP-P proteins exhibited varying degrees of reduced RNA binding and/or protein-protein interaction properties, which may account for the mislocalization of storage protein RNAs. In addition, partial loss of RBP-P function conferred a broad phenotypic variation ranging from dwarfism, chlorophyll deficiency, and sterility to late flowering and low spikelet fertility. Transcriptome analysis highlighted the essential role of RBP-P in regulating storage protein genes and several essential biological processes during grain development. Overall, our data demonstrate the significant roles of RBP-P in glutelin and prolamine mRNA localization and in the regulation of genes important for plant growth and development through its RNA binding activity and cooperative regulation with interacting proteins.

Predictors of failure to detect early hepatocellular carcinoma in patients with chronic hepatitis B who received regular surveillance

BACKGROUND

A proportion of chronic hepatitis B (CHB) patients are diagnosed with advanced hepatocellular carcinoma (HCC) despite regular surveillance.

AIMS

To determine predictors for HCC detection failure in CHB patients who underwent regular surveillance.

METHODS

CHB patients with well-preserved liver function, who underwent ultrasonography and alpha-foetoprotein (AFP) analysis every 6 months, were enrolled. Cox regression analysis was used to identify predictors for detection failure, defined as HCC initially diagnosed at Barcelona Clinic Liver Cancer (BCLC) stage B or C.

RESULTS

Of the 4590 CHB patients (mean age, 52.1 years; men, 61.6%), 169 patients were diagnosed with HCC (3.68%) and 35 (20.7%) HCC patients were initially diagnosed with HCC BCLC stage B or C. The cumulative incidence of HCC detection failure was 0.2% at year 1 and 1.3% at year 5. Multivariate analyses indicated that cirrhosis (hazard ratio [HR], 3.078; 95% CI, 1.389-6.821; P = 0.006), AFP levels ≥9 ng/mL (HR, 5.235; 95% CI, 2.307-11.957; P = 0.010), and diabetes mellitus (HR, 3.336; 95% CI, 1.341-8.296; P = 0.010) were independent predictors of HCC detection failure. Another model that incorporated liver stiffness (LS) values identified LS values ≥11.7 kPa (HR, 11.045; 95% CI, 2.066-59.037; P = 0.005) and AFP levels ≥9 ng/mL (HR, 4.802; 95% CI, 1.613-14.297; P = 0.005) as predictors of detection failure.

CONCLUSIONS

In CHB patients undergoing regular surveillance with ultrasonography and alpha-foetoprotein (AFP) analysis every 6 months, the HCC detection failure rate was not high (0.8% per person; 0.1% per test). However, careful attention should be paid in patients with advanced liver fibrosis (clinical cirrhosis or LS value >11.7 kPa), high AFP levels, or diabetes mellitus, who are prone to surveillance failure.

Plastidic phosphoglucomutase and ADP-glucose pyrophosphorylase mutants impair starch synthesis in rice pollen grains and cause male sterility

To elucidate the starch synthesis pathway and the role of this reserve in rice pollen, we characterized mutations in the plastidic phosphoglucomutase, OspPGM, and the plastidic large subunit of ADP-glucose (ADP-Glc) pyrophosphorylase, OsAGPL4 Both genes were up-regulated in maturing pollen, a stage when starch begins to accumulate. Progeny analysis of self-pollinated heterozygous lines carrying the OspPGM mutant alleles, osppgm-1 and osppgm-2, or the OsAGPL4 mutant allele, osagpl4-1, as well as reciprocal crosses between the wild type (WT) and heterozygotes revealed that loss of OspPGM or OsAGPL4 caused male sterility, with the former condition rescued by the introduction of the WT OspPGM gene. While iodine staining and transmission electron microscopy analyses of pollen grains from homozygous osppgm-1 lines produced by anther culture confirmed the starch null phenotype, pollen from homozygous osagpl4 mutant lines, osagpl4-2 and osagpl4-3, generated by the CRISPR/Cas system, accumulated small amounts of starch which were sufficient to produce viable seed. Such osagpl4 mutant pollen, however, was unable to compete against WT pollen successfully, validating the important role of this reserve in fertilization. Our results demonstrate that starch is mainly polymerized from ADP-Glc synthesized from plastidic hexose phosphates in rice pollen and that starch is an essential requirement for successful fertilization in rice.

Exposure to fine particulate matter associated with senile lentigo in Chinese women: a cross-sectional study

BACKGROUND

Skin ageing especially senile lentigo directly affects self-esteem. For decades, senile lentigo has been associated with chronic exposure to solar radiation. However, a study conducted recently in Caucasian subjects suggested that exposure to air pollution was significantly correlated with extrinsic skin ageing, in particular senile lentigines.

OBJECTIVE

To investigate the association between fine particulate matter (PM_2.5 ) and skin ageing, particularly senile lentigo and seborrheic keratosis.

METHODS

The study enrolled 400 Chinese women aged 40-90 years including 210 from the Yanqing county in Beijing (low PM_2.5 exposure group) and 190 from the Xuanwumen in Beijing (high PM_2.5 exposure group). Skin ageing symptoms, particularly senile lentigines and seborrheic keratoses, were clinically assessed using scores of intrinsic and extrinsic skin ageing. An ordinal logistic regression model was used to analyse the effect of PM_2.5 on skin ageing adjusted for factors underlying skin ageing.

RESULTS

In the study population of Xuanwumen, we found that senile lentigo on cheeks and back of hands was 1.48 times and 2.8 times higher, respectively, compared with those from Yanqing county. However, no association was found between PM_2.5 and seborrheic keratosis. We found that other variables such as smoking, second-hand smoking, contact with fossil fuels and skin types were significantly associated with skin ageing.

CONCLUSION

These results indicate that PM_2.5 was another extrinsic factor promoting skin ageing.

Rice Endosperm Starch Phosphorylase (Pho1) Assembles with Disproportionating Enzyme (Dpe1) to Form a Protein Complex That Enhances Synthesis of Malto-oligosaccharides

Starch synthesis in cereal grain endosperm is dependent on the concerted actions of many enzymes. The starch plastidial phosphorylase (Pho1) plays an important role in the initiation of starch synthesis and in the maturation of starch granule in developing rice seeds. Prior evidence has suggested that the rice enzyme, OsPho1, may have a physical/functional interaction with other starch biosynthetic enzymes. Pulldown experiments showed that OsPho1 as well as OsPho1 devoid of its L80 region, a peptide unique to higher plant phosphorylases, captures disproportionating enzyme (OsDpe1). Interaction of the latter enzyme form with OsDpe1 indicates that the putative regulatory L80 is not responsible for multienzyme assembly. This heterotypic enzyme complex, determined at a molar ratio of 1:1, was validated by reciprocal co-immunoprecipitation studies of native seed proteins and by co-elution chromatographic and co-migration electrophoretic patterns of these enzymes in rice seed extracts. The OsPho1-OsDpe1 complex utilized a broader range of substrates for enhanced synthesis of larger maltooligosaccharides than each individual enzyme and significantly elevated the substrate affinities of OsPho1 at 30 °C. Moreover, the assembly with OsDpe1 enables OsPho1 to utilize products of transglycosylation reactions involving G1 and G3, sugars that it cannot catalyze directly.

The plastidial starch phosphorylase from rice endosperm: catalytic properties at low temperature

Consistent with its essential role in starch biosynthesis at low temperatures, the plastidial starch phosphorylase from rice endosperm is highly active at low temperature. Moreover, contrary to results on other higher plant phosphorylases, the L80 peptide, a domain unique to plant phosphorylases and not present in orthologous phosphorylases from other organisms, is not involved in enzyme catalysis. Starch phosphorylase (Pho) is an essential enzyme in starch synthesis in developing rice endosperm as the enzyme plays a critical role in both the early and maturation phases of starch granule formation especially at low temperature. In this study, we demonstrated that the rice Pho1 maintains substantial enzyme activity at low temperature (<20 °C) and its substrate affinities for branched α-glucans and glucose-1-phosphate were significantly increased at the lower reaction temperatures. Under sub-saturating substrate conditions, OsPho1 displayed higher catalytic activities at 18 °C than at optimal 36 °C, supporting the prominent role of the enzyme in starch synthesis at low temperature. Removal of the highly charged 80-amino acid sequence L80 peptide, a region found exclusively in the plastidial Pho1 of higher plants, did not significantly alter the catalytic and regulatory properties of OsPho1 but did affect heat stability. Our kinetic results support the low temperature biosynthetic role of OsPho1 in rice endosperm and indicate that its L80 region is unlikely to have a direct enzymatic role but provides stability of the enzyme under heat stress.

Analysis of the Rice ADP-Glucose Transporter (OsBT1) Indicates the Presence of Regulatory Processes in the Amyloplast Stroma That Control ADP-Glucose Flux into Starch

Previous studies showed that efforts to further elevate starch synthesis in rice (Oryza sativa) seeds overproducing ADP-glucose (ADPglc) were prevented by processes downstream of ADPglc synthesis. Here, we identified the major ADPglc transporter by studying the shrunken3 locus of the EM1093 rice line, which harbors a mutation in the BRITTLE1 (BT1) adenylate transporter (OsBt1) gene. Despite containing elevated ADPglc levels (approximately 10-fold) compared with the wild-type, EM1093 grains are small and shriveled due to the reduction in the amounts and size of starch granules. Increases in ADPglc levels in EM1093 were due to their poor uptake of ADP-[(14)C]glc by amyloplasts. To assess the potential role of BT1 as a rate-determining step in starch biosynthesis, the maize ZmBt1 gene was overexpressed in the wild-type and the GlgC (CS8) transgenic line expressing a bacterial glgC-TM gene. ADPglc transport assays indicated that transgenic lines expressing ZmBT1 alone or combined with GlgC exhibited higher rates of transport (approximately 2-fold), with the GlgC (CS8) and GlgC/ZmBT1 (CS8/AT5) lines showing elevated ADPglc levels in amyloplasts. These increases, however, did not lead to further enhancement in seed weights even when these plant lines were grown under elevated CO2. Overall, our results indicate that rice lines with enhanced ADPglc synthesis and import into amyloplasts reveal additional barriers within the stroma that restrict maximum carbon flow into starch.

Substrate binding properties of potato tuber ADP-glucose pyrophosphorylase as determined by isothermal titration calorimetry

Substrate binding properties of the large (LS) and small (SS) subunits of potato tuber ADP-glucose pyrophosphorylase were investigated by using isothermal titration calorimetry. Our results clearly show that the wild type heterotetramer (S(WT)L(WT)) possesses two distinct types of ATP binding sites, whereas the homotetrameric LS and SS variant forms only exhibited properties of one of the two binding sites. The wild type enzyme also exhibited significantly increased affinity to this substrate compared to the homotetrameric enzyme forms. No stable binding was evident for the second substrate, glucose-1-phosphate, in the presence or absence of ATPγS suggesting that interaction of glucose-1-phosphate is dependent on hydrolysis of ATP and supports the Theorell-Chance bi bi reaction mechanism.

Effects of guar gum ingestion on postprandial blood pressure in older adults

OBJECTIVES

The aim of this study was to investigate the effects of guar gum on postprandial blood pressure in older people.

DESIGN

A randomized, double-blind, placebo-controlled, cross-over design.

SETTING

Community senior centers in B city, South Korea.

PARTICIPANTS

Twenty-two older female adults aged 67 to 88 with postprandial hypotension.

INTERVENTION

The participants were randomly assigned to guar gum (semi-fluid food with 9 gram) or placebo intervention during the first treatment phase. After a washout period of 1 week, the two interventions were switched to the other in the second treatment phase.

MEASUREMENTS

Blood pressure was measured during both phases before having a meal and every 15 minutes during 120 minutes after a meal with automated sphygmomanometer.

RESULTS

Change in systolic blood pressure (SBP) over time was significantly different between guar gum and placebo groups (F=4.07, p=0.001). Compared with placebo group, guar gum group had significantly low prevalence of postprandial hypotension (PPH) (guar gum group=18.2% vs. placebo group=72.7%; χ² =13.20, p<0.001). It also had significant difference in change of diastolic blood pressure (DBP) over time between guar gum and placebo groups (F=2.49, p=0.027).

CONCLUSION

This findings show that guar gum could be effective on postprandial drops in blood pressure in older female adults.

The role of the large subunit in redox regulation of the rice endosperm ADP-glucose pyrophosphorylase

The starch regulatory enzyme ADP-glucose pyrophosphorylase is activated by 3-phosphoglyceric acid (3-PGA) and inhibited by inorganic phosphate (Pi ). The activity of the plastid-localized enzyme is also subject to fine regulation by redox control in response to changing light and sugar levels. The less active oxidized form of the enzyme contains an inter-subunit disulfide bond formed between the pair of small subunit's Cys12 residues of the heterotetrameric enzyme. Although this cysteine residue is not conserved in the small subunits of cereal endosperm cytosolic AGPases, biochemical studies of the major rice endosperm enzyme indicate that the cytosolic isoform, like the plastidial enzymes, is subject to redox control. Kinetic analysis revealed that the reduced forms of the partially purified native and purified recombinant AGPases have 6- and 3.4-fold, respectively, more affinity to 3-PGA, rendering the enzymes more active at lower 3-PGA concentration than the non-reduced enzyme. Truncation of the large subunit by removal of N-terminal peptide resulted in a decrease in 3-PGA affinity and loss of redox response of the enzyme. Site-directed mutagenesis of the conserved cysteine residues at the N-terminal of the large subunit showed that C47 and C58, but not C12, are essential for proper redox response of the enzyme. Overall, our results show that the major rice endosperm AGPase activity is controlled by a combination of allosteric regulation and redox control, the latter through modification of the large subunit instead of the small subunit as evident in the plastid-localized enzyme.

The rice endosperm ADP-glucose pyrophosphorylase large subunit is essential for optimal catalysis and allosteric regulation of the heterotetrameric enzyme

Although an alternative pathway has been suggested, the prevailing view is that starch synthesis in cereal endosperm is controlled by the activity of the cytosolic isoform of ADPglucose pyrophosphorylase (AGPase). In rice, the cytosolic AGPase isoform is encoded by the OsAGPS2b and OsAGPL2 genes, which code for the small (S2b) and large (L2) subunits of the heterotetrameric enzyme, respectively. In this study, we isolated several allelic missense and nonsense OsAGPL2 mutants by N-methyl-N-nitrosourea (MNU) treatment of fertilized egg cells and by TILLING (Targeting Induced Local Lesions in Genomes). Interestingly, seeds from three of the missense mutants (two containing T139I and A171V) were severely shriveled and had seed weight and starch content comparable with the shriveled seeds from OsAGPL2 null mutants. Results from kinetic analysis of the purified recombinant enzymes revealed that the catalytic and allosteric regulatory properties of these mutant enzymes were significantly impaired. The missense heterotetramer enzymes and the S2b homotetramer had lower specific (catalytic) activities and affinities for the activator 3-phosphoglycerate (3-PGA). The missense heterotetramer enzymes showed more sensitivity to inhibition by the inhibitor inorganic phosphate (Pi) than the wild-type AGPase, while the S2b homotetramer was profoundly tolerant to Pi inhibition. Thus, our results provide definitive evidence that starch biosynthesis during rice endosperm development is controlled predominantly by the catalytic activity of the cytoplasmic AGPase and its allosteric regulation by the effectors. Moreover, our results show that the L2 subunit is essential for both catalysis and allosteric regulatory properties of the heterotetramer enzyme.

The potato tuber, maize endosperm and a chimeric maize-potato ADP-glucose pyrophosphorylase exhibit fundamental differences in Pi inhibition

ADP-glucose pyrophosphorylase (AGPase) is highly regulated by allosteric effectors acting both positively and negatively. Enzymes from various sources differ, however, in the mechanism of allosteric regulation. Here, we determined how the effector, inorganic phosphate (Pi), functions in the presence and absence of saturating amounts of the activator, 3-phosphoglyceric acid (3-PGA). This regulation was examined in the maize endosperm enzyme, the oxidized and reduced forms of the potato tuber enzyme as well as a small subunit chimeric AGPase (MP), which contains both maize endosperm and potato tuber sequences paired with a wild-type maize large subunit. These data, combined with our previous kinetic studies of these enzymes led to a model of Pi inhibition for the various enzymes. The Pi inhibition data suggest that while the maize enzyme contains a single effector site that binds both 3-PGA and Pi, the other enzymes exhibit more complex behavior and most likely have at least two separate interacting binding sites for Pi. The possible physiological implications of the differences in Pi inhibition distinguishing the maize endosperm and potato tuber AGPases are discussed.

The frequency and impact of ROS1 rearrangement on clinical outcomes in never smokers with lung adenocarcinoma

BACKGROUND

To determine the frequency and predictive impact of ROS1 rearrangements on treatment outcomes in never-smoking patients with lung adenocarcinoma.

PATIENTS AND METHODS

We concurrently analyzed ROS1 and ALK rearrangements and mutations in the epidermal growth factor receptor (EGFR), and KRAS in 208 never smokers with lung adenocarcinoma. ROS1 and ALK rearrangements were identified by fluorescent in situ hybridization.

RESULTS

Of 208 tumors screened, 7 (3.4%) were ROS1 rearranged, and 15 (7.2%) were ALK-rearranged. CD74-ROS1 fusions were identified in two patients using reverse transcriptase-polymerase chain reaction. The frequency of ROS1 rearrangement was 5.7% (6 of 105) among EGFR/KRAS/ALK-negative patients. Patients with ROS1 rearrangement had a higher objective response rate (ORR; 60.0% versus 8.5%; P = 0.01) and a longer median progression-free survival (PFS; not reached versus 3.3 months; P = 0.008) to pemetrexed than those without ROS1/ALK rearrangement. The PFS to EGFR-tyrosine kinase inhibitors in patients harboring ROS1 rearrangement was shorter than those without ROS1/ALK rearrangement (2.5 versus 7.8 months; P = 0.01).

CONCLUSIONS

The frequency of ROS1 rearrangements in clinically selected patients is higher than that reported for unselected patients, suggesting that ROS1 rearrangement is a druggable target in East-Asian never smokers with lung adenocarcinoma. Given the different treatment outcomes to conventional therapies and availability of ROS1 inhibitors, identification of ROS1 rearrangement can lead to successful treatment in ROS1-rearranged lung adenocarcinomas.

Exploiting leaf starch synthesis as a transient sink to elevate photosynthesis, plant productivity and yields

Improvements in plant productivity (biomass) and yield have centered on increasing the efficiency of leaf CO(2) fixation and utilization of products by non-photosynthetic sink organs. We had previously demonstrated a correlation between photosynthetic capacity, plant growth, and the extent of leaf starch synthesis utilizing starch-deficient mutants. This finding suggested that leaf starch is used as a transient photosynthetic sink to recycle inorganic phosphate and, in turn, maximize photosynthesis. To test this hypothesis, Arabidopsis thaliana and rice (Oryza sativa L.) lines were generated with enhanced capacity to make leaf starch with minimal impact on carbon partitioning to sucrose. The Arabidopsis engineered plants exhibited enhanced photosynthetic capacity; this translated into increased growth and biomass. These enhanced phenotypes were displayed by similarly engineered rice lines. Manipulation of leaf starch is a viable alternative strategy to increase photosynthesis and, in turn, the growth and yields of crop and bioenergy plants.

Plant growth promotion and Penicillium citrinum

BACKGROUND

Endophytic fungi are known plant symbionts. They produce a variety of beneficial metabolites for plant growth and survival, as well as defend their hosts from attack of certain pathogens. Coastal dunes are nutrient deficient and offer harsh, saline environment for the existing flora and fauna. Endophytic fungi may play an important role in plant survival by enhancing nutrient uptake and producing growth-promoting metabolites such as gibberellins and auxins. We screened roots of Ixeris repenes (L.) A. Gray, a common dune plant, for the isolation of gibberellin secreting endophytic fungi.

RESULTS

We isolated 15 endophytic fungi from the roots of Ixeris repenes and screened them for growth promoting secondary metabolites. The fungal isolate IR-3-3 gave maximum plant growth when applied to waito-c rice and Atriplex gemelinii seedlings. Analysis of the culture filtrate of IR-3-3 showed the presence of physiologically active gibberellins, GA1, GA3, GA4 and GA7 (1.95 ng/ml, 3.83 ng/ml, 6.03 ng/ml and 2.35 ng/ml, respectively) along with other physiologically inactive GA5, GA9, GA12, GA15, GA19, GA20 and, GA24. The plant growth promotion and gibberellin producing capacity of IR-3-3 was much higher than the wild type Gibberella fujikuroi, which was taken as control during present study. GA5, a precursor of bioactive GA3 was reported for the first time in fungi. The fungal isolate IR-3-3 was identified as a new strain of Penicillium citrinum (named as P. citrinum KACC43900) through phylogenetic analysis of 18S rDNA sequence.

CONCLUSION

Isolation of new strain of Penicillium citrinum from the sand dune flora is interesting as information on the presence of Pencillium species in coastal sand dunes is limited. The plant growth promoting ability of this fungal strain may help in conservation and revegetation of the rapidly eroding sand dune flora. Penicillium citrinum is already known for producing mycotoxin citrinin and cellulose digesting enzymes like cellulase and endoglucanase, as well as xylulase. Gibberellins producing ability of this fungus and the discovery about the presence of GA5 will open new aspects of research and investigations.

Identification of psychrophile Shewanella sp. KMG427 as an eicosapentaenoic acid producer

An isolate from holothurians was identified as an eicosapentaenoic acid (EPA)-producing bacterium KMG427, which is characterized by EPA synthesis efficiency, by thin layer and gas chromatographic analyses. The EPA production was maximized to more than 10% of the total fatty acids by incubation at 4o degrees C after cell proliferation at 20 degrees C. The isolated bacterium was categorized as Gramnegative, rod-shaped, aerobic, and motile with a single polar flagellum. According to phylogenetic analysis based on morphological and physiological specificities as an EPA-producing bacterium, the isolate KMG427 was found to belong to the genus Shewanella. The 16S rDNA of KMG427 was revealed to have 100% of sequence identity to that of S. hanedai CIP 103207T. Therefore, the isolate might be classified and identified as Shewanella sp. KMG427.

Mutation of the plastidial alpha-glucan phosphorylase gene in rice affects the synthesis and structure of starch in the endosperm

Plastidial phosphorylase (Pho1) accounts for approximately 96% of the total phosphorylase activity in developing rice (Oryza sativa) seeds. From mutant stocks induced by N-methyl-N-nitrosourea treatment, we identified plants with mutations in the Pho1 gene that are deficient in Pho1. Strikingly, the size of mature seeds and the starch content in these mutants showed considerable variation, ranging from shrunken to pseudonormal. The loss of Pho1 caused smaller starch granules to accumulate and modified the amylopectin structure. Variation in the morphological and biochemical phenotype of individual seeds was common to all 15 pho1-independent homozygous mutant lines studied, indicating that this phenotype was caused solely by the genetic defect. The phenotype of the pho1 mutation was temperature dependent. While the mutant plants grown at 30 degrees C produced mainly plump seeds at maturity, most of the seeds from plants grown at 20 degrees C were shrunken, with a significant proportion showing severe reduction in starch accumulation. These results strongly suggest that Pho1 plays a crucial role in starch biosynthesis in rice endosperm at low temperatures and that one or more other factors can complement the function of Pho1 at high temperatures.

Authentic seed-specific activity of the Perilla oleosin 19 gene promoter in transgenic Arabidopsis

The Perilla (Perilla frutescens L. cv. Okdong) oleosin gene, PfOle19, produces a 19-kDa protein that is highly expressed only in seeds. The activity of the -2,015 bp 5'-upstream promoter region of this gene was investigated in transgenic Arabidopsis plants using the fusion reporter constructs of enhanced green fluorescent protein (EGFP) and beta-glucuronidase (GUS). The PfOle19 promoter directs Egfp expression in developing siliques, but not in leaves, stems or roots. In the transgenic Arabidopsis, EGFP fluorescence and histochemical GUS staining were restricted to early seedlings, indehiscent siliques and mature seeds. Progressive 5'-deletions up to the -963 bp position of the PfOle19 promoter increases the spatial control of the gene expression in seeds, but reduces its quantitative levels of expression. Moreover, the activity of the PfOle19 promoter in mature seeds is 4- and 5-fold greater than that of the cauliflower mosaic virus 35S promoter in terms of both EGFP intensity and fluorometric GUS activity, respectively.

Identification of the ADP-glucose pyrophosphorylase isoforms essential for starch synthesis in the leaf and seed endosperm of rice (Oryza sativa L.)

ADP-glucose pyrophosphorylase (AGP) catalyzes the first committed step of starch biosynthesis in higher plants. To identify AGP isoforms essential for this biosynthetic process in sink and source tissues of rice plants, we analyzed the rice AGP gene family which consists of two genes, OsAGPS1 and OsAGPS2, encoding small subunits (SSU) and four genes, OsAGPL1, OsAGPL2, OsAGPL3 and OsAGPL4, encoding large subunits (LSU) of this enzyme heterotetrameric complex. Subcellular localization studies using green fluorescent protein (GFP) fusion constructs indicate that OsAGPS2a, the product of the leaf-preferential transcript of OsAGPS2, and OsAGPS1, OsAGPL1, OsAGPL3, and OsAGPL4 are plastid-targeted isoforms. In contrast, two isoforms, SSU OsAGPS2b which is a product of a seed-specific transcript of OsAGPS2, and LSU OsAGPL2, are localized in the cytosol. Analysis of osagps2 and osagpl2 mutants revealed that a lesion of one of the two cytosolic isoforms, OsAGPL2 and OsAGPS2b, causes a shrunken endosperm due to a remarkable reduction in starch synthesis. In leaves, however, only the osagps2 mutant appears to severely reduce the transitory starch content. Interestingly, the osagps2 mutant was indistinguishable from wild type during vegetative plant growth. Western blot analysis of the osagp mutants and wild type plants demonstrated that OsAGPS2a is an SSU isoform mainly present in leaves, and that OsAGPS2b and OsAGPL2 are the major SSU and LSU isoforms, respectively, in the endosperm. Finally, we propose a spatiotemporal complex model of OsAGP SSU and LSU isoforms in leaves and in developing endosperm of rice plants.

Subunit interactions specify the allosteric regulatory properties of the potato tuber ADP-glucose pyrophosphorylase

ADP-glucose pyrophosphorylase (AGPase) catalyzes the first committed step of starch synthesis in plants. The potato tuber enzyme contains a pair of catalytic small subunits (SSs) and a pair of non-catalytic large subunits (LSs). We have previously identified a LS mutant containing a P52L replacement, which rendered the enzyme with down-regulatory properties. To investigate the structure-function relationships between the two subunits with regard to allosteric regulation, putative SS mutants that could reverse the down-regulatory condition of LS(P52L) were identified by their ability to restore glycogen accumulation in an AGPase-deficient Escherichia coli glgC-strain. Two distinct LS-dependent classes, bona fide SS suppressors dependent on LS(P52L) but not LS(WT) and SS up-regulating allosteric mutants, were evident by kinetic analysis. These results indicate that both LS and SS have a regulatory function in controlling allosteric properties through enhancing cooperative subunit interactions.

Catalytic implications of the higher plant ADP-glucose pyrophosphorylase large subunit

ADP-glucose pyrophosphorylase, a key regulatory enzyme of starch biosynthesis, is composed of a pair of catalytic small subunits (SSs) and a pair of catalytically disabled large subunits (LSs). The N-terminal region of the LS has been known to be essential for the allosteric regulatory properties of the heterotetrameric enzyme. To gain further insight on the role of this region and the LS itself in enzyme function, the six proline residues found in the N-terminal region of the potato tuber AGPase were subjected to scanning mutagenesis. The wildtype and various mutant heterotetramers were expressed using our newly developed host-vector system, purified, and their kinetic parameters assessed. While P(17)L, P(26)L, and P(55)L mutations only moderately affected the kinetic properties, P(52)L and P(66)L gave rise to significant and contrasting changes in allosteric properties: P(66)L enzyme displayed up-regulatory properties toward 3-PGA while the P(52)L enzyme had down-regulatory properties. Unlike the other mutants, however, various mutations at P(44) led to only moderate changes in regulatory properties, but had severely impaired catalytic rates, apparent substrate affinities, and responsiveness to metabolic effectors, indicating Pro-44 or the LS is essential for optimal catalysis and activation of the AGPase heterotetramer. The catalytic importance of the LS is further supported by photoaffinity labeling studies, which revealed that the LS binds ATP at the same efficiency as the SS. These results indicate that the LS, although considered having no catalytic activity, may mimic many of the catalytic events undertaken by the SS and, thereby, influences net catalysis of the heterotetrameric enzyme.

ATP binding site in the plant ADP-glucose pyrophosphorylase large subunit

The ATP binding region in the catalytically inactive large subunit (LS) of the potato tuber ADP-glucose pyrophosphorylase was identified and investigated. Mutations at the ATP binding significantly affected not only the apparent affinities for ATP and Glc-1-P, and catalytic rate but also in many instances, sensitivity to 3-phosphoglycerate. The catalytic rates of the LS mutant enzymes correlated most strongly with changes in the affinity toward ATP, a relationship substantiated by photoaffinity labeling studies with azido-ATP analog. These results indicate that the LS, although catalytically defective, interacts cooperatively with the catalytic small subunit in binding substrates and effectors and, in turn, influencing net catalysis.

Rapid purification of the potato ADP-glucose pyrophosphorylase by polyhistidine-mediated chromatography

In an attempt to obtain facile methods to purify the heterotetrameric ADP-glucose pyrophosphorylase (AGPase), polyhistidine tags were attached to either the large (LS) or small (SS) subunits of this oligomeric enzyme. The addition of polyhistidine tag to the N-terminus of the LS or SS and co-expression with its unmodified counterpart subunit resulted in substantial induction of enzyme activity. In contrast, attachment of a polyhistidine-containing peptide through the use of a commercially available pET vector or addition of polyhistidine tags to the C-terminal ends of either subunit resulted in poor expression and/or production of enzyme activity. Preliminary experiment showed that these polyhistidine N-terminal-tagged enzymes interacted with Ni-NTA-agarose, indicating that immobilized metal affinity chromatography (IMAC) would be useful for efficient purification of the heterotetrameric AGPases. When ion-exchange chromatography step was employed prior to the IMAC, the polyhistidine-tagged AGPases were purified to near homogeneity. Comparison of kinetic parameters between AGPases with and without the polyhistidine tags revealed that attachment of the polyhistidine did not alter the allosteric and catalytic properties of the enzymes. These results indicate that polyhistidine tags will be useful for the rapid purification of preparative amounts of AGPases for biochemical and physical studies.

Allosteric regulation of the higher plant ADP-glucose pyrophosphorylase is a product of synergy between the two subunits

The higher plant ADP-glucose pyrophosphorylase (AGPase) is a heterotetramer consisting of two regulatory large subunits (LSs) and two catalytic small subunits (SSs). To further characterize the roles of these subunits in determining enzyme function, different combinations of wildtype LS (LWT) and variant forms (LUpReg1, LM345) were co-expressed with wildtype SS (SWT) and variant forms (STG-15 and Sdevo330) and their enzyme properties compared to those measured for the heterotetrameric wildtype enzyme and SS homotetrameric enzymes. Analysis of the allosteric regulatory properties of the various enzymes indicates that although the LS is required for optimal activation by 3-phosphoglyceric acid and resistance to Pi, the overall allosteric regulatory and kinetic properties are specified by both subunits. Our results show that the regulatory and kinetic properties of AGPase are not simply due to the LS modulating the properties of the SS but, instead, are a product of synergistic interaction between the two subunits.

Molecular cloning and expression analysis of 3-ketoacyl-ACP synthases in the immature seeds of Perilla frutescens

We report the isolation and expression analysis of two cDNAs encoding 3-ketoacyl-acyl carrier protein synthases (KAS) that are involved in the de novo synthesis of fatty acids in plastids of perilla (Perilla frutescens L.). The cDNAs, designated PfFAB1 and PfFAB24, encoded polypeptides with high sequence identities to those of KAS I and KAS II/IV, respectively, of various plants. Genomic Southern blots revealed that there was a single PfFAB1 gene but two PfFAB24 genes in the perilla genome. Of interest is that the expression of both genes was developmentally regulated in seeds. Their mRNA expression patterns in seeds were also discussed in comparison with the profile of fatty acid accumulation.

Infantile head injury, with special reference to the development of chronic subdural hematoma

An infantile head injury has unique features in that infants are totally helpless and dependent on their parents, and biomechanical characteristics of the skull and brain are very different from those of other age groups. The authors reviewed a total of 16 infant head injury patients under 12 months of age who were treated in our hospital from 1989 to 1997. Birth head injury was excluded. The most common age group was 3-5 months. Early seizures were noted in 7 cases, and motor weakness in 6. Three patients with acute intracranial hematoma and another 3 with depressed skull fracture were operated on soon after admission. Chronic subdural hematomas (SDHs) developed in 3 infants. Initial CT scans showed a small amount of SDH that needed no emergency operation. Resolution of the acute SDH and development of subdural hygroma appeared on follow-up CT scans within 2 weeks of injury. Two of these infants developed early seizures. Chronic SDH was diagnosed on the 68th and 111th days after the injuries were sustained, respectively. The third patient was the subject of close follow-up with special attention to the evolution of chronic SDH in view of our experience in the previous 2 cases, and was found to have developed chronic SDH on the 90th day after injury. All chronic SDH patients were successively treated by subduro-peritoneal shunting. In conclusion, the evolution of chronic SDH from acute SDH is relatively common following infantile head injury. Infants with head injuries, especially if they are associated with acute SDH and early development of subdural hygroma, should be carefully followed up with special attention to the possible development of chronic SDH

Molecular cloning and functional expression of Perilla frutescens 3-ketoacyl-(acyl carrier protein) synthase III

The 3-ketoacyl-acyl carrier protein synthase III (KAS III) is a condensing enzyme catalyzing the initial step of fatty acid biosynthesis. We isolated two KAS III cDNA isoforms (PfKAS3a and PfKAS3b) from a cDNA library specific to Perilla frutescens immature seeds. Two cDNAs coded for 401 and 400 amino acids, respectively, which showed high degree of sequence similarity to corresponding enzymes from various sources. Results of Southern hybridization indicated that the PfKAS3a gene is present as two copies, whereas the PJKAS3b gene is a single copy. While both genes were equally expressed in high levels during early stages of seed maturation in a development-specific manner, the PfKAS3b transcript showed more prolonged appearance. Expression of the functional recombinant perilla KAS III increased the myristate level in E. coli but it exerted no appreciable effect on cell growth.

Noise-induced chaos in an optically injected semiconductor laser model

The chaos induced by an intrinsic spontaneous-emission noise in an optically injected semiconductor laser is investigated through a single-mode injection model. A method is developed to quantitatively study the scale-dependent noise effect in general, and the noise-induced chaotic feature in particular. We find that noise at an experimentally measured level can induce chaos in the system. This suggests that noise-induced chaos may indeed exist in real systems. Certain required characteristics for noise to induce chaos are identified: the periodic state itself, when subject to weak noise, should undergo a process that is much more diffusive than the Brownian motion, and the adjacent chaotic states should still behave chaotically on certain finite scales when subject to noise. We believe they are generic features for noise to induce chaos. The correlation dimension of the clean and noisy attractors is also calculated to study noise-induced changes in the geometrical structure of the attractors.

Soft drugs. 12. Design, synthesis, and evaluation of soft bufuralol analogues

In the search for more potent but still short-acting beta-blockers (BB), the methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, 2-(1-adamantyl)ethyl, and methylthiomethyl esters of the acidic inactive metabolite of bufuralol were synthesized based on the "inactive metabolite" approach. The cleavage of the ester bond by blood and tissue esterases rapidly deactivates these compounds, resulting in an ultrashort duration of action. The beta-antagonist potencies and time courses of actions of the new "soft" BBs were characterized by recording ECG and intra-arterial blood pressure (BP) in rats. In the isoproterenol-induced tachycardia model, while bufuralol at an iv dose of 1 mg/kg (3.8 micromol/kg) diminished heart rate (HR) for at least 2 h, the effects of the soft drugs lasted for only 10-30 min at equimolar dose. The inactive metabolite did not decrease HR significantly. The first four members of this series of compounds showed the highest beta-blocking potencies, ranging between 25% and 50% of that of bufuralol. Next, the effects of these most active compounds on resting HR and BP were evaluated in comparison to esmolol. Infused for 10 min at a rate of 20 micromol/kg/min, esmolol decreased HR and mean arterial pressure (MAP) by 40% and 60%, respectively. The soft drugs at doses ranging only between 2 and 4 micromol/kg/min resulted in a 20-40% decrease in HR and a 30-50% reduction in MAP. However, the time courses of both the bradycardic and hypotensive effects of the soft drugs were superimposable to that of esmolol, diminishing within 60 min after the discontinuation of the infusions.

Secondary structural and phylogenetic implications of nuclear large subunit ribosomal RNA in the ectomycorrhizal fungus Tricholoma matsutake

The sequence of large subunit (LSU) and 5.8S rRNA genes has been determined for Tricholoma matsutake. A secondary structure model was predicted for both LSU and 5.8S rRNAs, showing most of the structural features consistent with those of the consensus secondary structure model proposed for the eukaryotic cytoplasmic LSU rRNAs. With a reconstructed eukaryotic phylogeny based on full-length LSU rDNA sequences, T. matsutake was placed on the same branch with Cryptococcus neoformans as its closest neighbor. We proposed that T. matsutake be considered as one of the representative members of the division Basidiomycota. Here we report for the first time the complete LSU rRNA gene sequence in T. matsutake, a member of Homobasidiomycetes.

Syntheses and cytotoxicities of four stereoisomers of muricatacin from D-glucose

Four stereoisomers of muricatacin 1a-d were prepared by the reaction of corresponding aldehydes 4a-d, which in turn were prepared from D-glucose, with the anion of triethylphosphonoacetate followed by reduction and cyclization under acidic conditions. Cytotoxicities of four stereoisomers were tested against in vitro A-549 cell line as well as MCF-7 cell line. Stereochemistry at C4 and C5 position of muricatacin did not affect the cytotoxicities significantly.

Small-subunit ribosomal DNA of an ectomycorrhizal fungus tricholoma matsutake: sequence, structure and phylogenetic analysis

A 2861 bp nucleotide sequence containing Tricholoma matsutake SSU rRNA gene and its flanking regions was determined and analyzed. Comparison with known SSU rDNA sequences and primer extension analysis revealed that the SSU rRNA coding region and intergenic spacer 2 (IGS2) are 1805 bp and 1043 bp in length, respectively. The IGS2 has an imperfect direct repeat (type 1) homologous to the region downstream to the 5S rRNA gene and the three imperfect tandem direct repeats (type 2) upstream to the SSU rRNA-encoding sequence. Structural analysis by a comparative method showed that the overall secondary structure of the SSU rRNA is generally similar to that of S. cerevisiae, whereas the secondary structures of the V4 regions predicted by the thermodynamics-based method showed different configurations between distantly related taxa, implying that these structural differences can provide phylogenetically informative features. Phylogenetic trees based on both the aligned SSU rRNA sequences with almost full-length sequences and V4 sequences revealed that T. matsutake is very closely related to other basidiomycetes belonging to Agaricales. Thus we propose that the V4 region is also a good source for the inference of phylogeny to support the SSU rRNA phylogeny.

Prolonged ethanol intake increases D2 dopamine receptor expression in the rat brain

Dopamine via interaction with its receptor is known to be involved in the behavioral and endocrine actions in the mammalian brain. Behavioral effects produced by ethanol appear to be due to its actions on the dopaminergic system. In the present study using in situ hybridization histochemistry and RNase protection assay, the effect of prolonged ethanol intake on the expression of D2 dopamine receptor mRNA was examined in the rat brain. Specific D1 and D2 receptor mRNA signals were detected in the caudate putamen, nucleus accumbens, olfactory tubercle, hippocampus, dentate gyrus, and amygdaloid complex of the rat brain. Within the hypothalamus, the level of receptor mRNA was low in most nuclei with a somewhat higher level in the arcuate nucleus. Only the supurachiasmatic nucleus showed moderate to dense dopamine receptor mRNAs. Prefrontal cortex showed hybridization signals but their intensity was very low. A considerable amount of D2 mRNA was localized in the substantia nigra but D1 mRNA was not. Ethanol (10%) intake for 5 weeks increased both the density of hybridization signal and number of cells expressing D2 dopamine receptor mRNA in the caudate putamen, and nucleus accumbens, but not in the olfactory tubercle. RNase protection assay revealed about a 1.5-fold increase in the D2 dopamine receptor mRNA level in the corpus striatum. These results provide a basis for the involvement of dopamine D2 receptor expression in alcoholism.

Cementless total hip arthroplasty with AML, PCA and HGP prostheses

Two hundred and fourteen patients who had 270 cementless hip prostheses were followed for 2 to 8 years. PCA (Porous-Coated Monatomic), AML (Monatomic Medullary Locking) and HGP (Harris-Galante-Porous) femoral stems and acetabular cups were used without any preference for the prostheses. The overall clinical results were similar for the three prostheses with average Harris hip scores of 93, 93 and 91 respectively. Four PCA prostheses had radiological aseptic loosening and one was revised because of polyethylene wear. There was no loosening in the AML and HGP prostheses. Pain in the thigh, usually slight, occurred in 17% of AML, 21% of PCA and 19% of HGP prostheses. Five years after operation, radiological changes such as migration, calcar remodelling and radiolucent lines were the same for the 3 prostheses, but bony ingrowth was greater with the AML femoral stems.

Growth hormone replacement therapy in adults with growth hormone deficiency; thrice weekly low dose administration

Recent reports on growth hormone (GH) therapy have shown that GH has various beneficial effects in GH deficient adults. In most of these studies, GH was administered daily. Because GH is still expensive and has to be delivered by subcutaneous injection, we studied the 6-month therapeutic effects of thrice weekly GH injection therapy and compared it with daily therapy. Twenty eight adult patients with GH deficiency were randomly assigned into group 1 (ten cases, thrice weekly injections of GH), group 2 (nine cases, daily injections), and group 3 (nine cases, placebo injections). Lean body mass, serum basal GH levels, and insulin-like growth factor 1 levels significantly increased after six months of GH therapy in both groups 1 and 2. According to computed tomography, the mean mid-thigh muscle mass significantly increased in group 1, while the visceral fat mass significantly decreased in group 2. GH levels significantly increased exercise rate-pressure product and hand grip strength only in group 1. These results suggest that thrice weekly injections of GH are as effective as daily injections in GH deficient adults.

Vascular injury during total hip arthroplasty: the anatomy of the acetabulum

We encountered a massive retroperitoneal haemorrhage due to perforation of the external iliac vein by a drill tip passing through the antero-superior quadrant of the acetabulum during cementless total hip arthroplasty. An anatomical study of the acetabulum was undertaken to determine the safe zones for transacetabular screw fixation. Five cadavera were studied to find the proper locations for screws using acetabular quadrants. The postero-superior and postero-inferior acetabular quadrants have good bone stock and are safe for the transacetabular replacement of screws. The antero-superior and inferior quadrants should be avoided. Screws placed in these quadrants may damage the external iliac artery and vein or the obturator vessels.

[Evaluation of radiation doses in mammography]

A dedicated X-ray mammography was introduced to our hospital from 1987 and an imaging receptor of xeroradiography was applied. We reported previously that the average air exposure was 0.79R and that the absorption dose of skin was 1.00 rad. These data are similar to literature reports. Screen-film mammography was introduced recently. To select the best breast imaging and the least radiation exposure, diverse methods were investigated. A dosimetry (Capintec model 192) and a PS-033 parallel ionization chamber were applied to compare the absorption dose on polystyrene phantom between various exposure factors, the application of breast clamp and the size of exposure field. Retrospective estimation of the radiation dose was obtained from the exposure factors of previous mammography since July, 1990 to May, 1992. There were 1035 xeromammographic examinations and 358 examinations with medium-speed screen-film mammography. Another 61 craniocaudal and 96 mediolateral projections with high-speed screen-film mammography were recruited during the recent two months. An ionization chamber (Exradin, Shonka-Wyckoff A5) with an electrometer (Keithley 617) wer selected to obtain the dose equivalent from air exposure between selected exposure factors. The radiation dose of mammography is linearly correlated with voltage/kV and current/mAs. The application of a breast clump reduces 10% of the skin dose. The average exposure factors of xeromammography are 45.6 kV, 163.5 mAs. These results remain the same as in our previous report. Xeromammography has a greater exposure to air, estimated average glandular dose and absorbed dose than screen-film mammography. The mean exposure factor of rapid screen-film mammography gains half the value of medium screen-film mammography, ie. 26.6 kV, 87.0 mAs vs. 26.0 kV, 164.5 mAs.(ABSTRACT TRUNCATED AT 250 WORDS)

Cementless total hip arthroplasty with PCA prosthesis

Eighty-one cases of cementless porous-coated total hip arthroplasties in 74 patients were analyzed. Hip rating scores as described by Harris were used, and AP and lateral radiographs were made serially: preoperatively, 3 months, 6 months, 1 year, and 2 years postoperatively. The average postoperative hip rating score was 91 points (range: 76 to 100 points) at 1 year and 93 points (range: 74 to 100 points) at 2 years. The overall clinical results were satisfactory in these patients at both 2 and 4 years. However, slight to mild thigh pain was observed in 16 (19.8%) of 81 hips at 2 years, and 10 (21.3%) of 47 hips at 4 years postoperatively. Moderate to severe limp was seen in 11 (13.6%) of 81 hips at 2 years and seven (14.9%) of 47 hips at 4 years postoperatively.

Induction of osteochondromas by periosteal resection

Forty immature and 40 mature rabbits which received periosteal resection from the proximal metaphyses or diaphyses of tibiae were evaluated for the occurrence of osteochondromas at the sites of periosteal defects. Thirteen of 20 immature tibiae with the periosteal defects at their proximal metaphyses showed osteochondromas covered by hyaline cartilage caps. We assume that the occurrence of osteochondroma at the metaphyseal region of growing long bone, where the periosteal defects were made, is due primarily to a decrease in the power of the periosteum to control the circumferential growth of the metaphysis, and is due secondarily to an abnormal proliferation of cartilage progenitors located in Ranvier's groove.

Changes of cardiac output during treadmill exercise by impedance cardiography

Nine athletes and ten nonathletes were selected randomly to study the changes of cardiac function during exercise by impedance cardiography. The speed of the treadmill was maintained at 3.4 mph, and its grade was increased by 1% (Balke protocol). The exercise was continued until the target heart rate (THR), 85% of maximum oxygen uptake (VO2max). The measured parameters for pre- and post-exercise were stroke volume (SV), heart rate (HR), and cardiac output (CO). Average stroke volume of athletes at pre-exercise, 71.1 ml, was higher than that of nonathletes, 64.6 ml, and stroke volume of the former at post-exercise, 97.0 ml, was also higher than that of the latter, 85.2 ml. Therefore, despite the lower heart rate, cardiac outputs of athletes at pre- and post-exercise, 4.98 and 16.3 L/min, were higher than those of nonathletes, 4.87 and 14.2 L/min. For the second phase of the study, cardiac outputs of three subjects were measured during the continuous treadmill exercise with newly developed electrodes and shoes for minimizing motion artifact. Though there were several studies measuring cardiac output during continuous bicycle exercise, this is thought to be the first study in the world measuring cardiac output during continuous treadmill exercise without aid of ensemble averaging.

Effects of ketamine on contractile responses in vascular smooth muscle

This study was designed to determine the effects of ketamine on contractions induced by norepinephrine (NE), K+ or histamine (Hist) and on agonist-induced calcium mobilization, in rabbit thoracic aorta with or without endothelium. Contractile responses to NE, K+ or Hist were markedly attenuated by prior exposure to ketamine. Subsequent addition of ketamine to the rabbit aorta undergoing an isometric contraction induced by NE, K+ or Hist also decreased the contractile responses in a calcium ion concentration-dependent manner. Preincubation with ketamine produced a concentration-dependent inhibition of contractile responses elicited by the addition of calcium ion (1.6 mM) to a Ca(++)-free depolarizing solution. However, the phasic contraction produced by NE with 2mM lanthanum pretreatment, which is release of intracellular calcium, was also inhibited by ketamine. Moreover, the tonic contraction produced by NE after depletion of the agonist-releasable pool of intracellular calcium, which is thought to be due to calcium influx, was depressed by ketamine. These data suggest that ketamine relaxes NE-contracted rings of rabbit thoracic aorta by decreasing calcium entry and by producing an extracellular calcium-independent relaxant effect.

Orderly stimulation of skeletal muscle motor units with tripolar nerve cuff electrode

An electrical nerve stimulation technique, using single tripolar electrode, was shown to be capable of recruiting motor units according to their size, while allowing simultaneous but independent control of firing rate in the active units. Test paradigms consisting of established fundamental physiological concepts of soleus-gastrocnemius architecture, motor units conduction velocity, firing rate behavior of motor units of different sizes, and their susceptibility to fatigue were employed to validate the technique and demonstrate its utility as a basic and applied research tool.