Association between non-vascularised bone graft failure and compartment of the defect in mandibular reconstruction: a systematic review and meta-analysis

Controversy exists regarding the influence of the graft placement site in the mandible on the success of non-vascularised bone grafts. In this study, we examine the association between the compartment of the mandibular defect and the bone graft failure rate. A systematic literature review and meta-analysis was performed using MEDLINE, Embase, and Cochrane databases. Failure rates according to the compartment of mandibular defect were extracted and analysed by meta-analysis. The Newcastle-Ottawa Scale was used to assess the quality of the studies, and publication bias was evaluated using funnel plots. The search strategy identified 27 publications. After screening, five were selected for review. Based on the result of comparison among these five, we found no significant statistical association between the bone graft failure rate and compartment of mandibular defect, although further investigation of prospective randomised cohort studies is required.

Risk factors for the delayed diagnosis of extrapulmonary TB

BACKGROUND: Extrapulmonary TB (EPTB) is more difficult to diagnose than pulmonary TB. The delayed management of EPTB can lead to complications and increase the socio-economic burden.METHODS: Patients newly diagnosed with EPTB were retrospectively enrolled from 11 general hospitals in South Korea from January 2017 to December 2018. The basic characteristics of patients were described. Univariable and multivariable analyses were performed between early and delayed diagnosis groups to identify risk factors for delayed diagnosis and treatment in EPTB.RESULTS: In total, 594 patients were enrolled. Lymph node TB (28.3%) was the predominant form, followed by abdominal (18.4%) and disseminated TB (14.5%). Concurrent lung involvement was 17.8%. The positivity of diagnostic tests showed no significant difference between the two groups. Acute clinical manifestations in disseminated, pericardial and meningeal TB, and immunosuppression were associated with early diagnosis. Delayed diagnosis was associated with outpatient clinic visits, delayed sample acquisition and diagnostic departments other than infection or pulmonology.CONCLUSION: The delay in diagnosis and treatment of EPTB was not related to differences in microbiological characteristics of Mycobacterium tuberculosis itself; rather, it was due to the indolent clinical manifestations that cause referral to non-TB-specialised departments in the outpatient clinic and delay the suspicion of TB and diagnostic testing.

Enhanced antimicrobial stewardship based on rapid phenotypic antimicrobial susceptibility testing for bacteraemia in patients with haematological malignancies: a randomized controlled trial

OBJECTIVES

Recently, rapid phenotypic antimicrobial susceptibility testing (AST) based on microscopic imaging analysis has been developed. The aim of this study was to determine whether implementation of antimicrobial stewardship programmes (ASP) based on rapid phenotypic AST can increase the proportion of patients with haematological malignancies who receive optimal targeted antibiotics during early periods of bacteraemia.

METHODS

This randomized controlled trial enrolled patients with haematological malignancies and at least one positive blood culture. Patients were randomly assigned 1:1 to conventional (n = 60) or rapid phenotypic (n = 56) AST. The primary outcome was the proportion of patients receiving optimal targeted antibiotics 72 hr after blood collection for culture.

RESULTS

The percentage receiving optimal targeted antibiotics at 72 hr was significantly higher in the rapid phenotypic AST group (45/56, 80.4%) than in conventional AST group (34/60, 56.7%) (relative risk (RR) 1.42, 95% confidence interval (CI) 1.09-1.83). The percentage receiving unnecessary broad-spectrum antibiotics at 72 hr was significantly lower (7/26, 12.5% vs 18/60, 30.0%; RR 0.42, 95% CI 0.19-0.92) and the mean time to optimal targeted antibiotic treatment was significantly shorter (38.1, standard deviation (SD) 38.2 vs 72.8, SD 93.0 hr; p < 0.001) in the rapid phenotypic AST group. The mean time from blood collection to the AST result was significantly shorter in the rapid phenotypic AST group (48.3, SD 17.6 vs 83.1, SD 22.2 hr).

DISCUSSION

ASP based on rapid phenotypic AST can rapidly optimize antibiotic treatment for bacteraemia in patients with haematological malignancy. Rapid phenotypic AST can improve antimicrobial stewardship in immunocompromised patients.

Morphometric and molecular characterization of populations of Pratylenchus kumamotoensis and P. pseudocoffeae (Nematoda, Pratylenchidae) newly recorded in Korea

At least 70 species of root-lesion nematodes, Pratylenchus spp., have been identified worldwide, many of which are serious pests of various agricultural crop plants. In Korea, only 14 species have been recorded in vegetable and fruit fields. Here, we report two new records of root-lesion nematode species in Korea based on morphometric and molecular methods. Soil samples were collected from chrysanthemum cultivars in various regions. Morphometric diagnosis showed that two new records for Korea: Pratylenchus kumamotoensis in Chilgok County and Pratylenchus pseudocoffeae in Geumsan County. In addition, molecular diagnosis using the two sequences of the internal transcribed spacer (ITS) and the D2-D3 region of ribosomal DNA showed that these two species were most similar with those from Japan, Costa Rica and USA. The similarities of the ITS and D2-D3 sequences were 99.85 and 99.74%, respectively, for Pratylenchus kumamotoensis and 99.99 with Costa Rica populations and 99.86% with USA populations, respectively, for Pratylenchus pseudocoffeae. To our knowledge, this is the first report of two species in Korea.

The Bradyrhizobium japonicum hsfA gene exhibits a unique developmental expression pattern in cowpea nodules

The Bradyrhizobium japonicum host-specific fixation gene hsfA was identified as essential for nitrogen fixation on cowpea, but not required for nitrogen fixation on soybean or siratro. The DNA sequence of the hsfA promoter contains a consensus RpoN, -24/-12 binding site, suggesting the involvement of a regulatory protein that binds to an upstream activating sequence (UAS). To further explore the regulation of this interesting gene, serial deletions of the hsfA promoter were made and fused with the beta-glucuronidase (GUS) gene. The HsfA3 deletion, containing 60 bp 5' of the -24/-12 sequence, showed a similar level of GUS expression to that shown by the longest fusion construct (HsfA1), containing 464 bp of upstream sequence. In contrast, the HsfA4-GUS fusion, containing only 20 bp 5' of the -24/-12 region, showed no GUS activity, delimiting the location of a putative UAS to a 40-bp region. During nodule development, GUS expression first appeared in nodules 12 days postinoculation (dpi) and reached a maximum level of expression in approximately 17-day-old nodules. By 28 dpi, HsfA-GUS expression had returned to a low, basal level. These data were consistent with the detection of hsfA mRNA by in situ hybridization in 17-day-old nodules, but not in 28-day-old nodules. In contrast to the stage-specific expression in cowpea, HsfA-GUS expression increased with nodule development in HsfA3-inoculated soybean. These data indicate that HsfA expression is regulated in cowpea in a unique developmental manner and that the DNA regulatory regions that control this expression are confined to a short, promoter-proximal region.

Cardiac Characteristics of Transgenic Mice Overexpressing Refsum Disease Gene-Associated Protein within the Heart

Arrhythmia is a common cardiac symptom of Refsum disease. Recently, we identified a novel neuron-specific PAHX-associated protein (PAHX-AP1), which binds to the Refsum disease gene (PAHX). In this report, we developed heart-targeted transgenic (TG) mice under the control of alpha-myosin heavy chain promoter to determine whether cardiac overexpression of PAHX-AP1 provokes cardiac involvement symptoms. Northern and in situ hybridization analyses revealed PAHX-AP1 transcript was overexpressed in TG atrium, especially in the sinoatrial node. TG mice showed tachycardia, and tachyarrhythmia was observed in 20% of TG mice. Isolated TG atria showed higher frequency beating and were more sensitive to aconitine-induced tachyarrhythmia than the wild-type, and 40% of the TG atria showed irregular beating. Action potential duration in TG atrial fiber was shortened much more than the wild-type. Systemic administration of arrhythmogenic agents induced arrhythmia in TG mice, while no arrhythmia with the same dose in nonTG mice. Our results indicate that the chronic atrial tachycardia by overexpressed neuron-specific PAHX-AP1 transgene in atrium may be responsible for the increased susceptibility to arrhythmia.

Structure and expression of the Arabidopsis thaliana homeobox gene Athb-12

We have isolated the Arabidopsis thaliana homeobox gene Athb-12, determined its structure and activation domain, demonstrated that its promoter is inducible in response to abscisic acid (ABA) treatment, and characterized the cellular distribution of its transcripts. The single intron of the gene interrupted the leucine-zipper domain region. The 5' regulatory region of Athb-12 can drive beta-glucuronidase (GUS) expression in tobacco transgenic plants. Athb-12 gene expression was further examined using in situ hybridization to determine the cellular distribution of Athb-12 transcripts during ABA induction. A complex pattern of Athb-12 expression was observed, often associated with regions of developing vascular tissues. Analysis of chimeras constructed from Athb-12 and the DNA-binding domain of the Saccharomyces cerevisiae transcription factor GAL4 revealed that the activation domain of Athb-12 lies in the C-terminal region (amino acids 180 to 235). Taken together, our data suggest that Athb-12 is a transcriptional activator important in regulating certain developmental processes as well as in the plant's response to water stress involving ABA-mediated gene expression.

Current multimodality management of infectious intracranial aneurysms

OBJECTIVE

To implement an algorithm for and assess multimodality (medical, endovascular, and microsurgical) treatment of patients with infectious intracranial aneurysms.

METHODS

Twenty patients with 27 infectious aneurysms were treated during a 10-year period. Bacterial endocarditis was the most common cause (65%). Most aneurysms presented with rupture (75%), and the middle cerebral artery was the most common location (70%).

RESULTS

Five patients were treated endovascularly, with direct coiling for three patients and parent artery occlusion for two patients. Ten patients (15 aneurysms) were treated surgically, with 6 aneurysms being trapped/resected, 2 trapped/bypassed, 4 clipped, and 3 wrapped. Five patients were treated medically. Treatment-associated neurological morbidity was observed for two patients (10%), and two patients died (10%). Good outcomes were observed for 16 patients (80%).

CONCLUSION

Factors that guide management decisions for these patients include aneurysm rupture, hematomas with increased intracranial pressure, and the eloquence of brain tissue supplied by the parent artery. Patients with unruptured infectious aneurysms are initially treated medically, with antibiotics and serial angiography. Patients with ruptured aneurysms that are not associated with hematomas and that do not involve eloquent vascular territory are treated endovascularly. Patients with ruptured aneurysms are treated surgically when there is a hematoma or the risk of ischemic complications in eloquent territory. Therefore, endovascular therapy is the first option for patients in stable condition with ruptured aneurysms; surgical therapy is the first option for patients in unstable condition with ruptured aneurysms and the second option for patients in stable condition who experience failure of endovascular therapy. Medically treated patients with enlarging or dynamic unruptured aneurysms also require direct surgical or endovascular intervention. Favorable patient outcomes can be achieved with this multimodality management.

Identification and characterization of multiple isoforms of a mouse ribosome receptor

We isolated multiple cDNA clones encoding various isoforms of a mouse ribosome receptor protein (mRRp). The cDNAs were isolated from a 13.5-day-old mouse conceptus cDNA library by polymerase chain reaction-based screening. The predicted proteins encoded by these cDNAs showed significant homology with ribosome receptors present in dogs (83%), humans (80%), and chickens (45%). The cDNA isoforms had highly identical N- and C-terminal sequences but differed in their central sequences, suggesting that these cDNA isoforms may be derived by alternative splicing from a single gene. Genomic Southern blot analysis confirmed the existence of only a single mouse ribosome receptor gene. Alignments of the deduced amino acid sequences of the mRRp cDNA isoforms revealed that they differ in the number of decapeptide repeats present in the central domain of the protein. These repeats have been previously suggested to mediate ribosome binding and thus differences in repeat number may translate to different ribosome binding abilities. The longest mRRp isoform had 61 tandem repeats. This is of interest because in the human and canine ribosome receptor proteins there are only 54 tandem repeats, suggesting that humans and dogs may also have larger ribosome receptor protein isoforms. Surprisingly, mRRp has a very short basic C-terminal sequence of only 35 amino acids, while in contrast, the known human and canine forms of this protein have acidic C-terminal regions comprised of 803 and 798 amino acid residues, respectively. Although the function of the C-terminal region is currently unknown, it may be that those C-terminal sequences that are present in human and canine RRp proteins but missing in mRRp do not play critical roles in RRp function. The cDNA of the ES/130 isoform, which lacks tandem repeats and presumably are unable to bind ribosomes, could be isolated by reverse transcriptase-PCR from E 13.5 mouse embryos. mRRp mRNAs were expressed in all tissues examined but expression levels of each isoform differed between tissues. The identification of multiple mRRp isoforms in the mouse will allow us to study the regulation and function of ribosome receptors on a genetic level.

Insulin stimulates production of nitric oxide via ERK in osteoblast cells

We explored to determine if iNOS could be induced by insulin in osteoblast-like UMR-106 cells. Insulin (100 nM) stimulated nitric oxide production by twofold and significantly increased iNOS mRNA and protein levels. Insulin also increased collagen synthesis, but had little effect on alkaline phosphatase activity. In contrast, IGF-1 had little effect on NO production below 10 nM and it stimulated NO production by only 57% at 100 nM. IGF-1 had little effect on collagen levels, whereas it inhibited alkaline phosphatase activities in a dose-dependent manner. When an MEK inhibitor was preincubated, insulin failed to stimulate NO production, whereas insulin dramatically increased NO production in the ERK1 overexpressed cells. Taken together, it is proposed that insulin increases iNOS mRNA, iNOS protein, and NO production, possibly via activation of ERK. These may play an important role in osteoblast functions such as collagen synthesis.

Cloning of the histidine biosynthetic genes from Corynebacterium glutamicum: organization and analysis of the hisG and hisE genes

The physically linked hisG and hisE genes, encoding for ATP-phosphoribosyltransferase and phosphoribosyl-ATP-pyrophosphohydrolase were isolated from the Corynebacterium glutamicum gene library by complementation of Escherichia coli histidine auxotrophs. They are two of the nine genes that participate in the histidine biosynthetic pathway. Molecular genetics and sequencing analysis of the cloned 9-kb insert DNA showed that it carries the hisG and hisE genes. In combining this result with our previous report, we propose that all histidine biosynthetic genes are separated on the genome by three unlinked loci. The coding regions of the hisG and hisE genes are 279 and 87 amino acids in length with a predicted size of about 30 and 10 kDa, respectively. Computer analysis revealed that the amino acid sequences of the hisG and hisE gene products were similar to those of other bacteria.

Identification and characterization of a new member of the placental prolactin-like protein-C (PLP-C) subfamily, PLP-Cbeta

We have isolated a complementary DNA (cDNA) clone that encodes a new member of the PRL-like protein-C (PLP-C) subfamily of the PRL gene family. The clone was amplified from a 13.5-day-old mouse conceptus cDNA library by PCR using primers based on conserved regions of PLP-C sequences. The full-length cDNA encodes a predicted protein of 241 residues, which contains a putative signal sequence and 2 putative N-linked glycosylation sites. The predicted protein shares 55-66% amino acid identity with mouse PLP-Calpha and rat PLP-D, PLP-H, PLP-Cv, and PLP-C and also contains 6 homologously positioned cysteine residues. Thus, we named this protein PLP-Cbeta for consistency. We have also isolated rat PLP-Cbeta from rat placenta cDNA library. Surprisingly, two messenger RNA (mRNA) isoforms of rat PLP-Cbeta were isolated: one mRNA (rPLP-Cbeta) encodes a 241-amino acid product, but another mRNA (rPLP-Cbetadelta39) lacks 39 bases that encode for a region rich in aromatic amino acids. The 39-bp region corresponds to exon 3 of other PLP-C subfamily members, such as PLP-Calpha, PLP-Cv, and d/tPRP. It suggests that the two isoforms are probably generated by an alternative splicing from a single gene. RT-PCR analysis revealed that the rPLP-Cbeta form was dominantly expressed in placenta, although both isoforms are coexpressed during placentation. The mouse PLP-Cbeta mRNA expression, which was specific to the placenta, was first detected by Northern analysis on embryonic day 11.5 (E 11.5) and persisted until birth. However, in situ hybridization analysis revealed mPLP-Cbeta expression on E 10.5 in specific trophoblast subsets, such as giant cells and spongiotrophoblast cells. mPLP-Cbeta mRNA was detected in the labyrinthine zone on E 18.5, suggesting that spongiotrophoblast cells had penetrated the labyrinthotrophoblast zone. Consistent with the observed expression in trophoblast giant cells, PLP-Cbeta expression was also detected in in vitro differentiated Rcho-1 cells, which express the trophoblast giant cell phenotype. In summary, overall high amino acid identity (79%), the locations of cysteine residues, and consensus sites for N-linked glycosylation between mouse and rat PLP-Cbeta clearly indicate that PLP-Cbeta is a bona fide member of the PLP-C subfamily. The conservation between mouse and rat, the presence of alternative isoforms, and the pattern of expression during gestation suggest the biological significance of PLP-Cbeta during pregnancy.

Identification and characterization of Psx-2, a novel member of the Psx (placenta-specific homeobox) family

Psx (now designated as Psx-1) is a murine placenta-specific homeobox gene. Here, we report the isolation and characterization of a second mouse Psx gene (Psx-2). Although 29bp were absent towards the 3' end of Psx-2, Psx-2 and Psx-1 cDNA had identical 5' and 3' ends. Overall sequence identity between the two cDNAs was 91% at the nucleotide level and 81% at the amino acid level. Both Psx proteins contain 227 amino acids. These results suggest that they arose through a recent gene duplication. A surprising finding is that the 81% sequence identity between Psx-1 and Psx-2 proteins drops at the level of homeodomain to 78%. Further, the amino acid at position 51, which is invariably an asparagine in other homeodomains and is known to contact DNA directly, is a methionine in the homeodomains of both Psx-1 and Psx-2. This suggests that Psx proteins may interact with DNA sequences differently to those bound by other homeodomains. Southern blot analysis indicated that the two Psx genes occur on separate loci in the mouse genome. The Psx-2 gene spans approx. 2. 6kb of mouse genome, and contains four exons and three introns.

Role of hsfA gene on host-specificity by Bradyrhizobium japonicum in a broad range of tropical legumes

Bradyrhizobium japonicum mutant strain NAD163, containing a 30-kb deletion mutant encompassing the hsfA gene, was inoculated onto a broad range of legume species to test host-specificity. Most legume species formed ineffective nodules except Vigna angularis var. Chibopat and Glycine max var. Pureunkong. A hsfA insertion mutant, BjjC211, gave similar results to strain NAD163, implying that many legume species require HsfA for host-specific nitrogen fixation. To determine whether other genes in the deleted region of NAD163 are also necessary, the hsfA gene was conjugally transferred into the NAD163 mutant. The transconjugant formed effective nodules on the host legume plants, which earlier had formed ineffective nodules with mutant NAD163. Thus, we conclude that the hsfA gene in the 30-kb region is the only factor responsible for host-specific nitrogen fixation in legume plants.

Psx homeobox gene is X-linked and specifically expressed in trophoblast cells of mouse placenta

We previously isolated a cDNA clone for a homeobox-containing gene with its expression restricted to the extraembryonic tissues. In this study, Psx gene expression was further examined using in situ hybridization to determine the cellular distribution of Psx transcripts during embryo development. Psx expression was first detected at embryonic day 8.5 only in trophoblast giant cells and chorionic ectoderm. At E 9.5 and E 13.5, the expression was restricted to the giant cells and the labyrinthine trophoblast layer. In addition, the gene expression was detected in differentiated Rcho-1 trophoblast cells in vitro, which is typical of trophoblast giant cells in vivo, but not in proliferating Rcho-1 cells and HRP-1 cells. Interestingly, rat Psx homologue mRNA is about 200 bp shorter than mouse Psx, suggesting that there is a high degree of sequence divergence between the mouse and rat Psx homologues. The sequence divergence, perhaps as a result of rapid evolution, is further supported by the zoo blot analysis because the Psx gene was detectable only in mouse and rat but not in other vertebrate species tested. Psx is localized to the murine X chromosome. Taken together, our results suggest that Psx gene plays a unique role in the function of differentiated trophoblast cells and also serves as a useful model for studying trophoblast cell lineages and the rapid evolution of homeobox genes.

Cloning of the argF gene encoding the ornithine carbamoyltransferase from Corynebacterium glutamicum

The argF gene encoding ornithine carbamoyl-transferase (OTCase; EC2.1.3.3) has been cloned from Corynebacterium glutamicum by transforming the Escherichia coli arginine auxotroph with the genomic DNA library. The cloned DNA also complements the E. coli argG mutant, suggesting a clustered organization of the genes in the genome. We have determined the DNA sequence of the minimal fragment complementing the E. coli argF mutant. The coding region of the cloned gene is 957 nucleotides long with a deduced molecular mass of about 35 kDa polypeptide. The enzyme activity and size of the expressed protein in the E. coli auxotroph carrying the argF gene revealed that the cloned gene indeed codes for OTCase. Analysis of the amino acid sequence of the predicted protein revealed a strong similarity to the corresponding protein of other bacteria.

Molecular cloning and analysis of the argC gene from Corynebacterium glutamicum

The argC gene encoding N-acetylglutamate 5-semialdehyde dehydrogenase has been cloned from Corynebacterium glutamicum by transforming Escherichia coli arginine auxotroph with the genomic DNA library. Based on the restriction map of the cloned DNA, we have subcloned and sequenced the minimal DNA fragment complementing the E. coli argC mutant. The coding region of the cloned gene is 1041 nucleotides long with a predicted molecular mass of about 38 kDa polypeptide. Enzyme activity and size of the expressed protein in the E. coli auxotroph carrying the recombinant argC gene revealed that the cloned gene indeed codes for N-acetylglutamate 5-semialdehyde dehydrogenase. Computer analysis of the amino acid sequences of the predicted protein revealed a strong similarity to the corresponding protein of other bacteria.

A new homeodomain-leucine zipper gene from Arabidopsis thaliana induced by water stress and abscisic acid treatment

We report the isolation and characterization of a new homeobox gene from Arabidopsis thaliana using a polymerase chain reaction (PCR) cloning strategy. The full-length cDNA, designated Athb-12, encodes a protein of 235 amino acids. It contains the conserved DNA binding domain and the leucine zipper motif, characteristic of the homeodomain-leucine zipper family of transcription factors. The deduced amino acid sequence of Athb-12 shows over 80% identity to the Arabidopsis Athb-7 in the homeodomain (82%) and the leucine zipper motif (80%) of the proteins. However, outside the homeodomain and the leucine zipper motif, the homology is significantly lower. RNA analysis identified only one 0.96 kb transcript consistent with the size of Athb-12 cDNA. The Athb-12 transcript was detected in stem, leaf, flower and root as well as in seedlings. Treatment with water stress and exogenous abscisic acid (ABA) resulted in the accumulation of Athb-12 mRNA, similar to that of Athb-7. However, the time course of the Athb-12 response to ABA differed from that of Athb-7, suggesting that both genes, in response to ABA, are regulated in different manners. Taken together, these data suggest that Athb-12 and Athb-7 are members of a related gene family involved in the plant's response to water stress.

Psx, a novel murine homeobox gene expressed in placenta

To identify homeobox genes involved in mouse embryo development, we have screened a mouse cDNA library prepared from the 13.5-day-old entire conceptus for homeobox-containing sequences using a polymerase chain reaction (PCR) cloning strategy. We identified a mouse homeobox gene that might be the prototype of a new class. The full-length cDNA, designated Psx (placenta specific-homeobox), encodes a protein of 247 amino acids. The expression patterns of the Psx during embryonic development and in adult tissues were studied by Northern blot analysis. The Psx transcript was first detected at embryonic day 8.5 of conceptus and persisted until birth. Psx mRNA is expressed in extraembryonic tissues, mainly in placenta, but not in fetus, pups and adult tissues tested, suggesting that Psx plays an important role in placenta. Psx is a new member of the murine homeobox genes which are expressed in extraembryonic tissues such as placenta and amnion.

Cowden's disease--a report on the first case in Korea and literature review

Cowden's disease, or multiple hamartoma syndrome, is an uncommon condition with characteristic mucocutaneous lesions associated with abnormalities of the breast, thyroid, and gastrointestinal tract. We describe a 32-year-old man with oral mucosal papillomatosis and plantar hyperkeratosis as a definite case of Cowden's disease according to the criteria proposed by Salem and Steck. The patient also had a thyroid mass and numerous gastrointestinal polyps endoscopically. Histologically the polyps were hamartomatous or hyperplastic polyps. The oral papillary lesions were fibroepithelial polyps and the thyroid mass was a follicular adenoma. We review the literature on this entity and summarize the pertinent findings. To the best of our knowledge, this is the first documented case of Cowden's disease in a Korean.

Hormonal and nutritional control of the fatty acid synthase promoter in transgenic mice

To study the molecular basis of tissue-specific and hormonally regulated expression of the fatty acid synthase (FAS) gene in vivo, we generated lines of transgenic mice carrying 2.1 kilobases of the 5'-flanking region (-2100 to +67) of the rat FAS gene fused to a chloramphenicol acetyltransferase (CAT) reporter gene. This reporter gene construct was strongly expressed in tissues that normally express high levels of FAS mRNA, which include liver and white adipose tissues. In contrast, CAT reporter activity was not detected in appreciable levels in lung, heart, kidney, and muscle tissues, which do not normally show significant levels of FAS activity. The relative levels of the CAT mRNA driven by the rat FAS promoter in various tissues of the transgenic animals approximated those of the endogenous mouse FAS mRNA. We also examined the hormonal and nutritional regulation of the FAS(2.1)-CAT reporter gene in transgenic mice. CAT activity was increased in both liver and white adipose tissue when fasted animals were refed a high carbohydrate, fat-free diet. These changes in CAT activity and CAT mRNA levels occurred in parallel to the changes in endogenous mouse FAS mRNA levels. On the other hand, fasting/refeeding did not change CAT activity appreciably in other tissues, such as muscle and brown adipose tissue. Administration of dibutyryl cAMP at the start of refeeding prevented an increase in CAT activity in liver. However, the cAMP effect was tissue-specific as cAMP treatment did not bring about change in CAT activity in adipose tissue. Next, to examine the effect of insulin, we made the transgenic mice insulin-deficient by streptozotocin treatment. Insulin treatment of the streptozotocin-diabetic mice increased both the CAT activity and CAT mRNA levels driven by the rat FAS promoter in liver and white adipose tissue. These changes in CAT expression by insulin paralleled those in endogenous FAS mRNA levels. Administration of glucocorticoids increased CAT activity in all tissues examined: liver, white and brown adipose tissues, lung, heart, and spleen. Overall, the first 2.1 kilobases of the 5'-flanking region of the rat FAS gene appear to contain sequence elements necessary to confer tissue-specific and hormonally regulated expression characteristic of the endogenous FAS gene.

Identification and characterization of a novel Bradyrhizobium japonicum gene involved in host-specific nitrogen fixation

To understand the genetic mechanism of host specificity in the interaction between rhizobia and their hosts, it is important to identify genes that influence both early and late steps in symbiotic development. This paper focuses on the little-understood genetics of host-specific nitrogen fixation. A deletion mutant of Bradyrhizobium japonicum, strain NAD163, was found to induce effective, nitrogen-fixing nodules on soybean and siratro plants but produced ineffective nodules on cowpea plants. Additional transposon and deletion mutants defined a small region that conferred this phenotype, and this region was sequenced to identify two putative open reading frames (ORFs). Data indicate that only one of these ORFs is detectable in bacteroids. This ORF was termed hsfA, with a predicted protein product of 11 kDa. The transcriptional start site of hsfA was determined and found to coincide with a predicted RpoN-dependent promoter. Microscopic studies of nodules induced by the wild type and hsfA mutants on cowpea and soybean plants indicate that the cowpea mutant nodules are slow to develop. The data indicate that hsfA appears to play a crucial role in bacteroid development on cowpea but does not appear to be essential for nitrogen fixation on the other hosts tested.

The function and differential sorting of a family of aplysia prohormone processing enzymes

We have cloned four members of the family of subtilisin-like endoproteases expressed in the bag cell neurons of Aplysia and have demonstrated that two of these enzymes are capable of correctly cleaving the egg-laying hormone precursor. The egg-laying hormone precursor undergoes an ordered series of cleavages, such that different peptides are differentially sorted into distinct secretory vesicles. We have used electron microscopic chemistry to demonstrate that at least one processing enzyme is differentially segregated into a class of secretory vesicles containing the bag cell peptides. The segregation of specific endoproteases, along with specific neuropeptides within a given cell type, may ensure appropriate cleavage and prevent inappropriate cleavage of the polyprotein precursors.

A Bradyrhizobium japonicum gene essential for nodulation competitiveness is differentially regulated from two promoters

We report the identification and nucleotide sequence of a new symbiotic gene (nfeC) from the soybean root nodule bacterium, Bradyrhizobium japonicum. A Tn5 insertion (NAD14) in this gene did not affect nitrogen fixation but caused a significant delay in soybean nodulation. In addition, this mutant exhibited a reduction in its competitive ability to nodulate soybean when coinoculated with the wild type. Sequence analysis of the mutated region revealed that the NAD14 Tn5 insertion mapped within an open reading frame of 825 bp. Primer extension using B. japonicum mRNA from three different growth conditions, aerobic, anaerobic, and bacteroids (i.e., symbiotic form) indicated that the upstream region of the gene contained two promoters, which were differentially regulated in response to the growth conditions. One promoter was expressed in bacteroids, but not under aerobic or anaerobic free-living conditions. The other promoter was expressed only under aerobic conditions.

nodZ, a unique host-specific nodulation gene, is involved in the fucosylation of the lipooligosaccharide nodulation signal of Bradyrhizobium japonicum

The nodulation genes of rhizobia are regulated by the nodD gene product in response to host-produced flavonoids and appear to encode enzymes involved in the production of a lipo-chitose signal molecule required for infection and nodule formation. We have identified the nodZ gene of Bradyrhizobium japonicum, whose product is required for the addition of a 2-O-methylfucose residue to the terminal reducing N-acetylglucosamine of the nodulation signal. This substitution is essential for the biological activity of this molecule. Mutations in nodZ result in defective nodulation of siratro. Surprisingly, although nodZ clearly codes for nodulation function, it is not regulated by NodD and, indeed, shows elevated expression in planta. Therefore, nodZ represents a unique nodulation gene that is not under the control of NodD and yet is essential for the synthesis of an active nodulation signal.

Diversity of retron elements in a population of rhizobia and other gram-negative bacteria

Genetic elements called retrons reside on the chromosome of Escherichia coli and the myxobacteria and represent the first reverse transcriptase-encoding element to be found in a prokaryotic cell. All known retrons produce a functionally obscure RNA-DNA satellite molecule called multicopy single-stranded DNA (msDNA). We report here the presence of msDNA-producing retron elements in a number of new bacterial groups, including strains of the genera Proteus, Klebsiella, Salmonella, Nannocystis, Rhizobium, and Bradyrhizobium. Among a population of 63 rhizobia strains, only 16% contain a retron element. The rhizobia retrons appear to be heterogeneous in nucleotide sequence and show little similarity to previously studied retrons of E. coli and the myxobacteria.