Anabolic effects of acellular bone marrow, platelet rich plasma, and serum on equine suspensory ligament fibroblasts in vitro

The purpose of this study was to investigate the response of suspensory ligament fibroblasts (SLF) to in vitro stimulation using acellular bone marrow (ABM), platelet rich plasma (in vitro PRP), and serum as potential treatment modalities for suspensory desmitis. Blood, bone marrow, and suspensory ligaments were collected from five horses. SLF were harvested, grown until confluent, and stimulated with various concentrations of ABM, PRP, equine serum, foetal bovine serum, and medium (control). The responses to the treatments were assessed using a combination of radio-labeling for total protein synthesis and an ELISA for quantification of Cartilage Oligomeric Matrix Protein (COMP) production. Addition of all of the samples resulted in significant increases in COMP and total protein synthesis over controls (P<0.001). ABM caused the greatest increase in both COMP and total protein synthesis by the SLF. Equine ABM, PRP, and serum contain anabolic factors that promote matrix synthesis by SLF in vitro, with ABM having the greatest effect. Application of bone marrow to injured ligaments may enhance healing by providing anabolic factors, other than or in addition to mesenchymal stem cells, which stimulate matrix production.

A comparison of serial halving and the rule of nines as a pre-hospital assessment tool in burns

Following endorsement of serial halving by the Faculty of Pre-Hospital Care of the Royal College of Surgeons of Edinburgh this study aimed to determine whether the technique was comparable to the rule of nines in making initial assessments of body surface area burned. Ten 'casualties' were made up to represent burn victims (range 6-61%). An external panel of six consultants and one specialist registrar in plastic surgery were invited to assess the simulated casualties. They gave individual and a consensus estimate of the burned areas. One hundred and twenty-five members of local emergency services and military paramedical staff were given a brief video and slide presentation describing either the rule of nines or serial halving method of burn area assessment. These techniques were then used to assess the 10 simulated casualties, giving 1250 estimates of burn surface area. The understanding of both techniques appeared adequate in both test groups. Estimates from serial halving and rule of nines groups differed from the assessments of the external panel. No statistical difference was demonstrated between serial halving and the rule of nines as an initial assessment tool when determining disposal. Serial halving has an inherent weakness when assessing certain sizes of burn. The rule of nines requires that the assessor knows and understands the proportionate areas of the body. The mathematics of percentages and fractions appeared to confuse some assessors.

A comprehensive expressed sequence tag linkage map for tiger salamander and Mexican axolotl: enabling gene mapping and comparative genomics in Ambystoma

Expressed sequence tag (EST) markers were developed for Ambystoma tigrinum tigrinum (Eastern tiger salamander) and for A. mexicanum (Mexican axolotl) to generate the first comprehensive linkage map for these model amphibians. We identified 14 large linkage groups (125.5-836.7 cM) that presumably correspond to the 14 haploid chromosomes in the Ambystoma genome. The extent of genome coverage for these linkage groups is apparently high because the total map size (5251 cM) falls within the range of theoretical estimates and is consistent with independent empirical estimates. Unlike most vertebrate species, linkage map size in Ambystoma is not strongly correlated with chromosome arm number. Presumably, the large physical genome size ( approximately 30 Gbp) is a major determinant of map size in Ambystoma. To demonstrate the utility of this resource, we mapped the position of two historically significant A. mexicanum mutants, white and melanoid, and also met, a quantitative trait locus (QTL) that contributes to variation in metamorphic timing. This new collection of EST-based PCR markers will better enable the Ambystoma system by facilitating development of new molecular probes, and the linkage map will allow comparative studies of this important vertebrate group.

Long-term outcomes of restorative proctocolectomy for Crohn's disease and indeterminate colitis

INTRODUCTION

The present study aims to evaluate the short-term and long-term outcomes of patients undergoing restorative proctocolectomy (RPC) for Crohn's disease (CD) and Indeterminate colitis (IC) and to identify factors associated with adverse outcomes.

METHODS

A descriptive study of 52 patients with CD or IC from a total of 1652 patients undergoing primary or salvage RPC in a single tertiary referral centre between 1978 and 2003. Primary outcomes were ileal pouch failure (excision or indefinite diversion), adverse events and functional outcomes (bowel frequency, urgency and continence).

RESULTS

Patients with IC or IC favouring ulcerative colitis (Group 1, n = 26) had a pouch failure rate of 11.5%vs 57.5% for patients with CD or IC favouring CD (Group 2, n = 26). Pouch salvage surgery was undertaken in 15 patients with a 13.3% failure rate. Patients in Group 2 were 2.6 times more likely (95% CI: 0.96-7. No significant differences were evident between CD and IC patients with regards to pelvic sepsis (19.2%vs 15.4%), anastomotic stricture (23.1%vs 21.7%), small bowel obstruction (26.9%vs 26.9%) or pouchitis (15.4%vs 11.5%). The 24-h bowel frequency (7.5 vs 8), faecal urgency, daytime or night time incontinence were similar between patients with CD or IC..17) to develop a pouch-related fistula than patients in Group 1.

DISCUSSION

Crohn's disease and to a great extent indeterminate colitis favouring CD were both associated with high failure rates and postoperative pouch-related fistula rates. Despite these problems, functional outcomes for patients with CD or IC were similar. Patients with IC should remain candidates for RPC but careful pre-operative assessment is advised to exclude clinical signs favouring the diagnosis of CD. The complications associated with failure are extensive and the option of reconstructive surgery in patients with CD should be questioned.

Evolution of salamander life cycles: a major-effect quantitative trait locus contributes to discrete and continuous variation for metamorphic timing

The evolution of alternate modes of development may occur through genetic changes in metamorphic timing. This hypothesis was examined by crossing salamanders that express alternate developmental modes: metamorphosis vs. paedomorphosis. Three strains were used in the crossing design: Ambystoma tigrinum tigrinum (Att; metamorph), wild-caught A. mexicanum (Am; paedomorph), and laboratory Am (paedomorph). Att/Am hybrids were created for each Am strain and then backcrossed to their respective Am line. Previous studies have shown that a dominant allele from Att (met(Att)) and a recessive allele from lab Am (met(lab)) results in metamorphosis in Att/Am hybrids, and met(Att)/met(lab) and met(lab)/met(lab) backcross genotypes are strongly associated with metamorphosis and paedomorphosis, respectively. We typed a molecular marker (contig325) linked to met and found that met(Att)/met(lab) and met(Att)/met(wild) were associated with metamorphosis in 99% of the cases examined. However, the frequency of paedomorphosis was 4.5 times higher for met(lab)/met(lab) than for met(wild)/met(wild). We also found that met(Att)/met(wild) and met(wild)/met(wild) genotypes discriminated distributions of early and late metamorphosing individuals. Two forms of phenotypic variation are contributed by met: continuous variation of metamorphic age and expression of discrete, alternate morphs. We suggest that the evolution of paedomorphosis is associated with genetic changes that delay metamorphic timing in biphasic life cycles.

TRANSVAGINAL SLING USING ACELLULAR HUMAN DERMAL ALLOGRAFT: SAFETY AND EFFICACY IN 253 PATIENTS

PURPOSE

We evaluated the safety and efficacy of using human dermal allograft material for transvaginal slings to treat female stress urinary incontinence (SUI).

MATERIALS AND METHODS

We present a prospective series of 253 patients with SUI treated with a transvaginal sling using a Repliform cadaveric human dermal allograft (LifeCell Corp., The Woodlands, Texas) and a bone anchor fixation kit. Clinical history, urogynecologic examination and videourodynamics were performed preoperatively. Results were assessed by a third party through validated quality of life questionnaires (Incontinence Impact Questionnaire and Urogenital Distress Inventory), overall impression and percent of improvement as perceived by the patients, and pad use. Scheduled followup examination were performed to rule out erosion, infection, obstruction, pain or recurrent incontinence.

RESULTS

Complete followup was available on 234 of 253 patients. Average followup was 18 months. Of the patients 78% were cured or improved according to the questionnaires. The average improvement was 80%. At 18 months of followup incontinence average distress and scores decreased 10 and 7 points, respectively. Complications were de novo urgency in 5% of cases, recurrent SUI in 15% with no cases of persistent SUI, retention in 2% and slow vaginal wall healing in 1.7%. Of 156 patients 51 (22%) had persistent urgency. There were no cases of vaginal or urethral erosion, osteitis pubis or osteomyelitis.

CONCLUSIONS

Our data indicate that use of human dermal allograft for transvaginal slings is associated with low complication rates and favorable outcomes at an average of 18 months of followup.

Evaluation of minimally invasive analysis system for cough leak point pressure measurement

PURPOSE

Leak point pressure (LPP) measurement has become standard in the diagnosis of stress urinary incontinence. Leak point pressure is determined by increasing abdominal pressure, which can be done with a Valsalva maneuver or coughing, that is Valsalva LPP and cough LPP (CLPP). It may be influenced by catheter size, bladder volume and interobserver variability. A new, computerized LPP measuring technique for routine use in daily urodynamic practice was tested at a female unit urodynamic practice to evaluate female urinary incontinence.

MATERIALS AND METHODS

A total of 28 female patients with a mean age of 54.07 years (range 23 to 82) and urinary incontinence underwent a new, minimally invasive measurement of the cough leak point. Measurements are made with the patient standing and repeated 3 times per patient. Additionally, parameters of the corresponding leak were recorded simultaneously. All patients underwent new CLPP measurement and a standard, complete urodynamic investigation, including filling cystometry with abdominal LPP and urethral pressure profile at rest. Statistical evaluation was done by linear regression analysis and the correlation coefficients among CLPP, age, standard abdominal LPP and maximum urethral pressure, and among the 3 measurements for each patient.

RESULTS

: The assignment of leakage to the pressure signal presented no problem. All CLPP data were reproducible in the 3 repeated measurements per patient. No correlation was seen between CLPP and abdominal LPP or the urethral pressure profile.

CONCLUSIONS

The study confirm that the CLPP is a practicable, consistent and minimally invasive method in routine use. Clinical use is easy and reproducible, and only 1 catheter is required for measurement.

Computer-identified nuclear localization signal in exon 1A of the transporter DMT1 is essentially ineffective in nuclear targeting

Divalent metal transporter 1 (DMT1; also called DCT1, Nramp2, or SLC11A2) has multiple isoforms that localize differently in many cell types. DMT1 +IRE species (encoded by mRNA with an iron-responsive element) are limited to the plasma membrane and cytosolic vesicles. In neural cells, -IRE isoforms of DMT1 (encoded by mRNA lacking an IRE) localize to the nucleus, plasma membrane, and cytosolic vesicles. In considering nuclear compartmentalization of -IRE isoforms, we hypothesized that the newly identified exon 1A in the N-terminus of this transporter might contain a nuclear localization signal. DNA constructs starting with exon 1A and ending with exons encoding alternative isoforms were made and transiently transfected into HEK293T and PC12 cells as well as rat sympathetic neurons. None of the constructs appeared in the nucleus despite the presence of exon 1A. Antibody specific for exon 1A was also used in both immunostaining and Western blots to investigate localization of exon 1A expressed both endogenously and ectopically in cells. Again, nuclear localization of DMT1 containing exon 1A was not observed. Our data suggest that exon 1A is neither sufficient nor necessary for DMT1 to appear in the nucleus.

Determination of Cryptosporidium parvum oocyst viability by fluorescence in situ hybridization using a ribosomal RNA-directed probe

AIMS

Fluorescence in situ hybridization (FISH) has been proposed for species-specific detection, and viability determination of Cryptosporidium parvum oocysts. FISH-based viability determination depends on rRNA decay after loss of viability. We examined the effects of RNase(s) and RNase inhibitors on FISH of C. parvum.

METHODS AND RESULTS

FISH was performed using a 5'-Texas red-labelled DNA oligonucleotide probe at 1 pM microl(-1). Intact and heat-permeabilized oocysts were treated with 1-100 microg ml(-1) RNase. FISH of intact oocysts appeared unaffected by exogenous RNase if this was neutralized before permeabilization. FISH fluorescence of heat-killed oocysts stored in phosphate-buffered saline at room temperature decayed by 1/2 after 55 h, but remained detectable after 6 days. Addition of vanadyl ribonucleoside complex (VRC) extended rRNA half-life of heat-permeabilized oocysts to 155 h.

CONCLUSIONS

Extended rRNA half-life may result in viability overestimation using FISH. RNase pretreatment before FISH is recommended to destroy residual rRNA in recently killed oocysts. Incorporation of 1-10 mM l(-1) VRC before FISH permeabilization steps should neutralize RNase activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Elimination of FISH fluorescence of nonviable C. parvum is desirable. Use of RNase and VRC is suggested to reduce numbers of false-positive 'viable' oocysts.

Metagenomics, gene discovery and the ideal biocatalyst

With the rapid development of powerful protein evolution and enzyme-screening technologies, there is a growing belief that optimum conditions for biotransformation processes can be established without the constraints of the properties of the biocatalyst. These technologies can then be applied to find the ‘ideal biocatalyst’ for the process. In identifying the ideal biocatalyst, the processes of gene discovery and enzyme evolution play major roles. However, in order to expand the pool genes for in vitro evolution, new technologies, which circumvent the limitations of microbial culturability, must be applied. These technologies, which currently include metagenomic library screening, gene-specific amplification methods and even full metagenomic sequencing, provide access to a volume of ‘sequence space’ that is not addressed by traditional screening.

Review and re-analysis of domain-specific 16S primers

The Polymerase Chain Reaction (PCR) has facilitated the detection of unculturable microorganisms in virtually any environmental source and has thus been used extensively in the assessment of environmental microbial diversity. This technique relies on the assumption that the gene sequences present in the environment are complementary to the "universal" primers used in their amplification. The recent discovery of new taxa with 16S rDNA sequences not complementary to standard universal primers suggests that current 16S rDNA libraries are not representative of true prokaryotic biodiversity. Here we re-assess the specificity of commonly used 16S rRNA gene primers and present these data in tabular form designed as a tool to aid simple analysis, selection and implementation. In addition, we present two new primer pairs specifically designed for effective "universal" Archaeal 16S rDNA sequence amplification. These primers are found to amplify sequences from Crenarchaeote and Euryarchaeote type strains and environmental DNA.

Characterization of the metabolic burden onEscherichia coli DH1 cells imposed by the presence of a plasmid containing a gene therapy sequence

The presence of a plasmid, containing gene sequences for DNA immunotherapy that are not expressed in microbial culture, imposed a degradation in bioreactor performance in cultures of the host E. coli strain. Significant decreases in growth rate (24%) and biomass yield (7%) and a corresponding increase in overflow metabolism were observed in a strain containing a therapeutic sequence (a hepatitis B antigen under the control of a CMV promotor). The observed increase in overflow metabolism was incorporated into a Metabolic Flux Analysis (MFA) model (as acetate secretion). Metabolic flux analysis revealed an increase in TCA cycle flux, consistent with an increased respiration rate observed in plasmid-containing cells. These effects are thought to result from increased ATP synthesis requirements (24%) arising from the expression of the Kanr plasmid marker gene whose product accounted for 18% of the cell protein of the plasmid-containing strain. These factors will necessitate significantly higher aeration and agitation rates or lower nutrient feed rates in high-density cultures than would be expected for plasmid-free cultures.

Comparison of CT and MRI in the pre-operative staging of rectal adenocarcinoma and prediction of circumferential resection margin involvement by MRI

OBJECTIVE

It has been suggested that MRI may be used as the sole modality of choice in pre-operative staging in rectal cancers. Knowledge of tumour stage and a threatened Circumferential Resection Margin (CRM) pre-operatively are essential for planning neo-adjuvant therapy and as predictors of local recurrence. At present most units utilize CT scanning to assess these parameters. The aim of our study was two fold: firstly to examine the accuracy of preop CT and MRI staging of rectal cancers compared with final histology and secondly to assess the accuracy of MRI in predicting penetration of the mesorectal envelope (ME).

PATIENTS AND METHODS

All patients with biopsy proven rectal adenocarcinoma underwent thin slice MRI and CT scan pre-operatively. Forty-seven patients have been prospectively entered into the study: 24 male (median age 68 years; range 38-91 years). Eleven patients were unsuitable for surgery leaving 36 patients available for study.

RESULTS

CT correctly staged patients with T1/T2 rectal cancers more often than MRI (77% vs. 43%, P = 0.226). Patients with T1/T2 tumours were overstaged more often by MRI compared with CT (54% vs. 23%, P = 0.226). A greater proportion of patients with T3 tumours were correctly staged by MRI than CT (76% vs. 41%, P = 0.08); and more T3 disease was understaged by CT than MRI (54 vs. 18%, P = 0.032). CT and MRI staged T4 disease equally. In the assessment of mesorectal envelope integrity, MRI had a sensitivity of 80% and a specificity of 84%. The positive predictive value was 44% and the negative predictive value 96%.

CONCLUSIONS

These results suggest significant differences between accurate pre-operative "T" staging by CT and MRI for rectal cancer. MRI has the potential however, to accurately assess mesorectal envelope invasion. Further analysis is required to assess whether MRI can be used as the sole modality in pre-operative staging of rectal cancers.

Randomized controlled trial of four-layer bandaging and simple venous surgery for venous ulceration

Background

No randomized controlled trials exist to show whether simple venous surgery benefits healing or maintenance of healing of venous ulcers.

Methods

Some 121 consecutive patients with new episodes of venous ulceration were identified; 45 patients were unfit or unwilling for randomization. The remaining 76 (39 women) were assigned randomly to received a four-layer bandage (n = 39) or simple venous surgery (n = 37). All patients were followed for a minimum of 6 months. Outcome was assessed at a minimum of 6 months as healing and health-related quality of life (HRQL).

Results

The two groups had similar co-morbidity and pattern of venous incompetence. There were no major complications in either group. The healing rate was 64 per cent (25 of 39) in the conservatively treated group and 68 per cent (25 of 37) in the operated group (P = 0·75, Pearson χ2 test). There was no significant difference between time to ulcer healing in the two treatment groups (log rank statistic = 0·69, P = 0·41). Patterns of venous incompetence did not affect the healing rate. There were no major differences in HRQL between the two groups.

Conclusion

This pilot study suggests that simple venous surgery gives no adjuvant benefit to four-layer bandaging in venous ulceration from the point of view of healing rate and quality of life.

Major colorectal cancer resection should not be denied to the elderly

AIMS

Adjuvant therapy after surgery for colorectal cancer is often denied to the elderly for various reasons. This study was to determine morbidity and mortality risk after surgery in the elderly and whether this is affected by adjuvant therapy.

METHODS

Data were collected prospectively and entered on a database for all patients undergoing resection of colorectal cancer between January 1994 and July 2000. A total of 304 patients were included, 65 aged 80 years and over.

RESULTS

There were 84 deaths, 21 (30%) in the over 80s, and 63 (26%) in the under 80s (P=0.51). The 'in-hospital' mortality was 10.1% in the over 80s and 3.8% in the under 80s (P=0.056). In the over 80s the colon was more affected than the rectum (P=0.002). The over 80s were less likely to be offered adjuvant therapy, 7.2% vs 42.1% (P<0.001). The 5 year survival (all-cause mortality) in the over 80s was 58.5% and 47.6% in the under 80s (P=0.25). Cox's regression analysis of all patients identified the following factors to be independently related to overall survival: age>80 years, post-operative leak, increasing Dukes stage and distant recurrence of disease.

CONCLUSION

This study has demonstrated that surgery should not be denied to elderly patients with colorectal cancer as despite a higher post-operative morbidity and mortality rate and with the absence of adjuvant therapy, favourable long-term outcome can be achieved by resectional surgery alone.

Randomised trial of pre-operative colour duplex marking in primary varicose vein surgery: outcome is not improved

OBJECTIVE

the ability of colour duplex to accurately locate incompetent venous sites has been widely published; its value in pre-operative marking in simple primary varicose vein surgery is evaluated in this study.

DESIGN OF STUDY

prospective randomised controlled trial.

SETTING

regional vascular service, hospital patients.

SUBJECTS

consecutive patients (149) undergoing primary varicose vein surgery where the only difference was one group of patients received duplex marking prior to surgery. Six weeks and 12 months post-operatively all patients had a colour duplex scan to determine the accuracy of surgery and the presence of residual/recurrent varicose veins and completed the Aberdeen, SF-36, and EuroQol quality of life questionnaires.

INTERVENTIONS

varicose vein surgery.

MAIN OUTCOME MEASURES

Duplex evidence of venous incompetence, quality of life measures using the SF-36 and Aberdeen Varicose Veins Questionnaire.

RESULTS

pre-operative marking of primary varicose veins by skilled duplex ultrasonography does not improve the accuracy or recurrence rate following surgery. Quality of life improved significantly following surgery in both groups, however there was no difference in this improvement between the groups.

CONCLUSION

the trial has not demonstrated any additional benefit of pre-operative colour duplex marking over that of clinical and hand held Doppler marking in terms of satisfactory varicose vein surgery performance at 6 weeks or 12 months in patients with primary varicose veins of the long saphenous system. It role in the short saphenous system is less clear.

Native Vaccinium spp. and Gaylussacia spp. infested by Rhagoletis mendax (Diptera: Tephritidae) in the Great Lakes Region: a potential source of inoculum for infestation of cultivated blueberries

In this study, we addressed the question of whether or not native stands of blueberry (Vaccinium spp.) and/or huckleberry (Gaylussacia spp.) support populations of blueberry maggot, Rhagoletis mendax Curran, in the Great Lakes region. Infestation of commercial blueberries by the blueberry maggot, R. mendax, is a serious problem in many areas where blueberries are grown. In the past 10-20 yr, commercial bighbush blueberry, Vaccinium corymbosum L., production has expanded into places such as southern Ontario and southern Quebec where blueberry maggot had not previously been reported. In the mid-1990s, isolated infestations of commercial highbush blueberry were reported in southern Ontario. Because R. mendax was not considered endemic to that area, it was widely assumed that the pests had come into the fields via movement from exotic localities. Here we present an alternative hypothesis, that the blueberry maggots infesting newly established highbush plantations are derived from native blueberries growing in the vicinity. To test this hypothesis, in 1997-1999, we sampled potential native hosts for R. mendax (Vaccinium spp. and Gaylussacia spp.) from 31 localities in the Great Lakes region, primarily in Michigan and Ontario. R. mendax was reared from fruits of native hosts collected at four sites in Michigan and one site each in Ontario, Indiana, and Ohio. V. corymbosum was the predominant host infested, with infestation of this host observed at five of the seven sites. However, two huckleberry species [Gaylussacia baccata (Wangenheim) K. Koch, and Gaylussacia dumosa (Andersson) Torrey & Gray] had the highest rates of infestation that we observed (25.4 and 17.6%, respectively). These data represent the first published reports of R. mendax infesting native host plants in the Great Lakes region, and support the hypothesis that infestations observed in commercial fields may have originated from infested native host plants.

Trimethoprim-sulfamethoxazole (TMP-SMZ) dose escalation versus direct rechallenge for Pneumocystis Carinii pneumonia prophylaxis in human immunodeficiency virus-infected patients with previous adverse reaction to TMP-SMZ

Trimethoprim-sulfamethoxazole (TMP-SMZ) is the most effective Pneumocystis carinii pneumonia (PCP) prophylactic agent, but adverse reactions are common among human immunodeficiency virus (HIV)-infected patients and limit its use. This randomized, double-blind controlled trial compared 2 methods of TMP-SMZ reintroduction, 6-day dose escalation and direct rechallenge, for PCP prophylaxis in HIV-infected patients who had experienced previous treatment-limiting reactions. The primary end point was the ability to take single-strength TMP-SMZ daily for 6 months. Seventy-five percent of the dose-escalation group and 57% of the direct-rechallenge group continued to receive daily single-strength TMP-SMZ for 6 months (P= .014). Among premature discontinuations, 58% of the dose-escalation group and 70% of the direct-rechallenge group were due to adverse reactions. None of these reactions was serious. This study provides evidence that it is possible to successfully reintroduce TMP-SMZ to a significant proportion of HIV-infected patients who have experienced mild-to-moderate treatment-limiting adverse reactions.

Development of a PCR test for the detection of Curtobacterium flaccumfaciens pv. flaccumfaciens

A chromosomal DNA library of the bacterial pathogen of bean, Curtobacterium flaccumfaciens pv.flaccumfaciens NCPPB 559 was constructed in the plasmid pGEM-7Zf(+). Several clones were identified that hybridised to all Curtobacterium flaccumfaciens pathovars including: C. f betae, C. f flaccumfaciens, C. f oortii, C. f. poinsettiae and, in addition, to some strains of Clavibacter michiganensis subsp. insidiosus and Clavibacter michiganensis subsp. One of these clones (pPMP-26), after subsequent digestion with restriction endonucleases EcoRI/SacI, yielded a fragment of approximately 0.2 Kb (pPMP-26D) that hybridised specifically to C. f flaccumfaciens and not to any of the other plant pathogenic members of the order Actinomycetales or any of the other prokaryotic bean pathogens tested. This fragment was subcloned and sequenced, analysis of the resultant 198 bp sequence showed that no significant homology existed with any other sequence currently deposited in public databases. Further analysis of these data facilitated the design of PCR primers which were subsequently tested against a wide range of plant pathogenic actinomycetes and other prokaryotic bean pathogens. Results show that these primers are highly specific for all strains of C. f flaccumfaciens with no cross-reaction to strains from any other bacterial taxa tested.

cAMP stimulation of HCO3- secretion across airway epithelia

To test for the presence of HCO(3)(-) transport across airway epithelia, we measured short-circuit current in primary cultures of canine and human airway epithelia bathed in a Cl(-)-free, HCO(3)(-)/CO(2)-buffered solution. cAMP agonists stimulated a secretory current that was likely carried by HCO(3)(-) because it was absent in HCO(3)(-)-free solutions. In addition, the cAMP-stimulated current was inhibited by the carbonic anhydrase inhibitor, acetazolamide, and by the apical addition of a blocker of cystic fibrosis transmembrane conductance regulator (CFTR), diphenylamine-2-carboxylate. The current was dependent on Na(+) because it was inhibited by removing Na(+) from the submucosal solution and by inhibition of the Na(+)-K(+)-ATPase with ouabain. The cAMP-stimulated current was absent in cystic fibrosis (CF) airway epithelia. These data suggest that cAMP agonists can stimulate HCO(3)(-) secretion across airway epithelia and that CFTR may provide a conductive pathway for HCO(3)(-) movement across the apical membrane.

Peroxisome biogenesis in the yeast Yarrowia lipolytica

Extensive peroxisome proliferation during growth on oleic acid, combined with the availability of excellent genetic tools, makes the dimorphic yeast, Yarrowia lipolytica, a powerful model system to study the molecular mechanisms involved in peroxisome biogenesis. A combined genetic, biochemical, and morphological approach has revealed that the endoplasmic reticulum (ER) plays an essential role in the assembly of functional peroxisomes in this yeast. The trafficking of some membrane proteins to the peroxisomes occurs via the ER, results in their glycosylation in the ER lumen, does not involve transit through the Golgi, and requires the products of the SEC238, SRP54, PEX1, and PEX6 genes. The authors' data suggest a model for protein import into peroxisomes via two subpopulations of ER-derived vesicles that are distinct from secretory vesicles. A kinetic analysis of the trafficking of peroxisomal proteins in vivo has demonstrated that membrane and matrix proteins are initially targeted to multiple vesicular precursors that represent intermediates in the assembly pathway of peroxisomes. The authors have also recently identified a novel cytosolic chaperone, Pex20p, that assists in the oligomerization of thiolase in the cytosol and promotes its targeting to the peroxisome. These data provide the first evidence that a chaperone-assisted folding and oligomerization of thiolase in the cytosol is required for the import of this protein into the peroxisomal matrix.

Conserved vertebrate chromosome segments in the large salamander genome

Urodele amphibians (salamanders) are important models for embryological, physiological, and natural history research and are also a biomedically important group because they are the only vertebrates capable of regenerating entire organ systems. To enhance the utility of salamanders for biomedical research and for understanding genome evolution, genetic linkage analysis was used to identify chromosome segments that are homologous between ambystomatid salamanders and distantly related vertebrate model organisms. A total of 347 loci (AFLPs, RAPDs, and protein-coding loci) were mapped using an interspecific meiotic mapping panel (Ambystoma mexicanum and A. tigrinum tigrinum; family Ambystomatidae). Genome size in Ambystoma was estimated to be 7291 cM, the largest linkage map estimate reported for any organism. However, the relatively large size of the salamander genome did not hinder efforts to map and identify conserved syntenies from a small sample of 24 protein-coding loci. Chromosomal segments that are conserved between fishes and mammals are also conserved in these salamanders. Thus, comparative gene mapping appears to be an efficient strategy for identifying orthologous loci between ambystomatid salamanders and genomically well-characterized vertebrate model organisms.