Overexpression of transcription factor FoxA2 in the developing skeleton causes an enlargement of the cartilage hypertrophic zone, but it does not trigger ectopic differentiation in immature chondrocytes

We previously found that FoxA factors are necessary for chondrocyte differentiation. To investigate whether FoxA factors alone are sufficient to drive chondrocyte hypertrophy, we build a FoxA2 transgenic mouse in which FoxA2 cDNA is driven by a reiterated Tetracycline Response Element (TRE) and a minimal CMV promoter. This transgenic line was crossed with a col2CRE;Rosa26^rtTA/+ mouse line to generate col2CRE;Rosa26^rtTA/+;TgFoxA2^+/- mice for inducible expression of FoxA2 in cartilage using doxycycline treatment. Ectopic expression of FoxA2 in the developing skeleton reveals skeletal defects and shorter skeletal elements in E17.5 mice. The chondro-osseous border was frequently mis-shaped in mutant mice, with small islands of col.10+ hypertrophic cells extending in the metaphyseal bone. Even though overexpression of FoxA2 causes an accumulation of hypertrophic chondrocytes, it did not trigger ectopic hypertrophy in the immature chondrocytes. This suggests that FoxA2 may need transcriptional co-factors (such as Runx2), whose expression is restricted to the hypertrophic zone, and absent in the immature chondrocytes. To investigate a potential FoxA2/Runx2 interaction in immature chondrocytes versus hypertrophic cells, we separated these two subpopulations by FACS to obtain CD24⁺CD200⁺ hypertrophic chondrocytes and CD24⁺CD200^- immature chondrocytes and we ectopically expressed FoxA2 alone or in combination with Runx2 via lentiviral gene delivery. In CD24⁺CD200⁺ hypertrophic chondrocytes, FoxA2 enhanced the expression of chondrocyte hypertrophic markers collagen 10, MMP13, and alkaline phosphatase. In contrast, in the CD24⁺CD200^- immature chondrocytes, neither FoxA2 nor Runx2 overexpression could induce ectopic expression of hypertrophic markers MMP13, alkaline phosphatase, or PTH/PTHrP receptor. Overall these findings mirror our in vivo data, and suggest that induction of chondrocyte hypertrophy by FoxA2 may require other factors in addition to Runx2 (i.e., Hif2α, MEF2C, or perhaps unknown factors), whose expression/activity is rate-limiting in immature chondrocytes.

A FoxA2+ long-term stem cell population is necessary for growth plate cartilage regeneration after injury

Longitudinal bone growth, achieved through endochondral ossification, is accomplished by a cartilaginous structure, the physis or growth plate, comprised of morphologically distinct zones related to chondrocyte function: resting, proliferating and hypertrophic zones. The resting zone is a stem cell-rich region that gives rise to the growth plate, and exhibits regenerative capabilities in response to injury. We discovered a FoxA2+group of long-term skeletal stem cells, situated at the top of resting zone, adjacent the secondary ossification center, distinct from the previously characterized PTHrP+ stem cells. Compared to PTHrP+ cells, FoxA2+ cells exhibit higher clonogenicity and longevity. FoxA2+ cells exhibit dual osteo-chondro-progenitor activity during early postnatal development (P0-P28) and chondrogenic potential beyond P28. When the growth plate is injured, FoxA2+ cells expand in response to trauma, and produce physeal cartilage for growth plate tissue regeneration.

A Highly Efficient Approach for the Synthesis of Novel Trifluoroacetylated Enaminones using DBU as a Base

An efficient methodology has been developed for the synthesis of a variety of novel trifluoroacetylated enaminones by using trifluoroacetic anhydride in DCE as solvent and DBU as a base via electrophilic trifluoroacetylation. X-ray crystallographic studies confirmed the trifluoroacetylation and E stereoisomeric form of the novel compounds. The synthetic strategy has the advantage of using an inexpensive and non-toxic base for producing excellent yields. Synthons bearing variety of functional groups may be further extended for the formation of heterocyclic compounds.

Ultrasound-Accelerated Amide Coupling Reactions Directed toward the Synthesis of 1-Acetyl-3-carboxamide-β-carboline Derivatives of Biological Importance

Several biologically important 1-acetyl-3-carboxamide-β-carboline derivatives were rapidly synthesized by ultrasound-promoted amide coupling of 1-acetyl-9H-pyrido[3,4-b]indole-3-carboxylic acid with substituted aromatic amines. The major advantages of the proposed method are that use of ultrasound irradiations afforded the desired products in a drastically reduced reaction time and in excellent yields compared with conventional stirring.

Efficient trifluoromethylation of C(sp2)–H functionalized α-oxoketene dithioacetals: a route to the regioselective synthesis of functionalized trifluoromethylated pyrazoles

An operationally simple approach for regioselective construction of substituted trifluoromethylated pyrazoles via ligand free nucleophilic trifluoromethylation of iodo-substituted α-oxoketene dithioacetals.

Persistence of Corynebacterium diphtheriae in Delhi & National Capital Region (NCR)

Despite the introduction of mass immunization, diphtheria continues to play a major role as a potentially lethal infectious disease in many countries. Delay in the specific therapy of diphtheria may result in death and, therefore, accurate diagnosis of diphtheria is imperative. This study was carried out at National Centre for Disease Control (NCDC), Delhi, India, on samples of suspected diphtheria cases referred from various government hospitals of Delhi and neighbouring areas during 2012-2014. Primary identification of Corynebacterium diphtheriae was done by standard culture, staining and biochemical tests followed by toxigenicity testing by Elek's test on samples positive for C. diphtheriae. The results showed persistence of toxigenic C. diphtheriae in our community indicating the possibility of inadequate immunization coverage.

Isolation and Characterization of Trichoderma spp. for Antagonistic Activity Against Root Rot and Foliar Pathogens

Trichoderma, soil-borne filamentous fungi, are capable of parasitising several plant pathogenic fungi. Twelve isolates of Trichoderma spp. isolated from different locations of South Andaman were characterized for their cultural, morphological and antagonistic activity against soil borne and foliar borne pathogens. The sequencing of these isolates showed seven different species. The isolates revealed differential reaction patterns against the test pathogens viz., Sclerotium rolfsii, Colletotrichum gloeosporioides and C. capsici. However, the isolates, TND1, TWN1, TWC1, TGD1 and TSD1 were most effective in percentage inhibition of mycelial growth of test pathogens. Significant chitinase and β-1,3-glucanase activities of all Trichoderma isolates has been recorded in growth medium. T. viride was found with highest chitinase whereas T. harzianum was recorded with highest β-1,3-glucanase activities.

Ossicular chain status in chronic suppurative otitis media in adults

This study was conducted to find out the status of the ossicles in cases of chronic suppurative otitis media (CSOM). One hundred and fifty cases of CSOM, who underwent surgery, were included and their intra-operative ossicular chain findings noted. Ossicular erosion was found to be much more common in unsafe CSOM than in safe CSOM. Malleus was found to be the most resistant ossicle to erosion whereas incus was found to be the most susceptible.

Spondylodiscitis (disc space infection) associated with negative microbiological tests: comparison of outcome of suspected disc space infections to documented non-tuberculous pyogenic discitis

Discitis, an infection of the disc space, is an uncommon diagnosis that, if missed, can lead to spinal deformity and neurological deterioration, although as many as 30% of these patients will have negative microbiological cultures. It was unclear, however, whether the prognosis differed between patients who had positive or negative cultures. A retrospective case note review was carried out to assess the differences in presentation and outcome between these two groups. There were 26 and 43 patients in the negative and positive groups, respectively. Those with a positive culture were more likely to present with pyrexia, have a neurological deficit and not be independently mobile at presentation. The mean CRP recorded at the time of presentation was 96 and 157 in the negative and positive groups respectively (p = 0.004). Similarly, the mean ESR in the positive group was 88 compared with 69 in the negative group (p = 0.02). In conclusion, these patients may be at different ends of a clinical spectrum: those patients with a positive culture having a greater local and systemic inflammatory reaction to the disc space infection.

Pelvic Ewing's sarcoma: a review from Scottish Bone Tumour Registry

PURPOSE

To review various treatment modalities on outcome of patients with pelvic Ewing's sarcoma.

METHODS

Between January 1948 and December 2004, 18 male and 15 female patients aged 3 to 48 (mean, 20) years with pelvic Ewing's sarcoma were retrospectively reviewed from the Scottish Bone Tumour Registry.

RESULTS

The commonest site involved was the ilium. The main presenting symptom was pain, followed by swelling and restricted hip movements. Treatments included surgery, radiotherapy, chemotherapy, or any of them in combination. Patients who had no metastasis at presentation (p<0.01) and underwent chemotherapy with ifosfamide (p<0.01) had significantly longer survival. Age (p=0.09), gender (p=0.95), delay in presentation (p=0.31), tumour site (p=0.9), surgery (p=0.73), and radiotherapy (p=0.23) were not predictive of survival in the univariate analysis. The 5-year event-free survival rate in patients with no metastasis at presentation was 35%.

CONCLUSION

Intense multi-agent neo-adjuvant chemotherapy including ifosfamide followed by wide excision and postoperative radiation are recommended. Local therapy should not take precedence over or interfere with systemic chemotherapy.

Wide excision and ulno-carpal arthrodesis for primary aggressive and recurrent giant cell tumours

Twenty-five patients underwent wide resection of the distal radial giant cell tumours (GCTs) followed by ulno-carpal arthrodesis. There were 15 male and ten female patients, with an average age of 21.5 years. Tumours included ten primary aggressive and 15 recurrent GCTs. Mean follow up was 2.4 years. Pain, swelling and reduced range of movement (ROM) were noted. Average time to fusion was 7.6 months. Five patients had persistent pain in the proximal forearm. Grip strength was 65% compared to the uninvolved side. Two patients had superficial wound infection, two underwent additional bone grafting and three implant removals due to hardware prominence were carried out. There was no evidence of carpal instability or arthritis on clinical or radiological examination at the time of final follow up. Fusion of the carpus to the ulna is a simple method of producing a painless stable wrist, though at the expense of mobility. The procedure allows wide resection with a lower rate of recurrence. Pain in the proximal forearm seems to persist for 3 to 4 months only to improve at subsequent follow up. The procedure provides a valid option for the management of primary aggressive and recurrent GCTs of distal radius.

A rare case of progressive bilateral congenital abduction contracture with shoulder dislocations treated with proximal deltoid release

The contracture of the deltoid muscle is an uncommon disorder. Amongst the various causes reported, post intramuscular injection and trauma leading to the fibrosis of the muscle are common. However, congenital cases are extremely rare. We report a case of congenital progressive bilateral abduction contracture left untreated for a long time leading to anteroinferior subluxation. A proximal release was performed with satisfactory outcome on both sides.

Locked-in syndrome in snakebite

Two young patients are described who made complete recovery from locked-in syndrome (LIS) after snakebites. LIS was a presenting feature in a patient of presumed snake bite who showed complete response to polyvalent Anti-snake venom (ASV). This case suggests that elapid snake bite should be suspected in unresponsive patient found in early morning in endemic areas of snake bite in monsoon season. The second case was admitted in complete LIS state with history of rapidly progressive ptosis, diplopia, ophthalmoplegia, bulbar symptoms and quadriparesis, 6 hours after snake bite. Complete improvement by ASV in second patient highlights the need of differentiation of complete LIS from coma and brain death in patient of snake bite, as former have good prognosis.

Intramedullary nailing for pathological femoral fractures

PURPOSE

To evaluate whether the operating time correlates with the survival and outcome in patients who underwent intramedullary nailing for metastatic femoral fractures.

METHODS

Records of 10 men and 11 women aged 43 to 86 (mean, 66) years who underwent intramedullary nailing (4 bilaterally) for metastatic femoral fractures between 1999 and 2003 were reviewed. The patients were followed up for at least 2 years or until their death. The main outcome measure was the correlation between operating time and survival. Operating time was categorised into 5 groups from 60 to 210 minutes, with 30-minute increments.

RESULTS

Operating time does not correlate with survival and outcome. The mean survival period was 9.4 months. Pain relief was achieved in 90% of the patients. There was no implant failure, but one loss of reduction.

CONCLUSION

Intramedullary nailing appears safe and effective for treatment of metastatic bone disease, and confers good functional results, pain relief, and mobility.

Reducing Diagnostic Errors in Musculoskeletal Trauma by Reviewing Non-Admission Orthopaedic Referrals in the Next-Day Trauma Meeting

INTRODUCTION

Diagnostic errors in orthopaedics are usually caused by missing a fracture or misreading radiographs. The aim of this study was to document the pick-up rate of the wrong diagnoses by reviewing X-rays and casualty notes in the next-day trauma meeting.

PATIENTS AND METHODS

The casualty notes and radiographs of 503 patients were prospectively reviewed in the daily trauma meeting between August 2002 and December 2002 in a district general hospital. The relevant data were collected and analysed by a single assessor.

RESULTS

The false positive rate for making an orthopaedic diagnosis was 12.6% (i.e.) diagnosing a fracture, when none existed). The false negative (missing) rate was 4%, while 2.4% incidental findings were missed, or at least not documented, after reading the X-rays. There were 7.8% wrong diagnoses made. The majority of the patients were seen by the senior house officers.

CONCLUSIONS

The medicolegal significance of false negative diagnosis is obviously greater. In a busy emergency department, where a large number of patients are seen, there is a greater risk. This study shows the importance in a small-to-medium sized accident and emergency unit as well, where there is no senior cover available out-of-hours for final radiological interpretation. A morning trauma meeting which covers reviewing admitted patients as well as non-admission orthopaedic referrals has an effective risk management solution to early detection of missed and wrong diagnoses.

Remodelling potential of paediatric cervical spine after type II odontoid peg fracture

We describe a case of odontoid process fracture below the synchondrosis associated with delayed diagnosis and anterior subluxation of C1 over C2. This was treated with an in situ posterior occipitocervical fusion. Long-term follow-up of 7 years showed excellent remodelling of the deformity.

An unusual cause of locking

This case report describes the discovery of a plastic foreign body in a patient's knee joint 21 years from the initial injury. The patient was thoroughly investigated radiologically with plain X-rays both immediately after the initial injury and years later in orthopaedic outpatients. He also subsequently received an MRI. All these were reported as normal. The patient's symptoms persisted and an arthroscopy was performed. At this procedure the presence of the foreign body was confirmed and the offending plastic was safely removed. The patient's symptoms of intermittent locking resolved. This experience stresses this importance of clinical suspicion despite apparently normal radiology.

A comparative evaluation of C-reactive protein as a short-term prognostic marker in severe unstable angina--a preliminary study

OBJECTIVE

The present study was done to evaluate the short-term prognostic significance of C-reactive protein (CRP) in unstable angina (UA) and to compare it with other known prognostic markers of UA, as there is a paucity of data from our country.

METHODOLOGY

This prospective study comprised of 44 UA patients (Braunwald Class II A, B) with age < 65 years, along with 40 age and sex matched healthy controls. Patients with h/o myocardial infarction (MI) in the preceding 1-month and evidence of infection, inflammation or neoplasm were excluded from the study. Complete clinical evaluation was done and presence of any prognostic variables of UA was noted (including Brauriwald high-risk variables). Apart from biochemical investigations and ECG, CRP was measured at the time of admission in the study group and controls using Microwell ELISA assay. Standard treatment protocol was followed for all patients and they were closely monitored during hospital stay and subsequently for 4 weeks for occurrence of any adverse cardiac events.

RESULTS

There was a statistically significant difference in the mean level of CRP between study group (6.12 +/- 6.134 mg/L) and controls (1.52 +/- 0.751 mg/L); p = 0.000. Among the 44 patients, 19 (43%) experienced any one or more outcome measures. Of the three variables (i.e. ongoing chest pain, ST depression > or = 1 mm and CRP > or = 4 mg/L) which showed statistical significance on univariate analysis with respect to adverse outcome measures (p = 0.001, 0.027 and 0.000 respectively), only CRP > or = 4 mg/L and ST depression > or = 1 mm showed independent prognostic significance on multiple logistic regression analysis (p = 0.000 and 0.002 respectively). The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and relative risk (RR) for CRP > or = 4 mg/L were 78.9%, 96%, 93.75%, 85.74% and 6.56 (95% CI; 2.62 - 16.4) and that for ST depression > or = 1 mm were 89.47%, 64%, 65.38%, 88.89% and 5.88% (95% CI: 1.54 - 22.38), respectively. Trop T could be done in eight patients only.

CONCLUSION

CRP > or = 4 mg/L by ELISA is an independent predictor of adverse cardiac outcome in severe UA in the short-term follow up and, hence, is useful for risk stratification of these patients. CRP has a higher specificity, PPV and overall RR for prediction of an outcome than ST segment depression, although it is less sensitive.

Neurological manifestations of HIV disease

We report the results of neurological evaluation of 1,527 HIV positive subjects. Neurological complications were seen in 457 patients (481 neurological events). The prevalence was 20.24% of patients attending the out-patient clinic and in 44.57% of in-patients. Involvement of all levels of neuraxes was documented. The commonest manifestations were neuropathies, including herpes zoster (28.27%), meningitis (17.88%) and mass lesions (16%). Cryptococcal meningitis was clearly commoner than tubercular meningitis (67.44% vs 18.60% of all cases of meningitis, respectivelv). Amongst mass lesions, 14/24 single lesions and 27/38 multiple lesions responded to anti-toxoplasma treatment and were diagnosed as CNS toxoplasmosis. In abscence of biopsy, it would be prudent to initiate empirical anti-toxoplasma treatment for all HIV patients with mass lesions and assess clinical and radiological response. To our knowledge this is the largest series of neurological manifestations of HIV disease documented in Indian literature.

Bacterial RNA polymerase subunit omega and eukaryotic RNA polymerase subunit RPB6 are sequence, structural, and functional homologs and promote RNA polymerase assembly

Bacterial DNA-dependent RNA polymerase (RNAP) has subunit composition beta'betaalpha(I)alpha(II)omega. The role of omega has been unclear. We show that omega is homologous in sequence and structure to RPB6, an essential subunit shared in eukaryotic RNAP I, II, and III. In Escherichia coli, overproduction of omega suppresses the assembly defect caused by substitution of residue 1362 of the largest subunit of RNAP, beta'. In yeast, overproduction of RPB6 suppresses the assembly defect caused by the equivalent substitution in the largest subunit of RNAP II, RPB1. High-resolution structural analysis of the omega-beta' interface in bacterial RNAP, and comparison with the RPB6-RPB1 interface in yeast RNAP II, confirms the structural relationship and suggests a "latching" mechanism for the role of omega and RPB6 in promoting RNAP assembly.

Increased lower denture security using the Myoloc system

PURPOSE OF THE STUDY

To assess whether the Myoloc System. Improves the stability of the mandibular complete denture.

METHOD

Unstable dentures move during function causing pain and discomfort to patients resulting in decreased denture security. Improvement in patients' perceived denture security was used to assess if the Myoloc System improved the stability of the mandibular complete denture. Complete dentures were constructed for 27 patients (20 female and seven male) by conventional methods. Patients were asked to mark a point on a visual analogue scale to indicate their denture security. Following this, copies of the mandibular dentures were made and Myoloc wings added to the dentures. Denture security was recorded once again. The two responses were statistically analysed for significant improvement.

RESULT

A statistically significant improvement in denture security was found to occur after addition of the Myoloc wings to the mandibular denture.

CONCLUSION

The Myoloc System improves the stability of the mandibular complete denture and may prove useful when conventional methods fail to provide adequate denture stability and the patient is not a candidate for surgery.

Corneal epithelial toxic effects and inflammatory response to perfluorocarbon liquid

We report an unusual case of corneal epithelial toxic effects associated with perfluorocarbon liquids (PFCLs). The clinical and histopathologic findings are described. An elderly man underwent vitreoretinal surgery for a complicated retinal detachment. Perfluorodecalin was used to repair the retina. It was left in situ for 8 weeks and removed via the pars plana. One month after removal of heavy liquids the patient developed a nonhealing corneal epithelial defect associated with limbitis. Perfluorodecalin was found under the superior conjunctiva. A conjunctival biopsy revealed the presence of vacuoles in the conjunctival stroma surrounded by an inflammatory response that consisted of lymphocytes, macrophages, and giant cells. On surgical removal of the PFCL from the subconjunctival space, the epithelial defect healed. The histopathologic and clinical evidence suggest that the inflammatory response and corneal epithelial ulceration were caused by the prolonged presence of PFCL in the subconjunctival space. To the best of our knowledge, PFCLs have not previously been reported to cause corneal epithelial defects or incite an inflammatory response in the human eye.

P-glycoprotein shows strong catalytic cooperativity between the two nucleotide sites

P-Glycoprotein (Pgp) (also known as multidrug-resistance protein) contains two nucleotide binding sites, both of which are catalytic ATPase sites. The covalent reagent 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole (NBD-Cl) reacts in catalytic sites, and full inactivation of ATPase activity occurs at a reaction stoichiometry of 1 mol of NBD-Cl/mol of Pgp. We show that, at reaction stoichiometry of < or = 1 mol/mol, both nucleotide sites become labeled in relatively nonselective fashion. There is therefore strong interaction between the two nucleotide sites because (a) reaction of one site with NBD-Cl severely impedes reaction of reagent with the other site, and (b) reaction of one site inhibits steady-state ATPase, i.e. both sites are inhibited. Vanadate-trapping experiments revealed that when one nucleotide site was reacted with NBD-Cl, not even a single ATPase turnover event could occur in the other, intact, nucleotide site. The data demonstrate therefore that catalytic cooperativity between the two nucleotide sites in Pgp is extremely strong and mandatory for catalysis.

Photoaffinity labelling of P-glycoprotein catalytic sites

Photoaffinity labelling of hamster P-glycoprotein was carried out after trapping of radioactive Mg-8-azido-ADP in the catalytic sites by vanadate or beryllium fluoride. With either trapping agent the same labelled peptide was obtained in homogeneous form, with the sequence -FNEVVFNxPTRPDI-, corresponding to residues 1034-1037 in the C-terminal nucleotide binding site. The missing residue 'x' corresponds to Tyr-1041, which is therefore a primary reaction target of 8-azido-ADP. This tyrosine is conserved in all hamster, mouse and human P-glycoproteins. A second major labelled peptide fraction was also identified. The major sequence in this fraction was -NIHFSxPSR-, corresponding to residues 393-401 of hamster P-glycoprotein, where 'x' corresponds to Tyr-398 in the N-terminal nucleotide binding site. Therefore Tyr-398, which is also conserved in other P-glycoproteins, is also a reaction target for 8-azido-ADP. In sequence alignment of the two nucleotide binding sites, Tyr-398 exactly corresponds to Tyr-1041. The data indicate that these two tyrosines lie close to the adenine ring of bound substrate MgATP in the respective catalytic sites of P-glycoprotein.

Inhibition of P-glycoprotein ATPase activity by beryllium fluoride

ATPase activity of P-glycoprotein (multidrug-resistance protein) was found to be potently inhibited by beryllium fluoride (BeFx) in combination with MgATP, MgADP, or corresponding Mg-8-azido-nucleotides. Inhibition was due to trapping of nucleoside diphosphate at catalytic sites. Full inhibition was achieved on trapping of 1 mol of nucleotide per mol of Pgp. Reactivation was slow (t(1/2) = 32 min at 37 degrees C), and release of trapped nucleotide correlated with recovery of ATPase. Trapping of 8-azido-ADP followed by UV irradiation yielded permanent inactivation and specific labeling of Pgp in plasma membranes. Both N- and C-terminal nucleotide binding sites were labeled. These findings give strong confirmation of the concepts that in intact Pgp both nucleotide sites are active in MgATP hydrolysis, and that they interact strongly. The characteristics of inhibition by BeFx were similar in general to those seen with vanadate. However, PPi gave strong protection against BeFx inhibition, and in this respect, inhibition by BeFx was clearly different from vanadate inhibition.

Inhibition of P-glycoprotein ATPase activity by procedures involving trapping of nucleotide in catalytic sites

Fluoroaluminate in combination with nucleotide inhibited ATPase activity of P-glycoprotein (Pgp) in plasma membranes and in pure reconstituted form. Low nucleotide concentrations were effective, e.g., half-maximal inhibition was obtained with 10 microM MgATP. With MgATP or MgADP, reactivation occurred with t1/2 = 7 min at 37 degrees C. With 8-azido-ATP, UV irradiation of inhibited Pgp gave specific photolabeling of both nucleotide sites. Fluoroaluminate therefore provides a valuable tool for functional and structural characterization of P-glycoprotein and probably of other ABC transporters. 2-Azido-ATP, in combination with vanadate, fluoroaluminate, or beryllium fluoride, inhibited Pgp ATPase activity. Low concentrations of 2-azido-ATP were effective. However, after UV irradiation of the inhibited Pgp species, in no case was there evidence of covalent labeling of nucleotide sites. Therefore in the Pgp catalytic sites, under conditions of nucleotide trapping, there is no suitable amino acid side chain adjacent to the photoactivated 2-position of bound 2-azido-nucleotide, and 8-azido-ATP is the preferred photolabeling analog.

Both P-glycoprotein nucleotide-binding sites are catalytically active

The technique of vanadate trapping of nucleotide was used to study catalytic sites of P-glycoprotein (Pgp) in plasma membranes from multidrug-resistant Chinese hamster ovary cells. Vanadate trapping of Mg- or Co-8-azido-nucleotide (1 mol/mol of Pgp) caused complete inhibition of Pgp ATPase activity, with reactivation rates at 37 degrees C of 1.4 x 10(-3) s-1 (t1/2 = 8 min) or 3.3 x 10(-4) s-1 (t1/2 = 35 min), respectively. UV irradiation of the inhibited Pgp yielded permanent inactivation of ATPase activity and specific photolabeling of Pgp. Mild trypsin digestion showed that the two nucleotide sites were labeled in equal proportion. The results show that both nucleotide sites in Pgp are capable of nucleotide hydrolysis, that vanadate trapping of nucleotide at either site completely prevents hydrolysis at both sites, and that vanadate trapping of nucleotide in the N- or C-terminal nucleotide sites occurs non-selectively. A minimal scheme is presented to explain inhibition by vanadate trapping of nucleotide and to describe the normal catalytic pathway. The inhibited Pgp-Mg-nucleotide.vanadate complex is probably an analog of the catalytic transition state, implying that when one nucleotide site assumes the catalytic transition state conformation the other site cannot do so and suggesting that the two sites may alternate in catalysis.

A shared and unique peptide in the human colon, eye, and joint detected by a monoclonal antibody

BACKGROUND/AIMS

Extraintestinal manifestations of inflammatory bowel disease include involvement of the eye and joint. However, the pathogenesis of ocular and joint complications is unknown. The aim of the current study is to examine the presence of cross-reactive peptide in the colon and ocular and joint tissue.

METHODS

Using a murine monoclonal antibody (7E12H12; immunoglobulin M isotype) developed against a colon epithelial protein, various parts of the eyes (n = 10) and joints (n = 8) were examined. A sensitive immunoperoxidase assay was used.

RESULTS

In the ocular and joint tissues, the reactivity of 7E12H12 monoclonal antibody was exclusively present in the nonpigmented epithelial cells of the ciliary processes and chondrocytes, respectively. Other structures of the eyeball, such as the sclera, cornea, iris, and retina, and the synovium of the joints did not react with 7E12H12 monoclonal antibody. Colonic epithelial cells examined in parallel also reacted with the monoclonal antibody.

CONCLUSIONS

The colon epithelial cells share a unique peptide with the nonpigmented ciliary epithelial cells and chondrocytes. Future studies of the peptide(s) expressing this common epitope shared by the colon and extracolonic organs known to be involved in colitis may provide further understanding of the pathogenesis of extraintestinal complications in patients with ulcerative colitis.

The effect of extraction of the intrafascicular contents of peripheral nerve trunks on perineurial structure

The intrafascicular contents have been extracted from the tibial nerve of the rabbit through perineurial incisions. Within 6--8 days following this procedure, the perineurial cells separate from one another, become dissociated from their basement membranes and assume a fibroblast-like appearance. The intrafascicular space becomes populated with endoneurial fibroblasts. With the ingrowth of regenerating axons, bundles of axons and associated Schwann cells become surrounded by cells of fibroblastic appearance which undergo perineurial transformation resulting in the development of multiple small fascicles. The cells of the surrounding perineurium appear to reassume a lamellar organization and to reestablish contacts with each other with the formation of junctional complexes. It is therefore suggested that neural structures may be responsible for the development and maintenance of the structural organization of the perineurium.