tert-butyl N-[2-[N-(N, N'-dicyclohexylureidocarbonylethyl)carbamoyl]prop-2-yl]carbamate

The title compound, C(25)H(44)N(4)O(5), exhibits a turn with the main chain reversing direction, held together by an intramolecular N-H.O hydrogen bond. In the urea fragment, a notable amide C-N bond between the carboxyl C and the tertiary N atom shows marked single-bond character [1.437 (2) A]. The dihedral angle of the beta-alanyl residue, centrally located in the turn, is gauche [69.2 (2) degrees ]. The packing is mediated by two intermolecular hydrogen bonds and van der Waals contacts involving the methyl moieties and the cyclohexyl rings.

Gender differences in relation to sputum submission and smear-positive pulmonary tuberculosis in Malawi

OBJECTIVE

To examine gender differences in sputum submission and sputum smear positivity.

METHODS

Laboratory registers in all diagnostic units in eight districts in Malawi were examined for the years 1995 and 1996.

RESULTS

During a 12-month period (averaged between 1995 and 1996), 26,624 new TB suspects submitted sputum samples, 3282 of which (12.3%) were smear-positive. Significantly more males submitted sputum (52%) compared with females (48%), and significantly more males (53%) were smear-positive compared with females (47%, P < 0.05). Rates of sputum submission per 100,000 adults were also significantly higher for males (1203) than females (1032).

CONCLUSION

In Malawi, fewer females are submitting sputum samples and are being diagnosed with smear-positive TB compared with males.

Palliative balloon pulmonary valvuloplasty in tetralogy of fallot: echocardiographic predictors of successful outcome

Although balloon pulmonary valvuloplasty (BPV) has been advocated as a means of palliating patients with tetralogy of Fallot (TOF), the results of this procedure were not uniformly good in this patient population. The purpose of this study was to review our institutionOs experience with BPV in patients with TOF, and to determine whether echocardiographic criteria exist that may be used to identify patients likely to derive prolonged benefit from this procedure. Between 1991 and 1999, nine patients with TOF, ages 0. 4Eth 26.1 weeks (mean, 7.4 +/- 7.6 weeks) underwent BPV due to cyanosis and other associated medical conditions (e.g., coronary artery anomalies, small size) that rendered immediate surgical intervention undesirable. Data from the catheterization and pre-BPV echocardiograms were analyzed. All patients had at least transient improvement in oxygen saturation. However, 4 patients (Group 1) required intervention (1 open-heart repair, 3 palliative shunts) within 5 weeks of BPV due to recurrent desaturation. In the remaining 5 patients (Group 2), open-heart repair was delayed 8Eth 36 weeks (mean, 23 +/- 13 weeks). Groups 1 and 2 did not differ regarding pulmonary valve annulus, main pulmonary artery or branch pulmonary artery diameter. However, the diastolic diameter of the right ventricular outflow tract (RVOT) was significantly smaller in Group 1 (18.3 +/- 3.5 mm/m2 versus 24.4 +/- 4.1 mm/m2 in Group 2; p < 0.05). Four out of five patients with a RVOT diameter < 23 mm/m2 were in Group 1, and all patients with RVOT diameter greater than 25 mm/m2 were in Group 2. We conclude that BPV can effectively palliate patients with TOF whose RVOT diastolic diameter is > 25 mm/m2. However, patients with a diastolic RVOT diameter < 23 mm/m2 are unlikely to have sustained improvement following BPV.

Biocatalytic preparation of a chiral synthon for a vasopeptidase inhibitor: enzymatic conversion of N(2)-

[4S-(4I,7I,10aJ)]1-Octahydro-5-oxo-4-[phenylmethoxy)carbonyl]amino]-7H-pyrido-[2,1-b] [1,3]thiazepine-7-carboxylic acid methyl ester (BMS-199541-01) is a key chiral intermediate for the synthesis of Omapatrilat (BMS-186716), a new vasopeptidease inhibitor under development. By using a selective enrichment culture technique we have isolated a strain of Sphingomonas paucimobilis SC 16113, which contains a novel L-lysine epsilon-aminotransferase. This enzyme catalyzed the oxidation of the epsilon-amino group of lysine in the dipeptide dimer N(2)-[N[phenyl-methoxy)-carbonyl] L-homocysteinyl] L-lysine)1,1-disulphide (BMS-201391-01) to produce BMS-199541-01. The aminotransferase reaction required alpha-ketoglutarate as the amino acceptor. Glutamate formed during this reaction was recycled back to alpha-ketoglutarate by glutamate oxidase from Streptomyces noursei SC 6007. Fermentation processes were developed for growth of S. paucimobilis SC 16113 and S. noursei SC 6007 for the production of L-lysine epsilon-amino transferase and glutamate oxidase, respectively. L-lysine epsilon-aminotransferase was purified to homogeneity and N-terminal and internal peptides sequences of the purified protein were determined. The mol wt of L-lysine epsilon-aminotransferase is 81 000 Da and subunit size is 40 000 Da. L-lysine epsilon-aminotransferase gene (lat gene) from S. paucimobilis SC 16113 was cloned and overexpressed in Escherichia coli. Glutamate oxidase was purified to homogeneity from S. noursei SC 6003. The mol wt of glutamate oxidase is 125 000 Da and subunit size is 60 000 Da. The glutamate oxiadase gene from S. noursei SC 6003 was cloned and expressed in Streptomyces lividans. The biotransformation process was developed for the conversion of BMS-201391-01 to BMS-199541-01 by using L-lysine epsilon-aminotransferase expressed in E. coli. In the biotransformation process, for conversion of BMS-201391-01 (CBZ protecting group) to BMS-199541-01, a reaction yield of 65-70 M% was obtained depending upon reaction conditions used in the process. Phenylacetyl or phenoxyacetyl protected analogues of BMS-201391-01 also served as substrates for L-lysine epsilon-aminotransferase giving reaction yields of 70 M% for the corresponding BMS-199541-01 analogs. Two other dipeptides N-[N[(phenylmethoxy)carbonyl]-L-methionyl]-L-lysine (BMS-203528) and N,2-[S-acetyl-N-[(phenylmethoxy)carbonyl]-L-homocysteinyl]-L-lysine (BMS-204556) were also substrates for L-lysine epsilon-aminotransferase. N-alpha-protected (CBZ or BOC)-L-lysine were also oxidized by L-lysine epsilon-aminotransferase.

Bench to bedside: tumor necrosis factor-alpha: from inflammation to resuscitation

Proinflammatory mediators such as tumor necrosis factor-alpha (TNF) have been implicated in the pathophysiology in a number of acute disease states. Tumor necrosis factor-alpha can contribute to cell death, apoptosis, and organ dysfunction. Tumor necrosis factor-alpha can be generated with sepsis or ischemia-reperfusion by activation of cell mitogen-activated protein kinases and nuclear factor kappa B, leading to TNF production. A number of strategies to modulate TNF have been recently explored, including factors directed toward mitogen-activated protein kinases, TNF transcription, anti-inflammatory ligands, heat shock proteins, and TNF-binding proteins. However, TNF may also play an important role in the adaptive response to injury and inflammation. Control of the deleterious effects of TNF and other proinflammatory cytokines represents a realistic goal for clinical emergency medicine. The purpose of this article is to provide a background of relevance to emergency medicine academicians on the production and regulation of TNF, the acute effects of TNF on pathophysiology, and the rationale for therapeutic interventions directed toward TNF and the clinical experience with these strategies.

Selective mitochondrial KATP channel opening controls human myocardial preconditioning: too much of a good thing?

BACKGROUND

Paradoxically, patients with noninsulin-dependent diabetes mellitus experience a higher cardiovascular mortality rate than patients with insulin-dependent diabetes mellitus. We have shown that K(ATP) channel inhibition, with oral sulfonylureas, prevents myocardial preconditioning and may explain the paradox of cardiovascular death in patients with noninsulin-dependent diabetes mellitus. Cardiac preconditioning is an attractive protective strategy against any elective ischemia/reperfusion (I/R) injury. The relationship between the K(ATP) channels and human myocardial preconditioning has not previously been elucidated.

METHODS

Human atrial trabeculae were harvested, placed in organ baths, and paced (1 Hz). Developed force was recorded during simulated 37 degrees C I/R (30/45 or 45/60 minutes). Before I/R, trabeculae were treated transiently with a selective mitochondrial K(ATP) channel opener for 5 minutes, followed by a 10-minute washout, or were exposed to the channel opener throughout ischemia. Recovery of function is expressed as percentage of baseline developed force. Conserved creatine kinase activity (units per gram of wet tissue) was measured at the end of reperfusion as an indicator of cellular protection.

RESULTS

Transient mitochondrial K(ATP) channel opening provided protection from both I/R insults. Surprisingly, there was no protection afforded by continuous mitochondrial K(ATP) channel opening.

CONCLUSIONS

Transient selective mitochondrial K(ATP) channel opening protects both viability and function of human myocardium against I/R injury, although prolonged opening of the mitochondrial K(ATP) channel does not. These results reinforce the concept of preconditioning as a transient event that must be completed before the onset of ischemia.

Structural and interactional homology of clinically potential trypsin inhibitors: molecular modelling of cucurbitaceae family peptides using the X-ray structure of MCTI-II

Several trypsin inhibitor peptides (with 28-32 amino acid residues) belonging to the Cucurbitaceae (LA-1, LA-2, MCTI-I, CMTI-I, CMTI-III, CMTI-IV), characterized by a distinctive tertiary fold with three conserved disulphide bonds and with mostly arginine at their active centre, were modelled using the high-resolution X-ray structure of a homologous inhibitor, MCTI-II, isolated from bitter gourd. All the inhibitors were modelled in both their native and complexed state with the trypsin molecule, keeping the active site the same as was observed in the trypsin-MCTI-II complex, by homology modelling using the InsightII program. The minimized energy profile supported the binding constants (binding behaviour) of the inhibitor-trypsin complexes in the solution state. A difference accessible surface area (DASA) study of the trypsin with and without inhibitors revealed the subsites of trypsin where the inhibitors bind. It revealed that the role of mutation of these peptides through evolution is to modulate their inhibitory function depending on the biological need rather than changing the overall structural folding characteristics which are highly conserved. The minor changes of amino acids in the non-conserved regions do not influence significantly the basic conformational and interactional sequences at the trypsin binding subsites during complex formation.

Selective mitochondrial adenosine triphosphate-sensitive potassium channel activation is sufficient to precondition human myocardium

OBJECTIVES

Recently, the mitochondrial adenosine triphosphate-sensitive potassium channel has been suggested to be the final common effector of myocardial preconditioning. The purpose of this study is to determine whether selective mitochondrial adenosine triphosphate-sensitive potassium channel activation alone can precondition human myocardium from an ischemia/reperfusion insult.

METHODS

Isolated human right atrial trabeculae were placed in tissue baths, paced, and subjected to 30 minutes of normothermic hypoxia (ischemia) followed by 45 minutes of reoxygenation (reperfusion). Trabeculae were preconditioned with a selective mitochondrial adenosine triphosphate-sensitive potassium channel opener (diazoxide 30 micromol/L) or a nonselective purinergic agonist, adenosine (125 micromol/L), for 5 minutes (adenosine) followed by a 10-minute washout period. Developed force at end reperfusion (mean +/- standard error) was compared with baseline, and tissue creatine kinase and adenosine triphosphate levels were measured after ischemia/reperfusion.

RESULTS

Trabeculae subjected to ischemia/reperfusion exhibited 30% +/- 2% of baseline developed force, whereas trabeculae subjected to selective adenosine triphosphate-sensitive potassium channel opening (diazoxide) and nonselective purinergic agonist (adenosine) recovered to 55% +/- 7% and 46% +/- 3% of baseline developed force, respectively. Tissue creatine kinase activity was preserved in both the diazoxide- and adenosine-treated trabeculae (5.4 +/- 12 and 5.4 +/- 14 micromol/L per gram wet tissue) compared with ischemia/reperfusion (1.8 +/- 0.2 U/mg wet tissue). Adenosine triphosphate levels at end reperfusion were also increased in the trabeculae treated with selective (diazoxide) and nonselective (adenosine) adenosine triphosphate-sensitive potassium channel opener (4.1 +/- 0.01 and 4. 4 +/- 0.2 micromol/L per gram wet tissue) compared with trabeculae subjected to ischemia/reperfusion (1.5 +/- 0.1 micromol/L per gram wet tissue).

CONCLUSIONS

These results suggest that selective mitochondrial adenosine triphosphate-sensitive potassium channel activation preconditions human myocardium and the protection conferred is equal to that of adenosine preconditioning. Targeted openers of mitochondrial adenosine triphosphate- sensitive potassium channels promote constructive protection of myocellular energy levels, contractile function, and cellular viability in human myocardium after ischemia/reperfusion.

Laser palatoplasty: evaluation of patient benefit using the Glasgow benefit inventory

Short-term results of laser palatoplasty have been encouraging. This study was undertaken to evaluate if there is a deterioration of benefit with time as seen in uvulopalatopharyngoplasty (UPPP). The Glasgow benefit inventory (GBI) was applied retrospectively by means of a postal questionnaire to measure the quality of benefit and to evaluate any deterioration in benefit with increasing post-operative time. Our results show that laser palatoplasty benefited 53 per cent of patients. With increasing post-operative time there was a decrease in the percentage of patients who felt the operation had made no difference, with a corresponding increase in the percentage of patients who felt worse. Although the number of patients who benefited remained fairly constant, there was deterioration in the quality of benefit in the first year, after which the benefit remained stable. This has implications in the pre-operative counselling of patients.

Bronchoscopic photodynamic diagnosis and therapy for lung cancer

Photodynamic diagnosis and therapy have exciting potential in lung cancer management. Fluorescence bronchoscopy enhances the detection of preinvasive lesions and early invasive carcinomas involving the central airways, whereas photodynamic therapy (PDT) provides an effective method for treating these lesions with preservation of lung tissue. However, the natural history of preinvasive lesions is poorly understood and so the value of treatment remains unclear. Although treatment for early invasive carcinomas'is not open to question, the possibility of undetected nodal disease means that PDT is unlikely to replace surgical resection in patients who are fit for thoracotomy. PDT also provides an effective method of palliating patients with advanced obstructing endobronchial tumors. Although it is considered superior to simple tumor debulking, its usefulness is limited by transient but potentially severe skin photosensitivity. There is therefore a need to develop new photosensitizing drugs with less severe side effects.

Dentine caries: take it or leave it?

In modern dentistry the primary aim when excavating carious dentine is to eradicate only the highly infected, irreversibly demineralized and denatured biomass in order to allow effective restoration of the cavity, restoration of the surface anatomy of the tooth and to prevent disease progression. However, the boundary between this superficial zone of dentine requiring excavation and the deeper, affected but repairable tissue is not always obvious either in the clinic or in the research laboratory. The inherent subjectivity in detecting this excavation boundary can result in clinically significant differences in the quality and quantity of dentine removed by different operators and makes the in vitro comparison of newer excavation techniques more difficult. This article discusses the rationale behind carious dentine excavation and the criteria available to the dentist, both clinical and laboratory, to help identify the dentine requiring removal.

Adenosine preconditioning reduces both pre and postischemic arrhythmias in human myocardium

INTRODUCTION

Consistently, clinical series record supraventricular tachyarrhythmias in approximately 30% of patients following coronary artery bypass surgery (CABG). Ischemic preconditioning and adenosine preconditioning (Ado-PC) decrease postischemia/reperfusion (I/R) myocardial stunning, infarct size, and pharmacologically induced arrhythmias in all species including man. We hypothesized that adenosine preconditioning would decrease spontaneous pre- and postischemic atrial arrhythmias in human myocardium. The purposes of this study were to determine the effect of in vivo and in vitro Ado-PC on atrial arrhythmias.

METHODS

Human atrial trabeculae were harvested from CABG patients, placed in organ baths, and paced (1 Hz). Developed force (DF) was recorded during simulated I/R (30/45 min). Prior to I/R, trabeculae were treated with Ado (125 microM) for 5 min (in vitro), or patients were treated with Ado (12 mg iv) 5 min (in vivo) prior to harvest of trabeculae. Contraction frequency >4 Hz (defined as atrial tachyarrhythmias) was recorded in all groups pre- and postischemia.

RESULTS

Control trabeculae exhibited increased tachyarrhythmias pre- and postischemia. In vivo and in vitro Ado-PC suppressed both pre- and postischemic arrhythmias.

CONCLUSIONS

Adenosine preconditioning suppresses the frequency of pre- and postischemic tachyarrhythmias against an ischemia/reperfusion insult in human myocardium. This antiarrhythmic effect occurs with both in vitro and in vivo administration of adenosine. Preconditioning with adenosine prior to elective ischemia/reperfusion is a promising strategy of reducing spontaneous atrial arrhythmias in patients undergoing myocardial revascularization.

Dentine caries excavation: a review of current clinical techniques

Since the invention and application of rotary instruments, the operative treatment of carious lesions has often resulted in considerable removal of tooth structure. More recently, newer techniques for removal of carious dentine have been developed in an attempt to minimise this excessive tissue loss. The following article reviews and discusses some of the techniques available to excavate demineralised dentine clinically. These methods can be classified as mechanical and non-mechanical, rotary and non-rotary and include: dental handpieces/burs, manual excavators, air-abrasion, air-polishing, ultrasonication, sono-abrasion, chemo-mechanical methods, lasers and enzymes. The advantages and disadvantages of each technique are discussed.

Protection against endotoxemia in rats by a novel tetrahydrobiopterin analogue

We studied the effects of a novel pterin antagonist of NO synthase, the 4-amino analogue of tetrahydrobiopterin (4-ABH4), in a rat model of endotoxic shock and compared its properties with those of N(G)-monomethyl L-arginine (L-NMMA). Treatment with a bolus dose of 4-ABH4 at 2 h after LPS challenge significantly improved the 6-day survival rate, compared with the controls treated with saline. L-NMMA treatment did not significantly influence the survival rate. This bolus treatment, using either compound, had no effect on the plasma nitrite + nitrate or plasma IL-6 levels. The continuous infusion of 4-ABH4 efficiently suppressed the enhanced calcium-dependent/independent NO synthase activities induced by endotoxin in lung homogenates and completely suppressed the increase in plasma nitrite + nitrate caused by endotoxin at 5 h, with no significant difference compared with the L- NMMA treatment. Treatment of RAW264.7 murine macrophages with 4-ABH4 but not with L-NMMA suppressed endotoxin-induced tumor necrosis factor-alpha release by the cells, whereas nitrite in the supernatant decreased in a dose-dependent fashion in both assay systems. Our data show that 4-ABH4, an inhibitor of inducible NO synthase, significantly improves survival in a rat model of endotoxic shock when administered in a bolus dose that does not reduce plasma total nitrite + nitrate levels. Because we observed no overt signs of toxicity and no influence on organ-specific tetrahydrobiopterin levels, we conclude that the novel compound 4-ABH4 is a promising drug candidate for protection against endotoxin-related mortality.

Evaluation of a unified treatment regimen for all new cases of tuberculosis using guardian-based supervision

SETTING

Ntcheu District, Malawi, using an oral antituberculosis treatment regimen.

OBJECTIVE

To determine whether directly observed treatment (DOT) during the initial phase of treatment supervised either in hospital, at health centres or by guardians in the community, was associated with 1) satisfactory 2-month and 8-month treatment outcomes, and 2) with a reduction of in-patient hospital-bed days.

DESIGN

Prospective data collection of all tuberculosis (TB) patients registered between 1 April 1996 and 30 June 1997, with 2-month and 8-month treatment outcomes, sputum smear conversion in smear-positive pulmonary TB patients (PTB) and in-patient hospital-bed days.

RESULTS

Among the 600 new patients, 302 had smear-positive PTB, 150 smear-negative PTB and 148 extrapulmonary TB (EPTB). Eight-month treatment completion was 65% for smear-positive PTB patients, which was significantly higher than in patients with smear-negative PTB (45%) and EPTB (54%), due mainly to high 8-month mortality rates. The site of the intensive phase was determined in 596 patients: 178 (30%) received DOT from guardians, 115 (19%) from a health centre and 303 (51%) in hospital. At 2 months, mortality rates were significantly higher in hospitalised patients. Two-month treatment outcomes (including sputum smear conversion rates in smear-positive PTB patients) were similar between patients receiving DOT at health centres or from guardians. Decentralised DOT resulted in a 25% reduction in hospital-bed days in patients alive at 2 months compared with that predicted using the old regimens.

CONCLUSION

Decentralising DOT to health centres and to guardians during the intensive phase is associated with satisfactory treatment outcomes.

Protein kinase C zeta isoform is critical for proliferation in human glioblastoma cell lines

Previous studies have confirmed that proliferation in glioblastoma cell lines can be blocked by non-isoform specific protein kinase C (PKC) inhibitors, e.g calphostin C, staurosporine. However, the exact mechanism of PKC involvement is poorly understood. The aim of this study was to explore the role of specific PKC isoforms in the aberrant growth of glioblastoma. Identification of the isoform(s) critical for proliferation in glioblastoma would present a better target for the design of chemotherapeutic strategies. To this end, we screened expression on PKC isoforms in four human glioblastoma cell lines both when proliferating and in a quiescent state using western assays. PKC isoforms alpha, beta, betaII and zeta were found to be expressed in all cell lines. PKC epsilon was detected in three out of four cell lines and PKC eta was detected in one out of four cell lines. Quiescence of growth resulted in down-regulation of PKC epsilon. We examined the role of these isoforms by studying the effect of PKC isoform-specific inhibitors bisindolylmaleimide-I and Gö6976 on proliferation in a panel of four human glioblastoma cell lines. Inhibition of PKC alpha and epsilon had no effect on proliferation, suggesting that previous studies targeting PKC alpha may not be of therapeutic benefit. More significantly, it was shown that inhibition of PKC zeta blocked proliferation. This suggests that the inhibition of PKC zeta may be an important chemotherapeutic target for arresting growth in glioblastoma.

Care seeking behaviour and diagnostic processes in patients with smear-positive pulmonary tuberculosis in Malawi

SETTING

Government hospitals in five districts in Malawi.

OBJECTIVE

To determine care seeking behaviour and diagnostic processes in patients newly diagnosed with smear-positive pulmonary tuberculosis (PTB).

DESIGN

Structured questionnaires completed by interview between January to September 1998.

RESULTS

During the study period 1,518 patients were registered with PTB, of whom 1,099 (72%) were interviewed. The median delay between onset of cough and diagnosis was 8 weeks. There was a variable pattern of care seeking behaviour, with 70% of patients initially visiting a place of orthodox medical care and 30% visiting traditional healers, grocery shops, etc. Of these, 867 (79%) patients had one or more subsequent contacts for help, with these visits targeted more to orthodox medical care. At all stages, antibiotics resulted in symptomatic improvement in up to 40% of cases. There was a median time of 7 weeks between cough and first submission of sputum specimens. Almost all patients received sputum smear results after a median length of 4 days; 474 (43%) of patients were only aware of their diagnosis at the time of receiving smear results, this observation being significantly associated with lack of schooling and not knowing another person with TB.

CONCLUSION

More needs to be done to educate communities and non-orthodox care providers about the diagnosis and treatment of TB.

Beta-carotene prolongs survival, decreases lipid peroxidation and enhances glutathione status in transplantable murine lymphoma

Carotenoids of dietary origin have recently been the subject of renewed research interest because of epidemiological evidence indicating an inverse relationship between intake of carotenoids-rich plant substances and risk of certain cancers. This study was attempted to understand the biological actions of dietary beta-carotene (BC) on Dalton's lymphoma (DL), a rapidly proliferating transplantable tumor, in effecting the survival of the lymphoma-bearing mice. The glutathione (GSH) level and the extent of lipid peroxidation in the liver, kidney and brain were monitored in BC-treated (100 mg/kg food) mice transplanted with DL. These markers showed substantial alterations during the whole length of tumor progression in lymphoma-bearing mice without BC supplementation. When treated with BC, both malondialdehyde contents (evidence of lipid peroxidation) and the GSH levels in different organs were found to be closer to normal values in the initial period of tumor progression. BC-mediated protection against lipid peroxidation was maximally found to be in hepatic tissue throughout the study following DL transplantation. This was fairly reflected in the higher BC concentration in hepatic tissue of BC-treated lymphoma group compared to untreated lymphoma control. Significantly higher survival time (51-55 days) was observed in BC-treated animals in comparison to their untreated DL counterparts (35-38 days). The prolonged survival observed in the BC-supplemented animals may be attributed to the higher resistance offered by animals receiving BC towards lipid peroxidation-related tissue injury.