The potential impact of structural genomics on tuberculosis drug discovery

Mycobacterium tuberculosis, the causative agent of tuberculosis (TB) in humans, is a devastating infectious organism that kills approximately two million people annually. The current suite of antibiotics used to treat TB faces two main difficulties: (i) the emergence of multidrug-resistant (MDR) strains of M. tuberculosis, and (ii) the persistent state of the bacterium, which is less susceptible to antibiotics and causes very long antibiotic treatment regimes. The complete genome sequences of a laboratory strain (H37Rv) and a clinical strain (CDC1551) of M. tuberculosis and the concurrent identification of all the open reading frames that encode proteins within this organism, present structural biologists with a wide array of protein targets for structure determination. Comparative genomics of the species that make up the M. tuberculosis complex has also added an array of genomic information to our understanding of these organisms. In response to this, structural genomics consortia have been established for targeting proteins from M. tuberculosis. This review looks at the progress of these major initiatives and the potential impact of large scale structure determination efforts on the development of inhibitors to many proteins. Increasing sophistication in structure-based drug design approaches, in combination with increasing numbers of protein structures and inhibitors for TB proteins, will have a significant impact on the downstream development of TB antibiotics.     

Effects of morphine on behavior maintained by four simple food-reinforcement schedules

Summary Rats conditioned on three values of FR, VR, FI and VI food reinforcement schedules were administered 1.0, 3.0 and 6.0 mg/kg I.P. of morphine or saline. Overall response rate varied with schedule, schedule value and morphine dose. The effect of morphine on overall rate varied with baseline saline rate generated by schedules, and the relative rate change also varied with the type of schedule.This research was supported in part by U.S.P.H.S. Research Grant MH-15349 to the University of Minnesota.Copies of representative cumulative records at each morphine dose and schedule value can be obtained by writing to the senior author at Box 392 Mayo, University of Minnesota, Minneapolis, Minnesota.     

Familial amentia, unusual ventricular calcifications, and increased cerebrospinal fluid protein.

A sibship originally reported by Friedman and Roy as showing severe mental retardation, strabismus, hyperactive tendon reflexes, lalling speech, and foot deformities was restudied. Three major additional findings were noted. The cerebrospinal fluid protein concentration was increased two to three times above normal in four siblings who were available for study. Radiographs of cranial structures in three siblings showed identical pathologic intracranial calcifications which correspond in distribution to the choroid plexus. The choroid plexus was not demonstrable in one patient when radiolabeled 99m-Tc-pertechnetate was injected without perchlorate. Neuropathologic findings in one sibling included small subcortical heterotopias and atrophy of the choroid plexus with encasement by glial fibrils. These findings denote a new heredofamilial neurologic syndrome associated with mental retardation and a disorder of choroid plexus.     

Impaired retinal vasodilator responses in prediabetes and type 2 diabetes

Purpose: In diabetes, endothelial dysfunction and subsequent structural damage to blood vessels can lead to heart attacks, retinopathy and strokes. However, it is unclear whether prediabetic subjects exhibit microvascular dysfunction indicating early stages of arteriosclerosis and vascular risk. The purpose of this study was to examine whether retinal reactivity may be impaired early in the hyperglycaemic continuum and may be associated with markers of inflammation. Methods: Individuals with prediabetes (n = 22), type 2 diabetes (n = 25) and healthy age and body composition matched controls (n = 19) were studied. We used the Dynamic Vessel Analyzer to assess retinal vasoreactivity (percentage change in vessel diameter) during a flickering light stimulation. Fasting highly sensitive c‐reactive protein (hs‐CRP), a marker of inflammation, was measured in blood plasma. Results: Prediabetic and diabetic individuals had attenuated peak vasodilator and relative amplitude changes in retinal vein diameters to the flickering light stimulus compared with healthy controls (peak dilation: prediabetic subjects 3.3 ± 1.8%, diabetic subjects 3.3 ± 2.1% and controls 5.6 ± 2.6%, p = 0.001; relative amplitude: prediabetic subjects 4.3 ± 2.2%, diabetic subjects 5.0 ± 2.6% and control subjects 7.2 ± 3.2%, p = 0.003). Similar findings were observed in retinal arteries. Levels of hs‐CRP were not associated with either retinal vessel response parameters. Conclusion: Retinal reactivity was impaired in prediabetic and type 2 diabetic individuals in parallel with reduced insulin sensitivity but not associated with levels of hs‐CRP. Retinal vasoreactivity measurements may be a sensitive tool to assess early vascular risk.     

Washout of heme-containing proteins dramatically improves tetrazolium-based infarct staining

INTRODUCTION: Methods to determine infarct size following ischemia-reperfusion injury include gross staining with triphenyltetrazolium chloride (TTC) and perfusion of colored dyes to demarcate the non-ischemic zone. Infarcted tissue (INF) can typically appear a mottled tan to brownish color, making a border between INF and TTC-positive tissue difficult to discern. Previous work in our lab indicated that following TTC staining, prolonged washing of thick sections dramatically sharpened this boundary. METHODS: Adult rats underwent 30 min ischemia via LAD ligation and reperfusion/recovery over 24 h. Hearts were then harvested, thick-sectioned, and stained with TTC. Stained sections were stored in PBS at 4 degrees C for up to 3 weeks. RESULTS: Histology on thin sections from infarcted hearts fixed directly after harvest revealed extensive hemorrhage within the INF. However, this hemorrhage is washed out when hearts are stored in PBS for 3 weeks. SDS-PAGE of PBS samples taken at 1, 2, and 3 weeks showed a low molecular weight band appearing over time. Peptide sequencing revealed the presence of several proteins including the heme-containing proteins (HCPs) hemoglobin, cytochrome c, and myoglobin. The loss of HCPs from thick sections to PBS corresponded with the blanching of the previously mottled INF within each section. HPLC analysis of these samples confirmed the loss of HCPs contributes to INF whitening. Further, analysis of infarct size values derived from heart slices with or without HCPs showed a significant decrease in measurement error when values were derived from slices without HCPs. DISCUSSION: These data suggest that HCPs in the heart tissue contribute to the non-uniform and discolored appearance of the INF, and that washout of these proteins produces an INF more easily distinguished from neighboring non-infarcted tissue. This method greatly reduces the error associated with infarct measurements and improves the analysis of the effects of drug treatments and other interventions designed to impact ischemia reperfusion injury.     

Personalized Medicine for Diabetes: A Genomics Study of Type 2 Diabetes Mellitus in U.S. Air Force Personnel

The military community is at high risk for type 2 diabetes (T2D), especially as it relates to military beneficiaries, although preventive measures can be implemented to reduce disease onset. This study evaluates the prevalence of risk-associated single nucleotide polymorphisms in patients diagnosed with T2D within active duty, retired military, and military-dependent populations on Lackland Air Force Base compared to nondiabetic controls. Results will be used as a basis of comparison to analyze risk-conferring genotypes in the young, healthy active duty population to generate the prevalence of T2D risk-associated factors in our current and future war fighters. Identifying genetic markers of T2D prior to abnormal glucose control and insulin resistance may ultimately adjust future risk through early detection, healthy lifestyle modifications, and disease management programs.     

Cost-effectiveness of screening for albuminuria with subsequent fosinopril treatment to prevent cardiovascular events: A pharmacoeconomic analysis linked to the prevention of renal and vascular endstage disease (PREVEND) study and the prevention of renal and vascular endstage disease intervention trial (PREVEND IT)

OBJECTIVE: This study estimated the cost-effectiveness,from the Dutch health care perspective, of screening for albuminuria in the general Dutch population to prevent cardiovascular events (CVEs) with subsequent angiotensin-converting enzyme inhibitor treatment, using data from the Prevention of REnal and Vascular ENdstage Disease Intervention Trial (PREVEND IT). METHODS: PREVEND IT was a single-center, double-blind, randomized, placebo-controlled trial with a 2 x 2 factorial design within the larger observational Prevention of REnal and Vascular ENdstage Disease (PREVEND) study. The PREVEND IT study was conducted to assess the effects of fosinopril 20 mg and pravastatin 40 mg on CVEs in subjects with specific inclusion criteria: urinary albumin excretion (UAE) rate in the range from 15 to 300 mg/d, blood pressure <160/100 mm Hg, and plasma cholesterol level <8.0 mmol/L. Cost-effectiveness estimates for the Dutch population were expressed in euros (2002; 1 euro = US 1.01 dollars) as net costs per life-year gained (LYG) in the baseline and sensitivity (stochastic) analyses. RESULTS: Data were assessed for 864 subjects, with a mean (SD) follow-up of 46 (7) months. CVEs occurred in 45 (5.2%) subjects. Subjects who received fosinopril had a 40% lower incidence of CVEs than subjects in the placebo group (3.9% vs 6.5%, respectively; P = NS). The cost-effectiveness of screening for albumnuria was determined to be euro 16,700/LYG for the study population. Stochastic analysis indicated that the probability of the cost-effectiveness being below the suggested Dutch threshold of euro 20,000/LYG was 59% in the baseline analysis. The probability of cost-effectiveness below euro 20,000/LYG would increase to 91% if only subjects with UAE >50 mg/d were treated with fosinopril. Limiting the screening to subjects aged >50 years and >60 years also improved cost-effectiveness. CONCLUSIONS: The results of our study suggest that screening the general Dutch population for albuminuria and subsequently treating those found positive with fosinopril may be cost-effective compared with no screening and adopting the Dutch health care perspective. However, confirmation from larger multicenter trials is needed.     

Efficacy and mechanism of orthotic devices to unload metatarsal heads in people with diabetes and a history of plantar ulcers

BACKGROUND AND PURPOSE: Total-contact inserts (TCIs) and metatarsal pads (MPs) frequently are prescribed to reduce excessive plantar stresses to help prevent skin breakdown in people with diabetes mellitus (DM) and peripheral neuropathy. The first purpose of this study was to determine the effect of a TCI and an MP on metatarsal head peak plantar pressures (PPP) and pressure-time integrals (PTI). The second purpose of this study was to determine a possible mechanism of pressure reduction by measuring contact area and loaded soft-tissue thickness (STT) under the metatarsal heads and second metatarsal shaft. SUBJECTS: Twenty subjects (12 men and 8 women; age [mean+/-SD]=57+/-9 years) with DM (duration [mean+/-SD]=16+/-11 years), peripheral neuropathy, and a history of plantar ulcers participated. METHODS: A repeated-measures research design was used, and outcome measures are reported for 3 footwear conditions: shoe, shoe with TCI, and shoe with TCI and MP. In-shoe plantar pressures were collected during walking and during spiral x-ray computed tomography (SXCT). The STT and identification of the pressure sensor and location of the MP in relationship to the metatarsal heads were determined by use of SXCT. RESULTS: The PPP and the PTI were 16% to 24% lower at the metatarsal heads in the TCI condition than in the shoe condition. The PPP and the PTI decreased an additional 15% to 28% (for a total reduction of 29% to 47%) with the addition of the MP. The contact area increased 27% with the TCI but not with the MP. The STT did not increase under the metatarsal heads in the TCI condition (compared with the shoe condition) but did increase 8% to 22% at metatarsal heads 2 to 5 with the addition of the MP. The PPP increased substantially (308%) and the STT decreased 14% under the shaft of the second metatarsal with the addition of the MP to the TCI-plus-shoe condition. DISCUSSION AND CONCLUSION: The TCI and the MP caused substantial and additive reductions of pressures under the metatarsal heads. The TCI reduces excessive pressures at the metatarsal heads by increasing the contact area of weight-bearing forces. Conversely, the MP acts by compressing the soft tissues proximal to the metatarsal heads and relieving compression at the metatarsal heads. These findings can assist in the design of effective orthotic devices to relieve excessive plantar stresses that contribute to skin breakdown and subsequent amputation in people with DM and peripheral neuropathy.