Self-navigated spiral fMRI: interleaved versus single-shot

This study compares the measured activation volumes in motor cortex as well as the fluctuation noise and off-resonance characteristics for 1-, 2-, and 4-shot spiral gradient-recalled echo blood oxygen level dependent contrast functional magnetic resonance imaging (fMRI) acquisitions, under conditions of constant resolution and scan time and with two readout durations. Reconstructions were made with and without self-navigator correction. It was found that the navigator correction provided a 50% reduction in image fluctuation noise with 4-shot acquisitions, and that multishot acquisitions perform as well as single-shot techniques when self-navigation is employed. An analysis of blurring showed that off-resonance delta f causes blurring when delta f > 1/(2*Tad), where Tad is the readout duration. Off-resonance effects were readily corrected during reconstruction with retrospective linear shim, even with the longer readout duration needed for single-shot methods. With navigator and shim correction, single-shot and multishot spiral methods are highly effective for fMRI acquisitions.

Incremental prognostic value of post-stress left ventricular ejection fraction and volume by gated myocardial perfusion single photon emission computed tomography

BACKGROUND

The incremental prognostic value of post-stress left ventricular ejection fraction (EF) and volume over perfusion has not been investigated.

METHODS AND RESULTS

We identified 1680 consecutive patients who underwent rest Tl-201/stress Tc-99m sestamibi gated single photon emission computed tomography (SPECT) and who were followed-up for 569+/-106 days. Receiver-operator characteristics analysis defined an EF<45%, an end-systolic volume (ESV) >70 mL, and an end-diastolic volume >120 mL as optimal thresholds, yielding moderate sensitivity and high specificity in the prediction of cardiac death. Patients with an EF> or = 45% had mortality rates <1%/year, despite severe perfusion abnormalities, whereas patients with an EF<45% had high mortality rates, even with only mild/moderate perfusion abnormalities (9.2%/year; P<0.00001). Similarly, an ESV< or = 70 mL was related to a low cardiac death rate (<1.2%/year), even for patients with severe perfusion abnormalities, whereas patients with an ESV>70 mL and only mild/moderate perfusion abnormalities had high death rates (8.2%/year; P<0.00001). Patients with an EF<45% and an ESV< or = 70 mL had low cardiac death rates (1.7%/year); those with an EF<45% but an ESV>70 mL had high death rates (7.9%/year; P<0.02). Multivariate Cox proportional hazards regression showed that perfusion variables and ESV were independent predictors of overall coronary events, whereas EF and ESV demonstrated incremental prognostic values over prescan and perfusion information in predicting cardiac death and cardiac death or myocardial infarction.

CONCLUSIONS

Post-stress EF and ESV by gated-SPECT have incremental prognostic values over prescan and perfusion information in predicting cardiac death, and they provide clinically useful risk stratification.

Identification of vascular structures as a major source of signal contrast in high resolution 2D and 3D functional activation imaging of the motor cortex at 1.5T: preliminary results

We have measured the T2* signal response associated with cortical activation due to finger motion at 1.5 Tesla. Both thin slice 2D and 3D images show signal intensity changes which vary from 2% to 32% depending on volunteer, echo time, slice thickness, and in-plane resolution. The largest signal change occurred for the thinnest slices and highest resolution (2 mm3). This is consistent with reducing partial volume effects and a simple difference in phase between the intravascular signal and surrounding parenchyma. No inflow enhancement was seen on the 2D or 3D scans, confirming the nature of the signal difference for this approach was due to local field inhomogeneity effects. Using 3D imaging, multiple effects can be seen simultaneously. With a 3D MRA method, it was possible to locate the vessel that was the source of the T2* behavior; it was in each case a vein on the surface of the cortical parenchyma.

High risk of HIV-related mortality is associated with selenium deficiency

To determine the independent contribution of specific immunologic and nutritional factors on survival in HIV-1 disease, CD4 cell count, antiretroviral treatment, plasma levels of vitamins A, E, B6, and B12 and minerals selenium and zinc were considered in relation to relative risk for HIV-related mortality. Immune parameters and nutrients known to affect immune function were evaluated at 6-month intervals in 125 HIV-1-seropositive drug-using men and women in Miami, FL, over 3.5 years. A total of 21 of the HIV-1-infected participants died of HIV-related causes during the 3.5-year longitudinal study. Subclinical malnutrition (i.e., overly low levels of prealbumin, relative risk [RR] = 4.01, p < 0.007), deficiency of vitamin A (RR = 3.23, p < 0.03), vitamin B12 deficiency (RR = 8.33, p < 0.009), zinc deficiency (RR = 2.29.1, p < 0.04), and selenium deficiency (RR = 19.9, p < 0.0001) over time, but not zidovudine treatment, were shown to each be associated with HIV-1-related mortality independent of CD4 cell counts <200/mm3 at baseline, and CD4 counts over time. When all factors that could affect survival, including CD4 counts <200/mm3 at baseline, CD4 levels over time, and nutrient deficiencies were considered jointly, only CD4 counts over time (RR = 0.69, p < 0.04) and selenium deficiency (RR = 10.8, p < 0.002) were significantly associated with mortality. These results indicate that selenium deficiency is an independent predictor of survival for those with HIV-1 infection.

A recent outbreak of human immunodeficiency virus type 1 infection in southern China was initiated by two highly homogeneous, geographically separated strains, circulating recombinant form AE and a novel BC recombinant

New outbreaks of human immunodeficiency virus type 1 (HIV-1) among injecting drug users (IDUs) are spreading in China along heroin trafficking routes. Recently, two separate HIV-1 epidemics among IDUs were reported in Guangxi, Southern China, where partial sequencing of the env gene showed subtype C and circulating recombinant form (CRF) AE. We evaluated five virtually full-length HIV-1 genome sequences from IDUs in Guangxi to determine the genetic diversity and the presence of intersubtype recombinants. Sequence analysis showed two geographically separated, highly homogeneous HIV-1 strains. B/C intersubtype recombinants were found in three IDUs from Baise City, in a mountainous region near the Yunnan-Guangxi border. These were mostly subtype C, with portions of the capsid and reverse transcriptase (RT) genes from subtype B. The subtype B portion of the capsid was located in the N-terminal domain, which has been shown to influence virus core maturation, virus infectivity, and binding to cyclophilin A, whereas the subtype B portion of RT was located in the palm subdomain, which is the active site of the enzyme. These BC recombinants differed from a BC recombinant found in Xinjiang Province in northwestern China. CRF AE strains were found in IDUs from Nanning, the capital of Guangxi, and in IDUs from Pingxiang City near the China-Vietnam border. The AE and BC recombinants were both remarkable for their low interpatient diversity, less than 1% for the full genome. Rapid spread of HIV-1 among IDUs may foster the emergence of highly homogeneous strains, including novel recombinants in regions with multiple subtypes.

An outbreak of tuberculosis caused by multiple-drug-resistant tubercle bacilli among patients with HIV infection

OBJECTIVE

To evaluate a nosocomial outbreak of tuberculosis caused by multiple-drug-resistant bacilli among patients with tuberculosis and HIV infection.

DESIGN

A case-control study.

PATIENTS

Patients with HIV infection and culture-proven tuberculosis.

MEASUREMENTS

Patient characteristics, date of diagnoses of HIV infection and disease, date of diagnosis of tuberculosis, Mycobacterium tuberculosis susceptibility results, and medical center contact.

RESULTS

Sixty-two patients who had tuberculosis caused by multiple-drug-resistant bacilli (cases) and 55 patients who had tuberculosis caused by susceptible or single-drug-resistant bacilli (controls) were identified. Controls were more likely to be black (odds ratio, 0.4; 95% CI, 0.2 to 0.9) or Haitian (odds ratio, 0.2; CI, 0.1 to 0.6) compared with cases, who were more likely to be homosexual men (odds ratio, 2.9; CI, 1.3 to 6.4). Forty-four cases (71%) had previous contact with an HIV clinic compared with 15 controls (27%) (P less than 0.0001). Cases were more likely to have had AIDS (odds ratio, 7.7; CI, 1.5 to 53.7), to have been hospitalized on an HIV ward (odds ratio, 8.3; CI, 2.3 to 29.7), to have been seen in an HIV clinic (odds ratio, 7.8; CI, 3.4 to 18.1), to have received intravenous therapy in an HIV clinic (odds ratio, 13.0; CI, 4.6 to 37.0), or to have received inhalation pentamidine in an HIV clinic before a diagnosis of tuberculosis was made. Multiple logistic regression analysis showed that a diagnosis of AIDS (odds ratio, 11.2; CI, 3.1 to 40.6) and HIV clinic visits (odds ratio, 13.0; CI, 2.7 to 63.7) before a diagnosis of tuberculosis were significantly associated with tuberculosis caused by multiple-drug-resistant bacilli. Using susceptibility patterns and appointment dates, we found that 22 cases had previous contact with a person who had tuberculosis caused by multiple-drug-resistant bacilli in the HIV clinic.

CONCLUSIONS

Nosocomial transmission of M. tuberculosis from other HIV-infected patients with tuberculosis caused by multiple-drug-resistant bacilli can occur. These findings have serious public health implications and demand strict adherence to acid-fast bacilli isolation precautions.

Responses to rare visual target and distractor stimuli using event-related fMRI

Previous studies have found that the P300 or P3 event-related potential (ERP) component is useful in the diagnosis and treatment of many disorders that influence CNS function. However, the anatomic locations of brain regions involved in this response are not precisely known. In the present event-related functional magnetic resonance imaging (fMRI) study, methods of stimulus presentation, data acquisition, and data analysis were optimized for the detection of brain activity in response to stimuli presented in the three-stimulus oddball task. This paradigm involves the interleaved, pseudorandom presentation of single block-letter target and distractor stimuli that previously were found to generate the P3b and P3a ERP subcomponents, respectively, and frequent standard stimuli. Target stimuli evoked fMRI signal increases in multiple brain regions including the thalamus, the bilateral cerebellum, and the occipital-temporal cortex as well as bilateral superior, medial, inferior frontal, inferior parietal, superior temporal, precentral, postcentral, cingulate, insular, left middle temporal, and right middle frontal gyri. Distractor stimuli evoked an fMRI signal change bilaterally in inferior anterior cingulate, medial frontal, inferior frontal, and right superior frontal gyri, with additional activity in bilateral inferior parietal lobules, lateral cerebellar hemispheres and vermis, and left fusiform, middle occipital, and superior temporal gyri. Significant variation in the amplitude and polarity of distractor-evoked activity was observed across stimulus repetitions. No overlap was observed between target- and distractor-evoked activity. These event-related fMRI results shed light on the anatomy of responses to target and distractor stimuli that have proven useful in many ERP studies of healthy and clinically impaired populations.

Theory and application of static field inhomogeneity effects in gradient-echo imaging

The influence of local static magnetic field inhomogeneities on gradient-echo imaging is discussed and the underlying theoretical aspects are reviewed. A high-resolution approach is suggested to suppress image distortion and restore signal loss due to spin dephasing. Acquisition of three-dimensional data sets not only overcomes part of the limitations associated with gradient echoes but also makes it possible to extract local information about the strength or direction of background gradients and relative susceptibility changes between different tissues. Applications of the suggested approach in the human brain for anatomical imaging as well as for extraction of physical and physiological parameters are presented and discussed.

Vacuolar H(+)-translocating ATPases from plants: structure, function, and isoforms

The vacuolar H(+)-translocating ATPase (V-type ATPase) plays a central role in the growth and development of plant cells. In a mature cell, the vacuole is the largest intracellular compartment, occupying about 90% of the cell volume. The proton electrochemical gradient (acid inside) formed by the vacuolar ATPase provides the primary driving force for the transport of numerous ions and metabolites against their electrochemical gradients. The uptake and release of solutes across the vacuolar membrane is fundamental to many cellular processes, such as osmoregulation, signal transduction, and metabolic regulation. Vacuolar ATPases may also reside on endomembranes, such as Golgi and coated vesicles, and thus may participate in intracellular membrane traffic, sorting, and secretion. Plant vacuolar ATPases are large complexes (400-650 kDa) composed of 7-10 different subunits. The peripheral sector of 5-6 subunits includes the nucleotide-binding catalytic and regulatory subunits of approximately 70 and approximately 60 kDa, respectively. Six copies of the 16-kDa proteolipid together with 1-3 other subunits make up the integral sector that forms the H+ conducting pathway. Isoforms of plant vacuolar ATPases are suggested by the variations in subunit composition observed among and within plant species, and by the presence of a small multigene family encoding the 16-kDa and 70-kDa subunits. Multiple genes may encode isoforms with specific properties required to serve the diverse functions of vacuoles and endomembrane compartments.

Human trophoblast and choriocarcinoma expression of the growth factor pleiotrophin attributable to germ-line insertion of an endogenous retrovirus

Retroviral elements are found in abundance throughout the human genome but only rarely have alterations of endogenous genes by retroviral insertions been described. Herein we report that a human endogenous retrovirus (HERV) type C is inserted in the human growth factor gene pleiotrophin (PTN) between the 5' untranslated and the coding region. This insert in the human genome expands the region relative to the murine gene. Studies with promoter-reporter constructs show that the HERV insert in the human PTN gene generates an additional promoter with trophoblast-specific activity. Due to this promoter function, fusion transcripts between HERV and the open reading frame of PTN (HERV-PTN) were detected in all normal human trophoblast cell cultures as early as 9 weeks after gestation (n = 7) and in all term placenta tissues (n = 5) but not in other normal adult tissues. Furthermore, only trophoblast-derived choriocarcinoma cell lines expressed HERV-PTN mRNA whereas tumor cell lines derived from the embryoblast (teratocarcinoma) or from other lineages failed to do so. We investigated the significance of HERV-PTN mRNA in a choriocarcinoma model by targeting this transcript with ribozymes and found that the depletion of HERV-PTN mRNA prevents human choriocarcinoma growth, invasion, and angiogenesis in mice. This suggests that the tissue-specific expression of PTN due to the HERV insertion in the human genome supports the highly aggressive growth of human choriocarcinoma and possibly of the human trophoblast.

The association between cigarette smoking and drug abuse in the United States

Cigarette smoking has been identified as an independent risk factor for many human diseases. However, the association between cigarette smoking and illegal drug use has not been thoroughly investigated. We have analyzed the 1994 National Household Survey on Drug Abuse to clarify whether cigarette smoking has any effect on the initiation of illegal drug use. Data from 17,809 respondents completing the 1994 "new" (1994-B) questionnaire were analyzed. Logistic regression analyses were performed with the use of statistical package SUDAAN, taking into consideration the multistage sampling design. The results show that those who had smoked cigarettes were far more likely to use cocaine (OR = 7.5; 95% CI: 5.7-9.9), heroin (OR = 16.0; 95% CI: 6.8-37.9), crack (OR = 13.9; 95% CI: 7.9-24.5) and marijuana (OR = 7.3; 95% CI: 6.2-8.7). The associations are consistent across age-strata and remain after adjusting for race and gender. This study suggests that cigarette smoking may be a gateway drug to illegal drug use.

Assessing the impact of coordinated COVID-19 exit strategies across Europe

As rates of new coronavirus disease 2019 (COVID-19) cases decline across Europe owing to nonpharmaceutical interventions such as social distancing policies and lockdown measures, countries require guidance on how to ease restrictions while minimizing the risk of resurgent outbreaks. We use mobility and case data to quantify how coordinated exit strategies could delay continental resurgence and limit community transmission of COVID-19. We find that a resurgent continental epidemic could occur as many as 5 weeks earlier when well-connected countries with stringent existing interventions end their interventions prematurely. Further, we find that appropriate coordination can greatly improve the likelihood of eliminating community transmission throughout Europe. In particular, synchronizing intermittent lockdowns across Europe means that half as many lockdown periods would be required to end continent-wide community transmission.

Positive surgical margins with radical retropubic prostatectomy: anatomic site-specific pathologic analysis and impact on prognosis

OBJECTIVES

To correlate the extent and location of positive surgical margins after radical prostatectomy with disease progression.

METHODS

Data on 495 patients who underwent radical prostatectomy by one surgeon were analyzed. All radical prostatectomy specimens were sectioned entirely using 2 to 3-mm step sections by one pathologist. One hundred fifty-one patients (30.5%) had one or more positive surgical margins and were subjected to further detailed analysis. Recurrence was defined as a serum prostate-specific antigen (PSA) level of 0.2 ng/mL and rising on at least two postoperative measurements.

RESULTS

The mean follow-up was 25.3 months (range 3 to 73). The overall recurrence rate was 13.3%. Neoadjuvant hormonal treatment was given to 37 (25%) of those with a positive margin. Patients with positive surgical margins had a significantly higher incidence of recurrence compared with those with negative margins (27.8% versus 6.9%, P = 0.001). The recurrence rate for various locations was 29% apex/urethra, 30% posterior, 33% anterior, 36% lateral, 48% posterolateral, and 57% bladder neck. Time to recurrence was shorter in patients older than 70 years (P<0.055); with a preoperative PSA greater than 10 ng/mL (P<0.0001); with a biopsy Gleason score greater than 7 (P = 0.02); with a prostatectomy Gleason score greater than 7 (P<0.001); with seminal vesicle invasion (P = 0.0001); having more than 1 location of a positive margin (P = 0.002); or having a positive margin at the bladder neck (P = 0.0003) or the posterolateral surface of the prostate (P = 0.02) compared with other locations. Multivariate proportional hazards analyses indicated that age older than 70 (P = 0.005), a prostatectomy Gleason score of 7 (P = 0.015) or 8 to 10 (P = 0.003), and positive margin(s) at the bladder neck (P = 0.003) were independently associated with a shorter time to recurrence among patients with a positive margin.

CONCLUSIONS

In our study, among patients with positive surgical margins, those with multiple positive margins, or a margin involving the bladder neck or the posterolateral surface of the specimen carried a higher risk of progression. A positive margin at the bladder neck appears to be the most significant adverse prognostic indicator. This information may help in decisions regarding additional therapy.

2D and 3D high resolution gradient echo functional imaging of the brain: venous contributions to signal in motor cortex studies

Recent emphasis on high resolution gradient echo studies in functional imaging has led to the conclusion that there are likely three domains of response to the blood circulation in the brain when considering field inhomogeneity effects of the venous blood pre- and during activation. The first is a coherent effect due to large or macroscopic vessels on the order of the size of the voxel (ca 200-500 microns in most studies). These can lead to very large signal changes (up to 100%). The second is at the venule level (ca 50-200 microns) and is associated with smaller parenchymal changes (usually ca 10% or less). The third is at the capillary level and is associated with much smaller signal changes at 1.5 T and even up to 4 T. The actual signal changes depend on field strength and sequence design. In this paper, we present our experience in detecting the first two domains with 2D and 3D gradient echo imaging at 1.5 T. We find that high resolution enables visualization of the larger small veins in motor cortex studies and that, on occasion, it is possible to see the venule effects as well. We suggest a simple model to explain the large signal changes based on susceptibility changes and partial volume effects. Comparisons of the functional imaging data to this model and to MR angiographic studies are also shown as evidence of the venous sources of the susceptibility changes.

Response to anti-tumour necrosis factor alpha blockade is associated with reduction of carotid intima-media thickness in patients with active rheumatoid arthritis

OBJECTIVES

To determine whether tumour necrosis factor (TNF)-alpha blockers may reduce carotid intima-media thickness (cIMT) in patients with active rheumatoid arthritis (RA) steadily responsive to such therapy.

METHODS

From 287 consecutive RA patients attending our out-patient clinic and diagnosed on the basis of the American College of Rheumatology (ACR) criteria, 49 without traditional cardiovascular risk factors and meeting the requirements for TNF-alpha blockers therapy were selected. Among them, 39 actually started TNF-alpha blockers, but only 30, who reached at least a response on the ACR 20% improvement criteria at 14 weeks, maintained during the whole year of treatment, were finally considered (group A). The remaining 10/49, homogeneous for age, sex, traditional cardiovascular risk factors, socioeconomic status, disease activity and duration, who did not consent to TNF-alpha-blocker administration, were used as controls (group B). Disease activity score in 44 joints (DAS44), erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) were evaluated before starting the study, and 3, 6, 12 months thereafter; cIMT was measured by ultrasound before and 12 months thereafter only.

RESULTS

Patients in group A showed a very significant cIMT reduction (P < 0.0001 and P < 0.0001, on the right and left side, respectively), preceded by an early and lasting significant decrease in DAS44, ESR and CRP. Moreover, a significant correlation was found between cIMT and DAS44 (r = 0.435, P < 0.05).

CONCLUSIONS

These results demonstrate that TNF-alpha blockade is associated with cIMT reduction in RA patients steadily responsive to therapy, probably by lowering inflammation.

Parametrically dissociating speech and nonspeech perception in the brain using fMRI

Candidate brain regions constituting a neural network for preattentive phonetic perception were identified with fMRI and multivariate multiple regression of imaging data. Stimuli contrasted along speech/nonspeech, acoustic, or phonetic complexity (three levels each) and natural/synthetic dimensions. Seven distributed brain regions' activity correlated with speech and speech complexity dimensions, including five left-sided foci [posterior superior temporal gyrus (STG), angular gyrus, ventral occipitotemporal cortex, inferior/posterior supramarginal gyrus, and middle frontal gyrus (MFG)] and two right-sided foci (posterior STG and anterior insula). Only the left MFG discriminated natural and synthetic speech. The data also supported a parallel rather than serial model of auditory speech and nonspeech perception.

Sexual and drug risk-related behaviours after initiating highly active antiretroviral therapy among injection drug users

OBJECTIVE

To assess whether initiation of highly active antiretroviral therapy (HAART) is associated with a subsequent resumption of sexual and drug use risk behaviors.

METHODS

Within an ongoing prospective study of HIV-seropositive injection drug users (IDUs), a subsample with at least one CD4 cell count < 500 x 106 cells/l after 1996 (when HAART became available) and three consecutive visits were selected for analysis. Patients underwent semi-annual interviews for risk behaviors and reports of medication use. Data from visits immediately prior to and following initiation of HAART for the treated group, and from consecutive visits for the eligible but untreated group were compared using linear growth curve analysis.

RESULTS

Of 316 eligible HIV-seropositive IDUs, 133 reported HAART use during the study period; 95% were African American, 76% were male, and median age at enrollment was 34 years. The proportion who reported any sexual activity increased over time from 55 to 61% for the HAART-treated group, but decreased from 67 to 63% in the untreated group (P = 0.03); the respective values for unprotected sex were 18 versus 20% and 36 versus 28% (P = 0.06). In both treated and untreated groups, the proportion injecting drugs declined (P = 0.04), whereas the proportion reporting needle sharing decreased marginally (P = 0.11). However, trends in use of shooting galleries between the groups differed (P = 0.04) increasing slightly from 2.3 to 3% in the treated group while decreasing from 12 to 5% in the untreated group.

CONCLUSION

In persons treated with HAART, self-report of high-risk behaviors remained stable or showed some increase. Persons initiating HAART should be counselled to refrain from high-risk behaviors.

Development of a fully integrated analysis system for ions based on ion-selective optodes and centrifugal microfluidics

A fully integrated, miniaturized analysis system for ions based on a centrifugal microfluidics platform and ion-selective optode membranes is described. The microfluidic architecture is composed of channels, five solution reservoirs, a measuring chamber, and a waste reservoir manufactured onto a disk-shaped substrate of poly(methyl methacrylate). Ion-selective optode membranes, composed of plasticized poly(vinyl chloride) impregnated with an ionophore, a proton chromoionophore, and a lipophilic anionic additive, were cast, with a spin-on device, onto a support layer and then immobilized on the disk. Fluid propulsion is achieved by the centrifugal force that results from spinning the disk, while a system of valves is built onto the disk to control flow. These valves operate based on fluid properties and fluid/substrate interactions and are controlled by the angular frequency of rotation. With this system, we have been able to deliver calibrant solutions, washing buffers, or "test" solutions to the measuring chamber where the optode membrane is located. An analysis system based on a potassium-selective optode has been characterized. Results indicate that optodes immobilized on the platform demonstrate theoretical responses in an absorbance mode of measurement. Samples of unknown concentration can be quantified to within 3% error by fitting the response function for a given optode membrane using an acid (for measuring the signal for a fully protonated chromoionophore), a base (for fully deprotonated chromoionophore), and two standard solutions. Further, the ability to measure ion concentrations by employing one standard solution in conjunction with acid and base and with two standards alone were studied to delineate whether the current architecture could be simplified. Finally, the efficacy of incorporating washing steps into the calibration protocol was investigated.

When to stress patients after coronary artery bypass surgery? Risk stratification in patients early and late post-CABG using stress myocardial perfusion SPECT: implications of appropriate clinical strategies

OBJECTIVES

The study compared the prognostic significance of myocardial perfusion single-photon emission computed tomography (SPECT) (MPS) in patients early and late after coronary artery bypass graft surgery (CABG).

BACKGROUND

The long-term effectiveness of CABG is limited by graft stenosis. The greatest incidence of graft occlusion occurs between five and eight years after surgery. However, little is known regarding the appropriate time to stress patients post-CABG with respect to risk stratification.

METHODS

We identified 1,765 patients, who underwent MPS 7.1 +/- 5.0 years post-CABG. All patients underwent rest T1-201/stress Tc-99m sestamibi MPS and were followed up > or =1 year after testing. Patients with early CABG or PTCA (<60 days after MPS) were censored. The prognostic population consisted of 1,544 patients. A semiquantitative visual analysis employing a 20-segment model was used to define summed stress score (SSS), summed rest score (SRS), summed difference score (SDS), and the number of nonreversible segments (NRS).

RESULTS

During follow-up, 53 cardiac deaths (CD) occurred. There was a significant increase in annual CD rates as a function of SSS. A multivariate analysis identified age, ischemia (SDS), and infarct size (NRS) as independent predictors of CD. Nuclear variables added incremental value to prescan information. The annual CD rate was relatively low (1.3%) in patients < or =5 years post-CABG. In this subgroup only age and infarct size (NRS) were predictive of CD.

CONCLUSION

MPS is strongly predictive of subsequent CD in post-CABG patients and adds incremental value over clinical and treadmill test information. Our data suggest that symptomatic patients < or =5 years and all patients >5 years post-CABG may benefit from testing.

In vivo measurement of changes in venous blood-oxygenation with high resolution functional MRI at 0.95 tesla by measuring changes in susceptibility and velocity

High-resolution functional imaging experiments at 0.95 Tesla have been performed to determine the changes in oxygen saturation in pial veins during motor activation by measuring both flow and susceptibility changes in the blood. Averaging across subjects, mean values for the change of the oxygenation level, deltaY = 0.16 +/- 0.08 (n = 7) and deltaY = 0.13 +/- 0.09 (n = 4), were obtained from the susceptibility sensitive and the flow sensitive acquisitions, respectively. The results suggest that the increase in blood flow is largely uncoupled from the oxygen consumption. The quoted errors reflect mainly the intersubject variability. In addition, low-resolution echo planar imaging (EPI) measurements were performed on the same volunteers to quantify signal intensity changes. Using the measured change in oxygenation, the observed signal changes in the EPI experiments can be attributed to a 5% venous blood volume.

Detection of Helicobacter pylori by PCR but not culture in water and biofilm samples from drinking water distribution systems in England

AIMS

To investigate treated water distribution systems in England as a source of Helicobacter pylori.

METHODS AND RESULTS

Water and biofilms were obtained from 11 domestic and seven educational properties and from hydrants, reservoirs and water meters supplied by three water utilities. Samples were cultured on nonselective and antibiotic containing media combined with immunomagnetic separation concentration. Viable helicobacters were not detected in any of the 151 samples but Helicobacter-specific PCR assays detected DNA in 26% of samples from domestic properties, schools and hydrants with the highest frequency in biofilms (42%). Direct sequencing of six selected amplicons confirmed >95% sequence homology to H. pylori.

CONCLUSIONS

While viable helicobacters were not isolated, evidence was obtained for the presence of Helicobacter DNA, including that of H. pylori. Biofilms on surfaces within water distribution systems may act either as sites for the passive accumulation of helicobacters or as potentially important reservoirs of infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our findings strengthen evidence that H. pylori may be transmitted through drinking water. However, there is currently no evidence that viable cells can survive the disinfection levels used in UK mains supplies and the health risk from this source remains unclear.

Sequential p53 mutation analysis of pre-invasive and invasive head and neck squamous carcinoma

Single-stranded conformational polymorphism (SSCP) and direct sequencing were performed on uninvolved mucosa, severe dysplasia and invasive carcinoma samples from 20 patients with head and neck squamous carcinoma. Seven (35%) of the non-invasive lesions and 15 (75%) of the invasive carcinomas manifested p53 mutations. Although the majority of mutations were mis-sense, resulting in single amino acid substitution, a silent mutation encoding for the same amino acid and 2 non-sense mutations encoding a stop codon were also observed. Mutations in invasive carcinoma were mostly in exon 8 and involved codons 296, 288 and 298; non-invasive lesions showed more mutations at exons 5 to 7. Five lesions showed simultaneous mutations in 2 different exons; in 3 both non-invasive and invasive carcinomas showed primary mutation at exons 5 to 7, and invasive carcinoma showed a secondary mutation at exon 8. Different codon mutations in the same exon between dysplastic and the corresponding carcinoma samples were found in 2 cases. p53 alterations were not observed in any of the normal mucosa samples. No apparent association between p53 mutations and conventional clinicopathologic parameters, including DNA content, was found in this cohort. Our study indicates that (i) p53 alteration is an early event in the genesis of a subset of head and neck squamous carcinomas, (ii) normal mucosa within the resected specimens lacked p53 mutation, (iii) sequential mutations of different exons of the p53 gene suggests accumulation of genetic alterations during the neoplastic transformation of these lesions and (iv) the difference in codon mutation of the same exon between dysplastic and corresponding carcinoma suggests an independent clonal development.

Uncoupling of the autonomic and cardiovascular systems in acute brain injury

We hypothesized that acute brain injury results in decreased heart rate (HR) variability and baroreflex sensitivity indicative of uncoupling of the autonomic and cardiovascular systems and that the degree of uncoupling should be proportional to the degree of neurological injury. We used HR and blood pressure (BP) power spectral analysis to measure neuroautonomic regulation of HR and BP and the transfer function magnitude (TF) between BP and HR as a measure of baroreflex modulation of HR. In 24 brain-injured patients [anoxic/ischemic injury (n = 7), multiple trauma (n = 6), head trauma (n = 5), central nervous system infection (n = 4), and intracranial hemorrhage (n = 2)], neurological injury and survival was associated with low-frequency (0.01-0.15 Hz) HR and BP power and TF. Brain-dead patients showed decreased low-frequency HR power [0. 51 +/- 0.36 (SE) vs. 2.54 +/- 0.14 beats/min2, P = 0.03] and TF [0. 61 +/- 0.16 (SE) vs. 1.29 +/- 0.07 beats . min-1 . mmHg-1, P = 0.05] compared with non-brain-dead patients. We conclude that 1) severity of neurological injury and outcome are inversely associated with HR and BP variability and 2) there is direct evidence for cardiovascular and autonomic uncoupling in acute brain injury with complete uncoupling during brain death.