Identification of semiochemicals attractive to Simulium vittatum (IS-7).

Many blackfly species (Diptera: Simuliidae) are economically important insect pests, both as nuisance biters and as vectors of pathogens of medical and veterinary relevance. Among the important blackfly pest species in North America is Simulium vittatum Zetterstedt sensu lato. The objective of this study was to identify compounds excreted by mammalian hosts that are attractive to host-seeking S. vittatum females. The attractiveness of putative compounds to colonized S. vittatum was tested through electrophysiological (electroantennography; n = 58 compounds) and behavioural (Y-tube assays; n = 7 compounds in three concentrations) bioassays. Five compounds were significantly attractive to host-seeking S. vittatum females: 1-octen-3-ol; 2-heptanone; acetophenone; 1-octanol, and naphthalene. These candidate compounds might be useful as attractants in traps that could be developed for use in alternative or complementary management tactics in programmes to suppress nuisance blackfly populations, or for the collection of samples in which to study the transmission ecology of pathogens transmitted by blackflies of the S. vittatum complex.

Modeling lesion counts in multiple sclerosis when patients have been selected for baseline activity.

The number of new gadolinium-enhancing lesions discovered via magnetic resonance imaging is a well-established outcome for multiple sclerosis studies, especially Phase II Studies. Due to the high cost of magnetic resonance imaging scans, many investigators select participants for the presence of lesions. While this selection procedure is thought to improve the power of inferences, the effect of screening for baseline activity on parameter estimation and interval coverage has not yet been examined. The objective of this study was to investigate the performance of the negative binomial distribution for modeling lesion count data in multiple sclerosis when patients have been selected for activity on a baseline scan. We performed computer simulations to investigate the influence of the screening process on inferences made using a negative binomial model about treatment effects in two independent samples. We also demonstrate how the statistical properties of screening can be incorporated into trial design. We demonstrate that when the negative binomial distribution is used to model lesion counts, while screening for baseline activity improves point estimation, this practice also has the potential to decrease interval coverage and inflate the Type I error rate. For data that is to be modeled using a negative binomial distribution, screening for baseline activity can create a trade-off between cost effectiveness and a higher than desired false positive rate that must be carefully considered in planning Phase II trials.

Mosquito and arbovirus activity during 1997-2002 in a wetland in northeastern Mississippi.

The species composition and population dynamics of adult mosquitoes in a wetland near Iuka, MS, were analyzed over a 6-yr period (1997-2002) and reverse transcription-polymerase chain reaction (PCR) detection rates of arboviruses determined during five of those years. Blood meals of three likely vector species were identified using a PCR-based method that allows identification of the host to species. Culex erraticus (Dyar & Knab) composed 51.9% of the population during the 6-yr period with 295 females collected per trap night. Eastern equine encephalomyelitis (EEE) virus was detected in six genera of mosquitoes [Coquillettidia perturbans (Walker), Culex restuans Theobald, Culex salinarius Coquillett, Culex erraticus (Dyar & Knab), Anopheles crucians Wiedemann, Anopheles quadrimaculatus Say, Aedes vexans (Meigen), Ochlerotatus triseriatus Say, and Psorophora ferox Humboldt) with positive pools occurring in 1998, 1999, and 2002. Culiseta melanura Coquillett occurred at a low level (< 1%) and was not infected. Saint Louis encephalitis virus was detected once in a single pool of Cx. erraticus in 1998. Neither West Nile virus nor LaCrosse virus was found. Minimum infection rates per 1000 females tested of competent vectors of EEE virus were variable and ranged from 0.14 for Cx. erraticus to 40.0 for Oc. triseriatus. Thirty-nine species of birds were identified in the focus with blood-engorged mosquitoes found to contain meals (n = 29) from eight avian species. The majority of meals was from the great blue heron, Ardea herodias L. (n = 55%), but when bird abundance data were adjusted for avian mass, the brown-headed cowbird, Molothrus ater (Boddaert); blue jay, Cyanocitta cristata (L.); and northern mockingbird, Mimus polyglottos (L.), were overrepresented as hosts.

The current status of onchocerciasis in the forest/savanna transition zone of Côte d'Ivoire.

Onchocerca volvulus exists in at least two strains in West Africa, while its black-fly vectors consist of sibling species, dwelling in the savanna and forest/transition zones. In transition and degraded forest zones both parasite strains and different sibling species of the vector can be sympatric. The strain of parasite in infected humans and in vector black-flies was determined in two bioclimes along the Bandama river of Côte d'Ivoire. The upper Bandama is located in the savanna bioclime while the Middle Bandama is located in a degraded forest zone. At both sites, savanna-dwelling sibling species of the Simulium damnosum sensu lato species complex predominated. The severe-strain of O. volvulus was the predominant strain at both sites. However, severe-strain parasites represented a significantly larger proportion of those found in the vector population than in the human population in the degraded forest of the Middle Bandama. These data suggest that in degraded forest areas recently invaded by savanna-dwelling species of S. damnosunz s.l. transmission of the severe-strain of the parasite might be more efficient than transmission of the mild-strain.

Dengue vector prevalence and virus infection in a rural area in south India.

We conducted a 2-year (1997-1999) longitudinal, entomological and virological study in three dengue endemic villages in Vellore district, Tamil Nadu, to understand the dynamics of dengue transmission. Aedes aegypti (Linn.), Ae. albopictus (Skuse) and Ae. vittatus (Bigot) were the prevalent vector species. Aedes aegypti was breeding throughout the year with a Breteau index ranging from 9.05 to 45.49. Aedes albopictus and Ae. vittatus were prevalent mainly in the rainy season. Small water holding containers (cemented tanks/cisterns) were the perennial breeding source of Ae. aegypti, and its abundance was significantly higher in semi-urbanized central areas than the peripheral areas of the villages. From 271 pools (4016 specimens) of adult females, eight dengue virus (DENV) isolates were obtained of which seven were from Ae. aegypti and one from Ae. albopictus. This is the first report of DENV isolation from Ae. albopictus in rural India. Infection rates in the two species were comparable. However, due to higher and perennial prevalence, Ae. aegypti is considered as primary vector with Ae. albopictus playing a secondary role. Despite circulation of all four serotypes (DENV 1-4) detected mainly during the transmission season, the high anthropophilic index of the vectors and their abundance, no human dengue case was reported, suggesting silent dengue transmission.

Prospective randomized trial compares suction versus water seal for air leaks.

BACKGROUND: Surgeons treat air leaks differently. Our goal was to evaluate whether it is better to place chest tubes on suction or water seal for stopping air leaks after pulmonary surgery. A second goal was to evaluate a new classification system for air leaks that we developed. METHODS: Patients were prospectively randomized before surgery to receive suction or water seal to their chest tubes on postoperative day (POD) #2. Air leaks were described and quantified daily by a classification system and a leak meter. The air-leak meter scored leaks from 1 (least) to 7 (greatest). The group randomized to water seal stayed on water seal unless a pneumothorax developed. RESULTS: On POD #2, 33 of 140 patients had an air leak. Eighteen patients had been preoperatively randomized to water seal and 15 to suction. Air leaks resolved in 12 (67%) of the water seal patients by the morning of POD #3. All 6 patients whose air leak did not stop had a leak that was 4/7 or greater (p < 0.0001) on the leak meter. Of the 15 patients randomized to suction, only 1 patient's air leak (7%) resolved by the morning of POD #3. The randomization aspect of the trial was ended and statistical analysis showed water seal was superior (p = 0.001). The remaining 14 patients were then placed to water seal and by the morning of POD #4, 13 patients' leaks had stopped. Of the 32 total patients placed to seal, 7 (22%) developed a pneumothorax and 6 of these 7 patients had leaks that were 4/7 or greater (p = 0.001). CONCLUSIONS: Placing chest tubes on water seal seems superior to wall suction for stopping air leaks after pulmonary resection. However, water seal does not stop expiratory leaks that are 4/7 or greater. Pneumothorax may occur when chest tubes are placed on seal with leaks this large.

Onchocerca volvulus: genetic diversity of parasite isolates from Sudan.

Onchocerciasis in Sudan exists in three distinct foci which exhibit differing clinical presentations. Previous studies have demonstrated that a tandemly repeated Onchocerca sequence family with a unit repeat length of 150 bp (the O-150 family) is a useful marker for deducing relationships among different O. volvulus populations. In the current study, the O-150 repeat families of O. volvulus from Sudan were analyzed and compared to each other and to those of parasites from West Africa. Similar to West African and American O. volvulus, the O-150 families of the Sudanese parasites could be divided into clusters within which little or no intracluster variation was evident, suggesting that the O-150 family in these parasites was subject to the forces of concerted evolution. Statistical analysis of the O-150 families from the different Sudanese parasite isolates, employing a nested algorithm based on an analysis of variance, revealed that O. volvulus endemic to the northern focus at Abu Hamed were significantly different from all other O. volvulus populations examined to date. In contrast, parasites from the southern and eastern foci of Sudan were indistinguishable from those endemic to the West African savanna. The significance of these data are discussed in light of knowledge of the biogeography and biology of transmission of O. volvulus in Africa.

Pneumoperitoneum after concomitant resection of the right middle and lower lobes (bilobectomy).

BACKGROUND: Removal of the right middle and lower lobes often leaves a pleural space problem that can cause prolonged air leaks. METHODS: A single surgeon prospectively randomized 16 patients who underwent bilobectomy. Eight patients had 1200 mL of air injected under the right hemidiaphragm after bilobectomy and 8 did not. The air was injected through a small transdiaphragmatic opening made in the right hemidiaphragm at the time of pulmonary resection. RESULTS: The age of the patients, preoperative pulmonary function, preoperative comorbidities, indications for surgery, and final pathology were not significantly different between the two groups. On postoperative day #1, a pneumothorax was present in 1 patient (13%) in the pneumoperitoneum group (P group) and in 4 patients (50%) in the nonpneumoperitoneum group (N-P group). On postoperative day 1, an air leak was present in 1 patient (13%) in the P group and 5 patients (63%) in the N-P group (p < 0.001). By the third postoperative day, no patient in the P group had an air leak; however, a leak was present in 4 patients (50%) in the N-P group (p < 0.001). Median hospital stay in the P group was 4 days (range, 3 to 6 days), compared with 6 days (range, 4 to 8 days) in the N-P group (p < 0.001). Three patients in the N-P group were sent home with a Heimlich valve. There was no operative mortality and no complications from the pneumoperitoneum. CONCLUSIONS: We conclude that pneumoperitoneum after bilobectomy is safe and easy to do. It decreases the incidence of air leaks and of pneumothoraces and shortens hospital stay without increasing morbidity. We recommend pneumoperitoneum after bilobectomy at the time of thoracotomy, especially if there are residual small air leaks that cannot be sealed before chest closure.

Effect of bupropion-SR on orgasmic dysfunction in nondepressed subjects: a pilot study.

UNLABELLED: The objective of this study was to determine whether the aminoketone antidepressant bupropion has beneficial effects in orgasmic dysfunction. DESIGN: Single-blind, sequential treatment order of three weeks each: placebo, bupropion-SR 150 mg/day, bupropion-SR 300 mg/day. SUBJECTS: Nondepressed women (n = 20) and men (n = 10) having nonphysiologic orgasmic delay or inhibition. MAIN OUTCOME MEASURES: Reported difficulty or delay in achieving orgasm, satisfaction with orgasm and erectile function, and subjective impressions of drug effect. RESULTS: In the women, there were significant improvements relative to baseline (p < .01) on both doses of bupropion-SR in all measured aspects of sexual function, and significant improvements relative to placebo (p < .05) in overall sexual satisfaction on both doses and satisfaction with intensity of orgasm on 150 mg/day (300 mg/day, p = .10). In the men, significant improvements over baseline (p < .01) were observed with both doses in overall sexual satisfaction, ability to achieve an erection, and delay in reaching orgasm/ejaculation; significant improvements relative to placebo (p < .05) were observed in overall sexual satisfaction on both doses, ability to achieve erection on 150 mg/day, and delay in orgasm/ejaculation on 150 mg/day. Seventy percent of subjects reported improvement in libido, arousal, or orgasmic function during bupropion administration. CONCLUSIONS: Bupropion-SR may be a useful agent for treating orgasmic delay and inhibition, and possibly disorders of sexual arousal. The results argue against bupropion's apparent prosexual effect in depressed patients being simply a result of its antidepressant activity.

31P-magnetic resonance spectroscopy studies of cardiac transplant patients at rest.

Studies in animal models and patients have suggested that 31P-magnetic resonance spectroscopy (MRS) may be useful in diagnosing transplant rejection, but such studies often are confounded by the late inclusion of patients after transplantation. The present study examined the utility of 31P-MRS in the diagnosis of acute allograft rejection during the first posttransplant month. Thirteen recent heart transplant recipients underwent 57 resting 31P-MRS studies within 24 hr of a biopsy. Subjects lay supine with a 10-cm surface coil placed over the heart. A 1-dimensionsal chemical shift imaging protocol was used to collect spectral information. Spectra from the heart were weighted for distance from the coil and summed before analysis. ANOVA and Duncan's multiple range test were used to analyze the data comparing phosphocreatine (PCr)/ATP ratios with biopsy scores. Transplant patients had significantly lower myocardial PCr/ATP ratios when compared with a normal control group (1.27 +/- 0.27 versus 1.61 +/- 0.22, p < 0.001). However, when the patient group was classified by biopsy score, the expected order of score, 0 > 1 > 2 > 3, was not obtained. Rather, the order was 2 > 0 > 1 > 3. Although the difference between scores 2 and 3 was significant (1.46 versus 1.14, alpha = 0.05 level), the lower three groups were statistically indistinguishable. In addition, the PCr/ ATP ratios were not predictive of future biopsies. Although significantly lower than normal control subjects, resting myocardial PCr/ATP ratios of transplant subjects are not useful in assessing thelevel of rejection. It is suggested that the measurement may be more predictive in mildly exercised myocardium.

Novel methods to evaluate controlled reperfusion techniques in cardiac surgery.

BACKGROUND: This manuscript describes two novel techniques that may be useful for comparing methods to reperfuse the heart during cardiac operations. These techniques are based on measurements of intra-myocyte ion content and the analysis of reperfusion arrhythmias. METHODS: Myocyte ion content was measured in normal porcine hearts before and after ischemia (cardioplegic arrest, CP arrest) using atomic absorption spectroscopy. A cobalt-EDTA complex served as the extra-cellular marker. Cobalt-EDTA was infused into the aorta together with blood or cardioplegia (CP) solution. Myocardial biopsies were taken prior to CP arrest and upon successful defibrillation 5 min after initiating reperfusion. Ventricular fibrillation (VF) was recorded prior to ischemia, and then during reperfusion. VF wavefront (WF) morphology and propagation patterns were analyzed using computer algorithms. Electrophysiologic variables for measuring VF included the multiplicity index (a descriptor of VF organization), the number of WFs detected (nwaves/s) and the mean peak first derivative of electrogram voltage with respect to time (mp d V/dt). RESULTS: Intra-cellular sodium content increased, while intra-cellular magnesium content decreased between control and reperfusion measurements (p < 0.05). Electrophysiologic recovery was characterized by increasingly rapid depolarization (i.e. more negative mp d V/dt) and an increasing nwaves/s during the first minute of post-CP reperfusion. CONCLUSIONS: Atomic absorption spectroscopy and computer-based analysis of reperfusion VF successfully measured metabolic and electrophysiologic events that occurred during controlled reperfusion. These methods may be useful for comparing controlled reperfusion techniques.

Familial painful restless legs syndrome correlates with pain dependent variation of blood flow to the caudate, thalamus, and anterior cingulate gyrus.

To understand the relationship of caudate, thalamic, and anterior cingulate perfusion to pain states, we investigated familial restless legs syndrome in a father and daughter during the state of pain induced by immobility using semiquantitative regional cerebral blood flow (rCBF) brain single photon emission computed tomography (SPECT). The father underwent 4 brain SPECT scans using the rCBF tracer 99mTc-HMPAO several weeks apart, at different pain levels and after treatment with L-dopa. Caudate, thalamic, and anterior cingulate rCBF indices were measured. The caudate nuclei showed a 13% reduction in rCBF with increasing pain. The thalami and anterior cingulate showed a 7 and 6.6% increase in rCBF, respectively, with increasing pain. Compared to normal controls at rest, there was a decrease in caudate rCBF by 13% and an increase in thalamic rCBF by 3%. Linear regression for the caudate nuclei revealed a significant reduction in rCBF (p < 0.05), as pain increased. The daughter underwent an identical rCBF brain SPECT scan procedure at a high pain level induced by immobilization. Her scan showed a 12% reduction in caudate rCBF and a 1.2% increase in the anterior cingulate rCBF compared to healthy controls. The study supports the association between pain and decreased regional cerebral blood flow to the caudate nucleus as reported in fibromyalgia syndrome. There is increase in anterior cingulate rCBF with increasing pain. Our findings also corroborate that there is increased thalamic rCBF with pain stimulation.

Symptoms of patients with myasthenia gravis receiving treatment.

The symptoms of myasthenia gravis (MG) are often simply classified as excessive fatigue rather than evaluated as different signs of disease progression. The purpose of this study was to evaluate the medical symptoms of patients with MG who had been under treatment for many years. Patients diagnosed with MG were compared to healthy controls. A survey questionnaire was used and differences were evaluated using non-parametric statistics. Health care givers should be aware of these differences in order to facilitate early appropriate treatment, to decrease disability, and to increase the quality of life.

Oxygen free radicals and contrast nephropathy.

Ionic, high-osmolality contrast medium causes nephrotoxicity associated with increased intrarenal adenosine production. To test the hypothesis that oxygen free radicals (produced during intrarenal adenosine catabolism to xanthine) should be implicated in the pathogenesis of ionic, high-osmolality contrast medium nephrotoxicity in humans and to determine whether magnesium protects the kidney from oxygen free radical injury following contrast, 39 patients with mild renal dysfunction were divided into low (LoMg++) and normal (NlMg++) magnesium states and randomized to precoronary angiography oral allopurinol (a xanthine oxidase inhibitor) or placebo. Creatinine clearance and urinary xanthine excretion were measured before and after angiography. Forty-eight hours after contrast medium exposure, placebo-treated LoMg++ and NlMg++ patients had 61%+/-5% and 67%+/-6% increases in urinary xanthine excretion, respectively; however, placebo-treated LoMg++ patients had a greater (79%+/-9% v 35%+/-6%; P < 0.01) decrease in creatinine clearance than placebo-treated NlMg++ patients. Allopurinol-treated LoMg++ and NlMg++ patients had no significant change in urinary xanthine excretion, but did have 40%+/-7% and 33%+/-5% decreases, respectively, in creatinine clearance 48 hours after contrast medium exposure. There was no difference in renal dysfunctional response among placebo-treated NlMg++ patients or allopurinol-treated LoMg++ or NlMg++ patients. These data suggest (1) that oxygen free radicals contribute to ionic, high-osmolality contrast medium nephrotoxicity in hypomagnesemic patients with mild renal disease and (2) that magnesium attenuates the nephrotoxicity mediated by oxygen free radicals.

Unreliability of the infrared tympanic thermometer in clinical practice: a comparative study with oral mercury and oral electronic thermometers.

BACKGROUND: This study was designed to determine the magnitude and frequency of measurement errors with infrared tympanic thermometers in the clinical setting. METHODS: In a convenience sample of 137 adult inpatients, we compared body temperatures measured by a Diatek 9000 Infrared Aural Thermometer and an IVAC 2090 CoreCheck Tympanic Thermometer between themselves, in right versus left ears, and against concurrently measured oral temperatures using both an electronic thermoprobe and conventional glass mercury thermometer. RESULTS: There was a significant between-brand difference of 0.6 degrees C (IVAC

Age distribution of lymphocytic choriomeningitis virus serum antibody in Birmingham, Alabama: evidence of a decreased risk of infection.

Lymphocytic choriomeningitis virus (LCMV) is an arenavirus that causes human disease ranging from a mild, flu-like illness to meningitis. Infections occur principally in and around the home due to contact with infected mice. Data on the incidence of LCMV infection in the United States are scarce but suggest that the risk of infection may have decreased over the past 30-40 years. To examine this hypothesis, sera from an age-stratified sample of hospital patients in Birmingham, Alabama were tested for LCMV antibody by ELISA. The overall prevalence of LCMV-specific IgG was 3.5% (56 of 1,600). The prevalence of antibody among those < 30 years of age was 0.3% (2 of 600), while the prevalence among those 30 years of age and older was 5.4% (P < 0.0001). Multiple logistic regression was used to identify risk factors for LCMV seropositivity. Age was positively associated (P < 0.0001) and socioeconomic status was negatively associated with a positive antibody test result (P < 0.03). These data are consistent with a decreased incidence of human LCMV infection in Birmingham over the past 30-40 years.

Comparative sexual side effects of bupropion, fluoxetine, paroxetine, and sertraline.

OBJECTIVE: To investigate patient reported prosexual side effects of the aminoketone antidepressant bupropion (INN, amfebutamone) and to compare directly the sexual side effects of bupropion and the selective serotonin reuptake inhibitor (SSRI) antidepressants fluoxetine, paroxetine, and sertraline. METHODS: One hundred seven psychiatric outpatient respondents receiving current treatment with one of the above antidepressants anonymously completed questionnaires that allowed reporting of both decreases and increases in sexual function. The main outcome measures were antidepressant-associated changes in libido, arousal, duration of time from arousal to orgasm, intensity of orgasm, and duration of orgasm relative to that experienced before the onset of the patients' psychiatric illnesses. RESULTS: Bupropion-treated patients reported significant increases in libido, level of arousal, intensity of orgasm, and duration of orgasm beyond levels experienced premorbidly. The three SSRIs to an equal degree significantly decreased libido, arousal, duration of orgasm, and intensity of orgasm below levels experienced premorbidly. Overall, 27% of the SSRI-treated patients had no adverse sexual side effects; in contrast, 86% of patients treated with bupropion had no adverse sexual effects, and 77% of bupropion-treated patients reported at least one aspect of heightened sexual functioning. CONCLUSIONS: SSRI-induced adverse sexual effects appear to be the rule rather than the exception and may be substantially underreported unless patients are specifically asked about the effects of these medications on various aspects of sexual function. In contrast, prosexual effects were reported by the majority of patients treated with bupropion. The findings are reviewed in light of the neurochemistry of these agents and the sexual response.

Vector-parasite transmission complexes for onchocerciasis in West Africa.

BACKGROUND: In West Africa, there are two strains of the filarial parasite Onchocerca volvulus, which differ in their ability to induce ocular disease. Transmission studies have suggested that six sibling species of the parasite vector, the black fly Simulium damnosum sensu lato, allow development of the two strains of O volvulus with varying efficiency. We aimed to test the hypothesis of parasite-vector complexes, whereby the two parasite strains, known as forest and savanna, are preferentially transmitted by distinct groups of the species of S damnosum S l. METHODS: During 1993 and 1994, wild black flies were collected from 11 river basins within the area covered by the Onchocerciasis Control Programme (OCP). The flies were dissected and filarial larvae, ovaries, and malpighian tubules removed. Genomic DNA was extracted from larvae, and PCR amplification was used to classify O volvulus parasites as forest or savanna strains. PCR-amplified DNA from ovaries and malpighian tubules was used to distinguish sibling species of S damnosum s l. S yahense and S squamosum were distinguished by body colour. FINDINGS: 214 of 105105 flies dissected were infected with filarial larvae; 84 of these were infected with mature O volvulus parasites. Of the 35 savanna-dwelling infected flies. 17 carried forest-strain parasites and 18 savanna-strain parasites. Of the 45 infected flies identified as the forest dwelling sibling species. 20 carried savanna-strain parasites and 25 forest-strain parasites. No significant differences were found in the numbers of mature larvae of each strain carried by the forest-dwelling species of fly or in the number of forest and savanna larvae in savanna-dwelling vector species. INTERPRETATION: Vector-parasite transmission complexes do not currently play a part in the biology of O volvulus transmission in the area of the OCP in West Africa. This finding has important strategic implications for the future of efforts to control onchocerciasis in West Africa.

Regional stability of cerebral blood flow measured by repeated technetium-99m-HMPAO SPECT: implications for the study of state-dependent change.

UNLABELLED: The replicability of resting state rCBF has implications for the analysis of cerebral activation protocols and the interpretation of rCBF in disease states. This study examined the stability of rCBF as measured by two resting state 99mTc-HMPAO brain SPECT scans with an emphasis on examining the contribution of specific cerebral regions to within and between subjects variance. METHODS: Nine normal, medically healthy subjects underwent two 99mTc-HMPAO brain SPECT scans under identical conditions separated by 48 hr. A reference system and semiautomated computer ROI method was used to enable accurate alignment and cortical analysis of the two scans. RESULTS: Mean within-subject difference between Scans 1 and 2 was 2.8% (range 0%-7.8%) for the 36 cortical ROIs. The mean between-subject coefficient of variation was 10% (range 7%-15%) for these ROIs. Correlation analysis of rCBF pattern replication for all slice levels yielded a highly significant overall consistency of pattern within subjects (Pearson r = 0.698, p = 0.0001). Variance component analysis revealed regional heterogeneity in between-subjects variance, with significantly greater variability found in frontal regions. The within-subject repeated measures variability was not significantly different across regions. CONCLUSION: Good within-subject 48-hr replicability indicates that individual resting state rCBF reflects fairly stable, subject-specific factors. This also justifies comparing state-dependent studies separated by a modest length of time. Although individual patterns of rCBF replicate well, the larger contribution of frontal regions to normal between-subjects variance makes evaluating the frontal effects of disease or activation more difficult.

Determining the prevalence of Onchocerca volvulus infection in vector populations by polymerase chain reaction screening of pools of black flies.

An important variable in the epidemiology of arthropodborne diseases is the intensity of transmission, which is a function of host-vector contact and the prevalence of infection in the vector population. This latter value is often difficult to estimate. It is possible to envision the application of polymerase chain reaction (PCR) assays to this problem. To accomplish this, the assay must detect a single infected vector in a pool containing a large number of uninfected individuals. It must also be possible to calculate the prevalence of infection from the number of positive pools. A PCR assay for detecting Onchocerca volvulus in pools of vector black flies is described, and an algorithm is presented to calculate the prevalence of infection in the vector population, based upon the proportion of PCR-positive pools. This algorithm should be applicable to any disease for which a PCR assay is available.