Genetic variation among temporally and geographically distinct West Nile virus isolates, United States, 2001, 2002

Analysis of partial nucleotide sequences of 22 West Nile virus (WNV) isolates collected during the summer and fall of 2001 and 2002 indicated genetic variation among strains circulating in geographically distinct regions of the United States and continued divergence from isolates collected in the northeastern United States during 1999 and 2000. Sequence analysis of a 2,004-nucleotide region showed that 14 isolates shared two nucleotide mutations and one amino acid substitution when they were compared with the prototype WN-NY99 strain, with 10 of these isolates sharing an additional nucleotide mutation. In comparison, isolates collected from coastal regions of southeast Texas shared the following differences from WN-NY99: five nucleotide mutations and one amino acid substitution. The maximum nucleotide divergence of the 22 isolates from WN-NY99 was 0.35% (mean = 0.18%). These results show the geographic clustering of genetically similar WNV isolates and the possible emergence of a dominant variant circulating across much of the United States during 2002.     

An alpha helix conformationally restricted peptide is recognized by cervical carcinoma patients' sera

Human papillomavirus type 16 (HPV-16) represents the major cervical carcinoma associated virus among women, especially in Colombia. It has thus become important to develop reliable inexpensive tests for detecting the presence of this virus. It has been shown that HPV16-E7 oncoprotein structural features have three alpha-helical structures and a loop-like structure. The hydrazone link approach was used to mimic helix secondary substructures. Sera from women with invasive cervical carcinoma were tested against conformationally restricted peptides and their respective linear peptides to identify conformational epitopes. One peptide that was conformationally restricted to an alpha-helix showed very strong positive reaction with sera from women having invasive cervical carcinoma; there was no reaction with sera from patients with other carcinomas, children, or healthy women. NMR studies confirmed this peptide's alpha-helical structure. The observation that constrained protein substructure peptidomimetics can identify new conformationally sensitive antibodies in cervical carcinoma patients' sera is very important, since these antibodies are almost all generated by native proteins, providing a new selection of antibodies for diagnostic and vaccine studies.     

Diffusion-weighted MRI of middle cerebral artery stroke in a newborn

Diffusion-weighted MRI of the brain is becoming clinically available as a tool to investigate cerebral ischaemia. We report a newborn girl presenting with seizures in whom diffusion-weighted MRI showed a large hyperintensity in the area perfused by the left middle cerebral artery. Short-term neurological follow-up before discharge was uneventful and the patient was discharged without sequelae. On follow-up clinical examination, right-sided spastic signs were noted which disappeared with time. Received: 3 April 2000 Accepted: 4 December 2000     

Allpahuayo virus: a newly recognized arenavirus (arenaviridae) from arboreal rice rats (oecomys bicolor and oecomys paricola) in northeastern peru

Allpahuayo virus was initially isolated from arboreal rice rats (Oecomys bicolor and Oecomys paricola) collected during 1997 at the Allpahuayo Biological Station in northeastern Peru. Serological and genetic studies identified the virus as a new member of the Tacaribe complex of the genus Arenavirus. The small (S) segment of the Allpahuayo virus prototype strain CLHP-2098 (Accession No. AY012686) was sequenced, as well as that of sympatric isolate CLHP-2472 (Accession No. AY012687), from the same rodent species. The S segment was 3382 bases in length and phylogenetic analysis indicated that Allpahuayo is a sister virus to Pichinde in clade A. Two ambisense, nonoverlapping reading frames were identified, which result in two predicted gene products, a glycoprotein precursor (GPC) and a nucleocapsid protein (NP). A predicted stable single hairpin secondary structure was identified in the intergenic region between GPC and NP. Details of the genetic organization of Allpahuayo virus are discussed.     

Practical exercises on diagnostic test interpretation

Although medical literature places great emphasis on therapy, diagnosis remains an essential part of medical practice. We present four clinical cases that show the interaction between pre-test probabilities and the accuracy of investigations (sensitivity, specificity, predictive values and likelihood ratios) The first example studies the influence of meningeal signs in the diagnosis of meningitis. The second one analyzes the diagnostic utility of investigations in patients suspected of dementia. The third example examines the change in the probability of carpal tunnel syndrome depending on the physical examination and the electrodiagnostic studies. The last example explains the use of ROC curves in the diagnosis of demyelinating disease with CSF-IgG index.     

Evaluation of a high dose to a finger from a 60Co accident

Electron spin resonance and fluorescence in situ hybridization were used to evaluate the dose to the finger of a worker who accidentally touched a radiotherapy 60Co therapy source in November 1995. In September 1999, the middle finger was amputated. We estimated the dose to the bone of the finger to be 6.4 +/- 0.5 Gy using the electron spin resonance additive dose method and a corrected dose of about 20 +/- 3 Gy could be inferred by translocation analysis in peripheral lymphocytes using the fluorescence in situ hybridization method. This retrospective dosimetry was performed for the victim 4 y after the accident, but the compatibility of the results obtained by physical and biological methods reinforce their validity, although in the case of partial-body exposure the biological method has limitations and demonstrates the need to find appropriate correction factors.     

Reperfusion demonstrated by apparent diffusion coefficient mapping after local intra-arterial thrombolysis for ischaemic stroke

Diffusion-weighted MRI (DWI) is becoming important for diagnosis and investigation of acute cerebral ischaemia. It has been reported that apparent diffusion coefficient (ADC) maps could be an indicator of reperfusion. Our aim was to use echo-planar technology to investigate this phenomenon. We report 19 patients treated by local intra-arterial thrombolysis for middle cerebral artery stroke within 6 h of the onset of symptoms, in whom we performed follow-up DWI. ADC were found to be higher in the patients with angiographically proven reperfusion. Received: 3 November 2000 Accepted: 10 January 2001     

Gut mucosal-arterial Pco2 gradient as an indicator of splanchnic perfusion during systemic hypo- and hypercapnia

OBJECTIVES: By accounting for influences of systemic acid-base disturbances, gut mucosal-arterial Pco2 gradient (Pico2 - Paco2) has been increasingly advocated as a more specific marker of splanchnic perfusion than Pico2 alone. We examined the stability of the Pico2 - Paco2 gradient compared with raw Pico2 measurements during induced systemic hypo- and hypercapnia. DESIGN: A prospective animal study. SETTINGS: A university research laboratory. SUBJECTS: Twenty anesthetized, paralyzed, and mechanically ventilated mongrel dogs. INTERVENTIONS: After a baseline period during which Paco2 was maintained near 40 torr, the animals were divided into four groups. Minute ventilation was then altered by adjusting tidal volume, frequency, or both to achieve group Paco2 values of 15, 20, 60, and 80 torr for groups 1 through 4, respectively. Portal blood flow was monitored and maintained near baseline levels by infusion of intravenous fluids. Intestinal Pico2 was measured continuously by using capnometric recirculating gas tonometry. MEASUREMENTS AND MAIN RESULTS: Mean (+/- SE) aggregate baseline Pico2 - Paco2 was 16.9+/-3.3 torr. After 60 mins of hypoventilation, Pico2 - Paco2 decreased to 14.2+/-1.1 and to 13.7+/-2.7 torr in groups 3 and 4, respectively (p = NS, compared with baseline for both). On the other hand, after 60 mins of hyperventilation, Pico2 - Paco2 increased to 37.9+/-3.6 and 28.0+/-6.3 torr in groups 1 and 2, respectively (p < .0001, compared with baseline for both). CONCLUSIONS: In this model of maintained portal blood flow, Pico2 - Paco2 remained essentially stable after hypoventilation but increased significantly after inducing hyperventilation. Our findings warrant cautious interpretation of Pico2 - Paco2 as an indicator of splanchnic perfusion during systemic hypocapnia.