Infection of Anopheles gambiae mosquitoes with entomopathogenic fungi: effect of host age and blood-feeding status

Physiological characteristics of insects can influence their susceptibility to fungal infection of which age and nutritional status are among the most important. An understanding of host–pathogen interaction with respect to these physiological characteristics of the host is essential if we are to develop fungal formulations capable of reducing malaria transmission under field conditions. Here, two independent bioassays were conducted to study the effect of age and blood-feeding status on fungal infection and survival of Anopheles gambiae s.s. Giles. Mosquitoes were exposed to 2 × 10¹⁰ conidia m⁻² of oil-formulated Metarhizium anisopliae ICIPE-30 and of Beauveria bassiana I93-825, respectively, and their survival was monitored daily. Three age groups of mosquitoes were exposed, 2–4, 5–8, and 9–12 days since emergence. Five groups of different feeding status were exposed: non-blood-fed, 3, 12, 36, and 72 h post-blood feeding. Fungal infection reduced the survival of mosquitoes regardless of their age and blood-feeding status. Although older mosquitoes died relatively earlier than younger ones, age did not tend to affect mosquito susceptibility to fungal infection. Non-blood-fed mosquitoes were more susceptible to fungus infection compared to all categories of blood-fed mosquitoes, except for those exposed to B. bassiana 72 h post-blood feeding. In conclusion, formulations of M. anisopliae and B. bassiana can equally affect mosquitoes of different age classes, with them being relatively more susceptible to fungus infection when non-blood-fed.     

Effects of antihypertensive drugs on ultrasound production and cardiovascular responses in 15-day-old rats

When exposed to extreme cold or injected with the alpha(2)-adrenoceptor agonist, clonidine, infant rats emit ultrasonic vocalizations (USVs). Based upon the cardiovascular changes that accompany these two manipulations, especially decreased venous return, it was hypothesized that USVs are the acoustic by-product of the abdominal compression reaction (ACR), a maneuver that increases venous return. If this hypothesis is correct, then other anithypertensive drugs that decrease venous return should evoke USVs. In Experiment 1, sodium nitroprusside (SNP, 400 microg/kg), a direct-acting dilator of arteries and veins, was administered to 15-day-old rats under thermoneutral conditions while cardiac rate and ultrasound production were monitored. In Experiment 2, femoral artery pressure was monitored after SNP administration. Infants responded to SNP administration with decreased arterial pressure and tachycardia and, in addition, significantly increased ultrasound production. In Experiment 3, chlorisondamine (5 mg/kg), a ganglionic blocker that causes vasodilation and bradycardia, and hydralazine (20 mg/kg), a selective dilator of arteries, was administered to 15-day-olds. As predicted, chlorisondamine evoked ultrasound production and hydralazine did not. These results introduce SNP and chlorisondamine as only the second and third known agents capable of independently evoking USVs in thermoneutral conditions, and provide further support for the notion that ultrasound production is triggered by decreased venous return.     

Spatial resolution in optical coherence elastography of bounded media

Dynamic optical coherence elastography (OCE) tracks mechanical wave propagation in the subsurface region of tissue to image its shear modulus. For bulk shear waves, the lateral resolution of the reconstructed modulus map (i.e., elastographic resolution) can approach that of optical coherence tomography (OCT), typically a few tens of microns. Here we perform comprehensive numerical simulations and acoustic micro-tapping OCE experiments to show that for the typical situation of guided wave propagation in bounded media, such as cornea, the elastographic resolution cannot reach the OCT resolution and is mainly defined by the thickness of the bounded tissue layer. We considered the excitation of both broadband and quasi-harmonic guided waves in a bounded, isotropic medium. Leveraging the properties of broadband pulses, a robust method for modulus reconstruction with minimum artifacts at interfaces is demonstrated. In contrast, tissue bounding creates large instabilities in the phase of harmonic waves, leading to serious artifacts in modulus reconstructions.     

Prion protein activates and fixes complement directly via the classical pathway: implications for the mechanism of scrapie agent propagation in lymphoid tissue

C1q-deficient and complement depleted mice are highly resistant to intraperitoneal scrapie infection. The molecular mechanisms of complement involvement in scrapie pathogenesis remain unclear. Previous detailed studies have indicated mouse prion protein interactions with human C1q but the question of subsequent complement activation has remained unaddressed. In this investigation, murine prion protein, both recombinant and also from diseased tissue sources, directly activated and fixed complement via the classical but not the alternative pathway. The importance of complexed cupric ions was observed. In addition, evidence of IgG-independent C4 fixation by prion proteins was also shown. Surface plasmon resonance binding studies using variously clustered immobilized recombinant mouse prion protein indicated strong interactions with both purified mouse C1q and also mouse Factor H. Binding, especially by C1q, was dependent upon the volume of immobilized prion protein, suggesting a threshold of clustering density required to support strong interactions. Furthermore, clustered immobilized prion protein appeared capable of promoting polymerization of soluble-phase monomeric prion protein. Direct covalent attachment of complement components to prion proteins via classical pathway activation illustrates a potential mechanism underpinning their trafficking to, and subsequent propagation within, lymphoid tissues.     

Reduced abundance of Ixodes scapularis (Acari: Ixodidae) and the tick parasitoid Ixodiphagus hookeri (Hymenoptera: Encyrtidae) with reduction of white-tailed deer

The principal vector for the pathogens of Lyme disease, human granulocytic ehrlichiosis, and human babesiosis is the tick Ixodes scapularis Say. A chalcid wasp, Ixodiphagus hookeri, in the family Encyrtidae parasitizes populations of the tick on several islands or other geographically isolated sites in New England with high densities of these ticks and white-tailed deer (Odocoileus virginianus), the principal host for adult I. scapularis. Deer densities were reduced at a forested tract in Bridgeport and the Bluff Point Coastal Reserve in Groton, Connecticut, from levels exceeding 90 animals per km2 in 1992 (Bridgeport) and 1994 (Bluff Point) to 17 and 10 animals per km2, respectively, by fall 2001. Tick densities declined with sustained reductions in the population of white-tailed deer. Similarly, prevalence of tick parasitism by Ixodes hookeri declined at both sites from 30 to 25% to <1.0% and was significantly correlated with previous year's deer density at both sites (r(s) = 0.933 and r(s) = 0.867, P < or = 0.0001) and with nymphal tick densities at Bridgeport (r(s) = 0.867, P < or = 0.0001), but was not as well correlated with tick densities in Groton. The virtual disappearance of I. hookeri in this study corresponds with a lack of I. hookeri in mainland I. scapularis at comparable deer and tick densities, suggesting that there is a threshold deer density of approximatley 10-20/km2, with corresponding tick densities necessary for I. hookeri to successfully parasitize I. scapularis.     

Anxiety-like effects of SR141716-precipitated delta9-tetrahydrocannabinol withdrawal in mice in the elevated plus-maze

Marijuana discontinuation has been recently reported to be anxiogenic in humans, which may predict relapse. Limited animal research has been carried out to model this withdrawal-associated negative affect. The current study sought to investigate the potential anxiety-like effects of cannabinoid withdrawal in mice. Male ICR mice were injected s.c. with delta9-tetrahydrocannabinol (THC) at 10 mg/kg or vehicle once daily for 10 days. To precipitate withdrawal, the cannabinoid CB1 antagonist SR141716 (0.3, 1.0, or 3.0 mg/kg) or vehicle was administrated i.p. 4 h following the last THC or vehicle treatment. Thirty minutes later, mice were tested on the elevated plus-maze (EPM) for 5 min. SR141716 did not significantly change EPM behaviors in vehicle-treated mice. In contrast, SR141716 precipitated a reduction in exploration of the open arms of EPM in mice repeatedly treated with THC vs vehicle. At 3.0 mg/kg, SR141716 significantly reduced % open arm entries of the total arm entries, % open arm time of total time in arms, and the absolute time spent in open arms. No significant differences in the number of closed or total arm entries were observed, indicating that the behavioral changes were not due to altered motor activity. Collectively, the present results constitute the first evidence that cannabinoid withdrawal produces anxiety-like effects in mice. This animal model may help to identify the mechanisms that contribute to adaptations in the neuronal circuitry of the brain that are expressed as emotional symptoms of cannabinoid withdrawal.     

Rhabdoid meningioma: intraoperative diagnosis using smear preparation

Tumors with rhabdoid morphology were first described by Beckwith and Palmer in 1978 as aggressive renal tumors in very young children. Subsequently, rhabdoid tumors and tumors with rhabdoid features have been described in many other organ systems and all tend to have a poor outcome no matter what the histogenesis of the original tumor. Rhabdoid cells are plump, with abundant eosinophilic fibrillary to hyaline cytoplasm and peripheral, vesicular, variably pleomorphic nuclei. Nucleoli are invariably present. While their morphology is well recognized in processed biopsy material, their presence on a smear preparation can be quite startling. A case is presented to highlight the appearance of rhabdoid cells on an intraoperative smear preparation of a rhabdoid meningioma. An accompanying secretory component added to the complex picture.