To cool or not to cool? Intestinal coccidians disrupt the behavioral hypothermia of lizards in response to tick infestation.

It is generally accepted that parasites exert negative effects on their hosts and that natural selection favors specific host responses that mitigate this impact. It is also known that some components of the host immune system often co-evolve with parasite antigens resulting in a host-parasite arms race. In addition to immunological components of the anti-parasitic response, host behavioral responses are also important in this arms race and natural selection may favor avoidance strategies that preclude contact with parasites, or shifts in the host's thermoregulatory strategy to combat active infections (e.g., behavioral fever). Ticks are widespread parasites with direct and indirect costs on their vertebrate hosts. Their saliva provokes hemolysis in the blood of their hosts and can transmit a plethora of tick-borne pathogens. We enquired whether tick infestation by Ixodes pacificus can provoke a thermoregulatory response in Sceloporus occidentalis. For this, we compared the thermoregulatory behavior of tick-infested lizards against tick-infested lizards co-infected with two different species of coccidians (Lankesterella occidentalis and Acroeimeria sceloporis). After this, lizards were kept in individual terraria with a basking spot and fed ad libitum. We found that tick-infested lizards sought cooler temperatures in proportion to their tick load, and this response was independent of the co-infection status by L. occidentalis. This was consistent in April and June (when tick loads were significantly lower) and suggests a conservative strategy to save energy which might have been selected to overcome tick infestations during phenological peaks of this parasite. However, this behavior was not observed in lizards co-infected with A. sceloporis, suggesting that co-infection with this intestinal parasite prompt lizards to be active. Cost of tick infestation was confirmed because housed lizards lost weight at a constant ratio to initial tick load, independently of other infections. The broader implications of these findings are discussed in the context of climate change.

Acute bone pain following renal transplantation: differentiation between benign bone edema and avascular necrosis.

Two patients are reported who presented within the first 3 months posttransplantation with acute bone pain where serial magnetic resonance imaging (MRI) allowed differentiation between bone edema, which resolved spontaneously, and avascular necrosis (AVN) requiring core decompression. Case 1 had ill-defined images consistent with bone edema that resolved, whereas case 2 developed well-demarcated lesions in the femoral condyles and tibial epiphyses which were confirmed as AVN at surgery. Alternative explanations for bone edema were not evident. We would suggest that in any transplant recipient who develops acute bone pain, MRI is the initial diagnostic modality of choice. Evidence of development of well-demarcated lesions on serial MR scans indicate early AVN. However, on current evidence it is difficult to predict which lesions will progress and until greater experience becomes available, we would recommend intraosseous plethysmography and venography so that incipient or early AVN can be treated by core decompression of the affected bone.

Novel spinal dysplasia in two generations.

We report on a father and son with a previously undescribed skeletal abnormality and severe short stature. Antenatal sonographic evaluation of the propositus (son), obtained due to maternal pre-eclampsia, suggested an abnormal spine. At birth, no congenital anomalies were noted and transition to extra-uterine life was smooth. Radiographs performed five days after birth showed spina bifida, hemivertebrae in the mid-thoracic region, and widened lumbar interpedicular distances. MRI of the lower thoracic and lumbar vertebrae documented crescent-shaped appearance of the affected vertebrae and abnormally narrow A-P diameter of the vertebral bodies. Intervertebral discs were small, and the posterior elements, as well as the spinous processes of the affected vertebrae, were markedly hypoplastic. However, there was no narrowness of the spinal canal, and the limbs were unaffected. CT scan with three-dimensional reformatting of the thoracic and lumbar vertebrae documented unusual sagittal clefting of all of the vertebral bodies, which has previously been undescribed. The father had severe kyphoscoliosis and a height of 131.6 cm (-7.5 S.D.). Radiographically, he was found to have multiple segmentation anomalies and diminished A-P diameter of his affected vertebral bodies. The multiple vertebral anomalies are the probable cause for the father's severe kyphoscoliosis. The pattern of inheritance suggests that an autosomal dominant gene is responsible for this condition and that the father represents a de novo mutation. These radiographic abnormalities have not been described previously and represent a new form of vertebral spinal dysplasia.

Spiral CT of the lungs: optimal technique and resolution compared with conventional CT.

OBJECTIVE: The purpose of this study was to compare the resolution of spiral and conventional CT for imaging the lungs and to optimize spiral CT techniques for imaging lung parenchyma. MATERIALS AND METHODS: A line-pair phantom, a dried lung specimen, and three human subjects were scanned. Spiral CT scans obtained on a Somatom PLUS-S CT scanner were compared with conventional CT scans. In addition, the influence of different collimation (1,3, 5, and 8 mm), pitch (1 and 2), display kernel (UltraHi, Hi, Standard, and Soft), and interpolation algorithms (360 degrees and 180 degrees linear interpolation) on spiral CT scans was evaluated. Scans obtained by using different techniques were compared for edge sharpness, contrast resolution, overall visibility of vessels, and noise. RESULTS: With the line bars parallel to the z-axis, a spatial resolution of 7.7 Ip/cm was obtained at all four levels of collimation used for both spiral and conventional CT scanning. Resolution in the z-axis (i.e., direction of table movement) on spiral CT scans decreased markedly when alignment of the line-pair phantom bars was changed to 45 degrees. Resolution along the z-axis decreased with increasing collimation, and this effect was more marked on spiral CT scans than on conventional CT scans. The relative decrease in resolution on spiral CT scans was visible on scans of human subjects only at narrow collimation (1 and 3 mm). Optimal visualization of structures in the lung parenchyma was obtained by using 3-mm collimation and the UltraHi display kernel. The choice of table speed (pitch 1 vs 2) and interpolation algorithm (360 degrees vs 180 degrees linear interpolation) did not significantly affect the image quality of scans of human subjects. CONCLUSION: CT scans of the lung obtained by using spiral and conventional modes at wide collimation (5 and 8 mm) show no differences in resolution, although, at narrow collimation (1 and 3 mm), curved structures such as walls of bullae and fissures are somewhat indistinct. On spiral CT scans of the lungs, narrow collimation and the UltraHi display kernel provide the best image resolution and have more effect on image quality than does choice of table speed or linear interpolation algorithm.

Frequency and management of pneumothoraces in heart-lung transplant recipients.

PURPOSE: To determine the frequency and describe the clinical relevance of simultaneous bilateral pneumothoraces in heart-lung transplant recipients. MATERIALS AND METHODS: The chest radiographs in 72 consecutive heart-lung transplant recipients were retrospectively reviewed. The study group consisted of 15 patients with a pneumothorax that occurred after removal of surgically placed drainage tubes and subsequent complete expansion of both lungs. RESULTS: Simultaneous bilateral pneumothoraces occurred in six patients (40%); 10 episodes of unilateral pneumothorax occurred in nine patients (60%). Causes of pneumothoraces included transthoracic fine-needle biopsy (n = 5), bronchoscopic biopsy (n = 3), placement of a central venous catheter (n = 3), and thoracentesis (n = 3); no cause was found in two cases. CONCLUSION: Physicians who perform transthoracic interventions in this patient population should be aware of the likelihood of persistent pleural communications and the possibility of potentially life-threatening bilateral pneumothoraces.