Effects of spaceflight on rhesus quadrupedal locomotion after return to 1G.

Effects of spaceflight on Rhesus quadrupedal locomotion after return to 1G. Locomotor performance, activation patterns of the soleus (Sol), medial gastrocnemius (MG), vastus lateralis (VL), and tibialis anterior (TA) and MG tendon force during quadrupedal stepping were studied in adult Rhesus before and after 14 days of either spaceflight (n = 2) or flight simulation at 1G (n = 3). Flight simulation involved duplication of the spaceflight conditions and experimental protocol in a 1G environment. Postflight, but not postsimulation, electromyographic (EMG) recordings revealed clonus-like activity in all muscles. Compared with preflight, the cycle period and burst durations of the primary extensors (Sol, MG, and VL) tended to decrease postflight. These decreases were associated with shorter steps. The flexor (TA) EMG burst duration postflight was similar to preflight, whereas the burst amplitude was elevated. Consequently, the Sol:TA and MG:TA EMG amplitude ratios were lower following flight, reflecting a "flexor bias." Together, these alterations in mean EMG amplitudes reflect differential adaptations in motor-unit recruitment patterns of flexors and extensors as well as fast and slow motor pools. Shorter cycle period and burst durations persisted throughout the 20-day postflight testing period, whereas mean EMG returned to preflight levels by 17 days postflight. Compared with presimulation, the simulation group showed slight increases in the cycle period and burst durations of all muscles. Mean EMG amplitude decreased in the Sol, increased in the MG and VL, and was unchanged in the TA. Thus adaptations observed postsimulation were different from those observed postflight, indicating that there was a response unique to the microgravity environment, i.e., the modulations in the nervous system controlling locomotion cannot merely be attributed to restriction of movement but appear to be the result of changes in the interpretation of load-related proprioceptive feedback to the nervous system. Peak MG tendon force amplitudes were approximately two times greater post- compared with preflight or presimulation. Adaptations in tendon force and EMG amplitude ratios indicate that the nervous system undergoes a reorganization of the recruitment patterns biased toward an increased recruitment of fast versus slow motor units and flexor versus extensor muscles. Combined, these data indicate that some details of the control of motor pools during locomotion are dependent on the persistence of Earth's gravitational environment.     

Efficacy of caspofungin and posaconazole in a murine model of disseminated Exophiala infection.

Disseminated phaeohyphomycosis is an uncommon infection affecting immunocompetent and immunocompromised individuals in which response to older antifungal agents has been variable. We compared the effect of six days of therapy with caspofungin, posaconazole, and amphotericin B in parallel studies of survival and fungal burden in an immunocompromised mouse model of Exophiala infection. Mice immunocompromised with cyclophosphamide were treated for 6 days starting one day after initiation of infection. Treatment regimens included amphotericin B, caspofungin, and posaconazole. In the survival studies, experimental animals were observed for 14 days. In the fungal burden tests the experimental animals were sacrificed 7 days after infection and brain and kidney burden determined. Treatment with any agent decreased mortality (P < 0.05), with 40%, 30%, and 80% observed survival of the animals treated with amphotericin B, caspofungin, and posaconazole, respectively. Amphotericin B and posaconazole treatment resulted in a decrease in fungal burden compared to untreated controls (P < 0.05). No reduction in fungal burden was noted in the caspofungin group. All three antifungals evaluated improved survival of immunocompromised mice in this otherwise fatal disseminated phaeohyphomycosis. Amphotericin B and posaconazole reduced fungal burden. Posaconazole and caspofungin appear to have potential for use in treatment of this rare infection.     

Processing of vestibular inputs by the medullary lateral tegmental field of conscious cats: implications for generation of motion sickness

The dorsolateral reticular formation of the caudal medulla, the lateral tegmental field (LTF), participates in generating vomiting. LTF neurons exhibited complex responses to vestibular stimulation in decerebrate cats, indicating that they received converging inputs from a variety of labyrinthine receptors. Such a convergence pattern of vestibular inputs is appropriate for a brain region that participates in generating motion sickness. Since responses of brainstem neurons to vestibular stimulation can differ between decerebrate and conscious animals, the current study examined the effects of whole-body rotations in vertical planes on the activity of LTF neurons in conscious felines. Wobble stimuli, fixed-amplitude tilts, the direction of which moves around the animal at a constant speed, were used to determine the response vector orientation, and also to ascertain whether neurons had spatial–temporal convergence (STC) behavior (which is due to the convergence of vestibular inputs with different spatial and temporal properties). The proportion of LTF neurons with STC behavior in conscious animals (25 %) was similar to that in decerebrate cats. Far fewer neurons in other regions of the feline brainstem had STC behavior, confirming findings that many LTF neurons receive converging inputs from a variety of labyrinthine receptors. However, responses to vertical plane vestibular stimulation were considerably different in decerebrate and conscious felines for LTF neurons lacking STC behavior. In decerebrate cats, most LTF neurons had graviceptive responses to rotations, similar to those of otolith organ afferents. However, in conscious animals, the response properties were similar to those of semicircular canal afferents. These differences show that higher centers of the brain that are removed during decerebration regulate the labyrinthine inputs relayed to the LTF, either by gating connections in the brainstem or by conveying vestibular inputs directly to the region.     

Short-Ti inversion-recovery pulse sequence: analysis and initial experience in cancer imaging

Inversion recovery (IR), commonly considered a pulse sequence capable of producing T1-weighted images with excellent display of normal anatomy, is versatile: The null point and peak time provide a useful, succinct summary of the properties of IR and its capacity for producing both T1- and T2-weighted images. Shortening of the inversion time (TI) and creation of a short-TI inversion-recovery (STIR) pulse sequence increases sensitivity to malignancy and other abnormalities by making the effects of prolonged T1 and T2 on signal intensity additive and by nulling the signal from fat. The authors examined over 300 patients with various malignancies and compared STIR images with T1- and T2-weighted images obtained at 0.5 T. In 43 cases, signal-difference-to-noise ratios (SD/Ns) were calculated between tumor, fat, and muscle. In general, STIR images demonstrated tumor as a conspicuously high-intensity area in a background of muted, discernible anatomic detail. The good contrast achieved with STIR sequences between tumor and fat (SD/N = 18.1) and tumor and muscle (SD/N = 12.9) consolidated into a single image the information contained separately on T1- and T2-weighted images, which facilitates efficient detection and localization of malignancy.     

US-guided percutaneous biopsy: use of a screw biopsy stylet to aid needle detection

Insertion of a screw biopsy stylet into a thin-walled biopsy needle greatly enhances detection of the needle during ultrasound-guided percutaneous biopsy. This technique is helpful when precise needle-tip localization is needed for biopsies of small lesions.     

Myometrial invasion by endometrial carcinoma: sonographic assessment

The depth of myometrial invasion by endometrial carcinoma was evaluated using real-time sonography (US) in 20 patients with histologically proved adenocarcinoma of the endometrium. In 14 of 20 (70%) cases, US-based estimation of the depth of myometrial invasion was within 10% of the actual measurement in the gross specimen. The US-based estimation of tumor invasion was low in seven patients, high in four patients, and agreed with pathologic findings (+/- 5%) in nine patients. In four patients with polypoid intraluminal extension of tumor, a deeply invasive tumor was suspected on US but was not found on pathologic examination. In 12 superficially invasive tumors, the continuity of the demarcating subendometrial halo was intact in nine and incomplete in three. In six patients with deeply invasive tumors, this zone was partially disrupted in four, totally disrupted in one, and intact in one. Errors of estimation of the depth of myometrial invasion on US most frequently occurred when a tumor had a significant intraluminal polypoid extension. Demonstration of a subendometrial halo usually indicated superficial invasion, whereas the absence of a halo was frequently associated with deep invasion.     

Use of specific antibody for rapid clearance of circulating blood background from radiolabeled tumor imaging proteins

A major problem that arises when radiolabeled serum proteins are used for tumor imaging is the presence of a large amount of circulating background activity that persists for several days. This delays imaging for at least 2 days following injection and necessitates computer subtraction of simulated background (second radiopharmaceutical injection) which introduces artifacts that are difficult to control. We propose here the injection of specific antibody immediately before imaging as an alternate way of reducing blood background through clearance of the immune complex by the liver. ¹¹¹In-alkyl human transferrin and IgG were injected IV in BALB/c tumor mice, and followed in 18 h by anti-human transferrin and anti-human IgG antibody IV. Two hours later, the tumor and organ distribution of activity was compared with control mice not receiving antibody. ¹¹¹In-transferrin blood activity was reduced to 1/48 of control with no decrease in tumor concentration: as a result, the tumor to blood ratio increased from 1.4:1 to 78:1. ¹¹¹In-IgG blood activity was reduced to 1/17 of control, again with no decrease in tumor. The tumor to blood ratios increased from 0.7:1 to 17:1. The liver picked up most of the blood activity with none of the complex going to spleen, bone marrow, or kidney. Dog experiments showed clearance of blood was 90% complete in less than 15 min following antibody injection. Simultaneous scintillation images showed complete clearance of activity from the heart and great vessels in the chest and neck, and over the abdomen, with a concomitant increase in liver activity but no increase in spleen, kidney, or bone marrow activity. These studies show the feasibility of using specific antibody to lower the blood background just minutes prior to tumor imaging procedures using radiolabeled proteins.These studies were supported in part by a Veterans Administration Research Grant, and PHS Grant Number 5 ROI CA 28343 (D Goodwin), and CA 16861, RCDA CA 00462 (C Meares)     

Solitary necrotic nodule of the liver: A riddle that is difficult to answer

Solitary necrotic nodule of the liver is an unusual lesion that is often an incidental finding on abdominal imaging, intraoperative examination, or post mortem. Most reported cases of solitary necrotic nodule have been in males, and over three quarters of these lesions have occurred in the right lobe of the liver. Pathologically, solitary necrotic nodule is a benign lesion characterized by a completely necrotic core that is often partly calcified, surrounded by a dense hyalinized fibrous capsule containing elastin fibres. The ultrasound appearance of solitary necrotic nodule is usually of a “target” lesion with a hyperechoic center, while on CT scan they appear as non-enhancing hypodense lesions that are typical of metastatic adenocarcinoma or peripheral cholangiocarcinoma. The impression of malignancy is further enforced with the finding of necrotic cellular material on biopsy and the macroscopically hard and “gritty” nature of the nodules. Currently, permanent histopathology of solitary necrotic nodules is the only accurate method of diagnosis. However, solitary necrotic nodules are usually of a bilobed or lobulated shape that is unusual for malignant liver lesions, and they often lie in close proximity to hepatic inflow structures. Solitary necrotic nodule should be suspected in liver lesions with this configuration, location, and on a biopsy showing a large amount of necrosis.