Event related potentials recorded from rats performing a reaction-time task

We recorded evoked potentials during performance of a reaction-time task, in which rats had to release a lever quickly in response to either a visual or an auditory stimulus for a food reward. We found two distinct peaks in their cortical evoked potentials. The first peak appeared at a fixed time after the stimulus, irrespective of the time it took the rat to release the lever. Its amplitude decreased with increasing reaction time. The second peak's latency was always longer when the rat took more time to release the lever, but its amplitude did not change. We believe that the first peak's amplitude is determined by the rat's "attention" to the stimulus, whereas the second peak's latency is related to the rat's "intention" to release the lever.     

CD1 assembly and the formation of CD1-antigen complexes

The CD1 antigen presentation system presents lipid antigens to effector T cells, which have diverse roles in antimicrobial responses, antitumor immunity and in regulating the balance between tolerance and autoimmunity. The trafficking of CD1 molecules and lipid antigens facilitates their intersection and binding in specific intracellular compartments. Recent studies have now identified unexpected accessory molecules that are critical to CD1 assembly and lipid loading. The atomic structures of CD1-antigen complexes have defined both the orientation of polar headgroups between the alpha1 and alpha2 helices of CD1 and the manner in which distinct CD1 isoforms bind a range of lipids that have different lengths and numbers of hydrocarbon chains.     

Legionella gormanii sp. nov

A new species of Legionella was isolated from soil collected from a creek bank. The name Legionella gormanii sp. nov. is proposed.     

Agouti-related peptide-expressing neurons are mandatory for feeding

Multiple hormones controlling energy homeostasis regulate the expression of neuropeptide Y (NPY) and agouti-related peptide (AgRP) in the arcuate nucleus of the hypothalamus. Nevertheless, inactivation of the genes encoding NPY and/or AgRP has no impact on food intake in mice. Here we demonstrate that induced selective ablation of AgRP-expressing neurons in adult mice results in acute reduction of feeding, demonstrating direct evidence for a critical role of these neurons in the regulation of energy homeostasis.     

Natural killer cell function in patients with acquired immunodeficiency syndrome and related diseases

This review describes current knowledge of changes in natural killer (NK) cell function in acquired immunodeficiency syndrome (AIDS)-related disorders, vis-à-vis associated abnormalities in NK cytolytic function, NK cell subset distribution, NK cytopathology, and lymphokine regulation. NK cells, which are closely associated with large granular lymphocytes, are spontaneously cytotoxic to tumor and virally infected targets. As such, they may play a role in natural resistance to human immunodeficiency virus type 1 (HIV-1)-associated disorders and other opportunistic infections. Yet, peripheral blood NK activity is frequently reduced in patients with HIV-1-induced disease. NK cells are heterogeneous both with respect to their expression of serologically defined membrane antigens and functional activity. In AIDS-related syndromes, there appears to be a diminution of the NK pool (CD16+ cells) involved in cytolytic function, while there is an elevation of the NK pool that coexpresses NK (Leu 7+) and T (CD8+) cell markers, which show little or no involvement in cytolytic function. The impairment of in vitro NK function is not associated with a reduced frequency of lytic conjugates of effectors and target cells nor with the recycling capacity of these effector cells but rather is associated with defects in the NK cell lytic machinery following formation of such conjugates. NK cells in AIDS patients show an impairment in effector cell microtubule rearrangement following target cell interaction. The causes of NK cell dysfunction in AIDS-related disorders remain unknown. NK cells do not appear to express the CD4 epitope of the HIV receptor, nor have they been demonstrated to be susceptible to infection by HIV-1. There appears to be a preponderance of immature NK cells and a lymphokine imbalance in patients with HIV-1 associated disease. Interleukin-2 can partially restore diminished in vitro NK function. Elucidation of the involvement of the NK compartment in natural resistance to HIV-1 merits further investigation.     

Rochalimaea henselae sp. nov., a cause of septicemia, bacillary angiomatosis, and parenchymal bacillary peliosis.

Nine strains of Rochalimaea spp. that were isolated from patients over a period of 4.5 years were characterized for their enzyme activities, cellular fatty acid compositions, and DNA interrelatedness among Rochalimaea spp., Bartonella bacilliformis, and Afipia felis (cat scratch disease bacillus). All except one isolate, which was Rochalimaea quintana, were determined to belong to a newly proposed species, Rochalimaea henselae sp. nov. After recovery from clinical material, colonies required 5 to 15 days of incubation to become apparent. Cells were small, gram-negative, curved bacilli and displayed twitching motility. Enzyme specificities for amino acid and carbohydrate substrates showed that R. henselae could be distinguished from Rochalimaea vinsonii by L-arginyl-L-arginine and L-lysyl-L-alanine peptidases, but not all strains could be distinguished from R. quintana on the basis of peptidases or carbohydrate utilization. R. henselae also closely resembled R. quintana in cellular fatty acid composition, with both consisting mainly of C18:1, C18:0, and C16:0 fatty acids. However, the strains of R. henselae all contained C18:0 in amounts averaging greater than or equal to 22%, in contrast to R. quintana, which contained this cellular fatty acid in amounts averaging 16 and 18%. DNA hybridization confirmed the identification of one clinical isolate as R. quintana and showed a close interrelatedness (92 to 100%) among the other strains. Under optimal conditions for DNA reassociation, R. henselae showed approximately 70% relatedness to R. quintana and approximately 60% relatedness to R. vinsonii. Relatedness with DNA from B. baciliformis was 43%. R. henselae was unrelated to A. felis. R. henselae is the proposed species of a newly recognized member of the family Rickettsiaceae, which is a pathogen that may be encountered in immunocompromised or immunocompetent patients. Prolonged fever with bacteremia or vascular proliferative lesions are clinical manifestations of the agent.     

Human infections caused by Brevibacterium casei, formerly CDC groups B-1 and B-3.

Forty-one clinical strains of CDC coryneform groups B-1 and B-3 were compared biochemically, by analysis of cell wall sugars, amino acids, and cellular fatty acids, and by DNA relatedness to the type strains of Brevibacterium casei, Brevibacterium epidermidis, and Brevibacterium linens. Twenty-two strains were shown to be B. casei, while five other strains formed a phenotypically inseparable genomospecies in the same genus. The remaining isolates were genetically heterogeneous, and most are probably members of the genus Brevibacterium. They were not further identified, but they were biochemically distinguishable from B. casei. Eleven of the clinical strains of B. casei were isolated from blood, and two each were isolated from cerebrospinal fluid and from pleural fluid. At least five isolates were from multiple blood or cerebrospinal fluid cultures. To our knowledge, these strains are the first described clinical isolates identified as B. casei, which was previously considered to be a nonpathogenic species.     

Evaluation of a reformulated CHROMagar Candida

CHROMagar Candida is a differential culture medium for the isolation and presumptive identification of clinically important yeasts. Recently the medium was reformulated by Becton Dickinson. This study was designed to evaluate the performance of the new formula of CHROMagar against the original CHROMagar Candida for recovery, growth, and colony color with stock cultures and with direct plating of clinical specimens. A total of 90 stock yeast isolates representing nine yeast species, including Candida dubliniensis, as well as 522 clinical specimens were included in this study. No major differences were noted in growth rate or colony size between the two media for most of the species. However, all 10 Candida albicans isolates evaluated consistently gave a lighter shade of green on the new CHROMagar formulation. In contrast, all 26 C. dubliniensis isolates gave the same typical dark green color on both media. A total of 173 of the 522 clinical specimens were positive for yeast, with eight yeast species recovered. The recovery rates for each species were equivalent on both media, with no consistent species-associated differences in colony size or color. Although both media were comparable in performance, the lighter green colonies of C. albicans isolates on the new CHROMagar made it easier to differentiate between C. albicans and C. dubliniensis isolates. In conclusion, the newly formulated Becton Dickinson CHROMagar Candida medium is as equally suited as a differential medium for the presumptive identification of yeast species and for the detection of multiple yeast species in clinical specimens as the original CHROMagar Candida medium.