Generation of targets for alloreactive CTL using purified H-2K in liposomes and polyethylene glycol

The ability of a purified major histocompatibility antigen to serve as the target cell antigen for alloreactive CTL (H-2^d anti-H-2^k) was examined. Tumor cells syngeneic with responding CTL were used as targets following modification with purified alloantigen (H-2K^k). A short incubation of tumor cells with H-2K^k liposomes followed by the addition of polyethylene glycol (PEG) yielded modified tumor cells that were recognized and lysed by CTL. The macrophage-like cell line P388D1 was readily recognized following liposome and PEG modification; apparently because these cells can withstand PEG mediated insertion of H-2K^k and lipid into their membrane. The generation of targets by PEG mediated modification was most efficient using liposomes prepared with an H-2K^k:lipid ratio of about 1:500. H-2K^k containing liposomes prepared with negatively charged phospholipids readily attached to P388D1 cells, however these cells were not targets for CTL unless PEG was added. The specificity of CTL recognition and lysis of liposome modified cells was shown by the reactivity of CTL primed against alloantigens other than H-2K^k and by antibody (anti-H-2K^k) blocking of recognition and lysis. These results demonstrate that purified H-2K^k can serve as the alloantigen for CTL lysis and suggest that the H-2 must be oriented in the target cell lipid bilayer to serve as the alloantigen for CTL mediated target cell lysis.     

Exploring and embracing complexity in a distance-learning curriculum for physicians.

The recent pressures on clinical medicine such as the attention to medical error and the challenges of interdisciplinary care have also exerted pressure on health professions education. Educators must now gauge how to redesign education systems to adapt quickly to these disruptions. Sometimes disruptions can be self-inflicted, such as the VA National Quality Scholars Fellowship's decision to use interactive video (IV) as its primary medium for delivering the curriculum to its six sites around the nation. The authors describe how this disruption to their education system helped to fashion a learning environment that is adaptable. Along the journey from a classroom-based curriculum to an IV-based curriculum, the authors and others involved in the program learned the basic tenets of IV sessions, redefined the roles of the teachers and learners, and discovered an IV environment that functions as a complex adaptive learning system. This distance-learning curriculum can be a model for other health professions education, since it starts with simple rules, changes from within, has a tolerance for unpredictability, and continually moves forward and transforms itself despite tension.     

Innate recognition of bacteria: engagement of multiple receptors

Until recently, consensus was that the mechanism of action of the innate immune system was a simplified one. Current research findings in the field of innate recognition of bacteria suggest that it involves complex associations of receptors depending on cell type and bacterial stimuli, CD14, integrins, Toll-like receptors (TLRs), CD55, ion channels, and activation clusters containing heat shock proteins, chemokine receptor 4 and a plethora of other molecules have been shown to serve as key molecules in bacterial recognition. In this article, we review all the advances in the field and discuss the possibility that the repertoire for recognition of pathogens is defined by the combinational engagement of multiple receptors.     

Muscular and postural synergies of the human hand

Because humans have limited ability to independently control the many joints of the hand, a wide variety of hand shapes can be characterized as a weighted combination of just two or three main patterns of covariation in joint rotations, or "postural synergies." The present study sought to align muscle synergies with these main postural synergies and to describe the form of membership of motor units in these postural/muscle synergies. Seventeen joint angles and the electromyographic (EMG) activities of several hand muscles (both intrinsic and extrinsic muscles) were recorded while human subjects held the hand statically in 52 specific shapes (i.e., shaping the hand around 26 commonly grasped objects or forming the 26 letter shapes of a manual alphabet). Principal-components analysis revealed several patterns of muscle synergy, some of which represented either coactivation of all hand muscles, or reciprocal patterns of activity (above and below average levels) in the intrinsic index finger and thumb muscles or (to a lesser extent) in the extrinsic four-tendoned extensor and flexor muscles. Single- and multiunit activity was generally a multimodal function of whole hand shape. This implies that motor-unit activation does not align with a single synergy; instead, motor units participate in multiple muscle synergies. Thus it appears that the organization of the global pattern of hand muscle activation is highly distributed. This organization mirrors the highly fractured somatotopy of cortical hand representations and may provide an ideal substrate for motor learning and recovery from injury.     

Virulence Differences in Mice of Type A and B Histoplasma capsulatum Yeasts Grown in Continuous Light and Total Darkness

Type B yeasts were more virulent for mice than type A under most experimental conditions. Mice infected with type B yeasts grown in the light lived significantly longer than those with type B yeasts grown in the dark. Virulence differences of type A yeasts grown in continuous fluorescent light versus total darkness were not statistically significant.     

Borrelia burgdorferi and Interleukin-1 Promote the Transendothelial Migration of Monocytes In Vitro by Different Mechanisms

A prominent feature of Lyme disease is the perivascular accumulation of mononuclear leukocytes. Incubation of human umbilical vein endothelial cells (HUVEC) cultured on amniotic tissue with either interleukin-1 (IL-1) or Borrelia burgdorferi, the spirochetal agent of Lyme disease, increased the rate at which human monocytes migrated across the endothelial monolayers. Very late antigen 4 (VLA-4) and CD11/CD18 integrins mediated migration of monocytes across HUVEC exposed to either B. burgdorferi or IL-1 in similar manners. Neutralizing antibodies to the chemokine monocyte chemoattractant protein 1 (MCP-1) inhibited the migration of monocytes across unstimulated, IL-1-treated, or B. burgdorferi-stimulated HUVEC by 91% ± 3%, 65% ± 2%, or 25% ± 22%, respectively. Stimulation of HUVEC with B. burgdorferi also promoted a 6-fold ± 2-fold increase in the migration of human CD4⁺ T lymphocytes. Although MCP-1 played only a limited role in the migration of monocytes across B. burgdorferi-treated HUVEC, migration of CD4⁺ T lymphocytes across HUVEC exposed to spirochetes was highly dependent on this chemokine. The anti-inflammatory cytokine IL-10 reduced both migration of monocytes and endothelial production of MCP-1 in response to B. burgdorferi by approximately 50%, yet IL-10 inhibited neither migration nor secretion of MCP-1 when HUVEC were stimulated with IL-1. Our results suggest that activation of endothelium by B. burgdorferi may contribute to formation of the chronic inflammatory infiltrates associated with Lyme disease. The transendothelial migration of monocytes that is induced by B. burgdorferi is significantly less dependent on MCP-1 than is migration induced by IL-1. Selective inhibition by IL-10 further indicates that B. burgdorferi and IL-1 employ distinct mechanisms to activate endothelial cells.     

Molecular mechanism of temperature sensing by the circadian clock of Neurospora crassa

Expression levels and ratios of the long (l) and short (s) isoforms of the Neurospora circadian clock protein FREQUENCY (FRQ) are crucial for temperature compensation of circadian rhythms. We show that the ratio of l-FRQ versus s-FRQ is regulated by thermosensitive splicing of intron 6 of frq, a process removing the translation initiation site of l-FRQ. Thermosensitivity is due to inefficient recognition of nonconsensus splice sites at elevated temperature. The temperature-dependent accumulation of FRQ relative to bulk protein is controlled at the level of translation. The 5'-UTR of frq RNA contains six upstream open reading frames (uORFs) that are in nonconsensus context for translation initiation. Thermosensitive trapping of scanning ribosomes at the uORFs leads to reduced translation of the main ORF and allows adjustment of FRQ levels according to ambient temperature.     

The degradation of serum amyloid A protein by activated polymorphonuclear leucocytes: participation of granulocytic elastase

To determine the role of inflammation in amyloidogenesis, we have studied the degradation of human serum amyloid A (SAA) protein by purified preparations of human blood polymorphonuclear leucocytes (PMN) and monocytes. When both PMN and monocytes were incubated in SAA-containing medium, the concentration of SAA as measured by a competitive anti-AA radioimmunoassay decreased over time. The rate of decrease of SAA was similar for both monocytes and PMN and there were no differences between four patients with amyloidosis and three normal controls. Resting PMN from normal volunteers were able to degrade SAA to smaller acid-soluble peptides within 16 hr while zymosan-activated PMN produced significant degradation within 1 hr (31%–50%). The supernatants from zymosan-treated PMN also caused marked SAA degradation within 1 hr.

The following enzyme inhibitors were able to prevent degradation of SAA by PMN supernatants; phenylmethylsulphonyl fluoride, a serine esterase inhibitor; α₁ anti-trypsin and soybean trypsin inhibitor; and acetyl-ala-ala-pro-val-chloromethyl ketone, an elastase inhibitor. The ability of a neutral lysosomal enzyme to degrade SAA was further confirmed by showing that purified PMN elastase significantly degraded ¹²⁵I-SAA.

We conclude that PMN contain one or more lysosomal enzymes capable of degrading SAA, an apoprotein of HDL₃ serum lipoproteins. Alteration in SAA proteolysis by activated PMN may contribute to the deposition of amyloid fibrils in the tissues of patients with chronic inflammatory disease.

     

A Topographic study of differences in the P300 between introverts and extraverts

This paper presents results of a study to establish a link between neurocognitive psychophysiological and psychological type data through the investigation of differences in topographic auditory event-related potential (AERP) (P300) patterns in strongly introverted (n = 17) and strongly extraverted ( = 16) high school males as identified by the Myers Briggs Type Indicator. Group data files were created for the auditory event related potential task and converted to ASCII form. Amplitude values were evaluated at each scalp site. Kruskal Wallis one way analysis of variance was performed to evaluate group differences. In processing of infrequent, target stimuli, the amplitude of the P300 waveform for introverts was higher than for extraverts. When processing for non-target stimuli was subtracted from target stimuli, statistical differences were found over nine central, parietal, and occipital sites. The findings support and extend theories of biologically-based and bio-psycho-social typology.