Modest Interference with Actin Dynamics in Primary T Cell Activation by Antigen Presenting Cells Preferentially Affects Lamellal Signaling

Dynamic subcellular distributions of signaling system components are critical regulators of cellular signal transduction through their control of molecular interactions. Understanding how signaling activity depends on such distributions and the cellular structures driving them is required for comprehensive insight into signal transduction. In the activation of primary murine T cells by antigen presenting cells (APC) signaling intermediates associate with various subcellular structures, prominently a transient, wide, and actin-associated lamellum extending from an interdigitated T cell:APC interface several micrometers into the T cell. While actin dynamics are well established as general regulators of cellular organization, their role in controlling signaling organization in primary T cell:APC couples and the specific cellular structures driving it is unresolved. Using modest interference with actin dynamics with a low concentration of Jasplakinolide as corroborated by costimulation blockade we show that T cell actin preferentially controls lamellal signaling localization and activity leading downstream to calcium signaling. Lamellal localization repeatedly related to efficient T cell function. This suggests that the transient lamellal actin matrix regulates T cell signaling associations that facilitate T cell activation.     

Functional classifications of coastal barrier island vegetation

Abstract. Due to the complexity of coastal barrier vegetation, it is useful to apply a functional-type approach to assess the response of barrier island vegetation to climate change. In this paper, a simple clustering analysis is applied to a group of 19 plant associations, based on six plant attributes and six environmental constraints. This analysis results in the suggestion that the main division of the vegetation types at Virginia Coast Reserve is between herbaceous and woody types, which differs from the existing classification which recognizes three groups: xeric-mesic herbaceous, woody and hydric-halophytic herbaceous. Considerations about grouping plant functional types are also addressed in this paper. At a global scale, inclusion of barrier plant functional types may not be so important for the climate-change response of vegetation, but it may be necessary to consider these important systems for spatially explicit modelling of landscape responses.     

Laboratory scale enclosure: concept, construction and operation

A laboratory scale enclosure (LSE) was devised for studyingthe seston dynamics in shallow, wind-mixed lakes. The LSE isa continuous flow system suitable for mass balance studies oflake water columns, and for cultivation of phytoplankton speciesas a reference for potential growth at the lake's light andmixing regime. The construction of the LSE is described in detail.Results are given on the operation with water from Lake Loosdrecht(The Netherlands). The coefficient of vertical mixing in theLSE was variable from 7.6 to 25.6 cm² s^–1, i.e. similarto values reported for shallow, wind-exposed lakes. On average,the vertical light attenuation and the spectral changes withdepth in the LSE agreed well with the in situ underwater lightclimate. Mass balances for phosphorus and oxygen could be accuratelyestablished, while the loss of paniculate matter due to settlingand wall growth was insignificant. The LSE may also be appliedas an incubator for primary production measurements in a ‘natural’light gradient and allowed prolonged continuous cultivationof Prochlorothrix hollandica.     

The influence of fitness on neuroendocrine responses to exhaustive treadmill exercise

Neuroendocrine and sympathoadrenal responses to exhaustive graded treadmill exercise were examined in 17 male subjects of varying degrees of fitness. The mean duration of exercise to exhaustion was 15.2 +/- 0.7 (+/- SE) min. Exercise duration was inversely correlated with baseline heart rate (P less than 0.05). Compared to standing baseline values, mean plasma norepinephrine and epinephrine levels increased 339% and 301%, respectively, in an integrated 2-min blood sample collected immediately after completion of exercise. Mean adrenocorticotrophic hormone (ACTH), beta-endorphin (beta-EP), beta-lipotropin (beta-LPH), and prolactin levels increased 282%, 720%, 372%, and 211%, respectively, in an integrated 4-min blood sample beginning 2 min after completion of exercise. Cortisol levels increased 183% in the sample collected 17-21 min after exercise. The magnitude of these neuroendocrine responses to exercise was similar among individuals at the same relative intensity of exhaustive exercise, regardless of the duration of exercise. The exercise-induced increases of the pro-opiomelanocortin (POMC)-derived peptides, ACTH, beta-EP, and beta-LPH, were highly correlated with each other (P values less than 0.001), and were correlated with prolactin increases, (P values less than 0.05). During a 20-min recovery period after exercise, changes in heart rate, ACTH, and beta-LPH levels were correlated with duration of exercise, (P less than 0.01, P less than 0.03, and P less than 0.03, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)     

A soybean vacuolar protein (P34) related to thiol proteases is synthesized as a glycoprotein precursor during seed maturation.

We have examined the synthesis, posttranslational processing, and localization of soybean P34, a member of the papain superfamily. P34 has been identified as a constituent of oil storage organelles or oil bodies isolated from seed lysates and has been assumed to be one of the oil body proteins. Electron microscopic immunocytochemistry with a monoclonal antibody demonstrated that P34 is localized in the protein storage vacuoles but not in the oil bodies. Immunocytochemical observations of partially disrupted seed cells showed that the association of P34 with oil bodies appears to occur as a consequence of cell lysis. In vitro synthesis of P34 results in the formation of a 46-kDa polypeptide that increases to 47 kDa due to core glycosylation by canine microsomes. In vivo synthesis studies in the presence and absence of tunicamycin, an inhibitor of N-linked glycosylation, indicate that pro-P34 is 47 kDa. Since the cDNA sequence of prepro-P34 contains a single putative glycosylation site in the precursor domain, we conclude that P34, like a few other vacuolar proteins, is synthesized as a glycoprotein precursor. Pulse-chase experiments showed that the processing of pro-P34 to mature P34 occurs in a single step and that this posttranslational cleavage occurs on the carboxyl side of an Asn, which is typical of seed vacuolar proteins. Pro-P34 (47 kDa) is detected in immunoblots of maturing seeds. Analysis of RNA indicates that the P34 genes are expressed only during seed maturation and that the P34 mRNA is related to other thiol protease mRNAs detectable in other organs and plants. Unlike other seed thiol proteases that are synthesized only after seed germination, P34 accumulates during seed maturation.     

A multisensory integration model of human stance control

A model is presented to study and quantify the contribution of all available sensory information to human standing based on optimal estimation theory. In the model, delayed sensory information is integrated in such a way that a best estimate of body orientation is obtained. The model approach agrees with the present theory of the goal of human balance control. The model is not based on purely inverted pendulum body dynamics, but rather on a three-link segment model of a standing human on a movable support base. In addition, the model is non-linear and explicitly addresses the problem of multisensory integration and neural time delays. A predictive element is included in the controller to compensate for time delays, necessary to maintain erect body orientation. Model results of sensory perturbations on total body sway closely resemble experimental results. Despite internal and external perturbations, the controller is able to stabilise the model of an inherently unstable standing human with neural time delays of 100 ms. It is concluded, that the model is capable of studying and quantifying multisensory integration in human stance control. We aim to apply the model in (1) the design and development of prostheses and orthoses and (2) the diagnosis of neurological balance disorders. Received: 25 August 1997 / Accepted in revised form: 8 December 1998     

Preparation of Agglutinating Antisera and Fluorescent-Antibody Conjugates Against Pasteurella tularensis in Equines

The serological response in burros and horses to the viable LVS strain of Pasteurella tularensis was studied. High-titered agglutinating antisera and fluorescent-antibody conjugates were obtained in both groups of animals. Maximum titers were obtained in horses 14 to 21 days after the start of vaccination and in burros 21 to 28 days after the start of vaccination. The use of Woodhour's adjuvants or booster inoculations did not result in increased titers.