Synaptic relationships between the chorda tympani and tyrosine hydroxylase-immunoreactive dendritic processes in the gustatory zone of the nucleus of the solitary tract in the hamster

The toxic lectin ricin was applied to the hamster chorda tympani (CT), producing anterograde degeneration of its terminal boutons within the gustatory zone of the nucleus of the solitary tract (NST). Immunocytochemistry was subsequently performed with antiserum against tyrosine hydroxylase (TH), and the synaptic relationships between degenerating CT terminal boutons and either TH-immunoreactive or unlabeled dendritic processes were examined at the electron microscopic level. Degenerating CT terminal boutons formed asymmetric axodendritic synapses and contained small, clear, spherical synaptic vesicles that were densely packed and evenly distributed throughout the ending, with no accumulation at the active synaptic. The degenerating CT terminated on the dendrites of TH-immunoreactive neurons in 36% (35/97) of the cases. The most frequent termination pattern involved the CT and two or three other inputs in synaptic contact with a single immunoreactive dendrite, resulting in a glomerular-like structure that was enclosed by glial processes. In 64% (62/97) of the cases, the degenerating CT was in synaptic contact with unlabeled dendrites, often forming a calyx-like synaptic profile that surrounded much of the perimeter of a single unlabeled dendrite. These results indicate that the TH-immunoreactive neurons of the gustatory NST receive direct input from the CT and taste receptors of the anterior tongue and that the termination patterns of the CT vary with its target neuron in the gustatory NST. The glomerular-like structure that characterizes many of the terminations of the CT provides an opportunity for the convergence of several functionally distinct inputs (both gustatory and somatosensory) onto putative dopaminergic neurons that may shape their responsiveness to the stimulation of the oral cavity.     

Coupling protein stability and protein function in Escherichia coli CspA

Idiopathic thrombocytopenic purpura (ITP, also known as immune thrombocytopenic purpura) in adults is principally a disease of young women. Although in some patients the onset is acute and complete resolution occurs, in most patients, the onset is insidious and the course is chronic. In spite of the relative frequency of ITP, there are important unresolved issues in its diagnosis and management. For this reason, the American Society of Hematology (ASH) chose ITP as the disease topic for its initial sponsored practice guideline in 1993. A major conclusion of the published guideline was the lack of firm evidence on which to base diagnostic procedures and management strategies. This review describes the clinical features of ITP in adults, emphasizes the principal unresolved issues in diagnosis and management, and outlines the critical areas for future research.     

Two reconstructive techniques for flatfoot deformity comparing contact characteristics of the hindfoot joints

The effect of two different methods of reconstruction of flatfoot deformity and the role of the posterior tibial tendon on the contact characteristics of the hindfoot joints were quantified using pressure-sensitive film. Each of 10 cadaver feet was loaded quasi-statically by an axial compressive force to simulate varying loads. First, a specimen was tested intact, then it was tested after sectioning the spring ligament and loading the specimen cyclically to create one type of flatfoot deformity. It was then tested again after reconstructing the deformity. Reconstructions used were the Dillwyn-Evans procedure (bone graft in osteotomy of the calcaneus) or the calcaneocuboid distraction arthrodesis (CCDA). We found that surgically produced flatfoot deformity altered mainly the talonavicular joint, by decreasing its contact area. The Dillwyn-Evans method had less effect on the talonavicular joint (altering 2 of 6 measured parameters) than the CCDA (3 of 6) and more effect on the anteriomedial facet (altering 3 of 6 parameters) than the CCDA (1 of 6). The Dillwyn-Evans method had more effect on the posterior facet (altering 2 of 6 measured parameters) than the CCDA (1 of 6). Function of the posterior tibial tendon had no effect on contact characteristics of the hindfoot joints after either type of reconstruction. These findings are based on measurements using a quasi-statically-loaded foot model at three selected positions, and results may be different with dynamic loading.     

Evidence that bacteria prefer to adhere to thrombus

This study was undertaken to investigate the possible association between thrombosis and infection using an in vitro test model in which fresh bovine blood was recirculated through test conduits (3.5 mm inner diameter) containing stent-like devices. Anticoagulation was adjusted so that the recirculating blood deposited thrombi on the stent to cause gradual occlusion, thus impeding the flow. Four stent-like devices were placed in separate conduits in each experiment, and blood was recirculated with the help of pneumatically driven ventricles. Flow through these conduits was monitored by ultrasonic flow detection. To quantitate bacterial interaction with thrombi, Staphylococcus epidermidis (15E10(9)) was labeled with 111Indium-oxine and added to the blood. Experiments lasted until the flow in the test conduits dropped to 10% of the starting flow. During this recirculation, as flow gradually decreased, one stent was taken out when flow was still at 100%, the second at 75%, the third at 50%, and the fourth at 10% of the starting flow. The number of bacteria associated with the thrombus was measured by gamma counting. The following observations were made: 1) the amount of thrombus increased with time in all experiments (this was confirmed in separate experiments by using autologous 111Indium labeled platelets); 2) bacterial adhesion showed a concomitant increase as thrombus size increased (this was confirmed by using 111Indium labeled bacteria), and 3) bacterial incorporation into the thrombus occurred regardless of whether they were viable or pretreated with the antibiotic rifampin. These observations suggest that as thrombi develop, they may preferentially attract micro-organisms. This suggests that devices with adherent thrombi may have greater susceptibility for infection.     

A neostriatal habit learning system in humans

Amnesic patients and nondemented patients with Parkinson's disease were given a probabilistic classification task in which they learned which of two outcomes would occur on each trial, given the particular combination of cues that appeared. Amnesic patients exhibited normal learning of the task but had severely impaired declarative memory for the training episode. In contrast, patients with Parkinson's disease failed to learn the probabilistic classification task, despite having intact memory for the training episode. This double dissociation shows that the limbic-diencephalic regions damaged in amnesia and the neostriatum damaged in Parkinson's disease support separate and parallel learning systems. In humans, the neostriatum (caudate nucleus and putamen) is essential for the gradual, incremental learning of associations that is characteristic of habit learning. The neostriatum is important not just for motor behavior and motor learning but also for acquiring nonmotor dispositions and tendencies that depend on new associations.     

Codistribution of procathepsin B and mature cathepsin B forms in human prostate tumors detected by confocal and immunofluorescence microscopy

Ascorbic acid can recycle alpha-tocopherol from the tocopheroxyl free radical in lipid bilayers and in micelles, but such recycling has not been demonstrated to occur across cell membranes. In this work the ability of intracellular ascorbate to protect and to recycle alpha-tocopherol in intact human erythrocytes and erythrocyte ghosts was investigated. In erythrocytes that were 80% depleted of intracellular ascorbate by treatment with the nitroxide Tempol, both 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) and ferricyanide oxidized alpha-tocopherol to a greater extent than in cells not depleted of ascorbate. In contrast, in erythrocytes in which the intracellular ascorbate concentration had been increased by loading with dehydroascorbate, loss of alpha-tocopherol was less with both oxidants than in control cells. Protection against AAPH-induced oxidation of alpha-tocopherol was not prevented by extracellular ascorbate oxidase, indicating that the protection was due to intracellular and not to extracellular ascorbate. Incubation of erythrocytes with lecithin liposomes also generated an oxidant stress, which caused lipid peroxidation in the liposomes and depleted erythrocyte alpha-tocopherol, leading to hemolysis. Ascorbate loading of the erythrocytes delayed liposome oxidation and decreased loss of alpha-tocopherol from both cells and from alpha-tocopherol-loaded liposomes. When erythrocyte ghosts were resealed to contain ascorbate and challenged with free radicals generated by AAPH outside the ghosts, intravesicular ascorbate was totally depleted over 1 h of incubation, whereas alpha-tocopherol decreased only after ascorbate was substantially oxidized. These results suggest that ascorbate within the erythrocyte protects alpha-tocopherol in the cell membrane by a direct recycling mechanism.     

Altered xanthophyll compositions adversely affect chlorophyll accumulation and nonphotochemical quenching in Arabidopsis mutants

Collectively, the xanthophyll class of carotenoids perform a variety of critical roles in light harvesting antenna assembly and function. The xanthophyll composition of higher plant photosystems (lutein, violaxanthin, and neoxanthin) is remarkably conserved, suggesting important functional roles for each. We have taken a molecular genetic approach in Arabidopsis toward defining the respective roles of individual xanthophylls in vivo by using a series of mutant lines that selectively eliminate and substitute a range of xanthophylls. The mutations, lut1 and lut2 (lut = lutein deficient), disrupt lutein biosynthesis. In lut2, lutein is replaced mainly by a stoichiometric increase in violaxanthin and antheraxanthin. A third mutant, aba1, accumulates normal levels of lutein and substitutes zeaxanthin for violaxanthin and neoxanthin. The lut2aba1 double mutant completely lacks lutein, violaxanthin, and neoxanthin and instead accumulates zeaxanthin. All mutants were viable in soil and had chlorophyll a/b ratios ranging from 2.9 to 3.5 and near wild-type rates of photosynthesis. However, mutants accumulating zeaxanthin exhibited a delayed greening virescent phenotype, which was most severe and often lethal when zeaxanthin was the only xanthophyll present. Chlorophyll fluorescence quenching kinetics indicated that both zeaxanthin and lutein contribute to nonphotochemical quenching; specifically, lutein contributes, directly or indirectly, to the rapid rise of nonphotochemical quenching. The results suggest that the normal complement of xanthophylls, while not essential, is required for optimal assembly and function of the light harvesting antenna in higher plants.