Spinocervical tract neurons responsive to light mechanical stimulation of the raccoon forepaw

1. The extracellular activity of 45 antidromically identified spinocervical tract (SCT) neurons responsive to light mechanical stimulation of the glabrous surfaces of the forepaw was examined in raccoons anesthetized with pentobarbital sodium. An additional seven neurons had peripheral receptive fields (RFs) located on hairy skin of the forelimb, and three had deep RFs. 2. All recording sites were histologically verified as falling within Rexed's laminae III and IV in spinal cord segments C6-T1. Antidromic conduction velocities of the 55 neurons ranged between 8.3 and 64.2 m/s. 3. Units with glabrous skin RFs were classified according to their response to a maintained mechanical stimulus as either rapidly adapting (n = 39) or slowly adapting (n = 6). Of 11 cells tested, 2 displayed enhanced responses to noxious stimuli and were classed as multireceptive. 4. RF areas were significantly smaller on digits (range = 0.4-45.0 mm2) than on palm pads (range = 5.6-76.0 mm2), and comparable in size to RF areas previously reported in raccoon cuneate nuclear cells (32). 5. RA neurons fell into three distinct categories with respect to the relationship between instantaneous spike frequency during displacement ramp stimulation, and ramp velocity, steep functions (as defined by the value of power function exponents), flat functions, and discontinuous functions; SA neurons fell into two categories, continuous, and discontinuous. 6. The results, in conjunction with those of previous studies, lead to two major conclusions: 1) raccoon and primate spinocervicothalamic systems are more similar to each other than either is to that of the cat and 2) the ability of the raccoon SCT to convey information from the glabrous skin of the forepaw regarding characteristics of light mechanical stimuli is at least as precise as that of neurons of the dorsal column-medial lemniscal system.     

Difference in the expression of three tight junction proteins, barmotin, occludin, and ZO-1, in phenotypically different human colon cancer cell lines

Epithelioid disorganization is a hallmark of gastrointestinal cancers and is believed to be associated with malignant phenotypes such as invasiveness and the potentiality for metastasis. Although tight junctions (TJs) are known to be crucial for the maintenance of polarized organization of the gastrointestinal epithelium, changes in the TJ proteins in human cancers have not yet been fully elucidated. In this report, we investigated the expression and localization of three TJ proteins-barmotin (7H6 antigen), occludin, and ZO-1-in three phenotypically different human colon cancer cell lines exhibiting differnt grades of epithelioid organization. All three proteins were localized at the most apical part of the cell border corresponding to the site of TJs in T₈₄ cells, in which epithelioid organization was well preserved. In contrast, in COLO320DM cells, which showed no epithelioid phenotypes, occludin was not detectable at either the protein or mRNA level, although barmotin and ZO-1 were present in the cytoplasm. In the third cell line, DLD-1, which showed an epithelioid phenotype intermediate between T₈₄ and COLO320DM, aberrant expression of occludin was found in the basolateral cell membrane. On the other hand, barmotin was present in the cytoplasm, whereas ZO-1 was localized at the cell border. These observations showed that changes in the expression of TJ proteins occur in close correlation with epithelioid disorganization in human colon cancers.     

An unusual surface peroxiredoxin protects invasive Entamoeba histolytica from oxidant attack

Peroxiredoxins are an important class of antioxidant enzymes found from Archaea to humans, which reduce and thereby detoxify peroxides and peroxynitrites. The major thiol-containing surface antigen of the invasive ameba, Entamoeba histolytica, is a peroxiredoxin and is likely to be important during the transition from the anaerobic environment of the large intestine to human tissues. The closely related species, Entamoeba dispar, is incapable of invasion and more sensitive to hydrogen peroxide, yet also has a peroxiredoxin. We cloned and expressed the two active recombinant enzymes and found that their activity was similar by a fluorometric stopped-flow assay, giving a Km of <10 microM for hydrogen peroxide. Three monoclonal antibodies produced to recombinant E. histolytica peroxiredoxin cross-reacted with Entamoeba dispar.E. histolytica contains as much as 50 times more peroxiredoxin than E. dispar as demonstrated by a sensitive capture ELISA. In addition, the peroxiredoxin is present largely on the outer surface of the cell, in contrast to E. dispar. This unusual peroxiredoxin localizes to the site of parasite-host cell contact where it can effectively counteract oxidants generated by host cells, thus facilitating invasion.     

Cloning of a truncated Babesia equi gene encoding an 82-kilodalton protein and its potential use in an enzyme-linked immunosorbent assay

To isolate Babesia equi genes encoding immunodominant proteins, a cDNA expression library prepared from B. equi mRNA was immunoscreened with B. equi-infected horse serum. Eighteen positive cDNA clones were obtained, and the clone that showed the strongest immunoreactivity, designated Be82, was further characterized. The Be82 gene consisted of 1,953 bp and contained a partial open reading frame lacking the 5'-terminal sequence. As shown by Western blot analyses, immune sera from mice intraperitoneally injected with the Be82 gene product recognized the 82- and 52-kDa proteins of B. equi but not those of Babesia caballi. The glutathione S-transferase fusion protein expressed in Escherichia coli that was purified and used as the antigen in the enzyme-linked immunosorbent assay reacted specifically with B. equi-infected horse sera. These results suggest that the Be82 gene product is a potential diagnostic antigen candidate in the detection of B. equi infection in horses that will be useful both in the performance of epidemiological studies and in the granting of quarantine passes.     

An autoradiographic study of binding of iodinated spider toxin to lobster muscle

Distribution of the binding sites of Joro spider toxin (JSTX), a specific inhibitor of the glutamate receptors in the crustacean neuromuscular synapse, was studied by using autoradiography. JSTX was synthesized and made radioactive by conjugation with iodine-125. 125I-JSTX irreversibly blocked the excitatory postsynaptic potentials of the lobster neuromuscular synapse in a similar manner as the natural spider toxin. Light microscopic autoradiography of 125I-JSTX treated muscle showed sporadic aggregates of reduced silver grains on the surface of muscles. Electron microscopy of adjoining ultrathin sections revealed that these spots corresponded to the fraction of sarcolemma apposed to axonal terminals with or without synaptic junctional profiles. This finding gives morphological support to the formulation that JSTX binds to the glutamate receptor-ion channel molecules.     

Human herpesvirus 6 downregulates major histocompatibility complex class I in dendritic cells

The expression of major histocompatibility complex (MHC) class I, class II, CD1a, and CD 83 in dendritic cells (DCs) after infection with human herpesvirus 6 (HHV-6) was examined. Whereas there was no significant change in the expression of CD1a, CD83, and MHC class II in infected DCs, MHC class I expression was downregulated after infection with HHV-6 variant A but not HHV-6B. The expression of HHV-6 immediate-early or early genes was required for the downregulation of MHC class I. The de novo synthesis of MHC class I was greatly suppressed by infection with HHV-6A in DCs, while its rate of degradation was only slightly elevated. These results suggest that HHV-6A may escape from the host immune system in DCs by causing the downregulation of MHC class I synthesis.     

Monoclonal antibodies to monkey brain choline acetyltransferase: production and immunohistochemistry

Two monoclonal antibodies to monkey brain choline acetyltransferase (ChAT) were obtained. Immunoblot analysis indicated that both antibodies revealed two adjacent protein bands on a sodium dodecyl sulfate-polyacrylamide gel electrophoresis. ChAT was demonstrated immunohistochemically by one of the antibodies in the motoneurons in the monkey brainstem and spinal cord. This antibody also revealed ChAT-positive terminal-like structures in the neuropils of lamina IX of the cervical spinal cord and interpeduncular nucleus.     

Morphological study of parafollicular cells and the parathyroid gland in the house shrew (Suncus murinus).

A morphological study of parafollicular cells in the thyroid gland and parathyroid gland of the house shrew (Suncus murinus) was made. The results indicated that (1) there were two pairs of parathyroid glands which were located in the upper part of the house shrew thyroid gland, (2) the volumes of the house shrew parathyroid glands ranged from 0.014 to 0.079 mm3, (3) the number of parafollicular cells along the follicles was largest in the upper part of the thyroid lobe, while no parafollicular cells were present in the isthmus, and (4) there were about 20 parafollicular cells per 100 follicular cells and 1.519 parafollicular cells per follicle. The number of parafollicular cells per 100 follicular cells was thus about 5 times larger than that in rats and the number of parafollicular cells per follicle about 2.5 times larger than that in rats.