Inhibition of neurite polarity by tau antisense oligonucleotides in primary cerebellar neurons

Neurons in culture can have fundamentally distinct morphologies which permit their cytological identification and the recognition of their neurites as axons or dendrites. Microtubules may have a role in determining morphology by the selective stabilization of spatially distinct microtubule subsets. The plasticity of a neurite correlates inversely with the stability of its component microtubules: microtubules in growth cones are very dynamic, and in initial neurites there is continuous incorporation of labelled subunits, whereas in mature neurites, microtubules are highly stabilized. The binding of microtubule-associated proteins to the microtubules very probably contributes to this stability. Cerebellar neurons in dissociated culture initially extend exploratory neurites and, after a relatively constant interval, become polarized. Polarity becomes evident when a single neurite exceeds the others in length. These stable neurites cease to undergo the retractions and extensions characteristic of initial neurites and assume many features of axons and dendrites. We have now studied the role of the neuronal microtubule-associate protein tau in neurite polarization by selectively inhibiting tau expression by the addition of antisense oligonucleotides to the culture media. Although the extension of initial exploratory neurites occurred normally, neurite asymmetry was inhibited by the failure to elaborate an axon.

MAP2 is localized to the dendrites of hippocampal neurons which develop in culture

The distribution of the microtubule-associated protein MAP2 in cultured hippocampal neurons was studied using immunocytochemistry with monoclonal antibodies. MAP2 was preferentially localized to dendritic, but not axonal, processes even in single isolated cells which developed without making intercellular contacts. Hence regional differences in the molecular composition of the neuronal cytoskeleton can develop independently of cell interactions. The presence of MAP2 may be a useful marker for identifying dendrites in cell culture.

Suppression of MAP2 in cultured cerebellar macroneurons inhibits minor neurite formation

We show here that antisense MAP2 oligonucleotides inhibit neurite outgrowth in cultured cerebellar macroneurons. Unlike control neurons, which first extend a lamellipodial veil followed by a consolidation phase during which the cells extend minor neurites, MAP2-suppressed cells persist with lamellipodia and later become rounded. The induction of microtubules containing tyrosinated tubulin, which parallels neurite outgrowth in control neurons, was blocked under antisense conditions. The small but significant increase in acetylated microtubules was not affected. In contrast, the suppression of tau, which selectively blocks axonal elongation, completely prevented the increase of acetylated microtubules, but did not modify the induction of labile microtubules. These results suggest that MAP2 and tau have different functions: the initial establishment of neurites depends upon MAP2, whereas further neurite elongation depends upon tau and microtubule stabilization.

Heterogeneity of microtubule-associated protein 2 during rat brain development

The electrophoretic pattern of the large microtubule-associated protein, MAP2, changes during rat brain development. Immunoblots of NaDodSO4 extracts obtained from the cerebral cortex, cerebellum, and thalamus at 10-15 days after birth reveal only a single electrophoretic species when probed with any of three MAP2 monoclonal antibodies. By contrast, adult MAP2 contains two immunoreactive species, MAP2a and MAP2b. The single band of MAP2 from immature brain electrophoretically comigrates with adult MAP2b. Between postnatal days 17 and 18, immature MAP2 simultaneously resolves into two species in both the cerebellum and cerebral cortex. Immunoblots of NaDodSO4 extracts from spinal cord demonstrate the adult complement of MAP2 by day 10, indicating that MAP2 does not change coordinately throughout the entire central nervous system. In vitro cAMP-dependent phosphorylation of immature MAP2 causes a band split reminiscent of that seen during brain development in vivo. The possibility that the developmentally regulated changes observed in MAP2 during brain maturation are due to timed phosphorylation events is discussed.

Immunocytochemical localization of actin and microtubule-associated protein MAP2 in dendritic spines

To determine whether dendritic spines contain actin, we evaluated the immunocytochemical localization of actin in the hippocampal formation and cerebral cortex of the rat. Monoclonal hybridoma antibodies were prepared against adult quail breast muscle actin. The culture supernatant of two cell lines (QAB1 and QAB2) was examined. Both antibodies bound only actin in crude brain homogenates, and neither exhibited species specificity. Electron microscopic analyses of sections reacted with QAB1 revealed staining of postsynaptic densities and dendritic microtubules but little staining of the cytoplasmic compartment of spines. However, sections reacted with QAB2 exhibited staining at the cytoplasmic compartment of spines as well as the sites stained by QAB1. We also evaluated the immunocytochemical distribution of beta-tubulin and high molecular weight microtubule-associated protein (MAP2) utilizing monoclonal antibodies. MAP2 was found in the dendritic spine as well as in the parent dendrite. However, beta-tubulin was found only in the postsynaptic density and in the microtubules of the parent dendrite. The combined results indicate that actin is present in the spine along with MAP2 and that there is a difference in the actin (or the state of actin) in the spine in comparison with other neuronal compartments.

Kinesin-mediated organelle translocation revealed by specific cellular manipulations

The distribution of membrane-bound organelles was studied in cultured hippocampal neurons after antisense oligonucleotide suppression of the kinesin-heavy chain (KHC). We observed reduced 3,3'-dihexyloxacarbocyanine iodide (DiOC6(3)) fluorescent staining in neurites and growth cones. In astrocytes, KHC suppression results in the disappearance of the DiOC6(3)-positive reticular network from the cell periphery, and a parallel accumulation of label within the cell center. On the other hand, mitochondria microtubules and microfilaments display a distribution that closely resembles that observed in control cells. KHC suppression of neurons and astrocytes completely inhibited the Brefeldin A-induced spreading and tubulation of the Golgi-associated structure enriched in mannose-6-phosphate receptors. In addition, KHC suppression prevents the low pH-induced anterograde redistribution of late endocytic structures. Taken collectively, these observations suggest that in living neurons, kinesin mediates the anterograde transport of tubulovesicular structures originated in the central vacuolar system (e.g., the endoplasmic reticulum) and that the regulation of kinesin-membrane interactions may be of key importance for determining the intracellular distribution of selected organelles.

Nerve growth factor potentiates the neurotoxicity of beta amyloid

The role of growth factors in the pathogenesis of Alzheimer disease is unknown. The beta-amyloid protein accumulates abnormally in the brain in Alzheimer disease and is neurotoxic to differentiated hippocampal neurons in culture. Nerve growth factor (NGF) increased the neurotoxic potency of a beta-amyloid polypeptide by a factor of approximately 100,000, which resulted in a reduction of the beta-amyloid neurotoxic EC50 from 0.1 microM to 1 pM. This potentiating effect of NGF was reversed by a monoclonal antibody against NGF and was not observed for a variety of other neurotrophic growth factors. Exposure of hippocampal neurons to very low concentrations of beta amyloid alone resulted in a marked induction of immunoreactive NGF receptors. Addition of NGF with beta amyloid resulted in the appearance of neurodegenerative changes in NGF receptor-positive neurons. The early and profound degeneration of hippocampal and basal forebrain cholinergic neurons that occurs in Alzheimer disease may result from a neurotoxic interaction of beta amyloid with NGF.

Expression of the class III beta-tubulin isotype in developing neurons in culture

The expression of the class III beta-tubulin isotype was studied in cultured brain neurons by means of a monoclonal antibody (TuJ1). The results obtained indicate that during early axonal outgrowth most of the class III beta-tubulin is not incorporated into microtubules, a phenomenon which is also observed under conditions which alter the rate and extent of the neurite outgrowth response. On the other hand, a dramatic increase in its incorporation into microtubules is observed after the neurons have differentiated their neurites as axons and dendrites. In addition, the appearance of colchicine-resistant microtubules containing this isotype, a phenomenon which occurs late in neurite development, is highly coincident with the appearance of stable microtubules containing high molecular weight microtubule-associated proteins (MAPs). This pattern is different from that of the accumulation and incorporation of other beta-tubulin isotypes into microtubules. Taken collectively, our results indicate that differences exist in the in vivo utilization of tubulin isotypes in developing brain neurons and suggest that the class III beta-tubulin isotype is not a primary factor involved in the regulation of microtubule assembly during early neurite outgrowth, but that it may be important for maintaining further neurite elongation and/or determining some unique binding property of MAPs to specific microtubule subsets.

Distribution and subcellular localization of calmodulin in adult and developing brain tissue

The distribution and subcellular localization of calmodulin in adult and developing cerebellum was studied in rats by immunocytochemistry. Calmodulin immunoreactivity was found both in neurons and in glial cells. Within neurons the staining was particularly intense in the cell nucleus and in dendrites, the cytoplasm of the cell body was more lightly stained than the nucleus, and light immunoreactivity was observed in axons. Electron microscopic analysis confirmed the association of calmodulin with the nuclear chromatin, while the nucleolus remained unstained. The reaction product was also found overlying the membranes of several organelles, in postsynaptic densities and decorating both dendritic and axonal microtubules. In developing Purkinje cells, calmodulin immunoreactivity was found as early as 5 days after birth. During the initial phases of dendritic development (5-10 days post-natal), the reaction product was associated with the organelles of the apical cone, while little or no staining was observed in the elongating dendrites or in the cell nucleus. Later in development, calmodulin was found in primary and secondary dendrites, and by 20 days after birth immunoreactivity appeared in the cell nucleus, and in the postsynaptic densities of immature spines located in dendrites. The presence of calmodulin in the apical cone suggests the possibility that this protein may participate in the regulation of microtubule formation during the initial stages of dendritic development. Its presence in dendrites at later stages (during the period of synaptogenesis) may indicate that it also participates in the formation of synapses between the parallel fibres and dendritic spines.

The Amblyomma maculatum Koch, 1844 (Acari: Ixodidae) group of ticks: phenotypic plasticity or incipient speciation?

BACKGROUND

The goal of this study was to reassess the taxonomic status of A. maculatum, A. triste and A. tigrinum by phylogenetic analysis of five molecular markers [four mitochondrial: 12S rDNA, 16S rDNA, the control region (DL) and cytochrome c oxidase 1 (cox1), and one nuclear: ribosomal intergenic transcribed spacer 2 (ITS2)]. In addition, the phenotypic diversity of adult ticks identified as A. maculatum and A. triste from geographically distinct populations was thoroughly re-examined.

RESULTS

Microscopic examination identified four putative morphotypes distinguishable by disjunct geographical ranges, but very scant fixed characters. Analysis of the separated mitochondrial datasets mostly resulted in conflicting tree topologies. Nuclear gene sequences were almost identical throughout the geographical ranges of the two species, suggesting a very recent, almost explosive radiation of the terminal operational taxonomic units. Analysis of concatenated molecular datasets was more informative and indicated that, although genetically very close to the A. maculatum - A. triste lineage, A. tigrinum was a monophyletic separate entity. Within the A. maculatum - A. triste cluster, three main clades were supported. The two morphotypes, corresponding to the western North American and eastern North American populations, consistently grouped in a single monophyletic clade with many shared mitochondrial sequences among ticks of the two areas. Ticks from the two remaining morphotypes, south-eastern South America and Peruvian, corresponded to two distinct clades.

CONCLUSIONS

Given the paucity of morphological characters, the minimal genetic distance separating morphotypes, and more importantly the fact that two morphotypes are genetically indistinguishable, our data suggest that A. maculatum and A. triste should be synonymized and that morphological differences merely reflect very recent local adaptation to distinct environments in taxa that might be undergoing the first steps of speciation but have yet to complete lineage sorting. Nonetheless, future investigations using more sensitive nuclear markers and/or crossbreeding experiments might reveal the occurrence of very rapid speciation events in this group of taxa. Tentative node dating revealed that the A. tigrinum and A. maculatum - A. triste clades split about 2 Mya, while the A. maculatum - A.triste cluster radiated no earlier than 700,000 years ago.

Plants used in Guatemala for the treatment of respiratory diseases. 1. Screening of 68 plants against gram-positive bacteria

Respiratory ailments are important causes of morbidity and mortality in developing countries. Ethnobotanical surveys and literature reviews conducted in Guatemala during 1986-88 showed that 234 plants from 75 families, most of them of American origin, have been used for the treatment of respiratory ailments. Three Gram-positive bacteria causing respiratory infections (Staphylococcus aureus, Streptococcus pneumoniae and Streptococcus pyogenes) were used to screen 68 of the most commonly used plants for activity. Twenty-eight of these (41.2%) inhibited the growth of one or more of the bacteria tested. Staphylococcus aureus was inhibited by 18 of the plant extracts, while 7 extracts were effective against Streptococcus pyogenes. Plants of American origin which exhibited antibacterial activity were: Gnaphalium viscosum, Lippia alba, Lippia dulcis, Physalis philadelphica, Satureja brownei, Solanum nigrescens and Tagetes lucida. These preliminary in vitro results provide scientific basis for the use of these plants against bacterial respiratory infections.

Tyrosinated and detyrosinated microtubules in axonal processes of cerebellar macroneurons grown in culture

We have used the monoclonal antibody YL 1/2 (Tyr) specific for tyrosinated tubulin, and a polyclonal antibody (Glu) specific for detyrosinated tubulin to visualize the distribution of microtubules and microtubule assembly sites during axonal outgrowth. Cerebellar macroneurons growing in culture initially extend several short and thin neurites which have the potential to differentiate either as axons or dendrites (Ferreira and Caceres: Developmental Brain Research 49:205-213, 1989). At the onset of axonal outgrowth the Tyr antibody labels the minor neurites, the axon, and its growth cone, while the Glu antibody only shows immunoreactivity in the axonal shaft. After nocodazole treatment, the Tyr staining disappears, whereas that produced by the Glu antibody remains practically unchanged. When nocodazole was removed, tyrosinated microtubules reappeared first at the tip of the axon, in a more distal region than that occupied by detyrosinated microtubules; another focal site of tyrosinated tubulin incorporation was detected in the cell body. Incorporation of tyrosinated tubulin into growing axons was also studied after taxol treatment. After long incubation periods in the presence of taxol, the Tyr staining disappeared from the axon but remained in the cell body; however, immunoreactivity in this site was negative when the cells were preincubated in the presence of protein synthesis inhibitors. Release from taxol results in the reappearance of Tyr immunoreactivity at the distal end of the axon. Taken collectively, the present results indicate 1) that in cerebellar macroneurons axonal differentiation is accompanied by a temporal and spatial differentiation of microtubules and 2) that there is an active site of tyrosinated tubulin assembly at the tip of axonal processes, and they suggest that the highly tyrosinated domain in this region is a consequence of rapid microtubule turnover and tubulin tyrosine ligase activity.

Tau protein function in axonal formation

Tau protein is a predominantly neuronal microtubule-associated protein that is enriched in axons and is capable of promoting microtubule assembly and stabilization. In the present article we review some of the key experiments directed to obtain insights about tau protein function in developing neurons. Aspects related to whether or not tau has essential, unique, or complementary functions during axonal formation are discussed.

Molecular karyotype variation in Leishmania (Viannia) peruviana: indication of geographical populations in Peru distributed along a north-south cline

Forty-one Leishmania peruviana isolates were selected along a north-south transect which crossed areas endemic for uta in three different biogeographical regions in the Peruvian Andes. The isolates were analysed by molecular karyotyping and hybridization with three chromosome-derived DNA probes. All the isolates could be distinguished from L. braziliensis by their pLb-134 hybridization patterns. However, the patterns with the other probes (pLb-168 and -22) could be used to cluster the Peruvian isolates in discrete groups (karyodemes) which varied in their level of similarity with L. braziliensis. The geographical distribution of these karyodemes supports the hypothesis that eco-graphical isolation has contributed to the heterogeneity of L. peruviana.

[Geographic distribution of Lutzomyia verrucarum (Townsend, 1913) (Diptera, Psychodidae, Phlebotominae), vector of human bartonellosis in Peru]

Lutzomyia verrucarum (Townsend, 1913) (Diptera: Psychodidae); the natural vector of Bartonella bacilliformis, agent of human bartonellosis (peruvian verruga or Carrion's disease), is a native species of Peru; its geographic distribution occurrs between latitudes 5 degrees and 13 degrees 25' South: in the Occidental and Interandean valleys of the Andean. The altitudinal distribution of Lu. verrucarum in the different valleys is as follows: Occidental between 1100 and 2980 m sea level and Interandean from 1200 to 3200 m sea level. Some discrepancies between the distribution of Carrion's disease and Lu. verrucarum suggest the existence of secondary vectors in certain areas where Lu. verrucarum is not present.

Tau protein and the establishment of an axonal morphology

Dissociated neuronal cultures from several regions of the nervous system elaborate two populations of neurites which have features of axons and dendrites. The microtubule-associated protein tau appears to segregate to the axon in some of these culture systems, however it does not do so until after the development of morphological polarity. Despite this observation, tau very likely has some role in the development of polarity because in cultured cerebellar macroneurons taken from the rat embryonic day 15 primordial cerebellum, the inhibition of tau expression by antisense techniques resulted in the failure of a single minor neurite to elongate and form an axon-like neurite. Tau antisense given continuously for up to 72 h kept neurons locked in a stage with minor neurites only; however when released from the effects of the antisense they fully recovered. The administration of tau antisense after the development of polarity resulted in the loss of the axon-like neurite, while dendrite-like neurites continued to grow. Together these results suggest that dendritic differentiation in cerebellar macroneurons requires the prior elaboration of an axon-like structure.

Phylogenetics of the phlebotomine sand fly group Verrucarum (Diptera: Psychodidae: Lutzomyia)

Within the sand fly genus Lutzomyia, the Verrucarum species group contains several of the principal vectors of American cutaneous leishmaniasis and human bartonellosis in the Andean region of South America. The group encompasses 40 species for which the taxonomic status, phylogenetic relationships, and role of each species in disease transmission remain unresolved. Mitochondrial cytochrome c oxidase I (COI) phylogenetic analysis of a 667-bp fragment supported the morphological classification of the Verrucarum group into series. Genetic sequences from seven species were grouped in well-supported monophyletic lineages. Four species, however, clustered in two paraphyletic lineages that indicate conspecificity--the Lutzomyia longiflocosa-Lutzomyia sauroida pair and the Lutzomyia quasitownsendi-Lutzomyia torvida pair. COI sequences were also evaluated as a taxonomic tool based on interspecific genetic variability within the Verrucarum group and the intraspecific variability of one of its members, Lutzomyia verrucarum, across its known distribution.

Extended pelvic resections for recurrent uterine and cervical cancer: out-of-the-box surgery

Patients with recurrent uterine and cervical cancer have poor prognoses. The objective of this study was to analyze the outcomes of patients with recurrent uterine and cervical cancer who had undergone attempted curative resection of pelvic bone, sidewall muscle, major blood vessels, and/or nerves. We reviewed the records of all 14 patients with recurrent uterine and cervical cancer who had extended pelvic resections at our institution between June 2000 and November 2006. Primary sites of disease were the uterus (11 patients) and cervix (3 patients). Tumor histology was as follows: adenocarcinoma, seven; squamous cell carcinoma, three; leiomyosarcoma, three; and adenosarcoma, one. Previous treatment included hysterectomy, 11; pelvic radiation, 9; chemotherapy, 9; and total pelvic exenteration, 2. Extended pelvic resections included removal of pelvic sidewall muscle, five; bone, five; common and/or external iliac vessel, five; femoral nerve, two; lumbosacral nerve root, one; and obturator nerve, one. Other procedures included total pelvic exenteration, three; posterior exenteration, two; and anterior exenteration, one. Complete resection with negative margins was obtained in 11 (78%) of 14 patients. Seven patients (50%) received high-dose rate intraoperative radiation therapy. Reconstructive procedures included continent or incontinent urinary diversion, four; femoral-femoral arterial bypass, two; myocutaneous flap, two; and urinary ileal interposition, one. Median total operating time was 628 min (range, 345-935 min) and median estimated blood loss was 900 mL (range, 300-16,000 mL). Seven patients (50%) had one or more major complication(s), including pelvic abscess, three; colonic fistula, two; massive intraoperative hemorrhage, one; postoperative bladder perforation, one; thrombosed femoral-femoral graft, one; and disruption of appendicocutaneous urinary anastomosis, one. At a median follow-up of 26 months (range, 5-84 months), ten patients (71%) are alive and four patients (29%) have died of disease at 8, 13, 33, and 42 months postoperatively.

Iridoids from Lippia graveolens

An investigation of the leaves of Lippia graveolens from Guatemala provided 10 iridoid and secoiridoid glucosides as well as their ester derivatives. Minor constituents were loganin, secologanin, secoxyloganin, dimethylsecologanoside, loganic acid, 8-epi-loganic acid and caryoptoside. Major constituents were the novel iridoids caryoptosidic acid and lippioside I and II consisting of caryoptosidic acid esterified at the C-6 position of glucose with p-coumaroyl or caffeoyl residues, respectively. Their structures were mainly elucidated by NMR spectroscopy.

Cystosonographic measurements of canine bladder tumours

The purpose of this study was to evaluate the variability of cystosonographic bladder tumor measurements with both operator and bladder volume changes. Ten dogs with bladder tumors were included. In each dog, three operators determined tumor dimensions for three different bladder volumes. Intraclass correlation coefficient was used to assess operator reliability. Response Evaluation Criteria in Solid Tumors (RECIST) and greater than or equal to 50% differences in tumor measurements were used as guidelines. Poor to fair correlations between operators were found for the different tumor dimensions (r(I) = 0.4 - 0.7). The percent differences in tumor dimensions with operator and bladder volume changes were significant enough to misclassify the tumors into the categories of partial response (PR) or progressive disease (PD). These results suggest that cystosonographic measurements of bladder tumors are affected by both changes in operator and bladder volume, and the discrepancies are significant enough to change response classification.

Furanocoumarins from the aerial parts of Dorstenia contrajerva

A new glycosylated furanocoumarin, alpha-L-rhamnopyranosyl-(1-->6)-beta-D-glucopyranosyl-bergaptol (1), has been isolated from Dorstenia contrajerva together with three known furanocoumarins, catechin and epicatechin. Their structures were established using high field 2D NMR techniques.

Immunocytochemical localization of tubulin and the high molecular weight microtubule-associated protein 2 in Purkinje cell dendrites deprived of climbing fibers

The modifications in the localization of tubulin and the high molecular weight microtubule-associated protein 2 were studied in the cerebellum after partial denervation. Both proteins were localized in 40 micron sections using monoclonal antibodies against beta-tubulin (clones Tu9B and Tu12) or microtubule-associated protein 2 (clones AP9 and AP13), and polyclonal antisera against alpha- and beta-tubulin or microtubule-associated protein 2, visualized with the immunoperoxidase method of Sternberger [Sternberger (1979) Immunocytochemistry; Sternberger and Sternberger (1983) Proc. natn. Acad. Sci. U.S.A. 80 6126-6130] or a biotin-avidin system. The destruction of the inferior olive was performed in adult male rats by electrocoagulation or by intraperitoneal administration of 3-acetylpyridine. One day after chemical destruction of the inferior olive, anti-microtubule-associated protein 2 staining with either of the monoclonal antibodies or with the polyclonal antiserum was almost identical to that observed in the cerebellum of non-denervated animals. Specific staining was intense in the cell somata and dendrites and absent in myelinated tracts and in parallel fibers. However, 3 days after the lesion anti-microtubule-associated protein 2 staining showed a clear decrease, both in the proximal and the distal portions of thick secondary and tertiary dendritic trunks of the Purkinje cell. The intensity of the staining was also considerably reduced in the fine dendritic ramifications. By 8 days post-lesion, microtubule-associated protein 2 immunoreactivity began to increase, but only in the portions of the dendrites deprived of the climbing fibre; on the contrary, low immunoreactivity was found in the fine dendritic ramifications which are contacted by normal parallel fibers; microtubule-associated protein 2 immunoreactivity increased considerably by 11 days post-lesion, giving a pattern quite similar to that of non-denervated Purkinje cells. The alterations in microtubule-associated protein 2 immunoreactivity were also accompanied by a dramatic decrease in the immunostaining for tubulin, beginning on day-3 post-lesion and lasting until day-15 post-lesion. These changes were observed with either the monoclonal antibodies against beta-tubulin or with the polyclonal antiserum against alpha- and beta-tubulin. The changes in both molecules were also observed in animals in which the inferior olive was destroyed by electrocoagulation, ruling out the possibility of a direct action of 3-acetylpyridine on dendritic microtubular proteins.(ABSTRACT TRUNCATED AT 400 WORDS)

New 12a-hydroxyrotenoids from gliricidia sepium bark

The investigation of a methanolic extract of Gliricidia sepium bark afforded, in addition to vestitol and 2'-O-methylvestitol, three new 12a-hydroxyrotenoids, gliricidol (1), 2-methoxygliricidol (2), and gliricidin (3). The structures of 1-3 were elucidated by analysis of their spectroscopic data. Compounds 1-3 exhibited activity against Artemia salina larvae.