“SIF” cells in the sympathetic ganglia of the bullfrog,Rana catesbeiana: variety in population and innervation

Summary Small intensely fluorescent (SIF) cells appeared singly or, more frequently, in variably-sized clusters in the sacroccygeal 8th and 9th sympathetic ganglia of the bullfrog. Smaller clusters containing only two to nine SIF cells accounted for 61% of 1773 clusters examined. The largest cluster contained 283 cells. The number of cells in individual ganglia also varied from 21 to 3332. SIF cells, solitary as well as in smaller clusters, received no distinct form of the synaptic contact. In contrast, the cells in larger clusters were frequently innervated by nerve endings that were similar in vesicular constitution to the nerve endings on principal ganglion (PG) cells. No synaptic contact was found between SIF cells and PG cells. SIF cells were also characterized by their location in the vicinity of blood capillaries with a continuous endothelium. p]Our observation seems to suggest that larger clusters of SIF cells receiving nerve endings are linked to a paracrine and/or endocrine system. Chemical influence via the blood stream and intraganglionic milieu for non-innervated SIF cells in the solitary or smaller clusters is a subject for speculation. An interneuronal role of SIF cells to relay stimuli to PG cells seems unlikely. The possible functions here assigned to SIF cells could be variable in efficiency depending on their population and density.     

The clinicopathological significance of angiogenesis in hindgut neuroendocrine tumors obtained via an endoscopic procedure

Background

As the World Health Organization grading system for gastroenteropancreatic-neuroendocrine tumors (GEP-NETs) may not always correlate with tumor progression, it is imperative that other independent predictors of tumor progression be established. To identify such predictors, we conducted a retrospective histopathological study of hindgut NETs, obtained from endoscopic procedures, and used statistical analyses to evaluate predictive factors.

Methods

We first obtained clinicopathological data of cases of hindgut NETs. Tissue sections from tumor samples were prepared and subjected to pathological examination. In particular, we calculated the microvessel density (MVD) and lymphatic microvessel density (LMVD) values, and performed appropriate statistical analyses.

Results

A total of 42 cases of hindgut NETs were selected for the study, 41 from the rectum and 1 from the sigmoid colon. Based on the Ki-67 labeling index, 34 cases were classified as NET G1 tumors and 8 as NET G2 tumors. MVD values ranged from 1.4/mm² to 73.9/mm² and LMVD values from 0/mm² to 22.9/mm². MVD and LMVD were identified as risk factors for venous and lymphatic invasion of hindgut NETs. Moreover, MVD positively correlated with the maximum diameter of the tumor.

Conclusions

Tumor progression of NETs may cause angiogenesis and lymphangiogenesis, via an unknown mechanism, as well as lymphovascular invasion. Angiogenesis likely plays an important role in occurrence and progression in the initial phase of hindgut NETs.

     

Novel RNA sequences associated with late male killing in Homona magnanima

Maternally inherited female-biased sex ratios have been documented in many invertebrate species. One cause of such biased sex ratios is male killing, i.e. only males die. In most species, male killing occurs during embryonic stages (early male killing) and is associated with cytoplasmic bacteria, including Wolbachia, Spiroplasma, Rickettsia, Flavobacteria and gamma proteobacteria. However, the oriental tea tortrix, Homona magnanima, is one of the few species in which male death occurs in the larval or pupal stage, and is thus an example of late male killing. We partially purified the agent causing late male killing in H. magnanima and showed that it consists of two RNA sequences. This represents an entirely novel agent causing late male killing.     

Isolation and identification of potent allelopathic substances in rattail fescue

Aqueous methanol extracts of rattail fescue (Vulpia myuros) inhibited the growth of roots and shoots of cress (Lepidium sativum), lettuce (Lactuca sativa), alfalfa (Medicago sativa), timothy (Phleum pratense), Digitaria sanguinalis and Lolium multiflorum. Increasing the extract concentration increased the inhibition, suggesting that rattail fescue may have growth inhibitory substances and possess allelopathic potential. The aqueous methanol extract of rattail fescue was purified and two main inhibitory substances were isolated and identified by spectral data as (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol. Both substances inhibited root and shoot growth of cress at concentrations greater than 0.3 μM. The concentrations required for 50% growth inhibition on root and shoot growth of cress, lettuce, alfalfa, timothy, D. sanguinalis and L. multiflorum were 2.7–19.7 μM for (−)-3-hydroxy-β-ionone, and 2.1–34.5 μM for (+)-3-oxo-α-ionol. The concentration of (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol, respectively, in rattail fescue was 7.8 and 3.7 μg g⁻¹ fresh weight. Considering the endogenous level and the inhibitory activity, (−)-3-hydroxy-β-ionone and (+)-3-oxo-α-ionol may work as allelopathic substances in rattail fescue through the growth inhibition of neighboring plant species.     

FINE STRUCTURE OF THE OCTOPUS RETINA

The fine structure of the visual and the supporting cells and of the blood capillaries in the octopus retina is described. Lamellated structures contained in the proximal segment of the visual cell consist of compact arrays of dense membranes each of which is quintuple-layered and divides at its margins into two thinner sheets or membranes which are connected directly with the agranular or granular endoplasmic reticulum. Proximal to the deeper extremities of the rhabdomeres, the lateral plasma membranes of two adjoining visual cells contact each other forming a quintuple-layered compound membrane, which results in occlusion of the intercellular space. The central layer of the compound membrane is of high density, so that the membrane, as a whole, appears to be a single thick layer at low magnifications. The supporting cells are connected with the neighboring visual cells by two types of junctions. Long slender processes extend from the supporting cells to the surface of the retina through narrow spaces among the distal segments of the visual cells. The capillary endothelial cells are characterized by luminal surfaces irregularly contoured and by lateral surfaces elaborately interdigitated. The functional significance of the close contact between adjoining visual cells is discussed.     

Length-dependent activation and auto-oscillation in skeletal myofibrils at partial activation by Ca2+

The length-dependent activation of skeletal myofibrils was examined at the single-sarcomere level with phase-contrast microscopy at sarcomere length (SL) >2.2 μm. At the maximal activation by Ca²⁺ (pCa 4.5) the active force linearly decreased with increasing SL, while at partial activation by Ca²⁺ (pCa 6.1-6.5) the larger active force was generated at longer SL. Throughout these experiments, the distribution of SL was kept homogeneous upon activation. In addition, we found that the spontaneous oscillation of force and SL frequently occurs in the SL range 2.2-2.6 μm at pCa 6.1-6.2. Either changes in [Ca²⁺] or osmotic compression of the myofilament lattice induced by the addition of dextran T-500, affected both the length dependence of activation and the occurrence of auto-oscillation. These results suggest that the force-generating properties of sarcomeres in striated muscle are determined not only by [Ca²⁺], but also by the lattice spacing as a function of SL.     

Location of the Bombyx mori 175kDa cadherin-like protein-binding site on Bacillus thuringiensis Cry1Aa toxin

To identify and gain a better understanding of the cadherin-like receptor-binding site on Bacillus thuringiensis Cry toxins, it is advantageous to use Cry1Aa toxin, because its 3D structure is known. Therefore, Cry1Aa toxin was used to examine the locations of cadherin-like protein-binding sites. Initial experiments examining the binding compatibility for Cry1Aa toxin of partial fragments of recombinant proteins of a 175kDa cadherin-like protein from Bombyx mori (BtR175) and another putative receptor for Cry1Aa toxin, amino peptidaseN1, from Bo.mori (BmAPN1), suggested that their binding sites are close to each other. Of the seven mAbs against Cry1Aa toxin, two mAbs were selected that block the binding site for BtR175 on Cry1Aa toxin: 2A11 and 2F9. Immunoblotting and alignment analyses of four Cry toxins revealed amino acids that included the epitope of mAb 2A11, and suggested that the area on Cry1Aa toxin blocked by the binding of mAb 2A11 is located in the region consisting of loops2 and 3. Two Cry1Aa toxin mutants were constructed by substituting a Cys on the area blocked by the binding of mAb 2A11, and the small blocking molecule, N-(9-acridinyl)maleimide, was introduced at each Cys substitution to determine the BtR175-binding site. Substitution of Tyr445 for Cys had a crippling effect on binding of Cry1Aa toxin to BtR175, suggesting that Tyr445 may be in or close to the BtR175-binding site. Monoclonal antibodies that blocked the binding site for BtR175 on Cry1Aa toxin inhibited the toxicity of Cry1Aa toxin against Bo.mori, indicating that binding of Cry1Aa toxin to BtR175 is essential for the action of Cry1Aa toxin on the insect.     

The MIDASIN and NOTCHLESS genes are essential for female gametophyte development in Arabidopsis thaliana

Female gametophyte development in Arabidopsis thaliana follows a well-defined program that involves many fundamental cellular processes. In this study, we report the involvement of the Arabidopsis thaliana MIDASIN1 (AtMDN1) gene during female gametogenesis through the phenotypic characterization of plants heterozygous for an insertional mdn1 mutant allele. The MDN1 yeast ortholog has previously been shown to encode a non-ribosomal protein involved in the maturation and assembly of the 60S ribosomal subunit. Heterozygous MDN1/mdn1 plants were semisterile and mdn1 allele transmission through the female gametophyte was severely affected. Development of mdn1 female gametophyte was considerably delayed compared to their wild-type siblings. However, delayed mdn1 female gametophytes were able to reach maturity and a delayed pollination experiment showed that a small proportion of the female gametophytes were functional. We also report that the Arabidopsis NOTCHLESS (AtNLE) gene is also required for female gametogenesis. The NLE protein has been previously shown to interact with MDN1 and to be also involved in 60S subunit biogenesis. The introduction of an AtNLE-RNA interference construct in Arabidopsis led to semisterility defects. Defective female gametophytes were mostly arrested at the one-nucleate (FG1) developmental stage. These data suggest that the activity of both AtMDN1 and AtNLE is essential for female gametogenesis progression.