Increase in levels of microbiota recoverable from male and larval Myrmecia gulosa (Fabricius) (Hymenoptera: Formicidae) following segregation from worker ants

The segregation of laboratory maintained male and larval Myrmecia gulosa from workers resulted in increased levels of culturable microbiota. After 29 days, microbial levels recovered from segregated males and larvae were 27 and 126 times greater than from males and larvae not segregated from workers. These findings are consistent with the hypothesis that metapleural gland secretions, absent in larvae and males, are transferred from workers to larvae, and males contribute to the inhibition of cuticular microbiota.     

Ultrastructure of neuro‐spirocyte synapses in the sea anemone Aiptasia pallida (Cnidaria,Anthozoa, Zoantharia)

Using transmission electron microscopy of serially sectioned tentacles from the sea anemone Aiptasia pallida, we located and characterized two types of neuro‐spirocyte synapses. Clear vesicles were observed at 10 synapses and dense‐cored vesicles at five synapses. The diameters of vesicles at each neuro‐spirocyte synapse were averaged; clear vesicles ranged from 49–89 nm in diameter, whereas the dense‐cored vesicles ranged from 97–120 nm in diameter. One sequential pair of synapses included a neuro‐spirocyte synapse with clear vesicles (81 nm) and a neuro‐neuronal synapse with dense‐cored vesicles (168 nm). A second synapse on the same cell had dense‐cored vesicles (103 nm). An Antho‐RFamide‐labeled ganglion cell and three different neurites were observed adjacent to spirocytes, but no neuro‐spirocyte synapses were present. Many of the spirocytes also were immunoreactive to Antho‐RFamide. The presence of sequential neuro‐neuro‐spirocyte synapses suggests that synaptic modulation may be involved in the neural control of spirocyst discharge. The occurrence of either dense‐cored or clear vesicles at neuro‐spirocyte synapses suggests that at least two types of neurotransmitter substances control the discharge of spirocysts in sea anemones. J. Morphol. 241:165–173, 1999. © 1999 Wiley‐Liss, Inc.     

Yield and quality of forage maize (<i>Zea mays</i> L.) with different levels of subsurface drip irrigation and plant density

The scarcity of water in arid and semiarid regions of the world is a problem that every day increases by climate change. The subsurface drip irrigation (SDI) and changes in population density of plants are alternatives that can be used to make a sustainable use of water. Therefore, the objectives of this study were to determine the combination that allows for an increased corn performance and efficient use of water without losing the quality of forage. Three different irrigation levels were applied through a system of a SDI at three different densities of forage maize plants in an arid region. The results demonstrated that by applying different levels of water, either enough or lack of soil moisture is created, which is directly reflected in crop yield, and its determining variables such as green forage and dry matter yield, and nutritional quality. The irrigation level to a 100% of potential evapotranspiration (PET), at a density of 80000 plants/ha, increased yield of green forage to 57664 kg/ha; crude protein was 8.59%, while the rest of the quality parameters decreased. This study allowed to conclude that the irrigation level was the major factor in the response of the crop.     

Effect of nitrogen source and concentration to produce proteins in mass cultures of the microalgae <i>Chaetoceros muelleri</i>

Proteins are one of the major metabolites in biomass from microalgae that constitute the diet of marine organisms grown in aquaculture, and are essential for their growth. The quantity of this component is influenced by nutrients, temperature and light intensity, among others. We examined the growth, biomass production and protein of Chaetoceros muelleri with two sources of nitrogen (nitrate and urea) at three concentrations, using the medium f/2 (0.88 mol/L) (nitrates) as control. The treatments were the medium 2f (3.53 mol/L) and 4f (7.05 mol/L) with NO_3^-, and the medium f/2 (0.88 mol/L), 2f (3.53mol/L) and 4f (7.05 mol/L) with urea. In general, the productive parameters were greater using urea than nitrate in the media. Higher cell concentrations (2.83 x 10⁶ cell/mL), average and cumulative growth rates (1.50 div/day and 6.01 divisions), dry weight (0.0044 g/L), and proportion of proteins (23.74%) were found when urea was used as the N source. However, most of the bands on the electrophoretic profile were present in the mediums with NO_3^- (~6.5 to 90 kDa).     

The first step of glycosylphosphatidylinositol biosynthesis is mediated by a complex of PIG-A, PIG-H, PIG-C and GPI1.

Biosynthesis of glycosylphosphatidylinositol (GPI) is initiated by transfer of N-acetylglucosamine (GlcNAc) from UDP-GlcNAc to phosphatidylinositol (PI). This chemically simple step is genetically complex because three genes are required in both mammals and yeast. Mammalian PIG-A and PIG-C are homologous to yeast GPI3 and GPI2, respectively; however, mammalian PIG-H is not homologous to yeast GPI1. Here, we report cloning of a human homolog of GPI1 (hGPI1) and demonstrate that four mammalian gene products form a protein complex in the endoplasmic reticulum membrane. PIG-L, which is involved in the second step in GPI synthesis, GlcNAc-PI de-N-acetylation, did not associate with the isolated complex. The protein complex had GPI-GlcNAc transferase (GPI-GnT) activity in vitro, but did not mediate the second reaction. Bovine PI was utilized approximately 100-fold more efficiently than soybean PI as a substrate, and lyso PI was a very inefficient substrate. These results suggest that GPI-GnT recognizes the fatty acyl chains of PI. The unusually complex organization of GPI-GnT may be relevant to selective usage of PI and/or regulation.     

Crosstalk between integrin αvβ3 and estrogen receptor-α is involved in thyroid hormone-induced proliferation in human lung carcinoma cells

A cell surface receptor for thyroid hormone that activates extracellular regulated kinase (ERK) 1/2 has been identified on integrin αvβ3. We have examined the actions of thyroid hormone initiated at the integrin on human NCI-H522 non-small cell lung carcinoma and NCI-H510A small cell lung cancer cells. At a physiologic total hormone concentration (10(-7) M), T(4) significantly increased proliferating cell nuclear antigen (PCNA) abundance in these cell lines, as did 3, 5, 3'-triiodo-L-thyronine (T(3)) at a supraphysiologic concentration. Neutralizing antibody to integrin αvβ3 and an integrin-binding Arg-Gly-Asp (RGD) peptide blocked thyroid hormone-induced PCNA expression. Tetraiodothyroacetic acid (tetrac) lacks thyroid hormone function but inhibits binding of T(4) and T(3) to the integrin receptor; tetrac eliminated thyroid hormone-induced lung cancer cell proliferation and ERK1/2 activation. In these estrogen receptor-α (ERα)-positive lung cancer cells, thyroid hormone (T(4)>T(3)) caused phosphorylation of ERα; the specific ERα antagonist ICI 182,780 blocked T(4)-induced, but not T(3)-induced ERK1/2 activation, as well as ERα phosphorylation, proliferating-cell nuclear antigen (PCNA) expression and hormone-dependent thymidine uptake by tumor cells. Thus, in ERα-positive human lung cancer cells, the proliferative action of thyroid hormone initiated at the plasma membrane is at least in part mediated by ERα. In summary, thyroid hormone may be one of several endogenous factors capable of supporting proliferation of lung cancer cells. Activity as an inhibitor of lung cancer cell proliferation induced at the integrin receptor makes tetrac a novel anti-proliferative agent.     

A proteolytic digestion technique for evaluating freeze-induced damage to acrosomes of chickens spermatozoa

Approximately 94% of freshly collected chicken spermatozoa were capable of digesting a gelatin membrane. The spermatozoa could undergo complete autolysis which resulted in disappearance of the sperm structure within the hole in the membrane. Freezing reduced the number of spermatozoa capable of membrane digestion from 94% in fresh semen to 65% in frozen semen. Storage in vitro at 40 °C reduced the ability of either fresh or frozen spermatozoa to completely digest the membrane. This technique appears to be an effective method for evaluating freezethaw damage to the acrosome of the chicken spermatozoon.     

Evidence that noradrenergic transmitter release is regulated by presynaptic receptors

A review is provided of the evidence in support of the existence of prejunctional alpha adrenoceptors on noradrenergic nerve terminals as well as the evidence for their physiological importance. The use of alpha-adrenoceptor agonists and antagonists has provided convincing data in support of the presynaptic receptor hypothesis. Moreover, there is ample evidence for the location of alpha adrenoceptors on nerve terminals. This evidence has often been forgotten in arguments opposing the presynaptic alpha-adrenoceptor hypothesis. The precise physiological role of presynaptic alpha adrenoceptors is still an open question, but there is support from a wide range of experiments in favor of a physiological role. Although it is not known which of these functions is most important, presynaptic alpha adrenoceptors may: regulate the pulse-to-pulse regulation of norepinephrine release during nerve stimulation, prevent noise, and protect the neuroeffector cell from excessive activation by transmitter during periods of rest or as physiological antagonists to the facilitation of transmitter release. In summary, evidence reviewed here strongly supports the existence of presynaptic alpha adrenoceptors. These receptors are clearly important pharmacologically and may play a physiological role in noradrenergic transmission. The exact physiological function must await further experimentation.     

Regulation of nicotine-evoked dopamine release from PC12 cells.

The nature of second messengers involved in the nicotine-evoked release of dopamine from PC12 cells was examined. Calmidazolium, a calmodulin inhibitor, abolished the nicotine-evoked release. A23187, a Ca2+ ionophore, enhanced dopamine release, and this was inhibited by calmidazolium. Further, 2', 5'-dideoxyadenosine abolished both the nicotine- and A23187-evoked release. Forskolin, dibutyryl-cyclic AMP, and rolipram (a cyclic AMP phosphodiesterase inhibitor) all enhanced dopamine release. 1, 9-Dideoxyforskolin, a forskolin analog which does not activate adenylate cyclase, did not alter dopamine release. These results suggest an obligatory role for Ca2+ and calmodulin-sensitive adenylate cyclase in the nicotine-evoked release process.