Synthesis, distribution, and levels of an egg lipoprotein from the apple snail Pomacea canaliculata (Mollusca: Gastropoda)

The site of synthesis of mollusc lipoproteins is hitherto unknown and was investigated for perivitellin 2 (PV2), an egg lipoprotein found in the freshwater snail Pomacea canaliculata. Tissues (albumen gland, gonad-digestive gland complex, and muscle) from vitellogenic females were incubated in vitro with 14C-leucine at 25 degrees C for 12 hr. At the end of incubation, soluble proteins from tissue homogenates and medium were analyzed for de novo protein synthesis by electrophoresis and HPLC, and radiolabeled proteins were quantified by liquid scintillation. Two albumen gland radiolabeled proteins (67 and 31 kDa) co-migrated with the subunits of PV2, and they represented 6.0% of the total labeled protein in that tissue. Western blot analysis confirmed the presence of PV2 only in the albumen gland. In vivo experiments where adult females were injected with 3H-leucine revealed that PV2 was not present in hemolymph. ELISA analysis in all tissues of the snail confirmed the PV2 presence only in the albumen gland and developing eggs with levels of 26 and 98 mg/g protein, respectively. Therefore, the albumen gland is the only site for PV2 synthesis, and no extra-gland synthesis, circulation, or accumulation could be found. PV2 subunits were further characterized analyzing N-terminal sequences which showed no homology with other proteins.     

Cloning and functional characterization of a homoglutathione synthetase from pea nodules

The thiol tripeptide glutathione (GSH; γ Glu-Cys-Gly) is very abundant in legume nodules where it performs multiple functions that are critical for optimal nitrogen fixation. Some legume nodules contain another tripeptide, homoglutathione (hGSH; γ Glu-Cys- β Ala), in addition to or instead of GSH. We have isolated from a pea ( Pisum sativum L.) nodule library a cDNA, GSHS2 , that is expressed in nodules but not in leaves. This cDNA was overexpressed in insect cells and its protein product was identified as a highly active and specific hGSH synthetase. The enzyme, the first of this type to be completely purified, is predicted to be a homodimeric cytosolic protein. It shows a specific activity of 3400 nmol hGSH min⁻¹ mg⁻¹ protein with a standard substrate concentration (5 m M β -alanine) and K_m values of 1.9 m M for β -alanine and 104 m M for glycine. The specificity constant (V_max/K_m) shows that the pure enzyme is 57.3-fold more specific for β -alanine than for glycine. Southern blot analysis revealed that the gene is present as a single copy in the pea genome and that there are homologous genes in other legumes. We conclude that the synthesis of hGSH in pea nodules is catalysed by a specific hGSH synthetase and not by a GSH synthetase with broad substrate specificity.     

Fluorescent staining as a method of assessing membrane damage and post-thaw survival of ram spermatozoa

We studied the relationship between motility and membrane damage, as assessed by fluorescent staining, in fresh and in frozen-thawed ram spermatozoa. Semen from Merino rams was incubated with 6-carboxyfluorescein diacetate and propidium iodide. In both fresh and frozen-thawed samples, the percentage of intact spermatozoa was lower than the motility rate, thus indicating the presence of damaged but motile spermatozoa. Freezing and thawing resulted in a marked loss of membrane integrity, whereas motility decreased to a lesser extent. There was a positive relationship (r=0.64; P<0.001) between membrane integrity immediately after thawing and motility after 8 h of incubation at 37 degrees C. These results demonstrate the usefulness of the fluorescent staining method for the prediction of ram sperm quality and post-thaw survival.     

Steroidogenic capacity and oxidative stress-related parameters in human luteal cell regression

The steroidogenic capacity and oxidative stress-related parameters of the human corpus luteum (CL) at different stages of the luteal phase were studied under basal and human chorionic gonadotropin (hCG)-stimulated conditions. Mid CL exhibited the maximal steroidogenic capacity, together with lower levels of glutathione and higher thiobarbituric acid reactants content, macrophage count, and superoxide dismutase (SOD) activity, compared to the late CL. Addition of hCG to luteal cell cultures led to a preferential increase in progesterone synthesis in the late CL compared to the mid CL, without changes in the oxidative stress-related parameters, except for the increased SOD activity found in the late CL. It is concluded that an oxidative stress condition is established in the mid CL, coinciding with the maximal steroidogenic capacity and macrophage infiltration of the organ, which be of relevance as one of the major mechanisms initiating CL involution in the human.     

Decomposition of Emission Multipliers in a National Accounting Matrix Including Environmental Accounts

This study defines a linear model of emission multipliers through the use of a national accounting matrix including environmental accounts (NAMEA) for the Catalan economy that integrates the regional economic information with the greenhouse gas emissions. As in the model of income multipliers, emission multipliers can be divided into own effects, open effects, and circular effects. This decomposition shows the channels of income generation and their effects on regional greenhouse gas emissions. Our results reveal significant differences among the three gases analyzed as well as important asymmetries at a sectorial level.     

Considerations on the thalamostriatal system with some functional implications

The thalamostriatal projections are largely neglected in current reviews dealing with basal ganglia function. In the past few years, however, several studies have re-evaluated these projections and have postulated their implication in more complex tasks within the basal ganglia organization. In this review, we try to focus on the morphological and functional importance of this system in the basal ganglia of the rat, cat and monkey. Special attention is paid to the thalamus as an important place for interaction between the input and the output systems of the basal ganglia through the thalamostriatal projections. Thus, we stress on the overlapping thalamic territories between the thalamic projection of the output nuclei of the basal ganglia and the thalamostriatal neurons. Our experimental data support the existence of several thalamic feedback circuits within the basal ganglia functional design. Finally, some considerations are provided upon the functional significance of these thalamic feedback circuits in the overall organization of the basal ganglia in health and disease.