Rabbit oocyte maturation: changes of membrane resistance, capacitance, and the frequency of spontaneous transient depolarizations

Immature oocytes from rabbits were examined with electrophysiological techniques to determine if their membrane properties change during maturation. The input resistance increased and input capacitance decreased during maturation, although no significant change in membrane potential was observed. The changes observed were consistent with a decrease of corona radiata-oocyte electrical coupling accompanying maturation. Spontaneous transient depolarizations were recorded from immature oocytes surrounded by corona radiata, but not from mature ova. Each event consisted of a rapid depolarization, sustained for 1-100 sec, and a slow repolarization to the resting potential. Spontaneous inward currents with a time course similar to the spontaneous transient depolarizations occurred when the oocyte's membrane potential was held constant by voltage clamp. The frequency with which spontaneous transient depolarizations occurred decreased during maturation. These findings are consistent with a model in which spontaneous depolarizations originate in corona radiata cells and are detected in the oocyte via electrical coupling.     

Clostridium thermoaceticum forms methanol from carbon monoxide in the presence of viologen dyes

Whole cells of Clostridium thermoaceticum, crude extracts of such cells as well as the supernatant of 100 000 × g centrifugations catalyse the reduction of carbon monoxide to methanol in the presence of viologens or cobalt sepulchrate. Without such a mediator methanol could not be detected. The reaction shows a marked optimum at pH 5. The incubation of [5-¹⁴C]methyltetrahydrofolate led only to the formation of ¹⁴C-labeled ethanol; the radioactivity in methanol was negligible. The reaction seems to be catalysed by carbon monoxide dehydrogenase.     

In-vitro antioxidant,in-vivo anti-inflammatory,and acute toxicity study of Indonesian propolis capsule from Tetragonula sapiens

Propolis is widely used as traditional medicine since ancient times. It was necessary to conduct the pre-clinical study because of its relevant curative properties. This study aimed to investigate in-vitro antioxidant, standardize quality parameters, study acute toxicity, and determine in-vivo anti-inflammatory. Three spectrophotometric methods were used to determine antioxidant activity. The standardization includes physical, chemical, and microbiological evaluation. Furthermore, an acute toxicity test was conducted using 20 female Sprague Dawley (SD) strain rats divided into 4 groups with different dose of propolis. The in vivo anti-inflammatory test was carried out using the carrageenan induction method on rats' soles. A total of 36 female SD rats were classified into 6 groups as follows, Group normal, negative control, diclofenac sodium, and three propolis groups (72; 144; and 288 mg/kg BW). The results demonstrated the IC₅₀ values of the DPPH and ABTS scavenging activity 9.694 ppm and 2.213 ppm, respectively. The FRAP reducing power was 189.05 mg AaE/g. The physical appearance of propolis capsule was vegicaps as white – white, size 0, with light brown granule. Moreover, the content weight was 418.88 mg with a disintegration time of 7 min 53 s, while the water, flavonoid, and polyphenol contents were 9.07%, 1.59%, and 98.0821 mg GAE/g respectively. The content of heavy metal and microbial contamination were not detected. The acute toxicity results showed LD₅₀ ≥ 5 g/kg BW, no toxicity symptoms, and no abnormalities in all rats. The anti-inflammatory inhibition percentage for groups III, IV, V, and VI was 11.86%, 6.53%, 7.81%, and 6.63% respectively, while the anti-inflammatory drugs effectiveness percentage compared to positive controls were 55.00%, 65.83%, and 55.83% respectively. Based on these results, it can be concluded that propolis capsules fulfilled the standardization requirements, and it is likely to be non-toxic, and effective as antioxidant and anti-inflammatory.     

On the occurrence of males and production of ephippial eggs in populations of Daphniopsis studeri (Cladocera) in lakes of the Vestfold and Larsemann Hills, East Antarctica

Populations of the cladoceran Daphniopsis studeri Rühe in freshwater and brackish lakes of eastern Antarctica have been thought to consist solely of females that reproduce parthenogenetically by the production of ameiotic subitaneous eggs. This note reports the presence of male D. studeri and the production of ephippial (sexual) eggs in a number of lakes of the Vestfold and Larsemann Hills, which indicate the possibility of sexual reproduction within these populations. Received: 12 May 1997 / Accepted: 8 September 1997     

Genetic analysis of the APC gene in taiwanese familial adenomatous polyposis

Colorectal cancer has become the third leading cause of death from cancer in Taiwan. Familial adenomatous polyposis (FAP) is an autosomal dominant inherited disease characterized by the presence of multiple adenomatous polyps in the colon and rectum. The gene responsible for FAP(APC) was cloned in 1991. Extensive analyses of the mutation spectra in FAP kindreds have been performed in different countries, but the results have been highly variable (30–80%). In this study, we used denaturing high-performance liquid chromatography (DHPLC) followed by automatic sequencing in an effort to establish the mutation spectrum of APC from DNA of peripheral blood cells. Among the 6 FAP probands analyzed, mutations were detected in 3 (50%), 2 of which were novel. The first novel mutation was at codon 2166, with a C to T transition, resulting in a stop codon. The second novel mutation was at codon 1971, with a C to G transversion, resulting in an amino acid change from serine to cysteine. The third mutation involved an A insertion in the sequence of -AAAAAA- at codons 1554–1556, which created a downstream stop codon (codon 1558). This study is the first to report mutation analysis in Taiwanese FAP probands.     

Exploring molecular and mechanical gradients in structural bioscaffolds

Most organisms consist of a functionally adaptive assemblage of hard and soft tissues. Despite the obvious advantages of reinforcing soft protoplasm with a hard scaffold, such composites can lead to tremendous mechanical stresses where the two meet. Although little is known about how nature relieves these stresses, it is generally agreed that fundamental insights about molecular adaptation at hard/soft interfaces could profoundly influence how we think about biomaterials. Based on two noncellular tissues, mussel byssus and polychaete jaws, recent studies suggest that one natural strategy to minimize interfacial stresses between adjoining stiff and soft tissue appears to be the creation of a "fuzzy" boundary, which avoids abrupt changes in mechanical properties. Instead there is a gradual mechanical change that accompanies the transcendence from stiff to soft and vice versa. In byssal threads, the biochemical medium for achieving such a gradual mechanical change involves the elegant use of collagen-based self-assembling block copolymers. There are three distinct diblock copolymer types in which one block is always collagenous, whereas the other can be either elastin-like (soft), amorphous polyglycine (intermediate), or silk-like (stiff). Gradients of these are made by an incrementally titrated expression of the three proteins in secretory cells the titration phenotype of which is linked to their location. Thus, reflecting exactly the composition of each thread, the distal cells secrete primarily the silk- and polyglycine-collagen diblocks, whereas the proximal cells secrete the elastin- and polyglycine-collagen diblocks. Those cells in between exhibit gradations of collagens with silk or elastin blocks. Spontaneous self-assembly appears to be by pH triggered metal binding by histidine (HIS)-rich sequences at both the amino and carboxy termini of the diblocks. In the polychaete jaws, HIS-rich sequences are expanded into a major block domain. Histidine predominates at over 20 mol % near the distal tip and diminishes to about 5 mol % near the proximal base. The abundance of histidine is directly correlated to transition metal content (Zn or Cu) as well as hardness determined by nanoindentation. EXAFS analyses of the jaws indicate that transition metals such as Zn are directly bound to histidine ligands and may serve as cross-linkers.     

Ca2+-dependent activator protein for secretion 1 is critical for constitutive and regulated exocytosis but not for loading of transmitters into dense core vesicles

Although CAPS1 was originally identified as a soluble factor that reconstitutes Ca(2+)-dependent secretion from permeabilized neuroendocrine cells, its exact function in intact mammalian cells remains controversial. Here we investigate the role for CAPS1 by generating stable cell lines in which CAPS1 is strongly down-regulated. In these cells, Ca(2+)-dependent secretion was strongly reduced not only of catecholamine but also of a transfected neuropeptide. These secretion defects were rescued by infusion of CAPS1-containing brain cytosol or by transfection-mediated expression of CAPS1. Whole cell patch clamp recording revealed significant reductions in slow burst and sustained release components of exocytosis in the knockdown cells. Unexpectedly, they also accumulated higher amounts of endogenous and exogenous transmitters, which were attributable to reductions in constitutive secretion. Electron microscopy did not reveal abnormalities in the number or docking of dense core vesicles. Our results indicate that CAPS1 plays critical roles not only in Ca(2+)-dependent, regulated exocytosis but also in constitutive exocytosis downstream of vesicle docking. However, they do not support the role for CAPS1 in loading transmitters into dense core vesicles.     

Biodegradation of naphthalene by enriched marine denitrifying bacteria

Numerous studies have been investigated on the PAHs biodegradation in aerobic and anaerobic environments; however, the biodegradation of PAHs under anoxic conditions, especially denitrifying conditions, has drawn less attention. In this study, four series of batch experiments were conducted to investigate the effect of temperature, pH, naphthalene concentration and nitrate concentration on the naphthalene degradation under denitrification condition. Our results showed that the degradation of naphthalene was most favorable at pH 7 and 25 °C. Results also indicated that 30 mg/l naphthalene inhibited the biodegradation and the removal efficiency was only 20.2%. Significant degradation (91.7% and 96.3%) of naphthalene occurred when nitrate concentrations were 1.0 and 5.0 mM. Moreover, the maximum degradation rates were 0.13 and 0.18 mg-NAP/(l h) depending on the concentration of nitrate. Based on 16S rDNA analysis, the denitrifying enriched culture was mainly composed of ??-Proteobacteria (19 clones out of a total of 23 clones) and Actinobacteria (4 clones). Using a primer set specific for naphthalene degrading functional gene nahAc, two operational taxonomy units were obtained in the clone library of nahAc. Both of them were closely related to nahAc genes of known species of Pseudomonas. Quantitative polymerase chain reaction (qPCR) was employed to quantify the change of naphthalene-degrading population during the degradation of naphthalene using nahAc gene as the biomarker. The maximum degradation rate and removal efficiency were strongly correlated with nahAc gene copy number, with R² of 0.69 and 0.79, respectively.