The Sertoli cell of the water buffalo (Bubalus bubalis) during the spermatogenic cycle

Summary Ultrastructural features and morphometric evaluations of buffalo Sertoli cells are reported for the six phases of the spermatogenic cycle. The phases of the tubular seminiferous epithelium are identified according to characteristic cellular associations with completed spermiation as demarcation between two cycles. Average tubular diameter (245 m) and epithelial height (61 m) do not vary significantly during the cycle. The relative Sertoli cell volume in the seminiferous epithelium varies between 30% (phase 4) and 39% (phase 8). The calculated volume of a single Sertoli cell increases from a nadir of 7118 m³ in phase 3 abruptly to a maximum of 8968 m³ in phase 4 and is then gradually reduced during the following phases. The Sertoli cell surface area shows a similar trend: it amounts to 11105 m² in phase 3 and to 14260 m² in phase 4. The contact area of the Sertoli cell with adjacent cells and structures is subject to characteristic changes; from the expansion of basal Sertoli-Sertoli contacts it is concluded that the blood-testis barrier in the buffalo is particularly tight during phases 8, 1 and 2. The irregularly contoured nucleus contains a vesicular nucleolus, has a calculated volume from 465 m³ to 543 m³ and occupies 5 to 7% of the cell. Volume percentages of mitochondria (4%), Golgi apparatus and lysosomal bodies are rather constant during the cycle. Whorls and orderly arranged aggregates of the smooth endoplasmic reticulum occur in basal location as well as in close association with elongating spermatids. Smooth ER is the organelle that exhibits the most prominent changes during the Sertoli cell cycle: it occupies 5.79% in phase 3 and 20.9% in phase 4 of the total cellular volume. Phagocytosis of residual bodies is insignificant in this species and a lipid cycle is absent in buffalo Sertoli cells.     

Streptomyces glucose/xylose isomerase has a single active site for glucose and xylose

A kinetic method which allows one to evaluate whether an enzyme acting on two different substrates has one or two active sites was employed to study the active site of glucose isomerase which catalyses the isomerization of both glucose and xylose. The experimental data on the rates of hydrolysis of mixtures of various concentrations of glucose and xylose by the glucose isomerase from Streptomyces coincides well with the theoretical values calculated for the case of a single active site.     

Device for miniscale isoelectric focusing of proteins

A simple device is developed for mini-scale electrofocusing of proteins. The main apparatus consists of only two glass tubes joined by a small tubing. No special cooling system, stopcocks, stands, etc., are needed. Even the need for a peristaltic pump for fractionation is eliminated. The apparatus does not require very high voltages and the amount of Ampholines is drastically reduced. The model can be used for analytical as well as semi-quantitative purposes.     

Insight into microwave irradiation and enzyme catalysis in enantioselective resolution of dl-(±)-3-phenyllactic acid

Lipase catalyzed kinetic resolution of DL-(±)-3-phenyllactic acid (DL-(±)-3-PLA) was investigated to study the synergistic effect of microwave irradiation and enzyme catalysis. Lipases from different sources were employed for the transesterification of DL-(±)-3-PLA under otherwise similar conditions, among which Novozyme 435 efficiently catalyzed the resolution of DL-(±)-3-PLA to L-(-)-O-acetyl-3-PLA using vinyl acetate as the acyl donor, showing excellent conversion (49?%) and enantiomeric excess (>99?%). The effect of various parameters affecting the initial rate, conversion and enantiomeric excess of the reaction were studied to establish kinetics and mechanism. There is a synergism between enzyme catalysis and microwave irradiation; an increase in initial rates up to 1.8-fold was observed under microwave irradiation than that under conventional heating. The analysis of initial rate data showed that reaction obeys ternary complex (ordered bi-bi) mechanism with inhibition by DL-(±)-3-PLA. The calculated and simulated rates match very well showing the validity of the proposed kinetic model.     

Competition between Folding, Native-State Dimerisation and Amyloid Aggregation in β-Lactoglobulin

We show that a series of peptides corresponding to individual β-strands in native β-lactoglobulin readily form amyloid aggregates and that such aggregates are capable of seeding fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are reduced. By contrast, preformed fibrils corresponding to only one of the β-strands that we considered, βA, were found to promote fibril formation by a full-length form of β-lactoglobulin in which the disulfide bonds are intact. These results indicate that regions of high intrinsic aggregation propensity do not give rise to aggregation unless at least partial unfolding takes place. Furthermore, we found that the high aggregation propensity of one of the edge strands, βI, promotes dimerisation of the native structure rather than misfolding and aggregation since the structure of βI is stabilised by the presence of a disulfide bond. These findings demonstrate that the interactions that promote folding and native-state oligomerisation can also result in high intrinsic amyloidogenicity. However, we show that the presence of the remainder of the sequence dramatically reduces the net overall aggregation propensity by negative design principles that we suggest are very common in biological systems as a result of evolutionary processes.     

<Emphasis Type="Italic">α</Emphasis>-Amylase inhibitor-1 gene from <Emphasis Type="Italic">Phaseolus vulgaris</Emphasis> expressed in <Emphasis Type="Italic">Coffea arabica</Emphasis>plants inhibits α-amylases from the coffee berry borer pest

Background  

Coffee is an important crop and is crucial to the economy of many developing countries, generating around US70 billion per year. There are 115 species in the < i > Coffea < /i > genus, but only two, < i > C. arabica < /i > and < i > C. canephora < /i > , are commercially cultivated. Coffee plants are attacked by many pathogens and insect-pests, which affect not only the production of coffee but also its grain quality, reducing the commercial value of the product. The main insect-pest, the coffee berry borer ( < i > Hypotheneumus hampei < /i > ), is responsible for worldwide annual losses of around US70 billion per year. There are 115 species in the Coffea genus, but only two, C. arabica and C. canephora, are commercially cultivated. Coffee plants are attacked by many pathogens and insect-pests, which affect not only the production of coffee but also its grain quality, reducing the commercial value of the product. The main insect-pest, the coffee berry borer (Hypotheneumus hampei), is responsible for worldwide annual losses of around US500 million. The coffee berry borer exclusively damages the coffee berries, and it is mainly controlled by organochlorine insecticides that are both toxic and carcinogenic. Unfortunately, natural resistance in the genus Coffea to H. hampei has not been documented. To overcome these problems, biotechnological strategies can be used to introduce an α-amylase inhibitor gene (α-AI1), which confers resistance against the coffee berry borer insect-pest, into C. arabica plants.