Studies on preimplantation development of buffalo embryos

A total of 71 lactating and nonlactating buffalo-cows of the Murrah breed and F(1)-F(3) crossbreds of Murrah x Bulgarian buffalo were used for a year as donors of embryos after a preliminary treatment for superovulation induction with pregnant mare serum gonadotrophin (PMSG) or follicle stimulating hormone (FSH) in combination with prostaglandin F-2 alpha analog (PGF-2 alpha) according to general application procedures in cows. From 36 to 72 h following prostaglandin injection, the buffalo-cows were checked with the help of a teaser bull for detection of estrus. The animals in estrus were inseminated twice either naturally or artificially with frozen semen. Nonsurgical flushing of the uterine horns was done in 45 of the buffalo-cows between 108 and 162 h after the onset of estrus. After slaughter the uterine horns and oviducts of the other 26 animals were flushed separately between 74 and 108 h after the beginning of estrus. Seven late morulae and eight hatched blastocysts were recovered between 114 and 116 h from the onset of estrus as a result of nonsurgical flushing. All of the 40 embryos recovered after 117 h were in the hatched blastocyst stage. As a result of flushing the oviducts and the uterine horns of slaughtered donors between 74 and 100 h, eggs were obtained only from the oviducts, while flushing conducted between 102 and 108 yielded eggs from both the oviducts and the uterine horns.     

Light-induced spectral absorbance changes in relation to photosynthesis and the epoxidation state of xanthophyll cycle components in cotton leaves

When cotton (Gossypium hirsutum L., cv Acaia SJC-1) leaves kept in weak light were suddenly exposed to strong red actinic light a spectral absorbance change took place having the following prominent characteristics. (a) It was irreversible within the first four minute period after darkening. (b) The difference in leaf absorbance between illuminated and predarkened leaves had a major peak at 505 nanometers, a minor peak at 465 nanometers, a shoulder around 515 nanometers, and minor troughs at 455 and 480 nanometers. (c) On the basis of its spectral and kinetic characteristics this absorbance change can be readily distinguished from the much faster electrochromic shift which has a peak at 515 nanometers, from the slow, so-called light-scattering change which has a broad peak centered around 535 nanometers and is reversed upon darkening, and from absorbance changes associated with light-induced chloroplast rearrangements. (d) The extent and time course of this absorbance change closely matched that of the deepoxidation of violaxanthin to zeaxanthin in the same leaves. (e) Both the absorbance change and the ability to form zeaxanthin were completely blocked in leaves to which dithiothreitol (DTT) had been provided through the cut petlole. DTT treatment also caused strong inhibition of that component of the 535-nanometer absorbance change which is reversed in less than 4 minutes upon darkening and considered to be caused by increased light scattering. Moreover, DTT inhibited a large part of nonphotochemical quenching of chlorophyll fluorescence in the presence of excessive light. However, DTT had no detectable effect on the photon yield of photosynthesis measured under strictly rate-limiting photon flux densities or on the light-saturated photosynthetic capacity, at least in the short term. We conclude that it is possible to monitor light-induced violaxanthin de-epoxidation in green intact leaves by measurement of the absorbance change at 505 nanometers. Determination of absorbance changes in conjunction with measurements of photosynthesis in the presence and absence of DTT provide a system well suited for future studies of meachanisms of dissipation of excessive excitation energy in intact leaves.     

The effect of enzyme concentration on the rate of the hydrolysis of cellulose

The relationship among extent of hydrolysis, reaction time, and enzyme dosage was investigated. For this, Sigmacell 50 and pretreated poplar wood (20 g/L) was hydrolyzed with varying dosages of cellulases from three different sources (5 to 100 FPU/g) for time periods ranging from 2 to 94 h. It was found that the formation of glucose can be described by summation of two parallel first order reactions. The extent of hydrolysis at fixed time increases with increasing enzyme dosage in a hyperbolic function. From the empirical data it is possible to calculate the fractions of easily and difficult hydrolyzable cellulose and the digestability which could maximally be obtained at infinite enzyme loadings. In the system Sigmacell 50 and Celluclast the easily and difficult hydrolyzable components are 43.0 and 57.0%, respectively, and the maximum digestability at 94 h is 82.6%. Poplar wood, steam treated at 200 degrees , 220 degrees , and 240 degrees C, showed with Celluclast at 24 h a maximum digestability (weight percentage of wood degraded to glucose) of 43.9, 64.9, and 68.0%. The relationships derived from experimental data allow one to compare objectively the effectiveness of different cellulase enzymes and different pretreatments.     

银缕梅属——中国金缕梅科一新属

在研究中国稀有濒危植物过程中,通过三年观察,作者发现小叶金缕梅绝无花瓣,无疑应从金缕梅族中分出,其形态特征又明显与无花瓣的蚊母树族和弗特吉族各属有差别,故成立新属——银缕梅属。     

Amine Accumulation in Acidic Vacuoles Protects the Halotolerant Alga Dunaliella salina Against Alkaline Stress

Amines at alkaline pH induce in cells of the halotolerant alga Dunaliella a transient stress that is manifested by a drop in ATP and an increase of cytoplasmic pH. As much as 300 millimolar NH₄⁺ are taken up by the cells at pH 9. The uptake is not associated with gross changes in volume and is accompanied by K⁺ efflux. Most of the amine is not metabolized, and can be released by external acidification. Recovery of the cells from the amine-induced stress occurs within 30 to 60 minutes and is accompanied by massive swelling of vacuoles and by release of the fluorescent dye atebrin from these vacuoles, suggesting that amines are compartmentalized into acidic vacuoles. The time course of ammonia uptake into Dunaliella cells is biphasic—a rapid influx, associated with cytoplasmic alkalinization, followed by a temperature-dependent slow uptake phase, which is correlated with recovery of cellular ATP and cytoplasmic pH. The dependence of amine uptake on external pH indicates that it diffuses into the cells in the free amine form. Studies with lysed cell preparations, in which vacuoles become exposed but retain their capacity to accumulate amines, indicate that the permeability of the vacuolar membrane to amines is much higher than that of the plasma membrane. The results can be retionalized by assuming that the initial amine accumulation, which leads to rapid vacuolar alkalinization, activates metabolic reactions that further increase the capacity of the vacuoles to sequester most of the amine from the cytoplasm. The results indicate that acidic vacuoles in Dunaliella serve as a high-capacity buffering system for amines, and as a safeguard against cytoplasmic alkalinization and uncoupling of photosynthesis.