Effects of sorbitol addition on the action of free and immobilized hydrolytic enzymes in organic media

The effect of the addition of sorbitol on the activity and stability of enzymes was examined by monitoring transesterification reactions performed in organic media at various water activities (a(w) = 0.08 to 0.97). Lipases from Chromobacterium viscosum and Candida rugosa immobilized on celite, and chymotrypsin, free or immobilized on celite, were used. When the sorbitol-containing enzymes were employed, higher reaction rates and less hydrolysis were observed. Immobilization of chymotrypsin resulted in high activity and operational stability, while the nonimmobilized enzyme was stable only in the presence of sorbitol. The activity of all preparations diminished after washing them with pyridine to remove sorbitol. Furthermore, severe stability problems occurred in the preparations lacking sorbitol. Sorbitol treatment, even after removal of the sorbitol itself, improved the activity of nonimmobilized chymotrypsin relative to the washed control. On the other hand, washing to remove sorbitol had a negative effect on the activity of both coimmobilized lipase and coimmobilized chymotrypsin. Addition of a substrate analogue, N-acetyl-L-phenylalanine, to chymotrypsin yielded a preparation that exhibited higher activity than both the control and its sorbitol-containing counterpart. Differential scanning calorimetry measurements revealed that the chymotrypsin-sorbitol complex was stable against thermal denaturation, undergoing transition at a high temperature (89 degrees C). The transition temperatures of the substrate-containing chymotrypsin and of the control were identical (72 degrees C). (c) 1995 John Wiley & Sons, Inc.     

A scanning electron microscope study of Craspedella sp. from the branchial chamber of redclaw crayfish,Cherax quadricarinatus,from Queensland,Australia

Epidermal topography was examined, including papillate ridges, grooves and ciliated sensory papillae of Craspedella sp. from the branchial chamber of redclaw crayfish, Cherax quadricarinatus, from Queensland, Australia. Rhandites were observed to discharge from ducts opening mainly in a small distal region of the ventral epidermis of the three central (of five) tentacles. These regions, devoid of ciliated sensory papillae, serve to adhere the anterior end of the worms during locomotion. Secretions from glands associated with the posterior attachment organ were observed to discharge from pores on the outside region of the ventral surface of the disc.A comparison of various scanning electron microscopy (SEM) fixation techniques showed that (1) hot fixatives at 90 °C provide most information on the largest number of epidermal structures and (2) different fixation regimes highlight different epidermal features.     

International study on Artemia. LIV. Morphological study of Artemia with emphasis to Old World strains. II. Parthenogenetic populations

Eleven morphometric and one meristic character in 15 parthenogeneticArtemia populations have been studied by using discriminant andcluster analysis as well as scanning electron microscopy.Discriminant analysis revealed five main groups of morphologicalpatterns: (i) the coastal Chinese populations together with apopulation from Kazakhstan, (ii) the inland Chinese salt lakepopulations, (iii) the Greek populations, (iv) one African populationfrom Namibia and (v) a Chinese population from Xuyu (Jiangsuprovince). Cluster analysis was not always in agreement withdiscriminant analysis and these results are discussed.     

Chromatin arrangements in intact interphase nuclei examined by laser confocal microscopy

Using a laser confocal microscope, chromatin arrangements in intact interphase nuclei were investigated in four plant species. Chromosomes in these plants have specific segments that can be stained with the fluorescent dye chromomycin A₃ (CMA). We stained centromeres inHordeum vulgare, sub-telomeric regions inSecale cereale, satellites inChrysanthemum multicore, and the satellites and the short arms of chromosomes with satellites inHemerocallis middendorfii. The following points were shown: (1) In mitotic interphase nuclei, the centromere and the telomeres of both arms touched the nuclear membrane and had evident polarity. Some CMA-bodies in sub-telomeric regions do not contact the nuclear membrane. (2) Differentiated nuclei had a non-random construction. Polarity of chromosomes is maintained, however, the chromosomes are far apart from the nuclear membrane. (3) Associations in sub-telomeric regions in the interphase nuclei ofSecale cereale were probably due to the association of heterochromatic regions with identical repeated sequences rather than telomere associlations. (4) In interphase nuclei ofChrysanthemum multicore, satellites fused during interphase.     

Structural energetics of barstar studied by differential scanning microcalorimetry.

The energetics of barstar denaturation have been studied by CD and scanning microcalorimetry in an extended range of pH and salt concentration. It was shown that, upon increasing temperature, barstar undergoes a transition to the denatured state that is well approximated by a two-state transition in solutions of high ionic strength. This transition is accompanied by significant heat absorption and an increase in heat capacity. The denaturational heat capacity increment at approximately 75 degrees C was found to be 5.6 +/- 0.3 kJ K-1 mol-1. In all cases, the value of the measured enthalpy of denaturation was notably lower than those observed for other small globular proteins. In order to explain this observation, the relative contributions of hydration and the disruption of internal interactions to the total enthalpy and entropy of unfolding were calculated. The enthalpy and entropy of hydration were found to be in good agreement with those calculated for other proteins, but the enthalpy and entropy of breaking internal interactions were found to be among the lowest for all globular proteins that have been studied. Additionally, the partial specific heat capacity of barstar in the native state was found to be 0.37 +/- 0.03 cal K-1 g-1, which is higher than what is observed for most globular proteins and suggests significant flexibility in the native state. It is known from structural data that barstar undergoes a conformational change upon binding to its natural substrate barnase.(ABSTRACT TRUNCATED AT 250 WORDS)     

Vascular morphology of the bovine spermatic cord and testis

Summary The highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 m; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.Supported by the Deutsche Forschungsgemeinschaft and the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

On the fine structure of some Chrysophycean cysts

Fine detail of the ornamentation and pore openings are given of a wide range of Chrysophycean cysts. The function of this intricate sculpturing is unknown. Four new types of cyst are described.     

Effects of Hydroclytic Enzymes on Plant-parasitic Nematodes

Proteases, lipase, and chitinase killed Tylenchorhynchus dubius in vitro and in soil. Tylenchorhynchus dubius was more susceptible to the enzymes than Pratylenchus penetrans. Papain was the most effective protease, and other enzymes were less effective. Heating enzymes to 80 C for 10 min greatly reduced nematicidal effectiveness. Scanning electron micrographs showed that papain and chitinase produced structural changes in the cuticle of T. dubius. Lipase removed a thin outer layer. Papain removed material filling the striata, or furrow, between the horizontal bands. When added to soil, chitinase, lipase, collagenase, and proteases (papain and bromelain) decreased motility of T. dubius populations up to 75%. Bromelain was the most active in soil against T. dubius, and collagenase was the most active in soil against P. penetrans.