Substrate effects in tower loop reactors

Summary Hansenula polymorpha was cultivated in a bubble column loop bioreactor employing ethanol and/or glucose as substrates. By varying the substrate concentration, the cultivations were carried out in non-limited, substrate limited and oxygen transfer limited growth ranges. The influence of the transitions from one range to another on reactor performance (OTR,k _L a, a) and cell productivity () were investigated. When employing ethanol as a substrate, the concentration considerably influences the fluid dynamics, mass transfer phenomena and cell productivity. When employing glucose as a substrate, glucose repression occurs. At high glucose concentrations no transition into the oxygen transfer limited growth is possible. The ethanol produced during the glucose repression influences the fluid dynamics, mass transfer phenomena and productivity. With decreasing glucose concentration the glucose repression can be gradually eliminated.     

Foam behaviour of biological media

Summary A simple method was developed for evaluating foam stability. The influence of KCl and MgSO₄ on foam stability of bovine serum albumin foams was investigated. These salts increase foaminess, but diminish foam stability by the same degree. Thus there is little overall.     

Degradation of long chain n-alkanes by Chlorococcales

Summary Four out of thirty-one algae strains belonging to the order Chlorococcales exhibited good growth on solid media containing n-alkanes. Chlorella vulgaris (397) was able to degrade n-tridecane in cooxidation. The corresponding secondary alcohols and ketones in C₂-to C₇-position could be identified in the culture broth. The same oxidation products could be found in the media of cultures grown in darkness with the addition of glucose. This demonstrates a subterminal degradation pathway of C. vulgaris.There was no indication for a mono-or diterminal oxidation of alkanes by algae.The fatty acid pattern of lipids exhibited an incease in long chain acids and a decrease in shorter chain acids. The growth rate of cells grown on alkanes increased after 72 h, but the release of autospores was retarded.     

Role of S-adenosylhomocysteine hydrolase in adenosine metabolism in mammalian heart.

S-Adenosylhomocysteine hydrolase of mammalian hearts from different species is exclusively a cytosolic enzyme. The apparent Km for the guinea-pig enzyme was 2.9 microM (synthesis) and 0.39 microM (hydrolysis). Perfusion of isolated guinea-pig hearts for 120 min with L-homocysteine thiolactone (0.23 mM) and adenosine (0.1 mM), in the presence of erythro-9-(2-hydroxynon-3-yl)adenine to inhibit adenosine deaminase, caused tissue contents of S-adenosylhomocysteine to increase from 3.5 to 3600 nmol/g. When endogenous adenosine production was accelerated by perfusion of hearts with hypoxic medium (30% O2), L-homocysteine thiolactone (0.23 mM) increased S-adenosyl-homocysteine 17-fold to 64.3 nmol/g within 15 min. In the presence of 4-nitro-benzylthioinosine (5 microM), an inhibitor of adenosine transport, S-adenosylhomocysteine further increased to 150 nmol/g. L-Homocysteine thiolactone decreased the hypoxia-induced augmentation of adenosine, inosine and hypoxanthine in the tissue and the release of these purines into the coronary system by more than 50%. Our findings indicate that L-homocysteine can profoundly alter adenosine metabolism in the intact heart by conversion of adenosine into S-adenosylhomocysteine. Adenosine formed during hypoxia was most probably generated within the myocardial cell.     

Ultrastructure of the lateral-line sense organs of the ratfish,Chimaera monstrosa

Summary The ultrastructure of the lateral-line neuromasts in the ratfish, Chimaera monstrosa is described. The neuromasts rest at the bottom of open grooves and consist of sensory, supporting, basal and mantle cells. Each sensory cell is equipped with sensory hairs consisting of a single kinocilium and several stereocilia. There are several types of sensory hair arrangement, and cells with a particular arrangement form patches within the neuromast. There are two types of afferent synapse. The most common afferent synapse has a presynaptic body and is typically associated with an extensive system of anastomosing tubules on the presynaptic side. When the tubules are absent, vesicles surround the presynaptic body. These synapses are often associated into synaptic fields, containing up to 35 synaptic sites. The second type of afferent synapse does not have a presynaptic body and is not associated with the tubular system. The afferent synapses of the second type do not form synaptic fields and are uncommon. The efferent synapses are either associated with a postsynaptic sac or more commonly with a strongly osmiophilic postsynaptic membrane. The accessory cells are similar to those in the acoustico-lateralis organs of other aquatic vertebrates. A possibility of movement of the presynaptic bodies and of involvement of the tubular system in the turnover of the transmitter is discussed. A comparison of the hair tuft types in the neuromasts of Ch. monstrosa with those in the labyrinth of the goldfish and of the frog is attempted.     

The relationship between the nuage and the chromatoid body during spermatogenesis in the Rat

Summary Cytoplasmic structures ultrastructurally similar to the nuage are present in the cytoplasm of all spermatogenic cells in adult rats. The nuage is a discrete organelle which should not be confused with the chromatoid body. In step 7–8 spermatids transient contact is established between the nuage and the chromatoid body. This indicates a very specific recognition of the nuage by the chromatoid body. It is suggested that the nuage and the chromatoid body are separate cell organelles the functions of which are somehow related to each other.