Factors affecting spore formation in a Candida albicans strain

Growth and spore formation of Candida albicans Y-45 was enhanced by low oxygen tension. Mycelium and chlamydospores were abundantly found on rice infusion-Tween 80 agar within 48 to 96 h, and abundant chlamdospore production occurred most rapidly under reduced oxygen tension and incubation at 30 degrees C. Zn, Mg, Mn, anf Fe were tested for their ability to promote filamentation in C. albicans Y-45. Filamentation under conditions of low Mg and high Mn suggested that morphogenesis is possibly correlated with the presence of salts of these heavy metals.     

The transport of morphologically abnormal sperm in the female reproductive tract of mice

Mice of the PL/J strain exhibit a high percentage of morphologically abnormal sperm and provide a model for studying the function of abnormal sperm. The ability of such sperm to reach the site of fertilization within the female reproductive tract has been investigated. We have found a decrease in the percentage of structurally abnormal sperm within the population that reaches the oviduct. This observation suggests either that there is an active selection against abnormal sperm or that they are physiologically disadvantaged in reaching the site of fertilization.     

500 MHz H-NMR studies of bile salt-phosphatidylcholine mixed micelles and vesicles Evidence for differential motional restraint on bile salt and phosphatidylcholine resonances

¹H nuclear magnetic resonance (NMR) spectra at 500 MHz have been obtained for taurocholate/egg phosphatidylcholine mixtures of varying composition. The excellent chemical shift dispersion permits identification of most resonances for each component. This high-resolution character of the NMR spectra is retained until the phosphatidylcholine (PC) mole fraction exceeds 60–70% (the exact limit depends on ionic strength). ¹H linewidths have been monitored as a function of solute composition in order to evaluate trends in local molecular mobility of each component as the distribution of aggregate particles is varied, and to examine the effects of added NaCl in altering micellar size and shape. Although prior light scattering studies (Mazer, N.A., Benedek, G.B. and Carey, M.C. (1980) Biochemistry 19, 601–615) and our own work indicate a 6-fold increase in particle hydrodynamic radius from pure taurocholate micelles to 1 : 1 taurocholate/PC mixtures containing 150 mM NaCl, both lipid components retain substantial motional freedom and exhibit narrow NMR signals in this compositional region. As the solubilization limit for PC is approached (approx. 2:1 PC:taurocholate), differential behavior is observed for the two components: the motion of taurocholate becomes preferentially restricted, while polar portions of the PC remain mobile until large multilayers predominate.     

DIFFERENTIAL ENRICHMENT OF CELLS FROM EMBRYONIC RAT CEREBRA BY CENTRIFUGAL ELUTRIATION

—Centrifugal elutriation was used to obtain different populations of cells dissociated from 16-day-old rat embryo cerebra. The cell populations recovered were viable and could be maintained for several weeks in vitro. Sterile conditions were maintained throughout a preparation. Rat pups were removed by Caesarean section, the cerebra dissected and the cells dissociated by brief exposure to trypsin (0.125%, 6 min). An equivalent volume of elutriation medium (Dulbecco's medium containing 1% fetal calf serum, sodium bicarbonate, penicillin and streptomycin, EDTA, and deoxyribonuclease) was added to the trypsin-cell suspension, the dissociated cells pelleted, resuspended in elutriation medium and counted. Up to 4 x 10⁸ cells were injected into the previously sterilized elutriator. Seven fractions were usually recovered from a preparation. The first fraction contained primarily red blood cells and cell debris, which could not be maintained in vitro. Upon culture, fraction 2 consisted of predominantly non-neuronal cells, while fractions 3–6 contained neuronal and non-neuronal cells. The morphological characteristics of the neurons differed in these fractions. Fraction 7 contained cells that had reaggregated during the elutriation procedure and exhibited a variety of cell types in vitro.     

γ-Glutamylamine cyclotransferase

Summary -Glutamylamine cyclotransferase, an enzyme found in a number of animal tissues and cells, catalyzes the conversion of -(L--glutamyl)-L-lysine to free lysine and 5-oxo-L-proline as well as the release of free amines and the formation of 5-oxo-L-proline from a variety of other L--glutamylamines. Among its substrates are both the mono- and di--glutamyl derivatives of putrescine, spermidine and spermine, and a derivative of -(L--glutamyl)-L-lysine in which both the -amino group and the carboxyl group of the lysine moiety are blocked. The enzyme does not act on most -glutamyl--amino acids, nor is it active toward the -lysyl derivatives of L-aspartic acid or D-glutamic acid. Derivatives of -(L--glutamyl)-L-lysine in which the -amino or the -carboxyl function of the glutamyl moiety is blocked also do not serve as substrates. The specificity of -glutamylamine cyclotransferase is in accordance with the proposal that it functions biologically in the latter stages of the catabolism of products of the action of transglutaminases. Some suggestions as to the manner in which -glutamylamine cyclotransferase serves this function are made based on present knowledge of protein degradation.     

Fine structure of Merkel cells in lampreys

Summary The structure of Merkel cells occurring in the epidermis of adult and larval stages of Lampetra spp. is described; it is comparable to that reported from the gnathostome classes. The cells bear microvilli, grouped on the distal and proximal aspects, and are associated with sparsely branching and varicose nerve fibres. One branch of the neurite bears a spur-like process which indents the proximal side of the Merkel cell. Most of the specific Merkel granules are situated in the vicinity of this neurite projection; the cell membrane adjacent to the tip of the spur process bears structures resembling presynaptic densities. Occasionally, desmosome-like junctions are found between the neurite and the Merkel cell.The authors thank the Fresh Water Biological Association and the Department of Biological Sciences, University of Bath, for supplying the material, Dr. H. Fox for giving some prepared blocks of Lampetra planeri adults, Mr. B.L. Pirie for technical assistance, and the Science Research Council for support through grant GR/A/3740.6     

The second polar lobe of theSabellaria cementarium embryo plays an inhibitory role in apical tuft formation

Summary The embryo ofSabellaria cementarium (Polychaeta) forms a polar lobe at each of the first two cleavage divisions which becomes absorbed into one of the blastomeres at the end of the division. Lobe removal experiments show that the polar lobe preceding first cleavage is necessary for the development of the apical tuft and the posttrochal region of the trochophore larva. The polar lobe preceding second cleavage is smaller than the first polar lobe and is necessary only for post-trochal region development. In blastomere isolation experiments, isolates containing the C but not the D blastomere form apical tufts. Isolates containing the D but not the C blastomere do not form apical tufts. When the polar lobe preceding second cleavage is removed and the C and D blastomeres are separated and raised in isolation, each can form an apical tuft. When the second cleavage is equalized with sodium dodecyl sulfate (SDS) such that both the C and the D blastomeres receive second polar lobe material, no apical tuft is formed. These results suggest that apical tuft determinants are distributed to both the C and D blastomeres at second cleavage but that the second polar lobe contains an inhibitor for apical tuft formation which is shunted to the D blastomere after the completion of second cleavage.     

Transformation of Adenine to 8-Hydroxyadenine by Strains of Oerskovia xanthineolytica

The 8-hydroxy derivative of adenine (6-amino-1,7-dihydro-8H-purin-8-one) is produced from adenine by two Oerskovia xanthineolytica strains. This transformation by a microorganism has not been reported previously. No novel products of dissimilation of xanthine (3,7-dihydro-1H-purine-2,6-dione) or hypoxanthine (1,7-dihydro-6H-purin-6-one) were found. Xanthine was oxidized to uric acid, but intermediates in the breakdown of hypoxanthine could not be demonstrated.