An Ultrastructural Investigation of 180°-Rotated Ciliary Meridians in Tetrahymena pyriformis*

SYNOPSIS. An ultrastructural investigation has been carried out on 180°-rotated ciliary meridians (inverted meridians) in Tetrahymena pyriformis temperature-sensitive mutant (mol^b/mol^b), syngen 1, strain B. The longitudinal, transverse and postciliary microtubular bands, the kinetodesmal fiber, and the parasomal sac, are shown to be disposed at a 180° angle to their normal positions or orientations. Other abnormalities are as folows: the first 2 basal bodies of the inverted meridian fail to organize into “couplets” and the inverted meridian intrudes into the anterior pole region; an extra longitudinal microtubular band is found in one of the cell lines.     

Stress-induced testicular hyposensitivity to gonadotropin in rats. Role of the pituitary gland

The time course of stress-induced testicular hyposensitivity to gonadotropins was studied in hypophysectomized or naloxone-treated rats exposed to various periods of immobilization. Blood was collected from a chronically indwelling intra-atrial catheter every hour for luteinizing hormone (LH) and testosterone (T) measurement. Eight hours of immobilization completely suppressed T secretion without significant effect on LH. Human chorionic gonadotropin (hCG, 5 IU/rat, i.m.) induced a marked increase in plasma T levels in normal control groups 3 h post-injection while in immobilized rats the response was completely abolished, even after only 30 min of stress. In hypophysectomized rats, as expected, plasma T levels were undetectable, but, contrary to results obtained in normal animals, hCG induced a similar increase of plasma T levels both in control and stressed rats. Immobilization stress failed to inhibit plasma T values in hypophysectomized rats pretreated for 4 days with human menopausal gonadotropin (hMG) + hCG, while it did so in similarly treated normal animals. Naloxone induced a rise of plasma LH and T levels in control rats, but did not antagonize the stress-induced fall of plasma T concentration. In all groups, steroid testicular content mimicked variations of plasma T values. In particular, in stressed animals the lack of accumulation of testicular 17-hydroxyprogesterone probably reflected a normal activity of 17-20 lyase. These results indicate that stress induces very rapidly a state of Leydig cell hyposensitivity to gonadotropins and a blockade of T biosynthesis. The causal relationship between the two effects is presently not clear but these events seem to be due to stress-induced release of an inhibitory factor of pituitary origin other that endorphin.     

Commitment to the First Cortical Reorganization During Conjugation in Stylonychia mytilus: An Argument for Homology with Cortical Development During Binary Fission

The asexual nature of the first cortical reorganization of conjugation in Stylonychia was analyzed by comparing the effect of amputation performed at different stages of early conjugation to that performed on vegetative cells at different stages of the cell cycle. Amputation of vegetative cells delineated a point of commitment to binary fission at 0.51–0.57 of the cell cycle. Cells amputated before this point were induced to undergo the regenerative mode of asexual development, but those amputated after this point continued with binary fission. In parallel, during conjugation a similar commitment was made around the time of formation of tight mating-pairs: early conjugants amputated around this time might undergo regeneration, and those operated on after this stage continued with the first cortical reorganization as in typical conjugants. The two mates of a pair might differ in their response to amputation, suggesting that the timing of commitment to the first cortical reorganization is not related to the events of conjugation, but rather is individually determined in the vegetative cycle of the cells before they pair up in mating. These observations provide support for the notion that the first cortical reorganization of conjugants is homologous to the asexual mode of cortical development in dividers, according to the theory of developmental heterochrony in the sexual reproduction of hypotrichs. The timing of commitment to the first cortical reorganization was found to temporally correlate with the entrance of the micronuclei into meiosis. Since the first cortical reorganization can proceed without the micronucleus, this raises the possibility that initiation of micronuclear meiosis is closely coupled with, and may be determined by, the commitment to the first cortical reorganization.     

Morphological studies of Asian rice and its related wild species and the recognition of a new Australian taxon

In order to clarify the taxonomy and the interrelationships among Asiatic cultivated rice, Oryza sativa , and its related wild species ( O. rufipogon, O. nivara and O . barthii ), 41 morphological characters were examined. Numerical taxonomic methods were used to analyse the data and to illustrate species relationships.
Distinctive differences among the materials studied suggest the retention of O. rufipogoon, O. nivara and O . sativa as three distinct species. The origin of O. sativa from O. nivara through domestication is discussed. An annual wild taxon from Australia, which had been classified as a form of O. nivara , is shown to be distinct from typical O. nivnra and is raised to specific rank. This species has been named O. meridionalis Ng.     

Effect of Lincocin Treatment on the Greening Process in Bean (Phaseolus vulgaris) Leaves

The effect of lincocin (a plastid protein synthesis inhibitor) treatment on the greening process of bean (Phaseolus vulgaris L.) leaves have been studied. In comparison with control leaves treated ones had a decreased rate of chloroplast development. They had a marked chlorophyll deficiency and a decreased chlorophyll a/b ratio. Some long and short wavelength forms of chlorophyll a were lacking as evidenced from the absorption spectra at 25°C and the fluorescence spectra at 77°K. The –¹⁴CO₂ fixation was inhibited by 80–90% in treated leaves. The fluorescence induced by the measuring light was greater in the treated leaves than in the control ones, and the kinetics of the decline of the relative fluorescence intensity were also different. Electron microscopic studies showed macrogranum-like structures and incomplete membrane vesicles in the treated plastids. After longer treatment a destruction of membranes was observed. The results indicate some structural and functional membrane deficiencies and instability of the membranes.     

Growth Requirements of San Francisco Sour Dough Yeasts and Bakers' Yeast

The growth requirements of several yeasts isolated from San Francisco sour dough mother sponges were compared with those of bakers' yeast. The sour dough yeasts studied were one strain of Saccharomyces uvarum, one strain of S. inusitatus, and four strains of S. exiguus. S. inusitatus was the only yeast found to have an amino acid requirement, namely, methionine. All of the yeasts had an absolute requirement for pantothenic acid and a partial requirement for biotin. Inositol was stimulatory to all except bakers' yeast. All strains of S. exiguus required niacin and thiamine. Interestingly, S. inusitatus, the only yeast that required methionine, also needed folic acid. For optimal growth of S. exiguus in a molasses medium, supplementation with thiamine was required.