The structure of the incompatibility factors of Schizophyllum commune: Constitution of the three classes of B factors

Summary The B factors of Schizophyllum commune are of 3 classes: The high recombining class I has 7 alleles and 7 alleles; the low recombining classes are class II with 7 allels and probably 2 alleles and class III with probably 2 (or also 2) alleles and 7 allels. A fourth hypothetical class (-) was not found and either does not exist or is indistinguishable from class III by the tests employed. The and alleles differ from and by either (a) mutations affecting both mating specificity and recombination frequency, or (b) deletions involving most of the B region.The research was supported by a grant from the Atomic Energy Commission of the U.S. No. (30-1)-3875 and was performed at the Biological Laboratories, Harvard University, Cambridge, Mass., U.S.A.     

On the inducibility of nitrate transport by tobacco cells

The question as to whether the nitrate transport system is induced by nitrate was addressed using a cell suspension of the XD line of Nicotiana tabacum L. cv. Xanthi as an experimental system. The cells were grown on area as the sole nitrogen source, and tungstate was used to render nitrate reductase non-functional. To avoid shock due to vacuum filtration, the cells, were harvested by gravity filtration. Nitrate uptake by cells, which were harvested, transferred to fresh medium, and immediately exposed to nitrate (freshly harvested cells), displayed a lag period of about 3 h.
In cells which were given incubation periods in fresh medium before exposure to nitrate (preincubated cells), the lag period was considerably shortened. After 3 h of preincubation in the absence of nitrate (recovered cells), the lag period was almost completely eliminated. Cycloheximide inhibited nitrate uptake by recovered cells within minutes, and prevented the development of nitrate uptake in freshly harvested cells. Cycloheximide did not affect uptake of α-aminoisobutyric acid (AIB) within the first 2 h after its addition. Recovery of the membrane potential from a low value just after the harvest of the cells to a maximal value 3 h later, was observed using the lipophilic cation methyltriphenylphosphonium (MTPP⁺), supplied at low concentrations, as a probe. Depolarization of the membrane potential by MTPP⁺, at the millimolar range, caused a rapid inhibition of nitrate uptake by recovered cells. The results indicate that nitrate transport by the XD cells depends on the membrane potential and on protein components with short half life. In addition, it requires a continuous protein synthesis. The effects of physical manipulation on nitrate uptake are discussed.     

The effects of calcium deficiency on Cucurbita pepo L. hypocotyl cells: A 31P nuclear-magnetic-resonance study

Calcium deficiency in zucchini (Cucurbita pepo L.) is associated with reduced growth and a reduced ability to transport auxin (Allan and Rubery, 1991, Planta 183, 604–612). An investigation of the effects of calcium-deficiency on zucchini hypocotyl cells was made using weak-acid uptake and ³¹P-nuclear-magneticresonance (³¹P-NMR) spectroscopy in vivo and in tissue extracts. Calcium-deficient tissue had the same cytoplasmic and vacuolar pHs as normal tissue when extracellular pH was near neutral. At acidic external pH the vacuolar pH was lower in deficient tissue. Adenine nucleotides were present predominantly as ATP in both control and calcium-deficient tissues. Addition of calcium to calcium-deficient tissue, under conditions which cause recovery of auxin transport induced no changes in the ³¹P-NMR spectra of deficient tissue. The content of mobile, phosphorylated metabolites was reduced in calcium-deficient tissue in comparison to control tissue. However, a substantial increase in the content of phosphorylcholine occurs in calcium-deficient tissues compared with controls; this may reflect changes in lipid turnover in calcium-stressed cells. We wish to thank Drs. Terry Moore and Jamie Vandenberg for technical assistance and Professor Peter Morris for providing the gated oxygen device. A.C.A. thanks the Cambridge Commonwealth Trust for a Prince of Wales Scholarship and the O.R.S. Awards Scheme for an award.     

CAENORHABDITIS ELEGANS Fertilization-Defective Mutants with Abnormal Sperm

Seven new fertilization-defective mutants of C. elegans have been isolated and characterized; six are temperature sensitive, one is absolute and all are autosomal recessive. One mutation is in a previously described gene, while the other six define six new fer genes that appear to code for sperm-specific functions necessary for normal fertilization. In all fer mutants, both males and hermaphrodites accumulate sperm in near normal numbers. In hermaphrodites, mutant sperm contact the oocytes, but fail to fertilize them. Instead, the sperm are swept into the uterus by the passing oocytes and are expelled when oocytes are laid. Males of two fer mutants do not transfer sperm during copulation, but the other mutant males transfer sperm that fail to move to the spermatheca. Spermatozoa from fer-1 and fer-4 mutants are motility-defective in vitro as well as in vivo, and their pseudopods have an altered morphology. The period of development during which mutant hermaphrodites are temperature sensitive for fertility overlaps the time of sperm development. Some mutants are temperature sensitive throughout the entire period, and others are temperature sensitive during or just prior to spermiogenesis. In fer-4/+ and fer-7/+ males, the fertility of the mutation-bearing sperm is diminished, reducing the transmission ratio. This implies some post-meiotic expression of these genes.—This set of mutants provides a variety of functional and structural alterations in nematode sperm that should help identify and analyze gene products involved in sperm morphogenesis and motility.     

Some observations in tetraclita squamosa rufotincta Pilsbry

Aspects of the biology of Tetraclita squamosa rufotincta Pilsbry were investigated. Although a tropical species, on the shores at Elat, Israel, its breeding is virtually restricted to the colder winter months. The causal factors are considered and the results of some experimental work relative to temperature control given.For a cirripede, T.s. rufotincta has a remarkably large ‘egg’ — unusual in a tropical or even warm-water species. The egg size is compared with that of other species and the survival value of large size considered; excess nutrients are carried over from the embryo to at least the first planktonic larva, and may aid survival in a relatively nutrient poor environment.The animals do not become sexually mature until the second year after their settlement. Growth takes place largély in the colder winter months and is seasonally separated from the period when gonadal tissue is developed.     

Selective expression of murine lymphocyte alloantigens controlled by the X-chromosome

Alloantisera specific to X-chromosome linked lymphocyte membrane antigens (Ly-X) were prepared by immunizing F1 male mice with identical F1 female lymphocytes. Independent B cell specific (anti Lyb-X) and T cell specific (anti Lyt-X) antibodies were detected. The Lyt-X antigen was expressed on Lyt-2⁺, 3⁺, and on Tla^–, Lyt-1⁺, 2⁺, 3⁺ T cell subpopulations. The problem of X-chromosome inactivation and the relationship ofH-2-linkedIr genes and Ia antigens, with X-linkedIr genes and lymphocyte alloantigens are discussed.     

Correlation between changes in the membrane organization and susceptibility to phospholipase C attack induced by ATP depletion of rat erythrocytes

About 20 and 43% of the total membrane phospholipids are hydrolized in fresh rat erythrocytes by treatment with phospholipase C (Bacillus cereus), or both sphingomyelinase and phospholipase C, respectively, without causing cell lysis. Treatment of ATP-depleted cells with phospholipase C alone results in 50% hydrolysis and extensive lysis. Depletion of ATP causes a marked increase in the aggregation of intramembranous particles accompanied by a similar increase in the smooth area between the particle clusters as revealed by the freeze-etch technique. Such changes are not induced by extensive phospholipid hydrolysis in absence of cell lysis in fresh cells.Based on these and additional data, it is suggested that the membrane phospholipid organization can be divided into 3 types: phospholipids exposed to phospholipase C; phospholipids protected against phospholipase C by presence of sphingomyelin; phospholipids which can be exposed following alteration of the proteinlipid interactions. Such alterations which might be induced by a variety of means, including ATP depletion, might result in clustering of intramembranous particles and increase of the free lipid bilayer phase of the membrane.     

Zoogeography of Intertidal Communities in the West Indian Ocean as Determined by Ocean Circulation Systems: Patterns from the Tetraclita Barnacles

The Indian Ocean is the least known ocean in the world with the biogeography of marine species in the West Indian Ocean (WIO) understudied. The hydrography of WIO is characterized by four distinct oceanographic systems and there were few glacial refugia formations in the WIO during the Pleistocene. We used the widely distributed intertidal barnacle Tetraclita to test the hypothesis that the distribution and connectivity of intertidal animals in the WIO are determined by the major oceanographic regime but less influenced by historical events such as Pleistocene glaciations. Tetraclita were studied from 32 locations in the WIO. The diversity and distribution of Tetraclita species in the Indian Ocean were examined based on morphological examination and sequence divergence of two mitochondrial genes (12S rDNA and COI) and one nuclear gene (histone 3, H3). Divergence in DNA sequences revealed the presence of seven evolutionarily significant units (ESUs) of Tetraclita in WIO, with most of them recognized as valid species. The distribution of these ESUs is closely tied to the major oceanographic circulation systems. T. rufotincta is distributed in the Monsoonal Gyre. T. ehsani is present in the Gulf of Oman and NW India. Tetraclita sp. nov. is associated with the Hydrochemical Front at 10°S latitude. T. reni is confined to southern Madagascan and Mauritian waters, influenced by the West Wind Drift. The endemic T. achituvi is restricted to the Red Sea. Tetraclita serrata consists of two ESUs (based on mtDNA analysis) along the east to west coast of South Africa. The two ESUs could not be distinguished from morphological analysis and nuclear H3 sequences. Our results support that intertidal species in the West Indian Ocean are associated with each of the major oceanographic circulation systems which determine gene flow. Geographical distribution is, however, less influenced by the geological history of the region.     

B lymphocyte inhibition of anti-tumor response depends on expansion of Treg but is independent of B-cell IL-10 secretion

The mechanisms by which B lymphocytes inhibit anti-tumor immunity remain poorly understood. Murine EMT-6 mammary tumors grow readily in immune competent mice (BALB/c), but poorly in B-cell-deficient μ^?/? BALB/c mice (BCDM). T regulatory cell (Treg) expansion and function were impaired in BCDM compared with BALB/c. In this study, we compared tumor growth, Treg cell proliferation, tumor lymphocyte infiltration and cytolytic T cell activity in BALB/c, BCDM and BCDM partially reconstituted with B cells by adoptive transfer (BCDM+B). Partial reconstitution of BCDM with adoptively transferred B cells restored EMT-6 tumor growth, which was independent of IL-10 secretion by B cells. Instead, high frequencies of intratumoral B cells were associated with increased recruitment and proliferation of Treg cells within the tumor microenvironment. The B-cell-dependent accumulation of Treg within the tumor microenvironment was associated with reduced tumor infiltration by CD49+ NK and CD8+ T cells and reduced cytotoxic T cell activity against EMT-6 targets. Our studies indicate that tumor-dependent immunosuppression of T-cell-mediated anti-tumor immunity is coordinated within the tumor microenvironment by B-cell-dependent cross talk with Treg cells, which does not require production of IL-10 by B cells.