TEMPERATURE-DEPENDENT CHANGES IN COLONY SIZE OF THE FRESHWATER PENNATE DIATOM ASTERIONELLA FORMOSA (BACILLARIOPHYCEAE) AND THEIR POSSIBLE ECOLOGICAL IMPLICATIONS1

Changes in colony size (cell number per colony) of Asterionella Formosa Hass. were experimentally evaluated in relation to water temperature using two types of clones having colony sizes of four or eight cells. The clones were isolated from two different temperate freshwater lakes. Both clones showed the same general trend with changing temperature. Most of the colonies were normal in size at low temperatures, but colony size was twice as large at high temperatures. Variable colony sizes were present at low percentages. Colony separation occurred at the oldest connection within the colony after cell division. Culture experiments showed that the rates of specific growth and colony separation were balanced except for a rather short period of time when the temperature was changed. Optical and scanning electron micrography did not show any distinctive morphological structure at the point of connection except for porelli and mucilage pads. Seasonal changes in colony size of A. formosa observed in a freshwater lake are discussed based on these temperature results.     

Genetic analysis of spo0A and spo0C mutants of Bacillus subtilis with a phi 105 prophage merodiploid system.

An 8.0-kilobase chromosomal fragment of Bacillus subtilis which contained an intact spo0A gene was recloned onto temperate phage phi 105 from the rho 11dspo0A+-1 transducing phage. A specialized transducing phage, phi 105-dspo0A+-1, was constructed and used to transduce the spo0A12 mutant strain 1S9. A Spo+ transductant which was a single lysogen of the phi 105dspo0A+-1 transducing phage was isolated. From competent cells of this Spo+ transductant was isolated a Spo- (Spo0A) strain which was immune to phi 105. It was used to prepare a lysate of the phi 105dspo0A12 phage. Transduction of the spo0C9V recE4 strain with the phi 105dspo0A12 and phi 105dspo0A+-1 phages was carried out. The phi 105dspo0A+-1 phage gave rise to a large number of heat-resistant cells, but the phi 105dspo0A12 phage formed no heat-resistant cells. These results indicate that the spo0A12 and spo0C9V mutant genes do not complement each other in the ability to sporulate and that the spo0C9V mutation is located within the spo0A gene. Although the spo0C9V strain was completely asporogenous, the spo0C9V/spo0C9V diploid strain produced heat-resistant cells at a frequency of ca. 10(-3) in the sporulation medium. This result indicates that two copies of the spo0C9V mutant gene partially restore the ability of these cells to sporulate.     

Defective expression of HLA class I antigens: A case of the bare lymphocyte without immunodeficiency

A case of the bare lymphocyte without apparent immunodeficiency was observed in a 33-year-old woman who had no history of severe infections but suffered from sino-bronchial disease. No HLA-A and -B antigens (class I antigens) were detected at the cell surface of lymphocytes, granulocytes, and platelets, but they were expressed, although at a reduced level, on the cultured B lymphoid cell line. T lymphocytes were normal in number and in the relative proportion of T4/T8 and responded to mitogens but not to PPD and candida. HLA-DR antigens (class II antigens) were present on B lymphocytes and showed intermediate MLR-stimulatory capacity, which made it possible to deduce the patient's HLA genotype. She was found to be homozygous at consanguinity for HLA-A, -B, and -DR antigens. The numbers of B lymphocytes, immunoglobulins, and complements were all in the normal range; there was, however, a low level of IgM. Two-dimensional gel analysis of class I antigens revealed the presence of normally expressed beta-2 microglobulins (B2M) and an apparently single set of class I heavy chains, allowing us to consider two alternative cellular mechanisms in this defect; the presence of one abnormal class I structural gene and the regulatory mechanism that acted in cis were suggested.Abbreviations used in this paper MLR mixed lymphocyte culture reaction - B2M beta-2 microglobulin - 2-D two-dimensional - IEF isoelectric focusing - SDS sodium dodecyl sulfate - PAGE polyacrylamide gel electrophoresis - MoAb monoclonal antibody - PBS phosphate-buffered saline - BSA bovine serum albumin - PHA phytohemagglutinin - PWM pokeweed mitogen - mol. wt. molecular weight     

A gene (sleB) encoding a spore cortex-lytic enzyme from Bacillus subtilis and response of the enzyme to L-alanine-mediated germination.

The Bacillus subtilis sleB gene, which codes for the enzyme homologous to the germination-specific amidase from Bacillus cereus, was cloned and its nucleotide sequence was determined. Sequence analysis showed that it had an open reading frame of 918 bp, coding for a polypeptide of 305 amino acids with a putative signal sequence of 29 residues. Enzyme activity was not found in germination exudate of B. subtilis spores, which differs from the case of B. cereus enzyme. A B. subtilis mutant with an insertionally inactivated sleB gene revealed normal behavior in growth and sporulation. However, the sleB mutant was unable to complete germination mediated by L-alanine.     

A Vertical Gradient of the Chloroplast Abundance among Leaves of Chenopodium album

The abundances of chloroplasts in leaves on the main stems ofChenopodium album at different height levels were investigatedin relation to the photosynthetic capacity and light environmentof the leaves. (1) The number of chloroplasts per mesophyllcell decreased with descending position of leaves, except foryoung developing leaves at the top of plants that had smallerchloroplast numbers per cell than matured leaves beneath them.Contents of chlorophyll and ribulose-1,5-bisphosphate carboxylase/oxygenaseper leaf area that were highest in the topmost young leavesand decreased with decreasing height level indicate that thereis a vertical gradient of chloroplast abundance per leaf areadecreasing from the top of the leaf canopy with depth. (2) Light-saturatingrate of photosynthetic oxygen evolution per leaf area of maturedleaves decreased more steeply with decreasing leaf positionthan the chloroplast number per cell. Gradients of chlorophylland the enzyme protein contents were also steeper than thatof the chloroplast number. Loss of photosynthesis in lower leavesis, therefore, ascribed partly to loss of whole chloroplastsand partly to reduced photosynthetic capacities of the remainingchloroplasts. (3) The chloroplast number per cell in newly expandedsecond leaves was comparable to those in leaves that have developedat later stages of the plant growth but decreased graduallyduring leaf senescence both in the dark and light. The formationof the vertical gradient of chloroplast abundance is, therefore,ascribed to loss of whole chloroplasts during senescence ofleaves. (4) Irradiance a leaf receives decreased sharply fromthe top of the canopy with depth. The physiological or ecophysiologicalsignificance of the vertical distribution of chloroplasts amongleaves was discussed taking light environments of leaves intoconsideration. (Received July 31, 1995; Accepted October 20, 1995)     

Responses to T cell receptor/CD3 and interleukin-2 receptor stimulation are altered in T cells from B cell non-hodgkin's lymphomas

T cells infiltrating (T-TIL) B cell non-Hodgkin's lymphomas (NHL) are thought to represent a local host response to the tumor. However, tumor progression in the presence of this T cell infiltrate suggests that the T-TIL may be functionally impaired. To address this issue we determined whether response to stimulation of T-TIL from 25 patients with NHL through the T cell receptor (TCR/CD3) and the interleukin-2 (IL-2) receptor (IL-2R) was intact, since activation of these receptors is important for proliferation and cytokine production. Our results demonstrate defects in response to stimulation via TCR/CD3 and the IL-2R in T-TIL cells from patients with NHL that were not observed with T cells from the peripheral blood. T-TIL showed minimal proliferation to anti-CD3 and only modest proliferation to IL-2 alone or when combined with anti-CD3. Moreover, cytokine production in T-TIL was impaired since stimulation through the TCR/CD3 complex did not induce mRNA for interferon (IFN), IL-2, IL-4 or IL-10. The functional unresponsiveness of these cells may be linked to altered signalling through the TCR/CD3 since an abnormal tyrosine phosphorylation pattern was detected in T-TIL after stimulation with anti-CD3.     

Phenotypic plasticity in age and size at maturity and its effects on the integrated phenotypic expressions of life history traits of Cardamine flexuosa (Cruciferae)

We analyzed variation in phenotypic plasticity of life history traits between two Cardamine flexuosa populations based on differences in plasticity of age and size at maturity. C. flexuosa (Cruciferae) is a facultative, vernalization-sensitive, long-day annual, and its phenology and the phenotypic expressions of many life history traits are largely controlled by photoperiod and vernalization in natural populations. We used plants from two populations which differed in their responses to chilling and photoperiod treatments. The timing of developmental processes was changed by controlling temperature and photoperiod regimes in growth chambers. Plasticity in size at maturity was analyzed as changes in a growth trajectory using two parameters, age at maturity (Δt) and growth rate (k). Both traits showed plasticity, but differences between the populations were found mostly for Δt. Distinctive differences in size at maturity of individuals in the two populations were mainly due to different amounts of plasticity in Δt. Variations in plasticity of nine other life history traits and their associations to age and size at maturity were also analyzed. Variation for eight of the traits can be described, at least in part, as a function of age and size at maturity for both populations, and most of the variation in the total number of seeds was explained by age and size at maturity. Only age at maturity had any effect on changes in resource allocation. The nine life history traits were integrated through associated character expressions with age and size at maturity. Changes in the association between a trait and age and/or size at maturity were rather conservative compared to changes in the plasticity of a trait between the two populations. Associations with age and size at maturity are mostly explicable in terms of inherent relationships in the developmental processes, and they may limit the ecological range expansion and the adaptive evolution of plasticity in C. flexuosa. The negative correlation between reproductive allocation and age at maturity can be a cost of delaying maturation in C. flexuosa.     

A Novel Myosin-like Protein (Myocilin) Expressed in the Connecting Cilium of the Photoreceptor: Molecular Cloning, Tissue Expression, and Chromosomal Mapping

We have isolated a human cDNA clone encoding a novel acidic protein of MW 55,000 that we designated “myocilin” since it has homology to myosin and is localized preferentially in the ciliary rootlet and basal body of the connecting cilium of photoreceptor cells. The deduced amino acid sequence of human myocilin showed significant homologies with nonmuscle myosin ofDictyostelium discoideumin the N-terminal region and also with olfactomedin of bullfrog in the C-terminal region. Myocilin contained a leucine zipper-like motif similar to that seen in kinectin and other cytoskeletal proteins. These findings suggest that myocilin is a novel cytoskeletal protein involved in the morphogenesis of ciliated neuroepithelium such as photoreceptor cells. The myocilin gene (MYOC) was mapped to human chromosome 1q23–q24 by fluorescencein situhybridization.     

Genomic Organization and Complete Nucleotide Sequence of the HumanPWP2Gene on Chromosome 21

The humanPWP2gene is the human homologue of the yeast periodic tryptophan protein 2 (PWP2) gene and is a member of the gene family that contains tryptophan-aspartate (WD) repeats. Genomic sequencing revealed that the humanPWP2gene consists of 21 exons spanning approximately 24 kb and locates just between the two genes EHOC-1 and KNP-I and distal to aNotI site of LJ104 (D21S1460) on chromosome 21q22.3. Analysis of the 5′-flanking DNA sequence revealed that the upstream region of thePWP2gene is associated with a CpG island containing theNotI site of LJ104. SincePWP2is considered to be a candidate for genetic disorders mapped in the 21q22.3 region, the information including nucleotide sequence and genomic organization of thePWP2gene should be invaluable for the mutation analysis of the corresponding genetic disorders.