Avelina Q. Paulsen

Functional and ultrastructural injury to photosynthesis in wheat by high temperature during maturation

Abstract Wheat (Triticum aestivum L. cv. Len) plants were exposed to 15/10, 25/20, and 35/30°C day/night temperature regimes after anthesis until plants grown at 25/20°C reached physiological maturity. Increasing temperature during maturation enhanced leaf senescence, accentuated the loss of chloroplast integrity, increased thylakoid luminal volume and decreased extent of appressed thylakoid membrane area, and accelerated the decline of PSII-mediated electron transport. Stomatal conductance declined slower than other photosynthetic processes at high temperature. Lability of PSII and stability of PSI activities to prolonged high temperature contrasted with measurements of Chl-binding proteins, such as LHCII, type-II LHCI and the PsaA-PsaB polypeptides. While the activity of PSII declined rapidly, the LHCII polypeptides remained as prominent thylakoid membrane components. Activity of PSI, in contrast, was sustained despite a diminished 735:685 nm fluorescence emission ratio and severe damage to the Chl-binding proteins, such as PsaA-PsaB and type-II LHCI. The dissimilar responses of LHCII and type-II LHCI to high temperature injury may be related to their localization in the thylakoid membrane; LHCII, predominantly in the appressed membrane regions, may be relatively shielded from proteolytic activity as compared with type-II LHCI in the exposed membrane regions.

Use of electron microscopic and immunogold labeling techniques to determine polyomavirus recombinant VP1 capsid-like particles entry into mouse 3T6 cell nucleus.

Murine polyomavirus major structural protein VP1 could assemble into capsid-like particles when expressed in the baculovirus system. The recombinant capsid-like particles that were purified by CsCl density gradient centrifugation were capable of packaging host DNA. Electron microscopic and immunogold labeling techniques were used to study the entry of these VP1 recombinant capsid-like particles into mouse 3T6 cells. It was found that these VP1 recombinant capsid-like particles, which lack polyomavirus minor structural proteins (VP2 and VP3), use the same mechanism to enter mouse 3T6 cell cytoplasm and nucleus as that used by native polyomavirus virions.

Murine polyomavirus infection of 3T6 mouse cells shows evidence of predominant necrosis as well as limited apoptosis

The current study was developed to determine if polyomavirus infected 3T6 mouse cells evoked an apoptotic or a necrotic mechanism during infection. Infected cells were analyzed by flow cytometry, transmission electron microscopy (TEM), DNA electrophoresis and by measuring caspase-3 enzymatic activity. Infected cells that were analyzed at 72 h post-infection showed the following: flow cytometry analysis revealed a 5% increase in apoptotic cells and a 46% increase in necrotic cells when compared to uninfected cells; electron microscopy showed 10% cells with characteristic apoptotic morphology and 40% with necrotic appearance; caspase-3 activity was found to increase two fold when compared to uninfected cells and DNA fragmentation (laddering) was clearly evident late in infection. It was concluded that infected cells predominantly showed necrosis, although some cells showed apoptosis in late infection. Recombinant capsid-like particles composed of the polyomavirus structural proteins were not able to induce cell death.

Embryogenesis, hatching and larval development of Artemia during orbital spaceflight☆

Developmental biology studies, using gastrula-arrested cysts of the brine shrimp Artemia franciscana, were conducted during two flights of the space shuttle Atlantis (missions STS-37 and STS-43) in 1991. Dehydrated cysts were activated, on orbit, by addition of salt water to the cysts, and then development was terminated by the addition of fixative. Development took place in 5 ml syringes, connected by tubing to activation syringes, containing salt water, and termination syringes, containing fixative. Comparison of space results with simultaneous ground control experiments showed that equivalent percentages of naupliar larvae hatched in the syringes (40%). Thus, reactivation of development, completion of embryogenesis, emergence and hatching took place, during spaceflight, without recognizable alteration in numbers of larvae produced. Post-hatching larval development was studied in experiments where development was terminated, by introduction of fixative, 2 days, 4 days, and 8 days after reinitiation of development. During spaceflight, successive larval instars or stages, interrupted by molts, occurred, generating brine shrimp at appropriate larval instars. Naupliar larvae possessed the single naupliar eye, and development of the lateral pair of adult eyes also took place in space. Transmission electron microscopy revealed extensive differentiation, including skeletal muscle and gut endoderm, as well as the eye tissues. These studies demonstrate the potential value of Artemia for developmental biology studies during spaceflight, and show that extensive degrees of development can take place in this microgravity environment.

Virus protein assembly in microgravity.

The coat of polyomavirus is composed of three proteins that can self-assemble to form an icosahedral capsid. VP1 represents 75% of the virus capsid protein and the VP1 capsomere subunits are capable of self assembly to form a capsid-like structure. Ground-based and orbiter studies were conducted with VP1 protein cloned in an expression vector and purified to provide ample quantities for capsomere-capsid assembly. Flight studies were conducted on STS-37 on April 5-9, 1991. Assembly initiated when a VP1 protein solution was interfaced with a Ca+2 buffer solution (pH 5.0). After four days a second alignment terminated the assembly process and allowed for glutaraldehyde fixation. Flight and ground-based samples were analyzed by electron microscopy. Ground-based experiments revealed the assembly of VP1 into capsid-like structures and a heterogenous size array of capsomere subunits. Samples reacted in microgravity, however, showed capsomeres of a homogenous size, but lack of capsid-like assembly.

CeReS-18 inhibits growth and induces apoptosis in human prostatic cancer cells

Polypeptide growth factors are positive and negative regulators of prostatic growth and function, and many positive regulators of growth in the prostate have been extensively studied. However, very few inhibitors of prostate cell proliferation have been identified. We have isolated a unique 18‐kDa sialoglycopeptide (CeReS‐18) which inhibits cell proliferation of three separate lines of human prostate cancer cells, as well as inducing cellular cytotoxicity via an apoptotic pathway unrelated to the Bcl‐2 family of proteins.

CeReS-18, a novel cell surface sialoglycopeptide, induces cell cycle arrest and apoptosis in a calcium-sensitive manner

Very few growth inhibitors have been identified whichcan inhibit the proliferation of a broad spectrumof human breast cancer cell lines. CeReS-18, anovel cell surface sialoglycopeptide growth inhibitor, can reversiblyinhibit the proliferation of both estrogen receptor positive(MCF-7) and negative (BT-20) human breast cancer celllines. In addition, at concentrations above those requiredfor the reversible inhibition of cell proliferation, CeReS-18can also induce cell death in MCF-7 cells.Changes in nuclear and cytoplasmic morphology, characteristic ofapoptosis, were detected in MCF-7 cells treated witha cytotoxic concentration of CeReS-18, and internucleosomal DNAcleavage was also observed. The sensitivity of MCF-7and BT-20 cells to the biological properties ofCeReS-18 could be influenced by altering the calciumconcentration in the extracellular growth medium, such thatwhen the calcium concentration in the environment wasdecreased, an increased sensitivity to CeReS-18-induced growth inhibitionand cytotoxicity were observed. The addition of thecalcium chelating agent EGTA to MCF-7 cells, culturedin a normal calcium environment, could mimic theincreased sensitivity to the biological effects of CeReS-18observed under reduced calcium conditions.

Clover development during spaceflight: A model system

The development of legume root nodules was studied as a model system for the examination of gravitational effects on plant root development. In order to examine whether rhizobial association with clover roots can be achieved in microgravity, experiments were performed aboard the KC-135 parabolic aircraft and aboard the sounding rocket mission Consort 3. Binding of rhizobia to roots and the initial stages of root nodule development successfully occurred in microgravity. Seedling germination experiments were performed in the sliding block device, the Materials Dispersion Apparatus, aboard STS-37. When significant hydration of the seeds was achieved, normal rates of germination and seedling development were observed.

Preliminary observations on the effects of selenate on the development of the embryonic skate, Raja eglanteria

Morphogenesis of the clearnose skate, Raja eglanteria, was not significantly inhibited as a result of 7 days of exposure to 1-2 mM selenate in the sea water during Days 59-69 of embryonic development (hatching would normally have occurred at 82 +/- 4 days of incubation). Although corneal transparency appeared normal in the eye, preliminary measurements of the thickness of Bowmans layer of the cornea suggested that it was significantly thinner in the corneas of embryos exposed to 1-2 mM selenate. Selenate is an ion reported to inhibit sulfation of glycosaminoglycans in connective tissue.

Kansas Phytopathological Notes: 1969

Weather Conditions Disease development is closely associated with environmental factors, especially moisture and temperature. Therefore, weather data are helpful in understanding many disease situations. Conditions were dry particularly in western and central Kansas during April. In May and June timely rains favored crops so that a bumper wheat crop of 305 million bushels was harvested. Weather was raier dry during July but rains came in August and September to the extent that wheat seeding was delayed in western Kansas. The fall months were unusually cold so that the late seeded wheat was small during the winter of 1969-70.