A comparative analysis of photosynthetic characteristics of hulless barley at two altitudes on the Tibetan Plateau

To determine the photosynthetic characteristics of C₃ plants and their sensitivity to CO₂ at different altitudes on the Tibetan Plateau, hulless barley (Hordeum vulgare L. ssp. vulgare) was grown at altitudes of 4,333 m and 3,688 m. Using gas-exchange measurements, photosynthetic parameters were simulated, including the maximum net photosynthesis (P _max) and the apparent quantum efficiency (α). Plants growing at higher altitude had higher net photosynthetic rates (P _N), photosynthesis parameters (P _max and α) and sensitivities to CO₂ enhancement than plants growing at lower altitude on the Tibetan Plateau. The enhancements of P _N, P _max, and α for plants growing at higher altitude, corresponding with 10 μmol(CO₂) mol⁻¹ increments, were approximately 0.20∼0.45%, 0.05∼0.20% and 0.12∼0.36% greater, respectively, than for plants growing at lower altitude, respectively, where CO₂ levels rose from 10 to 170 μmol(CO₂) mol⁻¹. Therefore, on the Tibetan Plateau, the changes in the photosynthetic capacities and the photosynthetic sensitivities to CO₂ observed in the C₃ plants grown above 3,688 m are likely to increase with altitude despite the decreasing CO₂ partial pressure.     

Structural basis of human erythrocyte glucose transporter function in reconstituted system. Hydrogen exchange

Hydrogen exchange kinetic behavior of human erythrocyte glucose transporter protein in vesicles was studied in the absence and in the presence of D-glucose or a well known inhibitor, cytochalasin B. This is to detect a proposed channel of water penetrating into the protein through which the sugar molecule passes and to monitor any conformational changes induced by the substrate or inhibitor. Analyses of the kinetic data revealed several classes of hydrogens which exchange with readily distinguishable rates. Of 660 hydrogens detected per transporter, approximately 30% exchanged with rates generally characterized as those of free amide hydrogens indicating they are interfaced to solvent water. Since the transporter is known to be embedded deep in the hydrophobic area of the membrane with minimum exposure to the outside of the membrane lipid bilayer, a significant portion of these free amide hydrogens must be at the purported channel rather than outside of the membrane. D-Glucose and cytochalasin B affected the exchange kinetics of these presumably channel-associated free amide hydrogens rather differently. D-Glucose reduced the apparent rate constants, but not the total number. Cytochalasin B on the other hand reduced the total number to one-half without significantly changing the apparent rate constants. The remaining 70% of the labeled hydrogens exchanged with much slower rates which vary 10-10,000-fold, indicating that they are internally structured peptide amide and side chain hydrogens. Both D-glucose and cytochalasin B further reduced the rates of these hydrogens, indicating a global stabilization of the protein structure.     

Clinical manifestations of taeniasis in Taiwan aborigines.

From 1974 to 1989, a total of 24,500 aborigines at 67 villages in ten mountainous districts/towns in Taiwan were examined for the Taiwan Taenia infection and 12% were found to be infected. In order to define the clinical manifestations of taeniasis caused by the Taiwan Taenia, 1661 aborigines in ten mountainous districts were surveyed. The overall clinical rate was 76%. The clinical rate was highest among Atayal aborigines (81%), followed by Bunun (66%) and Yami (61%) aborgines and lowest among Ami aborigines (40%). Among 1153 infected people, 10% had passed gravid segments in the faeces for less than 1 year, 24% for 1-3 years, 17% for 4-5 years, 23% for 6-10 years, 16% for 11-20 years, 7% for 21-30 years, and 3% over 30 years. Twenty-six occurrences of gastrointestinal and neurological symptoms were reported by 1258 infected persons. Passing proglottides in the faeces (95%) was the most frequent sign, followed by pruritis ani (77%), nausea (46%), abdominal pain (45%), dizziness (42%), increased appetite (30%), headache (26%), etc.     

Detection of luteinizing hormone beta messenger ribonucleic acid (RNA) in individual gonadotropes after castration: use of a new in situ hybridization method with a photobiotinylated complementary RNA probe

Patterns of gonadotropin storage in individual gonadotropes change with alterations in the physiological state. After castration in the male rat, there is a 2.5-fold increase in the percentage of gonadotropes and an increase in the proportion of gonadotropes storing both LH and FSH. In addition, there are 6- to 8-fold increases in the pituitary concentrations of LH beta subunit mRNAs. In order to determine whether these changes are due to increases in the number of gonadotropes containing subunit mRNA, or the amount of mRNA per cell or both, an in situ hybridization technique using a photobiotinylated rat LH beta cRNA probe (bio-LH beta-cRNA) was applied to detect LH beta mRNA in fixed whole rat pituitary cells from intact or castrated rats. After hybridization, the bio-LH beta-cRNA was localized with either avidin-biotin peroxidase complex or the fluorescent streptavidin phycoprobe methods. The cells containing LH beta mRNA were then counted and the amount of mRNA per cell was measured by video microdensitometry. Ten percent of the anterior pituitary cells from intact animals contained LH beta mRNA. After castration (2-4 weeks) this percentage rose to 19-24.5%. Image and microdensitometric analyses showed that castration produced a 1.9-fold increase in the amount of LH beta mRNA per cell, and a 2.2-fold increase in the area of cells containing LH beta mRNA. Hence, castration resulted in an increase in the level of LH beta mRNA per cell as well as the number of LH beta mRNA-containing cells. When in situ hybridization was followed by immunocytochemistry in cells from intact rats, 83% of gonadotropes that stained for LH beta and 80% of gonadotropes that stained for FSH beta contained LH beta mRNA whereas after castration 99% of LH-storing and 93% of FSH-storing cells contained LH beta mRNA. This new in situ hybridization protocol is rapid and allows quantification of mRNA within individual gonadotropes. In addition, since the hybridization protocol does not apparently alter the gonadotropin antigens, the hormone content of the same gonadotrope may be defined by immunocytochemistry.     

Linkage studies with chromosome 17 DNA markers in 45 neurofibromatosis 1 families

A locus for von Recklinghausen neurofibromatosis (NF1) has recently been mapped near the chromosome 17 centromere. We have extended these linkage studies by genotyping 45 NF1 families with three DNA probes known to be linked to the chromosome 17 centromeric region. Of 34 families informative for NF1 and at least one of the three probes, 28 families show no recombinants with the disease gene. These data provide additional support for genetic homogeneity of NF1 and for a primary NF1 locus linked to the chromosome 17 centromere. Among the informative families were 7 families with apparent new NF1 mutations. Our data suggest that these mutations are probably at the chromosome 17 NF1 locus.     

Influence of thyroidal status on pituitary content of thyrotropin beta- and alpha-subunit, growth hormone, and prolactin messenger ribonucleic acids

Thyroidectomized rats were used to study the effects of a single injection of T3 on pituitary mRNA synthesis and hormone secretion. T3 was injected ip at doses of 0, 0.2, 1, or 5 micrograms/100 g body weight, and and animals were killed 24 h later. T3 caused a significant decrease in serum TSH, but caused no significant change in either serum GH or PRL. Pituitary mRNA was quantified by slot blot hybridization with cDNA probes specific for alpha-TSH, beta-TSH, PRL, and GH. We found that both the alpha and beta mRNA subunits decreased, that PRL mRNA remained relatively unchanged, and that GH mRNA increased with increasing T3 dose. The data show that a single dose of T3 can profoundly influence mRNA levels in the anterior pituitary; the lowest dose of T3 caused maximum inhibition of alpha-TSH mRNA while beta-TSH mRNA declined further in a dose-dependent manner.     

Production and characterization of antibodies against HT-2 toxin and T-2 tetraol tetraacetate.

Three new immunogens which were prepared by conjugation of the carboxymethyl oxime (CMO) derivatives of HT-2 toxin, T-2 tetraol (T-2 4ol), and T-2 tetraol tetraacetate (T-2 4Ac) to bovine serum albumin (BSA) were tested for the production of antibodies against the major metabolites of T-2 toxin. Antibodies against HT-2 toxin and T-2 4Ac were obtained from rabbits 5 to 10 weeks after immunizing the animals with CMO-HT-2-BSA and CMO-T-2 4Ac-BSA conjugates. Immunization with CMO-T-2 4ol-BSA resulted in no antibody against T-2 4ol. The antibody produced against HT-2 toxin had great affinity for HT-2 toxin as well as good cross-reactivity with T-2 toxin. The relative cross-reactivities of anti-HT-2 toxin antibody with HT-2 toxin, T-2 toxin, iso-T-2 toxin, acetyl-T-2 toxin, 3'-OH HT-2, 3'-OH T-2, T-2 triol, and 3'-OH acetyl-T-2, were 100, 25, 10, 3.3, 0.25, 0.15, 0.12 and 0.08%, respectively. Antibody against CMO-T-2 4Ac was very specific for T-2 4Ac and had less than 0.1% cross-reactivity with T-2 toxin, HT-2 toxin, acetyl-T-2 toxin, diacetoxyscirpenol, deoxynivalenol, and deoxynivalenol triacetate as compared with T-2 4Ac. The detection limits for HT-2 toxin and T-2 4ol by radioimmunoassay were approximately 0.1 and 0.5 ng per assay, respectively.     

Natural killer cell-target interactions: the role of 4F2 antigen in the human system

The manner by which natural killer cells discriminate between target and nontarget cells is a subject of intense investigation. Recently, the antigen recognized by the 4F2 monoclonal antibody has been implicated as the target recognition molecule of cloned human natural killer cells. Here we report the results of our studies on the possible role of 4F2 antigen in target recognition by natural killer cells present in the peripheral blood. In our hands, the 4F2 antibody only weakly blocked the killing of K562 leukemia cells by human natural killer cells. Furthermore, no correlation was observed between the level of cell surface 4F2 antigen and the natural killer susceptibility of several tumor cell lines, the ability of these cells to bind to natural killer cells, or the ability of these cell lines to compete with K562 cells in a natural killer assay. Therefore, the 4F2 antigen does not appear to be the target recognition molecule of most peripheral blood natural killer cells.