Nuclear-encoded subunits of human cytochrome c oxidase: SstI restriction fragment length polymorphism

A DNA polymorphism of the nuclear-encoded subunit Va of the human cytochrome c oxidase (COX), a mitochondrial respiratory enzyme, is reported. No polymorphism was detected in genes for the subunits IV and Vb of the same enzyme.     

T cell recognition of melanoma antigens in association with HLA-A1 on allogeneic melanoma cells

Previous studies have shown that recognition of melanoma by cytotoxic T lymphocytes may be restricted by HLA-A1, A2 and other HLA antigens. The present study examined the cytotoxic specificity and major histocompatibility complex restriction of cloned cytotoxic T lymphocytes (CTL) isolated from a patient with the HLA phenotype A3,31 who had been immunized with a vaccine prepared from HLA-A1,3 melanoma cells. Cytotoxic assays against HLA-typed allogeneic melanoma cells indicated that cloned CTL from the patient were able to kill allogeneic melanoma cells expressing HLA-A1 but not other HLA-A1-positive cells. Studies on a representative clone indicated that proliferation and cytokine (tumour necrosis factor ) production in response to melanoma cells was also associated with HLA-A1 on melanoma cells. Response to the melanoma cells was associated with interleukin-4 (IL-4) rather than IL-2 production. The antigen recognized in the context of HLA-A1 on allogeneic melanoma cells was detected in cytotoxic assays on cells from 9 of 12 HLA-A1⁺ melanoma cell lines and did not appear to be the product of the MAGE-1 or-3 genes. These findings suggest that T cells can recognize melanoma antigens in the context of alloantigens and that allogeneic vaccines containing immunodominant alloantigens may generate CTL that are ineffective against autologous melanoma. The study does not, however, exclude the possibility that CTL with specificity to the latter may be activated by allogeneic vaccines, and further studies are needed to answer this question.     

1.56 Å structure of mature truncated human fibroblast collagenase

The X-ray crystal structure of a 19 kDa active fragment of human fibroblast collagenase has been determined by the multiple isomorphous replacement method and refined at 1.56 Å resolution to an R-factor of 17.4%. The current structure includes a bound hydroxamate inhibitor, 88 waters and three metal atoms (two zincs and a calcium). The overall topology of the enzyme, comprised of a five stranded β-sheet and three α-helices, is similar to the thermolysin-like metalloproteinases. There are some important differences between the collagenase and thermolysin families of enzymes. The active site zinc ligands are all histidines (His-218, His-222, and His-228). The presence of a second zinc ion in a structural role is a unique feature of the matrix metalloproteinases. The binding properties of the active site cleft are more dependent on the main chain conformation of the enzyme (and substrate) compared with thermolysin. A mechanism of action for peptide cleavage similar to that of thermolysin is proposed for fibroblast collagenase. © 1994 Wiley-Liss, Inc.     

Variability in life history traits of the aphid,Acyrthosiphon pisum (Harris), from sexual and asexual populations

Many aphid species have shown remarkable adaptability by invading new habitats and agricultural crops, although they are parthenogenetic and might be expected to show limited genetic variation. To determine if the mode of reproduction limits the level of genetic variation in adaptively important traits, we assess variation in 15 life history traits of the pea aphid, Acyrhosiphon pisum (Harris), for five populations sampled along a north-south transect in central North America, and for three traits for three populations from eastern Australia. The traits are developmental times and rates as affected by temperature, body weights as affected by temperature, fecundity, measures of migratory tendency, and photoperiodic responses. The most southerly population from North America is shown to be obligately parthenogenetic, as are the Australian populations, and the four more northerly North American populations are facultatively parthenogenetic with the number of parthenogenetic generations per year increasing from north to south. The broad-sense heritabilities of life history traits varied from 0.36 to 0.71 for nine quantitive traits based on a comparison of within-and between-lineage variances. Using these traits, 7–13 distinct genotypes (i.e. clones) were identified among each of the 18 lines sampled from the North American populations, but the number did not differ significantly among populations. The level of genetic variation differed from trait to trait. For 4 of 12 quantitative traits, the level of variation in the obligately parthenogenetic population from North America was lowest, but significantly lower than all the sexual populations for only 1 trait. The obligately parthenogenetic population had the highest level of genetic variation for two traits, and had intermediate levels for the others. The most northerly population, which was sexual and had relatively few parthenogenetic generations each year, had the lowest level of variation for 5 of 12 traits and the highest level of variation for 2 traits. There was no decline in variability from north to south correlated with the increase in the annual number of parthenogenetic generations. The Australian populations showed no less variation than the North American populations for two of three traits, although the pea aphid was introduced to Australia only 5 years prior to the study, whereas the aphid has been in North America for at least 100 years. The mode of reproduction has not had a substantial impact on the level of genetic variation in life history traits of the pea aphid, but there are population-specific factors that effect the level of variation in certain traits.     

Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes

A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species. Drought increased mortality of P. furcata. In contrast, irrigation did not affect measures of photosynthetic capacity determined with an oxygen electrode or from photosynthesis-CO₂ response curves in the field. Drought stress limited field photosynthesis and leaf and plant survivorship without affecting photosynthetic capacity during late dry season. Leaves grown in high light in naturally occurring treefall gaps had higher photosynthetic capacity, dark respiration and mass per unit area than leaves grown in the shaded understory. P. furcata had the lowest acclimation to high light for all of these characters, and plant mortality was greater in gaps than in shaded understory for this species. The higher photosynthetic capacity of gap-grown leaves was also apparent when photosynthetic capacity was calculated on a leaf mass basis. Acclimation to high light involved repackaging (higher mass per unit leaf area) as well as higher photosynthetic capacity per unit leaf mass in these species. The three species showed two distinct syndromes of functionally-related adaptations to low light. P. limonensis and P. marginata had high leaf longevity (3 years), high plant survivorship, low leaf nitrogen content, and high leaf mass per unit area. In contrast, P. furcata had low leaf survivorship (1 year), high plant mortality (77–96% in 39 months), low leaf mass per unit area, high leaf nitrogen content, and the highest leaf area to total plant mass; the lowest levels of shelf shading, dark respiration and light compensation; and the highest stem diameter growth rates. This suite of characters may permit higher whole-plant carbon gain and high leaf and population turnover in P. furcata. Growth in deep shade can be accomplished through alternative character syndromes, and leaf longevity may not be correlated with photosynthetic capacity in shade adapted plants.     

Effects of fire on water and salinity relations of riparian woody taxa

Water and salinity relations were evaluated in recovering burned individuals of the dominant woody taxa from low-elevation riparian plant communities of the southwestern U.S. Soil elemental analyses indicated that concentrations of most nutrients increased following fire, contributing to a potential nutrient abundance but also elevated alluvium salinity. Boron, to which naturalized Tamarix ramosissima is tolerant, was also elevated in soils following fire. Lower moisture in the upper 30 cm of burned site soil profiles was attributed to shifts in evapotranspiration following fire. Higher leaf stomatal conductance occurred in all taxa on burned sites. This is apparently due to higher photosynthetic photon flux density at the midcanopy level and may be partially mitigated by reduced unit growth in resprouting burned individuals. Predawn water potentials varied little among sites, as was expected for plants exhibiting largely phreatophytic water uptake. Midday water potentials in recovering Salix gooddingii growing in the Colorado River floodplain reached levels which are considered stressful. Decreased hydraulic efficiency was also indicated for this species by examining transpiration-water potential regressions. Recovering, burned Tamarix and Tessaria sericea had enriched leaf tissue ¹³C relative to unburned controls. Higher water use efficiency following fire in these taxa may be attributed to halophytic adaptations, and to elevated foliar nitrogen in Tessaria. Consequently, mechanisms are proposed which would facilitate increased community dominance of Tamarix and Tessaria in association with fire. The theory that whole ecosystem processes are altered by invading species may thus be extended to include those processes related to disturbance.     

Immunological determination of digestive rates in the syntopic scorpions Urodacus armatus Pocock and Urodacus novaehollandiae Peters

Scorpions have lengthy periods of inactivity, which may be caused either by a long physiological digestion time or predator avoidance or both. We used a quantitative immunological assay to monitor the amount of prey antigen remaining in the hepatopancreas of Urodacus armatus and U. novaehollandiae for 32 days after a meal to test the hypothesis of a long digestion time. In both species, prey antigen concentration in the hepatopancreas increased between 0.25 and 0.5 days after feeding, probably because of incomplete transfer of prey proteins from the large preoral cavity to the hepatopancreas at this stage of digestion. This was followed by a rapid decline, and by 3 days after feeding less than 25% of ingested antigen remained in each species. Small prey residues could still be detected up to 32 days. Prey decay curves in both species were best fitted by a log-log transformation, and were not significantly different. Since digestion is essentially complete after 3 days, it appears that longer periods of post-feeding inactivity are for predator avoidance, not digestion. However, the 32-day detection period exceeds those reported for other invertebrates, and suggests an unusual digestive physiology in scorptions.     

Evaluation of monoammonium phosphate and bacterial strains to increase tree growth and fruit yield in apple replant problem soil

The long-term effects of biological agents alone and in combination with monoammonium phosphate on tree growth and fruit production of apple trees planted on apple replant soil was studied for five years. Application of monoammonium phosphate (MAP) in the year of planting increased shoot growth, cross-sectional trunk area and fruit yield of McIntosh on M.26 rootstock for the first two years. The application of bacterial agents alone were not effective in increasing young tree growth except BACT-1 in 1987. None of the bacterial agents increased fruit yield when applied alone. The addition of certain bacterial agents to MAP application increased young tree growth in various years. The combination of bacterial agent B-10 and MAP reduced young tree growth and yield compared with the MAP treatment alone. These results suggest that the application of MAP alone may be sufficient to alleviate the replant problem and the addition of BACT-1, EBW-4 or B8 bacterial agents to this treatment may be beneficial to increase tree growth in some years. Contribution number 822. Contribution number 822.     

Improving the mineral reserves and protein quality of maize (Zea mays L.) kernels using unique genes

The effects of the maize genes, o ₂ and Mal, on the concentrations of mineral nutrient cations and amino acid levels in mature maize (Zea mays L) kernels of various inbred lines were studied. Previously, the o ₂ gene has been used to improve the protein quality and increase the mineral nutrient content of kernels from some inbred lines. Genotypes possessing the Mal (multiple aleurone layer) gene, contain more than one row of aleurone cells in their kernels and this gene enhances the effect of the o ₂gene on improving kernel protein quality. Incorporating these genes into the maize genome increased accumulation of several mineral nutrients (including Ca, Mg, Zn, Fe, Mn, Zn and Cu) in some of the experimental lines studied. The physiological basis for this increase of mineral nutrients in the kernels is discussed. The effect of the Mal gene on the kernel amino acid composition and protein quality was also examined. Possibly, these genes could be used in combination in breeding programs to improve kernel quality and nutritional value of maize.