Isolation of Chromosome 21 Specific DNA Probes and Their Use in the Study of Down's Syndrome

Down's syndrome is caused by the presence in an individual of three copies of gene loci in a critical region in the long arm of chromosome 21. Usually a complete extra copy of chromosome 21 is present (trisomy) and at birth this has an overall frequency of 1 in 700. The most important clinical effect is severe mental retardation, and Down's syndrome represents the most commonly identified cause of human mental handicap. The phenotype also includes dysmorphic features, malformations of major organs, an increased risk of leukaemia and presenile Alzheimer-type dementia. Older cytogenetic studies of chromosomal heteromorphisms have shown that in 80% of cases the additional chromosome in trisomy 21 is of maternal origin. Surprisingly this proportion did not seem to be increased in older mothers (over 35 years) who are known to have an increased frequency of Down's syndrome offspring. The cytogenetic studies were, however, uninformative in many cases. The main aim of the present project was to isolate polymorphic DNA probes from chromosome 21 which could be used to study nondisjunction in Down's syndrome families and to construct a genetic linkage map of chromosome 21. Cloned sequences derived from the critical region were to be analysed for expression in an attempt to identify expressed genes of pathogenic importance. Two chromosome 21-specific recombinant libraries were screened and of 486 bacteriophage clones initially selected, 29 recombinants were further analysed. Fourteen of these were shown to contain highly repetitive DNA sequences and were not studied further. The remaining 15 clones contained single- or low-copy number sequences and these were regionally mapped on chromosome 21 using a panel of somatic cell hybrids. Five of the single-copy sequences (JG21/D21S86, JG62/P21S90, JG72/P21S92, JG90/D21S95, JG99/D21S97) mapped in the 21q21-q22.1 region. A further six (JG12/D21S85, JG22/P21S87, JG24/P21S88, JG63/D21S91, JG81/D21S94, JG108/D21S99) were localised in the 21q22.1-qter region and one (JG77/D21S93) in the 21q22.1-q22.2 region. Probe JG373 (D21S101) was mapped in the distal part of band 21q22.3. The remaining two DNA sequences (JG51 and JG73) are mildly repetitive and were mapped to the pericentromeric region of chromosome 21. Although these clones were isolated separately from the same recombinant library and have different human insert sizes, they appear to detect homology with the same series of sequences in the human genome, which are present on chromosome 21 and on other chromosomes. The results obtained with these two probes suggest that they are part of the alphoid repeat family, members of which are present at the centromere of every human chromosome. Eight of the probes isolated in the present project were tested with a total of 25 restriction endonucleases and five restriction fragment length polymorphisms (RFLPs) were discovered : JG77/D21S93 detects an Msp I polymorphism, with alleles of 6kb and 3kb, of frequencies 0.67 and 0.33, respectively; JG81/D21S94 detects two RFLPs, with the enzymes Pvu II and Eco RV - the allele sizes and frequencies (in parenthesis) for these two RFLPs are 8.5kb (0.83)/8kb(0.17) for Pvu II and 5kb(0. 88)/4. 5kb(0.12) for Eco RV; JG90/D21S95 detects an RFLP with the enzyme Nde II, with allele sizes/frequencies of 2.2kb(0.7) and 1.8kb(0.3); the other RFLP is detected by JG99/D21S97 with the enzyme Pst I and has 7kb(0.16) and 6.6kb(0.84) alleles. The Msp I RFLP detected by JG77/D21S93 was used in conjunction with 4 other previously described polymorphic chromosome 21 probes to analyse the origin of nondisjunction in a total of 33 Down's syndrome families. Cytogenetic analysis by Q-banding was also used in some of these families. The parental origin of the additional chromosome was determined in 12 cases (36%) - in 9 of these (75%) the additional chromosome was of maternal origin, while in the other 3 (25%) it was derived from the father. These proportions are in agreement with those obtained previously from studies of cytogenetic heteromorphisms. (Abstract shortened by ProQuest.)

Humboldt Bay power plant canal remediation

Application No. 9A13A062

Effects of sediment removal techniques on avian communities and vegetational attributes in restored prairie pothole wetlands

With the loss and degradation of wetlands in some areas of the Prairie Pothole Region (PPR) reaching 80-90%, it is critical that resource managers ensure that the habitat that is put back on the landscape is as high quality as possible. Resource managers have been excavating sediment and topsoil, to promote the “hemi-marsh” condition, during the wetland restoration process in the PPR for over 20 years. I refer to the commonly held perception that the hemi-marsh condition supports the most diverse avian communities in small prairie pothole wetlands as the hemi-marsh condition hypothesis. The literature currently does not address the effects of excavation on the proportion of vegetative zones (i.e., sedge meadow, emergent vegetation, and open water) or avian communities in semi-permanent wetlands that are less than 0.6 ha, yet there are thousands of these wetlands throughout the PPR. Understanding the effects of excavation and testing the hemi-marsh condition hypothesis in small prairie wetlands is important to resource managers because these small wetlands are critical for maintaining the integrity of prairie wetland complexes. I conducted vegetation surveys, avian surveys, and estimated nest success on 40 small ( \u3c 0.6 ha), semi-permanent wetlands in the PPR of Minnesota to assess the influence of excavation on vegetation and avian communities. My data indicated a significant difference in the proportion of all vegetative zones between wetlands that were excavated until topsoil was exposed (topsoil excavations) and wetlands that were excavated until subsoil was exposed (subsoil excavations) (F3, 148 = 21.533, P \u3c 0.001, ηp2 = 0.304). The subsoil excavation technique increased the proportion of the open water zone (subsoil excavations: = 20.5%, SD = 18.1 and topsoil excavations: = 15.7%, SD = 14.8) by inhibiting plant growth in exposed subsoil. Altering the topography within basins decreased the proportion of the sedge meadow zone when the subsoil excavation technique was used (subsoil excavations: = 46.8%, SD = 20.7 and topsoil excavations: = 69.9%, SD = 13.6). This technique resulted in an increase in the proportion of the emergent vegetation zone (subsoil excavations: = 32.7%, SD = 23.4 and topsoil excavations: = 14.6%, SD = 12.5) by replacing sedge meadow with deeper water habitat. My analyses did not show a significant difference in Shannon-Weiner Diversity Index (F2, 70 = 0.770, P = 0.467, ηp2 = 0.022), Simpson’s Index of Diversity (F1.844 = 0.016, P = 0.979, ηp2 \u3c 0.001), or daily survival probability (F1 = 1.334, P = 0.254, ηp2 = 0.029) between topsoil and subsoil excavations. However, avian density (F1.688 = 3.497, P = 0.041, ηp2 = 0.047) and nest density (F1 = 9.863, P = 0.003, ηp2 = 0.180) were significantly higher in subsoil excavations. With red-winged blackbird (Agelaius phoeniceus) and sora (Porzana Carolina) accounting for over 83.5% of the nests in my study, I expected to see greater avian densities and nest densities in subsoil excavations since these species required emergent vegetation for nesting substrate. My statistical models indicated that avian diversity is best predicted by a combination of the proportion of emergent vegetation spring, proportion of emergent vegetation summer, and wetland area more so than by the proportion of emergent vegetation alone which is the basis of the hemi-marsh condition hypothesis. Clearly, small, less than 0.6 ha, prairie pothole wetlands function differently than their larger counterparts. Resource managers need to recognize the limitations in small wetlands; therefore, promoting the hemi-marsh condition in small wetlands is not the most efficient use of management dollars. My recommendations are to restore small prairie wetlands to their historical topography by using the topsoil excavation technique because resource managers do not currently know the potential negative impacts that exposing subsoil could have on plant and macroinvertebrate communities

ADSORPTION OF SALICYLHYDROXAMIC ACID ON SELECTED RARE EARTH OXIDES AND CARBONATES

Adsorption behavior of the anionic collector salicylhydroxamic acid (SHA) on a selected group of rare earth oxides (REOs) and carbonates (RECs) was studied via experimental methods and modelling software. Synthetic oxide and carbonate powders of the rare earth elements cerium (Ce), praseodymium (Pr), europium (Eu), and terbium (Tb) were tested for this research. Studies were conducted at different pH levels to analyze the kinetics of collector adsorption onto the oxide and carbonate surfaces in attempts to optimize recovery parameters for commercial flotation processes using SHA. In addition, thermodynamic software StabCal was implemented to compare theoretical adsorption behavior of collectors SHA and octylhydroxamic acid (OHA) on these four rare earth oxides and carbonates. Theoretical points of zero charge were also estimated via StabCal and compared to experimental values to establish validity. Results for oxides indicate that both the amount and rate of SHA adsorption are highest for lighter REOs, decreasing as ionic diameter increases, a chelation phenomenon common with hydroxamates. However, results for the carbonates exhibit the opposite trend: strongest SHA adsorption was seen in the heavy RECs. This pattern correlates to the increasing stability of the carbonate such that ionic diameter of the REs becomes more amenable to chelation due to differences in bonding chemistry. Overall, adsorption kinetics appear dependent on pH, coordination chemistry, and cation size