Biomedical subjects

B M Christensen

Publications and source records attributed to B M Christensen.

117 records · Page 7Linked to original sources

PubMed1975

Organ fluid changes and electrolyte excretion of rats exposed to high altitude.

Electrolyte balances, serum electrolyte concentrations, and fluid changes in the liver, spleen, kidney, heart, and brain of albino rats were studied at Denver (1620 m) and Pike's Peak (4300m), in Colorado. Control animals were subjected to pair feeding and equal transportation stress. Animals were sacrificed after 2, 4, 6, 8, 10, and 12 h, and 1, 2, 3, 6, 9, and 12 d of exposure. There was no significant growth depression after the first 24 h at altitude. The water content of all tissues were increased during the first day of exposure. Liver showed an increased percent dry weight following 1 d, possibly due to an increase in fat content. Serum Na plus concentrations were significantly increased throughout the 12 d of exposure while K plus was decreased. Hematocrit and hemoglobin values were immediately increased at altitude with the RBC count being significantly higher by Day 9. Altitude rats retained more Na plus, K plus, Ca plus plus, and Mg plus plus than controls, with K plus and Ca plus plus showing the highest retention. The data indicated a shift of fluids from the extra- to the intracellular compartment, especially during the first 12 h of exposure.

Altitude↗

PubMed1975

Effects of a glucose meal on human pulmonary function at 1600-m and 4300-m altitudes.

The effects of a high-glucose meal on pulmonary function were observed in seven healthy males at medium (1,600 m) and high (4,300 m) altitude. Thirty minutes after the ingestion of 410 kcal (109.9 g cerelose) of glucose, peak serum glucose values were noted with a subsequent decrease over 3 h to below fasting levels at both elevations. At the same time, triglyceride levels continued to decline from 104.2 to 83.3 mg at 1,600 m and 103.7 to 80.5 mg/100 ml at 4,300 m, with differences being significant after 2 h. Both V-E and V-T increased in response to translocation to altitude; however, only V-T increased by 10.9% and 13.3% at 0.5 h for 1,600 m and 4,300 m, respectively. The V-o-2 increased during glucose elevation at 4300 m, while P-A-O2 remained essentially unchanged except for differences associated with translocation to altitude. A 13.9% increase was noted in D-L-CO followign glucose ingestion at 4,300 m along with a decreased triglyceride levels. The elevated D-L-CO values suggest an increase in gas exchange at the alveolar-capillary (A-c) level following the ingestion of a glucose meal for individuals transported to high altitude.

Adult↗

PubMedDate not supplied

Phenol oxidase activity in hemolymph compartments of Aedes aegypti during melanotic encapsulation reactions against microfilariae.

Monophenol oxidase (MPO) and diphenol oxidase (DPO) activity was assessed in hemocytes, cell-free plasma and complete hemolymph collected from Aedes aegypti Liverpool strain, intrathoracically inoculated with saline alone, immune activated by the inoculation of Dirofilaria immitis microfilariae (mff), and uninoculated. Enzyme activities between groups were compared using a radiometric hydroxylation assay (MPO) and a high pressure liquid chromatography with electrochemical detection assay (DPO). There were no significant differences in enzyme activity in hemocytes, cell-free plasma, and complete hemolymph between uninoculated and saline-inoculated controls. Both MPO and DPO activity of mosquito hemocytes and complete hemolymph from immune-activated mosquitoes were significantly increased at 12 and 24 h postinoculation as compared with the enzyme activity from saline-inoculated mosquitoes, but no significant increase in enzyme activity was detected in cell-free plasma from immune-activated mosquitoes. Increases of MPO and DPO activity in hemocytes and hemolymph following immune activation were proportional, thereby suggesting that a single enzyme might react with both monophenols and o-diphenols within the hemolymph of A. aegypti. Results also suggest that augmented phenol oxidase activity associated with melanotic encapsulation reactions is associated primarily with hemocytes.

Aedes↗

PubMedDate not supplied

Biochemical pathway of melanotic encapsulation of Brugia malayi in the mosquito, Armigeres subalbatus.

The mosquito, Armigeres subalbatus, is naturally resistant to the filarial worm, Brugia malayi, and microfilariae (mf) penetrating the midgut are killed by melanotic encapsulation reactions in the hemocoel within 48 h following ingestion. This vector-parasite system was used to assess changes in hemolymph tyrosine, tyrosine derivatives, and catecholamine-metabolizing enzyme activities using high pressure liquid chromatography with electrochemical detection (HPLC-ED) during melanotic encapsulation reactions against mf. Tyrosine and dopa were detected in the hemolymph of both control and immune-activated (mf-exposed) mosquitoes, but not dopamine or N-acetyl dopamine (NADA). Tyrosine was significantly increased in immune-activated mosquitoes at 6 and 12 h post blood feeding, but was depleted following intrathoracic inoculation of mf in the absence of a blood meal. Dopa also was elevated in immune-activated mosquitoes at 6, 12, and 24 h post-exposure to mf. There were significant increases in phenol oxidase (PO) and dopa decarboxylase (DDC) activities in immune-activated mosquitoes as compared to controls, and these elevated activities were correlated with changes in tyrosine and dopa levels in the hemolymph. No significant differences in N-acetyl transferase (NAT) and dopachrome conversion enzyme (DCE) activities between control and immune-activated mosquitoes were observed. The possible roles these molecules play in melanotic encapsulation reactions of A. subalbatus against mf are discussed.

Animals↗

PubMedDate not supplied

Monoclonal antibodies against Manduca sexta hemocytes bind Aedes aegypti hemocytes: characterization of six monoclonal antibodies that bind hemocytes from both species.

The mechanisms by which hemocytes mediate a mosquito's defense response to parasites or pathogens are not well understood. This is due in part to difficulty in collecting intact mosquito hemocytes for experiments and to a lack of reagents, such as antibodies. Our objectives were to collect adult Aedes aegypti hemocytes under conditions suitable for immunofluorescence microscopy, and to test whether monoclonal antibodies, generated against larval Manduca sexta hemocytes, bind adult Ae. aegypti hemocytes. We present immunofluorescence micrographs of M. sexta and Ae. aegypti hemocytes stained by six monoclonal antibodies. Two antibodies, MS11 and MS32, immunolocalized to hemocyte nuclei in both species. On Western blots, these antibodies generate one signal at approximately 40 kDa and four others between 10 and 25 kDa. Immunofluorescence staining patterns of the other four antibodies were more complex. That these antibodies bind hemocytes from both species suggests significant molecular similarities exist between hemocytes from evolutionarily divergent species.

Aedes↗

PubMedDate not supplied

Comparative linkage maps for the mosquitoes (Culex pipiens and Aedes aegypti) based on common RFLP loci.

We report construction of a comparative linkage map for the mosquito (Culex pipiens) based on restriction fragment length polymorphisms (RFLPs) using cDNA clones from Aedes aegypti as probes to Southern blots of Cx. pipiens genomic DNA. Seventy-one cDNA clones were screened for hybridization and genetic diversity among three Cx. pipiens strains. Fifty-two of 71 cDNA clones, isolated from and previously mapped in Ae. aegypti (73.2%), were hybridized under high-stringency conditions with Cx. pipiens genomic DNA. Thirty-four clones (47.9%) reflected strain-specific polymorphisms. The map consists of 21 cDNA markers that identify 22 loci covering 165.8 cM. The loci mapped in Cx. pipiens cover 7.1 cM on chromosome 1, 80.4 cM on chromosome 2, and 78.3 cM on chromosome 3. Linkage relationships of the RFLP markers for chromosome 1 in Cx. pipiens are the same as chromosome 1 in Ae. aegypti, indicating that chromosome 1 is highly conserved between the two species. The comparative RFLP linkage maps for chromosomes 2 and 3 in Cx. pipiens and Ae. aegypti reflect apparent whole-arm translocations. RFLP markers for chromosome 2 in Ae. aegypti identified homologous loci on one arm of chromosomes 2 and 3 in Cx. pipiens, and RFLP markers for chromosome 3 in Ae. aegypti identified homologous loci on the opposite arms of chromosomes 2 and 3 in Cx. pipiens.

Aedes↗

PubMedDate not supplied

Comparisons of genetic variability and genome structure among mosquito strains selected for refractoriness to a malaria parasite.

Restriction fragment length polymorphism (RFLP) markers were used to evaluate Aedes aegypti genome structure and genetic variability within and between substrains selected for different levels of refractoriness to the malaria parasite, Plasmodium gallinaceum. The MOYO-R substrain was previously selected for complete refractoriness and the MOYO-IS substrain for intermediate susceptibility from the Moyo-In-Dry (MOYO) strain by selective inbreeding (F = 0.5). Eighteen mapped RFLP markers were used to provide coverage of the mosquito genome. The two substrains showed reduced genetic diversity compared with the MOYO strain, including significant reductions in mean heterozygosity, number of alleles per locus, and proportion of polymorphic loci. Genetic differentiation between the two substrains was statistically significant, as reflected by differences in allele frequencies. Significant pairwise linkage disequillbrium among the RFLP loci was detected in all three strains, most evidently in the MOYO strain. This is surprising because the RFLP loci examined are separated by large map distances, and therefore linkage disequilibrium should decay to zero after many generations of laboratory culture. Our hypothesis to explain this phenomena is that lack of recombination, or low recombination rates in some regions of the A. aegypti genome, is a result of chromosome inversions. Finally, we used graphical genotyping, wherein whole genome genotypic information for individual mosquitoes is represented in a simple graphic format, to illustrate genome structure and allelic variation within and among the mosquito strains. Our analysis revealed an apparent chromosomal deletion on chromosome 3 for some individuals in the MOYO strain and MOYO-IS substrain.

Aedes↗

PubMedDate not supplied

Linkage map for Aedes aegypti using restriction fragment length polymorphisms.

We report construction of a genetic linkage map for the mosquito, Aedes aegypti, based on restriction fragment length polymorphisms (RFLPs). The map consists of 50 DNA markers that identify 53 loci covering 134 map units across three linkage groups. Determination of linkage associations between RFLP markers and several mutant marker loci allowed for partial integration of the RFLP markers with an existing classical genetic linkage map for A. aegypti. The RFLP markers include 42 random cDNA clones, three random genomic DNA clones, and five cDNA clones of known genes. We discuss the influence of autosomal sex determination, characteristic of culicine mosquitoes, in relation to its observed influence on segregation ratios. This has important ramifications for future efforts to identify quantitative trait loci associated with the ability of these mosquitoes to transmit various pathogens and parasites to man and other animals.

Aedes↗

PubMedDate not supplied

Isolation and identification of Aegyptianella pullorum (Rickettsiales, Anaplasmataceae) in wild turkeys from North America.

Isodiagnosis of blood from Rio Grande wild turkeys from southern Texas revealed a small, intraerythrocytic rickettsia, Aegyptianella pullorum Carpano, 1928, in 24 of 300 samples. Identification of this first isolate from North America was made using both light and transmission electron microscopy. It is suggested that the translocation of wild turkeys from Texas to other states could spread this pathogen to both wild birds and domestic poultry.

Anaplasmataceae↗