The annual lipid cycle and feeding behavior of Alaskan redpolls

Summary Total lipids were extracted from 161 redpolls (Acanthis spp.) collected each month of the year from October 1962 to September 1963, in interior Alaska. A lipid index (Weight of ether extract x100/live body weight) was calculated for each sample. Lipids were also extracted from sections of pectoral muscle, livers and hearts representing each month.Body weight and lipid index were significantly positively correlated being highest in January and lowest in September. Total lipid content was significantly inversely correlated with air temperature; the high autumn and spring pre-migratory lipid peaks of migratory species were only weakly expressed in the redpolls. Liver lipid showed a significant annual variation being highest in December and lowest in August, while lipid from heart and pectoral muscle did not vary seasonally.Five birds were held in captivity during spring and summer at a constant temperature of 22°C. Food consumption was 5.1 g/day or 22.4 kcal. The caloric value of the most extensively utilized natural food, birch seed (Betula papyrifera), was determined (5.4–5.5 kcal/g dry wt). When esophageal diverticulae are full (2.0 g wet wt) of birch seeds, the resulting energy yield may sustain an individual for only a fraction of a 24 h winter day in contrast to other arctic herbivores (e.g. ptarmigan, Lagopus sp.) in which a full crop may suffice for the full 24 h period.     

The role of glucagon in the regulation of blood glucose: Model studies

Mathematical models afford a procedure of unifying concepts and hypotheses by expressing quantitative relationships between observables. The model presented indicates the roles of both insulin and glucagon as regulators of blood glucose, albeit in different ranges of the blood glucose concentrations. Insulin secretion is induced during hyperglycemia, while glucagon secretion results during hypoglycemia. These are demonstrated by simulations of a mathematical model conformed to data from the oral glucose tolerance test and the insulin infusion test in normal control subjects and stable and unstable diabetic patients. The model studies suggest the parameters could prove of value in quantifying the diabetic condition by indicating the degree of instability. Presented at the Society for Mathematical Biology Meeting, University of Pennsylvania, Philadelphia, August 19–21, 1976.     

Controlling the exotic diseases: 2. Nursing management.

Advance planning can facilitate the care of a patient with an exotic disease who is admitted to a hospital that lacks facilities for high-security isolation. The Department of National Health and Welfare contingency plan for dealing with such patients lacks specific information in a number of areas of medical care, as described in this paper. Consideration must be given to the number of personnel trained and readied for employment, the criteria for selection and special preparation. The protective clothing generally used for hospital isolation procedures is inadequate. Several types of special clothing, including a respirator, are available for total protection of personnel; the clothing may be uncomfortable when worn for long periods, and does restrict movement, vision and communication. All persons entering the isolation suite must change into fully protective clothing, and double layers of clothing are required for direct patient care. All personnel must shower and change before leaving the isolation suite. Suitable facilities for dressing and showering, together with entry and exit routines, must be considered. Hand washing, daily cleaning procedures and disposal of liquid and solid wastes all require special procedures. The social and psychologic problems of patients and their families must also be considered. Preplanning is required to decrease the risks involved in monitoring vital signs and implementing emergency procedures requiring contact with the patient''s blood.     

Nucleotide assignment of alkali-sensitive sites in mouse mitochondrial DNA

Mature, closed circular mouse mitochondrial DNA contains a significant number of ribonucleotides throughout the genome. Previous studies have implicated the two origins of DNA replication as preferred sites of ribonucleotide retention. We have analyzed the site specificity of ribosubstitution by direct sizing of alkali-treated restriction fragments in comparison with the DNA sequence of untreated restriction fragments of cloned mouse mitochondrial DNA. These results have confirmed the observations that ribonucleotides are retained at the two origins of replication and are most likely remnants of RNA priming events associated with DNA replication. The map location of ribonucleotides at the light strand origin of replication has been refined to a triplet nucleotide (5'-CGG-3') in the light strand initiation region. This approach has demonstrated that all four deoxyribonucleotides are subject to ribosubstitution and no single base (or subset of the four bases) predominates. An examination of selected regions of the mitochondrial DNA genome including the putative coding region for cytochrome oxidase subunit III and regions containing the genes for tRNAPhe, tRNAVal, 12 S rRNA, and 16 S rRNA reveals preferred sites for ribosubstitution. These preferred sites do not relate in any obvious way to the functional aspects of these domains. In addition, the data indicate that every position in the DNA sequences examined can be ribosubstituted at a very low frequency.     

Ultrastructure of unique plasmodesmata in Selaginella willdenowii

Summary All meristematic cells of dorsal angle meristems of Selaginella willdenowii Baker cultured in vitro possessed expanded plasmodesmata, unlike the conventional plasmodesmata which were also found in these cells. Apical tissues of stems, roots and shoots from intact plant also possessed these structures though to a lesser degree than angle meristems. Root tips and stem apices had numerous conventional plasmodesmata in their walls. The expanded plasmodesmata, with their marked symmetry, represent a unique variation of plasmodesmatal structure.This study was partially supported by NSF Grant GB 37945 to Zachary S. Wochok.     

Thymidylate nucleotide supply for mitochondrial DNA synthesis in mouse L-cells. Effect of 5-fluorodeoxyuridine and methotrexate in thymidine kinase plus and thymidine kinase minus cells.

The effects of 5-fluorodeoxyuridine and methotrexate on [3H]thymidine and 32P labeling of mtDNA were studied in two lines of mouse L-cells. LMTK- cells, which lack the major cellular thymidine kinase (EC 2.7.1.21) but contain a genetically distinct mitochondrial enzyme, were compared to LA9 cells, which contain both thymidine kinase activities. LMTK- cells were resistant to 5-flurodeoxyuridine by a factor of 200 in comparison to LA9 cells. In both cells lines appropriate drug treatment increased utilization of exogenous thymidine for mtDNA synthesis. The maximum enhancement was 10- to 12-fold for LA9 cells and approximately 20-fold for LMTK- cells when treated with 10 muM methotrexate. The rates of mtDNA and nuclear DNA synthesis during drug treatment were analyzed with 32P labeling and 5-bromo-2'-deoxyuridine density labeling experiments. Synthesis of both mtDNA and nuclear DNA were strongly inhibited by drug treatment of either LA9 or LMTK- cells in the absence of exogenous thymidine. The rate of mtDNA synthesis substantially exceeded that of nuclear DNA in LA9 cells treated with 4 muM 5-fluorodeoxyuridine and less than 5 muM thymidine. Both synthetic rates approached those of untreated LA9 control cultures if 20 muM thymidine was present during 5-fluorodeoxyuridine treatment. In contrast, in LMTK- cells treated with 10 muM methotrexate and 20 muM thymidine, mtDNA synthesis continued at 50 to 60% of the control rate for at least 10 hours while nuclear DNA synthesis was 96% inhibited. Synthesis of mtDNA mass-labeled in both strands with 5-bromouracil occurred when LMTK- cells were incubated for 30 hours with 10 muM methotrexate and 20 muM 5-bromodeoxyuridine. These results indicate that mtDNA synthesis is resistant to a limitation of the thymidine triphosphate supply and is not strictly dependent upon concomitant nuclear DNA synthesis in these cells.     

Genomic investigation of phenotypic variation in Campylobacter jejuni flagellin.

Western blots of whole-cell sonicates of 10 different clones of a faecal isolate of Campylobacter jejuni 533 detected the expression of flagella antigens of either 59 or 62 kDa. Other antigenic proteins appeared identical both in the parent and all the clones. The mechanism for this phenotypic variation was studied using Southern blotting with a flagellin-specific gene probe and products of a polymerase chain reaction (PCR) using flagellin-gene primers. Restriction-enzyme digestion and Southern blotting did not detect any genomic rearrangements in the flagellin genes of the different phenotypes nor did restriction-enzyme analysis of the PCR products.     

Properties of reaction centers of Rhodopseudomonas sphaeroides in dried gelatin films.: Linear dichroism and low temperature spectra

Methods of preparing dried gelatin films containing purified reaction centers of Rhodopseudomonas sphaeroides are described. The spectral properties of reaction centers in solution are essentially maintained in dried gelatin films. These films are uniform and have excellent optical properties, showing little particulate scattering at temperatures down to about 4K. Film contraction on cooling to 90K is less than 1% in linear dimension. Linear dichroism spectra are reported for films at room and low temperature. Reaction centers show a moderate amount of linear dichroism in unstretched gelatin films; the magnitude of the linear dichroism becomes much greater when the films are stretched. In stretched films, linear dichroic ratios ($\text{A}{}_{\mathrm{\parallel }}\text{A}{}_{\mathrm{\perp }}$; absorbance measured with electric vector parallel and perpendicular to stretching direction) between 1.7 and 2.2 were obtained for the 860 nm absorption band of the bacteriochlorophyll component that undergoes primary photooxidation. The relative polarizations of light-induced absorption changes of reaction centers in stretched films are similar to those reported by Vermeglio and Clayton ((1976) Biochim. Biophys. Acta 449, 500–515) and support their hypothesis that absorbance decreases, maximal near 860 and 810 nm, and an increase near 790 nm are associated with the respective disappearance and appearance of discrete bands characteristic of the reduced and oxidized bacteriochlorophyll dimer. This interpretation is also supported by the polarization of the absolute absorption spectrum near 810 and 860 nm. An absorption band near 540 nm, ascribed to the Q_x transitions of two molecules of bacteriopheophytin in the reaction center, is split at low temperatures into two bands having similar polarizations. This splitting is probably not due to exciton coupling of the two molecules, since excition theory predicts different polarizations.