Kinetics of electron transfer between the primary and the secondary electron acceptor in reaction centers from Rhodopseudomonas sphaeroides.

Photoreduction of the two ubiquinone molecules, UQ1 and UQ2, bound to purified reaction center from Rhodopseudomonas sphaeroides induces different absorption band shifts of bacteriochlorophyll and bacteriopheophytin molecules depending on which ubiquinone is photoreduced. This allows us to study electron transfer between UQ1 and UQ2 directly by absorption spectrometry. The results support a model in which electrons are transferred one by one from UQ1 to UQ2 with a half-time 200 micro seconds, and two by two from fully reduced UQ2 to the secondary acceptor pool.     

Orientation of the hemes of high potential cytochromes relative to photosynthetic membranes, as shown by the linear dichroism of oriented preparations

The orientations of high potential cytochromes with respect to photosynthetic membranes was investigated in spinach chloroplasts and in Rhodopseudomonas viridis. The general approach consists in detection with polarized light of photoinduced absorbance changes related to the oxidation of the cytochromes. The orientation of cytochrome c-558 was measured at room temperature in chromatophores and whole cells of Rps. viridis, oriented on glass slides and in a magnetic field, respectively. The orientation of cytochrome b-559 of green plants was detected at 77 K in magnetically oriented chloroplasts. In both cases the dichroic ratio for the band shows that the heme plane makes an angle greater than 35°C with the membrane plane. Moreover, the dichroic ratio is not constant throughout the and β bands, for both cytochrome c-558 and b-559. Linear dichroism spectra of oriented pure horse heart cytochrome c and cytochrome c₂ of Rhodopseudomonas sphaeroides in stretched polyvinyl alcohol films show that the variations of the dichroic ratio in the and β bands can be explained by the occurrence of x- and y-polarized transitions absorbing at slightly different wavelengths.     

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.     

EFFECTS OF ICE ON ASCOPHYLLUM NODOSUM WITHIN THE GREAT BAY ESTUARY SYSTEM OF NEW HAMPSHIRE-MAINE12

The, effects of ice on Ascophyllum nodosum (L.) Le Jolis within the Great Bay Estuary System of New Hampshire-Maine, U.S.A. were assessed during the winter of 1980–81. Approximately 50% of the plants late fall standing crop, or an estimated 136 tonnes dry weight, was removed by ice-rafting. Pieces of Ascophyllum removed averaged 22 cm in length, 15 g in fresh weight and generally represented 2–3 years of growth. Although the winter of 1980–81 wax somewhat extreme, a similar pruning process probably occurs each year contributing to the characteristic bushy habit of attached inner estuarine plants. Ascophyllum fragments rafted in ice and deposited into salt marshes are suggested as a major source of the, ecad scorpioides (Hornemann) Hauck.     

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.     

EPR properties of the reaction center of Rhodopseudomas gelatinosa in situ and in a detergent-solubilized form

The photochemical reaction centers from a variety of purple photosynthetic bacteria are composed of a trimer of protein subunits. However, the recently isolated reaction center from Rhodopseudomonas gelatinosa appears to have only two subunits. In this paper we examine the EPR characteristics of the primary photochemical reactants in this species, and compare them with those of other species. Despite of the differences in protein composition, no dramatic differences in EPR properties are seen in vivo, although some interesting effects are seen upon solubilization of the reaction center, which may be related to the unusual lability of the isolated preparation. Perhaps the most noteworthy phenomenon seen in Rps. gelatinosa is the apparent ability of electrons on the reduced intermediary electron carrier to tunnel at low temperatures to the oxidized c-type cytochrome, which has not been seen in other species studied to date.     

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.