Rationalization of some genetic anticodonic assignments

The genetic code appears to be a logic matrix in which, generally speaking, there is a correlation between the hydrophobicities of amino acids and their anticodonic nucleotides. There are several exceptions to this generality, however, and using previous data on hydrophobicity and binding constants, coupled with new data on reaction rates, we rationalize several of the anticodonic assignments.     

Age and growth of a colonizing minnow,Barbus anoplus,in a man-made lake in South Africa

Synopsis Aspects of the life history of Barbus anoplus were studied in Lake le Roux, a turbid man-made lake on the Orange River, South Africa. This minnow underwent a population explosion and successfully colonized the shoreline of the newly-formed lake during the early phases of reservoir filling. Male and female B. anoplus reach sexual maturity in one year at about 40 mm fork length. They have a multiple spawning habit with the first spawning in November–January and the second in February–March. The growth of the two resulting cohorts is discussed. It is proposed that the offspring from the second spawning not only acts as a ‘back-up’ but is capable of prolonging the life of that year-class into an additional reproductive season. Most of the minnows die after their second summer, but more offspring from the second spawning, especially females, live into a third summer. Females attain a larger maximum size (73 mm FL) and age (3–4 years) than males (60 mm FL, 2–3 years). B. anoplus is small and short-lived with a high seasonal reproductive potential, which is in contrast to the larger Barbus species in the Orange River system. These life-history traits enable the species to colonize and successfully inhabit unstable environments and probably account for its widespread distribution.     

Reduction in headache patients' medical expenses associated with biofeedback and relaxation treatments

Comparisons are made of self-reported medical costs from a sample of headache patients who underwent various combinations of relaxation training and biofeedback training. The average costs for the 2 years prior to self-regulatory treatment were $955±480 (3 SEM) for 45 patients; for the 2 years after completing treatment the average costs were $52±28 (3 SEM) for patients. Within the limitations of the study, medical costs do seem to have been markedly reduced.This research was supported by a grant from NINCDS, NS-15235.     

Management of localized non-Hodgkin's lymphoma

Non-Hodgkin''s lymphomas (NHLs) are a heterogeneous group of disorders that vary widely in response to therapy. In Canada the modified Rappaport classification is used to categorize NHL. To facilitate the reporting and comparison of treatment results all cases should also be categorized in the terminology of the National Cancer Institute''s working formulation. The choice of therapy should be guided by specific prognostic factors: stage and bulk of the disease, patient''s age, presence of systemic symptoms and histologic subtype. Of these, the last appears to be the most important. Radiotherapy (RT) is the treatment of choice in localized low-grade lymphomas with favourable prognoses, while bimodal therapy (RT and chemotherapy [CT]) is warranted in presentations with unfavourable prognoses. Regional irradiation alone is indicated in intermediate-grade lymphomas with good prognoses (i.e., pathological stage I or II or clinical stage IA or IIA localized disease of small bulk in young patients). All other patients require CT followed by RT. The results of CT alone are encouraging but remain experimental. Aggressive therapy with multidrug regimens that include central nervous system prophylaxis is the foundation for successful treatment of high-grade NHL such as lymphoblastic lymphoma and diffuse small-noncleaved-cell lymphomas. Low-dose RT should be given to sites of bulky disease.     

Geographical and temporal variation in the calls of the Manx shearwater Puffinus puffinus and British storm petrel Hydrobates pelagicus

The geographical variation in the calls of the Manx shearwater Puffinus puffinus and British storm petrel Hydrobales pelagicus was investigated, as well as its temporal stability in the shearwater. Within-island call variation was not apparent in Puffinus , although male calls were relatively more distinct locally than female calls. This is discussed in relation to the differential dispersal of the sexes. Between-island call variation was apparent in both Puffinus and Hydrobates , but the variation was continuous, and not discrete. Call divergence is unrelated to inter-island distance, and may reflect the influence of coastlines on each species'dispersal opportunities. The calls of a shearwater population changed over a period of six to seven years, apparently due to the appearance of new birds rather than surviving birds altering their calls. Male calls changed more than female calls, which, taken with dispersal factors, suggests that calls are transmitted across generations at least in part by cultural copying. The vocal'drift'over time therefore probably results from errors in this copying process.     

Changes in density of DNA after interaction with dipicolinic acid and its possible role in spore heat resistance

We examined the effect of interacting dipicolinic acid and its calcium chelate on the wet and dry density of DNA. Complexes are produced whose densities are different from those of the individual components. Also, we observed two modes of binding, one strong the other weak, between DPA or CaDPA and DNA. The strength of the binding modes was reflected in the rate of dissolution of the complexes as monitored by changes in wet density with time and temperature. We conclude from these and other data in the literature that the interaction of dipicolinic acid with DNA not only influences the spore wet density and the ratio of core/core⁺ cortex volume, but may also influence the spore heat resistance.     

Components of Selection in X Chromosome Lines of DROSOPHILA MELANOGASTER: Sex Ratio Modification by Meiotic Drive and Viability Selection

Selection coefficients and segregation parameters have been estimated in 18 randomly chosen lines carrying wild X chromosomes on the cn bw genetic background. Each line was studied in replicated crosses of four types, with approximately 100 replications per line per cross. Crosses in which male X chromosomes differed exhibited significant sex ratio heterogeneity. Maximum likelihood estimation of segregation parameters revealed two lines in which the proportion of X-bearing gametes produced by males was significantly different from Mendelian expectations. These observations suggest that segregation distortion is a common feature of naturally occurring genetic variation. Non-Mendelian segregation has important evolutionary implications.     

Growth Kinetics, Cell Shape, and the Cytoskeleton of Primary Astrocyte Cultures

Abstract: We examined correlations among growth kinetics, cell shape, and cytoskeletal protein content in rat astrocytes grown in primary culture. Cell suspensions from brains of newborn rats were seeded at densities from 0.2 to 3 × 10⁵/cm². At initial densities above 1 × 10⁵ the population increased to reach confluency by 10–12 days, after which cell number remained stable for many weeks. At low initial densities, 0.2–0.4 × 10⁵/cm², cells did not increase in number. Final density increased with increasing plating densities. High-density cells had small perikarya and several long cytoplasmic processes; low-density cells appeared flat and polygonal. All cultures were almost entirely astrocytic, as judged by immunofluorescent staining with antiserum against glial fibrillary acidic protein (GFAP). Cytoskeletal proteins were analyzed by gel electrophoresis after extraction from cells with nonionic detergent. Relative amounts of the proteins differed, in that low-density cells contained large amounts of cytoskeletal actin relative to the intermediate filament (IF) proteins vimentin and GFAP, whereas high-density cells contained relatively less actin and more IF proteins. Such differences in cytoskeletal proteins between the high- and low-density cultures were mirrored in the relative rates of synthesis of the cytoskeletal proteins. In the low-density cells amino acid incorporation into cytoskeletal-associated actin was more active than that into the IFs, whereas in the high-density cells higher rates of IF protein synthesis were observed.     

Quantitative measurement of smooth muscle shortening in isolated pig trachea

Matched porcine tracheal rings were exposed to theophylline and increasing doses of carbachol in Krebs solution. Histological sections of each ring were traced and each of the following dimensions measured: the external perimeter (Pe) and external area (Ae) defined by the outer border of smooth muscle and inner surface of cartilage, and the internal perimeter (Pi) and internal area (Ai) defined by the luminal surface of the epithelium and the muscle length (L) along its outer border. Absolute wall area (WA = Ae - Ai) and relative wall area (PW = WA/Ae) were calculated. Carbachol-treated tracheal ring dimensions were compared with those of their matched theophylline-treated rings. In tracheal rings with intact cartilage, maximal smooth muscle shortening of 44% was achieved with 10(-2) M carbachol. In tracheal rings in which anterior and posterior segments of cartilage were excised, the trachealis muscle passively shortened by 20% and maximal shortening (10(-3) M carbachol) was 57%. Although Ai decreased with maximal smooth muscle shortening, there were no changes in the length of Pi or in WA. These data show that the cartilage in the porcine trachea exerts both a preload that passively stretches the trachealis muscle and an afterload that limits maximal smooth muscle shortening.