Nanosecond fluctuations of the molecular backbone of collagen in hard and soft tissues: a carbon-13 nuclear magnetic resonance relaxation study

We have determined the amplitude of nanosecond fluctuations of the collagen azimuthal orientation in intact tissues and reconstituted fibers from an analysis of 13C NMR relaxation data. We have labeled intact rat calvaria and tibia collagen (mineralized and cross-linked), intact rat tail tendon and demineralized bone collagen (cross-linked), and reconstituted lathyritic (non-cross-linked) chick calvaria collagen with [2-13C]glycine. This label was chosen because one-third of the amino acid residues in collagen are glycine and because the 1H-13C dipolar coupling is the dominant relaxation mechanism. Spin-lattice relaxation times (T1) and nuclear Overhauser enhancements were measured at 15.09 and 62.98 MHz at 22 and -35 degrees C. The measured NMR parameters have been analyzed by using a dynamic model in which the azimuthal orientation of the molecule fluctuates as a consequence of reorientation about the axis of the triple helix. We have shown that if root mean square fluctuations in the azimuthal orientations are small, gamma rms much less than 1 rad, the correlation function decays with a single correlation time tau and T1 depends only upon tau and gamma rms and not the detailed model of motion. Our analysis shows that, at 22 degrees C, tau is in the 1-5-ns range for all samples and gamma rms is 10 degrees, 9 degrees, and 5.5 degrees for the non-cross-linked, cross-linked, and mineralized samples, respectively. At -35 degrees C, gamma rms is less than 3 degrees for all samples. These results show that mineral and low temperature significantly restrict the amplitude of nanosecond motions of the collagen backbone.(ABSTRACT TRUNCATED AT 250 WORDS)     

Murine retrovirus-induced spongiform encephalomyelopathy: host and viral factors which determine the length of the incubation period.

A molecular clone of wild mouse ecotropic retrovirus CasBrE (clone 15-1) causes a spongiform neurodegenerative disease with a long incubation period, greater than or equal to 6 months. This virus infects the central nervous system (CNS) at low levels. In contrast, a chimeric virus, FrCasE, containing env and 3' pol sequences of 15-1 in a Friend murine leukemia virus background, infects the CNS at high levels and causes a rapid neurodegenerative disease with an incubation period of only 16 days. With both viruses, the induction of neurologic disease is dependent on inoculation during the perinatal period. Since the length of the incubation period of this disease appears to be a function of the relative level of CNS infection, we have attempted to identify the viral and host factors which determine the relative level of virus infection of the CNS. It was previously shown that the CNS is susceptible to infection only during the perinatal period (M. Czub, S. Czub, F. J. McAtee, and J. L. Portis, J. Virol. 65:2539-2544, 1991). Here we have found that the susceptibility of the CNS wanes progressively or gradually as a function of the age of the host, this age-dependent resistance being complete by 12 to 14 days of age. Utilizing a group of chimeric viruses, we found that the relative level of CNS infection achieved after inoculation of mice at 1 day of age was a function of the kinetics of virus replication and spread in peripheral organs. Viruses which reached peak viremia titers early (5 to 7 days of age) infected the CNS at high levels, and viruses which reached peak titers later infected the CNS at lower levels. Among the group of viruses examined in the current study, the kinetics of peripheral virus replication and spread appeared to be influenced primarily by sequences within the R-U5-5' leader region of the viral genome. These results suggested that the relative level of CNS infection was determined very early in life and appeared to be a function of a dynamic balance between the kinetics of virus replication in the periphery and a progressively developing restriction of virus replication in the CNS.     

Q fever urban cases in Romania

Q fever urban sporadic cases in Romania in the 1981-87 period are reviewed as concerns their incidence, seasonality and epidemiological data. Urban cases represented 76.8% as against 23.2% rural cases from the 134 Q fever sporadic cases detected in this period. Cases were distributed throughout all months with peaks during April (18.4% of cases) and June (19.4%). Infections were not related to contact with livestock or domestic birds or with raw milk drinking. Cases could not be identified as Q fever occupational ones. 36.7% of patients were working in nonalimentary industry and only 12.6% were involved in meat industry, veterinary or human medical practices. New studies concerning unusual sources of urban infection such as dogs, cats or urban street pigeons are emphasized.     

Genetic variation for aerial dispersal behavior in the Banks grass mite

Banks grass mites, Oligonychus pratensis (Banks), exhibit a behavior that facilitates their dispersal as aerial plankton over long distances. The propensity to display this behavior and its latency varies among individual mites. Some of this variation can be attributed to genetic differences among individuals. Mother-daughter resemblance and bi-directional selection were used to estimate the genetic component of latency of the aerial dispersal behavior in a wild population collected from corn plants. Mother-daughter regression analysis suggested that up to 10% of variation in initiation of aerial dispersal behavior was attributable to an additive genetic component. Subsequent selection for shorter and longer latency resulted in significant divergence between selected lines after 9 generation, but the response was not symmetrical. Realized heritability for shorter latency was 0.09, while that for longer latency was not different from 0. This response to selection was consistent with results of the mother-daughter analysis, and the response asymmetry may explain the high variability in the mother-daughter regression. In both their natural habitat and in a corn agroecosystem, mites survive by using a succession of temporarily available hosts. Aerial dispersal behavior by Banks grass mites facilitates colonization of new hosts. The genetic basis and selection response of behavior initiating aerial dispersal is consistent with its role in mites population dynamics in this setting.     

Albino inflorescence proliferation of Dendrocalamus latiflorus

Summary Inflorescence proliferation is a plant tissue culture technique that, can be used to obtain in vitro inflorescences year-round without the intervening development of vegetative organs. In this study, we used albino mutant inflorescences of Dendrocalamus latiflorus as the original explant material to investigate, the effect of plant growth regulators on long-term inflorescence proliferation. The albino inflorescences proliferated on solidified Murashige and Skoog (MS) basal medium supplemented with thidiazuron (TDZ), and the optimal concentration for successful long-term inflorescence proliferation was 0.45 μM TDZ. A combination of α-naphthaleneacetic acid (NAA) with 0.45 μM TDZ inhibited the inflorescence proliferation. Inflorescences cultured on a TDZ-free medium supplemented with 26.82 μM NAA rooted in 21 d, vegetative shoots formed by 42 d and, in one case, flowering occurred after 63 d. The auxins 2,4-dichlorophenoxyacetic acid (2,4-D, 4.52 μM) and pieloram (4.14 μM) induced shoot formation. The protocol described can be used to produce large numbers of mutant inflorescences within a relatively short period of time.