Search

Yield of decade groups of maize (Zea maysL.) cultivars typical of those used by U.S. Corn Belt farmers in each of the decades since 1930 was evaluated across a range of soil fertility and climatic environments. This study gave estimates of the rate of genetic improvement in yield for each environment. In addition, a measure of the advisability of continued development and deployment of high yielding, management responsive single cross maize hybrids in light of potential reductions in fertilizer inputs and potentially less favorable future climatic conditions was provided. These cultivars were grown in replicated field trails in a total of 11 environments from Tennessee to Colorado in 1980 and 1981. All plots were grown according to accepted modern agronomic practices except that a low soil fertility treatment was included in both years and two limited irrigation stress treatments were included in 1981. Mean yield of cultivars from more recent decades was consistently higher than those from older decades across or within environments. Regression analysis of mean decade group yield on decade of use within each environment and on an environmental index (treatment/location/year mean yield) across environments gave significant correlations and b values which were always positive, regardless of environment. These results are consistent with the conclusion that U.S. maize production will be best served by the continued development and deployment of improved single cross maize hybrids even if less favorable soil fertility or climatic conditions should Occur.

Cloned probes of herpes simplex virus type 2 DNA were used in cytological hybridization experiments to detect herpesvirus RNA transcripts in the neoplastic cells of tumors of the uterine cervix. Virus-specific RNA was shown to represent transcription of limited regions of the genome, of which one is known to code for a DNA-binding protein that can be found by immunoperoxidase staining in the neoplastic cells of these tumors and has also been detected in cells transformed in vitro by this virus.

The accumulation of human papillomavirus type 16 (HPV-16)-specific RNAs in tissue sections from biopsies of patients with genital precancers was studied by in situ hybridization with single-stranded 35S-labeled RNA. These analyses revealed that the most abundant early-region RNAs were derived from the E4 and E5 open reading frames (ORFs). RNAs homologous to the E6/E7 ORFs were also detected, whereas RNAs homologous to the intervening E1 ORF were not. This suggests that the E4 and E5 mRNAs are derived by splicing to the upstream E6/E7 ORFs, consistent with studies of HPV-11 in condylomata (L. T. Chow et al., Cancer Cells (Cold Spring Harbor) 5:55-72, 1987). Abundant RNAs homologous to the 5' portion of L1 were also detected. These RNAs were localized to the apical strata of the epithelium. HPV-16 RNAs accumulated in discrete regions of these lesions, and when present were most abundant in the upper cell layers of the precancerous epithelium. RNAs homologous to early ORFs were also detected in some germinal cells within the basal layer of the epithelium.

We cloned the DNA from a novel human papillomavirus (HPV) present in a cervical condyloma. When DNA from this isolate was hybridized at high stringency with HPV types 1 through 50 (HPV-1 through HPV-50), it showed weak homology with HPV-6 and -16 and stronger homology with HPV-26. A detailed restriction endonuclease map was prepared which showed marked differences from the maps for other HPVs that have been isolated from the female genital tract. Reassociation kinetic analysis revealed that HPV-26 and this new isolate were less than 10% homologous; hence, the new isolate is a novel strain of HPV. The approximate positions of the open reading frames of the new strain were surmised by hybridization with probes derived from individual open reading frames of HPV-16. In an analysis of 175 genital biopsies from patients with abnormal Papanicolaou smears, sequences hybridizing under highly stringent conditions to probes from this novel HPV type were found in 4.2, 6.1, and 2.4% of biopsies containing normal squamous epithelium, condylomata, and intraepithelial neoplasia, respectively. In addition, sequences homologous to probes from this novel isolate were detected in one of five cervical carcinomas examined.

We combined molecular hybridization and histological analysis of 58 biopsy samples from the uterine cervix to correlate the presence of certain strains of human papillomaviruses (HPVs) with specific pathological changes. HPV sequences were frequently detected (85%) in biopsies that contained a broad spectrum of precancerous changes. The presence of HPV 16 correlated strongly with precancers that exhibited morphological aberrations commonly found in invasive carcinomas and precancers that have a high risk of progression. This association underscores the potential importance of HPV type 16 in the genesis of genital cancers and emphasizes the value of histological analysis for detecting potentially oncogenic HPVs.

The influence of tobacco mosaic virus (TMV) infection on nucleotide binding and phosphorylation of an Mr 68,000 host-encoded protein (p68) was examined. The phosphorylation of p68 in homogenates from TMV-infected tissues was 4-fold greater than in homogenates from mock inoculated tissues. Phosphorylation of p68 in extracts from mock inoculated tissues was enhanced by the addition of double-stranded (ds) RNA. Nucleotide photoaffinity labeling experiments indicate that p68 contains an ATP binding site with characteristics consistent with protein kinase activity. Antiserum raised against a dsRNA-dependent protein kinase activity. Antiserum raised against a dsRNA-dependent protein kinase from interferon-treated human cells immunoprecipitated p68 from extracts of TMV-infected tissue, and p68-containing immunocomplexes catalyzed the phosphorylation of endogenous p68. These data suggest that p68 may be an autophosphorylating, dsRNA-dependent protein kinase involved in viral pathogenesis. Based upon analogous functions demonstrated for dsRNA-dependent protein kinases in mammalian systems, p68 may have a role in the regulation of protein synthesis and viral replication in infected cells.