Search

This concurrent validity study of Salter Environmental Type Assessment scores was conducted with the Group Environment Scale. A principal components factor analysis with varimax rotation of 191 college students' responses suggested two factors that accounted for 51% of the variance. The factor-analytic results and concurrent validity coefficients were consistent with previous research with both assessments and theoretical assumptions behind the two approaches to measuring group climate. Implications for the assessment of groups are discussed. [ABSTRACT FROM AUTHOR]

Because campus officials are relying on personal communication technologies to communicate with students, a question arises about access and usage. Although communication technologies are popular among college students, some evidence suggests that differences exist in ownership and use. We examined patterns of student ownership and use of cell phones and use of instant messaging, focusing on three predictors of digital inequality: gender, ethnicity, and income. Logistic and hierarchical linear regression analyses were used to analyze results from 4,491 students. The odds that female and white students owned cell phones were more than twice as high as for men and African-American students. Students in the $100,000-$149,000 per year income bracket were more than three times as likely to own a cell phone than those from the median bracket. However, being female, African-American, and/or from the highest income brackets was positively predictive of the number of text messages sent and the amount of time spent talking on a cell phone per week. We found no differences between students on the use of instant messaging. Implications of these results, as well as areas for further research, are provided.

Selective modification of proteins by ubiquitination is directed by diverse families of ubiquitin-protein ligases (or E3s). A large collection of E3s use Cullins (CULs) as scaffolds to form multisubunit E3 complexes in which the CUL binds a target recognition subcomplex and the RBX1 docking protein, which delivers the activated ubiquitin moiety. Arabidopsis and rice contain a large collection of CUL isoforms, indicating that multiple CUL-based E3s exist in plants. Here we show that Arabidopsis CUL3a and CUL3b associate with RBX1 and members of the broad complex/tramtrack/bric-a-brac (BTB) protein family to form BTB E3s. Eighty genes encoding BTB domain-containing proteins were identified in the Arabidopsis genome, indicating that a diverse array of BTB E3s is possible. In addition to the BTB domain, the encoded proteins also contain various other interaction motifs that likely serve as target recognition elements. DNA microarray analyses show that BTB genes are expressed widely in the plant and that tissue-specific and isoform-specific patterns exist. Arabidopsis defective in both CUL3a and CUL3b are embryo-lethal, indicating that BTB E3s are essential for plant development.

We compared tyrosinase cDNA sequences from a line of autosomal albino and Black Silky chickens isolated from cultured melanocytes by reverse transcription-polymerase chain reaction (RT-PCR). Both sources produce a single DNA fragment of predicted normal tyrosinase size. Direct sequencing of the PCR product showed three mutated sites in the tyrosinase gene of the albino chicken. Two silent point mutations and a deletion of six nucleotides (-deltaGACTGG) at 817 bp in the tyrosinase cDNA sequence were observed when compared with the White Leghorn and Black Silky cDNA sequences. The deduced albino chicken tyrosinase protein lacks two amino acids, aspartic acid and tryptophan. The position of these amino acids is consistent with one of the potential copper-binding sites that should be indispensable for function of the enzyme. We speculate that the six-base deletion is responsible for the inactive tyrosinase in this line of albino chickens.

The interactions between the subgroup A avian leukosis virus [ALV(A)] envelope glycoproteins and soluble forms of the ALV(A) receptor Tva were analyzed both in vitro and in vivo by quantitating the ability of the soluble Tva proteins to inhibit ALV(A) entry into susceptible cells. Two soluble Tva proteins were tested: the 83-amino-acid Tva extracellular region fused to two epitope tags (sTva) or fused to the constant region of the mouse immunoglobulin G heavy chain (sTva-mIgG). Replication-competent ALV-based retroviral vectors with subgroup B or C env were used to deliver and express the two soluble tv-a (stva) genes in avian cells. In vitro, chicken embryo fibroblasts or DF-1 cells expressing sTva or sTva-mIgG proteins were much more resistant to infection by ALV(A) ( approximately 200-fold) than were control cells infected by only the vector. The antiviral effect was specific for ALV(A), which is consistent with a receptor interference mechanism. The antiviral effect of sTva-mIgG was positively correlated with the amount of sTva-mIgG protein. In vivo, the stva genes were delivered and expressed in line 0 chicken embryos by the ALV(B)-based vector RCASBP(B). Viremic chickens expressed relatively high levels of stva and stva-mIgG RNA in a broad range of tissues. High levels of sTva-mIgG protein were detected in the sera of chickens infected with RCASBP(B)stva-mIgG. Viremic chickens infected with RCASBP(B) alone, RCASBP(B)stva, or RCASBP(B)stva-mIgG were challenged separately with ALV(A) and ALV(C). Both sTva and sTva-mIgG significantly inhibited infection by ALV(A) (95 and 100% respectively) but had no measurable effect on ALV(C) infection. The results of this study indicate that a soluble receptor can effectively block infection of at least some retroviruses and demonstrates the utility of the ALV experimental system in characterizing the mechanism(s) of viral entry.

A significant incidence of bursal lymphomas with long latencies was noted in transgenic breeders carrying a benign defective subgroup A avian leukosis provirus, ALVA6, in their germline and maintained free of exposure to avian retroviruses. Serotype 2 Marek's disease (MD) vaccine virus, strain SB-1, a component of the bivalent MD vaccine used to vaccinate the breeders, was suspected as a contributory factor in the increased bursal lymphoma incidence. Although these bursal lymphomas had several characteristics similar to retroviral-induced bursal lymphomas, we found no evidence of retroviral influence based on many virological, immunological and molecular tests that were performed on plasma and tumour cells. These tumours were therefore classified as spontaneous bursal lymphomas, similar to those reported for some specific pathogen-free (SPF) chicken lines. Long-term in vivo experiments in plastic isolators and carefully maintained pens with homozygous and hemizygous ALVA6 and ALVA6-free female chickens (line 0) that were either non-vaccinated, serotype 3 (herpesvirus of turkeys [HVT]; monovalent)-vaccinated, or HVT/SB-1 (bivalent) vaccinated, demonstrated that the incidence of spontaneous bursal lymphomas were significantly higher in those chickens that were vaccinated with the bivalent MD vaccine (P ⩽0.05). In addition, this incidence did not depend on the ALVA6 proviral insert since there was no significant difference in spontaneous bursal lymphoma incidence between bivalent vaccinated hemizygous ALVA6 and ALVA6-free line 0 female chickens. Thus, the increased incidence of spontaneous bursal lymphomas is correlated solely with the presence of SB-1 and is not dependent on the presence of ALVA6.

The ALVA11 germline insert in chickens is a defective subgroup A avian leukosis virus (ALV) proviral insert that expresses a low-to-moderate level of subgroup A ALV envelope glycoprotein. Chicks carrying or lacking ALVA11 were evaluated for response to challenge by RPL-42, a pathogenic field strain of subgroup A ALV, by either exposure to chicks shedding RPL-42 or direct injection with various doses of RPL-42. Chicks carrying ALVA11 were significantly more resistant, as measured by infectious virus and viral antibody status, to horizontal infection and direct injection of RPL-42 than chicks lacking ALVA11.

Avian leukosis virus (ALV) is an economically important pathogen of chickens. Both antisense RNA and antisense oligodeoxynucleotides (ODN) have been used to diminish the replication and spread of other retroviruses. The use of antisense RNA and ODN to inhibit ALV replication has been examined in cultured RP30 cells. Using an expression system that constitutively transcribes antisense ALV RNA, one transfected cell clone showed a significant reduction in virus growth. However, this effect was not reproducibly observed in other transfected cell lines or in cells in which the antisense transcript was expressed from a regulatable promoter, even though a substantial amount of antisense transcript was generated. Antisense ODN complementary to several different target sites near the 5' end of the ALV genome were also tested for antiviral activity, by comparison of antisense ODN effects to those of randomized sequence controls. An antisense ODN complementary to the ALV primer binding site demonstrated a reproducible reduction in viral replication. However, when the corresponding region was specifically employed as a target for intracellular antisense RNA expression, there again was no significant inhibition of ALV. These results suggest that in vivo expression of antisense RNA is unlikely to be an effective way to generate transgenic poultry that are resistant to field strains of ALV.

We have constructed a helper cell line and vector system based on the Bryan high titer (BH) strain of Rous sarcoma virus (RSV). BH-RSV is a defective virus which lacks an env gene; however, if env is supplied in trans, it replicates to a very high titer. Like BH-RSV, the vector contains gag and pol genes and lacks an env gene. The helper cell line supplies env in trans and permits the production of infectious virions. To construct the helper cell line the subgroup A env gene from the Schmidt-Ruppin-A (SRA) RSV was stably transfected into Qt6 cells, a chemically transformed quail fibroblast line. To minimize homology between the vector and helper cell line, transcription of the env gene is driven by a MuLV LTR, and 3' processing is controlled by the simian virus 40 (SV40) polyadenylation signal. This combination of vector and helper cells can be used to produce high-titer viral stocks in which recombinant replication-competent virus have not been detected even when the stocks were used to inoculate chickens. This system should be useful for developing transgenic chickens, studying cell lineage, and introducing genes into cultured cells.

The promoter regions of the chicken skeletal muscle alpha-actin (alpha sk-actin) and the cytoplasmic beta-actin genes were linked to the bacterial chloramphenicol acetyltransferase (CAT) gene. Replication-competent retroviral vectors were used to introduce these two actin/CAT cassettes into the chicken genome. Chickens infected with retroviruses containing the alpha sk-actin promoter expressed high levels of CAT activity in striated muscle (skeletal muscle and heart); much lower levels of CAT activity were produced in the other nonmuscle tissues. In contrast, chickens infected with retroviruses containing the beta-actin promoter linked to the CAT gene expressed low levels of CAT activity in many different tissue types and with no discernible tissue specificity. Data are presented to demonstrate that the high levels of CAT activity that were detected in the skeletal muscle of chickens infected with the retrovirus containing the alpha sk-actin promoter/CAT cassette were not due to preferential infectivity, integration, or replication of the retrovirus vector in the striated muscles of these animals.

A major mode of transmission of avian leukosis virus (ALV) is from a dam that is viremic with and immunologically tolerant to ALV, through the egg to the progeny. The authors have produced a line of chickens transgenic for a defective ALV provirus that expresses envelope glycoprotein, but not infectious virus, and is very resistant to infection with Subgroup A ALV. In the present experiment the authors sought to prevent or reduce congenital transmission by mating viremic-tolerant hens to males carrying the inserted provirus, thus introducing a gene for resistance into the progeny. Mature viremic females were mated with males hemizygous for the transgene to produce over 80 progeny each with and without the transgene. The chicks were hatched and maintained for 36 wk and observed for viremia, antibody, and the incidence of bursal lymphomas. Over 90% of the transgene-negative controls remained viremic through 36 wk of age and 51% developed bursal lymphomas. In contrast, 27% of the transgene-positive birds remained viremic and 18% died with bursal lymphomas. Thus, expression of Subgroup A envelope protein in the developing embryo reduced but did not eliminate congenital infection.

The development of transgenic technology in poultry has lagged behind that in mammals because of the unique reproductive system of birds. Therefore, we chose to use wild-type and recombinant replication-competent avian leukosis viruses to determine whether these retroviruses could be artificially introduced into the germ line by injecting them near the blastoderm of fertile eggs just before incubation. We generated 23 proviral inserts that were stably inherited through two generations. Twenty-one inserts coded for complete avian leukosis virus. Two interesting inserts failed to produce complete virus. One coded for envelope glycoprotein only and the other coded for the group-specific antigen and envelope glycoprotein. Cell culture and animal studies showed that one of these inserts was very resistant to infection and oncogenesis by subgroup A field strains of avian leukosis virus. Therefore, this represents a model system for introducing genes from the pathogen into the host to induce host resistance to the pathogen. Future studies should be aimed at developing more efficient systems for introducing replication-defective retroviral vectors or cloned DNA into the germ line of poultry so that the regulation of gene expression can be studied and transgenic technology can be applied to the improvement of this highly reproductive group of farm animals.

Shedding and congenital transmission of endogenous avian leukosis viruses were studied in viremic White Leghorn hens exogenously infected with viruses with endogenous long terminal repeats (LTRs) and in four semicongenic lines of hens that naturally express infectious endogenous viruses (EVs). Relatively high titers of infectious virus EV7 (encoded at locus ev7), Rous-associated virus-0 (RAV-0), and recombinant 882/-16 RAV-0 were detected in blood cells and sera from exogenously infected hens, but marked differences were noted in the incidence of congenitally infected progeny. In enzyme immunoassays that detect viral group-specific antigen, little or no p27 was detected in albumens from dams infected with RAV-0. However, hatchmates infected with either EV7 or recombinant 882/-16 RAV-0, which was constructed with an RAV-0 LTR, shed high titers of p27. Similarly, semicongenic hens that expressed RAV-0 (EV2) (encoded at locus ev2) shed little or no p27 into albumens, but hens that harbored ev10, ev11, and ev12 shed high titers of p27. A slower electrophoretic mobility of p27, considered to be characteristic of EVs that are restricted in congenital transmission, was not associated with low levels of shedding or congenital transmission; p27 from other EVs and p27 from an avian leukosis virus field strain, all of which are shed at high levels, had mobilities identical to that of p27 from RAV-0. Although shedding and congenital transmission appear to be controlled by the viral genome, there was no correlation between low efficiency of shedding or congenital transmission and endogenous LTR or p27 sequences.

Because the available avian leukosis viral (ALV) vectors are moderately oncogenic in vivo, they are not suitable for insertion into the germ line. A significant reduction in the oncogenicity of the ALV vectors can be achieved by substituting the noncoding long terminal repeats (LTR) regions of the ALV virus with the LTR of the nononcogenic endogenous RAV-O virus. There is good evidence that the resulting RAV-O LTR vectors can be inserted into the germ line of domestic chickens and have the potential for inserting cloned sequences that can be used for poultry improvement.

Antibody raised against the purified human erythrocyte glucose transporter specifically precipitated four proteins from normal and Rous sarcoma virus-transformed chicken embryo cells: a major protein of Mr 41,000 and minor proteins of Mr 68,000, 73,000, and 82,000. The Mr 41,000 and 82,000 proteins were found only in a membrane fraction, not in the soluble fraction, and displayed a heterogeneous mobility on NaDodSO4/polyacrylamide gel electrophoresis, suggesting glycosylation. The Mr 41,000 and 82,000 proteins were increased in amount after malignant transformation in direct proportion to the increase in hexose transport rate, and the increase was dependent on the expression of the src gene product, as revealed with a temperature-conditional src mutant. We suggest that the Mr 41,000 and 82,000 proteins are the glucose transporter of chicken embryo fibroblasts, or a component of the glucose transporter. These experiments provide direct evidence that malignant transformation increases the rate of glucose transport by increasing the number of transporters in the membrane.

We have measured uptake of 3H-hexoses into diploid human cells by exposing them to brief pulses of isotopic sugar during the log-growth, subconfluent-growth, and confluent-growth (contact inhibited) phases of the strain HSWP derived from human skin. 3H-deoxyglucose appears to be taken up three times faster than 3H-glucose. After exposure to 3H-glucose for longer than one minute, the cells excrete approximately 70% of the isotope into the medium as lactate. If lactate production (and hence excretion) is abolished by treating the cellls with iodoacetic acid or dinitrofluorobenzene, neither of which inhibits transport, the uptake of 3H-glucose is found to be in fact somewhat larger than that of 3H-deoxyglucose. If cells are deprived of glucose for 24 hours, apparent uptake of 3H-glucose is enhanced 10-fold or more. This latter increase is accounted for by 2- to 3-fold enhancement of true transport plus retention of greater than 90% of the radioactivity, since little lactate is formed or excreted in glucose-deprived cells. Deoxyglucose, galactose, or pyruvate when present during glucose deprivation each have quantitatively different effects on the cells' capacity to produce lactate from a short pulse of glucose, but none of them prevents the enhancement of hexose transport. After restoration of 5 mM glucose to starved cells, their metabolsim returns to normal (in the sense that approximately 70% of the glucose taken up in a pulse is again excreted as lactate), with a half-time of 0.5 hour; but the transport of hexoses returns to control levels much more slowly, with a half-time of approximately 6 hours. The two processes appear to be independently regulated.

We injected chick syncytial strain of reticuloendotheliosis virus (CS-REV) and wild type and recombinant avian leukosis virus (ALV) near the blastoderm of unincubated fertilized embryos and CS-REV intra-abdominally at day of hatch, and we progeny tested the surviving ALV viremic males and REV viremic males and females for transmitted viral genetic material. A number of positive progeny were identified and their deoxyribonucleic acid (DNA) analyzed for restriction enzyme fragments that hybridized with viral genetic material. Most of the progeny had simple restriction enzyme patterns unlike the viremic parents or congenitally infected progeny. This is suggestive evidence that retroviral genetic information has been inserted into the germ line of chickens.

Pooled semen from several inbred special chicken strains was diluted with solutions containing glycerol or dimethylacetamide as a cryoprotectant. One-half milliliter samples in capped glass vials were frozen at 3 C/min to -35 C in a programmable freezer and stored in a nitrogen vapor tank. One vial of thawed semen was used to inseminate 4 hens by intravaginal, intrauterine, or intramagnal procedures. The intramagnal technique required minor surgery but always produced chicks in seven lines in contrast to the nonsurgical methods. Frozen semen of one strain stored for 29 weeks produced 12 to 14 chicks per vial when inseminated into 4 hens. This method, therefore, will reliably rescue gene pools from semen after long-term storage.

Transport rates of a number of nutrients and ions have been surveyed in chicken embryo fibroblasts that were density inhibited, growing exponentially, or transformed by Rous sarcoma virus. All the transport systems examined displayed changes associated with changes in growth rate. The rate of ouabain-sensitive potassium transport declined in density-inhibited cells, and increased rapidly in response to serum stimulation. This transport system was regulated both by changes in the activity of the transporters and by the number of transporters in the cell membrane. The rate of transport of the amino acid analog alpha-aminoisobutyric acid declined when cells became density inhibited, but also showed alterations in regulation that were associated with malignant transformation. The rate of glucose transport displayed both growth state-related and transformation-specific changes. The increased rate of glucose transport seen in transformed cells is due to an increase in the number of glucose transporters in the cell membrane. Increased glucose transport is necessary for subsequent changes in glycolysis, and temporally precedes some of the changes in activity of glycolytic enzymes.

The flavonol quercetin, a phloretin analog, inhibits transport of 2-deoxyglucose and 3-O-methylglucose in a cultured human diploid fibroblast. This inhibition is related to transport itself and not to the reported effects of flavonoids on membrane-bound ATPases. From concentration-inhibition curves at several pH's we conclude that uncharged (acid) quercetin (pK = 7.65) is the inhibitory form of the molecule (K1 = 10micron). Quercetin, unlike phloretin, is rapidly degraded in 0.1 N NaOH; the degradation products are weakly inhibitory to hexose transport.

We have artificially introduced 23 avian leukosis virus (ALV) proviral inserts into the chicken germ line by injection of wild-type and recombinant subgroup A ALV near the blastoderm of fertile eggs just before incubation. Eight viremic males were identified as germline mosaics because they transmitted proviral DNA to their generation 1 (G-1) progeny at a low frequency. Eleven female and 9 male G-1 progeny carried 23 distinct proviruses that had typical major clonal proviral-host DNA junction fragments detectable after digestion of their DNA with SacI, Southern blotting and hybridization with a probe representing the complete ALV genome. These proviruses, identified by their typical proviral-host DNA junction fragments, were transmitted to approximately 50% of their G-2 progeny after mating the G-1 parents to a line of chickens lacking endogenous ALV proviral inserts. One G-1 female carried 2 proviruses and another 3. The proviruses appeared to be scattered throughout the genome. One of the 14 proviruses carried by females was on the sex (Z) chromosome. Two of the 3 proviruses carried by a single G-1 female were linked with a recombination frequency of about 0.20. Twenty-one of the proviruses coded for infectious ALV. Two proviruses coded for envelope glycoprotein, and cell cultures carrying them were relatively resistant to subgroup A sarcoma virus, but failed to produce infectious ALV. One of these proviruses coded for internal gag proteins, had a deletion in pol, but produced non-infectious virus particles. The other failed to code for gag proteins and had no detectable internal deletions nor did it produce virus particles. Thus, we have shown that replication-competent ALV can artificially infect germ-line cells and that spontaneous defects in the inherited proviruses occur at a rather low rate.

This report describes the unique biological properties of a transgenic chicken line that contains a defective avian leukosis virus (ALV) proviral insert that we call alv6. Chick embryo fibroblasts (CEF) containing this insert express subgroup A envelope glycoprotein since they yield focus-forming pseudotype virus when co-cultivated with transformed quail cells expressing envelope-defective Bryan high-liter Rous sarcoma virus (RSV). In addition, these cells display high interference to subgroup A RSV but not to subgroup B RSV infection. Chickens containing this insert are highly resistant to pathogenic subgroup A ALV infection, but show little immunological tolerance to subgroup B ALV infection. Thus we have artificially inserted a dominant gene for resistance to avian leukosis infection into the chicken germ line.

Transformation by Rous sarcoma virus results in a dramatic increase in the rate at which the transformed cells transport glucose across the cell membrane. The increased transport rate is a consequence of an increased number of transporters in the transformed cells. Utilizing antibody raised against the purified human erythrocyte glucose transporter, we have identified the glucose transporter as a membrane glycoprotein with a monomer Mr of approximately 41,000. The increased rate of glucose transport is dependent on the activity of pp60src, the transforming protein of Rous sarcoma virus. This protein has been shown to be a protein kinase that phosphorylates on tyrosine residues. We have examined the tyrosine phosphorylation of a major cellular protein of Mr 36,000 in cells infected with a panel of partially transforming mutants of Rous sarcoma virus. One of these mutants (CU2) increases the rate of glucose transport only slightly and does not render the infected cells fully anchorage independent or tumorigenic (although other transformation parameters are fully induced). Cells infected with this mutant display a 36,000-dalton protein that is phosphorylated to a considerably lesser extent than cells infected with wild-type virus. Analyses of this sort may help to identify the cellular targets of pp60src whose phosphorylation is necessary for the increased glucose transport rate.

We infected early chicken embryos by injection of wild-type and recombinant avian leukosis viruses into the yolk of unincubated, fertile eggs. The viremic males (designated generation 0 (G-0] were tested for transmission of proviral DNA to their G-1 progeny. Nine of 37 G-0 viremic males were mosiac and proviral DNA was transmitted to their progeny at frequencies varying from 1 to 11%. All of the G-1 progeny examined by restriction enzyme analysis for clonality of proviral junction fragments had one to three simple but different fragments. The proviral DNA was transmitted from G-1 to the G-2 progeny in a Mendelian fashion thus proving that retroviral genes have been inserted into the chicken germ line. One of the viruses is a candidate vector for insertion of foreign genes into the chicken germ line.

Epizootiological studies were conducted on a commercial turkey breeder flock naturally infected with nondefective reticuloendotheliosis (RE) virus. Although RE virus was isolated from 27 (46%) of the 59 hens studied, only 4 of the 45 hens tested transmitted RE virus to progeny during a 6-week observation period and the overall transmission rate was 1.8%. The transmitter hens were of two types: three hens were consistently viremic and antigenemic and lacked antibody; one hen was viremic but lacked detectable viral antigen and possessed antibody. Toms appeared to play no role in vertical transmission of the infection. Of several tests evaluated for detection of transmitter hens, the direct enzyme-linked immunosorbent assay on albumen was probably best, since it detected three of four transmitter hens, detected relatively few nontransmitter hens, and had the best consistency of any test. No significant differences in hatchability were found between eggs from viremic and non-viremic hens. These findings can be utilized in the development of programs for eradication of RE virus from turkey breeding flocks.