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Biomedical subjects

S M Gray

Publications and source records attributed to S M Gray.

At least 19 recordsLinked to original sources
PubMed2001

Vector specificity of barley yellow dwarf virus (BYDV) transmission: identification of potential cellular receptors binding BYDV-MAV in the aphid, Sitobion avenae.

Two proteins (SaM35 and SaM50) isolated from head tissues of the aphid vector, Sitobion avenae, were identified as potential receptors for barley yellow dwarf virus MAV isolate (Luteoviridae) based on MAV virus overlay assays and immunoblots of urea SDS 2-D gels. An anti-idiotypic antibody (MAV4 anti-ID) that mimics an epitope on MAV virions and competes with MAV in antibody binding assays also bound to SaM50 and SaM35 and to six additional proteins including a GroEL homolog. No MAV-binding proteins were detected from the nonvector aphid, Rhopalosiphum maidis, although MAV4 anti-ID did react with four proteins from R. maidis. It is hypothesized that SaM35 and SaM50 may be MAV receptors involved in MAV transmission based on their high affinity for MAV and their unique association with the vector, S. avenae. The additional aphid proteins binding the MAV4 anti-ID may represent less specific virus-binding proteins facilitating transmission through different aphid tissues.

Animals↗
PubMed2001

Seasonal abundance of aphids (Homoptera: Aphididae) in wheat and their role as barley yellow dwarf virus vectors in the South Carolina coastal plain.

Aphid (Homoptera: Aphididae) seasonal flight activity and abundance in wheat, Triticum aestivum L., and the significance of aphid species as vectors of barley yellow dwarf virus were studied over a nine-year period in the South Carolina coastal plain. Four aphid species colonized wheat in a consistent seasonal pattern. Greenbug, Schizaphis graminum (Rondani), and rice root aphid, Rhopalosiphum rufiabdominalis (Sasaki), colonized seedlingwheat immediately after crop emergence, with apterous colonies usually peaking in December or January and then declining for the remainder of the season. These two aphid species are unlikely to cause economic loss on wheat in South Carolina, thus crop managers should not have to sample for the subterranean R. rufiabdominalis colonies. Bird cherry-oat aphid, Rhopalosiphum padi (L.), was the second most abundant species and the most economically important. Rhopalosiphum padi colonies usually remained below 10/row-meter until peaking in February or March. Barley yellow dwarf incidence and wheat yield loss were significantly correlated with R. padi peak abundance and aphid-day accumulation on the crop. Based on transmission assays, R. padi was primarily responsible for vectoring the predominant virus serotype (PAV) we found in wheat. Pest management efforts should focus on sampling for and suppressing this aphid species. December planting reduced aphid-day accumulation and barley yellow dwarf incidence, but delayed planting is not a practical management option. English grain aphid, Sitobion avenae (F.), was the last species to colonize wheat each season, and the most abundant. Sitobion avenae was responsible for late-season virus transmission and caused direct yield loss by feeding on heads and flag leaves during an outbreak year.

Animals↗
PubMed2000

Tagging potato leafroll virus with the jellyfish green fluorescent protein gene.

A full-length cDNA corresponding to the RNA genome of Potato leafroll virus (PLRV) was modified by inserting cDNA that encoded the jellyfish green fluorescent protein (GFP) into the P5 gene near its 3' end. Nicotiana benthamiana protoplasts electroporated with plasmid DNA containing this cDNA behind the 35S RNA promoter of Cauliflower mosaic virus became infected with the recombinant virus (PLRV-GFP). Up to 5% of transfected protoplasts showed GFP-specific fluorescence. Progeny virus particles were morphologically indistinguishable from those of wild-type PLRV but, unlike PLRV particles, they bound to grids coated with antibodies to GFP. Aphids fed on extracts of these protoplasts transmitted PLRV-GFP to test plants, as shown by specific fluorescence in some vascular tissue and epidermal cells and subsequent systemic infection. In plants agroinfected with PLRV-GFP cDNA in pBIN19, some cells became fluorescent and systemic infections developed. However, after either type of inoculation, fluorescence was mostly restricted to single cells and the only PLRV genome detected in systemically infected tissues lacked some or all of the inserted GFP cDNA, apparently because of naturally occurring deletions. Thus, intact PLRV-GFP was unable to move from cell to cell. Nevertheless, PLRV-GFP has novel potential for exploring the initial stages of PLRV infection.

Animals↗
PubMed1999

Expression of hexokinase 1 and hexokinase 2 in mammary tissue of nonlactating and lactating rats: evaluation by RT-PCR.

Because the initial step in the metabolism of glucose involves phosphorylation by hexokinase (HK), we tested the hypothesis that the expression of the isozymes, hexokinase type 1 (HK1) and hexokinase type 2 (HK2), would be different in rat mammary tissue during pregnancy and lactation. RNA was extracted from mammary tissue dissected from timed pregnant rats (from gestional days 10 to 21) and nursing rat mothers (up to postnatal day 5) for mRNA examination by reverse transcriptase and polymerase chain reaction (RT-PCR) using isozyme specific oligonucleotide primers to the HK1 and HK2 cDNAs. The HK1 mRNA was expressed in both the nonlactating and lactating mammary gland tissue, but HK2 mRNA was found only during lactation. We speculate that the pattern of HK expression might affect human milk production and quality.

Animals↗
PubMed1999

Application of random effects models and other methods to the analysis of multidimensional quality of life data in an AIDS clinical trial.

BACKGROUND: Current analytic methods applied to multidimensional health-related quality of life (HRQOL) data do not borrow strength across analyses and do not produce summary estimates of effect. OBJECTIVES: To compare a random effects modelling approach for the analysis of multidimensional HRQOL data to the following: (1) separate analyses for each dimension; (2) O'Brien's global test procedure; and (3) multivariate analysis of variance (MANOVA). RESEARCH DESIGN: Randomized clinical trial comparing 3 treatments (Trimethoprim-Sulfamethoxazole [TS], Dapsone-Trimethoprim [DT], and Clindamycin-Primaquine [CP] for Pneumocystis carinii pneumonia [PCP]). SUBJECTS: Patients with PCP enrolled in AIDS Clinical Trials Group Protocol 108. MEASURES: A 33-item battery assessing 7 dimensions of HRQOL: physical functioning, pain, energy, general health perceptions, disability, pulmonary symptoms, and constitutional symptoms. RESULTS: Analyses focused on changes in score from baseline to Day 7 (n = 145). Separate analyses for each dimension suggested a trend favoring CP versus TS, but using a Bonferroni correction no differences were statistically significant. O'Brien's global procedure for a test of no-treatment effect versus superiority of one treatment yielded P = 0.07. MANOVA did not reveal significant differences among treatment groups. A random effects model using fixed treatment and dimension effects and separate random effects for each person showed a significant overall treatment effect (P = 0.02); changes in scores for CP averaged 10 points greater than for TS. CONCLUSIONS: Random-effects models provide a flexible class of models for analyzing multidimensional quality of life data and estimating treatment effects because they borrow strength across dimensions.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Mechanisms of arthropod transmission of plant and animal viruses.

A majority of the plant-infecting viruses and many of the animal-infecting viruses are dependent upon arthropod vectors for transmission between hosts and/or as alternative hosts. The viruses have evolved specific associations with their vectors, and we are beginning to understand the underlying mechanisms that regulate the virus transmission process. A majority of plant viruses are carried on the cuticle lining of a vector's mouthparts or foregut. This initially appeared to be simple mechanical contamination, but it is now known to be a biologically complex interaction between specific virus proteins and as yet unidentified vector cuticle-associated compounds. Numerous other plant viruses and the majority of animal viruses are carried within the body of the vector. These viruses have evolved specific mechanisms to enable them to be transported through multiple tissues and to evade vector defenses. In response, vector species have evolved so that not all individuals within a species are susceptible to virus infection or can serve as a competent vector. Not only are the virus components of the transmission process being identified, but also the genetic and physiological components of the vectors which determine their ability to be used successfully by the virus are being elucidated. The mechanisms of arthropod-virus associations are many and complex, but common themes are beginning to emerge which may allow the development of novel strategies to ultimately control epidemics caused by arthropod-borne viruses.

Animals↗
PubMed1998

Developmental expression of hexokinase 1 and 3 in rats.

Mammalian hexokinase types one and three (HK1 and HK3) are 100 kDa isozymes that phosphorylate glucose to glucose-6-phosphate. HK1 is present in most tissues but is especially prominent in brain and kidney. HK3 is less well studied, but may be most prominent in the spleen and lymphocytes. In this study, we determined the ontogeny of the expression of these isoforms in the rat. Using immunohistochemistry, we identified HK1 and HK3 immunoreactivity in the brain, heart, kidney, liver, skeletal muscle and spleen from gestational day 14 (E14) to 45 days after birth (P45). With the exception of the liver and spleen, we observed a similar age- and cell-dependent staining pattern for both isoforms in all organs studied. The brain and spleen were analyzed in more detail to identify specific regions of immunoreactivity during maturation. A transient expression of HK1 and HK3 was noted in the cell bodies of mature neurons, including layers V and VI of the cerebral cortex and the cerebellar Purkinje cells followed by localization to the white matter of the cerebrum and cerebellum. In the spleen, HK3 immunoreactivity was detected postnatally and appeared to track with the infiltration of B cells. Our demonstration of changing patterns of immunoreactivity for HK1 and HK3 in fetal and postnatal organs suggests that these HK isoforms are involved the process of development. We speculate that HK1 and HK3 share a complex interaction during development of these organs and regulate glucose metabolism at multiple levels during development.

Animals↗
PubMed1998

Estimating a treatment effect from multidimensional longitudinal data.

Multidimensional longitudinal data result when researchers measure an outcome through time that is quantified by many different response variables. These response variables are often defined on different numerical scales. The objective of this paper is to present a method to summarize and estimate an overall treatment effect from this type of longitudinal data. A regression model is proposed that assumes the treatment effect can be parameterized as an acceleration or deceleration of the time scale of each response variable's trajectory. Generalized estimating equations are used to estimate the model parameters. Cognitive and functional ability data from Alzheimer's disease patients and quality of life data from an AIDS clinical trial are used to illustrate the model.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Two distinct mechanisms regulate luteovirus transmission efficiency and specificity at the aphid salivary gland.

Barley yellow dwarf luteovirus (BYDV) particles are transmitted by aphids in a species-specific manner. Transmission to plants requires that the virus particles be transported across the basal lamina and plasmalemma of the accessory salivary gland (ASG). To characterize the role of the ASG basal lamina in regulating BYDV transmission, five aphid species were microinjected with purified New York isolates BYDV-PAV or -RPV. Both viruses associated specifically only with the ASG basal lamina. The ability of virions to penetrate the basal lamina was separate from the ability to penetrate the plasmalemma. When the salivary glands of vector, Sitobion avenae, or non-vector, Rhopalosiphum maidis, aphids were incubated in vitro with New York isolate BYDV-MAV, virions only attached to the ASG basal lamina of S. avenae. When anionic and cationic ferritin were microinjected into aphids, only cationic ferritin aggregated on the surface of the ASG basal lamina and at openings of plasmalemma invaginations into the cytoplasm, suggesting that these sites had a net negative charge. In vitro studies of anionic and cationic gold penetration of ASG basal laminae indicated a macromolecular size exclusion limit of approximately 20 nm that depended on charge. Anionic gold particles did not accumulate in the basal lamina as densely as the 25 nm BYDV particles, suggesting that the virus particles have a greater affinity for the ASG basal lamina. These results indicate that both the ASG basal lamina and plasmalemma contain specific components independently involved in the recognition and transmission of luteoviruses.

Animals↗
PubMed1996

Aphid transmission and systemic plant infection determinants of barley yellow dwarf luteovirus-PAV are contained in the coat protein readthrough domain and 17-kDa protein, respectively.

Proteins encoded by open reading frames (ORF) 3, 4, and 5 of the barley yellow dwarf luteovirus genome are translated from a single subgenomic RNA. The structural proteins are encoded by ORF 3 (coat protein) and ORF 5 (readthrough domain) and contain undefined domains that regulate the movement of virus through aphid vectors. The biological function of the nonstructural 17-kDa protein encoded by ORF 4 is unknown. A complementation method was employed to test the ability of barley yellow dwarf virions carrying mutations within the readthrough domain and the 17-kDa protein to be transmitted by aphids and to cause systemic infections in plants. We show that the readthrough domain is required for aphid transmission; however, it is not required for virus to be taken up by aphid hindgut cells and released into the hemocoel. The circulative pathway of luteoviruses in aphid vectors requires that virus be actively transported from the hemolymph into the salivary system. Thus, it appears that the readthrough domain is required for transport of virus through membranes of the aphid salivary glands. Furthermore, the readthrough domain was not required for systemic infection of plants, but did influence the accumulation of virus in infected plants. The 17-kDa protein is required for the systemic infection of plants.

Animals↗
PubMed1996

Plant virus proteins involved in natural vector transmission.

Plant viruses transmitted by invertebrate vectors either reversibly bind to vector mouthparts or are internalized by the vector and later secreted. Viral proteins mediate the binding of plant viruses to vector mouthparts and the transport of virus across vector-cell membranes. Both mechanisms probably involve conformational changes of virus proteins during their association with the vector.

Animals↗
PubMed1995

Readthrough protein associated with virions of barley yellow dwarf luteovirus and its potential role in regulating the efficiency of aphid transmission.

Purified particles of barley yellow dwarf luteovirus (BYDV) contain a major 22-kDa protein and a minor protein of approximately 58 kDa. The 22-kDa capsid protein is encoded by open reading frame (ORF) 3. ORF 5 is immediately downstream and in frame with ORF 3 and a 72-kDa protein can be translated via a readthrough suppression of the ORF 3 termination codon. Antibodies were produced against two Escherichia coli expressed polypeptides that represent the amino- and carboxyl-terminal halves of a putative 50-kDa protein encoded by ORF 5. Immunological analyses indicated that the 58-kDa protein associated with purified virions contained sequences encoded by ORF 3 and ORF 5. The carboxyl terminal portion of the full-length (72 kDa) readthrough protein was absent from the 58-kDa protein. The full-length readthrough protein was detected in infected oat protoplasts and plant tissue, but was not associated with virus particles purified from plants. The carboxyl-terminal portion of the 72-kDa readthrough protein was not required for aphid transmission; however, virus was transmitted more efficiently from protoplast extracts containing virions and soluble 72-kDa readthrough protein than from mock-inoculated protoplast extracts to which plant purified virus was added. The full-length readthrough protein, although not required for transmission, may increase the transmission efficiency of BYDV by aphids.

Animals↗
PubMed1994

Hexokinase binding in ischemic and reperfused piglet brain.

Hexokinase catalyzes the first step in cerebral glucose utilization and is a rate-limiting enzyme in glycolysis. Glucose utilization is tightly coupled to cerebral blood flow so that during ischemia the brain has a decreased supply of glucose, as well as oxygen. We studied hexokinase enzymatic activity in a newborn piglet model of ischemia-reperfusion to determine if any changes in the activity or mitochondrial binding of the enzyme occurred. We observed that mitochondrial binding of cortical HK increased from 55 to 71% with ischemia and returned toward control levels, but did not completely recover, after 2 h of reperfusion.

Animals↗
PubMed1994

Success of audit in reducing the time taken to administer thrombolysis and aspirin in patients with acute myocardial infarction.

We assessed whether audit might reduce the time taken to give thrombolysis and aspirin in patients with acute myocardial infarction (N = 116). A retrospective analysis was performed of the sources of delay in giving the drugs (N-60) and the data were presented to clinical staff accompanied by guidelines aimed at eliminating delays. A prospective survey was undertaken (N = 56) after these interventions. Audit resulted in an overall 31% reduction (P = 0.013) in the time to administer thrombolysis (median 55 minutes [range 21-148] v 38 [15-155]): there was a 57% fall (P < 0.0001) in the time to record an electrocardiogram (14 minutes [4-34] v 6 [1-19]) and a 33% decrease (P = 0.047) in the time taken to begin thrombolysis in the coronary care unit (15 minutes [0-110) v 10 [5-70]). The time taken to give aspirin was also reduced (P = 0.001) from 58 minutes (15-400) to 15 (3-235). The time taken to administer thrombolysis and aspirin to patients admitted with acute myocardial infarction can be reduced by audit.

Adult↗
PubMed1992

Localization of a surface domain of the capsid protein of barley yellow dwarf virus.

We describe a method for localizing protein domains situated at the surface of virus particles. A cDNA clone of the New York PAV isolate (NY-PAV) of barley yellow dwarf virus (BYDV) containing the capsid protein gene was generated and sequenced. A defined set of overlapping cDNA fragments specific to the capsid protein ORF of NY-PAV was subcloned into the pGEX expression vectors. Cells of Escherichia coli carrying these plasmids synthesize recombinant glutathione S-transferase/capsid proteins. These proteins were used in immunoblot experiments to localize the epitopes of three PAV-BYDV-directed monoclonal antibodies to a 20 amino acid-long segment of the NY-PAV capsid protein. All three monoclonal antibodies reacted with NY-PAV virions in a triple antibody sandwich enzyme-linked immunosorbent assay, indicating that their epitopes are located at the virion surface.

Amino Acid Sequence↗
PubMed1991

Use of group-specific primers and the polymerase chain reaction for the detection and identification of luteoviruses.

A general diagnostic assay for a number of distinct luteoviruses was developed using the polymerase chain reaction (PCR) and restriction enzyme analysis. Two minimally degenerate, group-specific primers were derived from previously published RNA sequences of three luteoviruses. This primer pair generated specific PCR fragments of about 530 bp from extracts of plants infected with potato leafroll virus, beet western yellows virus, or New York barley yellow dwarf virus (BYDV) serotypes MAV, PAV, RMV, RPV and SGV, which span much of the respective viral coat protein gene. Each virus was easily distinguished from the others by restriction enzyme analysis of the amplified DNA products. Samples from BYDV-infected oat and wheat collected in Nebraska were identified as containing PAV-like serotypes; micro-heterogeneity was detected in several samples. This method provides a rapid, sensitive and relatively inexpensive means of luteovirus detection and identification. It is the first test capable of simultaneously detecting all five BYDV serotypes.

Base Sequence↗
PubMed1988

The mechanism and control of rabbit oviduct fluid formation.

The formation of rabbit oviduct fluid was monitored continuously by using an in situ vascular perfusion technique. Oviduct fluid was secreted linearly for at least 3 h at a mean rate of 20.8 +/- 1.5 microliter/h in estrous does. The rate more than doubled on Day 1 following mating, was similar to the value at estrus on Day 2, and dropped to 8.3 microliter on Day 3. Dibutyryl cyclic adenosine 3',5'-monophosphate (cAMP, 1 mM) added to the vascular medium abolished fluid secretion. The same response was obtained, after a lag period, following the addition of cholera toxin (1 mM), forskolin (1 mM), theophylline (1 mM), phorbol dibutyrate (40 microM), A23187 (2 micrograms/ml), 4-acetamido-4'-isothiocyonatostilbene-2,2'-disulphonic acid (SITS, 1 mM), and bumetanide (10 microM) to the vascular medium. N-ethylmaleimide (1 mM), which inhibits adenylate cyclase, stimulated oviduct fluid formation. The transmural potential difference (p.d.) across the oviduct was 5.46 +/- 1.01 mV. This was increased after cAMP addition to 8.7 +/- 1.22 mV. The p.d. in oviducts taken 3 days post-ovulation was 7.6 +/- 1.75 mV, and was increased by cAMP to 12.7 +/- 0.53 mV. Exposure to cholera toxin and forskolin almost doubled the cAMP content of the oviduct. The undirectional flux of chloride ions from the vascular compartment into the lumen was reduced by about 75% after the addition of cAMP, SITS, and bumetanide. A tentative model to account for the formation and regulation of rabbit oviduct fluid in terms of ion fluxes and cAMP and calcium ion concentrations is presented.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗