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T Rowe

Publications and source records attributed to T Rowe.

At least 37 records · Page 2Linked to original sources
PubMed1998

Navigation through vector addition.

During short foraging excursions away from their home, central place foragers update their position relative to their point of departure by processing signals generated by locomotion. They therefore can home along a self-generated vector without using learned references. In rodents and other mammals, this path integration process (dead reckoning) can occur on the basis of purely internal signals, such as vestibular or proprioceptive (re)afferences. We report here that hamsters are also capable of proceeding to a previously learned feeding site through vector information from locomotion only. The subjects compute the direction and distance to the goal by subtracting their current-position vector from the stored nest-to-goal vector. This computation pertains to locations per se and therefore occurs in absolute space, independently of landmark objects. If available, prominent visual cues merely serve to confirm the path planned through the addition of self-generated vectors, whereas visual as well as nonvisual references confirm that the subject has arrived at the goal site.

Animals↗
PubMed1998

Role of vesicle-associated syntaxin 5 in the assembly of pre-Golgi intermediates.

Syntaxins are thought to function during vesicular transport as receptors on the target membrane and to contribute to the specificity of membrane docking and fusion by interacting with vesicle-associated receptors. Here, syntaxin 5 (Syn5) was shown to be an integral component of endoplasmic reticulum-derived transport vesicles. This pool, but not the target, Golgi-associated Syn5 pool, was essential for the assembly of vesicular-tubular pre-Golgi intermediates and the delivery of cargo to the Golgi. The requirement for vesicle-associated Syn5 in transport suggests a reevaluation of the basis for operation of the early secretory pathway.

Adenosine Triphosphate↗
PubMed1998

Characterization of an avian influenza A (H5N1) virus isolated from a child with a fatal respiratory illness.

An avian H5N1 influenza A virus (A/Hong Kong/156/97) was isolated from a tracheal aspirate obtained from a 3-year-old child in Hong Kong with a fatal illness consistent with influenza. Serologic analysis indicated the presence of an H5 hemagglutinin. All eight RNA segments were derived from an avian influenza A virus. The hemagglutinin contained multiple basic amino acids adjacent to the cleavage site, a feature characteristic of highly pathogenic avian influenza A viruses. The virus caused 87.5 to 100 percent mortality in experimentally inoculated White Plymouth Rock and White Leghorn chickens. These results may have implications for global influenza surveillance and planning for pandemic influenza.

Amino Acid Sequence↗
PubMed1998

GBV-C/HGV coinfection in HIV-1-positive men: frequent detection of viral RNA in blood plasma but absence from seminal fluid plasma.

Sequential paired samples of blood and seminal fluid were obtained from a cohort of 54 HIV-1-infected homosexual males. The prevalence of GBV-C/HGV RNA in the cell-free fractions of some of these patients was determined using reverse-transcription polymerase chain reaction (RT-PCR). To assess the effects of HIV-1 and HCV infection upon GBV-C/HGV RNA status, blood CD4 cell counts, HCV RNA status, and HIV-1 proviral DNA and viral RNA titres were also determined. GBV-C/HGV RNA was detected in 8/30 (27%) of the blood plasma samples obtained at the start of the study, and was present at a frequency of 14/64 (22%) in all the blood plasma samples tested. By contrast, GBV-C/HGV RNA was not detected in the 26 seminal fluid samples obtained at the start of the study, including 8 samples obtained from patients for which GBV-C/HGV RNA was detected in the corresponding blood sample. Of the samples tested for the presence of both GBV-C/HGV and HCV RNA, there was no evidence of coinfection. Although GBV-C/HGV RNA detection rates were significantly higher in individuals with blood CD4 cell counts greater than 200 cells per microlitre, there were no significant differences in the median blood CD4 cell counts or HIV-1 proviral DNA or viral RNA titres observed between the GBV-C/HGV-positive and -negative individuals. The failure to detect GBV-C/HGV RNA in seminal fluid samples obtained from this cohort would suggest that further studies need to be carried out to determine the roles of sexual transmission and of seminal fluid in GBV-C/HGV infection.

CD4 Lymphocyte Count↗
PubMed1998

A pedal dynamometer for off-road bicycling.

This paper describes the design and accuracy evaluation of a dynamometric pedal, which measures the two pedal force components in the plane of the bicycle. To realize a design that could be used during actual off-road cycling, a popular clipless pedal available commercially was modified so that both the form and the function of the original design were maintained. To measure the load components of interest, the pedal spindle was replaced with a spindle fixed to the pedal body and instrumented with eight strain gages connected into two Wheatstone bridge circuits. The new spindle is supported by bearings in the crank arm. Static calibration and a subsequent accuracy check revealed root mean square errors of less than 1 percent full scale (FS) when only the force components of interest were applied. Application of unmeasured load components created an error less than 2 percent FS. The natural frequency with half the weight of a 75 kgf person standing on the pedal was greater than 135 Hz. These performance capabilities make the dynamometer suitable for measuring either pedaling loads due to the rider's muscular action or inertial loads due to surface-induced acceleration. To demonstrate this suitability, sample pedal load data are presented both for steady-state ergometer cycling and coasting over a rough surface while standing.

Acceleration↗
PubMed1998

Comparisons of highly virulent H5N1 influenza A viruses isolated from humans and chickens from Hong Kong.

Genes of an influenza A (H5N1) virus from a human in Hong Kong isolated in May 1997 were sequenced and found to be all avian-like (K. Subbarao et al., Science 279:393-395, 1998). Gene sequences of this human isolate were compared to those of a highly pathogenic chicken H5N1 influenza virus isolated from Hong Kong in April 1997. Sequence comparisons of all eight RNA segments from the two viruses show greater than 99% sequence identity between them. However, neither isolate's gene sequence was closely (>95% sequence identity) related to any other gene sequences found in the GenBank database. Phylogenetic analysis demonstrated that the nucleotide sequences of at least four of the eight RNA segments clustered with Eurasian origin avian influenza viruses. The hemagglutinin gene phylogenetic analysis also included the sequences from an additional three human and two chicken H5N1 virus isolates from Hong Kong, and the isolates separated into two closely related groups. However, no single amino acid change separated the chicken origin and human origin isolates, but they all contained multiple basic amino acids at the hemagglutinin cleavage site, which is associated with a highly pathogenic phenotype in poultry. In experimental intravenous inoculation studies with chickens, all seven viruses were highly pathogenic, killing most birds within 24 h. All infected chickens had virtually identical pathologic lesions, including moderate to severe diffuse edema and interstitial pneumonitis. Viral nucleoprotein was most frequently demonstrated in vascular endothelium, macrophages, heterophils, and cardiac myocytes. Asphyxiation from pulmonary edema and generalized cardiovascular collapse were the most likely pathogenic mechanisms responsible for illness and death. In summary, a small number of changes in hemagglutinin gene sequences defined two closely related subgroups, with both subgroups having human and chicken members, among the seven viruses examined from Hong Kong, and all seven viruses were highly pathogenic in chickens and caused similar lesions in experimental inoculations.

Amino Acid Sequence↗
PubMed1997

Immune stimulation may contribute to enhanced progression of SIV induced disease in rhesus macaques.

A number of rhesus macaques experimentally infected with SIV isolates such as SIVmac251, fail to seroconvert, develop high plasma viremia and die rapidly (within 6-7 months p.i.). We hypothesized that such rapid progression is a result of a state of hyperimmune activation and concomitant immune suppression of these animals at the time of virus challenge. In efforts to test the hypothesis that immune activation leads to rapid progression of lentivirus-induced disease, adult rhesus macaques were infected with SIV mac251 and received an alternate monthly schedule of repeated immunization with allogeneic cells, keyhole limpet hemocyanin and tetanus toxoid (group I). For purposes of controls, a group of monkeys was infected with the same pool and dose of virus but were not immunized (group II) and a group was immunized with the same schedule of multiple antigens as group I but were not infected with SIV (group III). All the animals in group I (n = 3) either failed to seroconvert or developed very low levels of SIV antibodies, had high plasma p27 defined antigenemia, and died within 8 months (2/3 died within 4 months). Of the animals in group II (n = 8), two patterns emerged as we had noted before. One subgroup (3 animals), displayed the same profile as group I (failure to fully seroconvert, high p27 levels and death by 8 months), whereas the other subgroup (5 animals) seroconverted, had low plasma p27 levels, and survived past 11 months (2/5 still alive past 22 months). All 3 animals in group III remained healthy. The data provided herein suggest that either experimental or natural (due to factors not clear at present) immune stimulation may lead to accelerated lentivirus induced disease progression most likely due to immune suppression and has implications for the understanding of the mechanisms for the rate of disease progression in human HIV-1 infection.

Animals↗
PubMed1996

Coevolution of the mammalian middle ear and neocortex.

Phylogenetic analysis with x-ray computed tomography of fossilized and recent crania implicates differential growth of the neocortex in the evolution and development of the mammalian middle ear. In premammalian tetrapods, the middle ear evolved as a chain of bones attached to the mandible and cranium, but in adult mammals the chain is detached from the mandible and lies behind it. The neocortex evolved concurrently with detachment of the chain. In mammalian development the auditory chain arises connected to the mandible but later detaches, recapitulating the phylogenetic transformation. In modern didelphid development, the auditory chain reaches mature size by the third week after birth and is then separated from the jaw and displaced caudally as the neocortex grows for another 9 weeks.

Animals↗
PubMed1996

The organization of endoplasmic reticulum export complexes.

Export of cargo from the ER occurs through the formation of 60-70nm COPII-coated vesicular carriers. We have applied serial-thin sectioning and stereology to quantitatively characterize the three-dimensional organization of ER export sites in vivo and in vitro. We find that ER buds in vivo are nonrandomly distributed, being concentrated in regional foci we refer to as export complexes. The basic organization of an export complex can be divided into an active COPII-containing budding zone on a single ER cisterna, which is adjacent to budding zones found on distantly connected ER cisternae. These budding foci surround and face a central cluster of morphologically independent vesicular-tubular elements that contain COPI coats involved in retrograde transport. Vesicles within these export complexes contain concentrated cargo molecules. The structure of vesicular-tubular clusters in export complexes is particularly striking in replicas generated using a quick-freeze, deep-etch approach to visualize for the first time their three-dimensional organization and cargo composition. We conclude that budding from the ER through recruitment of COPII is confined to highly specialized export complexes that topologically restrict anterograde transport to regional foci to facilitate efficient coupling to retrograde recycling by COPI.

Animals↗
PubMed1996

COPII vesicles derived from mammalian endoplasmic reticulum microsomes recruit COPI.

ER to Golgi transport requires the function of two distinct vesicle coat complexes, termed COPI (coatomer) and COPII, whose assembly is regulated by the small GTPases ADP-ribosylation factor 1 (ARF1) and Sar1, respectively. To address their individual roles in transport, we have developed a new assay using mammalian microsomes that reconstitute the formation of ER-derived vesicular carriers. Vesicles released from the ER were found to contain the cargo molecule vesicular stomatitis virus glycoprotein (VSV-G) and p58, an endogenous protein that continuously recycles between the ER and pre-Golgi intermediates. Cargo was efficiently sorted from resident ER proteins during vesicle formation in vitro. Export of VSV-G and p58 were found to be exclusively mediated by COPII. Subsequent movement of ER-derived carriers to the Golgi stack was blocked by a trans-dominant ARF1 mutant restricted to the GDP-bound state, which is known to prevent COPI recruitment. To establish the initial site of coatomer assembly after export from the ER, we immunoisolated the vesicular intermediates and tested their ability to recruit COPI. Vesicles bound coatomer in a physiological fashion requiring an ARF1-guanine nucleotide exchange activity. These results suggest that coat exchange is an early event preceding the targeting of ER-derived vesicles to pre-Golgi intermediates.

ADP-Ribosylation Factor 1↗
PubMed1995

Characterization of a HTLV-I-infected cell line derived from a patient with adult T-cell leukemia with stable co-expression of CD4 and CD8.

A long-term T-cell line, termed SP+, was developed from a human T-cell leukemia virus type I (HTLV-I)-infected patient with adult T-cell leukemia that is dependent on exogenous IL-2 for growth. The SP+ expresses a full complimentation of HTLV-I-specific viral proteins, and contains replication competent viral particles. Restriction enzyme digestion followed by Southern blot analysis demonstrated the presence of a single integrated proviral copy and limiting dilution analysis confirmed the clonality of the cell line. Interestingly, phenotypically, the SP+ cell line is CD2+, CD3+ and coexpresses CD4 and CD8, yet lacks TCR alpha beta and TCR tau delta expression. Further ontogenetic characterization of the SP+ cell line demonstrated the lack of thymic T-cell precursor markers, including absence of cell surface expression of CD1, intracellular thymic terminal deoxynucleotidyl transferase (TdT) enzyme, as well as message expression for V(D)J recombinase activating gene-1 (RAG-1). Furthermore, the SP+ cell did express the message for the CD3 delta chain. Taken together, these data suggest that the SP+ cell line resulted from HTLV-I infection of a mature CD4+/CDB+ lymphocyte. This cell line can be potentially useful as a model, both for regulation of cellular functions by HTLV-I and for immunologic functions of mature dual CD4/CD8 positive T-cells.

Antigens, Viral↗
PubMed1995

Sequential coupling between COPII and COPI vesicle coats in endoplasmic reticulum to Golgi transport.

COPI and COPII are vesicle coat complexes whose assembly is regulated by the ARF1 and Sar1 GTPases, respectively. We show that COPI and COPII coat complexes are recruited separately and independently to ER (COPII), pre-Golgi (COPI, COPII), and Golgi (COPI) membranes of mammalian cells. To address their individual roles in ER to Golgi transport, we used stage specific in vitro transport assays to synchronize movement of cargo to and from pre-Golgi intermediates, and GDP- and GTP-restricted forms of Sar1 and ARF1 proteins to control coat recruitment. We find that COPII is solely responsible for export from the ER, is lost rapidly following vesicle budding and mediates a vesicular step required for the build-up of pre-Golgi intermediates composed of clusters of vesicles and small tubular elements. COPI is recruited onto pre-Golgi intermediates where it initiates segregation of the anterograde transported protein vesicular stomatitis virus glycoprotein (VSV-G) from the retrograde transported protein p58, a protein which actively recycles between the ER and pre-Golgi intermediates. We propose that sequential coupling between COPII and COPI coats is essential to coordinate and direct bi-directional vesicular traffic between the ER and pre-Golgi intermediates involved in transport of protein to the Golgi complex.

ADP-Ribosylation Factor 1↗
PubMed1994

Sar1 promotes vesicle budding from the endoplasmic reticulum but not Golgi compartments.

Two new members (Sar1a and Sar1b) of the SAR1 gene family have been identified in mammalian cells. Using immunoelectron microscopy, Sar1 was found to be restricted to the transitional region where the protein was enriched 20-40-fold in vesicular carriers mediating ER to Golgi traffic. Biochemical analysis revealed that Sar1 was essential for an early step in vesicle budding. A Sar1-specific antibody potently inhibited export of vesicular stomatitis virus glycoprotein (VSV-G) from the ER in vitro. Consistent with the role of guanine nucleotide exchange in Sar1 function, a trans-dominant mutant (Sar1a[T39N]) with a preferential affinity for GDP also strongly inhibited vesicle budding from the ER. In contrast, Sar1 was not found to be required for the transport of VSV-G between sequential Golgi compartments, suggesting that components active in formation of vesicular carriers mediating ER to Golgi traffic may differ, at least in part, from those involved in intra-Golgi transport. The requirement for novel components at different stages of the secretory pathway may reflect the recently recognized differences in protein transport between the Golgi stacks as opposed to the selective sorting and concentration of protein during export from the ER.

Amino Acid Sequence↗