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Biomedical subjects

D Wheeler

Publications and source records attributed to D Wheeler.

At least 73 records · Page 4Linked to original sources
PubMed1992

Transverse agarose pore gradient gel electrophoresis of DNA.

Transverse agarose pore gradient gels were prepared on GelBond in the concentration range of nominally 0.2-1.5% SeaKem GTG agarose, using density stabilization by glycerol and incorporation of a dye to define the gel concentration at each point on the pore gradient gel. The distribution of the dye was evaluated by photography, video-acquisition and digitization of the gradient mixture and by densitometry of the gel. The gel was applied to the electrophoresis of a 1-kb standard ladder of DNA fragments, using standard submarine apparatus. The method extends to agarose gel electrophoresis the benefits of semi-automated analysis of 'Ferguson curves' described in application to polyacrylamide gel by Wheeler et al. (J. Biochem. Biophys. Methods 24, 171-180).

Coloring Agents↗
PubMed1992

Kallmann syndrome gene on the X and Y chromosomes: implications for evolutionary divergence of human sex chromosomes.

The recently identified gene for X-linked Kallmann syndrome (hypogonadotropic hypogonadism and anosmia) has a closely related homologue on the Y chromosome. The X and Y copies of this gene are located in a large region of X/Y homology, on Xp22.3 and Yq11.2, respectively. Comparison of the structure of the X-linked Kallmann syndrome gene and its Y homologue shed light on the evolutionary history of this region of the human sex chromosomes. Our data show that the Y homologue is not functional. Comparative analysis of X/Y sequence identity at several loci on Xp22.3 and Yq11.2 suggests that the homology between these two regions is the result of a complex series of events which occurred in the recent evolution of sex chromosomes.

Base Sequence↗
PubMed1992

Medical management of spinal epidural abscesses: case report and review.

Although the traditional management of spinal epidural abscesses includes antibiotic therapy and surgical drainage, numerous reports have appeared in the literature that describe a nonsurgical approach. We report the successful nonsurgical management of a case of an extensive spinal epidural abscess in which the patient was closely monitored by serial studies with magnetic resonance imaging. Review of the literature from 1970 to 1990 revealed 37 cases that describe conservative management of spinal epidural abscesses. Despite successful conservative management reported for some cases, sudden neurological deterioration of patients receiving appropriate antibiotic therapy has also occurred. A true index of the success of nonsurgical therapy is difficult to discern since cases may have been selectively reported and unsuccessful attempts at conservative management may have never been reported once a laminectomy was performed. A prospective investigation that includes clearly defined indications for conservative management vs. surgical intervention and that can be studied with an intention-to-treat analysis is needed.

Abscess↗
PubMed1991

Identification of vitellogenin in the ant, Camponotus festinatus: changes in hemolymph proteins and fat body development in workers.

Vitellogenin has been identified in the ant Camponotus festinatus, both in queens and workers. In the workers, it is already present before adult eclosion in low concentrations (less than 1 microgram/microliter hemolymph). Vitellogenin and vitellin are immunologically identical and are composed of a single type of apoprotein with an apparent Mr = 185,000. The molecular weight of the native molecules was estimated as approximately 460,000 by pore limiting gradient electrophoresis. Vitellogenin was detected as a major protein in the hemolymph of young workers, both under queenright and queenless conditions. Thus, in spite of their sterility in the presence of the queen, C. festinatus workers are able to synthetize vitellogenin which is identical both in size and immunologically to the queen vitellogenin. About 6-7 weeks after adult eclosion, however, vitellogenin was usually undetectable in the hemolymph of queenright workers, particularly the minor workers, while it constituted about 30% of total protein in queenless workers. Protein concentration in the hemolymph of queenless insects increased up to 20-fold as compared to 1-day-old insects. Queenless workers also developed large amounts of perivisceral fat body, while queenright workers, particularly the minor workers, showed a dramatic fat body regression about 6 weeks after emergence.

Animals↗
PubMed1991

Expression of SPARC/osteonectin in tissues of bony and cartilaginous vertebrates.

To explore the biological functions of SPARC (secreted protein, acidic, rich in cysteine), a Ca(2+)-binding extracellular glycoprotein, we have examined its expression in an evolutionary diverse group of organisms. Similar patterns of SPARC mRNA expression were observed in adult mouse and rat tissues. SPARC transcripts represented 0.0002-0.0025% of the total RNA found in calvarium, lung, brain, and heart, whereas relatively low levels of SPARC RNA were detected in liver and kidney. Within nonmuscular tissues, a statistically significant correlation was observed between the tissue distribution of SPARC and cytoskeletal actin transcripts. Southern blot analysis revealed SPARC as a low or single-copy gene in an evolutionary diverse group of vertebrates. No hybridization signal was observed with the invertebrates examined. The tissue distribution of SPARC transcripts in the vertebrates examined was similar, except for sea lamprey and sea skate, two vertebrates that do not form mineralized bone. These data suggest that SPARC has multiple functions in mineralized and nonmineralized tissues of vertebrates.

Actins↗
PubMed1991

Eales' disease with central nervous system infarction.

Eales' disease is a noninflammatory occlusive disorder of the retinal vasculature that causes recurrent hemorrhages into the retina and vitreous and ischemic changes in the eye. Extraocular manifestations of Eales' disease are rare and limited to the central nervous system. We report the case of a patient with Eales' disease and ischemic stroke, and we review the neurologic manifestations of this primarily ophthalmologic vasculopathy.

Cerebral Infarction↗
PubMed1991

Vertebral osteomyelitis caused by Nocardia asteroides: report and review of the literature.

A 65-year-old man with 9 months of radicular lower back pain was admitted for treatment of presumed malignancy of the lumbar spine. Lumbar radiographs showed destruction of the L4-L5 endplates and obliteration of the disc space, which was more compatible with an infectious process. After 2 different closed biopsy specimens failed to reveal an etiologic organism, N. asteroides was cultured from an open biopsy sample of the affected vertebrae. This and 8 other cases in the English literature of vertebral osteomyelitis caused by N. asteroides are reviewed.

Aged↗
PubMed1989

A child with nocturnal croup.

The domiciliary management of a four-year-old with suspected croup is difficult. The differential diagnosis ranges from relatively benign viral illnesses to acute epiglottitis and even diphtheria. Complete obstruction can occur with little warning, and the social situation may further complicate arrangements. As it is not possible to admit every patient with such symptoms, clinical judgement is vitally important.

Child, Preschool↗
PubMed1989

Can we imagine how objects look from other viewpoints?

Many psychologists who study cognition believe that perception achieves object-centered representations that make it possible to extract representations of how the object would appear from differing viewpoints. Others believe we can achieve representations of how an object would appear by a process of visualization or mental rotation. We report experiments in which the subject tries to imagine how three-dimensional novel wire objects would appear from positions other than the one they are in. Subjects are unable to perform this task unless they make use of strategies that circumvent the process of visualization. It is suggested that the linear increase in time required to succeed in mental rotation tasks as a function of the angular discrepancy between the figures compared is the result of increasing difficulty rather than of the time required for rotation.

Adult↗
PubMed1988

The use of bacteriophage as tracers of aerosols liberated by sludge suction appliances.

Three bacteriophage tracers were added to 600-1 containers of water and simulated latrine sludge to provide high titres of tracer in aqueous and semi-aqueous media. After a period of mixing and stabilization, media were removed from the containers with suction hoses coupled to the vacuum pump of one of two sludge suction tankers. Exhaust air from the appliances was sampled by cyclone sampler and assayed for the presence of tracer organisms carried over during the emptying process. In the experiments the appliances were operated at different vacuum pump speeds, drawing both aqueous and semi-aqueous (simulated sludge) media. Air around one tanker was also sampled during the emptying, under pressure, of the vacuum vessel. The degree of aerosolization and expulsion of tracer bacteriophage by the vacuum appliances was consistently low, regardless of medium and pump air flow. In contrast, the proportion of tracer retained within the appliances was very high, exceeding the proportion expelled by a minimum of 8 log10 orders of magnitude and a maximum of greater than 11 log10 orders. The highest total of tracer bacteriophage was recovered during the pressure emptying of the vacuum vessel of one tanker. The results may be used for assessing and comparing potential public health hazards associated with the handling of wastewater sludge by vacuum appliances.

Aerosols↗
PubMed1988

Bacteriophage tracer experiments in groundwater.

Three tracer experiments employing three different bacteriophage were performed at one groundwater site near Beverley, Humberside. In two of the experiments the bacteriophage were injected into the aquifer by a borehole at a distance of 366 m from the pumping borehole. In the other experiment they were injected at a distance of 122 m. Regular samples were taken of water abstracted at the pumping boreholes as well as from the injection boreholes. The objectives were to: (1) investigate the pattern of bacteriophage recovery from the aquifer; (2) calculate the total number of bacteriophage recovered and the rate of their migration; and (3) detect any differences in bacteriophage behaviour which could be directly related to the morphology of the three bacteriophage. In all experiments the pattern of recovery was similar, exhibiting a peak of high numbers reaching the pumping borehole soon after injection. The highest percentage of original inoculum recovered was 1.9%. In the majority of cases, however, recovery was usually one log10 lower than this. The fastest migration rates were very rapid, reaching 2.8 cm/s in one experiment. No variation in percentage recovery or transit time could be directly attributed to morphology of bacteriophage. The most important factor governing the pattern of migration was undoubtedly the hydrogeological conditions.

Bacteriophages↗