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Biomedical subjects

J Barrow

Publications and source records attributed to J Barrow.

10 recordsLinked to original sources
PubMed2001

Single molecule detection of double-stranded DNA in poly(methylmethacrylate) and polycarbonate microfluidic devices.

Single photon burst techniques were used to detect double-stranded DNA molecules in poly(methylmethacrylate) (PM MA) and polycarbonate (PC) microfluidic devices. A confocal epi-illumination detection system was constructed to monitor the fluorescence signature from single DNA molecules that were multiply labeled with the mono-intercalating dye, TOPRO-5, which possessed an absorption maximum at 765 nm allowing excitation with a solid-state diode laser and fluorescence monitoring in the near-infrared (IR). Near-IR excitation minimized autofluorescence produced from the polymer substrate, which was found to be significantly greater when excitation was provided in the visible range (488 nm). A solution containing lambda-DNA (48.5 kbp) was electrokinetically transported through the microfluidic devices at different applied voltages and solution pH values to investigate the effects of polymer substrate on the transport rate and detection efficiency of single molecular events. By applying an autocorrelation analysis to the data, we were able to obtain the molecular transit time of the individual molecules as they passed through the 7 microm laser beam. It was observed that the applied voltage for both devices affected the transport rate. However, solution pH did not alter the transit time for PM MA-based devices since the electroosmotic flow of PMMA was independent of solution pH. In addition, efforts were directed toward optimizing the sampling efficiency (number of molecules passing through the probe volume) by using either hydrodynamically focused flows from a sheath generated by electrokinetic pumping from side channels or reducing the channel width of the microfluidic device. Due to the low electroosmotic flows generated by both PMMA and PC, tight focusing of the sample stream was not possible. However, in PMMA devices, flow gating was observed by applying field strengths > -120 V/cm to the sheath flow channels. By narrowing the microchannel width, the number of molecular events detected per unit time was found to be four times higher in channels with 10 microm widths compared to those of 50 microm, indicating improved sampling efficiency for the narrower channels without significantly deteriorating detection efficiency. Attempts were made to do single molecule sizing of lambda-DNA, M13 (7.2 kbp) and pUC19 (2.7 kbp) using photon burst detection. While the average number of photons for each DNA type were different, the standard deviations were large due to the Gaussian intensity profile of the excitation beam. To demonstrate the sensitivity of single molecule analysis in the near-IR using polymer microfluidic devices, the near-IR chromophore, NN382, wasanalyzed using ourconfocal imager. A detection efficiency of 94% for single NN382 molecules was observed in the PC devices.

Bacteriophage lambda↗
PubMed1997

Haplotype analysis of hemochromatosis: evaluation of different linkage-disequilibrium approaches and evolution of disease chromosomes.

We applied several types of linkage-disequilibrium calculations to analyze the hereditary hemochromatosis (hh) locus. Twenty-four polymorphic markers in the major histocompatibility complex (MHC) class I region were used to haplotype hh and normal chromosomes. A total of 169 hh and 161 normal chromosomes were analyzed. Disequilibrium values were found to be high over an unusually large region beginning 150 kb centromeric of HLA-A and extending nearly 5 Mb telomeric of it. Recombination in this region was approximately 28% of the expected value. This low level of recombination contributes to the unusually broad region of linkage disequilibrium found with hh. The strongest disequilibrium was found at locus HLA-H (delta = .84) and at locus D6S2239 (delta = .85), a marker approximately 10 kb telomeric to HLA-H. All disequilibrium methods employed in this study found peak disequilibrium at HLA-H or D6S2239. The cys282tyr mutation in HLA-H, a candidate gene for hh, was found in 85% of disease chromosomes. A haplotype phylogeny for hh chromosomes was constructed and suggests that the mutation associated with the most common haplotype occurred relatively recently. The age of the hh mutation was estimated to be approximately 60-70 generations. Disequilibrium was maintained over a greater distance for hh-carrying chromosomes, consistent with a recent mutation for hh. Our data provide a reasonable explanation for previous difficulties in localizing the hh locus and provide an evolutionary history for disease chromosomes.

Evolution, Molecular↗
PubMed1989

Regulation of the mesocorticolimbic dopamine system by glutamic acid receptor subtypes.

Glutamic acid and excitatory amino acids specific for the glutamate receptor subtypes were microinjected into the A10 region of the rat. Glutamate produced an increase in motor behavior that was antagonized by pretreatment with the dopamine D2 receptor antagonist, haloperidol. This motor stimulant effect was produced by kainate, but not by N-methyl-D-aspartate (NMDA) or quisqualic acid. By using in vivo dialysis it was found that dopamine release in the nucleus accumbens and locomotor activity were enhanced by glutamate injection into the A10 region. Whereas glutamate was found to increase the postmortem concentration of dopamine metabolites in the medial prefrontal cortex, nucleus accumbens and A10 region, NMDA selectively increased dopamine metabolism in the prefrontal cortex, and kainate produced increases in the nucleus accumbens and A10 region. When glutamate and the NMDA receptor antagonist, 3-[(+/-)-2-carboxypiperazine-4-yl)propyl-1-phosphonic acid (CPP) were coadministered, CPP selectively abolished the effect of glutamate on medial prefrontal cortical dopamine metabolites. A physiological role for the NMDA receptor modulation of A10 dopamine neurons was shown by intra-A10 pretreatment with CPP antagonism of mild footshock-induced increase in dopamine metabolites in the prefrontal cortex. These data argue that glutamate is a regulatory transmitter of A10 dopamine neurons, and that the NMDA receptor subtype modulates neurons projecting to the prefrontal cortex whereas the kainate subtype modulates mesoaccumbens neurons.

Amino Acids↗
PubMed1980

Carcinoma of the bladder presenting as gonococcal cystitis.

A patient with gonococcal infection presented with frank haematuria. On subsequent investigation a transitional cell carcinoma was found. Because the haematuria resolved rapidly after treatment with ampicillin no sinister cause for the bleeding was suspected. Since gonorrhoea is rarely associated with gross haematuria, when it does occur a thorough investigation should be undertaken.

Adult↗
PubMed1979

The need for a chlamydial culture service.

In a prospective study of unselected, female patients attending a sexually transmitted disease clinic one in eight patients would have been errouneously declared free of infection in the absence of a chlamydial culture service. Chlamydia trachomatis is now accepted as a causative organism of non-specific urethritis and post-gonococcal urethritis in men and non-specific genital infection in women. Thus, facilities for isolation of C. trachomatis should be an essential aid in the management of women attending STD clinics. Male patients would also benefit if such facilities were readily available.

Bacteriology↗
PubMed1976

Diagnosis of gonorrhoea in women.

250 consecutive female contacts of men with gonorrhoea were examined in Lydia Department of Genito-urinary Medicine, St Thomas' Hospital, London, and 165 (66 per cent.) were found to be positive for gonorrhoea. Over 99 per cent. of the positive results were found by the first two sets of genital investigations. These results are compared with earlier and more recent results from our own and other centres and it is postulated that the higher early diagnosis rate is due to the introduction of a highly selective but non-inhibitory culture medium (VCNT), combined with a new incubator which accurately regulates temperature, humidity, and CO2 content. Reasons for the negative findings in 35 per cent. of the female gonorrhoea contacts are discussed.

Culture Media↗
PubMedDate not supplied

Barriers to enrollment in a state child health insurance program.

OBJECTIVE: To identify barriers to enrollment into Colorado's Child Health Insurance Plan (CHP+) for non-Hispanic (NH), Hispanic (H), and uninsured families. DESIGN: Telephone survey of 1) random samples of families who requested an application but did not complete it (N = 273 NH, N = 159 H) and 2) families with uninsured children identified by random-digit-dial statewide surveys (N = 165). RESULTS: Major reasons for not enrolling included 1) got other insurance (NH 16.5%; H 27.2% P <.01), 2) thought household income was too high to qualify (NH 21.0%; H 11.9% P =.01), and 3) paperwork (NH 13.4%; H 14.7%, P = NS). Of those who thought their income was too high (N = 76, 17.6%), 58.5% appeared eligible based on reported income. Of uninsured families, only 41.7% had heard of CHP+. Of those who had never applied, major remediable reasons included not knowing enough about the program (20.9%) and thinking household income was too high (9.3%). CONCLUSIONS: Effective marketing and education to increase awareness of CHP+ and ensure understanding of eligibility are critical to the success of the program.

Child↗