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Biomedical subjects

A Harris

Publications and source records attributed to A Harris.

At least 91 records · Page 5Linked to original sources
PubMed2001

Photodetector sensitivity level and heidelberg retina flowmeter measurements in humans.

PURPOSE: In vitro models suggest that Heidelberg retina flowmeter (HRF) measurements are affected by changes in photodetector sensitivity. We measured blood flow in a single volume of human retinal tissue in vivo at various sensitivity (DC) levels. METHODS: The peripapillary retinal regions of 12 normal subjects were examined by HRF under five different sensitivity settings: (1) average DC range below 100; (2) average DC range below 125; (3) average DC range near 150 (normal sensitivity); (4) average DC range above 175; and (5) average DC range above 200 or extremely overexposed. The distributions of flow values were examined by pointwise analysis. All pixels from a common tissue location were analyzed, and the effect of their brightness on the flow measurement was evaluated by ANOVA with Fisher's protected least significant difference model. RESULTS: ANOVA analysis of image DC level showed that significantly different DC levels were achieved for each of the five sensitivity settings (P < 0.0001). Flow values decreased with increasing DC for each of the 25th percentile, 50th percentile (P: < 0.0001 for each), 75th percentile (P: = 0.0026), 90th percentile (P: = 0.0216), and mean (P: = 0.0004) flow values. The percentage of pixels with values of zero (avascular tissue) increased with increasing photodetector sensitivity (P< 0.0001). CONCLUSIONS: Improper sensitivity settings alter the detected percentage of avascular tissue and the blood flow measurements in tissue containing capillaries. Consistent assessment of retinal blood flow requires consistent photodetector sensitivity settings between longitudinal images.

Adult↗
PubMed2001

Ocular blood flow measurements and their importance in glaucoma and age-related macular degeneration.

This survey of methods for assessing ocular hemodynamics in glaucoma and age-related macular degeneration is not complete, but it does cover those likely to be encountered in the literature. A fundamental problem in getting to grips with the ocular blood flow literature is the difficulty in comparing the results of similar studies employing different assessment techniques. As evident from the discussion above, each technique evaluates a portion of the ocular circulation in a distinct way. Some of the methods overlap with regard to the tissues that can be used for examination, while others are directed at entirely different parts of the ocular vasculature. Despite these difficulties, hemodynamic studies of glaucoma and AMD are likely to grow in importance. On the basis of accumulating epidemiological and clinical evidence, it is becoming apparent that intraocular pressure is not the sole etiological factor in glaucoma, and retinal pigment epithelium senescence is not the sole etiological factor in AMD. Circumstantial evidence of vascular involvement in glaucoma and AMD has now been bolstered by experimental evidence. If the current pace of refinement of newly established technologies for evaluating ocular blood flow is maintained, they will soon be ready for deployment in the clinic. The only problem is the availability of expensive instruments and trained personnel. The ultimate beneficiaries of work in this area will not be researchers, but patients.

Angiography↗
PubMed2001

Transpupillary thermotherapy for subfoveal occult choroidal neovascularization: effect on ocular perfusion.

PURPOSE: To perform a descriptive analysis of the effects on ocular blood flow of transpupillary thermotherapy (TTT) for occult subfoveal choroidal neovascular membranes (CNVMs) in age-related macular degeneration (AMD). METHODS: Eleven subjects with occult subfoveal CNVM due to AMD were assessed in a masked fashion by color Doppler imaging (CDI) within 24 hours before, 24 hours after, and 1 month after undergoing TTT. RESULTS: In the posterior ciliary arteries (PCAs), there were no statistically significant changes observed in the peak systolic velocity (PSV), end diastolic velocity (EDV), or resistive index (RI) at 24 hours. At 1 month, the mean EDV decreased 36% (P = 0.0105) and the mean RI increased 3.8% (P = 0.0305) in the nasal PCA. Although there was a similar trend in the temporal PCA, the differences did not reach statistical significance. In the central retinal artery (CRA), the mean PSV decreased 16% (P = 0.0137), and the mean EDV decreased 21% (P = 0.0222) at 24 hours after treatment. There were no statistically significant differences in the CRA blood flow indices at 1 month after treatment. In the ophthalmic artery, there were no statistically significant differences observed in the mean PSV, EDV, or RI at 24 hours or 1 month after treatment. CONCLUSIONS: TTT is associated with transiently decreased volumetric blood flow in the retinal circulation 24 hours after treatment. In the posterior ciliary arteries that supply the choroid, there were no changes observed at 24 hours, but at 1 month, there was a decrease in the mean EDV and an increase in the RI in the nasal and temporal PCAs, reaching statistical significance in the nasal PCA only. This study suggests that TTT could lead to alterations in choroidal blood flow, as assessed by CDI. Further study is warranted.

Aged↗
PubMed2000

[Color Doppler imaging of central retinal artery in retinopathy of prematurity].

Color Doppler imaging (CDI) is a noninvasive technique, combining 2-dimensional brightness-modulated (B-mode) ultrasound evaluation of eye and orbital structures, with simultaneous color-coded Doppler imaging of orbital blood flow. It has been used to characterize various ophthalmic disorders in adults. Currently there is no data describing orbital blood flow parameters in either normal children or in those with ophthalmic disease, such as the retinopathy of prematurity (ROP). We evaluated blood flow in the central retinal artery of preterm infants undergoing examination for ROP. We also investigated whether useful readings could be obtained on a consistent basis, and the reproducibility of differences in central retinal artery blood flow between subjects with and without ROP (including the influence of "plus" disease). We obtained hemodynamic readings in 43 of 46 eyes of preterm infants. 13 eyes had no signs of ROP; 18 had ROP (at least stage 1) without "plus" disease, and 12 had ROP with "plus" disease. There were no statistically significant differences in systolic blood flow velocity within the 3 groups. However the average velocity was slower in the "plus" disease group, correlating with the clinical finding of dilated and tortuous blood vessels which characterize the posterior retina of ROP eyes with "plus" disease.

Blood Flow Velocity↗
PubMed2000

Multiple potential intragenic regulatory elements in the CFTR gene.

The CFTR gene exhibits a complex pattern of expression that shows temporal and spatial regulation though the control mechanisms have not been fully elucidated. We have mapped DNase I hypersensitive sites (DHS) flanking the CFTR gene to identify potential regulatory elements. We previously characterized DHS at -79.5 and -20.9 kb with respect to the CFTR translational start site, DHS 3' to the gene at 4574 + 5.4-7.4 and 4574 + 15.6 kb, and a regulatory element in the first intron of the gene at 185 + 10 kb. We generated a cosmid contig to provide probes to evaluate the whole of the CFTR gene for DHS and have now mapped novel sites in introns 2, 3, 10, 16, 17a, 18, 20, and 21. These DHS show different patterns of cell-specific expression.

Caco-2 Cells↗
PubMed2000

Aging affects the retrobulbar circulation differently in women and men.

BACKGROUND: While aging clearly has protean biological effects on every organ system, the differential effects of aging in women and men in the retrobulbar vasculature, to our knowledge, have never been investigated. Because glaucoma and age-related macular degeneration are closely linked to advanced age, we performed a cross-sectional study using color Doppler imaging of 4 retrobulbar vessels in both healthy women and men. OBJECTIVE: To define the influence of aging per se on ocular hemodynamics. METHODS: Women (n = 73) and men (n = 55), aged from 20 to 90 years, free of ocular and systemic disease, and with normal intraocular pressure, were recruited for this study. Postmenopausal women who were not receiving estrogen replacement therapy were also recruited. Studies involved color Doppler imaging analysis of the ophthalmic, central retinal, and nasal and temporal posterior ciliary arteries. Ophthalmic arterial peak systolic and end-diastolic velocities and a Pourcelot resistance index were determined for each vessel. RESULTS: In both sexes, ophthalmic arterial end-diastolic velocity decreased and the Pourcelot resistance index rose with advancing age (each P<. 001); peak systolic velocity in the ophthalmic vessel was age-independent. In contrast, central retinal arterial flow velocities were unaffected by age in both sexes. In the posterior ciliary arteries, in men, flow velocities and the Pourcelot resistance index were independent of age. However, in women, end-diastolic velocity decreased with age in both the nasal and temporal posterior ciliary vessel (each P<.05); peak systolic velocity was constant; the Pourcelot resistance index in each ciliary artery rose with advancing age (each P<.05). CONCLUSION: In healthy women and men, aging-induced changes in retrobulbar hemodynamics are comparable to alterations seen in patients with glaucoma or age-related macular degeneration, suggesting that vascular changes with senescence may contribute to increased risk for these diseases in older age. Arch Ophthalmol. 2000;118:1076-1080

Adult↗
PubMed2000

Eradication of helicobacter pylori for non-ulcer dyspepsia.

BACKGROUND: Helicobacter pylori (H pylori) is the main cause of peptic ulcer disease. The role of H pylori in non-ulcer dyspepsia is less clear. OBJECTIVES: To determine the effect of H pylori eradication on dyspepsia symptoms and quality of life scores in patients with non-ulcer dyspepsia. SEARCH STRATEGY: Trials were identified through electronic searches of the Cochrane Controlled Trials Register (CCTR), MEDLINE, EMBASE, CINAHL and SIGLE, using appropriate subject headings and keywords, searching bibliographies of retrieved articles, and through contacts with experts in the fields of dyspepsia and with pharmaceutical companies. SELECTION CRITERIA: All parallel group randomised controlled trials (RCTs) comparing drugs to eradicate H pylori with placebo or other drugs known not to eradicate H pylori for patients with non-ulcer dyspepsia. DATA COLLECTION AND ANALYSIS: Data were collected on individual and global dyspeptic symptom scores, quality of life measures and adverse effects. Dyspepsia outcomes were dichotomised into minimal/resolved versus same/worse symptoms. MAIN RESULTS: Seven randomised controlled trials were included in the systematic review. Five trials compared proton pump inhibitor dual or triple therapy with a proton pump inhibitor + placebo antibiotics, and evaluated dyspepsia at 6-12 months in 1,385 patients. H pylori eradication was significantly superior to placebo in treating non ulcer dyspepsia (relative risk reduction = 7%; 95% CI = 1% to 12%; p=0.02) and there was no significant heterogeneity between the studies. The number needed to treat to cure one case of dyspepsia = 19 (95% CI = 11 to 132). A further two trials compared Bismuth based H pylori eradication with an alternative pharmacological agent. These trials were smaller and had a shorter follow-up but suggested H pylori eradication was more effective than either H2 receptor antagonists or sucralfate in treating non-ulcer dyspepsia. REVIEWER'S CONCLUSIONS: H pylori eradication may be an effective therapy for H pylori positive non-ulcer dyspepsia. This result is not robust and further evidence on the efficacy of H pylori eradication in non ulcer dyspepsia would be helpful. The effect is modest and economic models would help establish whether this approach is cost-effective. This review will be updated as results from other ongoing trials (Malfertheiner 2000) are made available.

Anti-Bacterial Agents↗
PubMed2000

Regenerating motor neurons express Nna1, a novel ATP/GTP-binding protein related to zinc carboxypeptidases.

To identify genes involved in axon regeneration, differential screening was applied to RNA isolated from spinal cord of mice subjected to sciatic nerve transection or crush injury. A 4-kb transcript, termed nna1, was identified that was rapidly induced in affected motor neurons in both paradigms. The levels of nna1 transcript levels declined in motor neurons within 1-2 weeks after nerve crush, coincident with target reinnervation. If reinnervation was blocked by nerve cut and ligation, nna1 was continuously expressed in motor neurons. In addition, in situ analysis of developing embryonic nervous tissue showed nna1 was highly expressed in differentiating neurons, but not proliferating populations. Nna1 is predicted to be a zinc carboxypeptidase that contains nuclear localization signals and an ATP/GTP binding motif. Cultured neurons transfected with green fluorescent protein (GFP)-nna1 expressed GFP-Nna1 in cytoplasmic and nuclear compartments. Thus, Nna1 may contribute to nuclear signaling events in differentiating and regenerating neurons.

Adenosine Triphosphate↗
PubMed2000

Retrobulbar hemodynamics in normal-tension glaucoma with asymmetric visual field change and asymmetric ocular perfusion pressure.

PURPOSE: To investigate retrobulbar hemodynamics by means of color Doppler imaging in normal-tension glaucoma with asymmetric visual field change and asymmetric ocular perfusion pressure. METHODS: Forty-nine consecutive patients who met the enrollment criteria were enrolled in a prospective study. We measured intraocular pressure at 2-hour intervals for 24 hours and performed color Doppler imaging of the orbital arteries, 48-hour ambulatory blood pressure monitoring, and visual field testing. Color Doppler parameters were compared between subjects with higher ocular perfusion pressure in the eye that had a better mean deviation (concordant group) and worse mean deviation (discordant group). RESULTS: In the eyes with the better mean deviation, the end-diastolic velocity of the ophthalmic artery was significantly slower in the discordant group (P=.0145), while in the eyes with the worse mean deviation, the peak systolic and end-diastolic velocities of the ophthalmic artery were significantly slower and the resistance index of the ophthalmic artery was significantly higher in the discordant group (P=.0395, P=.0088, and P=.0324, respectively). In the concordant group, the end-diastolic velocity of the central retinal artery was slower in eyes with a worse mean deviation. CONCLUSION: Retrobulbar hemodynamics are significantly altered in patients with normal-tension glaucoma who have better ocular perfusion pressure in the eye that has a worse mean deviation.

Adult↗
PubMed2000

Estrogen-replacement therapy: effects on retrobulbar hemodynamics.

PURPOSE: Estrogen-replacement therapy causes vasodilation and increased blood flow in major peripheral arteries. We examined the role that estrogen may play in enhancing perfusion within the watersheds of several major and minor retrobulbar arteries. METHODS: Postmenopausal women receiving estrogen-replacement therapy (n = 16) were compared with both age-matched women not receiving estrogen (n = 16) and with young women (n = 20). Studies involved color Doppler imaging analysis of flow velocities measured in the ophthalmic, central retinal, and nasal and temporal posterior ciliary arteries. RESULTS: In the ophthalmic artery, young women and postmenopausal women receiving estrogen exhibited reduced resistance indexes as compared with postmenopausal women not receiving estrogen (each P <. 001). In contrast, flow velocities in the central retinal artery were similar among the three groups of women. In the posterior ciliary arteries, a different pattern emerged: young women, as compared with either group of postmenopausal women, showed greater peak systolic and end-diastolic velocities at similar resistance index (each P <.05). CONCLUSIONS: Estrogen-replacement therapy in postmenopausal women apparently helps reduce vascular resistance distal to the ophthalmic artery to levels matching those of young women. However, estrogen replacement has little impact on flow velocities in the posterior ciliary arteries. In those vessels, aging per se may reduce perfusion, potentially contributing to the age-dependent risk of major eye diseases, such as glaucoma and age-related macular degeneration.

Adult↗
PubMed2000

A comparative study of betaxolol and dorzolamide effect on ocular circulation in normal-tension glaucoma patients.

OBJECTIVE: To determine whether dosages of a selective beta-blocking agent (betaxolol) and a topical carbonic anhydrase inhibitor (dorzolamide), sufficient to significantly lower intraocular pressure (IOP), have similar or disparate impact on the retinal and retrobulbar circulation. DESIGN: Counterbalanced crossover, with open-label use of medications. PARTICIPANTS: Nine persons with normal-tension glaucoma (NTG). INTERVENTION: After a 3-week drug washout, NTG patients were studied after 1 month of treatment with either dorzolamide or betaxolol, with determinations of IOP and retinal and retrobulbar hemodynamics. MAIN OUTCOME MEASURES: At baseline and after treatment with each drug, retinal arteriovenous passage time was determined by scanning laser ophthalmoscopy after fluorescein dye injection, and flow velocities in the central retinal and ophthalmic arteries were measured with color Doppler ultrasonography imaging. RESULTS: Betaxolol and dorzolamide each lowered IOP significantly, with these changes apparent and maximal after 2 weeks (each P < 0.05). In contrast, dorzolamide (but not betaxolol) accelerated arteriovenous passage of fluorescein dye in the inferior temporal quadrant of the retina (P < 0.05). Neither drug affected arteriovenous passage in the superotemporal retina or any aspect of central retinal or ophthalmic artery flow velocity after either 2 or 4 weeks. CONCLUSIONS: Although both dorzolamide and betaxolol are effective ocular hypotensive agents and their topical instillation leaves retrobulbar hemodynamics unaltered, dorzolamide alone accelerates inferotemporal retinal dye transit.

Adrenergic beta-Antagonists↗
PubMed2000

Visualization of Taylor-Couette and spiral Poiseuille flows using a snapshot FLASH spatial tagging sequence.

A new magnetic resonance imaging technique was applied to the Taylor-Couette and spiral Poiseuille (Taylor-Couette with superposed mean axial flux) flows for the first time. The experimental technique is a combination of spatial tagging methods and a snapshot FLASH imaging sequence, which allows the full-field visualization of 2-D slices of the flow field, with image acquisition times approximately half a second. By acquiring images every few seconds, direct visualization of flow patterns can be obtained in the form of cinematography. Tagged images of the Taylor-Couette flow were acquired in both the axial and transverse planes and confirmed previously reported numerical predictions of Taylor cell size. Tagged images of the spiral Poiseuille flows verified that the cells in this flow propagate at a higher velocity than the mean axial flow. In addition, intermittent cell formation was observed as the axial flow was increased.

Equipment Design↗
PubMed2000

Gamma activity in schizophrenia: evidence of impaired network binding?

OBJECTIVES: Gamma ('40 Hz') rhythms may play a role in the integration of sensory processing activity. Impaired temporal integration may be a key feature of the associated disturbances in schizophrenia. This is the first study to examine the time course of Gamma activity induced in response to stimuli in this disorder. METHODS: Gamma activity induced in response to task-relevant and irrelevant auditory oddball stimuli was examined in 35 medicated schizophrenics and 35 age- and gender-matched normal controls. We employed a moving Welch window with short time FFT to examine the time course of Gamma amplitude. The amplitude spectrum for each time point was de-trended to eliminate any contribution of broad spectrum activity (EEG or EMG) to Gamma amplitude. RESULTS: For targets, schizophrenics showed a significant decrease in post-stimulus Gamma response amplitude in left hemisphere and frontal sites and an increase in right hemisphere and parieto-occipital sites (P<0.0009). The abnormalities correlated with PANSS general symptom scores. In the non-targets (at a different latency), schizophrenics showed a widespread Gamma decrease (P<0.0005). CONCLUSIONS: The Gamma findings in non-targets may reflect an abnormality in appropriately processing irrelevant stimuli. This could result in defective processing of the context (integration) of relevant target information.

Adult↗
PubMed2000

Misattribution of sensory input reflected in dysfunctional target:non-target ERPs in schizophrenia.

BACKGROUND: While numerous studies have found disturbances in the Event-Related Potentials (ERPs) of patients with schizophrenia linked to task relevant target stimuli (most notably a reduction in P300 amplitude), few have examined ERPs to task irrelevant non-targets. We hypothesize, from current models of dysfunction in information processing in schizophrenia, that there will be less difference between ERPs to targets and non-targets in patients with schizophrenia than in controls. METHODS: EEGs were recorded for 40 subjects with schizophrenia and 40 age and sex matched controls during an auditory oddball reaction time task. ERPs to the targets and non-targets immediately preceding the targets were averaged separately. RESULTS: There was a disturbance in ERPs to targets but also to non-targets (reduced N100 amplitude and earlier P200 latency) and the difference between target and non-target ERP components (N100 and P200 amplitude and P200 latency), was significantly reduced in the schizophrenic group compared with controls. CONCLUSIONS: These findings suggest a disturbance in processing task relevant and irrelevant stimuli, consistent with Gray's (1998) hypothesis of misattributions in the 'match:mismatch' of novel (target) and familiar (non-target) sensory input compared with stored information.

Adult↗
PubMed2000

High-performance liquid chromatographic method for determination of biogenic amines in feedstuffs, complete feeds, and animal tissues.

Numerous methods to analyze biogenic amines in biological materials have been described. A versatile and rapid methodology to analyze these compounds in feedstuffs, complete feeds, and animal tissues, however, has not been reported. The current method was developed to address this need. Biogenic amines in feedstuffs, complete animal feeds, and animal tissues were extracted with 10% trichloroacetic acid, reacted with O-phthaladehyde using high-performance liquid chromatographic employing a cation exchange column. Detection limits were 50 pmol/mL for tyramine, histamine, putrescine, and spermine; 40 pmol/mL for cadaverine; and 25 pmol/mL for spermidine. Extraction efficiency of biogenic amines in feedstuffs, duodenum, liver, ileum + jejunum, and whole shrimp and shrimp hepatopancreas ranged between 99-105, 93-135, 80-85, 65-102, 88-98, and 88-97%, respectively. It can be concluded that the current method can be applied to individual feedstuffs, complete feeds, and animal tissues for the rapid and accurate determination of concentration of biogenic amines.

Animal Feed↗
PubMed2000

Triterpene glycosides from Cimicifuga racemosa.

Eight new triterpene glycosides named cimiracemosides A-H, respectively, and eight known triterpene glycosides were isolated from the rhizome extracts of black cohosh (Cimicifuga racemosa). The new compounds were determined by spectral data to be 21-hydroxycimigenol-3-O-alpha-L-arabinopyranoside (1), 21-hydroxycimigenol-3-O-beta-D-xylopyranoside (2), cimigenol-3-O-alpha-L-arabinopyranoside (3), 12beta-acetoxycimigenol-3-O-alpha-L-arabinopyranoside (4), 24-acetylisodahurinol-3-O-beta-D-xylopyranoside (5), 20(S),22(R), 23(S),24(R)-16beta:23;22:25-diepoxy-12beta-acetoxy-3be ta,23, 24-trihydroxy-9,19-cycloanost-7-ene-3-O-beta-D-xylopyranoside (6), 20(S),22(R),23(S),24(R)-16beta:23;22:25-diepoxy-12beta -acetoxy-3beta, 23,24-trihydroxy-9,19-cycloanost-7-en-3-O-alpha-L-arabinopyrano side (7), and 20(S),22(R),23(S), 24(R)-16beta:23;22:25-diepoxy-12beta-acetoxy-3beta,23, 24-trihydroxy-9,19-cycloanostane-3-O-beta-D-xylopyranoside (8).

Glycosides↗