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Biomedical subjects

S Lai

Publications and source records attributed to S Lai.

At least 163 records · Page 9Linked to original sources

Assessment of cerebral blood flow reserve using functional magnetic resonance imaging.

Imaging of activated brain areas based on changes of blood deoxyhemoglobin levels is now possible with MRI. Acetazolamide (ACZ) increases cerebral blood flow (CBF) without changing cerebral oxygen consumption; this results in signal changes observed in gradient echo MR images from the areas with an increase in CBF. We assessed signal changes after ACZ application in seven healthy subjects with a conventional 1.5-T MRI scanner. The susceptibility-sensitized three-dimensional fast low-angle shot (FLASH) sequence was used to visualize signal changes induced by ACZ. We analyzed anatomic localization of different ranges of detected signal changes. ACZ caused significant signal changes in the gray matter and at the edge of the cerebral cortex, the latter corresponding to draining surface veins. No significant differences were seen among different brain areas within the same slice. Using the maximal intensity projection technique, we were able to partially separate signal changes originating in draining veins from signal originating in the gray matter microvasculature. Signal changes from the microvessels reflect cerebrovascular reserve. Blood-oxygen-level-dependent (BOLD) based MRI can evaluate CBF reserve with high spatial and temporal resolution. To assess cerebrovascular reserve, it is necessary to separate signal changes originating in large vessels from signal from brain microvasculature.

Acetazolamide↗

Theory and application of static field inhomogeneity effects in gradient-echo imaging.

The influence of local static magnetic field inhomogeneities on gradient-echo imaging is discussed and the underlying theoretical aspects are reviewed. A high-resolution approach is suggested to suppress image distortion and restore signal loss due to spin dephasing. Acquisition of three-dimensional data sets not only overcomes part of the limitations associated with gradient echoes but also makes it possible to extract local information about the strength or direction of background gradients and relative susceptibility changes between different tissues. Applications of the suggested approach in the human brain for anatomical imaging as well as for extraction of physical and physiological parameters are presented and discussed.

Artifacts↗

FAIR exempting separate T (1) measurement (FAIREST): a novel technique for online quantitative perfusion imaging and multi-contrast fMRI.

A new pulse sequence, dubbed FAIR exempting separate T(1) measurement (FAIREST) in which a slice-selective saturation recovery acquisition is added in addition to the standard FAIR (flow-sensitive alternating inversion recovery) scheme, was developed for quantitative perfusion imaging and multi-contrast fMRI. The technique allows for clean separation between and thus simultaneous assessment of BOLD and perfusion effects, whereas quantitative cerebral blood flow (CBF) and tissue T(1) values are monitored online. Online CBF maps were obtained using the FAIREST technique and the measured CBF values were consistent with the off-line CBF maps obtained from using the FAIR technique in combination with a separate sequence for T(1) measurement. Finger tapping activation studies were carried out to demonstrate the applicability of the FAIREST technique in a typical fMRI setting for multi-contrast fMRI. The relative CBF and BOLD changes induced by finger-tapping were 75.1 +/- 18.3 and 1.8 +/- 0.4%, respectively, and the relative oxygen consumption rate change was 2.5 +/- 7.7%. The results from correlation of the T(1) maps with the activation images on a pixel-by-pixel basis show that the mean T(1) value of the CBF activation pixels is close to the T(1) of gray matter while the mean T(1) value of the BOLD activation pixels is close to the T(1) range of blood and cerebrospinal fluid.

Brain↗

Hepatitis C virus infection in a sexually active inner city population. The potential for heterosexual transmission.

The prevalence of hepatitis C virus (HCV) infection and associated risk factors in an inner city sexually active heterosexual population participating in a prospective study for the evaluation of heterosexual transmission of human immunodeficiency virus type-1 (HIV-1) were examined. Individuals with prior history of injection drug use or receipt of blood products were excluded from the study. Of 571 participants, 25 (4.4%) were seropositive for HCV, 39 (7%) for HIV, and 125 (22%) for hepatitis B virus (HBV). Multivariate analysis revealed that those with more than ten heterosexual partners in the past 5 years (OR = 3.7; 95% CI = 1.3, 10.2; P = 0.01), engaging in sexual practices more than once per week (OR = 3.3; 95% CI = 1.1, 10.1; P = 0.04), with antibody to hepatitis B core (HBc) antigen (OR = 2.9; 95% CI = 1.1, 7.4; P = 0.03), and antibody to HIV-1 (OR = 5.8; 95% CI = 1.9; 17.6; P = 0.002) were independently associated with HCV infection. These findings suggest that heterosexual transmission of HCV may occur in an inner city sexually active heterosexual population.

Adolescent↗

Complementary adenoviral vectors for oncolysis.

Replication-competent adenoviruses (Ads) were used for oncolytic virotherapy soon after they were discovered. Recently mutated and genetically engineered Ads have been shown to selectively lyse tumor cells. We have split the human Ad type 5 genome into two defective viruses that complement each other only in certain tumor cells. The genome of one of these vectors, GT5610, contains only the minimal viral elements required in cis for replication and packaging and the E1 viral genes with E1A under the control of the human alpha-fetoprotein promoter. This "controlled" vector has a capacity for 30 kilobases of foreign DNA. The supplemental vector, AdHbeta, contains all adenoviral genes except for E1. Both vectors were designed to carry heterologous reporter genes whose expression could be detected throughout the tumor. Coinfection of hepatocarcinoma cells that have the capacity to transcribe genes under the control of the alpha-fetoprotein promoter leads to cell lysis and copropagation. The oncolytic spread of these complementary vectors in vivo was demonstrated by the intratumoral injection of human hepatocarcinomas xenografted in severe combined immunodeficient (SCID) mice. This system presents safety and gene capacity features that could yield a therapeutic advantage over oncolysis by a single virus.

Adenocarcinoma↗

HIV-related risk behaviors and seropositivity among homeless drug-abusing women in Miami, Florida.

This article examines the multifaceted interactions among homelessness, HIV, substance abuse, and gender. Data were collected on 1,366 chronic drug users using a nationally standardized validated instrument within the Miami CARES project of a multisite federally funded program. HIV testing accompanied by pretest and posttest counseling was conducted on-site by certified phlebotomists and counselors. In addition to descriptive analyses and corresponding tests of significance, logistic regression analyses were used to clarify the complex associations between the outcome variables of homelessness and HIV, recognizing difficulties of determining temporal sequence. HIV infection was found to be 2.35 times more prevalent among homeless women than homeless men and significantly higher for homeless women. The findings indicate that among women, homelessness and HIV have a highly interactive effect increasing the vulnerability of this population and thus rendering them an extremely important priority population on which to focus public health efforts and programs.

Adolescent↗

Adoption of injection practices in heroin users in Guangxi Province, China.

This preliminary study collected data from 326 heroin users in Guangxi Province, China, in 1997. Logistic regression analysis was performed to identify the risk factors for injection. Survival analysis identified factors independently associated with time from initiation of heroin use to adoption of injection. Four factors were independently associated with injection: number of friends who used heroin in the last year, duration of heroin use, dose of heroin consumed, and total number of times detoxified in drug treatment and rehabilitation centers. Only gender and duration of heroin use were independently associated with time to first injection. Median time to first injection was 11 months for males and 22 months for females. Median time to first injection varied by age. Median time to injection for those who used heroin for more than one year was 8.1 months; it was 19.1 months for on to five years of use, and 40.5 months for more than five years of use. This study's preliminary findings suggest that younger, more recent heroin users, and males are at increased risk of becoming injectors, a major risk behavior for HIV acquisition.

Adolescent↗

Socio-economic and behavioural factors related to caries in twelve-year-old Sardinian children.

Our aim was to describe socio-economic and behavioural factors related to caries experience in school children in Sassari, Sardinia (Italy). Four hundred and three 12-year-old schoolchildren were randomly selected and their teeth clinically examined after air drying, under standard light using a plain mirror and WHO community periodontal index for treatment needs (CPITN) ballpoint probe. The clinical DMFS index was recorded following a diagnostic threshold, CPITN following the WHO indications. A questionnaire concerning oral hygiene habits (OHH), the onset of toothbrushing habits (OTH), frequency of dental check-ups (DCU), sweet food and soft drink consumption and socio-economic background factors, i.e. parents' occupational status (SOCFAM) and parents' age, was filled in by children and parent(s)/guardian(s). The caries prevalence was 61.6%. A positive skewness of DMFS was observed. Regarding caries, a significant linear trend (p<0.05) was found among odds ratios at each exposure level in SOCFAM, OHH, OTH and CPITN. A logistic regression model for caries was constructed using related factors. CPITN (gingival conditions) gave a significant contribution in the predictive model (p = 0.01). Gender acted as an effect modifier on CPITN, so logistic regression models were constructed for males and females separately. CPITN was the only statistically significant covariate in males and OHH the only one in females. Our results confirm a high caries prevalence and also a need for preventive and educational programmes for caries in Sardinia.

Age Factors↗

A simple way to prevent indocyanine green from entering the subretinal space during vitrectomy for retinal detachment due to myopic macular hole.

PURPOSE: To present a safe and simple method of preventing indocyanine green (ICG) from entering the subretinal space in patients undergoing vitrectomy for retinal detachment caused by myopic macular hole. PATIENTS AND METHODS: Four consecutive highly myopic eyes (three phakic, one pseudophakic) with retinal detachment due to myopic macular hole were operated on by pars plana vitrectomy. The ICG-assisted peeling of the internal limiting membrane was performed after temporarily closing the macular hole by means of a small bubble of perfluorocarbon liquid (PFCL) in order to prevent ICG from entering the subretinal space. RESULTS: Retinal reattachment was successful in all patients, and anatomic closure of the macular hole occurred during the follow-up period (range 3 to 10 months). CONCLUSIONS: A small bubble of PFCL prevents ICG dye from entering the subretinal space during vitrectomy for retinal detachment due to macular hole in highly myopic eyes.

Coloring Agents↗

Behavior changes among crack-using rural and urban women.

This study compared rural and urban crack-using women and examined their responses to two interventions. A prospective cohort study design was employed to assess the effectiveness of standard and innovative HIV prevention interventions on 541 urban and 268 rural women in Florida. Generalized estimating equation analysis, accounting for repeated measures, found that for combined urban and rural samples, the innovative intervention was more effective than the standard for a number of drug and sexual risk behaviors. However, the analysis indicated no significant differences in intervention efficacy between rural and urban women. The results imply that there is a need for similar HIV prevention services in both areas.

Adolescent↗

Phase II study of vinorelbine with low dose prednisone in the treatment of hormone-refractory metastatic prostate cancer.

A phase II trial of vinorelbine and low dose prednisone in hormone-refractory metastatic prostate cancer was conducted in order to investigate its safety, efficacy and impact on quality of life. Vinorelbine was administered at the dose of 25 mg/m(2) i.v. weekly for 12 weeks and then biweekly, along with 10 mg of daily oral prednisone until time of progression. Fourteen patients, median age of 74 years, were treated. The treatment was generally well tolerated with leukopenia and anemia as the major side effects. One patient achieved partial remission and eleven remained with stable disease. One of the eleven patients with stable disease had a dramatic PSA response from 1000 to 236 ng/ml; seven of these progressed after week twelve when vinorelbine was given biweekly. PSA response occurred in 5 of 14 patients. The median time to progression was 28 weeks and the median survival was 17 months. Nine out of the 14 accrued patients were evaluable for quality of life assessment. Five of them improved, three remained unchanged and two had a slight worsening. Four patients had improvement in pain control and fatigue. Our preliminary data suggest that the combination of vinorelbine/prednisone has modest activity in metastatic prostate cancer with a very favorable toxicity profile and is very well tolerated in this group of elderly patients.

Adenocarcinoma↗

Enhanced recovery of avian influenza virus isolates by a combination of chicken embryo inoculation methods.

Since 1993, 14 cases of avian influenza from four different states in the U.S.A. have been diagnosed by virus isolation from eight avian species. Only 11 of the 14 avian influenza virus (AIV) primary isolations would have been successful if only the standard protocol for AIV isolation, i.e., inoculation of specific-pathogen-free embryonating chicken eggs (ECEs) by the chorioallantoic sac (CAS) route, had been followed. Primary isolation attempts were negative for AIV in three cases in which ECEs were inoculated by the CAS route; AIV could not be detected by hemagglutinating activity, agar gel immunodiffusion test or negative stain electron microscopy. However, in these three cases, primary isolations of AIV were achieved by inoculation of ECEs into either the yolk sac or onto the chorioallantoic membrane.

Animals↗

Intravitreal triamcinolone in the treatment of serous pigment epithelial detachment and occult choroidal neovascularization secondary to age-related macular degeneration.

PURPOSE: To report two cases of occult choroidal neovascularization (CNV) and serous pigment epithelial detachment (PED) treated with intravitreal triamcinolone (IVT) injections. METHODS: Interventional case reports. RESULTS: Both patients showed an increase in visual acuity and a complete flattening of the PED at 10 months (Case 1) and 4 months (Case 2) after IVT injections. No complications or adverse effects are reported. CONCLUSIONS: Future studies should be designed to investigate if IVT can effectively influence the clinical and functional outcome of eyes with serous PED and occult CNV secondary to age-related macular degeneration, for which at the moment no treatment has been shown to be effective.

Aged↗

Intravitreal triamcinolone acetonide as primary treatment for diffuse diabetic macular edema: a prospective noncomparative interventional case series.

PURPOSE: To evaluate the efficacy and safety of one intravitreal injection of 25 mg of triamcinolone acetonide as primary treatment for diffuse diabetic macular edema. METHODS: Intravitreal triamcinolone acetonide injection was performed in 30 eyes with previously untreated diabetic macular edema. The main outcome measures were logMAR visual acuity (VA) and central macular thickness (CMT) at 1, 3, and 6 months. A secondary outcome was intraocular pressure progression. RESULTS: Visual acuity results for 30 eyes that had a follow-up of at least 6 months are presented. Twenty of them were followed up to 10.1+/-2.38 months. Preoperatively, VA was 0.54+/-0.27. At 1, 3, and 6 months follow-up, VA was 0.44+/-0.29 (p=0.001), 0.43+/-0.28 (p=0.001), and 0.45+/-0.29 (p=0.006), respectively. Preoperatively, CMT was 417.3+/-143.5 microm. At 1, 3, and 6 months follow-up, CMT was 277.3 +74.0 microm (p<0.0001), 279.6+/-94.4 microm (p<0.0001), and 297.07+/-114.87 microm (p=0.002), respectively. For the 20 eyes with a follow-up of 10.1+/-2.38 months, VA was 0.5+/-0.25 and 0.50+/-0.32 at baseline and at the last follow-up visit, respectively (p>0.05). Preoperatively, intraocular pressure (IOP) was 15.13+/-1.48 mmHg. IOP was 18.26+/-2.71 mmHg, 20.07+/-4.27 mmHg, and 20.4+/-6.18 mmHg, at 1, 3, and 6 months, respectively (p<0.0001). Four eyes underwent uncomplicated filtrating surgery for intractable glaucoma. CONCLUSIONS: Intravitreal triamcinolone as primary treatment effectively increases VA and reduces CMT due to diffuse diabetic macular edema. Longer follow-up and randomized clinical trial are warranted. Safety results highlight the need to further study the relationship between triamcinolone and intraocular pressure.

Aged↗

[Relation of dental classes and TMJ. Survey of 2100 students].

The Authors have examined 2100 students of Sassari (mean age 17 years) to point out eventual relationship between different Angle Classes and the health of TMJ. There was found an incidence of disorders more high in the right TMJ. This datum is turned out valid to statistical table.

Adolescent↗

[Chemo-mechanical system of selective caries removal].

Carious cavities treated with traditional system and with chemo-mechanical system have been compared at Sem. The pulpal biocompatibility and toxicity absence are clinically and radiographically observed and verified on elements subjected to direct and indirect pulpal capped treatment.

Aminobutyrates↗