Biomedical subjects

H P Ho

Publications and source records attributed to H P Ho.

8 recordsLinked to original sources

PubMed2006

Application of two-dimensional spectral surface plasmon resonance to imaging of pressure distribution in elastohydrodynamic lubricant films.

What we believe to be a novel two-dimensional spectral surface plasmon resonance imaging technique determining pressure distribution in elastohydrodynamic lubricant films is presented. This technique makes use of the spectral characteristics associated with the surface plasmon resonance (SPR) effect, and it provides more spectral information in refractive index mapping than conventional contrast SPR imaging. Two-dimensional imaging is demonstrated and applied to a highly pressurized liquid lubricant trapped inside an elastohydrodynamic lubrication (EHL) dimple. The hydrostatic pressure inside the EHL dimple causes a localized change of the refractive index of the lubrication oil. This also results in a shift in the spectral SPR absorption dip. By monitoring the color changes within the SPR image and calibrating with lubricants of known refractive index profiles, we can obtain a direct measurement of the refractive index distribution within the EHL dimple. PB 2400 lubricant dimples were studied in our experiments. The proposed SPR imaging approach is irrespective of the absolute lubricant film thickness h, therefore overcoming the major limitations of a conventional optical interference technique. With further development of the two-dimensional refractive index mapping technique, widespread applications in various fields are possible, including high-throughput sensors and the detection of bioaffinity interactions.

Journal Article↗

PubMed2005

Real-time optical biosensor based on differential phase measurement of surface plasmon resonance.

We report a real-time differential phase measurement technique which can be implemented in optical surface plasmon resonance biosensors. The important feature of our design is that sensitivity has been greatly improved by measuring the differential phase change between the s and p-polarizations. Real-time measurement capability is achieved by using a phase extracting routine which continuously monitors the waveforms captured by two photo-detectors. Measurement capability of our setup is demonstrated through real-time monitoring of bovine serum albumin (BSA)/anti-BSA binding reaction. The estimated sensitivity of our current setup is 7.4 ng/ml.

Biosensing Techniques↗

PubMed2004

Highly sensitive differential phase-sensitive surface plasmon resonance biosensor based on the Mach-Zehnder configuration.

A high-sensitivity surface plasmon resonance (SPR) biosensor based on the Mach-Zehnder interferometer design is presented. The novel feature of the new design is the use of a Wollaston prism through which the phase quantities of the p and s polarizations are interrogated simultaneously. Since SPR affects only the p polarization, the signal due to the s polarization can be used as the reference. Consequently, the differential phase between the two polarizations allows us to eliminate all common-path phase noise while keeping the phase change caused by the SPR effect. Experimental results obtained from glycerin-water mixtures indicate that the sensitivity limit of our scheme is 5.5 x 10(-8) refractive-index units per 0.01 degrees phase change. To our knowledge, this is a significant improvement over previously obtained results when gold was used as the sensor surface. Such an improvement in the sensitivity limit should allow SPR biosensors to become a possible replacement for conventional biosensing techniques based on fluorescence. Monitoring of the bovine serum albumin (BSA) binding reaction with BSA antibodies is also demonstrated.

Antigen-Antibody Complex↗

PubMed2001

[Serotonin uptake inhibitors provide rapid relief from premenstrual dysphoria. New findings shed light on how serotonin modulates sex hormone-related behavior].

Premenstrual dysphoria (PMD) is a severe form of premenstrual syndrome, afflicting 5-10% of all women. The cardinal symptom--surfacing between ovulation and menstruation, and disappearing within a few days after the onset of the bleeding--is irritability. Serotonin reuptake inhibitors (SRIs), but not non-serotonergic antidepressants, reduce the symptoms of PMD very effectively. Since the, onset of action of SRIs is rapid when used for PMD, medication may be restricted to the luteal phase. The finding that SRIs are effective for PMD lends support for the hypothesis that a major role for brain serotonin is to modulate sex steroid-driven behavior.

Adult↗

PubMed2001

The serotonin reuptake inhibitor fluoxetine reduces sex steroid-related aggression in female rats: an animal model of premenstrual irritability?

The aggressive behavior displayed by some (but not all) female Wistar rats when an unfamiliar rat is being introduced into their home cage (the resident intruder paradigm) was found to be higher in non-receptive phases (metestrus, diestrus) than in the receptive phases (proestrus, estrus) of the estrus cycle, and effectively reduced by ovariectomy. When removal of the ovaries was followed by administration of estradiol and progesterone, in a regimen mimicking the normal cyclical release of these hormones, aggressive behavior was elicited, two days after estrus, in animals that had displayed aggressive behavior before ovariectomy, but not in those that had not. Short-term administration of a serotonin reuptake inhibitor (fluoxetine hydrochloride; 10 mg/kg, i.p.; 4-5 days) reduced both the aggressive behavior displayed during the diestrus phase by normally cycling rats, and the aggressive behavior elicited by administration of estradiol plus progesterone after ovariectomy. It is suggested that the aggressive behavior displayed by the female Wistar rat in the resident intruder paradigm may serve as an animal model of premenstrual dysphoria.

Aggression↗

PubMed2001

Prenatal cytokine exposure results in obesity and gender-specific programming.

Prenatal events appear to program hormonal homeostasis, contributing to the development of somatic disorders at an adult age. The aim of this study was to examine whether maternal exposure to cytokines or to dexamethasone (Dxm) would be followed by hormonal consequences in the offspring at adult age. Pregnant rats were injected on days 8, 10, and 12 of gestation with either human interleukin-6 (IL-6) or tumor necrosis factor-alpha (TNF-alpha) or with Dxm. Control dams were injected with vehicle. All exposed offspring developed increased body weight (P < 0.05--0.001), apparently due to an increase of 30--40% in adipose tissue weight (P < 0.05--0.01). Corticosterone response to stress was increased in the IL-6 group (P < 0.05-0.01). Dxm-treated male rats exhibited blunted Dexamethasone suppression test results. In male rats, insulin sensitivity was decreased after IL-6 exposure (P < 0.01), whereas basal insulin was elevated in the TNF-alpha group (P < 0.01). In female rats, plasma testosterone levels were higher in all exposed groups compared with controls (P < 0.01--0.001), with the exception of Dxm-exposed offspring. Males in the TNF-alpha group showed decreased locomotor activity (P < 0.05), and females in the IL-6 group showed increased locomotor activity (P < 0.05). These results indicate that prenatal exposure to cytokines or Dxm leads to increased fat depots in both genders. In females, cytokine exposure was followed by a state of hyperandrogenicity. The results suggest that prenatal exposure to cytokines or Dxm can induce gender-specific programming of neuroendocrine regulation with consequences in adult life.

Adipose Tissue↗

PubMed1997

Effectiveness of the Sonicare sonic toothbrush on reduction of plaque, gingivitis, probing pocket depth and subgingival bacteria in adolescent orthodontic patients.

The Sonicare sonic toothbrush and a traditional manual toothbrush were compared for efficacy in improving periodontal health in young orthodontic patients with existing gingival inflammation. A 4-week, single-blind clinical trial was employed. Twenty-four subjects, ages 11-17 years, who were fully bonded and banded with fixed orthodontic appliances were selected. Subjects were randomly assigned to use either the manual or the Sonicare toothbrush, instructed in its use, and asked to brush each morning and evening for 2 minutes. Plaque index, gingival index, percentage of sites which bled on probing, pocket depth, and total gram-negative bacteria in a subgingival plaque sample were assessed at baseline and 4 weeks around the banded teeth. The results demonstrate that the Sonicare brush was significantly more effective than the manual brush in all clinical parameters. Sonicare was statistically superior to the manual brush in supragingival plaque reduction (57% vs. 10%, respectively; p < 0.001). Gingival Index scores fell by 29 percent in the Sonicare group, but only 3 percent in the manual group. Reduction of bleeding on probing was significantly greater in the Sonicare group than in the manual group (p < 0.001). The Sonicare group decreased from 78% bleeding sites at baseline to 24.5% after 1 month. In the manual group there was only a slight reduction in bleeding on probing (70% of sites at baseline and 64.6% sites after 1 month). Mean pocket depths were significantly reduced compared to baseline values in both the Sonicare and the manual groups (p < 0.001). Pocket depth reduction in the Sonicare group was, however, significantly greater than in the manual group (28% vs. 6%, respectively: p < 0.001). Total gram-negative bacteria in subgingival plaque samples from banded test teeth of a subset of patients were reduced in the Sonicare group (p < or = 0.05), but increased in the manual group. These results clearly demonstrate that the Sonicare sonic toothbrush is superior to a manual toothbrush in improving periodontal health in adolescent orthodontic patients with existing gingivitis.

Adolescent↗

PubMed1984

Effect of caloric restriction during pregnancy on maternal and fetal body composition in the obese Sprague-Dawley rat.

The effects of 15, 30 or 50% caloric restriction during pregnancy on maternal and fetal compartments was determined in obese Sprague-Dawley rats. Pregnant and nonpregnant animals were assigned on a weight basis to one of the dietary treatments. All nutrients, except calories, were fed at levels to meet dietary requirements. Animals were killed on day 20 of treatment and fetuses were taken by Caesarian section. Pregnant animals achieved positive weight gain during 20 days of gestation at all levels of caloric restriction. Nonpregnant animals lost body weight when calories were restricted by 30 and 50%. Number of fetuses, fetal body nitrogen, and pup weight were not statistically different (P less than 0.05) among groups. Animals fed the 30 and 50% calorie-restricted diets showed a significant (P less than 0.05) decrease in total-body fat. Percent carcass protein tended to increase as dietary caloric restriction increased. The fetal compartment was apparently not affected by maternal caloric restriction up to 50% during pregnancy provided that all other nutrients were supplied in adequate amounts. Maternal stores were adversely affected at levels of 30 and 50% caloric restriction.

Animal Nutritional Physiological Phenomena↗