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Biomedical subjects

F Flores

Publications and source records attributed to F Flores.

At least 19 recordsLinked to original sources
PubMed2003

Phonon softening, chaotic motion, and order-disorder transition in Sn/Ge(111).

The phonon dynamics of the Sn/Ge(111) interface is studied using high-resolution helium atom scattering and first-principles calculations. At room temperature we observe a phonon softening at the Kmacr; point in the (sqrt[3]xsqrt[3])R30 degrees phase, associated with the stabilization of a (3x3) phase at low temperature. That phonon band is split into three branches in the (3x3) phase. We analyze the character of these phonons and find out that the low- and room-temperature modes are connected via a chaotic motion of the Sn atoms. The system is shown to present an order-disorder transition.

Journal Article↗
PubMed2001

Effect of ketamine on spinal cord nociceptive transmission in normal and monoarthritic rats.

The effects of systemically and intrathecally administered ketamine on spinal wind-up of normal and monoarthritic rats were studied by using C-fiber reflex responses evoked by repetitive (0.6 Hz) electric stimulation. Both systemic and intrathecal ketamine induced dose-dependent depression of wind-up activity in normal rats, as revealed by the dose-related inhibitory effects of the drug. At the same intraperitoneal doses, ketamine produced a greater inhibitory effect on wind-up activity of monoarthritic rats, compared to normal animals. The intrathecal administration of ketamine also produced wind-up inhibition, the efficacy being higher in the monoarthritic rats. Results indicate that ketamine depresses spinal wind-up, specially in rats submitted to chronic pain, probably due to its antagonistic properties on dorsal horn NMDA receptors, which play a crucial role in the maintenance of chronic pain.

Animals↗
PubMed2001

Surface soft phonon and the sqrt[3] x sqrt[3] <--> 3x3 phase transition in Sn/Ge(111) and Sn/Si(111).

Density functional theory calculations show that the reversible Sn/Ge(111) sqrt[3]xsqrt[3]<-->3x3 phase transition can be described in terms of a surface soft phonon. The isovalent Sn/Si(111) case does not display this transition since the sqrt[3]xsqrt[3] phase is the stable structure at low temperature, although it presents a partial softening of the 3x3 surface phonon. The rather flat energy surfaces for the atomic motion associated with this phonon mode in both cases explain the experimental similarities found at room temperature between these systems. The driving force underlying the sqrt[3]xsqrt[3]<-->3x3 phase transition is shown to be associated with the electronic energy gain due to the Sn dangling bond rehybridization.

Journal Article↗
PubMed2000

Other novel immunosuppressants.

The use of immunosuppressive agents in dermatology has increased widely. The role of these medications has become increasingly important for the treatment of dermatologic disorders in an inpatient setting, where there is frequently a requirement for highly potent, fast-acting, effective agents. This article presents an overview of the general application, mechanisms of action, metabolism, and adverse effects commonly associated with systemic immunosuppressive agents used in dermatology.

Azathioprine↗
PubMed2000

Is there a special relationship between CD30-positive lymphoproliferative disorders and epidermal proliferation?

The relationship between CD30+ lymphoma and epithelial proliferations is not well defined. CD30+ lymphoma and lymphomatoid papulos (LyP) share immunohistochemical epitopes and some other features. A single case of LyP associated with multiple keratoacanthomas (KAs) was recently reported. We report two cases of atypical lymphocytic proliferation with features of CD30+ lymphoma and LyP intimately associated to KA and squamous cell carcinoma (SCC), KA type. This similar combination of an epidermal tumor and apparent involvement with atypical lymphocytic infiltrates raises the possibility of an association between the two entities. We speculate that the association may be more than expected to occur by chance and suggest several mechanisms by which the association may evolve.

Aged↗
PubMed2000

Dose-response and onset/offset characteristics of rapacuronium.

BACKGROUND: A rigorous study of the dose-response relation of rapacuronium has, to our knowledge, yet to be performed. In addition, there is little information available regarding the onset or offset profile of rapacuronium when administered in subparalyzing doses. These issues necessitate further study. METHODS: Forty-seven adult patients, American Society Anesthesiologists physical status I or II, were studied. Tracheal intubation was accomplished without muscle relaxants. Anesthesia was maintained with use of nitrous oxide, propofol, and alfentanil. The electromyogram of the first dorsal interosseous muscle was measured using a monitor. Single stimuli at 0.10 Hz were administered. A single dose of rapacuronium was administered. After log-dose or logit transformation of the data, the best-fit line of regression was determined using the method of least squares. For each subject, the authors estimated the 50% effective dose (ED50) and 95% effective dose (ED95) from the Hill equation using the slope obtained from regression analysis. The onset times to 50 and 90% of peak effect were estimated in a subset of 10 individuals in which peak twitch depression decreased to the range of 90-99%. RESULTS: The calculated ED50 and ED95 values for rapacuronium were 0.39 +/- 0.08 (SD) and 0.75 +/- 0.16 mg/kg, respectively. After a single ED95 dose, 90% of the drug's peak effect was evident in 77 +/- 17 s. After this dose, rapacuronium has a clinical duration of 6.1 +/- 1.1 min. CONCLUSIONS: The authors found the ED95 of rapacuronium to be substantially less than suggested by previous estimates. Rapacuronium has an onset profile that is not different from that previously reported for succinylcholine. The rate of spontaneous recovery was faster after rapacuronium than the authors previously observed after mivacurium administration but was slower than after succinylcholine, using an identical protocol.

Adult↗
PubMed1999

Comparison of a silicone gel-filled cushion and silicon gel sheeting for the treatment of hypertrophic or keloid scars.

BACKGROUND: The exact mechanisms of action responsible for the effectiveness of silicone gel dressings are unknown, although it has been proposed that static electricity generated by friction could be the reason for their anti-scarring effects. OBJECTIVE: We compared the efficacy of a cushion of silicone filled with liquid silicone gel reported to induce greater negative static-electric charge with silicone gel sheeting in the treatment of hypertrophic and keloid scars. METHODS: The size, volume, symptoms (tenderness and itching), and signs (color and induration) of hypertrophic (10 patients) or keloid scars (22 patients) were measured at baseline at 16 weeks following use of either the silicone gel cushion or silicone gel sheeting, as determined by random assignment. RESULTS: Both the silicone gel cushion and the silicone gel sheeting treatments were effective in decreasing scar volume, 53.0% and 36.3%, respectively. The percentages of keloids and hypertrophic scars benefiting from the silicone cushion and the silicone sheeting were similar with respect to reduction in tenderness (36.3% vs 33.3%), itching (45.5% vs 33.3%), and redness (0.1% vs 0.1%), and in the degree of softening (45.5 vs 25.0%). CONCLUSIONS: Both the silicone gel cushion and the silicone gel sheeting treatments were effective in the treatment of keloids and hypertrophic scars, although no statistically significant differences were found between the two treatment modalities.

Adult↗
PubMed1998

Efficacy of pentoxifylline in the treatment of pruritic papular eruption of HIV-infected persons.

BACKGROUND: Pruritic papular eruption (PPE) of HIV/AIDS is a common manifestation of HIV infection. Unfortunately, treatments for the unremitting pruritus have yielded only partial relief. OBJECTIVE: Our purpose was to assess the clinical efficacy of pentoxifylline in the treatment of pruritus in HIV-infected patients with PPE while measuring its effects on HIV viral load and levels of serum triglycerides, tumor necrosis factor (TNF)-alpha, and interleukin (IL)-4. METHODS: Eleven of the 12 patients with PPE and HIV infection placed on a regimen of oral pentoxifylline completed the 8-week study. The degree of pruritus both before and after therapy was measured by means of a patient-reported visual analog scale (0 = none and 10 = worst experienced). A global assessment of the number and size of PPE lesions was performed by the investigator, and serum TNF-alpha, IL-4, and triglyceride levels, as well as HIV viral load, were measured. RESULTS: The average degree of pruritus was significantly reduced (p = 0.0009) from 6.5 at baseline examination to 3.6 at the end of the study. Ten of 11 patients experienced a reduction in their pruritus, ranging from 22.6% to 87.3%. The global assessment of PPE lesions decreased from baseline in most patients and increased slightly in one patient. Serum TNF-alpha was detectable in one patient at baseline, but was undetectable at the end of the study period. Similarly, the two patients who had detectable serum IL-4 at baseline had undetectable serum IL-4 levels at the end of the study. Triglyceride levels in six patients decreased an average of 23.9% by week 8. Although when compared with baseline values, HIV viral loads in seven patients decreased, one patient had no change, and three patients had an increase in their viral load at the end of the study, the magnitude of the changes were of little clinical importance. CONCLUSION: Pentoxifylline is a safe and efficacious treatment of pruritus in HIV-infected patients with PPE. Future controlled studies are needed to confirm the effectiveness of this treatment.

Adult↗
PubMed1998

The treatment of hypertrophic scars and keloids.

Keloid and hypertrophic scarring develop as a result of a proliferation of dermal tissue following skin injury. It is generally thought that tension plays a major pathophysiologic role. These proliferative scars are characterized by increased collagen and glycosaminoglycan content, as well as increase collagen turnover. The therapeutic management of hypertrophic scars and keloids includes occlusive dressings, compression therapy, intralesional corticosteroid injections, cryosurgery, excision, radiation therapy, laser therapy, interferon therapy and other promising, lesser known therapies directed at collagen synthesis. Although the most commonly used occlusive dressings include silicone based materials, the anti-keloidal effect is the result of the occlusion and hydration effected rather than the silicone itself. Pressure devices, through local tissue hypoxia, have proven effective in reducing scar height. Intralesional steroids decrease the connective tissue components and scar volume. Post-operative steroid injections reduce keloid recurrence to less than 50%. Cryosurgery is most effective when combined with intralesional corticosteroids. Excision only of hypertrophic scars and keloids results in 45-100% recurrence. Radiation therapy, using various protocols, has been a safe and efficacious modality in reducing recurrence. The CO2, Nd:YAG, and Argon lasers have been used as destructive modalities for the treatment of proliferative scarring. The pulsed-dye laser offers symptomatic improvement and reduces the erythema associated with these scars. Intralesional interferon -gamma and -alpha 2b have been used successfully to decrease scar height and reduce the number of post-operative recurrences.

Adrenal Cortex Hormones↗
PubMed1997

Recurrence rates of excised keloids treated with postoperative triamcinolone acetonide injections or interferon alfa-2b injections.

BACKGROUND: Keloids that are surgically removed commonly recur within the excision sites. OBJECTIVE: Our purpose was to determine whether postsurgical adjunctive therapy reduces such recurrences. METHODS: We determined the rate of recurrence after excision alone (n = 43) and postoperative injection with triamcinolone acetonide (TAC; n = 65) or interferon alfa-2b (IFN-alpha 2b; n = 16). RESULTS: Of lesions excised without postoperative injections, 51.1% (22 of 43) recurred; 58.4% of TAC-treated lesions (38 of 65) recurred and 18.7% of IFN-alpha 2b-treated lesions (3 of 16) recurred (p = 0.025). CONCLUSION: Postoperative TAC injections do not reduce the number of keloid recurrences. However, injection of keloid excision sites with IFN-alpha 2b offers a therapeutic advantage over keloid excision.

Adolescent↗