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Biomedical subjects

D Garcia

Publications and source records attributed to D Garcia.

At least 19 recordsLinked to original sources
PubMed1999

Local recurrence after vertical partial laryngectomy, a conservative modality of treatment for patients with Stage I-II squamous cell carcinoma of the glottis.

BACKGROUND: Based on an inception cohort of 103 patients who had local recurrence (Group I) and a witness group of 311 patients who achieved local control (Group II) after vertical partial laryngectomy for Stage I-II glottic carcinoma, the current retrospective study documented the consequences and management of local recurrence. METHODS: Three hundred two patients (97.1%) in Group II and all 103 patients (100%) in Group I were followed until death or for a minimum of 10 years. Statistical analysis of survival, lymph node control, and distant metastasis was based on the Kaplan-Meier product limit method. RESULTS: The 10-year actuarial survival estimate was 30.8% for Group I patients and 63.1% for Group II patients. Survival was statistically more likely to be reduced in Group I patients (P < 0.0001) than in Group II patients. The percentage of patients who died of their initial disease was 44.6% in Group I and 6.3% in Group II. The 10-year actuarial lymph node control estimate was 70.2% for Group I and 96.1% for Group II. Lymph node recurrence was statistically more likely to occur in Group I patients than in Group II patients (P < 0.0001). The 10-year actuarial estimate for patients without distant metastasis was 80.2% for Group I and 96.7% for Group II. Distant metastasis was statistically more likely to occur in Group I patients than in Group II patients (P < 0.0001). Salvage treatment was unsuitable for 4.7% of patients with local recurrence; for other patients, it yielded a 86.7% local control rate, a 21.4% laryngeal preservation rate, a 4.5% death rate, and an 11.2% rate of incidence of severe complications. CONCLUSIONS: Among patients with Stage I-II glottic carcinoma managed with vertical partial laryngectomy, local recurrence results in a reduced rate of survival as well as a high rate of necessity for salvage total laryngectomy.

Adult↗
PubMed1999

Maturational changes in cerebral lactate and acid clearance following ischemia measured in vivo using magnetic resonance spectroscopy and microdialysis.

Intraischemic hyperglycemia has different effects on neurologic outcome in mature vs. immature brain, and may reflect differences in the extent or duration of cerebral lactic acidosis. We examined the hypotheses that post-ischemic lactate and acid clearance rates depend on the severity of intraischemic cerebral acidosis, and that rates of clearance change as a function of brain maturation. In vivo 31P and 1H magnetic resonance spectroscopy (MRS) was used to compare intracellular acid and lactate clearance rates in newborn and 1-month old swine following a 14-min episode of transient near-complete global ischemia. In the same animals, in vivo microdialysis was used to determine if extracellular lactate clearance changed as a function of cerebral lactic acidosis or differed between age groups following ischemia. Plasma glucose concentration was altered in individual animals to study a range of intraischemic cerebral lactic acidosis. For both age-groups, maximal brain acidosis and lactosis occurred in the post-ischemia interval, indicating a delay in the re-establishment of oxidative metabolism following ischemia. Clearance half-lives of both cerebral acidosis and lactosis increase as a function of increased intraischemic cerebral acidosis. For either age group, the clearance half-life for acidosis was faster than the half-life for lactate. However, the subgroup of 1-month old swine who experienced severe cerebral acidosis (i.e., pH<6.1) had a longer cerebral lactate clearance half-life as compared to the subgroup of newborn animals with a similar severity of acidosis. In both age groups, there were comparable maximal increases in extracellular lactate concentrations in the post-ischemic period and similar rates of decline from the maximum. These results demonstrate that post-ischemic lactate and acid clearance are altered by the extent of intraischemic acidosis, and the extent of post-ischemic uncoupling between brain acid and lactate clearance increases with advancing age. The transmembrane clearance of lactate was not a prominent mechanism that differentiated lactate clearance rates between newborn and 1-month old swine.

Acidosis, Lactic↗
PubMed1999

A multimodal strategy for the treatment of patients with T2 invasive squamous cell carcinoma of the glottis.

BACKGROUND: The current conservative standard of care for T2 squamous cell carcinoma of the glottis is either partial laryngectomy or radiation therapy. METHODS: Based on an inception cohort of 100 patients with T2 squamous cell carcinoma of the glottis and a minimum of 3 years of follow-up, the present study documented the results achieved with a multimodal strategy using platinum-based induction chemotherapy and partial laryngeal surgery. Statistical analysis of survival and local control was based on the Kaplan-Meier actuarial life table method. Univariate analysis was performed to determine whether there was a correlation among various factors and toxicity, clinical response, histologic regression, local control, and survival. RESULTS: A complete clinical response and a partial response after induction chemotherapy was achieved in 24% and 58% of patients, respectively. Complete histologic regression was noted in 31%. A significant statistical relation (P < 0.0001) was noted between a complete clinical response after induction chemotherapy and a complete histologic regression. The 5-year actuarial survival estimate was 85.8%. The 5-year actuarial local control estimate was 95.7% (97.7% if the vocal cord was mobile and 93.8% if the motion of the vocal cord was impaired). Salvage treatment resulted in an overall 99% rate of local control and a 95% rate of laryngeal preservation. CONCLUSIONS: Because this represents a nonrandomized retrospective study, no definitive conclusions can be derived. However, when compared with the data reported in a large series using radiation therapy or partial laryngectomy alone, this 10-year experience suggests that, in patients with "early" invasive squamous cell carcinoma of the glottis, the use of platinum-based induction chemotherapy prior to a conventional conservative treatment modality should be investigated further.

Adult↗
PubMed1999

Recurrent gustatory sweating (Frey syndrome) after intracutaneous injection of botulinum toxin type A: incidence, management, and outcome.

OBJECTIVE: To evaluate the duration of effectiveness of intracutaneous injection of botulinum toxin type A for gustatory sweating as well as the incidence, severity, management, and outcome of recurrent gustatory sweating. DESIGN: An inception cohort with a minimum of 18 months of follow-up. SETTING: A tertiary care center and university teaching hospital. PATIENTS: Thirty-three patients with severe gustatory sweating. INTERVENTION: Intracutaneous injection of 25 to 175 IU (mean, 86 IU) of botulinum toxin type A. MAIN OUTCOME MEASURES: Analysis of the effectiveness of the intracutaneous injection of botulinum toxin type A using the Kaplan-Meier actuarial life-table method; completion of the Minor starch-iodine test in patients without symptomatic recurrent gustatory sweating; and the patients' self-assessment of the severity of the recurrent gustatory sweating. RESULTS: The 1-, 2-, and 3-year actuarial estimate for symptomatic recurrent gustatory sweating was 27%, 63%, and 92%, respectively. In the 7 patients without symptomatic recurrent gustatory sweating, the Minor starch-iodine test revealed persistent gustatory sweating in 6, resulting in an overall 97% rate (32 of 33 patients) for recurrent gustatory sweating. No statistical relationship could be demonstrated between the duration of effectiveness, the incidence of recurrent gustatory sweating, the severity of recurrent gustatory sweating, and the following variables: age, sex, cause of gustatory sweating, skin surface involved, and dose of botulinum toxin type A injection. Within the group of 26 patients with symptomatic recurrent gustatory sweating, (1) the severity of the recurrent gustatory sweating was always reduced when compared with the severity of the initial gustatory sweating, and (2) the recurrent gustatory sweating always remained amenable to reinjection of botulinum toxin type A. CONCLUSIONS: The present series demonstrated a linear regression in the effectiveness of the intracutaneous injection of botulinum toxin type A in patients with gustatory sweating, while no factors appeared to be statistically related to the duration of effectiveness and/or the incidence of recurrent gustatory sweating. However, because the severity of recurrent gustatory sweating is reduced when compared with the severity of the initial gustatory sweating and because recurrent gustatory sweating remains amenable to reinjection of botulinum toxin type A, we believe that the intracutaneous injection of botulinum toxin type A should become the first-line treatment option in patients with gustatory sweating.

Adolescent↗
PubMed1999

Structure-functional effects of ethanol on Drosophila melanogaster acetylcholinesterase probed by kinetic studies with substrate and inhibitors.

Ethanol is commonly used to extract and dissolve insecticides acting as inhibitors of acetylcholinesterase (EC 3.1.1.7). Here, experiments were undertaken to investigate the influence of solvent on the reaction and inhibition of the enzyme from Drosophila melanogaster. Ethanol (up to 20% by volume) is shown to induce a dramatic reduction of the affinity of acetylcholinesterase for the acetylthiocholine iodide substrate and all the edrophonium chloride, paraoxon ethyl and propidium diiodide inhibitors, with little influence on the rate constants. Taken together, these results point to a main perturbation of active-center related components involved in the formation and/or stability of Michaelis complexes. Inactivation and ligand-stabilization studies of acetylcholinesterase activity further indicate the occurrence of specific "conformational scrambling" at catalytic and regulatory sites. It is proposed that ethanol affects the enzyme reactivity by modifying the conformation of the aromatic gorge containing the active centre and hence, interactions involved in the molecular recognition of substrates and ligands.

Acetylcholinesterase↗
PubMed1999

A new flow model for Doppler ultrasound study of prosthetic heart valves.

BACKGROUND AND AIM OF THE STUDY: Steady and pulsatile flow models used to assess the hydrodynamic aspects of prosthetic heart valves are generally made of Plexiglas and Lucite tubing. They often allow continuous-wave and pulsed-wave Doppler ultrasound velocity measurements to be made parallel to the flow, but cannot be used as such for ultrasound scanning of valve inflow and outflow velocities because of ultrasonic reverberation and refraction by the tubing. The aim of the study was to develop a new flow model which allowed ultrasonic scanning of the prosthetic valve flow for three-dimensional (3D) reconstruction of color Doppler flow distributions. METHODS: The flow model, designed with left ventricular and aortic chambers composed of agar gel which mimics the ultrasound characteristics of biological tissues, was developed and tested for comparative in vitro hydrodynamic and Doppler ultrasonic studies of aortic prosthetic valves. An electromagnetic flowmeter and a pressure monitor provided the flow and pressure signals for the hydrodynamic tests. The Doppler ultrasonic evaluation was performed with an Ultramark 9 HDI ultrasound system and a 3D ultrasound imaging system. The model was designed to enable assessment of prosthetic valve performance by pulsed-wave and continuous-wave Doppler velocity measurements, as well as by 3D color Doppler velocity measurements obtained by ultrasonic scanning of the left ventricle or aortic chamber with an ultrasound probe mounted on a motorized translation assembly. RESULTS: The study results showed that this new flow model can provide 3D color Doppler velocity distributions as well as accurate comparisons of hydrodynamic parameters of mechanical and bioprosthetic heart valves derived from Doppler and catheter measurements, both under steady and pulsatile flow conditions. CONCLUSION: This new flow model can be used to evaluate the usefulness of hydrodynamic parameters for the assessment of prosthetic heart valves using both conventional Doppler echocardiography, as currently used in patients, and 3D color Doppler ultrasonic imaging.

Blood Flow Velocity↗
PubMed1999

Ethnic variation in the health burden of self-reported diabetes in adults aged 75 and older.

OBJECTIVE: The health burden of self-reported diabetes was compared across three ethnic groups of older adults. METHODS: Analysis of variance and logistic regression were used to compare ethnic differences in the rates of co-morbid chronic health conditions, complications, and disability for older diabetics vs non-diabetics, in a sample of 173 Mexican Americans, 201 African Americans, and 181 non-Hispanic whites, all aged 75 and older. RESULTS: The prevalence of self-reported diabetes was significantly higher in older Mexican Americans (17.6%) and African Americans (16.4%) than in non-Hispanic whites (8.5%). In all three ethnic groups, and after controlling for sociodemographic characteristics, diabetics were found to be generally at higher risk for chronic conditions such as heart disease, stroke, and hypertension, circulation and foot problems, obesity, and impaired vision and activities of daily living. Multivariate analyses indicated that the burden of diabetes appeared to be greatest among non-Hispanic white diabetics. We suggest that this is the result of higher diabetes-mortality rates among minority diabetics at earlier ages. CONCLUSIONS: Diabetes is known to be increasing in prevalence and incidence, particularly among the elderly, the fastest growing segment of the population. Our findings indicate that regardless of ethnicity, diabetes carries an increased burden that affects both the functioning and the quality of life of older adults.

Activities of Daily Living↗
PubMed1998

Age-related differences in the effect of dichloroacetate on postischemic lactate and acid clearance measured in vivo using magnetic resonance spectroscopy and microdialysis.

Numerous studies using adult animal models suggest that dichloroacetate (DCA) may have neuroprotective properties by virtue of its ability to increase rates of metabolism and, therefore, clearance of brain lactic acidosis, which may accumulate during cerebral ischemia. We tested the hypothesis that postischemic DCA administration affects lactate and acid clearance to different extents in immature versus mature brain. 31P and 1H magnetic resonance spectroscopy were used to measure intracellular acid and lactate clearance rates in vivo in newborn and 1-month-old swine after a 14-min episode of transient near-complete global ischemia. Simultaneous monitoring of extracellular lactate efflux and clearance was measured in the same animals by in vivo microdialysis. Plasma glucose concentrations were elevated in order to study animals with severe cerebral lactic acidosis. Maximal levels of brain lactosis (16-20 micromol/g) and acidosis (PHintracellular 5.8-6.0) were reached during the first 10 min of recovery and were the same in age groups and in subgroups either acting as controls or treated with DCA (200 mg/kg) given from the last minute of ischemia to 5-7 min after ischemia. For newborns, DCA administration improved the postischemic clearance rate of cerebral acidosis and cerebral phosphocreatine, with similar trends for the clearance of lactosis and increased rates of recovery of nucleotide triphosphates, compared with controls. In contrast, DCA administration in 1-month-olds resulted in a modest trend for improvement of cerebral lactate clearance, but did not affect acid clearance or the recovery rate of phosphocreatine or nucleotide triphosphates. Extracellular brain lactate concentrations had similar relative increases and rates of decline for subgroups of either age treated with DCA versus controls. The results of this study indicate that postischemic DCA administration helps to resolve cerebral acidosis to a greater degree in immature than more mature brain, suggesting that DCA may have cerebroprotective properties for neonatal hypoxic-ischemic encephalopathy.

Acids↗
PubMed1997

Characterization of the reaction center bound tetraheme cytochrome of Rhodocyclus tenuis.

Properties of the tetrahemic reaction center bound cytochrome have been investigated by different techniques. The mid-point potentials of the four hemes were determined by redox titration. The best fit of the data was obtained with a (n = 1) Nernst curve by using the following values of the redox parameters: Em = +420 mV for the two high-potential hemes and Em = +110 and +60 mV for the two low-potential hemes. The mid-point potentials of the two high-potential hemes are the highest reported so far. The spectral properties of the four hemes in the alpha-band have been determined by absorption spectroscopy and measurements of light-induced difference spectra in membranes of Rhodocyclus tenuis. The two high potential hemes present very similar spectra centered at 557 nm. The absorption spectra of the two low-potential hemes are very similar, and their alpha-band centered around 551 nm. Spectral properties at 100 K and the linear dichroism of optical transitions allow the determination of the relative orientations of the hemes with respect to the membrane plane. The orientation patterns thus obtained corresponds to none of the arrangements described so far for reaction center bound cytochromes.

Bacterial Proteins↗
PubMed1997

A risk profile of street youth in northern California: implications for gender-specific human immunodeficiency virus prevention.

PURPOSE: To assess human immunodeficiency virus (HIV) risk behaviors of street youth and to determine whether risk behaviors differ by gender or housing status. METHODS: Using systematic street-based sampling in four Northern California cities, we recruited 429 street youth (mean age = 19.2 years). Participants completed a structured interview which was used to assess sexual and drug HIV risk behaviors. RESULTS: The majority of youth were heterosexual (85%), white (77%), male (68%), and currently without any type of stable housing (75%). Although 60% of the sample had had vaginal sex in the past 30 days, only 44% used a condom the last time they had sex. About one-third (32%) of the sample reported ever injecting drugs, and almost all reported lifetime use of multiple drugs including D-lysergic acid diethylamide (96%), marijuana (90%), alcohol (81%), cocaine (70%), and speed (70%). Compared to males, females were equally likely to use injection and noninjection drugs, but were more likely to be sexually active (P < .001), were more likely to have been diagnosed with a sexually transmitted disease (P = .005), and were less likely to report consistent condom use (P = .003) or intent to use condoms consistently in the future (P = .005). Compared with those with stable housing, youth who were currently without such housing reported higher rates of injection, and other drug use; females without stable housing were less likely to have used condoms the last time they had vaginal intercourse. CONCLUSION: The high level of HIV risk behavior in this street-based sample of youth, particularly females and youth without stable housing, suggests an urgent need for gender-specific prevention efforts and an increased range of housing options.

Adolescent↗
PubMed1997

Modest hypothermia provides partial neuroprotection when used for immediate resuscitation after brain ischemia.

Intraischemic reduction in temperature of 2-3 degrees C (modest hypothermia) has been demonstrated to provide partial neuroprotection in neonatal animals. This investigation determined if modest hypothermia initiated immediately after brain ischemia provides neuroprotection. Piglets were studied with rectal temperature maintained during the 1st h after 15 min of brain ischemia at either 38.3 +/- 0.3 degrees C (normothermia, n = 11) or at 35.8 +/- 0.5 degrees C (modest hypothermia, n = 11). The severity of brain ischemia was similar between groups as indicated by equivalent reduction in mean blood pressure (90 +/- 15 to 24 +/- 3 versus 92 +/- 13 to 26 +/- 3 mm Hg), and changes in cerebral metabolites and intracellular pH (pH(i)) measured by magnetic resonance spectroscopy (beta-nucleoside triphosphate = 44 +/- 9 versus 42 +/- 18% of control, control = 100%, pH(i): 6.25+/- .15 versus 6.24 +/- 0.22 for normothermic and modestly hypothermic groups, respectively). In the first 90 min after ischemia, there were no differences between groups in the duration and extent of brain acidosis, and relative concentrations of phosphorylated metabolites. Categorical assessment of neurobehavior was evaluated at 72 h postischemia (n = 16), or earlier if an animal's condition deteriorated (n = 6). Postischemic hypothermia was associated with less severe stages of encephalopathy compared with normothermia (p = 0.05). Histologic neuronal injury was assessed categorically in 16 brain regions, and postischemic hypothermia resulted in less neuronal injury in temporal (p = 0.024) and occipital (p = 0.044) cortex at 10 mm beneath the cortical surface, and in the basal ganglia (p = 0.038) compared with that in normothermia. Modest hypothermia for 1 h immediately after brain ischemia provides partial neuroprotection and may represent an adjunct to resuscitative strategies.

Animals↗
PubMed1997

Initial screening for antituberculous drug resistance at an inpatient facility in Leon, Nicaragua.

Antituberculous (anti-TB) drug resistance has become a major tuberculosis control issue in the United States, where this situation has closely paralleled the current acquired immunodeficiency syndrome epidemic associated with human immunodeficiency virus type-1 (HIV-1) infections. In less developed countries, especially those like Nicaragua with an apparently low prevalence of known HIV-1 infections, less is known about the epidemiology of antituberculous drug resistance. To understand the potential extent of this problem in Nicaragua, we conducted a cross-sectional prevalence study at Nicaragua's only inpatient tuberculosis treatment facility, located in Leon, Nicaragua. A radiometric method was used during recovery, purification, and drug susceptibility testing of clinical Mycobacterium tuberculosis isolates. Resistance to at least one of the major anti-TB medications was found in 15 (40.5%) of 37 sputum isolates, of which seven (19%) were resistant to either isoniazid alone, or to isoniazid plus another agent other than rifampin. Five were resistant to at least isoniazid and rifampin (i.e., 13.5% demonstrated multidrug resistance). Two isolates were resistant to pyrazinamide alone, and one was resistant to streptomycin alone. These initial results suggest that anti-TB drug resistance is a defined problem for tuberculosis control programs in Nicaragua, a problem that is largely related to individual noncompliance, lack of extensive drug susceptibility testing facilities, and a general unavailability of expensive anti-TB medications for re-treatment. Ongoing surveillance for drug resistance, using the methodology presented here, might assist Nicaraguan public health officials in their tuberculosis control programs.

Adult↗
PubMed1996

Brachytherapy or electron beam boost in conservation therapy of carcinoma of the breast: a nonrandomized comparison.

PURPOSE: The results of breast-conservation therapy using breast irradiation and a boost to the tumor excision site with either electron beam or interstitial 192Ir implant are reviewed. METHODS AND MATERIALS: A total of 701 patients with histologically confirmed Stage T1 and T2 carcinoma of the breast were treated with wide local tumor excision or quadrantectomy and breast irradiation. The breast was treated with tangential fields using 4 or 6 MV photons to deliver 48 to 50 Gy in 1.8 to 2 Gy daily dose, in five weekly fractions. In 80 patients the regional lymphatics were irradiated. In 342 patients with Stage T1 and 107 with Stage T2 tumors, boost to the primary tumor excision site was delivered with 9 MeV and, more frequently, with 12 MeV electrons. In 91 patients with Stage T1 and 38 patients with Stage T2 tumors an interstitial 192Ir implant was performed. Tumor control, disease-free survival, cosmesis, and morbidity of therapy are reviewed. Minimum follow-up is 4 years (median 5.6 years; maximum, 24 years). RESULTS: The overall local tumor recurrence rates were 5% in the T1 and 11% in the T2 tumor groups. There was no significant difference in the breast relapse rate in patients treated with either electron beam or interstitial 192Ir boost. Regional lymph node recurrences were 1% in patients with T1 and 5% with T2 tumors. Distant metastases were recorded in 5% of the T1 and 23% of the T2 groups. The 10-year actuarial disease-free survival rates were 87% for patients with T1 and 75% with T2 tumors. Disease-free survival was exactly the same in patients receiving either electron beam or interstitial 192Ir boost. Cosmesis was rated as excellent/good in 84% of patients with T1 tumors treated with electron beam and 81% of patients treated with interstitial implant, and 74 and 79% respectively, in patients with T2 tumors. CONCLUSIONS: Breast-conservation therapy is an effective treatment for patients with T1 and T2 carcinoma of the breast. There is no difference in local tumor control, disease-free survival, cosmesis, or morbidity in patients treated with either electron beam or interstitial 192Ir implant boost. Clinical trials in progress will further elucidate this controversial subject.

Brachytherapy↗
PubMed1996

Morning report: a forum for reporting adverse drug reactions.

BACKGROUND: Most hospitals that monitor adverse drug reactions (ADRs) through reporting by nurses, pharmacists, medical record technicians, and quality improvement staff experience low rates of reporting. In teaching hospitals, inadequate orientation about the hospital activities, frequent changes in rotations between hospitals, and time commitments to educational pursuits may all undermine house staff's ability to perform ADR monitoring. The authors describe their experience since 1989 at the Department of Veterans Affairs Medical Center in Amarillo, Texas, in the use of verbal ADR reporting by physicians (mostly house staff) during the morning report in the medical service. ADR MONITORING PROGRAM: The morning report begins with a discussion of adverse outcomes of medications, usually from the previous 24 hours. The staff physicians use the opportunity to address the nature of the ADRs and the clinical circumstances leading up to them. Some ADR episodes require further peer review by a physician before being forwarded to the Pharmacy and Therapeutics Committee. EFFECT OF THE PROGRAM: Since the start of the ADR monitoring program in 1989, the number of self-reported ADRs in the medical service has increased over historical controls, even though no special training was given to house staff to detect ADRs. The surgical and psychiatric services, which did not hold morning reports, did not experience the same increase in ADR reports. CONCLUSIONS: The ADR monitoring program is notable for the simplicity of the reporting mechanism, the integration of the reporting into the regular work flow activities, the concurrent nature of the reporting, the educational opportunities, and the potential benefit for quality improvement of patient care.

Adverse Drug Reaction Reporting Systems↗
PubMed1996

Mapping 638 STSs to regions of human chromosome 3.

The initial step of mapping STSs to chromosome 3 has been by mapping to a reference panel of 21 somatic cell hybrids containing fragments of chromosome 3. In this study we map 638 STSs to 23 bins on chromosome 3. The bin information greatly facilitates further mapping by radiation hybrids and YAC clones.

Chromosome Mapping↗