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Biomedical subjects

M A Lopez

Publications and source records attributed to M A Lopez.

At least 19 recordsLinked to original sources
PubMed2001

Sequence of centromere separation: effect of 5-azacytidine-induced epigenetic alteration.

The factors which control the sequential separation of the various chromosomes in a genome at the meta-anaphase junction are not well understood. In genomes in which separation is correlated with the quantity of pericentric heterochromatin one factor appears to be the epigenetic nature, namely condensation, of pericentric heterochromatin. When we induced decondensation of pericentric heterochromatin in mouse cells with 10(-6), 4x 10(-6) and 6x10(-6) M 5-azacytidine (5-AC) for 8 h, it resulted in alteration of the sequence of centromere separation. The centromeres which lacked pericentric heterochromatin appeared not to have been affected because there could not be an epigenetic alteration induced by 5-AC. The major effect was on chromosomes with the largest quantity of pericentric heterochromatin. These chromosomes separated at significantly higher frequency than in the untreated population. We also treated human cells, in which separation does not depend upon the quantity of heterochromatin, with 2x10(-5) and 6x10(-6) M 5-AC for 5 and 8 h. Compared with the control, 5-AC treatment resulted in an increased frequency of separated centromeres of acrocentric chromosomes in relation to those of non-acrocentric chromosomes. In the control the acrocentric chromosomes are the last to separate; in the treated population there was almost random separation of the two types of chromosomes. This epigenetic alteration might be another factor which results in genesis of aneuploidy.

Animals↗
PubMed2000

Increasing the calcium content of mealworms (Tenebrio molitor) to improve their nutritional value for bone mineralization of growing chicks.

The purpose of these studies was to determine the husbandry variables that optimize the Ca content of mealworms (Tenebrio molitor) and to determine the bioavailability of this Ca for bone mineralization in chicks that consume the mealworms. To determine the optimal level of Ca in the substrates used in short-term (< 14 days) holding of mealworms and to determine the length of time that mealworms should be exposed to high-Ca substrates, mealworms were placed in either a wheat bran or a chicken starter substrate supplemented with 0, 4, 8, or 12% Ca from CaCO3. The mealworms were harvested after 0.5, 1, 2, 3, 4, 7, or 14 days. The Ca content of the mealworms was greatest with the use of chicken starter and increased linearly with the Ca content of the substrate. In general, the Ca content of the mealworms increased during the first 24 hr and decreased after > or = 1 wk, especially at the higher levels of Ca supplementation. The chicken starter also resulted in higher levels of vitamin D in mealworms. Mealworms held in wheat bran with 8% Ca were fed to growing chicks. Ca bioavailability was calculated from the chicks' bone ash. The Ca in these mealworms was 76% as bioavailable as the Ca in oyster shell.

Animal Feed↗
PubMed1999

The free-to-total serum prostatic specific antigen ratio as a predictor of the pathological features of prostate cancer.

OBJECTIVES: To analyse the role of the ratio of serum free (f) to total (t) prostatic specific antigen (f/tPSA) as a predictor of the pathological features in patients with clinical stage T1c disease submitted for radical prostatectomy. PATIENTS AND METHODS: Total and fPSA were determined before surgery in 76 consecutive patients with clinical stage T1cN0M0 disease and a serum tPSA level of 4-20 ng/mL. The pathological stage was defined as organ-confined in 47 (62%), with capsular penetration in 27 (35%) and seminal vesicle infiltration in two (3%). In 18 of the specimens (24%) the surgical margins were positive. The pathology was favourable in 41 patients (55%). Total and fPSA were determined using the Tandem and Tandem-free PSA immunoassays (Hybritech Inc, Belgium) RESULTS: The mean tPSA was: 8.7 ng/mL when the tumour was organ-confined and 8.6 ng/mL when the disease was extraprostatic (P>0.05); 8.4 ng/mL when the tumour was specimen-confined and 9.3 ng/mL when positive margins or seminal vesicle involvement were detected (P>0.05); and 8.3 ng/mL when the pathology was favourable and 9.0 ng/mL when unfavourable (P>0.05). The f/tPSA was 11.8% when the tumour was organ-confined and 9.1% when it was not (P<0.03), 11.9% when the tumour was specimen-confined and 7.6% when not (P<0.002) and 12.1% when the pathology was favourable and 9.1% when unfavourable (P<0.008). A threshold of 11% f/tPSA provided an odds ratio for organ-confined disease of 2.7, for specimen-confined disease of 7.6 and for a favourable pathology of 3.9. CONCLUSION: The f/tPSA seems to provide useful information in the prediction of the pathological features of patients with clinical T1c prostate cancer and a tPSA of 4.1-20 ng/mL.

Adult↗
PubMed1999

Intermittent reperfusion fails to prevent posttourniquet neurapraxia.

This study examined the effects of intermittent reperfusion on peripheral nerve function. Rabbits were randomized to undergo 4 hours of 350 mm Hg tourniquet compression to a hind limb either continuously, interrupted by a single 10-minute reperfusion interval after 2 hours, or interrupted by 10 minutes of reperfusion after each hour. A control group had the tourniquet applied for 4 hours but it was never inflated. The animals were examined clinically for neuromuscular dysfunction and the structure and function of the peripheral nerves were evaluated 1 week after tourniquet compression. Animals that underwent compression had a foot drop and decreased toe-spread reflex. There was greater intraneural edema and slower nerve conduction velocity in nerve segments that were directly compressed by the tourniquet but no apparent abnormalities in segments distal to the tourniquet. Intermittent reperfusion failed to diminish the clinical, structural, or functional consequence of the neurologic injury.

Animals↗
PubMed1999

Effects of tourniquet compression on neuromuscular function.

Neuromuscular function in New Zealand White rabbits was evaluated after thigh tourniquet compression in the directly compressed quadriceps muscles and the distal tibialis anterior by measuring isometric contractile function after supramaximal stimulation of the motor nerve. Tourniquet compression resulted in markedly decreased force production beneath and distal to the tourniquet. Two days after compression, maximal quadriceps force production was decreased to 46% of control values with 125 mm Hg compression and 21% of control values after 350 mm Hg compression. Maximum tibialis anterior force production declined to 70% of control values after 125 mm Hg thigh compression and 24% of control values after 350 mm Hg thigh compression. Functional deficits were greater in the directly compressed quadriceps muscles, but the quadriceps and tibialis anterior had significantly increased impairment when the tourniquet inflation pressure was increased from 125 mm Hg to 350 mm Hg. Three weeks after compression, quadriceps function had returned to 94% of control value after 125 mm Hg compression and 83% after 350 mm Hg. Tibialis anterior function returned to 88% of control values after 125 mm Hg thigh compression and 83% after 350 mm Hg. Clinically, the use of lower inflation pressures may minimize the complications of tourniquet use and enhance postoperative recovery.

Animals↗
PubMed1998

Self-concept and social competence of university student victims of childhood physical abuse.

OBJECTIVE: This study examined the impact of childhood physical abuse on self-concept and social competency of older adolescents and assessed perception of parental relationships as a mediator for consequences of abuse on social adjustment. METHOD: College undergraduates (n = 660) completed: (a) the Social Skills Inventory (SSI), a measure of social competence, (b) the Self-Description Questionnaire-III (SDQ-III), a multidimensional measure of self-concept, (c) the parent scales of the Inventory of Parent and Peer Attachment (IPPA), a measure of perceived parental support, and (d) the Assessing Environments-III (AE-III), a retrospective report of family environment and parenting practices. RESULTS: Analyses, controlling for socioeconomic status and ethnicity, showed that a history of physical abuse was predictive of current self-concept, but did not predict social competence as an older adolescent. Further analyses lend support to a mediational model, suggesting that physical abuse has a negative impact on self-concept through its negative effect on parent-child relationships. CONCLUSIONS: The findings indicate that childhood physical abuse has a negative impact on the self-concept of the older adolescent. However, this impact can be better understood by investigating its potentially harmful effect on parent-child relationships. The impact of physical abuse on adolescents' social competence was not supported in this study.

Adolescent↗
PubMed1998

Neuropsychologic impact of facial deformities in children. Neurodevelopmental role of the face in communication and bonding.

The face is the primary tool of human communication. In early childhood, the face plays a crucial role in bonding and attachment. Severe craniofacial problems may alter bonding and attachment, thereby resulting in future risk for emotional, behavioral, and social problems. Clinical and research findings, while incomplete, suggest that this is the case. This conceptual understanding of the key role of face-to-face communication in early childhood provides a compelling rationale for early repair of craniofacial deformations.

Adolescent↗
PubMed1997

Growth hormone secretagogue increases muscle strength during remobilization after canine hindlimb immobilization.

Twenty-two beagles were divided into two equal groups, and the right hindlimb of each animal was immobilized at 105 degrees of knee flexion by external fixation. After 10 weeks of fixation, the device was removed, allowing free mobility for the following 5 weeks. Each day throughout the 15 weeks, one group received a growth hormone secretagogue (treatment) at a dose of 5 mg/kg, and the other received a lactose placebo (control). At weeks 0, 10, and 15, strength as indicated by maximum isometric extension torque was measured in the right hindlimb, biopsies of the vastus lateralis muscle were taken, and the dogs were weighed. Weekly blood samples were analyzed for insulin-like growth factor-1, blood urea nitrogen, and creatine phosphokinase. Between weeks 0 and 10, tetanic torque declined by about 60% (p < 0.001) in both groups, with no significant difference between the groups (p > 0.7). Between weeks 10 and 15, tetanic torque in the treated group increased by 0.81 Nm; this was significantly greater than the increase of 0.25 Nm in the placebo group (p < 0.05). The diameters of slow (type-1) and fast (type-2) fibers measured from the vastus lateralis muscle followed the same trend. At all time points, fiber diameter correlated strongly with torque; this argues against nonmuscular causes such as nerve injury for strength loss. The mean levels of insulin-like growth factor-1 increased 100% by week 4 in the treated group and remained elevated by about 60% throughout the experiment. Levels of insulin-like growth factor-1 in the placebo group decreased 30% within week 1 and remained depressed throughout the experiment. Our interpretation of these data suggests that the growth hormone secretagogue elevated levels of serum insulin-like growth factor-1, which in turn increased the size and strength of the quadriceps muscle during remobilization. These data may ultimately have therapeutic application to humans during rehabilitation after prolonged inactivity.

Animals↗
PubMed1997

Comparison of aceclofenac with piroxicam in the treatment of osteoarthritis.

A multicentre, double-blind, randomised, parallel group study was undertaken to investigate the efficacy and safety of aceclofenac (123 patients, 100 mg twice daily) in comparison to piroxicam (117 patients, 20 mg once daily and placebo once daily) in patients with osteoarthritis of the knee. The treatment period of two months was preceded by a washout period of one week duration. On completion of the study, patients in both aceclofenac and piroxicam-treated groups exhibited significant improvement in pain intensity and functional capacity of the affected knee, as represented by the Osteoarthritis Severity Index (OSI) (p < 0.0001 and p < 0.001 respectively). This was further substantiated following the patient's assessment of pain intensity using the Visual Analogue Scale (VAS), in which significant improvements were demonstrated at all time points for each treatment group (p < 0.001). Although both treatment groups showed a significant improvement in all investigator's clinical assessments (functional exploration of the knee, knee flexion and extension (EXT)), there were no significant differences between the groups. There was, however, a more rapid improvement in knee flexion in the aceclofenac group after 15 days of treatment. Both aceclofenac and piroxicam were well tolerated by patients, the most commonly reported adverse events being gastrointestinal, although their incidence was low. Only 24 patients on aceclofenac, as opposed to 33 on piroxicam complained of dyspepsia, epigastralgia and pyrosis. While 7 patients in each group were withdrawn because of adverse events, only one patient with piroxicam was withdrawn because of severe upper gastrointestinal bleeding. Twice as many reports of fecal blood loss were made in the piroxicam group in comparison to the aceclofenac group. In summary, this study confirms the therapeutic efficacy of aceclofenac and suggests that it is a well-tolerated alternative NSAID to piroxicam in the treatment of osteoarthritis.

Adult↗
PubMed1997

Interstitial laser coagulation in the treatment of benign prostatic hyperplasia using a diode-laser system with temperature feedback.

OBJECTIVE: To report the initial results of the treatment of patients with benign prostatic hyperplasia using interstitial laser coagulation (ILC) performed with a temperature-sensing laser system. PATIENTS AND METHODS: Twenty-five patients were treated using ILC and in 12, 78 temperature-power curves were recorded. The aim of the treatment was to maintain a temperature of 100 degrees C during the entire treatment cycle, using the temperature-triggered feed-back system. The time to reach the maximum temperature, the maximum temperature and the energy delivered were related to the location of the punctures within the prostate. The clinical outcome at 1 and 3 months was evaluated with symptom scores and uroflowmetry variables. RESULTS: Heating at the apex seemed to require less energy to achieve and maintain higher temperatures than heating of the median lobe or base of the prostate. Patients improved markedly 1 and 3 months after treatment; the respective mean symptom scores improved from 20.6 before treatment to 9.4 and 6.9, the maximum urinary flow rates from 9.1 mL/s to 14.1 mL/s and 20.3 mL/s and the post-void residual volume decreased significantly from 71 mL to 31 mL and 11 mL. No significant complications (incontinence, impotence or haemorrhage requiring transfusion) occurred. CONCLUSION: The energy needed to achieve coagulation differed at sites within the prostate, depending on local circumstances. Good results were obtained using the tissue-adaptive laser system.

Aged↗
PubMed1997

The effects of oral versus written instructions on parents' recall and satisfaction after pediatric appointments.

This study explored the differential effects of written versus oral instructions on parents' recall of information and satisfaction after pediatric appointments. Ninety-six parents completed descriptive information and satisfaction ratings, and four pediatricians completed ratings concerning the complexity level of the appointment. After the appointment, parents were randomly assigned to the Written condition (to receive a transcription of the pediatrician's instructions) or Oral condition (verbal instruction only). Parents were telephoned 5 to 7 days later to report their recall of instructions and satisfaction with the appointment. For the Oral condition parents only, more previous appointments with a given pediatrician were associated with greater parental satisfaction and recall of instructions, and more previous appointments and more time spent with the pediatrician were related to fewer forgotten instructions. Parental characteristics, such as age, number of children, and occupational status, were associated with satisfaction and accurate recall. Implications of these findings are discussed.

Adolescent↗
PubMed1996

Effects of an antioxidant in a rabbit model of tourniquet-induced skeletal muscle ischemia-reperfusion injury.

The purpose of this study was to evaluate the effects of U74006F, a new antioxidant, on isometric contractile function after tourniquet-induced ischemia-reperfusion injury. Twenty-six NZW rabbits underwent either 2 or 4 hr of thigh tourniquet compression. Animals were randomized to receive U74006F or an equal volume of its citrate vehicle. When tibialis anterior function was tested 2 days later, there was no difference between treatment groups in peak tension, rate of force production, contraction time, half relaxation time, or resistance to fatigue. The use of U74006F failed to improve functional outcome in this model of ischemia-reperfusion injury.

Animals↗
PubMed1996

Mineral content modifications during ripening of asparagus (Asparagus officinalis, L.).

The essential elements: calcium (Ca), magnesium (Mg), sodium (Na) potassium (K) and phosphorus (P) were analyzed in fresh asparagus to determine the effect of the ripening of the asparagus on the mineral content. Asparagus samples were classified in two groups by diameter (< 11 mm and > 14 mm). Asparagus from a sample group with the same diameter were divided into two portions (apical and basal) according to distance from the tip. The concentrations of calcium, magnesium and phosphorus increased with the ripening process of the asparagus while the content of sodium decreased when the white asparagus turned into a green ripening state. No significant differences were established for potassium. The green ripening state was the group with the greater concentration of calcium, magnesium and phosphorus. Statistically significant differences (p < 0.001) were observed between portions of asparagus (tip and rest of stem) in the contents of the five mineral elements analyzed. The levels of mineral elements investigated increased notably in the tip of the asparagus with the exception of sodium and potassium of which the levels in the apical portion decreased or hardly modified. The variance analyses determined statistically significant differences (p < 0.001) in the concentration of magnesium, sodium and phosphorus between asparagus diameters (< 11 and > 14 mm) and no significant differences (p > 0.05) were found for calcium and potassium. The mean element levels were (mg/kg dry weight): Ca = 324 +/- 1186; Mg = 1818 +/- 490; Na = 368 +/- 86; K = 37297 +/- 4167 and P = 6809 +/- 2481.

Analysis of Variance↗
PubMed1995

Comparison of soluble and membrane-bound pyroglutamyl peptidase I activities in rat brain tissues in the presence of detergents.

Pyroglutamyl peptidase I activity from soluble and membrane-bound fractions of rat brain homogenates is inhibited by the presence of sodium deoxycholate but not by triton X-100. Biobeads SM2, a polystyrene adsorbent reported to be useful in removing detergents from aqueous solutions, inhibits enzymatic activity in both fractions regardless of the presence of these detergents, probably because of partial adsorption of the enzyme by the polymeric microspheres. These effects seem to be enzyme-specific since other aminopeptidase activities are not affected by detergents or biobeads. The results suggest that soluble and membrane-bound forms of the enzyme represent the same protein in two different cell compartments.

Aminopeptidases↗
PubMed1995

Properties of rat brain dipeptidyl aminopeptidases in the presence of detergents.

Rat brain dipeptidyl aminopeptidases I to IV were assayed in the soluble and membrane-bound fractions of rat brain, and the effects of the detergents Triton X-100 and sodium deoxycholate on their activities were studied. Dipeptidyl aminopeptidases I and II were significantly inhibited in the presence of sodium deoxycholate, but were not affected by the presence of Triton X-100. However, dipeptidyl aminopeptidase III was not influenced by either detergent, whereas the activity of dipeptidyl aminopeptidase IV was stimulated in the presence of Triton X-100, but remained unaffected by deoxycholate. These effects were partially or totally reversed after detergents were removed from the medium with adsorbent polymeric beads. Although detergents may have different effects on each DAP activity, the behavior of each enzyme activity in the presence of these substances was similar regardless of their subcellular location. These findings suggest that, as with other aminopeptidases, each of these proteins corresponds to the same molecular species in two different cell compartments.

Animals↗
PubMed1995

Acanthamoeba keratitis. Contact lens and noncontact lens characteristics.

PURPOSE: To identify potential differences in time to diagnosis and final visual outcome between contact lens and noncontact lens users with Acanthamoeba keratitis. BACKGROUND: Prior studies have shown early diagnosis and therapy to be related to outcome but have not analyzed differences among patients with and without contact lenses. METHODS: A retrospective analysis of 11 consecutive cases (involving 13 eyes) of Acanthamoeba keratitis diagnosed at one institution over a 3-year period. RESULTS: Mean time to diagnosis was significantly longer in noncontact lens users versus those who wore contact lenses (mean, 5.8 versus 3.3 weeks). Fifty percent of patients who did not wear contact lenses had a poor outcome (visual acuity worse than 20/40 or penetrating keratoplasty) versus 14% of patients who wore contact lenses. CONCLUSION: Diagnoses were made later in patients without contact lenses, and these patients had a worse visual outcome than those with Acanthamoeba keratitis who wore contact lenses. All patients with unresponsive microbial keratitis, even those without contact lens use, should be evaluated for Acanthamoeba.

Acanthamoeba↗