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Biomedical subjects

A Poblano

Publications and source records attributed to A Poblano.

At least 19 recordsLinked to original sources
PubMed1997

[Auditory provoked potentials in children with neonatal risk for hypoacusia].

Auditory evoked potentials of the brain stem (AEPBS) provide a simple noninvasive method of evaluating hearing function and have been widely used for early detection of hypoacusis in children. Between April 1992 and May 1994, a study was done of 400 Mexican children who presented at least one neonatal risk factor for hearing impairment. The average age of the children studied was 6.6 months and their average gestational age at birth was 35.1 weeks. Just over half of them (51%) had been treated with amikacin. The study found 1427 risk factors (3.5 per child), the most common ones being exposure to ototoxic substances, hyperbilirubinemia, and birthweight of less that 1500 g. In 27% of the children, peripheral auditory changes were found, and 13% did not respond to auditory stimuli. Low birthweight and young gestational age at birth, high serum concentration of bilirubin, sepsis, subependymal or intraventricular hemorrhage, mechanical ventilation, and exposure to ototoxic substances were significantly associated with the presence of severe or profound hypoacusis.

Child↗
PubMed1996

Electro-oculographic recordings reveal reading deficiencies in learning disabled children.

This study was undertaken in order to learn the functional differences in reading tasks between two groups of children: those identified as learning disabled and a group of control children. During the earliest stages of learning to read, children adopt a logographic strategy, in which letter order is ignored and phonologic factors are secondary. The children later move into an alphabetic and then to an orthographic reading stage. Reading strategies can be studied by electro-oculographic (EOG) recordings during text reading. This investigation uses EOG to study text reading time, and number of saccadic and regressive movements, to test if learning disabled children show altered strategies on text reading. Nineteen learning disabled and thirteen control subjects were included in the study. Learning disabled children showed longer text reading time, and greater number of saccadic and regressive eye movements. Electro-oculographic recording is not a test customarily performed on learning disabled children. However, our results concerning the dynamic discriminative reading have shown that it can be a useful tool for the examination of learning disabled children.

Child↗
PubMed1996

Pattern-visual evoked potentials in thinner abusers.

Organic solvents cause injury to lipids of neuronal and glial membranes. A well known characteristic of workers exposed to thinner is optic neuropathy. We decided to look for neurophysiologic signs of visual damage in patients identified as thinner abusers. Pattern reversal visual evoked potentials was performed on 34 thinner abuser patients and 30 controls. P-100 wave latency was found to be longer on abuser than control subjects. Results show the possibility of central alterations on thinner abusers despite absence of clinical symptoms.

Administration, Inhalation↗
PubMed1994

Prenatal and perinatal low level lead exposure alters brainstem auditory evoked responses in infants.

Wave III latency and the III-V interpeak interval of brainstem auditory evoked responses in infants in the first weeks of life decreased and increased, respectively, in association with mid-pregnancy maternal blood lead levels (2.5-35 micrograms/dl) in a group of 30 prospectively followed healthy pregnancies and deliveries. The rapid myelination of brainstem auditory pathways occurring around mid-pregnancy and the lengthening of the III-V interpeak interval with increased mid-pregnancy maternal lead suggest that brain structures involved in spatial localization of sound may be compromised by prenatal lead exposure. The data also indicate that maternal blood lead measurements during pregnancy provide an adequate surrogate index of fetal exposure.

Adult↗
PubMed1993

[Brainstem auditory evoked potentials in low and high risk newborns].

Brainstem auditory evoked potentials (BAEP) were performed in a population of preterm infants of 32-34, 35-37 and 38-41 weeks of gestational age (GE) high risk newborns, and in 38-41 weeks GE low risk newborns. Statistical differences were found between both 38-41 weeks GE groups. High risk newborns showed longer latencies of waves III and V (P < 0.001), and I-III and I-V interwave intervals (P < 0.01). Our data show that auditory brainstem system suffer in high risk newborns. Results is discussed in relationship with other brainstem auditory evoked potentials studies in high risk newborns due it's clinical implications of present data.

Evoked Potentials, Auditory, Brain Stem↗
PubMed1992

Recovery of vestibular function in young guinea pigs after streptomycin treatment. Glutamate decarboxylase activity and nystagmus response assessment.

Fifty-day streptomycin (STP) treatment in guinea pigs causes specific vestibular hair cell (VHC) types I and II (HCI; HCII) degeneration, depletion of glutamate decarboxylase (GAD) and a gradual disappearance of postrotatory nystagmus response (PRNR), which is a sign of vestibular function alteration. In order to look for a possible spontaneous reversibility and its time course guinea pigs receiving 300 mg/kg STP daily were monitored for PRNR and vestibular GAD loss. Once PRNR was lost, STP was interrupted and the animal was allowed to recover; at the time that PRNR was completely reestablished, vestibular GAD was measured. PRNR was lost within 22-25 days of STP treatment. Vestibular GAD showed a loss that, with time of treatment, gave two slopes: a fast decrement (45% in 20 days) and a slow one (40% in the remaining 30). Stopping of the STP treatment after 22-25 days and animal recovery resulted in the return of both PRNR and GAD activity 22 days after STP stoppage. These results suggest two STP-susceptible GAD-containing VHC populations, one more sensitive than the other, possibly HCI followed by hair cell II (HCII). As hypothetic HCI loss and PRNR disappearance is simultaneous, the important role of the former for vestibular function could be inferred. Interruption of STP treatment after PRNR loss results in a long range restoration of both GAD activity and vestibular function, and thus recovery of HCI, the first evidence of its occurrence in a mammalian vestibule, could be suggested. The intimate mechanism of this recovery remains to be seen.

Animals↗
PubMed1991

[Brain-stem auditory evoked potentials and median latency in children with Down's syndrome].

We studied 20 milliseconds of the brainstem auditory evoked responses and 50 milliseconds of the middle latency responses in 11 children with Down's syndrome, between 6-9 years of age. The results were compared with those from 10 control children. We found a significative reduction of the amplitude of waves I, III, V in the former group. Central transmission time was shortest and frequently wave Pa was absent in patients with Down's syndrome patients. We hypothesized that the abnormalities of amplitude of the evoked responses may be related to presence of less neurons in the brain of patients with Down's syndrome. The reduction of central transmission time may be related to presence of microcephalia and significantly accelerated rates of action potential depolarization, repolarization and decreased spike duration. Wave Pa may have been absent due to microgyria of Heschl's temporal gyrus previously reported in patients with Down's syndrome.

Acoustic Stimulation↗
PubMed1991

[Auditory brain stem evoked potentials of average latency in dyslexics and controls].

The goal of this paper was to study the auditory pathway of nine controls and nine pure dyslexic subjects using brainstem auditory evoked responses and middle latency responses. We found no differences in latency and amplitude between both groups; only a small difference in the V right/V left relation in favour of the right V wave in controls and left V wave in dyslexics. This findings is discussed in relation to cerebral dominance.

Acoustic Stimulation↗
PubMedDate not supplied

Prenatal and perinatal lead exposures alter acoustic cry parameters of neonate.

We performed acoustic analyses on cries elicited from a subset of healthy babies born to the Mexico City Prospective Lead Study at 2 days (n = 75), 15 days (n = 176), and 30 days (n = 166). Lead was measured in maternal blood every 8 weeks during pregnancy from week 12 to delivery and in umbilical cord (1-38 micrograms/dL, 0.05-1.84 mumol/L). Percent nasalization and number of cries decreased in babies born to mothers with higher lead levels in the last two trimesters while median fundamental frequency increased in babies born to mothers with higher lead at 12 weeks of pregnancy, and with higher cord lead in multiple regression analysis. Decreased percent nasalization was related to increased brainstem auditory evoked response latencies and interpeak intervals in a subset of the sample. The results suggest an effect of gestational exposure to lead on apparatus innervated by cranial nerves and/or lead effect on cry mediated by lead-altered auditory function. Altered baby cry and auditory function associated with lead might contribute to developmental delays by affecting early communication between caretaker and baby.

Acoustics↗
PubMedDate not supplied

Thinner abuse alters optokinetic nystagmus parameters.

BACKGROUND: Deliberate self-inhalation of solvents such as thinner is a recognized problem in underdeveloped countries, with chronic abuse resulting in neurological impairment. In this article, we use electronystagmography (ENG) to study optokinetic nystagmus abnormalities (OKN) that may be induced by thinner consumption. METHODS: Twenty-five patients exposed to thinner for 5-20 years, in an irregular fashion of consumption, were recruited from a toxicologic center. Twenty-five control subjects were invited to participate as volunteers matched by age (+/-2 years) and gender. At the time of evaluation, all had abstained from intoxicants for at least 4 weeks. ENG recordings were performed by clinicians masked to the patient's group. Clockwise and counterclockwise stimulation were performed at 20 and 40 degrees /sec. RESULTS: None of the patients showed spontaneous nystagmus during the test period. Differences between thinner abusers and controls on clockwise and counterclockwise OKN on number of beats of nystagmus elicited on the 40 degrees /sec velocity were identified. The thinner abusers group showed a lesser number of nystagmus (p level was 0.02 and 0.005, respectively). CONCLUSIONS: The present results confirm the sensibility of OKN as an early marker of solvent abuse. These results were obtained in middle-term chronic exposure to solvent mixtures and are in favor of both cortical and brainstem dysfunction.

Adolescent↗
PubMedDate not supplied

Phonological and visuo-spatial working memory alterations in dyslexic children.

BACKGROUND: Working memory allows the retention of a limited amount of information for a brief period of time and the manipulation of that information. This study was undertaken to compare possible differences in working memory between dyslexic and control children. METHODS: To test the executive central process that controls attention, subjects were requested to assemble a 100-piece puzzle. To test the phonological loop, subjects were requested to repeat orally a 10-item list with the following characteristics: digits spanning two numbers; phonologically similar words, and unfamiliar pseudowords. The visuo-spatial sketchpad was tested by means of assembling a 25-piece puzzle. RESULTS: Forty dyslexic and and forty control children were studied. Dyslexic children recall a lesser number of similar words in the phonological loop and spend a longer time in puzzle assembly in the visuo-spatial sketchpad. No statistical difference in the central executive process was found. CONCLUSIONS: Present results suggest the importance of visuo-spatial and phonological loop alterations in dyslexic children that may result in difficulties with similar words and spatial information.

Child↗
PubMedDate not supplied

Electrophysiological and behavioral methods in early detection of hearing impairment.

BACKGROUND: Recent advances in neonatal life-support systems have contributed to the survival of high-risk newborns. However, protection of the auditory system and the prevention of sequelae is still paramount in neonatal neurology. The aim of this study was to compare auditory-evoked responses with a toy test and acoustic reflex in the early detection of hearing loss in infants. METHODS: Three groups were studied. The first was composed of infants showing less than a 30 dB biaural threshold in the neurophysiological test. The second group was made up of infants showing peripheral alterations on one side or both ears. The third group was comprised of infants who showed no responses at 95 dB HL in both ears after neurophysiological testing. The neurophysiological test, toy test, and acoustic reflex were performed on the same day, with masked results given to each investigator. Sensitivity and specificity for each toy test and acoustic reflex were calculated afterward. RESULTS: Forty-five controls, 44 peripheral alterations, and 8 non-response infants were studied. Most patients studied were born prior to the 37(th) week of gestation with a birthweight of less than 2,250 g, received required administration of potential ototoxic drugs and mechanical ventilation, and showed hyperbilirubinemia and hypoxia. Sensitivity for each toy was as follows: drum 0.54; wooden rattle 1.0, and metallic ratle 0.88. Specificity was 0.95, 1.0, and 1.0, respectively. Acoustic reflex sensitivity was 0.38 and specificity was 0.97. CONCLUSIONS: Results suggest that the wooden and the metallic rattles of the toy test can be useful tools in the study of hearing in the high-risk infant and deserve more attention in future studies.

Deafness↗
PubMedDate not supplied

Brainstem auditory evoked response at five years and prenatal and postnatal blood lead.

Previous work from this laboratory demonstrated an association between higher maternal blood lead level at 20 weeks of pregnancy and increased I-V and III-V interpeak intervals in the brainstem auditory evoked response (BAER) recorded in 1-month-old infants. We repeated the BAER measurements with a larger group of children (n = 100-113) from the same study at 5-7 years. Maternal blood lead level at 20 weeks of pregnancy (geometric mean = 7.7 microg/dl; range 1-30. 5 microg/dl) was the only prenatal blood lead level significantly associated with I-V and III-V interpeak interval in a multiple regression model controlling for head circumference and age at time of testing and sex. In contrast to the findings at 1 month of age, interpeak intervals decreased as a linear function of increasing 20-week maternal blood lead. A nonlinear, orthogonal, second-order polynomial model was a significantly better fit to the data than the linear model. The nonlinear model showed I-V and III-V interpeak intervals decreased as blood lead rose from 1 to 8 microg/dl, and then increased as blood lead rose from 8 to 30.5 microg/dl. We hypothesized that the negative linear term was related to lead effect on brainstem auditory pathway length, and that the positive quadratic term was related to neurotoxic lead effect on synaptic transmission or conduction velocity. We found support for the brainstem length interpretation in the data, showing that 6-year-old head circumference in these children significantly decreased with increased maternal 20-week blood lead level. Increasing postnatal blood lead at 12 and 48 months was related only to decreased BAER conduction intervals across the entire blood lead range, suggesting only pathway length effects. Alterations in BAER at this age may indicate that the effect of prenatal lead exposure on the auditory brainstem is permanent, as response latencies reach essentially adult values by 4 years of age.

Analysis of Variance↗
PubMedDate not supplied

Cellular target of streptomycin in the internal ear.

The cellular target of streptomycin (STP) was investigated by analyzing the activity of glutamate decarboxylase (GAD) or choline acetyltransferase (ChAT) enzymes of synthesis of GABA and acetylcholine (Ach), respectively, [supposedly located in hair cells (GAD) or efferent terminals (ChAT)] in control and in 50 day-STP-treated colored guinea pig vestibular homogenates. Vestibular and auditory function were assessed by measuring postrotatory nystagmus response (PNR) and auditory brainstem evoked potentials (ABP). Morphological changes were followed by light and electron microscopy. STP-treated animals exhibited a GAD decrease of 83.6% with respect to controls whereas ChAT did not suffer any change. Assessment of PNR and ABP showed that STP affected only the former since animals lost it between the 20th and the 30th day of treatment, whereas ABP was not modified. Morphological experiments detected vestibular hair cell deterioration as the only cell type affected by STP. These results confirm the predilection of STP to affect vestibular function by damage to hair cells and show that this effect can be followed by measurement of GAD and ChAT in the vestibule as markers for hair cells and efferent terminals, respectively.

Animals↗
PubMedDate not supplied

[Neurosciences and philosophy].

The goal of this paper is to show the paralelism between the objectives of both, neurosciences and philosophy. First, a historical review of the common works on both fields of study is made; next, the implications of the brain-mind relationship and how the use of a cerebral function theory that help us to solve the problem are discussed. Finally, the social implications of cooperation between neurosciences and philosophy are analyzed.

Brain↗
PubMedDate not supplied

[Risk factors for hypoacusis and audiometric findings in preschool children who had been admitted to neonatal intensive care units].

Thirty preschool children who survived from a neonatal intensive care unit were studied with pure tone audiometry between 125 to 8000 Hertz. Examinations were performed in a cross-sectional study at 36 to 72 postnatal months of age. Hypoacusis was found in three patients. Risk factors most frequently found in hypoacusic children were hyperbilirubinemia, hypoxia neonatorum and ototoxic exposure. All hypoacusic children had a history of preterm birth, one suffered hypoxia neonatorum, and two hyperbilirubinemia. The patients' group had an average of 2.26 risk factors. These data suggest that perinatal auditory damage occurs in the presence of additional hearing damage risk factors leading to hypoacusis.

Age Factors↗