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Biomedical subjects

J C Mendoza

Publications and source records attributed to J C Mendoza.

17 recordsLinked to original sources
PubMed1997

Plasticity of responses to off-vertical axis rotation.

This study assessed whether a change in the magnitude of the angular vestibulo-ocular reflex (VOR) influences the magnitude of the linear VOR, thereby suggesting a common gain element for these reflexes. The responses to linear acceleration using yaw off-vertical axis rotation (OVAR) at 30 degrees tilt were recorded before and after an adaptation protocol designed to increase the angular VOR gain. Subjects included eight asymptomatic healthy young individuals. Eye movements, recorded with electro-oculography, were analyzed to yield gain of the horizontal angular VOR and the magnitude of the modulation and bias components of the response to OVAR. Results indicated that there was no consistent influence of angular VOR gain on the eye movement response to OVAR. Since previous studies have shown that responses to earth horizontal axis rotation are influenced consistently by angular VOR gain, our study suggests that high intensity otolithic stimulation is required to observe changes in the linear VOR following modification of the angular VOR.

Acceleration↗
PubMed1997

Incidence of autoantibodies in the infertile population.

The purpose of this study was to determine the incidence of autoantibodies in patients with no term pregnancies. Patients selected included 43 with primary infertility and 110 with a history of pregnancy loss. In the first group the incidence of antinuclear antibodies (ANA) and IgG and IgM antiphospholipid antibodies (APL) was 37.2% (p < 0.05) and 53.5% (p < 0.05), respectively. In the group of patients with a history of miscarriage, 31.8% (p < 0.05) were positive for ANA and 38.2% (p < 0.05) for APL. Controls were 35 healthy patients with proven fertility and no history of pregnancy loss or autoimmune disease. In this group the incidence of ANA was 5.7% and 11.4% for APL. The high incidence of autoantibodies found in patients with primary infertility might suggest a direct involvement of these antibodies in reproductive failure and consequently in IVF and assisted fertility procedures. The prevalence of ANA and APL has been extensively described in patients with a history of recurrent pregnancy losses (RPL). In this study we observed antibodies even after the first miscarriage. We therefore conclude that patients with a history of reproductive failure should be immunologically evaluated and treated before undergoing assisted fertilization techniques or before a new pregnancy in those cases of RPL.

Abortion, Spontaneous↗
PubMed1996

Tactile influences on astronaut visual spatial orientation: human neurovestibular studies on SLS-2.

Human spatial orientation in spaceflight is initially disturbed by the absence of usable graviceptor information from the otolithic organs. Experiments measuring astronaut visually induced motion (vection) strength on various flight days during the first 10 days of the Spacelab Life Sciences-2 mission demonstrated two new phenomena in addition to confirming the initial increased weighting of visual and localized tactile cues. The reliance on tactile and visual noninertial cues apparently declined after a week in space, as the crew became able to utilize their internal reference frame. Subjects also showed that even nondirectional tactile cues served as a direction anchor and inhibited visually induced roll sensation relative to a new loosely tethered test condition. Individual perceptual styles were again revealed among the four astronauts tested. The readaptation to 1 G similarly shows a period of reinterpretation of inertial and visual cues to spatial orientation. The results are discussed in terms of an internal-model representation of body orientation, with time-varying weights applied to extrinsic and intrinsic signals.

Adult↗
PubMed1995

Autoantibodies to phospholipids and nuclear antigens in non-pregnant and pregnant Colombian women with recurrent spontaneous abortions.

Autoantibodies to negatively charged phospholipids have been reported to be associated with thrombotic events, thrombocytopenia and adverse pregnancy outcome, such as intrauterine growth retardation and recurrent spontaneous abortions (RSAs). In this study, autoantibodies to 6 phospholipid antigens and antinuclear antibody (ANA) were tested in Colombian women with a history of RSAs. Sixty-eight non-pregnant and 25 pregnant women with a history of RSAs comprised the study group. Twenty-five non-pregnant normal healthy women and thirty-one normal pregnant women served as controls. The non-pregnant women with RSAs showed a higher incidence of autoantibodies to cardiolipin (23% positive) as compared with non-pregnant normal controls (0% positive; P < 0.005). The incidence of autoantibodies to cardiolipin (28%; P < 0.005), phosphatidylethanolamine (16%; P < 0.005), phosphatidylserine (16%; P < 0.05), phosphatidylglycerol (16%; P < 0.05), phosphatidic acid (16%; P < 0.01) and phosphatidylinositol (20%; P < 0.01), in the pregnant women with RSAs was significantly higher than that of normal pregnant controls. There was no difference in the incidence of ANA in either group. In conclusion, women with a history of RSAs have a higher incidence of autoantibodies to phospholipids when compared to pregnant and non-pregnant normal controls. Autoimmune serological work-up is indicated during pregnancy in women with a history of RSAs.

Abortion, Habitual↗
PubMed1995

Effect of vergence on the gain of the linear vestibulo-ocular reflex.

We measured the linear vestibulo-ocular reflex (LVOR) and vergence, using binocular search coils, in 3 humans. The subjects were accelerated sinusoidally at 0.5 Hz and 0.2 g peak acceleration, in complete darkness, while performing three different tasks: i) mental arithmetic; ii) tracking a remembered target at either 0.34 m or 0.14 m distance; and iii) maintaining vergence at either of these distances by means of audio biofeedback based on vergence. Subjects could control vergence using the audio feedback; there was greater convergence with the near audio target. However, there was no significant difference in vergence between the near and far remembered target conditions. With audio feedback, the amplitude of smooth tracking was not consistently different for the near and the far conditions. However, the amplitude of tracking (saccades and smooth component) in the remembered target conditions was greater for near than for far targets. These results suggest that linear VOR amplitude is not determined by vergence alone.

Attention↗
PubMed1994

Vergence can be controlled by audio feedback, and induces downward ocular deviation.

We measured horizontal and vertical eye positions, using binocular search coils, in three humans. Subjects could maintain vergence by means of audio biofeedback. Feedback consisted of a pair of audio tones, one variable and one fixed at a reference frequency. The variable tone was controlled by instantaneous vergence and provided immediate feedback on the vergence state. The reference frequency, which they attempted to match, was set to correspond to a target distance of either 0.34 m or 0.14 m. Subjects could maintain vergence consistently, even while undergoing lateral motions at 0.5 Hz and 0.2 g peak acceleration in darkness. There was also a consistent tendency for the eyes to deviate downward during near vergence. The results may be useful in experiments in which one wishes to control vergence without providing a visual reference which might inhibit conjugate eye movements.

Adult↗
PubMed1991

Follow-up of patients who underwent arterial switch repair for transposition of the great arteries.

Thirty infants underwent arterial switch for transposition of the great arteries within the first week of life (mean age, 2.8 days). An additional three patients underwent repair at 5 1/2, 8, and 9 1/2 months of age. Six (18.2%) of 33 patients died. All the survivors were not receiving cardiac medications or diuretics at the time of the last follow-up visit. Examination of 24 of 27 survivors at 1 to 5 years of age revealed normal growth in 75% of the patients. Two patients had height, weight, and head circumference below the fifth percentile for age. Four patients had height and weight appropriate for age but head circumference below the fifth percentile. Neurodevelopmental testing yielded normal findings in 18 patients. Three patients were considered suspect and an additional three were abnormal neurodevelopmentally. Head circumference less than the fifth percentile, abnormalities on computed tomographic scans of the brain, and emergency balloon atrial septostomy or emergency switch operation were more likely to occur in patients who had low neurodevelopmental scores. We conclude that the majority of patients who undergo arterial switch repair demonstrate normal growth and development and no impairment of cardiovascular function. However, significant morbidity in the form of neurodevelopmental problems may occur.

Child Development↗
PubMed1991

Early-onset Hemophilus influenzae sepsis in the neonate.

Hemophilus influenzae sepsis has been increasingly reported in recent years. Thirteen neonates have been treated in our institution in the past 8 years, 12 of whom were admitted within the last 4 years. H influenzae is responsible for 8% of neonatal sepsis occurring during the first 3 days of life. It is usually transmitted before or at the time of birth and is more frequently encountered in premature and low birthweight infants. It is strongly associated with maternal obstetric complications particularly genitourinary tract infections and prolonged rupture of membranes before delivery. Most cases are caused by non-type-b strains and are susceptible to ampicillin. Neonatal H influenzae sepsis presents clinically like early-onset group B streptococcal disease and is especially fulminant in neonates born prematurely.

Amniotic Fluid↗
PubMed1991

Direct intrafollicular insemination. A case report.

This is the first case report of a documented pregnancy initiated with a new assisted reproductive technique based on direct insemination of a preovulatory follicle with ultrasonographic guidance using a transvaginal probe in women with at least one patent fallopian tube and controlled ovarian stimulation.

Adult↗
PubMed1991

Lateralization of brain lesions following extracorporeal membrane oxygenation.

The cranial ultrasound and computed tomography scan films of 180 patients who underwent extracorporeal membrane oxygenation were reviewed. Sixteen patients were considered to have moderate to severe brain lesions. Of these, 6 were ischemic and 10 were hemorrhagic. Five (83.3%) of the 6 ischemic lesions involved the right side and only 1 ischemic injury occurred on the left. Seven (70%) of the 10 hemorrhagic lesions occurred solely or predominantly on the side opposite the carotid ligation and 3 were found on the same side as the ligation. One patient suffered a right temporal hemorrhage following cannulation of the left common carotid artery. There was no predominance of brain lesions for either side when both hemorrhagic and ischemic lesions were combined. These observations implicate alterations in cerebrovascular hemodynamics accompanying carotid ligation and reperfusion in the pathogenesis of central nervous system lesions associated with the extracorporeal membrane oxygenation procedure. It is suggested that systematic classification of brain lesions associated with extracorporeal membrane oxygenation be made to get a better understanding of their pathology.

Brain Ischemia↗
PubMed1990

Vaginal gamete intrafallopian transfer. Experience with 14 cases.

A procedure utilizing transvaginal aspiration of stimulated gametes followed by transcervical, ultrasound-guided catheterization of the tubal ostia was performed as a modification of the standardized gamete intrafallopian transfer (GIFT) technique. Among 14 patients with 16 cycles there were four normal, intrauterine pregnancies and one ectopic pregnancy. In two patients the beta-human gonadotropin level rose significantly and then started to fall; the patients aborted spontaneously. The procedure can be performed with a higher degree of patient acceptance than can traditional GIFT, and the success rate in this small series was promising.

Adult↗
PubMed1989

Vaginal intratubal insemination (VITI) and vaginal GIFT, endosonographic technique: early experience.

A new technique for vaginal intratubal insemination (VITI) and transvaginal gamete intra-Fallopian transfer (TV-GIFT) using endosonography has been developed. A total of 47 infertile couples were treated using a K-JITS 1000-1100 catheter (William Cook, Australia; Jansen Anderson Intratubal Transfer Set) introduced by Jansen and Anderson in Sydney, Australia, and endosonographic control with a Kretz Combison 310 echograph and a 5/7.5 MHz vaginal sectorial transducer. In 40 couples, the VITI technique was used, and in the other seven couples, TV-GIFT was used. Fifteen pregnancies (37.5%) were obtained in 63 VITI cycles (23.8% per treatment cycle) and three with TV-GIFT (42% per treatment cycle). A review is also presented of the migration--sedimentation technique used for management of male factor in an artificial insemination programme.

Adult↗
PubMedDate not supplied

Use of extracorporeal life support in total anomalous pulmonary venous drainage.

OBJECTIVE: The objective of this study was to analyze the clinical course and neurodevelopmental outcome of infants with total anomalous pulmonary venous drainage (TAPVD) who were treated with venoarterial extracorporeal life support (ECLS). STUDY DESIGN: The study was done by retrospective national survey of ECLS centers located in the United States and Australia. Sixty-six patients from 28 centers that reported cases from 1976 to October 1992 to the Extracorporeal Life Support Organization registry were included in the study. Data regarding type of TAPVD, whether the diagnosis was known or suspected before the initiation of ECLS, method of diagnosis, timing of repair if done, outcome, and follow-up were collected. RESULTS: Fifty-six of the patients were placed on ECLS at ages < 14 days (neonatal) and 10 patients underwent ECLS at ages > or = 14 days (pediatric). TAPVD was known or suspected before the initiation of ECLS in 35 (53%) of 66 and was most commonly diagnosed by color-flow Doppler echocardiography if initially missed. Surgical repair was not attempted in four of the 66 patients, leaving a total of 62 patients for comparison. The overall operative survival for both neonatal and pediatric patients was 24 (39%) of 62. The survival rate for neonates who underwent repair before ECLS was seven (54%) of 13, for those who underwent repair after ECLS it was six (60%) of 10, and for those who underwent repair during ECLS survival was seven (24%) of 29. Neonatal survival (20/52, 38%) was statistically more likely (p = 0.05) if the repair was done before or after ECLS rather than during ECLS, with each group compared separately. Follow-up data were available on 13 of 20 neonates and three of four pediatric patients. Bayley Scales of Infant Development scores were normal in only six (54%) of 11 survivors who returned for testing. CONCLUSIONS: The diagnosis of TAPVD was often known before the initiation of ECLS. Neonates were more likely to survive if the repair could be done before or after ECLS rather than during ECLS. The lower survival of infants who underwent repair during ECLS reflects the degree of illness in many of these infants who were placed on ECLS on an emergency basis because their condition was too unstable to permit detailed cardiac evaluation. The survival rate of infants with TAPVD requiring ECLS is poor, with approximately one half of the survivors having mental and motor deficiencies; however, these infants represent a subset of patients with TAPVD who probably would have died without ECLS. We recommend that infants who are not starting to wean from ECLS at 7 days undergo reevaluation with color-flow Doppler echocardiography with consideration for cardiac catheterization if the diagnosis is in doubt. We also recommend that before infants with known TAPVD are placed on ECLS parents should be informed that survival with the use of ECLS is no different from survival with operation alone and that many of the survivors are impaired. Each active ECLS center should periodically review its accuracy in making this definitive diagnosis.

Extracorporeal Membrane Oxygenation↗
PubMedDate not supplied

Visual-vestibular interaction during off-vertical axis rotation.

The aim of this study was to further define the eye movement response to combined visual and vestibular stimulation, especially during linear acceleration. Subjects included 15 asymptomatic healthy individuals (8 females and 7 males) between the ages of 20 and 31 years. Vestibular stimulation consisted of earth-vertical axis rotation and off-vertical axis rotation (OVAR). Visual stimuli consisted of projected vertical stripes that were rotated for optokinetic trials and stationary for visual augmentation trials. A small laser target (0.5 mW, 0.5 degree arc) that rotated with the subject was used for fixation trials. Eye movements were measured with electro-oculography. Results showed that visual-vestibular interaction during sinusoidal rotation was not affected by a 15 degree off-vertical tilt. Constant velocity OVAR induced a continuous nystagmus whose slow component velocity contained a nonzero baseline, that is, a bias, and a periodic fluctuation at the rotation frequency, that is, a modulation component. The modulation component during visual fixation was reduced as compared with that seen during rotation in the dark, but was not absent. Constant velocity OVAR in the presence of earth-fixed stripes induced a consistent sinusoidal modulation. Our results suggest that visual-vestibular interaction for otolith stimulation differs from visual-vestibular interaction for semicircular canal stimulation. The modulation component of the response to OVAR appears to be modified by visual stimulation to a lesser extent than other vestibular-induced eye movements and thus may reflect a more "direct" vestibulo-ocular response. The bias component of the response to OVAR can be substantially influenced by vision and thus may depend upon more "indirect" pathways.

Acceleration↗
PubMedDate not supplied

Risk factors for intracranial hemorrhage in the extracorporeal membrane oxygenation patient.

The need for cardiopulmonary resuscitation and repeated correction of persistent acidosis identifies extracorporeal membrane oxygenation patients more likely to develop an intracranial hemorrhage. The objective of this study was to identify risk factors for an intracranial hemorrhage (ICH) in infants on extracorporeal membrane oxygenation (ECMO). This study was a retrospective-matched, case-controlled study of infants with ICH on ECMO compared with infants without ICH on ECMO. Data collected included patient demographics, ventilator parameters, blood gases, coagulation parameters, the need for cardiopulmonary resuscitation (CPR), neurologic findings, and outcome. The Neonatal Intensive Care Nursery at Kosair Children's Hospital in Louisville, Ky., was the setting. Twenty-three infants who developed an ICH (excluding subarachnoid hemorrhage) on ECMO were matched with a control group of 23 infants without an ICH on ECMO. The presence of acidosis (pH < 7.19 or HCO3 < 17; p < 0.01 and p < 0.05, respectively) and the need for CPR (heart rate < or = 80 or mean blood pressure < or = 30 mm Hg, p < 0.003) shortly before or during cannulation correlated with the development of an ICH in infants on ECMO. The infants with an ICH required more frequent platelet transfusions (p < 0.005), had difficulty maintaining activated clotting times (ACTs) within a normal range (p < 0.03), and had abnormal neurologic examinations shortly before or after the ICH was detected with head ultrasound. The ultrasound was obtained as soon as possible after a change in the neurologic status. The need for CPR and repeated correction of persistent acidosis before or during cannulation identifies ECMO patients more likely to develop an ICH. We found that elevated ACTs and low platelet counts requiring transfusion showed a statistical association with the development of an ICH. Daily head ultrasounds and frequent neurologic checks are thus valuable tools in assessing the ECMO patient who demonstrates difficulty in maintaining coagulation values in the normal range or who requires frequent platelet transfusions.

Blood Gas Analysis↗