The future of measles in highly immunized populations. A modeling approach

Little is known about how an intensive measles elimination program changes the overall immune status of the population. A computer model was created to study the effect of the measles elimination program in the United States on the number of susceptibles in the population. The simulation reveals that in the prevaccine era, approximately 10.6% of the population was susceptible to measles, most of whom were children less than 10 years of age. With the institution of the measles immunization program, the proportion of susceptibles in the population fell to 3.1% from 1978 through 1981, but then began to rise by approximately 0.1% per year to reach about 10.9% in the year 2050. The susceptibles at this time were distributed evenly throughout all age groups. The model did not consider the potential effect of waning immunity. The results of this study suggest that measles elimination in the United States has been achieved by an effective immunization program aimed at young susceptibles combined with a highly, naturally immunized adult population. However, despite short-term success in eliminating the disease, long-range projections demonstrate that the proportion of susceptibles in the year 2050 may be greater than in the prevaccine era. Present vaccine technology and public health policy must be altered to deal with this eventuality.

Mixture distributions in psychiatric research

This paper describes the application of Gaussian mixture distributions to biological marker research in psychiatry. Mixtures of univariate and multivariate normal distributions can be used to determine if diagnostically similar psychiatric patients belong to biologically distinct subpopulations. The resulting biological subtypes may be important in understanding the etiology of psychiatric disorders. The general model and estimation procedure are described (EM algorithm; Dempster, Laird and Rubin 1977). The method is illustrated using two examples of biological data: (1) red cell membranes and monoamine oxidase activity data in normal individuals having no family history of psychiatric illness, the first-degree relatives of bipolar depressed patients and a heterogeneous patient population; and (2) smooth pursuit eye movements that classify relatives of schizophrenics, nonschizophrenics and normal controls into biologically distinct populations.

A clinical model for treatment of dyslexia

Children with moderate learning disabilities often fail to qualify for special education programs in public schools, but are ill-suited for placement in private schools concerned with the severely disabled. Parents of such children may place their hopes in the promises of private teachers or clinics. Yet the quality of services provided in the private sector varies widely. This paper describes a model program against which parents and private service providers can measure the strengths and weaknesses of the programs they are concerned with. The model places special emphasis on thorough evaluation, frequent reevaluation, staff accountability, program flexibility, and recognition of the parents' role in the child's education.

Relatives of unipolar and bipolar patients have normal pursuit

Impaired smooth pursuit eye movements are significantly less prevalent among the first-degree relatives of patients who have major affective disorders than among the first-degree relatives of schizophrenics. The distribution of normal and abnormal smooth pursuit among the relatives of unipolar and bipolar patients does not differ from that of normal individuals having no family history of major psychosis. Smooth pursuit impairment is thus specific to relatives of schizophrenic patients and is not characteristic of relatives of patients with major affective disorders.

Eye movement dysfunctions in psychiatric patients: a review

Impairments of smooth pursuit eye movements occur in a high proportion of schizophrenic patients and in a lower but significant percentage of patients with affective psychoses, as well as patients with structural and metabolic disorders of the central nervous system. These findings have been confirmed using a wide range of tracking tasks, recording techniques, and scoring procedures, and therefore cannot be attributed to measurement artifact. The eye movement disruption in schizophrenics does not seem to result from drug treatment or simple inattention. Eye tracking pattern appears to be under genetic control and some impairments may reflect a predisposition to functional psychosis. The smooth pursuit eye movement impairment has been attributed to a central nervous system dysfunction that manifests itself in a disorder of nonvoluntary attention. The study of other oculomotor functions, such as the oculocephalic reflex, optokinetic and vestibular nystagmus, and saccadic eye movements, suggests that the locus of the central nervous system disruption is above the brainstem.

Effects of phencyclidine, secobarbital and diazepam on eye tracking in rhesus monkeys

Rhesus monkeys were trained to track a moving disk using a procedure in which responses on a lever were reinforced with water delivery only when the disk, oscillating in a horizontal plane on a screen at a frequency of 0.4 Hz in a visual angle of 20 degrees, dimmed for a brief period. Pursuit eye movements were recorded by electrooculography (EOG). IM phencyclidine, secobarbital, and diazepam injections decreased the number of reinforced lever presses in a dose-related manner. Both secobarbital and diazepam produced episodic jerky-pursuit eye movements, while phencyclidine had no consistent effects on eye movements. Lever pressing was disrupted at doses which had little effect on the quality of smooth-pursuit eye movements in some monkeys. This separation was particularly pronounced with diazepam. The similarities of the drug effects on smooth-pursuit eye movements between the present study and human studies indicate that the present method using rhesus monkeys may be useful for predicting drug effects on eye tracking and oculomotor function in humans.

Vestibular dysfunction and psychopathology

A review of the empirical findings linking vestibular response abnormalities to psychopathology, and particularly to schizophrenia, indicates that these data do not unequivocally document the presence of peripheral or central disease of the vestibular system in any patient group. The reasons for this ambiguity include: use of imprecise stimulation techniques, inaccurate measures of responsiveness, unreliable measures of quantification, and the absence of experimental control over extravestibular variables. Future directions for research in this area are discussed, including the localizing information derived from properly conducted tests of the vestibulo-ocular reflex in studies of oculomotor function.

Premature rupture of membranes prior to term: consequences of nonintervention

Consequences of nonintervention in the management of prematurely ruptured membranes prior to term were assessed in 143 maternal charts and 145 corresponding infant records during a 2-year period. Patients were hospitalized at bed rest and were not given tocolytics or steroids. Antibiotics were used only when clinical examination indicated infection. Labor was induced in 13 patients. Time in utero was extended 1 week or more in 19% of cases. Maternal infection was identified in 15 women, all of whom recovered. There were 18 neonatal deaths and 4 stillbirths in the series. Three deaths might have been prevented by earlier delivery. Nonintervention in the management of premature rupture of the membranes did not have adverse effects on the incidence of maternal or neonatal infection but was relatively ineffectual in achieving significant extensions of time in utero

Serum complement activity in pre-term pregnancies: relationship to duration of ruptured membranes and clinical infection

Physiologic changes occurring during the latent period of prematurely ruptured membranes (PRM) are poorly understood. Indicators predicting maternal and neonatal infectious morbidity do not correlate well with clinical outcomes. A previous report suggested that in vivo complement consumption occurred in response to the event of membrane rupture. In this prospective study, complement activity was measured serially throughout the latent period in cases of preterm PRM. In addition to total hemolytic complement activity (CH50), C4-pro-activator (C3PA), a primary component of the alternate complement pathway, was measured in maternal and cord sera. As with CH50, cord serum C3PA levels are significantly less than those in matched maternal samples. Neither maternal nor cord serum complement activity correlated with either the duration of the latent period or maternal-neonatal infection.

Maternal and infant transport program in Louisiana

The concept of maternal transport has evolved from that of neonatal transport as part of a regionalized perinatal care system. Experience has suggested that perinatal outcome for infants transported before delivery is improved over that for infants transported neonatally. This report describes the initial 2 years' experience of the first such program in Louisiana. When compared with infants transported after delivery, those transported before delivery had a slightly better corrected survival rate (90 versus 87%) and a shorter average stay in the neonatal intensive care unit (11.8 versus 21.4 days), but the differences were not statistically significant as measured by the chi2 test.

Maternal and cord blood complement activity: relationship to premature rupture of the membranes

Human complement levels are known to reflect the presence of clinical infection, with low levels indicative of increased utilization in the body's immune response. Premature rupture of the membranes (PRM) is associated with an increased maternal-fetal infectious morbidity, yet histopathologic and bacteriologic parameters often do not reflect this. In this prospective study maternal and cord serum total hemolytic complement activity (CH50) was measured in 102 patients without evidence of infection, with and without PRM, to determine if there exists within the maternal-fetal unit an immunologic response to this event. It was found that maternal serum CH50, regardless of length of gestation, is similar to that of the nonpregnant adult population, except in cases of PRM greater than 12 hours in which it is significantly lower. The CH50 in term newborn infants was significantly lower than that of matched maternal samples and dropped with decreasing gestational age. CH50 in cord serum from babies of mothers with PRM failed to show a significant decrease when compared to those of mothers without PRM.

Fetal response to cardiopulmonary bypass

The fetal heart rate (FHR) was continuously monitored by ultrasonography during a mitral valve replacement in a patient at 22 weeks' gestation. The changes in FHR were analyzed in relationship to events of cardiopulmonary bypass. The baseline FHR dropped substantially during bypass with initial loss of variability. After the pump run, a brief episode of fetal tachycardia was followed by stabilization to preoperative levels. The patient delivered at 30 weeks' gestation and the infant did well.

Deviant eye tracking in twins discordant for psychosis. A replication

An earlier study of smooth-pursuit eye movements (SPEMs) in monozygotic (MZ) and dizygotic (DZ) twins discordant for functional psychosis reported high concordance of pursuit abnormalities in MZ pairs and moderate concordance in DZ pairs. That study was repeated with younger pairs of twins and with some quantitative refinements in scoring. Results show the same levels of concordance for pursuit dysfunctions, thus replicating the earlier study. The data support an interpretation of genetic factors contributing to variability in SPEMs.

Vestibular responses in schizophrenia

In a study of vestibular responses to caloric stimulation that controlled opportunity for fixation and state of alertness, we evaluated previous findings of diminished nystagmus in schizophrenia. We failed to replicate earlier reports in these respects: (1) None of the psychotic patient groups, when compared with normal controls, showed lower response intensity, latency, or culmination time of the nystagmic response. (2) The schizophrenic groups did not manifest a prevalence of clinically significant asymmetry. We did, however, observe that chronic deteriorated schizophrenics and recent schizophrenics have significantly greater dysrhythmic responses. This diminished orderliness of nystagmus may explain previous reports of absent or diminished nystagmus in the schizophrenics. The results are not compatible with peripheral vestibular disease in schizophrenia, but they may reflect state-related phenomena consistent with disturbances in alertness, which are not necessarily voluntary or motivational in origin.

Abnormal-pursuit eye movements in schizophrenia. Evidence for a genetic indicator

Disordered smooth-pursuit eye movements occur in a high percentage of schizophrenic patients and their first-degree relatives. A Test of the hypothesis that these disorders represent a genetic indicator of schizophrenia was undertaken by testing pursuit eye movements in a sample of monozygotic and dizygotic twins discordant for clinical schizophrenia. Deviant eye tracking is significantly concordant within monozygotic twin pairs, and less so with dizygotic twin pairs discordant for schizophrenia. A genetic interpretation is consistent with these results.

Visual interference on vestibular response. A case study

Eliminating opportunity for visual fixation as well as providing for the maintenance of an optimal degree of a patient's mental alertness are necessary for a valid assessment of nystagmic response to caloric stimulation. Controlling only for alertness can result in suppressed, absent, or dysrhythmic nystagmus. Data from four normal patients dramatically illustrate the suppressing effects of fixation opportunity despite an alert state. A new clinical instrument for obtaining optimal control over visual influences is described.

Smooth pursuit eye movements, attention, and schizophrenia

In previous studies, smooth pursuit eye movements (SPEM) have been shown to be disordered in about 70% of schizophrenics and about 45% of their first-degree relatives. In this report, the role of attention in these eye movements is addressed in three experiments (using as subjects schizophrenics, their first-degree relatives, and normals administered chloral hydrate) that recruit focused attention to the task. These studies show that voluntary attention in the form of inattention, "heedless negligence," or failure to cooperate, is not the specific attentional quality that is disordered in SPEM of schizophrenics and their relatives. Rather, the data both indicate that nonvoluntary attending is specifically disordered in these persons, and implicate a neurophysiological substrate that can be described as a failure of inhibitory, synchronizing integrating systems which may be located in the brain stem.

47,XXX karyotype obtained by amniocentesis

A 29-year-old pregnant patient, gravida 4, para 3, sought genetic counseling because of a daughter who had Down's syndrome. Amniotic fluid obtained by amniocentesis indicated the fetal karyotype to be 47,XXX. The pregnancy was terminated and the karyotype was confirmed by typing venous blood from the fetus and the finding of double Barr bodies in the histologic sections of fetal tissue.

The specificity of gonadotropin binding by the human corpus luteum

The specificity of gonadotropin binding was studied in fresh and frozen human corpora lutea. Ovine, bovine, and porcine luteinizing hormone (LH) competed with 125I-labeled human LH (125I-hLH) and 125I-labeled human chorionic gonadotropin (125I-hCG) for binding to tissue receptors in homogenates of human corpora lutea frozen for 3 to 12 months. In contrast, oLH, bLH, and pLH competed minimally for 125I-hLH and 125I-hCG binding sites in homogenates of fresh human corpora lutea. Ovine follicle-stimulating hormone (FSH) and thyroid-stimulating hormone (TSH) did not compete in homogenates of fresh or frozen tissue. Competition of oLH and hCG for 125I-hCG binding sites at several dose levels in a homogenate of a fresh corpus luteum was studied. One hundred micrograms of oLH and ten nanograms of hCG gave an equivalent competition--a 10,000-fold difference in competitive potency. Only hCG competed with 125I-hCG for binding when the competition of oLH, bLH, pLH, oFSH, oTSH, hCG and hCG subunits, and hCG were compared at the 10-mug level in a homogenate of fresh human corpus luteum. The binding of 125I-labeled homologous human hormones by the corpus luteum was examined in a limited fashion. 125I-Prolactin did not bind to preparations of fresh stroma from a patient with polycystic ovaries nor did it bind to three separate preparations of fresh corpora luteum which did bind 125I-hCG. 125I-hTSH did not show significant binding to a fresh human corpus luteum preparation which did bind 125I-hCG. These studies indicate that the gonadotropin receptor of the fresh human corpus luteum possesses a unique species specificity and illustrate the importance of working with human corpora lutea in their most native state.

Persistent brow presentation: a new approach to management

When the fetal vertex is extended on the spinal column and the brow becomes the presenting part, it is termed "brow presentation." Persistent brow presentation occurs when there is no spontaneous conversion after the onset of active labor. Since there is a risk in the vaginal delivery of such fetuses, it should not be attempted where there is known maternal disease or evidence of acute or chronic intrauterine fetal distress. During labor, cesarean section is indicated if there is cephalopelvic disproportion, if the fetal head is not in the frontoanterior position, if there is abnormal labor, or if there is evidence of fetal distress. Continuous lumbar epidural anesthesia should be given, and only manual conversion is used. The fetus is monitored continuously.

Smooth-pursuit eye movements, and diazepam, CPZ, and secobarbital

This study examined the effects on smooth-pursuit eye tracking of single doses of CPZ (0.667 and 1.334 mg/kg), diazepam (0.071, 0.142, and 0.284 mg/kg), and secobarbital (100 mg). Only the barbiturate significantly affected the ability to follow a moving target with smooth-pursuit eye movements. In repeated testing of a single subject, 130 mg of secobarbital disrupted smooth-pursuit movements at least until 24 hrs after ingestion.