Nucleotide sequence of bacteriophage T4 gene 23 and the amino acid sequence of its product.

We have determined the nucleotide sequence of gene 23 of bacteriophage T4 by the methods of Maxam and Gilbert and of Sanger. The identities of approximately 80% of the amino acid residues of the major capsid protein which is encoded by gene 23 were determined additionally by Edman degradation of the intact protein and its peptides. Fifteen gene 23 amber mutation sites have been located within the sequence, and the 3' transcription termination site for genes 21, 22 and 23 has been identified.

Neurologic and electroencephalographic correlates in glutethimide intoxication.

Neurologic and electroencephalographic (EEG) examinations were performed every two hours during a case of severe glutethimide intoxication resulting from the acute ingestion of at least 15 grams of glutethimide. Neurologic data were reduced to 10 measurements of brainstem function and plotted as an index that varied cyclically in amplitude during the clinical course. Electroencephalographic data were computer-processed by power spectral methods and related to the brainstem function index. Good positive correlation existed between the frequency and reactivity of EEG activity and the level of brainstem function as reflected in the index. The cyclic and, sometimes, unilateral nature of the clinical findings previously reported in glutethimide coma was confirmed and seen to be reflected in the EEG. The present case also indicates that, in the absence of cerebral ischemia or hypoxemia secondary to cardiopulmonary depression, complete clinical recovery from glutethimide-induced coma is possible no matter how severe the presenting neurologic and EEG signs.

Excretion of amines and their metabolites by two patients in hepatic coma treated with L-dopa.

Two patients in hepatic coma were treated with L-dopa. The first patient showed clear clinical improvement, but the second patient did not. Analyses of urinary metabolites indicated that L-dopa was not absorbed by the second patient. There was evidence that L-dopa had the following beneficial effects in the first patient: (1) increased production of urine, which could have been accompanied by increased excretion of toxins; (2) displacement of tyramine from transmitter sites (because increased excretion of p-hydroxyphenylacetic acid, a major metabolite of tyramine, occurred during L-dopa treatment in patient 1); (3) replenishment of dopamine, and to a much lesser extent, norepinephrine, at central or peripheral neuroeffector junctions; and (4) scavenging of methyl groups by L-dopa, because ratio of methylated amines to catecholamines was higher than normal in both comatose patients before L-dopa treatment, and this ratio decreased during L-dopa treatment in patient 1.

Prognostic value of brainstem auditory evoked potentials in neonates.

The clinical outcome in 74 children at risk for audiologic or neurologic sequelae of a variety of perinatal insults was correlated with brainstem auditory evoked potentials (BAEPs) in the newborn period. No constant relationship was found between BAEP findings and later hearing status in preterm infants or in infants with severe brain damage. However, persistent patterns of wave I abnormality correctly predicted the presence and type of hearing loss in other infants. Central BAEP abnormalities recorded in preterm infants or in infants who had just suffered anoxia had little predictive value. The abnormalities had greater prognostic value when there was a delay between acute injury and testing. Prognostic errors could be minimized in this population by obtaining repeated recordings at least one month post term and after injury from infants who showed BAEP abnormalities in the neonatal period.

Brainstem auditory-evoked responses. Normal variation as a function of stimulus and subject characteristics.

Brainstem auditory-evoked responses (BAERs) were elicited from 64 neurologically and audiometrically normal adults and 77 normal, full-term neonates with broadband rarefaction or condensation clicks at sensation levels (hearing levels in neonates) of 30 to 70 dB and at rates of ten and 80 clicks per second. In addition to the known effects of rate, previously unrecognized effects of acoustic phase and stimulus intensity on BAER interpeak latencies (IPLs), and an interaction of all three stimulus parameters, were found. Stimulus characteristics, age, and sex can account for much of the inter- and intrasubject variability of BAER IPLs and morphology. The BAER effects of many of these variables and their interactions have not been appreciated in clinical applications of BAER. Recognition and control of such reducible, methodological sources of BAER variability will enhance the sensitivity and specificity of the test in neurologic diagnosis.

EEG correlations with biochemical abnormalities in Reye syndrome.

A patient with Reye syndrome was studied throughout the course of the illness with continuous EEG monitoring, and these patterns were correlated with serial determinations of serum ammonia and short-chain fatty acid concentrations. There was high correlation between degree of EEG abnormality, clinical symptoms, and elevations of the short-chain fatty acids, while serum ammonia concentrations correlated poorly with the EEG and with the clinical state.

Brain stem auditory-evoked responses in suspected central pontine myelinolysis.

Central pontine myelinolysis was suspected in two chronic alcoholics who developed and recovered from a progressive spastic paresis of all muscles, that derived innervation at and below the level of the pons. In both cases, short-latency auditory-evoked responses aided in the diagnosis by indicating a slowing of conduction in the pontine auditory pathway, which varied in degree with the severity of the clinical manifestations of pontine demyelination.

Central pontine myelinolysis. A clinical reappraisal.

We discuss three patients with clinical findings of central pontine myelinolysis (CPM). Two patients survived with minimal neurological deficits, and one patient died from medical complications while recovering from his neurological deficit. Postmortem examination showed the typical lesion of CPM. Brain stem auditory evoked potential studies in two of our patients indicate that there was impairment of function in auditory pontine pathways that returned to normal as the patients improved clinically. We conclude that CPM can be diagnosed clinically and that patients may recover if intercurrent illnesses are vigorously treated.

Electroencephalographic findings in phencyclidine intoxication.

The first report of electroencephalographic findings in clinically encountered phencyclidine intoxication is presented. When first seen, the patient was in a coma, initially distinguished only by nystagmus, waxy rigidity of the extremities, and an EEG with a widespread, sinusoidal theta rhythm interrupted every few seconds by periodic slow-wave complexes. The similarity of the EEG to that of deep ketamine anesthesia suggested intoxication with a ketamine-related (phenylcyclohexylamine) drug. Phencyclidine, the prototype of the phenylcyclohexylamine compounds and a widely abused hallucinogen, was subsequently identified in the urine and blood.

Brainstem auditory evoked potentials in 20 patients with palatal myoclonus.

Brainstem auditory evoked potentials (BAEPs) were obtained in 20 patients with palatal myoclonus. The group included 14 men and six women whose ages ranged from 19 to 82 years. Six of the patients had abnormal BAEPs: two with severe head trauma and one each with a brainstem infarct, tumor, demyelination, and an indeterminate inflammatory process. The 14 patients with normal BAEPs had palatal myoclonus secondary to head trauma (five patients), brainstem infarcts (four patients), cerebellar tumors (two patients), degenerative processes (two patients), and an Arnold-Chiari malformation (one patient). Since the auditory pathways are separate from the structures associated with palatal myoclonus, it is possible to have discrete lesions producing palatal myoclonus with sparing of the auditory structures, whereas diffuse or multifocal lesions of the brainstem are more likely to be associated with abnormal BAEPs.

Clinical and pathologic correlates of brain stem auditory response abnormalities.

Short-latency auditory evoked responses were recorded in over 100 neurologic patients. Abnormalities of each response component were correlated with postmortem or radiologic localization of different brain stem lesions. These findings suggested that waves I-VII largely reflect activity at the following levels of the auditory pathway: acoustic nerve (I), pontomedullary junction (II), caudal pons (III), rostral pons or midbrain (IV), midbrain (V), thalamus (VI), and thalamus or auditory radiation (VII). When this information was applied prospectively to the evaluation of brain stem dysfunction, response abnormalities proved useful in detecting and localizing certain lesions not revealed by other tests. Serial recordings provided information about the evolution of brain stem lesions and their response to therapy.

Detection and localization of occult lesions with brainstem auditory responses.

Seven vertex-positive potentials--the brainstem auditory response--can be recorded from the human scalp within 10 milliseconds of an appropriate acoustic stimulus. The first of these potentials is generated in the acoustic nerve, the third in the pons, and the fifth in the midbrain. Measurement of the relative latencies and amplitudes of these potentials allowed detection of subclinical lesions in 37 (53 percent) of 70 patients with suspected multiple sclerosis who had no signs or symptoms of brainstem involvement by the disease. Abnormalities in the brainstem auditory response provided the first evidence of the pressence of multiple lesions in 14 (35 percent) of 40 patients with suspected multiple sclerosis who had clinical evidence of only a single spinal or cerebral lesion. Response abnormalities also suggested the presence of tumors of the posterior fossa in three patients with nonspecific symptoms and normal neurologic examinations, the test indicated the need for contrast studies, which then led to the correct diagnosis of infratentorial neoplasm.

Clinically useful applications of evoked potentials in adult neurology.

Recent advances in the field of sensory evoked potentials (EPs) have allowed assessment of function in regions of the nervous system that were previously inaccessible to noninvasive electrophysiologic study. Pattern visual and brainstem auditory EPs, respectively, are more sensitive to certain optic nerve or posterior fossa lesions than either clinical or laboratory tests. Short-latency somatosensory EPs from the upper and lower extremities are sensitive to pathology at cervicomedullary and thoracolumbar levels of the neuraxis as well as to suprasegmental lesions. This article reviews the development of these tests as clinically useful tools and the applications in which they have contributed most to the practice of adult neurology.

Targeting childhood obesity in schools: an examination of the stability and utility of the value added index.

BACKGROUND: High rates of childhood obesity and overweight have promoted interest in school-based interventions. As a way to identify schools with high unexpected prevalence of obesity and the greatest need, Procter and associates developed a 'Value Added Index' (VAI). It compares rates of obesity in entry level and advanced students in elementary schools, quantifying the extent to which rates for advanced students are higher than what would be expected given entry level rates and socio-demographic characteristics. METHODS: This paper replicates their analysis using data over a 4 year time span from 17 schools in the western United States. Our analysis compared results obtained with the relatively complicated mixed-model approach, which was used by Procter and associates, and a more simple linear regression, which could be easily used by local school officials. Results were also compared across the 4 years for which data were available. RESULTS: Identical results were found when the two methods were compared. There was little stability in the rank ordering of schools, based on the VAI, from 1 year to another. CONCLUSIONS: Our results cast doubts on the utility of the VAI for policy makers and suggest policy makers consider a universalistic, rather than targeted, approach to interventions.

Transient elevation of threshold of the neonatal auditory brain stem response.

Auditory brain stem responses (ABRs) of 33 high risk, full term or near term newborns with transient elevation of ABR threshold (transient group) were compared with those of normal infants (normal group) and high-risk infants with known conductive (conductive group) and known sensorineural hearing loss (sensorineural group). ABRs of infants in the transient group initially were not significantly different from those of the conductive group in terms of wave I latency, wave V latency, and the slope of the latency-intensity (L-l) function of wave V. In infants with transient unilateral threshold elevation, significantly shorter interpeak latencies were recorded in the affected ear than in the ear that passed. This finding has been previously described in infants with conductive disorders. On follow-up, ABRs in the transient group closely resembled those of the normal group with respect to the same measures. Otologic histories in the transient group were unremarkable in the majority of cases. Increased slope of the L-l function in infants with confirmed conductive disorders was an unexpected finding. Previous studies of patients with conductive loss had not revealed a significant deviation from normal for this measure. An age interaction for the effect might explain the discrepancy between this and previous studies.