Double-blind, placebo-controlled food challenge (DBPCFC) as an office procedure: a manual

There is now enough experience with the use of double-blind, placebo-controlled, food challenge (DBPCFC) to recommend its use as an office procedure for most patients complaining of adverse reactions to foods. This manual discusses the practical methods required for the allergist to undertake DBPCFC in the office. Thorough histories supplemented by food allergen skin testing are used to design a DBPCFC that carefully attempts to reproduce the history of food-induced symptoms described by the patient. Precautions that must be taken are delineated before challenge, as is treatment that may be required if a reaction occurs. For those foods to which challenges are positive, longitudinal evaluation with repeated challenge at appropriate intervals help to determine whether or not the problem will resolve over a period of time.     

Effects of OFF-BF tones on responses of chopper units in ventral cochlear nucleus. I. Regularity and temporal adaptation patterns.

1. We have recorded the responses of neurons in the anteroventral cochlear nucleus (AVCN) of barbiturate-anesthetized cats to pure tones [either at the unit's best frequency (BF) or at another frequency (OFF-BF)] and to two-tone combination stimuli. 2. The effects of OFF-BF input (either alone or presented simultaneously with a BF tone in a two-tone stimulus) on the response patterns of choppers may include not only rate inhibition but changes in the discharge regularity and the temporal adaptation properties of the spike trains. 3. In the majority of cases we studied (119 of 146 frequencies examined in 45 units), the discharge regularity of a response to an OFF-BF or two-tone stimulus is comparable with that of a "rate-matched" BF tone response. In a minority of cases (27 of 146 frequencies examined), however, OFF-BF input (either alone or in a two-tone stimulus format) changed the regularity compared with that of a rate-matched BF tone response. 4. In the majority of cases studied (139 of 171 frequencies examined in 53 units), the initial pattern of rate adaptation ["temporal adaptation pattern" (TAP)] was the same in response to a short tone burst at BF, to an OFF-BF tone burst, or to a pair of tones. The TAP can, however, be significantly altered by OFF-BF input, although this is a comparatively infrequent occurrence in our data sample (32 of 171 frequencies examined), from the response to BF tone to the response to the two-tone or OFF-BF stimulus, are as follows: sustained to slowly adapting; slowly adapting to transiently adapting, and transiently adapting to slowly adapting. Changes in the TAPs of chopper unit responses have been recorded from both regular and irregular choppers and cannot be accounted for on the basis of changes in sustained firing rate. These changes in the discharge regularity and TAP in the small minority of cases suggest that (at least in these cases) the inhibitory effect of OFF-BF input is not simply the result of two-tone suppression at the level of the auditory nerve fiber input. 5. We have observed that regular choppers may be transformed into irregular choppers by OFF-BF (rate inhibitory) input.(ABSTRACT TRUNCATED AT 400 WORDS)     

The exploding head syndrome: polysomnographic recordings and therapeutic suggestions

Attention has recently been drawn to a condition termed the exploding head syndrome, which is characterized by unpleasant, even terrifying sensations of flashing lights and/or sounds during reported sleep. Nine patients complaining of sensations of explosions in the head during sleep or drowsiness were investigated with polysomnographic recordings. None of them had any neurological disorder. Five patients reported explosions during the recording sessions. According to the recordings, the attacks always took place when the patients were awake and relaxed. In two cases abrupt electroencephalographic (EEG) and electromyographic changes indicating increasing alertness were recorded at the time of the reported attacks. In the remaining three cases no EEG changes were seen. Thus, there were no indications of an epileptic etiology to the condition. In all patients the symptoms ameliorated spontaneously with time. The severity of the symptoms was reduced by reassurance of the harmlessness of the condition. Clomipramine was prescribed to three patients who all reported immediate relief of symptoms. It is concluded that symptoms of this type are probably not true hypnagogic phenomena but may be an expression of emotional stress in the awake state.     

Empirical evaluation of the transfusion medicine tutor

Previous research during the development of Antibody IDentification Assistant (AIDA) revealed that many medical technology students and other laboratory personnel have serious difficulties in determining the specificity of blood group alloantibodies, especially weak or multiple antibodies. Based on these previous results, AIDA was modified to provide a teaching environment for medical technology students. We report the results of a rigorous, objective evaluation of the resultant system, the Transfusion Medicine Tutor (TMT). The results show that the students who were taught by an instructor using TMT to provide the instructional environment went from 0 percent correct on a pretest case to 87 percent correct on posttests (n = 15). This increase compares with an improvement rate of 20 percent by a control group (n = 15) who used a passive version of the system with the tutoring functions turned off.     

Abnormal maternal serum levels of human chorionic gonadotropin free subunits in trisomy 18

We have measured maternal serum levels of free alpha and beta subunits of human chorionic gonadotropin between 8 and 12 weeks of gestation in 704 women at increased risk for trisomy. This group was studied because of advanced maternal age or a previous birth with chromosomal abnormality. All sera had been collected prior to chorion villus biopsy for prenatal diagnosis. Serum levels of free alpha and beta hCG were determined by specific monoclonal antibody-based immunoradiometric assays. Analysis of chorionic tissue showed that in 38 of 704 (5.4%) pregnancies the fetus had a chromosome abnormality. There were 8 fetuses with trisomy 18 (1.1%) and 9 (1.3%) with trisomy 21. In all pregnancies carrying a trisomy 18 fetus, we observed either high levels of free alpha hCG or low levels of free beta hCG or both. More importantly, the calculated ratio of free beta hCG/alpha hCG was less than 0.25 multiples of the median (MoM) in 6 of 8 (75%) trisomy 18 cases. Only 21 of 666 mothers (3.2%) carrying a normal fetus had a ratio less than 0.25 MoM (P less than 0.0001). There was no difference between this ratio in trisomy 21 and normal pregnancy. Thus, when adjusted for gestational age, a low free beta hCG/alpha hCG ratio in maternal serum indicates a pregnancy at high risk [RR = 72 (95% CI 32, 162)] for trisomy 18.     

Integration of viral into chromosomal deoxyribonucleic acid in an inducible line of polyoma-transformed cells

RNA-DNA hybridization has shown that in poiyoma-transformed rat cells which can be induced to synthesize infectious virus (LPT cells), polyoma DNA sequences are associated with chromosomal DNARNA complementary to the viral DNA (cRNA) was synthesized in vitro, using purified viral DNA as a template and Escherichia coli RNA polymerase. High-molecular-weight chromosomal DNA was fractionated from linear and supercoiled viral DNA molecules by centrifugation of whole cells through alkaline glycerol gradients. Hybridization carried out between the cRNA and fractionated chromosomal DNA showed that the amount of RNA hybridized to the LPT DNA was two to three times larger than the amount hybridized to DNA from normal rat cells. cRNA was also hybridized, under the same conditions, with mixtures containing a constant amount of normal cell DNA and varying quantities of purified viral DNA. These assays have established that a linear relationship exists between the amount of cRNA specifically hybridized with a given sample of DNA and the quantity of viral DNA in the sample. Using this relationship, it is estimated that LPT chromosomal DNA contains 6–9 genome-equivalents of polyoma DNA per cell. This quantity represents 18–29% of the amount of polyoma DNA found in the cells, as determined by hybridization of cRNA with unfractionated LPT DNA.To exclude the possibility that the chromosomally associated viral DNA is an artifact due to incomplete removal of the extrachromosomal viral DNA, control experiments were performed in which the cells were superinfected with polyoma virus (m.o.i.-500; 3 hr infection). In these experiments, less than 1% of the viral DNA introduced into the cells by the superinfecting virus were found by the same techniques to be associated with chromosomal DNA. Other experiments show that LPT cells do not contain significant amounts of complex viral DNA molecules which sediment in the vicinity of chromosomal DNA. It is therefore suggested that viral and chromosomal DNA are bound to each other by bonds which cannot be disrupted by alkali treatment.     

Immunochemical analysis of class II molecules expressed by a human B cell line with the unusual class II genotype, DR5+, MB1+, (MB3-), MT2+

The human B lymphoblastoid cell line FPA was established from a consanguineous individual homozygous for the unusual serologically defined Class II genotype, DR5+, MB1+, (MB3-), MT2+. The MB1 allodeterminant is classically found only in association with DR1, 2, or w6 and DR5 is almost invariably associated with MB3. Class II molecules expressed by this unusual DR5 homozygous cell line have been characterized by immunochemical analysis using two-dimensional gel electrophoresis. These molecules were isolated from the FPA cell line by anti-DR5, anti-MT2, and anti-MB1 allosera, as well as a monoclonal antibody which defines an MB1-like determinant. However, an anti-MB3 alloserum and a monoclonal antibody which defines an MB3-like determinant did not immunoprecipitate Class II molecules from FPA. These studies document that the MB1 allodeterminant resides on DS molecules from this DR5 cell line and provide additional evidence that MB1 and MB3 are alleles of the same Class II antigen system.