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Sequences of basis sets can be constructed so as to approach the 'infinite basis set limit' in molecular electronic structure calculations. Extrapolation procedures can also be devized to provide accurate values of this limit. However, some care is required since the 'infinite basis set limit' may not correspond to the limit supported by a complete basis set. Extrapolation procedures can then lead to limiting values, which are not estimates of the exact solutions.

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Three groups of subjects, children, young adults, and elderly persons with presbyacusis, were tested in a directed attention, quasidichotic paradigm in which continuous speech was monitored for syntactically and/or semantically anomalous words. The task evoked an event-related potential (ERP) characterized by a positive peak in the latency region of 600 to 1,000 msec. ERPs were separately averaged for target-word-right and target-word-left conditions. Amplitude and latency measures at the peak of the global field power waveform were calculated. Amplitude was significantly larger in children than in either adult group. In children and young adults, both amplitude and latency measures were equivalent for target-right and target-left conditions, but in elderly persons, latency was significantly greater in the target-left than in the target-right condition. Topographic maps of amplitude at the peak of the ERP waveform showed maximal positivity symmetrically distributed around the midline centroparietal area in both right-attended and left-attended conditions. In elderly persons, however, maximal positivity in the left-attended condition was significantly delayed relative to maximal positivity in the right-attended condition. Results are consistent with previous findings of interaural asymmetry in a dichotic listening task in elderly persons.

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In an attempt to develop a more ecologically valid measure of speech understanding in a background of competing speech, we constructed a quasidichotic procedure based on the monitoring of continuous speech from loudspeakers placed directly to the listener's right and left sides. The listener responded to the presence of incongruous or anomalous words imbedded within the context of two children's fairy tales. Attention was directed either to the right or to the left side in blocks of 25 utterances. Within each block, there were target (anomalous) and nontarget (nonanomalous) words. Responses to target words were analyzed separately for attend-right and attend-left conditions. Our purpose was twofold: (1) to evaluate the feasibility of such an approach for obtaining electrophysiologic performance measures in the sound field and (2) to gather normative interaural symmetry data for the new technique in young adults with normal hearing. Event-related potentials to target and nontarget words at 30 electrode sites were obtained in 20 right-handed young adults with normal hearing. Waveforms and associated topographic maps were characterized by a slight negativity in the region of 400 msec (N400) and robust positivity in the region of 900 msec (P900). Norms for interaural symmetry of the P900 event-related potential in young adults were derived.

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Zinc-containing neurons are cells that sequester zinc in their presynaptic vesicles and release it in a calcium- and impulse-dependent manner. The zinc-containing neurons are a subclass of the glutaminergic neurons: all known zinc-containing pathways are also glutaminergic pathways. With a few exceptions, zinc-containing neurons are located only in the telencephalon. The major glutaminergic systems of the brain stem, thalamus, and cerebellum, for example, all lack vesicular zinc, whereas many cerebrocortical systems are zinc containing. Within the telencephalon, the zinc-containing fiber systems form a vast associational network that reciprocally interconnects isocortical, allocortical and 'limbic' structures. Because the hippocampal, amygdalar, and perirhinal regions are prominent nodes in this network, it is presumed that vesicular zinc is involved in epileptic phenomena (in pathology) and (in normal function) in the synaptic plasticity of developmental and experiential learning. Zinc ions are potent modulators of amino acid receptors [especially the N-methyl-D-aspartate (NMDA) receptor] and corelease of zinc along with glutamate would provide a mechanism for modulating postsynaptic excitability levels. One useful hypothesis is that synaptically released zinc controls a 'window' of postsynaptic excitability, having little or no effect at physiological firing rates, but selectively depressing excitability (by NMDA receptor depression) when firing rates reach dangerous, paroxysmal levels.

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Fourteen patients with primary cytomegalovirus infection diagnosed by serological screening at antenatal attendances were examined for their responses in the lymphocyte transformation test against cytomegalovirus. Tests were done during pregnancy, shortly after the diagnosis of primary infection. Eight women showed positive lymphocyte transformation responses and gave birth to uninfected babies. Six showed negative responses and four of the babies were born congenitally infected. Cellular immunity therefore plays a part in preventing intrauterine transmission of cytomegalovirus, and its depression after primary infection in the mother during pregnancy may be used as an early marker of fetal infection.

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Platelet 3H-imipramine binding was examined in a cross-sectional study of 70 Caucasian women in pregnancy and the early post-partum period, and in 23 nonpregnant women of childbearing age. Mood was also assessed in the pregnancy and post-partum sample. No significant differences in number of binding sites (Bmax) were found, but an increase in the equilibrium dissociation constant (Kd) was demonstrated at 5-7 days post-partum.

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A total of 233 cervical smears were stained by immunocytochemical methods for epithelial membrane antigen (EMA); the findings were compared with those from Papanicolaou-stained smears from the same women. Squamous epithelial cells from normal cervices did not stain, but cells shed from cervices with cervical intraepithelial neoplasia (CIN) did express the EMA marker. Metaplastic cells from normal and abnormal cervices also frequently stained. The results confirm that this marker detects cervical intraepithelial neoplasia in vitro, but its potential use in an automated screening program may be limited by the staining of the metaplastic cells.

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Smears made from cervical scrapes have been stained immunocytochemically for epithelial membrane antigen using a polyclonal antiserum and two monoclonal antibodies. With the polyclonal antiserum malignant cells and those showing dysplasia consistently expressed the antigen. Normal cells were generally negative, with the exception of some metaplastic cells. The monoclonal antibodies, although they stained the abnormal cells less consistently, gave the same pattern of staining. All three antibodies showed considerable heterogeneity in the intensity of stain. This appears to be a general feature of the expression of this type of epitope in epithelial cells. While the results confirm that an immunohistochemical stain might have potential application for improved diagnostic methods, the staining of metaplastic cells with the presently available antibodies limits the usefulness of an antiserum to epithelial membrane antigen.

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The distribution of three tumor markers, epithelial membrane antigen (EMA), carcinoembryonic antigen (CEA) and prekeratin (PK) was studied in exfoliated epithelial cells in cervical smears using an immunoalkaline phosphatase staining technique to demonstrate the antigens. EMA was expressed by abnormal cells in a consistent and reproducible fashion whereas the other two markers were variably expressed by both normal and abnormal cells. Our results suggest that immunocytochemical staining for EMA could be of value not only for the diagnosis of cervical intraepithelial neoplasia but also for the automated screening of cervical smears.

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Integrating microdensitometry has been used to quantify the glycoprotein, epithelial membrane antigen (EMA), which is frequently expressed on the cytoplasmic membrane of neoplastic cells of the cervix uteri. The technique was able to identify and quantify the antigen over a wide concentration range and could also be semi-automated using a microcomputer interfaced to the microdensitometer and programmed with the simple high level language BASIC.

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