Membrane Currents Influencing Action Potential Latency in Granule Neurons of the Rat Cochlear Nucleus

Granule cells are the most numerous neurons in the cochlear nucleus, but, because of their small size, little information on their membrane properties and ionic currents is available. We used an in vitro slice preparation of the rat ventral cochlear nucleus to make whole-cell recordings from these cells. Under current clamp, some granule neurons fired spontaneous action potentials and all generated a train of action potentials on depolarization (threshold current, 10–35 pA). Hyperpolarization increased the latency to the first action potential evoked during a subsequent depolarization. We examined which voltage-gated currents might underlie this latency shift. In addition to a fast inward Na⁺ current, depolarization activated two outward potassium currents. A transient current was rapidly inactivated by membrane potentials positive to -60 mV, while a second, more slowly inactivating current was observed following the decay of the transient current. No hyperpolarization-activated conductances were observed in these cells. Modelling of the currents suggests that removal of inactivation on hyperpolarization accounts for the increased action potential latency in granule cells. Such a mechanism could account for the 'pauser'-type firing patterns of the fusiform cells which receive a prominent projection from the granule cells in the dorsal cochlear nucleus.     

Serum glycoprotein hormone alpha subunit levels in patients with cancer.

The serum glycoprotein hormone alpha subunit concentration was measured in 957 nonpregnant patients with benign disorders and 683 patients with unselected malignancies. Postmenopausal women had significantly higher alpha levels than premenopausal women or men. When the patients were subdivided according to age, sex or disease sites, significant population differences were found for women less than 50 years of age and patients with cancers of presumed neural crest origin. However, individual serum alpha levels in patients with benign disorders or malignancies demonstrated considerable overlap. No population differences in serum alpha concentrations were demonstrated between patients grouped according to stage of disease, suggesting that serum alpha were not directly related to tumor burden. Similarly, there was no statistical association between clinical improvement or deterioration and change in the serum alpha subunit concentration. These results indicate that measurement of the glycoprotein hormone alpha subunit concentration in the serum is not useful for screening patients for cancer or for monitoring the clinical course of patients with the vast majority of cancers.     

Evaluation of Papanicolaou smear and effect of sample biopsy in follow-up of cervical dysplasia.

In a prospective study of women with dysplasia, a superficial sampling biopsy of the cervix was carried out as a periodic check of the cytological findings. The relationship of smear and biopsy results was evaluated, as well as the effect of the biopsy procedure on the subsequent course of dysplasia. We found sufficiently close agreement between smear and biopsy results to conclude that smears and biopsies measure similar aspects of dysplasia. It would appear unwise, however, to rely on Papanicolaou smears exclusively in following women with a history of dysplasia, since negative smears in such women may occasionally show dysplasia in the corresponding biopsy. Periodic corroborative biopsy procedures are therefore indicated in the follow-up care of women with a history of dysplasia. There was no evidence that a superficial sampling biopsy significantly altered the short-term course of dysplasia. There was also no evidence of a cumulative effect of repeated sampling biopsies. These results do not rule out possible effects of other forms of biopsy procedures and schedules on the subsequent course of dysplasia.