Ultrastructure of cat superior vestibular commissural neurons

The ultrastructure of the feline superior vestibular commissural neurons (CNs) was studied after labeling by contralateral injection of horseradish peroxidase. These small spindle-shaped cells are found in clusters oriented in a rostrocaudal, dorsoventral or lateromedial direction. The CNs have a cleft nucleus, with the majority of nerve terminals contacting the CN near the emergence of polar dendrites. Polarization of the afferent synaptic profiles suggests a bidirectional nature of inputs to CNs by the vestibular nerve, contralateral CNs, and/or cerebellar systems. One type of labeled cell does not conform to this pattern, instead resembling a vestibulo-ocular neuron. Hence, it may function as a commissural and a vestibulo-ocular neuron. Characterization of different types of synapses, based on the size and eccentricity of their synaptic vesicles, indicates a continuum rather than separate populations. Volume fraction of intracellular organelles showed a larger volume fraction percent of polyribosomes in larger cells. Since this organelle is involved with protein synthesis, this finding may indicate that larger CNs have a more extensive dendritic tree.     

Intraventricular hemorrhage in utero

A case of fetal intraventricular hemorrhage related to subependymal hemorrhage diagnosed by ultrasound scanning at 27 weeks of PMA is reported. No etiology was found. The outcome was favorable. This case suggests that some cases of neonatal idiopathic hydrocephalus may be explained by fetal subependymal/intraventricular hemorrhage.     

Radiological rickets in extremely low birthweight infants

Forty-eight infants of birthweight less than 1000 g who survived for more than 28 days, had wrist X-rays to prospectively determine the incidence of radiological rickets. Twelve infants (25%) had normal X-rays throughout, 10 infants (21%) showed osteopenia and 26 infants (54%) had classical changes of rickets of which 8 (17% of the total) had spontaneous fractures. There was poor correlation between peak values of serum alkaline phosphatase and the radiological changes.     

Suicide rates and religious commitment in young adult males in Utah

Previous studies have used population data to demonstrate an inverse association between suicide rates and religious commitment. This report examines Utah suicide rates for young men aged 15-34 years, stratified by their membership in and commitment to the Church of Jesus Christ of Latter-day Saints (LDS), the predominant religion in Utah. All state death records for males from 1991 to 1995 were obtained and linked to LDS church deceased membership records to obtain a measure of religious commitment that is not self-reported. Religious commitment for LDS church members was determined by age-appropriate priesthood office. Of the 27,738 male deaths reported, 15,555 (56%) linked to an LDS church record using a probabilistic linking program. Using active (high religious commitment) LDS as the reference group, the less-active (low religious commitment) LDS group had relative risks of suicide ranging from 3.28 (ages 15-19 years) to 7.64 (ages 25-29 years); nonmembers of the LDS church had relative risks ranging from 3.43 (ages 15-19 years) to 6.27 (ages 20-24 years). Although the mechanism of the association is unclear, higher levels of religiosity appear to be inversely associated with suicide.     

Voluntary modification of automatic arm movements evoked by motion of a visual target

We have investigated whether the processes underlying the visually evoked, automatic adjustments to a reach are: (1) modifiable by the subject's intention, and (2) available to initiate movement of a stationary arm. Unpredictable movement of a target (80 m/s through 10 cm, left or right in a third of trials) either evoked a mid-flight adjustment of a reaching movement or else acted as a trigger to start an arm movement. Subjects were instructed to respond as rapidly as possible by moving their finger either in the same or in the opposite direction to the target. The target shift evoked an early (125-160 ms) and/or a later (> 160 ms) class of response in the reaching arm. The early response was highly automatic in that it could not be reversed (move opposite) by the subjects' intention. However, the subjects' intention did influence the frequency of occurrence and the size of this early response. The later response was totally modifiable in that it changed direction according to the subjects' intention. Similar classes of response were observed in stationary limbs, but the early, more automatic response was substantially weaker than that elicited during a reach. Two possible mechanisms are proposed to explain these results. The first is a dual-pathway model, which assumes that the two response classes are each generated by separate visuo-motor processes with different properties. The second model assumes both responses are generated by a single visuo-motor mechanism that is under the control of a higher, attentional process.