Cat phrenic nucleus architecture as revealed by horseradish peroxidase mapping

Cat phrenic motoneurons, labeled by intradiaphragmatic injection of horseradish peroxidase, formed a tight cluster in the most ventral portion of the ventral horn in lamina IX of the lower cervical cord. Cell counts were symmetrically distributed for 17 to 21 mm along the longitudinal axis of the cord with a unimodal peak at the junction of segments C5 and C6. The phrenic nucleus was bilaterally organized on either side of the cord with anatomical symmetry and in no case was there evidence for the crossing of phrenic axons in the cord. Assessment of cellular geometry and intercellular relationships demonstrated that phrenic cell diameters approximated a normal distribution with a single peak at 26 mum while longitudinal cell lengths average 76 mum. Cells of different size were mixed randomly at all levels of the nucleus. The minimum distance between cells was about 10 mum and the maximum cell packing density approached 2 cells per 10(6) mum3. The results confirm the location of the cat phrenic nucleus, extend the knowledge of phrenic motoneuronal geometry, and provide an anatomical basis for the understanding of recruitment and synchronization phenomena within the phrenic nucleus.

Sympathetic neurons in the cat spinal cord projecting to the stellate ganglion

Horseradish peroxidase (HRP) was injected into the stellate ganglia of anesthetized cats. After a 2-day survival time the spinal cord was processed for the HRP reaction to study the distribution of the preganglionic neurons which project to the stellate ganglia. HRP-labeled neurons in the cord were located exclusively on the side ipsilateral to the injected stellate ganglia and were concentrated in four distinct areas: (1) intermediolateral cell column (78.2%), (2) lateral funiculus (18.5%), (3) intercalated area and (4) central autonomic area (3.3%) for the latter 2 areas). Their distribution pattern in the very rostral pole of the thoracic sympathetic preganglionic cell column was different from the typical thoracic pattern in that a greater proportion of the cells were located in the lateral funiculus, and a few labeled cells were observed in the ventral horn. Longitudinally, a wide range (C8-T8) of spinal cord levels projected to the stellate ganglia, with a peak at the T2 level. These observations infer that a large population of axonal processes of sympathetic preganglionic neurons traveled several segments of the spinal cord through an intraspinal pathway before exiting a particular ventral root.

Ascending pressor and depressor pathways in the cat spinal cord

Blood pressure responses to stimulation of the cervical dorsolateral sulcus (DLS) of the spinal cord and lumbar dorsal roots were studied in anesthetized, vagotomized, and paralyzed cats. Stimulation of the lumbar dorsal roots elicited pressor responses with high-frequency stimulation (50 Hz, 10 V, 1 ms) and depressor responses with low-grequency stimulation (1 Hz, 10 V, 1 ms). Pressor responses were converted to depressor responses after bilateral lesions were made in the DLS area rostral to the site of stimulation. These results suggest that the ascending spinal pressor pathways are localized in the DLS region. Furthermore, these depressor responses were abolished by placing additional bilateral lesions in the dorsolateral funiculus (DLF) rostral to the site of stimulation. These data indicate the presence of ascending depressor pathways in the DLF which are anatomically separate from pressor pathways. Both pathways were found to be bilateral systems, and decussation of fibers appears to be complete within three segments rostral to their entry into the spinal cord. Ascending depressor pathways have a low optimal frequency of activation, as opposed to the ascending pressor pathways which have a relatively high optimal frequency of activation. Neurophysiological evidence obtained by recording unit activity from the cervical sympathetic trunk confirmed the localization of the ascending pressor and depressor pathways.

Effect of isolated head heating and cooling on sweating in man

A double climate chamber which permitted the independent regulation of temperature in each chamber was used to produce isolated head heating and cooling in three subjects. Deep body temperature was recorded from the tympanic membrane, oral cavity, esophagus, and rectum. Skin temperature was measured on nine body regions and a weighted mean skin temperature was calculated. Sweating rate was measured by resistance hygrometry from six regions. When head skin temperature was increased, deep body temperature measured at the tympanic membrane and oral cavity increased more than esophageal temperature, while rectal temperature remained essentially unchanged. Sweating rate increased when head skin temperature increased and again, somewhat later, as the tympanic membrane and oral temperatures began to rise. When head skin temperature was decreased, tympanic membrane and oral temperatures decreased and sweating again followed the changes in skin temperature as well as the changes in tympanic membrane and oral temperatures. Since it has been shown that head skin temperature is particularly important in determining thermal comfort and sweating rate when compared to other body regions, it is suggested that this particular sensitivity is in part due to a thermal counter-current exchange between venous blood draining the head and arterial blood ascending to intracranial thermoreceptors. Such an exchange would correspond to similar mechanisms present in other species.

Reliability of computer-generated prediction tracing

The reliability of a commercially available computer prediction program (Quick Ceph II) was evaluated using pretreatment and posttreatment cephalograms of 30 patients who were treated during an active period of growth. The computer prediction was compared with the actual treatment result, and the growth forecast with the computer program was compared with the growth forecast using a manual method. Using paired student's t-tests, predictions for 5 of the 10 variables measured were found to be statistically reliable. Comparing the relative accuracy of growth prediction in terms of absolute values, the computer came closer to the actual result in four of the nine variables, while the manual method came closer in three variables. Predictions for the other two variables were virtually the same using both methods. The manual method of prediction was sufficient to give a reasonably good graphic representation of growth changes to create a VTO. However, the computer offers the added advantages of quicker access to information and somewhat greater accuracy in producing the tracing, as well as its use in patient education.