Physician Articles
Prenatal development of the receptive
fields of individual trigeminal ganglion cells in the rat
N. L. Chiaia, W. R. Bauer and R. W. Rhoades
Department of Anatomy, Medical College of Ohio, Toledo 43699.
1. Extracellular single-unit recording and receptive-field mapping techniques were used to evaluate the response characteristics of trigeminal (V) ganglion cells in unanesthetized, decerebrate, fetal rats between the ages of embryonic (E-) day 15 and E-20 (E-0 is the day of conception).
2. The receptive-field properties of the cells (n = 282) recorded at all of these ages except E-15 were remarkably similar; V primary afferents were generally silent in the absence of peripheral stimulation (94.3%) and gave rapidly adapting responses to innocuous tactile stimuli (97.5%). Rapid response decrements to repeated stimuli were observed in 9 of the 14 cells (64%) tested.
3. None of the cells recorded were activated by either heat or cold. No attempt was made to evaluate responses to noxious mechanical stimuli.
4. Particular attention was paid to neurons whose receptive fields involved mystacial vibrissae follicles. At all ages, neurons were recorded that responded to indentation of the skin at the base of the vibrissae, but vibrissa deflection was not an adequate stimulus for any of the cells tested. At all ages, nearly all (89.0%) of the 127 cells with vibrissa-related receptive fields responded to indentation of one and only one follicle.
5. These results indicate that the response properties (e.g., adaptation characteristics, ability to respond to repeated stimuli) of V primary afferents in fetal rats differ substantially from those of V ganglion cells in adult animals, but that the receptive-field size for these neurons in prenatal rats is, with very rare exceptions, adult-like from the earliest age at which they can be recorded.
6. These results, when considered together with the results of previous retrograde tracing experiments in fetal animals, suggest that the initial projections of V primary afferents to their peripheral targets may be quite accurate.
Effects of neonatal transection of the infraorbital nerve upon the structural and functional organization of the ventral posteromedial nucleus in the rat |
| Nicolas L. Chiaia, William R. Bauer, Shujie Zhang, Tod A. King, Paul C. Wright, Scott C. Hobler, Keith A. Freeman |
| Department of Anatomy, Medical College of Ohio, Toledo, Ohio 43699 |
| The present study examined the way in which an indirect partial deafferentation of the medial portion of the ventrobasal complex (VPM/VPL) induced by neonatal transection of the infraorbital nerve (ION) altered the structural and functional properties of its constituent neurons. This manipulation significantly reduced the volume of the contralateral VPM/VPL. In addition, cell counts in Nissl-stained material revealed a significant reduction of the number of VPM/VPL neurons contralateral to neonatal ION transection. We also analyzed the effect of neonatal ION transection on the soma-dendritic morphology of individual neurons in the ventral posteromedial nucleus of the thalamus (VPM) by intracellular injection of horseradish peroxidase (HRP) in vivo and Lucifer yellow in fixed slices. Neonatal transection of the ION resulted in increased dendritic length, area, and volume of VPM neurons in both preparations; however only the changes observed in fixed slices reached statistical significance. Alterations in the functional characteristics of VPM neurons were also observed following neonatal nerve damage. There was a significant decrease in the percentage of vibrissae-sensitive neurons and a corresponding increase in the percentages of neurons responsive to guard hair deflection or that were unresponsive to peripheral stimulation. Neonatal nerve damage also resulted in significantly longer latencies of VPM cells after stimulation of either trigeminal nucleus principalis or subnucleus interpolaris. |
| The present results indicate that the development of normal response properties and soma-dendritic morphology of VPM neurons is dependent upon intact afferent input during development. Indirect partial deafferentation of VPM/VPL by neonatal transection of the ION results in reduced neuron number, which may result in decreased competition among the dendrites of these neurons. This proposal is consistent with observations of increased dendritic dimensions of VPM neurons contralateral to neonatal ION damage. © 1992 Wiley-Liss, Inc. |
PROACT: A Phase II Randomized Trial of Recombinant Pro-Urokinase by Direct Arterial Delivery in Acute Middle Cerebral Artery Stroke
Gregory J. del Zoppo, MD; Randall T. Higashida, MD; Anthony J. Furlan, MD;
Michael S. Pessin, MD†; Howard A. Rowley, MD; Michael Gent, DSc; and the PROACT Investigators
Background and Purpose—To test the safety and recanalization efficacy of intra-arterial local delivery of plasminogen activators in acute ischemic stroke, a randomized trial of recombinant pro-urokinase (rpro-UK) versus placebo was undertaken in patients with angiographically documented proximal middle cerebral artery occlusion.
Methods—After exclusion of intracranial hemorrhage by CT scan, patients with abrupt onset of symptoms of focal ischemia likely to receive treatment within 6 hours who satisfied all clinical eligibility criteria underwent carotid angiography. Patients displaying Thrombolysis in Acute Myocardial Infarction grade 0 or 1 occlusion of the M1 or M2 middle cerebral artery were randomized 2:1 to receive rpro-UK (6 mg) or placebo over 120 minutes into the proximal thrombus face. All patients received intravenous heparin. Recanalization efficacy was assessed at the end of the 2-hour infusion, and intracerebral hemorrhage causing neurological deterioration was assessed at 24 hours.
Results—Of 105 patients who underwent angiography, 59 were excluded from randomization. Among the 46 patients randomized, 40 were treated with rpro-UK (n526) or placebo (n514) a median of 5.5 hours from symptom onset. Recanalization was significantly associated with rpro-UK (2P5.017). Hemorrhagic transformation causing neurological deterioration within 24 hours of treatment occurred in 15.4% of the rpro-UK–treated patients and 7.1% of the placebo-treated patients (2P5.64). Both recanalization and hemorrhage frequencies were influenced by heparin dose.
Conclusions—Intra-arterial local rpro-UK infusion was associated with superior recanalization in acute thrombotic/ thromboembolic stroke compared with placebo. In this regimen, heparin dose influenced hemorrhage frequency and recanalization. Although symptomatic hemorrhage remains a concern, this study suggests that recanalization is enhanced with rpro-UK and heparin. (Stroke. 1998;29:4-11.)
Is Hypertrophy Limited in Elderly Muscle Fibers? A Comparison of Elderly and Young Strength-Trained Men
Robert S. Hikida, Seamus Walsh, Nicole Barylski, Gerson Campos, Fredrick C. Hagerman and Robert S. Staron
Department of Biomedical Sciences and Department of Biological Sciences, College of Osteopathic Medicine, Ohio University, Athens, Ohio, USA
Abstract
To investigate the capacity to hypertrophy and the satellite cell populations to change with age, the nucleo-cytoplasmic relationships and satellite cells were compared in skeletal muscles of young and elderly men before and after strength training. Vastus lateralis muscle biopsies were taken before and after 8 (young) or 16 weeks (elderly men) of strength training and compared to muscle from untrained men. The young men had more myonuclei in type II fibers than in type I, and the cytoplasm per nucleus was smaller. As muscle fibers hypertrophied with strength training, the larger cross-sectional area was matched by increasing nuclear numbers, maintaining a constant nucleus-to-cytoplasm ratio. The numbers of myonuclei were similar in elderly and young muscles, and strength training increased both, but not significantly. Myonuclear number was related to cross-sectional area in young untrained and trained muscles, but no relationship was found in untrained elderly men. With training, this relationship was restored in the elderly muscles. The relative increase in cross-sectional area in elderly muscles was similar to the young, but the elderly muscles began with such small fibers, that the hypertrophied fibers in the trained elderly muscles reached the size of untrained young muscle fibers. The results suggest that the increase in myonuclear number accompanies and is proportional to fiber hypertrophy in the young, but it is still unclear to what extent this occurs in the elderly. The percentage of satellite cells did not differ between young and elderly muscles. These satellite cells, responsible for contributing to myonuclear increase, did not decrease in numbers with aging.