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Biomedical subjects

N C Adams

Publications and source records attributed to N C Adams.

6 recordsLinked to original sources
PubMed1997

Complexities in the thalamocortical and corticothalamic pathways.

It is now a century since Kölliker (Handbuch der Gewebelehre des Menschen. Nervensystemen des Menschen und der Thiere, Vol. 2, 6th edn. Engelmann, Leipzig, 1896) described the thalamic reticular nucleus as the 'Gitterkern' or lattice nucleus on the basis of the fibrous latticework that is the characteristic feature of this part of the ventral thalamus and adjacent parts of the internal capsule. We suggest that the fibre reorganization produced in this lattice is a fundamental requirement for linking orderly maps in the thalamus to corresponding cortical maps by two-way thalamocortical and corticothalamic connections; these connections involve divergence, convergence and mirror reversals, which all have to occur between the thalamus and the cortex. Apart from the thalamic reticular nucleus, two transient groups of cells, the perireticular nucleus (located in the internal capsule lateral to the reticular nucleus) and the cells of the cortical subplate, are prominent along the course of axons linking the cortex and thalamus early in development. The functions of these two cell groups are not known. However, since early in development complex patterns of reorganization, defasciculation and crossings occur in the regions of these cells, it is likely that they play a role in creating the latticework of the adult. The latticework that characterizes the thalamic reticular nucleus of mammals can also be identified in the ventral thalamus of non-mammalian brains, formed along the course of the fibres that join the dorsal thalamus to the telencephalon. We suggest that the ubiquitous presence of such a zone of fibre reorganization is integral to the functioning of the thalamocortical pathways, and that the complexity of thalamic connections produced in the lattice has been central to the evolutionary success of the thalamotelencephalic system.

Animals↗
PubMed1995

Cells of the perireticular nucleus project to the developing neocortex of the rat.

The perireticular nucleus is a recently described thin sheet of small cells among the fibres of the internal capsule, lying lateral to the thalamic reticular nucleus and medial to the globus pallidus (Clemence and Mitrofanis [1992]. J. Comp. Neurol. 322:167-180). During development, the perireticular nucleus is relatively large, lying in the path of the growing corticofugal and thalamocortical axons and filling the area of the internal capsule lateral to the thalamic reticular nucleus. After these axons have formed their connections, the perireticular nucleus rapidly decreases in size, leaving only a few cells in the adult (Mitrofanis [1992] J. Comp. Neurol. 320:161-181). In this study, we aimed to investigate the connections between the developing cortex and thalamus by making injections of tracer into the cortical plate. Injections of Horse Radish Peroxidase (HRP), Wheat Germ Agglutinin bound to HRP (WGA-HRP) and 1'dioctadecyl-3,3,3',3 tetramethycarbocyanine perchlorate (DiI) were made in vivo between embryonic day (E) 18 and adult and DiI was placed in the fixed brains of rats aged between E16 and postnatal day (P)1. Between E17 and P10, the retrograde perikaryal labelling resulting from these injections revealed a transient projection from the perireticular nucleus to the ipsilateral cortical plate. No cells were labelled in the thalamic reticular nucleus. This suggests that the perireticular nucleus must be regarded as a group of cells distinct from the thalamic reticular nucleus and having a separate role in development. Comparisons between the perireticular cells and the cells of the cortical subplate suggest that both may be playing comparable roles in early development, possibly guiding fibres towards their end stations or serving to rearrange the complex mapped projections linking the thalamus and cortex.

Animals↗
PubMed1991

Transmission of measles in medical settings--United States, 1985-1989.

Measles cases reported to the Centers for Disease Control from 1985 to 1989 were analyzed to determine the characteristics of measles cases transmitted in medical settings. A total of 1,209 medial setting cases were identified, which represented 3.5% of all reported cases. Of medical setting cases, 66% (795) were in known or presumed patients and 28% (341) were in health care workers. The largest groups of health care workers with measles were nurses (101, 29.6%) and physicians (65, 19.1%). Health care workers acquired measles from patients (90.6%) and other health care workers (9.4%), and transmitted measles to patients, other health care workers, and family members. Of 333 (97.7%) health care workers with known measles vaccination status, 232 (68.0%) were eligible for vaccine; only 46 (19.8%) had received a documented dose. Twenty-nine percent of health care workers with measles were born before 1957, older than the age for routine measles vaccination. The relative risk of measles for physicians and nurses was 8.4 (95% confidence interval [CI], 6.6, 10.8) and 2.1 (95% CI, 1.8, 2.7) respectively, compared with nonhealth care workers of the same ages. In 1989 the Immunization Practices Advisory Committee (ACIP) recommended that health care workers be required to document two doses of measles vaccine or other evidence of measles immunity at the time of employment. Implementation of ACIP recommendations for health care workers and appropriate isolation precautions for known and suspected patients with measles could reduce the transmission of measles in medical settings.

Adolescent↗
PubMed1989

Patterns of transmission in measles outbreaks in the United States, 1985-1986.

Since the licensing of measles vaccine in 1963, the incidence of reported measles in the United States has declined to less than 2 percent of previous levels. To characterize the current epidemiology of measles in the United States, we analyzed measles outbreaks that occurred during 1985 and 1986. There were 152 outbreaks (defined as five or more cases related epidemiologically), which accounted for 88 percent of the cases reported during those two years. There were two major types of outbreaks: those in which most of the cases occurred among preschool-age children (those under 5 years of age) (26 percent) and those in which most of the cases occurred among school-age persons (those 5 to 19 years of age) (67 percent). The outbreaks among preschool-age children ranged in size from 5 to 945 cases (median, 13); a median of only 14 percent of the cases occurred in vaccinated persons, and a median of 45 percent of the cases were classified as preventable according to the current strategy. Outbreaks among school-age persons ranged in size from 5 to 363 cases (median, 25); a median of 60 percent of the cases occurred in vaccinated persons, and a median of only 27 percent of the cases were preventable. The outbreaks among preschool-age children indicate deficiencies in the implementation of the national measles-elimination strategy. However, the extent of measles transmission among highly vaccinated school-age populations suggests that additional strategies, such as selective or mass revaccination, may be necessary to prevent such outbreaks.

Adolescent↗