Biomedical subjects

Y Smith

Publications and source records attributed to Y Smith.

101 records · Page 6Linked to original sources

PubMed1984

The striatopallidal and striatonigral projections: two distinct fiber systems in primate.

The use of the fluorescence retrograde double-labeling method has revealed that striatal neurons projecting to the globus pallidus in the squirrel monkey are mainly confined to the putamen whereas those projecting to the substantia nigra occur mostly in the caudate nucleus. Only about 10% of the striatal neurons were found to be double-labeled after injections into the globus pallidus and substantia nigra. The segregation of the putaminofugal and caudatofugal projections was further confirmed by the anterograde tracing of WGA-HRP. These findings do not fit in the current unitary concept of the striatofugal fiber system. Instead, they suggest that the striatopallidal and striatonigral projections exist largely as two distinct subsystems in the primate.

Animals↗

PubMed1984

Distribution of acetylcholinesterase-containing neurons in the basal forebrain and upper brainstem of the squirrel monkey (Saimiri sciureus).

The topographical distribution of neurons containing acetylcholinesterase (AChE, EC 3.1.1.7) in the basal forebrain and upper brainstem of the squirrel monkey (Saimiri sciureus) was studied by means of Butcher's pharmacohistochemical technique which involves staining for AChE at various times after the systemic administration of the AChE inhibitor di-isopropylphosphorofluoridate (DFP). Only those neurons whose AChE staining was as intense as that of known cholinergic neurons present in the same material (e.g., neurons of cranial nerve nuclei) were examined and mapped. Three major collections of such strongly-stained AChE neurons were disclosed in squirrel monkey brain: one located in the striatum, the other lying along the ventralmost aspects of the basal forebrain, and a third one present within the midbrain-pontine tegmentum. The striatal AChE neurons vary in shape from fusiform with 2 thick processes to polygonal with 4-5 thinner processes. They are uniformly scattered throughout the caudate nucleus and putamen and represent only a small proportion of the total striatal cell population (4-6 cells/mm2). They most likely correspond to the aspiny type II cells described in Golgi material of monkey striatum. Similar neurons occur also in ventral striatal areas comprising nucleus accumbens septi and the deep polymorph layer of the olfactory tubercle. The second major AChE neuronal population is composed of the magnocellular neurons that form a somewhat continuous chain of neuronal aggregates extending rostrocaudally from the septal region to the caudal pole of the lentiform nucleus. It includes the neurons of the medial septal nucleus, the nucleus of the diagonal band of Broca and the nucleus basalis of Meynert, all displaying strikingly similar morphological and histochemical characteristics. The AChE neuronal population of nucleus basalis encroaches markedly upon the lateral hypothalamus laterally and the globus pallidus dorsally. The third important AChE cell collection occurs within the pedunculopontine nucleus area in upper brainstem. In that constellation, the AChE neurons are clustered in 2 continuous cell groups: one located dorsolaterally, the other lying ventromedially to the brachium conjunctivum. The thick processes of these neurons form impressive AChE neuronal networks that surround and pervade the brachium conjunctivum over long distances. This cell group, which is one of the most highly AChE reactive structures of the entire brain in the squirrel monkey, may provide a major cholinergic input to various basal ganglia structures, particularly the substantia nigra.

Acetylcholinesterase↗

PubMed1983

The output organization of the substantia nigra in primate as revealed by a retrograde double labeling method.

The cellular origin and degree of collateralization of the efferent projections of the substantia nigra pars reticulata (SNr) in the squirrel monkey (Saimiri sciureus) were studied using the following combinations of fluorescent retrograde tracers: Evans blue and DAPI-Primuline, Fast blue and Nuclear yellow, True blue and Nuclear yellow. In a first series of experiments one tracer was injected in the ventral anterior (VA) and ventral lateral (VL) thalamic nuclei, and the complementary tracer was delivered in the peribrachial area of midbrain tegmentum. After thalamo-tegmental injections numerous nigrothalamic neurons occur in clusters, particularly in rostrolateral part of SNr, whereas the nigrotegmental neurons prevail in caudomedial segment of SNr. However, a significant overlap exists between these two populations. The nigrothalamic and nigrotegmental neurons are present in about equal number in SNr with as much as 60% of these neurons being double-labeled. In a second series of experiments injections were made concomitantly in VA/VL nuclei and in superior colliculus. After thalamo-collicular injections the nigrothalamic neurons are found in larger number than the nigrocollicular neurons which are mostly confined to the middle third of SNr. About 15-20% of all SNr positive neurons are double-labeled, although this proportion climbs to 30-40% in certain sections taken through the middle third of SNr. Finally, injections were made concomittantly in superior colliculus and in midbrain tegmentum. In contrast to the findings obtained after thalamo-tegmental and thalamo-collicular injections, only about 10% of SNr neurons appear to be double-labeled after colliculo-tegmental injections. All injections made in present study have produced retrograde cell labeling in contralateral SNr. However, by far the largest number of contralateral labeled neurons is found after superior colliculus injection. These findings reveal that the SNr neurons in primate, as those in rat and cat, display a high degree of axonal branching. As such, the output organization of SNr appears to differ markedly from that of the substantia nigra pars compacta, but is remarkably similar to that of the internal pallidum which is the other major output structure of the basal ganglia.

Animals↗

PubMed1982

Evolution of porencephalic cysts from intraparenchymal hemorrhage in neonates: sonographic evidence.

Ninety-four low-birth-weight neonates were screened consecutively with real-time sonography for evidence of cerebroventricular hemorrhage. Among them, 13 were found to have intraparenchymal hemorrhage beyond the area of the germinal matrix. Weekly follow-up sonograms revealed progression to porencephaly in every surviving infant. Four different sonographic patterns were observed during the evolution from the original hemorrhage to the porencephalic cyst. The size of the mature porencephalic cyst correlated directly with the size of the intraparenchymal hemorrhage. After ventriculoperitoneal shunting, the porencephalic cysts became smaller or remain unchanged. One small cyst was no longer identified after successful shunting, but reappeared with shunt failure.

Brain Diseases↗

PubMed1981

Real-time ultrasonography of neonatal intraventricular hemorrhage and comparison with computed tomography.

Thirty-three low-birth-weight neonates were diagnosed prospectively as having an intraventricular hemorrhage, using a real-time sonographic sector scanner. Ultrasound findings were corroborated in 27 patients by computed tomography (CT) or autopsy. Intraventricular blood is hyperechoic and, in a fresh hemorrhage, a continuous cast-like pattern of increased echogenicity replaces the usually minute, echo-free lateral ventricles. After one to three days, the lateral ventricles begin to enlarge around the echogenic clot if hydrocephalus complicates the hemorrhage. The sonographic findings indicating intraventricular hemorrhage and its progression to hydrocephalus are presented. The accuracy of sonographic real-time sector scanning in the evaluation of neonatal intraventricular hemorrhage is discussed and compared to CT.

Cerebral Hemorrhage↗

PubMed1981

Real-time sonography of the neonatal and infant head.

Fifty neonatal and infant heads were examined using a 5 MHz real-time sector scanner. Anatomic detail superior to that previously described was achieved by this method. Normal structures routinely imaged included the entire ventricular system and many parts of the subarachnoid spaces. The gray scale detail of parenchymal structures was usefully demonstrated. Routinely visualized vascular structures included the anterior cerebral artery system, the middle cerebral arteries, the choroid plexus, and the posterior cerebral arteries. Hydrocephalus, as well as intraventricular hemorrhage and its sequelae, were investigated. Computed tomography (CT) is considered diagnostic in hydrocephalus and intraventricular hemorrhage, but evaluation by sonography compares favorably. Among other advantages of sonography are the feasibility of bedside scans without removing the patient from the intensive care nursery and the elimination of ionizing radiation.

Cerebral Angiography↗

PubMed1981

Comparative effects of azathioprine, cyclophosphamide and frentizole on cellular immunity in mice.

This report extends previous observations on the immunosuppressive properties of cyclophosphamide (CPA), azathioprine and frentizole (15) to include murine models of cellular immunity. Systemic and local graft vs host reactions (GVHR) were most effectively suppressed by CPA. In contrast to frentizole, both CPA and azathioprine were found to inhibit the proliferation of parental T-cells in a systemic GVHR. However, CPA was the only agent capable of inhibiting the proliferation of T-cells following contact sensitization with oxazolone. Mice pretreated with a high dose of CPA or frentizole prior to inoculation with the murine sarcoma virus exhibited accelerated tumor growth. However, there was no accelerated growth of murine sarcoma virus induced tumors or an SaI spindle cell fibrosarcoma during rather prolonged therapy with immunosuppressive doses of CPA, azathioprine or frentizole. Normal mice treated with CPA showed a more drastic reduction in lymphoid elements of the spleen and thymus than mice treated with azathioprine or frentizole. Studies on the mitogenic responsiveness of spleen cells obtained from normal mice after an eight day course of therapy suggested that CPA has some selectivity of action on B-cells and azathioprine on T-cells.

Animals↗

PubMed1979

Comparative effects of azathioprine, cyclophosphamide and frentizole on humoral immunity in mice.

Data is presented comparing the activities of three immunosuppressive agents, cyclosphosphamide, frentizole and azathioprine in models of humoral immunity in mice. Cyclophosphamide and frentizole suppressed the primary and secondary plaque forming cell responses to sheep erythrocytes at lower doses than did azathioprine. Prolonged suppression of serum antibody titers occurred following short-term therapy with cyclophosphamide or frentizole, but not azathioprine. Azathioprine was also the least effective agent in suppressing a primary response to the T-independent antigen, trinitrophenylated lipopolysaccharide. All three agents were found to inhibit the induction and activity of suppressor cells at immunosuppressive doses.

Animals↗

PubMedDate not supplied

Examination of an altered bar code on a vehicle tax disc.

Altered vehicle excise licences (tax discs) are regularly submitted for questioned document examination in order to reveal the original vehicle details. A bar code printed on tax discs permits the electronic storage and transfer of vehicle licensing information. In a recent case involving a tax disc on which the printed serial number had been partially removed, it was possible to restore and manually decode an obliterated bar code. This allowed recovery of the complete serial number of the disc and subsequent retrieval of the original entries.

Journal Article↗

PubMedDate not supplied

Periventricular leukomalacia in combination with intraventricular hemorrhage: sonographic features and sequelae.

Periventricular leukomalacia (PVL) is well recognized as a relatively uncommon yet particularly serious complication of prematurity. Although the sonographic features of PVL have been described, its association with intraventricular hemorrhage (IVH) has not been emphasized. Reviewing 26 consecutive cases of PVL in neonates of 34 weeks or less gestational age, significant associated hemorrhage was found in six (23%). Small quantities of blood were also noted in most of the other 20 infants. Of the six infants with both significant IVH and PVL, five required ventricular shunt and all had particularly poor clinical outcomes. In the neonates who required surgical intervention, rapid ventricular enlargement was accompanied by extensive periventricular cyst formation. Eventually, the septations within the cysts and frequently even the ependyma of superior/posterior lateral ventricles degenerated. Cysts merged imperceptibly with the ventricles giving an appearance that mimicked severe hydrocephalus. This was termed "pseudoventricle formation," as the large intracerebral cerebrospinal fluid spaces are primarily porencephaly and not enlarged ventricles. Response to shunting was minimal by sonography in all five cases and multiple shunt revisions were required in four. Clinical follow-up in children with significant IVH in combination with PVL has shown severe mental retardation and tetraplegia in all cases.

Cerebral Hemorrhage↗

PubMedDate not supplied

Cerebral intraparenchymal hemorrhage in neonates: sonographic appearance.

The real time sonographic findings of five neonates with cerebral intraparenchymal hemorrhage are reported. In each case, areas of markedly increased echogenicity corresponded to the site of hemorrhage. Excellent correlation was found between computed tomography (CT) and sonography. Although the sonographic appearance of intraparenchymal hemorrhage is characteristic, it is difficult to separate blood from other contiguous highly reflective structures in the head, including choroid plexus, bone, and the tentorium. It appears that real time sonography may offer an alternative to CT in the diagnosis of cerebroventricular hemorrhage in neonates.

Cerebral Hemorrhage↗