Quantification of tissue plasma volume in the rat by contrast-enhanced magnetic resonance imaging

Magnetic resonance imaging enhanced with a macromolecular contrast medium (MMCM), albumin-Gd-DTPA, was used to estimate the plasma volume in vivo in the myocardium, lung, liver, and skeletal muscle of 10 normal rats. The plasma volumes of the same tissues in a parallel group of six rats were estimated in vitro by a conventional radioisotopic technique (¹¹¹In-transferrin). Plasma volumes of myocardium, lung, liver, and skeletal muscle estimated by the MR technique (μl plas. ia cc-¹ of tissue) were 101,109,163, and 11.0, respectively, while plasma volumes measured by the In-transferrin radioisotope technique (mg plasma g-¹ of tissue) were 78.6, 215,143, and 11-2, respectively. Assuming a ratio of densities of aerated lung to blood of 0.45 and of other tissues to blood of 1.0, correlation between the methods was excellent (R² = 0.99) indicating that MR imaging enhanced with MMCM permits reliable in vivo estimation of tissue plasma volume in the rat.     

An autoradiographic study of periodontal development in the mouse

Tritiated thymidine was injected into 10- and 13-day-old mice because at this age the third molar is at the appropriate stage of development. At set intervals, the mice were killed and the distribution of labeled cells within the dental papilla and follicle examined. The change in labeling index with time was measured for defined areas in the papilla and follicle. It was shown that, during the late bell stage of development, cells moved from the papilla into the follicle. It was concluded that the pulp, rather than the investing layer of the follicle, is the source of the periodontium and that growth of the pulp and periodontal tissues could generate an important force contributing to tooth eruption.     

Putative glutamatergic and/or aspartatergic cells in the main and accessory olfactory bulbs of the rat

The "transmitter-specific" retrograde axonal tracer 3H-D-aspartate has been used to demonstrate neurons in the olfactory bulb which putatively utilize aspartate and/or glutamate as their neurotransmitter and which send an axon either to the piriform cortex or within the bulb itself. Injections of 3H-D-aspartate into layer I of the anterior piriform cortex, in the zone of termination of axons from the olfactory bulb, labeled only a few cells in the main olfactory bulb, located in the mitral and external plexiform layers. Although these cells resembled mitral and tufted cells, they tended to have smaller somata than other mitral or tufted cells and apparently form a distinct subpopulation of relay cells. In contrast, many of the mitral cells of the accessory olfactory bulb were labeled by the same injections of 3H-D-aspartate, probably as a result of involvement of the accessory olfactory tract or its bed nucleus in the injection site. Similar injections of the "nonspecific" tracer HRP into the anterior piriform cortex labeled most of the cells in the mitral cell layer of both the main and accessory olfactory bulbs, and some tufted cells in the external plexiform layer. It is concluded that only a small, distinct subpopulation of the mitral or tufted cells of the main olfactory bulb are aspartatergic and/or glutamatergic, while many (at least) of the mitral cells of the accessory olfactory bulb use the excitatory amino acids as transmitters. Injections of 3H-D-aspartate directly into the main olfactory bulb also failed to label the mitral and deeply situated tufted cells. However, a few cells were labeled in the periglomerular region, the superficial external plexiform layer, and the granule cell layer near the injection site. These labeled cells were smaller than mitral and tufted cells but generally larger than periglomerular or granule cells. They may represent a population of glutamatergic or aspartatergic short axon cells. In addition, small cells of an unknown type were labeled in the olfactory nerve layer following injections in the deepest part of the bulb. These cells do not correspond to any of the well characterized cell types of the olfactory bulb.     

Safety and Efficacy of ECT in Depressed Patients with Dementia: A Review of Clinical Experience

The authors review the results of electroconvulsive therpay (ECT) in 135 cases of depression occurring in conjunction with organic dementia, subcortical leukoencephalopathy without dementia, and depressive dementia (22 cases). Overall, 86% had a positive therapeutic response to ECT, whereas 21% experienced significant cognitive or memory side effects, virtually all of which were transient and reversible. Forty-nine percent of the patients with organic or depressive dementias experienced improvement in cognitive or memory function consequent to ECT.     

Comparative genomic hybridization of 49 primary retinoblastoma tumors identifies chromosomal regions associated with histopathology,progression, and patient outcome

Forty-nine primary retinoblastoma (Rb) tumors were analyzed by the use of comparative genomic hybridization (CGH), and clinical/histological correlations were performed. Adverse histological factors were present in 13 patients. Chromosomal imbalance was a frequent phenomenon, seen in 96% of the tumors. Gain of 6p represented the most frequent event (69% of the tumors), whereas +1q was observed in 57%, confirming that these abnormalities are key secondary events in retinoblastoma tumor progression. Loss of 13q and 16 was significantly associated with tumors displaying adverse histo-prognostic factors, whereas -16q was significantly associated with tumors without adverse features. In three patients who developed an extra-ocular relapse, the tumors showed -13q and 2/3 had -5q, suggesting that these abnormalities may be associated with metastasis. Children >or= 36 months of age at enucleation tended to have more CGH abnormalities per tumor than children < 12 months (median numbers 11 vs. 3). In addition, +1q, +13q, -16, and -16q were more frequent in children with an older age at enucleation. Identical CGH changes were found in both tumors from one patient with bilateral tumors, suggesting a common origin. It is possible that tumors displaying loss of 13q and 5q indicate those patients who may suffer an adverse outcome and who would require alternative or more intensive therapy. CGH analysis on larger cohorts and in prospective clinical trials will be invaluable in determining whether a genetic classification of retinoblastoma represents a reliable measure of prognosis.     

Mutations in the retinal guanylate cyclase (RETGC-1) gene in dominant cone-rod dystrophy

The dominant cone-rod dystrophy gene CORD6 has previously been mapped to within an 8 cM interval on chromosome 17p12-p13. The retinal- specific guanylate cyclase gene (RETGC-1), which maps to within this genetic interval and previously was implicated in Leber's congenital amaurosis, was screened for mutations within this family and in a panel of small families and individuals with various cone and cone- rod dystrophy phenotypes. A missense mutation (E837D) was identified in affected members of the CORD6 family, as well as a second missense mutation (R838C) in three other families with dominant cone-rod dystrophy. RETGC-1 is only the fourth gene to be implicated in cone-rod dystrophy and this is the first report of dominant mutations in this gene.