Double-labeled metabolic maps of memory

The physical changes representing a memory are believed to be localized to specific neurons, widely distributed in multiple parallel pathways in the brain. 2-Fluorodeoxyglucose, labeled with two discriminable radioactive tracers, was used to construct quantitative metabolic maps in split-brain cats during a visual task. One side of the brain served to estimate the metabolic variability of nonspecific influences. The other side was used to map metabolic changes related to the presence of previously learned visual cues, as well as changes related to nonspecific influences, in the same periods of time. When the two sides were compared, between 5 million and 100 million neurons (depending upon the significance level selected) were identified in which activity increased during presentation of the familiar cues. The wide distribution of these neurons throughout the brain is compatible with prior evidence of a distributed memory system. However, the large number of neurons involved is difficult to reconcile with theories in which individual neurons are dedicated to specific memories.

Rapid rejection of fetal chick neocortical xenografts into the spinal cord of adult rats

Xenografts of embryonic day 5 chick cortex were placed into the dorsal column of the spinal cord of 15 adult male Sprague-Dawley rats. This implantation site is known to support comparable E11 rat cortex for months. At 1 DPI (day postoperative), transplanted chicken cortex formed neuroepithelia with a surround of transplanted cells. By 3 DPI, all transplanted cells contained cytoplasmic lipid droplets or lysosomes, as well as necrotic cells. By 7 DPI, the fetal chicken cortical xenograft had necrosed or was phagocytized. The rapid cross-class xenograft rejection is unique since grafts of various rodent tissues tend to survive in the adult rodent central nervous system.

Viability of mature superior cervical ganglia transplants in peripheral nerve of adult rat

Allografts of mature rat superior cervical ganglia (SCG) survived for up to 120 days following transplantation to regenerating and degenerating peripheral nerves of adult rats. Transplants contained the constituents of normal superior cervical ganglia and there was evidence of outgrowth of catecholamine containing fibers from the transplants. However, fibers did not attain the length necessary to enter peripheral muscles and no muscle response could be elicited by electrical stimulation of the implanted nerve where the transplanted mature SCG was the only source of nerve fibers.

Structure and function of fetal cortex implanted into degenerating peripheral nerve of adult rat

The growth, differentiation and function of E11 fetal cortex was studied over 4 months after implantation into the degenerating nerve to the biceps femoris muscle of 70 rats. At 7 days postimplantation (DPI) the implant formed a neuroepithelium which contained mainly undifferentiated cells within a reconstituted perineurium. At 14-21 DPI the neurons contained differentiated, mature nuclei, poorly developed Nissl bodies and normal cytoplasmic organelles. Neuroglia were also observed with typical nuclei and a dense cytoplasmic ground. At 30 days the implants reached their greatest degree of differentiation. Neurons had mature nuclei and cytoplasmic organelles. There were few axosomatic synapses or neuronal cell processes. Neuroglia were prominent with many cell processes. The neuropil contained myelinated and unmyelinated nerve fibers, dendrites and many axodendritic synapses. At 40-50 DPI the neurons and neuronal cell processes were degenerating. At 60-120 DPI the implant contained only neuroglia. Stimulation of only the implant resulted in biceps femoris muscle contraction in 5 animals at 30 DPI and one animal at 40, 45 and 50 days. Injection of 10 microliter of WGA-HRP into the biceps femoris muscle resulted in at least 20 neurons in 3 30-day implants that contained HRP reaction product. These data show that fetal cortical neurons can assume functions different from normal, functionally reinnervate adult muscle and can differentiate and form an ectopic nervous system for at least 30-days after implantation into a degenerating adult host peripheral nerve.

Studies of the mode of action of antitumor triazenes and triazines. 6. 1-Aryl-3-(hydroxymethyl)-3-methyltriazenes: synthesis, chemistry, and antitumor properties

1-Aryl-3-(hydroxymethyl)-3-alkyltriazenes [ArN = NN(CH3)CH2OH] have been synthesized by diazonium coupling to the carbinolamine (RNHCH2OH), generated in situ from the alkylamine and formaldehyde mixtures. The (hydroxymethyl)triazene structure has been confirmed by IR, NMR, and mass spectral analysis and also by the preparation of a crystalline benzoate derivative. The mass spectra of the (hydroxymethyl)triazenes suggest that they fragment by loss of formaldehyde to give the methyltriazene, which is also the product of hydrolysis in solution. The degradation of the (hydroxymethyl)triazenes in solution has been followed by UV spectroscopy and by HPLC analysis, and the half-lives were determined under a variety of conditions. The half-lives of the corresponding methyl- and (hydroxymethyl)triazenes are very similar. Both methyl- and (hydroxymethyl)triazenes decompose on silica plates during TLC analysis to give products consistent with known diazo-migration reactions. The (hydroxymethyl)triazenes have pronounced antitumor activity against the TLX5 tumor in vivo; in vivo-in vitro bioassay experiments suggest that the (hydroxymethyl)triazenes exert their in vivo antitumor activity via the degradation product, the alkyltriazene.

The effect of short-term occlusion on the cutaneous flora in atopic dermatitis and psoriasis

The effect of occlusion on the cutaneous microbial flora in patients with atopic dermatitis and psoriasis was measured. Significant increases in the density of Staphylococcus aureus and lipophilic diphtheroids were noted after occlusion in eczematous and psoriatic skins. While the incidence of S. aureus increased in psoriatic skin after occlusion, this trend was not noted in dermatitic skin.