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Biomedical subjects

P Hall

Publications and source records attributed to P Hall.

310 records · Page 18Linked to original sources
PubMedDate not supplied

Synthesis of green fluorescent protein-ricin and monitoring of its intracellular trafficking.

We performed genetic engineering to fuse enhanced green fluorescent protein (EGFP) to the N terminus of RTA, expressed the fusion protein in Escherichia coli, purified and reassociated EGFP-RTA with plant RTB, and purified EGFP-ricin by size exclusion HPLC. The fusion heterodimer was able to bind galactosides, intoxicate cells, and show strong fluorescence. Mammalian cells incubated with EGFP-ricin showed strong cell surface fluorescence at 4 degrees C and, on incubation at 37 degrees C, distributed initially to endosomes and then to Golgi vesicles. Variable sensitivity of mammalian cells to ricin and ricin fusion proteins may be due in part to different patterns of intracellular routing. Cells were incubated with ricin or EGFP-ricin, and inhibition of protein synthesis was measured. Human hepatocellular carcinoma Hep3B cells were 10-fold more sensitive to ricin and 85-fold more sensitive to EGFP-ricin than human epidermoid carcinoma KB cells. Epifluorescence microscopy of cells incubated with EGFP-ricin showed greater localization of the fluorescence signal in the Golgi compartments in Hep3B cells than in KB cells. These data support a model requiring a Golgi-dependent step in cell intoxication by ricin. The work further identifies the usefulness of green fluorescent protein fusions in the study of retrograde transport of internalized peptides.

Cell Survival↗
PubMedDate not supplied

Hypotension as a complication of hypoglycemia leads to enhanced energy failure but no increase in neuronal necrosis.

The hypothesis that arterial hypotension aggravates hypoglycemic brain damage was tested. Thirty minutes of insulin induced hypoglycemia with a flat EEG ("isoelectricity") was compared in seven series of rats. In three series of animals, the energy state of the cerebral cortex was determined at blood pressures of 140, 100 and 80 mm Hg respectively. Hypotension during hypoglycemia exacerbated cortical energy failure. In the fourth to sixth series, blood pressure was adjusted during isoelectricity to 160, 100 and 60 mm Hg, respectively. A seventh series had induced hypotension to 60 mm Hg only in the recovery period. Quantitation of neuronal death was performed in the fourth to seventh series of rats by direct visual counting of acidophilic neurons in sub-serially sectioned brains after one week survival. Although the first three series demonstrated enhanced deterioration of the cerebral energy state with lower blood pressures during hypoglycemia, the fourth to seventh series showed no augmentation of quantitated hypoglycemic neuronal necrosis. The distinct distribution of hypoglycemic brain damage, suggesting a fluid-borne toxin, was present at normal and reduced blood pressures, with no tendency toward an ischemic pattern of pathology. In spite of previously demonstrated reductions of cerebral blood flow to ischemic levels in regions with pronounced loss of autoregulation, no regional exacerbation of neuronal necrosis was seen in these brain areas. It is concluded that hypoglycemic brain damage is distinct from ischemic brain damage, and that the two insults are not additive. Furthermore, moderate hypotension to 60 mm Hg does not aggravate the damage in spite of an enhanced energy failure.

Animals↗
PubMedDate not supplied

A study of experimental syringomyelia by scanning electron microscopy.

Experimental hydromyelia and syringomyelia, induced by kaolin in dogs, has been investigated by scanning electron microscopy. This study demonstrated that communication between the 4th ventricle and the spinal central canal is normally occluded by a plug of acellular material lying within the central canal. This plug is broken down following the onset of hydrocephalus and communication is rapidly established between the ventricles and the central canal. The canal distends and ruptures dorsally into the spinal gray matter with the development of extensive intramedullary cavities, lined by glial and neuronal elements. The morphological changes demonstrated are consistent with a physical destructive process of the cord resulting from CSF dissection.

Animals↗