Xenopus rhodopsin promoter. Identification of immediate upstream sequences necessary for high level, rod-specific transcription.

To understand the mechanisms that control the cell-specific visual pigment gene transcription, the Xenopus rhodopsin 5' regulatory region has been characterized in vivo using transient transfection of Xenopus embryos and transgenesis. The principal control sequences were located within -233/+41, a region with significant conservation with mammalian rhodopsin genes. DNase footprinting indicated seven distinct regions that contain potential cis-acting elements. Sequences near the initiation site (-45/+41, basal region) were essential, but not sufficient, for rod-specific transcription. Two negative regulatory regions were found, one between -233 to -202, with no apparent similarity to known elements, and a second Ret-1-like CAAT (-136/-122) motif. Deletion of either sequence led to a 2-3-fold increase in expression levels, without a change in rod specificity. Sequences between -170 to -146, which contain an E-box motif, were necessary for high level expression in transgenic tadpoles but not in transient transfections. Sequences between -84 and -58, which contained an NRE-like consensus were found to be necessary for high level expression in both assays. Although expression levels were modulated by various proximal sequences in the rhodopsin promoter, none of the tested sequences were found to be necessary for rod specificity. Promoter constructs with a consensus BAT-1 sequence in conjunction with an NRE-like element upstream of the basal promoter directed low level green fluorescent protein expression in the central nervous system in transgenic tadpoles. These results suggest that rod cell-specific expression of rhodopsin is controlled by redundant elements in the proximal promoter.

Immediate upstream sequence of arrestin directs rod-specific expression in Xenopus.

Arrestins are a family of proteins that modulate G protein-coupled receptor responses with distinct arrestin genes expressed in rods and cones. To understand the regulatory mechanisms controlling rod-specific expression, the abundant Xenopus rod arrestin cDNA and a partial genomic clone, containing the immediate upstream region and amino terminus of the polypeptide, have been characterized. The deduced polypeptide has approximately 69% identity to other vertebrate rod arrestins. Southern blot analysis and polymerase chain reaction of intronic sequences demonstrated multiple alleles for rod arrestin. DNase I footprinting with retinal proteins revealed four major DNA binding sites in the proximal promoter, coinciding with consensus sequences reported in mammalian promoters. Purified bovine Crx homeodomain and mouse Nrl proteins protected a number of these sites. A dual approach of transient embryo transfections and transgenesis was used to locate transcriptional control sequences essential for rod-specific expression in Xenopus. Constructs containing -1287/+113 of 5' upstream sequence with or without intron 1 directed high level expression, specifically in rods. A construct containing only -287/+113 directed expression of green fluorescent protein solely in rod cells. These results suggest that the Crx and Nrl binding sites in the proximal promoter are the primary cis-acting sequences regulating arrestin gene expression in rods.

The efficacy of routine completion operative angiography in reducing the incidence of perioperative stroke associated with carotid endarterectomy.

Routine operative angiography was performed during a 14 1/2-year period ending June 1982, during which 603 consecutive carotid endarterectomies were performed. For the purpose of standardization, a functional classification of stroke in terms of severity was established: class I--minimal, class II--moderate, class III--marked, class IV--severe, and class V--coma or death. Patients were analyzed to determine the cause of the stroke, the severity of the stroke, and the efficacy of routine operative angiography in reducing the incidence of perioperative stroke caused by technical error. Perioperative stroke occurred in 18 patients (2.9%), with only one having been caused by technical error. Fifteen patients underwent revision of the endarterectomy before wound closure because of unsatisfactory operative angiography results. None of the patients developed permanent neurologic deficits. Permanent perioperative neurologic deficits resulted from embolization (six patients), hypertensive episodes with cerebral hemorrhage (three patients), conversion of ischemic to hemorrhagic infarcts (two patients), spontaneous thrombosis (one patient), clamp ischemia (two patients), and other factors (three patients). Nine patients died, two of myocardial infarction and seven of stroke, for a combined mortality and morbidity rate of 3.3%. There were three class II, five class III, two class IV, and eight class V strokes that were determined to be related to the procedure. In this series stroke may have been prevented in 15 patients who underwent revision of the endarterectomy because of an unacceptable technical error demonstrated on operative angiography.

Spatial disorientation and the Dyke-Davidoff-Masson syndrome.

A patient with Dyke-Davidoff-Masson Syndrome had a lifelong history of spatial disorientation and visual-spatial cognitive defects demonstrated by psychological tests. We suggest that the abnormalities of behavior and test performance may be related atrophic lesions demonstrated by pneumoencephalography and computerized axial tomography. We consider several explanations to account for the lack of compensation for these cognitive defects.

Amaurosis and primary reticulum cell sarcoma of the brain: clinicopathologic study of a case.

A 63-year-old man developed headache, left hemiparesis, and progressive visual loss. Craniotomy demonstrated reticulum cell sarcoma within the right temporal lobe. Necropsy revealed extensive involvement of optic nerves by primary RCS. Autopsy suggested that local compression of optic nerves by tumor cell infiltrates may produce atrophy in addition to sustained, generalized elevation of intracranial pressure.