We have characterized the biosynthesis and intracellular transport of a membrane glycoprotein, designated plgp57, which is found predominantly in the prelysosome compartment (PLC) of Madin-Darby bovine kidney cells. In pulse-chase experiments, plgp57 was found to be initially synthesized as a 35 kDa precursor which was modified to yield a diffuse approximately 57 kDa mature form. Digestion with endoglycosidase H (endo H) demonstrated that the 35 kDa precursor contained three endo H-sensitive, high mannose-type oligosaccharides which became modified to endo H-resistant, complex-type sugars on the approximately 57 kDa mature form. Labelling cells in the presence of tunicamycin and treatment of the 35 kDa precursor with endo H revealed that plgp57 has a core protein of 24 kDa to which three N-asparagine-liked oligosaccharides are attached. Other experiments indicated that plgp57 could be differentially glycosylated on a common 24 kDa core protein in different cell types. The half-lives of the glycosylated and non-glycosylated forms of plgp57 were approximately 18 and approximately 13 h, respectively. Glycosylated and non-glycosylated plgp57 exhibited similar steady-state intracellular distributions, indicating that targeting of plgp57 to the PLC does not require carbohydrate address markers. Pulse-labeling of cells followed by organelle fractionation at various chase times revealed a t1/2 = approximately 1 h for the transit of newly synthesized plgp57 to the PLC. Finally, amino terminal sequencing of plgp57 revealed the similarity of this protein to the CD63/ME491 family of membrane glycoproteins.

Amino Acid Sequence↗

PubMedDate not supplied

Electrophysiological findings in poliomyelitis patients at the subacute phase.

Electrodiagnostic tests-needle EMG, nerve conduction and somatosentory evoked potential (SEP) studies of the upper and the lower limbs were performed in three patients during the subacute phase of poliomyelitis. Although poliomyelitis is traditionally considered a "pure motor" disease, involvement of the sensory system was demonstrated by prolonged sensory nerve conduction and by delayed latencies and amplitude asymmetries of SEPs obtained from the lower limbs. Sensory deficit in poliomyelitis is well known to exist during the acute phase of illness. The present report describes the electrophysiological findings in patients during the subacute phase, several months after onset of illness. Sensory nerve action potentials and sensory evoked potentials were abnormal, especially those elicited by lower limb stimulation although the patients had no overt signs of sensory loss at that time. The associated EMG findings are described, and the probable pathologic changes of the motor unit are discussed.

Adolescent↗

PubMedDate not supplied

Evaluation of EMG examination as an indicator of worker susceptibility to organophosphates exposure.

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Adult↗