W Loewenstein | PubMed Health

PubMed1989

Enhancement of gap junctional communication by retinoids correlates with their ability to inhibit neoplastic transformation.

Retinoids that cause inhibition of methylcholanthrene-induced neoplastic transformation of C3H/10T1/2 cells enhance gap-junctional communication in carcinogen-initiated cells. Dose-response studies using retinoids of diverse structures and potency demonstrated a good correlation between these two events. Junctional permeability was enhanced by retinol and tetrahydrotetramethylnaphthalenyl propenylbenzoic acid (TTNPB) at concentrations from 10(-10) to 10(-6) M, and by retinoic acid between 10(-8) and 10(-6) M, the same concentrations that inhibited neoplastic transformation. Retinoic acid inhibited permeability at 10(-10) M, at which concentration transformation was enhanced. Retinoids caused similar alteration sin communication in parental 10T1/2 cells. Communication between initiated and 10T1/2 cells was not influenced by TTNPB. The tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) inhibited junctional communication in initiated cells, in 10T1/2 cells and between these two cell lines. After repeated exposure of 10T1/2 cells to TPA only retinoid-enhanced communication was blocked; in contrast, basal communication became refractory. It is proposed that much of the chemopreventive action of retinoids can be explained by the enhanced junctional communication of growth regulatory signals.

Animals↗

PubMed1986

Peripheral nerve conduction studies in passively addicted neonates.

Neurologic signs dominate the manifestations of the neonatal abstinence syndrome (NAS). To help delineate this dysfunction, peripheral nerve conduction studies (NCS) were made in 25 neonates born to methadone-maintained mothers; 12 of the mothers abused other controlled substances concomitantly. Median and common peroneal motor nerve conduction velocities (NCV) in these infants were normal, both at three to seven days and three to four weeks of age, and were unaffected by maternal drug intake pattern, severity of neonatal abstinence symptoms, treatment with either camphorated tincture of opium or phenobarbital, intrauterine growth retardation, or abstinence-associated seizurer. Electromyographic findings were normal in 21/23 infants; two others showed minimal partial denervation, characterized by fibrillations and positive sharp waves. NCV in the NAS may enhance gestational age assessment and therefore increase validity of neurobehavioral follow-up. Our studies continue to point to a central rather than a peripheral motor dysfunction exhibited by passively addicted infants at birth, which may persist on two-to-five-year follow-up.

Electromyography↗