Altered thyroid hormone binding to plasma lipoproteins in the syndrome of resistance to thyroid hormones.

Lipoproteins, especially HDL, are carriers of a small fraction of the thyroid hormones in plasma and participate in the intracellular transport of T4. In previous work we showed that a brief period of hypothyroidism alters the hormone distribution among the lipoproteins, causing a decrease in VLDL and LDL binding despite a relative increase in VLDL and LDL cholesterol, an increase in HDL binding, and a reversal of T4 and T3 binding to the smallest HDL size subgroup. The present study of three patients with thyroid hormone resistance and largely compensated hypothyroidism showed thyroid hormone distribution that differed markedly from both normal and hypothyroid subjects. The most striking difference was a much lower binding of both T4 and T3 to HDL and a much higher binding to LDL. If confirmed in a larger group of patients, this might serve as a marker for thyroid hormone resistance.     

Microvascular anastomosis: vascular cuff technique

A technique is described for reinforcing and sealing a microvascular anastomosis by using a detached vessel segment as a cuff around the anastomosis. This may allow fewer microvascular sutures to be used. This would allow a simpler, less traumatic, and more rapid repair and may allow "more vessels to be repaired by more people."     

The actin domain of Gardner-Rasheed feline sarcoma virus inhibits kinase and transforming activities.

The transforming gene product, P70gag-actin-fgr, of Gardner-Rasheed feline sarcoma virus (GR-FeSV) is a single polypeptide composed of regions derived from cellular and viral genes. Gamma actin and c-fgr genes are the two known cellular components of the GR-FeSV genome. In the present study, sequences representing each cell-derived gene were deleted and the resulting constructs were tested for transforming activity by transfection of NIH 3T3 cells. Constructs lacking a portion of the c-fgr proto-oncogene failed to induce focus formation, demonstrating the essential nature of this component for GR-FeSV oncogenic activity. In contrast, the construct lacking the actin domain was more active than GR-FeSV DNA in transformation assays. Protein specified by the actin deletion mutant possessed a 2.4-fold greater specific protein-tyrosine kinase activity compared with that of the wild-type gene product. Furthermore, the actin domain had no detectable effect on the ability of the fgr kinase to associate with cytoskeleton or to phosphorylate unique cellular proteins on tyrosine. Our findings demonstrate that the actin domain inhibits focus formation and impairs protein-tyrosine kinase activity.     

Whole-cell recording of neuroblastoma x glioma cells during downregulation of a major substrate, 80K/MARCKS,of protein kinase C

Summary Differentiated neuroblastoma cells exhibit both the delayed rectifier potassium current (I _K) and the M-current (I _M). The present study was designed to determine the roles of protein kinase C (PKC) and of the calmodulin-binding protein 80K/MARCKS, a prominent substrate for PKC and possible regulator of these currents. Neuroblastoma x glioma (NG108-15) hybrid cells transfected with m1 muscarinic receptors were grown with 1% fetal bovine serum (FBS) without the prostaglandin E₁ (PGE₁) and isobutylmethylxanthine (IBMX) usually added in preparation for electrophysiological studies. Under these conditions, the usual pleomorphism was largely abolished, leaving two populations of small cells with stellate and spherically symmetrical geometries. Whole-cell patch clamping indicated that the two cell types had identical electrophysiological properties, displaying: I _k, a small current through a T-like Ca²⁺ channel, and no M-current.Stimulation with carbachol shifted the distribution of cells to a more stellate morphology within 24 hr and later (after 48 hr) reduced the PKC substrate 80K/MARCKS by 22±7%. In contrast to the stimulation of I _k observed with cardiac cells, PKC activation produced only a small inhibition of I _k, which was independent of carbachol pretreatment. Thus, PKC and 80K/MARCKS can be dissociated from the regulation of I _k in neuroblastoma cells.Supported in part by research grants from the National Institutes of Health (DK-40145 and EY-08343) and from the U.K. Medical Research Council.We thank Dr. Peter J. Parker for his generous gift of PKC, and Yvonne Vallis for her skillful assistance with the cultures and harvesting of the NG108-15 transfected cells.     

Phenylpropanoid defence responses in transgenic Lotus corniculatus: II. Modelling plant defence responses in transgenic root cultures using thiol and carbohydrate elicitors

Transformed root cultures of Lotus corniculatus L. cv. Leo weretreated with a range of thiol and carbohydrate elicitors. Boththiol reagents and fungal carbohydrate preparations resultedin an increase in the activity of phenylalanine ammonia lyase(PAL) in a concentration-dependent manner. One representativethiol elicitor, glutathione (GSH), and one fungal elicitor,derived from Rhynchosporium orthosporum autoclaved cell walls(Ro), were analysed in more detail. Both elicitors induced thetransient accumulation of vestitol, an isoflavan phytoalexin,in tissue and in culture medium. Treatment of Lotus root cultureswith the Ro elicitor resulted in a more rapid initial accumulationof this end product when compared with GSH, however, sativan(the 2–methoxy ester of vestitol) previously reportedto co-accumulate in Lotus leaves was only detected followingelicitation with high concentrations of GSH. Ro and GSH elicitorsalso induced the accumulation of a number of other phenylpropanoidcompounds putatively identified as chalcones. The addition ofthiol and carbohydrate elicitors to Lotus root cultures alsoresulted in characteristic changes in root morphology. Glutathione,in particular, resulted in the inhibition of root growth dueto differential damage of meristem cells. Key words: Lotus corniculatus, hairy roots, elicitors, phytoalexins.