Inhibitory effect of membrane active compounds on the uptake of 14C-alpha-aminoisobutyric acid (AIB) in cultured chick embryo liver cells.

High concentrations of beta-adrenoceptor blocking drugs with membrane active properties and of the membrane active compounds quinidine and lidocaine inhibit the uptake of ∝-aminoisobutyric acid by chick embryo liver cells in culture. Beta-adrenoceptor blockers without membrane active properties were without effect. These results are in accordance with previous findings which showed partial inhibition of incorporation of amino acids into proteins caused by membrane active drugs in this system.     

Immunofluorescent studies of epidermal protein during UV induced carcinogenesis.

Previous studies with agar diffusion technique demonstrated that antibodies produced in rabbits by injection of urea extractable proteins of rat cornfied cells cross react with proteins extracted from normal epidermis of hairless mice using the same technique. In the present study we investigated by indirect immunofluorescence microscopy the immunoreactivity of epidermal proteins in normal and ultraviolet light (UVB) induced hyperplasia and malignant transformation. Reactivity to the antibody was seen over the entire epidermis of nontreated skin and hypertrophied epidermis which occurred at 6-8 weeks after initiation of UVB irradiation. However, the reactivity diminished when malignant changes took place in the epidermal cells. Almost complete disappearance of the immunoresponse was observed in squamous cell carcinoma produced by further UVB radiation. These results suggest that the reactivity of this urea extractable protein serves as an additional immunologic marker for normal epidermal cells. Alterations in the immunoreactivity parallels UVB induced carcinogenesis.     

Advances in salt tolerance

Summary Advances in and prospects for the development of salt tolerant crops are discussed. The genetic approach to the salinity problem is fairly new, but research has become quite active in a short span of time. Difficulties and opportunities are outlined. Salinity varies spatially, temporally, qualitatively, and quantitatively. In addition, the responses of plants to salt stress vary during their life cycle. Selection and breeding, including the use of wide crosses, are considered the best short-term approaches to the development of salt tolerant crops, but the new biotechnological and molecular biological techniques will make increasingly important contributions. Cooperation is called for among soil and water scientists, agronomists, plant physiologists and biochemists, cytologists, and plant geneticists, breeders, and biotechnologists. Given such cooperation and adequate support for these endeavors, the potential for increasing productivity in salt-affected areas can be realized.     

Influx of na, k, and ca into roots of salt-stressed cotton seedlings : effects of supplemental ca

High Na⁺ concentrations may disrupt K⁺ and Ca²⁺ transport and interfere with growth of many plant species, cotton (Gossypium hirsutum L.) included. Elevated Ca²⁺ levels often counteract these consequences of salinity. The effect of supplemental Ca²⁺ on influx of Ca²⁺, K⁺, and Na⁺ in roots of intact, salt-stressed cotton seedlings was therefore investigated. Eight-day-old seedlings were exposed to treatments ranging from 0 to 250 millimolar NaCl in the presence of nutrient solutions containing 0.4 or 10 millimolar Ca²⁺. Sodium influx increased proportionally to increasing salinity. At high external Ca²⁺, Na⁺ influx was less than at low Ca²⁺. Calcium influx was complex and exhibited two different responses to salinity. At low salt concentrations, influx decreased curvilinearly with increasing salt concentration. At 150 to 250 millimolar NaCl, ⁴⁵Ca²⁺ influx increased in proportion to salt concentrations, especially with high Ca²⁺. Potassium influx declined significantly with increasing salinity, but was unaffected by external Ca²⁺. The rate of K⁺ uptake was dependent upon root weight, although influx was normalized for root weight. We conclude that the protection of root growth from salt stress by supplemental Ca²⁺ is related to improved Ca-status and maintenance of K⁺/Na⁺ selectivity.     

Identification and characterization of a Ca2+-calmodulin-sensitive cyclic nucleotide phosphodiesterase in a human lymphoblastoid cell line.

This study examines the pattern and regulatory properties of cyclic nucleotide phosphodiesterases in a human lymphoblastoid B-cell line (RPMI 8392) established from a patient with acute lymphocytic leukaemia. In this cell line, phosphodiesterase activity measured at 0.25 microM-cyclic AMP is approx. 7-fold greater than that in isolated human peripheral-blood lymphocytes, and 16% of the phosphodiesterase activity in RPMI 8392 cells is associated with particulate fractions. Phosphodiesterase activity in crude fractions of this cell line is reproducibly stimulated by about 60-80% by Ca2+-calmodulin. In the presence of 20 nM-calmodulin, half-maximal stimulation occurs at 0.7 microM-Ca2+. The cytosolic phosphodiesterase activity of RPMI 8392 cells is separated into two forms by DEAE-Sephacel chromatography. The first form is eluted at approx. 0.2 M-sodium acetate, catalyses the hydrolysis of both cyclic AMP and cyclic GMP, and is stimulated 3-fold by Ca2+-calmodulin. This form exhibits non-linear kinetics for cyclic AMP in the absence of calmodulin, with extrapolated Km values of 0.8 and 4 microM, and non-linear kinetics in the presence of calmodulin, with extrapolated Km values of 0.5 and 1 microM. The Vmax. values are increased approx. 3-fold by calmodulin. The second form is eluted at approx. 0.6 M-sodium acetate, is specific for cyclic AMP, and insensitive to stimulation by Ca2+-calmodulin. The Ca2+-calmodulin-sensitive phosphodiesterase from the DEAE-Sephacel column can be adsorbed to a calmodulin-Sepharose affinity column and eluted with EGTA. This enzymic activity can also be immunoprecipitated by a monoclonal antibody directed against a calmodulin-bovine heart phosphodiesterase complex. This study documents the existence of Ca2+-calmodulin-sensitive phosphodiesterase in a cultured lymphoblastoid cell line derived from a leukaemic patient.     

Ontogenetic changes in adenylate cyclase, cyclic AMP phosphodiesterase and calmodulin in chick ventricular myocardium.

The activities of cyclic AMP phosphodiesterase (3',5'-cyclic nucleotide 5'-nucleotidohydrolase, EC 3.1.4.17) and adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and calmodulin content during development of chick ventricular myocardium were determined. The specific activity of cyclic AMP phosphodiesterase was relatively low in early embryos, increased during embryogenesis by about 4-fold to reach highest values just before hatching, and then decreased by approx. 30% within 1 week after hatching. In contrast, adenylate cyclase did not change during embryonic development, but increased by approx. 50% within 1 week after hatching. Calmodulin content remained constant at 9 micrograms/g wet wt. during embryonic development and decreased to 6 micrograms/g wet wt. by 1 week after hatching. DEAE-Sephacel chromatography of chick ventricular supernatant revealed a single major form of cyclic nucleotide phosphodiesterase activity in early embryonic (9-day E) and hatched (6-day H) chicks. This enzyme form was eluted at approx. 0.27 M-sodium acetate, hydrolysed both cyclic AMP and cyclic GMP, and was sensitive to stimulation by Ca2+-calmodulin, with an apparent Km for calmodulin of approx. 1 nM. In contrast, ventricular supernatant from late-embryonic (18-day E) chicks contained two forms of phosphodiesterase separable on DEAE-Sephacel: the same form as that seen at other ages, plus a cyclic AMP-specific form which was eluted at approx. 0.65 M-sodium acetate and was insensitive to stimulation by Ca2+-calmodulin. The ontogenetic changes in cyclic AMP phosphodiesterase activity in chick ventricular myocardium are consistent with reported ontogenetic changes in the steady-state contents of cyclic AMP in this tissue and suggest that this enzyme may be responsible for the changes that occur in this nucleotide during development of chick myocardium.     

The mouse homolog of the human amyloid beta protein (AD-AP) gene is located on the distal end of mouse chromosome 16: further extension of the homology between human chromosome 21 and mouse chromosome 16

The human amyloid beta protein is the major constituent of the brain amyloid plaques found in Alzheimer disease. The gene that encodes this protein is located on chromosome 21, and individuals with Down syndrome (trisomy 21) also exhibit an early onset form of Alzheimer disease. We have used the cloned human amyloid beta protein gene and a panel of somatic cell hybrids to map the location of the mouse homolog of this gene. We report here that the mouse gene is located on chromosome 16 within the region 16C3----ter, in common with three other genes which map within the Down syndrome region of human chromosome 21.     

The highly modified membrane of cornified cells in stratified squamous epithelia: A comparison of heterogenous deposits in keratinized and nonkeratinized epithelia

Summary The chemical nature of the thickened plasma membrane of cornified cells in stratified squamous epithelium was investigated in comparison with that in noncornified epithelium. Localizations of transglutaminase, molecular weight 92000 daltons, and detection of epidermal cysteine proteinase inhibitor were effected with a monoclonal antibody and a monospecific rabbit anti-inhibitor immunoglobulin, respectively, directed to the antigens. N-(7-dimethylamino-4-methylcoumarinyl) maleimide was used to demonstrate S-S cross-linking. In all keratinizing epithelia, the enzyme and inhibitor were deposited on membranes of granular cells. S-S bonds were formed in cornification with the appearance of electron-dense material by the inner leaflet. Both enzyme and inhibitors occurred on the corneal epithelium, but S-S linkage and the thickened plasma membrane did not form even at the last stage of maturation. On the other hand, the internal vaginal epithelium in the proestrous stage without keratinization contained the enzyme, but neither inhibitor nor S-S linkage. Both antigens and S-S bonds were detected when keratinization proceeded during estrus. The staining patterns in the epithelium near the vaginal introitus were identical to those in the skin. Cuboidal and simple epithelia exhibited none of those constituents. The findings indicated that heterogenous components contribute to modification of the plasma membrane of cornified cells, but S-S cross-linkages are associated exclusively with formation of the ultrastructurally unique membrane structure. In addition, findings suggested hormonal regulation in the chemical modification of the membrane in estrogen-sensitive internal vaginal epithelium.     

Transfer of granulomatous inflammation with nonviable preparations of schistosome granulomas in naive mice

Hepatic granulomas of euthymic (nu/+) mice infected with Schistosoma mansoni were freeze-dried or freeze-thawed 3 times and transplanted subcutaneously into naive nu/+ and athymic (nu/nu) mice. The grafted sites, studied histologically, showed formation of organized granulomas in nu/+ mice similar to donor granulomas as observed after grafting of freshly isolated granulomas. On the other hand, in nu/nu mice, the nonviable transplants elicited small and disorganized granulomas, like hepatic granulomas in nu/nu mice with schistosomiasis, but different from fresh nu/+ transplants in nu/nu skin. The findings indicate viable cells are not required for transfer of granulomatous reactions, but T cells are needed for full expression.     

A new moderately repetitive DNA sequence family of novel organization.

In cloning adenovirus homologous sequences, from a human cosmid library, we identified a moderately repetitive DNA sequence family consisting of tandem arrays of 2.5 kb members. A member was sequenced and several non-adjacent, 15-20 bp G-C rich segments with homology to the left side of adenovirus were discovered. The copy number of 400 members is highly conserved among humans. Southern blots of partial digests of human DNA have verified the tandem array of the sequence family. The chromosomal location was defined by somatic cell genetics and in situ hybridization. Tandem arrays are found only on chromosomes 4 (4q31) and 19 (q13.1-q13.5). Homologous repetitive sequences are found in DNA of other primates but not in cat or mouse. Thus we have identified a new family of moderately repetitive DNA sequences, unique because of its organization in clustered tandem arrays, its length, its chromosomal location, and its lack of homology to other moderately repetitive sequence families.