Circular dichroism study of NaSCN effect on conformation of poly-L-lysine

Effects of NaSCN, urea and KCl on alpha, beta and random conformations of poly-L-lysine (PLL) in water at room temperature were examined and compared quantitatively on the basis of the rotational strength of maximal peak by means of circular dichroism (CD) measurement. Alpha and beta helical conformational change of PLL was markedly concentration dependent in both the cases of NaSCN and urea, but not KCl. Among these salts, the distortion potency of millimolar concentrations of NaSCN on both alpha and beta conformations was undoubtedly several hundred times stronger than for the other salts, showing a slightly lesser effect on the alpha conformation as compared with that on the beta helical one, while there was no significant effect on random conformations even in maximal salt concentrations. The concentration required to alter the peptide conformation was substantially smaller for urea than for KCl, but both urea and KCl exhibited more effectiveness on alpha than beta conformation in contrast to NaSCN throughout the respective concentrations.     

Behavioral characteristics of old female Japanese monkeys in a free-ranging group

Fourteen female Japanese monkeys of the Arashiyama-B group ranging in age from 11 to 29 years were observed to elucidate the behavioral characteristics of aging monkeys. A positive significant correlation was found between the occurrences of rest and age, and a negative significant correlation between the occurrences of auto-grooming and age. Younger female monkeys tended to be in contact with or in proximity to group members, while older female monkeys tended to spend much more time alone. As for the grooming interactions, younger female monkeys more often groomed others than did older female monkeys. Also, the former engaged in grooming more frequently than in being groomed, while the latter spent more time in being groomed than in grooming. The old female monkeys showed no marked decline in rank, but some of them were surpassed by their adult daughters.     

The Schizosaccharomyces pombe cdc6 gene encodes the catalytic subunit of DNA polymerase δ

The cdc6 mutants of Schizosaccharomyces pombe have been classified as being defective in progression through the G2 phase of the cell cycle. We cloned an S. pombe gene that could complement the temperature-sensitive growth of the cdc6-23 mutant. Unexpectedly, the cloned gene was allelic to pol3, which encodes the catalytic subunit of DNA polymerase δ. Integration mapping confirmed that cdc6 and pol3 are identical. The cdc6-23 mutant carries one amino acid substitution in the conserved N3 region of Pol3. Received: 17 October 1996 / Accepted: 19 November 1996     

Transient appearance of Ca-binding protein (spot 35-calbindin) in bronchial epithelial cells,thyroid parafollicular cells and thymic epithelial cells during the development of rats

Summary Tracheobronchial epithelium, thyroid organ, thymus, of the developing rats were examined by immunohistochemistry using anti-spot 35 calbindin-antiserum. At E 14, weak to moderate immunoreactivity for spot 35-calbindin was detected in the airway epithelia of the distal half of the trachea and the extrapulmonary bronchus. The immunoreactive cells increased in intensity at E 16–E 21, but decreased markedly after birth. These cells were non-ciliated cells and comprised a majority of the epithelial cells especially in the ventral/cartilaginous portion of the airway. They were characterized by microvilli, vacuoles, granular and agranular endoplasmic reticulum. Typical ciliated cells, which were much less numerous than the immunopositive non-ciliated cells, were immunonegative. In thyroid gland, calbindin-immunoreactive cells first appeared at E 18. They increased in number at E 20-P 1 and decreased gradually after P 7. These cells were the parafollicular cells characterized by numerous secretory granules and situated in close proximity to the basal surface of the follicular cells. In the thymus, immunoreactive cells appeared in the thymic medulla at E 20. They increased in number at P 1, but decreased gradually after P 7. They were stellate in shape and had vesicles, vacuoles, intermediate filaments and represented a subpopulation of thymic reticular epithelial cells. Such a transient appearance of spot 35-calbindin in these cells suggests that this protein may be involved in the regulation of differentiation or may be involved in the process of secretion during the limited developmental period.     

Induction of erythroid differentiation by cytoplast fusion in mouse erythroleukemia (Friend) cells

An intracellular activity, which is induced by dimethyl sulfoxide (DMSO) or hexamethylenebisacetamide (HMBA) and leads to erythroid differentiation in mouse Friend cells, was characterized by cell fusion between genetically marked intact cells and cytoplasts. For this, a procedure for rapid selection of cybrids was devised by sensitizing non-fused cells with oligomycin. We were able to demonstrate that cytoplasts derived from DMSO- (or HMBA)-treated cells trigger erythroid differentiation upon fusion with UV-irradiated cells. The activity in the cytoplasts remained only transiently and its induction was inhibited by biologically active phorbol esters or cycloheximide. The activity, however, was not induced in cytoplasts by directly treating them with DMSO (or HMBA). These results indicate that (1) the intracellular erythroid-inducing activity is located in cytoplasts, (2) it acts in trans and induces erythroid differentiation as a dominant factor and (3) its production requires de novo nuclear protein synthesis. The mechanisms of the induction of the intracellular activity and of how it triggers erythroid differentiation are discussed.     

Mutations in the tobacco mosaic virus 30-kD protein gene overcome Tm-2 resistance in tomato.

A resistance-breaking strain of tobacco mosaic virus (TMV), Ltb1, is able to multiply in tomatoes with the Tm-2 gene, unlike its parent strain, L. Nucleotide sequence analysis of Ltb1 RNA revealed two amino acid changes in the 30-kD protein: from Cys68 to Phe and from Glu133 to Lys (from L to Ltb1). Strains with these two changes generated in vitro multiplied in tomatoes with the Tm-2 gene and induced essentially the same symptoms as those caused by Ltb1. Strains with either one of the two changes did not overcome the resistance as efficiently as Ltb1, although increased levels of multiplication were observed compared with the L strain. Results showed that both mutations are involved in the resistance-breaking property of Ltb1. Sequence analysis indicated that another resistance-breaking strain and its parent strain had two amino acid changes in the 30-kD protein: from Glu52 to Lys and from Glu133 to Lys. The fact that the amino acid changes occurred in or near the well conserved regions in the 30-kD protein suggests that the mechanism of Tm-2 resistance may be closely related to the fundamental function of the 30-kD protein, presumably in cell-to-cell movement.     

The occurrence and frequency of 2n pollen in 2x, 4x,and 6x wild,tuber-bearing Solanum species from Mexico,and Central and South America

Summary The occurrence of 2n pollen-producing plants was investigated in 187 plant introductions (PIs) of 38 wild species of tuber-bearing Solanum. These 2x, 4x, and 6x species are from Mexico, and Central and South America. The determination of 2n pollen-producing plants was conducted using acetocarmine glycerol. Plants with more than 1% large-size pollen were regarded as 2n pollen-producing plants. 2n pollen-producing plants were identified in the following species: 10 out of 12 Mexican 2x species, seven of nine South American 2x species, seven of seven Mexican and Central American 4x species, five of five South American 4x species, and five of five Mexican 6x species. The frequency of 2n pollen-producing plants varied among species at the same ploidy level, but the range of frequency, generally between 2 and 10% among species, was similar over different ploidy levels. The general occurrence of 2n pollen in both 2x and polyploid species, which are evolutionarily related, is evidence that the mode of polyploidization in tuber-bearing Solanums is sexual polyploidization. Furthermore, the frequencies of 2n pollen-producing plants in autogamous disomic polyploid species were not markably different from those of their related diploid species. It is thought that the frequent occurrence of 2n gametes with autogamy tends to disturb the fertility and consequently reduce fitness of polyploids. Thus, we propose that the breeding behavior of polyploids and the occurrence of 2n gametes may be genetically balanced in order to conserve high fitness in polyploid species in tuberbearing Solanum.Paper No. 3114 from the Laboratory of Genetics. Research supported by the College of Agriculture and Life Sciences; International Potato Center; USDA, SEA, CGRO 84-CRCR-1-1389; and Frito Lay, Inc.     

Determinants of Slow Walking Speed in Ambulatory Patients Undergoing Maintenance Hemodialysis

Walking ability is significantly lower in hemodialysis patients compared to healthy people. Decreased walking ability characterized by slow walking speed is associated with adverse clinical events, but determinants of decreased walking speed in hemodialysis patients are unknown. The purpose of this study was to identify factors associated with slow walking speed in ambulatory hemodialysis patients. Subjects were 122 outpatients (64 men, 58 women; mean age, 68 years) undergoing hemodialysis. Clinical characteristics including comorbidities, motor function (strength, flexibility, and balance), and maximum walking speed (MWS) were measured and compared across sex-specific tertiles of MWS. Univariate and multivariate logistic regression analyses were performed to examine whether clinical characteristics and motor function could discriminate between the lowest, middle, and highest tertiles of MWS. Significant and common factors that discriminated the lowest and highest tertiles of MWS from other categories were presence of cardiac disease (lowest: odds ratio [OR] = 3.33, 95% confidence interval [CI] = 1.26–8.83, P<0.05; highest: OR = 2.84, 95% CI = 1.18–6.84, P<0.05), leg strength (OR = 0.62, 95% CI = 0.40–0.95, P<0.05; OR = 0.57, 95% CI = 0.39–0.82, P<0.01), and standing balance (OR = 0.76, 95% CI = 0.63–0.92, P<0.01; OR = 0.81, 95% CI = 0.68–0.97, P<0.05). History of fracture (OR = 3.35, 95% CI = 1.08–10.38; P<0.05) was a significant factor only in the lowest tertile. Cardiac disease, history of fracture, decreased leg strength, and poor standing balance were independently associated with slow walking speed in ambulatory hemodialysis patients. These findings provide useful data for planning effective therapeutic regimens to prevent decreases in walking ability in ambulatory hemodialysis patients.     

Rabbit autoantibodies to actin induced by immunization with modified homologous actins

Actin is a major antigen involved in the reaction of smooth muscle antibody positive sera from patients with chronic active hepatitis. In the present study, actin extracted from rabbit skeletal muscle was denatured by sodium dodecyl sulfate and was immunized into the rabbit, a homologous animal for actin. The rabbits, thus immunized, produced antibodies reactive with actins of homologous and heterologous animals. In addition, the antibodies showed reactivity with autologous actin. It indicates that the denatured homologous actin is capable of terminating immunological tolerance to actin and induces formation of autoantibody to rabbit actin. This phenomenon may be implicated in the occurrence of anti-actin antibody in sera from patients with chronic liver disease and several other diseases.