Specification of chimeric flowering shoots in wild-type Arabidopsis

Within wild-type Arabidopsis populations, a subset of the plants were found to have a single chimeric shoot on their primary shoot axes. The chimeric shoots were located below the lowest primary-axis flower; and they exhibited features of both flowers and paraclades (lateral flowering shoots). Morphological analyses of chimeric shoots indicated that they developed from single primordia. In each chimeric shoot, the side furthest from the apical meristem was specified as 'flower'--while the side closest to the meristem was specified as 'paraclade'--suggesting that a stimulus from outside the apical meristem can directly induce primordia to develop as flowers. It is concluded that the development of the teratological chimeric shoots resulted from the overlap of the vegetative and floral specification processes within single primordia.     

Passive smoke exposure and otitis media in the first year of life. Group Health Medical Associates

OBJECTIVE: This study examined, in a health maintenance organization population of children, the associations between parents' smoking and otitis media (OM) in their children while controlling for other known risk factors. METHODS: Healthy newborns (1246) in a large health maintenance organization were enrolled at birth, and 1013 (81%) were followed prospectively for the first year of life. Their medical records were reviewed for the diagnosis of otitis media. Information on risk factors for recurrent OM (ROM) was collected, including a number of variables related to parental smoking. RESULTS: After controlling for other known risk factors for ROM including gender, day care, other siblings in the home, parental history of hay fever, and method of feeding, it was found that heavy maternal smoking of 20 or more cigarettes per day was a significant risk factor for ROM but not for nonrecurrent otitis. Heavy maternal smoking was associated with a threefold risk for ROM if the infant weighed less than the mean at birth (3.5 kg) after controlling for other risk factors. No association was found with paternal smoking. CONCLUSIONS: Heavy maternal smoking is a significant risk factor for ROM in the first year of life. This smoking effect seems to be stronger among infants of lower birth weight.     

Annotation: the impact of puberty

Tau Isolated from paired helical filaments, aberrant structures that appear in Alzheimer disease (AD) patients' brains, show at least two posttranslational modifications: phosphorylation (Grundke-Iqbal et al., 1986; Ihara et al., 1986) and glycation (Ledesma et al., 1994; Yan et al., 1994). To test whether these modifications could affect the capacity of tau to self-aggregate, recombinant tau was phosphorylated and glycated, and its capacity to form polymers analyzed. Our results indicate that on phosphorylation and glycation, the capacity of tau to form aggregates increases, and that glycation of tau could stabilize the assembled polymers and could facilitate formation of bundles from these polymers.     

Peripheral nervous system of the ticks, Amblyomma tuberculatum Marx and Argas radiatus Railliet (Acari: Ixodoidea)

The peripheral nervous system of an ixodid and an argasid tick include the following components: (1) paired optic, cheliceral and pedipalpal nerves and unpaired stomodeal nerve arising from the pre-esophageal portion of the central nervous system (synganglion); (2) 4 pairs of pedal nerve trunks (each with appendicular and hemal branches) and 4 major pairs of opisthosomal nerves (including the paraspiracular, genital, postlateral-myosomal, and ano-myosomal nerves); and (3) the lateral "sympathetic" plexuses formed by contributions of hemal nerves arising from pedal ganglia and from the paraspiracular nerves. The salivary glands are multiply innervated by 4 pairs of nerves. The 1st pair arise from the pedipalpal nerves, the 2nd and 3rd from the lateral sympathetic plexuses, and the 4th from the paraspiracular nerves. Portions of the integument and the majority of non-appendicular muscles are innervated by various fine nerves arising from the lateral sympathetic plexuses and from the 4 pairs of opisthosomal nerves.     

Phosphotyrosine 1173 mediates binding of the protein-tyrosine phosphatase SHP-1 to the epidermal growth factor receptor and attenuation of receptor signaling

The protein-tyrosine phosphatase SHP-1 binds to and dephosphorylates the epidermal growth factor receptor (EGFR), and both SH2 domains of SHP-1 are important for this interaction (Tenev, T., Keilhack, H., Tomic, S., Stoyanov, B., Stein-Gerlach, M., Lammers, R., Krivtsov, A. V., Ullrich, A., and B?hmer, F. D. (1997) J. Biol. Chem. 272, 5966-5973). We mapped the EGFR phosphotyrosine 1173 as the major binding site for SHP-1 by a combination of phosphopeptide activation, phosphopeptide competition, and receptor YF mutant analysis. Mutational conversion of the EGFR sequence 1171-1176 AEYLRV into the high affinity SHP-1 binding sequence LEYLYL of the erythropoietin receptor (EpoR) led to a highly elevated SHP-1 binding to the mutant EGFR (EGFR1171-1176EpoR) and in turn to an enhanced dephosphorylation of the receptor. SHP-1 expression interfered with EGF-dependent mitogen-activated protein kinase stimulation, and this effect was more pronounced in case of EGFR1171-1176EpoR. Reduced SHP-1 binding to the EGFR Y1173F mutant resulted in a reduced receptor dephosphorylation by coexpressed SHP-1 and less interference with EGF-dependent mitogen-activated protein kinase stimulation. The effects of receptor mutations on SHP-1 binding were, however, stronger than those on receptor dephosphorylation by SHP-1. Therefore, receptor dephosphorylation may be the result of the combined activity of receptor-bound SHP-1 and SHP-1 bound to an auxiliary docking protein.     

Cloning and characterization of RLPK, a novel RSK-related protein kinase

A novel protein kinase whose activity can be stimulated by mitogen in vivo was cloned and characterized. The cDNA of this gene encodes an 802-amino acid protein (termed RLPK) with the highest homology (37% identity) to the two protein kinase families, p90(RSK) and p70(RSK). Like p90(RSR), but not p70(RSK), RLPK also contains two complete nonidentical protein kinase domains. RLPK mRNA is widely expressed in all human tissues examined and is enriched in the brain, heart, and placenta. In HeLa cells, transiently expressed epitope-tagged RLPK can be strongly induced by epidermal growth factor, serum, and phorbol 12-myristate 13-acetate, but only moderately up-regulated by tumor necrosis factor-alpha and other stress-related stimuli. The activity of RLPK stimulated by epidermal growth factor was not inhibited by several known protein kinase C inhibitors nor by rapamycin, a known specific inhibitor for p70(RSK), but could be inhibited by herbimycin A, a tyrosine kinase inhibitor, and partially inhibited by PD98059 or SB203580, inhibitors for the mitogen-activated protein kinase pathways. Recombinant RLPK possesses high phosphorylation activity toward histone 2B and the S6 peptide, RRRLSSLRA. Although purified recombinant RLPK can be phosphorylated by ERK2 and p38alpha in vitro, its activity is not affected by this phosphorylation. Moreover, the treatment of RLPK with acid phosphatase did not reduce its in vitro kinase activity. These data suggest that RLPK is structurally similar to previously isolated RSKs, but its regulatory mechanism may be distinct from either p70(RSK) or p90(RSK)s.     

Relationship between p21 expression and mutation of the p53 tumor suppressor gene in normal and malignant ovarian epithelial cells

In many cell types, p53-mediated growth inhibition is dependent on induction of p21, which is an inhibitor of cyclin-dependent kinases that are required for cell cycle progression. Failure of mutant p53 proteins to transactivate p21 may lead to uncontrolled proliferation. Because many ovarian cancers have mutations in the p53 gene, we examined p21 levels in normal and malignant ovarian epithelial cells to determine whether p21 expression is dependent on wild-type p53. Normal ovarian epithelial cells and two ovarian cancer cell lines with wild-type p53 expressed readily detectable levels of p21, whereas in p53 null and mutant cell lines, expression of p21 was diminished strikingly. A correlation between the status of the p53 gene and p21 expression also was noted in 23 primary epithelial ovarian cancers. Normal levels of p21 RNA were seen in 4/7 (57%) cancers with wild-type p53, whereas 14/16 (88%) cancers with mutant p53 had reduced p21 expression (P < 0.05). In addition, we found that lambda-irradiation of normal and malignant ovarian epithelial cells with wild-type, but not mutant, p53 resulted in induction of p21. These data are suggestive that induction of p21 is a feature of p53-mediated growth inhibition in normal ovarian epithelial cells. Conversely, mutation of the p53 gene in ovarian cancers usually is associated with decreased p21 expression. The lack of an absolute correlation between p21 expression and the status of the p53 gene in ovarian cancers is consistent with other studies that have suggested that p21 may also be regulated by p53-independent pathways.     

Trauma patients 75 years and older: long-term follow-up results justify aggressive management

BACKGROUND: Long-term survival rate and functional status after trauma for one of the fastest growing segments of the population, patients 75 years and older, is poorly documented. METHODS: Trauma patients 75 years and older who were discharged from our Level I trauma center between June 1988 and July 1992 (n = 279) were contacted by mail or phone. Public death records were used to identify patients who had died. A stepwise logistic regression analysis was performed to determine predictors of poor outcome (death within 6 months). Main outcome measures included mortality and self-assessed functional status. RESULTS: A minimum 4-year follow-up was obtained for 81% of the 279 study patients. The mean follow-up period was 5.4 +/- 1.1 years. Mean age at time of injury was 81 +/- 5 years (range, 75-101 years); mean Injury Severity Score was 9.4 +/- 7.7. At follow-up, 132 patients (47%) had died, 93 patients (33%) were contacted, and 54 patients (19%) could not be located. Twelve percent of patients survived less than 6 months after discharge. Poor survival was predicted by preexisting diseases (dementia, p = 0.001; hypertension, p = 0.02; and chronic obstructive pulmonary disease, p = 0.05) and not by age or severity of injury. The mean age of patients still living was 85 +/- 3.9 years (range, 79-99 years), and 77 of 93 patients were living in an independent setting (33 alone, 44 with spouse or family); of these, 57% reported no difficulties in performing 12 of 14 activities of daily living. CONCLUSION: Despite higher than expected mortality after discharge, aggressive management of trauma patients 75 years and older is justified by the favorable long-term outcome.     

Renal excretion of sodium in individuals with stabilized renal graft function

In subjects with a transplanted kidney frequently tubular functions are impaired even when the glomerular filtration is within the normal range. In the present work the authors are dealing in more detail with the problem of tubular sodium reabsorption in the transplanted kidney. The purpose of the investigation was to assess to what extent these changes can be explained as the consequence of adaptational changes due to reduction of the number of nephrons and whether these changes have to be taken into consideration in the differential diagnosis of acute changes of graft function. The glomerular filtration rate (GF) was assessed on the basis of polyfructosan clearance, fractional sodium and potassium excretion (FENa and FEK) in a group of 12 subjects with a stabilized function of a transplanted kidney (group A), in 11 subjects after nephrectomy in healthy donors for transplantation (group B) and in 27 subjects after nephrectomy indicated for a pathological process in one kidney (group C). The mean values of GFR were as follows: Group A: 1.21 (+/- 0.19)ml/s/1.73 sq.m Group B: 1.19 (+/- 0.17)ml/s/1.73 sq.m Group C: 1.24 (+/- 0.21)ml/s/1.73 sq.m The mean values of GFR in different groups did not differ significantly. The mean values of FENa in different groups were as follows: Group A: 3.02 (+/- 1.59)% Group B: 2.05 (+/- 0.77)% Group C: 2.01 (+/- 1.17)% The mean value of FENa in group A was significantly higher than the mean value in group B (p < 0.01) and in group C (p < 0.01). The assembled findings support the idea that reduced tubular sodium reabsorption in the transplanted kidney (with a stabilized value of GFR) cannot be explained only as a manifestation of adaptation of tubular function as a result of the reduced number of functioning nephrons. The persisting osmotic sodium diuresis in the transplanted kidney must be viewed from the aspect of possibly impaired water preservation and the development of dehydration associated with a drop of GFR and must be differentiated from rejection.