Light-Regulated Gravitropism in Seedling Roots of Maize

Red light-induced changes in the gravitropism of roots of Zea mays variety Merit is a very low fluence response with a threshold of 10⁻⁹ moles per square meter and is not reversible by far red light. Blue light also affects root gravitropism but the sensitivity of roots to blue is 50 to 100 times less than to an equal fluence of red. In Z. mays Merit we conclude that phytochrome is the sole pigment associated with light-induced changes in root gravitropism.     

Protein translocation into Escherichia coli membrane vesicles is inhibited by functional synthetic signal peptides

A synthetic peptide corresponding to the signal sequence of wild type Escherichia coli lambda-receptor protein (LamB) inhibits in vitro translocation of precursors of both alkaline phosphatase and outer membrane protein A into E. coli membrane vesicles (half-maximal inhibition at 1-2 microM). By contrast, the inhibitory effect was nearly absent in a synthetic peptide corresponding to the signal sequence from a mutant strain that harbors a deletion mutation in the LamB signal region and displays an export-defective phenotype for this protein in vivo. Two peptides derived from pseudorevertant strains that arose from the deletion mutant and exported LamB in vivo were found to inhibit in vitro translocation with effectiveness that correlated with their in vivo export ability. Controls indicated that these synthetic signal peptides did not disrupt the E. coli membrane vesicles. These results can be interpreted to indicate that the presequences of exported proteins interact specifically with a receptor either in the E. coli inner membrane or in the cytoplasmic fraction. However, biophysical data for the family of signal peptides studied here reveal that they will spontaneously insert into a lipid membrane at concentrations comparable to those that cause inhibition. Hence, an indirect effect mediated by the lipid bilayer of the membrane must be considered.     

Impaired responsiveness of homosexual men with HIV antibodies to plasma derived hepatitis B vaccine.

Thirty five homosexual men (17 positive for antibody to the human immunodeficiency virus (HIV) and 18 consistently negative) were vaccinated against hepatitis B virus infection. Eight of the 17 seropositive patients failed to develop detectable hepatitis B surface antibody within three months of the third injection compared with only one of the 18 seronegative patients (p less than 0.01). HIV infection is prevalent in the developed world in groups at risk for hepatitis B infection and in certain Third World countries where widespread vaccination programmes exist. This study shows the impact that coincident HIV infection may have on an otherwise efficacious vaccine. The efficacy of this and other vaccines in patients infected with HIV needs to be studied urgently.     

Evidence for a phytochrome-mediated phototropism in etiolated pea seedlings

Entirely etiolated pea seedlings (Pisum sativum, L. cv Alaska) were tested for a phototropic response to short pulses of unilateral blue light. They responded with small curvatures resembling in fluence-dependence and kinetics of development a phytochrome-mediated phototropic response previously described in maize mesocotyls. Irradiations from above with saturating red or far-red light, either immediately before or after the unilateral phototropic stimulus, strongly reduced or eliminated subsequent positive phototropic curvature. Only blue light from above, however, entirely eliminated curvature at all fluences of stimulus. It is concluded that the phototropism is primarily a result of phytochrome action.     

In vivo crosslinking of nuclear proteins to DNA by cis-diamminedichloroplatinum (II) in differentiating rat myoblasts

When cells are briefly exposed to cis-diamminedichloroplatinum (II) before lysis in high sodium dodecyl sulfate-urea solutions, the high molecular-weight nucleic acids pelleted by ultracentrifugation contain an increased level of bound proteins when compared to a similar fraction from untreated cells. Subsequent shearing of the pelleted DNA followed by treatment with DNase permits electrophoretic and immunoblot analysis of the crosslinked proteins. In the present study such experiments were carried out with reference to nuclear envelope pore complex proteins in the differentiating L8 rat skeletal muscle cells. The results show that (i) whereas the major lamin proteins crosslinked to DNA in both myoblast and myotubes, lamin B is crosslinked to a greater extent to DNA in myotubes; (ii) a 62-kDa lectin-binding glycoprotein is apparently situated differently with respect to DNA in myotube nuclei; and (iii) the crosslinking pattern of the nuclear matrix proteins to DNA is qualitatively similar in myoblast and myotubes. In addition, lamin C′, a modified form of lamin C, not observed in intact nonmuscle cells previously [[31.] J. Biol. Chem. 260, 1895–1900], exists as a native component of the nuclear lamina in rat skeletal myotubes but not in myoblasts. These results point to significant structural alterations in the proteins of the nuclear lamina-pore complex during myogenesis.     

Immunoreactivity to the pancreatic polypeptide family in the nervous system of the adult human blood fluke,Schistosoma mansoni

Summary The presence and distribution of neuropeptides belonging to the pancreatic polypeptide family have been demonstrated by an indirect immunofluorescence technique in the nervous systems of adult male and female Schistosoma mansoni. Seven antisera of differing regional specificity to pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY) were employed on both whole-mount and cryostat-sectioned material. Positive immunoreactivity (IR) was obtained with all antisera except an N-terminally-directed antiserum to NPY. In the CNS, immunoreactivity was restricted to cell bodies and nerve fibres in the anterior ganglia, central commissure and dorsal and ventral nerve cords of both sexes, whereas, in the PNS, positive-IR was present in the plexuses innervating the subtegumental musculature and the oral and ventral suckers. Intense immunoreactivity was observed in a plexus of nerve fibres and cell bodies in the lining of the gynaecophoric canal and in fine nerve fibres innervating the dorsal tubercles of the male. In contrast, in the female, strong immunoreactivity was evident in nerve plexuses innervating the lining of the ovovitelline duct and in the wall of the ootype, but most notably in a cluster of cells in the region of Mehlis' gland. Results suggest that molecules with C-terminal homology to the PP-family are present in S. mansoni. These peptides would appear to be important regulatory molecules in the parasite's nervous system and may play a role in the control of egg production.     

Principal/agent theory and decision making in health care

Principal/agent theory, an economics concept that defines an agency relationship as "a contract under which one or more persons engage another person (the agent) to perform some service on their behalf which involves delegating some decision-making authority to the agent," is held to be applicable to the patient/physician relationship, in contrast to the view that this is a fiduciary relationship, not a contractual one. The distinction between fiduciary and contractual relationships is illuminated in the process of evaluating objections to the application of the principal/agent theory to the patient/physician relationship. The ability of the principal/agent theory to reveal important features of advance directives, understood as public documents rather than as confidential instructions from patient to physician, is also examined.     

Influence of Synchro-Mate-B and breed composition on estrous response and pregnancy rate in spring- and fall-bred Brahman crossbred beef cows

Estrous response, pregnancy rate, and the relationship between palpable corpora lutea (CL) and plasma progesterone concentrations were studied during the spring (n = 149) and fall (n = 146) breeding seasons using postpartum, crossbred beef cows consisting of 0-Brahman, 1 4 - Brahman , or 1 2 Brahman breeding. At the start of each breeding season, a jugular blood sample was collected for progesterone analysis; each cow was palpated for the presence of a CL and randomly alloted within breed to a non-treated control or Synchro-Mate-B (SMB) treatment. Fewer (P<0.01) fall than spring bred cows exhibited estrus within the first 21 d of breeding. Within 48 h of implant removal, 84 and 64% (spring and fall, respectively) of synchronized cows exhibited estrus. In both seasons, more SMB than control cows became pregnant by 7 d of breeding. Percentage of Brahman breeding did not influence estrous response or pregnancy rate. On the basis of 292 evaluations, palpation per rectum correctly assessed ovarian status 74% of the time. These data indicate that although season can influence response. SMB can be used effectively to synchronize Brahman crossbred cows. In addition, it was found that there is a close relationship between palpation per rectum and plasma concentrations of progesterone.     

Changes in bone mineralization pattern: a response to local stimulus in maxilla and mandible of dogs

A pilot study was carried out in order to verify the pattern of changes in mineralization of bone in the maxillas and mandibles of dogs which had a tooth extraction or luxation. Bone mineral content was determined using computerized microdensitometry. Significant changes in patterns of mineralization were found for alveolar bone, cortical bone and trabecular bone at the sites adjacent to the area of operation. These findings suggest that the three envelopes of jaw bones of the dogs are influenced by Regional activation phenomenon (RAP). These results have important implications for the design of clinical studies of periodontium. A more detailed study should elucidate the cellular mechanisms by which these changes occur.