Absence of the Lhcb1 and Lhcb2 proteins of the light-harvesting complex of photosystem II - effects on photosynthesis,grana stacking and fitness

We have constructed Arabidopsis thaliana plants that are virtually devoid of the major light-harvesting complex, LHC II. This was accomplished by introducing the Lhcb2.1 coding region in the antisense orientation into the genome by Agrobacterium-mediated transformation. Lhcb1 and Lhcb2 were absent, while Lhcb3, a protein present in LHC II associated with photosystem (PS) II, was retained. Plants had a pale green appearance and showed reduced chlorophyll content and an elevated chlorophyll a/b ratio. The content of PS II reaction centres was unchanged on a leaf area basis, but there was evidence for increases in the relative levels of other light harvesting proteins, notably CP26, associated with PS II, and Lhca4, associated with PS I. Electron microscopy showed the presence of grana. Photosynthetic rates at saturating irradiance were the same in wild-type and antisense plants, but there was a 10-15% reduction in quantum yield that reflected the decrease in light absorption by the leaf. The antisense plants were not able to perform state transitions, and their capacity for non-photochemical quenching was reduced. There was no difference in growth between wild-type and antisense plants under controlled climate conditions, but the antisense plants performed worse compared to the wild type in the field, with decreases in seed production of up to 70%.     

Predicted SAR in Sprague-Dawley rat as a function of permittivity values

Specific absorption rate (SAR) value is dependent on permittivity value. However, variability in the published permittivity values for human and animal tissue and the development of sophisticated 3-dimensional digital anatomical models to predict SAR values has resulted in the need to understand how model parameters (permittivity value) affect the predicted whole body and localized SAR values. In this paper, we establish the partial derivative of whole body SARs and localized SAR values (defined as SAR for individual organs with respect to a change in the permittivity values of all tissue types, as well as for those tissues with the most variable permittivity values. Variations in the published permittivity values may substantially influence whole body and localized SAR values, but only under special conditions. Orientation of the exposed object to the incident electromagnetic wave is one of the most crucial factors. Published 2001 Wiley-Liss, Inc.     

Distinct steps in the adsorption of pulmonary surfactant to an air-liquid interface

To investigate the mechanisms by which vesicles of pulmonary surfactant adsorb to an air-liquid interface, we measured the effect of different phospholipids and of their concentration both in the subphase and at the interface on this process. Adsorbing vesicles contained the hydrophobic surfactant proteins mixed with the following four sets of surfactant phospholipids that varied the content of anionic headgroups and mixed acyl chains independently: the complete set of purified phospholipids (PPL) from calf surfactant; modified PPL (mPPL) from which the anionic phospholipids were removed; a mixture of dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG) (9:1, mol:mol); and DPPC alone. The initial reduction in surface tension depended strongly on the anionic phospholipids and the subphase concentration. The acyl groups had no effect. Adsorption beyond the initial stage depended more on the mixed acyl groups, became increasingly independent of subphase concentration, and was determined instead by the interfacial concentration of the surface film. The different constituents produced the same effects in vesicles adsorbing to a clean interface or in a preexisting film to which vesicles of SP:DPPC adsorbed. Adsorption for vesicles of SP:PPL adsorbing to DPPC or of SP:DPPC to PPL above a certain threshold surface concentration followed exactly the same isotherm. Our results fit best with a two-step model for adsorption. The anionic phospholipids first promote the initial juxtaposition of vesicles to the interface. Compounds with mixed acyl constituents at the point of contact between vesicle and interface then facilitate fusion with the surface.     

Incorporation of adeno-associated virus in a calcium phosphate coprecipitate improves gene transfer to airway epithelia in vitro and in vivo

Adeno-associated virus (AAV) is inefficient at infecting differentiated airway epithelia because of a lack of receptors at the apical surface. We hypothesized that incorporation of AAV in a calcium phosphate coprecipitate would circumvent this barrier. Interestingly, coprecipitation of AAV type 2 improved gene transfer to differentiated human airway epithelia in vitro and to the mouse lung in vivo. These results suggest that delivery of AAV as a CaP(i) coprecipitate may significantly enhance its utility for gene transfer to the airway epithelia in vivo.     

Reproductive performance of lactating dairy cows treated with gonadotrophin-releasing hormone (GnRH) and/or prostaglandin F2a (PGF2a) for synchronization of estrus and ovulation

The objective of this study was to determine the reproductive performance of lactating dairy cows treated with GnRH and/or PGF2a for synchronization of estrus and ovulation. Between Days 43 and 57 post partum, a total of 374 dairy cows was divided into 4 groups. Cows in Group 1 (n = 62) were treated with 25 mg, i.m. PGF2a on Days 43 and 57; cows in Group 2 (n = 65) were not treated at this time; cows in Group 3 (n = 118) were treated with 100 ug, i.m. GnRH on Day 50, 25 mg, i.m. PGF2a on Day 57, 100 ug, i.m. GnRH on Day 59, and time-inseminated 16 h later; cows in Group 4 (n = 129) were treated with 25 mg, i.m. PGF2a once on Day 57. Cows in Groups 1 and 4 were inseminated at an induced estrus within 7 d after the last PGF2a treatment, and cows in Group 2 were inseminated at a noninduced estrus within a corresponding period of time. Conception rate, estrus detection rate and pregnancy rate were analyzed using logistic regression, and controlled for lactation number, body condition score and time of year. Days from calving to conception were analyzed using the GLM procedures of SAS, and the model included group, body condition score, lactation number, time of year, and their interactions. Cows in Group 3 had a significantly higher pregnancy rate than cows in Groups 1, 2 and 4. Orthogonal contrasts of mean days from calving to conception showed that cows in Group 3 had significantly (P < 0.01) less days from calving to conception than cows in Group 1 and Group 4. There was a significant effect of time of year on pregnancy rate and days from calving to conception, but there was no interaction between time of year and these reproductive characteristics. There was no effect of body condition score and lactation number on the reproductive characteristics evaluated. From the results of this study, it was concluded that better reproductive performance was observed in cows inseminated at a synchronized ovulation than in those inseminated at a synchronized estrous period.     

HSP70 expression in the CNS in response to exercise and heat stress in rats

We havepreviously documented the regional distribution of 70-kDa heat shockprotein (HSP70) in brains of rats made hyperthermic by brief exposureto high-powered microwaves (HPM; 2.06 GHz). We now compare HSP70expression induced by HPM exposure to that induced by exertionaland/or environmental heat stress. Rats were chronicallyimplanted with a temperature probe guide in the hypothalamic region ofthe brain (T_br). After recovery,the following treatment groups were examined: HPM; sham exposed;treadmill exercise at room temperature (24°C; Ex-1); treadmillexercise in a warm environment (34°C; Ex-2); and sedentary groups(Sed-1 and Sed-2), in which ambient temperature was adjusted so thatthe T_br mimicked the T_br in the corresponding exercisegroups. Significant HSP70 expression occurred only in the hyperthermic(Ex-2, Sed-2, and HPM) groups. The pattern of HSP70 expression wassimilar among Ex-2 and Sed-2 rats but differed from that in HPM rats.We conclude that 1) the pattern ofHSP70 expression differs between HPM and nonmicrowave heating, and2) exercise alone was not sufficientto induce central HSP70 expression.

     

Food availability and sex reversal in Mytella charruana,an introduced bivalve in the southeastern United States

We studied the reproductive biology of Mytella charruana to determine the potential reproductive success of this newly introduced bivalve species from Central/South America. We analyzed gonad morphology, gametogenesis, and the sex ratios of introduced populations throughout a 12 month period. In the non‐native habitat M. charruana shows the same strategy of gametogenesis that had been observed in its native environment, which is an opportunistic type of gonadal cycle with gametes produced throughout the year. Instead, the spawning period of M. charruana along the southeastern US coast is extended compared to that found in the native environment. We determined the minimum size (shell length) of sexually reproductive mussels to be 1.25 cm. Interestingly, throughout the year the population samples were typically composed of a higher proportion of females. The female to male sex ratio varied within a wide range from 1:0 to 1:3.3. Upon this discovery we tested the effects of food availability on the gametogenesis of adult animals. The sex ratio of mussels collected from different locations and maintained in the laboratory with or without food changed toward a male‐bias under starvation conditions within a month. This is the first study directly showing that food availability can trigger sex reversal in an adult bivalve. According to our data this mussel species will likely continue to spread along the east coast of the US. Moreover, M. charruana may prove to be a model organism in the study of alternative sexuality in bivalves. Mol. Reprod. Dev. 77: 222–230, 2010. © 2009 Wiley‐Liss, Inc.     

Natural Killer Cells Promote Long-Term Hepatobiliary Inflammation in a Low-Dose Rotavirus Model of Experimental Biliary Atresia

ConclusionsLower inoculation of RRV-induced progressive liver injury and fibrosis via NK cells. These findings point to the potential use of NK cell-depleting strategies to block progression of liver disease in biliary atresia.     

Activation of NOTCH1 or NOTCH3 Signaling Skews Human Airway Basal Cell Differentiation toward a Secretory Pathway

Airway basal cells (BC) function as stem/progenitor cells capable of differentiating into the luminal ciliated and secretory cells to replenish the airway epithelium during physiological turnover and repair. The objective of this study was to define the role of Notch signaling in regulating human airway BC differentiation into a pseudostratified mucociliated epithelium. Notch inhibition with γ-secretase inhibitors demonstrated Notch activation is essential for BC differentiation into secretory and ciliated cells, but more so for the secretory lineage. Sustained cell autonomous ligand independent Notch activation via lentivirus expression of the intracellular domain of each Notch receptor (NICD1-4) demonstrated that the NOTCH2 and 4 pathways have little effect on BC differentiation into secretory and ciliated cells, while activation of the NOTCH1 or 3 pathways has a major influence, with persistent expression of NICD1 or 3 resulting in a skewing toward secretory cell differentiation with a parallel decrease in ciliated cell differentiation. These observations provide insights into the control of the balance of BC differentiation into the secretory vs ciliated cell lineage, a balance that is critical for maintaining the normal function of the airway epithelium in barrier defense against the inhaled environment.