RESUMO
We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.
RESUMO
High-field electron paramagnetic resonance (HF EPR) has been employed to investigate the primary electron donor electronic structure of Blastochloris viridis heterodimer mutant reaction centers (RCs). In these mutants the amino acid substitution His(M200)Leu or His(L173)Leu eliminates a ligand to the primary electron donor, resulting in the loss of a magnesium in one of the constituent bacteriochlorophylls (BChl). Thus, the native BChl/BChl homodimer primary donor is converted into a BChl/bacteriopheophytin (BPhe) heterodimer. The heterodimer primary donor radical in chemically oxidized RCs exhibits a broadened EPR line indicating a highly asymmetric distribution of the unpaired electron over both dimer constituents. Observed triplet state EPR signals confirm localization of the excitation on the BChl half of the heterodimer primary donor. Theoretical simulation of the triplet EPR lineshapes clearly shows that, in the case of mutants, triplet states are formed by an intersystem crossing mechanism in contrast to the radical pair mechanism in wild type RCs. Photooxidation of the mutant RCs results in formation of a BPhe anion radical within the heterodimer pair. The accumulation of an intradimer BPhe anion is caused by the substantial loss of interaction between constituents of the heterodimer primary donor along with an increase in the reduction potential of the heterodimer primary donor D/D+ couple. This allows oxidation of the cytochrome even at cryogenic temperatures and reduction of each constituent of the heterodimer primary donor individually. Despite a low yield of primary donor radicals, the enhancement of the semiquinone-iron pair EPR signals in these mutants indicates the presence of kinetically viable electron donors.
Assuntos
Bacterioclorofilas/química , Espectroscopia de Ressonância de Spin Eletrônica/métodos , Hyphomicrobiaceae/química , Complexo de Proteínas do Centro de Reação Fotossintética/química , Transporte de Elétrons , Mutação , Oxirredução , Multimerização ProteicaRESUMO
Intra-abdominal lymphangiomas are rare benign tumours that usually arise in the mesentery of the small bowel. We present the case of an intra-abdominal lymphangioma that involved both the jejunum and its adjacent mesentery that ultrasound and CT scanning suggested was an ovarian tumour. Laparoscopy confirmed normal ovaries and a jejunal mass which was resected at laparotomy. This circumstance has very rarely been described in the literature and represents a diagnostic dilemma of which clinicians should be aware. Intra-abdominal lymphangioma should be included with other non-gynaecological diseases in the differential diagnosis of a pelvic mass, and requires a multi-specialty approach.
Assuntos
Neoplasias do Jejuno/diagnóstico , Linfangioma/diagnóstico , Mesentério , Neoplasias Ovarianas/diagnóstico , Neoplasias Peritoneais/diagnóstico , Dor Abdominal , Diagnóstico Diferencial , Feminino , Humanos , Neoplasias do Jejuno/cirurgia , Laparoscopia , Linfangioma/cirurgia , Neoplasias Ovarianas/cirurgia , Neoplasias Peritoneais/cirurgia , Tomografia Computadorizada por Raios X , Adulto JovemRESUMO
The morphology of neurons in the subthalamic nucleus (STN) of the lesser bushbaby (Galago senegalensis) is described in coronal brain sections processed by Golgi- and Nissl-staining techniques. Quantitative and statistical methods are used to evaluate (1) soma size and shape, (2) dendritic field size, shape, and branch frequency, (3) the number of dendritic and somatic spines per neuron, and (4) neuron location within the STN. Principal components analysis of these variables suggests that three classes of neurons are present. Two of these classes are considered to be projection cells, referred to as elongate-fusiform and radiate neurons, respectively. Elongatefusiform neurons have somata and dendritic fields which are large in diameter, extremely fusiform in shape, and give rise to few appendages. Somata and dendritic fields of radiate neurons are smaller in diameter, more rounded in shape, and support more spines than the elongate-fusiform neurons. The third class of cells in Galago STN is tentatively identified as consisting of interneurons on the basis of small soma and dendritic field size, thin and varicose dendritic morphology, and the presence of multilobulated dendritic appendages.
Assuntos
Dendritos/ultraestrutura , Galago/anatomia & histologia , Complexo de Golgi/ultraestrutura , Neurônios/citologia , Núcleos Talâmicos/citologia , Animais , Neurônios/classificaçãoRESUMO
The morphology of neurons in the centromedian (CM) and parafascicular (PF) nuclei in the lesser bushbaby (Galago senegalensis) is described in coronal and horizontal brain sections using Golgi-, horseradish peroxidase (HRP)-, and Nissl-staining procedures. The CM contains two types of cells referred to as principal neurons and Golgi type II (like) neurons. Cell bodies of principal neurons are relatively large in cross-sectional area (mean = 130.42 micron2), round to spindle in shape, support short somatic spines, and give rise to three to five primary dendrites. The dendrites branch in a "radiate" pattern and possess numerous appendages consisting of narrow, stalk-supported swellings. The presumed axons of these cells are impregnated only in their initial segments. On the basis of the similarity of principal neuron soma shapes and cross-sectional areas with those of HRP-reactive somata following cortical HRP implantation, it is concluded that at least some of the principal neurons in Galago CM project to somatic sensory-motor cortex. Golgi type II (like) neurons have small (mean = 79.43 micron2), round somata which support several spines and give rise to three to four small-diameter dendrites. The dendrites are infrequently branched, sinuous in their courses, and give rise to complex appendages and beaded processes. However, the axons of these cells could not be seen to ramify in the immediate vicinity of the dendritic field or soma, and there is considerable overlap in the cross-sectional areas of Golgi type II (like) neurons seen in Golgi preparations and HRP-stained cells following cortical implant of HRP pellets. Consequently, although Golgi type II (like) cells have traits characteristic of classically described intrinsic neurons, a cortical projection of these cells cannot be ruled out by the present study. The parafascicular nucleus contains two groups of large, radiate cells characterized by the presence or absence of somatic spines. Cells with somatic spines also contain numerous appendages on the dendrites. Cells without somatic spines support only a few, isolated, short dendritic appendages. Numerous small cell-bodied neurons are present in Nissl-stained sections of PF; however, cells which resemble Golgi type II neurons were not observed in the PF in the present Golgi-impregnated material. In contrast to the CM, the large cell-bodied neurons in PF were not found to project to somatic sensory-motor cortex in Galago.
Assuntos
Galago/anatomia & histologia , Núcleos Talâmicos/anatomia & histologia , Animais , Axônios/ultraestrutura , Córtex Cerebral/anatomia & histologia , Dendritos/ultraestrutura , Vias Neurais/anatomia & histologia , Coloração e Rotulagem , Núcleos Talâmicos/citologiaRESUMO
The neuronal architecture of the ventrobasal complex (VB) in dog is examined in coronal and horizontal brain sections processed by Golgi- and Nissl-staining methods. Presumed projection and intrinsic neurons are identified by differences in soma size and shape, dendritic branch pattern, the morphology and distribution of appendages, and the appearance of axons. Forty-five projection neurons are examined by quantifying (1) soma cross-sectional area, (2) dendritic field extent and shape, (3) appendages on the soma, primary dendrites, and in a defined major dendritic branch zone, and (4) location in the VB. When considered independently, each variable offers little evidence for separation into morphological classes. However, several of the variables have wide ranges and show significant correlation with other parameters. Using the multivariate descriptive methods of principal components analysis and cluster analysis, a separation of the projection neurons into three morphological classes designated as large, medium, and small neurons is indicated. The features most critical in distinguishing between the groups are, in descending order of importance: (1) dendritic field extent; (2) number of primary dendrites; (3) soma cross-sectional area; (4) number of appendages per major branch point (MBP); (5) number of appendages on the soma; and, (6) number of appendages on the primary dendrites. Dendritic field shape and neuron location have little influence in determining classification.
Assuntos
Diencéfalo/citologia , Neurônios/classificação , Análise de Variância , Animais , Contagem de Células , Dendritos/classificação , Cães , Secções Congeladas , Interneurônios/análise , Vias Neurais/citologia , Neurônios/análise , Neurônios/ultraestrutura , Prata , Coloração e RotulagemRESUMO
Previous studies indicate that limiting tyrosine and phenylalanine intake in the diet decreases tumor growth and metastasis. General health status, immune status, and platelet function were studied in nine healthy human subjects consuming low-protein foods supplemented with formula diets free of tyrosine and phenylalanine to maintain total daily intake of tyrosine at 2.4 mg/kg body wt and phenylalanine at 3.5 mg/kg body wt. This regimen decreased plasma tyrosine (p less than 0.05) but not phenylalanine. Blood indicators of protein status were not changed. Platelet aggregation decreased in response to adenosine diphosphate and platelet activating factor in seven of nine subjects. Natural killer, T-helper, and T-cytotoxic/suppressor lymphocyte numbers proportionally increased relative to neutrophils (p less than 0.05). Natural killer cell activity increased in six of nine subjects. Increased natural killer cell activity and decreased platelet aggregation are two indices associated with decreased tumor growth and metastasis.
Assuntos
Dieta , Imunocompetência , Fenilalanina/administração & dosagem , Tirosina/administração & dosagem , Composição Corporal , Proteínas Alimentares/administração & dosagem , Feminino , Humanos , Células Matadoras Naturais/imunologia , Masculino , Agregação Plaquetária , Linfócitos T Citotóxicos/imunologia , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/imunologiaRESUMO
Benzoquinone (BQ), deuterobenzoquinone (d4-BQ), and hydroquinone (BQH2) are investigated in ethylene glycol by means of direct detection fast time-resolved EPR spectroscopy after laser flash photolysis. The development of the magnetization as a function of time and magnetic field is obtained and analyzed in terms of the Bloch equations and hyperfine parameters. The signals are attributed to the semiquinones BQH(*) and d4-BQH(*). The presence of 1,2-dihydroxyethyl radicals during the photolysis of BQ and d(4)-BQ is verified. No alkyl radicals are observed in solutions of BQ with excess BQH2. Detailed analysis of the chemically induced dynamic electron polarization spectra with respect to their development in time shows that polarization patterns of the semiquinones can be traced back to a superposition of triplet mechanism and radical pair mechanism, the latter arising from geminate T-pairs. Hence, two independent pathways for polarization are assumed: reaction of triplet benzoquinone with ethylene glycol leads to the semiquinone and dihydroxyethyl radicals with all signals in emission, whereas the reaction of triplet BQ and BQH2 yields two semiquinones exhibiting both net emissive and multiplet emissive/absorptive intensity distributions.
RESUMO
The morphology of neurons in the ventral basal complex (VBC) of the adult opossum (Didelphis virginiana) is described from thick coronal brain sections, using Golgi-, horseradish peroxidase (HRP)-, and Nissl-staining methods. Soma cross-sectional area, dendritic field shape, and the number of appendages (spines) in a defined major branch zone (MBZ) are quantified and statistically analyzed. Results indicate that neurons in opossum VBC have relatively large cell bodies, dendrites which branch in a tufted pattern, and numerous dendritic appendages. These neurons are designated as relay cells because of (1) their tufted dendritic branch patterns, considered characteristic of thalamic relay cells (Ramon-Moliner, '62), and (2) the similarity of their soma sizes with HRP-labeled somata after somatosensory cortical injections. Neurons with traditionally described interneuron morphology do not appear to be present in the VBC of this animal, and, in this respect, the neuronal morphology of opossum VBC is similar to that in rat (McAllister and Wells, '81). Based on statistical analysis of the structural features observed, the presumed relay cells in opossum VBC do not show significant differences in morphology, and consequently are not subdivided into classes. Opossum VBC neurons are recognized as forming a single category in which broad and continuous variations in morphology are indicated. Recognition of a singular class of relay cell is consistent with descriptions for rat and cat VBC (Scheibel and Scheibel, '66), but at variance with a previous report for the primate Galago VBC (Pearson and Haines, '80) subdividing thalamic relay cells into Types I, II, and intermediate categories.
Assuntos
Complexo de Golgi/ultraestrutura , Gambás/anatomia & histologia , Tálamo/ultraestrutura , Animais , Dendritos/ultraestrutura , Neurônios/citologia , Neurônios/ultraestrutura , Tálamo/citologiaAssuntos
Clorofila , Espectroscopia de Ressonância de Spin Eletrônica , Espectroscopia de Ressonância Magnética , Matemática , Conformação Molecular , Peso Molecular , Plantas/análise , Rhodospirillum rubrum/análise , Especificidade da Espécie , Espectrofotometria Ultravioleta , Relação Estrutura-AtividadeAssuntos
Flavoproteínas , Animais , Soluções Tampão , Bovinos , Cromatografia por Troca Iônica , Computadores , Cianobactérias , Deutério , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres , Glicerol , Hidrogênio , Concentração de Íons de Hidrogênio , Espectroscopia de Ressonância Magnética , Oxirredução , Conformação Proteica , Soroalbumina Bovina , TemperaturaAssuntos
Fotossíntese , Bactérias , Carotenoides , Clorofila , Espectroscopia de Ressonância de Spin Eletrônica , Flavinas , Plantas , PorfirinasAssuntos
Instrução por Computador , Educação em Enfermagem/organização & administração , Serviços de Informação/organização & administração , Armazenamento e Recuperação da Informação , Internet/organização & administração , Pesquisa em Enfermagem/organização & administração , Comunicação , Instrução por Computador/métodos , Instrução por Computador/normas , Humanos , Hipermídia , Armazenamento e Recuperação da Informação/métodos , Armazenamento e Recuperação da Informação/normas , Cooperação Internacional , Relações Interprofissionais , Conhecimento , Multimídia , Sistemas On-Line/organização & administração , Política , Apoio SocialRESUMO
High-resolution pyrolysis gas-liquid chromatography was applied to three bacteria (Escherichia coli NCTC 9001, Pseudomonas putida (NCIB 9494, and Staphylococcus aureus NCTC 8532) grown under a variety of conditions. Changing the culture medium drastically altered the quantitative aspects of the pyrograms of all three organisms, but the effects of culture time and incubation temperature were less severe. Mathematical analysis of the relative peak heights showed that four peaks could be used to discriminate the three bacteria however they were cultured.
Assuntos
Cromatografia Gasosa , Escherichia coli/classificação , Pseudomonas/classificação , Staphylococcus aureus/classificação , Meios de Cultura , Escherichia coli/crescimento & desenvolvimento , Matemática , Pseudomonas/crescimento & desenvolvimento , Staphylococcus aureus/crescimento & desenvolvimentoRESUMO
Crystalline inclusion bodies resembling those seen in Clostridium cochlearium were detected in cultures of Bacillus thuringiensis infected with bacteriophage.
Assuntos
Bacillus/citologia , Bacteriófagos , Animais , Proteínas de Bactérias , Corpos de Inclusão Viral , Insetos , Microscopia EletrônicaRESUMO
In vitro and in vivo triplet state electron paramagnetic resonance (epr) spectra of bacteriochlorophylls (Bchls) show important differences in (a) electron spin polarization (esp), and (b) zero field splitting (ZFS) parameters. The unusual esp and ZFS properties of the observed in vivo triplet state are best interpreted as arising from a short-lived radical pair precursor (not directly observable by epr) formed in or with the special pair of bacteriochlorophyll molecules involved in the primary photo-act.
RESUMO
Evidence from electron paramagnetic resonance (e.p.r.) studies suggests that the unpaired spin in oxidized P700+. or P865+. is shared by two special chlorophyll a (Chl a) or bacteriochlorophyll a (Bchl a) molecules respectively. Three classes of models have been proposed for special pair reaction centre chlorophyll: asymmetric, in which one Chl a (or Bchl a) acts as electron donor to a second acting as acceptor; models with translational symmetry only; and models with C2 symmetry. Models with C2 symmetry have been synthesized in vitro with two chlorophyll macrocycles tied together by a covalent link. The singlet and triplet states of the in vitro models have been characterized by e.p.r., nuclear magnetic resonance, and optical studies involving absorption, emission, and lasting behaviour. The fact that lasting occurs only from the folded configuration of the linked dimers suggests the availability of a highly effective nonradiative decay path from the S1 state of the excited open dimer. A radical-pair mechanism that accounts for the unusual spin polarization of the special pair triplet is proposed for the primary photochemistry in the reaction centre.