Monomers, dimers, and tetramers of 4-n-propyl-5-ethyl farnesyl bacteriochlorophyll c in dichloromethane and carbon tetrachloride

Absorption (ABS) and circular dichroism (CD) spectra were recorded for 6 concentrations (2.0-290 μM) of bacteriochlorophyll (BChl) c in each solvent. Monomer spectra were obtained by adding methanol (1:200) to each sample. The monomer showed an ABS peak and a CD trough at 664 nm in CH2Cl2 (ABS peak at 665 nm in CCl4). Dimer-plus-monomer spectra were obtained by subtracting high concentration (e.g., 290 μM) spectra appropriately scaled from lower concentration (e.g., 26 μM) spectra. Pure dimer spectra were then obtained by subtracting monomer spectra appropriately scaled from dimer-plus-monomer spectra. The dimer showed an ABS peak at 679 nm in both CH2Cl2 and CCl4 and a CD trough at ca. 670 nm in CH2Cl2. The optical properties of the dimer do not agree with the model for bacteriochlorophyllide d [Smith KM, Bobe FW, Goff DA and Abraham RJ (1986) J Am Chem Soc 108: 1111-1120]. Higher aggregate spectra were obtained by subtracting appropriately scaled monomer and dimer spectra from high concentration (e.g., 290 μM) spectra. The aggregate showed ABS shoulders at ca. 636 and 678 nm with a peak at 702 nm in CH2Cl2 and at 708 nm in CCl4; the CD spectrum in either solvent showed peaks at 638 and 679 nm with troughs at 658 and ca. 710 nm. These spectra are consistent with an excitonic interaction between 4 chromophores in the aggregate. Each of the 12 original ABS spectra was deconvoluted in terms of the appropriate monomer, dimer and aggregate spectra, and the concentrations of each component were determined. Plots of log aggregate concentration vs. log dimer concentration lay on or near a line of slope 1.9 for CH2Cl2 and on or near a line of slope 2.1 for CCl4. The aggregate was thus shown to be a tetramer. The theoretical relationship between dimers and monomers (slope 2.0) was not observed in all cases.

The amino acid sequence of a major protein component in the light harvesting complex of the green photosynthetic bacterium Chlorobium limicola f. thiosulfatophilum

A 7.5-kDa protein has been isolated from chlorosomes of Chlorobium limicola f. thiosulfatophilum and the complete primary structure determined by a combination of automatic Edman degradation and plasma desorption mass spectrometry. The 74-residue protein shows great homology to a similar protein of unknown function which has been isolated from Pelodictyon luteolum but otherwise no significant homology to other proteins can be found. The possible role of the protein in the structure and function of the chlorosome is discussed.

Monte Carlo comparison of preliminary methods for ordering multiple genetic loci

We carried out a simulation study to compare the power of eight methods for preliminary ordering of multiple genetic loci. Using linkage groups of six loci and a simple pedigree structure, we considered the effects on method performance of locus informativity, interlocus spacing, total distance along the chromosome, and sample size. Method performance was assessed using the mean rank of the true order, the proportion of replicates in which the true order was the best order, and the number of orders that needed to be considered for subsequent multipoint linkage analysis in order to include the true order with high probability. A new method which maximizes the sum of adjacent two-point maximum lod scores divided by the equivalent number of informative meioses and the previously described method which minimizes the sum of adjacent recombination fraction estimates were found to be the best overall locus-ordering methods for the situations considered, although several other methods also performed well.

Bacteriochlorophyll c monomers, dimers, and higher aggregates in dichloromethane, chloroform, and carbon tetrachloride

Bacteriochlorophyll c in vivo is a mixture of at least 5 homologs, all of which form aggregates in CH2Cl2, CHCl3 and CCl4. Three homologs exist mainly in the 2-R-(1-hydroxyethyl) configuration, whereas the other two homologs, 4-isobutyl-5-ethyl and 4-isobutyl-5-methyl farnesyl bacteriochlorophyll c, exist mainly in the 2-S-(1-hydroxyethyl) configuration (Smith KM, Craig GW, Kehres LA and Pfennig N (1983) J. Chromatograph. 281: 209-223). In CCl4 the S-homologs form an aggregate of 2-3 molecules whose absorption (747 nm maximum) and circular dichroism spectra resemble those of the chlorosome. In CH2Cl2, CHCl3 and CCl4 the 4-n-propyl homolog (R-configuration) forms dimers absorbing at ca. 680 nm and higher aggregates absorbing at 705-710 nm. In CCl4 the dimerization constant is approx. 10 µM(-1) (1000 times that for chlorophyll a). The difference between the types of aggregates formed by the 4-n-propyl and 4-isobutyl homologs is attributed to the difference between the R- and S-configurations of the 2-(1-hydroxyethyl) groups in each chlorophyll.

Fluorescence lifetimes of dimers and higher oligomers of bacteriochlorophyll c from Chlorobium limicola

Fluorescence lifetimes have been measured for bacteriochlorophyll (BChl) c isolated from Chlorobium limicola in different states of aggregation in non-polar solvents. Two different homologs of BChl c were used, one with an isobutyl group at the 4 position, the other with n-propyl. Species previously identified as dimers (Olson and Pedersen 1990, Photosynth Res, this issue) decayed with lifetimes of 0.64 ns for the isobutyl homolog, 0.71 ns for n-propyl. Decay-associated spectra indicate that the absorption spectrum of the isobutyl dimer is slightly red-shifted from that of the n-propyl dimer. Aggregates absorbing maximally at 710 nm fluoresced with a principal lifetime of 3.1 ns, independent of the homolog used. In CCl4, only the isobutyl homolog forms a 747-nm absorbing oligomer spectrally similar to BChl c in vivo. This oligomer shows non-exponential fluorescence decay with lifetimes of 67 and 19 ps. Because the two components show different excitation spectra, the higher oligomer is probably a mixture of more than one species, both of which absorb at ∼747 nm.

Circular dichroism of green bacterial chlorosomes

Positive and negative bands in previously measured circular dichroism (CD) spectra of Chlorobium limicola chlorosomes appeared to be sign-reversed relative to those of Chloroflexus aurantiacus chlorosomes in the 740-750 nm spectral region where bacteriochlorophyll (BChl) c absorbs maximally. It was not clear, however, whether this difference was intrinsic to the chlorosomes or was due to differences in the procedures used to prepare them. We therefore repeated the CD measurements using chlorosomes isolated from both Cb. limicola f. thiosulfatophilum and Cf. aurantiacus using the method of Gerola and Olson (1986, Biochim. Biophys. Acta 848: 69-76). Contrary to the earlier results, both types of chlorosomes had very similar CD spectra, suggesting that both have similar arrangements of BChl c molecules. The previously reported difference between the CD spectra of Chlorobium and Chloroflexus chlorosomes is due to the instability of Chlorobium chlorosomes, which can undergo a hypsochromic shift in their near infrared absorption maximum accompanied by an apparent inversion in their near infrared CD spectrum during isolation. Treating isolated chlorosomes with the strong ionic detergent sodium dodecylsulfate, which removes BChl a, does not alter the arrangement of BChl c molecules in either Chloroflexus or Chlorobium chlorosomes, as indicated by the lack of an effect on their CD spectra.

Regulation of glycolysis in the pectoralis muscles of seasonally acclimatized American goldfinches exposed to cold

Regulation of glycolysis was assessed in winter- and summer-acclimatized goldfinches (Carduelis tristis). We exposed birds to a thermo-neutral temperature (30 degrees C), moderate cold (-15 degrees C), and severe cold (0 degrees C in an atmosphere of 21% O2-79% He), and then measured concentrations of glycogen, glycolytic intermediates, and citrate in the pectoralis muscles. Winter birds used less glycogen when exposed to moderate cold than did summer birds, confirming the carbohydrate sparing noted by Marsh and Dawson [Am. J. Physiol. 242 (Regulatory Integrative Comp. Physiol. 11): R563-R569, 1982]. However, depletion of muscle glycogen did not correlate with thermoregulatory failure in this study. Concentrations of glucose 6-phosphate and fructose 6-phosphate in the pectoralis muscles were approximately 1.9 and 0.3 mumol/g wet mass in birds exposed to thermoneutral temperatures. The levels of these intermediates fell 50-70% under conditions known to enhance flux through glycolysis as indicated by increased glucose turnover and glycogen depletion. This information identifies phosphofructokinase (PFK) as a major regulated step in glycolysis in these highly aerobic skeletal muscles. Winter birds maintained the inhibition of this step under conditions of moderate cold. However, concentrations of citrate, which have been hypothesized to be an important inhibitor of PFK, did not correlate with the observed pattern of inhibition. Therefore, if the enhanced beta-oxidative capacity of winter birds is important in the regulation of glycolysis, a mechanism other than the accumulation of citrate may be involved.

PET imaging of human gliomas with ligands for the peripheral benzodiazepine binding site

Human gliomas were imaged in vivo using ligands for the peripheral-type benzodiazepine binding site (or omega 3 binding site) and positron emission tomography (PET). Although gliomas have a high density of the peripheral-type benzodiazepine binding site, PET scans with a selective ligand for this site, [11C] Ro5-4864, failed to demonstrate higher radioactivity levels in human gliomas than in brain. In vitro studies of surgically removed specimens of human glioma demonstrated little binding of Ro5-4864 but high levels of binding of another selective ligand, PK 11195. Scans with [11C]PK 11195 demonstrated increased radioactivity in glioma compared to brain in 8 of 10 patients. Radioactivity in tumor and the ratios of radioactivity in tumor to that in remote gray and in white matter correlated significantly with the specific activity of [11C]PK 11195, suggesting that accumulation represents saturable high-affinity binding. We conclude that the PK 11195 manifests greater binding than Ro5-4864 to the peripheral-type benzodiazepine binding site on human gliomas and that human gliomas can be successfully imaged using [11C]PK 11195 and PET.

Tetanus: an uncommon cause of dysphagia

A 53-year-old woman was examined at our medical center because of progressive dysphagia of 14 days' duration and a severe inability to open her mouth and swallow saliva. A barium esophagogram showed no obstruction, but pooling of barium in the hypopharynx suggested a neuromuscular disorder. The clinical diagnosis of tetanus was confirmed by electromyography. With appropriate therapy, the patient recovered during a period of 6 weeks. This case illustrates both an uncommon cause of dysphagia and an uncommon initial manifestation of tetanus.

Alternative genetic models for the inheritance of the phenylthiocarbamide taste deficiency

Pedigree segregation analysis was used to examine several one- and two-locus models of the inheritance of phenylthiocarbamide (PTC) taste deficiency that extend the traditional one-locus recessive model by the addition of either another allele or another locus, and in some cases predict two types of nontasters. These models allow nontaster by nontaster matings to produce taster offspring, consistent with our data and several previous studies which use the Harris and Kalmus [Annals of Eugenics 15:24-32, 1949] dilution method. The models fit our data set of 1,152 individuals from 120 families significantly better than the one-locus recessive model. The best fit was obtained with a two-locus model in which one locus controls PTC tasting and the other locus controls a more general taste ability. This model is consistent with research on the physiology of PTC tasting and with results from genetic linkage studies. Further study is suggested to evaluate better the accuracy of the proposed model.

Synthesis of a high specific activity 125I-labeled analog of PK 11195, potential agent for SPECT imaging of the peripheral benzodiazepine binding site

The peripheral benzodiazepine binding site ligand PK 11195 has been 125I-labeled by direct displacement of aromatic chlorine under solid-state conditions in 50-76% radiochemical yield and greater than 94% radiochemical purity. Purification by high pressure liquid chromatography increased the specific activity of the product from an initial 15-17 Ci/mmol to a final activity of 260-910 Ci/mmol. To determine the affinity of this [125I]PK 11195 analog for human glioma cells, saturation experiments were performed on monolayers of U251 human glioblastoma cells. Scatchard analysis of saturation data demonstrated that the [125I]PK 11195 analog binds to a single class of sites with a KD of 8.0 +/- 1.7 nM and maximal binding of 3.8 +/- 0.1 pmol/mg protein. These values are similar to those obtained when [3H]PK 11195 was assayed in U251 cells (KD = 14 +/- 3.4, Bmax = 4.1 +/- 1.3) suggesting that iodination does not appreciably alter the binding of PK 11195 to human glioma cells. In vivo autoradiographic studies of brain in C6 glioma bearing rats demonstrate selective binding of the radioligand to the tumor. These results suggest that this [125I]PK 11195 analog may be a useful radiotracer for the study of peripheral benzodiazepine binding sites.

Isoquinoline and peripheral-type benzodiazepine binding in gliomas: implications for diagnostic imaging

Binding of the isoquinoline PK 11195 and of the benzodiazepines Ro5-4864 and flunitrazepam was compared in glioma cells and tissues. In human and rat glioma cell cultures [3H]PK 11195 bound with higher affinity (Kd = 14.01 and 15.76 nM, respectively) than either Ro5-4864 (Ki = 1200 and 84.9 nM, respectively) or flunitrazepam (Ki greater than 10,000 and = 848 nM, respectively). Autoradiograms of postmortem human brain sections containing glioma revealed that [3H]PK 11195 bound specifically to intact tumor cells and not to cells of normal cerebral cortex or necrotic areas of the tumor. Total [3H]Ro5-4864 or [3H]flunitrazepam binding to these sections was indistinguishable from nonspecific binding, and regions of tumor and normal brain could not be delineated. These results support the use of radiolabeled PK 11195 for clinical trials of imaging human gliomas by positron emission tomography.

Presence of peripheral-type benzodiazepine binding sites on human erythrocyte membranes

A nanomolar affinity peripheral-type benzodiazepine binding site is described in human erythrocyte membranes. [3H]PK 11195 is displaced from this binding site by unlabeled drugs with the rank order PK 11195 greater than Ro 5-4864 greater than flunitrazepam much greater than clonazepam. Neither GABA nor a non-hydrolyzable analog of GTP have an effect on binding parameters. These data provide evidence that a peripheral-type benzodiazepine binding site, pharmacologically similar to the intracellular binding site described in other tissues, is present in the plasma membrane of human erythrocytes.

Misattribution, preparatory information, and speech anxiety

In two experiments with undergraduate subjects, I compared the effects of misattribution versus information manipulations on speech anxiety. In Experiment 1, some subjects were allegedly exposed to subliminal noise while reading a speech in front of a camera. These subjects were told that subliminal noise makes people feel either unpleasantly aroused or pleasantly relaxed or that it has no effect. Subjects in a fourth condition were given accurate information about how they would feel (unpleasantly aroused) but were not exposed to the subliminal noise misattribution source. In Experiment 2, I replicated the arousing noise and accurate information conditions from the first study and added two new groups incorporating a delay that should preclude misattribution. In both experiments, the alleged presence of arousing subliminal noise reduced subjects' speech dysfluencies during the speech task, whereas the presentation of accurate information alone did not have a comparable ameliorative effect. Thus, both experiments supported the misattribution interpretation of why neutral labels for arousal can reduce emotionality.

Misattribution, preparatory information, and speech anxiety

In two experiments with undergraduate subjects, I compared the effects of misattribution versus information manipulations on speech anxiety. In Experiment 1, some subjects were allegedly exposed to subliminal noise while reading a speech in front of a camera. These subjects were told that subliminal noise makes people feel either unpleasantly aroused or pleasantly relaxed or that it has no effect. Subjects in a fourth condition were given accurate information about how they would feel (unpleasantly aroused) but were not exposed to the subliminal noise misattribution source. In Experiment 2, I replicated the arousing noise and accurate information conditions from the first study and added two new groups incorporating a delay that should preclude misattribution. In both experiments, the alleged presence of arousing subliminal noise reduced subjects' speech dysfluencies during the speech task, whereas the presentation of accurate information alone did not have a comparable ameliorative effect. Thus, both experiments supported the misattribution interpretation of why neutral labels for arousal can reduce emotionality.

Thermogenic capabilities of the opossum Monodelphis domestica when warm and cold acclimated: similarities between American and Australian marsupials

1. Monodelphis domestica is a small marsupial mammal from South America. Its thermogenic abilities in the cold were determined when the opossums were both warm (WA) and cold (CA) acclimated. Maximum heat production of M. domestica was obtained at low temperatures in helium-oxygen. 2. Basal metabolic rate (BMR) in the WA animals was 3.2 W/kg and mean body temperature was 32.6 degrees C at 30 degrees C. These values were lower than those generally reported for marsupials. Nevertheless, these M. domestica showed considerable metabolic expansibility in response to cold. Sustained (summit) metabolism was 8-9 times BMR, while peak metabolism was 11-13 times BMR. These maximum values were equal to, or above, those expected in small placentals. 3. Cold acclimation altered the thermal responses of M. domestica, particularly in warm TaS. However, summit metabolism was not significantly increased; nor did M. domestica show a significant thermogenic response to noradrenaline, which in many small placentals elicits non-shivering thermogenesis. The thermoregulatory responses of this American marsupial were, in most aspects, similar to those of Australian marsupials. This suggests that the considerable thermoregulatory abilities of marsupials are of some antiquity.

Effects of stress and characteristic adaptability on semen quality in healthy men

Semen from 28 healthy volunteers was assessed for basic semen measure and percent of abnormal morphologic forms every 2 weeks for 6 months. Concurrent self-reports were obtained on abstinence, frequency of ejaculation, health behavior and status, experienced stress, social support, and life events. A single assessment of characteristic adaptability (ego resiliency) also was obtained. Significant between-subject positive correlations were reported among selected semen measures, abstinence, and ego-resiliency. Stress was correlated negatively with semen measures of volume and percent normal morphologic forms.

Autoradiographic localization of cerebellar excitatory amino acid binding sites in the mouse

We have investigated the cellular localization of cerebellar excitatory amino acid binding sites in normal mice, in mice deficient in granule cells and, perhaps, stellate, basket and Golgi cells (granuloprival mice) and in mice lacking Purkinje cells. In the molecular layer of normal mouse cerebellum, the quisqualate-sensitive binding sites were the predominant type of excitatory amino acid receptor and there were relatively few N-methyl-D-aspartate or kainate-sensitive binding sites. The granule cell layer of normal mice contained a mixture of all 3 types, the N-methyl-D-aspartate-sensitive binding sites being predominant. In the molecular layer of granuloprival mice, the number of quisqualate-sensitive binding sites was increased to 214% of control (P less than 0.01), whereas N-methyl-D-aspartate-sensitive binding sites were decreased to 62% of control (P less than 0.001) and kainate-sensitive binding sites were unchanged. In the granule cell layer of these mice, quisqualate-sensitive binding sites were increased to 200% (P less than 0.01), N-methyl-D-aspartate-sensitive binding sites were decreased to 47% (P less than 0.001) and kainate-sensitive binding sites were decreased to 49% (P less than 0.01 of their respective control values. In the molecular layer of mice lacking Purkinje cells, quisqualate-sensitive binding sites were reduced to 29% (P less than 0.001) of control and N-methyl-D-aspartate-sensitive binding sites were unchanged. In the granule cell layer of these mice, neither quisqualate nor N-methyl-D-aspartate-sensitive binding sites were changed. These results suggest that (1) quisqualate-sensitive binding sites are located principally on dendrites of Purkinje cells and that they up-regulate after deafferentation; (2) N-methyl-D-aspartate-sensitive binding sites are located on granule cells and, perhaps, stellate, basket and Golgi cells, and (3) kainate binding sites are located on cell bodies of granule and, perhaps, Golgi cells.

Barriers to receiving adequate prenatal care

One hundred eleven postpartum patients who received varying amounts of prenatal care (no care, inadequate care, intermediate care, and adequate care) were assessed for demographic, medical and sociocultural factors by interview and review of the medical chart. Six sociocultural factors identified by stepwise multiple regression contributed to 49% of the variance for amount of prenatal care: amount of insurance, attitudes toward health professionals, delays in suspecting pregnancy, delay in telling others about the pregnancy, perception of the importance of prenatal care, and initial attitudes about being pregnant. Results are discussed in terms of developing outreach programs altered to the patient's needs and life-styles.

Stability of basic semen measures and abnormal morphology within individuals

Semen from 15 healthy volunteers was assessed for basic semen measures every 2 weeks over a 6-month period to determine the relative stability of these factors. The parameters were: sperm count, semen volume, sperm motility, and normal morphology, along with the type of abnormal morphologic forms. Basic semen measures were generally more stable than the morphologic forms. Using three samples, seven semen factors (sperm count, normal morphology, semen volume, sperm motility, microcephaly, tapering and round tail) were found to be stable and contributed to the identification of the fifteen individuals with a classification accuracy of 75.0%. While individuals do have characteristic patterns of spermatogenesis, the biologic basis for these findings is as yet undetermined.

Correlation of serum estradiol levels and ultrasound monitoring to assess follicular maturation

Thirty-eight patients underwent 38 cycles of induction of ovulation using stepwise human menopausal gonadotropin and human chorionic gonadotropin (hCG) administration. Ultrasonography was performed on the day of hCG injection. The mean age +/- standard error of the mean (SEM) of the patients was 32.9 +/- 0.8 years, and the duration of infertility ranged from 1 to 14 years (median, 2.8). Ultrasonographic measurements were obtained of the largest diameter and the volume of the dominant follicles as well as all other follicles in both ovaries. Data were analyzed by Student's t-test, regression analysis, and analysis of variance. The mean +/- SEM diameter of dominant follicles was 1.8 +/- 0.1 cm, and the volume of dominant follicles was 3.5 +/- 0.8 cm. The mean +/- SEM serum estradiol (E2) level before hCG administration was 659 +/- 62 pg/ml. Significant correlations were found between preovulatory serum E2 levels and the total follicular volume of both ovaries (r = 0.41, P less than 0.05) and follicular volume of the ovary containing the dominant follicle (r = 0.42, P less than 0.01). No significant correlation was observed between the diameter of the dominant follicle and serum E2 levels. These results suggest that ultrasound findings reflect growth, whereas serum E2 levels primarily detect functional activity of follicles.

A new bacteriochlorophyll a-protein complex associated with chlorosomes of green sulfur bacteria

Chlorosomes were prepared from Chlorobium limicola f. thiosulfatophilum by sucrose density gradient centrifugation. Cells broken in the presence of 2 M NaSCN yielded three chlorosome fractions in the gradient: low density (no sucrose), medium density (approx. 18% sucrose), and high density (approx. 26% sucrose). All fractions were stable at any chlorosome concentration. Cells broken in the absence of 2 M NaSCN also yielded three fractions, but only the high-density fraction contained stable chlorosomes. The medium-density chlorosomes were stable only when highly concentrated. Upon dilution, bacteriochlorophyll (BChl) c was degraded to bacteriopheophytin c and concomitantly a band at 794 nm (BChl a) was revealed. Two 794-nm fractions were observed with the same densities as low- and medium-density chlorosomes. The protein composition of the 794-nm fractions was similar to that of the stable chlorosome fractions. All showed a 4-5 kDa (Mr) protein as a major component, but no trace of the 40-kDa protein characteristic of the water-soluble BChl a-protein of green sulfur bacteria. BChl a was present in all types of chlorosomes, in stable chlorosomes the BChl c/BChl a ratio was approx. 90. A special BChl a-protein (794 nm) inside the chlorosome is postulated to mediate energy transfer from BChl c to the water-soluble BChl a-protein in the baseplate.

Photosynthesis 3.5 thousand million years ago

The recent discovery of stromatolites and microfossils in 3.5-Ga-old sedimentary rock formations is evidence for the existence of phototrophic prokaryotes at that time. Values of δ(13)C for sedimentary organic carbon strongly suggest autotrophic CO2 fixation, and the existence of large deposits of sedimentary sulfate is consistent with a photosynthesis dependent on reduced sulfur compounds for reducing power. The ancient photoautotrophs are though to have contained only one kind of reaction center with either chlorophyll a or bacteriochlorophyll a as primary electron donor and with one or more iron-sulfur centers as secondary electron acceptors. Light-harvesting pigments might have been chlorophyll a, bacteriochlorophyll a, or possibly bacteriochlorophyll c.A new proposal is made to explain how these organisms could have survived an intense UV flux at the earth's surface in the absence of an ozone layer. Photochemically produced ferric iron was abundant in sediments, and the UV-absorption of this ferric iron would have been sufficient to shield those organisms living below the watersediment interface.

Variation of semen measures within normal men

Variation in semen measures was assessed bimonthly in 15 healthy men over a 6-month period. Average within-subject coefficients of variation for sperm count, morphologic features, motility, and semen volume demonstrate considerable variation. Each day of abstinence increased the volume by an increment of 0.62 ml, the count by 17.6 X 10(6)/ml, and motility by 1.2%. Sperm count and semen volume correlated positively within subjects. Intraclass and serial correlations of semen measures provided an empirical clinical guide to the number and spacing of specimens. Three specimens spaced no more than 2 weeks apart established a reliable semen profile. Findings can be applied to basic research and clinical practice.

Autoradiographic characterization of N-methyl-D-aspartate-, quisqualate- and kainate-sensitive glutamate binding sites

Quantitative autoradiography was used to characterize the pharmacological specificity and anatomical distributions of subtypes of L-[3H]glutamate binding sites in rat brain. One population of sites was sensitive to N-methyl-D-aspartate (NMDA) and other compounds thought to be specific for the NMDA receptor. This site was enriched in stratum radiatum of hippocampus (CA1) where it constituted about 80% of glutamate binding sites and it represented a variable portion of glutamate binding sites throughout the brain. A second population of sites had a high affinity for quisqualate. Approximately 80% of glutamate binding sites in cerebellar molecular layer were of the high affinity quisqualate type. The number of these sites was greatly increased in the presence of Cl- and Ca++ ions. A subset of the high affinity quisqualate sites was sensitive to competition by kainate, particularly in stratum lucidum of hippocampus; the density of these high affinity kainate-sensitive sites was decreased in the presence of Ca++ but not Cl- ions. At high concentrations quisqualate competes for all glutamate binding sites, as reported previously. There was a good correspondence between the density and distribution of low affinity quisqualate sites and NMDA-sensitive sites. Pharmacological analysis suggested that the low affinity quisqualate site and the NMDA site are equivalent. Anatomical and pharmacological evidence suggests that the NMDA-, (high affinity) quisqualate- and kainate-sensitive glutamate binding sites may correspond to the physiologically defined NMDA, quisqualate and kainate receptors.

Depression, psychopathology, and self-serving attributions

Depressed and non-depressed psychiatric in-patients and non-depressed non-psychiatric controls classified their performance on a verbal recognition task as either a success or a failure, and made attributions about the causes of their perceived success or failure. In all three groups, subjects who classified their performance as a success attributed their outcome more to internal and less to external factors than did subjects who classified their performance as a failure. These results suggest that depression and attributional style may not necessarily be related. Discussion centres on the idea that individuals' expectations of success can affect their subsequent attributions.

Protein carboxymethylation during in vitro culture of human peripheral blood monocytes and pulmonary alveolar macrophages

Protein carboxymethylase (PCM) activity was evaluated for long-term in vitro cultures of human peripheral blood monocytes and pulmonary alveolar macrophages. Both cell types exhibited increases in endogenous (without addition of the exogenous substrate, gelatin) and total (with gelatin) enzyme activity with increased time in culture. Monocytes developed increased activity after a 5-day lag period; three-to four-fold increases over day 1 values in both total and endogenous specific activity occurred. In contrast, PCM activity increased for pulmonary alveolar macrophage (PAM) without a detectable lag period. Although the increase in endogenous activity of 10--14-day PAM culture was similar to comparable age monocyte cultures, total enzyme activity increased only two-fold above day 1 values. The observation of changes in PCM endogenous specific activity in monocyte cultures may reflect alterations in enzyme activity and/or levels of endogenous methyl-acceptor proteins.

Evolution of photosynthetic reaction centers

The common ancestor of all photosynthetic prokaryotes and organelles contained chlorophyll (Chl) a. All green and purple photosynthetic bacteria descended from a common bacteriochlorophyll (Bchl) a-containing ancestor which diverged from the Chl a line. Separate PS-I and PS-II reaction centers may have evolved before the appearance of Bchl a. When the transition to Bchl a occurred, the resultant organism contained two types of reaction center, "PS-I" and "PS-II." One line of development eliminated "PS-II" and evolved into the green bacteria. The other line eliminated "PS-I" and became the purple bacteria. In the Chl a-containing organisms the evolution of PS-II continued until oxygen evolution was achieved.

Chlorophyll organization in green photosynthetic bacteria

Light-harvesting BChl c, d or e is thought to be located inside the rod elements which fill the chlorosome appressed to the inside of tbe cytoplasmic membrane of green photosynthetic bacteria. BChl a is known to be a part of BChl a-protein which forms a crystal-line baseplate between the rod elements in the chlorosome and the inside of the cytoplasmic membrane. Reaction-center complexes are most probably buried under the baseplate inside the membrane. Energy transfer is from BChl c, d or e in the rod elements to BChl a in the baseplate and then to BChl a in the reaction-center complexes. The rod elements in green sulfur bacteria are thought to be composed of approx. 15-kdalton protein subunits, each associated with 12-14 BChl c, d or e molecules. Six subunits would be required to form a 10-nm ring, and about 35 rings would be necessary to form a 100-nm rod element. The baseplate appears to be a two-dimensional crystal (trigonal space group P31) of BChl a-protein trimers with the 3(1) screw axis tilted 25 degrees out of the plane membrane. The reaction-center complex is thought to be made up of a 100-kdalton carotenoid reaction-center core and five 50-kdalton subunits, each containing seven BChl a molecules. Each reaction-center complex is apparently linked directly to two BChl a-protein trimers in the baseplate. The reaction centers in green sulfur bacteria may be of one type (containing P-840), or of two types (containing P-830 or P-842). In filamentous gliding bacteria the reaction centers appear to contain only P-865. The number of BChl a molecules in these reaction centers is not known, but is assumed to be at least two.

Seven-fold exciton splitting of the 810-nm band in bacteriochlorophyll A-proteins from green photosynthetic bacteria

We report comparative absorbance and fourth derivative absorbance spectra of two different bacteriochlorophyll a-proteins at 5 K in each of two different cryogenic solvent mixtures. In previous studies at 5 K each protein was observed in only one of these mixtures (not the same one). For the protein from Prosthecochloris aestuarii strain 2K, whose structure is known, the solvent effect is relatively small; for the protein from Chlorobium limicola f. sp. thiosulfatophilum strain 6230 (Tassajara), the effect is much more pronounced. From these results together with earlier results at 300 K, we conclude there may be slight conformational differences of the Prosthecochloris protein between the crystalline form used for X-ray diffraction studies and that in a cryogenic solvent. By comparing spectral features of the two proteins in the same solvent, we are able for the first time to assign all seven of the expected exciton levels in each protein. These occur at 793, 801, 806, 810, 814, 819, and 825 nm in the Prosthecochloris protein, and at 793, 802, 806, 810, 816, 820, and 823 nm in the Chlorobium protein.

The amino acid sequences of the cytochromes c-555 from two green sulphur bacteria of the genus Chlorobium

Amino acid seauences are proposed for the cytochromes c-555 from Chlorobium thiosulphatophilum and from the Chlorobium limicola component of "Chloropseudomonas ethylica 2K". Each is a sincle polypeptide chain, the former of 86, the latter of 99 residues, and, when aligned so as to give the best match, 47 residues are common to the two sequences. The sequences show some resemblance to those of cytochromes c5 and f. The bacteriochlorophyll a-proteins were also isolated and purified, and their amino acid compositions compared (see the Appendix). There are significant differences in the compositions, but not as great as those found for the cytochromes c-555. The significance of these observations for the taxonomy of the Chlorobiaceae and for the further development of the comparative biochemistry of cytochrome c is discussed. Detailed evidence for the sequences of the cytochromes c-555 has been deposited as Supplementary Publication SUP 50073 (36 pages) at the British Library Lending Division, Boston Spa, Wetherby, West Yorkshire LS23 7BQ, U.K., from whom copies may be obtained on the terms given in Biochem. J. (1976) 153, 5.

An enriched reaction center preparation from green photosynthetic bacteria

Bacteriochlorophyll a reaction-center complex I from Chlorobium limicola f. thiosulfatophilum 6230 (Tassajara) was incubated in 2 M guanidine - HCl and then chromatographed on cross-linked dextran or agarose gel. Two principal components were separated: a larger component with photochemical activity (bacteriochlorophyll a reaction-center complex II) and a smaller component without activity (bacteriochlorophyll a protein). Complex II contains carotenoid, bacteriochlorophyll a, reaction center(s), and cytochromes b and c, but lacks the well characterized bacteriochlorophyll a protein contained in Complex I. Complex II carries out a light-induced reduction of cytochrome b along with an oxidation of cytochrome c.

Exciton interaction among chlorophyll molecules in bacteriochlorophyllaproteins and bacteriochlorophyllareaction center complexes from green bacteria

Absorption and CD spectra of bacteriochlorophyll a proteins and bacteriochlorophyll a reaction center complexes from two strains of Chlorobium limicola were recorded at 77 degrees K. Visual inspection showed that the Qy-band of chlorophyll in either protein was split into at least five components. Analysis of the spectra in terms of asymmetric Gaussian component pairs by means of computer program GAMET showed that six components are necessary to fit the spectra from strain 2K. These six components are ascribed to an exciton interaction between the seven bacteriochlorophyll a molecules in each subunit. The clear difference between the exciton splitting in the two bacteriochlorophyll a proteins shows that the arrangement of the chlorophyll molecules in each subunit must be slightly different. The spectra for the bacteriochlorophyll a reaction center complexes have a component at 834 nm (absorption) and 832 nm (CD) which does not appear in the spectra of the bacteriochlorophyll a proteins. The new component is ascribed to a reaction center complex which is combined with bacteriochlorophyll a proteins to form the bacteriochlorophyll a reaction center complex. The complete absorption (or CD) spectrum for a given bacteriochlorophyll a reaction center complex can be described to a first approximation in terms of the absorption (or CD) spectrum for the corresponding bacteriochlorophyll a protein plus the new component ascribed to the reaction center complex.