Structure function analysis of theH-2 Ab p gene

The gene encoding the H-2A ^p class II chain was isolated from a B10.P genomic library and sequenced. This gene was also used to construct transfectants of the CH12 lymphoma clone CH12.LX, which express the Ab^p gene product in association with the endogenous A ^k chain. We present here the first report of the complete nucleotide coding sequence of Abp. The predicted amino acid sequence of Abp reveals only five residues different from Ab q, four of which are present in the mature peptide. These four amino acid changes could account for the differential susceptibility of H-2 q vs H-2 p mice to the development of collagen-induced arthritis (CIA). Antibodies specific for the transfected Abp protein induce CH 12. LX cells to secrete immunoglobulin in the presence of antigen. Comparison of the amino acid sequence with other A chains that have been tested in signal transduction experiments suggests that amino acid 9 may be important to the signaling ability of class II A molecules.     

Calcium-induced associations of the caseins: Thermodynamic linkage of calcium binding to colloidal stability of casein micelles

The caseins occur in milk as colloidal complexes of protein aggregates, calcium, and inorganic phosphate. As determined by electron microscopy, these particles are spherical and have approximately a 650 Å radius (casein micelles). In the absence of calcium, the protein aggregates themselves (submicelles) have been shown to result from mainly hydrophobic interactions. The fractional concentration of stable colloidal casein micelles can be obtained in a calcium caseinate solution by centrifugation at 1500g. Thus, the amount of stable colloid present with varying Ca²⁺ concentrations can be determined and then analyzed by application of equations derived from Wyman's Thermodynamic Linkage Theory. Ca²⁺-induced colloid stability profiles were obtained experimentally for model micelles consisting of only _s1- (a calcium insoluble casein) and the stabilizing protein -casein, eliminating the complications arising from - and minor casein forms. Two distinct genetic variants _s1-A andB were used. Analysis of _s1-A colloid stability profiles yielded a precipitation (salting-out) constantk ₁, as well as colloid stability (salting-in) parameterk ₂. No variations ofk ₁ ork ₂ were found with increasing amounts of -casein. From the variation of the amount of colloidal casein capable of being stabilized vs. amount of added -casein an association constant of 4 L/g could be calculated for the complexation of _s1-A and -casein. For the _s1-B and -casein micelles, an additional Ca²⁺-dependent colloidal destabilization parameter,k ₃, was added to the existingk ₁ andk ₂ parameters in order to fully describe this more complex system. Furthermore, the value ofk ₃ decreased with increasing concentration of -casein. These results were analyzed with respect to the specific deletion which occurs in _s1-caseinA in order to determine the sites responsible for these Ca²⁺-induced quaternary structural effects.     

Localisation régionale des gènes humains LDHB,TPI, ENO2, PepB,PGK, αGALA,G6PD et HGPRT par l'hybridation cellulaire interspécifique

Summary Twenty-two independent man-mouse (A9, HGPRT^-) and manhamster (CH, HGPRT)-hybrids using male human with balanced reciprocal translocation XY t(X;12)(q2,3;q1,2) were analysed for human genes localized on chromosome 12 (LDH_B, PepB, ENO₂, TPI), on chromosome X (PGK, GAL_A, G6PD) and for human chromosomes in relation with the balanced reciprocal translocation (chromosome 12, 12q^-, Xq⁺). The human chromosome 12q^- was not analysed because of its morphology is similar to some rodent chromosomes.The following results were obtained:1.Man-mouse hybrids (12 independent hybrids):The chromosome 12 is absent. A positive correlation is observed between Xq⁺, PGK, and PepB. Four hybrids are Xq⁺+PGK+PepB+ and eight hybrids are Xq⁺-PGK-PepB-This result indicate that the genes for human PGK, PepB are on the chromosome Xq+. 2.Man-hamster hybrids (10 independent hybrids):A positive correlation is observed between Xq⁺, PGK, GAL_A. Two hybrids are Xq⁺+PGK+GAL_A+ and eight hybrids are Xq⁺-PGK-GAL_A-.A positive correlation is observed between Xq⁺, PGK, GAL_A, PepB with the seven hybrids missing the normal human chromosome 12. One hybrid is Xq⁺+PGK+GAL_A+PepB+ and six hybrids are Xq⁺-PGK-GAL_A-PepB-. These results indicate that the genes for human PGK, GAL_A, PepB are on the chromosome Xq⁺. 3.Man-mouse and man-hamster hybrids:The highest percentage of presence in the hybrids is observed for the following markers: G6PD (100%), LDH_B, TPI, ENO₂ (90%). This is explained by the fact that these hybrids selected in HAT medium, had to retain a segment of X (Xq⁺ or 12q^-) bearing the human HGPRT gene. The different results indicated that the segment of X retained in these hybrids must be on the 12q^- and not on the Xq⁺, for Xq⁺ is rarely present in man rodent hybrids.The different results implicate finally the following localisations:LDH_B, TPI, ENO₂ on 12 q12 12pter,PepB on 12 q12 12qter;PGK, GAL_A on X q23 Xpter;HGPRT, G6PD on X q23 Xqter.     

Analysis of the 5′ flanking sequence of the Gγ globin gene by denaturing gradient gel electrophoresis confirms the heterogeneity of the Bantu βs haplotype

Summary The GCTT polymorphism recently described at positions — 1106 and — 1105 in the 5 flanking region of the G globin gene for the Bantu ^S haplotype was analysed by denaturing gradient gel electrophoresis. We studied 108 ^S chromosome and 122 ^A chromosomes. The TT sequence was found as follows: in all of 80 chromosomes bearing the Bantu ^S haplotype with the 6-bp deletion -400 nt from the G gene in 3 out of 5 Bantu ^S chromosomes without the deletion, in 1 out of 122 ^A chromosomes from different ethnic origins but in none of 23 ^S chromosomes bearing the Senegal, Benin or Cameroon haplotypes. These results confirm the heterogeneity of the Bantu ^S haplotype and allow a tentative evolutionary sequence for the different alleles at this locus to be presented.     

Expression pattern of voltage-dependent calcium channel α1 and β subunits in adrenal gland of N-type Ca2+ channel α1B subunit gene-deficient mice

The Ca²⁺ channel _1B subunit is a pore-forming component capable of generating N-type Ca²⁺ channel activity. Although N-type Ca²⁺ channel plays a role in a variety of neuronal functions, _1B-deficient mice exhibit normal life span without apparent abnormalities of behavior, histology or plasma norepinephrine level, presumably owing to compensation by some other Ca²⁺ channel ₁ or subunit. In this study, we studied the levels of _1A, _1C, _1D, _1E, ₁, ₂, ₃ and ₄ mRNAs in adrenal gland of _1B-deficient mice. The _1A mRNA in homozygous mice was expressed at higher level than in wild or heterozygous mice, but no difference in the expression levels of _1C, _1D, _1E, ₁, ₂, ₃ and ₄ was found among wild, heterozygous and homozygous mice. The protein level of _1A in homozygous mice was also expressed at higher level than in wild or heterozygous mice. To examine whether increased expression is induced by cis-regulatory element within 5-upstream region of _1A gene, we examined lacZ expression in _1B-deficient × _1A6.3-lacZ mice (carrying a 6.3-kb 5-upstream fragment of _1A gene fused to E. coli lacZ reporter gene), which express lacZ in medullar chromaffin cells, but not in cortex. The levels of lacZ expression in homozygous _1B-deficient × _1A6.3-lacZ mice were higher than in wild or heterozygous mice. Therefore, a possible explanation of the normal behavior and plasma norepinephrine level of _1B-deficient mice is that compensation by _1A subunit occurs and that 6.3-kb 5-upstream region of _1A gene contains enhancer cis-element(s) for compensation in adrenal medulla chromaffin cells. (Mol Cell Biochem 271: 91–99, 2005)     

The kinetic mechanism by which CCCP (carbonyl cyanidem-Chlorophenylhydrazone) transports protons across membranes

Summary We demonstrate that a simple kinetic model describes the transport of protons across lipid bilayer membranes by the weak acid CCCP (carbonyl cyanidem-chlorophenylhydrazone). Four parameters characterize this model: the adsorption coefficients of the anionic and neutral forms of the weak acid onto the interface ( _A and _HA) and the rate constants for the movement of A^– and HA across the membrane (k _A andk _HA). These parameters were determined by equilibrium dialysis, electrophoretic mobility, membrane potential, membrane conductance, and spectrophotometric measurements. From these equilibrium and steady state measurements on diphytanoyl phosphatidylcholine/chlorodecane membranes we found that _A= _HA=1.4 10^-3cm,k _A=175 s^–1 andk _HA=12,000 sec^–1. These parameters and our model describe our kinetic experiments if we assume that the protonation reactions, which occur at the interfaces, remain at equilibrium. The model predicts a single exponential decay of the current in a voltage-clamp experimetn. The model also predicts that the decay in the voltage across the membrane following an intense current pulse of short duration (50 nsec) can be described by the sum of two exponentials. The magnitudes and time constants of the relaxations that we observed in both voltage-clamp and charge-pulse experiments agree well with the predictions of the model for all values of pH, voltage and [CCCP].     

A new base substitution in the 5′ regulatory region of the humanAγ globin gene is linked with the βs gene

A new TA base substitution, identified inside the 5 regulatory region of the human^A globin gene (^A –499 T A), is reported. This nucleotide change was found to be linked incis with the mutation producing sickle cell anemia (CD6 GAGGTG: ^s gene).     

Thermal Stability of Glucose Oxidase from Penicillium adametzii

The thermal stability of glucose oxidase was studied at temperatures between 50 and 70°C by kinetic and spectroscopic (circular dichroism) methods. The stability of glucose oxidase was shown to depend on the medium pH, protein concentration, and the presence of protectors in the solution. At low protein concentrations (<15 g/ml) and pH > 5.5, the rate constants k _in, s^–1, for thermal inactivation of glucose oxidase were high. Circular dichroic spectra suggested an essential role of structures in stabilizing the protein globule. At a concentration of 15 g protein/ml, the activation energy E _Aof thermal inactivation of glucose oxidase in aqueous solution was estimated at 79.1 kcal/mol. Other thermodynamic activation parameters estimated at 60°C had the following values: H= 78.4 kcal/mol, G= 25.5 kcal/mol, and S= 161.9 entropy units. The thermal inactivation of glucose oxidase was inhibited by KCl, polyethylene glycols, and polyols. Among polyols, the best was sorbitol, which stabilized glucose oxidase without affecting its activity. Ethanol, phenol, and citrate exerted destabilizing effects.     

Thermodynamics of methylenetetrahydrofolate reduction to methyltetrahydrofolate and its implications for the energy metabolism of homoacetogenic bacteria

The thermodynamics of the methylenetetrahydrofolate reduction to 5-methyltetrahydrofolate was studied with the methylenetetrahydrofolate reductase purified from the homoacetogenic bacterium Peptostreptococcus productus. The equilibrium constants were determined for the forward and backward reactions of methylenetetrahydrofolate reduction with NADH or acetylpyridine adenine dinucleotide (APADH), respectively, as the electron donors. From the equilibrium constants and the known standard redox potentials at pH 7 (E ^o ) of the couples NAD⁺/NADH or APAD⁺/APADH the E ^o of the couple methylene-/methyltetrahydrofolate was determined to be about-200mV. This value is different from values reported before for this couple. The implications for the mechanism of energy conservation of homoacetogens is discussed.Abbreviations FH₄ tetrahydrofolate - CH₂=FH₄ 5,10-methylenetrahydrofolate - CH₃-FH₄ 5-methyltetrahydrofolate - K _eq equilibrium constant - G ^o Gibb's free energy change under standard conditions (all concentrations of reactants = 1 M) - G ^o G ^o at pH 7 ([H⁺]=10^-7 M) - E ^o standard redox potential - G ^o standard redox potential difference of two reactants - E ^o E ^o at pH 7 - R gas constant - F Faraday constant - APAD acetylpyridine adenine dinucleotide (NAD⁺-analogue)     

The minimal polymorphism of class II Eα chains is not due to the functional neutrality of mutations

Given the extensive allelic amino acid sequence polymorphism present in the first domain of A, A, and E chains and its profound effects on class II function, the minimal polymorphism in the mouse E chain (and in its human homologue DR) is paradox. Two possible explanations for the lack of polymorphism in E are: (1) the E chain plays such a uniquely critical structural/functional role in antigen presentation, T-cell activation, repertoire selection, and/or pairing with E or other proteins for expression that it cannot vary, and mutations are selected against; (2) the E chain plays a less significant role than the outer domains of other major histocompatibility complex (MHC) proteins in determining the interactions with processed peptides or with T-cell receptor (TCR), so there is no selective pressure to maintain new mutations. To explore this question we compared the ability of transfectants expressing wild type (wt) EE ^d and mutant E wt E ^d proteins to present peptides and bacterial superantigens to T-cell hybridomas. Mutations at the E amino acid positions 31, 52, and 65&66, to residues that represent allelic alternatives in A chains, significantly reduced activation of peptide-specific T hybridomas, and mutations at 71 sometimes enhanced T-cell stimulation. None of the E mutations reduced, and some enhanced, superantigen stimulation of T-cell hybridomas. These results argue against the hypothesis that E chains are minimally polymorphic because mutations in E are functionally neutral.     

L cells expressing DQ molecules of the DR3 and DR4 haplotypes: reactivity patterns with mAbs

cDNAs coding for the HLA class II DR and DQ and chains of the diabetogenic haplotypes DR3 and DR4 were introduced into a mammalian expression vector and transfected into L-cell mouse fibroblasts to produce cells expressing individual human class II molecules. Stable L transfectants were generated expressing each of the DR or DQ isotypes of the cis-encoded and chains of the DR3 or DR4 haplotypes, as well as the trans-encoded and chains of the DQ molecules of the two haplotypes. However, isotype mismatched combinations (DR/DQ or DQ/DR) did not result in any stable transfectants. The stable DQ L-cell transfectants obtained, along with homozygous B-cell lines expressing the DQ2 and DQ8 specificities, were tested against a large panel of twentyone anti-HLA class II monoclonal antibodies (mAbs). Their unusual reactivity patterns are described including the failure of most pan-DQ mAbs to react with all DQ expressing L-cell transfectants. Interestingly, some mAbs react with certain heterodimers expressed on B-LCL but fail to recognize the same heterodimers expressed on the transfectants. This is suggestive of minor structural modifications that class II molecules undergo depending on the cells they are expressed on.The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession number U07848. The name DQB1 ^* 0202 was officially assigned by the WHO Nomenclature Committee in April 1994. This follows the agreed policy that, subject to the conditions stated in the most recent Nomenclature Report (Bodmer et al. 1992), names will be assigned to new sequences as they are identified. Lists of such new names will be published in the following WHO Nomenclature Report     

A light microscopic study of nuclear and cytoplasmic size of the aggregate acidophil population in the hypophysis cerebri,pars distalis,of adult male mule deer,Odocoileus hemionus hemionus,relative to seasons of the photoperiod and antler cycles

Summary Nuclear and cytoplasmic size (²) of acidophils in the pars distalis of adult male deer were measured and the data analyzed statistically with reference to the four classical seasons of the photoperiodic cycle and five periods and two events of the antler cycle. The seasons, and the respective mean cross-sectional areas of cell nuclei and cytoplasm, are: Spring (21 March–20 June; increasing photoperiod greater than 12 hours), 28.45 and 48.68 ²; Summer (21 June–20 September; decreasing photoperiod greater than 12 hours), 27.81 and 44.25 ²; Fall (21 September–20 December; decreasing photoperiod less than 12 hours), 30.40 and 45.07 ²; Winter (21 December–20 March; increasing photoperiod less than 12 hours) 27.28 and 40.30 ². Beginning in late winter and early spring the components of the antler cycle, and the respective cross-sectional areas of cell nuclei and cytoplasm, are: Initial Antler Growth, 28.08 and 38.58 ²; Growth of Velvet Antler Form, 28.93 and 50.61 ², Antlers Hardening, 27.53 and 40.83 ²; Velvet Shedding, 29.03 and 53.20 ²; Rutting Season, 29.95 and 44.97 ²; Preparation for Shedding, 26.50 and 40.38 ²; Antlers Recently Shed, 27.53 and 47.85 ². Shedding of boney antlers, growth of velvet antlers and increases in nuclear and cytoplasmic areas of acidophil cells in the pars distalis occur when the photoperiod is increasing. Construction and retention of hard antlers occur when photoperiod is decreasing. This lessening of day length appears to influence the gonadotrophs that regulate secretion of testosterone.A part of a dissertation submitted in partial fulfillment of the requirements for the degree Doctor of Philosophy, Anatomy, Colorado State University. Specimens were contributed by Colorado Federal Aid Project W-105-R, Colorado Division of Game, Fish and Parks, Game Research Center, Fort Collins and investigations of them was supported by grant T1-DE130 from the National Institutes of Health, Bethesda, Maryland, U.S.A.NIDR Predoctoral Trainee.     

Reaction centers from three herbicide resistant mutants of Rhodobacter sphaeroides 2.4.1: Kinetics of electron transfer reactions

Electron transfer rates were measured in RCs from three herbicide-resistant mutants with known amino acid changes to elucidate the structural requirements for last electron transfer. The three herbicide resistant mutants were IM(L229) (Ile-L229 Met), SP(L223) (Ser-L223 Pro) and YG(L222) (Tyr-L222 Gly). The electron transfer rate D⁺Q_A ^-Q_BD⁺Q_AQ_B (k _AB) is slowed 3 fold in the IM(L229) and YG(L222) RCs (pH 8). The stabilization of D⁺Q_AQ_B ^- with respect to D⁺Q_AQ_B ^- (pH 8) was found to be eliminated in the IM(L229) mutant RCs (G⁰ 0 meV), was partially reduced in the SP(L223) mutant RCs (G⁰=–30 meV), and was unaltered in the YG(L222) mutant RCs (G⁰=–60 meV), compared to that observed in the native RCs (G⁰=–60 meV). The pH dependences of the charge recombination rate D⁺Q_AQ_B ^-DQ_AQ_B (k _BD) and the electron transfer from Q_A ^- (k _QA ^-Q_A) suggest that the mutations do not affect the protonation state of Glu-L212 nor the electrostatic interactions of Q_B and Q_B ^- with Glu-L212. The binding affinities of UQ₁₀ for the Q_B site were found in order of decreasing values to be native IM(L229) > YG(L222) SP(L223). The altered properties of the mutant RCs are used to deduce possible structural changes caused by the mutations and are dicscussed in terms of photosynthetic efficiency of the herbicide resistant strains.Abbreviations Bchl bacteriochlorophyll - Bphe bacteriopheophytin - cholate 3,7,12-trihydroxycholanic acid - D donor (bacteriochlorophyll dimer) - EDTA ethylenediamine tetraacetic acid - Fe²⁺ non-heme iron atom - LDAO lauryl dimethylamine oxide - PS II photosystem II - Q_A and Q_B primary and secondary quinone acceptors - RC bacterial reaction center - Tris tris(hydroxymethyl)aminomethane - UQ₀ 2,3-dimethoxy-5-methyl benzoquinone - UQ₁₀ ubiquinone 50     

Formation of the imidazolides of dinucleotides under potentially prebiotic conditions

Summary Imidazolides of dinucleotides such as ImpApA can be formed from the corresponding dinucleotides in a two-stage process, which gives up to 15% yields under potentially prebiotic conditions. First a solution of the dinucleotide and sodium trimetaphosphate is dried out at constant temperature and humidity. This produces polyphosphates such as pnApA in excellent yield (80%). The products are dissolved in water, imidazole is added, and the solution is dried out again. This yields the 5-phosphorimidazolides.Abbreviations P₃! trimetaphosphate - A adenosine - U uridine - EDTA ethylenediaminetetraacetic acid - Ap adenosine 2(3)-phosphate - Ap! adenosine cyclic 2:3-phosphate - pA adenosine 5-phosphate - pA²p adenosine 2, 5-diphosphate - pA³p adenosine 3, 5-diphosphate - pAp! 5-phospho-adenosine cyclic 2:3-phosphate - ATP adenosine 5-triphosphate - ImpA adenosine 5-phosphorimidazolide - A²pA adenylyl-[25]-adenosine - A³pA adenylyl-[35]-adenosine - A²pU adenylyl-[25]-uridine - A³pU adenylyl-[35]-uridine - pA²pA 5-phosphoadenylyl-[25]-adenosine - pA³pA 5-phospho-adenylyl-[35]-adenosine - pA²pU 5-phospho-adenylyl-[25]-uridine - pA³pU 5-phospho-adenylyl-[35]-uridine - pApN (N= A, U) 5-phosphate of a dinucleoside phosphate - p_nApN (N = A, U; n = 2, 3, 4.) 5-polyphosphate of a dinucleoside phosphate - ImpA²pA imidazolide of pA²pA - ImpA³pA imidazolide of pA³pA - ImpA²pU imidazolide of pA²pU - ImpA³pU imidazolide of pA³pU - ImpApN imidazolide of pApN     

Biochemical and immunological responses of hairy cell leukemia patients to interferonβ

Summary Ten hairy-cell leukemia patients were treated with interferon (IFN-) at a dose rate of 2 × 10⁶ IU/m² × 5 days for 4 weeks (induction therapy) and, thereafter, at the same dose three times a week for 11 months (maintenance therapy). The effect of this treatment on serum neopterin, 2-microglobulin, (2–5)oligoadenylate [(2–5)A _n ] levels, intracellular (2–5)A _n values and human Mx protein synthesis was analysed. There were significant rises in serum neopterin and (2–5)A _n levels during both induction and maintenance, whereas 2-microglobulin levels rose only during induction. Rises in intracellular (2–5)A _n were documented mainly during induction, but they were not significantly higher than pretherapy values. IFN provoked an increase in human Mx protein synthesis over the entire induction — maintenance period, but was only significantly higher than baseline during induction. All markers proved useful for monitoring the effects of IFN dose schedules, but were not predictive of clinical outcome. Natural killer activity and IFN production, which were initially defective, followed a different trend from that of the other factors studied, in that increases were documented only late in the course of therapy when the disease was already in remission.     

A detailed serological analysis of a xenogeneic anti-Ia serum

Rabbit anti-mouse-Ia serum was raised against Ia specificities present in CBAJH (H-2 _k) serum. This xenogeneic antiserum was considered to react with similar specificities to those detected by mouse anti-Ia^k alloantisera and more evidence is now presented for this contention. By absorption, the xenogeneic antiserum was found to react with spleen, lymph node, bone marrow, and thymus, reactions similar to that found with the allogeneic anti-Ia^k antiserum. Furthermore, red cells, platelets, brain, kidney, and liver could not absorb the activity from the xenogeneic antiserum, demonstrating the selective tissue distribution of the antigens reactive with this serum. This reactive population was previously shown to consist of B cells and a subpopulation of T cells. In a backcross study of (C57BL/6 × A)F₁ × C57BL/6, the rabbit anti-Ia and mouse anti-Ia reactions were found to segregate together, and some evidence for the genetic regulation of the expression of Ia specificities was also found. By direct testing, and by absorption testing using a number of strains, the xenogeneic antiserum was shown to contain high titers of antibody to Ia.1, 3, 7, 15, and 17; lower titers to Ia.19, and 22; little antibody to Ia.18, and no reaction for the private specificity Ia. 2, although the multiple absorptions required to define these specificities may have observed some reactions. The data indicate that the xenogeneic and allogeneic anti-Ia_k antisera recognize similar Ia determinants, which map to theLA, IE andIC subregions of theH-2 complex. These have been given the same specificity designation as the allogeneic specificities, but they are separately identified by a prime (').     

Transient state characteristics of adaptation to changes in light conditions for the cyanobacterium Oscillatoria agardhii

Transitions in growth irradiance level from 92 to 7 Em^-2 s^-1 and vice versa caused changes in the pigment contents and photosynthesis of Oscillatoria agardhii. The changes in chlorophyll a and C-phycocyanin contents during the transition from high to low irradiance (HL) were reflected in photosynthetic parameters. In the LH transition light utilization efficiencies of the cells changed faster than pigment contents. This appeared to be related to the lowering of light utilization efficiencies of photosynthesis. As a possible explanation it was hypothesized that excess photosynthate production led to feed back inhibition of photosynthesis. Time-scales of changes in the maximal rate of O₂ evolution were discussed as changes in the number of reaction centers of photosystem II in relation to photosynthetic electron transport. Parameters that were subject to change during irradiance transitions obeyed first order kinetics, but hysteresis occurred when comparing HL with LH transients. Interpretation of first order kinetic analysis was discussed in terms of adaptive response vs changes in growth rate.Non-standard abbreviations Chla chlorophyll a - CPC C-phycocyanin - PS II photosystem II - PS I photosystem I - RC II reaction center of photosystem II - P photosynthetic O₂-evolution - I irradiance, Em^-2 s^-1 - light utilization efficiency of cells, mmol O₂·mg dry wt^-1·h^-1/Em^-2 s^-1 - light utilization efficiency of photosynthetic apparatus, mol O₂·mol Chla ^-1·h^-1/Em^-2 s^-1 - P_max maximal rate of O₂ evolution by cells, mol O₂·mg dry wt^-1·h^-1 - P_max maximal rate of O₂ evolution by photosynthetic apparatus, mol O₂·mol·Chla ^-1·h^-1 - LL low light, E m^-2 s^-1 - HL high light, E m^-2 s^-1 - LH low to high light transition - HL high to low light transition - k specific rate of adaptation, h^-1 - specific growth rate, h^-1 - Q pool size of cell constituent, mol·mg dry wt^-1 - q net synthesis rate of cell constituent, mol·mg dry wt^-1·h^-1     

Mode of uptake of sterol by Arthrobacter simplex

The mechanism of uptake of water-insoluble -sitosterol by a newly isolated strain of Arthrobacter simplex SS-7 was studied. The production of an extracellular sterol-pseudosolubilizing protein during growth of A. simplex on -sitosterol was demonstrated by isolating the factor from the cell-free supernatant and its subsequent purification by Sephadex G-150 column chromatography. The M _r of the purified sterol-pseudosolubilizing protein determined by SDS–PAGE was 19kDa. The rate of sterol pseudosolubilization (5.2×10^–3g l^–1h^–1) could not adequately account for the rate of sterol uptake (72×10^–3g l^–1h^–1) and the specific growth rate (56×10^–3 h^–1). However in the unfavourable growth condition, when the cells were treated with sodium azide at the level of 30–60% of MIC, the sterol pseudosolubilization accounted for nearly 74% of the total growth containing 96% free cells. Cellular adherence to substrate particles was found to play an active role in the normal growth of the strain on -sitosterol. Unlike sodium acetate-grown cells, whose surface activity was negligible (60mNm^–1), the sterol-grown cells had strong surface activity (40mNm^–1). The high lipid content and long chain fatty acids in the cell-wall of -sitosterol-grown cells probably contribute to the high sterol adherence activity of the cells.     

β-Globin gene polymorphism in the Saudi Arab population

Summary DNA mapping with the restriction endonucleases, Hpa I and Mst II, has been used to investigate -globin gene polymorphism in the Saudi Arab population. Using Hpa I digestion, 13.0kb and 7.6kb fragments were found in association with the ^A and ^S genes. The frequency of the polymorphic forms in two regions investigated vary significantly. In Al-Hafouf and the surrounding villages, situated in the Eastern Province of Saudi Arabia, the frequencies of association of the ^S gene with the Hpa I 7.6kb, 7.0kb, and 13.0kb fragments were 0.866, 0.043, and 0.071, respectively. The frequency of association of ^A with the 7.6kb and 13.0kb fragments resulting from the Hpa I digestion were 0.875 and 0.125. In Khaiber, Tehamat-Aseer, and surrounding villages, in the Western Province, the frequency of association of ^S with 7.6kb, 7.0kb, and 13.0kb fragments were 0.836, 0.027, and 0.0136, respectively, while that of ^S was 0.250 and 0.750 with 7.0kb and 13.0kb Hpa I fragments, respectively. Using Mst II digestion, ^A was found to be linked to a 1.15kb fragment, while ^s was linked to a 1.35kb fragment. The normal (Hb AA), heterozygotes (Hb AS), and homozygotes (Hb SS) gave 1.15, 1.15/1.35, and 1.35kb fragments, respectively. The results of this study show extensive polymorphism at the Hpa I restriction site of the ^A and ^S globin genes with the different polymorphic forms existing at a variable frequency in different regions of Saudi Arabia.     

Cloned T cells recognize Trichinella spiralis antigen in association with an Ek βEk α restriction element

A method is described for the production of T-cell lines and clones specific for solubilized Trichinella spiralis antigens. hese T cells are antigen-specific and do not respond to challenge with a third party antigen (lysozyme). The proliferation responses of the cloned T cells are specifically inhibited by anti-I-E but not by anti I-A subregion monoclonal reagents. The inhibition patterns obtained are consistent with cis-gene complementation in B10.K cells involving the E^k -chain and the E^k -chain of the I-E molecule. Inhibition is obtained with an E^k -specific monoclonal antibody (H9-14.8) but not with an A^k -specific monoclonal antibody (10-2.16). Inhibition was also observed with Ia.7-specific (H40-242) or Ia.22-specific (17-3-3) monoclonal antibodies. The inhibition patterns were confirmed by antigen presentation experiments using recombinant inbred mice. Only B 10.K (E^k E^k spleen cells and not B 10.A(5R) (E^b E^k ) or B10.S(9R) (E^s E^k ) spleen cells could effectively present T. spiralis antigens. The role of hybrid Ia molecules in the immune response to T. spiralis is discussed.