Effects of mot gene expression on the structure of the flagellar motor

Direct freezing procedures have enabled us to visualize distinctive intramembrane particle ring structures in the cytoplasmic membranes of peritrichously flagellated bacteria by means of freeze-fracture electron microscopy. These structures were identified as flagellar motor components because their distribution matched that of flagella, and because they were absent in non-flagellated mutants of Escherichia coli. Particle rings were present in both the Gram-positive Streptococcus and the Gram-negative E. coli. In E. coli, a non-functional mocha operon produced flagellated but immotile cells lacking the particle rings. Simultaneous introduction of the motA and motB genes, led to recovery of both motility and the ring structures but neither gene alone was sufficient. The concomitant loss of the rings and motility is consistent with the ring particles having a central role in the flagellar motor.     

The use of the probit model to predict pregnancy status of buffalo based on physio-chemical properties of estrual mucus

Improper timing of artificial insemination with respect to ovulation is one of the major factors hampering the conception rate in buffalo. The present study was an attempt to relate physio-chemical changes in estrual mucus to subsequent pregnancy status in order to find their optimal values for determining the time for artificial insemination (AI). Serum estradiol, total protein and dry matter contents of estrual mucus were evaluated to predict the subsequent pregnancy in 36 buffalo during October 1988 to February 1989. Serum estradiol was determined by radioimmunoassay (RIA); spinnbarkeit, dry matter and total protein were determined by standard methods. Multivariate probit analyses were carried out to relate these variables to subsequent pregnancy status. Elasticity and protein concentration were significantly related to prediction probability of pregnancy status, and they predicted the pregnancy status 86% of the times correctly (P < 0.05). The probability of pregnant animals being correctly classified was 0.76, whereas the corresponding value for non-pregnant animals was 0.95. The present study demonstrated the possibility of using such a statistical model on mucus characteristics for determining proper AI time for better conception rates in Nili-Ravi water buffalo.     

Copper(II) (3,5-diisopropylsalicylate)2 oxidizes thiols to symmetrical disulfides and oxidatively converts mixtures of 5-thio-2-nitrobenzoic acid and nonsymmetrical 5-thio-2-nitrobenzoic acid disulfides to symmetrical disulfides

L-cysteine, D-penicillamine, and L-glutathione were oxidized to symmetrical disulfides in the presence of Cu(II)(3,5-DIPS)2 and air-oxygen at physiologic pH, 7.3. Air-oxygen caused the oxidation of thiol reduced copper, Cu(I), to Cu(II), as evidenced by expected spectrophotometric changes in these reaction mixtures. L-cysteine, D-penicillamine, and L-glutathione formed mixed disulfides and TNB with the addition of DTNB to solutions of these thiols. The observed order of reactivity for these thiols with DTNB was: L-cysteine greater than D-penicillamine greater than L-glutathione. Surprisingly, Cu(II)(3,5-DIPS)2 converted these mixed disulfides to their symmetrical disulfides and DTNB, and although the initial conversion rate was rapid, complete conversion required more than two hours. These observations suggest caution with regard to the spectrophotometric determination of thiols immediately after the addition of Ellman's reagent. These results also clarify an earlier report concerning the oxidation of thiols by Cu(II)(o-phenanthroline)2 and offer caution with regard to the determination of thiols using DTNB in the presence of copper complexes. Spectrophotometric data are provided in support of the suggestion that analysis of plasma or cellular samples for thiols be done in the absence of copper(II) complexes to avoid false negative results.     

Comparison of the carbohydrate composition of rat and human corticosteroid-binding globulin: species specific glycosylation.

We have examined the carbohydrate composition of corticosteroid-binding globulin (CBG) obtained from rat and human serum. Rat CBG contained a carbohydrate composition that was strikingly different from that of human CBG. Like other glycoproteins that circulate in human plasma, human CBG had a carbohydrate composition that was consistent with the presence of biantennary and triantennary oligosaccharide structures. In contrast, the carbohydrate composition of rat CBG indicated the presence of more than one sialic acid residue per antenna. It is not clear whether rat CBG contains a carbohydrate structure with sialic acids attached to both galactose and N-acetylglucosamine on the same antenna, or a terminal disialylated structure (sialic acid linked alpha 2-8 to sialic acid). These structural variations may play a role in the interaction of CBG with its receptor.     

The molecular mechanism of inhibition of alpha-type DNA polymerases by N2-(butylphenyl)dGTP and 2-(butylanilino)dATP: variation in susceptibility to polymerization.

Calf thymus DNA polymerase alpha (pol alpha) and bacteriophage T4 DNA polymerase (pol T4) were exploited as model enzymes to investigate the molecular mechanism of inhibitory action of N2-(p-n-butylphenyl)dGTP (BuPdGTP) and 2-(p-n-butyl-anilino)dATP (BuAdATP) on the BuPdNTP-susceptible alpha polymerase family. Kinetic analysis of inhibition of pol alpha with mixtures of complementary and noncomplementary template:primers indicated that both nucleotides induced the formation of a polymerase: inhibitor:primer-template complex. Primer extension experiments using the guanine form as the model analog indicated that pol alpha cannot utilize these nucleotides to extend primer termini. In contrast, pol T4 polymerized BuPdGTP, indicating that resistance to polymerization is not a common feature of the inhibitor mechanism among the broad membership of the alpha polymerase family.     

Differential and analytical subfractionation of rat liver components internalizing insulin and prolactin

Receptor-mediated endocytosis of 125I-insulin and 125I-prolactin into liver parenchymal cells has been studied by quantitative subcellular fractionation. Differential centrifugation yielded three particulate fractions, N (nuclear), ML (large granule), and P (microsomes), and a final supernatant (S). Quantitative differences in the extent and rates of accumulation of 125I-insulin and 125I-prolactin into the fractions were observed. The acidotropic agent chloroquine and the microtubule disrupting agent colchicine were administered separately to rats. The agents increased significantly the T 1/2 of hormone clearance from the liver and augmented the accumulation of both ligands in the low-speed ML fraction. However, differences in the rates of accumulation of insulin and prolactin into all cell fractions were still maintained. Analytical centrifugation of each of the particulate fractions was carried out in order to determine if different endocytic components were specific to insulin or prolactin internalization. This was not the case. An "early" endosomal component of density 1.11 was identified in microsomes. A "late" endosome of density 1.10 was identified in the large granule (ML) fraction. Both endosomal components appeared to accumulate insulin and prolactin but at different rates. Marker enzyme analysis identified the presumed plasma membrane component in microsomes (density approximately 1.155). This component showed a significant difference in the rate of loss of 125I-insulin (T 1/2 approximately 4.1 min) as compared to that of 125I-prolactin (T 1/2 approximately 12.7 min). A further difference in the handling of the ligands was observed in early endosomes.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cloning and expression of a cDNA encoding a catalytically active fragment of calf thymus DNA polymerase alpha

A calf thymus cDNA expression library was constructed in the EcoRI site of lambda gt11 and probed with an antibody raised against calf thymus DNA polymerase alpha. Three classes of antibody-reactive clones were isolated. The largest class carried a 1.9 kilobase calf cDNA insert and expressed a 165-175 kilodalton beta-galactosidase:calf fusion protein which displayed DNA polymerase activity. The characteristic responses of the polymerase activity to alpha-specific inhibitors and antibodies identified the 1.9 kilobase cDNA as a sequence specifically derived from the structural gene encoding the pol alpha catalytic core.     

Limnology and plankton periodicity of Jos Plateau water reservoir,Nigeria, West Africa

Limnological data (Dec. 1980–Jan. 1982) on the plankton and water chemistry of Lamingo Dam, located within the Jos biotite granite area of the Plateau State (Nigeria) are presented. The water-body falls in Beadle's (1981) category I of African lakes (conductivity < 40 µS cm^–1). Alkalinity (% MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGabmiEayaara% aaaa!3914!\[\bar x\] = 0.3 meq l^–1), principally composed of bicarbonates, dominated the anions % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGak0Jf9crFfpeea0xh9v8qiW7rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaaK4waiaajI% eacaqIdbGaaK4tamaaxababaGaeyOeI0caleaacaaIZaaabeaakiaa% b6dacaqIdbGaaKiBaiaaj2cacaqG+aGaaK4uaiaaj+eadaqhaaWcba% GaaKinaaqaaiaajkdacaqITaaaaOGaaKyxaaaa!4657!\[\user1{[HCO}\mathop -\limits_3 {\text{ > }}\user1{Cl - }{\text{ > }}\user1{SO}_\user1{4}^{\user1{2 - }} \user1{]}\]The plankton were characterized by a moderate standing crop of phytoplankton, and zooplankton were, generally, very limited in species and abundance. The order of dominance for the categories of phyto and zooplankton was: [Bacillariophyceae > Chlorophyceae > Dinophyceae] and [Rotifera > Crustacea] respectively. A diel cycle was characterized by nocturnal upward migration of the zooplankton, and the reverse behaviour in the phytoplankton.Interrelations between the biotic assemblages of plankters and various physical and chemical variables are discussed.     

Influence of the presence of Zymomonas anaerobia on the conversion of cellobiose, glucose, and xylose to ethanol by Clostridium saccharolyticum

To convert sugar mixtures containing cellobiose, glucose, and xylose to ethanol in a single step, the possibility of using a coculture consisting of Clostridium saccharolyticum and Zymomonas anaerobia was studied. In monoculture, C. saccharolyticum utilized all three sugars; however, it preferentially utilized glucose and produced acetic acid in addition to ethanol. The formation of acetic acid from the metabolism of glucose inhibited the growth of C. saccharolyticum and, consequently, the utilization of cellobiose and xylose. In monoculture, Z. anaerobia utilized glucose at a rate of 50 g/L day, but it did not ferment cellobiose or xylose. In coculture, Z. anaerobia converted most of the glucose to ethanol during the lag phase of growth of C. saccharolyticum, which then converted cellobiose and xylose to ethanol. The use of this coculture increased both the rate and the efficiency of the conversion of these three sugars to ethanol, and produced relatively small amounts of acetic acid.