Flow rate and vertical position influence ingestion rates of colonial zebra mussels (Dreissena polymorpha)

1. Zebra mussels aggregate to form dense colonies where, depending on the flow rate, individuals in different vertical locations within the colony may experience restricted food availability. 2. Using ³²P‐labelled Chlamydomonas angulosa, we found ingestion rates of individual mussels located at the surface to exceed those in the bottom of a 6 cm thick colony by up to 75%. 3. Higher velocities (10 and 20 cm s^?1) increased algal delivery to the colony's middle layer (2–4 cm depth), subsequently increasing ingestion rates to equal those in the surface layer, while increasing ingestion only for the smallest mussels in the bottom (4–6 cm). 4. At all vertical locations within the colonies, smaller mussels showed higher ingestion rates per unit mass than larger mussels, particularly at higher flow rates.     

Phosphorylation of rat muscle acetyl-CoA carboxylase by AMP-activated protein kinase and protein kinase A

Winder, W. W., H. A. Wilson, D. G. Hardie, B. B. Rasmussen,C. A. Hutber, G. B. Call, R. D. Clayton, L. M. Conley, S. Yoon, and B. Zhou. Phosphorylation of rat muscle acetyl-CoA carboxylase byAMP-activated protein kinase and protein kinase A. J. Appl. Physiol. 82(1): 219-225, 1997This studywas designed to compare functional effects of phosphorylation of muscleacetyl-CoA carboxylase (ACC) by adenosine 3,5-cyclicmonophosphate-dependent protein kinase (PKA) and by AMP-activatedprotein kinase (AMPK). Muscle ACC (272 kDa) was phosphorylated and thensubjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresisfollowed by autoradiography. Functional effects of phosphorylation weredetermined by measuring ACC activity at different concentrations ofeach of the substrates and of citrate, an activator of the enzyme. Themaximal velocity(V_max) and theMichaelis constants(K_m) for ATP,acetyl-CoA, and bicarbonate were unaffected by phosphorylation by PKA.Phosphorylation by AMPK increased theK_m for ATP andacetyl-CoA. Sequential phosphorylation by PKA and AMPK, first withoutlabel and second with label, appeared to reduce the extent of label incorporation, regardless of the order. The activation constant (K_a) forcitrate activation was increased to the same extent by AMPKphosphorylation, regardless of previous or subsequent phosphorylation by PKA. Thus muscle ACC can be phosphorylated by PKA but with noapparent functional effects on the enzyme. AMPK appears to be the moreimportant regulator of muscle ACC.

     

Bacterial Symbionts in the Sugar Beet Root Maggot, Tetanops myopaeformis (von Röder)

Aerobic heterotrophic and facultative anaerobic bacteria were isolated from all developmental stages of the sugar beet root maggot, Tetanops myopaeformis (von Röder). Two distinct bacterial symbiotic relationships were observed. Serratia liquefaciens and Serratia marcescens were found to be associated with all developmental stages. Bacterial symbiont transmission occurred from one generation to the next. Symbionts were transferred from the male reproductive system to the female reproductive system, where both an internal infiltration of the egg chorion and an external smearing of the eggs occurred during oviposition. Pseudomonas maltophilia was found in association with the larval gut and the inner surface of the puparium. Electron microscopy of the inner puparial surface revealed symbionts within the chitinous wall. In vitro symbiont chitinase production was found, using both nephelometric (turbidimetric) and N-acetylglucosamine assays. A relationship appeared to exist between adult fly emergence and enzymatic chitin degradation of the puparium by the bacterial symbionts.     

A plasmid cloning vector for KpnI-cleaved DNA

A plasmid cloning vector containing a single site for KpnI has been generated by insertion of a 3.5-kb EcoRI/HindIII fragment of pCR1 into the EcoRI/HindIII sites of pBR322. KpnI cleavage yields 3′ rather than 5′ “sticky ends” which allows reconstitution of the recognition site after cloning by a homopolymer joining procedure. This is an advantage shared with only one or two other commercially available restriction enzymes.     

Inhibition of rosette formation by antithymocyte globulin

Summary The peripheral blood leukocytes from 29 patients with adenocarcinoma of the colon were studied sequentially for the T-cell level, the rosette-inhibition titer of antithymocyte globulin and the blastogenic response to PHA and Con A to evaluate the T-cell immunocompetence. The level of E-rosette-forming cells and the blastogenic response did not reflect the immunocompetence of the T-cell population. Fluctuations in the rosette-inhibition titer of antithymocyte globulin (ATG) were observed; an increased ATG titer indicated an unfavorable clinical course, while a decreased ATG titer was observed with patients who had a favorable clinical course. The rosette-inhibition titer with antithymocyte globulin was observed to be an important indicator of competent T cells in patients with colorectal cancer.Supported by the Physicians' Medical Education and Research Foundation and General Research Supports FundsAbbreviations used that are not spelled out in the text are: AET 2-aminoethylisothiouronium bromide; ATG Antithymocyte globulin; ALG Antilymphocyte globulin; E-RFC Erythrocyte rosette-forming cells; PHA Phytohemagglutinin; Con A Concanavalin A; E Sheep erythrocyte     

The recombination activating genes,RAG 1 and RAG 2, are on chromosome 11p in humans and chromosome 2p in mice

The recombination activating genes RAG-1 and RAG-2 are adjacent genes that act synergistically to activate variable-diversity-joining (V(D)J) recombination. Southern analysis of hybrid cell lines derived from patients with the Wilms tumor-aniridia-genitourinary defects-mental retardation (WAGR) syndrome and from mutagenized cell hybrids selected for deletions in chromosome 11 has allowed us to map the chromosomal location of the human RAG locus. The RAG locus defines a new interval of human chromosome 11p, but is not associated with any genetically mapped human disease. Guided by the chromosomal localization of the human recombination activating genes, we have also mapped the location of the mouse Rag locus.     

Evidence for WT1 as a Wilms tumor (WT) gene: intragenic germinal deletion in bilateral WT.

The inactivation of two alleles at a locus on the short arm of chromosome 11 (band 11p13) has been suggested to be critical steps in the development of Wilms tumor (WT), a childhood kidney tumor. Two similar candidate WT cDNA clones (WT33 and LK15) have recently been identified on the basis of both their expression in fetal kidney and their location within the smallest region of overlap of somatic 11p13 deletions in some tumors. These homozygous deletions, however, are large and potentially affect more than one gene. Using a cDNA probe to the candidate gene, we have analyzed DNA from both normal and tumor tissue from WT patients, in an effort to detect rearrangements at this locus. We report here a patient with bilateral WT who is heterozygous for a small (less than 11 kb) germinal deletion within this candidate gene. DNA from both tumors is homozygous for this intragenic deletion allele, which, by RNA-PRC sequence analysis, is predicted to encode a protein truncated by 180 amino acids. These data support the identification of this locus as an 11p13 WT gene (WT1) and provide direct molecular data supporting the two-hit mutational model for WT.     

Female competition and reproductive success in northern elephant seals

The probability of weaning a healthy pup increases with age in female northern elephant seals, Mirounga angustirostris. On Año Nuevo Island, California, weaning success among ‘prime’ females, those 6 years of age or older, was more than double that of ‘young’ females, those 3 to 5 years old. Prime females were better mothers than young females because of superior size, higher social dominance, and greater maternal experience; they were more likely to mate with high-ranking males and gave birth at an optimal time and place, circumstances that maximized the probability that their pups would survive, develop, and reproduce. The competitive advantage of prime-age mothers over younger ones was greatest when female and pup density was high. Young females improved their chances of reproducing successfully by emigrating from crowded harems and establishing new colonies.