Effects of gamma-irradiation on chromosomes of cultured lymphocytes from rheumatoid arthritis patients and their family members

Increased rates of spontaneous or induced chromosome breakage are seen in many types of diseases, including the 'collagen-type' autoimmune diseases. Using a 60Co gamma cell, we irradiated lymphocyte cultures from three related rheumatoid arthritis patients, their immediate family members, and two unrelated rheumatoid arthritis patients. Although these individuals had not shown abnormally high levels of spontaneous chromosome breakage, they did show an abnormal sensitivity to irradiation, which was manifested in several ways. Two of the probands showed induced breakage rates that were twice as high as those seen in controls. In addition, the reduction of mitotic index, due either to increased cell death or to induction of a G2 lag period, was higher in the arthritis group (including non-symptomatic family members) than in the control group. Finally, we observed a high frequency of an unusual type of cell in the arthritis group. These unusual cells resembled c-anaphases seen with extended colcemid treatment, and may indicate that the mitotic apparatus in cells from this group is particularly sensitive to ionizing radiation.     

In vivo assembly of a biological membrane of defined size, shape, and lipid composition.

At restrictive temperature, mutant ts1 of bacteriophage PM2 makes membrane vesicles inside infected Alteromonas espejiana. A shift from restrictive to permissive temperature resulted in rapid maturation to infectious virions. The membrane vesicles were isolated from cellular membranes by sucrose density gradient centrifugation. Analysis of the unique peak at rho = 1.190 g/cm3 showed spheres of two diameters, 50 nm and 54 nm. The wild-type virus is icosahedral with an average diameter of 60 nm. Gel electrophoresis indicated the absence in the vesicles of the coat and spike proteins. sp27 and sp43, respectively, and the presence of only one viral structural protein, sp6.6. DNA was also present. The lipid in the vesicles was composed of phosphatidylglycerol and phosphatidylethanolamine in a proportion similar to that of the wild-type virus, whose ratio is nearly the inverse of that found in the host membrane. Thus, membrane vesicles made by mutant ts1 resembled the membrane of the wild-type virus in size, shape, and lipid composition, but contained only one of the four structural proteins of the virus. This hydrophobic protein, sp6.6 may be responsible for stimulating membrane morphogenesis.     

In vivo metabolism of a mutant apolipoprotein, apoA-IIowa, associated with hypoalphalipoproteinemia and hereditary systemic amyloidosis.

Apolipoprotein (apo) A-I is the major protein constituent of plasma high density lipoproteins (HDL). A kindred has been identified in which a glycine to arginine mutation at residue 26 in apoA-I is associated with hypoalphalipoproteinemia and hereditary systemic amyloidosis. We isolated the mutant protein, termed apoA-IIowa, from the plasma of an affected subject and studied its in vivo metabolism compared to that of normal apoA-I in two heterozygous apoA-IIowa subjects and two normal controls. Normal and mutant apoA-I were radioiodinated with 131I and 125I, respectively, reassociated with autologous plasma lipoproteins, and simultaneously injected into all subjects. Kinetic analysis of the plasma radioactivity curves demonstrated that the mutant apoA-IIowa was rapidly cleared from plasma (mean fractional catabolic rate [FCR] 0.559 day-1) compared with normal apoA-I (mean FCR 0.244 day-1) in all four subjects. The FCR of normal apoA-I was also substantially faster in the heterozygous apoA-IIowa subjects (mean FCR 0.281 days-1) than in the normal controls (mean FCR 0.203 days-1). Despite the rapid removal from plasma of apoA-IIowa, the cumulative urinary excretion of its associated radioactivity after 2 weeks (44%) of the injected dose) was substantially less than that associated with normal apoA-I (78% of injected dose), indicating extravascular sequestration of radiolabeled apoA-IIowa.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of the amino acid sequences of tissue-specific parvalbumins from chicken muscle and thymus and possible evolutionary significance

Chicken leg muscle parvalbumin was digested with cyanogen bromide or trypsin or trypsin after citraconylation. Peptides isolated by reverse phase HPLC at pH 7.0 were subjected to acid hydrolysis and amino acid analysis and, in some cases, sequencing. The chicken muscle parvalbumin amino acid sequence has ca. 80% sequence identity with alpha-type parvalbumins from mammalian (rabbit, human and rat) muscle. By contrast, the chicken thymus parvalbumin ("avian thymic hormone") sequence is very similar to reptile (turtle, salamander and frog) muscle beta-type parvalbumins. We hypothesize that the evolutionary appearance of the warm-blooded reptiles was accompanied by recruitment of the beta parvalbumin isozyme for promotion of lymphocyte maturation.     

Partial characterization of a Trypanosoma cruzi-released decomplementing factor

Trypanosoma cruzi releases a factor (SCAF) when grown in vitro which decomplements normal mouse, human, and guinea pig sera. The production and potency of SCAF was dependent on the density of cultured parasites, parasite viability and proliferative capacity, and duration of culture. The in vitro interaction between SCAF and serum complement (C') occurred rapidly and was complete within 30 min of mixing. The administration of SCAF to normal mice resulted in up to 50% reduction in hemolytic C' activity, whereas SCAF had no effect on the C' levels in mice infected wit T. cruzi for more than 10 days. The active moiety of SCAF was shown to be a nonproteinaceous substance(s) with a molecular weight of approximately 23,000 daltons.     

The topology of genome-scale metabolic reconstructions unravels independent modules and high network flexibility

The topology of metabolic networks is recognisably modular with modules weakly connected apart from sharing a pool of currency metabolites. Here, we defined modules as sets of reversible reactions isolated from the rest of metabolism by irreversible reactions except for the exchange of currency metabolites. Our approach identifies topologically independent modules under specific conditions associated with different metabolic functions. As case studies, the E.coli iJO1366 and Human Recon 2.2 genome-scale metabolic models were split in 103 and 321 modules respectively, displaying significant correlation patterns in expression data. Finally, we addressed a fundamental question about the metabolic flexibility conferred by reversible reactions: “Of all Directed Topologies (DTs) defined by fixing directions to all reversible reactions, how many are capable of carrying flux through all reactions?”. Enumeration of the DTs for iJO1366 model was performed using an efficient depth-first search algorithm, rejecting infeasible DTs based on mass-imbalanced and loopy flux patterns. We found the direction of 79% of reversible reactions must be defined before all directions in the network can be fixed, granting a high degree of flexibility.     

Exercise increases the release of NAMPT in extracellular vesicles and alters NAD + activity in recipient cells

Aging is associated with a loss of metabolic homeostasis, with cofactors such as nicotinamide adenine dinucleotide (NAD⁺) declining over time. The decrease in NAD⁺ production has been linked to the age‐related loss of circulating extracellular nicotinamide phosphoribosyltransferase (eNAMPT), the rate‐limiting enzyme in the NAD⁺ biosynthetic pathway. eNAMPT is found almost exclusively in extracellular vesicles (EVs), providing a mechanism for the distribution of the enzyme in different tissues. Currently, the physiological cause for the release of eNAMPT is unknown, and how it may be affected by age and physical exercise. Here, we show that release of small EVs into the bloodstream is stimulated following moderate intensity exercise in humans. Exercise also increased the eNAMPT content in EVs, most prominently in young individuals with higher aerobic fitness. Both mature fit and young unfit individuals exhibited a limited increase in EV‐eNAMPT release following exercise, indicating that this mechanism is related to both the age and physical fitness of a person. Notably, unfit mature individuals were unable to increase the release of eNAMPT in EVs after exercise, suggesting that lower fitness levels and aging attenuate this important signalling mechanism in the body. EVs isolated from exercising humans containing eNAMPT were able to alter the abundance of NAD⁺ and SIRT1 activity in recipient cells compared to pre‐exercise EVs, indicating a pathway for inter‐tissue signalling promoted through exercise. Our results suggest a mechanism to limit age‐related NAD⁺ decline, through the systemic delivery of eNAMPT via EVs released during exercise.     

Detecting Invasions of Marine Organisms: Kamptozoan Case Histories

Detecting marine invasions can be challenging, especially for lesser-known taxa, and requires (a) thorough field surveys of the region of interest for members of the taxon, (b) systematic analyses to identify all species found, (c) literature searches for the worldwide distribution of these species and for previous records of the taxon in this region, and (d) application of rigorous criteria to assess whether each species found is native or introduced. We carried out these steps in order to detect and document kamptozoan (entoproct) invasions on the American mid-Atlantic coast. We report on the occurrence of two colonial kamptozoans (Barentsia benedeni, Loxosomatoides laevis) in Chesapeake Bay (Maryland and Virginia, USA). On the American Atlantic coast, B. benedeni had previously only been reported from Massachusetts, although this species has a worldwide distribution in bays and harbors. The genus Loxosomatoides had not previously been reported from North America and L. laevis was known only from India. Since the genus Loxosomatoides was very poorly characterized, we briefly review all four of its species, which differ only slightly from each other. We have also synonymized L. japonicum with L. laevis. We did not find any of the kamptozoan species previously recorded in surveys of Chesapeake Bay and the American Atlantic coast. This is the first detailed consideration of anthropogenic influences on kamptozoan distributions, and we emphasize that most kamptozoan species are cryptogenic pending further investigation.     

Diet and dentition in tropical ariid catfishes from Australia

Synopsis The diets of 13 species of ariid catfishes from the tropical waters of the Gulf of Carpentaria are described and compared. Fishes were collected from two estuaries and inshore and offshore marine areas. Up to 10 species have been recorded from a single estuary. Although all are carnivorous and consume a variety of prey, diet analyses and statistical ordination reveal three feeding guilds - piscivores, polychaete-eaters and molluscivores. The diets of most species are similar between sites. There are strong relationships between dietary guild and the size and arrangement of the palatine teeth. The piscivorous group of catfish (guild 1) have large mouths with relatively large multiple palatine tooth plates, either in a band or in a triangular pattern and armed with sharp recurved teeth. The primarily polychaete-feeding group (guild 2) have a variable mouth size but it is usually smaller than that of guild 1 fish; their palatine teeth plates are fewer and smaller, and they have small, sharp recurved teeth. Guild 3 eat mainly molluscs, and have a small mouth and large posteriorly situated palatine plates with globular, truncated teeth. Overlaps in diet between species are probably reduced by differential distribution patterns within estuaries and different habitat preferences. The mouth-width and tooth-plate arrangements of ariids in tropical Australia are suitable for dealing with broad classes of prey rather than specific items, conferring dietary flexibility. This probably optimizes the trade-off for most species between occupation of broad feeding niches and the ability to shift diet easily.