Microbial Transport, Survival, and Succession in a Sequence of Buried Sediments

Abstract Two chronosequences of unsaturated, buried loess sediments, ranging in age from <10,000 years to >1 million years, were investigated to reconstruct patterns of microbial ecological succession that have occurred since sediment burial. The relative importance of microbial transport and survival to succession was inferred from sediment ages, porewater ages, patterns of abundance (measured by direct counts, counts of culturable cells, and total phospholipid fatty acids), activities (measured by radiotracer and enzyme assays), and community composition (measured by phospholipid fatty acid patterns and Biolog substrate usage). Core samples were collected at two sites 40 km apart in the Palouse region of eastern Washington State, near the towns of Washtucna and Winona. The Washtucna site was flooded multiple times during the Pleistocene by glacial outburst floods; the Winona site elevation is above flood stage. Sediments at the Washtucna site were collected from near surface to 14.9 m depth, where the sediment age was approximately 250 ka and the porewater age was 3700 years; sample intervals at the Winona site ranged from near surface to 38 m (sediment age: approximately 1 Ma; porewater age: 1200 years). Microbial abundance and activities declined with depth at both sites; however, even the deepest, oldest sediments showed evidence of viable microorganisms. Same-age sediments had equal quantities of microorganisms, but different community types. Differences in community makeup between the two sites can be attributed to differences in groundwater recharge and paleoflooding. Estimates of the microbial community age can be constrained by porewater and sediment ages. In the shallower sediments (<9 m at Washtucna, <12 m at Winona), the microbial communities are likely similar in age to the groundwater; thus, microbial succession has been influenced by recent transport of microorganisms from the surface. In the deeper sediments, the populations may be considerably older than the porewater ages, since microbial transport is severely restricted in unsaturated sediments. This is particularly true at the Winona site, which was never flooded.     

Anaphase A Chromosome Movement and Poleward Spindle Microtubule Flux Occur At Similar Rates in Xenopus Extract Spindles

We have used local fluorescence photoactivation to mark the lattice of spindle microtubules during anaphase A in Xenopus extract spindles. We find that both poleward spindle microtubule flux and anaphase A chromosome movement occur at similar rates (~2 μm/min). This result suggests that poleward microtubule flux, coupled to microtubule depolymerization near the spindle poles, is the predominant mechanism for anaphase A in Xenopus egg extracts. In contrast, in vertebrate somatic cells a “Pacman” kinetochore mechanism, coupled to microtubule depolymerization near the kinetochore, predominates during anaphase A. Consistent with the conclusion from fluorescence photoactivation analysis, both anaphase A chromosome movement and poleward spindle microtubule flux respond similarly to pharmacological perturbations in Xenopus extracts. Furthermore, the pharmacological profile of anaphase A in Xenopus extracts differs from the previously established profile for anaphase A in vertebrate somatic cells. The difference between these profiles is consistent with poleward microtubule flux playing the predominant role in anaphase chromosome movement in Xenopus extracts, but not in vertebrate somatic cells. We discuss the possible biological implications of the existence of two distinct anaphase A mechanisms and their differential contributions to poleward chromosome movement in different cell types.     

Localization of the fourth locus (GLC1E) for adult-onset primary open-angle glaucoma to the 10p15-p14 region.

One of the major causes of blindness is primary open-angle glaucoma, which affects millions of elderly people worldwide. Genetic studies have so far mapped three loci for the adult-onset form of this condition to the 2cen-q13, 3q21-q24, and 8q23 regions. Herein, we report the localization of a fourth locus, to the 10p15-p14 region, in one large British family with a classical form of normal-tension open-angle glaucoma. Of the 42 meioses genotyped in this pedigree, 39 subjects (16 affected) inherited a haplotype compatible with their prior clinical designation, whereas the remaining 3 were classified as unknown. Although a maximum LOD score of 10.00 at a recombination fraction of straight theta=.00 was obtained with D10S1216, 21 other markers provided significant values, varying between 3.77 and 9.70. When only the affected meioses of this kindred were analyzed, LOD scores remained statistically significant, ranging from 3.16 (D10S527) to 3.57 (D10S506). Two critical recombinational events in the affected subjects positioned this new locus to a region of approximately 21 cM, flanked by D10S1729 and D10S1664. However, an additional recombination in a 59-year-old unaffected female suggests that this locus resides between D10S585 (or D10S1172) and D10S1664, within a genetic distance of 5-11 cM. However, the latter minimum region must be taken cautiously, because the incomplete penetrance has previously been documented for this group of eye conditions. A partial list of genes that positionally are considered as candidates includes NET1, PRKCT, ITIH2, IL2RA, IL15RA, IT1H2, hGATA3, the mRNA for open reading frame KIAA0019, and the gene for D123 protein.     

Human leukemic cells: Biological action of exogenous human leukemic DNA

Intact exogenous human leukemie DNA derived from cells in culture was taken up by both normal and leukemic recipient human cells, wherein it migrates to the nucleus and becomes associated with host genome. Uptake of exogenous DNA averages about 15–20 percent and was relatively higher in leukemic than in normal cells in a given culture medium.Isologous and homologous human leukemic cells were more sensitive to inhibition by this exogenous DNA than were normal human cells. Both DNA and RNA synthesis were inhibited, but protein synthesis was stimulated — effects similar to those described consequent to exposure to certain viruses.Immunological studies of hamster cells treated with human leukemic DNA failed to show any presence of human surface antigens. The in vivo studies showed that this metabolically active radioactive DNA had migrated to several organs of hamsters and gerbils, the highest labeled DNA activity being found in the testis and kidney of these animals.Prolonged exposure to exogenous leukemic DNA resulted in marked phenotypic changes in normal human fibroblasts, which thus far appear to be heritable. Search for evidence of genotypic changes in these altered cells which might relate these observations to «neoplastic transformation is in progress.     

Approach to Assessment of Risk Factors in Mild Hypertension

Criteria are urgently needed for the early detection of subjects with only mildly raised blood pressure who may be at high risk of developing the complications of hypertension. As a step towards the establishment of such criteria we have examined the association of certain possible “risk” factors—namely, x-ray evidence of cardiac enlargement, high serum cholesterol levels, effort pain, E.C.G. abnormalities, and high systolic blood pressure—with fatal or morbid endpoints in a five-year follow-up study of subjects whose diastolic pressure had been found initially to be between 95 and 114 mm Hg. The index group consisted of 22 patients in whom these end-points occurred. They comprised death from cardiovascular disease, clinical or E.C.G. deterioration, and either an increase in diastolic pressure of at least 10 mm Hg or a diastolic pressure of 115 mm Hg or both. The control group consisted of 22 subjects chosen at random from other respondents with the same range of diastolic pressures and the same age and sex distribution.“Any two or more” of the possible risk factors examined were found to occur significantly more often in the index group than in the controls, suggesting a possible approach to the early detection of high-risk subjects. The value of longterm studies along these lines and the urgent need for them are emphasized.     

Some pathological studies in two species of Phytophthora

Summary The paper deals with some detailed pathological investigations with two species ofPhytophthora, viz.,Phytophthora palmivora andP. parasitica var.macrospora causing severe fruit rots ofAchras sapota andAnona squamosa respectively. Both the isolates were found pathogenic to a variety of fruits including papaya, tomato, chillis, banana, fig, apple, cucumber, guava, orange, onion bulb and potato tuber. They were, however, non-pathogenic to carrot, zinger, turmeric andColocasia corms. In the seedling inoculation experiment they showed pathogenic nature to castor bean, brinjal, cotton, sesamum, pea, French bean,Cactus sp. andBryophyllum leaves. It is interesting to note that only the Isolate S caused infection to the plants ofVinca rosea L., whereas the Isolate C failed to do so.This work frames up a part of Senior author's M.Sc. (Agri.) Thesis, approved by the University of Poona, India.Respectively, Ex-Junior Research Fellow (1958–60), Indian Council of Agricultural Research, New Delhi; Principal and Professor of Plant Pathology, College of Agriculture, Junagad, (Gujarat) and Mycologist, Wheat Rust Research Station, Mahabaleshwar (Satara Dist.) India.     

Physiologic rate of carrier-mediated Ca2+ entry matches active extrusion in human erythrocytes.

The intracellular Ca2+ concentration of nearly all cells is kept at submicromolar levels. The magnitudes of transmembrane Ca2+ movement that maintain this steady state in the human red blood cell have long been debated. Although there is agreement that the physiologic extrusion of Ca2+ by the well-characterized Ca2+. ATPase amounts to 45 mumol/liter cells per h (1982. Nature (Lond.). 298:478-481), the reported passive entry rates in physiological saline (2-20 mumol/liter cells per h) are all substantially lower. This discrepancy could be due to incomplete inhibition of the pump in the previous measurements of Ca2+ entry. We therefore examined both rate and mechanism of entry after completely inactivating the pump. This required pretreatment with iodoacetamide (to lower the intracellular ATP concentration) and vanadate (to inhibit any residual Ca2+ pump activity). The rate of Ca2+ entry (53 mumol/liter cells per h) was now found to be comparable to the accepted extrusion rate. Entry closely obeyed Michaelis-Menten kinetics (Vmax = 321 +/- 17 nmol Ca/g dry wt per h, Km = 1.26 +/- 0.13 mM), was competitively inhibited by external Sr2+ (Ki = 10.8 +/- 1.2 mM), and was accelerated by intracellular Ca2+. 45Ca2+ efflux from these pump-inactivated cells was also accelerated by either external Ca2+ or Sr2+. These accelerating effects of divalent cations on the opposite (trans) face of the membrane rule out a simple channel. Substrate-gated channels are also ruled out: cells equilibrated with 45Ca2+ lost the isotope when unlabeled Ca2+ or Sr2+ was added externally. Thus, passive Ca2+ movements occur predominantly by a reversible carrier-mediated mechanism for which Sr2+ is an alternate substrate. The carrier's intrinsic affinity constants for Ca2+ and Sr2+, 1.46 and 0.37 mM-1, respectively, indicate that Ca2+ is the preferred substrate.     

Differential effects of general anesthesia on cGMP-mediated pulmonary vasodilation.

We investigated the effects of an intravenous (pentobarbital sodium) and an inhalational (halothane) general anesthetic on guanosine 3',5'-cyclic monophosphate- (cGMP) mediated pulmonary vasodilation compared with responses measured in the conscious state. Multipoint pulmonary vascular pressure-flow plots were generated in the same nine dogs in the fully conscious state, during pentobarbital sodium anesthesia (30 mg/kg iv), and during halothane anesthesia (approximately 1.2% end tidal). Continuous intravenous infusions of bradykinin (2 micrograms.kg-1.min-1) and sodium nitroprusside (5 micrograms.kg-1.min-1) were utilized to stimulate endothelium-dependent and -independent cGMP-mediated pulmonary vasodilation, respectively. In the conscious state, both bradykinin and nitroprusside decreased (P less than 0.01) the pulmonary vascular pressure gradient (pulmonary arterial pressure-pulmonary arterial wedge pressure) over the entire range of flows studied; i.e., bradykinin and nitroprusside caused active flow-independent pulmonary vasodilation. Pulmonary vasodilator responses to bradykinin (P less than 0.01) and nitroprusside (P less than 0.05) were also observed during pentobarbital anesthesia. In contrast, during halothane anesthesia, the pulmonary vasodilator responses to both bradykinin and nitroprusside were abolished. These results indicate that, compared with the conscious state, cGMP-mediated pulmonary vasodilation is preserved during pentobarbital anesthesia but is abolished during halothane anesthesia.