Models for the diversification of life

The diversification of life through geological time a rise from presumably one species to many millions today. The diversification of marine families in the past 600 million years (Myr) appears to have followed two or three logistic curves, with equilibrium levels that lasted for up to 200 Myr. In contrast, continental organisms clearly show an exponential pattern of diversification, and although it is not clear whether the empirical diversification patterns are real or are artefacts of a poor fossil record, the latter explanation seems unlikely. Perhaps marine and continental organisms diversified in different ways, or perhaps the appearance of equilibrium patterns for marine organisms is an artefact of taxonomic structures.     

Dating placentalia: Morphological clocks fail to close the molecular fossil gap

Dating the origin of Placentalia has been a contentious issue for biologists and paleontologists. Although it is likely that crown‐group placentals originated in the Late Cretaceous, nearly all molecular clock estimates point to a deeper Cretaceous origin. An approach with the potential to reconcile this discrepancy could be the application of a morphological clock. This would permit the direct incorporation of fossil data in node dating, and would break long internal branches of the tree, so leading to improved estimates of node ages. Here, we use a large morphological dataset and the tip‐calibration approach of MrBayes. We find that the estimated date for the origin of crown mammals is much older, ～130–145 million years ago (Ma), than fossil and molecular clock data (～80–90 Ma). Our results suggest that tip calibration may result in estimated dates that are more ancient than those obtained from other sources of data. This can be partially overcome by constraining the ages of internal nodes on the tree; however, when this was applied to our dataset, the estimated dates were still substantially more ancient than expected. We recommend that results obtained using tip calibration, and possibly morphological dating more generally, should be treated with caution.     

Virus in Water. II. Evaluation of Membrane Cartridge Filters for Recovering Low Multiplicities of Poliovirus from Water

The efficiency of a Millitube MF cartridge filter, a membrane filter, for recovery of poliovirus from 100-gal volumes of both fresh (tap) and estuarine water was determined. In the high multiplicity of virus input-output experiments, recovery of 97% or greater of input virus was achieved in both types of water when the final concentration of divalent cation as Mg(2+) was 1,200 mug/ml and the pH was 4.5. Virus was effectively eluted from the membrane cartridge with 5x nutrient broth in 0.05 M carbonate-bicarbonate buffer at pH 9.0. Four elutions of 250 ml each were used. In the low multiplicity of virus input-output experiments under the same cationic and pH conditions, up to 67% of the input virus was recovered when the virus was further concentrated from the eluates by the aqueous polymer two-phase separation technique. The volume reduction was 126,000-190,000 to 1. The use of the combined techniques, i.e., membrane adsorption followed by aqueous polymer two-phase separation, provided a highly sensitive, simple, and remarkably reliable sequential methodology for the quantitative recovery of poliovirus occurring at multiplicities as low as 1 to 2 plaque-forming units per 5 gal of water.     

Biochemical Evidence of Selective Nerve Cell Changes in the Normal Ageing Human and Rat Brain

Abstract: Atrophy with ageing of human whole brain, entire temporal lobe, and caudate nucleus was assessed in autopsy specimens, by biochemical techniques. Only the caudate nucleus showed changes. Markers for several neurotransmitter systems were also examined for changes with age. In neocortex and temporal lobe of human brain, small decreases were detected in markers of cholinergic nerve terminals, whereas a large decrease (79%) occurred in the caudate nucleus. Findings were similar in striatum from 3–33-month-old rats. No change occurred in binding of [³H]quinuclidinyl benzilate by human samples. Markers of serotonergic terminals were also unchanged in human and rat brain. By contrast, binding of [³H]lysergic acid diethylamide and [³H]serotonin was decreased (32–81%) in human neocortex and temporal lobe, but not in caudate nucleus. A 43% loss of a marker of γ-aminobutyrate terminals occurred in human neocortex, while [³H]muscimol binding increased (179%). No changes were detected in markers of catecholamine synapses in temporal lobe or rat striatum. Hence, with human ageing there appears to be a loss of markers of γ-aminobutyrate neurones intrinsic to neocortex and acetylcholine cells intrinsic to the caudate nucleus, as well as a change in postsynaptic serotonin receptors in neocortex. These losses are accompanied by relative preservation of markers of ascending projections from basal forebrain and brain stem.     

The current status of medullosan seed ferns

The compression and permineralized fossil record of presumed medullosan plants is reviewed and evaluated. Recent studies of stelar architecture suggest that stems are monostelic rather than polystelic as commonly believed. Imparipinnate fronds are mostly of the Neuralthopteris/Alethopteris type with Myeloxylon anatomy; the affinity between medullosan stems and neuropterid fronds is uncertain. It is suggested that the reproductive organs of the family should be restricted to those pollen organs believed to have produced Monoletes pollen and to ovules, for the most part, of the Trigonocarpus/Pachytesta type. It is doubtful that reproductive organs replaced lateral pinnules; it is more likely that they terminated pinnae or were borne abaxially along the pinna rachis. In some cases they may have been borne directly on penultimate axes or were, as in Codonotheca and Goldenbergia, borne on fertile fronds or fertile portions of vegetative fronds. Recent research involving pollen organs is emphasized and a phylogeny of Monoletespollen organs is proposed. It is suggested that the fossil record of medullosans is best interpreted from a punctuational perspective.     

Differentiation of Trichoplusia ni MEV and Autographa californica MEV by macrophage migration inhibition tests

The macrophage migration inhibition test (MMI), an in vitro correlate of delayed hypersensitivity, was found to be an effective means of differentiating Trichoplusia ni and Autographa californica multiple embedded nuclear polyhedrosis viruses (NPV). Peritoneal exudate cells from guinea pigs sensitized to virions of T. ni NPV demonstrated significantly different MMI when challenged with T. ni vs A. californica virions. Similarly, when virions of A. californica NPV were employed as the sensitizing antigen, different percentages of MMI were observed in the homologuus versus heterologous challenges.The susceptibility of the fall armyworm, Spodoptera frugiperda, to these two pathogens was very similar as revealed by a comparison of LD₅₀'s, slopes, and fiducial limits of dose-mortality regression lines. In contrast, the cabbage looper, T. ni, was much more susceptible to A. californica NPV.The polyhedral sizes, shapes, and virion occlusion patterns of the two species of NPV were virtually indistinguishable.     

Survival of parasite eggs upon storage in sludge

Destruction rates of parasite eggs in stored sludge were examined to help understand the fate of these agents of enteric diseases in sludge lagoons. Eggs from the roundworms, Ascaris spp., Toxocara spp., Trichuris spp., and the tapeworm, Hymenolepis spp., were treated with domestic sludges by aerobic or anaerobic processes. Sludge samples seeded with eggs were stored at 4 or 25 degrees C or in a container inserted into the ground to simulate lagoon conditions. The number of eggs recovered from the samples decreased with storage time. The viability and infectivity of eggs recovered were related to the storage temperature; i.e., the eggs stored at 4 degrees C remained viable longer than those stored at 25 degrees C. After 25 months at 4 degrees C, the Toxocara eggs and some Ascaris eggs remained both viable and infective, whereas most of these eggs stored at 25 degrees C were rendered nonviable after 10 to 16 months of storage in sludge. Although storage temperature was found to be the most important factor affecting the destruction and viability of these eggs, other factors, such as the type of sludge digestion, whether or not the eggs were digested along with the sludge or added later, storage in the soil versus sludge, pH, and egg species also exhibited some minor effects. These controlled laboratory studies suggest that lagooning of sludge can be an effective method for the elimination of parasite eggs, particularly in warmer geographical locations.