Factors affecting the yield of virus in a cloned cell line of Trichoplusia ni infected with a nuclear polyhedrosis virus

The TN-368 tissue culture line of the cabbage looper, Trichoplusia ni, has been cloned. The doubling times of three clones at 27°C were 27.6 ± 3.4 hr, 21.9 ± 1.7 hr, and 27.4 ± 5.9 hr and that of the uncloned culture was 15.8 ± 1.5 hr. Growth of cells in all cultures was arrested after infection with a nuclear polyhedrosis virus of T. ni. There was little difference in the yield of polyhedra from cultures of uncloned or cloned cells infected at a multiplicity of infection (m.o.i) = 4. Yields of polyhedra were about the same when a m.o.i. was in the range of 0.01–4.0, but the yield tripled in the range m.o.i. = 20–30. At higher multiplicities, up to m.o.i. = 500 the yield of polyhedra progressively fell. It is concluded that the observed variation in numbers of polyhedra borne by individual cells in culture is not due to genetic variability among cells, nor can it be accounted for as a consequence of differing m.o.i. by virus. It is postulated that variation in polyhedra yield among cells in culture may be due to such factors as (1) strain differences in the virus, (2) the stage in the cell cycle at which a particular cell is present when infected.     

Determination of the amount of small messenger ribonucleic acid-containing particles free in liver cytoplasm.

To assess the contribution made by mRNA-containing particles to the heterogeneity previously observed among rat liver 40S ribonucleoprotein particles, the amount of poly(A)-containing RNA in subribosomal particles was determined. RNA was labelled with orotate in vivo for 24h and then for 50min. Poly(A)-containing RNA was trapped on filters impregnated with poly(U). Very little poly(A)-containing RNA was found in conventionally prepared ribonucleoprotein particles after fractionation in sucrose. However, after preparation of ribonucleoprotein particles by sedimentation through 1 M-sucrose in the presence of 0.15M-KCl or by precipitation with Mg2+ as described by Leitin & Lerman [(1969) Biokhimiya 34, 839-849], amounts of poly(A)-containing RNA were similar to amounts of mRNA found by other workers in total ribonucleoprotein particles. Even in such preparations, less than 5% of the total rapidly labelled RNA in native subribosomal-particle fractions was mRNA. It seems that mRNA-containing particles make up only a very small part of the population of subribosomal particles in liver.     

Dental Implications of Pharmacological Management of the Alzheimer's Patient

Medications used for the management of the Alzheimer's patient are of two types: agents prescribed for treatment of cognitive disorders and agents used for symptomatic relief of mood disorders. This article reviews the mechanisms of action and side-effects of the more common of these agents. In addition, dental management of the Alzheimer's patient is discussed in relation to specific medications being taken.     

Bacteriophage T4 DNA primase-helicase. Characterization of oligomer synthesis by T4 61 protein alone and in conjunction with T4 41 protein

The bacteriophage T4 41 and 61 proteins function as a primase-helicase which in vitro both unwinds double-stranded DNA and synthesizes the pentaribonucleotides used to initiate DNA synthesis on the lagging strand. We demonstrate that 61 protein alone possesses a weak DNA template-dependent oligomer synthesizing activity, whose products differ in size and nucleotide specificity from those made by the 61 and 41 proteins together. We have previously shown that the 61 and 41 proteins make primarily ribonucleotide pentamers of the sequence pppApC(pN)3, although some pentamers beginning with G were also detected on phi X174 single-stranded DNA. The pentamers pppApC(pN)3 have also been shown to initiate T4 DNA chains in vivo (Kurosawa, Y., and Okazaki, T. (1979) J. Mol. Biol. 135, 841-861). We now show that in contrast, the major products made by 61 protein alone on phi X174 DNA with [alpha-32P]CTP and the other three ribonucleoside triphosphates are not pentamers, but the dimers pppApC and pppGpC. In addition, minor amounts of products from 3 to approximately 45 nucleotides in length are also synthesized. Unlike the 61/41 protein reaction, 61 protein alone can substitute dATP or dGTP for ATP or GTP. Addition of 41 protein greatly stimulates oligomer synthesis, especially the synthesis of products made with ATP and CTP and products 5 nucleotides in length. Thus, both 61 and 41 proteins are needed to obtain efficient synthesis of the biologically relevant pentamers pppApC(pN)3. We demonstrate that the glucosylated hydroxymethylcytosines present in T4 DNA do not support the initiation of primer synthesis by the 61 protein on this template. With glycosylated hydroxymethyl T4 DNA, pppApC but not pppGpC oligomers are detected. If the T4 DNA is modified by hydroxymethylation but not glucosylation, pppApC and only a trace of pppGpC products are seen. In the accompanying paper (Nossal, N.G., and Hinton, D.M. (1987) J. Biol. Chem. 262, 10879-10885), we examine DNA synthesis primed by 61 protein in the absence of 41 protein.     

Evolution of the C4 photosynthetic pathway: events at the cellular and molecular levels

The biochemistry and leaf anatomy of plants using C₄ photosynthesis promote the concentration of atmospheric CO₂ in leaf tissue that leads to improvements in growth and yield of C₄ plants over C₃ species in hot, dry, high light, and/or saline environments. C₄ plants like maize and sugarcane are significant food, fodder, and bioenergy crops. The C₄ photosynthetic pathway is an excellent example of convergent evolution, having evolved in multiple independent lineages of land plants from ancestors employing C₃ photosynthesis. In addition to C₃ and C₄ species, some plant lineages contain closely related C₃–C₄ intermediate species that demonstrate leaf anatomical, biochemical, and physiological characteristics between those of C₃ plants and species using C₄ photosynthesis. These groups of plants have been extremely useful in dissecting the modifications to leaf anatomy and molecular biology, which led to the evolution of C₄ photosynthesis. It is now clear that great variation exists in C₄ leaf anatomy, and diverse molecular mechanisms underlie C₄ biochemistry and physiology. However, all these different paths have led to the same destination—the expression of a C₄ CO₂ concentrating mechanism. Further identification of C₄ leaf anatomical traits and molecular biological components, and understanding how they are controlled and assembled will not only allow for additional insights into evolutionary convergence, but also contribute to sustainable food and bioenergy production strategies.     

Stridulatory organs in spiny orb-weaver spiders

A stridulatory organ is here described for the first time in the family Argiopidae. The file is on the surface of the lungbook covers, and the scraper is on the base of the femora. Altogether seven different kinds of stridulatory organs have been distinguished in spiders according to the positions of the files and scrapers. The organ now described in the spiny orb-weavers of the genus Micrathena was previously known only in a few genera of the family Erigonidae. In one of the species of Micrathena the ridges of the stridulatory file are sufficiently close together to give bright diffraction spectra at incidences near grazing. The primitive polygonal pattern on the surface of the cuticle of spiders is illustrated, and the mode of formation of the stridulatory file is suggested.     

Focus: Preventive Medicine: 2020 Evaluation of Portable Vision Screening Instruments

Amblyopia is the most common cause of preventable visual impairment in children and occurs as a result of unilateral or bilateral impairment in best-corrected visual acuity. Early diagnosis and proper treatment are crucial to prevent poor visual outcomes in adulthood. Advances in technology have provided more objective diagnostic tools, which can now be used by a wide range of healthcare providers. Here, we highlight tools that have gained popularity in the past two decades and compare clinically relevant parameters to guide primary care providers seeking to incorporate instrumental vision screening in pediatric patient care.     

Stejneger's beaked whale strandings in Alaska, 1995–2020

Presented here is the first comprehensive and updated compilation of history, distribution, and findings of Stejneger's beaked whales (Mesoplodon stejnegeri) in Alaska. Stejneger's beaked whales are a poorly understood, elusive, deep-diving cetacean species found in the North Pacific Ocean. Since Stejneger's beaked whale strandings data in Alaska through 1994 were last published, 35 additional strandings have been documented. Twenty-seven animals stranded in the Aleutian Islands, seven stranded in Southcentral Alaska, and one animal stranded on St. Lawrence Island. Twenty-two carcasses were necropsied, but only four were fresh. Seventeen of the 22 died during mass stranding events and cause of death could not be definitively determined. Barotrauma was suspected in three cases and infectious disease possibly complicated by barotrauma occurred in two cases. We documented an expansion of strandings into the northern Bering Sea, characterized a sex bias, examined stomach contents that included macroplastic, and identified parasites not previously associated with Stejneger's beaked whales. Also included are data on the largest known mass stranding of Stejneger's beaked whales, which occurred on Adak Island in 2018. The history, distribution, and findings presented here are central to further our understanding of this species.