Control of Bacteriophage-induced Enzyme Synthesis in Cells Infected with a Temperature-sensitive Mutant

The timing of "early" and "late" protein synthesis in Escherichia coli infected with T-even bacteriophage was studied with a temperature-sensitive phage mutant, T4 tsL13. This strain was completely unable to direct the synthesis of phage deoxyribonucleic acid (DNA) at 44 C because it makes a deoxycytidylate hydroxymethylase which cannot act at that temperature. However, the mutant did multiply normally at 30 C. No detectable formation of the late protein, lysozyme, occurred at 44 C, in agreement with the idea, proposed by several workers, that DNA replication is necessary for activation of late genetic functions. However, the formation of an early enzyme, thymidylate synthetase, was shut off at about 10 min, as in normal infection. This implied that separate mechanisms were responsible for cessation of early functions and activation of late ones. That the infected cell at 44 C retained the capacity for synthesis of early enzymes was shown by the fact that DNA synthesis occurred after a culture was transferred from 44 to 30 C as late as 30 min after infection. This synthesis was inhibited by chloramphenicol, indicating that de novo synthesis of an early enzyme can take place at a late period in development. It is suggested that cells infected under normal conditions maintained an appreciable rate of early enzyme synthesis throughout the course of infection.     

Teaching of Fertility Regulation in Medical Schools: A Survey in the United States and Canada, 1964

Fertility regulation is taught didactically in 82 of 94 medical school departments of obstetrics and gynecology in the United States and Canada, but students are given clinical experience in only 59 medical schools, according to a survey conducted in 1964 by a committee of the American Public Health Association. Legal prohibitions impeded teaching in 1964 in two States and in all of Canada. Nearly all schools teach that help with fertility regulation should be offered for medical and socioeconomic stress, and most teach that it should be offered routinely in premarital counselling and in the postpartum period, but only two-thirds teach that this help should be given to unmarried adults and only one-third teach that any person requesting help with fertility regulation should receive it.     

FOWLER'S BACILLUS AND ITS PARASPORAL BODY

Fowler's bacillus is one of several organisms which form a non-viable inclusion or parasporal body during the process of sporulation. This body is globular and may be as large as or larger than the spore. Its position in the cell is not random; the spore is terminal and the body paracentral, lying between the spore and the remaining vegetative cell chromatin bodies. On completion of sporulation both spore and body are contained within an exosporium. The sequence in the development of the cell structures was followed in ultrathin sections of material fixed in permanganate. When sporulation is well advanced the body begins to grow from a single crystal, then presumably as a result of some disorientation in the growth process it develops as a multicrystalline body with the lattices orientated at different angles. When the body approximates the spore in size, a lamella coat is formed and an exosporium develops which eventually encircles the body and the spore. Other lamella systems microscopically similar to those surrounding the parasporal body develop free in the cytoplasm outside the exosporium. In both of these systems the number of lamellae is variable. The spore coat of Fowler's bacillus, consisting of an outer lamella layer and an inner unresolved amorphous layer has been found microscopically identical to the spore coat of B. cereus. In both organisms the lamella layer of the spore coat consists, in contrast to the other lamella systems, of a regular number of lamellae. Physiological tests would indicate that Fowler's bacillus is a variety of B. cereus.     

Indirekte Regelmechanismen der Stoffwechselgröße von Fischen

Metabolic rate does not strictly follow changes of influencing parameters. O₂-consumption by fish is ordinarily said to be independent from O₂-pressure throughout a wide range. This constancy is probably the result of a regulation. The metabolic rate itself or an auxiliary mechanism “before” or “after” metabolism may be regulated. On the basis of vanDam's paper (1938) and our own experiments, the problem whether or not O₂-pressure in blood serves as a regulated auxiliary mechanism in order to maintain a certain metabolic constancy is discussed. The disadvantage of such a regulation would be the energy demand of increased ventilation and circulation as compensating mechanisms. In accordance with this assumption we have found a rise in O₂-consumption at a somewhat reduced O₂-pressure. Locomotory behaviour supports the constancy of metabolic rate; thus a contrary shift of the temperature preferendum after application of substances which influence metabolism has been found.     

A method for studying vegetation dynamics when there are no obvious individuals: Virtual-population analysis applied to the tundra shrub Betula nana L.

A method is presented to study dynamics of plants that cannot be separated into individuals such as many grassland, salt marsh and tundra species. A virtual population is created by using a permanent transect line through the vegetation and individuals are defined as the branch segments distal to the intercept with the transect line. Addition and loss of individuals together with growth or shrinkage form the basis for constructing a size-structured transition matrix. A discrete-event simulation demonstrates that: 1) a virtual population of individuals grows at the same rate as the parent population; and, 2) size-structured transition matrices for a virtual population and parent vegetation have similar dominant and subdominant eigenvalues so a virtual population can be used to describe the dynamics of a parent vegetation.Dwarf birch, Betula nana L., was studied in the northern foothills of the Brooks Range, Alaska, by using photography to record branch intercepts along permanent transect lines. The distal branch segments constitute a virtual population of the parent vegetation. Transects were photographed in 1985 and again in 1986 and changes of branch segments were used to construct two transition matrices for shrubs with and without elevated fertilizer treatment. Analysis of the virtual populations suggests that although Betula nana may show increased branch growth with increased fertilizer, in the long run this shrub may decline in the tundra in response to such treatment.     

Production planning of a flexible manufacturing system in a material requirements planning environment

Early flexible manufacturing system (FMS) production planning models exhibited a variety of planning objectives; typically, these objectives were independent of the overall production environment. More recently, some researchers have proposed hierarchical production planning and scheduling models for FMS. In this article, we examine production planning of FMS in a material requirements planning (MRP) environment. We propose a hierarchical structure that integrates FMS production planning into a closed-loop MRP system. This structure gives rise to the FMS/MRP rough-cut capacity planning (FMRCP) problem, the FMS/MRP grouping and loading (FMGL) problem, and the FMS/MRP detailed scheduling problem. We examine the FMRCP and FMGL problems in detail and present mathematical programming models for each of these problems. In particular, the FMRCP problem is modeled as a generalized assignment problem (GAP), and a GAP-based heuristic procedure is defined for the problem. We define a two-phase heuristic for the FMGL problem and present computational experience with both heuristics. The FMRCP heuristic is shown to solve problems that exhibit a dependent-demand relation within the FMS and with FMS capacity utilization as high as 99 percent. The FMGL heuristic requires very little CPU time and obtains solutions to the test problems that are on average within 1.5 percent of a theoretical lower bound. This FMS/MRP production planning framework, together with the resulting models, constitutes an important step in the integration of FMS technology with MRP production planning. The hierarchical planning mechanism directly provides for system-level MRP planning priorities to induce appropriate production planning and control objectives on the FMS while simultaneously allowing for necessary feedback from the FMS. Moreover, by demonstrating the tractability of the FMRCP and FMGL problems, this research establishes the necessary groundwork upon which to explore systemwide issues pertaining to the coordination of the hierarchical structure.     

Enhancement of habitat heterogeneity and species richness on rocky shores inundated by sand

Summary Many rocky shores are subject to periodic inundation by sand, which is often thought to reduce species richness by eliminating organisms intolerant of sand scour or sand smothering. However, regular disturbance (e.g. inundation) should promote richness by preventing the development of low diversity climax communities. A study of faunal richness on 10 regularly inundated shores showed that inundation does promote richness, but by increasing habitat heterogeneity. Some species are excluded from parts of the shore by sand, but because of the patchiness of sand deposits they are rarely excluded from the entire shore. Other species are found only on rocks associated with sand, while typically sandy shore animals occur in the sand deposits themselves. Total richness (281 species) was greater than for local noninundated shores and sandy beaches combined.     

Structures of poly(dA-dT, ip5dU) containing various small amounts of the antiherpetic 5-isopropyl-2'-deoxyuridine.

Three different concentrations of the antiherpetic agent 5-isopropyl-2'-deoxyuridine (ip5dU) were introduced into the synthetic DNA poly(dA-dT) to analyze resulting copolymers by electron microscopy, UV absorption and CD spectroscopy. The poly(dA-dT, ip5dU) containing 1.3 and 4.3% ip5dU did not much differ from the parent poly(dA-dT) but poly (dA-dT, ip5dU) with 7.1% ip5dU behaved in an unusual way. Results are explained by the notion that if bulky isopropyls occur sufficiently close to each other then stable hairpins protruding from the double helix are formed, presumably to accommodate the ip5dU-s into the loops.     

Developmental regulation of expression of the malate synthase gene in transgenic plants

The cucumber malate synthase (MS) gene, including 1856 bp of 5 non-trnascribed sequence, has been transferred into Petunia (Mitchell) and Nicotiana plumbaginifolia plants using an Agrobacterium binary vector. The transferred gene is found in variable copy number in different transformants, and is stably transmitted in each case as a single Mendelian character. Transgene mRNA accumulates in the seedling during the first three days of germination, then declines in amount as the cotyledons emerge from the seed. The decline is more pronounced in light-grown seedlings than in dark-grown seedlings. Expression of the MS transgene is also detected at a low level in petals of transformed Petunia plants. In these respects the pattern of MS gene expression is similar in cucumber and in trnasformed plants, showing that the transferred DNA fragment contains a functional MS gene. A 1076 bp fragment of 5 sequence was linked to the -glucuronidase reporter gene and transferred into Nicotiana, where it was shown to direct temporal and spatial patterns of expression similar to that of the complete MS gene. However, histochemical localisation of -glucuronidase activity demonstrated that the chimaeric gene is expressed not only in cotyledons of transgenic plants, but also in endosperm and some hypocotyl cells during early germination. The relevance of these findings to the control of malate synthase gene expression is discussed.