bluuebunny/crossref_metadata_2025_split huggingface dataset:
Organic-walled microfossils (palynomorphs)
Authors: Jones Robert Wynn 
Published: November 2023

Abstract
This chapter deals with organic-walled microfossils or palynomorphs. These range in size from 5-2000 µ,. Preparation of samples for organic-walled microfossil study generally consists of hydrochloric and fuming nitric acid leaching of calcareous material and hydrofluoric acid leaching of siliceous material followed by sieving. Excess amorphous organic material can be removed with Schulze’s solution. The final concentrate is made up into a strew slide for examination under a powerful transmitted light microscope.
Paleodose evaluation
Authors: Aitken M J 
Published: November 2023

Abstract
In the preceding chapter we have been concerned with the ‘tools of the trade’ required for observation of OSL. We now turn to procedures that have been developed for their utilization in evaluation of paleodose. (For some of these there is need for an additional facility, namely a light source for laboratory bleaching; suitable sources are indicated in Section 6.1.2.)
It will be recalled from Chapter 1 that the paleodose is a measure of the accumulated dosage of radiation that the sample has received since deposition and that the depositional age is derived by dividing the paleodose by the rate at which the sample has received that dosage-evaluated as indicated in Chapter 2. Basically the paleodose is assessed by comparing the natural OSL with the artificial OSL induced in the sample by a known dose of laboratory radiation. One essential is that components unrelated to burial dosage are excluded from the value used for the natural OSL; another is that the natural and the artificial OSL must be ‘cleansed’ of contributions from traps whose electron retention lifetime does not substantially exceed the age-during burial there will have been leakage from such traps. In the present chapter, as well as to some extent in Chapters 6 and 7, the procedural strategies that have been devised to meet these requirements are discussed.
Thermal effects
Authors: Aitken M J 
Published: November 2023

Abstract
As has been indicated in earlier chapters, before dating measurements are made there is the need for preheating, at any rate with most samples. Besides the wanted effects of such preheating there are also unwanted effects which have relevance to the effectiveness of zeroing. These are now documented, prior to discussion of the preheating procedures and of electron-retention lifetimes. Discussion of photo transfer during shine-down is also included (Section 7.2.1) although it is not a thermal effect.
Although OSL can be rapidly bleached to a very low level, this is not the end of the story-as has been mentioned several times earlier. Preheating has the effect of raising the observed OSL above that very low level even though there has been no dosing subsequent to the bleaching; an increase may also occur simply through storage at ambient temperature. Although lying dormant at the immediate conclusion of depositional bleaching this increase is effectively a ‘starting signal’, usually small in absolute terms, which vitiates the ideal of ‘zero OSL for zero age’. Obviously it is important for young samples rather than for old, and unless allowance can be made the evaluated age is liable to be significantly in excess, sometimes substantially; on the other hand for the majority of not-so-young samples it is barely significant. Transfer effects can also occur during bleaching, adversely affecting rapidity.
Morphology of cholinergic projections from the brainstem reticular formation to the lateral geniculate nucleus and other thalamic nuclei in the cat
Authors: Fitzpatrick D , Raczkowski D 
Published: November 2023

Abstract
The dorsal thalamus receives projections from the brainstem reticular formation which are thought to play an important role in regulating its sensitivity to afferent stimulation. Electrical stimulation of the reticular formation results in changes in thalamic neuronal excitability that mimic those found during arousal from sleep or drowsiness: the spontaneous activity of thalamic neurons is increased and their mode of firing changes from rhythmic bursts to single spike discharges that can faithfully transmit sensory information to the cortex (Singer 1977; Burke and Cole 1978; Steriade and Deschenes 1984; Sherman and Koch 1986; Steriade and Llinas 1988). A variety of evidence suggests that cholinergic mechanisms are at least partly responsible for this state-dependent activation of thalamic neurons. First, the region surrounding the brachium conjunctivum in the midbrain and pons contains a large number of neurons that are immunoreactive for ChAT, the ACh synthesizing enzyme and these neurons are retrogradely labelled following injections of tracers into the thalamus (Armstrong et al. 1983; Mesulam et al. 1983; De Lima and Singer 1987; Hallanger et al. 1987; Smith et al. 1988; Fitzpatrick et al. 1988, 1989). Second, the increased excitability of thalamic neurons produced by reticular formation stimulation is blocked by cholinergic antagonists (Singer 1973; Francesconi et al. 1988). Third, the application of ACh to thalamic neurons in a tissue slice preparation produces a slow depolarization that could shift neurons from the burst firing mode to the single spike mode characteristic of arousal (McCormick and Prince
1987).
Control of the mammillothalamic axis by brainstem cholinergic laterodorsal tegmental afferents: Possible involvement in mnemonic processes
Authors: Pare D , Steriade M 
Published: November 2023

Abstract
Learning is generally thought to involve lasting modifications in the connections between neurons (Squire 1987). Such durable changes in synaptic efficacy were first observed at the level of the synapse between perforant path fibres and dentate granule cells following tetanic stimulation of afferent fibres (Bliss and Lom0 1973; Bliss and Gardner-Medwin 1973). The long-term potentiation (LTP) induced by this procedure lasted for hours and was homosynaptic, that is, it was restricted to the tetanized pathway. More recently, iontophoretically-applied ACh has been shown to produce lasting changes in cellular responsiveness at the cortical level (see Chapter 11 in this book). We now report that stimulation of the brainstem cholinergic laterodorsal tegmental (LDT) nucleus can induce a long-lasting enhancement in the synaptic responsiveness of anterior thalamic (AT) neurons to both cortical and subcortical inputs. Such cholinergic effects and especially those of synapticallyreleased ACh had not been demonstrated previously in the dorsal thalamus. The AT complex is, through the mammillary nuclei (MN), intimately linked to the hippocampal formation, a neuronal structure believed to be critical for memory processes. The first section in this chapter is a brief overview of the connections between the LDT nucleus, the AT nuclear complex, the MN, and the hippocampal formation. The second section summarizes a recent series of experiments designed to study the effects of LDT stimulation on AT neurons. The enhancement in synaptic responsiveness induced by LDT stimulation will be compared to the hippocampal LTP. We then discuss the relevance of these findings for memory processes in the light of the neuropathological studies implicating the medial diencephalon and the hippocampal formation in amnesia.
Genetic and environ mental control of inherited disorders
Authors: Nicholas F W 
Published: November 2023

Abstract
In Chapter 10 we saw that there is genetic variation in hosts for resistance to parasites and pathogens, and we saw how this can be utilized to breed animals with enhanced resistance. It remains for us now to turn our attention to diseases that are not caused by parasites or pathogens, i.e. to inherited disorders. As we saw in Chapter 6, the heritability for liability to any disorder is usually greater than zero; there is usually some genetic variation in liability to any disorder. This raises the possibility of artificial selection for decreased liability as a means of decreasing the incidence of the disorder.
Quantitative variation
Authors: Nicholas F W 
Published: November 2023

Abstract
The majority of traits of interest in animal breeding are continuously varying in the sense that animals cannot be readily classified into distinct classes. Milk production, fleece weight, body weight, and speed over a certain distance are just a few examples of continuously varying traits. Even a trait like egg production, which is not strictly continuous, can be considered as continuously varying because there are a large number of classes into which hens can be fitted according to the number of eggs laid in a certain period. Continuously varyin.gtraits are called quantitative traits or metric traits, and variation in them is called quantitative variation or continuous variation. Because they are measured on a continuous scale, it is not immediately obvious how variation in quantitative traits can result from the action of genes, which of course are discrete entities. The aim of this chapter is to describe the basis of quantitative variation, and to show how it can be partitioned into genetic and non genetic components.
Selection between populations
Authors: Nicholas F W 
Published: November 2023

Abstract
Artificial selection occurs whenever humans choose to breed from certain animals and not from others. The choice can be made between populations and/or within populations. In the former, it involves a decision as to the most appropriate source of breeding stock or commercial progeny. In the latter, it involves continual efforts to alter a population by breeding from only those animals which by some criteria are the most desirable within that population. In both cases, selection is exploiting genetic variation.
Selection and regular crossing
Authors: Nicholas F W 
Published: November 2023

Abstract
Traditionally, many stud breeders have regarded crossing as an insult to them and to their animals, and as a threat to their livelihoods. The aim of this chapter is to explain why these opinions are incorrect, and to illustrate that the most profitable future for both stud breeders and commercial breeders lies in breeding programmes that involve both selection and regular crossing.
The basic model: statics
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
In this chapter, we restrict attention to the steady state of the basic model defined in Chapter 3. That is, we assume there is no time dependence in the variables X9 Y, Z of eqns (3.11)—(3.13), so that they depend only on host ages, a: X(a)9 Y(a), Z(a).
Dynamic aspects of eradication and control
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
We have just seen that host-microparasite associations have a strong propensity to oscillate, so that even the endemic equilibrium state is often one of self-sustained cycles. The initiation of a programme of immunization, by its nature, constitutes a perturbation to such a host-microparasite system, and consequently is likely to evoke oscillations even if they are absent in the pre-immunization state. In other words, it is not to be expected that the incidence of infection will change smoothly and monotonically from its pre-immunization equilibrium value to some new and lower value (or to zero if eradication is achieved) under immunization, but instead we should often expect to see oscillations—sometimes quite pronounced—superimposed on the trends.
Indirectly transmitted microparasites
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
Many important microparasitic infections of humans are indirectly transmitted from person to person by biting arthropods such as mosquitoes. A list of the major infections is presented in Table 14.1. An idea of their global significance is provided by the observation that the protozoan malarial infections on the continent of Africa alone are estimated to cause in excess of one million child deaths annually (Walsh and Warren 1979). The term ‘vector transmitted’ is often used to describe these infections but it should be noted that the vector is invariably a true intermediate host, in the sense that the parasite undergoes a phase of obligatory development (and often reproduction) within the arthropod.
Acquired immunity
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
In this and the following four chapters, we turn to a series of biological complications that can have important influences on the transmission dynamics and population regulation of macroparasites. The first is that of acquired immunity. As mentioned in Chapter 15, this topic is one of much current debate. Unlike many microparasitic organisms, helminths do not induce sterile immunity to reinfection following primary exposure. Acquired host responses, however, can act to reduce rates of parasite establishment, fecundity, and survival as demonstrated by a large body of experimental work based on laboratory rodent-helminth systems (see Mitchell 1979; Dean 1983, Wakelin 1984).
Indirectly transmitted helminths
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
For several reasons, we devote this chapter to describing models for the study of the transmission of two important indirectly transmitted infections, namely the schistosome flukes and the filarial nematodes. Their inclusion is in part due to a fascination with the complexity of their life cycles, which has resulted in much research on the biology of infection in human and snail populations, in part due to their historical significance in the development and use of mathematical models in the field of parasitology and tropical medicine, and in part for completeness.
Parasites, genetic variability, and drug resistance
Authors: Anderson Roy M , May Robert M 
Published: November 2023

Abstract
Much of conventional theory and practice in epidemiological and ecological research is based on the premise that an understanding of observed patterns and processes can be achieved by reference to the average phenotypic characteristics of a group or sample of individuals and to some measure of variance. This approach is widely adopted despite the certain knowledge that populations of organisms are genetically heterogeneous. It is clearly an ‘economy of thought’ which often works well in practice when the genetical structure of the population under study is relatively stable and not subject to strong directional selection. In other instances the failure to recognize the variable genetical constitution of a population can lead to erroneous conclusions concerning the factors responsible for observed trends.
Is parasitism symbiosis? A definition of terms and the evolution of concepts
Authors: Cheng Thomas C 
Published: November 2023

Abstract
A common language in science is essential if investigators world-wide are to communicate. Here I re-examine what we mean by ‘parasitism’ and ‘symbiosis’ in the perspective of what is known today. The term ‘symbiosis’ was coined by Antoine de Bary in 1879. It literally means ‘living together’. De Bary was interested in the association between species of algae and fungi that form lichens. In his original definition (De Bary 1879), he did not include any suggestion of exchange of mutually beneficial factors between the algae and fungi; the term was coined strictly to define intimate heterospecific associations.
Gating mechanisms of calcium channels
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
As is clear from the preceding chapter, a distinctive feature of calcium channels in excitable membranes is their ability to activate (to open) upon a change of the transmembrane electric field. These channels are closed at high membrane potential level and pass Ca2+ ions across the membrane only during depolarization. Since the study of calcium channels started later than that of other voltage-operated channels (sodium, potassium), the understanding of the mechanism of their activation was much influenced by the data obtained earlier with respect to the latter channels. For sodium and potassium channels it is generally accepted that, together with structural components which determine the ability to select and to pass a definite ion type (the so-called ‘selectivity filter’), there are structural components able to respond to a change of intramembrane electric field by opening or closing a pathway for the movement of ions along their electrochemical gradient (‘gating’ mechanism). This idea arose from the studies of Hodgkin and Huxley (1952), who suggested a model for such a gating mechanism which is now widely accepted.
Inactivation of calcium channels
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
Inactivation of voltage-operated ion channels is phenomenologically a wellknown process, which manifests itself in a gradual decline of the current during sustained membrane depolarization. This phenomenon has been studied in detail on sodium channels of the squid axon and frog nerve fibre membranes (reviewed by Meves 1978). Quantitatively, inactivation is taken into account by the introduction, in the corresponding equations, of the variable h (see Chapter 3). Another manifestation of inactivation is the stationary diminution of the maximal amplitude of the ionic current elicited by a test depolarization when the membrane potential was initially held at a decreased level. The dependence of this diminution on the holding potential level has an S-shaped form and is described as the steady-state inactivation function, h∞ ( V).
Modulation of calcium-channel functioning
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
The ‘classical’ concept concerning the functioning of ion channels considers them as being operationally independent of cellular metabolism. The genetic apparatus of the cell controls the synthesis of protein macromolecules, which are transported by the mechanism of intracellular transport to the relevant sites, incorporated into the surface membrane, and then act there for a while, being replaced in time by new ones. Metabolic processes create only the necessary prerequisite for the function of the channels: they form, through the activity of the metabolically driven pumps, constant transmembrane gradients of the main inorganic ions. As long as these gradients are present, the membrane maintains its ability to respond to external stimuli by active responses in the form of ionic currents triggered by conformational changes in channels that open the pathway for ions. Cellular metabolism is not necessary for these changes; the membrane has only to maintain its labile structure, characteristic of the living cell. This concept seemed to be quite universal; however, in the past few years it has become more and more obvious that it considerably simplifies reality and that channel function can, in fact, be under the direct control of intracellular metabolic processes; this is especially true for calcium channels.
Development of calcium conductance during ontogenesis
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
It has been established that the presence of specialized ion-conducting structures, ion channels, in the surface membrane is one of the primordial properties of living cells; they can, for example, be clearly demonstrated in the oocytes of invertebrates. Microelectrode studies of such convenient objects as oocytes of Tunicates and Echinodermata showed the presence of membrane potentials of small value (several millivolts). At such a potential a cell was not capable of generating active responses, but if the membrane was hyperpolarized by electric current, action potentials appeared upon removal of the hyperpolarizing current, which indicates the presence of electrically operated ion channels in the cell membrane (Miyazaki et al. 1974). The study of the dependence between action potentials and ionic composition of the medium, as well as the action of different toxins, showed that, just as in differentiated cells, the action potential of oocytes has ‘sodium’ and ‘calcium’ components, i.e. several types of ion channels are involved in its generation (Miyazaki et al. 1975).
Functional role of calcium ions in the nerve cell
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
The functional role of the influx of Ca2+ ions from the extracellular medium into the cell during its activity is not always obvious. In some structures such an influx is directly connected to the triggering of a specific cellular function, and the role of these ions as messengers between the cellular membrane and the effector apparatus can be precisely analysed. This is the case for synaptic terminals which liberate a transmitter, and muscle fibres which contract in response to membrane depolarization. The important role of calcium in muscle contraction had already been defined by Ringer at the end of the nineteenth century. Subsequent numerous investigations have firmly established the fact that in all kinds of muscle fibres the intracellular level of ionized calcium is the primary regulator of the contraction-relaxation cycle, although some details of such regulation, particularly the role of Ca2+ ions entering from the extracellular space and liberated from intracellular stores, may substantially differ in different fibres.
General conclusions
Authors: Kostyuk Platon G 
Published: November 2023

Abstract
As can be seen from the findings summarized in this book, we now know quite a lot about the succession of events in which calcium participates during nerve-cell functioning. The basis of this participation—a highly asymmetric distribution of calcium ions between the extracellular medium and the cytoplasm—is a fundamental characteristic of the living state, and the influx of these ions into the cell, driven by their steep electrochemical trans membrane gradient, is an obligatory component of each cycle of neuronal activity.
Procedural and symbolic learning after large unilateral thalamic lesions in monkeys
Authors: Deuel Ruthmary K , Anderson Terry W 
Published: November 2023

Abstract
To examine the role of anterior medial thalamic nuclei in laterally distributed attention and motor behaviour, large unilateral lesions were created in five monkeys by implantation of radioactive pellets. Lesions were well-circumscribed, and destroyed Medialis Dorsalis, Ventralis Anterior and portions of Ventralis Lateralis and Ventralis Posterior Lateralis nuclei in all animals, as well as interrupting mamillo-thalamic and other anterior thalamic white matter tracts. Behavioural testing revealed no evidence for hemispatial neglect but marked impairment in a simple motor procedural task when it was carried out by the hand contralateral to the lesion. Learning and performance of three other tasks proceeded without deficit. The data are pertinent to understanding the pathophysiology of unilateral thalamic damage and localization of function in the primate cerebrum, particularly as it relates to thalamo-cor- tical interactions in higher-order motor activities.
Partial truths: a review of the use of concepts in the evolutionary sciences
Authors: Horder T J 
Published: November 2023

Abstract
For many reasons - among them the early disillusionment that followed the promises of Haeckelian recapitulation, and the continuing obscurities of the nature of developmental mechanisms - embryology has occupied an ill-defined and peripheral position among the disciplines contributing to evolutionary science. This paper argues, however, that embryological considerations are obligatory if we are to arrive at a rational foundation for many concepts basic to the evolutionary sciences (including homology, recapitulation, Bauplan, allometry, heterochrony, and paedomorphosis): they also expose the limitations of the modern synthesis (in its emphasis on selection and genetic reduction) and in methods of phylogenetic reconstruction and of character choice in systematics. An understanding of the complex, multifactorial nature of the actual developmental mechanisms demonstrates how such concepts are partially valid abstractions: their uses and definition depend on their interrelations with concepts and data across all biological disciplines.