Somatostatin: a historical perspective

Following the discovery and biochemical characterization of natural somatostatin its action profile has been thoroughly investigated. Although the name somatostatin was coined in virtue of its growth hormone release-inhibiting properties, a number of central and peripheral endocrine and paracrine actions have been ascribed to this peptide. Its inhibitory effect on a series of pituitary and gastrointestinal hormones has characterized somatostatin as a classical brain-gut hormone. Circulating and tissue levels of somatostatin and its possible physiological role are analyzed and clinical implications are drawn.     

Intermediate filaments: a historical perspective

Intracellular protein filaments intermediate in size between actin microfilaments and microtubules are composed of a surprising variety of tissue specific proteins commonly interconnected with other filamentous systems for mechanical stability and decorated by a variety of proteins that provide specialized functions. The sequence conservation of the coiled-coil, alpha-helical structure responsible for polymerization into individual 10 nm filaments defines the classification of intermediate filament proteins into a large gene family. Individual filaments further assemble into bundles and branched cytoskeletons visible in the light microscope. However, it is the diversity of the variable terminal domains that likely contributes most to different functions. The search for the functions of intermediate filament proteins has led to discoveries of roles in diseases of the skin, heart, muscle, liver, brain, adipose tissues and even premature aging. The diversity of uses of intermediate filaments as structural elements and scaffolds for organizing the distribution of decorating molecules contrasts with other cytoskeletal elements. This review is an attempt to provide some recollection of how such a diverse field emerged and changed over about 30 years.     

The Tinel sign: a historical perspective

The Tinel sign is one of the most well-known and widely used clinical diagnostic tools in medicine. Aside from Jules Tinel, after whom the sign is named, several authors have described the famous "tingling" sign seen in regenerating injured nerves. In fact, Tinel was not the first to present the sign to the scientific community. The clinical value and utility of the Tinel sign have remained in question since its introduction; many may misinterpret the sign as a prelude to complete functional recovery of injured nerves, when in fact it only signals the progress of nerve regeneration. Today the Tinel sign is widely associated with the diagnosis of carpal tunnel syndrome and in the evaluation of regenerating peripherally injured nerves. Knowledge of the history and misconceptions surrounding the sign provides clinicians today with a greater appreciation of current debates on the use of the Tinel sign.     

BioMetals: a historical and personal perspective

Understanding of BioMetals developed basically from a starting point about 60 years ago to current mechanistic understanding of the biological behavior of many metal ions from protein structural and functional studies. Figure 1 shows a Biochemical Periodic Table, element by element, with requirements, roles and biochemistry of the specific ions indicated. With few exceptions, the biology is of the ions formed and not of the elemental state of each. Early BioMetals efforts defined nutritional growth needs for animals, plants and microbes for inorganic “macro-nutrients” such as magnesium, calcium, potassium, sodium, and phosphate and of “micronutrients” such as copper, iron, manganese and zinc. Surprises came early with regard to microbes, for example the finding that Escherichia coli (then and now the standard microbial model) grows happily in the apparent total absence of calcium, sodium, and chloride, which are certainly major animal nutrients. Some elements such as mercury and arsenic are never required by living cells, but are always toxic, often at very low levels. Therefore, the division into nutrient elements and toxic elements came soon. For most inorganic nutrients, excessive amounts can be toxic as well, for example for copper and iron.     

Basal medium development for serum-free culture: a historical perspective

The evolution of basal synthetic formulations to support mammalian cell culture applications has been facilitated by the contributions of many investigators. Definition of minimally-required nutrient categories by Harry Eagle in the 1950's spawned an iterative process of continuous modification and refinement of the exogenous environment to cultivate new cell types and to support emerging applications of cultured mammalian cells. Key historical elements are traced, leading to the development of high potency, basal nutrient formulations capable of sustaining serum-free proliferation and biological production. Emerging techniques for alimentation of fed batch and continuous perfusion bioreactors, using partial nutrient concentrates deduced from spent medium analysis, can enhance medium utilization and bioreactor productivity.     

Type III restriction-modification enzymes: a historical perspective

Restriction endonucleases interact with DNA at specific sites leading to cleavage of DNA. Bacterial DNA is protected from restriction endonuclease cleavage by modifying the DNA using a DNA methyltransferase. Based on their molecular structure, sequence recognition, cleavage position and cofactor requirements, restriction–modification (R–M) systems are classified into four groups. Type III R–M enzymes need to interact with two separate unmethylated DNA sequences in inversely repeated head-to-head orientations for efficient cleavage to occur at a defined location (25–27 bp downstream of one of the recognition sites). Like the Type I R–M enzymes, Type III R–M enzymes possess a sequence-specific ATPase activity for DNA cleavage. ATP hydrolysis is required for the long-distance communication between the sites before cleavage. Different models, based on 1D diffusion and/or 3D-DNA looping, exist to explain how the long-distance interaction between the two recognition sites takes place. Type III R–M systems are found in most sequenced bacteria. Genome sequencing of many pathogenic bacteria also shows the presence of a number of phase-variable Type III R–M systems, which play a role in virulence. A growing number of these enzymes are being subjected to biochemical and genetic studies, which, when combined with ongoing structural analyses, promise to provide details for mechanisms of DNA recognition and catalysis.     

Great Salt Lake microbiology: a historical perspective

Over geologic time, the water in the Bonneville basin has risen and  fallen, most dramatically as freshwater Lake Bonneville lost enormous volume 15,000–13,000 years ago and became the modern day Great Salt Lake. It is likely that paleo-humans lived along the shores of this body of water as it shrunk to the present margins, and native peoples inhabited the surrounding desert and wetlands in recent times. Nineteenth century Euro-American explorers and pioneers described the geology, geography, and flora and fauna of Great Salt Lake, but their work attracted white settlers to Utah, who changed the lake immeasurably. Human intervention in the 1950s created two large sub-ecosystems, bisected by a railroad causeway. The north arm approaches ten times the salinity of sea water, while the south arm salinity is a meager four times that of the oceans. Great Salt Lake was historically referred to as sterile, leading to the nickname “America’s Dead Sea.” However, the salty brine is teaming with life, even in the hypersaline north arm. In fact, scientists have known that this lake contains a diversity of microscopic lifeforms for more than 100 years. This essay will explore the stories of the people who observed and researched the salty microbiology of Great Salt Lake, whose discoveries demonstrated the presence of bacteria, archaea, algae, and protozoa that thrive in this lake. These scientists documented the lake’s microbiology as the lake changed, with input from human waste and the creation of impounded areas. Modern work on the microbiology of Great Salt Lake has added molecular approaches and illuminated the community structures in various regions, and fungi and viruses have now been described. The exploration of Great Salt Lake by scientists describing these tiny inhabitants of the brine illuminate the larger terminal lake with its many facets, anthropomorphic challenges, and ever-changing shorelines.     

Laticifers: An historical perspective

This review describes the development of the laticifer concept, with emphasis upon the nonarticulated type, from early observations of plant exudates and “juices” to the presentation of laticifers by Esau (1953). Classical writers and herbalists described practical applications of these substances. With the advent of the microscope early investigators believed that these substances occurred in structures present in most, if not all, plants and, wrongly, equated these structures to the circulatory system in animals. Introduction of the term, latex, into botany derived from its early use as a term for a blood component by physicians, and not for analogy to milk. However, the origin of the terms, laticifer and laticiferous, remains uncertain. Initial studies of laticifers were marked by the controversy of whether they represented intercellular spaces or elongated cells. Confirmation of their cellular character led to the designation of nonarticulated and articulated laticifers. Nonarticulated laticifers were shown to arise during early embryogeny in some plants. The ontogenetic origin of the articulated laticifer was unclear to early workers, but new laticifers were detected to be formed by cambium activity. Nonarticulated laticifers were described to develop by intrusive growth whereby tips of the cell penetrated between adjacent cells. The coenocytic condition of the nonarticulated laticifer resulted from nuclear divisions along the cell positioned in the growth region of the shoot and the subsequent distribution of the daughter nuclei along the length of the cell.     

Born in a follicle--a historical perspective

A review of major studies of tetrapod skin development since the 1870s illustrates how knowledge of structure and mechanism progressed through phases emphasizing Natural History, morphology, endocrinology, and tissue manipulation prior to the prevailing "molecular era." Each successive phase of investigation, while suffering from its own limitations and constraints, has produced conceptual advances. At various times, different systems in various organisms have been research models of choice for practical and/or technical reasons. Comparative studies of scaled and non-scaled integuments and appendages thereof, e.g., nails, claws, glands, hair, and especially feathers, revealed data that suggested new directions for research programs. Some non-mammalian models still offer unique opportunities for pursuit of specific questions pertinent to studies of hair: arguments between American and British schools concerning feather development that originated in the 1930s remain unresolved and may thus affect interpretation of recent investigations. The current emphasis on the study of diffusible molecules involved in papilla-follicle interactions in hair development and replacement can only be understood in the context of the interwoven history of questions relating sequentially to evolutionary homology, physiological controls of tissue homeostasis, embryonic induction, and, most recently, molecular genetics.     

Questions remaining in sulfolipid biosynthesis: a historical perspective

The plant sulfolipid sulfoquinovosyldiacylglycerol was discovered by A.A. Benson in the late 1950s. The increasing availability of radioisotope-containing biological substrates such as ³⁵S-sulfate provided the means to discover novel biological compounds and to sketch out their biosynthetic pathways. During this time the structure of sulfolipid with its 6-deoxy-6-sulfo-α-d-glucose (sulfoquinovose) headgroup was determined. Immediately, the origin of this unusual biological sulfonic acid mystified the scientific community and several proposals for its biosynthesis were developed and tested. Strong supportive evidence for the nucleotide pathway of sulfolipid biosynthesis became available with the discovery of the bacterial and plant genes encoding the enzymes of sulfolipid biosynthesis during the 1990s. This latter work was based on the foundations laid by A.A. Benson and confirmed one initial hypothesis on sulfolipid biosynthesis. An abbreviated summary of the turning points in defining the mechanism for sulfolipid biosynthesis and remaining issues in sulfolipid biochemistry are provided.     

Exercise and insulin signaling: a historical perspective.

Over the past 30 years, a considerable body of evidence has revealed that a prior bout of exercise can increase the ability of insulin to stimulate glucose transport and glycogen synthesis in skeletal muscle. Apart from its clinical implications, this work has led to a considerable effort to determine at a molecular level how exercise causes this effect and, in particular, whether it does so by enhancing specific events in the insulin-signaling cascade. The objective of this review is to discuss from a historical perspective how our current thinking in this area has evolved and the people responsible for it. Areas to be discussed include the effect or lack of effect of prior exercise on the insulin-signaling pathway, effects of exercise on the regulation by insulin of the GLUT-4 glucose transporter in muscle, and the emerging role of AMP-activated protein kinase as a mediator of exercise-induced signaling events. In addition, we will discuss briefly some of the avenues that research in this area is likely to follow.     

Transplantation tolerance from a historical perspective

Although transplantation immunology as a distinctive field began with the development of experimental models that showed the feasibility of bone marrow transplantation, organ engraftment was accomplished first in humans, and was thought for many years to occur by drastically different mechanisms. Here, we present our view of the concepts of allograft acceptance and acquired tolerance from a historical perspective, and attempt to amalgamate them into simple and unifying rules that might guide improvements in clinical therapy.     

Urban biodiversity in local newspapers: a historical perspective

Due to rapid urbanization the conservation and values of urban wildlife are becoming increasingly important study objects. Unfortunately, the lack of historical data makes it difficult to assess the effects of long-term urban land-use changes and human attitudes on local biodiversity. In this paper we show that old newspapers may in some cases provide useful historical data on both urban wildlife and local attitudes towards it. In the city of Turku, southwest Finland, the leading newspaper published 316 observations or reports on local urban mammals, birds and reptiles in 1890–1920, and in addition to these a lot of information on contemporary attitudes towards urban wildlife. At least 12 species of noncaptive mammals, 32 species of birds, and three reptile species were documented in newspapers. The newspaper data seem fairly reliable, and provide valuable information on the development of urban biodiversity. In the study period animals visiting urban areas were often persecuted, in which both adults and children (mainly schoolboys) participated actively. Birds were persecuted less frequently than mammals or reptiles. Some bird species, especially 'song-birds', were actively supported by winter-feeding and by constructing nest-boxes. According to newspapers local people were interested in local biodiversity, especially on phenological events, and benefited from it by getting esthetic pleasure, pet animals, and information on seasonal changes.     

Simian AIDS: an historical perspective

The author has had the unique opportunity to participate, over the last 35 years, in the retrovirus research field that proceeded and followed the discovery of human, simian and feline AIDS. The onset of human AIDS was certainly unanticipated, but in retrospect, the warning signs had been present for at least a decade in captive macaques. I will briefly summarize the key scientific knowledge and 'mindset' leading up to these events and will outline the major contributions and unanswered questions arising from the simian model of AIDS.     

Visual homing: an insect perspective

The ability to learn the location of places in the world and to revisit them repeatedly is crucial for all aspects of animal life on earth. It underpins animal foraging, predator avoidance, territoriality, mating, nest construction and parental care. Much theoretical and experimental progress has recently been made in identifying the sensory cues and the computational mechanisms that allow insects (and robots) to find their way back to places, while the neurobiological mechanisms underlying navigational abilities are beginning to be unravelled in vertebrate and invertebrate models. Studying visual homing in insects is interesting, because they allow experimentation and view-reconstruction under natural conditions, because they are likely to have evolved parsimonious, yet robust solutions to the homing problem and because they force us to consider the viewpoint of navigating animals, including their sensory and computational capacities.     

Costs of reproduction in a historical perspective

Costs of reproduction constitute a core assumption of life history theory. After reformulation by G.C. Williams, the cost hypothesis soon became a major foundation of phenotypic life history models. More-recent studies have approached reproductive costs from the perspective of quantitative genetics. Here, we present a brief historical perspective to the development of the cost of reproduction hypothesis. We evaluate the status and heuristic value of the different approaches, and outline how the approaches have originated.