Translating the seminal findings of Carl Lüderitz: A description in English of his extraordinary studies of gastrointestinal motility accompanied by a historical view of peristalsis

The enteric nervous system

Of all the organ systems in the body, the gastrointestinal tract is the most complicated in terms of the numbers of structures involved, each with different functions, and the numbers and types of signaling molecules utilized. The digestion of food and absorption of nutrients, electrolytes, and water occurs in a hostile luminal environment that contains a large and diverse microbiota. At the core of regulatory control of the digestive and defensive functions of the gastrointestinal tract is the enteric nervous system (ENS), a complex system of neurons and glia in the gut wall. In this review, we discuss 1) the intrinsic neural control of gut functions involved in digestion and 2) how the ENS interacts with the immune system, gut microbiota, and epithelium to maintain mucosal defense and barrier function. We highlight developments that have revolutionized our understanding of the physiology and pathophysiology of enteric neural control. These include a new understanding of the molecular architecture of the ENS, the organization and function of enteric motor circuits, and the roles of enteric glia. We explore the transduction of luminal stimuli by enteroendocrine cells, the regulation of intestinal barrier function by enteric neurons and glia, local immune control by the ENS, and the role of the gut microbiota in regulating the structure and function of the ENS. Multifunctional enteric neurons work together with enteric glial cells, macrophages, interstitial cells, and enteroendocrine cells integrating an array of signals to initiate outputs that are precisely regulated in space and time to control digestion and intestinal homeostasis.

Annotated translation of Georg Meissner's first description of the submucosal plexus

BACKGROUND

The discovery and detailed descriptions of the enteric nervous system dates back only ˂200 years. The 19th century was a golden age of histological, morphological, and physiological breakthroughs propelled by technological advances in microscopy, electricity, and scientific methodology. As a matter of fact, German-speaking scientists were highly successful during this period as can still be appreciated by the sheer number of German eponyms in anatomy. Therefore, the main language in scientific literature of this field was German at the time, thus, limiting the accessibility to the publications and scientific discussions from back then for the broader English-speaking scientific community today.

PURPOSE

Here, an annotated translation of Meissner's first description of the submucosal plexus is provided along with a short biography of Georg Meissner and a review of the scientific literature and controversy surrounding his discovery.

How big is the little brain in the gut? Neuronal numbers in the enteric nervous system of mice, Guinea pig, and human

BACKGROUND

Despite numerous studies on the enteric nervous system (ENS), we lack fundamental knowledge on neuronal densities or total neuron numbers in different species. There are more anecdotal than actual figures on nerve counts.

METHODS

We used standardized preparation techniques and immunohistochemistry with validated panneuronal markers (human or mouse anti-HuD/C) to determine neuronal densities in specimen from the entire gastrointestinal tract of mice, guinea pig, and humans. In parallel, we measured the dimensions of the gastrointestinal regions in mouse and guinea pig. For humans, we had to rely on literature data.

KEY RESULTS

The average neuronal densities along the gastrointestinal tract were 35,011 ± 25,017 1/cm² for the myenteric and 16,685 ± 9098 1/cm² for the submucous plexus in mice, 24,315 ± 16,627 and 11,850 ± 6122 1/cm² for guinea pig myenteric and submucous plexus, respectively, and 21,698 ± 9492 and 16,367 ± 5655 1/cm² for human myenteric and submucous plexus, respectively. The total number of neurons in the ENS was 2.6 million for mice, 14.6 million for guinea pig, and 168 million for human.

CONCLUSIONS & INFERENCES

This study reports the first comprehensive nerve cell count in mice, guinea pig, and human ENS. Neuronal densities were comparable between the three species and the differences in the total numbers of enteric neurons are likely due to body size and intestinal length. The number of enteric neurons is comparable to the number of neurons in the spinal cord for all three species.

Analysis of Intestinal Movements with Spatiotemporal Maps: Beyond Anatomy and Physiology

Over 150 years ago, methods for quantitative analysis of gastrointestinal motor patterns first appeared. Graphic representations of physiological variables were recorded with the kymograph after the mid-1800s. Changes in force or length of intestinal muscles could be quantified, however most recordings were limited to a single point along the digestive tract.In parallel, photography and cinematography with X-Rays visualised changes in intestinal shape, but were hard to quantify. More recently, the ability to record physiological events at many sites along the gut in combination with computer processing allowed construction of spatiotemporal maps. These included diameter maps (DMaps), constructed from video recordings of intestinal movements and pressure maps (PMaps), constructed using data from high-resolution manometry catheters. Combining different kinds of spatiotemporal maps revealed additional details about gut wall status, including compliance, which relates forces to changes in length. Plotting compliance values along the intestine enabled combined DPMaps to be constructed, which can distinguish active contractions and relaxations from passive changes. From combinations of spatiotemporal maps, it is possible to deduce the role of enteric circuits and pacemaker cells in the generation of complex motor patterns. Development and application of spatiotemporal methods to normal and abnormal motor patterns in animals and humans is ongoing, with further technical improvements arising from their combination with impedance manometry, magnetic resonance imaging, electrophysiology, and ultrasonography.

The role of enteric inhibitory neurons in intestinal motility

The enteric nervous system controls much of the mixing and propulsion of nutrients along the digestive tract. Enteric neural circuits involve intrinsic sensory neurons, interneurons and motor neurons. While the role of the excitatory motor neurons is well established, the role of the enteric inhibitory motor neurons (IMNs) is less clear. The discovery of inhibitory transmission in the intestine in the 1960's in the laboratory of Geoff Burnstock triggered the search for the unknown neurotransmitter. It has since emerged that most neurons including the IMNs contain and may utilise more than one transmitter substances; for IMNs these include ATP, the neuropeptide VIP/PACAP and nitric oxide. This review distinguishes the enteric neural pathways underlying the 'standing reflexes' from the pathways operating physiologically during propulsive and non-propulsive movements. Morphological evidence in small laboratory animals indicates that the IMNs are located in the myenteric plexus and project aborally to the circular muscle, where they act by relaxing the muscle. There is ongoing 'tonic' activity of these IMNs to keep the intestinal muscle relaxed. Accommodatory responses to content further activate enteric pathways that involve the IMNs as the final neural element. IMNs are activated by mechanical and chemical stimulation induced by luminal contents, which activate intrinsic sensory enteric neurons and the polarised interneuronal ascending excitatory and descending inhibitory reflex pathways. The latter relaxes the muscle ahead of the advancing bolus, thus facilitating propulsion.

Woran starben Dr. Carl Lüderitz (1854–1930) und seine Vor- und Nachfahren?

Diagnostik allein auf der Basis von Symptomen und Symptombeschreibungen ist heute selten, war aber im 18. und 19. Jahrhundert eher die Regel.

Methoden In diesem medizinhistorischen Projekt wurden die Todesursachen von 25 Vor- und Nachfahren des Berliner Arztes und Wissenschaftlers Dr. Carl Lüderitz (1854–1930) aus historischen Quellen zusammengetragen und mit Daten zur Todesursachenstatistik des 18. und 19. Jahrhunderts verglichen. Zehn aktiven Gastroenterologen/-innen wurde ein Tagebuchausschnitt des laienhaft beschriebenen Todes eines Berliner Kaufmanns (des Großvaters von Carl Lüderitz) im Jahr 1846 durch seinen Sohn vorgelegt mit der Bitte um eine Verdachtsdiagnose.

Ergebnisse Vier bzw. 5 Fälle von vermutlicher Leberzirrhose unter den 26 Angehörigen der Familie Lüderitz sind überproportional im Vergleich zu Sterbestatistiken in Berlin und auf dem Lande, während die Schwindsucht (Tuberkulose) mit nur einem Fall unterrepräsentiert ist. Durchschnittlich wurden Frauen in dieser Familie 10 Jahre älter, unabhängig vom Jahr des Todes (1787 bis 2006). Acht der befragten Gastroenterologen/-innen waren der Meinung, dass der Tod aufgrund einer dekompensierten Leberzirrhose mit Blutungen aus Ösophagusvarizen eintrat, mit Ödemen auf der Basis einer daraus folgenden Herzinsuffizienz.

Schlussfolgerung Auch historische Dokumente können zur Aus- und Fortbildung oder zur Qualitätskontrolle in der Gastroenterologie beitragen.