Paolo Mazzarello

The history of radial glia

Radial glial cells are now recognized as a transient population that serves as scaffolding for neuronal migration. The recognition of the existence and role of radial glia has not been smooth, and here we provide a brief historical overview on the pioneering studies on this subject. The histologists and embryologists Albert Kölliker and Wilhelm His performed seminal investigations on cortical morphogenesis in the last decades of the 19th century. However, the introduction of the silver impregnation Golgi technique, and its diffusion in the late 1880s, played a crucial role in the detection of radial glial processes. The radial arrangement of fibers emerging from the neuroepithelium lining the central canal was initially detected in the embryonic spinal cord by Camillo Golgi himself. The first Golgi impregnation of the cerebral cortex of mammalian fetuses was performed by Giuseppe Magini, who detected radial fibers extending from the ventricular neuroepithelium, and observed cells intercalated along these processes. Radial fibers, regarded as epithelial or ependymal processes, were then observed in the developing spinal cord and cerebral cortex by several investigators. Santiago Ramón y Cajal was the first to suggest that radial fibers were modified astrocytic processes functioning as a support during cortical histogenesis. Cajal acknowledged Maginis findings, but he criticized Maginis observations on the existence of neurons along radial fibers. With the advent of electron microscopy, the existence of radially arranged glial processes along which young neurons migrate was finally ascertained in the early 1970s by Pasko Rakic, thus opening a new era in the cellular and molecular biology of radial glia.

A Study to Compare Oral Sumatriptan with Oral Aspirin plus Oral Metoclopramide in the Acute Treatment of Migraine

In a double-blind, placebo-controlled study, the efficacy, safety and tolerability of 100 mg oral sumatriptan, given as a dispersible tablet, was compared with that of 900 mg oral aspirin plus 10 mg oral metoclopramide in the acute treatment of migraine. A total of 358 patients treated up to three migraine attacks within 3 months, recording clinical information on a diary card. In attack 1, headache relief after 2 h, defined as a reduction in severity from severe or moderate pain to mild or no pain, was recorded in 56% (74/133) of patients who took sumatriptan and 45% (62/138) of patients who took aspirin plus metoclopramide (p = 0.078). This analysis of the primary efficacy end point was not statistically significant. However, for attacks 2 and 3 (secondary end points), headache relief was achieved in 58 versus 36% of patients (p = 0.001) and 65 versus 34% of patients (p less than 0.001), respectively. Relief from nausea, vomiting, photophobia and phonophobia was similar in both treatment groups. Rescue medication was required by fewer patients treated with sumatriptan than by those who received aspirin plus metoclopramide (attack 1, 34 versus 56%, p less than 0.001; attack 2, 32 versus 51%, p = 0.001, and attack 3, 35 versus 54%, p = 0.001). Sumatriptan also produced a faster improvement and resolution of migraine attacks. Comparing the sumatriptan and aspirin plus metoclopramide treatment groups, complete resolution of the attack occurred within 6 h in 32 versus 19% (attack 1), 35 versus 23% (attack 2) and 32 versus 20% of patients (attack 3).(ABSTRACT TRUNCATED AT 250 WORDS)

The cerebellar network: From structure to function and dynamics

Since the discoveries of Camillo Golgi and Ramón y Cajal, the precise cellular organization of the cerebellum has inspired major computational theories, which have then influenced the scientific thought not only on the cerebellar function but also on the brain as a whole. However, six major issues revealing a discrepancy between morphologically inspired hypothesis and function have emerged. (1) The cerebellar granular layer does not simply operate a simple combinatorial decorrelation of the inputs but performs more complex non-linear spatio-temporal transformations and is endowed with synaptic plasticity. (2) Transmission along the ascending axon and parallel fibers does not lead to beam formation but rather to vertical columns of activation. (3) The olivo-cerebellar loop could perform complex timing operations rather than error detection and teaching. (4) Purkinje cell firing dynamics are much more complex than for a linear integrator and include pacemaking, burst-pause discharges, and bistable states in response to mossy and climbing fiber synaptic inputs. (5) Long-term synaptic plasticity is far more complex than traditional parallel fiber LTD and involves also other cerebellar synapses. (6) Oscillation and resonance could set up coherent cycles of activity designing a functional geometry that goes far beyond pre-wired anatomical circuits. These observations clearly show that structure is not sufficient to explain function and that a precise knowledge on dynamics is critical to understand how the cerebellar circuit operates.

DNA repair mechanisms in neurological diseases: facts and hypotheses.

DNA repair mechanisms usually consist of a complex network of enzymatic reactions catalyzed by a large family of mutually interacting gene products. Thus deficiency, alteration or low levels of a single enzyme and/or of auxiliary proteins might impair a repair process. There are several indications suggesting that some enzymes involved both in DNA replication and repair are less abundant if not completely absent in stationary and non replicating cells. Postmitotic brain cell does not replicate its genome and has lower levels of several DNA repair enzymes. This could impair the DNA repair capacity and render the nervous system prone to the accumulation of DNA lesions. Some human diseases clearly characterized by a DNA repair deficiency, such as xeroderma pigmentosum, ataxia-telangiectasia and Cockayne syndrome, show neurodegeneration as one of the main clinical and pathological features. On the other hand there is evidence that some diseases characterized by primary neuronal degeneration (such as amyotrophic lateral sclerosis and Alzheimer disease) may have alterations in the DNA repair systems as well. DNA repair thus appears important to maintain the functional integrity of the nervous system and an accumulation of DNA damages in neurons as a result of impaired DNA repair mechanisms may lead to neuronal degenerations.

The centenarian Golgi apparatus

One hundred years ago, Camillo Golgi described the cellular apparatus that has since become synonymous with his name. Although its existence was questioned for 50 years, this organelle is now established as the cells centre for the processing and secretion of proteins.

Giulio Bizzozero: a pioneer of cell biology

The Italian pathologist Giulio Bizzozero began his haematological investigations more than 130 years ago. Among his outstanding achievements was the discovery of the role of platelets in haemostasis and the identification of the bone marrow as the site of production of blood cells. One hundred years after his untimely death, the significance of these, and many more of his findings, is still recognized.

Discovery and rediscoveries of Golgi cells

When Camillo Golgi invented the black reaction in 1873 and first described the fine anatomical structure of the nervous system, he described a ‘big nerve cell’ that later took his name, the Golgi cell of cerebellum (‘Golgischen Zellen’, Gustaf Retzius, 1892 ). The Golgi cell was then proposed as the prototype of type‐II interneurons, which form complex connections and exert their actions exclusively within the local network. Santiago Ramón y Cajal (who received the Nobel Prize with Golgi in 1906) proceeded to a detailed description of Golgi cell morphological characteristics, but functional insight remained very limited for many years. The first rediscovery happened in the 1960s, when neurophysiological analysis in vivo revealed that Golgi cells are inhibitory interneurons. This finding promoted the development of two major cerebellar theories, the ‘beam theory’ of John Eccles and the ‘motor learning theory’ of David Marr, in which the Golgi cells regulate the spatial organisation and the gain of input signals to be processed and learned by the cerebellar circuit. However, the matter was not set and a series of pioneering observations using single unit recordings and electron microscopy raised new issues that could not be fully explored until the 1990s. Then, the advent of new electrophysiological and imaging techniques in vitro and in vivo demonstrated the cellular and network activities of these neurons. Now we know that Golgi cells, through complex systems of chemical and electrical synapses, effectively control the spatio‐temporal organisation of cerebellar responses. The Golgi cells regulate the timing and number of spikes emitted by granule cells and coordinate their coherent activity. Moreover, the Golgi cells regulate the induction of long‐term synaptic plasticity along the mossy fibre pathway. Eventually, the Golgi cells transform the granular layer of cerebellum into an adaptable spatio‐temporal filter capable of performing several kinds of logical operation. After more than a century, Golgis intuition that the Golgi cell had to generate under a new perspective complex ensemble effects at the network level has finally been demonstrated.

Thiamin Contents of Cerebrospinal Fluid, Plasma and Erythrocytes in Cerebellar Ataxias

Free thiamin and thiamin monophosphate have been found in the cerebrospinal fluid, plasma and in erythrocytes of patients suffering from ataxia of different origins. In erythrocytes, thiamin pyrophosphate was also measured. In a limited number of cases, uptake of 14C-thiamin by erythrocytes was found as well. Controls were hospitalized patients affected by chronic neurological diseases without any clinical sign of thiamin deficiency. The results showed a significant decrease in thiamin and thiamin monophosphate in the cerebrospinal fluid and in the plasma of ataxic subjects, in comparison to controls. In erythrocytes, only thiamin pyrophosphate levels had decreased. The uptake of 14C-thiamin by erythrocytes was similar in both ataxic and control groups. These results were comparable to those observed in thiamin-deficient individuals, like alcoholic patients, and prompted further investigation into thiamin metabolism in these diseases.

The sarcoplasmic reticulum: its discovery and rediscovery

In 1902, Emilio Veratti made the most accurate description, by light microscopy, of a reticular structure in the sarcoplasm. However, this structure was almost lost to mans knowledge for more than 50 years and was rediscovered during the 1960s, following the introduction of electron microscopy. Since then, biochemistry, electron microscopy and electrophysiology have unravelled the crucial role of the sarcoplasmic reticulum in the control of muscle contraction.

The first images of nerve cells: Golgi on the olfactory bulb 1875.

The third paper by Camillo Golgi on his new method was on the olfactory bulb. This paper has never been translated into English, but is of special interest both for its pioneering description of olfactory bulb cells and for containing the first illustration by Golgi of cells stained with his new method. A translation into English is provided in this paper, together with commentaries on the significant points in his descriptions. These results are placed in the perspective of Cajals subsequent first publication on the olfactory bulb and brief mention of the work of other early histologists. This perspective allows one to see more clearly Golgis fundamental contributions to the olfactory bulb in particular and to the description of the neuronal architecture of the brain in general.