Showing papers by "University of Milan published in 1968"

Discharge of frontal eye field neurons during saccadic and following eye movements in unanesthetized monkeys

Abstract: The cortical mechanism of eye-movement control was investigated by recording single cell activity from the frontal eye field (FEF) in unanesthetized monkeys seated in a primate chair with head restrained. Two types of cells (I and II) were found. Type I neurons fired during voluntary saccades occurring in a given direction and during the fast phase of nystagmus. Cells of this type were silent during slow pursuit movement. Type II cells showed steady discharge when the eyes were oriented in a specific direction. These cells discharged also during smooth pursuit movements and the slow phase of nystagmus, provided that the eyes were moving across positions which would have been associated with neuronal activity had the eyes come to rest there. All of Type II and a few of Type I neurons were identified by antidromic response to stimulation of the cerebral peduncle. These results indicate that cortical neurons have patterns of discharge distinctly related either to saccadic or to pursuit movements, in line with the view that these two different types of eye movement are generated by distinct neuronal mechanisms.

Positive and negative work performances and their efficiencies in human locomotion.

Abstract: Walking at a constant speed on a steep incline, the ratio of the mechanical work performed, as calculated by the body lift, to the energy expended, as calculated by the oxygen consumption, generally referred to as “efficiency”, is independent of the incline, and it amounts to 0.25 walking uphill and to — 1.2 walking downhill. These values can be regarded as the “efficiency” values for positive (uphill) and negative (downhill) work. Walking on the level or on a mild incline, both positive and negative work are performed within the step cycle. When an equal amount of positive and negative work is performed (level walking or running) the energy level of the body at the end of the performance does not change, and the “efficiency” as calculated amounts to 0.207. This work may be consideredwasted: it reaches a maximal amount on the level of 0.044 kgm/m kg walking, and of 0.088 kgm/m kg running. For this reason a constant pull in the direction of the movement cannot replace completely the pull given by the muscles, as when other systems of progression such as cycling, skiing, skating etc. are adopted. By far the greatest amount of energy spent in walking or running at a constant speed is spent in positive work performance to counteract the deceleration (negative work) taking place at the end of each step. Very little energy is supplied for internal work, i.e. to meet the resistance to progression due to friction within the body or at the contact of the foot with the soil.

Analysis of electrical potentials evoked in the cerebellar anterior lobe by stimulation of hindlimb and forelimb nerves.

Abstract: Responses were evoked in the anterior lobe of the cerebellum by volleys in group I and II fibers of forelimb and hindlimb nerves — cutaneous, muscular, joint and fascial. These responses have been observed along microelectrode tracks that traverse the whole depth of the anterior lobe. These tracks have been identified in histological sections, and the recording sites along these tracks have been determined. It has been shown that there are many distinguishing features for the responses produced by the two types of afferent input to the cerebellum: climbing fibers and mossy fibers. The depth profiles are of particular importance in the differentiation of the CF and MF responses, and they correspond to those already determined for the exposed surface areas of the cerebellar cortex. As would be expected from the distribution of synapses by the CF fibers to the Purkinje cell dendrites, there is a maximum extracellular negativity deep in the molecular layer with sources superficial and deep thereto. In contrast, the mossy fiber input produces a powerful synaptic excitation in the granular layer, which is recorded there as a negative wave (N2). The mossy fiber input by sequential relay also produces a negative wave (N3) in the molecular layer. This wave is distinguished from the CF-evoked negative wave because it is not reversed in the fissura and the adjacent superficial molecular layer. An important distinguishing feature of the MF- and CF-evoked responses is that the latencies of the former are shorter by 6–12 msec for forelimb nerves and by 9–15 msec for hindlimb nerves. It is thus possible to measure the sizes of the MF and CF responses in the same traces. Another distinguishing feature is the failure of the CF responses with stimulus frequencies of 5–15/sec, whereas the MF-evoked potentials are well maintained above 15/sec. Also CF-evoked responses show much more size and latency variance than the MF-evoked responses, and often the facilitation of two or three volleys is required in order to evoke a stable CF response. By utilizing these various tests it is always possible to distinguish between the CF- and the MF-evoked responses recorded along the microelectrode tracks in the anterior lobe.

Pineal gland, melatonin and the control of luteinizing hormone secretion.

Abstract: Subjecting adult male rats to pinealectomy causes testicular hypertrophy, enhances the weight of the ventral prostate and of the seminal vesicles and increases pituitary LH stores. These data show that pinealectomy stimulates synthesis and release of pituitary LH and suggest that the pineal gland usually exerts an inhibitory influence on LH secretion. In order to determine whether such an effect of the pineal gland was taking place through a direct action on the pituitary gland or via the mediation of nervous structures, fragments of pineal tissue or crystals of melatonin (a neurohumor specifically synthesized in the gland) were implanted stereotaxically in the median eminence (ME), in the midbrain reticular substance (RS) and in the pituitary gland of castrated male rats. Placement of pineal fragments or of melatonin in the ME and in the RS is followed by a significant reduction of pituitary LH stores. ME and RS implants of melatonin also cause a reduction of plasma LH levels. Melatonin is unable to redu...

Topographical investigations on the climbing fiber inputs from forelimb and hindlimb afferents to the cerebellar anterior lobe.

Abstract: Volleys in group I and II fibers of muscle nerves and group II fibers of cutaneous, joint and fascial nerves have evoked CF responses in the anterior lobe of the cerebellum. In the pars intermedia there is a fairly sharp somatotopic localization of the forelimb CF responses to the Vth lobule (Larsell) and the hindlimb to the IVth and IIIrd lobules. In the vermis there is much more admixture, with the hindlimb-evoked responses tending to dominate in the lateral vermis of the Vth lobule, and the forelimb more medially. In the IVth and IIIrd lobules forelimb responses were rare and were never large. In the medial vermis up to 1–1.7 mm from the midline there were no CF-evoked responses from the limb nerves. These distributions of CF-evoked responses are remarkably different from those reported by Oscarsson, and consideration is given to the factors responsible for this discrepancy.

Relationship between O2 consumption, high energy phosphates and the kinetics of the O2 debt in exercise.

Abstract: The oxygen consumption together with lactic acid production and concentration of ATP, ADP, and creatinephosphate was measured during exercise and recovery on an isolated dog gastrocnemius Oxygen debt contraction and payment follow an exponential path with a half reaction time of about 20 sec The concentration of ATP and ADP at steady state seem to be unaffected by the intensity of the exercise when this is submaximal and no appreciable production of lactic acid takes place The concentration of creatinephosphate in muscle at steady state decreases with the intensity of the exercise The ratio of the oxygen consumption at steady state to the alactic oxygen debt is identified with the speed constant of the resynthesis of phosphagen in muscle; the half reaction time of this process is 17–20 sec The total alactic oxygen debt amounts to about 50 ml/kg of muscle These figures are in good agreement with earlier data found in man

Distribution of dorsal root fibers in the medulla oblongata of the cat.

Abstract: Afferent fibers to the medulla oblongata of the cat were studied in 25 animals following section of one or more dorsal roots. Using the Nauta-Laidlaw stain a map was constructed of the distribution of the fibers to the dorsal column nuclei and a survey made of the afferents to other bulbar nuclei: nucleus cuneatus lateralis, lateral reticular nucleus, descending root of the fifth cranial nerve and the nucleus tractus solitarii. In the intermediate segment of the nucleus gracilis and the caudal two thirds of the nucleus cuneatus, there is a somatotopical arrangement with a dorso-ventral and medio-lateral shifting of the fibers from the dorsal roots as one goes from caudal segments to more cranial ones. A bilateral projection is demonstrated in the nucleus gracilis after section of nearly all the coccygeal-sacro-lumbar-thoracic roots; the contralateral degeneration is confined to the rostral pole of the nucleus gracilis. No bilateral degeneration is found in the nucleus cuneatus after section of the roots projecting to it. Degenerated axons in the nucleus cuneatus lateralis and in the lateral reticular nucleus are always present beginning from T6–T7 while in the descending root of the fifth cranial nerve they are recognizable in only one case with a section of the third sacral root.

Brain receptors sensitive to indole compounds: function in control of luteinizing hormone secretion.

Abstract: The placement of melatonin and of 5-hydroxytryptophol in the median eminence of castrated male rats is followed 5 days later by a significant decrease in pituitary stores of luteinizing hormone. Pituitary reserve of this hormone is also depleted after the implantation of melatonin, 5-hydroxytryptophol, and 5-methoxytryptophol in the reticular formation of the midbrain. It is suggested that these indole compounds, which are normally synthesized in the pineal gland, may intervene in the control of the secretion of luteinizing hormone, possibly by acting on specific receptors localized in the median eminence and in the midbrain.

Developmental changes of the endoplasmic reticulum and ribosomes in nerve cells of the spinal ganglia of the domestic fowl

Abstract: The changes of the endoplasmic reticulum (ER) and ribosomes in developing nerve cells of the spinal ganglia of the domestic fowl have been studied by light and electron microscopy. The thin rim of cytoplasm encircling the nucleus of the undifferentiated cells contains numerous free ribosomal clusters and a scanty endoplasmic reticulum. The primitive neuroblasts are spindle-shaped and their two processes contain filamentous structures. In comparison with the undifferentiated cells, primitive neuroblasts have many more free ribosomes and a prominent rough-surfaced ER consisting of long, interconnected channels often continuous with the nuclear envelope. The remarkable development of the ER is one of the main characteristics of differentiating ganglionic nerve cells. Subsurface cisternae become apparent first in the primitive neuroblasts. The ER and ribosomes of the intermediate neuroblast are confined in the peripheral region of the perikaryon; mitochondria, Golgi complexes, dense bodies, microtubules, neurofilaments, etc. are located more centrally. Units of the smooth-surfaced ER appear first in the intermediate neuroblasts. In the pseudo-unipolar nerve cells, the cisternae of the ER and the ribosomes are mainly grouped in discrete areas (Nissl bodies). The rough-surfaced ER is more developed and highly organized in the intermediate neuroblasts and especially in the pseudo-unipolar nerve cells than in the primitive neuroblasts. In the pseudo-unipolar nerve cells, peculiar relationships between ER and Golgi complexes have been observed. Both free and membrane-attached ribosomes are arranged in clusters (polysomes) in all the developmental stages of the ganglionic nerve cells. The highest number of ribosomes in the membrane-attached polysomes is at least 13. The electron microscopic images suggest that the ER of the developing neuroblasts might take its origin from the nuclear envelope and afterwards might increase in volume through an intrinsic expansive growth of its membranes.

Level Density of Light Nuclei

Abstract: The level density of light nuclei ($A\ensuremath{\le}70$) is studied by analyzing statistical reaction spectra, slow-neutron resonances, and level widths at high excitation energy. Further evidence seems to indicate that, as proposed in a preceding work, the effective excitation energy of excited nuclei, appearing in the Lang-Le Couteur level-density formula, must be calculated by means of the following expression: $U=(E\ensuremath{-}\ensuremath{\Delta}+\frac{70}{A})$ $E$ is the usual excitation energy, $\ensuremath{\Delta}$ is the pairing energy, and $\frac{70}{A}$ MeV is a term that shifts, in a smooth manner, the zero of the energy scale of different nuclei. In this case the Lang-Le Couteur formula, assuming $R\ensuremath{\cong}1.5{A}^{\frac{1}{3}}$ F, $\mathcal{I}=0.7{\mathcal{I}}_{\mathrm{rig}}$, $a=(0.127A)$ Me${\mathrm{V}}^{\ensuremath{-}1}$, gives, without further changes of its parameters, a correct estimation of the slope and absolute value of the level densities of light nuclei for energies ranging from ($1+\ensuremath{\Delta}$) up to \ensuremath{\sim}20 MeV. It is also shown that the preceding choice of the parameters of Lang-Le Couteur level-density expression allows one to reproduce very well the experimental distributions of low-energy levels observed with reactions which proceed, at least partially, through the formation of a compound nucleus.

Cells Related to Fighting Behavior Recorded from Midbrain Central Gray Neuropil of Cat

Abstract: Cells were recorded in the midbrain central gray neuropil of the cat that responded with action potentials only during fighting behavior and not while the cat was resting or while control manipulations were performed. Some other cells in the same region responded maximally during fighting, and all cells responded to at least one manipulation. Brain stimulation at sites of cells related to fighting caused the animals to hiss.

Ultrastructure of growth hormone-producing cells of rat pituitary after injection of hypothalamic extract.

Abstract: The effects of intracarotid injection of hypothalamic extracts on the ultrastructure of pituitary growth hormone (GH)-producing cells are reported. Male rats were killed 15, 30 and 90 min after injection of hypothalamic extract. After 15 min the secretory granule content of pituitary GH cells was similar to that of nonstimulated glands. However, the release of granules into the perivascular spaces was greatly increased. The releasing phenomenon was still present 30 min after the injection; at this time a prominence of the endoplasmic reticulum as well as of the Golgi apparatus was also noticed. At 90 min the release of secretory granules was reduced to a normal rate; numerous lytic bodies were present. The number of secretory granules seemed to be within a normal range. The relevance of these morphological findings to the understanding of the action of hypothalamic extracts on the GH cells is discussed. (Endocrinology 83: 1278, 1968)

Studies on the cytotoxic action of silica dusts on macrophages in vitro.

Abstract: Experiments were performed in order to investigate the site of cellular damage induced by silica psrticles in vitro to peritoneal guinea pig macrophages. Considerable amounts of cytoplasmic enzymes, lactate dehydrogenase and aldolase, were released into the medium a short time after addition of silica to the cultures, whereas lysosomal enzymes, acid phosphatase and RNAase, were detected only after more prolonged incubation and in lower quantities. Correspondingly, loss of fluorochromasia from macrophages occurred in a matter of minutes after contact with silica particles. When coarse, nonphagocytabte silica particles were used, a rapid loss of fluorochromasia and early release of cytoplasmic enzymes were also seen.

Cerebroside and sulphatide deficiency in the brain of 'jimpy mice', a mutant strain of mice exhibiting neurological symptoms.

Abstract: THERE is a primary defect of brain lipid metabolism in several pathological conditions of the central nervous system in human and animal species.

Hydroxy fatty acids from cerebrosides of the central nervous system: GLC determination and mass spectrometric identification.

Abstract: A method has been developed for GLC determination of hydroxy fatty acids (HFA) from cerebrosides of the central nervous system

Cardiovascular Changes during Preparation for Fighting Behaviour in the Cat

Abstract: IT has been suggested recently that animals such as the cat and dog, when warned of an impending emotional or exertional task, anticipate the task with centrally induced cardiovascular changes similar to those that take place during the emotion or exertion itself1,2. Particular emphasis has been placed on muscle vasodilatation, preparatory to and independent of muscle contraction, mediated through sympathetic fibres supposed to be cholinergic, because the vasodilatation can be abolished by atropine1,3. Most of the data on which the “preparatory pattern” hypothesis is based, however, have been obtained by electrical stimulation of certain regions in the hypothalamus or subthalamus, from which are evoked either cardiac changes similar to those during exercise but without concomitant muscle activity2 or cardiovascular changes as well as manifestations of defence behaviour1,4. It should be realized, however, that the most quoted experiment on unanaesthetized, naturally behaving animals that may be relevant to this hypothesis, is that by Abrahams et al.5 which showed an increase in muscle venous temperature, blocked by atropine, when “alerting” was induced by various sensory stimuli. The evidence it provides, however, rests on unverified assumptions that the venous temperature increase accurately reflected muscle vasodilatation, that there was no muscle activity which could have provided a metabolic vasodilatation, and that the behaviour was one preparatory to exertion or emotion.

Ultrastructural study of giant cells and “langerhans cell granules” in cutaneous lesions and lymph-node and liver biopsies from four cases of subacute disseminated histiocytosis of letterer-siwe

Abstract: The authors analyse submicroscopic caracteristics of the infiltrate and the morphology and genesis of so-called “Langerhans' cell granules” in four cases of Letterer-Siwe's disease. Some giant cellular elements “main cells” were observed; their ultrastructure is similar to the Hodgkin and Sternberg cells of malignant lymphogranuloma, but clearly different from the normal histiocytic elements, epitheloid cells and also from the reticular cells of reticulosarcoma. Moreover in the skin of one of the studied patients numerous “Langerhans' cell”-like elements were found. The viral nature and the specifity of so-called “Langerhans' cell granules” is denied on the base of their morphology and of their localisation in different cellular elements.