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PubMedDate not supplied

Functional brain studies with H2(15)O-PET: strategies and problems for approaching higher brain functions with H2(15)O-PET.

Activation study using H2(15)O and PET is promising as a noninvasive approach to higher brain functions in humans. However before reaching a more complex paradigm, many fundamental problems need to be solved. In this study, we investigated the following issues: (1) reproducibility of regional cerebral blood flow in the resting state as measured by this method, (2) effect of physiological stimulation on cerebral blood flow, and (3) identification of activated areas on anatomical structures. Our data suggest that relative CBF images and their paired subtraction are more suitable for tapping functional localization. Changes in rCBF in the association cortex for more complicated tasks are, in general, smaller than those in the primary cortex. Combined display of PET images with three-dimensional reconstructed brain surface MR images was the most reliable technique for anatomical identification of the activated site.

Acoustic Stimulation↗
PubMedDate not supplied

[Microvascular anatomy of the skin and its appendages].

The microcirculatory bed of the skin has traditionally been divided into small arteries, precapillary arterioles, capillaries and venules. Also the most recent classification emphasize that the blood supply of the human dermis is a microcirculatory bed. Therefore, considering for example the skin of the lower limbs, there are too much anatomic and topographic peculiarities of the skin and subcutaneous tissue, so that a generalization of the microcirculatory patterns appears to be illusory and misleading. In fact, the foots plant is a "special microcirculatory region", and so the finger tips and the nail beds. Rich on arterio-venous anastomoses, on endoarterious blocking devices regulating the capillary blood flow, this "microcirculatory region" is characterized by haemodynamic patterns which are not comparables with those of other regions where AVA or other "special vessels" are absent. The microangiotectonic, i.e. the distribution in the tridimensional space of the dermis, adipose tissue and muscle of the smallest blood vessels show relevant differences in the foots, legs, knees or thighs. Normally, it is admitted that the majority of the papillary dermal vessels are postcapillary venules, but the ultrastructure of the arterioles and venules in the mid and lower dermis differs from the ultrastructure of comparable vessels of the deeper layers or of the subcutaneous fat. For these reason and on the basis of bioptic specimens of the skin, adipose tissue and muscles of the whole lower limbs, the subdivision in "microcirculatory regions" is proposed. The criteria are the presence or absence of AVA, the structure and localization of the endoarterious blocking devices, the structure of valve-containing venules and the microvessels-tissue relationship. Computerized Laser-Doppler Flowmetry and infra red Photo-Pulse Plethysmography, computerized Telethermography with physical stimulations, High Performance Contact Thermography and continuous registration of the skin temperature associated with pharmacological vasoactive stimulation, are helpful to identify and characterize functionally the "microcirculatory regions" of the lower limbs.

Capillaries↗
PubMed1990

[The neuronal responses of the caudate nucleus in the cat to sensory stimulation].

Responses of caudate neurons to a large variety of visual and other sensory stimuli were studied in alert cats. Sharp drops in the spontaneous activity of the unknown origin and differences in the activity level were revealed in adjacent parts of the caudate nucleus. The following types of neurons were recorded: neurons responding to visual stimulation; neurons responding to somatic stimulation; neurons responding to combined visual-somatic stimulation. The best response was observed to moving visual stimuli that attracted the animal's attention, alimentary objects specifically. The caudate nucleus of each hemisphere contained representation of both contra- and ipsilateral half of the animal body. Cell responses to sensory stimuli from the caudate nucleus have been compared with those from some cortical areas.

Animals↗
PubMed1989

Changes in the capillary flow of gingiva due to the influence of some impulses.

75 healthy men and women, aged from 20 to 45 years, were divided into five groups of 15 persons each. Na131I resorption halftime values from the examined area of the gingiva, pulse frequency as well as systolic and diastolic blood pressure were examined. Tests were carried out twice. One group served as a control group. During the second test emotional, light, sound or tactile impulses were applied to the other groups. The control group that was not exposed to any of the impulses investigated during the second examination showed no significant differences in values with any of the observed indices. Under the influence of emotional, sound or light impulses, a significant increase in pulse frequency as well as in systolic and diastolic blood pressure was noted. This suggested that both the one-minute volume and the peripheral resistance of the circulation system increased. Na131I resorption half-time values from the examined area of the gingiva significantly increased under the influence of emotional and sound impulse by 64%, of light impulse by 84% and of tactile impulse by 93%. This meant that the blood flow through the capillary gingival bed had significantly reduced due to the influence of these impulses. It is to assume that their long-term influence could contribute to the development of parodontopathies.

Acoustic Stimulation↗
PubMed1989

[Effects of early multimodal stimulation on preterm newborn infants].

During the last trimester of pregnancy, newborns are deprived of both maternal biorhythms, tactile, kinesthetic and auditory stimulation which characterize the intrauterine environment. The purpose of this study is to determine if supplemental multimodal stimulation improves neurobehavioral performance, increases weight gain and shortens hospital stay. Nine neonates with the following characteristics were included in an early multimodal stimulation program: 1) gestational age less than or equal to 34 weeks, 2) feeding through orogastric tubing, 3) hemodynamically stable, with no signs of hemorrhaging, infections, or any suggestion of neurological damage, convulsions or congenital malformations. A control group with the same characteristics was also included in the study. Risk factors for each patient were evaluated and their evolution was closely watched while still in the hospital. Both the postural reflexes and neurobehavioral performance were assessed at the time the child left the hospital and a month afterwards. Statistically significant differences were found in the neurobehavioral performance and postural reflexes of those included in the study group.

Acoustic Stimulation↗
PubMed1989

Amacrine cell interactions underlying the response to change in the tiger salamander retina.

The neural circuitry and pharmacology underlying transient signal formation at the bipolar-amacrine cell interface were studied. Synaptic currents were measured with whole cell patch clamp in retinal slices. Cell types were identified with Lucifer yellow staining. Activity was initiated with puffs of kainate of known time course and spatial spread delivered at bipolar dendrites. OFF bipolar cells responded to kainate with a sustained inward current, but ON bipolar cells were silent. Two types of amacrine cell were found: (1) narrow field cells, with processes that extended laterally less than 200 microns, responding with a sustained inward current, and (2) wide field cells, with processes that extended laterally by up to 1 mm, responding with a brief transient inward current followed by a more sustained outward current. We pharmacologically dissected the synaptic interactions underlying the transient current in the wide field amacrine cell. In the presence of 5-aminovaleric acid (AVA), the time course of this transient current was increased so that it resembled the response of bipolar cells. Because AVA is a GABAB antagonist, it appears to block an opposing signal that truncates the sustained excitatory bipolar input, thereby generating the transient. GABAB specificity is confirmed by (1) block of the transient inward current by baclofen, a GABAB agonist, and (2) block of the baclofen effect by AVA. The site of GABAB action appears to be presynaptic to the amacrine cell membrane because neither baclofen nor AVA, in combination with picrotoxin, had a direct effect at the amacrine cell membrane. GABAB receptors are often found at presynaptic terminals where they modulate calcium or potassium conductances. It has been shown that bipolar cell terminals receive a GABAergic synaptic input (Vaughn et al., 1981; Wu et al., 1981; Tachibana and Kaneko, 1987). The narrow field sustained-responding amacrine cells appear to be GABAergic (Werblin et al., 1988). This suggests that transient activity measured in wide field amacrine cells is formed at a population of bipolar cell terminals by GABAergic feedback from narrow field amacrine cells at GABAB receptors.

Animals↗
PubMed1987

Eicosanoid production by the coronary microvascular endothelium.

Cultured rabbit coronary microvessel endothelial (RCME) cells have been used as an in vitro model to study the regulation of microvascular endothelial cell prostaglandin (PG) production by hormones, vasoactive drugs, and inflammatory mediators in an environment that can be tightly controlled and that is unaffected by interactions with other cell types, physical stimulation, or alterations in oxygenation. The most potent stimuli for RCME cell PG secretion were substances associated with inflammation, including histamine, interleukin 1, leukotriene D4, fMet-Leu-Phe, interferon-gamma, and exogenous phospholipases. Inhibition of calcium availability by lower [Ca2+]o or by treatment with calcium channel blockers reduced A23187-stimulated PG release but increased PG synthesis from exogenous arachidonic acid (AA). These observations suggest that Ca2+ may regulate several steps in the pathway leading to PG synthesis and release. Elevated intracellular [Ca2+] may, on the one hand, promote PG production by stimulating phospholipase A2 leading to AA release and, on the other hand, limit the magnitude of the response by increasing the rate of AA reacylation. Glucocorticoids reduce PG production by RCME cells via an action that requires new protein and mRNA synthesis and appears to involve the production of an endothelial cell-derived phospholipase inhibitory protein, or "endocortin." Thus, microvascular endothelial cells can both contribute to (by the release of PGs and possibly platelet-activating factor-acether) and limit (by the production of endocortins) the degree of a local inflammatory response in the heart.

Animals↗
PubMed1987

Pressor response to stress and exercise in the young: intracellular ion content relationships and prognostic implications.

The relationships between intracellular Na+ (Nai) and K+ (Ki) content, blood pressure and peripheral hemodynamics were investigated in young subjects with a family history of hypertension or with borderline hypertension. A direct correlation was found between Nai and pressor response to stress and exercise; after a short-term low-salt diet a parallel decrease was found in Nai and in pressor response to provocative tests. On the contrary, Ki was inversely related to diastolic blood pressure (DBP) both a rest and during mental and physical stimulation. The mechanism by which alterations in intracellular ion content lead to hemodynamic changes may be mediated by a reduced vasodilatory capacity. In fact, during handgrip testing, the increase in forearm vascular resistance (FVR) was directly related to the Nai/Ki ratio while after the exercise, FVR decrease in subjects with normal Nai/Ki and increases in those subjects with high Nak/Ki. In borderline subjects FVR at rest was inversely related to Nai but acute salt loading causes an increase in FVR proportional to Nai. These observations suggest that in subjects with borderline hypertension FVR at rest is normal perhaps as a response to a high cardiac output; however, a further hemodynamic load (salt loading) causes an increase in FVR directly related to Nai and inversely related to Ki. The study of Nai can also give useful information about the risk of developing sustained hypertension. While no subject with borderline hypertension with normal Nai developed hypertension within five years, 31% of those subjects with high Nai developed hypertension after five years.

Adult↗
PubMed1987

Afferent sensillar inputs to the Retzius cell of the leech Hirudo medicinalis.

Water-wave and photic stimulation of the sensilla elicits synaptic potentials identical to those elicited by electrical stimulation of the segmental roots. Mechanical stimulation elicits a localized IPSP and a generalized EPSP in the RCs and an IPSP in the AE motoneurons. Photic stimulation gives rise to a generalized EPSP in the RCs alone. The impulse discharges elicited in the afferent fibers by the two kinds of stimuli is transmitted along the cord both anteriorly and posteriorly to the stimulated segment. This implies that the afferent impulses excite a pool of intersegmental neurons in each ganglion, which distribute their discharges to the adjacent ganglia. The evidence for occlusion between cordal and photically elicited volleys indicates that it shares with the sensillar input a common pool of interneurons. The possible functional significance of the inhibitory and excitatory inputs is discussed.

Afferent Pathways↗
PubMed1987

Determinants of multisensory integration in superior colliculus neurons. I. Temporal factors.

One of the most impressive features of the central nervous system is its ability to process information from a variety of stimuli to produce an integrated, comprehensive representation of the external world. In the present study, the temporal disparity among combinations of different sensory stimuli was shown to be a critical factor influencing the integration of multisensory stimuli by superior colliculus neurons. Several temporal principles that govern multisensory integration were revealed: (1) maximal levels of response enhancement were generated by overlapping the peak discharge periods evoked by each modality; (2) the magnitude of this enhancement decayed monotonically to zero as the peak discharge periods became progressively more temporally disparate; (3) with further increases in temporal disparity, the same stimulus combinations that previously produced enhancement could often produce depression; and (4) these kinds of interactions could frequently be predicted from the discharge trains initiated by each stimulus alone. Since multisensory superior colliculus neurons project to premotor areas of the brain stem and spinal cord that control the orientation of the receptor organs (eyes, pinnae, head), they are believed to influence attentive and orientation behaviors. Therefore, it is likely that the temporal relationships of different environmental stimuli that control the activity of these neurons are also a powerful determinant of superior colliculus-mediated attentive and orientation behaviors.

Acoustic Stimulation↗
PubMed1979

The role of the musculature in injuries to the medial collateral ligament.

With a knee-testing device we measured the valgus stiffness of the medial musculoligamentous complex of the knee in five volunteers. Tests were done with the muscles quiescent and with contraction of the sartorius and vastus medialis. Contraction of those muscles substantially increased the valgus stiffness. In eight subjects the voluntary reaction times were measured. With either a visual or a tactile impulse for prophylactic muscle contraction, the muscles acted too slowly to augment the stiffness of the knee so as to prevent injury. In fifty-one volunteers we applied the maximum torque to the leg, just short of eliciting pain, and showed that even then the muscle contraction would occur too late to protect the knee in typical sports situations.

Adolescent↗