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Biomedical subjects

G Macchi

Publications and source records attributed to G Macchi.

At least 37 records · Page 2Linked to original sources
PubMed1992

Potentiation of electroencephalographic spindles by ibotenate microinjections into nucleus reticularis thalami of cats.

It is well known that the electroencephalogram of the cat in the early stages of slow wave sleep is mainly characterized by rhythmic wave activity at 7-14 Hz, termed spindles, which recur periodically with a slow rhythm of 0.1-0.2 Hz. From early stimulation, decortication and transection studies (see Ref. 14), spindle oscillations were thought to originate in the thalamus. The search for the anatomical substrate of thalamic spindling, however, moved from medial (intralaminar nuclei) to lateral thalamic nuclei, and recently focused on the extreme shell-shaped collection of GABA-ergic cells, the nucleus reticularis thalami. This proposition was based on its structural, hodological, and physiological aspects. There is accumulating evidence that the nucleus reticularis may act as a conditional pacemaker, synchronizing the activity of cortically projecting thalamic neurons. The introduction of glutamate analogues with excitotoxic properties such as ibotenic acid provided the opportunity of studying the immediate effects of chemical excitation of this nucleus on synchronized electroencephalographic activity. We found that, in cats, spindle density was dramatically increased following infusion of ibotenic acid into the rostral pole of the nucleus, supporting the role of this sector in spindle-related rhythmicity.

Animals↗
PubMed1992

White matter lesions in Creutzfeldt-Jakob disease. A short review.

This short review takes in consideration the role played by the cerebral white matter in Creutzfeldt-Jakob disease (CJD) and analyzes three different hypotheses on the meaning of the involvement of the white matter only as secondary phenomenon or as primary neuropathological damage related to the causative agent(s) of the disease.

Astrocytes↗
PubMed1992

An in vivo and post mortem MRI study in multiple sclerosis with pathological correlation.

A young woman affected by multiple sclerosis (MS) was examined by magnetic resonance (MRI) during a relapse. Three months later the patient died from acute pulmonary embolism. An imaging and quantitative MRI study was performed on the formalin-fixed brain. Finally, the left hemisphere was examined by light microscopy after histological and immunocytochemical staining. While fixation significantly reduced T1 and T2 relaxation times, MRI signal and image contrast of the fixed brain were satisfactory. Lesion distribution was very similar in corresponding MRI slices and histological sections. The post mortem MRI scan and pathological study detected several new lesions, as expected from the patient's clinical course. Thus, it was possible to evaluate the age of lesions by comparing the MRI scans. In this study, signal intensity of MS lesions varied according to their histological features, i.e. to their age.

Adult↗
PubMed1991

GABAergic interneurons and neuropil of the intralaminar thalamus: an immunohistochemical study in the rat and the cat, with notes in the monkey.

Immunohistochemistry using antibodies to glutamic acid decarboxylase (GAD) was used to investigate the intralaminar nuclei of the thalamus in rat, cat and monkey. Antibodies to gamma aminobutyric acid (GABA) were also used in the cat. Intralaminar immunoreactive cell bodies were not detected in the rat, but were clearly present in cat and monkey. In the latter species, GABA- or GAD-immunopositive perikarya were distributed throughout the anterior intralaminar nuclei, whereas in the posterior intralaminar complex they prevailed in the lateral part of the centre median nucleus and around the fasciculus retroflexus. Measurements of the area of immunostained intralaminar cell bodies in cat and monkey indicated that they are represented by small neurons. Experiments in the cat, based on retrograde tracers injections involving large sectors of the frontal and parietal cortices and the head of the caudate nucleus, revealed that the GABA- or GAD-immunoreactive cells and the retrogradely labeled projection neurons represented two separate intralaminar cell populations, although the latter also included small cells. Considerable differences were observed in the immunoreactive GABAergic neuropil of the anterior and posterior intralaminar nuclei. Clusters of densely packed bouton-like immunoreactive elements were detected in the former structures in the rat, cat and monkey, and were especially evident in the central lateral nucleus; immunopositive varicose fibers and puncta were diffusely distributed in the posterior intralaminar structures. Taken together with data from the literature, the present findings indicate that in cat and monkey local circuit inhibitory cells regulate not only the activity of principal thalamic nuclei which project densely upon restricted cortical fields, but also of the intralaminar structures which are widely connected with the cerebral cortex and the striatum. Regional variations in the distribution of GABAergic fibers and terminals suggest major differences in the organization of inhibitory circuits and synaptic arrangements of the anterior and posterior intralaminar thalamus.

Animals↗
PubMed1991

A procedure for the simultaneous visualization of two anterograde and different retrograde fluorescent tracers. Application to the study of the afferent-efferent organization of thalamic anterior intralaminar nuclei.

The present report describes a method for the simultaneous visualization, in the same structure, of two different sets of afferent pathways and the neurons of origin of some efferent projections. This method has been applied in the cat for studying, in the thalamic anterior intralaminar nuclei, the topographical relationships of afferent arising from the spinal cord and deep cerebellar nuclei with neurons projecting to different cortical areas. Spino- and cerebello-thalamic terminals were anterogradely labeled by injections of the fluorescent dyes fast blue (FB) and 1,1'-dioctadecyl-3,3,3',3'-tetramethyl-indocarbocyanine perchlorate (DiI) in the spinal cord and cerebellum. Thalamo-cortical neurons were retrogradely labeled by injections of fluorescent tracers in the precruciate and anterior suprasylvian cortices. The findings show that spinal and cerebellar afferent fibers and the cells of origin of intralaminocortical projections are organized in a clear modular manner and indicate that the method used here is suitable for analyzing simultaneously, in light microscopy, multiple input-output interrelationships of a single structure.

Afferent Pathways↗
PubMed1991

Clinical-electrophysiological correlations in a long-term case of subacute sclerosing panencephalitis with partial clinical improvement.

An electrophysiological follow-up was performed in a rare case of subacute sclerosing panencephalitis (SSPE) that from the vegetative stage had an extremely favourable course, lasting 4 years, in which clinical conditions passed, according to the Risk and Haddad scale, from stage 3 to stage 1. In this period of time, 5 CT scans and a series of EEGs, visual evoked potentials (VEPs) and brainstem auditory evoked potentials (BAEPs) were performed to investigate the correlation between clinical course and electrophysiological diagnostic data. The results showed a significant improvement in diagnostic results, directly correlated with the remission of clinical symptoms. Electrophysiological signs of improvement in VEPs were obtained before observable improvement was seen on CT scans. These results indicate that an accurate electrophysiological study (through cerebral evoked potentials) has an important role in investigating suspected cases of SSPE, in following the clinical evolution of this disease and providing prognostic data.

Adolescent↗
PubMed1991

Combination ultrafiltration and 6 M urea treatment of human growth hormone effectively minimizes risk from potential Creutzfeldt-Jakob disease virus contamination.

Although genetically engineered human growth hormone (hGH) is now commercially available, native pituitary-derived hGH is still used by physicians in many countries for the treatment of hormone deficiency states. We describe a method using ultrafiltration and 6 M urea that reduced infectivity in human pituitary tissue that had been deliberately contaminated with scrapie virus (an animal analogue of human Creutzfeldt-Jakob disease virus) from an initial level of 10(9.7) infectious units to just 5 infectious units. Based on estimates of the frequency of contamination and infectivity levels in batches of human pituitaries, the use of this protocol to prepare GH from cadaveric human glands yields a calculated probability of exposure to a contaminated vial of not greater than 1 in 3.2 million recipients; therefore, native hormone prepared by this method may be considered to be essentially risk-free. The same methodology may be useful in the preparation of other hormones, such as prolactin, for which no synthetic substitutes are currently available, as well as biological products derived from sheep or cattle, that may be infected with scrapie or bovine spongiform encephalopathy.

Animals↗
PubMed1991

[Percutaneous mitral commissurotomy: immediate and short-term results].

31 symptomatic patients with mitral stenosis were selected for percutaneous transvenous mitral commissurotomy using Inoue catheter. The patients were selected using the echocardiographic score for: leaflets mobility, leaflets thickening, subvalvular thickening, degree of calcifications. All patients had a score less than or equal to 8 and represented 17.5% of the patients studied in our echocardiographic laboratory for mitral stenosis. We were able to perform the commissurotomy in 30 of them. Mean left atrial pressure decreased from 26 +/- 5.2 mmHg to 14.6 +/- 6 mmHg (p less than 0.001). The mean mitral diastolic pressure gradient decreased from 8.9 +/- 3.1 mmHg to 3.9 +/- 1.3 mmHg (p less than 0.001). The mitral valve area, using the echocardiographic Pressure Half Time (PHT), increased from 0.94 +/- 0.17 cmq to 1.96 +/- 0.33 cmq (p less than 0.001). Mitral regurgitation, angiographically evaluated in 29 patients, increased in 11 (38%), being of degree + + + in 3 patients. There were 2 heart tamponades and 5 cases (16.6%) of left-to-right shunt with Qp / Qs less than 2. After 3 months, the follow-up showed improvement of one or more functional classes in 96.6% of all patients. The mitral valve area, determined after 6 months in 24 patients by PHT, was stable (1.98 +/- 0.31 vs 1.93 +/- 0.25) (p = 0.5); we did not find mitral stenosis recurrence in any instance. In the first 10 patients, after 1 year, the results are stable (1.85 +/- 0.28 cmq vs 1.93 +/- 0.21 cmq) (p = 0.5) without mitral stenosis recurrence. These data suggest that in selected tight mitral stenosis the percutaneous transvenous commissurotomy may be alternative to the open surgical solution. Using an Inoue catheter, the percutaneous transvenous mitral commissurotomy is easier and the complications are few. The major procedural hazards derive from the transseptal technique.

Adult↗
PubMed1990

Considerations on a group of 13 patients with Creutzfeldt-Jakob disease in the region of Parma (Italy)

We report a group of 13 cases of Creutzfeldt-Jakob disease treated in the region of Parma (Italy) between 1975 and 1984. An extensive study did not point to any common source of infection. The clinical stereotypy and distinctive neuropathology in this temporo-spatially confined group of patients might be stressed, but the possibility of infection by a single strain of the CJD agent remains speculative.

Aged↗
PubMed1990

A case of epidermal nevus syndrome with carotid malformation.

Epidermal Nevus Syndrome (ENS) is characterized by linear verrucous lesions of the skin and congenital anomalies including bone deformities, eye and central nervous system (CNS) malformations. We describe a case of ENS associated with an abnormality of the carotid artery which is considered a risk for stroke.

Adult↗
PubMed1990

Neuronal cell types in the thalamic intralaminar central lateral nucleus of the cat.

The existence of Golgi type II neurons was verified in the anterior intralaminar central lateral (CL) nucleus of the cat thalamus, and its projection cell types were identified, by means of Golgi impregnation. CL principal neurons were found to display a large- or medium-sized cell body and a radiate dendritic pattern. Their primary dendrites were limited in number, and had a rather long course; they were poorly ramified. The axons of principal neurons were impregnated only occasionally and for a short distance. Projection neurons of the 'bushy' or tufted type, described in the main thalamic sensory nuclei, were not identified in the CL in the present study. Typical Golgi type II neurons were found throughout CL. They were mainly small-sized, and displayed a rich dendritic arborization characterized by dendritic appendages. The axons of Golgi type II neurons were seen to give rise to extensive local arborizations. The present findings indicate that in the cat CL, principal cells are mainly represented by radiate neurons. Typical local circuit neurons also are evident in CL, suggesting that the activity of anterior intralaminar structures is regulated by intrinsic mechanisms similar to those operating in the main thalamic relay nuclei.

Animals↗
PubMed1990

[Cardiac effects of exhausting isometric muscular contraction in trained and endurance athletes].

The effect of exhausting isometric contraction (60% of the maximal voluntary contraction) on left ventricular function has been investigated using echocardiography (M and B mode) in 4 groups, each of 8 subjects (27 +/- 5 years; mean +/- SD): weight lifters, 2 years of training; amateur cyclists, 4 years of training; sedentary controls, and hypertensive subjects, 1st WHO class. Heart rate, arterial pressure, ventricular diameters (diastolic and systolic), wall thickness, wall stress and the double product (heart rate x arterial pressure) were determined at rest, at exhaustion and after 30, 90 and 180 s of recovery. Maximal voluntary contraction was 48 +/- 9 kg in weight lifters; 32 +/- 5 kg in amateur cyclists; 32 +/- 4 kg in sedentary control and 36 +/- 7 kg in 1st WHO class. Exhaustion time ranged from 80 s to 120 s. Our results showed that: 1) in all subjects at exhaustion, arterial pressure and heart rate increased significantly and the index of ventricular function was decreased but not significantly; 2) after 180 s of recovery both arterial pressure and heart rate returned to the pre-exercise value; 3) wall stress was significantly lower in weight lifters than in sedentary controls; 4) the double product (index of myocardiac oxygen consumption) resulted lower in amateur cyclists that in sedentary controls. The hypertrophy of the heart could justify the slight increase in wall stress observed in weight lifters during isometric exercise. However, the low index of myocardiac oxygen consumption in amateur cyclists probably reflects the changes in cardiovascular function due to the endurance training. In hypertensive subjects, the isometric contraction causes significant and substantial increase of the wall stress and the double product.

Adult↗