Rocco Cicciarello

Quantitative study of blood-brain barrier permeability changes after experimental whole-brain radiation

Basic mechanisms underlying the tolerance and reaction of the central nervous system to ionizing radiation are not known precisely. We investigated the possibility of a change in blood-brain barrier (BBB) function as a causative factor for early delayed whole-brain radiation-induced cerebral dysfunction. Rats were exposed to conventional fractionation (200 cGy/d, 5 d/wk; total dose, 4000 cGy). BBB changes were assessed by means of the quantitative 14C-alpha-aminoisobutyric acid technique and electron microscopy. Studies of the passage of horseradish peroxidase across the BBB permitted comparative quantitative isotopical and qualitative morphological data. Experiments were carried out 2 to 3 weeks after the completion of the radiation exposure. The transport of 14C-alpha-aminoisobutyric acid across the BBB increased significantly in cerebral cortex and cerebellar gray matter, averaging 1.3 to 1.5 times over the normal values. Electron microscopy disclosed an intense vesicular response of the cortical microvascular endothelium that occurred without the opening of the tight junctions and resulted in an intense transport of HRP across the intact endothelium. The present data indicate that moderate doses of whole-brain radiation induce well-defined changes in BBB function, which possibly are involved in the pathogenesis of radiation-induced cerebral dysfunction in humans.

Blood-Brain Barrier Permeability Changes after Experimental Subarachnoid Hemorrhage

Basic mechanisms underlying cerebrovascular permeability responses to subarachnoid hemorrhage (SAH) are still to be defined in detail. Previous investigations examining the occurrence of blood-brain barrier (BBB) breakdown after SAH in the experimental setting have yielded conflicting results. In a rat model of SAH, we assessed BBB changes by means of the quantitative [14C]-alpha-aminoisobutyric acid technique. Experiments were carried out on the second day post-SAH. In blood-injected rats [14C]-alpha-aminoisobutyric acid transport across the BBB increased significantly in cerebral cortices and cerebellar gray matter, averaging 1.3 to 1.5 times control values. The present data indicate that SAH induces well-defined changes in BBB function, possibly involved in the pathogenesis of post-SAH cerebral dysfunction in humans. Results reported here have also potential clinical implications for the management of aneurysm patients.

Regional changes in spinal cord glucose metabolism in a rat model of painful neuropathy

Spinal cord patterns of metabolic activity in a model of neuropathic pain were assessed in unanesthetized rats by the [14C]-2-deoxyglucose (2-DG) technique. Rats used in this procedure had demonstrable thermal hyperalgesia ipsilateral to sciatic nerve ligation and ipsilateral hindpaws that were lifted in a guarded position. The latter indicated possible spontaneous pain. Sciatic nerve ligation produced significant increases in glucose utilization in the dorsal and ventral horns of both sides, with greater activity present on the ipsilateral as compared to the contralateral side. Peak activity was in laminae V-VI, a region involved in nociceptive processing. Thus, a chronic increase in neuronal activity in these regions may reflect spontaneous neuropathic pain.

Time-related ultrastructural changes in an experimental model of whole brain irradiation.

To stimulate therapeutic irradiation, we exposed rats to conventional fractionation (200 +/- 4 cGy/d, 5 d/wk; total dose, 4000 cGy). The effects of this regimen were assessed by electron microscopic examinations of brain microvascular and parenchymal cells 15 and 90 days after irradiation. Studies of the transendothelial passage of horseradish peroxidase provided information about the functional status of the blood-brain barrier. At 15 days after irradiation, there was an increased vesicular transport of horseradish peroxidase across the intact endothelium without opening of the tight junctions, and without evidence of structural alterations of neuropil, neuronal bodies, and astrocytes. Ninety days after irradiation, well-defined ultrastructural alterations were observed, involving the microvasculature, the neuropil, the neuronal bodies, and astrocytes. The main ultrastructural feature of cortical microvessels was their collapsed aspect, associated with perivascular edema containing cell debris. Altered neurons and reactive activated astrocytes were also noticeable. These data suggest a possible association, not necessarily causal, between damage of the microvascular/glial unit of tissue injury and development of radiation-induced brain toxicity.

Radiation-Induced Blood-Brain Barrier Changes: Pathophysiological Mechanisms and Clinical Implications

The pathophysiology of whole-brain radiation (WBR) toxicity remains incompletely understood. The possibility of a primary change in blood-brain barrier (BBB) associated with microvascular damage was investigated. Rats were exposed to conventional fractionation in radiation (200 +/- cGy/d, 5d/wk; total dose, 4,000 cGy). BBB changes were assessed by means of the quantitative 14C-alpha-aminoisobutyric acid (AIB) technique coupled with standard electron microscopy (EM) and morphometric techniques as well as studies of the transcapillary passage of horseradish peroxidase (HRP). At 15 days after WBR, AIB transport across BBB increased significantly in cerebral cortex. EM disclosed vesicular transport of HRP across the intact endothelium without opening of the tight junctions. Ninety days after WBR, well-defined alterations of the microvasculature were observed. The main feature of cortical microvessels was their collapsed aspect, associated with perivascular edema containing cell debris. Data suggest a possible association between damage of the microvascular/glial unit of tissue injury and development of radiation-induced brain cerebral dysfunction. We hypothesize the following sequence of pathophysiological events: WBR causes an early increase in BBB permeability, which produces perivascular edema and microvascular collapse. The interference with microcirculation affects blood flow and energy supply to the tissue, resulting in structural damage on an ischemic/dysmetabolic basis.

Eruptive Syringomas with Calcium Deposits in a Young Woman with Down’s Syndrome

Eruptive syringomas are uncommon in the general population. We describe here an 18-year-old female, affected by Down’s syndrome, who presented with an abrupt eruption of small skin-colored or reddish papules on the face, neck and limbs. Light microscopy allowed us to diagnose syringomas, whereas the study of the ultrastructural features revealed calcium deposits in many lumina and also in the mitochondria. This observation confirms the hypothesis that the syringeal structure plays a role in the pathogenesis of calcinosis cutis.

Brain energy metabolism in the acute stage of experimental subarachnoid haemorrhage: Local changes in cerebral glucose utilization

SummaryAn experimental model was used to investigate acute alterations of cerebral metabolic activity in rats subjected to subarachnoid haemorrhage (SAH). Haemorrhages were produced in anaesthetized animals by injecting 0.3 ml of autologous, arterial nonheparinized blood into the cisterna magna. Control rats received subarachnoid injections of mock-cerebrospinal fluid to study the effect of sudden raised intracranial pressure, or underwent sham operation. Three hours after SAH rats were given an intravenous injection of [14C]-2-deoxyglucose. Experiments were terminated by decapitation, and the brains were removed and frozen. Regional brain metabolic activity was studied by quantitative autoradiography. In comparison with sham-operated controls, cerebral metabolic activity was diffusely decreased after SAH. Statistically significant decreases in metabolic rate were observed in 23 of 27 brain regions studied. Subarachnoid injections of mock-cerebrospinal fluid also produced depression of cerebral metabolic activity, but quantitatively these changes were not as pronounced and diffuse as in SAH rats. The present study shows that a widespread depression of brain metabolism occurs in the acute stage after experimental SAH and is probably secondary to the Subarachnoid presence of blood itself and/or blood products.

Chronic heat-induced skin lesions (erythema ab Igne): ultrastructural studies.

Erythema ab igne (EI) is an uncommon skin lesion caused by mild and repeated exposure to infrared sources. The aim of this study was to investigate the ultrastructural alterations in this condition. The ultrastructural study was carried out on 5-outpatients who presented typical EI of their exposed sites. Skin punch biopsies were processed for standard electron microscopy. The epidermis was hyperpigmented, with focal regressive changes of basal keratinocytes. An apparent functional activation of melanocytes with numerical increase of dendritic processes was also observed. The dermis showed abundant melanophages and occasional elastic fiber alterations similar to actinic elastosis. No alterations consistent with preneoplastic skin conditions were observed. The ultrastructural findings associated with EI seem to be nonspecific and consistent with moderate regressive changes of keratinocytes as well as a consensual melanocytic activation and elastic fiber modifications. Similar alterations can be observed in chronic actinic skin damage. This condition is presumably more benign than the ultraviolet exposure.The association of EI and premalignant skin lesions, though occasionally described, seems relatively infrequent.

Effect of whole brain radiation on local cerebral glucose utilization in the rat.

We assessed, by means of the [14C]-2-deoxy-D-glucose autoradiography method, the effect of whole-brain x-radiation on local cerebral glucose utilization in the rat brain. Animals were exposed to conventional fractionation (200 +/- 4 cGy/day, 5 days/week; total dose, 4000 cGy). Metabolic experiments were made 2 to 3 weeks after completion of the radiation exposure. In comparison with control and sham-irradiated animals, cerebral metabolic activity was diffusely decreased after irradiation. Statistically significant decreases in metabolic activity were observed in 13 of 27 brain regions studied. In general, the brain areas with the highest basal metabolic rates showed the greatest percentage of decrease in glucose utilization. The concept that radiation suppresses glucose utilization before any morphological change takes place in the cell structures was the basis of this study. Metabolic alterations after irradiation may explain the syndrome of early delayed deterioration observed in humans after whole-brain radiotherapy. These studies have applications to observations made with the [18F]-fluorodeoxyglucose method in conjunction with positron emission tomographic scans in patients receiving radiation therapy for intracranial malignancies. The data reported here also have potential clinical implications for the evaluation of a risk/benefit ratio for radiotherapy in patients with benign neurosurgical diseases or children undergoing prophylactic treatment of the central nervous system.

The effect of the calcium antagonist nimodipine upon local cerebral glucose utilization in the rat brain

The new calcium antagonist Nimodipine has been shown to have more powerful dilator action on cerebral than peripheral vessels. The effect of the drug on cerebral metabolism was studied in conscious rats using the /14C/-2-deoxyglucose quantitative autoradiographic technique. Intravenous injection of Nimodipine, 2 mcg/Kg, determined significant increases in local cerebral glucose utilization that appeared to be homogeneous in magnitude and anatomic distribution throughout the brain. This study raises the question whether Nimodipine affects brain functions by other mechanisms than an increase in cerebral blood flow.