John S. Meyer

Granules and Thyrocalcitonin-like Activity in Medullary Carcinoma of the Thyroid Gland

Abstract A medullary carcinoma of the thyroid gland was examined by electron microscopy, histochemistry and bioassay for thyrocalcitonin. Numerous secretory granules were present in the cytoplasm o...

Cerebral metabolism during epileptic seizures in man

Abstract In order to estimate cerebral metabolic changes during epileptic seizures in man, arterial and cerebral venous PO2, oxygen saturation, PCO2, pH, Na+ and K+, blood pressure, expiratory CO2, EEG and cerebral venous flow were recorded during 22 seizures in eleven volunteer epileptic subjects. Generalized seizures with multiple spike and sharp waves in the EEG, “electro-decremental seizures” and petit mal seizures with 3/sec spike and wave complexes were recorded and compared. No changes in the parameters measured of cerebral metabolism or circulation were seen preceding any type of seizure. During seizures some evidence was adduced for an increase of cerebral oxygen consumption and CO2 production, which was most evident during generalized seizures and minimal during petit mal. The brain tissue was hypoxic during the first phase of all seizures except the “electro-decremental” type. Following generalized seizures there was severe cerebral and systemic acidosis with marked hyperoxia of cerebral venous blood associated with isoelectric EEG and post-ictal paralysis. Evidence was also adduced compatible with a gain of sodium and loss of potassium by the brain during generalized and “electro-decremental seizures”. This was not found during petit mal seizures. It was concluded that post-epileptic paralysis with flattening of the EEG appeared to be initiated by cerebral anoxia but was maintained by cerebral acidosis.

Transport of gases through brain and their extravascular vasomotor action.

Abstract The rate of transport of oxygen and nitrogen through living cat brain was compared with that through dead brain and effects of extravascular gases on cerebral vasomotor action were investigated. For these purposes gases were directly supplied to cerebral cortex using a plastic tent over the exposed cortex while brain-oxygen tension and cortical blood flow were recorded by the polarographic and thermistor methods, respectively. Transport of oxygen and nitrogen through living brain tissue was far faster than through dead brain. Capillary blood flow played an important role in the transport of gases. Direct external application of oxygen to cerebral cortex by plastic tent caused cerebral vasoconstriction. Carbon dioxide gas applied directly and from without to cerebral cortex resulted in dilation of cerebral vessels and this action was inhibited by previous intravenous injection of large amounts of acetazoleamide.

Autoregulation of Cerebral Blood Flow: Electromagnetic Flow Measurements During Acute Hypertension in the Monkey

Changes in blood flow through the internal carotid, vertebral and external carotid arteries were measured by electromagnetic flowmeters during and after acute hypertension induced by closing a clamp around the thoracic aorta in anesthetized monkeys. The internal carotid and vertebral arterial system showed both rapid and delayed autoregulatory responses to rapid increases in blood pressure; the rapid (primary) responses occurred within seconds, the progressive (delayed) within 3 to 4 minutes. In contrast, the flow response within the external carotid system appeared to be passive. Cervical sympathetic innervation and myogenic reflexes (Bayliss reflex) both appear to play a part in the rapidly occurring (primary) regulation of cerebral blood flow. The mechanism responsible for delayed and progressive (secondary) autoregulation in the cerebral vasculature appeared to be metabolic, since it was predominantly influenced by changes in blood Pco2. Changes in intracranial pressure did not seem to be involved in autoregulation.

Effect of stimulation of the brain-stem reticular formation on cerebral blood flow and oxygen consumption ☆

Abstract The brain-stem reticular formation in the pons was stimulated in twelve monkeys while recording cerebral blood flow and oxygen consumption by the use of electromagnetic flowmeters and cerebral arterio-venous oxygen differences. During stimulation, cerebral blood flow and oxygen consumption usually increased if the EEG showed desynchronization. The EEG desynchronization was associated with a mean increase in cerebral oxygen consumption of 7.7% and an increase in cerebral blood flow of 9.7%. After discontinuing the stimulation, cerebral oxygen consumption returned to the steady state within 3 min while the EEG reverted to the resting pattern immediately after the stimulus was discontinued. Less well defined EEG changes were induced by stimulation of the femoral nerve, weak stimulation of the reticular formation or after transection of the cerebral spinal cord. Such poorly defined EEG changes were associated with little or no increase in cerebral blood flow and oxygen consumption. The increase of cerebral blood flow appeared to be caused by increased cerebral metabolism associated with EEG desynchronization.

Cerebral Hemodynamics, Blood Gases, and Electrolytes during Breath-Holding and the Valsalva Maneuver

Continuous recordings of arterial and internal jugular blood oxygen tension, oxygen saturation, carbon dioxide tension, pH, sodium and potassium, together with PECO2, blood pressure, and electroencephalogram were obtained to compare the effects of inspiratory and expiratory breath-holding and the Valsalva maneuver on the cerebral circulation and cerebral oxygen availability in man.During the interval of tolerated breath-holding for 69 seconds or less, jugular venous oxygen tension was increased owing to increased cerebral blood flow resulting from an increase of arterial carbon dioxide tension. There was a statistically significant correlation between changes in JPO2 and PaCO2, which proved to be more or less linear for both increases and decreases of PaCO2 4 mm. above and below control levels. No threshold was found for changes in PaCO2 altering effective cerebral perfusion and cerebral venous PO2, extremely small changes in PaCO2 (less than 1 mm. Hg) altered cerebral oxygen availability within 10 to 20 seconds.During the Valsalva maneuver a consistent reduction of jugular oxygen tension was found associated with the sudden fall in arterial blood pressure and reduction of arterial carbon dioxide tension. The rapid changes in cerebral hemodynamics and cerebral oxygen availability during the procedure are briefly discussed.

Cerebral Oxygen, Glucose, Lactate, and Pyruvate Metabolism in Stroke Therapeutic Considerations

Cerebral blood flow, oxygen, glucose, lactate, and pyruvate metabolism were measured in 13 subjects with completed stroke. Cerebral blood flow and oxygen consumption were reduced, glucose consumption and pyruvate production were normal, and lactate production was increased, suggesting a shift from aerobic to anaerobic cerebral glycolysis.To test this hypothesis, cerebral blood flow and oxygen delivery were decreased by hyperventilation and increased by inhalation of 5% CO2 in air. Hyperventilation decreased cerebral oxygen consumption (CMRO2) and increased cerebral lactate production. Inhalation of 5% CO2 in air increased cerebral blood flow and oxygen delivery and increased both glucose and oxygen consumption. Relationships between reduction in PaCO2 and cerebral venous PO2 and increased cerebral lactate production were found.Increasing cerebral blood flow by 5% CO2 inhalation improved circulation and oxygen delivery to ischemic cerebral areas and improved oxygen and glucose metabolism in the majority of cases since these procedures do not alter CMRO2 in normal persons. Intravenous injection of glucose increased cerebral glucose uptake but insulin did not.

Electroencephalographic monitoring during reconstructive surgery of the neck vessels

Abstract EEGs were recorded at the operating room in 25 patients during 29 operations on the arteries of the neck for cerebrovascular disease. In twenty cases no EEG changes were observed and the post-operative course was excellent. In one case no EEG changes appeared at the time of operation, but a post-operative thrombosis developed. In three cases severe EEG changes consisting primarily of ipsilateral delta waves occurred. All these patients had post-operative neurological deficits. In one case rhythmic bifrontal delta waves followed by flattening was seen during exploration without clamping of the carotid artery. EEG recovery occurred in one minute and no neurological deficit ensued. These changes were attributed to carotid sinus hypersensitivity. In four cases with “mild” EEG changes (transient theta or intermittent delta waves) no neurological complications were observed. It is concluded that EEG is useful for diagnosis of cerebral ischemia in the operating room and for establishing prognosis of post-operative course. Operations performed under local anesthesia in patients with normal or minimally abnormal pre-operative EEG, without occlusion of the contralateral carotid or in whom blood flow in both hemispheres is not depending only on the artery being operated, have the best post-operative prognosis.

A CRITICAL EVALUATION OF RHEOENCEPHALOGRAPHY IN CONTROL SUBJECTS AND IN PROVEN CASES OF CEREBROVASCULAR DISEASE.

When an alternating current passes through a part of the body, modulated changes of impedance occur due to the pulsatile flow of blood, and the possibility of correlating such changes with modifications of the peripheral circulation (Mann, 1937) stimulated the development of the technique. Several modifications of the technique have been used for studies of peripheral circulation (Nyboer, 1944; Holzer and Polzer, 1945) in various parts of the body. The principles and application were lately summarized in Nyboers monograph (1959). Recording changes of electrical impedance with electrodes applied to the head was first reported by Polzer and Schuhfried (1950). Several authors have published results using similar techniques, including Auinger, Kaindl, and Neumayr (1953), Kaindl, Kraus, and Partan (1955), Oehninger, Stanham, Cortes, Fiandra, and Ferrari (1955), Spunda (1955), Serra and Urso (1956), Colonna and Ricciardi (1957), Garbini and Poppi (1957), Gentili, Garbini, and Orlandi (1957), Pratesi, Nuti, and Sciagra (1957), Orlandi, Garbini, and Gentili (1957), Gastaut, Rodler, Lechner, Bostem, and Naquet (1959), Kunert (1961), Lifshitz (1963), and others. Jenkner (1957) has termed this procedure rheoencephalography, and his work over a period of years has culminated in the publication of a monograph (Jenkner, 1962) in which he has summarized his observations in over 10,000 clinical records. Development of a method for continuous recording of cerebrovascular changes by a simple and harmless procedure, if reliable, would be of great clinical usefulness. For this reason we have evaluated rheoencephalography (R.E.G.) in a number of proven cases of cerebrovascular disease and compared the records with those from a group of normal controls.

Auscultation of the Neck in Occlusive Cerebrovascular Disease

D URING the last decade the importance of atherosclerosis of the carotid and vertebral arteries in the neck as a eause of cerebral ischemia or infaretion has become recognized. This has led to revision of older views that cerebral infaretion almost invariably resulted from oeclusion of the middle cerebral or the intracranial arteries. Recent arteriographic and pathologic studies have demonstrated frequent stenosis of one or both carotid or vertebral arteries in the neck in patients with cerebrovascular symptoms.1- It is evident from routine examination of the cervical and cranial vessels in unselected cases at necropsy,j in subjects dying of stroke and by arteriography in the living, that atherosclerotic plaques occur most frequentlyin well-defined sites of the internal. carotid vessels. The commonest site for plaque formation is in the internal carotid artery witlh atherosclerotic stenosis or occlusion in the region of the carotid sinus, usually at the origin of the internal from the comnmion carotid artery or a few eentimeters distal to this point.7 Surgical removal of atheroselerotic. plaques at this site is quite feasible anid an impressive number of successful. cases have been reported.3 -16 Atherosclerotic plaques of the vertebral-basilar arterial svstem are usually more diffuse. The commonest site is the basilar artery itself. Meyer, Sheehan, and Bauer17 in an arteriographic study of subjects admitted to a general hospital with