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Biomedical subjects

R B Page

Publications and source records attributed to R B Page.

At least 37 records · Page 2Linked to original sources
PubMed1984

Resistance vessels supplying the median eminence of the rabbit, rat, and cat.

The ultrastructure of arterioles supplying the median eminence of eight rats, eight rabbits, and two cats was studied after vascular perfusion with phosphate buffered aldehyde fixatives. There were terminal arterioles with a lumen diameter of 50-70 micron within the pars tuberalis. Smaller arterioles (precapillary sphincters and metarterioles) with a lumen diameter of 15-20 micron were present on the surface of the median eminence. Arterioles were not observed to penetrate the neuropil but were seen to supply the external capillary plexus of the median eminence. Direct innervation of arterioles supplying the median eminence was not present and hence regulation of median eminence blood flow by peripheral sympathetic mechanisms appears unlikely. Resistance vessels were found to be closely related to axon terminals on the surface of the median eminence and to fenestrated capillaries of the external plexus. In addition, the endothelial cells of arterioles were characterized by the presence of pits and vesicles which may play a role in transendothelial transport. These findings suggest two mechanisms by which blood flow into the median eminence can be regulated: (a) by central catecholaminergic systems terminating in the median eminence and (b) by catecholamine secretions from the adrenal medulla.

Animals↗
PubMed1984

Aerobic glycolysis by the pituitary gland in vivo.

Arteriovenous differences of glucose, lactate, and pyruvate were measured across the pituitary glands of overnight-fasted female pigs to determine whether net uptake of glucose occurred, and if so, whether it was oxidized or converted to lactate. Arteriovenous differences were also measured across a portion of the cerebral cortex as a control. Cerebral cortex oxidized 84% of the glucose taken up, but this was not true in the pituitary gland, where glucose was almost completely converted to lactate. The arteriovenous difference across the pituitary gland was 0.61 mumol/ml for glucose while the venoarterial differences of lactate and pyruvate were 1.0 and 0.07 mumol/ml, respectively. The results indicated that little net oxidation of glucose either by the Krebs cycle or the pentose phosphate pathway occurs in the pituitary gland in vivo. Estimates of the amount of energy released from aerobic glycolysis indicate that, unless the requirements of the neurohypophysis are very different from those in the rest of brain, very little energy could be derived from the metabolism of glucose.

Aerobiosis↗
PubMed1983

Cerebral glucose utilization in awake unstressed rats.

Regional cerebral glucose utilization (rCMRGlc) was measured in awake unstressed rats by use of [2-14C]glucose autoradiography. Rats prepared by chronic catheterization of the jugular and epigastric veins were placed in specially designed chambers after surgery. The catheters were passed through the top of the chambers. Seven days after surgery, plasma glucose was normal (7.5 mM), plasma ketone bodies were low (0.13 mM), and body weight was maintained. Plasma epinephrine was 31 pg/ml; approximately 3% of the level for stressed (immobilized) rats. Injections and blood sampling through the catheters did not produce changes in heart rate, blood pressure, plasma catecholamines, or blood metabolites. Visual observations did not reveal any signs that the rats were aware of the [2-14C]glucose injections and the subsequent blood sampling. The rCMRGlc in stressed rats was significantly greater than in unstressed rats. This method provides a model for physiological studies in unstressed unanesthetized rats.

Animals↗
PubMed1982

Optic neuropathy and paratrigeminal syndrome due to Aspergillus fumigatus.

Chronic Aspergillus meningitis and cerebral vasculitis occurred in a 67-year-old man. He experienced periorbital pain that increased in severity during a ten-month period. Although no focal neurologic deficits were initially present, oculosympathetic paresis, corneal hypesthesia, and optic neuropathy developed. This is the first report, to our knowledge, of paratrigeminal syndrome with optic neuropathy due to aspergillosis. The case was also unusual because it was chronic and there was no extracerebral infection or predisposing factors, such as underlying malignancy or collagen vascular disease.

Aged↗
PubMed1982

Pituitary blood flow.

The direction of pituitary blood flow, the amount of pituitary blood flow, its regional control, and the role of the median eminence microcirculation are the subjects of this review. Present concepts of pituitary blood flow are focused almost entirely on its direction and arouse from studies of pituitary vascular anatomy performed almost 50 years ago. The development of new anatomic techniques has led to a reappraisal of pituitary angioarchitecture, stimulated physiological studies to clarify the pattern of blood flow within the entire gland, and led to a reappraisal of accepted concepts of directional pituitary blood flow. The availability of techniques to accurately measure organ blood flow has permitted study of pituitary blood flow; and, when combined with knowledge of pituitary anatomy, the application of these techniques promises to provide a means to develop insight into control of the mechanisms by which chemical messengers are delivered to the pituitary to control its function. New anatomic techniques promise to develop new understanding of the three-dimensional arrangement of median eminence microvasculature and yield new concepts of blood flow regulation within the median eminence that can be tested by physiological means.

Animals↗
PubMed1982

Optic nerve blood flow and its regulation.

Intracranial optic nerve blood flow was measured by the radiolabeled microsphere technique in 30 adult sheep under light barbiturate anesthesia. Regional blood-flow rates were determined under basal conditions. The responses of regional blood flow to alterations in PaCO2 and to changes in arterial blood pressure were also measured. Under basal conditions blood flow was comparable to that found in other cerebral white matter (14 +/- 1 ml/100 gm/min). Responses to hypercarbia and hypocarbia were also similar to reported measurements for other cerebral white matter. With alteration of arterial blood pressure, intracranial optic nerve blood flow remained constant within the limits of cerebral autoregulation.

Animals↗
PubMed1981

Regional neurohypophyseal blood flow and its control in adult sheep.

Regional neurohypophyseal and cerebral blood flows were measured by the radiolabeled microsphere technique in 30 adult sheep under light barbiturate anesthesia. Regional blood flows were determined under basal conditions. The responses of regional blood flow to alterations in arterial PCO2 and to changes in arterial blood pressure wee also determined. In addition, the relationship between regional neurohypophyseal blood flow and neurosecretory activity as judged by plasma arginine vasopressin levels was assessed. Under basal conditions median eminence blood flow averaged 461 ml.100 g-1.min-1 and did not significantly differ from neural lobe blood flow (436 ml.100 g-1.min-1). Blood flow in the neurohypophysis was about 8 times cortical and 16 times white matter blood flow in these animals. Median eminence and neural lobe blood flow proportionately increased far less than regional cortical or white matter blood flow under conditions of hypercarbia. With alteration of arterial blood pressure, regional neurohypophyseal blood flow remained constant beyond the limits of cerebral autoregulation. The neurohypophysis demonstrates a degree of blood flow homeostasis that exceeds that of any other brain area studied. Although the neurohypophysis is a diverticulum of the brain, its vascular system forms a unique functional as well as a unique anatomic unit.

Animals↗
PubMed1980

Choroid plexus blood flow in the sheep.

Choroid plexus blood flow was measured in 29 adult female sheep using the radioactive microsphere technique. Basal blood flow, response to change in arterial carbon dioxide tension, and response to change in mean arterial blood pressure were determined. The results were compared to cerebral cortical blood flow values in the same sheep. Mean choroid plexus blood flow was 601 ml/100 g/min under basal conditions. Choroid plexus blood flow fell 31% with hypocarbia, a reduction comparable to that seen in cortex. With hypercarbia choroid plexus blood flow rose only 27% whereas cortical blood flow increased by 199%. Unlike cortical blood flow, choroid plexus blood flow fell significantly with pharmacogenic hypertension. The latter finding may reflect the absence of a blood-brain barrier in choroid plexus.

Animals↗
PubMed1980

Cerebral oxidative metabolism in perinatal post-hemorrhagic hydrocephalus.

Survivors of perinatal intraventricular hemorrhage often develop a distinct clinical syndrome characterized by hydrocephalus and biochemical abnormalities in cerebrospinal fluid. The authors investigated six neonates with post-hemorrhagic obstructive hydrocephalus in order to identify cerebral metabolic disturbances responsible for the hypoglycorrhachia observed in this disorder. Lactic acid concentraions and lactate/pyruvate ratios in ventricular fluid were significantly elevated in infants with post-hemorrhagic hydrocephalus compared with the values in five with congenital (non-hemorrhagic) obstructive hydrocephalus. Comparable degrees of ventricular dilatation and intracranial hypertension were present in the two groups. There is evidence that neither residual cellular elements in ventricular fluid nor a disrupted blood-CSF barrier can fully explain the observed alterations in ventricular-fluid glucose, lactate or lactate/pyruvate ratios. It is suggested that when periventricular hemorrhage occurs, the associated cerebral ischemia leads to focal anaerobic glycolysis and increased glucose requirement. With inadequate cerebral glucose glycolysis and increased glucose requirement. With inadequate cerebral glucose delivery from the blood, glucose diffuses into the brain from the ventricular fluid, resulting in hypoglycorrhachia. Cerebral lactic acid production is enhanced, which accumulates in ventricular fluid in the presence of ventricular obstruction.

Birth Injuries↗
PubMed1979

Pituitary-brain vascular relations: a new paradigm.

Vascular casts of the pituitary gland have demonstrated a paucity of veins extending from the adenohypophysis to the systemic circulation and have suggested that some adenohypophyseal venous blood returns to the neurohypophysis. The neurohypophyseal capillary bed may function as a vascular switch and in this article a series of 14 questions are proposed regarding the vascular dynamics of the pituitary. Together these questions raise the larger question, namely, whether pituitary hormones are transported directly to the brain to modify brain function?

Animals↗
PubMed1979

Luteinizing hormone and follicle-stimulating hormone production in the pars tuberalis of hypophysectomized rats.

Luteinizing hormone and follicle-stimulating hormone were identified by immunocytochemistry in the same cells of the pituitary pars tuberalis, following hypophysectomy in the rat. A marked hyperplasia and hypertrophy of these cells occurred in response to hypophysectomy. These findings are discussed in light of the potential for hormone production by pars tuberalis gonadotropes following hypophysectomy performed as part of an experimental protocol, as well as that performed for palliation of human metstatic breast cancer.

Animals↗
PubMed1979

The morphology of extrachoroidal ependyma overlying gray and white matter in the rabbit lateral ventricle.

A morphologic investigation of ependyma over gray matter (caudate nucleus) and over periventricular white matter (tapetum) of the rabbit lateral ventricle was undertaken prior to evaluation of morphological changes which occur with experimental hydrocephalus. Ependymal cells over the caudate nucleus are cuboidal and heavily ciliated. Numerous microvilli cover the cell surface. The lateral margins are straight and interdigitations between adjacent ependymal cells are absent. Ependymal cells over white matter are squamous. Nonciliated as well as ciliated cells contribute to the epithelial lining. Microvilli are present at the cell surface but tend to aggregate near the cellular borders. The lateral margins are convoluted and complex interdigitations are present between adjacent cells. Morphologic differences between ependymal cells over the caudate nucleus and those over periventricular white matter may help to explain the differential response to hydrocephalus observed in these two regions of the lateral ventricle.

Animals↗
PubMed1979

Radionuclide blood flow studies before and after gelfoam embolization of intracranial meningiomas.

Radionuclide blood flow studies were employed to evaluate the success or failure of preoperative Gelfoam embolization in two patients with intracranial meningiomas. In both cases, the initial radionuclide blood flow study showed tumor visualization during the arterial phase. Immediately following the embolization procedure, the radionuclide blood flow study showed no visualization of the meningioma during the arterial phase, indicating a successful embolization procedure in preparation for removal of the tumor in a relatively bloodless field.

Cerebrovascular Circulation↗