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Biomedical subjects

R B Page

Publications and source records attributed to R B Page.

48 records · Page 3Linked to original sources
PubMed1978

The neurohypophyseal capillary bed. II. Specializations within median eminence.

Vascular casts of the pituitary gland, median eminence and hypothalamus from several mammalian species were examined by scanning electron microscopy. These observations were correlated with light microscopic studies of injected, cleared median eminence-pituitary specimens and with light microscopic examination of serial sections of injected hypothalamic, median eminence, and pituitary specimens employing reflected lighting or epi-illumination. Transmission electron microscopy was employed to study long portal vessels on the ventral surface of the rat median eminence. In each of the species examined, the median eminence (infundibular) capillary bed is subdivided into an external and an internal plexus. The external plexus (the neurohemal contact zone) receives an arterial supply from the superior hypophyseal arteries and is continuous with the capillary bed of the infundibular stem and process. Egress from the external plexus is possible via three vascular routes: (a) by fenestrated portal vessels and capillaries to the adenohypophysis, (b) by capillary connections to the medial basilar hypothalamus and, (c) by internal plexus capillaries to the ependyma of the median eminence. Median eminence vasculature is structurally organized to deliver (1) hypothalamic and neurohypophyseal peptides to the glandular pituitary via portal vessels, (2) hypothalamic and pituitary secretions to the medial basilar hypothalamus via capillaries, and (3) hypothalamic and pituitary secretions to distant brain sites through cerebrospinal fluid via ventricular and subarachnoid routes.

Animals↗
PubMed1978

Can the pituitary secrete directly to the brain? (Affirmative anatomical evidence).

Vascular casts of 10 rhesus monkey pituitary glands and three vascular casts of the rhesus monkey cavernous sinus were examined by scanning electron microscopy. A continuous neurohypophyseal capillary bed was found uniting the infundibulum, infundibular stem, and infundibular process. The neurophypophysis was supplied by three groups of arteries: superior hypophyseal, middle hypophyseal, and inferior hypophyseal. Numerous anastomoses were found between individual arteries, and some hypophyseal arteries formed anastomotic links between different portions of the circle of Willis. Veins located at the caudal pole of the infundibular process, capillaries linking the infundibulum to the hypothalamus, and portal vessels extending from the infundibulum to the adenohypophysis provided efferent vascular pathways from the neurohypophysis. The adenohypophysis received no direct arterial supply; its entire afferent vascular supply was provided by portal vessels. Lateral hypophyseal veins were not found; small adenohypophyseal veins joined larger neurohypophyseal veins to form confluent pituitary veins which extended to the cavernous sinus. The capacity of the venous connections draining the adenohypophysis directly to the cavernous sinus appeared small when compared to that of of the long portal vessels supplying the adenohypophysis. However, many of the short portal vessels interposed between the adenohypophysis and the infundibular stem and process were well arranged to function as alternative efferent routes from the adenohypophysis. The limited potential for venous drainage directly to the cavernous sinus suggests that blood leaves the adenohypophysis by other routes; blood carried via long portal vessels from the infundibulum to the adenohypophysis may return to the neurohypophyseal capillary bed via short portal vessels. This anatomical study suggests that hypothalamic and adenohypophyseal secretions are conveyed to the capillary bed of the neurohypohysis. These secretions may leave the neurohypophysis via any of seven potential routes: one efferent route is directed to the adenohypophysis, another route is directed to the systemic circulation, but five of the potential efferent routes are directed toward the brain.

Animals↗
PubMed1977

Patterns of degeneration in the external cuneate nucleus after multiple dorsal rhizotomies.

Unilateral, intradural dorsal rhizotomies (C3-Cs) were performed on adult rats to study the patterns of synaptic organization of ascending dorsal root fibers in the external cuneate nucleus (ECN). Animals were permitted to survive for periods of time ranging from 3 hours to 12 days. Sham-operated animals presented a morphology indistinguishable from that of normal, unoperated animals. In rhizotomized animals, degeneration was observed ipsilaterally at all survival periods. After postoperative survivals of 3 to 14 hours some terminal boutons displayed clumping and diminution in numbers of synaptic vesicles and, in addition, degeneration myelinated axons were observed at this time. There was considerable degeneration in the neuropil between 24 and 48 hours postoperative. Two forms of degeneration occurred in axons and terminal boutons with comparable frequency: electron lucent degeneration and electron opaque degeneration. Reactive phagocytic glial cells contained degenerated masses, lipoid droplets, lysosome-like structures and myelin fragments. After postoperative survivals of four to six days, lucent and opaque degenerating terminals were less numerous. Neurofilamentous degeneration was observed only occasionally. Unaltered synaptic membrane specializations were present and were usually abutted by glia. At 12 days postoperative, synaptic glomeruli and serial synapses were not seen. Invaginating dendritic spines were rarely seen. Bouton populations that remained unualtered were: small (0.3-3.0 micron) boutons that contact dendritic shafts and somata, nodal synaptic boutons and boutons containing granular vesicles (80-100 nm).

Animals↗
PubMed1977

Pituitary secretes to brain. Experiments in sheep.

Because vascular casts of the pituitary demonstrated that there are a few venous connections from the adenohypophysis to the juxtaposed cavernous sinus, it was predicted that some portal vessels must carry blood from the adenohypophysis back to the neurohypophysis. Physiological studies confirmed this prediction and verified earlier observations that blood-flow within the neurohypophysis can be towards the median eminence. In the present study, increased concentrations of prolactin and growth hormone were found in blood sampled from intracranial vessels (internal carotid artery and sagittal sinus). It was concluded that the neurohypophyseal capillary bed not only receives trophic hormones produced in the adenohypophysis but, under certain physiological circumstances, delivers those hormones directly to the brain.

Animals↗
PubMed1977

The neurohypophyseal capillary bed. I. Anatomy and arterial supply.

Vascular casts of the pituitary-median eminence complex of mice,rats, dogs, sheep and monkeys were examined with the scanning electron microscope. Microfil-injected specimens of the rabbit and monkey pituitary-median eminence complex were examined by light microscopy after intracranial internal carotid artery occlusion. In each species a common neuropophyseal capillary network was found uniting infundibulum (median eminence), infundibular stem and infundibular process. This capillary bed is supplied from above by superior hypophyseal arteries and from below by inferior hypophyseal arteries. An artery to the infundibular stem was found in some species. With occlusion of the intracranial internal carotid arteries, flow through superior hypophyseal arteries did not occur. Yet the entire neurohypophyseal capillary bed filled upon injection with Microfil. These observations suggest the concept of a restricted arterial supply to the median eminence with drainage to the underlying adenohypophsis on one hand and to the infundibular process with drainage to the systemic circulation on the other must be modifed and that blood flow within the neurohypophyseal capillary bed (between infundibular process and median eminence) occurs.

Animals↗
PubMed1976

Scanning microscopy of pituitary vascular casts.

Vascular casts of the pituitary-median eminence complex from seventeen adult female rabbits were examined with the scanning electron microscope. The results of this study confirm the presence of a single capillary bed common to the entire neurohypophysis. Arterial supply to the rabbit pituitary is only to the neurohypophysis. A direct supply to adenohypophysis was not found. Within the median eminence there are an external and internal capillary plexus. The internal capillary plexus is directed toward the infundibular recess of the third ventricle. It does not receive a direct arterial supply but derives its blood supply from the external plexus before draining to the adenohypophysis. Vessels of the posterior median eminence are confluent with vessels of the infundibular stem. On the basis of these studies, it is proposed that the entire neurohypophysis, not simply the median eminence, serves as the final common pathway to the glandular pituitary. It is also proposed that in the median eminence, vessels are organized to deliver blood containing hypothalamic releasing and inhibiting hormones as well as posterior lobe neural hormones (antidiuretic hormone and oxytocin) to the ventricular surface for subsequent transport to cerebrospinal fluid and distribution to the brain.

Animals↗
PubMed1975

Scanning electron microscopy of the ventricular system in normal and hydrocephalic rabbits. Preliminary report and atlas.

The author used the scanning electron microscope to study the ependyma in six control rabbits and six rabbits made hydrocephalic by infusion of silicone oil into the cisterna magna. The ependymal lining of the third ventricle, head of the caudate nucleus, superior angle of the caudate, and atrium of the lateral ventricle was examined. In the hydrocephalic animals, clusters of cilia emanating from the ependyma over periventricular white matter become separated; the author believes this is secondary to ingrowth of new ependymal cell processes covered with microvilli. The addition of these cells to the ependymal surface permits ventricular dilatation without ependymal disruption and provides more surface containing microvilli, presumably capable of increased transventricular fluid transfer. No such changes occur over gray matter masses since their surfaces are not deformed by moderate ventricular dilatation. The morphological alterations in the ependyma that occur in moderate hydrocephalus do not appear to be simply manifestations of ependymal destruction but rather suggest a modification in its function from that of a surface capable of propelling cerebrospinal fluid to one capable of increased transfer of transventricular fluid. As hydrocephalus progresses, compensation may fail because of the relative decrease in microvilli so that the cell surface provides a less efficient mechanism for absorption.

Animals↗
PubMedDate not supplied

Glioblastoma multiforme metastatic to the neck.

Glioblastoma multiforme, a rapidly growing intracranial neoplasm, rarely metastasizes unless operated upon, and even after surgical exposure metastasis is uncommon unless the patient is a long-term survivor. The most likely site of metastasis is the cervical lymph nodes. A patient developed a rapidly expanding cervical metastasis a year after surgery and irradiation for the primary. The 6-cm neck mass responded dramatically to radiation therapy and lomustine. The patient is clinically without evidence of progression of disease 20 months after the initial diagnosis, and there is no palpable recurrence in the neck. It is recommended that the patient who has a cervical mass and a history of surgically treated glioblastoma multiforme undergo a careful otolaryngologic examination prior to open biopsy. In general, such a patient can be spared an extensive "unknown primary" evaluation before biopsy.

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