Competitive incentive program. Analysis and proposal.
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Insurance, Health, Reimbursement↗
Biomedical subjects
J Stone
Publications and source records attributed to J Stone.
Is reactive gliosis a property of a distinct subpopulation of astrocytes?
We have shown previously that the A2B5 monoclonal antibody distinguishes two types of glial fibrillary acidic protein-containing astrocytes in semithin frozen sections of adult rat optic nerve: A2B5- (type-1) astrocytes are found mainly at the periphery of the nerve, where they form the glial limiting membrane, while A2B5+ (type-2) astrocytes are found mainly in the interior of the nerve and constitute more than 65% of the astrocytes in the adult optic nerve. In the present study we show that although most astrocytes in semithin frozen sections of adult rat corpus callosum and optic nerve are A2B5+, the great majority of reactive astrocytes in similar sections of corpus callosum examined 20 weeks after a stab lesion, and in optic nerve examined 20 weeks after adult transection, are A2B5-. Although both A2B5+ and A2B5- astrocytes are stimulated to synthesize DNA in the first week after transection, adult optic nerves examined 20 weeks after transection contain only half as many astrocytes as do normal optic nerves: While A2B5+ astrocytes are reduced almost 10-fold, A2B5- astrocytes are increased by about 25%. We consider the simplest interpretation of these findings to be that type-1 astrocytes are largely responsible for forming glial scars in adult white matter following either a stab lesion or Wallerian degeneration and that in transected optic nerves, most type-2 astrocytes eventually die, possibly because they depend on axons for their long-term survival.
Animals↗
Retinal input to the nucleus of the optic tract of the cat assessed by antidromic activation of ganglion cells.
We have studied the physiological properties of ganglion cells in the retina of the cat. The experiments were designed to identify those ganglion cells which project to direction-selective cells in the nucleus of the optic tract (NOT), by demonstrating their antidromic activation at low threshold from an electrode in the NOT. These ganglion cells presumably provide the retinal drive to the optokinetic reflex. Altogether, 11 such ganglion cells were identified in a population of 578 cells studied. All 11 were W-cells, with slow-conducting axons. Five of the 11 had on-centre direction-selective receptive fields; the other 6 had a variety of receptive field patterns. Thus, on centre-selective cells form a much higher proportion of the retinal input to direction-selective cells in the NOT than of the overall ganglion cell population. However, their receptive field properties were too varied fully to account for the selectivity of NOT cells for horizontal stimulus movement. In summary the retinal input to the NOT appears to be formed principally or entirely by W-class ganglion cells, including many which are direction selective. It still seems necessary, however, to postulate, some non-retinal mechanism to account for all the receptive field properties of direction-selective NOT cells.
Afferent Pathways↗
The site of commencement of retinal maturation in the rabbit.
In the developing retina of the rabbit the ganglion cell layer can first be identified between E(embryonic day) 20 and 24, but the regional variations found in the adult retina, particularly the visual streak, are not well developed until shortly before birth. At about E31, the last day of gestation, the laminar structure of the retina begins to mature, cytogenesis begins to cease and the outer plexiform layer starts to form. These processes commence in far temporal retina, at or near the site of the area centralis, and spread preferentially along the visual streak.
Animals↗
Cell division in the developing cat retina occurs in two zones.
Cytogenesis in the kitten retina has been investigated with [3H]thymidine autoradiography and a stain for mitotic figures. The nuclei of cells in S-phase are located adjacent to the inner margin of the cytoblast layer, near the inner plexiform layer. The nuclei then migrate toward the outer limiting membrane (OLM) to divide. Evidence is presented that in a small population of mitotic cells, the nucleus does not migrate to the OLM, but divides in the inner part of the cytoblast layer or, after the outer plexiform layer has formed, in the inner nuclear layer. Cell division in this inner zone begins and ends later than at the OLM. Cells dividing there are fewer in number than those at the OLM, their mitotic spindles are oriented randomly rather than parallel to the retinal surface and their nuclei move little between S- and M-phases of the mitotic cycle. The zones of cytogenesis at the OLM and in the inner cytoblast layer resemble, respectively, the ventricular and subventricular zones of other areas of the developing central nervous system.
Animals↗
Multiphoton ionization under sequential excitation by coherent pulses.
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Journal Article↗
Cytogenesis in the developing retina of the cat.
Cytogenesis in the cat retina was studied using tritiated (3H) thymidine autoradiography and nuclear stains. Three zones of cell division were recognized. In the first zone cell cleavage occurs at the outer limiting membrane. The distribution of these mitotic figures is uniform as early as an embryonic age of 29 days (E29) until E50. At about E50 a "cold spot", made apparent by the absence of mitotic figures, is evident at the site of the developing area centralis. This spreads to encompass the whole retina by postnatal day 10 (P10). A second zone of cell division was recognized by the presence in the developing inner nuclear layer of 3H-thymidine labelled nuclei which do not migrate to the outer limiting membrane (ventricular surface) to divide. Some of these labelled nuclei are located in regions of the retina where cytogenesis at the ventricular surface has ceased. A third zone was observed in the optic nerve fibre/ganglion cell layers from about E54 until beyond the first postnatal month. This activity gives rise to vascular endothelial cells in the nerve fibre/ganglion cell layers. Once established, the developing vascular cells invade the inner plexiform and inner nuclear layers to form the deeper capillary net.
Animals↗
The area centralis of the retina in the cat and other mammals: focal point for function and development of the visual system.
In many mammals, particularly species with frontalised eyes, a small region o retina is strongly specialised for high resolution, binocular vision. The region is typically located near the centre of the retina, a few millimetres temporal to the optic disc, and is termed the "area centralis" or, in some primates in which the specialisation is particularly well developed, the "fovea centralis". Where the specialisation is well developed, the area or fovea centralis dominates the organisation of the adult visual system. Studies of the histogenesis of the retina of the cat indicate that the process of retinal maturation is centred on the area centralis, which thus seems to be an organising focus in the ontogeny as well as the adult function of the visual system.
Aging↗
Priorities for computed tomography and lymphography in the staging and initial management of Hodgkin's disease.
Thirty-five patients with Hodgkin's disease were staged with the aid of chest radiographs, bipedal lymphograms and computed tomography (CT) scans. Computed tomographic findings altered management in only two patients (6%) by indicating enlargement of their radiotherapy fields. After lymphography, five patients (14%) were changed from Stage II (clinical and CT staging) to Stage III, so altering their management. Because either technique may show more extensive disease, CT and lymphography are complementary. Computed tomography should be performed initially. If it reveals no abnormality in the lymphogram area, lymphography, too, should be undertaken. Inverted Y fields are easier to visualise and design from lymphograms than from CT sections.
Combined Modality Therapy↗
Effects of propranolol and timolol on left ventricular volumes during exercise in patients with coronary artery disease.
The hemodynamic effects of beta-receptor blocking agents on the ejection fraction of patients with coronary artery disease during exercise have been studied previously using radionuclide techniques. Left ventricular volume measurements and the peak systolic pressure/end-systolic volume (PSP/ESV) index have been shown to be variables of left ventricular function that are less influenced by preload and afterload than is ejection fraction. Left ventricular volumes and PSP/ESV were therefore measured in 18 patients with proven coronary artery disease in the control state and after 2 weeks of daily maintenance therapy with either 240 mg propranolol or 60 mg timolol. Values at rest and during symptom-limited upright exercise were compared using the first pass technique and a multicrystal scintillation camera. Left ventricular volumes were measured by the area-length method. Because there was no difference between the propranolol and timolol groups, the results for both groups were combined. The ejection fraction at rest after beta-receptor blocker treatment was not significantly different from pretreatment measurements because of an increase in both end-diastolic and end-systolic volumes (p less than 0.01). However, the value for peak systolic pressure/end-systolic volume (PSP/ESV) index at rest was lower after treatment. The exercise ejection fraction was greater after treatment (p less than 0.01), owing to an increase in end-diastolic volume and unchanged end-systolic volume. In addition, there was a significant improvement in the directional change in the PSP/ESV ratio between rest and exercise from pretreatment to treatment (-1.1 +/- 2.5 to +0.2 +/- 1.2, p less than 0.02).(ABSTRACT TRUNCATED AT 250 WORDS)
Adult↗
Spiral organisms in endoscopic biopsies of the human stomach.
A retrospective light microscopic study of 310 consecutive endoscopic gastric biopsy specimens was performed. Spiral bacteria were found in 42% of cases and, apart from occasional organisms in parietal cell canaliculi, were confined to the surface of the glands and epithelium. Electron microscopic study of selected cases showed the bacteria to be approximately 6 micron maximum length and 0.7 micron diameter with a spiral periodicity of 1.2 micron. A significant association between the occurrence of spiral bacteria and gastritis was noted but not with carcinoma, peptic ulceration, or high pH of the gastric aspirate.
Adult↗
Time course of morphological differentiation of cat retinal ganglion cells: influences on soma size.
We have examined the growth of ganglion cell somas during development of the cat's retina. Until approximately E (embryonic day) 50, ganglion cell somas show no sign of the several variations in their size apparent in the adult. At about E50, the somas begin to accumulate granular cytoplasm. The accumulation proceeds first among area centralis cells which, for a few days, are the largest ganglion cells in the retina (whereas in the adult they are the smallest). By E57 three of the adult soma size trends have become apparent: the differentiation of soma size related to functional class, the nasal-temporal difference in soma size, and the small mean size of somas in the visual streak. The early appearance of these trends in soma size suggests that individual cells may be intrinsically programmed to develop as cells of a particular class, such as alpha-, beta-, or gamma-cells, even before their morphological differentiation begins. A fourth trend in soma size, the centro-peripheral difference, appears only after an initial period of ganglion cell growth; the small size of ganglion cells at the area centralis seems to be determined, at least partly, by a local "environmental" factor, the crowding of ganglion cells.
Animals↗
A lifetime of careful listening. A centennial retrospective on the work of William Carlos Williams (1883-1963).
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History, 19th Century↗
Oral route as method for immunizing against mucosal pathogens.
In the past three decades significant strides have been made in attempts at nonparenteral immunization. Appreciation of the importance of secretory immunity led to attempts to stimulate antibody production locally. The vaccines developed against respiratory pathogens as a result of this new knowledge have many practical limitations, such as the need for highly trained personnel, expensive equipment, very cooperative recipients for intranasal or aerosol administration, and a vaccine that is both adequately attenuated, immunogenic, and stable during storage. With recognition of the presence of a common mucosal defense system, new approaches to vaccine development have become possible. Oral immunization, by stimulating GALT, presents a promising approach for protecting many secretory surfaces against a variety of infectious agents. Recently, emphasis has been placed on developing an oral vaccine against S. mutans. McGhee et al. have demonstrated antibody to S. mutans in saliva and tears following oral ingestion of that antigen, without a rise in serum antibody, in both humans and rats. The rats were afforded protection from caries after rechallenge with both the original and cross-reacting serotypes of S. mutans. Similar results have recently been seen with viral antigens. Mice have been shown to have significant protection against influenza infection following oral immunization. And in a pilot study with human volunteers, the secretory antibody response in nasal washes was similar following either oral or parenteral vaccination. Oral immunization may prove to be far superior to parenteral vaccination against a variety of pathogens, because of fewer side effects and greater ease in vaccine preparation and administration.
Administration, Oral↗
Prediction and prevention of child abuse--an empty hope?
The effectiveness of the use of objective data available at birth to predict and prevent child abuse was assessed in a group of 2802 non-Asian infants born in Bradford in 1979. Two-thirds of the actual abuse occurred in the 18% predicted to be at risk, but supportive measures did not prevent abuse. Those who needed and received the most attention from social workers and health visitors fared worst. Other indices suggested poor parenting in the at-risk families. Child abuse seems to be predictable but prevention is more difficult.
Child Abuse↗
A pilot study of cyclical chemotherapy with high-dose methotrexate and CHOP (MTX-CHOP) in poor-prognosis non-Hodgkin's lymphoma (NHL).
In a pilot study of cyclical chemotherapy in patients with poor-prognosis non-Hodgkin's lymphoma (NHL), high-dose methotrexate (MTX) 1 g/m2 with folinic acid rescue was given as initial treatment and then between cycles of a single-arm CHOP combination administered every 4 weeks. Of 21 patients with previously untreated or minimally treated grade 2 (high-grade) histology stage II/III/IV NHL, 13 (62%) achieved complete remission (CR); the CR rate for stage III/IV patients was 56%. Of all 25 patients with grade 2 stage II/III/IV NHL, including previously treated patients, 16 (64%) achieved CR. The median follow-up of patients who completed treatment is currently 22 months and only 1 relapse has been recorded in the CR group. Only five of 24 grade 2 patients given the initial 'test' MTX failed to show any response, and eight patients achieved partial remission (PR) as a result of this single treatment. The response to MTX-CHOP in nine patients with grade 1 (low-grade) histology NHL was poor; only two achieved CR. These findings lend support to other data which indicate a useful role for MTX in the induction chemotherapy of advanced high-grade NHL, though the optimum dosage and drug sequence have yet to be determined.
Adolescent↗
Topographical organisation of the retina in a monotreme: Australian spiny anteater Tachyglossus aculeatus.
The topography of the ganglion cell layer of the retina has been examined in the spiny anteater or echidna, Tachyglossus aculeatus. The retina measures about 70 mm2 in area and contains approximately 60,000 ganglion cells. The somas of the cells do not form distinct size groupings, as they do in other mammals, where the size groupings are related to functional differences. There is only a weak gradient in the density of ganglion cells between central and peripheral regions of the retina. In particular, there is no sign of a localised concentration of cells, such as at the fovea or area centralis of other species, and only very weak evidence of a visual streak. There is thus very little regional variation in the structure of the echidna retina, less than in any mammal previously studied. Implications for the understanding of comparative retinal topography are discussed.
Anatomy, Comparative↗