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Query: UMLS:C0851184 (thinning)
 11,252 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The water permeability and physical characteristics of the basement membrane (lens capsule) of the crystalline lens of the adult rat have been investigated. The hydraulic conductivity of the basement membrane at low pressure is 50 +/- 9.5 X 10(-12) m s-1 Pa-1 and at high pressure 17 +/- 7.5 X 10(-12) m s-1 Pa-1. This decrease in permeability occurs despite a 75% increase in area of the membrane and a 65% reduction in its thickness. Conventional theories of a membrane possessing pores or of a fibre matrix of filaments of a constant diameter fail to explain the decreasing permeability of the membrane with increasing hydrostatic pressure. The present data suggest that the structure of the membrane is changed by pressure and the coiled filaments of which it is composed are extended as stress is applied to the membrane. If allowance is made both for thinning and for compaction of the membrane and the extension of its area the permeability of the membrane can be predicted satisfactorily at varying pressures. Thus the hydraulic conductivity of basement membrane at a given pressure can be adequately described by the product of a constant and a dimensionless 'deformation coefficient'. This deformation coefficient is equal to the square of the product of the thickness ratio and elongation ratio of the membrane at the given filtration pressure.
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PMID:The water permeability of basement membrane under increasing pressure: evidence for a new theory of permeability. 612 39

Peculiar ultrastructural features of the kidney internal medullary substance have been studied in some typical representatives of the Middle Asia desert and semi-desert fauna (Spermophilopsis leptodactylus and Meriones erythrourus). Papillary organization in the species studied has a specific high differentiation of the fine nephron loop (Henle's) parts; flattening (especially in Meriones erythrourus) of epithelium in the collecting tubes while its cytoplasm is rather poor in organelle; high contents of the interstitial cells and their tight junction with canaliculi, capillaries, floccular material of the interstitial tissue; thinning of the interstitial sheets, especially between the collecting tubes and vessels, presence of collagene fibres in the interstitium, that is especially, specific for all the species of the Spermophilopsis leptodactylus studied. It is possible to suppose that development of similar features in the structure of the kidney internal medullary substance, where the main water resorption takes place in the species investigated, is connected with their life in similar environmental conditions with low hydratation level and is aimed to increase efficiency of the concentrating apparatus work.
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PMID:[Ultrastructure of the internal medullary substance of the kidney in rodents of an arid zone]. 621 17

The present study was undertaken to devise an electrophysiological method for detecting diabetic retinopathy in rats. The electroretinogram (ERG) and visual evoked potential (VEP) were recorded from unanesthetized and unrestrained rats rendered diabetic with a single i.v. injection of streptozotocin (STZ) at 35 or 40 mg/kg. The STZ-treated rats showed signs of diabetes: hyperglycemia, glucosuria, hypoinsulinemia, polyuria and increased water intake. Amplitudes of the ERG a- and b-waves and oscillatory potentials (OPs) on the b-wave were decreased and latencies of these waves were prolonged gradually after STZ was administered. Especially, latencies of the OPs became significantly different from the pre-treatment values. Latency of the VEP N1 wave showed a slight prolongation, which might be secondary to the depression of retinal function. Histological examination showed swelling and proliferation of the lens epithelium and swelling and vacuolization of the lens fiber were observed in the eyeball 9 weeks after STZ-treatment. Moreover, thinning of each retinal layer was observed in a few rats. Daily s.c. injection of insulin at 10 units/rat/day started from the 4th week. The ERG values returned to the control values after 2-3 weeks of insulin therapy. These results indicate that the ERG and VEP recording procedure used in the present study is useful for early detection of the diabetic retinopathy in rats and that the OP of the ERG appears to be vulnerable to diabetes in the rat as it is in the human.
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PMID:[An electrophysiological method for detecting diabetic retinopathy in rats]. 639 51

Intrasellar arachnoid cyst is very rare. We report a case of intrasellar arachnoid cyst and review 15 cases which were previously reported. A 58-year-old male was admitted for evaluation of visual disturbance on April 24, 1981. Neurological examination revealed bilateral decreased visual acuity, optic atrophy and bitemporal hemianopsia. X-ray film of the skull showed a balloon-shaped sella turcica with thinning of the cortex of the sella floor. Axial and coronal CT scan showed a cystic lesion with water-density occupying the intrasellar and suprasellar region. After administration of contrast medium, no enhancement was noted. Bilateral carotid angiographies demonstrated that the carotid siphons were stretched and displaced laterally, the A1 portions of the anterior cerebral arteries were raised. Pneumoencephalography revealed the upward displacement of the floor of the third ventricle indicating the presence of the suprasellar mass. On May 7, 1981, the sella turcica was reached via the transsphenoidal rhinoseptal approach. A cyst with a white colored thin wall which contained water-like fluid was encountered, and a biopsy was taken of the cyst wall. The roof of the cyst pulsated downward and ruptured spontaneously. Cerebrospinal fluid flowed out. The cavity was filled with muscle and adipose tissue. Postoperative course was uneventful during the first few days and the visual disturbance improved. On the fourth postoperative day cerebrospinal fluid rhinorrhea occurred, but it subsided in nine days. The patient was discharged on June 26 with satisfactory improvement of visual field and visual acuity. Histological examination of the biopsied specimen revealed arachnoid membrane consisting of collagen fibers and scattered cells. Symptoms, signs and radiological findings of the intrasellar archnoid cyst are similar to that of various sellar lesions including pituitary adenoma, craniopharyngioma and the other space occupying mass in the sellar region. Intrasellar arachnoid cysts can be treated by a transsphenoidal approach as well as a subfrontal approach with craniotomy.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:[A case of intrasellar arachnoid cyst]. 646 41

We recently described a method by which the resistance to water flow of the luminal membrane of ADH-stimulated toad bladder can be quantitatively distinguished from that of barriers lying in series with it. This method requires estimated of both total bladder water permeability (assessed by transbladder osmotic water flow at constant gradient) and luminal membrane water permeability (assessed by quantitation of the frequency of ADH-induced luminal membrane particle aggregates). In the present study we examined the effect of bladder distension on transepithelial osmotic water flow before and during maximal ADH stimulation. Base-line water flow was unaffected by bladder distension, but hormonally stimulated flow increased systematically as bladders became more distended. Distension had no effect on the frequency of ADH-induced intramembranous particle aggregates. By comparing the relationships between aggregate frequency and hormonally induced water permeability in distended and undistended bladders, we found that distension appeared to enhance ADH-stimulated water flow by decreasing the resistance of the series permeability barrier while the apparent water permeability associated with each single luminal membrane aggregate was unaffected. In that bladder distension caused tissue thinning, the series resistance limiting ADH-stimulated water flow appears to be accounted for by deformable barriers within the bladder tissue itself, probably unstirred layers of water.
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PMID:Effect of distension on ADH-induced osmotic water flow in toad urinary bladder. 679 49

Ultrastructure and distribution of glycosaminoglycanes (Hale's method) have been studied in the renal internal medullary substance zone in the white rat and in four species of wild rodents of various ecology: Arvicola terrestris, Microtus afganus, Spermophylosis leptodactylus, Rhombomus opimus. A tight contact of the structural components in the renal papilla, clearly manifested differences in the epitheliocyte structure of the nephron loop parts, thinning of the collecting tube epithelium and that of the interstitial layers in the more arid species are evidently connected with a high level of water reabsorbtion. Increasing area of the apical surface, development of the lysosomal apparatus, abundance of the apical vesicles when general contents of organells in the collecting tube cells is high (in terrestrial rats), is accompanied with hypertrophy of glycocalix and with presence of glycosaminoglycanes within the vesicles and phagosomes. All the species of rodents studied are characterized with the presence of the interstitial "gel filter", with a maximal contents of glycosaminoglycanes in the white rat renal papilla interstitium near the collecting tubes.
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PMID:[Glycosaminoglycan distribution in the internal zone of the kidney medulla in various rodent species]. 687 May 64

Rats were given 2,5-hexanediol in their water for more than 5 weeks. The changes in the optic pathways were studied both qualitatively and quantitatively. Increase in 10-nm filaments within axons was noticeable from 10 days onwards in the superior colliculus and in the brachium of the superior colliculus. From then onwards there was a steady increase in the number of affected axons, and their gross enlargement occurred. The proportion of affected fibres in the brachia was in fact few, but all fibres were of retinotectal origin. Less than half of those in the superior colliculus that were swollen were of retinal origin. Measurement of axon diameter versus myelin sheath thickness showed gross relative thinning of the latter. Axon degeneration did not occur but there was increasing ultrastructural evidence of impairment of transport of organelles both centrifugally and centripetally as the filamentous masses accumulated.
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PMID:The early evolution of neurofilamentous accumulations due to 2,5-hexanediol in the optic pathways of the rat. 689 Jan 50

Retinoids profoundly influence epidermal differentiation, but neither the nature of their antikeratinizing activity nor their mechanism of action is known. In this study, we have correlated morphologic and histochemical findings with an assessment of stratum cohesion and water barrier integrity in adult hairless mice treated with either 13-cis-retinoic acid or the aromatic retinoid, RO 10-9359. Both the synthetic retinoids produced dose-dependent alterations in transepidermal water loss, which were about 5 to 10 times greater in RO 10-9359-treated animals. In contrast to essential fatty acid deficiency, where diminished intercellular lamellar lipids may account for defective barrier function, these lipid-rich structures were intact in retinoid-treated tissues. Instead, retinoids produced both epidermal and stratum corneum loosening, manifested both by the ready production of intraepidermal friction blisters and by ease of removal of cornified cells by tape stripping. Dyshesion correlated with loss of desmosomes and intra- and intercellular accumulation of amorphous material in the upper epidermis. Since these deposits lacked the tinctorial properties of mucin, dyshesion could not be ascribed to the development of mucous metaplasia. Finally, dyshesion could not be attributed to either gain or loss of membrane sugars demonstrated with rhodamine-conjugated lectins, since these changed only late in the course of retinoid treatment. We conclude that the antikeratinizing basis for retinoid activity comprises: (1) dose-dependent alterations in transepidermal water loss and (2) epidermal and stratum corneum loosening, which may, in turn, lead to loss of epidermal cohesion and abnormal barrier function. Neither mucous metaplasia nor stratum corneum thinning appear to play a major role.
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PMID:Retinoid effects on epidermal structure, differentiation, and permeability. 693 40

Pathological and hemodynamic concepts regarding the origin, growth, and rupture of intracranial saccular aneurysms are reviewed. Aneurysms form as a result of an interplay between hemodynamic factors, such as axial stream impingement and the water hammer effect, and structural weaknesses at apices of arterial bifurcations, such as congenital and acquired medial defects, funnel-shaped dilatations, and areas of thinning. Hypertension and time aid the formation of aneurysms. Unknown factors in women and in some families also play a role. Enlargement of aneurysms results from an interplay between mechanical factors, such as self-excitation and resonance, that produce structural fatigue and pathological processes of repair of the aneurysmal wall. Rupture of aneurysms is caused by the same hemodynamic factors that effect growth and is also influenced by extramural pressure. Pathologically, a major rupture may be preceded by fibrinous and leukocytic infiltration of the wall, bleb formation, and a minor hemorrhage. Such minor leaks can be followed by healing and growth. Aneurysms that escape major hemorrhage or heal successfully after a hemorrhage can grow to giant proportions, but remain susceptible to rupture despite their size, unless they become completely thrombosed. Intramural thrombosis may be stimulated by minor leaks and is dependent upon the physical characteristics of aneurysms. Experimental, angiographic, and clinical studies that pertain to the origin, growth, and rupture of aneurysms are also reviewed.
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PMID:Origin, growth, and rupture of saccular aneurysms: a review. 701 Feb 5

The feasibility of using hydrogel lenticular implants of high water content to alter the anterior corneal curvature for purposes of refractive keratoplasty has been investigated in rabbits. Lenticules (6 mm in diameter) of Permalens (Perfilcon-A) were trephined from contact lens and implanted within an intralamellar pocket in the cornea. The in vitro glucose flux across the hydrogel (0.23 mm thick) was measured at 131 +/- 7 micrograms/cm(2)/hr. For clinical comparison, non-water-permeable disks of Teflon were also implanted. The Teflon implant caused an aseptic ulcer to develop anterior and central to the implant by 9 +/- 4 days. The hydrogel lenticular implant did not cause central ulceration during the 7 month postoperative follow-up. There was a thinning and eventual erosion of the stroma anterior to the edge of the hydrogel implant, 16 +/- 7 weeks. The glycogen contents of the epithelium anterior to (1) the sham operation, i.e., lamellar pocket dissection, (2) the implanted hydrogel lenticule with or without the presence of an erosion, and (3) the control corneas were statistically from the same population. Yet there was a slight dehydration of the stroma anterior to the hydrogel implant when compared to control tissue. A thin-edged implant lenticule design should overcome the stromal thinning caused by the thick-edge implants. During the short-term follow-up, the hydrogel lenticular implant proved to be successful as a refractive keratoplasty implant material.
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PMID:Refractive keratoplasty with intrastromal hydrogel lenticular implants. 725 Dec 94


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