Comparative study of carbohydrate-protein complexes. II. Determination of hydroxylysine and its glycosides in human skin and scar collagens by an improved method.
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A modification of the existing methods for measuring hydroxylysine, galactosylhydroxylysine, and glucosylgalactosylhydroxylysine is described. The method is based on analysis with an automated amino acid analyzer using a conventional separation system for basic amino acids. The prior removal of acidic and neutral amino acids was necessary. This was achieved by passing an alkaline hydrolysate of collagen through a column of Amberlite CG-120, Type II (H+) and washing the column with 8% aqueous pyridine. A basic fraction containing the hydroxylysine compounds was then recovered from the column by elution with 3 M NH4OH. Model experiments showed that hydroxylysine and its glycosides could be analyzed with an hour and that recoveries exceeded 90%. This method was applied to human tissues to investigate whether the dermal scar is different in collagen composition from normal skin. With the limited number of samples analyzed, the data suggested that long-standing scar tissues reverted to a composition similar to that of normal skin. The composition of hydroxylysine-linked carbohydrate units is also discussed on the basis of the age-related change. (+info)
Platelet-aggregating activity of type I and type III collagens from human aorta and chicken skin.
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Human or chicken type III collagen dissolved in 0.1 M-acetic acid was much more potent than type I collagen at inducing platelet aggregation. After incubation in 0.38M-Na2HPO4 to promote fibrillogenesis, the platelet-aggregating activity of both collagen types increased, and type I was then virtually equiactive with type III. Preincubation in cell-free plasma increased the activity of chicken but not that of human collagen. The platelet-aggregating activity of type III collagen did not appear to depend on the integrity of the intrachain disulphide bonds. (+info)
Receptive fields, geometry and conduction block of sensory neurones in the central nervous system of the leech.
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1. In segmental ganglia of the leech, the cutaneous mechanosensory neurones responding to to touch innervated the skin of their own segment and of part of the anterior and posterior adjacent segments. Each touch receptive field could be divided into three non-overlapping areas: a central part innervated by the branches of the cell which ran in the nerve roots of the ganglion containing the cell body, and anterior and posterior parts innervated by its branches which ran in the nerve roots of the anterior and posterior adjacent ganglia. 2. Impulses originating from the anterior and posterior parts of the receptive fields were susceptible to conduction block within the central nervous system when the touch cells fired repetitively at frequencies that could readily be elicited with weak mechanical stimulation. In contrast, impulses originating from the central part of the receptive fields were less susceptible to block. 3. The morphology of touch cells revealed by intracellular injection of horseradish peroxidase suggested that conduction block occurred at specific bifurcation points where small cell processes joined the main process. Different physiological experiments supported this conclusion. 4. In some touch cells, bifurcation points with particularly low safety margins of conduction operated as low-pass filters, limiting the frequency of impulses capable of invading certain branches. 5. The results suggest that mechanical stimuli which would likely be encountered by the animal can lead to conduction block within its central nervous system and as a result modify its integrative activities. (+info)
The thermal sensitivity of the polymodal nociceptors in the monkey.
(68/19537)
1. The static and dynamic sensitivities to thermal and mechanical stimuli of polymodal nociceptors in hairy skin of the anaesthetized monkey have been investigated by recording activity in their primary nerve fibres. 2. Polymodal nociceptors responded to skin pricking, pinching and heating to temperatures higher than 40 degrees C. They did not respond to touch, stretch or cold. The conduction velocity of their axons was from 0.6 to 1.1 m/sec. 3. Three types of cutaneous receptive fields have been observed: single spot-like areas of 1-2 mm2; multiple spot-like areas of 1-2 mm2; and larger areas up to 25 mm2 with heterogeneous sensitivity. 4. Polymodal nociceptors were subjected to heat stimuli that commenced from a 33 or 37 degrees C adapting temperature. A series consisted of heating their receptive fields to 43, 45, 47 and 50 degrees C from one or the other adapting temperatures at a constant rate of 0.2 degrees C/sec. Each heat stimulus intensity was maintained for 4 min after which the skin was returned to the adapting temperature. Immediately after the first series the identical series was repeated in order to determine the effect of prior heating upon the dynamic responses to re-heating. The dynamic responses were characterized by three phases: an initiation of a discharge at a threshold level of skin temperature; a dynamic discharge during the suprathreshold change, that reached a peak frequency when the temperature reached its maximum; and an adaptation phase while the temperature remained at the high intensity. Adaptation was rapid initially, and then slowed during the final minutes at the high intensity. 5. Adapting the receptive field to either 33 degrees C or to 37 degrees C before the heat stimuli did not affect the sensitivity and the discharge pattern of the polymodal nocicpetors. 6. During the first series of stimulations, the threshold at which the individual polymodal nociceptors began to discharge to heat stimuli varied from 40 to 46.5 degrees C. The mean threshold of the population was 42.5 degrees C. 7. No change in the threshold was observed when responses to 0.2 and 1.5 degrees C/sec rates of heating were compared... (+info)
Optimum porphyrin accumulation in epithelial skin tumours and psoriatic lesions after topical application of delta-aminolaevulinic acid.
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Photodynamic therapy with topically applied delta-aminolaevulinic acid is used to treat skin tumours by employing endogenously formed porphyrins as photosensitizers. This study examines the time course of porphyrin metabolite formation after topical application of delta-aminolaevulinic acid. Porphyrin biosynthesis in human skin tumours (basal cell carcinoma, squamous cell carcinoma), in psoriatic lesions, and in normal skin was investigated. Skin areas were treated with delta-aminolaevulinic acid, and levels of total porphyrins, porphyrin metabolites and proteins were measured in samples excised after 1, 2, 4, 6, 9, 12 and 24 h. There was an increase in porphyrin biosynthesis in all tissues with maximum porphyrin levels in tumours between 2 and 6 h and in psoriatic lesions 6 h after treatment. The pattern of porphyrins showed no significant difference between normal and neoplastic skin, protoporphyrin being the predominant metabolite. The results suggest that optimum irradiation time for superficial epithelial skin tumours may be as soon as 2 h after application of delta-aminolaevulinic acid, whereas for treatment of psoriatic lesions an application time of 6 h is more suitable. (+info)
Assessment of the effects of endothelin-1 and magnesium sulphate on regional blood flows in conscious rats, by the coloured microsphere reference technique.
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There is evidence to suggest that magnesium (Mg2+) is beneficial in the treatment of a number of conditions, including pre-eclampsia and acute myocardial infarction. The mode of action of Mg2+ in these conditions is not clear, although the vasodilator properties of Mg2+ are well documented both in vitro and in vivo. Previously, we demonstrated that i.v. infusion of magnesium sulphate (MgSO4) alone, or in the presence of vasoconstrictors, caused increases in flow and conductance in the common carotid, internal carotid and hindquarters vascular beds, in conscious rats. Therefore, the objective of the present study was to investigate the regional and subregional changes in haemodynamics in response to the vasoconstrictor peptide endothelin-1 (ET-1) and MgSO4 in more detail, using the coloured microsphere reference technique. Infusion of ET-1 and MgSO4 had similar effects on heart rate and mean arterial pressure as in our previous study. Infusion of ET-1 caused a rise in mean arterial pressure and a fall in heart rate, and infusion of MgSO4 returned mean arterial pressure to control levels with no effect on heart rate. The responses to MgSO4 in the presence of ET-1 showed considerable regional heterogeneity with blood flow increasing (e.g. skeletal muscle), decreasing (e.g. stomach) or not changing (e.g. kidney). Of particular interest was the finding that MgSO4 caused increases in flow in the cerebral and coronary vascular beds. This, and our previous studies, have shown that MgSO4 can reverse vasoconstriction in a number of vascular beds, and indicate that this compound may have therapeutic benefit in conditions associated with vasospasm. (+info)
Detection of autonomic sympathetic dysfunction in diabetic patients. A study using laser Doppler imaging.
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OBJECTIVE: To study signs of the disturbed reflex autonomic sympathetic nerve function in type 1 and type 2 diabetic patients. RESEARCH DESIGN AND METHODS: Measurements were made on 15 type 1 (duration 13-32 years) and on 50 recently diagnosed type 2 diabetic patients (duration 3-4 years). The vasoconstrictor responses in the distal phalanx of the middle finger (locally heated to 40 degrees C) to the cooling of the contralateral arm were measured using Laser Doppler Imaging (LDI). A vasoconstriction index (VAC) was calculated taking age into account and was compared with reference values obtained in 80 control subjects. The diabetic patients were also studied with deep-breathing tests (i.e., the heart-rate variation expressed as the expiration-to-inspiration [E/I] ratio, a test of parasympathetic nerve function). RESULTS: The vasoconstrictor responses to indirect cooling (VAC) were significantly reduced in the fingers of the diabetic patients, both type 2 (0.77 +/- 0.02 V; P < 0.01) and type 1 (0.83 +/- 0.04 V; P < 0.001), compared with the healthy control subjects (0.65 +/- 0.01); the age-corrected VAC (VACz) was slightly more impaired in type 1 than in type 2 diabetic patients. The frequency of an abnormal VACz corresponded well to the frequency of an abnormal E/I ratio in type 1 diabetic patients (approximately 50%), whereas the frequency of an abnormal VACz was significantly higher than an abnormal E/I ratio among type 2 diabetic patients (11/50 vs. 4/50; P < 0.05). CONCLUSIONS: Both type 1 and type 2 diabetic patients have impaired cutaneous blood flow regulation. The VAC index seems to be a promising tool for detection of subclinical changes in autonomic sympathetic function. (+info)
Multiple mechanisms contribute to the avoidance of avian epidermis by sensory axons.
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In birds, sensory innervation of skin is restricted to dermis, with few axons penetrating into the epidermis. This pattern of innervation is maintained in vitro, where sensory neurites avoid explants of epidermis but grow readily on dermis. We have used this coculture paradigm to investigate the mechanisms that impede innervation of avian epidermis. The lack of epidermal innervation in birds has been attributed to diffusible chondroitin sulfate proteoglycans (CSPGs) secreted by the epidermis, although direct experimental evidence is weak. We found that elimination of CSPG function with either chondroitinase or neutralizing antibodies did not promote growth of DRG neurites onto epidermis in vitro, indicating that CSPGs alone are not responsible for preventing epidermal innervation. Moreover, the failure of sensory neurites to invade epidermis is not due exclusively to soluble chemorepulsive factors, since sensory neurites also avoid dead epidermis. This inhibition can be overridden, however, by coating epidermis with the growth-promoting molecule laminin, but only if the tissue is killed first. Epidermal innervation of laminin-coated epidermis is even more robust when CSPGs are also eliminated. Thus, the absence of growth-promoting or permissive molecules, such as laminin, may contribute to the failure of sensory neurites to invade avian epidermis. Together these results show that the inhibitory character of avian epidermis is complex. Cell- or matrix-associated CSPGs clearly contribute to the inhibition, but are not solely responsible. (+info)