摘要:

The phenomenon of resetting and the possible mechanisms responsible for it were investigated in aortic baroreceptors having unmyelinated axons. Recordings were obtained from 31 aortic baroreceptor C‐fibers in 20 normotensive Wistar Kyoto rats (WKY) and 37 baroreceptor C‐fibers in 11 spontaneously hypertensive rats (SHR). The recordings were obtained from the left aortic nerve of an in vitro aortic nerve‐aortic arch preparation. The thresholds for activation of baroreceptor C‐fibers were not different between SHR's and WKY's at 16 weeks of age (139±7 and 133±5 mmHg, respectively). However, the thresholds for activation in SHR at 36 weeks of age were considerably higher (163±4 mmHg) indicating resetting of the receptors in the older rats. The pressure‐discharge curves were not different between SHR's and WKY's at 16 weeks of age and WKY's at 35 weeks of age, but were shifted to the right for SHR's at 36 weeks of age. The receptors showed greater responses to pulsatile pressures than to steady state pressures at the same mean level of pressure. We found that aortic C‐fibers were not reset during the early established phase of hypertension in SHR's because of enhanced receptor strain sensitivity. This is likely to be of importance for tonic vasomotor control at this time. In later stages of hypertension and despite enhanced strain sensitivity the endings were reset to higher pressures probably due to an increased collagen content in t

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07182.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Previous measurements by microspheres have shown a higher blood flow in outer cortex and a lower blood flow in inner cortex than found by diffusible tracers. During vasodilation microspheres have indicated a disproportionate increase in deep cortical blood flow, whereas diffusible tracer distributions remained unchanged. These discrepancies could possibly be explained by a variable net inward transport of diffusible tracers in postglomerular vessels, the transport existing in control, but disappearing during vasodilation. To test this hypothesis H2gas was produced electrolytically for 1 s at a platinum electrode in midcortex and the resulting gas concentration curve measured polarographically at two electrodes placed above and below the source. Analysis of a mathematical model showed that the ratio of the curve maxima at the two electrodes (Cmo/Cmi) would best reveal a radial net transport. Average Cmo/Cmiat 25 positions in 7 clamped dog kidneys was close to unity, but rose to 1.24 at control flow. During acetylcholine infusion Cmo/Cmirose to 1.68. Local washout rates at the two electrodes increased equally. Calculations indicated a small outwardly directed net transport in control (3×10‐4cm/s), becoming slightly reinforced during vasodilation (5×10‐4cm/s). Thus the control transport direction is opposite to the hypothesis, and the change during vasodilation was estimated to be too small to explain the disparity between diffusible tracer uptake and microsphere distribution in control. H2concentration maximum was obtained earlier under control flow than in the clamped kidney, indicating an increase in apparent D of the gas in tissue from 3×10‐5cm2/s to 5×10‐5cm2/s, probably due to mixing of H2gas in the capilla

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07183.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Selected estimates of the lipid peroxidative capacity were assayed in the red and white skeletal muscles of control and endurance‐trained mice. Endurance training decreased the lipid peroxidation rate in vitro in both muscle types. The concentration of lipids susceptible to Fe2+‐induced lipid peroxidation was greater in the red than in the white skeletal muscle and increased after endurance training in the red muscle. Endurance training, however, decreased highly significantly the sensitivity of red muscle to in vitro stimulated lipid peroxidation. The activity of catalase and the concentration of vitamin E were considerably higher in the red muscle, whereas the activity of glutathione peroxidase was slightly higher in the white muscle. Endurance training caused no changes in these antioxidants. Endurance training increased the concentrations of reduced and total non‐protein glutathione in the red skeletal muscle but not in the white muscle. The total sulfhydryl group contents were unaffected. Our results suggest that endurance training may increase the resistance of skeletal muscle to injuries caused by lipid peroxid

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07184.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

In order to determine the total number of fibres and the extent to which the relative occurrence of different fibre types varies within m. vastus lateralis, 15 μm thick cross‐sections of whole muscles were prepared. The total number of type 1 and type 2 fibres was determined in every 48th square millimetre of the section, and the results thus obtained were analysed using a computer program allowing an assessment of bivariate data in the form of contour plots. The total number of fibres varied both in proximal to distal direction in the same muscle and between individuals. No obvious correlation existed between the mean fibre area and the muscle cross‐sectional area. The proportion of type 1 fibres in the whole muscle varied between individuals (from 44% to 57%) with a mean value for all five of 52%. The distribution of different fibre types varied within the muscle, mainly as a function of depth, with a predominance to type 2 fibres at the surface and type 1 fibres in deeper regions of the muscle. Thus, the fibre type distribution in m. vastus lateralis is not random. This must be taken into consideration when data on fibre type composition are compared with functional varia

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07185.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

Electrostatic capillary barrier characteristics was studied in the isolated maximally vasodilated rat hindquarter by use of a modified “tissue uptake” technique (Rippe et al. 1979). The hindquarters were artificially perfused with oxygenated horse serum at isogravimetry. As tracers two isoenzymes of lactate dehydrogenase (LDH) were used, having indentical size (41 Å, Mw˜ 140000) but with differing molecular charge and labelled with two separable isotopes. LDH‐H4(125I) is negatively charged and LDH‐M4(131I) slightly positive, at physiological pH. The negatively charged protein LDH‐H4was more retarded in its transcapillary passage than LDH‐M4. Net clearance of H4was 0.0242±0.0045 ml/min × 100 g and that of M4was 0.0748±0.0092 ml/min × 100 g (n= 11, p<0.001). This difference is suggested to be due to an interaction of the polyanionic tracer with a barrier of negative molecular charge, most effective at the small pore equivalent. Clearance data for H4and for albumin (Rippe et al. 1979) are compatible with an equivalent large pore radius of 520 Å. Neither vesicular transport (Palade 1953) nor the impact of fibre pore matrix (Michel 1980) is considered to be involved in the transcapillary passage of proteins. Negatively charged proteins probably pass through the large pore equivalent exclusively, while neutral macromolecules also utilize part of the small pore equivalent, for their tran

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07186.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A pulsed doppler ultrasound technique has been used to measure changes in blood velocities in the superior sagittal sinus, the jugular veins and intracranial and extracranial arteries in 13 neonates, and in the jugular veins and an extracranial artery in 13 adults, during unilateral and bilateral jugular venous compressions. The results have enabled us to determine how the subject under examination functionally uses his cranial venous drainage system in the resting state, and whether or not he can shunt obstructed venous flow through other cranial venous channels. We have found great variability between the subjects. In the resting situation the range of possibilities from total dependence on one jugular vein alone to usage of both jugular veins and the vertebral veins exists. Shunting of blood on jugular compression from either or both jugular veins to the vertebral veins may occur, and contralateral shunting between the jugular veins may be possible in both directions, in one direction or not at all.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07187.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

摘要:

A substance P analogue, (D‐Pro2, D‐Trp7,9)‐SP, has been described to have SP antagonistic and SP agonistic effects in different tissues. We have investigated the effects of (D‐Pro2, D‐Trp7,9)‐SP on the sphincter pupillae muscle, the blood aqueous barrier (BAB) and the intraocular pressure (IOP) in the albino rabbit eye. We also investigated the modifying effects of (D‐Pro2, D‐Trp7,9)‐SP on miosis, BAB damage and IOP rise caused by SP, prostaglandin E1(PGE1), capsaicin and on the miosis caused by electrical intracranial antidromic trigeminal nerve stimulation (NV stim). Endogenous PG synthesis was inhibited by systemic indomethacin i. v., cholinergic influence on the pupil size was inhibited with biperiden, i. v., adrenergic nerve influence by cervical sympathectomy just prior to the expts. Tubocurarine chloride was used to cause relaxation of striated muscles in the expts with NV stim. We found 100 μg (D‐Pro2, D‐Trp7,9)‐SP to cause miosis, breakdown of the BAB with heavy leakage of Evans blue into the ciliary processes and aqueous humor, and a rise in IOP. At 10 μg (D‐Pro2, D‐Trp7,9)‐SP caused slight miosis and did not inhibit the miosis caused by SP or capsaicin, but caused a significant reduction of the miotic response caused by PGE1and NV stim. The rise in protein concentration in the aqueous humor caused by SP or PGE1was slightly but significantly lower after pretreatment with (D‐Pro2, D‐Trp7,9)‐SP. Thus (D‐Pro2, D‐Trp7,9)‐SP was found to act as a SP agonist on the sphincter pupillae muscle, on the BAB and IOP. However, (D‐Pro2, D‐Trp7,9)‐SP seemed to have some SP antagonistic effects on mechanisms that require sensory nerve conduction e. g. miosis caused by PGE1and NV stim. The antagonistic mechanism is not clear. The SP analogue may have an unspecific membrane stabilizing effect or a toxic effect or block SP receptors on the sensory nerve fibers. Such effects of (D‐Pro2, D‐Trp7,9)‐SP may explain also why the rise in protein concentration in the aqueous humor caused by SP and PGE1

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07188.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07189.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07190.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1983.tb07191.x

出版商:Blackwell Publishing Ltd    

年代:1983

数据来源: WILEY