[Treatment of man's voice disorder (gynecophonus) by microcomputer]

Using the microcomputer, as a voice training method in the treatment of gynecophonus was presented in 2 cases, to further study the treatment of this kind of voice disorder. Satisfactory results were gained. Meanwhile, the method and effect were also discussed.

A capillary method to measure water transmission through polyurethane membranes

A capillary method has been developed to measure the rate of water transmission through polyurethane membranes prepared for use as ventricles in artificial hearts. The system consisted primarily of a leak-proof sample chamber containing the water, a glass capillary flow meter, and a receiver compartment with continuous dry air ventilation. The capillary flow meter monitored the volume of water loss in the sample chamber. The rate of water transmission through the test membrane was found to be proportional to the water loss in the sample chamber, and dependent on the membrane thickness. For thicknesses from 0.09 mm to 0.34 mm, water vapor transmission rates ranged from 7.53 x 10(-8) to 2.76 x 10(-8) mol/s cm2, respectively. Although the concentration of water vapor in the receiver compartment did affect the rate of water vapor transmission through the membrane, within the pressure range 50-200 mmHg, there was very little effect. These findings suggest that water transmission through a polyurethane membrane is dominated by a diffusion process rather than by bulk convection.

Oncogenic c-Ki-ras but not oncogenic c-Ha-ras up-regulates CEA expression and disrupts basolateral polarity in colon epithelial cells

Colon carcinomas commonly contain mutations in Ki-ras4B, but very rarely in Ha-ras, suggesting that different Ras isoforms may have distinct functions in colon epithelial cell biology. In an earlier study we had demonstrated that oncogenic Ki-ras4BVal-12, but not oncogenic Ha-rasVal-12, blocks the apicobasal polarization of colon epithelial cells by preventing normal glycosylation of the integrin beta1 chain of the collagen receptor. As a result, only the Ki-ras mutated cells exhibited altered cell to substratum attachment, whereas mutation of either Ras isoform activated mitogen-activated protein kinases. We have now asked whether intercellular adhesion proteins implicated in establishing basolateral polarity in colon epithelial cells are modulated by oncogenic Ki-Ras4BVal-12 proteins but not oncogenic Ha-RasVal-12 proteins. The embryonic adhesion protein carcinoembryonic antigen (CEA) was up-regulated on the mRNA and protein levels in each of three stable Ki-rasVal-12 transfectant lines but in none of three stable Ha-rasVal-12 transfectant lines. The elevated protein levels of CEA in Ki-ras4BVal-12 transfectant cells were decreased by blocking expression of Ki-ras4BVal-12 with antisense oligonucleotides. N-cadherin levels were decreased in only the Ki-ras transfectants, whereas E-cadherin levels were unchanged. Immunohistochemical analysis demonstrated that Ki-ras4BVal-12 transfectant cells did not polarize into cells with discrete apical and basal regions and so could not restrict expression of CEA to the apical region. These unpolarized cells displayed elevated levels of CEA all along their surface membrane where CEA mediated random, multilayered associations of tumor cells. This aggregation was both calcium-independent and blocked by Fab' fragments of anti-CEA monoclonal antibody col-1. Trafficking of the lysosomal cysteine protease cathepsin B may also be altered when cell polarity cannot be established. Ki-ras4BVal-12 transfectant cells expressed 2-fold elevated protein levels of the lysosomal cysteine protease cathepsin B but did not up-regulate cathepsin B mRNA expression. One function of oncogenic c-Ki-Ras proteins in colon cancer progression may be to up-regulate CEA and thus to prevent the lateral adhesion of adjacent colon epithelial cells that normally form a monolayer in vivo.

Preparation and Characterization of Active Carbon Adsorbents for Wastewater Treatment from Elutrilithe

Active carbon adsorbents were prepared from natural elutrilithe by chemical activation with K2CO3. The effect of pyrolysis temperature and time and K2CO3/elutrilithe ratio on the surface area, porosity, and ash content of the adsorbents was studied. Various prior and post treatments have been tried to improve the quality of the adsorbents. An ideal active carbon adsorbent with a BET surface area of 1236 m2/g and a total pore volume of 0.679 cm3/g has been obtained. The adsorbent is hydrophobic in nature and exhibits large adsorption capacities for various phenolic compounds from aqueous solutions. Copyright 1997Academic Press

[The relations between mutations of p53 anti-oncogene in atherosclerosis and levels of lipids in serum]

OBJECTIVE

To further understanding the pathogenesis of human atherosclerosis, we studied the mutations of p53 anti-oncogene in Chinese atherosclerosis lesions and the relations between p53 gene mutations with the levels of serum lipoprotein and the contents of lipids in AS tissues.

METHODS

p53 gene mutations were detected by a-32P-dCTP labelled radiative PCR-SSCP and the biochemical analyses of lipids in serum and AS tissues.

RESULTS

In 89 cases studied, 9 were found the p53 gene multi-hotsports exons mutations. The TC, TG and CE contents in vascular AS tissues in p53 gene mutation group were higher than those in non-mutations group (ANOV: F = 4.56-9.97, P < 0.05-0.01, no differences in PL contents). But there were no statistic differences in serum levels of TC, TG, CE and apoAI between the two groups (P > 0.05-0.25). All the levels of the serum lipoproteins studied were almost in normal ranges.

CONCLUSION

The DNA structural mutations of p53 anti-oncogene in Chinese adults' AS tissues have remarkable relations with the severity of AS lesions. The mutations of p53 gene may play some important roles in the formation of human atherosclerosis. In addition to serum lipid disorders, this may be a new mechanism in the pathogenesis of human atherosclerosis.

Bcl-2 phosphorylation required for anti-apoptosis function

The protooncogene Bcl-2 functions as a suppressor of apoptosis in growth factor-dependent cells, but a post-receptor signaling mechanism is not known. We recently reported that interleukin 3 (IL-3) and erythropoietin, or the protein kinase C activator bryostatin-1 (Bryo), not only suppresses apoptosis but also stimulates the phosphorylation of Bcl-2 (May, W. S., Tyler, P. G., Ito, T., Armstrong, D. K., Qatsha, K. A., and Davidson, N. E. (1994) J. Biol. Chem. 269, 26865-26870). To test whether phosphorylation is required for Bcl-2 function, conservative serine --> alanine mutations were produced at the seven putative protein kinase C phosphorylation sites in Bcl-2. Results indicate that the S70A Bcl-2 mutant fails to be phosphorylated after IL-3 or Bryo stimulation and is unable to support prolonged cell survival either upon IL-3 deprivation or etoposide treatment when compared with wild-type Bcl-2. In contrast, a Ser --> Glu mutant, S70E, which may mimic a potential phosphate charge, more potently suppressed the etoposide-induced apoptosis than wild type in the absence of IL-3. Since the loss of function S70A mutant can heterodimerize with its partner protein and death effector Bax, these findings demonstrate that Bcl-2:Bax heterodimerization is not sufficient and Bcl-2 phosphorylation is required for full Bcl-2 death suppressor signaling activity.

[Role of endothelial-derived nitric oxide and its synthase in the development of hypoxic pulmonary hypertension in rat]

To clarify the role of endothelial-derived nitric oxide (EDNO) and its synthase (NOS) in the normal and hypertensive pulmonary vasculature, activity of endothelial NOS in the lungs, ENDO-dependent vasodilating response induced by bradykinin (BK), and cGMP content of lung tissue in normoxic and hypoxic rats were investigated. We also studied the effects of NOS inhibitor-L-NAME on the activity of NOS, cGMP content, mean pulmonary arterial pressure (mPAP) and carotid systolic arterial pressure (CAPs) in both rats. The results were as follows (1) In normoxic rats there was no NOS activity in the endothelium of small vessels (phi < or = 80 microns) and no relaxing response to BK. Long-term administration of L-NAME obviously inhibited the activity of ecNOS and cGMP content in the lungs of normoxic rats, therefore it led to the increment of CAPs but failed to elevate mPAP. (2) After hypoxic exposure for 10 days, NADPH-diaphorase (NADPH-d and ecNOS immunoreactivity turned to be positive in the endothelium of small vessels with diameter less than 80 microns. BK-induced EDNO-dependent vasodilation, the enzyme activity of cNOS and cGMP content in the lungs of hypoxic rats were significantly enhanced as compared with normoxic rats. Long-term administration of L-NAME in hypoxic rats markedly inhibited the enhancement of cNOS enzyme activity, the production of EDNO and cGMP content in rat lungs, consequently it significantly decreased mPAP but elevated CAPs obviously. These results suggest that the role of EDNO in maintaining the low basal tone of normal adult pulmonary circulation remain to be studied more precisely. The increased activity of ecNOS and the enhancement of EDNO synthesis might act to moderate the hypertension. The excess synthesis of EDNO might be toxic to the endothelium of pulmonary vessels, therefore potentiating the development of pulmonary hypertension.

The Dialine II graft: a new collagen-impregnated warp-knitted polyester arterial prosthesis

The Dialine graft, a new prototype of knitted vascular prosthesis that uses a different brand of polyester fibers as an alternative to Dacron fibers, has been shown to offer excellent in vitro physical performance and in vivo healing. Although it still requires preclotting, the Dialine prosthesis was made impervious by impregnation of bovine type I collagen cross-linked with vapors of formalin. The purpose of the present investigation was to compare the in vitro physical characteristics of the Dialine II graft with those of the collagen-impregnated Hemashield graft. In addition, we studied the healing performance as a thoracoabdominal bypass in dogs for prescheduled periods of implantation ranging from 4 hours to 6 months. In vitro, the bursting strength, resistance to dilatation, and suture retention strength properties of the Dialine II prosthesis were all shown to exceed those of the Hemashield control graft. In the first weeks after implantation, the Dialine II grafts induced a discrete inflammatory response, as shown by the constant leukocyte counts observed both before implantation and when the animals were killed, as well as by the histologic observation of a few inflammatory cells in contact with the collagen. Consequently, the Dialine II grafts showed a slow rate of bioresorption of cross-linked collagen. At 1 month, a thin internal collagenous capsule was present at both anastomoses, laying over the original collagen coating. At 3 and 6 months, areas of thrombotic deposits and endothelialized areas were observed on the luminal surface. Because results of early clinical trials have been highly satisfactory, this prosthesis may be recommended for use without restriction as a medium- and large-diameter blood conduit.

Dissociation of modular humeral head components: a biomechanical and implant retrieval study

In vivo dissociation of the Morse-taper of shoulder arthroplasty modular humeral components has been reported. The incidence of this complication appears to be approximately 1:1000. The objective of this study was to identify conditions that might affect the Morse-taper interface strength in humeral components. Mechanical tests were performed to load and dissociate humeral heads from the humeral stems (titanium). The effect of loading rate, load amplitude, and number of impactions was investigated. Dissociation force was measured after the taper was contaminated with water, oil, blood, and bone cement particles. The mean dissociation force after two impactions with a mallet was 2926 +/- 955 N. Dissociation force was linearly proportional to impaction force. Repetitive loading beyond two impactions did not significantly increase taper strength. Contamination of the taper with as little as 0.4 ml of fluid could prevent fixation of the taper.

Arterial wall mechanical characteristics after treatment in collagenase: an in vitro aneurysm model

OBJECTIVE

To investigate the mechanical characteristics of canine aortas treated with buffered collagenase as a first step in developing an animal model of aortic aneurysm for the validation of stent-grafts.

DESIGN

In vitro study of canine aortas.

INTERVENTIONS

Canine thoraco-abdominal arteries were divided into the descending thoracic aorta the suprarenal artery and the infrarenal artery; these segments were incubated separately in a buffered collagenase solution for 1 to 6 hours. Some segments were left untreated as controls.

OUTCOME MEASURES

Mean arterial wall thickness, measured with Vernier callipers and computerized histomorphometric methods and longitudinal tensile strength of control and treated vessel segments.

RESULTS

The arterial wall thickness decreased with incubation time. After 1 hour of incubation the reduction was approximately 15% for the descending thoracic aorta, 16% for the suprarenal artery and 18% for the infrarenal artery. After 6 hours the total reduction in wall thickness was 32%, 41% and 44% respectively for the 3 segments. The tensile strength of the treated arterial segments also decreased with the incubation period. Initially, the infrarenal segment displayed the greatest strength; however, this was reversed as the period of incubation increased. The inelastic limit of the descending thoracic aorta control segment was reached at 100% elongation, whereas that of the suprarenal artery was reached at 80% and that of the infrarenal artery was reached at 60% elongation. All of the arterial segments became weaker as the period of incubation in buffered collagenase increased.

CONCLUSION

This in vitro incubation technique successfully altered the structure of the collagen fibre network within the arterial wall. This method may be an option in developing an aneurysm model to test stent-grafts in vivo.

[Localization and expression of dopamine receptors in stomach and duodenum in rats]

Dopamine is an important neurotransmitter which may contribute to the regulation of gastrointestinal function, but its mechanism remains elusive.

OBJECTIVE

The existence, localization and expression of dopamine receptor mRNAs in rat stomach and duodenum were examined by in situ hybridization.

METHODS

The oligonucleotide probes were selected and synthesized according to the previous work. All the probes were labelled with alpha S35dATP using the terminal deoxynucleotide transferase, then were hybridized with the frozen, fixed preparation of rat stomach and duodenum. The density of silver granules were counted and analyzed by the image analysis computer system.

RESULTS

It was found that all five subtypes of dopamine receptor mRNAs existed in the stomach and duodenum with greatly different expression. The distribution of dopamine mRNAs in the stomach were mainly localized in the lamina propria near the lamina muscularis mucosae and parallel to the longitudinal axis of the tract. Whereas, all five MRNAs were spread over the entire layer of the duodenal mucosa. With the image analysis system, abundant expressing levels of D5 and D4 mRNAs were documented unexpectedly.

CONCLUSION

All these results suggest that dopamine produced its effect via dopamine receptors especially D5 subtype and D4 receptor might be act as a modulator.

The mouse Spam1 maps to proximal chromosome 6 and is a candidate for the sperm dysfunction in Rb(6.16)24Lub and Rb(6.15)1Ald heterozygotes

We have determined the chromosomal localization of the murine gene encoding the 68-kDa sperm adhesion molecule 1, Spam1 or Ph-20. Using two independent approaches, fluorescence in situ hybridization (FISH) and interspecific backcross analysis we show the Spam1 maps to proximal mouse Chromosome (Chr) 6. This map position is within the conserved linkage group corresponding to human Chr 7q, where the human homolog, SPAM 1, has been shown to map previously. Genetic mapping shows the gene to be very closely linked to Met, one of the most proximal loci on MMU 6. It thus places the gene near the centromere and the junction of the Rb(6.16)24Lub and Rb(6.15)1Ald translocations. The essential role of the Spam1 sperm antigen in mouse sperm-egg interactions and its gene location provide strong support for its candidacy as the gene involved in the dysfunction of mouse sperm bearing the Rb(6.16)24Lub or Rb(6.15)1Ald translocation.

Are intraaortic balloons suitable for reuse? A survey study of 112 used intraaortic balloons

To assess the safety of reusing single-use intraaortic balloon devices (IABs), 112 used devices were investigated in terms of physical integrity, gas leakage inspection, mechanical performance, surface chemistry and morphology, and physical stability. These IABs were all used clinically only once, and the duration of the IABs in vivo ranged from 6 to 312 h. Macroscopic examination of the balloons and the outer catheters revealed no obvious change in either shape or color. No discernible abrasions or cracks were observed on the balloons. However, 61% of the balloons were creased, and 40% of the central lumens and 21% of the sheaths showed visible bending flaws. Moreover, 65% of the balloons and 38% of the central lumens were contaminated by visible residual organic debris. The physical integrity of each device was verified in a specially designed leakage-fatigue tester for 72 h. Ninety-seven percent of the devices passed the leakage inspection. Stress-strain testing, differential scanning calorimetry, attenuated total reflection-Fourier transform infrared, and scanning electron microscopy analyses clearly indicated that there were no significant differences in the mechanical properties, bulk material morphology, surface chemistry, and external surface morphology between the used balloons and virgin controls. Although some surface modifications occurred on the internal side of the balloons, the external surfaces of most balloons suffered no trauma. Most of the used IABs examined in this study maintained physical and mechanical properties similar to those of the virgin devices. The chemistry of the balloon material was stable after short-term in vivo use. However, it does not seem possible to establish a rigorous protocol of cleaning, sterilization, and inspection to guarantee a safer reuse of these devices. The presence of residual organic debris that cannot be eliminated results in an imperative preclusion not to reuse the IABs.

Polyester Arterial Prostheses

To evaluate recent developments in the design and production of polyester vascular prostheses in eastern Europe, a series of in vitro physical and chemical tests and an in vivo study was performed on three new prototype devices from the Czech Republic and one from Poland. The in vitro results for these four prostheses, referred to as the Ra-1n (warp knitted, uncrimped), Ra-1v (warp knitted, crimped), Mikrofroté (weft knitted, uncrimped), and Dallon (warp knitted, crimped) prostheses, were compared against values for three commercial devices of western origin, namely the Triaxial, the Vasculour II, and the Cooley II grafts. The animal trial involved implanting the four prototype devices as a thoracoabdominal bypass in dogs for eight different periods ranging from 4 hrs to 6 months and undertaking histologic and structural investigations on the retrieved grafts. Because of its poor long-term dimensional stability in vivo, the continued use of a weft knitted structure, like the Mikrofroté prosthesis, is to be deprecated. Conversely, the introduction of a more dimensionally stable warp knitted structure in three prototypes is to be acknowledged. However, the presence of surface contaminants was most likely responsible for the excessive inflammatory reaction generated by all four prostheses during the first month in vivo, which resulted in delayed healing performance. In addition, an unusually high surface carbon-oxygen ratio suggests that the crimping process needs further refinement. Improved cleaning and packaging procedures are essential before these products can complete against existing commercial prostheses of western origin. In conclusion, these new developments illustrate that the technology of warp knitting, which is now spreading worldwide, should be evaluated.

Pure-phase plates for super-Gaussian focal-plane irradiance profile generations of extremely high order

A set of recursive formulas for diffractive optical plates design is described. The pure-phase plates simulated by this method homogeneously concentrate more than 96% of the incident laser energy in the desired focal-plane region. The intensity focal-plane profile fits a 12th-order super-Gaussian function and has a nearly perfect f lat top. Its fit to the required profile measured in the mean square error is 3.576 x 10(-3).

Efficiency of an external support to reduce lipid infiltration into venous grafts: in vitro evaluation

Excessive distension of venous grafts due to arterial pressure enhances the convective water transport (filtration flow) through the vessel wall, and thus might affect the infiltration of macromolecules such as lipoproteins. In this paired experimental study, filtration velocities were measured at 100 mm Hg for canine jugular veins with or without external supports of expanded polytetrafluoroethylene (ePTFE) arterial prostheses. In addition, to assess the effect of filtration velocity on lipid infiltration or uptake, canine jugular veins were wrapped over half of their lengths with ePTFE arterial prostheses and perfused with dog serum containing 3H-cholesterol at a pressure of 100 mm Hg. At 100 mm Hg, the average filtration velocity of the wrapped jugular veins was 7.9 +/- 1.3 x 10(-6) cm/s whereas the average filtration velocity of the unwrapped veins was 27.3 +/- 2.7 x 10(-6) cm/s (p < 0.005). Moreover, the unwrapped veins had a significantly higher uptake rate of labeled cholesterol than the wrapped veins (10.9 +/- 7.3 x 10(-4) cm/h and 5.0 +/- 1.6 x 10(-4) cm/h, respectively, p < 0.005). In conclusion, under arterial pressure, veins experience excessive distention, which leads to significant increases in both filtration flow and cholesterol uptake. An external wrap or support of ePTFE material protects veins from excessive distension and thus may prevent atherosclerosis in venous grafts by reducing cholesterol uptake.

Can collagen impregnated polyester arterial prostheses be recommended as small diameter blood conduits?

A collagen impregnated graft and its parent preclotted prosthesis were implanted as thoraco-abdominal bypasses in dogs for periods ranging from 4 hr to 6 months and evaluated for their ease of handling, imperviousness, and healing behavior in terms of luminal surface thrombogenicity using labeled platelets and fibrinogen, prostacyclin (PGI2) secretion, histomorphometric determination of internal capsule thickness, and histopathologic and scanning electron microscopic studies. The collagen impregnated graft was impervious to blood and both grafts showed excellent handling characteristics. Fibrin uptake was negligible on both grafts; however, platelet uptake was higher on the collagen impregnated graft than on the control graft at 4 and 24 hr. The healing behavior of the collagen impregnated graft was also found to be different than that of the control graft between 1 and 6 months post implantation. The development of a host collagenous internal capsule at the anastomoses, and a confluent endothelial lining, was observed in both grafts at 1 month; in later implantation periods, the healing of the medial region was found to be more irregular in the collagen impregnated grafts, showing a lower mean PGI2 secretion than the preclotted control grafts. Histomorphometric analysis showed the internal capsule on the collagen impregnated grafts to be thicker than on the control grafts for most periods of implantation. The current study illustrates that the healing process of collagen impregnated grafts is delayed and that bovine collagen has a stimulating effect on tissue encapsulation. Current impregnated polyester arterial prostheses therefore cannot be recommended as small diameter blood conduits.

Influence of anti-inflammatory and antioxidant agents on endothelial permeability alterations induced by bradykinin

Increased vascular permeability to plasma proteins and altered hemodynamics at the site of inflammation are characteristics of inflammation. In the present study, alterations in endothelial barrier permeability were evaluated in different organs/tissues 6 h after a systemic inflammatory response induced by intravenous injection of bradykinin (BK; 1.7 mg/kg). The effect of intravenous pretreatment with indomethacin or ibuprofen (cyclooxygenase inhibitors), N-acetyl-L-cysteine (NAC, an oxygen free radical scavenger), and allopurinol (a xanthine oxidase inhibitor) was determined. Endothelial permeability was evaluated by determining tissue water content (TWC), 125I-labeled human serum albumin (HSA) flux, and albumin leakage index (ALI) in various organs/tissues. The vasodilation in the local tissues was reflected by tissue blood content (TBC), measured by 51Cr-labeled red blood cells. The results indicate that albumin flux significantly increased in the peritoneum, pancreas, stomach, PSI, DSI, colon, kidneys, liver, lungs, and brain, TBC significantly increased in the kidneys, liver, lungs, and heart, as well as in the intestine, and an increased ALI, assaying endothelial permeability considering local hemodynamic alterations was noted in the pancreas, kidneys, liver, lungs, PSI, and DSI in the group with BK alone. These changes were to varying degrees reversed by pretreatment with indomethacin, ibuprofen, N-acetyl-L-cysteine, or allopurinol, where the protective effect tended to be organ-dependent.

Alterations in endothelial barrier permeability in multiple organs during overactivation of macrophages in rats

Macrophage hyperactivity has been suggested to play an important role in septic complications and the development of multiple organ failure. Intraperitoneal administration of macrophage stimulants, e.g., zymosan, induce a systemic inflammatory response, with concomitant gut origin sepsis, and organ dysfunction. However, little is known about alterations in endothelial permeability during macrophage hyperactivation. In the present study, the effect of macrophage hyperactivation on endothelial permeability, assessed by 125I-labeled HSA and 51Cr-labeled EDTA, and the difference between cytolytic and noncytolytic inflammatory macrophages induced by i.p. injection of .25 or .50 mg/g of zymosan, concanavalin A (Con A) or thioglycollate medium (TM) diluted in 4 mL of paraffin, as well as the potential relationship with the doses used, were evaluated in the rat. Overactivation of cytolytic inflammatory macrophages induced a pronounced alteration in endothelial barrier permeability, characterized by a decrease in whole body plasma volume and an increase in whole body interstitial fluid volume, while overactivation of noncytolytic inflammatory macrophages only induced leakage of proteins and plasma to several of the organs studied. Macrophage activators, like zymosan, Con A and TM, exhibited varying effects on endothelial permeability related to the dose used. The results in the present study imply that overactivation of cytolytic inflammatory macrophages may play an important role in endothelial barrier injury and that zymosan possesses a more potent effect as compared to Con A when administered at the same dose.

[Monoamine concentrations in experimental ulcers in rats]

A high performance liquid chromatography with electrochemical detection (HPLC-ECD method was employed for determination of monoamines, including epinephrine (E), norepinephrine (NE), 3,4-dihydroxyphenylacetic acid (DOPAC), dopamine (DA), 5-hydroxy-3-indole acetic acid (5HIAA), homovallilic acid (HVA) and 5-hydroxytryptamine (5HT), in body, antrum and duodenal mucosa of normal rats and rats with MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) induced ulcers. Abundant contents of DA and DOPAC were emerging in normal gastric body, antrum and duodenal mucosa while subsequent reduction of DA concentration were observed in gastric body and duodenal mucosa of rats by MPTP intracerebroventricular injection and persisted for a long time. The degree of reduction was correlated with time and dosage of MPTP administered. The decrease of 5HT in gastric body and its increase in duodenum were also observed at the same time. Such variation of concentrations implied that DA might play an important role in the pathogenesis of ulcerous diseases and 5HT might probably contribute to the development of ulcers.

Role of nitric oxide in short-term and prolonged effects of angiotensin II on renal hemodynamics

Short-term infusions of angiotensin II (Ang II) increase renal vascular resistance and thereby endothelial shear stress and nitric oxide (NO) release. Prolonged stimulation of Ang II can decrease the expression of NO synthase isoforms in the macula densa, but prolonged increases in shear stress can increase transcription of endothelial NO synthase. Therefore, we designed these studies to test the hypothesis that Ang II exerts time-dependent effects on renal NO generation as assessed from renal excretion of nitrate and nitrite, percent increases in renal vascular resistance during inhibition of NO synthase with intravenous NG -nitro-L-arginine methyl ester (L-NAME), or decreases in renal vascular resistance during stimulation of endothelial NO synthase with intravenous acetylcholine. Rats were tested during graded short-term (30 to 90 minutes intravenous) or prolonged (5 to 6 days subcutaneous) Ang II infusions that led to dose-dependent increases in blood pressure and renal vascular resistance and reductions in renal blood flow. Captopril was administered for 3 to 4 days to suppress Ang II generation. The renal excretion of nitrate and nitrite was increased during short-term Ang II infusions (from 205 +/- 22 to 331 +/- 58 pmol.min-1, P < .05) but was unchanged during prolonged Ang II infusion (control group, 197 +/- 33 versus Ang II, 245 +/- 42 pmol.min-1, P=NS). The percent increase in renal vascular resistance with L-NAME was potentiated dose dependently by short-term but not long-term Ang II infusions. The increase in renal vascular resistance with L-NAME in control rats without Ang II infusions was +150 +/- 13%. At an Ang II infusion of 200 ng.kg-1.min-1, the L-NAME-induced percent increase in renal vascular resistance was significantly (P < .01) increased compared with controls in short-term Ang II-infused rats (+369 +/- 70%) but was not significantly different in prolonged infused rats (+190 +/- 33%). Intravenous acetylcholine caused dose-dependent renal vasodilation that was not significantly changed in rats receiving short-term intravenous Ang II but was significantly (P < .005) potentiated in those receiving prolonged Ang II infusions (change in renal vascular resistance with acetylcholine at 10 micrograms.kg-1.min-1 versus control, -21.5 +/- 5.0%; with short-term Ang II, -24.9 +/- 4.5%; with long-term Ang II, -52.1 +/- 7.2%). In conclusion, short- and long-term Ang II infusions caused equivalent changes in blood pressure and renal blood flow and hence presumably equivalent increases in endothelial shear stress. However, only short-term Ang II infusions increased NO generation and the dependence of the renal circulation on NO, whereas acetylcholine-induced NO release was enhanced selectively during long-term Ang II infusions. This suggests that during long-term Ang II, renal NO release may become uncoupled from shear stress yet remains highly responsive to receptor-mediated stimulation.

The popliteofibular ligament. Rediscovery of a key element in posterolateral stability

We have recently become aware of a strong direct attachment of the popliteal tendon to the fibula. To investigate the importance of this attachment, we examined 20 cadaveric knees. The popliteofibular ligament was identified in all 20 knees. The cross-sectional area of the popliteofibular ligament was 6.9 +/- 2.1 mm2, compared with 7.2 +/- 2.7 mm2 for the lateral collateral ligament. Biomechanical testing of these structures, simulating a purely varus stress on the knee, revealed that the lateral collateral ligament always failed first, followed by the popliteofibular ligament, and then the muscle belly of the popliteus. The mean maximal force to failure of the popliteofibular ligament approached 425 N (range, 204 to 778), compared with 750 N (range, 317 to 1203) for the lateral collateral ligament. Our results indicate that the popliteofibular ligament contributes to posterolateral stability.

Theoretical modelling of the release rate of low-density lipoproteins and their breakdown products at arterial stenoses

Arterial stenoses and luminal-surface irregularities at anastomoses cause blood-flow disturbances with slow recirculation. The authors created a computer simulation to study the rates of the release into blood of atherogenic substances such as low-density lipoproteins and their breakdown products from within the arterial walls at stenoses. Finite-difference methods were used to solve the Navier-Stokes equations (in the form of stream function and vorticity function) and the steady-state mass transfer equation for bell-shaped stenoses with two different degrees of constriction. This simulation indicated that the efflux rates of lipids and their breakdown products from the vessel walls were suppressed in the region of disturbed flow, with slow circulation distal to stenoses. The lowest efflux rate was found at the point of flow separation, and this rate was much lower than rates in regions of undisturbed flow. Therefore, this mathematical model predicts that locally disturbed blood flow at arterial stenoses and arterial anastomoses is responsible for two distinct phenomena: first, it provides favourable conditions for lipid infiltration into vessel walls; and, second, it impairs the release into the blood of atherogenic substances accumulated in the vessel wall. Such mass transfer abnormalities may account for atherogenesis and the late failures of arterial reconstructions at these sites.

[Effect of Chinese herbs on the circadian rhythm of body temperature and heart rate in rabbits with hypothyroidism (yang deficiency)]

The rectal temperature (Tr) and heart rate (HR) of three groups of New Zealand white rabbits, i. e. thyroidectomized (G1), thyroidectomized and treated with Chinese herbs (a decoction composed of tonifying kidney-yang herbs) (G2) and pseudothyroidectomized for control (G3), were observed dynamically for 26 hours. The results indicated that the Tr and HR in G1 were decreased, and the circadian rhythms of the Tr and HR disordered significantly, while these changes in G2 were corrected obviously.