实验性糖性与萘性白内障动物模型的制作及评价

目的:选择适当的动物、试剂及给药途径,制备能动态显示白内障形成的动物模型。方法:（1）豚鼠,0.4％d-半乳糖,0.2mL/（眼·d）,球后注射19天;（2）大鼠,50％　d-半乳糖腹腔注射,25g/（kg·d）,共24天;（3）家兔,30％萘混悬液灌胃,2.65mL/（kg·d）,共8天。应用裂隙灯显微镜观察不同动物模型晶状体混浊度变化并测定其生化指标。结果:成功获得了糖性及萘性白内障动物模型。结论:此两类模型是深入研究白内障的发病机理及药效学的可靠实验手段。     

Changes in acetylcholine receptor distribution and binding properties at the neuromuscular junction during aging

Junctional and extrajunctional acetylcholine receptors were characterized in diaphragm muscle obtained from mature adult and aged rats. Rhodamine-conjugated -bungarotoxin was used to visualize receptor localization. At this level of resolution, there were no major changes in receptor distribution, and nerve terminals were consistently associated with receptors and vice versa. Specific binding characteristics were assayed by measuring ¹²⁵I--bungarotoxin binding. Maximal binding to intact junctional and extrajunctional tissue samples was greater in the older rats. The association rate constant in minced tissue decreased in the older animals. Retardation of the initial rate of toxin binding by d-tubocurarine was described by a two-component nonlinear Hofstee plot; values of K_i were about the same for both age groups, but there was a significant shift towards the low-affinity values in the aged rats. Miniature end-plate currents (m.e.p.c.s) were recorded under voltage-clamp conditions before and after AChE inhibition. When AChE activity was inhibited m.e.p.c. amplitudes and decay time-constants increased in both age groups. The magnitude of these increases was larger in the older animals. Inhibition of AChE did not affect mean channel open time, which was estimated from spectral analyses of ACh-induced membrane noise. Lipid composition was assayed in whole muscle and isolated sarcolemma. Muscle cholesterol concentration rose 15–20 percent, but phospholipid concentrations were maintained. However, neither cholesterol, phospholipid levels, nor membrane fluidity changed significantly with age in isolated sarcolemmal membrane fractions.

These data indicate that the numbers of junctional and extrajunctional receptors increase with age. In the junctional region, this is quite likely due to an expanded field of receptors and not an increased density. This is associated with an increased fraction of receptors with lower binding affinity during aging. These changes apparently are not caused by major changes in membrane fluidity or lipid composition.     

Simultaneous measurement of [F]FDOPA metabolism and cerebral blood flow in newborn piglets

Available information on the dopamine (DA) metabolism of the immature brain is rare. In order to establish a useful animal model we have performed PET experiments in anesthetized neonatal pigs using 6-[[18]F]-fluoro-L-DOPA (FDOPA) as tracer. In this study, we have simultaneously determined the cerebral blood flow and the rate constant of FDOPA conversion by the aromatic amino acid decarboxylase, the ultimate enzyme in the synthesis of dopamine. The estimated values of FDOPA decarboxylation in the basal ganglia were similar to values calculated in adult animals and humans. However, in contrast to those studies a significant decarboxylation was also found in the frontal cortex and the cerebellum. HPLC analysis of brain samples also revealed extensive and rapid metabolism of FDOPA in the five investigated brain regions. At 8 min after tracer injection about 80% of FDOPA was already converted to FDA and its metabolites. Surprisingly, a rather high fraction (16^fn221%) of [[18]F]-fluoro-3-methoxytyramine was found which may indicate a low storage capacity of vesicular DA at this perinatal stage. It is suggested that the findings are related to the ontogenetic development of the dopaminergic system. The knowledge of the regulation of the DA metabolism in the immature brain may have implications for the understanding of neurodevelopmental effects of perinatal oxygen deprivation.     

Tissue perfusion in relation to cardiac output during continuous positive-pressure ventilation and administration of propranolol or verapamil

Background : Our objective was to determine whether administration of propranolol or verapamil modifies the hemodynamic adaptation to continuous positive-pressure ventilation (CPPV), in particular the regional distribution of cardiac output (CO).
Methods : General hemodynamics and regional blood flows assessed by microsphere technique (15 (μm) were recorded in 16 anesthetized pigs during spontaneous breathing (SB) and CPPV with 8 cm H₂O end-expiratory pressure (CPPV8) before and after intravenous administration of propranolol (0.3 mg · kg⁻¹ followed by 0.15 mg · kg⁻¹ · h⁻¹, n=8) or verapamil (0.1 mg · kg⁻¹ followed by 0.3 mg · kg⁻¹ · h⁻¹, n=8).
Results : CPPV8 depressed CO by 25% without shifts in its relative distribution with the exception of a noteworthy increase in adrenal perfusion. Propranolol increased arterial blood pressure, and due to a fall in heart rate, CO dropped by 25%. The kidneys and, to a lesser extent, the splanchic region and central nervous system received increased fractions of the remaining CO at the expense of skeletal muscle flow. Similar patterns were seen during SB and CPPV8 such that the combination of propranolol and CPPV8 depressed CO by 50%. The circulatory effects of verapamil were less evident but myocardial perfusion tended to increase.
Conclusions : The combination of propranolol or verapamil with CPPV does not result in any specific hemodynamic interaction in anesthetized pigs, except that the combined effect of propranolol and CPPV may severely reduce CO.     

锌在豚鼠卡那霉素中毒性耳聋中的作用

应用给豚鼠注射硫酸锌的方法，观察了锌对豚鼠卡那霉素中毒性耳聋的影响。通过观察给药组和对照组动物的耳廊反射（ＰＲ）阈，脑干听觉诱发电位（ＢＡＥＰｓ）阈变化及耳蜗底回外毛细胞缺失率，发现硫酸锌注射组和对照组豚鼠的４、６、８ＫＨｚＰＲ阈在处死时分别升高１４．５６±３．１２ｄＢ，１５．８８±３．３８ｄＢ，１８．１２±２．７０ｄＢ和１７．１２±３．５６ｄＢ，１６．１５±２．５８ｄＢ，１９．２５±３．０１ｄＢ（Ｐ＞０．０５）。实验结果说明补充锌对卡那霉素中毒性耳损害无明显对抗作用     

氯胺酮雾化吸入对气道反应性的影响

目的：探讨雾化吸人氯胺酮对气道反应性及肺和小气道病理改变的影响。方法：用整体引喘法分别测定雾化吸人1％-5％氯胺酮5min后和3％氯胺酮雾化吸人3、5、10、15、30min后对豚鼠气道反应性的变化。每天豚鼠雾化吸人5％氯胺酮2h，连续6天后观察肺部的病理变化。测定雾化吸人3％或5％氯胺酮30min后小鼠的痛阈改变。结果：2％-5％氯胺酮雾化吸人5min后有明显的气道舒张作用(P＜0．05)。3％氯胺酮雾化吸人5min以上均有舒张气道的效应(P＜0．05)，且各时点之间无明显区别(P＞0．05)。3％和5％氯胺酮雾化吸人对小鼠的痛域无影响(P＞0．05)。连续6天雾化吸人5％氯胺酮后末见气道与肺明显的病理变化。结论：3％-5％氯胺酮雾化吸人5min以上有良好的平喘作用。氯胺酮雾化吸人对外周痛阈不产生明显影响。氯胺酮雾化吸人对肺和小气道不产生病理影响。     

中国小型猪阻塞型睡眠呼吸暂停模型的建立

目的　建立一个稳定、可靠、与临床病理状态接近的阻塞型睡眠呼吸暂停 (OSA)动物模型。方法　中国小型猪 10头 ,分为A、B两组 ,A组采用凝胶外部注射法制作模型 ;B组采用凝胶内部注射法制作模型。手术过程中及结束后 ,用多导睡眠仪检测脑电图、口鼻气流、鼾声、胸式呼吸、腹式呼吸、血氧饱和度。 1周后复查多导睡眠图。 2周后行CT检查 ,3个月后处死动物行病理形态学检查。结果　手术结束后两组动物均出现呼吸暂停或低通气及血氧饱和度下降 ,组间相比呼吸暂停时间、呼吸暂停指数、血氧饱和度无明显差别。 1周后复查 ,两组呼吸暂停时间、呼吸暂停指数均较术后当天明显增加 ,血氧饱和度明显下降 ,P <0 0 5 ,B组上述指标的变化更为明显 ,P <0 0 5。CT检查结果 :A组咽腔有一定程度的狭窄 ;B组咽腔呈明显狭窄状。病理形态学结果 :光镜下可见呈交联状的凝胶 ,表面有一层由排列整齐的胶原纤维和弹性纤维形成的结缔组织薄膜 ,胶原纤维和弹性纤维向凝胶内部生长。结论　凝胶注射法建立的慢性阻塞型睡眠呼吸暂停模型稳定、可靠、重复性好 ,与临床病理状态接近 ,可进行长期的、动态的研究 ,可广泛应用于睡眠呼吸暂停综合征发病机制、病理生理及治疗学等领域的研究 ,相比而言 ,内部注射法更优。     

Anaphylactic bronchoconstriction in immunized guinea pigs provoked by inhalation and intravenous administration of hexahydrophthalic anhydride and methyltetrahydrophthalic anhydride

We established a guinea-pig model of anaphylactic bronchoconstriction provoked in immunized animals by inhalation and intravenous administration of 4,4-methyltetrahydrophthalic anhydride (MTHPA) and hexahydrophthalic anhydride (HHPA). Guinea pigs were immunized intradermally with either MTHPA ( n = 8) or HHPA ( n = 8) suspended in olive oil. Control animals ( n = 8) were injected with olive oil alone. After 4 weeks, the animals were challenged during mechanical ventilation by inhalation or intravenous administration of MTHPA or HHPA conjugated with guinea-pig serum albumin (GPSA). Airway flow, and airway and esophageal pressures were measured. Resistance ( R ) and static compliance (Cst) of the respiratory system (rs), lung (1), and chest wall were studied with the flow-interruption technique. After challenge with MTHPA-GPSA or HHPA-GPSA, R , rs and R , 1 increased dramatically while Cst, rs and Cst,1 decreased, and severe arterial hypoxia developed. The reaction occurred at a well-defined dose of anhydride and lasted about 30 min. When the same dose was repeated after 30 min, the response was much attenuated. MTHPA and HHPA can induce asthma in guinea pigs. The dose-response curve at antigen challenge is steep. Once a threshold dose is reached, a severe reaction occurs. The reactivity is then exhausted. This model may be suitable for assessing occupational asthma caused by acid anhydrides and possibly by other low-molecular-weight chemicals.     

Glycinergic Inhibitory Synaptic Currents and Related Receptor Channels in the Zebrafish Brain

To extend our study of the inhibitory synaptic network we have developed an isolated whole-brain preparation of the 52-h-old zebrafish (Brachydanio redo) in which the structural and functional integrity of the brain is preserved. We report the characterization of quantal inhibitory events and the correlation of their properties with those of the underlying activated channels. During whole-cell recordings of the Mauthner cells, applications of 10^?6 M tetrodotoxin greatly reduced the frequency and amplitude of the spontaneously occurring synaptic events, which were dominated by Cl^?-dependent inhibitory postsynaptic currents (IPSCs). Lowering Ca²⁺ and adding Mg²⁺ to tetrodotoxin-containing solutions resulted in a further decrease in amplitude of the recorded synaptic currents, the remaining ones being considered as miniature IPSCs (mISCs). Applications of 0.5–1 μMM strychnine in the presence of tetrodotoxin eliminated > 90% of the inhibitory currents in the preparation. The amplitude histograms of these mIPSCs exhibited two initial equally spaced peaks, followed by a skewed distribution for higher values. The first two components were well fitted by the sum of two Gaussian curves, giving a mean quantal amplitude of 35.7 pA (at a holding potential of-50 mV) and a coefficient of variation of 0.25 for the first peak. Outside-out recordings showed at least two classes of glycine receptor channels, one having multiple conductance levels with a main state of 81–86 pS and another displaying only one opening level of 41–43 pS. These two mean conductance states had similar mean open times, of 0.6–1 and 4.5–6 ms respectively. In addition, three mean closed times were observed for the 41–43 pS level. The shortest group (0.6–1 ms) was considered as representing gaps within bursts. Burst analysis revealed three mean burst durations, of 0.6, 4 and 35 ms. Comparisons of the amplitude of the first class of mIPSCs and of the open channel conductances indicated that one quantum opens 14–22 channels. Moreover, the correspondence between the mean decay time of mIPSCs and the mean open time or medium burst duration (4–5 ms) suggests that glycine-activated channels open only once in response to a single exocytosis. The pre-and postsynaptic origins of mIPSCs amplitude fluctuations are discussed in the context of multivesicular release versus the hypothesis of postsynaptic receptor saturation.     

Guinea Pigs as Models to Study the Hypocholesterolemic Effects of Drugs

Guinea pigs are useful models to investigate the mechanisms of the hypocholesterolemic effects of drugs. Like humans, guinea pigs are one of the few species that carry the majority of cholesterol in LDL. This animal model has also been shown to develop atherosclerosis when challenged with hypercholesterolemic diets. In addition, plasma lipid profiles in males, females and ovariectomized guinea pigs, a model for menopause, follow similar patterns to those observed in humans. In this report, drugs aimed at lowering plasma cholesterol and triglycerides in hyperlipidemic individuals are reviewed. Studies analyzing the hypolipidemic effect of HMG‐CoA reductase inhibitors, acyl CoA cholesterol acyltransferase inhibitors, fibrates, bile acid resins, apical sodium bile acid transporter inhibitors, and others show that guinea pigs and humans have comparable responses to drug therapy. In addition, results from the limited clinical reports addressing specific effects of drugs on LDL catabolism or VLDL synthesis are in agreement with observations in guinea pigs. From the review of these studies, it is apparent that the guinea pig is a useful animal model to further explore the mechanisms of action of lipid lowering drugs including effects on specific receptors and regulatory enzymes involved in cholesterol metabolism and on early atherosclerosis development.