Compensatory adaptation of the heart to chronic rate overload: increase in calcium transport ATPase activity of myocardial sarcoplasmic reticulum

This study was undertaken to test the hypothesis that a compensatory response of the heart to a chronic and continuous, metabolic and heart rate overload was an increase in the calcium sequestering activity of the myocardial sarcoplasmic reticulum. Calcium sequestering activity was estimated by determination of the calcium-dependent ATPase (Ca2+-ATPase) activity of isolated microsomes. Chronic rate overload was modelled by comparing: dysthyroid and control rats; control swine and swine with implanted cardiac pacemakers set at 180 beats/min; and different species of mammals with widely different heart rates. The myocardial sarcoplasmic reticulum Ca2+-ATPase pump activity was significantly increased by 39% for hyperthyroid rats compared to control rats and by 87% for control rats compared to thyroidectomized rats; by 63% for paced swine compared to control swine; and by 43% for rats compared to guinea pigs, by 140% for guinea pigs compared to dogs and by 120% for dogs compared to cows. These data indicate that calcium sequestering activity of myocardial sarcoplasmic reticulum increases in equivalent proportion to the chronotropic demand and that heart rate is a hemodynamic correlate of the sarcoplasmic reticulum Ca2+-ATPase activity.     

Normothermic renal artery perfusion: A comparison of perfusates

Hypothermia and preservative perfusates have been used to decrease ischemic renal injury. This study was performed to identify the preservative function of perfusates independent of the effects of hypothermia. Rats underwent 45 minutes of renal ischemia. Rectal and renal parenchyma temperatures were monitored and maintained within 1° C of normal. Perfusates were University of Wisconsin solution (UW), Euro-Collins solution, normal saline solution, and Ringer's lactate solution. A nonperfused ischemic control and a nonischemic control group were also evaluated. Parameters evaluated included serum creatinine and blood urea nitrogen levels, renal ischemic injury grade, renal weight, and gross appearance of the injured kidney. Rats treated with UW solution were found to have a significantly lower creatinine, blood urea nitrogen, and injury grade than the other three perfused groups. The external gross appearance of the UW-treated kidneys was normal, whereas that of the other groups demonstrated moderate to severe injury. Although the mean right/left renal weight difference of the UW-treated group was lower than that of the other three groups, this was not statistically significant. Under normothermic conditions in rats, UW solution affords significant renal protection from ischemia. Euro-Collins, normal saline, and Ringer's lactate solutions display no significant protective effect.Presented at the Twentieth Annual Meeting of the Peripheral Vascular Surgery Society, New Orleans, La., June 10, 1995.     

Effect of a gonadotropin releasing hormone analog on cerebral hemodynamics in premenopausal women.

BACKGROUND: Impaired reactivity of cerebral blood vessels is associated with increased risk of stroke. Female sex hormones have vasoactive effects in a number of vascular beds but their effects upon the cerebral circulation are not well understood. Ultrasound techniques allow us to examine the ability of intracranial vessels to dilate in response to a pharmacological stimulus (the carbonic anhydrase inhibitor acetazolamide). We studied intracranial hemodynamics in a group of premenopausal women before and after induction of a temporary hypoestrogenic state. METHODS: We examined middle cerebral artery mean flow velocity, common and internal carotid artery pulsatility index and cerebrovascular reactivity to acetazolamide (CVR) in a group of women undergoing treatment for menstrual disorders. Volunteers underwent ultrasound examination during the follicular phase of the menstrual cycle and after completing treatment with gonadotropin releasing hormone (GnRH, goserelin 3.6 mg) administered subcutaneously every 28 days for 12 weeks. The study was conducted in a prospective, single-blind fashion and analyzed using parametric comparisons of means to examine change in intracranial hemodynamic parameters between pre- and postmenopausal states. RESULTS: Twelve premenopausal women aged 37.2+/-7 years and without overt vascular disease completed the protocol. GnRH reduced serum estrogen concentration (215.6+/-122 pg/ml vs. 82.4+/-12 pg/ml, p=0.0047) but this was not associated with a change in CVR (145+/-19% and 146+/-14% for follicular and post-GnRH studies, respectively (p=0.6). No significant changes in blood pressure, internal carotid or middle cerebral artery pulsatility or mean flow velocity were observed between time points. CONCLUSION: Neither resting cerebral hemodynamics nor reactivity of cerebral resistance vessels to a potent vasodilatory stimulus changed when the circulating concentration of estradiol was artificially decreased using a GnRH agonist. Induction of a hypoestrogenic state does not appear to influence cerebral vasodilatory capacity in the short term.     

环孢菌素A阻断人HL－60抗药性细胞于G_1期而诱导敏感细胞凋亡

进一步研究了抗三尖杉酯碱的ＨＬ－６０细胞（ＨＲ２０）抗细胞凋亡的机制及该抗性和抗药性的关系。结果表明，环孢菌素Ａ（ＣｓＡ）２０，１０μｇ·ｍｌ￣（－１）诱导ＨＬ－６０细胞发生凋亡，而阻断ＨＲ２０细胞于Ｇ＿１期，就不能诱导细胞发生凋亡。低浓度的ＣｓＡ明显增加柔红霉素在ＨＲ２０细胞内的积聚，其逆转抗药性作用与阻断细胞周期运行无关。ＣｓＡ１０μｇ·ｍｌ￣（－１）处理ＨＲ２０细胞，可引起５０ｋＤａ的蛋白质高度磷酸化。结果提示：环孢菌素Ａ阻断抗三尖杉酯碱的ＨＬ－６０细胞于Ｇ＿１期，而诱导敏感的ＨＬ－６０细胞发生凋亡，其阻断作用与抗药性无关     

Comparison of two automated multichannel haematology analysers in domestic animals

Blood samples from 33 dogs, 28 cats, 24 horses and 25 cattle were analysed in duplicate on the Coulter Counter S-Plus IV and the Baker 9000 multichannel haematology analysers. The precisions of each instrument and the correlations between the instruments were evaluated. The precisions of both systems were good but, the Baker 9000 system showed more variability between duplicate determinations for all parameters. The Baker 9000 had better precision for white blood cell count, haemoglobin concentration, and MCV. Correlations between the two instruments were excellent except for MCHC. Neither analyser reliably provided feline platelet counts and the Baker 9000 also failed to report error messages for 8 of 10 apparently false platelet counts. The Coulter instrument consistently reported higher haemoglobin concentrations and higher feline and lower canine white blood cell counts than the Baker 9000.