The effects of inhibition of the sarcolemmal Ca-ATPase on systolic calcium fluxes and intracellular calcium concentration in rat ventricular myocytes

 The effects of carboxyeosin, an inhibitor of the sarcolemmal Ca-ATPase, were studied on intracellular Ca and membrane currents in isolated rat ventricular myocytes. In the absence of carboxyeosin, 150-ms-duration depolarizing pulses from –40 to 0 mV resulted in an L-type Ca current on depolarization and a Na-Ca exchange ”tail” current on repolarization. The calculated entry of Ca on the L-type current was 1.3 times greater than the efflux via the Na-Ca exchange. The addition of carboxyeosin (20 μM) resulted in either an increase of the Na-Ca exchange current or a decrease of the L-type Ca current such that the Ca entry and efflux were exactly equal. These results suggest that, under control conditions, a carboxyeosin-sensitive Ca-ATPase contributes about 24% of the total Ca efflux from the cell and, therefore, that the sarcolemmal Ca-ATPase has a significant role in regulation of sarcolemmal Ca fluxes. Received: 9 December 1998 / Received after revision: 1 February 1999 / Accepted: 2 February 1999     

Induction of food intake by a noradrenergic system using clonidine and fusaric acid in the neonatal chick

To clarify noradrenergic systems on food intake of the neonatal chicks, we examined the effects of i.c.v injection of clonidine (CLON), an alpha2-receptor agonist, and fusaric (5-butylpicolinic) acid (FA), a dopamine (DA)-beta-hydroxylase (DBH) inhibitor. Although a high dose (250 ng) of CLON induced a narcoleptic response and reduced food intake, food intake at 30 min post-injection was enhanced by lower doses (25 and 50 ng) of CLON. Central administration of FA (25, 50 and 100 microg) increased food intake in a dose-dependent fashion. It is suggested that feeding behavior is stimulated by low levels of CLON and decreased by further production of norepinephrine (NE), and FA may play the disturbance of sleeping and then enhance food intake.     

Increased expression of prion protein is associated with changes in dopamine metabolism and MAO activity in PC12 cells

Prion diseases of humans and animals occur following infection with infectious agents containing PrP(Sc) or in situations in which there is a mutation of the prion protein (PrP) gene. The cellular prion protein (PrP(C)) is a sialoglycoprotein that is expressed predominantly in neurons. PrP(C) is converted into a pathogenic form of PrP (PrP(Sc)), which is distinguishable from PrP(C) by its relative resistance to protease digestion. A number of postulates have been advanced for the function of normal PrP (PrP(C)), but this issue has not been resolved. To investigate the function(s) of PrP(C), we established clonal PC12 cell lines, which have elevated PrP(C) expression. The results show that there were alterations in dopamine metabolism and in monoamine oxidase (MAO) activity in transfected PC12 cells that overexpress PrP(C). There was an increase in concentration of DOPAC, a metabolite of dopamine, and in MAO activity in cells overexpressing PrP(C). MAO is involved in oxidative degradation of dopamine (DA). Our data suggest that PrP(C) plays a role in DA metabolism by regulating MAO activity.     

Progression of burn wound depth by systemical application of a vasoconstrictor: an experimental study with a new rabbit model

The final depth of a necrosis resulting from burn trauma is determined within 3 days. The zone of stasis has the potential for complete regeneration or there may be ischemic influences that lead to necrosis. In our model, we examined the dermal influence of vasoconstrictors with reference to the development of burn necrosis. On the backs of New Zealand white rabbits (4.0–4.5 kg) standardized lesions were made with a heated aluminum stamp at 80°C, 14 s in duration.

The lesions were intradermal, whereby the border zone of the coagulated tissue was found in the middle two quarters of the dermis in 100% of untreated animals after 72 h. For dermal vasoconstriction epinephrine in a dose of 0.5 μg/kg/min was used.

There were two groups of seven animals each. One group received epinephrine and the dosage was dependent on the clinical state of the animal. Several cycles were administered within a 3-day period. The reduction of skin perfusion was documented by Laser–Doppler-flowmetry. After 3 days, the skin with the lesions was excised and using a hematoxylin dye, a histological examination followed. The parameter used to determine the efficacy was the thickness of the uncoagulated part of the excised dermis.

Over a period of 48 h, an average of 2.3 epinephrine cycles of average of 88 min per animal in duration resulted in an average reduction of skin diffusion of 41%. The uncoagulated part of the dermis in the epinephrine group was 28.6% average; in the control group, this was 43.5%. The statistical analysis revealed significant differences with a p-value of 0.0312 (significant, when value is less than 0.05). The test results indicate that temporary reduction of skin perfusion through external administration of vasocontrictors may lead to progression of burn necrosis in our animal model.

Clinically, this result indicates that for patients with burn injuries and systemic inflammatory response syndrome who have insufficient volume therapy, the administration of vasocontrictors may produce similar results in the injured area.     

Facilitators and barriers to use of the female condom: qualitative interviews with women of diverse ethnicity

Women in the United States, particularly African-Americans and Hispanics, are at increased risk for HIV. The female condom now offers women a potentially important option for HIV prevention, yet few efforts have been made to increase its use. To elucidate strategies to promote the use of the female condom, we conducted in-depth interviews with 62 women recruited from the four major racial/ethnic groups of the U.S. (African-American, Asian-American, Hispanic, and white). Subject recruitment took place at a family planning clinic in San Francisco during 1996-97. We identified four major types of facilitators and barriers to use of the female condom: mechanical, psychosexual, interpersonal, and situational. Specifically, the mechanical facilitators and barriers included positive and negative aspects of the device, and difficulty with insertion. The psychosexual factors were female empowerment, more options for contraception and disease prevention, discomfort with vaginal insertion, and condom use norms. The interpersonal factors included: enhanced communication, relationship status, partner preferences, and partner objections. Finally, the situations that made women disinclined to use the device were: no access to the female condom when having sex and using other forms of contraceptives. The implications of these findings for HIV prevention and future research are discussed.     

Effect of topically applied 0.1% dexamethasone on endothelial healing and aqueous composition during the repair process of rabbit corneal alkali wounds

PURPOSE: The effects of topical dexamethasone on the endothelial healing and the change of aqueous compositions were investigated during the repair process of alkali-wounded rabbit cornea. METHODS: A central corneal alkali wound was produced by a 60 sec application of a 5.5 mm round filter paper soaked in 1N NaOH onto one eye of each rabbit. The eyes subsequently were treated topically with either 0.1% dexamethasone or a balanced salt solution (BSS) 4 times per day for 8 weeks. Endothelial wound morphometry was performed after alizarin red and trypan blue staining. The concentrations of ascorbic acid, glucose, and the ions, Na+, K+, Ca2+ and Mg2+, were measured in the aqueous humor. RESULTS: Endothelial healing in control (alkali-wounded but not treated with dexamethasone) corneas showed a biphasic pattern of healing: an initial short-term healing for the first week and then a late long-term healing following the secondary endothelial breakdown. Topical administration of 0.1% dexamethasone deterred endothelial healing during the early period and prevented the secondary endothelial breakdown. However, the total repair process of endothelium was accelerated by the dexamethasone-treatment. Among the various components of the aqueous humor examined, ascorbic acid seemed the most sensitive to change caused by the alkali injury and dexamethasone treatment. CONCLUSIONS: The present data indicate that dexamethasone may have a therapeutic potential in the management of endothelial healing after corneal alkali injury.