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Biomedical subjects

M Ortega

Publications and source records attributed to M Ortega.

At least 109 records · Page 6Linked to original sources
PubMed1987

Atrial natriuretic peptide (ANP), guanylate cyclase, and intraocular pressure in the rabbit eye.

Synthetic rat atrial natriuretic peptide (ANP) was examined for effects on guanylate-and on adenylate cyclase activity in ciliary process homogenates and for effects on intraocular pressure in the albino rabbit eye. Ciliary process guanylate cyclase was associated predominantly with the particulate fraction and was partially activated by ANP (EC50, approximately 1 nM) relative to a maximal dose of Na Nitroprusside (2 uM), whereas particulate adenylate cyclase (basal as well as forskolin-stimulated activity) showed no responses to ANP at doses up to 0.3 uM. Particulate cAMP phosphodiesterase activity was stimulated by low doses of cGMP (1-5 uM) in ciliary processes. Thus, ANP, acting via guanylate cyclase, has the potential to regulate phosphodiesterase activity and indirectly decrease cAMP levels in membranes derived from ciliary processes. Intravitreous injection of ANP (2-4 ug/eye) caused a small decrease (1-1.5 mm Hg) in intraocular pressure measured 16-24 hours after injection but the pressure had returned to normal by 40 hours. The findings demonstrate regulation of biochemical and pharmacological responses by ANP in the albino rabbit eye suggesting that this peptide may play a physiological role in secretory functions of ciliary processes.

Adenylyl Cyclases↗
PubMed1987

Effects of inorganic ions on rabbit ciliary process adenylate cyclase.

The interaction of several inorganic ions (Mn2+, Ca2+, VO3-, and F-) with adenylate cyclase in the albino rabbit ciliary process particulate fraction was studied. Effects of these substances were determined on three activity states of the enzyme (basal, Gs-protein stimulated activity via isoproterenol activation of beta-adrenergic receptors, forskolin-activated catalytic unit) in the presence of 3 mM Mg2+, 1 mM EDTA and 0.2 mM EGTA. A different pattern of effects was found for each of the four ions. Addition of Mn2+ (2 mM) increased all three responses; basal by up to ten-fold, isoproterenol and forskolin by four to five-fold. Added Ca2+ (1 mM) increased basal by two to three-fold, but inhibited isoproterenol and forskolin responses by 25-50%. Added vanadate (1-10 mM) increased basal by two to four-fold, had no effect on the isoproterenol response, but doubled the forskolin response at 3 mM. Added F- (10 mM) increased basal by 30-40-fold, decreased the isoproterenol response and potentiated the forskolin response. The response to F- which directly activates G-proteins was much greater than that of non-hydrolysable GTP analogs, which also directly activate G-proteins. The results suggest that more than one type of adenylate cyclase and/or several modes of regulation of adenylate cyclase with different ionic requirements may be present in ciliary process membranes.

Adenylyl Cyclases↗
PubMed1985

Keratosis punctata of the palmar creases.

A 44-year-old man with no family history of keratosis punctata showed, at the age of 19 years, punctiform hyperkeratotic elements confined exclusively to the flexion creases of the palms and digits. We review the literature and comment on the clinical, histologic, and therapeutic aspects of this exceptional dermatosis.

Adult↗
PubMed1984

The use of biodegradable norethisterone implants as a 6-month contraceptive system.

The effects of a 6-month contraceptive system of biodegradable norethisterone (NET) implants on the menstrual cycle, estradiol and progesterone levels, the presence of side effects, its contraceptive effectiveness, and the NET levels achieved were studied in a group of nine women. There was practically no disruption of the menstrual cycle and no important side effects. Ovulation was inhibited in four subjects, and another four subjects remained ovulatory. In all the subjects a cyclic secretion of estradiol was maintained. No pregnancies occurred. The circulatory levels of NET were very stable throughout the 6-month period of implant use.

Adult↗
PubMed1979

Myrtus communis L. phytohemagglutinins as a clarifying agent for lipemic sera.

Phytohemagglutinins from sees of Myrtus communis L., either in solution or adsorbed by glutaraldehyde-treated erythrocytes, constitute an effective system for clarification of lipemic sera. It can be used in clinical analysis to avoid the interference produced by turbidity in spectrophotometric determinations. Parameters such as glucose, bilirubin, urea, uric acid, GPT, GOT, and LDH, amongst others, can be determined without interference. The content in triglycerides of 1 ml of serum can be decreased by more than seventy per cent by treatment with 50 mg of lyophilized glutaraldehyde-treated erythrocytes saturated with Myrtus communis L. phytohemagglutinins.

Erythrocytes↗
PubMedDate not supplied

Endothelin-1 expression during early response after antigen challenge in brown-norway rats.

The objective of this study is to investigate if endothelin-1 (ET-1) gene expression changes during the early response phase following antigen challenge. We used sensitized Brown-Norway rats known to develop an early airway response after antigen challenge. After ovalbumin challenge, sensitized rats presented an early response, characterized by an increase in pulmonary pressure (209+/-14.53%,P<0. 01) and diminished functional parameters (inspiratory capacity, forced vital capacity (FVC) and expiratory flow at 75% of FVC), compared to their respective basal values. ET-1 mRNA expression was assessed by reverse transcription and polymerase chain reaction using specific primers for prepro-ET-1. A group of unsensitized rats was used as control. ET-1 expression was significantly enhanced in sensitized rats during the early response (290+/-62%,P<0.01) compared to the control group. In conclusion, antigen challenge induces an activation of ET-1 gene expression during the early response in Brown-Norway rats, suggesting a contribution of this protein to the development of bronchoconstriction.

Animals↗