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Biomedical subjects

M Rojas

Publications and source records attributed to M Rojas.

At least 163 records · Page 9Linked to original sources
PubMed1986

In vivo formation and persistence of DNA adducts in mouse and rat skin exposed to (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene and (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene.

The in vivo DNA adduct formation of (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene (BPD) and (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha-epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene (anti-BPDE) were compared and the persistence and disappearance of the adducts in both mouse and rat epidermis determined. BPD (100 nmol/mouse in 150 microliter acetone and 200 nmol/rat in 300 microliter acetone) and anti-BPDE (77 nmol/mouse in 150 microliter tetrahydrofuran and 154 nmol/rat in 300 microliter tetrahydrofuran) were topically applied to 50-day-old male Swiss mice and 35-day-old Wistar rats. To improve the identification of the DNA adducts formed, an acid hydrolysis technique was used to convert the BPD- and anti-BPDE-deoxyribonucleoside adducts formed in mouse and rat skin to BP tetrols. The modified deoxyribonucleosides and BP tetrols obtained by hydrolysis of adducts were isolated by reverse-phase h.p.l.c. At approximately similar doses per unit area of treated skin, the initial total binding of these compounds to epidermal DNA and the level of modified deoxyribonucleosides was approximately 6-fold lower in rat skin epidermis than in mouse skin epidermis. Similar ratios of (+/-)-anti-BPDE-deoxyguanosine (dGuo) to (+/-)-syn-BPDE-dGuo adducts (5.7 and 6.1, determined by h.p.l.c. analysis of BP tetrols obtained by hydrolysis of modified dGuo) were found in both mouse and rat epidermis a short time (6 h) after topical application of (+/-)-trans-BPD. Three hours after topical application of (+/-)-anti-BPDE, the ratios of BP-7,10/8,9-tetrol to 7/8,9,10-tetrol were 9:1 in mouse epidermal DNA and 6:1 in rat epidermal DNA. One and three weeks after application of these two compounds, only (+)-anti-BPDE-dGuo was detected in mouse epidermis; 2 and 0.2% of the initial (+)-anti-BPDE-dGuo level was found to persist in the epidermal DNA from BPD- and anti-BPDE-treated mice respectively. No DNA adducts were detected in rat epidermis 3 weeks after BPD and anti-BPDE treatment. Thus, 3 weeks after topical application of BPD and anti-BPDE to mouse and rat skin, the DNA adducts completely disappeared from rat epidermis while they persisted in mouse epidermis. The results suggest that: the persistence of (+)-anti-BPDE-dGuo may be related to carcinogenesis in mouse epidermis by BPD and anti-BPDE; the complete disappearance of the anti-BPDE-dGuo adduct may also account in part for the relative resistance of tissue from this species to the carcinogenic action of benzo[a]pyrene.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1986

Antibodies to basement membrane protein nidogen in Chagas' disease and American cutaneous leishmaniasis.

About 50 to 70% of sera from patients with American cutaneous leishmaniasis and chronic Chagas' disease possessed antibodies which reacted in enzyme and radioimmunoassays with nidogen obtained from a tumor basement membrane. The antibodies were of the immunoglobulin M and G classes in acute American cutaneous leishmaniasis but mainly of the immunoglobulin G class in chronic Chagas' disease. Similar antibodies could not be detected in patients suffering from a variety of other infectious or inflammatory diseases when compared with healthy control groups. Inhibition and immunoadsorption studies indicated a close relationship of epitopes recognized by patients' antibodies on nidogen and on another basement membrane protein, laminin. Since rabbit antisera to both proteins do not cross-react, a special nature of the epitopes involved in the reaction with patient sera is suggested. Similar epitopes may exist on various forms of Leishmania or Trypanosoma protozoa.

Antibodies↗
PubMed1986

Effects of intracisternal glucose or insulin injections on glucose homeostasis in cat.

The injection of glucose (100 mg) into the cisterna magna of intact anesthetized cats elicited immediate glycosuria and natriuresis without significant changes in blood glucose concentration. Immunoreactive insulin (IRI) increased 140% in plasma, and Na+ concentration decreased in cerebrospinal fluid (CSF). After kidney denervation there was a significant decrease in glucose and Na+ concentrations in urine. Control injections with mannitol did not elicit changes in the studied parameters. Abdominal vagotomy abolished the rise in IRI levels and the decrease in Na+ concentration in CSF. Vagotomy or adrenalectomy also attenuated the glycosuria and the rise in urine Na+ concentration. The intracisternal injection of insulin (0.5 U/kg) caused first, a decrease in glucose concentration in CSF and afterwards a longer latency in plasma. Again, these responses were significantly attenuated when insulin was administered in vagotomized cats. These experiments indicate that the nervous system, through the vagi, adrenal glands, and kidneys, plays an important role in glucose homeostasis after increasing glucose or insulin levels in the CSF above physiologic concentrations. The results obtained with a denervated kidney confirm the participation of nervous system in the effector mechanism that brings the sugar and Na+ into the urine. Evidence is presented for an interrelationship between glucose and Na+ concentrations in blood, urine, and CSF.

Adrenalectomy↗
PubMed1984

The lack of transformation activity of 9-hydroxybenzo[a]pyrene related to the absence of modified deoxyribonucleosides in DNA of C3H/10T1/2 cells.

Sephadex LH-20 chromatography of DNA digests of C3H/10T1/2 cells treated with [3H]9-hydroxybenzo[a]pyrene (9-OH-BaP) and [14C]BaP-7,8-diol showed: (i) the presence only of uncharacterized 3H radioactivity eluted in the early portion of the gradient; [3H]9-OH-BaP-4,5-oxide-modified deoxyribonucleosides were not observed. (ii) The total amount of [14C]-labelled radioactivity corresponded to nucleoside moieties which were modified by anti- and syn-benzo[a]pyrene diol-epoxide. The absence of nucleosides modified by 9-OH-BaP-4,5-oxide in C3H/10T1/2 cells observed in this study may account in part for the relative resistance of these cells to the mutagenic and transforming action of 9-OH-BaP.

Animals↗
PubMed1984

Antibodies to laminin in American cutaneous leishmaniasis.

We found that serum samples from patients with different clinical forms of American cutaneous leishmaniasis (ACL) contained immunoglobulin G and immunoglobulin M antibodies which reacted with laminin but not with various other purified connective tissue components, such as collagen types I, III, IV, and V and fibronectin. Eighty-one percent of ACL patients had high antilaminin antibody levels, with a relationship existing between ACL ulcers and antibody levels. This was not, however, the case with patients having treated and healed ACL ulcers; only 34% of these patients had elevated antilaminin antibodies. Eighty-four percent of chronic Chagas' disease patients were also found to contain antilaminin antibodies that were limited to the immunoglobulin G class, but these were not detected in patients suffering from any of 11 other infectious diseases.

Adolescent↗
PubMed1984

Scanning electron microscopy of the final phase of the life cycle of Trypanosoma cruzi in the insect vector.

Scanning electron micrographs showed that both epimastigotes and metacyclic trypomastigotes of Trypanosoma cruzi are attached by the flagellum to the epithelium of the rectal gland of Triatoma dimidiata. The flagellates tended to cover the surface of the gland and there was a marked predominance of epimastigotes with a round posterior end. Reproduction and metacyclogenesis seem to take place in situ, the latter apparently by twisting and elongation of the epimastigotes. Metatrypomastigotes remain attached for some time, probably by a weaker mechanism which easily allows them to loosen, facilitating expulsion with the urine or feces.

Animals↗
PubMed1983

The persistence of benzo[a]pyrene diol-epoxide deoxyguanosine adduct in mouse skin and its disappearance in rat skin.

Male Swiss mice and Wistar rats, susceptible and resistant, respectively, to the carcinogenic effects of benzo[a]pyrene, were treated topically with 250 nmol/mouse and 1000 nmol/rat of tritium labelled benzo[a]pyrene (BaP). The initial formation of BaP diol-epoxide deoxyguanosine adduct was approximately similar in the skin epidermis of the two species. After 3 weeks, the persistence of some 6.5% of initial BaP diol-epoxide deoxyguanosine was observed in mouse skin DNA, while this adduct was completely removed from DNA of rat skin. The total excision of BaP diol-epoxide deoxy-guanosine adduct in rat epidermis may contribute in part for the relative resistance of rat skin to the carcinogenic actions of BaP.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1981

Sulfatide role in the sodium pump.

Sodium efflux was studied in 22Na-loaded red blood cells in the presence of arylsulfatase, an enzyme that specifically hydrolyzes sulfatide. Sodium efflux was inhibited in proportion to the amount of arylsulfatase present. Maximum inhibition was almost as high as the efflux obtained in medium with K+ absent. At maximum inhibition 83.2% of the sulfatide content of the fragmented red blood cell membranes was hydrolyzed and ouabain-sensitive (Na+ + K+)-ATPase activity was inhibited by 100%. Sodium efflux, sulfatide content, and (Na+ + K+)-ATPase activity were unaffected with arylsulfatase in the presence of a high concentration of sulfatide. These results indicate that sulfatide plays a specific role in sodium and potassium ion transport. They also suggest that most sulfatide is localized externally in the red blood cell membrane.

Animals↗
PubMed1981

[Digestibility and protein quality of quinua: comparative study of quinua (Chenopodium Quinoa) seed and flour in children].

Based on the hypothesis that the digestibility of quinua seed is the limiting factor in the utilization of nutrients from this staple, two quinua-based diets were prepared using quinua seeds and quinua flour. Theses diets were offered to children recovering from malnutrition. The digestibility and protein quality of the quinua diets were compared to those of a casein control diet by analyzing the children's metabolic balance. Results showed that digestibility of the quinua diets were compared to those of a casein control diet by analyzing the children's metabolic balance. Results showed that digestibility of the quinua seed is the limiting factor in the protein and energy utilization, and that milling improves significantly the digestibility of fat and carbohydrates. Findings also confirmed that the protein quality of quinua seeds is adequate for human consumption.

Body Weight↗
PubMed1979

[In vitro inhibition of tRNA methyltransferases by queen substance, a pheromone of queen honeybees].

The Queen Substance 1, a pheromone of the queen Honeybee Apis mellifica is an in vitro inhibitor of E. coli B tRNA methylations. This activity is not specific of the methylase source, as inhibitions have been observed with preparations from queen honeybee ovaries, Rat liver or a Mouse plasmocytoma 1-adenine methylase. These results, together with preceding ones concerning t, t-farnesyl-acetone 3, are discussed.

Animals↗
PubMed1979

Effect of hypophysectomy upon renal kallikrein-kinin system in rats.

It is confirmed that urinary kallikrein is significantly and persistently decreased in totally hypophysectomized rats. In addition, kallikrein activity in the kidneys in these animals is significantly reduced (p less than .001) as compared to partially hypophysectomized and sham-operated rats. The administration of 125 mU of ACTH twice a day for 2 months, did not modify urinary kallikrein excretion. Negative effects were also obtained in subsequent periods, by injection of 10 microgram corticosterone and 10 microgram aldosterone, twice a day for 9 and 6 days, respectively. The administration of rat pituitary anterior lobe homogenates, freshly prepared, increased significantly urinary kallikrein level in hypophysectomized rats.

Adrenocorticotropic Hormone↗
PubMed1978

Effects of prostaglandin E2 and prostaglandin F2alpha upon urinary kallikrein excretion in rats.

1. In normally hydrated rats prostaglandin F2alpha (PGF2alpha) in doses of 5 microgram/100 g body weight given subcutaneously every 2 h (three times) induced a significant increase in urinary kallikrein activity, and in sodium, potassium and water excretion for 8 h after the first injection. In moderately hyperhydrated rats loaded 2.5% of body wt. with 0.5% NaCl solution, PGF2alpha produced similar changes in kallikrein activity and electrolyte excretion. 2. In normally hydrated rats prostaglandin E2 (PGE2) in the same conditions and doses as in 1 had no effect on kallikrein activity, showing a tendency to decrease potassium and water excretion. 3. PGE2 in doses of 5, 12.5 and 25 microgram/100 g body wt. in overhydrated rats given 2.5% and 0.5% NaCl and 5% of tap water/100 g body wt. 1 h later, significantly increased kallikrein activity in the urine collected for 120 min after the injections. A significant decrease in potassium and water excretion was observed with the highest dose. 4. PGF2alpha, had no effect on kallikrein activity in overhydrated rats, but an increase in sodium and a decrease in potassium excretion was seen at the highest dose. 5. The different actions of PGE2 and PGF2alpha may be part of a regulatory mechanism associated with the kallikrein-kinin system which contributes maintainance of extracellular fluid homeostasis.

Animals↗
PubMed1977

[Inhibition of biological methylations by t,t-farnesylacetone, a constituant of the androgenic gland of the male crab, Carcinus maenas].

t, t-farnesylacetone 1 and hexahydrofarnesylacetone 2 have been previously identified in extracts from the androgenic gland of the male Crab Carcinus maenas. These compounds inhibit in vitro the methylation of E. coli B tRNA and of Calf thymus histones with S-adenosylmethionine methyl-14C as methyl donor and methylases from Crab testis. Rat liver or a 1-adenine methylase from a Mouse plasmocytoma (1 is approximately 200 times more active than 2).

Animals↗