Biomedical subjects

N Rojas

Publications and source records attributed to N Rojas.

15 recordsLinked to original sources

PubMed2002

Improvement of reproductive performance in crossbred zebu anestrous primiparous cows by treatment with norgestomet implants or 96 h calf removal.

The aim of the present study was to compare the effect of norgestomet implants (NI) and calf removal (CR) for 96 h on estrus induction and first service fertility in crossbred zebu primiparous anestrous cows after 120 days postpartum. A total of 152 cows in a tropical environment were allotted to three experimental groups: CR for 96 h (n = 51), NI for 9 days plus 500 IU of PMSG at implant removal (n = 51) and a control group (CG) without treatment (n = 50). Estrous rate (%) and mean interval to first estrus (days) were 50.9 and 26.3+/-6.8; 60.7 and 13.8+/-6.8; 16.0% and 61.8+/-5.9 days for groups CR, NI and CG, respectively. CR and NI were statistically similar, however, both groups were different (P < 0.01) when compared with CG. Calving interval to first service and to conception were: CR: 151.2+/-8.4 and 157.8+/-21.4; NI: 145.2+/-8.5 and 150.9+/-21.3; CG: 186.8+/-7.3 and 201.0+/-18.5. A difference (P < 0.01) was found in both intervals when comparing the CR and NI with CG, with longer intervals for cows in the CG group. First service conception rates were 61.5, 67.7 and 62.5% for groups CR, NI and CG, respectively, and were not different (P > 0.05). These results demonstrate the efficacy of NI + PMSG or temporary CR for 96 h in inducing a fertile estrus and shortening the interval to estrus and to conception in primiparous crossbred anestrous zebu cows in the tropics.

Anestrus↗

PubMed2001

Modulation of the susceptibility of human erythrocytes to snake venom myotoxic phospholipases A(2): role of negatively charged phospholipids as potential membrane binding sites.

Cerrophidion (Bothrops) godmani myotoxins I (CGMT-I) and II (CGMT-II), Asp-49 and Lys-49 phospholipases A(2) (PLA2s), which drastically differ in enzymatic activity, were devoid of direct hemolytic effects on erythrocytes (RBC) from different species despite the fact that enzymatically active CGMT-I was able to hydrolyze RBC membrane phospholipids and disrupt liposomes prepared from RBC lipids. Human RBC did not become susceptible to the toxins after treatment with neuraminidase or after altering membrane fluidity with cholesterol or sublytic concentrations of detergent. Unlike normal RBC, significant hemolysis was induced by CGMT-II and another similar Lys-49 isoform, B. asper MT-II (BAMT-II), in RBC enriched with phosphatidylserine (PS). Hemolysis was greater in RBC preincubated with pyridyldithioethylamine (PDA), a potent inhibitor of aminophospholipid transport. RBC enriched with phosphatidic acid (PA) also became susceptible to the myotoxins but was unaffected by PDA. Cells enriched with phosphatidylcholine (PC) remained resistant to the action of the toxins. BAMT-II also induced damage in black lipid membranes prepared with PS but not PC alone. When RBC binding of BAMT-II was measured by enzyme-linked immunosorbent assay, it was observed that PS- and PA-enriched erythrocytes were always able to capture more toxin than normal and PC-enriched RBC. This effect was significantly improved by PDA (in the case of PS) and it was observed either in the presence or in the absence of calcium in the medium. These data suggest that negatively charged lipids in the outer leaflet of cell membranes constitute myotoxic PLA2 binding sites. The scarcity of anionic phospholipids in the outer leaflet of RBC could explain their resistance to the action of these PLA2s.

Animals↗

PubMed2001

Substance abuse and criminal recidivism: a prospective study of adolescents.

Studies of substance abuse among delinquents have shown mixed results on criminal recidivism. The present study evaluates personality traits associated with substance abuse and recidivism among delinquent boys, and prospectively determines the extent to which these factors are predictive of criminal recidivism. 134 incarcerated boys (x = 15.9 +/- 1.1) completed the Weinberger Adjustment Inventory and the Substance Abuse Screening Inventory. Youth were prospectively followed for up to 4.5 years following release. Among incarcerated delinquents, personality traits are predictive of a positive substance abuse screen and recidivism. A trend indicating a possible interaction between personality and treatment is observed. If these findings are replicated, personality traits may play a role in predicting substance abuse as well as individual delinquent responses to treatment.

Adolescent↗

PubMed2001

Do adolescent smokers experience withdrawal effects when deprived of nicotine?

This is the first controlled prospective study of the effects of nicotine deprivation in adolescent smokers. Heart rate and subjective withdrawal symptoms were measured over an 8-hr period while participants smoked normally. Seven days later, participants were randomized to wear a 15-mg (16-hr) nicotine patch or a placebo patch for 8 hr, and they refrained from smoking during the session. Those wearing the placebo experienced a decrease in heart rate across sessions and an increase in subjective measures of nicotine withdrawal. Those wearing the active patch also reported significant increases for some subjective symptoms. Expectancy effects were also observed. The findings indicate that adolescent smokers experience subjective and objective changes when deprived of nicotine. As in previous research with adults, expectancies concerning the effects of nicotine replacement also influenced perceptions of withdrawal.

Administration, Cutaneous↗

PubMed2001

Comparison of the antibody response in adult cattle against different epitopes of Brucella abortus lipopolysaccharide.

The comparison of serological responses in a sample of adult, vaccinated and held-infected bovines with Brucella abortus is reported. Indirect enzyme immunoassav (EIA) titration curves and Western blotting tests for smooth-type lipopolysaccharide (S-LPS), rough-type LPS (R-LPS) and lipid A were performed. In the initial screening of sera, an overall prevalence of 20.5% was found, which corresponds to a country with a high incidence of brucellosis. End-point EIA titres against LPS antigens from vaccinated and field-infected cows were not significantly different. However, the absorbance values in the titration curves were significantly higher for S-LPS as compared with the other antigens. A high correlation coefficient (r = 0.933) was obtained when the titres to R-LPS versus lipid A were compared. Western blotting reactions of vaccinated and held-infected animals were indistinguishable. S-LPS, R-LPS and lipid A epitopes were recognized in a heterogeneous manner. In general, the number of bovines that reacted against LPS was higher in the field-infected group, with a stronger binding to S-LPS. Based on our observations, the vaccinated and field-infected bovines are capable of producing similar antibody responses to the Brucella main outer surface antigen, LPS. It should be emphasized that the humoral response of cattle to Brucella LPS contains significant amounts of antibodies to other antigenic moieties of this important surface molecule, which may contribute to the immunity to brucellosis.

Animals↗

PubMed1999

A polyisoprenylated benzophenone from Cuban propolis.

A novel polyisoprenylated benzophenone (1) has been isolated from an ethanol extract of Cuban propolis. Its structure has been determined using high-field 2D NMR techniques. Compound 1 showed significant antimicrobial and antifungal activity against a variety of bacteria and yeasts.

Anti-Bacterial Agents↗

PubMed1999

[In vitro immunosuppressive effect of low density lipoproteins].

BACKGROUND: Immune cells participate in the formation of atheromatous plate, however little is known about the effects of native or oxidatively modified lipoproteins on these cells. AIM: To study the effects of lipoproteins on in vitro mononuclear cell proliferation. MATERIAL AND METHODS: Peripheral blood mononuclear cells were obtained from 10 patients with type 2 diabetes mellitus (aged 52 +/- 9 years old with a disease duration of 8.2 +/- 5.7 years and a mean glycosilated hemoglobin of 9.3 +/- 2.2%) and 10 non diabetic healthy controls (aged 50.3 +/- 7.1 years old). These were stimulated with phytohemagglutinin (PHA) alone or in the presence of native LDLS, malondialdehyde modified LDLs or glycated LDLs. Proliferation was measured as 3H-thymidine incorporation and expressed as Stimulation Index (SI). RESULTS: SI of patients and healthy subjects, after PHA stimulation were similar: (57.5 +/- 29.8 and 61.1 +/- 23.5) respectively LDLs did not induce proliferation in neither group. Native LDLs produced a 98% inhibition of PHA induced proliferation. Malondialdehyde modified and glycated LDLs caused a 50% inhibition. The suppressive effect was maintained when lipoproteins were incorporated to culture media 60 min prior or after PHA stimulation. CONCLUSIONS: Lipoproteins inhibit in vitro PHA induced peripheral blood mononuclear cell proliferation both in diabetic and in non diabetic subjects.

Adult↗

PubMed1997

[Immune response against modified low-density lipoproteins in patients with non-insulin-dependent diabetes mellitus].

BACKGROUND: Diabetes mellitus is a risk factor for atherosclerosis. Low density lipoproteins are considered a key factor in the formation of atheroma and the immune system has an important contribution to this process. AIM: To quantify the immune response against modified low density lipoproteins in patients with non insulin dependent diabetes mellitus. MATERIAL AND METHODS: LDLs obtained from blood of healthy subjects, were glycated or altered with malondialdehyde and used as antigens. Serum autoantibodies against these LDLs were measured by ELISA in 22 patients with non insulin dependent diabetes mellitus aged 46 to 67 years old and 13 healthy controls aged 41 to 65 years old. Basal and LDL stimulated tumor necrosis factor a production in vitro, by peripheral leukocytes of diabetics and controls was also measured. RESULTS: The ratio of glycated LDL/native LDL antibodies was higher in diabetics than in controls (9.37 +/- 2.72 and 0.41 +/- 0.11 respectively p < 0.05) and the ratio of MDA modified LDL/native LDL antibodies was not significantly different (8.64 +/- 3.83 and 2.14 +/- 1.26 respectively, NS). Tumor necrosis or production by leukocytes was higher in diabetics than in controls in basal conditions (53.3 +/- 15.3 and 26.9 +/- 14.7 arbitrary units (a.u.) respectively), when stimulated with native LDL (46.5 +/- 5 and 24.3 +/- 9.4 a.u. respectively), when stimulated with malondialdehyde modified LDL (50 +/- 16.2 and 24.4 +/- 7.7 a.u. respectively) or when stimulated with glycated LDL (38.3 +/- 8.8 and 14.4 +/- 7.5 a.u. respectively). CONCLUSIONS: Diabetic patients have an enhanced immune response against low density lipoproteins, factor that could contribute to the accelerated atherogenesis of this disease.

Adult↗

PubMed1995

Heterogeneity of Brucella abortus lipopolysaccharides.

This work demonstrates that Brucella lipopolysaccharide (LPS) preparations are a family of related molecules which display heterogeneity not only at the level of the O polysaccharide, but also at the core oligosaccharide and the lipid A. Sodium dodecyl sulphate/polyacrylamide gel electrophoresis and Western blotting showed that LPS from Brucella strains displayed molecular weight and antigenic heterogeneity. Smooth-type LPS (S-LPS) from B. abortus demonstrated three broad high-molecular-weight bands corresponding to S-LPS, and a low-molecular-weight band corresponding to O antigen lacking rough-type LPS (R-LPS). B. abortus R-LPS displayed four bands in increasing proportions as the molecular weight diminished. Immunodetection on high-performance thin-layer chromatography (HPTLC) with monoclonal antibodies (mAb) showed that R-LPS displayed three diffuse bands. HPTLC of O polysaccharide revealed two fast migrating bands recognized by antibodies. Gel chromatography and HPTLC analysis of core oligosaccharides from R-LPS demonstrated molecular weight heterogeneity as well as heterogeneous banding pattern, with no obvious correspondence between the two profiles. Immunodetection of lipid A on HPTLC plates revealed two major and three minor bands. Reactivity with mAbs suggested that regardless of the lipid A heterogeneity the basic structure of lipid A backbone is maintained.

Brucella abortus↗

PubMed1994

Immunochemical identification of Brucella abortus lipopolysaccharide epitopes.

Sera from Brucella abortus-infected and -vaccinated bovines recognized four lipopolysaccharide (LPS) determinants: two in the O-polysaccharide (A and C), one in the core oligosaccharide from rough Brucella LPS (R), and one in lipid A (LA). From 46 different hybridomas secreting monoclonal antibodies (MAbs) against various LPS moieties, 9 different specificities were identified. Two epitopes, A and C/Y, were present in the O-polysaccharide. Two epitopes were found in the core oligosaccharide (R1 and R2) of rough Brucella LPS. MAbs against R1 and R2 epitopes reacted against LPS from different rough Brucella species; however, MAbs directed to the R2 epitope also reacted against enterobacterial LPS from deep rough mutants. Three epitopes (LA1, LA2, and LA3) were located in the lipid A backbone. Different sets of MAbs recognized two epitopes in the lipid A-associated outer membrane protein (LAOmp3-1 and LAOmp3-2). LPS preparations from smooth brucellae had small amounts of rough-type LPS. Although LPS from rough brucellae did not show smooth-type LPS in western blots (immunoblots), two hybridomas generated from mice immunized with rough B. abortus produced antibodies against smooth B. abortus LPS. Results are discussed in relation to the structure and function of B. abortus LPS and to previous findings on the epitopic density of the molecule.

Animals↗

PubMed1992

[Persistent microalbuminuria in insulin-dependent diabetics and cardiovascular risk factors].

A possible association of cardiovascular risk factors and early diabetic nephropathy was investigated in 32 patients. Microalbuminuria (radioimmunoassay), total and HDL cholesterol and triglycerides (enzymatic methods), glycosylated hemoglobin (colorimetric methods), Apo A1 and B (immunonephelometric) and LDL were measured. Microalbuminuria was present in 28% of patients. Compared to subjects with no microalbuminuria they had increased levels of cholesterol (200.2 +/- 13.5 (SE) vs 168.6 +/- 9.4 mg/dl, p < 0.025) and LDL cholesterol (171.9 +/- 14.1 vs 137.4 +/- 9.1 mg/dl, p < 0.025). Systolic blood pressure was also higher in patients with microalbuminuria (127.8 +/- 3.9 vs 114.5 +/- 2.8 mmHg, p < 0.01). Microalbuminuria was correlated to the level of diastolic blood pressure (r = 0.74, p < 0.025). Thus, persistent microalbuminuria in insulin dependent diabetic patients is associated to cardiovascular risk factors which may explain the increased cardiovascular morbidity and mortality in these patients.

Adolescent↗

PubMed1989

[Tuberculosis and diabetes mellitus: a longitudinal-retrospective study in a teaching hospital].

We analyzed 1529 diabetic patients seen between 1959 and 1982 at a teaching hospital in Concepción, Chile. 116 of them were insulin dependent diabetics. Gestational diabetes was excluded. The 10 year actuarial risk of acquiring tuberculosis was 24.2% for insulin-dependent diabetics and 4.8% for the rest (p less than 0.001). The risk of the diabetic population as a whole was 5.9% compared to 0.8% for the population at large. Thus, diabetics are a high risk group for tuberculosis, especially insulin-dependent patients whose risk is about 38 times higher than the general population under 40 years of age.

Actuarial Analysis↗

PubMed1988

[Spermatogonia types in tepezcuintle (Cuniculus paca). Ultrastructural study].

Ultrastructural studies of different types of spermatogonia by thin section techniques and transmission electron microscopy showed that Cuniculus paca has two types of Type A spermatogonia (A-O and A-1). Samples were taken at different stages of the cycle in the seminiferous tubule epithelium presented a similar pattern as those of other rodents. Type B spermatogonia are similar to those of the rat, the difference being that the heterochromatic zones are larger and more numerous. Both characteristics differentiate them from preleptotenic spermatocytes.

Animals↗

PubMed1971

[Not Available].

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History, Early Modern 1451-1600↗

PubMedDate not supplied

[Significance of human leptospirosis in Mexico. Detection of Leptospira antibodies in a blood donor population].

The presence of specific serum antibodies has been used as a diagnostic test for human leptospirosis. The presence of these antibodies in humans is indicative of an active natural infection. Its detection after exposure denotes the presence of immunity. Serum samples from 206 adult blood donors were analyzed with a microscopic agglutination assay against 7 serovars of Leptospira interrogans. A total of 7% were positive with the following serovar distribution; shermani 53%, canicola 33%, pyrogens 20%, pomona 13% and icterohaemorrhagiae 6%. The highest frequency of seropositivity was found in the 20 year to 39 age group. These results in asymptomatic individuals show that leptospirosis is a frequent zoonosis in Mexico.

Adolescent↗