Biomedical subjects

J C Arce

Publications and source records attributed to J C Arce.

9 recordsLinked to original sources

PubMed2001

Large nondipole effects in the angular distributions of K-shell photoelectrons from molecular nitrogen.

Measurements of angular distributions of K-shell electrons photoejected from molecular nitrogen are reported which reveal large deviations at relatively low photon energies (Planck's omega < or = 500 eV) from emission patterns anticipated from the dipole approximation to interactions between radiation and matter. A concomitant theoretical analysis incorporating the effects of electromagnetic retardation attributes the observed large nondipole behaviors in N2 to bond-length-dependent terms in the E1 [multiply sign in circle] (E2,M1) photoelectron emission amplitudes which are indicative of a potentially universal nondipole behavior in molecular photoionization.

Journal Article↗

PubMed2000

Effects of continuous estrogen and estrogen-progestin replacement regimens on cardiovascular risk markers in postmenopausal women.

OBJECTIVE: To evaluate the influence of 2 continuous combined estrogen-progestin replacement products, compared with unopposed estrogen and placebo, on cardiovascular risk markers in postmenopausal women in a randomized, double-blind, placebo-controlled trial. METHODS: Two hundred seventy healthy postmenopausal women were randomly assigned to 1 of 4 treatment groups: placebo, unopposed 17-beta estradiol (1 mg), 1 mg of 17-beta estradiol with 0.25 mg of norethindrone acetate, or 1 mg of 17-beta estradiol with 0.5 mg of norethindrone acetate. The primary outcome variable was change from baseline in low-density lipoprotein cholesterol concentration. Additional outcome variables included changes in other serum lipid levels, hemostatic variables, and indicators of carbohydrate metabolism. RESULTS: The low-density lipoprotein cholesterol level was reduced to a similar degree in all groups receiving active treatment (10%-14% from baseline; P =.001 for 17-beta estradiol with 0.5 mg of norethindrone acetate, P =.004 for 17-beta estradiol with 0.25 mg of norethindrone acetate, and P =. 001 for 1 mg of 17-beta estradiol vs placebo). Compared with unopposed 17-beta estradiol, 17-beta estradiol with 0.5 mg of norethindrone acetate enhanced the reductions in total cholesterol and apolipoprotein B levels (P<.01 vs 17-beta estradiol). 17-beta Estradiol plus norethindrone blunted or reversed the increases in levels of high-density lipoprotein cholesterol, apolipoprotein A-I, and triglycerides produced by 17-beta estradiol alone. Effects of 17-beta estradiol plus norethindrone on hemostatic variables were similar to those of 17-beta estradiol except for factor VII activity, which was significantly reduced with 17-beta estradiol combined with 0.25 mg (P<.01) and 0.5 mg (P<.05) of norethindrone acetate. 17-beta Estradiol plus norethindrone appeared to blunt reductions in C-peptide and insulin levels produced by unopposed 17-beta estradiol but did not elevate these values compared with placebo. CONCLUSIONS: 17-beta Estradiol plus norethindrone produced favorable changes in most cardiovascular risk markers evaluated and has a profile distinct from that of unopposed 17-beta estradiol. The impact of these differences on cardiovascular events warrants investigation. Arch Intern Med. 2000;160:3315-3325.

Aged↗

PubMed2000

A combination of low doses of 17 beta-estradiol and norethisterone acetate prevents bone loss and normalizes bone turnover in postmenopausal women.

The effects of 17 beta-estradiol (E2) 1 mg combined with low doses of norethisterone acetate (NETA) on postmenopausal bone loss and turnover were investigated in a 2-year, randomized, double-masked, placebo-controlled trial. A total of 135 postmenopausal women with a lumbar spine bone mineral density (BMD) T-score between -2 and +2 were randomized to daily treatment with an oral tablet of either placebo, E2 1 mg/NETA 0.25 mg, or E2 1 mg/NETA 0.5 mg. Significant (p < 0.001) increases in BMD at the lumbar spine (L1-4) were observed with E2 1 mg/NETA 0.25 mg (5.2%) and E2 1 mg/NETA 0.5 mg (5.4%) compared with placebo (-0.9%). The total hip BMD increased significantly in the E2 1 mg/NETA 0.25 mg (3.1%) and E2 1 mg/NETA 0.5 mg groups (3.3%) compared with placebo. At the femoral trochanter, the increase in BMD in the E2 1 mg/NETA 0.5 mg group (6.3%) was significantly different from the placebo group (0.8%), while that in the E2 1 mg/NETA 0.25 mg group (3.3%) was not. No statistical differences were found between the active groups and placebo for the change in BMD at the femoral neck. Significant increases in BMD at the distal radius and total body were found for both E2 1 mg/NETA 0.25 mg (0.9% and 2.5%, respectively) and E2 1 mg/NETA 0.5 mg (2.1% and 3.0%, respectively) compared with placebo (-0.7% and 0.4%, respectively). At the end of the treatment, urinary pyridinoline type I collagen C-telopeptide had decreased by 65% and 60% in the E2 1 mg/NETA 0.25 mg and E2 1 mg/NETA 0.5 mg groups, respectively, while the mean serum concentrations of osteocalcin had decreased by 39% and 34%, bone-specific alkaline phosphatase by 32% and 29%, and C-terminal propeptide of type I collagen by 21% and 19% had decreased by 34-39%, 29-32%, and 19-21% in the E2 1 mg/NETA 0.25 mg and E2 1 mg/NETA 0.25 mg groups, respectively. In conclusion, combinations of E2 1 mg and NETA 0.25 or 0.5 mg prevent bone loss in postmenopausal women at the lumbar spine, hip, distal radius and total body, and normalize bone turnover.

Aged↗

PubMed1999

Uterine bleeding in postmenopausal women on continuous therapy with estradiol and norethindrone acetate. Endometrium Study Group.

OBJECTIVE: To investigate the incidence of uterine bleeding during 12 months of treatment with 17beta-estradiol (E2) 1 mg, unopposed or in combination with three doses of norethindrone acetate. METHODS: This study was a prospective, double-masked, randomized, multicenter trial. A total of 1176 healthy postmenopausal women age 45 years and older without evidence of endometrial abnormalities were randomly assigned to receive either unopposed E2 1 mg, or continuous-combined formulations of E2 1 mg and norethindrone acetate 0.1 mg, 0.25 mg, or 0.5 mg. Any spotting or bleeding episodes during the treatment period were recorded in a daily diary and reported by weekly telephone calls. RESULTS: The incidence of bleeding was low in the combination groups, even during the initial 3 months of treatment (24-28%), after which it decreased with increasing doses of norethindrone acetate. Conversely, the incidence of bleeding increased over time with unopposed E2 1 mg. After the initial 3 months, the incidence of bleeding among the combination groups was lowest in the norethindrone acetate 0.5 mg group. Among women initiating therapy close to menopause, fewer reported bleeding with norethindrone acetate 0.5 mg than with the other combination groups. There was a significantly (P<.05) lower discontinuation rate due to bleeding in the norethindrone acetate 0.5 mg group compared with all other treatment groups. CONCLUSION: Continuous-combined formulations of E2 1 mg with norethindrone acetate 0.1, 0.25, or 0.5 mg are associated with a low incidence of uterine bleeding. After the initial 3 months of treatment, bleeding profiles improved with increasing doses of norethindrone acetate.

Adult↗

PubMed1998

Do combinations of 1 mg estradiol and low doses of NETA effectively control menopausal symptoms?

OBJECTIVES: This study compared two continuous-combined hormone replacement therapy (HRT) formulations, 1 mg estradiol (E2)/0.25 mg norethisterone acetate (NETA) and 1 mg E2/0.5 mg NETA, with placebo, with regard to the efficacy for vasomotor symptom relief in menopausal women. METHODS: A total of 119 women aged 45-61 years with moderate and severe hot flushes and with amenorrhea for at least 3 months were randomly assigned to 12 weeks' treatment with 1 mg E2/0.25 mg NETA, 1 mg E2/0.5 mg NETA or placebo. The number and severity of hot flushes, as well as any vaginal bleeding, were recorded on a daily basis. The Kupperman Menopausal Index, Greene Climacteric Scale and visual analog scales for various symptoms were assessed before and after treatment. Subpopulation analysis according to menopausal status was performed. RESULTS: Both combinations significantly reduced the number and severity of hot flushes, compared to placebo. A reduction of approximately 85% in vasomotor symptomatology occurred in the two combination groups by week 4 of treatment, and this was further diminished throughout the study to approximately 97% reduction by week 12. At the end of the study, 85% of the women receiving 1 mg E2/0.5 mg NETA and 71% of the women receiving 1 mg E2/0.25 mg NETA were considered to the clinically adequate responders to treatment. Both combinations were associated with significant improvements, compared to placebo, in visual analog scales for overall general condition, Kupperman Menopausal Index, and Greene Climacteric vasomotor and psychological subscales. While both combinations resulted in similar bleeding profiles in postmenopausal women, the combination of 1 mg E2/0.5 mg NETA resulted in the lowest incidence of bleeding in late perimenopausal women. CONCLUSIONS: The combinations of 1 mg E2/0.25 mg NETA and 1 mg E2/0.5 mg NETA rapidly relieve vasomotor symptoms and are efficacious in the majority of menopausal women, including those with severe hot flushes.

Estradiol↗

PubMed1994

Gonadal hormones and semen quality in male runners. A volume threshold effect of endurance training.

Eleven high mileage runners (HR) (108.0 +/- 4.5 km.wk-1), 9 moderate mileage runners (MR) (54.2 +/- 3.7 km.wk-1) and 10 sedentary controls (SC) of similar age (28.3 +/- 1.5 yr) were studied to evaluate the effects of volume of endurance training on reproductive function in male runners. Levels of reproductive, adrenal and thyroid hormones were measured during a 1-hr period of serial blood sampling (q20 min) and urinary excretion of 24-hr luteinizing hormone (uLH) was determined on two separate days. Semen exams and sperm penetration of standard cervical mucus (Penetrak) were performed 2-5 times. Levels of total testosterone (TT) and free testosterone (FT) were significantly lower in HR (15.3 +/- 1.3 nmol.l-1 and 60.2 +/- 5.1 pmol.l-1) compared to MR (21.4 +/- 1.6 nmol.l-1 and 86.0 +/- 6.1 pmol.l-1) and SC (19.5 +/- 0.9 nmol.l-1 and 75.9 +/- 3.6 pmol.l-1). No differences (p > 0.05) were found in uLH, serum LH, follicle-stimulating hormone (FSH), and prolactin (PRL) among the three groups. No other hormonal differences (p > 0.05) were observed among the groups. Total motile sperm count and density were lower (p < 0.05) in HR than SC. Decreased (p < 0.0006) sperm motility and an increased (p < 0.004) population of immature sperm and round cells were observed in HR compared to MR and SC. Sperm penetration of bovine cervical mucus was also decreased (p < 0.024) in HR compared to SC. Volume of training, defined by km.wk-1 run, was significantly correlated to sperm motility, density and number of round cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1994

Clinical tests explain blunted cortisol responsiveness but not mild hypercortisolism in amenorrheic runners.

To investigate mechanisms of blunted adrenocortical responsiveness to exercise and mild hypercortisolism in amenorrheic runners, adrenocorticotropic hormone [ACTH-(1-24) 0.25 mg Cortrosyn] stimulation tests were performed in the presence and absence of overnight dexamethasone (1 mg) suppression (DX and NDX condition, respectively) in six eumenorrheic sedentary women (ES), nine eumenorrheic runners (ER), and nine amenorrheic runners (AR). Before the NDX stimulation test, plasma cortisol was higher (P < 0.001) in AR than in ER and ES. The cortisol response to the NDX stimulation test was blunted (P < 0.001) in AR but reached similar (P > 0.7) peak levels in all groups. Dexamethasone suppressed (P < 0.001) cortisol to similar (P > 0.5) levels (approximately 20 nmol/l) in all groups. In AR, cortisol responses to the DX test were larger (P < 0.03) than to the NDX test and similar (P > 0.6) in the three groups, again reaching comparable (P > 0.8) peak levels. The blunted cortisol response to stimulation in AR in the presence of their mild hypercortisolism appears to be due to a normal limitation in maximal adrenal secretory capacity. Extrapituitary modulators of adrenal responsiveness to ACTH may explain the mild hypercortisolism observed in AR, but limitations of these tests prevent a central negative-feedback defect or an intrinsic adrenal abnormality from being excluded until results of additional studies with even lower doses of dexamethasone and submaximal doses of ACTH-(1-24) are available.

Adolescent↗

PubMed1993

Exercise and male factor infertility.

Recent advances in the study of andrology are unfolding some of the idiopathic components of male factor infertility. The inclusion of exercise training as a component of male factor infertility has been proposed secondary to changes observed in the reproductive hormone and semen profile of some endurance trained male athletes. Evidence exists that a subset of endurance trained men, particularly runners, present with subclinical changes in their reproductive hormone profile. These changes include a reduction in total and free testosterone, alterations in luteinising hormone release and alterations in pituitary responses to gonadotrophin-releasing hormone and other pharmacological perturbations. Less attention has been directed towards identifying changes in spermatogenesis and fertility capacity as a result of endurance training. The semen ejaculate of some endurance trained athletes presents with nonspecific modifications including a low normal sperm count, decreased motility and several morphological changes that may compromise fertility. Thus, although a subset of high mileage endurance trained runners present with subclinical modifications in their reproductive hormone and semen profile, to date there is no evidence that endurance training causes male infertility. Future investigations should focus on the clinical impact these hormone and semen alterations may have on fertility capacity in endurance trained athletes.

Exercise↗

PubMed1993

Subclinical alterations in hormone and semen profile in athletes.

STUDY OBJECTIVE: To investigate the effects of two forms of exercise, endurance training (running) and resistance training (weight lifting), on reproductive function in male athletes. DESIGN: Cross-sectional study. SETTING: Reproductive Endocrinology and Exercise Laboratory. SUBJECTS: Twenty-eight healthy male volunteers, 18 to 35 years of age, including 10 endurance-trained runners, 8 resistance-trained weight-lifters, and 10 sedentary controls. MAIN OUTCOME MEASURE(S): Hormonal evaluation included determination of plasma levels of total testosterone (T), serum levels of free T, luteinizing hormone (LH), follicle-stimulating hormone, prolactin, and estradiol, and urinary excretion of LH. Semen analyses included an evaluation of sperm characteristics in terms of density, count, motility, and morphology, and a determination of in vitro sperm penetration of standard bovine cervical mucus. RESULTS: Compared with sedentary controls, endurance-trained and resistance-trained athletes presented with significantly lower levels of total and free T. There were no significant differences in the serum levels of all other circulating and urinary hormone measurements among the three groups. Sperm density, motility, and morphology were significantly altered only in the endurance-trained runners. In vitro sperm penetration of standard cervical mucus was significantly reduced in the endurance-trained runners. CONCLUSION: Both endurance and resistance training modify the male reproductive hormone profile in a similar manner; however, only endurance training, in the form of running, is associated with subclinical modifications in semen characteristics.

Adolescent↗