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Biomedical subjects

R Huerta

Publications and source records attributed to R Huerta.

At least 37 records · Page 2Linked to original sources
PubMed2000

Adrenocortical hyperresponsivity to adrenocorticotropic hormone: a mechanism favoring the normal production of cortisol in 21-hydroxylase-deficient nonclassic adrenal hyperplasia.

OBJECTIVE: To test the hypothesis that patients with nonclassic adrenal hyperplasia (NCAH) exhibit a generalized exaggeration in their response to ACTH stimulation that favors the normal production of F. Patients with 21-hydroxylase (21-OH)-deficient NCAH do not demonstrate cortisol (F) deficiency. DESIGN: Prospective controlled study. SETTING: Tertiary university clinic. PATIENT(S): Twenty-four untreated patients with NCAH diagnosed by a 17 alpha-hydroxyprogesterone (17-HP) level of >30.3 nmol/L (>10 ng/mL), and 37 age- and body mass-matched healthy eumenorrheic nonhirsute controls. INTERVENTION(S): All study subjects underwent a 60 minute acute stimulation using 0.25 mg of ACTH-(1-24) i.v. MAIN OUTCOME MEASURE(S): Basal and stimulated serum levels of pregnenolone (PREG), 17-hydroxypregnenolone (17-HPREG), dehydroepiandrosterone (DHA), progesterone (P4), 17-HP, androstenedione (A4), 11-deoxycortisol (S), and cortisol (F). RESULT(S): The median basal (i.e., Steroid(0)) or ACTH-stimulated (i. e., Steroid(60)) serum levels of PREG, 17-HPREG, DHA, P4, 17-HP, A4 and, most importantly, S were higher in NCAH patients than in controls. In contrast, the levels of F at either 0 minute or 60 minutes of stimulation were similar between NCAH and control women. The proportion of NCAH patients with stimulated steroids levels of >the 95th percentile of controls were as follows: 84.21% for PREG(60), 87.5% for 17-HPREG(60), 95.8% for DHA(60), 89.5% for P4(60), 100% for 17-HP(60), 91.7% for A4(60), 29.2% for S(60), and 4. 1% for F(60). CONCLUSION(S): A generalized adrenocortical hyperresponsivity to ACTH stimulation seems to be present in patients with 21-OH-deficient NCAH, with an exaggerated production of S evident in approximately 30%. The excess production of S in these NCAH patients may, in part, account for their normal F production.

17-alpha-Hydroxypregnenolone↗
PubMed1999

11beta-hydroxyandrostenedione and delta5-androstenediol as markers of adrenal androgen production in patients with 21-hydroxylase-deficient nonclassic adrenal hyperplasia.

OBJECTIVE: To determine the sensitivity of 11beta-hydroxyandrostenedione (11-OHA4) and delta5-androstenediol (ADIOL) as markers of excessive adrenal androgen production. DESIGN: Prospective study. SETTING: Academic medical centers. PATIENT(S): Thirteen women with untreated 21-hydroxylase-deficient nonclassic adrenal hyperplasia (NCAH) and 18 healthy, eumenorrheic, nonhirsute controls matched for age and body mass index. INTERVENTION(S): All subjects were studied before and after acute adrenal stimulation with 0.25 mg of IV ACTH-(1-24). MAIN OUTCOME MEASURE(S): Basal levels of total testosterone, sex hormone-binding globulin, DHEAS, and free testosterone were measured. Levels of androstenedione (A4), DHEA, 11-OHA4, and ADIOL were determined before (Steroid0) and 60 minutes after (Steroid60) acute ACTH-(1-24) stimulation. RESULT(S): Patients with NCAH had higher median basal levels of DHEAS and total and free testosterone than controls. Patients with NCAH had higher median A4(0), A460, DHEA(0), DHEA60, 11-OHA4(0), ADIOL0, and ADIOL60 levels but similar 11-OHA4(60) levels compared with controls. Among patients with NCAH, 30%, 54%, 15%, and 85% had 11-OHA4(0), ADIOL0, 11-OHA4(60), and ADIOL(60) levels, respectively, above the 95th percentile of controls. CONCLUSION(S): Overall, serum levels of 11-OHA4 did not appear to be a very sensitive marker of excessive adrenal androgen production, at least in patients with NCAH. Although ACTH-stimulated ADIOL levels were elevated in 85% of the patients studied, they did not appear to have any advantage over the measurement of A4 or DHEA levels.

Adrenal Hyperplasia, Congenital↗
PubMed1999

Origin of coherent structures in a discrete chaotic medium.

Using as an example a large lattice of locally interacting Hindmarsh-Rose chaotic neurons, we disclose the origin of ordered structures in a discrete nonequilibrium medium with fast and slow chaotic oscillations. The origin of the ordering mechanism is related to the appearance of a periodic average dynamics in the group of chaotic neurons whose individual slow activity is significantly synchronized by the group mean field. Introducing the concept of a "coarse grain" as a cluster of neuron elements with periodic averaged behavior allows consideration of the dynamics of a medium composed of these clusters. A study of this medium reveals spatially ordered patterns in the periodic and slow dynamics of the coarse grains that are controlled by the average intensity of the fast chaotic pulsation.

Journal Article↗
PubMed1999

Dynamic control of irregular bursting in an identified neuron of an oscillatory circuit.

In the oscillatory circuits known as central pattern generators (CPGs), most synaptic connections are inhibitory. We have assessed the effects of inhibitory synaptic input on the dynamic behavior of a component neuron of the pyloric CPG in the lobster stomatogastric ganglion. Experimental perturbations were applied to the single, lateral pyloric neuron (LP), and the resulting voltage time series were analyzed using an entropy measure obtained from power spectra. When isolated from phasic inhibitory input, LP generates irregular spiking-bursting activity. Each burst begins in a relatively stereotyped manner but then evolves with exponentially increasing variability. Periodic, depolarizing current pulses are poor regulators of this activity, whereas hyperpolarizing pulses exert a strong, frequency-dependent regularizing action. Rhythmic inhibitory inputs from presynaptic pacemaker neurons also regularize the bursting. These inputs 1) reset LP to a similar state at each cycle, 2) extend and further stabilize the initial, quasi-stable phase of its bursts, and 3) at sufficiently high frequencies terminate ongoing bursts before they become unstable. The dynamic time frame for stabilization overlaps the normal frequency range of oscillations of the pyloric CPG. Thus, in this oscillatory circuit, the interaction of rhythmic inhibitory input with intrinsic burst properties affects not only the phasing, but also the dynamic stability of neural activity.

Animals↗
PubMed1999

Age at menopause in women with type 2 diabetes mellitus.

OBJECTIVE: Considering that chronic diseases such as diabetes mellitus (DM) may determine premature ovarian failure by various mechanisms, we studied the age at menopause in women without diabetes and in women with type 2 DM. DESIGN: We studied 409 women without diabetes and 404 patients with type 2 DM, selected from 45 to 55 years of age, for analysis with the status quo method. The age at menopause was calculated with a logistic regression on the proportions of menopausal women for each age group. RESULTS: In the groups, 172 women without diabetes and 207 women with diabetes had menopause. The regression procedure gave a median age of 49.7 +/- SD 1.7 years for the whole group, 49.6 +/- 1.6 years for the nondiabetic group, and 49.8 +/- 1.7 years for women with diabetes. Women without diabetes were 1.4 years younger, but this factor did not have an influence on the results. Smoking habits, vegetarianism, and somatometric variables were similar in both groups, except for waist/hip and abdomen/hip ratios, larger in the group of women with diabetes. The mean for years since diagnosis in patients < 45 years of age was 4.9 years. For older patients, the figure increased to 8.9 years. CONCLUSIONS: No difference for age at menopause was found between women without diabetes and women with type 2 diabetes who were 5 to 8 years since the diagnosis was made.

Age Distribution↗
PubMed1998

Basic principles for generating motor output in the stomatogastric ganglion.

The lobster stomatogastric ganglion contains 30 neurons and when modulated can produce two distinct rhythmic motor patterns--the gastric mill and the pyloric. The complete neural circuitry underlying both patterns is well known. Without modulatory input no patterns are produced, and the neurons fire tonically or are silent. When neuromodulators are released into the ganglion from specific neurons or are delivered as hormones, the properties of the neurons and synapses change dramatically and modulator-specific gastric mill and pyloric patterns are produced. In general the rhythmicity derives from the induced burstiness of the neurons, and the pattern from the strengths of the electrical and chemical synapses. The organized activity can be traced to a marked reduction of chaotic activity in individual neurons when they shift from the unmodulated to the modulated state.

Animals↗
PubMed1997

High-frequency FSH and LH pulses in obese menopausal women.

We studied the pulsatile luteinizing hormone (LH) and follicle-stimulating hormone (FSH) secretory patterns, at early or intermediate years of menopause in seven normal women with different degrees of obesity, taking blood samples every minute for 40 min to 2 h. The hormones were assayed with an immunoradiometric assay (IRMA) system, analyzing with the cluster pulse algorithm. All women showed hormone pulses every 8-10 min. In five of them were found periods of discrete pulses with oscillations of high amplitude alternating with periods of pulses of low amplitude. In two cases, the high-frequency oscillatory pattern with low amplitude was found around low mean levels of 22.8 and 25.7 IU/L. The LH oscillatory pattern also had a high frequency, but at a lower level, giving a high FSH/LH ratio. The coincidence index of FSH with LH peaks was 76.6%. We concluded that at menopause, the frequency of FSH and LH secretion increases with a high FSH/LH ratio. Obese menopausal women may have the same high-frequency oscillatory patterns, but at low levels.

Body Mass Index↗
PubMed1997

Menopause in normal and uncomplicated NIDDM women: physical and emotional symptoms and hormone profile.

OBJECTIVE: To compare the physical characteristics, emotional symptoms and metabolic conditions of menopausal women with and without non insulin dependent diabetes mellitus (NIDDM). METHODS: We studied 100 menopausal women 45-72 years of age, 51 with and 49 without NIDDM, in a cross-sectional design. Biological characteristics were collected and emotional symptoms were assessed with a modified Hamilton and Bech-Rafaelsen scale, scoring depression, anxiety, non specific symptoms of depression (NSSD) and the empty nest syndrome (ENS). Weight, body mass index (BMI), waist/hip and abdomen/hip ratios and percent of body fat were registered. The sulfoconjugated form of the dehydroepiandrosterone (DHEAS), follicle stimulating hormone (FSH), cortisol and fasting, as well as postprandial insulin/glucose ratios, were measured in blood. RESULTS: Women with NIDDM had earlier mean age for menopause, more central obesity and less peripheral fat; they had also more prevalent emotional symptoms than non diabetic menopausal women. In women with NIDDM, symptoms were associated with years since diagnosis and with BMI. In non diabetic menopausal women schooling and attitudes to sexuality were associated with symptoms. FSH was inversely associated with BMI in both diabetic and non diabetic women; postprandial insulin/glucose ratio was correlated with central obesity in the group without NIDDM and cortisol with sitting systolic blood pressure (SBP) in the group with NIDDM. CONCLUSION: The diagnosis of NIDDM and its metabolic conditions were associated with an increased frequency of some symptoms in menopausal women.

Aged↗
PubMed1997

Negative effects of chemical mutagenesis on the adaptive behavior of vesicular stomatitis virus.

Changes in adaptability of vesicular stomatitis virus (VSV) upon treatment with chemical mutagens have been investigated. Results showed no improvement in virus viability or adaptability at any given level of mutagenesis. In fact, increasing inhibition of virus production and adaptability was observed with increasing levels of mutagenesis. This was true for all tested VSV variants replicating either in changing or constant host cell environments. Results also showed that mutagen-treated RNA virus populations which had undergone severe fitness declines were able to recover lost fitness completely after several large-population passages in BHK21, cells. The present findings illustrate the highly optimized states of RNA viruses and their potential to adapt readily. These results are significant for the possible development of specific antiviral agents designed to be mutagenic.

Adaptation, Physiological↗
PubMed1996

Reproducible nonlinear population dynamics and critical points during replicative competitions of RNA virus quasispecies.

RNA virus evolution is generally considered to be highly unpredictable, but tests of determinism in the evolution of competing populations during viral infections have not been performed. Here we study the fate of two closely related evolving quasispecies of vesicular stomatitis virus, by determining the relative concentration of a wild-type clone and a surrogate marked virus subclone (MARM-C) upon extensive competitive replication in a constant cell culture environment. A highly predictable nonlinear behaviour of the two competing populations was found. In addition, the presence of critical points, which are defined as points from which viral competitions may follow different trajectories, has been documented. Critical points were reached after nearly constant periods of time. The dynamics of relative fitness values for both competing populations were calculated during the replication passages. Concomitant with expected fitness gain of both competing viral populations (which follow the Red Queen hypothesis) a tendency for the MARM-C to gain less fitness than the wild-type was observed. Although fitness variations were noisy, this tendency was seen in all evolutionary replicas. Thus, despite the stochastic process of mutation that leads to a continuous generation of mutant genomes during RNA virus replication, a nonlinear, nearly deterministic evolutionary behaviour has been observed. It is proposed that such a behaviour is mediated by a low-pass filter (averaging of mutational noise signals) due to competitive selection among variants.

Analysis of Variance↗
PubMed1996

Synchronized action of synaptically coupled chaotic model neurons.

Experimental observations of the intracellular recorded electrical activity in individual neurons show that the temporal behavior is often chaotic. We discuss both our own observations on a cell from the stomatogastric central pattern generator of lobster and earlier observations in other cells. In this paper we work with models with chaotic neurons, building on models by Hindmarsh and Rose for bursting, spiking activity in neurons. The key feature of these simplified models of neurons is the presence of coupled slow and fast subsystems. We analyze the model neurons using the same tools employed in the analysis of our experimental data. We couple two model neurons both electrotonically and electrochemically in inhibitory and excitatory fashions. In each of these cases, we demonstrate that the model neurons can synchronize in phase and out of phase depending on the strength of the coupling. For normal synaptic coupling, we have a time delay between the action of one neuron and the response of the other. We also analyze how the synchronization depends on this delay. A rich spectrum of synchronized behaviors is possible for electrically coupled neurons and for inhibitory coupling between neurons. In synchronous neurons one typically sees chaotic motion of the coupled neurons. Excitatory coupling produces essentially periodic voltage trajectories, which are also synchronized. We display and discuss these synchronized behaviors using two "distance" measures of the synchronization.

Action Potentials↗
PubMed1995

Symptoms at perimenopausal period: its association with attitudes toward sexuality, life-style, family function, and FSH levels.

We studied the association of symptoms with attitudes toward sexuality, life-style, family functioning, and follicle-stimulating hormone (FSH) levels in perimenopausal women. We collected data on depression, anxiety, nonspecific index of depression, and the empty nest syndrome in 222 women with a mean age of 47.7 (47.2-48.2, 95% CI) years (102 of them were at menopause). Family functioning was evaluated with the McMaster model, and attitudes toward sexuality with questions about women's opinions on sexuality. Scores of depression were higher in women with more than 1 year of menopause. Attitudes to sexuality was significantly associated with all four symptoms. For family function, affective involvement, control of behavior, the roles of the members in the family, and communication were associated with some symptoms. Serum FSH was associated with body mass index, abdomen/hip ratio, and depression. We concluded that: (1) Attitudes toward sexuality was the main regressor for symptoms; (2) the function of the family is also associated with some symptoms; and (3) FSH levels may be lower in obese menopausal women and higher in women with depression or anxiety.

Adult↗
PubMed1995

Symptoms at the menopausal and premenopausal years: their relationship with insulin, glucose, cortisol, FSH, prolactin, obesity and attitudes towards sexuality.

The symptoms of 81 premenopausal and 70 menopausal women were studied to determine the association with obesity, attitudes towards sexuality (ATS), and diverse hormone values: fasting and postprandial glucose (FG, PG) and insulin (FI, PI), cortisol, prolactin, follicle-stimulating hormone (FSH). The mean age of the women studied was 49.1 years. The frequency of symptoms was 35.4% for depression, 34.3% for nonspecific symptoms of depression (NSSD), 38.6% for empty nest syndrome (ENS), and 42.3% for anxiety. NSSD, ENS, FSH and cortisol levels all possessed higher values at late-menopausal stage. A multiple regression analysis revealed the following results; NSSD was associated to ATS (negative); sleep alterations were correlated to prolactin, FSH, PI/PG, FI/FG and waist/hip ratio; FSH was associated with both a decreased sexual interest and depression. In the study of hormone levels it was found that cortisol, insulin and FI/FG were associated with ATS; PI, cortisol, FI/FG and PI/PG were associated with body mass index (BMI) and FSH; prolactin and FI/FG were associated with age. We concluded that: (1) data indicative of insulin resistance correlated to both depression and sleep alterations; (2) overweight is related to NSSD, sleep alterations, and hormonal changes.

Adult↗