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Biomedical subjects

V Padmanabhan

Publications and source records attributed to V Padmanabhan.

117 records · Page 7Linked to original sources
PubMedDate not supplied

Dynamical analysis of diastolic heart sounds associated with coronary artery disease.

In a new approach to noninvasively diagnose coronary artery disease (CAD), auditory correlates attributed to blood flow turbulence have been associated with stenosed coronary arteries. These auditory components have been detected in diseased subjects by spectral estimation of diastolic heart sound recordings made on the surface of the chest. In this study, we investigated the dynamics of the process that produces these sounds in diseased subjects by applying the techniques of dimensional analysis. Our results indicate a difference in the "correlation dimension" between heart sounds of diseased and normal subjects. In particular, diseased subjects show a fractal dimension, implying the presence of a strange attractor and the possible existence of low-dimensional chaos in sounds associated with coronary artery disease.

Algorithms↗
PubMedDate not supplied

D-valine medium maintains prolactin production in primary culture.

Prolactin secretion by bovine pituitary cells in L-valine-containing medium decreases approximately 96% from day 3 to day 11 of culture. We hypothesized that this decrease was caused by overgrowth of these cultures by fibroblasts. Our present objective was to maintain the synthesis and secretion of PRL by bovine pituitary cells in culture. We attempted this by growing pituitary cells in D-valine-containing medium to achieve selective suppression of fibroblast growth. Substitution of D-valine for L-valine in Earle's or Swim's medium resulted in undiminished PRL synthesis and release over a 30-day culture period. In contrast, comparable measures for cells maintained in medium with L-valine decreased more than 90% from day 5 to day 20 of culture and remained low thereafter. Cells cultured in medium containing D-valine retained their ability to release PRL in response to thyrotropin-releasing hormone throughout the 30-day culture period, although there was a decrease in magnitude of response with time. Similarly, estradiol increased PRL release by pituitary cells maintained in D-valine, but this stimulatory effect was no longer demonstrable by day 20 of culture. The amount of growth hormone (GH) and luteinzing hormone (LH) released into the medium decreased with time and this decrease was independent of the valine isomer contained in the medium. We conclude that substituting D-valine for L-valine in culture medium allows PRL synthesis and release to persist undiminished for at least 30 days in culture.

Animals↗
PubMedDate not supplied

Neuroendocrine vs. paracrine control of follicle-stimulating hormone.

In spite of the pivotal role FSH plays in the regulation of gametogenesis, we are far from understanding the regulatory mechanisms involved in the control of its synthesis, secretion, and functions. Part of the problem relates to its molecular heterogeneity and the unavailability of assay methods capable of distinguishing the various isoforms of FSH. Recent work has confirmed the existence of two modes of FSH secretion, the basal and the episodic modes. The major portion of FSH secretion appears to be in the basal mode. The episodic mode appears to consist of both GnRH-associated and non-GnRH-associated pulses of FSH. The intracellular mechanisms by which differential release of LH and FSH are facilitated by GnRH are just beginning to be unraveled and may involve different second-messenger systems. Local pituitary regulators such as activins, inhibins, and follistatins are receiving considerable attention in recent years as a means by which differential release of LH and FSH can be facilitated by GnRH and other neuroendocrine factors. In parallel, the search for a selective FSH-releasing factor (FSH-RF) continues. Identification of variant forms of GnRH in recent years has opened up the possibility that one GnRH variant may be the long-sought-after FSH-RF. From a functional aspect, an understanding of how FSH heterogeneity is regulated is also important, as the different mixes of FSH isoforms have the ability to fine-tune the follicular recruitment and selection process. This review focuses on the recent advances made in the neuroendocrine and paracrine regulation of FSH synthesis/secretion/heterogeneity and pinpoints areas of gaps in our knowledge.

Activins↗
PubMedDate not supplied

Specific regulatory actions of dihydrotestosterone and estradiol on the dynamics of FSH secretion and clearance in humans.

The authors investigated immunoactive and bioactive follicle-stimulating hormone (FSH) secretion and clearance in six healthy young men during steady-state infusions of vehicle (basal, B, 28 hours), dihydrotestosterone (DHT, 4.5 days), or estradiol (4.5 days) accompanied by blood sampling at 10-minute intervals for 28 hours. Serum FSH concentrations were assayed by a two-site immunoradiometric assay (IRMA) and two separate in vitro bioassays (rat granulosa and Sertoli cell systems). FSH measurements included: 24-hour mean serum concentrations (IRMA and bioassay), multiple-parameter deconvolution of 24-hour pulsatile FSH time series and FSH release in response to exogenous gonadotropin-releasing hormone (GnRH) boluses (IRMA) to assess secretion and clearance, and circadian serum FSH concentration rhythms by cosinor analysis (IRMA). We found: 1) a significant decrease in 24-hour mean IRMA FSH concentrations during DHT infusion while both in vitro estimates of FSH bioactivity were unchanged; 2) significant decreases in the mass of IRMA FSH secreted per 24 hours during DHT infusion; 3) significant decreases in the IRMA FSH half-life during estradiol infusion without any change in FSH interpulse interval; 4) no steroidal effects on FSH secretory responses to exogenous GnRH; and 5) abolition of basal circadian FSH rhythms during sex-steroid infusions. Based on these findings, we conclude that steady-state sex-steroid hormone infusions selectively alter IRMA FSH secretion and clearance without affecting IRMA FSH pulse frequency or mean concentrations of bioactive FSH.

Adult↗
PubMedDate not supplied

Fine needle aspiration cytology of chondroid syringoma and syringocystadenoma papilliferum. A report of two cases.

Fine needle aspiration cytology of one case each of chondroid syringoma and syringocystadenoma papilliferum with histopathologic confirmation are reported. The aspirate of chondroid syringoma was characterized by the presence of two distinct components, a mesenchymal element with a chondroid appearance and an epithelial component. The chondroid element predominated in the smears. The aspirate from syringocystadenoma papilliferum showed papillalike clusters and dyshesive, monomorphic epithelial cells in a background of inflammatory cells. The clinical diagnosis and differential cytodiagnoses are discussed.

Adenoma, Sweat Gland↗
PubMedDate not supplied

Neuropsychological impairment and altered thyroid hormone levels in epilepsy.

BACKGROUND: Neuropsychological impairment is a common problem in epilepsy which interferes with the quality of life of patients. Similarly, thyroid hormone levels have been observed to be abnormal in patients with epilepsy on various treatments. This study aimed to ascertain any possible correlation between neuropsychological performance and thyroid hormone levels among epilepsy patients. METHODS: Thyroid hormone levels, indices of neuropsychological performance and social adaptation of 43 epilepsy patients were compared with those of age- and sex-matched healthy control subjects. RESULTS: Epilepsy patients exhibited significantly (p < 0.001) lower scores on attention, memory, constructional praxis, finger tapping time, and verbal intelligence quotient (i.q.) when compared with controls. Their T3, T4 and Free T3 levels were significantly lower; and TSH and Free T4 levels were significantly higher than that of controls. There was no statistically significant correlation between the indices of neuropsychological performance and thyroid hormone levels. CONCLUSION: We did not observe any correlation between neuropsychological impairment and thyroid hormone levels among patients with epilepsy.

Adult↗