Plasma acylation stimulating protein (ASP) is a small basic protein isolated from human plasma that stimulates triglyceride synthesis (TGS) and glucose transport (GT) in human skin fibroblasts and adipocytes. ASP was measured in fasting samples of 59 age-matched controls and 208 patients with documented coronary artery, disease (CAD). Overall, plasma ASP was higher in the CAD patients than in the controls and within the CAD patients, plasma ASP was highest in the group that had neither an FHTG-type (hypertriglyceridemic normal apoB) nor an FH-type (marked hypercholesterolemia and apoB with normal plasma triglyceride) phenotype. The relations between plasma ASP, triglyceride rich lipoproteins and apoB in the remaining CAD subjects were examined and ASP increased with either increasing triglyceride or apoB. In 208 CAD subjects, 47 subjects had ASP greater than 95th percentile (greater than 65 nM). Within those 47 subjects, 66% had increased plasma apoB (apoB > 105mg/dl). / The relationship between ASP and hyperapoB (apoB > 105mg/dl) was further investigated in cell culture study. Human skin fibroblasts were obtained from normals and hyperapoB patients. The fibroblasts from the three groups of subjects (normal subjects:NASP-NB, hyperapoB subjects with normal plasma ASP:NASP-HB, and hyperapoB subjects with high plasma ASP:HASP-HB) were studied for TGS and GT in response to ASP, PMA (4beta phorbol 12-myristate 13-acetate, a protein-kinase C stimulator) and insulin stimulation. The competition binding of 125I ASP to the fibroblasts from the three groups of subjects was also examined. / The data showed that only HASP-HB cells have a lower response to ASP in TGS and GT. The responses to insulin and PMA in TGS and GT are normal. There is no significant difference among the three groups in the Kd values (NASP-NB Kd: 163 +/- 23nM) for binding to 125I ASP. The Bmax value for the H ASP-HB group is 50% lower than the other two groups (N ASP-NB:NASP-HB:HASP-H B: 334 +/- 81:427 +/- 92:146 +/- 33 pmoles/mg cell protein). / The reduced receptor of ASP on the cell surface of HASP-H B patients can lead to the reduced response to ASP.

The effects of taurine deficiency on aspects of retinal cGMP metabolism were examined. Rats were made taurine deficient by the administration of 1% GES. The activities of the key enzymes of cGMP metabolism, phosphodiesterase and guanylate cyclase, were indirectly determined by the response of retinas to light and to low calcium. Dark-adapted retinas of rats treated with GES for 4 and 8 weeks exhibited significantly smaller decreases in cGMP in response to light exposure as compared to control retinas. Retinas from 4 and 8 week GES-treated rats also exhibited smaller increases in cGMP when they were exposed to 0.1nM calcium. In addition, dark-adapted retinas of 8 week GES-treated rats had 36% less cGMP than dark-adapted control retinas. Since a light-induced decrease of cGMP is of central importance in phototransduction, these results support the hypothesis that abnormalities in the retinal cGMP metabolism of taurine-deficient rats may account for the electro-retinographic deficits observed in these animals.

The purpose of this study was two-fold: (1) to examine the relationship between the amount of airway smooth muscle and the airway responsiveness to inhaled aerosolized methacholine (MCh) in guinea pigs, and (2) to characterize the distribution of airway narrowing following MCh. / In summary: (1) the quantity of airway smooth muscle (ASM) does not appear to determine differences in maximal bronchoconstriction among normal guinea pigs; the lack of a correlation between responsiveness and amount of ASM may be explained by the heterogenous distribution of bronchoconstriction among the airways studied or the modality of challenge; (2) the sensitivity to MCh appears to be related to differences in the amount of ASM in intraparenchymal cartilaginous airways; (3) variability in the EC$ sb{50}$ may also reflect differences in airway cross-sectional area; (4) lung resistance appears to be a good measure of constriction since the morphometric measure of airway narrowing correlated well with resistance; (5) the heterogeneity of airway narrowing does not appear to be determined by differences in ASM.

Generalized spike and wave (SW) activity of feline generalized penicillin epilepsy (FGPE), an experimental model of epilepsy exhibiting a sufficient degree of similarity with human generalized 3 Hz SW discharge, depends upon both cortical and thalamic mechanisms. Cortical neurons under the influence of systemic penicillin become more excitable and respond more vigorously to thalamocortical volleys normally inducing spindles or recruiting responses. This increased response of cortical neurons activates phasic recurrent inhibition which remains intact during FGPE as is shown by the preservation of antidromically evoked recurrent inhibition of pyramidal tract cells. Thus, an oscillation between periods of increased and decreased neuronal firing probability ensues which underlies SW discharge in the EEG. The cortex imposes this oscillatory pattern of neuronal discharge upon the thalamus, which by itself, however, is incapable of responding in this matter to systemic penicillin, as it appears from experiments performed in decorticated cats. Nevertheless, the thalamus is not a mere passive follower of the cortex in SW activity, since thalamocortical inputs remain necessary to maintain it. Furthermore thalamic neurons, like cortical ones, undergo a cyclically alternating pattern of increased and decreased firing probability. They display three different modes of phase-locked timing of their discharges in relation to cortical SWs and the cortical neuronal firing pattern. Two groups of cells fire coincidentally with the "spike" of the SW complex, one group reaching its maximum firing probability slightly before, the other slightly after that of the simultaneously recorded cortical neuron. The third group fires during the "wave" of the SW complex and its firing pattern is therefore about 180(DEGREES) out of phase with that of the cortical and the other two groups of thalamic neurons. Thus the substrate of generalized SW discharge seems to be oscillatory activity within a c

No description available.

This thesis examines in vivo and in vitro the effects of prolonged exposure of target cells to PTH on PTH receptors and postreceptor components of the adenylate cyclase system. Using a vitamin D-deficient ($-$D) rat model, hyperparathyroidism in vivo resulted in a decreased number of PTH receptors in kidney and a decreased amount of G protein $ alpha$ subunits. The decreased amount of G$ sb{ rm s} alpha$ was shown to be specific for PTH target tissue and may have played a role in the heterologous desensitization of CT-stimulated adenylate cyclase, demonstrated in renal membranes from the $-$D rats. The study of the control of PTH receptors was pursued using an osteosarcoma clonal cell line, UMR-106, in vitro. Initial characterization of these cells revealed abundant, saturable, cell surface PTH receptors linked to the adenylate cyclase system. Demonstration that the majority of PTH binding was associated with morphologically distinct cells in the UMR-106 population indicated that PTH receptors may be maximally expressed during specific stages in the cell cycle. PTH receptors in UMR-106 cells were shown to be regulated by distinct homologous and heterologous mechanisms. PTH-mediated, homologous desensitization was associated with down-regulation of PTH receptors and loss of G$ sb{ rm s} alpha$ protein form the cell membrane. Heterologous desensitization of PTH responses by PGE$ sb2$ was shown to be cAMP mediated, resulting in a reversible modification of the PTH receptors. This work has demonstrated that multiple mechanisms exist for the regulation of PTH responses both in vivo and in vitro that involve modifications of both the PTH receptors and postreceptor components of the adenylate cyclase system.

These studies investigated possible relief of spasticity in hemiparetic subjects by transcutaneous electrical nerve stimulation (TENS) and its underlying mechanisms. The first two studies quantified the disorders in reflex and voluntary motor functions and addressed the reproducibility of their measurement and their correlation with spasticity scores. Soleus stretch reflexes were enhanced and isometric voluntary contraction force was decreased linearly with increasing spasticity. The last two studies addressed the effects of single and repetitive TENS stimulation on spasticity, reflex and isometric voluntary contractions. Compared to placebo stimulation, single 45 min sessions of TENS prolonged H and stretch reflex latencies for up to 60 min following stimulation. Repetitive (15 daily, 60 min) applications significantly decreased spasticity scores, Hvib/Hctl ratios, stretch reflexes and co-contraction while improving dorsiflexion force. The improvement in spasticity and voluntary motor control may partly have been mediated by presynaptic inhibition and reduced hyperactive stretch reflexes thereby 'unmasking' descending control.

No description available.

No description available.

The cystic fibrosis transmembrane conductance regulator (CFTR) constitutes an ohmic chloride channel, the gating of which is dependent on cAMP-dependent phosphorylation of a regulatory (R) domain and ATP binding and hydrolysis by two nucleotide binding domains (NBDs). Previous studies have suggested that CFTR activation results from PKA phosphorylation of the R-domain, which either relieves its inhibition of the channel, or induces a positive catalytic effect of this domain on ATP dependent gating. In this study, the function of the R-domain was examined using a CFTR variant lacking the entire R-domain. These split channels assemble from separate polypeptides corresponding to the two halves of CFTR after translation of a single mRNA. Even though the back half of the split CFTR channel is expressed as a core glycosylated protein, both halves are able to fold independently and associate with one another to form a PKA-independent, constitutively active channel; however, this occurs with low efficiency. (Abstract shortened by UMI.)