This work concerns the role of spinal sympathetic pathways in the transynaptic regulation of adrenal medullary tyrosine hydroxylase activity (ATHA) and catecholamines. Cord transection in adult rats above the origin of the sympatho-adrenal preganglionic neurons (SAPN) causes after 3 days progressive reductions of ATHA, of the Vmax for tyrosine hydroxylation and of adrenal dopamine content. These effects are prevented by prior splanchnicotomy; they may result from a lowering of modulatory impulses of decentralized SAPN. The effect of spinal section on ATHA is accentuated by the repeated injection of serotonergic and muscarinic agonists which could inhibit the SAPN. Following spinal hemisection at various levels, the responses of ATHA and of adrenal epinephrine content to immobilization stress or to administration of apomorphine, insulin or 2-deoxyglucose are mediated by direct and crossed descending projections from supraspinal neurons generating net facilitatory and possibly inhibitory effects. A high performance liquid chromatographic method with amperometric detection was developed to measure simultaneously the three main adrenal catecholamines.

In acute C1 spinal cats, electrical stimulaton of myelinated femoral (L5-L6) or pelvic (S1-S3) nerve afferents or natural stimulation of receptors of pelvic nerve bladder afferents increased or decreased the activity of thoracic (T1-T7) sympathetic preganglionic neurons (SPNs) projecting to the cervical sympathetic trunk. A similar proportion of these SPNs responded to electrical stimulaton of myelinated radial (C7-T1) nerve afferents. The responses of SPNs to electrical or natural activation of pelvic nerve afferents in acute spinal animals were compared with those of SPNs in CNS intact or midcollicular decerebrate animals. Myelinated somatic and visceral afferents can activate propriospinal systems which connect with SPNs many segments away from the entry point of these afferents. The proportion of SPNs actively responding to input transmitted via these pathways seems independent of the entry point of the input. These pathways are likely to be operative in the CNS intact or decerebrate preparation.

Since cortisol (F) can influence fetal lung maturation in late gestation, interconversion between cortisol and its inactive analogue cortisone (E), catalyzed by 11(beta)-hydroxysteroid dehydrogenase (11-HSD) (E.C.1.1.1.146), may be an important mechanism for controlling the level of F in the fetal lung parenchyma. The objects of this study were to: (1) resolve conflicting data; and (2) to study possible regulating factors of the 11-HSD. Human fetal lungs (HFL) of gestational ages 9-20 weeks were grown as monolayer cultures or as explants with ('3)H-F and ('3)H-E or ('14)C-E (0.01-17 ng/ml), for 6-16 days. Extracts of tissue culture medium were chromatographed to separate the steroids, and the per cent conversion was calculated. From the differences observed between explant and monolayer cultures it was concluded that: (1) the E to F activity observed in midgestational HFL monolayer cultures is an artefact of the culture system and is therefore not physiological, thus resolving the conflicting data; (2) F to E activity predominates in midgestational HFL and resides in undifferentiated epithelial cells; and (3) the 11-HSD in fibroblast-like cells is a different enzyme from the 11-HSD in HFL epithelial cells. These studies suggest that a decrease in the epithelial cell enzyme activity, elevating intracellular F levels at term, may be critically involved in maturation of the HFL.

The effect of CO$ sb2$ on sympathetic preganglionic neuron (SPN) activity and hindlimb neurogenic vascular resistance (HVR) was investigated in cats. Both variables increased as continuous functions of systemic arterial PCO$ sb2$, from hypocapnia to hypercapnia. Eucapnic PCO$ sb2$ was responsible for a significant component of SPN background activity and HVR. The carotid body chemoreceptors were shown to contribute to the CO$ sb2$ response of SPNs, since section of the carotid sinus nerves, after prior section of the aortic nerves, reduced the CO$ sb2$ response of SPNs. A significant ventral medullary contribution to this CO$ sb2$ relationship was demonstrated, since the CO$ sb2$ response persisted after peripheral chemodenervation, was lost after acute spinal transsection and was markedly attenuated by cold-block of either the entire exposed ventral surface of the medulla or the specific bilateral area "S". Superficial ventral medullary chemoreceptor involvement was confirmed, since changes in HVR, comparable to those caused by altering arterial PCO$ sb2$, occurred with changes in the (H$ sp+$) and PCO$ sb2$ in artificial CSF perfusing these structures.

No description available.

Graft-versus-host reactions induced thymic epithelial cell injury, which was associated with a block in T cell maturation. No suppressor cells were detected in these thymuses. Thymic epithelial cell injury neither affected the acquisition of theta alloantigen nor interfered with homing of haemopoietic stem cells to the thymus, however, it impeded the ability of GVH thymuses to process the normal haemopoietic cells into mature T cells. / GVHBM cells repopulated the lymphoid organs of irradiated normal mice, and restored cell mediated humoral and splenic PHA, and ConA responses when transferred into T cell deprived mice. / The GVH reaction also induced B cell functional deficiencies. No suppressor cells were detected in the GVHBM. However, the colony forming ability of GVHBM cells was significantly decreased. / Thus, the GVH reaction resulted in a block of both T and B cell maturation which explained, at least in part, why GVH mice remained permanently immunosuppressed.

Nucleocytoplasmic trafficking of macromolecules and heat shock proteins are key elements of the stress response; the analysis of nuclear transport and hsp70s will therefore contribute significantly to our understanding of cell physiology. / To study the formation of the Ran/Gsp1p nucleocytoplasmic gradient, an essential component of many nuclear transport reactions, I have used mutant strains of the yeast Saccharomyces cerevisiae. My experiments have identified the nucleoporins Nup133p, Rat2p/Nup120p, Nup85p, Nic96p and the enzyme acetyl-CoA carboxylase (MTR7) as proteins that regulate the distribution and cellular concentration of Ran/Gsp1p. Moreover, I have defined the mechanisms that underlie the control of the Ran/Gsplp gradient formation by these factors. / Using HeLa cells as a model system, I have demonstrated that the C-terminal part of mammalian hsc73 contains a unique targeting signal that is necessary and sufficient for stress-induced nuclear accumulation. This C-terminal segment promotes shuttling between nucleus and cytoplasm and has unique requirements for stress-dependent nuclear import.

The importance of hypertension as a risk factor for the development of AF is well recognized. Despite this leading importance, the role of essential hypertension in providing a substrate for AF is incompletely understood. The present study was undertaken to investigate the possibility of having rats as an adequate animal model for the relationship between hypertension and AF in man and to elucidate the role of hypertension as a risk factor for AF. The results of this study show that structural remodeling especially in the form of increased amount of interstitial fibrosis seems to be the major contributing factor to the AF sustainability. Although it can be concluded that hypertension could accelerate the accumulation of fibrosis which occurs during the normal process of aging, a clear relationship between hypertension and AF in this rat model was not found. Further work in the other animal models of hypertension would be interesting.

The Cyclic Nucleotide Binding Domain (CNBD) is conserved in a number of ion channels that belong to three distinct families, the Ether-A-Go-go (EAG); the Cyclic Nucleotide Gated (CNG) and the Hyperpolarization activated Cyclic Nucleotide modulated (HCN) channel families. Extensive biophysical characterizations have established that the function of these channels is directly modulated by cyclic nucleotides in a manner independent of kinase activity and channel phosphorylation. However, the role for this domain in the EAG family is unclear. In addition, although the biophysical properties of CNBD-containing channels are well understood, little is known about the biogenesis of these channels. The original goal of this thesis was to identify trafficking signals in the C-terminus of the Human Ether-a-go-go Related Gene (HERG) potassium channel with the aim of understanding the underlying mechanisms associated with mutations in this gene that cause the Long Q-T Syndrome (LQTS) and associated cardiac arrhythmia. By exploiting the unique biochemical properties of HERG, we identify a discrete C-terminal segment between residues 860-899 that is critical for the exit of the ion channel from the Endoplasmic Reticulum (ER). To substantiate the role of residues 860-899 in trafficking of HERG, we show defective biogenesis associated with a number of LQTS-causing mutations that interfere with this segment. Subsequent functional, biochemical and immunolocalization experiments identify the CNBD of HERG as the trafficking critical segment. Deletions of any of the structural motifs of the CNBD cause retention of the ion channel inside the ER. Likewise, removal of the entire CNBD prevents Golgi transit and cell surface localization of tetrameric channels. We show that all known arrhythmogenic mutations in this domain render HERG channel nonfunctional as a result of ER retention. Subsequent analyses indicate that the CNBD is indispensable for ER exit of a relat

Sodium/proton exchangers (NHEs) are secondary active transporters that catalyze the electroneutral exchange of Na+ and H+ down their respective concentration gradients using the inward electrochemical Na+ gradient established by the plasma membrane Na+ /K+-ATPase. NHEs play a fundamental role in maintaining the intracellular pH (pHi) homeostasis and cell volume which are required for stable protein activity, and ultimately cell survival. To date, nine NHE isoforms (NHE 1-9) have been identified, and are expressed in a tissue/cell specific manner, which indicates a degree of specialization in their respective cellular functions. NHE1 through 5 are plasmalemmal-type exchangers, whereas NHE6 and 7 accumulate predominantly in organellar compartments. Substantially less information is known about NHE8 and NHE9. Initial reports have shown that both NHE8 and NHE9 mRNA are ubiquitously expressed, and that NHE8 protein can be detected in the proximal tubules of kidney nephrons (Goyal et al., 2003; de Silva et al., 2003). / To gain further insight into the subcellular distribution and function of these latter isoforms, full length cDNAs of NHE8 and NHE9 were cloned, epitope tagged and transfected into cultured cell lines. Examination of their subcellular localization by confocal microscopy showed that NHE8 and NHE9 are targeted to lysosomes and endosomes respectively. Furthermore, co-immunoprecipitation experiments indicated that NHE9 can form homodimeric complexes. Co-immunoprecipitation studies and confocal microscopy also indicated that NHE9 may form heterocomplexes with NHE8. In order to further characterize NHE9 under native conditions, a native polyclonal antibody was raised against a distinct region of its C-terminal cytoplasmic tail.