Vanadium is a trace element found in most living systems. It has various biological properties. In the last 10 years numerous reports showed that Vanadium administered orally could improve the metabolic state of diabetic animals. The combination of vanadate and H$ sb2$O$ sb2$ produced the new agents called peroxoVanadium (pV) compounds which exerted more potent insulin mimetic effects by activating the insulin receptor kinase. Their application in the treatment of diabetes could be of great benefit clinically in the future. We demonstrated that long-term oral bpV (phen) (a new pV compound) treatment resulted in a lowering of blood glucose levels, with less toxicity than vanadate in STZ-diabetic rats. bpV(phen) was the first agent other than insulin, that was able to maintain the insulin-deprived diabetic BB rats in good apparent health without ketonuria for 25 days by intraperitoneal injection (IP). Although bpV(phen) was ineffective in reducing glucose levels by IP injection in BB rats, it caused a significant decrease of insulin and C peptide levels and in the insulin dose required to maintain the aglycosuric state of the diabetic BB rats. These observations are consistent with a mechanism of bpV(phen) action at tissue levels. The exploration of the properties of pV compounds may help elucidate both the mechanisms of insulin action and the cause of diabetes, and also may give rise to insulin substitutes which could be orally administered for the treatment of diabetes in the future. However IP injection of bpV (phen) also caused severe toxic side effects. The toxic effects of bpV(phen) included inhibition of food and water intake, acceleration of the onset of diabetes and death. Further studies are required to identify second generation pV compounds with better therapeutic/toxicity ratios and to find ways of delivering pVs orally.

The mitogen Platelet Derived Growth Factor (PDGF) has been linked to cellular proliferation in atherosclerosis and pulmonary fibrosis. We hypothesized that the PDGF may also be involved in the change in airway smooth muscle (ASM) mass following allergen challenge. Allergic bronchoconstriction was confirmed in the airways of OA sensitized and challenged Brown Norway (BN) rats, a model of allergic asthma. To examine PDGF mRNA expression, total lung RNA was extracted and amplified by RT-PCR for PDGF-A and PDGF-B isoforms. Both PDGF isoforms were found in the control and OA challenged groups. PDGF-B expression was increased after OA challenge in the small airways and parenchyma but no difference was detectable for PDGF-A. Western blotting on the lung tissue homogenate indicated that PDGF-B levels increased after OA challenges. Immunocytochemistry was used to localize the expression of PDGF-B in the ASM and epithelium. Morphometric analysis of the lung sections revealed increases in PDGF-B in the ASM and epithelium of the OA group. / Our results indicate that PDGF-A and PDGF-B mRNA are expressed in BN rat lung. Also, PDGF-B protein is upregulated in the airways following allergen challenge. We postulate that aspects of remodeling might be explained by the increased expression of PDGF-B.

The binding of eukaryotic ribosomes to mRNA is a complex process that is considered to be rate-limiting in translation initiation, and consequently a key target for translational regulation. Ribosome binding to mRNA is facilitated by the 5' cap structure, m7GpppN (where N is any nucleotide). The initiation factor eIF4F plays a key role in regulating translation rates. eIF4F is a three-subunit complex composed of eIF4E, the cap-binding protein; eIF4A, an RNA helicase; and eIF4G (p220), which bridges eIF4E and eIF4A, and enhances dramatically the interaction of eIF4E with the mRNA 5' cap structure. eIF4F in conjunction with another initiation factor, eIF4B, is thought to unwind the mRNA 5 '-secondary structure to facilitate the binding of mRNA to ribosomes The activity of eIF4F, and the regulation of mRNA binding to ribosomes is tightly correlated with the growth status of the cell. Recently, proteins that interact with eIF4E, termed 4E-BPs, have been identified; these proteins link translation initiation and growth promoting signal transduction pathways. Phosphorylation of 4E-BPs in response to insulin and mitogens decreases their affinity for eIF4E. 4E-BPs compete with eIF4G for binding to eIF4E through binding domains that share common sequence motifs. Consequently, 4E-BPs restrain eIF4E from forming an active cap-binding complex, eIF4F, and prevent subsequent binding of 40S ribosomal subunit to capped mRNAs. Under these conditions, the binding of eIF4E to the mRNA cap structure is extremely inefficient. As a result, cap- and eIF4E-dependent translation is downregulated. Modulation of eIF4F activity is also observed following infection by certain viruses. One of the most dramatic examples of this occurs upon picornaviral infection. As we report here, eIF4G alone is a relatively poor substrate for cleavage by the rhinovirus 2A proteinase (2Apro). However, an eIF4G-eIF4E complex is cleaved efficiently by the 2Apro suggesting that eIF4F is a preferred target for di

The aim of these studies was to examine in detail selected post-translational modifications of the biosynthetic derivatives of pro-opiomelanocortin (31K POMC) in the rat intermediate pituitary gland, and to study effects that these modifications have on biological activity. / Partial processing of the N-terminal fragment of POMC (or 16K) resulted in three derivatives: 16K$ sb{1-49},$ 16K$ sb{50-74}$ and 16K$ sb{1-74}.$ Lys$ gamma sb3$MSH, i.e. 16K$ sb{50-74},$ was completely N-glycosylated at asparagine-65 (with 4 N-acetyl-glucosamine residues). All forms of 16K$ sb{1-74}$ contained N-linked sugars in the $ gamma$-MSH portion and most have O-linked carbohydrate structures at threonine-45 (with 2 N-acetyl-galactosamine residues). The remaining 16K$ sb{1-74}$ lacked O-linked sugars, and the 1 to 49 fragment was devoid of amino sugars. All N-terminal derivatives had the same disulfide bridge arrangement. / These N-terminal peptides had no intrinsic corticotropic activities in a dispersed rat adrenal cell bioassay, but they had synergistic effects with ACTH. Nanomolar concentrations of Lys$ gamma sb3$MSH increased the steroidogenic response induced by ACTH. The O-glycosylated form of 16K$ sb{1-74}$ had greater potentiating actions which may be due to increased resistance to degradation. These findings suggest that the extent of O-glycosylation in the N-terminal fragment may direct proteolytic processing and enhance its biological activity.

Microencapsulation of the enzyme phenylalanine ammonia-lyase (PAL) was developed for in vivo depletion of systemic phenylalanine (PHE) in Phenylketonuric (PKU) rats. Phenylalanine ammonia-lyase was successfully microencapsulated within artificial cells. The immobilized enzyme had an assayed activity of 20% $ pm$ 4% (Mean $ pm$ S.D.) of the free enzyme in solution. The immobilized enzyme maintained a higher enzyme activity at very low pH compared to the free enzyme in solution. The pH optimum of the free and immobilized enzyme was 8.5. This pH optimum corresponds to the average pH range of the small intestine. / PKU induced rats had a 10 to 20-fold increase in the amino acid phenylalanine in the systemic circulation. This amino acid elevation was comparable to the plasma phenylalanine increase in human PKU patients. Daily oral administration of artificial cells containing 5 units of the enzyme PAL, to PKU rats, lowered on an average the systemic phenylalanine level to 20% $ pm$ 8% (Mean $ pm$ S.D.) of the original levels in 7 days (P $<$ 0.001). After 7 days of this form of enzyme therapy, systemic blood phenylalanine levels of PKU treated rats were lowered to levels not significantly different from those of normal rats. Unlike control PKU rats, the treated group showed no signs of abnormal behavior or weight loss. / HPLC analysis of free amino acids in the plasma, cerebro-spinal fluid and brain of PKU rats was carried out in the following groups: (1) Normal rats, (2) PKU rats on a normal diet, (3) PKU rats on a high phenylalanine diet, (4) PKU rats on a phenylalanine free diet, and (5) PKU treated rats with PAL-loaded artificial cells. Amino acid compartmental distribution was different in all these groups. / The oral administration of PAL-loaded artificial cells decreased the hyperphenylalaninemia in all the compartments studied. It also corrected the imbalance of many amino acids, including tyrosine and tryptophan, in the CSF and the brain. This enzyme therapy was more effective in compartmental PHE level depletion, than a PHE-free diet.

Obstructive sleep apnea (OSA) is a disease process characterized by collapse of the upper airway during periods of sleep leading to the cessation airflow despite persistent respiratory efforts. The aim of this research project is to investigate for associations and correlations between OSA and other clinical entities using two separate prospective studies. The initial objective was to evaluate the prevalence of laryngopharyngeal reflux (LPR) in patients with OSA. LPR was present in 26/28 (93%) of OSA patients. Moreover, there were significant correlations between LPR and OSA severity (eg. r = 0.57, p = 0.001). The second objective of this research study was to determine the prevalence of OSA in patients with cancer of the oral cavity and oropharynx, and to correlate the presence of OSA and the occurrence of postoperative morbidities. OSA was present in 76% of patients. Overall, postoperative complications were observed in 67% of OSA and 25% of non-OSA patients, although this difference was not yet significant (p = 0.27, Fisher exact test).

Cerebrovascular disease, as manifested by stroke, is the most common acute neurological illness in the North America. The ischemic insult results in an interruption of blood flow to the central nervous system (CNS). Transient global cerebral ischemia-reperfusion is known to cause disruption of the blood-brain-barrier (BBB) and edema formation. Past investigations have indicated that following reperfusion, oxygen free radicals, superoxide in particular, are formed and played a major role in the development of neurological disorders and brain dysfunctions. The present first generation blood substitute consisting of a cross-linked hemoglobin (PolyHb) solution is useful for perfusing obstructed regions of vessels; however, this solution is not able to scavenge reactive oxygen radicals. / Since our newly developed second-generation hemoglobin-based blood substitute, PolyHb cross-linked with superoxide dismutase and catalase (PolyHb-SOD-CAT), has the ability to scavenge reactive oxygen radicals, we hypothesize that this oxygen-carrying agent is able to deliver the required oxygen to brain tissue and remove the harmful oxygen free radicals in the same instance. In this investigation, we compare the physiological effects of this formulation with that of the first-generation hemoglobin-based blood substitute (PolyHb) on rat brain tissue using a 60-minutes transient global ischemia-reperfusion rat brain model. / Comparative molecular distribution was performed to observe the cross-linking process. Verifications of superoxide dismutase (SOD) and catalase (CAT) activity and oxygen-carrying property of PolyHb-SOD-CAT were also conducted. Tracking of cerebral water contents and colorimetric assay of Evans blue influx into brain tissue were used to evaluate the integrity of the blood-brain-barrier (BBB). This study shows that PolyHb-SOD-CAT can supply oxygen to ischemic tissues without causing reperfusion injury in a global stroke model.

The importance of discontinuous hormonal signals in endocrine communications is suggested by the ability of sustained hormonal signals to shut down, as opposed to stimulate, target cells, and by the observation that a change in pulse pattern can alter the response elicited. Serial sampling of the serum in catheterized, conscious, freely-moving rats was employed to investigate two aspects of pulsatility in the hypothalamo-pituitary-testicular feedback loop regulating reproduction in the adult male. First, in response to treatment with moderate to high doses of the testosterone (T) metabolite, dihydrotestosterone (DHT), pituitary responsiveness to exogenous LHRH was suppressed, and elevated post-castration mean LH levels declined due to a dose-dependent suppression of LH pulse frequency and amplitude. LH pulse amplitude was not suppressed by low dose DHT treatment, in spite of a dramatic suppression of pituitary responsiveness as measured, implying that a stimulatory androgenic influence on amplitude might be exerted upon hypothalamic LHRH release; blocking the endogenous opioid peptide system did not abolish this phenomenon. A stimulation of LH pulse amplitude was observed in orchidectomized rats given a low (sub-physiological) dose of T, and again, this effect was apparently mediated at a supra-pituitary site as pituitary responsiveness appeared unaltered at this T dose. These results suggest that the feedback regulatory actions of exogenous DHT, like those of T, are mediated at both the hypothalamus and the pituitary; this is consistent with the hypothesis that endogenous DHT mediates some of the negative and positive feedback effects of T in intact or T-treated orchidectomized animals. A second aspect of pulsatility was investigated in testes-intact rats. Fluctuations in serum T concentration are of a dual nature, reflecting both acute pulsatile bursts and prolonged episodes of testicular secretory activity, the precise pattern of which varies between and withi

This study was designed therefore, to investigate potential contributions of the cardiopulmonary bypass (CPB) procedure to the chronotropic limitation during exercise in surgically corrected CHD adolescents. Patients were divided into 3 groups: operated ventricular septal defect, where CPB is required (VSDop: n = 15); VSD closed spontaneously, no surgery or CPB required (VSDnop: n = 17); and operated patent ductus arteriosus, where surgery does not require CPB (PDA: n = 20). Fifteen healthy age-matched subjects served as the control group (C). All subjects were submitted to a graded maximal exercise cycle egometer test and completed 3 levels of submaximal exercise. Maximal oxygen consumption was similar in all groups. Cardiac index and stroke volume index at rest and during submaximal exercise were slightly lower in VSDop and PDA than VSDnop and C, however no statistical significance was found. The heart rate at rest was similar in all groups, however it was significantly lower in VSDop than all other groups. (Abstract shortened by UMI.)

Brown Norway rats show increased airway smooth muscle content following repeated allergen challenges. Macrophages synthesize many growth factors in vitro which potentially stimulate proliferation of airway smooth muscle cells. Leukotriene C$ sb4$, an important mediator of allergic airway responses, can stimulate macrophages to release platelet-derived growth factor (PDGF) which is a potent stimulator of proliferation. The purpose of this study was to investigate the role of the macrophage in the proliferative response of airway smooth muscle cells leading to airway remodelling. Macrophages were harvested from 7- to 9-week-old male Brown Norway rats, allowed to adhere to plastic 25cm$ sp2$ culture flasks for 25 minutes, rinsed with sterile PBS at 37$ sp circ$C to wash off cells other than macrophages and maintained in short-term culture in serum-free medium. Airway smooth muscle cells were also harvested and cultured. Supernatant from macrophages significantly stimulated airway smooth muscle cell proliferation 5-fold as compared to controls (p $<$ 0.05). This stimulation was affected neither by the addition of the cyclooxygenase inhibitor ASA, nor by the addition of the LTD$ sb4$ inhibitor MK-571. However, stimulation was decreased by the addition of the PDGF inhibitor suramin, as well as by an anti-PDGF polyclonal antibody. Maximal inhibition observed with antibody was 34% (p $<$ 0.01). We conclude that macrophages have the ability to stimulate airway smooth muscle cell proliferation by releasing growth factors, that one of these growth factors is PDGF, and that PDGF contributes 34% of the total airway smooth muscle cell proliferation. Therefore, it is likely that macrophages play an important role in airway remodelling and that this airway remodelling may be an important component in the pathology of asthma. (Abstract shortened by UMI.)