Search PubMed⌕ Search

Biomedical subjects

J Polak

Publications and source records attributed to J Polak.

At least 37 records · Page 2Linked to original sources
PubMed1998

Erosive oesophagitis: outcome of repeated long term maintenance treatment with low dose omeprazole 10 mg or placebo.

AIMS: To investigate the efficacy of daily maintenance treatment with omeprazole 10 mg in reducing the relapse rate of healed erosive oesophagitis. METHODS: Three hundred patients with erosive oesophagitis (grade 2 or greater) received omeprazole 20 mg daily for 12 weeks, followed by 40 mg daily for a further 12 weeks if required. After healing, patients were randomised to double blind treatment with omeprazole 10 mg daily or placebo for up to 18 months. On relapse the treatment cycle was repeated. RESULTS: The cumulative healing rate at 12 weeks in the initial healing period was 95%, and 96% and 98% on rehealing courses after relapse in the first and second maintenance periods respectively. After 12 weeks of treatment, 98% of patients were free from heartburn and 97% were free of all reflux related symptoms. Relapse in the subgroup of patients who relapsed in both maintenance periods was infrequent on omeprazole 20 mg daily: only 9% at two years. Gastrin concentrations rose above normal in one third of patients. One patient had linear hyperplasia of endocrine cells and another had micronodular hyperplasia. There were no side effects definitely attributable to omeprazole. CONCLUSION: Maintenance treatment with omeprazole 10 mg daily keeps about 60% of patients with erosive oesophagitis in prolonged remission. Patients relapsing once are likely to do so again; they can subsequently be treated effectively with omeprazole 20 mg daily.

Anti-Ulcer Agents↗
PubMed1998

Immunization and challenge with toluene diisocyanate decrease tachykinin and calcitonin gene-related peptide immunoreactivity in guinea pig central airways.

Toluene diisocyanate (TDI) is a potent sensitizer that causes occupational asthma in a significant proportion of subjects exposed. We used an animal model to investigate whether neuropeptide changes occur in the airways of immunized and TDI-challenged guinea pigs. Animals were immunized by weekly intradermal injections, challenged with TDI (5 to 20 ppb) after the third injection, and killed 6 h after exposure. Control guinea pigs received injections of saline. Lung tissue was processed immediately and analyzed for nerves using the streptavidin-biotin complex peroxidase method with antisera to the neural marker protein gene product 9.5 (PGP 9.5), substance P (SP), and calcitonin gene- related peptide (CGRP). We also quantified the inflammatory infiltrate in the submucosa of central airways, and we measured the serum level of specific IgG and IgG1. Specific antibodies against TDI were present only in immunized animals. Immunized as compared with nonimmunized animals had a significant increase in eosinophils in the submucosa of central airways, and a further increase was observed 6 h after TDI challenge. Immunization and TDI challenge did not modify the number of mononuclear cells in the submucosa of central airways in both nonimmunized and immunized animals. TDI exposure did not change the overall innervation in both nonimmunized and immunized animals, but the density of PGP 9.5-positive nerves was significantly different between nonimmunized and immunized TDI-challenged animals. The density of SP-, and CGRP-immunostained nerves was significantly lower in immunized TDI-challenged than in nonimmunized animals. TDI exposure significantly decreased the density of SP-positive nerves in nonimmunized animals. A negative relationship was found between the presence of airway inflammation, as indexed by eosinophil cell infiltration, and the density of PGP 9.5-, SP-, and CGRP-immunostained nerves. In conclusion, TDI produces airway inflammation and neuropeptides changes in the central airways of immunized guinea pigs 6 h after TDI challenge. These findings support an interaction between tachykinins, inflammatory (i.e., eosinophils) and possibly immune cells.

Animals↗
PubMed1998

Functional role of rRNAs in plant translation system tested with antisense strategy.

There are regions in rRNA which are evolutionary conserved and exposed on ribosomal surface. We selected in plant material (Lupinus luteus) two of them: the alpha-sarcin domain of 26S rRNA (L-rRNA) and C loop of 5S rRNA, to be further investigated using antisense oligomers as research tools. We found inhibition of the model polypeptide biosynthesis (up to 80%) due to specific hybridization of oligomers addressed to alpha-sarcin domain and loop C. Based on our results we present the evidence for the key role played by these regions of rRNAs during protein biosynthesis in plant system. According to our hypothesis, conformational changes of these two regions are synchronised and cooperative during transition of pre- to post-translocation state of the ribosome. The correlation of structure and activity of rRNA domains in translation is shown.

Base Sequence↗
PubMed1997

The Kluver-Bucy syndrome.

Evolution of psychological disorders following head injury including memory and other cognitive disorders are common. The best known are psychiatric disturbances of various kinds after lesions of the frontal lobes. Cognitive, behavioural and emotional disorders are not usually seen in patients with bilateral temporal lesions. In our Department of Neurotraumatology we have observed 4 patients with posttraumatic lesions localized bitemporally. They developed Kluver-Bucy syndrome-rarity in human pathology-combined with three or more of the following symptoms and signs: increased oral activity, hypersexuality, hypermetamorphosis, memory disorders, placidity, loss of people recognition, bulimia. Several symptoms responded dramatically to carbamazepine. We conclude that it may be a useful agent in the treatment of this unusual syndrome.

Adult↗
PubMed1997

Pituitary neuromedin B content in experimental fasting and diabetes mellitus and correlation with thyrotropin secretion.

Fasting and diabetes mellitus in the rat model have been associated with abnormalities of thyrotropin (TSH) secretion. Neuromedin B is a bombesin-like peptide highly concentrated in the pituitary gland that has been shown to have inhibitory action on TSH secretion, acting as an autocrine/paracrine factor. Here, we aimed to determine if the pituitary content of neuromedin B would change in fasted rats (1, 2, 3, and 4 days of food deprivation) and streptozotocin (55 mg/kg body weight)-diabetic rats. The total pituitary content of neuromedin B was decreased in fasted rats, except at 2 days of fasting, as was the total protein content in the gland; however, the concentration of the peptide (femtomoles per milligram protein) did not significantly change until the fourth day of food deprivation, when an abrupt decrease in total protein happened and therefore neuromedin B concentration increased. In rats after 20 days of diabetes induction, pituitary neuromedin B increased. Serum thyroxine (T4) and triiodothyronine (T3) decreased in both disorders, whereas serum TSH was normal or decreased in 4-day fasted rats. Therefore, the caloric deprivation of diabetes and fasting changed the pituitary neuromedin B content and concentration, by mechanisms that remain to be elucidated. Since neuromedin B has been shown to act as a local inhibitor of TSH release, the results raise the possibility that increased neuromedin B concentration might be involved in the altered TSH secretion of diabetes mellitus and fasting.

Animals↗
PubMed1997

Advanced glycation end products in human penis: elevation in diabetic tissue, site of deposition, and possible effect through iNOS or eNOS.

OBJECTIVES: We hypothesized that advanced glycation end product (AGE) formation contributes to erectile dysfunction (ED) by quenching nitric oxide. Our first goal was to identify the specific AGE pentosidine in the diabetic human penis. Because AGE-mediated effects may involve inducible nitric oxide synthase (iNOS), we performed immunohistochemical and Western blot analysis of diabetic and nondiabetic human penile tissue for iNOS. Finally, because AGEs may act intracellularly to affect proteins, we set out to identify endothelial NOS (eNOS) in the human penis as an initial step in examining a possible intracellular interaction between eNOS and AGEs. METHODS: We performed high-performance liquid chromatographic analysis of diabetic human penile corpus cavernosum and serum for pentosidine and performed immunohistochemical, electron microscopic (EM), and Western blot analysis of the diabetic and nondiabetic penile corpus cavernosum and tunica for pyrraline, iNOS, and eNOS (and neural NOS [nNOS] for comparative purposes) via standard methods. RESULTS: We found a significant elevation of pentosidine in the penile tissue but not the serum of diabetic patients (average age 55.6 +/- 2.3 years) compared with that of nondiabetic patients (average age 61.8 +/- 3.6 years). Pentosidine was 117.06 +/- 9.19 pmol/mg collagen in the diabetic tunica versus 77.58 +/- 5.5 pmol/mg collagen in the nondiabetic tunica (P < 0.01) and 74.58 +/- 8.49 pmol/mg collagen in the diabetic corpus cavernosum versus 46.59 +/- 2.53 pmol/mg collagen in the nondiabetic corpus cavernosum (P < 0.01), suggesting a tissue-specific effect of the AGEs. We localized the site of deposition of the specific AGE pyrraline to the human penile tunica and the penile corpus cavernosum collagen. Immunohistochemical and EM analysis localized eNOS and iNOS to the cavernosal endothelium and smooth muscle. Western blot analysis in 6 patients revealed the following: iNOS, but no eNOS, in penile tissue from 1 insulin-dependent diabetic man; eNOS only in 1 man after radical prostatectomy; both eNOS and iNOS in 2 men with Peyronie's disease, as well as in 2 other men with impotence and hypertension. Finally, the specific iNOS inhibitor PNU-19451A significantly augmented relaxation of precontracted human cavernosal tissue, from 64.7% +/- 5.58 to 80.03% +/- 4.55 at 10 microM acetylcholine and 65.06% +/- 2.84 to 86.16% +/- 3.96 at 0.1 mM acetylcholine (n = 4, P < 0.002 and P < 0.02, respectively). CONCLUSIONS: AGEs are elevated in diabetic human penile tissue, but not in serum, and are localized to the collagen of the penile tunica and corpus cavernosum. We identified eNOS and iNOS in the human penile cavernosal smooth muscle and endothelium. The augmentation of cavernosal relaxation with a specific iNOS inhibitor, combined with the identification of iNOS protein, but not eNOS, in a patient with severe diabetes and ED, allows for speculation of a pathophysiologic mechanism for AGE-mediated ED via upregulation of iNOS and downregulation of eNOS. These data provide further insight into the mechanisms of advanced glycation end product-mediated ED and provide a foundation for further study.

Adult↗
PubMed1997

The role of nitric oxide in experimental murine sepsis due to pyrogenic exotoxin A-producing Streptococcus pyogenes.

Nitric oxide (NO) produced by inducible NO synthase (iNOS) mediates hypotension in endotoxemia. In this study, NO induction by a toxin-producing Streptococcus pyogenes isolate, H250, and by recombinant streptococcal pyrogenic exotoxin A (rSPEA) has been examined, both in vitro and in vivo. Streptococcal supernatants, but not rSPEA, induce production of nitrite by murine macrophages when both are coincubated with gamma interferon. Intraperitoneal injection of rSPEA did not cause significant production of NO. However, an elevated level of nitrate in serum was detected in a model of streptococcal fasciitis due to live H250. iNOS was localized to Kupffer cells, hepatocytes, and renal tubular cells by immunostaining. Administration of a NOS inhibitor, N(G)-monomethyl-L-arginine (L-NMMA), reduced peak concentrations of nitrate in serum but did not affect survival. NO is induced by H250, both in vitro and in vivo, mainly via SPEA-independent mechanisms. In this model, iNOS is expressed predominantly in the liver. Furthermore, in this model L-NMMA is not protective.

Animals↗
PubMed1997

Effects of ozone on epithelium and sensory nerves in the bronchial mucosa of healthy humans.

Neuropeptides released from sensory nerves during inflammation have potent effects on bronchomotor tone, airway secretion, and inflammatory cells. We investigated the effects of ozone on sensory nerves by exposing 12 healthy, nonsmoking subjects to 0.2 ppm ozone and filtered air (FA) for 2 h on separate occasions, with intermittent exercise and rest. Spirometry was performed at baseline and 15 min after exposures, and bronchoscopy (bronchial biopsy and bronchoalveolar lavage [BAL]) was done 6 h after exposure. Frozen sections were immunostained for the anatomic neural marker protein gene peptide (PGP) 9.5 and the sensory neutropeptides substance P (SP) and calcitonin-gene-related peptide (CGRP). Nerves in the submucosa were quantified by image analysis. A trend toward an increase in the levels of polymorphonuclear leukocytes (PMNs) (air versus ozone, median [interquartile range]: 3.5 [2 to 5.3%] versus 9.8 [4.2 to 16.3%], p = 0.07) and ciliated epithelial cells (median [interquartile range]: 1.6 [1.3 to 3.4%] versus 5 [2.2 to 9.8%], p = 0.05) was observed in the BAL fluid (BALF). There was a significant decrease in SP immunoreactivity following ozone exposure (median [interquartile range]: 0.6 [0.05 to 1.2] versus 0.15 [0.08 to 0.18], p < 0.05). A significant inverse correlation was observed between SP immunoreactivity and: (1) percent PMNs and ciliated epithelial cells in the BALF; and (2) percent change in FEV1 following exposure to ozone. These findings indicate that short-term exposure to 0.2 ppm ozone causes epithelial shedding and stimulates subepithelial sensory nerves to release SP into the airways. The release of SP could contribute to bronchoconstriction and subsequent neutrophil infiltration into the airways.

Adult↗
PubMed1997

The Kluver-Bucy syndrome.

Evolution of psychological disorders following head injury including memory disorders and other cognitive ones are common. The best known are psychiatric disturbances of various kind after lesions of frontal lobes. Cognitive, behavioural and emotional disorders are not usually seen in patients with bilateral temporal lesions. In our Department of Neurotraumatology we observed 4 patients with post-traumatic lesions localized bitemporally. They developed Kluver-Bucy syndrome--rarity in human pathology--with combination of three or more the following syndromes: increased oral activity, hypersexuality, hypermetamorphosis, memory disorders, placidity, loss of people recognition, bulimia. Several symptoms responded dramatically to carbamazepine. We conclude that it may be a useful agent in treatment of this unusual syndrome.

Adult↗
PubMed1997

Histamine H2 receptor antagonist-refractory oesophagitis: the efficacy of long-term omeprazole maintenance treatment.

BACKGROUND: Erosive oesophagitis refractory to high dose histamine H2 receptor antagonists (definition: failure to heal fully after > or = 3 months' treatment with cimetidine 3.2 g or ranitidine 0.9 g) responds well to omeprazole 40 mg daily but frequently relapses when the patients are put back on maintenance H2 receptor antagonists at medium or even high dose (e.g. cimetidine 1.6 g and 3.2 g, respectively). AIM: To investigate the efficacy of maintenance omeprazole 20 mg daily in refractory erosive oesophagitis. PATIENTS & METHODS: In this open, sequential study, patients with H2 receptor antagonist-refractory oesophagitis were healed on omeprazole 40 mg daily and then put on maintenance H2 receptor antagonists (cimetidine 1.6 g or 3.2 g). Relapses were re-treated with omeprazole 40 mg; upon rehealing, patients were put on maintenance omeprazole 20 mg daily for up to 4.5 years. RESULTS: Healing on omeprazole occurred in 38 out of 39 patients (97%) at 12 weeks. Only six of the 38 patients (16%) relapsed (asymptomatic in half) during subsequent maintenance treatment, whereas all had relapsed earlier on high dose H2 receptor antagonists. CONCLUSION: Within the limits of interpretation of an open study, omeprazole 20 mg daily seems effective in maintaining prolonged remission in this group of patients with H2 receptor antagonist-refractory oesophagitis.

Adult↗
PubMed1996

Effect of thyroid hormones on pituitary neuromedin B and possible interaction between thyroid hormones and neuromedin B on thyrotropin secretion.

Neuromedin B (NB), a bombesin-like peptide, has been recently characterized as a physiological paracrine/autocrine inhibitor of thyrotropin (TSH) secretion. We hypothesized on the basis of our prior experiments that thyroid hormones stimulate pituitary NB secretion which mediates, at least in part, the TSH-suppressive effect of thyroid hormone. Here, we evaluated the time-course of the effect of thyroid hormones administration to eu- and hypothyroid rats on the anterior pituitary content of NB and on serum TSH. As previously reported, the pituitary content of NB increased in hyperthyroidism and decreased in hypothyroidism. Chronic treatment of hypothyroid rats with a physiological dose of thyroxine (0.8 microgram/100 g b.w. s.c, for 3 or 5 days) normalized pituitary NB content, while 5 days of treatment with a pharmacological dose of thriiodothyronine (0.4 microgram/100 g b.w.) induced an increase above that of normal pituitaries. Thyroxine and triiodothyronine injected once, s.c., into hypothyroid rats required 30 min to normalize NB content, which reached higher than normal values in 3-6 h. At these times, the increment in NB preceded or was simultaneous with the suppression of serum TSH. This rapid and marked effect on pituitary neuromedin B content, associated in time with TSH suppression, is in agreement with the hypothesis that neuromedin B may mediate at least in part, the acute suppression of TSH release by thyroid hormone, a hypothesis that still needs further verification.

Animals↗
PubMed1996

Streptococcal pyrogenic exotoxin A release, distribution, and role in a murine model of fasciitis and multiorgan failure due to Streptococcus pyogenes.

The role of streptococcal pyrogenic exotoxin A (SPEA) was evaluated in a murine model of fasciitis and multiorgan failure due to a toxigenic strain of Streptococcus pyogenes. Increased serum levels of SPEA at 15 and 21 h were associated with a survival time of <24 h. Levels of SPEA correlated with interleukin-6 levels. Immunostaining showed SPEA localized to renal and hepatic cells. Neutralizing rabbit antibody to SPEA was administered to mice challenged with S. pyogenes, but no effect on survival was observed. Vaccination of mice with recombinant SPEA enhanced mortality due to streptococcal infection, despite the development of neutralizing immunity to the toxin prior to infection. Hence, SPEA is produced systemically during S. pyogenes soft-tissue infection, and increased levels are associated with reduced survival. In this model, however, SPEA did not appear to play a dominant role in pathogenesis; passive immunization against SPEA was not protective, and active immunization enhanced mortality.

Animals↗
PubMed1996

Role of neuromedin B in the in vitro thyrotropin release in response to thyrotropin-releasing hormone from anterior pituitaries of eu-, hypo-, and hyperthyroid rats.

A role of neuromedin B (NB), a bombesin-like peptide, as an inhibitory paracrine/autocrine regulator of thyrotropin secretion has been suggested. We previously reported (10) that basal thyroid-stimulating hormone (TSH) release in vitro was decreased by NB and increased in the presence of a highly potent antiserum against NB (aNB). In these experiments, we studied the effects of NB (10(-11) - 10(-7) M) and antiserum against NB (aNB, 1:2000 dilution) on basal TSH release and the response to thyrotropin-releasing hormone (TRH) (0.5 x 10(-8) M) from incubated anterior pituitaries from eu-, hypo-, and hyperthyroid rats. As expected, in euthyroid rats NB decreased basal and TRH-stimulated TSH release, but only at the highest concentration tested (10(-7) M). Incubation of the pituitaries from euthyroid rats with the antiserum against NB increased basal TSH release above that from glands of normal rabbit serum-incubated controls, as anticipated based on the concept that NB inhibits TSH release from the pituitary glands of euthyroid animals. The antiserum did not augment the response to TRH, suggesting that NB released in this situation, although suppressing basal release, had no effort on the stimulated release induced by TRH. Glands from hypothyroid rats had a slightly lower basal TSH release and decreased response to TRH than glands from euthyroid rats. They responded with a decrease in basal TSH release at a much lower concentration of NB (10(-9) M) than pituitaries from euthyroid animals. Surprisingly, pituitaries from hypothyroid rats showed a paradoxical increased release of TSH in response to the lowest concentration of NB (10(-11) M), which decreased with increasing concentrations and was not distinguishable from control release in the presence of TRH at the highest concentration of NB (10(-7) M). We hypothesize that the increased responsiveness to the inhibition of basal TSH release by NB in the hypothyroid pituitaries may be related to an upregulation of NB receptors in this situation, in which the release of NB is diminished because of loss of feedback via thyroid hormones. The view that NB secretion was reduced in the hypothyroid situation was supported by the fact that there was no change in TSH release or the response to TRH following treatment with aNB in these animals. Remarkably, in the glands from the hyperthyroid rats, although basal TSH secretion was significantly lower than that from euthyroid pituitaries and response to TRH was also decreased, NB (10(-11)-10(-7) M) instead of decreasing TSH release augmented it significantly. Also, the response to TRH was significantly augmented but only at the lowest concentration of NB tested (10(-11 M). That NB was probably being secreted in vitro from the hyperthyroid pituitaries was indicated by an increased basal TSH release as well as a higher TSH medium concentration after TRH in the presence of the aNB. These results support the concept that the glands from the hyperthyroid animals secrete more NB because of positive feedback of thyroid hormones directly on the thyrotropes to increase NB synthesis and release which downregulates NB receptors on the gland. This downregulation of receptors in some manner reverses the inhibitory action of NB on basal and TRH-stimulated TSH release. In conclusion, the results provide further evidence for an important role of NB as an autocrine regulator of TSH release, which is modulated by increased release of NB induced by thyroid hormones.

Animals↗
PubMed1994

Inducible nitric oxide synthase is increased in murine lung epithelial cells by cytokine stimulation.

Nitric oxide (NO) is detectable in exhaled air. To elucidate whether airway epithelial cells could be a source of NO, we investigated the expression of inducible nitric oxide synthase (iNOS) by the murine lung epithelial cell line, LA-4, in response to cytokine stimulation and the ability of corticosteroids to modulate this effect. Stimulation with cytomix, a combination of interleukin-1 beta, tumor necrosis factor-alpha, and interferon-gamma, elevated nitrite levels by 873% in the culture supernatants and enhanced the conversion of arginine to citrulline by 273% at 24 h. An increased number of cells stained for iNOS and an increase in iNOS mRNA was also observed. Dexamethasone decreased the cytokine-induced increase in nitrite levels, NOS activity, iNOS immunoreactivity, and mRNA but did not change the half life of iNOS mRNA. These results show that lung epithelial cells can release NO, a process which can be inhibited by dexamethasone.

Amino Acid Oxidoreductases↗