Effects of the Ca2+ chelators EGTA and EDTA on ethanol- or stress-induced gastric mucosal lesions and gastric secretion

Ca2+ modulates gastric function and dysfunction as well as the release of cysteine proteases and metalloproteinases which have been implicated in the pathogenesis of gastric mucosal lesions. We thus tested the hypothesis that pretreatment with the Ca2+ chelators, ethylene diamine tetraacetic acid (EDTA) and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) might reduce the experimental gastric mucosal damage induced by restraint cold stress or 1.0 ml of 75% ethanol. Other rats were prepared with chronic indwelling gastric cannulas and the effects of EDTA and EGTA on conscious basal gastric acid output were assessed. In addition, rats were pretreated with EGTA or EDTA prior to pylorus ligation and their effects on acid and pepsin output assessed. Both EDTA and EGTA reduced significantly the extent of ethanol-induced gastric mucosal damage as well as the degree of stress-induced gastric lesions. To further characterize the mechanism of Ca2+ chelator protection against ethanol-induced gastric lesions, some rats were vagotomized or adrenalectomized prior to treatment with EGTA or EDTA, followed by ethanol or stress. Both adrenalectomy and vagotomy abolished gastroprotection by EGTA and slightly reduced that induced by EDTA in both models of experimental gastric mucosal injury. Both EDTA and EGTA reduced significantly basal gastric acid output, an effect which persisted for at least 2 h following their administration. Both compounds also decreased significantly acid and pepsin output in pylorus-ligated rats. We conclude that Ca2+ chelators attenuate both acid-dependent and acid-independent gastric lesions.(ABSTRACT TRUNCATED AT 250 WORDS)

Iodoquinol associated seizures and radiopacity

This case report describes seizures and encephalopathy in a nine year-old boy treated with iodoquinol for amebiasis. The toxicity of iodoquinol and other 8-hydroxyquinolines is discussed. The radiopacity of this medication, used worldwide for the treatment of diarrheal illnesses and dermatitis, may be diagnostically useful.

Intramuscular pentamidine for the prevention of Pneumocystis carinii pneumonia in patients infected with human immunodeficiency virus

We retrospectively reviewed the charts of 96 patients infected with human immunodeficiency virus (HIV) who received intramuscular pentamidine for the prevention of Pneumocystis carinii pneumonia (PCP). These patients, all of whom had either a history of PCP or a CD4 lymphocyte count of < or = 0.2 x 10(9)/L, were intolerant of sulfa drugs, neutropenic, or intolerant of aerosolized treatment. Intramuscular pentamidine was given monthly by the Z-track technique at a dosage of 300 mg (4 mg/kg if the patient weighed < 50 kg). During a total of 350 months of primary prophylaxis in 47 patients and 426 months of secondary prophylaxis in 49 patients, only three cases of PCP occurred. More than 73% of the patients were receiving zidovudine concomitantly. Adverse reactions to intramuscular pentamidine included two episodes of hypotension, three of sterile abscess, two of glucose intolerance, and one of asymptomatic hypoglycemia. The administration of intramuscular pentamidine by the Z-track technique for PCP prophylaxis appears to be highly effective and minimally toxic.

Somatostatin depleting potency of cysteamine-related thiols and amines in the rat: structure-activity relation

Cysteamine, a potent duodenal ulcerogen, stimulates gastric acid and gastrin secretion and decreases immunoreactive somatostatin (IRS) from the gut and hypothalamus of the rat. To elucidate the structural requirements for this effect, we tested a series of cysteamine analogs for their IRS decreasing activity in comparison with their nucleophilic and reducing potencies. Adult female rats were sacrificed 4 hr after p.o. administration of the test chemicals given in molar equivalents to 30 mg/100 g of cysteamine-HCl. IRS decreasing activity in gastric mucosa, expressed as percentage of controls is listed in descending order: cystamine (55%), cysteamine (59%), 2-dimethylaminethanethiol (59%), ethylamine (66%), 1,3-propanedithiol (70%), propylamine (75%) and 3-aminothiophenol (79%). The following thiols and amines had no IRS decreasing effect (80% of controls): L-cysteine, ethanethiol, 1-propanethiol, penicillamine, dimercaprol, 1-4-dithiothreitol, ethanolamine, propionitrile, n-butyronitrile, o-, m- or p-aminophenol. The aryl 2-, 3- or 4-aminothiophenols, unlike most of their aminophenol analogs also decreased immunoreactive prolactin in the pituitary by 38 to 78%. IRS decreasing activity was independent of the reducing potency of cysteamine derivatives but was correlated significantly (r = 0.793, P < .01) with electron affinity of -SH, -NH2, -OH and -CN radicals in terminal alkyl chemicals. The structural requirement for decreasing activity is the presence of either -SH and -NH2 on a 2 to 3 carbon alkyl or aryl molecule. Both radicals when present together increase potency.(ABSTRACT TRUNCATED AT 250 WORDS)

Renal aspergilloma: an unusual cause of infection in a patient with the acquired immunodeficiency syndrome

The case of a 36-year-old man with the acquired immunodeficiency syndrome (AIDS) and a renal aspergilloma is reported. Aspergillus infections are uncommon in patients with AIDS. Isolated renal aspergillomas have rarely been reported in the non-AIDS population (14 cases) and have never been reported in a patient with AIDS. The patient we describe was clinically symptomatic and initially treated medically, but he did not respond to intravenous amphotericin and oral itraconazole. He eventually required nephrectomy; however, there was local recurrence of the aspergilloma postoperatively. We comment on some issues in the spectrum of Aspergillus infections in AIDS and review the literature on the manifestations and treatment of renal aspergillomas.

Glutathione, protein sulfhydryls and cysteine proteases in gastric mucosal injury and protection

Glutathione is one of the endogenous protective chemicals, like prostaglandins, in the gastric mucosa. Depletion of these agents aggravate the chemical- or stress-induced gastric erosions and ulcers. However, gastroprotection can be achieved even in the presence of low mucosal concentration of glutathione and prostaglandins, indicating the presence of other protective chemicals (e.g. polyamines, growth factors, neurotransmitters, steroids) in the stomach. Protein sulfhydryls were also implicated in the mechanism of action of gastroprotective drugs. We recently tested the hypothesis that cysteine proteases might be a target of gastroprotective and antiulcer agents, and decided to look for the presence of proteases and protease inhibitors (PI) in the gastric mucosa and juice. Protease activity and PI were measured with general substrates hemoglobin, azocasein and albumin at optimal pH (2.0, 5.6, 7.4) of aspartic, cysteine and serine proteases. Homogenates of glandular stomach mucosa and gastric juice from fasted rats were incubated in the presence or absence of specific inhibitors and gastroprotective SH alkylators such as NEM or iodoacetate. PI was measured after acid and heat inactivation of endogenous proteinases and addition of pepsin, cysteine proteinase papain, or trypsin. Our results indicate that of the proteases found in the stomach 98% was pepsin at pH 2.0, and up to 56% or 24% was SH-sensitive at pH 5.6 or 7.4, respectively. Intragastric administration of SH alkylators such as NEM or iodoacetate exerted a dose- and time-dependent gastroprotection against chemically induced acute erosions and ulcers. Thus, in addition to glutathione, proteinases and their specific endogenous inhibitors may also be involved in gastric mucosal injury and protection.

Subtentorial subdural empyema: Case report

We present a case of an extensive subtentorial subdural empyema of otorhinological origin. Although 3%-6% of all intracranial suppurations are infratentorial, there is no report on extensive multiloculated subtentorial empyema so far.

Endothelin induces vascular and mucosal lesions, enhances the injury by HCl/ethanol, and the antibody exerts gastroprotection

Vascular factors play an important role in the pathogenesis and prevention of acute gastric mucosal lesions. Endothelin-3 (ET-3), a potent vasoactive peptide, was infused intra-arterially to induce gastric microvascular and hemorrhagic mucosal lesions, and to enhance the damaging effects of dilute HCl and ethanol. ET-3 antibody was injected intravenously to decrease hemorrhagic mucosal lesions induced by ethanol. Locally infused ET (0.01, 0.1, and 1.0 nmol.100 g-1.min-1 for up to 15 min) was followed in some cases by intragastric dilute ethanol or HCl, which alone caused no or only mild vascular and mucosal lesions. Monastral blue was used to visualize and quantify vascular injury. ET-3 produced dose-dependent vascular lesions that affected the walls of mucosal capillaries and venules and induced mucosal congestion and focal endothelial labeling in vessels of the gastric muscular layers. The highest dose of ET induced hemorrhagic gastric mucosal lesions, mortality, and periods of hyper- and hypotension in the rat. Medium and low doses of ET-3 caused vascular injury, and dose-dependently potentiated the vascular and hemorrhagic mucosal lesions caused by dilute HCl and ethanol. Indomethacin slightly enhanced damage induced by ET and 50% ethanol, suggesting a limited mediatory role of prostaglandins in the ET-induced mucosal lesions. Anti-ET-3 serum dose-dependently decreased but did not abolish the hemorrhagic gastric mucosal lesions induced by 75% ethanol. Thus, ET-3 causes endothelial damage in capillaries and venules of rat stomach and predisposes to mucosal damage even after exposure to dilute ethanol or HCl. ET is more potent than leukotrienes and histamine and thus may play an important role in the mechanisms of acute gastric mucosal injury and protection where the vascular network appears to be a major target.

Experimental gastric mucosal injury: laboratory models reveal mechanisms of pathogenesis and new therapeutic strategies

Gastric ulcer is a multifaceted, pluricausal illness. Knowledge of the pathophysiology of gastric ulcer disease remains incomplete. Current pharmacological management of gastric ulceration is directed primarily at the reduction or neutralization of gastric acid secretion despite evidence that patients with this disease often exhibit normal gastric secretory activity. Attempts have been made to prevent or reduce gastric mucosal injury by cytoprotective agents without diminishing gastric acidity. We review several alternate explanations for the cause of gastric ulcers by examining various experimental models of gastric mucosal damage, including ethanol-, stress-, and nonsteroidal antiinflammatory drug-induced gastric lesions. We also discuss possible new strategies for the treatment of ulcer disease, particularly novel pharmacological targets arising from research conducted with these models. Growing realization that factors other than gastric secretion contribute significantly to the development of gastric ulcer disease prompts the conclusion that these same factors represent viable treatment alternatives.

Pathways, mediators and mechanisms of gastroduodenal mucosal injury

This review provides evidence that gastroduodenal mucosal injury is a complex process because of the heterogeneous structure and multiple functions of the gut. The action of exogenous etiologic agents is usually mediated in part, or amplified by endogenous mediators which very often exert biphasic, i.e., damaging and protective effects. The pathogenetic pathways involve direct/indirect chemical injury, vascular damage and its consequences, and acute or chronic inflammatory processes following infectious, chemical or ischemic injury. The role of oxygen, free radicals, calcium and proteases as well as the components and forms of gastroduodenal injury, e.g., reversible and irreversible cell injury, tissue necrosis, acute and chronic inflammation are also briefly discussed. Only a slight or moderate direct cytoprotection was demonstrated in vitro using isolated, mixed rat gastric mucosal cells by the known gastroprotective drugs including PG and SH compounds. Thus, the terms of organo or gastroprotection are more descriptive then the misleading "gastric cytoprotection".

Cysteamine protects gastric epithelial cell monolayers against drug induced damage: evidence for direct cellular protection by sulphydryl compounds

The sulphydryl containing drug cysteamine protects gastric mucosa in vivo against acute injury. It is not known whether this protection includes a direct effect on gastric cells. Using gastric epithelial cell monolayers derived from a well differentiated human cell line, we evaluated whether cysteamine protects against taurocholate or indomethacin induced damage in conditions which completely exclude the influence of vascular, hormonal, and neural factors. The effect of cysteamine on prostaglandin production by monolayer cells in vitro was also assessed. Cysteamine decreased damage brought about by sodium taurocholate and indomethacin by 40% (p less than 0.01) and 50% (p less than 0.01) respectively. The sulphydryl blocker iodoacetamide prevented the protective effect of cysteamine. Pretreatment with indomethacin, which inhibited prostaglandin E2 output by 60%, did not prevent protection by cysteamine; incubation with cysteamine decreased prostaglandin E2 production by cultured cells. We conclude that (i) cysteamine directly protected gastric epithelial cells in vitro (ii) this protection occurred with indomethacin, which interferes with cellular metabolism of prostaglandins, and taurocholate, whose damaging action at neutral pH is unrelated to interference with prostanoid metabolism, (iii) cysteamine protection in vitro is unrelated to endogenous prostaglandins and is probably mediated by endogenous sulphydryl compounds.

Interaction between stimuli with different taste qualities evaluated by reaction time

The influence of adaptation to taste stimuli of 1 quality on tastants with other qualities was investigated by comparing the reaction time (RT) to a test solution after adapting-solution flow with the RT to the same test solution after water flow. Adapting solutions were strong concentrations of NaCl, HCl, QHCl, and sucrose; test solutions were the same compounds but in lower concentrations. Adaptation to sucrose significantly shortened RT to NaCl and HCl, and to a lesser degree to QHCl. A similar cross-enhancement was found in sucrose when other compounds served as adapting solutions, In all other taste combinations, only a cross-adaptation effect was observed. Results are discussed in relation to some adaptation phenomena, water taste data, and magnitude-estimation data.

Sulphydryl mediation in the protection of gastric mucosal cells in tissue culture by acetaminophen

Acetaminophen protects gastric mucosa in vivo against acute drug-induced damage and has also been shown to protect gastric epithelial cells in vitro. Protection afforded by acetaminophen in vitro is not associated with increased prostaglandin output. The present study evaluated whether protection of gastric epithelial cells by acetaminophen in vitro may be mediated by endogenous sulphydryls. Monolayers from a well-differentiated human gastric epithelial cell line were studied. Sodium taurocholate was used as a damaging agent and cell damage was assessed by the 51Cr release assay. Acetaminophen dose-dependently protected gastric cell monolayers against damage induced by sodium taurocholate. The sulphydryl blocker iodoacetamide dose-dependently decreased the concentration of nonprotein glutathione and cysteine and counteracted the protection afforded by acetaminophen. This suggests that sulphydryl compounds may mediate the protection of gastric epithelial cells by acetaminophen in vitro.

Duodenal ulcer. Discovery of a new mechanism and development of angiogenic therapy that accelerates healing

The complete purification of the first angiogenic molecule, basic fibroblast growth factor (bFGF), was carried out in the authors' laboratory in 1983. Application of this peptide to chronic wounds enhances angiogenesis and accelerates wound healing. The authors showed that an acid-stable form of bFGF (i.e., bFGF-CS23) could be administered orally to rats with duodenal ulcers. The peptide promoted a ninefold increase of angiogenesis in the ulcer bed and accelerated ulcer healing more potently than cimetidine. Basic fibroblast growth factor did not reduce gastric acid. The authors now show that bFGF exists as a naturally occurring peptide in rat and human gastric and duodenal mucosa. This endogenous bFGF is present also in the bed of chronic ulcers in rats. Sucralfate binds bFGF and protects it from acid degradation. The sucralfate is angiogenic, based on its affinity for bFGF. When sucralfate is administered orally to rats, it significantly elevates the level of bFGF in the ulcer bed. Cimetidine, by its capacity to reduce gastric acid, also elevates bFGF in the ulcer bed. A hypothetical model is proposed in which prevention of ulcer formation or accelerated healing of ulcers by conventional therapies may be FGF dependent. Acid-stable bFGF-CS23 may be considered as a form of replacement therapy in the treatment of duodenal ulcers.

Role of vascular factors, including angiogenesis, in the mechanisms of action of sucralfate

This brief overview of our recent results implicates vascular factors in the mechanisms of acute and chronic actions of sucralfate. Pretreatment of rats with sucralfate and its components, such as SOS and sodium sulfate, prevented the ethanol-induced microvascular injury and maintained blood flow in the gastric mucosa. Thus, preservation of microvascular integrity seems to be one of the mechanisms of acute gastroprotection by sucralfate. Chronic experiments with subcutaneously implanted sponges containing sucralfate or SOS revealed that both compounds stimulated angiogenesis, whereas only sucralfate enhanced the area of granulation tissue. These processes may have a role in the ulcer-healing action of sucralfate.

Predicting chemically induced duodenal ulcer and adrenal necrosis with classification trees

Binary tree-structured statistical classification algorithms and properties of 56 model alkyl nucleophiles were brought to bear on two problems of experimental pharmacology and toxicology. Each rat of a learning sample of 745 was administered one compound and autopsied to determine the presence of duodenal ulcer or adrenal hemorrhagic necrosis. The cited statistical classification schemes were then applied to these outcomes and 67 features of the compounds to ascertain those characteristics that are associated with biologic activity. For predicting duodenal ulceration, dipole moment, melting point, and solubility in octanol are particularly important, while for predicting adrenal necrosis, important features include the number of sulfhydryl groups and double bonds. These methods may constitute inexpensive but powerful ways to screen untested compounds for possible organ-specific toxicity. Mechanisms for the etiology and pathogenesis of the duodenal and adrenal lesions are suggested, as are additional avenues for drug design.

Time course of recovery from gustatory adaptation to NaCl

Recovery from adaptation to NaCl was tested by comparing some relevant parameters of response to the adapting and test stimuli separated by different recovery intervals. The time course of response was determined using magnitude estimations and using the flow chamber for stimulus delivery. The course of recovery for all parameters used was a negatively accelerated function of the rest time, but the recovery rate of different parameters did not prove to be equal. Recovery was fastest for the initial maximum taste magnitude, followed by the time needed for the taste to disappear. The taste effect summed over time and the time required for the taste magnitude to decrease to 30% of its preadapted maximum were the slowest to recover. Although the recovery processes proceeded at a rapid rate during the initial period, all parameters remained depressed over a rather long period.

Magnitude estimation of adaptation to salt using a flow chamber for stimulus delivery

Adaptation course to NaCl was estimated using a flow chamber for stimulus delivery and changes in the perceived taste magnitude as the criterion. The adapting stimulus of different durations was applied to one side of the tongue. Magnitude estimates were made by comparing the intensity of taste at the end of each adaptation time with the perceived intensity of the same stimulus applied briefly to the unadapted side of the tongue. The course of adaptation followed a negatively accelerated decreasing function. The relationship between taste magnitude and the duration of the adapting stimulus can be approximated by a logarithmic equation and, somewhat less accurately, also by an exponential equation, which can be related to the Beidler theory of taste stimulation. Some advantages of the closed flow technique and comparison of taste magnitudes on the adapted and unadapted sides of the tongue are discussed.

Extremely long protection by pyrazole derivatives against chemically induced gastric mucosal injury

We tested the hypothesis that the gastrotoxicity of ethanol and other damaging agents is influenced through the modulation of alcohol dehydrogenase (ADH) by using either the ADH-inhibitor pyrazole or the noninhibitor derivatives of pyrazole. In time course experiments, the protection by both compounds was evident up to 48 hr before ethanol administration. Both drugs were also protected, from about 24 hr, from gastric mucosal damage induced by aspirin and hydrochloric acid. In order to examine the role of endogenous prostaglandins and sulfhydryls in this protection, indomethacin and N-ethylmaleimide were used, of which only the sulfhydryl alkylator antagonized (by about 50%) the protection by pyrazole and 3-methylpyrazole. Studies with monastral blue B revealed the protective role of both pyrazole and 3-methylpyrazole against early vascular injury in the gastric mucosa. We conclude that because both the ADH-inhibitor pyrazole and the noninhibitor derivatives of pyrazole exert gastro-protection, and because both compounds protect against aspirin and HCI, ADH inhibition is not involved in this protection. We also suggest that although prostaglandins appear to have minimal involvement in the mechanism of protection, endogenous sulfhydryls may be important mediators. Furthermore, the functional and structural mechanism of this protection seems to be the prevention of acute vascular injury.

Surrogate markers for survival in patients with AIDS and AIDS related complex treated with zidovudine

OBJECTIVE

To determine whether early effects of zidovudine treatment on CD4+ lymphocyte count and concentrations of beta 2 microglobulin, neopterin, or HIV p24 antigen or antibody are correlated with survival in patients with AIDS or AIDS related complex.

DESIGN

Retrospective study of changes in laboratory markers and survival.

SETTING

Multicentre trial at university hospital clinics.

SUBJECTS

90 Patients with AIDS or AIDS related complex.

INTERVENTION

Patients started zidovudine 200 mg orally every four hours. Fifty six of the patients died a median 17 months after starting zidovudine; the remaining 34 patients were followed up for a median 25.5 months.

MAIN OUTCOME MEASURES

Changes in CD4+ lymphocyte count and serum concentrations of p24 antigen and antibody, beta 2 microglobulin, and neopterin; survival of the patient.

RESULTS

The pretreatment characteristics that independently predicted poor survival were determined using a multivariate proportional hazards model: a diagnosis of AIDS (v AIDS related complex), age over 45 years, and the logarithm of serum neopterin concentration. When these baseline characteristics were controlled for the logarithm of CD4+ lymphocyte count at weeks 8-12 of treatment (p = 0.007) and an increase in serum beta 2 microglobulin concentration at weeks 8-12 (p = 0.05) also independently correlated with survival. In the 38 patients with a better pretreatment prognosis, 24 month survival estimated by the product-limit method was 88% for those with a good response on both surrogate markers during early treatment compared with only 50% for those with a poor response on either marker. In the 38 with a worse pretreatment prognosis, 24 month survival was estimated to be 49% for those with a good response on both surrogate markers compared with only 18% for those with a poor response on either.

CONCLUSION

These data suggest that CD4+ lymphocyte count at 8-12 weeks and, perhaps, change in serum beta 2 microglobulin concentration could be surrogate end points for clinical outcome in trials of antiretroviral drugs for patients with HIV disease.

The mode of action of sucralfate: the 1 x 1 x 1 mechanism of action

Of the multiple actions of sucralfate, not all are equally relevant. In fact, certain actions of the drug contribute to healing of acute ulcers or to ulcer prevention, whereas other actions are more important in accelerating the healing of gastric and duodenal ulcers. The action of sucralfate can now be defined by the '1 x 1 x 1' mechanism of action--that is, one action of sucralfate is important for acute prevention, one is relevant to both acute and chronic protection, and one is important for chronic ulcer healing. Maintenance of mucosal vascular integrity and of blood flow, which ensures rapid epithelial restitution to repair superficial defects, are the most important acute actions of sucralfate. On the other hand, increased bicarbonate and mucus secretion seem to be relevant in both acute and chronic protection of the gastroduodenal mucosa. Finally, the enhanced binding by sucralfate of fibroblast growth factor and epidermal growth factor stimulates angiogenesis, granulation tissue, and epithelization for ulcer healing. This 1 x 1 x 1 theory of the mechanism of action of sucralfate concentrates on the relevant effects of this drug (which has more than a dozen actions) and may help to elucidate the molecular mechanism of action.

Interaction between stimuli with different taste qualities evaluated by reaction time

The influence of adaptation to taste stimuli of 1 quality on tastants with other qualities was investigated by comparing the reaction time (RT) to a test solution after adapting-solution flow with the RT to the same test solution after water flow. Adapting solutions were strong concentrations of NaCl, HCl, QHCl, and sucrose; test solutions were the same compounds but in lower concentrations. Adaptation to sucrose significantly shortened RT to NaCl and HCl, and to a lesser degree to QHCl. A similar cross-enhancement was found in sucrose when other compounds served as adapting solutions, In all other taste combinations, only a cross-adaptation effect was observed. Results are discussed in relation to some adaptation phenomena, water taste data, and magnitude-estimation data.

Dopamine in gastrointestinal disease

Dopamine is an important enteric neuromodulator. Herein we review the data that support a role for dopaminergic involvement in experimental duodenal and gastric ulceration; gastric, pancreatic, and duodenal secretion; gastrointestinal motility; and gastric and intestinal submucosal blood flow regulation. There also is support for a role for dopamine and dopamimetic agents in the treatment of certain experimental gastrointestinal diseases because some highly selective dopamine agonists are gastroprotective when given either parenterally or centrally. Based upon these observations, we suggest that dopamine is a key element of the "brain-gut axis" and represents a potentially important target for pharmacotherapeutic exploitation.