PubMed Health⌕ Search

Biomedical subjects

L Guerra

Publications and source records attributed to L Guerra.

At least 19 recordsLinked to original sources
PubMed1992

Na+/H(+)-exchange in A6 cells: polarity and vasopressin regulation.

We have analyzed the mechanism of Na(+)-dependent pHi recovery from an acid load in A6 cells (an amphibian distal nephron cell line) by using the intracellular pH indicator 2'7'-bis(2-carboxyethyl)5,6 carboxyfluorescein (BCECF) and single cell microspectrofluorometry. A6 cells were found to express Na+/H(+)-exchange activity only on the basolateral membrane: Na+/H(+)-exchange activity follows simple saturation kinetics with an apparent Km for Na+ of approximately 11 mM; it is inhibited in a competitive manner by ethylisopropylamiloride (EIPA). This Na+/H(+)-exchange activity is inhibited by pharmacological activation of protein kinase A (PKA) as well as of protein kinase C (PKC). Addition of arginine vasopressin (AVP) either at low (subnanomolar) or at high (micromolar) concentrations inhibits Na+/H(+)-exchange activity; AVP stimulates IP3 production at low concentrations, whereas much higher concentrations are required to stimulate cAMP formation. These findings suggest that in A6 cells (i) Na+/H(+)-exchange is located in the basolateral membrane and (ii) PKC activation (heralded by IP3 turnover) is likely to be the mediator of AVP action at low AVP concentrations.

Amiloride↗
PubMed1992

Characterization of basolateral Na/H exchange (Na/H-1) in MDCK cells.

MDCK cells were grown to confluent monolayers on permeant filter supports; pH was analysed by using the pH-sensitive fluorescent probe 2'7'-biscarboxyethyl-5,6-carboxyfluorescein and a routine spectrofluorometer equipped with a perfusion cuvette [Krayer-Pawlowska et al. (1990) J Membr Biol 120:173-183]. Superfusion of the basolateral (but not apical) cell surface with Na(+)-containing solutions led to immediate recovery of pHi from an acid load (NH4 prepulse). This pHi recovery was reversibly inhibited by ethylisopropylamiloride indicating Na/H exchange activity. Na/H exchange activity showed an apparent Km for Na+ of about 25 nM Na+ and an apparent Ki for inhibition by dimethylamiloride of around 0.2 microM; inhibition by dimethylamiloride was competitive with Na+ interaction. Lowering pHi prior to analysis of Na/H exchange leads to sharp activation of Na/H exchange; the apparent Vmax for Na/H exchange is increased more than tenfold by lowering the pHi from 7.0 to 6.7 without an effect on apparent Km values for Na+ interaction. It is concluded that MDCK cells (strain I) grown on a permeant support contain only basolateral Na/H exchange activity, most likely Na/H-1 [for nomenclature see Igarashi et al. (1991) Kidney Int 40:S84-S89].

Amiloride↗
PubMed1992

Aldosterone actions on basolateral Na+/H+ exchange in Madin-Darby canine kidney cells.

In recent studies, there has been a re-evaluation of the polarity of Na+/H+ exchange in Madin-Darby canine kidney (MDCK) cells. This study was designed to examine aldosterone actions on basolaterally located Na+/H+ exchange of MDCK cell monolayers grown on permeant filter supports; pHi was analysed in the absence of bicarbonate by using the pH-sensitive fluorescent probe 2',7'-bis(carboxyethyl)-5,6-carboxyfluorescein. Pre-exposure of MDCK cells to aldosterone led within 10-20 min to an alkalization of pHi (approximately 0.3 pH unit); this effect is prevented by an addition of dimethylamiloride to the basolateral superfusate. Addition of aldosterone led to stimulation of the basolaterally located Na+/H+ exchange activity (Na(+)-dependent recovery from an acid load); this effect required preincubation (more then 3 min) and was observed at 0.1 nM aldosterone. Pre-exposure (15 min) of MDCK monolayers to phorbol 12-myristate 13-acetate also led to an activation of Na+/H+ exchange; pre-exposure to 8-bromo-cAMP led to inhibition of Na+/H+ exchange activity. An inhibitory effect of aldosterone was observed if Na+/H+ exchange activity was analysed in the presence of aldosterone; the highest inhibitory effects (20%-30%) occurred at concentrations of 5 nM and higher. Aldosterone-dependent inhibition does not require preincubation and is fully reversible; it was only observed at low (20 mM) but not at high Na+ concentrations (130 mM). The data suggest that aldosterone has an instantaneous inhibitory effect on basolaterally located Na+/H+ exchange activity under conditions of low Na+, but stimulates the rate of transport activity upon preincubation under conditions of physiological Na+ concentrations.

Aldosterone↗
PubMed1992

Role of foods in the pathogenesis of chronic paronychia.

BACKGROUND: Chronic paronychia is a condition that is pathologically characterized by spongiotic inflammation; it can be exacerbated by various and concomitant factors. OBJECTIVE: The aim of this study was to assess whether chronic paronychia in food handlers may have clinical, pathologic, and immunohistochemical similarities with immediate contact dermatitis caused by foods. METHODS: Twenty food handlers affected by chronic paronychia were submitted to patch tests with the fresh foods that were suspected of being the cause of the dermatitis. RESULTS: Nine patients had a positive reaction to a 20-minute open patch test with fresh foods applied on the proximal nailfold. In two patients the pathologic study of the positive open patch test site showed acanthosis, exocytosis, and spongiosis of the epidermis and the presence of an inflammatory lymphocytic infiltrate in the dermis. CONCLUSION: Our results confirm the view that an immediate hypersensitivity reaction to foods can be responsible for some cases of chronic paronychia in food handlers.

Adolescent↗
PubMed1992

Antagonism towards endogenous adenosine and inhibition of cGI-PDE in the cardiac effects of amrinone, milrinone and related analogues.

1. The effect of amrinone, milrinone and of three milrinone analogues was tested on spontaneous chronotropic and inotropic activity of guinea-pig isolated atria, on the activity of cGMP-inhibited phosphodiesterase (cGI-PDE) from guinea-pig heart and on specific binding of N6-cyclohexyl[3H]adenosine ([3H]CHA) to Ri adenosine receptors in guinea-pig atria. 2. The Ki-values towards [3H]CHA binding to Ri receptors were linearly related to the EC50S for the increase in force of contraction but not to the EC50S for the increase in frequency of the atria. The Ki values towards cGI-PDE were linearly related to the EC50S for the positive chronotropic effect.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1992

Advantages of cyclosporine as sole immunosuppressive agent in children with transplanted kidneys.

A prospective study of intentional stopping of steroids 6 months after transplantation was done with 29 pediatric renal transplant recipients with a mean age of 10.4 +/- 3.4 years. Immunosuppression consisted of cyclosporine and methylprednisolone. We stopped giving MP to 24 children: to twenty after six months, four after 11-20 months. "Crude graft survival" was 97% during a mean follow-up of 36.7 +/- 15 months. The rejection rate was 48% during the first 6 months and 29% in the period after stopping MP. At present, 20/24 children (83%) have remained on CsA alone (18 patients) or CsA and azathioprine (2 patients) during a mean follow-up of 30 +/- 17 months. CsA nephrotoxicity occurred in 20.6% of patients, gum hypertrophy in 45%, hypertrichosis in 24%, and neurological symptoms in two patients (6.8%). Linear growth significantly improved after stopping MP: mean catch-up growth for prepuberal children 1.38 height standard deviation score (HSDS) and for pubertal children 1.6 HSDS. Bone age did not increase more rapidly than chronologic age. Weight/height index (W/HI) also improved. There was also a significant reduction in the use of antihypertensive drugs. Calculated glomerular filtration rate was decreased, though not significantly, after stopping MP. Thus, when graft survival is good, stopping corticosteroids corrects the major handicap of children with irreversible uremia--the poor linear growth--and improves the W/HI and control of arterial pressure. Longer follow-up periods are necessary to exclude significant worsening of renal function and an increased incidence of chronic rejection after stopping the steroid.

Adolescent↗
PubMed1992

Contact dermatitis in hairdressers: the Italian experience. Gruppo Italiano Ricerca Dermatiti da Contatto e Ambientali.

A multicenter study was performed in 9 Italian centers by members of the GIRDCA, to evaluate the frequency and source of contact sensitization in a group of 302 hairdressers with dermatitis. Occupational habits and use of preventive measures were specifically investigated both in these 302 hairdressers and in a further group of 240 hairdressers who answered a questionnaire. The results showed the presence of an occupationally relevant sensitization in 60.9% of the 302 hairdressers. This proportion included 52 hairdressers who had negative patch tests to the hairdressers' series but showed positive reactions to other allergens, such as nickel, rubber additives, preservatives and fragrances, which were judged relevant to their occupation. Among hair dyes, PPD caused 73 reactions (24.2%), PAP 32 reactions (10.6%), ONPPD 24 reactions (7.9%), and PTD 40 reactions (13.2%). A low incidence of sensitization was detected in our hairdressers to resorcinol and pyrogallol (1.3% for each substance). Among permanent wave allergens, positive reactions to GMTG were found in 11.3% of patients, while ATG gave a lower rate of positive reactions (5.0%). Allergic contact dermatitis due to APS was also relatively common (11.3%). 4 hairdressers in this study gave a positive reaction 30 min after a provocative test with latex gloves, patch testing to the rubber series being negative. Enquiry regarding preventive measures revealed that the majority of hairdressers use gloves when doing hair dyeing, but rarely use them for washing dyed hair or for doing permanent waving. The infrequent use of preventive measures by Italian hairdressers was confirmed by the results of the questionnaire, and possibly explains the high frequency of skin problems (12.5%) in the hairdressing population that was specifically interviewed.

Adolescent↗
PubMed1992

Contact dermatitis in hairdressers' clients.

The aim of our study was to report the frequency of sensitization to hairdressing allergens in a group of patients with contact dermatitis, in whom previous treatments with hair dyes or permanent wave solutions were suspected to be the cause. 49 of 261 hairdressers' clients (18.7%), who were patch tested with the hairdressers' screening series in the years 1985-1990, showed one (27) or more (22) positive reactions to hairdressing chemicals. This study confirms hair dyeing to be the procedure associated with the highest risk of sensitization among hairdressers' clients. Among hair dye allergens, PPD is the most frequent sensitizer (7.3%). A low rate of sensitization to the PPD derivatives PAP, ONPPD and PTD was detected in these clients, there being no differences in the frequency of sensitization to the 3 substances (4.2%, 4.6% and 4.6%, respectively). Only 0.4% of clients were positive to resorcinol, while pyrogallol showed a 2.3% rate of sensitization. Sensitization to GMTG was found in 3.3% of patients. ATG was an infrequent sensitizer (1.1%). Allergic contact dermatitis due to APS is quite rare (2.7%), in view of the widespread use of this compound. A positive open patch test in 1 hairdressers' client, who complained of generalized urticaria after hair bleaching, confirmed the diagnosis of immediate contact reaction due to APS. Sensitization to hairdressing allergens among consumers (18.7%) is possibly more frequent than sensitization to other cosmetic ingredients. We previously detected a 14.3% rate of sensitization to cosmetic ingredients in patients with suspected allergic contact dermatitis caused by cosmetics. On the other hand, reactions to cosmetic ingredients were also common in our patients. This may indicate that hairdressers' clients make greater use of cosmetics than average.

Adolescent↗
PubMed1992

[Myxedema coma].

Five patients, 4 female and 1 male, aged 45 to 73, were observed in myxedema coma between 1984 and 1992. In three patients hypothyroidism was not known. Depressed consciousness, hypothermia, bradycardia and no goiter were common to all and a precipitating factor could be identified in 3 of them. Therapy included L-thyroxine and/or triiodothyronine by nasogastric tube, hydrocortisone and supportive measures. Outcome was good in the 2 patients with known precipitating event, less impaired consciousness and normalization of body temperature by the third day of treatment.

Aged↗
PubMed1992

[Hyperthyroidism caused by non-neoplastic inappropriate TSH secretion].

We report a case of hyperthyroidism due to non-neoplastic inappropriate thyrotrophin secretion in a 31 year old woman. Increased T3 and THS levels after thyroidectomy led us to suspect the diagnose. Serum levels were further increased by TRH and only partially suppressed by triiodothyronine and computerised axial tomography showed a normal sellar region. These features are characteristic of inappropriate TSH secretion due to thyrotroph resistance to thyroid hormones. Bromocriptine and octreotide were ineffective in lowering TSH levels. Pregnancy and breastfeeding postponed 3,5,3'-triiodothyroacetic acid therapy.

Adult↗
PubMed1991

Characterization of in vitro chemosensitivity of perioperative human ovarian malignancies by adenosine triphosphate chemosensitivity assay.

We report the in vitro chemosensitivity of primary and recurrent human ovarian tumor samples analyzed by adenosine triphosphate chemosensitivity assay. We defined sensitivity as a greater than or equal to 70% decrease in intracellular adenosine triphosphate versus control at 20% of the reported peak plasma concentration per agent tested. Twenty of 21 assays (95.24%) were completed successfully. Single-agent and combined dose-response patterns consisting of decreasing viability with increasing drug concentration were observed consistently. Thirteen primary tumors were assayed, with 15.4% sensitive to cisplatin, 7.7% sensitive to 4-hydroxycyclophosphamide and 53.8% sensitive to their combination. Seven recurrent tumors were assayed, with 14.3% sensitive to cisplatin, 28.6% sensitive to 5-fluorouracil, and 42.9% sensitive to their combination. Dose-response characteristics and in vitro sensitivity rates reported in this article are consistent with reports of patient response in the literature. We conclude that adenosine triphosphate chemosensitivity assay is an efficient and reliable instrument for the in vitro chemosensitivity assessment of human tumors and warrants further clinical investigation.

Adenosine Triphosphate↗
PubMed1991

Melanin content and hydroperoxide metabolism in human melanoma cells.

Human melanoma cells were grown to exponential and stationary phases showing melanin contents of 4.2 +/- 0.3 and 11.3 +/- 0.6 micrograms/10(6) cells, respectively. The cells were separated in four subpopulations by a Percoll gradient; the subpopulation of density 1.07 (g/ml) was the most enriched in pigmented cells and produced 28 and 58% of the cells in exponential and stationary phases, respectively. Melanoma cells had similar superoxide dismutase and glutathione peroxidase activities in exponential and stationary phases. Moreover melanoma cells exhibited a higher catalase activity in the stationary phase: whole homogenate and cytosol activities were 7.0 +/- 0.3 and 10.8 +/- 0.6 U/mg protein, whereas in exponential phase the activities were 4.9 +/- 0.1 and 7.6 +/- 0.3 U/mg protein for whole homogenate and cytosol, respectively. The intracellular H2O2 steady-state concentration was 3.3 +/- 0.2 and 2.1 +/- 0.2 microM H2O2 for exponential and stationary phases, respectively. The spontaneous chemiluminescence of the two culture phases was 169 +/- 27 cps/10(6) cells (exponential) and 78 +/- 24 cps/10(6) cells (stationary). The cytotoxicity of H2O2 generated extracellularly by glucose oxidase was determined after 60 min of exposure. IC50 values for exponential and stationary cell cultures were 0.9 and 2.4 mU/ml of glucose oxidase, respectively. The increased catalase activities in the stationary phase as compared with the exponential phase are consistent with the decreased intracellular H2O2, with the decreased spontaneous chemiluminescence, and with the increased resistance to exogenous H2O2.

Catalase↗
PubMed1991

Alopecia totalis: is treating nonresponder patients useful?

The purpose of this study was to assess the effectiveness of different treatments in patients with alopecia totalis or universalis who did not respond to sensitizing therapies. Twenty-six patients, who had been receiving sensitizing therapy for at least 1 year without any response, were randomly assigned to receive the following treatments: topical 10% cyclosporine in oily solution (eight patients), PUVA (eight patients), and intravenous thymopentin (ten patients). None of them had any acceptable regrowth after at least 6 months of treatment. Our results suggest that other treatments are not useful in patients with 100% hair loss who fail to respond to sensitizing therapies.

Administration, Topical↗