Search PubMed⌕ Search

Biomedical subjects

A Gomez

Publications and source records attributed to A Gomez.

At least 91 records · Page 5Linked to original sources
PubMed1991

Hepatocellular carcinoma and squamous cell carcinoma in a patient with Fanconi's anemia.

Acute leukemia, hepatocellular carcinoma, and squamous cell carcinoma have been reported in patients with Fanconi's anemia. We report on a 31-year-old woman who developed squamous cell carcinoma of the esophagus and hepatocellular carcinoma. Jaundice and hepatic tumor developed in 1981, after she had received oxymetholone for 10 years. Liver biopsy revealed peliosis hepatis. Androgenic therapy was stopped and the jaundice resolved. However, the hepatic tumor was observed to be unchanged. The patient died of disseminated squamous cell carcinoma, but no metastatic lesions from hepatocellular carcinoma were detected in the autopsy. The association of Fanconi's anemia and squamous cell carcinoma is reviewed, and the malignant potential of androgen-related hepatic tumors is discussed.

Adult↗
PubMed1991

Limiting-dilution analysis of the HLA restriction of anti-Epstein-Barr virus-specific cytolytic T lymphocytes.

Human Epstein-Barr virus (EBV) specific cytotoxic T lymphocytes (CTL) play an important role in maintaining the virus/host equilibrium during persistent infections. We analysed precursors of anti-EBV CTL by the limiting-dilution technique. Seven healthy EBV-seropositive and two EBV-seronegative donors were tested. All the donors seropositive for EBV gave clear-cut positive results, and it was remarkable that the frequency of CTL precursors (CTLp) observed was much higher than that reported for other viruses. In contrast, in the seronegative donors the frequency of CTLp was undetectable. The CTLp were derived from the CD4-CD8+ population only, although EBV-specific CD4+ cytolytic T cell clones have been described. A study of the HLA restriction showed that some HLA-A or HLA-B antigens can function as preferential restricting molecules, but that CTLp restricted by the other HLA-A or HLA-B molecules also exist. However, the dominant population of CTL present in primary responses is sometimes different from that of long term cell lines established from the same donor.

B-Lymphocytes↗
PubMed1991

Adrenal cyst: a case report.

The authors describe the case of a patient with a large adrenal cyst. They review the existing literature and discuss the problem of diagnosis an treatment.

Adolescent↗
PubMed1990

hemofiltration reverses left ventricular dysfunction during sepsis in dogs.

Depressed left ventricular (LV) contractility in sepsis has been ascribed to the presence of circulating cardiodepressant substance (filterable cardiodepressant factor in sepsis [FCS]); however, this finding is controversial. The authors hypothesized that if a decrease in LV contractility indeed occurred due to a circulating depressant substance, then removal of this substance by hemofiltration would reverse by dysfunction. In this study, LV mechanics were examined before and after hemofiltration in anesthetized dogs during continuous intravenous infusion of live Escherichia coli. Left ventricular anterior-posterior and apex-base dimensions were measured by subendocardial ultrasonic crystal transducers implanted 4 weeks before the experiments. Left ventricular contractility was determined from the end-systolic pressure-dimension relationship. The slope of this relationship (Emax) is an index of contractility. After 4 h of sepsis, Emax was reduced by one half. Hemofiltration resulted in a return of Emax to control values. The FCS activity in the plasma was also assessed by the percent reduction in isometric contraction of electrically stimulated, isolated right ventricular trabeculae obtained from nonseptic dogs. The FCS activity reached a peak 4 h after sepsis and was reduced after 2 h of hemofiltration. The results show that during experimental sepsis, a circulating substance of less than 30,000 d produces a decrease in LV contractility and that this LV dysfunction may be improved by hemofiltration.

Animals↗
PubMed1990

Insensitivity of maximum expiratory flow to bronchodilation in normal dogs.

We examined the effects of the inhaled parasympatholytic agent atropine and the sympathomimetic agent salbutamol on partitioned frictional pressure (Pfr) losses to the site of flow limitation (choke point, CP) in dogs to see how changes brought about by these agents would affect maximum expiratory flow (Vmax) and response to breathing 80% He-20% O2 (delta Vmax) in terms of wave-speed theory of flow limitation. In open-chest dogs, a Pitot-static tube was advanced down the right lower lobe to locate CP, to determine CP lateral and end-on pressures (PE), and to partition the airway into peripheral (alveoli to sublobar) and central (sublobar to CP) segments. Measurements were obtained at approximately 50% vital capacity. After inhalation, CP locations were unchanged with both bronchodilating agents. After atropine inhalation, Pfr central was decreased by one-half compared with base line. Despite the decrease in Pfr central, however, Vmax failed to increase after atropine because of altered bronchial area pressure (BAP) behavior at the CP site. After salbutamol inhalation, Pfr peripheral was reduced by about one-half compared with base line. However, Vmax failed to increase, because this reduction was too small to significantly increase the CP pressure head (i.e., PE). delta Vmax was also insensitive to these agents. Our results show mechanisms by which small changes in Pfr, as well as the complex interaction of changes in Pfr and BAP, may limit the use of Vmax in detecting bronchodilation at different airway sites.

Airway Resistance↗
PubMed1990

Circadian rhythm in muscarinic receptor subtypes in rat forebrain.

The binding of different ligands to muscarinic receptors in the central nervous system is regulated by several factors. Among these are the administration of drugs, disease, ontogeny or aging. Studies carried out in rat brains have demonstrated changes in the density of the muscarinic receptors at different times of the day. These changes might be related to variations in the circadian rhythms. In this work we have studied the binding of the [3H]-N-methyl-escopolamine, the agonist carbachol and the antagonist pirenzepine to muscarinic receptors in rat forebrains at 10.00, 14.00, 18.00, 22.00, 02.00 and 06.00 hr. We have observed changes in the density of muscarinic receptors but not changes in affinity to the radioligand. The Bmax values obtained by saturation studies were maximum at 14.00 hr and minimum at 02.00 hr (P less than 0.05 Mann-Whitney's test). Inhibition studies in the presence of the non-selective agonist carbachol and the selective antagonist pirenzepine, at the same time-points, did not show statistically significant changes in the Bmax values. These data indicate that changes in the Bmax values are only observed in the total population of muscarinic receptors and are not due to modifications in the subtypes of muscarinic receptors nor to the different affinity states of agonist binding.

Animals↗
PubMed1989

A virus-specific CD4+ cell-mediated cytolytic activity revealed by CD8+ cell elimination regularly develops in uncloned human antiviral cell lines.

Antiviral HLA class II-restricted cytotoxic CD4+ clones have been relatively well characterized in vitro but their significance in the immune response remains unknown. Here anti-influenza A and anti-EBV CD4+ CTL have been studied by using permanent cell lines either untreated or depleted of CD8+ cells. In bulk cultures, HLA class I-restricted anti-viral CD8+ CTL account for all of the detectable killer cell activity, whereas after elimination of CD8+ cells an HLA class II-restricted killer activity mediated by CD4+/2H4-/4B4+ cells was consistently observed. The CD4+ CTL were fully differentiated in all of the cultures tested from the third in vitro passage because they could be demonstrated immediately after elimination of CD8+ cells. These CD4+ killer cells were equivalent to the CD8+ cells in terms of their lytic capacity. The absence of any class II-restricted antiviral activity in bulk cultures seems to be related to the very small numbers of CD4+ cells present in these antiviral cell lines. However, CD4+ cytolytic activity could not be detected during the first two in vitro passages, even when limiting dilution analysis of the CTL precursors were performed, showing that the killer function of Th cells differentiate only after several in vitro stimulations.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Role of different lymphocyte subsets in human anti-viral T cell cultures.

We have systematically studied uncloned human cell lines derived from anti-influenza A virus or anti-Epstein-Barr virus (EBV) bulk cultures, or from cultures highly enriched for CD4+ or CD8+ lymphocytes. The most noteworthy results are the following: (1) Anti-viral bulk cultures consisted of more than 90% of CD8+ cells in all cases. In contrast, anti-HLA cell lines are composed of approximately 50% CD8+ and 50% CD4+ cells. All of the CD8+ and CD4+ cells present in the culture were also 4B4+/2H4-. (2) In anti-viral bulk cultures, the cytolytic activity was restricted by HLA class I molecules and almost exclusively through a single HLA class I molecule. (3) Positively or negatively selected CD8+ lines showed the same restriction pattern. They grew less efficiently than bulk cultures but could be maintained in the absence of CD4+ cells. The CD4+ cells were however necessary at the beginning of the culture for the development of cytolytic anti-influenza virus CD8+ cells, whereas they were not required for the development of cytolytic anti-EBV CD8+ cells. (4) The CD4+ cell lines grew more actively than bulk cultures. A cytolytic activity for virus-infected cells was constantly detected in these culture from the third passage onward and it was always restricted by HLA class II molecules. This activity was maintained throughout the culture period. However, class II-restricted cytolytic cells were not detected during primary or secondary responses in vitro.

Antigens, Differentiation, T-Lymphocyte↗
PubMed1989

Chronic intoxication by heroin; histopathological effects on seminiferous tubules.

Seminiferous tubules from heroin abusers and from rats chronically intoxicated by heroin samples presented a striking reduction in the thickness of the germinal epithelium. Light and electron microscopical studies showed a considerable increase of lipids and phagosomes in Sertoli cells, disorganization of their junction complexes, detachment of immature germ cells which appeared free in the tubular lumen, and formation of giant multinucleate spermatids. These alterations point out that Sertoli cells could be the target element for the toxic effect of heroin samples on the seminiferous epithelium.

Adult↗
PubMed1989

Tungsten and molybdenum heteropolyacids as staining and contrasting agents: reactivity with epoxyresin-embedded cell and tissue structures.

In this work, we carry out a further approach to the knowledge of the reaction mechanism of phosphotungstic and phosphomolybdic acids (PTA and PMA), as well as some derivatives, with cell structures from epoxyresin-embedded materials. Applied on thin sections from glutaraldehyde-fixed tissues, PTA and PMA induced a strong electron contrasting reaction in spermatid acrosomes, goblet cell mucin, callose and plant cell walls, endexine, intine and starch granules. In light microscopy, the localization of heteropolyacids on these structures was achieved by treatments of semithin sections with suitable reducing agents (titanous sulfate, stannous chloride, sodium borohydride, or p-phenylenediamine) to form the mixed-valence heteropolyblues, or with Schiffs's reagent. The use of PTA-dye complexes (pyronin-PTA and Mallory's PTA-hematoxylin) also showed the same staining pattern. Taking into account the chemical characteristics of the PTA- and PMA-reactive tissue elements, the present results indicate that heteropolyacids selectively enter into the highest hydrophilic structures from non-polar epoxy-embedded sections; after brief washing, they appear predominantly retained in tissue structures containing a great amount of carbohydrate components.

Animals↗
PubMed1989

Epidural neurostimulation in the treatment of frostbite.

Epidural spinal cord stimulation (SCS) and conventional treatment produced good therapeutic effects in four young patients with frostbite of the lower limbs. The mechanism of action is unknown but the treatment resulted in rapid recovery with reduced pain and a more peripheral level of amputation. These preliminary results warrant further studies of SCS in the treatment of frostbite.

Adult↗
PubMed1989

Diltiazem enhances gentamicin nephrotoxicity in rats.

The effect of the calcium antagonist, diltiazem, was examined in gentamicin-induced nephrotoxicity states in rats. Animals were injected for 5 days with diltiazem intraperitoneally (40 mg/kg/day), or gentamicin subcutaneously (100 mg/kg/day) or simultaneously with both preparations using the same doses. At the time of sacrifice, the urea and creatinine clearances, as well as urine osmolality were determined and the renal tissues were processed for examination by light microscopy. Gentamicin-injected rats demonstrated the typical pattern of aminoglycoside nephrotoxicity characterized by poliuric renal failure and necrosis of the proximal tubular epithelium. Rats injected with diltiazem revealed only mild depression of urine osmolality. There was no elevation of blood urea nitrogen and serum creatinine or depression of urea and creatinine clearances, and no focal tubular cell necrosis was detected. However, concomitant administration of both compounds considerably increased nephrotoxicity by according both histological indications and renal function measurements. Thus, we conclude that the combination of diltiazem and gentamicin must be used carefully in human clinical practice.

Acute Kidney Injury↗
PubMed1989

Flow changes in hepatic veins in congestive cardiac insufficiency. A study using pulsed Doppler US.

Ten patients with right heart failure and tricuspid regurgitation were studied with both B Scan and pulsed Doppler ultrasound. Variations in the Doppler waveforms were seen in portal vein recordings which indicated flow characteristics similar to those of hepatic veins due to transmission of retrograde pressure waves through the hepatic capillary bed. It was concluded that the pulsed Doppler will permit non-invasive determination of physiological events that may have great practical importance in the diagnosis and treatment of patients with right heart failure.

Aged↗
PubMed1988

Characterization of muscarinic receptor subtypes in human tissues.

The affinities of selective, pirenzepine and AF-DX 116, and classical, N-methylscopolamine and atropine, muscarinic cholinergic receptor antagonists were investigated in displacement binding experiments with [3H]Pirenzepine and [3H]N-methylscopolamine in membranes from human autoptic tissues (forebrain, cerebellum, atria, ventricle and submaxillary salivary glands). Affinity estimates of N-methylscopolamine and atropine indicated a non-selective profile. Pirenzepine showed differentiation between the M1 neuronal receptor of the forebrain and the receptors in other tissues while AF-DX 116 clearly discriminated between muscarinic receptors of heart and glands. The results in human tissues confirm the previously described selectivity profiles of pirenzepine and AF-DX 116 in rat tissues. These findings thus reveal the presence also in man of three distinct muscarinic receptor subtypes: the neuronal M1, the cardiac M2 and the glandular M3.

Brain↗
PubMed1988

Expiratory flow limitation in dogs with regional changes in lung mechanical properties.

We examined maximum expiratory flow (Vmax) in two canine preparations in which regional changes in lung mechanical properties were produced. In one experiment serial bronchial obstructions were made to determine whether flow-limiting sites (choke points, CP) would occur in series. With the right lung tied off, constrictions were placed at the left lower lobar bronchus (LLL) and left main-stem bronchus. On deflation from total lung capacity, the obstructed LLL and nonobstructed left upper lobe (LUL) emptied into the obstructed left main-stem bronchus. Although a CP common to both lobes was identified at the main-stem obstruction, which limited total Vmax, we questioned whether there was also a CP at the lobar obstruction that fixed LLL flow. In that case the rate of LLL emptying would not be dependent on the presence of the common (i.e., central) CP and thus the flow contribution of the LUL. We found that when the LUL was removed, the LLL increased its rate of emptying. Thus a lobar CP did not fix LLL flow and CP did not occur in series. In a second experiment emphysema was produced in the left lung to reduce lung recoil, whereas the right lung was normal. CP were identified at approximately lobar bronchi of each lung, and the lungs were emptied at different rates. A CP common to both lungs was not identified. Our results indicate that in localized lung disease, if flows from the different regions are high enough, then wave speed is reached in proximal airways, and a CP occurs centrally rather than peripherally. On the other hand, if flows are low, then wave speed is reached peripherally and a CP common to all lung regions does not occur.

Airway Obstruction↗
PubMed1988

Aminophylline has little positive inotropic effect and a slightly negative diastolic effect on the left ventricle during hypoxic conditions in dogs.

We examined the effect of aminophylline on left ventricular (LV) mechanics and central hemodynamics under normoxic and hypoxic conditions in respective groups of dogs. In an open-chest preparation, LV end-systolic and diastolic dimensions were measured with ultrasonic crystal transducers seated subendocardially along the anterior to posterior and apex to base axes. In the group studied during hypoxia, measurements were obtained during 3 conditions: normoxia; hypoxia to a PO2 of 30 mm Hg; and during hypoxia when aminophylline was infused to a blood level of about 15 mg/L. In the group studied under normoxic conditions, measurements were initially obtained during normoxia after which aminophylline was also infused to a blood level of 15 mg/L. Intravascular volume was given or removed to maintain LV filling pressures at about 10 mm Hg during all conditions. In the normoxic group, aminophylline caused an increase in stroke volume (SV) and had a positive inotropic effect on the LV. End-systolic dimensions were reduced, while end-diastolic dimensions did not change with aminophylline. On the other hand, under hypoxic conditions, aminophylline did not have a positive inotropic effect: SV did not increase and end-systolic dimensions remained unchanged. Under hypoxic conditions, moreover, aminophylline caused a slight decrease in end-diastolic dimensions by augmenting hypoxia-induced increases in myocardial resting tension. Our results indicate that unlike normoxic conditions, aminophylline may have little beneficial effect on LV performance during hypoxic conditions.

Aminophylline↗
PubMed1988

Stereotactic CT localization and biopsy of brain tumours using the Leksell frame. A study of 45 cases.

The authors have explored 45 patients presenting with clinical and CT evidence of space-occupying process in the brain. They endeavoured to determine the nature of the processes by performing stereotactic biopsy after localization by CT in 43 cases, by magnetic resonance imaging in 2 cases and by angiography in 1 case. The method proved reliable: the quality of the biopsy specimens obtained enabled the pathologist to make a satisfactory diagnosis by light microscopy after freezing in almost every case. Moreover, the orifice of penetration of the Leksell-Sedan needle provided a very accurate localization of the lesion when surgery was needed. Several specimens were taken during each session, since histological findings may vary according to the site of biopsy. All explorations were carried out under local anaesthesia. Two cases of haemorrhage were recorded; they were without long-term consequences but required surgery.

Biopsy↗