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Biomedical subjects

M Martin

Publications and source records attributed to M Martin.

At least 559 records · Page 31Linked to original sources
PubMed1992

Transport of beta-hydroxybutyrate and acetoacetate along rat nephrons: a micropuncture study.

The transport of ketone bodies across the luminal membrane of the nephron was studied by means of micropuncture techniques in rats in normal acid-base state. The concentration of beta-hydroxybutyrate (beta-HB) and acetoacetate (AcAc) in plasma, tubular fluid and urine was measured by an ultramicromethod using enzymatic cycling. At endogenous plasma ketone body concentration, approximately 80% of the filtered load of beta-HB and AcAc was reabsorbed in the proximal convoluted tubule, the remaining fraction being almost completely reabsorbed between the late proximal convoluted and the distal tubule; under these conditions, the urinary excretion of ketone bodies was less than 1% of the filtered load. A progressive elevation to steady-state levels of plasma beta-HB resulted in a progressive reduction of the fractional reabsorption of beta-HB and AcAc in the proximal convoluted tubule, which means that reabsorption of ketone bodies in this nephron segment is saturable. No net secretion of ketone bodies could be demonstrated along the nephron even at the highest plasma ketone body concentrations reached. In clearance experiments, the capacity of the rat kidney for reabsorbing both beta-HB and AcAc was found to be limited by a maximal tubular capacity (Tm). The data suggest that, in the young Wistar rat nephron, most of the reabsorption of ketone bodies is carrier mediated.

3-Hydroxybutyric Acid↗
PubMed1992

Role of diethylnitrosamine, 2-acetylaminofluorene and partial hepatectomy in the expression of glutathione-S-transferase-P and gamma-glutamyltranspeptidase in the early steps of rat liver carcinogenesis.

Three factors involved in the Solt and Farber model of rat liver carcinogenesis were studied alone and in various combinations: diethylnitrosamine (DEN) initiating dose, 2-acetylaminofluorene (2-AAF) feeding and partial hepatectomy. The administration of DEN alone (200 mg/kg) was able to switch on glutathione-S-transferase, placental type (GST-P) expression 3 weeks later at a low level (85 U/micrograms protein) which was stable for 10 weeks in the absence of histopathological lesions. During the same time, gamma-glutamyl transpeptidase (GGT) activity presented 2 waves of increase. The feeding of 0.03% 2-AAF for 2 weeks appeared as a determinant factor in the expression of GST-P protein as well as GGT induction (15- and 7-fold versus DEN alone, respectively). The addition of partial hepatectomy enhanced again GST-P expression (1.5-fold) and GGT induction (2-fold). However, GST-P foci increased in size, not in number while GGT foci increased both in size and in number. These data indicated that 2-AAF was a crucial component of the selection procedure since partial hepatectomy alone, with or without DEN initiation was inefficient in promoting GST-P expression. Therefore, 2-AAF would be able to promote the growth of GST-P-positive cells initiated by DEN, a mechanism likely responsible for its tumor-promoting effect.

2-Acetylaminofluorene↗
PubMed1992

Comparison of mitogen- and virus-induced interferon production in whole blood cell cultures of patients with various solid carcinomas and controls.

Using a sensitive immunoassay, the mitogen-induced production of interferon-gamma (IFN-gamma) and virus-stimulated IFN-alpha production was investigated in whole blood cell cultures of 115 control subjects and 225 untreated patients with various solid carcinomas. In the cultures of the tumor patients, significantly lower levels of IFN-gamma were found as compared to the controls (p < or = 0.001) and the differences were most evident in those tumor groups containing mostly patients with advanced clinical stages. IFN-alpha values were only slightly lower in the cultures of the carcinoma patients, with p values < or = 0.05. Statistically, there was no correlation between IFN-alpha and IFN-gamma values. Since the IFN-gamma differences between tumor and controls and the correlation to groups with higher tumor stages were much clearer than IFN-alpha differences, we conclude that IFN-gamma measurements after polyclonal induction may be the better parameter for showing a depressed cellular immunological activity in patients with malignancies than virus-induced IFN-alpha secretion.

Adult↗
PubMed1992

A buffer value index to evaluate effects of buffers on ruminal milieu in cows fed high or low concentrate, silage, or hay diets.

Our objective was to develop a buffer value index that would incorporate alterations in both ruminal fluid pH and buffering capacity as indicators of the influence of dietary buffering and alkalinizing agents on ruminal acid-base status. This index was evaluated using ruminal fluid from four lactating Holstein cows fed either sorghum silage or alfalfa hay in high or low concentrate diets. Ruminal fluid was incubated in vitro for 1, 2, 3, 4, or 5 h with no buffer or with 7.1 g of either NaHCO3, sodium sesquicarbonate, or a multielement buffer added per liter of ruminal fluid. Ruminal fluid pH was lower for diets based on high concentrate or alfalfa; buffering capacity between pH 5 and 7 was greater for high concentrate diets but was not affected by forage type. Ruminal fluid pH was higher for sesquicarbonate than for NaHCO3, the multielement buffer, or the control; however, ruminal fluid H+ concentration was similar between sesquicarbonate and NaHCO3, and both were lower than for the multielement buffer. Hydrogen ion concentration for the multielement buffer was lower than for the control. Buffering capacity was highest for NaHCO3, followed by sesquicarbonate, the multielement buffer, and the control. The buffer value index, which accounted for alterations in both H+ concentration and buffering capacity, was highest for NaCHO3, followed by sesquicarbonate, the multielement buffer, and the control. The poor response to the multielement buffer may be attributable to our relatively short incubation interval (less than 5 h). Dietary buffers increase both ruminal fluid pH and buffering capacity; both of these responses are beneficial.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗
PubMed1992

Misremembering a familiar object: mnemonic illusion, not drawing bias.

It was reported by Jones (1990) that the design of British coins is systematically misremembered. Although the Queen's head in fact faces right, most people draw it facing left. It is possible, however, that the origin of this phenomenon does not reside in memory but instead in a leftward drawing bias. Two experiments of the three reported here tested this hypothesis. In Experiment 1, British participants attempted to recall the direction of the Queen's head but responded verbally instead of pictorially. The results were similar to those of Jones and thus contradict the hypothesis that misremembering of the Queen's head is caused by a leftward drawing bias. In Experiment 2, Canadian participants attempted to draw a Canadian coin. Leftward misremembering was not observed in this case. Thus the hypothesized importance of a leftward drawing bias was again not supported. Instead, the results provided support for the schema explanation of the Queen's Head memory illusion proposed by Jones. The results of Experiment 3, which compared memory for British coins and stamps, further bolstered this conclusion.

Adolescent↗
PubMed1992

[Combination of chemotherapy (vindesine, lomustine, cisplatin, cyclophosphamide) and thoracic radiotherapy in nonresectable non-small cell bronchial carcinoma: final results of a phase II clinical trial].

Seventy-five patients with locally advanced non small cell lung carcinoma were entered in a phase II study combining chemotherapy (vindesine, lomustine, cisplatin and cyclophosphamide) and radical thoracic radiotherapy delivering a total dose of 60-65 Gy. Patients were regularly assessed by radiological and fiberoptic bronchoscopy examinations in order to evaluate local control. An objective response was observed in 22 patients (29%) after initial chemotherapy (2 complete remissions and 20 partial responses). The complete response rate after the combined schedule was 30%. Toxicity of this combination was acceptable. Median survival was 13.5 months. Actuarial risk of developing distant metastases at 3 years was 60%. However, the main cause of failure was local with 80% of uncontrolled or recurrent thoracic tumor in the first 2 years of follow-up. The present study shows that local control remains a major problem in the management of patients with inoperable non metastatic non small cell lung cancer.

Adult↗
PubMed1992

[Thrombolysis-block technique--a new local form of treatment of distal venous and arterial occlusions of the leg].

Lysis-block technique is a new treatment form for deep vein and arterial thrombosis. A strictly local lysis is achieved by using "BIERS blockade" combined with a peripheral intravenous injection of the lytic substance. The new technique is demonstrated on four patients. Two patients had popliteal vein thrombosis. One patient was treated with urokinase. The other patient (unsuccessfully) with urokinase and (subsequently) successfully with rt-PA. In both cases full recanalization of the vessels was achieved. Two patients had occlusions of lower leg arteries. Clinically and angiographically perfusion could be distinctively improved by fibrinolytic treatment with urokinase. Analysis of fibrinogen and plasminogen levels showed no systemic fibrinolytic effect. This was of importance in one patient with a meningioma and in another patient with peptic ulcers of the stomach where otherwise no fibrinolysis would have been possible. Thus, lysis-block-therapy is an important new alternative to systemic fibrinolytic treatment especially in those patients with contraindications for systemic lysis.

Adult↗