Conserved proline residues prevent dimerization and aggregation in the ß-lactamase BlaC.

Evolution leads to conservation of amino acid residues in protein families. Conserved proline residues are usually considered to ensure the correct folding and to stabilize the three-dimensional structure. Surprisingly, proline residues that are highly conserved in class A ß-lactamases were found to tolerate various substitutions without large losses in enzyme activity. We investigated the roles of three conserved prolines at positions 107, 226, and 258 in the ß-lactamase BlaC from Mycobacterium tuberculosis and found that mutations can lead to dimerization of the enzyme and an overall less stable protein that is prone to aggregate over time. For the variant Pro107Thr, the crystal structure shows dimer formation resembling domain swapping. It is concluded that the proline substitutions loosen the structure, enhancing multimerization. Even though the enzyme does not lose its properties without the conserved proline residues, the prolines ensure the long-term structural integrity of the enzyme.

The role of smell, taste, flavour and texture cues in the identification of vegetables.

It has been shown that the identification of many foods including vegetables based on flavour cues is often difficult. The effect of providing texture cues in addition to flavour cues on the identification of foods and the effect of providing taste cues only on the identification of foods have not been studied. The aim of this study was to assess the role of smell, taste, flavour and texture cues in the identification of ten vegetables commonly consumed in The Netherlands (broccoli, cauliflower, French bean, leek, bell pepper, carrot, cucumber, iceberg lettuce, onion and tomato). Subjects (n = 194) were randomly assigned to one of four test conditions which differed in the sensory cues available for vegetable identification: taste, smell (orthonasal), flavour (taste and smell) and flavour-texture (taste, smell and texture). Blindfolded subjects were asked to identify the vegetable from a list of 24 vegetables. Identification was the highest in the flavour-texture condition (87.5%). Identification was significantly lower in the flavour condition (62.8%). Identification was the lowest when only taste cues (38.3%) or only smell cues (39.4%) were provided. For four raw vegetables (carrot, cucumber, onion and tomato) providing texture cues in addition to flavour cues did not significantly change identification suggesting that flavour cues were sufficient to identify these vegetables. Identification frequency increased for all vegetables when perceived intensity of the smell, taste or flavour cue increased. We conclude that providing flavour cues (taste and smell) increases identification compared to only taste or only smell cues, combined flavour and texture cues are needed for the identification of many vegetables commonly consumed in The Netherlands.

[Acute abdomen caused by a large vesical cystine calculus]. / Acute buik veroorzaakt door een grote cystineblaassteen.

A 73-year-old man underwent an emergency laparotomy because of acute abdominal pain and a palpable mass in the lower abdomen. A giant vesical calculus was found which had perforated the bladder, small intestine and sigmoid colon due to pressure necrosis. The stone had a length of 11.5 cm and weighed 1280 g. Further analysis revealed benign prostate hyperplasia, bladder diverticula and cystinuria as underlying causes. Initial therapy consisted of stone removal, partial bladder resection, a Hartmann procedure and partial resection of the small intestine. Secondarily, lifestyle advice was given and transurethral resection of the prostate followed later.

[Disorders of concentration and memory in young adults and middle-aged persons]. / Concentratie- en geheugenstoornissen op jongvolwassen en middelbare leeftijd.

Four patients, two women aged 29 and 52 and two men aged 46 and 25, respectively, consulted a neurologist for attention and memory disorders. Further investigation revealed that the symptoms were caused by metachromatic leucodystrophy, Graves' disease, Huntington's disease, and a psychological background, respectively. The first patient became dependent in 1.5 years, the second recovered after treatment, the third was independent with slowly progressive symptoms after 1 year, and the fourth was advised to consult a psychologist. Disorders of attention and memory in relatively young people deserve a detailed evaluation at the very first visit, involving the elaboration of an initially extensive differential diagnosis. Too early a separation between a psychic and an organic pathogenesis should be avoided. Indications for the presence of a neurological condition include: consultation at the initiative of others, a relatively brief duration of symptoms without a clear provoking factor, the absence of a psychiatric history or life event, cognitive dysfunction in several areas, abnormal behaviour and an incriminating family history.

Human primary T lymphocytes have a low capacity to amplify MLV-based amphotropic RCR and the virions produced are largely noninfectious.

The presence of replication-competent retrovirus (RCR) in retroviral-based gene therapy products poses a potential safety risk for patients. Therefore, RCR testing of clinical gene therapy products and monitoring of patients enrolled in gene therapy trials is required to assure viral safety. The requirement to test ex vivo-transduced cells originates from the presumed amplification of adventitious RCR during the transduction procedure. However, data on the capacity of different cell types to do so are lacking. In this study, we sought to analyze the amplification potential of primary human T lymphocytes after infection with amphotropic MLV-based RCR. The total number of viral particles produced after 1 or 2 weeks was measured by a quantitative 4070A env-specific RT-PCR assay. The fraction of infectious replication-competent viral particles was analyzed in the PG-4 S+L- assay. From this study, we conclude that the total number of viral particles RCR produced by T lymphocytes is 2-4 logs lower than the number produced by NIH-3T3 cells. Surprisingly, less than 1% of the viral particles produced by primary T lymphocytes appeared to be infectious, while nearly all virions produced by NIH-3T3 were. We conclude that primary human T lymphocytes are low producers of MLV-based amphotropic RCR.

Repeated pain assessment in Alzheimer's disease.

In previous studies, patients with probable Alzheimer's disease (AD) have indicated that they experienced less pain intensity and affect from their painful conditions than nondemented elderly persons. However, in those studies, pain assessment occurred only once. Therefore, it may be possible that pain which had occurred, for example, a day earlier, could have been forgotten. Therefore, in the present study, AD patients' pain was assessed daily, i.e. once a day and even three times a day, during a longer period. The results parallel those of earlier studies, i.e. compared to elderly persons without dementia, AD patients appear to perceive less pain intensity and pain affect. These findings support the hypothesis that AD is characterized by an alteration in pain experience.

A moderate elevation of blood glucose level increases the effectiveness of thermoradiotherapy in a rat tumor model. I. Relative contributions of glucose and heating to tumor acidification.

PURPOSE: To establish dose-effect relationships for tumor acidification induced by heat and glucose as a basis for testing the value of adding glucose administration to combined heat and x-ray treatment at clinically achievable glucose and temperature levels. METHODS AND MATERIALS: Rhabdomyosarcoma BA1112 was grown s.c. in the upper leg of 16-20-week-old Wag/Rij rats. Animals were given 2 consecutive 100-min periods of saline (S) or glucose (G) infusion, while keeping tumor temperature at 37 degrees, 42 degrees, or 43 degrees C for 1 or 2 periods, in various combinations, each involving 6 animals. Glucose was infused i.v. as a 20% solution at 2.4-3 g/kg/h. Tumors were heated using 2,450-MHz electromagnetic radiation, and tumor pH was measured using a 0.7 mm fiberoptic probe. RESULTS: Mean overall baseline pH was 7.00 (SD 0.10). The change induced by G37G43 (i.e., glucose infusion for a full 200 min, first 100 min at 37 degrees C, final 100 min at 43 degrees C) was -0.48 +/- 0.03 (SEM) pH units, and -0.17 +/- 0.03 for S37S43. The effect of G37G42 was -0.37 +/- 0.03 pH units, compared with -0.08 +/- 0.02 for S37S42 and -0.28 +/- 0.04 for glucose alone (G37G37). Glucose was less effective when given after or fully parallel to heating: -0.21 +/- 0.02 pH units for S43G37 and -0.37 +/- 0.02 for G43G43. CONCLUSION: The glucose-induced tumor pH drop is much more pronounced than that induced by heat, both of which are dose dependent. The effects of glucose and heat seem additive if heating is started when glucose-induced acidification has reached its plateau level, but the overall effect is diminished if administration is fully simultaneous or in reversed order. Schedule G37G43 is optimal with respect to tumor acidification. Its predicted superiority in thermoradiotherapy as compared with S37S42, S37S43, and G37G42 treatment regimens was confirmed in a subsequent experimental tumor control study.

A moderate elevation of blood glucose level increases the effectiveness of thermoradiotherapy in a rat tumor model II. Improved tumor control at clinically achievable temperatures.

PURPOSE: To assess the therapeutic gain (at the TCD(50) level) that can be obtained by boosting thermoradiotherapy with intravenous glucose infusion at different temperatures. This completes our series of studies to determine the optimal conditions and the effectiveness of glucose administration at clinically achievable glucose levels and treatment temperatures. METHODS AND MATERIALS: Subcutaneous rat rhabdomyosarcoma BA1112 was irradiated with graded single doses of 300-kV X-rays (dose range 0-60 Gy). Fifteen minutes after irradiation, a 100-min intravenous infusion was started, consisting of either glucose (20% solution, 2.4-3 g/kg/h) or saline as a control. Then heat was applied to the tumors at 42 degrees C or 43 degrees C (water bath) during a subsequent 100-min period of infusion. Tumor control was scored as the absence of palpable growth at 100 days after treatment. RESULTS: Glucose infusion enhanced tumor control independent of temperature in the range 42-43 degrees C. At 42 degrees C, the TCD(50) for X-irradiation decreased by 5.9 Gy (SEM 1.8 Gy), from 41.6 (1.6) to 35.7 (1.5) Gy, and at 43 degrees C from 33.3 (1.6) to 27.3 (1.5) Gy, representing a glucose enhancement ratio of approximately 1.2. At doses corresponding to the TCD(50) at either 42 or 43 degrees C, the addition of glucose increased tumor control from 50% to 70%. An enhancement ratio of 2.1 was found for the combination of irradiation, glucose infusion, and heating at 43 degrees C, with respect to irradiation alone (TCD(50) 56.3 Gy, reanalyzed earlier data). The contribution of combined heat and glucose to tumor control represented an additive effect, probably on the hypoxic cell population. CONCLUSION: Moderate glucose administration (blood concentration 300 mg/100 mL) sizably improves experimental tumor control after combined X-irradiation and hyperthermia under clinically feasible conditions. Clinical treatment should benefit from this additional modality, in particular if unsatisfactory local control rates are due to insufficient heating. The therapeutic gain has to be evaluated further in clinical studies.

Renal dysplasia in three young adult Dutch kooiker dogs.

Chronic renal failure as consequence of renal dysplasia was diagnosed in three young adult Dutch kooiker dogs (Dutch decoy dogs). Two animals were anorectic from an early age and were thinner than healthy dogs of the same breed. All three were presented because of apathy and weakness. Laboratory examination revealed anaemia and uraemia. One dog was presented with severe dehydration and died during emergency treatment. One dog was euthanatised because of a poor prognosis, and one was given a low-protein diet. This dog survived for 7 months after the diagnosis of chronic renal failure. At necropsy all three animals had shrunken, pale, and firm kidneys that showed microscopical lesions characteristic of canine renal dysplasia, such as asynchronous differentiation of nephrons, persistent immature mesenchyme, persistent metanephric ducts, and adenomatoid proliferation of the tubular epithelium. Secondary degenerative and inflammatory changes consisted of interstitial fibrosis and predominantly lymphocytic/plasmacytic inflammation. This is the first report of renal dysplasia in the Dutch kooiker dog. The disease should be included in the differential diagnosis in young Dutch kooiker dogs with signs of chronic renal failure. The presentation of three cases of this rare disease in this breed, which is based on a rather small gene pool, suggests that it is a familial or hereditary nephropathy.

Do serum ALAT values reflect the inflammatory activity in the liver of patients with chronic viral hepatitis?

A retrospective study was carried out in 40 patients with chronic viral hepatitis, to assess whether serum alanine aminotransferase reflects the inflammatory process in the liver. Twenty liver biopsy specimens were included for each disease. Five histological aspects were scored: periportal inflammation, lobular inflammation, ballooning, Councilman bodies and lymphocyte follicles. Logarithmic values of alanine aminotransferase were correlated with each aspect using the Spearman correlation coefficient. For the hepatitis B cohort a statistical significant correlation was found between alanine aminotransferase and periportal inflammation (p = 0.0001), lobular inflammation (p = 0.0002) and Councilman bodies/area (p = 0.003). In the hepatitis C study population alanine aminotransferase correlates with both periportal inflammation (p = 0.007) and lymphocyte follicles/Area (p = 0.02). In conclusion, these results suggest that alanine aminotransferase can be used as an indicator of inflammatory activity. A prospective study is needed, to further analyze the use of alanine aminotransferase, as a monitor of disease activity in patients with chronic viral hepatitis.

Temporary vascular occlusion and glucose: effects on tumour and normal tissue pH in animal experiments.

The relationship between duration of a period of vascular occlusion and magnitude of pH decrease in tumour and normal tissue was investigated in rats. To acidify tissue pH further, moderate dose glucose (2.4-3.0 g.kg(-1).hr(-1)) was administered intravenously through a catheter positioned in a tail vein, immediately after the clamp was released. This sequence of pH modifying modalities was chosen since it is employed in clinical regional isolation perfusion for recurrence of malignant melanoma of the limbs. Tumour pH in rat rhabdomyosarcoma BA1112 decreased more than normal tissue pH under 10, 20, 30 or 60 min of temporary vascular occlusion. Administration of glucose following any period of clamping always decreased tumour pH further. The largest pH decrease (0.29 pH units) was obtained after 30 min of clamping followed by 60 min glucose and 60 min saline infusion. In the clinic the combination of a maximum of 30 min of clamping followed by moderate dose glucose infusion, which can decrease tumour pH effectively, can be easily achieved in the setting of regional isolation perfusion. It can be used for treatment modalities that are known to be enhanced at lowered tissue pH, such as hyperthermia and certain chemotherapeutic drugs. These results form the basis for studying the therapeutic gain which can be obtained with this model.

Flucloxacillin-associated hepatic injury.

Eleven cases of hepatic injury attributed to the intake of flucloxacillin were reported to the Netherlands Center for Monitoring of Adverse Reactions to Drugs between 1982 and 1992. They concerned four men and seven women, with a mean age of 57 years, treated for 2-28 days with an oral dose varying from 1500-4000 mg per day. Symptoms mostly appeared 10 to 30 days after starting treatment with flucloxacillin. Biochemically, the pattern was compatible with cholestatic hepatitis in seven cases, with a mixed cholestatic-hepatocellular type of injury in one case, a hepatocellular pattern in two cases, and mild liver enzyme elevations in one patient. Two patients died, one due to fatal bleeding from the liver after biopsy, and the second patient to a combination of hepatic and cardiac failure. The other patients recovered, on average 72 days after peaking of serum aminotransferase values. Histology in seven cases showed cholestatic hepatitis in five, with cholangitis or cholangiolitis in four of these patients. In the other two patients, there was centrilobular cholestasis with extensive bridging fibrosis and portal-central bridging necrosis, respectively.

[The immunological aspects of primary chronic septic endocarditis in acquired heart defects. The treatment approaches]. / Immunologicheskie aspekty pervychnogo khronicheskogo septicheskogo éndokardita na fone priobretennykh porokov serdtsa. Podkhody k lecheniiu.

A total of 266 patients with degree I primary chronic septic endocarditis concurrent with acquired heart disease and 101 apparently healthy subjects were examined. The patients were found to have scarce T helper cells and higher levels of T suppressors (quite the reverse in some patients), decreased proliferative responses of T and B cells and normal levels of circulating immune complexes. It was conceived that there was a block in the synthesis of specific antibodies and a decrease in their affinity. It was proposed that cytokine (enzyme) genes (initiators or repressors) should be exposed at intervals as immunomodulating therapy of immune diseases, as well as in some hereditary diseases.

Course of hepatitis B and D virus infection in auxiliary liver grafts in hepatitis B-positive patients. A light-microscopic and immunohistochemical study.

Four patients who received an auxiliary partial liver graft for decompensated liver cirrhosis due to hepatitis B (HBV), associated in two cases with hepatitis D virus (HDV) superinfection, were studied. The sequential appearance of hepatitis B and D antigens in the grafts was investigated in serial liver biopsies by immuno-histochemical methods and compared with the viral antigenic profiles of the host livers. The histological changes in the liver grafts were studied in relation to the viral expression patterns. One week after transplantation, expression of HBsAg was already apparent in two grafts. HBcAg was found in the graft of the only patient with HBcAg in the host liver. HDAg was expressed in the grafts of both patients with HDV superinfection; in one of these cases HDAg was present without HBsAg. At 3 months, viral antigen expression was maximal. Expression of HBsAg and HBcAg in the grafts of the two HDV-positive patients was, however, less extensive than in the two HBV-positive patients. All patients developed a mild lobular hepatitis, histologically demonstrated between the 47th and 107th posttransplantation day. In the two HBV-positive, HDV-negative patients, cirrhotic transformation of the graft occurred within 1 year. In the HDV-positive patients only a mild chronic active hepatitis with slight or moderate fibrosis was observed after 1 year. We conclude that recurrence of HBV and HDV infection in auxiliary liver grafts is demonstrable within 1-3 weeks. HBV infection in liver grafts may be a rapidly progressive disease. Coinfection with HDV does not aggravate the acute hepatitis and may even suppress the progression of chronic HBV.

Dose-effect relationships for glucose-induced tumour acidification and its erythrocyte flux.

Preclinical investigations were performed with glucose administration in WAG/Rij rats carrying the rhabdomyosarcoma BA1112 in two sites per animal: one in the subcutis of the flank (for pH measurements in the tumour tissue) and one in the transparent "sandwich" chamber for measuring the erythrocyte flux in the tumour tissue as an indication for changes in tumour blood flow. A glucose solution (20%) was slowly infused intravenously in a range of dose levels, similar to those reported for inducing long-term hyperglycaemia in man. The eventual aim of such investigations is to sensitise tumours for hyperthermic treatment. This approach is not new, but the present experiments were performed with the aim to explore the level of the minimal amount of glucose which would nonetheless yield a likely therapeutic effect. Endpoints in this study were the blood glucose level and pH and the relative erythrocyte flux in the tumour tissue. Obviously, as one would expect, many significant changes in the various parameters were found as a response to administration of glucose. However, the changes in the blood glucose level, the induced decrease in tumour pH and the influence of the tumour volume did not show a well-defined relationship which was reliable enough to predict the exact influence of the various parameters on the magnitude of the desired changes in individual animals and/or tumours. This was probably caused by interfering differences in physiological feedback mechanisms. Nonetheless, the data indicate that the optimal effect was not obtained with the highest treatment level, but with moderate doses of glucose, i.e. 2.4-3 g.kg/h which induced a satisfactory tumour acidification of 0.25 pH units. This may turn out to a clinically useful pH drop for enhancing the cytotoxic effect of hyperthermia. The erythrocyte flux through the tumour tissue does not appear to be influenced to a sizeable extent by such a treatment.

Tissue-localizing properties of some photosensitizers studied by in vivo fluorescence imaging.

Using fluorescence imaging, the tissue-localizing properties of five photosensitizers were studied in vivo in tumours in 'sandwich' observation chambers and in tumours growing on thigh muscle. The preliminary results indicate that of the three photodynamically active dyes tested (haematoporphyrin derivative, Photofrin II and aluminium phthalocyanine tetrasulphonate), the phthalocyanine possesses the best tumour-localizing properties. This makes it possible to combine tumour fluorescence detection and photodynamic therapy with reduced skin photosensitivity. The two photodynamically inactive dyes tested (uroporphyrin I and acridine red) may be useful for application in fluorescence imaging to localize superficial tumours without inducing skin photosensitivity. In particular, acridine red has remarkable tumour-localizing properties, but is rather toxic.