Comparing reconstruction with ileocecal graft to jejunal interposition pouch after total gastrectomy in rats.

After total gastrectomy, the ileocecal graft may act as a reservoir and protect against reflux but give rise to transposition of the ileum and cause possible changes in bile acid metabolism and nutrition. This study compared the ileocecal graft and jejunal pouch. Male Wistar rats weighing 265 +/- 22 g were submitted to sham operation (S), ileocecal interposition graft (IIG), and jejunal pouch interposition graft (JP) after total gastrectomy. Eight weeks later, the esophagus was examined for evidence of esophagitis. Nutritional biochemistry and weight profile were documented preoperatively and 8 weeks after surgery. The oral glucose tolerance test was performed. Thirty-three rats were operated on and 30 survived for 8 weeks. Esophagitis occurred in seven JP rats. Body weight was significantly higher in IIG than in JP rats (p < .05). Normal glucose tolerance to intragastric glucose load was observed in sham and operated rats. JP rats had a significant decrease in serum albumin, glucose, transferrin, hemoglobin, iron, folate, and calcium, compared to sham (p < .05). Cobalamine was significantly lower in IIG rats than in JP rats (p < .05). In the IIG and JP groups, serum/hepatic total bile acid did not differ significantly from preoperative and sham values. In conclusion, the IIG interposition graft in rats prevented esophagitis, preserved nutrition, and did not interfere with enterohepatic total bile acid circulation.     

Peripheral spin exchange nuclear spin resonance angiography: Studies of the effect of blood flow on contrast

Sequential two-dimensional (2-D) inflow MR-angiography (SDSMRA) utilizes the bloodflow-induced changes in the MR-signal for intraluminal vessel contrast. To assess the effect of the peripheral arterial flowpulse on the average intraluminal MR-signalintensity (MIMRSI) seven healthy subjects, mean age 31 +/- 4 years, were studied using color Doppler flow mapping and SDSMRA. In each subject the regional MIMRSI was measured in 21 vascular segments and correlated with the regional flowpulse in a simple regression model. MIMRSI ranged from 915 +/- 299 in the right profunda femoris to 1378 +/- 283 in the distal abdominal aorta: distally, the trifurcation it was, with the exception of the posterior tibial artery in three subjects (MIMRSI = 545 +/- 64), not measurable. The regional differences in the peripheral flowpulse were without statistically measurable effect on MIMRSI. MIMRSI was best correlated to the systolic forward flow in 14, to the backward flow in 3, and to the mean forward flow in 1 vascular segment, respectively. The mean correlation coefficient (r) was 0.56, ranging from r = 0.11 in the right popliteal artery to r = 0.93 in the right superficial femoral artery. In the distal abdominal aorta no positive correlation between the blood flow and MIMRSI was determined. The regional differences in the peripheral arterial flow-pulse have no significant effect on MIMRSI in healthy men. MIMRSI correlates best with the systolic forward flow. However, on the average, 44% of the MIMRSI appear to be related to flow-independent yet unidentified factors. Optimal design of SDSMRA pulse sequences will require a better characterization of flow-dependent and flow-independent MIMRSI parameter.     

Phosphatase activity on the cell wall of Fonsecaea pedrosoi.

The activity of a phosphatase was characterized in intact mycelial forms of Fonsecaea pedrosoi, a pathogenic fungus that causes chromoblastomycosis. At pH 5.5, this fungus hydrolyzed p-nitrophenylphosphate (p-NPP) to p-nitrophenol (p-NP) at a rate of 12.78 +/- 0.53 nmol p-NP per h per mg hyphal dry weight. The values of Vmax and apparent Km for p-NPP hydrolyses were measured as 17.89 +/- 0.92 nmol p-NP per h per mg hyphal dry weight and 1.57 +/- 0.26 mmol/l, respectively. This activity was inhibited at increased pH, a finding compatible with an acid phosphatase. The enzymatic activity was strongly inhibited by classical inhibitors of acid phosphatases such as sodium orthovanadate (Ki = 4.23 micromol/l), sodium molybdate (Ki = 7.53 micromol/l) and sodium fluoride (Ki = 126.78 micromol/l) in a dose-dependent manner. Levamizole (1 mmol/l) and sodium tartrate (10 mmol/l), had no effect on the enzyme activity. Cytochemical localization of the acid phosphatase showed electrondense cerium phosphate deposits on the cell wall, as visualized by transmission electron microscopy. Phosphatase activity in F. pedrosoi seems to be associated with parasitism, as sclerotic cells, which are the fungal forms mainly detected in chromoblastomycosis lesions, showed much higher activities than conidia and mycelia did. A strain of F. pedrosoi recently isolated from a human case of chromoblastomycosis also showed increased enzyme activity, suggesting that the expression of surface phosphatases may be stimulated by interaction with the host.     

Drug conditioning induced by intrastriatal apomorphine administration

The present study examined (1) whether the neostriatum is involved in a drug-induced conditioned locomotor response and; (2) whether this structure participates in the development of behavioral sensitization. Moreover, the present study addressed the question whether the development of behavioral sensitization is necessary for the induction of conditioning. Rats received injections of either apomorphine (2 μg) or vehicle (solution of 0.1% ascorbate/saline) into the dorsal neostriatum daily for 7 days. These treatments were performed immediately prior to (apomorphine-paired group and vehicle group) or 30 min following (apomorphine-unpaired group) 10-min placement in an open field which served as the test environment. After a 3-day drug withdrawal period, the animals were given a 10-min non-drug vehicle test trial in the test environment. Three days later, a drug test with apomorphine was administered to the animals of the paired and unpaired treatment groups; the vehicle group again received an injection of vehicle. The analysis of locomotor activity in the open field (measured as the distance traversed) revealed that locomotor activity in the apomorphine-paired group was higher than in the other groups. There were no indications for behavioral sensitization to intrastriatal apomorphine, since the locomotor response in the apomorphine-paired group did not increase, but rather decreased with daily repeated injections of apomorphine. Furthermore, only the apomorphine-paired animals showed a higher locomotor response when tested after an intrastriatal injection of vehicle in the previously apomorphine-paired environment, which is indicative of a conditioned drug effect. These results suggest that the neostriatum is directly involved in the development of drug-induced conditioning of locomotor behavior but not in the establishment of behavioral sensitization.     

Towards cellular receptors for prions

Transmissible spongiform encephalopathies (TSE) are attributed to the conversion of the cellular prion protein (PrP(c)) into an abnormal isoform (PrP(sc)). This can be caused by the invasion of living organisms by infectious particles, or be inherited due to mutations on the PrP(c) gene. One of the most intriguing problems of prion biology is the inability to generate the infectious agent in vitro. This argues strongly that other cellular proteins besides those added in test tubes or found in cellular preparations are necessary for infection. Despite recent progress in the understanding of prion pathology, the subcellular compartments in which the interaction and conversion of PrP(c) into PrP(sc) take place are still controversial. PrP(c) interacts with various macromolecules at the cell membrane, in endocytic compartments and in the secretory pathway, all of which may play specific roles in the internalisation of PrP(sc) and conversion of PrP(c). A specific interacting protein required for the propagation of prions was originally proposed as a prion receptor, and later referred to as a ligand, a cofactor, protein X, or a partner. However, current studies indicate that PrP(c) associates with multi-molecular complexes, which mediate a variety of functions in distinct cellular compartments. It is proposed that a deeper understanding of the mechanics of such interactions, coupled to a better knowledge of the corresponding signalling pathways and ensuing cellular responses, will have a major impact on the prevention and treatment of TSE.     

Solubilization and immunological identification of presynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat hippocampus

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been identified mostly as postsynaptic receptors mediating fast glutamatergic synaptic transmission. However, neurochemical studies based on the modulation of neurotransmitter release have suggested the existence of presynaptic AMPA receptors. We have used a recently described technique that allows a high-purity fractionation of the pre- and postsynaptic proteins of synaptic junctions to evaluate the distribution of the different AMPA receptor subunits in rat hippocampal synapses. Surprisingly, we found very high levels of GluR1- and GluR2/3-like immunoreactivity in the presynaptic fraction, but also in the postsynaptic and extrasynaptic fractions. GluR4-like immunoreactivity was much less abundant but was still detected, predominantly in the postsynaptic fraction. This methodology appears to be far more sensitive than the classical immunogold electron microscopy to determine the localization of synaptic receptors.     

How important is the 'quality' of the cytotoxic T lymphocyte (CTL) response in protection against HIV infection?

Cytotoxic T lymphocyte (CTL) responses have been associated with protection from HIV-1 infection in people with a high degree of exposure to HIV and who show no serological evidence of HIV infection (HEPS, highly exposed persistently seronegative). However, it remains unclear how protective CTL responses could apparently develop in a minority of people, whilst the great majority of HIV-infected people make strong CTL responses yet progress to AIDS and death. In this paper we review the data which supports the hypothesis that the quality of the T-cell response, rather than its magnitude, may be an important factor that merits further investigation.