N-hydroxymethylpentamethylmelamine,a major in vitro metabolite of hexamethylmelamine

N-Hydroxymethylpentamethylmelamine (HMPMM) was identified by HPLC and by GLC-MS after derivatization, as a metabolite of the anticancer drug hexamethylmelamine (HMM) in incubation mixtures with fortified mouse liver 9000 × g and microsomal preparations. HMPMM formation was dependent on the presence of NADPH and oxygen. N-demethylated metabolites were also found. HMPMM displays appreciable chemical stability and 29% was recovered after 60 min incubation in buffer. HMPMM constituted more than 50% of total HMM metabolites in 30 min incubations. The known chemical reactivity of carbinolamines means that HMPMM could be involved in the pharmacological or toxic effects of HMM.     

Human Ia molecules carrying DC1 or BR4X7 determinants are not homologous to murine I-E molecules

An anti-I-E^k alloantiserum was shown to react with purified human Ia preparation. All Ia preparations tested were actively bound irrespective of their HLA-DR phenotypes. However, from a quantitative point of view, DR7 molecules were significantly less reactive. No reaction was observed with isolated Ia subunits. Only molecules carrying DR determinants, but not those carrying either DC1 or BR4X7 determinants, were bound.     

PERFUSION FOR MYOCARDIAL REVASCULARIZATION WITHOUT AN ARTIFICIAL OXYGENATOR (New Method to Reduce Surgical Morbidity)

Thirteen patients were submitted to direct myocardial revascularization (saphenous vein graft) without the use of an artificial oxygenator. The perfusion was done by a left ventricle-to-aorta bypass and autogenous oxygenation. Most patients had three grafts implanted plus endarterectomy of the distal right coronary artery. There was one hospital death that was apparently not related to the method used. Perfusion time ranged from 45 minutes to 4 hours. Body temperature during perfusion was kept between 25 and 30 degrees C. Perfusion flow was maintained between 25 to 50 ml per kg of body weight per minute. Ischemic, hypothermic cardiac arrest was employed. We demonstrated for the first time that perfusion for this kind of heart surgery could be done with no artificial oxygenators and, apparently, is safer for the patients. There were no bleeding problems even in perfusions as long as 4 hours. There was no respiratory dysfunction, and artificial respiration was used for only 6 to 12 hours. The patients awoke at the end of surgery with no signs or symptoms of central nervous system damage, and vasopressor drugs were rarely used after surgery. Although the experience is very small, it suggests that many postoperative problems, especially those related to bleeding and respiratory dysfunction may be reduced or eliminated by this new method.     

Evaluation of several enrichment procedures for the isolation of recombinant plasmid DNA

A number of methods for the selective enrichment of recombinant plasmids were examined; these include alkaline phosphatase treatment of the restricted pBR322 vector, as well as a combination of this and S1 nuclease treatment of the ligated mixture of pBR322 and pCR1 plasmids orS. griseus DNA followed by D-cycloserine treatment to enrich for cells carrying recombinant molecules. The relative efficiencies of these methods were compared.     

Light-driven proton translocations in Halobacterium halobium

The purple membrane of Halobacterium halobium acts as a light-driven proton pump, ejecting protons from the cell interior into the medium and generating an electrochemical proton gradient across the cell membrane. However, the typical response of cells to light as measured with a pH electrode in the medium consists of an initial net inflow of protons which subsides and is then replaced by a net outflow which exponentially approaches a new lower steady state pH level. When the light is turned off a small transient acidification occurs before the pH returns to the original dark level. We present experiments suggesting that the initial inflow of protons is triggered by the beginning ejection of protons through the purple membrane and that the initial inflow rate is larger than the continuing light-driven outflow. When the initial inflow has decreased exponentially to a small value, the outflow dominates and causes the net acidification of the medium.The initial inflow is apparently driven by a pre-existing electrochemical gradient across the membrane, which the cells can maintain for extended times in the absence of light and oxygen. Treatments which collapse this gradient such as addition of small concentrations of uncouplers abolish the initial inflow.The triggered inflow occurs through the ATPase and is accompanied by ATP synthesis. Inhibitors of the ATPase such as N,N′-dicyclohexylcarbodiimide (DCCD) inhibit ATP synthesis and abolish the inflow. They also abolish the transient light-off acidification, which is apparently caused by a short burst of ATP hydrolysis before the enzyme is blocked by its endogenous inhibitor.Similar transient inflows and outflows of protons are also observed when anaerobic cells are exposed to short oxygen pulses.     

Hepatocyte population dynamics during hydrocortisone and thioacetamide treatment

Summary The orderly organization in a number of discrete classes of weight persists in the hepatocytes during acute and chronic poisoning with thioacetamide and during a prolonged treatment with hydrocortisone, though many striking cytological and structural changes occur in the liver.The number of hepatocyte classes decreases under hydrocortisone treatment and during acute and chronic thioacetamide poisoning, and increases during recovery after acute thioacetamide poisoning and during the late phases of chronic thioacetamide poisoning. This is due to decrements and increments in dry mass of the hepatocytes, which occur by steps, through repeated losses and additions of a constant amount of solids substantially corresponding to the class period.Such a mechanism is similar to that acting in the hepatocyte atrophy due to starvation and in the hepatocyte enlargement occurring during postnatal development. Therefore, the increment and the decrement in dry mass by defined steps takes place in the hepatocytes in both physiological and pathological conditions.This work was supported by a grant of the Consiglio Nazionale delle Ricerche, Rome, Italy.     

Biosynthesis of the sesquiterpenoid ageratriol

Ageratriol is biosynthesized from agerol through a diepoxide derivative. Mevalonic acid incorporation revealed that the formation of the isopropenylic double bond is not stereospecific.     

Efficient colonization of the endophytes Herbaspirillum huttiense RCA24 and Enterobacter cloacae RCA25 influences the physiological parameters of Oryza sativa L. cv. Baldo rice

Several important bacterial characteristics, such as biological nitrogen fixation, phosphate solubilization, 1-aminocyclopropane-1-carboxylate deaminase activity and production of siderophores and phytohormones, can be assessed as plant growth promotion traits. Our aim was to evaluate the effects of nitrogen fixing and indole-3-acetic acid (IAA) producing endophytes in two Oryza sativa cultivars (Baldo and Vialone Nano). Three bacteria, Herbaspirillum huttiense RCA24, Enterobacter asburiae RCA23 and Staphylococcus sp. 377, producing different IAA levels, were tested for their ability to enhance nifH gene expression and nitrogenase activity in Enterobacter cloacae RCA25. Results showed that H. huttiense RCA24 performed best. Improvement in nitrogen fixation and changes in physiological parameters such as chlorophyll, nitrogen content and shoot dry weight were observed for plants co-inoculated with strains RCA25 and RCA24 in a 10:1 ratio. Based on confocal laser scanning microscopy analysis, strain RCA24 was the best colonizer of the root interior and the only IAA producer located in the same root niche occupied by RCA25 cells. This work shows that the choice of a bio-inoculum having the right composition is one of the key aspects to be considered for the inoculation of a specific host plant cultivar with microbial consortia.     

Critical threshold meal size and molt initiation in Rhodnius prolixus

The molting process and body growth in Rhodnius prolixus (Hemiptera: Reduviidae) (Ståhl, 1859) are significantly influenced by the availability and quality of food. Based on the body weight of each stage, the present study provides estimates of a potential critical weight threshold required for molt initiation in R. prolixus. In addition, a new measure given by the area under the weight curve is proposed, which encapsulates both body weight and time. It is shown that this measure is consistent with the data, and allows the estimation of a pre‐refractory period (i.e. the time interval between the moment at which the critical weight threshold is reached and the moment when no further meals are accepted). The present analysis estimates the critical weight threshold as 1.6, 5.3, 12.9, 42.0 and 97.0 mg for stages 1–5, respectively, whereas the values of the area under the curve threshold as 5, 16, 31.2, 159.7 and 329.9 mg days for stages 1–5, respectively. The results of the present study confirm the existence of a weight‐dependent mechanism for the initiation of molting in R. prolixus.