Use of a cysteine proteinase from Carica candamarcensis as a protective agent during DNA extraction

We describe the use of a plant cysteine proteinase isolated from latex of Carica candamarcensis as a protective agent during isolation of bacterial DNA following growth in culture of these cells. Between 100 to 720 units of proteinase (1 microgram = 6 units) afforded good DNA protection when incubated with various kinds of microorganisms. Agarose gel electrophoresis showed that the resulting DNA was similar in size to DNA preparations obtained by treatment with proteinase K. The viability of the resulting material was checked by PCR amplification using species-specific primers. After standing at room temperature (25 degrees C) for 35 days, the enzyme lost 10% of its initial activity. The enzyme stability and good yield of DNA suggest the use of this proteinase as an alternative to proteinase K.     

Activation of the ATM kinase by ionizing radiation and phosphorylation of p53

The p53 tumor suppressor protein is activated and phosphorylated on serine-15 in response to various DNA damaging agents. The gene product mutated in ataxia telangiectasia, ATM, acts upstream of p53 in a signal transduction pathway initiated by ionizing radiation. Immunoprecipitated ATM had intrinsic protein kinase activity and phosphorylated p53 on serine-15 in a manganese-dependent manner. Ionizing radiation, but not ultraviolet radiation, rapidly enhanced this p53-directed kinase activity of endogenous ATM. These observations, along with the fact that phosphorylation of p53 on serine-15 in response to ionizing radiation is reduced in ataxia telangiectasia cells, suggest that ATM is a protein kinase that phosphorylates p53 in vivo.     

Preconditioning of isolated rabbit cardiomyocytes: no evident separation of induction, memory and protection

Cardiomyocytes isolated from rabbit hearts were preconditioned in vitro by 10 min of ischemia or treatment with 100 microM adenosine. Protection was assessed as average integrated mortality following osmotic swelling and determination of viability by trypan blue exclusion over 60-180 min ischemia. Repetitive sub-maximal stimulations with 1 microM adenosine amplified the protective response. Treatment with adenosine only at the onset of prolonged ischemia afforded a dose-dependent protection. The PKC inhibitor calphostin C (500 nm) blocked preconditioning and, when added during ischemic incubation of non-preconditioned cells, significantly increased injury. The memory of adenosine-induced preconditioning decayed over a 60 min post-incubation period. Light activation of calphostin C initially added to preconditioned ischemic cells in the dark indicated that a 10 min period of PKC activity at the onset of ischemia affords full protection. The reversible PKC inhibitors chelerythrine (5 microM) or staurosporine (100 nM) added only to bracket induction of ischemia, reduced but did not abolish protection. Protection was abolished when either drug was present during induction and a subsequent 30 min post-incubation period. Staurosporine included during initiation and post-incubation but washed out in the final 5 min of post-incubation allowed significant protection to occur. It is concluded that a single adenosine receptor-stimulation induces protection as it preconditions, and PKC activity appears to be required for both induction and protection. Memory may reside in post-receptor amplification of an initial protective response.     

Electrophysiological mechanisms and determinants of vagal maneuvers for termination of paroxysmal supraventricular tachycardia

BACKGROUND: The vagal maneuvers used for termination of paroxysmal supraventricular reentrant tachycardia (PSVT) appear to involve more complex mechanisms than we have known, and further study should be done to explore the possible mechanisms. METHODS AND RESULTS: In this study, 133 patients with PSVT and 30 age- and sex-matched control subjects were included. We assessed the effects of different vagal maneuvers on termination of PSVT and compared baroreflex sensitivity and beta-adrenergic sensitivity between the patients with PSVT and control subjects. Out of 85 patients with atrioventricular reciprocating tachycardia (AVRT), vagal maneuvers terminated in 45 (53%). Of these, 28 (33%) terminated in the antegrade limb and 17 (20%) terminated in the retrograde limb. Out of 48 patients with atrioventricular nodal reentrant tachycardia (AVNRT), vagal maneuvers terminated the tachycardia in the antegrade slow pathway (14%) or in the retrograde fast pathway (19%). Baroreflex sensitivity was poorer but isoproterenol sensitivity test better in patients with AVNRT. Poorer antegrade atrioventricular node conduction properties and better vagal response determined successful antegrade termination of AVRT by vagal maneuvers. Poorer retrograde accessory pathway conduction property but better vagal response determined successful retrograde termination of AVRT. Better sympathetic and vagal response associated with poorer retrograde atrioventricular node conduction determined retrograde termination of AVNRT by the Valsalva maneuver. CONCLUSIONS: Both the vagal response and conduction properties of the reentrant circuit determine the tachycardia termination by vagal maneuvers. Improved understanding of the interaction of autonomic and electrophysiological mechanisms in maintaining or terminating PSVT may provide important insight into the pathophysiology of these two tachycardias.     

Improved results in the management of surgical candidates with lung cancer

BACKGROUND: Perioperative mortality and morbidity after lung resection for carcinoma are generally reported to be 3% to 6% and 15% to 30%, respectively, and higher in the elderly and those with limited cardiopulmonary reserve. METHODS: To minimize this risk and extend the surgical option to more high-risk patients, we adopted a protocol in 1991 that included preoperative digitalis, subcutaneous heparin and venoocclusive stockings, aggressive perioperative pulmonary toilet, and video-directed limited resections for many patients with limited pulmonary reserve. In October 1996, we reviewed our results with 173 consecutive patients (median age, 60 years; range, 17 to 89 years) undergoing operation for suspected lung carcinoma. Forty-one patients were 70 years old or older, and 70 patients were considered high risk on the basis of advanced age (> or = 70 years), poor cardiac or pulmonary reserve, or serious medical comorbidity. Procedures included pneumonectomy (n = 31), lobectomy (n = 83), bilobectomy (n = 12), and limited resection (n = 45). Two patients had unresectable disease. RESULTS: Hospital mortality was 1.6% (3/173) and morbidity was experienced by 15% (26/173). Among the high-risk subgroup mortality was 4.2% (3/70) and morbidity was 20% (14/70; p < 0.03). For the older patients these values were 4.8% (2/41) and 17.9% (7/41), respectively. CONCLUSIONS: Morbidity and mortality from lung resections may be minimized with the perioperative management strategy outlined above. This would allow more high-risk patients to benefit from surgical resection, and do so with an acceptably low risk.     

The importance of prenatal factors in childhood blindness in India

The causes of visual loss in 1411 children attending schools for the blind in different geographical areas in India are described. Ninety-three percent (1318) of the children were severely visually impaired (SVI) or blind (i.e. corrected acuity in the better eye of <20/200 [<6/60]). In 60% of SVI/blind children vision loss was attributable to factors operating in the prenatal period, in 47% the prenatal factors were known and definite, and in 13% prenatal factors were the most probable causes. Hereditary retinal dystrophies and albinism were seen in 19% of SVI/blind children and 23% had congenital ocular anomalies. There were variations in the relative importance of different causes by state. The observed pattern of causes of visual loss is intermediate between those seen in industrialised countries and in the poorest developing countries. This suggests that strategies to combat childhood blindness in India need to address concurrently both preventable and treatable causes. The need for aetiological studies, particularly on anophthalmos and microphthalmos, is highlighted.