Advantages of potassium cardioplegia and perfusion hypothermia in left ventricular hypertrophy

An attempt was made to determine the effect of hypothermic potassium cardioplegia (35 mEq of potassium chloride) on the hypertrophic ventricle. Puppies with induced left ventricular hypertrophy were divided into four groups and studied after one hour on global ischemia. Myocardial adenosine triphosphate (ATP) was best preserved in the hypothermically perfused groups and correlated well with measurements of coronary sinus creatine phosphokinase (CPK). In Groups 1 and 2 (anoxic arrest at 37 degrees C and KC1 perfusion at 37 degrees C), CPK at 30 minutes of reperfusion was 1,031 and 198 IU, respectively, compared to 35 IU in Group 3 (KC1 perfusion at 4 degrees C) and 44 IU in Group 4 (Ringer's lactate at 4 degrees C). Myocardial injury was milder in Groups 3 and 4 regardless of whether potassium chloride was added. It is apparent that hypothermic perfusion of a hypertrophic ventricle was the major factor in myocardial preservation, as determined by myocardial ATP and coronary sinus CPK.

Protein synthesis in chloroplasts. VII. Initiation of protein synthesis in isolated intact pea chloroplasts

Isolated intact pea chloroplasts use light energy to synthesise N-formayl [35S]-methionylpuromycin when incubated with L-[35S]methionine and puromycin. Control experiments establish that this synthesis occurs on chloroplast ribosomes, and not on contaminating mitochondrial or bacterial ribosomes. The amount of N-formylmethionylpuromycin formed suggests that each messenger RNA that is being translated in vitro undergoes initiation at least twice. We conclude that isolated, intact pea chloroplasts carry out the initiation of protein synthesis, as well as the elongation and termination of polypeptide chains.

Distal coronary artery bypass: local occlusion vs. ischemic arrest

A retrospective study was performed on 65 patients with intractable angina and subtotal coronary occlusions undergoing aortocoronary artery bypass (ACB) to determine whether the local occlusion (L.O.) or the ischemic arrest (I.A.) technique was perferable in performing the distal coronary artery bypass. In 23 patients who had the method of local occlusion, a 45.7 percent incidence of myocardial injury was observed, compared to 42 patients undergoing ACB with ischemic arrest in whom an incidence of 22.5 percent occurred. Both serum glutamic oxaloacetic transaminase (SGOT) and creatine phosphokinase activity (CPK) determinations at 24 hours following operation in those patients not demonstrating evidence of postoperative injury were statistically higher in the local occlusion group compared to the ischemic arrest group. In the L.O. group SGOT was 155 I.U. compared to 77 I.U. in the I.A. group (p less than 0.01). CPK was 72 I.U. in the L.O. groupcompared to 34 I.U. in the I.A. group (p less than 0.05). These data suggest that, in subtotal coronary artery obstruction, the use of the L.O. technique is associated with a higher incidence of myocardial injury than is the technique of total cardiac I.A.

Immunologic competence of regional lymph nodes in patients with breast cancer

In 24 patients undergoing radical mastectomy, the degree of sensitization to breast cancer was compared between lymphocytes obtained from regional lymph nodes and circulating lymphocytes. Using the direct lymphocyte migration inhibition assay a greater immunologic response was observed in regional lymph node lymphocytes as compared to circulating lymphocytes when challenged with breast cancer antigen in vitro. In the breast cancer group, migration inhibition (M.I.) was 21% plus or minus 3% in the regional lymph node (R.L.N.) lymphocytes, as compared to 7% plus or minus 3% in the peripheral blood (P.B.) lymphocytes (p smaller than .01). In the control group M.I. was - 10% plus or minus 2% in the R.L.N. lymphocytes, as compared to - 2% plus or minus 3% in the P.B. lymphocytes (p equal to n.s.) indicating no immunologic response to the breast cancer antigen. A significant delayed hypersensitivity response (M.I.greater 20%) was found in 17/24 regional lymph nodes of the radical mastectomy graoup, as compared to 7/24 in the peripheral blood samples tested in the same group, indicating a superior immune response in the regional lymph node lymphocyte population. These data support the concept that regional lymph nodes in breast cancer patients are immunologically competent, and that the lymphocytes in these nodes are more reactive with a tumor antigen than are the circulating lymphocytes.

Protein synthesis in chloroplasts. Characteristics and products of protein synthesis in vitro in etioplasts and developing chloroplasts from pea leaves

The function of plastid ribosomes in pea (Pisum sativum L.) was investigated by characterizing the products of protein synthesis in vitro in plastids isolated at different stages during the transition from etioplast to chloroplast. Etioplasts and plastids isolated after 24, 48 and 96h of greening in continuous white light, use added ATP to incorporate labelled amino acids into protein. Plastids isolated from greening leaves can also use light as the source of energy for protein synthesis. The labelled polypeptides synthesized in isolated plastids were analysed by electrophoresis in sodium dodecyl sulphate-ureapolyacrylamide gels. Six polypeptides are synthesized in etioplasts with ATP as energy source. Only one of these polypeptides is present in a 150 000g supernatant fraction. This polypeptide has been identified as the large subunit of Fraction I protein (3-phospho-D-glycerate carboxylyase EC 4.1.1.39) by comparing the tryptic 'map' of its L-(35S)methionine-labelled peptides with the tryptic 'map' of large subunit peptides from Fraction I labelled with L-(35S)methionine in vivo. The same gel pattern of six polypeptides is seen when plastids isolated from greening leaves are incubated with either added ATP or light as the energy source. However, the rates of synthesis of particular polypeptides are different in plastids isolated at different stages of the etioplast to chloroplast transition. The results support the idea that plastid ribosomes synthesize only a small number of proteins, and that the number and molecular weight of these proteins does not alter during the formation of chloroplasts from etioplasts.

Protein synthesis in chloroplasts. IV. Polypeptides of the chloroplast envelope

Envelope membranes were isolated from washed chloroplasts of pea seedlings. As judged by the protein-to-chlorophyll ratio, average preparations contain less than 8 percent contamination with internal lamellar membranes. Electrophoresis on sodium dodecylsulphate polyacrylamide gels shows that the envelope membranes contain at least 25 polypeptides. The molecular weight distribution of the envelope polypeptides is different from that of the lamellar polypeptides, there being more polypeptides of molecular weights above 50 000 in the envelopes. Two envelope polypeptides become labelled when isolated intact chloroplasts are incubated in the light with (35S) methionine. One of these is similar in molecular weight to the main polypeptide labelled in lamellae, but the other is unique to the envelope fraction. Incorporation of label into both polypeptides is totally light-dependent and is inhibited by chloramphenicol. When (35S) methionine is fed to detached pea shoots with and without cycloheximide, the labelling of other envelope polypeptides is inhibited. We conclude that two polypeptides of the chloroplast envelop are synthesised by chloroplast ribosomes.

Ribonucleic acid synthesis in chloroplasts

Chloroplasts isolated from young spinach leaves incorporate [(3)H]uridine into RNA. This incorporation shows an absolute requirement for light and does not occur in lysed chloroplasts. Fractionation by polyacrylamide-gel electrophoresis of the RNA synthesized in vitro reveals a major discrete product of molecular weight 2.7x10(6) and two minor products of molecular weight 1.2x10(6) and 0.47x10(6). These discrete products are super-imposed on a background of polydisperse RNA. The incorporation of (32)P(i) into chloroplast rRNA species (mol.wt. 1.05x10(6) and 0.56x10(6)) in excised spinach leaves proceeds after a distinct lag period compared with the incorporation into cytoplasmic rRNA species (mol.wt. 1.34x10(6) and 0.7x10(6)). Incorporation of (32)P(i) into chloroplast RNA species of molecular weight 2.7x10(6), 1.2x10(6), 0.65x10(6) and 0.47x10(6) proceeds without such a time-lag. The kinetics of labelling of the individual RNA components is consistent with the rapidly labelled RNA species of molecular weight 1.2x10(6) and 0.65x10(6) being precursors to the more slowly labelled rRNA species of molecular weight 1.05x10(6) and 0.56x10(6) respectively.

Inhibition of grana formation by lincomycin

The antibiotic lincomycin is a specific inhibitor of chloroplast ribosomal activity in greening leaves of Pisum sativum at 1 μg/ml, and prevents both the formation of chloroplast membranes and their stacking into grana. This finding suggests that one function of chloroplast ribosomes is to synthesise at least one protein component of thylakoid membranes.