COLONY DEVELOPMENT IN EUDORINA ELEGANS (CHLOROPHYTA,VOLVOCALES)1

A detailed ultrastructure study was made of cell division and colony development in Eudorina elegans Ehrenberg. At the onset of cell division and prior to nuclear division the nucleus moved from the cell center to the cell surface. During nuclear division the nuclear membrane remained intact, except for openings occurring at the nuclear poles. The spindle microtubules appeared to arise from a MTOC-like (microtubule organizing centers) structure, while centrioles were absent from the nuclear poles. Following telophase, daughter nuclei formed which were separated by several distinct bands of endoplasmic reticulum. Cytokinesis occurred with formation of a cleavage furrow, associated with a typical phycoplast band of microtubules. However, cytokinesis was incomplete, resulting in formation of cytoplasmic bridges between the plakeal cells. Upon completion of up to five successive cell divisions, the plakea underwent inversion, which appeared to involve the production of colonial envelope material and rearrangement of cytoplasmic bridges. A new hypothesis concerning inversion is postulated based on these observations.     

Growth of endothelial and HeLa cells on a new multipurpose microcarrier that is positive,negative or collagen coated

A new cell culture microcarrier that can be covalently bonded by cell attachment proteins and can be thin-sectioned for electron microscopy was synthesized. It was easily made by sulfonating cross-linked polystyrene beads for a negative surface charge followed by covalent attachment of polyethylenimine for a positive charge. Cell attachment proteins, e.g. collagen, was covalently bonded directly to the microcarrier using a carbodiimide or after activating the microcarrier surface with glutaraldehyde. HeLa-S3 cells attached, spread and grew to confluence more efficiently on the positive microcarriers and those coated with collagen than on the negative ones. Endothelial cells grew best on those with a negative surface charge. The nature of the microcarrier surface was not the only aspect involved in cell adhesion but also the type of serum proteins adsorbed. Qualitatively different proteins coated the microcarriers depending upon whether the carrier was negative, positive or coated with collagen. Comparison of various types of available microcarriers indicated that the modified cross-linked polystyrene beads used here were best for transmission and scanning electron microscopy. Endothelial cells grown on the microcarriers had the same ultrastructure as cells grown in monolayers in culture dishes. Of a variety of microcarriers tested the modified cross-linked polystyrene beads were the only ones that could be used for both ultrastructural and biochemical techniques.     

Antigen-binding receptors on T cells from long-term MLR. Evidence of binding sites for allogeneic and self-MHC products

Antibody inhibition of radiolabelled stimulator membrane vesicle binding by T blasts activated in the mixed lymphocyte reaction (MLR) was used to identify responder-cell determinants involved in the binding phenomenon. Antisera or monoclonal antibodies against Thy-1, Lyt-1, Lyt-2 and Ly-6 antigens were not inhibitory. However, antibodies against heavy-chain V region (V_H) determinants strongly inhibited vesicle binding by both primary and longterm MLR blasts. Anti-Ia (both alloantisera and monoclonal reagents) caused inhibition of antigen binding by primary MLR blasts only. T blasts from long-term MLR lines were neither Ia-positive, nor susceptible to blocking of antigen binding with anti-Ia. However, these cells were capable of specifically absorbing soluble syngeneic Ia material, with the concomitant appearance of vesiclebinding inhibition with anti-Ia sera. Acquisition of syngeneic Ia by T blasts was effectively blocked with the anti-V_H reagent. Passively bound self-Ia did not interfere with vesicle binding in the absence of anti-Ia. These results strongly suggest the existance of specific self-Ia acceptor sites closely linked to the receptors for stimulator alloantigens on T cells proliferating in MLR. A receptor model based on these findings is briefly discussed.Abbreviations used in this paper B10 C57BL/10 - Con A concanavalin A - FcR Fc receptor - FCS fetal calf serum - H heavy chain - Ia I-region associated antigen - Ig immunoglobulin - LPS lipopolysaccharide - Lyt T-lymphocyte differentiation antigen - MHC major histocompatibility complex - MLR mixed lymphocyte reaction - PM plasma membrane - T thymus derived - Tcr T-cell receptor - V variable region of Ig     

Genetic polymorphism of serum complement components in the chimpanzee

Significant polymorphism of serum complement components Bf, C2, C3, C6, and C8 in the chimpanzee has been demonstrated. The data are consistent with the hypothesis thatC2 andBf are closely linked toChLA and argue against close linkage ofChLA toC3 or toC8, as in man. In addition, a blank allele for C6 and C6 deficiency was detected in several chimps.     

Origin of the left anterior descending coronary artery from the pulmonary artery: An unusual cause of angina in a middle-aged woman

A 48-year-old woman was admitted to our institution with angina pectoris and a systolic murmur. At cardiac catheterization, she was found to have an anomalous origin of the left anterior descending coronary artery from the pulmonary trunk. There was also an associated atrial septal defect and a bicuspid aortic valve.     

Traumatic disruption of the fibrous skeleton of the heart, with injury of the tricuspid and mitral valves, aortic annulus, and ventricular septum

In an automobile accident, a young man sustained blunt trauma to the chest that caused injury to the fibrous skeleton of the heart. The mitral and tricuspid valves and their annuli were lacerated, the aortic annulus was separated from the ventricular septum, and the ventricular septum was disrupted; however, with surgical management, the patient survived.     

2-carboxy-d-hexitol 1,6-bisphosphate: An inhibitor of d-ribulose 1,5-bisphosphate carboxylase/oxygenase

2-Carboxy-d-hexitol 1,6-bisphosphate (CHBP) has been prepared from d-fructose 1,6-bisphosphate and cyanide. DEAE-Sephadex chromatography separated the reaction products into two fractions which were identified as CHBP and CHBP-lactone. CHBP is presumably a mixture of two diastereomers, 2-carboxy-d-glucitol 1,6-bisphosphate and 2-carboxy-d-mannitol 1,6-bisphosphate, but an attempt to separate these compounds was not successful. The material in the CHBP-lactone peak had no effect on d-ribulose 1,5-bisphosphate (RuBP) carboxylase. However, CHBP was a potent reversible inhibitor of RuBP carboxylases. This compound displayed an inhibition constant (K_i at pH 8.0 and 30 °C) of 1–2 μm with the enzymes from spinach and barley, while the K_i was 60–70 μm with bacterial RuBP carboxylases from Pseudomonas oxalaticus and Rhodospirillum rubrum. The mode of inhibition was competitive with respect to RuBP for all the carboxylases, and noncompetitive with respect to CO₂ for the enzymes from spinach, P. oxalaticus and R. rubrum. The results indicate that, in the binding of certain organic phosphates by RuBP carboxylases, there may be a fundamental difference between the enzymes isolated from microbial and from higher plant sources. RuBP oxygenase activities from spinach and P. oxalaticus were also inhibited by CHBP, with K_i values which were similar to those obtained with the carboxylase activity of the same enzymes. The mode of inhibition of the oxygenase activities was also competitive with respect to RuBP. Thus, it seems that the binding of CHBP is similar for the carboxylase and oxygenase reactions of the same enzyme.     

High-yield method for immobilization of enzymes

Two types of polyethylenimine-coated glass microbeads (13–44 μm) were synthesized and used for the immobilization of glucose oxidase from Aspergillus niger and catalase from A. niger and beef liver. The two types of beads were distinguishable by differences in their surface topography. Immobilizations were performed by adsorption followed by treatment with glutaraldehyde. The immobilized-enzyme activities per unit support of all of the enzymes tested were compared with and found to be superior to the immobilized activities attainable on aminopropyl-activated glass microbeads. When enzyme was present in less than saturating amounts, the coated beads were able to remove 100% of the glucose oxidase activity initially present in the immobilization solution, with 78–87% of that activity expressed on the support surface. Bound glucose oxidase was more stable to thermal inactivation than native enzyme.