Changes in the vulnerable period of the rat myocardium during hypoxia, hyperventilation and heart failure

Changes in the duration and size of the vulnerable period of the myocardium in the presence of respiratory changes were studied in acute experiments on rats. The limits of the vulnerable period were determined by directly stimulating the heart during ventilation via the enlarged respiratory dead space, during hyperventilation and during heart failure. In the control group (normal ventilation without enlargement of the dead space), the vulnerable period lasted 5.7 +/- 0.76 ms. During ventilation via the enlarged dead space, hypercapnic hypoxaemia developed and the vulnerable period was markedly prolonged (18.55 +/- 5.29 ms) by a shift of its inner limit to the left. Hyperventilation caused normoxic to hyperoxic hypocapnia and markedly reduced the duration of the vulnerable period (8.17 +/- 2.21 and 9.31 +/- 2.38 ms respectively). The vulnerable period lengthened the most in heart failure (25.46 +/- 3.93), mainly as a result of a shift of its outer limit. In all the experimental groups there was a shift of the vulnerable period to the right, which was fastest in hypercapnic hypoxaemia and slowest in hyperoxic hypocapnia. The administration of Inderal (3 mg/kg i.p.) or Arfonad (50 mg/kg i.p.) markedly shortened the vulnerable period during hypercapnic hypoxaemia (9.87 +/- 2.78 and 9.32 +/- 2.16 ms respectively), but did not block the shift. Lengthening of the vulnerable period during hypercapnic hypoxaemia was probably due to activation of sympathetic nerves via beta-adrenergic receptors.     

Microcalorimetric assay of acetylcholinesterase

Comparative assays were made in a spectrophotometer and a microcalorimeter for the reaction between acetylcholinesterase (EC 3.1.1.7) and acetylthiocholine. The rate of light absorbance change and the rate of heat flow were measured from similar and simultaneous reactions in spectrophotometer and microcalorimeter, respectively. At the enzyme activity levels studied, i.e., 0.05–0.15 I.U. in calorimetry and 1–4 I.U. in spectrophotometry, the reaction rates were linear and showed first-order kinetics. A highly significant positive correlation was seen between the two methods (r = 0.997). More importantly, spectrophotometric assay with acetylthiocholine (which utilized a secondary reaction with chromagen, dithiobisnitrobenzoic acid) stood in highly significant positive correlation with calorimetric assays (which did not require a chromagen) either with the same substrate (r = 0.976) or with acetylcholine (r = 0.900). It appears that microcalorimetry can be used in preference to spectrophotometry for enzyme kinetic studies to overcome the complexity of reaction mixture and interference problems and with the advantage of using natural substrates.     

Two-dimensional gel analysis of swine histocompatibility antigens

Miniature swine MHC antigens from three inbred herds were examined by two-dimensional gel electrophoresis. These antigens were found to constitute a series of complex glycoproteins displaying haplotype-specific patterns that allowed the distinction of both class I and class II molecules among the three haplotypes. Selected outbred pig antisera reacted with a subset of class I antigens, suggesting the presence of at least two distinct molecular species among these antigens. Similarly, alloantisera reacting with mouse Ia antigens and a monoclonal anti-human DR were shown to immunoprecipitate a subset of class II molecules. Examination of the cells from two recombinant haplotypes demonstrated that both independent recombinational events took place between the class I and class II genes.     

Genetic and morphological characterization of ftsB and nrdB mutants of Escherichia coli.

The ftsB gene of Escherichia coli is believed to be involved in cell division. In this report, we show that plasmids containing the nrdB gene could complement the ftsB mutation, suggesting that ftsB is an allele of nrdB. We compared changes in the cell shape of isogenic nrdA, nrdB, ftsB, and pbpB strains at permissive and restrictive temperatures. Although in rich medium all strains produced filaments at the restrictive temperature, in minimal medium only a 50 to 100% increase in mean cell mass occurred in the nrdA, nrdB, and ftsB strains. The typical pbpB cell division mutant also formed long filaments at low growth rates. Visualization of nucleoid structure by fluorescence microscopy demonstrated that nucleoid segregation was affected by nrdA, nrdB, and ftsB mutations at the restrictive temperature. Measurements of beta-galactosidase activity in lambda p(sfiA::lac) lysogenic nrdA, nrdB, and ftsB mutants in rich medium at the restrictive temperature showed that filamentation in the nrdA mutant was caused by sfiA (sulA) induction, while filamentation in nrdB and ftsB mutants was sfiA independent, suggesting an SOS-independent inhibition of cell division.     

Social behavior in a captive chimpanzee (Pan troglodytes) group

A group of captive chimpanzees, consisting of one adult male and three mother/infant pairs, was systematically observed over a 15-month period. Over 200 hr of data were collected, using both sequential and time sampling techniques, and compared to the available data on wild chimps. Unlike many captive groups, most behavior patterns were remarkably similar, both qualitatively and quantitatively, to that of wild chimpanzees including: play, grooming, infant sexual development, tool use, food sharing, prosocial partner preferences, and aggressive displays.     

Glycerol models of the ciliated epithelium of bronchial mucosa and their use in the diagnosis of chronic nonspecific lung diseases

The method of extraction of ciliated epithelium from biopsy samples of human bronchial mucosa with glycerol is suggested. Permeabilized cilia of glycerol-extracted cells can be easily reactivated by exogenous ATP. This method was used for the study of ciliary dyskinesia in patients with chronic lung diseases. It was shown that in patients with Kartagener's syndrome neither freshly-isolated, nor glycerol-extracted ATP-treated cilia were motile. On the other hand, in some patients with bronchial asthma ATP reactivated glycerol-extracted cilia, while cilia of freshly-isolated cells remained immotile. The study shows that glycerol permeabilization and reactivation by ATP can be used for the analysis of cilial contractile apparatus in patients with chronic lung disease.     

Enzymic synthesis ofL-Lysine fromDL-α-Amino-ε-caprolactam by new microbial strains

The production of L-lysine fromDL-α-amino-ε-caprolactam (DL-ACL) by new strains producingL-α-amino-ε-caprolactamase and aminocaprolactam racemase is described. Optimal conditions for hydrolysis ofL-ACL byCryptococcus sp. and for racemization of ACL by cells of a strain isolated in nature and identified asPseudomonas sp. were determined. Synthesis ofL-α-amino-ε-caprolactamase is induced byDL-ACL orL-lysine with the same effectivity. A positive effect of phosphates (potassium salts) on reduction of the induction lag was detected, the synthesis of this enzyme was found to be repressed by glucose and some possibilities of the reversion of this repressive effect were demonstrated. Under conditions optimal for the production of both enzymes a quantitative theoretical conversion of 10 % aqueousDL-ACL toL-lysine by a mixture of native cells in a mass ratio of 1: 2 (producer of ACL-hydrolase to producer of ACL-racemase) occurred in 8 h at 40 °C and pH 8.0     

The release of prostaglandins in human aqueous humour following intraocular surgery. Effect of indomethacin

Inflammatory reaction to ocular trauma is known to be related to prostaglandins. To further evaluate this phenomenon in human, PGE₁ and E₂ were measured by R.I.A. after silicic acid chromatography in aqueous humour of 26 patients before and 3 days after surgery for unilateral senile cataract (posterior chamber implant after extracapsular surgery). 13 out of these patients were treated with indomethacin by enteral route and 13 were not treated.PGE₂ levels increased in all non-treated patients from : m < 214 pg/ml before surgery, to 2666 ± 869 pg/ml (range : 257 - 8728) p < 0.001 after surgery. PGE₂ levels did not increase in indomethacin-treated patients. PGE₁ levels did not increase significantly in non-treated as in treated patients.1) Intra-ocular surgery is followed in human by a constant increase of the only PGE₂ in the aqueous humour. 2) Indomethacin inhibits this increase. 3) The post-surgical increase in the permeability of blood-aqueous barrier appears to be related to a release of PGE₂.