Effect of disuse on the ultrastructure of the achilles tendon in rats

We examined the influence exerted, through disuse of the hindlimb, on the collagen fibres of the achilles tendon in rats. With disuse the body mass decreased by 28%, and the mass of soleus muscle decreased by 20%. A decrease in the surface area and diameter was observed in the experimental group when compared to the control group. A histogram of the collagen fibres showed a decrease of the thick fibres in the experimental group. The maximum surface area of collagen fibres in the experimental group was seen to be only 43% of that of the control group. These results showed a decrease in the thickness of the collagen fibres of the achilles tendon through disuse. This seemed to suggest that resistance to tension is decreased by disuse.     

Responses in muscle sympathetic activity to acute hypoxia in humans

Responses in muscle sympathetic activity (MSA) to acute hypoxia were studied in 13 healthy male subjects under hypobaric hypoxic conditions at a simulated altitude of 4,000, 5,000, and 6,000 m. Efferent postganglionic MSA was recorded directly with a tungsten microelectrode inserted percutaneously into the tibial nerve. Heart rate (HR) and respiratory rate (RR) were counted respectively from the R wave of an electrocardiogram and from the respiratory tracing recorded by the strain-gauge method. The average values of the MSA burst rate and total activity of MSA (burst rate x mean burst amplitude) at 4,000, 5,000, and 6,000 m were 36.4 +/- 2.6, 39.1 +/- 3.1, and 40.2 +/- 4.2 (SE) bursts/min and 616 +/- 138, 794 +/- 190, and 764 +/- 227 arbitrary units, respectively. These values were significantly higher than the values of 27.1 +/- 2.9 bursts/min and 446 +/- 28 at sea level. HR increased significantly at altitudes, but RR did not show significant change. Under severe hypoxic conditions beyond 5,000 m, there were large interindividual differences in the MSA responsiveness to hypoxia. The results indicate that MSA is activated under hypoxia by stimulating the chemoreceptors. However, the central controlling mechanisms that would be affected by hypoxia may also influence the MSA responsiveness under severe hypoxia.     

Correlation between the virulence ofFrancisella tularensis in experimental mice and its acriflavine reaction

Correlation between the virulence of Francisella tularensis in experimental mice and its acriflavine reaction was studied. The cultures derived from all four strains (Ebina, CMB2, Schu, and N9) that had long been subcultured on agar media yielded two types of colonies, i.e., acriflavine reaction-positive (acf+) and acriflavine reaction-negative (acf-) colonies. All acf+ colonies, regardless of their parent strains, were shown to be low virulent in mice. Acf- colonies were shown to be either high (Ebina, CMB2) or low (Schu, N9) virulent. The low-virulent acf- colonies gained virulence during several passages in mice, whereas the acf+ colonies remained low virulent even after the animal passages.     

Two monoclonal antibodies against small-cell lung cancer show existence of synergism in binding

Summary Murine IgG1 monoclonal antibodies (mAbs), ITK-2 and ITK-3, were generated against a small-cell lung cancer (SCLC) cell line. Enzyme-linked immunosorbent assay using a variety of established cell lines as substrates, immunoperoxidase staining of freshly frozen tissue sections, and fluorescence-activated cell sorter analysis of peripheral blood leukocytes showed that these mAbs recognize a part of the SCLC-associated cluster 1 antigen. In immunoprecipitation studies, both ITK-2 and ITK-3 bound to a 145-kDa glycoprotein of SCLC cell membrane extracts, as did MOC-1 and NKH-1, which both recognize the cluster 1 antigen. However, because the binding of¹²⁵I-labeled ITK-2 to SCLC cells was not inhibited by MOC-1 or NKH-1, the binding site of ITK-2 on SCLC cells appeared to be different from that of either MOC-1 or NKH-1. Unexpectedly, binding of¹²⁵I-labeled ITK-2 to SCLC cells increased in the presence of ITK-3. This ITK-3-induced increase in ITK-2 binding was due partly to an increase in the number of binding sites for ITK-2 on SCLC cells. Addition of ITK-3 may, therefore, improve the effectiveness of ITK-2-based tumor detection or therapy.     

Mutants with Altered Ca2+-Channel Properties in PARAMECIUM TETRAURELIA: Isolation, Characterization and Genetic Analysis

Dancers are a group of mutants in Paramecium tetraurelia whose Ca²⁺ current inactivates poorly and are likely to be defective in the structure of their Ca²⁺ channels. These mutants show prolonged backward swimming in response to K⁺ and Ba ²⁺ in the medium and were selected by this property in a galvanotactic trough. The dancer mutants are semidominant, and all isolated mutants belong to one complementation group; they are not allelic to any of the previously isolated behavioral mutants of P. tetraurelia. The phenotypic change from the homozygous parent to heterozygous F₁ generation takes three to five fissions. There is no evidence of a cytoplasmic factor capable of converting the dancer to the wild-type phenotype, as has been demonstrated in the mutants pawn and cnr. We suggest that the dancer locus is a structural gene for the Ca²⁺ channel.     

Studies on the biological activity of an insulin-stimulating peptide from a tryptic digest of bovine serum albumin

Summary A two-chain polypeptide, which corresponds to amino acid residues 115–143 and 144–184(185) of bovine serum albumin, connected to each other by a disulfide bridge, potentiated the effects of insulin on glucose transport and glucose metabolism in isolated rat adipocytes. Although the peptide alone had little activity, it shifted the concentration-response curves of insulin-stimulated D-[I-¹⁴C]glucose oxidation, 2-deoxyglucose transport, and lipid synthesis from D-[U-¹⁴C]glucose to lower insulin concentrations. It also increased the maximal responses of these parameters to insulin. However, it did not affect insulin binding to adipocytes. The peptide protected insulin considerably from degradation, but this effect alone cannot account for its effect in increasing the maximal responses to the hormone, and even when degradation of a submaximal concentration of insulin was suppressed by bacitracin, the peptide still had an enhancing effect. These results suggest not only that the peptide influences a step distal to receptor-mediated insulin binding but also that inhibition of insulin degradation alone cannot explain its total effect.The peptide lost its insulin-stimulating activity completely when it was further digested with V8 or lysinespecific endopeptidase, or when it was reduced and then carboxamidomethylated or oxidized with performic acid. Similar active tryptic fragments were obtained from human and rat albumins.Insulin-stimulating peptides should be useful in studies on the mechanisms of insulin action including both the sensitivities and responsiveness of target cells to the hormone.Abbreviations ISP insulin-stimulating peptide - HEPES N-(2-hydroxyethyl)piperazine-N-2-ethanesulfonic acid - HPLC high-performance liquid chromatography - SDS sodium dodecyl sulfate     

Immunotherapy with bestatin for acute nonlymphocytic leukemia in adults

Summary In a cooperative randomized control study of immunotherapy with bestatin in combination with chemotherapy in adults with acute nonlymphocytic leukemia (ANLL), 101 patients (48 in the bestatin group and 53 in the control group) out of 115 patients registered were evaluated as eligible. The bestatin group achieved a statistically significant prolongation of survival compared with the control group in overall ANLL and acute myelogenous leukemia. In the analysis of patient age, the bestatin group achieved a statistically significant prolongation of both the remission duration and survival in patients aged 50 to 65 years, while the differences were not significant in the 15 to 49 age group. The bestatin group tended to achieve a higher rate of reinduction of remission in patients who had recurrence of leukemia. Side effects developed in only 5 (9.6%) of 52 patients treated with bestatin. None of these side effects were particularly serious in nature. It is concluded that bestatin is useful for prolongation of survival of adult patients with ANLL, making for a longer remission duration especially in elderly patients and with few side effects.     

Performance of noncountermovement jump with both knee and hip joints fully extended

The relationships between neuromuscular performance and biomechanical variables were studied in maximum vertical jumps to examine the factors influencing the performance of a noncountermovement jump. Keeping their knee and hip joint fully extended, five healthy subjects performed four kinds of noncountermovement jumps and one countermovement jump, during which ankle joint angle, platform force, and surface electromyograms of a triceps surae muscle were recorded. In the four noncountermovement jumps, the magnitude of activation and force at the onset of a shortening contraction of the triceps surae muscle were controlled at four different levels. Performance parameters of the noncountermovement jumps, maximum angular velocity of the ankle angle and flight time, correlated with the platform force at the onset of the plantar flexion. Furthermore the integrated electromyograms of the triceps surae muscle before the plantar flexion were correlated with the maximum angular velocity of the ankle angle and the force at the plantar flexion onset. The findings suggest that the efficient utilization of the muscle characteristic contributes to an enhancement of the noncountermovement jump.