An influx of extracelluar calcium is required for initiation of the human sperm acrosome reaction induced by human follicular fluid

The role of Ca²⁺ in the human sperm acrosome reaction was investigated using the fluorescent calcium indicator fura-2. Previous experiments have shown that a Sephadex G-75 column fraction of human follicular fluid can stimulate the human sperm acrosome reaction [Suarez SS, Wolf DP, Meizel S (1986): Gamete Res 14:107–121]. Using fura-2, we demonstrated that this Sephadex G-75 fraction also stimulates a rapid, transient increase in intracellular free Ca²⁺. This Ca²⁺ transient is blocked either by chelation of extracellular calcium or by addition of the Ca²⁺ antagonist La³⁺. We have also been able to stimulate the acrosome reaction in human sperm without significant loss of motility, using the divalent cation ionophore ionomycin. Acrosome reactions stimulated by whole follicular fluid, the G-75 fraction, or ionomycin are all blocked by removal of extracellular Ca²⁺. These results strongly suggest that an influx of extracellular Ca²⁺ is responsible for intiating the acrosome reaction in human sperm treated with human follicular fluid. This is the first demonstration in mammalian sperm that a potentially physiological stimulus can cause an increase in intracellular Ca²⁺ concomitant with the acrosome reaction.     

Evidence for neuropeptide Y mediation of eating produced by food deprivation and for a variant of the Y1 receptor mediating this peptide's effect.

Neuropeptide Y (NPY) elicits eating when injected directly into the paraventricular nucleus (PVN) or perifornical hypothalamus (PFH). To identify the essential regions of the NPY molecule and the relative contributions of Y1 and Y2 receptors, the eating stimulatory potency of NPY was compared to that of its fragments, analogues, and agonists when injected into the PVN or PFH of satiated rats. Additionally, antisera to NPY was injected into the cerebral ventricles (ICV) to determine whether passive immunization suppresses the eating produced by mild food deprivation. Tests with NPY fragments revealed that NPY(2-36) was surprisingly potent, nearly three times more so than intact NPY. In contrast, fragments with further N-terminal deletions were progressively less effective or ineffective, as was the free acid form of NPY. Collectively, this suggests that both N- and C-terminal regions of NPY participate in the stimulation of eating. Tests with agonists revealed that the putative Y1 agonist [Pro34]NPY elicited a strong dose-dependent feeding response, while the putative Y2 agonist, C2-NPY, had only a small effect at the highest doses. Although this suggests mediation by Y1 receptors, the uncharacteristically high potency of NPY(2-36) may additionally suggest that the receptor subtype underlying feeding is distinct from that mediating other responses. Additional results revealed that ICV injection of antisera to NPY, which should inactivate endogenous NPY, produced a concentration-dependent suppression of eating induced by mild food deprivation. This finding, along with published work demonstrating enhanced levels of hypothalamic NPY in food-deprived rats, suggests that endogenous NPY mediates the eating produced by deprivation.     

The osmotic/calcium stress theory of brain damage: Are free radicals involved?

This overview presents data showing that glucose use increases and that excitatory amino acids (i.e., glutamate, aspartate), taurine and ascorbate increase in the extracellular fluid during seizures. During the cellular hyperactive state taurine appears to serve as an osmoregulator and ascorbate may serve as either an antioxidant or as a pro-oxidant. Finally, a unifying hypothesis is given for seizure-induced brain damage. This unifying hypothesis states that during seizures there is a release of excitatory amino acids which act on glutamatergic receptors, increasing neuronal activity and thereby increasing glucose use. This hyperactivity of cells causes an influx, of calcium (i.e. calcium stress) and water movements (i.e., osmotic stress) into the cells that culminate in brain damage mediated by reactive oxygen species.Special issue dedicated to Dr. Frederick E. Samson     

Static and dynamic assessment of the Biodex dynamometer

The validity and accuracy of the Biodex dynamometer was investigated under static and dynamic conditions. Static torque and angular position output correlated well with externally derived data (r = 0.998 and r greater than 0.999, respectively). Three subjects performed maximal voluntary knee extensions and flexions at angular velocities from 60 to 450 degrees.s-1. Using linear accelerometry, high speed filming and Biodex software, data were collected for lever arm angular velocity and linear accelerations, and subject generated torque. Analysis of synchronized angular position and velocity changes revealed the dynamometer controlled angular velocity of the lever arm to within 3.5% of the preset value. Small transient velocity overshoots were apparent on reaching the set velocity. High frequency torque artefacts were observed at all test velocities, but most noticeably at the faster speeds, and were associated with lever arm accelerations accompanying directional changes, application of resistive torques by the dynamometer, and limb instability. Isokinematic torques collected from ten subjects (240, 300 and 400 degrees.s-1) identified possible errors associated with reporting knee extension torques at 30 degrees of flexion. As a result of tissue and padding compliance, leg extension angular velocity exceeded lever arm angular velocity over most of the range of motion, while during flexion this compliance meant that knee and lever arm angles were not always identical, particularly at the start of motion. Nevertheless, the Biodex dynamometer was found to be both a valid and an accurate research tool; however, caution must be exercised when interpreting and ascribing torques and angular velocities to the limb producing motion.     

Functional torque-velocity and power-velocity characteristics of elite athletes

Technical limitations of some isokinetic dynamometers have called into question the validity of some data on human muscle mechanics. The Biodex dynamometer has been shown to minimize the impact artefact while permitting automatic gravity correction. This dynamometer was used to study quadriceps muscle torque and power generation in elite power (n = 6) and elite endurance (n = 7) athletes over 12 randomly assigned isokinetic velocities from 30 degrees.s-1 to 300 degrees.s-1. The angle at peak torque varied as a negative, linear function of angular velocity, with the average angle across test velocities being 59.5 degrees (SD 10.2 degrees). Power athletes developed greater peak torque at each angular velocity (P less than 0.05) and experienced a 39.7% decrement in torque over the velocity range tested. Endurance athletes encountered a 38.8% decline in peak torque. Torques measured at 60 degrees of knee flexion followed a similar trend in both groups; however the greatest torques were recorded at 60 degrees.s-1 rather than at 30 degrees.s-1. Leg extensor muscle power increased monotonically with angular velocity in both power (r2 = 0.728) and endurance athletes (r2 = 0.839); however these curves diverged significantly so that the power athletes produced progressively more power with each velocity increment. These inter group differences probably reflected a combination of natural selection and training adaptation.     

Capitalist Philanthropy and Russian Revolutionaries: The Jesup North Pacific Expedition (1897-1902)

This review of the Jesup North Pacific Expedition, still the most important expedition in American anthropology, gives an idea of the goals and hazards of fieldwork around 1900, the pitfalls of international research, the tensions between anthropologists and host populations, the careers of early anthropologists, the role of private philanthropy, and the character of anthropology at the turn of the century. Franz Boas was the Expedition's linchpin. His organization of the Expedition, the way he handled problems, and his personal concerns reveal aspects of his view of anthropology and some of his basic attitudes.     

Potentiation and suppression of mouse liver cytochrome P-450 isozymes during the acute-phase response induced by bacterial endotoxin

Infection and inflammation are known to affect the metabolism and disposition of drugs and carcinogens. We report a detailed study of the effects of bacterial endotoxin on the constitutive and inducible expression and activities of cytochrome P-450 isozymes from families P-450I, P-450IIB, P-450IIC and P-450III. In general high doses of high endotoxin caused very marked suppression of P-450 isozymes and associated activities. However, this effect was differential, the expression of certain isozymes being only slightly reduced whereas others were suppressed to almost undetectable levels. Low doses of endotoxin also gave differential effects on cytochrome P-450 expression. Of particular interest was the very marked potentiation of the inductive effect of both 3-methylcholanthrene and phenobarbital. In the case of 3-methylcholanthrene the 10-fold induction of activity was increased to 24-fold by concomitant endotoxin administration. In this regard it was interesting that 3-methylcholanthrene was an effective inducer of a wide variety of acute-phase proteins including metallothionein, serum amyloid A, fibrinogen and hemopexin. These data show that endotoxin, and therefore bacterial infection and inflammation, can have profound and differential effects on components of the cytochrome-P-450 monooxygenase system which could result in significant changes in susceptibility to the effects of drugs, chemical toxins and carcinogens.     

The LEC11 Chinese hamster ovary mutant synthesizes N-linked carbohydrates containing sialylated, fucosylated lactosamine units. Analysis by one- and two-dimensional 1H NMR spectroscopy

Glycoproteins synthesized by the Chinese hamster ovary cell mutants LEC11 and LEC12 carry the Lex determinant (Gal beta 1,4(Fuc alpha 1,3)GlcNAc), while those synthesized by LEC11 cells also carry the sialyl-Lex determinant (NeuAc alpha 2,3Gal beta 1,4(Fuc alpha 1,3)GlcNAc), and both mutants have been shown to possess a distinct alpha(1,3)-fucosyltransferase of the appropriate specificity to synthesize these determinants (Campbell, C., and Stanley, P. (1983) Cell 35, 303-309; Campbell, C., and Stanley, P. (1984), J. Biol. Chem. 259, 11208-11214; Howard, D. R., Fukuda, M., Fukuda, M. N., and Stanley, P. (1987) J. Biol. Chem. 262, 16830-16837). The LEC11 cells therefore provide a source of carbohydrates terminating in sialylated, fucosylated lactosamine, a relatively rare structure not previously characterized by 1H NMR spectroscopy when in association with an N-linked carbohydrate. In this paper we use a monoclonal antibody specific for Lex to show that the G glycoprotein of vesicular stomatitis virus (VSV) grown in LEC11 and LEC12 cells possesses the Lex determinant and that G from LEC11/VSV also possesses sialylated Lex. Biantennary carbohydrates purified from LEC11/VSV and LEC12/VSV were therefore used to examine the effects on the 1H NMR spectrum of the presence of alpha(1,3)-fucose residues on sialylated and unsialylated lactosamine units. Comparisons of one-dimensional spectra obtained at 500 MHz from LEC11/VSV and LEC12/VSV glycopeptides before and after neuraminidase treatment with spectra of biantennary carbohydrates lacking alpha(1,3)-fucose allowed the assignment of several new resonances. Resolution of certain signals and determinations of coupling constants were achieved by two-dimensional correlation spectroscopy (COSY) at 400 MHz and allowed the assignment of several more resonances in the one-dimensional spectrum.