Spermatogenesis in an infertile XYY man

Summary Testicular histology and meiosis has been studied in an XYY male patient identified at an infertility clinic. This man was found to have an XYY sex chromosome complement in 15% of spermatogonial metaphases. There was no clear evidence of 2 Y chromosomes at diakinesis but there appeared to be a slight excess of sperm with a fluorescent Y body.     

Laser light-scattering investigations of the teleost swimbladder response to acoustic stimuli.

When a laser pencil is directed through the teleost swimbladder fringe patterns can be seen in the far-field that are (a) highly sensitive to the orientation and position of the swimbladder with respect to the incident pencil and (b) a representation of contributions from each membrane through which the light passes. The fringe pattern fluctuates in intensity, and to some extent in position, in response to driving forces that distort the swimbladder. The spectrum of these very small distortions can be measured by standard light scattering techniques. This method was used to study the response of in situ swimbladders to imposed acoustic fields and evidence for a sharp roll-off of the response at frequencies above 1,000 Hz was found. Models for these effects are discussed.     

Moths complement bumblebee pollination of red clover: a case for day-and-night insect surveillance

Recent decades have seen a surge in awareness about insect pollinator declines. Social bees receive the most attention, but most flower-visiting species are lesser known, non-bee insects. Nocturnal flower visitors, e.g. moths, are especially difficult to observe and largely ignored in pollination studies. Clearly, achieving balanced monitoring of all pollinator taxa represents a major scientific challenge. Here, we use time-lapse cameras for season-wide, day-and-night pollinator surveillance of Trifolium pratense (L.; red clover) in an alpine grassland. We reveal the first evidence to suggest that moths, mainly Noctua pronuba (L.; large yellow underwing), pollinate this important wildflower and forage crop, providing 34% of visits (bumblebees: 61%). This is a remarkable finding; moths have received no recognition throughout a century of T. pratense pollinator research. We conclude that despite a non-negligible frequency and duration of nocturnal flower visits, nocturnal pollinators of T. pratense have been systematically overlooked. We further show how the relationship between visitation and seed set may only become clear after accounting for moth visits. As such, population trends in moths, as well as bees, could profoundly affect T. pratense seed yield. Ultimately, camera surveillance gives fair representation to non-bee pollinators and lays a foundation for automated monitoring of species interactions in future.     

Comparison of vascular smooth muscle cells from adult human,monkey and rabbit in primary culture and in subculture

Summary A method is presented for growing large numbers of pure isolated smooth muscle cells from adult human, monkey, and rabbit blood vessels in primary culture.In the first few days in culture these cells closely resembled those in vivo and could be induced to contract with angiotensin II, noradrenaline and mechanical stimulation. They stained intensely with antibodies against smooth muscle actin and myosin. Fibroblasts and endothelial cells did not stain with these antibodies thereby allowing the purity of each batch of cultures to be monitored. This was consistently found to be better than 99%. The smooth muscle cells modified or dedifferentiated after about 9 days in culture to morphologically resemble fibroblasts. At this stage cells could no longer be induced to contract and did not stain with the myosin antibodies. Intense proliferation of these cells soon resulted in a confluent monolayer being formed at which stage some differentiated characteristics returned. The modification or dedifferentiation process could be inhibited by the presence of a feeder layer of fibroblasts or endothelial cells, or the addition of cAMP to the culture medium.Smooth muscle cells which had migrated from explants in primary culture, and cells in subculture, had morphological and functional properties of dedifferentiated cells at all times.The advantages of differentiated rather than dedifferentiated smooth muscle cells in culture for the study of mitogenic agents in atherosclerosis is discussed.The authors wish to thank Professor H.H. Bentall of the Royal Postgraduate Medical School, Hammersmith Hospital, London, for making available human material, and Dr. S. Zeki of Department of Anatomy, University College London for material from monkeys. We are also extremely grateful to Professor G. Burnstock for the use of his laboratory facilitiesHolder of a John Halliday Travelling Fellowship from the Life Insurance Medical Research Fund of Australia and New ZealandResearch Fellow with the National Heart Foundation of AustraliaSupported by the Deutsche Forschungsgemeinschaft     

Snow depth manipulation and its influence on soil frost and water dynamics in a northern hardwood forest

Climate change will likelyresult in warmer winter temperatures leading toless snowfall in temperate forests. Thesechanges may lead to increases in soil freezingbecause of lack of an insulating snow cover andchanges in soil water dynamics during theimportant snowmelt period. In this study, wemanipulated snow depth by removing snow for twowinters, simulating the late development of thesnowpack as may occur with global warming, toexplore the relationships between snow depth,soil freezing, soil moisture, and infiltration.We established four sites, each with two pairedplots, at the Hubbard Brook Experimental Forest(HBEF) in New Hampshire, U.S.A. and instrumentedall eight plots with soil and snow thermistors,frost tubes, soil moisture probes, and soillysimeters. For two winters, we removed snowfrom the designated treatment plots untilFebruary. Snow in the reference plots wasundisturbed. The treatment winters (1997/1998 and1998/1999) were relatively mild, withtemperatures above the seasonal norm and snowdepths below average. Results show the treatedplots accumulated significantly less snow andhad more extensive soil frost than referenceplots. Snow depth was a strong regulator ofsoil temperature and frost depth at all sites.Soil moisture measured by time domainreflectometry probes and leaching volumescollected in lysimeters were lower in thetreatment plots in March and April compared tothe rest of the year. The ratio of leachatevolumes collected in the treatment plots tothat in the reference plots decreased as thesnow ablation seasons progressed. Our data showthat even mild winters with low snowfall,simulated by snow removal, will result inincreased soil freezing in the forests at theHBEF. Our results suggest that a climate shifttoward less snowfall or a shorter duration ofsnow on the ground will produce increases insoil freezing in northern hardwood forests.Increases in soil freezing will haveimplications for changes in soil biogeochemicalprocesses.     

Characterizing the complexity of enzymes on the basis of their mechanisms and structures with a bio-computational analysis

Enzymes are basically composed of 20 naturally occurring amino acids, yet they catalyse a dizzying array of chemical reactions, with regiospecificity and stereospecificity and under physiological conditions. In this review, we attempt to gain some understanding of these complex proteins, from the chemical versatility of the catalytic toolkit, including the use of cofactors (both metal ions and organic molecules), to the complex mapping of reactions to proteins (which is rarely one-to-one), and finally the structural complexity of enzymes and their active sites, often involving multidomain or multisubunit assemblies. This work highlights how the enzymes that we see today reflect millions of years of evolution, involving de novo design followed by exquisite regulation and modulation to create optimal fitness for life.     

Human histone gene organization : Identification of a histone gene polymorphism prevalent in a black population

Analysis of the restriction enzyme digests of total genomic DNAs from a broad spectrum of human cell lines and from individuals with different genetic backgrounds, by hybridization with a series of cloned human histone sequences, indicated restriction site polymorphisms (RSPs) for two adjacent human histone genes which reside on chromosome 1. In most cell lines and individuals examined we observed a single 2.05 kb H4 histone HindIII fragment and a 7.0 kb H3 histone HindIII fragment. In contrast, the polymorphisms were manifested as a 2.15 kb H4 HindIII fragment and a 9.1 kb H3 HindIII fragment. From population studies, we were able to show that there is no linkage disequilibrium between these two polymorphic restriction sites. Nor was there any apparent correlation between the presence of the H3/H4 histone polymorphisms and maintenance of the transformed karyotype, passage in culture, transformation or tumor progression. These chromosome 1 H3 and H4 histone gene polymorphisms are common in the American Black population and, in our survey of individuals, were not found in the American Caucasian population. Among the American Blacks studied, the frequency of the H3 HindIII(-) allele is 43% and of the H4 HindIII(-) allele 30%. In limited family studies, we were unable to detect recombination between these two physically linked alleles.     

The relation of life to electricity

Conclusions and summary The experiments described in this paper tend to show that the relation between stainability and electromotive forces: + basophilic substance / acidophilic substance — holds not only for fats but likewise for esters, alcohols, hydrocarbons, etc., in short for a large number of substances which bear just a remote relationship to tissue constitutents. Exceptions to this rule are very rare and are hardly found prevailing in tissue.In these experiments esters, alcohol, and other substances were rendered basophilic by the addition of a water insoluble acid or else acidophilic by the addition of a water insoluble base; measurements of the electromotive force were made. The system measured was the following: The measurements were performed by combining each ester, alcohol, or other fluid with phenol using the apparatus described in part I of this report. The difference between two such measurements may be considered to be the electromotive force of such a cell. This was demonstrated previously be means of measurements with triacetin. The reason for this is that the electromotive forces of such battery systems, as those described, are located almost entirely at the phase boundary between the aqueous solution and the water immiscible fluid.To Dr. G. W.Crile the writers wish to express their appreciation for his kind interest in the progress of this work.