Morphogenetic factors influencing the shape of the sperm head

Mature sperm of Acheta domesticus, Acheta assimilis, Nemobius fasciatus, Nemobius confusus, Melanoplus femur-rubrum, Romalea microptera, Scudderia curvicauda, and Ceuthophilus nigricans were examined for DNA configuration by means of polarized fluorescence microscopy. In all cases, the results suggest that the DNA lies in unsupercoiled array, predominantly parallel to the elongate sperm head axes. Detailed calculations of the factors influencing the degree of polarization of the fluorescent emission from supercoiled DNA are contained in an appendix.

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Protamine-DNA interaction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081863 ◽

1978 ◽

Vol 36 (2) ◽

pp. 200-201

Author(s):

D.P. Bazett-Jones ◽

F.P. Ottensmeyer

Keyword(s):

Small Volume ◽

Double Helix ◽

Dna Interaction ◽

Dark Field ◽

Sperm Head ◽

Nuclear Proteins ◽

Field Electron Microscopy ◽

Dark Field Electron ◽

Dna Double Helix ◽

Positively Charged

Dark field electron microscopy has been used for the study of the structure of individual macromolecules with a resolution to at least the 5Å level. The use of this technique has been extended to the investigation of structure of interacting molecules, particularly the interaction between DNA and fish protamine, a class of basic nuclear proteins of molecular weight 4,000 daltons.Protamine, which is synthesized during spermatogenesis, binds to chromatin, displaces the somatic histones and wraps up the DNA to fit into the small volume of the sperm head. It has been proposed that protamine, existing as an extended polypeptide, winds around the minor groove of the DNA double helix, with protamine's positively-charged arginines lining up with the negatively-charged phosphates of DNA. However, viewing protamine as an extended protein is inconsistent with the results obtained in our laboratory.

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Factors influencing adhesive bonding at the bone/implant interface

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130201 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1114-1115

Author(s):

Julie A. Martini ◽

Robert H. Doremus

Keyword(s):

Electron Microscopy ◽

Adhesive Bonding ◽

Microscopy Study ◽

Electron Microscopy Study ◽

Bone Implant ◽

Factors Influencing ◽

Lr White ◽

Transmission Electron ◽

New Zealand White Rabbits ◽

Scanning Electron

Tracy and Doremus have demonstrated chemical bonding between bone and hydroxylapatite with transmission electron microscopy. Now researchers ponder how to improve upon this bond in turn improving the life expectancy and biocompatibility of implantable orthopedic devices.This report focuses on a study of the- chemical influences on the interfacial integrity and strength. Pure hydroxylapatite (HAP), magnesium doped HAP, strontium doped HAP, bioglass and medical grade titanium cylinders were implanted into the tibial cortices of New Zealand white rabbits. After 12 weeks, the implants were retrieved for a scanning electron microscopy study coupled with energy dispersive spectroscopy.Following sacrifice and careful retrieval, the samples were dehydrated through a graduated series starting with 50% ethanol and continuing through 60, 70, 80, 90, 95, and 100% ethanol over a period of two days. The samples were embedded in LR White. Again a graduated series was used with solutions of 50, 75 and 100% LR White diluted in ethanol.

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Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100180045 ◽

1990 ◽

Vol 48 (1) ◽

pp. 258-259

Author(s):

J.L. Carrascosa ◽

G. Abella ◽

S. Marco ◽

M. Muyal ◽

J.M. Carazo

Keyword(s):

Three Dimensional ◽

The Other ◽

Two Dimensional ◽

Series Method ◽

Three Dimensional Reconstruction ◽

Structural Components ◽

E Coli ◽

Dimensional Reconstruction ◽

Morphogenetic Factors ◽

Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

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Factors Influencing Electrophysiologic Responsivity in Normal Adults

Journal of Speech and Hearing Research ◽

10.1044/jshr.0804.323 ◽

1965 ◽

Vol 8 (4) ◽

pp. 323-347

Author(s):

Robert Goldstein ◽

Benjamin RosenblÜt

Keyword(s):

Conditioned Stimulus ◽

White Light ◽

Pure Tone ◽

Alpha Rhythm ◽

White Women ◽

White Men ◽

Inverse Relation ◽

Factors Influencing ◽

Electrodermal Responses ◽

Normal Adults

Electrodermal and electroencephalic responsivity to sound and to light was studied in 96 normal-hearing adults in three separate sessions. The subjects were subdivided into equal groups of white men, white women, colored men, and colored women. A 1 000 cps pure tone was the conditioned stimulus in two sessions and white light was used in a third session. Heat was the unconditioned stimulus in all sessions. Previously, an inverse relation had been found in white men between the prominence of alpha rhythm in the EEG and the ease with which electrodermal responses could be elicited. This relation did not hold true for white women. The main purpose of the present study was to answer the following questions: (1) are the previous findings on white subjects applicable to colored subjects? (2) are subjects who are most (or least) responsive electrophysiologically on one day equally responsive (or unresponsive) on another day? and (3) are subjects who are most (or least) responsive to sound equally responsive (or unresponsive) to light? In general, each question was answered affirmatively. Other factors influencing responsivity were also studied.

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