The Application of Freeze-Cleaving Technics to Studies on Red Blood Cell Fine Structure

A simplified freeze-cleave and replication method of tissue preparation forexamination in the electron microscope is applied to studies on red blood cellfine structure. With this technic, the cytoplasm of red blood cells appearsto have a uniform pattern of packed granularity, with individual particles approximating the dimensions anticipated for replicas of individual hemoglobinmolecules. The cell surface is smooth and partially covered with small particles which may represent antigens, enzymes, or some structural proteins.The possibility that particles seen in cells and on cell membranes may represent an artifact is discussed. Pretreatment of cells prior to freezing influencesthe plane of cleavage through packed cells so that the plane of cleavage canbe preferentially directed either through the cytoplasm or along red cellmembranes. The freeze-cleave technic may be of particular value in applications where extensive areas of membrane must be surveyed, such as searchingfor leukemogenic viruses budding through cell membranes.

Submitted on August 16, 1966 Accepted on November 24, 1966     

Circular dichroism and fluorescence spectroscopic analyses of a proline-rich glycoprotein from human parotid saliva

A proline-rich glycoprotein (PRG) was isolated from human parotid saliva and examined by circular dichroism and fluorescence spectroscopy. Addition of guanidine hydrochloride to PRG labeled with an extrinsic dansyl probe had no effect on the fluorescence spectra's 511 nm lambda-max location. Thermodynamic calculations supported the contention that PRG has no significant tertiary structure. Circular dichroism results for PRG were simulated by computer and a secondary structure composed of 70% random coil and 30%β-form conformation was predicted. Circular dichroism of PRG failed to detect either poly-L-proline type I or II structures. Deglycosylation of PRG had no measurable effect on the circular dichroism spectrum, indicating that the carbohydrate side chains had little influence on PRG secondary structure. Based upon mathematical calculations, β-turns were predicted around three glycosylated Asn residues of PRG. These collective data suggest that PRG is composed of a disordered polypeptide chain with at least three of the N-linked Asn residues participating in some type of β-turn.     

Refractoriness of Rhesus Monkeys to Repeated Ovarian Stimulation by Exogenous Gonadotropins is Caused by Nonprecipitating Antibodies

ABSTRACT: Oocytes obtained from superstimulated rhesus monkeys are needed for in vitro fertilization experiments. The animals become refractory to repeated ovarian stimulation by pregnant mare serum gonadotropin (PMSG). Production of antibodies against PMSG was suspected. Antibodies were not detected by gel-diffusion tests, but were found using ELISA procedures in sera from all monkeys that had been treated with PMSG. Sera from seven of nine treated monkeys had antibodies that cross-reacted with FSH-P. An ovarian stimulation test using golden hamsters showed that sera from PMSG-treated rhesus monkeys completely blocked superstimulation of follicle development and ovarian weight gain by PMSG. This study demonstrates that the refractoriness of rhesus monkeys to repeated ovarian stimulation by PMSG is due to the production of nonprecipitating antibodies to PMSG that effectively block the activity of PMSG on the ovary. Formation of these antibodies may preclude use of other gonadotropin preparations in refractory monkeys. Alternative ovarian stimulation procedures avoiding use of gonadotropin preparations need to be developed to permit repeated treatment of rhesus monkeys for multiple oocyte collection.     

Suppression of Ventricular Tachycardia With Dronedarone: A Case Report

Suppression of Ventricular Tachycardia With Dronedarone . Introduction: Dronedarone is a multichannel blocker with similar electrophysiological properties to amiodarone. Dronedarone has not been studied in humans as an agent to suppress ventricular arrhythmias. Methods: This case report describes the dramatic antiarrhythmic effects of dronedarone in a patient with nonischemic cardiomyopathy and recurrent ventricular tachycardia, which was resistant to multiple antiarrhythmic agents and endocardial catheter ablation. Results: Dronedarone was effective in completely suppressing ventricular tachycardia. Conclusion: Further research is needed to establish a potential larger role for dronedarone in controlling ventricular arrhythmias in humans. (J Cardiovasc Electrophysiol, Vol. 22, pp. 201‐202, February 2011)     

Differences in the lipid constituents of sebum from pre-pubertal and pubertal subjects

Significant differences have been reported in the composition of skin surface lipid in pre-pubertal subjects when compared to pubertal subjects. Analytical studies were performed to determine whether group mean changes in the fatty acid composition of the triglyceride and wax ester fractions of sebum could be detected in pre-pubertal versus pubertal subjects. Twenty males (ages 6–9), twenty females (ages 6–9) and twelve teenagers (ages 11–16) were studied. Skin surface lipid was examined by densitometry and gas chromatography. There were significant changes in the fatty acid composition of the wax fraction of sebum in the 11–16-year-old children when compared to the 6–9-year-old group. As wax is of sebaceous gland origin, this may represent a change in sebum composition probably in response to the hormonal stimulus. Changes in the fatty acid fraction of triglycerides were also noted with age, but this may be due to the change in source of triglyceride from predominantly epidermal origin to sebaceous gland origin.