1942-bjorksten.pdf: “The Chemistry of Duplication”, Johan Bjorksten
1951-bjorksten.pdf: “Cross Linkages in Protein Chemistry”, (1951-01; ):
This chapter provides an overview of scattered and diverse data on the ability of proteins to form cross linkages that connect molecules or micelles, thus leading to the formation of larger aggregates. Even a single cross linkage between two large molecules has the immediate result of combining them into a unit having a molecular weight equal to the sum of the molecular weights of the molecules involved; repeated cross linkages multiply the size of molecules that are already extremely large. The immediately observable results are reduced solubility or peptizability, increased resistance to hydrothermal influences, and reduced resilience or elasticity accompanied by darkening in color, and in extreme cases, brittleness. The presence of many reactive groups in protein molecules make them particularly susceptible to cross-linking reactions. Aldehydes can form a methylene bridge, or can react with amino groups linking protein molecules together with the formation of Schiff bases. Dicarboxylic and particularly disulfonic acids can form cross-linking bridges by reaction with amino groups. The chapter briefly describes some of the principal purposes that have stimulated industrial experimentation with reactions involving cross linkage of proteins. It also outlines the types of industrial problems handled by cross-linking reactions. Further, the chapter describes cross-linking processes indicated in the literature.
1958-bjorksten.pdf: “A Common Molecular Basis For The Aging Syndrome”, (1958-10; ):
Degenerative changes must have a basic cause on the molecular level. For example, the possible role of protein immobilization by means of progressive cross-linking reactions is critically examined in the light of known data on potential cross-linking agents present in the bloodstream, and of related physio-logic facts.
1960-bjorksten.pdf: “Fundamentals Of Aging: A Comparison Of The Mortality Curve For Humans With A Viscosity Curve Of Gelatin During The Cross-Linking Reaction”, Johan Bjorksten, Fred Andrews
1965-andrews.pdf: “The reaction of an autoxidized lipid with proteins”, (1965-09; ):
Evidence is presented which indicates that an interaction occurs between proteins and an autoxidizing unsaturated lipid. Using a model system approach, it has been established that two purified proteins (gelatin and insulin) are chemically modified in the presence of an autoxidizing lipid, methyl linoleate.
The insulin-methyl linoleate interaction has been studied chromatographically after acid and alkaline hydrolysis, and also by using the Sanger end group analysis method. The data indicate that lipid intermediates react with theε-amino group of lysine, and also with phenylalanine and glycine, the N-terminal amino groups of insulin.
Hydrogen fluoride solubility and enzyme hydrolysis determinations indicate that the autoxidation products of methyl linoleate interact with protein to produce new chemical entities through cross-linking.
1965-andrews-2.pdf: “Chemical Composition Of Enzyme-Fractionated Aged Heart Tissue”, (1965-02; ):
Fractionation of the enzyme-nonhydrolyzable constituents of human heart muscle from persons 64–74 years old resulted in separation of a fluorescing fraction, insoluble in anhydrous hydrogen fluoride, and containing 4.6% nitrogen (corresponding to 30% protein). This fraction was free from hydroxyproline and is therefore not derived from collagen.
An aromatic aldehyde was consistently separated when the enzymatically nonhydrolyzable fraction was broken down by destructive acid hydrolysis. Infrared data indicate a structure having characteristics in common with coenzyme Q.
1968-bjorksten.pdf: “The Crosslinkage Theory Of Aging”, (1968-04; ):
For many decades the theory and practice of cross-linking (bonding that ties two or more large molecules together side to side) have been developed in industry, but only since the 1940’s has the theory been considered in the field of medicine as a primary reaction underlying age-dependent changes.
Cross-linking is damaging to the tissues and involves loss of elasticity, reduced swelling capacity, increased resistance to hydrolases and probably enzymes generally, and thus an increase in molecular weight and a tendency toward embrittlement. There is a growing amount of direct evidence and much indirect evidence for postulating the relationship between cross-linking and aging.
Cross-linking agents present in the living organism include aldehydes, lipid oxidation products, sulfur, alkylating agents, quinones, free radicals induced by ionizing radiation, antibodies, polybasic acids, polyhalo derivatives and polyvalent metals. The latter four types of compound are slow-acting but can also accumulate in the body to form a frozen metabolic pool. Sufficient amounts of all these potential cross-linking materials are present in the body to make the changes of aging unavoidable.
1970-bjorksten.pdf: “Nitrogenous Compounds Immobilized In An Aged Rat”, (1970-02; ):
A pregnant rat received 8 mc of tritiated tyrosine at the time of giving birth (from seven days before, to six days after). No radioisotopes were ever given directly to the litter born. A male from this litter died from pneumonia at age 809 days. After removal of water and acetone solubles and of phospholipids, hydrolysis of the residue released the following radioactive amino acids, parts of molecules fixed until death and containing tritium present at birth: lysine, arginine, aspartic acid, glutamic acid, serine, listed in order of decreasing radioactivity, with lysine carrying 29% of the total tritium present.
1971-bjorksten-2.pdf: “Approaches And Prospects For The Control Of Age‐Dependent Deterioration”, John Bjorksten
1971-bjorksten.pdf: “Gerogenic Fractions In The Tritiated Rat”, (1971-07; ):
A rat that had received tritiated acetate perinatally was killed at the age of 609 days, and was found to have retained substantial quantities of tritium in all organs examined. This study was focussed on the liver, which—after a succession of extractions with a series of various solvents followed by catalytic hydrolysis at body temperature—yielded a residue that was-insoluble in a wide range of common solubilizing media. Treatment with hot mineral acid partially dissolved this residue and electrophoretic fractionation further led to 4 fractions of which a single fraction contained most of the tritium in the insoluble residue.
Our analyses showed that the insoluble residue contained a variety of common amino acids and a considerable amount of phosphorus. The solubilized fractions derived from the insoluble residue all contained substantial concentrations of pentose, deoxypentose, and phosphorus. They showed ultraviolet absorption spectra qualitatively similar to those of nucleic acids. From their chromatographic behavior on crosslinked dextran columns, all 4 solubilized fractions showed molecular weights greater than 5000. In addition, these fractions showed substantially greater resistance to hydrolytic degradation than do authentic RNA and DNA. Taken together, this is interpreted as evidence that the gerogenic insoluble residue is composed of a highly crosslinked network of at least RNA, DNA and protein, which is stabilized by covalent cross-linkages of unusual stability. Formation of these crosslinked structures could easily interfere with the function of certain critical molecules of RNA, DNA or other polymers, leading to impaired cell function and death.
1972-bjorksten.pdf: “Enzymatic Lysis in Vitro of Hyalin Deposits in Human Kidney”, (1972-05; ):
Vascular hyalin was readily dissolved in vitro from sections of the formalin-preserved, paraffin-embedded kidney of a hypertensive patient, by means of an enzyme (BJ-B-66) isolated from Bac. cereus. The enzyme attacked other hyalins and tissue components as well. The enzyme is active at body temperature and pH, and appears substantially nontoxic to rats and hamsters.
1976-bjorksten.pdf: “The Crosslinkage Theory of Aging: Clinical Implications”, Johan Bjorksten
1977-bjorksten-2.pdf: “Pathways to the Decisive Extension of the Human Specific Lifespan”, (1977-09; ):
3 approaches to reversal or removal of gerogenic aggregations of macromolecules have shown promise. Of these the enzyme approach is the most gentle, and can be made specific. Aside from this, the lower the molecular weight of an enzyme, the better chance it will have to be immunologically tolerated as well as replicated synthetically in whole or in part. The chelating approach provides a powerful means for removing a single class of unwanted, random crosslinkages, ie., those due to extraneous polyvalent metals such as lead, cadmium and aluminum. The free hydroxyl radical approach is the most penetrant and most versatile means for removing otherwise insoluble aggregates, but its very lack of specificity will demand great foresight in control and use. Together, these three methods, when properly applied, might bring some principal objectives of gerontology within closer range.
1977-bjorksten.pdf: “Some Therapeutic Implications Of The Crosslinkage Theory Of Aging”, Johan Bjorksten
1978-bjorksten.pdf: “A Unifying Concept for Degenerative Diseases”, John Bjorksten
1981-bjorksten.pdf: “Selenium In Nutrition”, (1981-07-01; ):
Every useful substance—water, salt, air, nutrients, and vitamins as well as therapeutic agents—has a range below which it loses effectiveness and above which it becomes harmful. With selenium the optimum range is fairly narrow, and the penalties for transgression can he dramatic.
…Selenium has had dramatic acceptance in animal husbandry. However, in those countries where selenium content is minimal, the farmer who feeds his cattle selenium supplement is often himself the victim of infarctions that would have been prevented by a selenium supplement. Knowledge has gradually accumulated, and the hazards defined. Use of selenium in human nutrition and preventive medicine has become feasible.
While most of the United States has adequate selenium, some natural deficiency occurs in areas where heavy rains are common. Inclusion of selenium in dietary supplements was discussed at the U. S. Quartermaster Conference on Antioxidants in Natick, MA in 1979. A detailed specific geriatric formula in which selenium was one ingredient was published in the proceedings.15 This formula is not patented and has not been on the market, but has been used regularly by some persons for several years with apparent satisfaction.
1982-bjorksten.pdf: “Dietary aluminum and Alzheimer's disease”, Johan Bjorksten
1982-bjorksten-2.pdf: “Aluminum as a Cause of Senile Dementia”, (1982-05; ):
The evidence reviewed shows that senile dementia may be similar in origin to Alzheimer’s disease and to dialysis encephalopathy. There is general agreement that aluminum, once attached to the chromatin in a neuron, cannot be dislodged by any means available to the organism. Yet the presence of aluminum in serum shows that at least some trace will always be able to pass biologic barriers and ultimately reach critical neuronal chromatin. Alfrey shows that the aluminum content of heart and brain remains relatively low until the bone content nears a saturation point, after which aluminum deposition in heart and brain accelerates (Figure 1).16 The data on aluminum content of the human aorta by Zinsser, Bjorksten, et al indicate that aluminum content peaks from age 40 to 50 years, and declines moderately thereafter.17 Thus, it is possible that persons who have the highest body level of aluminum may not survive for five years, but more data are needed to prove this theory.
“The role of aluminum and age-dependent decline”, (1989-05):
[Letter to the editor about aluminum poisoning and aging. Bjorksten argues that cross-linkage, contrary to the discussed researchers claims, can be the main mechanism of the poisoning despite the tiny absolute amount of cross-linking agents.]
The cross-linking agents correspond to the ropes connecting a ship to a pier. Of all known types of chemical reactions, cross-linking is among those of which the smallest possible quantity of a reagent has the largest possible insolubilizing effect. A cross-linking agent is anything that has at least two reactive sites at some distance from each other. The aluminum ion is one of the most effective cross-linking agents and has for a century been used as such (6). More recent implications of these effects were covered in Bjorksten et al. (8, 9).
1990-bjorksten.pdf: “The crosslinking theory of aging—Added evidence”, (1990; ):
The cross-linking theory of aging has been gaining acceptance at a steady pace, as evidenced by many independent rediscoveries. While several earlier studies were indicative, none seemed conclusive until it was shown, using Differential Scanning Calorimetry (DSC), that protein from young human brains could be made to closely resemble protein from old brains by exposing it to either of two entirely different cross-linking agents (glutaraldehyde and dipotassium diperoxy sulfate). This work has now been repeated with additional brain material, and a statistically-more-significant number of determinations. It is now shown that a treatment of brain protein with either one or two chemically totally different compounds which have no property in common except that both are cross-linkers, changes young brain protein so that it greatly resembles old, crosslinked protein. This shows that cross-linking reactions are involved in the age related changes in the studied proteins.
[Keywords: cross-linking, aging, differential scanning calorimetry]
2014-dean.pdf: “Dr Ward Dean Q&A [on Johan Bjorksten]”, Ward Dean