Fine structure of the osteocyte capsule and of the wall of the lacunae in bone

Summary Bone tissue from femura of adult and old rats and from young mice, as well as from dogs, were fixed in osmium tetroxide, potassium permanganate, in an osmium tetroxide — potassium permanganate combination, and in glutaraldehyde followed by osmium tetroxyde — potassium permanganate. The results of the different fixatives were found to complement one another in such a way that existing controversies and uncertainties concerning the fine structure could be settled. This was especially true of the question whether or not the so-called capsule of the osteocyte contains collagen fibrils. Notwithstanding considerable variations in the structure of the capsule it was definitely shown that cross-banded fibrils are present in a mucopolysaccharide-containing ground substance. The material of the capsule corresponds, therefore, to the matrix of connective tissue in general, and its ground substance is, as in any connective tissue, the medium of transport between the blood and the tissue. In respect to the organic structures the intralacunar matrix is similar to the interlacunar mineralized matrix. In sections of demineralized bone, especially after osmium tetroxide fixation, the wall of the lacuna and canaliculi is marked by a dark line which is described as a special osmiophilic lamina. Since the same line, although thinner and less distinct, was found also in tissue fixed with agents other than osmic acid it was concluded that the osmiophilic lamina is a true structure which must be permeated by substances passing to and from the interlacunar matrix. The osmiophilic lamina belongs to a wider border zone which differs from the bulk of the mineralized matrix by its thinner and less tightly packed fibrils. Accordingly, the bone crystals were found to be less orderly arranged than those deeper inside the mineralized matrix. Bordering directly on the intralacunar pathway they were described as the coastal crystals and are believed to represent the labile bone minerals which are metabolically available without any change in the bone structure. The findings about the fine structure of the capsule of the osteocyte and of the wall of the lacunae were discussed in terms of the transport problems in bone. The osteocyte itself, by its fine structure and relationship to the intralacunar matrix seems to be engaged not only in the maintenance of the open pathways in bone but also in the transport mechanism itself.This investigation was carried out under the auspices of the United States Atomic Energy Commission and was supported, in part, by research career program award 5-K3-DE 7, 272 and research grants De-01406 and DE-01716 from the National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland.     

Agents related to a potent activator of the acetylcholine receptor of Electrophorus electricus

The synthesis of a number of compounds related to trans-3,3′-bis[α-(trimethylammonium)methyl]azobenzene dibromide (trans-3,3′-BisQ) (1)1 is described. Among the compounds are: [¹⁴C]-trans-3,3′-BisQ (1)1 diiodide, cis-3,3′-BisQ (2)1 dibromide, the trans-2,2′ (7)1 and 4,4′ (11)1 isomers of BisQ, 2,2′, (12)1, 3,3′ (13)1 and 4,4′ (14)1 isomers of bis-benzyldimethylammonium analogues, and related compounds in which the azo bridge between the two aromatic rings is replaced by diketo and amide bridges. Of them all, trans-3,3′-BisQ (1)1 was the most active cholinergic compound in the electroplax system of Electrophorus electricus; the pure cis isomer (2)1 was without activity. Intermediate activities were found for some of the other compounds and others were inhibitors. The relationship of the structure of these agents to a proposed conformation and topography of the binding site of the acetylcholine receptor (AChR) is discussed.     

TIMA Part 2. TIMA-based instructive evolution of macromolecules and organs and structures

In extending a previous paper (TIMA Part 1, Wassermann, 1982) “template induced molecular assembly” (TIMA) is being further explored. It is suggested that TIMA could first have evolved proteins without coevolution of mRNA-like systems, in the absence of tRNAs. Some of these early proteins could, by self-assembly, have built up ribosomes. Ribosomes jointly with amino acids could have served as assembly templates for the TIMA-based evolution of tRNAs. Once tRNAs had evolved, TIMA could have participated, via a modified Mekler (1967) mechanism, in the evolution of new proteins and the coevolution of corresponding mRNA-like strands. TIMA also requires gene duplications and/or random mutations of DNA, to produce partial matching by duplicated and/or randomized DNA sequences of TIMA-generated cDNA which is complementary to the mRNA-like strands. The cDNA could then become incorporated by crossover into the position of the partially matching DNA sequences of, say, duplicate genes in genomes of germ-line cells. Since one requires only partial matching between duplicate (and/or randomly generated) DNA and non-randomly, TIMA-generated cDNA, TIMA theory avoids the need to assume (as in the Baldwin effect) that complete genes were randomly evolved. While rejecting crude Lamarckism, TIMA equally avoids the assumption that genes evolved only by combined random events, gene duplications, and adaptive selection. The resulting theory explains typical pseudo-exogenous adaptations via TIMA. Darwinian selection—now in the guise of “molecular selection” (and favourable environmental adaptive selection where present)—combined with TIMA could account for Waddington's “genetic assimilation”, thereby conceding Lamarck's notion that the environment can help to model heredity (while rejecting crude Lamarckism).     

Biomonitoring of genotoxic exposure among stainless steel welders.

A biosurvey in the Danish metal industry measured the genotoxic exposure from stainless steel welding. The study comprised measurements of chromosomal aberrations (CA), sister-chromatid exchanges (SCE), unscheduled DNA synthesis (UDS) in peripheral lymphocytes and serum immunoglobulin G. Environmental monitoring of welding fumes and selected metal oxides, biomonitoring of chromium and nickel in serum and urine and mutagenic activity in urine, and evaluation of semen quality were also done. Manual metal arc (MMA) welding and tungsten inert gas (TIG) welding were the dominant welding processes. A higher frequency of chromosomal aberrations, classified as translocations, double minutes, exchanges and rings, was observed in stainless steel welders than in non-welders. SCE was lower in welders working with both MMA and TIG welding than in reference persons. N-Acetoxy-N-acetylaminofluorene (NA-AAF)-induced UDS was lower in 23 never-smoking welders than in 19 unexposed never-smokers. Smoking was a confounding factor resulting in significantly higher CA, SCE, NA-AAF binding to DNA and mutagenic activity in urine. Age was also a confounder: CA, SCE, NA-AAF binding to DNA and UDS increased significantly with age. No significant correlation between SCE and CA or between CA and UDS was found. UDS decreased significantly with increasing lymphocyte count and a higher lymphocyte count was seen in MMA welders than in reference persons and in smokers than in non-smokers. Differences in the composition among lymphocytes in exposed persons compared with non-exposed are suggested. MMA welding gave the highest exposure to chromium, an increased number of chromosomal aberrations and a decrease in SCE when compared with TIG welding. Consequently improvements in the occupational practice of stainless steel welding with MMA is recommended.     

Biochemical factors involved in the FSH action on amino acid transport in immature rat testes.

Testes of 15-day-old rats preincubated and incubated during different times with various doses of FSH (0.2; 2.0 and 20.0 mU/ml) in Krebs-Ringer bicarbonate (KRb) buffer increase the uptake of [14C] methylaminoisobutyric acid and [14C] aminoisobutyric acid. The basal and FSH stimulated amino acid transport occurs at absolute lower levels when the protein or glycoprotein synthesis is inhibited by cycloheximide (350 mumol/l) or tunicamycin (12 mumol/l) or when the microtubules are depolymerized with colchicine (1.2 mumol/l). However, the proportional increase of amino acid transport produced by FSH was maintained. The blockage of the voltage-dependent Ca++ channels with verapamil or the competitive inhibition of the bivalent ion channels by Co++ or Ni++ nullified the stimulatory action of FSH on the amino acid transport. Also quinine, that blocks the ATP dependent K+ channels, abolished the FSH action. It was concluded that in immature rat testes FSH stimulates amino acid transport through a mechanism involving voltage-dependent Ca++ channels and ATP-sensitive K+ channel.     

Plasma steroid concentrations in relation to the reproductive cycle of cultured male Rhamdia quelen

Seepage water through a lake bottom and the layering of tight and high-permeable layers in the aquifer produce groundwater under greater pressure than the water column of the lake. This results in under-water springs and seepages. When spawning substrata were available, there was a spatial correlation between the degree of groundwater influx and the redd density of brown trout Salmo trutta . In high density spawning areas with > 100 observed redds ha⁻¹, the mean seepage water influx during spring was c . 1200 ml m⁻² min⁻¹ compared to a mean flux of 113 ml m⁻² min⁻¹ in low density spawning areas with 5–10 redds ha⁻¹.     

Detecting recombination from gene trees

In this article, a method is proposed for detecting recombination in the sequences of a gene from a set of closely related organisms. The method, the Homoplasy Test, is appropriate when the sequences are rather similar, differing by 1%-5% of nucleotides. It is effective in detecting relatively frequent recombination between a set of rather similar strains, in contrast to previous methods which detect rare or unique transfers between more distant strains. It is based on the fact that, if there is no recombination and if no repeated mutations have occurred (homoplasy), then the number of polymorphic sites, v, is equal to the number of steps, t, in a most-parsimonious tree. If the number of "apparent homoplasies" in the most-parsimonious tree, h = t-v, is greater than zero, then either homoplasies have occurred by mutation or there has been recombination. An estimate of the distribution of h expected on the null hypothesis of no recombination depends on Se, the "effective site number," defined as follows: if ps is the probability that two independent substitutions in the gene occur at the same site, then Se = 1/ps. Se can be estimated if a suitable outgroup is available. The Homoplasy Test is applied to three bacterial genes and to simulated gene trees with varying amounts of recombination. Methods of estimating the rate, as opposed to the occurrence, of recombination are discussed.      

OBSERVATIONS ON FIBRILLOGENESIS IN THE CONNECTIVE TISSUE OF THE CHICK EMBRYO WITH THE AID OF SILVER IMPREGNATION

A technique is described which combines silver impregnation and ultrathin sectioning for the electron microscopic demonstration of fibrils in the connective tissue of the chick embryo. The electron micrographs presented in this paper provide evidence for the specificity and completeness of the silver-impregnation technique. It has been shown that, in this particular tissue after fixation in neutral formalin and at the stage of development represented by our material, the argyrophil fibers are embedded in a material which is continuous with the body of the fibroblasts.     

Genetic characterization and phylogenetic position of Echinococcus felidis (Cestoda: Taeniidae) from the African lion

Echinococcus felidis had been described in 1937 from African lions, but was later included in Echinococcus granulosus as a subspecies or a strain. In the absence of any genetic characterization, most previous records of this taxon from a variety of large African mammals remained unconfirmed due to the lack of diagnostic criteria and the possible confusion with the sympatric E. granulosus sensu stricto, Echinococcus ortleppi and Echinococcus canadensis. In this study, we obtained taeniid eggs from lion feces in Uganda and amplified DNA from individual eggs. Mitochondrial and nuclear DNA sequences showed similarities with those of other Echinococcus spp., but high values of percentage divergence of mitochondrial genes indicated the presence of a distinct species. In a second step, we compared this material with the preserved specimens of adult E. granulosus felidis, which had been identified morphologically approximately 40 years ago in South Africa. All DNA fragments (<200 bp) that could be amplified from the adults showed 100% similarity with the Ugandan material. In the phylogenetic tree of Echinococcus which was constructed from the mitochondrial genes, E. felidis is positioned as a sister taxon of E. granulosus sensu stricto. The data obtained will facilitate the development of diagnostic tools necessary to study the epidemiology of this enigmatic parasite.     

Predicting maximal strength in trained postmenopausal woman

The purpose of this study was to present an equation that accurately predicts 1 repetition maximum (RM) over a wide range of repetitions to fatigue (RTF) for 4 different machine resistance exercises in postmenopausal women. Seventy trained women (age = 57.4 +/- 3.1 years) performed maximal and submaximal repetitions on leg press, bench press, rowing, and leg adduction machines at the conclusion of a 2-year training program. Maximal repetitions were performed on each exercise in the following ranges: 3-5RM, 6-10RM, 11-15RM, and 16-20RM. Special regard was taken to maintain the identical execution of each test (i.e., range of motion, starting angle, speed of movement). One cubic polynomial (w(i) [0.988-0.0000584 r(i)(3) + 0.00190 r(i)(2) + 0.0104 r(i),] where w(i) is the load of measurement I, and r(i) is the number of repetitions) accurately predicted 1RM from RTF with mean absolute differences between actual 1RM and predicted 1RM for the 4 exercises of 1.5-3.1% and with coefficients of variation of <3.3%. Equation accuracy was independent of the exercise type or the number of RTF. Thus, this study supported the validity of RTF to adequately estimate 1RM over a wide range of repetitions and within different exercises in trained, older female subjects.