Skin Tensile Strength Research Articles

Correlation of High-Speed Tensile Strength with Collagen Content in Control and Lathyritic Rat Skin

Severity of lacerative skin injury depends on the applied load and the resistance of the tissue. At low (static) rates of loading there is a high degree of correlation between skin tensile strength and the degree of collagen crosslinking, with little added strength due to collagen interactions with the glycosaminoglycan matrix. We examined the effects of high (ballistic) rates of loading in order to determine the contributions to strength made by both the degree of collagen crosslinking and the collagen-matrix interaction. Tensile failure experiments were conducted using the dorsal skin of rats 1.5-6 months of age. Test specimen orientations were cut parallel and transverse to the body axis at cephalad and caudad locations on the dorsum. Tensile strength was measured at nominal strain rates of 30%/sec (low speed) and 6000%/sec (high speed) using both control and lathyrogen fed rats. Biochemical analyses were conducted to determine the amount of total and crosslinked (insoluble) collagen. In low-speed tests, there was a significant correlation ( r ⩾ 0.900) between collagen content and skin tensile strength measured both transverse and parallel to the spine. The degree of correlation was higher with insoluble ( r = 0.973) collagen content than with total ( r = 0.901) collagen. The effect of a lathyrogen diet produced a significant ( P < 0.001) reduction (two- to threefold) in tensile strength compared to control. In both high- and low-speed groups, tensile strength was greatest in the transverse samples with a significant correlation to collagen content ( r ⩾ 0.858). In the high-speed experiments, the skin tensile strength was significantly ( P < 0.001) increased (two- to threefold) compared to low-speed results at each age tested. Because this increase occurred in identical tissues, these data support our hypothesis that the more dynamic strength properties of skin involve the influence of matrix interactions with collagen.

Fruit Cracking in Tomato

The environmental and physiological causes of cracking or splitting of soft fruits and citrus as they ripen are not well understood. This paper explores factors contributing to radial cracking in tomatoes, gives suggestions for prevention of cracking, and suggests directions for future research. Fruit cracking occurs when there is a rapid net influx of water and solutes into the fruit at the same time that ripening or other factors reduce the strength and elasticity of the tomato skin. In the field, high soil moisture tensions suddenly lowered by irrigation or rains are the most frequent cause of fruit cracking. Low soil moisture tensions reduce the tensile strength of the skin and increase root pressure. In addition, during rain or overhead irrigation, water penetrates into the fruit through minute cracks or through the corky tissue around the stem scar. Increases in fruit temperature raise gas and hydrostatic pressures of the pulp on the skin, resulting in immediate cracking in ripe fruit or delayed cracking in green fruit. The delayed cracking occurs later in the ripening process when minute cracks expand to become visible. High light intensity may have a role in increasing cracking apart from its association with high temperatures. Under high light conditions, fruit soluble solids and fruit growth rates are higher. Both of these factors are sometimes associated with increased cracking. Anatomical characteristics of crack-susceptible cultivars are: 1) large fruit size, 2) low skin tensile strength and/or low skin extensibility at the turning to the pink stage of ripeness, 3) thin skin, 4) thin pericarp, 5) shallow cutin penetration, 6) few fruits per plant, and 7) fruit not shaded by foliage. Following cultural practices that result in uniform and relatively slow fruit growth offers some protection against fruit cracking. These practices include maintenance of constant soil moisture and good Ca nutrition, along with keeping irrigation on the low side. Cultural practices that reduce diurnal fruit temperature changes also may reduce cracking. In the field, these practices include maintaining vegetative cover. Greenhouse growers should maintain minimal day/night temperature differences and increase temperatures gradually from nighttime to daytime levels. For both field and greenhouse tomato growers, harvesting before the pink stage of ripeness and selection of crack-resistant cultivars probably offers the best protection against cracking. Areas for future research include developing environmental models to predict cracking and exploring the use of Ca and gibberellic acid (GA) sprays to prevent cracking.

The Effects of Sex, Age, and Feed on Tensile Strength of Broiler Skin

Abstract Skins from male and female broilers, aged 6.5 to 8.5 weeks at slaughter, fed on the different energy:protein (E/P) rations, were measured for fat content and tensile strength. Tensile strength of both male and female broiler skins increased with age. The tensile strength of male skins was higher than that of females (1078 g vs. 842 g, average, respectively). Female skins contained more fat than males (36.9 vs. 32.2%, average, respectively). Dietary E/P rations did not consistently affect skin fat content or tensile strength. In spite of the skin’s fat tendency to increase with age, tensile strength increased with age. Therefore, other factors play a role in determining tensile strength in broilers.

Reduced strength of skin in osteogenesis imperfecta.

The biochemical properties and ratio collagen type I/type III of skin biopsies from nine patients with osteogenesis imperfecta and nine age- and sex-matched controls were studied. Four of six patients with osteogenesis imperfecta Sillence type I had pronounced reductions in skin tensile strength, decreased ratios of collagen type I/type III, primarily accomplished by reduced amounts of collagen type I, moderate or no disability. The three patients with osteogenesis imperfecta Sillence type III had severe skeletal deformities, but normal skin tensile strength, and ratios of collagen type I/type III within the normal range. These observations may be explained as resulting from various structural defects in the type I collagen of patients with osteogenesis imperfecta.

Effects of cloxacillin, doxycycline, fusidic acid and lincomycin on mineralization and solubility of collagen in young rats.

The antibiotics doxycycline, fusidic acid and lincoymcin have recently been shown to reduce growth of bones and tensile strength of skin in young rats. Such adverse effects were not found in rats receiving cloxacillin. The present investigation deals with the influences of these four antibiotics on the mineralization of bones and on the solubility of collagen in skin. In rats receiving doxycycline the content of calcium and phosphorus in bones and the concentration of albumin in serum were reduced. None of the antibiotics had a detectable effect on the solubility of collagen.

Hydrodynamic properties of collagen fibril and aging.

One biochemical approach to aging research has been to isolate bodily structural components, study their physiochemical properties, and establish the molecular basis for bodily changes during the aging process. This approach has been particularly fruitful in the field of connective tissue research, ever since soluble collagen was first isolated from tendon, and synthetic fibrils were reconstituted from the soluble collagen in vitro (1). When, in addition to soluble collagens and soluble ground substances, connective tissue components with high order structures, observable as collagen fibril, collagen fiber, and collagen fiber bundle (2) are isolated and characterized, such age-related changes as shrinkage temperature and tensile strength of skin (3) may be able to be expressed in terms of the physiochemical properties of their structural components.

Dose-response studies of penicillamine and related compounds in reducing skin—Tensile strength of rats

Penicillamine (I) and certain related compounds are known to reduce the skin tensile strength (sts) of rat dorsal skin when they are given in the diet. This effect seems significant to studies of the biochemistry of collagen and of diseases of collagen, perhaps including the arthritides. The reduction of sts appears to be caused by diminution of collagen crosslinking. The effects of several such compounds were studied after intraperitoneal (ip) injection, in order to determine structure-activity relationships divorced from possible anorexic or gastrointestinal complications seen after oral dosing, and to examine the relation of ip dose to response. A cyclopentyl analog (II) of I was at least as active as I, showing that structural variants of I can be active when given ip. A dimethylthiazolidine (V) and a zinc chelate (III, rather toxic) of I were nearly as active as I, showing that probable in vivo precursors of I can be obtained that will be active when given ip. The disulfide of I and a zinc chelate of cysteine were inactive. Maximum response for several compounds seemed to occur at intermediate dose levels, with larger or smaller doses affording less sts reduction.

Mechanical and chemical properties of various connective tissue organs in rats as influenced by non-steroidal antirheumatic drugs.

Mechanical and chemical properties were studied in established and in newly formed collagenous tissues of rats after 10 days' treatment with various doses of acetylsalicylic acid, phenylbutazone and indomethacin. Breaking strength of femur bone, tensile strength of femoral epiphyseal cartilage, tensile strength of skin, tensile strength of tail tendons and tensile strength of granulomas induced by implantation of glass rods were measured. Soluble fractions of collagen, insoluble and total collagen were estimated. Glycosaminoglycan fractions were determined by papain digestion, cetylpyridinium chloride precipitation and column chromatography.High doses of each of the antirheumatic drugs induced an increase of strength in all collagenous tissues. However, the degree of the increase and the sensitivity to low doses varied greatly between the different organs. Tail tendons showed an increase of tensile strength with low doses and gave steep dose response curves for each drug.Tensile strength of skin also para...

Emphysema-like changes in the lungs of the blotchy mouse.

The Blotchy allele is one of several mutations at the Mottled locus on the mouse X-chromosome. Affected males and heterozygous females within the several allelic groups possess varying degrees of connective tissue abnormalities similar to those found in copper-deficient and lathyritic animals, including aortic aneurysms and reduced skin tensile strength. There is evidence that defective inter- and intramolecular cross-links in collagen and elastin account for these abnormalities. The lung of the Blotchy mouse is also structurally and functionally abnormal. Hemizygous males have larger total lung volumes, markedly increased mean linear intercepts, and diminished internal alveolar surface area when compared to normal control animals. Light microsbopy and scanning electron microscopy show abnormal architecture with enlargement of air spaces and effacement of alveolar septa. Static air and saline pressure-volume curves show that lungs of Blotchy mice have decreased elastic recoil and are significantly more compliant than normal. These abnormalities in the lung of the Blotchy mouse suggest that the defects of the connective tissue proteins described in skin and aorta also involve the lung. The Blotchy strain may be a useful model in which to investigate how abnormalities of connective tissue proteins influence pulmonary structure and function.

Effects of D-Penicillamine and Prednisolone on Connective Tissue in Rats

The effects of D-penicillamine and prednisolone acetate on connective tissue were studied in rats using various techniques. Tensile strength of skin strips decreased even after 2 days' oral treatment with D-penicillamine. This effect was dose-related and was much more pronounced after 10 days' treatment. Injections of prednisolone acetate caused an increase of skin tensile strength which was antagonized by simultaneous treatment with D-penicillamine. In contrast to skin there was almost no influence of D-penicillamine in doses up to 300 mg/kg p.o. on tensile strength of femoral epiphyseal plates of rats. In addition, the antagonism against prednisolone was very small in epi- physeal cartilage.D-penicillamine caused no effect on exudative inflammation (granuloma pouch) whereas prednisolone was very effective. Connective tissue proliferation measured as wet weight of glass rod granuloma was not influenced by D-penicillamine, whereas a significant weight reduction was found after prednisolone injections. In ...

Collagen, Hexosamine and Tensile Strength of Rabbit Skin During Aging

The process of aging is accompanied by changes in the chemistry of connective tissue. As a general rule collagen seems to accumulate with increasing age. Analysis of this material on the basis of its solubility indicates that what is being accumulated is insoluble fibrous material, whereas the soluble collagens, present in significant amounts in young skin, drop to low values in older age. These observations have been reviewed in detail by Harkness (1).