Unit Area Of Skin Research Articles

A lesion on the abdomen in an infant

A 4-month-old girl presented to the pediatric dermatology clinic due to an enlarging growth on the abdomen. The child was born to a 32-year-old G8P6 woman via spontaneous vaginal delivery at 39 weeks and 5 days. Her mother identifies as South Sudanese. She received all recommended prenatal care. Pregnancy was complicated by low weight gain and cerclage placement. Delivery was complicated by meconium-stained amniotic fluid but otherwise uneventful and APGARS was 8,9. Newborn skin examination was completely normal, and her 2-week-old well check was also unremarkable. At her next appointment (5 weeks of age), a new skin growth was noted on the right abdomen. There was no ulceration or bleeding, and the growth did not appear to be bothersome to the infant. The plaque continued to enlarge, and she was referred to the pediatric dermatology clinic. On examination, there was a solitary 0.8 × 1.0 cm dark brown plaque with slight pink hue at the edges (Figure 1). Dermoscopy was performed (Figure 2). Dermoscopy showed mainly red lacunae with white septa consistent with an infantile hemangioma. This case underscores the utility of dermoscopy in diagnosing vascular growths such as infantile hemangioma (IH) in more deeply pigmented skin. In darker skin types, diagnosis of vascular lesions on general examination is made more challenging by the presence of melanin in the epidermis. Dermoscopy allows for enhanced visualization of structures below the stratum corneum to the level of the superficial dermis and allows for more accurate diagnosis of both melanocytic and non-melanocytic lesions.1 To date, the utility of dermoscopy in diagnosing vascular lesions in skin of color has not been well described. In both lighter and darker phototypes, the primary dermoscopic feature of the hemangioma is the red lacuna (lake of blood), usually separated by pale septae.2 In darker phototypes, dermoscopy may be particularly useful in distinguishing these red lacunae from brown globules (which are seen in melanocytic lesions), and from red structureless areas with white collarettes (which are seen in pyogenic granulomas).1 Dermoscopy of superficial port wine stain can show a uniform “lawn” of dotted and occasionally tortuous vessels, sometimes with an overlying gray-white veil if there is a deeper component.3 In some cases, the color of lacunae on dermoscopy may help clarify the depth of the lesion (superficial IHs tend to have bright red lacunae, while the lacunae of deeper IHs may have a more blue or violaceous hue). However, melanin can impart a blue hue; thus, one must take into consideration the patient's phototype and other clinical clues (ie, nodularity and height) when assessing depth.1 Serial dermoscopic examination can also help to identify subtle changes in hemangiomas; a superficial white cast portending ulceration can often be more easily appreciated with a dermatoscope.4 Infantile hemangioma is more commonly diagnosed in Caucasians compared with other ethnicities, and girls are more commonly affected than boys.5 Prematurity also appears to be a significant contributing risk factor.5 In one retrospective analysis of the National Hospital Discharge Survey, a doubling of IH incidence rate was observed in White infants between 1976 and 2006, thought to be explained at least partly by increasing rates of low birth weight births in White people in that time period.6 Infantile hemangioma is an uncommon diagnosis in neonates of African descent, for reasons that have not been fully clarified. One hypothesis for this variation by ethnic background is the protein fibromodulin, which is secreted by melanocytes. Though individuals with darker skin do not have increased melanocyte number per unit skin area, they may produce more fibromodulin, which has been identified as a key regulator of angiogenesis.7 Speculatively, the activity of fibromodulin could partly account for the decreased incidence of diseases of vascular proliferation in individuals of African descent, which include both IH and age-related macular degeneration.8 One report identified three African American infants with segmental IHs requiring systemic therapy with propranolol. All three cases were associated with hypertension (an association that has not otherwise been reported with IHs), and two of the three infants experienced improvement in blood pressure with propranolol therapy. All three infants otherwise responded well to propranolol therapy with regards to their hemangiomas. The full significance of these findings is unknown due to the rarity of segmental hemangiomas in infants of African descent. In conclusion, IHs are less common in phototype IV, V, and VI skin, but do occur. Dermoscopy can facilitate rapid and accurate diagnosis and ensure timely intervention when indicated.

ВЛИЯНИЕ УРОВНЯ КОРМЛЕНИЯ СУЯГНЫХ МАТОК ТУШИНСКОЙ ПОРОДЫ НА МОРФОЛОГИЧЕСКИЕ ПОКАЗАТЕЛИ КОЖИ ПОТОМСТВА ПРИ РОЖДЕНИИ

Feeding during the suyagny period is crucial in obtaining strong and healthy offspring. In 2018-2020, in the peasant farm "Dzhigkaev Valery Sergeevich" of the Ardon district of the Republic of North Ossetia-Alania, the influence of the feeding level of suyag queens on the morphological indicators of offspring was studied. For the experiment, after the end of the breeding company, 120 queens of the Tushinsky breed were selected, going to the third lambing, which were divided into 4 groups of 30 heads each. The sheep of the control group received a household ration compiled in accordance with the norms of the VIZ. The diet of sheep of the second, third and fourth groups was increased in total nutrition by 10, 15 and 20%, respectively, compared with the diet of the control group. During lambing, five heads of sheep and young sheep were selected, in which morphological parameters of the skin were studied, according to preparations made from lambs ' skin samples taken from 5 heads from each group. It was found that as a result of the increased level of feeding of queens during the dry period, there was an increase in the thickness of the skin and its layers, the depth of the hair follicles, the diameter of the bundles of collagen fibers. The different level of feeding of the queens during the suyag period did not affect the number of hair follicles laid in the skin of newborn lambs. At the same time, the number of formed wool fibers of newborn lambs depends on the level of feeding of their mothers during the fruiting period. The greatest number of rudimentary follicles in the hair or on the unit area of skin (43,1 – 44,2%) had lambs received from Queens, who was in the business environment of feeding level, the lowest – in lambs whose mothers received by 15 and 20% more nutrients in the diet that is high feeding level (28,9 – 34,2%).

ВЛИЯНИЕ УРОВНЯ КОРМЛЕНИЯ СУЯГНЫХ МАТОК ТУШИНСКОЙ ПОРОДЫ НА МОРФОЛОГИЧЕСКИЕ ПОКАЗАТЕЛИ КОЖИ ПОТОМСТВА ПРИ РОЖДЕНИИ

Feeding during the suyagny period is crucial in obtaining strong and healthy offspring. In 2018-2020, in the peasant farm "Dzhigkaev Valery Sergeevich" of the Ardon district of the Republic of North Ossetia-Alania, the influence of the feeding level of suyag queens on the morphological indicators of offspring was studied. For the experiment, after the end of the breeding company, 120 queens of the Tushinsky breed were selected, going to the third lambing, which were divided into 4 groups of 30 heads each. The sheep of the control group received a household ration compiled in accordance with the norms of the VIZ. The diet of sheep of the second, third and fourth groups was increased in total nutrition by 10, 15 and 20%, respectively, compared with the diet of the control group. During lambing, five heads of sheep and young sheep were selected, in which morphological parameters of the skin were studied, according to preparations made from lambs ' skin samples taken from 5 heads from each group. It was found that as a result of the increased level of feeding of queens during the dry period, there was an increase in the thickness of the skin and its layers, the depth of the hair follicles, the diameter of the bundles of collagen fibers. The different level of feeding of the queens during the suyag period did not affect the number of hair follicles laid in the skin of newborn lambs. At the same time, the number of formed wool fibers of newborn lambs depends on the level of feeding of their mothers during the fruiting period. The greatest number of rudimentary follicles in the hair or on the unit area of skin (43,1 – 44,2%) had lambs received from Queens, who was in the business environment of feeding level, the lowest – in lambs whose mothers received by 15 and 20% more nutrients in the diet that is high feeding level (28,9 – 34,2%).

Characterization of cavitation-radiated acoustic power using diffraction correction.

A method is developed for compensating absolute pressure measurements made by a calibrated passive cavitation detector (PCD) to estimate the average acoustic power radiated from a region of interest (ROI) defined to encompass all cavitating bubbles. A diffraction correction factor for conversion of PCD-measured pressures to cavitation-radiated acoustic power per unit area or volume is derived as a simple analytic expression, accounting for position- and frequency-dependent PCD sensitivity. This approach can be applied to measurements made by any PCD without precise knowledge of the number, spatial, or temporal distribution of cavitating bubbles. The diffraction correction factor is validated in simulation for a wide range of ROI dimensions and frequencies. The correction factor is also applied to emission measurements obtained during in vitro ultrasound-enhanced sonophoresis experiments, allowing comparison of stable cavitation levels between therapeutic configurations with different source center frequencies. Results incorporating sonication at both 0.41 and 2.0 MHz indicate that increases in skin permeability correlate strongly with the acoustic power of subharmonic emissions radiated per unit skin area.

The relationship between UV exposure and incidence of skin cancer.

The incidence rates of skin cancer increase with decreasing latitude in most western countries. Ultraviolet (UV) radiation is a main risk factor for skin cancer. We have studied the relationship between UV exposure and skin cancer incidence rates of squamous cell carcinoma (SCC), basal cell carcinoma (BCC), and cutaneous melanoma (CM), and tried to fit different mathematical models to the experimental data. The incidence-UV exposure relationship for all three cancers is best described by the power law: ln(RTD) = Ab ·ln(annual UVEry dose), with relative tumor density (RTD) being age-adjusted incidence rate per unit area of skin, and the power parameter Ab being the biological amplification factor. For SCC, the RTD is a factor of 16-19 times larger on the head than on the trunk. For BCC, this factor is 7 and for CM it is 0.9-1.3. Ab for CM has remained almost unchanged from the 1960s until recently. The incidence-sun exposure relationship for all three cancers is well described by the power law. SCC is dependent on total UV exposures, while BCC, and even more CM, is dependent also on exposure patterns, with intermittent exposures being most carcinogenic.

Characterisation of skin barrier function using bioengineering and biophysical techniques.

To characterise skin barrier function in vivo at two distinct anatomic sites using minimally invasive bioengineering and biophysical tools. In healthy human volunteers, the quantities of stratum corneum (SC) per unit area of skin on the forearm and forehead were quantified by gravimetric and imaging techniques. Organisation of the SC intercellular lipids was evaluated as a function of position using attenuated total reflectance infrared spectroscopy (ATR-IR). The constituents of natural moisturising factor (NMF) were extracted from tape-stripped samples of the SC and by reverse iontophoresis; 21 components were identified and quantified by liquid chromatography with mass spectrometric detection. SC was quantified more accurately by imaging and was significantly thinner on the forehead than on the forearm. Intercellular lipids were more disordered near the skin surface at both sites; however, throughout forearm SC, the lipids were substantially better organised than those in the forehead. Compositionally, the NMF from forearm and forehead SC was similar, but the total amount extractable from the forehead was smaller. Taken together, the bioengineering and biophysical techniques employed demonstrate, in a complementary, objective and quantitative fashion, that SC barrier function on the forehead is less competent than that on the forearm.

Modeling of bioheat equation for skin and a preliminary study on a noninvasive diagnostic method for skin burn wounds

Heat transfer in a unit three-dimensional skin tissue with an embedded vascular system of actual histology structure is computed in the present work. The tissue temperature and the blood temperatures in artery and vein vessels are solved with a multi-grid system. The mean temperature of the tissue over the cross-section of the unit skin area is evaluated. The resulting one-dimensional function is regarded as the temperature of healthy tissue (or injured skin but the blood perfusion is still normally working) for large area of skin in view of the symmetric and periodic structure of the paired artery–vein vessels in nature. A three-dimensional bioheat equation then is formulated by the superposition of the skin burn wound effect and the healthy skin temperature with and without thermal radiation exposure. When this bioheat equation is employed to simulate ADT process on burn wounds, the decaying factor of the skin surface temperature is found to be a sharply decreasing function of time in the self-cooling stage after a thermal radiation heating. Nevertheless, the boundary of non-healing (needing surgery) and healing regions in a large burn wound can be estimated by tracking the peak of the gradient of decaying factor within 30s after the thermal radiation is turned off. Experimental studies on the full ADT procedure are needed to justify the assumptions in the present computation.

Comparison of three different techniques for application of water solutions to Finn Chambers®

With regard to contact allergy, the dose of a sensitizer per unit skin area is an important factor for both sensitization and elicitation, and therefore a known amount/volume of test preparation should be applied at patch testing. To compare three different techniques for the application of aqueous solutions to Finn Chambers, in order to determine the precision and accuracy of each technique when the recommended 15 µl volume is applied. Four technicians applied formaldehyde 1.0% aq. (wt/vol) and methylchloroisothiazolinone/methylisothiazolinone 200 ppm (wt/vol) in sets of 10 onto Finn Chambers, with three different techniques: (i) micro-pipetting; (ii) dripping the solutions; and (iii) dripping the solutions followed by removal of excess solution with a soft tissue. Assessment of the variations was performed with the use of descriptive data. The ability to apply the exact amount was assessed by Fisher's exact test by categorizing each application as in or out of the range 12-18 µl. The micro-pipette technique had the best accuracy and precision, as well as the lowest inter-individual variation. The technique in which excess solution was removed had good precision, but failed in the application of the defined amount, i.e. 15 µl.

Dose per unit area - a study of elicitation of nickel allergy

Experimental sensitization depends upon the amount of allergen per unit skin area and is largely independent of the area size. This study aimed at testing if this also applies for elicitation of nickel allergy. 20 nickel allergic individuals were tested with a patch test and a repeated open application test (ROAT). Nickel was applied on small and large areas. The varying parameters were area, total dose and dose per unit area. In the patch test, at a low concentration [15 microg nickel (microg Ni)/cm(2)], there were significantly higher scores on the large area with the same dose per area as the small area. At higher concentrations of nickel, no significant differences were found. In the ROAT at low concentration (6.64 microg Ni/cm(2)), it was found that the latency period until a reaction appeared was significantly shorter on the large area compared to the small area. It was also found that the ROAT threshold (per application) was lower than the patch test threshold. For elicitation of nickel allergy, the size of the exposed area and therefore the total amount of applied nickel, influence the elicitation reaction at some concentrations, even though the same dose per unit area is applied.

Fiber production and properties in genetically furred and furless rabbits

The objectives of this study were to describe and compare means and measures of variability of fiber characteristics and fiber production between genetically furred and furless rabbits and among classes of furless rabbits. An F1 generation of rabbits was produced by mating New Zealand White does to a rare, furless Mini Lop buck. All F1 offspring had normal coats of fur. Inter se random matings of the F1 stock (barring full-sibling matings) were made to produce the F2 generation that consisted of approximately 75% furred and 25% furless progeny. Furless animals were further subjectively classified into 3 distinct classes (1 to 3) having increasingly more fur. In yr 1, 17 furred and 20 furless rabbits (age 28 to 49 d) were randomly assigned to growing pens, and in yr 2, 17 additional furless and 9 additional furred rabbits were included to increase the size. After 6 wk, the rabbits were weighed, and a measured area of fur (approximately 20 cm2) was shorn from the left flank of each rabbit. This fiber was weighed and measured for staple length, fiber diameter, prickle factor (% of fibers > 30 microm in diameter), and fiber curvature. Fiber production per unit area of skin was calculated and fiber production per animal was estimated. In yr 2, all of the furless and 2 of the furred rabbits were shorn over their entire bodies to obtain direct measurements of total fur weight. Furless rabbits were 9% heavier (1,941 vs. 1,783 g of BW, P < 0.01) and produced approximately 90% less fiber per unit area of skin than furred rabbits (1.74 vs. 15.83 mg/cm2, P < 0.01). The fibers from furless rabbits were shorter (1.54 vs. 2.56 cm, P < 0.01) and coarser (15.8 vs. 14.5 microm diameter, P < 0.01) than those from furred rabbits and exhibited greater prickle factor (11.3 vs. 3.5%, P < 0.01) and curvature values (47.5 vs. 38.5 deg/mm, P < 0.01). Class 3 furless rabbits were heavier than rabbits of classes 1 and 2 (2,075 vs. 1,817 and 1,981 g of BW, respectively, P < 0.05). Means for actual total fiber production per animal for classes 1 to 3 were 0.64, 2.07, and 8.68 g, respectively, compared with 23.0 g for furred rabbits (P < 0.01). Although some similarities were present, several of the correlations involving fiber properties and BW were substantially different (e.g., BW vs. staple length and fiber diameter vs. weight of fiber per unit area) for furred and furless groups. These results, and those reported elsewhere from a series of experiments, support the potential for production of furless rabbits in arid and tropical environments.

Reduction of experimental Salmonella and Campylobacter contamination of chicken skin by application of lytic bacteriophages.

Lytic bacteriophages, applied to chicken skin that had been experimentally contaminated with Salmonella enterica serovar Enteritidis or Campylobacter jejuni at a multiplicity of infection (MOI) of 1, increased in titer and reduced the pathogen numbers by less than 1 log(10) unit. Phages applied at a MOI of 100 to 1,000 rapidly reduced the recoverable bacterial numbers by up to 2 log(10) units over 48 h. When the level of Salmonella contamination was low (< log(10) 2 per unit area of skin) and the MOI was 10(5), no organisms were recovered. By increasing the number of phage particles applied (i.e., MOI of 10(7)), it was also possible to eliminate other Salmonella strains that showed high levels of resistance because of restriction but to which the phages were able to attach.

Skin characteristics and quality of onion cultivars given different nitrogen and irrigation treatments

SummarySkin quality of onions from commercial sources and experiments was assessed using a rotating drum to simulate handling damage. Differences in skin quality between cultivars were of greater significance than those induced by manipulating nitrogen and water supply. The drum test discriminated between samples and may be valuable for comparing varieties and indicating those appropriate for commercial use. Skin splitting and cracking decreased with an increase in numbers of skins per bulb, skin thickness and, more particularly, skin specific dry weight (the amount of plant structure per unit area of skin). Strength and stiffness of skins were less well associated with resistance to fracture and skin loss. There was no relationship with skin moisture content. Some characteristics, particularly stiffness and moisture content, varied with skin position. Inner skins contained more moisture and were more flexible. Breeding for improved skin quality through increased numbers and using specific skin weight as a primary screen appears to provide the best strategy for improvement.

Protection against endogenous and UVB-induced oxidative damage in stratum corneum lipids by an antioxidant-containing cosmetic formulation.

A 16-week human clinical study was carried out to determine the ability of antioxidants in a cosmetic vehicle to inhibit the induction of lipid peroxidation in stratum corneum lipids. The study consisted of a twice daily application of material for 12 weeks followed by a 4-week regression phase. Stratum corneum lipids were collected and then exposed to 500 mJ/cm2 of ultraviolet B (UVB) radiation in order to avoid excessive erythemal damage to the subjects. Lipid peroxides were assayed by a methylene blue derivative assay and expressed per unit area of skin. During the treatment period, decreases in the level of lipid peroxides were observed on the sites treated with the compositions containing antioxidants, as compared to the untreated sites, and expressed as percent differences. Decreases were observed in endogenous as well as UV-induced lipid peroxides followed by a return to baseline levels. These results demonstrate that antioxidants in a topical cosmetic formulation were effective in protecting human stratum corneum lipids against endogenous oxidation or if challenged by 500 mJ/cm2 UVB.

Body site distribution of cutaneous malignant melanoma in relationship to patterns of sun exposure.

A study of all newly incident melanoma patients in British Columbia in 1991-1992 was undertaken to test the hypothesis raised by an earlier study, which showed that in younger patients the incidence rate of melanoma per unit area of skin was higher on intermittently exposed skin areas than on continuously exposed areas. Using 1,033 patients and a more detailed body site categorisation than was previously possible, our results confirmed that in both men and women under age 50 the highest melanoma density was on the back. At ages over 50, the greatest density occurred on fully exposed sites, such as the face, though the dorsum of the hand and forearm, likely also to have high exposure, show very low melanoma densities. Differences between males and females correlate well with differences in likely exposure patterns. These results were seen for all invasive cutaneous melanomas combined; the patterns were similar for subtypes and for both invasive and in situ melanoma, with the exception of lentigo maligna melanoma (LMM), which occurs almost exclusively on the face, even at younger ages. Comparison with the earlier study (1976-1979) shows that the age-standardised rates for melanoma excluding LMM have increased by 60%, with the greatest proportional increase being at younger ages; in the recent data, the age-standardised rate for intermittently exposed sites exceeds that for usually exposed sites. Our results confirm that intermittent sun exposure has a greater potential for producing melanoma than continuous exposure at ages below about 50, though at older ages melanoma is more common on body sites with continuous sun exposure.

In vitro/in vivo Difference in Enhanced Skin Permeation of Nicardipine Hydrochloride by the 1-Menthol-Ethanol System

The in vitro/in vivo difference in enhanced skin permeation of nicardipine hydrochloride (NC) by simultaneous use of 1-menthol and ethanol (MEW system, 1-menthol:ethanol:water = 5:40:55) was investigated in hairless rats. First, the cutaneous blood flow clearance (clearance from skin to blood flow) of NC per unit area of skin (CLCB/A), which was comparable to the permeability coefficient across skin (PC), was calculated from intracutaneous and intravenous injection data using the deconvolution method; the value was 1.67 microliters/h/cm2. Two formulations containing NC and the MEW system, solution (SOL) and 15% hydroxypropyl cellulose gel (GEL), were used for in vitro and in vivo permeation experiments. The in vitro PC of NC via excised skin from SOL (23.3 microliters/h/cm2) was significantly higher than CLCB/A, and that from GEL (1.48 microliters/h/cm2) was similar to CLCB/A. Consequently, the steady-state concentration of NC in skin during in vivo application of SOL was 6.6 times higher than corresponding in vitro data. In vivo PCs from SOL and GEL were however significantly lower than CLCB/A. These results may be explained by the findings, using a laser Doppler flowmeter, that cutaneous blood flow was decreased by the application of MEW.

Cutaneous circulation is correlated with Merino wool production

Laser Doppler velocimetry was used to investigate the cutaneous circulation and its relationship to wool growth in Finewool and Strongwool Merinos. Skin blood flow measured with the laser Doppler velocimeter (LDV) was highly correlated with estimates of blood flow obtained using 57Co-labelled microspheres (R2 = 0.85; P &lt; 0.01), although the absolute values estimated by the microsphere technique were significantly higher (P &lt; 0.001). Strongwool Merinos had a greater rate of blood flowing through the skin than Finewool Merinos, and this was associated with both wool production per unit area of skin (R2 = 0.27, P &lt; 0.01) and with the total volume of germinative tissue in the skin (R2 = 0.54; P &lt; 0.04). The relationship between the microvascular anatomy of the skin and blood flow was also examined in four Finewool Merinos and four Strongwool Merinos. Silicone rubber was infused into the deep circumflex iliac artery within the abdominal flank, from which an index of the area of vascular tissue per unit volume of skin was estimated. This index was not related to blood flow, wool growth or follicle density within nor between strains of Merinos. Both the usefulness and limitations of the LDV are discussed, and it was concluded that (a) blood flow has an important role in the level of wool produced both within and between strains of Merinos, and (b) laser Doppler velocimetry is a useful tool for the study of blood flow in the skin of sheep.

Follicular determinants of the length and diameter of wool fibres. 2. Comparison of sheep differing in thyroid hormone status

The thyroid hormone status of Corriedale sheep was manipulated in order to produce a change in the rate of fibre elongation (L) with no concomitant change in the diameter (D) of the fibres, to allow the follicular factors responsible for fibre L to be determined. Thyroidectomy resulted in a 60% decrease in wool growth per unit area of skin and a 40% decrease in the rate of fibre volume output, due largely to a decline in fibre L from 412 ,8m/day to 277 8m/day ( P &lt; 0.0001) while fibre D was unchanged (23.9 8m v. 21.9 pm, P &gt; 0-05). Elevation of plasma thyroxine levels to 250% of Control values had no significant effect on fibre L and D, but patch wool growth was increased ( P &lt; 0.05). A high proportion (22.9%) of the follicles in the hypothyroid sheep was inactive in comparison to the low levels of inactivity in the control (1.2%) and hyperthyroid animals (0.1%). The rate of division of follicle bulb cells was depressed by hypothyroidism and increased by hyperthyroidism (P &lt; 0.0001), but there was no effect of thyroid status on the size of the cortical cells released from the wool fibres. Hypothyroid sheep had slightly smaller follicle bulbs and dermal papillae than the control and hyperthyroid animals. The proportion of dividing cells entering the fibre cortex (estimated from cortical cell volume, rate of fibre volume growth and rate of cell division) was depressed by thyroidectomy suggesting that relatively more dividing cells entered the inner root sheath in the follicles of hypothyroid sheep. This is supported by the lower production ratio (ratio of area of fibre to area of fibre-plus-inner root sheath) of the hypothyroid sheep. It is concluded that the rate of fibre elongation is depressed in hypothyroid sheep as a result of both a reduction in the rate of division of cells in the follicle bulb and fewer of these dividing cells entering the fibre cortex. This mechanism allows rapid changes in the rate of fibre elongation to occur with little change in the size of the follicle bulb, and may account for a number of scenarios in which fibre length changes rapidly with no concomitant change in fibre diameter. Fibre diameter, on the other hand, appears to be closely related to the dimensions of the follicle bulb, and by association, to the rate of bulb cell production. Selection of sheep with small follicle bulbs and at the same time, high production ratios, may be means of increasing fibre length whilst maintaining low fibre diameter.

Influence of dietary intake and genetic capacity for wool growth on the composition of mid-trunk skin of Merino sheep

Some nitrogenous constituents in the skin were examined in sheep from two flocks with different genetic capacities for wool growth and in sheep consuming different diets. In the first comparison, in which the sheep consumed a maintenance (1 x M) ration, the average water, lipid and nitrogen contents of skin were similar for the two flocks. The collagen content of skin from sheep with low wool growth (Fl-) was greater than that in skin of high producers (I?]+)-0.40 v. 0.36 g g-1 dry defatted skin (P &lt; 0.05). The F1+ sheep also maintained lower concentrations of non-peptide cystine in plasma (51 v. 68 8mol L-l: P &lt; 0.05) and in skin (1.1 v. 1.9 8mol g-l dry defatted skin: P &lt; 0.05). In a second experiment, sheep bred from the two flocks (Fl+ and F1-), consumed rations providing either 0.8 x M or 2 x M (the latter diet containing 12.5% formaldehyde treated casein). Trephine-sampled skin from the high producing sheep and from the sheep with greater intake had lower concentrations of collagen per unit mass of skin (P &lt; 0.05), but similar collagen per unit area of skin. Both diet and flock influenced the weight of skin sampled by trephine. The distribution ratios of non-peptide a-amino nitrogen and of cystine between skin and plasma were significantly greater in the F1+ derived sheep: 4.35 v. 3.1 L plasma kg-1 skin for cystine. In a third comparison, skin was sampled from sheep of an unselected flock (n = 50) after each received one of four dietary treatments ranging from 0.7 x M to 2.6 x M (ad lib.) for 60 days. As the dietary allowance increased, the weight of skin per unit area of skin increased, the quantities of total protein and of saponifiable lipid per unit mass of dry skin remained constant, but the content of hydroxyproline significantly decreased from 0.20 to 0.13 mmol g-l dry skin (P &lt; 0.05). The quantities of non-collagenous protein solubilized by first sodium chloride (0.5 mol L-l) and then tartaric acid (0.1 mol L-l) per unit mass of collagen increased significantly with increased intake of feed.

Nutritional responses in wool growth by four Merino genotypes of differing wool growth performance

Sheep from four Merino flocks, different in annual clean fleece production when grazed together, were offered a range of nutritional treatments to compare their ability to digest dietary organic matter (experiment 1) and to compare the relationships of wool growth and fibre diameter with nutrient intake (experiment 2). The sheep were selected from a finewool (Fl), a strong wool (S), and two medium-Peppin (MP6 and MP10) flocks. The nutritional treatments varied intakes of two pelleted diets-B and F. Diet B consisted of oat grain, lucerne chaff, and oaten straw, while diet F was as for B but fortified with fishmeal. The digestibility of both diets was negatively related to the level of intake, and there were some differences between the flocks in their ability to digest organic matter. Clean wool growth per unit area of skin was curvilinearly related (P &lt; 0.001) to N intake, but was not influenced by diet per se. The regression coefficient for the relationship of clean wool growth with N intake and the estimated maximum wool growth rate of flock F1 were less than the other flocks. However, flock MP10 grew less wool than flocks S and MP6 at any given intake. Variation in (fibre diameter)2 accounted for 0.6 of the variation in wool growth, with responses in fibre diameter to intake being similar to those observed in wool growth. The responses in plasma cystine of the flocks to N intake differed, with the relationship for flock F1 being curvilinear and reaching a maximum at an intake of 27 g N day-1, while the responses of the other flocks were essentially linear. The relationships between plasma cystine level and wool growth differed between the flocks such that wool growth of sheep from flocks S and MP6 was more responsive to increased plasma concentration of cystine.

The relationship between skin cancers, solar radiation and ozone depletion.

During the period 1957-1984 the annual age-adjusted incidence rate of cutaneous malignant melanoma (CMM) increased by 350% for men and 440% for women in Norway. The annual exposure to carcinogenic sunlight in Norway, calculated by use of measured ozone levels, showed no increasing trend during the same period. Thus, ozone depletion is not a cause of the increasing trend of the incidence rates of skin cancers. The incidence rates of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) increase with decreasing latitude in Norway. The same is true for CMM in Norway, Sweden, and Finland. Our data were used to estimate the implications of a future ozone depletion for the incidence rates of skin cancer: a 10% ozone depletion was found to give rise to a 16-18% increase in the incidence rate of SCC (men and women), a 19% increase in the incidence rate of CMM for men and a 32% increase in the incidence rate of CMM for women. The difference between the numbers for men and women is almost significant and may be related to a different intermittent exposure pattern to sunlight of the two sexes. The increasing trend in the incidence rates of CMM is strongest for the trunk and lower extremities of women, followed by that for the trunk of men. The increasing incidence rates of skin cancers as well as the changing pattern of incidence on different parts of the body is most likely due to changing habits of sun exposure. Comparisons of relative densities of CMM, SCC, LMM and SCC falling per unit area of skin at different parts of the body indicate that sun exposure is the main cause of these cancer forms although other unknown factors may play significant roles as well. For the population as a whole sun exposure during vacations to sunny countries has so far been of minor importance in skin cancer induction.