Protein status of the elderly as measured by dietary intake, hair tissue, and serum albumin

The nutritional status of 95 Medicare-age individuals was evaluated by dietary intake, physical condition, and components of urine, blood, and hair roots. Correlations between protein intake and five variables (serum albumin, red blood cell count, percentage of anagen hairs, protein content per anagen hair root, and anagen bulb diameter) selected as indicators of protein nutriture were studied. Deficient protein intake correlated positively with the protein content of anagenic hair roots. The protein content of anagenic hair roots correlated positively with the serum albumin levels. Protein intake did not correlate with serum albumin level. It is likely that with the relative depletion of protein stores there is impaired synthesis of hair root protein before a decrease in the synthesis of serum albumin which serves a more vital function.

Dynamic response and transfer characteristics of joint neurons in somatosensory thalamus of the cat

1. The dynamic response of neurons sensitive to knee joint rotation in the cat somatosensory thalamus was studied during sinusoidal variation of joint angle. The input sine waves were applied with a precise voltage-controlled, electromechanical actuator. The average rate of discharge of a single cell was considered as the output parameter. Describing functions of the sensory system were extracted by correlation and spectral analysis techniques. The effects of anesthetic, bias angle, and excursion angle were investigated. Discrete and swept sinusoidal waveforms between 0.1 and 7.0 Hz were used as inputs.2. The majority of joint cells in the thalamus were rapidly adapting and had frequency-response curves that were characterized as highpass filters. Although the major features of the response curves for individual cells were very similar, they could not all be fit with a single transfer function. The describing function of all the rapidly adapting cells averaged together was well fit by a transfer function that could be termed velocity sensitive in the bandwidth between 0.1 and 6.5 Hz. Most of these phasic cells showed a phase-locking tendency, particularly at high frequencies.3. The dynamics of the response for the rapidly adapting cells was relatively independent of anesthetic, bias angle, and excursion angle. Threshold and saturation effects were exhibited by some cells for very small (less than 1 degree) and large (greater than 10 degrees) input amplitudes, respectively. In addition a few (17%) showed a bidirectional response, i.e., responded at both flexion and extension of the limb. The anesthetic had a strong effect in depressing the spontaneous discharge of the cells and seemed to change the character of the tonic response by introducing a bursting component.4. The transfer characteristic of the thalamic cells was found to be a single-pole low-pass filter plus a time delay. The optimized value for the filter was found to have a corner frequency of 6.0 Hz with a time delay of 6 ms.5. Of the knee joint sensitive cells, 17% were slowly adapting or tonic, and more tonic cells were found in the unanesthetized animals. Only one tonic cell was studied in detail, and its dynamic characteristics were similar to that of the slowly adapting joint receptors at low frequencies. In this respect the rapidly adapting and slowly adapting joint cells in the thalamus have strikingly different frequency-response curves, the former curves have a much steeper slope in the magnitude.6. The functional implications of these results and of other recent findings in relation to the probable role of joint receptors in mediating proprioception are discussed.

The effects of x-irradiation on collagen metabolism in rat skin

Collagen metabolism in rat skin and the response to X-radiation are studied during three consecutive hair-cycles. Collagen biosynthesis and turnover, assessed by the hydroxylation of [U-14C]-proline, proceeds as a function of the periodic hair-growth phenomenon. A single X-radiation treatment to the skin does not affect the amino-acid composition of collagen, but reduces the proline hydroxylation capacity of the fibroblasts. The initial damage to the tissue, resulting in a reduced collagen concentration of the skin, particularly noticeable after several hair-cycles, is at least partially responsible for the delayed skin lesions after irradiation.

Effects of diets on cold tolerance and metabolic responses to cold in fasted rats

Effects of high-fat and high-protein diets on cold tolerance in fasted rats were investigated. High-fat diets caused significant increases in body weight, blood-free fatty acids (FFA), ketone bodies and glucose, while high-protein diet did not modify any of these parameters. Rats on high-fat diets that were exposed to cold after clipping exhibited an intermediate cold tolerance as assessed by the rate of fall in colonic temperature between control rats on a standard diet and cold-acclimated rats. The extent of increase of blood FFA and decrease of blood glucose due to cold exposure was less in the high-fat diet group than in control group, but greater than in cold-acclimated group. The lower fall in colonic temperature due to cold exposure was signifcantly associated with less increase in blood FFA and less decrease in blood glucose. In this relation the high-fat diet group was also intermediate between the control and cold-acclimated groups. The high-protein diet did not make any difference in cold tolerance and cold-induced changes in blood metabolites as compared with those in control standard diet, although it resulted in a marked increase in urinary nitrogen excretion. These results indicate that a high-fat diet could exert a significant favorable effect on cold tolerance in fasted rats, but the effect would not be as much as as in cold acclimated rats.

[Energy equilibrium during sleep in ruminants]

Measurements of heat exchanges were made in calves and sheep before and after shearing isolated in a gradient-layer calorimeter which also operates as an open-circuit separation chamber or the head maintained in a hood for respiration exchanges. Sheep with fleeces were in negative heat balance during periods of sleep. In calves and shorn sheep, heat production and heat loss were equally reduced during sleep.

Comparative anatomical studies of the SmL face cortex with special reference to the occurrence of "barrels" in layer IV

In the SmL cortex of mice and rats there are cytoarchitestonically identificable groups of cells -- called barrels -- some of which have been shown to be directly related to whiskers and other sensory hairs on the contralateral face. In this study we have used a comparative approach to determine the incidence and variation of the barrels. The brains of 27 mammalian species have been examined histologically to determine whether barrels exist in layer IV of what is known or likely to be the face area of SmI. Thick sections (50-100 mum) were taken tangential to the pia overlying SmI and stained with thionin. The patterns of facial whiskers were also mapped by dissection of the facial skin. Barrels were seen only in brains of species belonging to three of the seven mammalian orders examined. We have confirmed Weller's ('72) observation of barrels in the Australian brush-tailed possum but have not found barrels in two marsupials from the western hemisphere. Barrels were demonstrable in representatives of four of five rodent suborders examined and in the rabbit. From the study of the rodent brains, a number of trends emerge. (1) The organization of the barrel fields is "dictated" by the organization of the sensory periphery. Animals with five rows of large mystacial (moustache-like) vibrissae have five rows of PMBSF (Posteromedial barrel sub-field) barrels. (2) The barrels are confined to layer IV of (what is known or likely to be) the SmI face area. The pattern and cortical location of the barrel field is consistent among different specimens of the same species. (3) Certain behavioral patterns do not preclude the existence of the barrels. Species which possess well developed visual systems and behaviors (e.g., grey squirrel) and forms which do not actively explore the environment by whisking their vibrissae (e.g., guinea pig) have barrels. (4) Within a given rodent suborder, the barrels become more difficult to identify, as the brains become larger. We have not yet been able to demonstrate barrels in the largest rodent, the capybara.

Response of ventrobasal thalamic cells to hair displacement on the face of the waking monkey

1. In the unanaesthetized, moving monkey, single cell firing patterns in the region of the ventrobasal complex (VB) of the thalamus that respond to facial hair displacement were the basis for a statistical analysis of the effects of tactile, thermal and behavioural stimuli. 2. There were facial hair responses throughout the dorsoventral extent of the ventralis posterior medialis (VPM) nucleus of the contralateral thalamus over a rostro-caudal distance of about 2 mm (Fr. 5.1 to Fr. 7.1). 3. The three different anatomical types of facial hairs that activated thalamic neurones were common facial hairs, circumoral vibrissae and facial whiskers. 4. Displacement of the intermediate length, soft, yellow-brown common facial hairs on the central and lateral face from fields of 1-9 cm2 produced a fast-adapting burst discharge in single thalamic cells in the upper half of the contralateral VPM. 5. Tactile stimuli applied to the short, stiff, white circumoral vibrissae in fields of 0-2-0-9 cm2 along the margins of the upper and lower lips resulted in fast-adapting phasic firing of units in the lower half of the contralateral VPM. Engagement or disengagement of the interlocking hairs of upper and lower lips resulted in increased or decreased, respectively, firing of these thalamic units. 6. Bending a single, long, stiff, black facial whisker extending out from the side of the face resulted in a sustained increased firing of contralateral VPM cells with directional sensitivity. 7. Cells in the ventrobasal thalamus relay mechanoreceptor input from three specialized hair types on the face of the monkey. These somatotopically organized hairy receptive fields are unique, registering response patterns from tactile, thermal and behavioural stimuli. Facial hairs must play an important part in primate feeding, drinking, and oral-exploration.

Mouse-killing by devibrissaed and facially anesthetized rats

18 mouse-killing Long Evans male rats were devibrissaed and facially anesthetized to determine relative importance of facial tactual sensation in detection, pursuit, and killing behavior. With vibrissae clipped plus local anesthesia of the vibrissal pads, all rats attacked and killed mice with efficiency comparable to pretest baseline measures. Results were interpreted as indicating a nonsignificant role of vibrissal sensation in maintenance of this rodent's predatory kill response. Although initial killing may be contingent upon multiple sensory cues, established killing is independent of intact perception of the target.

Surface adaptations of the vertebrate epidermis to friction

Epidermal surfaces in representative vertebrates specialized for lowered or increased friction were studied with the scanning electron microscope. Microvillous and microridged patterns predominate in aquatic vertebrates. In squamate reptiles, the complex and varied ornamentation of the Oberhäutchen functions both in adhesive modifications and in modulating surface reflectivity. Frictional surfaces in birds and mammals are characterized more by anatomical than by cytologic specializations, the detailing of surface cells being mostly a function of turnover rate.

Afferent fibers from mystacial vibrissae of cats and seals

1. Studies of vibrissae of cats and seals revealed minor species-specific differences in functional characteristics of the afferent fibers: vibrissal fibers from the seal showed a significantly higher rate (P smaller than 0.05) and frequency of occurrence (P smaller than 0.01) of spontaneous activity, and a significantly greater percentage (P smaller than 0.01) responded to vibrations greater than 256 Hz. None of these differences could be interpreted as an adaptation to the aquatic environment. 2. Of 455 afferent fibers obtained from the infraorbital nerve, a large proportion (66% in cats and 85% in seals) served vibrissae. A population study of 357 such fibers showed that two-thirds were rapidly adapting (RA) and the remainder were slowly adapting (SA). Neither group displayed preferential directional sensitivity, but for 75% of the individual fibers in cats and 71% in seals, a particular direction elicited maximal response. 3. On the basis of their tuning curves, the RA fibers were divisible into three major groups: insensitive, sensitive, and those with frequency-dependent tuning curves. Single RA fibers provided little information about vibratory stimulus amplitude. However, it is postulated that the range of thresholds in the RA fiber group within each follicle represents a mechanism of encoding the intensity of vibratory stimuli. 4. By contrast, single SA fibers encoded precisely the intensity of steady stimuli. The average fiber conveyed 2.7 bits of information about the magnitude of vibrissal deflections of smaller than 17 degrees (1.5 mm, at 5 mm from skin). 5. Each type of fiber abstracted one or more features from the environment, and conveyed these abstractions by its individual pattern of neural activity. It is postulated that vibrissae provide fine textural information about surfaces.

Transfer processes in animal coats. II. Conduction and convection

According to reliable literature, the thermal conductivities of animal coats range from about 40 to 150 mW m -1 K -1 compared with 25 mW m -1 K -1 for still air at 20 °C. Greater rates of heat transfer in coats can be accounted for by ( a ) radiative transfer between hairs; ( b ) free convection induced by temperature gradients. A simple theoretical analysis of radiative transfer for the special case of a linear temperature gradient showed that in the region where boundary effects are negligible, a radiative conductivity can be estimated from 4 b /3 p where b is the increase of black-body radiant flux per degree Kelvin and p is the interception function defined by Cena & Monteith (1975 a ). Taking account of radiation, the combined molecular and radiative conductivity of coats is expected to fall between 30 and 45 mW m -1 K -1 . Higher values, e.g. for fleece, can be accounted for by free convection. The importance of free convection in a sample of fleece with a diameter of 20 cm was demonstrated by showing that the thermal conductivity was independent of windspeed but increased with the temperature difference between the skin and the air or ( T s — T a ). When the sample was held vertically, the Nusselt number for free convection was given by 1.66 ( T s — T a ) 0.7 . The Nusselt number for a 2 cm fleece was very close to the value expected for a flat plate with the same diameter.

Transfer processes in animal coats. I. Radiative transfer

A silicon cell and a radiometer were used to measure the transmission of short wave (0.4-1 µm) and long wave (3-100 µm) radiation through the coats of sheep and cattle. The reflectivity of the same coats was measured in a spectrophotometer. Measurements of transmission and reflexion were interpreted in terms of a theory of radiation scattering developed (for vegetation) by Cowan (1971), assuming that radiation striking a single hair could be absorbed or scattered either towards or away from the skin. One of the parameters used in the theory is the fraction of radiation intercepted by a ray in unit depth of coat ( p ). For diffuse radiation the appropriate mean value of the interception function ( p̄ ) is approximately twice the value of p for a ray at normal incidence. The value of p̄ ranged from about 9 cm -1 for sheep’s fleece to 36 cm -1 for calf and deer coats. In the short wave spectrum, mean reflexion coefficients for the whole coat ranged from 0.30 for Welsh Mountain Sheep (black fleece) to 0.79 for Dorset Down Sheep (white fleece); corresponding values of the absorption coefficient for individual hairs were 0.02 and 0.002. On the basis of these and related figures, the absorption of solar radiation by the skin surface was evaluated for different combinations of fleece and skin colour. The combination of a light fleece and a dark skin is a trap for solar radiation because the scattering by hair is predominantly forwards.

Transfer processes in animal coats. III. Water vapour diffusion

The diffusion of water vapour through samples of cured and uncured fleece and fibreglass wool was measured. The diffusion resistance of the fibreglass was close to the value expected for still air, i.e. 4.2 s cm -1 per centimetre for samples ranging in depth from 1 to 7 cm. The resistance for natural fleece was similar to the resistance for still air up to a depth of 4 cm but at 7 cm deep was only 2.5 s cm -1 per centimetre. The difference in behaviour of the three materials was interpreted in terms of liquid movement. By appeal to principles of similarity, an equation for sensible heat transfer by free convection from an isolated sample of fleece is used to estimate corresponding rates of latent heat transfer when the skin is wetted by sweat. When a sheep is exposed to air at a temperature close to deep body temperature the exchange of sensible heat between the skin and the air may be a trivial component of the heat balance but provided the skin is wet, the evaporative heat flux from the skin may reach 200-300 W m -2 .

Sex and genetic differences in hair color changes during early childhood

Hair color was assessed routinely from three months to six years for children participating in a longitudinal study of twins: 169 female twin pairs, 161 male pairs, and 60 opposite-sex pairs. Age trends, established by sampling only one number of every pair, showed marked changes in hair color for both sexes, but there was a consistent excess of light-haired males and dark-haired females. Within-pair concordance rates were calculated for same-sex pairs whose zygosity had been determined independently through bloodtyping. A high rate of concordance was found for MZ twins at every age in spite of the general change in hair color, indicating a strong genetic influence in the timing of color changes. The results are discussed in terms of accelerated maturation of females, and the need for genetic models of the inheritance of hair color which are age- and sex-specific.