Quantitative analysis of neocortical gyrencephaly in African elephants (Loxodonta africana) and six species of cetaceans: comparison with other mammals.

This study provides quantitative data on the extent of gyrencephaly in the large-brained African elephant and several species of cetaceans (from smaller to larger brained) in comparison with other mammals. Across three mammalian orders (primates, carnivores, and artiodactyls), the species with the larger brains are more gyrencephalic with each order, exhibiting a specific negative allometry. The African elephant, with a 5-kg brain, has a gyrencephalic index (GI) of 3.

The effect of body fat, aging, and diabetes on vertical and shear pressure in and under a waist belt and its effect on skin blood flow.

Background: Much attention has been given to the effect of pressure on skin blood flow in the feet of older people and people with diabetes. However, little attention has been paid to other areas of the body, especially under the belt at the waist where pressure might be high during body movements associated with exercise. This may be very important when devices such as heat packs are worn during the day under the belt because their safety relies on appropriate skin blood flow to dissipate the heat; in diabetes populations burns have been seen.

The influence of environmental temperature on the response of the skin to local pressure: the impact of aging and diabetes.

Background: To protect against ischemia, pressure-induced vasodilation (PIV) causes an increase in skin blood flow. Endothelial dysfunction, which is commonly found in older patients and those with diabetes, and global temperatures can affect the resting blood flow in skin, which may reduce the blood flow during and after the application of local pressure. The present study investigated the PIV of the skin with exposure to three global temperatures in younger and older populations and those with diabetes.

Multiple stressors and the response of vascular endothelial cells: the effect of aging and diabetes.

Background: The present study examined the effects of local heat, global heat, and the interaction between these two endothelial stressors on the blood flow of the skin of the foot in people who are older and who have diabetes.

Methods: Subjects who were older (mean age 64.2 +/- 5.

The influence of age and diabetes on the skin blood flow response to local pressure.

Background: Previous data has shown that when pressure is applied to the skin of the ankle and on the foot, there is a reactive increase in circulation. In the present investigation, these studies were expanded to look at the response of the hand, back, and foot to applied pressure.

Material/methods: Ten young subjects whose average age was 26.

The influence of ageing on the ability of the skin to dissipate heat.

Background: Ageing reduces the resting blood flow to the skin as well as the blood flow response to thermal stimuli. However, the interrelationships between skin thickness, subcutaneous fat, and skin blood flow in determining the heat dissipation characteristics of the skin have not been investigated.

Material/methods: In the present investigation, 60 male and female subjects were examined with either a continuous 0.

The use of an isometric handgrip test to show autonomic damage in people with diabetes.

Background: Vascular endothelial and autonomic damage are hallmarks of type 1 and type 2 diabetes. However, while much has been published on impairment of the autonomic nervous system, much less has been published on the interrelationship between autonomic damage and exercise.

Study Design: The present investigation examined the change in heart rate, blood pressure, skin and limb blood flow, and sweat during non-fatiguing (10% and 25% maximum strength [maximal voluntary contraction (MVC)]) and a fatiguing isometric contraction (40% MVC) in people with type 2 diabetes compared to younger and older controls to see if a simple handgrip test could show the extent of autonomic damage in people with diabetes.

The effect of the moisture content of a local heat source on the blood flow response of the skin.

Numerous studies have examined the effect of local and global heating of the body on skin blood flow. However, the effect of the moisture content of the heat source on the skin blood flow response has not been examined. Thirty-three subjects, without diabetes or cardiovascular disease, between the ages of 22 and 32 were examined to determine the relationship between the effects of dry vs.

Skin heat dissipation: the influence of diabetes, skin thickness, and subcutaneous fat thickness.

Background: It is well established that diabetes impairs vascular endothelial function. However, the impact of impaired endothelial function on thermal conductivity of the skin, especially in relation to a constant versus a sudden heat stress, has not been established. Further, there is some evidence that aging reduces skin dermal thickness and subcutaneous fat thickness.

The effects of skin moisture and subcutaneous fat thickness on the ability of the skin to dissipate heat in young and old subjects, with and without diabetes, at three environmental room temperatures.

The Pennes model predicts the ability of the skin to dissipate heat as a function of conductive heat transfer and blood flow. Conductive heat exchange may be affected by skin moisture and subcutaneous fat thickness, factors not considered by Pennes. In the present investigation, we sought to expand the Pennes model by examining subcutaneous fat and skin moisture as factors of heat dissipation and their effects on heat exchange and blood flow.

Relationship between multiple stimuli and skin blood flow.

Background: The environment surrounding vascular endothelial cells determines the contractile state of vascular smooth muscle. The present investigation examined the interrelationships between 3 factors known to effect skin blood flow (global heat, local heat and electrical stimulation) to see how they interacted.

Material/methods: Twenty two males participated in 3 series of experiments.

Estimation of the distribution of intramuscular current during electrical stimulation of the quadriceps muscle.

Electrical stimulation is commonly used for strengthening muscle but little evidence exists as to the optimal electrode size, waveform, or frequency to apply. Three male and three female subjects (22-40 years old) were examined during electrical stimulation of the quadriceps muscle. Two self adhesive electrode sizes were examined, 2 cm x 2 cm and 2 cm x 4 cm.

Interrelationships between body fat and skin blood flow and the current required for electrical stimulation of human muscle.

There is variability between individuals in the current needed to elicit a contraction in human muscle with surface electrodes. To understand what might be causing some of this variability, 25 subjects whose average age was 24.4+/-2.

The interrelationships between electrical stimulation, the environment surrounding the vascular endothelial cells of the skin, and the role of nitric oxide in mediating the blood flow response to electrical stimulation.

Background: Electrical stimulation (ES) is a commonly used modality in physical therapy for treating wounds such as diabetic ulcers and pressure sores but the mechanism of its effect on skin blood flow (BF) has not been determined.

Material/methods: Ten subjects were examined during ES of the skin above the quadriceps muscle with biphasic sine wave stimulation at a frequency of 30 Hertz, pulse width 250 microseconds. BF was measured between the electrodes with a Laser Doppler Flow meter.