Study of the relative timing of shear forces on the sole of the forefoot during walking.

A portable recording device for the measurement of ambulatory longitudinal shear forces in a horizontal plane under the forefoot is described. The timing of the shear forces under 40 feet has been investigated, together with the relationships to each other and to body weight, leg length, cadence, velocity and stride length: they are compared by regression analysis. Shear forces under the forefoot are shown to occur for approximately 73-80% of the stance time. The maximum longitudinal shear forces and the maximum vertical forces are shown to occur at the same time under the first, fourth and fifth metatarsal heads.

The extent of small fibre sensory neuropathy in diabetics with plantar foot ulceration.

Thresholds for cutaneous warming and cooling stimuli were measured in 20 diabetics with neuropathic foot ulcers. All patients had a profound disturbance of sensory perception in the ulcerated foot with complete loss of perception of warming; thresholds for vibration and cooling were highly abnormal in all but two patients. Measurements of thermal threshold were made on both feet in 10 patients: warming was lost bilaterally in all, and cooling was bilaterally absent in six. There was no clear pattern of sensory loss in those diabetics with unilateral foot ulceration to suggest that sensory impairment was the determining factor for the development of a plantar ulcer. Measurements of thermal thresholds were made at additional sites in 13 patients and although the most marked abnormalities of sensation were always found in the feet, in some severe neuropaths, abnormal thresholds on the hand and even the face were demonstrated. Thresholds for warming were invariably more abnormal than thresholds for cooling. The diabetics with neuropathic ulceration in this study all had severe generalised peripheral nerve disease involving large myelinated as well as both small myelinated and unmyelinated sensory fibres. The quantitative evidence on the distribution of sensory loss for thermal sensations supports the hypothesis that the neuropathic process affecting the small myelinated and unmyelinated fibres is length dependent.

Photosynthetic responses to salinity in two clones of Agrostis stolonifera.

The response of photosynthesis, Fe , to salinity was examined in two clones of Agrostis stolonifera, one derived from a salt marsh (SM) and the other from an inland site (IL). The response of young and old leaves was examined over one week of salt treatment and changes in leaf water relations and concentrations of Na+ , Cl- and K+ ions were also monitored. Sodium+ and chloride- concentrations rose much more sharply in the older leaves of both clones and Fe declined to ca. zero by Day 4. Fe in the young leaves of the SM clone was unaffected by salt whilst the young leaves of the IL clone showed a 20% reduction in Fe within 24 h of salt application. This decline was due to a decline in stomatal conductance and a reduction in the photosynthetic capacity of the mesophyll and was associated with a greater accumulation of Na+ and Cl- ions and loss of K+ ions than in the SM clone. The significance of the salt exclusion from the young leaves of the SM clone to its growth on the salt marsh is discussed.

Genetic considerations in human cancer incidence.

Analysis by the methods of genetic demography can offer plausible explanations for the unusual distribution of cancer in an area of high incidence. The important demographic characteristics include inbreeding, founder effect, and racial admixture. Inbreeding would elevate cancer incidence if autosomal recessive genes played a role in cancer etiology. Founder effect would limit this phenomenon to those recessive genes observed in the founding group and result in a cancer spectrum different from that of the surrounding populations. The preference of a racially admixed group for classification as white could result in an excess of cancer patients being classified as white. The population groups in southern Louisiana typify the kind of "human genetics laboratory" that inbred groups offer to investigators of the genetic aspects of cancer.

Acrocephalosyndactyly and partial trisomy 6.

A partial trisomy of the long arm of chromosome 6 was found in an infant with acrocephalosyndactyly (not Apert acrocephalosyndactyly). The mother had a balanced translocation involving the long arms of chromosomes 6 and 10. Other reports of similar aberrations are reviewed.