Is release of the posterior lamella enough? A cadaveric exploration of posterior component separation techniques.

BACKGROUND: As posterior component separation techniques continue to gain popularity there is uncertainty regarding the degree of fascial advancement afforded by the various techniques. Our study seeks to compare the degree anterior rectus sheath translation seen in full transversus abdominus release compared to simple release of the posterior lamella of the rectus sheath. METHODS: Ten hemi-abdomens in five fresh cadavers were dissected. One hemi-abdomen underwent external oblique release. The contralateral hemi-abdomen underwent retrorectus dissection and initial release of the internal lamella of the internal oblique, followed by full transversus abdominus release. A 4 kg weight was suspended from the fascia and excursion was measured after 1) external oblique separation, 2) posterior lamella of the internal oblique separation, and 3) transversus abdominis separation. RESULTS: Average unilateral hemifascial translation after release of the external oblique provided an average unilateral hemi-fascial translation of 3.38 cm (+/- 0.69). Release of the posterior lamella of the internal oblique provided 3.98 cm (+/- 0.94). After transversus release the average translation increased to 4.31 cm (+/- 0.89). CONCLUSIONS: In this cadaveric study, the majority (92%) of fascial advancement afforded by posterior component separation was achieved by an intermediate step in the transversus abdominus release operation: division of the posterior lamella of the internal oblique.

Tom Gibson, Plastic Surgeon (1915-93): Allograft rejection by the immune system and prediction of free tissue transplantation.

Tom Gibson made enormous contributions to the modern development of Plastic and Reconstructive Surgery. His key 1943 paper 'The fate of skin homografts in man' described the 'second set' phenomenon attributing graft rejection to an immunological phenomenon. Later in his career he visualised the concept of microvascular tissue transplantation and inspired many young surgeons through his various roles of Director of the unit at Canniesburn Hospital, Professor of Bioengineering and President of the Royal College of Physicians and Surgeons of Glasgow.

Tom Gibson, plastic surgeon (1915-93): his life, the second set phenomenon, the host versus graft reaction, and the birth of tissue transplantation.

In the early 1940s Tom Gibson, a member of an MRC unit investigating infection in burns at the Glasgow Royal Infirmary, developed an interest in skin grafting. With Peter (later Sir Peter) Medawar, he described the 'Second Set' phenomenon which in 1943 laid the foundations for tissue transplantation. After war service (1944-47) he was the major force in the development of plastic surgery services in the West of Scotland. His researches at the Universities of Glasgow and Strathclyde earned him an international reputation.

Switch of flow direction in an Antarctic ice stream.

Fast-flowing ice streams transport ice from the interior of West Antarctica to the ocean, and fluctuations in their activity control the mass balance of the ice sheet. The mass balance of the Ross Sea sector of the West Antarctic ice sheet is now positive--that is, it is growing--mainly because one of the ice streams (ice stream C) slowed down about 150 years ago. Here we present evidence from both surface measurements and remote sensing that demonstrates the highly dynamic nature of the Ross drainage system. We show that the flow in an area that once discharged into ice stream C has changed direction, now draining into the Whillans ice stream (formerly ice stream B). This switch in flow direction is a result of continuing thinning of the Whillans ice stream and recent thickening of ice stream C. Further abrupt reorganization of the activity and configuration of the ice streams over short timescales is to be expected in the future as the surface topography of the ice sheet responds to the combined effects of internal dynamics and long-term climate change. We suggest that caution is needed when using observations of short-term mass changes to draw conclusions about the large-scale mass balance of the ice sheet.

Past and Future Grounding-Line Retreat of the West Antarctic Ice Sheet.

The history of deglaciation of the West Antarctic Ice Sheet (WAIS) gives clues about its future. Southward grounding-line migration was dated past three locations in the Ross Sea Embayment. Results indicate that most recession occurred during the middle to late Holocene in the absence of substantial sea level or climate forcing. Current grounding-line retreat may reflect ongoing ice recession that has been under way since the early Holocene. If so, the WAIS could continue to retreat even in the absence of further external forcing.

Protein kinase C activity is reduced in epidermal cells from energy-restricted SENCAR mice.

Female SENCAR mice were pre-fed a control or 40% energy-restricted (ER) diet with energy removed from fat and carbohydrate, or a control, balanced high fat (BHF, with similar energy from fat and carbohydrate), 35% energy restricted from fat (HCR) or 35% energy restricted from carbohydrate (HFR) diet. Epidermal cells were isolated by trypsin digestion for measurement of protein kinase C (PKC) activity, lipid composition or lipid metabolism. Dietary restriction of fat or carbohydrate energy (HFR or HCR group) reduced particulate PKC activity in epidermal cells compared with cells from control mice. The ratio of soluble particulate PKC activity was higher in epidermal cells from mice fed the HCR diet compared with those fed the HFR diet. Diet did not affect soluble PKC activity. Inositol accumulation was measured in the water- or lipid-soluble fractions of prelabeled ([3H]inositol) epidermal cells following a 1-h incubation in media with LiCl. Phosphatidylinositol, inositol biphosphate and inositol triphosphate fractions were more heavily labeled in cells from mice fed the ER diet. Energy restriction did not modify epidermal total lipid or phospholipid composition, but 1,2-diacylglycerol levels were elevated in relation to cell number in epidermal cells from mice fed the ER diet. These data suggest that dietary energy restriction modified PKC activity through a pathway other than alteration in membrane lipid composition or inositol lipid metabolism.

The Occupational Safety and Health Administration's 1990-1991 survey of occupational medical surveillance prevalence and type of current practices.

For all industry divisions, the likelihood that an establishment will have a medical surveillance program increases directly with size of establishment. Among establishments with 1 to 19 employees, only 4% have medical surveillance programs whereas 56% of establishments that employed 250 or more employees had such programs. The most common time to administer medical surveillance is preemployment. The second most common time to conduct medical surveillance is at periodic intervals. The most common component of medical surveillance programs is a general physical examination. This component of medical surveillance is also the most common element of preemployment surveillance, preplacement surveillance, periodic surveillance, preexit examinations, and surveillance for respirator users. Among the group of Phase II establishments, audiometric testing was the most common periodic test identified. Musculoskeletal testing is performed by 45% of firms administering preplacement examinations and by 38% of firms with preemployment examinations. Across all industry divisions, 14% of establishments that have a medical surveillance program also perform biologic monitoring of some employees.

The purposes of occupational medical surveillance in US industry and related health findings.

The primary purpose for implementing medical surveillance is to protect the general health and fitness of all employees. The next most frequent purpose of medical surveillance programs is to determine whether employees have the physical capability to perform their jobs (ie, surveillance to establish "fitness for duty"). The most commonly reported uses of medical surveillance data for establishments across all industry divisions were to implement or change work practices, to implement or change administrative control programs, to modify training programs, and to change personal protective equipment. Eighteen percent of establishments in all size classes and industries that have medical surveillance programs have identified adverse health effects among employees. The health effects most commonly identified by the medical surveillance programs were repetitive trauma, hearing loss, and skin disorders. Programs designed to detect hearing loss and cumulative trauma disorders, are in fact, finding these adverse effects. Among employees actually receiving periodic medical surveillance tests (6 million), 5% were found to have an abnormal test result.

Effects of occupational medical surveillance programs as perceived by respondents to the Occupational Safety and Health Administration's 1990-1991 survey.

Among all establishments perceiving a change as a result of their medical surveillance program, 43% of those employing 250 or more employees did so; for the smallest establishments, this figure drops to 7%. The changes most often perceived, regardless of size class of establishment or industry division, were in employee relations, injury rates, and insurance costs. Establishments with the most comprehensive risk reduction strategies were most likely to attribute benefits to their medical surveillance programs. Benefits of medical surveillance perceived by the Phase II respondents include reduced costs, early detection of medical problems, increased productivity, and a reduced injury or illness rate. Most firms have no systematic method or procedures for evaluating the effectiveness of their medical surveillance programs.

Analysis of blink-induced vertical motion of contact lenses.

This report discusses blink-induced vertical motion of contact lenses as measured with a slit lamp. The motion seen this way represents the displacement of the lens from its position just before a blink to its position immediately after the blink. Motion amplitudes reported in the literature will be discussed in the context of a hypothesis which seeks to account for lens motion by taking into consideration the post-lens tear film characteristics, the diameter of the lens, and the geometry of the anterior segment of the eye.

Further studies of contact lens motion during blinking.

Contact lens motion is felt to be of increasing importance in connection with debris elimination, particularly in extended wear lenses. Thus an improved analysis is made of a simple model for investigating the initial motion of a hard contact lens over the eye during blinking. It is shown that the assumption of constant tear film thickness is a reasonable one. This greatly simplifies the analysis. Various vertical force vs. time variations are considered and lens velocity/time graphs and maximum lens displacement calculated. These are in good agreement with the results of experiment.