Sagittal suture as an external landmark for the superior sagittal sinus.

OBJECT: Historically, the sagittal suture has been used as an external landmark to indicate the middle portion of the superior sagittal sinus (SSS). The goal of this study was to verify this relationship. METHODS: The authors examined 30 adult cadavers to reveal the location of the SSS with respect to the sagittal suture. Their findings demonstrated that the SSS is deviated to the right of the sagittal suture in the majority of observed specimens, although the maximum displacement to the right side was never more than 11 mm. CONCLUSIONS: This information should be useful to the neurosurgeon who must be aware of the SSS and its relationship with superficial skull landmarks.

The denticulate ligament: anatomy and functional significance.

OBJECT: The authors conducted a study to examine the detailed anatomy of the denticulate ligaments and to assess their classic role in spinal cord stability within the spinal canal. METHODS: Detailed observation of the denticulate ligaments in 12 adult cadavers was performed. Stress was applied in all major planes to discern when the ligaments would become taut, and at the same time, gross motion of the cord was observed at sites distal to the stresses applied. Tension necessary for avulsion of the ligaments in various areas of the spinal cord was also measured. CONCLUSIONS: These results show that the denticulate ligaments do not inhibit cord motion to such discrete areas of the cord as was once thought. The authors have determined that the ligaments are stronger in the cervical region and that they decrease in strength as the spinal cord descends. These findings are demonstrative of the denticulate ligaments being more resistant to caudal compared with cephalad stresses in the cord. Anterior and posterior motion is constrained by these ligaments but to a limited degree, especially as one descends inferiorly along the cord. Further embryological and functional studies of these ligaments is needed in non-formalin fixed tissues.

Surgical landmarks for the proximal portion of the axillary nerve.

OBJECT: The proximal segment of the axillary nerve (ANp) is often difficult to identify without extensive dissection deep into the axilla. The present study was performed to find reliable surgical landmarks for this nerve. METHODS: Thirty dissections of human cadavers were performed to determine the relationships between the ANp and specific anatomical structures. The authors found that the ANp is consistently located within an anatomical triangle constructed by lines passing between the coracobrachialis and pectoralis minor muscles and the axillary artery. In addition, the ANp was routinely found 4 cm distal to the coracoid process of the scapula. CONCLUSIONS: These findings should assist the surgeon in locating the ANp during brachial plexus reconstruction.

Superficial surgical landmarks for the transverse sinus and torcular herophili.

OBJECT: The purpose of this anatomical study is to identify reliable external landmarks that can be used to determine accurately the lower border of the proximal segment of the transverse sinus (TS). METHODS: The authors used 15 formalin-fixed cadaveric specimens for this project. Various anatomical structures were dissected and measurements of the distance between these structures and the proximal TS were obtained. The data collected in this study demonstrate that the inion is not always a reliable external landmark to use when determining the internal location of the very proximal TS and its drainage into the area of the torcular herophili. In addition, the authors found that the most accurate external landmark to use in reliably estimating the internal placement of the proximal TS is the point of insertion of the musculus semispinalis capitus and not the superior nuchal line. In the present study, this muscle never covered more than 5 mm of the inferior edge of the TS and was found to be a reliable anatomical structure for avoiding the medial segment of the TS. CONCLUSIONS: These findings could aid the surgeon in localizing the TS with various midline approaches to the posterior fossa and the craniocervical junction.

Solvent selection for whole cell biotransformations in organic media.

Although they were used historically as antimicrobial agents, there is a modern requirement to devise organic solvent systems for exploitation in the biotransformation by intact cells of substrates that are poorly soluble in water. Water-immiscible solvents are normally less cytotoxic than are water-miscible ones. While a unitary mechanism is excluded, damage to the membrane remains the likeliest major mechanism of cytotoxicity, and may be conveniently assessed using an electronic biomass probe. Studies designed to account for the mechanisms of action of general anesthetics and of uncouplers parallel those designed to account for the cytotoxicity of organic solvents. Although there are hundreds of potential physical descriptors of solvent properties, many are broadly similar to each other, such that the intrinsic dimensionality of solvent space is relatively small (< 10). This opens up the possibility of providing a rational biophysical basis for the optimization of the solvents used for biotransformations. The widely used descriptor of solvent behavior, log P (the octanol:water partition coefficient), is a composite of more fundamental molecular descriptors; this explains why there are rarely good correlations between cytotoxicity and log P when a wide variety of solvents is studied. Although the intrinsic dimensionality of solvent space is relatively small, pure solvents still populate it rather sparsely. Thus, mixtures of solvents can and do provide the opportunity of obtaining a solvent optimal for a biotransformation of interest.

New materials and technology for cell immobilization.

The choice of the most effective manner in which to operate an immobilized cell system is both complicated and, to some extent, a matter of guesswork. There is increasing awareness of the factors affecting reactor choice, and present work is aimed at making reactor performance more predictable.

New materials and technology for cell immobilization.

The choice of support materials for immobilizing cells is rapidly expanding. The literature that has appeared over the past year suggests that hydrogels will remain the first choice for the forseeable future, even though they are associated with many widely recognized problems. There is increasing interest in the use of tougher polymeric materials, and especially of inorganic ceramic supports. However, the most suitable cell support can be selected only after the process or form of reactor in which it is to be used has been assessed.

Myectomy reduces ileal motility after ileoanal anastomosis.

The hypothesis tested was that myectomy of the distal ileum would produce a long-lasting decrease in ileal motility, and so render single-lumen ileum more suitable for use as a rectal substitute in the course of restorative proctocolectomy, without the need for a pelvic ileal reservoir. Ileal motility, both spontaneous and in response to intraluminal volatile fatty acids (VFA), was studied after proctocolectomy in 25 female adult beagles, at least 6 months after ileoanal anastomosis alone (IAA, n = 6), IAA with myectomy (n = 8), IAA with myectomy and an ileal valve (n = 5) or IAA with a duplicated (J) ileal reservoir (n = 6). VFA were found to stimulate ileal motility significantly in each group. Myectomy significantly reduced the number of ileal contractions (P less than 0.01), the mean amplitude of contractions (P less than 0.05) and the motility index (P less than 0.01). The addition of the valve to myectomy made no significant difference.

Single lumen ileum with myectomy: a possible alternative to the pelvic reservoir in restorative proctocolectomy.

An alternative procedure to construction of a pelvic ileal reservoir was assessed which avoids the need for a pouch, while providing an adequate rectal substitute and good continence. Thirty-six female adult beagles were allotted randomly to undergo total colectomy with (a) ileo-anal anastomosis alone, (b) ileo-anal anastomosis with two 15 cm myectomies, (c) ileo-anal anastomosis and myectomy with an ileo-ileal valve, or (d) ileo-anal anastomosis with a duplicated J pouch. The animals were studied before operation and at 4-weekly intervals for 20 weeks after operation. Mortality rates were similar. Ileal compliance was increased significantly by myectomy from 0.64 ml/mmHg (median, interquartile range 0.49-0.78) after ileo-anal anastomosis alone to 1.65 mmHg (1.16-1.93), P less than 0.01, an increase which was maintained. Ileal capacity was also increased both by myectomy and by the J pouch: ileo-anal anastomosis = 85 ml (75-100 ml), ileo-anal anastomosis and myectomy = 139 ml (116-156 ml), ileo-anal anastomosis and myectomy and ileo-ileal valve = 125 ml (range 85-145 ml), ileo-anal anastomosis and J pouch = 130 ml (range 75-165 ml) (P less than 0.01). Bowel function in the other three groups was markedly superior to ileo-anal anastomosis alone. Mean transit time was significantly less after ileo-anal anastomosis, 5.2 h (2.6-8.2 h) than after both ileo-anal anastomosis and myectomy, 10.5 h (9.6-13.9 h), P less than 0.05 and ileo-anal anastomosis and J pouch, 11.0 h (8.4-13.0 h), P less than 0.05, but addition of an ileo-ileal valve did not produce a further increase in transit time, 12.9 h (range 10.5-14.5 h), P = n.s.. Myectomy of single lumen ileum may be a useful alternative to a pelvic ileal reservoir in restorative proctocolectomy.

Hydrodynamic deposition: a novel method of cell immobilization.

A novel method of cell immobilization is described. The cell support consists of ceramic microspheres of approximately 50-75 microns diameter. The spheres are hollow, having a wall thickness of 10-15 microns and one entrance (ca. 20 microns diameter). The walls are porous with a mean pore size of approximately 90 nm. When a cell suspension (of S. cerevisiae) is passed through a column of such particles, cells are immobilized. Conditions are devised such that the overwhelming majority of cells are held in the central cavity of the support and not between the particles. Provided turbulence is avoided, the distribution of cells along the column length in the steady state is rather homogeneous. The facts that (a) essentially all particles, regardless of orientation, entrap cells, and (b) nonporous particles also entrap cells with high efficiency, indicate that filtration effects are irrelevant and that heretofore unrecognized hydrodynamic forces are alone responsible for the cell immobilization. Cells can be immobilized to high biomass densities, while the hydrodynamic properties of columns containing such immobilized cells are excellent. We describe an on-line electronic method for the real-time measurement of immobilized cellular biomass. Cell growth (so recorded) and metabolism continue to occur in such particles at high rates. Using the glycolytic production of ethanol by S. cerevisiae as a model reaction, volumetric productivities as great as any published are obtained. Thus the "lobster-pot effect" or "hydrodynamic deposition" represents a novel, promising, and generally applicable method of cell immobilization.