Lesions of the atlas and axis.

The atlas and axis support the head on the lower cervical spine while providing for considerable mobility in flexion, extension, rotation and lateral bending. The first two vertebrae also function as conduits for the cervical cord and vertebral arteries. Lesions of the atlas and axis, therefore, can cause instability with loss of support and encroachment on the upper cord and vertebral arteries, or less often stiffness with restricted motion. Congenital lesions of the occipito-cervical spine such as occipitalization of the atlas or accessory occipital vertebrae can constrict the upper cord with osseous, dural, or fibrous compression. Such encroachment on the cord at this level produces a varying array of clinical complaints and findings frequently difficult to interpret. Instability of the upper cervical spine can result from congenital, traumatic, inflammatory or neoplastic disruptions of the interlocking mechanism of the atlas and axis. Such factors as the loss of structural integrity of the dens or stretching or tearing of the transverse ligament can permit instability with cord involvement. Because of the serious potential of these lesions, patients with abnormalities of the atlas and axis require prompt recognition and treatment.     

Functional organization of input from areas 17 and 18 to an extrastriate area in the cat

In the cat, areas 17 and 18 have 2 main cortical targets: area 19 and a large region of suprasylvian cortex, referred to here as the Clare-Bishop area (Hubel and Wiesel, 1969). The functional organization of the latter area is not well understood. It seems likely that its organization reflects, in part, the organization of its inputs from areas 17 and 18, and I therefore studied the functional organization of these inputs. Responses were recorded directly from afferents terminating in the Clare-Bishop area after silencing its cells by local injections of kainic acid. Afferents were precisely ordered according to preferred orientation in a fashion resembling the columnar organization of area 17. Preferred direction was also an important organizing parameter. Within sizable regions of cortex, directional preference changed gradually or not at all, while at these regions' boundaries, preferred direction reversed by 180 degrees. Except for a loose grouping according to eye dominance, afferents were not ordered according to other response properties. It is possible that the afferent array is also compartmentalized according to the area of origin of each afferent. Inputs from areas 17 and 18, for example, might end in separate territories in the Clare-Bishop area. However, physiological recording, as well as anatomical experiments, failed to show a clear segregation. This study provides the first direct demonstration that a cortico-cortical pathway can be organized according to particular response properties. While the existence of an organization according to preferred orientation was not surprising, the high degree of order was unexpected. It is also interesting that afferents were well ordered according to 1 parameter, directional preference, that is weakly organized, at best, in area 17.     

Intraocular effects of lipoxygenase pathway products in arachidonic acid metabolism

Arachidonic acid is metabolized through the lipoxygenase pathways to hydroperoxy acids (HPETEs), hydroxy acids (HETEs), and leukotrienes, derivatives of 5-HPETE. 5-HETE, 12-HETE, 15-HETE, and 15-HPETE were injected intracamerally in rabbits and leukotriene B4 (LTB4), leukotriene C4 (LTC4 and leukotriene D4 (LTD4) were injected intracamerally in guinea pigs, rabbits and cats. The effects on the intraocular pressure, aqueous humour protein and leukocyte concentration as well as pupil diameter were assessed. 5-HETE, 12-HETE, 15-HETE and 15-HPETE did not cause any change in the parameters studied. LTB4 caused a marked accumulation of leukocytes in the aqueous humour of cats and rabbits, and to some extent in guinea pigs. LTC4 and LTD4 were ineffective in guinea pigs and rabbits, but caused an intense long-lasting non-muscarinic miosis in cats. Thus, most of the lipoxygenase products tested showed little activity in the anterior segment of the eye, except LTB4, that caused leukocyte infiltration, and LTC4 and LTD4 that caused miosis in cats.     

An experience of virtual leadership development for human resource managers

Problem  

Strong leadership and management skills are crucial to finding solutions to the human resource crisis in health. Health professionals and human resource (HR) managers worldwide who are in charge of addressing HR challenges in health systems often lack formal education in leadership and management.     

Maternal serum androgens in human pregnancy: early increases within the cycle of conception

Previous studies have demonstrated elevations in testosterone and androstenedione initiated within the cycle of conception in pregnant non-human primates, and minimal data in the human support the same picture. In the present study we have investigated a group of patients scheduled for artificial insemination with regular menstrual cycles. For this study all patients provided blood samples at 5 days after the luteinizing hormone (LH) surges and daily through the luteal phase and into early pregnancy (n = 12). Patients who did not become pregnant served as normal controls (n = 9). We have measured 17- hydroxyprogesterone (17-OHP) as a marker of luteal activity not obscured by progesterone within the cycle of conception and testosterone and androstenedione as the major androgens. There were no significant changes in testosterone and androstenedione in the non- pregnant controls, but both testosterone and androstenedione were significantly elevated in the pregnant luteal phase, with the first increases occurring at 15 and 14 days respectively after the LH surge. Three of 12 pregnant patients did not demonstrate a dramatic increase in either testosterone or androstenedione and when examined more carefully a corresponding lack of increase in 17-OHP in those same subjects indicated less than optimal luteal activity, suggesting that these androgens were products of the corpus luteum. In three subjects in which consecutive non-pregnant and pregnant cycles were followed there was a dramatic increase from the non-pregnant luteal phase to the pregnant luteal phase indicating that the more important observation may be the concentrations of androgens in the conceptive luteal phase compared to some baseline, either previous luteal phase or even follicular phase. We have also studied changes in dehydroepiandrosterone sulphate and found that there was no significant contribution to this increase in androgens in early conception. These studies demonstrate a significant increase in both testosterone and androstenedione presumably of ovarian, specifically luteal, origin and that adrenal androgen production is not a factor in these changes.      

Complement activation in stored platelet concentrates

Activation of platelets during preparation and/or storage of platelet concentrates in plastic containers at room temperature has recently been recognized. Many different biologic causes of this activation have been postulated. Activated complement, as a multi-enzyme system, is one of the possible sources of molecules leading to platelet activation. To detect complement activation, functional complement activity and the generation of complement-derived ligands were investigated in platelet concentrate supernatant plasma during 5 days of storage at room temperature. Hemolytic tests for functional classical and alternative pathway activity were used, as was the kinetic test for complement- mediated inhibition of immune complex precipitation. The presence of C3 activation products (C3, C3c, C3dg) was investigated in plasma by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western blotting procedures and on platelets by immunofluorescence. Activation of complement was evident during storage, and C3c and C3d fragments were clearly demonstrated in plasma. The amount of C3d fragments on platelets gradually rose during the first 3 days of storage. At the end of 5 days of storage, the platelets became C3d negative. There are two possible mechanisms of C3d disappearance–shedding and/or further degradation of C3d fragments. Those results indicated that complement activation and the generation of complement-dependent ligand-receptor interaction may be mechanisms for platelet activation in concentrates stored at room temperature.     

A comparative study of whole body DWIBS MRI versus bone scan for evaluating skeletal metastases

Background

Skeletal metastases in oncology patients are identified by Bone scan and/Positron Emission Tomography (PET) scan. But developing countries in the world still lack adequate numbers of these imaging facilities.

Aims

Since Magnetic Resonance Imaging (MRI) is widely available as compared to bone scan or PET scan; a double blind study was undertaken to see if whole body imaging with MRI can give an idea of skeletal metastases.

Method

Diffusion weighted whole body Magnetic Resonance Imaging with background body signal suppression (DWIBS) was performed using 1.5 Tesla (T) MRI on histopathologically proven cases of carcinoma of breast within two months of mastectomy and followed up after a year of surgery. Similarly bone scan was also performed in these patients.

Results

DWIBS MRI demonstrated the presence and extent of bone metastases in 10 out of a total 18 patients included in study while bone scan could demonstrate them in only three cases. A highly significant difference between proportions of the skeletal metastases detected by whole body DWIBS-MRI than that by bone scan at one year follow-up. (i.e. p<0.01, z=2.66) was seen.

Conclusion

DWIBS MRI scores high in demonstrating skeletal metastases. Further comparative studies are necessary to evaluate if DWIBS can replace bone scan or PET scan.     

The use of visual information for planning accurate steps in a cluttered environment

When an observer walks across irregular terrain, he uses vision to plan his steps. How far in advance of each step does he acquire the critical information? We trained cats to walk accurately down a cluttered alley, and then turned out the light in mid-trial. Cats usually continued to walk without error for one to four steps, indicating that they had acquired the information to guide each step well before foot contact.