The dentino-enamel junction revisited

The dentino-enamel junction is not an simple inert interface between two mineralized structures. A less simplistic view suggests that the dentino-enamel junctional complex should also include the inner aprismatic enamel and the mantle dentin. At early stages of enamel formation, fibroblast growth factor (FGF)-2 is stored in and released from the inner aprismatic enamel, possibly under the control of matrix metalloproteinase (MMP)-3. The concentration peak for MMP-2 and -9 observed in the mantle dentin coincided with a very low labeling for TIMP-1 and -2, favoring the cross-talk between mineralizing epithelial and connective structures, and as a consequence the translocation of enamel proteins toward odontoblasts and pulp cells, and vice versa, the translocation of dentin proteins toward secretory ameloblasts and cells of the enamel organ. Finally, in X-linked hypophosphatemic rickets, large interglobular spaces in the circumpulpal dentin were the major defect induced by the gene alteration, whereas the mantle dentin was constantly unaffected. Altogether, these data plead for the recognition of the dentino-enamel junctional complex as a specific entity bearing its own biological characteristics.     

Timing of Diosgenin Appearance in Suspension Cultures of Dioscorea deltoidea

Cycloheximide and compactin were added to cell suspension cultures of DIOSCOREA DELTOIDEA. Cycloheximide inhibited growth and diosgenin biosynthesis completely at 40 mg/l when added during the growth phase. Compactin partially inhibited growth and diosgenin production at 100 microg/l when added during the growth phase. [1- (14)C]-Acetate incorporation into diosgenin was about 20-fold higher when added during the early stages of growth as compared to addition in the stationary phase. Incorporation of [1- (14)C]-acetate into diosgenin was inhibited by compactin only during the early stages of growth. These results indicate the formation of an accumulating intermediary metabolite during the early stages of growth which is transformed into diosgenin when D. DELTOIDEA cells are in the stationary phase.     

Osteogenic potential of culture-expanded rat marrow cells as assayed in vivo with porous calcium phosphate ceramic

It has been established that, when whole marrow is introduced into porous calcium phosphate ceramic, bone forms on the walls of the pores. To extend earlier studies, bone marrow cells derived from the femora of inbred rats were introduced into tissue culture and the adherent cells cultivated, mitotically expanded, passaged, harvested, placed in small cubes of porous calcium phosphate ceramics and grafted into subcutaneous sites of syngeneic rats. Marrow-derived, cultured mesenchymal cells introduced into ceramics showed strong osteogenic potential, with bone forming in the pore regions of ceramics as early as 2 wk after implantation. Osteogenesis could be observed after the eighteenth passage. With increasing passage number, the initiation of osteogenesis and the apparent rate of bone formation declined and the course of osteogenesis was delayed. In the future, it may be possible to culture marrow cells as a source for reparative cells for implantation back into autologous in vivo sites.     

The alien hand sign. Localization, lateralization and recovery

The alien hand sign was first described by Brion and Jedynak as a "feeling of estrangement between the patient and one of his hands." The affected hand frequently shows a grasp reflex and an instinctive grasp reaction as well as elements of what Denny-Brown referred to as a "magnetic apraxia" associated with frontal lobe damage. Most notably, however, the affected hand is observed to perform apparently purposive behaviors that are perceived as being outside the volitional control of the patient. The patients interpret the behavior of their own affected limb as being controlled by an external agent. They do not feel that they are initiating or controlling the behavior of the hand and often express dismay at the hand's "extravolitional" activity. The patients attempt to control behavior of the alien hand with the unimpaired hand by forcibly restraining the affected limb, an act that may be termed "self-restriction." In this paper, we report an additional four cases of alien hand sign in right-handed subjects: two involving the right hand and two involving the left hand. In each case, the clinical findings were associated with extensive unilateral damage of the medial frontal cortex of the hemisphere contralateral to the affected hand. Furthermore, the alien movement gradually disappears over the course of 6-12 months after the stroke. These clinical case studies are presented and discussed in the context of the "dual premotoer systems hypothesis," an anatomicophysiological model that proposes that action is organized by two separate but interactive premotor brain systems corresponding to evolutionarily defined medial and lateral cortical moieties. It is hypothesized that the alien mode behavior results from unconstrained activity of the lateral premotor system in the damaged hemisphere. The residual volitional control in the limb occurs through the activity of the intact medial premotor system of the ipsilateral hemisphere. Recovery may occur through extension of these ipsilateral control mechanisms by compensatory changes in subcortical systems controlling hemispheric activation associated with adaptive behavior. This observation may be important in understanding mechanisms involved in motor recovery after stroke.     

Regional cerebral blood flow and cognitive function in Huntington's disease and schizophrenia. A comparison of patients matched for performance on a prefrontal-type task

Matching patients with etiologically distinct but clinically overlapping cognitive disorders on performance of a regionally specific neuropsychological task is a novel and potentially powerful approach to highlighting differences in the pathophysiological mechanisms of impaired cognition. We used this strategy to compare patients with Huntington's disease (HD) and schizophrenia (SC), disorders that share similarities in cognitive impairment. Patients were matched on the basis of performance on the Wisconsin Card Sorting test of "prefrontal" function, after which neuropsychological test data and regional cerebral blood flow data were determined while patients who performed the Wisconsin Card Sorting test were examined. Patients with HD performed worse on visuospatial tasks and recall memory than did patients with SC, although Wechsler Adult Intelligence Scales-Revised IQ and Wechsler Memory Scale memory quotients were equivalent. These differences could not be attributed to differences on the index task, the Wisconsin Card Sorting Test. Patients with HD and SC exhibited a double dissociation in regional cerebral blood flow. The patients with SC had relatively low frontal and high parietal flows, while patients with HD exhibited the reverse of this pattern. Thus, the regional cerebral blood flow and neuropsychological findings in this study appeared to demonstrate that the single final common cognitive impairment of executive function in HD and SC is associated with two markedly dissimilar pathophysiological states.     

Audit of intensive care unit admissions from the operating room

An audit of 265 intensive care unit (ICU) admissions from the operating room was performed for the year 1991. In a quality assurance exercise we identified 34 unanticipated ICU admissions (UIAs) by a retrospective peer review of the medical charts. Of these UIAs, 16 were deemed predictable and seven preventable. Five of the seven potentially preventable UIAs were judged to have had inappropriate intravenous fluid management. This has prompted changes in our education programme. In an assessment of our resource management, we evaluated prospectively collected data on the Apache II scores on the day of admission, the incidence of ICU-specific interventions, length of stay in ICU, and outcomes. ICU-specific interventions were not initially required in 36% of admissions and these patients had a low risk (1.1%) of eventually requiring ICU-specific interventions. In comparison with patients requiring ICU-specific interventions, they had lower Apache II scores (10.2 vs 13.1), shorter ICU stays (medians of one vs two days), lower ICU mortality (0 vs 8.2%), P < 0.05, but hospital mortality was not different (7.4 vs 15.3%). This audit has prompted re-organisation of our intensive care services, so that patients not requiring ICU-specific interventions will be managed in an intermediate care area with nurse.patient ratios of 1:3 or 4, in comparison with 1:1 or 2 ratios in the intensive care area.