Distribution of cartilage molecules in the developing mouse joint.

This study describes the precise spatial and temporal patterns of protein distribution for aggrecan, fibromodulin, cartilage oligomeric matrix protein (COMP) and cartilage matrix protein (CMP) in the developing mouse limb with particular attention to those cells destined to form articular chondrocytes in comparison to those cells destined to form a mineralized tissue and become replaced by bone. Mouse glenohumeral joints from fetal mice (12-18 days post coitus (dpc) to the young adult (37 days after birth) were immunostained with antibodies specific for these molecules. Aggrecan staining defined the general chondrocytic phenotype, whether articular or transient. Fibromodulin was associated with prechondrocytic mesenchymal cells in the interzone prior to joint cavitation and with the mesenchymal cells of the perichondrium or the periosteum encapsulating the joint elements of the maturing and young adult limb. Staining was most intense around developing articular chondrocytes and much less abundant or absent in those differentiating cells along the anlage. CMP showed an almost reciprocal staining pattern to fibromodulin and was not detected in the matrix surrounding articular chondrocytes. COMP was not detected in the cells at the articular surface prior to cavitation but by 18 dpc, as coordinated movement of the mouse forelimb intensifies, staining for COMP was most intense around the maturing articular chondrocytes. These results show that the cells that differentiate into articular chondrocytes elaborate an extracellular matrix distinct from those cells that are destined to form bone. Fibromodulin may function in the early genesis of articular cartilage and COMP may be associated with elaboration of a weight-bearing chondrocyte matrix.

A simplified technique for histologic analysis of central nervous system tissues using glycol-methacrylate plastic coupled with pre-embedding immunocytochemistry.

Paraffin and some plastic embedding techniques will destroy many antigens routinely detected by immunocytochemistry performed on frozen tissue sections. However, morphologic quality is compromised to varying extents in frozen tissue, even with the use of cryoprotection. We report a simple glycol-methacrylate (GMA) embedding technique using vibratome-sectioned mouse brain reacted for tyrosine hydroxylase (TH) immunoreactivity before plastic embedding. In this study we used a short (4 h) simple, GMA embedding procedure which subsequently provided 1.5-5.0 microns sections yielding morphologic details superior to frozen or paraffin sections. Prior to embedding we used a peroxidase-antiperoxidase (PAP) reaction with the 3,3'diaminobenzidine tetrahydrochloride (DAB) chromogen visualizing TH. Several different counterstains were used, demonstrating the versatility of this embedding procedure.

Intermittent medication for schizophrenic outpatients: who is eligible?

The Medication Clinic of a large, urban Mental Health Center was screened for schizophrenic patients eligible for an intermittent medication approach. A total of 112 patients were evaluated, and 39, or 34.8 percent of the sample, met our basic inclusion criteria. No sex or age differences were found for eligibility. Sufficient eligible patients were found to make the intermittent medication approach a useful part of a comprehensive psychopharmacological program for schizophrenia, if the efficacy of the approach is demonstrated in clinical trials.

A neural network approach to the acoustic startle reflex and prepulse inhibition.

Prepulse inhibition (PPI) is the normal suppression of the startle reflex when an intense stimulus is preceded by a weak non-startling prestimulus. PPI is widely used as a model for sensorimotor gating processes and has been shown to be impaired in various neuropsychiatric disorders, including schizophrenia. We have reproduced startle-like behavior and basic PPI modifications with a neural network. The network design was constrained by the attempt (1) to use as few connections as possible and (2) to relate neuroanatomical structures to the simulated network. Performance of the network was evaluated by the behavior of the simulated motor neurons in response to prepulse and pulse stimuli presented with various lead intervals and prepulse intensities. A delayed inhibitory pathway via the pedunculopontine nucleus (PPTg) to the caudal pontine reticular nucleus was found to be a necessary but insufficient requirement to reproduce basic PPI output patterns. Additional requirements included (a) a low threshold at or below the caudal pontine reticular formation, (b) signal amplification in the inhibitory pathway and (c) prolongation of activity in the inhibitory pathway. On the grounds of the most appropriate output patterns of the simulations, we propose a mechanism of sustained activation in the PPTg due to recursive connections. Relations between stimuli, behavior (motor output) and the underlying architecture are discussed. Potentially, this modeling technique can be extended to investigate the impact of drugs and higher brain regions on PPI.

A new method for preparation of undecalcified bone sections.

A new method for preparation of sections of undecalcified bone is described. Samples of ovine bone were embedded in methylmethacrylate and thick-sectioned with a cutoff machine or commercial band saw. Composite slides were prepared by gluing white acrylic to glass using cyanoacrylate glue. Bone sections were glued to the composite slide and then surface polished by grinding or ultramilling. The polished surface of the section was then etched and stained. The techniques described in this paper reduce the time spent grinding or milling sections and improve resolution of surface-stained features of undecalcified bone sections.