The foreign body response to the Utah Slant Electrode Array in the cat sciatic nerve.

As the field of neuroprosthetic research continues to grow, studies describing the foreign body reaction surrounding chronic indwelling electrodes or microelectrode arrays will be critical for assessing biocompatibility. Of particular importance is the reaction surrounding penetrating microelectrodes that are used to stimulate and record from peripheral nerves used for prosthetic control, where such studies on axially penetrating electrodes are limited. Using the Utah Slant Electrode Array and a variety of histological methods, we investigated the foreign body response to the implanted array and its surrounding silicone cuff over long indwelling periods in the cat sciatic nerve. We observed that implanted nerves were associated with increased numbers of activated macrophages at the implant site, as well as distal to the implant, at all time points examined, with the longest observation being 350 days after implantation. We found that implanted cat sciatic nerves undergo a compensatory regenerative response after the initial injury that is accompanied by shifts in nerve fiber composition toward nerve fibers of smaller diameter and evidence of axons growing around microelectrode shafts. Nerve fibers located in fascicles that were not penetrated by the array or were located more than a few hundred microns from the implant appeared normal when examined over the course of a year-long indwelling period.

Mechanostasis in apoptosis and medicine.

Mechanostasis describes a complex and dynamic process where cells maintain equilibrium in response to mechanical forces. Normal physiological loading modes and magnitudes contribute to cell proliferation, tissue growth, differentiation and development. However, cell responses to abnormal forces include compensatory apoptotic mechanisms that may contribute to the development of tissue disease and pathological conditions. Mechanotransduction mechanisms tightly regulate the cell response through discrete signaling pathways. Here, we provide an overview of links between pro- and anti-apoptotic signaling and mechanotransduction signaling pathways, and identify potential clinical applications for treatments of disease by exploiting mechanically-linked apoptotic pathways.

Positive N-methyl-D-aspartate receptor modulation by selective glycine transporter-1 inhibition in the rat dorsal spinal cord in vivo.

In this study we have employed the selective glycine transporter-1 (GlyT-1) and GlyT-2 transporter inhibitors R-(-)-N-methyl-N-[3-[(4-trifluoromethyl)phenoxy]-3-phenyl-propyl]glycine (1:1) lithium salt (Org 24598) and 4-benzyloxy-3,5-dimethoxy-N-[1-(dimethylaminocyclopently)methyl]benzamide (Org 25543), respectively, and microdialysis perfusion to determine the effect of GlyT transporter inhibition on extracellular amino acid concentrations in the lumbar dorsal spinal cord of the halothane-anaesthetised rat. Reverse dialysis of Org 24598 (0.1-10 microM) induced a concentration-related increase in extracellular glycine accompanied by a progressive increase in citrulline, but not aspartate, glutamate or GABA, efflux. Org 25543 (10 microM) by the same route induced a similar increase in glycine levels without affecting the efflux of other amino acids quantified. To test the hypothesis that the increase in citrulline efflux resulted from activation of the N-methyl-D-aspartate receptor (NMDA-R)/nitric oxide synthase (NOS) signalling cascade, the sensitivity was determined of GlyT-1 inhibition-induced effects to NMDA-R antagonism or NOS inhibition. Co-administration by reverse dialysis of the selective NMDA-R channel blocker MK-801 (0.5 mM) or the selective antagonist of the strychnine-insensitive glycine site, 7-chlorokynurenic acid (1 mM), with Org 24598 (10 microM) did not affect the uptake inhibition-induced increase in glycine efflux, but did significantly attenuate the increase in extracellular citrulline. Similarly, co-administration with Org 24598 of the isoform non-selective and selective neuronal NOS inhibitors Nomega-nitro-L-arginine methyl ester (1 mM) or 1-(2-trifluoromethylphenyl)imidazole (0.2 mM), respectively, prevented Org 24598-induced citrulline efflux with no effect on increased glycine efflux. These data provide evidence that the observed increased in extracellular citrulline is a consequence of positive modulation of NMDA-R, secondary to increased extracellular glycine and support a protective role for GlyT-1 against fluctuations in extracellular glycine uptake at glutamatergic synapses in the dorsal spinal cord. Such a mechanism could be important to NMDA-R-mediated synaptic plasticity in the spinal cord and be of relevance to the clinical usage of GlyT-1 inhibitors.

Excitation by dopamine of rat subthalamic nucleus neurones in vitro-a direct action with unconventional pharmacology.

Recent anatomical and physiological studies have pointed to a functional innervation of the subthalamic nucleus by dopamine. This nucleus has a pivotal role in basal ganglia function and voluntary movement control and the possibility that dopamine, and dopaminergic medication used in Parkinson's disease, might directly influence its activity is of considerable interest. We have evaluated electrophysiologically the action and pharmacology of dopamine on single subthalamic neurones in rat brain slices. Dopamine increased firing rate to up to a mean of 60% in 98% of the 261 neurones tested when examined using extracellular single-unit recording. This excitation was unaffected by the GABA antagonist picrotoxin, and the glutamate receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione, and persisted in a low Ca(2+)/raised Mg(2+) solution, indicative of a direct action, independent of synaptic transmission. Of the 33 cells examined using whole patch-clamp recording, only 13 showed measurable increases in firing rate and/or depolarisations in response to dopamine. Dopamine-responsive cells displayed significantly greater access resistance, suggesting that an unidentified cytoplamic constituent, removed by whole-cell dialysis, was required for the response. Using extracellular recording, the D2-like dopamine receptor agonists quinpirole and bromocryptine, but not the D1-like receptor agonist 1-phenyl-2,3,4,5-tetrahydro-(1H)-3-benzazepine-7,8-diol, also consistently caused an excitation. This was mimicked by the catecholamine releaser amphetamine in 60% of cells tested. However, the dopamine excitation was not significantly reduced either by the D1-like receptor antagonist 7-chloro8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine or the D2-like receptor antagonists (-)-sulpiride, eticlopride and (+)-butaclamol, and the quinpirole excitation was also unaffected by (-)-sulpiride. In contrast, (-)-sulpiride, eticlopride and (+)-butaclamol all abolished the D2-like receptor-mediated inhibition by dopamine of substantia nigra pars compacta neurones. The alpha-adrenoceptor antagonist phentolamine was a weak antagonist of dopamine excitations, but not of those caused by quinpirole. Dopamine excitations also showed weak sensitivity to the 5-HT(2) antagonist ritanserin, but were unaffected by the alpha(1)-adrenoceptor antagonist prazocin and the beta-adrenoceptor antagonist propranolol. The pharmacology of this dopamine excitation is inconsistent with an action on any known catecholamine receptor. However, the effect of amphetamine indicates that an unidentified monamine--possibly dopamine--can be released within the subthalamic nucleus to cause an excitation. The anomalies of its pharmacological characterisation do not strongly support a physiologically relevant direct action of dopamine in the rat subthalamic nucleus.

Ligament replacement for chronic instability of the ulnar collateral ligament of the metacarpophalangeal joint of the thumb.

Static and dynamic procedures have been described for reconstruction of chronic instability of the ulnar collateral ligament of the thumb metacarpophalangeal joint. This study presents a technique of ligament replacement utilizing a free tendon graft passed through two gouge tracks in the proximal phalanx and one in the metacarpal in a manner that closely approximates normal anatomy. We retrospectively reviewed 26 patients who underwent replacement. The follow-up period averaged 4.5 years. In 24 of 26 cases the joint was rendered stable by the replacement and the patient was relieved of pain. Eighty-five percent of the arc of motion was maintained. Postoperative key pinch measured 20 lb. on the operated side compared to 21 lb. on the unoperated side. Results were excellent in 20 patients, good in 4, and fair in 2. This technique successfully restores stability to the ulnar collateral ligament of the thumb metacarpophalangeal joint, diminishes pain and weakness with minimal loss of motion, and holds up over time.

Vibration perception threshold: influence of age, height, sex, and smoking, and calculation of accurate centile values.

Vibration perception threshold (VPT) is increasingly used as a measure of large nerve fibre function in studies of patients with diabetes and in other disorders. In order to establish the influence of age, height, sex, and smoking on VPT values in the normal population and to allow the calculation of accurate age-related percentile charts, 1365 healthy volunteers were studied using a biothesiometer. Measurements were made bilaterally on thumbs, great toes, and over medial malleoli. Multivariate regression analysis confirmed age to be the major determinant of VPT levels at all sites (p less than 0.001). Height was a significant factor for toes and ankles (p less than 0.001) but not thumbs. Sex had no overall effect at toe or thumb but there were differences regarding ankle VPT (p less than 0.01). Log transformation of VPT data produced a linear relationship with age at all sites except at the thumbs in elderly females where there was significant deviation from this model (p less than 0.001) and inverse square root transformation was more appropriate. Smoking had no effect on VPT levels. Age-related centile charts were produced for each site and an easy-to-use computer program was developed to calculate centile values based on raw VPT data, age, height, and sex.

Pubertal development in black and white Johannesburg girls.

A study of the sexual maturation of 362 black and 355 white girls was conducted in Johannesburg in 1976 and 1977. It was found that the first sign of breast development occurs at the same mean age of 11.5 years for both groups, but that white girls develop pubic hair and experience menarche some 9 months earlier than black girls. The menarche in black girls occurs at a younger age than that recorded in the 1960s. The average black girl reaches full maturity later and has a longer maturational period than her white contemporary. In addition the time-span between maturational events in black girls differs from that in white girls.

A longitudinal study of height and weight in black and white Johannesburg children.

A 2-year longitudinal survey of height and weight was conducted on 2,058 Johannesburg children aged 3.5 - 18.5 years. The principal findings were that both height and weight increased more rapidly in white than in black children, and that attained height and weight were significantly greater in whites. The ponderal index (a measure of weight-for-height) was greatest in black females and lowest in black males. Comparison with a survey carried out 12 years previously suggests that there has been an increase in the mean weight of the black population over this period.

Rapid turnover of mannitol-1-phosphate in Escherichia coli.

The phosphate moiety of D-mannitol-1-phosphate in Escherichia coli is subject to rapid turnover and is in close equilibrium with Pi and the phosphorus of fructose-1,6-bisphosphate. These three compounds account for the bulk of 32P label found in cells after several minutes of uptake of 32Pi and mannitol-1-phosphate represents some 30% of this label. Mannitol-1-phosphate occurs in E. coli grown on a variety of carbon sources, in the absence of D-mannitol, and is synthesized de novo even in mutants lacking mannitol-1-phosphate dehydrogenase. The mannitol moiety of mannitol-1-phosphate was not affected during the total chase of the P moiety, which exchanged with a half-life of about 30 s. These findings suggest that the rapid equilibration of the phosphorus is a function of an enzyme, possibly a component of the phosphotransferase system, capable of forming a complex that allows the exchange of the phosphate without the equilibration of the mannitol moiety with free mannitol.

The orthotic treatment of stable ankle fractures.

Fifteen limbs with stable lateral malleolar fractures treated with an adjustable, functional orthosis were compared to 12 limbs managed with short leg walking casts. The limbs managed with the adjustable orthosis were clinically healed at an average of 3.3 weeks with no fracture tenderness and with the ability to bear full weight without pain. Range of motion in the orthotic group at the end of treatment was significantly better than the casted group. Patient compliance was excellent. The advantages of the orthotic treatment include a more physiologic gait pattern due to the rocker bottom sole, ease of application, lighter weight, removability for range of motion exercises and bathing, and adjustability to maintain a good fit as posttraumatic swelling resolves.

An experimental analysis of bivalent interlocking in spermatocytes of the new Triturus vulgaris.

Interlocked bivalents at 1st meiotic metaphase are relatively uncommon in spermatocytes of the newt Triturus vulgaris, but their frequency of occurrence can be significantly increased by subjecting newts to a 24-h heat shock. Newt spermatocytes are sensitive to a heart shock at any stage between the end of premeiotic S and mid to late pachytene. The heat shock does not cause evidence desynapsis, nor does it significantly affect chiasma frequency; therefore the interlocked condition induced in spermatocytes which were subjected to a heat shock when they were in zygotene or pachytene is unlikely to be a consequence of synaptic trapping. By way of explanation it is suggested that a heat shock may cause telomers to detach from the nuclear membrane, or from the synaptonemal complex where the latter is attached to the membrane, thus allowing non-homologous chromonemata to become interwined before chiasmata have formed. If this explanation is valid, it is then further suggested that the recombination process which results in chiasma formation probably takes place in chromosomal regions lying outside the synaptonemal complex, rather than inside, between its 2 lateral elements.

Third system for neutral amino acid transport in a marine pseudomonad.

Uptake of leucine by the marine pseudomonad B-16 is an energy-dependent, concentrative process. Respiratory inhibitors, uncouplers, and sulfhydryl reagents block transport. The uptake of leucine is Na+ dependent, although the relationship between the rate of leucine uptake and Na+ concentration depends, to some extent, on the ionic strength of the suspending assay medium and the manner in which cells are washed prior to assay. Leucine transport can be separated into at least two systems: a low-affinity system with an apparent Km of 1.3 X 10(-5) M, and a high-affinity system with an apparent Km of 1.9 X 10(-7) M. The high-affinity system shows a specificity unusual for bacterial systems in that both aromatic and aliphatic amino acids inhibit leucine transport, provided that they have hydrophobic side chains of a length greater than that of two carbon atoms. The system exhibits strict stereospecificity for the L form. Phenylalanine inhibition was investigated in more detail. The Ki for inhibition of leucine transport by phenylalanine is about 1.4 X 10(-7) M. Phenylalanine itself is transported by an energy-dependent process whose specificity is the same as the high-affinity leucine transport system, as is expected if both amino acids share the same transport system. Studies with protoplasts indicate that a periplasmic binding protein is not an essential part of this transport system. Fein and MacLeod (J. Bacteriol. 124:1177-1190, 1975) reported two neutral amino acid transport systems in strain B-16: the DAG system, serving glycine, D-alanine, D-serine, and alpha-aminoisobutyric acid; and the LIV system, serving L-leucine, L-isoleucine, L-valine, and L-alanine. The high-affinity system reported here is a third neutral amino acid transport system in this marine pseudomonad. We propose the name "LIV-II" system.

Biochemical characterization of a cortexless mutant of a variant of Bacillus cereus.

Previous studies on this cortexless mutant of Bacillus cereus var. alesti indicated that the forespore membrane was the site of the biochemical lesion. This hypothesis is supported by the results presented here: fatty acid composition of sporulating cells of themutant is altered, while in vegetative cells it is comparable to the parent; soluble precursors of peptidoglycan synthesis are accumulated in the mutant, at the time of cortex formation; homogenates of the mutant prepared at the time of cortex formation are unable to incorporate tritiated diaminopimelic acid into peptidoglycan, while homogenates of cells forming germ cell wall do so to an extent comparable to that of the parent; lipid-linked intermediates are formed by the mutant as in the parent. Apparently the mutant is unable either to transfer disaccharide penta-peptide units from the carrier lipid to the growing peptidoglycan acceptor, or to transport lipid-linked intermediates across the forespore membrane.

Spore refractility in variants of Bacillus cereus treated with actinomycin D.

Refractility as indicated by light microscopy, electron microscopy of thin sections, and freeze fracture etching was increased and maintained in a cortexless mutant, A(-)1, of Bacillus cereus var. alesti by the addition during sporulation stage 4 of actinomycin D, which prevents the terminal lysis of spore core associated with sporulation in this organism. (45)Calcium uptake levels and dipicolinic acid (DPA) content were similarly maintained. The location of these components appears to be in the spore protoplast. In the parent A(-), treated with actinomycin D during stage 4, spore particles with similar morphology to the mutant, that is without a cortex and with the characteristics of refractility, were obtained. A major difference in sensitivity to actinomycin D between the processes of (45)Ca uptake and DPA synthesis was observed. Some heat resistance in A(-) made cortexless by actinomycin D could be observed. These studies indicate that the role of the cortex is not to produce the dehydrated refractile spore state but to maintain it.

Sporulation of a cortexless mutant of a variant of Bacillus cereus.

A stage 4 sporulation mutant of a strain of Bacillus cereus var. alesti fails to synthesize a cortex although all other structural components appear normal. With terminal lysis the spore core as well as the sporangium is lysed. Both the uptake of (45)Ca and the synthesis of dipicolinic acid (DPA) are similar to these activities in the parent strain, but these components (DPA and Ca) are lost to the medium with the drastic lysis. The first stage of diaminopimelic acid incorporation, that into germ cell wall mucopeptide, is intact in the mutant; the second stage, that into cortical mucopeptide, is absent. These biochemical studies as well as phospholipid metabolism and freeze-etch analysis suggest the lesion lies in the outer forespore membrane.