Acetylcholine receptor agonists stimulate [3H]taurine release from rat sympathetic ganglia

The endogenous taurine content, and the uptake and release of [3H]taurine were examined using the rat superior cervical ganglion. Taurine was found to be one of the most abundant amino acids in the superior cervical ganglion, and the superior cervical ganglion took up [3H]taurine from the incubation medium. Carbachol stimulated the release of [3H]taurine in a concentration-dependent manner with an EC50 of 26 microM and maximal stimulation at 100 microM. The nicotinic receptor agonist 1,1-dimethyl-4-phenylpiperazinium stimulated release with the same potency but with greater efficacy than carbachol. The nicotinic receptor antagonist hexamethonium (1 mM) inhibited carbachol-stimulated release by 74%. (+/-)-Muscarine stimulated release with an EC50 of 8 microM but with a maximal effect of only 32% of that produced by 100 microM carbachol. Oxotremorine, another muscarinic receptor agonist, was ineffective, even at 1 mM. The muscarinic receptor antagonist atropine inhibited carbachol-stimulated release by 30% at 10 microM. These results show that [3H]taurine release from rat superior cervical ganglion can be stimulated by cholinergic receptor agonists. Release is mediated predominantly by a nicotinic receptor and partially by a muscarinic receptor.

Gas chromatographic determination of total fat extracted from food samples using hydrolysis in the presence of antioxidant

A method for the quantitative measurement of total fat in foodstuffs is described. Fat is extracted by hydrolysis and inter-esterified to fatty acid methyl esters for gas chromatographic analysis. Total fat and fatty acid patterns are calculated to comply with the regulations for food label declaration under the Nutrition Labeling and Education Act of 1990. Quantitative recovery of fat from soy oil is obtained in the presence of the antioxidant pyrogallol. Extraction and measurements of fat from a variety of food samples (e.g., cereal, baked goods, dairy, and fish) are also reported, and fat levels ranged from 0.8 to 95% (w/w). Coefficients of variation of < or = 5% demonstrate the efficiency of the method.

The level of GAD67 protein is highly sensitive to small increases in intraneuronal gamma-aminobutyric acid levels

Increases (> 2.5-fold) in GABA levels in rat brain lead to a large decrease in the level of the 67-kDa form of glutamate decarboxylase (GAD67) through a mechanism involving either a change in GAD67 protein stability or a change in GAD67 mRNA translation. In the present study, brain levels of GABA were manipulated by treating rats with various doses of gamma-vinyl-gamma-aminobutyric acid (GVG), and the dependence of total GAD activity and levels of GAD67 and GAD65 protein on the levels of GABA was analyzed. Initial studies showed that both GABA and GAD67 protein levels reached new steady-state levels after two to four daily injections; GABA increased 1.5- (30 mg of GVG/kg) and fourfold (150 mg of GVG/kg), and GAD67 protein content decreased by 30 and 70%. To assess the sensitivity of GAD67 to GABA, rats were injected with eight different doses of GVG (15-150 mg/kg) for 5 days. With increasing doses of GVG, we observed a gradual increase in both whole-tissue and synaptosomal GABA levels and a gradual decrease in GAD67 protein and GAD activity. The levels of GAD65 remained constant at all GVG doses. GAD67 was remarkably sensitive to GABA. The synaptosomal GAD67 level decreased approximately 12% and the whole-neuron GAD67 level decreased approximately 3% for each 1% increase in nerve terminal GABA content when it was close to its physiological level. Our results clearly demonstrate that GAD67 is tightly controlled by intraneuronal GABA, and we suggest that this regulatory mechanism has important implications for the physiological regulation of GABAergic function in the mammalian brain.

Coxsackievirus B4 alters pancreatic glutamate decarboxylase expression in mice soon after infection

The 64,000-M(r) (64K) islet autoantigen, which is considered to be a target protein of beta cell destruction in insulin-dependent diabetes mellitus (IDDM), has recently been identified as the enzyme glutamic acid decarboxylase (GAD). We reported a two- to three-fold increased expression of the antigen in islets of diabetes-susceptible mice following infection with a diabetogenic strain of Coxsackievirus B4 (CB4) at 72-h postinfection (p.i.), a time point of active virus replication in the islets. Most of the infected animals subsequently developed 64K autoantibodies and hyperglycemia. Since the infection increases 64K expression, we have analysed immunoreactive GAD expression with a panel of peptide antisera and two widely-used polyclonal antisera against GAD, and measured GAD activity in the brain, pancreas and islets of these mice. Two isoforms, GAD65 and GAD67, are detected in these tissues from non-infected mice. Both GADs are also present in the infected mice brain at 72 h p.i.; however, their islets contain about three-fold more GAD65, and essentially no detectable GAD67. GAD activity is significantly higher in the brain compared with whole pancreas or islets, and islet GAD activity is higher than pancreas GAD activity. The infection significantly reduces islet GAD activity, but not brain GAD activity. CB4-induced abnormalities in islet GAD expression may play a role in virus-induced diabetes.

Primary extensor tendon reconstruction in dorsal hand defects requiring free flaps

This study reports results in nine patients with extensive loss of soft tissue, extensor tendon, and bone, treated with an emergency free flap for skin cover, primary bone grafts, and tendon grafts passed through individual tunnels in the free flap. Four had a good result, four were fair and one poor. Six patients returned to work, two were not working and one was retired. In select patients, emergency reconstruction of severe extensor tendon injuries appears to produce better function, with fewer operations, a shorter hospital stay, minimal complications, and a shorter period of disability.

Synaptosomal glutamate uptake declines progressively in the spinal cord of a mutant mouse with motor neuron disease

It has been suggested that the degeneration of motor neurons in amyotrophic lateral sclerosis is a consequence of excitotoxicity resulting from a loss of synaptosomal glutamate uptake. The role of synaptosomal glutamate uptake in the pathogenesis of motor neuron disease was studied in the Mnd mouse. Glutamate uptake in spinal-cord synaptosomes declined in parallel with the onset of behavioral deficits in Mnd mice but lagged considerably behind the appearance of pathology in motor neurons. Glutamate uptake did not decline significantly in corpus striatum, and GABA uptake did not change significantly in either spinal cord or striatum. The presence of pronounced histopathological changes before the loss of glutamate uptake suggests that the decline of glutamate uptake is a consequence rather than the primary cause of motor neuron disease in the Mnd mouse.

Beta-adrenergic-agonist stimulated taurine release from astroglial cells is modulated by extracellular [K+] and osmolarity

Astroglial cells are known to release taurine in response to stimulation by a variety of stimuli including beta-adrenergic receptor agonists such as isoproterenol (IPR). The effects of changing osmolarity and extracellular [K+] on IPR-stimulated taurine release were studied with LRM55 cells, a continuous astroglial cell line. IPR-stimulated taurine release decreased almost 8% for each 1% increase in osmolarity, indicating that IPR-stimulated release is highly regulated by the osmolarity of the medium. IPR-stimulated taurine release was greatly enhanced when external [K+] was increased isosmotically by substituting KCl for NaCl but was strongly suppressed when external [K+] was increased hyperosmotically by adding KCl to the medium. Both IPR-stimulated and K(+)-stimulated taurine release depended on external [Cl-]; IPR-stimulated release declined approximately in parallel to K(+)-stimulated release as [Cl-] in the medium was reduced. The high sensitivity of IPR-stimulated release to factors that change cell volume (osmolarity, external [K+], external [Cl-]) is consistent with the idea that IPR, elevated [K+], and reduced osmolarity all elicit taurine release via a single tension-controlled mechanism.

Studies directed toward the design of orally active renin inhibitors. 1. Some factors influencing the absorption of small peptides

A systematic evaluation of structure-absorption relationships using a high throughput intraduodenal rat screening model has led to the delineation of a set of structural parameters that appear to govern bioavailability in a series of peptide-based renin inhibitors. Optimum structures, exemplified by 25 and 41, incorporated a single, solubilizing substituent at the C- or N-terminus combined with a lipophilic P2-site residue. Both inhibitors gave unprecedented plasma drug levels upon intraduodenal administration to monkeys, and the calculated bioavailability for 41 (14 +/- 4%) is the highest reported for any peptidic renin inhibitor.

Effects of increased gamma-aminobutyric acid levels on GAD67 protein and mRNA levels in rat cerebral cortex

Rats were injected with saline or the gamma-aminobutyric acid (GABA) transaminase inhibitor gamma-vinyl-GABA for 7 days and the effects on GABA content and glutamic acid decarboxylase (GAD) activity, and the protein and mRNA levels of the two forms of GAD (GAD67 and GAD65) in the cerebral cortex were studied. gamma-Vinyl-GABA induced a 2.3-fold increase in GABA content, whereas total GAD activity decreased by 30%. Quantitative immunoblotting showed that the decline in GAD activity was attributable to a 75-80% decrease in GAD67 levels, whereas the levels of GAD65 remained unchanged. RNA slot-blotting with a 32P-labeled GAD67 cDNA probe demonstrated that the change in GAD67 protein content was not associated with a change in GAD67 mRNA levels. Our results suggest that GABA specifically controls the level of GAD67 protein. This effect may be mediated by a decreased translation of the GAD67 mRNA and/or a change in the stability of the GAD67 protein.

The use of skin hooks and hypodermic needles in tendon surgery

The skin hook can be used to reduce the need for direct tendon handling and to make the task of tendon repair easier and less traumatic.

Regulation of gamma-aminobutyric acid synthesis in the brain

gamma-Aminobutyric acid (GABA) is synthesized in brain in at least two compartments, commonly called the transmitter and metabolic compartments, and because regulatory processes must serve the physiologic function of each compartment, the regulation of GABA synthesis presents a complex problem. Brain contains at least two molecular forms of glutamate decarboxylase (GAD), the principal synthetic enzyme for GABA. Two forms, termed GAD65 and GAD67, are the products of two genes and differ in sequence, molecular weight, interaction with the cofactor, pyridoxal 5'-phosphate (pyridoxal-P), and level of expression among brain regions. GAD65 appears to be localized in nerve terminals to a greater degree than GAD67, which appears to be more uniformly distributed throughout the cell. The interaction of GAD with pyridoxal-P is a major factor in the short-term regulation of GAD activity. At least 50% of GAD is present in brain as apoenzyme (GAD without bound cofactor; apoGAD), which serves as a reservoir of inactive GAD that can be drawn on when additional GABA synthesis is needed. A substantial majority of apoGAD in brain is accounted for by GAD65, but GAD67 also contributes to the pool of apoGAD. The apparent localization of GAD65 in nerve terminals and the large reserve of apoGAD65 suggest that GAD65 is specialized to respond to short-term changes in demand for transmitter GABA.(ABSTRACT TRUNCATED AT 250 WORDS)

Increased intracellular gamma-aminobutyric acid selectively lowers the level of the larger of two glutamate decarboxylase proteins in cultured GABAergic neurons from rat cerebral cortex

The regulation of glutamate decarboxylase (GAD; EC 4.1.1.15) was studied by using cultures of cerebral cortical neurons from rat brain grown in serum-free medium. About 50% of the neurons in the cultures were gamma-aminobutyric acid (GABA)ergic as determined by two double-staining procedures. Immunoblotting experiments with four anti-GAD sera that recognize the two forms to varying degrees, demonstrated that the cultures contained the two forms of GAD that are present in rat brain (apparent molecular masses = 63 and 66 kDa). GAD activity was reduced by 60-70% when intracellular GABA levels were increased by incubating the cultures with the GABA-transaminase inhibitor gamma-vinyl-GABA for greater than 5-10 h or with 1 mM GABA itself. Neither baclofen nor muscimol (100 microM) affected GAD activity. Immunoblotting experiments showed that only the larger of the two forms of GAD (66 kDa) was decreased by elevated GABA levels. These results, together with previous results indicating that the smaller form of GAD is more strongly regulated by pyridoxal 5'-phosphate (the cofactor for GAD), suggest that the two forms of GAD are regulated by different mechanisms.

Synthesis and release of neuroactive substances by glial cells

Glia contain, synthesize, or release more than 20 neuroactive compounds including neuropeptides, amino acid transmitters, eicosanoids, steroids, and growth factors. The stimuli that elicit release differ among compounds but include neuropeptides, neurotransmitters, receptor agonists, and elevated external [K+]. The mechanisms of release are poorly understood in most cases. Many of the neuroactive compounds are localized in discrete subpopulations of glia. Thus, glia are equipped to send as well as receive chemical messages and appear to be present as classes of cells with differing abilities to communicate chemically. It is possible that glia are as diverse as neurons in their functional characteristics.

Regulatory properties of brain glutamate decarboxylase (GAD): the apoenzyme of GAD is present principally as the smaller of two molecular forms of GAD in brain

The apoenzyme of glutamate decarboxylase [enzyme without bound cofactor, pyridoxal 5'-phosphate (pyridoxal-P)] serves as a reservoir of inactive glutamate decarboxylase (GAD) that can be activated when additional GABA synthesis is required. We have investigated which of two molecular forms of GAD is present as apoenzyme in synaptosomes and in cortex, caudate nucleus, hippocampus, and cerebellum of rat brain. Endogenous glutamate apodecarboxylase (apoGAD) was labeled by incubating extracts of synaptosomes or punches of each region with 32P-pyridoxal-P, followed by reduction with NaBH4, to link covalently the 32P-pyridoxal-P to GAD. Proteins were separated by SDS-PAGE. Punches from all four brain regions and forebrain synaptosomes contained two forms of GAD with apparent Mrs of 63 and 65 kDa as identified by immunoblotting with four antiGAD sera. Punches and synaptosomes contained a major 32P-pyridoxal-P-labeled band with an apparent Mr of 63 kDa that was stained on immunoblots by the antiGAD serum 1440 and the monoclonal antibody GAD-6, and a minor labeled band at 65 kDa that was stained by the 1440, 6799, and K2 antisera. Synaptosomes contained remarkably few other strongly labeled proteins, but punches contained several other labeled bands. Three additional lines of evidence indicate that the labeled 63-kDa protein is apoGAD: (1) it was purified by immunoaffinity chromatography with the GAD-1 monoclonal antibody; (2) it yielded one major labeled peptide when digested with chymotrypsin, and that peptide appeared identical in peptide-mapping experiments to the labeled active-site peptide isolated from chromatographically prepared rat brain GAD; and (3) its labeling was selectively blocked by 4-deoxypyridoxine 5'-phosphate, a competitive inhibitor of the binding of pyridoxal-P to GAD.(ABSTRACT TRUNCATED AT 250 WORDS)

GAD and GABA in an enriched population of cultured GABAergic neurons from rat cerebral cortex

To study various aspects of GABAergic metabolism in an easily accessible system, dissociated cells from postnatal rat cerebral cortex were cultured in a serum-based medium and characterized morphologically and biochemically. The majority (70-96%) of the neurons were GABAergic as determined by three double-labeling procedures. The specific activity of glutamine synthetase in the cultures was 4-5% of the levels in rat astrocyte cultures and intact rat brain, indicating that glia were a minor component. The developmental increase of GABA levels preceded the increase of GAD activity in both immunocytochemical and biochemical experiments. GABA turnover rates also increased with culture age and were 20-30% of GAD activity. Four anti-GAD antibodies, which recognize GAD subunits with differing molecular masses to varying degrees, were used to stain cultured neurons and make immunoblots. Immunoblots showed that the neurons contained two major subunits of GAD which differed in mass by 2 kDa. All four antibodies immunostained both neuronal perikarya and neurites but one antibody, which on the immunoblots predominantly labeled the GAD protein with the lower molecular weight, showed a somewhat more pronounced punctate staining, possibly indicating a principal localization to neurites.

Cofactor interactions and the regulation of glutamate decarboxylase activity

More than 50% of glutamate decarboxylase (GAD) in brain is present as apoenzyme. Recent work has opened the possibility that apoGAD can be studied in brain by labeling with radioactive cofactor. Such studies would be aided by a compound that inhibits specific binding. One possibility is 4-deoxy-pyridoxine 5'-phosphate, a close structural analog of the cofactor pyridoxal 5'-phosphate. The effects of deoxypyridoxine-P on the cyclic series of reactions that interconverts apo- and holoGAD was investigated and found to be consistent with simple competitive inhibition of the activation of apoGAD by pyridoxal-P. As expected from the cycle GAD was inactivated when incubated with glutamate and deoxypyridoxine-P even though cofactor was present, but no inactivation was observed with deoxypyridoxine-P in the absence of glutamate. Deoxypyridoxine-P also stabilized apoGAD against heat denaturation. These effects were quantitatively accounted for by a kinetic model of the apo-holoGAD cycle. Deoxypyridoxine-P inhibited the labeling by [32P]pyridoxal-P of GAD isolated from rat brain. Hippocampal extracts were labeled with [32P]pyridoxal-P and analyzed by SDS-polyacrylamide gel electrophoresis. Remarkably few bands were strongly labeled. The major labeled band (at 63 kDa) corresponded to one of the forms of GAD. Other strongly-labeled bands were observed at 65 kDa (corresponding to the higher molecular weight form of GAD) and at 69--72 kDa. Labeling of the 63- and 65-kDa bands was inhibited by deoxypyridoxine-P, but the 69-72 kDa bands were unaffected, suggesting that the latter were non-specifically labeled. The results suggest that the 63-kDa form of GAD makes up the majority of apoGAD in hippocampus.

GABA synthesis in brain slices is dependent on glutamine produced in astrocytes

The rate of gamma-aminobutyric acid (GABA) synthesis in rat-brain slices was determined by inhibiting GABA transaminase with 20-microM gabaculine and measuring the increase of GABA. Added 500-microM glutamine increased the rate of GABA synthesis by 50%, indicating that glutamate decarboxylase is not saturated in brain slices. The stimulation of GABA synthesis with added glutamine in brain slices was much less than that reported for synaptosomes. The lower stimulation in slices was attributable to astrocytic glutamine production, as the rate of GABA synthesis decreased by 44% when glutamine production was inhibited with methionine sulfoximine. Added glutamine restored the rate to the maximal value observed in brain slices. The rate of GABA synthesis was decreased by 65% in slices pretreated with an inhibitor of glutaminase, and added glutamine did not reverse this effect. These results suggest that glutamine produced by astrocytes is a quantitatively important precursor of GABA synthesis in cortical slices.

Isoproterenol selectively releases endogenous and [14C]-labelled taurine from a single cytosolic compartment in astroglial cells

Taurine is stored in and released from astroglial cells. We have investigated whether taurine is stored in multiple subcellular compartments and whether taurine is released from a distinct pool. Taurine compartmentation was examined by determining the subcellular distribution of labelled taurine and by comparing the specific radioactivities of taurine in cells with that of the taurine released into the superfusion medium during receptor stimulation. Three observations indicate that taurine is found in a single subcellular pool. First, labelled taurine was localized exclusively within a freely exchangeable pool and not sequestered in membrane-bound compartments. Second, endogenous and newly acquired [14C]taurine was released identically by the beta-adrenergic agonist isoproterenol (IPR). Third, measurements of the specific radioactivity of taurine indicate that accumulated [14C]taurine mixes homogeneously with endogenous taurine and both are simultaneously released from the same pool. Chemical analysis revealed net uptake of taurine from the medium during loading and a net loss during IPR-stimulated release. Taurine was selectively released by IPR; five other amino acids found in the superfusion medium were unaffected. One possible mechanism capable of explaining these results is that receptor-mediated taurine release from astroglia occurs by a selective transporter moving taurine from a single cytoplasmic pool to the extracellular space.

The epidemiology and clinical aspects of the hemolytic uremic syndrome in Minnesota

BACKGROUND

The frequency of the hemolytic uremic syndrome, characterized by microangiopathic hemolytic anemia, thrombocytopenia, and renal failure, is increasing. Although Escherichia coli serotype O157:H7 has been implicated as a causative agent, more information is needed about the basic epidemiology and clinical aspects of this syndrome.

METHODS

We conducted a retrospective population-based study of hemolytic uremic syndrome in Minnesota residents less than 18 years of age from 1979 through 1988 to assess trends in disease occurrence, describe the clinical illness, and identify predictors of disease severity and outcome. We also conducted a case-control study of patients with onsets of illness from 1986 through 1988 to examine risk factors.

RESULTS

One hundred seventeen patients were identified. The mean annual incidence increased from 0.5 case per 100,000 child-years among children less than 18 in 1979 (6 cases) to 2.0 cases per 100,000 in 1988 (26 cases) (P = 0.000004). E. coli O157:H7 was isolated from 13 of 28 patients (46 percent) who had stool specimens submitted for testing. For those who presented with typical hemolytic uremic syndrome, an elevated polymorphonuclear-leukocyte count on hospital admission, a shorter duration of prodrome, and the presence of bloody diarrhea were predictive of severe disease. In the case-control study, the patients were more likely to attend large daycare centers (more than 50 children) than were the controls (odds ratio, 10.2; P = 0.03), suggesting that day-care attendance may be a risk factor. On the basis of the population-attributable risk, however, this factor could account for no more than 16 percent of the cases.

CONCLUSIONS

This study provides evidence for an increase in the incidence of hemolytic uremic syndrome, which is probably related to an increased incidence of E. coli O157:H7 infections. Hemolytic uremic syndrome has become an important pediatric and public health problem.

Glutamate-dependent active-site labeling of brain glutamate decarboxylase

A major regulatory feature of brain glutamate decarboxylase (GAD) is a cyclic reaction that controls the relative amounts of holoenzyme and apoenzyme [active and inactive GAD with and without bound pyridoxal 5'-phosphate (pyridoxal-P, the cofactor), respectively]. Previous studies have indicated that progression of the enzyme around the cycle should be stimulated strongly by the substrate, glutamate. To test this prediction, the effect of glutamate on the incorporation of pyridoxal-P into rat-brain GAD was studied by incubating GAD with [32P]pyridoxal-P, followed by reduction with NaBH4 to link irreversibly the cofactor to the enzyme. Adding glutamate to the reaction mixture strongly stimulated labeling of GAD, as expected. 4-Deoxypyridoxine 5'-phosphate (deoxypyridoxine-P), a close structural analogue of pyridoxal-P, was a competitive inhibitor of the activation of glutamate apodecarboxylase by pyridoxal-P (Ki = 0.27 microM) and strongly inhibited glutamate-dependent labeling of GAD. Analysis of labeled GAD by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis showed two labeled proteins with apparent molecular masses of 59 and 63 kDa. Both proteins could be purified by immunoaffinity chromatography on a column prepared with a monoclonal antibody to GAD, and both were labeled in a glutamate-dependent, deoxypyridoxine-P-sensitive manner, indicating that both were GAD. Three peaks of GAD activity (termed peaks I, II, and III) were separated by chromatography on phenyl-Sepharose, labeled with [32P]pyridoxal-P, purified by immunoaffinity chromatography, and analyzed by SDS-polyacrylamide gel electrophoresis. Peak I contained only the 59-kDa labeled protein. Peaks II and III contained the both the 59- and 63-kDa proteins, but in differing proportions.(ABSTRACT TRUNCATED AT 250 WORDS)

Water-soluble renin inhibitors: design of a subnanomolar inhibitor with a prolonged duration of action

Incorporation of nonreactive polar functionalities at the C- and N-termini of renin inhibitors led to the development of a subnanomolar compound (21) with millimolar solubility. This inhibitor demonstrated excellent efficacy and a long duration of action upon intravenous administration to monkeys. While activity was also observed intraduodenally, a comparison of the blood pressure responses indicated low bioavailability. Subsequent experiments in rats showed that, although the compound was absorbed from the gastrointestinal tract, extensive liver extraction severely limited bioavailability.

Stimulation of synaptosomal gamma-aminobutyric acid synthesis by glutamate and glutamine

gamma-Aminobutyric acid (GABA) synthesis was studied in rat brain synaptosomes by measuring the increase of GABA level in the presence of the GABA-transaminase inhibitor gabaculine. The basal rate of synaptosomal GABA synthesis in glucose-containing medium (25.9 nmol/h/mg of protein) was only 3% of the maximal activity of glutamate decarboxylase (GAD; 804 +/- 83 nmol/h/mg of protein), a result indicating that synaptosomal GAD operates at only a small fraction of its catalytic capacity. Synaptosomal GABA synthesis was stimulated more than threefold by adding 500 microM glutamine. Glutamate also stimulated GABA synthesis, but the effect was smaller (1.5-fold). These results indicate that synaptosomal GAD is not saturated by endogenous levels of its substrate, glutamate, and account for part of the unused catalytic capacity. The greater stimulation of GABA synthesis by glutamine indicates that the GAD-containing compartment is more accessible to extrasynaptosomal glutamine than glutamate. The strong stimulation by glutamine also shows that the rates of uptake of glutamine and its conversion to glutamate can be sufficiently rapid to support GABA synthesis in nerve terminals. Synaptosomes carried out a slow net synthesis of aspartate in glucose-containing medium (7.7 nmol/h/mg of protein). Aspartate synthesis was strongly stimulated by glutamate and glutamine, but in this case the stimulation by glutamate was greater. Thus, the larger part of synaptosomal aspartate synthesis occurs in a different compartment than does GABA synthesis.

The role of osmotic pressure and membrane potential in K(+)-stimulated taurine release from cultured astrocytes and LRM55 cells

The effects of [K+]o on taurine release from glial cells were studied with primary cultures of cerebellar astrocytes and with LRM55 cells, a continuous glial cell line. The characteristics of K(+)-stimulated taurine release were virtually identical in the 2 cell types. Both cerebellar astrocytes and LRM55 cells released taurine when stimulated with high-K+ medium prepared by isosmotically substituting KCl for NaCl, but neither cell type released taurine when stimulated with hyperosmotic high-K+ medium prepared by adding solid KCl to control medium. The membrane potential of LRM55 cells was measured by intracellular recording and was insensitive to changes in [K+]o below 20 mM. LRM55 cells released taurine when stimulated with nondepolarizing concentrations of K+ (13-22 mM) if the isosmotically prepared high-K+ medium was used, but the cells did not release taurine when treated with a depolarizing concentration of K+ (50 mM) if hyperosmotic high-K+ medium was used. The time course of K(+)-stimulated taurine release was quite slow, having a time to peak of 10-15 min. Small changes (2.5-10%) in the osmolarity of the medium strongly affected taurine release by cerebellar astrocytes and LRM55 cells. K(+)-stimulated taurine release from both cell types was inhibited when the osmolarity was increased with sucrose or NaCl and was enhanced when the osmolarity was reduced. Similarly, baseline taurine release was suppressed by small elevations in osmolarity and increased by reduced osmolarity.(ABSTRACT TRUNCATED AT 250 WORDS)

The use of semi-permeable membranes for wound management

This paper reports a study comparing bags made from expanded polytetrafluoroethylene semi-permeable membranes and standard plastic bags to treat burns of the hands. There was much less maceration in the PTFE bag, which allowed easier assessment of the extent and depth of burn, and only one daily dressing change was needed. The two types of bag were similar with regard to ease of use, low bacterial contamination and allowing good mobilisation of the hand. Ease of use has meant that a greater number of patients with superficial burns can be treated as outpatients and many are able to do their own daily dressing change, so fewer attendances at the clinic are needed.

Use of a reverse cross-finger flap as a vascularized vein graft carrier in ring avulsion injuries

We describe the use of a reverse cross-finger pedicle flap, previously described by Atasoy, that carries veins used as vascularized grafts to restore venous drainage in ring avulsion injuries. In addition, vascularized soft tissue is provided to cover extensor tendon and exposed bone.

Effects of ethanol and acetaldehyde on collagen synthesis, prostaglandin release and resorption of fetal rat bone in organ culture

We tested the effect of ethanol and its metabolite, acetaldehyde, on bone formation as measured by [3H]proline incorporation into collagenase digestible protein (CDP) and noncollagen protein (NCP), and on DNA synthesis as measured by [3H]thymidine (TdR) incorporation in fetal rat calvaria. We also determined the effects of ethanol and acetaldehyde on prostaglandin E2 (PGE2) release from calvaria and on bone resorption as measured by 45Ca release from fetal rat long bones. Bones were cultured in multiwell plastic dishes (open system) or in stoppered Erlenmeyer flasks (closed system) for 24 to 96 h. In the open system, 1% ethanol (v/v; 172 mM) resulted in a 31% decrease in TdR incorporation at 24 h with no effect on CDP and NCP. At 0.1% (17.2 mM), ethanol increased TdR by 22%, CDP by 73% and NCP by 67% at 24 h, but these effects were not sustained at 96 h. At 24 h, 1% and 0.3% ethanol decreased PGE2 release by 88% and 75% respectively. This effect was sustained for 96 h only at the higher concentration. In the closed system, 0.1% ethanol increased TdR incorporation by 38% at 24 h. However, there was no effect on the labeling of CDP or NCP. Because its boiling point is 21 degrees C, acetaldehyde could only be tested in the closed system. Acetaldehyde markedly inhibited bone metabolism. At 24 h, 0.003% (0.54 mM) to 0.01% (1.79 mM) acetaldehyde caused a dose-related inhibition of TdR incorporation from 23 to 45%. At 0.01% and 0.03% acetaldehyde inhibited proline incorporation into CDP by 48% and 94% and NCP by 40% and 74% respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

An outbreak of shigellosis associated with the consumption of raw oysters

We describe an outbreak of Shigella sonnei infection among 24 persons who had eaten raw oysters in restaurants in southeastern Texas within five days before the onset of symptoms. The oysters in all eight restaurants were supplied by the same dealer, but examination of a routine water sample collected six days before the probable time of contamination showed the waters where the oysters were harvested to be free of fecal contamination, making widespread sewage contamination unlikely. The suspect oysters were traced to a single boat. Stool swabs from that boat's oyster harvesters allowed the identification of one asymptomatic carrier who had a strain of S. sonnei (determined by colicin typing, plasmid analysis, and testing for susceptibility to antibiotics) that was similar to or the same as that infecting the patients. Although the source of this man's infection was unknown, he reported having eaten no oysters. Investigation revealed that 5-gallon (19-liter) pails were used as toilets aboard the oyster boats. Sewage collected in these pails was often dumped overboard into the harvesting area. We conclude that this outbreak of S. sonnei resulted from poor sanitary procedures that probably allowed stool from a carrier to contaminate oysters either just before or after they were taken aboard the boat.

Pyruvate carboxylase deficiency: acute exacerbation after ACTH treatment of infantile spasms

Pyruvate carboxylase deficiency results in congenital lactic acidosis. We report the significant finding in a child with infantile spasms controlled with adrenocorticotrophin hormone (ACTH) but who then developed severe lactic acidosis; pyruvate carboxylase deficiency was subsequently diagnosed. Blood lactate, pyruvate, and alanine levels were elevated, as well as cerebrospinal fluid alanine. Plasma alanine concentration was doubled by ACTH therapy. Fibroblasts contained extremely low pyruvate carboxylase activity. The patient died at 12 weeks of age after recurrent episodes of profound acidosis. At autopsy, the brain manifested cystic degeneration and demyelination. Pyruvate carboxylase deficiency is associated with neonatal onset of acidosis, delayed development, seizures, hypotonia, recurrent profound acidosis, and early death. The dramatic rise in plasma alanine content coincident with ACTH therapy suggest that ACTH played a role in precipitating the catastrophic metabolic acidosis.

Spontaneous and beta-adrenergic receptor-mediated taurine release from astroglial cells are independent of manipulations of intracellular calcium

Stimulation of beta-adrenergic receptors on LRM55 astroglial cells results in cAMP-dependent release of taurine. We have previously demonstrated that extracellular Ca2+ is not required for either spontaneous or receptor-mediated taurine release (Martin et al., 1988b). In the present series of experiments we investigated the relationship between changes in intracellular free Ca2+ ([Ca2+]i) and taurine release. [Ca2+]i was measured using the fluorescent probe fura-2 and was manipulated by changing the concentration of Ca2+ in the incubation medium and by using the Ca2+ ionophore ionomycin. [Ca2+]i was reduced from 150 +/- 95 nM (n = 46) in control medium (containing 1.1 mM CaCl2) to 46 +/- 10 nM (n = 43) in saline containing no CaCl2 and 10 microM EGTA. [Ca2+]i was rapidly elevated to greater than or equal to 1 microM in medium containing 100 microM CaCl2 and 10 microM ionomycin. Taurine release, either spontaneous or stimulated by isoproterenol, was not significantly affected by these manipulations of [Ca2+]i. [Ca2+]i did not change when cells were stimulated with 100 nM isoproterenol in either control saline containing 1.1 mM CaCl2 or in CaCl2-free saline containing 10 microM EGTA. Other secretogogs (serotonin and ethanol) did not cause changes in [Ca2+]i. These data indicate that neither spontaneous or receptor-mediated taurine release from astroglial cells is Ca2+ dependent. However, when cells were preloaded with Ca2+, allowed to recover briefly, and then stimulated with isoproterenol, it was possible to demonstrate transient increases in Ca2+.(ABSTRACT TRUNCATED AT 250 WORDS)

Spontaneous and beta-adrenergic receptor-mediated taurine release from astroglial cells do not require extracellular calcium

Astroglial cells release taurine when stimulated by beta-adrenergic agonists and other neuroactive agents. The Ca2+-dependency of taurine release by an LRM55 astroglial cell line was investigated by removing Ca2+ from the perfusion medium and by using three inorganic and three organic Ca2+-channel blockers (Mn2+, Co2+, Cd2+, verapamil, nifedipine, and diltiazem). Spontaneous release and release stimulated by the beta-adrenergic agonist isoproterenol were not inhibited when cells were perfused with medium containing no added Ca2+ and 10 microM EGTA. Isoproterenol-stimulated taurine release was not blocked when extracellular Ca2+ was completely replaced by Mn2+, Co2+, or Cd2+, nor was it blocked by verapamil, nifedipine, or diltiazem. In fact isoproterenol-stimulated taurine release was increased by 50 microM diltiazem and when Ca2+ was replaced by Co2+. The rate of spontaneous release increased slowly and continually when Co2+ was substituted for Ca2+ but was almost unaffected by substitution of Mn2+ or Cd2+. Application of diltiazem increased spontaneous release significantly, while verapamil and nifedipine appeared to cause small increases. These results indicate that entry of Ca2+ from the extracellular medium is not required for either receptor-mediated or spontaneous taurine release from astroglial cells. Some other changes in the medium did strongly affect release. Both spontaneous and isoproterenol-stimulated release were inhibited by elevated osmotic pressure, and spontaneous release was greatly increased when Ca2+ was completely removed without substituting another divalent cation. Spontaneous release increased when antagonistic metal ions were replaced with Ca2+ and when organic channel blockers were removed.

Inactivation of cyclic AMP-dependent taurine release from astroglia

When astroglial cells are exposed to beta-adrenergic agonists for long periods of time (greater than 20 min), transient increases in taurine release and intracellular cyclic AMP (cAMP) are observed. Three phases of taurine release can be distinguished: activation, inactivation, and an elevated steady state. In this article, we present data describing the relationship between intracellular cAMP levels and inactivation of taurine release. To do this, we compared the apparent first-order rate constants for the inactivation of taurine release (ktau) with the apparent first-order rate constant for the decline of intracellular cAMP (kcAMP). We also measured ktau under experimental conditions that were chosen to provide a wide range of intracellular cAMP concentrations or to stimulate release without the involvement of the beta-adrenergic receptor and adenylate cyclase. When taurine release was stimulated with a saturating concentration of isoproterenol, the inactivation of release was significantly faster than the decline of intracellular cAMP. Furthermore, there were no significant differences in ktau measured under any of the experimental conditions used. Thus, inactivation of taurine release does not involve changes in the activity of the beta-adrenergic receptor and adenylate cyclase, i.e., desensitization, and appears to be independent of the intracellular concentration of cAMP. These results indicate that cAMP-mediated events can be regulated by mechanism(s) in addition to those that control receptor-adenylate cyclase interactions and the synthesis of cAMP.(ABSTRACT TRUNCATED AT 250 WORDS)

Entropy as a factor in the binding of gamma-aminobutyric acid and nipecotic acid to the gamma-aminobutyric acid transport system

Nipecotic acid is one of the most potent competitive inhibitors and alternative substrates for the high-affinity gamma-aminobutyric acid transport system in neurons, but the structural basis of this potency is unclear. Because gamma-aminobutyrate is a highly flexible molecule in solution, it would be expected to lose rotational entropy upon binding to the transport system, a change which does not favor binding. Nipecotic acid, in contrast, is a much less flexible molecule, and one would expect the loss of conformational entropy upon binding to be smaller thus favoring the binding of nipecotic acid over gamma-aminobutyric acid. To investigate this possibility, the thermodynamic parameters, delta G degrees, delta H degrees, and delta S degrees, were determined for the binding of gamma-aminobutyrate and nipecotic acid to the high affinity GABA transport system in synaptosomes. In keeping with expectations, the apparent entropy change for nipecotic acid binding (112 +/- 13 J.K-1) was more favorable than the apparent entropy change for gamma-aminobutyric acid binding (61.3 +/- 6.6 J.K-1). The results suggest that restricted conformation per se is an important contributory factor to the affinity of nipecotic acid for the high-affinity transport system for gamma-aminobutyric acid.

Controlling the medicinal leech

A simple method is presented for applying a medicinal leech (Hirudo medicinalis) to the precise area in which the clinician desires the leeching to take place.

Effects of mild hyperthyroidism on levels of amino acids in the developing Lurcher cerebellum

This study examines the question of whether intrinsically defective mutant Lurcher Purkinje cells, which degenerate during postnatal weeks two to five, followed by later loss of granule cells are competent to respond to neonatal hyperthyroidism, which is known to cause premature differentiation of Purkinje cells and an acceleration of the peak of proliferation in granule cells in normal rodent cerebellum. Both total amounts and concentrations (per mg wet weight) of Tau, Glu, Asp and GABA were assayed as markers of cell function in Lurcher and wild-type mice made very mildly hyperthyroid by feeding nursing dams high-thyroxine food. Tau, which is present in relatively high concentrations in Purkinje cells, was affected by hyperthyroid treatment in the Lurcher in a manner that is most consistent with an acceleration of the degenerative process in Purkinje cells. The acidic amino acids Glu and Asp show later changes and response to hormone which seem to be a reaction to the Purkinje cell pattern, probably in the granule cells. We conclude that the Lurcher cerebellum is particularly sensitive to thyroid hormone, and that it responds to low levels of hyperthyroidism in a distinct way.

Postnatal development of GABA-mediated synaptic inhibition in rat hippocampus

Developmental alterations in GABAergic synaptic transmission were examined physiologically and biochemically in hippocampus of rats from 3 days of age to adulthood. Neither antidromic nor orthodromic stimulation could elicit identifiable inhibitory postsynaptic potentials in CA1 neurons in slices from rats 5 or 6 days of age. In contrast, at this age these stimuli result in large inhibitory postsynaptic potentials in CA3 pyramidal cells. In the latter cells orthodromic stimulation produced a brief monosynaptic excitatory postsynaptic potential which was followed by a large prolonged biphasic hyperpolarization. These signals were strikingly similar to those recorded in 1-month-old rats. In addition, large recurrent inhibitory postsynaptic potentials were produced by antidromic stimulation. By postnatal day 9 similar inhibitory postsynaptic potentials could be elicited in a majority of neurons of the CA1 subfield. As in mature pyramidal cells, application of GABA antagonists, such as bicuculline, selectively eliminated the antidromic inhibitory postsynaptic potential and the first component of the biphasic inhibitory postsynaptic potential generated by stimulation of stratum radiatum. In the CA3 subfield, this blockade of GABA receptors resulted in prolonged afterdischarges in slices from immature but not month-old rats. Measurements of the equilibrium potential and the conductance of antidromic inhibitory postsynaptic potentials in CA3 neurons were very similar when made during the first postnatal week and at 1 month of age. While on days 10-11 the equilibrium potential was very similar to measurements made at these other ages, the conductance was 3-4 times greater. The activity of glutamate decarboxylase, the synthetic enzyme for GABA, was very low at 3 days in hippocampus, and increased until 30 days of age at which time adult values were obtained. By comparison, hippocampal GABA levels were high early in postnatal life. Glutamate decarboxylase activities in microdissected CA3 and CA1 subfields were similar in immature hippocampus. These results demonstrate dramatic differences in the ontogenesis of functional GABAergic inhibitory synaptic transmission in the CA1 and CA3 subfields of rat hippocampus. The late development of GABA-mediated synaptic inhibition in the CA1 subfield could play a role in the susceptibility of immature hippocampus to seizures. However, the large GABA-mediated inhibitory postsynaptic potentials present in the CA3 subfield at the same age have a critical role in dampening neuronal excitability.(ABSTRACT TRUNCATED AT 400 WORDS)

Stability and activation of glutamate apodecarboxylase from pig brain

The stability and activation of glutamate apodecarboxylase was studied with three forms of the enzyme from pig brain (referred to as the alpha, beta, and gamma forms). Apoenzyme was prepared by incubating the holoenzyme with aspartate followed by chromatography on Sephadex G-25. Apoenzyme was much less stable than holoenzyme to inactivation by heat (for beta-glutamate decarboxylase (beta-GAD) at 30 degrees C, t1/2 values of apo- and holoenzyme were 17 and greater than 100 min). ATP protected holoenzyme and apoenzyme against heat inactivation. The kinetics of reactivation of apoenzyme by pyridoxal-P was consistent with a two-step mechanism comprised of a rapid, reversible association of the cofactor with apoenzyme followed by a slow conversion of the complex to active holoenzyme. The reactivation rate constant (kr) and apparent dissociation constant (KD) for the binding of pyridoxal-P to apoenzyme differed substantially among the forms (for alpha-, beta-, and gamma-GAD, kr = 0.032, 0.17, and 0.27 min-1, and KD = 0.014, 0.018, and 0.04 microM). ATP was a strong competitive inhibitor of activation (Ki = 0.45, 0.18, and 0.39 microM for alpha-, beta-, and gamma-GAD). In contrast, Pi stimulated activation at 1-5 mM but inhibited at much higher concentrations. The results suggest that ATP is important in stabilizing the apoenzyme in brain and that ATP, Pi, and other compounds regulate its activation.

Characterization of Alkaloid Uptake by Catharanthus roseus (L.) G. Don Protoplasts

The accumulation of alkaloids by protoplasts of Catharanthus roseus (L.) G. Don var. Little Bright Eye was studied to determine the specificity of uptake and the role of ion trapping in the storage of alkaloids. Accumulation of the indole alkaloids vindoline, ajmalicine, tabersonine, and vinblastine was found to be biphasic, with an initial burst of uptake followed by a slow, prolonged phase of accumulation. The concentration and pH dependence of the initial burst of uptake for vindoline suggested that uptake occurred by simple diffusion. Uptake of nicotine was monophasic, with a half life of 5.2 minutes. The accumulation ratio (Ci/Ce) for nicotine at steady state and for the initial burst of uptake for vindoline and ajmalicine suggested that accumulation was driven by the pH gradient between the vacuole and the external assay medium. The second, sustained phase of uptake of vindoline was sensitive to inhibition by either 20 millimolar NaN(3) or 0.5 millimolar Cu(2+). In azide-treated protoplasts, the uptake for vindoline conformed to the kinetics of simple diffusion, with a half life of 4 minutes. The second phase of uptake for ajmalicine, although sensitive to inhibition by Cu(2+), was insensitive to inhibition by NaN(3). The biphasic uptake of the indole alkaloids was not due to any significant metabolism. It is concluded that accumulation and storage of the indole alkaloids is due only partly to ion trapping of the alkaloids by the low pH of the vacuole lumen. In the case of vindoline, there appears to be a specific energy-requiring uptake that is not seen with nicotine (which is not endogenous to Catharanthus). Accumulation of ajmalicine appears to involve both ion trapping and an azide-insensitive component, which may be due to complexation with organic counterions and phenolics.

Free amino acids in cerebrospinal fluid from patients with infantile spasms

Profiles of free amino acids in cerebrospinal fluid (CSF) were determined by high-performance liquid chromatography for 20 nonneurologic control patients and 12 patients with infantile spasms. Statistical comparisons showed significantly elevated levels of lysine (p less than 0.001) and the excitatory neurotransmitter, glutamate, (p less than 0.01) for the infantile spasms group as compared to the nonneurologic control group. When the infantile spasms patients were subdivided according to the presence or absence of etiologic associations, highly elevated amino acid levels were observed only in CSF from patients of the symptomatic subgroup. The idiopathic subgroup showed levels of free amino acids that were not statistically different from those of the nonneurologic control group. These results indicate that while abnormalities of amino acid metabolism often accompany infantile spasms, no specific pattern of the major free amino acids in CSF appears to be directly related to this seizure disorder. Elevated levels of the excitatory amino acids, aspartate and glutamate, do not necessarily accompany infantile spasms, and in this study were only observed in symptomatic patients.

Step-advancement island flap for fingertip reconstruction

An island flap is described for fingertip reconstruction, based on one neurovascular bundle. The design incorporates the stepladder principle, which ensures the provision of ample skin with full tactile sensibility in the required position, without the risk of longitudinal volar scarring and with good nail support when necessary. Fourteen such repairs have been carried out with satisfactory results and no complications.

Reuse of disposable medical devices in Canadian hospitals

A survey of all Canadian hospitals was undertaken in 1986 to determine the extent of the reuse of disposable medical devices meant for "single use only." It was found that 41% of hospitals regularly reused disposable medical devices, and reuse was significantly higher in hospitals with more than 200 beds. Only 38% of hospitals that regularly reused had written procedures for reuse, and 32% indicated a mechanism for determining the number of times a device was reused. Cost analysis studies had been undertaken by only 29% of regular reusers, and items of respiratory therapy equipment were the most commonly reused devices.