Biomedical subjects

A Barber

Publications and source records attributed to A Barber.

At least 73 records · Page 4Linked to original sources

PubMed1991

Diabetes impairs the late inflammatory response to wound healing.

Diabetes mellitus is recognized as a risk factor for compromised wound healing. This study examines leukocyte infiltration and the appearance of tumor necrosis factor-alpha (TNF) and IL-6 in wound chambers implanted in normal and streptozotocin-induced diabetic mice. Perforated silicone wound chambers containing a strip of polyvinyl alcohol sponge were implanted along the flanks of normal and diabetic mice. Wound fluid aspirated from the chambers 1, 3, and 7 days following implantation was analyzed for the total number of leukocytes and TNF and IL-6 levels. While the number of leukocytes in the wound fluid was similar on Days 1 and 3 following implantation, there were significantly fewer inflammatory cells in wound fluid from diabetic animals (13.8 X 10(6)/ml) than in wound fluid from normal animals (28.5 Z 10(6)/ml) on Day 7 following implantation. TNF levels in the cell-free exudate fluid were similar between the two groups on all days examined. IL-6 levels were similar on Days 1 and 3 following implantation between the two groups, but there was significantly more IL-6 in wound fluid from normal animals (10,998 U/ml) than in wound fluid from diabetic animals (2096 U/ml) on Day 7 following implantation. Histologic evaluation of chambers 8 days following implantation revealed decreased neovascularization and less organization of granulation tissue. These data suggest that delayed healing in diabetes is associated with altered leukocyte infiltration and wound fluid IL-6 levels during the late inflammatory phase of wound healing.

Animals↗

PubMed1991

On the multiplicity of glucose analogues transport systems in rat intestine.

A study has been made to test if in intact epithelium of rat jejunum with in vivo and in vitro techniques, two transport systems for glucose and analogues, as those characterized in brush border membrane vesicles from guinea pig jejunum, are operative. The passive and mediated transport components of the D-galactose and methyl alpha-D-glucopyranoside intestinal absorption and the mutual inhibitions between both substrates at different relative concentrations have been measured. The effects of cytochalasin B and low temperature (20 degrees C) on the transport in vitro have also been observed. Cytochalasin B inhibits galactose and alpha-methylglucoside transport at 0.1 and 40 mM concentrations in similar percentage. Transport of 0.1 and 40 mM galactose is inhibited 61 and 77% respectively by low temperature (20 degrees C). The transport of galactose and alpha-methylglucoside could be explained by the assumption of just one transport system shared by both substrates, with a higher affinity for alpha-methylglucoside. Operation of two systems was not demanded by the results, due perhaps to species specificity or to the distorting action of the unstirred water layers.

Animals↗

PubMed1991

Effect of DTNB on rat intestinal galactose transport in vivo.

The effect of the non-penetrating reagent of -SH groups: acid 5,5'-dithiobis (2-nitrobenzoic), (DTNB), on 1 mM galactose absorption in rat intestine in vivo has been studied. DTNB inhibits sugar absorption in about 35%, which is due to an action on the mediated transport component, but without affecting the diffusional passive one. Consequently it does not modify galactose absorption in the presence of 0.5 mM phlorizin or that of the non-transportable sugar 2-deoxy-glucose. Galactose transport inhibition appears after a not longer than 5 min preexposure period and it remains constant at least up to 30 min. The inhibitory effect does not vary between 0.1 and 1 mM DTNB and it reverses completely with 0.5 mM dithioerythritol. Protection by excess of substrate has not been observed. Results show that DTNB affects sulfhydryl groups very probably located at the luminal side and related to the proteins of the cotransport system.

Animals↗

PubMed1991

Operations for Wolff-Parkinson-White syndrome.

Forty-six patients with symptomatic tachycardia underwent operations to divide 55 atrioventricular accessory pathways. Mean age was 29 years (range 11 to 63). Ten patients (22%) had associated cardiac disease, including two with a congenital diverticulum of the coronary sinus and six (13%) who had concomitant surgical procedures. A bipolar hand-held electrode was used in 22 operations, and simultaneous multisite mapping in the last 24 operations. Ten patients (22%) had multiple accessory pathways. A modified endocardial approach was used. The overall patient success rate was 93% with 91% to 93% of accessory pathways successfully divided. The perioperative morbidity was 17%. There were two reoperations. There were no early or late deaths. Patients have been followed up for a mean of 16 months. There were five recurrences of preexcitation (two early, three late). Two of these patients (both with a congenital diverticulum of the coronary sinus) had reoperation. One patient had late recurrence of atrial fibrillation. Operation for the Wolff-Parkinson-White syndrome has a high probability of success with a low operative risk.

Adolescent↗

PubMed1990

Identification of a novel tumor necrosis factor alpha/cachectin from the livers of burned and infected rats.

Tumor necrosis factor alpha (TNF-alpha)/cachectin is a monocyte/macrophage-derived cytokine implicated as a proximal mediator of many of the catastrophic host responses to infection or endotoxin. However, circulating levels of TNF-alpha/cachectin have only been episodically detected in hospitalized patients with life-threatening bacterial infections. In the present report, increased quantities of immune-reactive TNF-alpha/cachectin were recovered from the livers of rats 3 days following a lethal burn and infection. Two species of TNF-alpha/cachectin were detected, one of approximately 29 kd and the other 17 kd, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. In murine peritoneal macrophages and rat Kupffer cells stimulated in vitro with endotoxin, a 29-kd cell-associated and 17-kd secreted form were also detected. We conclude that the increased appearance in vivo of a 29-kd form of TNF-alpha/cachectin from the livers of lethally burned and infected rats represents a novel cell-associated form of the protein.

Animals↗

PubMed1989

Catheter ablation of the atrioventricular junction in patients with refractory atrial arrhythmias.

Twelve patients with refractory symptomatic atrial arrhythmias were evaluated for closed chest ablation and permanent pacemaker implantation. This was successful in nine of the 11 patients in whom ablation was attempted. Two of these nine patients required two separate ablative procedures. Three patients underwent open surgical ablation. Electrical ablation had failed in two of these patients and had not been undertaken in the remaining patient (inadequate His recording). The mean His amplitude and delivered energy levels were not significantly different between the two groups. Complications occurred in three patients and were minor. Because ventricular arrhythmias and late sudden death are recognised complications in a minority of patients undergoing closed chest ablation of the A-V junction it should be restricted to patients with symptomatic atrial arrhythmias who have failed maximal medical treatment.

Adult↗

PubMed1989

Antinociceptive effects of the 5-HT2 antagonist ritanserin in rats: evidence for an activation of descending monoaminergic pathways in the spinal cord.

The antinociceptive properties of the 5-HT2 antagonist ritanserin have been investigated in the writhing test using rats implanted with chronic lumbar catheters. The antinociceptive action of 15 mg/kg ritanserin applied subcutaneously (s.c.) was powerfully inhibited by the intrathecal (i.t.) application of ritanserin (50 nmol), methysergide (15 nmol), yohimbine (20 nmol), alpha-flupenthixol (20 nmol) or naloxone (15 nmol), but not atropine (30 nmol), at doses which themselves produced no change in nociceptive threshold. It is concluded that ritanserin acts supraspinally to activate pain-modulating descending serotonergic, noradrenergic, dopaminergic and possibly opioidergic pathways, while spinopetal cholinergic pathways do not seem to be involved. Hyperalgesic effects of s.c. ritanserin following the i.t. application of methysergide or yohimbine were interpreted in terms of the co-release of an excitatory transmitter, possibly substance P, from descending serotonergic and noradrenergic nerve fibres. The supraspinal mechanism by which ritanserin activates spinopetal pathways and its dependence on 5-HT2 receptors have not yet been established.

Animals↗

PubMed1989

Comparative X-ray crystallographic evidence for a beta-bend conformation as the active structure for peptide T in T4 receptor recognition.

A sequence similarity has been found between two segments of endothiapepsin (acid proteinase, 2APE), bovine pancreatic ribonuclease A, and peptide T, a segment of the gp120 protein of human immune deficiency virus (HIV), which has been implicated in blocking viral attachment to the T4 receptor. The two similar sequences of the acid proteinase enzyme are Leu-Ile-Asp-Ser-Ser-Ala-Tyr-Thr (residues 169-176) and Tyr-Thr-Gly-Ser-Leu-Asn-Tyr-Thr (residues 175-182). Since the X-ray crystallographic structures of the acid proteinase and ribonuclease are known, it has been possible to determine whether the three-dimensional structures of the segments are similar. Portions of both the segments of acid proteinase are directly superimposable on the structure of the RNase A 19-26 segment. The fact that the three similar sequences from two completely unrelated proteins give rise to almost identical structures raises the possibility that these segments may be involved in nucleating the folding of these proteins. In addition, this provides further support for the concept that the octapeptide sequence of peptide T of HIV, which is also similar in sequence to the 19-26 sequence of RNase A, is also structurally similar to these residues, which adopt a beta-bend conformation. Furthermore, comparison of similarities and differences in the structure of these similar sequences provides an explanation for alterations in the biological activity of various truncated or substituted derivatives of peptide T and additional confirmation of the structural requirements for peptide T in T4-receptor recognition.

Animals↗

PubMed1989

Starvation leads to decreased levels of mRNA for myofibrillar proteins.

Malnutrition is a common complicating factor in surgical illness. To investigate the cellular changes and mechanisms responsible for the protein wasting associated with nutritional deprivation, Sprague-Dawley rats were subjected to total protein-calorie starvation for 3 (n = 12) or 5 days (n = 12) and compared to freely fed animals monitored for 3 (n = 8) or 5 (n = 8) days. Gastrocnemius protein and RNA content and levels of mRNA coding for the myofibrillar proteins myosin heavy chain, myosin light chain, and alpha-actin were measured. Starvation resulted in a significant decrease in gastrocnemius mass and protein content, and was associated with decreases in mRNA levels for the three myofibrillar proteins assayed. We conclude that changes in mRNA levels for these proteins likely contribute to the loss of peripheral protein which occurs during total nutritional deprivation. In addition, the changes in mRNA levels for these three structural proteins appear to be coordinate, suggesting that transcription of no single myofibrillar protein is rate-limiting in the regulation of skeletal muscle protein content.

Actins↗

PubMed1989

Effects of small insertions on the RNA-dependent DNA polymerase activity of HIV-1 reverse transcriptase.

We have described a strain of Escherichia coli that expresses high levels of enzymatically active, soluble, HIV-1 reverse transcriptase (A. Hizi, C. McGill, and S. H. Hughes, Proc. Natl. Acad. Sci. USA, 85, 1218-1222, 1988). The clone can be used as a source of the enzyme and to generate and characterize mutations in the reverse transcriptase. We have made a series of small in-frame insertions in the region that encodes the reverse transcriptase. When the mutant plasmids are reintroduced into E. coli, they induce the synthesis of mutant forms of the enzyme. With one interesting exception, the reduction in RNA-dependent DNA polymerizing activity seen in the mutants correlates well with the degree of sequence conservation among the various reverse transcriptases. Insertions into regions that are evolutionarily conserved have a more profound effect on RNA-dependent DNA polymerase activity than do insertions into regions that are less conserved. The exception to this simple correlation is that a small insertion into the region encoding RNase H gives rise to a protein with essentially no RNA-dependent DNA polymerase activity. We suggest that this mutation may affect the ability of the reverse transcriptase to fold properly, which might explain our previous observation that small carboxyl terminal deletions profoundly affect RNA-dependent NAD polymerase activity.

Binding Sites↗

PubMed1989

Total parenteral nutrition and bowel rest modify the metabolic response to endotoxin in humans.

Intestinal mucosal atrophy, as induced by total parenteral nutrition (TPN) and/or prolonged bowel rest, is hypothesized to enhance bowel endotoxin (LPS) translocation and may alter host responses to infection. To examine the effect of TPN-induced bowel atrophy on the response to LPS, 12 healthy volunteers were randomized to receive either enteral feedings (ENT, n = 6) or seven days of TPN without oral intake (TPN, n = 6). Enteral or TPN feedings were terminated 12 hours before the study period when a constant dextrose infusion (50 mg/kg/hour) was initiated and continued throughout the subsequent study period. After placement of arterial, hepatic vein, and femoral vein catheters, metabolic parameters were determined before and for six hours after an intravenous E. coli LPS challenge (20 U/kg). Subsequent peak levels of arterial glucagon (ENT, 189 +/- 39 pg/mL; TPN, 428 +/- 48; p less than 0.01), arterial epinephrine (ENT, 236 +/- 52 pg/mL; TPN, 379 +/- 49; p less than 0.05) and hepatic venous cachectin/tumor necrosis factor (cachectin/TNF) (ENT, 250 +/- 56 pg/mL; TPN, 479 +/- 136; p less than 0.05) were significantly higher in the TPN group than in the ENT group. The extremity efflux of lactate (ENT, -16 +/- 4 micrograms/min-100cc tissue; TPN, -52 +/- 13; t = 2 hours; p less than 0.05) and of amino acids (ENT, -334 +/- 77 nmol/min-100cc tissue; TPN, -884 +/- 58; t = 4 hours; p less than 0.05) were higher in the TPN subjects after the endotoxin challenge. Circulating C-reactive Protein (CRP) levels measured 24 hours postendotoxin were also significantly higher in the TPN subjects (ENT, 1.7 +/- 0.2 mg/dL; TPN, 3.2 +/- 0.3; p less than 0.01). Hence the counter-regulatory hormone and splanchnic cytokine responses to LPS were enhanced after TPN and bowel rest. This is associated with a magnified acute-phase response, peripheral amino acid mobilization, and peripheral lactate production. Thus antecedent TPN may influence the metabolic alterations seen in infection and sepsis via both an exaggerated counter-regulatory hormone response as well as an enhanced systemic and splanchnic production of cytokines.

Adult↗

PubMed1989

Cachectin/TNF or IL-1 alpha induces cachexia with redistribution of body proteins.

Macrophage secretory products are suspected to participate in the severe lean tissue wasting related to chronic illness. The protein metabolic effects of chronic, 7-day cachectin/tumor necrosis factor (cachectin) or interleukin 1 alpha (IL-1 alpha) administration in vivo were studied in male Wistar rats that were 1) freely fed, 2) pair fed, 3) total protein and calorie starved, 4) twice daily lipopolysaccharide (LPS) administered, 5) twice daily cachectin administered, and 6) twice daily IL-1 alpha administered. LPS, cachectin, or IL-1 alpha administration produced anorexia; weight loss in these groups was comparable to respective pair-fed animals. However, LPS, cachectin, or IL-1 alpha accelerated peripheral protein wasting while preserving liver protein content, unlike the pattern in the pair-fed or starved animals in which loss of liver proteins and relative preservation of skeletal muscle protein were observed. The decrease in skeletal muscle protein content in LPS- or cytokine-treated animals was associated with coordinate decreases in muscle mRNA levels for the myofibrillar proteins myosin heavy chain, myosin light chain, actin, and in the 18S and 28S subunits of ribosomal RNA. We conclude that chronic exposure to the cytokines, IL-1 alpha or cachectin, can simulate those body and muscle protein changes seen in experimental LPS administration or chronic disease and markedly differ from the pattern of protein redistribution due to caloric restriction.

Animals↗

PubMed1989

Inhibition of sugar and amino acid transport across rat jejunum by cadmium, copper and mercury.

Cd2+, Cu2+ and Hg2+ (0.5 mM) inhibit the absorption of D-galactose (1 mM) across rat jejunum in vivo. The inhibition increases by 3-5 min previous exposure of the mucosa to the heavy metals, and is appreciably reversed by washing the intestinal lumen with 10 mM EDTA, and in higher proportion with 10 mM dithioerythritol. The metals do not affect the passive absorption of galactose (sugar transport blocked by 0.5 mM phlorizin), or that of L-sorbose. In vitro accumulation of D-galactose by jejunum rings is also inhibited by Cd and Cu. This inhibition is reversed by washing more readily than in vivo. The metals do not affect sugar entry into the tissues in the presence of 0.5 mM phlorizin. The inhibition of the transport component follows a non-competitive kinetics. Cd and Cu inhibit also the L-phenylalanine accumulation by the jejunum rings, but they do not modify the passive entry (in the presence of 40 mM methionine) or that in the absence of Na+. Heavy metals appear to inhibit sugar and amino acid intestinal absorption by their binding to proteins (prevailing to thiol groups) of the luminal membrane of enterocytes, which pertain or are functionally related to the corresponding Na(+)-substrate cotransport system.

Animals↗

PubMed1989

Sugar and amino acid intestinal transport systems in land snail Helix aspersa.

The intestine of Helix aspersa snail is able to actively transport sugars and amino acids. D-glucose, D-galactose and 3-oxymethylglucose share the same transport system with competitive inhibition between them, which is strictly Na(+)-dependent. Phlorizin has high affinity for that system and inhibits it competitively. D-fructose and L-arabinose are not actively transported, do not inhibit the transport of other sugars, and enter the tissue at a lineal rate with their concentration, which coincides with that of mannitol and with that of actively transportable sugars in the presence of 10(-4)M phlorizin. Galactose seems to enter the tissue from the serosal side through another carrier, with different specificity, Na(+)-independent, inhibited by phloretin but not by phlorizin. There are also transport systems for neutral amino acids, for the basic ones and for imino acids. Neutral amino acids present affinity for the other systems, whereas the basic ones and the imino acids seem to use only those proper to them. The system for imino acids is strictly Na(+)-dependent, but neutral amino acids and the basic ones continue to be transported and accumulated, although to a lesser extent, in the absence of Na+. Transport of sugars and amino acids is scarcely O2 dependent, although it is inhibited by 10(-4)M DNP. It is also partially inhibited by harmaline and by ouabain.

Amino Acids↗

PubMed1988

Inhibition by cadmium of D-galactose and L-phenylalanine transport by rat intestine in vitro.

The effect of cadmium (CdCl2) on galactose and phenylalanine uptake by rat everted intestinal rings has been studied. The rings were preincubated (15 min) and incubated (5 min) in the presence of Cd. Galactose uptake (from 0.5 mM to 10 mM) was inhibited by 0.5 mM Cd about 25%. Only the phlorizin-dependent galactose transport was affected by cadmium, being a non-competitive type inhibition. A 15 min washing with saline solution significantly reduced the cadmium induced inhibition, which was practically reversed by washing with 5 mM EDTA. The uptake of 0.5 mM phenylalanine was not affected by 0.5 mM Cd but it was depressed by 1 mM Cd. Such inhibition was exerted on the sodium-dependent phenylaline transport. Washing with 5 mM EDTA diminished only slightly the inhibition of the transport by cadmium. It is suggested that the inhibition of intestinal transport of galactose and phenylalanine by cadmium may be due to its reversible interaction with metal-binding ligands, possibly sulfhydryl groups, related to the luminal transport systems.

Animals↗

PubMed1987

Do local vasomotor effects elicit the motor deficits induced by intrathecally applied substance P antagonists in the rat?

The intrathecal application of the substance P (SP) antagonists [D-Pro2,D-Trp7,9]SP (DPDT) and [D-Arg1, D-Pro2, D-Trp7,9, Leu11]SP (DAPTL) to the lumbar region of intact, freely moving rats produced laming of the hindlimbs at doses of 0.375 nmol and above, and 1.5 nmol and above, respectively. In addition, the administration of DPDT (doses of 25 and 0.18 nmol) and DAPTL (25 and 0.6 nmol) produced a powerful constriction of the dorsal median spinal vein (DMSV) in decerebrated, unanaesthetised rats. Intrathecal SP (25 or 1.0 nmol) had a similar action on the spinal circulation to DPDT and DAPTL, though laming was first observed at doses of 30 nmol and higher. This suggests that intrathecally applied SP antagonists do not elicit laming by causing an obstruction of the venous drainage of the spinal cord. Disturbances of the spinal circulation could, however, influence the results of behavioural or physiological experiments in which SP or its analogues are administered intrathecally.

Animals↗

PubMed1987

The distributions of nucleotides near bacterial transcription initiation and termination sites show distinct signals that may affect DNA geometry.

Compilation and analysis of all bacterial sequences which are aligned by their transcription initiation sites show a dramatic behavior of the four nucleotides. Large peaks of T and A are observed. This highly nonrandom distribution is likely to affect the DNA geometry in addition to affecting the strength of binding between the two DNA strands. Following this site, the G and C rise above their overall bacterial mean. Alignment by transcription termination sites indicates that this behavior continues till the mRNA 3' termini. At this site the concentrations of A and T rise again above the mean. Analysis of the distributions of the 256 quartets in the 1000 nucleotide regions surrounding both transcription initiation and termination sites has been carried out. Some A/T combination sequences may serve as signals to the bacterial transcription machinery, in addition to the well-established TTGACA and TATAAT at positions -35 and -10, respectively, and a run of Ts at the transcription termination site. The frequent occurrences of (dA)/(dT) runs in the vicinity of these sites may result in curved DNA structures, affecting recognition and the nature of the interaction between the RNA polymerase and the DNA.

Bacteria↗

PubMed1987

Interactions among amino acid transport systems in snail Helix aspersa intestine.

Interactions among the transport of diverse amino acids in everted intestine of snail Helix aspersa have been studied. The uptake of 0.5 mM methionine is clearly inhibited by high concentrations (40 mM) of leucine, and not by proline or lysine, whereas the last two amino acids inhibit cycloleucine uptake. Methionine strongly inhibits proline and lysine uptake, which is significantly inhibited by their analogs hydroxiproline and arginine, respectively. Results suggest that in Helix intestine the transport systems for basic amino acids and iminoacids are shared with high affinity by methionine whereas the neutral amino acids transport systems do not seem to be shared, or are so very weakly, by the basic ones or by the imino acids.

Animals↗