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Biomedical subjects

K B Rogers

Publications and source records attributed to K B Rogers.

At least 19 recordsLinked to original sources
PubMed1993

Preconditioning against myocardial dysfunction after ischemia and reperfusion by an alpha 1-adrenergic mechanism.

Preconditioning may find ready applicability in humans facing scheduled global cardiac ischemia-reperfusion (IR) during bypass or transplantation, where such a maneuver is feasible before arrest. Our objective was to delineate and exploit the endogenous preconditioning mechanism triggered by transient ischemia (TI) and thereby attenuate myocardial postischemic mechanical dysfunction by clinically acceptable means. Preconditioning by 2 minutes of TI followed by 10 minutes of normal perfusion protected isolated rat left ventricle function assessed after 20 minutes of global, 37 degrees C ischemia and 40 minutes of reperfusion. Final recovery of developed pressure (DP) was improved (91.5 +/- 1.9% of equilibration DP versus unconditioned IR control, 57.4 +/- 2.4%, P < .01) and was accompanied by increased contractility (+/- dP/dt). Norepinephrine release increased after TI, and reserpine pretreatment abolished TI preconditioning. This suggests that endogenous norepinephrine mediates functional preconditioning in rat. Brief pretreatment (2 minutes) with exogenous norepinephrine reproduced the protection (89.1 +/- 1.4%) of postischemic function. Functional protection persisted after the hemodynamic effects had resolved. Norepinephrine-induced preconditioning was simulated by phenylephrine and blocked by alpha 1-adrenergic receptor antagonist. TI preconditioning was similarly lost after selective alpha 1-adrenergic receptor blockade. We conclude that transient ischemic preconditioning is mediated by the sympathetic neurotransmitter release and alpha 1-adrenergic receptor stimulation. Although the postreceptor mechanism remains unclear, functional protection after IR does not seem related to the magnitude of ATP depletion and elevation of resting pressure during ischemia. Rather, the endogenous mechanisms facilitate both recovery of mechanical function and ATP repletion during reperfusion.

Animals↗
PubMed1992

Cardiac 5'-nucleotidase activity increases with age and inversely relates to recovery from ischemia.

The metabolic basis for the enhanced tolerance of immature hearts to ischemia remains to be elucidated. Loss of high-energy phosphate nucleotides occurs during ischemia/reperfusion in mature (adult) hearts through the breakdown of adenosine triphosphate, diphosphate, and monophosphate (nondiffusible) to adenosine (freely diffusible). However, previous work has shown that after ischemia nondiffusible nucleotides are better retained by immature (neonatal) hearts than by mature hearts. The enzyme responsible for the conversion of adenosine monophosphate to adenosine is 5'-nucleotidase. We therefore hypothesized lower activity of this enzyme in neonatal than in adult myocardium. The purposes of this study were (1) to document 5'-nucleotidase activities in neonatal and adult rabbit myocardium and (2) to correlate differences of 5'-nucleotidase activity with functional recovery from ischemia. Neonatal (5- to 10-day-old) and adult (4- to 6-month-old) rabbit hearts were isolated and perfused (retrograde Langendorff). A left ventricular balloon measured functional parameters. Hearts were subjected to 20 minutes of global 37 degrees C ischemia and 10 minutes of reperfusion followed by freeze clamping. Tissue homogenates were assayed for 5'-nucleotidase by the linked formation of nicotinamide-adenine dinucleotide at 340 nm (Arkesteijn method). Postischemic recovery of developed pressure was 86% +/- 3% in neonates (n = 5) versus 38% +/- 3% in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). 5'-Nucleotidase activity was 4400 +/- 1208 nmol/min/gm in neonates (n = 5) versus 13,938 +/- 830 nmol/min/gm in adults (n = 8) (mean +/- standard deviation) (p less than 0.01). We conclude that (1) 5'-nucleotidase activity is 68% lower in neonatal than in adult myocardium and (2) functional recovery after ischemia inversely relates to 5'-nucleotidase activity.

5'-Nucleotidase↗
PubMed1991

The behavioral genetics of colony defense in honeybees: genetic variability for guarding behavior.

Guard honeybees stand at the entrance of colonies and facilitate the exclusion of nonnestmates from the colony. In this study, we examined the hypothesis that genetic variability among individuals in colonies might explain variability in guarding activity. To do this, we cross-fostered honey bees between colonies with high-defensive responses and colonies with low-defensive responses in alarm pheromone tests. Individuals from high-defensive colonies were more likely to guard in their own colonies (controls) than cross-fostered bees from low-defensive colonies. Cross-fostered high-defensive bees also were more like to guard in low-defense colonies. These results support the hypothesis that interindividual differences in guarding behavior are at least partially under genetic control. A positive correlation between number of guards and response to alarm pheromone demonstrates a link between behaviorally separated components of the overall defensive response.

Agonistic Behavior↗
PubMed1991

Oxygen metabolite effects on creatine kinase and cardiac energetics after reperfusion.

Noninvasive 31P nuclear magnetic resonance measurements indicate that during the initial reperfusion phase myocardial tissue contents of phosphocreatine (PCr) recover rapidly, while ATP levels remain low and recover slowly. There is also a burst of H2O2 during the first 10 min of reperfusion, as indicated by the in vivo inactivation of catalase that occurs only when H2O2, and the inactivator 3-aminotriazole (AMT), are simultaneously present. Neither H2O2 production nor CK inactivation was discernable after ischemia alone. In excitable tissue the PCr and ATP pools are equilibrated by the enzyme creatine kinase (CK), but myocardial CK activity is decreased by 20% after reperfusion, though not by simple washout. Extrapolating from the well-known air sensitivity of CK, we find that limited exposure in vitro to small concentrations of H2O2 can markedly diminish CK activity. We postulate that failure of certain CK isoenzymes at energy-using termini may decouple the relative rates of PCr production and ATP regeneration and hence cause elevated PCr-to-ATP ratios. The assumptions of 1) CK equilibrium during the reperfusion period to calculate free ADP levels and 2) cardiac recovery deduced from the elevation of PCr levels may require reexamination.

Adenosine Triphosphate↗
PubMed1991

Pretreatment with a nontoxic derivative of endotoxin induces functional protection against cardiac ischemia/reperfusion injury.

We hypothesized that low-dose pretreatment of an intact animal with a nontoxic derivative of endotoxin, monophosphoryl lipid A (MPL), would induce protection against cardiac ischemia/reperfusion (I/R) injury. The purposes of this study were to investigate whether MPL pretreatment would induce functional protection against cardiac I/R injury, to delineate the temporal induction of protection, and to examine antioxidant enzyme induction as a mechanism of protection. Rats were administered a 5 mg/kg dose of MPL at 2 hours and 24 hours before a 25-minute, global, 37 degrees C ischemic insult followed by reperfusion (modified Langendorff). At 40 minutes of reperfusion, ventricular function was assessed (ventricular balloon; developed pressure, rate of contraction, rate of relaxation). Hearts from rats pretreated with MPL 24 hours before isolation exhibited preservation of ventricular function (p less than 0.05). After I/R, hearts from rats pretreated with MPL 24 hours before isolation had increased (p less than 0.05) catalase activity compared to saline pretreated controls and rats pretreated with MPL 2 hours before isolation. We conclude that (1) pretreatment with MPL induces functional protection against cardiac I/R injury, (2) protection (not evident at 2 hours) is maximal at 24 hours, suggesting enzyme induction, and (3) increased catalase activity correlates with the functional protection.

Analysis of Variance↗
PubMed1985

Paratyphoid fever presenting with grand mal fits and cerebellar signs.

We report a case of Salmonella paratyphi B infection in a man who presented with cerebellar signs and convulsions. Later he developed vertebral osteomyelitis and a paravertebral abscess. He was treated successfully with chloramphenicol for 14 days and then long-term amoxycillin.

Abscess↗
PubMed1983

Pseudomonas aeruginosa colonisation in an intensive therapy unit: role of cross infection and host factors.

Despite the sparsity of Pseudomonas aeruginosa in the environment colonisation and infection with this organism was found at several sites by selective culture in 20 out of 46 patients in an intensive therapy unit. Three patients developed Ps aeruginosa pneumonia. Serial serogrouping and phage typing identified multiple strains in the unit and in the same patient. Rectal carriage occurred in 16 patients but rectal strains did not subsequently appear in tracheal aspirates; strains varied in their affinity for the upper respiratory tract. Colonisation was not directly related to length of stay and was detected in 16 of those colonised within 24 hours of admission. In intubated patients, who were colonised more frequently than those not intubated, upper respiratory tract colonisation correlated strongly with low initial arterial pH values. Personnel were probably responsible for cross infection among patients when the unit was busy. Strain differences and the susceptibility of patients also influenced colonisation and infection. Elimination of major reservoirs of Ps aeruginosa and compliance with procedures to control cross infection remain essential if patients in hospital are to escape colonisation by the organism.

Cross Infection↗
PubMed1980

An investigation into the efficiency of disposable face masks.

Disposable face masks used in hospitals have been assessed for the protection afforded the patient and the wearer by challenges of simulated natural conditions of stress. Operating theatre masks made of synthetic materials allow the wearer to breathe through the masks, and these have been shown to protect the patient well but the wearer slightly less. Cheaper paper masks are worn for ward duties, and of these only the Promask protected in area in front of the wearer: air does not pass through this mask, expired air is prevented from passing forward, and the wearer breathes unfiltered air. All the other paper masks tested allowed many bacteria-laden particles to pass through them.

Air Microbiology↗
PubMed1975

Urine microscopy as an aid to detection of bacteriuria.

Fresh, uncentrifuged urine specimens obtained from children attending a renal clinic were examined microscopically for leucocytes and bacteria, and the results were compared with quantitative bacterial cultures. Of the 51 specimens giving colony-counts larger than or equal to 10-5 per ml., 6 (12 per cent) showed no microscopical bacteriuria and 22 (43 per cent) contained smaller than 10 leucocytes per c.mm.; only 3 specimens (6 per cent) showed neither bacteria nor excess cells. Of the 186 uninfected specimens, bacteria were seen microscopically in 32 (17 per cent) and an excess of leucocytes in 27 (15 per cent); in only 9 (5 per cent) were both observed. Leucocyte-counting alone is therefore an unreliable technique, but microscopy for both bacteria and leucocytes affords a simple and rapid method of preselecting urine specimens for culture, with a high probability of predicting the correct result. While not suitable for population screening, it is ideal for use in hospital clinics and wards, as well as in general practice.

Adolescent↗
PubMed1975

The agglutinating antibody response in the duodenum in infants with enteropathic E. coli gastroenteritis.

The agglutinating antibody responses in duodenal fluid and serum were measured serially in 15 infants with enteropathogenic E. coli gastroenteritis. Peak levels of duodenal agglutinins were recorded eight to 18 days after the onset of symptoms, and the titres fell within the next seven to 14 days. These antibodies were mainly of the IgA class but IgM antibodies were detected early in the response, especially in the youngest infants. Serum antibody responses were detected in eight patients, but they correlated poorly with the titres of intestinal antibodies. No rise in serum antibodies was found in six infants. Further studies are required to determine whether these differences are host-derived or whether they reflect different pathogenic properties of the infecting organisms.

Agglutinins↗
PubMed1972

The isolation of an X-dependent strain of haemophilus from otitis media identified as H. haemoglobinophilus (canis).

The growth factor requirements, together with the serological results, would seem to justify the view that strain M.G., isolated from a child, M.G., with otitis media, in pure culture has to be regarded as H. haemoglobinophilus (canis). It is interesting to note that two out of the three strains of H. haemoglobinophilus (canis) available in this laboratory agglutinate to a titre of 1:80 with the serum produced against H. aphrophilus, the only other X-dependent haemophilus we had used for the preparation of antiserum.

Agglutination↗
PubMed1971

Cloxacillin-resistant staphylococci in a children's hospital.

Two hundred and thirty-seven selected, penicillin-resistant isolates of Staph. aureus collected over a 13-month period were examined retrospectively for cloxacillin/methicillin resistance; 44 were found to be resistant. Six other strains which had been preserved from an earlier period were also found to be resistant. All 50 cloxacillin-resistant strains were in addition resistant to streptomycin and several other antibiotics. According to their resistance patterns and reactions to phages, they could be classified into two categories. The proportion of cloxacillin-resistant strains among the total number of staphylococci isolated during the 13-month period was estimated to be 2.7%. Children most at risk from infection were those undergoing long-term hospital treatment and on several occasions children transferred from other hospitals in the region were found to be carrying resistant strains. Most infections caused by these strains were minor but they were nevertheless capable of producing severe illness and they were responsible for 33% of all staphylococcal wound infections.

Bacteriophage Typing↗