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Biomedical subjects

B Harvey

Publications and source records attributed to B Harvey.

At least 55 records · Page 3Linked to original sources
PubMed1990

Effect of mucosal H+ and chemical modification on transcellular K+ current in frog skin.

A transcellular K+ current (IK) was established across the skin of the frog Rana temporaria, whose apical K+ permeability had been previously stimulated by exposure to K(+)-rich media. Short-term (less than or equal to 15 s) mucosal pH-titration of IK indicated two titrated groups (A and B), with apparent pKA of 6 and pKB of 3. The height of the titration steps, A and B, varied from skin to skin. Intracellular (i) H(+)-sensitive microelectrode studies on Rana esculenta skin (which lacks apical PK) were conducted in order to assess possible changes in pHi and basolateral K+ conductance as a consequence of the rise in mucosal [H+]. Cell pH decreased only at mucosal pH lower than 5.4 which caused a drop in basolateral K+ conductance as estimated from I-V records of the serosal membranes. These effects were much too slow to account for the fast mucosal pH effects on IK (Rana temporaria). Thus, we conclude that the two-step titration curves reflect solely the interaction of external H+ with the mucosal side of apical membrane K+ channels. Exposure to the SH-reagent PCMB, and to the carboxy-modifying EEDQ markedly reduced total IK at neutral pH; however, PCMB seemed to preferentially affect titration step B while EEDQ virtually eliminated step A. When the saturating IK kinetics were studied at different mucosal pH, protons showed a 'mixed' type inhibition of K+ current in the range of titration step A; at pH values less than 5, protons blocked IK by competition with K+ ions. These results are compatible with the presence of two K+ channel populations in the apical membrane which are discernible by their different interactions with external protons and chemical modifiers.

Animals↗
PubMed1990

Lithium modulation of cortical cyclic nucleotides: evidence for the Yin-Yang hypothesis.

Rats were subjected to chronic treatment with lithium chloride (0.2-0.3%) over a period of 3 weeks. The activity of cortical phosphodiesterase (EC 3.1.4.17) was determined simultaneously with cyclic AMP and cyclic GMP content and compared to control, untreated animals. Lithium, at therapeutic serum concentrations was found to suppress cyclic AMP levels with a concomitant increase in cyclic AMP-phosphodiesterase activity. A simultaneous two-fold increase in cyclic GMP was observed. Through the alteration of cortical cholinergic activity with physostigmine and the use of cyclic GMP as a cholinergic marker, we were able to demonstrate a novel cholinotropic property of lithium to stimulate synthesis of cyclic GMP. This effect appears to be linked, in a Yin-Yang mechanism, to the observed suppression of cyclic AMP induced by lithium through activation of cyclic AMP-phosphodiesterase.

Animals↗
PubMed1990

Services and charges by PPO physicians for PPO and indemnity patients. An episode of care comparison.

Physicians who participate in preferred provider organizations (PPOs) usually agree to various types of utilization review and sometimes discount their charges or agree to accept lower fees. This study was performed to determine whether they provided more or fewer services to their PPO patients than to their indemnity patients and whether the discounting resulted in lower expenditures for each episode of illness. In 1984, Metropolitan Life offered PPO coverage to Dade County (Florida) school board employees and dependents but only a standard indemnity plan to Dade County government employees and dependents. Episodes of care were examined for patients with chest pain, hypertension, joint pain, gastrointestinal or liver disorders, and lower back pain cared for by physicians who treated patients in both the PPO and indemnity employee groups. For PPO patients, charges per physician service were the same or lower, but total physician charges during an episode were higher. For services such as laboratory tests, diagnostic x-rays, and room and board, PPO and indemnity patients' charges were not significantly different.

Fees, Medical↗
PubMed1989

Surgery, sepsis, and nonspecific immune function in neonates.

An audit of 143 neonatal surgical operations identified low birth weight infants as being at particular risk of developing post-operative sepsis following major surgical trauma. Activity of the nonspecific immune system was examined pre- and post-operatively in order to elucidate the susceptibility to post-operative sepsis of these infants. A chemiluminescence micro-method was developed specifically for this purpose. Neonatal plasma was shown to have significantly impaired opsonising activity, and activity was further reduced in low birth weight infants. Levels of immunoglobulin and complement factors were also reduced, particularly in the low birth weight infant. Following major surgical trauma polymorph activity was significantly lower in low birth weight infants than in mature neonates.

Anti-Bacterial Agents↗
PubMed1988

Remote intramuscular injection of immobilising drugs into fish using a laser-aimed underwater dart gun.

Sixty coldwater and warmwater fish ranging in weight from 2 to 35 kg were injected intramuscularly with the hypnotics alphaxalone-alphadolone and metomidate hydrochloride and the non-depolarising muscle relaxant gallamine triethiodide using a laser-aimed underwater dart gun. Alphaxalone-alphadolone produced sufficient sedation for easy netting within five to 20 minutes at doses between 0.3 and 0.5 ml/kg, with induction being somewhat faster in warmwater species. The pattern of induction was similar with metomidate but required doses of 40 to 60 mg/kg. The muscle relaxant gallamine triethiodide showed promise as a practical agent for the capture and handling of large fish by virtue of its smooth induction of paralysis at doses between 1 and 3 mg/kg and its reversible supplementation with orally administered metomidate hydrochloride.

Anesthetics↗
PubMed1987

A severe outbreak of Escherichia coli O157:H7--associated hemorrhagic colitis in a nursing home.

In September 1985, an outbreak of Escherichia coli O157:H7 enteritis affected 55 of 169 residents and 18 of 137 staff members at a nursing home. The outbreak was characterized by two phases: a primary wave whose source was probably a contaminated sandwich meal and a secondary wave compatible with person-to-person transmission of infection. Among the elderly residents, the incubation period was 4 to 9 days (mean, 5.7 +/- 1.2). Older age and previous gastrectomy increased the risk of acquiring the infection (P = 0.01 and 0.03, respectively). Antibiotic therapy during exposure was associated with acquiring a secondary infection (P = 0.001). Hemolytic uremic syndrome developed in 12 affected residents (22 percent), 11 of whom died. Overall, 19 (35 percent) of the affected residents died, 17 (31 percent) from causes attributable to their infection. Antibiotic therapy after the onset of symptoms was associated with a higher case fatality rate in the more severe cases, possibly because patients with more severe disease tended to be treated with antibiotics. There were no complications or deaths among the affected members of the staff. Evidence of infection by verotoxin-producing E. coli O157:H7 was detected in 30 of 70 cases on the basis of isolation of this organism or demonstration of free verotoxin in stools. All isolates belonged to the same phage type. The high morbidity and mortality associated with this condition emphasize the need for proper food hygiene, rapid identification of outbreaks of disease, and prompt institution of infection-control techniques among the institutionalized elderly.

Adolescent↗
PubMed1986

In vitro studies on the reactivation by oximes of phosphylated acetylcholinesterase--I. On the reactions of P2S with various organophosphates and the properties of the resultant phosphylated oximes.

The rates of formation and decomposition of a series of phosphylated oximes derived from P2S (2-hydroxy-iminomethyl-1-methylpyridinium methane-sulphonate) have been measured. The rates of inhibition of AChE by these phosphylated oximes and the parent (and related) organophosphates have also been measured. Possession of these rate data now permits a detailed analysis of the reactivation of phosphylated AChE by P2S to be made (see following paper).

Acetylcholinesterase↗
PubMed1986

In vitro studies on the reactivation by oximes of phosphylated acetylcholinesterase--II. On the formation of O,O-diethyl phosphorylated AChE and O-ethyl methylphosphonylated AChE and their reactivation by PS2.

The in vitro reactivation profiles of O,O-diethyl phosphorylated AChE and O-ethyl methyl phosphonylated AChE by P2S (2-hydroxy iminomethyl-1-methyl-pyridinium methane sulphonate) have been determined. Whilst reinhibition of the reactivated AChE by phosphorylated oxime (POX) is not important in determining the reactivation profile of O,O-diethyl phosphorylated AChE, reinhibition of the reactivated AChE by phosphonylated oxime can, however, be important in determining the reactivation profile of O-ethyl methylphosphonylated AChE and the extent of this reinhibition is determined by the initial concentration of phosphonylated AChE. Kinetic analysis of the reactivation profiles demonstrated that the generally accepted scheme for this reactivation process is incorrect and that phosphylated AChE cannot be considered as a single species although an adequate description of the present data is afforded by a model using a 1:1 mixture of two species each with its own rate of reactivation. In the case of O,O-diethyl phosphorylated AChE the main kinetic difference between these two species is found not in the formation or stability of the phosphorylated AChE-P2S complex but in its subsequent reaction. From results with O-ethyl methylphosphonylated AChE prepared from two pairs of enantiomers as well as from the racemic fluoridate it was concluded that phosphonylation of AChE may not always occur via a mechanism involving inversion of configuration at phosphorus but can also occur with retention of configuration. Reactivation by P2S of O-ethyl methylphosphonylated AChE prepared from (S) organophosphates proceeds with inversion of configuration at phosphorus. Inversion also occurs in the reinhibition of AChE by the POX produced in the initial reactivation.

Acetylcholinesterase↗
PubMed1986

Topical absorption of gonadotropin-releasing hormone (GnRH) in goldfish.

The studies reported here show that exogenous GnRH can be absorbed by goldfish from the intraperitoneal (ip) cavity, gill surface, or surrounding water. Mammalian rather than teleost GnRH was applied in order to ensure that GnRH measurement in plasma did not reflect the native form. A radioimmunoassay (RIA) specific to mammalian GnRH was used to measure the concentration of absorbed GnRH; validation for this approach was provided by HPLC and cross-reactivity studies in which mammalian GnRH was shown not to be present in control goldfish brain or pituitary extracts. Plasma concentration of GnRH was highest at the first sampling time, 4 min after administration, for all three routes. For intraperitoneal injection, plasma concentration was halved in 12 min, a period comparable with the half-life in rats. The pituitary content of GnRH also increased rapidly during the first 4 min after ip injection and remained high for 60 min. Absorption of GnRH from the gill was equally effective with water or dimethyl sulfoxide (DMSO) as vehicle.

Administration, Topical↗
PubMed1986

Evaluation of C3b/C3bi opsonization and chemiluminescence with selected yeasts and bacteria using sera of different opsonic potential.

C3 fragment opsonization and chemiluminescence were assessed using two yeasts (Saccharomyces cerevisiae and Candida albicans) and two strains of bacteria (Staphylococcus aureus and Escherichia coli) following incubation with sera previously shown to be either efficient or poor in the opsonization of baker's yeast. Sera with poor function consistently fixed lower levels of C3 fragments and generated less chemiluminescence with all four organisms than sera with normal function. The differences were most marked with the two yeasts. We conclude that sera with normal complement function but manifesting a relatively common defect in the opsonization of baker's yeast have a general opsonic defect.

Adult↗
PubMed1985

DIAG: a computer-assisted dermatologic diagnostic system--clinical experience and insight.

Over the past few decades, the computer has been utilized in various ways to assist physicians in formulating their differential diagnoses, usually on an experimental basis. Following a review of the three major technics employed in computer-assisted diagnosis, statistical pattern classification, production rules, and cognitive models, a new system (DIAG) is described. The sole function of DIAG is to assist in the formulation of the differential diagnosis of skin diseases. At the beginning of the fourth year of development, the accuracy of the program in reaching diagnoses has been shown, on many occasions, to be comparable to its expert counterparts. However, it has been demonstrated that the system is not utilized within the dermatology clinic routinely. In response to this, aspects of DIAG have been modified in order to improve its clinical acceptability. Until this acceptance is achieved, these tools will not fulfill their potential to affect patient care.

Diagnosis, Computer-Assisted↗
PubMed1984

The reactivation by oximes of phosphonylated acetylcholinesterase: the possible erroneous interpretation of reactivating potency.

A comparative study of the reactivation by two oximes of acetylcholinesterase inhibited by several organophosphates has been made, with particular reference to the dependence of the degree of reactivation produced by an oxime (reactivating potency) upon the concentration of inhibited enzyme. In the case of one inhibitor it is demonstrated that the relative reactivating potency of the two oximes can be reversed by a change in experimental conditions. It is concluded that the measurement of the reactivation produced by two or more oximes, particularly when carried out under standardized conditions, is of little value in determining their relative reactivating potencies, and of negligible value in predicting their likely therapeutic effectiveness against organophosphate poisoning.

Acetylcholinesterase↗
PubMed1984

Gonadotropin-releasing hormone (Gn-RH) in striped mullet (Mugil cephalus), milkfish (Chanos chanos), and rainbow trout (Salmo gairdneri): comparison with salmon Gn-RH.

Immunoreactive gonadotropin-releasing hormone (Gn-RH) was extracted from brains of striped mullet, milkfish, rainbow trout, and chum salmon with acetone/HCl and petroleum ether. High pressure liquid chromatography and cross-reactivity studies show mullet, milkfish, and trout brains to contain a peptide chromatographically and immunologically identical to synthetic salmon Gn-RH, while the mammalian form of Gn-RH is detectable in none of these fishes. Gn-RH is present in immature 7-month-old and 4-year-old milkfish. A second immunoreactive peptide is separable by HPLC in all the fish studied. This "early-eluting" form of Gn-RH is unlikely to be a precursor; its cross-reactivity with antisera R-42 and #185 suggests that any modification is in the C-terminal region. Several possible roles for this peptide are advanced.

Animals↗