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Biomedical subjects

R D Baker

Publications and source records attributed to R D Baker.

At least 55 records · Page 3Linked to original sources
PubMed1989

Dose-response curves for suxamethonium in neonates, infants and children.

Single dose-response curves were determined for suxamethonium in neonates, infants and children during thiopentone-fentanyl-nitrous oxide anaesthesia. During onset of neuromuscular block, suxamethonium produced an increase in muscle tone which was greatest in neonates and infants. The dose-response curves for the three groups were parallel. The effective doses producing 90% depression of twitch height were significantly greater in neonates and infants compared with children (517 and 608 v. 352 micrograms kg-1). These values were greater than those obtained in a comparable study in adults. In view of their higher ED values compared with adults and a marked individual variability in response to small doses of suxamethonium, we recommend an intubating dose of 3 mg kg-1 for neonates and infants and 2 mg kg-1 for children. These doses are 50-100% greater than those previously recommended for paediatric patients.

Anesthesia↗
PubMed1989

Skin blood flow and limited joint mobility in insulin-dependent diabetes mellitus.

Hand skin blood flow in 32 insulin-dependent (IDDM) diabetics was compared with 13 healthy controls at room temperature and after immersion of the hands in warm and cold water. Subjects were examined for limited joint mobility (LJM) to analyse the association between this and blood flow. Digital arteries remained patent in IDDM compared to controls after cold challenge (p = 0.0001), and the difference persisted to a lesser degree 15 min (p = 0.009) and 30 min (p = 0.03) after recovery. Capillary blood flow was reduced in IDDM at room temperature at the finger nailbeds (p less than 0.02) and the palms (p = 0.004) and remained so after warm water immersion in the palms (p = 0.002), where further vasoconstriction was observed immediately after cold water immersion (p less than 0.001) and 15 and 30 min into recovery (p = 0.07 and p = 0.009 respectively). Thermographic analysis confirmed a pattern of predominantly distal rewarming after cold challenge in IDDM with a greater mean index finger temperature than the controls. Together, these features suggested enhanced arteriovenous anastomotic blood flow. All IDDM and IDDM males with LJM had reduced palm capillary flow immediately after cold challenge (p less than 0.05). After warm water (p less than 0.03) and 30 min after cold challenge (p less than 0.05) IDDM males with LJM had reduced palm capillary flow compared to those IDDM without. A microvascular aetiology for LJM is proposed by virtue of reduced nutritional blood flow and evidence of enhanced arteriovenous shunting in the hands of insulin-dependent diabetics.

Adolescent↗
PubMed1989

Conceptual model for the use of aerial color infrared photography by mosquito control districts as a survey technique for Psorophora columbiae oviposition habitats in Texas ricelands.

Two photographic missions per year are recommended to provide information on land-use and mosquito oviposition habitats. A winter mission, following a rain, will-provide a view of low areas within fields which may be obscured by summer vegetation. A summer mission will provide current land-use and crop distribution information and may show plant stress conditions due to excessive soil moisture. An aerial color infrared photographic survey with directed ground verification should result in a substantial savings in cost and increased efficiency in surveillance of mosquito producing habitats over ground survey techniques currently employed by mosquito control districts.

Animals↗
PubMed1989

Anaesthetic induction in children: the effects of maternal presence on mood and subsequent behaviour.

Forty-nine children, aged from 1 to 9 years, undergoing elective surgery under general anaesthesia, were studied in two groups. In one group, each child's mother was present during induction of anaesthesia, whereas in the other group no parent was present. Children's moods and cooperation during waiting and induction periods did not differ significantly between the groups, neither was the incidence of technical difficulties with anaesthetic induction different. Induction took longer (P = 0.005) if the mother was present. Mothers, when present, were calm and supportive to their children, with one exception. No mother was critical or interfering. Each child's behaviour was assessed by questionnaire pre-operatively and 4 weeks post-operatively. There was a significant overall improvement in behaviour scores post-operatively. There were no significant differences in direction or magnitude of behaviour changes between the two groups.

Affect↗
PubMed1989

Calculating the basic reproductive rate Ro when there are 2 or more pathogens.

Some reasons why observed prevalences of the 3 major trypanosomes in cattle and livestock animals might not be independent are discussed. Apart from genuine interactions between the infections, averaging over heterogeneous populations produces an apparent correlation between pathogens. More subtly, chemotherapy and mortality both induce a positive correlation between pathogens. The calculation of the basic reproductive rate Ro for one pathogen in the endemic presence of another is explained, and illustrated by a simple calculation. Although multi-pathogen calculations are difficult, the calculation of Ro is both useful and feasible.

Africa↗
PubMed1988

Trypanosoma congolense: the distribution of enzymic variants in east and west Africa.

A total of 114 stocks of Trypanosoma congolense originating from Kenya, Uganda, Tanzania, Zambia and Sudan, but including, for comparison, stocks from The Gambia, Liberia, Ivory Coast, Nigeria and Cameroun, were compared by isoenzyme electrophoresis for 6 enzymes. The zymodemes were grouped, both from a dendrogram and using a cladistic method, after calculating the dissimilarity, or distance, between profiles. Previous observations are broadly confirmed, the zymodemes clustering separately according to geographical origin and ecological zone. Thus, one group was composed almost entirely of East African stocks, and another of stocks from both East and West Africa, although each group was of savanna origin. A third group was composed of stocks from the humid, rain-forest zones of West Africa, and was particularly characterized by isoenzyme variants of superoxide dismutase and glucose-phosphate isomerase. Two stocks from the Kenyan coast formed a markedly separate group, which may be taxonomically distinct.

Africa, Eastern↗
PubMed1988

A model of tsetse-transmitted animal trypanosomiasis.

The data needed to develop analytical models of trypanosomiasis transmission have become available only recently. By making some simplifying assumptions, models of the dynamics of the disease in vector, cattle and wild mammal populations can be constructed in order to determine criteria for successful disease control by mass and targetted chemotherapy, and by vector control. The heterogeneity in transmission due to tsetse fly feeding preferences and the variability of immunological characteristics among the vertebrate hosts account for differences in prevalence of Trypanosoma vivax and T. congolense, and also lead to an increase in the basic reproductive rates of the parasites and a corresponding decrease in the vector population density threshold for disease eradication or persistence. The long life-span of the vectors relative to the duration of the parasites' developmental period lead to high infection rates in the vector and high values of R0. The efficacy of chemotherapeutic regimes depends on the relationship between treatment rate and the duration of prophylaxis conferred by the drugs used. The model's predictions of the effects of vector control are shown to be in broad agreement with published field data for Mkwaja Ranch, Tanzania. Vector control programmes are frequently blighted by reinvasion, and the implications of this are discussed in terms of a model for fly immigration. With immigration of vectors, the disease is always endemic, though the infection rate in the fly population is modified by the effect of differential mortalities inside and outside the controlled area on cohorts of incubating flies. Sensitivity analysis of the model, using Monte-Carlo methods, enables an assessment of the relative importance of the parameters to be made. The results emphasize the need for studies of the wild animal reservoir to be carried out alongside entomological surveys. The relative accuracy with which field measurements need to be made in order to minimize the uncertainty in predictions of trypanosomiasis prevalence is discussed.

Animals↗
PubMed1988

Comparison of atracurium-induced neuromuscular blockade in neonates, infants and children.

The potency of atracurium was determined in neonates, infants and children during thiopentone-fentanyl-nitrous oxide in oxygen anaesthesia using single dose-response curves. The effective doses producing 50% depression of the first twitch of the train-of-four were significantly lower in neonates and infants than in children (82 and 112 v. 135 micrograms kg-1). Following a standard dose of atracurium 0.5 mg kg-1, 95% depression of the first twitch occurred more rapidly in neonates than in children (0.9 v. 1.4 min), while recovery to 10% of the control twitch height occurred more rapidly in neonates than in the other two groups (22.7 v. 29.7 and 28.6 min). It is concluded that neonates and infants require less atracurium to produce a given degree of neuromuscular blockade compared with older children. However, prompt recovery can be expected in all healthy paediatric patients following a standard intubating dose of atracurium 0.5 mg kg-1.

Anesthesia, General↗
PubMed1988

Altered hand skin blood flow in type 1 (insulin-dependent) diabetes mellitus.

Disturbed upper limb skin blood flow has been described in insulin-dependent (Type 1) diabetes mellitus, but the pathophysiological mechanism remains unclear. Hand skin blood flow was therefore measured at room temperature and following immersion of hands in cold and warm water in 13 healthy control subjects, in 10 patients with Type 1 diabetes mellitus and cardiovascular autonomic neuropathy, and a further 10 Type 1 diabetic patients with normal cardiovascular autonomic tone. Following cold challenge there was failure of digital artery clampdown in all diabetic patients in comparison with healthy control subjects (p less than 0.005), and the index finger temperature fell less (p less than 0.05). Laser Doppler flow was reduced at the palms at room temperature or following the warm challenge (p less than 0.008), as well as on the dorsum at room temperature (p less than 0.05), in all diabetic patients. In addition laser Doppler flow in the diabetic patients was reduced at the palms and dorsum immediately following cold water challenge (p less than 0.004) and this reduction persisted 15 min (p less than 0.05) and 30 min (p less than 0.01) into the recovery phase. In comparison to those diabetic patients with normal cardiovascular tone, those with cardiovascular autonomic neuropathy had reduced laser Doppler flow at the pulp 15 min after cold water immersion (p less than 0.05), at the nailbed immediately after cold water immersion (p less than 0.01), and at the palms immediately after warm water challenge (p less than 0.01).

Adult↗
PubMed1988

Autonomic neuropathy in systemic sclerosis.

Autonomic function assessed by tests of cardiovascular reflexes was studied in 25 patients with systemic sclerosis and 10 patients with primary Raynaud's phenomenon. A comparison was made with 13 normal healthy subjects. Significant abnormalities in the cardiovascular reflexes were found in systemic sclerosis, both in the CREST (calcinosis, Raynaud's phenomenon, oesophageal dysmotility, sclerodactyly, telangiectasia) variant and also in those patients with diffuse involvement. There was sympathetic and parasympathetic dysfunction. These findings suggest that autonomic neuropathy is a feature of systemic sclerosis.

Adult↗
PubMed1988

Effect of age and norgestomet on endocrine parameters and production of embryos in superovulated beef cows.

Effects of age of cow and a norgestomet (N) implant on number of embryos and endocrine responses to induction of superovulation were studied in old (greater than 12 yr) and young (5 to 7 yr) lactating beef cows. Seventeen cows (8 old and 9 young) received a 6-mg N ear implant on d 4 or 5 of the cycle (d 0 = estrus); the remaining 17 cows (9 old and 8 young) served as untreated controls (C). All animals were treated with 38 mg of porcine follicle-stimulating hormone (FSH-P) in decreasing dosages over a 4.5-d period beginning on d 10 or 11. Regression of the corpus luteum was induced with injections of PGF2 alpha at 0800 and 2000 on d 4 of FSH-P treatment; implants were removed at the second injection of PGF2 alpha. Cows were inseminated artificially 12 and 24 h after onset of estrus. Embryos were collected on d 7 or 8 postinsemination. Blood samples were obtained daily at 0800 from 2 d prior to initiation of treatment with FSH-P until collection of embryos. An additional sample was collected each day at 2000, from the first injection of PGF2 alpha to 1 d after onset of estrus. Samples were assayed for luteinizing hormone (LH), progesterone (P4), follicle stimulating hormone (FSH) and estradiol-17 beta (E2). Total number of embryos plus ova recovered was lower (P less than .01) in N-treated (5.2 +/- 1.1) than in C-treated (10.6 +/- 1.6) cows.(ABSTRACT TRUNCATED AT 250 WORDS)

Age Factors↗
PubMed1987

Effect of pulsed short wave diathermy on skeletal muscle injury in rabbits.

The purpose of this study was to determine whether short wave diathermy (SWD) would enhance healing of a skeletal muscle injury. Thirty-two rabbits were divided into the following four groups: Experimental Group 1 (n = 8), which was given SWD twice daily for 8 consecutive days; Control Group 1 (n = 8), which was followed for 8 days but not given treatment; Experimental Group 2 (n = 8), which was given SWD twice daily for 16 consecutive days; and Control Group 2 (n = 8), which was followed for 16 days but not given treatment. The muscle injury was induced by giving all 32 rabbits three local injections of a myotoxic drug into the right gastrocnemius muscle. After the 8 or 16 days, all muscles were removed, then embedded in paraffin or frozen, sectioned, stained with adenosine triphosphatase or hematoxylin and eosin and examined with a light microscope. No statistically significant differences in the degree of muscle healing were found between the animals in Experimental Group 1 and Control Group 1 and those in Experimental Group 2 and Control Group 2. A trend toward faster resolution of the muscle injury was observed among those rabbits in Experimental Group 2 as compared with those rabbits in Control Group 2. Further study is required to determine whether SWD can be more effective for enhancing recovery from skeletal muscle injury.

Animals↗
PubMed1987

Estrous synchronization and establishment of pregnancy in bovine embryo transfer recipients.

Characteristics of donors, embryos, recipients, and transfer procedures were examined for relationships with establishment of pregnancy. Data were from records of 1202 embryos transferred by the professional staff of a large embryo transfer company. Average pregnancy rate was 74.6%. Variables affecting establishment of pregnancy were service sire, embryo quality, stage of estrous cycle in recipient, quadratic effect of synchrony, and transfer quality. Because the direct or indirect effect of sire must be established at conception, these data demonstrate a latent effect of sire on pregnancy. One would expect the highest pregnancy rate among excellent quality embryos transferred with no delays or complications into recipients that had displayed estrus at the same time or prior to the donor yet were relatively early in their estrous cycles. There also was a tendency for pregnancy rate to decrease with advancing maturity of the embryo.

Animals↗
PubMed1987

Dental implants.

Explore the source record for details and available documents.

Dental Implantation↗
PubMed1986

Pollen grain granuloma: a new clinicopathologic entity.

Chronic ulceration of the ankle developed in a woman who had been stepped on by a cow. Microscopic examination revealed a florid foreign body granulomatous reaction in which pollen grains were found both within giant cells and lying free in fibrous tissue. The grains resembled those of the Asteraceae, or Compositae, family. This is the first report of pollen grains associated with an invasive tissue process. The morphologic features of pollen grains and their differentiation from other foreign bodies are discussed.

Female↗
PubMed1986

Intestinal sugar transport: does the Na+ gradient provide all the energy?

It has not yet been established that the energy released from the Na+ gradient during Na+-sugar cotransport by small intestine is sufficient, by itself, to drive uphill sugar transport under conditions in which other sources of energy are available and in which sugar is being vigorously transported. This work attempts to test the thermodynamic sufficiency of the Na+ mechanism under such conditions using hamster jejunum in vitro. From data on tissue uptake of D-galactose and unstirred layer considerations, the concentration ratio for galactose across the apical membrane during mucosal-to-serosal galactose transport was estimated to be at least 50 when concentration in the bulk mucosal solution was 2.2 mM. This estimate and reasonable assumptions regarding intracellular Na+ activity and apical membrane potential were used to calculate the minimum physiological coupling ratio (i.e., the ratio of coupled net fluxes of Na+ and galactose) required if all the energy necessary for galactose transport is transferred from Na+. The minimum physiological coupling ratio required was roughly 1.4. An estimate based on the ratio of transepithelial chord permeabilities to galactose, instead of the apical concentration ratio, would be higher. The measured physiological coupling ratio (0.4) was considerably less than that required. For reasons discussed, this result should be interpreted with caution. It can be concluded that the issue of energetic adequacy is not yet settled.

Animals↗
PubMed1986

Age, dose of FSH and other factors affecting superovulation in Holstein cows.

Effects of age of donor and other factors on superovulation and production of transferable embryos were investigated. Data were obtained on 987 recoveries of embryos performed between November 1980 and June 1984 by Select Embryos, Inc. The 339 Holstein donors ranged in age from 1.8 to 17.8 yr. The effects of age of donor and dose of follicle stimulating hormone (FSH) were examined using regression analysis. For on-farm recoveries, numbers of embryos, rates of fertilization, quality scores of all embryos and numbers of transferable embryos decreased (P less than .01, P less than .001, P less than .05, P less than .01, respectively) with increasing age of donor. For in-clinic recoveries, numbers of embryos plus ova recovered were affected by age of donor, dose of FSH and the interaction of the two (P less than .05). Among older donors, increasing doses of FSH were associated with an increase in the number of ova plus embryos recovered. However, among younger donors, increasing doses of FSH had a negative effect. Numbers of embryos, rates of fertilization and numbers of transferable embryos decreased (P less than .05) with advancing age and increased (P less than .05) with increasing doses of FSH. Greater numbers of ova plus embryos were recovered when treatment with FSH was begun on d 10 or 11 as compared with d 7, 8, 9, 12, 13 or 14 (P less than .001). It was concluded that an increase in age of donor had a negative influence on the success of superovulation and the production of transferable embryos, and that the response to FSH was affected by age of donor.

Animals↗