Biomedical subjects
D Allen
Publications and source records attributed to D Allen.
Evaluation of Starling forces in the equine digit.
A pump-perfused extracorporeal digital preparation was used to evaluate blood flow, arterial pressure, venous pressure, isogravimetric capillary filtration coefficient, capillary pressure, and vascular compliance in six normal horses. From these data, pre- and postcapillary resistances and pre- and postcapillary resistance ratios were determined. Vascular and tissue oncotic pressures were estimated from plasma and lymph protein concentrations, respectively. By use of the collected and calculated data, tissue pressure in the digit was calculated using the Starling equation. In the isolated equine digit, isogravimetric capillary pressure averaged 36.7 mmHg, plasma and lymph oncotic pressures averaged aged 19.12 and 6.6 mmHg, respectively, interstitial fluid pressure averaged 25.6 mmHg, and the capillary filtration coefficient averaged 0.0013 ml.min-1.mm-1.100 g-1. Our results indicate that digital capillary pressure in the laterally recumbent horse is much higher than in analogous tissues in other species such as dog and human. However, the potential edemagenic effects of this high digital capillary pressure are opposed by at least two mechanisms: 1) a high tissue pressure and 2) a low microvascular surface area for fluid exchange and/or a low microvascular permeability to filtered fluid.
Comparison between lysine vasopressin and a long-acting analogue (N alpha-triglycyl-lysine vasopressin) used as local hemostatic agents for conization.
Lysine vasopressin and a long-acting analogue N alpha-triglycyl-lysine vasopressin were compared in a prospective randomized double-blind study including 71 women undergoing cold knife conization of the uterine cervix. Hemodynamic and hemostatic variables were studied. N alpha-triglycyl-lysine vasopressin had the following advantages over lysine vasopressin: it gave significantly less skin pallor, becoming evident at a later stage during the operation. The diastolic blood pressure was significantly lower, as also was the incidence of postoperative hemorrhages. Factor VIII related antigen was lower. On the other hand reduction in heart rate (values before conization compared with values during conization) was more pronounced when N alpha-triglycyl-lysine vasopressin was used, but there was no difference in absolute values between the two groups during conization.
Survey of patients' satisfaction with access to general practitioners.
The north west England faculty patients' liaison group, supported by community health councils and family practitioner committees, surveyed patients' perceptions of accessibility to general practitioners in seven districts in 1985 and 1986. Findings on appointment systems, telephone access and out-of-hours calls are compared with those from other surveys. The results show that patients' satisfaction with appointment systems is related to the efficiency of their own general practitioner's system. The results also show higher levels of dissatisfaction with waiting times for outof- hours visits than in studies 10 years ago and that a large proportion of patients would like direct telephone access to their general practitioner.
Capillary permeability to endogenous macromolecules in the equine digit.
Microvascular permeability characteristics were evaluated in digits of 7 adult horses. After capillaries were isolated and an extracorporeal perfusion circuit for the digit was established, a lymphatic vessel draining the distal portion of the phalangeal region was cannulated at the level of the coronary band. Venous pressure was increased in a stepwise manner, and lymph flow, lymph protein concentration (Cl), and plasma protein concentration (Cp) were determined after measured variables were allowed to reach steady state. Lymph-to-plasma protein concentration ratios (Cl/Cp) and lymph and plasma oncotic pressures were determined from samples collected during steady state. The osmotic reflection coefficient was determined after Cl/Cp became constant, regardless of increasing lymph flow, and was expressed as 1--Cl/Cp. The osmotic reflection coefficient for the digit was 0.67. Seemingly, the microvasculature bed of the digit was relatively permeable and could maintain only 67% of the endogenous macromolecules within the vasculature.
Patient access and appointment systems.
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Making shared governance work: a conceptual model.
Most of the nursing literature offers little substantive rationale for why Shared Governance works or how to evaluate it. This article presents a model of Shared Governance that is based on more than fifty research articles on participation in decision-making. It gives administrators an overview of why Shared Governance impacts satisfaction and organizational commitment. The model should facilitate both designing a Shared Governance system to fit a particular organization and evaluating that system.
Use of a bone plate for treatment of middle phalangeal fractures in horses: seven cases (1979-1984).
Four adult horses and 3 foals with middle phalangeal fractures were treated by arthrodesis of the proximal interphalangeal joint, using a bone plate. Six of the 7 horses survived greater than 2 years; 2 of the 6 horses had intermittent lameness after hard work, and 4 horses didn't have evidence of lameness. The use of a bone plate for arthrodesis of the proximal interphalangeal joint was a successful treatment alternative for middle phalangeal fractures in horses.
Hemorrhagic fibrinonecrotic duodenitis-proximal jejunitis in horses: 20 cases (1977-1984).
Records of 20 horses with small intestinal disease causing acute colic and affecting the proximal portion of the small intestine were examined retrospectively. The disease was characterized by severe to moderate pain, which was replaced by depression, fever, gastric reflux, slight distention of the affected small intestine, leukocytosis, and high concentrations of total protein in the peritoneal fluid. Grossly, the affected intestines were hemorrhagic and had yellow discoloration. Histopathologic findings included submucosal edema, neutrophilic infiltration of the submucosal and laminal propria, and mucosal slough at the villous tips. Advanced lesions were characterized by mucosal sloughing with transmural edema, hemorrhage, fibrin deposition, and necrosis. No cause was determined. In 6 horses, bypass of most of the affected small intestine was helpful by alleviating the severe gastric reflux.
Noradrenergic regulation of alpha 1-receptors during the postnatal development of the guinea pig.
In guinea pig brain, alpha 1-noradrenergic receptor concentrations undergo region-specific fluctuations during the first weeks of postnatal life. However, the factors involved in the regulation of these receptors have yet to be identified. In this study, the ontogeny of one possible regulatory factor, norepinephrine, was examined in relation to postnatal changes in alpha 1-receptor levels in several different regions of guinea pig brain. Results from these studies showed that while the activity of the noradrenergic system increased throughout the first weeks of postnatal development in each brain area examined, the concentration of alpha 1-receptors decreased in preoptic area and hypothalamus and increased in cortex. In subsequent experiments, the effects of noradrenergic lesions with 6-hydroxydopamine on alpha 1-receptor levels were assessed to examine the possibility that alpha 1-receptors are differentially sensitive to noradrenergic stimulation in cortex and preoptic area/hypothalamus in immature guinea pigs. Noradrenergic lesions which reduced norepinephrine levels by 87-94% resulted in significant elevations in alpha 1-receptors in all regions examined. These results are discussed with reference to the anatomical distribution of alpha 1-receptors and their regulation by norepinephrine.
Serum concentrations of secondary amine tricyclic antidepressants may be lower than those measured from plasma.
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Plasma-serum differences in the assessment of tricyclic antidepressant blood levels.
Concomitant plasma and serum tricyclic determinations were performed on 20 patients chronically administered imipramine (N = 10), amitriptyline (N = 10), desipramine (N = 10), and nortriptyline (N = 10). Plasma levels for these tricyclic antidepressants were significantly greater than the corresponding serum levels. Plasma-serum differences for the secondary amines (DMI/NT) were more than twice those for the tertiary amines (IMI/AMI). The authors thus suggest that clinicians and investigators specify the specific source of blood sample when assessing blood levels of the secondary tricyclic antidepressants.
Timing, genetic requirements and functional consequences of somatic hypermutation during B-cell development.
While somatic antibody mutants are rare in the preimmune repertoire and in primary immune responses, they dominate secondary and hyperimmune responses. We present evidence that somatic hypermutation is restricted to a particular pathway of B-cell differentiation in which distinct sets of B-cell clones are driven into the memory compartment. In accord with earlier results of McKean et al. (1984) and Rudikoff et al. (1984), somatic mutation occurs stepwise in the course of clonal expansion, before and after isotype switch, presumably at a rate close to 1 X 10(-3) per base pair per generation. At this rate, both selectable and unselectable mutations accumulate in the rearranged V region genes. The distribution of replacement mutations in the V regions shows that a fraction of the mutations in CDRs is positively selected whereas replacement mutations are counterselected in the FRs. By constructing an antibody mutant through site-specific mutagenesis we show that a point mutation in CDR1 of the heavy chain, found in most secondary anti-NP antibodies, is sufficient to increase NP binding affinity to the level typical for the secondary response. Somatic mutation may contribute to the immune repertoire in a more general sense than merely the diversification of a specific response. We have evidence that clones producing antibodies which no longer bind the immunizing antigen can be kept in the system and remain available for stimulation by a different antigen. Somatic mutations are 10 times less frequent in DJH loci than in either expressed or non-expressed rearranged VDJH or VJ loci. We therefore conclude that a V gene has to be brought into the proximity of the DJH segment in order to fully activate the hypermutational mechanism in these loci.
Management of fractures and exostosis of the metacarpals and metatarsals II and IV in 25 horses.
Twenty-five cases of fractures of the second and fourth metacarpal and metatarsal (splint) bones were reviewed. Fourteen fractures involved a thoracic limb and 11 involved a pelvic limb. Fractures of the proximal one-third of splint bones are reported in one of two forms: fractures that are closed, or fractures with a permanent or intermittent draining sinus. Thirteen of the fractures presented were closed fractures and the remaining 12 were open. All of the closed fractures were managed by surgical excision of the distal fragment and the exostosis at the fracture site, followed by primary surgical wound closure. Lag screw fixation of the proximal fragment was used in three cases. All of the open fractures were managed surgically by excision of the distal splint fragment and debridement of the contaminated fracture site. Primary wound closure was used in 11 of the 12 cases. All closed fractures healed by primary intention, and 10 of 13 were free from lameness at one year follow-up. The 11 open wounds which were operated and subsequently closed under suture healed by primary intention. The wound left open healed by granulation, scar contraction, and epithelialisation. Eight of these horses were sound one year later. The remainder of the open fractures were lost to follow-up.
A case of private sector success: supplying home-care haemodialysis patients.
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Does the National Health Service differ from private industry?
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Does developmental content influence the effectiveness of anticipatory guidance?
We conducted a prospective, controlled study to evaluate the value of discussing developmental stages with mothers while providing anticipatory guidance during health maintenance visits. Eighty-three inner city mothers and their healthy, first-born infants were recruited within three days of birth and randomly assigned to either a control or intervention group. All mother-infant pairs were seen by the same pediatric provider for health maintenance visits when the infants were 2 weeks, 2 months, 4 months, and 6 months of age. At each visit, anticipatory guidance for all mothers included discussions of such age-appropriate issues as nutrition, safety, sleep, and common problematic behaviors. For the 39 intervention group mothers, the basis for such information was explained through age-specific discussions of affective, cognitive, and physical development. Dependent variables measured after the 6-month visit included maternal-infant interaction; maternal perceptions of infant temperament, family adaptation and adjustment, and satisfaction with the infant's behavior and development; and maternal satisfaction with pediatric services. Analyses of variance demonstrated no significant effect of treatment group on any of the outcome measures. These results do not support the importance of routinely discussing developmental stages during anticipatory guidance and suggest that specific, age-appropriate issues may be discussed without emphasizing the developmental basis for such information.
Surgical management of chronic laminitis in horses: 13 cases (1983-1985).
Thirteen horses with chronic refractory laminitis were evaluated and treated. In each horse, deep digital flexor tenotomy was performed on all affected limbs at the level of the midpastern. Five horses returned to limited athletic endeavors, 6 horses improved and were comfortable on pasture, 1 horse improved clinically, but was euthanatized for economic reasons, and 1 horse improved, but deteriorated 9 months after surgery and was euthanatized. Results of this study indicated that deep digital flexor tenotomy at the level of the midpastern can be used effectively as a salvage procedure in horses with chronic refractory laminitis.