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Biomedical subjects

M A Holmes

Publications and source records attributed to M A Holmes.

At least 55 records · Page 3Linked to original sources
PubMed1994

Fracture of the wing of the ilium, adjacent to the sacroiliac joint, in thoroughbred racehorses.

During a two year period, sagittal fractures of the wing of the ilium were diagnosed in 10 Thoroughbred horses. All were spontaneous fractures sustained during normal exercise in training and racing, with no history of inciting trauma. When ultrasound scans of the surface of the pelvis were performed, the fracture was clearly visible as a discontinuity of the sacral wing of the ilium. In 3 horses, an irregular contour suggestive of periosteal callus was seen in the vicinity of the acute fracture. All horses examined by gamma scintigraphy had a focal increase in uptake of isotope just lateral to the tuber sacrale. Nine of the horses were treated conservatively by rest. The other horse had bilateral fractures and was subjected to euthanasia at the time of the injury. Six horses returned to full training, and 2 subsequently won, without recurrence of lameness.

Animals↗
PubMed1993

An improved method for the scintigraphic detection of acute bone damage to the equine pelvis by probe point counting.

A fracture of the pelvis in a horse can be detected scintigraphically by probe point counting. However, the pelvis is covered by a large and variable muscle mass, and is close to the urinary bladder, both of which can introduce errors. This paper describes an improved technique which uses a larger set of sampling points and analyses the data with a small computer to construct a three dimensional graph of the gamma-ray output across the pelvis, thus helping to improve the interpretation of the data. The scintigraphic plot from a normal horse, three cases of fracture (confirmed by radiography, ultrasound imaging or post mortem examination) and examples of the artefacts produced by isotope in the bladder and by marked muscle wasting are presented.

Animals↗
PubMed1993

Equine T-lymphocyte MHC II expression: variation with age and subset.

This paper describes the characteristics of a monoclonal antibody (CVS10) that reacts with an equine leukocyte antigen. On the basis of tissue distribution and biochemical characteristics, this antigen is equine MHC II. The equine MHC II antigen was found on a large subset of T-lymphocytes in addition to all B-lymphocytes, as has been reported previously. In addition MHC II was found to be present on a large proportion of both the mutually exclusive equine T-lymphocyte subpopulations which express either the equine homologues of CD4, or CD8. In a study of changes in equine MHC II expression with age it was found that far fewer lymphocytes express MHC II in neonatal foals than in adult horses. An increase with age was demonstrated. This age related change in MHC II expression was shown to occur principally within the T-lymphocyte subpopulation. It is proposed that this change may be associated with the development of a memory T-lymphocyte population, and that MHC II expression may be a marker for memory T-lymphocytes.

Aging↗
PubMed1993

Concentration of citrate in the mammary secretion of sows during lactogenesis II and established lactation.

The functional significance of citrate in the mammary secretion of six sows was investigated during the second stage of lactogenesis (lactogenesis II) and established lactation. The changes in the concentrations of progesterone and lactose in the maternal blood, and lactose, Na and K in the mammary secretion, suggested that lactogenesis II began during the final day of pregnancy. The concentration of citrate in the mammary secretion of the sows during lactogenesis II was high and varied from 5.4 (SEM 0.5) mM at day 0.5 post partum to 6.8 (SEM 0.4) mM at day 1.5 post partum. There was a decline of approximately 30% in the concentration of citrate in the milk of sows during the first week of lactation. These findings suggest that, in contrast to all other species studied previously, milk citrate is not a harbinger of lactogenesis II in the sow. However, the changes in the concentration of citrate in the mammary secretions of sows may reflect changes in the rate of de novo synthesis of fatty acids that take place in the mammary glands of sows during lactogenesis II and established lactation.

Animals↗
PubMed1993

The application of correlated sampling to the computation of electron beam dose distributions in heterogeneous phantoms using the Monte Carlo method.

Although the Monte Carlo method is capable of computing the dose distribution in heterogeneous phantoms directly, there are some advantages to computing a heterogeneity correction factor. If this approach is adopted there are savings in time using correlated sampling. This technique forces histories to have the same energy, position, direction and random number seed as incident on both the heterogeneous and homogeneous water phantom. This ensures that a history that has, by chance, travelled through only water in the heterogeneous phantom will have the same path as it would have through the homogeneous phantom, resulting in a reduced variance when a ratio of heterogeneous dose to homogeneous dose is formed. Metrics to describe the distributions of uncertainty, efficiency, and degree of correlation are defined. EGS4 Monte Carlo calculation of the dose distribution from a 20 MeV electron beam on water phantoms containing aluminum or air slab heterogeneities illustrate that this technique is the most efficient when the heterogeneity is deep within the phantom, but that improved efficiency can be realized even when the heterogeneity is at or near the surface. This is because some correlation between the two histories is retained despite passage through the heterogeneity.

Electrons↗
PubMed1992

In vitro production of specific antibody by equine peripheral blood mononuclear cells using tetanus toxoid as a recall antigen.

Anti-tetanus toxoid (TT) antibody (Ig) levels in the supernatant of cultured, pre-immunised equine peripheral blood mononuclear cells (PBMC) were measured by an indirect enzyme-linked immunoabsorbent assay (ELISA). Optimal anti-TT Ig production occurred at concentrations of stimulating, purified TT of between 0.001 and 0.1 micrograms ml-1, which varied depending on the cell concentration. Optimal anti-TT Ig production was most consistently produced when the cell concentration was 5 x 10(6) ml-1. At this cell concentration maximal anti-TT Ig was induced using 0.1 micrograms ml-1 TT. At a cell concentration of 5 x 10(6) ml-1 and a TT concentration of 0.1 micrograms ml-1 anti-TT Ig was first detectable in supernatant on day 5 of stimulation. Maximal levels of anti-TT Ig were present in the supernatant by day 10. No anti-TT Ig was produced in cultures of PBMC from non-immune animals.

Animals↗
PubMed1991

Structures of met and azidomet hemerythrin at 1.66 A resolution.

The crystallographic refinement of met and azidomet hemerythrin has been carried out at 1.66 A resolution in an attempt to characterize precisely the binuclear iron center in this protein. Restrained least-squares refinement has produced molecular models giving R-values of 18.9% for met (65,683 reflections from 10 A to 1.66 A) and 17.6% for azidomet hemerythrin (68,747 reflections from 10.0 A to 1.66 A). The protein structure in each derivative is very similar to that of myohemerythrin. The mu-oxo bridged iron center differs between the two forms. The complex in met hemerythrin is asymmetric with the bridging oxygen closer to one of the iron atoms while the complex in azidomet hemerythrin is symmetric. After investigations of the effects of correlation in the refinement, we believe this difference between the two complexes is associated with chemical differences and is not a refinement artefact.

Animals↗
PubMed1991

Structures of deoxy and oxy hemerythrin at 2.0 A resolution.

The crystallographic structure analyses of deoxy and oxy hemerythrin have been carried out at 2.0 A resolution to extend the low resolution views of the physiological forms of this oxygen-binding protein. Restrained least-squares refinement has produced molecular models giving R-values of 16.8% for deoxy (41,064 reflections from 10 A to 2.0 A) and 17.3% for oxy hemerythrin (40,413 reflections from 10.0 A to 2.0 A). The protein structure in each derivative is very similar to that of myohemerythrin and the various met forms of hemerythrin. The binuclear complex in each derivative retains an oxygen atom bridging the two iron atoms, but the bond lengths found in deoxy hemerythrin support the idea that, in that form, the bridge is protonated, i.e. the bridging group is a hydroxyl. Dioxygen binds to the pentaco-ordinate iron atom in deoxy hemerythrin in the conversion to oxy hemerythrin. The interatomic distances are consistent with the proposed mechanism where the proton from the bridging group is transferred to the bound dioxygen, stabilizing it in the peroxo oxidation state by forming a hydrogen bond between the peroxy group and the bridging oxygen atom.

Binding Sites↗
PubMed1991

A study of bovine and equine immunoglobulin levels in pony foals fed bovine colostrum.

As part of a project to raise specific pathogen free (SPF) Welsh Mountain Pony foals, free from exposure to Equid herpesvirus type 1, foals were removed from their dams at birth and fed bovine colostrum. This study characterises the uptake of bovine colostral immunoglobulin and production of endogenous immunoglobulin, in 10 SPF foals. An enzyme-linked immunoadsorbent assay was developed to measure serum concentrations of bovine IgG1 (boIgG1) to assess the efficiency of transfer, and rate of elimination of boIgG1 by the foal. The endogenous production of equine IgG was studied using a single radial immunodiffusion test. Foals were given 1.2 to 2 litres of bovine colostrum achieving peak serum boIgG1 concentrations of 18.9 to 34.2 g/litre (mean 28.0). The mean half-life of boIgG1 in the foals was 7.4 days. Endogenous immunoglobulin production resulted in equine IgG concentrations greater than 2 g/litre in six of 10 foals by 14 to 19 days of age, and greater than 7 g/litre in eight of 10 foals by 37 to 50 days of age. All foals had equine IgG serum concentrations greater than 10 g/litre by 102 to 135 days of age.

Animals↗
PubMed1991

Three monoclonal antibodies identifying antigens on all equine T lymphocytes, and two mutually exclusive T-lymphocyte subsets.

The aim of this study was to produce monoclonal antibodies (mAb) recognizing equine lymphocyte surface antigens. Fusions were conducted using BALB/c mice hyperimmunized with equine thymocytes. Hybridoma supernatants were screened by flow cytometry and positive hybridomas were cloned twice by limiting dilution. These mAb were then characterized for tissue distribution by immunohistology and flow cytometry, and by precipitation and analysis of the lymphocyte antigens which they recognized. Three mAb (CVS5, CVS4 and CVS8) are described which recognize only T lymphocytes in peripheral blood. Two-colour immunofluorescent studies showed that CVS5 recognized all T lymphocytes and that CVS4 and CVS8 recognized two mutually exclusive subsets of CVS5-positive cells. In the thymus there was a large population of CVS4/CVS8 double-positive cells. Immunohistochemical staining with these mAb was restricted to T-lymphocyte areas. CVS4 and CVS5 precipitated molecules of 58,000 and 69,000 MW, respectively, in both reducing and non-reducing conditions. CVS8 precipitated two molecules of 32,000 and 39,000 MW in reducing conditions, and one molecule of 69,000 MW in non-reducing conditions. This evidence suggests that CVS5, CVS4 and CVS8 recognize the equine homologues of CD5, CD4 and CD8, and that the characteristics of these antigens are similar to those of other species.

Animals↗
PubMed1990

Changes in the concentrations of glucose and galactose in the peripheral blood of sucking piglets.

Changes in the concentrations of glucose and galactose were measured in the peripheral blood of ten piglets after they had ingested milk during a natural sucking. In addition, the mild stress associated with the experimental procedure was determined by sampling nine fasted piglets over a period of 9 to 12 min. During this period there was a significant increase in the concentration of glucose in the blood of the piglets but no change in the concentration of galactose. After milk ingestion during a natural sucking the concentrations of both glucose and galactose increased from 5.7 mM and 19 microM to reach peak values of 7.7 mM and 122 microM, respectively, by 30 to 35 min. The concentrations of glucose and galactose returned to initial values in 60-80 min and 80-100 min, respectively, after sucking. Since the change in the concentration of galactose in the peripheral blood was much lower than the change in the concentration of glucose, we conclude that galactose was rapidly removed by the livers of sucking piglets. However, after the ingestion of milk the percentage increase (from initial to peak values) in the concentration of galactose in the blood was much larger (650%) than the increase in the concentration of glucose (43%). Thus, we propose that the determination of galactose in the peripheral blood may provide a qualitative method for monitoring the digestion and absorption of milk lactose in sucking piglets.

Animals↗
PubMed1990

Cardiovascular actions of common anesthetic adjuvants during desflurane (I-653) and isoflurane anesthesia in swine.

To determine the cardiovascular actions of drugs commonly combined with inhalation anesthetics, we administered one drug from each of several classes of adjuvants to seven swine already anesthetized with equipotent concentrations (1.2 MAC) of desflurane, formerly I-653, a new inhaled anesthetic, or isoflurane. Succinylcholine (1 and 2 mg/kg), atracurium (0.6 mg/kg), and atropine (5 micrograms/kg) plus edrophonium (5 mg/kg) had no cardiovascular effects. Fentanyl was given in amounts that decreased MAC for the inhaled anesthetics by 25%-35%. A dose of 50 micrograms/kg IV had no cardiovascular effects during either anesthetic, whereas 100 micrograms/kg IV modestly increased systemic vascular resistance without changing other variables. Naloxone (100 micrograms/kg IV) during infusion of fentanyl decreased systemic vascular resistance and increased cardiac output during both desflurane and isoflurane anesthesia, increased heart rate during only isoflurane anesthesia, and did not affect mean arterial blood pressure during either anesthetic. Thiopental (2.5 and 5.0 mg/kg IV) decreased mean aortic blood pressure, cardiac output, stroke volume, and systemic vascular resistance during both anesthetics without altering heart rate or left- or right-sided cardiac filling pressures. The addition of 60% nitrous oxide caused no cardiovascular changes during desflurane anesthesia, but increased systemic vascular resistance and decreased cardiac output and stroke volume during isoflurane without altering heart rate or cardiac preload. We conclude that the usual clinical doses of adjuvants commonly administered during anesthesia have no untoward cardiovascular actions during 1.2 MAC desflurane or isoflurane anesthesia in swine.

Adjuvants, Anesthesia↗
PubMed1990

Hepatocellular integrity in swine after prolonged desflurane (I-653) and isoflurane anesthesia: evaluation of plasma alanine aminotransferase activity.

Desflurane, formerly known as I-653 (CF2H-O-CFH-CF3), is a new inhalation anesthetic derived by fluorine substitution for the alpha-ethyl chlorine of isoflurane (CF2H-O-CClH-CF3). The lower solubility and increased stability of desflurane provided by the C-F bond lessen biotransformation to potentially hepatotoxic metabolites. Repeated administration of desflurane to rats, with or without induced hepatic enzymes, does not result in evidence of hepatic injury. In the recent study we extended the tests for liver cell injury to another species, the pig. Our test included prolonged exposure to desflurane or isoflurane, both in the absence and presence of commonly used adjuvants. We measured plasma alanine aminotransferase activity in eight young female swine anesthetized in random order with desflurane (0.8-1.6 MAC) and isoflurane (0.7-1.4 MAC), for a total dose of about 5.5 MAC-hours of each anesthetic, 3-8 days apart. Plasma alanine aminotransferase activities remained in the normal range, and were not significantly greater over baseline values in samples drawn immediately after, 4 h after, or 3-8 days after (mean +/- SD, 6.1 +/- 2.1) the administration of either anesthetic was discontinued after the first study with either desflurane or isoflurane. Five additional pigs were given a mean total dose of 9.7 MAC-hours of desflurane or isoflurane in conjunction with succinylcholine, N2O, fentanyl, naloxone, atracurium, thiopental, edrophonium, and atropine. No changes in plasma alanine aminotransferase activity were detected in blood samples drawn at termination of the anesthesia, 24 h later, and 4-7 days later (mean +/- SD, 5.8 +/- 1.3).(ABSTRACT TRUNCATED AT 250 WORDS)

Alanine Transaminase↗
PubMed1989

Natural cytotoxicity in the dog: description of two new allogeneic tumour targets.

Three canine tumour cells were studied for their susceptibility to cytotoxicity by allogeneic canine natural killer (NK) cells: a lymphoma line, 3132 of B cell origin, and two adherent cell lines emanating from the same non-lymphoid tumour isolate, one (A72F) with a fibroblast morphology and one (A72E) with an epithelioid appearance. Both 3132 and A72E have preliminary evidence of retrovirus infection. Unstimulated canine peripheral blood mononuclear cells, used as the source of NK cells, were able to mediate significant lysis of 3132 and A72F cells at effector cell:target cell ratios of under 50:1, although an 18 h incubation was necessary for maximum cytotoxicity. NK activity against the 3132 tumour cells proved to be variable both within a group of dogs as well as on different occasions utilising the same individual donor. The epithelioid form of the A72 tumour cell line, A72E, had gained a marked resistance to NK lysis, although like the 3132 cells, there is preliminary evidence of persistent retrovirus infection in this cell line. Interestingly the A72F cells were as successful as homologous 3132 cells in the cold target inhibition of labelled 3132 cytotoxicity, while A72E did not. This latter result could indicate that not only do A72F and 3132 share NK determinants recognised by the same NK receptor, but the A72E line has lost this important recognition determinant.

Animals↗