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Biomedical subjects

G T Jones

Publications and source records attributed to G T Jones.

At least 37 records · Page 2Linked to original sources
PubMed1995

Ultrastructure of the afferent arteries of experimental femoral arteriovenous fistulae in rabbits.

Using transmission electron microscopy, the aorta and ilio-femoral arteries of 12 normocholesterolemic rabbits with femoral arteriovenous fistulae were investigated (49 to 895 days post-operatively) to determine whether the fibrofatty lesions in arteries proximal to chronic fistulae were ultrastructurally consistent with human atherosclerosis. The contralateral ilio-femoral arteries from the same animals and the vessels of 4 additional rabbits (2 with femoral arteriotomies) served as control material for comparison. There were microfractures adjacent to complete tears of the internal elastic lamina which had abrupt margins. These tears were observed mostly in the ilio-femoral arteries proximal to the fistula. They were most numerous, extensive and associated with considerable intimal proliferation near the fistula. Further proximally the tears were associated with progression to severe atrophy of the wall, the media in places being reduced in width to no more than 2 or 3 smooth muscle cells without any evidence of cellular degeneration. Intimal proliferation near the fistula and the naturally occurring intimal thickenings at branching sites proximal to the fistula, not only extended peripherally and progressed with time post-operatively, but exhibited ultrastructural changes consistent with atherosclerosis. These changes comprised dystrophic basement membrane, granulovesicular degeneration (matrix vesicles) and necrosis of smooth muscle cells, disruption of the elastic laminae, the appearance of extracellular and to a lesser extent intracellular lipid, adherence of monocytes, accumulation of foam cells, intimal fibrin deposition and sub-endothelial hemorrhage. Such results indicate that augmented hemodynamic stresses associated with femoral arteriovenous fistulae are consistent with those of human atherosclerotic lesions.

Animals↗
PubMed1995

The ultrastructure of arteries proximal to chronic experimental carotid-jugular fistulae in rabbits.

The afferent arteries from 11 normocholesterolemic rabbits with carotid-jugular arteriovenous fistulae ranging in duration from 107 to 718 days were examined by transmission electron microscopy to determine long term effects of an arteriovenous shunt on the afferent artery. Extensive tears and fragmentation of the internal elastic lamina of the elastic common carotid arteries were observed in all animals. Fragmentation and loss of elastic tissue as well as loss of muscle in the media accompanied progressive mural atrophy and tortuosity. Close to the fistula and in regions of tortuosity, fibromusculoelastic intimal proliferation was superimposed on the atrophic medial changes. The accumulation of matrix vesicles (cell debris), bizarre shaped smooth muscle cells, irregularly thickened multilaminated and reticulated basement membrane material beneath the endothelium and about smooth muscle cells, and abnormal shaped collagen fibrils were observed in the intima. Lipid was frequently found in the extracellular matrix and within smooth muscle cells while monocytes and lipid-laden macrophages were a feature of the more advanced intimal changes. These experiments confirm that in the absence of hypercholesterolemia the hydraulic stresses associated with an arteriovenous shunt cause severe mural atrophy and proliferative changes in the intima similar in nature to those of atherosclerosis.

Animals↗
PubMed1994

Ultrastructural changes in arteries proximal to short-term experimental carotid-jugular arteriovenous fistulae in rabbits.

The afferent arteries of 10 carotid-jugular arteriovenous fistulae in rabbits were examined by transmission electron microscopy to determine the early ultrastructural changes in the vicinity of haemodynamically induced tears of the internal elastic lamina. No significant changes appeared to precede the development of the tears but radially orientated partial fractures were observed adjacent to some major tears. The elastic tissue tears became more numerous, extended proximally along the artery and with time involved the innermost medial elastic laminae. Endothelial discontinuities were present over only a few early tears and the small size suggested repair was rapid. Endothelial cells overlying the elastic tissue tears increased in density and thickness. They were adherent to the underlying matrix and eventually to the thickened and multilaminated basal lamina. In the floor of the tears between the edges of the torn internal elastic lamina there were some smooth muscle cells of the synthetic type, degenerative and necrotic muscle cells and areas devoid of matrix with scarce proteoglycan material suggestive of oedema. Sixteen days post-operatively the smooth muscle cells in the floor of the tears were all of the contractile variety with thickened basal laminae overlaid by a relatively normal endothelial layer. There was no suggestion that inflammatory cells were responsible for the elastic tissue tears. The abrupt edges and the adjacent microfractures are consistent with the concept of mechanical failure of the elastic tissue.

Animals↗
PubMed1993

Endothelium in the aorta and ilio-femoral arteries proximal to femoral arteriovenous fistulae in rabbits.

The endothelium and underlying internal elastic lamina of the aorta and ilio-femoral arteries from 15 rabbits with femoral arteriovenous fistulae (2 to 92 days postoperatively) and 3 rabbits with control femoral arteriotomies were examined using the en face technique and scanning electron microscopy. The rapidity of development of the tears in the internal elastic lamina of the muscular ilio-femoral arteries was greater than in fistulae involving the elastic common carotid artery. The elastic tissue tears appeared to have a predilection for certain anatomical regions possibly related to regions of specific hemodynamic stress. A few tears were observed in the aorta near the origin of the renal arteries. Initially the elastic tissue tears in the afferent ilio-femoral arteries were longitudinally orientated and the endothelium overlying the elastic tissue tears soon exhibited increased cell density relatively restricted to the floor of the tears. This cellular pattern was similar to that in the carotid-jugular fistulae. With time the endothelium assumed a more conventional morphology.

Animals↗
PubMed1992

Endothelium and elastic tears in the afferent arteries of experimental arteriovenous fistulae in rabbits.

The endothelium and underlying internal elastic lamina of the arteries from 16 carotid-jugular arteriovenous fistulae in rabbits were examined using the en face technique and scanning electron microscopy respectively. Tears appeared in the internal elastic lamina of the arteries 3 days post-operatively. The overlying endothelium exhibited cytoplasmic pallor, loss of argyrophilia of cell borders, and at times attenuated endothelial cells bridging thrombus covered regions of denudation. Early endothelial lesions repaired rapidly and were found only 3-7 days post-operatively despite progressive increase in frequency and extent of tears and the development of interconnecting longitudinal tears with time. Following repair endothelial cells over the tears were small with hyperchromatic nuclei and oriented mostly parallel to the arterial axis. Endothelial cell density overlying these elastic tissue tears increase to three times that in contralateral arteriotomized common carotid arteries. These endothelial changes were sharply delineated by the margins of the elastic tears. Cell density over the tears reached its maximum 9-11 days post-operatively with mitotic figures both in the floor of the tears and over islands of residual elastic lamina. With time the cell density progressively diminished and endothelial cells assumed a more conventional elongated spindle shape.

Animals↗
PubMed1987

Bone levels of cephradine and cefuroxime after intravenous administration in patients undergoing total hip replacement.

A randomised, comparative study is reported of single intravenous doses of cephradine 2 g or cefuroxime 1.5 g given as prophylactic cover for total hip replacements in 40 patients. The serum and bone levels of cephalosporin achieved were higher in the cephradine treated group in proportion to the higher dose employed. Both agents provided adequate bone levels on average, cephradine 25.34 mcg/g, cefuroxime 17.39 mcg/g, although bone penetration was more variable with cefuroxime.

Adult↗
PubMed1987

The origin of proteinuria at high altitude.

Urinary protein excretion was measured before and after the intravenous infusion of lysine in 14 normal subjects after 4-6 days' acclimatization at 4846 m. Urinary albumin excretion before lysine was elevated in 11 subjects but alpha 1-microglobulin was detected in only four. After lysine a large increase in albumin excretion occurred in all subjects. Together with the absence of alpha 1-microglobulin before lysine this implies that increased glomerular capillary permeability is the major cause of proteinuria after acclimatization to high altitude. The estimated minimum glomerular fluid albumin concentration was increased two to three fold above the published values in normal controls.

Acclimatization↗
PubMed1986

The synergistic activity of tiamulin and chlortetracycline: in-feed treatment of bacterially complicated enzootic pneumonia in fattening pigs.

The antibacterial effects of a combination of tiamulin and chlortetracycline in vitro against a number of field isolates of Pasteurella multocida, Haemophilus pleuropneumoniae and Bordetella bronchiseptica were examined. There was a marked synergism between the two antibiotics against all eight isolates of P multocida, against seven of nine isolates of H pleuropneumoniae and against the single strain of B bronchiseptica tested. Two field trials were carried out on a herd with a history of complicated enzootic pneumonia where the presence of Mycoplasma hyopneumoniae and P multocida had been established and subsequently the presence of H pleuropneumoniae was discovered. Feed containing tiamulin at 100 ppm combined with chlortetracycline at 300 ppm was given for seven days to pigs affected with pneumonia, and the results were compared with untreated controls and pigs receiving chlortetracycline at 300 ppm. There was a follow-up observation period of three weeks when all groups received unmedicated feed. During the medication period the combination treated groups showed a statistically significant increase in average daily weight gain of 156 g (20.4 per cent) and in feed conversion efficiency of 0.576 (20.8 per cent) and a numerical improvement in average disease score in comparison with the untreated controls. These improvements were approximately double those observed in the groups treated with 300 ppm chlortetracycline which showed improvements of 93 g (12.2 per cent) in average daily gain and 0.301 (10.9 per cent) in feed conversion efficiency. During the following three weeks most of the initial gains were lost, probably owing to the reinfection of the treated groups by the untreated controls.

Animal Feed↗
PubMed1985

The clinical assessment of acute mountain sickness.

During three expeditions to high altitude the Birmingham Medical Research Expeditionary Society has studied the effects of the ascents on its members. The severity of acute mountain sickness (AMS) produced was assessed by three methods, interview, self assessment and peer review. Physical examination was unhelpful. The results of the three methods were closely correlated. Clinical interview permitted allowances to be made for individual factors such as fatigue. There was no tendency for self assessment to indicate effects consistently more or less than the other methods. Peer review revealed a wide spread of opinions but the large number of observers allowed the derivation of plausible mean values. Correlation of AMS with arterial pH and PaCO2 showed little relationship but correlation with PaO2 was good, particularly for self assessment. As all the methods are subjective a combination of techniques is recommended for future expeditions.

Acute Disease↗
PubMed1985

The Environmental Symptoms Questionnaire in acute mountain sickness.

A self-completed questionnaire (modified Environmental Symptoms Questionnaire) was evaluated in a study of acute mountain sickness (AMS). The questionnaire scores for headache, nausea, and the general feeling of ill health correlated well with AMS scores obtained by clinical interview. Modifications in the instructions and the phrasing of some of the questions are suggested and we doubt whether factor analysis provides any better data than more simple statistical methods. The questionnaire is a useful additional method for the assessment of symptoms of AMS.

Acute Disease↗
PubMed1983

Gastrointestinal necrosis in acute leukemia: a complication of induction therapy.

Gastrointestinal complications in acute leukemia have been infrequently reported. Reported here is a review of all patients on the hematology teaching service with acute leukemia from 1974 to 1980 and those with intestinal complications. Of the 50 patients with acute leukemia, 14 (28%) developed an acute abdominal catastrophe. They presented with an acute surgical abdomen, diarrhea, gastrointestinal bleeding, and a paralytic ileus. All were granulocytopenic and thrombocytopenic. All but one episode was associated with the death of the patients; survival ranged from 4 to 26 days (median 9 days) after their last dose of chemotherapeutic drugs. Cytarabine was administered in 13 of the 14 patients. It is believed that bowel necrosis which causes death in acute leukemia occurs more frequently than previously thought. There is a close association of the clinical syndrome with chemotherapeutic drugs, especially cytarabine.

Cytarabine↗
PubMed1982

Acyclovir and vidarabine monophosphate: comparison of iontophoretic and intravenous administration for the treatment of HSV-1 stromal keratitis.

We determined the therapeutic efficacy of iontophoretic application of acyclovir and vidarabine monophosphate (ara-AMP) for the treatment of herpes simplex virus (HSV) type 1-induced stromal keratitis in rabbits. The therapeutic efficacy of intravenous administration of acyclovir was assessed in the same model. Stromal keratitis was produced by intrastromal injection of 10 microliters purified HSV-1, McKrae strain. Treatment began the first day after intrastromal injection. Iontophoresis (0.5 mAmp for four minutes) of 3.4 percent (0.1 M) ara-AMP and 5.0 percent (0.22 M) acyclovir was performed once daily for five consecutive days in two treatment groups. Intravenous administration of 50 mg acyclovir/kg was performed twice daily for eight consecutive days. Intravenous administration of NaCl (0.14 M) and ocular iontophoresis of NaCl (0.14 M) were performed as controls in the two treatment groups. At least two scorers performed a single masked evaluation of the disease severity (lesion scoring) of the conjunctiva, corneal epithelium, stroma, and iris by still lamp examination. The eyes were scored daily for 12 consecutive days, and then every other day up to day 22. Iontophoresis of acyclovir or ara-AMP significantly reduced the course of the disease compared with iontophoresis of NaCl. Intravenous administration of acyclovir significantly reduced the disease compared with intravenous NaCl. This suggests that iontophoresis of acyclovir or ara-AMP either alone or in combination with intravenous administration of acyclovir may be of value in the treatment of HSV-1 stromal keratitis.

Acyclovir↗
PubMed1981

A study of fluctuations in Escherichia coli sensitivity patterns from pigs fed a halquinol supplemented diet.

Escherichia coli isolated from pigs fed on a medicated diet containing 120 p.p.m. halquinol did not develop any resistance to this addition over a 6-week period. Sensitivity patterns of the E. coli isolates to eight antimicrobial substances, although fluctuating slightly during the test period (but no more than a control group), did not significantly alter. However, the patterns did change significantly when for 17 days after the completion of the halquinol trial the pigs were fed a normal commercial ration medicated with a commonly used feed additive containing chlortetracycline hydrochloride, procaine penicillin and sulphadimidine.

Animals↗
PubMed1980

Cigarette smoking and plasma high-density lipoprotein cholesterol. The Lipid Research Clinics Program Prevalence Study.

The relationship between cigarette smoking and high-density lipoprotein (HDL) cholesterol was examined in 2663 men and 2553 women ages 20-69 years in 10 North American populations. Men and women who were smokers had significantly (p < 0.01) lower HDL cholesterol levels than nonsmokers, and heavier smokers had lower HDL cholesterol levels than lighter smokers. Using multiple linear regression analysis to adjust for differences in age, obesity, alcohol consumption and regular exercise increased the differences in HDL cholesterol levels between smokers and nonsmokers. For men who smoked 20 or more cigarettes/day, adjusted values averaged 5.3 mg/dl (11%) lower than those for nonsmokers (p < 0.01). Women who used gonadal hormones were analyzed separately from those who did not. In both groups, women who smoked 20 or more cigarettes/day had lower HDL cholesterol levels than nonsmokers: 9.4 mg/dl (14%) lower in hormone users and 8.6 mg/dl (14%) lower in nonusers (both p < 0.01). These findings indicate that cigarette smoking is associated with substantially lower levels of HDL cholesterol. Further, this association appears to be dose-dependent and is consistent with other research, indicating a possible causal relationship between cigarette smoking and lower HDL cholesterol.

Adult↗
PubMed1979

Birmingham Medical Research Expeditionary Society 1977 Expedition: changes in renal function observed during a trek to high altitude.

Changes in renal function were observed in 17 subjects during the course of a trek to high altitude. Comparison was made between these changes and the clinical assessment of acute mountain sickness (AMS). Periods of natriuresis occurred during ascent and descent, that during ascent being related to a fall in plasma aldosterone. Alterations in serum and urinary potassium suggested that potassium retention occurred during the ascent to altitude. No significant correlation occurred between changes in renal function and the severity of AMS before the illness being clinically apparent. When this was so, the severity of AMS correlated with a decreasing urine output, increasing positive fluid balance and a decreasing excretion of sodium and potassium; these changes were produced in part by a decrease in glomerular filtration rate.

Adult↗