Biomedical subjects
Publications and source records attributed to J W Mackenzie.
Actinomycosis is typically a chronic infection of the cervicofascial, thoracic, or abdominal region. Involvement of the heart occurs but is unusual. We present a case of chronic constrictive pericarditis caused by actinomycetes. The actinomycosis infection was present for 20 years, thereby representing the longest duration reported in the literature, to our knowledge.
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Two hundred adult patients aged 16-65 years scheduled to undergo operation under general anaesthesia in a Day Bed Unit were assessed for anxiety at the time of booking and on the day of operation. The nature of previous anaesthetic experience was the prime determinant of the anxiety scores obtained at booking. The score at booking was the prime determinant of the score on the day of operation, with previous experience and type of operation as secondary independent factors. Patients scheduled to undergo oral surgery were particularly anxious. Nineteen percent of patients would have liked to have received something to relieve their anxiety.
A strain gauge device called the electronic contractility meter (ECM) was designed to measure quantitatively intestinal ischemic damage by delivering electrical stimuli to the intestine. Threshold stimulus level (TSL) was the minimum stimulus in milliamps necessary to produce a smooth muscle contractile response. TSL scale ranged from zero to 100 milliamps. Resection and anastomosis in ischemic intestinal segments was carried out in 30 dogs to compare TSL, intestinal color, peristalsis, Doppler ultrasound and resection margin histology with survival. There were five fatal anastomotic leaks, all resulting from intestinal necrosis. Doppler pulse in the marginal artery (MA) was absent at four of the five anastomoses that leaked versus eight of the 25 that healed (p less than or equal to 0.01). Mean TSL at the resection site was 38 +/- 7 milliamps in surviving dogs versus 51 +/- 4 milliamps in nonsurvivors (p less than or equal to 0.001). Mean TSL of normal intestine was 22 +/- 2 milliamps. Both TSL and Doppler ultrasound also correlated with resection margin histology (p less than or equal to 0.02 and p less than or equal to 0.005, respectively). Presence of peristalsis did not correlate with histologic grade or survival rate. Intestinal color correlated with resection margin histology (p less than or equal to 0.001) but not survival. The ECM and Doppler ultrasound were both superior to gross visual assessment in predicting intestinal survival. The ECM quantitatively measures tissue damage, a potential advantage over Doppler ultrasound, which provides only an estimate of local arterial blood flow.
The effect of intravenous (i.v.) nifedipine (5 micrograms/kg/min) on regional O2 supply/consumption variables was determined in 14 anesthetized open-chest dogs subjected to left anterior descending coronary artery (LAD) stenosis sufficient to reduce blood flow 50%. Myocardial blood flow was measured using radioactive microspheres, and regional arterial and venous O2 saturations were determined using microspectrophotometry. During LAD occlusion, blood flow and O2 consumption were decreased in the ischemic region while O2 extraction was increased. With nifedipine treatment, LAD flow (flow probe) was increased 44% as compared with the initial occluded value, with most of this increase going to the subepicardium (microspheres). Flow to the ischemic subendocardium was not changed with nifedipine treatment. Ischemic subepicardial O2 consumption increased slightly in nifedipine-treated animals as compared with saline values, whereas O2 extraction decreased slightly. In the subendocardial region, nifedipine resulted in a significant decrease in O2 extraction, with a slight decrease in O2 consumption as compared with saline controls. The O2 supply/demand ratio was significantly improved with nifedipine only in the subendocardium of the ischemic region. This suggested that nifedipine could increase O2 consumption in the ischemic subepicardium through proportional increase in O2 supply while it decreased O2 consumption in the subendocardium relative to O2 supply.
Quantitative levels of mRNAs coding for elastin, types I and III procollagen and gamma-actin were measured in porcine vascular material following balloon catheterization. A balloon catheter was introduced into the thoracic aorta and jugular vein of 3-6 week old pigs; following distention and six days of postoperative recovery, tissue samples were obtained for histopathology, electron microscopy, RNA extraction and mRNA quantitation. Using a series of mammalian cDNA clones and the procedure of slot blot hybridization, we have shown that elastin and types I and III procollagen mRNA levels rose significantly during the postoperative period following vascular distention. The increase correlated with an increase in the cell mass present in both the venous and arterial intimal layers. Changes in gamma-actin mRNA levels were also associated with this rapid proliferative response but in arterial tissue only.
Gastrointestinal (GI) complications after cardiac surgical procedures are infrequent but severe. Thirty-three GI complications were identified in 25 patients who underwent cardiac surgery during a 7-year period (2.0% incidence). The mortality rate for patients having these GI complications was 44%. Acute acalculous cholecystitis was the most lethal complication (86%). Acute pancreatitis was the most common complication (eight patients). Most patients responded well to conservative measures. Five patients had upper GI hemorrhage and three had lower GI bleeding that required more than 2 U of packed red blood cells. All patient conditions were diagnosed endoscopically and none necessitated operation. Of the remaining patients, one was operated on because of perforated duodenal ulcer, one because of perforated diverticulitis, and one because of pseudo-obstruction of the colon, and one patient underwent diagnostic laparotomy and showed negative results for presumed acalculous cholecystitis. Liver failure was fatal in all three patients in whom it occurred. GI complications correlated significantly with advanced age, prolonged bypass times, valve surgery, and the female sex. We conclude that septic GI complications--particularly acute acalculous cholecystitis and perforated viscus--after cardiac surgery are uncommon but lethal. Clinical features are often subtle, and a high index of suspicion is necessary for an early diagnosis and the institution of appropriate treatment.
We have isolated and characterized a cDNA clone containing DNA sequences coding for the noncollagenous carboxy-terminal domain of human pro alpha 2(IV) collagen. Using this cDNA clone in both Southern blot analysis of DNA isolated from human-mouse somatic-cell hybrids and in situ hybridization of normal human metaphase chromosomes, we have demonstrated that the gene coding for human pro alpha 2(IV) collagen is located at 13q33----34, in the same position on chromosome 13 as the pro alpha 1(IV) collagen gene.
Carbon tetrachloride-induced liver damage is a well-characterized experimental model for studying liver fibrosis. We used this model to examine alpha 1(I), alpha 1(III), and alpha 1(IV) procollagen mRNA levels during the development of liver fibrosis. Rats were given 0.5 ml of carbon tetrachloride/kg of body weight for 1-6 weeks. The liver tissue was assayed for collagen content by measuring total hydroxyproline content. Specific increases in procollagen mRNAs were assayed by slot blot hybridization. There was a significant increase in hydroxyproline content of liver tissue following 3 weeks of carbon tetrachloride treatment. The increase in tissue collagen content correlated with an increase in alpha 1(I) procollagen mRNA levels. At 5 and 6 weeks of treatment, there was an increase in alpha 1(III) procollagen mRNA levels. alpha 1(IV) procollagen levels increased slightly with five injections of carbon tetrachloride treatment. These results suggest that specific increases in procollagen mRNAs in liver fibrosis parallel, but do not precede, increases in tissue collagen content.
The usefulness of urinary RNA catabolites as markers for the early detection of a transplantable rat tumor and for the completeness of its resection was evaluated. The lack of correlation between tumor growth or size and the time of appearance of the elevated catabolites precludes their use for the early detection of cancer in this model. Complete removal of the tumor restored the elevated levels to normal but, if regrowth occurred, the elevated levels persisted, suggesting their possible use in monitoring the effectiveness of surgery. The data suggest that increased excretion of RNA catabolites is derived primarily from host tissue.
Valvar aortic stenosis can result in myocardial underperfusion with or without coronary obstruction. The purpose of this study was to determine how hearts with valvar aortic stenosis without hypertrophy can maintain their oxygen supply/consumption balance with partial left anterior descending coronary artery (LAD) occlusion. Open-chested, anesthetized dogs (n = 9) were subjected to mild valvar aortic stenosis and then to a reduction of LAD flow to 50% of baseline, while controls (n = 9) received partial LAD occlusion without aortic stenosis. Blood flows were determined before and after aortic stenosis and after LAD occlusion using radioactive microspheres. The hearts were then removed for microspectrophotometric analysis of regional venous and arterial oxygen saturation. Aortic stenosis resulted in a pressure gradient of approximately 50 mm Hg, representing mild aortic stenosis. Only a slight increase in myocardial blood flow was seen with aortic stenosis. Ischemia resulted in a significant drop in blood flow in control (40%) and aortic stenosis (55%) animals compared with their own preocclusion values. These ischemic region flows were not different from each other. Aortic stenosis itself did not alter oxygen extraction, although partial occlusion similarly increased extraction for all groups in the ischemic zone. The LAD occlusion resulted in a decreased oxygen consumption in the occluded region of all groups, with no differences noted between control and aortic stenosed animals. Thus, mild, acute aortic stenosis without hypertrophy does not appear to significantly increase the severity of an ischemic episode precipitated by partial LAD occlusion.
A device capable of quantitative measurement of intestinal ischemic damage has been designed. The device is called the electrical contractility meter and employs a clip-on strain gauge transducer that delivers a precisely controlled electrical stimulus to the bowel. Threshold stimulus level (TSL) is the stimulus current in milliamperes (mA) that is necessary to produce a clearly defined smooth-muscle contraction. In 30 dogs, TSL was used to establish viability boundaries in 40 cm ischemic bowel segments. Bowel viability was assessed with the use of TSL in comparison with gross features (color, peristalsis) and blood flow measured by means of Doppler ultrasound at 2 cm intervals in the ischemic small-bowel segments. The TSL scale ranges to 100 mA and varied from a low of 22 +/- 2 mA in normal bowel outside the ischemic segment to 97 +/- 4 mA in grossly gangrenous bowel. There was a consistent correlation between rising TSL and worsening bowel color, disappearance of visible peristalsis, and progressive disappearance of audible Doppler signals. Resection and anastomosis were performed in three groups of 10 dogs at TSL measurements of 30 mA, 40 mA, and 50 mA, respectively. Dogs were killed and anastomoses were inspected on the tenth postoperative day. There were no leaks at TSL = 30 mA, one leak at TSL = 40 mA, and four leaks at TSL = 50 mA. The number of leaks at TSL = 50 mA was significantly greater than at TSL = 30 mA (p less than 0.04, Fisher's exact test). These results show that the quantitative myoelectric parameters established by this device provide a reliable in vivo assessment of bowel viability. The electrical contractility meter is easy to use and may have clinical applicability.
A survey of chief residents in general surgery was conducted to evaluate debt and moonlighting, planned practice characteristics, the influence of oversupply and gender. Debt and moonlighting were closely related. The latter also correlated statistically with the perceived oversupply of general surgeons. Most residents planned to practice in a suburban area, in a community or university affiliated hospital with some teaching responsibilities. General surgeons were those more likely to choose a rural area, a community hospital and no teaching responsibilities. Subspecialists were those more likely to choose an urban area, a university hospital and a complete teaching environment. Two-thirds of residents thought there was an oversupply of general surgeons. They were more likely to take fellowships, especially those in transplantation, vascular, trauma, oncologic and colorectal surgery. Women represented less than 10 per cent of chief residents. They differed from men in the types of fellowships chosen, moonlighting activity and interest in teaching.
Using dual-laser sorted chromosomes and spot-blot analysis, we have previously assigned genomic DNA sequences coding for human alpha 1 (IV) procollagen to chromosome 13 (Pihlajaniemi et al. 1985). By in situ hybridization to normal chromosomes and chromosomes with 13q deletions, we now report the localization of this gene to the terminal end of the long arm of chromosome 13. In addition, Southern and slot blot hybridization analysis clearly show that these genomic sequences are present only once per haploid genome.
A new device designed to quantitatively measure viability in ischemic bowel was studied in 20 dogs. This strain gauge device is clipped on the serosal surface and can rapidly deliver an electrical stimulus. The threshold stimulus level (TSL) was the stimulus necessary to produce a clearly defined smooth muscle contraction. TSL was compared with blood flow measured by Doppler ultrasound at 2-cm intervals in 30-cm ischemic segments as a determinant of bowel viability. Doppler readings were taken from the bowel wall (BW), peripheral arteriolar branches of the marginal artery (PA), and marginal artery (MA), itself, at each 2-cm interval. Bowel color and peristalsis were correlated with Doppler and TSL data. TSL scale ranged from 0 to 100 mA and varied from 21 +/- 2 mA in normal bowel to 98 +/- 2 mA in gangrenous bowel. At the locus of the last audible Doppler signal in the BW, PA, and MA, mean TSL readings were 27 +/- 5, 34 +/- 6, and 48 +/- 16 mA, respectively. These readings were each significantly greater than the TSL of normal bowel at P less than or equal to 0.0001 level. Portions of each ischemic segment were resected and reanastomosed. Absence of Doppler signals in the BW and PA did not preclude healing of ischemic bowel. These data suggest that TSL measurement is more sensitive than either Doppler ultrasound or gross visual evaluation in assessment of bowel viability.
A case is described of retropharyngeal haematoma due to spontaneous bleeding from the inferior thyroid artery and causing acute upper airway obstruction. Results of the haematological investigations were suggestive of underlying polycythaemia rubra vera. The presentation and findings in this case are discussed.
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