Low-energy laser irradiation reduces formation of scar tissue after myocardial infarction in rats and dogs.

BACKGROUND: Low-energy laser irradiation (LELI) has been found to attenuate various biological processes in tissue culture and experimental animal models. The aim of the present study was to investigate the effect of LELI on the formation of scar tissue in experimentally induced chronic infarct in rats and dogs. METHODS AND RESULTS: Myocardial infarction (MI) was induced in 50 dogs and 26 rats by ligation of the left anterior descending coronary artery. After induction of MI, the laser-irradiated (LI) group received laser irradiation (infrared laser, 803-nm wavelength) epicardially. Control MI-induced non-laser irradiated (NLI) dogs were sham-operated, and laser was not applied. All dogs were euthanized at 5 to 6 weeks after MI. Infarct size was determined by TTC staining and histology. The laser treatment (P:<0.05) lowered mortality significantly, from 30% to 6.5%, after induction of MI. The infarct size in the LI dogs was reduced significantly (P:<0.0001) (52%) compared with NLI dogs. Histological observation of the infarct revealed a typical scar tissue in NLI dogs and cellularity in most of the LI dogs. Only 14+/-3% of the mitochondria in the cardiomyocytes in the ischemic zone (4 hours after MI) of LI MI-induced rats were severely damaged, compared with 36+/-1% in NLI rats. Accordingly, ATP content in that zone was 7.6-fold (significantly) higher in LI than in NLI rats. CONCLUSIONS: Our observations indicate that epicardial LELI of rat and dog hearts after chronic MI caused a marked reduction in infarct size, probably due to a cardioprotective effect of the LELI.

Testicular neovascularization by "omentotesticulopexy': a possible adjuvant in the surgical correction of high undescended testes.

The surgical repair of "very high" undescended testes may bring about testicular atrophy, as a result of impaired vascular supply, whether caused unintentionally by extensive dissection, or deliberately when the Fowler-Stephens operation is employed. In this experimental study, improvement of the vascular supply by means of "omentotesticulopexy" (an omental flap pexied to the rat testis) before or concomitant with spermatic vessel division (known as the Fowler-Stephens operation) was achieved and demonstrated by angiographic studies. The authors believe that the addition of "omentotesticulopexy" to the Fowler-Stephens operation will reduce the rate of testicular atrophy among patients with high undescended testes.

Jejunal mucosal function of the isolated bowel segment created by omentoenteropexy in dogs: a study by in situ luminal perfusion.

An isolated bowel segment (IBS) was created in dogs by omentoenteropexy, using staged procedures. (1) Omentoenteropexy was performed at the antimesenteric border of a 15-cm jejunal segment, which was exteriorized at both ends (IBSB). (2) After 6 weeks, once dual vascularization to the IBS had been established, its mesentery was divided (IBSA) or longitudinally split, thus achieving its elongation (IBSE). A control dog underwent a Thiry-Vella (T-V) loop procedure of an identical jejunal segment. Viability of the IBSB and IBSA was previously proven by the authors, through angiographic studies. In the present study, the absorption capability of IBS variants was assessed using in situ luminal perfusion, with a bicarbonate buffer containing glucose and labeled glycine. Jejunal transport rates of these solutes were calculated from the differences in their concentrations in the perfusion solution and in the effluent. Comparisons were made among the IBS variants and between them and the T-V loop. No significant difference in the absorption capability of glucose and glycine was noted between the various IBS variants. There was a marked reduction of glucose absorption and a moderate reduction of glycine absorption in all IBS variants. when compared with the fresh T-V loop, most probably because of disuse atrophy of the mucosa. In conclusion, absorption of glucose and glycine is preserved in the IBS, created by omentoenteropexy, both after its mesenteric division and following the IBS elongating procedure.

Tissue precooling for thermochemical damage reduction during laser surgery.

This report describes a preliminary investigation of the possibility of reducing the thermal damage induced by lasers in the course of laser surgery. Skin incisions made by CO2 laser beams--with and without precooling--were evaluated and compared with scalpel cuts. Full thickness cuts were carried out on the flank of adult cats. Precooling was achieved by spraying chlorethyl just before the laser application. Both the precooled and the regular laser incisions were bloodless. The precooled cuts however produced considerably less amount of charring and therefore smoother and cleaner cut edge. The incisions were sutured and the cats were kept under supervision. Upon inspection four weeks later all incisions were completely healed. No skin thickening or keloid were present. The scar produced by the regular laser technique was much more pronounced and wide relative both to the scars of the precooled or the scalpel cuts which were almost alike.

Effects of nonischemic hypoxia on jejunal mucosal structure and function: study of an experimental model in dogs.

A model of nonischemic hypoxia of the jejunum was designed in dogs, by shunting of blood from the inferior vena cava directly into the regional mesenteric arterial supply, thereby lowering the PaO2 of the blood that reached the jejunal wall from 98.6 +/- 3 to 62 +/- 5 mm Hg. Absorption rates of sodium, glucose, fructose, glycine, and the dibasic aminoacid lysine were studied by in situ luminal perfusion of a 30-cm proximal jejunal segment with a bicarbonate buffer solution containing phenol red as a nonabsorbable marker for determination of water fluxes. During periods of control, hypoxia, and after discontinuation of the venoarterial admixture (recovery), effluent perfusate was collected and mucosal biopsies were obtained for assay of lactase, maltase and sucrase activity, mucosal ATPase activity and ATP content, and for light- and electron microscopic examination. Mesenteric supply with hypoxic blood was associated with a significant inhibition of Na+,K+-ATPase activity (p less than 0.001) and a rise in mucosal ATP content (p less than 0.05). There was a significant reduction in the absorption rates of sodium (p less than 0.001), glucose, and glycine (p less than 0.01), but no change in the transport of fructose and of lysine. Brush border enzymes were unaltered. The histological appearance of the mucosa remained normal throughout the experiment, but on electron microscopy a distinct swelling of the enterocyte mitochondria was noted during the hypoxia period.(ABSTRACT TRUNCATED AT 250 WORDS)

The "jaundiced heart": a possible explanation for postoperative shock in obstructive jaundice.

Patients with obstructive jaundice are susceptible to postoperative shock and kidney failure. The cause of these potentially fatal complications has not been fully clarified. The present study was designed to assess the role of myocardial dysfunction in the hemodynamic disturbance of obstructive jaundice. We studied the effect of isolated cholemia on left ventricular performance in five conscious dogs before and 2 weeks after choledochocaval anastomosis by using measurements of systolic time intervals (STIs) and maximal dp/dt. Mean left ventricular ejection tiem (LVET) decreased after cholemia from 159 +/- 2.8 msec to 139 +/- 2.6 msec (p less than 0.005), while mean preejection period (PEP) and mean PEP/LVET were increased from 41 +/- 8.5 msec to 87 +/- 14 msec (p less than 0.05) and from 0.39 +/- 0.06 to 0.62 +/- 0.1 (p less than 0.01), respectively. During cholemia, STIs were unchanged after intravenous administration of ouabain, whereas in the control period, there was shortening of mean PEP from 71 +/- 8.8 msec to 58 +/- 7.6 msec (p less than 0.05) and of Q-S2 from 257 +/- 12 msec to 235 +/- 14 msec (p less than 0.005) in response to ouabain. Maximal dp/dt decreased after choledochocaval anastomosis from 4543 +/- 593 mm Hg/sec to 3666 +/- 648 mm Hg/sec (p less than 0.025). We conclude that cholemia in the dog is clearly associated with impaired left ventricular performance. The present data also support a previously published in vitro study from our laboratory showing that cholemia blunts the myocardial contractile response to sympathomimetic agents. The cardiodepressor effect of cholemia may explain the increased tendency of patients with obstructive jaundice to postoperative shock and renal failure.

Systemic hypotension and decreased pressor response in dogs with chronic bile duct ligation.

Vascular instability as defined by systemic hypotension and unresponsiveness to endogenous or exogenous vasoactive substances is a feature of both patients and experimental animals with obstructive jaundice. In this study, we have attempted to dissect the possible mechanisms for these abnormalities using both in vivo and in vitro methods. In vivo cumulative pressor responses (Rmax) to intravenous and intraarterial infusions of norepinephrine and angiotensin II and to intravenous infusion of angiotensin I were studied pre- and postoperatively in chronic bile duct-ligated dogs and compared to sham-operated dogs. Preoperatively, the pressor responses to the cumulative infusion of six doses of vasoactive substances in the pre-sham operated and pre-chronic bile duct-ligated dogs were not significantly different. Postoperatively, in the sham-operated dogs, there was no significant change in systemic blood pressure at 1 and 3 weeks, and only in isolated instances were significantly different pressor responses found compared to the preoperative result. In chronic bile duct-ligated dogs, the mean systemic blood pressure fell significantly from 117.2 +/- 3.1 to 107.2 +/- 3.0 mm Hg (p less than 0.01) at 1 week and remained significantly lower at 3 weeks [109.7 +/- 2.6 mm Hg (p less than 0.05)]. The Rmax to intravenous, but not intraarterial norepinephrine, was significantly decreased. In contrast, the Rmax to both intravenous and intraarterial angiotensin II infusions were significantly depressed at both 1 and 3 weeks. Similarly, the response to intravenous angiotensin I was significantly depressed. Cardiac output rose moderately in two sham-operated dogs from an average of 3.1 to 3.5 liters per min by 3 weeks associated with a decrease of 14.8% in peripheral vascular resistance.(ABSTRACT TRUNCATED AT 250 WORDS)

Measurement of the laser exposure levels for burn threshold in biological tissue.

Experiments for the evaluation of the laser energy density required to induce burn threshold in biological tissue are presented. The results are compared with a theoretical model. The values obtained for soft tissue are higher than the pain threshold and the safety standards for the maximum permissible exposure. This is due to the different nature of injury associated with the surgical process.

Effect of isolated cholaemia on systemic haemodynamics and kidney function in conscious dogs.

1. Systemic haemodynamics and kidney function were studied in the same dogs before and 14 days after choledochocaval anastomosis. 2. All dogs became deeply jaundiced whereas parenchymal liver function remained unchanged as assessed biochemically. 3. After choledochocaval anastomosis there was a decrease in mean arterial pressure (118 +/- 18 to 98 +/- 13 mmHg, P less than 0.005), and total peripheral resistance (4073.8 +/- 620.0 to 3327.6 +/- 244.9 kPa 1-1 s kg, P less than 0.01), whereas mean cardiac index and plasma volume corrected for body weight did not change. 4. Despite their disturbed systemic haemodynamics the cholaemic dogs and normal mean glomerular filtration rate and renal plasma flow. Maximal ability to concentrate and dilute the urine was, however, impaired during cholaemia. 5. It is concluded that cholaemia per se causes peripheral vasodilatation, hypotension and renal tubular dysfunction. Similar phenomena in jaundiced patients may contribute to their susceptibility to postoperative shock and acute renal failure.

The effect of intrarenal infusion of bile on kidney function in the dog.

1. Obstructive jaundice sensitizes the kidney to anoxic damage. To clarify further this phenomenon the effect of unilateral infusion of bile on kidney function was studied. The contralateral intact kidney served as control. 2. Intrarenal infusion of diluted bile (1:10) resulted in an ipsilateral fourfold increase in mean rate of urinary flow (P less then 0.01), threefold increase in mean fractional excretion of sodium (P less then 0.05) and more than 50% increase in mean rates of potassium excretion (P less then 0.05). Urinary flow rate and electrolyte excretion returned to baseline upon cessation of bile infusion. The mean clearances of inulin and rho-aminohippurate were unchanged during intrarenal bile infusion. 3. Intrarenal infusion of isotonic taurocholate solution (20 mmol/l) mimicked the diuretic, natriuretic and kaliuretic effects of diluted bile, whereas intrarenal infusion of bilirubin did not cause any change in the excretion of electrolytes. 4. It is concluded that increase in circulating bile acids rather than hyperbilirubinaemia may alter kidney function during obstructive jaundice. Acute cholaemia may cause volume depletion by increasing urinary salt loss. This in turn may aggravate the direct nephrotoxicity of circulating bile compounds.