Does conventional early life academic excellence predict later life scientific discovery? An assessment of the lives of great medical innovators

BACKGROUND

Perhaps, as never before, we need innovators. With our growing population numbers, and with increasing pressures on our education systems, are we in danger of becoming more rigid and formulaic and increasingly inhibiting innovation? When young can we predict who will become the great innovators? For example, in medicine, who will change clinical practice?

AIMS

We therefore determined to assess whether the current academic excellence approach to medical school entrance would have captured previous great innovators in medicine, assuming that they should all have well fulfilled current entrance requirements.

METHODS

The authors assembled a list of 100 great medical innovators which was then approved, rejected or added to by a jury of 12 MD fellows of the Royal Society of Canada. Two reviewers, who had taken both the past and present Medical College Admission Test as part of North American medical school entrance requirements, independently assessed each innovator's early life educational history in order to predict the innovator's likely success at medical school entry, assuming excellence in all entrance requirements.

RESULTS

Thirty-one percent of the great medical innovators possessed no medical degree and 24% would likely be denied entry to medical school by today's standards (e.g. had a history of poor performance, failure, dropout or expulsion) with only 24% being guaranteed entry. Even if excellence in only one topic was required, the figure would only rise to 41% certain of medical school entry.

CONCLUSION

These data show that today's medical school entry standards would have barred many great innovators and raise questions about whether we are losing medical innovators as a consequence. Our findings have important implications for promoting flexibility and innovation for medical education, and for promoting an environment for innovation in general.

Propentdyopent: the scaffold of a heme metabolite as an electron reservoir in transition metal complexes

The dipyrrin-1,9-dione scaffold of heme metabolite propendyopent coordinates late transition metals (Co, Ni, Cu, and Zn) forming homoleptic, pseudo-tetrahedral complexes. Electrochemical and spectroscopic studies reveal that the monoanionic, bidentate ligands behave as electron reservoirs as the complexes reversibly host one or two ligand-based radicals.

Targeted concurrent and sequential delivery of chemotherapeutic and antiangiogenic agents to the brain by using drug-loaded nanofibrous membranes

Glioblastoma is the most frequent and devastating primary brain tumor. Surgery followed by radiotherapy with concomitant and adjuvant chemotherapy is the standard of care for patients with glioblastoma. Chemotherapy is ineffective, because of the low therapeutic levels of pharmaceuticals in tumor tissues and the well-known tumor-cell resistance to chemotherapy. Therefore, we developed bilayered poly(d,l)-lactide-co-glycolide nanofibrous membranes that enabled the sequential and sustained release of chemotherapeutic and antiangiogenic agents by employing an electrospinning technique. The release characteristics of embedded drugs were determined by employing an in vitro elution technique and high-performance liquid chromatography. The experimental results showed that the fabricated nanofibers showed a sequential drug-eluting behavior, with the release of high drug levels of chemotherapeutic carmustine, irinotecan, and cisplatin from day 3, followed by the release of high concentrations of the antiangiogenic combretastatin from day 21. Biodegradable multidrug-eluting nanofibrous membranes were then dispersed into the cerebral cavity of rats by craniectomy, and the in vivo release characteristics of the pharmaceuticals from the membranes were investigated. The results suggested that the nanofibrous membranes released high concentrations of pharmaceuticals for more than 8 weeks in the cerebral parenchyma of rats. The result of histological analysis demonstrated developmental atrophy of brains with no inflammation. Biodegradable nanofibrous membranes can be manufactured for long-term sequential transport of different chemotherapeutic and anti-angiogenic agents in the brain, which can potentially improve the treatment of glioblastoma multiforme and prevent toxic effects due to systemic administration.

Hemoperfusion in 1981

The present status of hemoperfusion using the principle of artificial cells is described in detail using coated charcoal hemoperfusion as an example. The laboratory and clinical results show that in 1981 increasing numbers of new commercial models are approaching the efficiency and blood compatibility of the ACAC laboratory system. The results of hemoperfusion for uremia, acute intoxication and hepatic coma are analyzed. Other approaches are briefly discussed.

Androgen receptor (AR) differential roles in hormone-related tumors including prostate, bladder, kidney, lung, breast and liver

The androgen receptor (AR) is expressed in many cell types and the androgen/AR signaling has been found to have important roles in modulating tumorigenesis and metastasis in several cancers including prostate, bladder, kidney, lung, breast and liver. However, whether AR has differential roles in the individual cells within these tumors that contain a variety of cell types remains unclear. Generation of AR knockout (ARKO) mouse models with deletion of AR in selective cells within tumors indeed have uncovered many unique AR roles in the individual cell types during cancer development and progression. This review will discuss the results obtained from various ARKO mice and different human cell lines with special attention to the cell type- and tissue-specific ARKO models. The understanding of various results showing the AR indeed has distinct and contrasting roles in each cell type within many hormone-related tumors (as stimulator in bladder, kidney and lung metastases vs as suppressor in prostate and liver metastases) may eventually help us to develop better therapeutic approaches by targeting the AR or its downstream signaling in individual cell types to better battle these hormone-related tumors in different stages.

Numerical investigation of non-Newtonian microcirculatory blood flow in hepatic lobule

The circulation in the liver is unique at macroscopic and microscopic levels. At the macroscopic level, there is an unusual presence of portal and arterial inputs rather than a single arterial input. At the microscopic level, a series of microenvironments in the acinar system is essential in controlling the functional characteristics of hepatic parenchymal cells. Since the hemodynamics is much less studied in the multifunctional liver, an attempt is made to study the hepatic hemodynamics in a segment of a hepatic lobular structure, that is made up of high-pressure oxygenated arteriole, low-pressure nutrient-rich portal venule, fenestrated sinusoidal space and hepatic venule. Our goal is to dispel some of the myths of this complex vascular bed by means of finite volume blood flow simulation. Flow features like high-velocity gradients near the fenestrations, flow reversal and Dean vortices in the sinusoidal space are analyzed within the non-Newtonian framework. Since no distinct exact or numerical solutions are available for this complex vascular bed, the present simulated results are compared with the available clinical observations. Results revealed that the pressure plays a key role in hepatic blood flow.

Present status of modified hemoglobin as blood substitutes and oral therapy for end stage renal failure using artificial cells containing genetically engineered cells

Artificial cell or bioencapsulation has been developed for use in bioartificial organs, drug delivery, blood substitutes, and other areas. Recent rapid advances in modified hemoglobin blood substitutes have resulted in advance stages of Phase III clinical trials. Another area of use is in oral therapy, using artificial cells microencapsulated with genetically engineered cells for use in end stage renal failure and other conditions.

Neurohormonal control of exocrine pancreas

The exocrine pancreas is regulated by various hormonal factors derived from the gut through hormone-hormonal and neurohormonal interactions. Physiologic stimuli entering the upper small intestine elicit the release of intestinal hormones and activate sensory reflex mechanisms from the intestinal mucosa to stimulate or inhibit exocrine pancreatic secretion. In addition, the endocrine pancreas, intrapancreatic nerves, and some extrapancreatic neural pathways, with or without mediation by the vagus nerve, are known to participate in regulation of exocrine pancreatic secretion. It has been established that two key intestinal hormones, secretin and cholecystokinin (CCK), in physiologic doses, act through the vagal afferent pathway and interact with each other as well as with other gut hormones. The releases of these two hormones are mediated through the corresponding releasing peptides. In the past few years, the roles of secretin- and CCK-releasing peptides have become more clearly defined. The participation of several neurotransmitters and regulatory peptides in the regulation of exocrine pancreatic secretion has also been established. In addition, neurotransmitters and neuropeptides released from the central nervous system may participate in the regulation of pancreatic secretion. It is conceivable that a few neurotransmitters and neuropeptides are involved in each neural regulatory pathway. However, their roles and sites of action in each pathway remain to be determined.

Pancreatic phospholipase A2 from the small intestine is a secretin-releasing factor in rats

A secretin-releasing activity exists in the upper small intestine and pancreatic juice in the rat and the dog. Group I pancreatic phospholipase A2 (PLA2) in canine pancreatic juice and porcine pancreatic PLA2 stimulate the release of secretin from both STC-1 cells and a secretin-producing cell (S cell)-enriched preparation isolated from rat duodenal mucosa. We investigated the distribution and release of pancreatic PLA2-like immunoreactivity in the gastrointestinal tract and the role of PLA2 on the release of secretin and pancreatic exocrine secretion in response to duodenal acidification in anesthetized rats. PLA2-like immunoreactivity was detected in the mucosa throughout the gastrointestinal tract. High concentrations of PLA2 were found in both the small intestine and the pancreas. Duodenal acidification significantly increased the release of PLA2 from the upper small intestine (385% over basal secretion). Intravenous infusion of an anti-PLA2 serum (anti-PLA2) dose-dependently inhibited the release of secretin and pancreatic exocrine secretion in response to duodenal acid perfusion. Preincubation of the concentrate of intestinal acid perfusate (10-fold) from donor rats with the anti-PLA2 significantly suppressed its stimulation of secretin release and pancreatic exocrine secretion in recipient rats. We conclude that pancreatic PLA2 also functions as a secretin-releasing factor in the small intestine that mediates acid-stimulated release of secretin in rats.

Clinical analysis and literature review of massive duodenal diverticular bleeding

A duodenal diverticulum (DD) appears in 2.5% of upper gastrointestinal (UGI) examinations and up to 22% of endoscopic retrograde cholangiopancreaticographies (ERCP) and autopsies. Most of these patients are asymptomatic, but the lesion is occasionally associated with bleeding, inflammation, perforation, obstruction of the duodenum or biliary-pancreatic duct (or both), fistula formation in the bile duct, and bezoar formation inside the diverticulum. A total of 816 patients have undergone ERCP examination at our institution since January 1987, and 100 (12.25%) of them have DD. Seven (7%) patients presented with bloody or tarry stools from massive UGI bleeding followed by shock. Only two could be diagnosed by UGI endoscopy preoperatively. The lesions were demonstrated in angiographic studies in another four cases. However, only one was correctly interpreted and one required reoperation after a correct repeat endoscopic finding. The lesions in the other two patients were identified by thorough exploration during laparotomy. The remaining case was diagnosed by intraoperative endoscopy via pyloroduodenotomy. Six underwent surgical intervention, and one was successfully treated by expectant treatment. Three (50%) had leakage from the duodenotomy but recovered uneventfully with conservative treatment. In conclusion, we believe that DD bleeding is more frequent than usually thought. A high index of suspicion should be raised in cases of UGI bleeding when more obvious and common causes have been excluded by routine endoscopy. Aggressive but careful endoscopic examination combined with accurate angiography can help us diagnose most of the cases preoperatively. Diverticulectomy is an effective surgical procedure, though it is associated with a considerable leakage rate. The morbidity is minimal if we can identify the lesion earlier and evacuate the lesion without delay.

MEK inhibits secretin release and pancreatic secretion: roles of secretin-releasing peptide and somatostatin

We investigated the mechanism of action of methionine enkephalin (MEK) on HCl-stimulated secretin release and pancreatic exocrine secretion. Anesthetized rats with pancreatobiliary cannulas and isolated upper small intestinal loops were perfused intraduodenally with 0.01 N HCl while bile and pancreatic juice were diverted. The effect of intravenous MEK on acid-stimulated secretin release and pancreatic exocrine secretion was then studied with or without coinfusion of naloxone, an anti-somatostatin (SS) serum, or normal rabbit serum. Duodenal acid perfusate, which contains secretin-releasing peptide (SRP) activity, was collected from donor rats with or without pretreatment with MEK, MEK + naloxone, or MEK + anti-SS serum, concentrated by ultrafiltration, and neutralized. The concentrated acid perfusate (CAP), which contains SRP bioactivity, was infused intraduodenally into recipient rats. MEK increased plasma SS concentration and inhibited secretin release and pancreatic fluid and bicarbonate secretion dose-dependently. The inhibition was partially reversed by naloxone and anti-SS serum but not by normal rabbit serum. In recipient rats, CAP increased plasma secretin level and pancreatic secretion. CAP SRP bioactivity decreased when it was collected from MEK-treated donor rats; this was partially reversed by coinfusion with naloxone or anti-SS serum. These results suggest that in the rat, MEK inhibition of acid-stimulated pancreatic secretion and secretin release involves suppression of SRP activity release. Thus the MEK inhibitory effect appears to be mediated in part by endogenous SS.

Roles of 5-HT receptors in the release and action of secretin on pancreatic secretion in rats

5-Hydroxytryptamine (serotonin, 5-HT) is a hormone and neurotransmitter regulating gastrointestinal functions. 5-HT receptors are widely distributed in gastrointestinal mucosa and the enteric nervous system. Duodenal acidification stimulates not only the release of both 5-HT and secretin but also pancreatic exocrine secretion. We investigated the effect of 5-HT receptor antagonists on the release of secretin and pancreatic secretion of water and bicarbonate induced by duodenal acidification in anesthetized rats. Both the 5-HT(2) receptor antagonist ketanserin and the 5-HT(3) receptor antagonist ondansetron at 1-100 microg/kg dose-dependently inhibited acid-induced increases in plasma secretin concentration and pancreatic exocrine secretion. Neither the 5-HT(1) receptor antagonists pindolol and 5-HTP-DP nor the 5-HT(4) receptor antagonist SDZ-205,557 affected acid-evoked release of secretin or pancreatic secretion. None of the 5-HT receptor antagonists affected basal pancreatic secretion or plasma secretin concentration. Ketanserin or ondansetron at 10 microg/kg or a combination of both suppressed the pancreatic secretion in response to intravenous secretin at 2.5 and 5 pmol x kg(-1) x h(-1) by 55-75%, but not at 10 pmol x kg(-1) x h(-1). Atropine (50 microg/kg) significantly attenuated the inhibitory effect of ketanserin on pancreatic secretion but not on the release of secretin. These observations suggest that 5-HT(2) and 5-HT(3) receptors mediate duodenal acidification-induced release of secretin and pancreatic secretion of fluid and bicarbonate. Also, regulation of pancreatic exocrine secretion through 5-HT(2) receptors may involve a cholinergic pathway in the rat.

Long-term results of duodenectomy with highly selective vagotomy in the treatment of complicated duodenal ulcers

BACKGROUND

Highly selective vagotomy and complete circular or partial duodenectomy have been applied to complicated duodenal ulcer for many years. These procedures seem to provide better clinical results than truncal vagotomy and antrectomy.

METHODS

A retrospective analysis was conducted of 120 patients with complicated duodenal ulcer who underwent surgical treatment between 1986 and 1999. Patients with obstruction were treated with either circular complete (17) or partial duodenectomy (3) combined with highly selective vagotomy or truncal vagotomy and antrectomy (37). Those with perforation were treated primarily with highly selective vagotomy and partial duodenectomy, highly selective vagotomy alone, or truncal vagotomy and pyloroplasty. Every patient was followed up either by a clinic visit (75%) or questionnaire to determine the presence of ulcer pain, dumping, diarrhea, vomiting, weight loss, and Visick grade.

RESULTS

Long-term follow-up of patients treated with duodenectomy and highly selective vagotomy for obstruction showed that 94% had sustained weight gain whereas more than half of those treated with truncal vagotomy and antrectomy had weight loss. In patients with perforation, duodenectomy and highly selective vagotomy offered no advantage over highly selective vagotomy alone.

CONCLUSIONS

Highly selective vagotomy and complete circular or partial duodenectomy provide fewer sequelae and better weight gain long term than truncal vagotomy and antrectomy for patients with obstructing duodenal ulcers.

Procedures for microencapsulation of enzymes, cells and genetically engineered microorganisms

Methods to microencapsulate enzyme, cells, and genetically engineered cells have been described in this article. More specific examples of enzyme encapsulation include the microencapsulation of xanthine oxidase for Lesch-Nyhan disease; phenylalanine ammonia lyase for pheny, ketonuria and microencapsulation of multienzyme systems with cofactor recycling for multistep enzyme conversions. Methods for cell encapsulation include the details for encapsulating hepatocytes for liver failure and for gene therapy. This also includes the details of a novel two-step method for encapsulation of high concentrations of smaller cells. Another new approach is the detailed method of the encapsulation of genetically engineered Escherichia coli DH5 cells for lowering urea, ammonia, and other metabolites in kidney or, liver failure and other diseases.

Red blood cell substitutes

Soluble polymerized haemoglobin (polyhaemoglobin) is now in a phase III clinical trials. Patients have received up to 20 units (10 litres) in trauma surgery and other surgery. Polyhaemoglobin can be stored for more than 1 year. Haemoglobin solutions have no blood group antigen and can be used as a 'universal donor' oxygen carrier. They can also be sterilized. With a circulation half-life of 24 hours they are undergoing trials for peri-operative use. For conditions with potential for ischaemia-reperfusion injuries, a new polyhaemoglobin-superoxide dismutase-catalase, which can reduce oxygen radicals, is being developed. Recombinant human haemoglobin has been tested in clinical trials, and a new type of recombinant human haemoglobin that has low affinity for nitric oxide is being developed for clinical trials. To increase the circulation time, artificial red blood cells have been prepared with a bilayer lipid membrane (haemoglobin liposomes) or with a biodegradable polymer membrane-like polylactide (haemoglobin nanocapsules). Synthetic chemicals such as perfluorochemicals are also being developed and tested in clinical trials as red blood cell substitutes.

Artificial cell biotechnology for medical applications

Artificial cells are prepared in the laboratory for medical and biotechnological applications. The earliest routine clinical use of artificial cells is in the form of coated activated charcoal for hemoperfusion. Implantation of encapsulated cells are being studied for the treatment of diabetes, liver failure and the use of encapsulated genetically engineered cells for gene therapy. We recently found that daily orally administered artificial cells containing a genetically engineered microorganism can lower the elevated urea level in uremic rats to normal levels and increase the survival of the animal. Furthermore, this can remove potassium, phosphate, uric acid and other waste metabolites from uremic plasma. Blood substitutes based on modified hemoglobin are already in phase-III clinical trials in patients with as much as 20 units infused into each patient during trauma surgery. Artificial cells containing enzymes are being developed for clinical trials in hereditary enzyme deficiency diseases and other diseases. Artificial cells are also being investigated for drug delivery and other uses in biotechnology, chemical engineering and medicine.

Artificial cells microencapsulated genetically engineered E. coli DH5 cells for the lowering of plasma creatinine in-vitro and in-vivo

High level of plasma creatinine occurs in renal insufficiency, uremia, and other diseases. At present lowering of this metabolite is done by using dialysis and other techniques. In this article, we report the use of artificial cells microencapsulated genetically engineered E. coli DH5 cells for lowering plasma creatinine in-vitro and in-vivo. Result shows that artificial cells were able to lower plasma creatinine in-vitro from 21.80 +/- 1.10 mg/dl to 21.80 +/- 1.10 mg/dl in 60 minutes and to 19.34 +/- 0.60 mg/dl in 3 hours. Result also shows that when given orally on a daily basis, artificial cells microencapsulated genetically engineered E. coli DH5 cells were also able to lower plasma creatinine in rats.

Cellular mechanism of sodium oleate-stimulated secretion of cholecystokinin and secretin

Long-chain fatty acids are potent stimulants of secretin and CCK release. The cellular mechanisms of fatty acid-stimulated secretion of these two hormones are not clear. We studied the stimulatory effect and mechanism of sodium oleate (SO) on secretin- and CCK-producing cells. SO stimulated the release of secretin or CCK from isolated rat mucosal cell preparations enriched in either secretin- or CCK-producing cells, respectively. SO also time- and dose-dependently stimulated secretin and CCK release from STC-1 cells. In STC-1 cells, SO-stimulated secretin and CCK release was potentiated by IBMX and inhibited by a protein kinase A-selective inhibitor and a cAMP-specific antagonist. SO-stimulated releases of the two hormones were also inhibited by downregulation or inhibitors of protein kinase C, a calmodulin antagonist and an inhibitor of calmodulin-dependent protein kinase II. Chelating of extracellular Ca(2+) or addition of an L-type calcium channel blocker diminished SO-stimulated hormone releases. SO caused an increase in intracellular Ca(2+) concentration that was partially reversed by diltiazem but had no effect on production of cAMP, cGMP, or inositol-1,4,5-triphosphate. These results indicate that SO acts on secretin- and CCK-producing cells. Its stimulatory effect is potentiated by endogenous protein kinase A and mediated by activation of Ca(2+) influx through the L-type channels and of protein kinase C and Ca(2+)/calmodulin-dependent protein kinase II.

Effects of bone marrow cells on hepatocytes: when co-cultured or co-encapsulated together

Bone marrow cells co-cultured with hepatocytes resulted in hepatocytes that can be maintained in culture for 14-21 days. This is compared to 7-10 days with hepatocytes alone under the same conditions. Similarly, when bone marrow cells are co-encapsulated together with hepatocytes, the viability of hepatocytes in culture medium is prolonged to 28 days. This is compared to 14 days when hepatocytes are encapsulated alone under the same conditions. These results suggest that bone marrow cells can contribute to the viability and maintenance of hepatocytes. It addition, this principle could be applied to other situation as in helping the regeneration of hepatocytes in liver failure and also for other cells and organs.

In vitro and in vivo uric acid lowering by artificial cells containing microencapsulated genetically engineered E. coli DH5 cells

Increase in systemic uric acid occurs in renal insufficiency, gout, chemotherapy, and other diseases. Dialysis can lower this metabolite but is expensive. The use of drugs can, sometime, result in side effects. Therefore, a suitable affordable method for this is required. In this article, for the first time, we report the use of artificial cells containing micro encapsulated genetically engineered E. Coli DH5 cells for lowering uric acid in vitro and in vivo. Results show that this novel approach has the ability to significantly lower uric acid from 84.80 +/- 3.40 mg/dl to 9.32 +/- 0.05 mg/dl in vitro and from the plasma of the experimental animals from the control levels of 71.00 +/- 27.49 mg/dl to 20.33 +/- 17.92 mg/dl in vivo. Continued daily oral administration maintained the plasma uric acid concentration of experimental uremic rats to the normal plasma uric acid level range during the entire test period.

Endogenous nitric oxide mediates pancreatic exocrine secretion stimulated by secretin and cholecystokinin in rats

Nitric oxide (NO) is one of the important biologic mediators in regulation of gastrointestinal (GI) functions, but the influence of NO on the release of secretin and cholecystokinin (CCK) and exocrine pancreatic secretion has not been adequately investigated in the rat. The aim of this study was to determine the role of NO on endogenous and exogenous secretin- or CCK-stimulated pancreatic exocrine secretion both in anesthetized and conscious rats. Experiments were carried out in four different groups of rats with duodenal pancreatobiliary cannulas and jugular vein catheters. Group 1: During duodenal infusion of 0.05N HCl or 15% casein (pH 7.0), N-nitro-L-arginine (NNA), an inhibitor of NO-synthase in graded doses (2.5, 5, 10 mg/kg/h), was infused intravenously. Group 2: One hour after starting intravenous secretin at 5 pmol/kg/h or intravenous CCK-8 at 0.06 microg/kg/h, NNA in graded doses was administered intravenously. Group 3: In conscious rats, NNA (5 mg/kg/h) was given intravenously for 1 hour after a meal. Group 4: L-Arginine at 100 mg/kg/h was infused intravenously during the period of NNA (5 mg/kg/h) infusion in groups 1, 2, and 3. Pancreatic juice was collected at 30-minute intervals to measure volume, as well as output of bicarbonate and protein. At the end of the experiment, plasma secretin, vasoactive intestinal polypeptide (VIP) and CCK levels were determined by radioimmunoassay (RIA). NNA dose dependently inhibited the pancreatic secretion of fluid and bicarbonate stimulated by duodenal acidification, exogenous secretin, and a meal. NNA dose dependently inhibited the pancreatic secretion of protein stimulated by duodenal infusion of casein, exogenous CCK, and a meal. L-Arginine significantly reversed the NNA-induced inhibition of pancreatic secretion in all experiments. NNA did not alter significantly the plasma levels of secretin, VIP, and CCK. Our results indicated that endogenous NO plays a significant role in the regulation of pancreatic exocrine secretion stimulated by secretin and CCK. However, NO does not influence the release of secretin, VIP, or CCK in the rat.

Two future generations of blood substitutes based on polyhemoglobin-SOD-catalase and nanoencapsulation

This paper discusses our research on two new generation blood substitutes. One is based on the crosslinking of hemoglobin, superoxide dismutase(SOD) and catalase (CAT) to form polyhemoglobin-SOD-CAT. This is being investigated for use in conditions with potential problems related to ischemia-reperfusion injuries as in severe hemorrhagic shock, stroke and other conditions. The second one is based on biodegradable polymeric nanocapsules containing hemoglobin and enzymes. In this form, the hemoglobin and enzymes are separated from the external environment. Furthermore, modifications of the polymeric membrane can result in increase in circulation time.

A secretin releasing peptide exists in dog pancreatic juice

Canine pancreatic juice has been shown to stimulate exocrine pancreatic secretion in the dog. In the present study we investigated whether there is a secretin-releasing peptide in canine pancreatic juice. Pancreatic juice was collected from the dogs with Thomas gastric and duodenal cannulas while pancreatic secretion was stimulated by intravenous administration of secretin at 0.5 microg/kg/h and CCK-8 at 0.2 microg/kg/h, respectively. The pancreatic juice was separated into three different molecular weight (MW) fractions (Fr) by ultrafiltration (Fr 1; MW > 10,000, Fr 2; MW=10,000-4,000 and Fr 3; MW < 4,000), respectively. All the fractions were bioassayed in anesthetized rats. Fraction 3 dose-dependently and significantly stimulated pancreatic juice flow volume from 78.0% to 99.4% (p<0.05) and bicarbonate output from 128.9% to 202.1% (p<0.01), respectively. Plasma secretin concentration also increased from 1.2 +/- 0.5 pM to 5.0 +/- 0.8 pM and 6.0 +/- 1.0 pM (p<0.05). None of these fractions increased pancreatic protein secretion or plasma CCK level. The stimulatory effect of Fraction 3 on pancreatic secretion and the release of secretin was completely abolished by treatment with trypsin (1 mg/ml for 60 min at 37 degrees C) but not by heating (100 degrees C, 10 min). Intravenous injection of a rabbit anti-secretin serum, which rendered plasma secretin almost undetectable in rat plasma, also abolished Fr 3-stimulated pancreatic secretion of fluid and bicarbonate secretion. These observations suggest that a secretin-releasing peptide exists in the canine pancreatic juice. It is trypsin-sensitive and heat-resistant. This peptide may play a significant physiological role on the release of secretin and regulation of exocrine pancreatic secretion.

Canine vagus nerve stores cholecystokinin-58 and -8 but releases only cholecystokinin-8 upon electrical vagal stimulation

Cholecystokinin-58 has been shown to be the major form of cholecystokinin (CCK) released to the circulation upon lumenal stimulation of the small intestine in humans and dogs. In anesthetized dogs, electrical vagal stimulation evokes pancreatic exocrine secretion that is in part mediated through the release of CCK. We studied the molecular form of CCK stored in canine vagus nerves and that released into circulation upon electrical vagal stimulation. Gel filtration and radioimmunoassay of the water and acid extracts of canine vagus nerves indicated CCK-8 (35%) and CCK-58 (65%) as the major molecular forms in the vagus nerve. Both forms of CCK isolated from the vagal extracts were equally bioactive as the standard CCK-8 and CCK-58, respectively, in stimulation of amylase release from isolated rat pancreatic acini. Analysis of plasma collected after electrical vagal stimulation indicated that CCK-8 is the only form released into the circulation. The release of CCK-8 upon electrical vagal stimulation was not affected by application of lidocaine to the upper small intestinal mucosa, suggesting that it was released from vagal nerve terminals.

Inhibition of gastric acid secretion in rat stomach by PACAP is mediated by secretin, somatostatin, and PGE(2)

Pituitary adenylate cyclase-activating polypeptide (PACAP), existing in two variants, PACAP-27 and PACAP-38, is found in the enteric nervous system and regulates function of the digestive system. However, the regulatory mechanism of PACAP on gastric acid secretion has not been well elucidated. We investigated the inhibitory action of PACAP-27 on acid secretion and its mechanism in isolated vascularly perfused rat stomach. PACAP-27 in four graded doses (5, 10, 20, and 50 microg/h) was vascularly infused to determine its effect on basal and pentagastrin (50 ng/h)-stimulated acid secretion. To study the inhibitory mechanism of PACAP-27 on acid secretion, a rabbit antisecretin serum, antisomatostatin serum, or indomethacin was administered. Concentrations of secretin, somatostatin, PGE(2), and histamine in portal venous effluent were measured by RIA. PACAP-27 dose-dependently inhibited both basal and pentagastrin-stimulated acid secretion. PACAP-27 at 10 microg/h significantly increased concentrations of secretin, somatostatin, and PGE(2) in basal or pentagastrin-stimulated state. The inhibitory effect of PACAP-27 on pentagastrin-stimulated acid secretion was reversed 33% by an antisecretin serum, 80.0% by an antisomatostatin serum, and 46.1% by indomethacin. The antisecretin serum partially reduced PACAP-27-induced local release of somatostatin and PGE(2). PACAP-27 at 10 microg/h elevated histamine level in portal venous effluent, which was further increased by antisomatostatin serum. However, antisomatostatin serum did not significantly increase acid secretion. It is concluded that PACAP-27 inhibits both basal and pentagastrin-stimulated gastric acid secretion. The effect of PACAP-27 is mediated by local release of secretin, somatostatin, and PGE(2) in isolated perfused rat stomach. The increase in somatostatin and PGE(2) levels in portal venous effluent is, in part, attributable to local action of the endogenous secretin.

Acute colonic intramural hematoma due to blunt abdominal trauma

Trauma to the colon is uncommon and accounts for only 3-5% of all blunt abdominal injuries. Among them, intramural hematoma of the colon is a rare complication and the acute form is rarer than the chronic form. We report a 37-year-old man who presented with abdominal pain followed by intestinal obstruction due to a blunt trauma. The initial diagnosis was done by sonography and proved by computed tomography (CT). Abdominal sonography also detected an increment in the size of the hematoma with progressive abdominal cramping pain that prompted urgent laparotomy. Ileocolic segmental resection with end-to-end ileocolostomy was performed and the patient recovered uneventfully. Based on our experience with a patient suffering from an intramural colonic hematoma following blunt abdominal trauma (BAT) and based on a review of the literature, we discuss the different clinical manifestations, difficulties of diagnosis, and different treatment modalities of this disease entity. We conclude that acute colonic hematoma can be diagnosed by sonography and/or CT in contrast to the early reported cases, in the pre-CT era, when they could only be diagnosed at laparotomy. Endoscopy may also be helpful for diagnosis in some cases. Although expectant therapy may be successful in some cases, the majority of the cases may need operation.

Sustained drug release characteristics of biodegradable composite poly(d,l)lactic acid-poly(l)lactic acid microcapsules containing ciprofloxacin

Ciprofloxacin polylactic microcapsules were prepared by the phase separation process. Two types of polylactic acid, poly(d,l)lactic acid and poly(l)lactic acid were combined as membrane materials to prevent the aggregation which happened frequently in the phase separation process. The polymer compositions of the microcapsules can influence the release rate of Ciprofloxacin. The optimal release rate of the drug can be obtained by modifying microcapsule compositions. Poly(d,l)lactic acid is superior in slowing the rate of drug release than poly(l)lactic acid. However, poly(l)lactic acid is necessary in the preparation of the microcapsules to prevent aggregation.

Purification of two secretin-releasing peptides structurally related to phospholipase A2 from canine pancreatic juice

We previously showed that canine pancreatic juice contains a secretin-releasing factor activity. In this study, we carried out isolation of two secretin-releasing peptides (SRPs) from canine pancreatic juice. Through ultrafiltration, anion and cation exchange, and reverse-phase high-performance liquid chromatography (HPLC) steps and an in vitro bioassay in STC-1 cells, two SRPs, SRP-1 and SRP-2, were isolated and purified to homogeneity. Both SRPs dose-dependently stimulated secretin release from STC-1 cells. The results of mass spectral analysis indicated that SRP-1 and SRP-2 had molecular masses of 14,061 Da and 14,053 Da, respectively. N-terminal amino acid sequence analysis indicated that SRP-1 was identical to canine pancreatic PLA2 in the 25 residues determined; whereas SRP-2 had 71% sequence homology to the enzyme in the first 21 residues. Commercially available porcine pancreatic PLA2 dose-dependently stimulated secretin release from STC-1 cells. Porcine pancreatic PLA2 also stimulated secretin release from a secretin-producing cells-enriched preparation isolated from rat duodenal mucosa. These results suggest that pancreatic PLA2 and its related peptide may participate in regulation of secretin secretion.

Artificial cell microcapsules containing genetically engineered E. coli DH5 cells for in-vitro lowering of plasma potassium, phosphate, magnesium, sodium, chloride, uric acid, cholesterol, and creatinine: a preliminary report

Lowering of plasma Mg, P, Na, Cl, uric acid, cholesterol, and creatinine is required in renal failure and other diseases. In this preliminary report, we studied the ability of artificial cells microencapsulated genetically engineered E. coli DH5 cells in lower K, Mg, P, Na, Cl, uric acid, cholestrol, creatinine, and billirubin from plasma in-vitro. Result shows that this novel approach has the ability to significantly lower these metabolites from the plasma in-vitro.

Differences in gastric emptying between highly selective vagotomy and posterior truncal vagotomy combined with anterior seromyotomy

Gastric emptying has been reported to be both delayed and unchanged following posterior truncal vagotomy combined with anterior seromyotomy (PTV + AS). When compared to highly selective vagotomy (HSV), our clinical experience was that PTV + AS not uncommonly produced postprandial distress. We studied gastric emptying of both liquids and solids 3 and 12 months following HSV and PTV + AS to determine what if any differences there were in gastric emptying between the two procedures. We compared these results with those from studies done in both normal subjects and unoperated duodenal ulcer patients. In 26 duodenal ulcer patients with perforation (n = 18) or bleeding (n = 8), who were treated with HSV (n = 10) or PTV + AS (n = 16), gastric emptying of liquids and solids was evaluated at 3 months and 12 months postoperatively. At 3 months, gastric emptying of liquids was delayed in both the HSV and PTV + AS groups as compared to values in both normal subjects and unoperated duodenal ulcer patients. The emptying of solids was markedly delayed by PTV + AS in contrast to HSV at 3 months (167.1 +/- 28.4 minutes vs. 79.9 +/- 16.7 minutes; P <0.05). The lag duration was not affected. A limited number of patients studied at 12 months showed similar and near-normal emptying of solids in both the HSV and PTV + AS groups (67.5 +/- 7.0 minutes vs. 70 +/- 6.6 minutes). PTV + AS in contrast to HSV produces more marked delayed emptying of liquids and solids at 3 months; with time (1 year) these values return to near normal.

Comparison of bilirubin conjugation in encapsulated hepatocytes, hepatocyte homogenate and intact hepatocytes

Homogenized rat hepatocytes, whole hepatocytes and encapsulated hepatocytes were incubated with bilirubin and UDP-glucuronic acid to test their ability to form bilirubin conjugates. Bilirubin monoconjugated and diconjugated were detected in all the three preparations by HPLC analysis. The UDP-glucuronosyltransferase (UDPGT) activity of homogenized hepatocytes was 0.002 +/- 0.00006 mM/min per million cells; that of intact hepatocytes was 0.001 +/- 0.00006 mM/min per million cells and that of encapsulated hepatocytes was 0.0005 +/- 0.00002 mM/min per million cells.

Kinetic studies of hepatocyte UDP-glucuronosyltransferase: evidence of an allosteric enzyme

The kinetic analysis of the enzyme UDP-glucuronosyltransferase (UDPGT) responsible for the conjugation of bilirubin, suggest that it is a multisubunit enzyme in which there is cooperative binding of substrate to the subunits. The binding of bilirubin to UDP-glucuronosyltransferase shows positive cooperativity with an apparent dissociation constant of 7.824 x 10(-4) +/- 6.405 x 10(-4) mM. The apparent Hill coefficient for bilirubin to UDPGT is 2.9. The binding of UDP-glucuronic acid exhibits kinetics with mixed cooperativity. Analysis with the Hill equation give an apparent dissociation constant of 6.873 +/- 3.816 mM and a Hill coefficient of 4.028 +/- 1.045. These values of the Hill coefficient are consistent with an enzyme being an oligomer with 6 subunits, since the actual number of subunits must be greater than the apparent Hill coefficient.

Artificial cells, encapsulation, and immobilization

The basic principles of artificial cells, encapsulation and immobilization form the basis for a number of bioartificial organs. Hemoperfusion based on encapsulated adsorbent has been in routine clinical uses for many years to remove toxins or drugs from the circulating blood. Blood substitutes based on crosslinked hemoglobin or encapsulated hemoglobin are being developed and tested in phase II and Phase III clinical trials. Enzyme therapy using microencapsulated enzymes have been studied in animal studies and in a preliminary human study. Encapsulation or other ways of immobilization of cells are being developed extensively by many groups. This includes the encapsulation or immobilization of islets, hepatocytes and genetically engineered cells.

Biodegradable polylactic acid nanocapsules containing ciprofloxacin: preparation and characterization

Nanocapsules have been studied as carriers to deliver different types of drugs into macrophages. Many studies have shown that the nanocapsules can enhance the biological response of the drugs. In this study, we prepared ciprofloxacin nanocapsules with polylactic acid. The ciprofloxacin is an antibacterial agent. The ciprofloxacin nanocapsules prepared have a means diameter of 168 nm. In phosphate buffer at pH 7.4, high encapsulation rate was obtained. The nanocapsules with high encapsulation rate can also be made from ciprofloxacin base.

Growth kinetics of genetically engineered E. coli DH 5 cells in artificial cell APA membrane microcapsules: preliminary report

This paper describes the growth kinetics of genetically engineered E. coli DH5 cells inside the APA membrane artificial cells. The APA microcapsule membrane found does not significantly affects the growth of the encapsulated E. coli DH5 cells. The total protein production of the E. coli DH5 cells inside the APA microcapsules were not significantly different from that of the bacterial cells grown in the free bacterial media. The result also show that the log phase APA artificial cells containing genetically engineered E. coli DH5 would be highly effective for the conversion of various external metabolites.

Porcine pancreatic phospholipase A2 stimulates secretin release from secretin-producing cells

We have isolated, from canine pancreatic juice, two 14-kDa proteins with secretin-releasing activity that had N-terminal sequence homology with canine pancreatic phospholipase A2 (PLA2). In this study we have obtained evidence that secretin-releasing activity is an intrinsic property of pancreatic PLA2. Porcine pancreatic PLA2 from Sigma or Boehringer Mannheim was fractionated into several peaks by reverse phase high performance liquid chromatography. They were tested for stimulation of secretin release from murine neuroendocrine intestinal tumor cell line STC-1 and secretin cells enriched mucosal cell preparations isolated from rat upper small intestine. Each enzyme preparation was found to contain several components of secretin-releasing activity. Each bioactive fraction was purified to homogeneity by rechromatography and then subjected to mass spectral analysis and assays of PLA2 and secretin-releasing activities. It was found that the fraction with highest enzymatic activity also had the highest secretin-releasing activity and the same Mr as porcine pancreatic PLA2. Moreover, it also had the same N-terminal amino acid sequence (up to 30 residues determined) as that of porcine pancreatic PLA2, suggesting that it was identical to the enzyme. Purified porcine pancreatic PLA2 also stimulated secretin release concentration-dependently from both STC-1 cells and a mucosal cell preparation enriched in secretin-containing endocrine cells isolated from rat duodenum. Abolishment of the enzymatic activity by pretreatment with bromophenacyl bromide did not affect its secretin-releasing activity. The stimulatory effect of purified pancreatic PLA2 on secretin secretion from STC-1 cells was inhibited by an L-type Ca2+ channel blocker, by down-regulation of protein kinase C or by pretreatment of the cell with pertussis toxin. It is concluded that porcine pancreatic PLA2 possesses an intrinsic secretin-releasing activity that was independent of its enzymatic activity. This action is pertussis toxin-sensitive and is in part dependent on Ca2+ influx through the L-type channel and activation of protein kinase C.

Vagus nerve modulates secretin binding sites in the rat forestomach

Secretin is well known for its inhibitory action on gastric motility. It has been reported that secretin in a physiological dose inhibits gastric motility through mediation by the vagal afferent pathway. Secretin also elicited relaxation of carbachol-stimulated rat forestomach muscle strips by binding to its receptors, suggesting a direct action on this peripheral tissue. We hypothesized that vagal input may affect the action of secretin by modulating the level of secretin receptor in the forestomach. Several treatments, including vagal ligation, vagotomy, perivagal application of capsaicin or colchicine, intravenous infusion of tetrodotoxin, and intraperitoneal injection of atropine, were performed to investigate their effects on secretin receptor binding to forestomach membranes. Specific binding of 125I-labeled secretin to forestomach membranes was significantly decreased (45%) by vagal ligation, vagotomy (50%), or perivagal colchicine treatment (40%). On the contrary, specific binding of 125I-secretin was not affected by perivagal capsaicin treatment, intravenous infusion of tetrodotoxin, or intraperitoneal injection of atropine. By Scatchard analysis of the binding data, the capacity of the high-affinity binding sites in forestomach membranes was found to decrease significantly after vagal ligation compared with membranes from the sham-operated group. However, the affinity at the high-affinity binding sites, the binding parameters of the low-affinity binding sites, and binding specificity were not changed. Vagal ligation but not perivagal capsaicin treatment reduced the inhibitory effect of secretin on bethanechol-stimulated contraction of isolated forestomach muscle strips, causing a right shift in the dose-response curve. These results suggest that vagal input through axonal transport plays a significant role on secretin action by modulating the capacity of secretin binding sites (but not affinity or specificity), at least in rat forestomach.

A different approach to treatment of phenylketonuria: phenylalanine degradation with recombinant phenylalanine ammonia lyase

Phenylketonuria (PKU), with its associated hyperphenylalaninemia (HPA) and mental retardation, is a classic genetic disease and the first to have an identified chemical cause of impaired cognitive development. Treatment from birth with a low phenylalanine diet largely prevents the deviant cognitive phenotype by ameliorating HPA and is recognized as one of the first effective treatments of a genetic disease. However, compliance with dietary treatment is difficult and when it is for life, as now recommended by an internationally used set of guidelines, is probably unrealistic. Herein we describe experiments on a mouse model using another modality for treatment of PKU compatible with better compliance using ancillary phenylalanine ammonia lyase (PAL, EC 4.3.1.5) to degrade phenylalanine, the harmful nutrient in PKU; in this treatment, PAL acts as a substitute for the enzyme phenylalanine monooxygenase (EC 1.14.16.1), which is deficient in PKU. PAL, a robust enzyme without need for a cofactor, converts phenylalanine to trans-cinnamic acid, a harmless metabolite. We describe (i) an efficient recombinant approach to produce PAL enzyme, (ii) testing of PAL in orthologous N-ethyl-N'-nitrosourea (ENU) mutant mouse strains with HPA, and (iii) proofs of principle (PAL reduces HPA)-both pharmacologic (with a clear dose-response effect vs. HPA after PAL injection) and physiologic (protected enteral PAL is significantly effective vs. HPA). These findings open another way to facilitate treatment of this classic genetic disease.

Thoracic epidural anesthesia for pain relief and postoperation recovery with modified radical mastectomy

The purpose of this study was to investigate whether thoracic epidural anesthesia (TEA) provides better postoperative pain relief and recovery than general anesthesia (GA) for modified radical mastectomy (MRM) surgery. Sixty-four patients rated as American Society of Anesthesiologists (ASA) 1 to 3 who underwent MRM surgery were included in the study. In TEA group patients, 2% lidocaine (15-20 ml) was administered via the epidural route as primary anesthesia, in conjunction with midazolam (5-10 mg) and fentanyl (<250 microg) for amnesia. The GA patients were maintained with isoflurane and 50% nitrous oxide in oxygen. After operation the patients were given pethidine (1 mg/kg IM) as required for pain relief. The time to first pethidine requirement, total pethidine consumption, worst pain score, bed rest time, satisfaction score, and anesthesia-related side effects were recorded for 2 days after surgery. The results show that TEA provided a more prolonged analgesic effect than GA after operation. A longer time to first pethidine requirement (19.2 +/- 1.5 vs. 7.6 +/- 2.5 hours) (p < 0. 001) and decreased pethidine consumption (17.2 +/- 7.0 vs. 76.3 +/- 17.4 mg) (p < 0.001) were observed in the TEA group than in the GA group, respectively. A worse visual analog scale (VAS) pain score was observed in the GA group (5.7 +/- 0.6) than in TEA patients (4.3 +/- 0.4) (p < 0.01). The average bed rest time was significantly shorter in the TEA group (16.9 +/- 0.9 hours) (p < 0.01) than in the GA group (27.1 +/- 4.1 hours). Overall satisfaction scores were significantly higher in the TEA group (4.4 +/- 0.1) (p < 0.01) than in the GA group (3.5 +/- 0.2). Side effects were observed at a higher frequency in the GA group (16/32) (p < 0.0001) than in the TEA group (3/32). The frequency of pethidine injection for pain relief was significantly lower in the TEA group (8/32) (p < 0.0001) than in the GA group (24/32). The total hospital cost (NT 64,392 +/- 3,523 vs. NT 53,806 +/- 2,817) (p = 0.0342) and anesthesia cost (NT 7,968 +/- 246 vs. NT 5,268 +/- 262) (p < 0.0001) are also significantly lower in the TEA group than the GA group. In conclusion, TEA provided better postoperative pain relief and recovery and lower cost than GA for MRM surgery.

Liver, spleen and tumor volume measured by personal computer

BACKGROUND/AIMS

Computed tomography (CT) scans are common examinations for patients with chronic liver diseases. To quantitate the organ or tumor volume from the scans and to accomplish the task in an efficient way with the most economic equipment, we developed a system based on a personal computer.

METHODOLOGY

We used color-markers and transparency to sketch the edges of liver, hepatoma, and spleen. Each organ or tumor of interest is marked out by fine-point markers on pieces of transparency. The sketch was scanned into a digitized image format on a personal computer (Pentium 133). The calculation involves edge detection, three-dimensional reconstruction, and voxel counting. By using summation-of-the-area and trapezoid approximation technique, the voxels of each structure are counted. In this study, we illustrate the potential application in the management of a hepatic cancer patient.

RESULTS

After digitalization, the data size of CT images is about 1 to 1.5 megabytes. It takes less than 5 min to complete volume calculation.

CONCLUSIONS

By this method, tumor load before and after chemotherapy can be estimated easily and accurately. This would be helpful in clinical practice.

Future prospects for artificial blood

Concern about potential infective agents in donated blood has stimulated the recent development of blood substitutes. Chemically cross-linked hemoglobins are already undergoing clinical trials and might soon be ready for routine use. New generations of modified hemoglobin are being prepared to modulate the effects of nitric oxide and oxygen radicals, and artificial red blood cells are also under development.

Modified hemoglobin blood substitutes: present status and future perspectives

Biotechnological techniques of cross-linking and microencapsulation of hemoglobin result in blood substitutes that can replace red blood cells. Unlike red blood cells they can be sterilized by pasteurization, ultrafiltration and chemical means. This removes microorganisms responsible for AIDS, hepatitis, etc. Since they are free of red blood cell blood group antigens, there is no need for cross-matching or typing. This saves time and facilities and allows on-the-spot transfusion such as the infusion of salt solution. Furthermore, they can be stored for a long time. Hemoglobin for modification can be extracted from human red blood cells. Other sources of hemoglobin include bovine hemoglobin and recombinant human hemoglobin. Clinical trials are ongoing testing the possible uses of cross-linked hemoglobin in cardiac, orthopedic, trauma and other types of surgery. It is also being tested for the replacement of lost blood in severe bleeding due to trauma or other causes. Cross-linked hemoglobins are first generation blood substitutes that only fulfil some of the functions of red blood cells. New generations of more complete red blood cell substitutes are being developed. These include cross-linked hemoglobin-catalase-superoxide dismutase and microencapsulated hemoglobin-enzyme systems.