Plant cell wall fractionation and structural analysis.

The structure of the major plant polysaccharides contributing to dietary fiber, their organization within the plant cell wall, and the problems associated with their analysis are briefly reviewed. Alkaline, acidic, and detergent fractionation methods are described and considered in relation to their specificity. The analysis of pectin, often ignored as a component of dietary fiber, is examined in detail. The solubility of pectins from a number of common plant foods was determined, indicating that a considerable portion of pectin polyuronide is lost to many of the commonly used analytical procedures.

Hemodynamic pathogenesis of ischemic hepatic injury following cardiogenic shock/resuscitation.

Post-ischemic hepatic injury is observed commonly following cardiogenic or hypovolemic shock. We evaluated the putative roles of the alpha-adrenergic sympathetic nervous system and the renin-angiotensin axis in the pathogenesis of hepatic injury following cardiogenic shock. Previous studies have characterized the hepatic hemodynamic response to shock, while the relationship of these hemodynamic changes to ischemic hepatic injury has not been defined. Sustained (4 h) periods of pericardial tamponade (after mild hemorrhage) followed by 2 h of resuscitation generated a reproducible model of cardiogenic shock and consequent post-ischemic hepatic injury in anesthetized pigs. In a separate group of pigs, the alpha-adrenergic component of the sympathetic nervous system was ablated with phenoxybenzamine or, in other groups, the renin-angiotensin axis was ablated by either prior nephrectomy or, separately, by confirmed angiotensin converting enzyme inhibition with teprotide. The hepatic injury response in each case was reevaluated. Compared to sham-shocked pigs, those subjected to tamponade alone manifested selective splanchnic vasospasm and consequent biochemical and histological evidence of classic post-ischemic liver injury (centrilobular necrosis involving about a third of each hepatic lobule). These manifestations of splanchnic vasospasm and the consequent ischemic injury were not ameliorated by confirmed alpha-adrenergic blockade, but significantly attenuated by either method of prior ablation of the renin-angiotensin axis. This model of sustained cardiogenic shock and resuscitation generates the manifestations of ischemic hepatic injury associated with selective splanchnic vasospasm, findings consistent with previous, short-term, hemodynamic studies. The major mediator of this response, and the consequent hepatic injury, is the selective hypersensitivity of the mesenteric vasculature to the renin-angiotensin axis.

Control of gastric vascular resistance in cardiogenic shock.

That local splanchnic ischemia is associated with the acute gastric "stress" erosions seen in shock is well established. The hemodynamic mechanism mediating that ischemia is unknown. Pericardial tamponade was produced in anesthetized pigs while hemodynamic parameters were monitored in the systemic circulation as a whole and in the vascular beds of the celiac and left gastric arteries, respectively. Stepwise increases in pericardial pressure produced progressive decreases in arterial pressure and cardiac output (i.e., reproducible, quantitable, and rapidly reversible levels of cardiogenic shock). This produced a profound reduction in blood flow in the celiac and gastric beds that was significantly disproportionate to the reduction in cardiac output. This was due to significant increases in celiac and gastric vascular resistance that were more than twice as great as those seen in the systemic circulation as a whole (i.e., selective splanchnic vasoconstriction). This response was abolished by ablation of the renin-angiotensin axis, whether by bilateral nephrectomy, captopril, or saralasin, and mimicked, without tamponade, by the infusion of angiotensin II. Levels of celiac artery blood flow and resistance correlated significantly with endogenous levels of plasma renin activity. On the other hand, this response was not abolished by confirmed alpha-adrenergic blockade (phenoxybenzamine) or by sympathectomy. In this model, cardiogenic shock produces regional splanchnic ischemia in the celiac and gastric vascular beds by inducing a severe and disproportionate vasospasm that is mediated primarily by the renin-angiotensin axis.

Laparoscopic splenectomy in the management of immune thrombocytopenia purpura.

The role of splenectomy in the management of immune thrombocytopenia purpura is well known. Recent improvements in laparoscopic technology have significantly expanded the variety of general surgical procedures amenable to a minimally invasive approach. An initial experience of four cases of immune thrombocytopenic purpura managed by laparoscopic splenectomy is presented. The entire procedure was completed under laparoscopic guidance in three of four cases, and a counterincision was required to control bleeding in one patient. The procedure is performed with five operating ports including a camera port, two retraction ports, and two dissection ports. Dissection begins at the lower pole of the spleen and progresses cephalad to the hilum where major vessels are individually ligated and divided. The short gastric vessels are divided with a linear laparoscopic stapler. The lateral peritoneal attachments are divided, and the spleen is removed intact through a 6 cm fascial incision at the umbilicus. Laparoscopic splenectomy appears to be a safe and efficacious procedure that is useful in the management of certain hematologic diseases and may ultimately be performed for a variety of pathologic conditions involving the spleen.

Intrinsically disordered protein.

Proteins can exist in a trinity of structures: the ordered state, the molten globule, and the random coil. The five following examples suggest that native protein structure can correspond to any of the three states (not just the ordered state) and that protein function can arise from any of the three states and their transitions. (1) In a process that likely mimics infection, fd phage converts from the ordered into the disordered molten globular state. (2) Nucleosome hyperacetylation is crucial to DNA replication and transcription; this chemical modification greatly increases the net negative charge of the nucleosome core particle. We propose that the increased charge imbalance promotes its conversion to a much less rigid form. (3) Clusterin contains an ordered domain and also a native molten globular region. The molten globular domain likely functions as a proteinaceous detergent for cell remodeling and removal of apoptotic debris. (4) In a critical signaling event, a helix in calcineurin becomes bound and surrounded by calmodulin, thereby turning on calcineurin's serine/threonine phosphatase activity. Locating the calcineurin helix within a region of disorder is essential for enabling calmodulin to surround its target upon binding. (5) Calsequestrin regulates calcium levels in the sarcoplasmic reticulum by binding approximately 50 ions/molecule. Disordered polyanion tails at the carboxy terminus bind many of these calcium ions, perhaps without adopting a unique structure. In addition to these examples, we will discuss 16 more proteins with native disorder. These disordered regions include molecular recognition domains, protein folding inhibitors, flexible linkers, entropic springs, entropic clocks, and entropic bristles. Motivated by such examples of intrinsic disorder, we are studying the relationships between amino acid sequence and order/disorder, and from this information we are predicting intrinsic order/disorder from amino acid sequence. The sequence-structure relationships indicate that disorder is an encoded property, and the predictions strongly suggest that proteins in nature are much richer in intrinsic disorder than are those in the Protein Data Bank. Recent predictions on 29 genomes indicate that proteins from eucaryotes apparently have more intrinsic disorder than those from either bacteria or archaea, with typically > 30% of eucaryotic proteins having disordered regions of length > or = 50 consecutive residues.

Pathophysiology of hepatic ischemia in cardiogenic shock.

The hepatic hemodynamic response to cardiogenic shock was investigated in a porcine model produced by pericardial tamponade to better understand the pathophysiology of postshock hepatic insufficiency. Reductions of cardiac output to 50 percent of baseline levels produced marked hepatic ischemia by causing disproportionate reductions in blood flow through the celiac and hepatic arteries and portal vein. These were due to selective vasoconstriction of the splanchnic resistance vessels that was mimicked without tamponade by the infusion of angiotensin II, ablated by angiotensin-converting enzyme blockade, unaffected by alpha-adrenergic ablation, and correlated closely with levels of plasma renin activity. The ischemic liver injury of cardiogenic shock appears to be largely due to an exquisite responsiveness of the splanchnic vascular smooth muscle to endogenously released angiotensin II.

Protection of the small intestine from nonocclusive mesenteric ischemic injury due to cardiogenic shock.

In a pericardial tamponade model of cardiogenic shock in pigs, we had previously shown that acute reductions in cardiac output produce severe mesenteric ischemia due to disproportionate splanchnic vasoconstriction. In this study, we extended the period of cardiogenic shock in order to investigate the pathogenesis of ischemic injury to the small intestinal wall. Four hours of tamponade produced sustained changes in splanchnic hemodynamics, similar to those observed in the prior short-term experiments. The resultant mesenteric ischemia caused necrotic lesions of the small intestine which were characteristic of those seen in nonocclusive mesenteric ischemia in human subjects. Prior alpha-adrenergic blockade failed to prevent either sustained mesenteric vasospasm or ischemic injury. In contrast, prior blockade of the renin-angiotensin axis, whether by nephrectomy or angiotensin-converting enzyme inhibition, blocked the splanchnic vasoconstriction, and thereby protected the small intestine from ischemic injury. The primary hemodynamic and pathologic features of this model of nonocclusive mesenteric ischemia appear to be mediated by the renin-angiotensin axis.

The Baltimore experience with laparoscopic management of acute cholecystitis.

Laparoscopic cholecystectomy has rapidly emerged as a popular alternative to traditional laparotomy and cholecystectomy. Acute cholecystitis has been considered to be a relative or absolute contraindication to laparoscopic surgery. After gaining extensive experience in laparoscopic biliary tract surgery, this procedure was attempted in 15 patients with acute cholecystitis. All patients were operated on within 72 hours of admission. In five patients, the laparoscopic procedure was converted to an open laparotomy; in one patient, a localized abscess was found, and in the other four patients, extensive inflammation and edema precluded a safe dissection of the vascular and ductal structures. Laparoscopic cholangiography was performed in 14 patients and proved valuable in demonstrating the ductal anatomy. Patients were discharged an average of 2.7 days after the laparoscopic procedure. Laparoscopic cholecystectomy may be safely performed by experienced surgeons in patients with acute cholecystitis. To ensure a low complication rate, a low threshold for converting the procedure to an open laparotomy must be maintained if the ductal and vascular anatomy cannot be safely demonstrated.

Laparoscopic guided cholecystectomy.

Cholecystectomy remains the most effective form of therapy for patients with symptomatic cholelithiasis. An alternative method of gallbladder removal, laparoscopic guided cholecystectomy, was attempted in 100 patients. Five patients required conversion of the laparoscopic procedure to an open laparotomy for the following reasons: discovery of a pancreatic malignancy in one patient, extensive adhesions in one, presence of an aberrant accessory right hepatic duct in one, common hepatic duct injury in one, and avulsion of the cystic duct in one. Both ductal injuries occurred during the early phase of the clinical program. In those patients undergoing laparoscopic cholecystectomy, 93 were discharged within 24 hours of surgery and 94 returned to normal activity within 1 week. Laparoscopic guided cholecystectomy appears to offer a number of advantages in patient care as well as a significant reduction in health care expenses for gallbladder disease. Appropriate training in laparoscopic surgery is necessary in order to avoid operative complications.

Laparoscopic management of acute cholecystitis.

The role of laparoscopic surgery in patients presenting with acute cholecystitis remains controversial. From September 1989 through August 1992, a total of 720 patients underwent cholecystectomy. Ninety-six were unplanned admissions with a clinical diagnosis of acute cholecystitis. Laparoscopic surgery was attempted in 83 patients. Thirteen individuals were not offered laparoscopy because of the surgeon's inexperience. Twenty-two (27%) patients required the laparoscopic procedure converted to an open laparotomy. The mean postoperative hospital stay for patients undergoing laparoscopic cholecystectomy was 3.3 days versus 6.8 days for the laparotomy group. There was no mortality and no bile duct or major vascular injuries in either group. The overall operative morbidity rate was 16.9%. Laparoscopic cholecystectomy appears to be a safe and beneficial option in selected patients with acute cholecystitis. A low threshold for conversion to laparotomy appeared to be an important factor in maintaining a low incidence of operative complications. Several modifications to the technique of laparoscopic cholecystectomy have evolved over the 3-year study period and are described.

Laparoscopic management of acute and chronic cholecystitis.

Contrary to earlier predictions, it appears that acute cholecystitis should be considered a relative rather than an absolute contraindication to laparoscopic surgery. The most important parameter in determining the feasibility of attempting laparoscopic cholecystectomy in the setting of acute inflammation appears to be the experience of the surgeon. This also appears to be true when encountering individuals with elements of long-standing chronic cholecystitis. Although laparoscopic intervention in such patients is associated with a greater likelihood of conversion to open laparotomy, the incidence of major biliary and nonbiliary complications appears to be low. In addition, these patients enjoy the same benefits of laparoscopic surgery as those undergoing elective surgery.

Transarticular fixation in the treatment of non-union of supracondylar fractures of the femur: a salvage procedure.

We treated eleven non-unions of a supracondylar fracture of the femur with application of a bone graft and fixation with a Küntscher intramedullary rod driven across the knee joint. In ten of the eleven patients the fracture united and the patients obtained stability, relief of pain, and, in two patients, an increased range of motion of the knee. Most surgeons use the blade-plate or the compression screw for fixation, but the intramedullary nail may be a better device and may simplifty the surgical procedure.

Long-term results of tibiotalar arthrodesis.

One hundred and one tibiotalar arthrodeses were performed using a single surgical technique that has not been previously reported. The average follow-up was ten years (range, two to twenty-five years). The rate of pseudarthrosis was 5 per cent, four to five times less than in other recent large reports. Pseudarthrosis occurred only in patients with a sensory deficit. Secure fusion was radiographically documented in 95 per cent and the functional clinical result was good to excellent in 90 per cent. The ideal fusion position was found to be neutral or slight equinus angulation, and varus-valgus angulation equal to that of the contralateral side. More than 7 degrees of varus angulation of the heel was associated with symptomatic lateral metatarsalgia in all feet in which it occurred. Radiographic measurement documented an average 85 per cent (11-degree) increase in postoperative tarsal motion. Neither symptoms nor function correlated with the degree of tarsal hypermobility.

Radiographic changes following anterior cervical fusion.

In nine patients who underwent anterior cervical fusions for cervical spondylosis, preoperative cervical spine films were compared with radiographs taken seven to 15 years after fusion. Eight of the nine patients were found to have radiographic evidence of increased degenerative diseases located primarily below the level of fusion but occasionally occurring both above and below the fusion. Whether these degenerative changes are the body's response to altered mechanical forces on joints next to a now immobile spinal segment or whether these changes merely represent the natural progression of the degenerative disease process could not be ascertained from this study. Perhaps both factors contributed.

Differential alkali-extraction of hemicellulose and hydroxyproline from non-delignified cell walls of lupin hypocotyls.

The extraction by alkali of hemicellulose polysaccharides and polymer hydroxyproline from non-delignified, primary cell-walls of lupin hypocotyls has been studied, using sequential extractions at 0 degrees and 18-22 degrees. 10% Aqueous potassium hydroxide at 0 degrees rapidly removed about two-thirds of the hemicellulose normally extracted in 10% KOH at 18-22 degrees and including nearly all of the hemicellulose-A. Little hydroxyproline was released at 0 degrees. When the temperature was subsequently raised to 18-22 degrees, the remaining 10% KOH-soluble hemicellulose, along with most of the hydroxyproline, was released. The monosaccharide composition of these fractions changed markedly with the time of extraction. Arabinose increased from 35% of the polysaccharide extracted during the first hour at 18-22 degrees to similar to 65% of the polysaccharide extracted between 16 and 20 h at 18-22 degrees. Hydroxyproline changed similarly as a proportion of polymer. The implications of these and other results are discussed in relation to polysaccharide and polymer extraction without prior delignification and to models of the primary cell-wall.

Establishment of a laparoscopic cholecystectomy training program.

A recently developed alternative to traditional laparotomy and cholecystectomy is laparoscopic-guided cholecystectomy. This procedure has the advantages of reduced hospital stay, early return to work, diminished abdominal wall scarring, and less patient discomfort. The complex nature of this procedure and the current lack of extensive clinical experience preclude the traditional "hands-on" training normally practiced in surgical residency programs. At the University of Maryland, we have developed a program to instruct both surgeons and surgical residents in the techniques of laparoscopic surgery. Technical competence is achieved under the close supervision and guidance of an experienced laparoscopic surgeon. Training of residents in this procedure, therefore, is not very different than that for other general surgical procedures. Surgeons already in clinical practice, however, gain experience under somewhat different circumstances. Initial training involves didactic instruction through laparoscopic surgical atlases and educational videotapes. Further training uses a simulation device which enables the trainee to practice techniques of laparoscopic suturing, knot-tying, and clip application. Actual operative experience is acquired primarily in experimental animal preparations. Laparoscopic-guided removal of the gallbladder is performed in young swine (20-25 kg) under conditions that mimic those in the operating room. Further clinical experience can be acquired by assisting on several laparoscopic operations, usually involving diagnostic or pelvic procedures. Actual operative experience with laparoscopic cholecystectomy, of course, comprises the final phase of the educational program. The introduction of clinical laparoscopic training into general surgery residency programs should influence the widespread adoption of this new procedure.

A dynamic method of repair for acute and chronic acromioclavicular disruption.

The authors have presented a surgical procedure for disruption of the acromioclavicular joint with or without fracture of the lateral end of the clavicle. The results of the dynamic repairs have been excellent with restoration of stability and normal strength in all cases. The majority of this group were vigorous young high school college and professional athletes prior to their injury and all were returned to their previous activities.

Laparoscopic hernia repair: the learning curve.

The performance of a laparoscopic inguinal hernia repair requires unique technical and cognitive skills which, until recently, were not routinely taught to general surgeons. The initial experience of three surgeons with laparoscopic hernia repair was audited prospectively to assess the learning curve for the technique. From March 1992 to June 1994, transabdominal preperitoneal (TAP) mesh repair was attempted on 172 consecutive inguinal hernias. Three procedures were converted to traditional repairs. The three independent surgeons that performed the repairs had minimal or no prior clinical experience with the technique in the role as primary surgeon. The hernia repairs were divided into two groups. Group 1 consisted of the first 90 hernia repairs in the series, 30 repairs per surgeon. This group was compared to the subsequent 82 repairs (group 2), approximately 27 repairs per surgeon. Patients were followed up for a median of 31 months. Group 1 had more patients who were hospitalized overnight (37% versus 31%), a greater rate of conversion (2.2% versus 1.2%), a higher complication rate (11.7% versus 0%), a higher recurrence rate (12.2% versus 0%), and a longer delay in the return to full activity (11 weeks versus 8 weeks). Also, overall patient satisfaction with their hernia repair was slightly greater in group 2 (score, 9.0/10 versus 8.2/10). The lack of prior experience with the TAP technique (one surgeon) was associated with a marked increase in the number of conversions (two of three total conversions), complications (four of eight total), and hernia recurrences (8 of 11 total). This study demonstrates that a surgeon's initial experience with laparoscopic herniorrhaphy is associated with an identifiable learning curve. Significant improvements in complication and recurrence rates and overall patient satisfaction can be expected after the initial learning phase. Also, a complete lack of prior experience with laparoscopic herniorrhaphy is associated with a higher rate of conversion and significant increases in complications and hernia recurrences.