The role of phenylalanine at position 6 in glucagon's mechanism of biological action: multiple replacement analogues of glucagon.

Extensive evidence gathered from structure-activity relationship analysis has identified and confirmed specific positions in the glucagon sequence that are important either for binding to its receptor or for signal transduction. Fifteen glucagon analogues have been designed and synthesized by incorporating structural changes in the N-terminal region of glucagon, in particular histidine-1, phenylalanine-6, and aspartic acid-9. This investigation was conducted to study the role of phenylalanine at position 6 on the glucagon mechanism of action. These glucagon analogues have been made by either deleting or substituting hydrophobic groups, hydrophilic groups, aromatic amino acids, or a D-phenylalanine residue at this position. The structures of the new analogues are as follows: [des-His1, des-Phe6, Glu9]glucagon-NH2 (1); [des-His1,Ala6,Glu9]glucagon-NH2 (2); [des-His1,Tyr6,Glu9]glucagon-NH2 (3); [des-His1,Trp6,Glu9]-glucagon-NH2 (4); [des-His1,D-Phe6,Glu9]glucagon-NH2 (5); [des-His1,Nle6,Glu9]glucagon-NH2 (6); [des-His1,Asp6,Glu9]glucagon-NH2 (7); [des-His1,des-Gly4,Glu9]glucagon-NH2 (8); [desPhe6,-Glu9]glucagon-NH2 (9); [des-Phe6]glucagon-NH2 (10); [des-His1, des-Phe6]glucagon-NH2 (11); [des-His1, des-Phe6,Glu9]glucagon (12); [des-Phe6,Glu9]glucagon (13); [des-Phe6]glucagon (14); and [des-His1, des-Phe6]glucagon (15). The receptor binding potencies IC50 values are 48 (1), 126 (2), 40 (3), 19 (4), 100 (5), 48 (6), 2000 (7), 52 (8), 113 (9), 512 (10), 128 (11), 1000 (12), 2000 (13), 500 (14), and 200 nM (15). All analogues were found to be antagonists unable to activate the adenylate cyclase system even at concentrations as high as 10(-5) M except for analogues 6 and 8, which were found to be weak partial agonists/partial antagonists with maximum stimulation between 6-12%. In competitive inhibition experiments, all the analogues caused a right shift of the glucagon-stimulated adenylate cyclase dose-response curve. The pA2 values were 8.20 (1), 6.40 (2), 6.20 (3), 6.25 (4), 6.30 (5), 6.30 (7), 6.05 (8), 6.20 (9), 6.30 (10), 6.25 (11), 6.10 (12), 6.20 (13), 6.20 (14), and 6.35 (15).

Mapping of a gene for nonspecific X-linked mental retardation (MRX 75) to Xq24-q26.

Nonspecific X-linked mental retardation is a heterogeneous condition consisting of nonsyndromal mental retardation in males. It is caused by mutation in one of several genes on the X chromosome (MRX genes). Here we report on the localization of a presumptive MRX gene to chromosomal region Xq24-q26 in a German family with nonspecific X-linked mental retardation (MRX 75, HUGO Human Gene Nomenclature Committee). Two point linkage analysis with 23 informative markers gave a lod score of 2.53 at theta = 0 for markers DXS425, DXS1254, DXS1114, and HPRT.

Combined enteral-parenteral nutrition versus total parenteral nutrition in brain-injured patients. A comparative study.

A comparative nutritional study in brain-injured patients (BIP) was performed to assess the influence of a combined enteral-parenteral nutrition (CN) and a total parenteral nutrition (TPN) on protein catabolism in the early posttraumatic period. 20 male BIP (Glasgow coma scale 5-7) were randomized to one of the two feeding regimes. Nutritional support was based on 150-175% basic energy expenditure. Amino acid intake was 1.4 g/kg/day in the TPN and 2.4 g/kg/day in the CN group. Negative nitrogen balance (NNB) averaged means = 11.3 g/m2/day (SEM = 3.06 g/m2/day) in the TPN group and means = 10.2 g/m2/day (SEM = 2.33 g/m2/day) in the CN group. Between both feeding regimes not statistically significant differences could be observed concerning mortality, N-balance, creatinine and 3-methylhistidine excretions. Protein concentration of the regurgitated gastric fluid was significantly higher in the CN than in the TPN study group. Data imply that both alimentary regimes are of similar value, but BIP with impaired gastric function, such as high tube reflux, are better treated by TPN.

Anabolic steroids in polytrauma patients. Influence on renal nitrogen and amino acid losses: a double-blind study.

Severe trauma leads to considerable losses of nitrogen in the first days after the accident. As nutritional efforts cannot reduce these losses sufficiently, an adjunctive therapy using the anabolic steroid nandrolone decanoate (Nd) was applied. In a double-blind study 10 male multiple-traumatized patients each received 50 mg of Nd on day 3 and 25 mg of Nd on day 6 after the trauma, an additional 10 patients received placebo only. Both groups had identical nutritional support. Nitrogen balance, total nitrogen excretion as well as plasma amino acid concentration, and urine amino acid excretion were measured daily. The anabolic agent improved the nitrogen balance mainly by reducing nitrogen excretion. 3-Methylhistidine excretion and renal amino acid losses were decreased. Nandrolone decanoate increased the concentration of total plasma amino acids. The underlying principle seems to be an amino acid-saving mechanism with a renal site of action. It is shown that in the early posttraumatic period nandrolone decanoate improves nitrogen metabolism. Further studies are required to determine whether this offers a clinical benefit to trauma patients.

Pharmacokinetic evaluation of a new maintenance solution for severely injured patients.

Nine severely injured patients (SIP) and 9 healthy controls received 20 min iv infusions of Aminoplasmal-LS-10 (2.15 ml/kg body wt containing 0.215 g amino acids). Employing the values of the plasma amino acid (AA) concentrations 3, 7, 15, 30, 45, 70, and 150 min after the end of the infusion, we calculated the elimination half-life (t 1/2), the elimination constant (k2), the total clearance (Cltot), and the transfer of the individual AA. The AA showed t 1/2 between 6 (Glu) and 23 (Thr) min. Comparing the metabolic kinetics of healthy controls and SIP, there were no statistical differences in t 1/2 or in k2. In the SIP, nearly all plasma AA showed increased transfer and Cltot, significantly for Thr (p < 0.05), Pro, Gly, Ala, Arg (p < 0.02), Glu (p < 0.01), and Met (p < 0.005). In contrast, the Cltot for Phe and Tyr were decreased. Except for Phe, Tyr, Met (enhanced values) and Arg (no change), the fasting values of AA concentrations in the SIP were diminished compared to those in the healthy controls. Based on the measured transfer, we have developed a new maintenance solution adapted to SIP. Compared with Aminoplasmal, it is necessary to apply AA concentrations which are increased in Lys, His, Phe, Tyr, Val, Ala, and Ser, and reduced in Arg, Pro, Leu, Ile, and Gly.

A review of allograft processing and sterilization techniques and their role in transmission of the human immunodeficiency virus.

Human immunodeficiency virus (HIV) infection via vascular organ and tissue transplantation is well documented. The majority of these transmissions occurred before the development of HIV antibody testing, which is now a routine screening tool used before organ and tissue procurement and transplantation. There exists what is commonly referred to as a "window" of seronegativity after HIV infection. Potential donors may be infectious with the HIV virus but not yet detected with available HIV antibody tests. Bone and soft tissue retrieval may be done in either a sterile or clean, nonsterile manner. Deep freezing and freeze-drying (lyophilization) are two commonly used modes of preserving bone and soft tissue allografts. In 1985, a screened donor who was in the window of seronegativity underwent vascular organ and musculoskeletal tissue harvest. The bone and soft tissue procured underwent a variety of processing and preservation techniques. There have been no known cases of HIV transmission from the processed freeze-dried tissues. Evidence now exists that early HIV infection, before HIV antibody production, may be the most infectious period. The HIV antigen testing may allow earlier detection of an infectious donor, thus closing the window of seronegativity. It is unknown whether this nontransmission of HIV to the recipients of the processed and freeze-dried tissue was due to the processing or the nature of the tissue itself.

Isolated rupture of the popliteus with posterior tibial nerve palsy.

We report the case of a 59-year-old man with severe knee pain and inability to flex his toes or invert his plantar flexed foot after an external rotation injury to his knee. MRI showed rupture of the popliteus with a haematoma compressing the neurovascular bundle in the proximal calf, and electromyography demonstrated signs of an axonotmesis of the posterior tibial nerve. There was progressive nerve recovery over 24 weeks. Isolated rupture of the popliteus should be considered in any patient with an acute haemarthrosis, lateral tenderness and a stable knee, especially after an external rotation injury.

The rationale and technique for arthroscopic reconstruction of anterior shoulder instability using multiple sutures.

Recent anatomic and arthroscopic studies have increased knowledge of the pathology of traumatic anterior shoulder instability. Advances in arthroscopy have made reconstruction of the shoulder using this technique seem increasingly attractive. The authors review the rationale and technique of arthroscopic reconstruction with multiple sutures.

Current development of instrumentation for arthroscopy.

The advances in the field of arthroscopy have been keyed to the development of instrumentation. The most significant innovation has occurred in conjunction with the visualization system itself--cutting instrumentation for resection of soft tissues in bone and, more recently, in joints other than the knee. A brief history of the development of arthroscopic instrumentation is provided in this article.

Arthroscopic management of rotator cuff disease.

The etiology of rotator cuff disease is controversial, but is not always secondary to cuff impingement between the humeral head and the coracoacromial arch. Rotator cuff disease, and not impingement syndrome, more accurately describes this process. The spectrum of rotator cuff disease begins with rotator cuff inflammation (Stage I) and progresses to tendinitis (Stage II) and partial or full thickness tears (Stage III). Refractory Stage II and III disease without rotator cuff tears undergoes subacromial bursectomy and acromioplasty. Partial thickness tears are debrided with an acromioplasty, bursectomy, and removal of inferior clavicular osteophytes. Full thickness tears are treated arthroscopically or open, depending on the tear size and the patient expectations. In general, tears from 0 to 5 cm in active patients undergo subacromial decompression and a mini-open repair. Low demand patients with 0 to 5 cm tears or tears greater than 5 cm are treated with subacromial decompression and rotator cuff debridement.

Laser energy in arthroscopic meniscectomy.

Rationale and technique are discussed for performing arthroscopic meniscectomy with a carbon dioxide laser, including presentation of findings in limited rabbit and human studies.

Arthroscopic anterior shoulder capsulorrhaphy.

Shoulder dislocation is a common cause of upper extremity disability. The recurrence rate is inversely proportional to the patient's age at the initial dislocation. There are several pathologic variations of anterior/inferior glenohumeral ligament laxity. The indications, contraindications, as well as the surgical procedure are reviewed in the following text. The postoperative rehabilitation program is briefly described.

Brief communication: evidence of pathology on the frontal bone from Gongwangling.

The hominid fossil from Gongwangling (Lantian) is well known and described (Woo, [1965] Scientia Sinca 14:1032-1036; Woo [1966] Curr. Anthropol. 7:83-86; Wu and Dong [1985] in R Wu and JW Olsen (eds.): Palaeoanthropology and Paleolithic Archaeology in the People's Republic of China [New York: Academic Press, pp. 79-89]; Wu and Poirier [1995] Human Evolution in China: A Metric Description of the Fossils and a Review of the Sites [Oxford: Oxford University Press]). However, evidence of pathology on the frontal bone has been previously unreported. Two lesions occur on the right supraorbital region that can be distinguished from marks of erosion prevalent on this specimen. These are discrete and irregularly shaped, with evidence of secondary bone formation surrounding them. The cause of the condition is unclear. Possibilities include trauma or abscess from an unspecified infection.

A technique for arthroscopic subacromial decompression.

The control of bleeding and the determination of the appropriate amount of bone to resect are two common technical difficulties in performing arthroscopic subacromial decompression. We describe a technique that simplifies the procedure while providing more precise bone resection and contouring. First, the coracoacromial ligament is released by sectioning the anterior margin of the acromion. Bleeding is minimized with this technique because the coracoacromial ligament itself is not being cut, but rather its bony attachment is resected. An acromioplasty is then performed with the arthroscope in the lateral portal and the burr in the posterior portal. The shank of the cutter is rested against the posterior lip of the acromion, which acts as a fulcrum. The tip of the burr is placed at the deepest point of the concavity of the acromion. Bone is resected by sweeping the cutter from lateral to medial and progressing anteriorly while maintaining the angle of the burr, using the angle of the posterior acromion as a guide. In this way the appropriate amount of bone is automatically resected, resulting in a flat acromion which is tapered anteriorly and has a smooth transition to normal bone posteriorly.

A biochemical evaluation of the restraints to posterior shoulder dislocation.

The biomechanics of posterior dislocation of the shoulder was evaluated using nine cadaver shoulders. Each was arthroscoped, roentgenograms were obtained, and then each was dislocated in a testing device. Force displacement data was obtained during testing, and posttesting roentgenograms, arthroscopic evaluation, and subsequent open dissections were performed to evaluate the pathology created. Although instability was created in all cases with displacement of the humerus to the diameter of the humeral head, force displacement of the humerus to the diameter of the humeral head, force displacement curves did not show an inflection point, implying a continuum between subluxation and dislocation. All shoulders had posterior Bankart lesions or posterior capsular lesions, or both. Anterior pathology was not seen. Posterior instability is most likely a continuum between subluxation dislocation with progressive injury to the posterior capsule and attachments such as the labrum as the principal restraint to posterior displacement.

Arthroscopic manifestations of shoulder subluxation and dislocation.

Instruction in the arthroscopy of the normal and pathologic anatomy of various structures of the shoulder associated with instability syndromes is absolutely essential. Arthroscopy is not a substitute for a thorough clinical evaluation and physical examination of the shoulder, however. It provides confirmation of the clinical impression, especially in subtle cases of instability.

Arthroscopic findings in the subluxating shoulder.

The arthroscopic findings in 19 shoulders (18 patients) with subluxation are described. The clinical diagnosis of subluxation of the shoulder is primarily based on clinical history with inconsistent physical findings and radiographic studies. Arthroscopic findings in these patients were consistent. Increased translation of the humeral head in the anteroposterior plane was noted secondary to attenuation of the anteroinferior glenohumeral ligament. Incompetence of this ligamentous structure obviated its function as an anterior buttress and allowed the humeral head to translate anteriorly on the glenoid. Fraying, tearing, or detachment of the anteroinferior glenoid labrum and articular defects in the posterolateral humeral head were also consistent findings, thought to be secondary to repeated injury as the humeral head translates forward and backward in the glenoid fossa. In several cases the classic "click" that occurs with subluxation of the shoulder could be reproduced under arthroscopic visualization and corresponded to the defect in the posterolateral humeral head riding over the torn labrum and/or anterior glenoid rim. Shoulder arthroscopy is an accurate method for confirming the clinical impression of subluxation of the shoulder, especially in subtle glenohumeral instability, and should be helpful in selecting specific surgical reconstruction procedures.