In vitro biosynthesis, core glycosylation, and membrane integration of opsin.

A membrane-integrated , core-glycosylated form of bovine opsin was synthesized in vitro when bovine retina mRNA was translated in a wheat germ cell-free system supplemented with dog pancreas microsomal vesicles; glycosylation and integration of opsin into membranes were coupled to translation. Proteolysis with themolysin was used to probe the orientation of opsin within the dog pancreas microsomal membrane, and to compare it with that of opsin in rod cell disk membranes isolated from bovine retina. Intact microsomal or disk vesicles were required for production of discrete, membrane-associated thermolysin fragments of opsin; no discrete opsin fragments were detected when membranes were incubated with thermolysin in the presence of the nonionic detergent, Triton X-100. The major opsin fragments produced by themosylin treatment of intact microsomal vesicles resembled those from disk vesicles in their size, oligosaccharide content, and order of appearance. In each case, the first cleavage of opsin took place at the COOH-terminus, generating a glycosylated fragment, O', which was only slightly smaller than intact opsin. Both the microsomal and disk membrane forms of O' were next cleaved internally; glycosylated fragments of similar sizes in both cases were detected which were derived from the NH(2)-terminal portion of O'. Several smaller NH(2)-terminal fragments of opsin were detected only in thermolysin-treated microsomal membranes, and not in disk membranes. The data suggest that the topology of opsin integrated into dog pancreas microsomal vesicles is similar to that in rod cell disk vesicles, although not identical. In each case, the glycosylated NH(2)-terminal region of opsin is located within the lumen of the vesicle, while discrete COOH-terminal and internal segments of opsin apparently emerge at the outer, cytoplasmic face of the membrane. Thus, opsin in the heterologous microsomal membrane, like its counterpart in the native disk membrane, may cross the bilayer at least three times. The internal domain of the polypeptide that emerges at the outer membrane surface is apparently more highly exposed in the case of opsin in microsomal membranes, evidenced by the additional internal thermolysin cleavage sites detected.

Are speech-based techniques for determination of occlusal vertical dimension reliable?

This article describes the most common techniques used for clinical assessment of occlusal vertical dimension (OVD), and includes a discussion of recently published data which strongly suggest that techniques based on sibilant sounds are not as reliable as they are generally regarded to be for the evaluation of OVD. Assessment and establishment of OVD are sometimes difficult in edentulous patients, as well as for dentate patients with multiple missing posterior teeth and/or extensive wear. Techniques based on the use of interocclusal distance and facial soft-tissue contours, along with techniques based on sibilant sounds, are discussed. Although absolute scientific support for any technique is lacking, the careful use of the techniques described in this article, in combination, will usually result in the establishment of a clinically acceptable OVD for most patients.

Young children of alcoholics: a group treatment model.

This paper describes a therapeutically oriented psychoeducational group treatment model designed to assist young children of alcoholics. Researchers have identified children of alcoholics as a population at risk of emotional, interpersonal and substance abuse problems. Examples are used to illustrate activities and group processes characteristic of the beginning, middle and termination phases of treatment. While this approach appears promising and can be replicated in many health care settings, controlled studies are needed to measure the model's effectiveness more precisely.

Prosthetic rehabilitation of extensive facial defects.

Patients with extensive surgical defects of the palate, orbit, or nose are difficult to rehabilitate. Prosthetic rehabilitation in these areas often shortens hospitalization, speeds recovery, and reduces medical expenses. Specific factors in planning treatment are directed toward successful prosthetic rehabilitation, using a team approach, careful patient selection, and specific surgical principles keyed to each facial region.

Biogenesis of peroxisomes: intracellular site of synthesis of catalase and uricase.

The intracellular site of synthesis of two peroxisomal enzymes of rat liver, uricase (urate:oxygen oxidoreductase, EC 1.7.3.3) and catalase (hydrogen peroxide:hydrogen peroxide oxidoreductase, EC 1.11.1.6), has been localized on free ribosomes and not membrane-bound ribosomes. Free polysomes and membrane-bound polysomes, prepared by classical cell fractionation techniques from rat liver, were incubated for protein synthesis in a cell-free system derived from rabbit reticulocytes. Characterization of the total translation products by polyacrylamide gel electrophoresis in sodium dodecyl sulfate, as well as by immunoprecipitation with anti-rat albumin anti-serum, confirmed that good separation of the two polysome classes was achieved. Uricase and catalase were immunoprecipitable from translation products directed by free polysomes or phenol-extracted free polysomal mRNA but not from products of membrane-bound polysomes. Furthermore, unlike albumin, nascent uricase and catalase were not cotranslationally segregated by dog pancreas microsomal membranes. The results indicate that uricase and catalase are transferred to the interior of peroxisomes by a post-translational mechanism; an hypothesis is formulated here for the biogenesis of peroxisomes.

Prosthodontic principles in surgical planning for maxillary and mandibular resection patients.

Discussion between the surgeon and prosthodontist on surgical planning is important. It is necessary that they each be aware of the other's problems. Only in this way can continuity be established between surgical and prosthetic procedures. This will provide a maximum level of treatment for the maxillofacial patients, thereby returning them to society most expeditiously.

Maxillofacial prosthetic principles in the surgical planning for facial defects.

In many localities, particularly in larger medical centers, presurgical communication and planning is increasing because the prosthodontist is becoming a more active member of the oncology, trauma, and cleft palate teams. Individuals involved both directly or indirectly in maxillofacial prosthetic therapy should be cognizant of the situations and solutions discussed in this article. In this way the prosthodontist and surgeon will be able to provide a better consultancy and rehabilitation service for their patients.

Shear strength of lingual rest seats prepared in bonded composite.

A study based on the single criterion of resistance to loading forces was conducted to investigate the suitability of lingual composite rest seats for anterior teeth. The minimum acceptable resistance level was chosen from a review of the literature; other basic criteria were described; and the desirability of this technique was discussed.

Simplified technique to measure mandibular range of motion.

The validity and reliability of a simplified technique to measure mandibular range of motion was studied in 10 dentate subjects without symptoms. The simplified technique consisted of marking with a pencil the centric relation and maximum right, left, and protrusive positions and maximum opening. These markings were made on a tongue blade held against the maxillary anterior teeth with the mesioincisal embrasures between the mandibular central incisors used as a reference. Range of motion was also measured with a mandibular kinesiograph as the control. Each method was repeated five times on each subject by each of three investigators. Intraclass correlation coefficient demonstrated a moderate level of agreement between the two techniques and high inter-rater reliability for the three investigators for all positions except maximum left movement. These data support the hypothesis that this simplified technique is a valid and reliable way to measure mandibular range of motion.

Load cycling of lingual rest seats prepared in bonded composite.

A study to investigate the suitability of lingual composite rest seats for anterior teeth was based on the single criterion of repetitive load cycling. A 3-year minimum survival was chosen, with load and cycling values based on a review of the literature. An attempt was made to simulate the effect of saliva on composite.

Translocation of proteins across membranes: the signal hypothesis and beyond.

Proteins are translocated across membranes either coupled to translation (co-translationally) or after translation (post-translationally). The information for both modes of translocation is encoded in the protein in the form of a short-lived sequence extension (signal sequence). Additional information resides in the ribosome in the case of co-translational translocation, which proceeds via a ribosome--membrane junction. Translocation is mediated by specific receptors (ribosome and/or signal receptors) which are restricted in their location to distinct cellular membranes. In most cases the signal sequence is removed by a signal peptidase operating in an endoproteolytic mode. Membranes endowed with receptors for co-translational translocation are: the rough endoplasmic reticulum (RER) including the outer nuclear envelope membrane, the inner mitochondrial membrane and the thylakoid membrane of chloroplasts, in eukaryotic cells; and the plasma membrane in prokaryotic cells. Each of these membranes presumably contains a single distinctive signal receptor, ribosome receptor and signal peptidase. Membranes endowed with one distinct receptor each for post-translational translocation are both mitochondrial membranes, the chloroplast envelope membrane and the peroxisomal membrane. A signal sequence for co-translational translocation across the RER membrane that is identical in its secondary structure is shared by secretory, lysosomal and certain bitopic integral membrane proteins. Some integral membrane proteins presumably share another common sequence--referred to as stop-transfer sequence--which serves to interrupt translocation and thereby to orient the polypeptide chain in the lipid bilayer. Furthermore, the existence of a few specific 'sorting' sequences is postulated. These would be common to many proteins and would serve to route them to their final destination following translocation across or orientation within the membrane. Thus, the topological information which determines the intracellular pathway and the final location of a great number of proteins appears to reside in a small repertoire of specific sequences which are either a transient or a permanent part of the protein.