Laryngeal advancement surgery improves swallowing function in a reversible equine dysphagia model

REASONS FOR PERFORMING STUDY

Pharyngeal dysphagia is a debilitating, sometimes fatal condition in horses, with multiple aetiologies. The pathophysiology is complex and not fully understood. Treatment is largely supportive. Laryngeal advancement surgery may diminish symptoms of dysphagia and improve swallowing in affected horses.

OBJECTIVES

1) to induce reversible moderate and marked pharyngeal dysphagia by regional anaesthesia of branches of the glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves; 2) to characterise the dysphagia produced by each model; and 3) to determine whether laryngeal advancement surgery improves swallowing in these models.

STUDY DESIGN

Experimental design using 6 adult horses.

METHODS

Two dysphagia models were produced by blocking IX, the pharyngeal branch of X and XII unilaterally (moderate model) and only the pharyngeal branch of X bilaterally (marked model) within the guttural pouches. Both models were performed on each horse before and after surgery in order to assess the effectiveness of the surgical procedure as a potential treatment for pharyngeal dysphagia. Dysphagia was scored by partly blinded observers on a scale of 0-12 based on observations of eating (nonblinded), endoscopic examinations and fluoroscopic swallowing (blinded), where 0 = normal swallow and 12 = severe dysphagia with tracheal aspiration. Data were analysed by 3-factor ANOVA, with significance taken as P<0.05.

RESULTS

Dysphagia models were reversible, and horses swallowed normally within 3 h of model induction. The marked dysphagia model impaired movement of feed from the base of the tongue to the oesophagus and caused severe airway contamination. The average dysphagia score (mean ± s.d.) for the marked dysphagia model was 10.6 ± 1.1 before surgery and 6.1 ± 4.3 after surgery (P = 0.007). Laryngeal advancement surgery did not significantly improve the dysphagia scores in the moderate model (P = 0.5).

CONCLUSIONS

Laryngeal advancement surgery may improve swallowing and reduce aspiration in horses affected with diseases that cause pharyngeal dysphagia.

Longitudinal gradients of KCNQ4 expression in spiral ganglion and cochlear hair cells correlate with progressive hearing loss in DFNA2

Mutations in the human KCNQ4 gene were recently found by Kubisch et al. [Cell 96 (1999) 437-446] to cause a non-syndromic, autosomal dominant, progressive hearing loss, DFNA2. The mouse Kcnq4 orthologue was previously localized to the outer hair cells (OHCs) of the inner ear, suggesting the pathophysiological effects were due to dysfunctional OHCs. Yet, OHC dysfunction does not provide a plausible explanation for the progressive nature of the frequency specific hearing loss. We have re-examined and extended the expression analyses of KCNQ4 in the murine inner ear using RT-PCR and whole mount in situ hybridization. Our results confirmed that the rat KCNQ4 orthologue is expressed in both inner and outer hair cells. Reciprocal longitudinal gradients were found in inner hair cells (IHCs) and OHCs. The strongest expression of KCNQ4 in IHCc was in the base of the cochlea and in the apex for OHCs. Similar to the IHCs, a basal to apical gradient was present in the spiral sensory neurons. IHCs mediate hearing via their afferent sensory neurons, whereas OHCs function as active cochlear amplifiers. The complete absence of OHCs leads only to severe sensitivity reduction, but not complete hearing loss. Our data suggest that the primary defect leading to initial high frequency loss and subsequent progressive hearing loss for all frequencies may be due to spiral ganglion and/or IHC dysfunction, rather than an OHC aberration.

The double helix is dehydrated: evidence from the hydrolysis of acridinium ester-labeled probes

A highly chemiluminescent reporter molecule, acridinium ester (AE), was tethered to single-stranded oligonucleotide probes and hybridized to complementary as well as mismatched target sequences. When tethered to single-stranded probes, AE was readily hydrolyzed by water or hydroxide ion. In contrast, when hybridized to a complementary target, hydrolysis of the AE probe was markedly inhibited. Mismatches near AE eliminated the ability of the double helix to strongly inhibit AE hydrolysis. To establish the molecular basis for these remarkable hydrolysis properties of AE-labeled probes, the binding and hydrolysis mechanisms of AE-labeled probes were examined. When tethered to single- or double-stranded nucleic acids, hydrolysis of AE was found to proceed by generalized base catalysis in which a base abstracts a proton from water and the resulting hydroxide ion then hydrolyzes AE. Analysis of the hydrolysis rates of AE bound to DNA revealed that AE binds the minor groove of DNA and that its hydrolysis is inhibited by low water activity within the minor groove of the helix. Depending upon the sequence of the DNA, the water activity of the minor groove was estimated to be at least 2-4-fold lower than bulk solution. Hydrolysis measurements of AE tethered to RNA as well as RNA/DNA hybrids argued that the grooves of these double helices are also dehydrated relative to bulk solution. Remarkably, mismatched bases, regardless of their structure or sequence context, enhanced hydrolysis of AE by inducing hydration of the double helix that spread approximately five base pairs on either side of the mismatch.

Rapid detection of genetic mutations using the chemiluminescent hybridization protection assay (HPA): overview and comparison with other methods

The detection of genetic mutations is of paramount importance for the study, diagnosis, and treatment of human genetic disease. Methods of detection generally fall into one of two categories: those to scan for unknown mutations and those to detect known mutations. This review focuses on methods for the detection of known mutations. The hybridization protection assay (HPA) is described in detail. The HPA method utilizes short oligonucleotide probes covalently labeled with a highly chemiluminescent acridinium ester (AE). The assay format is completely homogeneous, requiring no physical separation steps, and can rapidly and sensitively detect all single-base mismatches as well as multiple mismatches, insertions, deletions, and genetic translocations. When very low copy number targets are assayed, HPA is coupled with transcription-mediated amplification (TMA), an isothermal method that amplifies DNA or RNA targets. Other methods that are described for the detection of known mutations include hybridization with sequence-specific oligonucleotides, hybridization to oligonucleotide arrays, allele-specific amplification, ligase-mediated detection, primer extension, and restriction fragment analysis. The advantages and limitations of each of these methods are discussed. Methods to scan for unknown mutations are briefly described.

Surgical removal of subfoveal iatrogenic choroidal neovascular membranes

OBJECTIVE

To present the cases of two patients with laser-induced iatrogenic subfoveal choroidal neovascular membranes (CNVMs) who underwent surgical removal of the membranes with favorable outcomes.

DESIGN

Interventional case reports.

PARTICIPANTS

Two patients with iatrogenic subfoveal CNVM. One case developed after laser treatment for macular edema due to branch retinal vein occlusion, and the second case developed after focal laser photocoagulation for diabetic retinopathy.

INTERVENTION

Surgical removal by pars plana vitrectomy.

MAIN OUTCOME MEASURES

Visual acuity, scotoma, retinal examination with fundus photography, and fluorescein angiography before surgery and during the postoperative period.

RESULTS

Both patients underwent surgical removal after progression of the membrane with severe visual loss of 20/200 was noted. At present follow-up, there is a significant improvement in visual acuity and a reduction in the size of the scotoma. No recurrence of CNVM is noted.

CONCLUSION

Both patients with laser-induced iatrogenic subfoveal CNVM achieved a good visual outcome after surgical removal of the membrane. The reasons for a good surgical result are thought to be twofold. First, the origin of the CNVM is extrafoveal at the site of laser application. The chance for foveal cone cell damage during the surgery is reduced. Second, the degree of cellular destruction in iatrogenic CNVM is usually focal without extensive retinal photoreceptor cell and retinal pigment epithelial damage. Therefore, a better chance of postoperative visual recovery is anticipated.

Advantages of 2'-O-methyl oligoribonucleotide probes for detecting RNA targets

We have compared various kinetic and melting properties of oligoribonucleotide probes containing 2'-O-methylnucleotides or 2'-deoxynucleotides with regard to their use in assays for the detection of nucleic acid targets. 2'-O-Methyl oligoribonucleotide probes bound to RNA targets faster and with much higher melting temperatures (Tm values) than corresponding 2'-deoxy oligoribonucleotide probes at all lengths tested (8-26 bases). Tm values of both probes increased with length up to approximately 19 bases, with maximal differences in Tm between 2'-O-methyl and 2'-deoxy oligoribonucleotide probes observed at lengths of 16 bases or less. In contrast to RNA targets, 2'-O-methyl oligoribonucleotide probes bound more slowly and with the same Tm to DNA targets as corresponding 2'-deoxy oligoribonucleotide probes. Because of their greatly enhanced Tm when bound to RNA, 2'-O-methyl oligoribonucleotide probes can efficiently bind to double-stranded regions of structured RNA molecules. A 17 base 2'-O-methyl oligoribonucleotide probe was able to bind a double-stranded region of rRNA whereas the same 17 base 2'- deoxy oligoribonucleotide probe did not. Due to their enhanced Tm when bound to RNA targets, shorter 2'-O-methyl oligoribonucleotide probes can be used in assays in place of longer 2'-deoxy oligoribonucleotide probes, resulting in enhanced discrimination between matched and mismatched RNA targets. A 12 base 2'-O-methyl oligoribonucleotide probe had the same Tm as a 19 base 2'-deoxy oligoribonucleotide probe when bound to a matched RNA target but exhibited a much larger decrease in Tm than the 2'-deoxy oligoribonucleotide probe when bound to an RNA target containing either 1 or 2 mismatched bases. The increased Tm, faster kinetics of hybridization, ability to bind to structured targets and increased specificity of 2'-O-methyl oligoribonucleotide probes render them superior to corresponding 2'-deoxy oligoribonucleotides for use in assays that detect RNA targets.

Detection of all single-base mismatches in solution by chemiluminescence

A rapid in-solution method for the detection of all 12 single-base mismatches is described. The technique is based on the hybridization protection assay (HPA) format that utilizes oligonucleotide probes labeled with a highly chemiluminescent acridinium ester (AE). Hydrolysis by weak base renders AE permanently non-chemiluminescent. When an AE-labeled probe hybridizes to an exactly complementary target, AE is protected from hydrolysis relative to the unhybridized conformation. Single-base mutations in the duplex adjacent to the site of AE attachment disrupt this protection resulting in rapid AE hydrolysis and loss of chemiluminescence. The discrimination effect was seen in both DNA and RNA. Studies of Tm values revealed that this effect is not due to a decrease in the overall stability of the duplex, suggesting the AE is responding to local structural changes in the double helix induced by mismatches. Using this principle all 12 single mismatches were clearly discriminated from the corresponding matched sequences. The assay is homogeneous, simple, sensitive, applicable to both amplified and non-amplified targets, and is completed in 30-60 min. An example showing discrimination between wild-type and mutant sequences corresponding to the reverse transcriptase coding region of HIV-1 is given.

Simultaneous detection of multiple nucleic acid targets in a homogeneous format

The acridinium ester 4-(2-succinimidyloxycarbonylethyl)phenyl-10-methylacridinium 9-carboxylate trifluoromethane sulfonate (AE), which reacts rapidly with alkaline hydrogen peroxide to produce light, has been used as a detection label in a number of assay procedures, including nucleic acid probe-based systems [Nelson et al. (1995) in Nonisotopic Probing, Blotting and Sequencing (Kricka, L. J., Ed.) pp 391-428, Academic Press, Inc., San Diego, CA]. We have synthesized a number of derivatives of this AE and characterized their chemiluminescent properties. These derivatives display significant differences in the kinetics of the chemiluminescence reaction as well as optimal pH for light production. These differences allow two or more derivatives to be simultaneously detected and quantitated in a single reaction vessel. Several of these derivatives have been covalently linked to nucleic acid probe molecules and have been further characterized in regard to chemiluminescence properties as well as hydrolysis of the ester bond in both single- and double-stranded conformations. On the basis of these properties, homogeneous assay formats utilizing DNA probes labeled with various AE derivatives were developed. Simultaneous detection and quantitation of Chlamydia trachomatis and Neisseria gonorrhoeae, the gag and pol regions of HIV, and wild-type and mutant HIV sequences was achieved with high sensitivity and discrimination.

Using an integrated point of care system: a nursing perspective

Nurses at LDS Hospital, Salt Lake City, Utah, have had the ability to document patient data and nursing care on a bedside computer for over nine years. This ability has had numerous ramifications for the medical record, nursing practice, and clinical decision making. This article is an effort to describe how and why certain decisions were made, the implications of these decisions, mistakes that were made and their solutions, and the tremendous impact on clinical decision making and improved patient outcomes that is only beginning to be realized by computerization of the medical record.

Bimanual technique of subfoveal neovascular membrane removal in presumed ocular histoplasmosis

We describe a bimanual technique of subfoveal neovascular membrane removal in a patient with presumed ocular histoplasmosis syndrome. His postoperative vision has improved from 20/400 to 20/100 at 3 months follow-up. No recurrence of the membrane was noted.

Internal choroidectomy of posterior uveal melanomas under a retinal flap

Local excision of uveal melanoma is an intriguing therapeutic modality in selected cases. An internal choroidectomy under a retinal flap has been developed as an alternative to retinochoroidectomy in managing posterior pole melanomas. This technique offers more adequate preservation of retinal architecture, thus potentially enhancing central visual function in patients with tumors located close to the fovea.

Posterior relaxing retinotomies: analysis of anatomic and visual results

Fifteen eyes with complicated retinal detachments--11 with proliferative vitreoretinopathy (C3 D3), 2 with posterior segment trauma, and 2 with inflammatory retinopathy--were treated with vitrectomy, membrane peeling, and large posterior retinotomy. All posterior relaxing retinotomies were circumferential, including temporal quadrants in all cases. With a minimum follow up of 6 months, 12 eyes (80%) were attached posterior to the retinotomy. Reproliferation resulted in redetachment in 3 eyes (20%). Visual acuity improved in 53%, remained unchanged in 20%, and decreased in 27%. Of the 11 eyes that achieved stable or improved visual acuity, 5 (45%) achieved 20/400 to 20/25 vision, 5 achieved counts fingers perception, and 1 patient remained stable at hand motion perception. Of all the eyes undergoing surgery, hypotony (intraocular pressure < 5 mm Hg) occurred in 6 eyes (40%); 3 of these were among the 12 eyes with attached retinas.

Use of perfluoroperhydrophenanthrene in the management of suprachoroidal hemorrhages

BACKGROUND

Suprachoroidal hemorrhage may cause the expulsion of intraocular contents. Generally, cases of nonexpulsive suprachoroidal hemorrhage have a better outcome than their expulsive counterparts. Those cases with massive nonexpulsive suprachoroidal hemorrhage do better with treatment than without. Treatment modalities have included suprachoroidal hemorrhage drainage with or without intraocular volume reformation, and vitrectomy.

METHODS

The authors used the liquid perfluorocarbon perfluoroperhydrophenanthrene in the treatment of three patients with nonexpulsive suprachoroidal hemorrhage. The perfluorocarbon was injected into the vitreous cavity while the suprachoroidal blood was drained through anterior sclerotomies.

RESULTS

With 5 months of follow-up, complete resolution of the suprachoroidal blood was noted in all patients. All three patients had attached retinas, and postoperative visual acuities were improved over preoperative visual acuities.

CONCLUSION

Perfluoroperhydrophenanthrene and other perfluorocarbon liquids may be beneficial in the treatment of certain cases of nonexpulsive suprachoroidal hemorrhages.

Surgical management of incarcerated retina in the sclerotomy

We used perfluoroperhydrophenanthrene (Vitreon) to release an incarcerated retina successfully from the pars plana sclerotomy site.

Vitreon, a short-term vitreoretinal tamponade

This investigation of the liquid perfluorocarbon, perfluorophenanthrene (Vitreon), establishes its safety and efficacy as a short-term vitreoretinal tamponade. We utilised Vitreon as an intraoperative tool and postoperative vitreoretinal tamponade in 16 patients. Proliferative vitreoretinopathy (PVR) (six), giant retinal tear (four), rhegmatogenous retinal detachment (three), retinal detachment with keratoprosthesis (two), and submacular and vitreous haemorrhage (one) were successfully repaired. Vitreon was left in the eye and removed 5 days to 4 weeks postoperatively. Complications encountered included proliferative PVR (five), limited peripheral retinal detachment (three), macular pucker (two) cataract (three), hypotony (two), excessive fibrin reaction (one), and elevated intraocular pressure (one). At the latest evaluation, all retinas are attached with a follow-up of 1.25 to 12 months (mean 6.8 months).

Tissue plasminogen activating factor assisted removal of subretinal hemorrhage

We used tissue plasminogen activator (tPA) to aid in the surgical evacuation of subretinal hemorrhages. Subretinal hemorrhage secondary to a ruptured retinal macroaneurysm was treated in two patients. The surgical technique involved using a micropipette to fashion a small retinotomy through which tPA was injected into the subretinal space and through which the dissolved clot was removed. Visual acuity improved from counts fingers to 20/50 in one patient and from counts fingers to 20/70 in the other. Three additional patients, with massive subretinal hemorrhages secondary to age-related macular degeneration, were similarly treated. In one, visual acuity improved from counts fingers to 20/400; in two others, visual acuity was stabilized; in the first patient, at 20/300, and in the second patient at 20/400. The use of tPA minimizes surgical manipulation of the sensory retina and greatly reduces the size of the retinotomy required for evacuation of subretinal blood.

Endemic goiter and endemic thyroid disorders

The primary role of iodine deficiency in goitrogenesis and the prevention and treatment of endemic goiter by iodine supplementation is firmly established. Unfortunately, implementation of iodine prophylaxis programs has met with considerable technical and socioeconomic difficulties. Besides, lack of knowledge concerning some of the other causative factors of endemic goiter has prevented development of appropriate measures for its complete eradication in those areas where goiter persists in spite of prolonged and adequate iodine supplementation. At present, no less than 5% of the world's population have goiters and associated disorders, resulting in a public health and socioeconomic problem of major proportions. Seventy-five percent of people with goiter live in less developed countries where iodine deficiency is prevalent. Goiter prevalence rates of more than 50% and the highest frequency of severe cases of iodine deficiency disorders, namely, cretinism, congenital hypothyroidism, and various degrees of impairment of growth and mental development are found in endemic areas with extreme iodine deficiency. Goiters are usually multinodular and of very large size, producing, on occasion, signs of compression that require surgery. Recurrence rates are as high as 25-30% and second surgery accounts for 16% of all thyroidectomies. Unfortunately, most of these goiters occur in areas with highly restricted medical and surgical facilities. Twenty-five percent of people with goiters live in more developed countries where goiter continues to occur in certain areas despite iodine prophylaxis. Iodine-sufficient goiters are associated with autoimmune thyroiditis, hypothyroidism, hyperthyroidism, and thyroid carcinoma. Goiter is of considerable surgical significance in iodine-sufficient endemic areas and, to a lesser degree, in nonendemic areas where it is called "sporadic" goiter. Recurrence rates of iodine-sufficient goiter are 10-19% following thyroidectomy. Since most of these goiters grow by mechanisms other than increased thyrotropin (TSH) stimulation, treatment with suppressive doses of L-thyroxine is inefficient and, because of possible complications, not recommended. Although Graves' hyperthyroidism is not directly related to endemic goiter, it does relate adversely with ingestion or administration of iodine. At present, Graves' disease is treated with 131I or antithyroid drugs in more than 90% of the cases. The incidence rates of papillary, follicular, and anaplastic thyroid carcinomas appear to be related to endemic goiter and iodine supplementation, with surgery being required in essentially all of these cases.

A technique for retinal pigment epithelium transplantation for age-related macular degeneration secondary to extensive subfoveal scarring

We describe the surgical excision of submacular scar in end-stage age-related macular degeneration and transplantation of autologous and homologous retinal pigment epithelial (RPE) cells. The technique involves the preparation of a large retinal flap encompassing the macula and the arcades, removal of the submacular scar, and replacement of the RPE cells, using either an autologous pedicle graft or homologous RPE cells and Bruch's membrane. Fourteen months following the procedure, visual acuity in a patient with a pedicle graft had improved from counts fingers to 20/400 and the patient fixated over the transplanted RPE cells. After 10 months, a homologous graft in a second patient had become encapsulated with a fine subretinal membrane without neovascular tissue; visual acuity had not improved. No intraoperative or postoperative complications resulting from the surgery occurred in either patient.

Nucleophilic addition to the 9 position of 9-phenylcarboxylate-10-methylacridinium protects against hydrolysis of the ester

The chemiluminescent reaction of an acridinium ester (AE) requires addition of peroxide to the 9 position of the acridinium ring. The addition of a hydroxide ion to the 9 position of an acridinium ester to form the carbinol adduct has also been well documented. We have observed a similar addition of other nucleophiles to the acridinium ring to form an acridan adduct. The adduct formed with bisulphite has been particularly well-characterized for rate of formation, rate of reversion, and reaction equilibrium. The formation of an adduct (other than H2O2) has been demonstrated to decrease significantly the reactivity of the adjacent ester bond to alkaline hydrolysis. The resulting, more stable adduct is very useful when the acridinium ester is used as a label in DNA probe-based assays. The adduct is highly resistant to hydrolysis under the conditions often desired for DNA probe-based assays (high temperature, elevated pH, extended storage).

Chemiluminescent DNA probes: a comparison of the acridinium ester and dioxetane detection systems and their use in clinical diagnostic assays

Nucleic acid hybridization has the potential to markedly improve the diagnosis of infectious and genetic diseases. Recently, chemiluminescent hybridization assays using acridinium esters and stabilized dioxetanes have been described with sensitivities comparable to those obtained with radioactive labels. Acridinium esters are used as direct labels that are attached to the probe throughout the hybridization reaction. Methods have been developed for labeling DNA probes with acridinium esters at high specific activity and for stabilizing the label under the relatively harsh conditions of hybridization reactions. The label does not affect the kinetics of the hybridization reaction or the stability of the resulting hybrid. The label emits light upon exposure to alkaline peroxide; thus, the assay format can be an extremely simple one. The acridinium ester labels are stable in storage and exhibit extremely rapid light-off kinetics which permit reading large numbers of samples within a brief period as well as limiting the contribution of background signal. A special property of acridinium esters allows chemical destruction of the label when it is present on unhybridized probe, whereas the label is stable to this process when the probe is hybridized. This behavior forms the basis of techniques to minimize assay background signals and allows a homogeneous assay format which does not require physical separation of hybridized and unhybridized probe. The adamantyl-stabilized 1,2-dioxetanes have been used to produce high-sensitivity detection systems for clinical assays. The probe is labeled with enzymes such as alkaline phosphatase or beta-D-galactosidase that hydrolyze the dioxetane derivative to produce a chemiluminescent molecule. As with other enzyme-based labeling systems, the signal increases with time, allowing greater sensitivity to be achieved with longer incubations. The amount of light generated is sufficient to expose sensitive photographic film with extended incubation; therefore, convenient assay formats not requiring instrumentation can be used. Excellent analytical sensitivities have been reported, and by using labels with different light emissions and/or different enzymes on the probes, it is possible to distinguish multiple target sites within a single assay. Because the label is suited for use with solid supports such as polyacrylamide gels, membrane filters, or microscope slides, applications include DNA sequencing, dot and Southern blot hybridizations, and in situ hybridization.

Assay formats involving acridinium-ester-labeled DNA probes

We describe the development of several hybridization assay formats involving acridinium-ester-labeled DNA probes. The simplest of these is a homogeneous assay procedure that requires only three steps to complete, including a 5-s detection step. Using this format, we have detected target sequences in the 10(-16) to 10(-17) mol range; when rRNA is the target, this translates to 3000 to 300 bacterial organisms. The entire assay can be carried out in less than 30 min. This is the first homogeneous DNA probe assay to be of practical use in the clinical laboratory, and it represents a major simplification of hybridization formats. We also demonstrate the use of this homogeneous assay format to discriminate single-base differences between two closely related target sequences and to detect DNA as well as RNA target molecules. By combining homogeneous hybrid discrimination with solid-phase separation, we have been able to decrease background readings from unhybridized probe to only a few parts per million. This enhances assay sensitivity about 10-fold, to a range of 10(-17) to 10(-18) mol of target. We are in the process of further improving the performance of these assays.

Assay formats involving acridinium-ester-labeled DNA probes

We describe the development of several hybridization assay formats involving acridinium-ester-labeled DNA probes. The simplest of these is a homogeneous assay procedure that requires only three steps to complete, including a 5-s detection step. Using this format, we have detected target sequences in the 10(-16) to 10(-17) mol range; when rRNA is the target, this translates to 3000 to 300 bacterial organisms. The entire assay can be carried out in less than 30 min. This is the first homogeneous DNA probe assay to be of practical use in the clinical laboratory, and it represents a major simplification of hybridization formats. We also demonstrate the use of this homogeneous assay format to discriminate single-base differences between two closely related target sequences and to detect DNA as well as RNA target molecules. By combining homogeneous hybrid discrimination with solid-phase separation, we have been able to decrease background readings from unhybridized probe to only a few parts per million. This enhances assay sensitivity about 10-fold, to a range of 10(-17) to 10(-18) mol of target. We are in the process of further improving the performance of these assays.

Selective protection of sulfhydryl groups in cAMP-dependent protein kinase II

The cysteine residues of cAMP-dependent protein kinase II from porcine heart have been probed using alkylation with iodoacetic acid. Alkylation of the dissociated catalytic subunit resulted in loss of activity that was concomitant with the alkylation of both cysteine residues, Cys 199 and Cys 343. In contrast, no loss of activity was observed following alkylation of the holoenzyme. Isolation of the C-subunit following dissociation of the alkylated holoenzyme with cAMP revealed that Cys 343 was fully alkylated whereas Cys 199 was completely protected from chemical modification. These results establish that Cys 343 is not essential for enzymatic activity and, furthermore, indicate that aggregation of the C- and R-subunits selectively protects Cys 199. Alkylation of the R-subunit was also characterized both in the presence and absence of C-subunit. Cysteines 97, 124, and 326 were alkylated in R2 both in the presence and absence of cAMP. Of these 3 residues only Cys 97 was protected from alkylation in the holoenzyme. In the presence of high concentrations of iodoacetic acid, partial alkylation of the remaining 3 cysteine residues was observed, and this labeling was eliminated by cAMP suggesting that cAMP results in a general tightening of the protein conformation rather than the selective protection of any single cysteine residue.

Modification of the catalytic subunit of bovine heart cAMP-dependent protein kinase with affinity labels related to peptide substrates

The modification and concomitant inactivation of the catalytic subunit of bovine heart cAMP-dependent protein kinase with affinity analogs of peptide substrates potentially capable of undergoing disulfide interchange with enzyme-bound sulfhydryl groups have been used to probe the active site associated with peptide binding. The regeneration of catalytic activity on treatment of the modified enzymes with dithiothreitol and the observation that prior reaction with 5,5'-dithiobis-(2-nitrobenzoic acid) blocks the modification of the kinase by these reagents are consistent with the proposal that only thiol residues are reacting. The affinity analog Leu-Arg-Arg-Ala-Cys(3-nitro-2-pyridinesulfenyl)-Leu-Gly, 1, and the closely related peptide AcLeu-Arg-Arg-Ala-Cys(3-nitro-2-pyridinesulfenyl)-Leu-Gly-OEt, 3, react with a single sulfhydryl as shown by the stoichiometry of the release of the 3-nitro-2-pyridinesulfenyl group and the amount of label incorporated in the enzyme when the radioactively labeled peptide analog of 3 (peptide 4) is employed as the modifying agent. The kinetics of the reaction of 1 with 4.3 microM catalytic subunit was monophasic (employing substrate in excess conditions), yielding an apparent value of KI of approximately 40 microM and a k2 value of approximately 0.25 s-1. The low value of the observed KI, together with the observation that protein kinase substrates inhibit the modification reactions, suggest strongly that the cysteine residue undergoing reaction is in the vicinity of the active site. By trypsin-catalyzed degradation and identification of the peptide segment modified by covalent attachment of the peptide portion of the radioactive analog 4, the single cysteine modified was identified as cysteine-198.

A case-comparison study of hypertension and hyperparathyroidism

The frequency of hypertension in patients with primary hyperparathyroidism has been compared with that found in cases matched for conditions of comparable surgical magnitude, age, race, sex, and days in the hospital. The mean blood pressure of the patients was 143/89 mm Hg, significantly higher than that of controls, which was 130/81 mm Hg (P less than 0.001 for systolic and diastolic pressures). The difference was especially notable in view of the fact that the mean weight of the controls was 169 lb compared to 153.9 lb for the patients. Actual hypertension, defined as a diastolic blood pressure of 90 mm Hg or more and or treatment with hypertensive therapy was much more frequent in the patients (90 of 124; 73%) than in the controls (53 of 124; 43%; P less than 0.001). Serum creatinine was 1.3 mm/dl in patients and 1.1 mm/dl in controls. The blood pressure difference between patients and controls persisted when patients with creatinine levels of 2.0 mm/dl or less were omitted. The blood pressure difference between patients and controls had disappeared by the end of hospitalization. We conclude that primary hyperparathyroidism is associated with modest blood pressure elevation, that renal damage is probably not the mechanism, and that surgical cure perhaps may lower blood pressure. The mean effect of primary hyperparathyroidism is to shift the blood pressure distribution curve to the right by approximately 15/10 mm Hg.

Affinity labeling of cAMP-dependent protein kinase with p-fluorosulfonylbenzoyl adenosine. Covalent modification of lysine 71

p-Fluorosulfonylbenzoyl 5'-adenosine (FSO2BzAdo) was shown previously to be an irreversible inhibitor of the catalytic subunit of cAMP-dependent protein kinase II from porcine skeletal muscle (Zoller, M. J., and Taylor, S. S. (1979) J. Biol. Chem. 254, 8363-8368). The catalytic subunit of porcine heart cAMP-dependent protein kinase was also inhibited following incubation with FSO2[14C]BzAdo, and inhibition was shown to result from the stoichiometric, covalent modification of a single lysine residue. The amino acid sequence in an extended region around the carboxybenzenesulfonyl lysine (CBS-lysine) was elucidated by characterizing both tryptic and cyanogen bromide peptides containing the 14C-modified residue. The sequence in this region was Leu-Val-Lys-His-Lys-Glu-Thr-Gly-Asn-His-Phe-Ala-Met-Lys(CBS)-Ile-Leu-Asp-Lys-Glu-Lys-Val-Val-Lys-Leu-Lys-Gln-Ile. The covalently modified residue corresponded to lysine 71 in the overall polypeptide chain. Homologies to bovine heart catalytic subunit and to a site modified by FSO2BzAdo in phosphofructokinase are considered.

Microchromatography of hemoglobins. V. Thin-layer chromatography of some hemoglobins on CM-cellulose

By means of thin-layer ion-exchange chromatography, human hemoglobins A, S, and C in various combinations can be distinctly separated. Also, hemoglobin F can be separated from the A, S, and C components of cord blood samples from infants and in adult blood samples with a relatively high percentage of F (15% or more). The procedure uses CM-cellulose and solutions of Tris-HCl, NaCl, and KCN. A 0.3-mg sample in 5-10 mul of solvent is required. Development can be completed in 30-40 min.

Portal and peripheral vein immunoreactive glucagon concentrations after arginine or glucose infusions

Catheterization of the portal vein via the umbilical vein was performed under local anesthesia in eight nondiabetic subjects before exploratory laparotomy for a variety of conditions. Levels of immunoreactive glucagon (IRG) and immunoreactive insulin (IRI) were determined in simultaneously obtained portal and peripheral vein plasma before, during and after a fifteen minute arginine infusion (30 gm.) in five subjects. The mean portal vein to peripheral vein glucagon ratio in the postabsorptive state was 1.7 ± 0.5. A biphasic portal vein IRG response to arginine was observed, with the initial glucagon peak occurring within one minute of the beginning of the infusion. Peripheral IRG concentrations did not reflect the biphasic response. The portal vein IRI response to arginine was also mildly biphasic, and the first phase occurred before a detectable increase in blood glucose. The portal vein IRG peak either preceded or coincided temporally with the portal vein IRI peak. In three nondiabetic subjects, portal vein IRG decreased rapidly to its nadir within two minutes after a two minute glucose infusion (25 gm.) was started.

Portal vein insulin concentrations in diabetic subjects

Portal vein immunoreactive insulin (IRI) concentrations following intravenous glucose were compared in diabetics and nondiabetics. Diminished pancreatic insulin secretion rather than extrapancreatic factors explains the peripheral insulinopenia observed in diabetics. Early insulin release (acute pool) was impaired more than delayed release (chronic pool) in the diabetics.

Portal and peripheral vein immunoreactive insulin concentrations following tolbutamide administration

The effect of tolbutamide on portal and peripheral vein immunoreactive insulin concentrations in man was assessed and compared with that of a glucose stimulus. The portal vein IRI responses to both stimuli were similar. The ratios of peripheral vein to portal vein insulin response (area under the curve) following tolbutamide administration were the same or lower than that following a glucose infusion.

Portal and peripheral vein immunoreactive insulin concentrations before and after glucose infusion

Catheterization of the portal vein via the umbilical vein was performed under local anesthesia in twelve nondiabetic subjects prior to exploratory laporatomy for a variety of conditions. Immunoreactive insulin (IRI) in simultaneously obtained portal and peripheral vein plasma was determined before, during, and after a two-minute glucose infusion (25 gm.). Two phases of insulin secretion were apparent from portal vein IRI concentrations. A rapid secretory phase beginning one minute after start of the infusion and lasting three to four minutes was followed by a slower secretory phase beginning approximately ten minutes after start of the glucose infusion. The absolute amount of “big” insulin (proinsulin-like material) in the portal vein was similar during the first phase and the early part of the second phase of insulin secretion. A significant positive correlation between portal vein and peripheral vein IRI responses to glucose was noted.