Hotspot Regions of Quantitative Trait Loci and Candidate Genes for Ear-Related Traits in Maize: A Literature Review

In this study, hotspot regions, QTL clusters, and candidate genes for eight ear-related traits of maize (ear length, ear diameter, kernel row number, kernel number per row, kernel length, kernel width, kernel thickness, and 100-kernel weight) were summarized and analyzed over the past three decades. This review aims to (1) comprehensively summarize and analyze previous studies on QTLs associated with these eight ear-related traits and identify hotspot bin regions located on maize chromosomes and key candidate genes associated with the ear-related traits and (2) compile major and stable QTLs and QTL clusters from various mapping populations and mapping methods and techniques providing valuable insights for fine mapping, gene cloning, and breeding for high-yield and high-quality maize. Previous research has demonstrated that QTLs for ear-related traits are distributed across all ten chromosomes in maize, and the phenotypic variation explained by a single QTL ranged from 0.40% to 36.76%. In total, 23 QTL hotspot bins for ear-related traits were identified across all ten chromosomes. The most prominent hotspot region is bin 4.08 on chromosome 4 with 15 QTLs related to eight ear-related traits. Additionally, this study identified 48 candidate genes associated with ear-related traits. Out of these, five have been cloned and validated, while twenty-eight candidate genes located in the QTL hotspots were defined by this study. This review offers a deeper understanding of the advancements in QTL mapping and the identification of key candidates associated with eight ear-related traits. These insights will undoubtedly assist maize breeders in formulating strategies to develop higher-yield maize varieties, contributing to global food security.

A potential candidate gene associated with the angles of the ear leaf and the second leaf above the ear leaf in maize

BACKGROUND

Leaf angle is a key trait for maize plant architecture that plays a significant role in its morphological development, and ultimately impacting maize grain yield. Although many studies have been conducted on the association and localization of genes regulating leaf angle in maize, most of the candidate genes identified are associated with the regulation of ligule-ear development and phytohormone pathways, and only a few candidate genes have been reported to enhance the mechanical strength of leaf midrib and vascular tissues.

RESULTS

To address this gap, we conducted a genome-wide association study (GWAS) using the leaf angle phenotype and genotyping-by-sequencing data generated from three recombinant inbred line (RIL) populations of maize. Through GWAS analysis, we identified 156 SNPs significantly associated with the leaf angle trait and detected a total of 68 candidate genes located within 10 kb upstream and downstream of these individual SNPs. Among these candidate genes, Zm00001d045408, located on chromosome 9 emerged as a key gene controlling the angles of both the ear leaf and the second leaf above the ear leaf. Notably, this new gene's homolog in Arabidopsis promotes cell division and vascular tissue development. Further analysis revealed that a SNP transversion (G/T) at 7.536 kb downstream of the candidate gene Zm00001d045408 may have caused a reduction in leaf angles of the ear and the second leaf above the ear leaf. Our analysis of the 10 kb region downstream of this candidate gene revealed a 4.337 kb solo long-terminal reverse transcription transposon (solo LTR), located 3.112 kb downstream of Zm00001d045408, with the SNP located 87 bp upstream of the solo LTR.

CONCLUSIONS

In summary, we have identified a novel candidate gene, Zm00001d045408 and a solo LTR that are associated with the angles of both the ear leaf and the second leaf above the ear leaf. The future research holds great potential in exploring the precise role of newly identified candidate gene in leaf angle regulation. Functional characterization of this gene can help in gaining deeper insights into the complex genetic pathways underlying maize plant architecture.

A 43 Bp-Deletion in the F3'H Gene Reducing Anthocyanins Is Responsible for Keeping Buds Green at Low Temperatures in Broccoli

Most broccoli cultivars or accessions exhibit green buds under appropriate growth conditions, which turn purple at cold temperatures. However, certain cultivars consistently maintain green buds both during normal growth and at cold temperatures. In this study, we used BSA-seq (bulked segregation analysis-sequencing), along with fine mapping and transcriptome analysis to identify a candidate gene (flavonoid 3'-hydroxylase, F3'H) responsible for reducing anthocyanin accumulation in the mutant GS and HX-16 broccoli (Brassica oleracea L. var. italica), which could retain green buds even at low temperatures. A 43-bp deletion was detected in the coding sequence (CDS) of the F3'H gene in HX-16 and the mutant GS, which significantly decreased F3'H expression and the accumulation of cyanidin and delphinidin in the mutant GS. Furthermore, the expression of F3'H was upregulated at low temperatures in the wild line PS. Our results demonstrated the efficacy of utilizing the 43-bp InDel (Insertion-Deletion) in predicting whether buds in B. oleracea L. will turn purple or remain green at cold temperatures across forty-two germplasm materials. This study provides critical genetic and molecular insights for the molecular breeding of B. oleracea and sheds light on the molecular mechanisms underlying the effect of low temperatures on bud color in broccoli.

Identification of Candidate QTLs and Genes for Ear Diameter by Multi-Parent Population in Maize

Ear diameter (ED) is a critical component of grain yield (GY) in maize (Zea mays L.). Studying the genetic basis of ED in maize is of great significance in enhancing maize GY. Against this backdrop, this study was framed to (1) map the ED-related quantitative trait locus (QTL) and SNPs associated with ED; and (2) identify putative functional genes that may affect ED in maize. To accomplish this, an elite maize inbred line, Ye107, which belongs to the Reid heterotic group, was used as a common parent and crossed with seven elite inbred lines from three different heterotic groups (Suwan1, Reid, and nonReid) that exhibited abundant genetic variation in ED. This led to the construction of a multi-parent population consisting of 1215 F₇ recombinant inbred lines (F₇RILs). A genome-wide association study (GWAS) and linkage analysis were then conducted for the multi-parent population using 264,694 high-quality SNPs generated via the genotyping-by-sequencing method. Our study identified a total of 11 SNPs that were significantly associated with ED through the GWAS, and three QTLs were revealed by the linkage analysis for ED. The major QTL on chromosome 1 was co-identified in the region by the GWAS at SNP_143985532. SNP_143985532, located upstream of the Zm00001d030559 gene, encodes a callose synthase that is expressed in various tissues, with the highest expression level in the maize ear primordium. Haplotype analysis indicated that the haplotype B (allele AA) of Zm00001d030559 was positively correlated with ED. The candidate genes and SNPs identified in this study provide crucial insights for future studies on the genetic mechanism of maize ED formation, cloning of ED-related genes, and genetic improvement of ED. These results may help develop important genetic resources for enhancing maize yield through marker-assisted breeding.

Mapping and Functional Analysis of QTL for Kernel Number per Row in Tropical and Temperate-Tropical Introgression Lines of Maize (Zea mays L.)

Kernel number per row (KNR) is an essential component of maize (Zea mays L.) grain yield (GY), and understanding its genetic mechanism is crucial to improve GY. In this study, two F₇ recombinant inbred line (RIL) populations were created using a temperate-tropical introgression line TML418 and a tropical inbred line CML312 as female parents and a backbone maize inbred line Ye107 as the common male parent. Bi-parental quantitative trait locus (QTL) mapping and genome-wide association analysis (GWAS) were then performed on 399 lines of the two maize RIL populations for KNR in two different environments using 4118 validated single nucleotide polymorphism (SNP) markers. This study aimed to: (1) detect molecular markers and/or the genomic regions associated with KNR; (2) identify the candidate genes controlling KNR; and (3) analyze whether the candidate genes are useful in improving GY. The authors reported a total of 7 QTLs tightly linked to KNR through bi-parental QTL mapping and identified 21 SNPs significantly associated with KNR through GWAS. Among these, a highly confident locus qKNR7-1 was detected at two locations, Dehong and Baoshan, with both mapping approaches. At this locus, three novel candidate genes (Zm00001d022202, Zm00001d022168, Zm00001d022169) were identified to be associated with KNR. These candidate genes were primarily involved in the processes related to compound metabolism, biosynthesis, protein modification, degradation, and denaturation, all of which were related to the inflorescence development affecting KNR. These three candidate genes were not reported previously and are considered new candidate genes for KNR. The progeny of the hybrid Ye107 × TML418 exhibited strong heterosis for KNR, which the authors believe might be related to qKNR7-1. This study provides a theoretical foundation for future research on the genetic mechanism underlying KNR in maize and the use of heterotic patterns to develop high-yielding hybrids.

The filamentous type III secretion translocon of enteropathogenic Escherichia coli

Enteropathogenic Escherichia coli (EPEC) uses a type III secretion system (TTSS) to inject effector proteins into the plasma membrane and cytosol of infected cells. To translocate proteins, EPEC, like Salmonella and Shigella, is believed to assemble a macromolecular complex (type III secreton) that spans both bacterial membranes and has a short needle-like projection. However, there is a special interest in studying the EPEC TTSS owing to the fact that one of the secreted proteins, EspA, is assembled into a unique filamentous structure also required for protein translocation. In this report we present electron micrographs of EspA filaments which reveal a regular segmented substructure. Recently we have shown that deletion of the putative structural needle protein, EscF, abolished protein secretion and formation of EspA filaments. Moreover, we demonstrated that EspA can bind directly to EscF, suggesting that EspA filaments are physically linked to the EPEC needle complex. In this paper we provide direct evidence for the association between an EPEC bacterial membrane needle complex and EspA filaments, defining a new class of filamentous TTSS.

Stroke in surgery of the thoracic aorta: incidence, impact, etiology, and prevention

OBJECTIVES

To determine the incidence, impact, etiology, and methods for prevention of stroke after surgery of the thoracic aorta.

METHODS

A total of 317 thoracic aortic operations on 303 patients (194 male, 109 female) aged 13 to 87 years (mean 61 years) were reviewed. There were 218 procedures on the ascending aorta and arch and 99 on the descending aorta. Of the 218 procedures on the ascending aorta and arch, 86 involved cardiopulmonary bypass, 122 involved deep hypothermic circulatory arrest, 2 involved antegrade cerebral perfusion, and 8 involved "clamp and sew" or left heart bypass. Of the 99 procedures on the descending aorta, 20 involved "clamp and sew," 69 involved left heart or full bypass, and 10 involved deep hypothermic circulatory arrest. A total of 206 cases were elective and 97 were emergency operations.

RESULTS

Twenty-three (7.3%) of 317 patients had a stroke. Fifteen strokes occurred in operations on the ascending aorta and 8 in operations on the descending aorta (6.9% vs 8.1%; P =.703). Stroke occurred in 16 (16.5%) of 97 emergency operations and 7 (3.4%) of 206 elective operations (P =.001). In the 300 patients surviving the operation, stroke was a significant predictor of postoperative death (9/23 [39.1%] vs 23/277 [8.3%]; P =.001). Analysis of operative reports, brain images, and neurologic consultations revealed 15 of the 23 strokes were embolic, 3 were ischemic, 3 hemorrhagic, and 2 indeterminate. Patients with stroke had longer intensive care unit stays (18.4 vs 6.8 days; P =.0001), longer times to extubation (12.7 vs 3.8 days; P <.0012), longer postoperative stays (31.4 vs 14.3 days; P =.001), and decreased age-adjusted survival (relative risk 2.775; P =.0013). After implementation of a rigorous antiembolic regimen, both strokes and mortality trended downward.

CONCLUSIONS

(1) Stroke complicates surgery of both the ascending and descending thoracic aorta and warrants consideration in decision making. (2) Strokes are largely embolic. (3) Antiembolic measures for particles and air are essential, including gentle aortic manipulation, thorough debridement, transesophageal echocardiography to identify aortic atheromas, carbon dioxide flooding of the field, and (in descending cases) proximal clamp application before initiating femoral perfusion.

Role of EscF, a putative needle complex protein, in the type III protein translocation system of enteropathogenic Escherichia coli

Type III secretion systems, designed to deliver effector proteins across the bacterial cell envelope and the plasma membrane of the target eukaryotic cell, are involved in subversion of eukaryotic cell functions in a variety of human, animal and plant pathogens. In enteropathogenic Escherichia coli (EPEC), several protein substrates for the secretion apparatus were identified, including EspA, EspB and EspD. EspA is a structural protein and the major component of a large transiently expressed filamentous surface organelle that forms a direct link between the bacterium and the host cell, whereas EspD and EspB seem to form the mature translocation pore. Recent studies of the type III secretion systems of Shigella and Salmonella pathogenicity island (SPI)-1 revealed the existence of a macromolecular complex that spans both bacterial membranes and consists of a basal structure with two upper and two lower rings and a needle-like projection that extends outwards from the bacterial surface. MxiH (Shigella) and PrgI (Salmonella) are the main components of the needle of the type III secretion complex. A needle-like complex has not yet been reported in EPEC. In this study, we investigated EscF, a protein sharing sequence similarity with MxiH and PrgI. We report that EscF is required for type III protein secretion and EspA filament assembly. Moreover, we show that EscF binds EspA, suggesting that EspA filaments are an extension of the type III secretion needle complexes in EPEC.

Coiled-coil domain of enteropathogenic Escherichia coli type III secreted protein EspD is involved in EspA filament-mediated cell attachment and hemolysis

Many animal and plant pathogens use type III secretion systems to secrete key virulence factors, some directly into the host cell cytosol. However, the basis for such protein translocation has yet to be fully elucidated for any type III secretion system. We have previously shown that in enteropathogenic and enterohemorrhagic Escherichia coli the type III secreted protein EspA is assembled into a filamentous organelle that attaches the bacterium to the plasma membrane of the host cell. Formation of EspA filaments is dependent on expression of another type III secreted protein, EspD. The carboxy terminus of EspD, a protein involved in formation of the translocation pore in the host cell membrane, is predicted to adopt a coiled-coil conformation with 99% probability. Here, we demonstrate EspD-EspD protein interaction using the yeast two-hybrid system and column overlays. Nonconservative triple amino acid substitutions of specific EspD carboxy-terminal residues generated an enteropathogenic E. coli mutant that was attenuated in its ability to induce attaching and effacing lesions on HEp-2 cells. Although the mutation had no effect on EspA filament biosynthesis, it also resulted in reduced binding to and reduced hemolysis of red blood cells. These results segregate, for the first time, functional domains of EspD that control EspA filament length from EspD-mediated cell attachment and pore formation.

EspA filament-mediated protein translocation into red blood cells

Type III secretion allows bacteria to inject effector proteins into host cells. In enteropathogenic Escherichia coli (EPEC), three type III secreted proteins, EspA, EspB and EspD, have been shown to be required for translocation of the Tir effector protein into host cells. EspB and EspD have been proposed to form a pore in the host cell membrane, whereas EspA, which forms a large filamentous structure bridging bacterial and host cell surfaces, is thought to provide a conduit for translocation of effector proteins between pores in the bacterial and host cell membranes. Type III secretion has been correlated with an ability to cause contact-dependent haemolysis of red blood cells (RBCs) in vitro. As EspA filaments link bacteria and the host cell, we predicted that intimate bacteria-RBC contact would not be required for EPEC-induced haemolysis and, therefore, in this study we investigated the interaction of EPEC with monolayers of RBCs attached to polylysine-coated cell culture dishes. EPEC caused total RBC haemolysis in the absence of centrifugation and osmoprotection studies were consistent with the insertion of a hydrophilic pore into the RBC membrane. Cell attachment and haemolysis involved interaction between EspA filaments and the RBC membrane and was dependent upon a functional type III secretion system and on EspD, whereas EPEC lacking EspB still caused some haemolysis. Following haemolysis, only EspD was consistently detected in the RBC membrane. This study shows that intimate bacteria-RBC membrane contact is not a requirement for EPEC-induced haemolysis; it also provides further evidence that EspA filaments are a conduit for protein translocation and that EspD may be the major component of a translocation pore in the host cell membrane.

The type III protein translocation system of enteropathogenic Escherichia coli involves EspA-EspB protein interactions

Enteropathogenic Escherichia coli (EPEC), like many bacterial pathogens, use a type III secretion system to deliver effector proteins across the bacterial cell wall. In EPEC, four proteins, EspA, EspB, EspD and Tir are known to be exported by a type III secretion system and to be essential for 'attaching and effacing' (A/E) lesion formation, the hallmark of EPEC pathogenicity. EspA was recently shown to be a structural protein and a major component of a large, transiently expressed, filamentous surface organelle which forms a direct link between the bacterium and the host cell. In contrast, EspB is translocated into the host cell where it is localized to both membrane and cytosolic cell fractions. EspA and EspB are required for translocation of Tir to the host cell membrane suggesting that they may both be components of the translocation apparatus. In this study, we show that EspB co-immunoprecipitates with the EspA filaments and that, during EPEC infection of HEp-2 cells, EspB localizes closely with EspA. Using a number of binding assays, we also show that EspB can bind and be copurified with EspA. Nevertheless, binding of EspA filaments to the host cell membranes occurred even in the absence of EspB. These results suggest that following initial attachment of the EspA filaments to the target cells, EspB is delivered into the host cell membrane and that the interaction between EspA and EspB may be important for protein translocation.

The coiled-coil domain of EspA is essential for the assembly of the type III secretion translocon on the surface of enteropathogenic Escherichia coli

Enteropathogenic E. coli (EPEC) utilize a type III secretion system to deliver virulence-associated effector proteins to the host cell. Four proteins, EspA, EspB, EspD, and Tir, which are integral to the formation of characteristic "attaching and effacing" (A/E) intestinal lesions, are known to be exported via the EPEC type III secretion system. Recent work demonstrated that EspA is a major component of a filamentous structure, elaborated on the surface of EPEC, which is required for translocation of EspB and Tir. The carboxyl terminus of EspA is predicted to comprise an alpha-helical region, which demonstrates heptad periodicity whereby positions a and d in the heptad repeat unit abcdefg are occupied by hydrophobic residues, indicating a propensity for coiled-coil interactions. Here we demonstrate multimeric EspA isoforms in EPEC culture supernatants and EspA:EspA interaction on solid phase. Non-conservative amino acid substitution of specific EspA heptad residues generated EPEC mutants defective in filament assembly but which retained the ability to induce A/E lesions; additional mutation totally abolished EspA filament assembly and A/E lesion formation. These results demonstrate a similarity to flagellar biosynthesis and indicate that the coiled-coil domain of EspA is required for assembly of the EspA filament-associated type III secretion translocon.

The type IV bundle-forming pilus of enteropathogenic Escherichia coli undergoes dramatic alterations in structure associated with bacterial adherence, aggregation and dispersal

BFP, a plasmid-encoded type IV bundle-forming pilus produced by enteropathogenic Escherichia coli (EPEC), has recently been shown to be associated with the aggregation of bacteria and dispersal of bacteria from bacterial microcolonies. In standard 3 h HEp-2 cell assays, EPEC adhere in localized microcolonies; after 6 h, bacterial microcolonies are no longer present, indicating that bacterial aggregation and dispersal occurs in vitro during EPEC adhesion to cultured epithelial cells. To examine the role of BFP in EPEC aggregation and dispersal, we examined HEp-2 cell adhesion of strain E2348/69 and defined E2348/69 mutants by immunofluorescence and immunoelectron microscopy. BFP was expressed initially as approximately 40 nm diameter pilus bundles that promoted bacteria-bacteria interaction and microcolony formation. BFP subsequently underwent a striking alteration in structural organization with the formation of much longer and thicker ( approximately 100 nm diameter) pilus bundles, which frequently aggregated laterally to form even thicker bundles often arranged in a loose three-dimensional network; EPEC dispersal from bacterial microcolonies was associated with this transformation of BFP from thin to thick bundles. Bacterial dispersal and transformation of BFP from thin to thick bundles did not occur with a bfpF mutant of strain E2348/69. It is concluded that BFP promotes both the formation and the dispersal of EPEC microcolonies, that the dispersal phase requires BfpF and that dispersal is associated with dramatic alterations in the structure of BFP bundles.

Free radial artery grafts: surgical technique and results

In the search for alternative conduits, the use of radial artery (RA) grafts has found renewed interest. This study sought to evaluate prospectively the perioperative morbidity, including the postoperative complications in the donor forearm, and mortality in the routine use of RA grafts in coronary artery bypass surgery. Data were obtained prospectively on 200 consecutive patients who underwent coronary revascularization using at least one RA graft from January 1995 to April 1997. The mean age of the patents was 61.9+/-10.5 years (mean+/-standard deviation [SD]). The RA was obtained from one forearm in 197 patients and both forearms in 3 patients. Two patients (1%) required exploration for donor site hematomas, 4 patients (2%) had temporary perioperative dysesthesias in the region of the lateral cutaneous nerve of the forearm, and none had donor site wound infection. Two patients (1%) had a myocardial infarction with electrocardiographic changes in the areas grafted by the RA in the immediate postoperative period, indicating graft failure. The two deaths in the series were due to comorbid factors. Our data suggest that the RA is a safe and suitable conduit for coronary revascularization, and it provides good clinical results. Long-term follow-up of these patients is necessary to confirm the patency of RA conduits. Free RA grafts have the potential for use in other areas of surgery where a conduit is necessary for revascularization procedures.

Should angiographically disease-free saphenous vein grafts be replaced at the time of redo coronary artery bypass grafting?

BACKGROUND

Controversy exists regarding the management of angiographically disease-free saphenous vein grafts at the time of redo coronary artery bypass grafting (CABG). Some authorities favor replacement of these disease-free grafts, arguing that occlusion is likely in the near future. Others believe that these grafts are "biologically privileged" and should not be replaced.

METHODS

One hundred thirty-two consecutive patients (113 men, 19 women, aged 46 to 88 years, mean 67 years) underwent redo revascularization with one or more angiographically disease-free saphenous vein grafts at the time of redo CABG. Thirty-six patients had the disease-free grafts replaced (R) and 96 did not (NR). The mean interval from the first CABG was 9.25 years.

RESULTS

Surgical mortality was comparable in the NR and R groups (5 of 96 or 5.2% versus 3 of 36 or 8.3%, respectively; p < 0.5). Survival at 1 and 3 years was higher in the NR group than the R group (98% versus 80%, and 95% vs. 66% respectively; p < 0.0001). Late myocardial infarction was less common in the NR group than in the R group (12 of 91 or 12.9% versus 12 of 33 or 36.4%; p < 0.003). Recurrent angina was less common in the NR than in the R group (21 of 91 or 23.1% versus 15 of 33 or 45.5%; p < 0.015). Cardiac hospitalization was required less commonly in the NR than in the R group (11 of 91 or 12.1% versus 12 of 33 or 36.4%; p < 0.002). In nondiseased grafts undergoing angiographic evaluation late after redo CABG, rate of new stenosis was lower in NR grafts than in R grafts (2 of 12 or 16.7% versus 2 of 3 or 66.7%; p < 0.05).

CONCLUSIONS

With a conservative approach that does not replace nondiseased saphenous vein grafts at redo CABG (1) there is no increase in operative mortality, (2) good late survival is obtained, (3) clinical ischemia related to the NR saphenous vein grafts is uncommon, and (4) NR grafts continue to be patent. We conclude that disease-free vein grafts may not require routine replacement at redo CABG. A randomized study is required for definitive resolution.

Ability of enteroaggregative Escherichia coli strains to adhere in vitro to human intestinal mucosa

A collection of 44 enteroaggregative Escherichia coli (EAggEC) strains isolated from infants with diarrhea in India and the United Kingdom were examined for their ability to adhere in vitro to human intestinal mucosa and by electron microscopy for production of putative adherence factors. None of the strains adhered to human duodenal mucosa, and six strains tested did not adhere to ileal mucosa; all 44 strains, however, adhered to human colonic mucosa in localized aggregates. Electron microscopy of infected colonic mucosa indicated fimbrially mediated adhesion of the EAggEC strains. Four morphologically distinct kinds of fimbriae, including a new morphological type of E. coli fimbriae consisting of bundles of fine filaments, were identified among the EAggEC strains; this new type of fimbria was observed in 43 of the 44 EAggEC strains. Forty-three of the 44 EAggEC strains were positive with a DNA probe developed to identify EAggEC, and most of the strains belonged to serotypes unrelated to the other major classes of diarrheic E. coli. These results suggest that EAggEC may be a large-bowel pathogen and colonize the colon by a fimbrially mediated adhesion mechanism.

Electrophysiological evaluation of phrenic nerve function in candidates for diaphragm pacing

The electrophyisological status of phrenic nerve function has been determined by an assessment of the conduction time and diaphragm muscle action potential in patients who were being evaluated as candidates for diaphragm pacing, or who were being studied for suspected phrenic nerve injury or disease. The conduction time and muscle action potential were evoked by transcutaneous phrenic nerve stimulation or by stimulation with a permanently implanted diaphragm pacemaker. In normal volunteers the conduction time was found to be 8.40 msec +/- 0.78 msec (SD). Transcutaenous phrenic nerve stimulation was successful in predicting phrenic nerve viability in 116 of 120 nerves studied. The four false negatives were due to technical difficulty in locating the nerves in obese or uncooperative subjects. In patients who were selected for implantation of a diaphragm pacemaker, a conduction time that was prolonged (10 to 14 msec) preoperatively did not preclude successful diaphragm pacing. Postoperatively, a prolonged (> 10 msec) conduction time was associated with severe systemic disease or local nerve injury caused by trauma or infection. The elucidation of phrenic nerve function by such electrophysiological studies serves as a valuable adjunct to the selection and management of patients undergoing diaphragm pacing.

Air entrapment as a cause of transient cardiac pacemaker malfunction

Air within a pacemaker pocket may cause transient malfunction of a replacement unipolar cardiac pacemaker. This was noted in a patient in whom entrapped air prevented tissue contact of the anode, resulting in complete cessation of myocardial stimulation and absence of an electrocardiographic pacemaker artifact. Methods for avoiding this complication are proposed.

Ventriculopleural shunting in the management of hydrocephalus

6 cases of ventriculopleural shunting for control of hydrocephalus are presented. In the other child and adult, drainage of cerebrospinal fluid into the pleural cavity seems to be well tolerated in exceptional circumstances where other shunt procedures, including intracranial shunts, are contraindicated. In the infant and young child, accumulation of fluid in the pleural space is enchanced by a poorly understood immune-related mechanism and may lead to significant pulmonary dysfunction. On the basis of our experience, this procedure appears contraindicated in this age-group.

Modifications in the treatment of the multiple injury patient

When burns complicate the management of an otherwise severely injured patient, modifications in treatment must be undertaken for both problems. The unique situation of this type of patient often requires the use of multiple therapeutic interventions which may differ from the usual. The use of controlled hypotension and aggressive surgical burn management was successful in allowing the postponement of vascular surgery in a young male patient with a traumatic aortic disruption and extensive burns resulting from a 60-foot fall and severe thermal burns.

Long-term ventilatory support by diaphragm pacing in quadriplegia

Thirty-seven quadriplegic patients with respiratory paralysis were treated by electrical stimulation of the phrenic nerves to pace the diaphragm. Full-time ventilatory support by diaphragm pacing was accomplished in 13 patients. At least half-time support was achieved in 10 others. There were two deaths unrelated to pacing in these two groups. Fourteen patients could not be paced satisfactorily, and 8 of these patients died, most of them from respiratory infections. The average time the 13 patients on total ventilatory support have had bilateral diaphragm pacemakers is 26 months. The longest is 60 months. Many of these patients are out of the hospital and several are in school or working. Injury to the phrenic nerves either by the initial trauma to the cervical cord or during operation for implantation of the nerve cuff was the most significant complication. Nerve damage from prolonged electrical stimulation has not been a problem thus far. A description of the pacemaker, the technique of its implantation, and the pacing schedule are reported.

Biological activity of bovine brain constituents

Bovine brain extracts have been fractionated into 89 different subfractions, and the serotonin-like and acetylcholine-like properties of each determined. Thirty-three of the subfractions exhibited biological activity: 6 possessed acetylcholine-like activity; 5 possessed serotonin-like activity; 12 possessed activity of an unknown type; and the remaining 10 possessed more than one type of activity. Eighty of the subfractions contained peptides as revealed by acid hydrolysis. However, it was not established whether the peptides accounted for the biological activities noted.