Ischaemia-reperfusion injury to the intestine

Ischaemia-reperfusion injury (IRI) is of obvious relevance in situations where there is an interruption of blood supply to the gut, as in vascular surgery, or in the construction of free intestinal grafts. It is now appreciated that IRI also underlies the guy dysfunction that occurs in early shock, sepsis, and trauma. The events that occur during IRI are complex. However, recent advances in cellular biology have started to unravel these underlying processes. The aim of this review is to provide an outline of current knowledge on the mechanisms and consequences of IRI. Initially, IRI appears to be mediated by reactive oxygen metabolites and, at a later stage, by the priming and activation of polymorphonuclear neutrophils (PMN). Ischaemia-reperfusion injury can diminish the barrier function of the gut, and can promote an increase in the leakage of molecules (intestinal permeability) or the passage of microbes across the wall of the bowel (bacterial translocation). Ischaemia-reperfusion injury to the gut can result in the generation of molecules that may also harm distant tissues.

Surgery on trial: an account of clinical trials evaluating operations

BACKGROUND

The objective of this study was to review published clinical trials to determine the level of compliance with issues relevant to operations.

METHODS

We evaluated 10 methodologic criteria in 186 trials that were published in 10 prestigious journals between January 1986 and December 1995.

RESULTS

One quarter of the trials failed to provide a clear account of the operative technique, 34% of the trials did not adequately detail the adverse events that occurred after operation, and 40% of the trials neglected to declare the nature and success of the follow-up of patients after the operation. Only 35% of the trials indicated that there was an attempt to standardize either the surgical procedure or perioperative care. In addition, less than 20% of the trials declared a method for assessing compliance with the surgical protocol or commented on the use of resources during the perioperative period.

CONCLUSIONS

Greater attention needs to be paid to the specific issues that arise when operations are evaluated in clinical trials.

Courtship and visual defects of cacophony mutants reveal functional complexity of a calcium-channel alpha1 subunit in Drosophila

We show by molecular analysis of behavioral and physiological mutants that the Drosophila Dmca1A calcium-channel alpha1 subunit is encoded by the cacophony (cac) gene and that nightblind-A and lethal(1)L13 mutations are allelic to cac with respect to an expanded array of behavioral and physiological phenotypes associated with this gene. The cacS mutant, which exhibits defects in the patterning of courtship lovesong and a newly revealed but subtle abnormality in visual physiology, is mutated such that a highly conserved phenylalanine (in one of the quasi-homologous intrapolypeptide regions called IIIS6) is replaced by isoleucine. The cacH18 mutant exhibits defects in visual physiology (including complete unresponsiveness to light in certain genetic combinations) and visually mediated behaviors; this mutant (originally nbAH18) has a stop codon in an alternative exon (within the cac ORF), which is differentially expressed in the eye. Analysis of the various courtship and visual phenotypes associated with this array of cac mutants demonstrates that Dmca1A calcium channels mediate multiple, separable biological functions; these correlate in part with transcript diversity generated via alternative splicing.

Evidence that the TIM light response is relevant to light-induced phase shifts in Drosophila melanogaster

Light is a major environmental signal for the entrainment of circadian rhythms. In Drosophila melanogaster, recent experiments suggest that photic information is transduced to the clock through the timeless gene product, TIM. We provide genetic and spectral evidence supporting the relevance of TIM light responses to clock resetting. A missense mutant TIM, TIM-SL, exhibits greater sensitivity to light in both TIM protein disappearance and locomotor activity phase shifting assays. We show that the wavelength dependence of light-induced decreases in TIM levels and that of light-mediated phase shifting are virtually identical. Analysis of dose response of TIM disappearance in a variety of mutant genotypes suggests cell-autonomous light responses that are largely independent of the canonical visual transduction pathway.

Isolation and chronobiological analysis of a neuropeptide pigment-dispersing factor gene in Drosophila melanogaster

In this article, the authors isolate a gene encoding a neuropeptide in Drosophila melanogaster. The substance is called pigment-dispersing factor (PDF), based on one of the roles it plays in crustaceans (the arthropods in which this factor was initially discovered). The PDF-encoding Drosophila gene (pdf) is intronless and present in a single copy per haploid genome. The cytological location of pdf is 97B on the third chromosome. The putative 102-amino-acid precursor (prepro-PDF) consists of a signal peptide and a PDF-associated peptide, followed by the mature PDF. The PDF-associated peptide region of the precursor is highly diverged from those of the crustacean precursors, whereas the primary structure of the mature PDF is conserved in other members of the pigment-dispersing hormone family. A single pdf transcript (ca. 0.8 kb) is expressed predominantly in the head; the expression levels of pdf mRNA are consistently higher in males than in females. Putative pdf homologous transcripts are present in other Drosophila species, which exhibit similar sexual dimorphic expression patterns. Cyclic expression of pdf over the course of the day and night was assessed, but the mRNA exhibited at best very gentle cycling. The pdf expression in two behaviorally arrhythmic mutants were examined; the expression was intact in a period0 mutant but absent in the disconnected mutant.

CYCLE is a second bHLH-PAS clock protein essential for circadian rhythmicity and transcription of Drosophila period and timeless

We report the identification, characterization, and cloning of another novel Drosophila clock gene, cycle (cyc). Homozygous cyc flies are completely arrhythmic. Heterozygous cyc/+ flies are rhythmic but have altered periods, indicating that the cyc locus has a dosage effect on period. The molecular circadian phenotype of homozygous cyc flies is like homozygous Clk flies presented in the accompanying paper: mutant flies have little or no transcription of the per and tim genes. Cloning of the gene indicates that it also encodes a bHLH-PAS transcription factor and is a Drosophila homolog of the human protein BMAL1. cyc is a nonsense mutation, consistent with its strong loss-of-function phenotype. We propose that the CYC:CLK heterodimer binds to per and tim E boxes and makes a major contribution to the circadian transcription of Drosophila clock genes.

A mutant Drosophila homolog of mammalian Clock disrupts circadian rhythms and transcription of period and timeless

We report the identification, characterization, and cloning of a novel Drosophila circadian rhythm gene, dClock. The mutant, initially called Jrk, manifests dominant effects: heterozygous flies have a period alteration and half are arrhythmic, while homozygous flies are uniformly arrhythmic. Furthermore, these flies express low levels of the two clock proteins, PERIOD (PER) and TIMELESS (TIM), due to low per and tim transcription. Mapping and cloning of the Jrk gene indicates that it encodes the Drosophila homolog of mouse Clock. The mutant phenotype results from a premature stop codon that eliminates much of the putative activation domain of this bHLH-PAS transcription factor, thus explaining the dominant features of Jrk. The remarkable sequence conservation strongly supports common clock components present in the common ancestor of Drosophila and mammals.

Molecular and behavioral analysis of four period mutants in Drosophila melanogaster encompassing extreme short, novel long, and unorthodox arrhythmic types

Of the mutationally defined rhythm genes in Drosophila melanogaster, period (per) has been studied the most. We have molecularly characterized three older per mutants-perT, perClk, and per04-along with a novel long-period one (perSLIH). Each mutant is the result of a single nucleotide change. perT, perClk, and perSLIH are accounted for by amino acid substitutions; per04 is altered at a splice site acceptor and causes aberrant splicing. perSLIH exhibits a long period of 27 hr in constant darkness and entrains to light/dark (L/D) cycles with a later-than-normal evening peak of locomotion. perSLIH males are more rhythmic than females. perSLIH's clock runs faster at higher temperatures and slower at lower ones, exhibiting a temperature-compensation defect opposite to that of perLong. The per-encoded protein (PER) in the perT mutant cycles in L/D with an earlier-than-normal peak; this peak in perSLIH is later than normal, and there was a slight difference in the PER timecourse of males vs. females. PER in per04 was undetectable. Two of these mutations, perSLIH and perClk, lie within regions of PER that have not been studied previously and may define important functional domains of this clock protein.

Analysis of temperature-sensitive mutants reveals new genes involved in the courtship song of Drosophila

cacophony (cac), a mutation affecting the courtship song in Drosophila melanogaster, is revealed to cause temperature-sensitive (TS) abnormalities. When exposed to high temperatures (37 degrees), cac flies show frequent convulsions and pronounced locomotor defects. This TS phenotype seems consistent with the idea that cac is a mutation in a calcium-channel gene; it maps to the same X-chromosomal locus that encodes the polypeptide comprising the alpha-1 subunit of this membrane protein. Analysis of the courtship song of some TS physiological mutants showed that slowpoke mutations, which affect a calcium-activated potassium channel, cause severe song abnormalities. Certain additional TS mutants, in particular para(ts1) and nap(ts1), exhibit subtler song defects. The results therefore suggest that genes involved in ion-channel function are a potential source of intraspecific genetic variation for song parameters, such as the number of cycles present in "pulses" of tone or the rate at which pulses are produced by the male's courtship wing vibrations. The implications of these findings from the perspective of interspecific lovesong variations in Drosophila are discussed.

Duration of antimicrobial prophylaxis in vascular surgery

BACKGROUND

This randomized clinical trial compares the incidence of wound infection after vascular surgery in patients who received prophylaxis using the same antibiotic as either a single-dose or a multiple-dose regimen (until the lines/drain tubes were removed, but not for more than 5 days).

METHODS

Each of the 302 patients who entered the study received ticarcillin 3.0 g/clavulanate 0.1 g (Timentin) intravenously immediately after the induction of anesthesia. Patients randomized to the multiple-dose group received an average of 14.3 doses (range 9 to 20).

RESULTS

The incidence of wound infections was 18% (28 of 153) for patients in the single-dose group and 10% (15 of 149) for patients in the multiple-dose group (P = 0.04; relative risk estimate = 2.00, 95% confidence interval = -1.02 to 3.92).

CONCLUSIONS

A multiple-dose antibiotic regimen, rather than single-dose therapy, provides optimal prophylaxis against wound infection for patients undergoing vascular surgery.

Development of an Enzyme-Linked Immunosorbent Assay for the Detection of Metosulam

A direct enzyme-linked immunosorbent assay (ELISA) was developed to quantitate the herbicide metosulam (N-(2,6-dichloro-3-methylphenyl)-5,7-dimethoxy-1,2,4-triazolo(1,5a)pyrimidine-2-sulfonamide) in soil and water. The ELISA had a detection limit of 0.3 ng.mL(-1), a linear working range of 0.5 ng.mL(-1) to 10 ng.mL(-1), and an IC(50) value of 2.8 ng.mL(-1). The metosulam antisera cross-reacted with 5-OH and 7-OH metosulam (N-(2,6-dichloro-3-methylphenyl)-5-hydroxy-7-methoxy-1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamide and N-(2,6-dichloro-3-methylphenyl)-5-methoxy-7-hydroxy-1,2,4-triazolo[1,5-a]pyrimidine-2-sulfonamide, respectively) and the manufacturing intermediate XDE-564 (N-(2,6-dichlorophenyl)-5-ethoxy-7-fluoro[1,2,4]triazolo[1,5-c]pyrimidine-2-sulfonamide). The assay was used to estimate, accurately and precisely, metosulam concentrations in soil and water samples. Water samples were analyzed directly while soil sample analysis required solvent extraction and dilution prior to analysis. Extraction efficiency was 95%. The ELISA estimations in water correlated well with those from HPLC analysis (r(2) = 0.99; slope = 0.99), making the ELISA a cheap and reliable alternative to conventional residue analysis techniques for quantification of metosulam.

The pathobiology of peritonitis

The peritoneum is more than a mechanical covering that allows for the easy gliding of opposed peritoneal surfaces. The peritoneal mesothelial cells facilitate the action of powerful innate immune mechanisms. In addition, the peritoneal-associated lymphoid tissues contain unique cells that may play a crucial role in the localization of intraperitoneal infection. A clearer understanding of the molecular and cellular events underlying peritoneal functions in both the unstimulated and stimulated state will aid future treatment of peritonitis.

Warm ischaemia time in a model for small bowel transplantation

Intestinal transplantation is associated with high rates of mortality and morbidity. This paper details our initial experience with 82 heterotopic small bowel transplants based upon the original rat model described by Monchik and Russell (Surgery 70:693-702, 1971). A key issue associated with mortality was a warm ischaemia time of more than 40 min (P < 0.01). Sixty-eight percent of the recipients (44/65) survived for more than 24 hr when the warm ischaemia time of the donor bowel was reduced to less than 40 min. Investigators establishing an animal model of heterotopic small bowel transplantation should pay particular attention to the warm ischaemia time of the donor bowel.

The role of wound infection as a clinical indicator after colorectal surgery

The objective of this study was to evaluate the role of wound infection as a clinical indicator after colorectal surgery. We assessed 553 patients who were entered into clinical trials at Royal Perth Hospital. In the clinical trials, the incidence of wound infection after colorectal surgery was 12%, however, this rose to 20% for patients over 60 years of age and with an American Society of Anaesthesia score of greater than 2. One-third of these infections occurred following discharge from hospital. We found that the incidence of wound infection following colorectal surgery was dependent upon patient characteristics, and many infections occurred after discharge from hospital. Collecting this data accurately is time consuming and expensive. Therefore, for this reason alone, wound infection may not be an appropriate clinical indicator for patients undergoing colorectal surgery.

Independent photoreceptive circadian clocks throughout Drosophila

Transgenic Drosophila that expressed either luciferase or green fluorescent protein driven from the promoter of the clock gene period were used to monitor the circadian clock in explanted head, thorax, and abdominal tissues. The tissues (including sensory bristles in the leg and wing) showed rhythmic bioluminescence, and the rhythms could be reset by light. The photoreceptive properties of the explanted tissues indicate that unidentified photoreceptors are likely to contribute to photic signal transduction to the clock. These results show that autonomous circadian oscillators are present throughout the body, and they suggest that individual cells in Drosophila are capable of supporting their own independent clocks.

Extended reproductive roles of the fruitless gene in Drosophila melanogaster revealed by behavioral analysis of new fru mutants

The fruitless mutants fru3 and fru4 were assessed for sex-specific reproductive-behavioral phenotypes and compared to the previously reported fru mutants. Among the several behavioral anomalies exhibited by males expressing these relatively new mutations, some are unique. fru3 and fru4 males are less stimulated to court females than fru1 and fru2. No courtship pulse song is generated by either fru3 or fru4 males, even though they perform brief wing extensions. fru3 and fru4 males display significantly less chaining behavior than do fru1 males. The hierarchy of courtship responses by fru males directed toward females vs. males, when presented with both sexes simultaneously, is that fru1 males perform vigorous and indiscriminant courtship directed at either sex; fru4 males are similarly indiscriminant, but courtship levels were lower than fru1; fru2 males prefer females; fru3 males show a courtship bias toward males. fru3 and fru4 males essentially lack the Muscle of Lawrence (MOL). On several reproductive criteria, there was no difference between fru-variant females and fru+. The increases in phenotypic severity measured for the new mutants are discussed in the context of the emerging molecular genetics of fru and with regard to the gene's position within the sex-determination pathway.

Purification and characterization of protein D/E, a putative sperm-binding protein involved in fertilization

We describe a method for the efficient purification of a 32 Kd glycoprotein from rat epididymal tissue. The glycoprotein was purified by gel filtration, ion-exchange, affinity, and reverse phase high pressure liquid chromatography. The highly purified glycoprotein was radiolabeled with an iodinatable, cleavable, photoreactive cross-linking agent, 1-[N-(2-hydrox-5-azidobenzoyl)-2-aminoethyl]-4-(-hydroxysuccini mid yl)-succinate (HAHS). The soluble radiolabeled glycoprotein was bound to washed epididymal spermatozoa in a time-dependent, saturable, and reversible manner. Scatchard analysis demonstrates that there are approximately 3,403 binding sites/spermatozoon. The binding efficiency (Kd) for spermatozoa was approximately 2.0 x 10(-10) M. The function of this glycoprotein was verified by using an in vivo artificial insemination fertilization assay. The fertility rate for control spermatozoa was approximately 53%, but the rate for spermatozoa exposed to polyclonal anti-glycoprotein antibodies was only 5%. These data suggest that the binding of the glycoprotein to the surface of rat spermatozoa is mediated by a receptor-type mechanism and is involved in the fertilization process.

Spatial and temporal expression of the period and timeless genes in the developing nervous system of Drosophila: newly identified pacemaker candidates and novel features of clock gene product cycling

The circadian timekeeping system of Drosophila functions from the first larval instar (L1) onward but is not known to require the expression of clock genes in larvae. We show that period (per) and timeless (tim) are rhythmically expressed in several groups of neurons in the larval CNS both in light/dark cycles and in constant dark conditions. Among the clock gene-expressing cells there is a subset of the putative pacemaker neurons, the "lateral neurons" (LNs), that have been analyzed mainly in adult flies. Like the adult LNs, the larval ones are also immunoreactive to a peptide called pigment-dispersing hormone. Their putative dendritic trees were found to be in close proximity to the terminals of the larval optic nerve Bolwig's nerve, possibly receiving photic input from the larval eyes. The LNs are the only larval cells that maintain a strong cycling in PER from L1 onward, throughout metamorphosis and into adulthood. Therefore, they are the best candidates for being pacemaker neurons responsible for the larval "time memory" (inferred from previous experiments). In addition to the LNs, a subset of the larval dorsal neurons (DNLs) expresses per and tim. Intriguingly, two neurons of this DNL group cycle in PER and TIM immunoreactivity almost in antiphase to the other DNLs and to the LNs. Thus, the temporal expression of per and tim are regulated differentially in different cells. Furthermore, the light sensitivity associated with levels of the TIM protein is different from that in the heads of adult Drosophila.

Multiple circadian-regulated elements contribute to cycling period gene expression in Drosophila

A new regulatory element necessary for the correct temporal expression of the period (per) gene was identified by monitoring real-time per expression in living individual flies carrying two different period-luciferase transgenes. luciferase RNA driven from only the per promoter was not sufficient to replicate the normal pattern of per RNA cycling; however, a per-luc fusion RNA driven from a transgene containing additional per sequences cycled identically to endogenous per. The results indicate the existence of at least two circadian-regulated elements--one within the promoter and one within the transcribed portion of the per gene. Phase and amplitude analysis of both per-luc transgenes revealed that normal per expression requires the regulation of these elements at distinct phases and suggests a mechanism by which biological clocks sustain high-amplitude feedback oscillations.

Rhythmic expression of a PER-reporter in the Malpighian tubules of decapitated Drosophila: evidence for a brain-independent circadian clock

The protein product (PER) of the Drosophila clock gene, period (per), is involved in a molecular feedback loop in which PER inhibits the transcription of its own mRNA. This feedback causes the PER protein to cycle in a circadian manner, and this cycling in specific regions of the brain (the presumed location of the central pacemaker) is responsible for the rhythmicity of locomotor activity and possibly eclosion. PER has also been detected in several nonneural tissues in the abdomen, but whether PER exhibits free-running and light-sensitive cycles in any of these tissues is not known. In this study, the authors assayed the spatial and temporal distribution of a PER-reporter expressed in transgenic flies carrying a per-lacZ construct, which was shown to cycle in per-expressing brain cells. The authors demonstrate that this PER-reporter fusion protein cycles in the Malpighian tubules, showing first cytoplasmic accumulation, which is then followed by translocation of the signal into the nucleus. To test whether this rhythm was controlled by the brain, flies were decapitated and assayed for 3 days after decapitation. Expression patterns of PER-reporter in decapitated flies were nearly identical to those in intact flies reared in normal light-dark cycles, reversed light-dark cycles (phase shifted), and constant darkness. These results suggest that the Malpighian tubules contain a circadian pacemaker that functions independently of the brain.