Trafficking of yellow-fluorescent-protein-tagged mu1 subunit of clathrin adaptor AP-1 complex in living cells

Clathrin adaptor protein AP-1 complex is thought to function in forming clathrin-coated vesicles at the trans-Golgi network (TGN) and mediating transport of cargo between the TGN and endosomes. To study trafficking of AP-1 in living cells, yellow fluorescent protein (YFP) was inserted in the middle of mu1 A subunit of AP-1. When expressed in a tetracycline-dependent manner in HeLa cells, YFP-mu1 was efficiently incorporated into the AP-1 complex, replacing endogenous mu1 in most of cellular AP-1. Time-lapse imaging revealed that YFP-mu1/AP-1 departs from TGN as isolated vesicles and spherical structures, or varicosities, associated with fine tubular processes. Typically, several vesicles or varicosities were seen moving sequentially along the same 'tracks' from TGN to cell periphery. These data suggest that AP-1 may function after formation of Golgi transport intermediates in facilitating their intracellular movement. Mutagenesis of YFP-mu1 determined that the structural requirements for its binding to tyrosine-containing sequence motifs are similar to those previously defined in mu2 subunit of AP-2. Moreover, the carboxyl-terminal half of mu2 could replace the corresponding fragment of mu1 without loss of the ability of the resulting mu1-YFP-mu2 chimeric protein to incorporate into AP-1 and bind tyrosine-containing motifs. Mutations that abolish binding capacity for tyrosine motifs did not mistarget AP-1 in the cell, suggesting that AP-1 interactions with this type of sorting signals are not essential for membrane docking of AP-1 at the TGN. Altogether, this study demonstrates that YFP-tagged mu1 protein can serve as a useful tool for visualizing the dynamics of AP-1 in living cells and for the structure-function analysis of mu1-cargo interactions.

Vital capacity in tetraplegics twenty years and beyond

OBJECTIVES

To observe the trends in vital capacity (VC) over time in tetraplegics 20 years and more after injury, the effects of age at injury, severity of injury and gender on this trend.

METHODS

The medical records of all spinal cord injured persons admitted to a regional spinal injury center from January 1960 to December 1996 were reviewed. Fifty-seven patients had documented post-rehabilitation VC (mean 1.3+/-1.1 years) and VC at 10 (mean 11.8+/-2.69) and 20 (20.60+/-2.67) years post injury and beyond.

RESULTS

The mean age at injury was 23.2+/-9.1 years. Severity of injury when classified according the system proposed by Coll et al were: Group 1: C1-4 Frankel A injury: 11.6%, Group 2: C5-8 Frankel A injury: 55.6%, Group 3: C2-8 Frankel B and C: 29.8% and Group 4: C2-8 Frankel D: 3.5% respectively. The mean VC at initial, 10 and 20 years post injury was 2586+/-948, 2803+/-940 and 2525+/-818 cc respectively. Multivariate analysis of variance revealed that there was significant difference in VC over a 20 year period, (F(2,54)=8.43, P<0.05). The difference between VC at 10 years and VC at 20 years accounted for the 19.8% of the variance in VC over time (F(1,55)=12.35, P<0.05). Age at injury, gender and severity of injury did not have a significant influence on the rate of decline in VC. Analysis of a subset of 26 patients who were followed up more than 20 years post injury (range 22 to 34.5 years) revealed similar, with a greater drop in the VC from 10 years post injury (F(1,23)=6.52, P<0.05). In this subset of patients, the mean VC at initial injury was 2840.9+/-847.3 cc, at 10 years was 2549.6+/-750.3 cc, at 20 years was 2400.9+/-724.1 cc and beyond 20 years was 2194.2+/-738.7 cc. There was no significant difference in mean VC between non smokers and ex/current smokers at initial, 10 and 20 years post injury, using the independent t-test (P>0.05).

CONCLUSION

Vital capacity in tetraplegics declines significantly over the years, with a greater decline occurring at more than 20 years post injury.

Gain in functional ability during medical rehabilitation as related to rehabilitation process indices and neurologic measures

OBJECTIVE

To determine the incremental value of neurologic and rehabilitation process indices in predicting gain in functional abilities during rehabilitation after spinal cord injury (SCI) and to describe a model for program evaluation that provides unbiased comparisons of rehabilitation process and normative comparison of individual patient gains in functional ability.

STUDY DESIGN

Multiple regression including variables in a prespecified hierarchical fashion. Linear models are formulated to gauge the incremental value of neurologic measures and rehabilitation process indices when investigating the rehabilitation process and the outcome of medical rehabilitation.

RESULTS

All measures and indices vary in predictable and expected manners across individual centers and injury groups; moreover, each has demonstrated the capacity to provide unique information to the investigation of the rehabilitation process. The comprehensive set of variables accounts for 52.8% of the variance in self-care gain and 53.3% of the variance in mobility gain. The rehabilitation process indices together contribute 15% of the variance of self-care gain and over 18% of the explained variance in mobility gain.

CONCLUSION

Forecasting gain in functional ability of patients in the domains of self-care and mobility may be enhanced when measures of neurologic impairment are supplemented with rehabilitation process indices. In addition, technical enhancements in measurement of rehabilitation process indices and gain in functional ability provide objective comparison of individual center differences and individual patient gains.

Inhibition of the receptor-binding function of clathrin adaptor protein AP-2 by dominant-negative mutant mu2 subunit and its effects on endocytosis

Although interactions between the mu2 subunit of the clathrin adaptor protein complex AP-2 and tyrosine-based internalization motifs have been implicated in the selective recruitment of cargo molecules into coated pits, the functional significance of this interaction for endocytosis of many types of membrane proteins remains unclear. To analyze the function of mu2-receptor interactions, we constructed an epitope-tagged mu2 that incorporates into AP-2 and is targeted to coated pits. Mutational analysis revealed that Asp176 and Trp421 of mu2 are involved in the interaction with internalization motifs of TGN38 and epidermal growth factor (EGF) receptor. Inducible overexpression of mutant mu2, in which these two residues were changed to alanines, resulted in metabolic replacement of endogenous mu2 in AP-2 complexes and complete abrogation of AP-2 interaction with the tyrosine-based internalization motifs. As a consequence, endocytosis of the transferrin receptor was severely impaired. In contrast, internalization of the EGF receptor was not affected. These results demonstrate the potential usefulness of the dominant-interfering approach for functional analysis of the adaptor protein family, and indicate that clathrin-mediated endocytosis may proceed in both a mu2-dependent and -independent manner.

Endocytosis of functional epidermal growth factor receptor-green fluorescent protein chimera

A chimera of the epidermal growth factor receptor (EGFR) and green fluorescent protein (GFP) has been engineered by fusing GFP to the carboxyl terminus of EGFR. Data are provided to demonstrate that the GFP moiety does not affect the expected functioning of EGFR. EGFR-GFP becomes phosphorylated at tyrosine residues in response to EGF and is capable of phosphorylating endogenous substrates and initiating signaling cascades. EGF-dependent association of the chimeric receptor with the clathrin adaptor protein AP-2, involved in endocytosis, and with Shc adaptor protein, which binds in close proximity to the fusion point, is not affected by the GFP moiety. Receptor down-regulation and internalization occur at rates similar to those in cells expressing wild-type EGFR. Western blot analysis reveals that lysosomal degradation of EGFR-GFP proceeds from the extracellular domain and that GFP is not preferentially cleaved. Time-dependent co-localization of EGFR-GFP and Texas Red-conjugated EGF in living cells using digital deconvolution microscopy demonstrates the trafficking of ligand-receptor complexes through the early and multivesicular endosomes followed by segregation of the ligand and receptor at the late stages of endocytosis. Time-lapse optical analysis of the early stages of endocytosis reveals localization of EGFR-GFP in the tubular-vesicular endosomal compartments. Rapid dynamics of membrane movement and fusion within these compartments were observed. This approach and the fidelity of the biochemical properties of the EGFR-GFP demonstrate that real-time visualization of trafficking and protein interactions of tyrosine kinase receptors in the presence or absence of the ligand are feasible.

Structure and Asn-Pro-Phe binding pocket of the Eps15 homology domain

Eps15 homology (EH) domains are eukaryotic signaling modules that recognize proteins containing Asn-Pro-Phe (NPF) sequences. The structure of the central EH domain of Eps15 has been solved by heteronuclear magnetic resonance spectroscopy. The fold consists of a pair of EF hand motifs, the second of which binds tightly to calcium. The NPF peptide is bound in a hydrophobic pocket between two alpha helices, and binding is mediated by a critical aromatic interaction as revealed by structure-based mutagenesis. The fold is predicted to be highly conserved among 30 identified EH domains and provides a structural basis for defining EH-mediated events in protein trafficking and growth factor signaling.

Eps15 is constitutively oligomerized due to homophilic interaction of its coiled-coil region

Eps15 is a member of an emerging family of proteins containing a novel protein/protein interaction domain, the EH domain, of as yet unknown function. Recent findings of Eps15 association with clathrin adaptor complex AP-2 and its localization in clathrin-coated pits have implicated Eps15 in the regulation of vesicle trafficking. Here we show that Eps15 exists in several multimeric states in vivo. When purified recombinant Eps15 or lysates of NIH 3T3 cells were treated with cross-linking reagents, covalent dimers of Eps15 and larger covalent multimers were detected in high yield. Large Eps15 oligomers co-immunoprecipitated with AP-2 at an efficiency higher than that of Eps15 dimers. Furthermore, cross-linking of the membrane-bound fraction of Eps15 in mildly permeabilized cells was as efficient as that of the cytosolic fraction. Size-exclusion column chromatography of recombinantly produced Eps15 and of total cell lysates was performed to examine the equilibrium ratio of the monomers versus the aggregated forms of Eps15. These experiments showed that essentially all the Eps15 was aggregated, whereas monomers of Eps15 could be obtained only under strong denaturing conditions. To map the region of Eps15 responsible for dimerization, fusion proteins corresponding to the three structural domains of Eps15 were prepared. Cross-linking analysis revealed that the central portion of Eps15, which possesses a coiled-coil region (residues 321-520), serves as the interacting interface. The possibility that hetero-oligomeric complexes of Eps15 dimers and AP-2 function during the recruitment of proteins into coated pits is discussed.

N-acetylaspartylglutamate, N-acetylaspartate, and N-acetylated alpha-linked acidic dipeptidase in human brain and their alterations in Huntington and Alzheimer's diseases

There is mounting evidence, primarily from research in experimental animals, that the dipeptide N-acetylaspartylglutamate (NAAG) and its metabolic enzyme, N-acetylated alpha-linked acid dipeptidase (NAALADase), are involved in glutamatergic neurotransmission. Previous studies in neuropsychiatric disorders associated with the dysregulation of glutamatergic neurotransmission, such as schizophrenia, seizure disorders, and amyotrophic lateral sclerosis (ALS), have revealed region-specific alterations in the levels of NAAG and in the activity of NAALADase. To establish better the cellular localization of these and related parameters in human brain, we have examined their alterations in two well-characterized selective neurodengenerative disorders, Huntington Disease (HD) and Alzheimer Disease (AD). Brain regions from postmortem controls and HD- or AD-affected individuals were assayed to determine the activity of NAALADase as well as the levels of NAAG, N-acetylaspartate (NAA), and several amino acids. The relationships between changes in these neurochemical parameters and changes in neuronal and glial cell density were determined. The present report demonstrates that the decreases in the levels of NAAG and NAA and in the activity of NAALADase in AD and HD brain correlate primarily with neuronal loss. By inference, the results suggest that NAAG and NAA have primarily a neuronal localization in human brain and that there is a close relationship between NAAG and the dipeptidase NAALADase in populations of affected neurons.

Clonal structure of the introduced freshwater snailPotamopyrgus antipodarum(Prosobranchia: Hydrobiidae), as revealed by DNA fingerprinting

Multi-locus DNA fingerprints were obtained from individuals of the hydrobiid snail, Potamopyrgus antipodarum (= P. jenkinsi), by using an RNA derivative (pSPT 18.15) of Jeffrey's 33.15 minisatellite core sequence. Whole-body homogenization of snails yielded 3.21 +/- 0.09 micrograms DNA per individual, producing complex profiles comprising 12-22 fragments within the 1.0-20.0 kilobase (kb) size range. Fingerprints from natural and experimental populations identified three distinct clonal genotypes corresponding to morphological strains A, B and C, with only rare mutational variants. Mother-offspring comparisons of genetic fingerprints revealed genetic stability during apomictic parthenogenesis. Data support the notion that British populations of P. antipodarum comprise three widespread obligate parthenogenetic clones resulting from a mid-19th Century introduction from Australasia. The present-day low levels of genotypic diversity are discussed in relation to the typical occurrence of P. antipodarum in man-made or immature habitats.

Prostate-specific membrane antigen is a hydrolase with substrate and pharmacologic characteristics of a neuropeptidase

This report demonstrates that the investigational prostatic carcinoma marker known as the prostate-specific membrane antigen (PSM) possesses hydrolytic activity with the substrate and pharmacologic properties of the N-acetylated alpha-linked acidic dipeptidase (NAALADase). NAALADase is a membrane hydrolase that has been characterized in the mammalian nervous system on the basis of its catabolism of the neuropeptide N-acetylaspartylglutamate (NAAG) to yield glutamate and N-acetylaspartate and that has been hypothesized to influence glutamatergic signaling processes. The immunoscreening of a rat brain cDNA expression library with anti-NAALADase antisera identified a 1428-base partial cDNA that shares 86% sequence identity with 1428 bases of the human PSM cDNA [Israeli, R. S., Powell, C. T., Fair, W. R. & Heston, W.D.W. (1993) Cancer Res. 53, 227-230]. A cDNA containing the entire PSM open reading frame was subsequently isolated by reverse transcription-PCR from the PSM-positive prostate carcinoma cell line LNCaP. Transient transfection of this cDNA into two NAALADase-negative cell lines conferred NAAG-hydrolyzing activity that was inhibited by the NAALADase inhibitors quisqualic acid and beta-NAAG. Thus we demonstrate a PSM-encoded function and identify a NAALADase-encoding cDNA. Northern analyses identify at least six transcripts that are variably expressed in NAALADase-positive but not in NAALADase-negative rat tissues and human cell lines; therefore, PSM and/or related molecular species appear to account for NAAG hydrolysis in the nervous system. These results also raise questions about the role of PSM in both normal and pathologic prostate epithelial-cell function.

The gene for the serpin thrombin inhibitor (PI7), protease nexin I, is located on human chromosome 2q33-q35 and on syntenic regions in the mouse and sheep genomes

Protease nexin I (PNI) is the most important physiologic regulator of alpha-thrombin in tissues. PNI is highly expressed and developmentally regulated in the nervous system where it is concentrated at neuromuscular junctions and also central synapses in the hippocampus and striatum. Approximately 10% of identified proteins at mammalian neuromuscular junctions are serine protease inhibitors, consistent with their central role in balancing serine protease activity to develop, maintain, and remodel synapses. Southern blot hybridization of PNI cDNA to somatic cell hybrids placed the structural gene for PNI (locus PI7) on human chromosome 2q33-q35 and to syntenic chromosomes in the mouse (chromosome 1) and sheep (chromosome 2).

The immunocytochemical localization of N-acetylaspartyl glutamate, its hydrolysing enzyme NAALADase, and the NMDAR-1 receptor at a vertebrate neuromuscular junction

Although glutamate is thought to be the neurotransmitter at the invertebrate neuromuscular junction, acetylcholine is accepted as the primary neurotransmitter of the vertebrate motoneurons. N-acetylaspartylglutamate, a dipeptide localized in putative glutamatergic neurons in brain, is also found in high concentrations (> mM) in mammalian motoneurons and the ventral roots of spinal cord. N-acetylaspartylglutamate, which is released from neurons by depolarization in a Ca(2+)-dependent fashion, is implicated in glutamatergic transmission in two ways: it is a partial agonist at NMDA receptors, and it is cleaved to yield extracellular glutamate and N-acetylasparate by the specific peptidase N-acetylated alpha-linked acidic dipeptidase. Given the localization of N-acetylaspartylglutamate in motor neuronal perikarya and axons, we wondered whether N-acetylaspartylglutamate or glutamate cleaved from N-acetylaspartylglutamate by N-acetylated alpha-linked acidic dipeptidase may also play a role in neuromuscular transmission. Here we describe the immunocytochemical detection at the rat neuromuscular junction of N-acetylaspartylglutamate in terminals of motoneurons, of N-acetylated alpha-linked acidic dipeptidase in perisynaptic Schwann cells, and of the NMDAR-1 glutamate receptor subunit on postsynaptic muscle membranes. These results point to a potential role for N-acetylaspartylglutamate at the rat neuromuscular junction. Further, this is the first demonstration of a glutamate receptor protein at vertebrate neuromuscular synapses. Together with other recent findings, our results suggest that glutamate-like molecules are involved in neuromuscular transmission not only in invertebrates but also in veretebrates where they may modulate signaling by acetylcholine.

N-acetylated alpha-linked acidic dipeptidase is expressed by non-myelinating Schwann cells in the peripheral nervous system

N-acetylated alpha-linked acidic dipeptidase is a membrane-bound brain peptidase which cleaves the neuropeptide N-acetyl-aspartyl-glutamate to N-acetyl-aspartate and glutamate. In the present study, we have determined the localization of N-acetylated alpha-linked acidic dipeptidase in the peripheral nervous system. Using enzyme assays and immunoblotting, we demonstrate that sciatic nerve, phrenic nerve, cervical dorsal root ganglion and superior cervical ganglion contain N-acetylated alpha-linked acidic dipeptidase activity as well as an N-acetylated alpha-linked acidic dipeptidase-like protein. Furthermore, we show that N-acetylated alpha-linked acidic dipeptidase-like immunoreactivity is extensively co-localized in peripheral nerves with immunoreactivity for glial fibrillary acidic protein, a known marker for non-myelinating Schwann cells. Using electron microscopy, we demonstrate N-acetylated alpha-linked acidic dipeptidase-like immunoreactivity in cell membranes of non-myelinating Schwann cells in the superior cervical ganglion. These results show that N-acetylated alpha-linked acidic dipeptidase is expressed in the peripheral nervous system by non-myelinating Schwann cells. This cellular localization suggests that N-acetylated alpha-linked acidic dipeptidase may be involved in the signalling between axons and Schwann cells, for example during development or regeneration.

No evidence for extrapair fertilizations in the merlin revealed by DNA fingerprinting

Broods of young merlins were compared with the adults in attendance at their nest by DNA fingerprinting. No offspring were found that mismatched genetically suggesting that intraspecific brood parasitism and extrapair fertilization are very rare in this population. The results are discussed in the light of the Paternity Assurance Hypothesis.

Genetic-Evidence for Extra-Pair Fertilizations in Socially Monogamous Short-Tailed Shearwaters, Puffinus-Tenuirostris (Procellariiformes, Procellariidae), Using Dna Fingerprinting

Genetic relationships between adults and nestlings of the short-failed shearwater, Puffinus tenuirostris, were analysed by multilocus DNA fingerprinting. Short-tailed shearwaters are socially monogamous, forming strong pair bonds, often for many years. The human polycore minisatellite probe, 33-6, revealed sufficient variation in shearwater DNA to allow individual-specific identification. A total of 22 nestlings and 32 adults, comprising 10 trios of nestling and both parents, and 12 pairs of nestling and only one parent, were examined. Analysis of fingerprint profiles revealed four cases where a nestling was not related to one of the attendant adults, and may have resulted from an extra-pair fertilisation. Extra-pair fertilisations, as an alternative breeding strategy, are discussed with respect to the biased and low reproductive output of this long-lived species.

Genetically epilepsy-prone rats have increased brain regional activity of an enzyme which liberates glutamate from N-acetyl-aspartyl-glutamate

N-Acetylated-alpha-linked acidic dipeptidase (NAALADase) is a membrane-bound peptidase which hydrolyzes the endogenous neuropeptide N-acetylaspartylglutamate (NAAG) to N-acetylaspartate (NAA) and the excitatory amino acid, glutamate (Glu). Although there is evidence that NAAG might be a neurotransmitter, this dipeptide could also function as a precursor form of Glu, which is liberated by the dipeptidase. We found that the activity of this NAAG hydrolyzing enzyme in genetically epilepsy-prone rats was 11-26% greater than control in brain regions, including the amygdala, hippocampus and cerebellum, as well as the pyriform, entorhinal and frontal cortices. This is consistent with possible increased availability of Glu in certain CNS synapses in these rats, which are reported to have increased susceptibility to audiogenically, electrically and chemically induced convulsions.

Criteria for the academic promotion of medical school-based psychiatrists

The objective of this study was to identify criteria used in recommending faculty for promotion in medical school-based departments of psychiatry. Chairs of 125 departments in the United States were asked to complete a 39-item questionnaire on departmental demographics and the expectations for academic performance of tenure-track, non-tenure-track, part-time, and medical research faculty. Different criteria were reported for the classifications of faculty studied, but not for promotion of the same class of faculty to different academic ranks. The increasing need for faculty to generate revenue blurs the distinction between tenure-track and non-tenure-track faculty and calls into question whether tenure track can practically continue as a faculty classification.

Residency training and the later use of marital and family therapy in psychiatric practice

Marital and family therapy training during psychiatry residency was compared to later use, in practice, for 87 psychiatrists. Respondents reported modest to minimal amounts of training in residency but practiced marital and family therapy with a variety of problems, identified a spread of effect to other treatment modalities, and preferred marital and family therapy second only to individual therapy. These results suggest a trend towards incorporating marital and family therapy into psychiatry and also indicate levels of training which must be exceeded in order to achieve basic competency.

Improved genetic fingerprinting using RNA probes

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Clonidine effect on spasticity: a clinical trial

Clonidine was used as an adjunct to baclofen in 55 patients with spasticity due to spinal cord injury. Dosage was held at the minimum effect amount for those who responded. No effect was seen in 24 patients (44%), although 31 (56%) benefitted from the drug. Patients were grouped as quadriplegics or paraplegics, having complete or incomplete lesions. Of all quadriplegics, seven of 11 complete (64%) and 17 of 25 incomplete patients (68%) responded; among the paraplegics, six of 15 complete (40%) and one of four incomplete patients (25%) improved. Side effects were limited to postural hypotension necessitating reduction in dosage in three patients that were successfully treated; in the unsuccessfully treated group, one patient had insomnia, one had dizziness, and one had drowsiness.

Profile of denials of durable medical equipment for SCI patients by third party payers

The difficulty in obtaining approval for payment of durable medical equipment by third party payers has impeded the rehabilitation program and discharge planning of many spinal cord patients throughout the country for many years. To gain some insight as to the number and level of patients affected, the kinds of equipment denied, the reasons given for the denial, which third party payers were mostly involved and how the patient and his/her family managed to cope or resolve this problem, a survey was undertaken. Letters were sent to 259 members of the American Spinal Injury Association (ASIA) asking them to list representative cases where requests for equipment deemed necessary were denied. Twenty-eight responses from different institutions were received from sixteen states describing 110 patients and 180 pieces of durable medical equipment denied in 1984 and 1985. Manual wheelchairs, motorized wheelchairs, shower/commode chairs, and environmental control units were the four most common equipment items denied by the third party payers. Government agencies ie., Medicaid, Medicare, Vocational Rehabilitation Departments and State Crippled Children's Services were the most frequent deniers, comprising 54% of the total sample. They were followed by private insurance (31%) and Workman's Compensation (3%). By far, the two most common reasons given for denials were: it was not covered by the insurance policy (38%) and it was not medically necessary (30%). Ninety (90) pieces of equipment (50%) were eventually obtained, most often by charity, or through the patient's family resources.

Ultrasonography of the shoulder. Static and dynamic imaging

High-resolution, real-time ultrasonography is an effective diagnostic technique for evaluating rotator cuff movements and is useful in detecting aberrations that correlate with rotator cuff biomechanics and impingement syndrome.

Structure-activity relationships for unsaturated dialdehydes. 1. The mutagenic activity of 18 compounds in the Salmonella/microsome assay

A considerable number of terpenes that contain an "unsaturated dialdehyde" functionality, and possess various biological activities, such as antimicrobial activity, pungency, antifeedant activity, and/or mutagenicity, have been isolated from natural sources. However, large qualitative and quantitative activity differences have been observed for the natural unsaturated dialdehydes, and small structural changes (e.g., stereoisomerization) seem to dramatically affect the biological activity. As part of a general attempt to study structure-activity relationships for unsaturated dialdehydes, the activity of compounds 1-18 (Table 1) in the Salmonella/microsome assay (strains TA98, TA2637 and TA100) has been investigated. 10 of the compounds were found to possess direct-acting mutagenic activity, although the mutagenic potencies vary considerably in this group (from 430 to 0.32 revertants per nmole in the Salmonella strain TA2637). Some structural features that appear to moderate the activity are discussed. The necessity of an intact unsaturated dialdehyde functionality for the mutagenic activity of isovelleral (1) (see Scheme 1 for names, numbers, and chemical structures) in the Salmonella/microsome assay was demonstrated by chemical conversions: modification of either aldehyde group or reduction of the double bond led to loss of activity.