Targeting vectors for intracellular immunisation

We define intracellular immunization as the inhibition or inactivation of the function of a molecule by the ectopic intracellular expression of antibody binding domains which recognise the molecule. Such recombinant antibodies can be directed to different compartments of eukaryotic cells by means of previously defined targeting signals, thus permiting the study of any molecule in any cellular compartment for which an antibody is available. For this purpose, we have created a set of vectors based on the VHExpress vector described [Persic, L., Roberts, A., Wilton, J., Cattaneo, A., Bradbury, A. and Hoogenboom, H.R. (1997) An integrated vector system for the eukaryotic expression of antibodies or their fragments after selection from phage display libraries. Gene 187, 000-000], which has been modified to express scFvs (single chain fragments) linked to specific targeting signals. These permit the localisation of scFvs to different intracellular compartments: the endoplasmic reticulum (scFvE-er), the nucleus (scFvE-nuclear), the mitochondria (scFvE-mit), the cytoplasm (scFvE-cyto), and as secreted proteins (scFvE-sec). The function of these vectors has been assessed by the immunofluorescence of COS cells transiently transfected with constructs containing the alphaD11 scFv.

Extending filamentous phage host range by the grafting of a heterologous receptor binding domain

fd and IKe are two similar filamentous phage which infect their hosts by means of pili found on the host membrane: fd infects bacteria bearing F pili, whereas IKe infects bacteria bearing N or I pili. Infection is mediated by the gene 3 protein (g3p), which of the nine proteins found in both phage is the most diverse. Previous attempts to incorporate g3p from one phage into the other by complementation have been unsuccessful [Bross et al. (1988) J. Gen. Microbiol. 134, 461-471]. Here we have grafted different parts of IKe g3p to the end of fd g3p and so augmented the host range of fd phage. We show that phage bearing such chimeric g3p are able to infect bacteria bearing both N and F pili providing they contain at least the receptor domain of IKe g3p, the infection of N bearing bacteria occurring at a level 70,000 times greater than background. This level of infection can be increased tenfold by including the glycine-rich domain as well. Addition of the penetration domain does not improve the level of infection above that of the receptor domain alone, indicating that the fd penetration domain is functional in the infection of bacteria bearing either N or F pili. Similarly derived fd phagemid also show increased infection of bacteria bearing N pili, albeit at much lower levels, suggesting that efficient infection requires more than one functional g3p on the surface of the phage.

A natural longer glycine-rich region in IKe filamentous phage confers no selective advantage

Filamentous phage infect bacteria bearing pili. The phage protein involved in the recognition of pili and subsequent penetration of the phage into bacteria is the gene 3 protein (g3p). This is a multi-domain protein with glycine-rich regions separating some of the domains. Here we have found an insertion within the glycine-rich domain of the g3p of IKe, a filamentous phage which infects bacteria bearing N pili. Although this insertion considerably increases the length of the glycine-rich domain it has no selective advantage or disadvantage in infection or production of phage, and can therefore be considered a neutral mutation.

Human recombinant antibody fragments neutralizing human immunodeficiency virus type 1 reverse transcriptase provide an experimental basis for the structural classification of the DNA polymerase family

We describe in this paper the binding and biochemical properties of two human antibody fragments directed against the human immunodeficiency virus type 1 reverse transcriptase (RT). These fragments were isolated from a synthetic combinatorial library of human Fab antibody fragments displayed on the surface of filamentous phage. The antibody fragments were selected by using recombinant heterodimeric human immunodeficiency virus type 1 RT purified from insect cells as a solid-phase selector. This procedure led to the isolation of two antibody fragments that completely neutralize the RNA-dependent DNA polymerase activity of RT at nanomolar concentrations. Both antibody fragments bind only to the enzymatically active form of the RT. The inhibitory activity of the anti-RT antibody fragments is competitive with respect to the template primer. The antibody fragments also neutralize the activities of RTs from avian and murine retroviruses and of DNA polymerases of prokaryotic origin as well as human DNA polymerase alpha. Thus, the antibody fragments selected and characterized in this study appear to recognize a structural fold that is common to the different DNA polymerases and necessary for their activity. The results provide an immunological experimental basis for a purely structural and evolutionary classification of the polymerase family.

Metabolite kinetics of ondansetron in rat. Comparison of hepatic microsomes, isolated hepatocytes and liver slices, with in vivo disposition

1. The kinetics of hydroxylation and N-demethylation of ondansetron have been determined in freshly isolated hepatocytes, hepatic microsomes and precision-cut liver slices from the male Sprague-Dawley rat. In vivo studies have also been carried out to characterize the pharmacokinetics of ondansetron and in vitro data have been assessed for their value as predictors of hepatic clearance. 2. In the three in vitro systems, the formation of hydroxylated and demethylated metabolites were characterized as a function of substrate concentration by a high-affinity, low-capacity site and a low-affinity, high-capacity site which was not saturated over the concentration range studied (2.5-500 microM). Slices gave consistently higher Km's (20 and 30 microM for hydroxylation and demethylation respectively) than hepatocytes (3 and 13 microM respectively) and microsomes (2 and 5 microM respectively.) The rank order of Vmax and CL(int) was the same for each system; hydroxylation rates exceeding demethylation rates. Although two hydroxylations (7- and 8-hydroxy metabolites) occurred exclusively in microsomes, these are believed to originate from a common precursor. 3. The high CL(int) of ondansetron (150 ml/min/SRW, where SRW is a standard rat weight of 250g) is well predicted by scaling either microsomal clearance for microsomal protein recovery or hepatocyte clearance for hepatocellularity (212 and 135 ml/min/SRW respectively). In contrast, the use of liver slice data scaled to a whole liver substantially underestimates CL(int) (9 ml/min/SRW).

Kinetics of drug metabolism in rat liver slices. II. Comparison of clearance by liver slices and freshly isolated hepatocytes

The kinetics of metabolism of diazepam, phenytoin, and caffeine have been determined in rat liver slices of 260 microns thickness. The formation of 4'-hydroxy metabolites of diazepam and phenytoin are described by one- and two-site Michaelis-Menten equations, respectively. The other oxidative pathways for diazepam are less readily saturable than the 4'-hydroxylation. This kinetic behavior is consistent with that previously reported for other in vitro systems. In contrast, the metabolism of caffeine, assessed by total metabolism, showed differences from that observed with other systems, and this is believed to result from the incubation conditions used. By determining the hepatocellularity of the standard slice used, CLint (Vmax/KM) data were expressed per million cells and compared with the same parameters derived from incubations with freshly isolated hepatocyte suspensions. Data on diazepam, phenytoin, and caffeine were combined with previously published data on tolbutamide, ethoxycoumarin, and ondansetron to give a total of nine CLint values representing different pathways. CLint values in slices are consistently less than those in hepatocytes (ratio differing from 0.4 to 0.05). The CLint ratio decreased in a regular fashion as the hepatocyte CLint increased from 1.4 microliters/min (caffeine) to 105 microliters/min (ondansetron). It was also observed that the KM value for a particular pathway in slices always exceeded the corresponding value in isolated hepatocytes (ratios differing from 1.09 to 7.59). The KM ratio was positively related to hepatocyte CLint. These observations are consistent with the delayed accessibility of substrate to all the cells within a slice. It is proposed that the parallel processes of drug transport and metabolism within the slice do not allow a distribution equilibrium to be achieved between all the cells within a slice and the incubation media.

Angiographic and duplex grading of internal carotid stenosis: can we overcome the confusion?

The stroke risk reduction benefit of surgical intervention in carotid occlusive disease has been validated in multicenter trials for various angiographically defined lesion severity categories. The two divergent angiographic grading methods used for internal carotid artery stenosis in these trials have caused confusion in the clinical application of their recommendations. Moreover, while today's highly accurate carotid duplex scanning can obviate the need for preoperative angiography in many cases, the duplex criteria must be tailored to achieve sufficiently reliable results on which therapeutic decisions can be made. This review offers a clarification of the discrepancies between the angiographic grading techniques and how their measurements of percent stenosis correlate to the duplex criteria needed to support the treatment decision-making process for carotid obliterative disease.

The use of phage display in neurobiology

Phage display is a new technique that is used extensively in molecular biology to study protein-protein interaction, receptor- and antibody-binding sites, to produce monoclonal antibodies against diverse antigens, some of which are too well conserved for the production of monoclonal antibodies by traditional means, and to improve or modify the affinity of proteins for their binding partners. This technique could have many applications in neurobiology. This review describes the background to the technique, and illustrates a number of possible uses in neurobiology, ranging from the production of antibodies to non-immunogenic proteins and to those that are available as cloned DNA sequences only, to the detailed study of receptor-ligand interaction using either ligands, their receptors or neutralizing antibodies.

The cloning of a cDNA encoding a protein (latrodectin) which co-purifies with the alpha-latrotoxin from the black widow spider Latrodectus tredecimguttatus (Theridiidae)

A cDNA encoding a polypeptide of 88 amino acids was cloned following the rapid amplification of cDNA ends (RACE) procedure using mRNA isolated from the venom glands of the Mediterranean black widow spider (Latrodectus tredecimguttatus) and oligonucleotides based on the sequence of a tryptic fragment putatively from alpha-latrotoxin. Apart from a potential signal peptide, the rest of this small protein, named latrodectin, was highly hydrophilic, having a calculated molecular mass of 7945 Da and a pI of 4.3. Northern-blot analysis showed that the mRNA was specifically expressed in the venom gland of L. tredecimguttatus and that it was well conserved between two geographically remote species (L. geometricus and L. indistinctus). A polyclonal serum raised in rabbits against the C-terminal sequence of latrodectin detected cross-reactive proteins in the venom fluid, venom gland extracts, and in purified alpha-latrotoxin, suggesting that latrodectin is intimately associated with alpha-latrotoxin. Finally, we produced a recombinant protein in a cell system infected with baculovirus and developed an immunoaffinity purification procedure for latrodectin to facilitate further structural and functional analyses of the molecule.

Kinetics of drug metabolism in rat liver slices. Rates of oxidation of ethoxycoumarin and tolbutamide, examples of high- and low-clearance compounds

Ethoxycoumarin (EC) and tolbutamide (TOL) were selected as examples of high- and low-clearance drugs, respectively, to investigate suitable methodologies for obtaining kinetic data on metabolism by precision-cut rat liver slices. A number of characteristics of the slice incubation were compound-dependent. TOL showed linear rates of metabolism over a longer time period than EC and was insensitive to the method of incubation (rotating vials and gyrating culture plates). Also, the need for complete tissue disruption (e.g. via sonication) before analysis was essential for EC but unimportant for TOL. This may suggest that conjugates do not freely diffuse out of the liver slice unlike oxidative metabolites. Both drugs showed rates of metabolism that were dependent on slice thickness (150-530 microns). A high turnover (intrinsic clearance 7.9 microliters/min) and low KM (1.3 microM) for EC, and a low turnover (intrinsic clearance 0.8 microliter/min) and high KM (707 microM) for TOL were determined in slices. These differences in kinetic behavior are comparable with those seen in hepatic microsomes, freshly isolated hepatocytes, and in vivo.

The use of the RACE method to clone hybridoma cDNA when V region primers fail

The technique of V region PCR to clone antibody V regions from hybridomas has been extensively used. However, in addition to, or even instead of, cloning the V regions with the desired specificity, myeloma cell derived V regions, V regions which are the result of non-productive rearrangements, and also V regions which are productive but which do not recognise the antigen of interest, may be isolated. In this paper we describe a comparison of the use of V region PCR and a modification of the RACE technique to clone the V region of the anti-NGF hybridoma, alpha D11. This hybridoma has heavy and light chain V regions which are refractory to amplification with V region primers, but which are easily amplified using RACE, a PCR based procedure which is independent of the variability within the V regions.

Use of living columns to select specific phage antibodies

Here we demonstrate that it is possible to confront two recombinant microorganisms in order to select one using the other. We have shown that an epitope derived from p21ras expressed within the outer membrane protein, LamB, can be recognized both by the monoclonal antibody Y13-259, as well as the single chain Fv fragment derived from it. This specificity, which is maintained when the Y13-259 single chain Fv is expressed as a fusion protein with the phage fd gene 3 protein, has allowed us to use the living column of LamB-ras to purify Y13-259 phage from a background of non-binding phage, even at dilutions as high as 10 phage in 10(10) irrelevant phage.

Cloning and expression of an anti-nerve growth factor (NGF) antibody for studies using the neuroantibody approach

1. The neuroantibody approach, based on the expression of selected monoclonal antibodies by cells of the nervous system, has recently been described (Cattaneo and Neuberger, 1987; Piccioli et al., 1991). In order to apply this experimental strategy to study the role of nerve growth factor (NGF) in the central nervous system (CNS), we exploited the monoclonal antibody (mAb), alpha D11, which neutralizes very efficiently the biological activity of NGF, both in vitro and in vivo (Cattaneo et al., 1988). 2. The alpha D11 antibody chains were cloned and expressed in COS cells as rat/human chimaeric proteins. The cloned antibody was shown to display all the properties of the parental alpha D11 antibody, including its ability to neutralize NGF biological activity. 3. This will allow us to engineer the expression of recombinant alpha D11 antibodies in the CNS, to study the role of NGF in the developing and adult nervous system. This approach can be extended to other neurotrophic factors for which neutralizing monoclonal antibodies are available.

Disposition of sumatriptan in laboratory animals and humans

Sumatriptan is a new 5HT1-like agonist that has proved a novel and effective treatment for migraine. The disposition of the 14C-radiolabeled drug in laboratory animals and humans after oral and parenteral administration is described. Oral absorption of sumatriptan is essentially complete in dogs and rabbits, but only approximately 50% in rat. In humans, at least 57% of an oral dose is absorbed. Bioavailabilities are species dependent (14, 23, 37, and 58% in humans, rabbits, rats, and dogs) reflecting differing degrees of first-pass metabolism. These data correlate well with hepatic extraction ratios, which are highest in rabbits and humans and lowest in dogs. Renal clearance is significant in all species and exceeds the glomerular filtration rate in rats, rabbits, and humans, but not in dogs. The compound is a weak base that shows widespread tissue distribution, including passage across the placental barrier and into milk, but low CNS penetration. Protein binding of sumatriptan is low in all species. Elimination half-lives of sumatriptan are approximately 1 hr in rats and rabbits, and approximately 2 hr in dogs and humans. In all species the majority of the absorbed dose is renally excreted, predominantly as the indole acetic acid metabolite and unchanged drug. Interesting species differences are evident in the metabolism of sumatriptan. Thus, in humans, the indole acetic acid metabolite is excreted partly as a glucuronide, whereas in animals conjugation of this metabolite is not apparent. In addition, demethylation of the sulfonamide side chain of the drug is evident in rodent and lagomorph species only.

Prospective audit of the pattern, severity and circumstances of injury sustained by vehicle occupants as a result of road traffic accidents

The pattern and severity of injuries sustained by 174 vehicle occupants consecutively admitted to the Accident and Emergency Department of the Edinburgh Royal Infirmary were prospectively documented. Drivers (DR) accounted for 66% of the patients, 20% were front seat passengers (FSP) and 14% were rear seat passengers (RSP). Injured patients were more likely to be male, young, intoxicated and not wearing a seat-belt. The position of the patient within the vehicle at the time of the accident and point of impact significantly affected the pattern of injury sustained. The majority of injuries were sustained by the upper body and the pattern of injury is discussed. Most accidents occurred at low speeds and higher speeds were associated with an increased severity of injury. Seat-belts reduced the overall severity of injuries, in particular those to the face and chest, but may increase the risk of neck injury. Head-rests do not appear to influence the incidence of neck injury. Clinically apparent alcohol intoxication was associated with a markedly increased risk of severe injury.

Pattern and severity of injury sustained by motorcyclists in road traffic accidents in Edinburgh, Scotland

The pattern, severity and circumstances of injury sustained by 52 motorcyclists admitted as the result of a road traffic accident were prospectively documented. Forty-eight of the patients were drivers and four were pillion passengers. Three of the drivers and all of the pillion passengers were female. Injuries to motorcyclists accounted for 0.4% of the total workload of the department during the course of the study, and for 14% of all injuries seen there arising from road traffic accidents. Eighty-nine per cent of the patients were aged less than 25 years and the oldest patient was aged 44 years. Patients under the age of 21 years were injured more severely than those aged 21 years or more. The majority of injuries (67%) involved the limbs with the right arm and leg being injured twice as often as the left arm and leg. Arms and legs were injured with equal frequency. Head and facial injuries comprised only 9% of the total. Two patients were observed not to be wearing helmets at the time of the accident. Patients admitted between midnight and 05.59 hours sustained injuries of greater severity than those admitted between 06.00 and 23.59. Fifty per cent of patients had an Injury Severity Score of less than five, and only four patients had Injury Severity Score of 25 or more. One third of patients were riding motorcycles with an engine size of 750cc or greater. This group of patients was younger than patients riding less powerful motorcycles and also sustained injuries of greater severity.

Directional bias in the perception of translating patterns

Recent findings suggest that the visual system is biased by its past stimulation to detect one direction of motion over others. Three experiments were designed to investigate whether this bias is mediated by the direction or by the velocity of the past stimulation, and whether this bias is offset by contradictory pattern or depth information. Observers were presented with two solid or random-dot patterns that moved across a display screen in antiphase. As the two patterns reached the center of the screen, they became superimposed in such a way that their subsequent directions were ambiguous. Results from experiment 1 showed that the probability of perceiving these patterns as continuing to move in the same directions was significantly greater when they moved at a constant velocity than when they moved at a variable velocity. Results from experiments 2 and 3 revealed that this directional bias was reversed only gradually as an increasing amount of contradictory pattern information was introduced, but that this reversal was quite abrupt when a relatively small amount of contradictory depth information was introduced. Collectively, these results suggest that a directional bias in the perception of moving patterns is mediated not only by the direction of the previous stimulation, but also by the velocity of that stimulation. Moreover, the analyses of pattern and motion information appear relatively independent during the early stages of visual processing, but the analyses of depth and motion information appear considerably more interdependent.

A recombinant cell line expressing a form of the Y13-259 anti-p21ras antibody which binds protein A and may be produced as ascites

We have recently reported the molecular cloning of the immunoglobulin genes encoding the variable regions of the rat anti-p21ras antibody, Y13-259. These genes were reassembled into expression vectors supplying DNA sequences encoding human gamma 1 and kappa constant domains, as well as the leader sequence for antibody secretion, thus yielding Hu-Y13-259, a secretory anti-p21ras antibody containing human constant regions. We now report the creation of a recombinant cell line, NS0/Hu-Y13-259/B6, secreting high levels of the Hu-Y13-259 Ig. The antigen specificity of this recombinant antibody was demonstrated to be identical to that of the parental Y13-259, i.e. the amino acid sequence 60-76 of the p21ras protein. Unlike the parental cell line, the recombinant cells could be grown as ascites in mice, allowing the production of large quantities of the protein A-binding Hu-Y13-259 antibody.

Neuroantibodies: molecular cloning of a monoclonal antibody against substance P for expression in the central nervous system

We present a strategy to study functional and/or developmental processes occurring in the nervous system, as well as in other systems, of mice. This strategy is based on the local expression of specific monoclonal antibodies (mAbs) by cells of the nervous system. As an application of this strategy, we report the cloning of the anti-substance P rat mAb NC1/34HL. Functional substance P-binding antibodies were reconstituted from the cloned variable domains by using vectors for expression in myeloma cells. With these and other vectors a general system for the cloning and expression of mAbs under a series of promoters (of the rat VGF8a gene, the neurofilament light-chain gene, and the methallothionein gene) has been created. The activity of these plasmids was confirmed by expressing the recombinant NC1/34HL mAb in GH3 pituitary cells, PC12 pheochromocytoma cells, and COS cells. DNA from the described constructs can be used to target the expression of the NC1/34HL mAb to the central nervous system of transgenic mice. This procedure will allow us to perturb substance P activity in a controlled way in order to dissect its multiple roles.

Molecular cloning of PC3, a putatively secreted protein whose mRNA is induced by nerve growth factor and depolarization

PC3 is an immediate early gene induced by nerve growth factor in PC12 cells, a cell line derived from a tumor of the adrenal medulla that undergoes neuronal differentiation in the presence of nerve growth factor. This induction is independent of new protein synthesis as it can occur in the presence of cycloheximide. PC3 is also induced with similar kinetics, but at lower levels, by membrane depolarization (both in vivo and in vitro) and epidermal growth factor. It is induced at much lower levels by fibroblast growth factor and interleukin 6. In vivo it is found expressed in tissues, such as brain at embryonic day 13.5, placenta, amnion, and spleen, which are proliferating and/or differentiating. The deduced protein sequence from the cDNA indicates the presence of a signal peptide, suggesting that PC3 is secreted.

Pattern and severity of injury sustained by pedestrians in road traffic accidents with particular reference to the effect of alcohol

The injuries sustained by 102 pedestrians consecutively admitted to the Accident and Emergency Department of the Royal Infirmary of Edinburgh were prospectively recorded. Injuries were categorized by body regions and the severity assessed by the ISS/AIS system. Pedestrian injuries were found to comprise 0.8 per cent of the department workload and 28 per cent of RTA injuries. The commonest sites of injury were the right leg and head. Injuries to the right side of the body were almost three times more frequent than those to the left. Patients considered to be under the influence of alcohol had more severe and widespread injuries, were more likely to have facial injuries, and were more likely to be detained as inpatients. Males were more commonly injured than females and the predominant age group was 20-29 years. The group affected by alcohol was predominantly male and young, whereas the group unaffected by alcohol included a considerable number of elderly people. The possible reasons for the pattern of injuries are discussed and the contribution of alcohol to the morbidity suffered by pedestrians is stressed.

Chromosomal localization of Cd1d genes in the mouse

Southern blot hybridization of DNA from Chinese hamster x mouse somatic cell hybrids was used to assign the mouse Cd1d genes to chromosome 3. Analysis of the progeny of an intersubspecies backcross was used to position these genes near the gene for glucocerebrosidase, Gba.

Expression of CD1 in the mouse thymus

The CD1 antigens are a family of differentiation antigens found predominantly, but not exclusively, in the human thymus. Although three antigens (CD1a-c) are described by monoclonal antibodies, five genes (CD1A-E) are found in the human genome. The cloning of the mouse CD1 genes (Bradbury, A., Belt, K.T., Nery, T.M., Milstein, C. and Calabi, F., EMBO J. 1988. 7:3081) demonstrated the presence of homologues to human CD1D, but not to any of the other human CD1 genes. In this work we have examined the expression of mouse CD1D mRNA in the thymus and shown that it is predominantly cortical, as is the expression of the CD1 antigens in man. Somewhat surprisingly, we also find that most CD1D mRNA in the mouse thymus is unspliced. Despite this, we have also been able to show, using a polyclonal antiserum directed against a bacterial fusion protein, the existence of the expected protein product.

The computerized medical record: an invitation to dialogue

This article is a companion to "Computerized Medical Records--the Need for a Standard" which appeared in the March 1990 issue of JAMRA. The author has created a workable image of the future with these two articles. In this vision of the future, the control of information appears as one of the greatest medical advances of all history, and the stewards of medical data take an honored position in patient care and research. The author requests that readers be critical in their evaluation of these articles. Great expense and the health of millions will depend upon timely definition of the optimal medical record. Such a task deserves the attention of many minds. We sincerely hope that these articles will elicit lively dialogue.

Computerized medical records: the need for a standard

Major concepts introduced in this paper are as follows. 1) Organization, with its attendant qualities of accuracy, consistency, legibility, completeness, and simplicity, is the heart of the medical record. Technology should not be allowed to obscure this goal. 2) The main function of the computerized medical record is data storage with the qualities of organization noted above. This function must be clearly separated from condensation, analysis, or other secondary manipulation of data. 3) Many aspects of data manipulation call for the judgment of a physician. This judgement may be aided by computer software, but not replaced by it. 4) Present technological barriers, most notably speed, permanent large storage, and voice input should not influence the design of the effective computerized record. Future technology will be able to service the carefully designed medical record. 5) Textual parts of the computerized medical record can follow a simple and machine independent outline format. All parts of the record should use a textual introduction emphasizing patient and record identification. 6) A patient profile is central to each patient file. Updating this profile as needed must be recognized as a primary function of the physician at every patient encounter. 7) Acceptance of a standard for the computerized medical record now, before technology has matured and software diversified, will avoid a pitfall commonly experienced in other fields and save substantial healthcare funds. This standard should be geared to the needs of physicians and patients, not to the constraints of technology. The future of medical computing is bright. Obstacles to the practical use of the computerized medical record exist, but we may expect these to vanish within a few years. The great challenge to physicians now is to take this opportunity to control a new technology, rather than to be driven by it. The soul of good medicine is not in the equipment available, but in the rational and carefully thoughtout use of those tools at hand. We must recognize now the need for a uniform style of computerized medical record before the technological establishment besieges us with a flood of specialized, non-interchangeable, and expensive machines. Indeed, a bit of careful thought now as the foundation is laid can prevent the tangled confusion so typical of new technology. We have a golden opportunity to avoid a new round of escalating medical costs.

The rabbit CD1 and the evolutionary conservation of the CD1 gene family

A comparison of the genes encoding the CD1 leucocyte differentiation antigens in man and mouse shows important differences which prompted us to analyze the CD1 genes of the rabbit. We have found that the rabbit genome contains multiple CD1 loci. Upon cloning and sequencing, one of these loci was found to encode the known rabbit CD1-like antigen (R-Ta) and to be closely related to the human CD1b gene, which is absent in the mouse, while a second rabbit gene is closely related to both the human R3 and the mouse CD1 genes. The data reinforce the notion of the existence of two classes of CD1 genes, one of which is conserved in all species, while the other, albeit also evolutionarily old, has been deleted in mice as well as in other rodents.

Mouse CD1 is distinct from and co-exists with TL in the same thymus

Human CD1 antigens have a similar tissue distribution and overall structure to (mouse) TL. However recent data from human CD1 suggest that the mouse homologue is not TL. Since no human TL has been conclusively demonstrated, we have analysed the murine CD1 genes. Two closely linked genes are found in a tail to tail orientation and the limited polymorphism found shows that, as in humans, the CD1 genes are not linked to the MHC. Both genes are found to be equally transcribed in the thymus, but differentially in other cell types. The expression in liver, especially, does not parallel CD1 in humans. This demonstrates conclusively that CD1 and TL are distinct and can co-exist in the same thymus. It is paradoxical that despite the structural similarity between mouse and human CD1, the tissue distribution of human CD1 is closer to TL. The possibility of a functional convergence between MHC molecules and CD1 is discussed.

Elevated shock threshold in sexually receptive female rats

Previous studies have found cyclic differences in wheel running, extinction of conditioned avoidance responses, and open field behavior as a function of the estrous cycle in rodents. The purpose of this study was to investigate possible sensory changes associated with estrus in rodents. Female rats were monitored for behavioral and physiological changes related to the estrous cycle. Using the method of constant stimuli and foot shock, jump thresholds were determined during the estrous cycle stages of sexual receptivity (proestrus) and non-receptivity (metestrus). A significantly higher jump threshold was demonstrated by animals during proestrus as compared to metestrus. Possible explanations for the failure of previous investigators to find attenuated sensitivity as a function of the estrous cycle are discussed.

The fate of fenclozic acid in the gut and its effect on some aspects of gut metabolism

In the rat [14C]fenclozic acid is not metabolized in the gut and passes into the portal blood unchanged. After intraduodenal administration of [14C]fenclozic acid, a small proportion of the dose binds to high molecular weight substances in the gut wall. The incorporation of L-[U-14C]leucine and N-[3H]acetyl-D-glucosamine into acid-precipitable materials by isolated mucosal cells and homogenates of gut mucosal cells was inhibited by fenclozic acid in a dose-dependent manner. Other non-steroidal anti-inflammatory drugs (indomethacin, phenylbutazone, prednisolone, salicylic acid and paracetamol) were tested for their potency as inhibitors of glycoprotein production by whole cell preparations and by homogenized gut cell preparations. Marked differences were observed in the inhibitory potency of indomethacin, paracetamol and salicylic acid in the two experimental systems. Fenclozic acid had no major effect on the rate of total glycoprotein production by the isolated perfused rat liver or by the duodenal mucosa in situ. Fenclozic acid displaces albumin-bound [3H]tryptophan and increases the level of hepatic tryptophan pyrrolase approx. threefold. The inhibition of gut glycoprotein production by fenclozic acid was not prevented by free tryptophan.

An antibody to a synthetic peptide that recognises SV40 small-t antigen

A peptide Tyr.Arg.Asp.Leu.Lys.Leu corresponding to the carboxy-terminal six amino acids of small-t antigen predicted from the DNA sequence of SV40 was synthesised, coupled to bovine serum albumin and to ovalbumin and used to raise antibody in rabbits. The sera obtained immunoprecipitated [125I]peptide. It also recognised SV40 small-t that was synthesised in vitro from SV40 mRNA or extracted from SV40 infected monkey cells. The immunoprecipitation of small-t was inhibited by added peptide. To demonstrate that the determinant was present at the carboxy-terminal end of the molecule, truncated versions of small-t coded for by 0.54-0.59 deletion mutants were tested. dl 890 small-t, which contains an in-phase deletion removing nine amino acids but leaving the carboxy-terminal sequences intact, was recognised by the antipeptide serum. By contrast dl 885 small-t, which has an out-of-phase deletion leading to an altered carboxy terminus coded in an alternative reading frame, was not recognised. The data confirm the location and specificity of the determinant recognised on small-t by the antipeptide serum.

Applications of high-voltage paper electrophoresis for the characterization of drug metabolites

1. The application of high-voltage paper electrophoresis (h.v.p.e.) to the identification of drug metabolites in urine and bile has been investigated. 2. The major urinary metabolite of [3H]salbutamol in man had an electrophoretic mobility indicative of a sulphate ester. 3. A metabolite of [14C]ranitidine present in rat bile was shown to contain an ionized group with a pKa corresponding to a carboxylic acid. 4. The electrophoretic mobility-pH profile of a metabolite of radiolabelled N"-cyano-N-[2-[5-(dimethylaminomethyl)-2-furanylmethylthio]ethyl]-N-methylguanidine (14C-AH 18801) excreted in dog urine suggested that oxidation of the tertiary amine group of the compound had occurred. 5. H.v.p.e. provided valuable information on the structure of both phases I and phase II metabolites at a stage when the material was insufficiently pure for identification by other techniques.

The enhanced biliary secretion of a taurine conjugate in the rat after intraduodenal administration of high doses of fenclozic acid

1. The metabolic fate of [14C]fenclozic acid (ICI 54450) in rat was determined after intraduodenal administration at different doses. 2. Increasing the dose from 2 to 100 mg/kg resulted in a five-fold increase in drug-related material secreted in bile. 3. At a dose of 2 mg/kg the taurine conjugate was a relatively minor metabolite, whereas at 100 mg/kg this conjugate was the major metabolite in bile and urine. 4. Enhanced biliary secretion of the taurine conjugate in rats receiving multiple doses of fenclozic acid results in exposure of the intestinal cells to much greater concn. of drug-related metabolites.