HIV-specific cytotoxic T lymphocytes in seropositive individuals

Virus-specific cytotoxic T lymphocytes (CTL) which kill virus-infected cells are thought to be a major host defence against viral infections. Here we report the existence of human immunodeficiency virus (HIV)-specific CTL in persons infected with this virus, the aetiological agent of AIDS (acquired immunodeficiency syndrome). Recombinant HIV-vaccinia viruses were used to express HIV antigens in B-cell lines established from subjects seropositive for HIV and seronegative controls. Circulating lymphocytes capable of killing HIV env-expressing autologous B cells were detected in eight of eight seropositive subjects; in addition, at least three seropositive subjects demonstrated gag-specific cytotoxic responses. No HIV-specific cytotoxicity was observed in seronegative subjects. Selective inhibition of the env-specific cytotoxicity by a CD3-specific monoclonal antibody indicates that the effectors are T cells. This demonstration of a cytotoxic T-cell immune response to HIV in infected individuals should prove useful in investigating the immunopathogenesis of HIV infection further and in evaluating AIDS vaccine strategies.

Role of sorbitol accumulation and myo-inositol depletion in paranodal swelling of large myelinated nerve fibers in the insulin-deficient spontaneously diabetic bio-breeding rat. Reversal by insulin replacement, an aldose reductase inhibitor, and myo-inositol

Axo-glial dysjunction refers to the disruption of important junctional complexes that anchor terminal loops of myelin to the paranodal axolemma in diabetic human and animal peripheral nerve. Neither axo-glial dysjunction nor the preceeding acute localized paranodal swelling has been specifically attributed to discrete metabolic consequences of insulin deficiency or hyperglycemia. Two metabolic sequelae of hyperglycemia in diabetic nerve, sorbitol accumulation via aldose reductase, and (Na,K)-ATPase deficiency related to myo-inositol depletion, were explored as possible underlying causes of acute paranodal swelling in the spontaneously diabetic bio-breeding rat. 3 wk of insulin replacement, or therapy with an aldose reductase inhibitor or myo-inositol completely reversed paranodal swelling in sural nerve fibers after 3 wk of untreated insulin deficiency. These observations suggest that insulin deficiency and hyperglycemia cause reversible paranodal swelling, and ultimately poorly reversible axo-glial dysjunction, via the myo-inositol-related (Na,K)-ATPase defect rather than by the osmotic effects of sorbitol accumulation within nerve fibers.

Prevention of diabetic retinal capillary pericyte degeneration and loss by pancreatic islet allograft

Degeneration and loss of retinal capillary pericytes are characteristic features of diabetic retinopathy. The effect of pancreatic islet cell allotransplantation across a major histocompatibility barrier on diabetic pericyte changes was examined in streptozotocin induced diabetic rats 14 months post-transplantation. Morphological studies of the retinal microvasculature were carried out using qualitative and quantitative morphological techniques. We describe significant prevention of pericyte degeneration and loss after successful allotransplantation suggesting that pancreatic islet allograft is a promising therapeutical approach in the prevention of diabetic retinopathy.

Aldose reductase in the BB rat: isolation, immunological identification and localization in the retina and peripheral nerve

Aldose reductase was purified from testis of non-diabetic BB rats using DEAE cellulose, hydroxylapatite and sephadex G-100 column chromatography. The molecular weight of the isolated enzyme was found to be 36,500 +/- 1000. Antibody against the isolated enzyme was raised in rabbits. It was purified by affinity chromatography, characterised by double immunodiffusion and Western blot analysis and used to localize the enzyme in retina and in peripheral nerve of the BB rat. In the retina, aldose reductase immunoreactivity was seen in the ganglion cells, Müller cell processes, retinal pigment epithelium and in the pericytes and endothelial cells of retinal capillaries. In peripheral nerve, aldose reductase immunoreactivity was found in the paranodal cytoplasm of Schwann cells and in pericytes and endothelial cells of endoneurial capillaries.

Expression of polyomavirus virion proteins by a vaccinia virus vector: association of VP1 and VP2 with the nuclear framework

The polyomavirus proteins VP1, VP2, and VP3 move from their cytoplasmic site of synthesis into the nucleus, where virus assembly occurs. To identify cellular or viral components which might control this process, we determined the distribution of VP1, VP2, and VP3 in a soluble fraction, a cytoplasmic cytoskeleton fraction, and a nuclear framework fraction of infected cells. All three proteins were detected in a detergent-extractable form immediately after their synthesis in polyomavirus-infected cells. Approximately 50, 25, and 40% of pulse-labeled VP1, VP2, and VP3, respectively, associated with the skeletal framework of the nucleus within 10 min after their synthesis. The remaining portion of each labeled protein failed to accumulate on the nuclear framework during a 40-min chase and was degraded. When expressed separately by recombinant vaccinia viruses, VP1 and VP2, but not VP3, accumulated on the nuclear framework. This association was not dependent on other polyomavirus proteins or viral DNA. The amount of total VP1 and VP2 which was bound to the nuclear framework approximated 45 and 20%, respectively. Indirect immunofluorescence demonstrated an exclusive nuclear localization of VP1 in situ. In coinfection experiments, a greater percentage of total VP2 and VP3 was bound to the nuclear framework of cells which cosynthesized VP1. These results indicate that although VP1 and VP2 can bind independently to the insoluble nuclear framework, the association of VP3 with this nuclear structure is promoted by the presence of VP1.

Rapid high-performance liquid chromatographic assay of acetaminophen in serum and tissue homogenates

The quantitation of a hepatorenal toxic drug, acetaminophen, in blood and target organ tissues is needed for toxicokinetic and distribution studies. A rapid, sensitive and simple method is described to assay acetaminophen in rat serum and liver or kidney homogenates by reversed-phase high-performance liquid chromatography, using an octadecyl (3 micron particle size) Apex column, a mobile phase consisting of a mixture of distilled water-acetonitrile (86:14) and ultraviolet detection at 245 nm. Short retention times of ca. 3.75 and 6.25 min are observed for acetaminophen and the internal standard (sulfamerazine), respectively. A sensitivity of 50 ng/ml is easily achieved for 100-microliter serum and liver or kidney homogenate samples. The proposed method proved to have satisfactory recovery, precision and accuracy. The preliminary results obtained with human plasma of volunteers and of patients treated with various drugs show that the assay, with a sensitivity of 25 ng/ml, would be of considerable interest in clinical monitoring of acetaminophen.

A rapid reproducible method for determination of basement membrane thickness in biological structures

A computerized method for the determination of basement membrane thickness is described. The program is written in HPL. The accuracy and reproducibility of the method and the program were determined using constructed and biological models.

Induction of CD4-dependent cell fusion by the HTLV-III/LAV envelope glycoprotein

Formation of syncytia, with progression to cell death, is a characteristic feature of in vitro cultures of susceptible cells infected with human T-lymphotropic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). Viral antigen-positive multinucleated giant cells have also been observed in histological sections from infected individuals. In vitro, formation of these multinucleated giant cells occurs through cell fusion which is dependent on cell-surface expression of the differentiation antigen CD4. Utilizing a recombinant vaccinia virus containing the gene for the envelope glycoprotein of HTLV-III/LAV, we demonstrate that cell-surface expression of this protein, in the absence of other HTLV-III/LAV structural or regulatory proteins, is sufficient to induce CD4-dependent cell fusion, leading to cell death, one of the characteristic manifestations of AIDS (acquired immune deficiency syndrome) virus cytopathology. This process may contribute to the loss of CD4+ T cells seen in AIDS.

Acute nephrotoxic potential of acrylonitrile in Fischer-344 rats

In view of its very limited information, we have evaluated the acute nephrotoxic potential of acrylonitrile (ACN) in male Fischer-344 rats. ACN was given i.p. in saline to groups of 6 rats at doses 0, 10, 20, 40, 60 and 80 mg/kg. Urines were collected for 48 h and the animals were sacrificed at 24 and 48 h after the exposure. Significant increased levels of urinary volumes, glucose as well as increased levels of N-acetyl-beta-D-glucosaminidase (NAG), were observed at higher dose levels of ACN at 24 h. Light microscopy showed an increase in size and number of renal lysosomes or dense bodies at 60 mg ACN per kg after 48 h. Ultrastructural studies showed increase of dense bodies and endocytotic vacuoles at the same higher dose of ACN at 48 h. Autophagic vacuole formation as well as dilatation of endoplasmic reticulum membranes was also noted at the higher dose level. Acute inhalation exposure to ACN at 200 ppm for 4 h produced increases in the urinary volumes, proteins, glucose, gamma-GT and NAG 24 h after the exposure. These results demonstrate that ACN could produce acute nephrotoxic insult preferably at the proximal tubular region of the rat kidney.

Intramolecular recombination between transfected repeated sequences in mammalian cells is nonconservative

When plasmids carrying a fragmented gene with segments present as direct repeats are introduced into mammalian cells, recombination or gene conversion between the repeated sequences can reconstruct the gene. Intramolecular recombination leads to the deletion of the intervening sequences and the loss of one copy of the repeat. This process is known to be stimulated by double-strand breaks. Two current models for recombination in eucaryotic cells propose that the reaction is initiated by double-strand breaks, but differ in their predictions as to the fate of the intervening sequences. One model suggests that these sequences are always lost, while the other indicates that the reaction will be conservative as a function of the position of the double-strand break. We have constructed a plasmid in which two overlapping portions of the simian virus 40 early region, which contains the origin and T-antigen gene, are present as direct repeats separated by sequences containing a plasmid with a simian virus 40 origin of replication. Recombination across the repeated segments could produce a plasmid with an origin of replication and/or a plasmid with a gene for a functional T-antigen which would drive the replication of both. Introduction of this construction into African green monkey kidney cells, without coinfection, establishes a condition in which the products of the recombination or gene conversion can be interpreted unambiguously. We find that the majority of the reconstruction reactions are nonconservative.

Effects of route of administration on the dose-dependent metabolism of acetaminophen in rats: relationship with its toxicity

The urinary metabolic excretion profile of acetaminophen (A) was reexamined in adult male Sprague-Dawley rats after administration of a single intraperitoneal (i.p.) or per oral (p.o.) dose of 100 or 750 mg/kg to 4 groups of animals, followed by collecting urines at 8, 24, 48 and 72 hr. The higher dose was administered in the form of a micronized suspension. The amounts of glucuronide, sulfate and mercapturate of A and unchanged A excreted in the urines were measured as a function of time. The pattern of urinary metabolic excretion of A was found to be dependent not only on the dose, but also on its route of administration as well as on the time of urine collection. When A was administered orally, the drug appears to be subjected to a gut and/or gut-wall first-pass elimination. The mean total urinary recovery of the drug was 70% after 72 hr following the administration of the higher dose of A. The hepatorenal toxicity was assessed by measuring the levels of serum glutamic-pyruvic transaminase activity and of urinary creatinine. The higher dose of A showed the potential to produce hepatic and renal toxicity when given i.p., but not when given orally. These toxic effects seem to be related with a high percentage of urinary A mercapturate and unchanged A when A was given i.p. as compared to those when it was given orally.

Simultaneous determination of the major metabolites of styrene and acetaminophen, and of unchanged acetaminophen in urine by ion-pairing high-performance liquid chromatography

An improved isocratic high-performance liquid chromatographic method for the quantitative determination of the major urinary metabolites of styrene in urine is described. The high separation efficiency of an ion-pairing system using tetrabutyl ammonium chloride allows also the simultaneous determination of acetaminophen and its three major metabolites with those of styrene in rat urine. Simplicity, reproducibility and a short analysis time provide a useful tool for the toxicokinetic studies of these two hepatorenotoxic xenobiotics after their co-administration. An aliquot of the diluted urine is directly injected into the liquid chromatograph. The limits of sensitivity and detection of the metabolites of styrene are better than those reported before. Preliminary works indicate that the method would also be applicable for analysis of these metabolites in human urine and would therefore be useful in monitoring styrene exposure to workers especially when they take acetaminophen.

Expression of the HTLV-III envelope gene by a recombinant vaccinia virus

The discovery that the aetiological agent of acquired immune deficiency syndrome (AIDS) is a retrovirus, referred to as human T-lymphotropic virus type III (HTLV-III) or lymphadenopathy-associated virus (LAV) (for review see ref. 1), has raised the possibility of developing a vaccine. In this regard, the envelope (env) proteins of murine retroviruses can induce protective immunity in mice. The HTLV-III env gene specifies a primary polypeptide of approximately 860 amino acids that is glycosylated to form a precursor of relative molecular mass (Mr) 160,000 (gp160), which gives rise to mature membrane-associated proteins of Mr 120,000 (gp120) and 41,000 (gp41). The HTLV-III env gene has been expressed in Escherichia coli and by simian virus 40 (SV40) vectors but formation of the authentic proteins has not been demonstrated. Here, we describe the expression of the complete env gene by a vaccinia virus vector. Evidence is presented that synthesis, glycosylation, processing and membrane transport of the env polypeptide occurred without other HTLV-III gene functions; the env protein was recognized by sera from unrelated AIDs patients; and a single vaccination with the infectious recombinant vaccinia virus induced antibodies to gp120 in mice.

Effects of cigarette smoke and 3-methylcholanthrene on the disposition of phencyclidine and its N-ethylamine analogue in the isolated perfused lung of rats

The isolated perfused lung (IPL) of rats were used to examine the pulmonary disposition and metabolism of radiolabeled phencyclidine (PCP) and N-ethyl-1-phenylcyclohexylamine (PCE). The IPL removed PCP and PCE from the perfusate and converted them to free and conjugated metabolites. At the conclusion of a 1-h perfusion, the lung accumulated at least 20% of the administered radioactivity and metabolized more than 30% of the added drug. Pretreatment of rats with 3-MC or cigarette smoke enhanced significantly PCP and PCE metabolism by the IPL. The concentration of conjugated PCE metabolite in the perfusate of the IPL was increased significantly by both 3-MC and cigarette smoke pretreatments whereas the concentration of conjugated PCP metabolite was not affected by cigarette smoke exposure and increased only slightly after 3-MC pretreatment. Pretreatment of rats with 3-MC or cigarette smoke also altered the amount of radioactivity accumulated by the lung tissue at the conclusion of a 1-h perfusion. Inasmuch as PCP and PCE are often abused by humans via smoke inhalation, a significant amount of these drugs may be stored or metabolized by the lung.

Vaccinia virus expression vector: coexpression of beta-galactosidase provides visual screening of recombinant virus plaques

We constructed a plasmid coexpression vector that directs the insertion of a foreign gene of interest together with the Escherichia coli beta-galactosidase (beta gal) gene into the thymidine kinase (TK) locus of the vaccinia virus genome. Tissue culture cells that had been infected with vaccinia virus were transfected with a plasmid vector containing a foreign gene. TK- recombinants could be selected by a plaque assay on TK- cells in the presence of 5-bromodeoxyuridine and distinguished from spontaneous TK- mutants by the addition of a beta-gal indicator to the agarose overlay. Plaques that expressed beta-gal stained dark blue within several hours at 37 degrees C. Alternatively, TK- selection could be eliminated, and recombinant plaques could be readily identified solely by their blue color. The reverse procedure, in which the starting virus expresses beta-gal (i.e., forms blue plaques) and the desired recombinant has deleted the entire beta-gal gene (i.e., forms white plaques), is another alternative. Each protocol was tested by constructing vaccinia virus recombinants that express hepatitis B virus surface antigen.

The BB-rat--an authentic model of human diabetic retinopathy

The pathogenesis of diabetic retinopathy has not been fully explained. The earliest histological lesion is the loss of intramural pericytes and thickening of the basement membrane. Increased activity of the polyol pathway is a probable mechanism for these two abnormalities. Investigations have suffered from the lack of an exact animal model simulating the human condition. Examination of the retina in the spontaneously diabetic BB-rat demonstrated degeneration and loss of intramural pericytes, a progressive increase in basement membrane thickness, and microinfarctions with areas of non-perfusion. Therefore, this model may be used to clarify the biochemical mechanism(s) linking the metabolic abnormalities of diabetes and the retinopathy.

Recombination and deletion of sequences in shuttle vector plasmids in mammalian cells

Shuttle vector plasmids were constructed with directly repeated sequences flanking a marker gene. African green monkey kidney (AGMK) cells were infected with the constructions, and after a period of replication, the progeny plasmids were recovered and introduced into bacteria. Those colonies with plasmids that had lost the marker gene were identified, and the individual plasmids were purified and characterized by restriction enzyme digestion. Recombination between the repeated elements generated a plasmid with a precise deletion and a characteristic restriction pattern, which distinguished the recombined molecules from those with other defects in the marker gene. Recombination among the following different sequences was measured in this assay: (i) the simian virus 40 origin and enhancer region, (ii) the AGMK Alu sequence, and (iii) a sequence from plasmid pBR322. Similar frequencies of recombination among these sequences were found. Recombination occurred more frequently in Cos1 cells than in CV1 cells. In these experiments, the plasmid population with defective marker genes consisted of the recombined molecules and of the spontaneous deletion-insertion mutants described earlier. The frequency of the latter class was unaffected by the presence of the option for recombination represented by the direct repeats. Both recombination and deletion-insertion mutagenesis were stimulated by double-strand cleavage between the repeated sequences and adjacent to the marker, and the frequency of the deletion-insertion mutants in this experiment was again independent of the presence of the direct repeats. We concluded that although recombination and deletion-insertion mutagenesis were both stimulated by double-strand cleavage, the molecules which underwent the two types of change were drawn from separate pools.