Inhibition of growth of Mycobacterium smegmatis and of cell wall synthesis by D-serine

d-Serine inhibited the growth of Mycobacterium smegmatis and induced the morphological alteration of the bacilli. The growth inhibitory action of d-serine was partially reduced by an equimolecular concentration of d-alanine. The combination of glycine with d-alanine reversed the growth inhibition produced by d-serine more than did d-alanine alone. In cells cultured in the presence of d-serine, the amounts of alanine, diaminopimelic acid, and glycine inserted into the cell wall mucopeptide were reduced, and serine was increased. The intracellular accumulation of a precursor of cell wall mucopeptide was increased by d-serine, and this accumulation was reduced by d-alanine. d-Serine competed with glycine for incorporation into the cell wall mucopeptide. The incorporation of l-aspartic acid into diaminopimelic acid residues in the cell wall mucopeptide was markedly inhibited by d-serine. Three mutants resistant to d-serine were isolated by nitrosoguanidine treatment. In these mutants the effects of d-serine on the sites of cell wall mucopeptide synthesis were all reduced. Thus, d-serine inhibition of the growth is due to replacement of glycine residues of the cell wall mucopeptide with d-serine and inhibition of the cell wall synthesis by blocking the formation of d-alanine and diaminopimelic acid.

Experience of a new surgical procedure for the treatment of unilateral obstructive lymphedema of the lower extremity: adipo-lymphatico venous transfer

We report five cases of adipo-lymphatico venous transfer (ALVT) performed to treat unilateral obstructive lymphedema of the lower extremity. ALVT is a surgical procedure that utilizes the long saphenous vein and its surrounding lymphatic tissue from the unaffected limb for the treatment of lymphedema. Since ALVT does not necessitate anastomoses of lymphatic vessels, it can be performed regardless of the severity and duration of lymphedema, and stable long-term results can be obtained when the transferred lymphatic tissue shows viability.

Protease-induced multicell formation in Staphylococcus haemolyticus

Multicellular cells were efficiently induced in Staphylococcus haemolyticus by the addition of protease to exponentially growing cultures at 30 C. Electron microscopy revealed the formation of tetrad-shaped multicells that were septated but not separated from each other. Incubation of the multicells with extract from the cells grown without protease resulted in a fourfold increase in the number of colony-forming units as compared with the untreated control. An electrophoretic analysis showed that protease caused a loss of cell wall-lytic activity of the cell, which possibly led to the formation of multicells through cessation of cross wall separation.

Lymphocyte proliferative responses to recombinant hepatitis C virus antigens in patients with chronic hepatitis C

The purpose of the present study was to analyse lymphocyte proliferative responses to recombinant hepatitis C virus (HCV) antigens in chronic hepatitis C. Four recombinant peptides derived from the NS3, core, E1 and E2/NS1 regions of the HCV genome were used as antigens in lymphocyte proliferative responses. Forty-two patients, classified into various sub-groups, and 17 healthy control subjects were tested and the specific response was expressed as a stimulation index. Responses were analysed with alanine aminotransferase (ALT) level and histological diagnosis. NS3- and core-antigen specific responses in all patient groups were significantly higher than in the healthy control group. E1- and E2/NS1-antigen-specific responses in the patient group with ALT levels exceeding 100 IU/L were significantly higher than those in other patient groups. Histological diagnosis was not correlated to the intensity of the core- and NS3-specific responses. E1- and E2/NS1-antigens induced significantly elevated responses in patients with chronic active hepatitis and liver cirrhosis compared with results in the healthy control group and in patients with chronic persistent hepatitis. In conclusion, the significantly elevated responses to core- and NS3-antigens may be related to HCV infection and such responses to E1- and E2/NS1-antigens could be related to the severity and activity of the disease.

Salt-induced L-forms of Staphylococcus aureus

When growing cultures of a salt-sensitive strain of Staphylococcus aureus were inoculated on nutrient agar containing 0.8 M NaCl and 0.5% bovine serum albumin, typical colonies of L-form developed extensively after 2 days of incubation at 30 C. Incubation of growing cultures with lipoteichoic acid, sodium polyanethole sulfonate and subtilisin resulted in inhibition of L-form induction.

Salt-induced cell lysis of Staphylococcus aureus

Cell lysis was efficiently induced in Staphylococcus aureus by the addition of 0.3 M NaCl to exponentially growing cultures at 30 degrees C. When cells harvested at the exponential phase were incubated in buffer with NaCl, autolysis occurred. Treatment with chloramphenicol failed to induce cell lysis by NaCl. The effects of NaCl on growing cells and harvested cells were inhibited by the addition of sodium polyanethole sulfonate, subtilisin, cardiolipin, and lipoteichoic acid. These agents diminished the activity of a cell wall-lytic enzyme liberated from the cells in the presence of NaCl. Lysis induced by salt appears to be catalyzed by a similar lytic enzyme in growing and harvested cells.

Mandibular reconstruction using computer-generated three-dimensional solid models

In mandibular reconstruction, it is necessary to know the exact, three-dimensional extent of the mandible and its defect; the bone graft must be the exact size and dimension of the defect, to assure a precise three-dimensional configuration of the mandible. Previously, the bone graft had to be reshaped during the operation by trial and error, often a time-consuming procedure. The operative procedure has been simulated in advance using three-dimensional, solid models, which has shortened the operating time required.

Transmission of hepatitis C in an isolated area in Japan: community-acquired infection. The South Kiso Hepatitis Study Group

BACKGROUND/AIMS

The spread of hepatitis C virus (HCV) infection not due to drug needle sharing or transfusion is largely unknown in communities. A search for risk factors for HCV infection in an endemic area might elucidate inapparent modes of transmission.

METHODS

We conducted screening for hepatitis virus markers and parenteral exposures to blood among 435 inhabitants in an isolated area known for its endemicity for non-A, non-B hepatitis and in a nonendemic area with 1542 inhabitants.

RESULTS

The prevalence of hepatitis B surface antigen was the same in both areas. The prevalence of antibody to HCV verified by the recombinant immunoblot assay was 32.4% in the highly endemic area and 2.3% in the nonendemic area (P < 0.001). Risk factors for HCV infection in the highly endemic area were complex but included folk remedies such as acupuncture and "vacuuming" for congested blood in muscle by the use of a warm glass bottle.

CONCLUSIONS

Folk remedies such as acupuncture and cutting of the skin using nonsterilized knives should be considered as possible routes of HCV transmission not associated with blood transfusion or sharing of drug paraphernalia.

Serum collagen type IV for the assessment of fibrosis and resistance to interferon therapy in chronic hepatitis C

Sixty-nine patients with chronic hepatitis C (CH-C) were treated with interferon therapy, and serum collagen type IV (s-collagen IV) levels were measured by enzyme immunoassay to analyze the responsiveness to interferon therapy. Classified by the improved pattern of serum alanine aminotransferase levels after interferon administration, 23 patients were judged as sustained responders, 23 as transient responders, and 23 as non-responders. Fibrotic grades of the liver sample correlated statistically with the levels of s-collagen IV (P < 0.01). Pre-therapy s-collagen IV levels of sustained responders were significantly lower than those of the other responders, and only sustained responders showed a significant decrease of s-collagen IV levels after interferon therapy, in accordance with histologic improvement. Multivariate analysis showed that s-collagen IV and hepatitis C virus genotype were the most important factors affecting the response to interferon therapy of all variates. Thus, s-collagen IV is one of the most useful aids for the evaluation of liver fibrotic grade in CH-C and a potent predicting indicator for the responsiveness to interferon therapy.

Type C chronic hepatitis associated with thrombocytopenia in two patients

Portal hypertension in the presence of chronic hepatitis is generally thought to develop during the progression of the chronic hepatitis to cirrhosis. Before the establishment of assays for diagnosing hepatitis C virus infection, such a case of portal hypertension without liver cirrhosis could be misdiagnosed as idiopathic portal hypertension. It had not fully determined whether portal hypertension might precede the onset of cirrhosis in type C chronic hepatitis. This report presents two cases of women with chronic hepatitis C who developed severe thrombocytopenia; each showed splenomegaly and hypersplenism due to portal hypertension. Angiographic study and histological analysis were conducted to determine the cause of the portal hypertension. Histological evaluation showed an intrahepatic presinusoidal block pattern and fibrotic changes in the periportal area, but no evidence of liver cirrhosis or of other incidental complications such as idiopathic portal hypertension. Both of these patients exhibited normal platelet counts after splenectomy. Thus, type C chronic hepatitis can lead to portal hypertension, as demonstrated in these two patients.

Establishment of Epstein-Barr virus-associated lymphoma cell line SUBL with t(2;3)(p11;q27) from a liver transplant patient

A new lymphoma cell line, designated SUBL, was established from a Japanese patient with Epstein-Barr virus (EBV)-associated lymphoma, which developed during FK 506 therapy after liver transplantation. This cell line has undergone 80 passages over a period of 22 months. The cultured cells were positive for CD19, CD20, CD21, CD22, CD23, and HLA-DR, and negative for CD10 and surface immunoglobulins. Immunoglobulin gene analysis revealed rearrangements of JH and JK. T-cell antigens or T-cell receptor gene rearrangements were not observed on the cell line. The SUBL cells were positive for Epstein-Barr virus nuclear antigen (EBNA). The EBV genome was detected in the original tissue and the cell line by the in situ hybridization method. These data indicate that this cell line represents the B-cell lineage at a pre-B-cell stage. SUBL cells showed successful heterotransplantation to mice with severe combined immunodeficiency (SCID). Chromosomal analysis revealed the karyotype 46,XY,t(2;3)(p11;q27). Molecular studies showed that c-myc, N-myc, and bcl-2 were not rearranged. This cell line will provide a useful in vitro system to study the relationship between chromosomal abnormalities and the activation of cellular oncogenes.

Immunological responses against an autologous human hepatocellular carcinoma cell line

We performed a detailed analysis of immune responses in a hepatocellular carcinoma (HCC) cell line and effector cells obtained from a patient with HCC. We examined the cytotoxic activity of natural killer (NK) cells, lymphokine-activated killer (LAK) cells and cytotoxic T lymphocytes (CTL) against an autologous tumour cell line (SUHC-1) to investigate the immune mechanism of human lymphocytes against HCC cells. Cytotoxic T lymphocytes were induced by co-culturing of peripheral blood lymphocytes (PBL) and SUHC-1 cells, mixed lymphocyte and tumour cell culture (MLTC). The susceptibility of SUHC-1 to NK and LAK cells was similar to that of other allogeneic cell lines, such as K562, PLC/PRF/5 and Mahlavu. Effector cells induced in the primary MLTC had high cytotoxic activity but were not specific for SUHC-1. Cytotoxic T lymphocytes with specific activity against SUHC-1 were induced after PBL were stimulated five times at 7-10 day intervals with SUHC-1 and low-dose recombinant interleukin-2 (rIL-2), suggesting that as the culture progressed, broadly reactive effector cells disappeared and specific effector cells survived. The specific effector cells were identified as CD3+/CD4+ and CD3+/CD8+ T-lymphocyte subsets. The recognition mechanisms of CD3+/CD4+ CTL remain unresolved because the cytotoxicities were not inhibited by anti-CD4 and anti-major histocompatibility complex (MHC) class II monoclonal antibodies (MoAb). Treatment of cells with anti-CD3, anti-CD8 and anti-MHC class I MoAb partially inhibited lysis. These results demonstrated that the T-cell receptor (TCR)/CD3 complex appeared to be involved in SUHC-1 specific antigen recognition and antigen recognition of CD3+/CD8+ CTL was MHC class I restricted.

Detection of active form of transforming growth factor-beta in cerebrospinal fluid of patients with glioma

We examined transforming growth factor-beta (TGF-beta) activity in cerebrospinal fluid of 39 patients with various brain tumors, and found it in 10 glioma cases that had lesions related to subarachnoid space or ventricle. In one glioma case, TGF-beta detected on admission disappeared after radiation and chemotherapy. We confirmed that five glioma cell lines produced TGF-beta, and that four of them produced active form of TGF-beta directly. The active form of TGF-beta was also identified from cerebrospinal fluid before the acidification treatment in two cases. The calculated contents were 110 ng/ml and 18 ng/ml. These results indicate that active form of TGF-beta is directly produced by tumor cells in patients with glioma, and may contribute to immunodeficiency of the host.

Caroli's disease in three siblings

Three sisters with cystic dilatation of the intrahepatic bile ducts (Caroli's disease) are reported. The index case, a 41-year-old woman with remittent high fever and right upper quadrant abdominal pain, was diagnosed as Caroli's disease with hepatic lithiasis and cholangitis based on findings of ultrasonography, computed tomography and endoscopic retrograde cholangiography. Her two older sisters were also examined and found to have the same disease without clinical symptoms. Their symptoms, locations of the dilated ducts and complications all varied. The hereditary mode of Caroli's disease in 13 families (32 cases) reported in the world literature including our study was examined. While Caroli's disease is thought to be an autosomal recessive disease, a conclusion on the hereditary mode of transmission could not be made in this study because of an insufficient investigation of family members, especially the parents.

New hepatocellular carcinoma cell line SUHC-1 established from a patient with hepatitis C virus RNA in serum

A new human hepatocellular carcinoma cell (HCC) line, designated SUHC-1, was derived from a Japanese patient with hepatocellular carcinoma having antibody to hepatitis C virus (HCV) and HCV-RNA in his serum, and established in tissue culture. This cell line exhibited typical epithelial cell morphology in culture as observed by phase-contrast and electron microscopy. The SUHC-1 cells produced albumin and alpha 2-macroglobulin. Chromosomal analysis showed several rearrangements at short and long arms of chromosome 1, 17 and 20 (1p-, 1q-, i(1q), i(17q) and 20q+) with a modal number of 91. HCV-RNA was not detected in the supernatant of SUHC-1 cells by nested polymerase chain reaction assay or in the SUHC-1 cells by the in situ hybridization method. We concluded that complete HCV does not exist in the SUHC-1 cell line. The SUHC-1 cell line is the first line of HCC to have been derived from a patient with persistent HCV infection, and may provide a suitable model for studies of hepatocarcinogenesis related to HCV.

Augmentation of natural killer cell activity in mice by Bru-Pel

The immunomodulatory and anti-tumor activity of Bru-Pel, an aqueous-ether extracted residue of Brucella abortus (strain 456), was investigated. Bru-Pel was administered to C57BL/6 mice intraperitoneally (i.p.) and tested for its effect on natural killer (NK) cell activity in spleen cells, liver, and peritoneal cavity. Three days after injecting 100 micrograms of Bru-Pel i.p., the cytotoxicity of spleen cells against YAC-1 target cells, assessed by LU20 increased by approximately two-fold and nonparenchymal cells of liver by greater than six-fold. The highest stimulatory effect of Bru-Pel was seen with peritoneal exudate cells, and 47-fold augmentation of NK cell activity was observed. Bru-Pel treatment made spleen, liver, and peritoneal exudate cells capable of lysing P815 mastocytoma cells, a tumor cell line highly resistant to lysis by unstimulated NK cells. In vivo, Bru-Pel inhibited the formation of experimental BL6 melanoma metastases; however, there was no significant effect on the eradication of established pulmonary metastatic lesions. These results demonstrate that in addition to its previously described macrophage-activating ability, Bru-Pel is highly efficient in stimulation of NK cell-mediated cytotoxicity in mice.

Formation of vesiculated large bodies of Staphylococcus aureus L-form in a liquid medium

A method is described in which cells of Staphylococcus aureus can be converted to vesiculated large bodies of L-form. When coccal cells were incubated in a liquid growth medium containing D-cycloserine, N-acetylmuramidase and subtilisin, a large number of vesiculated large bodies were formed. Electron microscopy revealed that development of internal vesicles arose after 6 hr of incubation.. When growth inhibitory concentrations of rifampicin, novobiocin, or chloramphenicol were added to the culture at 6 hr of incubation, small-sized nonvesiculated bodies were produced instead of vesiculated forms. The viability of cultures was reduced by rifampicin and novobiocin but not by chloramphenicol.

Cyclosporine enhances the growth of carcinogen-induced enzyme-altered foci in rat liver

Cyclosporine, a powerful immunosuppressant, has been used successfully for organ transplantation. Its efficacy on liver transplants of patients with primary hepatic tumors remains controversial because of a high rate of recurrence of the original tumors in the transplanted livers. In this study, we experimentally tested whether cyclosporine exerts any effects on the growth of carcinogen-initiated liver cells using the short-term assays of rat liver carcinogenesis. Dietary cyclosporine, which maintained sufficient levels of blood cyclosporine and suppressed host immune functions, enhanced the development of the glutathione S-transferase, placental form-positive hepatocyte foci in the liver of male F-344 rats treated with a single weekly dose of diethylnitrosamine (75 mg/kg) for 3 wk. Dietary cyclosporine also accelerated the growth of preformed glutathione S-transferase, placental form-positive foci induced by a single dose of diethylnitrosamine (250 mg/kg) followed by the promoting regimen of a choline-deficient diet. It is possible that the enhancement of the size of hepatocyte foci by cyclosporine could be due to stimulation of growth or inhibition of regression. The mechanisms by which cyclosporine modifies the growth of preneoplastic lesions in the liver are not yet fully understood. Possible involvement of immunologically relevant cells in the liver, Kupffer cells and pit cells in the process is suggested.

Cyclosporine promotes the induction of thymic lymphomas in C57BL/6 mice initiated by a single dose of gamma-radiation

We previously demonstrated that a single dose of gamma-radiation (350 rads) was able to induce thymic lymphomas in C57BL mice when followed by promoting treatment with oral cyclosporine (CsA), a non-genotoxic immunosuppressant. We have now tested the efficacy of various doses of gamma-radiation as an initiator of CsA promotion of the induction of thymic lymphomas in male C57BL mice. The effects of oral CsA on the splenic natural killer (NK) cell activity of non-irradiated and irradiated (400 rads, 1x) mice were tested by the standard 51Cr release assays against YAC-1 cells. The cumulative incidence of thymic lymphomas induced by a single dose of gamma-radiation at 100, 200, 400 and 600 rads were 10, 25, 63 and 75% respectively, after 42 weeks of CsA promotion. The splenic NK cell activity in non-irradiated mice given CsA for 4 weeks was twice as high as that in the control mice. CsA inhibited poly I:C-induced augmentation of the splenic NK cell activity. In mice given a single dose (400 rads) of gamma-radiation and CsA for 4 weeks, a similar but reduced enhancement of the splenic NK cell activity as seen in non-irradiated mice was observed. These results indicate that the efficacy of CsA promotion in the induction of thymic lymphomas is dependent on the initiating doses of gamma-radiation, and that CsA enhances host splenic NK cell activity during the early stage of tumor promotion.

Familial dilated cardiomyopathy and human leucocyte antigen. A report of two family cases

Two familial cases of dilated cardiomyopathy were evaluated by HL-A typing. In the case of the first family, the mode of inheritance is likely to be an autosomal dominant trait. Only the affected individuals carried the identical HL-A haplotype (A2, Bw54, Cw1, DR4, DQw3), while the unaffected members do not share this pattern. In the second family case, the disease is probably inherited by autosomal recessive traits. All of the family members examined shared the identical HL-A haplotype (A24, Bw52, DR2, DQw1), but only the affected individuals were homozygous for this haplotype.

Antigen presentation by human antigen-presenting cells to antigen-specific xenogeneic murine T cells

Successful antigen presentation by xenogeneic human antigen-presenting cells (APC) to stimulate the proliferation of antigen-specific, keyhole limpet hemocyanin (KLH)-specific, ovalbumin (OVA)-specific, and purified protein derivative of Mycobacterium tuberculosis (PPD)-specific murine T cells was observed. Evidence indicating a direct cell interaction between antigen-specific murine T cells and xenogeneic human APC was given by experiments using antigen-specific murine T cell clones. The OVA-specific B10.S(9R) T cell line (9-0-A1) and PPD-specific B10.A(4R) T cell line (4-P-1) were stimulated by both xenogeneic human APC and murine APC from syngeneic or I-A compatible strains, while the PPD-specific human T cell line (Y-P-5) was stimulated by autologous human APC but not by murine APC. Anti-HLA-DR monoclonal antibodies (MoAb) blocked the xenogeneic human APC-antigen-specific murine T cell clone interaction. Thus, human xenogeneic APC can stimulate antigen-specific murine T cells through HLA-DR molecules in the same manner as syngeneic murine APC do through Ia molecules coded for by the I region of the H-2 complex, while murine APC failed to present antigen to stimulate human antigen-specific T cells.

Cellular FITC-linked immunospecific assay (cell-FLISA) for detection of monoclonal antibodies against cell-surface antigens

A cellular fluorescein isothiocyanate (FITC)-linked immunospecific assay (Cell-FLISA) has been established using the recently developed fluorophotometer for microplates. In the Cell-FLISA system, monoclonal antibodies specific for the surface antigens of live cells are detected by measuring the fluorescence intensity of an FITC-labeled second antibody: goat anti-mouse immunoglobulin antibody. It takes only 2 min to count 96 samples in microplate wells using the fluorophotometer for microplates. Moreover, by this system, the analysis is finished within 2 hr. Thus, the Cell-FLISA system has advantages in screening a large number of samples, such as hybridoma cell lines secreting monoclonal antibodies against cell-surface antigens.

Relationship between beta-lactamase activity and resistance to beta-lactam antibiotics in Mycobacterium smegmatis

Penicillin-susceptible mutants and beta-lactamase-negative mutants were isolated from Mycobacterium smegmatis after nitrosoguanidine mutagenesis. Both the mutants were found to be susceptible to low levels of penicillin and cephalosporins by twofold dilution testing. Clavulanic acid reduced the minimal inhibitory concentrations of beta-lactamase-labile beta-lactams for the penicillin-susceptible mutants and the parent strain, but had no effect on the susceptibility of the beta-lactamase-negative mutants. Comparison of the beta-lactamase activities found in these mutants and the parent strain indicated that there was a rough correlation between the beta-lactamase level in these organisms and their susceptibility to beta-lactams.

Phylogenetic hierarchy of antigen-presenting ability in antigen-specific T cell activation

The phylogenetic hierarchy of antigen-presenting ability was shown to exist in xenogeneic mouse, rat and human T cell-antigen-presenting cell (APC) interaction. The antigen-presenting ability of human APC is dominant over that of rat APC and the ability of rat APC is dominant over that of mouse APC. The HLA-DR molecule was shown to function for antigen presentation to PPD-specific autologous human and xenogeneic murine T cells.

Interspecies cross-reactivity of Class II antigen of MHC determined by syngeneic, allogeneic and xenogeneic B and T cells

Although this chapter ought to summarize the role of MHC antigens in T cell activation, the immunobiological meaning of the polymorphism of Class II antigens, as well as that of Class I antigens, is still unresolved. The antigen-presenting ability of human APC is dominant over that of murine APC in the stimulation of antigen-specific xenogeneic T cells. In addition, xenoreactive murine T cells specific for human PBL failed to recognize the polymorphic determinant of Class II antigens of human MHC. On the basis of the data, Class II antigens may be seen to have some role as antigen-presenting molecules rather than as restricting molecules, at least, in the xenogeneic APC-T cell interaction or the xenogeneic MLR responses. These data together with the fact that the linkage disequilibrium found among the various groups of alleles encoding Class I and II antigens making up an MHC haplotypes suggest that the MHC may play a key role during evolution. These studies using xenogeneic cell interaction may shed some light on the immunobiological function of polymorphism of MHC antigens in the mechanisms of T cell activation, and the evolutional history of the polymorphism of the NHC in self or not-self recognition by T cells.

A case of asymptomatic primary biliary cirrhosis with an initial presenting feature of localized gastric varices

A case of asymptomatic primary biliary cirrhosis (PBC) with an initial presenting feature of localized gastric varices is reported. The patient, 64 years old female, underwent a barium meal examination because of ill-defined abdominal complaints and was found to have gastric varices localized at the cardia but no esophageal varices. Her blood chemistry showed high values of biliary tract enzymes such as alkaline phosphatase and gamma-glutamyl transpeptidase, but the serum bilirubin level was almost normal. Serum anti-mitochondrial antibody was positive. Histological findings of the surgically biopsied liver specimen were compatible with PBC. The clinical implication of gastric varices in PBC is discussed.

Protoplast formation of selected Mycobacterium smegmatis mutants by lysozyme in combination with methionine

Lysozyme-sensitive mutants of Mycobacterium smegmatis, isolated by nitrosoguanidine treatment, have been converted into protoplasts in a nutritionally enriched medium containing lysozyme and DL-methionine.

Amino acid transport in Mycobacterium smegmatis

The transport of d-alanine, d-glutamic acid, and d-valine in Mycobacterium smegmatis was compared quantitatively with that of their l-isomers. It appeared that the uptake of d-alanine was mediated by an active process displaying saturation kinetics characteristic of enzyme function, whereas the uptake of d-glutamic acid was accomplished by a passive process showing diffusion kinetics. Both processes were involved in the uptake of l-alanine, l-glutamic acid, d-valine, and l-valine. d-Valine competed with l-valine for entry into the cell through a single active process. d-Alanine and l-alanine also utilized the same active process, but the d-isomer could not enter the cell through the passive process. The passive process exhibited characteristics of diffusion, but was sensitive to sulfhydryl-blocking reagents and showed competition among structurally related amino acids. These last findings suggested that the passive process is a facilitated diffusion.