Subsenescent telomere lengths in fibroblasts immortalized by limiting amounts of telomerase

Human fibroblasts expressing the catalytic component of human telomerase (hTERT) have been followed for 250-400 population doublings. As expected, telomerase activity declined in long term culture of stable transfectants. Surprisingly, however, clones with average telomere lengths several kilobases shorter than those of senescent parental cells continued to proliferate. Although the longest telomeres shortened, the size of the shortest telomeres was maintained. Cells with subsenescent telomere lengths proliferated for an additional 20 doublings after inhibiting telomerase activity with a dominant-negative hTERT mutant. These results indicate that, under conditions of limiting telomerase activity, cis-acting signals may recruit telomerase to act on the shortest telomeres, argue against the hypothesis that the mortality stage 1 mechanism of cellular senescence is regulated by telomere positional effects (in which subtelomeric loci silenced by long telomeres are expressed when telomeres become short), and suggest that catalytically active telomerase is not required to provide a protein-capping role at the end of very short telomeres.

Induction of high level of specific antibody response to the neutralizing epitope ELDKWA on HIV-1 gp41 by peptide-vaccine

The monoclonal antibody 2F5 recognizing the neutralizing epitope ELDKWA on the C-domain could neutralize 90% of the investigated HIV-1 isolates. Low levels of ELDKWA-epitope-specific antibodies were observed in HIV-1-infected individuals. To induce high levels of antibodies to ELDKW-epitope, C-domain peptide (P2) was conjugated with a carrier peptide (KGGG)(7)-K (K/G). P2-K/G-conjugate induced high level of antibodies in mice by titer 1:25,600 to ELDKWA-epitope. P2-K/G-BSA-conjugate induced antibody response to ELDKWA-epitope (1:320-6400) in mice. The ELDKWA-epitope-specific antibodies of 19.8 and 34.6 microg/per milliliter serum were isolated from two rabbit antiserums (1:25,600). The levels of ELDKWA-epitope-specific antibodies induced in rabbits were greater than 1 microg/ml, a level considered to confer long-term protection. These results demonstrate the potential role of the C-domain peptide of gp41 to develop an effective ELDKWA-based epitope/peptide-vaccine against HIV-1.

[Apoptosis induced by cisplatin and verapamil or SDZ PSC 833 in human ovarian cell lines]

OBJECTIVE

To study the pharmaceutical mechanisms of cisplatin (DDP), verapamil (VP) and SDZ PSC833, and the mechanism of developing acquired drug resistance.

METHODS

Two ovarian carcinoma cell lines--one sensitive (COC(1)) and the other resistant (COC(1)/DDP) to cisplatin were used in this study. The cell viability was measured by trypan blue dye exclusion assay. The apoptotic cells were observed and distinguished by light and electron microscopy, and comet assay. Flow cytometry was used to measure the cell cycle. Six groups were set up according to drug(s) delivered: DDP, VP, SDZ PSC833, DDP and VP, DDP and SDZ PSC833, and control group.

RESULTS

(1) VP or SDZ PSC833 enhanced cytotoxicity of DDP (q > 1, P < 0.01). (2) The most prominent effect of DDP on cell cycle kinetics was a slowdown in S-phase transit during which cells undergo apoptosis (P < 0.05). (3) COC(1) and COC(1)/DDP cells had different rates of apoptosis when DDP added. SDZ PSC833 enhanced apoptosis of COC(1)/DDP cells induced by DDP.

CONCLUSIONS

VP and SDZ PSC833 increase sensitivity of the cell lines to DDP. SDZ PSC833 enhances apoptosis induced by DDP. Induction of apoptosis is one of the pharmaceutical mechanisms of DDP, and acquired drug resistance is associated with resistance to apoptosis. The most prominent effect of DDP on cell cycle kinetics is a slowdown in S-phase transit and apoptotic cells are at S-phase.

Epitope-vaccines: a new strategy to induce high levels of neutralizing antibodies against HIV-1

Based on the experimental evidence that gp120 subunit vaccine did not protect individuals from HIV-1 infection, we suggested that epitope-vaccines of HIV-1 gp41 may be a new strategy to induce high levels of neutralizing antibodies against HIV-1, and characterised immunogenicity of epitope-vaccines. Two epitopes, RILAVERYLKD-epitope (aa586-596) on the N-domain and ELDKWA-epitope (aa669-674) on the C-domain of gp41, were demonstrated by us and others to induce protective activity. After vaccination course, the RILAVERYLKD-dimer epitope-vaccine [C(RILAVERYLKDG)2-BSA] induced strong epitope-specific antibody response by about 1:25,600 dilution, and the ELDKWA-tetramer epitope-vaccine [C-(ELDKWAG)4-BSA] could yet induce strong antibody response to ELDKWA-epitope by 1:12,800-25,600 dilution of antisera in mice, while rgp41 subunit vaccine induced very weak antibody response to both epitopes (1:400). In rabbit experiments, the titres of ELDKWA-epitope-specific antibody induced by ELDKWA-epitope-vaccine [C-(ELDKWAG)4-BSA] reached to 1:6,400, while rgp41 subunit vaccine induced very weak antibody response to this epitope and to P1 and P2 peptides (1:400). Moreover, the ELDKWA-epitope-specific antibodies in mice and rabbit antisera induced by epitope-vaccine could very strongly interact with P2 peptide sequence-corresponding to the C-domain of gp41 (dilution by 1:25,600), and the RILAVERYLKD-epitope-specific antibodies in mice antisera induced by epitope-vaccine could also very strongly interact with P1 peptide sequence-corresponding to the N-domain of gp41 (dilution by 1:102,400). All these results provided experimental evidence that epitope-vaccine may be a new general strategy to induce high levels of neutralizing antibodies against HIV-1 or other viruses.

[A comparative study between clinical response and pathologic changes to preoperative chemotherapy in non-small cell lung cancer]

OBJECTIVE

To study the clinical response to preoperative chemotherapy in relation to pathologic changes in non-small cell lung cancer (NSCLC).

METHODS

Forty-six stage I-IIIa NSCLC patients were given 1-2 courses of preoperative chemotherapy with mitomycin C (MMC) 6 mg.M-2 on day 1, vindesine (VDS) 2.5-3 mg.M-2 on day 1, day 8 and/or day 15, and cisplatin (DDP) 90 mg.M-2 on day 1 (MVP regimen). 'The treatment was recycled every 28 days. Clinical response was assessed according to WHO criteria. Pathologic changes of the resected tumor were categorized to 3 grades. Grade I: No tumor under gross and microscopic observation. Grade II: Grossly no tumor present but residual tumor cells under microscopic observation. Grade III: Tumor reduced in size with clear margins; marked tumor cells degeneration and necrosis accompanied with fibrosis. Grade IV: Active proliferation of tumor cells with invasion. Grade I-II was considered to be chemotherapeutically effective.

RESULTS

(1) The clinical response rate was higher in patients who had received 2 courses than those received 1 course of treatment. More patients treated with 2 courses had their pathologic changes in Grade I-II than those treated with 1 course of chemotherapy but the response rate was not fully consistent with pathologic grading. (2) Pathologic grading significantly correlated with the extent of tumor involvement but not with the lymph node status. (3) Efficacy of chemotherapy should be evaluated jointly by the clinical response and grading of pathologic changes. (4) Chemotherapy with MVP regimen did not elicit severe toxic side effect. Nor did it lead to operative morbidity, operative mortality and a delay in postoperative recovery.

CONCLUSION

Preoperative chemotherapy with MVP regimen is effective in the treatment of NSCLC in stage I-IIIa.

Redox-dependent DNA binding of the purified androgen receptor: evidence for disulfide-linked androgen receptor dimers

Full-length histidine-tagged, dihydrotestosterone-bound human androgen receptor (AR) was purified to homogeneity by affinity and gel-filtration chromatography for antibody production and analysis of AR dimerization and DNA binding properties. A monoclonal antibody was raised that recognized human and rat AR epitope (360)ArgAspTyrTyrAsnPheProLeuAla(368) in the NH(2)-terminal domain and slowed migration of AR-DNA complexes in mobility shift assays. AR binding to androgen response element DNA had a K(d) of 2.0 nM and a Hill coefficient of 2.1, indicating high-affinity, cooperative binding. AR solution dimerization was detected only at >/=0.2 microM AR, and DNA binding increased dimerization up to 30-fold. Slow- and fast-migrating AR-DNA complexes were detected under different reducing conditions that differed 5-fold in their dissociation rates from DNA. Treatment with the sulfhydryl oxidizing reagent diamide formed the faster migrating, slower dissociating complex, indicating it represents disulfide-linked AR dimers bound to DNA. The results indicate that high concentrations of purified AR are required for solution dimerization and that cooperative DNA binding stabilizes two dimer forms that differ in redox state.

[Studies on flavonoids from Aquilegia oxysepala Trautv. et Mey]

OBJECTIVE

To study the chemical constituents in Aquilegia oxysepala.

METHOD

Various chromatographic techniques were used to separate and purify the constituents. The structures were determined by spectral analysis and chemical evidence.

RESULT

Five flavonoids were isolated from the plant and identified as genkwanin, apigenin, luteonlin, swertisin and tilianin.

CONCLUSION

All these compounds were isolated from the plant for the first time.

[Studies on chemical constituents of Thalictrum atriplex Finet et Gagnep]

OBJECTIVE

To study the chemical constituents in the aerial part of Thalictrum atriplex.

METHOD

Chromatography and spectral analysis were used to isolate and elucidate the constituents.

RESULT

Six compounds were isolated from the aerial part of Thalictrum atriplex, and elucidated as protocatechuic acid, caffeic acid, p-coumaric acid, kaempferol, beta-sitosterol and N-methylcorydaldine.

CONCLUSION

They are all isolated from the plant for the first time.

Fine-resolution mapping by haplotype evaluation: the examples of PFIC1 and BRIC

Loci for two inherited liver diseases, benign recurrent intrahepatic cholestasis (BRIC) and progressive familial intrahepatic cholestasis type 1 (PFIC1), have previously been mapped to 18q21 by a search for shared haplotypes in patients in two isolated populations. This paper describes the use of further haplotype evaluation with a larger sample of patients for both disorders, drawn from several different populations. Our assessment places both loci in the same interval of less than 1 cM and has led to the discovery of the PFIC1/BRIC gene, FIC1; this discovery permits retrospective examination of the general utility of haplotype evaluation and highlights possible caveats regarding this method of genetic mapping.

The RET/PTC3 oncogene: metastatic solid-type papillary carcinomas in murine thyroids

Our research goal is to better understand the mechanisms controlling the initiation and progression of thyroid diseases. One such disease, papillary thyroid carcinoma (PTC), is the leading endocrine malignancy in the United States. Recently, a family of related fusion proteins, RET/PTC1-5, has been implicated in the early stages of PTC. Although all five members of this family have the c-RET proto-oncogene kinase domain in their COOH terminus, little is known about how these genes alter follicular cell biology. Consequently, to answer questions related to the mechanism of the RET/PTC fusion protein action, we have devised a molecular genetic strategy to study PTC using a mouse model of thyroid disease. A new member of this fusion oncogene family, RET/PTC3, which has been implicated in more cases of solid tumor carcinoma (79%) than PTC1 or PTC2 and predominates (80%) in radiation-induced thyroid cancer of children, was investigated in our study. We have generated transgenic mice expressing human RET/PTC3 exclusively in the thyroid. These mice develop thyroid hyperplasia, solid tumor variants of papillary carcinoma and metastatic cancer. This new transgenic line will be useful in deciphering the molecular and biological mechanisms that cause PTC and histological variations in humans.

[Value of pulmonary diffusion capacity in predicting the short-term prognosis after lung resection in lung cancer patients.]

BACKGROUND

To determine the relationship between pulmonary diffusion capacity (DLCO) and the short-term prognosis after lung resection in patients with lung cancer.

METHODS

A retrospective analysis of 413 consecutive patients with lung cancer who underwent lung resection was performed. Among them , 27 had low DLCO before operation (DLCO < 60 %predicted for total pneumonectomy or bilobectomy , < 50 %predicted for lobectomy) , as a low DLCO (LDLCO) group ,and other 386 patients as a control group.

RESULTS

There were more patients with chronic bronchitis , history of heavy smoking and underwent chemotherapy or radiotherapy preoperatively in LDLCO group than those in control group. The hospital mortality rates within 30 days after lung resection were no significant difference between the two groups ( P > 0. 05) ,whereas incidence of respiratory complications in LDLCO group was higher than that in control group ( P < 0. 05) .

CONCLUSIONS

A reduction in DLCO before operation can remarkably increase respiratory complications after pulmonary resection. DLCO is one of important predictors of risk for lung resection.

Non-surgical therapy for patients with advanced non-small cell lung cancer

Advanced non-small cell lung cancer (NSCLC) denotes those of TNM stage III and IV. NSCLC has its specific characteristics in respect of oncological behaviour, molecular biology, sensitivity to chemotherapy (CT) and radiotherapy (RT), and requires different therapeutic strategies in comparison with small cell lung cancer. The therapies include: (1) surgery in combination with new effective drugs is resulted in improved RR from 15% a decade ago to 40-60% today. Cisplatin (C-DDP) is the most attractive drug in the treatment of NSCLC, in lengthening the life-span of Stage IV NSCLC patients and as an indispensable sensitizer in RT. Taxinol, Gemcitabine (GEM), Navelbine (NVB), Edatrexate (ETX), CPT-11 and high dose Epirubicin (EPI HD) are recommended as new effective drugs. Response rates recently reported for the combination CT with the drugs mentioned above for NSCLC are from 30-65%, and with 8-42 weeks of MST. Induction or neoadjuvant therapies for advanced NSCLC, with 40-69% of RR, 25-29% of complete resection rate, 8-34% of CR and 17-45% of one year SR are reviewed. Eight random studies comparing MST between CT with C-DDP and best supportive care for NSCLC are statistically significant. (2) RT for Stage III NSCLC with 2 year and 5 year survivals of 20 and 5% respectively. Although such outcome is hardly acceptable, RT sensitizer, modified RT techniques and chemoradiotherapy (CRT) are imperative to improve the effect of RT in advanced NSCLC. Clinical literature suggest that CRT is better than RT, though without marked difference. Further studies and sufficient follow-up are necessary to judge the efficacy in terms of long-term survival and toxic reaction. (3) Biological therapy: gene therapy of NSCLC is still in the experimental and developmental stage. Of biological response modifier (BRM), alpha IFN in 11 cases of NSCLC with RR of 9% and MST of 14 months, IL-2 and LAK cell treatment in 11 cases with RR of 9% and MST of 18 months are reported. Instillation of BRM such as IL-2 or alpha-IFN into the pleura after drainage of cancerous effusion has been reported as the most effective for those whose RR is of 80-90% and the clinical response time is fairly long. Hematological cytokine as a protective adjuvant therapy against CT/RT toxicity makes high dose of CT possible and raises the response and patient tolerance. In multimodality therapy, it plays an important role to reduce post CT infection and septicemia.

[Allele-specific chromosome 3p25 deletion detected by PCR-LOH analysis in non-small cell lung cancer.]

BACKGROUND

To ascertain whether the loss of heterozygosity (LOH) of allele on chromosome 3p25 region is associated with non-small cell lung cancer (NSCLC) .

METHODS

3p25 LOH was analysed in patients with NSCLC by polymerase chain reaction-based assays for dinucleatide repeat polymorphisms.

RESULTS

Eighty out of 158 (50. 6 %) cancer tissues of NSCLC were found to have 3p25 LOH , but no 3p25 LOH was observed in 5 normal fetal lung tissues and 4 tissues of the benign lung neoplasms. The deletion was detected in 62.0% of adenocarcinoma and 43.2% of the squamous carcinoma , indicating that the former was significantly higher than the latter ( P < 0. 05) . Loss frequences for TNM stages were further observed in 52.2% , 45.0% and 52.8% of the cases for stage I, II and III respectively , and these data showed no significant relationship between the loss frequence and TNM staging of NSCLC ( P > 0. 05) .

CONCLUSIONS

Above findings display that 3p25 LOH appear to be a common structural alteration occurred in NSCLC and there may be suppressor genes relevant to the carcinogenesis of the lung in 3p25 region.

A gene encoding a P-type ATPase mutated in two forms of hereditary cholestasis

Cholestasis, or impaired bile flow, is an important but poorly understood manifestation of liver disease. Two clinically distinct forms of inherited cholestasis, benign recurrent intrahepatic cholestasis (BRIC) and progressive familial intrahepatic cholestasis type 1 (PFIC1), were previously mapped to 18q21. Haplotype analysis narrowed the candidate region for both diseases to the same interval of less than 1 cM, in which we identified a gene mutated in BRIC and PFIC1 patients. This gene (called FIC1) is the first identified human member of a recently described subfamily of P-type ATPases; ATP-dependent aminophospholipid transport is the previously described function of members of this subfamily. FIC1 is expressed in several epithelial tissues and, surprisingly, more strongly in small intestine than in liver. Its protein product is likely to play an essential role in enterohepatic circulation of bile acids; further characterization of FIC1 will facilitate understanding of normal bile formation and cholestasis.

[The clinical significance of biological characters on non-small cell lung cancer]

OBJECTIVE

To study the biological characters of 137 cases of surgically treated NSCLC and their correlation with stages, types and survival rates.

METHOD

Electronmicroscopy, immunohistochemistry and FCM were employed in this prospective, randomized study. K-P curve, COX univariance and multivariance were used for statistic analysis.

RESULTS

(1) Electronmicroscopy showed that 40% of squamous cancer and 40% of adenocarcinoma diagnosed microscopically were mixed type. (2) The positive rate of p53 expression increased in advanced stage of NSCLC, and the survival rate was lower in cases with positive p53 expression. (3) A higher survival rate was seen in cases with positive Hras expression. (4) Lower survival rates were seen in cases with abnormal DI and PI. (5) Miscellaneous: expression rates of c-erbB2 and PCNA were related to adenocarcinoma and mixed type electronmicroscopically confirmed respectively.

CONCLUSION

From this study p53, Hras, DI, PI, c-erbB2 and PCNA were found related to stages, types and survival rates, respectively.

The developmental and circadian variation of melatonin receptors in the chicken spinal cord

The developmental variation of 2-[125I]iodomelatonin binding sites in membrane preparations of the chicken spinal cords was investigated. In 19-day-old embryos, the maximum number of binding sites (Bmax) was the highest during the development. With the increase in age posthatch, the Bmax decreased gradually and significantly from 1-day-old to 4-month-old chickens. However, there were no significant changes in equilibrium dissociation constant (Kd) among all age-groups studied. To study the circadian variation, the 2-[125I]iodomelatonin binding sites in the spinal cords of 3-week-old chickens were determined at 4-hour intervals throughout a 24-hour period under a 12-hour light/12-hour dark cycle. There was a diurnal rhythm in both Bmax and Kd of [125I]iodomelatonin binding sites in which Bmax decreased and Kd increased in the dark period. The characteristics of developmental and circadian variation of melatonin receptors in the chicken spinal cord suggest that melatonin may exert a direct action on spinal cord functions and that it plays a more important role in the young animal.

Localization and characterization of melatonin receptors in the rabbit spinal cord

Melatonin receptors in the rabbit spinal cord were studied. Using in vitro quantitative autoradiography we have localized and characterized 2-[125I]iodomelatonin ([125I]MEL) binding sites in the central gray substance (lamina X) of the rabbit spinal cord. Saturation study revealed a single class of high affinity binding sites in the central gray substance with an equilibrium dissociation constant (Kd) of 38.8 +/- 5.25 pM and a maximum number of binding sites of 5.69 +/- 0.84 fmol/mg protein in the mid-light period. These [125I]MEL binding sites were highly specific for melatonin. Coincubation with 10 microM or 50 microM guanosine 5'-O-(3-thiotriphosphate) produced a significant change in Kd. These results suggest that melatonin receptors in the rabbit spinal cord are coupled to a guanine-nucleotide-binding protein (G-protein). Our studies suggest that melatonin exerts a direct action on the rabbit spinal cord.

[Multimodality therapy of late stage lung cancer]

A prospective randomized study of 80 cases of stage III lung cancer treated with different multimodality therapy was carried out. Life table and Kaplan-Meir curve were employed to calculate survival rate. Log rank-multivariate analysis and time t test were used to evaluate statistical values of the 80 cases, 40 SCLC were randomly treated with either chemotherapy (CT)-surgery-CT or CT-radiotherapy (RT)-CT. The year survival rates were better in the group treated with CT-surgery-CT, a statistical difference was observed in 2yr survival rate (P < 0.05). Thus, surgical resection for SCLC was better than RT after CT. The remaining 40 cases of NSCLC were randomly treated with either CT-RT-CT or RT-CT. Multivariate analysis showed a better statistical meaning in the 20 cases treated with CT-RT-CT than the other group, their 1, 2 year survival rates were 27%, 40% and 22%, 15%, respectively. Thus preradiative CT was beneficial for survival.

Some features of lung cancer in China

In recent years, the high incidence of lung cancer has made the disease one of the principal causes of death in human beings. The significance of cancer morbidity in China, which holds 1/4 of the population on the globe, is naturally an issue of concern to the health organizations all over the world. As the incidence of cancer tends to rise with every passing day, China is likely to follow the track of the industrialized countries, and lung cancer will top the list of incidence and cause of death of all cancers in urban areas. Presented in this paper are the epidemiology, pathogenesis, diagnosis and treatment of lung cancer in China, which is intended to promote mutual understanding and to facilitate cooperation and research, so as to upgrade the effective control of lung cancer.

Substitution of Glu841 by lysine in the carbamate domain of carbamyl phosphate synthetase alters the catalytic properties of the glutaminase subunit

In previous studies a Glu841-->Lys replacement in the carbamate phosphorylating domain located in the COOH half of the synthetase subunit of Escherichia coli carbamyl phosphate synthetase was shown to reduce overall synthesis of carbamyl phosphate by 4 orders of magnitude with either glutamine or NH3 as nitrogen donor (Guillou et al., 1992). In the present study, the mutant enzyme has been further analyzed for its glutamine hydrolytic activity. The glutaminase activity of the mutant enzyme has the following properties. (1) In the absence of other substrates the turnover number is only marginally different from that of the wild-type complex. (2) The Km for glutamine is 60 times higher than in wild-type complex and three times higher than in the separated glutaminase subunit. (3) In the present study wild-type carbamyl phosphate synthetase has been shown to catalyze glutamine hydrolysis by a mechanism involving an enzyme-bound acyl ester intermediate (gamma-glutamyl thioester). This intermediate is formed and is hydrolyzed with rates consistent with overall glutamine hydrolysis. At physiological concentrations of glutamine (1.2 mM), the steady-state concentration of gamma-glutamyl thioester is 0.3 mol/mol of wild-type enzyme. Under the same conditions, only 0.02 mol of thioester is measured in the mutant enzyme. Maximal accumulation of this covalent intermediate by the mutant enzyme required 10 times higher concentrations of free glutamine. (4) The rate of reaction with 2-amino-4-oxo-5-chloropentanoate, a glutamine analog known to specifically alkylate an active site cysteine residue, is 2 orders of magnitude slower in the mutant.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of antihypertensive therapy on the kidney in patients with diabetes: a meta-regression analysis

OBJECTIVE

To assess the relative effect of different antihypertensive agents on proteinuria and renal function in patients with diabetes.

DATA SOURCES

We used MEDLINE and bibliographies in recent articles to identify studies of the effects of antihypertensive agents on renal function in patients with diabetes.

STUDY SELECTION

We selected 100 controlled and uncontrolled studies that provided data on renal function, proteinuria, or both, before and after treatment with an antihypertensive agent.

DATA EXTRACTION

Data on blood pressure, renal function, proteinuria, patient characteristics (for example, age, sex, and type of diabetes), and study design (for example, random allocation and the use of a placebo) were extracted from selected studies.

DATA SYNTHESIS

Multiple linear regression analysis indicated that angiotensin-converting enzyme (ACE) inhibitors decreased proteinuria independent of changes in blood pressure, treatment duration, and the type of diabetes or stage of nephropathy, as well as study design (P < 0.0001). Reductions in proteinuria from other antihypertensive agents could be entirely explained by changes in blood pressure. Blood pressure reduction in itself was associated with a relative increase in glomerular filtration rate (regression coefficient [+/- SE], 3.70 +/- .92 mL/min for each reduction of 10 mm Hg in mean arterial pressure; P = 0.0002); however, compared with other agents, ACE inhibitors had an additional favorable effect on glomerular filtration rate that was independent of blood pressure changes (3.41 +/- 1.71 mL/min; P = 0.05).

CONCLUSION

Angiotensin-converting enzyme inhibitors can decrease proteinuria and preserve glomerular filtration rate in patients with diabetes. These effects occur independent of changes in systemic blood pressure.

Localization of brain nitric oxide synthase (NOS) to human chromosome 12

Recent research has shown that nitric oxide is a novel neuronal second messenger and transmitter that may be involved in neuronal cell death and damage in neurological illness. To map the chromosomal localization of this important brain enzyme, a rat cDNA probe was prepared by RNA PCR from rat cerebellum RNA. This rat cDNA was used to isolate a human nitric oxide synthase (NOS) cDNA from a human cerebellum cDNA library. The human cDNA clone containing 1.2 kb of brain NOS cDNA was hybridized to Southern blots containing DNAs obtained from human-rodent hybrid cell line panels using EcoRI and HindIII digestion to ascertain the location of the human NOS gene. These data showed that the human brain nitric oxide synthase mapped within 12q14-qter on human chromosome 12.