精浆催乳素浓度与精子计数、活动率的关系

对107例男性进行精液分析并测定其精浆催乳素(PRL)浓度,精子活动率和精子密度正常男性的精浆PRL为11.53±5.36ng/ml,与精子活动率正常而少精子的男性相比(13.06±4.62ng/ml),两组间无显著性差异(t=0.91,t>0.2);而精子密度正常、正常精子活率组和低活率组相比,低活率组的精浆PRL水平(17.24 ±5.86ng/ml)明显增高(t=4.15,P<0.001).相关分析表明精浆PRL与精子活动率呈负相关(r=-0.38,P<0.001);与精子密度亦呈负相关(r=-0.37,P<0.001).49例受试者取精液前抽血测定血清PRL水平,精浆PRL水平与血清PRL无关(r=0.204,P>0.1).     

少弱精子症与精浆附性腺标志物的相关性分析

目的分析少弱精子症患者精液参数与精浆附性腺标志物的相关性,探讨附性腺功能对男性生育力的影响。方法采用精液常规、精子形态、精浆附性腺标志物分析方法,检测正常供精者和门诊就诊的少弱精子症患者的精液相关指标。结果少弱精子症组正常形态精子百分数、精子穿透功能、精浆中性α-糖苷酶显著低于正常对照组。相关分析结果显示,少弱精子症患者组,精液量与精子活动率呈负相关(r=-0.415,P<0.05),精子数与形态呈正相关(r=0.393,P<0.05)。结论少弱精子症患者同时存在不同程度的附睾功能障碍,精子功能下降,精子畸形率显著升高,睾丸生精功能越低下,精子畸形发生率越高。     

miR-34b在男性不育患者精浆中的表达及其临床意义

目的研究精浆游离miR-34b在体外不同条件下的稳定性及其与男性不育症患者精液参数的关系。方法选取男性不育症患者80例和同期因女方因素不孕前来检查的生育力评估正常的健康男性20例为正常对照组,将8例正常的精液标本分别在室温和-80℃下放置,以不同时间点检测精浆miR-34b的稳定性。采用实时荧光定量PCR检测精浆游离miR-34b的相对含量,精子浓度及精子活力用计算机辅助精子分析系统,精子存活率采用低盐膨胀实验检测,正常精子形态百分率采用Diff-Quick染色法。分析男性不育症组和正常对照组精液参数及miR-34b表达量的差异,对精浆游离rniR-34b在男性不育组精浆中的诊断价值进行ROC曲线分析,并采用Pearson直线相关分析miR-34b与男性不育组精液各参数的相关性。结果精浆游离miR-34b在室温和低温下不同时间点表达量无明显变化(F=0.13,P=0.97;F=0.35,P=0.84)。与正常组比较发现,男性不育组精浆游离miR-34b表达下调(P0.01)。两组的精子浓度、精子存活率、前向运动精子百分率(PR)和正常形态精子百分率均有差异(P0.01)。ROC曲线显示miR-34b能够较好的区分不育组与健康对照组,曲线下面积分比(AUC)为0.85(0.79-0.95,95%)。Pearson直线相关分析发现男性不育患者精浆miR-34b表达量与精子密度(r=0.28,P0.05)、精子活率(r=0.56,P0.01)、前向运动精子百分率(r=0.41,P0.01)正相关,与精子形态无相关性(r=O.15,P0.05)。结论精浆miR-34b在室温下稳定,并能在-80℃条件下长期保存,在男性不育患者精浆中表达下调,并与精子浓度、精子存活率、前向运动精子百分率呈正相关,与精子形态无相关性。     

硒与精液质量的相关性及硒对少弱精子患者精液质量影响

目的研究恩施土家族苗族自治州-富硒地区男性血清、精浆硒水平与健康育龄期男性和少弱精子症男性患者精液质量之间的关系。方法选择2018年来我院生殖医学中心就诊的456例富硒地区患者,其中200名患者精液参数正常,256名患者精液参数异常,采用原子吸收光谱检测血清和精浆中硒浓度,并分析血清、精浆中硒浓度与精液质量之间的相关性;少弱精子症患者进行常规治疗(生精胶囊及维生素E胶囊)以及常规治疗+硒元素补充治疗后,比较两种不同方案治疗后精液质量之间的差异。结果精液正常组与精液异常组患者年龄、精液体积无明显差异,而正常组精子浓度(70.03±34.42)、活力(51.12±7.21)和形态(11.75±3.74)明显高于少弱精子症组精子浓度(11.12±7.11)、活力(17.73±11.78)和形态(3.12±1.63),差异均具有显著性(P0.001);正常组的血清硒(104.22±22.82)和精浆硒(65.35±22.82)均高于少弱精子症组血清硒(74.01±20.86)和精浆硒(49.31±17.17),均具有统计学意义(P0.001)。同时,无论是正常组患者,还是少弱精子症组患者血清硒(r=0.680, P0.01)与精浆硒(r=0.651, P0.01)均呈明显正相关,有统计学差异;血清硒与少弱精子症组精子浓度(r=0.499, P0.01)、活力(r=0.360, P0.05)均呈正相关,精浆硒与少弱精子症组精子浓度(r=0.391, P0.05)、活力(r=0.353, P0.05)也呈正相关,有统计学意义;将少弱精子症组随机分为常规治疗组及常规治疗+硒元素补充治疗组,两组患者在精子浓度、活力、形态及硒浓度均无显著差异;进行常规治疗后,精子浓度(12.57±8.76)、活力(17.06±14.01)较治疗前精子浓度(10.72±6.99)和活力(15.80±11.87)有一定程度提高,均具有统计学意义(P0.05);常规治疗+硒元素补充治疗后,精子浓度(12.99±8.19)、活力(21.70±12.54)及形态(3.26±1.48)较常规治疗+硒元素补充前精子浓度(9.60±7.14, p0.001)、活力(17.62±12.27, P0.01)和形态(2.61±1.58, P0.05)明显提高,均具有统计学意义,血清硒(88.44±24.86)及精浆硒(55.06±19.32)浓度较常规治疗+硒元素补充前血清硒(79.39±22.93,P0.01)及精浆硒(47.08±19.17,P0.001)有明显升高,差异具有显著性。结论血清硒与精浆硒水平在男性不育症患者中普遍较正常患者偏低,硒元素直接影响精液质量,对少弱精子症患者行补硒治疗可明显提高精液质量。     

不育男性精浆总抗氧化能力与精子运动功能的关系

目的:研究不育男性精浆总抗氧化能力(TAC)与精子运动能力和方式之间的关系,探讨精浆TAC水平在男性生育中的临床意义。方法:113例精子密度正常的不育男性,28例正常生育男性作为对照组。精液于37℃液化后采用计算机辅助精液分析(CASA)系统进行精液常规分析,采用比色法进行精浆TAC分析。结果:正常生育组精浆TAC为(19.82±6.33)U,不育男性精子密度正常组精浆TAC为(14.37±8.45)U,不育男性精子密度正常组与正常生育组比较存在显著性差异(P<0.01)。精浆TAC与a级精子百分率(r=0.208,P<0.05)和(a+b)级精子百分率(r=0.231,P<0.05)呈显著正相关,精浆TAC与精子运动参数中的前向性(r=0.200,P<0.05)、直线性(r=0.208,P<0.05)、曲线速度(r=0.189,P<0.05)、直线速度(r=0.210,P<0.05)、平均移动速度(r=0.215,P<0.05)及鞭打频率(r=-0.248,P<0.01)之间有显著的相关性,其中前向性、直线性、直线速度、曲线速度、平均移动速度与TAC呈正相关(P<0.05),而鞭打频率与TAC呈负相关(P<0.01)。精浆TAC与摆动性、侧摆幅度、平均移动角度之间无显著相关。结论:精浆中TAC水平与精子运动能力和运动方式密切相关,适宜的精浆TAC为精子运动提供了良好的外部环境,精浆中过低的TAC水平与精子运动能力下降和运动方式改变有关,可能是引起男性不育的病因之一。精浆中TAC分析可为探讨男性不育的发病机制以及临床用药提供依据。     

精索静脉曲张不育患者氧化应激水平和精子DNA完整性及精液参数的相关性分析

目的:分析精索静脉曲张(VC)不育患者氧化应激同DNA完整性及精液参数的关系。方法:采用前瞻性研究,纳入98例患者,根据活性氧水平(ROS)将VC不育患者分为ROS低水平组(54例)及高水平组(44例),分析两组精子DNA碎片指数(DFI)、精子活力、形态等参数的差异,并分析它们之间的相关性。结果:ROS高水平组DFI显著高于ROS低水平组[(34.49±6.05)%vs(27.38±8.10)%,P=0.039]。与ROS低水平组比较,ROS高水平组精子活力[(25.21±18.22)%vs(36.16±22.83)%,P=0.017]、前向运动精子百分率[(16.34±9.22)%vs(23.34±11.53)%,P=0.041]、曲线速率[(20.62±4.38)%vs(27.03±6.21)%,P=0.013]及直线性率[(18.30±7.93)%vs(29.75±8.24)%,P=0.024]均显著降低,而精液白细胞数显著升高[(0.86±0.41)×106/ml vs(0.65±0.15)×106/ml,P=0.022]。Spearman相关性分析表明ROS水平同精液白细胞数(r=0.41,P0.01)及DFI(r=0.21,P=0.006)呈显著正相关,同曲线速率(r=-0.24,P=0.017)、直线性率(r=-0.24,P=0.021)、精子活力(r=-0.31,P=0.002)及前向运动精子百分率(r=-0.41,P=0.012)呈显著负相关。DFI同精子活力(r=-0.29,P0.01)、前向运动精子百分率(r=-0.34,P0.01)呈显著负相关。结论:精浆ROS水平同VC不育患者DFI显著正相关。氧化应激及DNA完整性可影响患者的精子参数。     

不育男性抗苗勒管激素与生殖激素及精液质量参数关系的研究

目的探讨男性不育患者精浆和血清抗苗勒管激素(AMH)与血清生殖激素及精液参数之间关系。方法选取2018年9~12月于我院生殖中心就诊的男性不育患者107例,按照《世界卫生组织人类精液检查与处理实验室手册(第五版)》操作规范检测精液体积、精子浓度、前向运动精子(PR)百分比、精子顶体酶、精子DNA完整性、正常形态精子率,根据精液参数分为4组:少精子症组(n=15)、弱精子症组(n=26)、少弱精子组(n=31)、正常精子组(n=35),比较各组患者精浆和血清AMH及血清FSH、LH、催乳素(PRL)、T、E 2之间的差异,并对精浆和血清AMH与生殖激素及精液参数的相关性进行统计分析。结果弱精子症组血清AMH水平高于其他3组,但各组间差异无统计学意义(P>0.05);正常精子组精浆AMH水平[中位数(四分位距)]为1.28(7.71)ng/ml,显著高于少精子症组[0.11(1.26)ng/ml]和少弱精子组[0.16(2.15)ng/ml](P<0.05)。相关性分析显示,血清AMH与生殖激素及精液参数不存在相关(P>0.05);精浆AMH与血清FSH、LH呈负相关(P<0.05),与血清T呈正相关(P<0.05);精浆AMH与精子总数、精子浓度、PR%呈正相关(P<0.05),与其他精液参数不相关(P>0.05)。结论不育男性精浆AMH与血清生殖激素及精子浓度、活力具有一定的相关性,一定程度上反映睾丸生精功能,对男性不育的诊断和治疗有一定的参考作用。     

生育与不育男性精浆总抗氧化能力分析

目的:分析生育与不育男性精浆中总抗氧化能力(TAC)及其在男性生育中意义。方法:225例男性不育患者分为6组,分别为:梗阻性无精子症组(n=10),非梗阻性无精子症组(n=42),少精子症组(n=20),弱精子症组(n=78),少弱精子症组(n=57),以及正常精子症组(n=18)。28例正常生育男性作为对照(生育组)。分别采用计算机辅助精液分析(CASA)系统进行精液参数分析,采用比色法检测精浆TAC水平。结果:生育组男性精浆TAC为(19.82±6.33)U,梗阻性无精子症组(1.71±1.33)U,非梗阻性无精子症组(12.73±9.44)U,少精子症组(10.85±6.64)U,弱精子症组(13.88±8.24)U,少弱精子症组(11.20±7.02)U,正常精子症组(18.07±8.73)U;与生育组精浆TAC[(19.82±6.33)U]相比,在各不育症组中,除正常精子症组精浆TAC与生育组差异无显著性外,其余各组均显著低于生育组(P<0.01)。精浆TAC与精子密度(r=0.182,P<0.05)和a级精子(r=0.150,P<0.05)呈显著正相关。结论:精浆中TAC水平与男性不育密切相关,精浆中过低的TAC水平可能是引起男性不育的病因之一。     

特发性弱精子症患者血清及精浆瘦素水平与精子活动力的关系

目的 通过研究特发性弱精子症(idiopathic asthenospermia,IAS)患者以及精液参数正常人群的血清、精浆瘦素,探讨瘦素与精子运动能力的关系.方法 IAS患者54例及精液参数正常者30例作为对照.常规CASA精液分析,放射免疫法检测血清及精浆瘦素.结果 排除体重指数差异的影响,(IAS患者与精液参数正常者体重指数比较差异无统计学意义,P>0.05),IAS患者血清瘦素水平与正常对照差异无统计学意义(P>0.05),而IAS患者精浆瘦素显著高于正常对照(P<0.05);精子活动率及精子活力与血清瘦素水平之间均无显著相关性(r=-0.213,P=0.249及r=-0.167,P=0.154),IAS患者的精子活动率及活力与精浆瘦素水平显著负相关(r=-0.31,P=0.034及r=-0.47,P=0.025).结论 IAS患者精浆瘦素水平显著增高,可能对精子运动能力有调控作用.     

精浆游离L-肉毒碱水平及其与精子密度、活动率及活力的相关性研究

目的:研究正常生育及不育男性精浆中游离L-肉毒碱水平差异及其与精子密度、活动率(a+b+c级精子百分率)及活力(a+b级精子百分率)之间的相关性,探讨精浆中游离L-肉毒碱水平对男性生育力的影响及其在不育症检查和治疗中的作用。方法:分别采用高效液相色谱法和计算机辅助精液分析系统,测定了230例不育症患者(精子密度正常117例,少精子症81例,无精子症32例)和30例正常生育男性精浆中游离L-肉毒碱水平及精子密度、活动率、活力等参数。根据检查结果对不育症患者分组后,以SPSS12.0软件包进行统计学分析,比较各组间游离L-肉毒碱水平的差异以及游离L-肉毒碱水平与精子密度、活动率、活力之间的相关性。结果:正常生育组精浆游离L-肉毒碱水平明显高于不育组(P<0.01)。精液中精子密度越低、活力越弱,这种差异性越显著。相关性分析结果显示,精浆游离L-肉毒碱水平与精子密度呈显著正相关关系(r=0.521,P<0.01),与精子活动率和活力之间也具有正相关关系(r=0.319,P<0.01;r=0.251,P<0.01)。结论:精浆L-肉毒碱水平与精子密度、活动率和活力之间密切相关,其含量测定作为一项有用的生化指标,可为男性不育症检查及临床诊治和进行有关男性生殖功能机制研究提供参考。     

Effect of smoking on seminal plasma ascorbic acid in infertile and fertile males

This work aimed to assess the relationship of seminal ascorbic acid levels with smoking in infertile males. One hundred and seventy men were divided into four groups: nonobstructive azoospermia [NOA: smokers (n = 20), nonsmokers (n = 20)]; oligoasthenozoospermia [smokers (n = 30), nonsmokers (n = 20)]; asthenozoospermia [smokers (n = 20), nonsmokers (n = 20)] and normozoospermic fertile men [smokers (n = 20), nonsmokers (n = 20)]. The patients underwent medical history, clinical examination, conventional semen analysis and estimation of ascorbic acid in the seminal plasma calorimetrically. There was a significant decrease in the mean seminal plasma ascorbic acid levels in smokers versus nonsmokers in all groups (mean +/- SD; 6.03 +/- 2.18 versus 6.62 +/- 1.29, 7.81 +/- 1.98 versus 9.44 +/- 2.15, 8.09 +/- 1.98 versus 9.95 +/- 2.03, 11.32 +/- 2.15 versus 12.98 +/- 12.19 mg dl(-1) respectively). Fertile subjects, smokers or not, demonstrated significant higher seminal ascorbic acid levels than any infertile group. Seminal plasma ascorbic acid in smokers and nonsmokers was correlated significantly with sperm concentration (r = 0.59, 0.60, P < 0.001), sperm motility (r = 0.65, 0.55, P < 0.001) and negatively with sperm abnormal forms per cent (r = -0.53, -0.50, P < 0.001). Nonsignificant correlations were elicited with semen volume (r = 0.2, 0.09) or liquefaction time (r = 0.03, 0.06). It is concluded that seminal plasma ascorbic acid decreased significantly in smokers and infertile men versus nonsmokers and fertile men, and is significantly correlated with the main sperm parameters: count, motility and normal morphology. Also, cigarette smoking is associated with reduced semen main parameters that could worsen the male fertilizing potential, especially in borderline cases.     

Assessment of seminal granulysin in infertile men with varicocele

Varicocele has a common association with male infertility, but its exact role is still debated. Apoptosis has been suggested as one of the mechanisms of varicocele‐associated infertility. Granulysin is a molecule that plays a role in apoptosis with no previous study about its role in male infertility. This case‐controlled study aimed to assess seminal plasma granulysin level in infertile patients with varicocele. This study involved 90 men that were allocated into fertile normozoospermic men (n = 20), infertile men without varicocele (n = 30) and infertile men with varicocele (n = 40). These men were subjected to history taking, clinical examination, semen analysis and estimation of seminal granulysin. In general, seminal granulysin level was significantly elevated in infertile men compared with fertile men. Infertile men with varicocele showed significantly higher seminal granulysin compared with infertile men without varicocele, in bilateral varicocele cases and in grade III varicocele. Seminal granulysin level was negatively correlated with sperm concentration, sperm motility, sperm normal forms percentage and testicular volumes. It is concluded that increased seminal granulysin has a negative impact on spermatogenesis in infertile men in general and in infertile men associated with varicocele in particular.     

Assessment of seminal plasma laminin in fertile and infertile men

Aim： To assess laminin levels in the seminal plasma of infertile and fertile men, and to analyze the correlation of laminin levels with sperm count, age, sperm motility and semen volume. Methods： One hundred and twenty-five recruited men were equally divided into five groups according to their sperm concentration and clinical examination： fertile normozoospermia, oligoasthenozoospermia, non-obstructive azoospermia （NOA）, obstructive azoospermia （OA） and congenital bilateral absent vas deferens （CBAVD）. The patients＇ medical history was investigated and patients underwent clinical examination, conventional semen analysis and estimation of seminal plasma laminin by radioimmunoassay. Results： Seminal plasma laminin levels of successive groups were： 2.82 ± 0.62, 2.49 ± 0.44, 1.77 ± 0.56, 1.72 ± 0.76, 1.35 ± 0.63 U/mL, respectively. The fertile normozoospermic group showed the highest concentration compared to all infertile groups with significant differences compared to azoospermic groups （P 〈 0.05）. Testicular contribution was estimated to be approximately one-third of the seminal laminin. Seminal plasma laminin demonstrated significant correlation with sperm concentration （r = 0.460, P 〈 0.001） and nonsignificant correlation with age （r = 0.021, P = 0.940）, sperm motility percentage （r = 0.142, P = 0.615） and semen volume （r = 0.035, P = 0.087）. Conelusion： Seminal plasma laminin is derived mostly from prostatic and testicular portions and minimally from the seminal vesicle and vas deferens. Estimating seminal laminin alone is not conclusive in diagnosing different cases of male infertility.     

Comparison of zinc concentrations in blood and seminal plasma and the various sperm parameters between fertile and infertile men

The aim of the study was to examine the relationships between concentrations of zinc in blood and seminal plasma and sperm quality among infertile and fertile men. One hundred seven male (infertile group) partners of couples who were undergoing investigation for infertility with no known cause for the infertility and 103 men (fertile group) whose wives were pregnant at the time of the study were recruited. The subjects' blood and seminal plasma concentration of zinc were determined by atomic absorption spectroscopy. Except for semen volume, all the other semen parameters for the infertile men were significantly lower than those for the fertile group. The geometric means of the seminal plasma zinc concentration were significantly lower in the infertile group compared with those in the fertile group; 183.6 mg/L (range, 63-499) versus 274.6 mg/L (range, 55-420). There were no significant differences in the geometric means of the blood zinc concentration between the 2 groups. Seminal plasma zinc concentration was significantly correlated with sperm density (r = 0.341, P < .0001), motility (r = 0.253, P < .0001), and viability (r = 0.286, P < .0001). On the basis of the findings of this study and those of other reports, zinc may contribute to fertility through its positive effect on spermatogenesis.     

Seminal plasma anti-Müllerian hormone level correlates with semen parameters but does not predict success of testicular sperm extraction (TESE)

AIM: To assess seminal plasma anti-Müllerian hormone (AMH) level relationships in fertile and infertile males. METHODS: Eighty-four male cases were studied and divided into four groups: fertile normozoospermia (n = 16), oligoasthenoteratozoospermia (n = 15), obstructive azoospermia (OA) (n = 13) and non-obstructive azoospermia (NOA) (n = 40). Conventional semen analysis was done for all cases. Testicular biopsy was done with histopathology and fresh tissue examination for testicular sperm extraction (TESE) in NOA cases. NOA group was subdivided according to TESE results into unsuccessful TESE (n = 19) and successful TESE (n = 21). Seminal plasma AMH was estimated by enzyme linked immunosorbent assay (ELISA) and serum follicular stimulating hormone (FSH) was estimated in NOA cases only by radioimmunoassay (RIA). RESULTS: Mean seminal AMH was significantly higher in fertile group than in oligoasthenoteratozoospermia with significance (41.5 +/- 10.9 pmol/L vs. 30.5 +/- 10.3 pmol/L, P < 0.05). Seminal AMH was not detected in any OA patients. Seminal AMH was correlated positively with testicular volume (r = 0.329, P = 0.005), sperm count (r = 0.483, P = 0.007), sperm motility percent (r = 0.419, P = 0.021) and negatively with sperm abnormal forms percent (r = -0.413, P = 0.023). Nonsignificant correlation was evident with age (r = -0.155, P = 0.414) and plasma FSH (r = -0.014, P = 0.943). In NOA cases, seminal AMH was detectable in 23/40 cases, 14 of them were successful TESE (57.5%) and was undetectable in 17/40 cases, 10 of them were unsuccessful TESE (58.2%). CONCLUSION: Seminal plasma AMH is an absolute testicular marker being absent in all OA cases. However, seminal AMH has a poor predictability for successful testicular sperm retrieval in NOA cases.     

Effect of omega-3 polyunsaturated fatty acid supplementation on semen profile and enzymatic anti-oxidant capacity of seminal plasma in infertile men with idiopathic oligoasthenoteratospermia: a double-blind, placebo-controlled, randomised study

Effective medical treatments of infertile men with idiopathic oligoasthenoteratospermia (OAT) have yet to be determined. This study considered two major aims: (i) to measure the changes in semen parameters, omega‐3 fatty acids (FA) compositions and anti‐oxidant activity; (ii) to determine if the administration of omega‐3 FA affect semen quality in infertile men with OAT. Two hundred thirty‐eight infertile men with idiopathic OAT were randomised to eicosapentaenoic (EPA) and docosahexaenoic acids (DHA), 1.84 g per day (EPAX 5500TG; Lysaker, Norway), or placebo for 32 weeks. The semen parameters were assessed according to WHO criteria, and the EPA and DHA concentrations were determined in red blood cells (RBCs), seminal plasma and sperm cells at baseline and 32‐week treatment period. Of randomised subjects, 211 (88.7%) completed the full 32‐week randomisation period. The anti‐oxidant status of seminal plasma was also evaluated by measuring the superoxide dismutase (SOD) and catalase‐like activity. In the total group of participants, all EPA and DHA levels in RBC, and seminal plasma, were statistically significantly correlated with those in spermatozoa (both P = 0.001). A significant improvement of sperm cell total count (from 38.7 ± 8.7 ′ 10⁶ to 61.7 ± 11.2 ′ 10⁶, P = 0.001) and sperm cell concentration (from 15.6 ± 4.1 ′ 10⁶ per ml to 28.7 ± 4.4 ′ 10⁶ per ml, P = 0.001) was observed in the omega‐3 group. A significant positive correlation was found between the EPA and DHA in seminal plasma and the semen parameters. Seminal plasma EPA and DHA concentrations were positively correlated with seminal plasma SOD‐like and catalase‐like activity (both P = 0.001). In seminal plasma, both SOD‐like and catalase‐like activity were positively correlated with sperm count, sperm motility, and sperm morphology. Oligoasthenoteratospermic men with low levels of EPA and DHA may benefit from omega‐3 FA supplementation. Further studies are warranted to shed more light on this important issue.