Why can humans (and guinea pigs and dry-nosed primates and bats) not make vitamin C and are thus open to scurvy without replacement?
Many years ago, I worked on a study of guinea pigs that had been fed a diet without vitamin C and thus developed scurvy. I knew that people, like the guinea pigs, could develop scurvy without adding the vitamin to our diet. This has been known for more than a century and in the last few years we have found out why it happens to these few animals.
The inability of humans to synthesize L-ascorbic acid is known to be due to a lack of an enzyme that is required for the biosynthesis of this vitamin. The enzyme is known as L-gulono-gamma-lactone oxidase (GULO). Isolation of a cDNA for the rat enzyme resulted in a study of the basic defect underlying this deficiency at the gene level and led to isolation of a human genomic clone related to L-gulono-gamma-lactone oxidase as well as three overlapping clones covering the entire coding region of the rat L-gulono-gamma-lactone oxidase cDNA. Sequence analysis study indicated that the human L-gulono-gamma-lactone oxidase gene has accumulated a large number of mutations since it stopped being active and that it now exists as a pseudogene in the human genome.
This genetic defect has not been selected against in natural selection as we are able to consume more than enough vitamin C from our diet. It is also suggested that organisms without a functional GULO gene have a method of "recycling" the vitamin C that they obtain from their diets using red blood cells.
- Cell. 2008 Mar 21;132(6):1039-48
- Hum Gene Ther. 2008 Dec;19(12):1349-58
- Am J Clin Nutr. 1991 Dec;54(6 Suppl):1203S-1208S.
For the past few decades, many clinicians have used the change in PSA over a 1 or 2 year period to determine whether a biopsy was needed (for example when my PSA increased by more than the limit at that time, I was encouraged to have a biopsy. I did.)
There has historically been considerable uncertainty about PSA kinetics for decisions about biopsy and initial treatment. It turns out that calculation of PSA velocity and doubling time is far from straightforward. More than 20 different methods have been proposed, and many of these give quite divergent results. There is clear evidence that PSA kinetics are critical for understanding prognosis in advanced or relapsed prostate cancer. However, PSA kinetics have no value for men with an untreated prostate: neither PSA velocity nor doubling time have any role in diagnosing prostate cancer or providing a prognosis for men before treatment.
Given current data on PSA velocity and doubling time, Vickers et al. proposed somewhat middle of the road these recommendations:
- High PSA velocity is not an indication for biopsy;
- for men with a low total PSA but a high PSA velocity, consideration should be given to measuring PSA at a shorter interval;
- men with an indication for biopsy should be biopsied irrespective of PSA velocity;
- changes in PSA after negative biopsy findings do not determine the need for repeat biopsy;
- monitoring PSA over time can aid judgment in decisions about biopsy, as informed by the clinical context;
- PSA velocity is uninformative of risk at diagnosis;
- high PSA velocity is not an indication for treatment in men on active surveillance;
- PSA velocity at the time of recurrence should be entered into prediction models (or "nomograms") to aid patient counseling.
- Br J Med Surg Urol. 2012 Jul 1;5(4):162-168.
- Urology. 2014 Mar;83(3):592-6
I recently was asked to comment on a series of troponin values from a general hospital.
Since this is a series of extremely high troponin, an MI was suspected. Although the EKG/ECG was not normal, there was no evidence of an AMI.
The apparent "change" in the TnI is probably due to the random error rather than a physiological change.
Table: Troponin Series
|Day ||Time ||Troponin 1 |
| 1|| 1325|| 2.6|
| 1|| 1724|| 2.4|
| 1|| 2035|| 2.3|
| 2|| 0248|| 2.2|
| 2|| 0646||2.1 |
I am sorry to say that, by the time I was asked to comment on this, the sample was gone and the patient had been discharged. My response had the sample still been available was to suggest that one or more of the samples be mixed 1+1 and 1+3 with a sample with a very low TnI level (approx. 0). Then assay the unmixed sample(s) and the dilutions. If the sample contained a heterophilic antibody (my thought) the values would not show linearity. If the troponin were truly TnI the sample would show linearity. Another/additional test would be to measure a not constituent measured by immunoassay such as TSH or hCG. A high value in these would also indicate a heterophilic antibody.
An interesting article on salivary cTnI appeared recently. In a group of 30 confirmed AMI and 28 non-MI
the cTnI were measured in both serum and saliva. The interquartile range for the saliva was 0.08-0.23 and for the AMI patients at 12 hrs. post-admission the range was 2.7-11.6 and at 24 hrs. the range was 2.1-9.0
In a similar study by the same authors higher CK levels in saliva were also recorded.
In both cases there was a positive correlation between serum levels of both CK and cTnI and salivary levels.
Indian J Med Res. Dec 2013; 138(6): 861-865
Iron deficiency (ID) is relatively common among the elderly population, contributing substantially to the high prevalence of anemia observed in the last decades of life, which in turn has important implications both on quality of life and on survival. In elderly subjects, ID is often multifactorial (i.e., due to multiple concurring causes, including inadequate dietary intake or absorption, occult bleeding, medications).
Moreover, because of the typical multi-morbidity of aged people, other conditions leading to anemia frequently coexist and make diagnosis of ID particularly challenging. Treatment of ID is also problematic in elderly, since response to oral iron is often slow, with a substantial fraction of patients showing refractoriness and requiring cumbersome intravenous administration. In the last decade, the discovery of the iron regulatory hormone hepcidin (an acute-phase reacting protein) has revolutionized our understanding of iron pathophysiology.
In serum samples, age- and gender-dependent reference values were determined using serum samples from healthy volunteers (n = 231). Hepcidin is stable for 1 day at room temperature, 6 days at +4°C and at least 42 days at -20°C. Breakfast and the type of sampling device do not affect hepcidin concentration. Reference values for females aged 18-50 years were 0.4-9.2 nmol/L, for those >50 years 0.7-16.8 nmol/L and for males ≥18 years 1.1-15.6 nmol/L.
- Front Pharmacol.2014 Apr 23;5:83.
- Bioanalysis.2014 Apr;6(8):1081-91
- Arthritis Rheum.2011 Dec;63(12):3672-80.
The human gut is home to trillions of microbes (the intestinal microbiota) that form a symbiotic relationship with the human host. During health, this intestinal microbiota provides many benefits to the host and is generally resistant to colonization by new species; however, disruption of this complex community can lead to pathogen invasion, inflammation, and disease.
Restoration and maintenance of a healthy gut microbiota composition requires effective therapies to reduce and prevent colonization of harmful bacteria (pathogens) while simultaneously promoting growth of beneficial bacteria (probiotics). Accumulating evidence indicates that the gut microbiota plays a significant role in the development of obesity, obesity-associated inflammation and insulin resistance.
Important to this subject is the concept of "crosstalk" (i.e., the biochemical exchange between host and microbiota that maintains the metabolic health of the superorganism and whose dysregulation is a hallmark of the obese state). Differences in community composition, functional genes and metabolic activities of the gut microbiota appear to distinguish lean vs obese individuals, suggesting that gut "dysbiosis" contributes to the development of obesity and/or its complications. The current challenge is to determine the relative importance of obesity-associated compositional and functional changes in the microbiota and to identify the relevant taxa and functional gene modules that promote leanness and metabolic health.
As diet appears to play a predominant role in shaping the microbiota and promoting obesity-associated dysbiosis, parallel initiatives are required to elucidate dietary patterns and diet components (e.g., prebiotics, probiotics) that promote healthy gut microbiota.
- Mol Aspects Med. 2013 Feb;34(1):39-58.
- J Mol Biol. 2014 Jun 6. pii: S0022-2836(14)00279-4.
- Gastroenterol Clin North Am. 2012
- Curr Opin Clin Nutr Metab Care. 2011
Pharmacol Ther. 2011
What have we learned about early treatment of HIV-1 from the "Mississippi Baby"?
Due to the increased risk of human immunodeficiency virus (HIV) infection during the child bearing years, voluntary screening during the prenatal period has been suggested. HIV testing was offered as a component of a prenatal laboratory panel, using informed refusal. During the first screening period, there were 20 seropositive women among the 14,143 patients (1.4/1000). Free treatment with zidovudine (AZT) for both mother and baby began in January 1994. The perinatal transmission rate was 33% before AZT treatment, during the period of assessment, and was reduced to 10% during the next 30 months.
A child, nicknamed the Mississippi Baby, did not receive any prenatal HIV care. Because of a greater risk of infection, she was started on a powerful HIV treatment just hours after labor. She continued to receive treatment until 18 months old, when doctors could not locate her. When she returned 10 months later, no sign of infection was evident though her mother had not given her HIV medication in the interim. Repeated tests showed no detectable HIV virus until last week. She had appeared free of HIV as recently as March, without receiving treatment for nearly 2 years. Doctors do not yet know why the virus re-emerged.
A second child with HIV was given early treatment just hours after birth in Los Angeles in April 2013. Subsequent tests indicate she completely cleared the virus, but that child also received ongoing treatment.
Only one adult is currently believed to have been cured of HIV. In 2007, Timothy Ray Brown received a bone marrow transplant from a donor with a rare genetic mutation that resists HIV. He has shown no signs of infection for more than 5 years.
- BBC News Medicine. July 10, 2014
- BBC News Medicine. March 4, 2013
- Pediatr AIDS HIV Infect. 1997 Feb;8(1):12-4
Quorum sensing (QS) is a bacterial communication process that depends on the bacterial population density. It involves small diffusible signaling molecules which activate the expression of myriad genes that control a diverse array of functions including virulence. Quorum sensing is a process of cell-cell communication that allows bacteria to share information about cell density and adjust gene expression accordingly.
This process enables bacteria to express energetically expensive processes as a collective only when the impact of those processes on the environment or on a host will be maximized. Among the many traits controlled by quorum sensing is the expression of virulence factors by pathogenic bacteria.
As QS is responsible for virulence in the clinically relevant bacteria, inhibition of QS appears to be a promising strategy to control these pathogenic bacteria. QS antagonists should be viewed as blockers of pathogenicity rather than as anti-microbials and because QS is not involved in bacterial growth, inhibition of QS should not yield a strong selective pressure for development of resistance. QS inhibitors hold great expectations and we may look forward to their application in fighting bacterial infections.
- EMBO Mol Med. 2009 Jul;1(4):201-10
- Recent Pat Antiinfect Drug Discov. 2013 Apr;8(1):68-83.
The kidney has a remarkable capacity to withstand insults for an extended period of time. The sensitivities of individual renal cells to injury vary depending on their type, position in the nephron, local vascularization, and the nature of injury. The resulting kidney injury is a product of the interplay between cell dysfunction, cell death, proliferation, inflammation, and recovery.
Acute kidney injury (AKI) is a common and serious condition in both the inpatient and outpatient settings, and its diagnosis depends on serum creatinine or cystatin C measurements.
Unfortunately, creatinine is a delayed and unreliable indicator of AKI. The lack of early biomarkers has limited our ability to translate promising experimental therapies to human AKI. Fortunately, understanding the early stress response of the kidney to acute injuries has provided a number of potential biomarkers. For example, neutrophil gelatinase-associated lipocalin (NGAL) is emerging as an excellent stand alone biomarker in the plasma and urine for predicting and monitoring clinical trials and in the prognosis of AKI. In recent years, a number of new biomarkers of AKI with more favorable test characteristics.
The two tables indicate the utility of the newer markers, some of which are commercially available indicate the utility of these markers compared to cystatin C. Because the pattern of appearance in the urine or serum, varies with the markers it may be necessary to use more than one marker to detect and monitor AKI.
Efforts to detect AKI in the earlier stage has resulted in some promising biomarkers such as KIM-1, NGAL, IL-18, and Clusterin. Cystatin C is a biomarker for glomerular filtration function, while 2-microglobulin, 1-microglobulin, NAG, RBP, IL-18, NGAL, Netrin-1, KIM-1, Clusterin, Sodium Hydrogen Exchanger Isoform and Fetuin A are biomarkers for tubular reabsorption function.
For Additional Reading
Anemia is a common condition in the elderly (for example, in a study of .6880 individuals, 2905 men and 3975 women, aged 65-95 [mean age 72.5], mild anemia [hemoglobin levels <10 g/dL] was found in 6.1% of women and 8.1% of men.) The reason that LDH shows up is that there is 20% more LDH in red cells than serum. More than 10% of the population over 70 years have iron and/or vitamin B-12 deficiency. Here is a flow chart that may help evaluate chronic anemia: http://asheducationbook.hematologylibrary.org/content/2012/1/183/F3.expansion.html
For Additional Reading
In a recent blog, I touched on some ideas and tools that are being used to build "labs on chips." The word nano operates significantly in this area. If you were as excited and intrigued with that blog, read on for now we are going to talk on "organs-on-a-chip" and even a "body-on-a-chip." Just how does one model, test, and learn about the communication and control of biological systems with individual organs-on-chips that are one-thousandth or one-millionth of the size of adult organs, or even smaller, i.e., organs for a milliHuman (mHu) or microHuman (μHu)?
With serious work being done to realize functioning artificial livers, kidneys, hearts, and lungs on chips, the next step is not only to interconnect these organs but also to consider the integration of stem cell technology to create interconnected patient-specific organs. Such a patient-specific body-on-a-chip requires a sophisticated set of tools for micropattering cell cultures in 3D to create interconnected tissue-like organ structures. It seems that anticipation that such a technology would have a wide area of application, primarily benefiting drug development, chemical safety testing, and disease modeling.
We are not there, yet. But it is certain that a large amount of work is going into these projects not just for the ‘fun' of creating, say, a kidney, on a chip but for the results will aid in drug testing and replacement medicine and individual (unique) drug treatment.
For Additional Reading
- Wikswo JP. Lab Chip. 2013 Sep 21;13(18):3496-511. Scaling and systems biology for integrating multiple organs-on-a-chip.
- Moraes C. Integr Biol (Camb). 2013 Sep;5(9):1149-61. On being the right size: scaling effects in designing a human-on-a-chip.
- Williamson A. Lab Chip. 2013 Sep 21;13(18):3471-80. The future of the patient-specific Body-on-a-chip.
Middle East Repiratory Syndrome (MERS) recently was said to be a "public health emergency of international concern." The MERS virus, which appeared in the Middle East in 2012, has spread through that area; cases have been found in Asia, Europe and the United States. The mortality rate is near 30%.
Two health workers at a hospital in Orlando, Fla., who were exposed to a patient with MERS exhibited flu-like symptoms, and one was hospitalized.
MERS, which causes coughing, fever and occasionally fatal pneumonia, is a virus from the same family as SARS, which has killed about 800 people worldwide since it first appeared in China in 2002.
MERS, a second coronavirus, SARS being the first, is transmissible from person to person, and its close relationship with several bat coronaviruses suggests that these animals may be the ultimate source of the infection. However, many key issues need to be addressed, including identification of the proximate, presumably zoonotic, source of the infection, the prevalence of the infection in human populations, details regarding clinical and pathological features of the human infection, the establishment of a small rodent model for the infection, and the virological and immune basis for the severe disease observed in most patients. Margaret Chan, Director-General of the World Health Organization, has called MERS-CoV "a threat to the entire world." There is no vaccine for MERS.
For Additional Reading
Helicobacter pylori has been associated with the colonization of gastro duodenal mucosa of humans from millions of years. The central burden of the disease is in the developing countries, due to overcrowding and poor hygiene. Wherever it is found, if left untreated, it leads to a number of consequences from minor to sinister diseases over time (these include including extra-gastric diseases like cerebrovascular, cardiovascular, idiopathic thrombocytopenia, sideroblastic anemia, mental diseases, and collagen vascular diseases).
The major challenges that remain are prevention of H. pylori-related diseases by effective treatment and screening procedures and development of a vaccine. It is also becoming increasingly difficult to eradicate and the main reason for this is growing primary antibiotic resistance rates in a world where antibiotics are frequently prescribed and readily available. Clinicians today must be prepared to face multiple treatment failures, and should be equipped to decide the appropriate salvage therapy when antibiotic resistance occurs. Established empiric second line treatment options include both bismuth based quadruple therapy and levofloxacin based triple therapy. Antibiotic testing is recommended prior to initiating third line treatment.
The prevention of cancer of the stomach, a worst sequel of H. pylori continues to be a significant challenge despite population screening and prevention underway in many countries. In contrast, the beneficial effects of H. pylori with respect to allergic diseases and obesity are now clear. Moreover, the problem of drug resistance for eradication of H. pylori has arisen for which novel treatments are being tried. Lactobacillus reuteri having anti H. pylori action is emerging as one of the promising treatment.
For Additional Reading
Immunotherapy for cancer has undergone a renaissance in
recent years, based both on technological developments such as the ease in
introducing genes into T cells and on an improved understanding of the
obstacles to eradicating cancer through immune mechanisms. Much remains to be
discovered, however, there is considerable optimism that this approach can have
a significant impact for patients, both alone and as an adjunct to
hematopoietic stem cell transplant. For a long time doctors suspected that the
immune system could affect certain cancers. Even before the immune system was
well understood, William Coley, a surgeon, first noted that getting an
infection after surgery seemed to help some cancer patients. In the late 1800s,
he began treating cancer patients by infecting them with certain kinds of
bacteria, which came to be known as Coley toxins. Although he had some success,
his technique was overshadowed when other forms of cancer treatment.
Since then, doctors have learned a good deal about the
immune system, deal with genetic therapy and they might be used to treat
cancer. In the last few decades immunotherapy has become an important part of
treating some cancers. Immunotherapy includes treatments that work in different
ways. Some boost the body’s immune system in a very general way. Others help
train the immune system to attack cancer cells specifically. Immunotherapy
works better for some types of cancer than for others. It’s used by itself for
some of these cancers, but for others it seems to work better when used with
other types of treatment.
Immunotherapy Boosts Pediatric Cancer Survival
New Method of Gene Therapy for Treating Advanced Melanoma
The Best American Science Writing 2012.
Many years ago, I came up with a sure way to lose weight –
take in fewer calories than you burn. What could be simpler?
I was not alone. A study of more than 1100 adults found that
61% of U.S. adulates that “personal choices about eating and exercise” were the
cause of overweight.
Over the past few years, data have been accumulating that
indicate that while I might be correct in many, even most cases, there was a
group of people with whom my plan would not work.
Today, molecular genetics is central to obesity research. In
2007, Mark McCarthy, Andrew Hattersley, and their colleagues in the UK
identified a common variant in FTO, the fat-mass and obesity–associated gene,
and gene hunters aided by the use of next-generation–sequencing technology
continue to identify gene variants or mutations. These studies reinforce what
some researchers have been insisting for more than a century: that obesity is
innate in some people, that for them weight regulation is not governed by a
uniform tally of “calories in–calories out,” Genetic predispositions, in tandem
with the development of food environments that facilitate overeating and built
environments requiring minimal energy expenditure, may help explain why so many
Americans are obese today.
Chin Jou, N Engl J Med 2014; 370:1874-1877
The prevalence of upper-extremity deep venous thrombosis
(DVT) has risen in conjunction with more frequent use of central venous
catheters. There are clear algorithms for diagnosing lower-extremity (e.g.
Wells), but not for upper-extremity, DVT. A multicenter study, a diagnostic
algorithm was evaluated in 406 patients with suspected upper-extremity DVTs.
The study included calculating a clinical decision score consisted of +1 point
each for the presence of a central venous catheter or lead, localized pain, or
unilateral edema and −1 point for a plausible alternate diagnosis. Scores of ≤1
implied that upper-extremity DVT was unlikely. The algorithm in addition to the
score included D-dimer testing, and ultrasonography. The patients were
follow-up after 3 months.
Fifty percent of patients (203) were assigned clinical
decision scores of 0 or 1 (upper-extremity DVT unlikely); 90 had normal D-dimer
tests and did not undergo further testing or treatment -- none developed
symptomatic DVTs. The 113 low-scoring patients with abnormal D-dimer tests
underwent ultrasonography: Ultrasonography was negative in 73 -- they did not
receive treatment, and none developed symptomatic DVTs. Upper-extremity DVTs
were diagnosed in 12 low-scoring patients. In the 203 patients with higher
scores, ultrasonography detected no upper-extremity DVTs in 83; those patients
underwent D-dimer testing and repeated ultrasonography if D-dimer test were
abnormal, with a yield of 3 additional DVT diagnoses. Rates of upper-extremity
DVT were significantly lower in patients with scores ≤1 than in those with
scores >1 (6% vs. 44%).
This study verifies the value of using d-dimer measurements
to rule out DVT.
Jamaluddin Moloo, reviewing Kleinjan A et al. Ann Intern Med
2014 Apr 1.