In a Horizon special, naturalist Sir David Attenborough investigates whether the world is heading for a population crisis.
Sir David has watched the human population more than double from 2.5 billion in 1950 to nearly seven billion. He reflects on the profound effects of this rapid growth, both on humans and the environment. Sir David examines whether it is the duty of individuals to commit not only to smaller families, but to change the way they live for the sake of humanity and planet Earth. “
David Attenborough is also the Optimum Population Trust Patron and describes the growth in human numbers as “frightening” and urged environmental organisations to spell out “loud and clear” the problems caused by population growth. The Optimum Population Trust is the leading think tank in the UK concerned with the impact of population growth on the environment.
Jeffrey Steinberg, a US doctor, is offering British couples the chance to choose the sex of their childAugust 24, 2009
Dr Steinberg provoked anger earlier this year when he said his fertility clinic could allow parents to produce “designer babies” – choosing eye, hair, skin colour and gender.
Under American law, he is allowed to use pre-implentation genetic diagnosis (PGD) to reveal an embryo’s sex. In Britain, it can only be used in screening for genetic diseases.
Half of the embryos undergoing tests in Dr Steinberg’s laboratory reportedly belong to British couples while four more will be tested next month.
“Britain is far more conservative than it used to be. They were the innovators but now they’ve got handcuffs on,” Dr Steinberg said.
“From a business standpoint, it’s the best thing going. From a medical standpoint, it’s a travesty.”
America has allowed sex selection – known by its supporters as “family balancing” – since 2001, but US pro-life groups have criticised the destruction of embryos deemed undesirable. Earlier this year, the Pope attacked the “obsessive search for the perfect child” and said a “new mentality is creeping in that tends to justify a different consideration of life and personal dignity”.
from The Daily Telegraph
Humans can’t process and absorb all of their consumed food. However our guts are home to trillions of commensal bacteria which help break down food our own cells cannot, allowing us to reap the benefits. Upwards of 90% of these bacteria fall within two groups called the Bacteroidetes and the Firmicutes. Research released in 2008 suggests that the proportion of these groups “is linked to the risk of becoming obese.”
Washington University scientists: Ruth Less, Peter Turnbaugh and Jeffrey Gordon, tested the hypothesis on mice that lack the hormone leptin. Leptin controls the body’s ‘fat thermostat’ and without it the mice quickly become obese. The scientists found that the obese mice had 50% fewer Bacteroidetes and 50% more Firmicutes in their bowel than their lean counterparts. In humans this was found to be the same. When obese people started to lose weight through low-fat and low-carbohydrate dieting, Bacteroidetes increased and in contrast Firmicutes decreased.
I find this a fascinating example of how little we understand the ways our gut microbiota influences our bodies and behaviour. Also, although our genes excert a great influence on our tendencies for obesity, other environmental factors like our bacterial composition have an equally important influence.
Notes of interest:
Can biosensors created to detect the levels of the hormone leptin in body indicate a potential obesiogenic future for that person?
Can the measurement of Bacteroidetes and Firmicutes be used to direct the future personal evolution of a person?
Will the products created in the p-evo clinics be required to react to genomic and environmental factors? If so, will there be a family of p-evo devices to predict certain gene and environmental factors?
Circadian rhythms are ingrained in our lives; however, little attention has been paid to their metabolic consequences. It has been suggested that disruption of the circadian system may be related to expression of the metabolic syndrome (MetS) (1). Thus, shift work, sleep deprivation and exposure to bright light at night have been shown to be related to increased adiposity and prevalence of MetS (1,2).
Recent findings support the notion that rhythmic expression of circadian genes exists not only in the brain but in several other tissues (3,4). Along these lines, we have shown clock gene expression in human adipose tissue (AT) (5) and demonstrated that this expression was associated with different components of the MetS (5). An important question is whether this circadian clockwork can oscillate accurately and independently of the suprachiasmatic nucleus (SCN) in human AT and whether other genes are controlled by this process.
The objective of the present research was to analyze the circadian expression of the clock genes hPer2, hBmal1 and hCry1 in AT explants from morbid obese women from subcutaneous (SAT) and visceral (VAT) AT, in order to elucidate whether this circadian clockwork can oscillate accurately and independently of the SCN and if glucocorticoid metabolism-related genes such as that glucocorticoid receptor (hGr) and 11-hydroxysteroid dehydrogenase 1 (h11Hsd1) and the master transcription factor peroxisome proliferator activated receptor (hPPAR) are controlled by clock genes.
Full article: Obesity research journal – http://www.nature.com/oby/journal/vaop/ncurrent/full/oby2009164a.html
Wikipedia on circadian clocks:
The primary circadian “clock” in mammals is located in the suprachiasmatic nucleus (or nuclei) (SCN), a pair of distinct groups of cells located in the hypothalamus. Destruction of the SCN results in the complete absence of a regular sleep/wake rhythm. The SCN receives information about illumination through the eyes. The retina of the eyes contains not only “classical” photoreceptors but also photoresponsive retinal ganglion cells. These cells, which contain a photo pigment called melanopsin, follow a pathway called the retinohypothalamic tract, leading to the SCN. If cells from the SCN are removed and cultured, they maintain their own rhythm in the absence of external cues.
It appears that the SCN takes the information on the lengths of the day and night from the retina, interprets it, and passes it on to the pineal gland, a tiny structure shaped like a pine cone and located on the epithalamus. In response the pineal secretes the hormone melatonin. Secretion of melatonin peaks at night and ebbs during the day and its presence provides information about night-length.
The circadian rhythms of humans can be entrained to slightly shorter and longer periods than the Earth’s 24 hours. Researchers at Harvard have recently shown that human subjects can at least be entrained to a 23.5-hour cycle and a 24.65-hour cycle (the latter being the natural solar day-night cycle on the planet Mars).
Determining the human circadian rhythm
The classic phase markers for measuring the timing of a mammal’s circadian rhythm are
- melatonin secretion by the pineal gland and
- core body temperature.
For temperature studies, people must remain awake but calm and semi-reclined in near darkness while their rectal temperatures are taken continuously. The average human adult’s temperature reaches its minimum at about 05:00 (5 a.m.), about two hours before habitual wake time, though variation is great among normal chronotypes.
Melatonin is absent from the system or undetectably low during daytime. Its onset in dim light, dim-light melatonin onset (DLMO), at about 21:00 (9 p.m.) can be measured in the blood or the saliva. Its major metabolite can also be measured in morning urine. Both DLMO and the midpoint (in time) of the presence of the hormone in the blood or saliva have been used as circadian markers.
However, newer research indicates that the melatonin offset may be the most reliable marker. Benloucif et al. in Chicago in 2005 found that melatonin phase markers were more stable and more highly correlated with the timing of sleep than the core temperature minimum. They found that both sleep offset and melatonin offset were more strongly correlated with the various phase markers than sleep onset. In addition, the declining phase of the melatonin levels was more reliable and stable than the termination of melatonin synthesis.
One method used for measuring melatonin offset is to analyze a sequence of urine samples throughout the morning for the presence of the melatonin metabolite 6-sulphatoxymelatonin (aMT6s). Laberge et al. in Quebec in 1997 used this method in a study which confirmed the frequently found delayed circadian phase in healthy adolescents.
Outside the “master clock”
More-or-less independent circadian rhythms are found in many organs and cells in the body outside the suprachiasmatic nuclei (SCN), the “master clock.” These clocks, called peripheral oscillators, are found in the esophagus, lung, liver, pancreas, spleen, thymus and the skin. Though oscillators in the skin respond to light, a systemic influence has not been proven so far. There is some evidence that also the olfactory bulb and prostate may experience oscillations when cultured, suggesting that also these structures may be weak oscillators.
There are many health problems associated with disturbances of the human circadian rhythm, such as seasonal affective disorder (SAD), delayed sleep phase syndrome (DSPS) and other circadian rhythm disorders. Circadian rhythms also play a part in the reticular activating system which is crucial for maintaining a state of consciousness. In addition, a reversal in the sleep-wake cycle may be a sign or complication of uremia, azotemia or acute renal failure.
A number of other disorders, for example bipolar disorder and some sleep disorders, are associated with irregular or pathological functioning of circadian rhythms. Recent research suggests that circadian rhythm disturbances found in bipolar disorder are positively influenced by lithium‘s effect on clock genes.
Disruption to rhythms in the longer term is believed to have significant adverse health consequences on peripheral organs outside the brain, particularly in the development or exacerbation of cardiovascular disease  The suppression of melatonin production associated with the disruption of the circadian rhythm may increase the risk of developing cancer.